Rubber composition for hose and hose

Abstract

The present invention addresses the problem of providing: a rubber composition for hoses, which has excellent processability, crack growth resistance and elongation fatigue resistance; and a hose comprising the rubber composition for hoses and having excellent crack growth resistance and elongation fatigue resistance. Provided as a solution is a rubber composition (1) for hoses, comprising: a rubber component comprising at least a chloroprene rubber; and carbon black, in which the content of the chloroprene rubber is 70 parts by mass or more per 100 parts by mass of the rubber component, the chloroprene rubber exhibits a Mooney viscosity of 43-53 M and a crystallization start time at 0 DEG C of 30-500 minutes, and the content of the carbon black is 40 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component. And the carbon black exhibits a nitrogen adsorption specific surface area (N2SA) of 30-55 m2 / g.

Description

Technical Field

[0001] The present disclosure relates to a rubber composition for a hose and a hose. Background Art

[0002] Currently, hoses such as hydraulic hoses are widely used in machines that operate with hydraulic pressure, such as construction machinery and industrial machinery. Generally, hydraulic hoses need to withstand high pressure to accurately and quickly transmit the driving force (pressure), and it is also important that they have high oil resistance and exhibit minimal volume expansion due to pressure. Furthermore, since the hydraulic oil heats up during machine operation, hydraulic hoses also need to have heat resistance. Hydraulic hoses typically have a laminated structure in which, starting from the inside, an inner tube rubber layer that comes into contact with the hydraulic oil, multiple reinforcement layers for withstanding the pressure of the hydraulic oil, and an outer covering rubber layer for preventing damage to these reinforcement layers and the inner tube rubber layer are sequentially laminated, with an intermediate rubber layer arranged between the multiple reinforcement layers.

[0003] Typically, brass-plated metal wires are used for the reinforcement layer, while various rubber compositions are used for the inner tube rubber layer, outer cover rubber layer, and intermediate rubber layer, depending on the required performance. Conventionally, because the rubber components of hoses, such as the inner tube rubber layer, outer cover rubber layer, and intermediate rubber layer, require a wide range of rubber properties, such as weather resistance, abrasion resistance, heat resistance, and oil resistance, chloroprene rubber (CR)-based rubber compositions, which exhibit a well-balanced combination of these properties, are primarily used (see Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 08-041249 Summary of the Invention

[0007] (Problem to be solved by the invention)

[0008] Chloroprene rubber (CR) is widely used not only in rubber products but also in other applications, resulting in a tight supply-demand balance and high cost. Consequently, in recent years, research has been conducted into using cheaper, general-purpose chloroprene rubber (CR) in rubber compositions to replace conventionally used high-grade chloroprene rubber (CR). However, while rubber compositions using cheaper, general-purpose chloroprene rubber (CR) than conventional chloroprene rubber excel in processability, such as rubber mixing and extrusion, and in preventing sheet breakage during winding, they lack crack growth resistance and elongation fatigue resistance.

[0009] Therefore, the present disclosure solves the problem of providing a rubber composition for a hose that is excellent in processability, crack growth resistance, and elongation fatigue resistance.

[0010] Furthermore, the present disclosure solves the problem of providing a hose that includes such a rubber composition for a hose and exhibits excellent crack growth resistance and elongation fatigue resistance.

[0011] (Solutions used to solve problems)

[0012] The rubber composition for a hose and the hose of the present disclosure for solving the above-mentioned problems are mainly configured as follows.

[0013] [1] A rubber composition for a hose comprising a rubber component containing at least chloroprene rubber and carbon black,

[0014] wherein the content of the chloroprene rubber is 70 parts by mass or more per 100 parts by mass of the rubber component,

[0015] wherein the Mooney viscosity of the chloroprene rubber is 43 to 53 M and the crystallization start time at 0° C. is 30 to 500 minutes,

[0016] wherein the content of carbon black is 40 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, and

[0017] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30 to 55 m 2 / g.

[0018] [2] The rubber composition for hose according to [1], wherein the weight average molecular weight of the chloroprene rubber is 20×10 4 to 40×10 4 .

[0019] [3] The rubber composition for a hose according to [1] or [2], wherein the content of the chloroprene rubber is 90 parts by mass or less per 100 parts by mass of the rubber component.

[0020] [4] The rubber composition for a hose according to any one of [1] to [3], wherein the rubber component further contains butadiene rubber.

[0021] [5] The rubber composition for a hose according to any one of [1] to [4], which is used for an intermediate layer of a hose.

[0022] [6] A hose having an intermediate layer made of the rubber composition for a hose according to any one of [1] to [5].

[0023] (Effects of the Invention)

[0024] According to the present disclosure, a hose rubber composition having excellent processability, crack growth resistance, and elongation fatigue resistance can be provided. In addition, according to the present disclosure, a hose comprising such a hose rubber composition and exhibiting excellent crack growth resistance and elongation fatigue resistance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the attached figure:

[0026] Figure 1 is a perspective view schematically illustrating a hose according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] Hereinafter, the rubber composition for a hose and a hose including the rubber composition for a hose of the present disclosure will be exemplified and described in detail based on embodiments thereof.

[0028] (definition)

[0029] The compounds disclosed herein may be partially or completely derived from fossil resources, biological resources such as plant resources, or recyclable resources such as scrap tires, etc. They may also be derived from a mixture of two or more of fossil resources, biological resources, and recyclable resources.

[0030] In this specification, when a numerical range is described as "A to B", it means that endpoints "A" and "B" are also included in the numerical range.

[0031] (Rubber composition)

[0032] The rubber composition for a hose of the present embodiment (hereinafter, sometimes simply referred to as "rubber composition") is a rubber composition for a hose comprising a rubber component containing at least chloroprene rubber and carbon black, wherein the content of the chloroprene rubber is 70 parts by mass or more per 100 parts by mass of the rubber component,

[0033] The Mooney viscosity of the chloroprene rubber is 43 to 53 M and the crystallization start time at 0° C. is 30 to 500 minutes,

[0034] The content of carbon black is 40 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, and

[0035] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30 to 55 m 2 / g.

[0036] By combining the above-mentioned chloroprene rubber and carbon black, the rubber composition for a hose of the present disclosure can be made into a rubber composition having excellent processability, crack growth resistance, and elongation fatigue resistance.

[0037] Hereinafter, each component constituting the rubber composition for a hose of the present disclosure will be described.

[0038] [Rubber component]

[0039] The rubber composition for a hose of the present disclosure includes a rubber component.

[0040] The rubber component of the present embodiment contains chloroprene rubber (CR) and may further contain other rubber components. As the other rubber component, a rubber containing butadiene units other than chloroprene rubber may be contained.

[0041] (Chloroprene rubber)

[0042] The rubber composition for a hose of the present disclosure contains chloroprene rubber as a rubber component.

[0043] The content of chloroprene rubber is 70 parts by mass or greater per 100 parts by mass of the rubber component. When the content of chloroprene rubber is 70 parts by mass or greater per 100 parts by mass of the rubber component, the elongation fatigue resistance and oil resistance of the rubber composition are improved. From the perspective of elongation fatigue resistance and oil resistance, the content of chloroprene rubber is preferably 75 parts by mass or greater, more preferably 77 parts by mass or greater, even more preferably 80 parts by mass or greater, and particularly preferably 83 parts by mass or greater per 100 parts by mass of the rubber component. From the perspective of low-temperature performance, the content of chloroprene rubber is preferably 90 parts by mass or less, more preferably 88 parts by mass or less, and particularly preferably 87 parts by mass or less per 100 parts by mass of the rubber component. When the content of chloroprene rubber is 90 parts by mass or less per 100 parts by mass of the rubber component, a hose rubber composition having excellent low-temperature performance can be obtained while maintaining elongation fatigue resistance.

[0044] The Mooney viscosity of the chloroprene rubber is 43 to 53 M. When the Mooney viscosity is within the range of 43 to 53 M, the processability of the rubber composition is improved. From the same viewpoint, the Mooney viscosity of the chloroprene rubber is preferably 44 to 52 M, more preferably 45 to 51 M, still more preferably 46 to 50 M, and even more preferably 47 to 50 M.

[0045] In this specification, the Mooney viscosity of chloroprene rubber is measured at 100° C. using a Mooney viscometer (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K6300-1.

[0046] The crystallization start time of chloroprene rubber at 0°C is 30 to 500 minutes. When the crystallization start time of chloroprene rubber is within this range, the processability and productivity of the rubber composition are improved. From the same viewpoint, the crystallization start time of chloroprene rubber is preferably 35 to 400 minutes, more preferably 35 to 300 minutes, still more preferably 40 to 200 minutes, and even more preferably 45 to 150 minutes.

[0047] The crystallization start time at 0°C refers to the time when chloroprene rubber starts to crystallize at 0°C.

[0048] In this specification, the crystallization start time of the chloroprene rubber is measured by isothermal crystallization measurement using a differential scanning calorimeter (manufactured by TA Instruments) in accordance with JIS K7121.

[0049] The weight average molecular weight (Mw) of the chloroprene rubber is preferably 20×10 4 to 40×10 4 When the weight average molecular weight (Mw) of the chloroprene rubber is within this range, the processability and durability of the rubber composition are improved. From the perspective of processability and durability, the weight average molecular weight of the chloroprene rubber in this embodiment is preferably 23×10 4 to 40×10 4 , more preferably 25×10 4 to 40×10 4 , and still more preferably 27×10 4 to 39×10 4 .

[0050] In this specification, the weight average molecular weight (Mw) of the chloroprene rubber is measured by molecular weight measurement using gel permeation chromatography (GPC).

[0051] (Other rubber components)

[0052] The hose rubber composition of the present disclosure may further include a rubber component other than chloroprene rubber. The rubber component other than chloroprene rubber may include, but is not limited to, a rubber containing butadiene units; for example, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), or modified products thereof may be used. These other rubber components may be used alone or in combination of two or more.

[0053] The rubber component other than chloroprene rubber is not particularly limited, but is preferably a rubber component having excellent low-temperature properties. In this case, in addition to crack growth resistance and elongation fatigue resistance, the low-temperature properties of the rubber composition also become excellent.

[0054] Preferably, the rubber component other than the chloroprene rubber contains butadiene rubber. By further containing butadiene rubber in the rubber composition, a rubber composition having excellent low-temperature properties in addition to crack growth resistance and elongation fatigue resistance can be obtained.

[0055] The content of the diene rubber is preferably 10 to 30 parts by mass, more preferably 10 to 25 parts by mass, and still more preferably 10 to 20 parts by mass per 100 parts by mass of the rubber component.

[0056] [Carbon black]

[0057] The rubber composition for a hose of the present disclosure contains carbon black. Carbon black can reinforce the rubber composition and improve the crack growth resistance and elongation fatigue resistance of the rubber composition.

[0058] The content of carbon black is 40 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component. When the content of carbon black is within this range, the rubber composition has high reinforcing properties and is excellent in crack growth resistance and elongation fatigue resistance. From the perspective of reinforcing properties, the content of carbon black is preferably 41 parts by mass or more, more preferably 42 parts by mass or more, and even more preferably 43 parts by mass per 100 parts by mass of the rubber component. From the perspective of elongation fatigue resistance, the content of carbon black is preferably 49 parts by mass or less, more preferably 48 parts by mass or less, even more preferably 46 parts by mass or less, and even more preferably 44 parts by mass or less, per 100 parts by mass of the rubber component.

[0059] In addition, the nitrogen adsorption specific surface area (N2SA) of carbon black is 30 to 55 m 2 / g. When the nitrogen adsorption specific surface area (N2SA) of carbon black is 30 to 55m 2 / g, the rubber composition has high reinforcement characteristics and is excellent in crack growth resistance and elongation fatigue resistance. From the same point of view, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 33 to 52 m 2 / g, more preferably 35 to 50m 2 / g, and still more preferably 38 to 47m 2 / g.

[0060] As carbon black, for example, FEF grade carbon black can be mentioned, but any grade of carbon black that satisfies the nitrogen adsorption specific surface area of ​​the present embodiment can be used. These carbon blacks can be used alone or in combination of two or more.

[0061] In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K6217-2.

[0062] (Other components)

[0063] In addition to the rubber component and carbon black, the hose rubber composition of the present disclosure may also contain various compounding ingredients. Examples of such compounding ingredients include fillers other than carbon black, softeners, vulcanizing agents (crosslinking agents), vulcanization accelerators, vulcanization accelerator aids, antioxidants, vulcanization retarders, waxes, foaming agents, oils, lubricants, tackifiers, ultraviolet absorbers, dispersants, compatibilizers, and leveling agents. These may be used alone or in combination of two or more.

[0064] [filler]

[0065] The hose rubber composition of the present disclosure may further contain fillers other than carbon black. By including fillers other than carbon black in the hose rubber composition, the rigidity of the hose rubber composition is improved. Examples of fillers include calcium carbonate, silica, aluminum hydroxide, aluminum oxide, and clay, with calcium carbonate and silica being preferred.

[0066] The filler content is not particularly limited, but is preferably 31 to 120 parts by mass, more preferably 40 to 90 parts by mass, per 100 parts by mass of the rubber component. When calcium carbonate is included as a filler, the calcium carbonate content is preferably 30 to 100 parts by mass, more preferably 40 to 80 parts by mass, per 100 parts by mass of the rubber component. The silica content is preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of the rubber component.

[0067] [Softener]

[0068] The rubber composition for a hose of the present disclosure may further include a softener. The softener is not particularly limited, and examples include oils. The oil is not particularly limited, and various oils can be used, such as mineral oils, vegetable oils, and synthetic oils. Examples of mineral oils include process oils, such as naphthenic oils and paraffin oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, and the like. Examples of synthetic oils include glyceride compounds, adipate compounds, polyether ester compounds, phthalate compounds, isosorbide compounds, and polycaprolactone compounds.

[0069] The content of the softener is not particularly limited, but is preferably 5 to 30 parts by mass, more preferably 10 to 20 parts by mass, per 100 parts by mass of the rubber component.

[0070] [Vulcanizing agent]

[0071] The rubber composition for hoses of the present disclosure may contain a vulcanizing agent (crosslinking agent). The vulcanizing agent crosslinks the rubber component and improves the breaking strength of the rubber composition. There are no particular limitations on the vulcanizing agent, and examples include sulfur.

[0072] The content of the vulcanizing agent is not particularly limited, but is preferably 1 to 10 parts by mass, more preferably 2 to 7 parts by mass, and still more preferably 3 to 5 parts by mass per 100 parts by mass of the rubber component.

[0073] [Vulcanization accelerator]

[0074] The rubber composition for a hose of the present disclosure may include a vulcanization accelerator. The vulcanization accelerator has the effect of increasing the vulcanization rate of the rubber composition. There is no particular limitation on the vulcanization accelerator, and examples include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (MBT) and dibenzothiazyl disulfide (MBTS); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide (CZ) and N-(tert-butyl)-2-benzothiazolesulfenamide (NS); and guanidine-based vulcanization accelerators such as 1,3-diphenylguanidine (DPG).

[0075] The content of the vulcanization accelerator is preferably 0.1 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, and still more preferably 0.6 to 1.5 parts by mass per 100 parts by mass of the rubber composition.

[0076] [Vulcanization accelerator additives]

[0077] The rubber composition for a hose of the present disclosure may include a vulcanization accelerator auxiliary. The vulcanization accelerator auxiliary is not particularly limited, and examples include zinc oxide (zinc white).

[0078] The content of the vulcanization accelerator auxiliary is not particularly limited, but is preferably 1 to 10 parts by mass, more preferably 3 to 7 parts by mass, and still more preferably 4 to 6 parts by mass per 100 parts by mass of the rubber component.

[0079] (Method for preparing rubber composition)

[0080] The preparation method of the rubber composition for hose of the present disclosure is not particularly limited, and a known method can be used. For example, the above components can be mixed using a mixer such as an open mixer, a Banbury mixer, or a closed mixing mixer.

[0081] (hose)

[0082] Will refer to Figure 1 An example of a laminated structure of a hose according to an embodiment of the present disclosure is described. Figure 1 In the present invention, the hose 1 includes an inner tube rubber layer 11, an intermediate rubber layer 13 located radially outside the inner tube rubber layer 11, and an outer cover rubber layer 14 located radially outside the intermediate rubber layer 13, and further, a reinforcement layer 12 is arranged between the inner tube rubber layer 11 and the intermediate rubber layer 13 and between the intermediate rubber layer 13 and the outer cover rubber layer 14, respectively.

[0083] The rubber composition of the present disclosure is preferably used for the intermediate rubber layer of the hose. By using the rubber composition of the present disclosure for the intermediate layer of the hose, a hose having excellent crack growth resistance and elongation fatigue resistance can be obtained.

[0084] The hose of the present disclosure preferably has an intermediate layer composed of the rubber composition of the present disclosure. By having an intermediate layer composed of the rubber composition of the present disclosure, a hose having excellent crack growth resistance and elongation fatigue resistance can be obtained.

[0085] The structure of the hose can be appropriately selected as needed, and for example the reinforcing layer and the intermediate rubber layer can each be composed of two or more layers. In addition, the intermediate rubber layer can be located between the reinforcing layers.

[0086] The reinforcement layer is preferably formed of a metal wire, and more preferably formed of a brass-plated wire.

[0087] (Hose Manufacturing Method)

[0088] The following method for manufacturing the hose 1 can be exemplified.

[0089] First, the rubber composition for inner tube rubber layer 11 is injection molded onto the outside of a core (mandrel) having a diameter approximately equal to the inner diameter of the hose, covering the mandrel, thereby forming inner tube rubber layer 11 (inner tube extrusion step). Next, a predetermined number of brass-plated wires are braided onto the outside of inner tube rubber layer 11 formed in the inner tube extrusion step to form two reinforcement layers 12 (braiding step), and a rubber sheet made from the rubber composition for a hose of the present disclosure is inserted and formed between the two reinforcement layers 12 to form intermediate rubber layer 13. Furthermore, outer cover rubber layer 14 made from the rubber composition is extruded and formed (outer cover extrusion step).

[0090] Next, the outer side of the outer cover rubber layer 14 formed in the outer cover extrusion step is appropriately coated with a suitable resin (resin mold coating step), and it is vulcanized under predetermined conditions (vulcanization step). After vulcanization, the coating resin is peeled off (resin mold peeling step), and the mandrel is removed (mandrel removal step), thereby obtaining the hose 1 having the reinforcing layer 12 and the intermediate rubber layer 13 between the inner tube rubber layer 11 and the outer cover rubber layer 14.

[0091] Example

[0092] Hereinafter, the present disclosure will be described in more detail with reference to Examples, but the present disclosure is not limited to the following Examples in any way.

[0093] (Measurement of Physical Properties of Chloroprene Rubbers 1 and 2)

[0094] For chloroprene rubber 1 (manufactured by Tosoh Corporation, trade name “Skyprene”, grade: B-30) and chloroprene rubber 2 (manufactured by Denka Co., Ltd., trade name “Denka Chloroprene”, grade: DCR-36), the following physical property measurements were performed.

[0095] (1) Mooney viscosity

[0096] Mooney viscosity was measured at 100°C using a Mooney viscometer (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K6300-1. After preheating at 100°C for 1 minute, the torque value after 4 minutes was measured in Mooney units. The smaller the Mooney viscosity value, the lower the unvulcanized viscosity; the larger the value, the harder the material.

[0097] The measurement result for chloroprene rubber 1 was 49M, and the measurement result for chloroprene rubber 2 was 80M.

[0098] (2) Crystallization start time

[0099] The crystallization start time was measured at 0° C. by isothermal crystallization measurement using a differential scanning calorimeter (DSC, manufactured by TA Instruments) in accordance with JIS K7121.

[0100] The measurement result for chloroprene rubber 1 was 120 minutes, and the measurement result for chloroprene rubber 2 was 3000 minutes.

[0101] (3) Weight average molecular weight

[0102] The weight average molecular weight (Mw) is measured by gel permeation chromatography [GPC: HLC-8020 manufactured by Tosoh Corporation, column: GMH-XL manufactured by Tosoh, detector: differential refractometer (RI)] using standard polystyrene manufactured by Tosoh as a reference.

[0103] The measurement result for chloroprene rubber 1 is 39×10 4 , and the measurement result for chloroprene rubber 2 is 57×10 4 .

[0104] (Preparation and Evaluation of Rubber Compositions)

[0105] The components shown in Table 1 were charged into an internal mixer and kneaded to prepare a rubber composition. The obtained rubber composition was evaluated by the following method. The evaluation results are shown in Table 1.

[0106] (1) Evaluation of processability

[0107] For each sample of Examples and Comparative Examples, after preheating the unvulcanized rubber composition at 127° C. for 1 minute, the torque value after 4 minutes was measured in Mooney units using a rotorless Mooney viscometer (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K6300-1.

[0108] The smaller the value, the better the processability such as kneading and extrusion.

[0109] (2) Evaluation of sheet fracture

[0110] For each sample of Examples and Comparative Examples, the unvulcanized rubber composition was formed into a sheet using a roller, and a tensile test was performed at room temperature in accordance with JIS K6251 to measure the 100% deformation modulus.

[0111] The larger the value, the better the prevention of sheet breakage during winding.

[0112] (3) Evaluation of elongation fatigue resistance (number of fractures)

[0113] As an index of elongation fatigue resistance, the number of fractures was measured.

[0114] For each sample of Examples and Comparative Examples, after vulcanization treatment, a DIN No. 3 test piece was subjected to repeated 200% elongation at 2.5 Hz using a tensile testing machine (manufactured by Orientec Co., Ltd.) This value indicates the number of elongations at which the test piece broke.

[0115] The larger the value, the better the elongation fatigue resistance.

[0116] The values ​​in Table 1 are the average of two measurements.

[0117] (4) Evaluation of crack growth resistance (number of De Mattia bending operations)

[0118] As an index of crack growth resistance, the number of De Mattia bending operations was measured.

[0119] For each sample of the Examples and Comparative Examples, after vulcanization, a linear 2.5 mm notch was made in the center of a 140 × 25 × 6.3 mm test piece. The number of bending operations at 35°C was measured using a De Mattia flex tester (manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6260. This value indicates the number of bending operations when the crack length along the long side of the test piece reaches 20 mm.

[0120] The larger the value, the better the crack growth resistance.

[0121] The values ​​in Table 1 are the average of two measurements.

[0122] [Table 1]

[0123]

[0124] *1: Butadiene rubber: manufactured by JSR Corporation, trade name "SBR#1500"

[0125] *2: Chloroprene rubber 1: manufactured by Tosoh Corporation, trade name "Skyprene", grade: B-30, Mooney viscosity at 100°C = 49 M, crystallization start time at 0°C = 120 minutes, weight average molecular weight (Mw) = 39 × 10 4

[0126] *3: Chloroprene rubber 2: manufactured by Denka Co., Ltd., trade name “Denka Chloroprene”, grade: DCR-36, Mooney viscosity at 100°C = 80 M, crystallization start time at 0°C = 3000 minutes, weight average molecular weight (Mw) = 57×10 4

[0127] *4: Carbon black 1: FEF grade carbon black, manufactured by Tokai Carbon Co., Ltd., trade name "SEAST F", nitrogen adsorption specific surface area (N2SA): 45 m 2 / g

[0128] *5: Carbon black 2: SRF grade carbon black, manufactured by Asahi Carbon Co., Ltd., trade name "#50", nitrogen adsorption specific surface area (N2SA): 28 m 2 / g

[0129] *6: Calcium carbonate: manufactured by Nitto Funka Co., Ltd., trade name "NS#100"

[0130] *7: Silica: manufactured by Tosoh Corporation, trade name "Nipsil AQ"

[0131] *8: Oil: Manufactured by JXTG Nippon Oil & Energy Corporation, trade name "Super Oil Y22"

[0132] *9: Sulfur: manufactured by Tsurumi Chemical Industry Co., Ltd., trade name "Sulfax 5"

[0133] *10: Vulcanization accelerator: manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., trade name "Nocceler NS-F"

[0134] *11: Zinc oxide: manufactured by Hakusui Tech Co., Ltd., trade name "No. 3 zinc oxide"

[0135] The rubber compositions of Examples 1 and 2 (in which chloroprene rubber and carbon black satisfying the specified conditions are combined) exhibit excellent non-rotor Mooney values, number of fractures, and number of De Mattia bending operations, and are found to be excellent in all aspects of processability, crack growth resistance, and elongation fatigue resistance. On the other hand, although the rubber compositions of Comparative Examples exhibit comparable processability, crack growth resistance, or elongation fatigue resistance to those of Examples 1 and 2, they are not all excellent in processability, crack growth resistance, and elongation fatigue resistance, and are found to be inferior to those of Examples 1 and 2.

[0136] Industrial applicability

[0137] The present disclosure provides a hose rubber composition having excellent processability, crack growth resistance, and elongation fatigue resistance. Furthermore, a hose comprising the hose rubber composition and exhibiting excellent crack growth resistance and elongation fatigue resistance can be provided.

[0138] Description of Reference Numerals

[0139] 1: Hose

[0140] 11: Inner tube rubber layer

[0141] 12: Enhancement layer

[0142] 13: Middle rubber layer

[0143] 14: Outer covering rubber layer

Claims

1. A rubber composition for a hose comprising a rubber component containing at least chloroprene rubber and carbon black, wherein the content of the chloroprene rubber is 70 parts by mass or more per 100 parts by mass of the rubber component, wherein the Mooney viscosity of the chloroprene rubber is 43M to 53M and the crystallization start time at 0°C is 30 minutes to 500 minutes, wherein the content of the carbon black is 40 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, and The nitrogen adsorption specific surface area (N2SA) of the carbon black is 30m 2 / g to 55m 2 / g.

2. The rubber composition for hose according to claim 1, wherein the weight average molecular weight of the chloroprene rubber is 20×10 4 to 40×10 4 . 3 . The rubber composition for a hose according to claim 1 , wherein the content of the chloroprene rubber is 90 parts by mass or less per 100 parts by mass of the rubber component. 4 . The rubber composition for a hose according to claim 1 , wherein the rubber component further comprises butadiene rubber. The rubber composition for a hose according to claim 1 , which is used for an intermediate layer of a hose. 6 . A hose comprising an intermediate layer made of the rubber composition for a hose according to claim 1 .

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