GB2030994A - Novel Foam Inhibiting Polymers and Lubricants Containing Them - Google Patents

Abstract

Terpolymers of 55-75% of a C6-16 alkyl acrylate, 15-30% of C1-6 alkyl acrylate, and 2-20% of a vinyl alkylether or vinyl alkanoate are useful in very small amounts in lubricating oils, especially gear lubricants, to inhibit foam. The preferred terpolymers are terpolymers of 2- ethylhexyl acrylate, ethyl acrylate and vinyl acetate.

Description

SPECIFICATION Novel Foam Inhibiting Polymers and Lubricants Containing them This invention relates to polymeric compositions of matter useful as foam inhibitors in lubricants, especially viscous lubricants such as gear lubricants. More particularly, it relates to polymeric compositions comprising: (A) From about 55% to about 75% by weight of units derived form at least one alkyl acrylate in which the alkyl groups contain from about 6 to about 16 carbon atoms; (B) from about 15% to about 30% of units derived from at least one alkyl acrylate other than that of A in which the alkyl groups contain from 1 to about 6 carbon atoms; and (C) from about 2% to about 20% of units derived from at least one monomer of the formula 0H2=CH-X wherein X is OR or

and R is a lower alkyl group.

The compounding of lubricating oils to provide properties essential for operation of engines, gear trains and the like is now an expedient well known to those skilled in the art. Many diverse types of additives are incorporated in such lubricating oils, to accomplish such purposes as dispersing and/or removing insoluble impurities, inhibiting oxidation and corrosion, and improving extreme pressure properties. It is usually found, however, that compounded lubricating oils containing such additives have an undesirable tendency to foam during use. Therefore, it is necessary to introduce anti-foam agents into the lubricant to counteract this tendency.

Typical of anti-foam agents suitable for use in lubricants are silicones of various structures and polymersierived from alkyl acrylates or from similar monomers. The polymers are exemplified by those disclosed in U.S. Patent 3,1B61588, including copolymers of two different alkyl acrylates in which the alkyl groups contain an average of at least three but less than seven carbon atoms, and copolymers of one alkyl acrylate and one of several other comonomers, vinyl acetate being one of the suitable comonomers.

In the compounding of additive-containing lubricants, it is necessary to achieve a balance between the amounts of the various additives so that they do not inhibit or undesirably enhance each other's activity. One feature to be considered in achieving this balance is that the amounts of additives (including foam inhibitors) which do not directly influence the lubricating quality of the compounded lubricant should be kept to the absolute minimum adequate to achieve their purpose. Thus, it is desirable to develop foam inhibitors which may be effectively incorporated in lubricants in extremely small amounts. It is also of interest to develop foam inhibitors which are capable of being effectively used in a wide variety of base stocks, both natural and synthetic.

A principal aim, therefore, was to produce new polymeric compositions of matter suitable for use in compounded lubricants, especially gear oils.

A further aim was to produce polymers which are useful as foam inhibitors for lubricating oils.

Another aid was to provide foam inhibiting polymeric additives which are effective in a wide variety of lubricating oil base stocks.

Still another aim was to provide additives of this type which are capable of effective operation when incorporated in the lubricant in extremely small amounts.

As will be apparent from the first paragraph hereof, the polymers of this invention are terpolymers, the major proportion of which (portion A) comprises units derived from at least one alkyl acrylate in which the alkyl groups contain from about 6 to about 16 carbon atoms.

Suitable alkyl acrylates for this purpose include the hexyl acrylates, the octyl acrylates (including 2-ethylhexyl acrylate), and the nonyl, decyl, dodecyl and hexadecyl acrylate, irrespective of the chain structure of the alkyl groups. The especially preferred acrylate for portion A is 2ethylhexyl acrylate.

Portion B comprises units derived from at least one acrylate in which the alkyl group has a chain length from 1 to about 6 carbon atoms. Thus, portion B may be derived from such monomers as methyl acrylate, ethyl acrylate, or the butyl, amyl or hexyl acrylates. When portion A has an alkyl chain length of about 6 (for example, when it is derived from a hexyl acrylate), the alkyl moiety of portion B will be of lesser chain length (for example. derived from an amyl acrylate).

Portion C is derivea from at least one vinyl monomer of the indicated formula; that is, from a vinyl lower alkanoate or a vinyl lower alkyl ether.

By "lower" is meant a group which contains no more than 7 carbon atoms. Thus, suitable vinyl carboxylates are vinyl acetate, vinyl propionate, the vinyl butyrates, and the vinyl hexanoates and heptanoates, all isomers being included; and suitable vinyl alkyl ethers include vinyl ethyl ether, the vinyl butyl ethers, the vinyl pentyl ethers, and the vinyl heptyl ethers, all isomers being included.

Vinyl acetate and vinyl ethyl ether are the preferred sources of portion C.

The polymers of this invention contain about 55~75% by weight of portion A units, preferably about 60~70% and most desirably about 6568%. Portion B comprises about 15~30% thereof, preferably about 20~30% and most desirably about 22-26%. Portion C comprises about 2~20% and most desirably about 510%. The number average molecular weights of the polymers are generally from about 10,000 to about 50,000, as determined by gel permeation chromatography.

The polymers of this invention may be prepared by any suitable method, typically involving the use of a free radical polymerization initiator. Polymerization in bulk, solution, suspension or emulsion is suitable. Preferrred is polymerization in solution in a substantially inert, normally liquid organic diluent, typically an aliphatic or aromatic hydrocarbon such as hexane, octane, naphtha, benzene, toluene, xylene, mineral oil or the like. Polymerization temperatures between about 600 and about 1 5000. are ordinarily suitable. In order to insure incorporation of the various monomeric units in the polymer in the desired proportions, it is often preferred to introduce the monomer mixture into the reaction vessel incrementally or gradually.

When polymerization is complete, the diluent may be removed if desired although removal thereof is frequently not necessary.

The preparation of the polymers of this invention is illustrated by the following examples.

All parts and percentages are by weight.

Example 1 A mixture of 250 parts of 2-ethylhexyl acrylate, 100 parts of ethyl acrylate, 20 parts of ethyl vinyl ether, 247 parts of toluene and 0.35 part of benzoyl peroxide is prepared and 25% thereof is charged to a reaction flask fitted with an addition funnel, a mechanical stirrer, a nitrogen sparging mechanism and a reflux condenser. This mixture is stirred for 15 minutes under reflux, with nitrogen sparging, whereupon polymerization begins. The remainder of the mixture is gradually added over 45 minutes, during which period the reaction temperature gradually increases to 11000. Heating is continued for about 1-1/2 hours, after which an additional 0.08 part of benzoyl peroxide is added and heating is continued for an additional 1-1/2 hours.The mixture is then filtered through a filter aid material to give viscous solution of the desired terpolymer comprising about 67% 2-ethylhexyl acrylate units, about 27% ethyl acrylate units, and about 6% ethyl vinyl ether units.

Example 2 Following substantially the procedure of Example 1, a terpolymer is prepared from 250 parts of 2-ethylhexylacrylate, 1 00 parts of ethyl acrylate, 20 parts of vinyl acetate, 247 parts of toluene and 0.43 part of benzoyl peroxide (added in 2 increments). The resulting terpolymer (obtained as a 60% solution in toluene) contains about 67% 2-ethylhexyl acrylate units, about 27% ethyl acrylate units, and about 6% vinyl acetate units.

Example 3 Following substantially the procedure of Example 1, a terpolymer is prepared from 250 parts of 2-ethylhexyl acrylate, 100 parts of ethyl acrylate, 40 parts of vinyl acetate, 260 parts of toluene and 0.43 part of benzoyl peroxide (added in 2 increments). The terpolymer is obtained as a 60% solution in toluene and contains about 64% 2-ethylhexyl acrylate units, about 26% ethyl acrylate units, and about 10% vinyl acetate units.

Its number average molecular weight is about 24,000.

Example 4 Following substantially the procedure of Example 1, a terpolymer is prepared from 250 parts of 2-ethylhexyl acrylate, 100 parts of ethyl acrylate, 80 parts of vinyl acetate, 287 parts of toluene and 0.45 part of benzoyl peroxide (added in increments of 0.35 and 0.10 part). The desired terpolymer is obtained as a 60% solution in toluene and comprises approximately 58% 2ethylhexyl acrylate units, 23% ethyl acrylate units, and 1 9% vinyl acetate units.

As previously indicated, the polymers of this invention are useful as additives for lubricants (especially lubricants of high viscosity such as gear lubricants), in which they function primarily as foam inhibitors. They can be employed in a variety of lubricants based on diverse oils of lubricating viscosity, including natural and synthetic lubricating oils and mixtures thereof.

These lubricants include crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, including automobile and truck engines, two-cycle engines, aviation piston engines, marine and railroad diesel engines, and the like. They can also be used in gas engines, stationary power engines and turbines and the like. Automatic transmission fluids, transaxle lubricants, gear lubricants, metal-working lubricants, hydraulic fluids and other lubricating oil and grease compositions can also benefit from the incorporation therein of the polymers of the present invention.

Natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil) as well as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils. Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins [ e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1- hexenes), poly( I -octenes), poly( 1 -decenes), etc.

and mixtures thereof]; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyis, etc.), alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc. constitute another class of known synthetic lubricating oils. These are exemplified by the oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methylpolyisopropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1000-1 500, etc.) or mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3~C8 fatty acid esters, or the C13 Oxo acid diester of tetraethylene glycol.

Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc.).Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid, and the like.

Esters useful as synthetic oils also include those made from C5 to C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils and silicate oils comprise another useful class of synthetic lubricants (e.g., tetraethyl silicate, tetraisopropyl silicate, tetra-(2-ethylhexyl) silicate, tetra-(4-methyl-2-ethylhexyl) silicate, tetra-(ptert-butylphenyl) silicate, hexa-(4-methyl-2pentoxy)-disiloxane, poly(methyl)siloxanes, poly (methylphenyl)siloxanes, etc.). Other synthetic lubricating oils include liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid, etc.), polymeric tetrahydrofurans and the like.

Unrefined, refined and rerefined oils (and mixtures of each with each other) of the type disclosed hereinabove can be used in the lubricant compositions of the present invention.

Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from distillation or ester oil obtained directly from an esterification process and used without further treatment would be an unrefined oil. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Many such purification techniques are known to those of skill in the art such as solvent extraction, acid or base extraction; filtration, percolation, etc. Rerefined oils are obtained by processes similar to those used to obtain refined oils applied to refined oils which have been already used in service.Such rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

Generally, the lubricants of the present invention contain an amount of the polymer of this invention sufficient to inhibit foam therein.

Normally this amount will be about 20 to about 2000 parts per million (ppm.), preferably about 50 to about 1000 ppm. In many instances the concentration of a polymer of this invention necessary to inhibit foam is substantially lower than that of other known foam inhibitors; for example, lower than about 100 ppm. Typical gear lubricants of this invention may comprise principally a relatively viscous (e.g. SAE 80, 90 or 80W~90) base oil known additives for gear lubricants in conventional proportions, and a polymer of any of Examples 1-4 in the amount of 75, 100,200,400 or 800 ppm.

The invention also contemplates the use of other additives in combination with the polymers of this invention. Such additives include, for example, detergents and dispersants of the ashproducing or ashless type, corrosion- and oxidation-inhibiting agents, pour point depressing agents, extreme pressure agents, color stabilizers and auxiliary anti-foam agents.

The ash-producing detergents are exemplified by oil-soluble neutral and basic salts of alkali or alkaline earth metals with sulfonic acids, carboxylic acids, or organic phosphorus acids characterized by at least one direct carbon-tophosphorus linkage such as those prepared by the treatment of an olefin polymer (e.g., polyisobutene having a molecular weight of 1000) with a phosphorizing agent such as phosphorus trichloride, phosphorus heptasulfide, phosphorus pentasulfide, phosphorus trichloride and sulfur, white phosphorus and a sulfur halide, or phosphorothioic chloride. The most commonly used salts of such acids are those of sodium, potassium, lithium, calcium, magnesium, strontium and barium.

The term "basic salt" is used to designate metal salts wherein the metal is present in stoichiometrically larger amounts than the organic acid radical. The commonly employed methods for preparing the basic salts involve heating a mineral oil solution of an acid with a stoichiometric excess of a metal neutralizing agent such as the metal oxide, hydroxide, carbonate, bicarbonate, or sulfide at a temperature above 5000. and filtering the resulting mass. The use of a "promoter" in the neutralization step to aid the incorporation of a large exess of metal likewise is known.Examples of compounds useful as the promoter include phenolic substances such as phenol, naphthol, alkylphenol, thiophenol, sulfurized alkylphenol, and condensation products of formaldehyde with a phenolic substance; alcohols such as methanol, 2-propanol, octyl alcohol, Cellosolve, Carbitol, ethylene glycol, stearyl alcohol, and cyclohexyl alcohol; and amines such as aniline, phenylenediamine, phenothiazine, phenyl-p- naphthylamine, and dodecylamine. A particularly effective method for preparing the basic salts comprises mixing an acid with an excess of a basic alkaline earth metal neutralizing agent and at least one alcohol promoter, and carbonating the mixture at an elevated temperature such as 60-200"0.

Ashless detergents and dispersants are so called despite the fact that, depending on its constitution, the dispersant may upon combustion yield a non-volatile material such as boric oxide or phosphorus pentoxide; however, it does not ordinarily contain metal and therefore does not yield a metal-containing ash on combustion. Many types are known in the art, and any of them are suitable for use in the lubricants of this invention. The following are illustrative: (1) Reaction products of carboxylic acids (or derivatives thereof) containing at least about 34 and preferably at least about 54 carbon atoms with nitrogen-containing compounds such as amine, organic hydroxy compounds such as phenols and alcohols, and/or basic inorganic materials.Examples of these "carboxylic dispersants" are described in British Patent 1,306,529 and in many U.S. patents including the following: 3,163,603 3,351,552 3,541,012 3,184,474 3,381,022 3,542,678 3,215,707 3,399,141 3,542,680 3,219,666 3,415,750 3,567,637 3,271,310 3,433,744 3,574,101 3,272,746 3,444,170 3,576,743 3,281,357 3,448,048 3,630,904 3,306,908 3,448,049 3,632,510 3,311,558 3,451,933 3,632,511 3,316,177 3,454,607 3,697,428 3,340,281 3,467,668 3,725,441 3,341,542 3,501,405 Re 26,433 3,346,493 3,522,179 (2) Reaction products of relatively high molecular weight aliphatic or alicyclic halides with amines, preferably polyalkylene polyamines.

These may be characterized as "amine dispersants" and examples thereof are described for example, in the following U.S. patents: 3,275,554 3,454,555 3,438,757 3,565,804 (3) Reaction products of alkyl phenols in which the alkyl group contains at least about 30 carbon atoms with aldehydes (especially formaldehyde) and amines (especially polyalkylene polyamines), which may be characterized as "Mannich dispersants". The materials described in the following U.S. patents are illustrative: 3,413,347 3,725,480 3,697,574 3,726,882 3,725,277 (4) Products obtained by post-treating the carboxylic, amine or Mannich despersants with such reagents as urea, thiourea, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boron compounds, phosphorus compounds or the like.Exemplary materials of this kind are described in the following U.S.

patents: 3,036,003 3,282,955 3,493,520 3,639,242 3,087,936 3,312,619 3,502,677 3,649,229 3,200,107 3,366,569 3,513,093 3,649,659 3,216,936 3,367,943 3,533,945 3,658,836 3,254,025 3,373,111 3,539,633 3,697,574 3,256,185 3,403,102 3,573,010 3,702,757 3,278,550 3,442,808 3,579,450 3,703,536 3,280,234 3,455,831 3,591,598 3,704,308 3,281,428 3,455,832 3,600,372 3,708,522 (5) Interpolymers of oil-solubilizing monomers such as decyl methacrylate, vinyl decyl ether and high molecular weight olefins with monomers containing polar substituents, e.g., aminoalkyl acrylates or acrylamides and poly-(oxyethylene)substituted acrylates.These may be characterized as "polymeric dispersants" and examples thereof are disclosed in the following U.S. patents: 3,329,658 3,666,730 3,449,250 3,687,849 3,519,565 3,702,300 The above-noted patents are incorporated by reference herein for their disclocures of ashless dispersants.

Extreme pressure agents and corrosion-and oxidation-inhibiting agents are exemplified by chlorinated aliphatic hydrocarbons such as chlorinated wax; organic sulfides and polysulfides such as benzyl disulfide, bis(chlorobenzyl)disu Ifide, dibutyl tetrasulfide, sulfurized methyl ester of oleic acid, sulfurized alkylphenol, sulfurized dipentene, and sulfurized terpene; phosphosulfurized hydrocarbons such as the reaction product of a phosphorus sulfide with turpentine or methyl oleate; phosphorus esters including principally dihydrocarbon and trihydrocarbon phosphites such as dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenyl phosphite, dipentylphenyl phosphite, tridecyl phosphite, distearyl phosphite, dimethyl naphthyl phosphite, oleyl 4-pentylphenyl phosphite, polypropylene (molecular weight 500)-substituted phenyl phosphite, diisobutyl-substituted phenyl phosphite; metal thiocarbamates, such as zinc dioctyldithiocarbamate, and barium heptylphenyl dithiocarbamate; Group II metal phosphorodithioates such as zinc dicyclohexylphosphorodithioate, zinc dioctylphosphorodithioate, barium di(heptylphenyl)-phosphorodithioate, cadmium dinonylphosphorodithioate, and the zinc salt of a phosphorodithioic acid produced by the reaction of phosphorus pentasulfide with an equimolar mixture of isopropyl alcohol and n-hexyl alcohol.

The compositions of this invention can be added directly to the lubricant. However, they are often diluted with a substantially inert, normally liquid organic diluent such as mineral oil, naphtha, benzene, toluene or xylene, to form an additive concentrate. These concentrates usually contain from about 5% to about 90% by weight of the polymer of this invention and may contain, in addition, one or more other additives known in the art or described hereinabove.

Claims (11)

Claims

1. A polymeric composition comprising: (A) From about 55% to about 75% by weight of units derived from at least one alkyl acrylate in which the alkyl groups contain from about 6 to about 16 carbon atoms; (B) from about 15% to about 30% of units derived from at least on alkyl acrylate other than that of A in which the alkyl groups contain from 1 to about 6 carbon atoms; and (C) from about 2% to about 20% of units derived from at least one monomer of the formula CH2=CH-X wherein X is OR or

and R is a lower alkyl group.

2. A composition according to claim 1 wherein the alkyl acrylate of A is 2-ethylhexyl acrylate.

3. A composition according to claim 2 wherein the alkyl acrylate of B is ethyl acrylate.

4. A composition according to claim 1 wherein the monomer of C is vinyl acetate or ethyl vinyl ether.

5. A composition according to claim 4 wherein the alkyl acrylate of A is 2-ethylhexyl acrylate.

6. A composition according to claim 5 wherein the alkyl acrylate of B is ethyl acrylate.

7. A composition according to claim 6 wherein the monomer of C is vinyl acetate.

8. A polymeric composition comprising from about 65% to about 68% by weight of 2ethylhexyl acrylate units, from about 22% to about 26% of ethyl acrylate units, and from about 5% to about 10% of vinyl acetate or ethyl vinyl ether units.

9. An additive concentrate comprising a substantially inert, normally liquid organic diluent and from about 5% to about 90% by weight of a polymer according to any one of claims 1-8.

10. A lubricating composition comprising a major amount of a lublicating oil and a minor amount of a polymer according to any of claims 1~8.

11. The invention in its several novel aspects.