SI9200219A - Dispersant poly(meth)acrylate viscosity index improvers - Google Patents

Abstract

This invention is concerned with copolymers derived from (a) one or more monomer selected from (C1-C24)alkyl methacrylates and (C1-C24)alkyl acrylates, and (b) one or more monomer selected from hydroxy(C2-C6)alkyl methacrylates and hydroxy(C2-C6)alkyl acrylates, and wherein the number of carbon atoms in the alkyl groups averages from about 7 to about 12. These polymers are useful as additives to lubricating oils for providing viscosity index improvement, dispersancy and low temperature fluidity properties without adversely affecting fluoropolymer seals and gaskets.

Description

(57) The present invention relates to copolymers derived from (a) one or more monomers selected from (C 1 -C 24) alkyl methacrylates and (C 1 -C 24) alkyl acrylates and (b) one or more monomers selected from hydroxy (C 2 -C 6) alkyl of methacrylates and hydroxy (C2-C6) alkyl acrylates, the average number of carbon atoms in the alkyl groups being from about 7 to 12. These polymers are useful as additives to lubricating oils to provide an improvement in the viscosity index, dispersibility or liquid properties at low temperature without detriment influences fluoropolymer seals.

Sl 9200219 A

ROHM AND HAAS ΟΟΜΡΑΝΥ

Poly (meth) acrylate dispersant viscosity index enhancers

The present invention relates to polymers derived from (a) one or more monomers selected from (C 1 -C 6 -alkyl methacrylates and / C 1 -C 6 -alkyl acrylates and (b) one or more monomers selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates and hydroxy (C ₂ C ₆ ) alkyl acrylates, wherein the number of carbon atoms in the alkyl groups averages from about 7 to about 12. These polymers are useful as additives to lubricating oils to provide an improvement in the viscosity, dispersibility and useful properties at low temperature without adversely affecting fluoropolymer seals New polymers are usually dissolved or dispersed in purified mineral lubricating oil for possible incorporation into mineral or synthetic base oil.

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Green lubricating oil for internal combustion engines, automatic transmission fluids and hydraulic fluids has relatively little change in viscosity over a wide temperature range, dispersing properties, and good low temperature fluidity, including low liquid point. Viscosity index (or VI) is a measure of the degree of viscosity change as a function of temperature; high viscosity index values indicate smaller variations in viscosity by varying temperature compared to low viscosity index values. Viscosity index enhancement additives having high viscosity index values combined with good low temperature fluidity allow the oil to flow at the lowest possible operating temperature, usually at engine start and when the temperature rises, to the operating range, the viscosity remains at a level suitable for good effect.

Polymer additives, according to various of these properties, are used to improve the effect of engine lubricating oils. Polymers of alkyl acrylates or alkyl methacrylates are successfully used to improve the viscosity index and as a depressant of the fluid point. Increased dispersion properties can be introduced into polymer compositions with polar, especially basic comonomers, such as e.g. vinyl heterocycles (e.g., N-vinylpyrrolidone, N-vinylimidazole, vinylpyridine, etc.), dialkylaminoalkyl methacrylates, N, N-dialkylaminoalkyl methacrylamides and the like. However, the grafting conditions required for the installation of basic comonomers containing nitrogen very often introduce poor shear properties. Additionally, viscosity indexing agents containing basic comonomers containing nitrogen may cause odor or reduce the performance of seals found in fluoropolymer-based automotive engines such as e.g. Viton fluoroelastomer.

US-A-3,311,597 illustrates a method for improving the viscosity index and dispersion properties of poly (methacrylate) polymers, including the copolymerization of alkyl methacrylates with tetrahydrofurfuryl methacrylate and the optional incorporation of hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-vinyl pyrrolidone or N-vinyl pyrrolidone. Poly (alkyl methacrylate) polymers with improved liquid point properties are based on the copolymerization of alkyl methacrylates with 9 to 23 mol% methacrylic acid followed by ethoxylation, with an average number of carbon atoms in the alkyl group of 12.5 to 14.3 shown in US-A-3,598,737. A lauryl methacrylate stearyl methacrylate copolymer of 23 mol% hydroxyethyl methacrylate is shown in US-A-3,249,545 for use in oil formulations containing bisphenol antioxidants.

In another method of providing dispersing agents for improving the viscosity index, EP-A-418610 demonstrates the use of polyalkyl (meth) acrylates, characterized in that 80-95.5% by weight of the copolymer is derived from (C ^ C ^ alkyl methacrylates and 0.5- 20% from hydroxy (C ₂ -C ₆ ) alkyl (meth) acrylate or multialkoxylated alkyl- (meth) acrylate, wherein the optional 0-17 wt% is derived from (C 1-6 alkyl) methacrylates.

Poly (methacrylate) polymers as oil additives for machine tools are based on 9299% (C 1 -C 6 alkyl methacrylate and 1-8% hydroxy (C ₂ -C ₃ ) alkyl methacrylate polymers with a number average molecular weight (M _n ) of 20,000- 60,000 are disclosed in Japanese Patent JP 52-018202B.These polymer additives are shown to be unfit for use as additives to dispersants for improving the viscosity index for engine oils.

None of these latter methods combine dispersibility, good viscosity index and compatibility with fluoropolymer sealants with good low temperature fluidity in each polymer. The present invention makes it possible to provide this combination of properties in a single polymer.

According to the present invention, a polymer is obtained by polymerization of monomers comprising:

(a) from about 90 to about 98% by weight of one or more monomers selected from (C 1 -C 6 alkyl methacrylates and (C 1 -C 6 alkyl alkyl acrylates; and (b) from less than 10 to about 2 wt% one or more monomers selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates and hydroxy- (C ₂ -C ₆ ) alkyl acrylates, and wherein the number of carbon atoms in the alkyl groups is on average from about 7 to about 12.

These polymers are useful as additives to lubricating oils to provide an improvement in the viscosity index, dispersibility and useful properties at low temperature without adversely affecting fluoropolymer seals. New polymers, when used in lubricating oils, are usually dissolved or dispersed in purified mineral lubricating oil for eventual incorporation into mineral or synthetic base oil. Examples of lubricating oils include casing oils, automatic transmission fluids, hydraulic fluids, gear oils and shock absorbing fluids.

Each of the monomers used according to the present invention may be a single monomer or a mixture with different numbers of carbon atoms in the alkyl moiety. The alkyl fraction of both (a) methacrylate and acrylate monomer and (b) hydroxyalkyl methacrylate and acrylate monomer is an important factor in the useful properties of the polymers of the invention. This means that the average number (n) of carbon atoms (C _n ) in the side chain of the alkyl and hydroxyalkyl groups of the acrylate or methacrylate backbone polymer is selected to maximize the viscosity index properties and to maintain the solubility of the polymer additive oil both in the new oil and in the used oil where the additive was already acting as a slurry agent. In general, if the average C _{n is} less than about 7, the resulting polymers may have poor solubility in the base oils and it is possible that the additives may not fully function as dispersants for improving the viscosity index. If the average C _{n is} significantly greater than about 12, worse low-temperature liquid properties can be observed. Low temperature means temperature below -5 ° C. Thus, the average number of carbon atoms in the alkyl group of acrylate or methacrylate monomers used to prepare the polymer additives is from about 7 to about 12, preferably from about to about 10, and more preferably from about 8 to about 10. In the case where the monomers or all acrylates or substantially all acrylates, the average carbon number of the side chain alkyl groups of the backbone polymer varies slightly and the average number of carbon atoms is the one that adjusts the solubility parameters of the corresponding acrylate backbone polymers. Such solubility parameters are already known and understood by those skilled in the art.

Preferably, monomer (a) is selected from (C ₁ -C ₆ alkyl methacrylates and (C ₁ -C ₆ alkyl alkyl acrylates and monomer (b), selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates and hydroxy (C ₂ -C ₆ ) alkyl The alkyl portion of one or the other monomer may be linear or branched Alkyl methacrylates and hydroxyalkyl methacrylates are preferred.

Mixtures of alkyl methacrylates and / or alkyl acrylates are preferably used to obtain a balance of desired useful properties relating to the improvement of the viscosity index, good dispersibility and usability at low temperature. Thus, in one embodiment of the invention, monomer (a) generally comprises (i) 0 to about 40% alkyl methacrylate or alkyl acrylate in which the alkyl group contains from 1 to 6 carbon atoms or mixtures thereof, (ii) from about 30 to about 90% alkyl methacrylate or alkyl acrylate in which the alkyl group contains from 7 to 15 carbon atoms, or mixtures thereof; and (iii) 0 to about 40% alkyl methacrylate or alkyl acrylate, in which the alkyl group contains from 16 to 24 atoms carbon or mixtures thereof, and monomer (b) comprises from less than 10 to about 2% hydroxyalkyl methacrylate or hydroxyalkyl acrylate in which the alkyl group contains 2 to 6 carbon atoms and is substituted by one or more hydroxyl groups or mixtures thereof. All percentages are by weight and are based on the total weight of the polymer and the total (i), (ii), (iii) and (b) is equal to 100% by weight of the polymer. The amount (s) in the polymer is preferably from 0 to about 25% and more preferably from 5 to about 15%; the amount (ii) is preferably from about 45 to about 85% and more preferably from about 50 to about 60%; the amount (iii) is preferably from about 5 to about 35% and more preferably from about 25 to about 35%; and the amount (b) is preferably from about 4 to about 8% and more preferably from about 5 to about 6%.

The proportion of the total weight of the monomers (a) and (b) may be from about 5 to about 40% by weight of (C 1 -C 6 alkyl methacrylates, (C 1 -C 6 alkyl alkyl acrylates, or mixtures thereof). (a) and (b) from about 5 to about 35% by weight of (C ₁₆ -C ₂₀ ) methacrylates, (C 1 -C 6) alkyl acrylates or mixtures thereof.

Examples of monomer (a), alkyl methacrylate and / or alkyl acrylate, where the alkyl group contains from 1 to 6 carbon atoms, also called short alkyl methacrylate or alkyl acrylate, are methyl methacrylate (MMA) methyl and ethyl acrylate, propyl methacrylate, butyl methacrylate. (BMA) and acrylate (BA), isobutyl methacrylate (IBMA), hexyl and cyclohexyl methacrylate, cyclohexyl acrylate and combinations thereof. Preferred short alkyl methacrylates are methyl methyl acrylate and butyl methacrylate.

Examples of monomer (a), alkyl methacrylate and / or alkyl acrylate, where the alkyl group contains from 7 to 15 carbon atoms, also referred to as middle alkyl methacrylates or alkyl acrylates are 2-ethylhexyl acrylate (EHA), 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, isodecyl methacrylate (IDMA based on a branched (C ₁₀ ) alkyl isomer mixture), undecyl methacrylate, dodecyl methacrylate (also known as lauryl methacrylate), tridecyl methacrylate, tetradecyl methacrylate, (also known as myristyl methacrylate) methacrylate, and combinations thereof. Also useful are: dodecyl-pentadecyl methacrylate (DPMA), a mixture of linear and branched isomers of dodecyl, tridecyl, tetradecyl and pentadecyl methacrylates; and lauryl myristyl methacrylate (LMA), a mixture of dodecyl and tetradecyl methacrylates. Preferred middle alkyl methacrylates are lauryl myristyl methacrylate and isodecyl methacrylate.

Examples of monomer (a), alkyl methacrylate and / or alkyl acrylate, where the alkyl group contains from 16 to 24 carbon atoms, also called long alkyl methacrylates or alkyl acrylates are hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, ezyl methacrylate, ether methacrylate and combinations thereof. Also useful are: cetyl eicosyl methacrylate (CEMA), a mixture of hexadecyl, octadecyl, goat and eicosyl methacrylate; and cetyl stearyl methacrylate (SMA), a mixture of hexadecyl and octadecyl methacrylate. Preferred long alkyl methacrylates are cetyl eicosyl methacrylate and cetyl stearyl methacrylate.

The medium and long alkyl methacrylates and alkyl acrylate monomers described above are generally prepared by standard esterification procedures, using the technical types of long-chain aliphatic alcohols and these commercially available alcohols are mixtures of alcohols of different chain lengths containing between 10 and 15 or 16 and 20 carbon atoms in the alkyl group. Thus, for the purposes of the invention, it is intended that alkyl methacrylate includes only so-called. alkyl methacrylate product, but also includes mixtures of alkyl methacrylates with a predominant amount, in particular e.g. alkyl methacrylate. Using these commercially available alcohols for the preparation of acrylate and methacrylate esters, the LMA, DPMA, SMA and CEMA monomer mixtures described above are obtained.

Examples of monomer (b) are those alkyl methacrylate and acrylate monomers, with one or more hydroxyl groups in the alkyl radical, especially those where the hydroxyl group is in position β (position 2) in the alkyl radical. Hydroxyalkyl methacrylate and acrylate monomers in which the substituted (C ₂ -C ₆ ) alkyl group is branched or unbranched are preferred. Hydroxyalkyl methacrylate and acrylate monomers suitable for use according to the present invention include 2-hydroxyethyl methacrylate (HEMA), 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, l-methyl-2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, l-hydroxypropyl acrylate methyl-2-hydroxyethyl acrylate, 2-hydroxybutyl methacrylate and 2-hydroxybutyl acrylate. Preferred hydroxyalkyl methacrylate and acrylate monomers are HEMA, 1-methyl-2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate. The mixture of the last two monomers is usually referred to as hydroxypropyl methacrylate or HPMA, which is more preferred hydroxyalkyl methacrylate than each of the components of HPMA.

Among the interesting hydroxyalkyl methacrylate and acrylate monomers are those monomers which are substantially free of the impurities of the descaling agent or precursor of the crosslinking agent, which may be present as a result of the monomer preparation process. By means of a crosslinker, we mean any polyfunctional substance that causes crosslinking of a polymer, such as e.g. ethylene glycol dimethacrylate. The presence of these cross-linking agents lowers the properties of the additives of the invention due to gel formation and related problems. Preferred hydroxyalkyl methacrylates and acrylates are those containing less than about 0.5% by weight and more preferably less than about 0.2% by weight and most preferably about 0.1% by weight or less of the crosslinker or the crosslinker precursor. In one embodiment of the invention, monomer (b) is selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates containing less than about 0.2% by weight of the crosslinker or the crosslinker precursor. In a further embodiment of the invention, monomer (b) is a mixture of 2-hydroxypropyl methacrylate and l-methyl-2hydroxyethyl methacrylate containing less than about 0.1% by weight of the crosslinker or the crosslinker precursor.

Preferred polymers are those where the monomer (a) comprises monomers where (i) is selected from one or more methyl methacrylate, butyl methacrylate and isobutyl methacrylate, (ii) is selected from one or more 2-ethylhexyl methacrylate , isodecyl methacrylate, dodecylpentadecyl methacrylate and lauryl myristyl methacrylate, (iii) selected from one or more cetyl stearyl methacrylate and cetyl eicosyl methacrylate and monomer (b) selected from one or more 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1-methyl-27 hydroxyethyl acrylate, 2-hydroxybutyl methacrylate and 2-hydroxybutyl acrylate.

A preferred polymer is one where the monomer (a) is about 10% methyl methacrylate, e.g. 55% isodecyl methacrylate and about 30% cetyl stearyl or cetyl eicosyl methacrylate and the monomer (b) is about 5% of a mixture of 2-hydroxypropyl methacrylate and the amount of l-methyl-2-hydroxyethyl methacrylate is about 5%.

Another preferred polymer is one in which the monomer (a) is about 20% butyl or isobutyl methacrylate, about 45% isodecyl methacrylate, and about 30% monomer selected from cetyl stearyl and cetyl eicosyl methacrylate and the monomer (b) is about 5 % of a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxyethyl methacrylate.

Another preferred polymer is one in which the monomer (a) is about 15% of the monomer selected from butyl and isobutyl methacrylate and about 80% of the monomer selected from lauryl myristyl and dodecyl-pentadecyl methacrylate and the monomer (b) is about 5% of the mixture 2-hydroxypropyl methacrylate and 1-methyl-2hydroxyethyl methacrylate.

Another preferred polymer is one in which the monomer (a) is about 5 to about 10% methyl methacrylate, about 85 to about 90% of the monomer selected from lauryl myristyl, isodecyl- or dodecyl-pentadecyl methacrylate and 0 to about 5% cetyl -Eicosyl methacrylate, and (b) is about 5% of a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxyethyl methacrylate.

A polymeric composition particularly preferred for use in automatic transfer fluids is one in which the additive is polymerized from monomers in which the monomer (a) is from about 0 to about 5% methyl methacrylate, about 80 to about 90% lauryl myristyl methacrylate and 0 to about 10% cetyl eicosyl methacrylate and monomer (b) about 5% mixture of 2-hydroxypropyl methacrylate and l-methyl-2-hydroxyethyl methacrylate.

Another preferred polymeric composition for use in automatic transmission fluids is one in which the additive is polymerized from monomers in which the monomer (a) is 0 to about 20% butyl methacrylate, about 65 to about 90% lauryl-myristyl methacrylate, and 0 to about 10% cetyl-eicosyl methacrylate and monomer (b) is about 5% of a mixture of 2-hydroxypropyl methacrylate and l-methyl-2-hydroxyethyl methacrylate.

In addition to the average number (n) of carbon atoms (C _n ) in the side chain alkyl and hydroxyalkyl groups of the acrylate or methacrylate backbone polymer, the nature of the alkyl fraction of methacrylate and acrylate monomers is an important factor in the useful properties of the polymers of the invention. E.g. a mixture of (C 1 -C 6 alkyl methacrylates and / or acrylates, (C ₇ -C ₁₅ ) alkyl methacrylates and / or acrylates and (C 1 -C 6 alkyl alkyl methacrylates and / or acrylates can be copolymerized with hydroxyalkyl (meth) acrylate such that the polymer has an average number of carbon atom contents in the alkyl side chains of 9. In this case, the viscosity and solubility index properties of the base oils are well balanced; additionally, the (C 1 -C 6 alkyl) meth acrylate portion of the polymer is wax-like and interacts with the wax components in the base oil, improving the low temperature properties, such as the fluid point, the low temperature pumping ability and starting the cold engine. If, on the other hand, an individual (C ₁₀ ) or (C ₁₂ ) alkyl (meth) acrylate monomer is copolymerized with hydroxyalkyl methacrylate to provide an average number of carbon atoms in the alkyl side chains 9, the resulting polymer additive has a satisfactory solubility in oil, but a low wax interaction which makes it worse e properties at low temperature, such as. poorer pumping ability due to enhanced viscosity, even if C _n values are similar for both types of polymer.

Thus, in order to obtain good usable properties at low temperature while maintaining a good balance of viscosity and solubility index properties in the base oils, it is preferable that the proportion of monomer (a) ranges from about 5 to about 40, preferably from about 5 to about 35, and more preferably from about 25 to about 35% by weight of (C 1 -C 6 -alkyl methacrylates and / or (C 1 -C 6 -alkyl acrylates, preferably an alkyl portion of C ₁₆ to C 4. Low temperature capacity refers to viscosities eg high shear and low shear conditions, eg cold engine start-up as measured by CCS (cold rotation simulator) viscosity, refers to viscosity at high shear conditions, on the other hand, the ability to pump oil at low temperatures as measured by mini rotational viscometer (MRV) refers to viscosity at low shear conditions, since long alkyl methacrylates and acrylate-like waxes act as depressants of the fluid point, with sp Remains the structure or morphology of the wax in the base oil at low temperatures. The amount of long alkyl methacrylate or acrylate used depends on the particular long alkyl methacrylate or acrylate selected, the base oil properties and the desired low temperature properties. In general, the greater the carbon content of the alkyl fraction, the more the monomers have wax-like properties and the less of this monomer is used. Because these long alkyl (meth) acrylates are similar to wax, too much of them can be caused by solidification in the base oil and loss of low temperature fluid.

The optimization of the ratio of long, medium and short alkyl (meth) acrylates depends on the base oils used in the formulation and the degree of desired performance. When the long monomer is optimized, then the ratio of the medium and short monomer is balanced to obtain the optimum viscosity and solubility index. The balanced formulation preferably has a carbon content of alkyl (C _n ) of from about 8 to about 10.

Therefore, in the preferred ranges for various monomers including hydroxyalkyl methacrylate and acrylate monomers and the average number of carbon atoms in the alkyl chain group of the fence polymer, the addition of the polymer of the present invention can give a machine oil composition having a viscosity and low temperature liquid oil properties with a lower degree of overall viscosity. E.g. SAE 10W-30 Oil meets the requirements and pumping capabilities of SAE 5W-30 Oil.

In these preferred areas, the polymers of the present invention also provide lower CCS viscosity while maintaining good pumping ability at low temperature (as measured by MR V) of lubricating oils, thus allowing the use of higher viscosity base oils. Therefore, the polymers of the invention allow for the more extensive use of these heavier base oils in formulated oils, resulting in lower costs, reduced oil consumption and also cleaner engines, since these heavier base oils are less volatile than low viscosity base oils and reduce the formation of piston loading. at high operating temperatures, especially for diesel engines.

Levels of short (C ₁ -C ₃ ) alkyl (meth) acrylates can be used to achieve a combination of polymer solubility, viscosity index, dispersion and low temperature properties (such as liquid point and cold start capability) of the polymers of the present invention. , such as methyl methacrylate from zero to about 25%, typically from about 5 to about 15% of the polymer. The solubility of a polymer refers to a property in which more hydrophilic or polar monomers, such as e.g. those with a low carbon (C ₁ -C ₃ ) content in the alkyl moiety provide a polymer that is less soluble in base oils than polymers from more hydrophobic monomers, such as e.g. those with a high carbon content (C ₄ or greater) in the alkyl chain. Therefore, if more than about 10% of methyl methacrylate is incorporated into some polymers, depending on the level of other polar monomers used, e.g. hydroxyalkyl methacrylate, the solubility in some base oils may not be sufficient for an additive to fully function as a dis10 pergressant to improve the viscosity index. On the other hand, using short (C ₄ -C ₆ ) alkyl (meth) acrylates, such as e.g. butyl methacrylate or isobutyl methacrylate can then be used from zero to about 40 wt.%, preferably 20 to 35 wt.% of these monomers, to ensure the optimum balance of the aforementioned properties, including solubility in the base oils.

The mass average molecular weight (M _w ) of the polymer of the present invention is not very critical. It must be sufficient to give the desired viscosity properties to the lubricating oil. As the mass-average molecular weights of polymers increase, they become more effective thickeners; however, they may be subject to mechanical degradation in specific applications. Finally, M _{w is} related to the thickening effect, cost, and type of application. Generally, the lubricating oil polymer additives of the present invention have M _w from about 100,000 to about 1,000,000 (as determined by gel permeation chromatography (GPC), using poly (alkylmethacrylate) standards); preferably, M _{w is} in the range of about 300,000 to about 800,000 in order to satisfy the specific purpose of using the oil, e.g. machine oil and automatic transmission fluid. Mass average molecular weights of from about 100,000 to about 300,000 are preferred for hydraulic fluids, gear oils and the like.

It will be apparent to those skilled in the art that the molecular weights stated throughout this description depend on the procedures by which they are determined. E.g. the molecular weights determined by gel permeation chromatography (GPC) and the molecular weights calculated by other methods may have different values. This is not molecular weight per se, but the derived properties and performance of the polymer additive (shear stability and compaction strength under applied conditions) are important. In general, the shear stability is inversely proportional to the molecular weight, and the use of a very shear stable additive requires more polymer to obtain good thickening.

The shear stability index (SSI) can be directly related to the molecular weight of the polymer and is a measure of the percentage viscosity contributed by the polymer additive due to shear and can be determined by measuring the sound shear stability according to ASTM D-2603-91 (issued by American Society for Testing and Materials). Generally, higher molecular weight polymers are exposed to a greater relative decrease in molecular weight when subjected to higher shear conditions, and as a result, these higher molecular weight polymers have higher SSI values. The SSI range of the polymers of the invention is from about 10 to about 75%, preferably from about 10 to about 25%, for low molecular weight polymers and from about 30 to about

50% for high molecular weight polymers. The desired SSI can be achieved either by changing the reaction conditions or by mechanical shear of a polymeric product of known molecular weight.

Typical representatives of the shear stability observed for lubricating oil additives of different mass average molecular weights (M _w ) are as follows: conventional poly (methacrylate) additives with M _w 130,000, 490,000 and. 880,000, have SSI values (99 ° C) of 0.5 and 20%, based on shear test on 3218 km of road for machine oil formulations; based on the 32.180 km test road for Automatic Transmission Fluid (ATF) formulations, SSI values (99 ° C) are 0.35 oz. 50%; and based on the 100-hour ASTM D-2882-90 pumping test for hydraulic fluids, SSI values (38 ° C) are 18, 68 oz. 76% (Effect of Viscosity Index Improver on In-Service Viscosity of Hydraulic Fluids, RJ Kopko and RL Stambaugh, Fuel and Lubricants Meeting, Houston, Texas, June 3-5,1975, Society of Automotive Engineers).

The polydispersity index in the oil of soluble polymers of the present invention may be from about 1.5 to about 15, preferably from 2 to about 4. The polydispersity index is a measure of the narrowness of the molecular weight distribution with a minimum value of 1.5 and 2.0 for polymers which include a chain termination with a combination or. disproportionation, and higher values represent increasing broader distributions. Preferably, the molecular weight distribution is as narrow as possible, but this is generally limited by the manufacturing process. Some approximations to ensure a narrow molecular weight distribution (low Might include one or more of the following processes. Anionic polymerization; reactor tank continuous charge and mixing technology (CFSTR); low conversion polymerization; temperature control, etc. during polymerization; mechanical shear, i.e. homogenization of polymers;

The polymers of the present invention having a polydispersive index of 2 to about 4 are preferred because these polymers allow the additive to be used more efficiently to meet the specially formulated viscosity specifications of machine oil, e.g. about 5 to 10% less additive may be sufficient to give a viscosity of about 9 x 10 ' ³ to about 2 χ 10' ² Pa.s (at 100 ° C) in 100N base oil compared to an additive having a polydispersive index of about 10 .

Thus, a fully effective polymer additive can provide a balance of shear stability and the ability to thicken at low usable levels to provide low temperature fluidity without compromising other properties, such as e.g. dispersion and is chemically neutral for fluoropolymer sealants. Typically, these useful properties in machine oils, automatic transmission fluid formulations, etc., have previously been achieved only by mixing two, three or more different additives, i.e. using a separate dispersing agent, a viscosity index additive, and a fluid point depressant additive. The additives of the present invention provide this combination of useful properties in a single polymer.

The polymers of the invention can be prepared by mixing monomers (a) and (b) in the presence of a polymerization initiator, a diluent, and optionally a chain transfer agent. The reaction may be carried out under stirring under an inert atmosphere at a temperature of from about 60 to 140 ° C and more preferably from 115 to 125 ° C. Typically, the reaction is exothermic to a polymerization temperature of 115-120 ° C. The reaction generally takes about 4 to 10 hours or until the desired degree of polymerization is achieved. As is known to those skilled in the art, the time and temperature of the reaction depend on the choice of initiator and can be varied accordingly.

The initiators useful for this polymerization are any of the well-known free radical-producing compounds such as e.g. peroxy, hydroperoxy and azo initiators including acetyl peroxide, benzoyl peroxide, laroyl peroxide, t-butyl peroxyisobutyrate, caproyl peroxide, cumene hydroperoxide, l, l-di (t-butyl peroxy) -3,3,5trimethylcycloisobutyl, butyl butyl peroctoate. The initiator concentration is normally between 0.025 and 1 wt% based on the total weight of the monomers and more preferably from 0.05 to 0.25%. Chain transfer agents can be added to the polymerization reaction to control the molecular weight of the polymer. Preferred chain transfer agents are alkyl mercaptans such as e.g. lauryl (dodecyl) mercaptan and the chain transfer agent concentration used is from 0 to about 0.5% by weight.

Diluents suitable for polymerization are aromatic hydrocarbons such as e.g. benzene, toluene, xylene and aromatic naphtha, chlorinated hydrocarbons such as e.g. ethylene dichloride, esters such as e.g. ethyl propionate or butyl acetate and also petroleum oils or synthetic lubricants.

After polymerization, the resulting polymer solution has a typical polymer content of between about 50 and 95% by weight. The polymer can be isolated and used directly in mineral or synthetic base oils, or the polymer and diluent solution may be used in concentrated form. If a concentrated form is used, the polymer concentration can be adjusted to any desired level with an additional diluent (eg paraffin base oil). The preferred concentration of polymer in the concentrate is from 30 to 70% by weight. If directly mixed into the lubricating base oil, it is more preferable to dilute any mineral oil such as e.g. 100 to 150 neutral oil (100 N or 150 N oil) compatible with the final lubricating base oil.

If the polymer of the present invention is added to lubricating base oils, such as e.g. automatic transmission fluids, hydraulic fluids and engine oils, either as pure polymer or as concentrate, the final polymer concentration in the lubricating base oil is preferably from about 0.5 to 15% by weight and more preferably from about 1 to 8% depending on the specific requirements of use. E.g. about 1.5 to about 5% in engine oils, automatic transmissions and shock absorbers, and above 10 to 15% in special gearbox and hydraulic fluid applications. Lubricating base oils can be either mineral oils (paraffinic or naphthenic) or synthetic types (polyolifine). The concentration of polymer used depends on the desired viscometric properties of the lubricating oil and the shear accuracy of the intended application; generally, if a low molecular weight polymer is used, a higher concentration is required to obtain adequate thickening in the mixture, and if a higher molecular weight polymer is used, a lower concentration in the oil may be used.

The polymers of the present invention are evaluated by a wide variety of performance tests commonly used for lubricating oils and are explained below.

Machine oils containing viscosity index enhancers generally have viscosity index (VI) values in the range of 120 to about 230, with values greater than about 140 depending on the specifications of the mixture. The higher the lower the value, the change in viscosity as the temperature rises or falls. The viscosity index enhancer compositions of the present invention offer high viscosity index values (Example 4) while maintaining good dispersibility (Example 5), good cold engine starting (Example 7) and good chemical neutrality against fluoropolymer sealants (Example 6).

The useful properties of the lubricating oil additives of the present invention have also been evaluated for the purity of the engine in a sequential VE test to measure the dispersion properties of slurry additives at low and medium temperature operating conditions under the conditions described in ASTM Research Report no. D-2: 1002. Machine parts are evaluated and recalculated after 12 days and cleanliness evaluated by the Coordinating Research Council (CRC) value system with a value of 10 representing the cleanest machine; the target values for the average suspension and for the suspension in the valve body (RAC) are greater than 9.00 or. 7,00.

The compositions of the present invention are also subjected to a compatibility test for fluorocarbon polymers, in particular viton fluoroelastomers. This test (engine seal compatibility test, Example 6) is used to evaluate the degree of compatibility of lubricating oil additives of the present invention with materials used in engine gaskets, etc. The test is based on the immersion of the sealing materials in liquids containing the candidates of the lubricating oil additive samples for 7 days, after which their elongation characteristics (percent burst elongation) or% ELB are determined. Relative change values in% ELB from 0 to -5% represent neutral conditions, i.e. compatibility with machine seals.

The compositions of the present invention are subjected to tests designed to measure the viscosity characteristics at low temperatures at low and high shear values, i.e. in accordance with SAE J300 Engine Oil Viscosity Classification, January 1991. In these circumstances, the viscosity of the formulated oil should be low enough to allow sufficient rotation speed to start the engine while ensuring adequate lubrication of all engine parts.

The simulated cold rotation test (CCS) determines the apparent viscosity of machine oils under the conditions where engine rotation and start-up are most difficult and based on the procedure defined in ASTM D-5293-92. E.g. The CCS oil viscosity specification of SAE 5W-30 type is less than 3.5 Pa.s at -25 ° C and with many commercially available viscosity index enhancers it is difficult to meet this requirement.

The low-temperature low-shear characteristics at engine start-up are measured using the MRV test procedure. The MRV test (Example 8) is a measure of the ability to pump machine oil, i.e. the engine oil must be sufficiently liquid so that it can be pumped into all machine parts after starting the engine to ensure proper lubrication. The viscosity index dispersing agents of the present invention provide a good low temperature characteristic when formulated over a wide range of different base oils.

The following examples are presented to illustrate preferred embodiments of the present invention. All ratios and percentages are by weight and all reagents are of good marketable quality unless otherwise stated. Examples 1 to 3 provide synthesis information for the preparation of polymers of the present invention and Examples 4 to 7 provide information for the characteristics of the oil formulations containing the polymers of the invention.

EXAMPLE 1

The monomer mixture was prepared from 30.0 parts of cetyl eicosyl methacrylate (100% base, 95% purity), 55.0 parts isodecyl methacrylate (100% base, 98% purity), 10.0 parts methyl methacrylate, 5.0 parts hydroxypropyl methacrylate, 0.06 parts of dodecyl mercaptan and 0.10 parts of 1,11-di (t-butyl peroxy) -3,3,5-trimethylcyclohexane. The remaining batch was prepared from 20.0 parts of a stock of paraffinic base oil (100 N oil) and 0.028 parts of 1,11-di (t-butyl peroxy) -3,3,5-trimethylcyclohexane. The remaining batch is then batched to a nitrogen-coated boiler equipped with a thermometer and temperature control thermocouple, water-cooled reflux condenser with nitrogen outlet, mixer, nitrogen inlet and an additional funnel to control the addition of the monomer mixture. The contents of the boiler are heated to 120 ° C and maintained at this temperature. The monomer mixture (100 parts) was then added uniformly over a 90 minute period and heated or cooled as needed to maintain the polymerization temperature at 115-120 ° C.

minutes after the monomer filling is completed, the first of the three retained doses of initiator is added, each containing 0.10 parts of 1, 1-di (t-butyl-peroxy) -3,3,5 trimethylcyclohexane in 10.0 parts of paraffinic base oil. The other two doses of initiator are added at 20 minute intervals. 20 minutes after the last addition of the initiator, 62 parts of paraffin base oil were added to bring the batch to theoretical solids of 50% polymer in the oil. Throughout the polymerization, the temperature is maintained at 115-120 ° C. 30 minutes after the addition of paraffin base oil, the batch is homogeneous and the polymerization is considered complete. The conversion of monomers to polymer is 95% and the polymer has a shear stability index (SSI) of 45 (according to ASTM D-2603-91).

EXAMPLE 2

The procedure is the same as in Example 1 except that the monomer mixture is 145 parts cetyl-eicosyl methacrylate, 225 parts isodecyl methacrylate, 99 parts butyl methacrylate, 24 parts hydroxypropyl methacrylate and 0.19 parts cumene hydroperoxide. The remaining batch is 106 parts of paraffinic base oil containing 0.1 g of cumene hydroperoxide and 0.83 parts of 95% tal-t-octylphenyldimethylammonium chloride in mixed butanols. Also, three retained initiation doses are added at 30 minute intervals, each consisting of 0.13 parts of cumene hydroperoxide and 0.83 parts of 25% melt-toctylphenyldimethyl ammonium chloride in mixed butanols in 3.6 parts of paraffinic base oil. The batch has theoretical solids of 52% polymer. The conversion of the monomer to the polymer is 93% and the polymer has an SSI of 73.3.

EXAMPLE 3

The monomer mixture was prepared from 5.0 parts of cetyl eicosyl methacrylate (100% base, 95% purity), 85 parts isodecyl methacrylate (100% base, 95% purity), 5.0 parts methyl methacrylate, 5.0 parts hydroxypropyl methacrylate, 0.29 parts of dodecyl mercaptan, 0.13 parts of t-butyl peroctoate (t-butyl peroxy-2-ethylhexanoate) and 4.9 parts of paraffinic base oil (100 N oil). A portion of the above monomeme mixture (40%) is flushed into a nitrogen-flushed boiler equipped with a thermometer and temperature control thermostat, a water-cooled reflux condenser with a nitrogen outlet, a mixer, a nitrogen inlet and an additional funnel to control the addition of the monomial mixture. . The contents of the boiler are heated to 105 ° C and allowed to heat exothermally to 130 ° C before being controlled for cooling to maintain the temperature below 130 ° C; if exothermic heating does not start after about 5 minutes at 105 ° C, the batch is slowly heated to 115 to 120 ° C until exothermic heating begins. When the temperature reaches 115 ° C during exothermic heating, the residue of the monomer mixture is added uniformly over a period of 45 minutes with cooling to maintain the exothermic heating below 125 ° C. The temperature was then maintained at 115-120 ° C for an additional 30 minutes. After this time, the first of the three retained doses of the initiator is added to the boiler, each consisting of 0.10 parts of t-butyl peroctoate and 9.8 parts of 100 N oil, and then maintaining the batch at the same temperature for 30 minutes. Two additional doses of initiator are given at 30 minute intervals. 30 minutes after the last addition of the initiator, about 65 parts of 100 N of base oil are added to dilute the batch to about 50% of the polymer. The batch temperature was then raised to 130 ° C and maintained for 30 minutes. The final diluted polymer solution has an SSI of 13.2.

EXAMPLE 4

The viscosity index (VI) is a measure of the effect of a change in temperature on the kinematic viscosity of an oil. The viscosity index is expressed as an arbitrage value based on ASTM calculation D-2270-74 for kinematic viscosity measured at 40 ° C and 100 ° C. Table 2 contains data on the viscosity index enhancers formulated in two different base oils. The viscosity index (VII) 1-2 composition constituents are poly (alkylmethacrylate) additives known in the art which do not contain hydroxyalkyl methacrylate monomer; compositions VII from 3 to 7 are representative of the present invention based on poly (MMA / IDMA / CEMA / HPMA) with relative monomer contents of 9-10 / 5356 / 28-30 / 4-6 wt. parts

TABLE 1

Viscosity index values

VII % HPMA Formulation 1 100 ° C 40 ° C VI Formulation 2 100 ° C 40 ° C VI 1 0 11,0 57.1 189 10.6 54,9 187 2 0 10.6 55,8 186 10.3 53,6 185 3 4 10.6 53.5 195 10.2 50.5 197 4 4 10.9 54,4 197 10.5 51.5 201 5 5 10.4 52,3 195 10.1 49.5 197 6 5 10.7 50.7 211 10.5 51,0 203 7 6 9.8 42,9 192 9.5 46.0 199

EXAMPLE 5

Useful properties in the sequential VE test (engine cleanliness) of the lubricating oil additives of the present invention are presented in Table 3. The values of the slurry listed in Table 3 are for the slurry for the valve body and the average slurry (target values are greater than 7, 0 and 9.0 respectively, with 10.0 being the purest engine). Each of the M to S formulations contains 4-8% of the tested oil additive, 8 to 10% of the marketable DI composition and 82-87% of the paraffinic base oil. Marketable DI compositions typically consist of an anti-wear or antioxidant component, such as e.g. zinc dialkildithiophosphate; ash-free dispersing agent such as e.g. polyisobutene-based succinimide; detergent, such as metal fenate or sulfonate; friction modifier, such as organic compounds containing sulfur; and foaming agents, such as e.g. silicone fluid: Hit 993 available from Ethyl Corporation and Amoco A-8004 available from Amoco Chemicals. The tested oil additives are based on poly (MMA / IDMA / CEMA / HPMA) with a relative content of monomer 9-10 / 5356 / 28-30 / 4-8 parts by weight. The paraffin oils used are Εχχοη 100 N or 150 N oils. The ingredients of the various formulations tested are:

,7 4.7% additive / 8% Hitchy 993 DI composition / 87% 150 N oil

N 4,5% additive / 8% Hitting 993 DI composition / 87% 150 N oil

About 6.9% additive / 10% Amoco A-8004 DI composition / 83% 100 N oil

P 6.7% additive / 10% Amoco A-8004 DI composition / 83% 100 N oil

Q 7.7% additive / 10% Amoco A-8004 DI composition / 82% 100 N oil

R 6.5% additive / 10% Amoco A-8004 DI composition / 83% 100 N oil

With 4.4% additive / 10% Amoco A-8004 DI composition / 78% 100 N oil /% 150 N oil

TABLE 2

Sequential VE test (engine cleanliness)% HPMAv

Formulation additive

Spray (for inlet valve control / avg)

M 5% 9.3 / 9.4 N 5% 9.3 / 9.1 Oh 5% 9.4 / 9.4 P 5% 9.2 / 9.4 Q 5% 9.3 / 9.6 R 4% 8.1 / 8.0 S 8% 9.4 / 9.5

EXAMPLE 6

The compositions of the present invention are subjected to a compatibility test (compatibility test with motor seals) for hydrocarbon polymers, in particular viton fluoroelastomers used in motor seals, etc. This test is run under conditions similar to those defined in the ISO-37-1977 (E) procedure (developed by the International Organization for Standardization (ISO / TC45) Technical Committee) using a S3A test sample in the form of a handle.

The evaluation is as follows: Immerse three S3A samples in the beaker in the form of a handle made of viton fluoroelastomer (AK6) into the test fluid so that 80 parts of the test fluid are present on one part of the test sample (volume / volume). The test fluid contains 5% (w / w) of the composition of the dispersant to improve the viscosity index being tested, together with the appropriate detergent inhibitor composition (Dl) at the recommended usable level in Εχχοη 150 N oil. The beaker is then covered with an hour glass and placed in an oven with forced air circulation maintained at 149-151 ° C. The test samples were subjected to the above conditions for 7 days, then removed, allowed to cool, and then gently washed with hexane to remove the remaining test liquid. The test specimens are then air-dried and then tensile strength and tensile properties (percent fracture elongation or% ELB) determined using a standard tensile-elongation measurement procedure at 14.61 cm elongation per minute. The change in elongation of viton elastomer test specimens is then compared with the elongation data of untreated viton elastomer specimens and the result is expressed as%:

[% ELB Processed -% ELB Raw] X100 =% ELB Change [% ELB Raw]

The greater the negative value for the% ELB change, the greater the aggressiveness of the test fluid against the viton fluoroelastomer sample. For the test conditions described, liquids giving a decrease in the original (untreated)% ELB value by more than 45% (expressed as% ELB change = -45%) are considered to be highly aggressive to the test sample and therefore incompatible with the viton fluoroelastomer motor test . % ELB values of change from 0 to -5% represent neutral conditions and therefore compatibility with engine seals. % ELB values of change about -20% or less i.e. the more negative ones show poor seal compatibility. The% ELB results are highly dependent on how the device is used and it is important that they include a comparison of the raw sample results with each new series of immersed test samples.

Useful properties in the lubricating oil additives compatibility test of the lubricating oil additives of the present invention and those representing marketable nitrogen-containing oil additives are presented in Table 4. Immerse viton fluoroelastomer samples in test liquids containing said additives. The% ELB change values are expressed as the average for the three samples tested in each fluid. In all cases, the test liquids contain 1.5% OLOA 267 (detergent inhibitor (D1) component composition available from Chevron Chemicals).

A-comparative: commercial poly (alkyl methacrylate) nitrogen-containing viscosity index enhancer

B-Comparative:

a marketable polyolephic agent for improving the nitrogen-containing viscosity index

Ingredients C to H represent polymer additives (type and relative weight shown) of the present invention (MMA is methyl methacrylate, IDMA is isodecyl methacrylate, CEMA is cetyl-eicosyl methacrylate, LMA is lauryl-myristyl methacrylate, HPMA is hydroxypropyl methacrylate) :

C MMA / LMA / HEMA (8/88/4)

D MMA / IDMA / CEMA / HPMA (10/56/30/4)

E MMA / IDMA / CEMA / HPMA (10/56/30/4)

F MMA / IDMA / CEMA / HPMA (10/56/29/5)

G MMA / IDMA / CEMA / HPMA (10/56/29/5)

H MMA / IDMA / CEMA / HPMA (9/53/29/9)

TABLE 3

Engine Seal Compatibility Test

Additive The guy % ELB change A-comparative containing nitrogen -47 B-Comparative containing nitrogen -39 C 4% HEMA 0 D 4% HPMA -2 E 4% HPMA -1 F 5% HPMA 3 Mr 5% HPMA -2 H 9% HPMA -3

EXAMPLE 7

The useful properties of the simulated cold rotation (CCA) test for the lubricating oil additives of the present invention are presented in Table 5. The mixtures of the additives tested in the base oil are prepared by mixing 2.24% (active) polymer additive and 11.4 % Dl of the composition available from Lubrizol Company as LZ-7838G) with a calculated amount of 100 N oil. For example, if the polymer additive is available as 50% solids in 100 N oil, then 4.48 parts of the polymer additive oil solution are mixed with 11.4 parts LZ-7838G and 84.12 parts 100 N oil to produce a brake oil composition which we are testing. The CCS viscosity specification for SAE 5W-30 oil is less than 3.5 Pa.s at -25 ° C.

TABLE 4

Simulated Cold Rotation Test (CCS)

Composition of CCS polymer additive viscosity

% MMA % IDMA % CEMA % HPMA Pa.s [-25 ° C1 0 70 30 0 3,39 0 65 30 5 3.45 0 60 30 10 3.42 5 65 30 0 3.4 5 60 30 5 3,36 5 55 30 10 3.25 10 60 30 0 3.6 10 55 30 5 3,38 10 50 30 10 3,39

EXAMPLE 8

The apparent viscosity of a mini-rotary viscometer (MRV) is determined by two different test procedures and is a measure of the ability to pump engine oil after starting a cold engine. ASTMD-3829-87 discusses the measurement of viscosity in the temperature range from 0 to -40 ° C and describes a standard MRV test. ASTMD-468489 addresses viscosity measurements in the temperature range from -15 ° to -30 ° C and describes the TP-1 MRV test. Table 6 contains data for 2 batches of 5 different compositions

SAE 5W-30 oils using 5 different commercial base oils. In one batch, a commercial poly (alkylmethacrylate) type of nitrogen-containing viscosity index agent is used, and in another batch a poly (10 MMA / 55 IDMA / 30 CEMA / 5 HPMA) additive composition of the present invention is used. The SAE J300 Engine Oil Viscosity Classification (January 1991) allows a maximum of 30 Pa.s at -30 ° C for SAE 5W-30 oil using the ASTM D-4684-89 test procedure.

TABLE 5

MRV pumping test

Source of the source Source of the oil for improving the viscosity index market A market B market C market D market E of the invention A of the invention B of the invention C of the invention D of the invention E

Viscosity at -30 ° C, [Pa.s]

TP-1MRV Std MRV 8.53 7.41 7.84 7.45 7.22 6.67 6.42 6.42 7.31 7.12 8.69 6.78 7.57 7.35 6.28 6.35 6.04 5.72 6.12 6.37

A - 100N base oil extracted in the solvent

B - 100N base oil extracted in the solvent C - hydrocracked, 100N base oil catalytically extracted D - 100N base oil extracted in the solvent E - 100N base extracted, hydrated, solvent extracted

For

ROHM AND HAAS ΟΟΜΡΑΝΥ:

Claims (33)

1. A polymer obtained by the polymerization of monomers, characterized in that it comprises: (a) from about 90 to about 98% by weight of one or more monomers selected from (C 1 -C 6 alkyl methacrylates and (C 1 -C 6 alkyl alkyl acrylates; and (b) less than 10 to 2% by weight of one or more monomers selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates and hydroxy- (C ₂ -C ₆ ) alkyl acrylates, and wherein the average number of carbon atoms in the alkyl groups is from about 7 to about 12. A polymer according to claim 1, characterized in that the proportion of the total weight of the monomers (a) and (b) is about 5 to about 40% by weight of (C 1 -C 6 alkyl methacrylates, (C 1 -C 6 alkyl acrylates or mixtures thereof. Polymer according to claim 1, characterized in that the average number of carbon atoms in the alkyl groups is from about 8 to about 10. Polymer according to claim 3, characterized in that the proportion of the total weight of the monomers (a) and (b) is from about 5 to about 35% by weight of (C ₁₆ -C ₂₀ ) alkyl methacrylates, (C ₁₆ -C ₂₀ ) alkylacrylates or mixtures thereof. 5. Polymer according to claim 4, characterized in that the monomer (b) is selected from 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1-methyl -2-hydroxyethyl acrylate, 2-hydroxybutyl methacrylate and 2-hydroxybutyl acrylate. A polymer according to claim 1, characterized in that the monomer (a) comprises: (i) from 0 to about 40% by weight of alkyl methacrylate or alkyl acrylate in which the alkyl group contains from 1 to 6 carbon atoms or mixtures thereof; (ii) from 30 to about 90% by weight of alkyl methacrylate or alkyl acrylate in which the alkyl group contains from 7 to 15 carbon atoms, or mixtures thereof; (iii) from 0 to about 40% by weight of alkyl methacrylate or alkyl acrylate in which the alkyl group contains from 16 to 24 carbon atoms, or mixtures thereof, and monomer (b) comprises less than 10 to about 2% by weight of hydroxyalkyl methacrylate; acrylate in which the alkyl group contains from 2 to 6 carbon atoms and is substituted by one or more hydroxyl groups, or mixtures thereof, wherein the monomer (b) contains less than about 0.5% by weight of the crosslinker or the crosslinker precursor, and is the total amount (i), (ii), (iii) and (b) is equal to 100% by weight of polymer. A polymer according to claim 6, characterized in that it comprises 0 to about 25% (i), about 45 to about 85% (ii), about 5 to about 35% (iii) and about 4 to about 8% (b ). A polymer according to claim 6, characterized in that the average number of carbon atoms is from about 8 to about 10. A polymer according to claim 6, characterized in that the monomer (b) is selected from hydroxy- (C ₂ -C ₆ ) alkyl methacrylates containing less than about 0.2% by weight of the crosslinker or precursor crosslinker. A polymer according to claim 9, characterized in that the polymer has a weight average molecular weight of from about 100,000 to about 1,000,000. A polymer according to claim 10, characterized in that it comprises 5 to about 15% (i), about 50 to about 60% (ii), about 25 to about 35% (iii) and about 5 to about 6% (b ). A polymer according to claim 10, characterized in that the polydispersion index has 1.5 to about 15. A polymer according to claim 11, characterized in that the polydispersion index has an approx 2 to about 4. A polymer according to claim 11, characterized in that the monomer (b) is selected from 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1-methyl -2-hydroxyethyl acrylate, 2-hydroxybutyl methacrylate, and 2-hydroxybutyl acrylate. A polymer according to claim 14, characterized in that the monomer (b) is a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxyethyl methacrylate containing less than about 0.1% by weight of the crosslinker or precursor of the crosslinker. 16. Polymer according to claim 15, characterized in that (i) it is about 10% methyl methacrylate, (ii) about 55% isodecyl methacrylate, (iii) about 30% cetyl-eicosyl methacrylate and the amount (b) is about 5% . 17. Polymer according to claim 11, characterized in that the polymer has a weight average molecular weight of from about 300,000 to about 800,000 and an average number of carbon atoms in the alkyl portion of the acrylate or methacrylate backbone polymer from about 8 to about 10. 18. Polymer according to claim 6, characterized in that (i) is selected from one or more of methyl methacrylate, butyl methacrylate and isobutyl methacrylate, (ii) is selected from one or more of 2-ethylhexyl methacrylate, isodecyl methacrylate, dodecyl-pentadecyl methacrylate and lauryl myristyl methacrylate, (iii) selected from one or more cetyl stearyl methacrylate and cetyl eicosyl methacrylate and (b) selected from one or more 2hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 1-methyl methacrylate 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1-methyl-2-hydroxyethyl acrylate, 2-hydroxybutyl methacrylate and 2-hydroxybutyl acrylate. A polymer according to claim 18, characterized in that the polymer has a weight average molecular weight of from about 100,000 to about 1,000,000. 20. Polymer according to claim 18, characterized in that (i) about 10% methyl methacrylate, (ii) about 55% isodecyl methacrylate, (iii) about 30% cetyl stearyl methacrylate, and (b) about 5% mixture 2 -hydroxy-propyl methacrylate and l-methyl-2hydroxyethyl methacrylate. 21. The polymer of claim 18, wherein (i) is about 20% butyl methacrylate, (ii) about 45% isodecyl methacrylate, (iii) about 30% monomer selected from cetyl stearyl methacrylate and cetyl eicosyl methacrylate, and (b) about 5% of a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxyethyl methacrylate. 22. Polymer according to claim 18, characterized in that (i) it is about 20% isobutyl methacrylate, (ii) about 45% isodecyl methacrylate, (iii) about 30% monomer selected from cetyl stearyl methacrylate and cetyl eicosyl methacrylate, and (b) about 5% of a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxyethyl methacrylate. A polymer according to claim 18, characterized in that (i) about 15% of the monomer is selected from butyl methacrylate and isobutyl methacrylate, (ii) about 80% of the monomer is selected from lauryl-myristyl methacrylate and dodecyl-pentadecyl methacrylate, the amount of (iii ) is 0% and (b) is about 5% of a mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxy-ethyl methacrylate. 24. The polymer of claim 18, wherein: (i) from about 5 to about 10% methyl methacrylate, (ii) from about 85 to about 90% monomer selected from lauryl-myristyl methacrylate, isodecyl methacrylate and dodecyl-pentadecyl methacrylate, (iii) 0 to about 5% cetyl-eicosyl methacrylate; and (b) about 5% mixture of 2-hydroxypropyl methacrylate and 1-methyl-2-hydroxy-ethyl methacrylate. 25. A process for the preparation of a polymer comprising the polymerization of monomers, characterized in that it comprises: (a) from about 90 to about 98% by weight of one or more monomers selected from (C 1 -C 6 alkyl methacrylates and (C 1 -C 6) alkyl acrylates; and (b) from less than 10 to about 2% by weight of one or several monomers selected from hydroxy (C ₂ -C ₆ ) alkyl methacrylates and hydroxy (C ₂ -C ₆ ) alkyl acrylates; and wherein the average number of carbon atoms in the alkyl groups is from about 7 to about 12. 26. Concentrate for use in lubricating oils, characterized in that it comprises (i) about 30 to 70% by weight of polymer according to any one of claims 1 to 24, or as prepared by the process of claim 25, and (ii) a diluent. 27. Concentrate according to claim 26, characterized in that the polymer comprises about 10% methyl methacrylate, about 55% isodecyl methacrylate, about 30% cetyl-eicosyl methacrylate, about 5% mixtures of 2-hydroxypropyl methacrylate and l-methyl-2hydroxyethyl methacrylate, and has a mass average molecular weight of ca. 100,000 to about 1,000,000. 28. Lubricating oil composition, characterized in that it comprises a lubricating oil and from about 0.5 to 15% by weight of polymer according to any one of claims 1 to 24 or prepared according to the method of claim 25. 29. Lubricating oil composition according to claim 28, characterized in that the polymer comprises about 10% methyl methacrylate, about 55% isodecyl methacrylate, about 30% cetyl-eicosyl methacrylate and about 5% mixture of 2-hydroxypropyl methacrylate and l-methyl-2 -hydroxyethyl methacrylate and having a weight average molecular weight of from about 100,000 to about 1,000,000. Automatic transmission fluid, characterized in that it comprises from about 1 to 8% by weight of polymer according to any one of claims 1 to 24 or prepared by the process of claim 25. Automatic transmission fluid according to claim 30, characterized in that the polymer comprises 0 to about 5% methyl methacrylate, about 80 to about 90% lauryl myristyl methacrylate, 0 to about 10% cetyl eicosyl methacrylate and about 5% of 2- hydroxypropyl methacrylate and l-methyl-2-hydroxyethyl methacrylate and has a weight average molecular weight of from about 100,000 to about 1000,000. Automatic transmission fluid according to claim 30, characterized in that the polymer comprises 0 to about 20% butyl methacrylate, about 65 to about 90% lauryl myristyl methacrylate, 0 to about 10% cetyl eicosyl methacrylate and about 5% of the 2- hydroxypropyl methacrylate and l-methyl-2-hydroxyethyl methacrylate and has a weight average molecular weight of from about 100,000 to about 1,000,000. Use of a polymer according to any one of claims 1 to 24 or prepared according to the method of claim 25, in a lubricating oil composition. For ROHM AND HAAS ΟΟΜΡΑΝΥ: 22167-IX-92 / MN, LZ