JP2014077095A - Resin composition and sealing member using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition that has a high creep strength and an excellent elastic recovery rate even at high temperature, and a sealing member using the resin composition as well as a resin composition that can maintain rubber elasticity even after long-term use at high temperature under pressure and that can provide excellent sealing properties in a wide temperature range over a long term, and a sealing member using the resin composition.SOLUTION: A sealing member is produced from a resin composition including a rubber component, a thermoplastic resin, and an aramid fiber. The aramid fiber used is one having a fiber length of 0.5-5.0 mm and is added at a percentage of 3.0-10.0 mass% based on the total of the resin composition. As the rubber component of the resin composition that constitutes the sealing member, an acrylic rubber is used. As the thermoplastic resin, polyvinylidene fluoride is used.

Description

  The present invention relates to a resin composition and a seal member using the same, and more particularly to a resin composition containing a rubber component, a thermoplastic resin and a filler, and a seal member using the same.

In recent years, in various fields including automobiles, there has been an increasing demand for resin materials having excellent heat resistance and low compression set.
As an application of such a resin material, for example, there is a sealing member (seal ring) for a hydraulic continuously variable transmission (hereinafter referred to as “CVT”). In the hydraulic CVT, the groove width of the pulley is changed in a correlated manner by the hydraulic pressure in the hydraulic chamber, and the speed change is changed steplessly by changing the diameter of the pulley. Usually, a fixed pulley is integrally formed on a drive shaft, and a movable pulley is formed on a housing that reciprocates along this shaft. The movable pulley is provided with a hydraulic chamber. By controlling the hydraulic pressure of the hydraulic chamber, the movable pulley comes into contact with and is separated from the fixed pulley. As a result, the width of the groove formed in both pulleys is increased / decreased, the rotational radius of the belt wound around the pulleys is increased / decreased, power is transmitted, and the gear ratio is changed. In order to fill the hydraulic chamber with oil and generate hydraulic pressure, a resin seal ring is attached to the shaft groove formed on the outer peripheral surface of the shaft.
In CVT, since the oil pump is stopped when the engine is stopped, no hydraulic pressure is generated and no load is applied. In a conventional seal ring, sufficient sealing performance can be obtained in a state where hydraulic pressure is generated. However, in a no-load state, adhesion with the inner peripheral surface of the housing is lost, and oil in the hydraulic chamber is drained. When the engine is restarted in such a state, it takes time until the hydraulic chamber is filled with oil. In addition, if the hydraulic chamber is started without being filled with oil, the rotating part of the CVT may be damaged due to seizure. Therefore, there is a need for a seal ring that can reduce oil leakage from the hydraulic chamber even when there is no hydraulic pressure and no load.

As shown in FIG. 1, an endless type resin ring 7 having a substantially rectangular cross section and disposed on the outer peripheral side, and an O-ring 6 disposed on the inner peripheral side and providing expansion force to the resin ring as shown in FIG. Combination seal rings composed of: have been used. In general, a polytetrafluoroethylene (PTFE) resin to which a filler is added is used as the material of the resin ring 7, and a rubber-like elastic body is used as the material of the O-ring 6.
In such a conventional combination seal ring, the O-ring 6 and the resin ring 7 are crushed and installed in the gap between the groove bottom 8 and the inner surface 4a of the housing 4. Assembling resistance is large when the shaft 3 to which is attached is inserted into the housing 4, and it is necessary to install the housing 4 by introducing a press-fitting device. For this reason, there is a problem in that the manufacturing cost increases, and it is impossible to detect an assembly failure of the seal ring. Therefore, in order to solve the problems in terms of mountability and cost of the combined seal ring, it is required to deal with a single seal ring.

In CVT, since a hydraulic pressure of about 7 MPa at maximum is generated in the hydraulic chamber, a seal ring having excellent wear resistance and sealing performance under high hydraulic pressure is required. In consideration of temperature rise due to heat generation during high-speed operation and use in cold regions, the seal ring is required to have resistance in a temperature range of −40 ° C. to 150 ° C. Therefore, as the seal ring material, a material obtained by filling a fluororesin such as polytetrafluoroethylene (PTFE), modified polytetrafluoroethylene, or ethylenetetrafluoroethylene (ETFE) with an additive such as carbon powder or carbon fiber is used. It has been.
For example, Patent Document 1 discloses a composition in which carbon black having a predetermined DBP absorption amount is blended with a PTFE resin as a resin composition applicable to CVT. The seal ring of this composition expands when it absorbs oil, and fills gaps in the radial direction of the seal ring due to creep deformation at high temperatures and improves low-temperature sealability. However, it is described that there is an excellent sealing property. Moreover, since the seal ring of patent document 1 is for high surface pressures, such as CVT, it is shown that a carbon fiber and graphite can be mix | blended for the purpose of improvement, such as abrasion resistance and creep resistance.

  By employing the seal ring of Patent Document 1, it is considered possible to reduce the amount of oil leakage at low temperatures (near room temperature). However, since the above-described configuration is mainly composed of PTFE resin, the seal ring is plastically deformed by being pressurized in high-temperature lubricating / working oil. For this reason, when the engine is stopped after the operation and is in a no-load state, it is difficult to maintain a close contact state (adhesion) with the inner peripheral surface of the housing, and it is difficult to prevent oil leakage from the hydraulic chamber. In order to solve such problems, a resin material having excellent heat resistance and excellent rubber elasticity and creep resistance in a wide temperature range is required.

As such a material, for example, Patent Document 2 discloses (A) (meth) acrylic block copolymer comprising (A1) (meth) acrylic polymer block and (A2) acrylic polymer block, ( B) a thermoplastic elastomer composition comprising a compound containing two or more amino groups in one molecule and (C) a thermoplastic resin, wherein (A) the (meth) acrylic block copolymer is converted to the compound (B) Thus, (C) a thermoplastic elastomer composition obtained by dynamically heat-treating in a thermoplastic resin, and further (D) adding a thermoplastic resin and kneading is disclosed. It is described that this composition has an excellent balance between hardness and mechanical strength, has excellent rubber elasticity over a wide temperature range, excellent high-temperature creep performance and molding processability, and is excellent in oil resistance and heat resistance while being a thermoplastic elastomer. ing.
However, a seal ring for CVT or the like is required to have creep resistance at a higher temperature range, and it is considered difficult to obtain sufficient performance with the composition of Patent Document 2. In order to improve the high temperature creep characteristics, it is considered effective to add a filler to increase the hardness of the resin composition. It is also shown that fillers such as glass fiber, mica, talc, calcium carbonate can be added to the composition of Patent Document 2. However, when the hardness is increased by the addition of the filler, the elastic recovery rate, which is a reciprocal characteristic, decreases, so that even if the creep resistance can be improved, sufficient sealing characteristics may not be obtained. .

  Conventional technology

JP 2006-283898 A JP 2005-264068 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin composition having a high creep strength and an excellent elastic recovery rate even at high temperatures and a seal member using the same. A further object of the present invention is to provide a resin composition that can maintain elasticity even after being used for a long time under high temperature and pressure, and that can exhibit excellent sealing properties over a long period of time in a wide temperature range, and a sealing member using the same. To do.

  As a result of earnest research in view of the above object, the present inventors have maintained an excellent elastic recovery rate in a wide temperature range by dispersing aramid fibers in a resin composition containing a rubber component and a thermoplastic resin. The present inventors have found that the hardness of the resin composition can be greatly improved and have arrived at the present invention. That is, the resin composition of the present invention is characterized by containing a rubber component, a thermoplastic resin, and an aramid fiber.

  Since the resin composition of the present invention has high hardness, it can suppress a decrease in creep strength at high temperature, and can maintain an excellent elastic recovery rate in a wide temperature range, so even after being used for a long time under high temperature and pressure. Excellent rubber elasticity can be maintained without deformation or breakage. Therefore, the sealing member comprised from the resin composition of the present invention can maintain excellent sealing characteristics over a long period of time even under severe use conditions.

It is sectional drawing which shows an example of the conventional sealing member.

Hereinafter, the resin composition of the present invention and the seal member using the same will be described in detail.
The resin composition of the present invention comprises a mixture containing a rubber component, a thermoplastic resin, and an aramid fiber. By dispersing aramid fibers in a resin composition containing a rubber component and a thermoplastic resin, the hardness of the resin composition can be greatly improved while maintaining an excellent elastic recovery rate in a wide temperature range. . As described above, since the resin composition of the present invention has high hardness, it is possible to suppress a decrease in creep strength at a high temperature and to maintain an excellent elastic recovery rate in a wide temperature range. Even after use, excellent rubber elasticity can be maintained without deformation or breakage. Therefore, the sealing member comprised from the resin composition of the present invention can maintain excellent sealing characteristics over a long period of time even under severe use conditions.
The aramid of the aramid fiber used in the present invention is not particularly limited, and poly (para-phenylene terephthalamide), poly (para-benzamide), poly (para-amide hydrazide), poly (para-phenylene terephthalamide-3,4 -Diphenyl ether terephthalamide), poly (4,4'-benzanilide terephthalamide), poly (para-phenylene-4,4'-biphenylenedicarboxylic acid amide), poly (para-phenylene-2,6-naphthalenedicarboxylic acid amide) ), Poly (2-chloro-para-phenylene terephthalamide), and co-poly (para-phenylene-3,4'-oxydiphenylene terephthalamide). Examples of commercially available aramid fibers include “Kevlar” manufactured by Toray DuPont Co., Ltd.
By dispersing the aramid fiber in a resin composition containing a rubber component and a thermoplastic resin described later, the hardness of the resin composition can be improved while maintaining an excellent elastic recovery rate. Here, the content of the aramid fiber with respect to the entire resin composition is preferably 3.0 to 10.0% by mass, and more preferably 3.0 to 7.0% by mass. By containing an aramid fiber in the above range, a resin composition having higher hardness and elastic recovery rate can be obtained. If the content of the aramid fiber is less than 3.0% by mass, sufficient hardness may not be obtained. On the other hand, if it exceeds 10.0% by mass, the elastic recovery rate may be lowered.
Moreover, in this invention, 0.5 mm-5.0 mm are preferable and, as for the fiber length of the aramid fiber contained in a resin composition, 1.0 mm-3.0 mm are more preferable. By setting the fiber length of the aramid fiber in the above range, the addition of fewer aramid fibers can sufficiently improve the hardness and tensile strength of the resin composition, so that an excellent elastic recovery rate can be realized. .
In the present invention, a rubber component, a thermoplastic resin, and an aramid resin, which will be described later, are preferably highly dispersed. By improving the dispersibility of each component of the resin composition, the mechanical properties of the resin composition obtained are improved. Strength and creep resistance can be further improved. In such a resin composition, it is possible to effectively prevent breakage (cracking) of the resin composition caused by deformation or cracking due to hydraulic pressure during use.

The A hardness of the resin composition of the present invention is preferably 70 or more. By setting the A hardness within this range, creep deformation of the resin composition in a high temperature range can be effectively suppressed. The A hardness is preferably 75 or more, more preferably 80 or more. Moreover, it is preferable that the elastic recovery rate in the temperature range of 20 degreeC (normal temperature)-150 degreeC of the resin composition of this invention is 70% or more. The elastic recovery rate is obtained by a load-unloading test. As this value increases, the rubber elasticity is maintained and excellent sealing characteristics are exhibited. The elastic recovery rate in the temperature range is more preferably 75% or more. By setting the A hardness and elastic recovery rate within the above ranges, excellent creep resistance and elasticity can be maintained even at high temperatures, and excellent sealing characteristics can be maintained for a long time even under severe use conditions.
Furthermore, the tensile strength at break of the resin composition of the present invention is preferably 3 MPa or more. By setting the A hardness and the tensile strength at break to the above ranges, creep deformation from both directions of compression and tension can be more effectively suppressed. The tensile strength at break is preferably 4 MPa or more, more preferably 5 MPa or more. Moreover, it is preferable that the elongation rate of the resin composition of this invention is 15% or more. By setting the elongation ratio within the above range, the resin composition can be effectively prevented from being broken (cripped) due to deformation or cracking due to hydraulic pressure during use.
The values of the A hardness and the elastic recovery rate can be controlled by the types and addition amounts of the thermoplastic resin and the aramid fiber. Since the A hardness and the elastic recovery rate are contradictory characteristics, usually, when the A hardness is improved, the elastic recovery rate tends to decrease. However, in the resin composition of the present invention, the addition of aramid fibers can greatly improve the A hardness while maintaining the excellent elastic restoration rate of the resin composition containing the rubber component and the thermoplastic resin.
By highly dispersing the rubber component, the thermoplastic resin and the aramid fiber, the injection moldability, mechanical strength, creep resistance, and rubber elasticity at high temperatures can be further improved.

The rubber component of the present invention may be added as a crosslinked rubber or a thermoplastic elastomer, or may be added as a dynamic crosslinked resin. The surface hardness of these rubber components is Shore hardness A, and is preferably 60 to 90.
Examples of the crosslinked rubber include natural rubber, synthetic isoprene rubber (IR), fluorine rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber ( IIR), halogenated butyl rubber, urethane rubber, silicone rubber, acrylic rubber and the like. Among these crosslinked rubbers, one kind can be used, but two or more kinds can also be mixed and used, and can be used in combination with a thermoplastic elastomer or a dynamically crosslinked resin described later.
Examples of the thermoplastic elastomer include polyester elastomers, polyolefin elastomers, fluorine elastomers, silicone elastomers, butadiene elastomers, polyamide elastomers, polystyrene elastomers, urethane elastomers, and the like. Among these thermoplastic elastomers, one type can be used, but two or more types can also be mixed and used. Among the thermoplastic elastomers, polyester elastomers and polyamide elastomers are preferable from the viewpoint of injection moldability and heat resistance.
Examples of commercially available polyester elastomers include "Hytrel" manufactured by Toray DuPont Co., Ltd., "Perprene" manufactured by Toyobo Co., Ltd., and "Primalloy" manufactured by Mitsubishi Chemical Corporation. , “Pebax” manufactured by ARKEMA, “UBESTAXPA” manufactured by Ube Industries, Ltd., and the like.

The dynamically crosslinked resin has a structure in which a crosslinked rubber phase is dispersed in a thermoplastic resin phase. The thermoplastic resin used for the dynamically crosslinked resin is not particularly limited, and examples thereof include polyester and polyamide (PA). On the other hand, the rubber is not particularly limited. For example, natural rubber, cis-1,4-polyisoprene, high cis polybutadiene, styrene-butadiene copolymer rubber, ethylene-propylene rubber (EPM), ethylene-propylene diene rubber (EPDM). ), Chloroprene rubber, butyl rubber, halogenated butyl rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber and the like.
The dynamically crosslinked resin can be produced by a known method. For example, a crosslinking agent is mixed with an uncrosslinked rubber component in advance, and a thermoplastic resin component and an uncrosslinked rubber component are melt-kneaded using a twin-screw extruder to simultaneously disperse and crosslink the rubber component. be able to. Such a dynamically crosslinked resin can be obtained as a commercial product. For example, as a commercially available product of a dynamically crosslinked resin in which acrylic rubber is dispersed in a polyester resin, “ETPV” manufactured by DuPont, “NOFAloy” manufactured by NOF Corporation (TZ660-7612-BK, TZ660-6602-BK, etc.) Etc. In addition, as a commercially available product of a dynamically crosslinked resin in which acrylic rubber is dispersed in a polyamide resin, “Zeotherm” manufactured by Nippon Zeon Co., Ltd. can be cited.
The content of the rubber component is preferably 60% by mass to 95% by mass and more preferably 80% by mass to 95% by mass with respect to the mass of the entire resin composition constituting the sealing member. By defining the content of the rubber component within the above range, the compression set of the resin composition becomes smaller, and better sealing characteristics can be obtained over a long period of time.

The surface hardness of the thermoplastic resin mixed with the rubber component is a Shore hardness D of preferably 70 or more, and more preferably 90 or more. Examples of the thermoplastic resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyester such as polyethylene naphthalate (PEN), polypropylene (PP), syndiotactic polystyrene resin, polyoxy Methylene (POM), polyamide (PA), polycarbonate (PC), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone (PSU) , Polyethersulfone, polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryle Preparative (PAR), polyether nitrile (PEN), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and the like. These resins may be a copolymer or a modified product, or may be a mixture of two or more. In consideration of injection moldability, heat resistance, etc., among the thermoplastic resins, PBT, PA, PPS, and PVDF are preferable.
The addition amount of the thermoplastic resin is preferably 5% by mass to 40% by mass, and more preferably 5% by mass to 20% by mass with respect to the mass of the entire resin composition constituting the seal member. By adding a thermoplastic resin within this range, the mechanical strength and creep resistance of the sealing member are improved, and excellent sealing properties can be maintained even after long-term use under pressure, with a higher PV value. It can also be used in the area.

As described above, the aramid fiber is added to the resin composition of the present invention, but depending on the intended use and required characteristics, other fillings may be used as long as the characteristics of the resin composition of the present invention are not impaired. Materials can also be added. Examples of other fillers include fibrous inorganic fillers and fibrous organic fillers. Specific examples of the fibrous inorganic filler include glass fiber, carbon fiber, carbon nanotube, alumina fiber, potassium titanate fiber, boron fiber, and silicon carbide fiber. On the other hand, examples of fibrous organic fillers other than aramid fibers include vinylon fibers and polypropylene fibers.
By using aramid fibers in combination with other fibrous fillers, the mechanical strength and creep resistance characteristics of the seal member are further improved, and there is a possibility that it can be used even in regions with higher PV values. Of the organic and inorganic fillers, carbon nanotubes are preferred. Carbon nanotubes not only exhibit a reinforcing function as a fibrous inorganic filler, but are also effective as fillers for improving sliding properties, as will be described later.

Further, other fillers can be added for the purpose of improving the sliding characteristics and the like. Other fillers include calcium carbonate, montmorillonite, bentonite, talc, silica, mica, mica, barium sulfate, calcium sulfate, calcium silicate, molybdenum disulfide, glass beads, graphite, fullerene, carbon (amorphous) powder, anthracite powder , Aluminum oxide, titanium oxide, magnesium oxide, potassium titanate, boron nitride, PTFE powder and the like.
The addition amount of the filler other than the aramid fiber is preferably 3% by mass to 20% by mass with respect to the mass of the entire resin composition constituting the sealing member. Moreover, when adding a carbon nanotube as a filler, it is preferable that the addition amount shall be 1 mass%-10 mass% with respect to the mass of the whole resin composition which comprises a sealing member. By adding a filler in this range, excellent mechanical strength and sliding characteristics can be obtained, and better sealing characteristics can be maintained over a long period of time.

  Although the mixing method of the resin composition in this invention is not specifically limited, It can mix using a lab plast mill, a twin screw extruder, etc. As described above, in order to improve the injection moldability, mechanical strength, creep resistance and rubber elasticity of the resin composition, it is effective to uniformly and highly disperse the rubber component, the thermoplastic resin and the aramid resin. In order to reliably achieve uniform and high dispersion, it is preferable to mix under high shear conditions using a twin screw extruder in which a kneading disk that generates shearing action is combined with a screw shaft. A commercially available high shear molding machine can also be used. The dispersibility can be controlled by the shape and length of the screw, the diameter of the feedback hole, the screw rotation speed, the shear mixing time, and the like.

The use of the resin composition of the present invention is not particularly limited, and it is used as a gasket, a tube, a packing, a hose, a seal member and the like in various fields. In particular, it is preferably used as a seal member. Examples of the seal member include a rotary motion seal ring and a reciprocating seal ring, and the seal member is particularly preferably applied to a seal ring mounted on a CVT of an automobile.
When the resin composition of the present invention is used as a seal ring for CVT, it is preferable to employ an endless type seal ring having no joint in order to reliably prevent oil leakage in a no-load state. Since the resin material of the present invention has flexibility, it is excellent in mounting property even as an endless type, and mounting is further facilitated by using a single type. On the other hand, an abutment can be provided depending on the application. The joint shape in this case is not particularly limited, and other known joints such as a right angle (straight) joint, an oblique (angle) joint, a stepped joint, a double angle joint, a double cut joint, and a triple step joint are adopted. be able to.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
Example 1
Polyester resin / acrylic rubber-based dynamically cross-linked resin as rubber component, polyvinylidene fluoride resin as thermoplastic resin, aramid fiber with 3 mm fiber length as filler, and φ92 mm screw that combines lead and kneading disc is installed And mixed with a twin screw extruder. Here, a polyester resin / acrylic rubber-based dynamically cross-linked resin, a polyvinylidene fluoride resin, and an aramid resin were respectively supplied by side feeders and mixed under shear conditions of a temperature of 240 ° C. and a screw rotation speed of 200 rpm to obtain pellets. . The polyester resin / acrylic rubber-based dynamically crosslinked resin and the polyvinylidene fluoride resin were commercially available, and the mass ratio (polyester resin / acrylic rubber-based dynamically crosslinked resin: polyvinylidene fluoride resin) was 90:10. Moreover, the addition amount of the aramid fiber was 10% by mass with respect to the entire resin composition. The obtained pellets were injection molded to prepare various measurement samples, and the surface hardness (A hardness) and elastic recovery rate were measured by the following methods, and a bending resistance test was performed. The results are shown in Table 1. In addition, A hardness and an elastic recovery rate were represented by the relative ratio by making the value of the comparative example 1 which has not added the filler mentioned later into 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Examples 2 to 5)
A measurement sample as in Example 1, except that the fiber length of the aramid fiber was 0.5 mm (Example 2), 1 mm (Example 3), 5 mm (Example 4), and 7 mm (Example 5). Was made. The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. In addition, A hardness and an elastic recovery rate were represented by the relative ratio by making the value of the comparative example 1 which has not added the filler mentioned later into 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Examples 6 to 10)
The content of aramid fibers is 2% by mass (Example 6), 3% by mass (Example 7), 5% by mass (Example 8), 7% by mass (Example 9) and the entire resin composition. A measurement sample was prepared in the same manner as in Example 1 except that the content was 12% by mass (Example 10). The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. In addition, A hardness and an elastic recovery rate were represented by the relative ratio by making the value of the comparative example 1 which has not added the filler mentioned later into 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Comparative Example 1)
A measurement sample was prepared in the same manner as in Example 1 except that no aramid fiber was added. The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. In addition, the A hardness and the elastic recovery rate were represented by the relative ratios of the values of the examples and other comparative examples, with the value of the comparative example 1 being 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Comparative Example 2)
A measurement sample was prepared in the same manner as in Example 1 except that carbon fiber was used instead of the aramid fiber. The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. In addition, A hardness and an elastic recovery rate were represented by the relative ratio by making the value of the comparative example 1 into 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Comparative Example 3)
A measurement sample was prepared in the same manner as in Example 1 except that glass fiber was used instead of aramid fiber. The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. The A hardness and the elastic recovery rate were expressed as relative ratios with the value of Comparative Example 1 being 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Comparative Example 4)
A measurement sample was prepared in the same manner as in Example 1 except that graphite (average particle diameter: 2 μm) was used instead of the aramid fiber. The surface hardness (A hardness) and elastic recovery rate of each sample were measured, and a bending resistance test was performed. The results are shown in Table 1. In addition, A hardness and an elastic recovery rate were represented by the relative ratio by making the value of the comparative example 1 into 100. In addition, the results of the bending resistance test were represented by ◎, ○, Δ, or × on the basis shown below.

(Measurement of surface hardness)
Shore A hardness was measured based on JIS K7215.
(Measurement of elastic recovery rate)
After the resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 were injection-molded to produce a sheet having a thickness of 2.0 to 5.0 μm, a diameter φ of 2.0 mm and a height of 1.0 to 3. A sample was cut out into a 0 mm cylindrical shape. Using a thermomechanical analyzer manufactured by SII Nano Technology, Inc., the temperature was raised to 150 ° C. in the air at a temperature rising rate of 10 ° C./min by the temperature raising method. Then, while maintaining the temperature at 150 ° C., the load was increased to 0.47 MPa at a load rate of 0.32 MPa / min, held at 0.47 MPa for 5 minutes, and then unloaded at 0.031 MPa / min. Stress and strain were measured. The elastic recovery rate was calculated using the obtained value.
(Measurement of tensile strength and elongation)
Based on JIS K7162, the tensile strength at break and elongation were measured.
(Bend resistance test)
The resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 were injection molded to produce ring-shaped measurement samples without joints. The obtained sample was placed vertically on a bending tester, a load was applied in the vertical direction, the vertical height was changed from 25 mm to 7 mm, and then bending back from 7 mm to 25 mm was repeated 300 times per minute. The presence or absence of cracks in the sample after the test and the maximum length of the cracks were confirmed with a microscope. Here, ◎ indicates that no crack was observed, ◯ indicates that a microcrack having a maximum length of 5 μm or less was observed, ○ indicates that a crack having a maximum length of more than 5 μm and 40 μm or less was detected, The case where the sample was broken and the case where a large crack with a maximum length exceeding 40 μm was observed was rated as x.

In Comparative Examples 2, 3, and 4 in which 10% by mass of carbon fiber, glass fiber, and graphite were added to the entire resin composition, respectively, as compared with Comparative Example 1 in which no filler was added, It was found that the A hardness was significantly increased. Then, it was confirmed that the elastic recovery rate sharply decreased against the increase in the A hardness. In addition, after the bending test, any sample of Comparative Examples 2, 3, and 4 was broken or a large crack was observed.
On the other hand, in Example 1 in which an aramid fiber having a fiber length of 3 mm was added in an amount of 10% by mass with respect to the entire resin composition, the A hardness increased by 21% while maintaining the elastic recovery rate close to that of Comparative Example 1. I understood it. In Example 1, it was confirmed that the resin composition was excellent in creep resistance, elasticity and mechanical strength with only slight cracks observed after the bending test.
From the results of Examples 1 to 5 in which the fiber length of the aramid fiber was changed in the range of 0.5 mm to 7 mm, the addition of the aramid fiber having a short fiber length can increase the A hardness while maintaining the elastic recovery rate. I understood. When the fiber length was increased, the A hardness increased, but the elastic recovery rate tended to decrease. The fiber length of the aramid fiber is preferably 0.5 mm to 5.0 mm, and more preferably 1.0 m to 3.0 mm.
From the results of Examples 1 and 6 to 10 in which the addition amount of the aramid fiber was changed in the range of 2% by mass to 12% by mass, when the addition amount of the aramid fiber was small, the A hardness was maintained while maintaining the elastic recovery rate. It turns out that it can be raised. When the aramid fiber was further increased, the A hardness increased, but the elastic recovery rate tended to decrease. The content of the aramid fiber is preferably 3.0% by mass to 10.0% by mass and more preferably 3.0% by mass to 7.0% by mass with respect to the entire resin composition.
In addition, the screw rotation speed was reduced from 200 rpm to 100 rpm, and the resin composition was similarly produced and evaluated. As a result, the effect of adding aramid fibers was recognized. However, it was confirmed that the mechanical strength, the creep resistance, and the elastic recovery rate reached the values of the above examples, and the effect of high dispersion.

Claims (9)

  A resin composition comprising a rubber component, a thermoplastic resin, and an aramid fiber.   The resin composition according to claim 1, wherein a fiber length of the aramid fiber is 0.5 mm to 5.0 mm.   Content of the said aramid fiber with respect to the said whole resin composition is 3.0 mass%-10.0 mass%, The resin composition of Claim 1 or 2 characterized by the above-mentioned.   The resin composition according to any one of claims 1 to 3, wherein the surface A hardness is 70 or more and the elastic recovery at 150 ° C is 70% or more.   The resin composition according to any one of claims 1 to 4, wherein the tensile strength at break is 3 MPa or more.   Elongation rate is 15% or more, The resin composition in any one of Claims 1-5 characterized by the above-mentioned.   The resin composition according to claim 1, wherein the rubber component is acrylic rubber.   The resin composition according to claim 1, wherein the thermoplastic resin is polyvinylidene fluoride. A sealing member using the resin composition according to claim 1.

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