JPH0841482A - Lubricating oil composition - Google Patents

Abstract

PURPOSE:To obtain a composition containing a specific polyalkylene glycol as a base oil, excellent in heat resistance and stability to oxidation of base oil and especially useful for film-stretching machines such as biaxially stretching machines. CONSTITUTION:This composition is obtained by blending (A) a base oil containing 5-100wt.% (preferably 10-100wt.%) of a polyalkylene glycol of formula I (R<1> and R<4> are each H or a 1-8C alkyl; R<2> and R<3> are each 2-18C alkylene; X+Y=1-20; Z is 0 or 1) with (B) 0.1-5.0wt.% (preferably 0.3-3.0wt.%) of a phosphite compound of the formula (R<10>-O)3-P (R<10> is a 1-24C alkyl, etc.), (C) 0.1-4.0wt.% (preferably 0.3-3.0wt.%) of an amine-based compound of formula II (R<13> is H or 1-10C hydrocarbon) and (D) 0.1-10.0wt.% (preferably 0.5-8.0 wt.%) of a phenolic compound of formula III [R<18> and R<19> are each H or a 1-4C hydrocarbon; R<20> is (CH2)k [(k) is 1-5]; (m) is 1-5; (n) is 1-4, etc.].

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lubricating oil composition containing a specific polyalkylene glycol as a base oil,
More specifically, it relates to a lubricating oil composition having excellent heat resistance of a base oil and improved oxidative stability. The lubricating oil composition of the present invention is particularly suitable as a lubricating oil composition used in a film stretching machine such as a biaxial stretching machine, because thermal decomposition of the base oil is unlikely to occur.

[0002]

2. Description of the Related Art Film stretching machines such as biaxial stretching machines
For example, there are various types such as vertical / horizontal stretching type flat sequential biaxial stretching device, vertical / horizontal restriction type flat method simultaneous biaxial stretching device, tubular stretching device, etc., but lubrication of each part such as roll, sprocket and clip running mechanism. for,
Various lubricating oils are used.

In a film stretching machine, a synthetic resin melt-extruded into a sheet or tube is stretched in a high temperature atmosphere. Therefore, the lubricating oil used for lubricating each part has not only high lubrication performance but also heat resistance. It is required to be excellent in various properties such as stability, oxidation stability, low evaporation property, and high viscosity index. Among general-purpose resins, polypropylene, polystyrene, etc. require a high temperature of 150 ° C or higher as the stretching temperature, and in the case of engineering plastics,
Lubricating oils are required to have high performance because higher temperatures are required.

If the heat resistance and oxidation stability of the lubricating base oil are insufficient, thermal decomposition of the lubricating oil occurs under the conditions of use of the film stretching machine. Pyrolysis of the base oil produces low volatility pyrolysis products that evaporate and contaminate films and equipment. When a film contaminated with a thermal decomposition product is vacuum-deposited with aluminum or the like, the adhesion of the deposited film is impaired. When the thermal decomposition product adheres, there is also a problem that it becomes difficult to recycle the film ears. It is also an important property for lubricating oils that the pyrolysis products do not polymerize into sludge. In addition, it is necessary for the lubricating oil to have an appropriate viscosity in a wide temperature range in order to exhibit high lubricating performance under stretching conditions. Therefore, the lubricating oil for a film stretching machine is required to have a high viscosity and a high viscosity index.

Conventionally, as a lubricating oil in the field of film stretching machines, polyalkylene glycol (hereinafter abbreviated as PAG) base oil such as polyethylene glycol or polypropylene glycol, or diphenyl ether base oil, and if necessary, an antioxidant, etc. Lubricating oil compositions containing various additives have been used. However, the diphenyl ether base oil has high thermo-oxidative stability, but it is not possible to obtain a highly viscous product, the viscosity index is low, and further, when the base oil is used at high temperature for a long time, solidification residue of the base oil remains. It has drawbacks such as increased amount.

On the other hand, since the PAG base oil is a polymer type synthetic oil, it is possible to produce a PAG base oil having a desired viscosity from low viscosity to high viscosity. Therefore, PA
The G base oil can easily obtain a high-viscosity product and has a good viscosity index. In addition, the PAG base oil generally has a low risk of contaminating the device and the film because the thermal decomposition product thereof becomes a low-molecular volatile gas. The risk of ignition due to the generation of volatile gases can be reduced by adding an antioxidant to raise the flash point. further,
Since the PAG base oil has a large dissolving power for polar substances, it can dissolve the thermal decomposition products of the base oil and the deteriorated products of various additives, and suppress the increase of the solidification residue.

However, conventional PAG base oils are inferior to other synthetic oils in stability against heat and oxidation, and in particular, they have the drawback that they undergo radical chain decomposition in the air. Under the operating conditions of the film stretching machine, hot air is often used, so that the PAG base oil is significantly deteriorated. Therefore, although various antioxidants are added to the PAG base oil to improve its heat and oxidation stability, the conventional known PAG base oil or PAG lubricant composition can provide sufficient performance. It wasn't done.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lubricating oil composition which is excellent in heat and oxidation stability and is suitable as a lubricating oil for a film stretching machine. We have
As a result of extensive research to overcome the problems of the above-mentioned prior art, polyalkylene glycol having a specific structure is
It has been found that not only it has good lubricating performance and viscosity characteristics, but it also has excellent heat resistance and oxidation stability, is difficult to decompose under film stretching conditions, and has excellent characteristics as a lubricating base oil. Further, they have found that by using this specific polyalkylene glycol as a base oil and adding it in combination with a specific antioxidant, a lubricating oil composition having markedly improved thermal oxidation stability can be obtained. . The present invention has been completed based on these findings.

[0009]

Thus, according to the present invention, there is provided a lubricating oil composition containing a polyalkylene glycol represented by the following general formula (1) as a base oil.

[0010]

Embedded image R ¹ and R ⁴ are each independently selected from a hydrogen atom and an alkyl group having 1 to 8 carbon atoms. R ² and R ³ : each is independently selected from linear or branched alkylene groups having 2 to 18 carbon atoms. X + Y = 1 to 20 Z = 0 or 1

According to the present invention, the base oil containing the polyalkylene glycol represented by the general formula (1) further comprises (a)
There is provided a lubricating oil composition containing a phosphite compound, (b) amine compound, and (c) phenol compound. Hereinafter, the present invention will be described in detail.

PAG-based base oil In the present invention, a polyalkylene glycol represented by the general formula (1) [hereinafter referred to as PAG (1)] is used as a lubricating base oil.
And abbreviations] are used alone or in combination with other PAG base oils. In the general formula (1), R ¹ and R
⁴ are each independently a hydrogen atom or a carbon atom number 1 to
It is selected from eight alkyl groups. Therefore, PAG
The terminal of (1) may be a diol, a monool (monoether), or a diether. In the general formula (1), (OR ² ) _X and (R ³ O) _Y are each independently a ring-opening polymer or copolymer of linear or branched alkylene oxide having 2 to 18 carbon atoms. It is a polyalkylene glycol moiety derived from coalescence. The polyalkylene glycol moiety is usually polyethylene glycol, polypropylene glycol, polybutylene glycol or the like. Z is 0 or 1 and the polyalkylene glycol moiety can be present on one or both of the bisphenol A backbones. X + Y is 1-2
When it is 0 and X or Y is 0, a hydroxyl group or an alkyl ether group is present on one side of the bisphenol A skeleton.

PAG (1) is obtained by ring-opening (co) polymerizing alkylene oxide such as polyethylene oxide, polypropylene oxide or a mixture thereof using bisphenol A as an initiator in the presence of an alkali catalyst. Can be synthesized by. PA
G (1) is a transparent liquid compound at room temperature. PAG
The number average molecular weight of (1) is usually 400 to 3000, preferably about 500 to 2000. PAG (1)
Can be used alone as a base oil, but other P
You may use together with AG base oil. Examples of other PAG base oils include polyalkylene glycols represented by the following general formula (2) [hereinafter abbreviated as PAG (2)].

[0014]

[Chemical 3] R ⁵ and R ⁶ : each independently selected from a hydrogen atom and an alkyl group having 1 to 8 carbon atoms. R ⁷ : a linear or branched alkylene group having 2 to 18 carbon atoms. a is number average molecular weight 1000-8000 in PAG (2)
Represents the number of repeating units of alkylene oxide sufficient to give

Specific examples of PAG (2) include polyethylene glycol, polypropylene glycol, polybutylene glycol, and copolymers thereof. P
The terminal of AG (2) may be any of monool (monoether), diol, diether and the like. PAG (2)
The preferred number average molecular weight of is 3,000 to 8,000. Other PAG base oils include, for example, polyalkylene glycols represented by the following general formula (3) [hereinafter abbreviated as PAG (3)].

[0016]

[Chemical 4] R ⁸ : a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R ⁹ : a linear or branched alkylene group having 2 to 18 carbon atoms. b represents the number of repeating units of alkylene oxide sufficient to give the PAG (3) a number average molecular weight of 200 to 2000. b is usually 1 to 20.

Specific examples of PAG (3) include polypropylene oxide stearyl phenyl derivatives and polyethylene oxide stearyl phenyl derivatives. The preferred number average molecular weight of PAG (3) is 500 to
It is 1000. In the present invention, a PAG-based base oil containing PAG (1) as an essential component is used, and the usage ratio thereof is 5 to 100% by weight in the PAG-based lubricating oil. From the viewpoint of thermal oxidation stability, it is preferable to use PAG (1) alone or to use it in a large proportion.
Therefore, from the viewpoint of thermal oxidation stability, PAG
The use ratio of (1) is preferably 10 to 100% by weight.

The PAG (2) contributes to adjusting the viscosity of the base oil and improving the viscosity index. PAG (3) contributes to heat resistance and viscosity adjustment. 100 of PAG base oil used in the present invention
The kinematic viscosity at 0 ° C. is usually 20 to 120 cSt, preferably 30 to 100 cSt, and the viscosity index is usually 40.
As described above, preferably 100 or more.

Phosphite Compound The phosphite compound used in the present invention is a compound represented by the following general formula.

[0020]

Embedded image R ^{10 is} a hydrocarbon group such as an alkyl group or an alkenyl group having 1 to 24 carbon atoms, or an aromatic group represented by the following formula.

[0021]

[Chemical 6] R ¹¹ and R ¹² are each independently selected from a hydrogen atom, an alkyl group having 1 to 24 carbon atoms, an alkenyl group, and an alkylphenyl group.

Specific examples of the phosphite compound used in the present invention include, for example, triisooctyl phosphite, tris (2-ethylhexyl) phosphite, triisodecyl phosphite, trilauryl phosphite,
Tris (tridecyl) phosphite, trioctadecylphosphite, tristearis phosphite, trioleylphosphite, phenyldiisodecylphosphite, diphenylisooctylphosphite, diphenyldecylphosphite, diphenylisodecylphosphite, diphenyl (tridecyl) phosphite , Triphenylphosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, diphenylnonylphenylphosphite, di (nonylphenyl) phenylphosphite, and the like. . Among these, tris (nonylphenyl) phosphite and di (nonylphenyl) phenylphosphite are preferable.

Amine-based compound The amine-based compound used in the present invention is a compound containing an amino group, preferably, alkylated phenyl-α-naphthylamine and alkylated diphenylamine represented by the following general formula. it can.

[0024]

[Chemical 7] R ¹³ : a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0025]

Embedded image R ¹⁴ and R ¹⁵ are each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 18 carbon atoms. R ¹⁶ and R ¹⁷ are each independently selected from a hydrocarbon group having 1 to 18 carbon atoms. Specific examples of amine compounds include octylphenyl-
α-naphthylamine, phenyl-α-naphthylamine,
Examples thereof include p, p'-dioctyldiphenylamine.

Phenolic Compounds The phenolic compounds used in the present invention include various hindered phenols represented by the following general formula.

[0027]

[Chemical 9] R ¹⁸ and R ¹⁹ are each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms. _{^{R 20 :-( CH 2) k -}} , (k = 1~5) m: 1~5 n: 1~4

[0028]

[Chemical 10] R ²¹ , R ²² , R ²³ and R ²⁴ : each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms. _{^{R 25 :-( CH 2) k -}} , (k = 1~5)

[0029]

[Chemical 11] R ²⁶ and R ²⁷ : each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms. R ²⁸ : a hydrocarbon group having 1 to 18 carbon atoms.

[0030]

[Chemical 12] R ²⁹ , R ³⁰ and R ³¹ are each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms.

[0031]

[Chemical 13] R ³² and R ³³ : each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms. m: 1-5 n: 1-5 1: 1-5

[0032]

Embedded image R ³⁶ , R ³⁷ , R ³⁸ and R ³⁹ : each independently selected from a hydrogen atom and a hydrocarbon group having 1 to 4 carbon atoms. m: 1-5 n: 1-8

Specific examples of the phenolic compound include, for example, triethylene glycol-bis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate] 1,6-hexanediol-bis [3. -(3,5-di-
t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di- t-butyl-4-
Hydroxyphenyl) propionate, n-octyl-3- (4-hydroxy-3 ′, 5′-
Di-t-butylphenyl) propionate and the like can be mentioned.

These phenol compounds usually have a molecular weight in the range of 300 to 1200. Molecular weight is 3
If it is less than 00, the heat resistance becomes insufficient, and conversely 1200
If it exceeds, the solubility in the base oil decreases. The phenol compound has a molecular weight of 500 to 120 from the viewpoint of heat resistance.
The range of 0 is preferable. However, since a phenolic compound having a molecular weight of 300 or more and less than 500 is excellent in the action of suppressing the generation of sludge, it is preferable to use a phenolic compound having various molecular weights in combination. Among the above, a combination of and is preferable.

Lubricating Oil Composition PAG (1) represented by the general formula (1) is a base oil,
It is used in a proportion of 5 to 100% by weight, preferably 10 to 100% by weight. PAG (2) and PAG (3) make up the balance of the base oil and are used in a proportion of 0 to 95% by weight. The (a) phosphite compound is usually 0.1 to 5.0% by weight, preferably 0.3, based on the total weight of the lubricating oil composition.
It is used in a proportion of up to 3.0% by weight. The (b) amine compound is based on the total weight of the lubricating oil composition,
Usually, 0.1 to 4.0% by weight, preferably 0.3 to 3.
Used in a proportion of 0% by weight. The (c) phenolic compound is usually 0.1 to 10.0% by weight, preferably 0.5, based on the total weight of the lubricating oil composition.
It is used in a proportion of ˜8.0% by weight. By combining these three components of additives and adding them to the base oil, the thermal oxidation stability is synergistically improved. If the use ratio of each additive is less than the above range, the effect of addition is small, and conversely, if it is large, it is not economical.

Further, as the phenolic compound, when a high molecular weight compound (c1) having a molecular weight of 500 to 1200 and a low molecular weight compound (c2) having a molecular weight of 300 or more and less than 500 are used in combination, sludge formation is more effective. Can be suppressed. c1: c2 = 30 to 70:70 to 30
The range of (weight ratio) is preferable. If necessary, additives such as a rust preventive agent, a defoaming agent, a metal detergent, an antiwear agent, and a pour point depressant can be added to the lubricating oil composition of the present invention.

[0037]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples 1 to 4 and Comparative Examples 1 to 7] As the base oil, PAGs (1), (2) and (3) were used in the proportions shown in Table 1 (% by weight in the base oil). Further, a phosphite compound, an aromatic amine compound, and a phenol compound were added to each base oil in the ratios shown in Table 1 (% by weight based on the total weight of the composition) (the rest is% by weight of the base oil). . The components used are as follows. PAG (1):

[0039]

[Chemical 15] (R ¹ = H, R ⁴ = H, X + Y = 10, molecular weight = 808) PAG (2):

[0040]

Embedded image (R ⁵ = C ₄ alkyl group, n = 30 to 45) PAG (3):

[0041]

[Chemical 17] (R ⁸ = C ₁₀ alkyl group, n = 14 to 16) Phosphite compound:

[0042]

Embedded image Aromatic amine compounds:

[0043]

[Chemical 19] Phenolic compound (Mw587):

[0044]

Embedded image Phenolic compound (Mw390):

[0045]

[Chemical 21] Phenolic compound (Mw638):

[0046]

[Chemical formula 22]

<Method of measuring physical properties> An iron catalyst (iron powder) was added to each lubricating oil composition (20 g per 100 g of the composition).
g), 25 g of lubricating oil composition weighed in a 50 cc beaker
And leave it in a hot air circulation type oven set at 230 ° C. The beaker is removed from the oven once a day and the weight loss of each lubricating oil composition is recorded. The lubricating oil composition sample in the beaker undergoes thermal oxidative deterioration, progresses in weight reduction, and finally solidifies. Therefore,
The solidification time of each lubricating oil composition was recorded.

Table 1 shows the weight reduction rate and solidification time of each lubricating oil composition. The smaller the weight loss rate and the longer the time to solidify, the more excellent the lubricating oil composition is in the resistance to thermal oxidation.

[0049]

[Table 1] From the results in Table 1, it can be seen that the lubricating oil composition of the present invention has excellent thermal oxidation stability.

[0050]

EFFECTS OF THE INVENTION According to the present invention, there is provided a lubricating oil composition which is excellent in heat and oxidation stability and is suitable as a lubricating oil for a film stretching machine.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C10M 107: 34 137: 02 133: 12 129: 76 129: 14) C10N 30:08 30:10 40 : 06

Claims (2)

[Claims] 1. A lubricating oil composition containing a polyalkylene glycol represented by the following general formula (1) as a base oil. Embedded image R ¹ and R ⁴ are each independently selected from a hydrogen atom and an alkyl group having 1 to 8 carbon atoms. R ² and R ³ : each is independently selected from linear or branched alkylene groups having 2 to 18 carbon atoms. X + Y = 1 to 20 Z = 0 or 1 2. The lubricating oil composition according to claim 1, wherein (a) a phosphite compound, (b) an amine compound, and (c) a phenol compound are contained in a base oil containing a polyalkylene glycol. .