JP2009161741A - Process for producing thermoplastic elastomer composition foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a styrene-based thermoplastic elastomer composition foam excellent in fineness and uniformity of its foam cells by injection foam molding. <P>SOLUTION: The process for producing the thermoplastic elastomer composition foam injects a thermoplastic elastomer composition and a foaming agent into a cavity of a mold for injection molding by an injection molding machine, keeps them for at least four seconds after completion of the injection, and then moves a wall surface of the cavity to a preset position to enlarge the volume of the cavity. The thermoplastic elastomer composition contains the following components (A), (B), and (C): (A): a hydrogenated product of a block copolymer having a block of an aromatic vinyl compound and a block of a conjugated diene compound, (B): a propylene-based resin, and (C): a mineral oil softener. To 100 pts.wt. of a component (A), the content of a component (B) is 5-150 pts.wt. and the content of a component (C) is 5-300 pts.wt. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a foamed thermoplastic elastomer composition.

A hydrogenated block copolymer containing a block composed of a monomer unit based on an aromatic vinyl compound and a block composed of a monomer unit based on a conjugated diene compound, and a polypropylene resin Foams made of styrene-based thermoplastic elastomer compositions are used in foamed members that require flexibility, heat resistance, and the like, such as automobile interior materials and household electrical appliance members.
As a method for producing such a foam, an injection foam molding method is used from the viewpoint of improving productivity. For example, Patent Document 1 discloses a hydrogenated product of a styrene-butadiene block copolymer and a propylene-ethylene block. A foam formed by injection foam molding of a thermoplastic elastomer composition containing a copolymer and a paraffinic oil is described. Patent Document 2 contains a hydrogenated styrene-butadiene-styrene block copolymer, a propylene-ethylene block copolymer, a paraffinic oil, and an elastomer composition of a polypropylene / ethylene-propylene copolymer. A foam obtained by injection foam molding of a thermoplastic elastomer composition is described.

Japanese Patent Laid-Open No. 6-218741 JP 2006-175825 A

However, in the foamed styrenic thermoplastic elastomer composition by the conventional injection foam molding method, the soft feeling is reduced due to the expansion of the foam cell or the non-uniform size and shape of the foam cell. As a result, the fineness of the foamed cells and the uniformity of the foamed cells were not fully satisfactory.
Under such circumstances, the problem to be solved by the present invention is to provide a method for producing a foam of a styrenic thermoplastic elastomer composition excellent in foam cell fineness and foam cell uniformity by injection foam molding. It is in.

This invention contains the following component (A), a component (B), and a component (C), content of a component (B) is 5-150 weight part per 100 weight part of component (A), C) A thermoplastic elastomer composition having a content of 5 to 300 parts by weight and a foaming agent are injected into a cavity of an injection mold by an injection molding machine and held for at least 4 seconds after the injection is completed. Further, the present invention relates to a method for producing a thermoplastic elastomer composition foam in which the cavity wall surface is moved to a preset position to increase the volume of the cavity.
(A): hydrogenated block copolymer having a block composed of monomer units based on an aromatic vinyl compound and a block composed of monomer units based on a conjugated diene compound (B): propylene Resin (C): mineral oil softener

  According to the present invention, it is possible to provide a method for producing a foam of a styrenic thermoplastic elastomer composition having excellent foam cell fineness and foam cell uniformity by injection foam molding.

The thermoplastic elastomer composition used in the present invention contains the following component (A), component (B) and component (C), and the content of component (B) is 5 to 100 parts by weight of component (A). The composition is 150 parts by weight and the content of component (C) is 5 to 300 parts by weight.
(A): Hydrogenated block copolymer having a block composed of monomer units based on an aromatic vinyl compound and a block composed of monomer units based on a conjugated diene compound (B): Propylene Resin (C): Mineral oil softener

  The hydrogenated component (A) is composed of a block composed of monomer units based on an aromatic vinyl compound (aromatic vinyl compound block) and a block composed of monomer units based on a conjugated diene compound (conjugated diene). Compound obtained by hydrogenating a block copolymer containing (compound block). Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene, vinylnaphthalene, vinylanthracene, and preferably styrene. It is. Two or more of these aromatic vinyl compounds may be used. Examples of the conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and the like, and are butadiene and isoprene. Two or more of these conjugated diene compounds may be used.

  The content of the aromatic vinyl compound block and the conjugated diene compound block is preferably from the viewpoint of increasing the mechanical strength and heat resistance of the foam, and the content of the aromatic vinyl compound block is preferably 5% by weight or more, The content of the conjugated diene compound block is 95% by weight or less, more preferably, the content of the aromatic vinyl compound block is 10% by weight or more, and the content of the conjugated diene compound block is 90% by weight or less. Further, from the viewpoint of enhancing the flexibility of the foam, the content of the aromatic vinyl compound block is preferably 50% by weight or less, and the content of the conjugated diene compound block is 50% by weight or more, more preferably The content of the aromatic vinyl compound block is 40% by weight or less, and the content of the conjugated diene compound block is 60% by weight or more. However, the total amount of the aromatic vinyl compound block and the conjugated diene compound block is 100% by weight.

  The block copolymer may be a diblock copolymer of an aromatic vinyl compound block-conjugated diene compound block structure, or a triblock such as an aromatic vinyl compound block-conjugated diene compound block-aromatic vinyl compound block structure. It may be a block copolymer.

  The hydrogenated product of the block copolymer is obtained by partially or completely hydrogenating double bonds of monomer units based on the conjugated diene compound constituting the conjugated diene compound block. Hydrogenation rate, that is, the amount of the double bond of the monomer unit based on the conjugated diene compound in the block copolymer before hydrogenation is defined as 100%, and by hydrogenation of the block copolymer out of the double bond The amount of the hydrogenated double bond is preferably 50% or more, more preferably 80% or more, from the viewpoint of enhancing the weather resistance and heat resistance of the foam.

  The weight average molecular weight of the hydrogenated product is preferably 50,000 or more, more preferably 100,000 or more, from the viewpoint of enhancing the fineness of the foamed cells, the uniformity of the foamed cells, and the mechanical strength of the foam. From the viewpoint of improving oil resistance, foam cell uniformity and mechanical strength of the foam, it is preferably 200,000 or more, more preferably 250,000 or more. Moreover, from a viewpoint of improving a moldability, Preferably it is 500,000 or less, More preferably, it is 400,000 or less. The weight average molecular weight is a weight average molecular weight in terms of polystyrene, and is measured by a gel permeation chromatograph (GPC) method.

  As a method for producing the hydrogenated product, for example, a block copolymer is produced by the method described in Japanese Patent Publication No. 40-23798, and then, for example, Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636. A method of hydrogenating the block copolymer can be mentioned by the method described in JP-A No. 59-133203 or JP-A No. 60-79005.

  Moreover, a commercial item can also be used as a hydrogenation thing. For example, the product name “KRATON-G” manufactured by Kraton Polymer Co., Ltd., the product name “Septon” manufactured by Kuraray Co., Ltd., the product name “Tough Tech” manufactured by Asahi Kasei Co., Ltd. and the like can be mentioned.

  The propylene resin of component (B) includes a propylene homopolymer, and a copolymer of propylene and at least one comonomer selected from the comonomer group consisting of ethylene and an α-olefin having 4 to 10 carbon atoms. can give. The copolymer may be a random copolymer or a block copolymer. More specifically, as the copolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-ethylene- Examples thereof include a 1-butene copolymer and a propylene-ethylene-1-hexene copolymer. The propylene-based resin is preferably a propylene homopolymer, a propylene-ethylene copolymer, or a propylene-1-butene copolymer.

  The content of the monomer unit (propylene unit) based on propylene in the polymer used for the propylene-based resin is usually more than 60% by weight, and preferably 80% by weight or more. However, the said polymer shall be 100 weight%.

  The melt flow rate of the propylene-based resin is preferably 0.1 to 300 g / 10 minutes, more preferably 0.5 to 200 g / 10 minutes, and further preferably 1 to 150 g / 10 minutes. The melt flow rate is measured according to JIS K7210 at a load of 21.18 N and a temperature of 230 ° C.

  The propylene-based resin can be produced by a known polymerization method using a Ziegler-Natta catalyst or a metallocene catalyst as a polymerization catalyst. Examples of the polymerization method include a solution polymerization method, a bulk polymerization method, a slurry polymerization method, and a gas phase polymerization method, and two or more of these may be combined.

  Examples of the mineral oil softener of component (C) include aromatic mineral oil, naphthenic mineral oil, and paraffinic mineral oil, preferably It is a paraffinic mineral oil. Further, those having an average molecular weight of 300 to 1500 and a pour point of 0 ° C. or less are preferable.

  The thermoplastic elastomer composition may contain various additives as long as the object of the present invention is not impaired. Specific additives include: various antioxidants such as phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants; various heat stabilizers such as hindered amine heat stabilizers; benzophenone ultraviolet absorbers, Various ultraviolet absorbers such as benzotriazole ultraviolet absorbers and benzoate ultraviolet absorbers; various antistatic agents such as nonionic antistatic agents, cationic antistatic agents and anionic antistatic agents; bisamide dispersants, waxes Various dispersants such as dispersants and organometallic salt dispersants; various chlorine supplements such as carboxylate chlorine supplements for alkaline earth metal salts; amide lubricants, wax lubricants, organometallic salt lubricants, esters Various types of lubricants such as oxidic lubricants; various decomposing agents such as oxide-based decomposing agents and hydrotalcite-based decomposing agents; hydrazine-based metal deactivators and amine-based metal deactivators Metal deactivators: Brominated organic flame retardants, phosphoric acid flame retardants, various flame retardants such as antimony trioxide, magnesium hydroxide, red phosphorus; talc, mica, clay, calcium carbonate, aluminum hydroxide, magnesium hydroxide Various inorganic fillers such as barium sulfate, glass fiber, carbon fiber, silica, calcium silicate, potassium titanate, wollastonite; organic fillers; organic pigments; inorganic pigments; inorganic antibacterial agents: organic antibacterial agents It is done.

  As a compounding quantity of the propylene-type resin of the component (B) in a thermoplastic elastomer composition, it is 5 weight part or more from a viewpoint of improving the heat resistance of a foam per 100 weight part of a component (A), Preferably it is 10 weight. Part or more, more preferably 20 parts by weight, still more preferably 40 parts by weight or more. Moreover, from a viewpoint of improving the softness | flexibility of a foam, it is 150 weight part or less, Preferably it is 120 weight part or less, More preferably, it is 100 weight part or less, More preferably, it is 80 weight part or less.

  The blending amount of the component (C) mineral oil softener in the thermoplastic elastomer composition is 5 parts by weight or more per 100 parts by weight of the component (A) from the viewpoint of enhancing the flexibility and molding processability of the foam. The amount is preferably 30 parts by weight or more, and more preferably 50 parts by weight or more. Further, from the viewpoint of improving the bleed resistance and heat resistance of the foam, it is 300 parts by weight or less, preferably 250 parts by weight or less, more preferably 200 parts by weight or less.

  The thermoplastic elastomer composition comprises a component (A) hydrogenated product, a component (B) propylene-based resin, a component (C) mineral oil softener, and other components blended as necessary. Can be obtained by melt kneading with a known melt kneader such as a mixing roll, kneader, Banbury mixer, extrusion kneader or the like.

  As a foaming agent used for this invention, well-known things, such as a chemical foaming agent and a physical foaming agent, can be used. Two or more chemical foaming agents and physical foaming agents may be used in combination. A chemical foaming agent and a physical foaming agent may be used in combination.

  Examples of the chemical foaming agent include inorganic compounds and organic compounds, and these may be used in combination of two or more. Examples of inorganic compounds include hydrogen carbonates such as sodium hydrogen carbonate, ammonium carbonate, and the like.

  Examples of the organic compound include polycarboxylic acid, azo compound, sulfone hydrazide compound, nitroso compound, p-toluenesulfonyl semicarbazide, and isocyanate compound. Examples of the polycarboxylic acid include citric acid, oxalic acid, fumaric acid, and phthalic acid. Examples of the azo compound include azodicarbonamide (ADCA). Examples of the sulfone hydrazide compound include p-methylurethanebenzenesulfonyl hydrazide, 2,4-toluenedisulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide and the like. Examples of the nitroso compound include dinitrosopentamethylenetetramine (DPT).

  Examples of the physical foaming agent include inert gases; volatile organic compounds such as butane and pentane. The physical foaming agent is preferably an inert gas, and examples of the inert gas include carbon dioxide, nitrogen, argon, neon, and helium. More preferred are carbon dioxide and nitrogen.

  The amount of the foaming agent used is usually 0.1 to 20 parts by weight, preferably 0.2 to 8 parts by weight per 100 parts by weight of the thermoplastic elastomer composition. Moreover, when using a chemical foaming agent and a physical foaming agent together, the usage-amount of a chemical foaming agent is 0.05-5 weight part normally per 100 weight part of thermoplastic elastomer compositions.

  In the production method of the present invention, a thermoplastic elastomer composition and a foaming agent are injected into a cavity of an injection mold by an injection molding machine and held for at least 4 seconds after the injection is completed. The foam is molded by enlarging the volume of the cavity by moving to a preset position.

  As a method of supplying a chemical foaming agent to an injection molding machine, a method of supplying a chemical foaming agent previously melt-mixed with a thermoplastic elastomer composition to an injection molding machine may be used. A method is used in which the pellets are blended into the thermoplastic elastomer composition pellets and the pellet blend is supplied to an injection molding machine.

  Examples of the method for supplying the physical foaming agent to the injection molding machine include a method of injecting the physical foaming agent into the molten thermoplastic elastomer composition in the nozzle or cylinder of the injection molding machine. From the viewpoint of improving the uniformity of the foamed cells, a method of injecting a physical foaming agent into the molten thermoplastic elastomer composition in the cylinder is preferable.

  Examples of the injection method include a single-axis injection method, a multi-axis injection method, a high-pressure injection method, a low-pressure injection method, and a method using a plunger.

  Before injecting the thermoplastic elastomer composition and the foaming agent into the mold cavity, the pressure in the cavity is usually set to atmospheric pressure or lower. The external appearance of a foam can be improved by making the pressure in a cavity below atmospheric pressure.

  A known method is used as a method for setting the pressure in the cavity to be equal to or lower than the atmospheric pressure. (1) A method in which the inside of the cavity is vacuum-sucked in advance using a mold capable of vacuum suction, (2) Gas venting Using a mold having a mechanism, the pressure generated when the molten thermoplastic elastomer composition and the foaming agent are injected into the cavity is released outside the cavity by the degassing mechanism. And a method of making the pressure equal to the atmospheric pressure.

  The volume of the thermoplastic elastomer composition injected into the cavity and the foaming agent may be the same as or smaller than the volume of the cavity. When the volume is small, the volume of the cavity may be reduced immediately after injection so that the volume of the thermoplastic elastomer composition and the foaming agent is the same as the volume of the cavity. The volume of the thermoplastic elastomer composition to be injected and the foaming agent is preferably the same as the volume of the cavity.

  The temperature during injection (molding temperature) is usually 180 to 250 ° C. The injection time is usually within 10 seconds. Moreover, the temperature of a metal mold | die is 5-80 degreeC normally,

  After completing the injection of the thermoplastic elastomer composition and the foaming agent into the cavity, the cavity is held for 4 seconds or more, and the cavity wall surface is moved to a preset position to expand the volume of the cavity. From the viewpoint of improving the fineness and uniformity of the foamed cell, the time from the completion of injection until the cavity wall surface is moved and the expansion of the cavity volume is started is preferably 5 seconds or more. The delay time is preferably 30 seconds or less from the viewpoint of improving the fineness and uniformity of the foamed cells.

  A known method is used as a method of expanding the cavity volume by moving the cavity wall surface of the mold. For example, the core portion of the mold is retracted (so-called core back) to enlarge the entire cavity. And a method of enlarging a part and / or the whole cavity by using a slide core.

  The cavity volume expansion rate when expanding the volume of the cavity is preferably 700% / second or more, more preferably 2000% / second or more. Further, the cavity volume expansion rate is usually 25000% / second or less in view of the performance of the apparatus. Note that the cavity volume expansion rate is 100% of the cavity volume at the completion of filling, and when the filling is performed by reducing the volume of the cavity immediately after injection, the cavity volume is the volume after the reduction.

  After moving the cavity wall surface to a preset position, the thermoplastic elastomer composition in the cavity is sufficiently cooled. After cooling, the foam is removed from the mold.

  The production method of the present invention may be carried out in combination with a molding method such as gas assist molding, melt core molding, insert molding, core back molding, or two-color molding.

  Moreover, you may paste a skin material on a foam. Examples of the skin material include woven fabric; non-woven fabric; knitted fabric; film or sheet formed of thermoplastic resin or thermoplastic elastomer; polyurethane sheet; rubber sheet; polyurethane foam; ethylene vinyl acetate copolymer foam; A polyethylene foam etc. can be mention | raise | lifted.

  The foam molded article obtained by using the thermoplastic elastomer composition for injection foam molding of the present invention is excellent in the fineness of the foamed cells and the uniformity of the foamed cells. Therefore, the foam is excellent in soft feeling, and can be excellent in lightness, rigidity and impact resistance.

  The foam molded article obtained by using the thermoplastic elastomer composition for injection foam molding of the present invention is suitably used for automobile interior materials, home appliances, furniture and the like.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples.

[I] Physical property measurement method (1) Weight average molecular weight Using a gel permeation chromatograph (GPC) method, the measurement was made under the following conditions (1) to (8).
(1) Equipment: Waters 150C manufactured by Water
(2) Separation column: TOSOH TSKgelGMH6-HT
(3) Measurement temperature: 140 ° C
(4) Carrier: Orthodichlorobenzene
(5) Flow rate: 1.0 mL / min
(6) Injection volume: 500 μL
(7) Detector: Differential refraction
(8) Molecular weight reference material: Standard polystyrene

(2) Melt flow rate (MFR)
According to JIS K7210, the load was 21.18 N and the temperature was 230 ° C.

(3) Fineness and uniformity of the foam cell Cut the foam and observe the cross section with a microscope (Digital Field Microscope DG-3, manufactured by SCARA Co., Ltd.). It was evaluated as follows.
Fineness of foamed cells ○: Number average diameter of cells is 500 μm or less.
X: The number average diameter of the cells exceeds 500 μm.
Uniformity of foamed cells ○: The size and shape of the cells are uniform.
(Triangle | delta): Although the cell which connected is not recognized, the magnitude | size and shape of a cell are non-uniform | heterogenous.
X: The cell which connected was recognized and the magnitude | size and shape of a cell are non-uniform | heterogenous.

(4) Oil resistance The thermoplastic elastomer composition is heated at 230 ° C. for 5 minutes, pressurized at 230 ° C. for 5 minutes to melt the thermoplastic elastomer composition, and then pressurized and cooled at 30 ° C. for 5 minutes. Then, a flat plate having a thickness of 1 mm was formed. A Teflon (registered trademark) cylinder (inner diameter: 38 mm, outer diameter: 42 mm, height: 15 mm) is placed on a flat plate, and 1.5 g of liquid paraffin is placed in the cylinder so that a constant load is applied to the flat plate. A weight of 500 g was placed on the plate, and the flat plate was allowed to stand at 80 ° C. for 24 hours under a constant load. After standing still, it cooled to room temperature, the swelling degree of the flat plate was observed, and it evaluated as follows.
None: No swelling is observed.
Existence: Swelling is observed.

[II] Raw material (1) Hydrogenated product of styrene-conjugated diene-styrene block copolymer A-1: Hydrogenated product of styrene-butadiene-styrene block copolymer (weight average molecular weight 320,000, styrene unit content 33) weight%)
A-2: Hydrogenated product of styrene-isoprene-styrene block copolymer (weight average molecular weight 129,000, styrene unit content 13% by weight)
A-3: Hydrogenated product of styrene-isoprene-styrene block copolymer (weight average molecular weight 126,000, styrene unit content 18% by weight)
A-4: Hydrogenated styrene-butadiene-styrene block copolymer (weight average molecular weight 101,000, styrene unit content 30% by weight)

(2) Propylene-based resin B-1: Sumitomo Chemical Co., Ltd. trade name Nobren HR100EG
(MFR = 19g / 10min)

(3) Mineral oil softener C-1: Idemitsu Kosan Co., Ltd. Product name Diana Process Oil PW-100
(Pour point: -15 ° C)

Example 1
(Preparation of thermoplastic elastomer composition)
100 parts by weight of hydrogenated styrene-conjugated diene-styrene block copolymer of A-1, 70 parts by weight of B-1 propylene-based resin per 100 parts by weight of A-1, and softening of mineral oil of C-1 180 parts by weight per 100 parts by weight of A-1 and 100 parts by weight of A-1, B-1, and C-1 with erucic acid amide (trade name Neutron S, manufactured by Nippon Seika) 05 parts by weight, 0.05 parts by weight of calcium stearate, antioxidant (trade name Irganox 1010: 0.1 parts by weight, manufactured by Ciba Specialty Co., Ltd., trade name Ultranox 626: 0.05, manufactured by GE Specialty Chemicals) 0.15 parts by weight) was melt-kneaded with a Banbury mixer, and then formed into pellets to obtain pellets of a thermoplastic elastomer composition. The oil resistance evaluation results are shown in Table 1.

(Manufacture of injection foam moldings)
As an injection molding machine, ES2550 / 400HL-MuCell manufactured by Engel Co., Ltd. (clamping force 400t), and as a mold, the dimensions of the molded part are 290mm x 370mm, height 45mm, thickness 1.5mmt (gate structure: valve gate, Injection foam molding was carried out using the one having a molded body central portion). A mixture of 100 parts by weight of a thermoplastic elastomer composition pellet and 1 part by weight of an organic acid salt foaming agent master batch (trade name MB3083, manufactured by Sankyo Kasei Co., Ltd.) as a chemical foaming agent is supplied to an injection molding machine. It was melted in a cylinder of the machine, and carbon dioxide was pressurized to 6 MPa and supplied into the cylinder (injection amount of carbon dioxide per 100 parts by weight of molten resin of pellets of thermoplastic elastomer composition: 0.6 parts by weight). Next, a thermoplastic elastomer composition and a foaming agent are injected at a molding temperature of 210 ° C., a mold temperature of 20 ° C., and an injection time of 2.6 seconds, completely filled into the mold cavity, and held for 8 seconds after filling. (Delay time 8 seconds). Next, the cavity volume is increased by 7000% / second (the cavity volume at the completion of injection is assumed to be 100%) by retreating the cavity wall surface by 3 mm to increase the cavity volume. Further, it was cooled and solidified to obtain a foamed molded product. The evaluation results are shown in Table 1.

Example 2
Instead of the hydrogenated styrene-conjugated diene-styrene block copolymer of A-1, 100 parts by weight of the hydrogenated styrene-conjugated diene-styrene block copolymer of A-2 was used, and propylene of B-1 The same procedure as in Example 1 was carried out except that 56 parts by weight of the system resin per 100 parts by weight of A-2 and 67 parts by weight of the mineral oil softener of C-1 per 100 parts by weight of A-2 were used. The evaluation results are shown in Table 1.

Example 3
Instead of the hydrogenated product of styrene-conjugated diene-styrene block copolymer of A-1, 100 parts by weight of the hydrogenated product of styrene-conjugated diene-styrene block copolymer of A-3 was used, and propylene of B-1 The same procedure as in Example 1 was carried out except that 56 parts by weight of the system resin per 100 parts by weight of A-3 and 67 parts by weight of the mineral oil softener of C-1 per 100 parts by weight of A-3 were used. The evaluation results are shown in Table 1.

Example 4
In place of the hydrogenated product of A-1 styrene-conjugated diene-styrene block copolymer, 100 parts by weight of the hydrogenated product of A-4 styrene-conjugated diene-styrene block copolymer was used, and propylene of B-1 Example 1 was carried out in the same manner as in Example 1 except that 50 parts by weight of the resin based on 100 parts by weight of A-4 and 100 parts by weight of the mineral oil softener of C-1 per 100 parts by weight of A-4 were used. The evaluation results are shown in Table 1.

Comparative Example 1
The same operation as in Example 1 was performed except that the delay time was changed to 2 seconds. The evaluation results are shown in Table 2.

Comparative Example 2
The same operation as in Example 2 was performed except that the delay time was changed to 2 seconds. The evaluation results are shown in Table 2.

Comparative Example 3
The same operation as in Example 3 was performed except that the delay time was changed to 2 seconds. The evaluation results are shown in Table 2.

Comparative Example 4
The same operation as in Example 4 was performed except that the delay time was changed to 2 seconds. The evaluation results are shown in Table 2.
Comparative Example 5
The same operation as in Example 1 was performed except that the delay time was changed to 2 seconds and the cavity volume expansion rate was changed to 70% / second. The evaluation results are shown in Table 2.

Claims (2)

The following component (A), component (B), and component (C) are contained, the content of component (B) is 5 to 150 parts by weight per 100 parts by weight of component (A), and the content of component (C) The thermoplastic elastomer composition and the foaming agent in an amount of 5 to 300 parts by weight are injected into a cavity of an injection mold by an injection molding machine and held for at least 4 seconds after the injection is completed. A method for producing a foamed thermoplastic elastomer composition, wherein a volume of a cavity is expanded by moving a wall surface to a preset position.
(A): hydrogenated block copolymer having a block composed of monomer units based on an aromatic vinyl compound and a block composed of monomer units based on a conjugated diene compound (B): propylene Resin (C): mineral oil softener   The method for producing a foamed thermoplastic elastomer composition according to claim 1, wherein the volume of the cavity is expanded at a cavity volume expansion rate of 700% / second or more.