THERMOPLASTIC ELASTOMER COMPOSITIONS, HOSE MADE BY USING THERMOPLASTIC ELASTOMER COMPOSITION, AND PROCESS FOR THE PRODUCTION THEREOF

Abstract: A thermoplastic elastomer composition containing a component (A) (thermoplastic polyolefin resin), component (B) (epoxy-group-containing ethylene acrylic ester copolymer rubber), and component (C) (acid-modified polyolefin resin) comprising a continuous phase of the component (A) in which the component (B) is dispersed as a dispersed phase and is cross-linked by a peroxide; a thermoplastic elastomer composition comprising a continuous phase of a thermoplastic polyolefin resin (A) and a dispersed phase of an epoxy-group-containing ethylene-acrylic ester copolymer rubber component (B) and acrylonitrile butadiene rubber component (C), which is dynamically cross-linked; and a hose having an inner tube, at least one reinforcing layer, and an outer cover, wherein the inner tube and the outer cover contain a thermoplastic elastomer composition comprised of a thermoplastic resin in which is blended an at least partially cross-linked elastomer component, the reinforcing layer is a brass-plated wire, and the reinforcing layer and inner tube and the reinforcing layer and outer cover have between them a maleic-acid-modified polyolefin thermoplastic resin.

Description: TECHNICAL FIELD The present invention relates to a thermoplastic elastomer composition superior in heat resistance, oil resistance, low compression set or heat aging characteristics, weatherability, low temperature properties, and oil resistance and a hose using that thermoplastic elastomer composition. Further, the present invention relates to a hose having with a strong bond between the thermoplastic elastomer composition and brass-plated wire reinforcing layer and superior in durability and flexibility. BACKGROUND ART Known in the art are hoses comprising an inner tube, a reinforcing layer, and an outer cover laminated on each other annularly in that order. In these hoses, the inner tube and outer cover are comprising a vulcanized rubber, or resin such as urethane, polyester, nylon, the reinforcing layer is composed of a fiber such as nylon, polyester, rayon, vinylon, aramide fiber, braided or spiralled, and the layers are treated to be bonded with each other using a rubber cement, urethane adhesive, etc. However, a so-called "rubber hose" using rubber for the inner tubes and outer covers requires a vulcanization step, and therefore the manufacturing process ends up becoming complicated. Further, a so-called "plastic hose" using just a thermoplastic resin for the inner tubes and outer covers has the problem that the hose is rigid and poor in flexibility and kinks when the hose is bent. As a proposal to solve the above problem, there has been proposed a hose using a thermoplastic elastomer composition comprising a thermoplastic resin such as a polyolefin thermoplastic resin, a polyvinyl chloride thermoplastic resin, a polyamide thermoplastic resin, a polyester thermoplastic resin, in which an at least partially cross-linked vulcanized rubber phase is dispersed (see for example Japanese Unexamined Patent Publication (Kokai) No. 6-64102). However, from the viewpoint of an oil resistant hose, since a general polyolefin thermoplastic elastomer composition comprises a polypropylene and an ethylenepropylene rubber and has no polar group in its molecular structure, it has the defect of being poor in oil resistance. On the other hand, to improve the oil resistance, thermoplastic elastomers comprises polypropylenes and acrylonitrile-butadiene rubbers and thermoplastic elastomers comprises ethylene-acrylic ester copolymer rubbers and polyolefins have been proposed, but while the former are superior in oil resistance, they have double bonds in the molecular structure, and therefore, have the defects of inferior heat resistance and weatherability, while the latter are superior in heat resistance and weatherability, but have ethylene portions in the molecular structure of the rubber, and therefore, have the defect of a continued insufficient oil resistance. To solve these problems, various studies have been made on thermoplastic elastomers comprising acrylic rubbers and polyolefin resins superior in oil resistance and heat resistance, but there is the problem that they lack compatibility. Japanese Unexamined Patent Publication (Kokai) No. 6-136190 discloses a thermoplastic elastomer comprising a thermoplastic polyolefin resin and an acrylic ester containing a nonconjugated diene. A polyolefin resin and acrylic rubber are inherently incompatible, but no compatibilizer is used for the thermoplastic elastomer. It is considered that an excess amount of peroxide acts on the polyolefin as well causing the production of a polyolefin having radicals and that these radicals and the nonconjugated diene portions of the acrylic rubber react and produce graft polymers of the two. Japanese Unexamined Patent Publication (Kokai) No. 7-149964 discloses a thermoplastic elastomer comprising an ethylene-acrylic ester copolymer rubber and an olefin copolymer. No compatibilizer is used for this thermoplastic elastomer as well. The ethylene sites are merely partially cross-linked. The compatibility is unknown. Further, the ethylene-acrylic ester copolymer rubber used here does not have an epoxy group. Japanese Unexamined Patent Publication (Kokai) No. 62-290741 discloses a thermoplastic elastomer comprising a polyolefin resin and an ethylene-acrylic ester copolymer rubber having an epoxy group. An embodiment using a compatibilizer is also disclosed, but in this thermoplastic elastomer, the epoxy groups are used as cross-linking sites. On the other hand, a plastic hose comprising an inner tube, a reinforcing layer, and an outer covering layer laminated with each other annularly in that order, using a resin such as a nylon, polyester elastomer, polyacetal, urethane, for the inner tube, using a zinc-plated hard steel wire etc. for the reinforcing layer, and interposing a polyolefin resin layer having a functional group between the layers is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 55-97948. Further, steel wire treated on its surface with a triazine thiol derivative to improve its corrosion resistance and bondability with rubber is disclosed in Japanese Examined Patent Publication (Kokoku) No. 7-122225. However, until now, no example has been known of use of these techniques for a thermoplastic elastomer composition comprising a thermoplastic resin in which is dispersed a cross-linked elastomer. On the other hand, a process for the production of a wire-reinforced plastic hose having two wire reinforcing layers sandwiching a bonding use sheet coated with an epoxy resin etc. or a synthetic resin sheet between the hose inner layer and outer covering where after the wires are covered, induction heating is applied to bond the wires and bonding use sheet and outer covering is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 54-159468. These related art relate to hoses using a nylon, polyester, polyurethane, or other resin for the inner tube and outer cover and to processes of production of such plastic hoses. Hoses using a nylon, polyester, polyurethane, or the like, however, were not sufficient in flexibility or durability. EP-A-0 177 151 describes thermoplastic resin compositions comprising an epoxy group containing copolymer, a polypropylene resin and a polyester resin. EP-A-0 299 486 discloses a polymer composition comprising a propylene polymer, an epoxy group containing ethylene copolymer and an acid modified polymer. EP-A-0 335 394 is directed to a resin composition comprising a modified polypropylene, an acid containing polymer component and an epoxy group containing copolymer. Until now, no wire-reinforced hose using a thermoplastic elastomer composition comprising a thermoplastic resin in which is dispersed a cross-linked elastomer was known. Development of a wire-reinforced hose using a thermoplastic resin flexible and superior in durability has therefore been desired. DISCLOSURE OF INVENTION Accordingly, an object of the present invention is to provide a thermoplastic elastomer composition which has improved compatibility and has a sufficient heat resistance, oil resistance, flexibility, and low compression set and an oil resistant hose using the same. Another object of the present invention is to provide a process for producing a hose with an inner tube, outer cover, and reinforcing layer strongly bonded, having both an excellent durability and high flexibility, and superior in these properties even under high pressures. In accordance with the present invention, there is provided a thermoplastic elastomer composition comprising a thermoplastic polyolefin resin (A) in which an epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is dispersed, which is cross-linked with a peroxide. Further, an acid-modified polyolefin resin (C) is added as a compatibilizer. The compounding ratio (ratio by weight) (A)+(C)/(B) of the components (A), (B), and (C) in the thermoplastic elastomer composition of the present invention is preferably 70/30 to 15/85. Further, in the thermoplastic elastomer composition of the present invention, the thermoplastic olefin resin (A) is preferably at least one resin selected from the group consisting of a polypropylene and propylene-α-olefin copolymer. The epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is preferably sufficiently cross-linked. Further, a thermoplastic elastomer composition where the epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is dynamically cross-linked is preferred. Further, according to the present invention, there is provided an oil resistant hose using the above thermoplastic elastomer composition, as specified in claims 6-8. Finally, the present invention relates to a process for producing said hose. This process is specified in claim 9. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be explained further below with reference to the drawings, wherein, Fig. 1 is a schematic view of an example of the laminar structure of the hose of the present invention. Fig. 2 is a perspective view of another example of the hose of the present invention. Fig. 3 is a schematic view of an example of the process of production of a hose of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in further detail below. As the thermoplastic polyolefin resin (A) used as the continuous phase in the present invention, a homo or copolymer of an olefin, that is, a homo or copolymer of ethylene, propylene, 1-butene, 1-pentene, 3-methyl-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene, and the like may be mentioned. These may be used alone or in mixtures of two or more types. Of these, as the polypropylene resin, a polypropylene homopolymer, propylene-ethylene block copolymer containing 2 to 60% by weight of ethylene, a propylene-ethylene random copolymer containing 0.5 to 20% by weight of ethylene, etc. may be mentioned. The melt flow rate of these polymers is 0.1 to 100 g/10 min, preferably 0.5 to 50 g/10 min. Problems arise in processability if the melt flow rate is smaller than 0.1 g/10 min or larger than 100 g/10 min. The epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) used in the present invention comprises (a) ethylene and (b) an acrylic ester. Methacrylic ester is included in (b) acrylic esters, but these are esters comprised of C 1 to C 8 alcohols. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, etc. may be given as examples. These may be used alone or in mixtures of two or more types. The ratio of the (a) ethylene and (b) acrylic ester or methacrylic ester in the epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) used in the present invention is, by molar ratio, 50 to 85:50 to 15, preferably 58 to 80:42 to 20. If the content of the acrylic ester or methacrylic ester is more than 50 mol%, the embrittlement point becomes higher, and therefore, the use, as an elastomer, at a low temperature becomes difficult. Further, if the content is less than 15 mol%, an elasticity sufficient for a copolymer elastomer is not obtained. The content of the epoxy groups in the epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is 0.05 to 5 mol% with respect to the sum of the moles of (a) and (b), preferably 0.1 to 3 mol%. Note that the above component (B) may be used alone or in combinations of two or more types. When the epoxy group is used as a cross-linking site, a polycarboxylic acid etc. may be used as the cross-linking agent, but in the present invention, where a peroxide is used to dynamically cross-link the resin component and rubber component, the epoxy group of the rubber component (B) reacts with the resin component or later described compatibilizer and contributes to the compatibilization. In the present invention, the ethylene sites of the component (B) and other components react with the peroxide and function as cross-linking sites. Since the resin component (A) and rubber component (B) of the present invention are inherently incompatible, the compatibility is raised by adding as a compatibilizer an acid-modified polyolefin resin (C). The acid-modified polyolefin resin (C) used in the present invention is the above polyolefin resin modified with maleic anhydride, fumaric acid, etc. In particular, a maleic acid-modified polypropylene resin is preferred. The compatibilizer (C) of the present invention reacts with the epoxy groups of the rubber component, that is, the component (B), to form a graft or block polymer. This lowers the surface tension of the rubber component and facilitates mixing with the resin component. The amounts of the components (A), (B), and (C) blended (ratios by weight) are, when (A)+(B)+(C)=100 parts by weight, ((A)+(C)]/(B) = 70/30 to 15/85, preferably [(A)+(C)]/(B) = 60/40 to 20/80, particularly preferably 50/50 to 30/70. By compounding the components (A), (B) and (C) in these ranges, it is possible to obtain a thermoplastic elastomer composition having a balance of physical properties. Further, the ratio of the component (C) based upon the components (A)+(C) is preferably 1 to 50% by weight, particularly preferably 1 to 30% by weight. This is because it is possible to make the resin component (A) and the rubber component (B) sufficiently compatible. As the peroxide used as the cross-linking agent in the present invention, an organic peroxide having a one-minute half life of at least 150°C is preferably used. Specifically, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy) cyclododecane, t-hexylperoxyisopropylmonocarbonate, t-butylperoxymaleic acid, t-butyperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluylperoxy)hexane, t-butylperoxyisopropylmonocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,2-bis(t-butylperoxy)butane, t-butylperoxybenzoate, n-butyl-4,4-bis(t-butylperoxy) valerate, di-t-butylperoxyisophthalate, α,α' bi(t-butylperoxy)diisopropylbenzene, dicumylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumylperoxide, di-t-butylperoxide, p-menthanehydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, diisopropylbenzenehydroperoxide, t-butyltrimethylsilylperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, cuminhydroperoxide, t-hexylhydroperoxide, t-butylhydroperoxide, etc. may be mentioned. The thermoplastic elastomer composition according to the present invention is sufficiently cross-linked with the above cross-linking agent. Here, "sufficiently cross-linked" means the gelation rate of the rubber is at least 80%, preferably means it is 85 to 100%, particularly preferably 90 to 100%. If the gelation rate is less than 80%, the low compression set of the thermoplastic elastomer composition obtained is insufficient, and therefore, this is not preferred. Here, the gelation rate is confirmed by finely pulverizing the obtained composition by freeze pulverization, then performing Soxhlet extraction over a number of stages. A plasticizer may be added to the thermoplastic elastomer composition of the present invention. The plasticizer used in the present invention is not particularly limited in the case of a paraffin process oil. Further, a napthtene or aroma process oil may be used together therewith. The amount of the paraffin process oil added is 3 to 30 parts by weight based upon 100 parts by weight of the epoxy-group-containing ethylene-acrylate copolymer (B). If the amount is less than 3 parts by weight, the moldability remarkably deteriorates, while if the amount is more than 30 parts by weight, bleeding may occur. Further, when a polyester plasticizer is used, a polypropylene adipate (PPA) or other polyester plasticizer may suitably be used in a compounded state. The amount of the polyester plasticizer added is 3 to 50 parts by weight based upon 100 parts by weight of the epoxy-group-containing ethylene-acrylate copolymer (B). If the amount is less than 3 parts by weight, the moldability remarkably deteriorates, while if the amount is more than 50 parts by weight, bleeding may occur. Further, the composition of the present invention may further contain, if necessary, compounding agents such as a cross-linking adjuvant, cross-linking accelerator, filler, softening agent, anti-aging agent. The thermoplastic elastomer composition of the present invention is preferably a thermoplastic elastomer composition which is produced by dynamic cross-linking, that is causing cross-linking of the rubber while mixing the thermoplastic resin and rubber composition, that is, dynamically advancing the cross-linking. By using this process of production, the thermoplastic elastomer composition obtained ends up comprised of a thermoplastic resin phase, at least part of which forms a continuous phase, in which is finely dispersed a cross-linked rubber phase, at least part of which forms a discontinuous phase; therefore the thermoplastic elastomer composition obtained exhibits behavior similar to that of cross-linked rubber. Since at least the continuous phase is a thermoplastic resin, when molding, processing in accordance with the thermoplastic resin becomes possible. In the process for production of the thermoplastic elastomer composition of the present invention, the machinery used for the mixing of the components (A), (B), and (C) is not particularly limited, but a screw extruder, kneader, Banbury mixer, twin-screw kneader/extruder, etc. may be mentioned. Among these, considering the mixing of the component (A) (resin component), component (B) (rubber composition), and component (C) (compatibilizer) and the dynamic cross-linking of the component (B), use of a twin-screw kneader/extruder is preferred. Further, it is possible to use two or more types of kneaders and to successively mix the mixture. Next, an example of the process of production will be illustrated in more detail based on mixing by a twin-screw kneader/extruder as is generally performed. First, the pelletized components (A) and (C) are charged from a first charging port of the twin-screw kneader/extruder, mixed by the twin screws, and heated and melted. On the other hand, the component (B) is mixed using a Banbury mixer or other rubber use kneader added with, if necessary, a reinforcing agent, anti-aging agent, processing aid etc. to make a so-called master batch, not containing a cross-linking system, which is then pelletized by a rubber use pelletizer. As explained above, the component (A) is heated and melted by the twin-screw kneader/extruder, then the thus pelletized component (B) is charged from a second charging port of the twin-screw kneader/extruder to disperse the component (B) in the component (A). Next, a cross-linking agent or further a cross-linking aid are charged from a third (fourth) charging port of the twin-screw kneader/extruder to cause the component (B) to cross-link (dynamically cross-link) under mixing. By performing the cross-linking in this way, the cross-linking can be performed in a state with the component (B) sufficiently dispersed in the component (A) and with the component (B) sufficiently fine in state, and therefore, a thermoplastic elastomer composition comprising a component (A) forming a continuous phase (matrix) in which a component (B) is stably dispersed as a dispersed phase (domain) is prepared. In such a thermoplastic elastomer composition, the particle size of the cross-linked rubber composition forming the dispersed phase is preferably not more than 50 µm, more preferably 10 to 1 µm. When compounding agents such as a filler, softening agent, anti-aging agent, is added to the composition of the present invention, the compounding agents for the component (B) may be added during the above mixing, but compounding agents other than the cross-linking agent may also be premixed before the above mixing. The compounding agents for the component (A) may be premixed before the above mixing or may be added during the above mixing. The conditions for the melting and mixing of the component (A), component (B), and component (C) are a mixing temperature of, for example, 150 to 250°C, particularly preferably 150 to 230°C, and a shear rate at the time of mixing of 500 to 7000 sec -1 , particularly preferably 1000 to 2500 sec -1 . The time of the overall melt mixing is 30 seconds to 10 minutes, while the cross-linking time after the cross-linking agent is added is preferably 15 seconds to 5 minutes. The thermoplastic elastomer composition thus obtained of the present invention is superior in flexibility, low compression set, heat resistance, and oil resistance. The thermoplastic elastomer composition of the present invention is not limited in application to an oil resistant hose and may also be suitably used for parts used near automobile or construction machinery engines requiring oil resistance and heat resistance. As one example of a hose of the present invention, as shown in Fig. 1, a hose composed of an inner tube 2, reinforcing layer 4, and outer cover 6 may be exemplified. Note that a bonding layer 3 or 5 may be provided between the layers. The hose of the present invention uses the thermoplastic elastomer composition of the present invention for at least one of the inner tube 2 and outer cover 6. Further, when there are a plurality of layers of inner tubes 2 or outer covers 6, the thermoplastic elastomer composition of the present invention may be used for at least one of the same. If the composition of the present invention is used for one of the inner tube 2 and outer cover 6, a hose with the desired performance is obtained, but the composition of the present invention may also be used for both of the inner tube 2 and the outer cover 6. In the hose of the present invention, when the thermoplastic elastomer composition of the present invention is used for one of the inner tube or outer cover or one of the layers when the inner tube and outer cover are composed of pluralities of layers, as substances which can be used together, vulcanized rubbers such as NBR, IIR, EPDM, thermoplastic elastomer compositions such as polyamide elastomers, polyester elastomers, polyolefin elastomers, PP/EPDM thermoplastic elastomer compositions may be mentioned. Among these, vulcanized rubber requires a vulcanization step, and therefore, there are few merits in the work process. Among the thermoplastic elastomer compositions, superior flexibility PP/EPDM thermoplastic elastomer compositions are preferred. In the hose of the present invention, the reinforcing layer is not particularly limited. One formed as a braid or one formed as a spiral may be used. Further, the material used may be a yarn or a wire. As the reinforcing yarn, yarns made from vinylon fibers, rayon fibers, polyester fibers, nylon fibers, aromatic polyamide fibers, etc. may be mentioned by way of example. Explaining the above fibers in more detail, as the polyester fiber, a polyethylene terephthalate (made by Toray Industries Inc., Tetron) may be mentioned. This is generally suitable for use. As the nylon fiber, nylon 6 or nylon 66 made by Asahi Chemical Co., Ltd., Leona) etc. may be mentioned. Further, as the reinforcing wire, hard steel wire may be mentioned. More specifically, steel wire plated with brass or zinc etc. for imparting rustproofness and bondability may be mentioned. When bonding the reinforcing layer, inner tube, and outer cover by high-frequency induction heating, it is necessary to use wire in the reinforcing layer. The hose according to the present invention may, for example, be produced in the following way. The thermoplastic elastomer composition 2 of the present invention is extruded onto a mandrel 1 coated in advance with a release agent so as to form a hose inner tube. Next, when necessary, a bonding layer 3 is coated or laid in the form of a sheet or formed by a cross-head extruder on the inner tube for bonding with the reinforcing layer 4, then a braider is used to braid one or more layers of a reinforcing yarn or reinforcing steel wire. A bonding layer of an adhesive etc. may also be provided between the reinforcing layers. When necessary, after the braiding, a bonding layer 5 of an adhesive etc. is formed for bonding with the outer cover. A thermoplastic elastomer composition 6 for the outer cover is extruded to form the outer cover using a cross-head extruder suited for extruding the composition for outer cover on this. Note that, as the bonding layer provided on the inner tube and reinforcing layer or between reinforcing layers, an acid-modified polyolefin resin or isocyanate, phenol resin, epoxy resin, and urethane adhesive may be used. If the inner tube, reinforcing layer, and outer cover are formed in this way, when the mandrel is finally pulled out, the oil resistant hose of the present invention is obtained. In this process of production, a mandrel is used when producing the hose, but since there is no vulcanization step as required when producing an ordinary rubber hose or hose of a composite rubber/resin structure, there is no compressive deformation due to the heat at the time of vulcanization and deformation due to the pressure at the time of vulcanization, therefore the dimensional precision of the hose is easy to maintain and thus production is of course possible without use of a mandrel other than when strict dimensional precision is required. Figure 2 is a perspective view of the hose of the present invention showing the layers exposed. The hose has an inner tube 2, reinforcing layer 4, and outer cover 6 and has bonding layers 3 and 5 between the reinforcing layer and inner tube and between the reinforcing layer and outer cover. The inner tube 2 of the present invention is characterized by including the thermoplastic elastomer composition of the present invention. In the hose of the present invention, for the bonding layer, a maleic acid-modified polyolefin, in particular a maleic acid-modified propylene, maleic acid-modified polyethylene, etc. may be used. The hose of the present invention is a hose having at least an inner tube, reinforcing layer, and outer cover. The layers may be bonded to each other by bonding layers. The inner tube and the outer cover may each be formed as single layers or multiple layers. One or more reinforcing layers may also be provided. Next, the process of production of the hose of the present invention will be explained using an embodiment shown in the attached drawings. Figure 3 is a schematic view of the production process for an example of the hose of the present invention. The hose according to the present invention may for example be produced in the following way. That is, as shown in Fig. 3, a thermoplastic elastomer composition for the inner tube is extruded from extruder 8 for an inner tube material onto a mandrel 7 coated in advance with a release agent and simultaneously a bonding layer is extruded onto this from an adhesive extruder 9 to form a tube-like shape in the inner tube molding die 10 and thereby form the inner tube 11. At this time, it is also possible to extrude and form the bonding layer on the inner tube after extruding the inner tube. Next, a reinforcing layer 13 is formed on the inner tube 11 and the bonding layer using a reinforcing layer forming machine 12. The reinforcing layer 13 is formed by braiding a plurality of reinforcing yarns or reinforcing wires etc. aligned with each other in a spiral or braid. Next, a high frequency is applied by a high-frequency induction heating apparatus 14 to the hose on which the reinforcing layer 13 has finished being formed so as to locally heat the reinforcing layer 13 for 0.1 to 5 seconds. At this time, when the reinforcing layer 13 is heated to 100 to 350°C, if the bonding layer is a maleic acid-modified polyolefin resin etc., the bonding layer is melted and sufficient bonding becomes possible. Further, the heating of the wires of the reinforcing material may be performed by hot-air heating or infrared heating in addition to induction heating using a high-frequency oven. Application of heat treatment results in sufficient bonding of the bonding layer and wire and an improvement in the durability of the hose. In particular, if high-frequency induction heating is used, it is possible to partially melt just the surface of the bonding layer in contact with the wire, the reinforcing layer 13 and the bonding layer can be strongly bonded physically and chemically, and there is little deterioration of the material. Further, since the heating and melting are performed instantaneously, there is also the merit of the work efficiency being high. Finally, in the same way as the inner tube, a bonding layer is extruded from an extruder 16 for a bonding layer on to the sufficiently heated reinforcing layer 13 and simultaneously a thermoplastic elastomer composition for the outer cover is extruded from an outer cover material extruder 17 to form a hose-like shape in the outer cover forming die 15 and thereby form the outer cover 18. When forming the outer cover, it is also possible to first extrude the bonding layer, then extrude the thermoplastic elastomer composition for the outer cover so as to form the outer cover 18. Further, in Fig. 2, the high-frequency induction heating of the reinforcing layer 13 was performed before forming the outer cover 18, but the outer cover 18 and the bonding layer can be strongly bonded in the same way even if this is done after the outer cover 18 is formed. After forming the hose in this way, the mandrel 7 is pulled out to obtain the desired hose. By using the above production process, since no vulcanization step is required as when producing a hose such as an ordinary rubber hose, the production process can be simplified and the production of the rubber hose becomes simpler. Further, since no vulcanization step is required, there is no compressive deformation due to the heat at the time of vulcanization, and therefore the dimensional precision of the hose is easy to maintain. Further, the bonding layer is heated after the reinforcing layer is formed or after the outer cover is formed, but by selecting high-frequency induction heating, it is possible to heat the bonding layer without the heat being bounced off the surface of the wire and lost, and therefore, the work efficiency is better compared with infrared heating, hot-air heating, and other heating methods. Further, the bonding layer can be heated uniformly. However, use of the high-frequency induction heating method is limited to cases of use of wire for the reinforcing layer. When the reinforcing layer is made of organic fiber, if an adhesive such as an isocyanate, phenol resin, epoxy, is provided between the reinforcing layer and the inner tube and outer cover, a sufficient bonding force can be obtained by the heat at the time of the extrusion of the outer cover without special heat treatment such as induction heating. The hose of the present invention obtained in this way uses the thermoplastic elastomer composition of the present invention for at least the inner tube, therefore is superior in heat aging characteristics, oil resistance, and low temperature properties. The reinforcing layer in the hose of the present invention uses a brass-plated wire. The brass-plated wire may for example be braided or spiraled. The brass-plated wire of the reinforcing layer is preferably treated by a sulfur-containing triazine compound of the following formula: In the formula, R is -OR' , -SR' , -NHR', or -N(R') 2 , R' is H, an alkyl group, alkenyl group, phenyl group, phenylalkyl group, alkylphenyl group, or cycloalkyl group, M is H, Na, Li, K, 1/2 Mg, 1/2 Ba, 1/2 Ca, aliphatic primary, secondary, or tertiary amine, quaternary ammonium salt, or phosphonium salt. Specifically, 1,3,5-triazine-2,4,6-trithiol, 1,3,5,-triazine-2,4,6-trithiol•diethanolamine, 6-dibutylamino-1,3,5-triazine-2,4-dithiol, 6-dibutylamino-1,3,5-triazine-2,4-dithiol•monoethylenediamine, 6-dibutylamino-1,3,5-triazine -2,4-dithiol•monoethanolamine, etc. may be mentioned. If the surface of the brass-plated wire is treated with the above sulfur-containing triazine compound, the corrosion resistance of the wire and the bondability with the elastomer composition are improved. The method of treating the surface of the brass-plated wire by the above sulfur-containing triazine compound (hereinafter referred to as the "triazine treatment") is not particularly limited. The conventional known method disclosed in Japanese Examined Patent Publication (Kokoku) No. 7-122225 etc. may be used. For example, the method of drawing the wire in a lubricant containing the sulfur-containing triazine compound, the method of immersing the wire and a counter electrode in a solution of the sulfur-containing triazine compound and applying a voltage across the same, etc. may be mentioned. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is of course not limited in scope to these Examples. Examples I-1 to I-6 and Comparative Examples I-1 to I-2 The various elastomer compositions shown in the following Table I-1 were prepared in the following way using resin components, rubber components, compatibilizers, and cross-linking agents and other various compounding agents. Process of Production of Elastomer Composition First, the rubber component and the compounding agents other than the cross-linking agent were charged into an internal rubber-use Banbury mixer, mixed, and then pelletized by a rubber-use pelletizer. Next, the resin component, pelletized rubber component, and compatibilizer were charged into a twin-screw kneader/extruder and mixed, then the cross-linking agent was continuous charged, whereby the rubber component dispersed as a domain in a matrix comprising the resin component and compatibilizer is dynamically cross-linked. The mixing conditions were a mixing temperature of 180°C and a shear rate of 1000 sec -1 . After the end of the dynamic vulcanization, the mixture was continuously extruded from the twin-screw kneader/extruder in the form of strands. These were then water cooled, then cut by a cutter to lengths of about 3 mm (diameter approximately 2 mm) to obtain a pelletized thermoplastic elastomer composition. The various thermoplastic elastomer compositions obtained were measured according to a JIS K6301 method for their hardness, tensile strength, elongation, and compression set and were measured for cross-linking degree by Soxhlet extraction. Further, they were measured according to a JIS K6301 method for heat aging characteristics by a hot air aging test (120°C, 336 hours) and for oil resistance by an immersion test (120°C, 336 hours). The results are shown in Table I-1. In the Table, the amounts of the components of the formulation are parts by weight. The notes to Table I-1 are as follows: Ethylene-acrylic ester copolymer I-1: Esprene EMA2752 (made by Sumitomo Chemical Co., Ltd.), containing epoxy groups. Ethylene-acrylic ester copolymer I-2: Esprene EMA2152 (made by Sumitomo Chemical Co., Ltd.), not containing epoxy groups. Polypropylene (homopolymer): RD121D (made by Tokuyama Corporation) Polypropylene (block polymer of propylene and ethylene): RD610 (made by Tokuyama Corporation) Polypropylene (P.E.R.): M552E (made by Tokuyama Corporation) Maleic acid-modified polypropylene: Admer QB540 (made by Mitsui Petrochemicals Industries, Ltd.) Plasticizer (paraffin family oil): Sunpar 2280 (made by Nippon Sun Sekiyu) Cross-linking agent (organic peroxide): Parkadox 14/40 (made by Kayaku Akzo Corporation) Antioxidant: Irganox 1010 (made by Ciba-Geigy Japan) Comparative Example I-1 did not use a maleic acid-modified polypropylene, and therefore, the compatibility was poor and the elongation insufficient. Comparative Example I-2 used an ethylene-acrylic ester copolymer rubber not having any epoxy groups, and therefore the compatibility was poor and the elongation insufficient. Examples I-7 to I-9, Comparative Example I-3, and Prior Art Example I-1 Preparation of Hose As shown in Table I-2, as the inner tube material, Examples I-2 and I-3, Comparative Example I-1, and acrylonitrile butadiene rubber were extruded onto mandrels. Brass-plated wire (diameter 0.25 mm) was then braided over each to form reinforcing layers. Next, outer covers composed of a PP/EPDM thermoplastic elastomer (Santoprene 101-73, AES Co.), the Example I-2 material, and a chloroprene rubber were extruded to form hoses. These were designated as Examples I-7 to I-9, Comparative Example I-3, and Prior Art Example I-1. In Examples I-7 to I-9 and Comparative Example I-3, as the adhesive for the inner tube and reinforcing layer and for the reinforcing layer and the outer cover, a maleic acid-modified polypropylene (Admer QB540 (made by Mitsui Petrochemicals Industries, Ltd.)) was used. The adhesive was applied by extrusion in two layers for the inner tube and the outer cover. After the outer covers were extruded, the hoses were passed through a high-frequency oven to be treated to bond the inner tubes with the reinforcing layers and the outer covers with the reinforcing layers by induction heating. The conditions at that time were a secondary power of the high-frequency oven of 15 kw, a heating temperature of 180°C, and a line speed of 5 m/min. For Prior Art Example I-1, after formation, the hose was vulcanized at 150°C and 20 kg/cm 2 for 45 minutes. The hoses prepared by the above method had inner diameters of 9 mm and thicknesses of the inner tube and outer cover of 1.5 mm and 1.0 mm respectively. The formulation of the acrylonitrile-butadiene rubber and chloroprene rubber used in Prior Art Example I-1 is shown in Table I-3. Inner tube use (NBR) Outer cover use (CR) NBR 100 - CR - 100 GPF 60 60 Stearic acid 2 2 Paraffin process oil - 20 DOP 20 - ZnO 3 4.5 Sulfur 2 - TT 1 - NA22 - 1 Physical Properties of Hoses The hoses of Examples I-7 to I-9, Comparative Example I-3, and Prior Art Example I-1 were evaluated for the following items. The results are shown in Table I-2. (1) Hose Durability The hoses were tested according to an SAE J188 Type 1. As the oil, automatic transmission use oil (made by Idemitsu Kosan Co., Ltd.) was used. Impulse pressure was repeatedly applied under conditions of 100°C and a pressure of 140 kg/cm 2 . The test was stopped when an abnormality occurred in the hose and the number of impulses was shown in Table I-2. For hoses which failed to show any abnormality after 1 million impulses, the test was stopped and a "good" rating given. (2) Hose Flexural Rigidity The hoses were bent along arcs of predetermined radii and the bending force measured. The measurement started from a bending radius of 10 times (10D) the outer diameter of the hoses, then the bending radius was successively changed up to 3D and the bending force measured (n=2). The method was adopted of reading the value at the time of the prescribed radius (4D) from the curve plotting the relationship between the bending force and the bending radius obtained. The data is the load by which the hoses of the Examples and Comparative Examples similarly deform expressed as relative values indexed to the value of the hose prepared by Prior Art Example I-1 as 100. (3) Work Steps The numbers of production steps of the hoses of the Examples and Comparative Examples were expressed as relative values indexed to the work steps for producing the hose of Prior Art Example I-1 as 100. As explained above, according to the first aspect of the present invention, by using a thermoplastic elastomer composition, comprised of a thermoplastic polyolefin family resin in which is dispersed an epoxy-group-containing ethylene-acrylic ester copolymer rubber which is cross-linked by a peroxide, as a hose, it is possible to obtain a hose superior in durability and flexibility with fewer work steps than a rubber hose.

Claims: A thermoplastic elastomer composition comprising the following components (A), (B), and (C): Component (A): thermoplastic polyolefin resin Component (B): epoxy-group-containing ethylene acrylic ester copolymer rubber Component (C): acid-modified polyolefin resin wherein the component (B) is dispersed in a continuous phase of the component (A) as a dispersed phase and is cross-linked by a peroxide. A thermoplastic elastomer composition as claimed in claim 1, wherein the ratio of compounding (ratio by weight) (A)+(C)/(B) of the components (A), (B), and (C) is 70/30 to 15/85. A thermoplastic elastomer composition as claimed in claim 1 or 2, wherein the thermoplastic olefin resin (A) is at least one resin selected from the group consisting of polypropylene homopolymers and propylene-α-olefin copolymers. A thermoplastic elastomer composition as claimed in any one of claims 1 to 3, wherein the epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is cross-linked at least 80% in the composition. A thermoplastic elastomer composition as claimed in any one of claims 1 to 4, wherein the epoxy-group-containing ethylene-acrylic ester copolymer rubber (B) is dynamically cross-linked. A hose using the thermoplastic elastomer composition as claimed in any one of claims 1 to 5 as the inner tube and/or outer cover of a hose having an inner tube, at least one reinforcing layer, and an outer cover. A hose using the thermoplastic elastomer composition as claimed in any one of claims 1 - 5 as at least the inner tube of a hose having an inner tube, at least one reinforcing layer, and an outer cover. A hose according to claim 7, wherein the reinforcing layer is a brass-plated steel wire, and the reinforcing layer and inner tube and the reinforcing layer and outer cover have between them a maleic acid-modified polyolefin thermoplastic resin. A process for producing a hose according to claim 7 or 8, comprising the steps of providing the reinforcing layer, then applying high-frequency induction heating to heat the brass-plated wire and bonding the maleic acid-modified polyolefin thermoplastic resin and brass-plated wire.

Inventors: HARA YUICHI, HATANAKA SUSUMU, IRII DAISUKE, KAWAGUCHI GOU, KURODA NORIAKI, SATOH TAKASHI, WATANABE JIRO, YAMAUCHI SHIGERU, HARA, YUICHI, HATANAKA, SUSUMU, IRII, DAISUKE, KAWAGUCHI, GOU, KURODA, NORIAKI, SATOH, TAKASHI, WATANABE, JIRO, YAMAUCHI, SHIGERU, HARA, Yuichi, The Yokohama Rubber Co., Ltd., HATANAKA, Susumu, The Yokohama Rubber Co., Ltd., IRII, Daisuke, The Yokohama Rubber Co., Ltd., KAWAGUCHI, Gou, The Yokohama Rubber Co., Ltd., SATOH, Takashi, The Yokohama Rubber Co., Ltd., WATANABE, Jiro, The Yokohama Rubber Co., Ltd., YAMAUCHI, Shigeru, The Yokohama Rubber Co., Ltd.
Applicants: YOKOHAMA RUBBER CO LTD, THE YOKOHAMA RUBBER CO., LTD.
Application year: 1997
Main classification: C08L23
IPC codes: C08L23, F16L11