JP5533745B2 - Refrigerant transport hose - Google Patents

Description

  The present invention relates to a refrigerant transport hose used in a vehicle air conditioner or the like.

  Refrigerant transport hoses used in various refrigeration cycle pipes such as vehicle air conditioners and indoor air conditioners generally have a multilayer structure in which a fiber reinforcing layer is interposed between a tubular rubber inner layer and a rubber outer layer. The refrigerant transport hose is required to have excellent refrigerant permeation resistance due to the problem of ozone destruction caused by the chlorofluorocarbon refrigerant and the problem of the performance of the refrigeration cycle that requires no refrigerant replenishment for several years.

  As a refrigerant, a relatively high-molecular-weight fluorocarbon refrigerant (for example, R134a) has been targeted, but recently, a fluorocarbon refrigerant R1234yf having a remarkably small global warming potential (GWP) compared to the existing fluorocarbons and the like. Is attracting attention.

  As a refrigerant transport hose having refrigerant permeation resistance, for example, a hose in which polyamide such as nylon 6 or nylon 66 is used for the inner layer and polyolefin polymer is used for the intermediate layer (for example, see Patent Document 1) is proposed. Has been. Further, the EVOH thin film layer is provided with a low water-permeable layer made of rubber that is one of butyl rubber, ethylene-propylene-diene copolymer rubber, or chlorinated polyethylene, on the outer peripheral side of the EVOH thin film layer, and the EVOH thin film layer A hose (see, for example, Patent Document 2) provided with a polyamide resin layer adjacent to both the inside and outside of this has been proposed. In addition, a hose (see, for example, Patent Document 3) that significantly prevents hydrolysis degradation of polyamide by using a copolymer of methylpentene as a resin for an inner layer has been proposed.

JP 60-91082 A Japanese Patent No. 3905225 JP 2010-184403 A

  The refrigerant transport hose described in Patent Documents 1 to 3 having a polyamide tubular layer on the inside is excellent in refrigerant permeation resistance. It became clear that there was.

  That is, in the refrigeration cycle of the vehicle air conditioner using R1234yf described above as the refrigerant, when the temperature in the engine room increases as the vehicle travels, R1234yf decomposes to generate hydrofluoric acid, and both oxidation degradation and hydrolysis degradation occur. This causes the polyamide to deteriorate. As a result, it has been found that the refrigerant permeation resistance of the refrigerant transport hose decreases, and in the worst case, cracks occur. In addition, since the refrigerant transport hose is required to have high refrigerant permeability, there is a problem in that the refrigerant permeability is lowered even if the resin does not reach the crack.

  On the other hand, the present inventor studied a technique for suppressing deterioration by adding an anti-degradation agent such as an antioxidant to the resin of the inner layer of the hose. However, in this method, the adhesion between the resin of the inner layer of the hose and the intermediate rubber layer is lowered, and the inner layer of the hose may be peeled off during use to cause cracks.

In view of the above points, the present invention is a refrigerant transport hose comprising a tubular gas poorly permeable layer and a rubber layer covering the surface of the gas hardly permeable layer, and using R1234yf as a refrigerant. It is an object of the present invention to provide a refrigerant transport hose capable of improving the refrigerant permeation resistance while ensuring adhesion with a rubber layer.

In order to achieve the above object, according to the first aspect of the present invention, the gas-impermeable layer (1) includes a layer (11) composed of a polyamide containing an organic antioxidant and an organic antioxidant. It is formed of two layers with a layer (12) composed of polyamide that does not contain an agent, and the organic layer (11) composed of polyamide that contains an organic antioxidant is in contact with the refrigerant. The layer (12) made of polyamide not containing an organic antioxidant and disposed on the inner side of the layer (12) made of polyamide containing no antioxidant is adhered to the rubber layer (2). It is characterized by having.

When the fluorocarbon refrigerant R1234yf is decomposed, hydrofluoric acid is generated. For this reason, the innermost layer of the refrigerant transport hose using R1234yf as the refrigerant is a layer (11) composed of polyamide containing an organic antioxidant, so that R1234yf is decomposed to generate hydrofluoric acid. Since the oxidative degradation and hydrolysis degradation of the polyamide can be suppressed, the refrigerant permeation resistance can be improved.

Meanwhile, according to the experimental study of the present inventors, organic antioxidants, were found to inhibit adhesion between rubber layer (2). For this reason, the layer (12) composed of polyamide containing no organic antioxidant is provided outside the layer (11) composed of polyamide containing the organic antioxidant which is the innermost layer. in, rubber adhesion surface between the rubber layer (2), it is possible to arrange the layer formed (12) in the polyamide containing no antioxidant organic, gas-impermeable layer (1) Adhesion with the film layer (2) can be ensured.

Therefore, while ensuring the adhesion of the gas-impermeable layer (1) rubber layer (2), it is possible to improve the resistance to refrigerant permeation.

Further, as in the invention according to claim 2 , in the refrigerant transport hose according to claim 1 , the organic antioxidant comprises at least one of a phenol compound, a phosphorus compound, and a sulfur compound. Also good.

  By the way, the melting point of an organic antioxidant is generally lower than that of polyamide. For this reason, when extruding the layer (11) composed of a polyamide containing an organic antioxidant, the organic antioxidant is liquefied and becomes oily. If this oily antioxidant is located on the screw surface of the extruder, the screw is idle and the polyamide is difficult to be extruded, so that the moldability may be deteriorated.

On the other hand, according to the experimental study by the present inventor, as in the invention according to claim 3 , in the refrigerant transport hose according to claim 1 or 2 , the content of the organic antioxidant is changed to polyamide. By setting the weight ratio to 0 to greater than 0% and not more than 5%, the refrigerant permeation resistance can be improved while ensuring good moldability.

Further, as in the invention according to claim 4 , in the refrigerant transport hose according to any one of claims 1 to 3 , the polyamide may be nylon 6.

The invention according to claim 5 is characterized in that in the refrigerant transport hose according to any one of claims 1 to 4 , the polyamide contains polyolefin.

In this way, rubber elasticity can be imparted to the gas permeable layer (1) by incorporating polyolefin into the polyamide constituting the gas permeable layer (1). For this reason, it becomes possible to improve the flexibility and softness of the refrigerant transport hose.

According to a sixth aspect of the present invention, in the refrigerant transport hose according to the fifth aspect , the polyolefin is made of polypropylene or a copolymer of polypropylene and polyethylene. According to this, it becomes possible to improve the stability with respect to the refrigerant.

  By the way, since polyolefin has high refrigerant permeability, the higher the content of polyolefin with respect to polyamide, the more flexible and flexible as a refrigerant transport hose, but there is a problem that the refrigerant permeability resistance decreases. .

On the other hand, according to the present inventors' experimental study, as in the invention described in claim 7 , in the refrigerant transport hose according to claim 5 or 6 , the polyolefin content is expressed in a weight ratio with respect to the polyamide. By making it larger than 0% and not more than 40%, it is possible to improve flexibility and flexibility as a refrigerant transport hose while suppressing a decrease in refrigerant permeation resistance to a practically usable range.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a partial abbreviation perspective view showing the hose for refrigerant transportation concerning the embodiment of the present invention. It is an axial sectional view showing a refrigerant transportation hose concerning an embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the present embodiment, the refrigerant transport hose of the present invention is applied to piping constituting the refrigeration cycle of the vehicle air conditioner. Note that the refrigerant transport hose of the present invention is not limited to a vehicle air conditioner and can be applied to piping of various refrigeration cycles such as an indoor air conditioner.

  FIG. 1 is a partially omitted perspective view showing a refrigerant transport hose according to an embodiment of the present invention, and FIG. 2 is an axial sectional view showing the refrigerant transport hose according to an embodiment of the present invention.

  As shown in FIGS. 1 and 2, the refrigerant transport hose has a tubular inner layer 1 as a gas hardly permeable layer, a tubular intermediate rubber layer 2 covering the surface of the interior 1, and a surface of the intermediate rubber layer 2. It is composed of a tubular fiber reinforcing layer 3 that covers and a tubular outer rubber layer 4 that covers the surface of the reinforcing layer 3. The inner layer 1 is composed of a layer composed of a polyamide (PA) containing an organic antioxidant (hereinafter referred to as an antioxidant-containing PA layer 11) and a polyamide not containing an organic antioxidant. It is composed of two layers including a layer (hereinafter referred to as an antioxidant-free PA layer 12).

  The antioxidant-containing PA layer 11 is disposed on the inner side than the antioxidant-free PA layer 12. That is, the antioxidant-containing PA layer 11 is disposed on the innermost side of the refrigerant transport hose.

  Preferable examples of the polyamide constituting the inner layer 1 include nylon 6, nylon 66, nylon 11, nylon 12 and the like. These polyamides may contain polyolefin. By containing polyolefin in the polyamide, rubber elasticity can be imparted to the inner layer 1, so that the flexibility and flexibility of the refrigerant transport hose can be improved.

  By the way, since polyolefin has high refrigerant permeability, the higher the content of polyolefin with respect to polyamide, the better the flexibility and flexibility as a refrigerant transport hose, but the lower the refrigerant permeability resistance. For this reason, the content of the polyolefin contained in the polyamide is preferably in the range of more than 0% and 40% or less in terms of the weight ratio to the polyamide. According to this, it is possible to improve flexibility and flexibility as the refrigerant transport hose while suppressing the decrease in the refrigerant permeation resistance to a practical range.

  Examples of the polyolefin include ethylene / butene copolymer, EPR (ethylene-propylene copolymer), modified ethylene / butene copolymer, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene). -Propylene-diene terpolymer), ionomer, α-olefin copolymer, modified IR (isoprene rubber), modified SEBS (styrene-ethylene-butylene-styrene copolymer), halogenated isobutylene-paramethylstyrene copolymer Examples thereof include a polymer, an ethylene-acrylic acid-modified product, an ethylene-vinyl acetate copolymer, an acid-modified product thereof, and a mixture containing these as a main component. These may be used alone or in combination of two or more. As the elastomer, polyolefins such as ethylene / butene copolymer, EPR (ethylene-propylene copolymer), and modified ethylene / butene copolymer are preferable. Elastomers, especially those modified with acid anhydrides such as maleic anhydride, alkyl acrylate esters such as glycidyl methacrylate, epoxies and modified products thereof, are fine particles based on ethylene / vinyl alcohol copolymers. An alloy structure can be obtained, which is preferable.

  The total thickness of the polyamide resin layer, that is, the inner layer 1 (antioxidant-containing PA layer 11 and antioxidant-free PA layer 12) is preferably 20 to 500 μm, particularly preferably 50 to 200 μm.

  As the organic oxidative degradation agent added to the antioxidant-containing PA layer 11, phenol-based, phosphorus-based, and sulfur-based compounds can be used. These may be used alone or in combination. Representative phenolic compounds include Sumilizer BHT (manufactured by Sumitomo Chemical Co., Ltd.), Irganox 1076 (manufactured by Ciba Geigy Japan), Irganox 1010 (manufactured by Ciba Geigy Japan), and Irganox 3114 (manufactured by Ciba Geigy Japan). ), Adeka Stub AO-40 (manufactured by Adeka Co., Ltd.), Irganox 245 (manufactured by Ciba Geigy Japan), and Adeka Stub AO-80 (manufactured by Adeka Co., Ltd.).

  By the way, the melting point of an organic antioxidant is generally lower than that of polyamide. For this reason, when the antioxidant-containing PA layer 11 is extrusion-molded, the organic antioxidant is liquefied and becomes oily. And when this oil-like antioxidant is located on the screw surface of an extrusion molding machine, since a screw will idle | coil and polyamide will become difficult to be extruded, there exists a possibility that a moldability may deteriorate.

  Therefore, the content ratio of the organic antioxidant is preferably in the range of more than 0% and not more than 5% by weight ratio to the polyamide. Thereby, the refrigerant permeation resistance can be improved while ensuring good moldability.

  The antioxidant-free PA layer 12 may include an inorganic material anti-aging agent. Examples of the anti-aging agent include potassium iodide and copper iodide.

  Examples of the rubber material of the intermediate rubber layer 2 include butyl bromide rubber, butyl rubber (IIR), chlorinated butyl rubber (C1-IIR), chlorinated polyethylene, chlorosulfonated polyethylene, brominated butyl rubber (Br-IIR), isobutylene- Bromoparamethylstyrene copolymer, EPR (ethylene-propylene copolymer), EPDM (ethylene-propylene-diene terpolymer), NBR (acrylonitrile butadiene rubber), CR (chloroprene rubber), hydrogenated NBR, acrylic Examples thereof include rubbers, blends of two or more of these rubbers, or blends with polymers mainly composed of these rubbers, preferably butyl rubbers and EPDM rubbers. In addition to the rubber material, the intermediate rubber layer 2 can be applied with a compounding formulation such as a commonly used filler, processing aid, anti-aging agent, vulcanizing agent, and vulcanization accelerator. The thickness of the intermediate rubber layer 2 is preferably 0.5 to 5 μm, particularly preferably 0.5 to 3 mm.

  For bonding the inner layer 1 (specifically, the antioxidant-free PA layer 12) and the intermediate rubber layer 2, an adhesive or an adhesive rubber is used. Alternatively, the adhesion can be strengthened through one or more layers of rubber, ionomer resin, thermoplastic elastomer, or thermoplastic resin. As the adhesive, any vulcanized adhesive for rubber, such as a chlorinated rubber adhesive, a hydrochloric acid rubber adhesive, a phenol resin adhesive, and an isocyanate adhesive, can be used. In this embodiment, it is preferable to use an adhesive. Specific examples of the material include Sunbond VP-9420 (manufactured by S & S Japan Co., Ltd.). When an adhesive is used, the thickness is generally 5 to 100 μm, and particularly preferably 5 to 30 μm.

  In the refrigerant transport hose of the present embodiment, the reinforcing layer 3 and the outer rubber layer 4 can be provided outside the intermediate rubber layer 2, thereby further improving the pressure resistance and heat resistance of the hose.

  The reinforcing layer 3 is provided on the outer side of the intermediate rubber layer 2 and is generally configured to withstand the pressure generated by the chlorofluorocarbon gas and carbon dioxide medium flowing in the hose. Examples of the material used for the reinforcing layer 3 that has excellent pressure resistance and does not hinder the flexibility of the hose include organic fibers made of vinylon, polyester, nylon, aramid, and the like. The thickness of these fibers is preferably 600d (denier) to 6000d.

  The reinforcing layer 3 is formed by winding or braiding the intermediate rubber layer 2 in a desired shape such as a spiral shape or a blade shape to a necessary thickness. In addition, you may comprise this reinforcement layer 3 in the multilayer for the purpose of improving pressure | voltage resistance further.

  In this embodiment, when the reinforcing layer 3 has a wound (spiral) structure, the density (one side) is preferably 75% or more. Moreover, when the reinforcement layer 3 has a partial assembly (blade) structure, it is preferable that the density is 90% or more. Thereby, it becomes easy to satisfy the high pressure resistance required when carbon dioxide is used as the refrigerant.

  In the case of a spiral structure, the density is 100% when the surface of the intermediate rubber layer 2 is completely covered with one reinforcing layer 3 in one direction on one side, and is defined for each side. When it is completely covered with two reinforcing layers 3 on both sides (the direction opposite to one direction), it becomes 100% respectively. The wound (spiral) structure preferably has both sides (one direction and the opposite direction).

  The density of the uneven structure (blade) structure is 100% when the surface of the intermediate rubber layer 2 is completely covered with one reinforcing layer 3 and 200% when the surface is completely covered with two reinforcing layers 3. Is defined as For example, it is 50% when the intermediate rubber layer 2 is halved with one reinforcing layer 3 and 100% when the intermediate rubber layer 2 is halved with two reinforcing layers 3.

  The thickness of the reinforcing layer 3 is preferably 0.5 to 3 mm, particularly preferably 0.5 to 2 mm.

  The outer rubber layer 4 is provided on the outer side of the reinforcing layer 3 for the purpose of preventing the reinforcing layer 3 from being scattered and improving the environmental resistance required depending on the installation location of the hose, such as weather resistance and heat resistance. The rubber material constituting the outer rubber layer 4 is preferably a rubber material that meets such a purpose and does not impair the flexibility of the entire hose. Examples of such a rubber material include butyl rubber (IIR), chlorinated butyl rubber (C1-IIR), chlorinated polyethylene, chlorosulfonated polyethylene, brominated butyl rubber (Br-IIR), isobutylene-bromoparamethylstyrene copolymer Polymer, EPR (ethylene-propylene copolymer), EPDM (ethylene-propylene-diene terpolymer), NBR (acrylonitrile butadiene rubber), CR (chloroprene rubber), hydrogenated NBR, acrylic rubber, ethylene alkyl acrylate Copolymers, acrylic resins, blends of two or more of these rubbers, or blends with polymers based on these rubbers, preferably butyl rubbers and EPDM rubbers. Acrylic rubber and acrylic resin are preferred. The acrylic rubber is preferably a copolymer of ethyl acrylate and / or butyl acrylate (preferably ethyl acrylate) and another monomer (preferably 2-chloroethyl vinyl ether or methyl vinyl ketone). The acrylic resin is preferably a copolymer of ethyl acrylate and another (meth) acrylate or ethylene. For vulcanization of acrylic rubber, ethyltetramine and tetraethylenetetramine are generally used.

  For the outer rubber layer 4, in addition to the material for rubber, a compounding formulation such as a filler, a processing aid, an anti-aging agent, a vulcanizing agent, and a vulcanization accelerator, which are usually used, can be applied. The thickness of the outer rubber layer 4 is preferably 0.5 to 5 mm, particularly preferably 0.5 to 3 mm, from the viewpoint of balance between strength and flexibility.

  If necessary, an adhesive or an adhesive rubber may be used between the layers, or the adhesion may be strengthened through one or more layers of rubber, ionomer resin, thermoplastic elastomer, or thermoplastic resin. As the adhesive, any vulcanized adhesive for rubber, such as a chlorinated rubber adhesive, a hydrochloric acid rubber adhesive, a phenol resin adhesive, and an isocyanate adhesive, can be used. In this embodiment, it is preferable to use an adhesive. When an adhesive is used, the thickness is generally 5 to 100 μm, and particularly preferably 5 to 30 μm.

  Various commercially available compounds can be used as the crosslinking agent for crosslinking (vulcanizing) the outer rubber layer 4. Sulfur-based crosslinking agents include powdered sulfur, highly dispersible sulfur, insoluble sulfur, etc., which are generally used as rubber crosslinking agents, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram mono Sulfides, thiurams such as dipentamethylene thiuram tetrasulfide, pipemidine dipentamethylenedithiocarbamate, pipecolline dipecarbyl dithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, N-ethyl-N-phenyl Zinc dithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, sodium dimethyldithiocarbamate, diethyldithiocarbamate Dithiocarbamates such as sodium phosphate, sodium dibutyldithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, tellurium diethyldithiocarbamate, xanthates such as zinc butylxanthate, zinc isopropylxanthate, sodium isopropylxanthate N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N, N-diisopropyl-2-benzothiazole Examples thereof include sulfenamides such as sulfenamide, and thiazoles such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide. The amount of the sulfur-based crosslinking agent used is preferably 0.5 to 4.0% by mass, particularly 1.0 to 2.5% by mass with respect to the rubber material.

The outer rubber layer 4 may contain carbon black. For example, SAF, ISAF, HAF, FEF, GPF, SRF (rubber furnace) and MT carbon black (pyrolytic carbon), which are carbon black standard varieties, can be mentioned. It is generally used in an amount of 0.1 to 80% by weight, preferably 0.1 to 70% by weight, based on the rubber material.
The high-pressure hose for transporting refrigerant of the present invention can be manufactured by a known method. For example, an inner layer material containing polyamide that can be produced as follows is extruded onto a highly rigid mandrel provided at the tip of an extruder to form the inner layer 1. Alternatively, the inner layer material and the intermediate rubber layer material are coextruded on a highly rigid mandrel provided at the tip of the coextrusion machine to form a laminate of the inner layer 1 and the intermediate rubber layer 2. Next, on the intermediate rubber layer 2, for example, 20 aramid fibers (yarns) of 4000 d (denier) are spiraled by a spiral knitting machine, and the same number of PET yarns are spiraled in the opposite direction to form the reinforcing layer 3. To complete. Thereafter, the outer rubber layer 4 is formed on the surface of the reinforcing layer 3 by an extruder, and then vulcanized under appropriate conditions, and the mandrel is extracted to obtain a refrigerant transport hose. The vulcanization conditions in this case are generally 130 to 180 ° C. and 60 to 120 minutes.

  Hereinafter, the present invention will be described in detail by way of examples. The present invention is not limited to the examples.

Example 1
1 wt% of nylon 6 (manufactured by Ube Industries, trade name: UBE nylon 1030B) as polyamide, and phenolic antioxidant (trade name: Adeka Stub AO-80, manufactured by Adeka Co., Ltd.) as an organic antioxidant The added antioxidant-containing PA layer-forming composition was extruded at 230 ° C. using an extruder and coated on a mandrel to form an antioxidant-containing PA layer 11 (thickness 75 μm).

  Next, nylon 6 (manufactured by Ube Industries, Ltd., trade name: UBE nylon 1030B) as a polyamide is extruded at 230 ° C. using an extruder, coated on a mandrel, and an antioxidant-free PA layer 12 (thickness) 75 μm) was formed.

Thereafter, a rubber-based adhesive (manufactured by S & S Japan Co., Ltd., trade name: Sunbond VP-500, viscosity: 0.8 Pa · s) is applied, and the intermediate rubber layer forming composition is used at 80 ° C. using an extruder. Extruded and coated on antioxidant-free PA layer 12 on a mandrel. The intermediate rubber has the following composition.
(Formulation of intermediate rubber layer forming composition)
Chlorinated butyl rubber 100 parts by weight FEF carbon 65 parts by weight Stearic acid 1 part by weight Paraffin oil 10 parts by weight Zinc white 5 parts by weight Sulfur 2 parts by weight Accelerator TT 1 part by weight Subsequently, 1100 dtex / 4 and 10 times / 10 cm Twenty-two aramid reinforcing yarns were aligned and wound in a spiral shape (density: 85.9% on both sides) to form a reinforcing layer 3. Thereafter, the following composition for forming the outer rubber layer was extruded to a thickness of 1.3 mm on the reinforcing layer 3 and vulcanized at 150 ° C. for 45 minutes to form the outer rubber layer 4. As a result, a refrigerant transport hose having an inner diameter of 11 mm and an outer diameter of 19 mm was obtained.
(Formulation of composition for forming outer rubber layer)
Ethylene / acrylate copolymer 100 parts by mass FEF carbon 100 parts by mass Stearic acid 1 part by mass Paraffin oil 70 parts by mass Zinc white 5 parts by mass Dicumyl peroxide (40% content) 10 parts by mass (Example 2)
The phenolic antioxidant (trade name: Adeka Stub AO-80 manufactured by Adeka Co., Ltd., trade name: Adeka Stub AO-80, manufactured by Adeka Co., Ltd.) was used instead of 1 wt% of the phenolic antioxidant (trade name: Adeka Stub AO-80 manufactured by Adeka Co., Ltd.). ) An antioxidant using 0.5 wt% in combination with 0.5 wt% of a phosphorus-based antioxidant (Adeka Co., Ltd., trade name: ADK STAB PEP36) was used.

(Example 3)
The phenolic antioxidant (trade name: Adeka Stub AO-80 manufactured by Adeka Co., Ltd., trade name: Adeka Stub AO-80, manufactured by Adeka Co., Ltd.) was used instead of 1 wt% of the phenolic antioxidant (trade name: Adeka Stub AO-80 manufactured by Adeka Co., Ltd.). ) 0.5 wt% and phosphorus-based antioxidant (Adeka Co., Ltd., trade name: Adeka Stub PEP36) 0.5 wt% and sulfur-based antioxidant (Adeka Co., Ltd., trade name: Adeka Stub AO-412S) 0 An antioxidant combined with 5 wt% was used.

Example 4
Instead of nylon 6 of Example 1 (product name: UBE nylon 1030B, manufactured by Ube Industries, Ltd.), nylon 6 containing polyolefin (product name: Zytel (registered trademark) ST811HS, manufactured by DuPont) is used as polyamide. It was.

(Comparative Example 1)
A refrigerant transport hose was obtained in the same manner as in Example 1 except that the antioxidant-free PA layer 12 was not provided on the inner layer 1, that is, only the antioxidant-containing PA layer 11 was provided as the inner layer 1.

  Specifically, nylon 6 (manufactured by Ube Industries, trade name: UBE nylon 1030B) as a polyamide, and phenolic antioxidant (trade name: Adeka Stub AO-manufactured by Adeka Corporation) as an organic antioxidant. The composition for forming an inner layer to which 1 wt% of 80) was added was extruded at 230 ° C. using an extruder and coated on a mandrel to form an inner layer 1 (thickness 150 μm).

  Then, a rubber adhesive (manufactured by S & S Japan Co., Ltd., trade name: Sunbond VP-500, viscosity: 0.8 Pa · s) is directly applied on the inner layer 1. Subsequently, the same intermediate rubber layer-forming composition as in Example 1 was extruded at 80 ° C. using an extruder and coated on the inner layer 1 on the mandrel. Thereafter, the reinforcing layer 3 and the outer rubber layer 4 were formed in the same manner as in Example 1.

(Comparative Example 2)
A refrigerant transport hose was obtained in the same manner as in Example 1 except that the antioxidant layer-containing PA layer 11 was not provided on the inner layer 1, that is, only the antioxidant-free PA layer 12 was provided as the inner layer 1.

  Specifically, a composition for forming an inner layer made of nylon 6 (trade name: UBE nylon 1030B, manufactured by Ube Industries, Ltd.) as a polyamide is extruded at 230 ° C. using an extruder, coated on a mandrel, and the inner layer 1 (Thickness 150 μm) was formed. A rubber-based adhesive rubber-based adhesive (manufactured by S & S Japan Co., Ltd., trade name: Sunbond VP-500, viscosity: 0.8 Pa · s) was directly applied thereon. Thereafter, the same composition for forming an intermediate rubber layer as in Example 1 was extruded at 80 ° C. using an extruder and coated on the inner layer 1 on the mandrel. Thereafter, a reinforcing layer and an outer rubber layer were formed in the same manner as in Example 1.

(Durability evaluation)
The refrigerant transport hoses obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were installed in a test apparatus simulating a vehicle air conditioner system, and durability was evaluated. 800 g of R1234yf (manufactured by DuPont) as a refrigerant and 100 g of ND12 (manufactured by Idemitsu Kosan Co., Ltd.) as an oil were sealed, and a system durability test was performed at 150 ° C. for 200 hours. Thereafter, the refrigerant transport hose was taken out from the system, and 3% strain was applied at room temperature, and the two-dimensional amplitude test was performed 1 million times. Thereafter, it was confirmed by visual inspection whether or not cracks occurred in the hose inner surface resin. The results are shown in Table 1.

  As shown in Table 1, in the refrigerant transport hose of Examples 1 to 4, no crack was found in the hose inner surface resin. On the other hand, in the refrigerant transport hoses of Comparative Examples 1 and 2, cracks were observed in the resin on the inner surface of the hose. In particular, in the refrigerant transport hose of Comparative Example 1, peeling between the inner layer 1 and the intermediate rubber layer 2 was observed at a crack occurrence location.

  Subsequently, in the refrigerant transport hose after the system durability test, the weight average molecular weight of the resin constituting the inner layer 1 was evaluated using GPC (gel permeation chromatography) (discharge solvent: HFIP). The results are shown in Table 1 above.

  As shown in Table 1, in the refrigerant transport hoses of Examples 1 to 4 and Comparative Example 1 in which the inner layer 1 contains an organic antioxidant, the deterioration from the initial value was small. On the other hand, in the refrigerant transport hose of Comparative Example 1 in which the inner layer 1 does not contain an organic antioxidant, the weight average molecular weight of the resin constituting the inner layer 1 after the durability test is about 1/3 of the initial value. The deterioration was great.

(Peel test)
For the refrigerant transport hose of Example 1 and Comparative Example 1, the peel strength was measured. Specifically, the peel strength of the test pieces made of the materials of Example 1 and Comparative Example 1 was measured.

  More specifically, a rubber adhesive similar to that in Example 1 is applied on a piece made of the same composition for forming an intermediate rubber as in Example 1, and the inner layer forming similar to that in Example 1 is applied to the surface. Glue the film composed of two layers of the composition, ie nylon 6 as in Example 1 (no antioxidant added) and nylon 6 with 1 wt% phenolic antioxidant as in Example 1 Then, a test piece of Example 1 was prepared.

  The test piece of Example 1 is laminated in the order of a composition for forming an intermediate rubber, a rubber adhesive, nylon 6 to which no antioxidant is added, and nylon 6 to which an antioxidant is added. In addition, the thickness of the film which consists of two layers of nylon 6 which added antioxidant and the nylon 6 which added antioxidant is 150 micrometers.

  Moreover, on the piece which consists of the composition for intermediate rubber formation similar to the comparative example 1, the rubber adhesive similar to the comparative example 1 is apply | coated, The composition for inner layer formation similar to the comparative example 1 on the surface, That is, a 150 μm-thick film made of nylon 6 to which 1 wt% of a phenolic antioxidant similar to Comparative Example 1 was added was bonded to prepare a test piece of Comparative Example 1.

  Subsequently, the peel strength of the test pieces of Example 1 and Comparative Example 1 created as described above was measured. The results are shown in Table 1 above.

  As shown in Table 1, the peel strength of the test piece of Example 1 in which the polyamide 6 not added with the antioxidant was arranged on the adhesive surface was 1.3 N / mm, indicating a very high peel strength. . On the other hand, the peel strength of the test piece of Comparative Example 1 in which the polyamide 6 added with the antioxidant is arranged on the adhesive surface is 0.9 N / mm, which is only 70% peel strength with respect to the test piece of Example 1. There wasn't.

  As described above, when the refrigerant that generates hydrofluoric acid by being decomposed by using the antioxidant transporting PA layer 11 as the innermost layer of the refrigerant transport hose, the oxidative degradation of polyamide by hydrofluoric acid is used. Further, since the hydrolysis degradation can be suppressed, the refrigerant permeation resistance can be improved. Further, by providing an antioxidant-free PA layer 12 on the outer side of the antioxidant-containing PA layer 11 which is the innermost layer, a polyamide containing no organic antioxidant on the adhesive surface with the intermediate rubber layer 2 Therefore, the adhesion between the inner layer 1 and the intermediate rubber layer 2 can be ensured. Accordingly, it is possible to improve the refrigerant permeation resistance while ensuring the adhesion between the resin of the inner layer 1 and the intermediate rubber layer 2.

  By the way, the fluorocarbon refrigerant R1234yf generates hydrofluoric acid when decomposed. For this reason, when R1234yf is used as the refrigerant, it is particularly effective to use the antioxidant-containing PA layer 11 as the innermost layer of the refrigerant transport hose.

1 Inner layer 11 Antioxidant-containing PA layer 12 Antioxidant-free PA layer

Claims (7)

Tubular gas-impermeable layer (1), and a rubber layer covering the surface of the gas-impermeable layer (1) (2), a refrigerant transporting hose using R1234yf as a refrigerant,
The gas-impermeable layer (1) includes a layer (11) composed of polyamide containing an organic antioxidant and a layer (12) composed of polyamide not containing an organic antioxidant. Formed from two layers,
The layer (11) composed of polyamide containing the organic antioxidant is disposed inside the layer (12) composed of polyamide not containing the organic antioxidant so as to be in contact with the refrigerant. A refrigerant transport hose characterized in that a layer (12) composed of polyamide that does not contain an organic antioxidant is adhered to the rubber layer (2) . 2. The refrigerant transport hose according to claim 1 , wherein the organic antioxidant comprises at least one of a phenol compound, a phosphorus compound, and a sulfur compound. 3. The refrigerant transport hose according to claim 1, wherein a content ratio of the organic antioxidant is greater than 0% and 5% or less in a weight ratio with respect to the polyamide. The refrigerant transport hose according to any one of claims 1 to 3 , wherein the polyamide is nylon 6. The refrigerant transport hose according to any one of claims 1 to 4 , wherein the polyamide contains a polyolefin. 6. The refrigerant transport hose according to claim 5 , wherein the polyolefin is made of polypropylene or a copolymer of polypropylene and polyethylene. The content of polyolefin, by weight relative to the polyamide, the refrigerant transporting hose according to claim 5 or 6, characterized in that more than 40% greater than 0%.

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