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Publication numberUS20030220427 A1
Publication typeApplication
Application numberUS 10/301,770
Publication dateNov 27, 2003
Filing dateNov 21, 2002
Priority dateMay 9, 2002
Also published asCA2482829A1, CA2485541A1, EP1504056A1, EP1504057A2, US6858664, US6969737, US20040002563, US20040002564, WO2003095550A1, WO2003095550A8, WO2003095550B1, WO2004009643A2, WO2004009643A3
Publication number10301770, 301770, US 2003/0220427 A1, US 2003/220427 A1, US 20030220427 A1, US 20030220427A1, US 2003220427 A1, US 2003220427A1, US-A1-20030220427, US-A1-2003220427, US2003/0220427A1, US2003/220427A1, US20030220427 A1, US20030220427A1, US2003220427 A1, US2003220427A1
InventorsGary Wentworth, Stephen O'Rourke, Kimberly Stefanisin, John English
Original AssigneeGary Wentworth, O'rourke Stephen, Kimberly Stefanisin, John English
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
A plasticizers mono, di- and tri-esters with long hydrocarbon chain; improving the adhesion of steel cord-embedding rubber tire
US 20030220427 A1
Abstract
A rubber composition including a natural or synthetic rubber, and an adhesive resin capable of unexpected adhesion to metal, polymer and glass substrates, particularly cords in radical tires, hoses, conveyor belts, transmission belts, and the like by the addition of long chain esters, including mono, di- and tri-esters.
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Claims(46)
What is claimed is:
1. A rubber composition comprising rubber selected from the group consisting of natural rubber, synthetic rubber, and a combination thereof; an adhesive resin in an amount of about 0.1% to about 15% by weight, based on the weight of rubber in the composition; a vulcanizing agent; and an ester adhesion promoter compound having formula I, II, III, IV or a mixture of any two or more of said adhesion promoter compounds in an amount of about 0.1% to about 15% by weight, based on the weight of rubber in the composition:
wherein R1 is a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; R2 is a C3-C24 saturated fatty acid residue, or an unsaturated fatty acid residue having 1 to 6 carbon-to-carbon double bonds;
wherein n=3-24, and R3 and R4, same or different, are a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds;
wherein R5 and R7, same or different, are a C3-C24 hydrocarbon chain, straight chain or branched, either saturated or having 1 to 6 carbon-to-carbon double bonds;
R6 and R8, same or different, are a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and
R10 and R11, same or different, are a C3-C24, saturated hydrocarbon chain, straight chain or branched; or an unsaturated C3-C24, hydrocarbon chain, straight chain or branched, having 1 to 6 carbon-to-carbon double bonds;
wherein R12, R14 and R18, same or different, are a C3-C24 hydrocarbon chain, straight chain or branched, either saturated or having 1 to 6 carbon-to-carbon double bonds;
R13, R15 and R19, same or different, are a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and
R16, R17 and R20, same or different, are a C3-C24 saturated hydrocarbon chain, straight chain or branched; or unsaturated C3-C24 hydrocarbon chain, straight chain or branched, containing 1 to 6 carbon-to-carbon double bonds.
2. A rubber composition in accordance with claim 1, wherein the adhesion promoter is selected from the group consisting of formula I, II, III, IV, and a combination of any two or more of said adhesion promoter compounds:
wherein R1 is a C3-C18 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds, and R2 is a C8-C18 saturated fatty acid residue, or an unsaturated fatty acid residue having 1 to 3 carbon-to-carbon double bonds;
wherein n=6-18 and R3 and R4, same or different, are a C3-C18 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds;
wherein R5 and R7, are a C6-C24 hydrocarbon chain, straight chain or branched; either saturated or having 1 to 3 carbon-to-carbon double bonds;
R6 and R8, same or different, are a C3-C18 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds, and
R10 and R11, same or different, are C3-C18 saturated hydrocarbon chain, straight chain or branched; or an unsaturated hydrocarbon chain, straight chain or branched, containing 1 to 3 carbon-to-carbon double bonds;
wherein R12, R14 and R18, same or different, are a C8-C18 hydrocarbon chain, straight chain or branched, either saturated or containing 1 to 3 carbon-to-carbon double bonds;
R13, R15 and R19, same or different, are a C6-C18 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and
R16, R17 and R20, same or different, are a C6-C18 saturated hydrocarbon chain, straight chain or branched; or an unsaturated C6-C18 hydrocarbon-chain, straight chain or branched, containing 1 to 3 carbon-to-carbon double bonds.
3. The rubber composition of claim 1, wherein the adhesive resin is a condensation product of a methylene acceptor and a methylene donor.
4. The rubber composition in accordance with claim 3, wherein the adhesive resin is selected from the group consisting of phenol-formaldehyde; melamine-formaldehyde; naphthol-formaldehyde; polyepoxide; a reaction product of triallyl cyanurate, resorcinol, and formaldehyde; a reaction product of p-chlorophenol, resorcinol, and formaldehyde; a copolymer of styrene, butadiene, and 2-vinlypyridine; and mixtures thereof.
5. The rubber composition in accordance with claim 4, wherein the phenol-formaldehyde resin is resorcinol-formaldehyde.
6. The rubber composition in accordance with claim 1, wherein the adhesive resin is selected from the group consisting of derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril monomers and oligomers of these monomers, which have been substituted on average at two or more positions on the monomer or on each unit of the oligomer with vinyl terminated radicals, the vulcanizable rubber composition being free of resorcinol.
7. The vulcanizable rubber composition in accordance with claim 6, wherein at least one of the additives has been further substituted on average at one or more positions with a radical which comprises carbamylmethyl or amidomethyl.
8. A vulcanizable rubber composition in accordance with claim 6, wherein the adhesive resin is selected from compounds of the formulas:
wherein, in each monomer and in each polymerized unit of the oligomers, Y is selected from methyl, phenyl and cyclohexyl, and, on average,
at least two R are —CH2—R1,
and any remaining R are H, and
at least 2 R1 are radicals selected from
wherein R2 is hydrogen or C1-C18 alkyl, and Z is a radical selected from
any remaining R1 radicals are selected from
wherein R3 is hydrogen or R4, and
R4 is a C1-C18 alkyl, alicyclic, hydroxyalkyl, alkoxyalkyl or aromatic radical, and in the oligomers,
P is 2to about 10, and
L is methylene or the radical
—CH2—O—CH2—
9. A vulcanizable rubber composition in accordance with claim 8, wherein on average at least one R1 in each monomer or in each oligomerized unit is
—NH—C(O)—OR4
wherein R4 is as defined in claim 8.
10. A vulcanizable rubber composition in accordance with claim 9, wherein the adhesive resin is a compound of the formula
wherein P, L and R are as defined in claim 8;
11. A vulcanizable rubber composition in accordance with claim 10, wherein in the formulas, on average at least one R radical in each monomer or in each oligomerized unit is
—CH2—NH—C(O)—OR4
wherein R4 is a C1-C18 alkyl, alicyclic, hydroxyalkyl, alkoxyalkyl or aromatic radical.
12. A vulcanizable rubber composition in accordance with claim 10, wherein on average at least two R radicals are selected from
and at least one R radical is selected from
—CH2—NH—C(O)—O—CH3, and —CH2—NH—C(O)—O—C3H7
13. A vulcanizable rubber composition in accordance with claim 8, further comprising an additional additive selected from hydroxymethylated and alkoxymethylated (alkoxy having 1-5 carbon atoms) derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril and their oligomers.
14. The composition in accordance with claim 6, wherein the adhesive resin is a derivative of melamine or an oligomer of melamine.
15. The composition in accordance with claim 6, wherein the adhesive resin is a derivative of acetoguanamine or an oligomer of acetoguanamine.
16. The composition in accordance with claim 6, wherein the adhesive resin is a derivative of benzoguanamine or an oligomer of benzoguanamine.
17. The composition in accordance claim 6, wherein the adhesive resin is a derivative of cyclohexylguanamine or an oligomer of cyclohexylguanamine.
18. A vulcanizable rubber composition in accordance with claim 1, wherein the adhesive resin is a self-condensing alkylated triazine resin selected from the group consisting of (i), (ii), and (iii):
(i) a self-condensing alkylated traizine resin having at least one of imino or methylol functionality and represented by the formula (I)
(ii) an oligoner of(i), or
(iii) a mixture of (i) and (ii), wherein
Z is —N(R)(CH2OR1), aryl having 6 to 10 carbon atoms, alkyl having 1 to 20 carbon atoms or an acetyl group,
each R is independently hydrogen or —CH2OR1, and
each R1 is independently hydrogen or an alkyl group having 1 to 12 carbon atoms,
provided that at least one R is hydrogen or —CH2OH and at least one R1 is selected from the alkyl group; and
wherein the vulcanizable rubber composition is substantially free of methylene acceptor coreactants.
19. The vulcanizable rubber composition in accordance with claim 18, wherein at least one R group is hydrogen.
20. The vulcanizable rubber composition in accordance with claim 19, wherein at least one R1 group is a lower alkyl group having 1 to 6 carbon atoms.
21. The vulcanizable rubber composition in accordance with claim 20, wherein the adhesive resin is a derivative of melamine, benzoguanamine, cyclohexylguanamine, or acetoguanamine, or an oligomer thereof.
22. The vulcanizable rubber composition in accordance with claim 20, wherein Z is —N(R)(CH2OR1).
23. The rubber composition in accordance with claim 4, wherein the phenol-formaldehyde resin is resorcinol-formaldehyde; and the melamine-formaldehyde resin is N-(substituted oxymethyl) melamine-formaldehyde.
24. A rubber,composition in accordance with claim 1, wherein the adhesion promoter has the formula II and comprises a saturated diester formed by the reaction of sebacic acid and a C6-C24 alcohol, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds.
25. A rubber composition in accordance with claim 24, wherein the alcohol is 2-ethylhexyl alcohol, and the adhesion promoter has the following formula:
26. A rubber composition in accordance with claim 1, wherein the adhesion promoter is an unsaturated diester formed by the reaction of a C36 dimer acid and a C3-C18 alcohol, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds.
27. A rubber composition in accordance with claim 26, wherein the alcohol is 2-ethylhexyl alcohol.
28. A rubber composition in accordance with claim 26, wherein the alcohol is tridecyl alcohol.
29. A rubber composition in accordance with claim 26, wherein the alcohol is oleyl alcohol.
30. A rubber composition in accordance with claim 1, wherein the adhesion promoter comprises the following dimerate acid reacted with a C3-C24 alcohol:
31. A rubber composition in accordance with claim 1, wherein the adhesion promoter comprises the following dimerate acid reacted with a C3-C24 alcohol:
32. A rubber composition in accordance with claim 1, wherein the adhesion promoter comprises the following dimerate acid reacted with a C3-C24 alcohol:
33. A rubber composition in accordance with claim 1, wherein the adhesion promoter is the reaction product of a C3-C24 alcohol with a tricarboxylic acid, having the following formula;
34. A rubber composition in accordance with claim 1 wherein the adhesion promoter is a combination of compounds of formula I, II, III, and IV.
35. A rubber composition in accordance with claim 34, wherein the adhesion promoter is a reaction product of a C3-C24 alcohol straight chain or branched, saturated, or unsaturated having 1 to 3 carbon-to-carbon double bonds, with a dimer acid having CAS #61788-89-4.
36. A rubber composition in accordance with claim 35, wherein the alcohol is 2-ethylhexyl alcohol.
37. A rubber composition in accordance with claim 35, wherein the alcohol is a tridecyl alcohol.
38. A rubber composition in accordance with claim 35, wherein the alcohol is a oleyl alcohol.
39. A method of increasing the adhesion of a rubber composition to a polymer, glass, or metal substrate, said rubber composition including a natural or synthetic rubber, a rubber vulcanizing agent, and an adhesive resin, comprising adding to said rubber composition, in an amount of about 0.1% to 15% by weight, based on the weight of the rubber, an ester adhesion promoter additive of formula I, II, III, IV, or mixtures thereof:
wherein R1 is a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; R2 is a C3-C24 saturated fatty acid residue, or an unsaturated fatty acid residue having 1 to 6 carbon-to-carbon double bonds;
wherein n=3-24 and R3 and R4, same or different, are a C3-C24 alkyl radical, straight chain or branched;
wherein R5 and R7, same or different, are a C3-C24 hydrocarbon chain, straight chain or branched, either saturated or having 1 to 6 carbon-to-carbon double bonds;
R6 and R8, same or different, are a C3-C24 alkyl radical, straight chain or branched; and
R10 and R11, same or different, are a C3-C24, saturated hydrocarbon chain, straight chain or branched; or an unsaturated C3-C24, hydrocarbon chain, straight chain or branched, having 1 to 6 carbon-to-carbon double bonds;
wherein R12, R14 and R18, same or different, are a C3-C24 hydrocarbon chain, straight chain or branched, either saturated or having 1 to 6 carbon-to-carbon double bonds;
R13, R15 and R19, same or different, are a C3-C24 alkyl radical, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and
R16, R17 and R20, same or different, are a C3-C24 saturated hydrocarbon chain, straight chain or branched; or unsaturated C3-C24 hydrocarbon chain, straight chain or branched, containing 1 to 6 carbon-to-carbon double bonds.
40. A method in accordance with claim 39, wherein the substrate is a plurality of cords.
41. A method in accordance with claim 39, wherein the substrate is a polymeric sheet or fabric.
42. A method in accordance with claim 39, wherein the substrate is metal flat stock material.
43. A cord-reinforced article of manufacture comprising a plurality of cords selected from polymeric cords, metal cords, glass cords, and a combination thereof, adhered to the rubber composition of claim 1.
44. The rubber composition in accordance with claim 1, wherein the R2, R5, R7, R12, R14 are fatty acid residues derived from animal or vegetable fatty acids.
45. The rubber composition of claim 44, wherein the fatty acids are selected from the group consisting of butter; lard; tallow; grease; herring; menhaden; pilchard; sardine; babassu; castor; coconut; corn; cottonseed; jojoba; linseed; oiticia; olive; palm; palm kernel; peanut; rapeseed; safflower; soya; sunflower; tall; tung; and mixtures thereof.
46. The rubber composition of claim 45, wherein the fatty acid residues are selected from the group consisting of hexanoic; octanoic; decanoic; dodecanoic; 9-dodecenoic; tetradecanoic; 9-tetradecenoic; hexadecanoic; 9-hexadecenoic; octadecanoic; 9-octadecenoic; 9-octadecenoic, 12-hydroxy; 9,12-octadecadienoic; 9,12,15-octadecatrienoic; 9,11,13-octadecatrienoic; 9,11,13-octadecatrienoic; 4-oxo; octadecatetrenoic; eicosanoic; 11-eicosenoic; eicosadienoic; eicosatrienoic; 5,8,11,14-eicosatetraenoic; eicosapentaenoic; docosanoic; 13-docosenoic; docosatetraenoic; 4,8,12,15,19-docosapentaenoic; docosahexaenoic; tetracosenoic; and 4,8,12,15,18,21-tetracosahexaenoic.
Description
CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation-in-part of pending U.S. patent application Ser. No. 10/144,229, filed May 10, 2002, the disclosure of which, in its entirety, is hereby incorporated by reference, and the 35 U.S.C. ง120 benefit of which is claimed.

FIELD OF THE INVENTION

[0002] The present invention is directed to adhesion promoters for adhering elastomers, including natural and/or synthetic rubbers, to natural or synthetic polymeric cord or fabric substrates, and/or metal cord or metal substrates, particularly cords in the manufacture of cord-reinforced rubber articles, such as tires, hoses, conveyor belts, transmission belts, and the like.

BACKGROUND OF THE INVENTION AND PRIOR ART

[0003] Many rubber articles, principally automobile tires, but also including hoses, conveyor belts, power train belts, e.g., transmission belts, and the like, are usually reinforced with fibrous or metal cords. In all such instances, the fiber must be firmly bonded to the rubber. This is so whether the fiber is a natural or synthetic polymer, or metallic, and whether the rubbers are natural or synthetic.

[0004] The conventional practice has been to prepare the fiber by pretreatment with a combination of hexamethoxymelamine or hexamethylene-tetramine and phenol-formaldehyde condensation product, wherein the phenol is almost always resorcinol. By a mechanism not completely understood, the resin reacts with the fiber and the rubber, effecting a firm reinforcing bond.

[0005] One method useful to prepare the rubber compositions described herein entails compounding a vulcanizing rubber stock composition with the components of an adhesive resin condensation product. The components of the condensation product include a methylene acceptor and a methylene donor. The most commonly employed methylene acceptor is a phenol, such as resorcinol, while the most commonly employed methylene donor is a melamine, such as N-(substituted oxymethyl)melamine. The effect achieved is resin formation in-situ during vulcanization of the rubber, creating a bond between the metal or polymeric cords and the rubber, irrespective of whether the cords have been pretreated with an additional adhesive, such as a styrene-butadiene latex, polyepoxides with a blocked isocyanate, and the like. The long chain ester additive/resin combinations described herein are particularly useful with steel cord, where adhesive pretreatment has been largely ineffective.

[0006] Resorcinol-free vulcanizable rubber compositions are known. For example, U.S. Pat. No. 5,298,539 discloses vulcanizable rubber compositions containing uncured rubber, a vulcanizing agent and at least one additive selected from the group consisting of derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril monomer and oligomers of these monomers. These derivatives are substituted on average at two or more positions on the monomer or each unit of the oligomer with vinyl terminated radicals and the composition is free of resorcinol.

[0007] Another manner of eliminating resorcinol from vulcanizable rubber compositions has relied on the use of alternative coreactants. U.S. Pat. No. 4,038,220 describes a vulcanizable rubber composition which comprises a rubber, a filler material, N-(substituted oxymethyl)melamine and at least one of α- or β-naphthol. This reference employs the monohydric phenols, α- or β-naphthol, as methylene acceptors in the resin, forming reaction during vulcanization in the absence of resorcinol. The use of resorcinol-formaldehyde resin to replace resorcinol in vulcanizable rubber compositions is also known. For example, see A. Peterson, et al., “Resorcinol Bonding Systems For Steel Cord Adhesion”, Rubber World (August 1984).

[0008] An increased need in the industry for fiber reinforcing of rubber to survive high dynamic stress, such as flexing, to avoid tire belt separation has brought about,a continuing search for other and better methods for achieving high adhesive strength.

[0009] Tires typically have a construction such that a carcass, edge portions of a belt, an under-belt pad and the like are intricately combined with each other in its shoulder portion. The under-belt pad provided continuously along the circumferential shoulder portion of the tire between a tread rubber portion and the carcass and extending outwardly of the belt edge portions along the width of the tire is a thick rubber layer, which is a structural characteristic for alleviating a shear stress possibly generated between the belt edge portions and the carcass. Further, since the under-belt pad is repeatedly subjected to loads during running, heat is liable to build up in the under-belt pad, thereby causing internal rubber destruction in the under-belt pad and adhesion failures between the rubber components and between a rubber portion and cords (steel cords) in the carcass. This causes separation of the belt edge portions and ply separation in the carcass resulting in breakdown of the tire. One conventional approach to this problem is that the under-belt pad is formed of a rubber compound which contains a reduced amount of carbon black for suppression of heat build-up.

[0010] However, the rubber compound for the under-belt pad is softened by the reduction of the carbon black content therein. This also results in the adhesion failure and the internal rubber destruction in the under-belt pad due to the heat build-up, thereby causing the ply separation and the belt separation in the tire during running. Therefore, this approach is not satisfactory in terms of the durability of the tire. The deterioration of the durability of the tire which results from the heat build-up attributable to the structural,characteristic of the under-belt pad is, a more critical problem, since the recent performance improvement of automobiles requires that tires have a higher durability under higher speed running and heavy loads.

[0011] Despite their good abrasion resistance, radial tires become unusable sooner than bias tires because of the belt separation which takes place while the tread still remains. One way that this problem has been addressed is by improving the tread or steel cord-embedding rubber. For example, an improved tread is of dual layer structure, with the inner layer (base tread adjacent to the belt) being made of a rubber composition which is saved from heat generation at the sacrifice of abrasion resistance, and the outer layer (cap tread) being made of a rubber composition of high abrasion resistance. Also, an improved steel cord-embedding rubber is made of a rubber composition containing an adhesive such as a cobalt salt of an organic acid, hydroxybenzoic acid, and resorcinol, which increases adhesion between rubber and steel cord. These improvements, however, are not completely successful.

[0012] Other adhesion promoters have been used in an attempt to avoid belt separation, for example, special latices such as, for example, a vinyl-pyridine latex (VP latex) which is a copolymer of about 70% butadiene, about 15% styrene and about 15% 2-vinylpyridine. Examples of other latices which are present in adhesion promoters are acrylonitrile rubber latices or styrene-butadiene rubber latices. These can be used as such or in combination with one another. Especially suitable adhesion promoters for polyesters are also those which are applied in multi-stage processes, for instance a blocked isocyanate being applied in combination with polyepoxide and the material then being treated using customary resorcinol-formaldehyde resins (RFL dip). It is also known to use combinations of RFL dips with other adhesion-promoting substances such as, for example, a reaction product of triallyl cyanurate, resorcinol and formaldehyde or p-chlorophenol, resorcinol and formaldehyde.

[0013] Not only is it necessary that adhesion between rubber and metal, e.g., steel or polymeric cord be high, but it is also necessary that a decrease in adhesion be as small as possible while tires are in use. In actuality, tires containing a steel cord-embedding rubber with good adhesion occasionally lose the initial adhesion to a great extent after use. The following are the possible reasons why adhesion between steel cord and rubber decreases while tires are in use,

[0014] (1) Tires are subject to many minute cuts when they run over gravel or sharp objects. The cuts reaching the inside of the tread permit air and moisture to infiltrate into the tire, promoting the aging and fatigue of the embedding rubber and also rusting the steelcord. All this leads to a decrease in adhesion.

[0015] (2) The adhesion improver incorporated into the steel cord-embedding rubber diffuses and migrates into the tread rubber during vulcanization or tire use. This leads to a decrease in adhesion.

[0016] (3) The softener and other additives incorporated into the tread migrate into the steel cord-embedding rubber. This also leads to a decrease in adhesion.

[0017] One aspect of the composition and articles described herein is to provide a radial tire for heavy load vehicles characterized by good adhesion between steel or polymeric cord and steel cord-embedding rubber, said adhesions lasting for a long time with only a small loss of adhesion while tires are in use.

[0018] Another aspect of the compositions and articles described herein is to provide a radial tire for vehicles and other cord-embedded rubber articles which are superior in cord adhesion to rubber.

[0019] Despite the various proposals made to improve the adherence of cord to rubber in vulcanizable rubber compositions, there is a continuing need for commercially available cost effective additives that improve the adhesion of rubber to fibrous or metal cords in vulcanizable rubber compositions.

[0020] The ester adhesion promoters of the present invention far surpass any extant adhesion promoters known in the art for adhesion of metal and/or polymeric cord to vulcanizable rubber.

SUMMARY OF THE INVENTION

[0021] In brief, it has been found that long chain ester plasticizers formed from mono, di-, and/or tri-carboxylic acids containing one, two, or three C6-C24 long chain radicals or fatty acid residues, reacted with an alcohol containing a C3-C24 alkyl group, when combined with an adhesive resin, such as a melamine-containing resin or a phenol-, e.g., resorcinol-containing resin, e.g., a Novolak resin, in a natural or synthetic vulcanizable rubber, unexpectedly increases the adhesion between the rubber and a metal or polymeric substrate, such as metal or polymeric surface, particularly cords used in reinforcing rubber in tires, hoses, conveyor belts, motor mounts, automotive drive train belts, including transmission belts, and the like. Examples of suitable substrates include steel, brass-coated steel, brass, polyester, Aramid, textiles, copper, glass, and the like. Application of the adhesive promoters of the invention is particularly contemplated with steel cord, brass-coated steel cord, brass cord, polyester fiber cord, Aramid fiber cord, glass cord, fabric and flat metal surfaces, and the like. While these resins have been used before to adhere metal tire cord to a vulcanizable rubber, and theoretically bond the rubber to the resin, surprisingly good adhesion has been found by adding one or more long chain mono-, di-, and/or tri-esters, particularly dimerate esters reacted from C18 fatty acids, and C3-C24 alcohols, preferably, C3-C18 alcohols, more preferably, C6-C18 alcohols. Preferably, the esters are formed by reacting a C3-C18 alcohol with a mixture of mono-, di-, and tri-fatty acids, e.g., primarily C18 carboxylic acids, and their dimers and trimers, to provide unexpected, tenacious bonding between polymeric or metal cord and rubber. It is theorized that the long chain esters of the invention strongly adhere both to the rubber and to the resin, with the resin providing sufficient ionic bonding to the reinforcing cords.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The long chain ester adhesion promoter additives useful to promote adhesion of rubber to metal and polymeric substrates, particularly metal and polymeric cord, are added to natural or synthetic rubber together with a vulcanizing agent, and an adhesive resin that preferably is a condensation product of a formaldehyde or methylene donor, and a formaldehyde or methylene acceptor, particularly a melamine-formaldehyde or a phenol-formaldehyde, e.g., resorcinol-formaldehyde condensation product. The adhesive resin may be added to the rubber composition as the condensation product or as the reactants to produce the resin condensation product, in-situ, during vulcanization of the rubber. Surprisingly, the long chain ester additives disclosed herein significantly increase the adhesion of the rubber composition to metal and polymeric substrates, particularly metal and polymeric cord.

[0023] The long chain esters may be monoesters, diesters, triesters, or mixtures thereof, that may include saturated or unsaturated hydrocarbon chains, straight chain or branched having none, one, two or three double bonds in the hydrocarbon chains.

[0024] The monoesters have a formula I, as follows:

[0025] wherein R1 is a C3-C24 alkyl, preferably C3-C18 alkyl, more preferably C6-C18 alkyl, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds. R2 is a C3-C24, preferably C6-C24, more preferably C8-C18 saturated, fatty acid residue, or an unsaturated fatty acid residue having 1 to 6, preferably 1 to 3 carbon-to-carbon double bonds.

[0026] The diesters have a formula II or III, as follows:

[0027] wherein n=3-24, preferably 6-18, and more preferably 3-10, and R3 and R4, same or different, are C3-C24 alkyl, preferably C3-C18 alkyl, more preferably C6-C18 alkyl radicals, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds.

[0028] wherein R5 and R7, same or different, are C3-C24, preferably C6-C24 hydrocarbon chains, more preferably C8-C18, straight chain or branched, either saturated or containing 1 to 6, preferably 1 to 3, carbon-to-carbon double bonds;

[0029] R6 and R8, same or different, are C3-C24 alkyl, preferably C3-C18 alkyl, more preferably C6-C18 alkyl, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and

[0030] R10 and R11, same or different, are a C3-C24, preferably C3-C18 saturated hydrocarbon chain, straight chain or branched; or an unsaturated C3-C24, preferably C3-C18, hydrocarbon chain, straight chain or branched, containing 1 to 6, preferably 1 to 3, carbon-to-carbon double bonds.

[0031] The triesters have a formula IV, as follows:

[0032] wherein R12, R14 and R18, same or different, are a C3-C24, preferably C6-C24, more preferably C8-C18, hydrocarbon chain, straight chain or branched, either saturated or containing 1 to 6, preferably 1 to 3, carbon-to-carbon double bonds;

[0033] R13, R15 and R19, same or different, are C3-C24 alkyl, preferably C3-C18 hydrocarbon chains, more preferably C6-C18 alkyl, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds; and

[0034] R16, R17 and R20, same or different, are C3-C24, preferably C3-C18 saturated hydrocarbon chains, more preferably C6-C18, straight chain or branched; or unsaturated C3-C24, preferably C3-C18, hydrocarbon chains, more preferably C6-C18, straight chain or branched, containing 1 to 6, preferably 1 to 3, carbon-to-carbon double bonds.

[0035] Examples of particularly useful diesters of formula II include a saturated diester formed by the reaction of sebacic acid and 2-ethylhexyl alcohol:

[0036] Other useful diesters falling within formula II include the saturated diester formed by the reaction of sebacic acid with tridecyl alcohol:

[0037] and the unsaturated diester formed by reaction of sebacic alcohol with oleyl alcohol:

[0038] Throughout the specification, the adhesion promoters are used in an amount of about 0.1% to about 15% by weight, usually about 1 wt % to about 10 wt %, and most typically from about 2 wt % to about 8 wt %, based on the weight of natural and synthetic rubber in the composition.

[0039] Useful cyclic diesters falling within Formula III include dimerate ester structures fonned by the reaction of a C36 dimer acid derived from tall oil fatty acids and C3-C24, preferably C3-C18, more preferably C6-C18 alcohol, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds. Examples of such cyclic esters include the following structures, wherein the dimer acid corresponding to structure A is formed by self reaction of linoleic acid, the dimer acid corresponding to structure B is formed by reacting linoleic acid with oleic acid, and the dimer acid corresponding to structure C is formed by reacting linoleic acid with linolenic acid:

[0040] wherein each R, same or different, in formulas (A), (B), and (C) is a C3-C24 radical, preferably C3-C18, more preferably C6-C18, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds. RX-13804 is another example of an unsaturated diester (dimerate ester) formed by the reaction of a predominantly C36 dimer acid reacted with 2-ethylhexyl alcohol; and RX-13824 is another unsaturated diester (dimerate ester) formed by the reaction of a predominantly C36 dimer acid with tridecyl alcohol.

[0041] A representative example of the triester (trimerate ester) of formula IV is the following structure (D);

[0042] wherein each R1, R2, and R3, same or different, is a C3-C24 radical, preferably C3-C18, more preferably C6-C18, straight chain, or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds.

[0043] A particularly useful blend of long chain esters is a blend of mono, dimerate, and trimerate esters, CAS#: 61788-89-4, which is a blend including, primarily, the above C36 and C54 dimerate and trimerate esters (A), (B), (C) and (D), shown in the above structures, that is predominantly (more than 50% by weight) the C36 dimerate esters (A), (B) and (C).

[0044] The fatty acid residues or hydrocarbon chains R2, R5, R7, R12, R14 and R18 of the esters of formulas I, II, III, and IV can be any C3-C24, preferably, C6-C24, more preferably C8-C18, hydrocarbon chain, either saturated or containing 1 to 6, preferably 1 to 3, carbon-to-carbon double bonds, derived from animal or vegetable fatty acids such as butter; lard; tallow; grease; herring; menhaden; pilchard; sardine; babassu; castor; coconut; corn; cottonseed; jojoba; linseed; oiticica; olive; palm; palm kernel; peanut; rapeseed; safflower; soya; sunflower; tall; and/or tung. Examples are the hydrocarbon chain residues from the following fatty acids, where the number in parentheses indicates the number of carbon atoms, and the number of double bonds, e.g., (C24-6) indicates a hydrocarbon chain having 24 carbon atoms and 6 double bonds: Hexanoic (C6-0); Octanoic (C8-0); Decanoic (C10-0); Dodecanoic (C12-0); 9-Dodecenoic (CIS) (C12-1); Tetradecanoic (C14-0); 9-tetradecenoic (CIS) (C14-1); Hexadecanoic (CIS) (C16-0); 9-Hexadecenoic (CIS) (C16-1); Octadecanoic (C18-0); 9-Octadecenoic (CIS) (C18-1); 9-Octadecenoic, 12-Hydroxy-(CIS) (C18-2); 9, 12-Octadecadienoic (CIS, CIS) (C18-2); 9, 12, 15 Octadecatrienoic (CIS, CIS, CIS) (C18-3); 9, 11, 13 Octadecatrienoic (CIS, TRANS, TRANS) (C18-3); 9, 11, 13 Octadecatrienoic, 4-Oxo (CIS, TRANS, TRANS) (C18-3); Octadecatetrenoic (C18-4); Eicosanoic (C20); 11-Eicosenoic (CIS) (C20-1); Eicosadienoic (C20-2); Eicosatrienoic (C20-3); 5, 8, 11, 14 Eicosatetraenoic (C20-4); Eicosapentaenoic (C20-5); Docosanoic (C22); 13 Docosenoic (CIS) (C22-1); Docosatetraenoic (C22-4); 4, 8, 12, 15, 19 Docosapentaenoic (C22-5); Docosahexaenoic (C22-6); Tetracosenoic (C24-1); and 4, 8, 12, 15, 18, 21 Tetracosahexaenoic (C24-6).

[0045] Commercially available blends of useful polybasic acids that can be reacted with C3-C24, preferably C3-C18, more preferably C6-C18 alcohols, straight chain or branched, saturated, or unsaturated containing 1 to 3 carbon-to-carbon double bonds to produce the dimerate and trimerate esters, as blends, include the following: EMPOLฎ 1010 Dimer Acid; EMPOLฎ 1014 Dimer Acid; EMPOLฎ 1016 Dimer Acid; EMPOLฎ 1018 Dimer Acid; EMPOLฎ 1022 Dimer Acid; EMPOLฎ 1024 Dimer Acid; EMPOLฎ 1040 Trimer Acid; EMPOLฎ 1041 Trimer Acid; EMPOLฎ 1052 Polybasic Acid; and similar PRIPOL™ products from Uniqema as well as UNIDYMEฎ products from Arizona Chemical.

[0046] Particularly useful long chain ester additives are made by reacting any of the long chain mono, dimer and/or trimer acids with one or more straight chain or branched C3-C24, preferably C3-C18, more preferably C6-C18 alcohols to produce the esters of formulas I, II, III and IV. The above dimer, trimer, and polybasic acids are produced by dimerizing, trimerizing, and polymerizing (oligomerizing) long chain carboxylic acids from the above-mentioned fatty acids. The fatty acids are mixtures, for example, the dimer acid produced from a C18 carboxylic acid (a mixture of stearic, oleic, linoleic, and linolenic) will result in a blend of numerous dimerate and trimerate esters, and cyclic dimerate and trimerate esters, as in Formulas III and IV, some saturated and some containing hydrocarbon chains having 1 to 6, generally 1 to 3, carbon-to-carbon double bonds. Any one, or any blend, of the esters of Formulas I, II, III and/or IV will function to increase the adhesion of natural or synthetic rubber to metal or polymeric cord, and to metal or polymeric substrates, such as polymeric woven or non-woven fabrics and metal flat stock materials.

[0047] The initial work with the dimerate ester adhesion promoters started with testing the esters in industrial rubber belts, containing polyester cords, for automotive power train systems. An important part of the construction of automotive belts is the bonding of the rubber to polyester cord. Polyester cord is used to provide strength and longevity to the belts. The polymer of choice for automotive belts is ethylene/propylene/diene polymer (EPDM). This polymer is excellent for the end use, but one of its drawbacks is poor adhesion to many substrates, such as polyester cord.

[0048] In the present application the term polymeric “cord” or “cords” is intended to include reinforcing elements used in rubber products including fibers, continuous filaments, staple, tow, yarns, fabric and the like, particularly cords for use in building the carcasses of tires such as truck tires.

[0049] The polymeric reinforcing element or cord comprises a plurality of substantially continuous fibers or monofilaments, including glass compositions, polyesters, polyamides and a number of other materials, useful in making the fibers for the reinforcing element or cords for polymeric rubber compositions and products are well known in the art. One of the preferred glasses to use is a glass known as E glass and described in “Mechanics of Pneumatic Tires,” Clark, National Bureau of Standards Monograph 122, U.S. Dept. of Commerce, issued November 1971, pages 241-243, 290 and 291, incorporated herein by reference. The number of filaments or fibers employed in the fiber reinforcing element or cord can vary considerably depending on the ultimate use or service requirements. Likewise, the number of strands of fibers used to make a fiber reinforcing element or cord can vary widely. In general, the number of filaments in the fiber reinforcing element or cord for a passenger car tire can vary from about 500 to 3,000 and the number of strands in the reinforcing element can vary from 1 to 10. Preferably the number of strands is from 1 to 7 and the total number of filaments about 2,000. A representative industry glass tire cord known as G-75 (or G-75, 5/0) has 5 strands each with 408 glass filaments. Another representative cord known as G-15 has a single strand containing 2,040 glass filaments.

[0050] Rubber companies go to great lengths to insure the proper adhesion between the EPDM and the polyester cord. At present, they use a treated cord that has a resorcinol-formaldehyde resin coating, and the resin-coated cords are then dipped in an adhesive. The resin-treated, adhesive coated cord is then bonded to the EPDM during the curing process. This is a time-consuming and expensive method to achieve rubber-to-polyester cord adhesion.

[0051] The adhesive promoters of the invention can be used in numerous applications, including bonding the steel braid to the natural and/or synthetic rubber material of hoses and the metal housing of motor mounts.

[0052] The term “vulcanization” used herein means the introduction of three dimensional cross-linked structures between rubber molecules. Thus, thiuram vulcanization, peroxide vulcanization, quinoid vulcanization, resin vulcanization, metal salt vulcanization, metal oxide vulcanization, polyamine vulcanization, radiation vulcanization, hexamethylenetetramine vulcanization, urethane cross-linker vulcanization and the like are included in addition to sulfur vulcanization which is usual and most important.

[0053] Rubbers useful in the compositions described herein can be natural rubbers (NR) and/or synthetic rubbers.

[0054] Synthetic rubbers include homopolymers of conjugated diene compounds, such as isoprene, butadiene, chloroprene and the like, for example, polyisoprene rubber (IR), polybutadiene rubber (BR), polychloroprene rubber and the like; copolymers of the above described conjugated diene compounds with vinyl compounds, such as styrene, acrylonitrile, vinyl pyridine, acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates and the like, for example, styrene-butadiene copolymeric rubber (SBR), vinylpyridine-butadiene-styrene copolymeric rubber, acrylonitrile-butadiene copolymeric rubber, acrylic acid-butadiene copolymeric rubber, methacrylic acid-butadiene copolymeric rubber, methyl acrylate-butadiene copolymeric rubber, methyl methacrylate-butadiene copolymeric rubber, acrylonitrile-butadiene-styrene terpolymer, and the like; copolymers of olefins, such as ethylene, propylene, isobutylene and the like with dienes, for example isobutylene-isoprene copolymeric rubber (IIR); copolymers of olefins with non-conjugated dienes (EPDM), for example, ethylene-propylene-cyclopentadiene terpolymer, ethylene-propylene-5-ethylidene-2-norbornene terpolymer and ethylene-propylene-1,4-hexadiene terpolymer; polyalkenamer obtained by ring opening polymerization of cycloolefins, for example, polypentenamer; rubbers obtained by ring opening polymerization of oxirane ring, for example, polyepichlorohydrin rubber and polypropylene oxide rubber which can be vulcanized with sulfur, and the like. Furthermore, halides of the above-described various rubbers, for example, chlorinated isobutylene-isoprene copolymeric rubber (CI-IIR), brominated isobutylene-isoprene copolymeric rubber (Br-IIR), fluorinated polyethylene, and the like are included.

[0055] Particularly, the compositions described herein are characterized in that the surfaces of the vulcanized rubbers of natural rubber (NR), and synthetic rubbers, e.g. styrene-butadiene copolymeric rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), isobutylene-isoprene, copolymeric rubber, halides of these rubbers (CI-IIR, Br-IIR) and copolymers (EPDM) of olefins with non-conjugated dienes, which are poor in the adhering ability, are improved to provide them a high adhering ability. Of course, the present invention can be applied to the other rubbers. All these rubbers may be kneaded with compounding agents conventionally used for compounding with rubber, for example, fillers, such as carbon black, silica, calcium carbonate, lignin and the like, softening agents, such as mineral oils, vegetable oils, prior to the vulcanization and then vulcanized.

[0056] The vulcanized rubbers, the surface of which has been improved with the ester adhesion promoters described herein can be easily adhered to the other materials, together with an adhesive resin, particularly metals and polymers, particularly in cord form.

[0057] The rubber compositions of the present invention contain an adhesive resin, particularly a condensation product of a methylene donor and a methylene acceptor, either pre-condensed, or condensed in-situ while in contact with the rubber. The term “methylene donor” is intended to mean a compound capable of reacting with a methylene acceptor (such as resorcinol or its equivalent containing a reactive hydroxyl group) and generate the resin outside of the rubber composition, or in-situ. Preferably, the components of the condensation product include a methylene acceptor and a methylene donor. The most commonly employed methylene acceptor is a phenol, such as resorcinol, while the most commonly employed methylene donor is a melamine, such as N-(substituted oxymethyl)melamine. The effect achieved is resin formation in-situ during vulcanization of the rubber, creating a bond between the metal or polymeric cords and the rubber, irrespective of whether the cords have been pretreated with an additional adhesive, such as a styrene-butadiene latex, polyepoxides with a blocked isocyanate, and the like. The long chain ester additive/resin combinations described herein are particularly useful with steel cord, where adhesive pretreatment has been largely ineffective. Examples of other methylene donors which are suitable for use in the rubber compositions disclosed herein include melamine, hexamethylenetetramine, hexaethoxymethylmelamine, hexamethoxymethylmelamine, lauryloxymethyl-pyridinium chloride, ethoxy-methylpyridinium chloride, trioxan hexamethoxy-methylmelamine, the hydroxy groups of which may be esterified or partly esterified, and polymers of formaldehyde, such as paraformaldehyde. In addition, the methylene donors may be N-substituted oxymethylmelamines, of the general formula:

[0058] wherein X is an alkyl having from 1 to 8 carbon atoms R3, R4, R5, R6 and R7 are individually selected from the group consisting of hydrogen, an alkyl having from 1 to 8 carbon atoms and the group —CH2OX. Specific methylene donors include hexakis(methoxymethyl)melamine; N,N′,N″trimethyl/N,N′,N″-trimethylol-melamine; hexamethylolmelamine; N,N′,N″-dimethylolmelamine; N-methylol-melamine; NN′-dimethylolmelamine; N,N′,N″-tris(methoxymethyl)melamine; and N,N′,N″-tributyl-N,N′,N″-trimethylol-melamine. The N-methylol derivatives of melamine are prepared by known methods.

[0059] The amount of methylene donor and methylene acceptor, pre-condensed or condensed in-situ, that are present in the rubber composition may vary. Typically, the amount of pre-condensed methylene donor and methylene acceptor is present will range from about 0.1% to about 15.0%; or each can be added separately in an amount of about 0.1% to about 10.0%, based on the weight of natural and/or synthetic rubber in the composition. Preferably, the amount of each of a methylene donor and methylene acceptor added for in-situ condensation ranges from about 2.0% to about 5.0%, based on the weight of natural and/or synthetic rubber in the composition.

[0060] The weight ratio of methylene donor to the methylene acceptor may vary. Generally speaking, the weight ratio will range from about 1:10 to about 10:1. Preferably, the weight ratio ranges from about 1:3 to 3:1.

[0061] Resorcinol-free vulcanizable rubber compositions also are useful in the rubber compositions described herein. For example, U.S. Pat. No. 5,298,539 discloses vulcanizable rubber compositions containing uncured rubber, a vulcanizing agent and at least one additive selected from the group consisting of derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril monomer and oligomers of these monomers. These derivatives are substituted on average at two or more positions on the monomer or each unit of the oligomer with vinyl terminated radicals and the composition is free of resorcinol.

[0062] Other resorcinol-free adhesive resins and adhesive compounds that are useful in the vulcanizable rubber compositions, together with the long chain ester adhesion promoters described herein, include those described in U.S. Pat. Nos. 5,891,938, and 5,298,539, both hereby incorporated herein by reference. The '938 patent discloses vulcanizable rubber compositions containing an uncured rubber and a self-condensing alkylated triazine resin having high imino and/or methylol functionality. U.S. Pat. No. 5,298,539 discloses rubber additives which are substituted derivatives based on cyclic nitrogen compounds such as melamine, acetoguanamine, cyclohexylguanamine, benzoguanamine, and similar alkyl, aryl or aralkyl substituted melamines, glycoluril and oligomers of these compounds. In particular, the adhesive resins and adhesive compounds which are useful as the adhesive resins in the rubber compositions described herein include the following: adhesive resins selected from the group consisting of derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril monomers and oligomers of these monomers, which have been substituted on average at two or more positions on the monomer or on each unit of the oligomer with vinyl terminated radicals, the vulcanizable rubber composition being free of resorcinol; and, these derivatives which have been further substituted on average at one or more positions with a radical which comprises carbamylmethyl or amidomethyl. Further, the adhesive resin can be any of the compounds of the following formulas:

[0063] wherein, in each monomer and in each polymerized unit of the oligomers, Y is selected from methyl, phenyl and cyclohexyl, and, on average,

[0064] at least two R are —CH2—R1,

[0065] and any remaining R are H, and

[0066] at least 2 R1 are radicals selected from

[0067] wherein R2 is hydrogen or C1-C18 alkyl, and Z is a radical selected from

[0068] any remaining R1 radicals are selected from

[0069] wherein R3 is hydrogen or R4, and

[0070] R4 is a C1-C18 alkyl, alicyclic, hydroxyalkyl, alkoxyalkyl or aromatic radical, and

[0071] in the oligomers,

[0072] P is 2to about 10, and

[0073] L is methylene or the radical

—CH2—O—CH2—

[0074] These adhesive compounds are particularly useful, wherein on average at least one R1 in each monomer or in each oligomerized unit is, —NH—C(O)—OR4, particularly the compounds of the following formulas:

[0075] Particularly useful adhesive resins include the above formulas wherein on average, at least one R radical in each monomer or in each oligomerized unit is

—CH2—NH —C(O)—OR4

[0076] wherein R4 is a C1-C18 alkyl, alicyclic, hydroxyalkyl, alkoxyalkyl or aromatic radical, and wherein, on average, at least two R radicals are selected from

CH2═C(CH3)—C(O)O—C3H6—O—CH2—

[0077] and

CH2═CH2—C(O)O—C2H4—O—CH2—

[0078] and at least one R radical is selected from

—CH2—NH—C(O)—O—CH3, and

—CH2—NH—C(O)—O—C3H7

[0079] These adhesive resins and compounds can include additional additives, particularly those selected from hydroxymethylated and alkoxymethylated (alkoxy having 1-5 carbon atoms) derivatives of melamine, acetoguanamine, benzoguanamine, cyclohexylguanamine and glycoluril and their oligomers.

[0080] Additional adhesive resins useful in the rubber compositions described herein include self-condensing alkylated triazine resins selected from the group consisting of (i), (ii), and (iii):

[0081] (i) a self-condensing alkylated traizine resin having at least one of imino or methylol functionality and represented by the formula (I)

[0082] (ii) an oligomer of (i), or

[0083] (iii) a mixture of (i) and (ii), wherein

[0084] Z is —N(R)(CH2OR1), aryl having 6 to 10 carbon atoms, alkyl having 1 to 20 carbon atoms or an acetyl group,

[0085] each R is independently hydrogen or —CH2OR1, and

[0086] each R1 is independently hydrogen or an alkyl group having 1 to 12 carbon atoms,

[0087] provided that at least one R is hydrogen or —CH2OH and at least one R1 is selected from the alkyl group; and

[0088] wherein the vulcanizable rubber composition is substantially free of methylene acceptor coreactants.

[0089] These adhesive resins are particularly useful wherein at least one R group is hydrogen and/or wherein at least one R1 group is a lower alkyl group having 1 to 6 carbon atoms, particularly where the adhesive resin is a derivative of melamine, benzoguanamine, cyclohexylguanamine, or acetoguanamine, or an oligomer thereof.

[0090] One particularly useful alkylated triazine adhesive resin of the above formula is wherein Z is —N(R)(CH2OR1).

[0091] The rubber compositions containing an adhesive such as a cobalt salt of an organic acid, hydroxybenzoic acid, and resorcinol, also function to increase the adhesion between rubber and metal or polymeric cord, together with the long chain esters described herein. These improvements, however, are not completely successful.

[0092] Another manner of eliminating resorcinol in an adhesive resin for rubber compositions, also useful herein, is N-(substituted oxymethyl)melamine and at least one of α- or β-naphthol. This adhesive resin employs the monohydric phenols, α- or β-naphthol, as methylene acceptors in the resin forming reaction during vulcanization in the absence of resorcinol.

[0093] Other adhesive resins useful in the rubber compositions described herein include special latices such as, for example, a vinyl-pyridine latex (VP latex) which is a copolymer of about 70% butadiene, about 15% styrene and about 15% 2-vinylpyridine; acrylonitrile rubber latices; and styrene-butadiene rubber latices. These can be used as such or in combination with one another. Another suitable adhesive resin useful herein, particularly for polyesters, are those which are applied in multi-stage processes, for instance a blocked isocyanate being applied in combination with polyepoxide and the material then being treated using customary resorcinol-formaldehyde resins (RFL dip). Additional useful adhesive resins include combinations of RFL dips with other adhesion-promoting substances such as, for example, a reaction product of triallyl cyanurate, resorcinol and formaldehyde or p-chlorophenol, resorcinol and formaldehyde.

[0094] Other suitable adhesive resins for use in the rubber and adhesion promoters described herein include polyurethane resins, epoxy resins, phenol aldehyde resins, polyhydric phenol aldehyde resins, phenol furfural resins, xylene aldehyde resins, urea formaldehyde resins, melamine formaldehyde resins, alkyd resins, polyester resins, and the like.

[0095] In order to cure a rubber composition a vulcanizing agent such as a sulfur or peroxide vulcanizing agent is dispersed throughout the composition. The vulcanizing agent may be used in an amount ranging from 0.5 to 6.0%, based on the weight of the natural and/or synthetic rubbers in the composition, with a range of from 1.0 to 4.0% being preferred. Representative examples of sulfur vulcanizing agents include elemental sulfur (S8), an amine disulfide, polymeric polysulfide and sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur.

[0096] Other suitable vulcanizing agents include thiuram, quinoid, metal salt, metal oxide, polyamine, vulcanization, radiation, hexamethylenetetramine, urethane cross-linker, and the like.

[0097] The commonly employed carbon blacks used in conventional rubber compounding applications can be used as the carbon black in this invention. Representative examples of such carbon blacks include N110, N121, N220, N231, N234, N242, N293, N299, S315, N326, N330, M332, N339, N343, N347, N351, N358 and N375.

[0098] The rubber compositions described herein are compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable or peroxide-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, sulfur donors, curing aids, such as activators and retarders and processing additives, such as oils, resins,including tackifying resins and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, retarders and peptizing agents. As known to those skilled in the art, the additives mentioned above are selected and commonly used in conventional amounts for tire tread applications. Typical amount of adhesive resins, comprise about 0.2 to about 10%, based on the weight of natural and/or synthetic rubbers, usually about 1 to 5%.

[0099] Typical amounts of zinc oxide comprise about 2 to about 5%. Typical amounts of waxes comprise about 1 to about 5% based on the weight of natural and/or synthetic rubbers. Often microcrystalline waxes are used. Typical amounts of retarders range from 0.05 to 2%. Typical amounts of peptizers comprise about 0.1 to 1%. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide. All additive percentages are based on the weight of natural and/or synthetic rubbers.

[0100] Accelerators may be used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. The accelerator(s) may be used in total amounts ranging from about 0.5 to about 4%, preferably about 0.8 to about 1.5%, based on the weight of natural and/or synthetic rubbers. Suitable types of accelerators that may be used are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. If included in the rubber composition, the primary accelerator preferably is a sulfenamide. If a second accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or thiuram compound.

[0101] When the long chain ester adhesion promoters described herein are used as a wire coat or bead coat, e.g., for use in a tire, the long chain ester is not an organo-cobalt compound, and may be used in whole or as a partial replacement for an organo-cobalt compound which serves as a wire adhesion promoter. When used in part, any of the organo-cobalt compounds known in the art to promote the adhesion of rubber to metal also may be included. Thus, suitable organo-cobalt compounds which may be employed, in addition to the non-cobalt adhesion promoter esters described herein, include cobalt salts of fatty acids such as stearic, palmitic, oleic, linoleic and the like; cobalt salts of aliphatic or alicyclic carboxylic acids having from 6 to 30 carbon atoms; cobalt chloride, cobalt naphthenate; cobalt carboxylate and an organo-cobalt-boron complex commercially available under the designation Comend A from Shepherd Chemical Company, Cincinnati, Ohio. Comend A is believed to have the structure:

[0102] wherein each R, same or different, is an alkyl group having from 9 to 12 carbon atoms, and B is a hydrocarbon chain, C4-C24, straight chain or branched, saturated or unsaturated.

[0103] Amounts of organo-cobalt compound which may be employed depend upon the specific nature of the organo-cobalt compound selected, particularly the amount of cobalt metal present in the compound. Since the amount of cobalt metal varies considerably in organo-cobalt compounds which are suitable for use, it is most appropriate and convenient to base the amount of the organo-cobalt compound utilized on the amount of cobalt metal desired in the finished composition. Accordingly, it may in general be stated that if an organo-cobalt compound is included in the rubber composition, the amount of organo-cobalt compound present in the stock composition should be sufficient to provide from about 0.01 percent to about 0.35 percent by weight of cobalt metal based upon total weight of the rubber in the composition, with the preferred amounts being from about 0.03 percent to about 0.2 percent by weight of cobalt metal based on the total weight of rubber in the composition.

[0104] The adhesion promoters described herein are especially effective in compositions in which the rubber is cis-polyisoprene, either natural or synthetic, and in blends containing at least 25% by weight of cis-polyisoprene with other rubbers. Preferably the rubber, if a blend, contains at least 40% and more preferably at least 60% by weight of cis-polyisoprene. Examples of other rubbers which may be blended with cis-polyisoprene include poly-1,3-butadiene, copolymers of 1,3-butadiene with other monomers, for example styrene, acrylonitrile, isobutylene and methyl methacrylate, ethylene/propylene/diene terpolymers, and halogen-containing rubbers such as chlorobutyl, bromobutyl and chloroprene rubbers.

[0105] The amount of sulphur in the composition is typically from 2 to 8 parts, for example from 3 to 6, by weight per 100 parts by weight of rubber, but lesser or larger amounts, for example from 1 to 7 or 8 parts on the same basis, may be employed. A preferred range is from 2.5 to 6 parts per 100 parts by weight of rubber.

[0106] Additional examples of vulcanization accelerators which can be used in the rubber compositions described herein are the thiazole-based accelerators, for example 2-mercaptobenzothiazole, bis(2-benzothiazolyl)disulphide, 2(2′,4′-dinitrophenyl-thio)benzothiazole, benzothiazole-2-sulphenamides for instance N-isopropylbenzothiazole-2-sulphenamide, N-tert-butyl-benzothiazole-2-sulphenamide, N-cyclohexylbenzo-thiazole-2-sulphenamide, and 2(morpholinothio)benzothiazole, and thiocarbamylsulphenamides, for example N,N-dimethyl-N′,N′-dicyclohexylthiocarbamoyl-sulphenamide and N(morpholinothiocarbonylthio)-morpholine. A single accelerator or a mixture of accelerators may be used. In the compositions described herein, these vulcanization accelerators are usually used in amounts of from 0.3 to 2, for example from 0.3 to 1.5, preferably from 0.4 to 1.0 and more preferably from 0.5 to 0.8, parts by weight per 100 parts by weight of rubber.

[0107] The long chain ester adhesion promoters described herein are very effective in promoting bonding between rubber and brass, for example the bonding between rubber and brass-coated steel. The brass typically has a copper content of from 60 to 70% by weight, more especially from 63 to 68% by weight, with the optimum percentage depending on the particular conditions under which the bond is formed. The brass coating on brass-coated steel can have a thickness of, for example, from 0.05 to 1 micrometer, preferably from 0.07 to 0.7 micrometer, for example from 0.15 to 0.4 micrometer.

[0108] Rubber can also be bonded effectively to alloys of cooper and zinc containing small amounts of one or more other metals, for example cobalt, nickel or iron.

[0109] For bonding rubber to zinc, as for example in bonding rubber to zinc-coated steel cords (which are widely used in the manufacture of conveyor belting) cobalt compounds have been used as adhesion promoters. Examples of such compounds are cobalt naphthenate and the cobalt-boron complexes described in GB-A02-0220089.

[0110] Vulcanization of the rubber composition described herein is generally carried out at conventional temperatures ranging from about 100ฐ C. to 200ฐ C. Preferably, the vulcanization is conducted at temperatures ranging from about 110ฐ C. to 180ฐ C. Any of the usual vulcanization processes may be used such as heating in a press or mold, heating with superheated steam or hot air or in a salt bath.

[0111] Upon vulcanization of the rubber composition at a temperature ranging from 100ฐ C. to 200ฐ C., the rubber composition can be used for various purposes. For example, the vulcanized rubber composition may be in the form of a tire, belt, hose, motor mounts, gaskets and air springs. In the case of a tire, it can be used for various tire components. Such tires can be built, shaped, molded and cured by various methods which are known and will be readily apparent to those having skill in such art. When the rubber composition is used in a tire, its use may be in a wire coat, bead coat, tread, apex, sidewall and combination thereof. As can be appreciated, the tire may be a passenger tire, aircraft tire, truck tire, and the like. Preferably, the tire is a passenger tire. The tire may also be a radial or bias, with a radial tire being preferred.

[0112] The invention may be better understood by reference to the following examples in which parts and percentages are by weight unless otherwise indicated.

[0113] In Part I of this project, compounds were mixed into existing EPDM recipes and tested for adhesion. The following varieties were tested:

Variable
1 2 3 4 5
Cyrez Cyrez Control- Cyrez Cyrez
CRA- CRA- Current CRA- CRA-
133M 148M EPDM 133M/ 148M/
Formula RX-13804 RX-13804

[0114] Cyrez CRA-133M-Melamine-formaldehyde resin with 27% calcium silicate

[0115] Cyrez CRA-148M-Melamine-formaldehyde resin with 27% calcium silicate

[0116] RX-13804=Di-2-ethylhexyl dimerate (EMPOL 1016 dimer acid esterified with 2-ethylhexyl alcohol, containing predominantly C36 dimer acids and C54 trimer acids, containing both saturated and unsaturated long chain (C6-C18) radicals with 0, 1, 2, and/or 3 carbon-to-carbon double bonds.

[0117] The melamine-formaldehyde resins are known as adhesion promoters in the tire industry. The need for rubber-to-cord adhesion generally requires the presence of a methylene donor/methylene acceptor resin system, as described above. The typical system consists of hexakismethoxymethylmelamine (HMMM) as the donor and a Novolak resin (such as resorcinol) as the acceptor.

[0118] Results

[0119] The table below shows adhesion results with polyester cord in Examples 1-5.

Adhesion-lbs-force
Compound Variable Room Temperature 257ฐ C.
Example 1: 23.48 2.91
(Cyrez CRA-133M)
Example 2: 21.57 3.58
(Cyrez CRA-148M)
Example 3: 22.21 4.88
(Control)
Example 4: 48.76 10.21
(Cyrez CRA-133M/
RX-13804)
Example 5: 47.70 14.21
(Cyrez CRA-148M/
RX-13804)

[0120] The control (Example 3) was EPDM with the polyester cord pretreated with a melamine formaldehyde resin and an adhesive from Lord Corporation (Cary, N.C.). The polyester cord used in Examples 1, 2, 4, and 5 were treated with melamine formaldehyde resin but not with an adhesive. Examples 1 and 2 contain just the melamine resin and provide basically equal adhesion to the control compound, which is significant since the cords used were not coated with adhesive. Examples 4 and 5 contain a combination of resin and the esters described herein, and show an unexpected increase in adhesion. The adhesive forces for Examples 4 and 5 are increased at least 100% compared to the control and resin only Examples (1-3).

[0121] These results indicate that the resin/ester combination provides a dramatic increase in adhesive force between EPDM and polyester cord compared to the control compound and the compounds containing only resin.

[0122] The formulation and data collected for Examples 1-5 are shown in Table I:

TABLE I
Example:
Recipe JE31-189 1 2 3 4 5
Nordel IP3720 (EPDM) 100.00 ————————————————————
N762 Carbon Black 56.00 ————————————————————
Kadox 930 Zinc Oxide 5.00 ————————————————————
Ricon 150 5.00 ————————————————————
Sartomer ST350 4.00 ————————————————————
Cyrez CRA-133M 7.00 — — 7.00 —
Cyrez CRA-148M 7.00 — 7.00
RX-13804 10.00 10.00
Subtotal 177.00 177.00 170.00 187.00 187.00
Mill Addition
Vulcup 40KE 7.00 ————————————————————
Total 184.00 184.00 170.00 194.00 194.0
Major Variable
CYREZ CYREZ
CYREZ CYREZ CRA-133M/ CRA-148M/
CRA-133M CRA-148M CONTROL RX13804 RX13804
Viscosity and Curing Properties Example 1 Example 2 Example 3 Example 4 Example 5
Mooney Viscosity at 212ฐ F.
Minimum Viscosity 41.3 41.9 41.8 30.3 33.9
T5, minutes 56.8
Mooney Viscosity at 250ฐ F.
Minumum Viscosity 31 32.7 34.9 25.9 28.5
t5, minutes 10.8 11.1 9.7 8.3 8.3
t10, minutes 11.8 12.8 11.3 9.3 9
t35, minutes 13.8 18.3 17 11.8
Oscillating Disc Rheometer at
350ฐ F.
ML 19 9 8.3 6.3 8.8
MH 151.9 159.3 156.6 57.8 62.9
ts2, minutes 0.92 0.92 0.83 0.92 1.2
t′c(90), minutes 7.5 7.2 7.9 5.7 6.3
1.25 * t′c(90), minutes 9.4 9 9.9 7.1 7.8
Cure Rate Index 15.2 16 14.1 21.1 19.7
Original Physical Properties
Stress @ 100% Elongation, MPa 13.1 14.1 15.2 4.7 4.9
psi 1905 2050 2200 680 705
Stress @ 200% Elongation, MPa 9.9 9.5
Stress @ 300% Elongation, MPa
Tensile Ultimate, MPa 19.0 18.1 18.7 12.5 10.9
psi 2760 2625 2705 1815 1580
Elongation @ Break, % 135 120 115 250 235
Hardness Duro A, pts. 83 83 80 78 75
Specific Gravity 1.1043 1.1085 1.1061 1.1075 1.1081

[0123] Adhesion Promoter

[0124] Part II

[0125] Based on Part I results that shows improved adhesion to polyester cord using the resin/ester combination, the resin/ester combination was evaluated in a standard natural rubber compound used for metal cord adhesion.

[0126] The compounds tested in this study were varied in ester content, with resin content kept constant. The following Table II lists the adhesion results for original, air oven aging, and humidity aging, in Examples 6-12, with parts by weight of resin and ester set forth in parentheses.

TABLE II
Recipe Variable
Standard Cyrez CRA-148
Resorcinol M(8)/SM
(3.85)/melamine Cyrez CRA- Cyrez CRA- Cyrez CRA- Cyrez CRA- RX-13804(6)/
formaldehyde Cyrez CRA- 148M(8)/SM 148M(8)/SM 148M(8)/SM 148M(8)/SM Sulfur(8.4)/Vulkacit
(4.23) 148M RX-13804(8) RX-13804(6) RX-13804(4) RX-13804(2) (0.75)
Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12
Adhesion to
Steel Cord
Original
Properties:
Max. Force,
lbs. (avg.)
Average 176.2 156 162.7 162.6 138.6 167.4 162
Coverage, % 100 95 100 100 100 99 100
Air Oven
Aging: 48 hrs @
121ฐ C. (250ฐ F.)
Max. Force,
lbs.(avg.)
Average 105.6 73.5 68.9 70.8 77.6 87.7 123
Coverage, % 99 93 97 97 99 95 95
Force Change, % −40 −53 −58 −57 −44 −48 −24
Adhesion to
Steel Cord
Humidity
Aging: 7 Days
@ 94ฐ C.
(200ฐ F.)
Max. Force,
lbs. (avg.)
Average 152.3 119.7 130.4 160.3 137.7 136.9 152.7
Coverage, % 100 98 100 100 100 100 99
Force Change, −14 −30 −20 −1.4 −0.65 −22 −5.7
Humidity
Aging: 14 Days
@ 94ฐ C.
(200ฐ F.)
Max. Force,
lbs. (avg.)
Average 123.7 94.9 130.2 115.3 116.8 125.3 148.6
Coverage, % 88 75 93 90 90 90 95
Force Change, % −30 −39 −20 −29 −16 −25 −8.3
Humidity
Aging: 21 Days
@ 94ฐ C.
(200ฐ F.)
Max. Force,
lbs.(avg.)
Average 101.4 64.4 82.6 107.9 90.3 108.1 127.3
Coverage, % 87 75 70 77 83 83 93
Force Change, % −43 −59 −49 −34 −35 −35 −27

[0127] The original wire cord adhesion results show the standard formulation to have sightly higher adhesion than formulations containing resin/ester combinations. The formulations containing resin/ester combinations are all very similar except for the resin/ester combination of 8/4. At this time, the reason why this formulation has poorer original adhesion is not known.

[0128] The humidity aging results are interesting in that Examples 9, 11 and 12 have the highest force levels and lowest percent change from the original. Example 12 has a 50% increase in curing agent amount to offset the addition of ester to the compound. This formulation had the highest force recorded and the least change from the original adhesion. This suggests that an increase in the amount of curing agent can, along with the resin/ester combination, improve aged adhesion. All the resin/ester compounds except for Example 8 (resin 8/ester 8) exhibited lower changes in recorded force than the standard compound.

[0129] The formulations for Examples 6-12 are shown in Table III.

TABLE III
Example:
Recipe JE32-250 6 7 8 9 10 11 12
SMR-L 100.00 —————————————————————————
N326 60.00 —————————————————————————
Kadox 930 10.00 —————————————————————————
Cobalt Naphthenate 2.00 —————————————————————————
Stearic Acid 1.20 —————————————————————————
Santoflex 13 1.00 —————————————————————————
PVI 0.20 —————————————————————————
Pennacolite(3.85)/Resimene(4.23) 8.08 — — — — — —
Cyrez CRA 148-M — 8.08 8.00 8.00 8.00 8.00 8.00
SM RX-13804 — — 8.00 6.00 4.00 2.00 6.00
Subtotal 182.48 182.48 190.40 188.40 186.40 184.40 188.40
Mill Addition
Sulfur 5.60 ——————————————— 8.40
Vulkacit DZ 0.50 ——————————————— 0.75
Total 188.58 188.58 196.50 194.50 192.50 190.50 197.55
Major Variable
Cyrez CRA-148
Cyrez CRA- M(8)/
Pennacolite Cyrez CRA- Cyrez CRA- Cyrez CRA- 148M(8)/SM SM RX-13804(6)/
(3.85)/ Cyrez CRA- 148M(8)/SM 148M(8)/SM 148M(8)/SM RX- Sulfur(8.4)/
Resimene (4.23) 148M RX-13804(8) RX-13804(6) RX-13804(4) 13804(2) Vulkacit(0.75)
Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12
Viscosity and
Curing
Properties
Mooney
Viscosity at
168ฐ C. (335ฐ F.)
Min. Viscosity 70.2 67.9 57.9 59.7 62.1 63.7 48.1
t5, minutes 1.4 1.8 1.9 1.8 2.2 2 1.7
t10, minutes 1.8 2 2.2 2.2 2.5 2.3 2
t35, minutes 2.9 2.6 2.8 2.8 3.3 2.9 2.6
Oscillating Disc
Rheometer at
168ฐ C. (335ฐ F.)
ML 16.6 16.9 14.1 14.8 15.7 15.8 16
MH 47.5 26.6 23.6 24.6 22.2 38.8 73.6
ts2, minutes 1.4 1.8 1.8 1.8 1.8 1.8 1.6
t′c(90), minutes 5.3 4.5 4.7 4.7 4.4 4.9 5.3
1.25 * t′c(90), 6.7 5.6 5.8 5.8 5.5 6.2 6.7
minutes
Cure Rate Index 25.6 36.4 35.2 35.2 37.5 31.6 26.7
Original Physical
Properties
Stress @ 100% 7.0 5.9 3.9 5.1 5.0 5.8 7.6
Elongation, Mpa
psi 1010 855 565 740 730 845 1105
Stress @ 200% 14.8 12.4 8.8 10.9 10.8 12.1 14.8
Elongation, Mpa
Stress @ 300% — 19.2 14.8 17.1 16.9 18.6 —
Elongation, Mpa
Tensile Ultimate, 20.4 20.9 21.5 20.6 21.2 20.7 20.1
Mpa
psi 2960 3025 3116 2990 3080 3010 2915
Elongation @ 275 330 415 370 380 335 285
Break, %
Hardness Duro 79 78 72 75 76 77 79
A, pts.
Specific Gravity AVERAGE 1.204 AVERAGE AVERAGE AVERAGE — 1.203

[0130] The use of the resin/ester combination in a sulfur-cured natural rubber formulation can improve wire cord adhesion after heat aging and humidity aging as compared to a standard natural rubber formulation.

[0131] In order to verify that the increased cure system of Example 12 was not solely responsible for the increased adhesion performance of Example 12, an additional formulation, Example 13, was tested. The only difference between Examples 6 and 13 is that Example 13 has a 50% increase in the amount of cure system additives (Sulfur and Vulkacit). Table IV provides comparative data which demonstrates that increasing the cure system of the “control compound” (i.e., the prior art formulation of Example 6) by 50% does not lead to an increased adhesive effect. Accordingly, these data confirm that the increase in adhesion observed in Example 12 cannot solely be attributed to the increased amount of cure system additives, i.e., the increased adhesion is due to the adhesion promoter.

TABLE IV
Recipe Variable
Pennacolite Cyrez CRA 148-
Pennacolite(3.85)/ (3.85)/ M(8)/
Resimene(4.23)/ Resimene SM RX-13804(6)/
Sulfur(8.4)/ (4.23) Sulfur(8.4)/
Vulkacit(0.75) “Control” Vulkacit(0.75)
Recipe NR-4M Example 13 Example 6 Example 12
SMR-L 100 ——————————
N 326 60 ——————————
Kadox 930 10 ——————————
Cobalt 2 ——————————
Napthenate
Stearic Acid 1.20 ——————————
Santoflex 13 1.00 ——————————
PVI 0.20 ——————————
Pennacolite 8.08 8.08 —
(3.85)/
Resimene(4.23)
Cyrez CRA — — 8.00
148-M
SM RX-13804 — — 6.00
Subtotal 182.48 182.48 188.40
Mill Addition
Sulfur 8.40 5.60 8.40
Vulkacit 0.75 0.50 0.75
Total 191.63 188.58 197.55
Major Variable
Cyrez CRA 148-
Pennacolite(3.85)/ Pennacolite M(8)/
Resimene(4.23)/ (3.85)/ SM RX-13804(6)/
Sulfur(8.4)/ Resimene(4.23) Sulfur(8.4)/
Processing Vulkacit(0.75) “Control” Vulkacit(0.75)
Properties Example 13 Example 6 Example 12
Viscosity and
Curing
Properties
Mooney
Viscosity at
168ฐ C. (335ฐ F.)
Minimum 69.3 77.2 66.4
Viscosity
t5, minutes 1.3 1.2 1.3
t10, minutes 1.6 1.3 1.6
t35, minutes 2.3 1.9 2.2
Oscillating
Disc
Rheometer at
168ฐ C. (335ฐ F.)
ML 17 20 17.3
MH 100.5 101.1 88.4
ts2, minutes 1.4 1.5 1.7
t′c(90), minutes 6.7 9.6 5.9
1.25 * t′c(90), 8.3 12 7.4
mins.
Cure Rate Index 19.1 12.4 23.5
Vulcanizate
Properties
Original Physical
Properties
Stress @ 100% 8.1 6.5 5.9
Elongation, MPa
psi 1170 945 850
Stress @ 200% 15.7 13.7 11.5
Elongation, MPa
Stress @ 300% — — 16.9
Elongation, MPa
Tensile Ultimate, 18.4 20.1 18.7
MPa
psi 2665 2920 2710
Elongation @ 240 300 330
Break, %
Hardness Duro 82 80 80
A, pts.
Specific Gravity 1.201 1.199 1.204
Adhesion to Steel
Cord
Original
Properties:
Maximum Force,
lbs. (avg).
Set 1 90.1 104.4 80.3
Set 2 78.4 99.3 80.6
Set 3 82.4 101.1 103.3
Average 83.6 101.6 88.1
Coverage, % 90 90 90

[0132] Adhesion Promoter

[0133] Part III

[0134] Next, natural rubber-to-metal bonding was evaluated to determine the effect of added ester(s), as described herein. This presents a large potential for automotive parts, such as motor mounts, brakes, hoses, and the like.

[0135] The first study focused on long chain esters in natural rubber and their effect on adhesion to metal (see Table V—Examples 14-17). The data indicate that the long chain ester adhesion promoters described herein improve adhesion to brass in a sulfur-cured rubber formulation. The use of the resin/ester combination did not improve adhesion versus compounds with ester only.

TABLE V
Example
Recipe NR-2 14 15 16 17
SMR-L 100.00 ——————————
Kadox 930 5.00 ——————————
Stearic Acid 2.00 ——————————
N 330 35.00 ——————————
Cyrez CRA-148M 6.95 — 6.95 —
RX-13804 6.95 5.00 6.95 —
Subtotal 155.90 147.00 155.90 142.00
Mill Addition
Sulfur 2.25 — — —
Santocure TBSI 0.70 — — —
DiCup 40KE — 5.00 —————————
Total 158.85 152.00 160.90 147.00
Major Variable
RX- RX-
13804/Cyrez 13804/Cyrez Control
CRA-148M RX-13804 CRA-148M Example
Example 14 Example 15 Example 16 17
Viscosity and
Curing
Properties
Mooney
Viscosity at
335ฐ F. (168ฐ C.)
Minimum 47.5 46.5 62 56
Viscosity
t5, minutes 2 1.1 0.75 0.85
t10, minutes 2.3 1.3 0.85 1
t35, minutes 3 1.7 1.1 1.8
Oscillating Disc
Rheometer at
335ฐ F.(168ฐ C.)
ML 13.4 12.4 11.4 13.1
MH 41.9 67 74.2 74.6
ts2, minutes 1.8 1.3 1.2 1.1
t′c(90), minutes 7.2 13.6 15.3 14.5
1.25 * t′c(90), 9 17 19.1 18.1
minutes
Cure Rate Index 18.7 8.1 7.1 7.5
Original
Physical
Properties
Stress @ 100% 2.0 4.0 5.5 5.1
Elongation,
MPa
psi 290 575 800 735
Stress @ 200% 5.6 14.7 — —
Elongation,
MPa
Stress @ 300% 10.6 — — —
Elongation,
MPa
Tensile 16.5 16.4 9.9 16.2
Ultimate, MPa
psi 2390 2385 1440 2355
Elongation @ 440 215 140 190
Break, %
Hardness Duro 52 57 62 61
A, pts.
Specific Gravity 1.097 1.082 1.105 1.090
Metal Sulfur Peroxide Peroxide Peroxide
Adhesion-
ASTM D429
Brass
Adhesion Force, 82.58 1.69 — —
lbf/in width
Failure Type R R R R
% Failure 100 100 100 100
Aluminum
Adhesion Force, — — — —
lbf/in width
Failure Type R R R R
% Failure 100 100 100 100
Steel
Adhesion Force, — — — —
lbf/in width
Failure Type R R R R
% Failure 100 100 100 100

[0136] Table VI provides data wherein a sulfur cure system was used in formulations containing resin only (Example 18), a resin combined with a long chain ester of the disclosure (Example 20), and a control containing no resin and no ester (Example 19). From these data, it can be seen that the formulation including the long chain ester adhesion promoter and resin performs best, and gives superior adhesive results when compared with the control formulation and the formulation, containing the resin without an ester of the disclosure.

TABLE VI
Recipe Variable
Cyrez CRA
Cyrez CRA Resin Resin
148M “Control” 148M/RX 13804
Recipe NR-6 Example 18 Example 19 Example 20
SMR-L 100 —————————————
Kadox 930 5.00 —————————————
Stearic Acid 2.00 —————————————
N 330 35.00 —————————————
Cyrez Resin 7.00 — 7.00
148-M
RX-13804 — — 7.00
Subtotal 149.00 142.00 156.00
Mill Addition
Sulfur 2.25 2.25 2.25
Santocure TBSI 0.70 0.70 0.70
Total 151.95 144.95 158.95
Viscosity and
Curing
Properties
Mooney
Viscosity at
168ฐ C.
(335ฐ F.)
Minimum 48.1 53.2 48.2
Viscosity
t5, minutes 2.1 1.5 2
t10, minutes 2.4 1.8 2.3
t35, minutes 3.2 2.6 2.9
Oscillating
Disc
Rheometer at
168ฐ C.
(335ฐ F.)
ML 13.7 14.6 13.5
MH 31.2 36 40.9
ts2, minutes 1.8 1.7 1.8
t′c(90), minutes 5.3 5.3 7.1
1.25 * t′c(90), 6.7 6.7 9
mins. 28.6 27.3 19
Cure Rate Index
Vulcanizate
Properties
Original
Physical
Properties
Stress @ 100% 1.9 1.8 2.0
Elongation, MPa
psi 280 255 300
Stress @ 200% 4.7 4.5 5.6
Elongation, MPa
Stress @ 300% 8.6 8.8 10.6
Elongation, MPa
Tensile Ultimate, 22.1 24.5 16.5
MPa
psi 3205 3560 2380
Elongation @ 555 565 440
Break, %
Hardness Duro 57 55 52
A, pts.
Specific Gravity — — 1.097
Metal
Adhesion -
ASTM D249
Brass
Adhesion Force, 118.2 46.3 138.9
lbf/in width
Failure Type R, RM R R, RM
% Failure Type 95, 5 100 95, 5
Aluminum
Adhesion Force, Fail Fail Fail
lbf/in width
Failure Type RM RM RM
% Failure 100 100 100
Steel
Adhesion Force, Fail Fail Fail
lbf/in width
Failure Type RM RM RM
% Failure 100 100 100

[0137] Next, the effect of the long chain esters described herein was evaluated in an EPDM rubber formulation for rubber to metal bonding. The cure system was also evaluated to determine the effect of peroxide versus a sulfur system. The sulfur formulations did not work, thus these formulations were discarded. The peroxide cured formulations were varied by using the ester alone and the resin/ester combination. The data below in Table VII (Examples 21-23), lists adhesion results for brass, aluminum and steel cord in EPDM.

TABLE VII
Major Variable
RX-13804/
RX-13804 Cyrez CRA-148M Control
Example 21 Example 22 Example 23
Brass
Adhesion Force, 1.26 52.43 —
lbf/in width
Failure Type R R R
% Failure 100 100 100
Aluminum
Adhesion Force, — — —
lbf/in width
Failure Type R R R
% Failure 100 100 100
Steel
Adhesion Force, 16.82 19.97 —
lbf/in width
Failure Type R R R
% Failure 100 100 100

[0138] The formulation containing the resin/ester has significantly greater adhesion to brass than the formulation with just ester, and the control. The steel adhesion results show that the formulation with ester does provide some adhesion, but the resin/ester combination is unexpectedly better. The control formulation has no adhesion to steel. None of the formulations has adhesion to aluminum.

[0139] The recipe/formulation data for Examples 21-23 is shown in Table VIII:

TABLE VIII
Example
Recipe EPDM1 21 22 23
Nordel IP 3720 100 ————————
N 762 56 ————————
Kadox 930 5.00 ————————
Ricon 150 5.00 ————————
SR 350 4.00 ————————
RX-13804 10.00 7.00 —
Cyrez Resin 148-M — 10.00 —
Subtotal 180.00 187.00 170.00
Mill Addition
VulCup 40KE 7.00 ————————
Total 187.00 194.00 177.00
Major Variable
RX-13804/
RX-13804 Cyrez CRA-148M Control
Example 21 Example 22 Example 23
Peroxide Cure
Viscosity and
Curing
Properties
Mooney
Viscosity at
Min. Viscosity 23.9 29.6 33.6
t5, minutes 9.5 11.2 7.5
t10, minutes 10.7 11.9 7.9
t35, minutes — 15.8 8.8
Oscillating Disc
Rheometer at
ML 6.6 12.2 9.2
MH 87.1 92.4 177
ts2, minutes 0.92 0.92 0.83
t′c(90), minutes 6.5 8.4 8.5
1.25 * t′c(90), 8.1 10.5 10.6
mins. 17.9 13.3 13
Cure Rate Index
Original Physical
Properties
Stress @ 100% 1.4 6.5 13.7
Elongation, MPa
psi 198 940 1990
Stress @ 200% 11.2 12 —
Elongation, MPa
Stress @ 300% — — —
Elongation, MPa
Tensile Ultimate, 12.2 13.0 19.7
MPa
psi 1770 1890 2860
Elongation @ 200 210 135
Break, %
Hardness Duro A, 80 83 86
pts.
Specific Gravity 1.099887 1.122098 1.114178

[0140] Table IX provides comparative data that supplements the data presented in Table VIII. Example 24, contains resin, but does not contain any of the long chain ester adhesion promoting additives disclosed herein. As can be seen from the data of Table IX, Example 24 did not promote adhesion between EPDM and metal substrates.

[0141] Table IX also contains formulations wherein the ester was varied. A saturated ester, UBS 020602, in accordance with the disclosure, was used to formulate Examples 25 and 26. In Example 25, the saturated ester additive was not combined with an adhesive resin as described herein, and failed to promote adhesion between EPDM and the metal substrates. However, in Example 26, the saturated ester was combined with an adhesive resin, and excellent adhesion between metal substrates and EPDM, more particularly between steel and EPDM, was obtained.

TABLE IX
Recipe Variable
RX-
13804/Cyrez UBS 020602/
CRA 148-M Cyrez CRA 148-M UBS 020602 Cyrez CRA 148-M Control
Recipe EPDM-4M Example 22 Example 24 Example 25 Example 26 Example 23
Nordel IP 3720 100.00 ————————————————————
N 762 56.00 ————————————————————
Kadox 930 5.00 ————————————————————
Ricon 150 5.00 ————————————————————
SR 350 4.00 ————————————————————
RX 13804 7.00 — — — —
Cyrez Resin 148-M 10.00 10.00 — 10.00 —
UBS 020602 — — 7.00 7.00 —
Subtotal 187.00 180.00 177.00 187.00 170.00
Mill Addition
Vulcup 40 KE 7.00 ————————————————————
Total 194.00 187.00 184.00 194.00 177.00
Recipe Variable
UBS 020602
Processing RX-13804/148M Cyrez148-M UBS 020602 Cyrez 148-m Control
Properties Example 21 Example 24 Example 25 Example 26 Example 23
Viscosity and
Curing Properties
Mooney Viscosity
at 121ฐ C.(250ฐ F.)
Minimum Viscosity 26.3 32.6 23.4 26.6 28.7
t5, minutes 12.8 9.8 11.4 11.1 9.7
t10, minutes 14.2 10.4 12.3 11.8 10.2
t35, minutes FAIL 12.7 17.8 14.8 11.4
Oscillating Disc
Rheometer at
177ฐ C.(350ฐ F.)
ML 6.7 10.8 6.7 8 8.8
MH 74.1 115.9 129 87.4 171.6
t52, minutes 0.92 0.92 1.1 1 1
t′c(90), minutes 7.4 10.1 9.1 9.3 10.3
1.25 * c(90), 9.3 12.6 11.4 11.6 12.9
minutes
Cure Rate index 15.4 10.9 12.5 12.1 10.7
Vulcanizate
Properties
Original Physical
Properties
Stress @ 100% 6.1 9.3 8.4 6.3 13.4
Elongation, MPa
psi 890 1350 1220 920 1945
Stress @ 200% 11.7 — — — —
Elongation, MPa
Stress @ 300% — — — — —
Elongation, MPa
Tensile Ultimate, 12.3 15.2 14.1 12.0 18.2
MPa
psi 1785 2200 2045 1735 2635
Elongation @ 205 160 145 180 125
Break, %
Hardness Duro 85 87 85 83 87
A, pts.
Specific Gravity 1.119 1.128 1.102 1.120 1.110
Metal
Adhesion - ASTM
D429
Brass
Adhesion Force, 91 61.5 FAIL 77.6 FAIL
lbf/in width
Failure Type R R RM R RM
% Failure 100 100 100 100 100
Aluminum
Adhesion Force, FAIL FAIL FAIL FAIL FAIL
lbf/in width
Failure Type RM RM RM RM RM
% Failure 100 100 100 100 100
Steel
Adhesion Force, FAIL 35.3 FAIL 77 FAIL
lbf/in width
Failure Type R RM RM RM-R RM
% Failure 100 100 100 67%, 33% 100

[0142] EPDM Rubber to Metal Bonding

[0143] Additional esters were evaluated to determine their effect on adhesion when combined with an adhesive resin. The esters evaluated were as follows:

Plasthall DOS A saturated diester based on 2-ethylhexyl alcohol
and sebacic acid.
RX-13577 An unsaturated monoester based on tridecyl
alcohol and tall oil fatty acid.
RX-13824 An unsaturated dimerate ester based on tridecyl
alcohol and a C-36 dimer acid. This ester is
similar to RX-13804, which uses the same dimer
acid, but RX-13804 is reacted with 2-ethylhexyl
alcohol (di-2-ethylhexyl dimerate).

[0144] The results indicate that the compound with DOS/resin provides good adhesion to brass and steel. The RX-13577/resin compound has excellent adhesion to brass and steel, and the force values for steel are greater than any of the other ester/resin combinations. The data suggests that a greater degree of ester unsaturation levels provides greater adhesion because RX-13577 does have more unsaturated sites by weight than RX-13804 or RX-13824. Another piece of data that helps support the above statement is the steel adhesion data for the ester only compounds. The RX-13577 compound had the only measurable adhesion while DOS and RX-13824 had no adhesion values.

[0145] The data is set forth in Table X, Examples 27-34:

TABLE X
Example
Recipe EPDM-2 27 28 29 30 31 32 33 34
Nordel IP 3720 100.00 —————————————————————————
N 762 56.00 —————————————————————————
Kadox 930 5.00 —————————————————————————
Ricon 150 5.00 —————————————————————————
SR 350 4.00 —————————————————————————
Plasthall DOS 10.00 7.0 — — — — — —
Cyrez CRA 148-M — 10.00 7.00 — 10.00 — 10.00 —
RX-13577 — — — 10.00 7.00 — — —
RX-13824 — — — — — 10.00 7.00 —
Control — — — — — — — —
Subtotal 180.00 187.00 177.00 180.00 187.00 180.00 187.00 170.00
Mill Addition
Vulcup 40KE 7.00 —————————————————————————
TOTAL 187.00 194.00 184.00 187.00 194.00 187.00 194.00 177.00
Major Variable
Plasthall
Plasthall DOS/Cyrez RX-13577/ RX-13824/
DOS CRA Cyrez CRA Cyrez CRA Cyrez CRA
(dioctylsebacate) 148-M 148-M RX-13577 148M RX-13824 148-M Control
Example 27 Example 28 Example 29 Example 30 Example 31 Example 32 Example 33 Example 34
Plasticizer
Processing
Properties
Viscosity
and Curing
Properties
Mooney
Viscosity at
250ฐ F.
(121ฐ C.)
Min. 19.9 26.1 32.2 21.1 26.1 21.3 26.8 30.9
Viscosity
t5, minutes 8.6 9.6 8.4 7.6 7.3 8.9 7.8 6.6
t10, minutes 9.3 11.8 8.9 8.6 7.9 9.8 8.3 6.9
t35, minutes FAIL FAIL 17.6 FAIL FAIL FAIL 10.2 8.3
Oscillating
Disc
Rheometer
at 350ฐ F.
(177ฐ C.)
ML 5.5 6.6 10 6.6 7.2 6.4 8.6 9.7
MH 88.6 63.1 84.9 58.8 52.8 75.3 58.5 125.8
ts2, minutes 0.92 0.92 0.92 1.3 0.92 1 0.92 0.83
t′c(90), mins. 6.3 6 6.1 6.9 6 6.1 5.9 6.3
1.25 * t′c(90), 7.8 7.5 7.6 8.7 7.5 7.6 7.4 7.8
minutes
Cure Rate 18.8 19.7 19.4 17.6 19.7 19.7 20 18.5
Index
Original
Physical
Properties
Stress @ 100% 4.8 5.0 6.4 3.8 4.5 4.2 4.7 8.2
Elongation,
MPa
psi 700 725 925 545 655 615 680 1195
Stress @ 200% 11.4 9.4 12.3 7.5 7.8 9.7 8.2 —
Elongation;
MPa
Stress @ 300% — — — 11.1 10.4 — — —
Elongation;
MPa
Tensile 13.5 11.1 13.9 12.7 10.4 11.7 10.4 18.1
Ultimate,
MPa
psi 1960 1650 2010 1835 1515 1690 1515 2620
Elongation @ 220 250 225 320 300 235 275 175
Break, %
Hardnes Dura 81 84 86 79 82 80 82 85
A, pts.
Specific 1.102 1.123 1.125 1.098 1.118 1.098 1.121 1.113
Gravity
Major Variable
Plasthall
Plasthall DOS/Cyrez RX-13577/ RX-13824/
DOS CRA Cyrez CRA Cyrez CRA Cyrez CRA
(dioctylsebacate) 148-M 148-M RX-13577 148M RX-13824 148-M Control
Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27
Metal
Adhesion -
ASTM D429
Brass
Adhesion — 128.1 51.1 — 139.4 — 133.5 —
Force,
lbf/in width
Failure Type RM RM R RM R RM R RM
% Failure 100 100 100 100 100 100 100 100
Aluminum
Adhesion — — — — — — — —
Force,
lbf/in width
Failure Type RM RM RM RM RM RM RM RM
% Failure 100 100 100 100 100 100 100 100
Major Variable
Plasthall
Plasthall DOS/Cyrez RX-13577/ RX-13824/
DOS CRA Cyrez CRA Cyrez CRA Cyrez CRA
(dioctylsebacate) 148-M 148-M RX-13577 148M RX-13824 148-M Control
Example 27 Example 28 Example 29 Example 30 Example 31 Example 32 Example 33 Example 34
Metal
Adhesion -
ASTM D429
Steel
Adhesion — 37.3 — 14.2 96.7 — 42.3 —
Force,
lbf/in width
Failure Type RM RM RM RM RM RM RM RM
% Failure 100 100 100 100 50 100 100 100

[0146]

TABLE XI
Materials of the Examples
Material Chemical Description Supplier
SMR-L Natural rubber Alcan
Kadox 930 Zinc Oxide The C. P. Hall
Company
Stearic Acid R.G. Stearic Acid, rubber grade The C. P. Hall
Company
N-330 Carbon Black JM Huber
Spider Sulfur Elemental Sulfur The C. P. Hall
Santocure TBSI N-tert-butyl-di- Harwick
(benzothiozolesulfen)
imide
RX-13577 Tridecyl tallate The C. P. Hall
Company
RX-13804 Di(2-ethylhexyl)dimerate The C. P. Hall
Company
RX-13824 Ditridecyl Dimerate The C. P. Hall
Company
Plasthall DOS Di(2-ethylhexyl)sebacate The C. P. Hall
Company
Paraplex A-8000 Polyester Adipate The C. P. Hall
Company
Staflex DBM Dibutyl maleate The C. P. Hall
Company
DiCup 40 KE Dicumyl Peroxide on Hercules
Burgess Clay
RX-13845 36% RX-13804, 36% The C. P. Hall
Cyrez D-148M, 28% Company
Hydrated Amorphous
Silica
Cyrex Resin D-148M Melamine Resin Powder Cytec
Concentrate
N-326 Carbon Black JM Huber
Cobalt Naphthenate Metal Carboxylate Sheperd
adhesion promoter
Santoflex 13 N-Isopropyl-N′-phenyl-p- Harwick
phenylenediamine
PVI N-(cyclohexylthio) Flexsys
phthalimide
Pennacolite Resin Formaldehyde Resin Indspec
Vulkacit DZ Benzothiazl-2- Bayer
dicylcolhexyl-
sulfenamide
Resimene Hexametharylmethyl- Harwick
melamine
Nordel IP3720 Hydrocarbon Rubber DuPont
N762 Carbon Black JM Huber

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7109264Jul 10, 2003Sep 19, 2006Cph Innovations Corp.Low polarity dimerate and trimerate esters as plasticizers for elastomers
US7232855Feb 7, 2003Jun 19, 2007Cph Innovations Corp.Improved low temperature properties; for application to conveyor belts, automotive drive train belts, transmission belts, hoses, motor mounts, and gaskets
US7285588Mar 29, 2004Oct 23, 2007Hallstar Innovations Corp.Low polarity dimerate and trimerate esters as plasticizers for thermoplastic compositions
Classifications
U.S. Classification524/284
International ClassificationC08L9/00, C08L101/00, B32B25/00, C08L7/00, C08K5/109, C08L21/00, C08K5/10, C08K5/3492, C08K5/101
Cooperative ClassificationC08K5/34922, C08K5/10, C08K5/109, C08L21/00, C08K5/101
European ClassificationC08L21/00, C08K5/109, C08K5/3492B, C08K5/101, C08K5/10
Legal Events
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Effective date: 20040315
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