Rubber composition for the outer surface of high-pressure hoses, and high-pressure hoses

Abstract

To provide a high-pressure hose with excellent abrasion resistance, oil resistance, flame retardancy, and scorch resistance. [Solution] A rubber composition for the outer surface of a high-pressure hose containing the following components (A) to (F), wherein the content ratio of component (A) is 40 to 55 parts by mass, the content ratio of component (B) is 40 to 55 parts by mass, the content ratio of component (C) is 5 to 10 parts by mass, and the content of component (F) is 2 to 5 parts by mass, based on 100 parts by mass of the total of components (A) to (C). (A) Chloroprene rubber (B) Butadiene rubber (C) Acrylonitrile Butadiene Rubber (D) At least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator. (E) At least one of a dithiocarbamate-based vulcanization accelerator and a thiram-based vulcanization accelerator. (F) Sulfur

Description

Technical Field

[0001] The present invention relates to a rubber composition for the outer surface of a high-pressure hose and a high-pressure hose. More specifically, for example, it relates to high-pressure hoses for industrial machines such as construction machines (construction machinery) and mining machines, and vehicles.

Background Art

[0002] High-pressure hoses used in construction machines, mining machines, etc. have a layer structure that can withstand high internal pressure. For example, in Patent Document 1, an intermediate rubber layer is formed on the outer peripheral surface of the inner rubber layer, a reinforcing layer made of plated wire is formed on the outer peripheral surface of the intermediate rubber layer, an intermediate rubber layer is formed on the outer peripheral surface of the reinforcing layer, and an outer rubber layer is formed on the outer peripheral surface of the intermediate rubber layer. A high-pressure hose is disclosed.

[0003] Also, in the same document, as the rubber component constituting the outer rubber layer, chloroprene rubber (CR), styrene butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), a blend rubber of SBR and EPDM, acrylonitrile butadiene rubber (NBR), etc. have been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Wear resistance, oil resistance, and flame retardancy are required for the outer layer of the high-pressure hose. From such a viewpoint, the present inventors have intensively studied by focusing on a method of using a rubber component in which chloroprene rubber, butadiene rubber, and acrylonitrile butadiene rubber are combined. As a result, it has been found that the above method has problems in characteristics different from wear resistance, oil resistance, and flame retardancy, such as scorch resistance, and it is difficult to satisfy these at the same time.

[0006] The inventors, having conducted further intensive research from the perspective of solving the above problems, have discovered that the above problems can be solved by setting the content ratios of chloroprene rubber, butadiene rubber, and acrylonitrile butadiene rubber to specific ranges, setting the content of sulfur, which is a vulcanizing agent, to a specific range, and further using a combination of these with a specific vulcanization accelerator.

[0007] This invention has been made in view of these circumstances and aims to provide a high-pressure hose that is excellent in abrasion resistance, oil resistance, flame retardancy, and scorch resistance. [Means for solving the problem]

[0008] In other words, the gist of the present invention is as follows: [1] to [6]. [1] A rubber composition for the outer surface of a high-pressure hose containing the following components (A) to (F), wherein the content ratio of component (A) is 40 to 55 parts by mass, the content ratio of component (B) is 40 to 55 parts by mass, the content ratio of component (C) is 5 to 10 parts by mass, and the content of component (F) is 2 to 5 parts by mass, based on 100 parts by mass of the total of components (A) to (C). (A) Chloroprene rubber (B) Butadiene rubber (C) Acrylonitrile Butadiene Rubber (D) At least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator. (E) At least one of a dithiocarbamate-based vulcanization accelerator and a thiram-based vulcanization accelerator. (F) Sulfur [2] Furthermore, the rubber composition for the outer surface of a high-pressure hose according to [1] contains aluminum hydroxide. [3] The rubber composition for the outer surface of a high-pressure hose according to [1] or [2], wherein the amount of acrylonitrile in component (C) above is 26 to 35% by mass. [4] A rubber composition for the outer surface of a high-pressure hose, as described in any of [1] to [3], which does not contain a silane coupling agent. [5] A rubber composition for the outer surface of a high-pressure hose according to any one of [1] to [4], comprising a sulfenamide-based vulcanization accelerator as component (D) above, and a dithiocarbamate-based vulcanization accelerator as component (E) above. [6] A high-pressure hose having an outer rubber layer made of a rubber composition for the outer surface of a high-pressure hose as described in any of [1] to [5]. [Effects of the Invention]

[0009] By using the rubber composition for the outer surface of high-pressure hoses of the present invention, it is possible to provide a high-pressure hose with excellent abrasion resistance, oil resistance, flame retardancy, and scorch resistance. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing an example of a high-pressure hose according to an embodiment of the present invention. [Figure 2] This is a schematic diagram showing an example of a high-pressure hose according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments. In this specification, when "X~Y" (where X and Y are any numbers) is used, unless otherwise specified, it means "X or greater and Y or less," and also includes the meanings of "preferably greater than X" or "preferably less than Y." Furthermore, with respect to the numerical ranges described in stages in this specification, the upper or lower limit of one stage of the numerical range can be arbitrarily combined with the upper or lower limit of another stage of the numerical range. Also, within the numerical ranges described in this specification, the upper or lower limit of that numerical range can be replaced with the values ​​shown in the examples.

[0012] [Outer rubber layer] The rubber composition for the outer surface of a high-pressure hose according to an embodiment of the present invention (hereinafter sometimes referred to as "the rubber composition for the present outer surface") is, for example, a material for the outer rubber layer constituting the outermost layer of a multilayer hose, and is a rubber composition for the outer surface of a high-pressure hose containing the following components (A) to (F). The content ratio of component (A) is 40 to 55 parts by mass, the content ratio of component (B) is 40 to 55 parts by mass, the content ratio of component (C) is 5 to 10 parts by mass, and the content of component (F) is 2 to 5 parts by mass with respect to a total of 100 parts by mass of components (A) to (C). (A) Chloroprene rubber (B) Butadiene rubber (C) Acrylonitrile-butadiene rubber (D) At least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator (E) At least one of a dithiocarbamate-based vulcanization accelerator and a thiuram-based vulcanization accelerator (F) Sulfur

[0013] In the research and development of high-pressure hoses, the inventor focused on and conducted repeated research on a rubber composition for the outer surface containing chloroprene rubber, butadiene rubber, and acrylonitrile-butadiene rubber. In the process of this research and development, although it is possible to satisfy each required property such as abrasion resistance, oil resistance, and flame retardancy to some extent, it has become clear that it is difficult to simultaneously satisfy other required properties such as scorch resistance and compression set. Specifically, for example, in a rubber composition for the outer surface containing chloroprene rubber, butadiene rubber, and acrylonitrile-butadiene rubber, when the content ratio of chloroprene rubber is relatively high or when the content ratio of acrylonitrile-butadiene rubber is relatively high, it has been difficult to satisfy the required properties of scorch resistance and compression set.

[0014] In the process of diligently conducting research from the perspective of satisfying the required characteristics of scorch resistance and compression set in addition to abrasion resistance, oil resistance, and flame retardancy, the inventors conceived the idea of ​​adjusting the blending ratio of chloroprene rubber, butadiene rubber, and acrylonitrile butadiene rubber to a different ratio than conventional methods to achieve a high degree of both flame retardancy and abrasion resistance, and further increasing hardness and crosslinking density by incorporating a relatively large amount of sulfur different from conventional methods, thereby improving abrasion resistance and oil resistance. However, it was difficult to satisfy the required characteristics of scorch resistance and compression set simply by increasing the sulfur content.

[0015] The inventors, through further experiments and verification, have found that in a rubber composition for the outer surface of a high-pressure hose containing chloroprene rubber, butadiene rubber, and acrylonitrile butadiene rubber, the content of chloroprene rubber is set to 40-55 parts by mass, the content of butadiene rubber to 40-55 parts by mass, and the content of acrylonitrile butadiene rubber to 5-10 parts by mass, and the sulfur content is set to a specific range of 2-5 parts by mass, and furthermore, by using at least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator, and at least one of a dithiocarbamate-based vulcanization accelerator and a thiuram-based vulcanization accelerator in combination, the required properties of abrasion resistance, oil resistance, and flame retardancy, as well as scorch resistance and compression set set, can be achieved.

[0016] By using this rubber composition for external applications, it is possible to provide a high-pressure hose with excellent abrasion resistance, oil resistance, flame retardancy, and scorch resistance. Furthermore, by using this external rubber composition, it is possible to provide a high-pressure hose with excellent compression set resistance.

[0017] The following describes in detail the rubber composition for exterior use and the high-pressure hose using this rubber composition (hereinafter sometimes referred to as "this hose").

[0018] (A) Chloroprene rubber This exterior rubber composition contains (A) chloroprene rubber (CR) from the viewpoint of oil resistance and flame retardancy. The content ratio of component (A) is 40 to 55 parts by mass per 100 parts by mass of the total of components (A) to (C), from the viewpoint of achieving the effects of the present invention. The content ratio of component (A) can be set appropriately within the above range, for example, 40 to 50 parts by mass or 40 to 48 parts by mass.

[0019] (A) Component(s) may be those conventionally known in the art, and may be used individually or in combination of two or more.

[0020] (A) Component is not limited to the following, but examples include sulfur-modified chloroprene rubber and non-sulfur-modified chloroprene rubber. Among these, non-sulfur-modified chloroprene rubber is preferred. Specifically, xanthogen-modified chloroprene rubber and mercapto-modified chloroprene rubber are preferred, and among these, mercapto-modified chloroprene rubber is preferred in terms of compression set.

[0021] The microstructure of the chloroprene rubber is not particularly limited, but for example, chloroprene rubber with a trans-1,4 bond unit content of 90% by mass or more can be used as appropriate.

[0022] (A) Component Mooney viscosity (ML 1+4 (100℃) is not particularly limited, but for example, it is 35 to 80, and 43 to 53 is preferred.

[0023] Mooney viscosity is measured in accordance with the provisions of JIS K6300-1:2013, using an L-shaped rotor, with a preheating time of 1 minute, rotor rotation time of 4 minutes, and a test temperature of 100°C.

[0024] (B) Butadiene rubber This exterior rubber composition contains (B) butadiene (BR) from the viewpoint of abrasion resistance and other properties. The content ratio of component (B) is 40 to 55 parts by mass per 100 parts by mass of the total of components (A) to (C), from the viewpoint of achieving the effects of the present invention. The content ratio of component (B) can be set appropriately within the above range, for example, 45 to 50 parts by mass.

[0025] (B) Component can be any that is conventionally known in the art, and can be used alone or in combination of two or more.

[0026] The microstructure of butadiene rubber (BR) is not particularly limited, but for example, low-cis-BR with a cis-1,4 bond unit content of 50% by mass or less, for example, around 30-40% by mass, or high-cis-BR with 90% by mass or more, can be used as appropriate.

[0027] (B) Component Mooney viscosity (ML 1+4 (100℃) is not particularly limited, but for example, it is 30 to 55, and 35 to 45 is preferred.

[0028] (C) Acrylonitrile Butadiene Rubber This exterior rubber composition contains (C) acrylonitrile butadiene rubber (NBR) from the viewpoint of oil resistance and other properties. The content ratio of component (C) is 5 to 10 parts by mass per 100 parts by mass of the total of components (A) to (C), from the viewpoint of achieving the effects of the present invention.

[0029] (C) Component can be any that is conventionally known in the art, and can be used alone or in combination of two or more.

[0030] The amount of acrylonitrile (AN) in acrylonitrile butadiene rubber (NBR) is not particularly limited, but from the viewpoint of further improving oil resistance, it is preferably 26 to 35% by mass, and more preferably 29 to 33% by mass.

[0031] (C) Mooney viscosity of component (ML)1+4 (100℃) is not particularly limited, but for example, it is 45 to 75 degrees Celsius, and 50 to 70 degrees Celsius is preferred.

[0032] The rubber composition for exterior use may optionally contain rubber components other than components (A) to (C), but it is preferable that components (A) to (C) be the main components of the rubber composition. Specifically, the total content of components (A) to (C) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass, relative to the total amount of rubber components (100% by mass) contained in the rubber composition for exterior use.

[0033] Furthermore, the total content of components (A) to (C) relative to the total amount (100% by mass) of the rubber composition for exterior use is, for example, 30 to 60% by mass, preferably 38 to 50% by mass.

[0034] (D) At least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator. This exterior rubber composition contains at least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator as a vulcanization accelerator. That is, this exterior rubber composition contains either a sulfenamide-based vulcanization accelerator, a thiazole-based vulcanization accelerator, or both. These can be used individually or in combination of two or more. Among these, a sulfenamide-based vulcanization accelerator is preferred from the viewpoint of scorch resistance and adhesion to the reinforcing layer.

[0035] Examples of sulfenamide-based vulcanization accelerators include N-oxydiethylene-2-benzothiazolyl sulfenamide (NOBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), Nt-butyl-2-benzothiazoyl sulfenamide (BBS), and N,N'-dicyclohexyl-2-benzothiazoyl sulfenamide. These can be used individually or in combination of two or more.

[0036] Examples of thiazole-based vulcanization accelerators include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), 2-mercaptobenzothiazole zinc salt (ZnMBT), and 2-(4'-morpholinodithio)benzothiazole. These can be used individually or in combination of two or more.

[0037] From the viewpoint of significantly achieving the effects of the present invention, the content of component (D) is preferably 0.8 to 1.6 parts by mass, more preferably 0.9 to 1.4 parts by mass, and even more preferably 1.2 to 1.4 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0038] (E) At least one of a dithiocarbamate-based vulcanization accelerator and a thiram-based vulcanization accelerator. This exterior rubber composition contains at least one of a dithiocarbamate-based vulcanization accelerator and a thiram-based vulcanization accelerator as a vulcanization accelerator. That is, this exterior rubber composition contains either a dithiocarbamate-based vulcanization accelerator, a thiram-based vulcanization accelerator, or both. These can be used individually or in combination of two or more. Among these, a dithiocarbamate-based vulcanization accelerator is preferred from the viewpoint of compression set and other factors.

[0039] Examples of dithiocarbamate-based vulcanization accelerators include zinc dibutyldithiocarbamate, piperidine pentamethylenedithiocarbamate, pipecholine pipericoldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, and zinc dimethyldithiocarbamate. These can be used individually or in combination of two or more.

[0040] Examples of thiram-based vulcanization accelerators include tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide (TETD), tetrabutylthiram disulfide (TBTD), tetrakis(2-ethylhexyl)thiram disulfide (TOT), tetrabenzylthiram disulfide (TBzTD), and tetramethylthiram monosulfide (TMTM). These can be used individually or in combination of two or more.

[0041] From the viewpoint of significantly achieving the effects of the present invention, the content of component (E) is preferably 0.2 to 0.8 parts by mass, more preferably 0.3 to 0.6 parts by mass, and even more preferably 0.4 to 0.5 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0042] It is important to use (D) and (E) in combination as vulcanization accelerators in this exterior rubber composition. If only one of them is included, or if different combinations of vulcanization accelerators are included, it tends to be difficult to fully achieve the effects of the present invention. In this rubber composition for exterior use, the mass ratio of component (D) to component (E) [(D) / (E)] is preferably 1.0 to 8.0, and more preferably 2.3 to 5.0, from the viewpoint of significantly achieving the effects of the present invention.

[0043] (F) Sulfur This exterior rubber composition contains (F) sulfur. From the viewpoint of achieving the effects of the present invention, the content of component (F) is 2 to 5 parts by mass per 100 parts by mass of the total of components (A) to (C). If the content of component (F) exceeds the above range, it tends to become difficult to achieve both scorch resistance and compression set, for example. The content of component (F) can be set appropriately within the above range, for example, 2.5 to 4 parts by mass.

[0044] (F) Examples of sulfur commonly used in this technology include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. These may be used individually or in combination of two or more types.

[0045] Other ingredients In addition to the components (A) to (F) above, this exterior rubber composition may optionally contain hydrated metal compounds such as aluminum hydroxide and magnesium hydroxide, silica, carbon black, and other optional materials such as plasticizers, antioxidants, and vulcanization aids.

[0046] (aluminum hydroxide) From the viewpoint of abrasion resistance, it is preferable to incorporate aluminum hydroxide into this outer rubber composition. The average particle size of aluminum hydroxide is not particularly limited, but is, for example, 0.5 to 3.0 μm, and preferably 0.8 to 1.5 μm. The average particle size is the volume average particle size, and can be derived, for example, by measuring a sample arbitrarily drawn from a population using a laser diffraction scattering particle size distribution analyzer.

[0047] From the viewpoint of significantly achieving the effects of the present invention, the content of aluminum hydroxide is preferably 5 to 15 parts by mass, and more preferably 7.5 to 10 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0048] (silica) As silica, any type conventionally known in this art can be used as appropriate, and it may be crystalline or amorphous. These can be used alone or in combination of two or more types.

[0049] The average particle size of silica is not particularly limited, but is preferably in the range of 5 to 40 μm, and more preferably 15 to 25 μm. The above average particle size can be measured, for example, using a laser diffraction scattering particle size distribution analyzer.

[0050] The pH of silica is not particularly limited, but is, for example, 5.0 to 11.5, and preferably 5.5 to 8.5.

[0051] From the viewpoint of significantly achieving the effects of the present invention, the silica content is preferably 5 to 15 parts by mass, and more preferably 7.5 to 12.5 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0052] (Carbon Black) As carbon black, conventionally known carbon blacks in this art can be used as appropriate, for example, various grades of carbon black such as SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, and MT grade. These can be used alone or in combination of two or more. Among these, FEF grade carbon black is preferred from the viewpoint of significantly demonstrating the effects of the present invention, particularly from the viewpoint of wear resistance and scorch resistance.

[0053] From the viewpoint of abrasion resistance and scorch resistance, the average particle size of carbon black is preferably 70 nm or less, more preferably 55 nm or less, and even more preferably 45 nm or less. There is no specific lower limit, but 20 nm or more is preferred. The average particle size of carbon black can be measured using a TEM or similar device.

[0054] From the viewpoint of significantly achieving the effects of the present invention, the carbon black content is preferably 50 to 90 parts by mass, and more preferably 60 to 80 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0055] (Plasticizer) Examples of plasticizers include aromatic oils, ether ester plasticizers, and process oils. These can be used individually or in combination of two or more. Examples of aromatic oils include Diana Process AC-12, Diana Process AC-460, Diana Process AH-16 (all manufactured by Idemitsu Showa Shell Co., Ltd.), JSO Aroma 790 (manufactured by Nippon Sun Oil Co., Ltd.), Aromax 1, and Aromax 3 (both manufactured by Fuji Kogyo Co., Ltd.). Examples of ether ester plasticizers include those that have both ether and ester bonds in a single molecule. Specifically, examples include adipic acid ether ester plasticizers such as bis[2-(2-butoxyethoxy)ethyl] adipate. Examples of process oils include naphthenic oils and paraffinic oils.

[0056] The plasticizer content is not particularly limited, but is, for example, 10 to 25 parts by mass, preferably 15 to 20 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0057] (Anti-aging agent) Examples of anti-aging agents include carbamate-based anti-aging agents, phenylenediamine-based anti-aging agents, phenol-based anti-aging agents, phenylamine-based anti-aging agents, diphenylamine-based anti-aging agents, quinoline-based anti-aging agents, imidazole-based anti-aging agents, and waxes. These can be used individually or in combination of two or more.

[0058] The amount of the anti-aging agent is not particularly limited, but is, for example, 1 to 10 parts by mass, preferably 3 to 8 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0059] (Vulcanization aid) Examples of vulcanization aids include zinc oxide, zinc oxide (ZnO), stearic acid, and magnesium oxide. These can be used individually or in combination of two or more. The amount of vulcanization aid is not particularly limited, but is, for example, 3 to 10 parts by mass, preferably 5 to 8 parts by mass, per 100 parts by mass of the total of components (A) to (C).

[0060] Furthermore, from the viewpoint of suppressing a decrease in scorch resistance, it is preferable that this rubber composition for exterior use does not contain a silane coupling agent.

[0061] For example, it is preferable that the product does not contain sulfide-based silane coupling agents. Specifically, for example, bis-(3-(triethoxysilyl)-propyl)-disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-(3-(triethoxysilyl)-propyl)-tetrasulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N- Examples include dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, and 3-trimethoxysilylpropyl methacrylate monosulfide. It is preferable that this rubber composition for exterior use does not contain these silane coupling agents.

[0062] Other silane coupling agents include, for example, mercapto-silane coupling agents, amine-silane coupling agents, epoxy-silane coupling agents, and vinyl-silane coupling agents, but it is preferable that this rubber composition for exterior use does not contain any of these silane coupling agents.

[0063] Furthermore, "does not contain silane coupling agents" means that it substantially does not contain silane coupling agents, specifically meaning that it contains 0.1% by mass or less of the total amount (100% by mass) of the rubber composition for exterior use, preferably 0.05% by mass or less, particularly preferably 0.01% by mass or less, and most preferably 0% by mass.

[0064] [Preparation of rubber composition for external use] The above rubber composition can be prepared, for example, by appropriately blending components (A) to (F) above, and various other materials as needed, and kneading them using a kneader, roll, Banbury mixer, or other kneading machine.

[0065] [Characteristics of rubber compositions for exterior use] By using this external rubber composition, a high-pressure hose with excellent abrasion resistance, oil resistance, flame retardancy, scorch resistance, and compression set can be provided. Specifically, for example, the external rubber composition preferably has an abrasion amount of 0.25 g or less, as measured by the method described in the following examples, and more preferably 0.2 g or less.

[0066] The rubber composition for exterior use preferably has a volume change rate ΔV (%) measured by the method described in the following examples of 125% or less, and more preferably 100% or less.

[0067] The rubber composition for exterior use preferably has a scorch time of 15 minutes or more, and more preferably 20 minutes or more, as measured by the method described in the following examples.

[0068] The rubber composition for exterior surfaces preferably has a compression set (%) of 50% or less, and more preferably 40% or less, as measured by the method described in the following examples.

[0069] The rubber composition for exterior use preferably has an oxygen index greater than 21, and more preferably 26 or higher, as measured by the method described in the following examples.

[0070] [Layered structure of the hose] The hose is not particularly limited in terms of the layer configuration or number of layers, as long as it has an outer rubber layer made of the outer rubber composition. For example, an example of a hose with a layer structure having an inner rubber layer made of the inner rubber composition, a reinforcing layer made of plated wire, and a rubber layer made of the outer rubber composition on the outside of the reinforcing layer.

[0071] (Reinforcement layer) This hose typically has a reinforcing layer made of plated wire to reinforce the overall strength of the hose. Specifically, the reinforcing layer is made by braiding plated wire in a braided or spiral shape.

[0072] Metal wires, particularly steel wires, are preferably used as the wires (strands) to be plated. Examples of plating treatments include copper plating, zinc plating, brass (copper-zinc alloy) plating, nickel plating, tin plating, and cobalt plating. Among these, brass (copper-zinc alloy) plating is preferred.

[0073] Specific examples of the layer structure in this hose include, but are not limited to, a hose having a three-layer structure of "inner rubber layer / reinforcement layer / outer rubber layer," in which the outer rubber layer is made of this outer rubber composition. Another example is a hose having a four-layer structure of "inner rubber layer / intermediate rubber layer / reinforcement layer / outer rubber layer," in which the outer rubber layer is made of this outer rubber composition. Yet another example is a hose having a five-layer structure of "inner rubber layer / reinforcement layer 1 / intermediate rubber layer / reinforcement layer 2 / outer rubber layer," in which the outer rubber layer is made of this outer rubber composition.

[0074] The inner diameter of this hose is not particularly limited, but is usually 5 to 85 mm, preferably 6 to 80 mm. The outer diameter of this hose is usually 9 to 100 mm, preferably 10 to 85 mm.

[0075] Furthermore, while there are no particular restrictions on the thickness of each layer, the thickness of the inner rubber layer is, for example, 0.7 to 4.0 mm, preferably 1.0 to 3.0 mm. The overall thickness of the intermediate rubber layer is, for example, 0.1 to 0.5 mm, preferably 0.2 to 0.4 mm. The thickness of the outer rubber layer is, for example, 0.5 to 2.5 mm, preferably 0.8 to 2.0 mm.

[0076] Furthermore, an embodiment of this hose will be described with reference to the figures, but the present invention is not limited to the structure shown in the figures. The high-pressure hose shown in Figure 1 is a hose having a five-layer structure in which an intermediate rubber layer 2a is formed on the outer circumferential surface of an inner rubber layer 1, a reinforcing layer 3 made of plated wire is formed on the outer circumferential surface of the intermediate rubber layer 2a, an intermediate rubber layer 2b is formed on the outer circumferential surface of the reinforcing layer 3, and an outer rubber layer 4 is formed on the outer circumferential surface of the intermediate rubber layer 2b. In this hose, the outer rubber layer 4 can be a rubber layer made of the outer rubber composition.

[0077] Furthermore, for example, the high-pressure hose shown in Figure 2 is a hose having a three-layer structure in which a reinforcing layer 3 made of plated wire is formed on the outer surface of the inner rubber layer 1, and an outer rubber layer 4 is formed on the outer surface of the reinforcing layer 3. In this hose, the outer rubber layer 4 can be a rubber layer made of this outer rubber composition.

[0078] When forming the inner rubber layer 1, as shown in Figure 1 for the high-pressure hose, a rubber with excellent oil resistance is preferred as the material. Examples include acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), acrylic rubber (ACM), ethylene acrylate rubber (AEM), chlorinated polyethylene (CM), chlorosulfonated polyethylene (CSM), and fluororubber (FKM). These can be used individually or in combination of two or more. Among these, NBR is preferred in terms of oil resistance, strength, and cost. In addition to rubber such as NBR, fillers, plasticizers, stearic acid, zinc oxide, vulcanizing agents, vulcanization accelerators, etc., may be appropriately blended as needed.

[0079] [Manufacturing method] The manufacturing method of this hose will be explained using an embodiment of the present invention shown in Figure 1 as an example. First, an inner rubber layer 1 is formed by extruding a rubber composition for forming the inner rubber layer onto a mandrel using an extrusion molding machine. Next, an intermediate rubber layer 2a is formed by extruding a rubber composition for forming the intermediate rubber layer onto the outer surface of the inner rubber layer 1. Subsequently, a reinforcing layer 3 is formed on the outer surface of the intermediate rubber layer 2a by spirally braiding plated wires such as brass plated wire. After that, an intermediate rubber layer 2b is formed by extruding a rubber composition for forming the intermediate rubber layer onto the outer surface of the reinforcing layer 3. Furthermore, an outer rubber layer 4 is formed by extruding a rubber composition for forming the outer rubber layer (this outer rubber composition) onto the outer surface of the intermediate rubber layer 2b. Finally, a high-pressure hose with the layer structure shown in Figure 1 can be manufactured by vulcanizing (steam vulcanization, etc.) this laminate under predetermined conditions (for example, 140-170°C for 10-60 minutes).

[0080] Furthermore, for example, when manufacturing a hose having a three-layer structure of "inner rubber layer / reinforcement layer / outer rubber layer" as shown in Figure 2, the same procedure as described above is followed: the outer rubber composition is extruded onto a mandrel using an extrusion molding machine to form the inner rubber layer 1; then, a reinforcement layer 3 is formed by spirally braiding plated wires, such as brass plated wires, onto the outer surface of the inner rubber layer 1; and finally, the outer rubber composition is extruded onto the outer surface of the reinforcement layer 3 to form the outer rubber layer 4. Finally, this laminate can be vulcanized (steam vulcanization, etc.) under predetermined conditions (for example, 140-170°C for 10-60 minutes) to produce a three-layer high-pressure hose.

[0081] [Application] This hose is suitable for use in high-pressure hoses, more specifically, in high-pressure hydraulic hoses used to circulate high-pressure fluids in construction machinery, civil engineering machinery, industrial machinery, vehicles, ships, etc. [Examples]

[0082] Next, the examples will be described together with comparative examples. However, the present invention is not limited to these examples.

[0083] First, prior to the examples and comparative examples, the following materials were prepared.

[0084] <<(A) Chloroprene rubber>> • Skyplane B-30 (manufactured by Tosoh Corporation)

[0085] <<(B) Butadiene rubber>> • UBEPOL BR-150 (manufactured by Ube Industries, Ltd.)

[0086] <<(C) Acrylonitrile Butadiene Rubber>> • Nipol DN202 (manufactured by Nippon Zeon Co., Ltd., AN content 31%)

[0087] <<(D) Sulfenamide / thiazole-based vulcanization accelerators>> • Noxellar MSA (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., a sulfenamide-based vulcanization accelerator) • Noxellar DM (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., a thiazole-based vulcanization accelerator)

[0088] <<(E) Dithiocarbamate / thiram-based vulcanization accelerators>> • Noxellar BZ (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., dithiocarbamate-based vulcanization accelerator) • Noxellar TET (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., thiram-based vulcanization accelerator (1)) • Noxellar TS (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., thiram-based vulcanization accelerator (2))

[0089] <<Other vulcanization accelerators>> • Noxellar D (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., a guanidine-based vulcanization accelerator)

[0090] <<(F) Sulfur>> • Sulfur (manufactured by Hosoi Chemical Industry Co., Ltd., 325 mesh) Note that the sulfur content in Table 1 is shown in terms of raw material equivalent.

[0091] <<Silica>> • NipSeal VN3 (manufactured by Tosoh Silica Co., Ltd.)

[0092] <<Aluminum hydroxide>> • KH-101 (manufactured by KC Corporation)

[0093] [Examples 1-9, Comparative Examples 1-5] Each component shown in Table 1 below was blended in the proportions shown in the table. Furthermore, 70 parts by mass of carbon black (Seast SO: manufactured by Tokai Carbon Co., Ltd.), 1.5 parts by mass of stearic acid, 5 parts by mass of zinc oxide, 20 parts by mass of plasticizer, and 7 parts by mass of antioxidant were added. The mixture was then kneaded using a kneader to prepare an unvulcanized rubber composition. The following properties were evaluated using the rubber compositions of the examples and comparative examples. The results are shown in Table 1 below.

[0094] <Abrasion Resistance> Each rubber composition was press-vulcanized at 150°C for 60 minutes to prepare cylindrical vulcanized rubber samples (16.0 mm in diameter, 6.0 mm in height). The amount of abrasion (g) was then measured using these rubber sheets in accordance with the JIS K6264-2 DIN abrasion test (abrasion distance 40 m test). The evaluation was as follows: abrasion of less than 0.2 g was marked "◎", 0.2 g or more and less than 0.25 g was marked "〇", and 0.25 g or more and less than 0.5 g was marked "△". On the other hand, abrasion of 0.5 g or more was marked "×".

[0095] ≪Oil resistance≫ Each rubber composition was press-vulcanized at 150°C for 30 minutes to produce rubber sheets (thickness: 2 mm, length: 100 mm, width: 100 mm). These rubber sheets were then used to form JIS No. 5 dumbbells, and the volume change rate ΔV (%) of each rubber composition was measured after immersion in IRM903 test oil at 120°C for 168 hours, in accordance with JIS K 6258:2003. Evaluation was as follows: ΔV (%) less than 100% was marked "◎", 100% or more and less than 125% was marked "〇", and 125% or more was marked "×".

[0096] <<Scorch Resistance>> For each rubber composition, the scorch time at 121°C was measured in accordance with JIS K 6300-1. A scorch time of 20 minutes or more was evaluated as "◎", a scorch time of 15 minutes or less but less than 20 minutes was evaluated as "○", and a scorch time of less than 15 minutes was evaluated as "×".

[0097] ≪Compression permanent deformation≫ Using the above rubber composition, a cylindrical vulcanized rubber sample was prepared by press vulcanization at 150°C for 60 minutes (diameter 29.0 mm, height 12.5 mm). Using this vulcanized rubber sample, the compression set was measured in accordance with JIS K 6262 under conditions of 120°C, 72 hours of testing, and a compressibility of 25%. The evaluation was as follows: a compression set of less than 40% was marked "◎", 40% to 50% was marked "○", and a compression set exceeding 50% was marked "×".

[0098] Flame retardant Using the above rubber composition, a rubber sheet (thickness: 2 mm, length: 100 mm, width: 100 mm) was produced by press vulcanization at 150°C for 60 minutes. To evaluate the flame resistance of this rubber sheet, the minimum oxygen concentration (volume %) required to sustain combustion of the rubber sheet was measured as the oxygen index, in accordance with JIS K 7201. The evaluation was as follows: an oxygen index of 26 or higher was marked "◎", an oxygen index between 21 and 26 was marked "○", and an oxygen index below 21 was marked "×".

[0099] [Table 1]

[0100] From the results in Table 1 above, it can be seen that the rubber composition according to the embodiment of the present invention is excellent in all aspects, including abrasion resistance, oil resistance, flame retardancy, scorch resistance, and compression set.

[0101] In contrast, Comparative Example 1 uses only a sulfenamide-based vulcanization accelerator as the vulcanization accelerator, and therefore does not satisfy the requirements of the present invention, and thus cannot be satisfied in terms of oil resistance. Furthermore, Comparative Example 2 uses a thiram-based vulcanization accelerator and a guanidine-based vulcanization accelerator as vulcanization accelerators, and therefore does not satisfy the requirements of the present invention, and thus cannot be satisfied in terms of scorch resistance.

[0102] Furthermore, Comparative Example 3 has a high sulfur content and does not satisfy the requirements of the present invention, and therefore is not satisfactory in terms of scorch resistance and compression set. Furthermore, Comparative Example 4 has a high content of (C) acrylonitrile butadiene rubber and does not satisfy the requirements of the present invention, and therefore is not satisfactory in terms of scorch resistance and compression set. Furthermore, Comparative Example 5 is not satisfactory in terms of scorch resistance and compression set because the content of (A) chloroprene rubber and (B) butadiene rubber does not satisfy the requirements of the present invention.

[0103] Furthermore, a detailed comparison of the flame retardancy evaluation results of Example 8 and Example 1 confirmed that Example 1 exhibited superior flame retardancy. [Industrial applicability]

[0104] The high-pressure hose of the present invention is useful as a high-pressure hydraulic hose for construction machinery, mining machinery, and industrial vehicles (forklifts, automated guided vehicles, etc.). [Explanation of symbols]

[0105] 1. Inner rubber layer 2,2a,2b ···Intermediate rubber layer 3,13a,13b...Reinforcement layer 4. Outer rubber layer

Claims

1. A rubber composition for the outer surface of a high-pressure hose containing the following components (A) to (F), wherein the content ratio of component (A) is 40 to 55 parts by mass, the content ratio of component (B) is 40 to 55 parts by mass, the content ratio of component (C) is 5 to 10 parts by mass, and the content of component (F) is 2 to 5 parts by mass, based on 100 parts by mass of the total of components (A) to (C). (A) Chloroprene rubber (B) Butadiene rubber (C) Acrylonitrile butadiene rubber (D) At least one of a sulfenamide-based vulcanization accelerator and a thiazole-based vulcanization accelerator. (E) At least one of a dithiocarbamate-based vulcanization accelerator and a thiram-based vulcanization accelerator. (F) Sulfur

2. Furthermore, the rubber composition for the outer surface of a high-pressure hose according to claim 1, further containing aluminum hydroxide.

3. The rubber composition for the outer surface of a high-pressure hose according to claim 1 or 2, wherein the amount of acrylonitrile in component (C) is 26 to 35% by mass.

4. A rubber composition for the outer surface of a high-pressure hose according to claim 1 or 2, which does not contain a silane coupling agent.

5. The rubber composition for the outer surface of a high-pressure hose according to claim 1 or 2, comprising a sulfenamide-based vulcanization accelerator as component (D) and a dithiocarbamate-based vulcanization accelerator as component (E).

6. A high-pressure hose having an outer rubber layer made of the rubber composition for the outer surface of a high-pressure hose according to claim 1 or 2.

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