JP2011236330A - Thermoplastic elastomer composition for injection foam molding, and injection foam molding formed of the resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic elastomer composition for injection foam molding, which has high foaming magnification, is good in mold transferability, and provides an injection foam molding having excellent soft feeling and heat resistance.SOLUTION: The thermoplastic elastomer composition for injection foam molding includes: 50-97 wt.% of a thermoplastic elastomer (A) having (A1) a melt flow rate of 1g/10 minutes to 80 g/10 minutes, (A2) type A hardness of 50-90, and (A3) a melting heat quantity (ΔH) of ≥4 mJ/mg at a temperature not lower than 100°C, calculated from the DSC curve obtained by a measurement method using a differential scanning calorimeter; and 3-50 wt.% of a modified polypropylene-based resin (B) satisfying (B1) a specific melt flow rate and specific melt tension and exhibiting (B2) strain hardening property.

Description

  The present invention relates to a thermoplastic elastomer composition for injection foam molding and an injection foam molding using the same.

  Foam is widely used in members that require shock absorbing performance and cushioning properties such as cushioning materials such as electronic devices and furniture, automobile interior materials, food packaging materials, and the like. Among them, a thermoplastic elastomer foam is suitably used for applications that require cushioning and flexibility.

  For example, Patent Document 1 proposes a method of mixing a polyolefin resin with a thermoplastic elastomer. However, the polyolefin used here uses a polyolefin with low fluidity in order to obtain a high expansion ratio. Specifically, a non-foamed sheet impregnated with a high-pressure gas and then foamed or extruded. Only the embodiment of the foam sheet is described.

  Patent Document 2 discloses extrusion molding of a mixture of a thermoplastic elastomer and a long-chain branched polypropylene. Although it is suggested that the present invention can be applied to injection foaming, it is presumed that the polypropylene resin having a melt flow rate of 2 to 4.1 described in the document has poor fluidity. In particular, when a high expansion ratio is obtained by mixing with a thermoplastic elastomer having poor foamability, it is necessary to increase the polypropylene resin ratio. In such a case, it is presumed that the fluidity is particularly poor. Further, when such a resin is used, the mold transferability at the time of injection molding tends to be inferior, and is not suitable for injection foam molding that requires fluidity at the time of injection filling and transferability of a fine pattern of the mold. .

  Patent Document 3 discloses a resin composition pellet having a melt flow rate of 50% by weight of a hydrogenated styrene copolymer and 50% of a propylene resin having a high melt flow rate, and a long chain having a melt flow rate of 3.5. Although it has been disclosed to injection foam molding a mixture of branched polypropylene, when such a polypropylene resin is used, the fluidity at the time of injecting the molten resin is insufficient and a high injection pressure is generated in the machine. Not only was the load applied more than necessary, but the mold transferability tended to be inferior, and the flow mark was liable to occur on the surface of the molded body, and the appearance tended to be impaired.

Japanese Patent Laid-Open No. 2001-348452 Japanese Patent Laid-Open No. 9-296063 JP 2003-41039 A

  An object of the present invention is to provide an injection foam molded article having a high expansion ratio, good mold transferability, excellent softness, and excellent heat resistance, particularly suitable for automobile interior materials such as instrument panels and door trims. It is to provide a thermoplastic elastomer composition for foam molding.

  By mixing a specific polypropylene-based resin with a specific thermoplastic elastomer, the present inventors have both fluidity and foamability at the time of injection filling, excellent mold pattern transferability, and an elastomer foam. It has been found that an injection-foamed molded article having a unique soft feeling and excellent heat resistance can be obtained, and the present invention has been completed.

That is, this invention consists of the following structures.
[1] Olefin elastomer (A) satisfying the following (A1) to (A3) 50 wt% or more and 97 wt% or less, and modified polypropylene resin (B) 3 wt% satisfying the following (B1) to (B2) An olefinic thermoplastic elastomer composition for injection foam molding, characterized by comprising 50% by weight or less [the total amount of (A) and (B) is 100% by weight].
(A1) MFR is 1 g / 10 min or more and 80 g / 10 min or less (A2) Type A hardness is 40 or more and 90 or less (A3) Calculated from a DSC curve obtained by measurement by differential scanning calorimetry, at 100 ° C. or more Of heat of fusion (ΔH ₁₀₀ ) of 4 mJ / mg or more,
(B1) Meets any of the following requirements (A) to (E) (A) Melt flow rate 4.5 g / 10 min or more and less than 10 g / 10 min, Melt tension 5 cN or more (B) Melt flow rate 10 g / 10 Min. To 30 g / 10 min., Melt tension 2 cN or more (c) melt flow rate 30 g / 10 min to 50 g / 10 min., Melt tension 1 cN or more. (2) melt flow rate 50 g / 10 min to 100 g / 10 min. Melt tension of 0.3 cN or more (e) Melt flow rate of more than 100 g / 10 minutes to 250 g / 10 minutes or less, Melt tension of 0.3 cN or more (B2) Strain hardenability [2] Injection foam molding according to [1] An injection-foamed molded article obtained by injection-foaming a thermoplastic elastomer composition for use.
[3] The injection-foamed molded article according to [2], wherein the expansion ratio is more than 2 times and 10 times or less, and the type A hardness is 30 or more and 80 or less.
[4] A foam molded article, characterized in that the thermoplastic elastomer composition for injection foam molding and the foaming agent according to [1] are supplied to an injection molding machine and then injected into a mold to perform foam molding. Manufacturing method.
[5] A mold including a fixed mold and a movable mold capable of moving forward and backward at an arbitrary position is used, and after completion of injection, the movable mold is moved backward to foam. [4] The manufacturing method of the foaming molding of description.

The thermoplastic elastomer composition for injection foam molding of the present invention comprises a suitable amount of a specific polypropylene resin relative to a thermoplastic elastomer having a specific heat resistance, and therefore has heat resistance and excellent foamability. Therefore, high foaming can be achieved. Therefore, it is possible to obtain an injection-foamed molded article having a soft feeling and a high expansion ratio.
Furthermore, the thermoplastic elastomer composition for injection foam molding of the present invention has excellent fluidity. Therefore, it is possible to obtain an injection-foamed molded article that has good thin-wall filling properties and is lightened by thinning the mold clearance during injection filling. Furthermore, since it is highly fluid and highly foamable, it is excellent in mold transferability. Therefore, it is possible to obtain an injection-foamed molded article that is soft at a high expansion ratio, is light in weight, and has excellent mold transferability and heat resistance.

FIG. 1 is a diagram for explaining a method of calculating a heat of fusion (ΔH ₁₀₀ ) from a DSC chart obtained by a differential scanning calorimetry method of a thermoplastic elastomer used in the present invention.

The thermoplastic elastomer composition for injection foam molding of the present invention comprises a specific olefin elastomer and a polypropylene resin in a specific ratio.

  The olefin elastomer (A) used in the present invention has a melt flow rate of 1.0 g / 10 min to 80 g / 10 min, preferably 2.0 g / 10 min to 70 g / 10 min. If the melt flow rate of the olefin elastomer is within the above range, fluidity is ensured and injection filling is possible without imposing excessive load on the molding machine or mold, and the desired hardness without uneven gloss and flow marks. It is easy to obtain an injection foam molded article.

  Here, the melt flow rate (hereinafter sometimes abbreviated as “MFR”) conforms to the provisions of Method A described in JIS K7210 (1999), and uses a melt indexer S-01 (manufactured by Toyo Seiki Seisakusho). It is a value converted from the amount of resin extruded from a die at a constant time under a load of 2.16 kg at 230 ° C. to the amount extruded in 10 minutes. The fixed time is 120 seconds when the melt flow rate exceeds 0.5 g / 10 minutes and 1.0 g / 10 minutes or less, and when the melt flow rate exceeds 1.0 g / 10 minutes and 3.5 g / 10 minutes or less. Is 30 seconds when it exceeds 3.5 g / 10 minutes and 10 g / 10 minutes or less for 60 seconds, 10 seconds when it exceeds 10 g / 10 minutes and 25 g / 10 minutes or less, and it exceeds 25 g / 10 minutes and 100 g / 10 If it is less than 5 minutes, it is 5 seconds, and if it exceeds 100 g / 10 minutes, it is 3 seconds. Three pieces cut out at the predetermined time are collected and the average value is calculated. If three pieces cannot be collected in one measurement, the measurement is continued until three pieces can be collected. If the melt flow rate measured in a certain number of seconds is not in the corresponding range, the measurement is performed again in the number of seconds corresponding to the melt flow rate.

  The olefin elastomer (A) used in the present invention has a type A hardness of 40 or more and 90 or less, preferably 50 or more and 80 or less. When the type A hardness is in the above range, it is easy to obtain a product having a good balance such as cushioning properties and heat resistance of the obtained injection foam molded article. Here, the type A hardness means a value measured by a type A durometer hardness test in an environment of 23 ° C. according to JIS K6253.

The olefin elastomer (A) used in the present invention has a heat of fusion (ΔH ₁₀₀ ) at 100 ° C. or higher of 4 mJ / mg, preferably 4.5 mJ / mg, more preferably 5 mJ / mg.

Here, the heat of fusion (ΔH ₁₀₀ ) is a numerical value derived from a DSC curve obtained in the measurement by the differential scanning calorimetry shown below, based on JIS K7122 (1987). The measurement conditions of the differential scanning calorimeter method include, for example, using a differential scanning calorimeter DSC6200 manufactured by Seiko Instruments Inc., and increasing the temperature of 4 to 10 mg of the used measurement sample from 10 ° C. to 210 ° C. at a rate of 10 ° C./min. After the thermal history of melting once and then cooling from 210 ° C. to 10 ° C. at a rate of 10 ° C./min, the temperature is raised again from 10 ° C. to 210 ° C. at a rate of 10 ° C./min and the DSC curve is To get. More specifically, the heat of fusion (ΔH ₁₀₀ ) is determined as follows.
In the obtained DSC curve, as shown in FIG. 1, a base line is drawn so as to extend a portion that can be regarded as a substantially straight line on both sides across the peak of the DSC curve, and the point a where the DSC curve is separated from the low-temperature side baseline a Out of the heat of fusion calculated from the area of the portion surrounded by the line ab connecting the point b away from the high temperature side baseline and the DSC curve, the region bcd (indicated by the hatched portion) having a temperature of 100 ° C. or higher the heat of fusion calculated from the area and [Delta] H _100. When the temperature of the point a exceeds 100 ° C., the heat of fusion calculated from the area of the portion surrounded by the line ab and the DSC curve is set to ΔH ₁₀₀ .
When two or more melting peaks appear independently, the above line ab is drawn for each peak, the heat of fusion calculated from the region of temperature of 100 ° C. or higher is ΔH _100, and two or more melting peaks overlap. In this case, ΔH ₁₀₀ is calculated as in the case of the single peak.

By the way, it is said that the interior temperature of the automobile, which is one of the preferred applications of the injection foam molded article of the present invention, is said to be about 70 to 80 ° C. in the summer, and a molded article having poor heat resistance is used as an instrument panel. When a high temperature object such as a can juice that has been warmed is placed and left standing, the dent may occur. On the other hand, there are few high-temperature bodies that come into contact with components under general use conditions, and the boiling point of water is less than 100 ° C., and the temperature rise when exposed to direct sunlight is generally about 100 ° C. or more. It is said that there is almost no temperature.
Here, the large amount of heat of fusion (ΔH ₁₀₀ ) of the elastomer used at 100 ° C. or higher means that more crystals remain undissolved at a high temperature, and the crystals become pseudo-crosslinking points. It is considered that the effect of preventing the deformation of components is high.

In the present invention, the amount of heat of fusion (ΔH ₁₀₀ ) of 100 ° C. or higher is within the above range, and the amount of the modified polypropylene to be described later is set to 3% or more, so that the obtained molded article is assumed to be actually used. Deformation is prevented even in contact with a high-temperature object under the environment, and there is an effect that the above-described problems hardly occur.

  Examples of the olefin elastomer (A) used in the present invention include an ethylene-α-olefin copolymer, a propylene-α-olefin copolymer, an ethylene-propylene-diene copolymer, an ethylene-vinyl acetate copolymer, and a polybutene. And chlorinated polyethylene. These olefin-based elastomers are not particularly limited as long as they have the above properties, and may be used alone or in combination of two or more.

  Further, from the viewpoints of easily obtaining dispersibility and desired hardness for the modified polypropylene resin (B) described later and being relatively inexpensive, an ethylene-α-olefin copolymer is preferable, and in particular, polypropylene or the like. The so-called reactor TPO in which the crystalline component and the elastomer component are introduced at the polymerization stage and exist as a hard component and a soft component, respectively, is preferable. Reactor TPO has a soft and finely dispersed soft component compared to compound type and cross-linked type soft resins in which amorphous elastomer is kneaded with polypropylene, and various processes such as workability, flexibility, and impact resistance. It is said that the balance of performance is excellent. As the reactor TPO, Newcon (Nihon Polypro), Catalloy (Sun Allomer), Prime TPO (Prime Polymer) and the like are generally known.

The modified polypropylene resin (B) used in the present invention has strain-hardening properties, and the modified polypropylene resin (B) used in the present invention has strain-hardening properties as a lower limit of the melt flow rate. Is 4.5 g / 10 min, preferably 5 g / 10 min, more preferably 10 g / 10 min. The upper limit of the melt flow rate is 250 g / 10 minutes, preferably 200 g / 10 minutes, more preferably 150 g / 10 minutes, and even more preferably 100 g / 10 minutes.
The effect of exhibiting strain-hardening properties is that an internal foam (cell) is hard to break during injection foam molding, and an injection foam molded article with a high foaming ratio excellent in transferability can be obtained.

  Strain hardenability is defined as an increase in viscosity with an increase in the stretching strain of a melt. Usually, the method described in JP-A-62-1121704, that is, an extensional viscosity measured by a commercially available rheometer, This can be determined by plotting the time relationship. Further, for example, strain hardening can be determined from the breaking behavior of the molten strand at the time of melt tension measurement. That is, when the take-up speed is increased, the melt tension increases abruptly, and when cutting, strain hardening is exhibited.

If the melt flow rate of the modified polypropylene resin (B) is less than 4.5 g / 10 minutes, the flowability is insufficient and the molding machine and the mold are unnecessarily burdened, and the injection foam molding has a complicated shape. In a body or a large injection-foamed molded body, it is difficult to fill the resin into every corner of the mold, and short shot defects are likely to occur. Furthermore, the transferability of a fine pattern applied to the mold is deteriorated, and a desired shape cannot be obtained, and gloss unevenness and a flow mark are easily generated on the surface of the molded product. If the melt flow rate exceeds 250 g / 10 min, the metering process may not be stable.
Here, the melt flow rate means a value measured in the same manner as the melt flow rate of the thermoplastic elastomer.

  The melt tension (melt tension) of the modified polypropylene resin (B) is a physical property that can be an index of foaming properties, but the appropriate value depends on the melt flow rate. The lower the melt flow rate, the more necessary the melt tension is. It tends to be higher. In the present invention, a melt tension value suitable for foaming is shown according to the melt flow rate of the modified polypropylene resin.

That is, the modified polypropylene resin (B) of the present invention has a melt tension that satisfies any of the following (A) to (E).
(A) When the melt flow rate is 4.5 g / 10 min or more and less than 10 g / 10 min, the melt tension is 5 cN or more, preferably 7 cN or more.
(B) When the melt flow rate is 10 g / 10 min or more and less than 30 g / 10 min, the melt tension is 2 cN or more, preferably 3 cN or more.
(C) When the melt flow rate is 30 g / 10 min or more and less than 50 g / 10 min, the melt tension is 1 cN or more, preferably 1.5 cN or more.
(2) When the melt flow rate is 50 g / 10 min or more and 100 g / 10 min or less, the melt tension is 0.3 cN or more, preferably 0.6 cN or more.
(E) When the melt flow rate exceeds 100 g / 10 min and is 250 g / 10 min or less, the melt tension is 0.3 cN or more, preferably 0.5 cN or more.

  When the melt flow rate and melt tension of the modified polypropylene resin (B) are within the above ranges, the resin has a good balance between fluidity and foamability, and internal bubbles (cells) are difficult to break during injection foam molding. It is easy to obtain an injection-foamed molded product with high expansion ratio with excellent transferability, and also prevents foam breakage at the molten resin flow tip during injection-foaming molding. An injection foam molding having the above is obtained. Polypropylene resins having a high melt flow rate and a high melt tension as described above tend to affect performance such as foamability, fluidity, and transferability, that is, they tend to greatly affect the performance of the entire composition even in a small amount.

  Here, the melt tension is equipped with an attachment for measuring melt tension, using a capillograph (manufactured by Toyo Seiki Seisakusho) having a 10 mmφ cylinder with an orifice having an inner diameter of 1 mmφ and a length of 10 mm at the tip. The strand discharged from the die when it is lowered at 10 ° C / min. At a temperature of 10 ° C. is pulled at a speed of 1 m / min on a pulley with a load cell 350 mm below, and after stabilization, the take-up speed is 200 m / min for 4 minutes. The load applied to the pulley with a load cell when the strand breaks is increased at a rate reaching the speed. If the strand does not break, the melt tension is the load at which the load applied to the pulley with the load cell does not increase even if the take-up speed is increased.

  As modified polypropylene resin (B) resin which has the above characteristics, what has a branched structure or a high molecular weight component is mentioned, for example. As a method for producing such a modified polypropylene resin (B), for example, radiation is applied to a linear polypropylene resin, or a linear polypropylene resin, a conjugated diene compound, and a radical polymerization initiator are melt mixed. The method is mentioned. In the present invention, those having a branched structure are particularly preferred. As a method for producing the same, a modified polypropylene resin obtained by melt-mixing a linear polypropylene resin, a conjugated diene compound and a radical polymerization initiator is expensive. It is preferable from the point that it can be manufactured inexpensively by not requiring it.

The linear polypropylene resin used in the production of the modified polypropylene resin (B) of the present invention is a polypropylene resin having a linear molecular structure, specifically, a propylene homopolymer. And a block copolymer and a random copolymer, which are crystalline polymers. As a copolymer of propylene, a copolymer containing propylene in an amount of 75% by weight or more is preferable in that the crystallinity, rigidity, chemical resistance, etc., which are characteristics of the polypropylene resin, are maintained.
The copolymerizable α-olefin is ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene. , 1-heptene, 3-methyl-1-hexene, 1-octene, 1-decene and the like, such as α-olefins having 2 or 4 to 12 carbon atoms, cyclopentene, norbornene, tetracyclo [6,2,11,8,13, 6] Cyclic olefins such as -4-dodecene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene Such as dienes, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, Examples thereof include vinyl monomers such as butyl acrylate, methyl methacrylate, maleic anhydride, styrene, methyl styrene, vinyl toluene, and divinyl benzene. These may be used alone or in combination of two or more.
Among these, ethylene and 1-butene are preferable from the viewpoints of improving cold brittleness resistance and low cost.

Examples of the conjugated diene compound include butadiene, isoprene, 1,3-heptadiene, 2,3-dimethylbutadiene, 2,5-dimethyl-2,4-hexadiene, and the like. These may be used alone or in combination of two or more.
Among these, butadiene and isoprene are particularly preferable because they are inexpensive and easy to handle and the reaction easily proceeds uniformly.

  The addition amount of the conjugated diene compound is preferably 0.01 parts by weight or more and 20 parts by weight or less, and more preferably 0.05 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the linear polypropylene resin. If the addition amount of the conjugated diene compound is less than 0.01 parts by weight, the effect of the modification may be difficult to obtain, and if the addition amount exceeds 20 parts by weight, the effect is saturated and may not be economical. is there.

  Monomers copolymerizable with the conjugated diene compounds, such as vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, acrylic acid Metal salts, metal methacrylate salts, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid esters such as 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid 2 -You may use together methacrylic acid esters, such as ethylhexyl and stearyl methacrylate.

The radical polymerization initiator generally includes peroxides, azo compounds, and the like, but those having a capability of extracting hydrogen from a polypropylene resin or the conjugated diene compound are preferable. Generally, ketone peroxides, peroxyketals, hydroperoxides are used. Organic peroxides such as oxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters are listed.
Of these, those having particularly high hydrogen abstraction ability are preferred, such as 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, Peroxyketals such as n-butyl 4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5 -Di (t-butylperoxy) hexane, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl Diacyl peroxides such as dialkyl peroxides such as -2,5-di (t-butylperoxy) -3-hexyne and benzoyl peroxides Side, t-butyl peroxyoctate, t-butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butyl peroxy 3,5,5-trimethylhexanoate, t-butyl peroxyisopropyl carbonate Peroxyesters such as 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate. It is done. These may be used alone or in combination of two or more.

  The addition amount of the radical polymerization initiator is preferably from 0.01 to 10 parts by weight, more preferably from 0.05 to 4 parts by weight, based on 100 parts by weight of the linear polypropylene resin. If the addition amount of the radical polymerization initiator is less than 0.01 parts by weight, the effect of the modification may be difficult to obtain. If the addition amount exceeds 10 parts by weight, the effect of the modification is saturated and it is not economical. There is a case.

  The equipment for reacting the linear polypropylene resin, the conjugated diene compound, and the radical polymerization initiator includes a kneading machine such as a roll, a kneader, a Banbury mixer, a Brabender, a single screw extruder, a twin screw extruder, and a biaxial surface. An updater, a horizontal stirrer such as a two-shaft multi-disc device, a vertical stirrer such as a double helical ribbon stirrer, and the like. Among these, a kneader is preferably used, and an extruder is particularly preferable from the viewpoint of productivity.

  There is no particular limitation on the order and method of mixing and kneading (stirring) the linear polypropylene resin, the conjugated diene compound, and the radical polymerization initiator. The linear polypropylene resin, the conjugated diene compound, and the radical polymerization initiator may be mixed and then melt-kneaded (stirred), or after the polypropylene resin is melt-kneaded (stirred), the conjugated diene compound or radical initiator may be mixed simultaneously. Alternatively, they may be mixed separately, collectively or divided. The temperature of the kneading (stirring) machine is preferably 130 ° C. or more and 300 ° C. or less from the viewpoint that the linear polypropylene resin melts and does not thermally decompose. The time is generally preferably 1 to 60 minutes.

  There is no restriction | limiting in the shape and magnitude | size of the modified polypropylene resin (B) obtained in this way, A pellet form may be sufficient.

In the present invention, the mixing method of the olefin elastomer (A) and the modified polypropylene resin (B) is not particularly limited, and can be performed by a known method. Examples of the mixing method include methods such as dry blending both pellets using a blender, a mixer, etc., melt mixing, and dissolving and mixing in a solvent.
In the present invention, the method of dry blending and then subjecting to injection foam molding is preferable because the heat history is small and the decrease in melt tension of the modified polypropylene resin (B) is small.

  The thermoplastic elastomer composition for injection foam molding of the present invention comprises 50% by weight or more and 97% by weight or less of the olefin elastomer (A) and 3% by weight or more and 50% by weight or less of the modified polypropylene resin (B). Preferably, the olefinic elastomer composition (A) comprises 60 wt% or more and 95 wt% or less, and the modified polypropylene resin (B) comprises 5 wt% or more and 40 wt% or less [(A) and (B). Is 100% by weight].

  When the blending ratio of the thermoplastic elastomer (A) and the modified polypropylene resin (B) is within the above range, the composition has fluidity suitable for use in injection foam molding and melt tension for preventing bubble breakage. In addition to being a product, it is possible to maintain a high heat resistance, and it is possible to obtain an injection foam molded article that is lightweight, has a high expansion ratio, has a soft feeling, and has excellent mold transferability and heat resistance.

  The foaming agent used in the present invention is not particularly limited as long as it can be usually used for injection foam molding, such as a chemical foaming agent and a physical foaming agent. A chemical foaming agent decomposes | disassembles and generate | occur | produces gas, such as a carbon dioxide gas, It can supply to an injection molding machine, after previously mixing with the said resin. Examples of the chemical foaming agent include inorganic chemical foaming agents such as sodium bicarbonate and ammonium carbonate, and organic chemical foaming agents such as azodicarbonamide and N, N′-dinitrosopentamethylenetetramine. These may be used alone or in combination of two or more.

  A physical foaming agent is injected into a molten resin in a cylinder of a molding machine as a gaseous or supercritical fluid, dispersed or dissolved, and functions as a foaming agent by being released from pressure after being injected into a mold. Is. Physical foaming agents include aliphatic hydrocarbons such as propane and butane, alicyclic hydrocarbons such as cyclobutane and cyclopentane, halogenated hydrocarbons such as chlorodifluoromethane and dichloromethane, nitrogen, carbon dioxide, air, etc. Inorganic gas. These may be used alone or in combination of two or more.

  Among these foaming agents, a normal injection molding machine can be used safely, and uniform fine bubbles are easily obtained. As a chemical foaming agent, an inorganic chemical foaming agent, as a physical foaming agent, nitrogen, Inorganic gases such as carbon dioxide and air are preferred.

  These foaming agents include, for example, foaming aids such as organic acids such as citric acid and inorganics such as talc and lithium carbonate, in order to stably and uniformly make the bubbles of the injection foam molded article. A nucleating agent such as fine particles may be added. Usually, the inorganic chemical foaming agent is used by preparing a masterbatch of a polyolefin resin having a concentration of 10 to 50% by weight from the viewpoints of handleability, storage stability, and dispersibility in a thermoplastic elastomer composition. Is preferred.

  What is necessary is just to set the usage-amount of the said foaming agent suitably with the foaming magnification of the injection foaming molding obtained, the kind of foaming agent, and the resin temperature at the time of shaping | molding. For example, in the case of an inorganic chemical foaming agent, it is usually preferably 0.5 parts by weight or more and 20 parts by weight or less, more preferably 1 part by weight or more with respect to 100 parts by weight of the thermoplastic elastomer composition for injection foam molding. It is used in the range of 15 parts by weight or less. By using an inorganic chemical foaming agent in the above range, it is easy to economically obtain an injection foam molded article having a foaming ratio of 2 times or more and uniform fine bubbles. In the case of a physical foaming agent, the injection is carried out in the range of 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polypropylene resin of the present invention. Used by supplying to a molding machine.

  As for the method of adding the foaming agent, a thermoplastic elastomer composition for injection foam molding, which is dry blended with a chemical foaming agent, or a material impregnated with a physical foaming agent may be supplied to an injection molding machine in advance. After the thermoplastic elastomer composition for injection foam molding other than the foaming agent is supplied to the injection molding machine, the foaming agent may be added from the middle of the molding machine cylinder.

In the present invention, if necessary, a fluidity improver such as a lubricant, a polyolefin wax, an antioxidant, a metal deactivator, a phosphorus processing stabilizer, and an ultraviolet absorber as long as the effects of the present invention are not impaired. , Stabilizers such as light stabilizers, optical brighteners, metal soaps, antacid adsorbents, crosslinking agents, chain transfer agents, nucleating agents, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic An additive such as an agent may be used in combination.
Of course, these additives used as needed are used within a range not impairing the effects of the present invention, but with respect to 100 parts by weight of the thermoplastic elastomer composition for injection foam molding of the present invention, Preferably, it is used in 0.01 parts by weight or more and 40 parts by weight or less.

  The thermoplastic elastomer composition for injection foam molding of the present invention obtained as described above is injection foamed into an injection foam molded article.

  Next, the manufacturing method of the injection foaming molding of this invention is demonstrated concretely.

  A known method can be applied as the production method itself, and the molding conditions may be appropriately adjusted depending on the melt flow rate of the thermoplastic elastomer composition for injection foam molding, the type of foaming agent, the type of molding machine, or the shape of the mold.

  In the case of the thermoplastic elastomer composition for injection foam molding of the present invention, the resin temperature is 170 to 250 ° C., the mold temperature is 10 to 100 ° C., the molding cycle is 1 to 60 minutes, the injection speed is 10 to 300 mm / second, and the injection pressure is 10 to 10. It is preferable to carry out under the condition of 200 MPa.

  There are various methods for foaming in the mold. Among them, a mold composed of a fixed mold and a movable mold capable of moving forward and backward at an arbitrary position is used. The so-called core back method (moving cavity method), which causes the foam to recede, has a non-foamed layer formed on the surface, the foamed layer tends to become uniform fine bubbles, has excellent lightness, and has a soft feeling. It is preferable because a molded body is easily obtained. As a method of retracting the movable mold, it may be performed in one step, or may be performed in multiple stages including two or more stages. In each stage, a process for stopping the movable mold is added, or the speed is continuously changed to reverse the movable mold. It is also possible to adjust the retraction speed as appropriate.

  In addition, injection foaming caused by silver streak is used in combination with a so-called counter pressure method in which a thermoplastic elastomer composition for injection foam molding is introduced into the mold while pressure is applied in advance in the mold with an inert gas or the like. Since the surface appearance defect of a molded object can be reduced, it is preferable.

  The clearance of the mold when injection-filling the molten mixture of the thermoplastic elastomer composition for injection foam molding of the present invention and the foaming agent is preferably 1.0 mm or more and 3.0 mm or less, more preferably 1.2 mm. It is preferable that it is 2.5 mm or less. By being in this range, it is easy to obtain an injection-foamed molded article having a high expansion ratio and excellent in lightness.

  The injection-foamed molded article of the present invention thus obtained has fine bubbles and is excellent in lightness and softness. Specifically, the foaming ratio is more than 2 times and 10 times or less, and the type A hardness is preferably 30 or more and 80 or less, more preferably 2.5 times or more and 10 times or less, and the type A hardness is 40 or more and 75 or less. It is preferable.

  The method for measuring the type A hardness of the injection-foamed molded article is the same as that for the olefin-based elastomer.

  The injection foam molded article obtained by the present invention is suitably used for automobile interior parts such as instrument panels and door trims because of its characteristics. When used in such applications, the injection-foamed molded article can be used alone, but it is usually preferable to laminate it on a hard substrate and use it as a skin.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  In the examples and comparative examples, the test methods and criteria used in various evaluation methods are as follows.

(1) Melt flow rate (MFR):
MFR is a resin that is extruded from a die under a load of 230 ° C. and 2.16 kg using a melt indexer S-01 (manufactured by Toyo Seiki Seisakusho) in accordance with the provisions of Method A described in JIS K7210 (1999). It was set as the value converted into the amount extruded from the amount for 10 minutes.
The fixed time is 120 seconds when the melt flow rate exceeds 0.5 g / 10 minutes and 1.0 g / 10 minutes or less, and when the melt flow rate exceeds 1.0 g / 10 minutes and 3.5 g / 10 minutes or less. Is 30 seconds when it exceeds 3.5 g / 10 minutes and 10 g / 10 minutes or less for 60 seconds, 10 seconds when it exceeds 10 g / 10 minutes and 25 g / 10 minutes or less, and it exceeds 25 g / 10 minutes and 100 g / 10 If it is less than 5 minutes, it is 5 seconds, and if it exceeds 100 g / 10 minutes, it is 3 seconds.
Three pieces cut out at the predetermined time are collected and the average value is calculated. If three pieces cannot be collected in one measurement, the measurement is continued until three pieces can be collected. If the melt flow rate measured in a certain number of seconds is not in the corresponding range, the measurement is performed again in the number of seconds corresponding to the melt flow rate.

(2) Heat of fusion (ΔH ₁₀₀ ), melting peak temperature:
Using a differential scanning calorimeter DSC6200 manufactured by Seiko Instruments Inc., a measurement method according to JIS K7122 (1987) was used to raise the temperature of 4 to 10 mg of the measurement sample from 10 ° C. to 210 ° C. at a rate of 10 ° C./min. Once melted and then cooled from 210 ° C. to 10 ° C. at a rate of 10 ° C./min, and then heated again from 10 ° C. to 210 ° C. at a rate of 10 ° C./min. DSC curve was obtained.
In the obtained DSC curve, as shown in FIG. 1, the base line is drawn so as to extend a portion that can be regarded as a substantially straight line on both sides of the peak of the DSC curve, and the DSC curve is separated from the low temperature side baseline. Of the heat of fusion calculated from the area of the portion surrounded by the line ab connecting a and the point b away from the high temperature side base line and the DSC curve, the region bcd having a temperature of 100 ° C. or higher (indicated by the hatched portion) the heat of fusion calculated from the area of the [Delta] H _100. When the temperature at the point a exceeded 100 ° C., the amount of heat of fusion calculated from the area of the portion surrounded by the line ab and the DSC curve was taken as ΔH ₁₀₀ .
On the other hand, in the obtained DSC curve, the temperature at the point where the endothermic amount becomes maximum at one melting peak was defined as the melting peak temperature. When there were two or more melting peaks, the maximum endothermic temperature at each peak was defined as the respective peak temperature, and it was clearly shown that there were two peak temperatures.

(3) Melt tension:
It is equipped with an attachment for melt tension measurement, using a capilograph (manufactured by Toyo Seiki Seisakusho) with a φ10 mm cylinder fitted with an orifice of φ1 mm and a length of 10 mm at the tip, at a piston descending speed of 10 mm / min. When lowered, the strand discharged from the die is applied to a pulley with a load cell 350 mm below and taken up at a speed of 1 m / min. After stabilization, the take-up speed is increased at a rate of reaching 200 m / min in 4 minutes. The load applied to the pulley with a load cell when ruptured was defined as melt tension. When the strand did not break, the load at the point where the load applied to the pulley with the load cell did not increase even when the take-up speed was increased was defined as the melt tension.

(4) Strain hardenability:
When measuring the melt tension, when the take-up speed is increased, the take-up load increases abruptly, and when it reaches the fracture, it indicates “strain hardenability”, otherwise, it indicates “no strain hardenability”. .

(5) Type A hardness:
In accordance with JIS K6253, a type A durometer hardness test was performed, and the hardness at 23 ° C. was measured.

(6) Injection pressure:
The peak pressure during injection filling was evaluated as one of the indicators of resin fluidity. For example, if the injection pressure is high, it can be said that the fluidity is poor.
Injection pressure is 130MPa or less ...
Injection pressure exceeds 130MPa and 140MPa or less
Injection pressure exceeds 140 MPa

(7) Foaming ratio:
The thickness is calculated by measuring the thickness of the bottom surface portion of the box-shaped injection-foamed molded article and dividing the thickness by the cavity clearance t ₀ in the mold-clamped state of the part.

(8) Internal void:
Cut the bottom of the box-shaped injection-foamed molded body at the center line including the gate, observe the cross section in the range from 30 mm to 60 mm from the gate, and create a void with a diameter of 1.5 mm or more in the foam layer (internal The presence or absence of coarse bubbles generated by the communication of air bubbles was examined.
No voids are observed ... ○
Things with voids ... ×

(9) Mold transferability:
The texture of the embossed pattern at a point 5 mm inside from the end of the molded product of the present invention was observed with an optical microscope at a magnification of 150 times, and a separately produced non-foamed molded product with a thickness of 3 mm (reference example) at the same location. Compared with the observation results, evaluation was made according to the following criteria.
The transfer status is the same level as the reference molded product ...
Those where transfer defects such as lack of fine uneven patterns are confirmed ... ×

(10) Heat resistance evaluation:
Prepare a plate-shaped test piece from which the bottom of the molded body was cut, and place a 360 g metal container with a diameter of 60 mmφ and a width of 1 mm on the surface side (textured surface side). And left in an oven at 110 ° C. for 24 hours. Then, the plate-shaped test piece is allowed to cool and returned to room temperature, and after removing the metal container from the plate-shaped test piece, observe the degree of the circumferential recess generated on the contact surface with the metal container on the test piece, Evaluation was made according to the following criteria.
No circumferential dent is observed ... ◎
Circumferential dents are observed even thin ... ○
Circumferential dents are clearly observed and crushing of wrinkles is also observed ... ×

Next, resin materials and foaming agents used in Examples and Comparative Examples are shown below.
(A) Olefin-based elastomer TP-1: Prime TPO M142E [manufactured by Prime Polymer, ethylene-propylene copolymer (reactor TPO), type A hardness 75, MFR (230 ° C.) 10 g / 10 min, heat of fusion of 100 ° C. or higher (ΔH ₁₀₀ ) 7 mJ / mg, melting peak temperature 153 ° C.]
TP-2: Prime TPO R110MP [manufactured by Prime Polymer, ethylene-propylene copolymer (reactor TPO), type A hardness 68, MFR (230 ° C.) 2 g / 10 min, heat of fusion at 100 ° C. or higher (ΔH ₁₀₀ ) 6 mJ / mg, melting peak temperature 109 ° C./155° C. (with two peaks)]
TP-3: Versify 3401 [manufactured by Dow Chemical Japan, ethylene-propylene copolymer, type A hardness 72, MFR (230 ° C.) 8 g / 10 min, heat of fusion at 100 ° C. or higher (ΔH ₁₀₀ ) 1 mJ / mg, melting peak Temperature 95 ℃]
TP-4: Vistamax 6202 [manufactured by ExxonMobil, ethylene-propylene copolymer, type A hardness 61, MFR (230 ° C.) 18 g / 10 min, heat of fusion at 100 ° C. or higher (ΔH ₁₀₀ ) 3 mJ / mg, melting peak Temperature 113 ° C]
(B) Modified polypropylene resin MP-1: 100 parts by weight of a propylene homopolymer having a melt flow rate of 45 g / 10 min as a linear polypropylene resin, and t-butyl peroxyisopropyl carbonate 0.6 as a radical polymerization initiator A mixture of parts by weight is supplied from a hopper to a 45 mmφ twin-screw extruder (L / D = 40) at 70 kg / hour and melt-kneaded at a cylinder temperature of 200 ° C. and a rotational speed of 150 rpm. By supplying 0.8 parts by weight (at 0.56 kg / hr) of isoprene monomer as a compound using a metering pump, melt-kneading in the twin screw extruder, and cooling and shredding the extruded strand. The obtained modified polypropylene resin (melt flow rate 6 g / 10 min, melt tension 13 cN, showing strain hardening)
MP-2: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 0.65 parts by weight and the amount of isoprene monomer supplied was changed to 0.5 parts by weight. Resin (melt flow rate 25 g / 10 min, melt tension 4.9 cN, showing strain hardening)
MP-3: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 0.4 parts by weight and the amount of supplied isoprene monomer was changed to 0.4 parts by weight. Resin (melt flow rate 43 g / 10 min, melt tension 1.9 cN, showing strain hardening)
MP-4: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 0.4 parts by weight and the amount of supplied isoprene monomer was changed to 0.35 parts by weight. Resin (melt flow rate 62 g / 10 min, melt tension 1.2 cN, strain hardening)
MP-5: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 1.0 part by weight and the amount of supplied isoprene monomer was changed to 0.3 part by weight. Resin (melt flow rate 56 g / 10 min, melt tension 5.2 cN, showing strain hardening)
MP-6: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 1.4 parts by weight and the amount of isoprene monomer supplied was changed to 0.25 parts by weight. Resin (melt flow rate 175 g / 10 min, melt tension 2.0 cN, strain hardening)
MP-7: Modified polypropylene obtained in the same manner as MP-1 except that the blending amount of t-butylperoxyisopropyl carbonate was changed to 1.4 parts by weight and the amount of supplied isoprene monomer was changed to 0.22 parts by weight. Resin (melt flow rate 207 g / 10 min, melt tension 1.2 cN, showing strain hardening)
MP-8: The melt flow rate of the propylene homopolymer used was changed to 15 g / 10 min, the blending amount of t-butylperoxyisopropyl carbonate was changed to 0.7 parts by weight, and the amount of supplied isoprene monomer was changed to 2.0 parts by weight. Except for this, a modified polypropylene resin obtained in the same manner as MP-1 (melt flow rate 3 g / 10 min, melt tension 17 cN, showing strain hardening)
PP-1: Commercially available linear polypropylene [propylene-ethylene block copolymer, melt flow rate 45 g / 10 min, melt tension 0.2 cN, does not exhibit strain hardening]
PP-2: Commercially available linear polypropylene [propylene homopolymer, melt flow rate 3 g / 10 min, melt tension 1.9 cN, does not exhibit strain hardening]
(C) Foaming agent BA-1: Chemical blowing agent master batch [manufactured by Eiwa Kasei Co., Ltd., Polyslen EE275F, decomposition gas amount 40 ml / g]

The injection molding machines and molds used in the examples and comparative examples are described below.
(A) Injection molding machine Electric injection molding machine [manufactured by Ube Industries Co., Ltd.] having a core back function and a shut-off nozzle with a clamping force of 350 t.
(B) Mold A mold composed of a fixed mold (concave mold) and a movable mold (convex mold) capable of moving forward and backward, in a box shape of length 250 mm × width 250 mm × height 100 mm, on the inner surface side (convex mold) Side) It has a cavity (standing wall: tilt 10 degrees, clearance 3 mm, bottom: clearance t ₀ = 2.0 mm) with a 100 μm deep skin texture pattern on the entire surface, and the center position of the bottom side of the fixed mold Mold with 2.5mmφ valve gate

(Reference example)
After supplying PP-1 alone to an injection molding machine set at a cylinder temperature of 220 ° C. and melt-kneading at a back pressure of 15 MPa, the clearance of the bottom surface is adjusted to 3.0 mm, the hot runner is 220 ° C., and the cavity surface is The mold was heated to 50 ° C. and injected and filled at an injection speed of 60 mm / second. Immediately after filling, a pressure holding process of 40 MPa was performed for 20 seconds, and then cooled for 45 seconds to take out a non-foamed molded body having a thickness of 3.0 mm.

Example 1
The thermoplastic elastomer and the modified polypropylene resin were dry blended at a composition ratio shown in Table 1 to obtain a thermoplastic elastomer composition for injection foam molding.
A composition obtained by adding 8 parts by weight of the chemical foaming agent BA-1 to 100 parts by weight of the composition is supplied to an injection molding machine set at a cylinder temperature of 200 ° C., melted and kneaded at a back pressure of 15 MPa, and then hot The runner was 200 ° C. and the cavity surface was heated to 30 ° C., and injection filled at an injection speed of 100 mm / sec. After completion of the injection filling, the movable mold was retracted so that the bottom surface portion had a desired thickness (foaming ratio), and the resin in the cavity was foamed. After completion of foaming, the product was cooled for 100 seconds, and the injection foamed molded product was taken out.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 2)
An injection foam molded article was obtained in the same manner as in Example 1 except that the blending ratio of the thermoplastic elastomer and the modified polypropylene resin was as shown in Table 1.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 3)
An injection foam molded article was obtained in the same manner as in Example 1 except that the ratio of the thermoplastic elastomer and the modified polypropylene resin was as shown in Table 1 and the foaming ratio was 2.2 times.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

Example 4
An injection-foamed molded article was obtained in the same manner as in Example 1 except that the ratio of the thermoplastic elastomer and the modified polypropylene resin was as shown in Table 1 and the expansion ratio was 4 times.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 5)
An injection foam molded article was obtained in the same manner as in Example 2 except that the thermoplastic elastomer was changed to TP-2.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 6)
An injection foam molded article was obtained in the same manner as in Example 1 except that the modified polypropylene resin was changed to MP-1.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 7)
An injection foam molded article was obtained in the same manner as in Example 1, except that the modified polypropylene resin was changed to MP-2.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 8)
An injection foam molded article was obtained in the same manner as in Example 1 except that the modified polypropylene resin was changed to MP-3.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

Example 9
An injection foam molded article was obtained in the same manner as in Example 5 except that the modified polypropylene resin was changed to MP-4.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 10)
An injection foam molded article was obtained in the same manner as in Example 5 except that the modified polypropylene resin was changed to MP-6.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

(Example 11)
An injection foam molded article was obtained in the same manner as in Example 5 except that the modified polypropylene resin was changed to MP-7.
Table 1 shows the physical properties of the obtained injection-foamed molded article.

  The thermoplastic elastomer composition for injection foam molding of the present invention exhibits excellent fluidity and can be molded with a relatively small injection pressure. In addition, since it has excellent foamability, there is no generation of voids and the like, there is no surface unevenness, it has excellent mold transferability, the expansion ratio without voids is 2.2 to 4 times, and the type A hardness is 57. A box-shaped injection-foamed molded article having a bottom portion of ˜79 was obtained.

(Comparative Example 1)
An injection foam molded article was obtained in the same manner as in Example 3 except that the thermoplastic elastomer was changed to TP-3.
Table 1 shows the physical properties of the obtained injection-foamed molded article. The obtained molded body was inferior in heat resistance.

(Comparative Example 2)
An injection foam molded article was obtained in the same manner as in Example 3 except that the thermoplastic elastomer was changed to TP-4.
Table 1 shows the physical properties of the obtained injection-foamed molded article. The obtained molded body was inferior in heat resistance.

(Comparative Example 3)
An injection foam molded article was obtained in the same manner as in Example 3 except that the modified polypropylene resin was not blended.
Table 1 shows the physical properties of the obtained injection-foamed molded article. In addition to the high injection pressure at the time of injection molding, the obtained molded body had voids and was inferior in heat resistance.

(Comparative Example 4)
An injection foam molded article was obtained in the same manner as in Example 2 except that the modified polypropylene resin was changed to MP-8.
Table 1 shows the physical properties of the obtained injection-foamed molded article. In addition to the high injection pressure at the time of injection molding, the obtained molded product was inferior in mold transferability.

(Comparative Example 5)
An injection foam molded article was obtained in the same manner as in Example 2 except that the modified polypropylene resin was changed to commercially available linear PP (PP-1) and the magnification was 2.2 times.
Table 1 shows the physical properties of the obtained injection-foamed molded article. The obtained molded body had voids generated at a magnification of 2.2.

(Comparative Example 6)
An injection foamed molded article was obtained in the same manner as in Example 2 except that the modified polypropylene resin was changed to commercially available linear PP (PP-2) and the magnification was 2.2 times.
Table 1 shows the physical properties of the obtained injection-foamed molded article. Not only was the injection pressure at the time of injection molding high, the resulting molded product had voids despite a magnification of 2.2, and the mold transferability was poor.

Claims (5)

Olefin-based elastomer (A) satisfying the following (A1) to (A3): 50 wt% or more and 97 wt% or less,
The modified polypropylene resin (B) satisfying the following (B1) to (B2) is contained in an amount of 3% by weight to 50% by weight [the total amount of (A) and (B) is 100% by weight] An olefin-based thermoplastic elastomer composition for injection foam molding.
(A1) MFR is 1 g / 10 min or more and 80 g / 10 min or less (A2) Type A hardness is 40 or more and 90 or less (A3) Calculated from a DSC curve obtained by measurement by differential scanning calorimetry, at 100 ° C. or more Of heat of fusion (ΔH ₁₀₀ ) of 4 mJ / mg or more,
(B1) Meets any of the following requirements (A) to (E) (A) Melt flow rate 4.5 g / 10 min or more and less than 10 g / 10 min, Melt tension 5 cN or more (B) Melt flow rate 10 g / 10 Min. To 30 g / 10 min., Melt tension 2 cN or more (c) melt flow rate 30 g / 10 min to 50 g / 10 min., Melt tension 1 cN or more. (2) melt flow rate 50 g / 10 min to 100 g / 10 min. Melt tension of 0.3 cN or more (e) Melt flow rate of more than 100 g / 10 min to 250 g / 10 min or less, melt tension of 0.3 cN or more (B2) Strain hardenability   An injection foam molded article obtained by injection foaming the thermoplastic elastomer composition for injection foam molding according to claim 1.   The injection-foamed molded article according to claim 2, wherein the expansion ratio is more than 2 times and 10 times or less, and the type A hardness is 30 or more and 80 or less.   A method for producing a foamed molded article, comprising: supplying the thermoplastic elastomer composition for injection foam molding according to claim 1 and a foaming agent to an injection molding machine; . 5. The mold according to claim 4, wherein a mold composed of a fixed mold and a movable mold capable of moving forward and backward at an arbitrary position is used, and after completion of injection, the movable mold is moved backward to foam. A method for producing a foam molded article.