Industrial hose, and vibration damping rubber member

Abstract

Provided are an industrial hose and the like having excellent vibration characteristics.　An industrial hose that is a single-layer or multilayer industrial hose having at least a layer comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber and (B) a polypropylene-based resin, and the dynamic magnification of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition (dynamic elastic modulus [MPa] measured at 100 Hz / static elastic modulus [MPa] measured at 15 Hz) is 1.70 or less.

Description

Industrial hose or vibration-proof rubber member

[0001] The present invention relates to an industrial hose or vibration-proof rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition. Specifically, the present invention relates to an industrial hose or vibration-proof rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition having a specific dynamic magnification.

[0002] Dynamically crosslinked thermoplastic elastomer (hereinafter sometimes referred to as "TPV") is one type of incompatible polymer blend. For example, it is produced by dynamic crosslinking in which a rubber phase is crosslinked while kneading a polypropylene resin and uncrosslinked rubber, and is a characteristic polymer material having both rubber-like elasticity and thermoplastic properties. TPV exhibits a sea-island structure with a thermoplastic resin as the sea phase and crosslinked rubber as the island phase. Despite the sea phase being a hard brittle resin, TPV exhibits rubber-like elasticity and high stretchability, and thus has attracted attention in recent years from the viewpoints of moldability and environmental protection.

[0003] For example, Patent Document 1 proposes a dynamically crosslinked thermoplastic elastomer having ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) as the island phase and polypropylene resin (PP) as the sea phase as a material for forming a water-based hose for fuel cell vehicles (Patent Document 1).

[0004] Japanese Patent Laid-Open No. 2013-037972

[0005] However, studies by the present inventors have revealed that conventional dynamically crosslinked thermoplastic elastomers composed of conventional ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) and polypropylene resin (PP) tend to have insufficient vibration characteristics. For example, when used as a material for forming industrial hoses, the pulsation absorption is low, so the generation of abnormal noise caused by pulsation becomes a problem. Furthermore, studies by the present inventors have also revealed that when the above-mentioned conventional dynamically crosslinked thermoplastic elastomer is used as a material for forming vibration-proof rubber members, it is difficult to achieve a low dynamic magnification.

[0006] In the process of diligently studying to solve the above problems, the inventor focused on using natural rubber instead of ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) and conducted extensive research. They discovered that by controlling the dynamic magnification of the crosslinked material of a dynamically crosslinked thermoplastic elastomer composed of natural rubber and polypropylene resin within a specific range, vibration characteristics can be improved. For example, when used as a material for forming industrial hoses, pulsation absorption is improved, and the generation of abnormal noise can be suppressed. This led to the present invention.

[0007] In other words, the gist of the present invention is as follows: [1] A single-layer or multi-layer industrial hose having at least a layer made of a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber and (B) polypropylene resin, and the dynamic modulus ratio (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less. [2] The industrial hose according to [1], wherein the plasticity residual index of (A) natural rubber is 50 to 90. [3] The industrial hose according to [1] or [2], wherein the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is 25:75 to 75:25. [4] The industrial hose according to any one of [1] to [3], wherein the melting point of (B) polypropylene resin is 145°C or higher. [5] The industrial hose according to any one of [1] to [4], wherein the (B) polypropylene resin is a propylene homopolymer. [6] The industrial hose according to any one of [1] to [5], wherein the dynamically crosslinked thermoplastic elastomer composition contains a (C) crosslinking agent, and the (C) crosslinking agent is at least one of a phenol resin crosslinking agent and an organic peroxide crosslinking agent. [7] The industrial hose according to [6], wherein the (C) crosslinking agent is an organic peroxide crosslinking agent. [8] The industrial hose according to any one of [1] to [7], wherein the dynamically crosslinked thermoplastic elastomer composition contains a (D) plasticizer. [9] The industrial hose according to [8], wherein the content of the (D) plasticizer is 10 to 70 parts by mass per 100 parts by mass of the total of components (A) and (B).

[10] The industrial hose according to [8] or [9], wherein the (D) plasticizer is at least one of a naphthenic oil and a paraffinic oil.

[11] A vibration-damping rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber and (B) a polypropylene resin, and the dynamic modulus ratio (dynamic modulus [MPa] measured at 100 Hz / static modulus [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less.

[12] The vibration-damping rubber member according to

[11] , wherein the plasticity residual index of (A) natural rubber is 50 to 90.

[13] The vibration-damping rubber member according to

[11] or

[12] , wherein the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is 25:75 to 75:25.

[14] The vibration-damping rubber member according to any one of

[11] to

[13] , wherein the melting point of (B) polypropylene resin is 145°C or higher.

[15] The vibration-damping rubber member according to any one of

[11] to

[14] , wherein the (B) polypropylene resin is a propylene homopolymer.

[16] The vibration-damping rubber member according to any one of

[11] to

[15] , wherein the dynamic crosslinking thermoplastic elastomer composition contains a (C) crosslinking agent, and the (C) crosslinking agent is at least one of a phenol resin crosslinking agent and an organic peroxide crosslinking agent.

[17] The vibration-damping rubber member according to

[16] , wherein the (C) crosslinking agent is an organic peroxide crosslinking agent.

[18] The vibration-damping rubber member according to any one of

[11] to

[17] , wherein the dynamic crosslinking thermoplastic elastomer composition contains a (D) plasticizer.

[19] The vibration-damping rubber member according to

[18] , wherein the content of the (D) plasticizer is 10 to 70 parts by mass per 100 parts by mass of the total of components (A) and (B).

[20] The vibration-damping rubber member according to

[18] or

[19] , wherein the plasticizer (D) is at least one of naphthenic oil and paraffinic oil.

[21] An industrial hose having at least one layer made of a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber, (B) a polypropylene resin and an organic peroxide crosslinking agent, the plasticity residual index of (A) natural rubber is 50 to 90, (B) the polypropylene resin is a propylene homopolymer with a melting point of 145 to 175°C, the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is 25:75 to 75:25, and the dynamic modulus of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) is 1.70 or less.

[22] A vibration-damping rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber, (B) a polypropylene resin, and an organic peroxide crosslinking agent, the plasticity residual index of (A) natural rubber is 50 to 90, (B) the polypropylene resin is a propylene homopolymer with a melting point of 145 to 175°C, the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is 25:75 to 75:25, and the dynamic modulus of elasticity of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) is 1.70 or less.

[0008] According to the present invention, industrial hoses and vibration-damping rubber members with excellent vibration characteristics can be provided.

[0009] For example, according to one embodiment of the present invention, the vibration characteristics of an industrial hose are improved, pulsation absorption is enhanced, and the generation of abnormal noise can be suppressed. Also, according to one embodiment of the present invention, the vibration characteristics of an anti-vibration rubber member are improved, and an excellent anti-vibration rubber member can be provided.

[0010] Embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments.

[0011] In this specification, when "X to Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Furthermore, for numerical ranges described in steps in this specification, the upper or lower limit of one step in the numerical range can be arbitrarily combined with the upper or lower limit of another step in the numerical range. In addition, in 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. Moreover, "X and / or Y (where X and Y are any combination)" means at least one of X and Y, and can mean X only, Y only, or X and Y.

[0012] The present invention relates to an industrial hose or vibration-damping rubber member containing a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition. An industrial hose or vibration-damping rubber member according to one embodiment of the present invention uses a dynamically crosslinked thermoplastic elastomer composition containing (A) natural rubber and (B) a polypropylene resin, and is characterized in that the dynamic modulus (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less.

[0013] By using a dynamically crosslinked thermoplastic elastomer composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the Composition"), the vibration characteristics of the crosslinked material become excellent. Therefore, for example, when used as a forming material for industrial hoses, pulsation absorption is improved, and the generation of abnormal noise caused by pulsation can be reduced. Furthermore, when used as a forming material for vibration-damping rubber members, an excellent vibration-damping rubber member can be provided.

[0014] Furthermore, according to one embodiment of the present invention, it is useful in that it can provide industrial hoses and vibration-damping rubber members that have excellent vibration characteristics as well as excellent mechanical properties such as tensile stress and fracture strength. Moreover, for example, automotive hoses and vibration-damping rubber members installed in automobiles are often used in high-temperature environments, and mechanical properties in high-temperature environments are important. According to one embodiment of the present invention, it is particularly useful in that it can provide industrial hoses and vibration-damping rubber members that have excellent vibration characteristics as well as excellent mechanical properties in high-temperature environments.

[0015] The following describes in detail industrial hoses and vibration-damping rubber components using a dynamically crosslinked thermoplastic elastomer composition according to one embodiment of the present invention.

[0016] The present invention provides a composition for forming industrial hoses and vibration-damping rubber components, which is manufactured, for example, by blending (A) natural rubber and (B) polypropylene resin, optionally (D) a plasticizer, and kneading the mixture in a molten or semi-molten state in the presence of (C) a crosslinking agent, while simultaneously crosslinking (dynamically crosslinking) component (A) under shear.

[0017] [(A) Component: Natural Rubber] As the natural rubber used in this invention, natural rubber (NR) used in the art can be used as appropriate. Natural rubber (NR) is produced by recovering the latex (sap) of natural rubber and solidifying the rubber components contained in the latex. Specifically, it is obtained by solidifying the sap (latex) collected from Hevea brasiliensis (rubber tree) and other trees cultivated in tropical regions.

[0018] As for natural rubber, for example, sheet rubber such as RSS and block rubber such as SMR (STANDARD MALAYSIAN RUBBER) can be used as appropriate, although they are not limited to the following. These may be used individually or in combination of two or more types.

[0019] The residual plasticity index of natural rubber is not particularly limited, but from the viewpoint of improving vibration characteristics and mechanical properties, it is preferably 40 to 70, and more preferably 45 to 65. Furthermore, the residual plasticity index of component (A) is not particularly limited, but from the viewpoint of further improving mechanical properties in a heated environment, it is preferably 50 to 90, more preferably 60 to 90, and may also be 60 to 80. The above residual plasticity index can be determined in accordance with JIS K 6300-3 (2019) "Unvulcanized rubber - Physical properties - Part 3: Method for determining plasticity and residual plasticity index (PRI) by rapid plastometer".

[0020] The content of component (A) is not particularly limited, but is usually 10% by mass or more, preferably 12 to 85% by mass, and more preferably 12 to 80% by mass, relative to the dynamic cross-linked thermoplastic elastomer composition (100% by mass). Furthermore, component (A) is the main component of the rubber component contained in the dynamic cross-linked thermoplastic elastomer composition, and is preferably 70% by mass or more, relative to the total amount of rubber component contained in the dynamic cross-linked thermoplastic elastomer composition (100% by mass), and may be 70 to 100% by mass, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, etc.

[0021] [Component (B): Polypropylene resin] Examples of component (B) include propylene homopolymer (homopolypropylene), copolymers such as block copolymers, random copolymers, and graft copolymers of propylene and α-olefins other than propylene, such as ethylene and 1-butene, and modified polypropylene modified with acid anhydrides such as maleic anhydride modified polypropylene and imine modified polypropylene. These may be used individually or in combination of two or more. Among these, propylene homopolymer is preferred from the viewpoint of improving mechanical properties.

[0022] Examples of the above-mentioned α-olefins include 2 to 20 carbon atoms such as ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene (excluding propylene, which has 3 carbon atoms). These may be used individually or in combination of two or more.

[0023] The melt flow rate (MFR) of component (B) is not particularly limited, but from the viewpoint of improving vibration characteristics and mechanical properties, it is preferably 0.1 to 50 g / 10 min, more preferably 0.3 to 30 g / 10 min, and even more preferably 0.5 to 15 g / 10 min. The melt flow rate (MFR) of component (B) can be appropriately set within the above range, for example, 1 to 10 g / 10 min or 1 to 5 g / 10 min. The MFR of the polypropylene resin is measured in accordance with JIS K 7210 (2014) under conditions of a measurement temperature of 230°C and a load of 2.16 kg.

[0024] The melting point of the polypropylene resin (B) described above is not particularly limited, but from the viewpoint of improving vibration characteristics and mechanical properties, it is preferably 145°C or higher, more preferably 145 to 175°C, and even more preferably 145 to 170°C. The melting point of polypropylene can be measured by a method in accordance with JIS K 7121 (2012).

[0025] The mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is preferably 25:75 to 75:25, and more preferably 30 / 70 to 70 / 30, from the viewpoint of improving vibration characteristics and mechanical properties. The above mass ratio (A:B) can be appropriately set within the above range, for example, 35 / 65 to 65 / 35, 40 / 60 to 60 / 40, 50 / 50 to 70 / 30, etc.

[0026] Furthermore, the total content of component (A) and component (B) relative to the total amount of the dynamic crosslinked thermoplastic elastomer composition (100% by mass) (total amount of component (A) and component (B) / total amount of the dynamic crosslinked thermoplastic elastomer composition × 100 [%]) is preferably 60 to 98% by mass, and more preferably 70 to 95% by mass.

[0027] [Component (C): Crosslinking agent] Examples of component (C) include phenol resin-based crosslinking agents and organic peroxide-based crosslinking agents.

[0028] (Phenol resin-based crosslinking agents) Examples of phenol resin-based crosslinking agents include condensates of phenols and aldehydes, resol-type phenol resins, novolac-type phenol resins, and rosin-modified phenol resins. These can be used alone or in combination of two or more. Examples of the condensates of phenols and aldehydes include alkylphenol resins.

[0029] Examples of alkylphenol resins include condensates of alkylphenol components and aldehydes. Examples of the alkylphenol components include phenols having alkyl groups with 1 to 18 carbon atoms, such as cresol, isopropylphenol, t-butylphenol, amylphenol, octylphenol (e.g., p-octylphenol), nonylphenol, dodecylphenol, allylphenol, and cyclohexylphenol, as well as various derivatives such as methylolated derivatives and halogenated derivatives thereof.

[0030] Examples of the above-mentioned aldehydes include formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, and paraxylenedimethyl ether.

[0031] Suitable examples of alkylphenol resins include alkylphenol acetylene resins, alkylphenol formaldehyde resins, and alkylphenol acetaldehyde resins.

[0032] The softening point of the phenolic resin crosslinking agent is not particularly limited, but is preferably 50 to 200°C, more preferably 60 to 150°C, and even more preferably 70 to 120°C. The softening point is measured by the ring-and-spherical method in accordance with JIS K 2207 (2006).

[0033] Examples of commercially available phenolic resin crosslinking agents include Tackirol 201 (alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), Tackirol 250-I (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), Tackirol 250-III (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), Schenectady SP1059, Schenectady SP1045, Schenectady SP-1055, and Schenectady SP-1056 (manufactured by Schenectady Chem).

[0034] (Organic peroxide crosslinking agents) Examples of organic peroxide crosslinking agents include 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)butane, n-butyl-4,4-bis( Peroxyketals such as t-butylperoxy)valerate, dialkylperoxides such as di-t-butylperoxide, dicumylperoxide, t-butylcumylperoxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, α,α'-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, as well as acetylperoxide and isobutylperoxide. Diacyl peroxides such as oxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-trioyl peroxide, and t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, di-t-butyl peroxy Examples include peroxyesters such as cyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and cumylperoxyoctate, as well as hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, and 1,1,3,3-tetramethylbutylperoxide. These can be used individually or in combination of two or more.

[0035] The content of component (C) is not limited to the following, but from the viewpoint of significantly achieving the effects of the present invention, it is, for example, 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, and even more preferably 2.5 to 8 parts by mass, based on 100 parts by mass of the total of components (A) and (B).

[0036] Furthermore, when a phenolic resin-based crosslinking agent is used as component (C), the content of the phenolic resin-based crosslinking agent is not limited to the following, but from the viewpoint of significantly achieving the effects of the present invention, it is, for example, 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, and even more preferably 2.5 to 8 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0037] Furthermore, when an organic peroxide-based crosslinking agent is used as component (C), the content of the organic peroxide-based crosslinking agent is not limited to the following, but from the viewpoint of significantly achieving the effects of the present invention, it is, for example, 0.05 to 6 parts by mass, more preferably 0.08 to 5 parts by mass, and even more preferably 0.1 to 4 parts by mass, per 100 parts by mass of the total of components (A) and (B). In addition, when a 100% pure raw material is not used as the organic peroxide-based crosslinking agent, it is formulated so that the ratio on a raw material basis falls within the above range.

[0038] [Component (D): Plasticizer] The dynamically crosslinked thermoplastic elastomer composition in the embodiments of the present invention may contain (D) a plasticizer. Examples of plasticizers include aromatic oils, ether ester plasticizers, and process oils. These may be used alone or in combination of two or more.

[0039] 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 having 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. Among these, paraffinic oils are preferred.

[0040] The plasticizer content is not particularly limited, but from the viewpoint of improving vibration characteristics and mechanical properties, for example, it is preferably 10 to 70 parts by mass, and more preferably 20 to 60 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0041] [Other Components] In addition to the above components, the dynamic crosslinking thermoplastic elastomer composition may contain various additives as needed, in a type and range that does not impair the effects of the present invention, such as crosslinking aids, sulfur, antioxidants, heat stabilizers, inorganic fillers, nucleating agents, and weathering agents.

[0042] (Crosslinking aids) When used with organic peroxide-based crosslinking agents, examples of crosslinking aids include divinyl compounds such as divinylbenzene, oxime compounds such as p-quinone dioxime, nitroso compounds such as N-methyl-N-4-dinitrosoaniline and nitrosobenzene, maleleimide compounds such as trimethylolpropane-N,N'-m-phenylenedimaleimide, and polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate. When used with phenolic resin-based crosslinking agents, examples of crosslinking aids include iron oxide, titanium oxide, magnesium oxide, silicon dioxide, zinc oxide, stannous chloride, ferric chloride, chlorinated paraffin, chlorinated polyethylene, and chlorosulfonated polyethylene.

[0043] The content of the crosslinking auxiliary may be appropriately set according to the content of the component (A), the type and amount of the crosslinking agent, and the like. For example, although not particularly limited, the content of the crosslinking auxiliary is, for example, 0.1 to 5 parts by mass, or about 0.1 to 3 parts by mass, relative to 100 parts by mass in total of the component (A) and the component (B).

[0044] As sulfur, powdered sulfur, precipitated sulfur, insoluble sulfur, or the like can be appropriately used. Sulfur-containing compounds such as alkylphenol disulfide may also be used. Vulcanization accelerators such as sulfenamide-based, guanidine-based, thiazole-based, aldehyde-ammonia-based, aldehyde-amine-based, and thiourea-based vulcanization accelerators may also be used in combination.

[0045] <Method for Preparing Dynamically Crosslinked Thermoplastic Elastomer Composition> The dynamically crosslinked thermoplastic elastomer composition is produced by kneading a mixture containing (A) natural rubber, (B) a polypropylene resin, (D) a plasticizer, and optionally added additives in a molten or semi-molten state in the presence of (C) a crosslinking agent, and simultaneously crosslinking (A) natural rubber (dynamic crosslinking) under shearing. The dynamically crosslinked thermoplastic elastomer composition has a sea-island structure in which crosslinked (A) natural rubber is finely dispersed as domains in a matrix of (B) polypropylene resin.

[0046] As conditions for producing the dynamically crosslinked thermoplastic elastomer composition by kneading in an extruder or the like, melt kneading is generally performed while heating to 150 to 300°C, preferably 150 to 250°C. The treatment time for performing the dynamic heat treatment is not particularly limited, but is generally about 0.1 to 30 minutes.

[0047] <Physical Properties of Dynamically Crosslinked Thermoplastic Elastomer Composition> As described above, the dynamic magnification of a crosslinked product of the dynamically crosslinked thermoplastic elastomer composition (dynamic elastic modulus [MPa] measured at 100 Hz / static elastic modulus [MPa] measured at 15 Hz) is 1.70 or less. From the viewpoint of improving vibration characteristics and mechanical properties, it is more preferably 1.68 or less, still more preferably 1.65 or less. The lower limit of the dynamic magnification is not particularly limited, but is, for example, 1.00 or more.

[0048] The dynamic magnification ratio described above is determined by preparing a strip-shaped test specimen in accordance with JIS K 6394 (2007) and measuring the dynamic modulus of elasticity (MPa) of the test specimen using the tensile method specified in JIS K 6394 (2007). The measurement is performed in an environment of 23°C, with the static modulus of elasticity (MPa) measured at 15 Hz and the dynamic modulus of elasticity (MPa) measured at 100 Hz. The value obtained by calculating "dynamic modulus of elasticity (MPa) / static modulus of elasticity (MPa)" is then used as the value of the dynamic magnification ratio.

[0049] The 100% modulus (M100) of the dynamically crosslinked thermoplastic elastomer composition is not particularly limited, but from the viewpoint of significantly demonstrating the effects of the present invention, it is preferably less than 19 MPa, and more preferably 3 to 13 MPa. The 100% modulus (M100) can be determined by performing a tensile test using a 2 mm thick sheet-like molded body prepared by the method described in the examples below, in accordance with JIS K 6251 (2019), at a measurement temperature of 23°C and a tensile speed of 500 mm / min.

[0050] The breaking strength of the dynamically crosslinked thermoplastic elastomer composition is not particularly limited, but from the viewpoint of significantly demonstrating the effects of the present invention, it is preferably 6 MPa or more, and more preferably 9 to 19 MPa, at a temperature of 23°C. The 100% modulus (M100) can be determined by performing a tensile test on a 2 mm thick sheet-like molded body prepared by the method described in the examples below, in accordance with JIS K 6250, 6251 (2019), at a measurement temperature of 23°C and a tensile speed of 500 mm / min.

[0051] The rate of change in breaking strength of the dynamically crosslinked thermoplastic elastomer composition is not particularly limited, but from the viewpoint of significantly demonstrating the effects of the present invention, it is preferably less than -50%, and more preferably -30% to -45%. The rate of change in breaking strength is determined by the following formula based on the breaking strength at 23°C and the breaking strength at 80°C. Formula: (Breaking strength at 80°C [MPa] - Breaking strength at 23°C [MPa]) / Breaking strength at 23°C [MPa] × 100 (%)

[0052] <Method for Manufacturing a Hose> An industrial hose, which is an example of an embodiment of the present invention, can be obtained by a known manufacturing method using the above-mentioned dynamic crosslinking thermoplastic elastomer composition. Specifically, for example, the dynamic crosslinking thermoplastic elastomer composition is extruded into a cylindrical shape using an extrusion molding machine or the like under conditions of 180 to 250°C.

[0053] The inner diameter, thickness, and length of an industrial hose, which is an example of an embodiment of the present invention, are not particularly limited, but for example, the inner diameter is preferably in the range of 2.5 to 30 mm, the thickness is preferably in the range of 0.5 to 5 mm, and the length is preferably in the range of 100 to 1500 mm.

[0054] An example of an embodiment of the present invention is an industrial hose, which may be a single-layer hose composed of only one layer made of a crosslinked material of a dynamically crosslinked thermoplastic elastomer composition, or a multi-layer industrial hose composed of multiple layers, each consisting of one layer made of a crosslinked material of a dynamically crosslinked thermoplastic elastomer composition and one or more other layers. When the industrial hose, which is an example of an embodiment of the present invention, is a single-layer hose, the thickness of the hose is in the range of 0.5 to 6 mm, and preferably in the range of 1 to 4 mm. When the industrial hose, which is an example of an embodiment of the present invention, is a multi-layer hose with two or more layers, the thickness of the layer made of the dynamically crosslinked thermoplastic elastomer composition is in the range of 0.1 to 3 mm, and preferably in the range of 0.3 to 1.5 mm.

[0055] (Applications) As an example of an embodiment of the present invention, an industrial hose is suitable for use as an automobile hose. In particular, it can be suitably used as an automobile hose, such as a radiator hose used to connect the engine and radiator in vehicles such as automobiles, a heater hose used to connect the engine and heater core, an engine cooling system hose, a refrigerant transport hose for coolers, a fuel cell vehicle hose such as a methanol fuel hose and a hydrogen fuel hose, and a gasoline fuel hose. It is especially suitable as an electric vehicle hose. It 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.).

[0056] As an example of an embodiment of the present invention, the vibration-damping rubber member is preferably used as a component of engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc., used in automobiles and the like. In addition, it can also be used as a component of vibration damping devices and seismic isolation devices such as vibration damping dampers for computer hard disks, vibration damping dampers for general home appliances such as washing machines, and vibration damping walls and dampers for buildings in the construction and housing sectors.

[0057] The following describes the examples along with comparative examples. However, the present invention is not limited to these examples unless it exceeds the essence of the invention. Unless otherwise specified, "parts," "%," etc., refer to mass.

[0058] First, I prepared the following materials.

[0059] [(A) Natural Rubber] ・Natural rubber (1) (Natural rubber with a residual plasticity index of 62) ・Natural rubber (2) (Natural rubber with a residual plasticity index of 78) ・Natural rubber (3) (Natural rubber with a residual plasticity index of 53) ・Natural rubber (4) (Natural rubber with a residual plasticity index of 48)

[0060] [(B) Polypropylene resins] ・Polypropylene resin (1) (Prime Polymer Co., Ltd., Prime Polypropylene E200GP [homopolypropylene, MFR (230℃) 2.0g / 10min]) ・Polypropylene resin (2) (Prime Polymer Co., Ltd., Prime Polypropylene B221WA [random polypropylene, MFR (230℃) 0.5g / 10min])

[0061] [(C) Crosslinking Agents] ・Phenolic resin-based crosslinking agent (Schenectady Chemicals, SP-1055) ・Organic peroxide-based crosslinking agent (Nippon Oil & Fats Co., Ltd., Perhexine 25B [Purity 40%, Half-life temperature at 1 hour = 149.9°C])

[0062] [(D) Plasticizer] Process oil (Idemitsu Kosan Co., Ltd., Diana Process Oil PW-100)

[0063] [Crosslinking aids] ・Crosslinking aid (1) (manufactured by Nippon Steel Chemical Co., Ltd., DVB-570 [mixture of divinylbenzene and ethylvinylbenzene [mass ratio divinylbenzene:ethylvinylbenzene = 55 parts:45 parts]]) ・Crosslinking aid (2) (manufactured by Hakusui Tech Co., Ltd., two types of zinc oxide)

[0064] [EPDM] ・EPDM (manufactured by Mitsui Chemicals, EPT3092M [ethylene-propylene-ENB copolymer rubber, Mooney viscosity 61 (ML) 1+4 (at 125°C), ethylene content 65%, diene content 4.6%)

[0065] [Examples 1-10, Comparative Example 1] Dynamically crosslinked thermoplastic elastomer compositions were prepared by mixing each material in the proportions shown in Table 1. Specifically, components (A), (B), and (D) were supplied to the hopper of a twin-screw extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.), kneaded at 180°C for 1 minute, and then (C) crosslinking agent and crosslinking aid were added and kneaded at 120°C for 0.5 minutes to obtain a kneaded product. The screw rotation speed was 200 rpm and the discharge rate was 10 kg / hour. After that, the kneaded product was cut to obtain pellets of the dynamically crosslinked thermoplastic elastomer composition.

[0066] <Vibration Characteristics Evaluation> A pellet of the above-mentioned dynamically crosslinked thermoplastic elastomer composition was press-molded at 200°C for 8 minutes, and then cooled and pressed at 25°C for 5 minutes to obtain a 2 mm thick press sheet. Strip-shaped test pieces were prepared from this press sheet in accordance with JIS K 6394 (2007), and the dynamic modulus of elasticity (MPa) of the above-mentioned strip-shaped test pieces was calculated and measured using the tensile method specified in JIS K 6394 (2007). The measurement was performed in an environment of 23°C, with the static modulus of elasticity (MPa) measured at 15 Hz and the dynamic modulus of elasticity (MPa) measured at 100 Hz. The "dynamic modulus of elasticity (MPa) / static modulus of elasticity (MPa)" was calculated, and this value was used as the dynamic magnification value and evaluated according to the following criteria. (Evaluation Criteria) ○ (very good) ... Dynamic magnification value is 1.70 or less × (poor) ... Dynamic magnification value is greater than 1.70

[0067] <Evaluation of Tensile Stress and Breaking Strength> A 2 mm thick press sheet was obtained by press-molding pellets of the above-mentioned dynamically cross-linked thermoplastic elastomer composition at 200°C for 8 minutes, and then cooling and pressing at 25°C for 5 minutes. From this press sheet, the tensile stress (M100) at 23°C and the breaking strength at 23°C and 80°C were measured using a tensile testing machine (AGS-X, manufactured by Shimadzu Corporation) in accordance with JIS K 6251 (2019), and evaluated according to the following criteria. (Evaluation criteria for tensile stress (M100)) ○ (very good)...less than 19 MPa △ (good)...19 MPa or more (Evaluation criteria for breaking strength at 23°C) ○ (very good)...9.5 MPa or more △ (good)...less than 9.5 MPa

[0068] Furthermore, the rate of change in breaking strength was calculated based on the breaking strength at 23°C and 80°C and evaluated according to the following criteria: (Formula) (Breaking strength at 80°C [MPa] - Breaking strength at 23°C [MPa]) / Breaking strength at 23°C [MPa] × 100 (%) (Evaluation criteria for rate of change in breaking strength) ○ (very good) ... Less than -50% △ (good) ... -50% or more

[0069]

[0070] From the results in Table 1, it can be seen that in Comparative Example 1, which corresponds to the conventional TPV (EPDM / PP), the vibration characteristics are insufficient. For example, the pulsation absorption is low, the generation of abnormal noise caused by pulsation cannot be suppressed, and it is difficult to reduce the dynamic magnification of the vibration-damping rubber member.

[0071] On the other hand, embodiments of the present invention possess excellent vibration characteristics and also excel in mechanical properties such as tensile stress and fracture strength. For example, they can be used to create industrial hoses with good pulsation absorption, which can suppress the generation of abnormal noises caused by pulsation, or vibration-damping rubber members with excellent vibration characteristics. Furthermore, the present invention provides industrial hoses and vibration-damping rubber members that are excellent in vibration characteristics as well as in mechanical properties under high-temperature environments.

[0072] 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.

[0073] The present invention is suitably used as an industrial hose. For example, it is suitable as an automotive hose. In particular, it can be suitably used as an automotive 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 present invention is suitably used as a vibration-damping rubber member. Specifically, for example, it can be suitably used as a component of engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc., used in automobiles and other vehicles.

Claims

1. An industrial hose having at least one layer made of a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber and (B) a polypropylene resin, and the dynamic modulus ratio (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less.

2. The industrial hose according to claim 1, wherein the plasticity residual index of the natural rubber (A) above is 50 to 90.

3. The industrial hose according to claim 1 or 2, wherein the mass ratio (A:B) of the above (A) natural rubber to the above (B) polypropylene resin is 25:75 to 75:

25.

4. The industrial hose according to claim 2 or 3, wherein the melting point of the polypropylene resin (B) above is 145°C or higher.

5. The industrial hose according to claim 2 or 3, wherein the (B) polypropylene resin is a propylene homopolymer.

6. The industrial hose according to claim 2 or 3, wherein the dynamic crosslinking thermoplastic elastomer composition contains (C) a crosslinking agent, and the (C) crosslinking agent is at least one of a phenol resin-based crosslinking agent and an organic peroxide-based crosslinking agent.

7. The industrial hose according to claim 6, wherein the crosslinking agent (C) above is an organic peroxide-based crosslinking agent.

8. The industrial hose according to claim 2 or 3, wherein the above-mentioned dynamically crosslinked thermoplastic elastomer composition contains (D) a plasticizer.

9. The industrial hose according to claim 8, wherein the content of the plasticizer (D) is 10 to 70 parts by mass per 100 parts by mass of the total of components (A) and (B).

10. The industrial hose according to claim 8 or 9, wherein the plasticizer (D) is at least one of a naphthenic oil and a paraffinic oil.

11. A vibration-damping rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber and (B) a polypropylene resin, and the dynamic modulus ratio (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less.

12. The vibration-damping rubber member according to claim 11, wherein the plasticity residual index of the natural rubber (A) above is 50 to 90.

13. The vibration-damping rubber member according to claim 11 or 12, wherein the mass ratio (A:B) of the above (A) natural rubber to the above (B) polypropylene resin is 25:75 to 75:

25.

14. The vibration-damping rubber member according to claim 12 or 13, wherein the melting point of the polypropylene resin (B) is 145°C or higher.

15. The vibration-damping rubber member according to claim 12 or 13, wherein the (B) polypropylene resin is a propylene homopolymer.

16. The vibration-damping rubber member according to claim 12 or 13, wherein the above-mentioned dynamically crosslinked thermoplastic elastomer composition contains (C) a crosslinking agent, and the above-mentioned (C) crosslinking agent is at least one of a phenol resin-based crosslinking agent and an organic peroxide-based crosslinking agent.

17. The vibration-damping rubber member according to claim 16, wherein the crosslinking agent (C) is an organic peroxide-based crosslinking agent.

18. The vibration-damping rubber member according to claim 12 or 13, wherein the above-mentioned dynamically crosslinked thermoplastic elastomer composition contains (D) a plasticizer.

19. The vibration-damping rubber member according to claim 18, wherein the content of the plasticizer (D) is 10 to 70 parts by mass with respect to 100 parts by mass of the total of components (A) and (B).

20. The vibration-damping rubber member according to claim 18 or 19, wherein the plasticizer (D) is at least one of a naphthenic oil and a paraffinic oil.

21. An industrial hose having at least one single-layer or multi-layer structure comprising a crosslinked material of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber, (B) a polypropylene resin, and an organic peroxide crosslinking agent, the plasticity residual index of (A) natural rubber being 50 to 90, the polypropylene resin being a propylene homopolymer with a melting point of 145 to 175°C, the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin being 25:75 to 75:25, and the dynamic modulus ratio (dynamic modulus [MPa] measured at 100 Hz / static modulus [MPa] measured at 15 Hz) of the crosslinked material of the dynamically crosslinked thermoplastic elastomer composition being 1.70 or less.

22. A vibration-damping rubber member comprising a crosslinked product of a dynamically crosslinked thermoplastic elastomer composition, wherein the dynamically crosslinked thermoplastic elastomer composition contains (A) natural rubber, (B) a polypropylene resin, and an organic peroxide crosslinking agent, the plasticity residual index of (A) natural rubber is 50 to 90, (B) the polypropylene resin is a propylene homopolymer with a melting point of 145 to 175°C, the mass ratio (A:B) of (A) natural rubber to (B) polypropylene resin is 25:75 to 75:25, and the dynamic modulus ratio (dynamic modulus of elasticity [MPa] measured at 100 Hz / static modulus of elasticity [MPa] measured at 15 Hz) of the crosslinked product of the dynamically crosslinked thermoplastic elastomer composition is 1.70 or less.

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