JPH0631373B2 - Synthetic lubricating fluid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a synthetic lubricating fluid obtained by blending synthetic cyclohexyl ester with branched polybutene.

In industrial machines such as automobiles and textile machines,
A large number of mechanisms have been adopted for rotating and driving a driven device via a transmission device of power from a power generation device. The present invention relates to a synthetic lubricating fluid used in such a power transmission device, and more specifically to a traction drive fluid.

(Prior Art) Conventionally, as a power transmission lubricating fluid, a mineral oil as a main component, a naphthene-based synthetic oil or a polyalpha-olefin-based synthetic oil as a main component, and two or more types of mineral oils or synthetic oils. It is known that a mixture of the. Of these, those containing naphthenic synthetic oil as the main component have higher performance than other power transmission lubricating fluids, and therefore many studies have been conducted so far.

Among the commercially available synthetic lubricating fluids, hydrogenated products of alpha-alkylstyrene dimers are currently considered to have the best power transmission performance. A typical example of such a synthetic lubricating fluid is "Sant Track" manufactured by Monsanto.
And is disclosed, for example, in JP-A-47-7664.
In the traction drive fluid, it is said that it may be possible to increase the traction coefficient by mixing two or more kinds of components rather than a single component. From such a viewpoint, hydrogenated products of the alpha-alkylstyrene dimer and styrene,
It has been attempted to mix naphthenes such as dimer, trimer or co-dimer hydrogenated products produced from beta-alkylstyrene or its derivatives with paraffin hydrocarbons to form a lubricating fluid. Japanese Patent Publication No. 47-35763.

(Problems to be Solved by the Present Invention) However, commercially available alpha-alkylstyrene dimer hydrogenated products have a drawback that the raw materials are expensive. Also,
In the industrial world, vigorous development is being carried out aiming at downsizing and efficiency improvement of the power transmission device, but in order to fully demonstrate the performance of the newly developed power transmission device,
As a synthetic lubricating fluid, it needs to be further improved in terms of traction coefficient.

The traction coefficient is defined as a ratio of a traction force generated by a slip of contact portions of rotating bodies contacting each other in a rolling friction type power transmission device to a normal load.

In recent years, the automobile industry has actively promoted the development of continuously variable transmissions. However, as the transmission has a higher traction coefficient of the lubricating fluid, the allowable transmission force can be increased in the same device, so the entire device can be increased. Since it is possible to reduce the size of the engine and to reduce the amount of exhaust gas that causes pollution problems, a lubricating fluid having a traction coefficient as high as possible is desired.

Generally, in traction fluids, it has been said that if two or more base oils are mixed, it is possible to obtain a fluid with a desired traction coefficient because it has an additive property, but depending on the component, the additive property may not be established. For example, it has been observed that the additivity of a naphthene-based synthetic oil blended with a viscosity index improver such as polymethacrylate in an amount of about 5 to 50 wt% does not hold.

In other words, if it is possible to develop a synthetic lubricating fluid that exhibits a high traction coefficient by combining other components that have a significant synergistic effect even with a fluid that does not exhibit a very high traction coefficient with a single component, a power transmission device for automobiles, tractors, etc. However, the present situation is that such a synthetic lubricating fluid is not found.

(Means for Solving Problems) The inventors of the present invention have conducted extensive studies to search for a fluid having an excellent traction coefficient as a lubricating fluid used in a power transmission device, and have made it a synthetic cyclohexyl ester. The present inventors have completed the present invention by finding that a fluid containing a specific amount of branched polybutene is a fluid that can meet such demands.

The demand for the present invention is a synthetic lubricating fluid in which cyclobutanol cyclohexanecarboxylic acid ester or a derivative thereof [hereinafter sometimes referred to as component A] is blended with branched polybutene [hereinafter sometimes referred to as component B], The content of the component B is 1 to 70% by weight of the total fluid.

The cyclohexanol cyclohexanecarboxylic acid ester or its derivative which is the component A is represented by the following general formula.

_Wherein, R 1, _{R 2} and _{R 3} represents one or more kinds selected from a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

Such an ester is produced by the following method. Cyclohexanecarboxylic acid or a derivative thereof is used as a raw material, and cyclohexanol or a derivative thereof is used, and a catalyst such as phosphoric acid is allowed to exist in the presence of excess alcohol, and a reaction is performed while blowing an inert gas such as nitrogen.

As the starting material cyclohexanecarboxylic acid or a derivative thereof, a carboxylic acid in which R ₁ in the above general formula is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms is used. Specifically, cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid,
Examples thereof include propylcyclohexanecarboxylic acid and isopropylcyclohexanecarboxylic acid.
Particularly preferred is cyclohexanecarboxylic acid.
As the starting material cyclohexanol or a derivative thereof, R ₂ and R ₃ in the above general formula are hydrogen atoms or a linear or branched cyclohexanol having 1 to 8 carbon atoms.

Specific examples thereof include cyclohexanol, methylcyclohexanol, ethylcyclohexanol, propylcyclohexanol, isopropylcyclohexanol and dimethylcyclohexanol, but cyclohexanol is particularly preferable.

As the catalyst, phosphoric acid, paratoluenesulfonic acid, sulfuric acid or the like can be used, but phosphoric acid is most preferably used in order to increase the reaction rate and yield of the ester.

In the esterification reaction, the alcohol is used in an amount of 1.5 to 3 times the mole of the acid, and the catalyst is used in an amount of 0.2 to 2 of the total amount of the alcohol and the acid.
It is preferably set to wt%. The reaction temperature is 150 to 250 ° C, preferably 170 to 230 ° C, and 10 to 40 hours, preferably 15 to 25 hours.
React for hours. The water generated by this esterification reaction and evaporated is trapped so as not to return to the reaction vessel. The reaction may be completed when the amount of water that evaporates becomes the same as the number of moles of the acid.

After the reaction, wash with an aqueous solution of sodium hydroxide or the like until it becomes alkaline, and then wash with water until it becomes neutral. Finally, vacuum distillation is performed to remove excess alcohol. 2 to
If it is 3 mmHg, alcohol distills at about 60-100 ° C.

The ester thus produced has a kinematic viscosity of 5 to 10 cst at 40 ° C., and has a traction coefficient of about 5 to 7% higher than that of a commercial traction base oil having the same viscosity range. Therefore, if the ester is used, a device that requires a high traction coefficient in a relatively low viscosity region, that is, if it is a fiber manufacturing machine or a food manufacturing machine, is expected to have a preferable effect as compared with a conventionally commercially available fluid. be able to.

However, in applications where a high traction coefficient is required in a higher viscosity region, that is, in large civil engineering machinery such as automobile transmissions and tractors, the ester of the A component alone is not sufficient, and the following branch as the B component is added to this. It is necessary to blend the polybutene that it has.

The polybutene as the B component has a quaternary carbon atom or a tertiary carbon atom in the main chain, and is a polymer of polybutene having 3 to 5 carbon atoms and its hydrogenated product. Preferred are polybutene and its hydrogenated products. Polybutene can be represented by the following structural formula:

The hydrogenated product is represented by the following structural formula.

However, the degree of polymerization n is 6 to 200.

Although such a polybutene may be a commercially available product, it can be produced by polymerizing isobutylene and n-butene by a known method. The hydrogenated product is produced by reacting polybutene in the presence of hydrogen. Particularly preferred polybutene and its hydrogenated product are those having a molecular weight range of 900 to 5,000. The molecular weight can be adjusted by decomposing high molecular weight polybutene, mixing low molecular weight polybutene, and the like.

The B component in the present invention, for example, polybutene, has a traction coefficient of 0.075 to 0.085. Therefore, if only the B component is used, it can be applied to a conventionally known power transmission device without any particular problem.

However, a traction drive device, which will be developed in the future, requires a traction coefficient of 0.1 or more, so that the above component B alone cannot satisfy the required quality, and a synthetic lubricating fluid obtained by mixing the above component A ester with the component B polybutene. Need to be used.

The inventors of the present invention conducted numerous tests on a mixed fluid of cyclohexanol cyclohexanecarboxylic acid esters and polybutene having a branch, and found that 1 to 70% by weight, especially 10 to 50% by weight of polybutene was added to the esters. It has been found that when compounded an unexpectedly large traction coefficient is exhibited.

INDUSTRIAL APPLICABILITY The synthetic lubricating fluid of the present invention can be applied to a power transmission device of an internal combustion engine such as an automobile or a tractor, or a general industrial machine such as a spinning machine or a food manufacturing machine, and particularly when the device is a traction drive device. It can exhibit excellent performance. Therefore, various additives can be added to the synthetic lubricating fluid of the present invention depending on the application.

That is, by adding a small amount of additives such as a viscosity index improver, an antioxidant material, and an anticorrosive agent, stable performance can be exhibited for a long period of time in any power transmission device.

However, when using a polymer that does not have gem-dimethyl type quaternary carbon in the main chain such as polymethacrylate as a viscosity index improver, the traction coefficient is often lowered, so the addition amount is about 10 weight. It must be less than or equal to%.

(Function) The reason why the synthetic lubricating fluid of the present invention has a traction coefficient significantly superior to that of the conventional fluid has not yet been sufficiently clarified, but basically, the peculiar characteristics of both A and B components are present. It is presumed to be due to the molecular structure.

That is, the ester as the component A of the present invention has two cyclohexyl rings in the compound molecule, and since they are bound by a carbonyl group, intermolecular dipole force acts on each other. It is considered that this inter-dipole force changes the fluid to a stable glass state under the high load condition of the traction device and increases the anti-shear force. On the other hand, since the component B of the present invention, which is a component B, is a hydrocarbon and has no polarity, the van der Waals force is dominant in the fluid, but it has an appropriate molecular weight and viscosity, and polybutene gem-dimethyl. It is thought that it has a high traction coefficient because there are many branches as typified by type quaternary carbon and it is difficult for the intramolecular rotation necessary for flow to occur. Furthermore, when these A component and B component are blended,
It is considered that the A component having a cyclohexyl ring and the B component having a gem-dimethyl type quaternary carbon mesh with each other firmly under a high load as if they were gears, and thus exhibit a remarkably excellent traction coefficient.

(Example) Examples 1-2 The component A (cyclohexanol cyclohexanecarboxylic acid ester) of the present invention was synthesized by the following method.

Cyclohexanecarboxylic acid 513g (4mol), cyclohexanol 800g (8mol) and phosphoric acid 10g (catalyst) were placed in a round bottom flask and blown with nitrogen for 20 hours, 20
Heated at 0 ° C. The water generated by the esterification and evaporated was trapped and prevented from returning to the flask. The reaction was terminated when 4 mol (72 cc) of water came out.

After the reaction, the mixture was washed with an aqueous sodium hydroxide solution until it became alkaline to remove unreacted cyclohexanecarboxylic acid and phosphoric acid. Next, the mixture was washed with water until it became neutral, washed with sodium hydroxide, and distilled under reduced pressure to remove excess cyclohexanol to obtain cyclohexanol cyclohexanecarboxylic acid ester as the component A. Finally, the yield of the component A was about 80%.

Next, polybutene (B ₂ ) is added to the component A (A ₁ ) synthesized in this way and the component A (A ₂ ) in which R ₁ is a methyl group and R ₂ and R ₃ are hydrogen atoms synthesized in the same manner. component)
Was blended to measure the traction coefficient. A Soda 4-roller traction tester was used as the measuring device, and the test conditions were: oil temperature 30 ° C, roller temperature 30 ° C, average Hertz pressure.
1.2 GPa, rolling speed 3.6 m / s and slip rate 3.0%
And Under these conditions, the traction coefficient becomes maximum at a slip rate of about 3% in any oil, so the measured traction coefficient can be regarded as the maximum traction coefficient. When the measurement was carried out while changing the molecular weight and the blending amount of polybutene, the results shown in Table 1 were obtained.

As a result, the B component with a molecular weight of 900 to 5000 is
It can be seen that a high traction coefficient is exhibited when 0 to 50% by weight is blended.

Comparative Examples 1 to 7 As the samples for comparison, the component A alone (A ₁ or A ₂ ), B
Ingredients alone, hydrogenated product of linear dimer of alpha-methylstyrene (Monsanto Co., "Santortrack"), commercially available naphthenic fluid (having 1 to 3 cyclohexyl rings), A ₁
The traction coefficient was measured by the method shown in the examples for the one in which polymethacrylate (PMA) was blended in the component and the _{one in} which the ethylene propylene copolymer (OCP) was blended in the A ₁ component.

As a result, the results shown in Table 1 were obtained, and it was found that all the comparative samples had a traction coefficient of 95% or less as compared with the synthetic lubricating fluid of the present invention.

(Effects of the Invention) The present invention selects cyclohexanol cyclohexanecarboxylic acid ester, which has not been conventionally used as a naphthenic base oil, and selects 1 component of a polybutene having a branch and a molecular weight of 500 to 10,000.
It is a synthetic lubricating fluid blended up to 70% by weight and has an extremely high traction coefficient.

Therefore, if the synthetic lubricating fluid of the present invention is applied to a power transmission device, particularly a traction drive device, the shearing force under a high load can be dramatically increased, and a power transmission device to be developed in the future can be downsized and operated with high efficiency. Such a great effect can be achieved.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C10N 20:04 30:00 40:04

Claims (2)

[Claims] 1. A general formula [Wherein _R 1, _{R 2} and _{R 3} are each a hydrogen atom or indicates one or more kinds selected from an alkyl group having 1 to 8 carbon atoms. ] The cyclohexanol cyclohexane carboxylic acid ester or its derivative of 1] to 70% by weight of polybutene having an average molecular weight of 900 to 5000 is blended. 2. The synthetic lubricating fluid according to claim 1, which contains 10 to 50% by weight of polybutene.