JP2010189502A - Biodegradable lubricating base oil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable lubricating base oil having both low-temperature fluidity and oxidation stability due to the use of substance obtained by acetylating triacylglyceride having a limited iodine value and a hydroxyl value or an equivalent substance thereof, and to provide a lubricating base oil having both low-temperature fluidity and oxidation stability which has biodegradability equivalent to natural oil fat and causes no problem on environment. <P>SOLUTION: The biodegradable lubricating base oil is a product obtained by acetylating a triacylglyceride mixture, as it is, having an iodine value of 20 or more and 80 or less, and a hydroxyl value of 40 or more and 140 or less, or by acetylating a mixture after undergoing fatty acid exchange reaction of the triacetylglyceride mixture. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention solves the problem of environmental destruction caused by mineral oil-based lubricants by providing a natural oil-based lubricant base oil that is free from environmental problems.

Conventionally, mineral oil has generally been used as a lubricating oil, but in recent years, natural fats and oils and fatty acid esters have been reviewed from the viewpoint of environmental pollution. In particular, natural fats and oils are triglycerides mainly composed of fatty acids having 16 or more carbon atoms and are biodegradable, and form a firm oil film on the metal surface. Therefore, the lubricating performance is said to be superior to that of mineral oil.

However, natural liquid fats and oils do not have sufficient oxidation stability, and when used at a high temperature for a long time, they become polymerized and thicken and eventually gel, so it is generally difficult to use them at 80 ° C or higher. It is used only to a limited extent. This is due to the double bond existing in the liquid oil.

The number of double bonds is indicated by an iodine value, and most liquid oils have an iodine value of 90 or more. Oils and fats having an iodine value of 80 or less have a pour point of 0 ° C. or more, are difficult to maintain a liquid state in winter, and are difficult to use as a stable lubricating oil. Oils and fats having an iodine value of 90 or more tend to be polymerized or gel formed under conditions of contact with air at high temperatures, and are not suitable for recent severe use conditions. This lack of oxidative stability and the problem of pour point is a fatal dilemma of liquid natural fats.

Rapeseed oil and soybean oil are typical liquid oils and fats, especially rapeseed oil is used as a lubricating oil in a certain range, but the iodine value is around 110, which is not suitable for high temperature and long time use conditions. Even with sunflower oil (iodine value: about 90) having a high oleic acid content by genetic recombination, the improvement in oxidation stability is insufficient.

Castor oil has an iodine value of 80-90, lower iodine value than other liquid oils and fats, and shows a stable liquid state in winter. The pour point is as low as -15 ° C or lower. Therefore, it has been used as a lubricating oil for a long time. However, disadvantages such as high viscosity at low temperature and difficulty in handling in winter, modern use conditions changing to high temperature and long time, tending to gum, and poor compatibility with mineral oil. And has been used only for limited purposes. A low viscosity index is also a drawback as a lubricating material.

A common commercial castor oil has an iodine value of 83-88 and a hydroxyl value of 155-165, and these values are the cause of defects as a lubricating material of castor oil.
Hydrogenated castor oil is a solid having an iodine value of 1-5 and a hydroxyl value of 152-162, an iodine value of too low, and a melting point of 80 ° C. or higher. The melting point is lowered to 5-10 ° C. by acetylation, but there is no fluidity in winter.

Coconut oil and palm kernel oil have a low iodine value and a low pour point, but they have a high content of medium-chain fatty acids having 14 or less carbon atoms, and are significantly more lubricious than fatty acids having 18 carbon atoms. It is inferior and unsuitable as a lubricating material.
Japanese Patent Laid-Open No. 8-331466 proposes a product in which trans fatty acid and medium chain fatty acid are introduced by lipase treatment, but the heat resistance improvement is insufficient and the lubricity is inferior. Japanese Patent Application Laid-Open No. 2007-077312 proposes a triglyceride having an oleic acid content of 60-80%, but the iodine value is 90 or more and the heat resistance improvement is insufficient. Castor oil and hydrogenated castor oil fatty acid esters have unsolved thermal stability problems, and hydrogenated castor oil fatty acid estolides and esters thereof have low low-temperature properties when the degree of condensation is low. Too high viscosity for oil. USP 2,049,072 acetylates castor oil as a solution to the defects of castor oil, improving mineral oil solubility and viscosity index (92 → 120). In addition, hydrogenated acetylated castor oil has been obtained with a viscosity index of 125. However, acetylated castor oil has an iodine number of about 80, and oxidation stability is still insufficient, and the pour point of the hydrogenated product is 15 ° C or higher. Also, the viscosity index of both is not sufficient. JAOCS. VOL. 76, 3313 says that it is necessary to improve low-temperature properties in order for vegetable oil to be widely accepted as a biodegradable lubricating oil. Although proposed, the iodine value of natural fats and oils is high, and the problem of poor thermal stability is merely diluted and not basically solved.

Provided is a lubricating base oil having both low-temperature fluidity and oxidation stability, which is composed of a fatty acid triglyceride as a main component and has good biodegradability.

 By subjecting a mixture of fatty acid esters mainly composed of triacylglycerides and having 20 ≦ iodine value ≦ 80 and 40 ≦ hydroxyl value ≦ 140, the lubricating base oil of interest is obtained.

The product of the present invention is a triacylglyceride similar to natural fats and oils, all acyl groups are fatty acids or equivalents, and have biodegradability equivalent to that of natural fats and oils. The point shows a low-temperature property of 0 ° C. or less, and is useful as a blended base oil of a biodegradable lubricating oil.

An object of the present invention is to provide a biodegradable lubricating base oil that has been considered difficult in the past and has both acid value stability and low-temperature fluidity. In order to bring the biodegradability to the level of natural fats and oils, the pour point was set to −3 ° C. or lower under the condition that the iodine value was 80 or less in order to obtain acid value stability within the range of the structure of glycerides.

The numerical limitation of “a mixture of fatty acid esters mainly composed of triacylglycerides and 20 ≦ iodine value ≦ 80 and 40 ≦ hydroxyl value ≦ 140” is due to the following reason.
(1) The iodine value is better from the standpoint of oxidation stability, but if it is too low, the fluidity becomes worse at low temperatures. (2) The hydroxyl group is necessary for esterification to improve the low temperature property, but if it is higher than 140, it is not preferable in terms of heat resistance and mineral oil solubility.

The inventor of the present invention is a lubricating base that has both oxidation stability and low-temperature fluidity by acetylating a mixture of castor oil, hydrogenated castor oil, and general fats and oils having no hydroxyl group under conditions where the iodine value and the hydroxyl value are moderate. I found that I could get oil. This mixture is further effective by acetylating after the fatty acid exchange reaction.

It is also effective to replace hydrogenated castor oil and castor oil partially or entirely with their respective ethylene oxide adducts. In this case, as the number of moles added of the ethylene oxide adduct increases, the lubricity and mineral oil solubility tend to decrease, and rust generation tends to occur, so the number of moles added is preferably 15 or less.
If natural fats and oils that do not have a hydroxyl group and hydrogenated products thereof are blended appropriately, the condition can be satisfied.

The mixture thus obtained becomes more desirable by performing a fatty acid exchange reaction using a lipase, an alkaline catalyst or the like. Examples of the alkaline catalyst include caseoida, sodium alcoholate, sodium carbonate, and lithium naphthenate.

Partially hydrogenated castor oil obtained by stopping the hydrogenation reaction of castor oil can also be used. Partially hydrogenated castor oil may be stopped at any stage, but an iodine value of 70-10 is effective, and 65-20 is more desirable.

Castor oil, hydrogenated castor oil, rescherella oil, castor oil ethylene oxide adduct, and hydrogenated castor oil ethylene oxide adduct have hydroxyl groups, and are all acetylated.
Acetylation improves compatibility with low temperature properties, viscosity index, mineral oil and the like.

Hydrogenated castor oil and its ethylene oxide adduct generally have an iodine value of 3 or less and excellent oxidation stability, but are solid at room temperature. However, it becomes liquid or semi-solid by acetylation and can be used in combination.

Common natural fats and oils that do not have a hydroxyl group include rapeseed oil, soybean oil, olive oil, palm oil, palm kernel oil, coconut oil, beef tallow, cottonseed oil, peanut oil, various fish oils, lard, safflower -Oils, sunflower oil, palm olein, other animal and vegetable oils, and oils with high oleic acid content by genetic manipulation are also included.

The triglyceride having a hydroxyl group and the triglyceride not having a hydroxyl group are mixed to improve the low temperature property due to the compatibility effect. Furthermore, the low temperature property is further improved by exchanging the fatty acid of each triglyceride by the fatty acid exchange reaction.

The mixing ratio of triglyceride having a hydroxyl group and triglyceride having no hydroxyl group is preferably from 3: 7 to 8: 2. Although it varies depending on the conditions of use as a lubricating oil, it requires 30% or more of triglyceride having a hydroxyl group to solve the low temperature and oxidation stability dilemma of natural fats and oils, and it has a hydroxyl group from the viewpoint of mineral oil solubility and viscosity index. It is desirable that there is 20% or more of triglycerides that are not. By acetylating this mixture, the low temperature property is improved, and a lubricating base oil with good biodegradability that combines the desired low temperature property and oxidation stability is obtained.

Acetylation can be easily performed by reacting acetic anhydride or acetyl chloride. In this case, a more desirable reaction can be carried out with a solvent such as pyridine, but from the viewpoint of cost and post-treatment, it is most advantageous to use acetic anhydride.

The amount of acetic anhydride used may be an equivalent amount or a slight excess of the hydroxyl group, and by-product acetic acid and unreacted acetic anhydride may be recovered at normal pressure and, if necessary, reduced pressure.
In some cases, it is desirable that the hydroxyl group remains to some extent. In such a case, the amount of acetic anhydride used may be less than or equal to the hydroxyl group.

The low iodine number and low temperature fluidity compounds according to the present invention can be made into respective lubricating oils by blending with mineral oil, PAO, esters and other lubricating oil materials. In addition, it can be used as an additive for various polymers, and functions of a flexibility imparting agent, a plasticizer, and a dispersing agent can be expected.

Hydrogenated castor oil (IV = 2, OHV = 158) 205 g (0.22 mol) and castor oil (IV = 86, OHV = 160) 111 g (0.12 mol) and rapeseed oil (IV = 110, OHV = 0) 100 g Of sodium carbonate (0.4 = 50, OHV = 120), fatty acid exchange reaction at 220 ° C. for 2 hours, cooling to 100 ° C., and adding 92 g (0.9 mol) of acetic anhydride, 120 The reaction was carried out at -130 ° C for 2 hours. Subsequently, the temperature was gradually raised to 180 ° C., and acetic esterification was completed while distilling and recovering by-product acetic acid. Residual by-product acetic acid and unreacted acetic anhydride were removed under reduced pressure, the temperature was adjusted to 110 ° C., 3 g of activated clay was added, the mixture was treated for 15 minutes, and filtered to obtain 405 g of a single yellow brown acetate ester.
IV = 48, pour point-10 ° C., viscosity index 160.

0.5 g of caustic soda was added to a mixture of castor oil 111 g (0.12 mol), hydrogenated castor oil 205 g (0.22 mol) and rapeseed oil 200 g (IV = 62, OHV = 87) at 220 ° C. for 2 hours. After the reaction, the reaction mixture was cooled to 100 ° C., 92 g (0.9 mol) of acetic anhydride was added, and the reaction treatment was carried out in the same manner as in Example 1 to obtain 502 g of a pale yellow liquid.
The iodine value was 60, the pour point was −14 ° C., and the viscosity index was 171.

0.5 g of caustic soda was added to a mixture (IV = 68, OHV = 75) of 111 g (0.12 mol) of castor oil, 112 g (0.12 mol) of hydrogenated castor oil and 250 g of hyolein sunflower oil (IV = 90). In addition, after reacting at 210 ° C. for 2 hours, the mixture was cooled to 100 ° C., 66 g of acetic anhydride was added, and the reaction treatment was performed in the same manner as in Example 1 to obtain 460 g of a pale yellow liquid.
The iodine value was 69, the pour point was −12 ° C., and the viscosity index was 183.

A mixture of castor oil 111 g (0.12 mol), hydrogenated castor oil ethylene oxide 3 mol adduct (molecular weight 1062, IV = 2, OHV = 140) and palm olein 100 g (IV = 90) (IV = 37, OH = 116) ), 0.6 g of lithium naphthenate was added, reacted at 220 ° C. for 2 hours, cooled to 100 ° C. and added with 107 g of acetic anhydride, and reacted in the same manner as in Example 1 to obtain 500 g of a light tan liquid.
The iodine value was 39, the pour point was −4 ° C., and the viscosity index was 146.

0.6 g of caustic soda was added to a mixture (IV = 70, OHV = 44) of 50 g of castor oil, 100 g of hydrogenated castor oil ethylene oxide 10 mol adduct (molecular weight 1370, OH = 110, IV = 1) and hyolein sunflower oil 300 g. In addition, after reacting at 200 ° C. for 2 hours, the mixture was cooled to 100 ° C., 35 g of acetic anhydride was added, and the reaction treatment was performed in the same manner as in Example 1 to obtain 446 g of a pale tan liquid.
Iodine number: 44, cloud point: -6, pour point: -5 ° C, viscosity index 190.

Claims (3)

A lubricating oil composition comprising, as an essential component, a product obtained by acetylating a mixture of triacylglycerides of 20 ≦ iodine value ≦ 80 and 40 ≦ hydroxyl value ≦ 140 as it is or after a fatty acid exchange reaction. The lubricating oil composition according to claim 1, wherein the mixture of triacylglycerides having 20 ≦ iodine value ≦ 80 and 40 ≦ hydroxyl value ≦ 140 according to claim 1 is a mixture of a triglyceride having a hydroxyl group and a triglyceride having no hydroxyl group. The triglyceride having a hydroxyl group according to claim 2 is one kind selected from castor oil, hydrogenated castor oil, castor oil ethylene oxide adduct and hydrogenated castor oil ethylene oxide adduct, or a mixture of two or more kinds. The lubricating oil composition according to claim 2, wherein the lubricating oil composition is one kind or a mixture of two or more kinds of natural fats and oils.