GB2043654A - Modified EPDM-type polymers - Google Patents

Abstract

The product obtained by reacting a terpolymer comprising units derived from (i) ethylene, (ii) a terminally unsaturated straight-chain mono-olefin having from 3 to 14 carbon atoms, e.g. propylene and (iii) one or more of the monomers:- (a) norbornene (b) a terminally unsaturated non- conjugated diolefin containing from 5 to 8 carbon atoms (c) dicylopentadiene, and (d) 5-methylene-2-norbornene. with a thiol acid having the formula (R<1>O) (R<2>O)P(S)(SH) wherein R<1> and R<2> are the same or different and are either C1 to C30 primary alkyl groups or C4 to C20 secondary alkyl groups or alkyl- substituted phenyl groups in which the alkyl substituent contains from 1 to 30 carbon atoms, is useful as a viscosity index improver lubricating oil additive having increased oxidation resistance.

Description

SPECIFICATION Polymeric viscosity index improver additive modified by reaction with thiol acid.

The present invention relates to the products obtained by modifying olefin/diene terpolymers with certain thiol acids and to the use of such products as lubricant additives.

Lubricating oils are normally classified in terms of their viscosity at some standard temperature but equally important is a property known as the viscosity index, which is an empirical number giving a measure of the extent to which the viscosity of an oil decreases as the temperature is raised. An oil which satisfies viscosity requirements at both extremes of the temperature range to which it may be subjected is said to have a high "viscosity index". This property can be controlled to some extent by refining, but in recent years the trend has been towards 'multi-grade' oils, of extremely high viscosity index, in which certain polymer compounds which function as viscosity index improvers are added.

One class of polymer compounds used extensively in recent years as a viscosity index improving agent is the terpolymer of ethylene, a C3 to C14 terminally unsaturated straight-chain mono-olefin eg, propylene, and one or more of the monomers norbornene, a C5 to C8 terminally unsaturated non-conjugated diolefin eg 1,4-hexadiene, dicyclopentadiene and 5-methylene-2-norbornene. A problem encountered in using these terpolymers is that they tend to suffer from oxidative attack under the severe conditions encountered in automative use of motor oils.

We have now found that the oxidative stability of such terpolymers can be improved, whilst retaining their viscosity index improver properties, by reacting the terpolymers with certain thiol acids.

Thus according to the present invention there is provided the product obtained by reacting a terpolymer comprising units derived from: (i) ethylene (ii) terminally unsaturated straight-chain mono-olefin having from 3 to 14 carbon atoms and (iii) one or more of the monomers: (a) norbornene, (b) a terminally unsaturated non-conjugated diolefin containing from 5 to 8 carbon atoms, (c) dicyclopentadiene and, (d) 5-methylene-2-norbornene, with a thiol acid having the formula:

wherein R1 and R2 are the same or different and are either C1 to C30 primary alkyl groups or C4to C20 secondary alkyl groups or alkyl-substituted phenyl groups in which substituent contains from 1 to 30 carbon atoms.

With regard to the terpolymer, the terminally unsaturated straight-chain mono-olefin may be, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene or mixed alkenes having from 12 to 14 carbon atoms. Preferably the mono-olefin is propylene. Suitable terminally unsaturated non-conjugated diolefins having from 5 to 8 carbon atoms include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2-methyl-1,5-hexadiene, 1,6-heptadiene and 1,7-octadiene. Preferably the diolefin is 1,4hexadiene. The terpolymer may contain up to 75% by weight of units derived from ethylene, up to 75% by weight of units derived from terminally unsaturated mono-olefin and up to 10% by weight of units derived from one or more of the monomers (a), (b), (c) or (d).

Method for preparing oil-soluble terpolymers are well-known in the art. Representative of such art is the book entitled "Linear and Stereoregular Addition Polymers" by Gaylord and Mark, published by Interscience Publishers, New York NY 1959. US Patents Nos 2,799,688; 2,975,159,2,933,480; 3,598,738 and 3,691,142 are also representative of such art.

Commerical available terpolymers which may be used to advantage in the process of the present invention are the Intolan range of solution polymerised polymers which comprise units derived from ethylene, propylene and 5-methylene-2-norbornene or dicyclopentadiene, manufactured by International Synthetic Rubber and the Nordel range of terpolymers which comprise units derived from ethylene, propylene and 1,4-hexadiene manufactured by E I du Pont de Nemours and Company. The preferred Intolan terpolymer is Intolan 140A which is an ethylenelpropylene/5-methylene-2-norbornene terpolymer in which the ethylene/propylene ratio is about 60:40 by weight, the 5-methylene-2-norbornene content is about 5.7% by weight, the weight average molecular weight is about 31,000 and the kinematic viscosity is about 280 cS.

The preferred Nordel terpolymer is Nordel 1320 which is an ethylene/propylene/1 ,4-hexadiene terpolymer in which the ethylene/propylene ratio is about 45:55, the 1,4-hexadiene content is about 2 to 3% by weight and the kinematic viscosity is about 204 cS. Other commerically available terpolymers which may be used in producing the product of the present invention include Royalene (Uniroyal) and Vistalon (Esso Chemicals) terpolymers.

Generally the terpolymers will have a kinematic viscosity in the range 100 to 1500, preferably 100 to 500 cS. Kinematic viscosity is defined in the Handbook of Chemistry and Physics, 44th Edition, page 2251, as the ratio of viscosity to density, the cgs unit of kinematic viscosity being the stroke (--- 100 centistrokes). The kinematic viscosity is indicative of the molecular weight of the polymer.

In the thiol acid of formula (I) the groups R1 and R2, which may be the same or different, are C1 to C30 primary alkyl groups, C4 to C20 secondary alkyl groups or alkyl-substituted phenyl groups in which the alkyl substituent contains from 1 to 30 carbon atoms. Preferably the primary alkyl group is a C4 to C18, even more preferably a C4 to C8-alkyl group. Preferably the alkyl substituent of the alkyl-substituted phenyl group is a C3 to C21 primary alkyl group and is even more preferably a C12 H25 - primary alkyl group. Preferably the phenyl group is substituted in the para-position.

Thiol acids having the formula (I) are well known in the art and are generally prepared by reacting phosphorus pentasulphide with a hydroxylic compound, eg an alcohol or a phenol. Alternatively a mixture of such hydroxylic compounds may be reacted with the P2S5.

The reaction conditions are well known in the art. Typically one mole of phosphorus pentasulphide may be reacted with about 4 moles of the hydroxylic compound at a temperature sufficient to cause reaction, eg 40 to 1000C and held at this temperature until evolution of H2S ceases, preferably whilst purging with an inert gas, eg nitrogen. The mixture may then be cooled and, optionally, unreacted phosphorus pentasulphide filtered off.

With regard to the reaction between the terpolymer and the thiol acid having the formula (I) elevated temperature may be used, suitably up to 1 50 C, preferably in the range from 75 to 1 20 C, although the reaction will proceed at ambient temperatures. Preferably the reaction is carried out in the presence of an inert hydrocarbon solvent which is preferably low-boiling to facilitate its removal from the product. A very suitable solvent is naptha. After removing the reaction solvent it is preferred to dilute the product with up to 20% by weight of a mineral lubricating oil. The product, as prepared, conveniently forms a concentrate which may be blended with oils of lubricating viscosity to form a finished lubricant composition.Other additives conventionally incorporated into finished lubricant compositions may be blended into the concentrate or incorporated directly into the finished lubricant composition.

Accordingly another aspect of the present invention provides a finished lubricant composition comprising a major amount of a lubricating base oil and a minor amount of the product as hereinbefore described.

In addition to the product of the invention the finished lubricant composition may contain other additives commonly used in lubricating oils, such as dispersants, detergents, antioxidants, corrosion inhibitors, pour-point depressants, etc.

The invention will now be illustrated by reference to the following Examples.

PREPARATION OF PRODUCTS Example 1 219 g of a 7% bw solution of Intolan 140A (an ethylene/propylene/5-methylene-2-norbornene terpolymer available from International Synthetic Rubber) dissolved in 100 Solvent Neutral base oil was mixed with 31 g of ASTM Naphtha and 3.5 g of the thiol acid obtained by reacting para-dodecylphenol with phosphorus pentasulphide. The mixture was heated to a temperature in the range 60 to 800C and held at a temperature in that range for 6 hours. At the end of the reaction period the naphtha was distilled off and the product allowed to cool.

Example 2 250 g of an 8% bw solution of Intolan 140A dissolved in 100 Solvent Neutral base oil was mixed with 100 g naphtha and 4.0 g of the thiol acid obtained by reacting a mixture of C7 to Cg primary alcohols with phosphorus pentasulphide. Thereafter the procedure of Example 1 was followed.

EVALUATION OF THE PRODUCTS Example 3 A 15% bw solution of the product of Example 1 in LP 501 base oil was prepared. The solution has a viscosity of 14.5 cst at 1 00 C. The anti-wear properties of the solution were determined using the Shell 4 Ball test. The results of the scar diameter determination are given in Table 1 and EP data in Table 2. The oxidation properties of the solution were determined in the Panel Coker test in which 0.3% bw iron octoate was added to the oil. The Panel Coker test results are given in Table 3.

Example 4 A 15% bw solution of the product of Example 2 in LP 501 base oil was prepared. The solution had a viscosity of 19.0 cst at 100"C. The acid number of the solution was 5.5 mm KOH/kg indicating that approximately 86% of the thiol acid available for reaction has in fact reacted. The anti-wear and oxidation properties were determined in the same manner as Example 1.

Comparison Test A 15% bw solution of Intolan 140A in LP 501 base oil was prepared. The solution has a viscosity of 17.2 cst at 100 C. The anti-wear and oxidation properties of the solution were determined in the same manner as Example 1.

TABLE 1 Antiwear properties Scar Diameter TestTime Example3 Example4 Comparison Test 30 0.68 0.25 0.67 45 0.73 0.27 0.70 60 0.79 0.41 0.80 TABLE 2 EP Data Nature of determination Example 3 Example 4 Comparison Test Initial seizure load (kg) 100 75 75 Weld point (kg) 160 160 140 TABLE 3 Panel Coker Tests Natureofdeterminaton Example 3 Example 4 Comparison Test Wt gain/mg 2.6 0.4 5.1 Panel appearance Clean Clean Clean The results indicate that the product of Example 1 is comparable with the unreacted ethylene/propylene/ 5-methylene-2-norbornene terpolymer, Intolan 140A in terms of anti-wear properties, though its thermal stability is improved. The product of Example 2 is superior to Intolan 140A in terms of both anti-wear and thermal stability.

Claims (13)

1. The product obtained by reacting a terpolymer comprising units derived from: (i) ethylene (ii) a terminally unsaturated non-conjugated diolefin containing from 5 to 8 carbon atoms (iii) one or more of the monomers: (a) norbornene (b) a terminally unsaturated non-conjugated diolefin containing from 5 to 8 carbon atoms, (c) dicyclopentadiene and, (d) 5-methylene-2-norbornene, with a thiol acid having the formula:

wherein R' and R2 are the same or different and are either C1 to C30 primary alkyl groups or C4 to C20 secondary alkyl groups or alkyl-substituted phenyl groups in which the alkyl substituent contains from 1 to 30 carbon atoms.

2. The product according to claim 1 wherein the terminally unsaturated straight-chain mono-olefin is propylene.

3. The product according to either one of claims 1 or 2 wherein the terminally unsaturated non-conjugated diolefin containing from 5 to 8 carbon atoms is 1,4-hexadiene.

4. The product according to any one of the preceding claims wherein the terpolymer contains up to 75% by weight of units derived from ethylene, up to 75% by weight of units derived from the terminally unsaturated mono-olefin and up to 10% by weight of units derived from one or more of the monomers (a), (b), (c) or (d).

5. The product according to any one of the preceding claims wherein the terpolymer is an ethylene/propylene/5-methylene-2-norbornene terpolymer in which the ethylene/propylene ratio is about 60:40 by weight, the 5-methylene-2-norbornene content is about 5.7% by weight, the weight average molecular weight is about 31,000 and the kinematic viscosity is about 280cS.

6. The product according to any one of claims 1 to 4 wherein the terpolymer is an ethylene/propylene/ 1,4-hexadiene terpolymer in which the ethyleneipropylene ratio is about 45:55, the 1,4-hexadiene content is from 2 to 3% by weight and the kinematic viscosity is about 204cS.

7. The product according to any one of claims 1 to 6 wherein the terpolymer has a kinematic viscosity in the range 100 to 500cS.

8. The product according to any one of the preceding claims wherein either or both the groups R1 and R2 in the thiol acid of formula (I) is a C4 to C8 primary alkyl group.

9. The product according to any one of claims 1 to 7 wherein the alkyl substituent of the alkyl-substituted phenyl group in the thiol acid of formula (I) is a C3 to C21 primary alkyl group.

10. The product according to any one of the preceding claims when obtained by reacting the terpolymer with the thiol acid having the formula (I) at a temperature in the range 75 to 1200C.

11. The product according to any one of the preceding claims when obtained by reacting the terpolymer with the thiol acid having the formula (I) in the presence of a hydrocarbon solvent.

12. The product according to claim 11 wherein the solvent is removed and the product is diluted with up to 20% by weight of a mineral lubricating oil.

13. A finished lubricant composition comprising a major amount of a lubricating base oil and a minor amount of the product as claimed in any one of the preceding claims.