Rubber compositions and rubber crosslinked products

Abstract

This invention provides a rubber composition and its crosslinked product that can be used in a wide range of applications safely and securely, as it has gas barrier properties and low-temperature sealing properties that can be used in the low-temperature storage of high-pressure hydrogen gas, and allows for the visual detection of blister formation. [Solution] The rubber composition according to the present invention is characterized by containing 3 to 50 parts by weight of an unsaturated metal salt, 0.5 to 5 parts by weight of a silane coupling agent, and 3 to 50 parts by weight of white carbon, per 100 parts by weight of ethylene-butene rubber.

Description

Technical Field

[0001] The present invention relates to a rubber composition and a crosslinked rubber product.

Background Art

[0002] In recent years, hydrogen energy has attracted attention as one of the global environmental and energy countermeasures. Since then, demand for polymer materials having hydrogen resistance in hydrogen infrastructures that handle hydrogen under high-pressure conditions has been increasing.

[0003] Conventionally, as sealing materials for high-pressure hydrogen containers, ethylene propylene diene rubber (EPDM) containing silicone rubber as a main component, ethylene propylene rubber (EPM), natural rubber (NR), isoprene rubber (IR), nitrile isoprene rubber (NIR) and the like have been used as a mixture, as disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-196527).

[0004] On the other hand, the aforementioned materials do not have a sufficient sealing function under low-temperature environments, and there has been a concern about the occurrence of leakage due to insufficient low-temperature sealing performance. In fuel cell vehicles that have been increasingly popularized in recent years, components that can exhibit a sealing function even at -50°C have been required, assuming use in extremely cold regions. For this reason, ethylene butene rubber (EBT), which is excellent in flexibility and adhesiveness at low temperatures, has come to be used, as disclosed in Patent Document 2 (Japanese Patent Application No. 2017-529847).

Related Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] Therefore, the inventors diligently conducted research to ensure higher safety for rubber rings used in fuel tanks of fuel cell vehicles and hydrogen stations at low temperatures. [Means for solving the problem]

[0008] Currently, rubber rings predominantly use carbon black as a filler, resulting in a black appearance. Research has revealed a problem: the black appearance of rubber rings makes it difficult to see air bubbles or cracks (blisters) that develop inside the rubber, potentially leading to a failure to detect gas leaks.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a rubber composition and its crosslinked product that can be used in a wide range of applications safely and securely, as it has gas barrier properties and low-temperature sealing properties that can be used in the low-temperature storage of high-pressure hydrogen gas, and as it allows for the visual detection of generated blisters.

[0010] The present invention solves the above problem by a solution described below as one embodiment.

[0011] The rubber composition according to the present invention is characterized by containing, per 100 parts by weight of ethylene-butene rubber, 3 to 50 parts by weight of an unsaturated metal acid salt, 0.5 to 5 parts by weight of a silane coupling agent, and 3 to 50 parts by weight of white carbon.

[0012] The rubber composition according to the present invention preferably contains 1 to 5 parts by weight of fatty acid amide per 100 parts by weight of ethylene-butene rubber.

[0013] Furthermore, the rubber crosslinked product according to the present invention is characterized in that the rubber composition according to the present invention has been crosslinked. In this specification, the term "rubber crosslinked product" includes rubber products in which the rubber composition has been crosslinked and molded. [Effects of the Invention]

[0014] The rubber composition and crosslinked rubber product according to the present invention have gas barrier properties and low-temperature sealing properties that can be used in the low-temperature storage of high-pressure hydrogen gas, and since the generated blisters can be visually inspected, it is possible to provide a rubber composition and crosslinked rubber product that can be used safely and securely in a wide range of applications. [Modes for carrying out the invention]

[0015] The rubber composition according to the present invention is characterized by containing 100 parts by weight or more of ethylene-butene rubber, and blending the composition and crosslinking material in a total amount of 200 parts by weight or less. Furthermore, the rubber composition according to the present invention contains, but is not limited to, an unsaturated metal acid salt, a silane coupling agent, white carbon, a fatty acid amide, and zinc oxide, and may contain any component as long as it does not impair the physical properties of the rubber composition.

[0016] A rubber composition is a composition for manufacturing a rubber crosslinked product. Typically, a crosslinking agent such as a vulcanizing agent for sulfur crosslinking (vulcanization) or a peroxide for peroxide crosslinking (PO crosslinking) is incorporated by the final stage of use. However, this is an optional component for achieving the objectives of the present invention. Therefore, when the present invention is applied to the rubber industry, which is its technical field, the rubber composition according to the present invention can correspond to both the masterbatch (A mixture) before the crosslinking agent is kneaded and the final batch (B mixture) after the crosslinking agent has been kneaded. The embodiments for carrying out the present invention will be described in detail below.

[0017] The rubber composition according to the present embodiment contains 3 to 50 parts by weight of an unsaturated acid metal salt, 0.5 to 5 parts by weight of a silane coupling agent, 3 to 50 parts by weight of white carbon, and 1 to 5 parts by weight of a fatty acid amide, relative to 100 parts by weight of ethylene-butene rubber. According to the combination and content ratio of these components, low-temperature seal resistance, blister resistance, and gas barrier properties are improved, and the composition can be applied to a wide range of uses.

[0018] Hereinafter, the substances constituting the rubber composition according to the present invention will be specifically described.

[0019] [Rubber Composition and Crosslinked Rubber Product] First, the ethylene rubber used in the rubber composition in the present embodiment is preferably ethylene-polyethylene propylene rubber, more preferably VNB-EPDM in which ethylidene norbornene is substituted with a metallocene catalyst, and still more preferably ethylene-butene rubber.

[0020] Ethylene-butene rubber has a glass transition temperature of -66°C, and has excellent low-temperature properties and adhesiveness. The rubber composition according to the present invention, with ethylene-butene rubber as the main component, has high gas barrier properties and low-temperature sealability, can be used in industrial products such as fuel cell vehicles and hydrogen tanks, and can be applied to a wide range of uses.

[0021] In addition, the ethylene-butene rubber in the present embodiment is mainly composed of an ethylene-butene-ethylidene norbornene terpolymer. This substance is a copolymer in which butene is introduced in place of ethylene in the copolymer structure of EPDM, the abbreviation for ethylene-propylene-diene rubber. Furthermore, VNB-EPDM, which is polymerized using ethylidene norbornene instead of a metallocene catalyst, also similarly includes copolymers in which butene is introduced in place of ethylene.

[0022] Furthermore, applicable brands of ethylene rubber used in this embodiment include, for example, Mitsui Chemicals' K-9330M and K-8370 as ethylene-butene rubber. Examples of ethylene-propylene rubber include ENEOS Corporation's EP331, EP342, EP251, EP65, EP35, EP33, EP T8241, EP25, EP24, EP123, EP103AF, EP107F, EP57F / C, EP27, EP93, etc. Other examples include Mitsui Petrochemical's EPT0045, EPT2060M, EPT3045, EPT3070, EBT3091, EPT3092M, EPT3110M, EBTX-4010M, EPT4021, EPT4045, EPT4045M, EPT4070, EPT9090M, etc.

[0023] Next, unsaturated metal salts will be described. In this embodiment, the amount of unsaturated metal salt is preferably 5 to 10 parts by weight, more preferably 5 to 20 parts by weight, and even more preferably 5 to 30 parts by weight, per 100 parts by weight of the ethylene-butene rubber composition. This allows for adjustment of the physical properties and translucency of the rubber composition.

[0024] Furthermore, applicable brands of unsaturated metal salts used in this embodiment include, for example, ZA30 (zinc acrylate), MA35 (magnesium acrylate), CA25 (calcium acrylate), PA (potassium acrylate), ZDA-100 (zinc acrylate), ZDA-90 (zinc acrylate), S-MA (sodium methacrylate), P-MA (potassium methacrylate), M-CP (zinc methacrylate), R-20S (zinc methacrylate), and R-MMA (magnesium methacrylate) from Asada Kogyo Co., Ltd. Other examples include Sun Ester SK-30 (zinc methacrylate) and Sun Ester SK-13 (magnesium methacrylate) from Sanshin Chemical Co., Ltd.

[0025] Next, the silane coupling agent will be described. In this embodiment, the silane coupling agent is an organosilicon compound that has the effect of causing silica aggregation collapse and reducing viscosity, thereby improving processability.

[0026] Furthermore, examples of substances applicable to the silane coupling agent used in this embodiment include vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and bis(triethoxysilylpropyl)tetrasulfide, and it is preferable to use one or more of these.

[0027] Next, white carbon will be described. In this embodiment, the amount of white carbon added is preferably 5 to 15 parts by weight, more preferably 5 to 20 parts by weight, and even more preferably 5 to 30 parts by weight, per 100 parts by weight of the ethylene-butene rubber composition. This is used to adjust the physical properties and translucency.

[0028] Furthermore, applicable brands of white carbon used in this embodiment include, for example, Aerosil 130, 200, and 300 from Nippon Aerosil, Carplex #67, #80, and #1120 from Shionogi, Silton R2 and A from Mizusawa Chemical, Nipseal VN3 from Nippon Silica, and Toxeal UR, NR, and GU from Tokuyama Soda.

[0029] Next, fatty acid amides will be described. In this embodiment, the amount of fatty acid amide is preferably 1 to 2 parts by weight, more preferably 2 to 3 parts by weight, and even more preferably 3 to 4 parts by weight, per 100 parts by weight of the ethylene-butene rubber composition. This allows for adjustment of the physical properties and processability.

[0030] Furthermore, examples of substances applicable to the fatty acid amides used in this embodiment include stearic acid amide, oxystearic acid amide, oleic acid amide, ricinoleic acid amide, methylolamide, methylenebisstearic acid amide, or bisamide forms of higher fatty acids.

[0031] In addition to the substances that make up the rubber composition as described above, peroxides, crosslinking activators, and processing aids related to rubber crosslinking are also added. This allows the rubber composition to have appropriate elasticity.

[0032] Substances applicable to the peroxide used in this embodiment include dialkyl peroxides such as dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 1,4(1,3)-bis[(t-butylperoxy)isopropyl]benzene, and 2,5-dimethyl-2,5-bis(t-butylperoxy)-hexane, as well as hydroperoxides, peroxyesters, and diacyl peroxides. It is preferable to use one or more of these.

[0033] Substances applicable to the crosslinking activator used in this embodiment include, for example, diethylene glycol dimethacrylate, triallyl isocyanurate, other functional methacrylates, other functional monomers, ammonium benzoate, etc., and it is preferable to use one or more of these.

[0034] Examples of processing aids used in this embodiment include fatty acids and fatty acid salts such as stearic acid, zinc stearate, ricinoleic acid, palmitic acid, myristic acid, barium stearate, calcium stearate, and magnesium stearate. The addition of these can contribute to improving the productivity of rubber compositions.

[0035] Crosslinking the rubber composition according to this embodiment yields a crosslinked rubber product. The crosslinked rubber product according to this embodiment has excellent hydrogen gas barrier properties and blister resistance, as well as excellent low-temperature sealing properties, making it applicable to a wide range of uses. Therefore, it can be officially used as a crosslinked rubber ring for low-temperature storage of high-pressure hydrogen gas.

[0036] [Rubber crosslinked products and methods for manufacturing rubber crosslinked products] Next, the method for producing the rubber composition according to this embodiment involves blending 3 to 50 parts by weight of an unsaturated metal acid salt, 0.5 to 5 parts by weight of a silane coupling agent, 3 to 50 parts by weight of white carbon, and 1 to 5 parts by weight of a fatty acid amide with 100 parts by weight of ethylene-butene rubber.

[0037] Furthermore, the method for manufacturing a crosslinked rubber product according to this embodiment involves crosslinking a rubber composition manufactured by the method for manufacturing a rubber composition according to this embodiment.

[0038] The details of the combination of components and blending ratios in the method for producing the rubber composition according to this embodiment are as described for the rubber composition according to this embodiment.

[0039] Furthermore, the rubber composition according to this embodiment can be manufactured by applying a conventional method for manufacturing rubber compositions, provided that the specified mixing ratios of each component are followed. The crosslinked rubber product can also be manufactured by applying a conventional crosslinking method to the manufactured rubber composition according to this embodiment. As an example, components including ethylene-butene rubber, unsaturated metal salt, white carbon, and silane coupling agent are added in a conventional order while being kneaded to obtain a so-called masterbatch (A-mix) before the addition of crosslinking agents, etc. This masterbatch is storable. For kneading, a kneader such as a Banbury mixer, internal mixer, or kneader, which are commonly used in the rubber industry, the technical field to which this invention belongs, can be used. Next, crosslinking agents (components) such as vulcanizing agents, vulcanization accelerators, vulcanization aids, vulcanization retarders, and peroxides are added to the masterbatch in a conventional order while being kneaded to obtain a so-called final batch (B-mix) after the addition of crosslinking agents, etc., and then dispensed using a roller machine. Afterward, this can be pressurized and heated to promote crosslinking and molded into the desired shape to obtain a rubber product. In this example, the rubber composition corresponds to the masterbatch (compound A) to the final batch (compound B), and the crosslinked rubber material corresponds to the rubber product. [Examples]

[0040] According to the example formulations shown in Table 1, the ingredients were kneaded according to standards using a Banbury mixer: 6D (manufactured by Kobe Steel, Ltd.) and a kneader: DX75-215 (manufactured by Nippon Spindle Manufacturing Co., Ltd.) to produce compositions containing 50% or more natural rubber. The materials used are listed below.

[0041] [Materials used] [Type of ingredient (substance) / Name of ingredient (substance)] Display name in Table 1: Product name (; Remarks) (Manufacturer), however, if the ingredient (substance) name and product name are the same, the product name is omitted. [Ethylene-butene rubber] EBT:EBN K-9330M (Mitsui Petrochemical Co., Ltd.) [Metal Oxides / Zinc Oxide] Zinc Oxide (1): Zinc Oxide Type 1 (Sakai Chemical Industry Co., Ltd.) [Metal Oxides / Zinc Oxide] Zinc Oxide (2): Activated Zinc (Seido Chemical Industry Co., Ltd.) [Reinforcement Material / White Carbon] White Carbon (1): Nip Seal VN3 (Nippon Silica Co., Ltd.) [Reinforcement Material / White Carbon] White Carbon (2): Aerosil 300 (Aerosil Japan Co., Ltd.) [Reinforcement Material / White Carbon] White Carbon (3): Silton R2 (Mizusawa Chemical Co., Ltd.) [Processing Agents / Higher Fatty Acids] Processing Agent (1): Bisamide (NOF Co., Ltd.) [Processing Agents / Higher Fatty Acids] Processing Agent (2): Oilelamide (Kao Corporation) [Processing aid / Stearic acid] Processing aid: Lunac S-10 (Kao Corporation) [Silane coupling agent / Bis(triethoxyserial propyl)tetrasulfide] coupling agent (1) (Sani Chemical Co., Ltd.) [Silane coupling agent / vinyltrimethoxysilane] coupling agent (2) (Shin-Etsu Chemical Co., Ltd.) [Unsaturated metal salt / zinc methacrylate] Unsaturated metal salt (manufactured by Asada Chemical Industries, Ltd.) [Crosslinking activator / Polyfunctional methacrylate monomer] Crosslinking activator (Seiko Chemical Co., Ltd.) [Peroxide / 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane]peroxide (NOF Corporation)

[0042] [Preparation of test samples] (Gas permeation test) Three discs, each approximately 50 mm in diameter, were prepared by punching out the rubber composition for each example in accordance with JIS K 6275:2022.

[0043] [Test Method] Gas permeability tests were conducted based on JIS K 6275:2022 "Vulcanized rubber and thermoplastic rubber - Method for determining gas permeability - Part 1: Differential pressure method". The test details were as follows: measurement method: pressure sensor; test temperature: 23±2℃; test gas composition: hydrogen (>99.9%); high-pressure side cell pressure: approximately 100 Pa (high-pressure side); permeability area: 30 mm diameter, 707 m². 2 The test equipment used was a gas permeability measuring device (BT-3) manufactured by Toyo Seiki Seisakusho, and the measurement time was until the maximum detectable pressure of the test equipment (approximately 15 kPa) was reached.

[0044] [evaluation] Based on the indicators shown below, the test samples of the rubber compositions for each example were evaluated. (processability) ○: The viscosity is appropriate, and the rubber has good fluidity. ×: The viscosity is high, and the rubber does not flow well. (transparency) ○: The object on the back of the test piece is visible. ×: The object on the back of the test specimen is not visible. (100% modulus) ○: The tensile stress at 100% elongation is 5.0 MPa or higher. ×: The tensile stress at 100% elongation is 5.0 MPa or less. (200% modulus) ○: The tensile stress at 200% elongation is 10.0 MPa or higher. ×: The tensile stress at 200% elongation is 10.0 MPa or less. (Cold compression set) ○: The compression set at -30℃ is less than 30%. ×: The compression set at -30°C is 30% or more. (Hydrogen diffusion coefficient) ○: Hydrogen diffusion of blister indicator (cm) 2 The / s value is 5.00E-06 or higher. ×: Hydrogen diffusion (cm) of the blister indicator 2 The / s value is less than 5.00E-06. (Hydrogen permeation coefficient) ○: Hydrogen permeation coefficient (mol·m / (m)) of gas barrier properties index 2 ·s·pa)) It is 2.70e-12 or higher. ×: Hydrogen permeation coefficient (mol·m / (m)) of gas barrier properties index 2 ·s·pa)) It is less than 2.70e-12.

[0045] [Test Results] Table 1 shows the formulations for each example and the test results for each example.

[0046] [Table 1]

[0047] As shown in Table 1, only Practical Examples 1 and 2 met the criteria for all evaluation items, while Comparative Examples 1-3 had items that did not meet the criteria. In the practical examples, since the criteria for each item were met, it can be confirmed that they have high gas barrier properties against high-pressure hydrogen gas and low-temperature sealing properties.

[0048] Furthermore, as shown in Table 1, practical examples 1 and 2 meet the transparency criteria. Because they possess sufficient transparency to allow visibility of what is on the back of the test specimen, they allow for visual confirmation of air bubbles and cracks (blisters) within the rubber, compared to conventional black, opaque rubber.

[0049] For example, when used in rubber rings, if the exterior is black, blistering that occurs inside the rubber may not be visible, and gas leaks may go unnoticed if the replacement period has passed. On the other hand, the rubber of this embodiment has excellent transparency, allowing for the inspection of blistering, so the rubber ring can be replaced before a gas leak occurs through visual inspection.

[0050] Based on the above results, it is preferable to contain 3 to 50 parts by weight of an unsaturated metal acid salt, 0.5 to 5 parts by weight of a silane coupling agent, and 3 to 50 parts by weight of white carbon per 100 parts by weight of ethylene-butene rubber. It is also preferable to contain 1 to 5 parts by weight of a fatty acid amide per 100 parts by weight of ethylene-butene rubber. The rubber composition with this configuration has gas barrier properties and low-temperature sealing properties that can be used in low-temperature storage of high-pressure hydrogen gas, and since the generated blisters can be visually inspected, it can be used safely and securely in a wide range of applications.

Claims

1. For 100 parts by weight of ethylene-butene rubber, 3 to 50 parts by weight of an unsaturated metal salt, 0.5 to 5 parts by weight of silane coupling agent, It contains 3 to 50 parts by weight of white carbon. A rubber composition characterized by the following.

2. The rubber composition contains 1 to 5 parts by weight of fatty acid amide per 100 parts by weight of ethylene-butene rubber. The rubber composition according to claim 1, characterized by the following:

3. A crosslinked rubber product comprising the rubber composition according to claim 1 or claim 2.

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