JP2006052367A - Pulse-absorbing rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse-absorbing rubber composition having excellent gas-barrier properties over a long period, exhibiting good pulse-absorbing effects, and providing a simple pulse-absorber having wide application range. <P>SOLUTION: The pulse-absorbing rubber composition usable as the pulse-absorber arranged in a pressure circuit is formed out of a foamed body of an elastomer comprising a polyisobutylene. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a pulsation absorbing rubber composition used for a pulsation absorber which is used to reduce pulsation of pressure fluid in a pressure line and efficiently absorbs pressure and flow rate pulsation of the pressure fluid flowing in the pipe.

Conventionally, as a means for suppressing pulsation of pressure fluid, a bladder and a diaphragm made of synthetic rubber are used in an accumulator to which a bladder and a diaphragm are attached (for example, Patent Document 1), and in the piston type accumulator type, the piston and the spring are used. The bellows type accumulator uses the bellows, and suppresses (absorbs) the pressure by changing the volume of the sealed gas or the spring in response to the pressure fluctuation in the fluid.
In addition, since these structures are complicated and expensive, recently, a pressure pulsation absorber using foamed rubber has been devised (for example, Patent Document 2).
Japanese Patent Laid-Open No. 10-159803 (Claims, Embodiment of the Invention, FIG. 1) JP-A-2004-83772 (Claims, Embodiments of the Invention)

However, in a simple structure in which foamed rubber is mounted in such a pressure fluid flow path to reduce fluid pressure pulsation, the air in the foamed rubber bubbles is in the liquid when the pulsation is repeated in the pressure fluid. There is a problem that the effect of preventing pulsation deteriorates at an early stage due to leakage into the rubber or liquid permeating into the foamed rubber through the rubber.

Accordingly, an object of the present invention is to provide a pulsation-absorbing rubber composition that can exhibit a good pulsation absorption effect with excellent gas barrier properties over a long period of time and is a simple and wide pulsation absorber.

  In order to solve the above-mentioned problems, the present invention relates to a pulsation-absorbing rubber composition used as a pulsation-absorbing body disposed in a pressure circuit, the foam comprising an elastic body. The pulsation-absorbing rubber composition is characterized in that the elastic body is polyisobutylene.

The invention according to claim 2 provides the pulsation absorbing rubber composition according to claim 1, wherein the polyisobutylene forming the elastic body is an addition-curing type.

  According to a third aspect of the present invention, there is provided the invention according to any one of the first or second aspect, wherein the foam is composed of a rubber composition containing thermally expandable microcapsules, and the rubber composition is heated and foamed. A pulsation-absorbing rubber composition characterized by having closed air bubbles.

  The invention according to claim 4 provides the pulsation absorbing rubber composition according to any one of claims 1 to 3, wherein the foam has a gas content of 20% to 90%.

A fifth aspect of the present invention provides the pulsation absorbing rubber composition according to any one of the first to fourth aspects, wherein the fluid used in the pressure circuit is a brake oil.

In the pulsation absorbing rubber composition according to claim 1, since the elastic body of the foam made of an elastic body is polyisobutylene having excellent oil resistance, particularly brake oil resistance, the penetration of liquid in the pressure circuit into the foam Gas leakage in the foam can be prevented for a long time. For this reason, it is excellent in gas barrier property over a long period of time, can exhibit the favorable pulsation absorption effect, and it can be set as the pulsation absorption rubber composition used as the pulsation absorber of the simple and wide application range.

In the pulsation-absorbing rubber composition of claim 2, since the polyisobutylene forming the elastic body is an addition curing type in claim 1, it can be cured in a short time by heating. For this reason, while being able to obtain the effect similar to Claim 1, it can be set as the pulsation absorption rubber composition used as a pulsation absorber of the simpler and wide application range.

The pulsation absorbing rubber composition according to claim 3 is the pulsation absorbing rubber composition according to claim 1 or 2, wherein the foam is composed of a rubber composition containing thermally expandable microcapsules, and the rubber composition is heated and foamed. The closed cells are covered with resin, so that even if the pulsation is repeated, the gas in the bubbles will not leak over a long period of time. Can be formed. For this reason, the same effect as that of claim 1 or claim 2 can be obtained, and the pulsation absorption can be achieved as a pulsation absorber having a simple and wide application range, which can exhibit a good pulsation absorption effect with excellent gas barrier properties for a long time. It can be set as a rubber composition.

In the pulsation absorbing rubber composition according to claim 4, since the foam has a gas content of 20% to 90% in any of claims 1 to 3, the same as in claims 1 to 3. An effect can be obtained and a good pulsation absorbing effect can be exhibited over a long period of time.

Further, as in claim 5, the pulsation absorbing rubber composition in any one of claims 1 to 4 is also used in the environment where the fluid used in the pressure circuit is brake oil. The same effect can be exhibited.

As the best mode of the pulsation absorbing rubber composition to be the pressure pulsation absorbing foam according to the present invention,
A pulsation absorbing rubber composition, which is used as a pulsation absorber disposed in a pressure circuit, is made of a foam made of an elastic body, and the foam is made of a rubber composition containing thermally expandable microcapsules, is described in detail below. explain.

The polyisobutylene constituting the rubber composition used as the pulsation absorbing rubber composition according to one embodiment of the present invention generally has a condensation curing type and an addition curing type, but the addition curing type is more preferable than various physical properties. Further, for the purpose of reducing the viscosity of polyisobutylene, oil or the like may be added, or a polymer in which oil is internally added may be used.

The thermally expandable microcapsule constituting the rubber composition used as the pulsation absorbing rubber composition according to one embodiment of the present invention is composed of a liquid gas encapsulated with a resin shell, and the particle size thereof is 2 to 2. At 50 microns, when heated, it expands to about 5 to 100 times the volume.
As the liquid gas, generally low molecular weight hydrocarbons are used. For example, ethane, propane, butane, isobutane, pentane, etc. can be used. As a resin constituting the shell, generally, A thermoplastic resin is used, and polyethylene, polypropylene, styrene resin, acrylic resin, vinylidene chloride resin, acrylonitrile resin, PET, PBT, fluororesin, polyvinyl alcohol, ethylene vinyl alcohol copolymer resin, and the like are preferably used.

The amount of thermally expandable microcapsules used in the pulsation absorbing rubber composition according to one embodiment of the present invention is generally 1 to 30 parts with respect to 100 parts by weight of the polymer. This is because if the amount is less than 1 part, a sufficient pulsation absorbing effect cannot be obtained, while if it exceeds 30 parts, the initial pulsation absorption characteristics are excellent but the durability is poor.

Moreover, the gas content rate contained in the foam used for the pulsation absorption rubber composition of this invention is 20%-90%, Preferably it is 40-80%. This means that when the gas content is less than 20%, a sufficient pulsation absorption effect cannot be obtained, whereas when the gas content is more than 90%, the initial pulsation absorption characteristics are excellent, but the durability is not satisfactory. This is to become a thing.

Furthermore, the pulsation absorbing rubber composition according to an embodiment of the present invention can optionally contain a reinforcing agent, a filler, a lubricant, a processing aid, and the like as necessary. The method for adjusting the pulsation absorbing rubber composition of the present invention is not particularly limited, and the pulsation absorbing rubber composition can be adjusted by adding the above components and mixing them with an ordinary kneader such as a kneader, a Banbury mixer, or an open roll.
The rubber composition thus prepared is usually vulcanized and foamed at 100 to 220 ° C. for about 2 to 30 minutes.

The method for producing a pulsation absorber comprising a pulsation absorbing rubber composition according to an embodiment of the present invention may be obtained by vulcanizing and foaming a preformed rubber composition by open vulcanization. In consideration of the amount of gas to be foamed, the amount of the composition reduced by that amount may be charged and molded into a cavity shape simultaneously with vulcanization foaming. The foam thus formed may be heat-treated at a temperature of 80 ° C. to 220 ° C. for about 30 minutes to 24 hours as necessary.

The pulsation absorber made of the pulsation absorbing rubber composition having closed cells formed in this way is placed in the pressure circuit to allow the pressure fluid to flow. For example, the pulsation absorber foam is formed by various control devices in the hydraulic circuit. Each holds a gas of closed cells and has a balloon shape rich in elasticity, and each foam changes its volume each time by fluid pressure and absorbs the pressure change. Each of the absorbers works efficiently, and each bubble part flexibly receives the bubble volume that changes in the vicinity of contact with the gas dispersed in the liquid, and there is no pulsation or pressure change. The fluid can be pumped to another device. Further, the pulsation absorber made of this pulsation absorbing rubber composition has closed cells covered with a resin, and the elastic body constituting the pulsation absorber is a rubber excellent in oil resistance, particularly brake oil resistance and gas barrier properties. A pulsation absorber that exhibits an excellent pulsation absorption effect over a long period of time.

In addition, the pulsation absorber made of this pulsation absorbing rubber composition can be realized in a small size with a simple structure, so it can be easily installed or removed in-line in piping or equipment, and space saving can be achieved. Since it is an elastic body, it can be shaped freely, so that it can be shaped with less fluid flow resistance, and the pressure loss is extremely small. Furthermore, since the volume of the foam changes flexibly with respect to the pulsation pressure, it is possible to absorb pulsation of a wide frequency range from a high frequency to a low frequency. For this reason, the pulsation absorber consisting of this pulsation absorbing rubber composition is simple and has a wide application range.

Next, the results of evaluating the pulsation absorption characteristics of the pulsation absorber comprising the pulsation absorbing rubber composition of the present invention will be described below.
Using a testing machine as shown in FIG. 1, pulsation absorption comprising pulsation absorbers comprising the pulsation absorbing rubber composition of the present invention as shown in Table 1 and Examples 1 and 2 and a conventional pulsation absorbing rubber composition. The pulsation absorption characteristics in the brake oil were measured for Comparative Examples 1, 2 and 3 as the body, and the amplitude after 168 hours durability is shown in Table 1 as the pulsation absorption characteristics as a result.
2 is a waveform diagram of the pulsation absorption characteristic measured without arranging the pulsation absorber in the path, and FIG. 3 is a pulsation absorption characteristic after 168 hours durability measured by arranging the pulsation absorber of Example 1 in FIG. FIG. 4 shows a waveform diagram of pulsation absorption characteristics after 168 hours durability measured by arranging the pulsation absorber of Comparative Example 2. FIG.

  From these results, Example 1 and Example 2, which are pulsation absorbers comprising the pulsation absorbing rubber composition of the present invention, are compared with pulsation absorbers comprising the conventional pulsation absorbing rubber composition in the amplitude of the pulsation absorption characteristics. It is smaller than Example 1, Comparative Example 2 and Comparative Example 3, and has excellent pulsation absorption characteristics.

  As described above in detail, the present invention can provide a pulsation-absorbing rubber composition that is excellent in gas barrier properties over a long period of time, can exhibit a good pulsation-absorbing effect, and is a simple and wide-applicable pulsation absorber.

The block diagram which showed the evaluation apparatus of the pulsation absorber which consists of a pulsation absorption rubber composition of this invention Waveform diagram of pulsation absorption characteristics measured without placing a pulsation absorber in the path Waveform diagram of pulsation absorption characteristics after 168 hours of endurance measured by placing the pulsation absorber of Example 1 which is a pulsation absorber comprising the pulsation absorption rubber composition of the present invention in the path Waveform diagram of pulsation absorption characteristics after 168 hours durability measured by placing the pulsation absorber of Comparative Example 1 which is a pulsation absorber made of a conventional pulsation absorbing rubber composition in the path

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Pulsation generator 3 Pressure gauge 4 Pulsation absorber 5 Flow control valve 6 Pressure gauge

Claims (5)

A pulsation absorbing rubber composition used as a pulsation absorber disposed in a pressure circuit, wherein the pulsation absorbing rubber composition is formed of a foam made of an elastic body, and the elastic body is polyisobutylene. 2. The pulsation absorbing rubber composition according to claim 1, wherein the polyisobutylene forming the elastic body is an addition-curing type. 3. The foam according to claim 1, wherein the foam is composed of a rubber composition containing thermally expandable microcapsules and has closed cells formed by heating and foaming the rubber composition. A pulsation absorbing rubber composition. The pulsation absorbing rubber composition according to any one of claims 1 to 3, wherein the foam has a gas content of 20% to 90%. The pulsation absorbing rubber composition according to any one of claims 1 to 4, wherein the fluid used in the pressure circuit is brake oil.

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