US 3814690 A
Description (OCR text may contain errors)
United States Patent 3,814,690 POLYMERIC POUR POINT DEPRESSANTS OF VINYL AROMATIC AND ALKYL FUMARATE Won R. Song, Maplewood, N.J., assignor to Esso Research and Engineering Company No Drawing. Filed Oct. 10, 1972, Ser. No. 296,121 Int. Cl. C10m 1/28 US. Cl. 252-56 D 5 Claims ABSTRACT OF THE DISCLOSURE Pour point depressants for petroleum distillates and lubricating oils comprise interpolymers, synthesized with the aid of free-radical initiators, from monomers comprising a C to C vinyl aromatic hydrocarbon with a mixture of straight chain alkyl fumarates wherein 20 to 80 mole percent of the alkyl groups are in the C1640 range, and 80 to 20 mole percent are in the C to C 4, range. These mixed alkyl groups can be obtained from: (A) an unsymmetrical C to C dialkyl fumarate in which the chain length of the alkyl radicals in the fumarate ester differs preferably by at least four carbon atoms; (B) at least two C to C symmetrical dialkyl fumarates which dilfer preferably in the length of the alkyl radicals in each ester by at least four carbon atoms; (C) mixtures of an unsymmetrical C to C dialkyl fumarate as in (A) with at least one symmetrical C to C dialkyl fumarate as in (B); and (D) mixtures of unsymmetrical dialkyl fumarates as in (A), or at least two symmetrical fumarate esters as in (B), or mixtures of symmetrical and unsymmetrical esters as in (C), with at least one vinyl alcohol ester of a C to C alkanoic acid.
The pour point depressants of this invention are particularly useful in lubricants compounded with polymeric ethylene-higher alpha-olefin viscosity index improving agents.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to novel oil-soluble interpolymers, i.e. polymers comprised of at least two monomer moieties, which are useful as pour point depressants when compounded with petroleum distillates or lubricants containing waxy or wax-like components.
More particularly, this invention is concerned with interpolymers comprised of: (A) C to C aromatic hydrocarbons with unsymmetrical C to C dialkyl fumarates in which the length of the alkyl radicals in the unsymmetrical ester differs preferably by at least four carbon atoms; ('3) C to C vinyl aromatic hydrocarbons with at least two C to C symmetrical dialkyl fumarates which differ preferably in the length of the alkyl radicals in each ester by at least four carbon atoms; (C) C to C vinyl aromatic hydrocarbons with unsymmetrical C to C dialkyl fumarates in which the length of the alkyl radicals in the unsymmetrical fumarate ester differs preferably by at least four carbon atoms, and at least one, preferably two symmetrical C to C dialkyl fumarates in which the length of the alkyl radicals in one of the symmetrical esters is equal to one of the alkyl radicals in the unsymmetrical ester or differs preferably from both by at least four carbon atoms; and (D) interpolymers of the monomers of (A), (B), (C), or mixtures thereof, with at least one vinyl alcohol ester of a C to C alkanoic acid.
As used herein, the term symmetrical hereinafter abbreviated to sym-, before a dialkyl fumarate indicates that both alkyl radicals in the diester are the same. The term unsymmetrical," hereinafter abbreviated to unsym- 3,814,690 Patented June 4, 1974 "ice indicates that the alkyl radicals in the dialkyl fumarate are different and differ preferably from each other by at least four carbon atoms.
Polymerization in all cases is catalyzed by free-radical initiators such as inorganic and organic peroxides and peracids, azo compounds, ultraviolet light, radiation from a cobalt-60 source of Van de Graft generator, or heat.
The polymeric pour point depressants of this invention possess particular utility when added to oils which have been compounded with ethylene-higher alapha olefin copolymers for the purpose of increasing the viscosity index of the oil. Examples of these copolymers, made with the aid of Ziegler-Natta catalysts are described in US. Pats. 3,522,180 and 3,551,336. In general, these ethylene copolymers comprise about 40 to 83 wt. percent ethylene, have a weight average molecular weight (M in the range of 10,000 to 200,000; a M /M ratio preferably less than about 7.0, e.g. less than 4.0, and a degree of crystallinity of less than 25%. The higher olefin will generally be in the range of C to C e.g. C to C alpha monoolefin, and usually is propylene. Minor amounts, e.g. 0.5 to 10 wt. percent of other olefins may be included in the polymer, e.g. 1,4 hexadiene. These ethylene copolymers are generally used in oil in an amount of about 0.5 to 10 wt. percent, while additive concentrates in oil may contain 10 to 40 wt. percent of the ethylene copolymer. One problem with these ethylene copolymers has been compatibility with other polymeric additives normally used in lube oil compositions and concentrates, particularly pour point depressants. Thus, these ethylene copolymers contain polyethylene segments which resemble natural petroleum waxes in structure and when compounded in an oil to which a conventional pour depressant has been added frequently interact with the pour depressant resulting in the phase separation when the compounded oil is held in storage. One aspect of this invention is the preparation of pour point depressants which are compatible in storage with Ziegler-Natta ethylene-higher alpha olefin viscosity index improvers.
The prior art Lubricant compositions comprising free-radical catalyzed copolymers of a vinyl aromatic hydrocarbon, such as styrene, and an unsaturated dicarboxylic ester such as sym-dioctyl fumarate having utility as a viscosity index improver have been disclosed in US. Pat. 2,366,517.
Polymers useful as detergent additives in lubricating oils comprising copolymers and terpolymers of an olefin, an alkyl or al-kenyl ester of an unsaturated mono or dibasic acid, and a hydroxyalkyl or aminoalkyl ester of an unsaturated acid, have been described in US. Pat. 2,892,790.
U .8. Pat. 2,978,395 discloses the preparation of viscosity index improvers and pour point depressants for lubricating oils by the copolymerization of styrene with a symdialkyl fumarate using high energy radiation.
US. Pat. 3,251,906 discloses the preparation of graft copolymers and terpolymers in which a lower alkyl acrylate is graft polymerized on to a partially polymerized higher alkyl acrylate which may have been copolymerized with minor proportions of vinyl aromatics such as styrene.
SUMMARY It has now been discovered that effective pour point depressants for petroleum distillates and lubricating oils, especially mineral lubricating oils which have been compounded with the aforesaid Ziegler-Natta viscosity-index (A) An unsym- C to C dialkyl fumarate such as ndodecyl, n-hexadecyl fumarate in which the chain length in each alkyl radical in the fumarate ester differs preferably by at least four carbon atoms;
(B) At least two C to C symdialkyl fumarates in which the chain length of the alkyl radicals in each ester differs preferably by at least four carbon atoms, such as a mixture of symditetradecyl furnarate and symdioctadecyl fumarate;
(C) Mixtures of an unsym- C to C dialkyl fnmarate as in (A), with at least one C to C symdialkyl furnarate, in which the length of the alkyl radicals in the symdialkyl fumarate may be the same as one of the alkyl radicals in the unsymester, such as a mixture of unsymdecyl, tetradecyl fumarate with symditetradecyl fumarate, or may be different such as a mixture of unsymdecyl, tetradecyl fumarate with symdioctadecyl fumarate; and
(D) Mixtures of the monomers of (A), (B) and/or (C) with at least one vinyl alcohol ester of a C to C alkanoic acid such as vinyl acetate or vinyl dodecanoate.
Structurally, the interpolymers comprising this invention may be illustrated for the various combinations of monomers detailed above as random interpolymers in which the monomer moieties are linked in the polymer chain in a random sequence and varying number as follows:
(I) H H RO-C=O H /,L l\ r], b \IL A R H -0R" vinyl unsymdialkyl aromatic iumarate wherein R is an aromatic or alkyl aromatic hydrocarbon radical of 6 to 12 carbon atoms, R and R" are independently selected from the group of C to C alkyl radicals and differ preferably in the number of carbon atoms in each radical by at least four, and x and m may vary from 1 to about 20.
wherein R, R R and x are the same as in (I) above and y and z are in the range of 1 to about 20.
(lb (HM- b \I IX 8 at H, i not II II o 0 whereinn R is an aromatic or alkylaromatic hydrocarbon radical of 6 to 12 carbon atoms, R, R" and R'" are independently selected from the group consisting of C to C alkyl radicals and at least one of said R, R" and R'" differs preferably in the number of carbon atoms from at least one other of R, R" and R by at least four, e.g. R is C and R is C or R and R are both C while R" is C R" is a C to C e.g. 1 to 8 alkyl radical, u and s are cardinal numbers in the range of 0 to about 20, x and v are cardinal numbers in the range of 1 to about 20.
It will be understood that the numerical values assigned to m, s, v, x, y and z above, are not totals for any monomer moiety present in any interpolymer of a given molecular weight, but that these numerical values generally express the number of times a given monomer may be repeated in the polymer chain before another monomer is interposed in the chain.
In general, the oil soluble, pour depressing polymers of the invention will have number average molecular weights in the range of about 2000 to 50,000, preferably about 4,000 to 30,000 as by vapor pressure osmometry. These polymers will be interpolymers of about 10 to 90, preferably 20 to 70, mole percent vinyl aromatic; 0 to 30 preferably 5 to 20, mole percent of vinyl alkanoate; and 90 to 10, preferably to 30, mole percent of dialkyl fumarate. The alkyl groups of the fumarate will be predominately a mixture of straight chain C to C alkyl groups, wherein 20 to 80, preferably 30 to 70, mole percent of the alkyl groups will have chain lengths in the range of C to C and 80 to 20, preferably 70 to 30, mole percent of the alkyl groups will have alkyl groups in the range of C to C Preferably, the mole equivalent average chain length of the C to C fraction will be about 4 carbons or more higher than the mole equivalent average chain length of the C to C fraction. To illustrate, if the C C fraction consists of 10 mole percent C 30 mole percent C and 10 mole percent of C alkyl groups, then its mole equivalent average chain length will be:
If the C to C alkyl fraction is 20 mole percent C and 30 mole percent C then its mole equivalent average chain length will be:
Thus, in this aforesaid illustration, the mole equivalent average chain length of the C alkyl fraction, i.e. C is greater than 4 carbons from the mole equivalent average chain length of the C1044 fraction, i.e. C Or a difference of 5 carbons, and this example is in the preferred scope of the invention.
The vinyl aromatic hydrocarbons useful in the invention include: styrene, para tert-butyl styrene, p-methyl styrene and p-ethyl styrene, all of which are made in commercial quantities and are available in a state of purity designated polymerization grade. Examples of other vinyl aromatics included in the invention are 3,5-dimethyl styrene, p-n-hexyl styrene, l-vinyl naphthalene or 4-methyl, 1- vinyl naphthalene which may be made by standard synthetic procedures in the literature such as reduction of the appropriate alkyl or dialkyl acetophenone or methyl alkyl naphthyl ketone to the alpha aryl ethanol followed by dehydration over a molten eutective of sodium and potassium hydroxides.
Examples of vinyl alkanoates, include vinyl alcohol esters of C to C preferably C to C saturated fatty acids. Preferred is vinyl acetate in a state of purity suitable for polymerization, and which is readily available in commercial quantities. Vinyl esters of the higher alkanoic acids may be obtained by direct synthesis from the higher acid and acetylene in the presence of a zinc phosphate catalyst, or may be made from the higher acid and vinyl acetate by ester interchange using a mercuric acetate catalyst.
The symdialkyl fumarates in which both alkyl radicals in the ester are the same are readily prepared from fumaric acid and the appropriate alcohol. A typical laboratory procedure is as follows: A quantity of fumaric acid, contained in a reaction flask fitted with a Dean- Stark water trap and a reflux condenser, is mixed with from to 20 mole percent excess of the alcohol, about 0.5 to 2 percent of an acid catalyst such as p-toluene sulfonic acid monohydrate, based on weight of reactants, and about 10 to 50 percent of an entraining agent such as benzene, toluene or xylene based on volume of reactants, and the mixture heated under reflux. The lower layer of water settling in the trap is usually withdrawn as formed, and the upper layer of hydrocarbon and alcohol returned to the flask. When no further formation of water is observed, the flask contents are cooled, washed with a dilute solution of an alkali to neutralize the acid catalyst, water washed, dried, filtered and the entrainer and excess alcohol removed by distillation, preferably under reduced pressure. The ester may be further purified by contacting with active charcoal, clay, or alumina or may be distilled under high vacuum.
Alternatively, the same procedure may be used with a small molal excess of fumaric acid, and the excess acid and half-ester removed by extraction with an alkaline solution. Final purification is the same as in the case where excess alcohol is used.
The unsymmetrical dialkyl fumarates can be prepared by a number of methods. In one method, which is similar to the aforedescribed method used to prepare the symesters, one molar equivalent of fumaric acid is mixed with one molar equivalent of each alcohol forming the unsymester. The acid catalyst and entraining agent are added and the mixture heated under a Dean-Stark trap and reflux condenser until the theoretical quantity of water has been obtained. The unsymester product is recovered and purified by the same procedures used for purification of the symesters.
In a second method, one molar equivalent of fumaryl chloride, which may be prepared by the action of phosphorus penta-chloride on either fumaric acid or maleic anhydride, is reacted with one molar equivalent of each of the alcohols forming the unsymester in the presence of an excess of pyridine. Isolation and recovery of the unsymester is the same as for the symesters.
In a third method, a slight excess of both alcohols may be used and the excess alcohols removed after esterification is complete, or an excess of acid may be used and the excess acid and any half-ester removed by extraction with an alkaline solution.
Mixed esters, comprising a mixture of both symand unsymesters, may be prepared by any of the three methods by the simultaneous esterification of a total of two moles of three or more alcohols with one mole of fumaric acid or fumaryl chloride. As in method three, an excess of alcohols or acid may be used.
Where the unsymester is not further purified by fractional distillation, it is to be understood that small quantities of symdialkyl fumarate esters corresponding to the individual alcohols comprising the unsymester may be present in the final product. Estimates of the purity of either the symor unsymester may be obtained from analyses for neutralization number, saponification number and from gas-chromatographic analysis.
A variety of polymerization methods, suitable for the preparation of the interpolymers of this invention, have been described in the scientific and patent literature. Emulsion and suspension systems may be used, but preferred are solution methods using peroxide, hydroperoxide, per acid and azo free-radical initiators. In a typical solution procedure, monomers, solvent and initiator contained in a reactor, are sparged with oxygen-free nitrogen to dis- EXAMPLES 1-5 A series of symdialkyl fumarates from symdidecyl fumarate to symdioctadecyl fumarate was prepared as follows: 87.5 grns. of fumaric acid (0.75 mole) was mixed with 200 gms. of mixed xylenes, 1.35 moles of the appropriate straight chain alcohol added, along with 2 wt. percent of p-toluene, sulfonic acid monohydrate, based on weight of fumaric acid and alcohol, and the mixture heated to reflux under a Dean-Stark trap. When no further water was formed, the flask contents were cooled, filtered and washed three times with 300 ml. portions of 3 wt. percent aqueous sodium hydroxide, adding diethyl other if necessary to aid separation of layers. The upper organic layer was then washed twice with 300 ml. portions of distilled water, dried over 30 gms. of anhydr. sodium sulfate, filtered, the ether removed on the steam bath and the xylene removed under a pressure of about 10 mm. Hg. The product was sparged with nitrogen under vacuum to remove the last traces of xylene. Table 1 gives the amounts of each alcohol and the quantity of toluene sulfonic acid used for each preparation.
TABLE I.--PREPARATION OF SYM-DIALKYL FUMARATES Grams Grams 1 Example Grams CH CsHr- H20 No. Fumarate ester alcohol S0311 recovered 2 Symdidecyl 213.3 6.00 23.4
2 Symdidodeeyl. 251. 5 6. 23. 2 3- Symditetradecy 289. 5 7. 52 24. 7 4--. Symdihexadeeyl 326. 7 8. 28 23. 9 5 Symdioctadecyl 365. 0 9.00 24.4
1 Monohydrate. 3 Theoretical water equals 24.3 grams.
EXAMPLE 6 Unsym-n-decyl, n-hexadecyl fumarate was prepared by essentially the same procedure used for the symesters in Examples 1 to 5. A reaction flask fitted with a heating mantle, Dean-Stark trap and reflux condenser was charged with: 87.5 grns. of fumaric acid, 106.7 gms. n-decanol, 163.4 grns. n-hexadecanol, 7.2 gms. p-toluene sulfonic acid monohydrate, and 200 gms. of mixed xylenes. The mixture was heated to boiling under reflux and the water formed in the reaction drawn 01f from the trap. 23.5 ml. of water was obtained. Isolation and recovery of the ester was the same as above for the symesters.
All of the polymerization experiments were run in thick-walled borosilicate polymerization tubes, contained in an oil bath maintained at 70 C., for a period of 6 hours. The tube contents were stirred during the reaction period by means of a glass enclosed magnetic stirring bar. Monomers, solvent and free-radical initiator were charged to the tube, air displaced by bubbling oxygenfree nitrogen through the reaction mixture and the tube then sealed. At the end of the reaction period the tube was opened and the viscous contents were added to about 20 volumes of rapidly agitated anhydrous methanol. The polymeric product which separates as a solid was collected and dried overnight in a vacuum oven at a pressure of torr. Samples of each product were checked for monomer content by infra-red spectroscopy and number average molecular weight at vapor pressure osmometry. The number average molecular weights of the resultant products were estimated to be in the range of about 5000 to about 20,000.
Samples of each of the polymeric products were tested for pour point at a concentration of 0.35 wt. percent in a compounded 10W40 base oil consisting of 84.7 parts of a solvent extracted, dewaxed neutral oil having a viscosity at 100 F. of 150 S.U.S., 5.4 parts of a solvent extracted, dewaxed neutral oil having a viscosity at 100 F. of 330 SUS and 9.9 parts of a detergent-inhibitor mixture comprising the condensation product of a poly(ethylene amine) with a polyisobutylene succinic anhydride; an alkaline earth mahogany sulfonate; zinc dithioclialkyl phosphate and an antioxidant. The compounded base oil had an A.S.T.M. pour point of F. and a viscosity of 6.2 centistokes.
Each of the polymeric products was tested for compatibility and pour point with a commercially available ethylene-propylene copolymer (hereinafter designated EPC) which had an ethylene content of about 75 wt. percent, a crystalline content of about a weight average molecular weight (M of about 80,000, and a number average molecular weight (M,,) of about 40,000, made by a hydrogen moderated Ziegler-Natta synthesis. Approximately wt. percent of the EPC was blended into the above compounded l0W40 base oil to yield an oil having a viscosity at 210 F. of 14.0 centistokes. The compounded base oil containing the EPC had a pour point of 0 F.
EXAMPLE 7 Type (A) and (AD) polymers The unsymester from Example 6, unsymn-decyl, nhexadecyl fumarate, was polymerized with styrene, and with styrene and vinyl acetate as follows:
TABLE II Example number 1 7 (A) 7 (AD) Unsymester of Example 6, gms-.. 9. 6 9. G Styrene, gms 4. 6 2. 3 Vinyl acetate, gms 1.9 Azo bis(isobutyronitrile) gms. 0. 2 0. 2 Cyclohexane, gms 10. 0 10. 0 Yield of polymer, gms. 11. 6 10.0 Pour point, F. (ASTM-D97):
0.35 wt. percent of polymer in base oil -31 31 0.35 wt. percent polymer in base oil plus EPC -28 29 1 Quantities of monomers, catalyst and solvent sealed in air-free tube, heated and stirred for 6 hrs. at 70 C.
t llgotduct isolated by precipitation in methanol, dried under vacuum a orr.
EXAMPLE 8 Type (B) and (BD) polymers The symester of Example 2, symdidodecyl fumarate, and the symester of Example 4, symdihexadecyl fumarate were mixed and interpolymerized with styrene (Type (B) interpolymer) and with styrene and vinyl acetate (Type (BD)) interpolymer as follows:
TABLE III Example number 1 8 (B) 8 (BD) Symdidodecyl iumarate, gms 4. 5 4. 5 Symdihexadecyl fumarate, gms 5. 6 5. 6 Styrene, gms 4. 6 2. 3 Vinyl acetate, gms 1.9 Azo bis(isobutyronitrile), gms 0. 2 0. 2 Cyclohexane, gms l0. 0 l0. 0 Yield of polymer, gmsl 11. 8 11.4 Pour point, F. (ASTM-D97):
0.35 wt. percent polymer in base oil 31 31 0.35 wt. percent polymer in base oil plus EPC -27 26 Footnotes 1 and 2 same as for Table II.
8 EXAMPLE 9 Type (C) interpolymer Unsymdecyl, hexadecyl fumarate from Example 6 was mixed with symdidecyl fumarate of Example 1, and symdihexadecyl fumarate of Example 4, and interpolymerized with styrene as follows:
TABLE IV Example No. 9L Unsymester of Example 6, gms 4.8 Symester of Example 1, gms 2.0 Symester of Example 4, gms. 2.8 Styrene, gms. 4.6 Azo bis-(isobutyronitrile) gms. 0.2 Cyclohexane, gms 10.0 Yield polymer, gms. 11.8
Pour point, F. (ASTM D97) 0.35 wt. percent polymer in base oil-i-EPC --24 Notes 1 and 2 same as in Table II.
Samples of the interpolymers compounded with the base oil and EPC showed no signs of incompatibility and were stable in storage. In contrast to the above results, samples of the same base oil containing EPC when mixed with several commercially available pour point depressants showed a rise in pour points and separation in storage.
While only one test concentration has been shown for the pour point depressants of this invention, namely 0.35 wt. percent, the interpolymers of this invention are eflective at a concentration in the range of 0.1 to 5.0, e.g. 0.1 to 2.0 Wt. percent in a wide variety of distillates, solvent extracted neutrals and residual bright stocks. The interpolymers are also compatible with a wide variety of viscosity index improvers, oiliness agents, antiwear additives, metallic and ashless detergents, antioxidants and antifoaming agents. The polymers of the invention can be used in mineral lubricating oils to thereby form automotive crankcase lubricants, aircraft engine lubricants, gear oils, transmission fluids, etc. The mineral lubricating oils can be of any usual type, including those derived from the ordinary parafiinic, naphthenic, asphaltic, or mixed base mineral crude oils by suitable refining methods. Concentrates comprising a minor proportion, e.g. 5 to 45, wt. percent of the polymer in a major amount of oil, e.g. 95 to 55, wt. percent oil, preferably a mineral lubricating oil, with or without other additives present, can also be prepared for ease of handling.
What is claimed is:
1. A lubricating oil composition comprising (a) a major proportion of a mineral lubricating oil, (b) 0.5 to 10 wt. percent of a Ziegler-Natta viscosity index-improving copolymer of ethylene and C to C alpha--o1efin comprising about 40 to 83 wt. percent ethylene and having a Weight average molecular weight of 10,000 to 200,000, said copolymer having a tendency to interact with Wax molecules in lubricating oils; and (c) 0.1 to 5.0 wt. percent of an oil-soluble pour depressant interpolymer which minimizes said ineraction wherein said interpolymer has a number average molecular weight of 2,000 to 50,000 and is derived from (i) 10 to 90 mole percent styrene or vinyl naphthalene or alkyl derivatives of said styrene or vinyl naphthalene having a total of 8 to 14 carbon atoms in the molecule with (ii) 10 to 90 mole percent of an unsymmetrical C to C dialkyl fumarate in which the mole equivalent average chain length in each alkyl radical in said dialkyl fumarate dilfers by at least 4 carbon atoms; wherein 20 to mole percent of the alkyl groups of said fumarate are in the range of C to C and 80 to 20 mole percent of said fumarate are in the range of C and C said fumarate being formed by the esterification of fumaric acid or fumaryl chloride with a mixture of a C to C alcohol and a C to C alcohol; and (iii) 0 to 30 mole percent of at least one vinyl alcohol ester of a C to C alkanoic acid.
2. The composition of claim 1 wherein said interpolymer is based on styrene and unsymmetrical-n-decyl, nhexadecyl fumarate.
3. The composition of claim 1 wherein said vinyl alcohol ester is vinyl acetate.
4. The composition of claim 1 wherein said alphaolefin is propylene.
5. The composition of claim 1 wherein said copolymer is an ethylene-propylene copolymer which contains about 75 wt. percent ethylene, has a crystalline content of about 5 wt. percent, a weight average molecular weight of about 80,000 and a number average molecular Weight of about 40,000.
References Cited UNITED STATES PATENTS Hollyday et a1 2525 6 D Cashman et al. 252--56 D X Tutwiler et al. 25256 D X 10 WARREN H. CANNON, Primary Examiner US. Cl. X.R.