JP2007292236A - Dust cover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively bond thermoplastic elastomer and a reinforcing member even when resin is used as the reinforcing member in a dust cover formed by using thermoplastic elastomer. <P>SOLUTION: The dust cover is formed by using acrylic rubber/polyamide based thermoplastic elastomer comprised of polyamide resin and crosslinked acrylic rubber. In the acrylic rubber/polyamide based thermoplastic elastomer, rubber is dispersed in polyamide resin by dynamically crosslinking acrylic rubber, and preferably, there is covalent crosslinking between the polyamide resin and the acrylic rubber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dust cover. More specifically, the present invention relates to a dust cover molded using a thermoplastic elastomer.

  A commonly used dust cover will be described with reference to FIG. The dust cover 1 is composed of a flexible material and a reinforcing member, and the flexible material has a bending function at the film portion 4, and at the fitting portion 3 that becomes a dynamic seal portion and the fitting portion 5 that becomes a static seal portion. Expresses the sealing function. The fitting part 3 includes the reinforcing member 2, and the fitting part 5 is caulked with a metal ring from the outer diameter part. In the dust cover having a reinforcing member inside as shown in this cross-sectional view, in order to improve the durability while maintaining the sealing performance, in order to firmly bond the reinforcing member and the surrounding flexible material, Need to be glued.

  Here, vulcanized rubber or thermoplastic elastomer (TPE) is used as the flexible material, and metal or high-strength resin is used as the reinforcing member, which further improves the recycling rate of recent automobile parts. Therefore, replacement of vulcanized rubber from thermoplastic elastomer as a flexible material and conversion from metal to resin as a reinforcing member are being attempted.

However, when resin is used as a reinforcing member, it is necessary to insert-mold or two-color molding of TPE, but it is very difficult to bond the resin and TPE during molding. It was an obstacle to commercialization.
Japanese Patent Publication No. 6-45743 JP-A-8-28547 Japanese Patent Laid-Open No. 10-205524

  An object of the present invention is to provide a dust cover formed using a thermoplastic elastomer, in which the thermoplastic elastomer and the reinforcing member are effectively bonded even when a resin is used as the reinforcing member. There is.

  The object of the present invention is achieved by a dust cover formed using an acrylic rubber / polyamide thermoplastic elastomer comprising a polyamide resin and a crosslinked acrylic rubber. As the acrylic rubber / polyamide thermoplastic elastomer, one obtained by dynamically crosslinking acrylic rubber to disperse the rubber in the polyamide resin, preferably one obtained by covalently crosslinking the polyamide resin and the acrylic rubber is used.

  The dust cover according to the present invention has an excellent effect that the thermoplastic elastomer and the reinforcing member are effectively bonded to each other even when resin is used as the reinforcing member, so that the molding can be easily performed. . Such a dust cover has good low and high temperature durability, grease resistance, oil resistance, molding processability, bending resistance, crack growth resistance, compression set resistance characteristics, weather resistance, due to the material properties of the thermoplastic elastomer. Satisfactory in terms of ozone resistance.

  The polyamide-based thermoplastic elastomer (acrylic rubber / polyamide-based thermoplastic elastomer) in which the cross-linked acrylic rubber used in the present invention is dispersed is preferably a rubber in a polyamide resin by dynamically cross-linking the acrylic rubber with a cross-linking agent. Are dispersed, and more preferably, a polyamide resin and an acrylic rubber are covalently crosslinked.

  The polyamide resin is used in a proportion of 20 to 60% by weight, preferably 20 to 55% by weight, based on the total amount of the polyamide resin and the crosslinked acrylic rubber. If the polyamide resin is used in a higher ratio, the hardness becomes higher and the elastomeric property is lost. On the other hand, if the polyamide resin is used in a lower ratio, the thermoplasticity is lost.

  As the polyamide resin, nylon resin, for example, nylon 3, nylon 4, nylon 6, nylon 7, nylon 8, nylon 4 2, nylon 4 6, nylon 6 6, nylon 6 9, nylon 6 10, nylon 11, nylon 12, A resin having a softening point or melting point of 160 ° C. to 280 ° C., such as nylon 666 (caprolactam-hexamethylene adipamide copolymer), a mixture, or a copolymer can be used.

  As the acrylic rubber to be covalently crosslinked, as described in Patent Documents 2 to 3, the covalent crosslinking with the polyamide resin is about 100 to 350 ° C., preferably about 150 to 300 ° C., more preferably about An α-olefin-alkyl (meth) acrylate copolymer rubber having excellent heat resistance is preferably used because it is performed by dynamic crosslinking under heating conditions of 180 to 280 ° C. Also, with emphasis on oil resistance, homopolymers or copolymers of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, copolymers of these with α-olefins, and polymer blends of these various polymers A thing etc. are also used suitably.

As the α-olefin, C ₂ -C ₁₂ α-olefin such as ethylene, propylene, butene-1, isobutylene, pentene, heptene, octene, decene, dodecene, etc. are used, preferably C ₂ -C ₄ α-olefin. Olefin is used. The alkyl (meth) acrylate, methyl acrylate, ethyl acrylate, n- butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, C ₁ -C ₁₂ alkyl groups such as dodecyl acrylate, preferably acrylates having an alkyl group of C ₁ -C _4, methyl methacrylate, ethyl methacrylate, n- butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, C ₁ -C _12, such as dodecyl methacrylate alkyl groups, preferably methacrylate having an alkyl group of C ₁ -C ₄ is used. As the alkoxyalkyl (meth) acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, methoxybutyl acrylate, ethoxyethyl acrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, methoxy butyl methacrylate, an alkoxyl group having C ₁ -C ₂ such as ethoxy butyl methacrylate and alkoxyalkyl (meth) acrylate having an alkyl group of C ₂ -C ₄ is used.

  In these copolymers, a crosslinkable group-containing (meth) acrylate having a carboxyl group, a hydroxyl group, a chlorine group, an epoxy group, a diene group, an isocyanate group, an amine group, an amide group, an oxazoline group or the like is further copolymerized. Preferably, as such a crosslinkable group-containing (meth) acrylate, those generally used for acrylic rubbers mainly composed of alkyl (meth) acrylate (and alkoxyalkyl (meth) acrylate) are used as they are. .

In the case of an α-olefin-alkyl (meth) acrylate copolymer rubber obtained by further copolymerizing such a crosslinkable group-containing (meth) acrylate, 10 to 69.9 mol% of α-olefin and alkyl (meth) acrylate Having a composition obtained by copolymerizing 29.6 to 89.5 mol% of a copolymer and 0.5 to 10 mol% of a crosslinkable group-containing (meth) acrylate, such a copolymer is essentially non-crystalline and has a glass transition temperature. Tg is below room temperature. An example of such an acrylic rubber copolymer is also described in Non-Patent Document 1 below. Regarding the alkoxyalkyl (meth) acrylate copolymer, the crosslinkable group-containing (meth) acrylate is 0.5 to 10 mol%, and the rest is an arbitrary copolymer composition of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate. What has is used. Furthermore, an ethylene-maleic acid monoalkyl ester copolymer or the like can also be used.
Rubber World Blue Book 393-4 (1987)

  The covalent crosslinking between the polyamide resin and the acrylic rubber copolymer is performed in the presence of a crosslinking agent according to the type of the crosslinkable group in the acrylic rubber copolymer, such as a polyol, a polyamine, a polyisocyanate, and an epoxy group-containing compound. Further, it is carried out by a dynamic crosslinking method in which the polyamide resin and the acrylic rubber copolymer are melt-mixed at the above temperature, generally by a method of adding a crosslinking agent while masticating with a biaxial kneader. As a crosslinking method other than such dynamic vulcanization, for example, without adding polyamide resin, acrylic rubber is sufficiently vulcanized by either dynamic or static method and then pulverized, and then the melting point of polyamide resin or Examples thereof include a method of mixing with a polyamide resin at a temperature equal to or higher than the softening point.

  The acrylic rubber / polyamide thermoplastic elastomer thus obtained is obtained by, for example, immersing its press film (thickness: about 0.2 mm) in an organic solvent such as dichloromethane, toluene, tetrahydrofuran and the like for 48 hours. % Or more, preferably 30% or more has a crosslinking density such that it is not extracted. Further, in this acrylic rubber / polyamide thermoplastic elastomer, a commonly used plasticizer or filler such as phthalate ester, phosphate ester, carbon black, silica or the like can be added and used.

  Such an acrylic rubber / polyamide thermoplastic elastomer can be produced by the method described above. In addition, a commercially available product such as the Zeotherm series manufactured by ZEON CHEMICALS can be used as it is for the same type in which only an acrylic rubber and polyamide are not covalently crosslinked.

  Various additives such as an antioxidant, a stabilizer, a tackifier, a release agent, a pigment, a flame retardant and the like can be added to the composition of the present invention. Furthermore, in order to improve strength and rigidity, a particulate reinforcing component, short fibers, and the like can be added.

  The acrylic rubber / polyamide thermoplastic elastomer composition is prepared by mixing using a known mixing method, for example, a twin screw extruder, blender, Henschel mixer, single screw extruder, roll, Banbury mixer, kneader or the like. Is called.

  On the other hand, the resin used for the reinforcing member is preferably a polyamide resin, specifically, various nylon resins similar to those exemplified for the thermoplastic elastomer.

  The polyamide reinforcing member and the acrylic rubber / polyamide thermoplastic elastomer are molded into the dust cover by insert molding. Insert molding can be performed in the same way as normal resin-to-resin insert molding. After a polyamide ring for reinforcing members is molded by a method such as injection molding, it is placed in a mold for dust cover molding, and acrylic rubber / A polyamide-based thermoplastic elastomer is molded in the same mold by a method such as injection molding. In any case, the injection molding is appropriately performed in a state where the material is plasticized by heating at 230 to 280 ° C. for about 1 to 10 minutes. At this time, two-color molding is also possible by continuously molding the polyamide ring and the acrylic rubber / polyamide thermoplastic elastomer.

  Next, the present invention will be described with reference to examples.

Example 1
Material pellets of nylon 6 (Ube Industries Ube Nylon 1013B) are dried at 100 ° C for 5 hours and then plasticized by heating at 260 ° C for about 3 minutes using an injection molding machine, and dust with a cross section of 3 x 3 mm and an inner diameter of 25 mm A reinforcing ring as a reinforcing member included in the cover was produced.

  Next, acrylic rubber / polyamide thermoplastic elastomer (Zeotherm 100-90B pellets) was dried at 100 ° C for 5 hours and then plasticized by heating at 260 ° C for 3 minutes using an injection molding machine. After setting in a molding die, injection molding was performed to prepare a dust cover (height 35 mm) including the reinforcing member shown in FIG.

Using the obtained dust cover molded product, functional evaluation was performed for adhesiveness, high-temperature durability and grease resistance.
Adhesiveness: After cutting the dust cover molded product and visually checking for the presence of TPE remaining on the polyamide ring surface when the TPE is peeled off from the polyamide ring using pliers, Adheres when TPE breaks and TPE remains on the entire surface of the polyamide ring, evaluates as partially bonded when the bonded part and the peeled part coexist, and evaluates as non-adhered when all peeled without any TPE remaining Durability: A ball joint with a predetermined amount of grease sealed in the dust cover is set in a rocking durability tester, and grease leaks from the fitting part 3 (small diameter part) that becomes a dynamic seal part in an environment of 120 ° C. Evaluate the time until occurrence Grease resistance: Measure the rate of change of the diameter of the membrane after the high temperature durability test Note that TPE with low grease resistance swells and increases the diameter of the membrane.

Examples 2-3
In Example 1, as an acrylic rubber / polyamide thermoplastic elastomer, an extrusion-grade 6-nylon and a cold-resistant acrylic rubber mainly composed of n-butyl acrylate and 2-methoxyethyl acrylate are covalently crosslinked. In this way, a product produced by a method of dynamic crosslinking with a twin-screw extruder was used. In Examples 2 and 3, the blending ratio of 6-nylon and acrylic rubber (weight ratio 35-45: 65-55) is different, and Example 3 is used with a higher rubber ratio of acrylic rubber. Yes.

Comparative Example 1
In Example 1, a polyester-based thermoplastic elastomer (DMS product Arniter PB582-H) was used in place of the acrylic rubber / polyamide-based thermoplastic elastomer.

Comparative Example 2
In Example 1, a polyester-based thermoplastic elastomer (Toray DuPont product Hytrel 4767B) was used instead of the acrylic rubber / polyamide-based thermoplastic elastomer.

Comparative Example 3
In Example 1, instead of the acrylic rubber / polyamide thermoplastic elastomer, a polyamide thermoplastic elastomer (EMS Showa Denko Grilon ELX50HNZ) was used.

The results obtained in the above examples and comparative examples are shown in the following table.
table
Example Comparative Example
Functional evaluation 1 2 3 1 2 3
Adhesive Adhesive Adhesive Adhesive Non-adhesive Non-adhesive Partially adhesive High temperature durability (hours) 550 800 950 150 200 300
Grease resistance (△%) +0 +0 +0 +5 +5 +6

  The dust cover of the present invention is attached to a ball joint in an automobile or general industrial machine.

It is sectional drawing which shows an example of the dust cover which includes a reinforcement member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dust cover 2 Reinforcement member 3 Fitting part (dynamic seal part)
4 Membrane part 5 Fitting part (Static seal part)

Claims (5)

  A dust cover molded from an acrylic rubber / polyamide thermoplastic elastomer consisting of polyamide resin and cross-linked acrylic rubber.   2. The dust cover according to claim 1, wherein the acrylic rubber / polyamide thermoplastic elastomer is obtained by dispersing rubber in a polyamide resin by dynamically crosslinking the acrylic rubber.   2. The dust cover according to claim 1, wherein the acrylic rubber / polyamide thermoplastic elastomer is obtained by covalently crosslinking polyamide resin and acrylic rubber.   The dust cover according to claim 2 or 3, wherein the acrylic rubber is an α-olefin-alkyl (meth) acrylate-crosslinkable group-containing (meth) acrylate copolymer rubber. The dust cover according to any one of claims 1 to 4, wherein a polyamide ring as a reinforcing member and an acrylic rubber / polyamide thermoplastic elastomer are bonded without using an adhesive.

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