JPWO1999048970A1 - Polyamide fiber reinforced elastic composition and method for producing the same - Google Patents

Abstract

(57) [Abstract] A polyamide fiber-reinforced elastomer composition exhibiting excellent processability and durability, as well as excellent modulus of elasticity, strength, and friction performance, comprises (a) 100 parts by weight of one or more rubbery polymers having a glass transition temperature of __°C or less, (b) 1 to 40 parts by weight of a polyolefin, (c) 1 to 70 parts by weight of thermoplastic polyamide fibers containing layered silicate, and (d) a silane coupling agent, and is suitable for vulcanization treatment.

Description

[Detailed Description of the Invention] Polyamide Fiber-Reinforced Elastomer Composition and Its Manufacturing Method Technical Field The present invention relates to a polyamide fiber-reinforced elastomer composition that is easy to work with and has excellent modulus, strength, and friction performance. It also relates to a vulcanizate thereof, a manufacturing method for the elastomer composition, and a manufacturing method for a vulcanizate of the elastomer composition. The elastomer composition and its vulcanizate of the present invention are preferably used in tire external components such as treads and sidewalls, tire internal components such as carcasses, beads, belts, and chafers, industrial products such as hoses, belts, rubber rolls, and rubber tracks, and footwear.

BACKGROUND ART Compositions with improved modulus and strength, i.e., fiber-reinforced elastomer compositions, have been produced by blending short fibers such as nylon, polyester, or vinylon into elastomer resin materials and vulcanizing them as needed, by dispersing short fibers in vulcanizable rubbery polymers such as natural rubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber.

The fiber-reinforced elastomer compositions obtained by the above-described conventional methods have insufficient strength and elongation for use in automobile tire components and the like. Therefore, a fiber-reinforced elastomer composition that overcomes these drawbacks has been sought. To meet this demand, fiber-reinforced elastomer compositions containing fine fibers, such as nylon, with an average diameter of submicrons have been proposed. Another known method involves melt-kneading a vulcanizable rubber, nylon, and a binder at a temperature above the melting point of nylon, extruding the resulting mixture into a string-like shape at a temperature above the melting point of nylon, and stretching or rolling the resulting string-like material. This fiber-reinforced elastomer composition is then blended with a vulcanizable rubber and a vulcanizing agent, and the resulting blend is then vulcanized. Among such conventional methods, a manufacturing method using a precondensate of a resol-type alkylphenol-formaldehyde resin as a binder is disclosed in Japanese Patent Publication No. 1-17494, a manufacturing method using a novolak-type alkylphenol-formaldehyde resin as a binder is disclosed in Japanese Patent Publication No. 5-71624, and a manufacturing method using a silane coupling agent as a binder is disclosed in Japanese Patent Publication Nos. 4-33300, 5-88860, and Japanese Patent Laid-Open Publication No. 7-278360.

However, although the above-mentioned conventional fiber-reinforced elastomer compositions are excellent in modulus and strength, as well as in processability and durability, they cannot be said to have excellent friction performance. Therefore, the use of the above-mentioned conventional fiber-reinforced elastomer resin compositions for applications such as tires and rolls has inevitably been limited to some extent.

DISCLOSURE OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a polyamide fiber-reinforced elastomer composition having excellent modulus, strength, and friction performance, a vulcanized product thereof, a method for producing a polyamide fiber-reinforced elastomer composition, and a method for producing a sulfide thereof.

The above object is achieved by the present invention.

The polyamide fiber-reinforced elastomer composition of the present invention contains the following components mixed together: (a) 100 parts by weight of at least one rubbery polymer having a glass transition temperature of 0°C or less, (b) 1 to 40 parts by weight of a polyolefin resin, (c) 1 to 70 parts by weight of a fibrous thermoplastic polyamide containing a dispersed layered silicate, and (d) a silane coupling agent.

The polyamide fiber-reinforced elastomer composition of the present invention can be vulcanized to form a vulcanizate.

The method for producing a polyamide fiber-reinforced elastomer composition of the present invention includes: (1) melt-kneading (a) 100 parts by weight of at least one rubbery polymer having a glass transition temperature of 0°C or lower, (b) 1 to 40 parts by weight of a polyolefin resin, and (d) a silane coupling agent to form a molten matrix; (2) melt-kneading (c) 1 to 70 parts by weight of a thermoplastic polyamide containing a layered silicate into the molten matrix; (3) extruding the kneaded composition containing components (a) to (d) at a temperature equal to or higher than the melting point of component (c) (thermoplastic polyamide); and (4) stretching or rolling the extrudate at a temperature lower than the melting point of component (c), thereby dispersing the layered silicate-containing thermoplastic polyamide into a fibrous form.

Alternatively, in the above method, a portion of 100 parts by weight of component (a), i.e., the rubbery polymer, may be used in step (1), with the remainder being added to the composition obtained in step (4).

A vulcanization step can be added to the above-described method for producing a polyamide fiber-reinforced elastomer.

In the polyamide fiber-reinforced elastomer composition and its manufacturing method of the present invention, it is preferred that 0.1 to 5.5 parts by weight of a silane coupling agent as component (d) be blended per 100 parts by weight of the total of components (a), (b), and (c).

Furthermore, in the polyamide fiber-reinforced elastic composition and its manufacturing method of the present invention, the layered silicate is preferably blended in a ratio of 0.05 to 30 parts by weight per 100 parts by weight of the thermoplastic polyamide.

BEST MODE FOR CARRYING OUT THE INVENTION The polyamide fiber-reinforced elastomer composition of the present invention, its vulcanizate, and their manufacturing methods are specifically described below.

In the polyamide fiber-reinforced elastomer composition of the present invention, component (a) includes at least one rubbery polymer having a glass transition temperature of 0°C or lower, preferably -20°C or lower. This rubbery polymer is an elastic solid at room temperature in its natural state. Specific examples of rubbery polymers for component (a) include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), chlorinated butyl rubber, brominated butyl rubber, chloroprene rubber (CR), diene rubbers such as acrylonitrile-chloroprene copolymer rubber, acrylonitrile-isoprene copolymer rubber, acrylate-butadiene copolymer rubber, vinylpyridine-butadiene copolymer rubber, and vinylpyridine-styrene-butadiene copolymer rubber; ethylene-propylene copolymer rubber (EPR), ethylene-propylene-diene copolymer rubber (EPDM), and ethylene-butene copolymer rubber. Examples of suitable rubbers include polyolefin rubbers such as ethylene copolymer rubber, ethylene-butene-diene copolymer rubber, chlorinated polyethylene rubber, and chlorosulfonated polyethylene rubber (CSM); rubbers with a polymethylene main chain such as acrylic rubber, ethylene acrylic rubber, polychlorinated trifluorinated rubber, and fluorinated rubber; rubbers containing oxygen atoms in the main chain such as epichlorohydrin rubber and ethylene oxide-epichlorohydrin copolymer rubber; silicone rubbers such as polyphenylmethylsiloxane rubber and polymethylethylsiloxane rubber; and rubbers containing carbon atoms and oxygen atoms in addition to carbon atoms in the main chain such as nitroso rubber, polyesterurethane rubber, and polyetherurethane rubber. These rubbers may also be epoxy-modified, silane-modified, or maleated for use in component (a).

Another specific example of the rubbery polymer constituting component (a) is a thermoplastic elastomer. Examples include styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, polyolefin-based thermoplastic elastomer, chlorinated polyolefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, 1,2-polybutadiene-based thermoplastic elastomer, trans-1,4-polyisoprene-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, and polyvinyl chloride-based thermoplastic elastomer.

The polyolefin resin used as component (b) preferably has a melting point in the range of 80 to 250°C, and may also have a Vicat softening point of 50°C or higher, particularly preferably 50 to 200°C. Suitable examples of polyolefin resins for component (b) include homopolymers and copolymers of C2 to C8 olefins, such as copolymers of C2 to C8 olefins and vinyl acetate, copolymers of C2 to C8 olefins and acrylic acid or esters thereof, copolymers of C2 to C8 olefins and methacrylic acid or esters thereof, and copolymers of C2 to C8 olefins and vinylsilane compounds.

Specific examples of polyolefin resins used as component (b) include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-propylene block copolymers, ethylene-propylene random copolymers, poly(4-methylpentene-1), polybutene-1, polyhexene-1, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-acrylic acid copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-propyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene-2-ethylhexyl acrylate copolymers, ethylene-hydroxyethyl acrylate copolymers, ethylene-vinyltrimethoxysilane copolymers, ethylene-vinyltriethoxysilane copolymers, and ethylene-vinylsilane copolymers. Specific examples of polyolefin resins used as component (b) include halogenated polyolefins such as chlorinated polyethylene, brominated polyethylene, and chlorosulfonated polyethylene.

Among the above polyolefin resins, particularly preferred are high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), ethylene-propylene block copolymer, ethylene-propylene random copolymer, poly-4-methylpentene-1 (P4MP1), ethylene-vinyl acetate copolymer (EVA), and ethylene-vinyl alcohol copolymer. Among these, those with a melt flow index (MFI) in the range of 0.2 to 50 g/10 min are most preferred. Component (b) may consist of a single polyolefin resin, or two or more polyolefin resins may be used in combination.

The layered silicate-containing thermoplastic polyamide, which constitutes component (c), contains layered silicate uniformly dispersed therein, and the thermoplastic polyamide is formed into a tough fiber by extrusion and stretching or rolling. This thermoplastic polyamide preferably has a melting point in the range of 135 to 350°C, particularly in the range of 160 to 265°C, which is higher than the melting point of the polyolefin resin used as component (b).

Specific examples of thermoplastic polyamides for component (c) include nylon 6, nylon 66, nylon 6-nylon 66 copolymer, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, nylon MXD6, polycondensation polymers of xylylenediamine and adipic acid, polycondensation polymers of xylylenediamine and pimelic acid, polycondensation polymers of xylylenediamine and suberic acid, polycondensation polymers of xylylenediamine and azelaic acid, polycondensation polymers of xylylenediamine and sebacic acid, polycondensation polymers of tetramethylenediamine and terephthalic acid, polycondensation polymers of hexamethylenediamine and terephthalic acid, polycondensation polymers of octamethylenediamine and terephthalic acid, and tetramethylethylenediamine and terephthalic acid. Examples of the polycondensation polymers include polycondensates of trimethylhexamethylenediamine and terephthalic acid, polycondensates of decamethylenediamine and terephthalic acid, polycondensates of undecamethylenediamine and terephthalic acid, polycondensates of dodecamethylenediamine and terephthalic acid, polycondensates of tetramethylenediamine and isophthalic acid, polycondensates of hexamethylenediamine and isophthalic acid, polycondensates of octamethylenediamine and isophthalic acid, polycondensates of trimethylhexamethylenediamine and isophthalic acid, polycondensates of decamethylenediamine and isophthalic acid, polycondensates of undecamethylenediamine and isophthalic acid, and polycondensates of dodecamethylenediamine and isophthalic acid.

Among the above thermoplastic polyamides, those having a melting point at least 30°C higher than that of the polyolefin resin constituting component (b) are particularly preferred. Specifically, nylon 6 (PA6), nylon 66 (PA66), nylon 6-nylon 66 copolymer, nylon 610, nylon 612, nylon 46, nylon 11, and nylon 12 are particularly preferred. These thermoplastic polyamides may be used alone or in combination of two or more. Furthermore, these thermoplastic polyamides preferably have a molecular weight in the range of 10,000 to 200,000.

The layered silicate uniformly dispersed in component (c) is effective in imparting excellent mechanical and frictional properties to the polyamide resin composition. This layered silicate typically has a thickness of 0.6 to 2 nm and a length of 0.002 to 1 μm. Component (c) of the present invention is characterized by the layered silicate being uniformly dispersed in the thermoplastic polyamide, each layer maintaining an average interlayer distance of 2 nm or more. Here, "interlayer distance" refers to the distance between the centers of gravity of the silicate layers, and "uniformly dispersed" refers to a state in which 50% or more, preferably 70% or more, of the layered silicate are dispersed parallel to each other and/or randomly, with a mixture of parallel and random layers, without forming agglomerates. Therefore, layered silicate is composed of fine layers with lengths of 1 to 1,000 nm and thicknesses of 0.6 to 2 nm. Examples of such layered silicates include layered phyllosilicate minerals composed of layered particles of magnesium silicate or aluminum silicate. Specific examples of layered silicates include smectite clay minerals such as montmorillonite, saponite, nontronite, hectorite, and stevensite, as well as vermiculite and halacite. These layered silicates may be natural or synthetic. Of these, montmorillonite is preferred. There are no particular limitations on the method for uniformly dispersing such layered silicates in polyamide resins. However, when the source of the layered silicate of the present invention is a multilayered clay mineral, it may be contacted with a swelling agent to expand the interlayer spaces and facilitate the incorporation of monomers between the layers, followed by mixing with a polyamide-forming monomer and polymerizing the monomer (see Japanese Patent Publication No. 8-22946). Alternatively, a polymeric compound may be used as a swelling agent to increase the interlayer spacing to 10 nm or more, and then the resulting mixture may be melt-kneaded with the polyamide resin or a resin containing the same to achieve uniform dispersion. The blending ratio of the layered silicate is preferably 0.05 to 30 parts by weight, more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the polyamide component. A blending ratio of less than 0.05 parts by weight of the layered silicate results in a small improvement in the rigidity and heat resistance of the resulting molded article, while a blending ratio of more than 30 parts by weight results in a significant decrease in the fluidity of the resin composition, which is undesirable.

Swelling agents include amino acids and nylon salts, specific examples of which include ω-aminoundecanoic acid, ω-aminododecanoic acid, and the like, as well as equimolar salts of diamines and dicarboxylic acids, such as nylon salts of tetramethylenediammonium adipate, hexamethylenediammonium adipate, and hexamethylenediammonium sebacate.

The silane coupling agent used as component (d) is a bonding agent that bonds components (a), (b), and (c) to one another. Specific examples of this silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltriacetylsilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylethyldimethoxysilane, γ-glycidoxypropylethyldiethoxysilane, N-β-(amino Examples of suitable silanes include N-(ethyl)aminopropyltrimethoxysilane, N-β-(aminoethyl)aminopropyltriethoxysilane, N-β-(aminoethyl)aminopropylmethyldimethoxysilane, N-β-(aminoethyl)aminopropylethyldimethoxysilane, N-β-(aminoethyl)aminopropylethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-[N-(β-methacryloxyethyl)-N,N-dimethylammonium(chloride)]propylmethoxysilane, and styryldiaminosilane. Among these, those having a group that easily removes a hydrogen atom from an alkoxy group and/or a polar group and a vinyl group are particularly preferred.

The amount of silane coupling agent is preferably 0.1 to 5.5 parts by weight, and particularly preferably 0.2 to 3.0 parts by weight, per 100 parts by weight of the total of components (a), (b), and (c). If the amount of silane coupling agent is less than 0.1 part by weight, the mutual bonding of components (a), (b), and (c) may be insufficient, and a high-strength composition may not be obtained. If the amount of silane coupling agent is more than 5.5 parts by weight, it may be difficult for the polyamide in component (c) to form a fine fibrous structure, making it difficult to obtain a composition with excellent modulus (elastic modulus).

An organic peroxide can be used in combination with the silane coupling agent used as component (d). The use of an organic peroxide forms radicals on the molecular chains of the resins (a), (b), and (c). These radicals react with the silane coupling agent to promote the bonding between the resins (a), (b), and (c), thereby bonding the resins (a), (b), and (c) together at their interfaces. The preferred organic peroxide has a one-minute half-life temperature ranging from the melting point of component (a) or component (c), whichever is higher, to approximately 30°C above that temperature.

Specifically, an organic peroxide having a one-minute half-life temperature of about 110 to 250° C. is preferably used. The amount of organic peroxide used is preferably in the range of 0.01 to 1.0 part by weight per 100 parts by weight of component (b).

Specific examples of organic peroxides that can be used in the present invention include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, 2,2-di-t-butylperoxybutane, 4,4-di-t-butylperoxyvaleric acid n-butyl ester, 2,2-bis(4,4-di-t-butylperoxycyclohexane)propane, peroxyneodecanoic acid, 2,2,4-trimethylpentyl, α-cumyl peroxyneodecanoate, t-butyl peroxyneohexanoate, t-butyl peroxypivalate, t-butyl peroxyacetate, t-butyl peroxylaurate, t-butyl peroxybenzoate, and t-butyl peroxyisophthalate.

Among these, those having a one-minute half-life temperature in the range of the melt-kneading temperature or a temperature about 30°C higher than that temperature, specifically those having a one-minute half-life temperature of about 80 to 250°C, are preferably used.

In the polyamide fiber-reinforced elastomer composition of the present invention, the blending ratios of components (a), (b), and (c) are as follows: 1 to 40 parts by weight, preferably 2 to 30 parts by weight, of the polyolefin resin (b) per 100 parts by weight of component (a). A content of component (b) less than 1 part by weight is undesirable because it makes it difficult to mold the resulting fiber-reinforced elastomer composition, for example, into pellets, and the physical properties in the direction perpendicular to the polyamide fiber orientation are degraded. A content of component (b) greater than 40 parts by weight is undesirable because it results in a composition with low rubber elasticity. Component (c) is included in a ratio of 1 to 70 parts by weight, preferably 1 to 60 parts by weight, per 100 parts by weight of component (a). A content of component (c) less than 1 part by weight results in insufficient modulus and braking performance of the resulting composition. Furthermore, if the content of component (c) exceeds 70 parts by weight, the resulting fiber-reinforced elastic body will have insufficient elongation. Most of component (c) is uniformly dispersed as fine fibers in a matrix consisting of components (a), (b), and (d). Specifically, preferably 70% by weight, more preferably 80% by weight, and even more preferably 90% by weight of component (c) is dispersed as fine fibers in the matrix.

The average fiber diameter of the dispersed fibers is preferably 1 μm or less, and their aspect ratio (ratio of fiber length to average fiber diameter) is preferably 20 or more and 1,000 or less. This ensures good dispersion of the c component fibers. Furthermore, components (a), (b), and (c) are mutually bonded at their respective interfaces.

The method for producing the polyamide fiber-reinforced elastomer composition of the present invention is described below. The method of the present invention comprises the following steps (1) to (4) and, optionally, step (5):

(1) melt-blending (partially or entirely) at least one rubbery polymer (a) having a glass transition temperature of 0°C or lower and a polyolefin (b) with a silane coupling agent (d) to prepare a molten matrix containing the components (a) and (b); (2) blending the molten matrix with a thermoplastic polyamide (c) having a layered silicate dispersed therein at a temperature equal to or higher than the melting point of the thermoplastic polyamide to produce a chemically modified melt-blended composition; (3) extruding the chemically modified melt-blended composition through a die at a temperature equal to or higher than the melting point of the thermoplastic polyamide (c) (preferably at least 10°C higher than the melting point); (4) stretching or rolling the extrudate while applying a draft at a temperature lower than the melting point of the thermoplastic polyamide (c), where the stretching or rolling temperature may be equal to or lower than the melting point of the thermoplastic polyamide (b).

(5) When only a portion of component (a) is used in step (1), the remainder of component (a) is kneaded with the composition obtained in step (4) to obtain a polyamide fiber-reinforced elastomer composition. When all of component (a) is used in step (1), step (5) is unnecessary.

Each step in the method for producing the polyamide fiber-reinforced resin composition of the present invention will now be described in more detail.

Step (1): A matrix of components (a) and (b) is prepared by melt-kneading all or a portion of component (a), a rubbery polymer having a glass transition temperature of 0°C or less, and component (b), a polyolefin, with component (d), a silane coupling agent. In this step (1), the melt-kneading temperature is equal to or higher than the melting point of component (b), preferably at least 10°C higher than this melting point. When this kneading is performed at a temperature at least 10°C higher than the melting point of component (b), components (a) and (b) react with the silane coupling agent of component (d) to form a reactive matrix. The melt-kneading operation can be performed using equipment commonly used in the kneading of resins and rubbers. Examples of such equipment include a Banbury mixer, kneader, kneader-extruder, open roll mill, single-screw kneader, and twin-screw kneader. These equipment can also be used in steps subsequent to step (1).

Step (2): The reaction matrix is mixed with a thermoplastic polyamide composite having the layered silicate (c) dispersed therein at a temperature equal to or higher than the melting point of the thermoplastic polyamide to produce a chemically modified mixed composition. The temperature at which component (c) is melt mixed is equal to or higher than the melting point of the polyamide (c), preferably at least 10°C higher than the melting point. In this manner, component (c) is dispersed in the molten matrix consisting of components (a), (b), and (d) in the form of fine spherical particles.

Step (3): The chemically modified mixture is extruded through a die at a temperature equal to or higher than the melting point of component (c) (preferably at least 10°C higher than the melting point) to form a shape suitable for stretching or rolling. In the extrusion step, the chemically modified molten mixture is extruded through a spinneret, inflation die, or T-die. This extrusion step (3) is carried out at a temperature higher than the melting point of the thermoplastic polyamide of component (c). Specifically, it is carried out at a temperature equal to or higher than the melting point of the thermoplastic polyamide of component (c), preferably at least 10°C higher. Extrusion below the melting point of the thermoplastic polyamide of component (c) does not allow the molten polyamide particles of component (c) to be formed into fine fibers.

Step (4): The extrudate is stretched or rolled while being drafted at a temperature lower than the melting point of component (c). The extruded string-like or thread-like material is continuously cooled to a temperature lower than the melting point of component (c) and stretched or rolled. The stretching or rolling is carried out at a temperature lower than the melting point of component (c). By stretching or rolling, tough polyamide fibers that reinforce the elastomer composition are formed.

The drawing or rolling is carried out, for example, by extruding the kneaded material through a spinneret and spinning it into a string or filament, which is then cooled and either wound onto a bobbin while being subjected to draft or cut into pellets. "Drafting" here means setting the winding speed faster than the spinneret speed. The ratio of winding speed to spinneret speed (draft ratio) is preferably in the range of 1.5 to 100, more preferably in the range of 2 to 50, and particularly preferably in the range of 3 to 30.

Although steps (1), (2), (3), and (4) have been described above, it is also possible to carry out continuous processing using a twin-screw extruder or the like having first, second, third, and fourth feed ports for feeding components (a), (b), (c), and (d), and optionally, an organic peroxide, and having first, second, third, and fourth kneading zones for kneading these components. This allows the production method of the present invention to be carried out more economically and stably.

Step (5): When only a portion of 100 parts by weight of component (a) is used in step (1), the remainder of component (a) is added and kneaded into the composition obtained in step (4).

The remaining amount of component (a) used in step (5) may be the same as the portion of component (a) used in step (1), or it may be a different rubbery polymer having a glass transition temperature of 0° C. or less.

When step (5) is performed, it is preferable to use 0.05 to 70 parts by weight of 100 parts by weight of component (a) in step (1), and the remaining 30 to 99.5 parts by weight in step (5). In this case, the remaining amount of component (a) used in step (5) is preferably 1/20 or less, and more preferably 1/10 to 1/0.5, of the weight of the polyamide fiber-reinforced elastomer composition (the product of step (4)) to which it is added. This facilitates the kneading operation.

The polyamide fiber-reinforced elastomer composition of the present invention can be vulcanized to form a vulcanizate. This vulcanization can be carried out by the following method. While masticating the polyamide fiber-reinforced elastomer composition, predetermined amounts of carbon black, process oil, antioxidant, zinc oxide, stearic acid, and other primary compounding ingredients are added and kneaded. The kneading equipment used is preferably a device commonly used in rubber compounding, such as a Prabender Plastograph, roll, or Banbury mixer. After this kneading, a vulcanizing agent such as sulfur and a vulcanization accelerator are added to the kneaded mixture on an open roll and further kneaded. The kneaded mixture is molded using a compression molding machine, extruder, injection molding machine, or the like, and heated for vulcanization. In this manner, a vulcanized polyamide fiber-reinforced elastomer composition of the present invention is obtained.

In the polyamide fiber-reinforced elastomer composition of this invention, components (a) and (b) form a matrix, with fine fibers of a composite of layered silicate and polyamide (component (c)) uniformly dispersed within this matrix. Components (a) and (b) and the fine fibers of the layered silicate-dispersed polyamide are firmly bonded to each other at their interfaces via the silane coupling agent (component (d)). This structure provides the fiber-reinforcement effect.

The mixing temperature for the fiber-reinforced resin composition and the remaining amount of component (a) added thereto in step (5) should be lower than the melting point of the thermoplastic polyamide (c), which constitutes the fine short fibers in the fiber-reinforced resin composition, and higher than the melting point of the polyolefin (b). Mixing at a temperature higher than the melting point of the thermoplastic polyamide in step (5) is undesirable because the fine short fibers in the fiber-reinforced resin composition may melt and deform into spherical particles. Mixing at a temperature lower than the melting point of the polyolefin resin (b) may result in insufficient uniformity of polyamide fiber dispersion, which may prevent the target strength and elongation from being achieved. Specifically, a temperature 20°C lower than the melting point of the thermoplastic polyamide (c) and 10°C higher than the melting point of the polyolefin (b) is preferred.

The fiber-reinforced resin composition used in step (5) is preferably in the form of pellets. By using a pelletized fiber-reinforced resin composition, the fiber-reinforced resin composition can be uniformly mixed with the added amount of component (a), and a polyamide fiber-reinforced elastomer composition in which fine fibers are uniformly dispersed can be easily obtained.

During the kneading process in step (5), carbon black, process oil, zinc oxide, stearic acid, and antioxidants may be added and kneaded. The temperature of the kneaded mixture rises during this process, but is controlled as necessary so as not to exceed the melting point of the thermoplastic polyamide (component (c)). The kneading temperature is preferably 160 to 180°C, and the kneading time is preferably 1 to 5 minutes. Various vulcanizing agents and vulcanization aids may be added together or sequentially in the required amounts at room temperature to 100°C. The thoroughly kneaded and dispersed composition is drawn into a sheet. The resulting sheet is molded and vulcanized to obtain a fiber-reinforced elastomer vulcanizate. The amount of vulcanizing agent used is preferably 0.1 to 5.0 parts by weight, and more preferably 0.5 to 3.0 parts by weight, per 100 parts by weight of the total amount of component (a). The amount of vulcanization aid is preferably 0.01 to 2.0 parts by weight, and more preferably 0.1 to 1.0 parts by weight, per 100 parts by weight of the total amount of component (a).

In the method of the present invention, known vulcanizing agents, such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide, can be used.

Vulcanization aids that can be used include aldehydes, ammonia compounds, aldehydes, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, and xanthates.

When vulcanizing the polyamide fiber-reinforced elastomer composition of the present invention by adding a vulcanizing agent, the vulcanization temperature is preferably about 100 to 180°C. However, the vulcanization temperature must be lower than the melting point of the thermoplastic resin that constitutes the fine fibers in the polyamide fiber-reinforced elastomer composition. If vulcanization is carried out at a temperature above the melting point of the thermoplastic resin, the fibers formed during the preparation of the fiber-reinforced resin composition will dissolve, making it impossible to obtain a polyamide fiber-reinforced elastomer composition with a high modulus.

In addition to the above-mentioned components, the polyamide fiber-reinforced elastomer composition of the present invention may contain auxiliary agents such as carbon black, white carbon, activated calcium carbonate, ultrafine magnesium silicate, high-styrene resin, phenolic resin, lignin, modified melamine resin, coumarone-indene resin, and petroleum resin; various fillers such as calcium carbonate, basic magnesium carbonate, clay, zinc oxide, diatomaceous earth, reclaimed rubber, powdered rubber, and ebonite powder; stabilizers such as amine-aldehydes, amine-ketones, amines, phenols, imidazoles, sulfur-containing antioxidants, and phosphorus-containing antioxidants; and various pigments.

EXAMPLES The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.

In the following examples and comparative examples, the physical properties of the polyamide fiber-reinforced elastomer composition and other fiber-reinforced resin compositions were measured by the following methods.

(1) Physical properties of unvulcanized product: (A) Organic composite layered silicate content : The layered silicate composite polyamide (montmorillonite composite nylon) was ignited at 650°C by thermogravimetric analysis, and the ignition residue weight was calculated using the following formula:

Organic composite montmorillonite content (%) = w/(a x b) w: Ignition residue weight % a: Inorganic content converted into organic content (0.791) b: Inorganic content converted into water of crystallization (0.9462) (B) Fiber shape : Form, dispersibility and average fiber diameter: After dissolving in hot xylene, the fibers were extracted and washed, and observed under a scanning electron microscope. If the fibers were found to be dispersed as fine fibers, the dispersibility was determined to be good. 200 dispersed fine fibers were observed under the above scanning electron microscope, and the fiber diameters were measured from the electron microscope image. The average of these measurements was taken as the average fiber diameter.

(C) Mooney viscosity : Mooney viscosity ML1+4 was measured at a temperature of 100°C.

(2) Physical properties of vulcanizates: (A) Tensile properties : Tensile strength, 100% modulus of elasticity, 300% modulus of elasticity and elongation were measured at 23°C and a pulling rate of 500 mm/min in accordance with JIS K6251, and expressed in MPa and %, respectively.

(B) Hardness : Measured using a JIS-A type tester in accordance with JIS K6253.

(C) Abrasion resistance : A Lambourn abrasion test was carried out in accordance with JIS K6254, and the abrasion resistance was expressed as an index, with Comparative Example 1 being 100.

(D) Dynamic friction coefficient : according to JIS K7125, a specimen is measured with a thickness of 0.2mm or less, a rectangular specimen with a width of 80mm and a length of 200mm, a transparent glass plate as a counter material, a load of 200g, a pulling speed of 500mm/min., and the larger the value, the better the slipperiness.Reference Example 1 (preparation of layered silicate-containing polyamide) Under atmospheric pressure, in a 20L Hastelloy reactor equipped with a stirrer and a temperature controller, 100g of layered silicate, montmorillonite, with an average width of 0.95nm and a length of about 100nm, and 10L of distilled water are put in, and montmorillonite is dispersed in water.While maintaining this dispersion at 35 ℃, 51.2g of 12-aminododecanoic acid and 24ml of concentrated hydrochloric acid are added, and the mixture is stirred for 5 minutes, and the particles are collected by filtration. The particles were then washed with water until the filtrate became neutral, collected by filtration, and dried in vacuum at 80°C for 48 hours, yielding a complex of 12-aminododecanoic acid ions and montmorillonite (hereinafter referred to as the montmorillonite complex).

The layered silicate content in the composite was approximately 80%. Next, 10 kg of ε-caprolactam, 1 kg of distilled water, and 180 g of the above-mentioned montmorillonite composite were added to the reactor and stirred at 100°C until the reaction mixture was homogenous. The temperature was then raised to 260°C and stirred for 1 hour under a pressure of 15 kg/ ^cm² (nitrogen pressure). The pressure was then returned to atmospheric pressure and the reaction continued at 260°C for 3 hours. The reaction mixture was then discharged in the form of strands from the bottom nozzle of the reactor, cooled with water, and cut into pellets consisting of polyamide (average molecular weight 15,000) and montmorillonite particles. The pellets were immersed in hot water at 90°C to extract and remove unreacted monomers and oligomers, and then vacuum-dried at 90°C for 48 hours. The resulting layered silicate-containing polyamide (montmorillonite-composite nylon 6) was ignited at 650°C, and the montmorillonite composite content was determined from the ignition residue weight, which was 2.0%. The results are shown in Table 1. Reference Examples 2 to 4 (Preparation of Layered Silicate-Containing Polyamide) In each of Reference Examples 2 to 4, a layered silicate-containing polyamide was prepared in the same manner as in Reference Example 1. However, the amount of the same montmorillonite complex used in Reference Example 1 was changed to 270 g, 360 g, or 720 g, and 10 kg of ε-caprolactam and 1 liter of water were used to produce montmorillonite-composite nylon 6 in the same manner as in Reference Example 1. The montmorillonite complex content in this montmorillonite-composite nylon 6 was 3.0%, 4.1%, and 7.9%, respectively. The results are shown in Table 1.

Table 1 Reference Example 5 (Preparation of a Polyamide Fiber-Reinforced Resin Composition of the Present Invention Containing a Portion of Component (a)) 100 parts by weight of natural rubber (SRM-L) as component (a), 100 parts by weight of low-density polyethylene (F522, manufactured by Ube Industries, Ltd., melting point 110°C, melt flow index 5 g/10 min) as component (b), and 1.5 parts by weight of γ-methacryloxypropyltrimethoxysilane as component (d) were melt-blended in a Banbury mixer at 110°C, a temperature above the melting point of component (b), to prepare a silane-modified matrix. This was dumped at 170°C and pelletized. 200 parts by weight of this pellet was mixed with 50 parts by weight of component (c), which consisted of the same montmorillonite-composite nylon 6 used in Reference Example 1, in a twin-screw extruder heated to 250°C, extruded into strands from the nozzle, taken up at room temperature, and pelletized using a pelletizer. Components (a) and (b) were extracted and removed from the pellets with hot xylene, and the resulting fine fibers of component (c), consisting of montmorillonite-composite nylon 6, were observed under a scanning electron microscope and found to have an average fiber diameter of 0.2 μm.

The results are shown in Table 2. Reference Examples 6 to 7 (Preparation of polyamide fiber-reinforced resin compositions of the present invention containing a portion of component (a)) In each of Reference Examples 6 to 7, fiber-reinforced resin compositions were obtained in the same manner as Reference Example 5, except that 100 parts by weight and 200 parts by weight of montmorillonite-composite nylon 6, component (c), were used. The evaluation results are shown in Table 2. Reference Examples 8 to 10 (Preparation of polyamide fiber-reinforced resin compositions of the present invention containing a portion of component (a)) In each of Reference Examples 8 to 10, fiber-reinforced resin compositions were obtained in the same manner as Reference Example 5, except that 50 parts by weight of montmorillonite-composite nylon 6, component (c), was used. The evaluation results are shown in Table 2. Reference Example 11 (Preparation of comparative polyamide fiber-reinforced resin composition) A fiber-reinforced resin composition was obtained in the same manner as Reference Example 5, except that 50 parts by weight of nylon 6, component (c), was used instead of montmorillonite-composite nylon 6, without using the montmorillonite-composite nylon 6. The evaluation results are shown in Table 2.

Table 2 (a): Rubber-like polymer, (b): Polyolefin, (c): Montmorillonite composite PA6, (d): Silane coupling agent . Example 1 : Five parts by weight of the fiber-reinforced resin composition of Reference Example 5 and 98 parts by weight of natural rubber (SRM-L) as additional component (a) were blended with carbon black (HAF), process oil, zinc oxide, stearic acid, antioxidant, vulcanization accelerator, and sulfur according to the formulation shown in Table 4. The blending procedure involved adding the natural rubber and fiber-reinforced resin composition to a Brabender Plastograph heated to 160°C and masticating for 30 seconds. The carbon black, process oil, zinc oxide, stearic acid, and antioxidant were then added in the listed order and kneaded for 4 minutes. The sulfur and vulcanization accelerator were then oriented on an open roll heated to 80°C. The resulting blend was vulcanized at 145°C for 30 minutes to obtain a polyamide fiber-reinforced elastomer composition. The Mooney viscosity of the blend containing carbon black and the physical properties of the vulcanized product were measured. The results are shown in Table 3. Examples 2 to 5: In each of Examples 2 to 5, 10, 15, 25, or 50 parts by weight of the fiber-reinforced resin composition of Reference Example 5 and 96, 94, 90, or 80 parts by weight of additional component (a) were used, but vulcanization was carried out in the same manner as in Example 1 to obtain vulcanized polyamide fiber-reinforced elastomer compositions. The Mooney viscosity of the compounds and the physical properties of the vulcanizates were measured. The results are shown in Table 3. Comparative Example 1 : Compounding and vulcanization were carried out in the same manner as in Example 1, using only natural rubber without the fiber-reinforced resin composition of Reference Example 5. The results are shown in Table 3. The dynamic friction coefficient of the vulcanizate was low and inferior. Comparative Examples 2 and 3: In each of Comparative Examples 2 and 3, 240 parts by weight of the fiber-reinforced resin composition of Reference Example 6 or 120 parts by weight of the fiber-reinforced resin composition of Reference Example 7 was used, and compounding and vulcanization were carried out in the same manner as in Example 1, except that the amount of natural rubber added was 20 or 80 parts by weight. The results are shown in Table 3. The resulting vulcanizate had low elongation and was inelastic, and also had poor abrasion resistance.

Table 3 (a): Rubber-like polymer (b): Polyolefin (c): Montmorillonite composite PA6 Examples 6-7 In each of Examples 6 and 7, 10 or 25 parts by weight of the fiber-reinforced resin composition of Reference Example 5, 66 or 50 parts by weight of natural rubber and 30 or 40 parts by weight of butadiene rubber (UBEPOL-150, manufactured by Ube Industries) as additional component (a), and compounding ingredients of the composition shown in Table 4 were used, but otherwise compounded and vulcanized in the same manner as in Example 1. The results are shown in Table 5.

Table 4 Comparative Examples 4-5: In Comparative Examples 4-5, vulcanized elastomer compositions were prepared in the same manner as in Example 4, except that no fiber-reinforced resin composition was blended, and 70 or 60 parts by weight of natural rubber and 30 or 40 parts by weight of butadiene rubber were used as the additional components of component (a) in the same manner as in Example 6 or 7. The results are shown in Table 5. The resulting vulcanized elastomers had low, inferior tensile moduli. Examples 8-12: In Examples 8-12, vulcanized elastomer compositions were prepared in the same manner as in Example 6, except that 9, 10, 10, 10, or 10 parts by weight of the fiber-reinforced resin composition of Reference Examples 6, 7, 8, 9, 10, or 11, respectively, and 97, 97.5, 97, 97, or 97 parts by weight of natural rubber were used as the additional components of component (a). The results are shown in Table 5. Comparative Example 6 An elastomer composition vulcanizate was prepared in the same manner as in Example 6, except that 25 parts by weight of the fiber-reinforced resin composition of Reference Example 11 and 90 parts by weight of natural rubber were used as an additional component (a). The results are shown in Table 5. The dynamic friction coefficient of the resulting vulcanizate was low and inferior.

Table 5 (a): Rubber polymer (b): Polyolefin (c): Montmorillonite composite PA6 Industrial Applicability The polyamide fiber-reinforced elastomer composition of the present invention is a fiber-reinforced elastomer in which fine thermoplastic polyamide fibers are dispersed in a matrix containing a rubbery polymer and a polyolefin, and since layered silicate is further dispersed at a microscopic level in the fine polyamide fibers, the composition of the present invention has good processability, excellent tensile strength and elastic modulus, and particularly an excellent balance between abrasion resistance and friction performance. The polyamide fiber-reinforced elastomer composition of the present invention is suitable for applications such as tires, rollers, flooring materials, and footwear.

─────────────────────────────────────────────────────── Continued from the front page (51) Int.Cl. ⁷ Identification Code FI C08L 77:00) (72) Inventor Yukihiko Asano 8-1 Goi Minamikaigan, Ichihara City, Chiba Prefecture, Japan Ube Industries, Ltd. Polymer Research Laboratory (Note) This publication is based on the gazette published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (1)

[Claims] 1. A polyamide fiber-reinforced elastomer composition containing the following components mixed together: (a) 100 parts by weight of at least one rubbery polymer having a glass transition temperature of 0°C or less, (b) 1 to 40 parts by weight of a polyolefin resin, (c) 1 to 70 parts by weight of a fibrous thermoplastic polyamide containing a dispersed layered silicate, and (d) a silane coupling agent. 2. The polyamide fiber-reinforced elastomer composition of claim 1, in which the silane coupling agent as component (d) is blended in an amount of 0.1 to 5.5 parts by weight per 100 parts by weight of the total of components (a), (b), and (c). 3. The polyamide fiber-reinforced elastomer composition of claim 1, in which the layered silicate-containing thermoplastic polyamide fibers have an average fiber diameter of 1 μm or less. 4. The polyamide fiber-reinforced elastomer composition according to claim 1, wherein the layered silicate-containing thermoplastic polyamide fiber contains 0.05 to 30 parts by weight of the layered silicate per 100 parts by weight of the thermoplastic polyamide. 5. A vulcanizate of the polyamide fiber-reinforced elastomer composition according to any one of claims 1 to 4. 6. A method for producing a polyamide fiber-reinforced elastomer composition, comprising: (1) melt-kneading (a) 100 parts by weight of at least one rubbery polymer having a glass transition temperature of 0°C or lower, (b) 1 to 40 parts by weight of a polyolefin resin, and (d) a silane coupling agent to form a molten matrix; (2) melt-kneading (c) 1 to 70 parts by weight of a thermoplastic polyamide containing a layered silicate into the molten matrix; (3) extruding the kneaded composition containing components (a) to (d) at a temperature equal to or higher than the melting point of the thermoplastic polyamide (c); and (4) stretching or rolling the extrudate at a temperature lower than the melting point of the thermoplastic polyamide (c), thereby dispersing the layered silicate-containing thermoplastic polyamide in a fibrous form. 7. The method for producing a polyamide fiber-reinforced elastomer composition according to claim 6, wherein only a portion of 100 parts by weight of component (a) is used to form the molten matrix in step (1), and the remainder of 100 parts by weight of component (a) is added to and mixed with the composition obtained in step (4). 8. The method for producing a polyamide fiber-reinforced elastomer composition according to claim 7 or 8, wherein 0.1 to 5.5 parts by weight of a silane coupling agent is added as component (d) relative to 100 parts by weight of the total of components (a), (b), and (c). 9. The method for producing a polyamide fiber-reinforced elastomer composition according to claim 7 or 8, wherein in the drawing or rolling step (4), the layered silicate-containing thermoplastic polyamide is dispersed in the form of fibers having an average fiber diameter of 1 μm or less. 10. A method for producing a polyamide fiber-reinforced elastomer composition according to claim 7 or 8, wherein the layered silicate is blended in an amount of 0.05 to 30 parts by weight per 100 parts by weight of the thermoplastic polyamide in component (c). 11. A method for producing a vulcanized polyamide fiber-reinforced elastomer composition, comprising mixing a vulcanizing agent with the polyamide fiber-reinforced elastomer composition obtained by the method according to any one of claims 7 to 10, and vulcanizing the mixture.