JPH10287776A - Partially crosslinked thermoplastic elastomer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a partially crosslinked thermoplastic elastomer compsn. which has improved processibility and degradation resistance and excellent mechanical properties and moldability by crosslinking a compsn. comprising a metallocene-catalyzed ethylene/α-olefin elastomer, a low-mol.-wt. ethylene polymer, a propylene polymer, and an oil. SOLUTION: An ethylene/6-12C α-olefin elastomer having a density of 0.8-0.9 g/cm<3> and a ratio of wt. average mol.wt. to number average mol.wt. (by GPC) lower than 3 is used as the ethylene/α-olefin elastomer. A compsn. comprising 100 pts.wt. ethylene/α-olefin elastomer, 5-100 pts.wt. low-mol.-wt. ethylene polymer having a number average mol.wt. of 20,000 or lower, 5-90 pts.wt. propylene polymer, and 5-250 pts.wt. oil for rubber is crosslinked with a free-radical initiator and a crosslinking aid to give the objective partially crosslinked thermoplastic elastomer compsn. Pref., the degree of crosslinking is 30-80%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partially crosslinked thermoplastic elastomer composition which is excellent in environmental degradation resistance and mechanical properties and is useful for automobile parts and the like.

[0002]

2. Description of the Related Art A so-called dynamic crosslinking is carried out by melt-kneading a radically crosslinkable olefin elastomer and an olefin resin having no radical crosslinkability such as polypropylene (PP) in an extruder in the presence of a radical initiator. The thermoplastic elastomer composition by crosslinking is a known technique, and is widely used for applications such as automobile parts.

[0003] Conventionally, this thermoplastic elastomer composition contains ethylene-
Propylene-diene rubber (EPDM) has been used. The diene component in the polymer chain is necessary to improve the crosslinkability, but the diene component makes the environmental degradation resistance insufficient, and improvement in quality has been desired. In addition, EPDM is usually produced using a Ziegler catalyst, but the polymer structure of pellets is limited, and EPDM having other structures is veiled, which is not preferable because it is complicated to handle. Further, even in the form of pellets, there is a problem of blocking caused by the ultra-low molecular weight component, which is also not preferable.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoplastic elastomer composition which has improved processability and environmental degradation resistance, which are problems of conventional olefin elastomers, and has excellent mechanical properties. Is to do. In particular, it is to provide a composition having excellent moldability.

[0005]

In recent years, various polymers have been developed with metallocene catalysts.
The present inventors have found that an olefin elastomer having a specific structure comprising ethylene and an α-olefin produced by a metallocene catalyst has extremely excellent radical crosslinking properties, has flexibility, and solves all of the above problems. The present inventors have found that the composition has the properties to be obtained, and that a composition controlled to a specific range of the degree of crosslinking by adding a low molecular weight ethylene-based polymer has excellent moldability, thereby completing the present invention.

That is, the present invention is as follows. [1] (1) It comprises ethylene and at least one or more α-olefins having 6 to 12 carbon atoms, and has a density of 0.8.
In the range of 0.9 g / cm ^3, and the ratio a is the molecular weight distribution of the gel permeation chromatography weight average molecular weight calculated by (GPC) (Mw) to the number average molecular weight (Mn) (Mw / Mn) Is less than 3.0, 100 parts by weight of an olefin elastomer, (2) a low molecular weight ethylene polymer having a number average molecular weight of 20,000 or less.
A mixture consisting of 100 parts by weight, (3) 5-90 parts by weight of a propylene-based polymer, and (4) 5-250 parts by weight of a rubber oil is crosslinked with a radical initiator or a radical initiator and a crosslinking assistant. Partially crosslinked thermoplastic elastomer composition comprising:

[2] The partially crosslinked thermoplastic elastomer composition according to the above [1], wherein the olefin-based elastomer is produced using a metallocene-based catalyst. [3] The partially crosslinked thermoplastic elastomer composition according to the above [1] or [2], wherein the degree of crosslinking is 30 to 80%.

[4] The partially crosslinked thermoplastic elastomer composition according to the above [1], [2] or [3], wherein the surface hardness A type specified in ASTM D2240 is 90 or less. Hereinafter, the present invention will be described in detail. (Olefin-based elastomer) The olefin-based elastomer which is a main component constituting the thermoplastic elastomer composition of the present invention is a copolymer of ethylene and at least one or more α-olefins having 6 to 12 carbon atoms, Molecular weight distribution (Mw / Mn) having a density of 0.8 to 0.9 g / cm ³ and a ratio between a weight average molecular weight (Mw) and a number average molecular weight (Mn) calculated by gel permeation chromatography (GPC). Is less than 3.0.

As the α-olefin having 6 to 12 carbon atoms, for example, hexene-1,4-methylpentene-1,
Heptene-1, octene-1, nonene-1, decene-
1, undecene-1, dodecene-1 and the like. The olefin elastomer used in the present invention may be any known olefin elastomer as long as it is as described above, and among them, those produced with a metallocene catalyst are preferable.

The metallocene-based catalyst is composed of a cyclopentadienyl derivative of a group IV metal such as titanium or zirconium and a co-catalyst, and is not only highly active as a polymerization catalyst, but also compared with a conventional catalyst such as a Ziegler-based catalyst. do it,
The molecular weight distribution of the obtained polymer is narrow, and the distribution of the comonomer α-olefin having 6 to 12 carbon atoms in the copolymer is uniform.

The olefin elastomer produced by using the metallocene catalyst has a different polymerization catalyst as compared with the conventional one using a Ziegler catalyst or the like, and the properties of the obtained polymer are greatly different from those of the conventional one. ing. The characteristics of the olefin elastomer composed of ethylene and α-olefin using a metallocene polymerization catalyst include, for example, the following points.

1. Since the polymerization catalyst has high activity, the composition of the comonomer α-olefin can be greatly increased as compared with the conventional one, and an elastomeric polymer having high flexibility can be obtained even without a plasticizer. 2. The comonomer distribution is uniform compared to Ziegler-based polymers. 3. Compared with Ziegler-based polymers, the molecular weight distribution is extremely sharp, the amount of low molecular weight components is extremely small, the mechanical strength and workability are excellent, and the quality is high.

4. ASTM D123 when long-chain branching was introduced despite the sharp molecular weight distribution
Melt index (I10) at 190 ° C./10 kgf specified by No. 8 and 190 ° C./2.16 kg
f to the melt index (I2) (I10
/ I2) has a large value and is excellent in processing characteristics. 5. Contains no diene component and has excellent environmental degradation resistance.

6. Even if the α-olefin copolymerization ratio is high, blocking hardly occurs and a pellet-like form is possible. In the case of an olefin-based elastomer which is a copolymer of ethylene and an α-olefin using a Ziegler catalyst, the above-mentioned melt index ratio (I10 / I2) and the molecular weight distribution show a substantially linear proportional relationship, and the molecular weight increases as the melt index ratio increases. The distribution also tends to increase. The molecular weight distribution is usually about 3 to 10.

On the other hand, in the case of an olefin polymer using a metallocene catalyst, the molecular weight distribution becomes a sharp value of less than 3.0, and the low molecular weight component is extremely small, regardless of the value of the melt index ratio. Therefore, the workability is extremely excellent. The molecular weight distribution (Mw / Mn) of these olefinic elastomers is calculated by GPC. The GPC device and the measuring method are not particularly limited,
In the present invention, the following apparatus and measuring method were used. 1. Equipment: Waters 150C GPC Column: SHOdex AT-807S 1 Tosoh TSK-GEL GMH-H6 2 3 in total 3. Solvent: 1,2,4-trichlorobenzene Measurement temperature: 140 ° C 5. Standard substance; polystyrene The density is preferably in the range of 0.8 to 0.9 g / cm ³ . By using an olefin elastomer having a density in this range, a thermoplastic elastomer composition having excellent flexibility and low hardness can be obtained.

The olefin elastomer used in the present invention has a melt index of 0.01 to 100.
g / 10 minutes (190 ° C., 2.16 kg load) are preferably used, and more preferably 0.2 to 10 g.
/ 10 minutes. If the amount exceeds 100 g / 10 minutes, the crosslinkability of the thermoplastic elastomer composition is not necessarily sufficient. If the amount is less than 0.01 g / 10 minutes, the fluidity tends to decrease and the processability tends to decrease. .

Surprisingly, the olefin-based elastomer having a specific structure as described above has excellent radical cross-linking properties comparable to conventional EPDM, and the cross-linking of the thermoplastic elastomer composition by dynamic cross-linking. It is the most suitable polymer as the reactive elastomer component. The olefin-based elastomer used in the present invention may be a mixture of a plurality of types, and it is possible to further improve processability.

The olefin elastomer comprising ethylene produced by a metallocene catalyst and at least one α-olefin having 6 to 12 carbon atoms includes:
Products such as "Engage" from DuPont Dow Elastomers are known. (Low molecular weight ethylene polymer) The low molecular weight ethylene polymer used in the present invention has a number average molecular weight of 20,000.
These are the following polymers. As the type of the polymer, for example,
Ethylene-vinyl ester copolymers such as polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymers such as ethylene-ethyl acrylate copolymer, ethylene-vinyl Alcohol copolymers and the like. Among them, an ethylene-α-olefin copolymer has excellent flexibility and is suitable without impairing the physical properties of the elastomer composition. Here, the α-olefin preferably has 3 to 12 carbon atoms.

The number average molecular weight is calculated by GPC.
The same GPC apparatus and measuring method as those used in the measurement of the molecular weight distribution of the olefin-based elastomer described above were used. The value obtained under these conditions is expressed in terms of the polyethylene conversion coefficient (0.4
Multiplied by 3) to obtain the number average molecular weight of the present invention. Such a low molecular weight ethylene polymer is well compatible with the olefin elastomer, under the dynamic crosslinking environment of the present invention,
The fluidity is not greatly reduced, and the degree of crosslinking of the olefin-based elastomer can be adjusted according to the amount added. That is, by changing the amount of the low molecular weight ethylene polymer in the range of 5 to 100 parts by weight, the degree of crosslinking of the olefin elastomer can be adjusted to 30 to 80% based on the weight of the olefin elastomer using the olefin elastomer. it can. If the amount is less than 5 parts by weight, it is not always easy to suppress the degree of crosslinking, and if it exceeds 100 parts by weight, the mechanical strength of the elastomer composition tends to decrease.

(Propylene Polymer) Specific examples of the propylene polymer used in the present invention include homo-isotactic polypropylene, propylene and ethylene, butene-1, pentene-1, hexene-1 and the like. And isotactic copolymers (including blocks and random) with other α-olefins.

At least one selected from these polymers
More than one polymer is used in a composition ratio of 5 to 90 parts by weight. If the amount is less than 5 parts by weight, the fluidity and processability of the composition decrease, and if it exceeds 90 parts by weight, the flexibility of the composition is insufficient, which is not desirable. The propylene polymer used in the present invention has a melt index of 0.1 to 100.
g / 10 min (230 ° C., 2.16 kg load) is preferably used. If the amount exceeds 100 g / 10 minutes, the heat resistance and mechanical strength of the thermoplastic elastomer composition are not necessarily sufficient. If the amount is less than 0.1 g / 10 minutes, the fluidity decreases and the moldability decreases. Tends to decrease.

(Rubber Oil) The rubber oil used in the present invention is preferably a paraffinic or naphthenic process oil. These are used in an amount of 5 to 250 parts by weight for adjusting the hardness and flexibility of the composition. If the amount is less than 5 parts by weight, flexibility and workability are insufficient. If the amount exceeds 250 parts by weight, oil bleeding becomes remarkable, which is undesirable.

The thermoplastic elastomer composition of the present invention comprises:
By combining the specific olefin-based elastomer, low-molecular-weight ethylene-based polymer, propylene-based polymer, and rubber oil described above in a specific composition ratio, mechanical strength and flexibility, the balance of processability is improved, It can be preferably used. In the thermoplastic elastomer composition of the present invention, it is necessary to partially crosslink the composition with a radical initiator such as an organic peroxide or a radical initiator and a crosslinking assistant. Thereby, it becomes possible to further improve the wear resistance, mechanical strength, heat resistance, and the like.

Here, specific examples of the radical initiator preferably used include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
1,1-bis (t-hexylperoxy) -3,3,5
-Trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-
Butylperoxy) cyclododecane, 1,1-bis (t
-Butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) octane, n-butyl-4,
Peroxy ketals such as 4-bis (t-butylperoxy) butane and n-butyl-4,4-bis (t-butylperoxy) valerate; di-t-butyl peroxide, dicumyl peroxide, t -Butylcumyl peroxide, α, α′-bis (t-butylperoxy-m
-Isopropyl) benzene, α, α'-bis (t-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane and 2,5-dimethyl-2,5 Dialkyl peroxides such as -bis (t-butylperoxy) hexine-3; acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexa Diacyl peroxides such as noyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide and m-trioyl peroxide; t-butylperoxyacetate, t
-Butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate,
Di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and cumylperoxyoctate Peroxyesters; and
Hydrogens such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and 1,1,3,3-tetramethylbutyl peroxide Peroxides can be mentioned.

Among these compounds, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl -2,5-bis (t-butylperoxy) hexane and 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3 are preferred.

These radical initiators are used in an amount of 0.02 to 3 parts by weight based on 100 parts by weight of the olefin elastomer.
Preferably it is used in an amount of 0.05 to 1 part by weight. 0.
If the amount is less than 02 parts by weight, crosslinking cannot always be said to be sufficient.
Even when the amount exceeds part by weight, further improvement in the physical properties of the composition is not so much observed. Further, as a crosslinking aid, divinylbenzene, triallyl isocyanurate, triallyl cyanurate, diacetone diacrylamide, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diisopropenylbenzene, P- quinone dioxime, P, P ^'- dibenzoyl quinone dioxime, phenylmaleimide, allyl methacrylate, N, ^N' -
m-phenylene bismaleimide, diallyl phthalate,
Tetraallyloxyethane, 1,2-polybutadiene and the like are preferably used. These crosslinking aids may be used in combination of two or more.

These crosslinking assistants are used in an amount of 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the olefin elastomer. If the amount is less than 0.1 part by weight, the crosslinking is not necessarily sufficient. If the amount exceeds 5 parts by weight, the physical properties of the composition are not further improved, and an excessive amount of the crosslinking aid tends to remain. As for the hardness of the thermoplastic elastomer composition of the present invention, the surface hardness A type defined by ASTM D2240 is preferably 90 or less. If it exceeds 90, the characteristic of the composition inherent in flexibility is not sufficiently exhibited.

If necessary, other resins and elastomers may be added to the thermoplastic elastomer composition of the present invention to such an extent that its characteristics are not impaired. Examples are polyethylene, polybutene, polyisobutene, ethylene-vinyl ester copolymers such as ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymers such as ethylene-ethyl acrylate copolymer, ethylene-vinyl alcohol There are copolymers, block copolymers composed of vinyl aromatic and conjugated dienes, and hydrogenated products of block copolymers composed of vinyl aromatic and conjugated diene.

The thermoplastic elastomer composition of the present invention can contain an inorganic filler and a plasticizer to such an extent that the characteristics thereof are not impaired. Examples of the inorganic filler used here include calcium carbonate, magnesium carbonate, silica, carbon black, glass fiber, titanium oxide, clay, mica, talc, and magnesium hydroxide. Also, as the plasticizer, for example,
Polyethylene glycol, dioctyl phthalate (DO
And phthalic acid esters such as P). Further, other additives, for example, organic / inorganic pigments, heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, flame retardants, silicone oils, and the like are also suitably used.

For the production of the thermoplastic elastomer composition of the present invention, general resins such as a Banbury mixer, a kneader, a single-screw extruder, and a twin-screw extruder used for the production of an elastomer composition are used. It is possible to adopt a method. Among them, a twin-screw extruder is preferably used.
The twin-screw extruder uniformly and finely disperses the olefin-based elastomer and the low-molecular-weight ethylene-based polymer and the propylene-based polymer, and further adds other components to cause a crosslinking reaction. It is more suitable for continuously producing an elastomer composition.

The form of the olefin-based elastomer, low-molecular-weight ethylene-based polymer, or propylene-based polymer to be used is preferably a finely divided form such as a pellet, powder, or crumb. As a specific example, the thermoplastic elastomer composition of the present invention can be produced through the following processing steps.

That is, an olefin-based elastomer, a low-molecular-weight ethylene-based polymer, and a propylene-based polymer are mixed well and then charged into a hopper of an extruder. The radical initiator and the crosslinking assistant may be added together with the olefin-based elastomer, the low-molecular-weight ethylene-based polymer, and the propylene-based polymer from the beginning, or may be added in the middle of the extruder. The rubber oil may be added from the middle of the extruder, or may be added separately at the beginning and during the middle. Some of the olefin-based elastomer, the low-molecular-weight ethylene-based polymer, and the propylene-based polymer may be partially added in the middle of the extruder. When heated and melted and kneaded in the extruder, the olefinic elastomer and the radical initiator and the cross-linking auxiliary undergo a cross-linking reaction. After sufficient time, remove from the extruder. Pellets can be obtained to obtain pellets of the thermoplastic elastomer composition of the present invention.

The degree of crosslinking is defined as a measure of the crosslinkability of the composition. 0.5 g of the thermoplastic elastomer composition of the present invention
Is refluxed for 4 hours in 200 ml of xylene. The solution is filtered through a filter paper for quantification, the residue on the filter paper is vacuum-dried, quantified, and calculated as a ratio (%) of the weight of the residue to the weight of the olefin-based elastomer in the composition. The degree of crosslinking of the thermoplastic elastomer composition of the present invention is from 30 to
Desirably, it is 80%. If it is less than 30%, crosslinking is not necessarily sufficient, and heat resistance such as compression set and physical properties such as rebound resilience tend to decrease. On the other hand, if it exceeds 80%, the moldability of the elastomer composition is reduced, and the surface of the molded product may be roughened.

From the thermoplastic elastomer composition thus obtained, various molded articles can be produced by any molding method. For example, injection molding, extrusion molding, compression molding, blow molding, calender molding, foam molding and the like are preferably used. Applications of the thermoplastic elastomer composition of the present invention include: automotive parts, automotive interior materials, airbag covers, mechanical parts, electrical parts, cables, hoses, belts,
It can be widely used for toys, miscellaneous goods, daily necessities, building materials, sheets, films, and other applications.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The evaluation methods and test methods for various physical properties are as follows. (1) Surface Hardness Four sheets having a thickness of 2 mm were piled up and evaluated according to ASTM D2240 using an A type in a 23 ° C. atmosphere.

(2) Tensile breaking strength [kgf / cm ² ] Evaluated at 23 ° C. according to JIS K6251. (3) Tensile elongation at break [%] Evaluated at 23 ° C. according to JIS K6251. (4) Compression set (C-Set) [%] Evaluated at 70 ° C. for 22 hours according to JIS K6301.

(5) Environmental Degradability Retention Rate Using a carbon arc type sunshine weather meter (manufactured by Suga Test Instruments), a black panel temperature of 63 ° C., rainfall time of 18 minutes / irradiation time of 120 was applied according to ASTM D1499.
And the tensile strength retention [%] after continuously exposing the 2 mm thick compression molded sheet for 150 hours.

(6) Formability A tubular molded product was prepared using an extruder (extrusion temperature: 220 ° C.), and the surface condition of the molded product was evaluated according to the following scale. ；: Smooth, △: Fine irregularities, X: Notable irregularities The raw materials used in Examples and Comparative Examples are as follows. 1] Component (a-1) olefin polymer; engage
8150 (manufactured by Dupont Dow Elastomers Co., Ltd., copolymer of ethylene and octene-1, α-olefin copolymerization ratio: 25% by weight, density: 0.87 g / cm ³ , Mw / M
n = 2.4, ASTM D1238 Melt Index 0.5, ASTM D2240 Hardness (Type A)
75).

2) Component (a-2) olefin polymer;
Engage 8445 (manufactured by Dupont Dow Elastomers, a copolymer of ethylene and octene-1, α-olefin copolymerization ratio: 9.5% by weight, density: 0.91 g / c)
m ³ , Mw / Mn = 2.7, ASTM D1238 melt index 3.5, ASTM D2240 hardness (type A) 96).

3) Component (a-3) Ethylene-propylene copolymer; polymerized using a Ziegler catalyst, propylene copolymerization ratio: 25% by weight, density: 0.86 g /
cm ³ , ASTM D1238 melt index
0.8, ASTM D2240 hardness (type A) 7
5. 4] Component (a-4) Ethylene-propylene-diene rubber (EPDM); polymerized using a Ziegler catalyst, propylene content: 27% by weight, diene component: ethylidene norbornene, diene content: iodine value 15, AST
MD1238 Melt Index 2, ASTM
D2240 hardness (type A) 65.

5] Component (b-1) low molecular weight ethylene-propylene copolymer; number average molecular weight 18,000, propylene content: 22% by weight 6) Component (b-2) low molecular weight ethylene-octene copolymer; number average Molecular weight 16,000, octene content: 24% by weight 7] Component (c) propylene-based polymer; isotactic polypropylene resin MA2 (manufactured by Nippon Polychem, AS
TM D1238 Melt Index 15).

8] Component (d) Paraffin oil; Diana Process Oil PW-380 (manufactured by Idemitsu Kosan Co., Ltd.) 9] Component (e) Radical initiator: 2,5-dimethyl-
2,5-bis (t-butylperoxy) hexane (trade name: Perhexa 25B, manufactured by NOF Corporation) 10] Component (f) Crosslinking aid; divinylbenzene

[0043]

Examples 1 to 4 and Comparative Examples 1 to 5 As an extruder, a twin screw extruder (40 mmφ, L /
D = 47) was used. As the screw, a double screw having a kneading portion before and after the injection port was used. After well blending pellets of the olefin-based elastomer, the low-molecular-weight ethylene-based polymer, and the propylene-based polymer shown in Table 1, the mixture is put into a hopper of a twin-screw extruder (cylinder temperature: 220 ° C.). A predetermined amount of a radical initiator and a crosslinking assistant are injected by a pump from an injection port at the center of the extruder. The mixture was heated, kneaded, crosslinked, and pelletized to obtain a composition pellet. The obtained composition pellets are again put into a hopper of a twin-screw extruder (cylinder temperature 220 ° C.). A predetermined amount of oil is injected by a pump from an injection port at the center of the extruder. The mixture was heated, kneaded, and pelletized to obtain pellets of the thermoplastic elastomer composition of the present invention.

A sheet having a thickness of 2 mm was prepared from the obtained thermoplastic elastomer composition by compression molding at 200 ° C., and each mechanical property and resistance to environmental degradation were evaluated. Table 1 shows the results.

[0045]

[Table 1]

As is clear from the results in Table 1, the thermoplastic elastomer composition provided by the present invention has good mechanical properties and resistance to environmental degradation. Comparative Example 1
Does not contain a low molecular weight ethylene polymer, has a high degree of crosslinking, and is inferior in moldability. In Comparative Example 2, it is difficult to obtain a composition having a low α-olefin copolymerization ratio, a high density and a low hardness of the olefin elastomer.

Comparative Example 3 is a composition using an ethylene-propylene copolymer, but has a lower degree of crosslinking and is inferior in compression set as compared with Example 4 having the same composition. Comparative Example 4, which is a composition using EPDM, is clearly inferior in environmental degradation resistance. Comparative Example 5, in which no radical initiator was used, had poor heat resistance, low compression set, and low environmental degradation resistance.

[0048]

Industrial Applicability The thermoplastic elastomer composition of the present invention has excellent physical properties such as resistance to environmental degradation as compared with a composition using conventional EPDM and the like, and has well-balanced mechanical properties. , Its utility value is extremely large. In particular, it has excellent moldability and can be effectively used for various applications.

Uses of the thermoplastic elastomer composition of the present invention include: automobile parts, automobile interior materials, airbag covers, mechanical parts, electric parts, cables, hoses, belts, toys, miscellaneous goods, daily necessities, building materials, sheets. , Films and other applications.

Claims (4)

[Claims] 1. (1) Gel permeation chromatography comprising ethylene and at least one α-olefin having 6 to 12 carbon atoms, having a density in the range of 0.8 to 0.9 g / cm ^3. Weight average molecular weight (Mw) and number average molecular weight (M
n) 100 parts by weight of an olefin-based elastomer having a molecular weight distribution (Mw / Mn) of less than 3.0,
A mixture comprising (2) 5 to 100 parts by weight of a low molecular weight ethylene polymer having a number average molecular weight of 20,000 or less, (3) 5 to 90 parts by weight of a propylene polymer, and (4) 5 to 250 parts by weight of a rubber oil. With a radical initiator or a radical initiator and a crosslinking assistant. 2. The partially crosslinked thermoplastic elastomer composition according to claim 1, wherein the olefin elastomer is produced using a metallocene catalyst. 3. The partially crosslinked thermoplastic elastomer composition according to claim 1, wherein the degree of crosslinking is 30 to 80%. 4. The partially crosslinked thermoplastic elastomer composition according to claim 1, wherein the surface hardness A type defined in ASTM D2240 is 90 or less.