JP3503352B2 - Thermoplastic elastomer composition - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic elastomer composition, which has flexibility, rubber elasticity, heat resistance, weather resistance,
The present invention relates to a thermoplastic elastomer composition which has excellent mechanical strength and moldability and has little bleeding of a softening agent. This composition is used for food, daily sundries, toys,
Exercise equipment applications, stationery applications such as desk mats, interior and exterior applications for automobiles, civil engineering and construction applications such as civil engineering sheets and waterproof sheets, AV / home appliance applications, OA / office equipment applications, clothing /
It can be used for footwear, textiles, medical devices such as various catheters, sanitary products such as disposable diapers and sanitary products, chemical and mining and industrial materials, packaging and transportation materials, agricultural, livestock and fisheries materials.

[0002]

2. Description of the Related Art In recent years, a thermoplastic elastomer (hereinafter abbreviated as TPE), which is a rubber-like soft material and does not require a vulcanization step and has a moldability similar to that of a thermoplastic resin, has been used for automobile parts, It is used in the fields of home electric appliances, medical equipment, food equipment parts, electric wires and sundries. Currently, such TPEs include polyolefin-based, polyurethane-based,
Polymers of various types such as polyester type and polystyrene type have been developed and are commercially available.

However, these TPEs have not reached the level of the vulcanized rubber in terms of quality in the use of the vulcanized rubber, which is one of the wide fields of application as a rubber, and therefore, the vulcanized rubber field. Use in is extremely limited. For example, polyolefin TPE is relatively inexpensive and has excellent heat resistance and weather resistance, but on the other hand, a soft one cannot be obtained.
JIS-A hardness (JIS-K630
In 1), it is about 70, which is still too hard compared to JIS-A hardness 60 of general vulcanized rubber.

Polyester type TPE and polyurethane type T
PE is also the most flexible one among the commercially available products according to JIS-
A hardness is 70 to 90, which is much harder than vulcanized rubber,
Not suitable for vulcanized rubber applications. On the other hand, a polymer having a styrene block-butadiene block-styrene block portion (SBS) or a polymer having a styrene block portion-isoprene block portion-styrene block portion (S
Polystyrene-based TPE such as IS) is more flexible and has better rubber elasticity than the above-mentioned polyolefin-based, polyester-based, and polyurethane-based TPE, but has a double bond in the polybutadiene block or polyisoprene block in the polymer. Therefore, there is a problem in heat aging resistance (heat stability) and weather resistance.

For example, as a blend of a polystyrene elastomer and a polyester elastomer, one using SBS or SIS in the polystyrene elastomer is introduced in Japanese Patent Laid-Open No. 82162/1975, but these are ozone resistant. It did not have sufficient performance such as heat stability. It is well known that an elastomer having improved thermal stability can be obtained by hydrogenating an intramolecular double bond of a copolymer having a styrene block portion and a conjugated diene block portion. A so-called polystyrene-based TPE in which such a block copolymer is used as a rubber component and an olefin-based resin (usually polypropylene resin), oil, filler, etc. is distributed has excellent flexibility as compared with the polyolefin-based TPE. Is.

However, for the purpose of exhibiting good rubber elasticity and heat resistance, a polystyrene type elastomer having a very high molecular weight must be used.
There is a problem that short shots and flow marks are likely to occur in the case where the fluidity at the time of melting is insufficient and a complicated shape is required or in the molding of an elongated shape having a large L / D.

[0007]

The object of the present invention is to provide thermoplastic elastomers with excellent flexibility, rubber elasticity, heat resistance,
It is an object of the present invention to provide a thermoplastic elastomer composition which does not impair physical properties such as weather resistance, has little bleeding of a softening agent, is rich in fluidity and is excellent in moldability.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above problems, and as a result, have found that a copolymer composed of a monovinyl-substituted aromatic hydrocarbon polymer block / a conjugated diene polymer block is A specific triblock copolymer and a diblock copolymer are used in combination as a hydrogenated block copolymer in which a double bond of a conjugated diene block portion is hydrogenated, and a softening agent for a hydrocarbon rubber and an olefin. It was found that by combining and combining the system polymers, the flexibility, rubber elasticity, heat resistance and weather resistance are excellent, the bleeding of the softening agent is small, the fluidity is dramatically improved, and the molding processability is excellent. As a result, the present invention has been completed.

That is, the thermoplastic elastomer composition of the present invention comprises: (a) a conjugated diene polymer block of a copolymer comprising a monovinyl-substituted aromatic hydrocarbon polymer block (A) and a conjugated diene polymer block (B). (B) Hydrogenated block copolymer in which the double bond of the moiety is hydrogenated:
30 to 60% by weight However, in the component (a), the double bond of the conjugated diene polymer block (B) portion of the triblock copolymer represented by (a-1) A-B-A is hydrogenated. Hydrogenated triblock copolymer having a weight average molecular weight of 100,000-40
The content of the polymer block (A) in the copolymer is 20
To 40% by weight of the copolymer and (a-2) a conjugated diene polymer block (B) of the diblock copolymer represented by AB.
A hydrogenated diblock copolymer in which a part of double bonds is hydrogenated, having a weight average molecular weight of 30,000 to 200,000 and a polymer block (A) content of 5 to 20% by weight. It is composed of a copolymer and the composition ratio (weight ratio) thereof is (a-1) component / (a-2) component = 99/1 to 80/20.

(B) Hydrocarbon softener for rubber: 70 to 4
0% by weight The present invention provides a thermoplastic elastomer composition in which 1 to 100 parts by weight of (c) an olefin polymer is mixed with 100 parts by weight of the above components (a) and (b).

[0011]

DETAILED DESCRIPTION OF THE INVENTION

(1) The polymer component forming the block (A) of the hydrogenated block copolymer (a component) is a polymer of styrene or its derivative. Specific examples of the styrene derivative include α-methylstyrene, 1-vinylnaphthalene, and 2
-Vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-
(Phenyl butyl) styrene etc. are mentioned. Among these, styrene and α-methylstyrene are preferable as the polymer component forming the block (A).

The conjugated diene monomer in the polymer block (B) is preferably butadiene or isoprene, or a mixture of both. When butadiene is used as the single conjugated diene monomer to form the polymer block (B), the block copolymer retains elastomeric properties after hydrogenation and saturation of the double bonds. For the purpose, 1, in the microstructure in polybutadiene
It is preferable to adopt a polymerization condition in which the 2-micro structure is 20 to 50%, and particularly the 1,2-micro structure is 35 to 4
5% is suitable.

The component (a-1) in the component (a) is AB-
A hydrogenated triblock copolymer in which the double bond of the conjugated diene block portion of the triblock copolymer represented by A is hydrogenated, for example, a hydrogenated product of a styrene / butadiene / styrene block copolymer (commonly called , Styrene-ethylene-butylene-styrene copolymer (hereinafter, simply [S
EBS]. )), Hydrogenated products of styrene / isoprene / styrene block copolymers (commonly known as
Styrene / ethylene / propylene / styrene copolymer (hereinafter sometimes simply abbreviated as [SEPS]),
Alternatively, a mixture of these can be preferably used.

The component (a-1) has a weight average molecular weight of 10
10,000 to 400,000, preferably 150,000 to 350,000, more preferably 200,000 to 300,000, and the proportion of the polymer block (A) in the copolymer is 20 to 40% by weight, preferably 25 to 35% by weight hydrogenated triblock copolymer. When the weight average molecular weight is less than 100,000, the rubber elasticity and heat resistance of the resulting thermoplastic elastomer are poor, while
If it exceeds 400,000, the viscosity tends to be high and the moldability tends to be poor.

Here, the "weight average molecular weight" is a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions. (Conditions) Equipment: 150C ALC / GPC (MILL
Column: AD80M / S (manufactured by Showa Denko KK) 3 solvents: o-dichlorobenzene temperature: 140 ° C. Flow rate: 1 ml / min Injection amount: 200 μl Concentration: 2 mg / ml (antioxidants 2, 6 -0.2% by weight of di-t-butyl-p-phenol was added. The concentration was detected by an infrared spectrophotometer MIRAN 1A manufactured by FOXBORO at a wavelength of 3.42 μm.)

When the content of the polymer block (A) in the copolymer is less than 20% by weight, the resulting thermoplastic elastomer is inferior in mechanical strength, rubber elasticity and heat resistance, and the polymer block (A) is poor. ) Is more than 40% by weight, flexibility and rubber elasticity are inferior and bleeding of the softening agent tends to be deteriorated. (A-2) in the component (A)
The component is a hydrogenated diblock copolymer in which the double bond of the conjugated diene block portion of the diblock copolymer represented by AB is hydrogenated, for example, a hydrogenated product of a styrene / butadiene block copolymer. (Styrene / ethylene / butylene copolymer (hereinafter sometimes simply abbreviated as [SEB])), hydrogenated styrene / isoprene block copolymer (styrene / ethylene / propylene copolymer (hereinafter, simply It may be abbreviated as [SEP])) or a mixture thereof can be preferably used.

The proportion of the polymer block (A) in the copolymer is 5 to 20% by weight, preferably 10 to 15% by weight.
Is. When the polymer block (A) is less than 5% by weight, mechanical strength, rubber elasticity and heat resistance of the obtained thermoplastic elastomer tend to be deteriorated. On the other hand, when the polymer block (A) exceeds 20% by weight, the effect of improving the fluidity and molding processability tends to be hardly exhibited.

The weight average molecular weight of the hydrogenated diblock copolymer as the component (a-2) is in the range of 30,000 to 200,000, preferably 40,000 to 150,000, and more preferably 50,000 to 100,000. Is. As the component (a), the component (a-2) A-
The B-type block copolymer may be prepared by polymerizing the B-type block copolymer and then synthesizing the A-B-A type block copolymer of the component (A-1) by coupling.

When the weight average molecular weight is less than 30,000, the thermoplastic elastomer obtained has poor rubber elasticity and heat resistance,
If it exceeds 200,000, the effect of improving the fluidity and molding processability tends to be hardly exhibited. As a method for producing these block copolymers, any method can be used as long as the above-mentioned structure can be obtained. For example, Japanese Patent Publication No. 40-
It can be obtained by block polymerization of styrene and butadiene or isoprene in an inert solvent using a lithium catalyst or the like according to the method described in Japanese Patent No. 23798.

The hydrogenation treatment of these block copolymers is carried out, for example, in Japanese Examined Patent Publication Nos. 42-8704 and 43-43.
According to the method described in JP-A-6636 or JP-A-59-133203 and JP-A-60-79005, hydrogenation is carried out by heating in an inert solvent in the presence of a hydrogenation catalyst. In this hydrogenation, at least 50% of the olefinic double bonds in polymer block B,
Preferably, 80% or more is hydrogenated, and 25% or less of the aromatic unsaturated bonds in the polymer block A are hydrogenated.

Such hydrogenated block copolymers are available from Shell Chemical Company under the name "KRATON-".
G ”and a product sold by Kuraray Co. under the trade name of“ Septon ”.

(2) Hydrocarbon-based rubber softener (component (b)) The hydrocarbon-based rubber softener used as component (b) in the present invention has a weight average molecular weight of 300 to 2,000.
Hydrocarbons of 0, preferably 500 to 1,500 are used, and mineral oil type or synthetic resin type is suitable. The mineral oil-based softening agent is a mixture of the aromatic ring, the naphthene ring and the paraffin chain, and the paraffin chain carbon number accounts for 50% or more of the total carbon is called paraffin oil. A naphthenic oil having a naphthene ring carbon number of 30 to 45% is called an naphthenic oil, and has an aromatic carbon number of 35.
% Or more are classified as aromatic oils. Among these, paraffinic oil is preferable as the softening agent for rubber.

The paraffinic oil has a kinematic viscosity at 40 ° C. of 20 to 800 cst (centistokes), preferably 50 to 600 cst, a pour point of 0 to -40 ° C., preferably 0 to -30 ° C., and a flash point ( COC) is 20
Oils of 0-400 ° C, preferably 250-350 ° C are preferably used. As the synthetic resin softener, polybutene, low molecular weight polybutadiene, etc. can be used,
Mineral oil softeners are preferred.

(3) Olefin-based Polymer (Component C) As the olefin-based polymer used as the component (C) in the present invention, an olefin homopolymer or copolymer can be used, and a differential calorimeter is used. The melting peak temperature measured by (DSC) of less than 130 ° C is 1 at 190 ° C.
The melt flow rate at 230 ° C (JIS-K7210, 2.16 kg load) of 30 ° C or higher is 0.0.
1 to 100 g / 10 minutes, preferably 0.05 to 80 g /
10 minutes, particularly preferably those of 0.1 to 60 g / 10 min, a flexural modulus of 500 kg / cm ² or more, preferably 1,000~20,000kg / cm ^2, more preferably 3,000～15, The one of 000 kg / cm ² is used.

Specifically, a crystalline ethylene polymer,
Examples thereof include propylene-based polymers, polybutene-1 and poly-4-methylpentene-1, and the crystalline olefin-based polymers are preferably ethylene-based polymers and propylene-based polymers. Examples of the ethylene-based polymer include high-density, (linear) medium-density or low-density polyethylene, ethylene / propylene copolymer, ethylene / butene-1 copolymer, ethylene / hexene-1 copolymer, ethylene. Heptene-1 copolymer, ethylene / octene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid alkyl ester Copolymers, ethylene / methacrylic acid copolymers, ethylene / methacrylic acid alkyl ester copolymers and the like can be mentioned. Preferred as the ethylene-based polymer are high density and (cotton-like).
Medium density and low density polyethylene.

Further, the propylene-based polymer includes polypropylene, propylene / ethylene (block or random) copolymer, propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer, propylene.
4-methylenepentene-1 copolymer and the like can be mentioned. Preferred as the propylene-based polymer are polypropylene and propylene / ethylene (block or random).
It is a copolymer.

(4) Other components In addition to the above-mentioned essential components, the thermoplastic elastomer composition of the present invention may be blended with other optional components according to various purposes within a range that does not significantly impair the effects of the present invention. be able to. As the optional component, for example, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a neutralizing agent, a lubricant, an antifogging agent,
Anti-blocking agent, slip agent, dispersant, colorant,
Flame retardants, antistatic agents, conductivity-imparting agents, cross-linking agents, cross-linking aids, metal deactivators, molecular weight regulators, fungicides, various additives such as optical brighteners, thermoplastics other than the above essential components resin,
Examples thereof include elastomers and fillers other than the above essential components, and any one of these may be used alone or in combination with 50 parts or less per 100 parts of the elastomer composition.

Examples of the thermoplastic resin other than the essential components include polyphenylene ether resins, polyamide resins such as nylon 6 and nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and polyoxymethylene homo. polymer,
Examples thereof include polyoxymethylene-based resins such as polyoxymethylene copolymers and polymethylmethacrylate-based resins.

As the optional elastomer, a polymer having a flexural modulus of less than 500 kg / cm ² , for example, ethylene / propylene copolymer rubber (EPM), ethylene / ethylene
Ethylene-based elastomers such as propylene / non-conjugated diene copolymer rubber (EPDM), ethylene / butene copolymer rubber (EBM), ethylene / propylene / butene copolymer rubber, the above-mentioned (a-1) component or (a-2) Other than the components, styrene-butadiene copolymer rubbers, styrene-based elastomers such as styrene-isoprene copolymer rubbers, polybutadiene, etc. can be mentioned, and the elastomer composition 10
Other than parts can be added to 0 part.

Further, examples of the filler include glass fiber, hollow glass sphere, carbon fiber, talc, calcium carbonate, mica, potassium titanate fiber, silica, titanium dioxide and carbon black.

(5) Blending amount of each component The blending ratio (weight ratio) of the component (a-1) / component (b-2) constituting the thermoplastic elastomer of the present invention is 99/1.
To 80/20, preferably 98/2 to 85/1
5, more preferably 97/3 to 90/10.
Less than 1% by weight of the component (ii-2) in the component (ii) [(ii-
1) the content of the component exceeds 99% by weight], the effect of improving the fluidity and molding processability tends to be hardly exhibited,
If the amount of the component (a-2) exceeds 20% by weight [the amount of the component (a-1) is less than 80% by weight], the rubber elasticity, heat resistance, and mechanical strength of the resulting thermoplastic elastomer are deteriorated, which is not preferable. .

The mixing ratio of the component (a) and the component (b) is (i)
(A) component is 30 with respect to the total amount of component and (b) component
-60% by weight [70% to 40% by weight of component (B)], preferably 35 to 55% by weight [65 to 45% by weight of component (B)]. When the amount of component (a) is less than 30% by weight [(b) component exceeds 70% by weight], the rubber elasticity and heat resistance of the obtained thermoplastic elastomer are poor, and the bleeding property of the softening agent tends to deteriorate. If the amount of component (a) exceeds 60% by weight [(b) component is less than 40% by weight], flexibility and moldability tend to deteriorate.

The content of the component (c) is 1 to 100 parts by weight, preferably 2 to 75 parts by weight, more preferably 3 parts by weight based on 100 parts by weight of the total amount of the components (a) and (b).
˜50 parts by weight. When the amount is less than 1 part by weight, the thermoplastic elastomer obtained has poor moldability, and when the amount is more than 100 parts by weight, the flexibility of the thermoplastic elastomer is lost and the bleeding property of the softening agent tends to be deteriorated.

(6) Preparation of Elastomer Composition The thermoplastic elastomer composition of the present invention can be prepared by a usual method of mechanically melt-kneading the above-mentioned components. Examples of the melt-kneader used in the mechanical melt-kneading include a single-screw extruder, a twin-screw extruder, a Brabender plastograph, a Banbury mixer, a kneader blender, and a roll, and preferably 145-300. It can be obtained by kneading each component in the temperature range of ° C. Upon kneading, each component may be kneaded at once, or a multi-stage divided kneading method may be adopted in which after kneading arbitrary components, the remaining components are added and kneaded.

(7) Molding method The above-mentioned thermoplastic elastomer composition is prepared by a conventionally known method.
Injection molding (insert molding method, two-color molding method, sandwich molding method, gas injection molding method, etc.), extrusion molding, inflation molding, T die film molding, laminate molding, blow molding, blow molding, compression molding, calender molding, etc. By the molding method, a practically useful molded product can be processed. The molded product thus obtained can be used for industrial parts such as automobile parts, home electric appliance parts, food packaging materials, medical equipment parts, furniture parts, daily sundries and the like.

[0036]

EXAMPLES The present invention will be specifically described with reference to the following examples. These examples and comparative examples were evaluated by the evaluation methods shown below. However, the measurement sample is
All using an in-line screw type injection molding machine (small size injection molding machine: IS90B manufactured by Toshiba Machine Co., Ltd.), injection pressure 500 kg / cm ² , injection temperature 220 ° C., mold temperature 30
Molded under the condition of ℃, 120mm × 80mm × 2mm
It was obtained by punching a thick sheet in the lateral direction.

(1) Flexibility JIS-A hardness was measured according to JIS-K6301. (2) Rubber elasticity and heat resistance In accordance with JIS-K6301, compression set (70 ° C x
(22 hours) [%] was measured.

(3) Mechanical Strength Punching was performed with a No. 3 dumbbell, and the tensile strength at break [kg / cm ² ] was measured according to JIS-K6301. (4) The softening agent bleed injection-molded sheet was allowed to stand at 23 ° C. for 30 days and then visually evaluated for stickiness.

(5) Fluidity In accordance with JIS-K7210, melt flow rate (2
30 ° C., 2.16 kg) [g / 10 minutes] was measured. (6) Molding processability In the injection-molded sheet obtained under the above-mentioned molding conditions, when there were no short shots and there were no significant visual defects such as flow marks, the molding processability was evaluated as good.

The components used in the examples and comparative examples are as follows. Component (a) Hydrogenated block copolymer of monovinyl-substituted aromatic hydrocarbon / conjugated diene block copolymer (a) Block structure of component, monomers constituting polymer blocks (A) and (B), weight The average molecular weight and polymer block (A) content are shown in Table 1.

[0041]

[Table 1]

(B) Component (O-1) Softener for hydrocarbon rubber: Paraffin oil “PW90” manufactured by Idemitsu Kosan Co., Ltd. 40 ° C. Kinematic viscosity: 95.54 cst Pour point: −15 ° C. Flash point: 272 ° C.

(O-2) Hydrocarbon rubber softening agent: paraffin oil "PW380" manufactured by Idemitsu Kosan Co., Ltd. 40 ° C Kinematic viscosity: 381.6 cst Pour point: -15 ° C Flash point: 300 ° C

(C) Component (Pφ-1) Olefin-based resin: High-density polyethylene Mitsubishi Polyethylene-HD “HJ490” Density: 0.958 g / cm ³ MFR: 20 g / 10 min (190 ° C., 2.16 kg) (Pφ -2) Olefin resin: polypropylene Mitsubishi Polypro "MA2P" MFR: 16g / 10 minutes (230 ° C, 2.16kg)

(Pφ-3) olefin resin: propylene / ethylene copolymer Mitsubishi Polypro "BC2" MFR: 15 g / 10 minutes (230 ° C, 2.16 kg) (Pφ-4) olefin resin: propylene / ethylene copolymer Polymer Mitsubishi Polypro "FG3D" MFR: 10g / 10min (230 ° C, 2.16kg)

(Pφ-5) olefin resin: propylene / ethylene copolymer "SPX9800" manufactured by Mitsubishi Chemical Co., Ltd. MFR: 1.0 g / 10 minutes (230 ° C, 2.16 kg)

Examples 1 to 10 and Comparative Examples 1 to 11 For a total amount of 100 parts by weight of the composition blended in the blending amounts (parts by weight) shown in Tables 2 and 3, a phenolic antioxidant (commercial product) 0.1 part by weight of "Irganox 1010") is added, compression ratio L / D = 33, cylinder diameter 45 mm
The temperature was set to 200 ° C. using the twin-screw extruder described above, melt-kneaded, extruded in a strand form from a die, and this was cut to obtain pellets of the thermoplastic elastomer composition.

The pellets were injection molded as described above into a sheet, and the obtained sheet was subjected to the above evaluation.
The evaluation results are shown in Tables 2 and 3. From the results of Examples 1 to 10 shown in Table 2, the thermoplastic elastomer composition of the present invention has flexibility, rubber elasticity, heat resistance, mechanical strength, and molding process as compared with Comparative Examples 1 to 11 shown in Table 3. It has an excellent balance of properties and there is no bleeding of the softening agent.
It can be seen that by mixing the components, the fluidity and the moldability are excellent.

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

[Table 5]

[0053]

The thermoplastic elastomer composition of the present invention is excellent in flexibility, rubber elasticity, heat resistance, mechanical strength and moldability.

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Claims (2)

(57) [Claims] 1. (a) Monovinyl-substituted aromatic hydrocarbon polymer block (A) and conjugated diene polymer block (B)
Hydrogenated block copolymer in which the double bond of the conjugated diene polymer block (B) part of the copolymer consisting of is hydrogenated block copolymer: 30 to 60% by weight. -BA is a hydrogenated triblock copolymer in which the double bond of the conjugated diene polymer block (B) portion of the triblock copolymer represented by -BA is hydrogenated and has a weight average molecular weight of 100,000 to 40.
The content of the polymer block (A) in the copolymer is 20
To 40 wt% of the copolymer, and (a-2) a hydrogenated diblock in which the double bond of the conjugated diene polymer block (B) portion of the diblock copolymer represented by AB is hydrogenated. The copolymer is a copolymer having a weight average molecular weight of 30,000 to 200,000 and a content of the polymer block (A) in the copolymer of 5 to 20% by weight, and its composition ratio (weight ratio) is (I-
1) component / (a-2) component = 99/1 to 80/20. (B) Hydrocarbon rubber softening agent: 70 to 40% by weight (c) Olefin polymer: 1 to 100 parts by weight based on 100 parts by weight of the above components (a) and (b). A thermoplastic elastomer composition obtained by the method. 2. The thermoplastic elastomer composition according to claim 1, wherein the component (c) is an ethylene polymer and / or a propylene polymer.