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Publication numberUSRE27158 E
Publication typeGrant
Publication dateAug 10, 1971
Filing dateNov 28, 1969
Priority dateNov 28, 1969
Publication numberUS RE27158 E, US RE27158E, US-E-RE27158, USRE27158 E, USRE27158E
InventorsClifton L. Kehr
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Crosslinking process
US RE27158 E
Abstract  available in
Images(3)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Aug. 1o, 1911 c, KEHR am CROSSLINKING PROCESS Re. :ms

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cRossLINkING PROCESS Aug. 1o, 1971 Sheets-Shoot :j

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Clifton L. Kehr James L. Gul/m klm N WQDK Aug. 10, if C VL, KEHR ETAL v R0. 21,158

GROSSLNKINQ POQSS '5 shutp-Bhut s Original Filed Oct. 241,; 1962 QQ QQ Qk` QQ QQ QQ QQ emu .25m Sis .2352. 323s 3 *EN sa. und waas! Nn e b Kfm@ om ruao* L rw Lm QMSvw/ ../,ewv A wmf.

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United States Patent O 27,158 CROSSLINKING PROCESS Clifton L. Kehr, Silver Spring, and James L. Guthrie, Ashton, Md., assignors to W. R. Grace & Co., New York, N.Y.

Original No. 3,226,356, dated Dec. 28, 1965, Ser. No. 232,771, Oct. 24, 1962. Application for reissue Nov. 28, 1969, Ser. No. 888,173

Int. Cl. C08d 11/00; C081. 3/02, 45/08 16 Claims Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specilication; matter printed in italics indicates the additions made by reissue.

ABSTRACT F THE DISCLOSURE The curing of alpha-olefins and of alpha-olefin copolymers with quinone dioxime esters is accelerated by the addition of a Lewis acid. The caring temperature is lowered still farther by the addition to the caring system of a synergistic agent consisting of a polar organic member of the group consisting of carboxylic acids, phosphoric acid, boric acid, and esters thereof, and fillers such as carbon black and/ or other conventional additives may be included.

This invention relates to crosslinked polymers derived from a-olens and copolymers containing same and methods of preparing same. More particularly this invention is concerned with crosslinking polymers derived from aoletins and copolymers containing same at temperatures above their processing temperature at a rapid rate with a novel cross-linking system.

In the eld of polymers derived from a-olens, there is a continuing search for new and better crosslinking agents. Of special interest are those which are unreactive at processing and compounding temperatures, but which can be triggered in some manner after the polymer compound is processed into its nal shape by molding, extruding or the like.

Thus in the polyolen art, there has been a long felt want for crosslinking agents which not only crosslink at operable and economical temperatures above the processing temperature of the polymer or copolymer but also crosslink at a rapid rate at said temperature so as to require a very short cure time.

In a copending application having Serial Number 168,025, filed I an. 18, 1962 and assigned to the same assignee, it has been discovered that esters, both mono and di, of quinone dioxime are excellent crosslinking agents for normally solid polyolelns. The only drawback, however, is that the curing temperature is necessarily high, e.g. for polypropylene a temperature of 225 C. is necessary to obtain a suciently high gel content in the polymer. Thus although the esters of quinone dioxime have excellent scotch (pre-cure) resistance at the high temperatures (U-200 C.), such exceptional stability is not required, in fact, is not desired in curing certain polymers derived from a-olens and copolymers containing same.

For example a copolymer derived from a-olens which has recently entered the market on a commercial scale is the poly nt-olefin copolymer, ethylene/propylene rubber (EPR). Because of low monomer cost, EPR promises to be the rubber industrys lowest priced elastomer. Due to its essentially nil double bond content, EPR is outstanding (relative to other vulcanizable elastomers) in its resistance to degradation by oxygen and ozone. For the same reason, however, EPR is rather diicult to vulcanize. For example, ethylene/ propylene rubber cannot be vulcanized With standard sulfur/accelerator recipes. Comp i ICC mercial manufacturers of EPR currently recommend a dicumyl peroxide vulcanization recipe (usually modified with a small quantity of sulfur to minimize degradation of the EPR during the cure). This system, although operable, has the following disadvantages: (l) obnoxious odors from a combination of acetophenone and mercaptan-like sulfur compounds, (2) high temperature/time curing cycles which are rather inflexible since there are no known accelerators or retarders for peroxides, and (3) the adhesion of the cured EPR to tire cords is extremely poor.

One commercial approach taken to overcome the disadvantages of EPR has been the development of a sulfur-curable hydrocarbon rubber based on ethylene and propylene. This product contains, beside ethylene and propylene, a third monomer unit derived from a nonconjugated diene and is sold under the trade name Nordel by E. `I. du Pont de Nemours and Co., Inc. The resulting terpolymer after polymerization contains a controlled degree of unsaturation which as in the case of butyl rubber, serves as curing sites for vulcanization with standard sulfur-containing accelerators. Although the odor problem is less critical by the use of this terpolymer, the curing rate is still sluggish requiring a cure of approximately 30 minutes at 160 C. By ordinary rubber industry standards, these conditions are too long and too high to be economical for general usage, especially in the tire industry.

The rubber tire industry generally desires a standard curing temperature range of 13G-150 C. for a period of no more than 10-20 minutes. At processing temperatures below said range, the crosslinking or vulcanizing agents employed must be relatively non-scorchy but when heated within said range the crosslinking agents must be able to rapidly cure the polymer. To employ crosslinking agents which cure at temperatures above the aforementioned range would be uneconomical for the ber tire industry as it would necessitate in many instances the introduction of higher pressure steam generating units and a redesign of present equipment to withstand the higher steam pressure.

Therefore, one object of this invention is to provide a novel crosslinking system which effects curing of polymers derived from a-olens and copolymers containing same, especially amorphous copolymers such as EPR, in the range 150 C. at an operable rate without scorching (pre-curing during processing). In fact, this novel crosslinking system is so versatile in the case ofIEP-R that one can, by proper choice of curing agent and accelerator, formulate compositions so that rapid and complete crosslinking will occur at any predesired temperature ranging between the limits of 130 C. and 215 C. In addition, temperatures can be selected readily so that curing cycles of extremely short duration, c g. 2 minutes or less, can be achieved.

Still another object of the present invention is to provide a class of synergistic agents which when combined with the crosslinking agents and accelerators therefor of this invention lower the curing temperature still further.

Other objects and advantages of this invention will become apparent from a reading hereinafter.

Summarily this invention relates to curing polymers derived from a-olens by admixing said polymers ywith a curing agent of the general formula,

As used herein the term a-olen means a hydrocaraon monomer which contains a single terminally unsatu- 'ated grouping of the formula -CH=CH2.

As used herein the term polymers derived from a-oleins includes coand terpolymers wherein at least 50 nole percent of the polymer is derived from a-olefins as lerein defined. Thus, polymers derived from a-oleiins vould include, but are expressly not limited to, polyethylene, polypropylene, ethylene/ propylene copolymers, ethylne/butylene copolymers, ethylene/propylene/diene terrolymers, and ethylene/ vinyl acetate copolymers, said atter two containing at least 50 mole percent of the poly t-olens. The polymers derived from a-olefins as meant lerein would also include polymers derived from a-oleins which had been further processed such as having been :hlorosulfonated, e.g. chlorosulfonated polyethylene as decribed in U.S. 2,212,786.

In this invention the term acyloxy means n which R is an aliphatic group.

substituents may be present in the ortho, meta and ara positions of the benzene ring of the benzoate group f the curing agent. substituents such as halogens, alkyl groups, alkoxy groups, nitro groups, etc. are operable. Xlso operable are other aromatic .groups besides the enzenoid ring. For example, quinone dioxime esters of or 2-naphthoic acid function as well as similar esters f =benzoic acid but in most cases are more costly. The luinone dioxime esters of the aliphatic carboxylic acids, .e., the aliphatic acyloxy-substituted quinone dioximes are tlso operable in substituted form. Substituents such as he halogens have been employed as will be shown lereinafter.

In the present invention the term Lewis acid means L substance which can fill the valence shell of one of its Ltoms with an unshared pair of electrons from another nolecule. Examples of Lewis acids include but are not imited to A1013, FeCl3, SnCl4, ZnClZ, TiCl4, CrCl3, JC14, A1Br3, HgCl2, BF3 and the like. Also included in his definition are mixtures of compounds which, when )rought together in the polymeric composition under ztandard conditions of processing interact with each other o -generate the Lewis acid in situ. Alsoincluded in the lefinition of Lewis acids herein are Lewis acid coordilation compounds which prior to addition to the rubber :ompound have their maximum coordination number satisfied, but which in the course of compounding and :uring interact with the curing agent. Examples of this atter type of Lewis acid coordination complexes are illusrated by but not limited to ferrc acetylacetonate, aluninum aoetylacetonate, boron fluoride, n-butyl etherate, :inc chloride: 2,2-dithiobisbenzothiazole complex and the ike. The addition of said Lewis acid accelerators to the :ystem causes optimum curing to occur (as shown by gel content of the polymer), at temperatures below the )ptimum curing temperature of the esters of quinone lioxime per se as will be shown hereinafter.

In addition it has been found that the optimum curing emperature of the novel curing agents and accelerators )f the instant invention can, if desired, be lowered still urther by adding to the system a synergistic agent con- `isting of a polar organic member of the group consisting lf carboxylic acids, phosphoric acid, boric acid, and :sters thereof. Examples of synergistic agents operable n the instant invention include, but are not limited to, 1-butyl stearate, tributyl citrate, tributyrin, tributyl phosihate, tributyl borate, stearic acid, and the like.

The amount of crosslinking agent used in this invention s not critical and can vary over wide limits depending lpon the polymer being crosslinked. Amounts of esters )f quinone dioxime crosslinking agent in the range ).1-30 parts per hundred parts of polymer by weight 4 preferably 0.5-20 parts per hundred parts of polymer are employed.

The amount of Lewis acid accelerator used is in the range 0.005211) part by weight per hundred parts of polymer and preferably 0.0l0.5 part on the same basis. The Lewis acid accelerator may, if desired, be added to the compounding step as a solution (5-20% by weight) in suitable solvents, for ease of handling and for uniformity of dispersion. Low boiling organic solvents such as acetone, isopropanol, ethanol, benzene, and the like are operable. The solvent is boiled olf in the compounding step.

The amount of synergistic agent employed herein is in the range 0.1-30 parts per hundred parts of polymer by weight and preferably 0.5-3.0 parts on the same basis.

The polymer compositions to be cured in accord with the present invention may, if desired, include such additives as antioxidants, fillers, pigments, anti-static agents, extending oils, plasticizers, tackifiers and the like within the scope of this invention. Such additives are usually but not necessarily added to the polymer composition by pre-blending prior to or during the compounding step. Operable fillers would include carbon black, clay, silica, alumina, carbonates, oxides, hydroxides, silicates, diatomaceous earth, talc, kaolin, barium sulfate, calcium sulfate, calcium carbonate and the like. The aforesaid additives may be present up to 200 parts or more per parts of polymer by weight and preferably 0.05-100 parts on the same basis.

Although the invention is operable with polymers derived from a-olelins and copolymers containing same, for ease of explanation and clarity the invention will, in the main, be explained using ethylene/propylene rubber (EPR) as the polymer to be cured.

The general procedure followed in performing this invention is to form a compound of the desired ingredients ina Bansbury mixer, two-roll mill, Brabender Plastograph and the like at temperatures in the range 25-200 C. The compounding temperature is determined by and is in excess of the softening point of the polymer but is below the curing temperature exhibited 'by the crosslinking agent. While milling the polymer above its softening point (which for EPR usually would be in the range 25-l20 C.), any filter and any synergistic agent are compounded in with continued milling. The crosslinking agent is then added followed by the addition of the Lewis acid accelerator. It is possible to add all the aforementioned components together to the softened polymer but for more uniform mixing and ease of handling, they are preferably added stepwise. The resulting compound is then processed into its final shape by an extruding or molding step under pressure at temperatures above the softening point of the polymer but below the curing temperature exhibited by the crosslinking agent. This step is followed by heating the shaped article to a higher temperature ran-ge, e.g. for EPR a temperature in excess of 130 C. whereat rapid curing of the polymer is effected. The curing temperature is dependent upon many factors, including (l) the polymer being cured, (2) the actual crosslinking agent and accelerator within the classes disclosed and the amounts thereof, and (3) whether or not a synergistic agent is added. As a ,general rule the curing temperature employed for optimum curing, i.e. where the state of cure (percent gel) plateaus out, in the instant invention is from to 200 C.

The following examples are set down as an aid in understanding the invention but are expressly not designed to limit its scope. In the example, unless otherwise noted, all parts and percentages are by weight per hundred parts of polymer.

Throughout the instant invention the melt indices (MI) were measured under the conditions specified in ASTM D-l238-52T, except for isotactic polypropylene, in which instaance the procedure was modified so that the test was run at 230 C. instead of 190 C. The densities of the polymers were measured under the conditions specified in ASTM D-1505-57T. The percent gel content of the polymers in the instant invention was measured by refluxing a weighed sample (approximately 0.5 g.) of polymer in a cellulose Soxhlet thimble in a suitable solvent (containing 0.3 weight percent 2,6- ditertiary-butyl-4-methyl-phenol commercially available under the trade name Ionol from Shell Oil Corp. for 24 hours. The insoluble portion of the polymer sample after drying was weighed to calculate percent gel as follows:

Weight insoluble sample total Weight sample In examples wherein an additive such as a filler, e.g. carbon black, clay and the like was present in the compound the percent rgel content was calculated so as to exclude the inert insoluble additive. Thus as used herein percent gel content is based solely on the polymeric hydrocarbon content of the cured polymer. Suitable solvents for the polymer compositions described herein include heptane, xylene, methylethyl ketone and the like, the only restriction being that the uncured polymer should be completely soluble in said solvent under conditions of the extraction procedure.

Mooney viscosity was measured in accord with the conditions specied in ASTM D164661.

In all examples, unless otherwise noted, a Brabender percent gel X l periods ranging from 1 to 15 minutes at various curing temperatures. The samples were then removed from the press and cooled in air. Samples of the cured specimens were then used to calculate the percent gel content by the aforementioned solvent extraction method.

Table I shows a comparative study of the accelerating effect of various Lewis acid accelerators and synergistic agents on the crosslinking agent in curing ethylene/propylene rubber (EPR). The compounding was performed ina Bra'benider Plastog-raph at 80-110 C. The components of the compound were milled together over a period of 10 minutes. Samples of the compounded EPR were cured by placing them Iin a 6 x 6" x 0.02 mold and pressing them in a platen press for 15 minutes and 625 p.s. i. at varying cure temperatures. Weighed samples of the cured EPR were then measured for gel content in reuxing n-heptane containing a small amount of an antioxidant for 24 hours.

TABLE I Example No 1266 1450 1450 1450 1450 1450 1450 1450 1450 1387 1450 1450 27-1 12-9 12-4 12-22 12-19 12-16 12-24 12-21 12-18 30-1 11-8 12-1 Compound 1 2 3 4 5 6 7 8 9 10 11 12 Polymer b- 100 100 100 100 100 100 100 100 100 100 100 Crosslinking age C uinonedioxime dibenzoate C uinonedioxime bis (p-mathoxyb enzoate) C uinonedioxime bis (p-chlorobenzoate) Cuinonedioxime distearate Qunonedioxime diheptanoata Qunonedioxime dibuty'rate Quinonedioxime diaeetate Quinonedioxime bis (ehloroacetate) Lewis acid accelerator:

c Synergistic agent:

S arie acid Tribntyl citrate.- Tributyl borate Tributyl phosphate Percent gel of cured polymer at C 1 1 2 3 2 4 4 4 1 41 27 7 C 1 32 1 2 29 4 2 2 0 73 69 C. 0 73 78 2 60 77 3 55 73 54 77 73 200 C. 54 82 81 66 8 1 83 39 79 81 61 78 77 225 C 82 S6 85 79 78 82 73 83 81 86 79 Example No 1387 1450 1450 1450 1450 1450 1450 1450 1450 1450 1450 1450 39-16 11-9 12-6 12-11 12-7 12-2 12-13 12-10 12-5 1212 12-8 12-3 Compound 1 18 14 15 16 17 18 29 10 21 22 23 24 Polymer b 100 100 100 100 100 100 100 100 100 100 100 100 Crosslinklng ag dibenzoata bis (p-methoxyb enzoate) bis (p-chlorob enzoate) distearate diheptanoate dbutyrate diacetate acid accelerator:

12 SDC14.5H1O

Fenic acetylaeetonate synergistic agent:

Stearic acid Trlbutyl citrate Tributyl boratc Tributyl phosphate Percent gel oi cured polymer at: 0

bis chloroacetate Table I Continued Example No 1387 1387 1387 1387 1007 1450 1007 1387 1387 1266 7-11 23-3 23-5 23-7 38-18 12-15 38-17 38-8 7-15 31-3 Compound 25 26 27 28 29 30 31 32 33 34 e 35 olymer b- 100 100 100 100 100 100 100 150 100 100 d 150 Crosslinking agen dibenzoate bis(pmethoxybenzoate) bis (p-chlorobenzoate) distearate diheptanoate...

Ferrie aeetylacetonate 1- synergistic agent: Ste i l Compound admixed in a Brabender Plastograph at Sil-110 C. for 5 minutes. h Ethylene/propylene rubber (E.P.R.) containing 58;|=5 mole percent ethylene. Mooney viscosity ML (212 F.) =42. e 15 minute curing time. E.P.R. percent gels measured after retluxing sample for 24 hours in n-heptane containing 0.3 weight percent, 2,6-diterd 100 parts ethylene/propylene rubber containing 58:1;5 mole percent ethylene admired with 50 parts Sterling MT carbon black. 100 parts ethylene/propyiene rubber containing 58:1:5 mole percent ethylene admired with 50 parts Spheron 9 carbon black.

As is readily seen in Table I, the addition of a Lewis icid accelerator to the curing agent of this invention :auses curing `at a lower temperature range than the :rosslinking agent per se; compare, e.g. compounds 1 md 2 or 4 and `5 and the like. In addition it is to be xoted that the addition of a synergistic agent to the :ompound causes curing to occur at a still lower temperature than the combination of curing agent and ae- :elerator; compare, e.g. compounds 2 and 3. The addi- :ion of the synergistic agent to the curing agent with- )ut any accelerator appears to give only a marginal irn- )rovement in lowering the curing temperature; compare :ompounds 1 and 31. However, when the accelerator s added to the curing system a substantial lowering )f the curing temperature is obtained. This is readily ipparent from FIGURE I which shows graphically the effect of a Lewis acid acceleartor i.e. ZnClZ and a synergistic agent i.e. tributyl citrate on a curing agent, quinone dioxine dibenzoate (DBGMF) for ethylene/ propylene rubber (EPR).

FIGURE II shows the accelerating effect of various Lewis acid :accelerators on the curing agent, quinone dioxime dibenzoate (DBGMF) for curing EPR in the presence of various synergistic agents. In all cases, euring occurred at a lower temperature in the presence of an accelerator than occurs with solely a curing agent.

Table II shows a comparative study of the accelerating eiect of the Lewis acid accelerators and synergistic agents on the crosslinking of various polymers derived from aolens. The compounding was performed during a 10 minute milling period in a Brabender Plastograph at temperatures ranging from 10-30 degrees centigrade above TAB L E II Example No Ferrie acetylacetonate Fe C la iynerglstic agent:

Stearic acid Tributyl citrate erceut gel of cured polymer at: h

l Compound admired in a Brabender Plastograph for 5-10 minutes. Rubbers milled at 80-110 C.; thermoplastic polymers milled at 15-25 C. above `heir melting point. b Polyethylene;

density 0.96 g./cc., melt index 0.7 and 137 C. melting point.

v Polypropylene; density 0.899 g./cc., melt index 4.4 and 172-173 C. melting point.

d Ethylene/butylene copolymer containing 1.0 weight percent butylene; density 0.93 g./cc l Chlorosulioneted polyethylene rubber, specific gravity L12-1.28, sold under trade name .Hypalon 20, E. I. du Pont & Co., Inc.

l Ethylenepropylsene/diene terpolymer rubber, specic gravity 0.85, sold under the trade name ECD-330, E. I. du Pont a Co., Inc., Mooney vis- :osity ML (212 F 5. l Ethylene/vinyl acetate copolymer containing 72 weight percent ethylene; density 0.95 g./cc. at 30 C., sold under the trade name "Elvax 250, E. I.

lu Pont & Co., Inc., melt index 15.

h 15 minute curing period. Percent gel measured after reiiuxing weighed sample for 24 hours in xylene for polyethylene, polypropylene, ethylene] Jutylene copolymer and ethylene/vinyl acetate copolymer; in methyl ethyl ketone for chlorosultonated polyethylene and in n-heptane for ethylene] propylene/diene terpolymer. All retluxing solvents contain 0.3 weight percent 2,6-d1tertiary-butyl-4-metl1y1 phenol.

the softening point of the thermoplastic polymers and at 80-110 Cf for the rubbers. Samples of the polymers lwere shaped into 6" x 6" x 0.02" tensile plaques in a platen press for 1 minute at 12S-165 C., depending on the softening point of the thermoplastic polymer, and atmospheric pressure, followed by a 2 minute press at 12S- 165 C. and 625 p.s.i. pressure. The samples were removed from the mold and cured in a platen press for minutes at 625 p.s.i. and varying curing temperatures. Weighed samples of the cured polymers derived from aolens were then measured for gel content in suitable reiluxing solvents containing a small amount of an antioxidant for 24 hours. The rubbers in Table II were cured and measured for percent gel in the same manner as the EPR in Table I except that for chlorosulfonated polyethylene the solvent used was methyl ethyl ketone.

The results in Table II show the operability of the Lewis acid accelerators and the synergistic agents of this invention in lowering the curing temperature of the curing agent for various polymers derived from a-olens.

FIGURE III shows a comparison of the curing system of the instant invention with the presently recommended commercial curing system for ethylene/propylene rubber (EPR) for 15 minute curing periods. The present commercially recommended curing system for EPR consists essentially of dicumyl peroxide with a small amount of sulfur to minimize degradation during the cure. Zinc Oxide (ZnO) is added to create a neutral or basic environment for the dicumyl peroxide and calcium stearate is added as a processing aid to prevent Scorch. From FIGURE III it is readily seen that the curing system of the instant invention causes curing to occur at a lower temperature and to a high degree within the preferred curing temperature range of 13G-150 C` for EPR.

We claim:

1. A curable composition consisting essentially of 100 parts by weight of a polymeric material containing at least 50 mole percent of a polymer derived from an olen, said polymeric material being selected from the group consisting of polyethylene, polypropylene, ethylenebutylene copolymer, chlorosulfonated polyethylene, ethylene, ethylene-vinyl acetate copolymer and ethylene-propylenediene terpolymer, 0.1 to 30 parts/ 100 parts of said polymeric material by Weight of a curing agent of the general formula:

wherein R is a member of the group consisting of benzoate and an aliphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0 part/ 100 parts of said polymeric material by weight of a Lewis acid selected from the group consisting of FeCl3, ferrie acetylacetonate, A1Cl3, [ZnClz] and SnCl4 5H2O.

2. A curable composition consisting essentially of 100 parts by weight of a polymeric material containing at least 50 mole percent of a polymer derived from an otolefn, said polymeric material being selected from the group consisting of polyethylene, polypropylene, chlorosulfonated polyethylene, ethylene-butylene copolymer, ethylene-vinyl acetate copolymer and ethylene-propylenediene terpolymer, 0.1 to 30 parts/ 100 parts of said polymeric material by weight of a curing agent of the general formula:

wherein R is a member of the group consisting of benzoate and an aliphatic acyloxy group containing 1 to 20 carbon atoms, 0.005 to 1.0 part/ 100 parts of said polymeric material by weight of a Lewis acid selected from the group consisting of FeCl3, ferric acetylacetonate, AlCl3, ZNClZ and SnCl45H2O and 0.1-30 parts/100 parts by weight of said polymeric material of a synergistic agent for curing said polymeric material consisting of a polar organic member of the group consisting of carboxylic acid, phosphoric acid, boric acid and esters thereof.

3. The method of curing polymeric material containing at least 50 mole percent of a polymer derived from an a-olen, said polymeric Imaterial being selected from the group consisting of polyethylene, polypropylene, chlorosulfonated polyethylene, ethylene-butylene copolymer, ethylene-vinyl acetate copolymer and ethylene-propyIenediene terpolymer comprising mixing together parts by weight of said polymeric material, 0.1 to 30 parts/ 100 parts of said polymeric material by weight of a curing agent of the general formula:

wherein R is a member of the group consisting of benzoate and an aliphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0 part/ 100 parts of said polymeric material by weight of a Lewis acid selected fro-m the group consisting of FeCl3, ferric acetylacetonate, A1Cl3, ,[ZnClg] and SnCl4-5H2O and thereafter heating the resultant mixture to effect curing of said polymeric material.

4. The method according to claim 3 wherein a synergistic agent for curing said polymeric material consisting of a polar organic member of the group consisting of carboxylic acids, phosphoric acid, boric acid and esters thereof is added to the mixture prior to heating said mixture to effect curing of said polymeric material.

5. The composition according to claim 1 in which the composition contains in addition, 0.05 to 200 parts/100 parts of said polymeric material by weight of a filter for said polymeric material.

6. The composition according to claim 5 wherein the liller is carbon black.

7. The method according to claim 3 wherein 0.05 to 200 parts/ 100 parts of said polymeric material by weight of a filler for said polymeric material is added to the mixture prior to heating said mixture to efrect curing of the polymeric material.

8. The method according to claim 7 wherein the liller is carbon black.

9. The composition according to claim 1 wherein.' the Lewis acid is FeCl3.

10. The composition according to claim 1 wherein the Lewis acid is ferrie acetylacetonate.

1]. The composition according to claim 1 wherein the Lewis acid is AlClS.

12. The composition according to claim 1 wherein the Lewis acid is SnCl4-5H2O.

13. The method according to claim 3 wherein the Lewis acid is FeCl3.

14. T he method according to claim` 3 wherein the Lewis acid is ferrz'c acetylacetonate.

15. The method according to claim 3 wherein the Lewis acid is AlCl.

16. The method according to claim 3 wherein the Lewis acid is SnCl4-5H20.

References Cited The following references, cited by the Examiner, are of record in the patented tile of this patent or the original patent.

UNITED STATES PATENTS 2,748,104 5/1956 Viohl 260-41 3,012,020 12/1961 Kirk et al. 260-41 3,093,614 6/1963 Mackenzie et a1. 260-41 OTHER REFERENCES Morton: Introduction to :Rubber Technology, Reinhold, New York, 1959, pp. 323-324.

ALLAN LIEBERMAN, Primary Examiner U.S. C1. X.R.

Classifications
U.S. Classification524/563, 524/586, 524/576, 525/147, 525/333.7, 525/331.7, 524/584, 525/333.9, 525/337, 525/330.5, 525/340, 525/377, 525/371
International ClassificationC08K5/29, C08K5/33
Cooperative ClassificationC08K5/33, C08K5/29
European ClassificationC08K5/33, C08K5/29