JP2013014660A - Brake fluid for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide brake fluid for an automobile readily developing lubricity based on a liquid film formed outside a liquid pressure chamber.SOLUTION: The brake fluid for an automobile includes at least one non-mineral oil-based base material selected from glycol, glycol ether and polyether polyol, and includes an aliphatic ester. It is preferable to include an aliphatic ester having 19 or more carbons, as the aliphatic ester in the brake fluid for automobile, and the content of the aliphatic ester in the brake fluid for an automobile is preferably 1-10 mass%.

Description

  The present invention relates to an automobile brake fluid containing a non-mineral oil base material.

  A vehicle brake fluid containing a non-mineral oil base such as glycols is known (see Patent Document 1).

JP 2002-536494 A

  By the way, the hydraulic system of an automobile brake includes a cylinder body, a piston that moves in the cylinder body, and a seal member that partitions the inside and outside of the hydraulic chamber in the cylinder body. The seal member is slidably contacted with the outer peripheral surface of the piston or the inner wall surface of the cylinder body as the cylinder body and the piston move relative to each other. For example, when the seal member is fixed to the cylinder body, the outer peripheral surface of the piston and the seal member are brought into sliding contact with the movement of the piston. Here, when the piston moves toward the outside of the hydraulic chamber, a part of the piston arranged in the hydraulic chamber is exposed to the outside of the hydraulic chamber. At this time, a liquid film of the brake fluid is formed on the exposed outer peripheral surface of the piston by slightly exuding the vehicle brake fluid from between the seal member and the piston. When the piston moves toward the inside of the hydraulic chamber, the frictional resistance between the seal member and the outer peripheral surface of the piston is reduced by being lubricated by the liquid film on the outer peripheral surface of the piston. This reduces the load on the seal member. Such lubrication with the brake fluid for automobiles is similarly performed between the inner wall surface of the cylinder body and the seal member even when the seal member is fixed to the outer peripheral surface of the piston.

  In the above-described lubrication with the brake fluid for automobiles, the liquid film is exposed to air outside the hydraulic chamber. Thus, if the liquid film is exposed to air and the state continues, there is a possibility that the lubricity based on the liquid film is difficult to be exhibited.

  The present invention has been made in view of such conventional circumstances, and an object thereof is to provide an automotive brake fluid that can easily exhibit lubricity based on a liquid film formed outside a hydraulic chamber. There is.

  In order to achieve the above object, the automotive brake fluid of the invention according to claim 1 includes at least one non-mineral oil base material selected from glycol, glycol ether, and polyether polyol. However, the gist is to contain an aliphatic ester.

The gist of the invention according to claim 2 is that the brake fluid for automobile according to claim 1 includes an aliphatic ester having 19 or more carbon atoms as the aliphatic ester.
The gist of the invention described in claim 3 is that the content of the aliphatic ester is 1 to 10% by mass in the brake fluid for an automobile according to claim 1 or claim 2.

  ADVANTAGE OF THE INVENTION According to this invention, the brake fluid for motor vehicles which is easy to exhibit the lubricity based on the liquid film formed in the outer side of a hydraulic pressure chamber is provided.

The embodiment which materialized brake fluid for vehicles of the present invention is described in detail.
The brake fluid for automobiles contains at least one non-mineral oil base material selected from glycol, glycol ether, and polyether polyol.

  Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, and hexylene glycol.

  The glycol ether may be its borate ester. Examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, boric acid ester of triethylene glycol monomethyl ether, And boric acid esters of tetraethylene glycol monomethyl ether.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). The number average molecular weight of the polyether polyol is preferably in the range of 150 to 5000, more preferably in the range of 500 to 4000, and still more preferably in the range of 1000 to 4000.

The non-mineral oil-based base material may be composed of a single species or may be composed of a plurality of species.
The content of the non-mineral oil-based base material in the brake fluid for automobiles is preferably 80% by mass or more, more preferably 85% by mass or more.

  The brake fluid for automobiles contains an aliphatic ester. The aliphatic ester is contained in the hydraulic system of the automobile brake in order to maintain a liquid film of the automobile brake fluid formed on the inner peripheral surface of the cylinder or the outer peripheral surface of the piston.

  The aliphatic ester is not particularly limited as long as it can be dissolved in the non-mineral oil base, and may be any of monoester, diester, and hindered ester, for example. As the aliphatic ester, for example, an aliphatic ester having 13 to 45 carbon atoms can be used.

  Examples of the aliphatic ester having 13 carbon atoms include NPG · di (n-butanoate) and NPG · di (2-methylpropanoate). However, “NPG” represents “neopentyl glycol”.

  Examples of the aliphatic ester having 15 carbon atoms include NPG · di (n-pentanoate) and NPG · di (2-methylbutanoate). Examples of the aliphatic ester having 16 carbon atoms include 2-ethylhexyl caprylate.

  Examples of the aliphatic ester having 17 carbon atoms include 2-ethylhexyl pelargonate, isopropyl myristate, NPG • di (n-hexanoate), NPG • di (2-ethylbutanoate), and NPG • di (3 -Ethylbutanoate). Examples of the aliphatic ester having 18 carbon atoms include 2-ethylhexyl caprate, TMP • tri (n-butanoate), and TMP • tri (2-methylpropanoate). However, “TMP” indicates “trimethylolpropane”.

  Examples of the aliphatic ester having 19 carbon atoms include methyl oleate, NPG · di (n-heptanoate), and NPG · di (2-ethylpentanoate). Examples of the aliphatic ester having 20 carbon atoms include 2-ethylhexyl laurate.

  Examples of the aliphatic ester having 21 carbon atoms include NPG · di (n-octanoate), NPG · di (2-ethylhexanoate), TMP · tri (n-pentanoate), and TMP · tri (2-methyl). Butanoate), PE.tetra (n-butanoate), and PE.tetra (2-methylpropanoate). However, “PE” indicates pentaerythritol.

  Examples of the aliphatic ester having 22 carbon atoms include 2-ethylhexyl myristate, isobutyl oleate, n-butyl stearate, and di-2-ethylhexyl adipate. Examples of the aliphatic ester having 23 carbon atoms include NPG · di (n-nonanate) and NPG · di (isonononate).

  Examples of the aliphatic ester having 24 carbon atoms include 2-ethylhexyl palmitate, diisononyl adipate, di-2-ethylhexyl phthalate, TMP • tri (n-hexanoate), and TMP • tri (3-ethylbutanoate). E)). Examples of the aliphatic ester having 25 carbon atoms include di-2-ethylhexyl azelate, di-n-octyl azelate, diisooctyl azelate, NPG · di (n-decanoate), PE · tetra (n-pentanoate). , PE.tetra (2-methylbutanoate), PE.tetra (2-methylbutanoate), and PE.tetra (2,2-dimethylpropanoate).

  Examples of the aliphatic ester having 26 carbon atoms include 2-ethylhexyl stearate, diisodecyl adipate, and diisodecyl azelate. Examples of the aliphatic ester having 27 carbon atoms include TMP · tri (n-heptanoate) and TMP · tri (2-ethylpentanoate).

  Examples of the aliphatic ester having 29 carbon atoms include diisodecyl azelate, PE • tetra (n-hexanoate), PE • tetra (2-ethylbutanoate), and PE • tetra (2,2-dimethylbutanoate). E)). Examples of the aliphatic ester having 30 carbon atoms include TMP · tri (n-octanoate) and TMP · tri (2 ethylhexanoate).

  Examples of the aliphatic ester having 33 carbon atoms include TMP • tri (n-nonanate), TMP • tri (isonononate), PE • tetra (n-heptanoate), and PE • tetra (2-ethylpentanoate). Is mentioned. Examples of the aliphatic ester having 36 carbon atoms include TMP • tri (n-decanoate) and TMP • tri (isodecanoate).

  Examples of the aliphatic ester having 37 carbon atoms include PE • tetra (n-octanoate) and PE • tetra (2-ethylhexanoate). Examples of the aliphatic ester having 41 carbon atoms include PE.tetra (n-nonanate) and PE.tetra (isonononate). Examples of the aliphatic ester having 45 carbon atoms include PE • tetra (n-decanoate) and PE • tetra (isodecanoate).

Of the aliphatic esters described above, NPG, TMP, or PE polyol esters are classified as hindered esters.
As the aliphatic ester, a single species may be used, or a plurality of species may be used in combination.

  The brake fluid for automobiles preferably contains an aliphatic ester having 19 or more carbon atoms among the aliphatic esters described above. When an aliphatic ester having 19 or more carbon atoms is included, for example, as the lipophilicity of the carbon chain is improved or the number of carbon chains in one molecule is increased, the aliphatic ester is added to the inner peripheral surface of the cylinder or the outer peripheral surface of the piston. It is presumed that it will be easily adsorbed on the surface. That is, when an aliphatic ester having 19 or more carbon atoms is included, the liquid film of the brake fluid for automobiles formed on the inner peripheral surface of the cylinder or the outer peripheral surface of the piston is further easily maintained.

  On the other hand, the upper limit of the carbon number of the aliphatic ester is preferably 45 or less, for example. In this case, it becomes easy to avoid an excessive increase in the kinematic viscosity of the aliphatic ester, that is, the kinematic viscosity of the brake fluid for automobiles. Moreover, it is preferable to include a hindered ester as the aliphatic ester from the viewpoint that the thermal stability and hydrolysis resistance of the aliphatic ester are easily obtained.

  The content of the aliphatic ester in the brake fluid for automobiles is preferably 1 to 10% by mass, more preferably 5 to 10% by mass. When the content of the aliphatic ester is 1% by mass or more, the effect of maintaining the liquid film is further easily obtained. On the other hand, when the content of the aliphatic ester exceeds 10% by mass, the kinematic viscosity of the brake fluid for automobiles increases, so that the responsiveness at the time of operating the brake tends to decrease.

The brake fluid for automobiles may contain additives other than aliphatic esters as necessary. Examples of the additive include a corrosion inhibitor, an antioxidant, and a pH adjuster.
Examples of the corrosion inhibitor include monocarboxylic acids such as lauric acid and oleic acid, and triazoles such as benzotriazole and tolyltriazole.

  Examples of the antioxidant include bisphenol compounds such as 4,4′-butylidenebis- (6-tert-butyl-3-methylphenol) and phenol compounds such as dibutylhydroxytoluene.

  Examples of the pH adjuster include amine compounds. Examples of the amine compound include alkanolamines such as triethanolamine and isopropanolamine, alkylamines such as dibutylamine, tributylamine, and dicyclohexylamine, and cyclic amines such as morpholine.

The brake fluid for automobiles may contain a viscosity modifier, a lubricant, a disinfectant, an antifoaming agent, or a dye as other additives.
Next, the usage state of the brake fluid for automobiles will be described together with the operation.

  A hydraulic system for an automobile brake includes a cylinder body, a piston that moves in the cylinder body, and a seal member that defines a hydraulic chamber in the cylinder body. The cylinder body and the piston are formed from a metal material or a resin material. Examples of the metal material include aluminum, cast iron, and steel. Examples of the resin material include a polyamide-based resin and a phenol-based resin.

  The seal member is formed from a rubber-based material. Examples of rubber-based materials include butyl rubber, isoprene rubber, natural rubber, butadiene rubber, 1,2-polybutadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, Examples include chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, silicone rubber, fluorine rubber, urethane rubber, polyisobutylene rubber, and butyl chloride rubber.

  The seal member is brought into sliding contact with the outer peripheral surface of the piston or the inner wall surface of the cylinder body as the cylinder body and the piston move relative to each other. At this time, the automobile brake fluid that has oozed out of the hydraulic chamber forms a liquid film on the outer peripheral surface of the piston or the inner peripheral surface of the cylinder. The liquid film lubricates the seal member and the outer peripheral surface of the piston or the inner wall surface of the cylinder body, thereby reducing the frictional resistance between the seal member and the outer peripheral surface of the piston or the inner wall surface of the cylinder body. This reduces the load on the seal member. Examples of the place where such lubrication is performed include brake actuators such as brake calipers and wheel cylinders in addition to the brake master cylinder.

  In the above-described lubrication with the brake fluid for automobiles, the liquid film is exposed to air outside the hydraulic chamber. Thus, if the liquid film is exposed to air and the state continues, there is a possibility that the lubricity based on the liquid film is difficult to be exhibited. In this respect, the automobile brake fluid of the present embodiment contains an aliphatic ester. The liquid film formed by the automobile brake fluid is easily maintained even if the state of exposure to air continues.

  The effect of the inclusion of the aliphatic ester can be confirmed by an acceleration test in which the brake fluid for automobiles is left under a predetermined temperature condition. In this acceleration test, for example, the brake fluid for automobiles is placed on a metal plate, left at 50 ° C. for 5 hours, and the dynamic friction coefficient between the metal plate after being left and the rubber member assumed as a seal member is measured. To do. As a result of this measurement, the smaller the coefficient of dynamic friction, the better the effect of containing the aliphatic ester.

The effects exhibited by this embodiment will be described below.
(1) The brake fluid for automobiles contains an aliphatic ester. Since the liquid film formed by this brake fluid for automobiles is easy to maintain even if the state of exposure to air continues, it is easy to exert lubricity based on the liquid film formed outside the hydraulic chamber. It becomes. Thereby, since the load to the seal member is reduced, for example, the durability of the seal member can be improved.

(2) By including an aliphatic ester having 19 or more carbon atoms as the aliphatic ester, it becomes easier to enhance the effect described in the above section (1).
(3) When the content of the aliphatic ester in the brake fluid for automobiles is 1 to 10% by mass, it is easier to enhance the effect described in the above (1) column, and the brake is activated. The influence on the responsiveness can be suppressed. Moreover, since it can suppress that kinematic viscosity of the brake fluid for motor vehicles increases because content of aliphatic ester is 10 mass% or less, for example, "6 types (BF-6" of JISK2233: 2006 is described. ) ”.

Next, the technical idea that can be grasped from the above embodiment will be described below.
(A) The automobile brake fluid, wherein the aliphatic ester has 45 or less carbon atoms.

  (B) In the automotive brake fluid, the aliphatic ester has 19 to 45 carbon atoms, and the aliphatic ester is at least one selected from monoesters, diesters, and hindered esters. .

Next, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1-6)
As shown in Table 1, the automobile brake fluid of each example was prepared by mixing an aliphatic ester with a non-mineral oil base. Triethylene glycol monomethyl ether was used as the non-mineral oil base. The “aliphatic ester A” shown in Table 1 is methyl oleate (carbon number: 19, manufactured by NOF Corporation, M-182A), and “aliphatic ester B” is trimethylolpropane and 6 to 10 carbon atoms. Hindered ester with an acid (carbon number: 24-36, manufactured by NOF Corporation, H-327R), “aliphatic ester C” is di-n-octyl azelate (carbon number: 25, Wako Pure Chemical Industries, Ltd.) Manufactured by Kogyo Co., Ltd.). The unit of the numerical value indicating the blending amount of each component in Table 1 is mass%.

(Comparative Example 1)
As shown in Table 1, the automotive brake fluid of Comparative Example 1 was composed only of triethylene glycol monomethyl ether, which is a non-mineral oil base material.

<Evaluation of lubricity>
One drop of automobile brake fluid was dropped on the metal plate, and the metal plate was left at 50 ° C. for 5 hours. Next, using a surface property tester (trade name: HEIDON, TYPE: 14FW manufactured by Shinto Kagaku Co., Ltd.), the upper surface of the metal plate to which the brake fluid for automobiles of each example adhered and a rubber member (ethylene-propylene- The coefficient of dynamic friction with diene rubber was measured. The measurement results of the automobile brake fluid in each example are shown in the “dynamic friction coefficient” column of Table 1.

各実施例の自動車用ブレーキ液の動摩擦係数は、比較例１の自動車用ブレーキ液の動摩擦係数よりも小さい。従って、各実施例の自動車用ブレーキ液では、潤滑性が発揮され易いことが分かる。

The dynamic friction coefficient of the automotive brake fluid of each example is smaller than the dynamic friction coefficient of the automotive brake fluid of Comparative Example 1. Therefore, it can be seen that the lubricating properties of the automotive brake fluid of each example are easily exhibited.

Claims (3)

  An automotive brake fluid containing at least one non-mineral oil base selected from glycols, glycol ethers, and polyether polyols, which contains an aliphatic ester.   The automobile brake fluid according to claim 1, wherein the aliphatic ester contains an aliphatic ester having 19 or more carbon atoms.   The automotive brake fluid according to claim 1 or 2, wherein the content of the aliphatic ester is 1 to 10% by mass.