Rubber composition and refrigerant transport hose

Abstract

To provide a rubber composition that is excellent in POE resistance, refrigerant permeability resistance and mechanical strength.SOLUTION: Provided are a rubber composition and a refrigerant transport hose, the rubber composition used in manufacture of an inner pipe of a refrigerant transport hose comprising at least the inner pipe and a reinforcing layer arranged on the outside of the inner pipe, and the rubber composition containing a butyl-based rubber, a flake-like filler, carbon black, and paraffin oil, where a butyl-based rubber content is 90 mass% or more of a total amount of a rubber component, a butyl-based rubber content is less than 30 mass% of the total amount of the rubber composition, and a paraffin oil content is 20 pts.wt. or more and less than 40 pts.wt. per 100 pts.wt. of the butyl-based rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a refrigerant transport hose. [Background technology]

[0002] In recent years, many eco-cars such as hybrid vehicles are equipped with electric compressors to compress refrigerants, and POE (polyol ester) is often used as the insulating oil (lubricant) that circulates through the system of the electric compressor. Furthermore, in the above-mentioned system, a hose is known that is used for transporting polyol ester, refrigerant, etc. (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 126591 Summary of the Invention [Problem to be solved by the invention]

[0004] Hoses used in the above systems are required to have excellent POE resistance, refrigerant permeation resistance, mechanical strength, etc. When the present inventors studied the rubber composition disclosed in Patent Document 1, they found that at least one of the POE resistance, refrigerant permeation resistance, and mechanical strength was low in some cases.

[0005] Therefore, an object of the present invention is to provide a rubber composition excellent in POE resistance, refrigerant permeation resistance and mechanical strength. Another object of the present invention is to provide a refrigerant transport hose. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by the following configuration.

[0007] [1] A rubber composition used in the manufacture of an inner pipe of a refrigerant transport hose including at least an inner pipe and a reinforcing layer disposed on the outside of the inner pipe, The rubber composition contains a butyl-based rubber, a flake filler, carbon black, and paraffin oil, the content of the butyl-based rubber is 90 mass% or more of the total amount of the rubber component, the content of the butyl-based rubber is less than 30 mass% of the total amount of the rubber composition, and the content of the paraffin oil is 20 parts by mass or more and less than 40 parts by mass per 100 parts by mass of the butyl-based rubber. [2] The rubber composition according to [1], wherein the total content of the scaly filler and the carbon black is 60 to 70 mass % of the total amount of the rubber composition. [3] A refrigerant transport hose comprising at least an inner pipe manufactured (formed) using the rubber composition according to [1] or [2], and a reinforcing layer disposed on the outside of the inner pipe. [4] A refrigerant transport hose as described in [3], comprising only the inner tube as the inner tube. [5] A refrigerant transport hose according to [3] or [4], wherein the inner tube is the innermost layer of the refrigerant transport hose. [6] The refrigerant transport hose according to any one of [3] to [5], which transports HFO-1234yf as a refrigerant and a polyol ester as a refrigeration oil. Effect of the Invention

[0008] According to the present invention, it is possible to provide a rubber composition excellent in POE resistance, refrigerant permeation resistance and mechanical strength. The present invention also provides a refrigerant transport hose. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cutaway perspective view of each layer of an example of a refrigerant transport hose of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of an evaluation cup used for evaluating the refrigerant permeation resistance of the rubber composition of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The following description of the configuration may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "~" means a range including the numerical values ​​written before and after "~". In the present specification, each component may be used alone or in combination of two or more kinds. In this specification, when two or more types of a component are used in combination, the "content" of the component means the total content of those two or more types, unless otherwise specified. In the present specification, the method for producing each component is not particularly limited unless otherwise specified. For example, a conventionally known method may be used.

[0011] [Rubber composition] The rubber composition of the present invention comprises: A rubber composition used in the manufacture of an inner pipe of a refrigerant transport hose including at least an inner pipe and a reinforcing layer disposed on an outer side of the inner pipe, The rubber composition contains a butyl-based rubber, a flake filler, carbon black, and paraffin oil, the content of the butyl-based rubber is 90 mass% or more of the total rubber component, the content of the butyl-based rubber is less than 30 mass% of the total rubber composition, and the content of the paraffin oil is 20 parts by mass or more and less than 40 parts by mass per 100 parts by mass of the butyl-based rubber.

[0012] The reason why the rubber composition of the present invention having the above-mentioned configuration can solve the problems of the present invention is not necessarily clear, but the present inventors speculate as follows. Note that the following speculation does not limit the mechanism by which the effect is obtained. In other words, even if the effect is obtained by a mechanism other than the following, it is included in the scope of the present invention. It is believed that the rubber composition of the present invention contains butyl rubber and paraffin oil in specified amounts, as well as flake filler and carbon black, thereby achieving an excellent balance between refrigerant permeation resistance, POE resistance, and mechanical strength. Hereinafter, superiority in at least one of the POE resistance, refrigerant permeation resistance, and mechanical strength is also referred to as "superior effect of the present invention."

[0013] [Butyl rubber] The rubber composition of the present invention contains a butyl-based rubber as a rubber component. The butyl rubber contained in the rubber composition of the present invention is not particularly limited as long as it is a polymer having repeating units formed by isobutylene and isoprene. For example, conventionally known butyl rubbers can be used. An example of the butyl rubber is butyl rubber (IIR).

[0014] In one preferred embodiment, the rubber component is solid at 23°C. Butyl rubber that is solid at 23°C is one of the preferred embodiments. From the viewpoint of obtaining superior effects of the present invention, the weight average molecular weight of the butyl-based rubber is preferably more than 50,000 and not more than 2,000,000. In the present invention, the weight average molecular weight of the butyl rubber is a standard polystyrene equivalent value based on a measurement value obtained by gel permeation chromatography (GPC) using THF (tetrahydrofuran) as a solvent.

[0015] (Rubber components other than butyl rubber) The rubber composition of the present invention may further contain, as the rubber component, a rubber component other than the butyl-based rubber (other rubber component). Examples of other rubber components include ethylene-propylene rubber (EPM) and ethylene-propylene-diene rubber (EPDM). There are no particular limitations on EPM and EPDM. For example, conventionally known rubbers can be used.

[0016] [Butyl rubber content in total rubber components] In the present invention, the content of the butyl rubber is 90% by mass or more of the total rubber component. By having the content of the butyl rubber in the total rubber component be within the above range, the rubber composition of the present invention has excellent POE resistance and refrigerant permeation resistance. From the viewpoint of obtaining superior effects of the present invention (particularly POE resistance and refrigerant permeation resistance), the content of the butyl rubber is preferably 95 to 100 mass % of the total amount of the rubber component, and more preferably 100 mass %.

[0017] [Butyl rubber content in total rubber composition] In the present invention, the content of the butyl-based rubber is less than 30 mass% of the total amount of the rubber composition of the present invention. By having the above content of the butyl-based rubber in the total amount of the rubber composition of the present invention, the rubber composition of the present invention has excellent POE resistance. From the viewpoint of obtaining superior effects of the present invention (particularly POE resistance and refrigerant permeation resistance), the content of the butyl-based rubber is preferably 10% by mass or more and less than 30% by mass, more preferably 20% by mass or more and less than 30% by mass, and even more preferably 26% by mass or more and less than 30% by mass, based on the total amount of the rubber composition of the present invention.

[0018] [Scaly filler] The rubber composition of the present invention contains a scaly filler. The scaly filler contained in the rubber composition of the present invention is a filler having a scaly shape. The shape of the scaly filler is not particularly limited as long as it is scaly. The outer periphery of the scaly filler may be irregular.

[0019] The average diameter of the scaly filler is not particularly limited, but from the viewpoint of obtaining superior effects of the present invention, it is preferably 0.1 to 700 μm, and more preferably 1 to 100 μm. In the present invention, the average diameter of the scaly filler is a volume average diameter determined by a laser diffraction method using a laser diffraction particle size distribution measuring device.

[0020] The aspect ratio (average diameter / thickness) of the scaly filler is preferably 5 to 80, from the viewpoint of achieving superior effects of the present invention. In the present invention, the thickness of the scaly filler is an average value calculated based on the measured values ​​obtained by observing the scaly filler at 10,000 times magnification using a scanning electron microscope (SEM), randomly selecting multiple scaly fillers from the observed field of view, and measuring their thicknesses.

[0021] Examples of the scaly filler include talc and mica. From the viewpoint of obtaining superior effects of the present invention, the scaly filler preferably contains talc. There is no particular limitation on the talc and mica, and examples thereof include those that are conventionally known.

[0022] In the present invention, the scaly filler may be either one that has been surface-treated or one that has not been surface-treated.

[0023] (Content of scale-like filler) The content of the scaly filler is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass, of the total amount of the rubber composition of the present invention, from the viewpoint of obtaining superior effects of the present invention.

[0024] [Carbon black] The rubber composition of the present invention contains carbon black. The carbon black contained in the rubber composition of the present invention is not particularly limited, and examples thereof include carbon blacks such as ISAF, HAF, FEF, GPF, and SRF. From the viewpoint of achieving superior effects of the present invention, the carbon black preferably contains carbon black having a DBP (dibutyl phthalate) oil absorption of 50 to 120 ml / g. The DBP oil absorption of carbon black can be measured in accordance with JIS K6217-4:2017. From the viewpoint of achieving better effects of the present invention, the carbon black preferably contains SRF carbon black and / or ISAF carbon black, and more preferably contains SRF carbon black.

[0025] (Carbon black content) From the viewpoint of obtaining superior effects of the present invention (particularly POE resistance and mechanical strength), the content of carbon black is preferably 30 to 60 mass % and more preferably 35 to 55 mass % of the total amount of the rubber composition of the present invention.

[0026] [Total content of flake filler and carbon black] The total content of the scaly filler and carbon black is preferably 60 to 70 mass %, and more preferably 63.0 to 70 mass %, of the total amount of the rubber composition of the present invention, from the viewpoint of obtaining superior effects of the present invention.

[0027] [Paraffin oil] The rubber composition of the present invention contains paraffin oil. The paraffin oil contained in the rubber composition of the present invention is not particularly limited as long as it is an aliphatic hydrocarbon compound that is liquid at 23°C. In the present invention, paraffin oil is liquid at 23°C if it has a kinetic viscosity of 20,000mm at 40°C. 2 / s or less.

[0028] From the viewpoint of obtaining a superior effect of the present invention (particularly POE resistance), the paraffin oil has a kinetic viscosity of 10 to 600 mm 2 / s is preferably 100 to 550 mm 2 The kinetic viscosity of paraffin oil can be measured at 40° C. in accordance with JIS K2283:2000.

[0029] [Paraffin oil content] In the present invention, the content of the paraffin oil is 20 parts by mass or more and less than 40 parts by mass per 100 parts by mass of the butyl-based rubber. By having the content of the paraffin oil in the above-mentioned range, the rubber composition of the present invention has excellent POE resistance, refrigerant permeation resistance, and mechanical strength. The content of paraffin oil is preferably 20 to 28 parts by mass relative to 100 parts by mass of the butyl rubber, from the viewpoint of obtaining better effects of the present invention (particularly refrigerant permeation resistance and mechanical strength).

[0030] (Additives) The rubber composition of the present invention may further contain additives, if necessary. Examples of additives include fillers other than scaly fillers (e.g. silica), resins (e.g. resin vulcanizing agents such as brominated alkylphenol-formaldehyde resins), stearic acid, zinc oxide, antioxidants, antioxidants, antistatic agents, flame retardants, vulcanizing agents such as sulfur, vulcanization accelerators, crosslinking agents such as peroxides, and adhesion aids. The additives are not particularly limited, and examples thereof include those conventionally known. The content of each additive can be appropriately adjusted.

[0031] (Manufacturing method, usage, etc.) The rubber composition of the present invention is not particularly limited in its production. For example, the above-mentioned essential components and additives that can be used as necessary are kneaded under conditions of 30 to 150°C using an internal mixer such as a Banbury or kneader, or a kneading roll machine to produce the rubber composition.

[0032] The conditions for vulcanizing or crosslinking the rubber composition of the present invention are not particularly limited. For example, the rubber composition of the present invention can be vulcanized or crosslinked under conditions of 140 to 160° C. while being pressurized.

[0033] [For use as inner tubes of refrigerant transport hoses] The rubber composition of the present invention is a rubber composition used for producing an inner pipe of a refrigerant transport hose including at least an inner pipe and a reinforcing layer disposed on the outside of the inner pipe. The refrigerant transport hose will be described later.

[0034] [Refrigerant transport hose] The refrigerant transport hose of the present invention is a refrigerant transport hose including at least an inner pipe produced using the rubber composition of the present invention and a reinforcing layer disposed on the outside of the inner pipe. In this specification, the refrigerant transport hose of the present invention is also referred to as the "hose of the present invention."

[0035] [Inner tube] The inner tube of the hose of the present invention is not particularly limited as long as it is an inner tube manufactured (formed) using the rubber composition of the present invention.

[0036] The hose of the present invention preferably includes, as the inner tube, only an inner tube (rubber layer) produced using the rubber composition of the present invention. When the hose of the present invention has only an inner tube manufactured using the rubber composition of the present invention as the inner tube, the number of manufacturing steps is preferably reduced compared to when the inner tube is made of multiple layers (laminate). Furthermore, when the hose of the present invention has only an inner tube manufactured using the rubber composition of the present invention as the inner tube, there is no need to consider peeling between the rubber layer and the EPDM layer in the inner tube, and deterioration of POE resistance and refrigerant permeation resistance due to the peeling can be suppressed, which is considered to be preferable compared to when the inner tube is a laminate having, for example, the rubber layer and further, for example, an EPDM layer vulcanized by peroxide.

[0037] From the viewpoint of obtaining superior effects of the present invention, it is preferable that the inner pipe produced using the rubber composition of the present invention is the innermost layer of the hose of the present invention.

[0038] [Reinforcement layer] The hose of the present invention has a reinforcing layer on the outside of the inner tube. The reinforcing layer may be one layer or multiple layers. The reinforcing layer may be adjacent to the inner tube, or an interlayer rubber layer or the like may be disposed between the inner tube and the reinforcing layer. Examples of materials used for the reinforcing layer include fiber materials such as polyester fibers, polyamide fibers, aramid fibers, vinylon fibers, rayon fibers, polyparaphenylene benzobisoxazole fibers, polyketone fibers, polyarylate fibers, and polyketone fibers; and metal materials such as hard steel wires, such as brass-plated wires and zinc-plated wires. The shape of the reinforcing layer is not particularly limited, and examples thereof include a blade-like and a spiral-like shape.

[0039] (outer tube) The hose of the present invention may further have an outer tube on the outside of the reinforcing layer. The outer tube is not particularly limited. For example, the outer tube of a conventionally known hose for transporting a refrigerant may be used. An interlayer rubber layer or the like may be disposed between the outer tube and the reinforcing layer. The outer tube may be made of one layer or multiple layers. When the outer tube is made of multiple layers, an interlayer rubber layer or the like may be disposed between adjacent outer tubes. The material constituting the outer tube is not particularly limited. For example, a rubber composition can be used. Examples of the material (rubber composition) constituting the outer tube include rubber compositions containing a rubber component such as styrene butadiene rubber, chloroprene rubber, and ethylene propylene diene rubber.

[0040] The hose of the present invention will be described in detail below with reference to the accompanying drawings, but the hose of the present invention is not limited to the drawings. FIG. 1 is a perspective view showing an example of a refrigerant transport hose of the present invention with each layer cut away. In Fig. 1, a hose 1 includes an inner pipe 2, a reinforcing layer 3 disposed on the outside of the inner pipe 2, and an outer pipe 4 disposed on the outside of the reinforcing layer 3. The inner pipe 2 is produced using the rubber composition of the present invention. The inner pipe 2 is the innermost layer of the hose 1.

[0041] The method for producing the hose of the present invention is not particularly limited. For example, the following method may be mentioned. First, the rubber composition of the present invention is extruded from a rubber extruder for inner tube rubber material onto a mandrel previously coated with a release agent to form an inner tube. Next, a reinforcing layer is formed on the inner tube (or on the adhesive layer, if any). There are no particular limitations on the method for forming the reinforcing layer. Furthermore, an outer tube material (for example, the material constituting the outer tube described above) can be extruded onto the reinforcing layer (or onto the adhesive layer, if there is one) to form the outer tube. The laminate of these layers is then vulcanized at 130 to 190° C. for 30 to 180 minutes to bond them together, thereby producing the hose of the present invention. Examples of the vulcanization method include steam vulcanization, oven vulcanization (hot air vulcanization), and warm water vulcanization.

[0042] The hose of the present invention can be used, for example, as a hose for air conditioners such as car air conditioners. The hose of the present invention can be used, for example, for high pressure and low pressure.

[0043] The hose of the present invention is a refrigerant transport hose. The hose of the present invention can be used to transport a refrigerant. The hose of the present invention can also be used to transport a refrigerant and a refrigeration oil (lubricating oil). Refrigerants that can be transported by the hose of the present invention include, for example, fluorine-based compounds, and specific examples include fluorine-based compounds having double bonds such as 1,2,3,3,3-pentafluoropropene, 1,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene (structural formula: CF3-CF=CH2, HFO-1234yf), 1,2,3,3-tetrafluoropropene, and 3,3,3-trifluoropropene; and saturated hydrofluorocarbons such as HFC-134a (structural formula: CF3-CFH2). Examples of refrigeration oils that can be transported by the hose of the present invention include polyol esters. Specific examples of polyol esters include esters of pentaerythritol such as pentaerythritol tetraheptanoate, and esters of trimethylolpropane such as trimethylolpropane tricaprate, trimethylolpropane coconut pre-distillate fatty acid ester, and trimethylolpropane trioleate.

[0044] The hose of the present invention can be suitably used, for example, as a refrigerant transport hose for transporting HFO-1234yf as a refrigerant and a polyol ester as a refrigerating machine oil. EXAMPLES

[0045] The present invention will be described in further detail below with reference to examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0046] <Production of Rubber Composition> The components in Table 1 below (the content of each component is in parts by mass) were mixed with a stirrer to produce a rubber composition.

[0047] <Evaluation> The rubber compositions produced as described above were subjected to the following evaluations, and the results are shown in Table 1.

[0048] (POE resistance) - Sheet fabrication Each of the rubber compositions produced as described above was vulcanized at 153° C. for 45 minutes using a press vulcanizer to prepare a sheet having a thickness of 2 mm. POE resistance test The sheet (length 15 cm, width 15 cm) prepared as described above was subjected to a POE resistance test in accordance with JIS K 6258-2016 by immersing it in polyol ester (product name ND-11, manufactured by JX Nippon Oil & Energy Corporation) heated to 100°C for 70 hours. The volume of the sheet was measured before and after the test, and the volume swelling ratio was calculated using the volume change calculation formula shown in JIS K6258-2016, Section 8.1.3. In the evaluation results, when the volume swelling ratio was 5.0% or less, the POE resistance was evaluated as excellent, and this was indicated by "●". The smaller the volume swelling ratio is from 5.0%, the better the POE resistance is. On the other hand, when the volume swelling ratio exceeded 5.0%, the POE resistance was evaluated as poor, and this was indicated by "X."

[0049] (Refrigerant permeability) - Sheet fabrication Each of the rubber compositions produced as described above was vulcanized at 153° C. for 45 minutes using a press vulcanizer to prepare a sheet having a thickness of 0.5 mm.

[0050] Refrigerant permeation test The method for evaluating refrigerant permeation resistance will be described below with reference to the accompanying drawings. FIG. 2 is a cross-sectional view of an evaluation cup used for evaluating the refrigerant permeation resistance of the rubber composition of the present invention. 2, the evaluation cup 30 includes a stainless steel cup 10 (hereinafter referred to as cup 10), a sheet 14 prepared as described above, a sintered metal plate 16, fixing members 18 and 19, a bolt 20, and a nut 22. A refrigerant 12 is contained inside the cup 10. First, refrigerant 12 was poured into cup 10 until it reached half its capacity, the opening of cup 10 was covered with sheet 14, and sintered metal plate 16 was placed on top of sheet 14. Next, the end of cup 10, sheet 14, and sintered metal plate 16 were fixed with bolts 20 and nuts 22 via fixing members 18 and 19, and the end of cup 10, sheet 14, and sintered metal plate 16 were brought into close contact with each other, thereby preparing evaluation cup 30. In this embodiment, HFO-1234yf (manufactured by Mitsui-DuPont Fluorochemicals) was used as the refrigerant.

[0051] The evaluation cup prepared as described above was subjected to a refrigerant permeation test in which it was placed under a condition of 90° C. for 7 days. The weight of the entire evaluation cup was measured before and after the test, and the amount of weight loss after the test was calculated. The gas permeability coefficient was calculated by applying the weight loss after the test to the following formula. Gas permeability coefficient (mg mm / 24hr cm 2 )=(M t) / (T A) In the formula, M is the weight loss [mg], t is the sheet thickness [mm], T is the test time [24 hr], and A is the permeation area [cm 2 ].

[0052] Gas permeability coefficient is 12.0 mg mm / 24 hr cm 2 If it was below this level, it was evaluated as having excellent refrigerant permeation resistance, and this was indicated by "●". Gas permeability coefficient is 12.0 mg mm / 24 hr cm 2 The smaller the value, the better the resistance to refrigerant permeation. On the other hand, the gas permeability coefficient is 12.0 mg mm / 24 hr cm 2 When the resistance to refrigerant permeation was exceeded, the resistance was evaluated as poor, and this was indicated by "X."

[0053] (Mechanical strength) - Sheet fabrication Each of the rubber compositions produced as described above was vulcanized at 153° C. for 45 minutes using a press vulcanizer to prepare a sheet having a thickness of 2 mm.

[0054] Tensile Test Using the sheet produced as described above, a tensile test was performed in accordance with JIS K 6251:2017 under conditions of a tensile speed of 500 mm / min and 23° C., and the 100% modulus (M100) was measured. When the 100% modulus exceeded 6.0 MPa, the mechanical strength was evaluated as excellent, and this was indicated by a "●". The greater the 100% modulus is 6.0 MPa, the better the mechanical strength is. On the other hand, when the 100% modulus was 6.0 MPa or less, the mechanical strength was evaluated as poor, and this was indicated by "X."

[0055] [Table 1]

[0056] Details of each component shown in Table 1 are as follows. ·IIR: Butyl rubber. Product name: BUTYL 301, manufactured by LANXESS, weight average molecular weight: 600,000

[0057] EPDM: Ethylene-propylene-diene rubber. The diene is ethylidene norbornene (ENB). Product name: EPT4070, manufactured by Mitsui Chemicals. NBR: Acrylonitrile butadiene rubber. Product name: Nipol 1041, manufactured by Zeon Corporation NBR-PVC: A blend of acrylonitrile butadiene rubber and polyvinyl chloride (NBR / PVC=70 / 30). Product name: Nipol DN508SCR, manufactured by Zeon Corporation.

[0058] Carbon black: SRF carbon black. Product name: Asahi #50, Asahi Carbon Co., Ltd.

[0059] Talc: ImerFlex T20, manufactured by Imerys Specialties Japan. Talc in the form of scales. Average diameter 6.1 μm, aspect ratio 6.

[0060] Resin: Brominated alkylphenol-formaldehyde resin, Takkiroll 250-I, manufactured by Taoka Chemical Co., Ltd. Zinc oxide 5 parts by mass: Product name "Zinc oxide 3 types", manufactured by Seido Chemical Industry Co., Ltd.

[0061] Paraffin oil 1: Product name Y Pure Spin G, manufactured by Cosmo Oil Bricant Co., Ltd. Paraffin oil refined in a hydrogen refinery. Dynamic viscosity 21mm 2 / s@40℃ Paraffin oil 2: Trade name SUNPAR 2280, manufactured by Nippon Sun Oil Co., Ltd. Paraffin oil refined in a hydrogen refinery. Kinematic viscosity 481mm 2 / s@40℃

[0062] (Comparison) Liquid polybutene (Grade HV-300): Liquid polybutene. Product name: Nisseki Polybutene HV-300, manufactured by ENEOS. Number average molecular weight: 1400. Viscous liquid at 23°C. Kinematic viscosity: 26,000mm 2 / s@40℃. The liquid polybutene has a kinetic viscosity of 20,000 mm at 40°C. 2 / s, so it does not fall under the category of paraffin oil in the present invention. Moreover, the liquid polybutene is not a solid at 23° C., and therefore does not fall under the category of butyl rubber as the rubber component in the present invention. Stearic acid: Stearic acid 50S, manufactured by Nisshin Rika Co., Ltd.

[0063] From the results in Table 1, it was confirmed that the rubber composition of the present invention exhibits the desired effects. Furthermore, the following was confirmed by comparing the examples. That is, from the results of Examples 1 and 2, when the carbon black content is, for example, 30 to 60 mass % (or 35 to 55 mass %) of the total amount of the rubber composition, the higher the carbon black content, the better the POE resistance and mechanical strength. The results of Examples 2 and 3 show that when the content of paraffin oil is low (for example, when the content of paraffin oil is 20 to 28 parts by mass per 100 parts by mass of butyl-based rubber), the refrigerant permeation resistance and mechanical strength were superior. From the results of Examples 2 and 4, the higher the content of butyl rubber, the better the POE resistance and refrigerant permeation resistance. From the results of Examples 2 and 5, the paraffin oil with a higher kinetic viscosity had better POE resistance. From the results of Examples 2 and 6, when the content of the scaly filler is, for example, 10 to 30 mass% (or 15 to 25 mass%) of the total amount of the rubber composition, the greater the content of the scaly filler (e.g., talc), the better the POE resistance, refrigerant permeation resistance, and mechanical strength.

[0064] On the other hand, Comparative Examples 1 to 3 in which the butyl rubber content was less than 90 mass% of the total rubber component, Comparative Example 4 in which the butyl rubber content was 30 mass% or more of the total rubber composition, Comparative Examples 5 and 6 in which the paraffin oil content was outside the specified range, and Comparative Example 7 in which no paraffin oil was contained but liquid polybutene was contained instead, had poor at least one of POE resistance, refrigerant permeation resistance, and mechanical strength. [Explanation of symbols]

[0065] 1 Hose (refrigerant transport hose) 2 Inner tube 3 Reinforcement layer 4 Outer tube 10 cups 12 Refrigerants 14 sheets 16 Sintered metal plate 18, 19 Fixing member 20 Volts 22 Nut 30 Evaluation Cup

Claims

1. A rubber composition used in the manufacture of an inner pipe of a refrigerant transport hose including at least an inner pipe and a reinforcing layer disposed on an outer side of the inner pipe, The rubber composition contains a butyl-based rubber, a flake filler, carbon black, and paraffin oil, the content of the butyl-based rubber is 90 mass% or more of the total amount of the rubber component, the content of the butyl-based rubber is less than 30 mass% of the total amount of the rubber composition, and the content of the paraffin oil is 20 parts by mass or more and less than 40 parts by mass per 100 parts by mass of the butyl-based rubber.

2. The rubber composition according to claim 1, wherein a total content of the scaly filler and the carbon black is 60 to 70 mass % of the total amount of the rubber composition.

3. A refrigerant transport hose comprising at least an inner pipe manufactured using the rubber composition according to claim 1 or 2, and a reinforcing layer disposed on the outside of the inner pipe.

4. The refrigerant transport hose according to claim 3 , comprising only the inner tube as an inner tube.

5. 4. The refrigerant transport hose of claim 3, wherein the inner tube is an innermost layer of the refrigerant transport hose.

6. The refrigerant transport hose according to claim 3, which transports HFO-1234yf as a refrigerant and a polyol ester as a refrigerating machine oil.

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