JP2012207748A - Heat-resistant air hose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant air hose achieving cost reduction by using a versatile rubber and having excellent heat resistance and interlayer adhesiveness.SOLUTION: The heat-resistant air hose includes an inner layer 1 and an outer layer 2 formed on an outer circumference of the inner layer. The inner layer 1 is formed of an acrylic rubber composition containing components of (a) an acrylic rubber and (b) carbon black having a hydroxyl group on the surface thereof. The outer layer 2 is formed of an ethylene-propylene rubber composition containing components of (A) an ethylene-propylene rubber and (B) a crosslinking agent. The inner layer 1 and the outer layer 2 are adhered to each other by using a silane-based adhesive.

Description

  The present invention relates to a heat-resistant air hose used in a transport machine such as an automobile.

  As part of environmental measures, vehicles equipped with turbocharger systems are becoming more popular in order to increase the thermal efficiency of internal combustion engines and to comply with exhaust gas regulations. The air introduced from the turbocharger to the intercooler and the engine may be at a high temperature and high pressure, and the hose material for transporting the air is required to have high heat resistance and oil resistance. Therefore, a hose material using acrylic rubber, fluorine rubber, silicone rubber or the like has been proposed.

  However, these synthetic rubbers are special and difficult to process, and are expensive and have high specific gravity. Therefore, in order to reduce cost and weight, for example, there is a heat-resistant air hose that uses acrylic rubber for the inner layer, and uses ethylene-propylene rubber that is more versatile than acrylic rubber and has a low specific gravity for the outer layer. It has been proposed (see Patent Document 1).

Japanese Patent Laid-Open No. 2005-199564

  By the way, the acrylic rubber layer and the ethylene-propylene rubber layer are inferior in interlayer adhesion, and in order to improve this, in the hose described in Patent Document 1, a peroxide crosslinking agent is contained in the acrylic rubber layer. It is necessary to blend a polyfunctional monomer and a thiourea derivative. Therefore, in the hose described in Patent Document 1, there is a problem that the blending design of the acrylic rubber layer is limited, and there is room for improvement.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a heat-resistant air hose excellent in heat resistance and interlayer adhesion by reducing the cost by using a highly versatile rubber.

In order to achieve the above object, the heat-resistant air hose of the present invention is a heat-resistant air hose having an inner layer and an outer layer formed on the outer periphery thereof, and the inner layer contains the following components (a) and (b): The outer layer is made of an ethylene-propylene rubber composition containing the following components (A) and (B), and the inner layer and the outer layer are made of a silane-based adhesive. It is configured to be bonded together.
(A) Acrylic rubber.
(B) Carbon black having a hydroxyl group on the surface.
(A) Ethylene-propylene rubber.
(B) Crosslinking agent.

  That is, the present inventor has intensively studied in order to obtain a heat-resistant air hose that is low in cost and excellent in heat resistance and interlayer adhesion. The inner layer of the heat-resistant air hose is formed of a material mainly composed of acrylic rubber excellent in heat resistance, and the outer layer of the heat-resistant air hose is mainly composed of ethylene-propylene rubber that is more versatile than acrylic rubber. An experiment was conducted in consideration of the formation of the material, but it was found that this material has poor interlayer adhesion. Accordingly, the present inventor conducted further experiments focusing on the silane-based adhesive. Silane-based adhesives are effective as adhesives for ethylene-propylene-based rubbers, but are considered to be not very effective as adhesives for acrylic rubbers, and this has been regarded as common technical knowledge. However, as a result of repeated research, when carbon black having a hydroxyl group on the surface is blended into the acrylic rubber of the inner layer, contrary to the above technical common sense, the interlayer adhesion of both layers is improved, low cost, and heat resistance The inventors have found that a heat-resistant air hose excellent in interlayer adhesion can be obtained, and have reached the present invention. Although the reason for this is not clear, it is considered that the interlayer adhesion between the inner layer and the outer layer is improved because the hydroxyl group of carbon black blended in the inner layer and the silane-based adhesive at the interface are bonded by chemical bonding or the like.

  As described above, in the heat-resistant air hose of the present invention, the inner layer is made of an acrylic rubber and carbon black having a hydroxyl group on the surface, and the outer layer is an ethylene-propylene rubber containing an ethylene-propylene rubber and a crosslinking agent. The composition is used, and the inner layer and the outer layer are bonded using a silane-based adhesive. Therefore, the heat-resistant air hose of the present invention is low in cost and excellent in heat resistance and interlayer adhesion. In addition, since it is not necessary to add a peroxide crosslinking agent, a polyfunctional monomer, and a thiourea derivative to the acrylic rubber of the inner layer, the degree of freedom in designing the acrylic rubber composition is expanded.

Further, when the nitrogen adsorption specific surface area of carbon black having a hydroxyl group on the surface (component b) is 35 × 10 ^{3 to} 125 × 10 ³ m ² / kg, the interlayer adhesion between the inner layer and the outer layer is further improved.

  And when content of carbon black (b component) which has a hydroxyl group on the surface is 30-80 weight part with respect to 100 weight part of acrylic rubber (a component), it was excellent, without reducing heat resistance Interlaminar adhesion can be maintained.

  Furthermore, pressure resistance improves when the heat-resistant air hose is provided with a reinforcing yarn layer at the interface between the inner layer and the outer layer.

It is a perspective view which shows an example of the heat-resistant air hose of this invention.

  Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

  For example, as shown in FIG. 1, the heat-resistant air hose of the present invention is configured such that a reinforcing yarn layer 3 is formed at the interface between the inner layer 1 and the outer layer 2.

In the present invention, the inner layer 1 uses an acrylic rubber composition containing the following components (a) and (b), and the outer layer 2 contains the following components (A) and (B): A propylene-based rubber composition is used, and the inner layer 1 and the outer layer 2 are bonded using a silane-based adhesive. This is the greatest feature of the present invention.
(A) Acrylic rubber.
(B) Carbon black having a hydroxyl group on the surface.
(A) Ethylene-propylene rubber.
(B) Crosslinking agent.

  The heat resistant air hose of the present invention preferably has the reinforcing yarn layer 3 from the viewpoint of pressure resistance, but may be omitted.

  Next, materials for forming each layer will be described.

<< Acrylic rubber composition >>
First, an acrylic rubber composition that is a material for the inner layer of the heat-resistant air hose of the present invention will be described.
The acrylic rubber composition contains acrylic rubber (component a) and carbon black having a hydroxyl group on the surface (component b) as essential components.

<< Acrylic rubber (component a) >>
Examples of the acrylic rubber (component a) include those having an acrylate content of 70 to 100% by weight, an ethylene content of 0 to 10% by weight, and a vinyl acetate content of 0 to 20% by weight. From the point of view, it is preferable.

  Examples of the acrylate ester include alkoxy acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, methoxyethyl acrylate, and the like.

  The acrylic rubber (component a) may be copolymerized with 0 to 5% by weight of a crosslinking site-containing monomer. As said monomer, the monomer etc. which have an active halogen group, an epoxy group, a carboxyl group, a hydroxyl group, an amide group, a diene group etc. are mention | raise | lifted, for example. Of these, epoxy groups such as glycidyl methacrylate and carboxyl groups such as monobutyl maleate are preferable.

<< Carbon black with hydroxyl group on the surface (component b) >>
Examples of the carbon black include furnace black such as HAF carbon black, MAF carbon black, FEF carbon black, SRF carbon black and GPF carbon black, and thermal black such as FT carbon black and MT carbon black. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area of the specific carbon black (component b) is preferably 7 × 10 ^{3 to} 125 × 10 ³ m ² / kg from the viewpoint of heat resistance, and particularly preferably 35 from the viewpoint of heat resistance and adhesiveness. × a ^{10 3 ~125 × 10 3 m 2} / kg.

  The nitrogen adsorption specific surface area can be measured, for example, according to the method described in JIS K 6217-2.

  Moreover, the OH amount of the specific carbon black (component b) is 0.20 to 0.65 meq. / G, particularly preferably 0.30 to 0.65 meq. / G.

The OH amount (hydroxyl group amount) can be determined, for example, by total acid group amount-strong acid group amount.
<Total amount of acidic groups>
The solution is obtained by adding sodium hydroxide aqueous solution to carbon black, shaking and centrifuging, then adding methyl orange to the supernatant and titrating with hydrochloric acid aqueous solution.
<Strongly acidic group amount>
After adding an aqueous sodium carbonate solution to carbon black, shaking and centrifuging, the supernatant is added with methyl orange and titrated with an aqueous hydrochloric acid solution.

  The content of the specific carbon black (component b) is preferably 30 to 80 parts by weight, particularly preferably 40 to 60 parts by weight, based on 100 parts by weight of the acrylic rubber (component a), from the viewpoint of heat resistance. It is. That is, when there is too little b component, the tendency for interlayer adhesiveness to worsen is seen, and conversely, when there is too much b component, the tendency for heat resistance to worsen is seen.

  The acrylic rubber composition used in the present invention includes an acrylic rubber (component a) and carbon black having a hydroxyl group on the surface (component b), a crosslinking agent, a polyfunctional monomer, a reinforcing material, and a white filler. Plasticizers, vulcanization accelerators, processing aids, anti-aging agents, flame retardants and the like may be blended as necessary. These may be used alone or in combination of two or more.

<Crosslinking agent>
As the crosslinking agent, for example, an amine crosslinking agent, an acid anhydride crosslinking agent, a urea crosslinking agent, a Lewis acid crosslinking agent and the like are used alone or in combination. Among these, an amine crosslinking agent is preferable from the viewpoint of heat resistance.

  Examples of the amine crosslinking agent include hexamethylene diamine, hexamethylene diamine carbamate, tetramethylene pentamine, N, N′-dicinnamylidene-1,6-hexane diamine, 4,4′-methylene bis (cyclohexylamine), 4, 4'-methylenedianiline, 4,4'-oxyphenyldiphenylamine, m-phenylenediamine, p-phenylenediamine, 4,4'-methylenebis (o-chloroaniline), 4,4'-diaminodiphenyl ether, 3,4 '-Diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene) dianiline, 4,4 '-(p-phenylenediisopropylidene) dianiline, 2,2'-bis [4- (4-aminophenoxy) Phenyl] propane, 4,4'-diaminoben Anilide, 4,4'-bis (4-aminophenoxy) biphenyl, m-xylylenediamine, p-xylylenediamine, 1,3,5-benzenetriamine, 1,3,5-benzenetriaminomethyl, hexamethylene Examples thereof include diamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt and the like. These may be used alone or in combination of two or more.

  The content of the crosslinking agent is preferably from 0.1 to 10 parts by weight, particularly preferably from 0.3 to 5 parts by weight, based on 100 parts by weight of the acrylic rubber (component a).

  The acrylic rubber composition used in the present invention, for example, is blended with acrylic rubber (component a) and carbon black having a hydroxyl group on the surface (component b), if necessary, with a crosslinking agent and the like. It can be prepared by kneading using a kneader such as a Banbury mixer or roll.

<< Ethylene-propylene rubber composition >>
Next, an ethylene-propylene rubber composition that is a material for the outer layer of the heat-resistant air hose of the present invention will be described.
The ethylene-propylene rubber composition contains ethylene-propylene rubber (component A) and a crosslinking agent (component B) as essential components.

<< Ethylene-propylene rubber (component A) >>
Examples of the ethylene-propylene rubber (component A) include ethylene-propylene-diene terpolymer rubber (EPDM), ethylene-propylene copolymer rubber (EPM), and the like, alone or in combination of two or more. Used.

  The ethylene-propylene rubber (component A) is preferably one having an iodine value in the range of 6 to 30 and an ethylene ratio in the range of 48 to 70% by weight, in view of excellent stability under high temperature and pressure. Preferably, the iodine value is in the range of 10 to 24, and the ethylene ratio is in the range of 50 to 60% by weight.

  The diene monomer (third component) contained in the EPDM is preferably a diene monomer having 5 to 20 carbon atoms, specifically 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene. 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5- Butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene and the like. Among these diene monomers (third component), dicyclopentadiene (DCP) and 5-ethylidene-2-norbornene (ENB) are preferable.

<< Crosslinking agent (component B) >>
As said crosslinking agent (B component), sulfur, a peroxide crosslinking agent (peroxide crosslinking agent), etc. are individual or used together, for example. Among these, a peroxide crosslinking agent is preferable in terms of heat resistance.

  Examples of the peroxide crosslinking agent include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3, 5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1-bis (t-butylperoxy) cyclohexane, 2, Pers such as 2-bis (t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) butane, n-butyl-4,4-bis (t-butylperoxy) valerate, etc. Oxyketals, di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α, α'-bis (t-butylperoxy-m-iso Propyl) benzene, α, α′-bis (t-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis Dialkyl peroxides such as (t-butylperoxy) hexyne-3, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl Diacyl peroxides such as peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-trioyl peroxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxide Oxy-2-ethylhexanoate , T-butyl peroxylaurate, t-butyl peroxybenzoate, di-t-butyl peroxyisophthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butyl peroxymalein Peroxyesters such as acid, t-butylperoxyisopropyl carbonate, cumylperoxyoctate, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2, And hydroperoxides such as 5-dihydroperoxide and 1,1,3,3, -tetramethylbutyl peroxide. These may be used alone or in combination of two or more.

  When sulfur is used as the crosslinking agent (component B), the content thereof is preferably 0.5 to 15 parts by weight, particularly preferably 1 with respect to 100 parts by weight of the ethylene-propylene rubber (component A). ~ 5 parts by weight. Moreover, when using a peroxide crosslinking agent as said crosslinking agent (B component), the content is preferable 1-20 weight part with respect to 100 weight part of ethylene-propylene-type rubber | gum (A component), especially. Preferably it is 3-15 weight part. That is, if the amount of the crosslinking agent (component B) is too small, the vulcanization is insufficient and the strength of the hose is inferior. This is because the scorch time is shortened and the workability tends to deteriorate.

  In addition to the ethylene-propylene rubber (component A) and the crosslinking agent (component B), the ethylene-propylene rubber composition used in the present invention includes a vulcanization accelerator, carbon black, a vulcanization aid, and a process. Oils, co-crosslinking agents, anti-aging agents, and the like may be appropriately blended as necessary. These may be used alone or in combination of two or more.

《Vulcanization accelerator》
Examples of the vulcanization accelerator include vulcanization accelerators such as thiazole, sulfenamide, thiuram, aldehyde ammonia, aldehyde amine, guanidine, and thiourea. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators are preferred because they are excellent in vulcanization reactivity.

  The content of the vulcanization accelerator is preferably from 0.1 to 10 parts by weight, particularly preferably from 0.5 to 3 parts by weight, based on 100 parts by weight of the ethylene-propylene rubber (component A).

  Examples of the thiazole vulcanization accelerator include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), and 2-mercaptobenzothiazole zinc salt (ZnMBT). Etc. These may be used alone or in combination of two or more. Among these, dibenzothiazyl disulfide (MBTS) and 2-mercaptobenzothiazole (MBT) are preferable in terms of excellent vulcanization reactivity.

  Examples of the sulfenamide-based vulcanization accelerator include N-oxydiethylene-2-benzothiazolylsulfenamide (NOBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and Nt. -Butyl-2-benzothiazoylsulfenamide (BBS), N, N'-dicyclohexyl-2-benzothiazoylsulfenamide and the like. These may be used alone or in combination of two or more.

  Examples of the thiuram vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT), and tetrabenzylthiuram. Examples thereof include disulfide (TBzTD). These may be used alone or in combination of two or more.

"Carbon black"
As the carbon black, those excellent in extrudability and reinforcing properties are preferable. For example, those of SAF class, ISAF class, HAF class, MAF class, FEF class, GPF class, SRF class, FT class, MT class, etc. Can be given. These may be used alone or in combination of two or more.

  The content of the carbon black is preferably 20 to 140 parts by weight, particularly preferably 60 to 120 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber (component A). That is, if the amount of carbon black is too small, the reinforcing effect is poor. Conversely, if the amount of carbon black is too large, the electrical resistance tends to be low and the electrical insulation tends to be poor.

《Vulcanization aid》
Examples of the vulcanization aid include zinc white (ZnO), stearic acid, magnesium oxide and the like. These may be used alone or in combination of two or more.

  The content of the vulcanization aid is preferably 1 to 25 parts by weight, particularly preferably 3 to 10 parts by weight, based on 100 parts by weight of the ethylene-propylene rubber (component A).

<Process oil>
Examples of the process oil include naphthenic oil, paraffinic oil, and aroma oil. These may be used alone or in combination of two or more.

  The content of the process oil is preferably 5 to 100 parts by weight, particularly preferably 20 to 80 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber (component A).

《Co-crosslinking agent》
As the co-crosslinking agent, for example, divinylbenzene, triallyl isocyanurate (TAIC) is preferably used, and together with these, triallyl cyanurate, diacetone diacrylamide, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, trimethylol. Propane trimethacrylate, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diisopropenylbenzene, p-quinonedioxime, p, p-dibenzoylquinonedioxime, phenylmaleimide, allyl Methacrylate, N, Nm-phenylene bismaleimide, diallyl phthalate, tetraallyloxyethane, 1,2 Polybutadiene and the like. These may be used alone or in combination of two or more.

  The content of the co-crosslinking agent is preferably 0.1 to 10 parts by weight, particularly preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber (component A).

《Anti-aging agent》
Examples of the anti-aging agent include carbamate-based, phenylenediamine-based, phenol-based, diphenylamine-based, quinoline-based anti-aging agents, waxes, and the like. These may be used alone or in combination of two or more.

  The content of the anti-aging agent is preferably 0.5 to 10 parts by weight, particularly preferably 1 to 4 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber (component A).

  The ethylene-propylene rubber composition used in the present invention includes, for example, a vulcanization accelerator, carbon black, vulcanization, if necessary, in the ethylene-propylene rubber (component A) and the crosslinking agent (component B). It can be prepared by blending an auxiliary agent, process oil and the like and kneading them using a kneader such as a kneader, a Banbury mixer, an open roll or the like.

<Silane adhesive>
Next, a silane-based adhesive that bonds the inner layer 1 and the outer layer 2 will be described.
As the silane-based adhesive, a room-temperature vulcanized silane adhesive (RTV) vulcanized with a mixture of a curing agent or air moisture, even if it is a heat-cured silane-based adhesive that is vulcanized by heating. Silicone) may be used, and specifically, an oligomer obtained by reacting a silane coupling agent and having an amino group, a vinyl group or the like as a functional group is preferable.

《Reinforcing yarn layer》
Next, the reinforcing yarn layer 3 formed at the interface between the inner layer 1 and the outer layer 2 will be described.

  Examples of the reinforcing yarn forming the reinforcing yarn layer 3 include vinylon (polyvinyl alcohol) yarn, polyamide (nylon) yarn, aramid yarn, polyethylene terephthalate (PET) yarn and the like. Among these, an aramid yarn is preferable from the viewpoint of heat resistance.

  Examples of the method for braiding the reinforcing yarn include spiral knitting, knitting knitting, and blade knitting.

  Next, the method for producing the heat-resistant air hose of the present invention will be specifically described. That is, according to the above-mentioned method, the acrylic rubber composition used as the inner layer material and the ethylene-propylene rubber composition used as the outer layer material are prepared. Next, an acrylic rubber composition (inner layer material) is extruded on a mandrel, and a silane-based adhesive is applied thereon by a method such as coating, brushing, or dipig. Subsequently, after braiding the reinforcing yarn in a spiral shape, an ethylene-propylene rubber composition (outer layer material) was extruded on the surface, and then the hose was vulcanized (for example, heated at 160 ° C. for 1 hour) Thereafter, it is further subjected to secondary vulcanization in an oven at 150 ° C. for 8 hours). Thereby, the heat resistant air hose (refer FIG. 1) by which the outer layer 2 is formed in the outer peripheral surface of the inner layer 1 via the reinforcement thread layer 3 can be obtained.

  The heat-resistant air hose of the present invention is not limited to the structure shown in FIG. 1, and a reinforcing outermost layer made of a rubber material may be further formed on the outer periphery of the outer layer 2. Further, the reinforcing yarn layer 3 can be omitted as described above.

  In the heat-resistant air hose of the present invention, the outer diameter of the hose is preferably 10 to 90 mm, particularly preferably 20 to 60 mm. Further, the thickness of the inner layer 1 is preferably 0.5 to 20 mm, particularly preferably 2 to 4 mm, and the thickness of the outer layer 2 is preferably 0.5 to 5 mm, particularly preferably 1 to 3 mm.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, prior to the examples and comparative examples, the following materials were prepared.

<< Preparation of acrylic rubber composition >>
The components shown in Table 1 below were blended in the proportions shown in the same table, and these were kneaded using a Banbury mixer or kneader to prepare an acrylic rubber composition.

[Acrylic rubber (component a)]
Nipol AR31 manufactured by Nippon Zeon

[Carbon black (i) (component b)]
Show Black N110 (nitrogen adsorption specific surface area: 135 × 10 ³ m ² / kg, OH amount: 0.59 meq./g) manufactured by Cabot Japan

[Carbon black (ii) (component b)]
Show black N220 (nitrogen adsorption specific surface area: 122 × 10 ³ m ² / kg, OH amount: 0.61 meq./g) manufactured by Cabot Japan

[Carbon black (iii) (component b)]
Show black N330 (nitrogen adsorption specific surface area: 76 × 10 ³ m ² / kg, OH amount: 0.55 meq./g) manufactured by Cabot Japan

[Carbon black (iv) (component b)]
SEAST SO (Nitrogen adsorption specific surface area: 35 × 10 ³ m ² / kg, OH amount: 0.31 meq./g), manufactured by Tokai Carbon Co., Ltd.

[Carbon black (v) (component b)]
Toast Carbon Co., Ltd., Seast S (Nitrogen adsorption specific surface area: 23 × 10 ³ m ² / kg, OH amount: 0.18 meq./g)

[Carbon black (vi) (component b)]
Thermax N990 manufactured by Cancarb, Inc. (nitrogen adsorption specific surface area: 7 × 10 ³ m ² / kg, OH amount: 0.1 meq./g)

[Processing aid (stearic acid)]
Made by Nippon Oil & Fats Co., Ltd. Beads stearic acid sakura

[Plasticizer]
Asahi Denka Kogyo Co., Ltd., Adeka Sizer RS735

[Anti-aging agent]
Made by Crompton, Nowguard 445

[Amine-based crosslinking agent]
Made by Ouchi Shinsei Chemical, Balnock AB

<< Preparation of ethylene-propylene rubber composition >>
The components shown in Table 2 below were blended in the proportions shown in the table, and kneaded using a Banbury mixer and an open roll to prepare an ethylene-propylene rubber composition.

[EPDM (component A)]
Esprene 505 manufactured by Sumitomo Chemical Co., Ltd.

[EPM (component A)]
Esplen 201 manufactured by Sumitomo Chemical Co., Ltd.

[Vulcanization aid]
Zinc oxide (Mitsui Mining & Mining, 2 types of zinc oxide)

[Vulcanization aid (stearic acid)]
Made by Nippon Oil & Fats Co., Ltd. Beads stearic acid sakura

〔Carbon black〕
SRF grade carbon black (manufactured by Cabot Japan, Show Black IP-200)

[Paraffinic oil]
Sunflex 2280, manufactured by Nippon Oil Corporation

[Anti-aging agent]
Nouchi MB, manufactured by Ouchi Shinsei Chemical Co., Ltd.

[Vulcanization accelerator (i)]
Made by Sanshin Chemical Industry Co., Ltd., Sunseller TT-G

(Vulcanization accelerator (ii))
Sunseller TET-G, manufactured by Sanshin Chemical Industry Co., Ltd.

[Vulcanization accelerator (iii)]
Sunseller CZ-G, manufactured by Sanshin Chemical Industry Co., Ltd.

(Vulcanization accelerator (iv))
Nouchira BZ-G made by Ouchi Shinsei Chemical Co., Ltd.

[Crosslinking agent (component B)]
Sulfur (Tsurumi Chemical Industry Co., Ltd., Sulfax T-10)

[Peroxide crosslinking agent (component B)]
Park Mill D40, manufactured by Nippon Oil & Fats Co., Ltd.

[Co-crosslinking agent]
TAIC (Nippon Kasei Co., Ltd.)

Moreover, the following were prepared as an adhesive agent for adhering the inner layer made of the acrylic rubber composition and the outer layer made of the ethylene-propylene rubber composition.
<< Silane adhesive (for Examples) >>
Road Far East, Chemlock AP-133
<< Polyolefin adhesive (for comparative example) >>
Lord Far East, Chemlock 6100

[Example 1]
An acrylic rubber composition (inner layer material) and an ethylene-propylene rubber composition (outer layer material) are laminated in the combinations shown in Table 3 below, and both layers are bonded using a silane adhesive, A heat-resistant air hose was produced. That is, an acrylic rubber composition (inner layer material) was extruded on a mandrel, and a silane adhesive was applied thereon by coating. Next, an ethylene-propylene rubber composition (outer layer material) is extruded on the surface, heated at 160 ° C. for 1 hour, and further subjected to secondary vulcanization in an oven at 150 ° C. for 8 hours, A heat-resistant air hose (inner diameter 12 mm, outer diameter 22 mm) in which an outer layer (thickness 2 mm) was formed on the outer peripheral surface of the inner layer (thickness 3 mm) was produced.

[Examples 2 to 10, Comparative Examples 1 and 2]
Except for changing the combination of the acrylic rubber composition (inner layer material) and the ethylene-propylene rubber composition (outer layer material) to the combinations shown in Tables 3 and 4 below, the same procedure as in Example 1 was performed. A heat-resistant air hose was produced. In Comparative Example 1, no adhesive was used, and in Comparative Example 2, a polyolefin adhesive was used instead of the silane adhesive.

  Using the heat-resistant air hoses of the examples and comparative examples thus obtained, each characteristic was evaluated according to the following criteria. These results are shown in Tables 3 and 4 above.

〔Heat-resistant〕
A JIS No. 5 dumbbell collected from the inner surface of each hose after aging at 170 ° C. × 600 hours was prepared, and the elongation at break (EB) was evaluated according to JIS K 6251.
<Evaluation>
○: Elongation is 200% or more Δ: Elongation is 100% or more and less than 200% ×: Elongation is less than 100%

(Interlayer adhesion)
From each heat-resistant hose, a test piece having a thickness of 3 mm (inner layer thickness 1.5 mm, outer layer thickness 1.5 mm) and width 25.4 mm was cut out, and the inner layer of the test piece was subjected to a tensile tester (JIS B 7721) Then, the film was peeled off at a speed of 50 mm per minute, and the interlayer adhesion (N / mm) at that time was measured.
<Evaluation>
○: 2.4 N / mm or more Δ: 2.0 N / mm or more and smaller than 2.4 N / mm ×: smaller than 2.0 N / mm

  From the results of Table 3 above, all of the example products were excellent in heat resistance and interlayer adhesion.

On the other hand, since Comparative Example 1 did not use an adhesive, the interlayer adhesion was inferior.
Moreover, since the comparative example 2 was using the polyolefin adhesive instead of the silane adhesive, the interlayer adhesiveness was inferior.

  The heat-resistant air hose of the present invention can be used for all hoses requiring heat resistance, but is suitably used as an air hose for automobiles through which high-temperature air flows such as a turbo air hose (supercharger air hose). However, the present invention is not limited to the air-based high heat-resistant hose of a transport device such as an automobile, and can be used for a transport device such as a tractor, a cultivator, or a ship.

1 Inner layer 2 Outer layer 3 Reinforcement yarn layer

Claims (5)

A heat-resistant air hose provided with an inner layer and an outer layer formed on the outer periphery thereof, the inner layer using an acrylic rubber composition containing the following components (a) and (b), and the outer layer: A heat-resistant air hose comprising an ethylene-propylene rubber composition containing the components (A) and (B), wherein an inner layer and an outer layer are bonded using a silane-based adhesive.
(A) Acrylic rubber.
(B) Carbon black having a hydroxyl group on the surface.
(A) Ethylene-propylene rubber.
(B) Crosslinking agent. ^2. The heat resistant air hose according to claim 1, wherein the component (b) has a nitrogen adsorption specific surface area of 35 × 10 ^{3 to} 125 × 10 ³ m ² / kg.   The heat-resistant air hose according to claim 1 or 2, wherein the content of the component (b) is 30 to 80 parts by weight with respect to 100 parts by weight of the component (a).   The heat-resistant air hose according to any one of claims 1 to 3, further comprising a reinforcing yarn layer at an interface between the inner layer and the outer layer.   The heat-resistant air hose according to any one of claims 1 to 4, wherein the heat-resistant air hose is an automotive air hose.

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