CN117651660A - Airbag housing cover, method for producing same, thermoplastic elastomer composition, molded body, and composite molded body - Google Patents

Abstract

The present invention relates to an airbag housing cover formed from a thermoplastic elastomer composition containing a propylene random copolymer and a styrene elastomer having a glass transition temperature in a range of-65 ℃ to-45 ℃ inclusive, wherein the total content of the propylene random copolymer and the styrene elastomer is more than 40 mass% and 100 mass% inclusive in 100 mass% of the thermoplastic elastomer composition.

Description

Air bag containing cover and manufacturing method thereof, thermoplastic elastomer composition, molded body and Composite molded body

Technical field

The present invention relates to an airbag containment cover excellent in low-temperature impact resistance, high-temperature strength, and light transmittance, a manufacturing method thereof, and a thermoplastic elastomer composition capable of providing such an airbag containment cover. The present invention also relates to a molded article and a composite molded article using the thermoplastic elastomer composition.

Background technique

The airbag system for automobiles is a system that protects the driver and passengers when a car or the like collides. It consists of a device that senses the impact during a collision and an airbag device. Airbag devices are installed on the steering wheel, the instrument panel in front of the passenger seat, the driver's seat and passenger seat, the front pillars and side pillars, etc.

Regarding the airbag accommodating cover in the airbag device, when the airbag is inflated, the cover accommodating the airbag may be damaged, causing fragments to scatter, or the cover mounting part to be damaged, causing the cover to scatter. Therefore, in order to prevent the cover from abnormal damage and scattering, various proposals have been made regarding its structure and material.

In the airbag housing cover, there is a risk of damage in low-temperature areas and high-temperature areas due to increased airbag deployment output. Therefore, from the viewpoints of enhanced safety, freedom of design, etc., it is desired to develop a thermoplastic elastomer composition as a material with improved low-temperature impact resistance and high-temperature strength.

It is known that such a thermoplastic elastomer composition for an airbag uses a propylene-based resin as a hard segment and an olefin-based rubber or styrene-based elastomer using an ethylene-propylene elastomer (EPDM, EPR, etc.) as a soft segment.

For example, there is known a thermoplastic elastomer composition for use in airbags that contains a propylene resin, a styrene-butadiene-styrene block copolymer (SBS), and an ethylene-α-olefin copolymer as described in Patent Document 1. .

On the other hand, in a thermoplastic elastomer composition containing a propylene-based resin and a styrene-based elastomer, a technology for improving transparency is known (Patent Documents 2 and 3).

Patent Document 4 proposes a polypropylene-based resin composition that is excellent in rigidity (flexural elastic modulus), impact resistance (impact strength), and transparency in addition to formability: a propylene-based resin, a styrene-based resin, and a styrene-based resin. A combination of elastomer and ethylene·α-olefin copolymer.

Regarding a thermoplastic elastomer composition containing a propylene-based random copolymer and a styrene-based elastomer, Patent Document 5 proposes a thermoplastic elastomer composition for powder molding that can easily produce fine powder at room temperature. , and can provide molded articles with excellent scratch resistance, heat resistance, molded appearance, etc.

As a thermoplastic elastomer composition for airbag accommodation covers, Patent Document 6 proposes low-temperature impact resistance, molded appearance, and injection molding obtained by blending a propylene polymer, an olefin elastomer, a styrene elastomer, and an acrylic resin. Thermoplastic elastomer composition for air bag containing covers with excellent performance.

Patent Document 1: Japanese Patent Application Publication No. 2019-38925

Patent Document 2: Japanese Patent Application Publication No. 2005-23148

Patent Document 3: Japanese Patent Publication No. 2012-512277

Patent Document 4: Japanese Patent Application Publication No. 2017-75209

Patent Document 5: Japanese Patent Application Publication No. 2004-137306

Patent Document 6: Japanese Patent Application Publication No. 2020-158615

In recent years, there has been a design in which a part of the airbag housing cover functions as a touch panel display. This type of airbag containment cover is composed of a surface layer made of a film as an interface of a touch panel display and an airbag containment cover layer provided in contact with the surface layer. A light source is embedded inside the airbag containment cover. switch. In such a structure, in order for the user to easily visually confirm the lighting of the switch, the airbag housing cover needs to be made of a material that transmits the light. Therefore, in addition to the low-temperature impact resistance and high-temperature strength required conventionally, the thermoplastic elastomer composition used for the air bag accommodation cover is required to have light transmittance to a level that allows the user to visually confirm the lighting of the switch.

According to detailed studies by the present inventors, the thermoplastic elastomer composition used in the airbag described in Patent Document 1 has good low-temperature impact resistance and high-temperature strength, but the above-mentioned light transmittance was not considered. In addition, as described in Patent Document 1, in thermoplastic elastomers in which propylene resin is used as the hard segment and olefin rubber such as ethylene-propylene elastomer (EPDM, EPR, etc.) is mainly used as the soft segment, in order to improve light transmission properties, it is necessary to make the refractive index of olefin rubber close to that of acrylic resin. Therefore, it was found that if a material with a low refractive index is selected as the olefin rubber, low-temperature impact resistance and high-temperature strength are impaired.

Although the thermoplastic elastomer composition described in Patent Document 2 has good transparency, it does not satisfy the low-temperature impact resistance and high-temperature strength required for air bag applications.

The thermoplastic elastomer compositions of Patent Documents 3 and 4 have good transparency and high-temperature strength, but do not satisfy low-temperature impact properties.

The thermoplastic elastomer compositions of Patent Documents 5 and 6 do not consider low-temperature impact resistance, high-temperature strength, transparency, or light transmittance.

In addition, in any of the above-mentioned conventional technologies, no research has been conducted on combining a resin film and an airbag housing cover that incorporate the operating functions and design of the touch panel into a touch panel display.

Contents of the invention

Technical problems to be solved by the present invention

The present invention has been accomplished in view of the above-mentioned problems of the prior art.

The technical problem of the present invention is to provide an airbag housing cover and a thermoplastic elastomer composition that are excellent in low-temperature impact resistance, high-temperature strength, and light transmittance and are also suitable for lamination with a touch panel film, as well as a combination containing the thermoplastic elastomer. Object formed bodies and composite formed bodies.

Means of solving technical problems

The inventors found that a thermoplastic elastomer composition containing a propylene random copolymer and a specific styrenic elastomer can provide excellent low-temperature impact resistance, high-temperature strength and light transmittance, and is also suitable for use with touch panels. The present invention was completed by constructing an airbag housing cover and a molded body composed of a composite film.

The gist of the present invention relates to the following [1] to [20].

[1] An air bag containing cover formed of a thermoplastic elastomer composition containing a propylene-based random copolymer and having a glass transition temperature in the range of -65°C or more and -45°C or less A styrenic elastomer in which the total content of the propylene random copolymer and the styrenic elastomer exceeds 40 mass% and is 100 mass% or less in 100 mass% of the thermoplastic elastomer composition .

[2] The airbag accommodating cover according to [1], which is arranged at a position where visual confirmation is possible.

[3] The airbag housing cover according to [1] or [2], wherein the styrenic elastomer is linear.

[4] The airbag housing cover according to any one of [1] to [3], wherein the thermoplastic elastomer composition has a melting temperature of 230° C. and a measurement load of 21.18 N in accordance with JIS K7210 (1999). The body flow rate is 1.0g/10 minutes or more and 50g/10 minutes or less.

[5] The airbag housing cover according to any one of [1] to [4], wherein the thermoplastic elastomer composition contains an amount of benzene based on 100 parts by mass of the propylene random copolymer. The content of the ethylene elastomer is 45 parts by mass or more and 250 parts by mass or less.

[6] The airbag housing cover according to any one of [1] to [5], wherein the thermoplastic elastomer composition further contains ethylene·α based on 100 parts by mass of the propylene random copolymer. - 10 parts by mass or more and 100 parts by mass or less of the olefin copolymer.

[7] The airbag housing cover according to any one of [1] to [6], wherein the styrene-based elastomer has a styrene unit content of 20 mass% or more and 25 mass% or less.

[8] The airbag housing cover according to [7], wherein the styrenic elastomer contains a styrene·conjugated diene block with a styrene unit content of 10% by mass or more and 15% by mass or less. The hydrogenated product (b1) of the copolymer and the hydrogenated product (b2) of the styrene·conjugated diene block copolymer having a styrene unit content of 25% by mass or more and 35% by mass or less.

[9] The airbag housing cover according to any one of [1] to [8], wherein the thermoplastic elastomer composition is obtained by injection molding under conditions of a resin temperature of 200°C and a mold temperature of 40°C. The total light transmittance measured based on JIS K7136-1 of the 2mm thick sheet test piece is 65% or more.

[10] The airbag housing cover according to any one of [1] to [9], wherein the thermoplastic elastomer composition is obtained by injection molding under conditions of a resin temperature of 200°C and a mold temperature of 40°C. The haze measured based on JIS K7136-1 for a 2 mm thick sheet test piece is 70% or less.

[11] The method for manufacturing an airbag accommodation cover according to any one of [1] to [10], which includes the step of injection molding the thermoplastic elastomer composition.

[12] A thermoplastic elastomer composition containing a propylene random copolymer and a linear styrenic elastomer, the linear styrenic elastomer having a styrene unit content of 20 mass % or more and 35% by mass or less, and has a glass transition temperature in the range of -65°C or more and -45°C or less, wherein in 100% by mass of the thermoplastic elastomer composition, the propylene-based random copolymer and the The total content rate of the linear styrenic elastomer exceeds 40 mass % and is 100 mass % or less, and the content of the linear styrenic elastomer is 100 parts by mass of the propylene random copolymer. 45 parts by mass or more and 250 parts by mass or less, and the thermoplastic elastomer composition has a melt flow rate of 1.0 g/10 minutes or more and 50 g/10 at a temperature of 230° C. and a measurement load of 21.18 N according to JIS K7210 (1999) minutes or less.

[13] The thermoplastic elastomer composition according to [12], wherein the thermoplastic elastomer composition is injection molded at a resin temperature of 200°C and a mold temperature of 40°C into a sheet with a thickness of 2 mm. The total light transmittance of the test piece measured based on JIS K7136-1 is 65% or more.

[14] The thermoplastic elastomer composition according to [12] or [13], wherein the thickness obtained by injection molding the thermoplastic elastomer composition at a resin temperature of 200°C and a mold temperature of 40°C The haze measured based on JIS K7136-1 for a 2 mm sheet test piece is 70% or less.

[15] The thermoplastic elastomer composition according to any one of [12] to [14], further containing 10 parts by mass of an ethylene·α-olefin copolymer based on 100 parts by mass of the propylene-based random copolymer. More than 100 parts by mass.

[16] The thermoplastic elastomer composition according to any one of [12] to [15], wherein the linear styrenic elastomer has a styrene unit content of 20% by mass or more and 25% by mass. %the following.

[17] The thermoplastic elastomer composition according to [16], wherein the linear styrenic elastomer contains a styrene co-elastomer with a styrene unit content of 10% by mass or more and 15% by mass or less. The hydrogenated product (b1) of the conjugated diene block copolymer and the hydrogenated product (b2) of the styrene·conjugated diene block copolymer having a styrene unit content of 25 mass% or more and 35 mass% or less.

[18] A molded article containing the thermoplastic elastomer composition according to any one of [12] to [17].

[19] A composite formed body having:

A first layer comprising the thermoplastic elastomer composition described in any one of [12] to [17]; and

The second layer contains a resin film.

[20] A composite formed body having:

A first layer comprising a thermoplastic elastomer composition containing a propylene-based random copolymer and a styrene-based elastomer having a glass transition temperature in the range of -65°C or more and -45°C or less. ;and

The second layer contains a resin film.

The present invention also includes the following <1> to <11>.

<1> A thermoplastic elastomer composition for airbags, which contains the following component (A) and component (B),

Ingredients (A): Propylene polymer

Component (B): A hydrogenated product of a styrene·conjugated diene block copolymer with a styrene unit content of 20 mass% or more and 35 mass% or less, and a glass transition temperature of -65°C or more and -45 below ℃.

<2> The thermoplastic elastomer composition for air bags according to <1>, wherein the thickness obtained by injection molding the thermoplastic elastomer composition for air bags at a resin temperature of 200°C and a mold temperature of 40°C The haze measured based on JIS K7136-1 for a 2 mm sheet test piece is 70% or less.

<3> The thermoplastic elastomer composition for airbags according to <1> or <2>, wherein the component (A) and the component (B) in 100% by mass of the thermoplastic elastomer composition for airbags The total content rate is 70 mass% or more and 100 mass% or less.

<4> The thermoplastic elastomer composition for air bags according to any one of <1> to <3>, wherein the content of the component (B) relative to 100 parts by mass of the component (A) is 20 More than 200 parts by mass and less than 200 parts by mass.

<5> The thermoplastic elastomer composition for air bags according to any one of <1> to <4>, which further contains 10 parts by mass of the following component (C) with respect to 100 parts by mass of the component (A). More than 100 parts by mass,

Component (C): ethylene·α-olefin copolymer.

<6> The thermoplastic elastomer composition for airbags according to any one of <1> to <5>, wherein:

The styrene unit content of the component (B) is 20 mass% or more and 25 mass% or less.

<7> The thermoplastic elastomer composition for airbags according to <6>, wherein:

The component (B) contains: a hydrogenated product (b1) of a styrene·conjugated diene block copolymer with a styrene unit content of 10 mass% or more and 15 mass% or less, and a styrene unit content of 25 mass%. % or more and 35 mass % or less of the hydrogenated product (b2) of the styrene·conjugated diene block copolymer.

<8> A molded article formed from the thermoplastic elastomer composition for air bags according to any one of <1> to <7>.

<9> A composite molded article having a first layer including the thermoplastic elastomer composition for air bags according to any one of <1> to <7>, and a second layer including a resin film.

<10> An airbag containing cover formed from the thermoplastic elastomer composition for airbags according to any one of <1> to <7>.

<11> A thermoplastic elastomer composition for airbags, which contains a propylene polymer and a styrenic elastomer with a glass transition temperature of -65°C or more and -45°C or less, wherein the thermoplastic elastomer composition for airbags is The haze measured in accordance with JIS K7136-1 of a 2 mm thick sheet-shaped test piece obtained by injection molding the elastomer composition at a resin temperature of 200°C and a mold temperature of 40°C was 70% or less.

Invention effect

The thermoplastic elastomer composition of the present invention is excellent in low-temperature impact resistance, high-temperature strength, and light transmittance, and is also suitable for lamination with a touch panel film. Therefore, the thermoplastic elastomer composition of the present invention can provide a molded article that is excellent in low-temperature impact resistance, high-temperature strength, and light transmittance, and is also suitable for compounding with a touch panel film, composite molded articles, and airbag housing covers. .

The airbag accommodation cover of the present invention can be applied to an airbag accommodation cover for a driver's seat, an airbag accommodation cover for a passenger's seat, an airbag accommodation cover for a pedestrian, a knee airbag accommodation cover, a side airbag accommodation cover, a curtain airbag accommodation cover, etc. Any kind.

In particular, the airbag housing cover of the present invention is suitable as an airbag housing cover incorporating a touch panel display due to its excellent transparency and adaptability to lamination with a touch panel film.

Detailed ways

Hereinafter, the present invention will be described in detail. The present invention is not limited to the following description, and may be arbitrarily modified and implemented within the scope that does not deviate from the gist of the present invention.

[Thermoplastic elastomer composition]

First, the thermoplastic elastomer composition of the present invention will be described.

The thermoplastic elastomer composition constituting the airbag housing cover of the present invention is a thermoplastic elastomer combination containing a propylene-based random copolymer and a styrene-based elastomer having a glass transition temperature in the range of -65°C or more and -45°C or less. object, wherein in 100% by mass of the thermoplastic elastomer composition, the total content of the propylene random copolymer and the styrenic elastomer exceeds 40% by mass and is 100% by mass or less (hereinafter, This thermoplastic elastomer composition is sometimes referred to as "thermoplastic elastomer composition I").

Furthermore, the thermoplastic elastomer composition of the present invention contains a propylene-based random copolymer and a styrene unit content of 20% by mass or more and 35% by mass or less and glass in a range of -65°C or more and -45°C or less. A thermoplastic elastomer composition of a linear styrenic elastomer with a chemical transition temperature, the total of the propylene random copolymer and the linear styrenic elastomer in 100% by mass of the thermoplastic elastomer composition The content rate exceeds 40 mass % and is 100 mass % or less, and the content of the linear styrenic elastomer is 45 mass parts or more and 250 mass parts or less with respect to 100 mass parts of the propylene-based random copolymer, According to JIS K7210 (1999), the melt flow rate of the thermoplastic elastomer composition at a temperature of 230° C. and a measured load of 21.18 N is 1.0 g/10 minutes or more and 50 g/10 minutes or less (hereinafter, the thermoplastic elastomer composition may be referred to as The body composition is called "thermoplastic elastomer composition II").

As described above, the thermoplastic elastomer composition II is a preferred embodiment in which a given styrenic elastomer among the styrenic elastomers in the thermoplastic elastomer composition I is used in a specific ratio.

Hereinafter, the thermoplastic elastomer composition I and the thermoplastic elastomer composition II are referred to as "the thermoplastic elastomer composition of the present invention."

<Mechanism>

The thermoplastic elastomer composition of the present invention exhibits the effects of being excellent in low-temperature impact resistance, high-temperature strength, and light transmittance, and is also suitable for lamination with a touch panel film.

The detailed reason why the thermoplastic elastomer composition of the present invention exhibits such an effect is not yet certain, but the reason why the thermoplastic elastomer composition exhibits such an effect is presumed to be as follows.

As propylene-based polymers, there are homopolymers of propylene and propylene-based copolymers. In addition, as propylene-based copolymers, there are propylene-based random copolymers and propylene-based block copolymers. Among them, those that contribute to light scattering are not included. An ethylene-propylene copolymer, and due to its lower crystallinity, the propylene-based random copolymer provides a thermoplastic elastomer composition with particularly excellent light transmittance.

In addition, it is known that the refractive index of the styrenic elastomer is also related to the styrene unit content rate, and as the styrene unit content rate increases, the refractive index becomes higher. Therefore, by setting the styrene unit content rate of the styrene-based elastomer within a specific range, the refractive index of the propylene-based random copolymer can be brought close to that of the styrene-based elastomer, thereby improving light transmittance.

In the present invention, as the styrenic elastomer, specifically, a hydrogenated product of a styrene/conjugated diene block copolymer can be used.

Here, the styrene unit content refers to the content of styrene units in the hydrogenated product derived from the raw material styrene and introduced into the styrene/conjugated diene block copolymer.

In addition, by using a styrene-based elastomer having a glass transition temperature in the range of -65°C or more and -45°C or less, it is more preferable to have a specific styrene unit content, and further preferably It is a linear styrenic elastomer that can achieve a higher level of low-temperature impact resistance, high-temperature strength and light transmittance.

Here, when the styrenic elastomer has two or more glass transition temperatures, at least one glass transition temperature may be in the range of -65°C or more and -45°C or less.

<Propylene random copolymer>

The propylene-based random copolymer used in the thermoplastic elastomer composition of the present invention is a random combination of propylene units and other monomer units such as ethylene units, α-olefin units other than propylene, and monomer units other than ethylene and α-olefins. copolymer.

The content of propylene units in the propylene-based random copolymer is usually 50 mass% or more, preferably 85 mass% or more, more preferably 90 mass% or more, still more preferably 94 mass% or more, and the upper limit is preferably 99 mass% or less. . When the propylene unit content of the propylene random copolymer is equal to or higher than the lower limit, heat resistance and rigidity tend to be improved. When the propylene unit content of the propylene random copolymer is equal to or less than the upper limit, the crystallinity is low, thereby improving the light transmittance of the resulting thermoplastic elastomer composition.

The content of the propylene units in the propylene-based random copolymer can be determined by infrared spectroscopy.

Examples of α-olefin units other than propylene contained in the propylene-based random copolymer include α-olefins having 4 or more carbon atoms and 20 or less carbon atoms. Examples of α-olefins having 4 or more and 20 or less carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1- Decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene Alkene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1- Pentene, 2-ethyl-1-hexene, 2,2,4-trimethyl-1-pentene, etc. Alpha-olefins having 4 to 10 carbon atoms are preferred, and ethylene, 1-butene, 1-hexene, and 1-octene are more preferred.

The propylene-based random copolymer may contain only one type of these α-olefin units and ethylene units, or may contain two or more types.

Specific examples of the propylene-based random copolymer include: propylene·ethylene random copolymer, propylene·1-butene random copolymer, propylene·1-hexene random copolymer, propylene·1-octene Ethylene random copolymer, propylene·ethylene·1-butene random copolymer, propylene·ethylene·1-hexene random copolymer, propylene·ethylene·1-octene random copolymer. Preferably, it is a random copolymer of at least one monomer selected from ethylene and α-olefin having 4 to 10 carbon atoms, and propylene.

Among them, from the viewpoint of balancing low-temperature impact resistance, high-temperature strength, and transparency, it is preferable to contain 6 mass% or less, for example, 1 mass% or more and 6 mass% or less selected from the group consisting of ethylene units, butene units, hexene units, and octyl units. A propylene-based random copolymer containing more than one monomer unit in the olefin unit.

The melt flow rate (MFR) of the propylene-based random copolymer is not limited, but is usually 0.1 g/min or more. From the viewpoint of the appearance of the molded article, it is preferably 10 g/10 min or more, and more preferably 20 g/10 min or more. , more preferably 25 g/10 minutes or more, usually 200 g/10 minutes or less, from the viewpoint of tensile strength, preferably 150 g/10 minutes or less, more preferably 100 g/10 minutes or less. The melt flow rate of the propylene-based random copolymer was measured under the conditions of a measurement temperature of 230°C and a measurement load of 21.18N in accordance with JIS K7210 (1999).

As a method for producing a propylene-based random copolymer, a known polymerization method using a known catalyst for olefin polymerization can be used. For example, a multistage polymerization method using a Ziegler-Natta catalyst can be used. As the multi-stage polymerization method, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, etc. may be used, or two or more of these may be combined.

As the propylene-based random copolymer used in the thermoplastic elastomer composition of the present invention, commercially available corresponding products can also be used. The propylene-based random copolymer can be obtained from the manufacturers listed below, and can be appropriately selected. Examples of commercially available products include Prime Polypro (registered trademark) from PRIME POLYMER, SUMITOMONOBLEN (registered trademark) from Sumitomo Chemical, polypropylene random copolymer from SUN ALLOMER, NOVATEC (NOVATEC) from JAPANPOLYPROPYLENE Registered trademark) PP, LyondellBasell's Moplen (registered trademark), Exxon Mobil's ExxonMobil PP, Formosa Plastics' Formolene (registered trademark), Borealis PP, LG Chemical's SEETEC PP, A.Schulman's ASIPOLYPROPYLENE , INEOS Olefins & Polymers' INEOS P P, Braskem's Braskem PP, Hanwha Total's Hanwha Total Petroc hemical Random PP, Sabic's Sabic (registered trademark) PP, TOTAL PETROCHEMICALS' TOTAL PETROCHEMICALS Polypropylene, SK's YU PLENE (registered trademark).

The thermoplastic elastomer composition of the present invention may contain only one type of propylene-based random copolymer, or may contain two or more types of propylene-based random copolymers with different monomer compositions, physical properties, etc.

<Styrenic elastomer>

The styrenic elastomer used in the thermoplastic elastomer composition of the present invention has a glass transition temperature in the range of -65°C or more and -45°C or less. If it is a styrenic elastomer with a glass transition temperature in the range of -65°C or more and -45°C or less, it can be combined with a propylene-based random copolymer to achieve light transmittance, low-temperature impact resistance, Thermoplastic elastomer composition with excellent high-temperature strength.

From the viewpoint of low-temperature impact resistance, the glass transition temperature of the styrenic elastomer is preferably in the range of -65°C or more and -50°C or less.

The glass transition temperature of styrenic elastomer is measured by DSC method.

When two or more types of styrene-based elastomers are used, the glass transition temperature of each styrene-based elastomer may be within the range of the above-mentioned glass transition temperature, or may be outside the range of the above-mentioned glass transition temperature. , the styrenic elastomer only needs to have at least one glass transition temperature in the range of -65°C or higher and -45°C or lower, preferably in the range of -65°C or higher and -50°C or lower.

In addition, from the viewpoint of low-temperature impact resistance, high-temperature strength, and light transmittance, the styrenic elastomer used in the present invention preferably has a styrene unit content of 20 mass% or more and 35 mass% or less.

From the viewpoint of strength and heat resistance, the styrene unit content of the styrenic elastomer is more preferably 21% by mass or more, and from the viewpoint of flexibility and impact resistance, it is more preferably 30% by mass or less, and still more preferably The content is 28% by mass or less, and particularly preferably 25% by mass or less.

The styrene unit content of the styrenic elastomer can be calculated by performing proton NMR measurement using a nuclear magnetic resonance device and quantifying the characteristic groups of styrene.

The styrene unit content rate when two or more types of styrene-based elastomers are used can also be calculated by ratio calculation based on the styrene unit content rate of each styrene-based elastomer and the blending mass ratio of each styrene-based elastomer. . At this time, the styrene unit content rate of each styrene-based elastomer may be within the preferred range of the styrene unit content rate, or may be calculated by ratio calculation outside the preferred range of the styrene unit content rate. It is sufficient that the total styrene unit content of the styrenic elastomer is within the preferred range of the styrene unit content.

For example, as the styrenic elastomer, a hydrogenated product (b1) of a styrene/conjugated diene block copolymer with a styrene unit content of 10 mass% or more and 15 mass% or less and a styrene unit content are obtained. It is a hydrogenated product (b2) of a styrene·conjugated diene block copolymer of 25 mass % or more and 35 mass % or less such that the styrene unit content is 20 mass % or more and 35 mass % or less, especially 20 mass %. It is easy to achieve both high-temperature strength, low-temperature impact resistance and light transmittance by combining them in a ratio of not less than % but not more than 25% by mass. The hydrogenated product (b1) of the styrene/conjugated diene block copolymer and the hydrogenated product (b2) of the styrene/conjugated diene block copolymer are each preferably a styrene/conjugated diene/styrene block. Hydrogenated copolymers.

Preferred conjugated dienes among hydrogenated products of styrene-conjugated diene block copolymers that are styrenic elastomers are butadiene, isoprene, or mixtures thereof. Examples of the hydrogenated product of the styrene/conjugated diene block copolymer include a hydrogenated product of the styrene/butadiene block copolymer (hereinafter sometimes abbreviated as “SEBS”).

By using a hydrogenated product of a styrene/conjugated diene block copolymer as a styrenic elastomer, it is different from using a styrene/butadiene/styrene block copolymer (SBS) which has a double bond in its molecular structure. Compared with the case of polymers, a thermoplastic elastomer composition with high transmittance of visible light and ultraviolet rays can maintain good light resistance.

In addition, by combining the styrene unit content in the propylene-based random copolymer with a styrene unit content of 20 mass% or more and 35 mass% or less, particularly 20 mass% or more and 25 mass% or less, and the temperature is -65°C or more and A hydrogenated product of a styrene/conjugated diene block copolymer having a glass transition temperature in the range of -45°C or lower can provide a thermoplastic elastomer composition excellent in low-temperature impact resistance, high-temperature strength, and light transmittance.

Furthermore, the styrenic elastomer used in the present invention is preferably a linear styrenic elastomer. If it is a linear styrene-based elastomer, it can be easily dispersed in a propylene-based random copolymer, and the light transmittance can be further improved.

Here, the linear styrenic elastomer refers to, for example, a hydrogenated product of a styrene/conjugated diene block copolymer in which the conjugated diene portion is butadiene, isoprene, or a mixture thereof. , specifically, a styrene·ethylene·butene·styrene copolymer, which is a hydrogenated product of a styrene·butadiene block copolymer.

The 1,2-microstructure analyzed by NMR method of the hydrogenated product of the styrene-conjugated diene block copolymer which is the styrenic elastomer is preferably 60 mol% or less, and more preferably 45 mol% or less. From the viewpoint of formability and flexibility, the 1,2-microstructure is preferably 60 mol% or less. In addition, from the viewpoint of weather resistance, the hydrogenation rate of the hydrogenated product of the styrene-conjugated diene block copolymer as the styrenic elastomer is preferably 90 mol% or more, and more preferably 95 mol% or more.

From the viewpoint of mold releasability, the mass average molecular weight (Mw) of the styrenic elastomer is preferably 40,000 or more, more preferably 45,000 or more, and still more preferably 48,000 or more.

In addition, from the viewpoint of transparency, the mass average molecular weight (Mw) of the styrenic elastomer is preferably 120,000 or less, more preferably 110,000 or less, and still more preferably 105,000 or less.

On the other hand, a material with high light transmittance and low transparency can form a molded body having an appearance like frosted glass. From the viewpoint of such an appearance, the lower limit of the mass average molecular weight (Mw) of the styrenic elastomer is preferably 125,000 or more, more preferably 130,000 or more, still more preferably 135,000 or more, and particularly preferably 140,000 or more. From the viewpoint of fluidity, the upper limit of the mass average molecular weight (Mw) in this case is preferably 350,000 or less, more preferably 325,000 or less, and still more preferably 300,000 or less. By setting the molecular weight of the styrene-based elastomer within the above range, light reaching the interior of the molded product is appropriately scattered and an appearance like frosted glass can be achieved.

The mass average molecular weight of the styrenic elastomer when two or more types of styrenic elastomers are used can be determined by measuring a mixture of each component of the styrenic elastomer using the GPC method described below. At this time, the mass average molecular weight of each styrenic elastomer may be within the preferred range of the mass average molecular weight of the styrenic elastomer, or may be outside the preferred range of the mass average molecular weight of the styrenic elastomer, It suffices as long as the mass average molecular weight of the styrenic elastomer, which is a mixture of styrenic elastomers, is within a preferred range.

The mass average molecular weight (Mw) of the styrenic elastomer is measured by gel permeation chromatography (GPC method), and can be measured under the following conditions, for example.

Equipment: "HLC-8220GPC(R)" manufactured by Tosoh Corporation

Column: "TSKgel Super HM-M (6.0mm I.D×15cm×2+G)" manufactured by Tosoh Corporation

Detector: Differential refractive index detector (RI/built-in)

Solvent: chloroform

Temperature: 40℃

Flow rate: 0.25mL/min

Injection volume: 0.1 mass% × 20 μL

Calibration sample: monodisperse polystyrene

Calibration method: polystyrene conversion

Calibration curve approximation formula: cubic formula (hyperbola): excluding limit setting time of 12 minutes

An example of a method for producing a styrenic elastomer is the method described in Japanese Patent Publication No. 40-23798, in which a styrene/conjugated diene block copolymer is synthesized in an inactive solvent using a lithium catalyst. Next, for example, by the method described in Japanese Patent Publication No. Sho 42-8704, Japanese Patent Publication No. Sho 43-6636, Japanese Patent Laid-Open No. Sho 59-133203, and Japanese Patent Laid-Open No. Sho 60-79005, in an inactive solvent, A method of hydrogenating in the presence of a hydrogenation catalyst.

Styrenic elastomers are also available as commercial products. Examples of styrenic elastomers include "KRATON (registered trademark) G" manufactured by KRATON POLYMER Co., Ltd., "SEPTON (registered trademark)" manufactured by KURARAY Co., Ltd., and "TUF TEC (registered trademark) manufactured by Asahi Kasei Co., Ltd. Trademark)" etc.

The thermoplastic elastomer composition of the present invention may contain only one type of styrenic elastomer, or may contain two or more types of styrenic elastomers with different monomer compositions, physical properties, etc.

<Ethylene·α-olefin copolymer>

From the viewpoint of low-temperature impact resistance, the thermoplastic elastomer composition of the present invention may further contain an ethylene·α-olefin copolymer.

Examples of the ethylene·α-olefin copolymer include propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, and 1-hexane as the α-olefin unit. Alkene, 4-methyl-1-pentene, and 1-octene are used as structural units. As the α-olefin, α-olefins having a carbon number of 4 to 8 and having a carbon-carbon double bond at the terminal carbon atom, such as propylene, 1-butene, 1-hexene, and 1-octene, are preferred. The ethylene/α-olefin copolymer may be a copolymer of only one α-olefin with ethylene, or may be a copolymer of two or more α-olefins with ethylene.

The ethylene unit content of the ethylene·α-olefin copolymer is preferably high in order to prevent welding due to blocking of the ethylene·α-olefin copolymer. From the viewpoint of impact resistance, a smaller amount is preferable. Specifically, the lower limit of the ethylene unit content of the ethylene·α-olefin copolymer is usually 50 mass% or more, preferably 55 mass% or more, and more preferably 100 mass% of the total of ethylene units and α-olefin units. 60 mass% or more, more preferably 65 mass% or more. On the other hand, the upper limit is usually 99 mass% or less, preferably 80 mass% or less.

The content of the ethylene unit, the content of the α-olefin unit, and the content of the non-conjugated diene unit described below in the ethylene·α-olefin copolymer can be determined by infrared spectroscopy.

The ethylene/α-olefin copolymer may have other monomer units such as monomer units based on non-conjugated diene (non-conjugated diene units) in addition to ethylene units and α-olefin units. Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, and 6-methyl-1,5- Heptadiene, 7-methyl-1,6-octadiene and other chain non-conjugated dienes; cyclohexadiene, dicyclopentadiene, methyltetrahydroindane, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2 -Norbornene and other cyclic non-conjugated dienes, etc. Preferred are 5-ethylidene-2-norbornene and dicyclopentadiene.

When the ethylene·α-olefin copolymer contains other monomer units such as non-conjugated diene units, the content is usually 10% by mass or less based on 100% by mass of the entire ethylene·α-olefin copolymer, which is preferably It is 5 mass% or less.

The melt flow rate (MFR) of the ethylene·α-olefin copolymer is not limited, but is usually 10 g/10 minutes or less. From the viewpoint of strength, it is preferably 8.0 g/10 minutes or less, and more preferably 5.0 g/10 minutes or less. , more preferably 3.0g/10 minutes or less. In addition, the melt flow rate of the ethylene·α-olefin copolymer is usually 0.01 g/10 minutes or more, and from the viewpoint of fluidity, it is preferably 0.05 g/10 minutes or more, and more preferably 0.10 g/10 minutes or more.

The melt flow rate of the ethylene·α-olefin copolymer was measured in accordance with ASTM D1238 under the conditions of a measurement temperature of 190°C and a measurement load of 21.18N.

From the viewpoint of low-temperature impact resistance, the density of the ethylene·α-olefin copolymer is preferably 0.88 g/cm ³ or less. On the other hand, from the viewpoint of transparency, that is, refractive index, it is preferably 0.86 g/cm ³ or more.

The density of the ethylene·α-olefin copolymer can be measured by the ISO 1183-A method (measurement temperature: 23°C).

Ethylene·α-olefin copolymer is also available as a commercial product. Examples of commercially available products corresponding to ethylene·α-olefin copolymers include Engage (registered trademark) and INFUSE (registered trademark) manufactured by Dow Chemical Company.

The thermoplastic elastomer composition of the present invention may contain only one type of ethylene·α-olefin copolymer, or may contain two or more types having different monomer compositions, physical properties, etc.

<Crystal nucleating agent>

The thermoplastic elastomer composition of the present invention may contain a crystallization nucleating agent. As the crystal nucleating agent, a diacetal crystal nucleating agent is preferred. By mixing a diacetal crystal nucleating agent, it is expected that the crystallization of the propylene-based random copolymer will be accelerated and the light transmittance will be improved.

As the diacetal crystal nucleating agent, well-known substances can be used, and examples thereof include: GEL ALL (registered trademark) D, GEL ALL (registered trademark) MD, and GEL ALL (registered trademark) of Shin Nippon Rika Co., Ltd. DXR, MILLAD 3988 of MILLIKEN Company (USA), MILLAD NX8000, MILLAD NX8000J, MILLAD NX8000K, MILLADNX8000ECO, SIPAXNA-2 of GCHTECH NOLORY Company (China), etc.

Only one type of these may be used, or two or more types may be used.

<Mixing ratio>

From the viewpoint of the effects of excellent low-temperature impact resistance, high-temperature strength, and light transmittance, the total content of the propylene-based random copolymer and the styrene-based elastomer in the thermoplastic elastomer composition of the present invention is smaller than that of the thermoplastic elastomer. 100% by mass of the composition usually exceeds 40% by mass, preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 75% by mass or more, particularly preferably 80% by mass or more, particularly preferably 85% by mass or more. The upper limit is 100% by mass.

In the thermoplastic elastomer composition of the present invention, the content ratio of the styrenic elastomer to 100 parts by mass of the propylene random copolymer is usually 20 parts by mass or more, preferably 45 parts by mass or more and 250 parts by mass or less. From the viewpoint of low-temperature impact resistance and light transmittance, the lower limit of the content ratio of the styrenic elastomer relative to 100 parts by mass of the propylene random copolymer is more preferably 60 parts by mass or more, and further preferably 70 parts by mass or more, Particularly preferably, it is 80 parts by mass or more. From the viewpoint of high-temperature strength, the upper limit of the content ratio of the styrenic elastomer relative to 100 parts by mass of the propylene random copolymer is more preferably 200 parts by mass or less, further preferably 150 parts by mass or less, and particularly preferably 140 parts by mass. or less, and particularly preferably 130 parts by mass or less.

When the thermoplastic elastomer composition of the present invention contains an ethylene·α-olefin copolymer, it is preferable that it contains 10 parts by mass or more and 100 parts by mass of the ethylene·α-olefin copolymer relative to 100 parts by mass of the propylene random copolymer. the following. By blending the ethylene·α-olefin copolymer so as to satisfy the above relationship, it is possible to obtain a molded article provided with low-temperature impact resistance while controlling the flexural elastic modulus within an appropriate range. From the viewpoint of low-temperature impact resistance, the lower limit of the content ratio of the ethylene·α-olefin copolymer relative to 100 parts by mass of the propylene random copolymer is more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, and particularly preferably It is 40 parts by mass or more. From the viewpoint of high-temperature strength, the upper limit of the content ratio of the ethylene·α-olefin copolymer relative to 100 parts by mass of the propylene random copolymer is more preferably 70 parts by mass or less, further preferably 60 parts by mass or less, and particularly preferably 55 parts by mass or less.

When the thermoplastic elastomer composition of the present invention contains a crystal nucleating agent, preferably a diacetal crystal nucleating agent, the content of the crystal nucleating agent in the thermoplastic elastomer composition of the present invention is relative to the propylene random copolymer, 0.05 parts by mass is preferably used for 100 parts by mass of the total of the styrene-based elastomer and the ethylene·α-olefin copolymer (the total of the propylene-based random copolymer and the styrene-based elastomer when the ethylene·α-olefin copolymer is not included) It is used in an amount of more than 5.0 parts by mass and not more than 0.05 parts by mass and not more than 1.0 parts by mass.

<Other ingredients>

In the thermoplastic elastomer composition of the present invention, in addition to the propylene random copolymer, styrenic elastomer, ethylene·α-olefin copolymer, and crystal nucleating agent, the effects of the present invention are not significantly impaired. Within the scope, the following additives, inorganic fillers, organic fillers, and resins other than propylene random copolymers, styrene elastomers, and ethylene α-olefin copolymers (hereinafter referred to as "others") can be blended according to various purposes. Resin") and other optional ingredients.

Examples of additives include colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, neutralizers, lubricants, anti-fogging agents, anti-blocking agents, slip agents, flame retardants, and dispersants. , antistatic agents, conductivity imparting agents, metal passivators, molecular weight regulators, antibacterial agents, fluorescent whitening agents and other additives. These additives can usually be blended in the range of 0.01 parts by mass or more and 2 parts by mass or less based on 100 parts by mass in total of the propylene-based random copolymer, the styrene-based elastomer, and the ethylene·α-olefin copolymer used if necessary. Additives are used.

Examples of other resins that may be included in the thermoplastic elastomer composition of the present invention include low-density polyethylene, polyester elastomer, polyurethane elastomer, polyester resin, polyamide resin, polyurethane resin, styrene resin, and polycarbonate. Ester resin, polyvinyl chloride resin, various elastomers other than those mentioned above (excluding elastomers corresponding to styrenic elastomers and ethylene·α-olefin copolymers), etc. The other resins listed above may include only one type, or may include two or more types.

<Production method of thermoplastic elastomer composition>

In the thermoplastic elastomer composition of the present invention, the propylene-based random copolymer and styrene-based elastomer, the ethylene/α-olefin copolymer used as necessary, and other components can be prepared using a common extruder, Banbury A banbury mixer, a roll, a Brabender plastometer, a Brabender kneader, etc. are kneaded according to a conventional method and manufactured. Among these production methods, it is preferable to use an extruder, especially a twin-screw extruder.

When the thermoplastic elastomer composition of the present invention is kneaded and produced using an extruder or the like, it is usually melt-kneaded in a state heated to 155°C or higher and 240°C or lower, preferably 180°C or higher and 220°C or lower. At this time, it is also possible to partially crosslink by blending a known crosslinking agent and a crosslinking auxiliary and dynamically performing heat treatment. From the viewpoint of light transmittance, it is preferable not to crosslink.

<Physical properties>

The thermoplastic elastomer of the present invention has excellent high-temperature strength and low-temperature impact resistance by containing the propylene-based random copolymer and styrene-based elastomer, an ethylene·α-olefin copolymer if necessary, and a crystallization nucleating agent. properties and light transmittance.

The thermoplastic elastomer composition of the present invention is preferably used for air bag containing covers. In the present invention, the "airbag accommodating cover" refers to the entire container accommodating the airbag. For example, in a container accommodating an airbag, it is an opening when the airbag is deployed or the entire container integrated with the opening.

In such applications, the thermoplastic elastomer composition of the present invention preferably has the following physical properties.

(Izod impact strength)

In the present invention, the Izod impact strength at -35°C, -40°C and -45°C according to ISO180 is used as an index of low-temperature impact resistance. The Izod impact strength of the molded article of the thermoplastic elastomer composition of the present invention is preferably 50 kJ/m ² or more, and more preferably 70 kJ/m ² or more. 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.

(MFR)

In the present invention, the melt flow rate (MFR) at a temperature of 230° C. and a measurement load of 21.18 N in accordance with JIS K7210 (1999) is used as an index of the injection moldability of the thermoplastic elastomer composition. In order for the thermoplastic elastomer composition of the present invention to have excellent injection moldability, its melt flow rate is preferably 1.0 g/10 minutes or more and 50 g/10 minutes or less. If the MF R of the thermoplastic elastomer composition for air bags is 1.0 g/10 minutes or more, the fluidity tends to be good, and if it is 50 g/10 minutes or less, burrs etc. during molding can be easily suppressed, so it is preferable. . From the viewpoint of fluidity, the MFR of the thermoplastic elastomer composition for airbags is more preferably 2.0 g/10 minutes or more, and further preferably 2.5 g/10 minutes or more. On the other hand, from the viewpoint of suppressing burrs during injection molding, the MFR of the thermoplastic elastomer composition is more preferably 40 g/10 minutes or less, further preferably 20 g/10 minutes or less, and particularly preferably 17 g/10 minutes or less. Particularly preferably, it is 15 g/10 minutes or less.

(Normal temperature tensile failure elongation·Tensile failure strength)

From the viewpoint of material strength, the tensile elongation at failure of the thermoplastic elastomer composition of the present invention at 23°C based on JIS K6251 is preferably 300% or more, and more preferably 350% or more. When the tensile elongation at break at 23° C. is equal to or higher than the lower limit, the material elongation is good, and therefore the expandability of the airbag accommodation cover formed of the thermoplastic elastomer composition of the present invention tends to be good. The upper limit of the tensile failure elongation of the thermoplastic elastomer composition of the present invention is not particularly limited, but is usually 1500% or less.

From the same viewpoint, the tensile failure strength measured when measuring the tensile failure elongation is preferably 10 MPa or more, and more preferably 12 MPa or more. When the tensile fracture strength at 23° C. is equal to or higher than the lower limit, the expandability of the airbag accommodating cover formed of the thermoplastic elastomer composition of the present invention tends to be improved because the material strength is high. The upper limit of the tensile fracture strength of the thermoplastic elastomer composition of the present invention is not particularly limited, but is usually 25 MPa.

(High temperature tensile failure strength)

From the viewpoint of material strength, the tensile failure strength of the thermoplastic elastomer composition of the present invention at 85° C. based on JIS K6251 is preferably 4.5 MPa or more, more preferably 5.0 MPa or more, and still more preferably 5.5 MPa or more. When the tensile fracture strength at 85° C. is equal to or higher than the lower limit, the material strength is high, and therefore the airbag accommodation cover formed of the thermoplastic elastomer composition of the present invention tends to have good deployability. The upper limit of the tensile fracture strength of the thermoplastic elastomer composition of the present invention is not particularly limited, but is usually 8 MPa or less.

(flexural elastic modulus)

The flexural elastic modulus measured in accordance with JIS K7203 of the thermoplastic elastomer composition of the present invention is preferably 600 MPa or less, and particularly preferably 200 MPa or more and 550 MPa or less. When the flexural elastic modulus of the thermoplastic elastomer composition is not more than the above upper limit, the low-temperature impact resistance tends to be good, and when it is not less than the above lower limit, the rigidity tends to be excellent.

(total light transmittance)

For the thermoplastic elastomer composition of the present invention, from the viewpoint of light transmittance, a 2 mm thick film obtained by injection molding the thermoplastic elastomer composition under conditions of resin temperature 200°C and mold temperature 40°C The total light transmittance of the sheet-shaped test piece measured based on JIS K7136-1 is preferably 60% or more, more preferably 65% or more, further preferably 70% or more, and particularly preferably 75% or more. By setting it within such a numerical range, when used as an airbag housing cover, the light transmittance is good and the lighting of the switch can be easily visually confirmed.

(Haze)

For the thermoplastic elastomer composition of the present invention, from the perspective of transparency, a test was performed on a sheet-shaped sheet with a thickness of 2 mm obtained by injection molding the thermoplastic elastomer composition under conditions of a resin temperature of 200°C and a mold temperature of 40°C. The haze measured based on JIS K7136-1 of the sheet is preferably 70% or less, more preferably 60% or less, further preferably 50% or less, and particularly preferably 40% or less. From the viewpoint of the visibility of the switch, it is necessary to make the total light transmittance good, and by making the haze, which is an evaluation index of transparency, satisfy the above numerical range, it is easier to see more clearly when used as an airbag housing cover. Check the confirmation switch to light up.

On the other hand, from the viewpoint of a design appearance like frosted glass, the haze is preferably more than 70%, more preferably 75% or more, and still more preferably 80% or more. At this time, the total light transmittance is preferably 60% or more, more preferably 65% or more, further preferably 70% or more, and particularly preferably 75% or more. By setting the haze and the total light transmittance to the above numerical ranges, it is possible to achieve an appearance like frosted glass that transmits light and has high haze.

<Molded objects such as air bag storage covers>

Using the thermoplastic elastomer composition of the present invention, a normal injection molding method can be used, or various molding methods such as gas injection molding, injection compression molding, and shortshot foam molding can be used to produce an air bag container as needed. Covers and other formed objects. Particularly preferably, the thermoplastic elastomer composition of the present invention is injection molded to form a molded article such as an air bag housing cover. The molding conditions for injection molding are as follows.

The molding temperature when injection molding the thermoplastic elastomer composition is usually 150°C or more and 300°C or less, preferably 180°C or more and 280°C or less. The injection pressure is usually 5 MPa or more and 100 MPa or less, preferably 10 MPa or more and 80 MPa or less. The mold temperature is usually 0°C or more and 80°C or less, preferably 20°C or more and 60°C or less.

<Composite molded body>

The composite molded body of the present invention having a first layer containing a thermoplastic elastomer composition containing a propylene random copolymer and a -65 A styrenic elastomer with a glass transition temperature in the range of ℃ or more and -45 ℃ or less.

That is, the thermoplastic elastomer composition of the present invention may be integrated with a resin film to form a composite molded article having a first layer including the thermoplastic elastomer composition of the present invention and a second layer including a resin film. The composite molded body is suitable as an airbag accommodation cover.

By using such a composite molded body, it is possible to combine the resin film and the airbag housing cover with the operating function and design of the touch panel. Examples of the resin film include a film made of polypropylene, a film made of polyethylene, a film made of a polyolefin-based thermoplastic elastomer, and a film made of polyester.

The composite molded body of the present invention can be formed by insert molding. In the insert molding method, a resin film is put into a mold before molding, and then the thermoplastic elastomer composition of the present invention is filled into the mold. Thus, a first product containing the thermoplastic elastomer composition of the present invention can be obtained. layer and a second layer including a resin film.

<Purpose>

The thermoplastic elastomer composition of the present invention has excellent high-temperature strength, low-temperature impact resistance, and light transmittance, and is suitable for use as a molding material for airbag accommodation covers. In particular, this airbag accommodating cover is suitable as an airbag accommodating cover for an airbag system that protects the occupants by inflating and deploying by sensing the impact and deformation when a collision occurs with a high-speed moving object such as a car.

In particular, due to its excellent light transmittance, the airbag housing cover of the present invention is suitable as an airbag housing cover disposed at a position that can be visually confirmed, such as a touch panel display.

<<1>～<11> thermoplastic elastomer composition for air bags>

In the thermoplastic elastomer composition for airbags described in <1> to <11>, an example of the propylene-based polymer of component (A) includes those contained in the thermoplastic elastomer composition of the present invention. propylene random copolymer. Examples of propylene-based polymers other than propylene-based random copolymers include propylene homopolymers containing, in addition to propylene units, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 6% by mass or less of ethylene. Propylene-based block copolymers such as monomer units other than propylene units, α-olefin units other than propylene, and monomer units other than ethylene and α-olefins. Preferable examples of the α-olefin unit contained in the propylene-based block polymer are the same as those in the α-olefin unit of the propylene-based random copolymer.

Examples of propylene-based polymers other than propylene-based random copolymers include propylene homopolymers, propylene-ethylene block copolymers, propylene-1-butene block copolymers, and propylene-1-hexene block copolymers. material, propylene·1-octene block copolymer, propylene·ethylene·1-butene block copolymer, propylene·ethylene·1-hexene block copolymer, propylene·ethylene·1-octene block copolymer products, propylene-based block copolymers obtained by polymerizing a propylene homopolymer in a first step and then polymerizing a propylene-ethylene copolymer in a second step. Preferably, it is a propylene homopolymer or a block copolymer of at least one monomer selected from ethylene and an α-olefin having 4 to 10 carbon atoms and propylene. The propylene homopolymer is polymerized in the first step, Next, in the second step, a propylene-based block copolymer obtained by polymerizing a propylene-ethylene copolymer is produced.

The physical properties and other properties of the propylene polymer of component (A) are the same as those of the propylene random copolymer.

Regarding the component (B) styrenic elastomer in the thermoplastic elastomer composition for airbags <1> to <11> and other detailed descriptions, the styrenic elastomer in the thermoplastic elastomer composition of the present invention is also applicable. body and other instructions.

Example

Hereinafter, the contents of the present invention will be explained more specifically using examples. The present invention is not limited to the following examples unless the gist thereof is exceeded. The values of various manufacturing conditions and evaluation results in the following examples have the meaning of preferable values as the upper limit or lower limit in the embodiment of the present invention. The preferable range can be determined by the upper limit or lower limit value and the following The range is defined by the values of the Examples or the combination of the values of the Examples.

<raw materials>

[Propylene random copolymer]

(A-1): NOVATEC (registered trademark) PP MG03E made by JAPAN POLYPROPYLENE Co., Ltd.

Propylene·ethylene random copolymer

MFR (JIS K7210 (1999)): 30g/10 minutes (measurement conditions: 230°C, load 21.18N (2.16kgf))

Propylene unit content: 96% by mass

[Styrenic elastomer]

(b-1): KRATON (registered trademark) G1652 made by KRATON POLYMER Co., Ltd.

Hydrogenated product of styrene·butadiene block copolymer (styrene·ethylene·butylene·styrene copolymer (SEBS))

Mass average molecular weight (Mw): 70000

Styrene unit content: 30% by mass

Glass transition temperature: -55℃

(b-2): KRATON (registered trademark) G1657 made by KRATON POLYMER Co., Ltd.

Hydrogenated product of styrene·butadiene block copolymer (styrene·ethylene·butylene·styrene copolymer (SEBS))

Mass average molecular weight (Mw): 110000

Styrene unit content: 13% by mass

Glass transition temperature: -55℃

(b-3): KRATON (registered trademark) G1654 made by KRATON POLYMER Co., Ltd.

Hydrogenated product of styrene·butadiene block copolymer (styrene·ethylene·butylene·styrene copolymer (SEBS))

Mass average molecular weight (Mw): 180000

Styrene unit content: 31% by mass

Glass transition temperature: -55℃

(b-4): KRATON (registered trademark) G1651 made by KRATON POLYMER Co., Ltd.

Hydrogenated product of styrene·butadiene block copolymer (styrene·ethylene·butylene·styrene copolymer (SEBS))

Mass average molecular weight (Mw): 260000

Styrene unit content: 33% by mass

Glass transition temperature: -55℃

[Other styrenic elastomers (Tg is outside the range of -65°C or more and -45°C or less)]

(b’-1): KRATON (registered trademark) G1643 made by KRATON POLYMER Co., Ltd.

Hydrogenated product of styrene·butadiene block copolymer (styrene·ethylene·butylene·styrene copolymer (SEBS))

Mass average molecular weight (Mw): 60000

Styrene unit content: 20% by mass

Glass transition temperature: -35℃

[Ethylene·α-olefin copolymer]

(C-1): Engage (registered trademark) 8100 manufactured by The Dow Chemical Company

Ethylene·octene copolymer

MFR (ASTM D1238): 1g/10 minutes (measurement conditions 190°C, load 21.18N (2.16kgf))

Density (ISO 1183-A method): 0.87g/cm ³ (Measurement temperature: 23°C)

(C-2): Engage (registered trademark) 8150 manufactured by The Dow Chemical Company

Ethylene·octene copolymer

MFR (ASTM D1238): 0.5g/10 minutes (measurement conditions 190°C, load 21.18N (2.16kg f))

Density (ISO 1183-A method): 0.87g/cm ³ (Measurement temperature: 23°C)

[Crystal nucleating agent]

(D-1): GEL ALL (registered trademark) MD manufactured by New Nippon Rika Co., Ltd.

1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol

Melting point: 255-267℃

[PMMA]

(E-1): ACRYPET (registered trademark) VH manufactured by Mitsubishi Chemical Corporation

PMMA (polymethylmethacrylate)

MFR (JIS K7210 (1999)): 2.0g/10 minutes (measurement temperature 230°C, measurement load 37.3N)

Load deflection temperature (ISO75-2): 100℃ (measured load 1.8MPa)

<Evaluation method>

1) Injection moldability: Melt flow rate (MFR)

According to JIS K7210 (1999), the measurement is performed under the conditions of temperature 230°C and load 21.18N.

In the following evaluations 2) to 6), the pellets of the thermoplastic elastomer composition obtained in each example were used, using an online screw-type injection molding machine ("IS130" manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MP a. Test pieces for each test were injection molded at a cylinder set temperature of 190°C (resin temperature of 200°C) and a mold temperature of 40°C.

2) Low temperature impact resistance: Izod impact strength

Through the injection molding, a notched test piece for Izod impact strength measurement with a thickness of 10 mm, a width of 4 mm, and a length of 80 mm was formed. According to ISO180 (2010), the temperature was -35°C, -40°C, and -45°C. Measured at ℃. In addition, let "P" be the case where it was not broken in the Izod impact test, let "H" be the case where a piece of skin remained just before being broken, and let "C" be the case where it was broken." Izod impact strength The larger the value is, or the more non-destructive "P" is, the more excellent the low-temperature impact resistance is evaluated.

3)Bending elastic modulus

In accordance with JIS K7203, the measurement was performed under the conditions of span 64mm and bending speed 1mm/min.

4) Tensile failure elongation at room temperature and tensile failure strength (23°C): Tensile failure test (JIS-3 dumbbell, tensile speed 500mm/min)

A test piece for the tensile test (sheet material with a thickness of 2 mm, a width of 120 mm, and a length of 80 mm) was punched out based on JIS K6251 (JIS-3 dumbbell). For this punched test piece, the tensile elongation at break and the tensile break strength were measured in air at 23°C in accordance with JIS K6251. The larger the values of the tensile failure elongation and the tensile failure strength are, the more excellent the evaluation is.

5) High temperature tensile failure strength (85℃): Tensile failure test (JIS-3 dumbbell, tensile speed 500mm/min) (unit: %)

A test piece for the tensile test (sheet material with a thickness of 2 mm, a width of 120 mm, and a length of 80 mm) was punched out based on JIS K6251 (JIS-3 dumbbell). For this punched test piece, the tensile failure strength was measured in air at 85°C in accordance with JIS K6251. The larger the value of the tensile fracture strength, the more excellent the evaluation.

In Table-1 described below, the numerical mark ">" on the tensile fracture strength at 85°C indicates that the measured strength reached the upper limit of the equipment and therefore there was no breakage. The numbers refer to the stress at which the upper limit of the device is reached, which in this evaluation can be considered the same as the breaking stress.

6) Haze

For an injection molded sheet having a thickness of 2 mm, a width of 120 mm, and a length of 80 mm, the haze is measured in accordance with JIS K7136-1. The smaller the haze value is, the more excellent the transparency is evaluated.

7) Total light transmittance

For an injection-molded sheet having a thickness of 2 mm, a width of 120 mm, and a length of 80 mm, the total light transmittance was measured in accordance with JIS K7136-1. The larger the value of the total light transmittance, the more excellent the light transmittance is evaluated.

<Examples/Comparative Examples>

[Example 1]

As shown in Table 1, 100 parts by mass of (A-1) and 100 parts by mass of (b-1) were added to a total of 100 parts by mass of (A-1) and (b-1). Product name IRGASTAB (registered trademark) FS301FF) 0.15 parts by mass, light stabilizer (HALS (SABOSTAB (registered trademark) UV119 manufactured by SONGWON Corporation)) 0.2 mass parts, ultraviolet absorber (TINUVIN (registered trademark) 326 manufactured by BASF JAPAN Corporation) 0.1 mass parts parts, 0.2 parts by mass of silicone oil (KF96-100CS manufactured by Shin-Etsu Chemical Industry Co., Ltd.) was mixed with a Henschel mixer for 1 minute, and the same direction twin-screw extruder ("TEM-26SS" manufactured by Toshiba Machinery Co., Ltd. at a speed of 25 kg/h , L/D = 48.5, number of cylinder blocks: 12) The mixture is put in, the temperature is raised in the range of 160°C or more and 210°C or less, and the mixture is melted and kneaded to produce particles of a thermoplastic elastomer composition.

The obtained particles of the thermoplastic elastomer composition were evaluated in the above 1) to 7). Their evaluation results are shown in Table-1.

Furthermore, insert molding was performed using the obtained pellets of the thermoplastic elastomer composition and a polypropylene film, thereby preparing a composite molded article.

Specifically, a film with a thickness of 0.5 mm obtained by pressing NOVATEC (registered trademark) PP MG03E manufactured by JAPAN POLYPROPYLENE Co., Ltd. was cut into 100 mm squares, set in a 100 mm×100 mm×3 mm mold, and the pellets were injection molded.

By this method, a composite molded article in which a first layer made of a thermoplastic elastomer composition and a second layer made of a polypropylene film are welded and integrated can be obtained.

[Example 2 to Example 8 and Comparative Example 1 to Comparative Example 3]

Pellets of a thermoplastic elastomer composition were obtained in the same manner as in Example 1, except that the blends shown in Table-1 and Table 2 were used. In the same manner as in Example 1, each of the propylene-based random copolymer, the styrene-based elastomer or other styrene-based elastomer, and the ethylene·α-olefin copolymer used as necessary was blended in a total of 100 parts by mass. Antioxidant (trade name IRGAST AB (registered trademark) FS301FF manufactured by BASF JAPAN Co., Ltd.) 0.15 parts by mass, light stabilizer (HALS (SA BOSTAB (registered trademark) UV119 manufactured by SONGWON Co., Ltd.)) 0.2 parts by mass, ultraviolet absorber (manufactured by BASF JAPAN Co., Ltd. T INUVIN (registered trademark) 326) 0.1 part by mass and silicone oil (KF96-100CS manufactured by Shin-Etsu Chemical Industry Co., Ltd.) 0.2 part by mass. Regarding their compounding amounts, descriptions are omitted in Table-1 and Table-2.

The obtained particles of the thermoplastic elastomer composition were evaluated in the above 1) to 7). Their evaluation results are shown in Table-1 and Table-2.

[Table 1]

<Table-1>

[Table 2]

<Table-2>

[Evaluation results]

In Examples 1 to 8, the high-temperature strength, low-temperature impact resistance, and light transmittance were all good.

Comparative Example 1 is an example in which (b'-1), a hydrogenated product of a styrene-butadiene block copolymer having a glass transition temperature exceeding -45°C, was blended. As a result, the low-temperature impact resistance was significantly deteriorated.

Comparative Example 2 is an example in which Example 2 corresponding to Patent Document 6 was blended, and as a result, the high-temperature strength was poor.

Comparative Example 3 is an example in which the propylene-based random copolymer and the styrene-based elastomer were blended so that the total content of the propylene-based random copolymer and the styrene-based elastomer was 37.5% by mass. As a result, the high-temperature strength was poor.

The present disclosure has been described in detail using specific aspects, but it will be apparent to those skilled in the art that various changes can be made without departing from the intention and scope of the present disclosure.

This application is based on Japanese Patent Application 2021-108344 filed on June 30, 2021, and Japanese Patent Application 2021-207288 filed on December 21, 2021, the entirety of which are incorporated herein by reference.

Claims (20)

1. An airbag housing cover formed from a thermoplastic elastomer composition comprising:

Propylene random copolymers; and

a styrene elastomer having a glass transition temperature in a range of-65 ℃ to-45 ℃,

in the thermoplastic elastomer composition of 100 mass%, the propylene random copolymer and the styrene elastomer total content exceeds 40 mass% and is 100 mass% or less.

2. The airbag housing cover according to claim 1, which is disposed in a visually identifiable position.

3. The airbag housing cover according to claim 1 or 2, wherein,

the styrene elastomer is linear.

4. The airbag-housing cover of claim 3, wherein,

the thermoplastic elastomer composition has a melt flow rate of 1.0g/10 min or more and 50g/10 min or less at a temperature of 230 ℃ under a measured load of 21.18N according to JIS K7210 (1999).

5. The airbag housing of claim 4, wherein,

in the thermoplastic elastomer composition, the content of the styrene elastomer is 45 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the propylene random copolymer.

6. The airbag housing cover according to claim 1 or 2, wherein,

the thermoplastic elastomer composition further comprises 10 parts by mass to 100 parts by mass of an ethylene/alpha-olefin copolymer per 100 parts by mass of the propylene random copolymer.

7. The airbag housing cover according to claim 1 or 2, wherein,

the styrene-based elastomer has a styrene unit content of 20 mass% or more and 25 mass% or less.

8. The airbag-housing cover of claim 7, wherein,

the styrenic elastomer comprises:

a hydrogenated product (b 1) of a styrene/conjugated diene block copolymer having a styrene unit content of 10 mass% or more and 15 mass% or less, and

a hydrogenated product (b 2) of a styrene/conjugated diene block copolymer having a styrene unit content of 25 mass% or more and 35 mass% or less.

9. The airbag housing cover according to claim 1 or 2, wherein,

the thermoplastic elastomer composition at a resin temperature of 200 degrees C, a mold temperature of 40 degrees C under the conditions of injection molding of a thickness of 2mm sheet test piece, based on JIS K7136-1 determination of total light transmittance is above 65%.

10. The airbag housing cover according to claim 1 or 2, wherein,

a sheet-like test piece having a thickness of 2mm, which is obtained by injection molding the thermoplastic elastomer composition at a resin temperature of 200 ℃ and a mold temperature of 40 ℃, has a haze of 70% or less as measured according to JIS K7136-1.

11. A method of manufacturing the airbag housing cover of claim 1 or 2, comprising:

and a step of injection molding the thermoplastic elastomer composition.

12. A thermoplastic elastomer composition comprising a propylene random copolymer and a linear styrene elastomer, wherein the linear styrene elastomer has a styrene unit content of 20 to 35 mass% and a glass transition temperature in the range of-65 to-45 ℃,

in the thermoplastic elastomer composition of 100 mass%, the propylene random copolymer and the linear styrene elastomer total content exceeds 40 mass% and is 100 mass% or less,

the content of the linear styrene-based elastomer is 45 to 250 parts by mass based on 100 parts by mass of the propylene-based random copolymer,

the thermoplastic elastomer composition has a melt flow rate of 1.0g/10 min or more and 50g/10 min or less at a temperature of 230 ℃ under a measured load of 21.18N according to JIS K7210 (1999).

13. The thermoplastic elastomer composition according to claim 12, wherein,

the thermoplastic elastomer composition at a resin temperature of 200 degrees C, a mold temperature of 40 degrees C under the conditions of injection molding of a thickness of 2mm sheet test piece, based on JIS K7136-1 determination of total light transmittance is above 65%.

14. The thermoplastic elastomer composition according to claim 12 or 13, wherein,

a sheet-like test piece having a thickness of 2mm, which is obtained by injection molding the thermoplastic elastomer composition at a resin temperature of 200 ℃ and a mold temperature of 40 ℃, has a haze of 70% or less as measured according to JIS K7136-1.

15. The thermoplastic elastomer composition according to claim 12 or 13, further comprising 10 parts by mass or more and 100 parts by mass or less of an ethylene/α -olefin copolymer per 100 parts by mass of the propylene random copolymer.

16. The thermoplastic elastomer composition according to claim 12 or 13, wherein,

the linear styrene elastomer has a styrene unit content of 20 to 25 mass%.

17. The thermoplastic elastomer composition according to claim 16, wherein,

the linear styrene elastomer comprises:

a hydrogenated product (b 1) of a styrene/conjugated diene block copolymer having a styrene unit content of 10 mass% or more and 15 mass% or less, and

a hydrogenated product (b 2) of a styrene/conjugated diene block copolymer having a styrene unit content of 25 mass% or more and 35 mass% or less.

18. A shaped body formed from the thermoplastic elastomer composition of claim 12 or 13.

19. A composite molded body, comprising:

a first layer comprising the thermoplastic elastomer composition of claim 12 or 13; and

a second layer comprising a resin film.

20. A composite molded body, comprising:

a first layer comprising a thermoplastic elastomer composition containing a propylene random copolymer and a styrene elastomer having a glass transition temperature in a range of-65 ℃ or more and-45 ℃ or less; and

a second layer comprising a resin film.