Dynamically crosslinked thermoplastic elastomer, method for producing the same, and molded article

Abstract

To provide a dynamic crosslinking type thermoplastic elastomer which is excellent in oil resistance and moldability.SOLUTION: There are provided a dynamic crosslinking type thermoplastic elastomer that is obtained by dynamically crosslinking a thermoplastic elastomer composition containing 100 pts.mass of a copolymer (A) of ethylene, α-olefin having 3 to 20 carbon atoms, and non-conjugated polyene, 5-80 pts.mass of a crystalline olefin polymer (B), 100-300 pts.mass of a softening agent (C), and 1-15 pts.mass of a phenol resin-based crosslinking agent (D), wherein a difference (R) of a gel fraction represented by the following expression exceeds 1.4 and 5.0 mass% or less; a method for producing the same; and a molding. Difference (R) of gel fraction (mass%)=gel fraction of 325 mesh (mass%)-gel fraction of 80 mesh (mass%).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a dynamically crosslinked thermoplastic elastomer, a method for producing the same, and a molded body.

Background Art

[0002] Thermoplastic elastomers are widely used in automotive parts, industrial machinery parts, electrical and electronic parts, building materials, etc. as energy-saving and resource-saving types of elastomers because of their light weight and easy recyclability, especially as a substitute for vulcanized rubber.

[0003] As a thermoplastic elastomer composition obtained by blending an olefin-based thermoplastic elastomer and a styrene-based thermoplastic elastomer, Patent Document 1 describes a thermoplastic elastomer composition containing an ethylene·α-olefin·non-conjugated polyene copolymer rubber, a crystalline olefin-based resin, a styrene-based copolymer, and a phenolic resin-based crosslinking agent. Further, for example, Patent Document 2 describes a thermoplastic elastomer composition containing an olefin-based copolymer rubber, a polyolefin-based resin, a styrene-based copolymer, and a phenolic resin-based crosslinking agent. Further, for example, Patent Document 3 discloses a thermoplastic elastomer composition containing 30 to 60 parts by mass of a crystalline olefin-based polymer (A), 100 parts by mass of an ethylene·α-olefin (having 3 to 20 carbon atoms)·non-conjugated polyene copolymer (B) satisfying the requirements (1) Mooney viscosity [ML (1+4) 125°C] of 50 to 230 and (2) a content of ethylene-derived structural units of 50 to 95 mol%, at least one polymer (C) selected from the group consisting of a copolymer of an aromatic vinyl compound and a conjugated diene compound, a hydrogenated product of a copolymer of an aromatic vinyl compound and a conjugated diene compound, and a hydrogenated conjugated diene compound polymer of 20 to 120 parts by mass, and 4 to 15 parts by mass of a phenolic resin-based crosslinking agent (D).

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-002085 [Patent Document 2] Japanese Patent Application Laid-Open No. 63-112649 [Patent Document 3] International Publication No. 2018 / 181121 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Thermoplastic elastomers are used in automotive parts and other applications due to their lightweight nature and ease of recycling. Automotive parts are often used in areas that come into contact with lubricants and greases. Generally, olefin-based thermoplastic elastomer compositions, which consist of crystalline polyolefins and olefin-based rubber, have low affinity for paraffin-based oils, and the rubber component in particular has low crystallinity at room temperature, making it prone to absorbing oil. As a result, the oil resistance of these compositions has been insufficient. Therefore, these automotive parts containing olefin-based thermoplastic elastomers also have low oil resistance, and further improvements have been needed. Olefin-based thermoplastic elastomers, made from ethylene-propylene-non-conjugated diene copolymers (EPDM) and crystalline polyolefins such as polypropylene, have a lower specific gravity and superior durability in terms of heat aging resistance and weather resistance compared to other thermoplastic elastomers. However, further improvements are required depending on the application. In oil-resistant applications, there is a demand for thermoplastic elastomer compositions that are low in hardness and have excellent moldability.

[0006] One embodiment of the present invention aims to solve the problem of providing a dynamically crosslinked thermoplastic elastomer with excellent oil resistance and moldability, and a molded article containing this dynamically crosslinked thermoplastic elastomer. Another embodiment of the present invention aims to solve the problem of providing a method for producing a dynamically crosslinked thermoplastic elastomer with excellent oil resistance and moldability. [Means for solving the problem]

[0007] The means for solving the above problems include the following embodiments. <1> 100 parts by mass of copolymer (A) of ethylene, α-olefin having 3 to 20 carbon atoms, and non-conjugated polyene. Crystalline olefin polymer (B) 5 to 80 parts by mass, Softener (C) 100 to 300 parts by mass, and A dynamically crosslinked thermoplastic elastomer obtained by dynamically crosslinking a thermoplastic elastomer composition containing 1 to 15 parts by mass of a phenol resin-based crosslinking agent (D), wherein the difference in gel fraction (R) represented by the following formula is greater than 1.4% by mass and less than or equal to 5.0% by mass. Difference in gel fraction (R) (mass%) = Gel fraction of 325 mesh (mass%) - Gel fraction of 80 mesh (mass%) <2> At least a portion of the copolymer (A) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene is crosslinked. <1> The dynamically crosslinked thermoplastic elastomer described above. <3> The crystalline olefin polymer (B) is at least one of a propylene homopolymer and a copolymer of propylene and an α-olefin having 2 to 20 carbon atoms (excluding propylene). <1> or <2> The dynamically crosslinked thermoplastic elastomer described above. <4> The Shore A hardness (instantaneous value) measured in accordance with JIS K 6253 (2012) is between 20 and 90. <1> ~ <3> A dynamically crosslinked thermoplastic elastomer as described in any one of the following. <5> Having a sea-island structure, <1> ~ <4> A dynamically crosslinked thermoplastic elastomer as described in any one of the following. <6> <1> ~ <5> A method for producing a dynamically crosslinked thermoplastic elastomer as described in any one of the following: A method for producing a dynamically crosslinked thermoplastic elastomer, comprising the steps of dynamically heat-treating a thermoplastic elastomer comprising: an uncrosslinked copolymer (A-1) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene; a crystalline olefin polymer (B); a thermoplastic elastomer composition containing a crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, and the crystalline olefin polymer (B); a softener (C); and a phenol resin-based crosslinking agent (D) to obtain the elastomer. <7> <1> ~ <5> A molded article comprising a dynamically crosslinked thermoplastic elastomer as described in any one of the following. <8> Used for oil-resistant applications, <7> The molded body described above. <9> Automotive hoses, <7> The molded body described above. <10> These are automotive boots. <7> The molded body described above. [Effects of the Invention]

[0008] According to one embodiment of the present invention, a dynamically crosslinked thermoplastic elastomer with excellent oil resistance and moldability, and a molded article containing this dynamically crosslinked thermoplastic elastomer are provided. According to another embodiment of the present invention, a method for producing a dynamically crosslinked thermoplastic elastomer with excellent oil resistance and moldability is provided. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1(a) shows an example of an image of a cross-section of a dynamically cross-linked thermoplastic elastomer corresponding to the comparative example, observed with a scanning electron microscope (SEM) at 1,000x magnification. Figure 1(b) shows an example of an image of a cross-section of a dynamically cross-linked thermoplastic elastomer corresponding to the comparative example, observed with a scanning electron microscope (SEM) at 3,000x magnification. [Figure 2] Figure 2(a) shows an example of an image of a cross-section of a dynamically cross-linked thermoplastic elastomer corresponding to an embodiment of the present invention, observed with a scanning electron microscope (SEM) at 1,000x magnification. Figure 2(b) shows an example of an image of a cross-section of a dynamically cross-linked thermoplastic elastomer corresponding to an embodiment of the present invention, observed with a scanning electron microscope (SEM) at 3,000x magnification.

Mode for Carrying Out the Invention

[0010] Hereinafter, the content of the present invention will be described in detail. The description of the content of the constituent elements described below may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, “~” indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value. In this specification, “~” indicating a numerical range means that the unit described on either side before and after it indicates the same unit unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. Hereinafter, the present invention will be described in detail.

[0011] (Dynamic Crosslinked Thermoplastic Elastomer) The dynamic crosslinked thermoplastic elastomer according to the present invention is a dynamic crosslinked thermoplastic elastomer obtained by dynamically crosslinking a thermoplastic elastomer composition containing 100 parts by mass of a copolymer (A) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, 5 to 80 parts by mass of a crystalline olefin polymer (B), 100 to 300 parts by mass of a softening agent (C), and 1 to 15 parts by mass of a phenolic resin-based crosslinking agent (D), and the difference (R) in gel fraction represented by the following formula exceeds 1.40% by mass and is 5.0% by mass or less. Difference in gel fraction (R) (% by mass) = Gel fraction (% by mass) of 325 mesh - Gel fraction (% by mass) of 80 mesh

[0012] As a result of intensive studies by the inventors, it has been found that the dynamic crosslinked thermoplastic elastomer according to the present invention has excellent oil resistance and moldability due to having the above configuration. Although the reason is not clear, it is presumed as follows. It is known that increasing the amount of rubber component in a thermoplastic elastomer is a strategy to increase its flexibility (i.e., to lower its hardness). However, it has been found that increasing the amount of rubber component to lower hardness reduces the fluidity of the thermoplastic elastomer, making it difficult to mold. As a result of diligent research, the inventors discovered that fluidity can be improved by broadening the particle size distribution of the rubber components that make up the island portion of the sea-island structure in a thermoplastic elastomer composition (i.e., by making the particle size distribution multi-peaked), which led to the present invention. The dynamically crosslinked thermoplastic elastomer according to the present invention is obtained by dynamically crosslinking a thermoplastic elastomer composition containing specific amounts of ethylene, a copolymer (A) of α-olefin having 3 to 20 carbon atoms and a non-conjugated polyene, a crystalline olefin polymer (B), a softener (C), and a phenol resin-based crosslinking agent (D). In the obtained dynamically crosslinked thermoplastic elastomer, the difference in gel fraction (R) is greater than 1.4 and less than or equal to 5.0% by mass. That is, because copolymers (A) with different particle sizes are present in the dynamically crosslinked thermoplastic elastomer, fluidity is improved, resulting in excellent formability, and because it contains specific amounts of components (A) to (D), it is presumed to have excellent oil resistance. The above-described dynamically crosslinked thermoplastic elastomer is obtained by dynamically crosslinking a thermoplastic elastomer composition. The components of the thermoplastic elastomer composition will be described in detail below. The method for dynamically crosslinking the thermoplastic elastomer composition will be described later.

[0013] <Thermoplastic elastomer composition> The thermoplastic elastomer composition comprises 100 parts by mass of a copolymer (A) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene (hereinafter also simply referred to as "polymer (A)"), 5 to 80 parts by mass of a crystalline olefin polymer (B), 100 to 300 parts by mass of a softening agent (C), and 1 to 15 parts by mass of a phenolic resin-based crosslinking agent (D). A dynamically crosslinked thermoplastic elastomer, obtained by dynamically crosslinking a thermoplastic elastomer composition containing the above components, exhibits excellent oil resistance and moldability.

[0014] <<Copolymer (A)>> Examples of α-olefins having 3 to 20 carbon atoms include linear α-olefins such as propylene (3 carbon atoms), 1-butene (4 carbon atoms), 1-hexene (6 carbon atoms), 1-octene (8 carbon atoms), 1-nonene (9 carbon atoms), 1-decene (10 carbon atoms), 1-nonadecene (19 carbon atoms), and 1-eicosene (20 carbon atoms); and linear α-olefins such as 4-methyl-1-pentene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. The above-mentioned α-olefins having 3 to 20 carbon atoms may be used individually or in combination of two or more. Among these, propylene is preferred as the above-mentioned α-olefin having 3 to 20 carbon atoms from the viewpoint of heat resistance.

[0015] Examples of non-conjugated polyenes include linear non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, and 5-isopropylidene-2-norbornene. Examples include cyclic non-conjugated dienes such as 6-chloromethyl-5-isopropenyl-2-norbornene; and trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,5-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene, 4,8-dimethyl-1,4,8-decatriene, and 4-ethylidene-8-methyl-1,7-nonadien. These unconjugated polyenes may be used individually or in combination of two or more. Among these, as non-conjugated polyenes, from the viewpoint of excellent oil resistance, cyclic non-conjugated dienes such as 1,4-hexadiene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene and mixtures of 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene are preferred, and 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene are more preferred.

[0016] Copolymer (A) includes ethylene-propylene-1,4-hexadiene copolymer, ethylene-1-pentene-1,4-hexadiene copolymer, ethylene-1-hexene-1,4-hexadiene copolymer, ethylene-1-heptene-1,4-hexadiene copolymer, ethylene-1-octene-1,4-hexadiene copolymer, ethylene-1-nonene-1,4-hexadiene copolymer, ethylene-1-decene-1,4-hexadiene copolymer, and ethylene-propylene-1-octene-1,4-hexadiene copolymer. Diene copolymer, ethylene-propylene-5-ethylidene-2-norbornene copolymer, ethylene-1-pentene-5-ethylidene-2-norbornene copolymer, ethylene-1-hexene-5-ethylidene-2-norbornene copolymer, ethylene-1-heptene-5-ethylidene-2-norbornene copolymer, ethylene-1-octene-5-ethylidene-2-norbornene copolymer, ethylene-1-nonene-5-ethylidene-2-norbornene copolymer, ethylene-1-decene-5-ethylidene- 2-norbornene copolymer, ethylene-propylene-1-octene-5-ethylidene-2-norbornene copolymer, ethylene-propylene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-pentene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-hexene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-heptene-5-ethylidene-2-norbornene Examples include 5-vinyl-2-norbornene copolymer, ethylene·1-octene·5-ethylidene-2-norbornene·5-vinyl-2-norbornene copolymer, ethylene·1-nonene·5-ethylidene-2-norbornene·5-vinyl-2-norbornene copolymer, ethylene·1-decene·5-ethylidene-2-norbornene·5-vinyl-2-norbornene copolymer, and ethylene·propylene·1-octene·5-ethylidene-2-norbornene·5-vinyl-2-norbornene copolymer. Among these, from the viewpoint of excellent oil resistance and moldability, copolymer (A) is preferably ethylene-propylene-5-ethylidene-2-norbornene copolymer or ethylene-butene-5-ethylidene-2-norbornene copolymer, and more preferably ethylene-propylene-5-ethylidene-2-norbornene copolymer.

[0017] From the viewpoint of mechanical strength, copolymer (A) preferably has an intrinsic viscosity [η] of 2.0 to 7.0 dl / g, more preferably 3.0 to 7.0 dl / g, and even more preferably 3.3 to 7.0 dl / g, measured in decalin (decahydronaphthalene) at 135°C. Furthermore, when copolymer (A) is spread using an oil-expanding agent such as a softener described later, the intrinsic viscosity [η] is determined by degreasing before measuring the intrinsic viscosity [η] and measuring the copolymer (A) alone.

[0018] Copolymer (A) may be used alone or in combination of two or more types. From the viewpoint of mechanical strength and heat resistance, copolymer (A) preferably contains ethylene-derived structural units [a] in the range of 50 to 95 mol%, more preferably 60 to 85 mol%, and even more preferably 65 to 80 mol%, relative to the total structural units of copolymer (A).

[0019] Furthermore, the copolymer (A) has a mass ratio [[a] / [b]] of structural units derived from ethylene [a] to structural units derived from α-olefin [b] that is typically in the range of 40 / 60 to 90 / 10, preferably 45 / 55 to 80 / 20, more preferably 50 / 50 to 75 / 25, particularly preferably 55 / 45 to 70 / 30, and most preferably 55 / 45 to 68 / 32.

[0020] The copolymer (A) contains structural units [c] derived from non-conjugated polyenes, preferably in the range of 0.1 to 10% by mass, more preferably 1 to 8% by mass, even more preferably 2 to 6% by mass, and particularly preferably 3 to 5% by mass, based on 100% by mass of the total structural units [a], [b] and [c].

[0021] [Method for producing copolymer (A)] The method for producing copolymer (A) is not particularly limited and can be produced by known methods. For example, refer to the production methods described in paragraphs

[0028] to

[0145] of International Publication No. 2018 / 181121.

[0022] From the viewpoint of excellent oil resistance and moldability, it is preferable that the copolymer (A) of ethylene, α-olefin having 3 to 20 carbon atoms, and non-conjugated polyene is crosslinked in at least a portion. That is, it is more preferable that copolymer (A) contains a crosslinked copolymer (A-2) of ethylene, α-olefin having 3 to 20 carbon atoms, and non-conjugated polyene (hereinafter also referred to as "crosslinked copolymer (A-2)") and an uncrosslinked copolymer (A-1) of ethylene, α-olefin having 3 to 20 carbon atoms, and non-conjugated polyene (hereinafter also referred to as "uncrosslinked copolymer (A-1)"). From the viewpoint of excellent oil resistance and moldability, the ratio of copolymer (A-1) to copolymer (A-2) contained in copolymer (A) is preferably 90:10 to 30:70 by mass, more preferably 85:15 to 40:60, and even more preferably 80:20 to 50:50.

[0023] There are no particular limitations on the method for crosslinking at least a portion of the copolymer (A), and crosslinking can be carried out using known crosslinking agents. The crosslinking agent is not particularly limited, but organic peroxides or the phenol resin-based crosslinking agent (D) described later are preferably used. Furthermore, the crosslinking agent can be used alone or in any combination and ratio of two or more types.

[0024] Examples of organic peroxides include aromatic organic peroxides and aliphatic organic peroxides. Specifically, examples include, but are not limited to, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, 1,3-bis(t-butylperoxyisopropyl)benzene, and 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; peroxyesters such as t-butyl peroxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexine-3; and hydroperoxides such as acetyl peroxide, lauroyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is preferred as the organic peroxide.

[0025] In addition to the organic peroxides mentioned above and the phenol resin-based crosslinking agent (D) described later, other crosslinking agents may also be used, such as silicon hydride compounds such as metrohydrogen silicon, peroxide auxiliary agents such as sulfur, p-quinone dioxime, p-dinitrosobenzene, and 1,3-diphenylguanidine; polyfunctional vinyl compounds such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, and diallyl phthalate; polyfunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl(meth)acrylate; compounds having a bismaleimide structure such as N,N'-m-phenylene bismaleimide and N,N'-m-toluene bismaleimide; and trimethylolpropane, trimethylolpropane trimethacrylate, and tin chloride (SnCl2). Among these, divinylbenzene is preferred.

[0026] <<Crystalline olefin polymer (B)>> The thermoplastic elastomer contains a crystalline olefin polymer (B) (hereinafter also simply referred to as "polymer (B)"). Polymer (B) plays a role in improving the fluidity and heat resistance of the dynamically crosslinked thermoplastic elastomer. Crystallinity, in this context, means that the melting point (Tm) can be measured using differential scanning calorimetry (DSC). Specifically, the melting point (Tm) is determined by the differential scanning calorimetry (DSC) measurement method described later.

[0027] Polymer (B) is not particularly limited as long as it is a crystalline polymer obtained from an olefin, but it is preferably a polymer consisting of a crystalline high molecular weight solid product obtained by polymerizing one or more monoolefins by either a high-pressure method or a low-pressure method. Examples of such polymers include isotactic monoolefin polymers and syndiotactic monoolefin polymers.

[0028] Polymer (B) may be obtained by conventionally known methods, or a commercially available product may be used. Polymer (B) may be used alone or in combination of two or more types. Examples of monoolefins that can be used as raw materials for polymer (B) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene. The above olefins may be used individually or as a mixture of two or more.

[0029] From the viewpoint of excellent heat resistance, oil resistance, and moldability, the crystalline olefin polymer (B) is preferably at least one of a propylene homopolymer and a copolymer of propylene and an α-olefin having 2 to 20 carbon atoms (excluding propylene) (propylene copolymer), and more preferably a propylene homopolymer. In the case of a propylene copolymer, the content of structural units derived from propylene is preferably 40 mol% or more, more preferably 50 mol% or more, and the monoolefin that becomes the monomer structural unit derived from the α-olefin having 2 to 20 carbon atoms (excluding propylene) is preferably the above monoolefin other than propylene, more preferably ethylene and butene.

[0030] The polymerization mode of polymer (B) may be random or blocky; any polymerization mode is acceptable as long as a crystalline resinous material is obtained.

[0031] Polymer (B) has a melt flow rate (MFR) (ASTMD1238-65T, 230°C, 2.16 kg load) of typically 0.01 to 100 g / 10 min, preferably 0.05 to 50 g / 10 min.

[0032] Polymer (B) has a melting point (Tm) obtained by differential scanning calorimetry (DSC) that is typically 100°C or higher, preferably 105°C or higher. Differential scanning calorimetry is performed, for example, as follows: A sample of about 5 mg is placed in a dedicated aluminum pan, and using a PerkinElmer DSC-Pyris1 or DSC-7, the temperature is increased from 30°C to 200°C at 320°C / min, held at 200°C for 5 minutes, then cooled from 200°C to 30°C at 10°C / min, held at 30°C for another 5 minutes, and the melting point is determined from the endothermic curve obtained when the temperature is increased at 10°C / min. If multiple peaks are detected during DSC measurement, the peak temperature detected on the highest side is defined as the melting point (Tm).

[0033] The content of polymer (B) is 5 to 80 parts by mass per 100 parts by mass of copolymer (A). From the viewpoint of excellent oil resistance and moldability, the content of polymer (B) is preferably 10 to 70 parts by mass, more preferably 20 to 50 parts by mass, and even more preferably 25 to 45 parts by mass, per 100 parts by mass of copolymer (A).

[0034] <<Softener (C)>> There are no particular restrictions on the softening agent (C), and any softening agent commonly used for rubber can be used. Examples of softeners (C) include petroleum-based softeners such as process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and petrolatum; coal tar-based softeners such as coal tar and coal tar pitch; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, soybean oil, and coconut oil; tall oil; sub(factis); waxes such as beeswax, carnauba wax, and lanolin; fatty acids or fatty acid salts such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, and zinc laurate; naphthenic acid; pine oil, rosin, or derivatives thereof; synthetic polymers such as terpene resins, petroleum resins, atactic polypropylene, and coumarone indene resin; ester-based softeners such as dioctyl phthalate, dioctyl adipate, and dioctyl sebacate; microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, liquid thiocol, and hydrocarbon-based synthetic lubricants. Among these, the softening agent (C) preferably contains a petroleum-based softening agent, more preferably contains a process oil, paraffin oil, or hydrocarbon-based synthetic lubricant, and even more preferably contains a process oil.

[0035] The content of these softeners (C) is 100 to 300 parts by mass per 100 parts by mass of copolymer (A). From the viewpoint of excellent oil resistance and moldability, the content of softener (C) is preferably 120 to 280 parts by mass, more preferably 140 to 250 parts by mass, and even more preferably 150 to 200 parts by mass per 100 parts by mass. When the softening agent (C) is present in the above-mentioned amount, the thermoplastic elastomer composition exhibits excellent fluidity during preparation and molding, improving the dispersibility of, for example, carbon black, and minimizing the deterioration of the mechanical properties of the resulting molded article. Furthermore, the resulting molded article exhibits excellent heat resistance, oil resistance, and moldability. The softening agent (C) may be a single type or a combination of two or more types.

[0036] <<Phenolic resin-based crosslinking agent (D)>> The phenolic resin crosslinking agent (D) (hereinafter also referred to as "crosslinking agent (D)") is a resol resin and is preferably produced by condensation of alkyl-substituted phenol or unsubstituted phenol with an aldehyde in an alkaline medium, preferably with formaldehyde, or by condensation of difunctional phenol dialcohols. For alkyl-substituted phenols, alkyl-substituted compounds with 1 to 10 carbon atoms are preferred. Furthermore, dimethylolphenols or phenolic resins substituted with alkyl groups having 1 to 10 carbon atoms at the p-position are preferred. The phenolic resin curing resin is typically a thermocrosslinkable resin and is also called a phenolic resin crosslinking agent or phenolic resin.

[0037] An example of a crosslinking agent (D) is the following general formula [XV].

[0038] [ka]

[0039] In the formula, Q is a divalent group selected from the group consisting of -CH2- and -CH2-O-CH2-, m is 0 or a positive integer from 1 to 20, and R' is an organic group.

[0040] Preferably, Q is a divalent group -CH2-O-CH2-, m is 0 or a positive integer from 1 to 10, and R' is an organic group having less than 20 carbon atoms. More preferably, m is 0 or a positive integer from 1 to 5, and R' is an organic group having 4 to 12 carbon atoms. Specifically, examples include alkylphenol formaldehyde resins, methylolated alkylphenol resins, halogenated alkylphenol resins, and the like, with halogenated alkylphenol resins being preferred, and even more preferably those in which the terminal hydroxyl groups are brominated. An example of a phenol resin-based cured resin with brominated terminals is shown in the general formula [XVI] below.

[0041] [ka]

[0042] In the formula, n is an integer from 0 to 10, and R is a saturated hydrocarbon group having 1 to 15 carbon atoms.

[0043] Examples of the aforementioned phenolic resin-based curing resins include Tackiroll® 201 (alkylphenol formaldehyde resin, manufactured by Taoka Chemical Industry Co., Ltd.), Tackiroll® 250-I (brominated alkylphenol formaldehyde resin with a bromination rate of 4%, manufactured by Taoka Chemical Industry Co., Ltd.), and Tackiroll® 250-III (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Industry Co., Ltd.). PR-4507 (manufactured by Gun-ei Chemical Industry Co., Ltd.), Vulkaresat 510E (manufactured by Hoechst), Vulkaresat 532E (manufactured by Hoechst), Vulkaresen E (manufactured by Hoechst), Vulkaresen 105E (manufactured by Hoechst), Vulkaresen 130E (manufactured by Hoechst), Vulkaresol 315E (manufactured by Hoechst), Amberol ST137X ( Rohm & Haas, Sumilight Resin (registered trademark) PR-22193 (Sumitomo Durez Co., Ltd.), Symphorm-C-100 (Anchor Chem.), Symphorm-C-1001 (Anchor Chem.), Tamanol (registered trademark) 531 (Arakawa Chemical Co., Ltd.), Schenectady SP1059 (Schenectady Chem.), Schenectady SP10 Examples include 45 (manufactured by SchenectadyChem.), CRR-0803 (manufactured by UCC), SchenectadySP1055F (manufactured by SchenectadyChem., a brominated alkylphenol-formaldehyde resin), SchenectadySP1056 (manufactured by SchenectadyChem.), CRM-0803 (manufactured by Showa Union Synthetic Co., Ltd.), and VulkadurA (manufactured by Bayer). Among these, halogenated phenol resin-based crosslinking agents are preferred, and brominated alkylphenol-formaldehyde resins such as Tackirol® 250-I, Tackirol® 250-III, and SchenectadySP1055F can be used more preferably.

[0044] Furthermore, specific examples of crosslinking thermoplastic vulcanized rubber with phenolic resin are described in U.S. Patents 4,311,628, 2,972,600, and 3,287,440, and these technologies can also be used in the present invention.

[0045] U.S. Patent No. 4,311,628 discloses a phenoliccurative system comprising a phenoliccuring resin and a cureactivator. The basic component of this system is a phenolic resin crosslinking agent produced by condensation of a substituted phenol (e.g., halogen-substituted phenol, C1-C2 alkyl-substituted phenol) or an unsubstituted phenol with an aldehyde, preferably formaldehyde, in an alkaline medium, or by condensation of difunctional phenol dialcohols (preferably dimethylolphenols with the para position substituted with a C5-C10 alkyl group). Halogenated alkyl-substituted phenolic resin crosslinking agents produced by halogenation of alkyl-substituted phenolic resin crosslinking agents are particularly suitable. Phenolic resin crosslinking agents comprising a methylolphenol curable resin, a halogen donor, and a metal compound are particularly recommended, and their details are described in U.S. Patents No. 3,287,440 and No. 3,709,840, respectively.

[0046] Non-halogenated phenolic resin crosslinking agents are used simultaneously with halogen donors, preferably with hydrogen halide acid acceptors. Normally, halogenated phenolic resin crosslinking agents, preferably those containing 2-10% by mass of bromine, do not require halogen donors. However, they are used simultaneously with hydrogen halide acid acceptors such as metal oxides, such as iron oxide, titanium oxide, magnesium oxide, magnesium silicate, silicon dioxide, and zinc oxide, preferably zinc oxide. These hydrogen halide acid acceptors, such as zinc oxide, are typically used in amounts of 0.1-20 parts by mass per 100 parts by mass of the phenolic resin crosslinking agent. The presence of such acid acceptors promotes the crosslinking action of the phenolic resin crosslinking agent. However, in the case of rubber that is not easily vulcanized by the phenolic resin crosslinking agent, it is desirable to use both a halogen donor and zinc oxide. The methods for producing halogenated phenol-based curable resins and their use in vulcanizing agent systems using zinc oxide are described in U.S. Patent Nos. 2,972,600 and 3,093,613, respectively, and these disclosures, along with the disclosures in U.S. Patent Nos. 3,287,440 and 3,709,840, are incorporated into this specification for reference. Examples of suitable halogen donors include, for example, stannous chloride, ferric chloride, or halogen-donating polymers such as chlorinated paraffin, chlorinated polyethylene, chlorosulfonated polyethylene, and polychlorobutadiene (neoprene rubber). The term “vulcanization accelerator” as used herein means any substance that substantially increases the crosslinking efficiency of phenolic resin crosslinking agents, and includes metal oxides and halogen donors, which are used alone or in combination. For further details on phenolic vulcanizing agents, see “Vulcanization and Vulcanizing Agents” (W. Hoffman, Palmerton Publishing Company).

[0047] The phenolic resin crosslinking agent and the brominated phenolic resin crosslinking agent may be commercially available or synthetic. Examples of commercially available products include the trade names "SP-1045," "CRJ-352," "SP-1055F," and "SP-1056" (all manufactured by Schenectady Chemicals, Inc.).

[0048] Crosslinking agent (D) is a suitable vulcanizing agent from the viewpoint of preventing fogging because it generates few decomposition products. Crosslinking agent (D) is used in an amount sufficient to achieve essentially complete vulcanization of the rubber.

[0049] In the present invention, when dynamic crosslinking is performed with the crosslinking agent (D), auxiliary agents such as peroxycrosslinking aids such as sulfur, p-quinone dioxime, p,p'-dibenzoylquinone dioxime, N-methyl-N,4-dinitrosoaniline, nitrosobenzene, diphenylguanidine, and trimethylolpropane-N,N'-m-phenylenedimaleimide, polyfunctional methacrylate monomers such as divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, and polyfunctional vinyl monomers such as vinyl butyrate and vinyl stearate can be incorporated.

[0050] By using the above-mentioned auxiliary agent, a uniform and gentle crosslinking reaction can be expected. Divinylbenzene is preferred as the auxiliary agent. Divinylbenzene is easy to handle, has good compatibility with copolymer (A) and polymer (B), and has the effect of solubilizing the crosslinking agent (D). It also acts as a dispersant for the crosslinking agent (D), resulting in a dynamic crosslinking thermoplastic elastomer composition with a homogeneous crosslinking effect by heat treatment and a good balance of fluidity and physical properties.

[0051] The above-mentioned auxiliary agent is used in an amount of typically 2 parts by mass or less, preferably 0.3 to 1 part by mass, per 100 parts by mass of copolymer (A).

[0052] Furthermore, a dispersion accelerator may be used to promote the decomposition of the crosslinking agent (D). Examples of decomposition accelerators include tertiary amines such as triethylamine, tributylamine, and 2,4,6-tri(dimethylamino)phenol; naphthenates of naphthenic acid with various metals (e.g., Pb, Co, Mn, Ca, Cu, Ni, Fe, Zn, rare earth elements), such as aluminum, cobalt, vanadium, copper, calcium, zirconium, manganese, magnesium, lead, and mercury.

[0053] The crosslinking agent (D) is 1 to 15 parts by mass per 100 parts by mass of the copolymer (A). By setting the content of the crosslinking agent (D) within the above range, a dynamically crosslinked thermoplastic elastomer with excellent moldability can be obtained, and the resulting dynamically crosslinked thermoplastic elastomer has high strength, excellent oil resistance, and sufficient heat resistance and mechanical properties. From the above viewpoint, the content of the crosslinking agent (D) is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 7 parts by mass, per 100 parts by mass of the copolymer (A).

[0054] -Other ingredients- The thermoplastic elastomer composition may contain components other than the copolymer (A), polymer (B), softener (C), and crosslinking agent (D) (hereinafter also referred to as "other components"), to the extent that the effects of the invention are not impaired. Other components include, but are not limited to, acid acceptors (E) and inorganic fillers (F). Additives include rubbers other than copolymers (A) (e.g., propylene-based elastomers such as polyisobutylene, butyl rubber, propylene-ethylene copolymer rubber, propylene-butene copolymer rubber, and propylene-butene-ethylene copolymer rubber, and ethylene-based elastomers such as ethylene-propylene copolymer rubber); resins other than crystalline olefin polymers (B), such as thermosetting resins and thermoplastic resins such as polyolefins; ultraviolet absorbers; antioxidants; heat stabilizers; anti-aging agents; light stabilizers, weather stabilizers; antistatic agents; metal soaps; aliphatic amides; lubricants such as waxes, and other known additives used in the field of polyolefins. Other ingredients may be used individually or in combination of two or more.

[0055] Examples of inorganic fillers (F) include calcium carbonate, calcium silicate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, molybdenum disulfide, graphite, carbon black, glass fiber, glass spheres, shirasu balloons, basic magnesium sulfate whiskers, calcium titanate whiskers, and aluminum borate whiskers.

[0056] These inorganic fillers (F) are typically used in an amount of 1 to 100 parts by mass, preferably 1 to 50 parts by mass, relative to 100 parts by mass of the total amount of copolymer (A) and polymer (B).

[0057] Examples of acid acceptors (E) include the aforementioned iron oxide, titanium oxide, magnesium oxide, magnesium silicate, silicon dioxide, and metal oxides such as zinc oxide. Among these, zinc oxide is preferred as the acid acceptor (E). The content of the acid acceptor (E) is preferably 0.1 to 1.0 parts by mass, more preferably 0.2 to 0.8 parts by mass, and even more preferably 0.3 to 0.7 parts by mass, per 100 parts by mass of the copolymer (A). If the thermoplastic elastomer composition contains an acid acceptor (E), the crosslinking action of the crosslinking agent (D) can be promoted.

[0058] Examples of anti-aging agents include aromatic 2-amine anti-aging agents such as phenylbutylamine and N,N-di-2-naphthyl-p-phenylenediamine; phenolic anti-aging agents such as dibutylhydroxytoluene and tetrakis[methylene(3,5-di-t-butyl-4-hydroxy)hydrocinnamate]methane; thioether anti-aging agents such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide; dithiocarbamate anti-aging agents such as dibutyldithiocarbamate nickel; and sulfur-based anti-aging agents such as 2-mercaptobenzoylimidazole, zinc salt of 2-mercaptobenzoylimidazole, dilaurylthiodipropionate, and distearylthiodipropionate.

[0059] When using rubber other than copolymer (A), the rubber is usually used in an amount of 2 to 200 parts by mass, preferably 5 to 150 parts by mass, per 100 parts by mass of the total of copolymer (A) and polymer (B).

[0060] Furthermore, the amount of additives other than those specifically mentioned in this specification is not particularly limited as long as the effects of the present invention are achieved, but it is preferably 10 parts by mass or less, more preferably 0.0001 or more and less than 10 parts by mass, and even more preferably about 0.01 to 5 parts by mass, based on 100 parts by mass of the total of copolymer (A) and polymer (B).

[0061] Dynamically crosslinked thermoplastic elastomers preferably have a sea-island structure. In a dynamically crosslinked thermoplastic elastomer having a sea-island structure, regions of copolymer (A) component (island) exist within polymer (B) regions (sea), resulting in excellent moldability of the obtained dynamically crosslinked thermoplastic elastomer. From the viewpoint of excellent moldability, the sea-island structure is preferably composed of island regions and sea regions of different sizes. The presence or absence of a sea-island structure in a dynamically crosslinked thermoplastic elastomer can be confirmed by preparing sections of the dynamically crosslinked thermoplastic elastomer with a thickness of 100 μm and observing these sections with a scanning electron microscope (SEM) (magnification: 1,000x to 3,000x).

[0062] <Difference in gel fraction (R)> A dynamically crosslinked thermoplastic elastomer has a gel fraction difference (R) expressed by the following formula that is greater than 1.4 mass% and less than or equal to 5.0 mass%. When the difference in gel fraction (R) of the dynamically crosslinked thermoplastic elastomer is within the above range, regions of copolymer (A) component of different sizes (island regions) exist within the polymer (B) region (sea region) in the dynamically crosslinked thermoplastic elastomer, resulting in excellent moldability of the obtained dynamically crosslinked thermoplastic elastomer. The difference in gel fraction (R) can be determined by the method described in the examples below.

[0063] Difference in gel fraction (R) (mass%) = Gel fraction of 325 mesh (mass%) - Gel fraction of 80 mesh (mass%)

[0064] From the viewpoint of excellent moldability, the difference in gel fraction (R) is preferably 1.5 to 4.5 mass%, more preferably 1.5 to 4.0 mass%, and even more preferably 1.6 to 3.0 mass%.

[0065] Furthermore, in a dynamically crosslinked thermoplastic elastomer, the difference in gel fraction (R) can be adjusted to a desired level by adjusting the composition ratio of the copolymer (A), polymer (B), softener (C), and crosslinking agent (D) in the thermoplastic elastomer composition.

[0066] From the viewpoint of excellent oil resistance and moldability, the dynamic crosslinked thermoplastic elastomer preferably has a Shore A hardness (instantaneous value) of 20 to 90, more preferably 25 to 80, and even more preferably 30 to 70, as measured in accordance with JIS K 6253 (2012). The Shore A hardness (instantaneous value) is determined by the measurement method described in the examples below.

[0067] (Method for manufacturing dynamically crosslinked thermoplastic elastomers) The above-mentioned dynamically crosslinked thermoplastic elastomer is obtained by dynamically crosslinking the above-mentioned thermoplastic elastomer composition. More specifically, the dynamically crosslinked thermoplastic elastomer is obtained by dynamically heat-treating a mixture containing a copolymer (A), a polymer (B), a softener (C), and additives as needed, in the presence of a crosslinking agent (D) to crosslink it (dynamic crosslinking).

[0068] In this invention, "dynamic heat treatment" means kneading the mixture in a molten state in the presence of a crosslinking agent. Furthermore, "dynamic crosslinking" means crosslinking the mixture while applying shear force.

[0069] The method for producing a dynamically crosslinked thermoplastic elastomer according to the present invention (hereinafter also simply referred to as "elastomer production method") preferably includes a step of dynamically heat-treating an uncrosslinked copolymer (A-1) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, the above-mentioned crystalline olefin polymer (B), a thermoplastic elastomer composition containing a crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, and the above-mentioned crystalline olefin polymer (B), a softening agent (C), and a phenolic resin-based crosslinking agent (D) to obtain the above-mentioned elastomer.

[0070] The method for producing the elastomer according to the present invention, by including the above steps, dynamically crosslinks the uncrosslinked copolymer (A-1), polymer (B), and crosslinked copolymer (A-2) with the crosslinking agent (D), resulting in a dynamically crosslinked thermoplastic elastomer with excellent oil resistance and moldability. The reason for this is not clear, but it is presumed to be as follows. In the elastomer manufacturing method including the above steps, an uncrosslinked copolymer (A-1) and a crosslinked copolymer (A-2) are used. Since the crosslinked copolymer (A-2) is a copolymer that has been dynamically crosslinked again after being crosslinked beforehand, it exists in the polymer (B) (sea portion) as a larger region (island portion) compared to the region (island portion) of the uncrosslinked copolymer (A-1). Since the uncrosslinked copolymer (A-1) is dynamically crosslinked in an uncrosslinked state, it exists in the polymer (B) (sea portion) as a smaller region (island portion) compared to the region (island portion) of the crosslinked copolymer (A-2). Furthermore, when the amount of uncrosslinked copolymer (A-1) is greater than the amount of polymer (B) (sea portion), the uncrosslinked copolymer (A-1) does not disperse in the polymer (B) (sea portion), and the polymer (B) (sea portion) tends to take on a co-continuous structure. However, since the crosslinked copolymer (A-2) is already crosslinked, it is presumed to be more likely to exist in the polymer (B) (sea portion) as an island portion. In other words, in the elastomer obtained by the elastomer manufacturing method according to the present invention, regions of different sizes (island regions) exist in the polymer (B) (sea region), so it is presumed that it has excellent fluidity and therefore excellent moldability.

[0071] The polymer (B), softener (C), and phenol resin-based crosslinking agent (D) used in the above process are synonymous with the polymer (B), softener (C), and phenol resin-based crosslinking agent (D) in the above thermoplastic elastomer composition, and the preferred embodiments are also the same. The uncrosslinked copolymer (A-1) used in the above process is synonymous with the polymer in the thermoplastic elastomer composition when polymer (A) is not crosslinked, and the preferred embodiment is the same as the preferred embodiment of the uncrosslinked polymer. The crosslinked copolymer (A-2) used in the above process is synonymous with the polymer in the case where polymer (A) in the thermoplastic elastomer composition is crosslinked, and the preferred embodiment is the same as the preferred embodiment of the crosslinked polymer.

[0072] In a dynamically crosslinked thermoplastic elastomer, the uncrosslinked copolymer (A-1), the crosslinked copolymer (A-2), and the polymer (B) may be partially dynamically crosslinked or fully dynamically crosslinked.

[0073] Dynamic heat treatment is preferably carried out in a closed-type apparatus, or preferably in an inert gas atmosphere such as nitrogen or carbon dioxide. The heat treatment temperature is usually in the range of the melting point of polymer (B) ~300°C, preferably 150~280°C, more preferably 170~270°C. The kneading time is usually 1~20 minutes, preferably 1~10 minutes. The shear force applied is usually 10~100,000 sec at the maximum shear rate. -1 Preferably 100 to 50,000 seconds -1 , more comfortably 1,000~10,000 sec -1 More preferably 2,000 to 7,000 seconds -1 It is within the range.

[0074] There are no particular restrictions on the kneading equipment used when performing dynamic heat treatment, and any known kneading equipment can be used. Examples of kneading equipment include mixing rolls, intensive mixers (e.g., Banbury mixers, kneaders, etc.), single-screw extruders, and twin-screw extruders. In addition, closed-type kneading equipment is preferred.

[0075] The method for producing the elastomer may further include steps other than the step of obtaining the elastomer. Examples of other steps include the step of preparing a crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, and the step of preparing a composition containing the crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, and the polymer (B).

[0076] The dynamically crosslinked thermoplastic elastomer according to the present invention has hardness and mechanical properties (tensile strength, elongation, etc.) that are equal to or better than those of conventional crosslinked thermoplastic elastomers, and can therefore be used in a variety of applications. Furthermore, the dynamically crosslinked thermoplastic elastomer according to the present invention has superior oil resistance compared to conventional thermoplastic elastomers, and can therefore be suitably used in areas where it is difficult to use conventional thermoplastic elastomers, such as automotive parts like hoses, pipes, and boots (blow-molded products) that come into contact with grease or lubricating oil and require superior oil resistance.

[0077] The dynamically crosslinked thermoplastic elastomer according to the present invention has excellent moldability and can be molded by various molding methods. Examples of such molding methods include extrusion molding, injection molding, compression molding, calendering, vacuum forming, press molding, stamping, and blow molding. Examples of blow molding include breath blow molding, direct blow molding, and injection blow molding.

[0078] (Molded body) The molded article according to the present invention preferably contains the dynamically crosslinked thermoplastic elastomer according to the present invention. The molded article may contain components other than the above-mentioned dynamically crosslinked thermoplastic elastomer, but it is more preferable that the molded article is formed from the dynamically crosslinked thermoplastic elastomer. Components other than the above-mentioned dynamically crosslinked thermoplastic elastomer include thermoplastic elastomers other than the above-mentioned dynamically crosslinked thermoplastic elastomer. Examples of such thermoplastic elastomers include known thermoplastic elastomers, which can be appropriately selected depending on the purpose. The molded article can be obtained, for example, by molding the above-mentioned thermoplastic elastomer composition or the above-mentioned dynamic crosslinked thermoplastic elastomer using conventional plastic molding methods such as extrusion molding, injection molding, or compression molding. Furthermore, the waste and burrs generated by such molding methods can be recovered and reused. The molded body is preferably used for oil-resistant applications.

[0079] Examples of molded products include automotive parts such as bumper parts, body panels, side shields, glass run channels, instrument panel surfaces, door surfaces, roof surfaces, weatherstrips, hoses, steering wheels, boots, wire harness covers, and seat adjuster covers; electrical components such as wire insulation, connectors, and cap plugs; footwear such as shoe soles and sandals; leisure goods such as swimming fins, goggles, golf club grips, and baseball bat grips; gaskets, waterproof fabrics, belts, and garden hoses; and various gaskets and sheets for civil engineering and construction. As a molded product, it is particularly suitable for applications requiring oil resistance, and automotive parts such as automotive hoses, automotive boots, and automotive gaskets are particularly preferred applications.

[0080] As mentioned above, automotive parts are preferred as molded articles, and more specific examples of automotive parts include mechanical components, interior components, exterior components, and other components. Mechanical components include CVJ boots, suspension boots, rack and pinion boots, steering rod covers, AT cushions, AT slide covers, leaf spring bushings, ball joint retainers, timing belts, V-belts, engine compartment hoses, air ducts, airbag covers, and propeller shaft cover materials.

[0081] Interior components include various surface materials (instrument panel, door trim, ceiling, rear pillar), console box, armrest, airbag case lid, shift knob, assist grip, side step mat, reclining cover, trunk seat, seat belt buckle, lever slide plate, door latch striker, seat belt components, switches, and more.

[0082] Exterior components include various molding materials (inner / outer window moldings, roof moldings, belt moldings, side trim moldings), door seals, body seals, glass run channels, mudguards, kicking plates, step mats, license plate housings, silencing gears, control cable covers, and emblems.

[0083] Other components include air duct gaskets, air duct hoses, air duct covers, air intake pipes, air dam skirts, timing belt cover seals, opening seals / trunk seal components, bonnet cushions, fuel tank bands, and cables.

[0084] The molded body may be general merchandise, daily necessities, or components thereof. Examples of general merchandise, daily necessities, or components thereof include grips (e.g., grips for ballpoint pens, mechanical pencils, toothbrushes, cups, disposable razors, handrails, cutters, power tools, screwdrivers, power cables, doors, etc.), assist grips, shift knobs, toys, notebook covers, gaskets (e.g., gaskets for dishes and Tupperware, etc.), various types of rubber feet, sports equipment (e.g., ski soles, ski boots, skis, ski bindings, ski soles, golf balls, goggle components, snowboard components, snowboard shoes, snowboard bindings, surfboard components, bodyboards, banana boats, kiteboards, snorkeling components, water ski components, parasailing components, wakeboard components, and other sports equipment), belts (e.g., watch straps, fashion belts, etc.), hairbrushes, bathtub panel button sheets, caps, shoe insoles, health equipment components, etc. [Examples]

[0085] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In the following description, "parts" refers to mass unless otherwise specified.

[0086] <Raw materials> <<Uncrosslinked copolymer (A-1)>> As an uncrosslinked copolymer (A-1) of ethylene, an α-olefin with 3 to 20 carbon atoms, and a non-conjugated polyene, an oil-expanded ethylene-propylene-non-conjugated polyene copolymer was used. Ethylene content = 63% by mass, Propylene content = 32.5% by mass, Non-conjugated polyene species: 5-ethylidene-2-norbornene, Non-conjugated diene content = 4.5% by mass, Non-conjugated diene content (iodine value) = 13, Intrinsic viscosity [η] = 3.4 (dl / g), Oil spread per 100 parts by mass of rubber component = 40 (PHR:) For the oil spreading of the uncrosslinked copolymer (A-1), the following softening agent (C) was used.

[0087] <<Thermoplastic elastomer composition (X): Olefin resin-based thermoplastic elastomer composition>> Content of crosslinked copolymer (A-2) of ethylene and α-olefin with 3 to 20 carbon atoms and non-conjugated polyene: 33% by mass, content of crystalline olefin polymer (B): 17% by mass, content of softener (C): 50% by mass Shore A hardness (measured by the measurement method described in the examples): 70, MFR (230℃, 10kg load): 50g / 10min The composition ratio of the crosslinked copolymer (A-2) is as follows: ethylene content = 63% by mass, propylene content = 32.5% by mass, non-conjugated polyene species: 5-ethylidene-2-norbornene, non-conjugated diene content = 4.5% by mass.

[0088] <<Crystalline olefin polymer (B)>> • Propylene polymer (B-1): Propylene homopolymer, MFR (230°C, 2.16 kg load) = 0.5 g / 10 min), melting point measured by DSC: 165°C)

[0089] <<Softener (C)>> • Softener (C-1): Paraffin-based process oil (Product name: Diana Process Oil (registered trademark) PW-100, manufactured by Idemitsu Kosan Co., Ltd.)

[0090] <<Phenolic resin-based crosslinking agent (D)>> • Crosslinking agent (D-1): Brominated alkylphenol formaldehyde resin (product name: SP-1055F, manufactured by Schenectady)

[0091] <<Other additives>> • Acid acceptor: Zinc oxide (two types of zinc oxide, manufactured by Hakusui Tech Co., Ltd.)

[0092] (Measurement method) The composition and physical properties of each component used in the examples and comparative examples were measured by the following methods. <Mass fraction of structural units> The mass fraction (mass%) of each structural unit in the crosslinked copolymer (A-2) contained in the above copolymer (A) or thermoplastic elastomer composition (X) is: 13 The results were obtained by measurement using 1C-NMR. Specifically, using an ECX400P nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd.), under the conditions of measurement temperature: 120°C, measurement solvent: orthodichlorobenzene / deuterated benzene = 4 / 1 (volume ratio), and number of cumulative cycles: 8000, the crosslinked copolymer (A-2) contained in the copolymer (A) or thermoplastic elastomer composition (X) was determined. 13 It was calculated from the 1C-NMR spectrum.

[0093] <Melt Flow Rate (MFR)> The MFR of crystalline olefin polymer (B) was measured in accordance with ASTM D-1238 under conditions of 230°C and a 2.16 kg load.

[0094] <Intrinsic viscosity> The intrinsic viscosity [η] (dl / g) of the uncrosslinked copolymer (A-1) was measured using a fully automatic intrinsic viscometer manufactured by Rigosha Co., Ltd., at a temperature of 135°C and using decalin as the measurement solvent.

[0095] <Melting point> The melting point of the polymer (B) described above was measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121 (2012). Specifically, pellets of crystalline olefin polymer (B) were heated at 230°C for 10 minutes, then cooled to 30°C at a rate of 10°C / min and held for 1 minute, and then heated again at a rate of 10°C / min. In the DSC curve obtained during this process, the temperature at which the amount of absorbed heat was maximum was defined as the melting point.

[0096] [Example 1] Copolymer (A) was prepared such that the mass ratio of uncrosslinked copolymer (A-1) to crosslinked copolymer (A-2) was 80:20. Then, polymer (B), softener (C), crosslinking agent (D), and other additives such as acid acceptors were added in the amounts shown in Table 1 to form the raw materials. Next, the entire amount of the above raw materials was dynamically crosslinked while being kneaded using an extruder (model number KTX-30, manufactured by Kobe Steel, Ltd., cylinder temperature: C1=50℃, C2=90℃, C3=100℃, C4=120℃, C5=180℃, C6=200℃, C7~C14=200℃, die temperature: 200℃, screw rotation speed: 500 rpm, extrusion rate: 40 kg / h) to obtain pellets of dynamically crosslinked thermoplastic elastomer.

[0097] [Examples 2-4 and Comparative Example 4] Except for preparing copolymer (A) such that the mass ratio of uncrosslinked copolymer (A-1) to crosslinked copolymer (A-2) was 75:25, the raw materials were prepared in the same manner as in Example 1, according to the formulations in Table 1, to obtain pellets of dynamically crosslinked thermoplastic elastomer.

[0098] [Comparative Examples 1-3] Except for preparing copolymer (A) such that the mass ratio of uncrosslinked copolymer (A-1) to crosslinked copolymer (A-2) was 100:0, the raw materials were prepared in the same manner as in Example 1, according to the formulations in Table 1, to obtain pellets of dynamically crosslinked thermoplastic elastomer.

[0099] <Moldability: Dynamically crosslinked thermoplastic elastomer (MFR)> The melt flow rate (MFR) of the dynamically crosslinked thermoplastic elastomers obtained in the examples and comparative examples was measured at 230°C and under a 10 kg load, in accordance with JIS K 7210. The results are shown in Table 1. A higher MFR value indicates superior fluidity and moldability.

[0100] <<Preparation of press sheets and test specimens>> Using the dynamic cross-linked thermoplastic elastomer pellets obtained in the examples or comparative examples, they were press-molded at 230°C for 6 minutes using a 100t electric automatic press (manufactured by Shoji Co., Ltd.), and then cooled and pressed at room temperature for 5 minutes to obtain a 2 mm thick flat press sheet. Subsequently, a No. 3 dumbbell piece was punched out from the resulting press sheet to create a 2mm thick test specimen.

[0101] <Shore A hardness> In accordance with JIS K 6253 (2012), three 2mm thick press sheets prepared using the method described above were stacked and used as a sample, and the Shore A hardness (instantaneous value) was determined using a durometer. The results are shown in Table 1.

[0102] <Tensile properties> Tensile tests (tensile speed: 500 mm / min, measurement temperature: 23°C) were performed on the dumbbell-shaped No. 3 test specimens prepared using the method described above, in accordance with JIS K 6251 (2017), and the stress (MPa) (M100), tensile breaking strength (MPa) (TB), and tensile breaking elongation (%) (EB) at 100% elongation were measured. The results are shown in Table 1.

[0103] <Compression set (CS)> In accordance with JIS K 6250, six 2mm thick press sheets were stacked to form a 12mm thick laminated sheet. The resulting laminated sheet was compressed 25% in the length direction at 70°C for 22 hours in accordance with JIS K 6262. After removal from the compression device, the length of the molded body was measured 30 minutes later, and the compression set was calculated. The results are shown in Table 1.

[0104] <Oil resistance: Oil resistance test (volume change rate when immersed in test oil)> Press sheets (2 mm thick) were cut into 10 cm squares and immersed in IRM903 oil at 125°C for 72 hours according to JIS K6258 (2016). The oil resistance was then measured by the volume change rate (ΔV) (volume %). The results are shown in Table 1. A smaller volume change rate indicates superior oil resistance.

[0105] <Calculation of the difference in gel fraction (R)> First, the gel fractions of 325 mesh and 80 mesh were determined using the dynamic cross-linked thermoplastic elastomer pellets obtained above.

[0106] <<Measurement of gel fraction>> Approximately 100 mg of a pellet of dynamically crosslinked thermoplastic elastomer was weighed out as a sample, wrapped in a 325-mesh or 80-mesh screen, and immersed in 30 mL of p-xylene (a sufficient amount for the pellet) in a sealed container at 140°C for 24 hours. Next, the sample was removed onto filter paper and dried at 80°C for at least 2 hours until a constant weight was achieved. The gel fractions (R) for 325 mesh and 80 mesh were determined using the following formula. Gel fraction [mass %] = [dry weight of sample after p-xylene immersion / weight of sample before p-xylene immersion] × 100

[0107] Using the gel fraction values ​​for 325 mesh and 80 mesh obtained from the above measurements, the difference in gel fraction (R) of the dynamically crosslinked thermoplastic elastomer was calculated using the following formula. Difference in gel fraction (R) (mass%) = Gel fraction of 325 mesh (mass%) - Gel fraction of 80 mesh (mass%)

[0108] Sections of the dynamically crosslinked thermoplastic elastomer pellets obtained from the above-mentioned examples and comparative examples were prepared to a thickness of 100 μm, and these sections were observed using a scanning electron microscope (SEM) (magnification: 1,000x or 3,000x). Comparing the sea-island structure of the dynamically crosslinked thermoplastic elastomer of the comparative example shown in Figure 1 with the sea-island structure of the dynamically crosslinked thermoplastic elastomer of the example shown in Figure 2, larger island structures were observed in the sea-island structure of the dynamically crosslinked thermoplastic elastomer of the example. From the above observation results, it can be seen that the size distribution of the island structures is wider in the dynamically crosslinked thermoplastic elastomer of the example.

[0109] [Table 1]

[0110] In Table 1, "parts" refers to parts by mass, and the parts of polymer (B), softener (C), crosslinking agent (D), and other additives are given in relation to 100 parts by mass of copolymer (A). In Table 1, the mass of copolymer A represents the total amount of the uncrosslinked copolymer (A-1), which is the rubber component excluding the oil spreadable portion, and the crosslinked copolymer (A-2) in the heat-crosslinkable elastomer composition (X).

[0111] The dynamically crosslinked thermoplastic elastomers and molded articles thereof of Examples 1 to 4 according to the present invention are found to have superior oil resistance and moldability compared to the dynamically crosslinked thermoplastic elastomers and molded articles thereof of Comparative Examples 1 to 4.

Claims

1. 100 parts by mass of a copolymer (A) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene. Crystalline olefin polymer (B) 20 to 50 parts by mass, Softener (C) 140 to 250 parts by mass, It contains 2 to 8 parts by mass of a phenolic resin-based crosslinking agent (D), The copolymer (A) is a dynamically crosslinked thermoplastic elastomer obtained by dynamically crosslinking a thermoplastic elastomer composition comprising a crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, and an uncrosslinked copolymer (A-1) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene, wherein the difference (R) of gel fractions represented by the following formula is 1.5 to 4.5% by mass. Difference in gel fraction (R) (mass%) = Gel fraction of 325 mesh (mass%) - Gel fraction of 80 mesh (mass%)

2. The dynamically crosslinked thermoplastic elastomer according to claim 1, wherein at least a portion of the copolymer (A) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene is crosslinked.

3. The dynamically crosslinked thermoplastic elastomer according to claim 1 or 2, wherein the crystalline olefin polymer (B) is at least one of a homopolymer of propylene and a copolymer of propylene and an α-olefin having 2 to 20 carbon atoms (excluding propylene).

4. A dynamically crosslinked thermoplastic elastomer according to any one of claims 1 to 3, wherein the Shore A hardness (instantaneous value) measured in accordance with JIS K 6253 (2012) is 20 to 90.

5. A dynamically crosslinked thermoplastic elastomer according to any one of claims 1 to 4, having a sea-island structure.

6. A method for producing a dynamically crosslinked thermoplastic elastomer according to any one of claims 1 to 5, A method for producing a dynamically crosslinked thermoplastic elastomer, comprising the steps of dynamically heat-treating a thermoplastic elastomer comprising: an uncrosslinked copolymer (A-1) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene; a crystalline olefin polymer (B); a crosslinked copolymer (A-2) of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene; a thermoplastic elastomer composition containing the crystalline olefin polymer (B); a softener (C); and a phenol resin-based crosslinking agent (D) to obtain the elastomer.

7. A molded article comprising a dynamically crosslinked thermoplastic elastomer according to any one of claims 1 to 5.

8. A molded article according to claim 7, used for oil-resistant applications.

9. The molded body according to claim 7, which is an automobile hose.

10. The molded body according to claim 7, which is an automobile boot.

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