Thermoplastic elastomer composition, crosslinked product thereof, and molded component

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic elastomer composition excellent in gas barrier properties, compression set resistance, and mechanical properties and also excellent in hardness and shrinkage resistance. SOLUTION: A thermoplastic elastomer composition according to the present invention contains at least (a) an isobutylene-isoprene copolymer rubber, (b) a polypropylene polymer, and (c) an ethylene-α-olefin copolymer and is substantially free of plasticizers and softeners.

Description

Thermoplastic elastomer composition, crosslinked product thereof, and molded part

[0001] The present invention relates to a thermoplastic elastomer composition, and more particularly to a thermoplastic elastomer composition that has excellent gas barrier properties and can give a molded part free from bleed-out of softeners, plasticizers, etc., and a molded part made thereof.

[0002] Rubber compositions used to manufacture medical rubber stoppers are primarily composed of various synthetic rubbers. Among these, butyl rubber has been put to practical use as a suitable material for rubber stoppers due to its high gas barrier properties against oxygen, water vapor, and other gases.

[0003] Generally, these butyl rubbers are used after crosslinking, and in order to adjust the hardness of the crosslinked rubber, oils such as mineral oil or vegetable oil are used as softeners, and plasticizers such as phthalates are added to impart flexibility (Patent Documents 1 to 3). However, when butyl rubbers whose physical properties are adjusted by blending softeners or plasticizers are used under high temperature conditions, these added components volatilize, causing problems such as changes in the physical properties of the rubber and bleeding out.

[0004] In response to the above-mentioned problems, Patent Document 4 proposes a thermoplastic elastomer composition that has an excellent balance of gas barrier properties, mechanical properties, and rubber elasticity (compression set) and is less likely to bleed out. The thermoplastic elastomer composition contains an isobutylene-isoprene copolymer rubber, an α-olefin-based crystalline thermoplastic resin, and an α-olefin-based amorphous thermoplastic resin, and is substantially free of any of a phthalate ester-based plasticizer, a fatty acid ester-based plasticizer, a trimellitate ester-based plasticizer, a petroleum-based softener, a vegetable oil-based softener, and polybutene oil.

[0005] JP 2017-155235 A JP 2000-119479 A JP 2015-205944 A JP 2008-056824 A

[0006] However, although the thermoplastic elastomer composition proposed in Patent Document 4 is excellent in gas barrier properties, mechanical properties, and rubber elasticity, it does not contain a softener or plasticizer, and therefore has the problem that it is difficult to obtain a molded product with excellent hardness (flexibility). Furthermore, because the thermoplastic elastomer composition contains a large amount of wax or hot-melt adhesive component, when used as a material for medical stoppers, there is the inconvenience that high-pressure steam sterilization cannot be applied, i.e., the heat resistance is insufficient.

[0007] Therefore, an object of the present invention is to provide a thermoplastic elastomer composition that is excellent in gas barrier properties, compression set resistance, and mechanical properties, as well as in hardness (flexibility) and heat resistance.

[0008] As a result of extensive research in light of the above circumstances, the present inventors have found that the above object can be achieved by forming a thermoplastic elastomer composition containing a specific component.

[0009] That is, various aspects of the present invention are as follows. [1] A thermoplastic elastomer composition comprising at least (a) an isobutylene-isoprene copolymer rubber, (b) a polypropylene-based polymer, and (c) an ethylene-α-olefin copolymer, and substantially free of plasticizers and softeners. [2] The thermoplastic elastomer composition according to [1], wherein the (c) ethylene-α-olefin copolymer has a softening temperature of 70°C or higher as measured in accordance with JIS K7196. [3] The thermoplastic elastomer composition according to [1], wherein the component (a) is contained in an amount of 60 to 80% by mass relative to the total amount of the components (a), (b), and (c). [4] The thermoplastic elastomer composition according to [1], wherein the component (b) is contained in an amount of 5 to 20% by mass relative to the total amount of the components (a), (b), and (c). [5] The thermoplastic elastomer composition according to [1], wherein the amount of component (a) is 1.5 to 5.5 times, by mass, the total amount of components (b) and (c). [6] The thermoplastic elastomer composition according to [1], further comprising (d) a crosslinking agent. [7] The thermoplastic elastomer composition according to [1], wherein the (c) ethylene-α-olefin copolymer comprises an ethylene-1-octene copolymer. [8] The thermoplastic elastomer composition according to [1], further comprising 1 to 50 parts by mass of one or more components (e) selected from the group consisting of petroleum resins, terpene resins, and rosins, based on 100 parts by mass of the total of components (a), (b), and (c). [9] A crosslinked product of the thermoplastic elastomer composition according to any one of [1] to [8].

[10] A molded article comprising the crosslinked product according to [9].

[0010] According to the present invention, by using an isobutylene-isoprene copolymer rubber in combination with a polypropylene-based polymer and an ethylene-α-olefin copolymer, it is possible to realize a thermoplastic elastomer composition that is excellent in gas barrier properties, compression set resistance, and mechanical properties, as well as in hardness (flexibility) and heat resistance, without containing a softener or plasticizer.

[0011] Figure 1 shows the temperature-loss tangent curves measured at frequencies of 1 Hz and 10 Hz for the thermoplastic elastomer composition of Example 14. Figure 2 shows the temperature-loss tangent curves measured at frequencies of 1 Hz and 10 Hz for the thermoplastic elastomer composition of Example 15.

[0012] <Definitions> In the present invention, numerical ranges expressed using "to" include both end values. In the present invention, the term "plasticizer" refers to known plasticizers used in the art, such as phthalate ester-based plasticizers, epoxy-based plasticizers, chlorinated plasticizers, phosphate-based plasticizers, adipic acid-based plasticizers, sebacic acid-based plasticizers, azelaic acid-based plasticizers, citric acid-based plasticizers, polyester-based plasticizers, fatty acid ester-based plasticizers, and trimellitic acid ester-based plasticizers. Furthermore, the term "softener" refers to known softeners used in the art, such as petroleum-based softeners (paraffin oil, paraffin wax, naphthenic oil, aromatic oil), hydrocarbons such as polybutadiene and polybutene; epoxidized oils such as epoxidized soybean oil and epoxidized linseed oil; esters such as carboxylic acid esters, phosphate esters, and sulfonic acid esters; and higher alcohols such as oleyl alcohol and stearyl alcohol.

[0013] The thermoplastic elastomer composition according to the present invention is a thermoplastic elastomer composition comprising at least (a) an isobutylene-isoprene copolymer rubber, (b) a polypropylene polymer, and (c) an ethylene-α-olefin copolymer, and further comprising, as necessary, (f) an antioxidant, and is characterized by being substantially free of plasticizers and softeners. The components constituting the present invention are described in detail below.

[0014] <Component (a): Isobutylene-Isoprene Copolymer Rubber> The isobutylene-isoprene copolymer rubber, which is one component of the thermoplastic elastomer composition of the present invention, is a rubbery amorphous copolymer with a low degree of unsaturation that contains structural units derived from isobutylene and structural units derived from isoprene. This isobutylene-isoprene copolymer rubber can be obtained, for example, by polymerizing isobutylene and a small amount of isoprene in methyl chloride using anhydrous aluminum chloride as a catalyst.

[0015] Other than in the examples, or where otherwise specified, all numerical values ​​used in the specification and claims should be understood to be modified by the term "about." Without attempting to limit the application of the doctrine of equivalents to the claims, each numerical value should be construed in light of the number of significant digits and by applying ordinary rounding techniques.

[0016] The proportion of isoprene-derived structural units contained in the (a) isobutylene-isoprene copolymer rubber is preferably 0.5 to 15 mol%, and more preferably 0.8 to 5.0 mol%, when the total amount of structural units is 100 mol%. If the proportion of isoprene-derived structural units is less than 0.5 mol%, the crosslinking reaction tends to be delayed, and the mechanical properties may be insufficient. On the other hand, if the proportion of isoprene-derived structural units exceeds 15 mol%, the crosslink density of the thermoplastic elastomer composition tends to increase excessively, and the mechanical properties tend to decrease.

[0017] The isobutylene-isoprene copolymer rubber may be, for example, a copolymer of isobutylene, isoprene, and an aromatic divinyl compound (for example, divinylbenzene) as disclosed in U.S. Pat. No. 3,584,080, or a modified isobutylene-isoprene copolymer rubber having a conjugated diene unsaturated bond by reacting it with an unsaturated compound having a functional group such as a carboxyl group, an acid anhydride group, a hydrosilyl group, an amino group, or an epoxy group as disclosed in JP-A-48-90385, JP-A-53-42289, JP-A-59-84901, JP-A-3-131643, and JP-A-2004-091766. Also usable are halides of isobutylene-isoprene copolymers, such as chlorinated products (C-IIR), brominated products (B-IIR), and brominated isobutylene-paramethylstyrene copolymers (BIMS).

[0018] As the component (a), one of these compounds or a mixture of two or more of them can be used.

[0019] The content of (a) isobutylene-isoprene copolymer rubber is preferably 50 to 90 mass%, more preferably 55 to 85 mass%, even more preferably 60 to 85 mass%, particularly preferably 60 to 80 mass%, and most preferably 70 to 80 mass%, based on the total amount of (a) isobutylene-isoprene copolymer rubber, (b) polypropylene polymer, and (c) ethylene-α-olefin copolymer. When the content of component (a) is within this range, a molded article having excellent mechanical properties (tensile strength, tensile elongation, etc.) and low surface hardness (i.e., excellent flexibility) can be obtained.

[0020] The amount of (a) isobutylene-isoprene copolymer rubber is preferably 1.0 to 10.0 times, more preferably 1.2 to 7.0 times, even more preferably 1.5 to 5.5 times, and particularly preferably 2.0 to 5.0 times the total amount of (b) polypropylene polymer and (c) ethylene-α-olefin copolymer. By setting the amount of component (a) relative to components (b) and (c) within the above ranges, it is possible to obtain a molded article having lower surface hardness (i.e., excellent flexibility) while maintaining mechanical properties.

[0021] <Component (b): Polypropylene-Based Polymer> The polypropylene-based polymer, which is one component constituting the thermoplastic elastomer composition of the present invention, is a polymer mainly containing structural units derived from propylene. Component (b) contributes to heat resistance and moldability. Here, "mainly containing structural units derived from propylene" means that the content of structural units derived from propylene is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and typically 75 to 100% by mass.

[0022] Examples of the component (b) include propylene homopolymers, random copolymers of propylene with small amounts of other α-olefin comonomers, and block copolymers of propylene with α-olefin comonomers.

[0023] Examples of the α-olefin comonomer include ethylene, 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl Examples of the α-olefin comonomer include 1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. The α-olefin comonomer may be one of these or a mixture of two or more of these.

[0024] Specific examples of the random copolymer of propylene with a small amount of other α-olefin comonomer include a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, a propylene-1-octene random copolymer, a propylene-ethylene-1-butene random copolymer, a propylene-ethylene-1-hexene random copolymer, and a propylene-ethylene-1-octene random copolymer.

[0025] The block copolymer of propylene and an α-olefin comonomer is a copolymer composed of a crystalline polypropylene component and a copolymer rubber component of propylene and an α-olefin comonomer. The crystalline polypropylene component is composed of a propylene homopolymer or a random copolymer of propylene and a small amount of another α-olefin comonomer.

[0026] From the viewpoint of heat resistance, the component (b) is preferably a propylene homopolymer or a block copolymer of propylene and an α-olefin comonomer in which the crystalline polypropylene component is a propylene homopolymer, and more preferably a propylene homopolymer.

[0027] Commercially available examples of the component (b) include propylene homopolymer "VS200A (trade name)" manufactured by SunAllomer Co., Ltd. and propylene homopolymer "PM900A (trade name)" manufactured by SunAllomer Co., Ltd.

[0028] As the component (b), one of these compounds or a mixture of two or more of them can be used.

[0029] From the viewpoint of moldability, the component (b) preferably has a melt mass flow rate (MFR) measured in accordance with JIS K 7210-1999 under conditions of 230°C and 21.18N of 0.1 to 100 g / 10 min, more preferably 10 to 50 g / 10 min.

[0030] From the viewpoint of heat resistance, the melting point of the component (b) is preferably 150°C or higher, more preferably 160°C or higher. The melting point here refers to the peak-top melting point of the peak appearing on the highest temperature side in a second melting curve (a melting curve measured during the final heating process) measured using a Diamond DSC differential scanning calorimeter manufactured by PerkinElmer Japan Co., Ltd., according to a program that involves holding at 230°C for 5 minutes, cooling to -10°C at 10°C / min, holding at -10°C for 5 minutes, and heating to 230°C at 10°C / min. There is no particular upper limit to the peak-top melting point, but for polypropylene-based polymers, the highest is 167°C.

[0031] The content of the (b) polypropylene polymer is preferably 1 to 30 mass%, more preferably 3 to 25 mass%, even more preferably 5 to 20 mass%, and particularly preferably 10 to 15 mass%, based on the total amount of the (a) isobutylene-isoprene copolymer rubber, the (b) polypropylene polymer, and the (c) ethylene-α-olefin copolymer. When the content of component (b) is within this range, a molded article having a smaller compression set can be obtained while maintaining the mechanical properties.

[0032] <Component (c): Ethylene / α-olefin copolymer> The ethylene / α-olefin copolymer, which is one component constituting the thermoplastic elastomer composition of the present invention, is a copolymer (including random copolymers and block copolymers) of ethylene and an α-olefin. Examples of the α-olefin include propylene, 1-butene, 1-hexene, and 1-octene. One or more of these can be used as the α-olefin.

[0033] (c) Examples of the ethylene-α-olefin copolymer include an ethylene-propylene copolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, and an ethylene-1-octene copolymer.

[0034] A preferred structure of the (c) ethylene / α-olefin copolymer is one having a multi-block structure in which the hard segments have crystalline blocks mainly composed of ethylene and containing an α-olefin, and the soft segments have amorphous or low-crystalline blocks mainly composed of ethylene and an α-olefin having a higher α-olefin content than the hard segments, and two or more, preferably three or more, of these blocks are alternately connected.

[0035] In one preferred embodiment, the (c) ethylene / α-olefin copolymer may contain an ethylene / 1-octene copolymer. In this case, the optimal structure of the ethylene / 1-octene copolymer is a multi-block structure in which the hard segments have crystalline blocks containing ethylene as the main component and 1-octene, and the soft segments have amorphous or low-crystalline blocks containing ethylene and 1-octene as the main component, and the soft segments have a higher 1-octene content than the hard segments, and two or more, preferably three or more, of these blocks are alternately connected.

[0036] In component (c), the ethylene content varies depending on the type and compositional distribution of the comonomer, but is preferably 55 to 99 mol%, more preferably 60 to 95 mol%, and even more preferably 65 to 90 mol%. When component (c) is an ethylene-1-octene copolymer having a multiblock structure, the ethylene content is preferably 25 to 97 mass%, more preferably 40 to 96 mass%, even more preferably 55 to 95 mass%, and particularly preferably 55 to 80 mass%.

[0037] The melt index (ASTM D1238, measurement temperature: 190°C, load: 2.16 kg) of component (c) is preferably 0.01 to 100 g / 10 min, more preferably 0.1 to 100 g / 10 min, even more preferably 0.2 to 60 g / 10 min, particularly preferably 0.3 to 30 g / 10 min, and most preferably 0.3 to 10 g / 10 min.

[0038] The density of the component (c), measured in accordance with JIS K 6760, is preferably 0.860 to 0.930 g / cm ３ and more preferably 0.865 to 0.890 g / cm ３ is.

[0039] Furthermore, the hardness of component (c) measured in accordance with JIS K 6253 (Shore A hardness, 15 seconds) is preferably 50 to 98, and more preferably 60 to 90.

[0040] In the present invention, the ethylene / α-olefin copolymer preferably has a softening temperature of 70°C or higher, more preferably 75°C or higher, as measured in accordance with JIS K7196. The use of an ethylene / α-olefin copolymer having a softening temperature of 70°C or higher can enhance heat resistance. The softening temperature of the ethylene / α-olefin copolymer can be adjusted by the ethylene content. Furthermore, in the case of an ethylene / α-olefin copolymer having a multi-block structure, the softening temperature can also be adjusted by the ratio of hard segments to soft segments. As such an ethylene / α-olefin copolymer, an ethylene / 1-octene copolymer, commercially available products such as INFUSE (trade name) D9010 and D9507 may be used.

[0041] From the viewpoint of compression set, it is preferable that the melting point of component (c) measured by DSC is 110 to 125°C, more preferably 115 to 123°C. Here, the melting point measured by DSC is the peak-top melting point obtained by a differential scanning calorimeter (DSC). Specifically, the melting point is measured by using a DSC, taking a 10 mg sample, holding it at 190°C for 5 minutes, crystallizing it to -10°C at a temperature decrease rate of 10°C / min, holding it at -10°C for 5 minutes, and then measuring it at a temperature increase rate of 10°C / min up to 200°C. When two or more melting peaks are observed, the peak-top temperature of the melting peak with the greatest peak-top height is taken as the melting point.

[0042] As the component (c), one of these compounds or a mixture of two or more of them can be used.

[0043] The content of component (c) ethylene-α-olefin copolymer is preferably 1 to 30 mass%, more preferably 3 to 25 mass%, even more preferably 4 to 22 mass%, particularly preferably 5 to 20 mass%, and most preferably 10 to 15 mass%, relative to the total amount of (a) isobutylene-isoprene copolymer rubber, (b) polypropylene polymer, and (c) ethylene-α-olefin copolymer. When the content of component (c) is within this range, a molded article with smaller compression set and higher heat resistance can be obtained while maintaining mechanical properties.

[0044] <Component (d): Crosslinking Agent> In addition to the above-described components (a), (b), and (c), the thermoplastic elastomer composition of the present invention may optionally contain a crosslinking agent for crosslinking component (a). Examples of crosslinking agents include organic peroxides, phenolic resin crosslinking agents, hydrosilylation crosslinking agents, sulfur, sulfur compounds, p-quinone, p-quinone dioxime derivatives, bismaleimide compounds, epoxy compounds, silane compounds, amino resins, polyol crosslinking agents, polyamines, triazine compounds, and metal soaps. Among these, sulfur-based compounds, organic peroxide crosslinking agents, and phenolic crosslinking agents including phenolic resins can be used. When using sulfur-based compounds, various vulcanization accelerators may be used in combination. When using organic peroxide crosslinking agents, various crosslinking aids may be used in combination. Examples of crosslinking methods include heat-treating a polymer composition containing a crosslinkable component such as a rubber component and a crosslinking agent, and dynamically crosslinking a mixture containing a crosslinkable component such as a rubber component and a crystalline resinous polyolefin resin in the presence of the above-described crosslinking agent.

[0045] Examples of organic peroxides include dicumyl peroxide, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylcumyl peroxide, di-t-amyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, α,α'-bis(t-butylperoxy) peroxyesters such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxymaleic acid, t-butyl peroxyneodecanoate, t-butyl peroxybenzoate, and di-t-butyl peroxyphthalate; and ketone peroxides such as dicyclohexanone peroxide. These can be used alone or in combination of two or more.

[0046] Examples of phenol-based crosslinking agents include p-substituted phenol-based compounds represented by the following formula, o-substituted phenol-aldehyde condensates, m-substituted phenol-aldehyde condensates, and brominated alkylphenol-aldehyde condensates, with p-substituted phenol-based compounds being particularly preferred. These may be used alone or in combination of two or more. (wherein n is an integer of 0 to 10, X is at least one of a hydroxyl group, a halogenated alkyl group and a halogen atom, and R is a saturated hydrocarbon group having 1 to 15 carbon atoms).

[0047] When a phenol-based crosslinking agent is used as the component (d) crosslinking agent, the blending amount thereof is preferably 0.5 to 25 parts by mass, more preferably 1 to 20 parts by mass, still more preferably 2 to 15 parts by mass, and particularly preferably 3 to 10 parts by mass, per 100 parts by mass of the (a) isobutylene-isoprene copolymer rubber, from the viewpoint of reliably obtaining the effect of use and from the viewpoint of moldability.

[0048] When a phenol-based crosslinking agent is used, a crosslinking accelerator may be used in combination. Examples of crosslinking accelerators that can be used in combination with the phenol-based crosslinking agent include metal halides such as stannous chloride and ferric chloride; and organic halides such as chlorinated polypropylene, brominated polypropylene, brominated butyl rubber, and chloroprene rubber. Furthermore, in addition to the above crosslinking accelerators, metal oxides such as zinc oxide and dispersants such as stearic acid may be used in combination. Metal oxides such as zinc oxide also function as halogen catchers. These may be used alone or in combination of two or more.

[0049] In the case where a phenol-based crosslinking agent is used as the component (d) crosslinking agent and the above-mentioned crosslinking accelerator is used in combination, the blending amount thereof is preferably 0.1 to 6 parts by mass, more preferably 0.3 to 4 parts by mass, and further preferably 0.5 to 2 parts by mass, per 100 parts by mass of the isobutylene-isoprene copolymer rubber (a), from the viewpoint of reliably obtaining the effect of use and from the viewpoint of moldability.

[0050] The sulfur or sulfur compound may be powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc. Examples of sulfur-based compounds include sulfur chloride, sulfur dichloride, polymeric polysulfides, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dimethyldithiocarbamate, etc. These may be used alone or in combination of two or more.

[0051] When sulfur or a sulfur compound is used as the crosslinking agent, it is preferable to use a crosslinking (vulcanization) accelerator in combination. Examples of the crosslinking accelerator include sulfenamide compounds such as N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-oxydiethylene-2-benzothiazole sulfenamide, and N,N-diisopropyl-2-benzothiazole sulfenamide; thiazole compounds such as 2-mercaptobenzothiazole (MBT), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, and dibenzothiazyl disulfide; guanidine compounds such as diphenylguanidine, triphenylguanidine, diorthonitrile guanidine, orthonitrile biguanide, and diphenylguanidine phthalate; and aldehyde amine or aldehyde-ammonia compounds such as acetaldehyde-aniline reaction product, butyraldehyde-aniline condensation product, hexamethylenetetramine, and acetaldehyde ammonia. imidazoline compounds such as 2-mercaptoimidazoline; thiourea compounds such as thiocarbanilide, diethylthiourea, dibutylthiourea, trimethylthiourea, and diorthotolylthiourea; tetramethylthiuram monosulfide, tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetrabutylthiuram disulfide, pentamethylenethiuram tetrasulfide, and dipentamethylenethiuram tetrasulfide dithioacid salt compounds such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate, and tellurium dimethyldithiocarbamate; xanthate compounds such as zinc dibutylxanthogenate; zinc oxide. These may be used alone or in combination of two or more.

[0052] <(e) Petroleum Resin, etc.> The thermoplastic elastomer composition of the present invention may further contain, as desired, one or more components selected from the group consisting of (e) petroleum resins, terpene resins, and rosins (hereinafter sometimes abbreviated as "(e) petroleum resin, etc."), to the extent that the object of the present invention is not adversely affected. By including (e) petroleum resin, etc., the vibration damping properties of the thermoplastic elastomer composition of the present invention can be improved.

[0053] The petroleum resin is an unsaturated hydrocarbon compound produced by decomposition of naphtha or the like, and is a polymer (including derivatives such as hydrogenated products of the polymer) of an unsaturated hydrocarbon compound having a large carbon number (usually about 4 to 20 carbon atoms).

[0054] The unsaturated hydrocarbon compound used as a monomer for the petroleum resin is typically an aliphatic unsaturated hydrocarbon compound and / or an aromatic unsaturated hydrocarbon compound.

[0055] Examples of the aliphatic unsaturated hydrocarbon compound include 1-butene, 2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 3-hexene, 1-heptene, 2-heptene, 3-heptene, 1,3-pentadiene, cyclopentadiene (cyclopenta-1,3-diene), methylcyclopentadiene, ethylcyclopentadiene, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), and dicyclopentadiene (tricyclo[5.2.1.02,6]deca-3,8-diene). One or more of these compounds can be used as the aliphatic unsaturated hydrocarbon compound.

[0056] Examples of the aromatic unsaturated hydrocarbon compound include styrene, α-methylstyrene, β-methylstyrene, 4-methylstyrene, vinylxylene, indene, methylindene, ethylindene, etc. One or more of these can be used as the aromatic unsaturated hydrocarbon compound.

[0057] Examples of the terpene resin include a polymer of terpene (a hydrocarbon having isoprene as a constituent unit), a copolymer of terpene with a monomer copolymerizable with terpene, such as a copolymer of terpene with phenol, or a copolymer of terpene with styrene. One or more of these can be used as the terpene resin.

[0058] Examples of the rosins include rosins such as gum rosin, wood rosin, and tall oil rosin, as well as rosin derivatives such as hydrogenated rosin and rosin ester (ester of rosin and polyhydric alcohol). One or more of these can be used as the rosins.

[0059] From the viewpoint of miscibility with the above components (a) to (c), the (e) petroleum resin etc. is preferably hydrogenated. The hydrogenation rate of the (e) petroleum resin etc. (the ratio of the number of bonds that have become carbon-carbon single bonds by hydrogenation to the number of carbon-carbon double bonds in the (e) petroleum resin etc. before hydrogenation) may be preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 to 100 mol %.

[0060] The hydrogenation can be carried out by a known method, for example, by treating the compound with a hydrogenation catalyst in an inert solvent.

[0061] From the viewpoint of heat resistance, the softening point of the (e) petroleum resin etc. may be preferably 90°C or higher, more preferably 100°C or higher, even more preferably 110°C or higher, still more preferably 120°C or higher, and most preferably 130°C or higher. On the other hand, from the viewpoint of moldability, the softening point of the (e) petroleum resin etc. may be preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower. The softening point here is measured in accordance with JIS K2207-1996, Section 6.4 Softening Point Test Method (Ring and Ball Method).

[0062] The amount of (e) petroleum resin, etc., blended is not particularly limited because it is an optional component. When vibration damping properties are important, a large amount of (e) petroleum resin, etc. may be blended. For example, the blending amount of (e) petroleum resin, etc., relative to the above components (a) to (c), may be preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of reliably obtaining the effect of enhancing vibration damping properties. On the other hand, the blending amount of (e) petroleum resin, etc., may be preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, from the viewpoint of gas barrier properties, heat resistance, and flexibility.

[0063] <Other Optional Components> The thermoplastic elastomer composition of the present invention may further contain, as desired, inorganic fillers, antioxidants, antioxidants, hydrolysis inhibitors, light stabilizers, various weather resistance agents such as ultraviolet absorbers, lubricants, nucleating agents, antistatic agents, and various organic and inorganic flame retardants, to the extent that the addition does not detract from the object of the present invention. Note that these additives are preferably highly compatible with the thermoplastic elastomer composition of the present invention in order to prevent problems such as bleed-out and blooming on the surface of the molded article.

[0064] In one embodiment, the thermoplastic elastomer composition of the present invention may be free of any one or more of the other optional components described above. Here, "free of" means that they are not intentionally blended.

[0065] (Method for Producing Thermoplastic Elastomer Composition) The thermoplastic elastomer composition of the present invention can be obtained by adding the above-mentioned components (a) to (c), and optionally the optional component (d) and other optional components simultaneously or in any order, and melt-kneading them using any kneader.

[0066] The melt-kneading is preferably carried out for 1 minute or more at a temperature of 180° C. or higher, and more preferably for 1 minute or more at a temperature of 190° C. or higher. The melt-kneading temperature may be usually 240° C. or lower, preferably 220° C. or lower, from the viewpoints of mechanical properties, manufacturability of the composition, and moldability.

[0067] Examples of melt kneaders include batch kneaders such as pressure kneaders and mixers; extrusion kneaders such as single-screw extruders, co-rotating twin-screw extruders, and counter-rotating twin-screw extruders; and calendar roll kneaders. These may be used in any combination. The resulting composition can be pelletized by any method and then molded into an article by any method.

[0068] The pelletization can be carried out by a method such as hot cutting, strand cutting, or underwater cutting.

[0069]

[0033] The molded article of the present invention is composed of the thermoplastic elastomer composition described above. The thermoplastic elastomer composition of the present invention is excellent in gas barrier properties, compression set resistance, and mechanical properties, as well as in hardness (flexibility) and heat resistance, and is therefore suitable for use as a material for rubber stoppers, particularly rubber stoppers for medical use.

[0070] Furthermore, since the thermoplastic elastomer composition of the present invention also has excellent vibration damping properties, it can be suitably used as a vibration-damping member or soundproofing member for automobiles, as well as a vibration-damping member or soundproofing member for home electric appliances such as audio equipment, refrigerators, vacuum cleaners, and air conditioners.

[0071] The molded article of the present invention can be obtained by molding the thermoplastic elastomer composition of the present invention into a desired shape by any molding method, such as blow molding, extrusion molding, injection molding, press molding, compression molding, or a combination of two or more of these.

[0072] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0073] <Raw materials used> (a) Isobutylene-isoprene copolymer rubber: (a-1) "Butyl 268 (trade name)" manufactured by Japan Butyl Co., Ltd.

[0074] (b) Polypropylene-based polymers: (b-1) Polypropylene homopolymer "PM900A (trade name)" manufactured by SunAllomer Corporation. Melt mass-flow rate: 30 (g / 10 min). (b-2) Polypropylene random copolymer "MG03E (trade name)" manufactured by Japan Polypropylene Corporation. Melt mass-flow rate: 30 (g / 10 min). (b-3) Polypropylene block copolymer "BC03B (trade name)" manufactured by Japan Polypropylene Corporation. Melt mass-flow rate: 30 (g / 10 min).

[0075] (c) Ethylene / α-olefin copolymers (c-1) Dow Chemical Co., Ltd.'s ethylene / 1-octene copolymer "INFUSE D9077 (trade name)". Melt mass flow rate: 0.5 (g / 10 min), hardness (Shore hardness A) 51, softening temperature 108°C. (c-2) Dow Chemical Co., Ltd.'s ethylene / 1-octene copolymer "INFUSE D9010 (trade name)". Melt mass flow rate: 0.5 (g / 10 min), hardness (Shore hardness A) 64, softening temperature 121°C. (c-3) Dow Chemical Co., Ltd.'s ethylene / 1-octene copolymer "INFUSE D9507 (trade name)". Melt mass flow rate: 5 (g / 10 min), hardness (Shore hardness A) 69, softening temperature 77°C. (c-4) Dow Chemical Co., Ltd.'s ethylene / 1-octene copolymer "INFUSE D9107 (trade name)". Melt mass-flow rate: 1 (g / 10 min), hardness (Shore hardness A) 60, softening temperature 66°C. (c-5) Mitsui Chemicals, Inc.'s ethylene / 1-butene copolymer "TAFMER DF610 (trade name)". Melt mass-flow rate: 1.2 (g / 10 min), hardness (Shore hardness A) 57, softening temperature <40°C.

[0076] (d) Crosslinking agent (d-1) Alkylphenol formaldehyde resin crosslinking agent "LQA7706N (product name)" manufactured by Taoka Chemical Co., Ltd. Tackirol 40% masterbatch product

[0077] (e) Petroleum resins, etc. (e-1) Idemitsu Kosan Co., Ltd.'s petroleum resin "Imarv P-140 (trade name)", which is a hydrogenated copolymer of dicyclopentadiene and an aromatic unsaturated hydrocarbon compound. Softening point: 140°C.

[0078] (Other components) Catalyst: tin chloride Halogen catcher: zinc oxide (two types) Plasticizer / softener: paraffin oil "PW-100 (trade name)" manufactured by Idemitsu Kosan Co., Ltd.

[0079] <Measurement Method> (1) Surface Hardness Using the composition obtained below, an injection molding machine with a clamping pressure of 120 tons was used to produce an injection sheet measuring 13 cm long x 13 cm wide and 2 mm thick at a molding temperature of 220°C. The obtained injection sheet was used to produce a press sheet with a thickness of 6 mm. Using the obtained press sheet as a sample, the durometer hardness (Type A) was measured 15 seconds later in accordance with ASTM D2240. (Evaluation Criteria) A surface hardness in the range of 30 to 80 was considered acceptable. The lower the value, the better the mechanical properties.

[0080] (2) Tensile test: In accordance with JIS K 6251-2010, a No. 3 dumbbell punched from the 2 mm thick injection sheet obtained above was used as a test piece, and measurements were taken at a tensile speed of 500 mm / min. (Evaluation criteria) A tensile strength of 6 MPa or more was considered acceptable. The higher the value, the better the mechanical properties. A tensile elongation of 400% or more was considered acceptable. The higher the value, the better the mechanical properties.

[0081] (4) Compression set: According to JIS K 6262-2003, the compression set was measured at 120°C for 22 hours after compressing by 25%. (Evaluation criteria) A compression set of less than 40% was considered acceptable. The smaller the value, the better the physical properties.

[0082] (5) Gas barrier properties (moisture permeability): Using the composition obtained below, an injection molding machine with a clamping pressure of 120 tons was used to produce an injection sheet having a length of 13 cm, a width of 13 cm and a thickness of 2 mm, which was punched out at a molding temperature of 220°C. The water vapor permeability was measured in accordance with JIS Z 0208 (cup method) under an environment of a temperature of 50°C and a relative humidity of 90%. (Evaluation criteria) Moisture permeability was 2.0 g / m ２ A lower value indicates higher moisture permeability and better gas barrier properties.

[0083] (6) Shrinkage: Using the same sample as used in the evaluation of surface hardness in (1), the shrinkage in the MD direction after leaving it for 24 hours in an environment at a temperature of 23°C and a relative humidity of 50% was calculated using the following formula: Shrinkage (%) = (MD length before leaving - MD length after leaving) / MD length before leaving × 100 (Evaluation criteria) A shrinkage of less than 10% was considered acceptable. The lower the value, the better the physical properties.

[0084] (7) Loss Tangent tanδ (Indicator of Vibration Damping Properties) Using a dynamic viscoelasticity measuring device, a sample measuring 25 mm in length and 10 mm in width was taken from a 1 mm-thick press sheet prepared using the thermoplastic elastomer composition. The sample was set so that the chuck distance was 5 mm. The sample was maintained in tensile mode at a frequency of 1 Hz at a temperature of -80°C for 1 minute, and then heated to 80°C at a heating rate of 4°C / min to obtain a temperature-loss tangent curve. Next, the peak-top temperature of the loss tangent and its value were calculated from the obtained temperature-loss tangent curve. Measurements were also performed in the same manner for a frequency of 10 Hz. Note that dynamic viscoelasticity measurements were performed only on the thermoplastic elastomer compositions of Examples 3, 14, and 15.

[0085] Examples 1 to 15 and Comparative Examples 1 and 2 The components in the amounts (parts by mass) shown in Table 1 were melt-kneaded using an apparatus manufactured by The Japan Steel Works, Ltd., equipped with a twin-screw extruder with a diameter of 28 mm and an L / D ratio of 42 and a water-cooled strand-cutting granulator, at a screw rotation speed of 600 rpm and an extruder outlet temperature of 200°C, to obtain pellets of the composition. Tests (1) to (7) described above were carried out. The results are shown in Table 1.

[0086] The temperature-loss tangent curves measured at frequencies of 1 Hz and 10 Hz for the thermoplastic elastomer composition of Example 14 are shown in Figure 1. The temperature-loss tangent curves measured at frequencies of 1 Hz and 10 Hz for the thermoplastic elastomer composition of Example 15 are shown in Figure 2.

[0087]

[0088] As is clear from the evaluation results in Table 1, by combining an isobutylene-isoprene copolymer rubber with a polypropylene-based polymer and an ethylene-α-olefin copolymer, molded articles having excellent gas barrier properties, compression set resistance, and mechanical properties, as well as excellent hardness (flexibility), can be obtained without the need for softeners or plasticizers (Examples 1 to 15). Furthermore, since the compression set measured at a temperature of 120°C is excellent, it is judged that the heat resistance is also good (applicable to high-pressure steam sterilization). Furthermore, as is clear from the temperature-loss tangent curves in Figures 1 and 2, the thermoplastic elastomer compositions of the present invention are also considered to have excellent vibration damping properties. On the other hand, a thermoplastic elastomer composition (Comparative Example 1) in which a polypropylene-based polymer is blended with an isobutylene-isoprene copolymer rubber but no ethylene-α-olefin copolymer is blended exhibits good mechanical properties, gas barrier properties, and shrinkage resistance, but exhibits high hardness and insufficient compression set resistance. Furthermore, it is clear that the thermoplastic elastomer composition (Comparative Example 2) containing a plasticizer / softener in addition to an isobutylene-isoprene copolymer rubber, a polypropylene-based polymer, and an ethylene-α-olefin copolymer has insufficient gas barrier properties.

Claims

1. A thermoplastic elastomer composition comprising at least (a) an isobutylene-isoprene copolymer rubber, (b) a polypropylene-based polymer, and (c) an ethylene-α-olefin copolymer, and substantially free of plasticizers and softeners.

2. The thermoplastic elastomer composition according to claim 1, wherein the ethylene / α-olefin copolymer (c) has a softening temperature of 70° C. or higher as measured in accordance with JIS K7196.

3. The thermoplastic elastomer composition according to claim 1, wherein the component (a) is contained in an amount of 60 to 80 mass % based on the total amount of the components (a), (b) and (c).

4. The thermoplastic elastomer composition according to claim 1, wherein the (b) component is contained in an amount of 5 to 20 mass % based on the total amount of the (a), (b) and (c).

5. The thermoplastic elastomer composition according to claim 1, wherein the amount of component (a) is 1.5 to 5.5 times the total amount of components (b) and (c) by mass.

6. The thermoplastic elastomer composition of claim 1, further comprising (d) a crosslinking agent.

7. The thermoplastic elastomer composition according to claim 1, wherein the (c) ethylene / α-olefin copolymer comprises an ethylene / 1-octene copolymer.

8. The thermoplastic elastomer composition according to claim 1, further comprising 1 to 50 parts by mass of one or more types of component (e) selected from the group consisting of petroleum resins, terpene resins, and rosins, based on 100 parts by mass of the total of components (a), (b), and (c).

9. A crosslinked product of the thermoplastic elastomer composition according to any one of claims 1 to 8.

10. A molded article comprising the crosslinked product of claim 9.

Images