JP2003327750A - Rubber composition for carbon dioxide refrigerant and transport hose for carbon dioxide refrigerant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a carbon dioxide refrigerant that does not foam in contact with carbon dioxide in the supercritical state and is hard to expand shortly after the contact, and a transport hose for the carbon dioxide refrigerant having an inner tube composed of the rubber composition. <P>SOLUTION: This rubber composition for the carbon dioxide refrigerant comprises a blended rubber which contains at least one nonpolar rubber. The composition has a tensile elongation at break (EB) of less than 200% and is used under such a condition as it comes in contact with carbon dioxide in the supercritical state. The transport hose for the carbon dioxide refrigerant has the inner tube composed of the rubber composition. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a carbon dioxide refrigerant which is used under conditions capable of contacting carbon dioxide in a supercritical state, and a carbon dioxide refrigerant having an inner tube made of the rubber composition. Regarding transportation hoses. More specifically, for transporting a carbon dioxide refrigerant having a rubber composition for a carbon dioxide refrigerant that does not foam even when contacted with carbon dioxide in a supercritical state and hardly expands immediately after contact, and an inner tube made of the rubber composition. Regarding the hose.

[0002]

2. Description of the Related Art Freon-based or alternative freon-based refrigerants (for example, R134a) are used as refrigerants for various cooler systems such as automobile coolers and household refrigerators. Global warming of these gases is used. The coefficient is as large as about 3100 times that of carbon dioxide (hereinafter referred to as “CO ₂ ”), and there is concern about its use. In recent years, CO ₂ has been drawing attention as a next-generation refrigerant gas.

Although this CO ₂ refrigerant has a low global warming potential, in its cooler system, CO ₂ reaches a supercritical state during its operation (when the refrigerant is pressurized), and when a conventional rubber hose for refrigerant transportation is used. , Has the following drawbacks. It is known that, when the hose comes into contact with CO ₂ in a supercritical state, the hose inner tube which comes into contact with the hose can undergo a dramatic change such as expansion and foaming in a short time depending on the constituent material of the hose inner tube. ing. When the hose inner pipe undergoes such a change, not only the pressure resistance performance of the hose is greatly impaired, but also the hose pipe line may be reduced or blocked,
The sealing property of the connection part with the hose fitting, which is expected in the hose inner tube, may be impaired.

As a technique for solving these drawbacks, a rubber material comprising a blend material of any one kind or two or more kinds of non-polar rubber and having a tensile breaking elongation (EB) of 200% or more. A hose for a CO ₂ refrigerant, which has a rubber inner tube layer using the rubber material, is described in JP-A-2000-239451. However, the rubber material returns to the original non-expansion state after a lapse of a predetermined time after contact with CO ₂ in a supercritical state, but the expansion coefficient (volume change rate) immediately after the contact with CO ₂ in a supercritical state is released. ) Is as large as 200 to 250%, and a hose using the rubber material may have a hose pipeline contracted or blocked immediately after the generation of CO _{2 in} a supercritical state.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rubber composition for a CO ₂ refrigerant, which does not foam even when contacted with CO ₂ in a supercritical state and hardly expands immediately after contact. Another object of the present invention is to provide a hose for transporting a carbon dioxide refrigerant, which has an inner tube made of the rubber composition, does not foam even when contacted with CO ₂ in a supercritical state, and does not easily expand immediately after contact. .

[0006]

From the above viewpoints, the present inventors diligently studied the effects of CO _{2 in the} supercritical state on various rubbers and their compositions, and as a result, any of non-polar rubbers was selected as the rubber component. By containing one or more blended rubbers and making the rubber composition containing additives and the like have a tensile elongation at break (EB) of less than 200%,
The present invention has been completed by finding that the composition does not foam even when contacted with CO ₂ in a supercritical state and does not easily expand immediately after contact.

That is, 1) The present invention relates to carbon dioxide in a supercritical state, which contains any one kind or two or more kinds of blended rubber of non-polar rubber and has a tensile elongation at break (EB) of less than 200%. Provided is a rubber composition for a carbon dioxide refrigerant, which is used under conditions where it can be contacted.

Here, the non-polar rubber is ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-).
IIR), styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), brominated isobutylene-p-methylstyrene copolymer rubber (BIMS) or isoprene rubber (IR), and EP
M, EPDM, IIR, Cl-IIR, Br-IIR,
BIMS is particularly preferred. The blended rubber can be used without particular limitation as long as it is a combination of non-polar rubbers that are co-crosslinked. In addition, the degree of swelling of the carbon dioxide refrigerant rubber composition under the following conditions is preferably 40% or less. Here, the swelling degree is obtained by immersing the sheet-shaped rubber composition in supercritical carbon dioxide at 120 ° C. and 10 MPa for 24 hours, taking out the rubber at room temperature and normal pressure, and then obtaining the volume change rate.

2) The present invention also provides a carbon dioxide refrigerant transportation hose having an inner tube made of the rubber composition for carbon dioxide refrigerant described in 1). The hose for transporting carbon dioxide refrigerant is a hose comprising at least three layers including an inner pipe, an outer pipe and a reinforcing layer disposed in the middle thereof, and the inner pipe is the rubber composition for carbon dioxide refrigerant according to 1). It is preferably composed of

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The first aspect of the present invention relates to any one of non-polar rubbers or
Contains two or more blended rubbers and has a tensile elongation at break (E
B) is less than 200%, supercritical CO ₂Contact with
CO in a supercritical state when used under possible conditions₂To
Rubber composition for carbon dioxide refrigerant that does not easily swell and foam
(Hereinafter, referred to as “composition of the present invention”). Of the present invention
In the first aspect, any one of non-polar rubber is used as the rubber component.
By containing one or more blended rubbers
And EB of a rubber composition containing additives and the like
When it is less than 00%, the composition is in a supercritical state.
CO₂Does not foam even when contacted with, and does not easily expand immediately after contact
It was found that the present invention has been completed.

The composition of the present invention has a tensile elongation at break (EB) of less than 200%, preferably 195% or less, particularly preferably 190% or less. When it is less than 200%, the composition does not foam even when it comes into contact with CO ₂ in a supercritical state, and is unlikely to expand immediately after the contact. The lower limit of EB is 50% or more, preferably 100% or more, and more preferably 150% or more. When it is 50% or more, the composition does not foam even when it comes into contact with CO ₂ in a supercritical state without impairing the properties (stretchability, etc.) of the rubber, and does not easily expand immediately after contact. The EB of the composition of the present invention can be prepared within the above range by appropriately selecting the type, content (blending amount) and the like of the additives described below.

The degree of swelling of the composition of the present invention under the following conditions is preferably 40% or less, more preferably 35% or less, and particularly preferably 30% or less. Within this range, the composition has a supercritical state of CO
_{Even when} it comes into contact with ₂ , it is difficult to expand immediately after it comes into contact, and it has practicality. Here, the degree of swelling is 24 at 120 ° C. under supercritical carbon dioxide at 10 MPa.
After immersing for a period of time and taking out the rubber at room temperature and atmospheric pressure, the volume change rate is calculated. When the degree of swelling under the above conditions is 40% or less, it can be used without any problems in practical use, and when it exceeds 40%, it is considered that CO _{2 in} a supercritical state is easily permeated (permeated) into the composition. The expansion immediately after contact with CO ₂ in the supercritical state is large, and there is a possibility that the hose conduit may be contracted or blocked.

The rubber component contained in the composition of the present invention is a so-called non-polar rubber (rubber having no polar group in the molecule), or a blend rubber of two or more kinds,
There is no particular limitation. In the composition of the present invention, the non-polar rubber may be used alone or in combination of two or more (blended rubber).
It may be used in combination with other rubbers, if necessary, within a range not impairing the object of the present invention.

Here, the blended rubber is a mixture of two or more non-polar rubbers, and the non-polar rubbers include ethylene-propylene rubber (EPM) and ethylene-propylene-.
Diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (B
r-IIR), styrene-butadiene rubber (SBR),
Butadiene rubber (BR), natural rubber (NR), brominated isobutylene-p-methylstyrene copolymer rubber (BIM
S) and isoprene rubber (IR) are C in a supercritical state.
It is preferably mentioned because swelling with O ₂ is particularly small, and E
PM, EPDM, BIMS, IIR, Cl-IIR, B
r-IIR and BIMS / IIR are particularly preferable in terms of less swelling.

In the rubber composition of the first aspect of the present invention, in addition to the above-mentioned non-polar rubber, additives can be compounded as necessary within the range not impairing the object of the present invention. , For example, fillers such as carbon black and clay, softening agents for paraffin oils (process oils, etc.), vulcanizing agents, vulcanization aids, vulcanization accelerators, plasticizers, processing aids, antioxidants, Examples include pigments, antistatic agents, antioxidants, flame retardants, adhesion aids, polymers and the like.

Examples of the filler include carbon black, silica, clay, talc, calcium carbonate, mica and diatomaceous earth. Of these, carbon black is preferable, and the type thereof is not particularly limited.

Examples of the vulcanizing agent include vulcanizing agents such as sulfur type, organic peroxide type, metal oxide type, phenol resin and quinone dioxime. Examples of sulfur-based vulcanizing agents include powdered sulfur, precipitable sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, and alkylphenol disulfide. Examples of the organic peroxide-based vulcanizing agent include benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,
Examples include 5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethylhexane-2,5-di (peroxylbenzoate). Other examples include magnesium oxide, litharge, p-quinonedioxime, p-dibenzoylquinonedioxime, poly-p-dinitrosobenzene, methylenedianiline and the like.

Examples of the vulcanization accelerators include aldehyde / ammonia-based, guanidine-based, thiourea-based, thiazole-based, sulfenamide-based, thiuram-based, dithiocarbamate-based vulcanization accelerators and the like. Aldehyde / ammonia-based vulcanization accelerators include, for example, hexamethylenetetramine (H); guanidine-based vulcanization accelerators, such as diphenylguanidine; and thiourea-based vulcanization accelerators, such as ethylenethiourea. A thiazole vulcanization accelerator, for example, dibenzothiazyl disulfide (DM), N-cyclohexyl-2-benzothiazolyl sulfenamide (CZ),
2-mercaptobenzothiazole and its Zn salt, etc .;
Examples of thiuram-based vulcanization accelerators include tetramethylthiuram disulfide (TT), dipentamethylene thiuram tetrasulfide, and the like; examples of dithiocarbamate vulcanization accelerators include Na-dimethyldithiocarbamate and Zn-dimethyl. Dithiocarbamate, Te
-Diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyldithiocarbamate and the like, respectively.

As the vulcanization aid, a general rubber aid can be used in combination, and examples thereof include zinc white, stearic acid, oleic acid, and Zn salts thereof.

The content of the above-mentioned vulcanizing agent, vulcanization accelerator and vulcanization aid is 0.1 to 10 relative to 100 parts by weight of the non-polar rubber component.
Parts by mass, preferably 0.5 to 5 parts by mass. Is less than 0.1 part by weight, vulcanization is insufficient, lowering the effective shield (permeability of CO ₂ in the supercritical state nonpolar rubber component three-dimensionally crosslink density is lowered from the CO ₂ in the supercritical state , It is difficult to contact the non-polar rubber component), and the swelling degree of the composition may increase. If it exceeds 10 parts by mass, the three-dimensional crosslink density becomes high, so that the EB is small and the characteristics (stretchability etc.) of the rubber are impaired, and it may not be suitable as a material for the hose.

These vulcanizing agents participate in the crosslinking reaction of the non-polar rubber component, and when the vulcanizing agent is added, the three-dimensional crosslinked structure of the rubber component becomes dense. Therefore, C in the supercritical state
It is considered that the non-polar rubber component cross-linked from O ₂ can be effectively shielded (the permeability of CO _{2 in} the supercritical state is reduced and it is difficult to contact the non-polar rubber component), so that the degree of swelling is small and foaming occurs. It is possible to obtain a rubber composition that does not.

As the plasticizer, dioctyl phthalate (DOP), dibutyl phthalate (DBP); dioctyl adipate, isodecyl succinate; diethylene glycol dibenzoate, pentaerythritol ester;
Butyl oleate, methyl acetylricinoleate; tricresyl phosphate, trioctyl phosphate; propylene glycol adipate polyester, butylene glycol adipate polyester, and the like. As the softening agent, those commonly used such as various paraffinic oils can be used, and specific examples thereof include process oils. The plasticizer and the softening agent may be blended in the amounts usually used for hoses.

Antiaging agents include N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (6PPD), N, N'-dinaphthyl-p-phenylenediamine (DNPD), N-. Examples thereof include isopropyl-N'-phenyl-p-phenylenediamine (IPPD) and styrenated phenol (SP). Examples of the antioxidant include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA). The antioxidant and the antioxidant may be blended in the amounts usually used for hoses.

Examples of the antistatic agent include quaternary ammonium salts; hydrophilic compounds such as polyglycol and ethylene oxide derivatives. Examples of the flame retardant include chloroalkyl phosphate, dimethyl methylphosphonate, bromine / phosphorus compound, ammonium polyphosphate, neopentyl bromide polyether and brominated polyether. The antistatic agent and flame retardant may be blended in the amounts usually used for hoses.

Adhesion aids include 1,3,5-triazine-2,4,6-trithiol, 6-butylamino-
Examples include triazine thiol compounds such as 1,3,5-triazine-2,4-dithiol, cobalt naphthenate, resorcin, cresol, resorcin-formalin latex, monomethylol melamine, monomethylol urea, and ethylene maleimide. The adhesion aid may be blended in a content usually used for hoses. As the polymer other than the rubber, a resin, a thermoplastic elastomer or the like which is usually used depending on the physical properties required for the rubber composition of the present invention can be used.

In the composition of the present invention, each of the above various additives may be used alone or in combination of two or more kinds. Further, the above additives can be arbitrarily selected and used according to the non-polar rubber component.

The rubber composition of the first aspect of the present invention is prepared by mixing the above-mentioned non-polar rubber with additives and the like, for example, from 140 to
A rubber composition is obtained by heat vulcanization at 200 ° C. for about 5 to 200 minutes.

The first aspect of the present invention thus obtained
The rubber composition of ₂Foams even when in contact with
Do not expand and it is difficult to expand immediately after contact. Therefore, the first aspect of the present invention
The rubber composition according to one embodiment is composed of CO in a supercritical state.₂Contact
Suitable for use in rubber compositions used under certain conditions
It is possible, but its use is not particularly limited, but more preferable
Is the CO₂Cooling of various cooler systems using
For use as a medium transport hose, seal member (O-ring), etc.
Can be, specifically, air conditioners for automobiles, home cooling
Hoses for transporting refrigerants in warehouses, sealing members (O-rings), etc.
Can be used for.

A second aspect of the present invention is a CO having an inner tube made of the rubber composition for CO ₂ refrigerant of the first aspect of the present invention.
_A hose for transporting ₂ refrigerants, wherein the hose for transporting CO ₂ refrigerant is a hose comprising at least three layers including an inner pipe, an outer pipe, and a reinforcing layer disposed between them, and the inner pipe is the first of the present invention. It is preferably composed of the rubber composition for CO ₂ refrigerant of one aspect. Hereinafter, the hose for transporting the CO ₂ refrigerant of the second aspect (hereinafter referred to as the “hose of the present invention”) will be described.

The hose of the present invention may be any hose having an inner tube made of the above-mentioned rubber composition for CO ₂ refrigerant (hereinafter sometimes simply referred to as “the above rubber composition”). May be a single layer or a plurality of layers, in which case at least one layer of the inner tube (the innermost layer capable of contacting with CO _{2 in the} supercritical state) may be composed of the above rubber composition. Also, the inner pipe,
A hose consisting of at least three layers, including an outer tube and a reinforcing layer arranged in between, is preferred. The inner pipe and /
Alternatively, a thermoplastic resin, a thermoplastic elastomer, or the like or a composition thereof may be used as a part of the outer tube layer as long as the flexibility and vibration absorption of the hose are not impaired. Further, it is preferable to further have a metal foil layer, a metal vapor deposition layer or a resin layer as a CO ₂ gas impermeable layer on the entire outer circumference of the inner tube.

The hose of the present invention will be described below based on the embodiment shown in FIG. 1, but the hose of the present invention is not limited to this. FIG. 1 is a perspective view showing notched layers (pipes) of a hose which is an embodiment of a hose of the present invention. The hose has an inner tube, a reinforcing layer and an outer tube 3
It is a layered hose. The hose 1 of the present invention has an inner pipe 2 made of the above rubber composition, a reinforcing layer 3 as an upper layer, and an outer pipe 4 as an upper layer.

The inner tube 2 is composed of one layer made of the above rubber composition and constitutes the innermost layer of the hose. The thickness of the inner tube may be arbitrarily designed as needed, but for example, it is preferably about 0.5 to 5.0 mm and 0.8 to 3.0 m.
m is preferred.

Further, the hose of the present invention does not necessarily have to have the reinforcing layer 3, but if the hose is provided, the tensile breaking strength of the hose, usable pressure range and fitting property of the metal fitting are improved. preferable. Examples of the reinforcing layer include a blade-like structure formed of reinforcing threads and reinforcing steel wires, a spiral shape, a net-like structure formed of reinforcing threads, and a film-like structure. Examples of the reinforcing yarn include yarns such as aramid fiber, nylon, rayon, vinylon, and polyester. As the reinforcing steel wire, a brass-plated or zinc-plated steel wire is used for the purpose of preventing rust and imparting adhesiveness. From the viewpoint of vibration absorption, the reinforcing yarn is more preferable.

The outer tube 4 consisting of one layer is the outermost layer of the hose, and is a layer that retains the weather resistance, heat resistance, and water permeation resistance of the hose. From this viewpoint, butyl rubber, halogenated butyl rubber, ethylene Propylene rubber, brominated isobutylene-p-methylstyrene copolymer rubber (BIM
S), ethylene-acrylic acid ester copolymer rubber (AE
M) and the like are preferable, but not limited thereto. The thickness of the outer tube may be arbitrarily designed as necessary, but a thickness of 0.5 to 3 mm is preferable, and 0.8 to 2 mm.
Is more preferable.

The composition of the present invention containing a non-polar rubber is excellent in gas permeation resistance, but when a CO ₂ gas impermeable layer is provided, it is preferable to provide it on the entire outer circumference of the inner tube. The material and the material are not particularly limited.
The one described in Japanese Patent Publication No. 000-239451 can be used.

The hose of the present invention has, for example, a spiral shape in which a plurality of reinforcing yarns or reinforcing wires are gathered around the outer circumference of the unvulcanized rubber composition formed in a cylindrical shape on the outer circumference of a mandrel or the like. A braid is braided to form a reinforcing layer, and an outer tube is extruded on the outer periphery of the reinforcing layer by extrusion molding. Then, the whole hose is heated. The heating temperature may be a temperature at which rubber is vulcanized, and preferably 1
20 degreeC or more, More preferably, it is 140-170 degreeC.
After cooling sufficiently, the hose of the present invention is obtained by pulling out from the mandrel.

The hose of the present invention thus obtained does not foam even when it comes into contact with CO ₂ in a supercritical state, and is unlikely to expand immediately after the contact. Therefore, the hose of the present invention can be preferably used for a hose used under the condition that it can come into contact with CO ₂ in a supercritical state, and more preferably, the refrigerant contains C
It can be used for transporting refrigerants such as various cooler systems using O _2. Specifically, it is a cooler for automobiles,
It can be used for transporting refrigerants such as household refrigerators.

[0038]

EXAMPLES The present invention will be described in more detail based on examples. <Rubber Composition for CO ₂ Refrigerant> For each non-polar rubber shown in Table 1, various additives are added to 100 parts by mass of each non-polar rubber as shown in the column of “Additive” in Table 1. Was added in an amount of the indicated numerical value, and kneaded according to a conventional method.

The following additives were used in the present invention. Zinc oxide is manufactured by Shodo Kagaku Kogyo Co., Ltd., zinc flower 3
No .; stearic acid manufactured by Kao Corporation, LUNAC YA; paraffin oil manufactured by Showa Shell Sekiyu KK, machine oil 22; sulfur manufactured by Karuizawa Smelting Co., powdered sulfur; tetramethylthiuram disulphide (TT) manufactured by Sanshin Chemical Industry Sanserra TT-PO; N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) is Sanshin Chemical Industry Co., Ltd.
It is a sun cellar CM-PO.

(Example 1) Non-polar rubber was BIMS (EXXPRO manufactured by Exxon Chemical Co., Ltd.), and carbon black was H.
AF Grade (Showa Cabot, Show Black N
(330T) 80 parts by mass, brominated alkylphenol resin (Takka Chemical Industry Co., Ltd., Tucky Roll 250-I), 3 parts by mass. (Example 2) As the non-polar rubber, a blend rubber in which 50 parts by mass of BIMS (EXXPRO manufactured by Exxon Chemical Co., Ltd.) and 50 parts by mass of IIR (exon butyl manufactured by Exxon Chemical Co., Ltd.) were used. Example 3 EPDM (Mitsui Petrochemical Co., Ltd., Mitsui EPT) was used as the non-polar rubber, and 150 parts by mass of SRF grade (Asahi Carbon Co., Ltd., Asahi 50) was used as the carbon black.

Comparative Example 1 The same as Example 1 except that the brominated alkylphenol resin was not added. (Comparative Example 2) The same as Example 2 except that the content of carbon black is 80 parts by mass. (Comparative Example 3) The same as Example 2 except that the content of carbon black is 90 parts by mass.

[0042]

[Table 1]

The rubber compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were vulcanized and molded, and the vulcanized molded articles were cut into shapes suitable for each test to obtain rubber composition test pieces. The following tests were carried out. The test results are shown in Table 1.

(Tensile Breaking Elongation (EB) Test) EB of each rubber composition was measured by preparing each rubber composition test piece according to the test method described in JIS K6251-1993.

(Swelling degree test (immersion test)) Examples 1 to 1
3 and the rubber compositions obtained in Comparative Examples 1 to 3 at a temperature of 1
It was heated at 50 ° C. for 1 hour and vulcanized into a sheet having a thickness of 2 mm. This sheet-shaped vulcanized molded product is (length) 20 ×
Each rubber composition test piece was cut into a rectangle (width) 30 mm × (thickness) 2 mm. The expansion of each rubber composition was evaluated by the following swelling degree (volume change rate) test. The rubber composition test pieces of Examples and Comparative Examples were placed in stainless steel autoclaves, and the lids were tightened with bolts. Then, liquefied CO ₂ was charged inside the autoclave, and the temperature inside the autoclave was raised to reach the critical point of CO ₂ (31 ° C).
(Above / above 7.39 MPa), specifically, under conditions of a temperature of 120 ° C. and a pressure of 10 MPa, CO ₂ was brought into a supercritical state, and the rubber composition test piece was treated for 24 hours in this state. The above conditions are the conditions under which the rubber composition of the present invention (hose of the present invention) is actually used in a cooler system.

After that, the inside of the autoclave was gently decompressed and returned to normal temperature and normal pressure, and then the rubber composition test piece was taken out, and the swelling degree at that time (immediately after opening) was measured. The degree of swelling was determined by measuring the dimensional change rate before and after the treatment, determining the volume change, and expressing the increase rate in%. The concrete method is JIS
The immersion test method described in K6258-1993 was followed. If the degree of swelling is 40% or less, it can be sufficiently used under the condition that it can come into contact with CO ₂ in a supercritical state.

(Foaming test) In the swelling test, the surface of each rubber composition test piece after being immersed in CO ₂ in a supercritical state was visually observed. The case where foaming can be confirmed is marked with "x", the case where there is no foaming but the surface slightly changes (foaming rupture flaws, bumps, etc.) is marked with "△", and when foaming and surface changes cannot be confirmed, it is marked with "◎". "
When it is “⊚”, it can be sufficiently used under the condition that it can come into contact with CO ₂ in a supercritical state.

Further, even when the rubber composition of Example 1 was repeatedly dipped under the condition that it could come into contact with CO ₂ in a supercritical state, deterioration due to repeated expansion and contraction of the inner tube was not observed.

<CO ₂ Refrigerant Transporting Hose> The rubber composition for CO ₂ refrigerant obtained in Example 1 was extruded on the outer periphery of a mandrel having a diameter of 6 mm with a crosshead die type extruder for rubber to give a thickness of 1 An inner tube of 0.5 mm was formed. On the inner tube,
Braiding a reinforcing material made of aramid yarn (1680d
tex, 60), and a reinforcing layer was formed. On the reinforcing layer,
The EPDM rubber composition was extruded using a crosshead die type extruder for rubber to form an outer tube having a thickness of 1.2 mm. Then, the whole hose was heated at 160 degreeC for 90 minutes. After confirming that the hose was sufficiently cooled, the mandrel was pulled out to obtain a hose for transporting CO ₂ refrigerant of the present invention.

The hose thus obtained was treated with CO ₂
Was evaluated for 96 hours (CO ₂ temperature of about 120 ° C., pressure of about 10 MPa) under the condition of becoming a supercritical state.

During the test, the hose (inner tube) was in the supercritical state CO ₂
It was difficult to expand immediately after contact with, and the inner tube of the hose did not change after the test, and neither foaming nor expansion was observed.

[0052]

Industrial Applicability According to the present invention, it is possible to provide a rubber composition for a CO ₂ refrigerant, which does not foam even when contacted with CO ₂ in a supercritical state and hardly expands immediately after contact. Further, it is possible to provide a hose for transporting a CO ₂ refrigerant, which has an inner tube made of the rubber composition, does not foam even when it comes into contact with CO ₂ in a supercritical state, and does not easily expand immediately after the contact.

[Brief description of drawings]

FIG. 1 is a perspective view in which each layer (each tube) of a hose that is a preferred embodiment of a CO ₂ refrigerant transport hose of the present invention is cut away.

[Explanation of symbols]

1 CO ₂ Refrigerant Transport Hose _{2 of the} Present Invention 2 Inner Tube 3 Reinforcing Layer 4 Outer Tube

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Kawamori             2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd.             Ceremony Company Hiratsuka Factory (72) Inventor Hiroaki Shibano             4-6-40 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Yokohama Ha             Idex Hiratsuka Office F-term (reference) 3H111 AA02 BA12 BA13 BA25 BA29                       BA31 BA34 CA53 CB04 CB14                       CC03 DA08 DA12 DB09 DB19                 4F100 AA37H AK01B AK28A AK29A                       AK47 AK64A AK74A AK75A                       AN00A AN00B AT00B BA02                       BA03 BA10A BA10B CA23                       DA11 DG11 DH00C JB07A                       JK08A YY00A                 4J002 AC011 AC031 AC061 AC081                       BB151 BB181 BB241 BC041                       FD010 FD020 FD140 FD150                       GM00

Claims (4)

[Claims] 1. A non-polar rubber containing one or more blended rubbers and having a tensile elongation at break (EB) of 2 or less.
A rubber composition for a carbon dioxide refrigerant, which is used under the condition of being less than 00% and capable of contacting carbon dioxide in a supercritical state. 2. The non-polar rubber is ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-II).
R), styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), brominated isobutylene-p-methylstyrene copolymer rubber (BIMS) or isoprene rubber (IR). A rubber composition for a carbon dioxide refrigerant as described above. 3. A hose for transporting a carbon dioxide refrigerant, which has an inner pipe made of the rubber composition for a carbon dioxide refrigerant according to claim 1 or 2. 4. A rubber composition for a carbon dioxide refrigerant according to claim 1 or 2, which is a hose comprising at least three layers including an inner pipe, an outer pipe and a reinforcing layer disposed between them. A carbon dioxide refrigerant transport hose composed of.