JPS61238891A - Oil film thickness improver for lubricant - Google Patents

Abstract

PURPOSE:To obtain the titled improver which can effectively prevent the damage to the surface of a metal and the fatigue of a mechanical element and can improve the service life of the mechanical element, by incorporating a base oil with a (co)polymer contg. a specific cyclohexyl acrylate compd. CONSTITUTION:1mol of a cyclohexyl acrylate compd. of the formula I (wherein R1 is H or a 1-20C hydrocarbon radical; and R2 is a hydrocarbon radical having a cyclohexyl ring) and optionally 100mol or less of monomers of the formulae II and III (wherein R3 is H or a 1-4 hydrocarbon radical; and R4 is H or a 1-30 hydrocarbon radical) which can form other constitutional units of a polymer are (co)polymerized in the presence of a catalyst at 20-100 deg.C for 0.5-10hr to obtain a (co)polymer containing a cyclohexyl acrylate compd. having a weight-average MW of several thousands - 300,000. 0.1-70wt% (co)polymer is added to a naphthene mineral oil and/or paraffin mineral oil so that the degree of film formation alpha defined by the formula IV (wherein Hm is the oil film thickness of the lubricant to which the oil film thickness improver has been added; and Ha is the oil film thickness determined from the apparent viscosity of the oil film improver) is 20% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention improves the elastohydrodynamic oil film thickness of lubricating oils in various ta#i elements that are formulated into lubricating oils and used in elastohydrodynamic lubrication conditions. This invention relates to an oil film thickness improver.

[Conventional technology]

Conventionally, various mechanical elements such as gears, rollers, chains, and bearings have been used to transmit power and change speeds, and damage to the metal surface of such mechanical elements at parts where metal-to-metal contact occurs, such as Lubricating oils are used to prevent wear, spalling, pitting, fretting, and fatigue of mechanical elements.

This lubricating oil penetrates into metal-to-metal contact and forms an oil film between these metals to prevent direct contact.
This prevents damage to metal surfaces and extends the life of mechanical elements, so the thicker the oil film formed between metals, the more ideal lubrication performance will be exhibited.

Therefore, conventionally, additives that react with metals to form metal-organic protective films or additives used for the purpose of preventing friction have been added to base oils used as lubricating oils. It is being done.

[Problem that the invention seeks to solve]

However, in any case, the conventional additives described above do not sufficiently improve the thickness of the oil film formed between metals, and there is a problem in that it is difficult to prevent damage to the metal surface over a long period of time.

[Means for solving problems]

The present invention was devised in view of this point of view, and is capable of increasing the elastohydrodynamic oil film thickness of a base oil used as a lubricating oil, thereby improving the performance of the lubricating oil. It provides an improving agent.

That is, the present invention is a polymer and/or copolymer containing at least a cyclohexyl acrylate compound as a polymer constituent unit, which is blended into a base oil and has a film forming rate of 20% to increase the elastohydrodynamic oil film thickness. The above is an oil film thickness improver for lubricating oil.

In the present invention, the cyclohexyl acrylate compound serving as a polymer constitutional unit is expressed by the following general formula [however, in the formula, R1
represents hydrogen or a hydrocarbon group having 1 to 2 carbon atoms; 1. R2
represents a hydrocarbon group having a cyclohexyl ring. ] is a compound represented by

The above R1 is preferably hydrogen or an alkyl group, more preferably hydrogen or a methyl group. Further, as the above R2, the following general formula (II)-(CH2),
() (X) (II) [However, in the formula, X has a carbon number of 1
~30 alkyl groups, cyclohexyl groups, or alkylcyclohexyl groups, and 1 and n are integers of 0 to 3.

], and specific examples of this substituent R2 include cyclohexyl group, methylcyclohexyl group, 3.3.5-trimethylcyclohexyl group, cyclohexylethyl group, bicyclohexyl group, etc. I can do it.

Specific examples of the cyclohexyl acrylate compounds used in the present invention include cyclohexyl acrylate, methylcyclohexyl acrylate, 3.3.5-
Examples include trimethylcyclohexyl acrylate, cyclohexylethyl acrylate, bicyclohexyl acrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, 3.3.5-trimethylcyclohexyl methacrylate, bicyclohexyl methacrylate, and the like. These cyclohexyl acrylate compounds may be polymerized alone, two or more of them may be copolymerized, or they may be copolymerized with monomers serving as other polymer constituent units. You can.

Monomers serving as other polymer constitutional units used for this purpose include the following general formula (If) [where R3 represents hydrogen or a hydrocarbon group having 1 to 4 carbon atoms, and R4 represents hydrogen or carbon It shows a hydrocarbon group having numbers 1 to 30. ] or the following general formula (IV) [However, in the formula, R and R4 are the same as above. ] In addition to the compounds represented by the above, examples include olefin compounds such as ethylene, propylene, butene-1, isobutyne, and 4-methylpentene-1, and diene compounds such as isoprene and butadiene. Specific examples of the compound represented by the above general formula (III) include vinylcyclohexane, methylvinylcyclohexane, propyl and nylcyclohexane, laurylvinylcyclohexane, stearylvinylcyclohexane, and decyl acrylate. , Also, as specific examples of the compound represented by the above general formula (IV), for example,
2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, decyl methacrylate,
Examples include 2-ethylhexyl methacrylate, lauryl methacrylate, and stearyl methacrylate.

A copolymer obtained by copolymerizing two or more cyclohexyl acrylate compounds that serve as the above polymer constituent units, or one or more cyclohexyl acrylate compounds that serve as other polymer constituent units. The copolymer obtained by copolymerizing monomers may be a binary copolymer or a ternary or higher copolymer, and may also be a random copolymer or a block copolymer. It may be either a polymer or a graft copolymer. In addition, in this copolymer, the amount of other monomers used per 1 mol of the cyclohexyl acrylate compound is 100 mol or less,
Preferably it is 50 mol or less.

The method for polymerizing the polymer and/or copolymer containing the cyclohexyl acrylate compound in the present invention includes:
Conventionally known methods such as suspension polymerization, solution polymerization, emulsion polymerization, and bulk polymerization can be employed. For example, when producing a copolymer using a suspension polymerization method, a polymerization raw material such as a cyclohexyl acrylate compound is suspended in water, an appropriate polymerization initiator, suspension stabilizer, etc. are added, and the 100℃
It can be produced by polymerizing for about 0.5 to 10 hours at a reaction temperature of It can be produced by dissolving it in a solvent, adding an appropriate polymerization initiator, etc., and polymerizing it at a reaction temperature of about 0 to 150° C. for about 0.5 to 10 hours while stirring.

The polymer and/or copolymer containing the cyclohexyl acrylate compound thus obtained has a weight average molecular weight of several thousand to 300,000, preferably 5,000 to 200,000; If it exceeds, it will not enter the working interface, that is, the contact surface between metals, and it will not be possible to improve the elastohydrodynamic oil film thickness and to exhibit the ability to increase the oil film thickness.

When the polymer and/or copolymer containing the above cyclohexyl acrylate compound is used as an oil film thickness improver for lubricating oil, the amount added to the base oil is usually 0.
It is 1 to 70% by weight, preferably 1 to 5011%. Polymers containing cyclohexyl acrylate compounds and/or
Alternatively, if the amount of the copolymer added is less than 0.1% by weight, the effect of using it as an oil film thickness improver will not be exhibited, and if it is more than 70% by weight, the viscosity and product cost will increase. (There is a problem that the polymer and/or copolymer containing a cyclohexyl acrylate compound is added to the base oil in a small amount. A method of mixing may be used, or, conversely, a method of mixing a small amount of base oil with the polymer and/or copolymer to make it viscous.

The base oil in which the oil film thickness improver of the present invention is used may be naphthenic mineral oil, paraffinic mineral oil, or mineral oil obtained by mixing these;
Synthetic lubricating oils, such as oligomeric dibasic acid esters of olefins, polyethers, synthetic naphthenic oils, phosphoric acid esters, etc., can also be used as they are or mixed with the various mineral oils mentioned above.

Furthermore, in the present invention, in order to use the polymer and/or copolymer containing a cyclohexyl acrylate compound as an oil film thickness improver for lubricating oil, the following relational expression % formula % () [where Ha is the oil film thickness It shows the oil film thickness of the lubricating oil to which the improver has been added, Hs shows the oil film thickness of the base oil, and +18 shows the oil film thickness determined from the apparent viscosity of the oil film thickness improver. ) is required to have a film forming rate (α) of 20% or more. Note that the larger the value of the film forming rate (α), the greater the effect of the oil film thickness improver in increasing the elastohydrodynamic oil film thickness.

Furthermore, the oil film thickness improver of the present invention can be used in combination with various conventionally known additives that are added to base oils to improve various physical properties required for general lubricating oils, such as viscosity index improvers, detergent dispersants, etc. , an antioxidant, an extreme pressure agent, an antifoaming agent, a demulsifier, an oily agent, a rust preventive, and the like.

[Effect]

The polymer and/or copolymer containing the cyclohexyl acrylate compound of the present invention selectively improves the oil film thickness of lubricating oil.

〔Example〕

Hereinafter, the oil film thickness improver of the present invention will be explained based on Examples and Comparative Examples.

Example 1 A mixture of cyclohexyl methacrylate (80 mol%) and alkyl acrylate (20 mol%), which is a mixture of compounds substituted with alkyl groups at 012 and C13, was prepared in toluene at a monomer concentration of 2°2 mol/I. azobisisobutyronitrile (
AIBN) was added at 0.5% by weight based on the monomer, and 7
Polymerization was carried out at 0°C for 4 hours. After the polymerization reaction was completed, a toluene solution was dropped into methanol to precipitate the polymer, which was separated and dried to obtain a cyclohexyl methacrylate-alkyl acrylate copolymer having the molecular weight shown in Table 1.

Next, the obtained polymer had a kinematic viscosity (40°C) of 26.63
C8t, was dissolved in base oil A to prepare a lubricating oil, and its kinematic viscosity, viscosity index, elastohydrodynamic oil film thickness, and film forming rate were measured. The results are shown in Table 1.

The elastohydrodynamic oil film thickness measurement described above is an optical interference measurement in which an oil film is created between a rotating glass disk and a freely rotating steel ball, and the thickness of the oil film at the center is measured using a Newton ring. The film formation rate was calculated based on the relational expression shown above.

Examples 2 and 3 After adding zinc chloride in ethyl acetate, cooling to -10°C and charging isobutyne, then heating to 55°C, adding cyclohexyl methacrylate in which AIBN was dissolved. The mixture was then polymerized at 60°C for 5 hours. In Example 2, the blending ratio of cyclohexyl methacrylate and isobutyne at this time was 40 mol% for the former and 60 mol% for the latter.
In Example 3, the former is 82 mol% and the latter is 18 mol%.
The mole percentage was high.

After the polymerization reaction is completed, the reaction mixture is dropped into methanol to precipitate the resulting polymer, separated and dissolved in toluene, washed with dilute hydrochloric acid, washed with water, separated, and dried to obtain a cyclohexyl methacrylate-isobutyne copolymer. A polymer was obtained.

Next, the obtained polymer was added to base oil A or kinematic viscosity (
A lubricating oil was prepared by dissolving it in base oil B of 10.10 cSt (40°C), and its kinematic viscosity, viscosity index, elastohydrodynamic oil film thickness, and film forming rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 20 mol% cyclohexyl methacrylate, 47 mol% isobutyne, and 27 mol% of the above alkyl methacrylates
A cyclohexyl methacrylate-isobutyne-alkyl methacrylate copolymer was produced in the same manner as in Example 2 except for the following.

Next, the obtained polymer had a kinematic viscosity (40°C) of 36, Bc
A lubricating oil was prepared by dissolving it in base oil C of St., and its kinematic viscosity, viscosity index, elastohydrodynamic oil film thickness, and film forming rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 1.3 and 4 The kinematic viscosity, viscosity index, and elastohydrodynamic oil film thickness of the base oils A, B, and C used in each of the above Examples were measured in the same manner as in Example 1.

The results are shown in Table 1.

Comparative Examples 2 and 5 A commercially available polymethacrylate viscosity index improver (product name: Niacroup 133 manufactured by Sanyo Chemical Co., Ltd.) was added to base oil A or C.
) was added in the proportions shown in Table 1 to prepare a lubricating oil, and the kinematic viscosity, viscosity index, elastohydrodynamic oil film thickness, and film forming rate were measured in the same manner as in Example 1. The results are shown in Table 1.

(Effects of the Invention) The oil film thickness improver of the present invention can significantly improve or increase the elastohydrodynamic oil film thickness when added to the base oil of lubricating oil. It is possible to produce a lubricating oil that can improve the lifespan of mechanical elements.

Patent applicant Nippon Steel Chemical Co., Ltd. Representative Patent attorney Katsuo Naruse (2 others)

Claims (3)

[Claims] (1) At least the following general formula (I
) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) [However, in the formula, R_1 represents hydrogen or a hydrocarbon group having 1 to 20 carbon atoms, and R_2 represents a hydrocarbon group having a cyclohexyl ring. A polymer and/or copolymer containing a cyclohexyl acrylate compound represented by ], characterized by having a film-forming rate of 20% or more that increases the elastohydrodynamic oil film thickness when blended into base oil. Oil film thickness improver for lubricating oil. (2) Claim 1, wherein the copolymer is a copolymer of a cyclohexyl acrylate compound and isobutylene.
An oil film thickness improver for lubricating oils as described in . (3) The oil film thickness improver for lubricating oil according to claim 1, wherein the copolymer is a copolymer of a cyclohexyl acrylate compound and an alkyl acrylate and/or an alkyl methacrylate.