JPH0321697A - Synthetic ester-based lubricating oil - Google Patents

Abstract

PURPOSE:To obtain the subject especially flame retardant lubricating oil, consisting essentially of a synthetic ester of a neopentyl type polyol with a mixed fatty acid, having a high flash point and viscosity index with a low pour point and excellent in thermal oxidation stability. CONSTITUTION:The objective lubricating oil, consisting essentially of a synthetic ester of (A) one or more alcohols selected from neopentyl type polyols and (B) a mixed fatty acid composed of (i) a 5-14C straight-chain saturated fatty acid mixture and (ii) an aliphatic dibasic acid accounting for 3-10mol% ratio of the whole fatty acids without containing unsaturated bonds and having >=270 deg.C flash point, <=-20 deg.C pour point, >=20cSt kinematic viscosity at 40 deg.C and >=150 viscosity index.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a ester-based lubricating oil that has a high flash point, a high viscosity index, and a low pour point, and has excellent thermo-oxidative stability. This is related to hydraulic oil. [Conventional technology] Currently, lubricating oils with high flash points are mainly used in the steel and metal machinery field, and due to disaster prevention and fire protection laws, oil-based lubricants with flash points higher than mineral oils are used. Flame-retardant hydraulic oil is used.

This type of flame-retardant hydraulic fluid is roughly divided into three types: phosphoric acid ester type, water-glycol type, and polyester type.

Phosphate ester-based hydraulic fluids have excellent flame retardancy, lubricity, and thermal oxidation stability, but they have the disadvantages of poor compatibility with sealing materials, easy hydrolysis, and low viscosity index. , there are economical problems when disposing of them.

Water-glycol hydraulic oil is generally 35 to 45% by weight.
glycol, 10-20% by weight polyether type thickener, 35-50% by weight water,
This hydraulic oil has particularly excellent flame retardancy, and also has good low-temperature fluidity, viscosity index, and thermal oxidation stability. However, since the change in viscosity under pressure is small and the viscosity does not increase when pressure increases, it cannot be used in areas that require extreme pressure properties, is not compatible with paints, and requires careful maintenance, making it impractical. is not very popular.

On the other hand, ester-based hydraulic fluids have the advantage of not only being excellent in lubricity, compatibility with sealing materials, and preventing metal corrosion, but also having no major problems when disposed of. For this reason, it is used in a wide range of fields as the most preferred type of hydraulic oil.

By the way, the flash point of the currently used synthetic ester-based flame-retardant hydraulic oil is 252°C to 266°C (
From a practical point of view, it is desired that the flash point be higher than this, that is, as a base oil for hydraulic oil, it is desired to have a flash point of 270° C. or higher.

In addition, since H-flammable hydraulic oil is used in a wide temperature range from low to high temperatures, it is required to have excellent low-temperature fluidity and viscosity-temperature characteristics. The use of additives such as additives to improve viscosity index is not preferred because they cannot withstand long-term use. For this reason, the base oil for hydraulic oil is required to have a pour point of -20° C. or lower and a viscosity index of 130 or higher, particularly preferably 150 or higher.

Furthermore, the kinematic viscosity at 40°C for this type of hydraulic oil is:
Although it varies depending on the type of hydraulic bomb, most hydraulic pumps require a pressure of 20 centistokes or more.

Conventionally known synthetic ester-based flame-retardant hydraulic fluids include:
Oleic acid esters of neopentyl polyols are widely used, and these esters can satisfy all of the above-mentioned required properties. However, because this ester has an unsaturated bond in its molecule, it suffers from poor thermal oxidative stability, resulting in oxidative deterioration and an increase in viscosity and acid value after long-term use. .

In order to solve this problem, it was considered to use a fatty acid without unsaturated bonds in place of oleic acid, but the saturated fatty acid-based Gakai ester, which has a high flash point, also has a high pour point. This may cause problems in use at low temperatures. On the other hand, if a fractionated saturated fatty acid is used to improve fluidity at low temperatures, the pour point will decrease, but another problem arises: the viscosity index will also decrease.

Furthermore, in order to improve the viscosity index, neopentyl-type synthetic esters using polybasic acids such as adipic acid in addition to monovalent saturated fatty acids have been developed (Japanese Patent Application Laid-Open No. 1983-1989-1).
102307, JP 53-127970, JP 62-21775, JP 63-408
No. 39), it has not yet been able to satisfy all required properties such as pour point, flash point, and thermo-oxidative stability. [Problem to be solved by the invention] As described above, conventionally known synthetic ester hydraulic fluids have
It was not possible to satisfy all the requirements regarding flash point, pour point, viscosity index, and thermal oxidative stability.

In view of the above circumstances, an object of the present invention is to provide a synthetic ester lubricating oil having a high flash point and viscosity index, a low pour point, and excellent thermal oxidative stability.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors found that two or more types of linear saturated fatty acids having a specific number of carbon atoms and a specific aliphatic dibasic fatty acid to be reacted with a neopentyl polyol. It was learned that a synthetic ester obtained by using a mixed fatty acid consisting of an acid can be used as a lubricating oil with a high flash point and viscosity index, a low pour point, and good thermal oxidative stability. , I have come to completely disclaim this invention.

That is, the present invention provides at least one alcohol selected from neopentyl type polyols and an alcohol having 5 to 14 carbon atoms.
Synthetic esters mainly consist of two or more types of saturated fatty acids selected from straight-chain saturated fatty acids and mixed fatty acids consisting of aliphatic dibasic acids that do not contain unsaturated bonds and account for 3 to 20 mol% of the total fatty acids. and the flash point is 270'
C or more, pour point is -20℃ or less, kinematic viscosity at 40℃ is 2
The present invention relates to a synthetic ester lubricating oil characterized by having a viscosity index of 0 centistokes or more and a viscosity index of 150 or more.

[Structure and operation of the invention]

Examples of the neopentyl type polyol in the present invention include neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, etc., and one type of these polyols may be used alone. However, two or more types may be used in combination. By using the latter mixture, favorable results are obtained due to the cold fluidity, especially when the proportion of each alcohol in the mixed alcohol is 5.
It is preferable that the amount is mol % or more because good low-temperature fluidity can be obtained.

The straight saturated fatty acids in the present invention include valeric acid, caproic acid, hebutanoic acid, cabrylic acid, pelargonic acid, cabric acid, undecanoic acid, lauric acid, tridecanoic acid,
ξ 5 to 14 carbon atoms, preferably 8 to 14 carbon atoms such as listic acid
A mixture of two or more types of straight chain saturated fatty acids is used. If only one type is used, it is difficult to maintain a balance of flash point, pour point, and viscosity index. Furthermore, if a straight chain saturated fatty acid with a carbon number of 4 or less is used, it will be difficult to meet the flash point of 270°C or higher, and if a straight chain saturated fatty acid with a carbon number of 15 or more is used, the pour point will be -20°C or lower. becomes difficult to meet.

In the present invention, the aliphatic dibasic acid that does not contain unsaturated bonds and is used in combination with the above-mentioned linear saturated fatty acid contributes to improvement of low temperature fluidity, viscosity index, etc. For example, if other polybasic acids such as dibasic acids containing unsaturated bonds are used instead, properties such as thermal oxidative stability are likely to be impaired, while the use of saturated fatty acids has the effect of improving viscosity index, etc. It will be inferior to

Examples of such aliphatic dibasic acids that do not contain unsaturated bonds include glucuric acid, adipic acid, azelaic acid, and sebacic acid. Considering the fact that it is industrially stable and available at low cost, aliphatic dibasic acids having 5 to 12 carbon atoms are preferred, and among these, sebacic acid is particularly preferred. The amount of the aliphatic dibasic acid that does not contain unsaturated bonds is determined so that its proportion in the total fatty acid is in the range of 3 to 20 mol%, preferably 5 to 10 mol%. If less than 3 mol% is used, the effect of improving low-temperature fluidity and viscosity index will not be sufficiently obtained, while if it is used in excess of 20 mol%, the viscosity of the resulting synthetic ester will become too high, making it impractical. Not good.

The synthetic ester in the present invention generally contains at least one alcohol selected from the above-mentioned neopentyl polyols, two or more saturated fatty acids selected from linear saturated fatty acids having 5 to 14 carbon atoms, and an unsaturated bond. It can be prepared by an esterification reaction with a mixed fatty acid consisting of an aliphatic dibasic acid. The reaction molar ratio of alcohol and mixed fatty acid is not particularly limited, but if the hydroxyl value of the resulting ester is too high, the viscosity index may be low, and if the acid value is too high, the viscosity index may be low. Since oxidation stability may be deteriorated or the flash point may be lowered, it is generally preferable to set the ratio of mixed fatty acids to 1 equivalent of alcohol to 0.9 to 1.1 equivalents.

The synthetic ester of the present invention can be purified by general purification steps such as deacidification, water washing, and adsorption treatment after the above-mentioned esterification reaction. From the above-mentioned viewpoint, the acid value and hydroxyl value of the combined ester after purification are 1 KOH/
It is preferable that the hydroxyl value is 40 ■KOH/g or less.

The lubricating oil of the present invention is mainly composed of the above-mentioned synthetic ester, and contains load-bearing additives, antioxidants, antifoaming agents, rust preventives, demulsifiers, fluidizing agents, etc. that are commonly used in this lubricating oil. Various additives such as a point depressant, a viscosity index improver, and an emulsifier can be added as necessary.

The ester-based lubricating oil of the present invention is structured as described above, and has a flash point of 270°C or higher and a pour point of -20°C.
The kinematic viscosity at 40°C is 20 centistokes or more,
It is characterized by having a viscosity index of 150 or more, particularly the high viscosity index as mentioned above, and at the same time, it is also characterized by excellent thermal oxidative stability.

〔Effect of the invention〕

The lubricating oil obtained by the present invention not only has a high flash point, but also has excellent low-temperature fluidity, viscosity index, and thermal oxidation stability, so it can be used as a flame-retardant hydraulic oil.
Can be used at high temperatures for long periods of time.

Moreover, the lubricating oil of the present invention can be used not only as a flame-retardant hydraulic oil but also as various turbine oils and various engine oils due to its well-balanced physical properties.

Furthermore, the lubricating oil of the present invention can sufficiently exhibit its effects even when various conventionally known additives are added thereto.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to these Examples. Example I A four-necked IJ flask was equipped with a stirrer, a thermometer, a nitrogen blowing tube, and a condenser tube. In this flask, add 142% of cabrylic acid. sg, cabric acid 1
3 9. 5 g, 138.2 g of lauric acid, 48.0 g of myristic acid, 60.6 g of sebacic acid, and 134.2 g of trimethylolpropane, and reacted at 220° C. for 10 hours while blowing nitrogen. As an esterification catalyst, p-toluenesulfonic acid was used in an amount of 3% by weight based on the total amount charged.

After completion of the reaction, unreacted acid was neutralized with KOH, washed with water, dehydrated at 95°C, 20 wmHg for 1 hour, and further filtered to obtain a compound ester 1, which was used in the present invention. The invention was made into an ester-based lubricating oil. Physical properties of this synthetic ester (kinematic viscosity at 40°C, viscosity index, flash point, pour point,
Acid value, hydroxyl value) were as shown in Table 1 below.

Next, in the same manner as above, synthesized ester llh2~N+
No. 19 was obtained, and each of these was used as the synthetic ester lubricating oil of the present invention. Table 1 shows the ratio of fatty acids and alcohol used in each ester and the same physical property values as described above.

Comparative Example 1 NnlO-417, a synthetic ester of neobentyl polyol and various saturated fatty acids (including fractional fatty acids and aliphatic dibasic acids), which does not fall under the present invention
were obtained according to Example 1, and these were used as synthetic ester lubricating oils for comparison. The composition and physical properties of each ester are shown in Table 1.

Comparative Example 2 Synthetic esters FhlB and Nal9 of neopentyl polyol and unsaturated fatty acid (oleic acid) were obtained according to Example 1, and these were used as synthetic ester lubricating oils for comparison. Table 1 shows the composition and physical properties of each ester.

Next, an oxidation stability test was conducted on the lubricating oils of Example 1 (ml-49) and Comparative Example 2 (Il8, Ilhl9) based on 3.1 of JIS K2514-1982. That is, 250 ml of sample oil was kept at 165.5°C in the presence of copper and steel catalysts and oxidized for 48 hours.
The increase in total acid value and the change in viscosity were investigated. The results are shown in Table 2 below.

It can be seen that it has excellent properties as shown in Table 2, and has a particularly high viscosity index.

Claims (1)

[Claims] (1) At least one type of alcohol selected from neopentyl type polyols and two or more types of saturated fatty acids selected from straight chain saturated fatty acids having 5 to 14 carbon atoms, and the proportion thereof in the total fatty acids is 3 to 20 mol%. The main component is a synthetic ester with mixed fatty acids made of aliphatic dibasic acids that do not contain unsaturated bonds, and has a flash point of 270°C or higher, a pour point of -20°C or lower, and a kinematic viscosity of 20 centistokes at 40°C. The synthetic ester lubricating oil is characterized by having a viscosity index of 150 or more.