CS212313B2 - A method for preparing a graft copolymer suitable as an additive to a lubricating oil or hydrocarbon motor fuel - Google Patents

Abstract

The invention relates to the preparation of a graft copolymer suitable as an additive to a hydrocarbon-based lubricating oil or motor fuel. According to the invention, the procedure is to intimately mix an oil-soluble substantially linear, substantially saturated rubbery ethylene-propylene polymer of main chains, a graft monomer system comprising maleic acid, maleic anhydride and at least one other monomer selected from the group comprising 1-olefins, N-vinylpyrrolidone, alkyl methacrylates, alkyl acrylates, styrene and diisobutylene and a radical initiator, wherein the temperature during mixing in the presence of the initiator is lower than the decomposition temperature of the initiator and then the temperature of the mixture is increased to the decomposition temperature of the initiator or to a temperature higher and then the subsequent reaction of the monomer system with a polyamino compound containing one primary or secondary amino group is carried out.

Description

The invention relates to a method for preparing a graft copolymer suitable as an additive to lubricating oil or hydrocarbon motor fuel. The graft copolymer prepared according to the invention has a multipurpose character. The invention is directed primarily to the preparation of such graft copolymers in which the grafted monomer units are derived from a monomer system comprising maleic acid or its anhydride and one or more further monomers which are copolymerizable with maleic acid or its anhydride.

Sludge in internal combustion engines is formed by the oxidative degradation of lubricating oils and by the partial oxidation of motor fuels and by the action of by-products formed by the combustion of motor fuels. The partially oxidized by-products of motor fuel combustion contain reactive intermediates such as aldehydes, acids and hydroxy acids which undergo complex condensation reactions to form insoluble resinous substances known as sludge and varnish deposits. If these components are not dispersed relatively soon after their formation, they precipitate out of the lubricant and settle, causing filter plugging and seizing of moving engine parts.

In the past, lubricating oils and hydrocarbon motor fuels were blended with several additives to provide them with various properties, such as improved viscosity as a function of temperature (improved viscosity index VI), reduced pour point, oxidation inhibiting properties, anti-corrosion properties and detergent properties. However, the addition of several additives significantly increases the cost of the lubricating oil or motor fuel and causes problems with the compatibility of the additives and the possibility of their mutual interactions. The graft copolymer additives of the present invention combine several of the above-mentioned properties in one substance and therefore represent a significant improvement compared to mixtures of additives.

Grafting polar monomers onto polyolefin backbones to form additives for lubricating oils and motor fuels is known, for example from U.S. Patent No. 3,404,091. The use of maleic anhydride as a grafting monomer is also known from U.S. Patent Nos. 3,687,849 and 3,687,905. However, the products obtained by these methods have various shortcomings in terms of their properties and/or are too expensive. This is mainly due to the fact that insufficient amounts of maleic acid or its anhydride are introduced into the graft copolymer and/or that the products contain too high amounts of by-products which are of little or no use, such as homopolymers. Maleic acid or its anhydride are particularly desirable as graft monomers because they are relatively inexpensive and because from a theoretical point of view they represent an economical means of introducing nitrogen compounds with dispersing properties into polymers by reacting these nitrogen compounds with the carboxy groups of maleic acid or its anhydride. In practice, however, maleic acid or its anhydride polymerizes only to a small extent during grafting. Therefore, with the help of these compounds, it is not possible to introduce into the polymer such a quantity of carboxy groups that would allow the incorporation of significant quantities of nitrogen compounds with dispersing properties into the polymer by reacting the carboxy groups with these nitrogen compounds. The graft copolymers according to the invention are prepared in a manner in which the maximum amount of maleic acid or its anhydride is introduced into the polymer while minimizing the formation of by-products.

The graft copolymers of the invention combine the effective thickening properties characteristic of polyolefin viscosity index improvers with the dispersing properties typical of nitrogen-containing substances. In their production, a monomer system comprising maleic acid or its anhydride and at least one other monomer which is copolymerizable with maleic acid or its anhydride by addition polymerization is used for grafting, and the grafted monomer system is then subsequently reacted with a polyamine. The copolymerizable monomers are selected with respect to their reactivity with maleic acid or its anhydride so that more maleic acid or its anhydride can be incorporated into the polymer than would be incorporated in the absence of these comonomers.

The graft copolymers of the invention are efficiently prepared by forming a perfect mixture of the backbone polymer, the copolymerizable monomer system and the radical initiator, the temperature of the mixture being maintained, at least for the time required for the initiator to be uniformly dispersed in the mixture, below the decomposition temperature of the initiator. The temperature is then raised to the temperature at which the initiator decomposes or above, preferably with continued stirring of the reaction mixture, to form the graft copolymer, and the resulting graft copolymer is subjected to an additional reaction with a polyamine. In this process, only small amounts of by-products are formed, representing losses, or these by-products are not formed at all.

The backbone polymer, i.e. the grafting substrate, preferably has a relatively high molecular weight corresponding to a viscosity average molecular weight of about 100,000 to 200,000. In contrast to prior art, the backbone polymer is not degraded prior to grafting. The molecular weight of the resulting graft copolymer is reduced by homogenization or other degradation techniques to achieve the desired balance of thickening properties, viscosity index improving properties, shear stability, detergency properties, and other additive properties in lubricating oils or motor fuels.

The graft copolymers of the invention have the significant advantage of low production costs compared to known nitrogen-containing viscosity index improvers and dispersants. In addition, in many cases, the graft copolymers of the invention have substantially the same performance as known nitrogen-containing graft copolymers, but at lower concentrations, which further increases their economic value.

Any substantially linear, substantially saturated rubbery olefinic hydrocarbon polymer that is oil-soluble, either before or after grafting of the copolymerized monomers, can be used as the grafting substrate, forming the polymer backbone. By substantially saturated is meant that the polymer contains less than 4, and preferably less than 2 mole percent, olefinically unsaturated double bonds. Polymers containing more olefinically unsaturated double bonds are too unstable to oxidation when used in lubricating oils. Suitable backbone polymers include ethylene/propylene copolymers, ethylene/propylene/diene terpolymers, hydrogenated styrene-butadiene copolymers, styrene/isoprene polymers, and atactic polypropylene. Examples of backbone polymers to which oil solubility is imparted by grafting or after grafting include low density polyethylene and the like. The backbone polymers may have a molecular weight over a wide range, for example on the order of about 10,000 to 200,000 (viscosity average molecular weight), more usually 100,000 to 150,000. Graft copolymerization usually increases the molecular weight up to about 200,000 to 400,000 and sometimes 500,000 or more. Usually, the molecular weight increases to about 200,000 to 400,000 (viscosity average molecular weight).

The choice of the molecular weight of the backbone polymer and the extent to which the molecular weight is allowed to increase during the graft copolymerization depends primarily on the handling properties of the starting polymer and the desired shear stability of the resulting product. Starting low molecular weight backbone polymers, which are prevented from increasing their molecular weight too much during the graft copolymerization, provide graft copolymer products with greater shear stability. Such products therefore require little or no additional degradation to reduce the molecular weight to a level that provides good shear stability. However, lower molecular weight starting polymer substrates for grafting are more difficult to handle because they are semi-liquids that exhibit cold flow at ambient temperatures (about 20°C) and it is often difficult or uneconomical to control the molecular weight during the graft copolymerization. Thus, while it is possible to avoid the need to degrade the graft copolymer product by using low molecular weight starting polymers, the difficulties in handling and processing such starting polymers tend to devalue this advantage. Consequently, it is preferable to use starting main chain polymers with a somewhat higher molecular weight, i.e., a viscosity average molecular weight of at least about 100,000, and thus avoid the above-mentioned problems. The molecular weight of the polymer substrate naturally varies depending on the type of main chain polymers.

Ethylene/propylene (EP) copolymers can have a wide range of ethylene to propylene ratios. Above about 80 mole percent ethylene, the copolymers are partially crystalline and thus lose oil solubility and are not suitable as substrates for the purposes of the invention. More useful ethylene/propylene substrates contain about 50 to about 70 mole percent ethylene, have a viscosity average molecular weight of about 10,000 to about 200,000, and a fflw/Hn ratio of less than 4, where flw is the weight average molecular weight and Sn is the number average molecular weight. Products with lower propylene content, higher molecular weight, and a broader molecular weight distribution can be used, but as previously noted, such copolymers result in grafted products that are generally less effective as viscosity index improvers. In terms of Mooney viscosity (ASTM Test D-646, ML 1+8 at 25°C), ethylene propylene substrates should have a value of about 20 to 40, preferably about 28°C, to prevent cold flow. Above 50, the mixture becomes too viscous for proper mixing.

Diene-modified ethylene/propylene terpolymers contain a small amount (preferably less than 10%) of non-conjugated diene, such as 1,4-hexadiene, dicyclopentadiene or ethylidene norbornene. The maximum ethylene content is determined by solubility (crystallization); a content of 45 to 55 mole % ethylene is preferred. The range of average viscosity molecular weight for preferred products is about 10,000 to 200,000 and the ratio Hw/fln is less than 8. Again, substrates whose properties do not fall within the ranges specified may be used, but this may result in the sacrifice of certain properties of the final product, such as viscosity index improvers.

The hydrogenated copolymers of styrene and butadiene are preferably random copolymers containing about 30 to 55% by weight of butadiene and having a viscosity average molecular weight of about 25,000 to 25,000. The hydrogenation is carried out so that more than 95% of the olefinically unsaturated bonds but less than 5% of the aromatic unsaturated bonds are hydrogenated.

In the case of substrates formed from hydrogenated copolymers of styrene and isoprene, block copolymers are preferably, but not exclusively, used. The polymers may contain 2 or more blocks. Styrene blocks typically have a molecular weight of about 5,000 to about 50,000 and their aromatic groups are at least about 50% hydrogenated, and isoprene blocks typically have a molecular weight of about 1,000 to about 1,000,000 and their olefinic bonds are also at least about 50% hydrogenated. Random copolymers having a similar composition in terms of units derived from styrene and butadiene may also be used.

Amorphous polypropylene with a viscosity average molecular weight of about 10,000 to about 200,000 can also be used as a grafting substrate. This class of substrates results in additives with generally good dispersing properties, but the resulting graft copolymers generally have somewhat poorer properties as viscosity index improvers.

All of the above polymer substrates are defined to provide graft copolymers that are both excellent dispersants and good viscosity index improvers. Polyolefin substrates whose properties do not fall within the above ranges can also be used but will provide products that are good dispersants but have somewhat inferior viscosity index improver properties.

As monomers copolymerizable with maleic acid or its anhydride (preferably with maleic anhydride), any alpha, beta-monoethylenically unsaturated monomers that are sufficiently soluble in the reaction medium and reactive towards maleic acid or its anhydride to allow a substantially higher amount of maleic acid or its anhydride to be introduced into the grafted polymer product than can be introduced using maleic acid or maleic anhydride alone. Suitable monomers are esters, amides and nitriles of acrylic and methacrylic acid and other monomers that do not contain free acid groups. Representative examples of substances from these groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, 2-ethylhexyl and isodecyl esters of acrylic or methacrylic acid. Other suitable monomers are styrene, alpha-methylstyrene, C1-C4-alkyl and alkoxy substituted styrenes such as p-methylstyrene, p-sec.butylstyrene, p-methoxystyrene and ()4-0,2 alpha-olefins such as 3 ^- isobutylene and the like. Other types of monomers are vinyl esters such as vinyl acetate, -propionate and -butyrate, vinyl ketones such as methyl and ethyl vinyl ketone; and other vinyl and vinylidene monomers such as vinyl chloride and vinylidene chloride. Any mixture of two or more of these comonomers may be used. Comonomers containing more than one polymerizable double bond and/or functional groups which may cause crosslinking or gelation such as hydroxy groups and primary or secondary amino groups are not suitable. Conjugated diolefins such as butadiene may be used in smaller amounts since these monomers have a lower tendency to crosslink than non-conjugated diolefins. Although the monomers may contain up to about 40 carbon atoms, monomers containing up to about .0 carbon atoms are preferred. Higher carbon content in the molecule increases weight and cost and has no particular advantage either in terms of ease of copolymerization with maleic acid or its anhydride or in terms of the resulting product properties as a viscosity index improver and dispersant.

Extensive studies have been made in the past on the reactivity of maleic anhydride with other monomers, and these studies also report the inactivity ratios (copolymerization parameters) for the individual systems. This allows the chemist to easily select the monomers and their ratios so that the introduction of maleic anhydride into the graft copolymers of the invention is optimal. Some monomers ideally alternate with maleic anhydride in each of the graft chains, some monomers form blocks with maleic anhydride in the graft chains, and some form irregular copolymer chains. Examples of these studies include Flory: Principles of Polymer Chemistry, Cornell University Press, 1953, pp. 178-199, especially Tables XX and XXII, and Tirandrup and Immergut: Polymer Handbook, Second Edition 1975, John Wiley and Sons, Inc., pp. 11-105, 11-227-229.

The monomer ratios depend on the reactivity of the monomers selected. A larger amount of comonomer is required when a monomer is selected that has a greater tendency to homopolymerize than to copolymerize with maleic anhydride. Typically, the ratio of maleic anhydride to comonomers is in the range of about 1:4 to 4:1, preferably in the range of about 1:2 to 2:1. Sufficient maleic anhydride should be present in the monomer system such that about 1 to 10% by weight of maleic anhydride, based on the weight of the product, is present in the graft copolymer product. The preferred amount of maleic anhydride is 2 to 6% by weight.

In addition to the fact that in the process of the invention a perfect mixture of the reactants with the radical initiator is formed at a temperature below the decomposition temperature of the initiator and then the reaction temperature is increased to a value higher than the decomposition temperature of the initiator, the graft copolymers are prepared by conventional radical copolymerization procedures. As a typical example of such a procedure for the case where an ethylene/propylene copolymer is used as the polymer substrate forming the backbones, the following procedure can be mentioned. The backbone polymer is dissolved in a suitable inert solvent, such as a halogenated aromatic hydrocarbon, at a temperature of about 80 to 150 ° C to a solution having a concentration of about 20 to 30% by weight. The dissolution of the polymer is assisted by suitable stirring, such as magnetic or mechanical stirring. The graft monomers are then mixed with the solution, usually at a lower temperature, such as at a temperature of about 80 ° C, preferably with stirring of the reaction mixture. The graft monomers are added to the mixture in a total amount of about 2 to 30% by weight, based on the ethylene/propylene copolymer, preferably in an amount of about 5 to 20% by weight. If necessary, the temperature of the mixture is reduced again to a temperature below the decomposition temperature of the initiator, and then the initiator is added and evenly distributed in the solution. The temperature, mixing, order and rate of addition are carefully selected so as to reduce homopolymerization and graft copolymerization to the lowest possible extent during this time. The initiator is added in an amount of about 0.5 to 2% by weight, based on the ethylene/propylene copolymer. After the initiator is evenly dispersed in the mixture, the temperature is gradually increased to the decomposition temperature of the initiator or a higher temperature. In the case of using tert-butyl peroxybenzoate, this temperature is about 120 to 140 ° C. This temperature is maintained until the reaction is substantially complete. A reaction time of about 1 to 2 hours is usually sufficient. The reaction product typically contains about 2 to 25% by weight, preferably about 4 to 20% by weight, of grafted monomers.

AND"

Any free radical source capable of abstracting hydrogen can be used as a radical initiator. Examples include alkyl peroxyesters, alkyl peroxides, alkyl hydroperoxides, diaeyl peroxides, etc. The preferred initiator is tert-butyl peroxybenzoate, but other initiators can also be used, such as tert-butyl peroxyoctoate, ditert-butyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, etc.

The temperature at which the grafting is carried out may range from about 80 to 150°C. The temperature selected, however, naturally depends on the decomposition temperature of the initiator © on the polymeric substrate and the grafted monomers. Consequently, it may be possible to carry out grafting at temperatures as low as 60°C and as high as about 250°C.

As already mentioned, before carrying out the grafting reaction, according to the invention, a perfect mixture of the polymer substrate, the grafted monomers and the initiator is produced and the temperature is maintained below the decomposition temperature of the initiator, at least during the addition and mixing of the initiator with the solution. This prevents the formation of free radicals until the reactants are completely and homogeneously mixed. This procedure eliminates or significantly reduces the formation of undesirable by-products such as homopolymer and increases the grafting of the polar oxygen-containing polymer.

During the grafting reaction, any solvent medium may be used to prepare the graft copolymer, provided that the medium is substantially inert to the reactants, i.e., the medium causes no or only minor chain transfer. Halogenated aromatic hydrocarbons, such as chlorobenzene or dichlorobenzene, especially dichlorobenzene, are preferred. However, aliphatic or aromatic hydrocarbons, including mineral oil, are suitable in some cases.

Although the process according to the invention has been explained so far as the copolymerizable reactants are dissolved in a solvent, if the polymer forming the grafting substrate and its mixture with the grafted monomers have a sufficiently low melt viscosity for homogeneous mixing and grafting at the reaction temperature, it is possible to work without a solvent. The order and rate of addition of the individual reactants and the initiator are not of fundamental importance if the temperature is controlled in the manner described above.

The carboxyl groups introduced into the grafted chains by maleic acid or maleic anhydride are further reacted with a non-polymerizable polyamine to form a structure which is referred to for simplicity as a carboxypolyamine adduct. The polyamine is added in sufficient quantity to react substantially all of the carboxyl groups. This reaction is often referred to as neutralization and the products are amide, imide, amidine and other structures. All of these structures are within the scope of the term carboxypolyamine adduct. The polyamine should contain essentially only one amino group which is reactive towards the carboxyl groups of the grafted maleic acid or maleic anhydride. Additional reactive amino groups tend to cause interfering reactions. The reactive amino group is a primary or secondary amino group. All remaining nitrogen in the polyamine should be substantially unreactive towards the grafted maleic acid or maleic anhydride.

. Polyamines can be characterized as aliphatic, cycloaliphatic, aromatic or heterocyclic and can be of mixed character. Polyamines can carry other functional groups, such as hydroxy groups, provided that these groups do not cause interfering reactions. Examples of suitable polyamines include:

dimethylaminoethylamine, dibutylaminoethylamine,

3-dimethylamino-1-propylamine,

4- methylethylamino-1-butylamine, pyri dy1e thylamin,

N-morpholinoethylamine, tetrahydropyridylethylamine, bis-(dimethylamino)propylamine, bis-(diethylamino)ethylamine,

N,N-dimethyl-p-phenylenediamine, piperidylethylamine,

1-aminoethylpyrazole,

1-(methylamino)pyrazoline,

1-methyl-4-aminooctylpyrazole,

1-aminobutylimidazole,

4-aminoethylthiazole,

2- aminoethyltriazine, dimethylcarbamoylpropylamine,

N-methyl-N-aminopropylacetamide,

N-aminoethylsuccinimide,

N-methylaminomaleimide,

N-aminobutyl-alpha-chlorosuccinimide,

3-aminoethyluracil,

2-aminoethylpyridine, o-aminoethyl-N,N-dimethylbenzenesulfamide,

N-aminoethylphenothiazine,

N-aminoethylacetamide,

1-aminophenyl-2-methylimidazoline,

N-methyl-N-aminoethyl-S-ethyldithiocarbamate,

N-phenylurea,

N-(3-aminopropyl)morpholine,

4-aminomethylpyridine,

N-(3-aminopropyl)-2-pyrrolidinone,

N-(3-aminopropyl)-N'-methylpiperazine,

1-(2-aminoethyl)-2-methyl-2-imidazoline,

N-(5-aminopentyl)-2,5-dimethylpyrrole,

2-aminothiazole and

2-aminobenzothiazole.

Thus, polyamides preferably contain one primary or secondary amino group and at least one tertiary amino group, such as a heterocyclic amino group. Examples of the latter include aminoalkyl-substituted piperidines, morpholines, piperazines, pyridines, pyrrolidines, pyrrolidines, pyrroles, benzopyrroles, quinolines, indoles, etc. Also suitable are polyamines containing non-reactive nitrogen in other groups, such as substituted primary or secondary amines, in which the substituent is derived from pyrrolidones, caprolactams, oxazolidones, oxazoles, thiazoles, pyrazoles, pyrazolines, imidazoles, imidezolines, thiazines, oxazines, diazines, in which the substituent is oxycarbamoyl, thiocarbamoyl, or in which the substituent is derived from uracils, hydantoins, thiohydantoins, guanidines, ureas, sulfonamides, phosphoramides, phenothiazines, amidines, etc. The polyamines may contain up to about 6 nitrogen atoms, preferably 2 to 4 nitrogen atoms, and 4 to about 30 carbon atoms, preferably 4 to about 12 carbon atoms.

The reaction of the graft copolymer with the polyamine is conveniently carried out in a solvent reaction medium containing the graft copolymer. If desired, the graft copolymer can be separated and redissolved, or the reaction product can be concentrated before the polyamine is added. The reaction is carried out at a temperature of about 80°C, preferably about 120 to 300°C, but not above the temperature at which the graft copolymer decomposes. Typically, the temperature range is from about 150 to 250°C. In order to ensure complete reaction, the polyamine is conveniently used in excess of the stoichiometric amount, on the order of about 1 to 10% excess. The reaction is substantially complete when titration shows that no more than about 2% of carboxyl groups remain in the graft copolymer.

When polymer viscosity index improvers are subjected to severe mechanical stress in the equipment in which they are used, polymer degradation can occur, thereby reducing the beneficial effect that these additives have on the temperature dependence of the viscosity of a lubricant or motor fuel. Polymers that resist this tendency to mechanical degradation during use are referred to as shear-stable polymers. The ability of viscosity index improvers to resist mechanical degradation during use depends on a number of factors, one of which is molecular weight. A polymer with a very high molecular weight initially provides excellent control of the temperature dependence of the viscosity of a lubricant or fuel, but degrades very severely during use and thus loses a significant part or almost all of its effect.

Graft copolymers produced by the process of the invention may have too high a molecular weight for their effective use, although they are good viscosity index improvers. However, they have poor shear stability. As already mentioned, this is due in part to the production technology implemented in the rubber industry, particularly in the production of ethylene-propylene copolymers and terpolymers. These polymers are typically produced at very high molecular weights so that the products are relatively hard solids that are easy to handle and transport. When these rubbers are produced at molecular weights suitable for use as viscosity index improvers, the polymers obtained have the nature of sticky solids that exhibit flow even at ambient temperatures. Although the technology for processing products with such molecular weight is known, such as the technology described in the oxidative degradation process in U.S. Patent Nos. 3,404,091 and 3,687,849, such polymers nevertheless require special handling. Also, the processing of such polymers is slower, which results in increased costs. Thus, when conventional ethylene/propylene rubbers are used in the process according to the invention, the products have too high a molecular weight to have acceptable shear strength.

Another factor that adversely affects shear stability is an aspect of the process of the invention itself. During grafting, the reaction mixture thickens considerably, and when the grafted copolymer was tested, it was found that the shear stability of the product deteriorated during grafting. This is likely because crosslinking may be part of the reaction. Although crosslinking can be eliminated, products in which crosslinking has been suppressed tend to have poorer dispersibility. It thus appears that a compromise must be made in the process of the invention in order to achieve optimum dispersibility.

There are simple means for reducing the molecular weight to a value in the desired range where shear stability is good. It is only necessary to subject the graft product to mechanical or thermal degradation to bring the molecular weight into the preferred range. It is estimated that while graft copolymer products have viscosity average molecular weights of up to about 500,000 or more, the desirable range for the resulting additive, which is useful as a dispersant and as a viscosity index improver, is about 30,000 to 80,000.

Any suitable degradation method may be used, such as gear pump or extruder degradation, but homogenization is preferred. In homogenization, the polymer is forced under high pressure through a device that includes throttle valves and narrow nozzles of various designs. Such a device can produce a shear stress level of about 5,000 s ^- ' and preferably about 10,000 to 1,000,000 s ^- '. Commercially available devices such as those manufactured by Manton-Gaulin Manufacturing Company or modifications thereof can be used. Such devices can operate at pressures up to about 137.5 MPa to achieve the required shear stress. Homogenization can be carried out either batchwise or continuously, depending on the degree of degradation desired.

An additional advantage of homogenization is that the products of the invention thus modified are even more effective thickeners than commercially available ethylene/propylene copolymers, which do not have

2,23,3 dispersing properties. The products of the invention therefore have, when homogenization is used, not only better dispersing properties, but also an excellent balance of thickening ability and shear stability.

The products of the invention can be used in a wide range of fuels and lubricants. Their primary application is in lubricants, where both their excellent dispersing ability and their effect on viscosity control depending on temperature are valuable. Suitable base lubricants are oils of both mineral (petroleum) and synthetic origin. The oils can have various viscosities, from spindle oils to engine oils and gear oils. Suitable synthetic fluids include esters such as dialkyl adipate, dialkyl sebacate or dialkyl azelate, trimethylolpropane triesters, pentaerythritol tetraesters, polyalkylene glycol esters, phosphoric acid esters or synthetic hydrocarbons of the poly-alpha-olefin or alkylbenzene type. Typical applications of such lubricants include hydraulic fluids, automatic transmission fluids, four-stroke engine lubricating oils, gear oils and greases.

The products of the invention may be used in lubricants in amounts of from about 0.1 to 5.0, preferably from about 0.3 to 2.0, but typically from about 0.6 to 1.5% by weight. Since the products of the invention are rubbery solids, they can conveniently be processed into viscous concentrates containing from about 7 to .5% solids in oil. The consumer can then use this concentrate in an amount corresponding to the content of the polymer component, so that the content of this component in the lubricant is within the above range.

Lubricants containing the products of the invention may also contain other additives to further enhance dispersancy and temperature-dependent viscosity control, to lower the melting point, to provide detergency and high temperature properties, corrosion inhibition, antiwear additives, antioxidants, additives to provide extreme pressure resistance, friction reducing agents, defoamers or colorants. Thus, succinimides or esters based on polybutene, phosphosulfurized polybutenes, polyacrylates or polymethacrylates, polyisobutylene, ethylene/propylene copolymers or terpolymers, hydrogenated copolymers of styrene and butadiene or styrene and isoprene, copolymers containing N-vinylpyrrolidone or dimethylaminoethyl methacrylate together with methacrylates, styrenic polyesters, ethylene vinyl acetate copolymers or oligomers, dialkyl fumarate polymers or copolymers, esterified copolymers or oligomers of styrene and maleic anhydride, Friedel-Crafts type hydrocarbon wax condensates with naphthalene, chlorinated hydrocarbons, alkaline earth sulfonates, phenolates, salioylates or phenolate sulfides, alkaline earth metal alkylnaphthalene sulfonates, dialkyldithiophosphates or diaryldithiophosphates of zinc or other metals, dithiocarbamates of zinc, cadmium, lead, molybdenum or other metals, sulfurized or phosphosulfurized esters or terpenes, sterically hindered phenols, phenothiazine or alkylated phenothiazines, naphthylamines, phenylenediamines, dibenzyldisulfide, sulfurized diisobutylene or triisobutylene, trialkyl or triaryl phosphites, tricresyl phosphate or silicate polymers, etc.

When the products of the invention are used in hydrocarbon motor fuels, where their excellent dispersant properties are primarily utilized, they are usually added in lower amounts, typically in the range of about 0.001 to 0.1% by weight. Both gasoline and diesel fuels may be used as fuels, and these fuels may also contain other additives such as antioxidants, metal deactivators, stabilizers, anti-corrosion additives, injector detergents, seeding system deposit suppressants, and other carburetor additives. All parts and percentages in the specification and examples are parts and percentages by weight unless otherwise indicated. The detergency test is based on the following procedures.

Test procedures for determining dispersant properties

A. Asphaltene test

This test, which determines the dispersing activity of any polymer, is based on the ability of the polymer to disperse asphaltenes in a typical mineral oil. The asphaltenes are obtained by oxidizing a naphthenic oil with air in the presence of traces of iron salts, such as ferric naphthenate, as a catalyst. The oxidation is conveniently carried out at 175°C for about 72 hours by bubbling a stream of air through the naphthenic oil to form a sludge which is separated by centrifugation. The sludge is deoiled (pentane extraction) and then taken up in chloroform. The concentration of the resulting solution is adjusted to 2% (weight/volume).

The polymer whose dispersant activity is being tested is dissolved in a standard oil, such as solvent extracted neutral oil 100. Mixtures containing from about 2% to 0.01% or less of the polymer in the oil are prepared.

A 10 ml sample of this mixture is treated with 2 ml of the standard solution of asphaltenes in chloroform. The sample and reagent are thoroughly mixed in a test tube and the test tube is placed in a forced-draft oven set at 90 or 150 °C. The test tube is left in the oven for 2 hours to drive off volatiles, then allowed to cool and the appearance of the sample is observed.

If the polymer has dispersant properties, the oil is clear, even if colored. Experience shows that if the polymer does not show dispersant properties in this test at a concentration below about 2%, it is not capable of improving the cleanliness of engine parts in actual engine tests.

B. Sequence V-C Test

This test is an engine test that evaluates four-stroke engine oil during engine operation at a combination of low to medium temperatures with respect to sludge and varnish deposits. The test also shows whether the oil has the ability to maintain cleanliness and good function of the positive crankcase ventilation (PCV) valves. In short, the test can be described as follows:

The test engine and parts kit supplied by Ford Motor Company under the designation 302 C.I.D. V-S Sequence V-C Oil Test Engine and Parts Kit are used in the test. The test engine is completely disassembled and assembled as described. It is then installed on a brake test stand with a dynamometer equipped with suitable accessories for controlling speed, load and other conditions. The engine is run using the approved MS-08 fuel in three stages. During the first stage, the engine is run for 120 minutes at high power and low oil and water temperatures and using a lean mixture (air/fuel ratio). During the second stage, the engine is run for an additional 75 minutes at higher oil and water temperatures. During the third stage, the engine is run for 45 minutes at low speed and low oil and water temperatures and using a rich mixture. This four-hour cycle is repeated four times each day for a total of 48 cycles (192 hours of engine operation).

At the end of the test, the engine is completely disassembled and the degree of wear, the amount of sludge and varnish deposits and the amount of deposits in the valves are determined. In addition, the clogging of the valve for forced ventilation of the crankcase, the lubricating rings and the oil strainer are determined. The test evaluates the 'dispersing properties of the lubricant for sludge when operating at low and medium temperatures. The operation of the test engine is carried out under the conditions described in the ASTíi standard.'Special Technical Publication No. 315 K.

Example 1

A. Preparation of graft copolymer

A 350 g sample of 50/50 ethylene/propylene copolymer (Epoar 506, Goodrich Chemical Co.) is introduced into a 5 liter flask containing 1050 g of o-dichlorobenzene. After ,

2.2313 nitrogen purge, the contents of the vessel are heated to about .50 °C and mixed with a metal stirrer type C until a homogeneous solution is formed. During this stage and throughout the reaction cycle, a nitrogen atmosphere is maintained over the reaction mixture. After 2 hours, a homogeneous solution is obtained. The polymer stream is then cooled to 80 °C and 35.0 g of methyl methacrylate (UMA) and 17.5 g of maleic anhydride (MAH) are added. These monomers are thoroughly mixed with the solution for 35 minutes. Then a mixture of 1.75 g of tert.butyl peroxobenzoate, as an initiator in 25 g of o-dichlorobenzene is added. The temperature is then increased to heat the reaction mixture to 140 °C within 45 minutes. Grafting begins at about 120 °C, which is evident from the increase in the viscosity of the solution. The solution temperature is maintained at .40 °C for 1 hour to complete the graft polymerization and then the reaction mixture is diluted with 1500 g of oil (100 neutral viscosity oil). The nitrogen supply is disconnected and a vacuum distillation apparatus consisting of a condenser and a receiver is connected. The volatile components are stripped from the solution at .40 °C under a pressure of 133.3 Pa. The total stripping time is about 3 hours. The presence of both methyl methacrylate and maleic anhydride in the resulting polymer product is confirmed by infrared analysis. Titration of the polymer solution shows that 89.1% of the maleic anhydride charged has been grafted. Analysis of the distillate obtained from the stripping shows that 88.5% of the methyl methacrylate has been grafted. The grafted olefinic polymer contains 8.9% methyl methacrylate and 4.5% maleic anhydride.

B. Modification of the graft copolymer by subsequent reaction

500 g of the 8.4% polymer solution prepared according to paragraph A are introduced into a 51-liter flask equipped with a thermometer, a stirrer and a nitrogen inlet. The solution is heated to 140 °C under nitrogen and 21.6 g of N-(3-aminopropyl)morpholine (NAPM) are added to it. Within 15 minutes, the viscosity of the solution increases considerably, in about 2 hours the viscosity of the solution returns to approximately its original level, probably when the amic acid is converted to the imide. The solution is further heated with stirring for 16 hours and then the nitrogen inlet is disconnected and replaced with a condenser and a receiving container. The remaining unreacted N-(3-aminopropyl)morpholine is removed by vacuum distillation for about 1 hour at a temperature of about 150 °C and a pressure of 267 ^: Pa. After driving off the N-(3-aminopropyl)morpholine, the solution is homogenized at 1.0 MPa in a triplex pump capable of delivering 206 MPa, Kobe type, size 3, to reduce the molecular weight. Analysis of the resulting product shows that the nitrogen content (Kjellach) is 0.76%, indicating that the N-(3-aminopropyl)morpholine content, expressed as maleimide, is 6.1%. Infrared analysis of the isolated polymer confirms the formation of the imide and the spectrum does not contain residual anhydride bands.

Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% asphaltenes at 150°C.

An oil with SAE 10W/40 classification is prepared by mixing 12.4% by weight of the resulting homogenized imide product concentrate, 1.5% by weight of zinc dialkyldithiophosphate anti-wear additive and 2.0% by weight of basic magnesium sulfate in an oil charge consisting of solvent refined lubricating oil. The oil therefore contains 1.04% of copolymer product. When tested using the above-described V-C engine test, the following excellent values are found: sludge 9.0; varnish 8.3; piston skirt varnish 7.2 after 200 hours of operation.

Example 2

The procedure described in Example 1 is repeated except that 22.5 g of N,N-dimethylaminopropylamine (NN-NMAPA) is used instead of N-(3-aminopropyl)morpholine and that the polymer product prepared according to paragraph A is used in the form of a solution with a concentration of 9.8%. Analysis of the final product shows a nitrogen content (Kjeldahl) of 0.94%, indicating that the content of N,N-dimethylaminopropylamine, expressed as maleimide, is 6.1%. The infrared spectrum of the isolated polymer contains imide bands but no residual anhydride bands.

Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% asphaltenes at 150°C.

An oil with SAE 10W/40 classification is prepared by mixing 14.6% by weight of the final homogenized product (1.43% polymer in the final mixture), 1.4% by weight of zinc dialkyl dithiophosphate anti-wear additive and 2.0% by weight of basic magnesium sulfate in a solvent refined lubricating oil base oil. When tested using the V-C engine test described above, the following excellent values are found: sludge 9.6; varnish 8.4; piston skirt varnish 7.9 after .92 hours of operation.

Example 3

The procedure described in Example 1 is repeated with the only difference that 30.0 g of 4-aminomethylpyridine (AMP) is used instead of N-(3-aminopropyl)morpholine and that the polymer product prepared according to paragraph A is used in the form of a solution with a concentration of 12.3%. Analytical determination of nitrogen according to Kjeldahl in the resulting product reveals a nitrogen content of 0.82%, which corresponds to a 4-aminomethylpyridine content, expressed as a maleimide content of 5.6%. The infrared spectrum of the polymer confirms the formation of the imide. Residual anhydride bands are not present.

Using the standard asphaltene dispersion test described above, it is found that 0.125 g of the polymer product disperses 0.4% asphaltenes at 150°C.

An oil with SAE 10W/40 classification is prepared by mixing 11.2% by weight of the resulting homogenized product (1.35% polymer in the resulting oil mixture), 1.5% by weight of zinc dialkyl dithiophosphate anti-wear additive and 2.0% by weight of basic magnesium sulfate in a solvent refined lubricating oil base oil. When tested using the above-described V-C engine test, the following excellent values are found: sludge 9.7; varnish 8.0; piston skirt varnish 7.4 after 192 hours of operation.

Example 4

The procedure described in Part A of Example 1 is repeated except that 20.0 g of styrene is used instead of methyl methacrylate. Analysis shows that the graft copolymer contains 5.0% styrene and 4.5% maleic anhydride.

The graft copolymer thus obtained is reacted with N-(3-aminopropyl)morpholine essentially as described in Part B of Example 1. The resulting product contains about 6.0% imide product and exhibits dispersant properties according to the asphaltene test described above.

Examples 5 to 9

The procedure described in paragraph A of Example 1 is essentially repeated except that 35.0 g of methyl acrylates are used as the graft comonomer together with maleic anhydride instead of methyl methacrylate. The graft copolymer product is then further reacted with the amines listed in Table I under substantially the same conditions as those set forth in Part B of Example 1 except that the amine-modified graft copolymer is not homogenized to reduce molecular weight. (The dispersant properties do not depend on the improved shear stability achieved by homogenization.) The degree of dispersant properties in the asphaltene test described above is shown in Table I. All of the products modified by the subsequent reaction exhibit dispersant properties and also provide viscosity index improvement when used in lubricating oils. The viscosity index improvement is imparted to the oils by the main polymer chain of these products.

Examples 10 to 16

The amines listed in Table I (Examples 10 to 16) were reacted with the product obtained by the method described in Part A of Example 1 under conditions substantially as described in Part B of Example 1 except that homogenization was not performed. The asphaltene dispersion test results shown

2123.3 in Table I show that the products have good dispersing properties in lubricating oils. The products also improve the viscosity index of the oils, which is mainly the effect of the polymer backbone.

Table I

Example Amine Amine used for additional reaction Degree of dispersion of asphaltenes h 5 N,N-dimethylaminopropylamine 6 6 N-(2-aminoethyl)morpholine 5 7 N-(3-aminopropyl)morpholine 4 8 1-(2-Aminoethyl)-2-methyl-2-imidazoline 1 9 N-(5-aminopentyl)-2,5-dimethylpyrrole 1 ,0 N-phenylurea 1 11 N-(2-aminoethyl)morpholine 3 12 2-(2-aminoethyl)pyridine 6 ,3 N-(3-aminopropyl)-2-pyrrolidone 5 14 N-(3-aminopropyl)-N'-methylpiperazine 6 15 2-aminothiazole 3 ,6 2-aminobenzothiazole 3

* = The degree of dispersion of asphaltenes is determined according to the following table:

Table

Degree of dispersion of asphaltenes

The concentration of the additive that must be used to achieve acceptable results

2.0

1.0

0.5

0.25

0.12

0.06

Example ,7

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer to which a mixture of maleic anhydride and a mixture of olefins is grafted

24.0 g of ethylene/propylene copolymer (Epcar 506) are introduced into a 500 ml flask containing 73.8 g of o-dichlorobenzene. After purging with nitrogen, the contents of the flask are heated to about 110 °C and mixed using a type C stirrer to form a homogeneous solution. During this stage and throughout the reaction, the mixture is maintained under a nitrogen atmosphere. When a homogeneous solution is formed, 3.92 g of maleic anhydride, 2.54 g of 1-tetradecene, 2.02 g of 1-hexadecene, 2.27 g of 1-octadecene and 2.52 g of ,-epicosene are added thereto and the mixture is brought into solution by thorough mixing for 30 minutes. 0.3046 g of t-butyl perbenzoate initiator in 2.2 g of o-dichlorobenzene is then added. The temperature, which is maintained at .10 °C during this addition, is now increased to .35 °C. After .t hour at 135 °C, the temperature is increased to 140 °C and maintained at this temperature for 1 hour to complete the graft polymerization. The mixture is then diluted with 276 g of oil (100 neutral viscosity oil). The nitrogen supply is disconnected and a vacuum distillation apparatus consisting of a condenser and a receiver is connected. The volatile components are removed from the solution at 140 °C at a pressure of 133.3 Pa. After the volatile components have been removed (after about 1 hour), 1.30 g of N,N-dimethylaminopropylamine (N,N-DMAPA) is added to the flask. The viscosity of the solution increases significantly within 15 minutes. As shown in Example 1, the viscosity

212313 14 the solution eventually decreases over time, probably because the amic acid is converted to the imide. After 1 hour, the solution is again evacuated at 140 °C at 133.3 Pa. After the volatiles have been removed, 6.0 g of n-butanol is added and the solution is stirred at 120-130 °C for 2 hours. The solution is then evaporated again at 150 °C at 66.7 Pa until the volatiles have disappeared. According to analysis, the resulting product contains 0.81% nitrogen (Kjeldahlization), indicating a content of 5.3% N,N-DMAPA, expressed as maleimide. Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% asphaltenes at 150 °C.

Example 18

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer onto which a mixture of maleic anhydride and 1-octene is grafted

The procedure described in Example 17 is essentially repeated except that 25.0 g of ethylene-propylene copolymers, 3.75 g of maleic anhydride, 73.0 g of o-DCB and 0.3169 g of tert-butyl peroxobenzoate are used. Instead of the olefin mixture used in Example 17, 4.50 g of 1-octene are used.

After the grafting reaction is complete and after vacuum evaporation, 3.0 g of N,N-DMAPA is added as in Example 7. After 1 hour, the solution is evaporated under vacuum at 155°C and 66.7 Pa until all volatile components are removed. Analysis shows that the nitrogen content of the final product (by Kjeldahl) is 0.73%, indicating a content of 4.8% N,N-DMAP expressed as maleimide. Using the standard asphaltene dispersion test described above, it is found that 0.0313 g of the polymer product disperses 0.4% asphaltenes at 150°C.

Example 19

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer to which a mixture of maleic anhydride and N-vinylpyrrolidinone is grafted

The procedure described in Example 17 is essentially repeated except that 25.0 g of ethylene-propylene copolymers, 2.50 g of maleic anhydride, 73.0 g of o-DCB and 0.3031 g of tert-butyl peroxybenzoate are used. N-vinylpyrrolidinone (NVP) is used instead of the olefin mixture used in Example 17. 3.0 g of N,N-DMAPA is used in the further processing of the reaction mixture. Analysis shows that the nitrogen content of the final product (by Kjeldahl) is 1.00%, indicating a content of 4.8% N,N-DMAPA expressed as maleimide. Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% asphaltenes at 150°C.

Example 20

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer onto which a mixture of maleic anhydride and a mixture of methacrylates is grafted

The procedure described in Example 18 is essentially repeated with the only difference that 1.00 g of maleic anhydride and 0.2827 g of tert-butyl peroxybenzoate are used. Instead of 1-octene, a mixture of 5.70 g of dodecylpentadecyl methacrylate and 2.45 g of cetylecosyl methacrylate is used. In the further processing of the grafted product, 1.1 g of N,N-DMAPA is used. Analysis of the resulting products (two samples) shows a Kjeldahl nitrogen content of 0.61 and 0.63 Si, indicating that the N,N-DMAPA content expressed as maleimide is 2.3 Z. Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% of asphaltenes at 150 °C.

Examples 21 to 27

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer onto which a mixture of maleic anhydride and tetradecene is grafted

2,23,3

The procedure described in Example 8 is essentially repeated except that 0.00 g of ethylene-propylene copolymer, 10.0 g of maleic anhydride, 192 g of o-DCB and 1.3877 g of tert-butyl peroxybenzoate are used. After vacuum stripping of the volatile components, the grafted polymer is reacted with the amines listed in Table II as described in Example 18. The resulting products have the Kjeldahl nitrogen content (N^) and the standard asphaltene dispersion test value listed in Table II.

Table II

Example Amine used in the reaction ^N k Asphaltenes 2, 1-(beta-aminoethyl)-2-imidazolidone 1.56 7P 22 N-3-aminopropylmorpholine 0.65 6P 23 4-aminomethylpyridine 0.82 6P 24 amines derived from hydrogenated tallow 6P 25 Kemamine D-970 (Humko-Sheffield) - (diamine derived from hydrogenated tallow) 0.80 6P 26 Kemamine D-150 (Humko-Sheffield) - ^G 20^ ^G 22 '>3P ^r °pendiamine 0.50 6P 27 N,N-dimethylaminopropylamine 0.64 6P

Example 28

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer to which a mixture of maleic anhydride and diisobutylene is grafted

The procedure described in Example 19 is essentially repeated except that 2.86 g of diisobutylene is used instead of NVP. Analysis shows that the final product contains 0.47% Kjeldahl nitrogen, indicating that the N,N-DMAPA content, expressed as maleimide, is 3.06%. Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer product disperses 0.4% asphaltenes at .50°C.

Example 29

Graft copolymer containing as the main chain polymer an ethylene/propylene copolymer onto which a mixture of maleic anhydride and CEMA is grafted

The procedure described in Example 9 is essentially repeated except that 5.00 g of cetyl ethylene methacrylate (CEMA) is used instead of octene and 1.87 g of 3-aminopropylmorpholine (3-AM) is used instead of N,N-DMAPA in the additional reaction. Analysis of the resulting product shows that the nitrogen content (according to Kjeldahl) is 1.11%, indicating a content of 8.97% 3-APM in the form of maleimide. Using the standard asphaltene dispersion test described above, it is found that 0.0625 g of the polymer disperses 0.4% asphaltenes at 150°C.

Claims (2)

SUBJECT OF THE INVENTION A process for preparing a graft copolymer suitable as an additive in a lubricating oil or hydrocarbon motor fuel, characterized in that it is intimately mixed: a) an oil-soluble linear, saturated rubbery backbone ethylene propylene polymer; b) a graft monomer system comprising maleic acid or maleic anhydride and at least one other monomer selected from the group consisting of 1-olefins, N-vinylpyrrolidone, alkyl methacrylates, 16 alkyl acrylates, styrene and diisobutylene; than the initiator decomposition temperature, and then the temperature of the mixture is raised to or above the initiator decomposition temperature, followed by subsequent reaction of the monomer system with a polyamino compound containing one primary or secondary amino group. 2. The process of claim 1 wherein the monomer-grafted backbone polymer is dissolved in a solvent and then the initiator is intimately mixed with the solution while maintaining the temperature below the decomposition temperature of the initiator.