JPS6213394B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ester lubricating oil composition, and more specifically, the ester lubricating oil contains an ester of a saturated fatty acid containing an α-position side chain fatty acid and a di- to hexa-hydric polyhydric alcohol having a neopentane skeleton; An ester lubricating oil composition comprising a mixed ester with a neopentyl complex ester obtained by introducing an aliphatic saturated dicarboxylic acid having 2 to 13 carbon atoms into a lubricating oil composition having improved low-temperature fluidity, heat resistance, and oxidation resistance stability. It is something. Applications that take advantage of the features of the present invention are particularly lubricants for internal combustion engines, particularly engine oils for automobiles.
It exhibits its excellent properties. In recent years, the speed of automobiles has become even faster due to the expansion of expressways, and the demand for higher output from automobile engines has become more severe year by year.On the other hand, the need for purification devices as a countermeasure against pollution due to automobile exhaust gas regulations, etc. It has become difficult to meet these demands with the performance of conventional automotive engine lubricating oils. In addition to excellent thermal oxidation stability, low-temperature fluidity, low-temperature startability, sludge dispersibility, and anti-wear properties, the performance required of future automobile engine oils will include extension of engine oil life, that is, oil change intervals, and Furthermore, it is necessary to reduce or eliminate the need for various additives to engine oil. Conventionally, many patents and reports have been published regarding ester lubricating oils, such as JP-A No. 46-6528, JP-A No. 48-27867, and JP-A No. 50-116865. Also, neopentyl polyol is used as the polyhydric alcohol component in the ester, and a linear saturated monocarboxylic acid with relatively small carbon number of _C10 or less is used as the fatty acid component to form neopentyl polyol ester. However, examples of its use as a lubricant for metal processing or for internal combustion engines (automobile engines) by mixing it with mineral oil are described. It is already known that these neopentyl polyol ester-based lubricants have superior thermal and oxidative stability compared to conventional mineral oils and general ester oils, and in fact, they have been developed to take advantage of this property. Application fields include use as a base oil or additive for grease, synthetic hydraulic oil, metal processing oil (rolling oil), engine oil, etc. In this way, neopentyl polyol ester has superior thermal and oxidative stability compared to other ester-based lubricating oils, but on the other hand, it has poor low-temperature fluidity, which is an important property as a lubricating oil base.
Dioctyl sebacate (D.
It is significantly inferior to diester oils such as OS). Furthermore, due to this drawback, neopentyl polyol ester has conventionally been limited to special uses without losing its versatility as a lubricating oil.
Furthermore, regarding lubricity, the alkyl chain length of the fatty acids constituting the esters is restricted from the viewpoint of maintaining fluidity, and it is necessary to mainly use fatty acids with carbon numbers of 10 or less. However, it is still not enough. The present inventors focused on these points in particular, and as a result of intensive research to improve the α-position side chain fatty acids, 30
An ester of an aliphatic saturated monocarboxylic acid containing ~70% by weight and neopentyl polyol (hereinafter referred to as ester); By appropriately mixing both esters (hereinafter abbreviated as esters), we have found further improvements in low-temperature fluidity, lubricity, and thermo-oxidative stability compared to conventional neopentyl esters. Applications that take advantage of these features of the present invention include, in addition to engine lubricating oils, hydraulic oils, low-temperature and high-temperature greases, rolling oils, and other industrial lubricating oils. To describe the present invention in more detail, the general formula of the aliphatic saturated monocarboxylic acid used for esterification is (1) R ₁ -CH ₂ -COOH and (2)

This is a mixture represented by the formula [Formula], which is synthesized from olefin by the oxo method, containing 30% to 70% of the side chain fatty acid represented by the formula (2), and is obtained by the formula R ₁ in the middle has 10 to 17 carbon atoms,
_R2 is an alkyl group having preferably 10 to 13 carbon atoms, R2 is an alkyl group having 7 to 16 carbon atoms, preferably 7 to 12 carbon atoms, and _R3 is an alkyl group having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms. Furthermore, the general formula of the aliphatic saturated dicarboxylic acid to be subjected to the ester is (3) HOOC-( _CH2 )n-COOH, where n is 0 or a natural number from 1 to 11, preferably a natural number from 4 to 8, 2 to 13 carbon atoms in the molecule,
It preferably consists of 6 to 10 dicarboxylic acids, and examples of dicarboxylic acids used include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. On the other hand, as for the above-mentioned ester and the polyhydric alcohol used for the ester, β-
A divalent to hexavalent neopentyl polyol that does not have a hydrogen atom at the carbon position, such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, trimethylolhexane, pentaerythritol, dipentaerythritol, etc. . These esters and aliphatic saturated monocarboxylic acids used in the esters mentioned above have a mixing ratio of α-position side chain fatty acids represented by formula (2).
If it is less than 30%, the low temperature fluidity will be insufficient,
On the other hand, if it exceeds 70%, thermal oxidative stability, especially viscosity changes will be severe, and lubricity will deteriorate, making it impossible to satisfy the present invention. Furthermore, the mixing ratio of esters to esters is ester:ester=
40-90% by weight: 60-10% by weight is required; if this ester is less than 40%, the thermal oxidative stability will decrease, especially the acid value of the product will increase sharply, and the lubricity (load capacity) will decrease. oxidation) and viscosity change due to oxidation, making it unsuitable for the present invention. In addition, the ester of the present invention and the method for producing the ester can be produced using a conventionally known method, that is, in the presence of a commonly used acid catalyst (sulfuric acid, para-toluenesulfonic acid, etc.) or an alkali catalyst (potassium hydroxide, sodium hydroxide, etc.). Although it can be obtained by an esterification dehydration reaction, stannous chloride is the most suitable catalyst for use in the ester of the present invention, and tetrabutoxytitanium is suitable for the ester. In addition, the carboxylic acids to be used in the present invention are converted into methyl esters in advance, and then transesterified with the above-mentioned polyhydric alcohols using a conventionally known transesterification catalyst (e.g., sodium methylate). It can also be easily produced by a method in which methanol produced is removed from the reaction system. In general, in the esterification reaction, if the raw acid or alcohol has a sterically hindered group (substituted alkyl group) in its molecule, the reaction is inhibited more than one without it due to its shielding effect. As mentioned above, the raw material monocarboxylic acid used for the ester of the present invention must contain 30 to 70% of a saturated fatty acid (formula (2)) having an alkyl side chain at the α-carbon in its molecule, and The partner neopentyl polyhydric alcohol also has a substituted alkyl group on the carbinol carbon atom in its molecule, so the present invention has a higher ester production rate than the conventional linear fatty acid ester production rate. Although it was predicted that it would be quite difficult based on the usual chemical reaction, as a result of various synthetic studies for ester lubricating oil, as mentioned above, the ester of the present invention and the production of the ester each require the following steps: By using stannous chloride and tetrabutoxytitanium as catalysts, the reaction proceeded more easily than with ordinary esterification catalysts, and their steric hindrance was eliminated. The ester of the present invention, which is a mixture of esters obtained by these methods, is much more effective than conventional neopentyl polyol esters of natural fat-based fatty acids due to the structural specificity of both its constituent fatty acids and polyhydric alcohols. Excellent low-temperature fluidity,
It has further improved thermal oxidation stability and lubricity (load-bearing capacity). The composition of the present invention may also contain extreme pressure additives, antioxidants, viscosity index improvers,
There is no problem even if a cleaning dispersant or the like is added. Next, the ester of the present invention will be explained using the general structural formula as follows. Structural formula (structural formula of ester) However, (A) or (A') is -CH ₃ , -CH ₂ CH ₃ , -CH ₂ CH ₂ CH ₃ , -(CH ₂ ) ₄
-CH ₃ , -CH ₂ OOCR and

Consisting of any of the groups such as [Formula]. R is -CH ₂ -R ₁ or and

[Formula] [However, R ₁ has 10 to 17 carbon atoms, R ₂ has 7 to 16 carbon atoms, and R ₃ has 1 to 8 carbon atoms, each of which is a mixed alkyl group] Structural formula (Structural formula of ester) However, n is 0 or a natural number from 1 to 11. R, (A) and (A') are the same as in the structural formula. Further, production examples of the ester of the present invention are shown below. Production example A Production of ester Esterification equipment equipped with a nitrogen flow tube, stirrer, thermometer, water test tube, and reflux condenser 2
In a four-necked reaction flask, add a linear saturated monocarboxylic acid represented by the general formula (1) (wherein R ₁ is an alkyl group having 10 to 13 carbon atoms) and a linear saturated monocarboxylic acid represented by the general formula (2). α-side chain saturated monocarboxylic acid (however, R ₂
990 parts by weight of linear, side chain mixed monocarboxylic acid with a mixing ratio of 30:70 ( _R3 is an alkyl group consisting of 7 to 12 carbon atoms and R3 is an alkyl group consisting of 1 to 5 carbon atoms), 211 parts by weight of trimethylolpropane, and 6 parts by weight of stannous chloride dihydrate was added, stirred, and an esterification reaction was carried out at 180 to 200° C. for 8 hours under a nitrogen stream. The acid value of the crude ester was 1.4. After this, 1% by weight of activated clay
After decolorizing by adsorption, the mixture was filtered. The obtained ester had an acid value of 0.4 and a hydroxyl value of 1.2. Production Example B Production of Ester Using the same reaction apparatus as Production Example A, 440 parts by weight of the same composition as Production Example A was used as a monocarboxylic acid, and azelaic acid ( n=7 in the formula), 229 parts by weight of neopentyl glycol, 3.2 parts by weight of tetrabutoxytitanium (catalyst), and 126 parts by weight of xylene as an azeotropic solvent, and the reaction was carried out at reflux temperature for about 9 hours. Ta. The acid value of the crude ester was 1.2. After removing the solvent, the mixture was adsorbed and decolorized using 1.0% activated clay, followed by filtration. The obtained ester had an acid value of 0.3 and a hydroxyl value of 0.8. Production Example C For the ester obtained in Production Example A and the ester obtained in Production Example B, ester:ester=
They were uniformly mixed at room temperature at a mixing ratio of 45:55 parts by weight. The features of the present invention obtained through these production examples will be described later. According to the above-mentioned Production Examples A (ester) and B (ester), esters ~ were produced, and the esters were mixed and used in the following examples.

[Table] The features of the esters listed in Table 1 above when compared with commercially available automotive engine oils (mineral oil-based) will be explained using the following examples. Example: The esters listed in Table 1 were blended as shown in Table 2, and their low temperature fluidity, lubricity, and viscosity were
Temperature characteristics are determined by pour point (℃) and load capacity (Kg/
cm) and viscosity index (VI _E ). In addition, mineral oil-based engine oil is used as a commercially available automobile engine oil.
A comparison was made using lubricating oil type 2, No. 2 for land internal combustion engines as described in SAE-30 and JIS-K-2216, and trimethylolpropane triester of capric acid, which is a commercially available fat-based fatty acid. The results are shown in Table 2. As is clear from the results in Table 2, the ester oil of the present invention had a lower pour point, higher viscosity index, and higher load carrying capacity than commercially available engine oils, and exhibited excellent characteristics as an engine oil. In addition, each test was conducted in the following manner. 1 Pour point (°C): According to JIS-K-2269 (Petroleum products pour point test method). 2 Kinematic viscosity (CST): According to JIS-K-2283 (Petroleum products kinematic viscosity test method). 3 Viscosity index (VI _E ): According to JIS-K-2284 (Petroleum product viscosity index calculation method). 4 Load-bearing capacity (Kg/cm): Tested using a Shell type high-speed four-ball friction tester, sample oil temperature 150℃, vertical axis rotation speed.
Seizure load (Kg/cm) was measured at 1200rpm.

[Table] Example 2 The same samples used in Example 1 were used to test their oxidation stability. The test method is
Put 200 g of sample oil into a four-necked flask with a capacity of 300 c.c., then put a clean copper plate of 10 x 20 x 1 mm into the sample oil, and heat it for 5 minutes at an oil temperature of 200°C and an air injection rate of 15/hr. It was carried out using the time air oxidation method. The oxidation stability of the oil after the test was evaluated based on the increase in acid value, change in viscosity, presence or absence of sludge generation, loss by volatilization, loss by corrosion of copper pieces, etc. The results are shown in Table 3. The commercially available engine oil described in Example 1 was used for comparison with the present invention. As is clear from Table 3, the ester oil of the present invention is
Compared to commercially available engine oils, the increase in acid value, change in viscosity, loss of volatilization, and loss of copper plate corrosion were all small, and no sludge formation was observed, indicating that it has extremely excellent oxidation stability.

【table】

Claims (1)

[Claims] 1 The general formula is (1) R ₁ —CH ₂ —COOH and (2)
[Formula] and an aliphatic saturated monocarboxylic acid formed by mixing (1) and (2) in a weight ratio of 30:70 to 70:30 (however, R ₁ in the formula has 10 to 70 carbon atoms)
17, R ₂ has 7 to 16 carbons, R ₃ has 1 to 8 carbons
It is an alkyl group having . ) and β in the molecule
40 to 90% by weight of an ester consisting of one or more types of polyhydric alcohol fatty acid esters obtained by reacting a di- to hexavalent neopentyl polyol that does not contain a hydrogen atom at the - position carbon and the above aliphatic saturated monomer. Carboxylic acid, the above polyhydric alcohol, and general formula (3)
HOOC-( _CH2 )n-COOH (where n in the formula is 0 or a natural number from 1 to 11) with 2 carbon atoms
10 to 60% by weight of a complex ester obtained from ~13 aliphatic saturated dicarboxylic acids.