CA1099047A - Epr dispersant vi improver - Google Patents

Abstract

ABSTRACT
Lubricating oil additives having both dispersant and viscosity-index improving properties are prepared by reacting an ethylene-propylene copolymer with chlorine and/or an alpha-beta-unsaturated dicarboxylic acid or derivative, and then reacting the resulting intermediate with certain amines and/or alkane polyols.

Description

~7 The newer engines place increased demands on the lubricants to be employed. In the past, a number of different additives have been added to lubricating oils to improve such properties as viscosity index and dispers-ancy. Significant reductions in cost can be made by employing a single ad-ditive that improves a number of lubricant properties. However, in attempt-ing to improve more than a single lubricant property, care must be taken in not causing the deterioration of other properties. For example, in United States Patent Numbers 3,687,905 and 3,864,268, copolymers of ethylene and propylene are first oxidized and degraded prior to an aminitation. This procedure results in the introduction of sites for future oxidative attack.
Significantly, known processes for making certain dispersants are not always applicable for the preparation of dispersants also having viscos-ity index-improving properties. For example, in United States Patent Number 3,172,892, a relatively low molecular weight polymer (having about 50 carbon atoms) is reacted with maleic anhydride and an ethylene amine to form a dis-persantj but, the reaction mechanism relies upon the presence of a single double bond that is inherently present at the end of the olefin polymer.
When the polymer has only 50 carbon atoms, sufficient dispersancy sites may be available through thesingle terminal double bond. However, when the poly-20 mer has over 500 carbon atoms, such as is necessary for it to impart someviscosity index-improving properties, thesingle terminal double bond will not be sufficient, and a difficult derivitization means is required in order to obtain adequate dispersancy.
In addition, it is important that the polymer dispersant-VI im-prover have a sufficient number and type of sites with dispersant activity.
Therefore, additives such as those disclosed in United States Patent Number 3,454,607, prepared with mono-carboxylic acid-producing compounds may be deficient.
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1(~990~7 A new additive has been prepared that is not oxidatively degraded prior to derivitization. In addition, the preparation process for the new additive is not dependent upon the presence of double bonds in the polymer chain in order to provide reaction sites. Further, the new additive possesses good dispersancy characteristics in addition to good viscosity index-improv-ing characteristics.
Ashless, oil-soluble additives having both dispersant and viscos-ity-index (VI) improving properties are prepared by the process comprising:
(a) reacting a high molecular weight amorphous copolymer of essen-tially ethylene and propylene, said copolymer having a number average molec-ular weight of between about 70,000 and about 300,000, with an alpha-beta unsaturated dicarboxylic acid, anhydride or ester preferably at a temper-ature of between about 150 C and about 250 C for between about 1 hour and about 24 hours, thereby forming a modified polymer; and (b) reacting said modified polymer with a Cl to C18 amine contain-ing 1 to 8 nitrogen atoms and/or an alkane polyol having at least two hydroxy groups preferably at a temperature of between about 150C and about 250 C.
Alternatively, the essentially ethylene-propylene copolymer is re-acted with chlorine and the alpha-beta unsaturated dicarboxylic compound prior -to imidization or esterification. This chlorination is radical chlorination as opposed to ionic chlorination, and is not dependent upon the presence of double bonds in the polymer backbone. The chlorination may take place prior to the addition of the dicarboxylic compound or at the same time. The rad-ical chlorination may take place in the presence of radical initiators such as azobisisobutyronitrile, tert-butylhydroperoxide, dibenzoyl peroxide and the like, or in the presence of ultraviolet radiation, however, this is not absolutely necessary, and radical chlorination may take place at temperatures above about 30 C. A solvent may be used.

~i ~ 99C~47 The amount of chlorine employed is typically between about 1 percent by weight and about 20 percent by weight, preferably between about 5 and about 15 percent by weight based on the weight of the ethylene-propyl-ene copolymer. Chlorination conditions include temperatures of between about 0 C and about 100 C, preferably between about 25 C and about 60 C, and con-tact times of between about 0.1 hour and about 2 hours.
The copolymers employed herein refer to amorphous copolymers de-rived essentially from ethylene and propylene, however, such copolymers may contain minor amounts, e.g. up to 10 percent, based on the molar amounts of the monomeric ethylene and propylene units in the copolymer, of polymerized units derived from other olefin monomers. Such other olefin monomers include olefins of the general formula RCH=CH2, in which R is an aliphatic or cyclo-aliphatic radical of from 2 to about 20 carbon atoms, for example, butene-l, hexene-l, 4-methyl-1-pentene, decene-l, etc.
Suitable ethylene-propylene copolymers contain from about 30 to about 65, preferably from about 35 to about 45 mole percent propylene, and have a number average molecular weight of between about 70,000 and about 300,000, preferably between about 80,000 and about 200,000. It is also pre-ferred that the ethylene-propylene copolymer contains at least 150 pendant methyl groups per 1,000 chain carbon atoms. Methods of preparation of these copolymers are well known, and are described in the United States Patents listed in United States Patent Number 3,864,268.
The ethylene-propylene copolymer is first reacted with a dicarbox-ylic compound, in particular an alpha-beta ethylenically unsaturated dicar-boxylic acid or its anhydride or ester derivatives. Suitable unsaturated acids and derivatives include maleic acid, maleic anhydride, dimethyl- and ` diethylmaleate, itaconic acid, dimethyl itaconate, methyl maleic anhydride, ' citraconic anhydride, and the like. Ma eic anhydride is especially preferred ~i ~

1(~9~47 The dicarboxylic compound and the ethylene-propylene copolymer are reacted together e.g. at a temperature of between about 150 C and about 250 C, preferably between about 180 C and about 230 C. The contacting time is e.g. between about 1 hour and about 24 hours, preferably between about 8 hours and about 16 hours. It is significant that the carboxylic groups are attached to the essentially saturated ethylene-propylene copolymer all along the polymer chain instead of only at the terminal double bond location as in the prior art. The process according to the prior art would not result in the attachment of sufficient carboxylic groups on the polymer chain to per-mit the attainment of sufficient dispersancy activity.
Various solvents may be employed in the carboxylic acid derivative addition step including generally olefin-free petroleum hydrocarbons, aro-matics and balogenated hydrocarbons. A preferred solvent is a lubricating oil basestock. A much preferred solvent is tri-chlorobenzene. Preferably, a concentration in the range of about 1 to about 10 percent by weight of the copolymer in solvent may conveniently be used for this conversion.
The amount of dicarboxylic compound employed to react with the ethylene-propylene copolymer varies from about 5 to about 25 percent by weight, preferably about 8 to about 15 percent by weight based on the weight of the copolymer.
The modified polymer is then reacted with an amine and/or an alkane polyol to form the oil-soluble product of the instant invention. The result-ing imides or esters of succinic acid and the like provide the dispersant function of the additive.
Suitable Cl to C18 amines are branched or unbranched, saturated, aliphatic, primary or secondary amines, containing 1 to 8 nitrogens, pref-erably mono- or diamines, such as ethylamine, butylamine, sec. butylamine, diethylamine, etc., but including higher polyamines such as alkylene poly-~U9~047 amines, wherein pairs of nitrogen atoms are joined by alkylene groups of 2 to 4 carbon atoms. Thus, polyamines of the formula:

NH2(CH2) ~ ( 2)n}m NH2 are included where n is 2 to ~ and m is 0 to 6. Examples of such polyamines include tetraethylene pentamine, tripropylene tetramine, N-aminoalkyl piper-azines, e.g., N-(2-aminoethyl) piperazine, N,N'-di(2-aminoethyl) piperazine, etc. Preferred is tetraethylene pentamine, as well as corresponding com-mercial mixtures such as "Polyamine H", and "Polyamine 500".
Suitable alkane polyols are alkane polyols having at least two and preferably at least four hydroxy groups such as the trihydroxyalkanes, e.g.
ethylene glycol, propylene glycol, polymethylene glycols, trihydroxybutanes, pentanes, hexanes, heptanes, octanes, nonanes, dodecanes, etc., as well as tetrahydroxy alkanes, pentahydroxy alkanes, hexahydroxy alkanes, as well as the sugar alcohols such as erythritol, pentaerythritol, tetritols, pentitols, hexitols, mannitol, sorbitol, glucose, and the like. Particularly preferred alcohols are pentaerythritol and mannitol. Especially preferred is penta-erythritol.
The molar ratio of amine or polyol to dicarboxylic compound is typically between about 0.1:1 and about 2:1, preferably between about 0.5:1 and about 2:1, most preferably about 1:1. The conditions during imidization or esterification are typically about 150 to 250C for between about 1 hour and about 20 hours.
In both reaction steps it is much preferred that the reactions take place in the absence of oxygen. A nitrogen blanket is often used to accomplish this result. The reason for performing the reaction in the absence of oxygen is that the resulting additive may be more oxidatively unstable if any oxygen is present during the formation of the additive.

If excess amine or polyol is employed, then it may be desirable to ~; .

1(~99~47 remove the excess. One means of doing this is to first add a volume of heptane equal to the volume of dissolved additive. Then an equal volume of methanol is added. Two separate layers are therein formed; one layer com-prising predominantly methanol and the unreacted amine or polyol and a sec-ond layer comprising predominantly heptane,the solvent and the additive product. After separating the methanol layer, the volatiles present in the other layer can then be removed by distillation. Alternatively the excess amine or polyol may be removed under a vacuum or with a stripping gas stream.
If the ethylene-propylene copolymer originally employed had a suf-ficiently low number average molecular weight, e.g. between about 70,000 and about 300,000, then the final additive product should have sufficient vis-cosity-index improving properties. However, it is possible to prepare the instant additive product starting with a copolymer having a high number average molecular weight between about 300,000 and about 1,000,000. When employing the higher molecular weight copolymer, it is necessary to subject the resulting higher molecular weight additive product to a shearing condi-tion in order to reduce the molecular weight of the additive to the desired molecular weight. One shearing mechanism involves adding a solvent such as heptane to the additive product in order to reduce the viscosity, and then pumping the solution through a Diesel injection nozzle at high pressures, such as above about 70 kg/cm . Other high shear devices include high shear mixers and pumps such as a gear pump. The molecular weight of the resulting polymer can be controlled by varying the number of times that the solution is pumped through the nozzle or high shear device. In addition to reducing the molecular weight of the additive product to within the desired range, shear-ing also narrows the molecular weight distribution since bigger molecules are sheared more readily than smaller molecules. This narrower molecular weight distribution is advantageous since it results in greater stability in the 1(~99~47 engine. It is preferred that the ratio of ~ be between about 1 and about 4 where Mw is the weight average molecular weight and M is the number aver-age molecular weight.
The reaction product of this invention can be incorporated in lub-ricating oil compositions, e.g., automotive crankcase oils, in concentrations e.g. within the range of about 0.1 to about 15, preferably about 0.1 to 3, weight percent based on the weight of the total compositions. The lubricat-ing oils to which the additives of the invention can be added include not only mineral lubricating oils, but synthetic oils also. Synthetic hydro-carbon lubricating oils may also be employed, as well as non-hydrocarbon synthetic oils including dibasic acid esters such as di-2-ethyl hexyl sebacate, carbonate esters, phosphate esters, halogenated hydrocarbons, polysilicones, polyglycols, glycol esters such as C13 oxo acid diesters of tetraethylene glycol, etc. When used in gasoline or fuel oil, e.g., Diesel fuel, No. 2 fuel oil, etc., then usually about 0.001 to 0.5 wt. percent, based on the weight of the total composition of the reaction product will be used. Concentrates comprising a minor proportion, e.g., 5 to 45 wt. per-cent, of said reaction product in a major amount of hydrocarbon diluent, e.g., 95 to 55 wt. percent mineral lubricating oil, with or without other additives present, can also be prepared for ease of handling.
In the above compositions or concentrates, other conventional addi-tives may also be present, including dyes, pour point depressants, antiwear agents, e.g., tricresyl phosphate, zinc dialkyl dithiophosphates of 3 to 8 carbon atoms, antioxidants such as phenyl-alpha-naphthylamine, tert. octyl-phenol sulphide, bis-phenols such as 4,4'-methylene bis(3,6-di-tert. butyl-phenol), viscosity index improvers such as the ethylene-higher olefin co-polymer, polymethylacrylates, polyisobutylene, alkyl fumarate-vinyl acetate copolymers, and the like as well as other ashless dispersants or detergents :

: ' 1~199~47 such as overbased sulphonates.
The invention is further illustrated by means of the following Examples.
Example 1 The base polymer was an essentially saturated (0.04 milliequivalents of unsaturation per gram polymer by ozone titration) ethylene-propylene co-polymer having a number average molecular weight of about 121,000 and a weight average molecular weight of about 202,000, containing about 62 mole percent ethylene.
415 g of this polymer was ground into crumbs and dissolved in 7.4 1 of a lube base stock. To this solution was added 33.2 g of maleic anhydride and the mixture heated to 225 C for eight hours. Unreacted maleic anhydride was then removed by vacuum distillation.
After cooling to 140C, 52 g of tetraethylene-pentamine was added and the mixture heated to 160C for one hour and 180-190C for two hours.
After cooling, the mixture was diluted with an equal volume of heptane and the mixture pumped through a homogeni~er until the viscosity of the heptane-free solution had decreased by about 30%.
The sheared solution was then filtered, washed with methanol and stripped of volatiles. The final product was 6200 g of an oil solution con-taining 6.770w active material.
Dispersancy of the product was assessed by a Spot Dispersancy Test.
In the Spot Dispersancy Test, one part of a 2% weight polymer solution in 100 parts neutral oil is mixed with two parts used, sludge-containing oil and heated overnight at 150 C. Blotter spots are then made on filter paper and the ratio of sludge spot diameter to oil spot diameter is measured after 24 hours. A poor value is under about 50% and a good value is 60% or greater.
The additive prepared above yielded a value of 64%. Unmodified starting _ g _ 99C~7 material gave a value of about 30~.
A fully formulated oil containing two percent of the product and a commercially-used detergent inhibitor package met lOW/50 viscosity require-ments.
Example 2 Another oil-soluble dispersant - ~I improver was prepared by first reacting the above ethylene-propylene copolymer with chlorine, and then with maleic anhydride and tetraethylene pentamine.
About 20 grams of the copolymer was dissolved in 380 g carbon tet-rachloride (CC14). A solution of one gram of chlorine in 13 ml of CC14 was added at room temperature. The mixture was then heated to 50 C for one hour. After one hour unreacted chlorine and HCl produced in the reaction was stripped with a nitrogen stream.
After stripping, 350 g of a standard lube base stock was added andthe CC14 distilled. ~wo grams of recrystallized maleic anhydride were added and the mixture heated to 180-200C for two hours. Excess maleic anhydride was then removed by application of vacuum.
After cooling to 120 C, 2.5 g tetraethylene pentamine was added and the mixture heated to 160C for one hour then to 190C for two hours.
The solution was then cooled and diluted with an equal volume of heptane.
A nitrogen atmosphere was maintained during all high temperature reaction steps.
After diluting with heptane, the solution was run through a hom-ogenizer three times to reduce the molecular weight and narrow the molecular weight distribution.
The solution was then filtered, washed with methanol and stripped of volatiles.
The final product had good dispersancy as illustrated by a Spot , ~99~347 Dispersancy Test value of 67%.
Thickening power of the dispersant-VI improver was demonstrated by the fact that 2% by weight of the polymer product increased the kinematic viscosity at 99 C of a lube base stock from 4 centistokes to 16 centistokes.
Example 3 Example 2 was essentially repeated, except that an essentially saturated ethylene-propylene copolymer having a number average molecular weight of about 96,ooo and a weight average molecular weight of about 172,000, containing about 65 mole percent ethylene was used.
The resulting polymer additive had a Spot Dispersancy Test value of about 61%.
Example 4 10 grams of the base copolymer of Example 1 was dissolved in 190 grams of trichlorobenzene. A solution of 270 milligrams of chlorine in four millilitres of CC14 was added at room temperature. The mixture was then heated to 50 C for one hour. After one hour, unreacted chlorine and HCl produced in the reaction was stripped with a nitrogen stream.
After stripping, 800 milligrams of maleic ànhydride was added and the mixture heated to 180 C for two hours under nitrogen. Unreacted maleic anhydride was then removed with the aid of vacuum distillation.
Temperature was increased to 200-205C for four hours after adding 900 milligrams pentaerythritol. ~ear the end of the reaction period vacuum was applied to remove water formed in the reaction. A nitrogen atmosphere was maintained up to the time vacuum was applied.
After reaction with pentaerythritol, the trichlorobenzene solvent was distilled off under vacuum and was replaced by a lube base stock. Un-reacted pentaerythritol was also removed by this procedure.
The oil solution was diluted with an equal volume of heptane, fil-1~996~47 tered, washed with methanol and stripped of volatiles.
The product had a Spot Dispersancy Test value of 61%.
A 2%w concentration of this additive in a common mineral lubricat-ing oil base stock increased the 99 C kinematic viscosity from 4 centistokes for the lube stock alone to 17 centistokes for -the lube oil plus additive.
This viscosity increase demonstrates the usefulness of the present additive as a VI improver.

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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An oil-soluble product prepared by the process comprising:
(a) reacting a high molecular weight amorphous copolymer of essentially ethylene and propylene, said copolymer having a number average molecular weight of between about 70,000 and about 300,000, with an alpha-beta unsaturated dicarboxylic acid, anhydride or ester and (b) reacting the product of step (a) with a C1 to C18 amine containing 1 to 8 nitrogen atoms and/or an alkane polyol having at least two hydroxyl groups.

2. The product of claim 1, wherein in step (a) the ethylene-propyl-ene polymer is reacted with chlorine prior to or at the same time of the re-action with the dicarboxylic compound.

3. The product of claim 1, wherein in steps (a) and (b) the temper-ature is between about 150 C and about 250°C.

4. The product of any one of claims 1-3, wherein the amount of di-carboxylic compound is between about 5 to about 25%w based on the ethylene-propylene polymer.

5. The product of any one of claims 1-3, wherein the ethylene-propylene copolymer comprises ethylene, from about 30 to about 65 mole per-cent propylene, and up to about 10 mole percent of an alpha-olefin of the general formula RCH=CH2, where R is an aliphatic or cycloaliphatic radical of from 2 to about 20 carbon atoms.

6. The product of any one of claims 1-3, wherein the dicarboxylic compound is maleic anhydride.

7. The product of claim 1, wherein the amine has the formula:
where n is 2 to 4 and m is 0 to 6.

8. The product of claim 7, wherein the amine is tetra-ethylene pentamine.

9. The product of any one of claims 1-3, wherein said alkane polyol is pentaerythritol.

10. The product of any one of claims 1-3, wherein the molar ratio of amine or polyol to dicarboxylic compound is between about 0.5:1 and about 2:1.

11. An oil-soluble product prepared by the process comprising:
(a) reacting a high molecular weight amorphous copolymer of essentially ethylene and propylene, said copolymer having a number average molecular weight of between about 300,000 and about 1,000,000, with an alpha-beta-unsaturated dicarboxylic acid, anhydride or ester;
(b) reacting the product of step (a) with a C1 to C18 amine containing 1 to 8 nitrogen atoms and/or an alkane polyol having at least two hydroxy groups and (c) subjecting the product of step (b) to a repeated shearing action so as to reduce the molecular weight of the oil-soluble product to be-tween about 70,000 and about 300,000, and the ratio of weight to number average molecular weight is between 1 and 4.

12. A lubricating composition comprising a major amount of a lub-ricating oil and a minor amount of the product of claims 1 or 11.