Rubber composition and hose for automobile

Abstract

The present invention improves the volume resistivity (Ω·cm) of a rubber composition that contains carbon black.　A rubber composition according to the present invention contains components (A)–(D). (A) A diene rubber, (B) carbon black for which the ratio (nitrogen adsorption specific surface area (m2 / g) / iodine adsorption (g / kg)) of nitrogen adsorption specific surface area to iodine adsorption is at least 1.0, (C) a tackifier that includes a structural unit derived from an aliphatic monomer, and (D) a vulcanizer.

Description

Rubber compositions and automotive hoses

[0001] This invention relates to rubber compositions. More specifically, it relates to an invention for improving the volume resistivity (Ω·cm) of rubber compositions containing carbon black. More specifically, it relates to an invention for improving the volume resistivity of, for example, engine cooling system hoses such as radiator hoses used to connect the engine and radiator in automobiles, heater hoses used to connect the engine and heater core, refrigerant transport hoses for coolers, fuel cell vehicle hoses such as methanol fuel hoses and hydrogen fuel hoses, and automobile hoses such as gasoline fuel hoses.

[0002] Carbon black is widely used as a filler in the forming materials of various rubber products. While carbon black excels in reinforcing rubber materials, such as improving their strength, its high conductivity makes it unsuitable for products requiring electrical insulation. For example, in automotive water-based rubber hoses, the small currents flowing through the vehicle body can cause the rubber hose itself to corrode and deteriorate, leading to water leaks. Therefore, when using carbon black as a forming material for rubber hoses, technology to improve electrical resistance is required.

[0003] Several methods have already been proposed to improve the electrical resistance of rubber products containing carbon black, such as using carbon black with larger particle sizes, or incorporating insulating fillers like clay (for example, Patent Document 1). However, there is still room for improvement from the standpoint of further enhancing the electrical resistance of rubber products.

[0004] Japanese Patent Publication No. 2001-031813

[0005] This invention has been made in view of these circumstances, and its objective is to improve the volume resistivity (Ω·cm) of a rubber composition containing carbon black.

[0006] In the process of conducting diligent research to solve the above problems, the inventors of the present invention discovered that by using a carbon black with specific surface activity and a tackifier containing constituent units derived from aliphatic monomers in combination, the volume resistivity (Ω·cm) of the rubber composition can be significantly improved.

[0007] The gist of the present invention is as follows: [1] A rubber composition containing the following components (A) to (D): (A) Diene rubber (B) Ratio of nitrogen adsorption specific surface area to iodine adsorption amount (nitrogen adsorption specific surface area [m²] ２ (1) Carbon black with an iodine adsorption capacity (g / kg) of 1.0 or more (2) Tackifier containing constituent units derived from aliphatic monomers (3) Vulcanizing agent [2] The DBP absorption amount of the above component (B) is 120 cm ３ [1] A rubber composition according to [1], wherein the amount of component (B) is 100 g or more. [3] A rubber composition according to [1] or [2], wherein the content of component (B) is 50 to 150 parts by mass per 100 parts by mass of component (A). [4] A rubber composition according to any one of [1] to [3], wherein the content of component (C) is 0.1 to 10 parts by mass per 100 parts by mass of component (A). [5] A rubber composition according to any one of [1] to [4], wherein component (C) is a tackifier containing constituent units derived from aliphatic monomers and constituent units derived from aromatic monomers. [6] A rubber composition according to any one of [1] to [5], wherein component (A) is ethylene-propylene-diene rubber. [7] A rubber composition according to any one of [1] to [6], further containing a bismaleimide compound. [8] An automobile hose comprising a rubber layer made of a vulcanized product of the rubber composition according to any one of [1] to [7]. [9] A method for producing a rubber composition according to any one of [1] to [7], comprising a step of kneading at least the above components (A) to (C) to obtain a kneaded product, wherein the temperature condition in the step of obtaining the kneaded product is 180°C or higher.

[0008] According to the present invention, the volume resistivity (Ω·cm) of a rubber composition containing carbon black can be improved.

[0009] According to one embodiment of the present invention, when used in automotive hoses, etc., it is possible to provide an automotive hose using a rubber composition that can suppress a decrease in electrical resistance and, for example, suppress corrosion and deterioration.

[0010] This is a perspective view showing an example of an embodiment of the hose of the present invention.

[0011] Next, embodiments of the present invention will be described in detail. In this specification, "main component" means a component that greatly affects the properties of the material, and unless otherwise specified, the content of the component is 50% by mass or more of the total material, preferably 60-100% by mass, 70-100% by mass, 80-100% by mass, 90-100% by mass, etc. Also, in this specification, "X and / or Y (X, Y are any configuration)" means at least one of X and Y, and means one of three possibilities: X only, Y only, or X and Y.

[0012] <<Rubber Composition>> The rubber composition of the present invention (hereinafter sometimes referred to as "this rubber composition") is characterized by containing components (A) to (D). (A) Diene rubber (B) Ratio of nitrogen adsorption specific surface area to iodine adsorption amount (nitrogen adsorption specific surface area [m²] ２ (C) Carbon black with an iodine adsorption capacity (g / kg) of 1.0 or more (D) Tackifier containing constituent units derived from aliphatic monomers

[0013] The inventors, with the aim of improving the volume resistivity of various rubber products containing carbon black, conceived of incorporating various tackifiers, and among them focused their research on methods of incorporating tackifiers containing constituent units derived from aliphatic monomers. In the course of this research, they learned that incorporating tackifiers containing constituent units derived from aliphatic monomers could improve volume resistivity, but their investigations revealed that this was still not satisfactory for materials used to form rubber products requiring higher insulation performance. As a result of diligent research with the aim of further enhancing the volume resistivity improvement effect, the inventors unexpectedly discovered that by using carbon black with specific surface properties in combination with a tackifier containing constituent units derived from aliphatic monomers, they could significantly improve volume resistivity, leading to the present invention.

[0014] The principle by which this rubber composition can significantly improve volume resistivity is not entirely clear, but the inventors surmise that by using a carbon black with specific surface activity in combination with a tackifier containing constituent units derived from aliphatic monomers, the efficient reaction between the two is promoted, and a non-conductive layer is efficiently formed on the surface of the carbon black, thereby significantly improving volume resistivity. Embodiments of the present invention will be described in more detail below.

[0015] [(A) Diene rubber] Examples of diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and ethylene-propylene-diene rubber (EPDM). These can be used alone or in combination of two or more. Ethylene-propylene-diene rubber (EPDM) is preferred as component (A).

[0016] Ethylene-propylene-diene rubber (EPDM) is a terpolymer obtained by copolymerizing ethylene-propylene rubber (EPM), which is a copolymer of ethylene and propylene, with a diene monomer as a third component (hereinafter sometimes abbreviated as "EPDM"). These can be used alone or in combination of two or more.

[0017] The diene monomer (third component) in ethylene-propylene-diene rubber (EPDM) is not particularly limited, but for example, diene monomers having 5 to 20 carbon atoms are preferred. Specifically, examples include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), and 5-butylidene-2-norbornene. These can be used alone or in combination of two or more. Among these, dicyclopentadiene (DCP) and 5-ethylidene-2-norbornene (ENB) are preferred.

[0018] The ethylene content of ethylene-propylene-diene rubber (EPDM) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, 45 to 70% by mass is preferred. The ethylene content of ethylene-propylene-diene rubber (EPDM) may also be 50 to 65% by mass or 55 to 60% by mass. The propylene content of ethylene-propylene-diene rubber (EPDM) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, 18 to 53% by mass is preferred, and 25 to 46% by mass is more preferred. The diene monomer content of ethylene-propylene-diene rubber (EPDM) is not particularly limited, but 2 to 12% by mass is preferred, and 4 to 10% by mass is more preferred. The iodine value of ethylene-propylene-diene rubber (EPDM) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, 6 to 30 is preferred, and 10 to 24 is more preferred.

[0019] Mooney viscosity (ML) of ethylene-propylene-diene rubber (EPDM) １+４, 125°C) is not particularly limited; however, from the viewpoint of significantly achieving the effect of the present invention, it is preferably 30 to 120, and more preferably 40 to 100. The Mooney viscosity described above is measured in accordance with JIS K 6300-1 (2001).

[0020] The content of component (A) is not particularly limited, but relative to 100% by mass of the present rubber composition, it is usually 25% by mass or more, preferably 27% by mass or more, more preferably 29 to 40% by mass, and even more preferably 29 to 35% by mass.

[0021] [(B) Specific Carbon Black] The component (B) used in the present rubber composition is the ratio of nitrogen adsorption specific surface area to iodine adsorption amount (nitrogen adsorption specific surface area [m ２ / g] / iodine adsorption amount [g / kg]) is carbon black having a ratio of 1.0 or more.

[0022] Here, the nitrogen adsorption specific surface area refers to the specific surface area of carbon black, which is the adsorption amount of nitrogen molecules per unit mass of carbon black (m ２ / g). In addition, the iodine adsorption amount is a value representing the specific surface area of carbon black as the adsorption amount of iodine molecules per unit mass of carbon black in the liquid phase (g / kg). The nitrogen adsorption specific surface area can be obtained by the method described in JIS K 6217-7:2013 "Test Methods for Basic Properties of Carbon Black for Rubber" (Reference: ASTM D6556-16). The iodine adsorption amount is a value measured in accordance with JIS K 6217-1 (Method A).

[0023] The value obtained by dividing the value of nitrogen adsorption specific surface area by the value of iodine adsorption amount (nitrogen adsorption specific surface area [m ２ / g] / iodine adsorption amount [g / kg]) is an index representing the surface activity of carbon black (in the present specification, "nitrogen adsorption specific surface area [m ２ / g] / iodine adsorption amount [g / kg]" may be referred to as "surface activity"). Here, as described above, the unit of nitrogen adsorption specific surface area for surface activity is m ２ / g, and the calculation is performed with the unit of iodine adsorption amount being g / kg. A higher surface activity means a larger amount of surface functional groups on the carbon black. When the amount of surface functional groups on the carbon black is large, a chemical reaction with component (C) is likely to occur via the surface functional groups on the surface of the carbon black. In other words, the value of the surface activity of carbon black quantitatively indicates the likelihood of a chemical reaction occurring on the surface of the carbon black.

[0024] The surface activity of component (B) is expressed as nitrogen adsorption specific surface area [m ２ / g] / iodine adsorption amount [g / kg]). From the viewpoint of further improving volume resistivity, for example, the surface activity is preferably 1.0 to 1.7, more preferably 1.1 to 1.6, and still more preferably 1.2 to 1.5.

[0025] As the nitrogen adsorption specific surface area of component (B), for example, it is 15 to 100 m ２ / g is preferable, more preferably 20 to 90 m ２ / g, still more preferably 25 to 80 m ２ / g. In addition, as the nitrogen adsorption specific surface area of component (B), for example, it is 25 to 60 m ２ / g, 25 to 50 m ２ / g, 25 to 40 m ２ / g, or the like.

[0026] As the iodine adsorption amount of component (B), for example, 12 to 100 g / kg is preferable, more preferably 14 to 90 g / kg, still more preferably 15 to 80 g / kg. In addition, the iodine adsorption amount of component (B) may be, for example, 18 to 60 g / kg, 18 to 50 g / kg, 18 to 40 g / kg, or the like.

[0027] As the DBP (dibutyl phthalate) absorption of component (B), from the viewpoint of improving volume resistivity, for example, it is 60 to 180 cm ３ / 100 g is preferable, more preferably 80 to 160 cm ３ / 100 g, still more preferably 100 to 140 cm ３ / 100 g. In addition, the DBP (dibutyl phthalate) absorption of component (B) is 120 cm ３ / 100 g, for example, 120 to 140 cm ３ / 100 g. The DBP absorption amount refers to the absorption amount of DBP per 100 g of carbon black (cm ３ / 100 g). The DBP absorption amount is a value measured in accordance with JIS K 6217-4.

[0028] From the viewpoint of improving volume resistivity, the average particle diameter of component (B) is preferably, for example, 20 to 90 nm, more preferably 25 to 80 nm, and still more preferably 30 to 70 nm.

[0029] From the viewpoint of improving volume resistivity, the content of component (B) is preferably, for example, 50 to 150 parts by mass, more preferably 60 to 140 parts by mass, and still more preferably 70 to 130 parts by mass, relative to 100 parts by mass of component (A).

[0030] [(C) Tackifier containing structural units derived from aliphatic monomers] Component (C) used in the present rubber composition is a tackifier containing structural units derived from aliphatic monomers. For example, component (C) includes addition polymers of aliphatic monomers having an ethylenic carbon-carbon double bond, such as isoprene, 1,3-pentadiene, and 2-methyl-2-butene. Component (C) may also be a homopolymer of the above monomers, a copolymer of two or more types of the above monomers in appropriate combination, or may be a product obtained by copolymerizing components other than aliphatic monomers, for example, indenes such as indene and methylindene, and aromatic monomers such as vinyltoluene, styrene, α-methylstyrene, β-methylstyrene, and isopropenyltoluene. Component (C) may also be modified with a phenolic compound, maleic anhydride, acrylic acid, methacrylic acid, or the like. Component (C) may be used alone or in combination of two or more thereof.

[0031] (C) Among the components, from the viewpoint of improving volume resistivity, aliphatic (C5) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, hydrogenated versions thereof, and various modified versions thereof (e.g., maleic anhydride modified versions) are preferred.

[0032] While there are no particular limitations on the aliphatic (C5) petroleum resin, a preferred aliphatic (C5) petroleum resin consists of one or more constituent units selected from the group consisting of isoprene, 1,3-pentadiene, 2-methyl-2-butene, cyclopentadiene, etc. Furthermore, while there are no particular limitations on the aliphatic / aromatic copolymer (C5 / C9) petroleum resin, a preferred aliphatic / aromatic copolymer (C5 / C9) petroleum resin consists of one or more constituent units selected from the group consisting of indene, styrene, and vinyltoluene, and isoprene and / or piperine. Among these, the aliphatic / aromatic copolymer (C5 / C9) petroleum resin is preferred.

[0033] As for component (C), from the viewpoint of further improving volume resistivity, the content of constituent units derived from aliphatic monomers relative to the total constituent units of component (C) is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. From a similar viewpoint, the content of constituent units derived from aliphatic monomers is preferably 90% by mass or less. Furthermore, the content of constituent units derived from aliphatic monomers relative to the total constituent units of component (C) can be appropriately set within the above range, for example, it may be 70 to 100% by mass.

[0034] Furthermore, when component (C) includes constituent units other than those derived from aliphatic monomers, and particularly when it includes constituent units derived from aromatic monomers, the content thereof is preferably 50% by mass or less, more preferably 45% by mass or less, and especially preferably 40% by mass or less, relative to the total constituent units of component (C). From a similar viewpoint, the content of constituent units derived from aromatic monomers is preferably 10% by mass or more. Also, the content of constituent units derived from aromatic monomers relative to the total constituent units of component (C) can be appropriately set within the above range, for example, it may be 10 to 30% by mass.

[0035] The softening point of component (C) is not particularly limited, but is preferably 60 to 110°C, and more preferably 70 to 100°C. The softening point is measured by the ring-ball method in accordance with JIS K 2207.

[0036] The weight-average molecular weight (Mw) of component (C) is not particularly limited, but is preferably 500 to 5000, and more preferably 1000 to 4000. The weight-average molecular weight is measured by GPC.

[0037] The content of component (C) is not particularly limited, but from the viewpoint of improving volume resistivity, it is preferably 0.1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 4 to 6 parts by mass, per 100 parts by mass of component (A).

[0038] [(D) Sulfurizing agent] Component (D) includes sulfur-based vulcanizing agents and peroxide-based vulcanizing agents. These can be used individually or in combination of two or more.

[0039] Examples of sulfur-based vulcanizing agents include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

[0040] Examples of peroxide-based vulcanizing agents include 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, n-butyl-4,4′-di-t-butylperoxyvalerate, dicumyl peroxide, t-butylperoxybenzoate, di-t-butylperoxydiisopropylbenzene, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexyn-3, and 1,3-bis-(t-butylperoxyisopropyl)benzene.

[0041] The content of component (D) is not particularly limited, but is preferably 0.5 to 15 parts by mass, more preferably 0.7 to 11 parts by mass, and even more preferably 0.9 to 7 parts by mass, per 100 parts by mass of component (A). The content of component (D) can be appropriately set within the above range, and may be, for example, about 1 to 5 parts by mass.

[0042] [Other Components] In addition to the components (A) to (D) above, this rubber composition may contain, without particular limitation, other components used in rubber compositions, such as vulcanization accelerators, fillers other than carbon black, plasticizers, vulcanization aids, antioxidants, processing aids, etc., as needed.

[0043] The vulcanization accelerator is not particularly limited, but examples include thiram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT), and tetrabenzylthiuram disulfide (TBzTD); N-oxydiethylene-2-benzothiazolyl sulfenamide (NOBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N-t-butyl Examples include sulfenamide-based vulcanization accelerators such as 2-2-benzothiazoylsulfenamide (BBS) and N,N'-dicyclohexyl-2-benzothiazoylsulfenamide; thiazole-based vulcanization accelerators such as dibenzothiadyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), and 2-mercaptobenzothiazole zinc salt (ZnMBT); dithioate-based vulcanization accelerators such as dibutyldithiocarbamate zinc (ZnBDC); and sulfur chloride and sulfur disulfide. These can be used alone or in combination of two or more.

[0044] The content of the vulcanization accelerator is not particularly limited, but is preferably 0.5 to 15 parts by mass, more preferably 0.7 to 11 parts by mass, and even more preferably 0.9 to 7 parts by mass, per 100 parts by mass of component (A).

[0045] The fillers are not particularly limited, but examples include talc, mica, clay, and calcium carbonate. These can be used alone or in combination of two or more. The content of the fillers is not particularly limited, but is preferably 10 to 150 parts by mass, more preferably 20 to 140 parts by mass, and even more preferably 30 to 130 parts by mass, per 100 parts by mass of component (A).

[0046] The plasticizers are not particularly limited, but examples 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 plasticizers that have both ether and ester bonds in a single molecule, specifically adipic acid ether ester plasticizers such as bis[2-(2-butoxyethoxy)ethyl] adipate. Examples of process oils include naphthenic oils and paraffinic oils. The content of the plasticizer is not particularly limited, but is preferably 10 to 120 parts by mass, more preferably 20 to 110 parts by mass, and even more preferably 30 to 100 parts by mass, per 100 parts by mass of component (A).

[0047] The vulcanization aid is not particularly limited, but examples include zinc oxide, zinc oxide (ZnO), stearic acid, and magnesium oxide. These can be used alone or in combination of two or more. Examples of zinc oxide include zinc oxide type 1, zinc oxide type 2, zinc oxide type 3, and fine zinc oxide. The content of the vulcanization aid is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 1 to 9 parts by mass, and even more preferably 2 to 8 parts by mass, per 100 parts by mass of component (A).

[0048] Furthermore, from the viewpoint of further improving the volume resistivity, this rubber composition may also contain bismaleimide compounds in addition to components (A) to (D). Bismaleimide compounds are compounds having two maleimide groups in their molecule, and examples include aromatic bismaleimide compounds and aliphatic bismaleimide compounds. These may be used alone or in combination of two or more.

[0049] Aromatic bismaleimide compounds are compounds comprising a bismaleimide structure and a structure having an aromatic ring. Examples of structures having an aromatic ring include aryl groups and arylene groups having 6 to 30 carbon atoms. The aryl groups and arylene groups may have substituents. Examples of structures having an aromatic ring include phenylene groups, methylphenylene groups, ethylphenylene groups, propylphenylene groups, butylphenylene groups, dimethylphenylene groups, diethylphenylene groups, dipropylphenylene groups, trimethylphenylene groups, tetramethylphenylene groups, dibutylphenylene groups, naphthylene groups, biphenylene groups, fluorenylene groups, phenantrenylene groups, and anthraquinolylene groups. Among these, phenylene groups are preferred.

[0050] Specific examples of aromatic bismaleimide compounds include, for example, N,N'-(1,3-phenylene)bismaleimide, N,N'-(4-methyl-1,3-phenylene)bismaleimide, N,N'-(1,4-phenylene)bismaleimide, N,N'-(1,2-phenylene)bismaleimide, N,N'-(1,5-naphthylene)bismaleimide, N,N'-(4-chloro-1,3-phenylene)bismaleimide, and N,N'-(methylenedi-p-phenylene) N,N'-(4,4'-biphenylene)bismaleimide, N,N'-(sulfonyldi-p-phenylene)bismaleimide, N,N'-(oxydi-p-phenylene)bismaleimide, N,N'-(3,3'-dimethyl-4,4'-biphenylene)bismaleimide, N,N'-(benzylidenedi-p-phenylene)bismaleimide, N,N'-[methylenebis(3-chloro-4-phenylene)]bismaleimide, N,N'-[meth Lenbis(3-methyl-4-phenylene)]bismaleimide, N,N'-[methylenebis(3-methoxy-4-phenylene)]bismaleimide, N,N'-(thiodi-p-phenylene)bismaleimide, N,N'-3,3'-benzophenonebismaleimide, N,N'-[methylenebis(3-methyl-5-ethyl-4-phenylene)]bismaleimide, N,N'-[tetramethylenebis(oxy-p-phenylene)]bismaleimide, 2,2-bis[ Examples include 4-(4-maleimidophenoxy)phenyl]propane, bis[4-(4-maleimidophenoxy)phenyl]sulfone, 1,4-phenylenebis(4-maleimidophenoxy), bis[3-(4-maleimidophenoxy)phenyl]sulfone, bis[4-(3-maleimidophenoxy)phenyl]ketone, 1,3-phenylenebis(4-maleimidophenoxy), and bis[4-(4-maleimidophenylthio)phenyl]ether. Among these, N,N'-(1,3-phenylene)bismaleimide is preferred.

[0051] Examples of aliphatic bismaleimide compounds include N,N'-(2,2,4-trimethylhexamethylene)bismaleimide, N,N'-decamethylenebismaleimide, N,N'-octamethylenebismaleimide, N,N'-heptamethylenebismaleimide, N,N'-hexamethylenebismaleimide, N,N'-pentamethylenebismaleimide, N,N'-tetramethylenebismaleimide, N,N'-trimethylenebismaleimide, N,N'-ethylenebismaleimide, N,N'-(oxydimethylene)bismaleimide, 1,13-bismaleimide-4,7,10-trioxatridecane, and 1,11-bismaleimide-3,6,9-trioxaundecane.

[0052] The content of the bismaleimide compound is not particularly limited, but from the viewpoint of further improving the volume resistivity, it is preferably 0.1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 4 to 6 parts by mass, per 100 parts by mass of component (A).

[0053] Furthermore, the mass ratio of the tackifier containing (C) aliphatic monomer-derived structural units to the bismaleimide compound (tackifier containing aliphatic monomer-derived structural units / bismaleimide compound) is not particularly limited, but from the viewpoint of improving volume resistivity, it is preferably 0.1 to 4, more preferably 0.5 to 3, and even more preferably 1 to 2.

[0054] The total content of the tackifier, which includes the bismaleimide compound and the (C) aliphatic monomer-derived structural units, is not particularly limited, but from the viewpoint of improving volume resistivity, it is preferably 1 to 20 parts by mass, more preferably 4 to 16 parts by mass, and even more preferably 8 to 12 parts by mass, per 100 parts by mass of component (A).

[0055] [Method for Manufacturing the Rubber Composition] The method for manufacturing the rubber composition includes a step of kneading at least the above components (A) to (C) to obtain a kneaded product, and it is preferable that the temperature condition in the step of obtaining the kneaded product is 180°C or higher. By setting the temperature condition to 180°C or higher, the dispersibility of the kneaded product is improved, and the reaction efficiency of components (B) and (C) can be promoted, thereby effectively improving the volume resistivity. The above temperature condition is preferably 180 to 210°C, more preferably 180 to 200°C, and even more preferably 180 to 190°C.

[0056] The method for producing this rubber composition more specifically comprises a first step of kneading at least the above components (A) to (C) to obtain a kneaded product, and a second step of adding component (D) to the kneaded product and kneading, wherein the temperature condition in the first step is preferably 180°C or higher. The temperature condition in the second step is not particularly limited, but for example, it is 40 to 120°C, preferably 60 to 100°C.

[0057] By using this rubber composition, a rubber material having excellent volume resistivity can be formed. The volume resistivity of the vulcanized body of this rubber composition is not particularly limited, but for example, 10 ８ Preferably Ω·cm or more, and more preferably 10 ９ Ω·cm or more, more preferably 10 １０ The volume resistivity is greater than or equal to Ω·cm. The above volume resistivity is measured by the method described in the examples below.

[0058] <<Laminated Hose>> This rubber composition is preferably used as a material for the rubber layer constituting a single-layer or laminated hose. The laminated hose includes, for example, a laminated structure in which a rubber layer made of a vulcanized product of this rubber composition and a resin layer which serves as an adherend to the rubber layer are laminated. The resin constituting the main component of the resin layer can be one or more selected from the group consisting of, for example, polyester such as polyethylene terephthalate, polyvinyl alcohol, aramid (aromatic polyamide), and polyamide such as polyamide 6 and polyamide 66.

[0059] The resin layer is not particularly limited as long as it performs specific functions such as reinforcement or permeability resistance, but it is preferably a reinforcement layer, and more preferably a reinforcement yarn layer composed of resin reinforcement yarns. Examples of reinforcement yarns that make up the reinforcement yarn layer include polyester yarns such as polyethylene terephthalate yarn, polyvinyl alcohol yarn, aramid (aromatic polyamide) yarn, polyamide 6, polyamide 66, and other polyamide yarns. These can be used alone or in combination of two or more. Among these, from the viewpoint of the durability of the laminated hose, at least one type of reinforcement yarn selected from the group consisting of polyamide yarn, polyethylene terephthalate yarn, and polyvinyl alcohol yarn is preferred. The reinforcement yarn layer may also be a reinforcement yarn layer that has been dipped with an adhesive. The dipped reinforcement yarn layer may be a layer formed by braiding together dipped reinforcement yarns, or a reinforcement yarn layer formed by braiding together reinforcement yarns may be dipped. The braiding method of the above-mentioned reinforcement yarns is not particularly limited, and examples include spiral braiding and braiding.

[0060] [Method for Manufacturing Laminated Hose] An example of a method for manufacturing a laminated hose using this rubber composition will be explained with reference to Figure 1. First, the components (A) to (D) above, and other components as needed, are blended and kneaded using a kneader such as a roll, kneader, or Banbury mixer to prepare the rubber composition. Then, the rubber composition is extruded into a hose shape, and a reinforcing thread layer 2 is formed by spirally winding, for example, reinforcing threads around the outer surface of the extruded product. Next, the rubber composition is extruded onto the outer surface of the reinforcing thread layer 2, and the resulting hose-shaped laminate is heated (vulcanized) under predetermined conditions. This results in a laminated hose with a three-layer structure (inner rubber layer 1 / reinforcing thread layer 2 / outer rubber layer 3) (see Figure 1), in which the reinforcing thread layer 2 is integrally formed on the outer surface of the inner rubber layer 1, and the outer rubber layer 3 is integrally formed on the outer surface of the reinforcing thread layer 2.

[0061] The dimensions of the laminated hose obtained in this way are not particularly limited. For example, the outer diameter of the laminated hose is usually about 5.5 to 80 mm, and the total thickness (hose wall thickness) of the laminated hose is usually about 0.5 to 20 mm. The thickness of each layer constituting the laminated hose is also not particularly limited as long as it is within a range in which the intended function of each layer can be sufficiently achieved. For example, the thickness of the inner rubber layer 1 is usually about 0.25 to 10 mm, and the thickness of the outer rubber layer 3 is usually about 0.25 to 10 mm.

[0062] In this invention, it is not necessary for both the inner rubber layer 1 and the outer rubber layer 3 to be rubber layers formed using a rubber composition containing the above components (A) to (D). It is also possible for either the inner rubber layer 1 or the outer rubber layer 3 to be a general-purpose rubber layer made from a general-purpose rubber material.

[0063] When forming a general-purpose rubber layer made from a composition other than the present rubber composition, the material is not particularly limited, but examples include chloroprene rubber (CR), styrene-butadiene rubber (SBR), acrylic rubber (ACM), ethylene acrylate rubber (AEM), chlorinated polyethylene (CM), chlorosulfonated polyethylene (CSM), etc. Alternatively, acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), acrylic rubber (ACM), ethylene acrylate rubber (AEM), chlorinated polyethylene (CM), chlorosulfonated polyethylene (CSM), fluororubber (FKM), ethylene-propylene-diene rubber (EPDM), etc. may also be used. These may be used individually or in combination of two or more. Furthermore, additives such as fillers and plasticizers may be appropriately blended into the rubber layer as needed.

[0064] Furthermore, the laminated hose according to the embodiment of the present invention is not limited to the three-layer structure (inner rubber layer 1 / reinforcing yarn layer 2 / outer rubber layer 3) shown in Figure 1. For example, a laminated hose including a laminated structure of "resin layer (innermost layer) / rubber layer" in which the rubber layer is made of the present rubber composition, and a laminated hose having a four-layer structure of "resin layer (innermost layer) / inner rubber layer / reinforcing layer (e.g., a reinforcing layer made of metal wire, etc.) / outer rubber layer" in which the inner rubber layer and / or outer rubber layer are made of the present rubber composition.

[0065] Furthermore, preferred specific examples of the layer structure in the laminated hose according to embodiments of the present invention are not limited to the following, but specifically include, for example, a laminated hose having a three-layer structure of "inner rubber layer / reinforcement yarn layer / outer rubber layer," in which the inner rubber layer and / or the outer rubber layer are rubber layers made of the rubber composition. Also, for example, a laminated hose having a four-layer structure of "inner rubber layer / intermediate rubber layer / reinforcement yarn layer / outer rubber layer," in which the intermediate rubber layer and / or the outer rubber layer are rubber layers made of the rubber composition. Also, for example, a laminated hose having a five-layer structure of "inner rubber layer / reinforcement yarn layer / intermediate rubber layer / reinforcement yarn layer / outer rubber layer," in which some of the inner rubber layer, intermediate rubber layer, and outer rubber layer (one or two layers) or all of the layers are rubber layers made of the rubber composition.

[0066] The applications of the laminated hose according to the present invention are not particularly limited, but it can be suitably used as an engine cooling system hose such as a radiator hose used to connect the engine and radiator in a vehicle such as an automobile, a heater hose used to connect the engine and heater core, a refrigerant transport hose for a cooler, a fuel cell vehicle hose such as a methanol fuel hose and a hydrogen fuel hose, and an automobile hose such as a gasoline fuel hose.

[0067] Next, embodiments of the present invention will be described together with comparative examples and comparative examples. However, the present invention is not limited to these embodiments.

[0068] First, prior to the examples and comparative examples, the following materials were prepared as components (A) to (D).

[0069] [Component A] ・EPDM (A1) Ningbo SK Performance Rubber SUPRENE S552 (Ethylene ratio: 58% by mass, ENB ratio: 4.1% by mass)

[0070] [Component B] Carbon black (B1) CABOT Corporation, SPHERON 5200 (surface activity 1.29 [nitrogen adsorption specific surface area 27 m²]) ２ [ / g, iodine adsorption amount: 21 g / kg], DBP absorption amount: 125 cm ３ (100g) Carbon Black (B2) Manufactured by Tokai Carbon Co., Ltd., Seast S (Surface activity 1.04 [Nitrogen adsorption specific surface area 27m²]) ２ [ / g, iodine adsorption amount: 26 g / kg], DBP absorption amount: 68 cm ３ (100g)

[0071] [Component B'] ・Carbon black (B'1) Manufactured by Tokai Carbon Co., Ltd., Seast SO (Surface activity 0.95 [Nitrogen adsorption specific surface area 42 m²] ２ [ / g, iodine adsorption amount: 44 g / kg], DBP absorption amount: 115 cm³ ３ ( / 100g) ・Carbon Black (B'2) CABOT Corporation, VULCAN 3D (Surface activity 0.94 [Nitrogen adsorption specific surface area 76 m²) ２ [ / g, iodine adsorption amount: 81 g / kg], DBP absorption amount: 102 cm³ ３ (100g)

[0072] [Component C] ・C5 / C9 petroleum resin (C1) Manufactured by Tosoh Corporation, PetroTac (registered trademark) 100V ・C5 / C9 petroleum resin (C2) Manufactured by Tosoh Corporation, PetroTac (registered trademark) 90HS

[0073] [Component D] ・Sulfur-based vulcanizing agent (D1) Sulfax® T-10, manufactured by Tsurumi Chemical Industries Co., Ltd.

[0074] [Other ingredients] ・Vulcanization accelerator: Sanshin Chemical Industry Co., Ltd., Sunceller TT-G ・Vulcanization aid: Sakai Chemical Industry Co., Ltd., Zinc oxide (2 types) ・Processing aid: NOF Corporation, Bead Stearic Acid Sakura ・Plasticizer: Idemitsu Kosan Co., Ltd., Diana Process PS-430 (paraffin-based process oil) ・Bismaleimide compound: Tokyo Chemical Industry Co., Ltd., N,N'-(1,3-phenylene)bismaleimide

[0075] [Example 1] Components (A) to (D) were used in the proportions shown in Table 1 below. Furthermore, 2 parts by mass of the vulcanization accelerator, 5 parts by mass of the vulcanization aid, 1 part by mass of the processing aid, and 50 parts by mass of the plasticizer (all proportions relative to 100 parts by mass of component (A)) were added, and these components were kneaded to prepare a rubber composition. Specifically, components (A) were mixed with all components except component (D) and the vulcanization accelerator, kneaded in a 1.7 L Banbury mixer at 180°C, then component (D) and the vulcanization accelerator were added, and the mixture was mixed using an 8-inch roll to prepare the rubber composition according to Example 1. In Table 1, the unit of the blending amount is parts by mass.

[0076] [Examples 2-4, Comparative Examples 1-2] Rubber compositions according to Examples 2-4 and Comparative Examples 1-2 were prepared in the same manner as in Example 1, except that the components and their contents were changed as shown in Table 1 below.

[0077] [Control Examples a-d] To verify the change in volume resistivity with and without component (C), control examples were prepared for each example. Specifically, control example a for Example 1 and Example 2 was prepared in the same manner as in Example 1 or 2, except that it did not contain component (C). Similarly, control examples b-d for Example 3 and Comparative Examples 1-2 were prepared.

[0078] The rubber compositions of the examples, comparative examples, and control examples obtained in this manner were evaluated for volume resistivity according to the following criteria. These results are also shown in Table 1 below.

[0079] <<Effect of improving volume resistivity>> The volume resistivity VR (Ω・cm) of a sample obtained by press vulcanization of the above rubber composition was measured according to JIS K 6271-1:2015 (Vulcanized rubber and thermoplastic rubber - Method for determining electrical resistivity) and evaluated according to the following criteria. Specifically, the volume resistivity VR was determined under the following conditions and evaluated according to the following criteria. Measurement method: Double ring electrode method Guard electrode: Outer diameter 80 mm, inner diameter 70 mm Main electrode: 50 mm Sample external dimensions: 100 mm × 100 mm Sample thickness: 2 mm Applied voltage: 1 V Detection current range: 200 pA to 20 mA (Evaluation criteria) ◎ (excellent): 1.0 × 10 ９ Ω·cm or more: Very good: 1.0 × 10 ８ Ω・cm or more 1.0×10 ９ Less than Ω·cm × (poor): 1.0 × 10 ８ Less than Ω·cm

[0080] Furthermore, the effect of component (C) was evaluated by the improvement in volume resistivity relative to the reference control example, converted to decibels (dB difference). The dB difference is calculated using the following formula: dB difference = 10 × log １０ (Resistivity of the sample to be evaluated / Resistivity of the reference example) (Evaluation criteria) ◎ (excellent): dB difference of 10 or more 〇 (very good): dB difference of 7 or more and less than 10 △ (good): dB difference of 5 or more and less than 7 × (poor): dB difference of less than 5 In principle, the reference example is the control example corresponding to each example (e.g., control example a for Examples 1 and 2), however, for Example 4, Example 1 was used as the reference for calculation.

[0081]

[0082] As shown in Table 1, in the case of rubber compositions that do not contain components (A) to (D), as in the comparative example, and especially in the case of rubber compositions that do not use components (B) and (C) in combination, the volume resistivity is low and the effect of improving the volume resistivity is small, and therefore it is not yet satisfactory. Specifically, surface activity (nitrogen adsorption specific surface area [m²]) ２In the case of a rubber composition using carbon black and component (C) in combination, where the iodine adsorption capacity (g / kg) is less than 1.0, for example, the volume resistivity is 10 ８ Since the value is less than Ω·cm and the dB difference indicating the improvement effect of the volume resistivity due to the (C) component is also less than 5, it was shown that the results are still not satisfactory.

[0083] On the other hand, as shown in Table 1, when the rubber composition contains components (A) to (D), as in the examples, and especially when the rubber composition uses components (B) and (C) in combination, the volume resistivity is high, and the effect of improving the volume resistivity is also large, so it has been shown to be quite satisfactory. Specifically, surface activity (nitrogen adsorption specific surface area [m²] ２ In the case of a rubber composition using carbon black with an iodine adsorption capacity (g / kg) of 1.0 or more and component (C) in combination, for example, the volume resistivity is 10 ９ The result was high, exceeding Ω·cm, and the dB difference indicating the improvement in volume resistivity due to the (C) component was 7 or more, demonstrating that it was sufficiently satisfactory.

[0084] Furthermore, as shown in Table 1, when components (A) to (D) are included along with a bismaleimide compound, as in Example 4, the volume resistivity is particularly high, and the effect of improving volume resistivity is also large, demonstrating particularly excellent results.

[0085] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0086] The rubber composition of the present invention is suitable, for example, as a material for forming the rubber layer of an automobile hose. It can be suitably used as an automobile hose, such as a radiator hose used to connect the engine and radiator in a vehicle such as an automobile, a heater hose used to connect the engine and heater core, an engine cooling system hose, a refrigerant transport hose for a cooler, a fuel cell vehicle hose such as a methanol fuel hose and a hydrogen fuel hose, and a gasoline fuel hose. Furthermore, the automobile hose of the present invention can be used not only for automobiles but also for other transport machinery (industrial transport vehicles such as airplanes, forklifts, excavators, and cranes, railway vehicles, etc.).

[0087] 1. Inner rubber layer 2. Reinforcement thread layer 3. Outer rubber layer

Claims

1. A rubber composition containing the following components (A) to (D): (A) Diene rubber (B) Ratio of nitrogen adsorption specific surface area to iodine adsorption amount (nitrogen adsorption specific surface area [m²] ２ (C) Carbon black with an iodine adsorption capacity (g / kg) of 1.0 or more (D) Tackifier containing constituent units derived from aliphatic monomers 2. The DBP absorption amount of component (B) above is 120 cm ３ The rubber composition according to claim 1, wherein the amount is 100g or more.

3. The rubber composition according to claim 1 or 2, wherein the content of component (B) is 50 to 150 parts by mass per 100 parts by mass of component (A).

4. The rubber composition according to any one of claims 1 to 3, wherein the content of component (C) is 0.1 to 10 parts by mass per 100 parts by mass of component (A).

5. The rubber composition according to any one of claims 1 to 4, wherein component (C) is a tackifier containing structural units derived from aliphatic monomers and structural units derived from aromatic monomers.

6. The rubber composition according to any one of claims 1 to 5, wherein the above component (A) is ethylene-propylene-diene rubber.

7. The rubber composition according to any one of claims 1 to 6, further comprising a bismaleimide compound.

8. An automobile hose comprising a rubber layer made of a vulcanized product of the rubber composition according to any one of claims 1 to 7.

9. A method for producing a rubber composition according to any one of claims 1 to 7, comprising the step of kneading at least the above components (A) to (C) to obtain a kneaded product, wherein the temperature condition in the step of obtaining the kneaded product is 180°C or higher.

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