JP2000136284A - Olefin-based thermoplastic elastomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an olefin-based thermoplastic elastomer having excellent balance of moldability and mechanical properties such as tensile properties and impact resistance. SOLUTION: This thermoplastic elastomer is composed of following components A and B and is obtained by dynamically heat-treating a composition produced by polymerizing the component B after a polymerization of the component A in the presence of an organic peroxide and making a gel fraction in the component B 5-70%. (A) A homopolymer of propylene having >=85% isotactic index or a copolymer component of propylene and a 2-8C other α-olefin, in an amount of 30-70 wt.% based on whole of the composition. (B) A copolymer component comprising a copolymer of propylene and 2-8C other α-olefins, containing propylene and ethylene as essential components and a content of α-olefins other than propylene is 30-70 wt.%, in an amount of 70-30 wt.% based on whole of the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an olefin-based thermoplastic elastomer having an excellent balance between moldability and mechanical properties such as tensile properties and impact resistance.

[0002]

2. Description of the Related Art In recent years, a styrene-based, olefin-based, polyester-based, soft rubber-like material that does not require a vulcanizing step and has the same moldability as a thermoplastic resin.
Polyamide-based, polyurethane-based thermoplastic elastomers are attracting attention from the viewpoint of process rationalization and recycling,
It is widely used in the fields of automobile parts, home appliance parts, medical equipment parts, electric wires, and miscellaneous goods. Among them, crystalline propylene polymer resin and ethylene-propylene copolymer rubber or ethylene-propylene-non- Mixtures with olefinic copolymer rubbers such as conjugated diene copolymer rubbers, or olefinic thermoplastics that are dynamically heat-treated in the presence of organic peroxides to crosslink the latter rubber to form partially crosslinked products Elastomers are attracting attention as economically advantageous materials because they are relatively inexpensive.

However, since this olefin-based thermoplastic elastomer is a mixture, it is easy for the rubber to be coarsely or unevenly dispersed. Therefore, the olefin-based thermoplastic elastomer is molded and processed as compared with other thermoplastic elastomers or conventional vulcanized rubber. There is an inherent problem that the balance between the mechanical properties such as tensile properties and impact resistance is poor.

On the other hand, in order to solve these problems, a method of producing a composition of a crystalline propylene polymer resin and an ethylene-propylene copolymer rubber by polymerization has been proposed. JP-A-3-20543
No. 9 discloses that (A) 10 to 60 parts by weight of a crystalline homopolymer or copolymer of propylene, (B-1) 10 to 40 parts by weight of a crystalline propylene-ethylene copolymer component,
(B-2) Amorphous propylene-ethylene copolymer component 3
An elasto-plastic polypropylene composition produced by sequential polymerization of 0 to 60 parts by weight is disclosed in
No. 7 discloses that (A) 10 to 50 parts by weight of a crystalline homopolymer or copolymer of propylene, (B-1) 5 to 20 parts by weight of a crystalline propylene-ethylene copolymer component,
-2) Amorphous propylene-ethylene copolymer component 40 to
Elastoplastic polypropylene compositions prepared by sequential polymerization of 80 parts by weight are each described.

However, according to the study of the present inventors, all compositions cannot always sufficiently improve the balance between moldability and mechanical properties such as tensile properties and impact resistance. Turned out not to be.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and therefore, the present invention provides a balance between molding workability and mechanical properties such as tensile properties and impact resistance. An object is to provide an excellent olefin-based thermoplastic elastomer.

[0007]

Means for Solving the Problems The present invention provides the following (A)
A composition comprising the component and the component (B), wherein the composition produced by the polymerization of the component (B) after the polymerization of the component (A) is dynamically heat-treated in the presence of an organic peroxide; ) An olefin-based thermoplastic elastomer having a gel content of 5 to 70% in the component. (A) an isotactic index of 85% or more,
Homopolymer of propylene or a copolymer component of propylene and another α-olefin having 2 to 8 carbon atoms; 30 to 70% by weight based on the whole composition (B) Propylene and ethylene are essential components A copolymer component comprising a copolymer of propylene and another α-olefin having 2 to 8 carbon atoms, wherein the content of α-olefin other than propylene is 30 to 70% by weight; the entire composition 70-30% by weight

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION One of the components (A) constituting the olefin-based thermoplastic elastomer composition of the present invention is a propylene homopolymer or propylene having an isotactic index of 85% or more, It is composed of a copolymer with another α-olefin having 2 to 8 carbon atoms, and among them, a homopolymer of propylene is preferable, and the isotactic index is preferably 90% or more. If the isotactic index of the component (A) is less than the above range, the balance between moldability and tensile properties of the thermoplastic elastomer of the composition will be poor.

Here, propylene and C 2 -C 8
Examples of other α-olefins in the copolymer with other α-olefins include ethylene, butene-1, 3
-Methylbutene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and the like. Among them, ethylene is preferable, and α-olefin other than propylene in the copolymer is used. The content is preferably at most 7% by weight.

The other component (B) constituting the composition of the olefinic thermoplastic elastomer of the present invention comprises propylene and ethylene as essential components, and propylene and other α-olefins having 2 to 8 carbon atoms. It consists of a copolymer with an olefin, and among them, a copolymer of propylene and ethylene is preferable.

Here, as the other α-olefin having 2 to 8 carbon atoms, the same as the above-mentioned component (A) can be mentioned.
The olefin content must be between 30 and 70% by weight; When the content of the α-olefin other than propylene in the component (B) is less than or greater than the above range, the balance between moldability and mechanical properties of the thermoplastic elastomer of the composition is inferior.

The component (B) further comprises 1,4-
Hexadiene, 5-methyl-1,5-hexadiene,
1,4-octadiene, cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-
Non-conjugated dienes such as 2-norbornene, 5-butylidene-2-norbornene and 2-isopropenyl-5-norbornene may be copolymerized in component (B) in an amount of 0.5 to 10% by weight. .

In the olefin thermoplastic elastomer composition of the present invention, the component (A) comprises 30 to 70% by weight, the component (B) comprises 70 to 30% by weight, and the component (A) comprises 40 to 60% by weight, and the component (B) is 60% by weight.
It is preferably from 40 to 40% by weight.

When the component (A) is less than the above range and the component (B) is above the above range, the moldability of the composition as a thermoplastic elastomer is inferior. If the component (B) is less than the above range, it is difficult to improve the balance between the formability and the impact resistance.

The olefin-based thermoplastic elastomer of the present invention comprises a composition produced by polymerizing the component (A) after the polymerization of the component (A), and the catalyst used in the sequential polymerization is an organic compound. An aluminum compound;
It is composed of a titanium atom, a magnesium atom, a halogen atom, and a solid component essentially including an electron donating compound.

Here, as the organoaluminum compound, a compound represented by the general formula R ¹ _m AlX
_3-m (wherein, R ¹ is a hydrocarbon residue having 1 to 12 carbon atoms, X
Represents a halogen atom, and m is a number of 1 to 3. For example, trialkylaluminums such as trimethylaluminum and triethylaluminum, dialkylaluminum halides such as dimethylaluminum chloride and diethylaluminum chloride, alkylaluminum sesquichlorides such as methylaluminum sesquichloride and ethylaluminum sesquichloride, and methyl Examples thereof include alkylaluminum dihalides such as aluminum dichloride and ethylaluminum dichloride, and alkylaluminum hydrides such as diethylaluminum hydride.

Further, as a solid component essentially containing a titanium atom, a magnesium atom, a halogen atom, and an electron-donating compound, a titanium compound which is also known in this kind of polymerization and which serves as a source of a titanium atom includes: General formula Ti (OR ² ) _4-n X _n (wherein R ² has 1 to 10 carbon atoms)
X represents a halogen atom, and n represents 0 to 4
Is the number of Among them, titanium tetrachloride, tetraethoxytitanium, tetrabutoxytitanium and the like are preferable, and as a magnesium compound serving as a source of a magnesium atom, for example, dialkylmagnesium, magnesium dihalide, Examples thereof include alkoxymagnesium and alkoxymagnesium halide, among which magnesium dihalide and the like are preferable. Incidentally, examples of the halogen atom include fluorine, chlorine, bromine and iodine. Among them, chlorine is preferable, and these are usually supplied from the titanium compound or the magnesium compound.
It may be supplied from other halogen sources such as aluminum halide, silicon halide and tungsten halide.

Examples of the electron donating compound include alcohols, phenols, ketones, aldehydes, carboxylic acids, oxygen-containing compounds such as organic acids and inorganic acids and derivatives thereof, ammonia, amines, nitriles, isocyanates, and the like. Among them, nitrogen-containing compounds and the like, among which inorganic acid esters, organic acid esters, organic acid halides and the like are preferable,
Silicates, phthalates, cellosolve acetates, phthalic halides and the like are more preferred, and the compounds represented by the general formula R ³
R ⁴ _3-p Si (OR ⁵ ) _p (wherein R ³ has ³ to 2 carbon atoms)
0, preferably 4 to 10 branched aliphatic hydrocarbon residues,
Or a cyclic aliphatic hydrocarbon residue having 5 to 20 carbon atoms, preferably 6 to 10 carbon atoms, and R ⁴ is a branched or straight-chain aliphatic hydrocarbon residue having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. R ⁵ represents an aliphatic hydrocarbon residue having 1 to 10, preferably 1 to 4 carbon atoms, and p is a number of 1 to 3. )), For example, t-butyl-methyl-dimethoxysilane, t-butyl-methyl-diethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-methyl-diethoxysilane and the like are particularly preferable.

In the method for producing the composition constituting the olefin-based thermoplastic elastomer of the present invention, in the first step, propylene or propylene and another α-C 2-8
The olefin is fed and the temperature is reduced to 50 to 50 in the presence of the catalyst.
150 ° C, preferably 50-100 ° C, partial pressure of propylene 0.5-4.5 MPa, preferably 1.0-3.5 M
Under the conditions of Pa, a propylene homopolymer or a propylene-α-olefin copolymer is polymerized to produce the component (A). Subsequently, in the second step, propylene and ethylene, or propylene and Ethylene and an α-olefin having 4 to 8 carbon atoms are supplied at a temperature of 5 in the presence of the catalyst.
A propylene-ethylene copolymer or propylene under the conditions of 0 to 150 ° C, preferably 50 to 100 ° C, and a partial pressure of propylene and ethylene of 0.3 to 4.5 MPa, preferably 0.5 to 3.5 MPa. The polymerization of the ethylene-α-olefin copolymer to produce the component (B).

The polymerization at this time may be any of a batch system, a continuous system, and a semi-batch system, and the first stage polymerization is preferably performed in a gas phase or a liquid phase, particularly preferably in a gas phase. ,
Also, the second stage polymerization is preferably carried out in the gas phase,
The residence time at each stage is 0.5 to 10 hours, preferably 1 to 5 hours.

In order to impart fluidity by eliminating stickiness and the like to the powder particles of the composition produced by the above-mentioned method, after the polymerization of the component (A) in the first step, the ( Before or during the polymerization of the component (B), an active hydrogen-containing compound is added to the solid component of the catalyst in an amount of 10 to titanium atoms.
It is preferably added in an amount of 0 to 1000 times the molar amount and 2 to 5 times the molar amount of the organic aluminum compound of the catalyst.

Here, examples of the active hydrogen-containing compound include water, alcohols, phenols, aldehydes, carboxylic acids, acid amides, ammonia, amines and the like.

The olefin-based thermoplastic elastomer of the present invention is obtained by dynamically heat-treating a composition comprising the component (A) and the component (B) in the presence of an organic peroxide.
The gel content in the component is 5 to 70%, and it is preferable that a polyene compound is further present during the dynamic heat treatment.

Here, the dynamic heat treatment means that the composition is kneaded in a molten state using a kneading apparatus such as a mixing roll, a kneader, a Banbury mixer, a Brabender plastograph, a single-screw or twin-screw extruder. And usually 100 to 350 ° C., preferably 120 to 28 ° C.
At a temperature of 0 ° C. for 0.2-30 minutes, preferably 0.5-2
Performed for 0 minutes.

In the present invention, a twin-screw extruder is preferred among the kneading apparatuses. In the twin screw extruder, the ratio of the screw length (L) to the screw diameter (D) (L /
D), the kneading characteristics are different depending on the biaxial rotation direction, the biaxial meshing mode (for example, separation type, contact type, partial meshing type, full meshing type, etc.). It is preferable that D is 10 to 100, the rotation direction is the same direction, the meshing form is a partial or complete meshing type.

The composition and the organic peroxide or the polyene compound are added to the kneading apparatus in the following order. Furthermore, a method of adding a polyene compound, melt kneading the composition in advance, and a method of adding an organic peroxide or a polyene compound further melt-kneaded thereto and the like, any method may be used, A preferred method is to melt knead the composition in advance and then add an organic peroxide or a polyene compound.

In the present invention, the organic peroxide used at the time of the dynamic heat treatment is, for example, an organic peroxide generally used in the production of a conventional partially crosslinked olefin-based thermoplastic elastomer. Di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5
Dialkyl peroxides such as -di (t-butylperoxy) hexine-3, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl- Peroxyesters such as 2,5-di (benzoylperoxy) hexine-3; diacyl peroxides such as benzoyl peroxide; hydroperoxides such as diisopropylbenzene hydroperoxide; Peroxides are preferred, and di-t-butyl peroxide is particularly preferred.

As the polyene compound, specifically,
For example, divinylbenzene, metaphenylene bismaleimide, quinone dioxime, 1,2-polybutadiene, triallyl cyanurate, triallyl isocyanurate,
Diallyl phthalate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate and the like,
Among them, divinylbenzene, triallyl cyanurate and triallyl isocyanurate are preferred.

The amount of the organic peroxide and polyene compound used is about 0.05 to 5 parts by weight, particularly about 0.2 to 3 parts by weight, based on 100 parts by weight of the composition. It is preferred that

The olefin-based thermoplastic elastomer of the present invention is characterized in that the composition comprising the components (A) and (B) is mixed with the organic peroxide, preferably the polyene compound,
(B) is a partially crosslinked product in which the gel content in the component (B) has been reduced to 5 to 70% by performing a crosslinking reaction in the component (B) by the dynamic heat treatment.
When the gel content of the component (B) is less than the above range, the balance between the moldability and the mechanical properties is not sufficiently improved. On the other hand, when the content exceeds the above range, the impact resistance is poor.

The olefin-based thermoplastic elastomer of the present invention has a melt flow rate of 3 to 50 measured at a temperature of 230 ° C. under a load of 5.0 kg according to JIS K7210.
g / 10 minutes, which is excellent in moldability.

The olefin-based thermoplastic elastomer of the present invention may be blended with a rubber softening agent which is usually blended to impart processability, flexibility and the like to the thermoplastic elastomer. The rubber softener is particularly preferably a mineral oil-based softener, which is generally a mixture of an aromatic ring, a naphthene ring, and a paraffin chain,
A paraffinic system in which the number of carbon atoms in the paraffin chain accounts for 50% or more of the total number of carbon atoms, a naphthenic system in which the number of carbon atoms in the naphthene ring accounts for 30 to 40% of the total number of carbon atoms, Although it is classified into an aromatic type which accounts for 30% or more of the number, a paraffin type is particularly preferred in the present invention.

The olefin-based thermoplastic elastomer of the present invention further includes various resins, rubbers, glass fibers, fillers such as calcium carbonate, silica, talc, mica and clay, antioxidants, light stabilizers, Various additives such as an inhibitor, a lubricant, a dispersant, a neutralizer, and a flame retardant, and a pigment such as carbon black may be blended as necessary.

The olefin-based thermoplastic elastomer of the present invention can be obtained as a simple substance or as a laminate with other materials by various molding methods applied to the thermoplastic elastomer, such as extrusion molding, injection molding, and compression molding. It is shaped into a desired shape to obtain a molded body.

[0035]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Example 1 1) Production of solid component catalyst 20 liters of dehydrated and deoxygenated n-heptane was introduced into a 50-liter tank equipped with a stirrer and purged with nitrogen, and then 4 mol of magnesium chloride and tetrabutoxytitanium 8
After reacting at 95 ° C. for 2 hours with the introduction of a mole, the temperature was lowered to 40 ° C., and methylhydropolysiloxane (viscosity of 20
After 480 ml of centistokes were introduced and allowed to react for another 3 hours, the reaction solution was taken out and the resulting solid component was washed with n-heptane.

Subsequently, 15 liters of dehydrated and deoxygenated n-heptane were introduced into the tank using the above-mentioned tank with a stirrer, and then 3 mol of the obtained solid component was introduced in terms of magnesium atom. A mixture obtained by adding 8 mol of silicon chloride to 25 ml of n-heptane was introduced at 30 ° C. over 30 minutes, the temperature was raised to 90 ° C., and the reaction was carried out for 1 hour. Was washed with n-heptane.

Subsequently, 5 liters of dehydrated and deoxygenated n-heptane were introduced into the tank using the tank equipped with a stirrer, and then the titanium-containing solid component 250 obtained above was added.
g, 750 g of 1,5-hexadiene, 130 ml of t-butyl-methyl-dimethoxysilane, 10 ml of divinyldimethylsilane, and 225 g of triethylaluminum were brought into contact with each other at 30 ° C. for 2 hours, and then the reaction solution was taken out. , N-heptane to obtain a solid component catalyst. The resulting solid component catalyst was 1,5
-The prepolymerization amount of hexadiene was 2.97 g per titanium-containing solid component.

2) Preparation of Composition A first-stage reactor having an inner volume of 550 liters was heated to 70 ° C.
And propylene and a pressure of about 3.2 MPa.
Triethylaluminum and polymer formation rate is 30
kg / hour of the solid component catalyst was continuously supplied, and further, hydrogen as a molecular weight controlling agent was continuously supplied to carry out polymerization in a liquid phase (first stage polymerization). ).

Subsequently, the produced polymer is introduced into a second-stage reactor having an internal volume of 1900 liters via a propylene purge tank, and the produced polymer is produced at a temperature of 60 ° C. and a pressure of 3.0 MPa. A solid component catalyst that continuously supplies propylene and ethylene according to the composition ratio in the polymer, further continuously supplies hydrogen as a molecular weight controlling agent, and supplies an active hydrogen compound in the first stage. The polymerization was carried out in the gas phase by supplying 200 moles per mole of titanium atoms and 2.5 moles per mole of triethylaluminum, and the resulting polymer was continuously transferred to a vessel. Then, the reaction was stopped by introducing nitrogen gas containing water (second stage polymerization).

3) Analysis of the composition The obtained composition was subjected to the following method to determine the weight ratio of the component (A) to the whole composition, the isotactic index of the component (A), and the component (B). , And the content of α-olefins (ethylene) other than propylene in the component (B) were calculated. As a result, the weight ratio of the component (A) was 45% by weight, the isotactic index was 98%, the weight ratio of the component (B) was 55% by weight, and the ethylene content was 43% by weight.

With respect to the entire composition of the component (A) and the component (B),
Weight ratio of the component (B) to the total composition [B
(%). ] Was calculated from the weight of the obtained polymer composition and the weights of propylene and ethylene supplied in the second stage polymerization. From this, the weight ratio of the component (A) to the entire composition [this is defined as A (%). ]
It was calculated by “100-B”.

Isotactic index of component (A)
It was measured as a Soxhlet extraction residue with sn-heptane. Ethylene content in component (B) Ethylene content of the polymer produced after the first stage polymerization [this is referred to as E _A %. And the ethylene content of the resulting polymer composition [this is referred to as E _{A + B} (%). ] Were respectively measured by infrared spectroscopy, and were calculated by the following equations. _{[E A + B -E A × (} A / A + B) ] / (B / A + B)

4) Dynamic heat treatment of the composition Tetrakis [methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane and tris (4-t
-Butyl-2,6-dimethyl-3-hydroxybenzyl) isocyanurate was added in an amount of 0.25 part by weight based on 100 parts by weight of the composition. ° C, rotation speed 200rpm
After melt-kneading for 2 minutes, di-t-
1 part by weight of butyl peroxide and 1 part by weight of triallyl cyanurate as a polyene compound were added, respectively, and the mixture was melt-kneaded for further 5 minutes to dynamically heat-treat to produce an olefin-based thermoplastic elastomer.

5) Measurement of Physical Properties of Thermoplastic Elastomer
The gel fraction, melt flow rate, tensile properties, and impact resistance were measured by the methods described below, and the results are shown in Table 1.

Gel fraction The obtained thermoplastic elastomer was subjected to Soxhlet extraction with boiling cyclohexane for 12 hours, and was calculated as an insoluble content after extraction of the component (B) in the thermoplastic elastomer. Melt flow rate According to JIS K7210, temperature 230 ° C, load 5.
It was measured at 0 kg.

Tensile Characteristics Using a test piece melted and injection molded at 230 ° C. with a minimax small-sized injection molding machine, in accordance with JIS K7113,
Using No. 2 test piece, temperature 23 ° C, tensile speed 50mm
/ Min, the tensile yield point strength, tensile break strength, and tensile break elongation were measured. In accordance with JIS K7110, using a test piece that was melted and injection-molded at 230 ° C. using a minimax small-sized injection molding machine with impact strength ,
At a temperature of −50 ° C., the notched Izod impact strength was measured.

Examples 2 to 4 and Comparative Examples 1 to 2 The same procedures as in Example 1 were carried out except that the amounts of the organic peroxide and the polyene compound added during the dynamic heat treatment were changed as shown in Table 1. An olefin-based thermoplastic elastomer was produced, and various physical properties were measured. The results are shown in Table 1.

Comparative Examples 3 and 4 As compositions, a propylene homopolymer resin ("Novatech PP TA3" manufactured by Nippon Polychem Co., Ltd., indicated as "PP" in the table) and a propylene-ethylene copolymer rubber (Nippon Synthetic Rubber) An olefin-based thermoplastic elastomer was produced in the same manner as in Example 1 except that a mixture of “EP07P” (manufactured by Sharp Corporation and “EPR” in the table) was used in the ratio shown in Table 1. The measurements were made and the results are shown in Table 1.

[0049]

[Table 1]

[0050]

According to the present invention, it is possible to provide an olefin-based thermoplastic elastomer having an excellent balance between moldability and mechanical properties such as tensile properties and impact resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F070 AA15 AA16 AB16 AC32 AC43 AC45 AC48 AC56 AC63 AC75 AE08 GA05 GA08 GA10 GC01 GC05 GC08 4J002 BB12W BB15X BP02W EK016 EK036 EK046 EK056 FD146 GB01 GC00 GN00 HA04B03 HA3 HB27 HB35 HB38 HB42 HB45 HB46 HB48 HB50 HE06 4J100 AA02Q AA03P AA04Q AA07Q AA09Q AA16Q AA17Q AA19Q AR17R AR18R AS01R AS15R CA01 CA04 CA05 DA41

Claims (3)

[Claims] 1. A composition comprising the following components (A) and (B), and produced by polymerizing the component (B) after the polymerization of the component (A), to obtain a composition containing an organic peroxide. An olefin-based thermoplastic elastomer, wherein the gel content in the component (B) is reduced to 5 to 70% by dynamically heat-treating the same. (A) an isotactic index of 85% or more,
Homopolymer of propylene or a copolymer component of propylene and another α-olefin having 2 to 8 carbon atoms; 30 to 70% by weight based on the whole composition (B) Propylene and ethylene are essential components A copolymer component comprising a copolymer of propylene and another α-olefin having 2 to 8 carbon atoms, wherein the content of α-olefin other than propylene is 30 to 70% by weight; the entire composition 70-30% by weight 2. The olefin-based thermoplastic elastomer according to claim 1, wherein the component (A) is a propylene homopolymer, and the component (B) is a copolymer of propylene and ethylene. 3. The olefin-based thermoplastic elastomer according to claim 1, which is further subjected to dynamic heat treatment in the presence of a polyene compound.