JPS5822516B2 - Hydraulic fluid composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic working fluid composition, and particularly to a highly stable working fluid composition for use in hydraulic brake and clutch systems.

In recent years, the burden placed on brake systems has been increasing due to increased vehicle speeds due to improvements in road equipment, increased traffic volume, and the spread of disc brakes.

Furthermore, from the perspective of resource conservation, it has become desirable to extend the lifespan of brake system components, leading to a demand for brake fluids with higher boiling points and longer lifespans.

Conventional brake fluids mainly contain polyglycols and polyglycol ethers, which are highly hygroscopic.
During use, the brake fluid absorbs moisture and deteriorates in performance, often resulting in serious failure of the brake system.

Deterioration in performance when moisture is absorbed means a decrease in the boiling point, which is the temperature at which paper lock occurs, a decrease in brake response due to an increase in viscosity at low temperatures, and a decrease in rust prevention performance for the various metal parts that make up the brake system. do.

In contrast to these brake fluids mainly composed of polyglycols and polyglycol ethers (hereinafter referred to as polyglycol brake fluids), silicone brakes mainly composed of non-hygroscopic diorgasopolysiloxanes, especially dimethylpolysiloxane, are used. liquid is proposed.

Dimethylpolysiloxane has a high boiling point, is non-hygroscopic, non-corrosive, has good viscosity properties, and is chemically inert, making it ideal as a base oil for brake fluids.

However, dimethylpolysiloxane has the property of shrinking sealing parts such as styrene-butadiene rubber (SBR) rubber cups and O-rings, which are most commonly used in brake systems. When used alone as brake fluid, it contracts sealing parts such as rubber cups and O-rings, causing brake fluid and pressure leaks.

Therefore, in order to obtain a preferable silicone brake fluid using dimethylpolysiloxane, an appropriate rubber swelling agent such as dioctyl adipate, dioctyl sebacate, dioctyl azelate, tributyl phosphate, trioctyl phosphate, etc. may be added alone or in combination of two or more. Therefore, it is necessary to improve rubber swelling properties.

Rubber swelling agents are required to have excellent heat resistance, cold resistance, and chemical stability, but more importantly, silicone brake fluids containing rubber swelling agents are required to have excellent heat resistance, cold resistance, and chemical stability. Since it may be used in combination with coal brake fluid, the change in performance when used together must be small.

Silicone brake fluid is generally not compatible with polyglycol brake fluid, so when the two are mixed, they separate into two layers.

However, strictly speaking, some of the rubber swelling agents mentioned above that should be added to dimethylpolysiloxane have a greater solubility in polyglycols or polyglycol ethers than in dimethylpolysiloxane. When a silicone brake fluid using a rubber swelling agent is mixed with a polyglycol brake fluid, the rubber swelling agent is transferred from the silicone brake fluid layer to the polyglycol brake fluid layer at a constant distribution ratio.

The inventors' research has revealed that in the silicone brake fluid layer after mixing, the amount of rubber swelling agent decreases due to migration of the rubber swelling agent, and the rubber swelling property becomes smaller than before mixing. .

On the contrary, the rubber swelling property of the polyglycol brake fluid layer after mixing becomes greater than before mixing.

That is, changes in rubber swelling properties during mixing are thought to cause shrinkage or excessive swelling of the rubber cup and O-IJ song seal parts, causing serious failures of the flake system such as liquid leaks or pressure leaks.

The present inventors conducted extensive research on hydraulic fluid compositions using dimethylpolysiloxane as a base oil, and found that α-
It has been found that a silicone brake fluid prepared by adding an olefin oligomer to dimethylpolysiloxane exhibits extremely small changes in rubber swelling properties when mixed with a polyglycol brake fluid.

That is, the present invention provides a hydraulic fluid composition consisting essentially of the following components (a) and (b).

(a) Dimethylpolysiloxane represented by the general formula (wherein R represents a methyl group and m is a value such that the kinematic viscosity of the compound at 25°C is 5 to 100 centistokes) is hydraulically operated. 51 to 99% of the total weight of the fluid, and (f) general formula (in the formula, an alkyl group having 4 to 12 carbon atoms, n is 2 to 1
1 to 49% of the total weight of the hydraulic fluid.

The dimethylpolysiloxane used in the present invention is produced by a known method, and its kinematic viscosity should be 5 to 100 centistokes, particularly 10 to 50 centistokes, at 25°C in consideration of fluidity. is preferred.

Next, the α-olefin oligomer used in the present invention is obtained by polymerizing a raw material α-olefin obtained by polymerizing ethylene or thermally decomposing paraffin wax in the presence of a catalyst, followed by distillation and hydrogenation. It will be done.

The side chain alkyl group of the α-olefin oligomer shown in the general formula has 4 to 4 carbon atoms in consideration of fluidity and viscosity index.
12, particularly preferably 8-10.

The hydraulic working fluid of the present invention has excellent thermal stability, oxidative stability,
It has anti-corrosion properties and lubricity, but for the purpose of further improving it, known antioxidants, metal rust inhibitors, lubricity improvers, etc. can be added.

As an example of the present invention, a silicone brake fluid having the following formulation example was formulated.

The blending ratio indicates weight %. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Next, the following silicone brake fluid was blended as a comparative example with respect to the example of the present invention.

The blending ratio indicates weight %.

Comparative Example 1 In order to investigate the performance of the hydraulic fluid in the present invention, the rubber swelling properties of each silicone brake fluid of Examples 1 to 8 and Comparative Examples 1 to 3 were measured according to the US Federal Motor Vehicle Safety Standards (Federa Motor Vehicle Safety Standards).
l Motor Vehicle 5afetySta
ndards, FMVSS) Al 16 (DOT
5 brake fluid).

Next, in order to investigate the change in rubber swelling when these silicone brake fluids are mixed with polyglycol brake fluids, silicone brake fluids and polyglycol brake fluids were mixed at a ratio of 1:1 (volume ratio), and after standing still. Two separated layers (
The silicone brake fluid layer (the silicone brake fluid layer and the polyglycol brake fluid layer) was taken out and its rubber swelling property was measured.

Table 1 shows the results of a series of rubber swelling measurements.

(Note 1) Rubber swelling property is SAE (Society o
The test was carried out by soaking at 120° C. for 70 hours using a standard SBR cup manufactured by Automotive Eugineers.

(Note 2) The polyglycol brake fluid used for mixing is S.
AE standard brake fluid RM-1 (Compatibili
ty Fluid).

In Table 1, the silicone brake fluid according to the present invention has the excellent feature that the rubber swelling property (increase in base diameter and change in hardness) hardly changes even when mixed with polyglycol brake fluid.

In contrast, the rubber swelling property of the silicone brake fluid of the comparative example changes significantly when mixed with the polyglycol brake fluid.

DO of FMVS S A116 for silicone brake fluids according to formulation examples 1, 3, and 7 of the present invention
Compliance with the T5 brake fluid standard was investigated.

The results were in full compliance with the standards.

Table 2 lists the results of measurements of FMVSSAl 16DOT5 brake fluid according to the test items.

Claims (1)

[Claims] 1 (a) Represented by the general formula (in the formula, R represents a methyl group, and m is a value such that the kinematic viscosity of the compound at 25°C is 5 to 100 centistokes) The total weight of dimethylpolysiloxane is 51~
99%, and (0) general formula , , (in the formula, an alkyl group having 4 to 12 carbon atoms, n is 2 to 1
(representing the number of 0) The α-olefin oligomer represented by
A hydraulic fluid composition consisting essentially of 49% of both components.