JPS6248717B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lubricating oil composition that has a high viscosity index and excellent detergent and dispersibility. Currently, it is known in the industry that hydrogenated products of ethylene/propylene copolymer rubber, polyalkyl methacrylate, polyisobutylene, and styrene/isoprene copolymer rubber are useful as viscosity index improvers for lubricating oils. . However, these lubricating oil additives are still far from being sufficient in terms of detergency and dispersion properties and oxidation stability. Because of the drawbacks such as a large amount of water, it is necessary to use a detergent and dispersant together in actual use. For this reason, various studies have been conducted to improve these drawbacks. For example, ethylene-propylene copolymer rubber is oxidized and then graft polymerized with monomers such as acrylonitrile or methyl methacrylate, which improves the viscosity index. It is also known that it is a lubricating oil additive with improved detergent and dispersibility (Tokuko Sho
48-42685, Special Publication No. 51-28288, etc.). In this technology, after the copolymer rubber is oxidized,
Since the two-step modification of graft polymerization is required, the operation to obtain the lubricating oil additive is complicated, the reproducibility of the modification reaction is poor, and during the oxidation stage, the polymer chain is coated with substances that cause deterioration. Since hydroperoxide groups and carbon-carbon double bonds are formed, the performance is not necessarily at a satisfactory level. The present inventors investigated a method of improving the clean dispersibility and low-temperature viscosity while retaining the advantages of ethylene copolymer rubber as a lubricating oil additive.
We have found that a method of grafting unsaturated esters of saturated carboxylic acids in one step in the presence of a radical initiator is effective. That is, according to the present invention, there is provided a lubricating oil composition comprising an oil-soluble graft polymer obtained by grafting an unsaturated ester of a saturated carboxylic acid onto an ethylene copolymer rubber, and a major amount of a lubricating oil. The oil-soluble graft polymer constituting the lubricating oil composition of the present invention is an ethylene copolymer rubber grafted with a saturated carboxylic acid unsaturated ester. The oil-soluble ethylene copolymer rubber used as a raw material for the graft polymer has a molecular weight of 5,000 or more, and preferably has a melt index at 190°C of 0.1 to 500, particularly preferably 1 to 500.
100, substantially no endothermic peak is observed by scanning differential calorimetry, and crystallinity of substantially 0% by X-ray diffraction is particularly suitable. For example, copolymer rubber of ethylene and α-olefin having 3 to 20 carbon atoms can be used. Particularly preferred are ethylene/propylene copolymer rubber or ethylene/1-
It is a butene copolymer rubber. Among these, those with an ethylene content of 40 to 80 mol%, especially 50 to 70 mol%
Mol% is also suitable. The carboxylic acid component of the saturated carboxylic acid unsaturated ester used in the grafting reaction has a carbon number of 1
It is preferable to use 1 to 18. Specifically, the carboxylic acid components include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, Straight-chain or branched carboxylic acids such as pentadecylic acid, palmitic acid, heptadecylic acid, and stearic acid can be mentioned, but among these, formic acid, acetic acid, butyric acid, caprylic acid, lauric acid, and stearic acid are preferred. Particularly preferred is acetic acid. Furthermore, aromatic carboxylic acids such as benzoic acid can also be used. Further, as the alcohol component of the unsaturated ester, it is preferable to use one having 1 to 18 carbon atoms. Specific examples of the alcohol component include vinyl alcohol, allyl alcohol, methallyl alcohol, crotyl alcohol, methyl vinyl carbinol, cinnamyl alcohol, undecenyl alcohol, oleyl alcohol, etc. Among them, vinyl alcohol, allyl alcohol, cinnamyl alcohol, and undecenyl alcohol are preferred, and vinyl alcohol is particularly preferred. Furthermore, in the graft reaction, two or more of these saturated carboxylic acid unsaturated esters may be used simultaneously, or unsaturated esters consisting of two or more alcohol components may be used. The oil-soluble graft polymer does not substantially contain gel, and its melt index at 190° C. is preferably from 0.1 to 500, particularly from 1 to 300. In addition, the saturated carboxylic acid unsaturated ester unit therein is, per 1 g of oil-soluble graft polymer,
Preferably it is from 10 ^-2 to 5 milligram equivalents, especially from 5×10 ^-2 to 1 milligram equivalent. In order to substantially prevent the formation of gel and to suppress the formation of homopolymers of unsaturated esters of saturated carboxylic acids during grafting, for example, in an alkyl aromatic hydrocarbon solvent, the technique described in Japanese Patent Publication No. 52-31276 can be used. This can also be achieved by performing a graft reaction using a method similar to the above. A radical initiator such as an organic peroxide or azonitrile can be used in the graft reaction. Organic peroxides include alkyl peroxides, aryl peroxides, acyl peroxides, aroyl peroxides, ketone peroxides, peroxycarbonates, peroxycarboxylates, hydroperoxides, and the like. Alkyl peroxides include diisopropyl peroxide and ditertiarybutyl peroxide, aryl peroxides include dicumyl peroxide, acyl peroxides include dilauroyl peroxide, and aroyl peroxides include dibenzoyl peroxide and ketone peroxide. Examples of the hydroperoxide include methyl ethyl ketone peroxide and cyclohexanone peroxide, and examples of the hydroperoxide include tertiary butyl hydroperoxide and cumene hydroperoxide.
Examples of azonitrile include azobisisobutyronitrile and azobisisopropionitrile. The alkyl aromatic hydrocarbon used as a solvent has one or more alkyl groups in the aromatic group, is liquid under the reaction conditions, and is capable of dissolving the raw material ethylene copolymer rubber, unsaturated ester of saturated carboxylic acid, and radical initiator. It is important that it is possible. The alkyl group may be linear or branched. For example, toluene, xylene, mixed xylenes, trimethylbenzenes, tetramethylbenzenes,
Ethylbenzene, cumene, cymene and the like can be mentioned, among which toluene, xylene, mixed xylene, ethylbenzene and mixtures thereof are preferred. In addition, as a solvent, a chain hydrocarbon other than the above-mentioned solvents (for example, hexane or decane) may be used.
Alternatively, chlorine-based hydrocarbons can also be used. The lubricating oil itself can be used as a solvent. In this case, as a radical initiator,
For example, the boiling point of the decomposition product of the radical initiator, such as tertiary butyl peroxide, tertiary butyl peroxyisobutyrate, tertiary butyl peroxyoctoate, etc., is lower than the boiling point of the ester monomer used, Alternatively, it is preferred to use an equivalent initiator. This is because, by subjecting the reaction solution to a normal degassing treatment after the reaction is completed, unreacted ester monomers and decomposed products of the initiator can be simultaneously removed. This method is particularly suitable because the step of isolating the grafted rubber from the graft reaction solution can be omitted and the reaction solution can be used as it is as an additive for lubricating oil. Furthermore, according to this method, the lubricating oil reacts with the unsaturated ester monomer at the same time as the ethylene copolymer rubber. Such modifications impart more desirable properties to lubricating oil compositions. The graft reaction is preferably carried out at a reaction temperature of 80 to 250°C, particularly 100 to 200°C.
If the reaction temperature is lower than the above range, it will not be possible to suppress the formation of a homopolymer of unsaturated esters of saturated carboxylic acids, and crosslinking of the ethylene copolymer rubber will easily occur, making it difficult to find suitable lubricant additives. It becomes difficult to obtain. Moreover, if the reaction temperature is higher than the above temperature, it is not preferable because the graft reaction becomes difficult to occur. The graft reaction is preferably carried out under conditions such that the concentration of the ethylene copolymer rubber is about 10 to 300 parts by weight and the radical initiator is about 0.2 to 20 parts by weight per 1000 parts by volume of the reaction solvent. Furthermore, it is preferable to select a reaction method that does not produce a homopolymer of unsaturated ester monomers. For example, there is a method in which the ethylene copolymer rubber is dissolved in a reaction medium and the unsaturated ester monomer and the radical initiator are simultaneously supplied at a temperature in the range of 80°C to 250°C, preferably 100°C to 200°C. preferable. Furthermore, a method of dissolving the ethylene copolymer rubber and the unsaturated ester monomer in a reaction solvent and supplying a radical initiator in the above temperature range, the ethylene copolymer rubber, the unsaturated ester monomer, and the radical initiator. It is also possible to adopt a method in which the reaction is carried out in the above temperature range after uniformly dissolving in a solvent. When lubricating oil is used as a reaction solvent, use the reaction liquid as it is or, if necessary, after the reaction is complete, perform deaeration treatment, and then dilute with the same or another lubricating oil and use it as lubricating oil. be able to. When lubricating oil is used as reaction solvent, 10 to 10% of the total supply of unsaturated ester monomer
Approximately 90% reacts with lubricating oil. When other reaction solvents are used, the oil-soluble graft copolymer is once isolated and then redissolved in lubricating oil for use. The concentration of the oil-soluble graft polymer in the lubricating oil composition is usually about 0.5 to 30% by weight. Other lubricating oil additives may be included in the lubricating oil composition. For example, other viscosity index improvers, detergent dispersants, extreme pressure additives, pour point depressants, antifoaming agents, antioxidants, etc. may be blended. The lubricating oil composition of the present invention has a high viscosity index, low low temperature viscosity, and excellent detergent dispersibility. Next, the present invention will be explained in more detail with reference to examples. Note that each test in the examples was conducted as follows. (1) Kinematic viscosity Measured according to JIS K2283 using a Canon-Fenske viscosity tube at a temperature of 100〓 or 210〓. (2) Viscosity index The viscosity index was determined according to JIS K2284. (3) Shear stability Measured according to ATSM D-2603-70. That is, the sample oil was irradiated with ultrasonic waves of 100 W and 10 KHz for 30 minutes, and the kinematic viscosity at 210〓 before and after the test (referred to as η ₁ and η _2, respectively) was determined using the following formula. Shear stability (viscosity reduction rate) η ₁ −η ₂ /η ₁ ×100 (%) (4) CCS low-temperature viscosity The low-temperature viscosity of 0 was measured using a low-temperature viscometer manufactured by Canon Inc. in accordance with JIS K2606. (5) Clean dispersibility Fed.Test Method STD.No.791B (Coking
The test was conducted using a panel caulking tester manufactured in accordance with the Tendency of Oil (Tendency of Oil) standard. Under the conditions of Al panel temperature 285℃ and sample temperature 125℃, the cycle of splasher rotation for 1 second and rest for 9 seconds was repeated, and after 5 hours, the weight of carbon sludge attached to the test piece surface (mg)
was measured. (6) Transparency of oil solution Purified kaolin and distilled water were used in accordance with the water turbidity measurement method in JIS K0101.
Turbidity standard solutions of 400 and 500 ppm were prepared and visually compared with the standard solutions. According to this method,
It is completely transparent or almost transparent when the kaolin content is up to 20 ppm, becomes slightly cloudy when the kaolin content is 30 to 50 ppm, and looks quite cloudy when the kaolin content exceeds 100 ppm. Judgment error after repeated testing is ±5ppm
It was hot. Example 1 Ethylene-propylene rubber (ethylene content 60 mol%, decalin reduced specific viscosity (RSV) at 135°C 1.0, melt index at 190°C (load 2160 g, orifice diameter 2 mmφ) 30 (g/10)
), number average molecular weight 18,000, Mw/Mn= by GPC
1.9 (no endothermic peaks by DSC, crystallinity 0% by X-rays) 200g of commercially available #100 neutral oil
The kinematic viscosity at 〓, 210〓 is 22.5cst and 4.27cst, respectively.
, viscosity index is 104, pour point -17.5℃) 800g
In addition, the liquid was replaced with nitrogen gas for 1 hour. The liquid temperature was raised to 150°C to completely dissolve the copolymer rubber. To this rubber-oil solution 1, 17.2 g of vinyl acetate and 7.3 g of ditertiary butyl peroxide were added dropwise at a temperature of 150 DEG C. over 4 hours. Stirring was further continued for 2 hours as a post-reaction. Subsequently, the temperature of the system was raised to 180° C. and nitrogen gas was blown into the reaction solution for 2 hours to remove volatile components such as unreacted monomers and decomposed products of peroxide in the system. The resulting denatured solution is clear and contains kaolin.
It corresponded to a standard solution of 15 ppm. This denaturing solution was mixed with commercially available #150 neutral oil (100〓, 210
A sample oil A with a kinematic viscosity of 33.1 and 5.36 cst at 210° and 17 cst at 210° was prepared by adding 13.4 wt% to the viscosity index of 105 and pour point of −17.5°C, respectively. Example 2 Acetone and hexane were added to 100 ml of the modified solution obtained in Example 1 to precipitate the polymer. The obtained polymer was washed repeatedly with acetone to obtain 16 g of purified graft rubber. The vinyl acetate unit content of this product was 1.5 wt% (0.18 meq/g), and the RSV was 0.80. As a result of analysis of this modified solution and volatile trapping solution, 18% of the vinyl acetate used was grafted onto the polymer, and 42.5% was reacted with neutral oil.
%, unreacted matter trapped as volatiles 39%,
The amount of unreacted material remaining in the denatured solution after degassing was 0.5%. The obtained purified graft rubber was once dissolved in #100 neutral oil to obtain a transparent oil solution with a polymer content of 20 wt%. Furthermore, this was used in Example 1.
Sample oil B was prepared by adding 13.3% to #150 neutral oil and having a kinematic viscosity of 17cst at 210㎓. Table 1 shows the various test results for these sample oils A and B. Comparative example 1 Ethylene-propylene rubber 200 same as Example 1
g was added to 800 g of the same #100 neutral oil as in Example 1 to prepare an oil solution having a polymer content of 20 wt% in the same manner as in Example 1. The transparency of this solution was equivalent to that of a solution containing 15 ppm of kaolin as a turbidity standard solution. This solution was further added in an amount of 12.7 wt% to the #150 neutral oil of Example 1 to prepare sample oil C having a kinematic viscosity of 17cst and 210㎓. The test results are shown in Table 1.

[Table] From the results in Table 1, it is clear that the graft copolymerized rubber produced by the method of the present invention has significantly improved cleaning dispersibility while maintaining good viscosity index improvement and shear stability before modification. be. Example 3 200g of the same copolymer rubber as the ethylene-propylene rubber used in Example 1 was added to xylene 1, and after the system was purged with nitrogen for 1 hour, the temperature of the system was raised to 125°C, and the polymer completely dissolved.
17.2 g of vinyl acetate and 1.35 g of dicumyl peroxide (dissolved in 20 ml of xylene) were added to the
It dripped over time. After completion of the dropwise addition, stirring was continued for an additional 2 hours to carry out post-reaction. After the reaction was completed, the reaction solution was cooled to room temperature, and a large amount of acetone was added to precipitate the polymer. The obtained precipitate was thoroughly washed with acetone and then vacuum-dried at room temperature to obtain a purified dry polymer. The vinyl acetate unit introduced into this graft copolymer rubber was determined from the oxygen content, and was found to be 1.2 wt%. This graft copolymer rubber was used in Example 1.
It was added to #100 neutral oil to make a 20wt% oil solution. The transparency of this solution is good, with 20ppm kaolin.
It was equivalent to the standard suspension containing it. This polymer solution was added to the #150 neutral oil used in Example 1 to prepare sample oil D of 17cst at 210%. The test results are shown in Table 3. Examples 4 to 6 Transparent modified-neutral oil solutions were obtained in exactly the same manner as in Example 1, except that vinyl butyrate, vinyl laurate, and allyl acetate were used as monomers to be grafted. Sample oils E, F, and G were obtained by adding 13.6, 12.7, and 13.0% of each denaturing solution to #150 neutral oil, respectively. Table 3 shows the test results for each sample oil.

[Table] Examples 7 to 9 A portion of the vinyl acetate modified solution (added amount 13.4 wt%) used in sample oil A prepared in Example 1 was added to the unmodified ethylene-propylene rubber used in Comparative Example 1.
By substituting #150 neutral oil solution, sample oils H, I, and J were obtained by diluting the modified rubber solution in sample oil A with an unmodified rubber solution. These results are shown in Table 4.

[Table] Examples 10 to 13 Modification solutions with different amounts of grafting in ethylene-propylene copolymer rubber were obtained by the same method as in Example 1, except for increasing and decreasing the supply amounts of vinyl acetate and ditertiary butyl peroxide. Ta. Further,
Similar to Example 1, dissolve in #150 neutral oil,
Sample oil K, L, M, N with 17cst at 210〓
was prepared. The test results are shown in Table 5.

[Table] Examples 14 and 15 Vinyl acetate modified solutions were obtained in the same manner as in Example 1, except that ethylene/propylene copolymer rubbers having different ethylene contents were used. By adding this to #150 neutral oil, sample oils O and P with 17cst at 210ⓓ were prepared. The results are shown in Table 6.

[Table] Examples 16, 17 and Comparative Example 2 Vinyl acetate was prepared in the same manner as in Example 1, except that the method of adding the modifiers vinyl acetate and ditertiary butyl peroxide was changed as shown in Table 7. of ethylene-propylene copolymer rubber modified with
A #100 neutral oil solution was prepared. This was prepared using the same method as in Example 1.
#160 neutral oil was added to prepare sample oils Q, R, and S at 17cst at 210㎓. The test results are shown in Table 7.

[Table] Example 18 Benzoyl peroxide as a radical initiator
6.05mg (60ml acetone solution), reaction temperature 100℃
A vinyl acetate-modified #100 neutral oil solution was obtained in the same manner as in Example 1, except for the following steps. The content of vinyl acetate in purified graft rubber is 1.9wt% (0.22 equivalent/g)
It was hot. This modified neutral oil solution was added to #150 in the same manner as in Example 1.
A clear sample oil T of 17 cst at 210㎓ was prepared by adding 13.6 wt% to a neutral oil.
As a result of testing this sample oil T, the viscosity index was
163, the amount of sludge adhered after the panel caulking test was 95 mg, and the viscosity reduction rate after ultrasonic irradiation was also
It showed good performance at 8.0%. Comparative Example 3 Ethylene content as ethylene/propylene rubber
60 mol% of decalin, 250 g of amorphous rubber with a reduced specific viscosity (RSV) of 4.5 at 135°C, was dissolved in 5 o-dichlorobenzene, and air was introduced into the system at a rate of 120/hour while stirring at a temperature of 180°C. After blowing for a certain period of time, the reaction solution was cooled to room temperature, and a large amount of acetone was added to obtain ethylene/propylene rubber that had been oxidized and degraded by air. Infrared absorption spectrum analysis of the resulting degraded rubber revealed the presence of oxygen-containing functional groups such as hydroxyl groups, aldehydes, ketones, carboxylic acids, and esters, as well as carbon-carbon double bonds due to cleavage of the polymer main chain. . The double bond content determined from the iodine value of this degraded rubber is approximately
It was 0.1 meq/g, and its RSV was 0.72. A graft modification reaction was carried out in the same manner as in Example 1, except that the thus obtained oil solution of degraded ethylene-propylene rubber was used. As a result, the vinyl acetate unit content of the modified rubber is
Although the concentration was 1.6 wt%, the viscosity of the reaction solution increased significantly. This reaction solution was added 12% to the #150 neutral oil used in Example 1, and a 17cst sample oil U was prepared at 210%. As a result of testing this sample oil U, the shear stability was 21%, and the amount of coating on panel caulking sludge was 305.
It was mg. Examples 19 and 20 Same method as in Example 1 except that ethylene/1-butene copolymer rubber or ethylene/4-methyl-1-pentene copolymer rubber is used in place of ethylene/propylene copolymer rubber in Example 1. A vinyl acetate modified solution was obtained. Each of these was added to #100 neutral oil to prepare sample oils V and W. The results are shown in Table 8.

【table】

Claims (1)

[Scope of Claims] 1. A lubricating oil composition comprising an oil-soluble graft polymer obtained by grafting an unsaturated ester of a saturated carboxylic acid onto an ethylene copolymer rubber, and a major amount of a lubricating oil. 2. The composition according to claim 1, wherein the ethylene copolymer rubber is an ethylene/propylene copolymer rubber. 3. The composition according to claim 1 or 2, wherein the ethylene copolymer rubber has a melt index at 190°C ranging from 0.1 to 500. 4. The composition according to any one of claims 1 to 3, wherein the ethylene composition of the ethylene copolymer rubber is in the range of 40 to 80 mol%. 5. The composition according to claim 1, wherein the ethylene copolymer rubber is an amorphous rubber with substantially no endothermic peak observed by scanning differential calorimetry and a crystallinity of 0% by X-ray diffraction. thing. 6. The composition according to claim 1, wherein the alcohol component of the unsaturated ester of saturated carboxylic acid has 1 to 18 carbon atoms. 7 Claim 6 wherein the alcohol component of the saturated carboxylic acid unsaturated ester is vinyl alcohol
Compositions as described. 8. The composition according to claim 1, wherein the carboxylic acid component of the unsaturated ester of saturated carboxylic acid has 1 to 18 carbon atoms. 9. The composition according to claim 8, wherein the carboxylic acid component of the unsaturated ester of saturated carboxylic acid is acetic acid. 10. The composition according to claim 1, wherein the saturated carboxylic acid unsaturated ester unit is contained in an amount of 10 ^-2 to 5 milliequivalents per gram of the oil-soluble polymer. 11. The composition according to claim 1, wherein part or all of the lubricating oil is modified with an unsaturated ester of a saturated carboxylic acid. 12 Dissolve the ethylene copolymer rubber in a lubricating oil, and react the saturated carboxylic acid unsaturated ester with the ethylene copolymer rubber and the lubricating oil under conditions that substantially do not produce a homopolymer of the saturated carboxylic acid unsaturated ester. A method for producing a lubricating oil composition, which comprises diluting the composition with a lubricating oil as necessary. 13. The method according to claim 12, wherein the ethylene copolymer rubber is an ethylene-propylene copolymer rubber. 14. The method according to claim 12 or 13, wherein the ethylene copolymer rubber has a melt index at 190°C ranging from 0.1 to 500. 15 The ethylene composition of the ethylene copolymer rubber is 40
Claim 12 in the range of 80 to 80 mol%
Or the method described in 13. 16. The method according to claim 12, wherein the ethylene copolymer rubber is an amorphous rubber with substantially no endothermic peak observed by scanning differential calorimetry and a crystallinity of 0% by X-ray diffraction. . 17. The method according to claim 12, wherein the alcohol component of the unsaturated ester of saturated carboxylic acid has 1 to 18 carbon atoms. 18. The method according to claim 17, wherein the alcohol component of the unsaturated ester of saturated carboxylic acid is vinyl alcohol. 19. The method according to claim 15, wherein the carboxylic acid component of the unsaturated ester of saturated carboxylic acid has 1 to 18 carbon atoms. 20. The method according to claim 19, wherein the carboxylic acid component of the unsaturated ester of saturated carboxylic acid is acetic acid. 21. The method according to claim 12, wherein the reaction temperature is 80°C to 250°C.