JP2008031315A - Thermoplastic resin elastomer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition excellent in gas barrier property, hygienic property, compression set, vibration-damping property, and fluidity in molding, and to provide a medicinal tap, a beverage cap liner and a damping material, using the composition. <P>SOLUTION: The composition comprises a thermoplastic elastomer (E) and 5-100 pts.wt. polypropylene-based resin (F), wherein 100 pts.wt. isobutylene-based polymer (A) having alkenyl at its terminal end is melt-kneaded with 10-300 pts.wt. polypropylene-based resin (B) and/or isobutylene-based block copolymer (C) comprising a polymer block (a) composed mainly of an aromatic vinyl-based compound and an isobutylene-based polymer block (b) and is dynamically crosslinked by a hydrosilyl-containing compound (D) to obtain the thermoplastic elastomer (E), and the polypropylene-based resin (F) has ≥40 g/10min melt flow rate of 230°C and 2.16 kg load. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composition excellent in gas barrier properties, hygiene properties, compression set properties, vibration damping properties, and fluidity, and a medical drug stopper, a beverage cap liner, and a vibration damping material using the composition.

  Conventionally, as a polymer material having elasticity, a material obtained by blending a rubber such as natural rubber or synthetic rubber with a crosslinking agent or a reinforcing agent and crosslinking under high temperature and high pressure has been widely used. However, such rubbers require a process of crosslinking and molding for a long time under high temperature and pressure, and are inferior in processability. Further, since the crosslinked rubber does not exhibit thermoplasticity, it cannot be recycled and molded like a thermoplastic resin. Therefore, in recent years, it has been possible to easily produce molded products using general-purpose melt molding technologies such as hot press molding, injection molding, and extrusion molding, as well as general thermoplastic resins, and recycling molding is possible. Various thermoplastic elastomers have been developed. As such thermoplastic elastomers, there are various types of polymers such as olefins, urethanes, esters, styrenes, vinyl chlorides, etc., which are also commercially available.

  Of these, olefin-based thermoplastic elastomers are excellent in heat resistance, cold resistance, weather resistance, and the like. Olefin-based thermoplastic elastomers include a crosslinked type and a non-crosslinked type. Non-crosslinked thermoplastic elastomers are not accompanied by a crosslinking reaction, so there is little variation in quality and the manufacturing cost is low. On the other hand, the cross-linked thermoplastic elastomer is excellent in terms of tensile strength, elongation at break, rubber properties (for example, permanent elongation, compression set) and heat resistance (see Non-Patent Document 1, Patent Documents 1-9, etc.). .

  However, non-crosslinked thermoplastic elastomers are not necessarily sufficient in tensile strength, elongation at break, rubbery properties (permanent elongation, compression set, etc.), heat resistance, and low temperature characteristics. In addition, the cross-linked thermoplastic elastomer improves the compression set by increasing the degree of cross-linking, thereby lowering the molding fluidity, flexibility, heat resistance, lowering the breaking strength and breaking elongation in the tensile test, or composition. Crosslinking to the surface, bleeding of softener, etc. occur. As described above, it is difficult to obtain a thermoplastic composition having an excellent balance of physical properties, and as with conventional thermoplastic resins, it can be easily molded by hot pressing, injection molding, etc. Development of an excellent thermoplastic elastomer composition is desired.

Japanese Patent Publication No.53-21021 Japanese Patent Publication No.55-18448 Japanese Patent Publication No.56-15741 Japanese Patent Publication No. 56-15742 Japanese Examined Patent Publication No. 58-46138 Japanese Patent Publication No.58-56575 Japanese Patent Publication No.59-30376 Japanese Patent Publication No.62-938 Japanese Examined Patent Publication No. 62-59139 Rubber Chemistry and Technology, A.R. Y. Coran et al., 53 (1980), 141 pages

  In view of the above-mentioned problems of the prior art, the object of the present invention is not only excellent in molding fluidity, flexibility, rubber characteristics and vibration damping properties, but also particularly good compression set characteristics, hygiene, gas barrier It is an object of the present invention to provide a thermoplastic elastomer composition exhibiting properties.

  As a result of intensive studies, the present inventors have completed the present invention.

  That is, the present invention relates to 100 parts by weight of an isobutylene polymer (A) having an alkenyl group at the terminal, a polymer block (a) mainly composed of a polypropylene resin (B) and / or an aromatic vinyl compound, and an isobutylene system. A thermoplastic elastomer (E) dynamically crosslinked with a hydrosilyl group-containing compound (D) while melt-kneading with 10 to 300 parts by weight of an isobutylene block copolymer (C) comprising a polymer block (b), and 230 ° C. 2. A thermoplastic elastomer composition comprising 5 to 100 parts by weight of a polypropylene resin (F) having a melt flow rate under a load of 16 kg of 40 g / 10 min or more.

  The present invention also relates to a thermoplastic elastomer composition characterized in that the polypropylene resin (B) has a melt flow rate of 40 g / 10 min or less at 230 ° C. and a load of 2.16 kg.

  As a preferred embodiment, the present invention relates to a thermoplastic elastomer composition characterized in that the softening agent (G) is contained in an amount of 1 to 500 parts by weight based on the isobutylene polymer (A).

The present invention also relates to a thermoplastic elastomer composition having an oxygen permeability coefficient (JIS K7126A method) of 15 × 10 ⁻¹⁶ mol · m / m ² · s · Pa or less.

  The present invention also relates to a medical drug stopper, a beverage cap liner, and a vibration damping material comprising the thermoplastic elastomer.

  The composition according to the present invention can be easily molded by a general technique such as hot pressing and injection molding, as in the case of conventional thermoplastic resins. The composition according to the present invention is not only excellent in fluidity, flexibility, rubber characteristics and vibration damping properties, but also exhibits particularly good compression set characteristics, hygiene and gas barrier properties. For this reason, it can be suitably used for various applications such as sealing materials such as medical drug stoppers and cap liners for beverages, vibration damping materials, vibration proof materials, automobile interior materials, cushion materials, and the like.

  The thermoplastic elastomer composition of the present invention comprises 100 parts by weight of an isobutylene polymer (A) having an alkenyl group at the terminal, a polymer block mainly composed of a polypropylene resin (B) and / or an aromatic vinyl compound ( Thermoplastic elastomer (E) dynamically crosslinked with hydrosilyl group-containing compound (D) while melt kneaded with 10 to 300 parts by weight of isobutylene block copolymer (C) comprising a) and isobutylene polymer block (b) And 5 to 100 parts by weight of a polypropylene resin (F) having a melt flow rate of 40 g / 10 min or more at a load of 230 ° C. and 2.16 kg.

  The isobutylene polymer (A) of the present invention is a polymer having isobutylene as a main component and having an alkenyl group at the terminal. From the viewpoint of gas barrier properties, the isobutylene polymer (A) preferably contains 50% by weight or more of isobutylene, more preferably 70% by weight or more, and still more preferably 90% by weight or more. The monomer other than isobutylene of the isobutylene polymer (A) is not particularly limited as long as it is a monomer component that can be cationically polymerized, but aromatic vinyls, aliphatic olefins, isoprene, butadiene, divinylbenzene, and the like. Examples thereof include monomers such as dienes, vinyl ethers, and β-pinene. These may be used alone or in combination of two or more.

  The number average molecular weight of the isobutylene polymer (A) is not particularly limited, but is preferably 1,000 to 500,000, particularly preferably 5,000 to 200,000. When the number average molecular weight is less than 1,000, mechanical properties and the like are not sufficiently exhibited, and when it exceeds 500,000, the moldability and the like are greatly deteriorated.

  The alkenyl group of the isobutylene polymer (A) is not particularly limited as long as it is a group containing a carbon-carbon double bond that is active for the crosslinking reaction of the component (A). Specific examples include aliphatic unsaturated hydrocarbon groups such as vinyl group, allyl group, methyl vinyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, cyclopropenyl group, cyclobutenyl group, cyclopentenyl group, cyclohexenyl group. And cyclic unsaturated hydrocarbon groups such as

  As a method for introducing an alkenyl group into the terminal of the isobutylene polymer of the present invention (a method for producing the polymer (A)), it is disclosed in JP-A-3-152164 and JP-A-7-304909. Examples thereof include a method of introducing a unsaturated group into a polymer by reacting a polymer having a functional group such as a hydroxyl group with a compound having an unsaturated group. In order to introduce an unsaturated group into a polymer having a halogen atom, a method of performing a Friedel-Crafts reaction with an alkenylphenyl ether, a method of performing a substitution reaction with allyltrimethylsilane in the presence of a Lewis acid, and the like. Examples include a method in which a Friedel-Crafts reaction with phenols is performed to introduce a hydroxyl group, and then the alkenyl group introduction reaction is further performed. Further, as disclosed in U.S. Pat. No. 4,316,973, JP-A 63-105005, and JP-A 4-288309, it is also possible to introduce an unsaturated group during polymerization of the monomer. Among these, those in which an allyl group is introduced at the terminal by a substitution reaction of allyltrimethylsilane and chlorine are preferable from the viewpoint of certainty.

  The amount of the alkenyl group at the end of the isobutylene polymer (A) can be arbitrarily selected depending on the required properties. From the viewpoint of the properties after crosslinking, at least 0.2 alkenyl groups per molecule are terminated. It is preferable that the polymer has If the number is less than 0.2, the effect of improving by crosslinking may not be sufficiently obtained.

  The hydrosilyl group-containing compound (D) is used for crosslinking the isobutylene polymer (A) having an alkenyl group introduced at the terminal. Although there is no restriction | limiting in particular in the hydrosilyl group containing compound which can be used, Hydrosilyl group containing polysiloxane is preferable and various things can be used. Of these, a hydrosilyl group-containing polysiloxane having 3 or more hydrosilyl groups and 3 or more and 500 or less siloxane units is preferred, and a polysiloxane having 3 or more hydrosilyl groups and 10 or more and 200 or less siloxane units. Is more preferable, and polysiloxane having 3 or more hydrosilyl groups and 20 to 100 siloxane units is particularly preferable. When the number of hydrosilyl groups is less than 3, sufficient growth of the network due to crosslinking tends not to be achieved and optimal rubber elasticity tends not to be obtained. When the number of siloxane units exceeds 500, the viscosity of the polysiloxane increases and the component (A ) The dispersibility into the inside tends to decrease, and the progress of the crosslinking reaction tends to be insufficient. The polysiloxane unit mentioned here refers to the following general formulas (I), (II), and (III).

[Si (R ¹ ) ₂ O] (I)
[Si (H) (R ² ) O] (II)
[Si (R ² ) (R ³ ) O] (III)
As the hydrosilyl group-containing polysiloxane, a linear polysiloxane represented by the general formula (IV) or (V);
_{^{R 1 3 SiO- [Si (R}} 1) 2 O] a - [Si (H) (R 2) O] b - [Si (R 2) (R 3) O] c -SiR 1 3 (IV)
_{^{HR 1 2 SiO- [Si (R}} 1) 2 O] a - [Si (H) (R 2) O] b - [Si (R 2) (R 3) O] c -SiR 1 2 H (V)
(In the formula, R ¹ and R ² represent an alkyl group having 1 to 6 carbon atoms or a phenyl group, R ³ represents an alkyl group having 1 to 10 carbon atoms or an aralkyl group. B represents 3 ≦ b, a, b. , C represents an integer satisfying 3 ≦ a + b + c ≦ 500.)
A cyclic siloxane represented by the general formula (VI);

（式中、Ｒ⁴およびＲ⁵は炭素数１〜６のアルキル基、または、フェニル基、Ｒ⁶は炭素数１〜１０のアルキル基またはアラルキル基を示す。ｅは３≦ｅ、ｄ，ｅ，ｆはｄ＋ｅ＋ｆ≦５００を満たす整数を表す。）等の化合物を用いることができる。

(In the formula, R ⁴ and R ⁵ represent an alkyl group having 1 to 6 carbon atoms or a phenyl group, R ⁶ represents an alkyl group having 1 to 10 carbon atoms or an aralkyl group. E represents 3 ≦ e, d, e , F represents an integer satisfying d + e + f ≦ 500.) And the like can be used.

  The isobutylene-based polymer (A) having an alkenyl group at the terminal and the hydrosilyl group-containing compound (D) can be mixed at an arbitrary ratio, but in terms of reactivity, the molar ratio of the alkenyl group to the hydrosilyl group (alkenyl group) / Hydrosilyl group) is preferably in the range of 5 to 0.2, more preferably 2.5 to 0.4. When the molar ratio is 5 or more, the crosslinking is insufficient and sticky, and the compression set tends to deteriorate. When the molar ratio is less than 0.2, a large amount of active hydrosilyl groups remain after crosslinking. Hydrogen gas is generated by hydrolysis and tends to cause cracks and voids.

  The cross-linking reaction between the isobutylene polymer (A) and the hydrosilyl group-containing compound (D) proceeds by mixing and heating the two components, but a hydrosilylation catalyst is added to advance the reaction more quickly. be able to. Such hydrosilylation catalyst is not particularly limited, and examples thereof include radical initiators such as organic peroxides and azo compounds, and transition metal catalysts.

  The radical initiator is not particularly limited, and examples thereof include di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di ( t-butylperoxy) -3-hexyne, dicumyl peroxide, t-butylcumyl peroxide, dialkyl peroxides such as α, α′-bis (t-butylperoxy) isopropylbenzene, benzoyl peroxide, p-chlorobenzoyl peroxide, of m-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, acyl peroxides such as lauroyl peroxide, peracid esters such as t-butyl perbenzoate, diisopropyl percarbonate, di-2-ethylhexyl percarbonate Peroxydicarbonate such as 1,1- Peroxyketals such as di (t-butylperoxy) cyclohexane, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,2′-azobisisobutyronitrile, 2,2 '-Azobis-2-methylbutyronitrile, 1,1'-azobis-1-cyclohexanecarbonitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azoisobutyrovalero Examples include azo compounds such as nitriles.

Also, it is not particularly limited as a transition metal catalyst, for example, platinum simple substance, alumina, silica, carbon black or the like dispersed in a platinum solid, chloroplatinic acid, chloroplatinic acid and alcohol, aldehyde, ketone, etc. And a platinum-olefin complex and a platinum (0) -dialkenyltetramethyldisiloxane complex. Examples of the catalyst other than platinum _{compounds, RhCl (PPh 3) 3,} RhCl 3, RuCl 3, IrCl 3, FeCl 3, AlCl 3, PdCl 2 · H 2 O, NiCl 2, TiCl 4 , and the like. These catalysts may be used alone or in combination of two or more. Although there is no restriction | limiting in particular as a catalyst amount, It is good to use in the range of 10 ^{< -1} > ^-10 <^-8> mol with respect to 1 mol of alkenyl groups of a component (A), Preferably it is the range of 10 ^{< -3} > ^-10 <^-6> mol. It is good to use. When the amount is less than 10 ⁻⁸ mol, crosslinking tends not to proceed sufficiently. Moreover, since a clear effect is not seen even if it uses 10 ^<-1 > mol or more, it is preferable that it is less than 10 ^{< -1} > mol from the surface of economical efficiency. Of these, platinum vinyl siloxane is most preferred in terms of compatibility, crosslinking efficiency, and scorch stability.
The dynamic cross-linking of the isobutylene polymer (A) with the hydrosilyl group-containing compound (D) is carried out by polymer block (a) mainly composed of polypropylene resin (B) or aromatic vinyl compound and isobutylene polymer block ( It is carried out by melt-kneading the isobutylene polymer (A) and the hydrosilyl group-containing compound (D) in the presence of the isobutylene block copolymer (C) comprising b).

  The polypropylene resin (B) means a homopolymer or copolymer having propylene as a main component. Examples of the monomer to be copolymerized include monomers selected from ethylene and α-olefins having 3 to 20 carbon atoms.

  The melt flow rate of the polypropylene resin (B) is not particularly limited, but the melt flow rate at 230 ° C. and 2.16 kg load is preferably 40 g / 10 min or less, and more preferably 3 g to 20 g / 10 min. preferable. When the melt flow rate of the polypropylene resin (B) is larger than 40 g / 10 minutes, heat resistance and mechanical strength tend to be inferior. Therefore, as the polypropylene resin (B), it is possible to use the same resin as the polypropylene resin (F) described later, but usually a polypropylene resin (B) is different from the polypropylene resin (F). Used as

  The isobutylene block copolymer (C) comprises a polymer block (a) mainly composed of an aromatic vinyl compound and an isobutylene polymer block (b).

  In the polymer block (a) mainly composed of an aromatic vinyl compound, the unit derived from the aromatic vinyl compound is preferably 60% by weight or more from the balance of processing temperature, hardness and physical strength, more preferably. Is a polymer block composed of 80% by weight or more.

  Aromatic vinyl compounds include styrene, o-, m- or p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, α-methyl-o. -Methylstyrene, α-methyl-m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl-p-methylstyrene, 2 , 4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-dimethylstyrene, β-methyl-2,4-dimethyl Styrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α-chloro-m- Chlorostyrene, α-chloro-p-chlorostyrene, β-chloro-o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α- Chloro-2,6-dichlorostyrene, α-chloro-2,4-dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4-dichlorostyrene, o-, m- or p- t-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, styrene derivatives substituted with silyl groups, indene And vinyl naphthalene. Among these, styrene, α-methylstyrene, and a mixture thereof are preferable from the viewpoint of industrial availability and glass transition temperature.

  In the polymer block (b) mainly composed of isobutylene, the unit derived from isobutylene is preferably 60% by weight or more, more preferably 80% by weight or more from the viewpoint of the balance between gas barrier properties and hardness and physical strength. It is a constructed polymer block.

  In any of the polymer blocks (a) and (b), a mutual monomer can be used as a copolymerization component, and other cationically polymerizable monomer components can be used. Examples of such a monomer component include monomers such as aliphatic olefins, dienes, vinyl ethers, silanes, vinyl carbazole, β-pinene, and acenaphthylene. These can be used alone or in combination of two or more.

  Aliphatic olefin monomers include ethylene, propylene, 1-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, hexene, cyclohexene, 4-methyl-1-pentene, vinylcyclohexane Octene, norbornene and the like.

  Examples of the diene monomer include butadiene, isoprene, hexadiene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, divinylbenzene, and ethylidene norbornene.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, (n-, iso) propyl vinyl ether, (n-, sec-, tert-, iso) butyl vinyl ether, methyl propenyl ether, ethyl propenyl ether and the like.

  Examples of the silane compound include vinyltrichlorosilane, vinylmethyldichlorosilane, vinyldimethylchlorosilane, vinyldimethylmethoxysilane, vinyltrimethylsilane, divinyldichlorosilane, divinyldimethoxysilane, divinyldimethylsilane, 1,3-divinyl-1,1,3. , 3-tetramethyldisiloxane, trivinylmethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and the like.

  The component (C) of the present invention is not particularly limited as long as it is composed of the block (a) and the block (b), and has, for example, a linear, branched, star-like structure. Any of a block copolymer, a diblock copolymer, a triblock copolymer, a multiblock copolymer, and the like can be selected. A preferable structure includes a triblock copolymer composed of (a)-(b)-(a) from the viewpoint of physical property balance and molding processability. These may be used alone or in combination of two or more in order to obtain desired physical properties and moldability.

  The ratio of the block (a) to the block (b) is not particularly limited, but from the viewpoint of flexibility and rubber elasticity, the content of the block (a) in the component (C) is 5 to 50% by weight. Is preferable, and it is further more preferable that it is 10 to 40 weight%.

  The molecular weight of component (C) is not particularly limited, but is preferably 30,000 to 500,000 in terms of weight average molecular weight by GPC measurement from the viewpoints of fluidity, molding processability, rubber elasticity, and the like. 000 to 300,000 is particularly preferable. When the weight average molecular weight is lower than 30,000, mechanical properties tend not to be sufficiently exhibited, whereas when it exceeds 500,000, fluidity and workability tend to deteriorate.

Although there is no restriction | limiting in particular about the manufacturing method of a component (C), For example, it can obtain by polymerizing a monomer component in presence of the compound represented by following General formula (1).
(CR ¹ R ² X) _n R ³ (1)
[Wherein X is a halogen atom, a substituent selected from an alkoxy group having 1 to 6 carbon atoms or an acyloxy group, R ¹ and R ² are each a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, R ¹ , R ² may be the same or different, R ³ is a monovalent or polyvalent aromatic hydrocarbon group or a monovalent or polyvalent aliphatic hydrocarbon group, and n represents a natural number of 1 to 6. . ]
The compound represented by the general formula (1) serves as an initiator, and is considered to generate a carbon cation in the presence of a Lewis acid or the like and serve as a starting point for cationic polymerization. Examples of the compound of the general formula (1) used in the present invention include the following compounds.

(1-Chloro-1-methylethyl) benzene [C ₆ H ₅ C (CH ₃ ) ₂ Cl], 1,4-bis (1-chloro-1-methylethyl) benzene [1,4-Cl (CH ₃ ) ₂ CC ₆ H ₄ C (CH ₃ ) ₂ Cl], 1,3-bis (1-chloro-1-methylethyl) benzene [1,3-Cl (CH ₃ ) ₂ CC ₆ H ₄ C (CH ₃ ) ₂ Cl], 1,3,5-tris (1-chloro-1-methylethyl) benzene [1,3,5- (ClC (CH ₃ ) ₂ ) ₃ C ₆ H ₃ ], 1,3-bis (1-Chloro-1-methylethyl) -5- (tert-butyl) benzene [1,3- (C (CH ₃ ) ₂ Cl) ₂ -5- (C (CH ₃ ) ₃ ) C ₆ H ₃ ]
Of these, bis (1-chloro-1-methylethyl) benzene [C ₆ H ₄ (C (CH ₃ ) ₂ Cl) ₂ ], tris (1-chloro-1-methylethyl) benzene [( ClC (CH ₃ ) ₂ ) ₃ C ₆ H ₃ ]. [Bis (1-chloro-1-methylethyl) benzene is also called bis (α-chloroisopropyl) benzene, bis (2-chloro-2-propyl) benzene or dicumyl chloride, and tris (1-chloro- 1-methylethyl) benzene is also referred to as tris (α-chloroisopropyl) benzene, tris (2-chloro-2-propyl) benzene, or tricumyl chloride.

When the component (C) is produced, a Lewis acid catalyst can be present together. Such Lewis acid may be any one that can be used for cationic polymerization. TiCl ₄ , TiBr ₄ , BCl ₃ , BF ₃ , BF ₃ .OEt ₂ , SnCl ₄ , SbCl ₅ , SbF ₅ , WCl ₆ , TaCl ₅ , VCl ₅ , FeCl ₃ , ZnBr ₂ , AlCl ₃ , AlBr _3, etc .; metal halides such as Et ₂ AlCl, EtAlCl _2, etc. can be preferably used. Of these, TiCl ₄ , BCl ₃ , and SnCl ₄ are preferable in view of the ability as a catalyst and industrial availability. The amount of Lewis acid used is not particularly limited, but can be set in view of the polymerization characteristics or polymerization concentration of the monomer used. Usually, it is 0.1-100 mol equivalent with respect to the compound represented by General formula (1), Preferably it is the range of 1-50 mol equivalent.

  In the production of the component (C), an electron donor component can be allowed to coexist if necessary. This electron donor component is believed to have the effect of stabilizing the growth carbon cation during cationic polymerization, and the addition of an electron donor produces a polymer with a narrow molecular weight distribution and a controlled structure. be able to. The electron donor component that can be used is not particularly limited, and examples thereof include pyridines, amines, amides, sulfoxides, esters, and metal compounds having an oxygen atom bonded to a metal atom.

  The polymerization of the component (C) can be carried out in an organic solvent as necessary, and the organic solvent can be used without particular limitation as long as it does not substantially inhibit cationic polymerization. Specifically, halogenated hydrocarbons such as methyl chloride, dichloromethane, chloroform, ethyl chloride, dichloroethane, n-propyl chloride, n-butyl chloride, chlorobenzene; benzene, toluene, xylene, ethylbenzene, propylbenzene, butylbenzene, etc. Alkylbenzenes; linear aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane; 2-methylpropane, 2-methylbutane, 2,3,3-trimethylpentane, 2 Branched aliphatic hydrocarbons such as 1,2,5-trimethylhexane; cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane and ethylcyclohexane; paraffin oil obtained by hydrorefining petroleum fractions, etc. .

  These solvents can be used alone or in combination of two or more in consideration of the balance of the polymerization characteristics of the monomer constituting the component (C) and the solubility of the polymer produced.

  The amount of the solvent used is determined so that the concentration of the polymer is 1 to 50 wt%, preferably 5 to 35 wt%, in consideration of the viscosity of the resulting polymer solution and the ease of heat removal.

  In carrying out the actual polymerization, each component is mixed at a temperature of, for example, −100 ° C. or more and less than 0 ° C. under cooling. In order to balance the energy cost and the stability of polymerization, a particularly preferred temperature range is −30 ° C. to −80 ° C.

  The addition amount of the polypropylene resin (B) and the isobutylene block copolymer (C) is such that (component (B) + component (C)) is 10 to 300 weights per 100 parts by weight of the isobutylene polymer (A). Parts, preferably 10 to 100 parts by weight. When the total amount of the polypropylene resin (B) and the isobutylene block copolymer (C) exceeds 300 parts by weight, the compression set tends to deteriorate significantly. The moldability tends to decrease significantly.

  The polypropylene resin (F) means a homopolymer or copolymer mainly composed of propylene having a melt flow rate of 40 g / 10 min or more at 230 ° C. and a load of 2.16 kg. When the melt flow rate of the polypropylene resin (F) is smaller than 40 g / 10 minutes, the molding fluidity tends to be inferior, and the melt flow rate is more preferably 100 g / 10 minutes or more. Examples of the monomer to be copolymerized include monomers selected from ethylene and α-olefins having 3 to 20 carbon atoms.

  The addition amount of the polypropylene resin (F) is 5 to 100 parts by weight, preferably 10 to 70 parts by weight with respect to the isobutylene polymer (A). When the blending amount of the polypropylene resin (B) exceeds 100 parts by weight, compression set characteristics and heat resistance tend to be significantly deteriorated, and when it is less than 5 parts by weight, molding fluidity tends to be lowered. .

  In the present invention, as the component (G), a softener can be used as necessary for the purpose of imparting flexibility and molding fluidity. Although it does not specifically limit as a softening agent, Generally, a liquid or liquid material is used suitably at room temperature. Examples of such softeners include various rubber or resin softeners such as mineral oils, vegetable oils, and synthetics. Mineral oils include naphthenic and paraffinic process oils, and vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, wax, pine Examples of synthetic systems include oil and olive oil, and liquid polybutene, low molecular weight polybutadiene, and the like. Among these, polybutene is preferably used from the viewpoint of compatibility with the component (A) and gas barrier properties. Examples of the liquid polybutene include homopolymers such as 1-butene, 2-butene, and isobutene, and copolymers having these as the main components. Among these, homopolymers of isobutene or isobutene are mainly used. A copolymer with 1-butene or / and 2-butene as a component is preferred. The liquid polybutene preferably has a number average molecular weight of 500 to 6,000. When the number average molecular weight is less than 500, the thermoplastic elastomer composition is inferior in heat resistance and tends to be bleed and sticky on the surface of the molded product. On the other hand, when it exceeds 6,000, it is uniform in the thermoplastic elastomer composition. It becomes difficult to disperse in

  These softeners may be used in an appropriate combination of two or more in order to obtain the desired hardness and melt viscosity.

  The amount of component (G) is preferably 1 to 500 parts by weight, more preferably 1 to 200 parts by weight, and more preferably 1 to 100 parts by weight per 100 parts by weight of component (A). Is more preferable. If it exceeds 500 parts by weight, the softening agent tends to bleed out from the surface of the molded article, which is not preferable.

  The timing for adding the component (G) is not particularly limited, and may be added at the time of dynamic crosslinking of the component (A) or after dynamic crosslinking.

  The isobutylene polymer (A) having an alkenyl group at the terminal was dynamically cross-linked with the hydrosilyl group-containing compound (D) when melt kneaded with the polypropylene resin (B) or the isobutylene block copolymer (C). In order to obtain the thermoplastic elastomer (E), a known method may be employed, and examples thereof include a method using a batch kneader or a continuous kneader.

  For example, in the case of producing using a closed or open batch kneader such as a lab plast mill, Brabender, Banbury mixer, kneader, roll or the like, a crosslinking agent (hydrosilyl group-containing compound (D There is a method in which all components other than)) are put into a kneading apparatus, melted and kneaded until uniform, then a crosslinking agent is added thereto, and the crosslinking reaction proceeds sufficiently, and then the melt-kneading is stopped.

  Moreover, when manufacturing using a continuous melt-kneading apparatus like a single screw extruder, a twin screw extruder, etc., all the components other than a crosslinking agent (hydrosilyl group containing compound (D)) are used as an extruder in advance. After melt-kneading until uniform using a melt-kneading apparatus, pelletize, dry blend a crosslinking agent into the pellet, and then melt-knead with a melt-kneading apparatus such as an extruder or a Banbury mixer to have an alkenyl group at the end. A method of dynamically crosslinking the isobutylene polymer component (A) with the hydrosilyl group-containing compound (D), and all components other than the crosslinking agent are melt-kneaded by a melt-kneading apparatus such as an extruder, and the extruder Examples thereof include a method in which a cross-linking agent is added from the middle of the cylinder and further melt-kneaded to dynamically cross-link the isobutylene polymer (A) having an alkenyl group at the terminal.

  In performing melt kneading, a temperature range of 140 to 230 ° C is preferable, and a temperature range of 150 to 200 ° C is more preferable. If the melt kneading temperature is lower than 140 ° C, the components (B) and (C) may not be melted and sufficient mixing may not be possible. If the melt kneading temperature is higher than 230 ° C, thermal decomposition of the isobutylene polymer (A) may occur. May start to happen.

  The thermoplastic composition according to the present invention has a melt flow rate of 40 g / 10 min or more at 230 ° C. under a load of 2.16 kg on the dynamically crosslinked composition (E) of the isobutylene polymer (A) obtained by the above-described method. It can be obtained by melt-kneading the polypropylene resin (F).

  For melt kneading, a known method may be employed, and the above-described batch kneader or continuous kneader can be used. For example, the dynamic cross-linking composition of the isobutylene polymer (A) and the component (F) are weighed, mixed with a tumbler, Henschel mixer, riboblender, etc., and then melted with an extruder, a Banbury mixer, a roll, etc. The method of kneading is mentioned. Although the kneading | mixing temperature at this time does not have limitation in particular, the range of 100-250 degreeC is preferable, and the range of 150-220 degreeC is more preferable. When the kneading temperature is lower than 100 ° C., melting tends to be insufficient, and when it is higher than 250 ° C., deterioration due to heating may start to occur.

  In addition, the composition of the present invention can be further subjected to, for example, ethylene-propylene copolymer rubber (EPM) or ethylene-propylene-diene terpolymer in a range that does not impair the physical properties according to the required properties according to each application. Flexible olefin-based polymers such as rubber (EPDM), ethylene-butene copolymer rubber (EBM), amorphous poly α-olefin (APAO), ethylene-octene copolymer, in addition to hindered phenols and phosphorus, Sulfur antioxidants, hindered amine UV absorbers, light stabilizers, pigments, surfactants, flame retardants, antiblocking agents, antistatic agents, lubricants, silicone oils, fillers, reinforcing agents, etc. can do. As inorganic fillers, light calcium carbonate, heavy or calcium carbonate, other calcium fillers, hard clay, soft clay, kaolin clay, talc, wet silica, dry silica, amorphous silica, wollastonite, synthetic or natural zeolite Diatomaceous earth, silica sand, pumice powder, slate powder, alumina, aluminum sulfate, barium sulfate, calcium sulfate, molybdenum disulfide, magnesium hydroxide, aluminum hydroxide, and those obtained by silane treatment. These additives can be used in combination of two or more. For example, it is possible to improve hardness and tensile strength by including an inorganic filler. In addition, when a metal hydroxide such as magnesium hydroxide or aluminum hydroxide is used as the inorganic filler, it may be possible to impart excellent flame retardancy. Further, as the anti-blocking agent, for example, silica, zeolite and the like are suitable, and these may be either natural or synthetic, and true spherical crosslinked particles such as crosslinked acrylic true spherical particles are also suitable. As the antistatic agent, N, N-bis- (2-hydroxyethyl) -alkylamines and glycerin fatty acid esters having an alkyl group having 12 to 18 carbon atoms are preferable. Further, the lubricant is preferably a fatty acid amide, and specific examples include erucic acid amide, behenic acid amide, stearic acid amide, oleic acid amide and the like.

  The thermoplastic elastomer composition of the present invention can be molded using a molding method and molding apparatus generally employed for a thermoplastic resin composition, for example, melt molding by extrusion molding, injection molding, press molding, blow molding or the like. it can. Further, the thermoplastic elastomer composition of the present invention is excellent in moldability, hygiene, vibration damping, gas barrier properties, compression set properties, sealing materials such as packing materials, sealing materials, gaskets, plugs, Specifically, medical medicine plugs and beverage cap liners, CD dampers, architectural dampers, vibration control materials such as vibration control materials for automobiles, vehicles and home appliances, vibration damping materials, automotive interior materials, cushion materials, daily necessities It can be used effectively as electrical parts, electronic parts, sports members, grips or cushioning materials, wire covering materials, packaging materials, various containers, and stationery parts.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these. Prior to the examples, various measurement methods, evaluation methods, and examples will be described.

(hardness)
Based on JIS K 6253, hardness (hereinafter abbreviated as JIS-A hardness) was measured with a spring type A durometer. The test piece used was a 12.0 mm thick press sheet.

(Melt viscosity)
In accordance with JIS K 7199, the melt viscosity (poise) under the conditions of 200 ° C. and shear rate = 1216 / s was measured by a method using a capillary die.

(Compression set)
In accordance with JIS K 6262, a 12.0 mm thick press sheet was used as a test piece. The measurement was performed at 100 ° C. for 22 hours under the conditions of 25% deformation.

(Vibration control)
For damping properties, dynamic viscoelastic properties were evaluated. The dynamic viscoelastic property was obtained by cutting two 5 mm × 6 mm test pieces from a 2.0 mm-thick sheet obtained by hot press molding and JIS K 6394.

  Based on (Testing method of dynamic properties of vulcanized rubber and thermoplastic rubber), measurement was performed in a shear mode under the conditions of a frequency of 10 Hz and a strain of 0.05%. The apparatus used is a dynamic viscoelasticity measuring apparatus DVA-200 (made by IT Measurement Control Co., Ltd.).

(Gas permeability)
The gas permeability was evaluated by the oxygen permeability coefficient. The oxygen permeability coefficient was measured by a differential pressure method at 23 ° C. and 1 atm in accordance with JIS K 7126 by cutting out a test piece of 100 mm × 100 mm from a 2.0 mm thick sheet obtained by hot press molding.

(Heat-resistant)
For heat resistance, the deformability at high temperature was evaluated. The test piece was a 12.0 mm thick press sheet. The change in dimensions of the material after being left in 121 ° C. high pressure steam for 1 hour was measured. The thing which 2% or more deformation | transformation was seen was set to x, and the thing which was not seen was set to (circle).

(Contents of description components such as Examples)
Component (A):
APIB: Polyisobutylene having an allyl group introduced at the end (Production Example 1)
Ingredient (B):
RPP: homopolypropylene, manufactured by Prime Polymer Co., Ltd. (trade name “Prime Polypro J215W”) MFR 9 g / 10 min
Ingredient (C):
SIBS: Styrene-isobutylene-styrene block copolymer (Production Example 2)
Component (D):
Polysiloxane: Methyl hydrogen polysiloxane, manufactured by Toshiba Silicone (trade name “TSF484”)
Ingredient (F):
SHFPP1: Homopolypropylene MFR 120g / 10min, manufactured by SUNOCO CHEMICALS (trade name CP1200B)
SHFPP2: Homopolypropylene MFR 1500 g / 10 min, Polyvisions Inc (trade name proFlow 1000)
Cross-linking catalyst:
1,1,3,3-Tetramethyl-1,3-dialkenyldisiloxane complex of zerovalent platinum, 3 wt% xylene solution component (E1): Isobutylene polymer (A) and polypropylene resin (B) Resin composition dynamically crosslinked with hydrosilyl group-containing compound (D) during melt kneading (Production Example 3)
Component (E2): a resin composition obtained by dynamically crosslinking the isobutylene polymer (A) with the hydrosilyl group-containing compound (D) during melt kneading with the isobutylene block copolymer (C) (Production Example 4)

(Production Example 1) [Production of Isobutylene Copolymer (APIB) Introduced with Alkenyl Group at Terminal]
A 3 L faucet, a thermocouple, and a stirring seal were attached to a 2 L separable flask, and nitrogen substitution was performed. After nitrogen substitution, nitrogen was flowed using a three-way cock. To this, 785 ml of toluene and 265 ml of ethylcyclohexane were added using a syringe. After adding the solvent, the water content was measured with a Karl Fischer moisture meter. After the measurement, it was cooled to about -70 ° C. 277 ml (2933 mmol) of isobutylene monomer was added. After cooling to about −70 ° C. again, 0.85 g (3.7 mmol) of p-dicumyl chloride and 0.68 g (7.4 mmol) of picoline were dissolved in 10 ml of toluene and added. When the internal temperature of the reaction system became -74 ° C and stabilized, 19.3 ml (175.6 mmol) of titanium tetrachloride was added to initiate polymerization. When the polymerization reaction was completed (90 minutes from the start of the reaction), 1.68 g (11.0 mmol) of a 75% allylsilane / toluene solution was added, and the mixture was further reacted for 2 hours. Then, it deactivated with the pure water heated at about 50 degreeC, Furthermore, the organic layer was wash | cleaned 3 times with pure water (70 to 80 degreeC), and the organic solvent was removed at 80 degreeC under reduced pressure, and APIB was obtained. . A polymer having Mn of 45500, Mw / Mn of 1.10, and an allyl group content of 2.0 / mol was obtained.

(Production Example 2) [Production of styrene-isobutylene-styrene block copolymer (SIBS)]
After the inside of the polymerization vessel of the 2 L separable flask was purged with nitrogen, 456.1 mL of n-hexane (dried with molecular sieves) and 656.5 mL of butyl chloride (dried with molecular sieves) were added using a syringe. After cooling the polymerization vessel in a dry ice / methanol bath at −70 ° C., a polytetrafluoroethylene liquid feeding tube was placed on a pressure-resistant glass liquefied collection tube with a three-way cock containing 232 mL (2871 mmol) of isobutylene monomer. Then, isobutylene monomer was fed into the polymerization vessel by nitrogen pressure. 0.647 g (2.8 mmol) of p-dicumyl chloride and 1.22 g (14 mmol) of N, N-dimethylacetamide were added. Next, 8.67 mL (79.1 mmol) of titanium tetrachloride was further added to initiate polymerization. After stirring at the same temperature for 1.5 hours from the start of polymerization, about 1 mL of the polymerization solution was extracted from the polymerization solution for sampling. Subsequently, a mixed solution of 77.9 g (748 mmol) of styrene monomer, 23.9 mL of n-hexane and 34.3 mL of butyl chloride, which had been cooled to −70 ° C. in advance, was added to the polymerization vessel. 45 minutes after adding the mixed solution, about 40 mL of methanol was added to terminate the reaction.

  After the solvent was distilled off from the reaction solution, the resulting solid was dissolved in toluene and washed twice with water. Further, the toluene solution was added to a large amount of methanol to precipitate a polymer, and the obtained polymer was vacuum-dried at 60 ° C. for 24 hours to obtain a target block copolymer. The molecular weight of the polymer obtained by the gel permeation chromatography (GPC) method was measured. The block copolymer in which the Mn of the isobutylene polymer before styrene addition is 50,000 and Mw / Mn is 1.40, the Mn of the block copolymer after styrene polymerization is 67,000 and Mw / Mn is 1.50. A polymer was obtained.

(Production Example 3) [Production of component (E1)]
Laboplast mill ((shares) (A) APIB, (B) RPP, (G) polybutene obtained in Production Example 1 were weighed to a total of 40 g in the proportions shown in Table 1 and set to 170 ° C. ) Produced by Toyo Seiki Seisakusho Co., Ltd. for 3 minutes, then (D) polysiloxane was added at the rate shown in Table 1, and the crosslinking catalyst was added at the rate shown in Table 1, and the torque value was the highest. Dynamic crosslinking was carried out by further melt-kneading at 170 ° C. until a value was shown. The dynamic cross-linking composition (E1) was taken out after 3 minutes of kneading after showing the maximum value of torque.

(Production Example 4) [Production of component (E2)]
Lab Plast Mill (manufactured by Toyo Seiki Seisakusyo Co., Ltd.) was weighed so that the components (A) APIB and (C) SIBS obtained in Production Example 1 were 40 g in total in the proportions shown in Table 1, and set to 170 ° C. ) For 3 minutes, and then (D) polysiloxane is added at the rate shown in Table 1, and after adding the cross-linking catalyst at the rate shown in Table 1, 170 until the torque value reaches the maximum value. It was further melt-kneaded at 0 ° C. for dynamic crosslinking. After showing the maximum value of the torque, the dynamic cross-linking composition (E2) was taken out after 3 minutes of kneading.

(Example 1)
The component (E1) and component (F) SHFPP1 obtained in Production Example 3 were weighed to a total of 40 g in the proportions shown in Table 2, and melt kneaded for 5 minutes using a lab plast mill set at 180 ° C. The thermoplastic elastomer composition was taken out. The obtained thermoplastic elastomer composition could be easily formed into a sheet shape at 190 ° C. with a heating press (manufactured by Shindo Metal Industry Co., Ltd.). The hardness, melt viscosity, compression set, vibration damping, gas permeability coefficient, and heat resistance of the obtained sheet were measured according to the above methods. Table 2 shows the physical properties of each sheet.

(Example 2)
A thermoplastic elastomer composition was obtained in the same manner as in Example 1 except that the amount of component (F) SHFPP1 was changed to 40 parts by weight, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Example 3)
A thermoplastic elastomer composition was obtained in the same manner as in Example 1 except that the component (F) was changed to SHFPP2, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

Example 4
A thermoplastic elastomer composition was obtained in the same manner as in Example 3 except that the amount of component (F) SHFPP2 was changed to 40 parts by weight, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Example 5)
Component (E1) A thermoplastic elastomer composition was obtained in the same manner as in Example 3 except that the component (E2) obtained in Production Example 4 was used, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Example 6)
A thermoplastic elastomer composition was obtained in the same manner as in Example 5 except that the component (F) was changed to SHFPP2, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Comparative Example 1)
The component (E1) was melt-kneaded for 5 minutes using a lab plast mill set to 180 ° C., and the thermoplastic elastomer composition was taken out. The obtained thermoplastic elastomer composition was able to be formed into a sheet shape at 190 ° C. with a heating press (manufactured by Shindo Metal Industry Co., Ltd.). The hardness, melt viscosity, compression set, vibration damping, gas permeability coefficient, and heat resistance of the obtained sheet were measured according to the above methods. Table 2 shows the physical properties of each sheet.

(Comparative Example 2)
A thermoplastic elastomer composition was obtained in the same manner as in Comparative Example 1 except that the component (E1) was changed to the component (E2), and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Comparative Example 3)
A thermoplastic elastomer composition was obtained in the same manner as in Example 2 except that the component (F) SHFPP1 was changed to the component (B) RPP, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Comparative Example 4)
A thermoplastic elastomer composition was obtained in the same manner as in Example 5 except that the component (F) SHFPP1 was changed to the component (B) RPP, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Comparative Example 5)
A thermoplastic elastomer composition was obtained in the same manner as in Example 1 except that the amount of component (F) SHFPP1 was changed to 200 parts by weight, and the physical properties were evaluated. The respective physical properties are shown in Table 2.

(Comparative Example 6)
5 minutes using a lab plast mill in which Santoprene 8211-55 manufactured by AES Japan, which is a composition obtained by melt-kneading ethylene-propylene-diene rubber (EPDM) in the presence of polypropylene and dynamically cross-linking EPDM, is set at 180 ° C. The thermoplastic elastomer composition was taken out by melt-kneading. The obtained thermoplastic elastomer composition was able to be formed into a sheet shape at 190 ° C. with a heating press (manufactured by Shindo Metal Industry Co., Ltd.). The hardness, melt viscosity, compression set, vibration damping, gas permeability coefficient, and heat resistance of the obtained sheet were measured according to the above methods. Table 2 shows the physical properties of each sheet.

  It can be seen that Examples 1 to 6 have high heat resistance and vibration damping properties, while having a hardness of 63 to 75 and a compression set of 25 to 41, which is rich in rubber elasticity. Furthermore, it turns out that it has high mold fluidity from low melt viscosity. The melt viscosities of Comparative Examples 1 and 2 to which no component (F) was added were as high as 4000 poise or more. Moreover, the comparative examples 3 and 4 which added the component (B) instead of the component (F) also had high melt viscosity of 3200 or more. Further, Comparative Example 5 in which the amount of component (F) added was 200 parts by weight was poor in heat resistance. It can be seen that Comparative Example 6 which is a commercially available dynamic cross-linked product has a low tan δ peak as an index of vibration damping properties, poor vibration damping properties, a large gas permeability coefficient, and poor gas barrier properties.

From the above, it can be seen that the composition according to the present invention is a material having a balance of hardness, molding fluidity, compression set characteristics, vibration damping properties, gas barrier properties, and heat resistance. Accordingly, it can be suitably used for beverage cap liners, medical plugs, vibration damping materials, and the like that require these characteristics.

Claims (7)

  100 parts by weight of an isobutylene polymer (A) having an alkenyl group at the terminal is added to a polymer block (a) mainly composed of a polypropylene resin (B) and / or an aromatic vinyl compound and an isobutylene polymer block (b And 10 to 300 parts by weight of an isobutylene block copolymer (C) comprising a thermoplastic elastomer (E) dynamically cross-linked with a hydrosilyl group-containing compound (D) while being melt-kneaded, and 230 ° C. under a load of 2.16 kg A thermoplastic elastomer composition comprising 5 to 100 parts by weight of a polypropylene resin (F) having a melt flow rate of 40 g / 10 min or more.   2. The thermoplastic elastomer composition according to claim 1, wherein the polypropylene resin (B) has a melt flow rate of 40 g / 10 min or less at 230 ° C. and a load of 2.16 kg.   The thermoplastic elastomer composition according to claim 1 or 2, further comprising (G) 1 to 500 parts by weight of a softening agent based on the isobutylene polymer (A). The thermoplastic elastomer composition according to any one of claims 1 to 3, wherein the oxygen permeability coefficient (JIS K7126A method) is 15 x 10 ^-16 mol · m / m ² · s · Pa or less.   The cap liner for drinks which consists of a thermoplastic elastomer in any one of Claims 1-4.   A medical drug stopper comprising the thermoplastic elastomer according to any one of claims 1 to 4.   A vibration damping material comprising the thermoplastic elastomer according to any one of claims 1 to 4.