JP7834997B2 - Crosslinked thermoplastic elastomer composition - Google Patents

Description

This invention relates to a crosslinked thermoplastic elastomer composition, a joining member made from this crosslinked thermoplastic elastomer composition, a composite molded article for automobiles using this joining member, and a corner material for automobiles.

Thermoplastic elastomer compositions obtained by melt-kneading polypropylene resins and styrene-butadiene block copolymers and then undergoing dynamic heat treatment exhibit rubber-like soft material properties while eliminating the need for a vulcanization process and possessing moldability similar to thermoplastic resins. For this reason, such thermoplastic elastomer compositions have attracted attention from the perspectives of rationalizing manufacturing processes and recyclability, and are widely used in fields such as automotive parts, home appliances, medical equipment parts, electric wires, and general merchandise. In particular, these thermoplastic elastomer compositions have been widely used as sealing materials for automobiles and building materials.

The components used in automotive and building sealants have complex structures, and the desired components are manufactured by joining these components together. Instead of using liquid or paste-like adhesives to join the components, a technique is known that uses connecting members to join them.

For example, a technique is known in which a joining member made of a specific thermoplastic elastomer composition is used to join members made of dynamically crosslinked thermoplastic elastomers (see Patent Documents 1 and 2).

Japanese Patent Publication No. 2019-131722 Japanese Patent Publication No. 2020-125442

Composite molded articles used as sealing materials for window frames in automobiles and other vehicles are obtained by fusing a joining member and a joined member at the joint surface. To prevent abnormal noise and sagging caused by repeated raising and lowering of windows, a technology that achieves a high level of both fusion durability and sliding properties is desired for these composite molded articles.

The joint members made of thermoplastic elastomer compositions described in Patent Documents 1 and 2 exhibit good sliding properties and fusion properties with the members to be joined. However, they have a drawback: when bent at the interface between the joint member and the members to be joined, they easily peel off from that interface. Therefore, there was room for improvement in the fusion durability at the joint between the joint member and the members to be joined.

Thus, currently, there are no thermoplastic elastomer compositions that offer a high level of both fusion durability and sliding properties, making them excellent as joining components for automotive composite molded articles.

The object of the present invention is to solve the problems of the prior art described above and to provide a crosslinked thermoplastic elastomer composition capable of forming a composite molded article with excellent fusion durability and sliding properties, a joining member made of this crosslinked thermoplastic elastomer composition, a composite molded article for automobiles equipped with this joining member, and a corner material for automobiles.

The inventors have discovered a novel finding, previously unknown, that a crosslinked thermoplastic elastomer composition obtained by melt-kneading a material composition containing component (A): styrene-based elastomer, component (B): unmodified polypropylene, component (C): modified polypropylene modified with (meth)acrylic acid and/or its derivatives, and component (D): lubricant, in the presence of component (f): crosslinking agent, or a crosslinked thermoplastic elastomer composition containing components (A), (B), (C), and (D) and having a tensile stress at break of 7 MPa or more and less than 15 MPa measured at 23°C in accordance with the ISO 37 Type 1A (test speed 500 mm/min) method, can achieve a high level of sliding properties in addition to excellent fusion durability. This discovery has allowed the inventors to solve the above-mentioned problems and complete the present invention.

In other words, the gist of this invention is as follows:

[1] A crosslinked thermoplastic elastomer composition obtained by melt-kneading a material composition containing the following components (A), (B), (C), and (D) in the presence of the following component (f).
Components (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene component modified with (meth)acrylic acid and/or its derivatives (D): Lubricant component (f): Crosslinking agent

[2] A crosslinked thermoplastic elastomer composition comprising the following components (A), (B), (C), and (D), wherein the tensile stress at break measured at 23°C in accordance with the ISO 37 Type 1A (test speed 500 mm/min) method for measuring tensile stress at break is 7 MPa or more and less than 15 MPa.
Components (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene component modified with (meth)acrylic acid and/or its derivatives (D): Lubricant

[3] The crosslinked thermoplastic elastomer composition according to [1] or [2], wherein the melt flow rate (MFR) of the unmodified polypropylene of component (B), measured in accordance with JIS K7210 (1999) at a measurement temperature of 230°C and a measurement load of 21.2 N, is 1 g/10 min or more and 60 g/10 min or less.

[4] A bonding member comprising a crosslinked thermoplastic elastomer composition as described in any of [1] to [3].

[5] A composite molded body for automobiles, comprising the joining member described in [4].

[6] An automotive corner material using the composite molded product described in [5].

According to the present invention, it is possible to provide a crosslinked thermoplastic elastomer composition capable of forming a composite molded article with excellent fusion durability and sliding properties, a joining member made of this crosslinked thermoplastic elastomer composition, a composite molded article for automobiles equipped with this joining member, and a corner material for automobiles.
The joining member made of the crosslinked thermoplastic thermoplastic elastomer composition of the present invention is useful as a joining member for automotive sealing materials and building material sealing materials, and is particularly useful as a joining member for automotive composite molded products such as automotive glass run channels, and especially for automotive composite molded products such as automotive corner materials.

This is a perspective view showing an example of an automotive glass run channel to which the present invention is applied.

The present invention will be described in detail below, but the present invention is not limited to the following description and can be modified and implemented as appropriate without departing from the spirit of the invention. In this specification, when "~" is used to enclose numerical values or physical properties, it is intended to include the values before and after it. Furthermore, in this specification, "(meth)acrylic acid" means either acrylic acid or methacrylic acid, or both.

[Cross-linked thermoplastic elastomer composition]
The crosslinked thermoplastic elastomer composition of the present invention is a crosslinked thermoplastic elastomer composition obtained by melt-kneading a material composition containing at least the following components (A), (B), (C), and (D) in the presence of component (f).
Components (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene component modified with (meth)acrylic acid and/or its derivatives (D): Lubricant component (f): Crosslinking agent

The crosslinked thermoplastic elastomer composition of the present invention also comprises the following components (A), (B), (C), and (D), and is a crosslinked thermoplastic elastomer composition in which the tensile stress at break measured at 23°C in accordance with the ISO 37 Type 1A (test speed 500 mm/min) method for measuring tensile stress at break is 7 MPa or more and less than 15 MPa.
Component (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene component modified with (meth)acrylic acid and/or its derivatives (D): Lubricant The tensile stress at break is related to the crosslinking state of the thermoplastic elastomer composition. The tensile stress at break tends to be high for non-crosslinked thermoplastic elastomer compositions and low for crosslinked thermoplastic elastomer compositions. The reason why the tensile stress at break tends to be low in crosslinked thermoplastic elastomer compositions is that the crosslinked portions in the crosslinked thermoplastic elastomer composition do not stretch, and stress is more concentrated in the non-crosslinked portions, which promotes slippage between molecular chains and makes it easier to break due to void formation. In other words, in crosslinked thermoplastic elastomer compositions, the interface between the rubber and resin parts is weaker compared to non-crosslinked thermoplastic elastomers, which tends to result in a lower stress at break.

[mechanism]
The crosslinked thermoplastic elastomer composition of the present invention exhibits excellent fusion durability and good sliding properties.

The detailed reasons why the crosslinked thermoplastic elastomer composition of the present invention exhibits such effects are not entirely clear, but they are thought to be as follows.
The crosslinked thermoplastic elastomer composition of the present invention is thought to have improved fusion durability because the presence of polar groups derived from (meth)acrylic acid and/or its derivatives of component (C) on the surface of the crosslinked thermoplastic elastomer composition promotes molecular entanglement at the bonding surface with the member to be joined during thermal fusion.
If the sole purpose is to improve sliding properties, then a larger amount of lubricant component (D) can be added, but this would worsen the fusion durability.
The crosslinked thermoplastic elastomer composition of the present invention is considered to have excellent sliding properties because, since component (B) and component (C) both have a common polypropylene main chain, component (B) and component (C) are compatible with each other, and high surface smoothness derived from the polypropylene portion of component (B) and component (C) is maintained.
The crosslinked thermoplastic elastomer composition of the present invention is preferable because it easily exhibits the effects of the above mechanism by controlling the matrix portion containing components (B), (C), and (D) to a domain matrix structure having a domain portion of component (A).

[Ingredient (A)]
The component (A) used in this invention is a styrene-based elastomer.

As styrene-based elastomers, block copolymers having at least two polymer block P (hereinafter sometimes simply referred to as "block P") mainly composed of aromatic vinyl compound units and at least one polymer block Q (hereinafter sometimes simply referred to as "block Q") mainly composed of conjugated diene compound units, and/or hydrogenated versions of said block copolymers, are preferred. Hereinafter, these block copolymers and/or their hydrogenated versions may be referred to as "(hydrogenated) block copolymers."

Here, "primarily" means that the target monomer unit is present in the target polymer block at a concentration of 50 mol% or more.

The aromatic vinyl compounds constituting Block P are not particularly limited, and examples include styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. Among these, styrene, α-methylstyrene, and p-methylstyrene are preferred from the viewpoint of availability and productivity. Styrene is more preferred.

Block P may consist of one type of aromatic vinyl compound unit, or it may consist of two or more types of aromatic vinyl compound units. Block P may also contain monomer units other than vinyl aromatic compound units.

The conjugated diene compound constituting Block Q is a diolefin having one pair of conjugated double bonds. Examples of conjugated diene compounds, though not limited to those listed below, include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of productivity. More preferably, 1,3-butadiene is used.

Block Q may consist of one type of conjugated diene compound unit, or it may consist of two or more types of conjugated diene compound units. Block Q may also contain monomer units other than conjugated diene compound units.

The mass percentage of block P, which mainly consists of aromatic vinyl compound units, in the block copolymer of component (A) is not limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, while preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less.

The chemical structure of the block copolymer of component (A) may be linear, branched, radial, or any other, but it is preferably a block copolymer represented by the following formula (1) or (2), and more preferably the structure of formula (1) below from the viewpoint of improving mechanical strength.

P-(Q-P)m (1)
(P - Q)n (2)
In the formula, P represents block P, Q represents block Q, m represents an integer from 1 to 5, and n represents an integer from 2 to 5.
If there are multiple blocks P and multiple blocks Q, the monomer units contained within them may be the same or different.

In equation (1) or (2), larger values of m and n are preferable in terms of lowering the order-to-disorder transition temperature of the rubbery polymer, but smaller values are preferable in terms of ease of manufacture and cost.

From the viewpoint of the rubber elasticity of the composition, component (A) is preferably a block copolymer represented by formula (1), more preferably a block copolymer represented by formula (1) where m is 3 or less, even more preferably a block copolymer represented by formula (1) where m is 2 or less, and particularly preferably a block copolymer represented by formula (1) where m is 1.

The component (A) used in this invention may be a hydrogenated block copolymer having block P and block Q. In this case, it is preferably a hydrogenated block copolymer represented by formula (1), more preferably a hydrogenated block copolymer represented by formula (1) where m is 3 or less, even more preferably a hydrogenated block copolymer represented by formula (1) where m is 2 or less, and particularly preferably a hydrogenated block copolymer represented by formula (1) where m is 1.

The number-average molecular weight of component (A) is not limited, but it is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 170,000 or more, and preferably 600,000 or less, more preferably 550,000 or less, and even more preferably 500,000 or less, as measured by gel permeation chromatography (hereinafter sometimes abbreviated as GPC) in terms of polystyrene equivalent.

Examples of component (A) include styrene-butadiene-styrene block copolymer and its hydrogenated products, styrene-isoprene-butadiene-styrene block copolymer and its hydrogenated products, etc.
Examples of hydrogenated styrene-butadiene-styrene block copolymers include styrene-ethylene-butylene-styrene copolymer (SEBS).
Examples of hydrogenated styrene-isoprene-butadiene-styrene block copolymers include styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS).
Among these, hydrogenated styrene-butadiene-styrene block copolymers are preferred because they tend to provide high fluidity and good fusion properties.

Examples of commercially available components (A) include "TAIPOL®-6151" and "TAIPOL®-6159" manufactured by Taiwan Synthetic Rubber Corporation (TSRC), "G1651" and "G1633" manufactured by Kraton Polymer Japan Co., Ltd., and "Septon® 4099" manufactured by Kuraray Co., Ltd.

The above component (A) may be used alone, or two or more components with different compositions and physical properties may be used in combination.

[Component (B)]
The component (B) used in this invention is unmodified polypropylene.

In this invention, "polypropylene" means a material having a propylene unit content of 50% by mass or more, and includes both materials composed of a single resin component and materials composed of multiple resin components.
The propylene unit content of unmodified polypropylene in component (B) is preferably 85 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 94 to 100% by mass. When the propylene unit content of component (A) is above the aforementioned lower limit, the heat resistance and rigidity tend to be good. The propylene unit content in component (A) can be determined by infrared spectroscopy.

Component (B) may be a propylene homopolymer, or it may be a propylene copolymer containing, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 6% by mass or less, ethylene units, α-olefin units other than propylene, monomer units other than ethylene and α-olefins, in addition to propylene units.

Examples of α-olefin units other than 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-heptene, 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-1-pentene, 2-ethyl-1-hexene, 2,2,4-trimethyl-1-pentene, etc. Preferably, α-olefins having 4 to 10 carbon atoms are used, and more preferably, 1-butene, 1-hexene, and 1-octene.
The propylene copolymer may contain only one of these α-olefin units and ethylene units, or it may contain two or more of them.

Specific examples of unmodified polypropylene (component (B)) include propylene homopolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-ethylene-1-butene copolymer, propylene-ethylene-1-hexene copolymer, propylene-ethylene-1-octene copolymer, and propylene-based block copolymers obtained by polymerizing a propylene homopolymer in the first step followed by polymerizing a propylene-ethylene copolymer in the second step. Preferably, it is a propylene-ethylene copolymer.

Among these, a propylene copolymer containing 6% by mass or less of one or more monomer units selected from ethylene units, butene units, hexene units, and octene units is preferred as component (B) from the viewpoint of compatibility with component (A).

The melt flow rate (MFR) of component (B) is not limited, but from the viewpoint of the fusion properties between the joining member and the members to be joined and the appearance of the molded article, it is usually 1 g/10 min or more, preferably 10 g/10 min or more, more preferably 20 g/10 min or more, and even more preferably 25 g/10 min or more.
Furthermore, the melt flow rate of component (B) is usually 100 g/10 min or less, preferably 80 g/10 min or less, and more preferably 60 g/10 min or less, from the viewpoint of tensile strength.
The melt flow rate of component (B) is measured according to JIS K7210 (1999) under conditions of a measurement temperature of 230°C and a measurement load of 21.2 N.

If component (B) consists of a blend of unmodified polypropylenes having different MFRs, the MFR of component (B) can be calculated by the following formula (I).
log(MFR blend) = w1log(MFR1) + w2log(MFR2) + ... + wilog(MFRi) + ... + wnlog(MFRn) ... (I)
In equation (I), wi is the weight fraction of component i, MFRi is the MFR of component i, and n is the total number of components in the blend. w1 + w2 + ... + wi + ... + wn = 1.

Preferably, the melting peak temperature of component (B) is observed at a temperature of at least 100°C or higher and less than 157°C.
The melting peak of component (B) being within the above numerical range is preferable from the viewpoint of heat resistance and compatibility with component (A).
The melting peak temperature of component (B) can be measured according to JIS K7121 by the following method.
Specifically, the melting behavior of polypropylene is measured by sequentially performing the following steps (1) to (3) using a differential scanning calorimeter (DSC6220 manufactured by SSI Nanotechnology Co., Ltd.).
In each process, time is plotted on the horizontal axis and the amount of heat of fusion on the vertical axis to obtain a melting curve, and the peak top of the peak observed in process (3) is defined as the melting peak temperature.
Step (1): Heat 5 mg of the sample from room temperature at a rate of 100°C/min from 40°C to 200°C, and hold for 3 minutes after the heating is complete.
Step (2): Cool the temperature from 200°C to 40°C at a rate of 10°C/min, and hold the temperature for 3 minutes after the cooling is complete.
Step (3): Increase the temperature from 40°C to 200°C at a rate of 10°C/min.

As a method for producing unmodified polypropylene of component (B), known polymerization methods using known olefin polymerization catalysts can be used. For example, a multi-stage polymerization method using a Ziegler-Natta catalyst can be cited. This multi-stage polymerization method can utilize slurry polymerization, solution polymerization, bulk polymerization, gas-phase polymerization, etc., and two or more of these may be combined.

Component (B) can also be a commercially available product. Component (B) can be procured from the manufacturers listed below and can be selected as appropriate. Examples of commercially available products include: Prime Polymer's Prime Polypro (registered trademark), Sumitomo Chemical's Sumitomo Noblen (registered trademark), Sun Allomer's Polypropylene Block Copolymer, Nippon Polypro's Novatec (registered trademark) PP, Lyondell Basell's Moplen (registered trademark), ExxonMobil's Vistamax (registered trademark), ExxonMobil PP, Formosa Plastics' Formolene (registered trademark), Borealis' Borealis PP, LG Chemical's SEETEC PP, and A. Examples include Schulman's ASI Polypropylene, INEOS Olefins & Polymers' INEOS PP, Braskem's Braskem PP, SAMSUNG TOTAL PETROCHEMICALS' Samsung Total, Sabic's Sabic® PP, TOTAL PETROCHEMICALS' TOTAL PETROCHEMICALS Polypropylene, and SK's YUPLENE®.

The above component (B) may be used alone, or two or more components with different compositions and physical properties may be used in combination.

[Component (C)]
The modified polypropylene (hereinafter sometimes referred to as "(meth)acrylic acid-modified polypropylene"), which is component (C) used in the present invention, functions as an improver in the crosslinked thermoplastic elastomer resin composition of the present invention to improve the fusion durability with the joined members during heat fusion.

As the polypropylene used as the raw material for component (C), unmodified polypropylene of component (B) can be used. Among these, propylene homopolymer and propylene-ethylene random copolymer are preferred because they are relatively inexpensive and readily available. From the viewpoint of obtaining high adhesion due to the molecular entanglement effect at the bonding surface with the joined members during heat fusion, propylene homopolymer is more preferred.

The density of the polypropylene used as a raw material for component (C) (according to ISO 1183 Method A (water displacement method)) is not particularly limited, but is preferably 0.85 g/ ^cm³ or more, more preferably 0.87 g/ ^cm³ or more, while is preferably 0.96 g/ ^cm³ or less, and more preferably 0.95 g/ ^cm³ or less.

Furthermore, the melt flow rate (MFR, compliant with JIS K7210:1999, 230°C, load 21.2N) of the polypropylene used as the raw material for component (C) is not particularly limited, but from the viewpoint of moldability, 0.01 to 200 g/10 min is preferred, and more preferably 0.1 to 80 g/10 min.

Many propylene-based copolymers, such as propylene homopolymers and propylene-α-olefin copolymers, that satisfy the above physical properties are commercially available in various grades from domestic and international manufacturers. Therefore, commercially available polypropylene products of various grades can be used as the raw material for component (C).

Component (C), (meth)acrylic acid-modified polypropylene, is obtained by modifying the aforementioned polypropylene with (meth)acrylic acid and/or its derivatives. Examples of (meth)acrylic acid derivatives include esters, amides, imides, and metal salts of (meth)acrylic acid. Specifically, examples include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, glycidyl (meth)acrylate, methacrylamide, sodium (meth)acrylate, and potassium (meth)acrylate.

(Meth)acrylic acid and/or its derivatives may be used individually, or two or more may be used in any combination in any ratio as appropriate.
Among these, (meth)acrylic acid and (meth)acrylic acid esters are preferred, and (meth)acrylic acid and (meth)acrylic acid glycidyl are more preferred.

The amount of (meth)acrylic acid and/or its derivative used for modifying polypropylene is usually 0.01 parts by mass or more, preferably 0.1 parts by mass or more, per 100 parts by mass of polypropylene used as a raw material for component (C), while usually 20 parts by mass or less, preferably 10 parts by mass or less. If the amount of (meth)acrylic acid and/or its derivative used is above the lower limit, the resulting crosslinked thermoplastic elastomer composition tends to have good adhesion. On the other hand, if it is below the upper limit, the generation of unreacted materials and by-products is suppressed, preventing deterioration of the product appearance due to fish eyes, blemishes, etc., in molded articles using the resulting crosslinked thermoplastic elastomer composition, and suppressing a decrease in adhesion.

The modification using (meth)acrylic acid and/or its derivatives described above is preferably performed by graft modification, and graft modification can be carried out by various conventionally known methods. Examples of modification methods include, but are not limited to, a melt modification method in which (meth)acrylic acid and/or its derivatives are added to molten polypropylene and graft copolymerization is performed; a solution modification method in which (meth)acrylic acid and/or its derivatives are added to polypropylene dissolved in a solvent and graft copolymerization is performed; and a solid-phase polymerization method in which (meth)acrylic acid and/or its derivatives are added to solid polypropylene and graft copolymerization is performed.

As a melt-modification method, polypropylene and (meth)acrylic acid and/or its derivatives are melted using an extruder or the like at a temperature above the melting point of the polypropylene (e.g., 170-290°C), and reacted for typically 0.5 to 10 minutes. As a solution-modification method, polypropylene, (meth)acrylic acid and/or its derivatives, and optionally a radical initiator are added to an organic solvent, and the mixture is reacted at a temperature above the melting point of the polypropylene (e.g., 170-290°C) for typically 0.5 to 15 hours, preferably 1 to 10 hours. As a solid-phase polymerization method, solid polypropylene, (meth)acrylic acid and/or its derivatives, and optionally a radical initiator are added, and the mixture is reacted at a temperature below the melting point of the polypropylene (e.g., 20-150°C) for typically 1 to 24 hours, preferably 1 to 10 hours. Among these, from a hygienic viewpoint, the melt-modification method and solid-phase polymerization method, which do not require the use of solvents, are preferred. Furthermore, to efficiently perform graft modification, it is preferable to perform the modification in the presence of a radical initiator.

While not particularly limited, organic peroxides or azo compounds are preferred as radical initiators, with organic peroxides being particularly preferred. Specifically, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,4-bis(t-butylperoxyisopropyl)benzene, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)balate, 2,2-bis(4,4-t-butylperoxycyclohexyl)propane, 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclododecane; t-butylperoxyacetate, t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylperoxylaurate, t-butylperoxybenzoate, t-butylperoxyisopropyl Examples of peroxy esters include peroxy carbonates, t-butyl peroxymalic acid, di-t-butyl peroxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexyn-3, and 2,5-dimethyl-2,5-di(toluylperoxy)hexane; diacyl peroxides include di-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, and dibenzoyl peroxide; hydroperoxides include t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, and 2,5-dimethyl-2,5-di(hydroperoxy)hexane; and ketone peroxides include methyl ethyl ketone peroxide and cyclohexanone peroxide, but are not particularly limited to these. Radical initiators can be used individually or in combination of two or more in any desired ratio.

Among these, radical initiators with a decomposition temperature of 100°C or higher at which a half-life of 1 minute is obtained are preferred from the viewpoint of graft modification efficiency. Specifically, dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyn-3, or peroxyesters such as t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexyn-3 are preferred.

The amount of radical initiator used is not particularly limited, but a ratio of 0.001 parts by mass to 1 part by mass per 100 parts by mass of the raw material polypropylene is preferred.

The modification rate of (meth)acrylic acid and/or its derivatives in (meth)acrylic acid-modified propylene is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more, relative to the total amount of (meth)acrylic acid-modified polypropylene. On the other hand, it is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less. While this can vary depending on the polypropylene used as the raw material, if the (meth)acrylic acid modification rate falls outside the above preferred range, the melt viscosity tends to increase or decrease, making it more likely for defects in the appearance of the molded product to occur.

Here, the modification rate (graft rate) can be measured, for example, by the following method. That is, (meth)acrylic acid-modified polypropylene is dissolved in a solvent such as orthodichlorobenzene or paradichlorobenzene, and ^13C nuclear magnetic resonance (NMR) is measured to distinguish and quantify the carbon atoms contained in the polypropylene skeleton and the carbon atoms contained in the (meth)acrylic acid and/or its derivative skeleton, and the graft rate can be measured from their area ratio. In the graft modification of (meth)acrylic acid-modified polypropylene, unreacted (meth)acrylic acid and/or its derivative may remain, but as specified herein, the graft rate refers to the value obtained when (meth)acrylic acid-modified polypropylene is measured by ^13C NMR, as described above.

The density of (meth)acrylic acid-modified polypropylene is not particularly limited, but is preferably 0.85 g/ ^cm³ or higher, more preferably 0.87 g/ ^cm³ or higher, and preferably 0.96 g/ ^cm³ or lower, and more preferably 0.95 g/ ^cm³ or lower, as measured in accordance with ISO 1183 Method A (water displacement method).
Furthermore, the melt flow rate (MFR) of (meth)acrylic acid-modified polypropylene is not particularly limited, but is preferably 0.01 to 3000 g/10 min, and more preferably 0.1 to 2500 g/10 min. Here, the MFR of (meth)acrylic acid-modified polypropylene refers to the value measured under conditions of 230°C and a load of 2.16 kg in accordance with JIS K7210:1999.

In the crosslinked thermoplastic elastomer composition of the present invention, component (C), the (meth)acrylic acid-modified polypropylene, may be used alone or in combination of two or more types.

A commercially available example of component (C) is "SCONA T Polypropylene 2110 FA" manufactured by BYK.

[Component (D)]
As the lubricant for component (D), a silicone-based lubricant can be suitably used, such as silicone oil, silicone masterbatch, or liquid siloxane wax. More preferably, a silicone oil is used.

[Component (E)]
The thermoplastic elastomer composition of the present invention may contain a softening agent as component (E).

The softening agent for component (E) is not particularly limited and any known softening agent can be used, but hydrocarbon-based rubber softening agents are particularly preferred. Examples of hydrocarbon-based rubber softening agents include mineral oil-based softening agents and synthetic resin-based softening agents, but mineral oil-based softening agents are preferred from the viewpoint of affinity with other components. Mineral oil-based softening agents are generally mixtures of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons. Those in which 50% or more of the total carbon atoms are paraffinic hydrocarbons are called paraffinic oils, those in which 30-45% of the total carbon atoms are naphthenic hydrocarbons are called naphthenic oils, and those in which 35% or more of the total carbon atoms are aromatic hydrocarbons are called aromatic oils. Among these, paraffinic oil is preferred in this invention.

The kinematic viscosity of component (E), the softener, at 40°C is not particularly limited, but is preferably 20 cSt or higher, more preferably 50 cSt or higher, and also preferably 800 cSt or lower, more preferably 600 cSt or lower. Furthermore, the flash point (COC method) of the softener is preferably 200°C or higher, more preferably 250°C or higher.

The softening agent for component (E) is available commercially. Examples of such commercially available products include the "Nisseki Polybutene® HV" series from JX Nippon Oil & Energy Corporation and the "Diana® Process Oil PW" series from Idemitsu Kosan Co., Ltd. The appropriate product can be selected and used from these options as needed.

The softening agent of component (E) may be used alone, or two or more types may be used in any combination and ratio.

[Component (f)]
The crosslinked thermoplastic elastomer composition of the present invention is obtained by dynamic heat treatment in the presence of a crosslinking agent of component (f). By performing dynamic heat treatment in the presence of a crosslinking agent of component (f) and crosslinking at least a portion of component (A), good rubber elasticity can be achieved. The crosslinked thermoplastic elastomer composition may contain crosslinking agent reaction products.

As crosslinking agents, organic peroxides, phenolic resins, and other crosslinking aids can be used. These crosslinking agents may be used individually or in combination of two or more.

Both aromatic and aliphatic organic peroxides can be used as crosslinking agents. Specifically, examples include dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, 1,3-bis(t-butylperoxyisopropyl)benzene, and 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; peroxyesters such as t-butyl peroxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)-3-hexine; and hydroperoxides such as acetyl peroxide, lauroyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is preferred.
These organic peroxides may be used individually or in combination of two or more types.

Examples of phenolic resins that can be used as crosslinking agents include alkylphenol formaldehyde and alkylphenol bromide formaldehyde. These phenolic resins may be used individually or in combination of two or more.

Examples of crosslinking aids other than those for phenolic resins include peroxide aids such as sulfur, p-quinone dioxime, p-dinitrosobenzene, and 1,3-diphenylguanidine; crosslinking aids for phenolic resins such as stannous chloride anhydrous, stannous chloride dihydrate, and ferric chloride; polyfunctional vinyl compounds such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, and diallyl phthalate; and polyfunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl(meth)acrylate. These may be used individually or in combination of two or more.

[Other ingredients]
In the production of the crosslinked thermoplastic elastomer composition of the present invention, other components may be used as raw materials as necessary, in addition to components (A) to (E) and (f), as long as they do not impair the effects of the present invention.

Other components include, for example, resins such as thermoplastic resins and elastomers other than components (A), (B), and (C), antioxidants, fillers, heat stabilizers, light stabilizers, UV absorbers, neutralizing agents, anti-fogging agents, anti-blocking agents, slip agents, dispersants, colorants, flame retardants, antistatic agents, conductivity imparters, metal deactivators, molecular weight modifiers, antibacterial agents, antifungal agents, fluorescent whitening agents, and various other additives. These can be used individually or in combination.

Examples of thermoplastic resins other than components (A), (B), and (C) include polyphenylene ether resins; polyamide resins such as nylon 6 and nylon 66; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyoxymethylene resins such as polyoxymethylene homopolymer and polyoxymethylene copolymer; polymethyl methacrylate resins; and polyolefin resins (excluding those corresponding to components (B) and (C)). Examples of elastomers other than components (A), (B), and (C) include polyester elastomers and polybutadiene.

Examples of antioxidants (hereinafter sometimes referred to as "component (G)") include phenolic antioxidants, phosphite antioxidants, and thioether antioxidants. When using an antioxidant, it is typically used in an amount of 0.01 to 3.0 parts by mass, preferably 0.15 to 0.6 parts by mass, per 100 parts by mass of the total component (A). Good thermal stability can be obtained within this range.

[Content ratio]
The crosslinked thermoplastic elastomer composition of the present invention preferably contains 40 to 120 parts by mass of component (B) per 100 parts by mass of component (A) from the viewpoint of achieving both moldability and flexibility. From the viewpoint of moldability, the lower limit of the content of component (B) is more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more. On the other hand, from the viewpoint of obtaining sufficient flexibility and hardness, the upper limit of the content of component (B) is more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less.

The crosslinked thermoplastic elastomer composition of the present invention preferably contains 1 to 50 parts by mass of component (C) per 100 parts by mass of component (A), from the viewpoint of sufficiently improving the fusion properties to thermoplastic elastomer compositions containing propylene resin as the base phase. From the viewpoint of improving compression set, the lower limit of the component (C) content is more preferably 6 parts by mass or more, and even more preferably 16 parts by mass or more. On the other hand, from the viewpoint of ensuring fluidity, the upper limit of the component (C) content is more preferably 42 parts by mass or less, and even more preferably 33 parts by mass or less.

The crosslinked thermoplastic elastomer composition of the present invention uses component (D) in an amount of typically 0.5 to 50 parts by mass, preferably 1 to 25 parts by mass, per 100 parts by mass of component (A). More preferably, by adding a small amount of component (D) of 20 parts by mass or less per 100 parts by mass of component (A), sufficient sliding properties can be obtained while suppressing a decrease in fusion properties.

In the crosslinked thermoplastic elastomer composition of the present invention, the lower limit of the amount of crosslinking agent in component (f) is preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, and even more preferably 0.20 parts by mass or more, per 100 parts by mass of component (A), from the viewpoint of ensuring sufficient crosslinking. On the other hand, the upper limit of the amount of crosslinking agent in component (f) is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4.0 parts by mass or less, per 100 parts by mass of component (A), from the viewpoint of controlling attack on the propylene chain.

When the crosslinked thermoplastic elastomer composition of the present invention contains component (E), the lower limit of the content of component (E) per 100 parts by mass of component (A) is usually 100 parts by mass or more, preferably 102 parts by mass or more, and more preferably 104 parts by mass or more, from the viewpoint of moldability. On the other hand, the upper limit of the content of component (E) is usually 140 parts by mass or less, preferably 138 parts by mass or less, and more preferably 136 parts by mass or less, from the viewpoint of flexibility.

When the crosslinked thermoplastic elastomer composition of the preferred embodiment of the present invention contains components other than components (A) to (D) and component (E), in order to fully obtain the effects of containing components (A) to (D) and component (E), the content of the other components is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, relative to 100 parts by mass of the total of components (A) and (B) (however, if component (E) is included, the total of components (A), (B), and (E) is 100 parts by mass or more). Furthermore, the content of the other components is preferably 30 parts by mass or less, more preferably 29 parts by mass or less, and even more preferably 28 parts by mass or less, relative to 100 parts by mass of the total of components (A) and (B) (however, if component (E) is included, the total of components (A), (B), and (E) is 100 parts by mass or less).

[Method for producing crosslinked thermoplastic elastomer compositions]
The crosslinked thermoplastic elastomer resin composition of the present invention is obtained by dynamic heat treatment by melt-kneading a material composition of a crosslinked thermoplastic elastomer composition containing components (A), (B), (C), and (D) in the presence of component (f). More preferably, it is obtained by dynamic heat treatment by melt-kneading a material composition containing components (A), (B), (C), (D), and (E) in the presence of component (f). By performing this dynamic heat treatment in the presence of component (f) and crosslinking at least a portion of component (A), the sliding properties can be improved.

In this invention, "dynamic heat treatment" means kneading in a molten or semi-molten state in the presence of an organic peroxide. This dynamic heat treatment is preferably performed by melt kneading, and suitable melt kneading equipment for this purpose includes, for example, a closed-type Banbury mixer, mixing rolls, a kneader, and a twin-screw extruder. Among these, the use of a twin-screw extruder is preferred. A preferred embodiment of the manufacturing method using this twin-screw extruder involves supplying each component to the raw material supply ports (hoppers) of a twin-screw extruder having multiple raw material supply ports and performing the dynamic heat treatment.

The temperature during dynamic heat treatment is typically 80 to 300°C, preferably 100 to 250°C. The duration of the dynamic heat treatment is typically 0.1 to 30 minutes.

When the crosslinked thermoplastic elastomer composition of the present invention is manufactured by dynamic heat treatment using a twin-screw extruder, it is preferable to extrude while maintaining the relationship shown in formula (i) below between the barrel radius (R (mm)), screw rotation speed (N (rpm)), and discharge rate (W (kg/hour)) of the twin-screw extruder, and more preferably while maintaining the relationship shown in formula (ii) below.
2.6<NW/ ^R3 <22.6 (i)
3.0<NW/ ^R3 <20.0 (ii)

For efficient production of thermoplastic elastomer compositions, it is preferable that the relationship between the barrel radius (R (mm)), screw rotation speed (N (rpm)), and discharge rate (W (kg/hour)) of a twin-screw extruder is greater than the lower limit. Conversely, it is preferable that the relationship is smaller than the upper limit, as this suppresses heat generation due to shear and reduces the likelihood of foreign matter causing appearance defects.

[Physical properties of crosslinked thermoplastic elastomer compositions]
From the viewpoint of moldability, the crosslinked thermoplastic elastomer composition of the present invention preferably has a melt flow rate (MFR) of 5 g/10 min or more, more preferably 10 g/10 min or more, and even more preferably 15 g/10 min or more, measured in accordance with the JIS K7210 standard at a measurement temperature of 230°C and a measurement load of 21.2 N. Furthermore, from the viewpoint of moldability, the melt flow rate (MFR) is preferably 150 g/10 min or less, more preferably 145 g/10 min or less, and even more preferably 140 g/10 min or less.

From the viewpoint of weight reduction, the crosslinked thermoplastic elastomer composition of the present invention preferably has a density of 1.11 g/ ^cm³ or less, more preferably 1.00 g/ ^cm³ or less, and even more preferably 0.97 g/ ^cm³ or less, as measured in accordance with ISO 1183 Method A (water displacement method). The lower limit of the density is generally 0.90 g/ ^cm³ or more, based on the density of polypropylene.

From the viewpoint of its use as a bonding member, the crosslinked thermoplastic elastomer composition of the present invention preferably has a hardness duro A measured 15 seconds after pressing a needle against a test piece, in accordance with ISO 7619, that is in the range of 35 to 98, and more preferably in the range of 40 to 95.

From the viewpoint of its application as a bonding member, the crosslinked thermoplastic elastomer composition of the present invention preferably has a lower limit of tensile stress at break measured at 23°C in accordance with the ISO 37 Type 1A (test speed 500 mm/min) method for measuring tensile stress at break, which is 7 MPa or higher, more preferably 8 Pa or higher, and even more preferably 9 MPa or higher. The upper limit of the tensile stress at break is usually less than 15 MPa, more preferably 14 MPa or lower, and even more preferably 13 MPa or lower.

From the viewpoint of its use as a bonding member, the crosslinked thermoplastic elastomer composition of the present invention preferably has a lower limit of elongation at break of 400% or more, more preferably 500% or more, and even more preferably 600% or more, measured according to the procedure compliant with the ISO 37 Type 1A (test speed 500 mm/min) method for measuring elongation at break. The upper limit of the elongation at break is preferably 1300% or less, more preferably 1200% or less, and even more preferably 1100% or less.

[Molded object/Application]
The crosslinked thermoplastic elastomer composition of the present invention can be molded into a molded article by various molding methods commonly used for crosslinked thermoplastic elastomer compositions, such as injection molding, extrusion molding, hollow molding, and compression molding, with injection molding being preferred among these. Furthermore, the molded article can also be subjected to secondary processing such as lamination molding or thermoforming after these molding processes.

Molded articles made from the crosslinked thermoplastic elastomer composition of the present invention can be applied to a wide range of fields, including automotive parts such as skins, weatherstrips, ceiling materials, interior sheets, bumper moldings, side moldings, air spoilers, air duct hoses, and sealing materials; civil engineering and construction material parts such as water-stopping materials, joint materials, window frames, and sealing materials; sports equipment such as golf club grips and tennis racket grips; industrial parts such as hose tubes and gaskets; home appliance parts such as hoses and packings; medical parts such as medical containers, gaskets, and packings; food product parts such as containers and packings; medical equipment parts; electric wires; and general merchandise.
Molded articles made from the crosslinked thermoplastic elastomer composition of the present invention are particularly suitable as automotive sealants and building material sealants among those listed above, and are especially suitable as automotive glass run channels.

[Joining members]
The joining member of the present invention consists of the crosslinked thermoplastic elastomer composition of the present invention described above, and is manufactured by injection molding a molten mixture obtained by melt-kneading the crosslinked thermoplastic elastomer composition of the present invention.

In particular, the joining member of the present invention is suitable as a joining member used in automotive composite molded articles such as automotive glass run channels.
Figure 1 is a perspective view showing an example of a glass run channel for automobiles as a composite molded body 3. This composite molded body 3 is formed by fusing together joined members 1A and 1B, which constitute linear portions manufactured separately by extrusion molding of a thermoplastic elastomer composition, at a corner portion which is a joining member 2 made of the crosslinked thermoplastic elastomer composition of the present invention.

Such a composite molded body 3 can be manufactured, for example, by inserting the joining ends of pre-fabricated members 1A and 1B into an injection molding die, and injecting the crosslinked thermoplastic elastomer composition of the present invention into the die to form the corner joining member 2, while simultaneously fusing and integrating it with the end faces of the members 1A and 1B.

The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples unless it exceeds its gist. The various manufacturing conditions and evaluation results in the following examples represent preferred upper or lower limits in the embodiments of the present invention, and the preferred range may be defined by a combination of the aforementioned upper or lower limits and the values in the following examples or between examples.

〔raw materials〕
The raw materials used in the following examples and comparative examples are as follows:

[Component (A): Styrene elastomer]
<A-1>
Hydrogenated styrene-butadiene-styrene block copolymer (having the structure of formula (1) above; styrene (block P) content: 32% by mass, number average molecular weight: 200,000) / "TAIPOL-6151" manufactured by Taiwan Synthetic Rubber Co., Ltd. (TSRC)

[Component (B): Unmodified polypropylene]
<B-1>
Propylene-ethylene copolymer (MFR (JIS K7210): 30 g/10 min (230°C, 21.2 N), melting peak temperature: 155°C, propylene unit content: 98% by mass, ethylene unit content: 2% by mass) / manufactured by Nippon Polypropylene Co., Ltd. "Novatec (registered trademark) PP MG03BD"

[Component (C): (meth)acrylic acid modified polypropylene]
<C-1>
Acrylic acid-modified homopolypropylene (MFR (JIS K7210): 3.6 g/10 min (230°C, load 21.2 N), modification rate: 2.0 mass%) / BYK "SCONA T Polypropylene 2110 FA"

[Ingredient (D): Lubricant]
<D-1>
Silicone oil / Shin-Etsu Chemical Co., Ltd. "KF96-100CS"

[Ingredient (E): Hydrocarbon-based rubber softener]
<E-1>
Paraffin-based rubber softener (kinematic viscosity at 40°C: 95.5 cSt, flash point: 272°C) / "Diana® Process Oil PW90" manufactured by Idemitsu Kosan Co., Ltd.

[Component (f): Crosslinking agent]
<f-1>
A mixture of 40 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 60 parts by mass of calcium carbonate / Kayahexa AD40C manufactured by Kayaku Akzo Co., Ltd.
<f-2>
A mixture of 55 parts by mass of divinylbenzene and 45 parts by mass of ethylvinylbenzene / Crosslinking aid for "Divinylbenzene" manufactured by Wako Pure Chemical Industries, Ltd.

[Ingredient (G): Antioxidant]
<G-1>
Phenolic antioxidant / BASF Japan's "Irganox® 1010"

[Evaluation Method]
The evaluation methods for the crosslinked thermoplastic elastomer compositions in the following examples and comparative examples are as follows.

For the measurements in (1) to (5) and (7) below, each cross-linked thermoplastic elastomer composition was used, and sheets (120 mm wide, 80 mm long, 2 mm thick) obtained by injection molding using an in-line screw-type injection molding machine (Toshiba Machine Co., Ltd. "IS130") under the conditions of injection pressure of 50 MPa, cylinder temperature of 220°C, and mold temperature of 40°C were used.

(1) Hardness Duro A: The value was measured 15 seconds after pressing the needle against the test specimen, in accordance with ISO 7619.

(2) Density: Measured using a method compliant with ISO 1183 Method A (water displacement method).

(3) Tensile stress at break: The tensile stress at break was measured at 23°C using a procedure compliant with ISO 37 Type 1A (test speed 500 mm/min).

(4) Elongation at break: The procedure was carried out in accordance with the measurement method for elongation at break of ISO 37 Type 1A (test speed 500 mm/min).

(5) Static friction coefficient and kinetic friction coefficient A sheet obtained by injection molding (120 mm wide, 80 mm long, 2 mm thick) was cut to a size of 63 mm long x 63 mm wide, and the test piece was set on a glass plate (110 mm long x 110 mm wide x 3 mm thick). A load of 500 g was placed on it and it was moved 30 mm at a speed of 100 mm/min to measure the static friction coefficient and kinetic friction coefficient. The measurement conditions were as follows.
(Measurement conditions)
Equipment: Shinto Kagaku Co., Ltd. "Tribogear Type: HEIDON-38"
Measurement mode: Constant load measurement; Measurement temperature: 23°C
Measurement indenter: ASTM flat indenter. The coefficient of dynamic friction was evaluated according to the following criteria.
○: Dynamic friction coefficient less than 1.00 △: Dynamic friction coefficient 1.00 or more and less than 1.10 ×: Dynamic friction coefficient 1.10 or more

(6) Method of fusion with thermoplastic elastomer composition containing propylene resin as the base phase and evaluation of fusion durability (bending test) A 1 mm thick injection-molded sheet of a thermoplastic elastomer composition containing propylene resin as the base phase ("TREXPRENE® 3855N", a dynamically crosslinked thermoplastic elastomer manufactured by Mitsubishi Chemical Corporation) was cut to a size of 10 cm x 5 cm and loaded into the mold of a 110 ton injection molding machine. Each crosslinked thermoplastic elastomer composition was injected into the mold with a cylinder temperature of 230°C and a mold temperature of 50°C to obtain a composite molded body by insert molding. The composite molded body was punched out with a JIS K7195 heat sag dumbbell (width 25 mm x length 150 mm), and a bending test was performed at a pace of once per second, with one set of 180-degree bends to the left and right around the fusion interface. In this process, the number of bending cycles at which cracks appeared at the fusion interface was recorded for a total of three test specimens, and the average value was calculated. A higher average value indicates superior fusion durability.
In this evaluation, the maximum number of folds was set at 100. In the table, "100" indicates that no cracks appeared even after 100 folds.
This evaluation assesses the fusion durability using injection-molded sheets, and the results of this evaluation allow for a reproducible assessment of the quality of fusion durability when a composite molded body is formed, as shown in Figure 1.

(7) Compression set: Measured in accordance with ISO 815 under conditions of 70°C, 22 hours, and 25% compression.

[Examples/Comparative Examples]
<Example 1>
(A-1) 100 parts by mass, (B-1) 100 parts by mass, (C-1) 16.7 parts by mass, (D-1) 10 parts by mass, (E-1) 133 parts by mass, (f-1) 2.0 parts by mass (a mixture of 40 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 60 parts by mass of calcium carbonate), (f-2) 2.0 parts by mass (a mixture of 55 parts by mass of divinylbenzene and 45 parts by mass of ethylvinylbenzene), and (G-1) 0.33 parts by mass were blended in a Henschel mixer for 1 minute to obtain a material composition. This material composition was fed into the feed section of a co-screw extruder (TEX30α manufactured by Japan Steel Works, L/D = 46, number of cylinder blocks: 13) at a total speed of 15 kg/h, heated to a temperature in the range of 110 to 220°C, and melt-kneaded to obtain pellets which are a crosslinked thermoplastic elastomer composition.
The obtained crosslinked thermoplastic elastomer composition was subjected to the mel flow rate (MFR) measurement at a measurement temperature of 230°C and a measurement load of 21.2 N, in accordance with the JIS K7210 standard, and the evaluations described in (1) to (7) above were performed. The evaluation results are shown in Table 1.

<Example 2, Comparative Example 1>
The procedure was carried out in the same manner as in Example 1, except that the blending ratios were as shown in Table 1, to obtain pellets that are a crosslinked thermoplastic elastomer composition. The obtained crosslinked thermoplastic elastomer composition was evaluated in the same manner as in Example 1. The results are shown in Table 1.

In Table 1, component (f-1) is shown not as the actual amount blended, but as the amount of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane only (40% by mass of the actual blended amount), and component (f-2) is also shown not as the actual amount blended, but as the amount of divinylbenzene only (55% by mass of the actual blended amount).
Furthermore, the information regarding component (G-1) in Table 1 has been omitted.

<Evaluation Results>
As shown in Table 1, the crosslinked thermoplastic elastomer compositions of Examples 1 and 2 exhibit excellent fusion durability and sliding properties.
Comparative Example 1 is an example that does not use component (C), but its fusion durability is inferior.

The crosslinked thermoplastic elastomer composition of the present invention can be used in a wide range of fields, including: automotive parts such as skins, weatherstrips, ceiling materials, interior sheets, bumper moldings, side moldings, air spoilers, air duct hoses, and sealants; civil engineering and construction materials such as water-stopping materials, joint materials, window frames, and sealants; sports equipment such as golf club grips and tennis racket grips; industrial parts such as hose tubes and gaskets; home appliance parts such as hoses and packings; medical parts such as medical containers, gaskets, and packings; food products such as containers and packings; medical equipment parts; electric wires; and general merchandise. Among these, the crosslinked thermoplastic elastomer composition of the present invention is particularly suitable as an automotive sealant and a building material sealant, and especially as an automotive corner sealant, particularly as an automotive glass run channel.

1A, 1B Joined member 2 Joined member 3 Composite molded body

Claims (6)

A crosslinked thermoplastic elastomer composition obtained by melt-kneading a material composition containing the following components (A), (B), (C), and (D) in the presence of the following component (f), wherein the crosslinked thermoplastic elastomer composition contains 40 to 120 parts by mass of component (B), 1 to 50 parts by mass of component (C), and 0.5 to 50 parts by mass of component (D) per 100 parts by mass of component (A) .
Component (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene modified with (meth)acrylic acid and/or its derivatives, wherein the (meth)acrylic acid derivative is selected from any of the esters, amides, imides, and metal salts of (meth)acrylic acid (D): Lubricant component (f): Crosslinking agent A crosslinked thermoplastic elastomer composition comprising the following components (A), (B), (C), and (D) in an amount of 40 to 120 parts by mass of component (B), 1 to 50 parts by mass of component (C), and 0.5 to 50 parts by mass of component (D) per 100 parts by mass of component (A), wherein the value of the tensile stress at break measured at 23°C in accordance with the method for measuring tensile stress at break of ISO 37 Type 1A (test speed 500 mm/min) is 7 MPa or more and less than 15 MPa.
Component (A): Styrene-based elastomer component (B): Unmodified polypropylene component (C): Modified polypropylene modified with (meth)acrylic acid and/or its derivatives, wherein the (meth)acrylic acid derivative is selected from any of the esters, amides, imides, and metal salts of (meth)acrylic acid (D): Lubricant The crosslinked thermoplastic elastomer composition according to claim 1 or 2, wherein the melt flow rate (MFR) of the unmodified polypropylene of component (B), measured in accordance with JIS K7210 (1999) at a measurement temperature of 230°C and a measurement load of 21.2 N, is 1 g/10 min or more and 60 g/10 min or less. A bonding member comprising a crosslinked thermoplastic elastomer composition according to any one of claims 1 to 3. A composite molded body for automobiles comprising the joining member described in claim 4. A corner material for automobiles using the composite molded body described in claim 5.