JP2000026881A - Viscosity index improver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a viscosity index improver which can reduce the amt. of a coking product by incorporating a copolymer of an alkyl (meth)acrylate and a specific alkoxyalkylene glycol mono(meth)acrylate into the same. SOLUTION: A viscosity index improver comprising a polymer having a wt. average mol.wt. of 10,000-500,000 is obtd. by subjecting 0-80 wt.% alkyl (meth)acrylate having a 1-24C linear or branched alkyl group, 20-90 wt.% alkoxyalkylene glycol (meth)acrylate of which the homopolymer has a solubility parameter of 8.7-9.3, 0-10 wt.% other free-radically polymerizable monomer, and 0-5 wt.% monomer having at least one atom selected from N, O, and S to free-radical polymn. in a mineral oil or a solvent in the presence of a polymn. catalyst. In the formula, R1 is (meth)acryloyl; R2 is 8-24C alkyl; (m) and (n) are each 0-8 provided (m+n) is 1-10; and [(CH2H4O)m/(C3H6O)n] means random copolymn. or block copolymn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a viscosity index improver. More specifically, the present invention relates to a viscosity index improver that produces a small amount of caulk.

[0002]

2. Description of the Related Art In recent years, there has been an increasing tendency to protect the global environment, and there has been a further demand for more fuel-efficient automobiles. In order to improve the fuel efficiency of automobiles, there is a method of adding a viscosity index improver to engine oil to make it multi-grade. In Japan, nearly 30% of engine oils used in diesel engine vehicles are multi-grade oils to which a viscosity index improver is added. This multi-grade oil uses a viscosity index improver (hereinafter abbreviated as OCP-based viscosity index improver) composed of an ethylene / propylene copolymer. However, in the future, when more fuel efficiency is required, lower viscosity of the engine oil is required. In this case, the engine oil desirably has a high viscosity index and a low high-temperature high-shear viscosity (hereinafter abbreviated as TBS viscosity). However, OCP-based viscosity index improvers have the disadvantages of low viscosity index and high TBS viscosity, and do not contribute to further improvement in fuel economy. On the other hand, an engine oil using a viscosity index improver composed of an alkyl (meth) acrylate polymer (hereinafter abbreviated as a PMA-based viscosity index improver) has a higher viscosity index than that using an OCP-based viscosity index improver. Because of its low TBS viscosity, more excellent fuel economy can be expected than the engine oil using the current OCP-based viscosity index improver.

However, an engine oil using a PMA-based viscosity index improver has a problem that the coking amount is large. Various proposals have been made to improve this point.
For example, a PMA-based viscosity index improver containing a specific hydroxyalkyl (meth) acrylate (JP-A-5-22
389, JP-A-5-287028, etc.). However, although the dispersibility of the sludge is excellent, the effect of reducing the amount of coking is not sufficiently exhibited.

[0004]

As a result of intensive studies, the present inventors have found a PMA-based viscosity index improver whose coking amount is less than or equal to that of an OCP-based viscosity index improver, and reached the present invention. That is, the present invention relates to a polymer comprising alkyl (meth) acrylate (a1) and an alkoxyalkylene glycol mono (meth) acrylate (a2) having a homopolymer solubility parameter of 8.7 to 9.3. Is a viscosity index improver.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The alkyl (meth) acrylate (a1) used in the present invention is not particularly limited, but usually has a linear or branched alkyl group having 1 to 24 carbon atoms (meth). ) Acrylate (methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2
-Ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl petamethacrylate, hexadecyl methacrylate, octadecyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate , Tridecyl acrylate, tetradecyl acrylate, pentadecyl petaacrylate, hexadecyl acrylate, octadecyl acrylate, etc.). Among these various (meth) acrylates, an alkyl (meth) acrylate having an alkyl group having 10 or less carbon atoms is preferable from the viewpoint of reducing the amount of coking.

The content of the monomer (a1) in the polymer (A) in the present invention is not particularly limited, but is usually 0 to 80% by weight based on the weight (A), and the amount of coking is reduced. Is preferably based on the weight (A).
0 to 80% by weight.

The alkoxyalkylene glycol (meth) acrylate (a2) used in the present invention is an esterified product of alkoxyalkylene glycol, which is an alkylene oxide adduct of alkyl alcohol, and (meth) acrylic acid. The monomer (a2) is not particularly limited as long as the homopolymer has a solubility parameter in the range of 8.7 to 9.3. When the solubility parameter of the homopolymer is less than 8.7, the viscosity index may be low, and when the solubility parameter of the homopolymer exceeds 9.4, the solubility may be poor. Preferably, it is an alkoxyalkylene glycol (meth) acrylate represented by the general formula (1). General formula R ¹ —O — [(C ₂ H ₄ O) m / (C ₃ H ₆ O) n] —R ² (1) {wherein R ¹ is a (meth) acryloyl group, and R ² is carbon number 8
To 24 alkyl groups. m is 0-8, n is 0-8,
It is a number of 1 to 10 in total of n and m. [(C ₂ H ₄ O) m /
(C ₃ H ₆ ) n] indicates random addition or block addition. More preferably, in the general formula (1), R ¹ is a methacryloyl group, R ² is an alkyl group having 8 to 12 carbon atoms, m is 0 to 5, n is 0 to 5, and the sum of n and m is 1 to 1. It is the number eight.

The content of the monomer (a2) in the polymer (A) in the present invention is not particularly limited, but is preferably 20% by weight based on the weight (A) in order to reduce the amount of coking. And particularly preferably the weight (A)
20 to 90% by weight based on

In the present invention, the copolymer (A) may contain other radically polymerizable monomers (b) as structural units in addition to (a1) and (a2). Examples thereof include unsaturated mono- and / or polycarboxylic acid esters having 1 to 30 carbon atoms in the alkyl group other than alkyl (meth) acrylate (butyl crotonate, octyl crotonate, dodecyl crotonate, dibutyl maleate, Dioctyl fumarate, dilauryl maleate,
Distearyl fumarate, dioctyl itaconate, dilauryl itaconate, etc.); vinyl aromatic compounds (styrene, vinyl toluene, etc.); vinyl esters (vinyl acetate, vinyl propionate, etc.); alpha olefins (decene, dodecene, etc.) Carboxylic acid compounds (maleic anhydride, methacrylic acid, crotonic acid, itaconic acid, etc.); acrolein; conjugated dienes (butadiene, isoprene, chloroprene, etc.); acetylene; substituted acetylene [alkyl acetylene (propyne, 1-butyne, 1 -Pentine, 1-hexyne, etc.), arylacetylene (phenylacetylene, p-methylphenylacetylene, etc.)]; alkyl vinyl ether [usually alkyl vinyl ether having a linear or branched alkyl group having 1 to 18 carbon atoms] Methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether, heptyl vinyl ether, octyl vinyl ether, nonyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tridecyl vinyl ether, tetradecyl vinyl ether, pentadecyl vinyl ether, hexadecyl vinyl ether, octadecyl Vinyl allyl ether]; alkyl allyl ether [generally, alkyl allyl ether having a linear or branched alkyl group having 1 to 18 carbon atoms (methyl allyl ether, ethyl allyl ether, propyl allyl ether, butyl allyl ether, amyl allyl ether, hexyl allyl) Ether, heptyl allyl ether, octy Allyl ether, nonyl allyl ether, decyl allyl ether, dodecyl allyl ether, tridecyl allyl ether, tetradecyl allyl ether, pentadecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether, and the like. Of these, preferred are vinyl aromatic compounds and alkyl vinyl ethers, and particularly preferred are styrene and alkyl vinyl ethers having 2 to 6 prime numbers.

[0010] The content of the monomer (b) in the polymer (A) in the present invention is not particularly limited, but is usually the weight (A).
0 to 10% by weight based on the weight, preferably 0 to 5% by weight based on the weight body (A).

Further, in the present invention, the copolymer (A) comprises:
If necessary, one or more monomers (c) having at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom may be contained as a structural unit. In this case, the viscosity index improver is preferable because it can impart clean dispersibility, antioxidant property, and the like. Examples thereof include N-vinylpyrrolidone, N-vinylthiopyrrolidone, vinylpyridine, N, N-dialkylaminoalkyl (meth) acrylate (the alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (Meth) acrylamide (the alkyl group usually has 1 to 4 carbon atoms), vinylimidazole, morpholinoalkylene (meth) acrylate, etc., aminophenothiazine, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole, amino Examples include pyrrole, aminoimidazoline, aminomercaptothiazole, and (meth) acrylate derivatives having an aminopiperidine residue. Of these, preferred are N-vinylpyrrolidone, N, N-dialkylaminoalkyl (meth) acrylate (the alkyl group usually has 1 to 4 carbon atoms), N, N-dialkylaminoalkyl (meth) acrylamide (alkyl group Are usually 1 to 4) and (meth) acrylate derivatives having an N-arylphenylenediamine residue.

The content of the monomer (c) in the polymer (A) in the present invention is not particularly limited, but is usually the weight (A).
0 to 5% by weight based on the weight, and preferably 0 to 3% by weight based on the weight body (A).

The viscosity index improver of the present invention has a preferred molecular weight. Usually, the weight average molecular weight (Mw) needs to be in the range of 1 to 500,000. If it is less than 10,000, the thickening effect is insufficient, and if it exceeds 500,000, the shear stability becomes poor.
When used for drive system lubricating oil (manual transmission oil, differential gear oil, automatic transmission oil, etc.), Mw is preferably 2
When used for hydraulic oil (hydraulic oil for construction machinery, power steering oil, shock absorber oil, etc.), Mw is preferably in the range of 30,000 to 200,000, and engine oil (for gasoline, When used for diesel applications, etc.), it is preferable that Mw is in the range of 130,000 to 500,000. In addition, this molecular weight is a molecular weight converted into polystyrene by gel permeation chromatography.

The copolymer (A) in the present invention can be easily obtained by a usual method. For example, it can be obtained by radical polymerization of the above monomers in mineral oil or a solvent. In this case, an azo type (eg, azobisisobutyronitrile, azobisvaleronitrile, etc.) or a peroxide type (eg, benzoyl peroxide, cumyl peroxide, lauryl peroxide, etc.) can be used as the polymerization catalyst. .

The copolymer (A) is a monomer (a1)
And (a2) graft polymerization of the monomer (c) with a peroxide polymerization catalyst to the polymer obtained by polymerizing the monomer (b) and / or (c) if necessary. Can be obtained by

The viscosity index improver of the present invention preferably further contains another pour point depressant. As the pour point depressant, a conventionally known poly (meth) acrylate is used. For example, when the carbon number of the alkyl group is 1
0-20 (meth) acrylates, or a combination of two or more (meth) acrylates having different compositions and molecular weights (for example, those described in JP-A-54-70305 and the like) ), And further, those having a very high molecular weight (for example, those of US Pat. No. 5,229,021). When the pour point depressant is contained as described above, the amount of the pour point depressant is usually 30 parts by weight or less, preferably 1 to 20 parts by weight, based on 100 parts by weight of the polymer (A).

The viscosity index improver of the present invention may contain other optional components such as detergents (sulfonate, salicylate, phenate, naphthenate, etc.), dispersants (isobutenylsuccinimide, Mannich condensation). Substances), antioxidants (zinc dithiophosphate, amines, hindered phenols, etc.), oil agents (fatty acids,
Fatty acid ester type), friction and wear modifier (molybdenum dithiophosphate, molybdenum carbamate, etc.), and extreme pressure agent (sulfur phosphorus type, chlor type, etc.) may be included.

[0018]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

(Synthesis example of alkoxyalkylene glycol monomethacrylate) Stirrer, heater, thermometer,
In a reactor equipped with a nitrogen blowing tube, methacrylic acid and a hydroxyl group (OH group) -containing compound in the amounts shown in Table 1 were added at an equivalent ratio of carboxyl group to hydroxyl group [(COOH group / OH
Base) = (1.1 / 1.0)] and the total weight is 2
Then, 1 g of sulfuric acid and 1 g of benzoquinone were charged, and dehydration and esterification were performed at 120 ° C. for 4 hours while blowing air. Next, after removing excess methacrylic acid at 120 ° C. under reduced pressure, the pressure was returned to normal pressure and the system was cooled to 40 ° C. or lower. After cooling, 200 g of a 10% sodium hydroxide solution was added and mixed with stirring, and the mixture was separated by standing. Take the upper layer and wash it with 200 g of water 5 times.
The described alkoxyalkylene glycol monomethacrylate was obtained.

[0020]

[Table 1]

(Synthesis Example of Alkoxyalkylene Glycol Monoacrylate) Acrylic acid and a hydroxyl group (OH group) -containing compound in the amounts shown in Table 2 were placed in a reactor equipped with a stirrer, a heating device, a thermometer, and a nitrogen blowing tube. , Equivalent ratio of carboxyl group to hydroxyl group [(COOH group / OH group) =
(1.1 / 1.0)] and the total weight is 200 g.
1 g of sulfuric acid and 1 g of benzoquinone were further charged.
While blowing air, dehydration and esterification were performed at 120 ° C. for 4 hours. Next, after removing excess athacrylic acid at 120 ° C. under reduced pressure, the pressure was returned to normal pressure and cooled to 40 ° C. or less. After cooling, 10% sodium hydroxide solution 20
0 g was added and mixed with stirring, and the mixture was separated by standing. The upper layer was removed and washed with 200 g of water five times to obtain the alkoxyalkylene glycol monoacrylate shown in Table 1.

[0022]

[Table 2]

EXAMPLE 1 150 g of mineral oil, 70 g of decyl methacrylate as a monomer, 20 g of (OP ₂ M), and 20 g of azo as a catalyst were placed in a reactor equipped with a stirrer, a heating device, a thermometer, and a nitrogen blowing tube. After charging 0.2 g of bisvaleronitrile and purging with nitrogen, a polymerization reaction was carried out at 70 ° C. for 4 hours in a sealed state. As a result, a viscosity index improver 1 of the present invention comprising a copolymer having a weight average molecular weight of 300,000 was obtained.

Example 2 A copolymer having a weight average molecular weight of 310,000 was obtained by conducting polymerization in the same manner as in Example 1, except that 20 g of (OP ₂ M) was changed to 20 g of (RP ₂ M) as a monomer. Was obtained.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of (RP ₈ M) as a monomer, and a copolymer having a weight average molecular weight of 300,000 was used. Was obtained.

Example 4 20 g of (OP ₂ M) as a monomer and 20 g of (RPEM)
Polymerization was carried out in the same manner as in Example 1 except that
A viscosity index improver 4 of the present invention comprising a copolymer having a weight average molecular weight of 320,000 was obtained.

Example 5 A copolymer having a weight average molecular weight of 320,000 was obtained by polymerization in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of (TP ₈ M) as a monomer. Was obtained.

Example 6 A copolymer having a weight average molecular weight of 330,000 was obtained by polymerization in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of (RP ₂ A) as a monomer. Was obtained.

Example 7 A copolymer having a weight average molecular weight of 330,000 was obtained by polymerization in the same manner as in Example 1, except that 20 g of (OP ₂ M) was changed to 20 g of (RP ₈ A) as a monomer. Was obtained.

Example 8 Polymerization was carried out in the same manner as in Example 1 except that 70 g of decyl methacrylate was changed to 70 g of 2-ethylhexyl methacrylate as a monomer, and the present invention was composed of a copolymer having a weight average molecular weight of 300,000. Was obtained.

Example 9 Example 1 was repeated except that 70 g of decyl methacrylate was changed to 70 g of 2-ethylhexyl acrylate as a monomer.
Polymerization was carried out in the same manner as described above to obtain a viscosity index improver 9 of the present invention comprising a copolymer having a weight average molecular weight of 290,000.

Example 10 In a reactor equipped with a stirrer, a heating device, a thermometer, and a nitrogen blowing tube, 150 g of mineral oil, 70 g of decyl methacrylate as a monomer, and 20 g of (OP ₂ M), and azo as a catalyst were used. After charging 0.2 g of bisvaleronitrile and purging with nitrogen, a polymerization reaction was carried out at 70 ° C. for 4 hours in a sealed state. Further, 0.2 g of t-butyl perbenzoate, N
-2 g of vinylpyrrolidone was charged, and graft polymerization was performed at 130 ° C for 2 hours. As a result, the weight average molecular weight was 32
A viscosity index improver 10 of the present invention comprising 10,000 polymers was obtained.

Example 11 Polymerization was carried out in the same manner as in Example 1 except that 0.5 g of n-butyl vinyl ether was used as a monomer, and the present invention comprised a copolymer having a weight average molecular weight of 280,000. A viscosity index improver 12 was obtained.

Example 12 70 g of decyl methacrylate as a monomer, (OP
The ₂ M) 20g, decyl methacrylate 20g, (OP ₂
M) Polymerization was carried out in the same manner as in Example 1 except that the amount was changed to 70 g, to obtain a viscosity index improver 12 of the present invention comprising a copolymer having a weight average molecular weight of 290,000.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of decyl methacrylate as a monomer. An inventive viscosity index improver ratio of 1 was obtained.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of 2-ethylhexyl methacrylate as a monomer, and a copolymer having a weight average molecular weight of 310,000 was obtained. Thus, the viscosity index improver ratio 2 of the present invention was obtained.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that 20 g of (OP ₂ M) was changed to 20 g of 2-ethylhexyl methacrylate as a monomer, and a copolymer having a weight average molecular weight of 310,000 was obtained. Thus, a viscosity index improver ratio 3 of the present invention was obtained.

COMPARATIVE EXAMPLE 4 OCP viscosity index improver comprising ethylene / propylene copolymer (Orfus M-12, manufactured by Mitsui Petrochemical Industries, Ltd.)
10) was set as the viscosity index improver ratio 4.

(Use Examples 1 to 12 and Comparative Use Examples 1 to 4)
The viscosity index improvers 1 to 12 of the present invention of Examples 1 to 12, the viscosity index improver ratios 1 to 4 of Comparative Examples 1 to 4 are 1 to 5%, and the DI package for CD grade diesel engine oil is 5%. Refined oil A (150 neutral oil having a viscosity index of 100) and solvent refined oil B (2 having a viscosity index of 100)
00 neutral oil) and engine oils 1-21 and ratios 1-3. At that time, the kinematic viscosity at 100 ° C.
0 to 10.4 cSt and a CCS viscosity of -20 ° C of 30
The blending amounts of the solvent refined oils A and B were adjusted to be 00 cP. These engine oils were subjected to a panel coking test and an oxidation stability test by the following methods. Table 3 shows the results. In addition, the TBS viscosity (150
° C, a shear rate of 10 ⁶ / sec) and a viscosity index are shown in Table 4.

(Method of Panel Coking Test) According to the panel coking test method Fed-791B, the engine oils 1 to 9 and the ratios 1 to 4 were subjected to a panel coking test at a panel temperature of 300 ° C. and an engine oil temperature of 100 ° C. for 4 hours. . After the test, the panel was washed with pentane, and the amount of coking was measured by a gravimetric method.

(Method of Oxidation Stability Test) The above engine oils 1 to 12 and ratios 1 to 4 were measured in accordance with JIS-K2514.
An oxidation stability test was performed at 165.5 ° C. for 96 hours. The increase in the total acid value of the engine oil before and after the test was measured.

[0042]

[Table 3]

As can be seen from Table 3, a polymer comprising the alkyl (meth) acrylate of the present invention and an alkoxyalkylene glycol mono (meth) acrylate having a homopolymer solubility parameter of 8.7 to 9.3 is a structural unit. The engine oil (use examples 1 to 9) using the coalesced viscosity index improver has a structural unit of an alkoxyalkylene glycol mono (meth) acrylate (a2) having a homopolymer solubility parameter of 8.7 to 9.3. The amount of coking can be significantly reduced as compared with the engine oil (Comparative Use Examples 1 and 2) using a viscosity index improver composed of a (meth) acrylate-based polymer, and the OCP viscosity which is conventionally said to be small The coking amount is equal to or less than that when the index improver is used (Comparative Use Example 4).

[0044]

[Table 4]

As can be seen from Table 4, the engine oil using the viscosity index improver of the present invention (Use Examples 1 to 10) is different from the engine oil using the OCP viscosity index improver of Comparative Use Example 4 Low TBS viscosity and high viscosity index.

[0046]

As is clear from the above examples, the engine oil using the viscosity index improver of the present invention is a
Since the coking amount can be reduced to equal to or less than that of the engine oil having the CP viscosity index improver and the TBS viscosity is lower and the viscosity index is higher than when the OCP viscosity index improver is used, future automobiles An excellent engine oil that can meet the demand for fuel economy of the present invention can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C10N 40:25 F term (Reference) 4H104 CB08C CB15C CB16C EA03C LA01 4J027 AC03 AC04 AC06 AJ01 AJ02 AJ06 BA02 BA03 BA04 BA05 BA07 BA10 BA13 BA14 BA15 CB03 CB09 CC02 4J100 AL03P AL04P AL05P AL08P AL08Q BA04Q BA08Q BA09Q CA04 DA01 FA03

Claims (5)

[Claims] 1. An alkyl (meth) acrylate (a1)
And the solubility parameter of the homopolymer is 8.7-9.
3 is an alkoxyalkylene glycol mono (meth)
A viscosity index improver comprising a polymer (A) containing acrylate (a2) as an essential constituent unit. 2. The viscosity index improver according to claim 1, wherein the content of (a2) in the polymer (A) exceeds 20% by weight. 3. The viscosity index improver according to claim 1, wherein (a2) is an alkoxyalkylene glycol mono (meth) acrylate represented by the general formula (1). General formula R ¹ —O — [(C ₂ H ₄ O) m / (C ₃ H ₆ O) n] —R ² (1) {wherein R ¹ is a (meth) acryloyl group, and R ² is carbon number 8
To 24 alkyl groups. m is 0 to 10, n is 0 to 1
0, a total of 1 to 10 of n and m. [(C ₂ H ₄ O)
m / (C ₃ H ₆ ) n] indicates random addition or block addition. ｝ 4. The viscosity index improver according to claim 1, wherein the alkyl group of (a1) is a (meth) acrylate having an alkyl group having 10 or less carbon atoms. 5. The polymer (A) having a weight average molecular weight of 1
The viscosity index improver according to any one of claims 1 to 4, wherein the viscosity index improver is from 000 to 500,000.