JP6855710B2 - Thermoplastic elastomer composition - Google Patents

Description

The present invention relates to a thermoplastic elastomer composition capable of providing a molded product having excellent appearance, low temperature impact resistance and tensile fracture elongation, and an airbag storage cover and an automobile interior material made of this thermoplastic elastomer composition.

The airbag system for automobiles is a system that protects drivers and passengers in the event of a collision of automobiles, etc., and is a collision detection device that detects the impact in the event of a collision and air in response to the collision detection of this collision detection device. It has an airbag device that operates to inflate the bag. The airbag device is installed on the steering wheel, the instrument panel in front of the passenger seat, the driver's seat and the passenger seat, the front and side pillars, and the like.

Various proposals have been made for the structure and material of the airbag storage cover in the airbag device so that the airbag storage cover can be cleaved as designed in a wide temperature range from low temperature to high temperature.

Conventionally, as a material for an airbag storage cover, for example, in Patent Document 1, a material composed of a hydrogenated additive of a styrene-conjugated diene block copolymer, a plasticizer for rubber, an olefin resin and an additive has been proposed. .. Further, Patent Documents 2 to 4 propose one composed of a propylene-based resin, an ethylene / α-olefin copolymer, and a styrene-based elastomer. Further, Patent Document 5 proposes an olefin-based elastomer, a propylene-based resin, and an ethylene-α / olefin copolymer. Further, Patent Document 6 proposes a propylene resin produced by multistage polymerization and an ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber.

Japanese Unexamined Patent Publication No. 5-38996 Japanese Unexamined Patent Publication No. 10-265628 Japanese Unexamined Patent Publication No. 2000-096752 Japanese Unexamined Patent Publication No. 2000-324901 Japanese Unexamined Patent Publication No. 2002-194088 Japanese Unexamined Patent Publication No. 2008-45037

In recent years, due to the flexibility of the instrument panel due to the upgrade of automobiles, the airbag storage cover and the instrument panel are deformed during the deployment test, and the airbag storage cover is damaged in the low temperature range due to the improvement of the airbag deployment output. There is concern. In addition, paint-less airbag cover materials are increasing in order to reduce the manufacturing process. Based on the above, from the perspective of enhancing safety, designing freedom, and reducing costs by reducing the insertion molding process of metal plates and nylon raw cloth, airbag storage covers, especially airbags for passenger seats, are used. It is desired to improve the appearance, tensile fracture elongation, and low temperature impact resistance of the storage cover. However, the material strength and low temperature impact resistance of the conventional materials for airbag storage covers as described in Patent Documents 1 to 6 are insufficient.

The problems to be solved by the present invention are a thermoplastic elastomer composition capable of obtaining a molded product having excellent appearance, low temperature impact resistance and tensile fracture elongation, and an airbag storage cover using this thermoplastic elastomer composition. And to provide automotive interior materials.

As a result of diligent studies to solve the above problems, the present inventors have obtained polypropylene-based resin, linear low-density polyethylene-based resin, ethylene / 1-butene copolymer rubber, and ethylene / 1-octene copolymer rubber. We have found that the molded product made of the thermoplastic elastomer composition contained therein is excellent in low-temperature impact resistance, tensile fracture elongation, and excellent appearance, and has reached the present invention. That is, the gist of the present invention lies in the following [1] to [8].

[1] A thermoplastic elastomer composition containing at least the following components (A) to (D).
Component (A): Polypropylene resin component (B): Linear low-density polyethylene resin component having a melt flow rate of 10 to 30 g / 10 minutes measured at 190 ° C. and 21.2 N load according to JIS K7210. (C): Ethylene / 1-butene copolymer rubber component (D): Ethylene / 1-octene copolymer rubber

[2] In a total of 100 parts by mass of the components (A) to (D), 20 to 40 parts by mass of the component (A), 20 to 50 parts by mass of the component (B), and 6 to 20 parts by mass of the component (C). The thermoplastic elastomer composition according to [1], which contains 6 to 20 parts by mass of the component (D).

[3] The thermoplastic elastomer composition according to [1] or [2], which further contains the following component (E).
Component (E): High-density polyethylene resin

[4] In a total of 100 parts by mass of the components (A) to (E), 20 to 40 parts by mass of the component (A), 20 to 50 parts by mass of the component (B), and 6 to 20 parts by mass of the component (C). The thermoplastic elastomer composition according to [3], which contains 6 to 20 parts by mass of the component (D) and 5 to 20 parts by mass of the component (E).

[5] The thermoplastic elastomer composition according to any one of [1] to [4], which is a composition for injection molding.

[6] An injection molded product of the thermoplastic elastomer composition according to any one of [1] to [5].

[7] An airbag storage cover made of the thermoplastic elastomer composition according to any one of [1] to [5].

[8] An automobile interior material comprising the thermoplastic elastomer composition according to any one of [1] to [5].

The injection-molded article, airbag storage cover, and automobile interior material of the present invention made of the thermoplastic elastomer composition of the present invention are excellent in appearance, low-temperature impact resistance, and tensile fracture elongation. Therefore, the airbag storage cover of the present invention can be suitably used for high-power airbags. Further, the automobile interior material of the present invention is excellent in durability.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and carried out without departing from the gist of the present invention. In addition, in this specification, when a numerical value or a physical property value is put before and after using "~", it is used as including the value before and after that.

[Thermoplastic Elastomer Composition]
The thermoplastic elastomer composition of the present invention contains at least the following components (A) to (D), and may further contain the following components (E).
Component (A): Polypropylene resin component (B): Linear low-density polyethylene resin component having a melt flow rate of 10 to 30 g / 10 minutes measured at 190 ° C. and 21.2 N load according to JIS K7210. (C): Ethylene 1-butene copolymer rubber component (D): Ethylene 1-octene copolymer rubber component (E): High-density polyethylene resin

The airbag storage cover made of the thermoplastic elastomer composition of the present invention has low-temperature impact resistance, tensile fracture elongation, etc., as compared with those using the conventional thermoplastic elastomers known in Patent Documents 1 to 6 and the like. It has the features of being excellent in quality and having a good appearance.
With the thermoplastic elastomer composition of the present invention containing the above components (A) to (D), the details of the mechanism of action capable of obtaining a molded product having excellent appearance, low temperature impact resistance and tensile fracture elongation are not clear. However, the linear short-chain branch of the polypropylene-based resin of the component (A) and the linear low-density polyethylene-based resin of the component (B) of the specific range MFR, and the high compatibility with the ethylene component, and the flexibility and low density. The ethylene / 1-butene copolymer rubber of the component (C) having a low glass transition temperature, and the ethylene / 1-ethylene of the component (D) having a long comonomer branched chain, good tensile elongation, flexibility and low density, and a low glass transition temperature. By appropriately entwining the octene copolymer, a molded product with excellent injection-molded appearance can be obtained by optimal balance, high tensile fracture elongation despite low relative molecular weight, and low-temperature impact resistance. It is thought that it will be obtained.
Further, when the thermoplastic elastomer composition of the present invention further contains the component (E), the balance between oil resistance, low temperature impact resistance and rigidity can be improved.

<Ingredient (A)>
The polypropylene-based resin of the component (A) contained in the thermoplastic elastomer composition of the present invention has a propylene unit content of 70% by mass or more. The polypropylene-based resin of the component (A) may be a homopolymer of propylene, or propylene / (ethylene and / or) containing an ethylene unit and an α-olefin unit other than ethylene and propylene in addition to the propylene unit. It may be an α-olefin) copolymer, or it may be a propylene-based block copolymer. Further, it may contain a monomer unit other than ethylene and α-olefin.

When the component (A) is a propylene-based copolymer having an α-olefin unit, examples of the α-olefin unit other than ethylene and propylene include α-olefins having 4 to 20 carbon atoms. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1 -Tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl Examples thereof include -1-pentene, 2-ethyl-1-hexene and 2,2,4-trimethyl-1-pentene. The α-olefin other than propylene is preferably an α-olefin having 4 to 10 carbon atoms, and more preferably 1-butene, 1-hexene, or 1-octene.

More specifically, the propylene-based resin of the component (A) includes a propylene homopolymer, a propylene / ethylene copolymer, a propylene / 1-butene copolymer, a propylene / 1-hexene copolymer, and a propylene / 1. − Ethylene such as octene copolymer, propylene / ethylene / 1-butene copolymer, propylene / ethylene / 1-hexene copolymer, propylene / ethylene / 1-octene copolymer, etc. and α with 4 to 10 carbon atoms- Examples thereof include a copolymer of propylene and at least one monomer selected from olefins. Further, a propylene-based polymer composed of a propylene-based polymer component (A1) having a propylene unit content of 90 to 100% by mass and an ethylene / propylene copolymer component (A2), preferably containing propylene units in the first step. Examples of propylene-based block copolymers obtained by polymerizing a propylene-based polymer having an amount of 90 to 100% by mass and then polymerizing an ethylene-propylene copolymer in the second step can be exemplified. Among these, as the component (A), from the viewpoint of low temperature impact resistance and high temperature strength, a propylene-based polymer having a propylene unit content of 90 to 100% by mass was polymerized in the first step, followed by the first step. It is preferable that it is a propylene-based block copolymer obtained by polymerizing an ethylene / propylene copolymer in two steps, and the propylene homopolymer (polypropylene) is selected from the viewpoints of impact resistance, heat resistance, moldability, and mechanical strength. Preferably, polypropylene is particularly preferred.

The propylene unit content of the polypropylene-based resin of the component (A) is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, based on the entire component (A). When the content of the propylene unit of the component (A) is at least the above lower limit value, the heat resistance and the rigidity tend to be good. The propylene unit content in the component (A) can be determined by infrared spectroscopy.

The component (A) is a propylene-based polymer composed of a propylene-based polymer component (A1) having a propylene unit content of 90 to 100% by mass and an ethylene-propylene copolymer component (A2), preferably the first step. In the case of a propylene-based block copolymer obtained by polymerizing a propylene-based polymer having a propylene unit content of 90 to 100% by mass and then polymerizing an ethylene-propylene copolymer in the second step, the components (A) preferably contains 60 to 95% by mass of the component (A1) with respect to the total amount of the component (A1) and the component (A2). If the content of the component (A1) in the component (A) is less than the above lower limit, the mechanical strength and rigidity tend to decrease, and if it is more than the above upper limit, the impact resistance is improved by containing the component (A2). The effect cannot be fully obtained. The content of the component (A1) in the component (A) is more preferably 65% by mass or more, further preferably 70% by mass, and more preferably 93% by mass or less.

The ethylene unit of the ethylene / propylene copolymer of the component (A2) may be such that it satisfies the preferable propylene unit content of the above-mentioned component (A), but is usually about 20 to 80% by mass.

The melt flow rate (MFR) (230 ° C., load 21.2 N (= 2.16 kg)) of the component (A) is usually 0.1 g / 10 minutes or more, and is usually 0.1 g / 10 minutes or more, from the viewpoint of the appearance of the molded product. It is preferably 10 g / 10 minutes or more, more preferably 20 g / 10 minutes or more, and further preferably 30 g / 10 minutes or more. The melt flow rate (190 ° C., load 21.2 N) of the component (A) is usually 200 g / 10 minutes or less, preferably 150 g / 10 minutes or less from the viewpoint of tensile strength, and more preferably 150 g / 10 minutes or less. It is 100 g / 10 minutes or less. The melt flow rate of the component (A) is measured according to JIS K7210 (1999) under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.2 N.

As the component (A), one of the above-mentioned polypropylene-based resins may be used alone, or two or more of them may be mixed and used, but when two or more of them are mixed and used, the component as a mixture. It is preferable that (A) satisfies the above-mentioned propylene unit content and melt flow rate.

As a method for producing the polypropylene-based resin of the component (A), a known polymerization method using a known catalyst for olefin polymerization is used. For example, a polymerization method using a Ziegler-Natta catalyst can be mentioned. As the polymerization method, a slurry polymerization method, a solution polymerization method, a massive polymerization method, a gas phase polymerization method and the like can be used, and two or more of these may be combined.

Further, as the component (A), it is also possible to use a commercially available applicable product. Specifically, it can be procured from the manufacturers listed below, and can be appropriately selected. Available commercial products include Prime Polymer Co., Ltd.'s Prim Polypro®, Sumitomo Chemical's Sumitomo Noblen®, SunAllomer's polypropylene block copolymers, Japan Polypropylene's Novatec® PP, and Lyondell Basell. Moplen (registered trademark), ExxonMobile PP from ExxonMobile, Forumolene (registered trademark) from Formosa Plastics, Borearis PP from Borearis, SEETEC PP from LG Chemical, A.M. Schulman's ASI POLYPROPYLENE, INEOS Olefins & Polymers, Inc. of INEOS PP, Braskem's Braskem PP, SAMSUNG TOTAL PETROCHEMICALS's Sumsung Total, Sabic's Sabic (registered trademark) PP, TOTAL PETROCHEMICALS company of TOTAL PETROCHEMICALS Polypropylene, SK Corporation of YUPLENE ( Registered trademark), etc.

<Ingredient (B)>
The linear low-density polyethylene-based resin (LLDPE) of the component (B) is a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 20 carbon atoms.
The α-olefin having 3 to 20 carbon atoms is preferably one having 3 to 12 carbon atoms, and specifically, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and the like. Examples thereof include 1-octene, 1-decene, and 1-dodecene. The content of these α-olefin units is usually selected in the range of usually 30 mol% or less, preferably 1 to 20 mol% in total with respect to all the monomer units constituting the component (B).

The melt flow rate (MFR) (190 ° C., load 21.2 N (= 2.16 kg)) of the component (B) is 10 to 30 g / 10 minutes, preferably 15 to 25 g / 10 minutes. If the MFR of the component (B) is less than 10 g / 10 minutes, the appearance of the obtained molded product will be inferior. When the MFR of the component (B) exceeds 30 g / 10 minutes, the tensile fracture elongation of the obtained molded product becomes inferior. The melt flow rate of the component (B) is measured according to JIS K7210 (1999) under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.2 N.

The density of the component (B) is 0.880 to 0.930 g / cm ³ , preferably 0.895 to 0.925 g / cm ³ , and more preferably 0.910 to 0.920 g / cm ³ . If the density is ^{less than 0.880 g / cm 3} , the heat resistance and mechanical strength tend to be inferior, and if the density ^{exceeds 0.930 g / cm 3} , the low temperature impact resistance tends to be inferior. The density value is a value measured in accordance with JIS K7112, but a catalog value can also be adopted for a commercially available product.

As the component (B), one type may be used alone, or two or more types having different monomer compositions and physical characteristics may be mixed and used, but when two or more types are mixed and used, a mixture is used. It is preferable that the component (B) as described above satisfies the above-mentioned melt flow rate and density.

The linear low-density polyethylene-based resin of the component (B) can be obtained by copolymerizing ethylene and α-olefin in the presence of a polymerization catalyst. Here, the polymerization catalyst is not limited, but it is preferably produced by a metallocene-based catalyst in which the composition distribution and the molecular weight distribution in the produced polymer are narrow and a high-strength molded product can be easily obtained. Further, a linear low-density polyethylene-based resin obtained by a catalyst other than the metallocene-based catalyst such as a Ziegler-based catalyst may be blended and used in order to reduce the cost without impairing the above characteristics.
The metallocene catalyst is a catalyst composed of a commonly known metallocene-almoxane catalyst, a compound that reacts with a metallocene compound to form a stable anion, and the like.
The linear low-density polyethylene-based resin according to the present invention is not limited in its production method, and can be produced by methods such as slurry polymerization, vapor phase polymerization, and solution polymerization.

Further, as the component (B), a commercially available applicable product can be used. Specifically, it can be procured from the manufacturers listed below, and can be appropriately selected. Available commercially available products include Novatec (registered trademark) LL of Nippon Polyethylene, Evolu (registered trademark) of Mitsui Chemicals, Suntech-LL of Asahi Kasei Chemicals, and QAMAR (registered trademark) of Saudi Petrochemicals.

<Component (C)>
The ethylene / 1-butene copolymer rubber used as the component (C) is a copolymer containing at least an ethylene unit and a 1-butene unit.

The ethylene unit content of the ethylene / 1-butene copolymer rubber of the component (C) is 20% by mass or more and 80% by mass with respect to the total amount of the ethylene unit content and the 1-butene unit content. It is preferable to have. The content of the ethylene unit of the component (C) is preferably large in order to improve the tensile elongation at break when the thermoplastic elastomer composition of the present invention is molded, and when the thermoplastic elastomer composition of the present invention is molded. From the viewpoint of low temperature impact resistance, it is preferable that the amount is small. The content of the ethylene unit of the component (C) is more preferably 25 to 75% by mass, still more preferably 30 to 70% by mass.
The content of ethylene units, the content of 1-butene units, and the content of other monomer units shown below in the component (C) can be determined by infrared spectroscopy, respectively.

The ethylene / 1-butene copolymer rubber of the component (C) contains α-olefin units other than 1-butene, for example, 1-propylene, 2-methylpropylene, 1-pentene, in addition to ethylene units and 1-butene units. , 3-Methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc., preferably 1-propylene, 1-hexene, 1-octene, etc. One or more α-olefin units other than 1-butene having 3,5 to 8 carbon atoms having a double bond, and other simple units such as a monomer unit based on a non-conjugated diene (non-conjugated diene unit). It may have a metric unit. Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadien, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadien. Chain non-conjugated diene; cyclohexadiene, dicyclopentadiene, methyltetrahydroinden, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropyridene-2-norbornene, 6- One or more of cyclic non-conjugated diene such as chloromethyl-5-isopropenyl-2-norbornene can be mentioned. Preferably, it is 5-ethylidene-2-norbornene, dicyclopentadiene.

When the component (C) contains an α-olefin unit other than 1-butene, an ethylene such as a non-conjugated diene unit, and a monomer unit other than 1-butene, the content of the other monomer unit is , It is usually 10% by mass or less, preferably 5% by mass or less, based on the whole component (C).

The melt flow rate (MFR) of the ethylene / 1-butene copolymer rubber of the component (C) is not limited, but is usually less than 10 g / 10 minutes, preferably 8 g / 10 minutes or less from the viewpoint of strength. It is more preferably 5 g / 10 minutes or less, and even more preferably 3 g / 10 minutes or less. The MFR of the component (B) is usually 0.01 g / 10 minutes or more, preferably 0.05 g / 10 minutes or more, and more preferably 0.10 g / 10 minutes or more from the viewpoint of fluidity. is there. Here, MFR is a value measured under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.2 N according to JIS K7210.

Further, the density of the component (C) from the viewpoint of low-temperature impact resistance, and at 0.88 g / cm ³ or less, preferably 0.87 g / cm ³ or less. On the other hand, the lower limit thereof is not particularly limited, but is 0.85 g / cm ³ or more. Here, the density of the component (C) is a value measured in accordance with JIS K6760, but a catalog value can also be adopted for a commercially available product.

As a method for producing the ethylene / 1-butene copolymer rubber of the component (C), a known polymerization method using a known catalyst for olefin polymerization is used. For example, as a catalyst for olefin polymerization, a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a non-metallocene complex can be used, and as a polymerization method, a slurry polymerization method, a solution polymerization method, a massive polymerization method, or a ki Examples include a phase polymerization method. It is also possible to use a commercially available applicable product. Examples of commercially available applicable products include Tuffmer (registered trademark) manufactured by Mitsui Chemicals, Inc., and Energy (registered trademark) manufactured by Dow Chemicals.

In the present invention, only one type of ethylene / 1-butene copolymer rubber may be used as the component (C), or two or more types having different physical characteristics, types of copolymerization components, composition, etc. may be used in combination. Good.

<Component (D)>
The ethylene / 1-octene copolymer rubber used as the component (D) is a copolymer containing at least an ethylene unit and a 1-octene unit.

The ethylene unit content of the ethylene / 1-octene copolymer rubber of the component (D) shall be 20 to 80% by mass with respect to the total content of the ethylene unit content and the 1-octene unit content. Is preferable. The content of the ethylene unit of the component (D) is preferably large for the mechanical strength when the thermoplastic elastomer composition of the present invention is molded, and the low temperature resistance when the thermoplastic elastomer composition of the present invention is molded is preferable. From the viewpoint of impact resistance, less is preferable. The content of the ethylene unit of the component (D) is more preferably 25 to 75% by mass, still more preferably 30 to 70% by mass.
The content of ethylene units, the content of 1-octene units, and the content of other monomer units shown below in the component (D) can be determined by infrared spectroscopy, respectively.

The ethylene / 1-octene copolymer rubber of the component (D) contains an α-olefin unit other than 1-octene, for example, 1-propylene, 1-butene, 2-methylpropylene, in addition to the ethylene unit and the 1-octene unit. , 1-Pentene, 3-Methyl-1-octene, 1-hexene, 4-methyl-1-pentene, etc., preferably 1-propylene, 1-butene, 1-hexene, etc. One or more α-olefin units other than 1-octene having 3 to 7 carbon atoms having a double bond, and other monomers such as a monomer unit based on a non-conjugated diene (non-conjugated diene unit). It may have a unit. Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadien, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadien. Chain non-conjugated diene; cyclohexadiene, dicyclopentadiene, methyltetrahydroinden, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropyridene-2-norbornene, 6- One or more of cyclic non-conjugated diene such as chloromethyl-5-isopropenyl-2-norbornene can be mentioned. Preferably, it is 5-ethylidene-2-norbornene, dicyclopentadiene.

When the component (D) contains ethylene such as α-olefin unit other than 1-octene and non-conjugated diene unit and other monomer unit other than 1-octene, the content of the other monomer unit is , It is usually 10% by mass or less, preferably 5% by mass or less, based on the whole component (D).

The melt flow rate (MFR) of the ethylene / 1-octene copolymer rubber of the component (D) is not limited, but is usually less than 10 g / 10 minutes, preferably 8 g / 10 minutes or less from the viewpoint of strength. It is more preferably 5 g / 10 minutes or less, and even more preferably 3 g / 10 minutes or less. The MFR of the component (B) is usually 0.01 g / 10 minutes or more, preferably 0.05 g / 10 minutes or more, and more preferably 0.10 g / 10 minutes or more from the viewpoint of fluidity. is there. Here, MFR is a value measured under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.2 N according to JIS K7210.

Further, the density of the component (D) from the viewpoint of low-temperature impact resistance, and at 0.88 g / cm ³ or less, preferably 0.87 g / cm ³ or less. On the other hand, the lower limit thereof is not particularly limited, but is 0.85 g / cm ³ or more. Here, the density of the component (D) is a value measured in accordance with JIS K6760, but a catalog value can also be adopted for a commercially available product.

As a method for producing the ethylene / 1-octene copolymer rubber of the component (D), a known polymerization method using a known catalyst for olefin polymerization is used. For example, as a catalyst for olefin polymerization, a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a non-metallocene complex can be used, and as a polymerization method, a slurry polymerization method, a solution polymerization method, a massive polymerization method, or a ki Examples include a phase polymerization method. It is also possible to use a commercially available applicable product. Examples of commercially available applicable products include Engage (registered trademark) manufactured by Dow Chemical Corp., Solumer (registered trademark) manufactured by SK Corp., and the like.

In the present invention, only one type of ethylene / 1-octene copolymer rubber may be used as the component (D), or two or more types having different physical characteristics, types of copolymerization components, composition, etc. may be used in combination. Good.

<Ingredient (E)>
The high-density polyethylene resin used as the component (E) has a density of 0.94 to 0.97 g / cm ³ , preferably 0.95 to 0.97 g / cm ³ , and more preferably 0.955 to 0. Those in the range of .965 g / cm ^{3 are preferable.} In the present invention, the density of the high-density polyethylene-based resin is a value measured in accordance with JIS K6760.
When the density of the component (E) is 0.94 g / cm ³ or more, the rigidity of the obtained molded product and the tensile fracture elongation tend to be good. On the other hand, when the density is 0.97 g / cm ³ or less, the toughness and appearance of the obtained molded product tend to be good.

The melt flow rate (MFR) (190 ° C., load 21.2 N (= 2.16 kg)) of the component (E) is preferably 0.01 to 5 g / 10 minutes, more preferably 0.05 to 1 g / g. 10 minutes. When the MFR of the component (E) is not more than the above lower limit, the moldability tends to be deteriorated and the appearance tends to be deteriorated, and when it is not more than the above upper limit, the low temperature impact resistance tends to be lowered.

The high-density polyethylene-based resin of the component (E) may be a homopolymer of ethylene, and ethylene and propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene. , 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicodecene and the like, preferably having 3 to 20 carbon atoms. It may be a copolymer with one or more of α-olefins having 4 to 10 carbon atoms.

A high-density polyethylene resin is produced as a homopolymer of ethylene or a copolymer of ethylene and a small amount of α-olefin by a process of a medium-low pressure method, and is a copolymer of ethylene and α-olefin. In some cases, the content of ethylene units in the high-density polyethylene resin is 80% by mass or more, particularly 90% by mass or more, and the content of α-olefin units is 0.1 to 10% by mass. It is preferable from the viewpoint of toughness balance.

The high-density polyethylene-based resin is usually obtained by homopolymerization of ethylene or copolymerization of ethylene and α-olefin using a catalyst composed of a transition metal compound and an organometallic compound.

Examples of the catalyst transition metal compound include one or more of transition metal compounds such as titanium, vanadium, and chromium, or those supported or reacted with silica, alumina, magnesium compounds, and the like. In particular, a solid catalyst component in which a titanium compound such as titanium chloride, haloalcolate, or alcoholate is supported or reacted with a magnesium compound such as magnesium dialcholate or magnesium chloride is preferably used.

As the organometallic compound, _{organic aluminum represented by the general formula AlR n} X _3-n (in the formula, R represents a hydrocarbon group having 1 to 14 carbon atoms, X represents a halogen atom, and n represents 1-3). Examples include compounds. Specific examples thereof include triethylaluminum, trin-propylaluminum, triisobutylaluminum, dimethylaluminum monochlorolide, and ethylaluminum sesquichloride.

Commercially available products can be used as the high-density polyethylene-based resin. For example, Novatec (registered trademark) HD of Nippon Polyethylene, Creolex (registered trademark) of Asahi Kasei Chemicals, Suntech HD (registered trademark), and Prime Polymer Co., Ltd. High density (registered trademark), Evolu H (registered trademark), QAMAR-HD (registered trademark) of Saudi Petrochemical Co., Ltd., etc. can be used.

In the present invention, only one type of high-density polyethylene-based resin as the component (E) may be used, or two or more types having different physical properties, types of copolymerization components, ethylene unit content, etc. may be used in combination. ..

<Amount of ingredients (A) to (E)>
In the thermoplastic elastomer composition of the present invention, 20 to 40 parts by mass of the component (A) and 20 to 50 parts by mass of the component (B) are contained in a total of 100 parts by mass of the components (A) to (D). It is preferable that C) is contained in an amount of 6 to 20 parts by mass and the component (D) is contained in an amount of 6 to 20 parts by mass. When the thermoplastic elastomer composition of the present invention further contains the component (E), 20 to 40 parts by mass of the component (A) is contained in a total of 100 parts by mass of the components (A) to (E). It is preferable that (B) is contained in an amount of 20 to 50 parts by mass, component (C) is contained in an amount of 6 to 20 parts by mass, component (D) is contained in an amount of 6 to 20 parts by mass, and component (E) is contained in an amount of 5 to 20 parts by mass.

When the content of the component (A) is at least the above lower limit, heat resistance and moldability are good, and when it is at least the above upper limit, low temperature impact resistance is good.
When the content of the component (B) is at least the above lower limit, the molded appearance is good, and when it is at least the above upper limit, the low temperature impact resistance is good.
When the content of the component (C) is at least the above lower limit, the low temperature impact resistance is good, and when it is at least the above upper limit, the rigidity and the mechanical strength are high.
When the content of the component (D) is at least the above lower limit, tensile elongation at break and low temperature impact resistance are good, and when it is at least the above upper limit, rigidity and mechanical strength are high.

When the thermoplastic elastomer composition of the present invention contains the component (E), the rigidity and mechanical strength are improved when the content is not less than the above lower limit, and the molded appearance is improved when the content is not more than the above upper limit. ..

In the thermoplastic elastomer composition of the present invention, 20 to 40 parts by mass of the component (A) and 20 to 50 parts by mass of the component (B) are contained in a total of 100 parts by mass of the components (A) to (D). It is more preferable to contain 6 to 20 parts by mass of C) and 6 to 20 parts by mass of the component (D). When the thermoplastic elastomer composition of the present invention further contains the component (E), 20 to 40 parts by mass of the component (A) is contained in a total of 100 parts by mass of the components (A) to (E). It is more preferable to contain 20 to 50 parts by mass of B), 6 to 20 parts by mass of the component (C), 6 to 20 parts by mass of the component (D), and 5 to 20 parts by mass of the component (E).

<Other ingredients>
In addition to the above components (A) to (E), the thermoplastic elastomer composition of the present invention includes the following additives and components (A) according to various purposes within a range that does not significantly impair the effects of the present invention. Any component such as a resin other than (E) or an elastomer (hereinafter, referred to as "other resin") can be blended.

Optional ingredients include colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, neutralizers, lubricants, cloud retardants, anti-blocking agents, slip agents, flame retardants, dispersants, antistatic agents. , Various additives such as conductivity imparting agent, metal inactivating agent, molecular weight adjusting agent, antibacterial agent, fluorescent whitening agent, and cross-linking agent described later can be mentioned. The blending amount of these additives is appropriately set according to the required characteristics and the like. For example, the antioxidant is used in the range of 0.01 to 0.5 parts by mass per 100 parts by mass of the total amount of the components (A) to (D) or the components (A) to (E).

Other resins that can be contained in the thermoplastic elastomer composition of the present invention include low-density polyethylene other than the component (B), styrene-based thermoplastic elastomer, polyester resin, polyamide resin, styrene resin, acrylic resin, polycarbonate resin, and poly. Examples thereof include vinyl chloride resin and various elastomers other than the above. The other resins listed above may contain only one type or two or more types. When a styrene-based thermoplastic elastomer is used, it is preferable to further use a hydrocarbon-based rubber softener.

However, when the thermoplastic elastomer composition of the present invention contains the above-mentioned other resins or elastomers, the content thereof is such that the components (A) to (D) or the components (A) to (E) are essential components. In order to effectively obtain the effect of the thermoplastic elastomer composition of the present invention, the components (A) to (D) or the components (A) to (E) are obtained from the viewpoints of appearance, low temperature impact resistance, rigidity, and mechanical strength. It is preferably 10% by mass or less with respect to 100 parts by weight.

<Crosslinking agent>
The thermoplastic elastomer composition of the present invention may contain the above-mentioned components and may be partially crosslinked. In this case, the method of cross-linking is not particularly limited, but usually, from the viewpoint of improving rubber elasticity and extrusion moldability, it is preferable to dynamically heat-treat (dynamically cross-link) in the presence of a cross-linking agent.

Here, the dynamic heat treatment (dynamic heat treatment) means kneading in a molten state or a semi-molten state. Usually, the dynamic heat treatment is performed by uniformly mixing each of the above components and then melt-kneading in the presence of a cross-linking agent and, if necessary, a cross-linking aid used.

As a cross-linking agent for partially cross-linking the thermoplastic elastomer composition of the present invention, it is preferable to use an organic peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. , 2,5-dimethyl-2,5-di (t-butylperoxy) hexin-3,1,3-bis (t-butylperoxyisopropyl) benzene, 1,1-di (t-butylperoxy) Examples thereof include 3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (peroxybenzoyl) hexin-3, and dicumyl peroxide.

Examples of the cross-linking aid used when partially cross-linking with these organic peroxides include compounds having N, N'-m-phenylene bismaleimide, toluylene bismaleimide, p-quinonedioxime, nitrobenzene, and the like. Compounds with radically polymerizable carbon-carbon double bonds such as diphenylguanidine, trimethylolpropane, divinylbenzene, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, and component (A) and / Or a compound having a functional group that reacts with the carbon linear portion of the component (B) can be mentioned.

The ratio of the cross-linking agent used is usually 0.01 to 3 parts by mass, preferably 0.04 to 1 part by mass with respect to 100 parts by mass of the components (A) to (D) or the components (A) to (E). It is a department.

<Manufacturing method of thermoplastic elastomer composition>
In the thermoplastic elastomer composition of the present invention, the above components (A) to (D) or the components (A) to (E) and other components used as necessary are used in an ordinary extruder, lavender mixer, or roll. , Brabender plastograph, kneader brabender, etc. can be used for kneading and manufacturing according to a conventional method. Among these manufacturing methods, it is preferable to use an extruder, particularly a twin-screw extruder.

When the thermoplastic elastomer composition of the present invention is kneaded and produced by an extruder or the like, it is usually melt-kneaded while being heated to 155 to 240 ° C., preferably 180 to 220 ° C. At this time, partial cross-linking can be performed by blending the above-mentioned cross-linking agent and cross-linking aid and dynamically heat-treating.

<Physical characteristics>
The thermoplastic elastomer of the present invention is excellent in molded appearance, low temperature impact resistance, tensile fracture elongation, etc. by containing the components (A) to (D) or the components (A) to (E).

(Izod impact strength)
In the present invention, the impact strength of the notched Izod at a temperature of −40 ° C. according to JIS K7110 is used as an index of low temperature impact resistance.
Izod impact strength of the thermoplastic elastomer composition of the present invention is preferably not 70 kJ / ^{m 2} or more, more preferably 80 kJ / ^{m 2} or more, still more preferably 90 kJ / ^{m 2} or more. On the other hand, the upper limit of the Izod impact strength of the thermoplastic elastomer composition of the present invention is not particularly limited, but is usually 150 kJ / m ² or less.

(Tensile fracture elongation)
From the viewpoint of material strength, the thermoplastic elastomer composition of the present invention preferably has a tensile fracture elongation of 300% or more at 23 ° C., and more preferably 350% or more, in accordance with JIS K6251. When the tensile fracture elongation at 23 ° C. is less than the above lower limit, the material elongation is inferior and the expandability of the airbag storage cover tends to decrease. The upper limit of the tensile elongation at break of the thermoplastic elastomer composition of the present invention is not particularly limited, but is usually 1500% or less.

(Flexural modulus)
The thermoplastic elastomer composition of the present invention preferably has a flexural modulus of 600 MPa or less, particularly 200 to 550 MPa, measured in accordance with JIS K7203. If the flexural modulus of the thermoplastic elastomer composition is larger than the upper limit, the low temperature impact resistance tends to decrease, and if it is smaller than the lower limit, the rigidity tends to be insufficient.

<Molding method>
The thermoplastic elastomer composition of the present invention can be molded by a known method as needed and used as various molded products. Examples of the molding method include a molding method usually used for thermoplastic elastomers, for example, an injection molding method, an extrusion molding method, a hollow molding method, a compression molding method, and a molding method described in the section of the airbag storage cover below. Can be mentioned. Further, after that, secondary processing such as laminating molding and thermoforming may be performed. The thermoplastic elastomer composition of the present invention may be used alone as a molded product, or may be combined with other materials to form a laminated body or the like.

[Airbag storage cover]
Using the thermoplastic elastomer composition of the present invention, generally, by using a usual injection molding method or, if necessary, various molding methods such as a gas injection molding method, an injection compression molding method, and a short shot foam molding method. By forming a molded body, it can be used as an airbag storage cover. In particular, the molding conditions for injection molding the airbag storage cover are as follows.

The molding temperature for injection molding the airbag storage cover is usually 150 to 300 ° C, preferably 180 to 280 ° C. The injection pressure is usually 5 to 100 MPa, preferably 10 to 80 MPa. The mold temperature is usually 0 to 80 ° C, preferably 20 to 60 ° C.

The airbag storage cover of the present invention obtained by molding the thermoplastic elastomer composition of the present invention operates by detecting the impact or deformation of a high-speed moving object such as an automobile in the event of a collision or the like. It is used as an airbag storage cover for airbag systems that protect occupants by expanding and deploying.

[Automotive interior materials]
Using the thermoplastic elastomer composition of the present invention, automobile interior materials such as instrument panels, front pillar trims, door trims, shift levers, various consoles, and skin materials for head linings are molded by extrusion molding or injection molding. be able to.

The molding temperature at the time of extrusion molding of an automobile interior material is usually 150 to 250 ° C., preferably 170 to 220 ° C. The molding temperature at the time of press molding is usually 150 to 250 ° C, preferably 190 to 240 ° C.
The molding conditions for injection molding the automobile interior material are the same as the injection molding conditions for the airbag storage cover described above.

The automobile interior material obtained by molding the thermoplastic elastomer composition of the present invention sufficiently satisfies the required characteristics such as durability, low temperature impact resistance, and appearance.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. The values of various production conditions and evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention, and the preferable ranges are the above-mentioned upper limit or lower limit values and the following. It may be in the range specified by the value of Examples or the combination of the values of Examples.

<Raw materials>
Ingredients (A) (polypropylene)
(A-1) Novatec (registered trademark) PP BC03B manufactured by Japan Polypropylene Corporation
MFR (230 ° C. 21.2N): 30 g / 10 minutes (a-2) Basell's Hifax® X1956A
MFR (230 ° C 21.2N): 1g / 10 minutes

Component (B) (Linear low density polyethylene resin)
(B-1): Novatec (registered trademark) LL UJ580 manufactured by Japan Polyethylene Corporation
Density: 0.920 g / cm ³
MFR (190 ° C. 21.2N): 20g / 10 minutes (b-2): Novatec (registered trademark) LL UF240 manufactured by Japan Polyethylene Corporation
Density: 0.920 g / cm ³
MFR (190 ° C 21.2N): 2g / 10 minutes (b-3): Novatec (registered trademark) LL UJ790 manufactured by Japan Polyethylene Corporation
Density: 0.920 g / cm ³
MFR (190 ° C 21.2N): 50g / 10 minutes

Component (C) (ethylene / 1-butene copolymer rubber)
(C-1): Toughmer (registered trademark) A1050S manufactured by Mitsui Chemicals, Inc.
Density: 0.86 g / cm ³
MFR (190 ° C 21.2N): 1.2g / 10 minutes
Mooney Viscosity ML _{1 + 4} (100 ° C): 40

Component (D) (Ethylene / 1-octene copolymer rubber)
(D-1): Energy (registered trademark) 8150 manufactured by Dow Chemical Co., Ltd.
Ethylene unit content: 39% by mass
Density: 0.86 g / cm ³
MFR (190 ° C 21.2N): 0.5g / 10 minutes
Mooney Viscosity ML _{1 + 4} (121 ° C): 33

Component (E) (High-density polyethylene resin)
(E-1): Novatec (registered trademark) HD HB330 manufactured by Japan Polyethylene Corporation
Density: 0.953 g / cm ³
MFR (190 ° C 21.2N): 4g / 10 minutes

<Evaluation method>
1) Appearance of injection molded product:
Using the obtained thermoplastic elastomer composition, an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) was used at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C., and a thickness of 2 mm ×. A sheet having a width of 120 mm and a length of 80 mm was molded, and the appearance of the obtained molded sheet was visually confirmed. Those without a flow mark were marked with ◯, and those with a flow mark were marked with x. Those without flow marks were evaluated as having an excellent molded appearance.

2) Low temperature impact resistance: Izod impact strength (unit: kJ / m ² )
Using the obtained thermoplastic elastomer composition, Izot impact strength was measured by an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. A test piece for use (a notched test piece having a thickness of 4 mm, a width of 12.7 mm, and a length of 64 mm) was formed. For the obtained test piece, the Izod impact strength at a temperature of −40 ° C. was measured according to JIS K7110. In the Izod impact test, the non-destructive one was designated as NB, and the destroyed one was designated as C. In this Izod impact test, the non-destructive (NB) one has an Izod impact strength of 70 kJ / m ² or more and is excellent in low temperature impact resistance.

3) Tensile fracture elongation: tensile fracture test (JIS-3 dumbbell, tensile speed 500 mm / min) (unit:%)
Using the obtained thermoplastic elastomer composition, an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) is used for a tensile test at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. A test piece (thickness 2 mm × width 120 mm × length 80 mm sheet) was formed and then punched out in accordance with JIS K6251 (JIS-3 dumbbell). The tensile fracture elongation of this punched test piece was measured in an atmosphere of 23 ° C. according to JIS K6251. It was evaluated that the larger the value of tensile fracture elongation, the better.

4) Flexural modulus (unit: MPa)
Using the obtained thermoplastic elastomer composition, flexural modulus was measured by an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. The test piece is molded into a test piece (thickness 4 mm x width 10 mm x length 90 mm), and the flexural modulus of this test piece is determined at a span spacing of 64 mm and a bending speed of 2 mm / min in accordance with JIS K7203. It was measured. The flexural modulus is preferably in the range of 200 to 600 MPa.

<Example / Comparative example>
[Example 1]
(A-1) 30.0 parts by mass, (b-1) 20.0 parts by mass, (c-1) 35.0 parts by weight, (d-1) 15.0, antioxidant (manufactured by BASF Japan Ltd.) Product name Ilganox (registered trademark) 1010) 0.1 parts by mass was blended with a Henshell mixer for 1 minute, and a twin-screw extruder in the same direction (Kobe Steel "TEX30α", L / D = 45, number of cylinder blocks = 13 ) At a rate of 20 kg / h, the temperature was raised in the range of 180 to 210 ° C., and melt-kneading was performed to produce pellets of the thermoplastic elastomer composition. The pellets of the obtained thermoplastic elastomer composition were evaluated in 1) to 4) above. The evaluation results are shown in Table-1.

[Examples 2 to 5 and Comparative Examples 1 to 6]
Pellets of the thermoplastic elastomer composition were obtained in the same manner as in Example 1 except that the resin components were blended as shown in Table 1, and the above 1) to 4) were evaluated in the same manner as in Example 1. The evaluation results are shown in Table-1.

From Table 1, component (A) and component (B) (component (b-1) having an MFR within the range of 10 to 30 g / 10 minutes), component (C), and component (D) are arranged in a predetermined ratio. According to the thermoplastic elastomer composition of the present invention including the above, it can be seen that a molded product having excellent appearance and tensile elongation at break and good low temperature impact resistance can be obtained.
On the other hand, in Comparative Example 1 which does not contain the component (b-1), the molded appearance is poor. Further, Comparative Examples 2, 5 and 6 having a low MFR of the component (B) have a poor molded appearance. On the other hand, in Comparative Example 3 in which the MFR of the component (B) is high, the tensile elongation at break is inferior. Further, even in Comparative Example 4 which does not contain the component (D), the tensile elongation at break is inferior. In Example 5 in which the content of the component (b-1) is too large, the low temperature impact resistance is lowered.

According to the thermoplastic elastomer composition of the present invention, the polypropylene-based resin of the component (A), the linear short-chain branch of the linear low-density polyethylene-based resin of the MFR component (B) in a specific range, and the ethylene component Ethylene 1-butene copolymer rubber of component (C), which has high compatibility, flexibility, low density, and low glass transition temperature, and long comonomer branched chain, good tensile elongation, flexible, low density, and glass transition temperature. By appropriately entwining the low component (D) ethylene / 1-octene copolymer rubber, the optimum balance provides high tensile fracture elongation and low temperature impact resistance despite the low relative molecular weight. On the other hand, it is considered that a molded product having an excellent injection-molded appearance can be obtained.

The thermoplastic elastomer composition of the present invention is excellent in molded appearance, low temperature impact resistance, tensile fracture elongation, etc., and is very useful as a molding material for airbag storage covers, automobile interior materials, and the like.

Claims (7)

A thermoplastic elastomer composition containing at least the following components (A) to (D), in which 20 to 40 parts by mass of the component (A) is contained in a total of 100 parts by mass of the components (A) to (D). A thermoplastic elastomer composition containing 20 to 50 parts by mass of (B), 6 to 20 parts by mass of component (C), and 6 to 20 parts by mass of component (D).
Component (A): Polypropylene resin component (B): Linear low-density polyethylene resin component having a melt flow rate of 10 to 30 g / 10 minutes measured at 190 ° C. and 21.2 N load according to JIS K7210. (C): Ethylene / 1-butene copolymer rubber component (D): Ethylene / 1-octene copolymer rubber The thermoplastic elastomer composition according to claim 1, further containing the following component (E).
Component (E): High-density polyethylene resin In a total of 100 parts by mass of the components (A) to (E), the component (A) is 20 to 40 parts by mass, the component (B) is 20 to 50 parts by mass, and the component (C) is 6 to 20 parts by mass. The thermoplastic elastomer composition according to claim 2, which contains 6 to 20 parts by mass of (D) and 5 to 20 parts by mass of the component (E). The thermoplastic elastomer composition according to any one of claims 1 to 3 , which is a composition for injection molding. The injection molded product of the thermoplastic elastomer composition according to any one of claims 1 to 4. An airbag storage cover made of the thermoplastic elastomer composition according to any one of claims 1 to 4. An automobile interior material comprising the thermoplastic elastomer composition according to any one of claims 1 to 4.