JP2019059861A - Polypropylene injection foam molding - Google Patents

Abstract

To provide a polypropylene injection foam molding that has excellent impact resistance and shows an excellent foamy state, having a high expansion ratio.SOLUTION: An injection molding body contains a conjugated diene modified polypropylene resin (A) that is a conjugated diene modified propylene homopolymer in which a melt flow rate is less than 1-80 g/10 min., and a polypropylene resin (B) that is a propylene-ethylene block copolymer in which a melt flow rate is less than 1-80 g/10 min., where, relative to 100 wt.% of the total of (A) component and (B) component, the content of (A) component is 1-25 wt.% and the content of (B) component is 99-75 wt.%. In a polypropylene resin composition, relative to 100 pts.wt. of the total of (A) component and (B) component, polyolefin wax is 0-2 wt.%, and the expansion ratio is 2.5-8.0.SELECTED DRAWING: None

Description

  The present invention relates to a high expansion ratio injection foam molded article using a polypropylene resin composition.

  Polypropylene resins have good physical properties and moldability, and their range of use is rapidly expanding as environmentally friendly materials. In particular, for automobile parts and the like, lightweight and highly rigid polypropylene resin products are provided. One such product is an injection molded foam of polypropylene resin. Among these, automobile parts are known to be a field where weight reduction is particularly strongly demanded. In order to reduce the weight, it is effective to set the expansion ratio of the injection foam molding to a high expansion ratio.

Generally, the properties of the polypropylene-based resin used for injection foam molding require fluidity to fill the resin in the entire mold and foamability to foam thereafter.
However, since the linear polypropylene resin generally used has low impact resistance, the foam is likely to be broken, making it difficult to apply to applications in which impact resistance is important. In addition, there was a tendency that a foaming defect was likely to occur, which was judged to be inferior in the cell state by visual observation. In particular, in the case of obtaining an injection molded foam with a high expansion ratio, the tendency of the foam to be easily broken and the tendency of being judged to be inferior in the cell state were remarkable.
For example, the following proposals have been made for their improvement.

  In Patent Document 1, a composition comprising (A) a linear polypropylene-based resin, (B) a resin composed of a modified polypropylene-based resin exhibiting strain hardening, and a foaming agent is injection-foamed into a mold. Methods and molded articles thereby obtained are disclosed, and it is described that high expansion ratio is possible and the surface appearance is good. However, as seen in Examples 1 to 4 thereof, although the expansion ratio is 2.4 times to 3.8 times, (B) having a melt flow rate of 0.5 to 3 (g / 10 min) is used. As a result, there is a concern that the flowability of the larger-sized molded product may be insufficient. In addition, as seen in Comparative Example 4, when (B) having a higher melt flow rate is used, the expansion ratio remains at 2.1 times, and the internal void state is compared with Examples 1 to 4. From the inferior point of view, it was apparent that an injection molded foam having a high expansion ratio could not be obtained simply by increasing the flowability of (B).

  Patent Document 2 discloses a process for producing (A) a modified polypropylene-based resin obtained by melt-kneading (a) a polypropylene-based resin, (b) an isoprene monomer, and (c) a radical polymerization initiator. It is described that the obtained (A) exhibits strain curability and may be used for foam molding. However, injection foam molding is not described, and in that case, there is neither description nor suggestion about the impact resistance and the cell state in the case of foaming, so it is not easy to apply to injection foam molding, The effect when applied was also completely unknown. At the same time, the use of the component (A) in combination with the non-modified polypropylene resin is not described.

  Patent Document 3 discloses foaming of (A) a modified polypropylene-based resin obtained by melt-kneading (a) a polypropylene-based resin, (b) an isoprene monomer, and (c) a radical polymerization initiator. The manufacturing method of the body is disclosed, and it is described that a foamed molded article having good heat resistance and excellent foaming ratio is obtained. However, injection foam molding is not described, and in that case, there is neither description nor suggestion about the impact resistance and the cell state in the case of foaming, so it is not easy to apply to injection foam molding, The effect when applied was also completely unknown. At the same time, the use of the component (A) in combination with the non-modified polypropylene resin is not described.

  In Patent Document 4, (A) a modified polypropylene-based resin obtained by melt-kneading (a) a polypropylene-based resin, (b) a monomer such as isoprene, and (c) a radical polymerization initiator is foamed. It is disclosed that the foam sheet is obtained, and the drawdown at heating is small and the closed cell rate is excellent. However, injection foam molding is not described, nor is it described or suggested about impact resistance and cell state when foamed, and thus it is not easy to apply to injection foam molding. The effect was also unknown at all. At the same time, the use of the component (A) in combination with the non-modified polypropylene resin is not described.

  Patent Document 5 discloses a method of injection foam molding a composition containing (A) a strain-curable modified polypropylene resin and (C) a foaming agent into a mold, and molding obtained thereby. A body is disclosed, and it is described that the foamability is good and the rigidity is excellent. In the examples, although an isoprene-modified propylene-ethylene block copolymer having a melt flow rate of 16 to 25 (g / 10 min) is used, the expansion ratio remains at 2.5 to 2.6 times, It was unclear whether it could be applied to higher expansion ratio than that. Moreover, since there is neither description nor suggestion about impact resistance, the effect at the time of applying to the use which gives importance to impact resistance was also completely unknown. At the same time, the use of the component (A) in combination with the non-modified polypropylene resin is not described. Comparative Examples 2 and 4 describe combining a propylene homopolymer having strain curing properties with a non-modified propylene-ethylene block copolymer, but the expansion ratio remains at 2.5 times. It was unclear whether or not it could be applied to a higher expansion ratio than that, and the melt flow rate of the above-mentioned strain-hardening propylene homopolymer was as low as 3 (g / 10 min), and thus larger-sized molding was possible. There was a concern about lack of liquidity in the body.

  Patent Document 6 discloses a gold-based melt of a polypropylene-based resin composition comprising (A) a linear polypropylene-based resin, (B) a polypropylene-based resin comprising a modified polypropylene-based resin, and a foaming agent. A method is described for injection into a mold to produce a foam molding. In the examples, an isoprene-modified propylene homopolymer having a melt flow rate of 0.5 to 3 (g / 10 min) is used, and although the expansion ratio is 2.4 times to 4.8 times, the melt is Because of the low flow rate (B), there is a concern that the flowability may be insufficient in a larger molded product.

  In Comparative Example 3 of Patent Document 7, an isoprene-modified propylene homopolymer having a melt flow rate of 56 (g / 10 min) and a propylene-ethylene block copolymer having a melt flow rate of 45 (g / 10 min) An injection-foamed molded article having a total expansion ratio of 10 times and consisting of coalescence and a chemical blowing agent is described. However, this injection-molded foam was inferior in cell structure, and therefore extremely brittle and not practical. In addition, there is no description or suggestion in this document about obtaining a practical injection molded foam in which these disadvantages are eliminated based on this injection molded foam.

  In Examples 1 and 5 to 20 of Patent Document 8, an isoprene-modified propylene homopolymer having a melt flow rate of 65 (g / 10 min) and a propylene having a melt flow rate of 30 (g / 10 min) are used. There is described an injection molded foam comprising an ethylene block copolymer, a wax or liquid paraffin, and a chemical foaming agent and having a maximum expansion ratio of 3.2 to 3.6. However, in this document, it is essential to blend a large amount (for example, 10% by weight) of wax in order to improve the formability such as flow marks, and the use exposed to a harsher environment (for example, car interior) In applications, depending on the country or region in which it is used, the indoor environment may become even higher in temperature), problems such as bleeding out of wax components may occur. Further, in this document, neither description nor suggestion has been made to obtain a good injection-foamed molded product while not blending a wax or setting it to a usual blending amount (for example, 2% by weight or less).

  As described above, in the polypropylene resin composition for injection foam molding, it has been difficult to obtain a polypropylene resin composition having both impact resistance and cell state when foamed. In particular, this was remarkable when trying to obtain an injection molded foam with a high expansion ratio.

JP, 2005-224963, A Japanese Patent Application Laid-Open No. 09-188729 JP 09-188774 A JP 2001-139716 A Unexamined-Japanese-Patent No. 2007-130992 JP, 2006-240051, A JP 2012-000909 A JP, 2016-003310, A

  An object of the present invention is to provide a high expansion ratio polypropylene injection molded foam having excellent impact resistance and a good foaming state.

The present invention is as follows.
Conjugated diene-modified polypropylene-based resin (A), which is a conjugated diene-modified propylene homopolymer having a melt flow rate of 10 g / 10 min or more and less than 80 g / 10 min measured at 230 ° C. and a 2.16 kg load ,
Containing a polypropylene-based resin (B) which is a propylene-ethylene block copolymer having a melt flow rate of 10 g / 10 minutes or more and less than 80 g / 10 minutes measured at 230 ° C. under 2.16 kg load,
The content of the component (A) is 1 to 25% by weight, and the content of the component (B) is 99 to 75% by weight with respect to a total of 100% by weight of the components (A) and (B).
About a polypropylene resin composition containing 0 to 2% by weight of polyolefin wax with respect to a total of 100% by weight of the (A) component and the (B) component,
It is an injection-foamed molded article obtained by injection-foaming it and having an expansion ratio of 2.5 to 8.0.

  The injection foam molded article of the present invention is an injection foam molded article having a high foaming ratio, which is excellent in impact resistance and has a good foaming state. Therefore, the polypropylene-based injection foam molded article of the present invention can be suitably used in applications such as automobile interiors.

  Hereinafter, embodiments of the present invention will be described.

  The present invention relates to a polypropylene based injection foam molded article. The polypropylene-based resin composition used for the polypropylene-based injection-molded foam according to the present invention has a conjugated diene composition whose melt flow rate measured at 230 ° C. under 2.16 kg load is 10 g / 10 min or more and less than 80 g / 10 min. Diene-modified polypropylene-based resin (A), which is a high-quality propylene homopolymer, and propylene having a melt flow rate of 10 g / 10 min or more and less than 80 g / 10 min measured at 230 ° C. and a 2.16 kg load The polypropylene block resin (B) which is an ethylene block copolymer is contained, and the content of the component (A) is 1 to 25% by weight, based on 100% by weight in total of the component (A) and the component (B) The content of the component is 99 to 75% by weight, and 0 to 2% by weight of a polyolefin wax is contained with respect to 100% by weight in total of the component (A) and the component (B). .

<Conjugated diene-modified polypropylene-based resin (A)>
The conjugated diene-modified polypropylene resin (A) of the present invention is a conjugated diene-modified propylene having a melt flow rate of 1 g / 10 minutes or more and less than 80 g / 10 minutes measured under conditions of 230 ° C. and 2.16 kg load. It is a homopolymer.

  When the melt flow rate of the component (A) is less than 1 g / 10 min, the flowability of the resin composition is insufficient, and molding failure such as short shot occurs in injection foam molding with a large mold and mold transferability is deteriorated. It may cause surface defects and the like. When the melt flow rate of the component (A) is 80 g / 10 min or more, the mixing with the component (B) may be insufficient or the impact resistance of the injection foam molded article may be insufficient. The melt flow rate of the component (A) is preferably 20 g / 10 min or more and less than 80 g / 10 min when importance is placed on mold transferability and surface properties of the molded article, and when importance is given to the impact resistance of the molded article. Is preferably 1 g / 10 minutes or more and less than 20 g / 10 minutes.

  Here, the melt flow rate (hereinafter sometimes abbreviated as “MFR”) is 230 ° C., using a melt indexer F-F01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K 7210: 1999. A value obtained by converting the amount of resin extruded from a die in a fixed time under the condition of a 2.16 kg load into the amount of resin extruded in 10 minutes. The converted value was calculated by MFR automatic calculation processing (method B). The calculation formula is as follows. The method was applied even if the melt flow rate exceeded 50 g / 10 min.

MFR (g / 10 min) = (427 × L × ρ) / t
L (interval of test conditions): 3 (cm)
溶 融 (melt density at the test temperature): A value calculated by the following equation using the cutting method (g / cm ³ ), but if the cutting method is impossible, 0.75 (g / cm ³ ) = M / (0.711 x L)
m: mass (g) of the sample that has flowed out by moving the above-mentioned interval L, which is measured by a cutting method
L: Same as the above interval t (interval moving time): actual measured value (seconds)
That is, when the clipping method can be applied, it may be calculated by the following formula.
MFR (g / 10 min) = (600 × m) / t

  The conjugated diene-modified polypropylene resin (A) of the present invention preferably has a melt tension of 1.0 gf or more, more preferably 2.0 gf or more, which is measured at 200 ° C. and 10 m / min. When the melt tension of the component (A) is 1.0 gf or more, it becomes easy to obtain an injection foam molded article having uniform fine cells, for example, at a foaming ratio of 3 or more.

  The conjugated diene-modified polypropylene resin (A) of the present invention is a conjugated diene-modified propylene homopolymer. The conjugated diene-modified propylene homopolymer is a resin obtained by reacting a conjugated diene compound with a propylene homopolymer to introduce a branched structure into a propylene homopolymer and polymerizing the branched structure. The conjugated diene-modified propylene homopolymer is preferably obtained by melt mixing a propylene homopolymer (a), a radical polymerization initiator (b) and a conjugated diene compound (c). This molten mixture is excellent in that it can be manufactured inexpensively without the need for expensive equipment.

<Propylene homopolymer (a)>
The propylene homopolymer (a) used to obtain the conjugated diene-modified polypropylene resin (A) is a linear polymer containing propylene as a component, and a polymer containing 99% by weight or more of the propylene component Point to.

  The propylene homopolymer (a) may be copolymerized with less than 1% by weight of a monomer copolymerizable with propylene in addition to propylene. As such a monomer copolymerizable with propylene, for example, ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4 4-12 α-olefins such as dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, 1-decene; cyclopentene, norbornene, tetracyclo [6,2,11,8,8 Cyclic olefins such as 13,6] -4-dodecene; 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6 Dienes such as octadiene; vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, Ethyl acrylic acid, butyl acrylate, methyl methacrylate, maleic anhydride, styrene, methyl styrene, vinyl toluene, vinyl monomers such as divinylbenzene; and the like. These may be used alone or in combination of two or more. Among these, α-olefins are preferable, and ethylene and 1-butene are more preferable in terms of improvement of cold resistance, low cost, and the like.

  Commercially available propylene homopolymers (a) include, for example, J105G (MFR = 9), J106G (MFR = 15), J108M (MFR = 45), J700GP (MFR = 8), manufactured by Prime Polymer Co., Ltd. Etc.

<Radical polymerization initiator (b)>
Examples of the radical polymerization initiator (b) used to obtain the conjugated diene-modified polypropylene-based resin (A) generally include peroxides and azo compounds, but the propylene-ethylene block copolymer (a) or Those having the ability to extract hydrogen from the conjugated diene compound (c) are preferred. Although it does not specifically limit, For example, organic peroxides, such as ketone peroxide, peroxy ketal, a hydroperoxide, a dialkyl peroxide, a diacyl peroxide, peroxy dicarbonate, peroxy ester, etc. are mentioned.

  Among these, those having high hydrogen extraction ability are particularly preferable, for example, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane Peroxyketal such as n-butyl 4,4-bis (t-butylperoxy) valerate and 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-butyl peroxide, 2,5- Dialkyl peroxides such as dimethyl-2,5-di (t-butylperoxy) -3-hexyne and diacyl peroxides such as benzoyl peroxide Oxide, t-Butyl peroxy octoate, t-Butyl peroxy isobutyrate, t-Butyl peroxy laurate, t-Butyl peroxy 3,5,5-trimethylhexanoate, t-Butyl peroxy isopropyl carbonate And peroxy esters such as 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate Be These may be used alone or in combination of two or more.

  The addition amount of the radical polymerization initiator (b) used to obtain the conjugated diene-modified polypropylene resin (A) is 0.05 parts by weight with respect to 100 parts by weight of the propylene-ethylene block copolymer (a) The content is preferably 10 parts by weight or less and more preferably 0.2 parts by weight or more and 5 parts by weight or less. If the addition amount of the radical polymerization initiator is less than 0.05 parts by weight, the modification may be insufficient, and if it exceeds 10 parts by weight, molecular chain cleavage takes priority over the modification, and the desired modification There may be no quality effect.

<Conjugated diene compound (c)>
Examples of the conjugated diene compound (c) used to obtain the conjugated diene-modified polypropylene resin (A) include butadiene, isoprene, 1,3-heptadiene, 2,3-dimethylbutadiene, and 2,5-dimethyl-. 2,4-hexadiene etc. are mentioned. These may be used alone or in combination. Among these, butadiene and isoprene are preferable from the viewpoints of being inexpensive, easy to handle, and capable of uniformly advancing the reaction.

  The addition amount of the conjugated diene compound (c) is preferably 0.01 parts by weight or more and 5 parts by weight or less, and more preferably 0.05 parts by weight or more and 2 parts by weight with respect to 100 parts by weight of the propylene-ethylene block copolymer (a). Part or less is more preferable. If the amount of conjugated diene compound added is less than 0.01 parts by weight, reforming may be insufficient, and if it exceeds 5 parts by weight, fluidity may be insufficient.

  In the production of the conjugated diene-modified polypropylene resin (A), a monomer copolymerizable with the conjugated diene compound may be used in combination with the conjugated diene compound. As such copolymerizable monomers, for example, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, acrylic acid Metal salts, metal methacrylates, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylate esters such as stearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid 2 -Methacrylic acid esters such as ethylhexyl and stearyl methacrylate and the like can be mentioned.

<Conditions relating to the production of conjugated diene-modified polypropylene resin (A)>
When manufacturing conjugated diene modified polypropylene resin (A), the addition amount of the radical polymerization initiator (b) is 0.1 times or more and 10 times or less (weight) of the addition amount of the conjugated diene compound (c) In the case of the standard), the melt flow rate of the conjugated diene-modified polypropylene resin (A) can be adjusted relatively easily in the range of 1 or more and less than 80. The addition amount of the radical polymerization initiator (b) is preferably 0.5 times or more and 7.5 times or less the addition amount of the conjugated diene compound (c), more preferably 0.75 times or more and 5 times or less It is.

  As a device for reacting propylene homopolymer (a), radical polymerization initiator (b), and conjugated diene compound (c) to obtain conjugated diene-modified polypropylene resin (A), rolls, co-kneaders , Banbury mixer, Brabender, kneader such as single screw extruder, twin screw extruder etc., twin screw surface renewal machine, horizontal stirrer such as twin screw multi disk device, vertical stirrer such as double helical ribbon stirrer , Etc. Among these, it is preferable to use a kneader, and in particular, an extruder is preferable from the viewpoint of productivity.

  In order or method of mixing and kneading (stirring) propylene homopolymer (a), radical polymerization initiator (b), and conjugated diene compound (c) to obtain conjugated diene-modified polypropylene resin (A) There is no particular restriction. The propylene homopolymer (a), the radical polymerization initiator (b), and the conjugated diene compound (c) may be mixed and then melt-kneaded (stirred), or the propylene homopolymer (a) may be melt-kneaded (stirred (stirred) After that, the radical polymerization initiator (b) and the conjugated diene compound (c) may be mixed simultaneously or separately, collectively or in portions. The temperature of the kneading (stirring) machine is preferably 130 to 300 ° C. in that the propylene homopolymer (a) melts and does not thermally decompose. The kneading (stirring) time is generally preferably 1 to 60 minutes.

  As described above, the conjugated diene-modified polypropylene resin (A) can be produced. There is no restriction on the shape and size of the conjugated diene-modified polypropylene resin (A) to be produced, and it may be in the form of pellets.

<Polypropylene resin (B)>
The polypropylene resin (B) of the present invention is a propylene-ethylene block copolymer having a melt flow rate of 1 g / 10 minutes or more and less than 80 g / 10 minutes, which is measured under conditions of 230 ° C. and a 2.16 kg load. . However, a propylene-ethylene block copolymer modified with a conjugated diene is not included in the category of polypropylene resin (B).

  When the melt flow rate of the component (B) is less than 1 g / 10 min, when the clearance of the mold cavity has a thin portion of, for example, about 1 to 2 mm when manufacturing the injection molded body, melting is performed at a relatively low pressure. It may be difficult to fill the resin into the mold, and continuous and stable injection molding may not be possible. If the melt flow rate of the component (B) is 80 g / 10 min or more, injection molding tends to be unstable because the flowability is excessive. The melt flow rate of the component (B) is more preferably 3 g / 10 minutes or more and 70 g / 10 minutes or less, and still more preferably 5 g / 10 minutes or more and less than 70 g / 10 minutes. The conditions for measuring the melt flow rate are the same as those described above.

  The polypropylene resin (B) of the present invention is a propylene-ethylene block copolymer. In the propylene-ethylene block copolymer, a polymer containing ethylene as a main component and an ethylene-propylene rubber-like copolymer are dispersed in a linear polymer containing propylene as a main component to form a sea-island structure. And propylene-based polymers. Such propylene-based polymers are conventionally referred to as impact-resistant polypropylene and block polypropylene etc. in Japan, but they are not block copolymers in a chemical sense. In the present invention, the propylene-ethylene block copolymer (a) is a homopolymer of propylene or a copolymer (a1) mainly composed of propylene, a homopolymer (a2) of ethylene and / or ethylene and a carbon number It is preferable that it is a mixture containing 3-10 copolymer with (alpha) -olefin (a3). At this time, (a1) corresponds to a linear polymer mainly composed of propylene which is a matrix, (a2) corresponds to a polymer mainly composed of ethylene, and (a3) is an ethylene-propylene rubber-like copolymer It corresponds to union.

  The propylene-ethylene block copolymer (a) is preferably a copolymer containing 51% by weight or more of a propylene component, and from the viewpoint of crystallinity, rigidity, chemical resistance, etc., 60% by weight or more of a propylene component The copolymer contained is more preferable, 70% by weight or more is more preferable, and 80% by weight or more is particularly preferable.

  The propylene-ethylene block copolymer (a) contains 1% by weight or more of the ethylene component from the viewpoint of impact resistance etc., but preferably 3% by weight or more, and more preferably 5% by weight or more Is more preferable, 8% by weight or more is further preferable, and 10% by weight or more is particularly preferable.

  The propylene-ethylene block copolymer (a) may be a copolymer of propylene and ethylene, and a monomer copolymerizable with propylene. As such a monomer copolymerizable with propylene, for example, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl 4 to 12 α-olefins such as -1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, 1-decene; cyclopentene, norbornene, tetracyclo [6,2,11,8,13, Cyclic olefins such as 6] -4-dodecene; 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene Dienes such as vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, acrylic acid Chill, butyl acrylate, methyl methacrylate, maleic anhydride, styrene, methyl styrene, vinyl toluene, vinyl monomers such as divinylbenzene; and the like. These may be used alone or in combination of two or more. Among these, α-olefins are preferable and 1-butene is more preferable in terms of improvement in cold resistance, low cost, and the like.

  Commercially available propylene-ethylene block copolymers (a) include, for example, J709QG (MFR = 55), J708UG (MFR = 45), J830HV (MFR = 30), J717ZG (MFR =, manufactured by Prime Polymer Co., Ltd.). 32), J707EG (MFR = 30), J707G (MFR = 30), J715M (MFR = 9), J705UG (MFR = 9), J704UG (MFR = 5), J702LB (MFR = 1.8) and the like. . For example, according to WO 2015/060201, J708UG has an ethylene-based polymer content of 14% by mass, and can be suitably used in the present invention.

<Polypropylene-based resin composition for injection foam molding>
The polypropylene resin composition used for the injection foam molded article of the present invention is excellent in impact resistance by using the above-mentioned conjugated diene-modified polypropylene resin (A) and the polypropylene resin (B) in combination. And, it is possible to provide an injection molded foam having a good foaming state. In order to obtain such an injection-molded article, both components are blended so that the content of the component (B) is larger than the content of the component (A). Specifically, the content of component (A) is 1 to 49% by weight, and the content of component (B) is 51 to 99% by weight, based on 100% by weight of components (A) and (B). . In this range, it is possible to obtain an injection foam molded article having excellent impact resistance and a good foaming state. From the viewpoint of impact resistance, the content of the component (A) is preferably 1 to 25% by weight, more preferably 5 to 25% by weight, and still more preferably 10 to 20% by weight.

  In addition, depending on the MFR of the component (B), the preferable range of the MFR and the content of the component (A) may vary. For example, when the MFR of the component (B) is less than 8 g / 10 minutes, the MFR of the component (A) is preferably 20 g / 10 minutes or more, more preferably 40 g / 10 minutes or more from the viewpoint of fluidity When the MFR of the component (A) is less than 20 g / 10 min, defects such as deterioration of mold transferability may occur due to lack of fluidity. When the MFR of the component (B) is less than 8 g / 10 minutes as described above, the amount of the component (A) added is preferably 5 to 49% by weight, and more preferably 10 to 35% by weight.

  The polypropylene-based resin composition for injection foam molding of the present invention is required to be able to withdraw the strand and exhibit a stress significantly greater than 0 gf, for melt tension measured at 200 ° C. and 5 m / min. Preferably they are 0.1 gf or more and less than 2.0 gf. When the melt tension of the polypropylene-based resin composition is in the above range, it is possible to obtain an injection foam molded article having excellent impact resistance and having a good foaming state. The melt tension of a resin composition is a numerical value measured after melt-kneading each component sufficiently, and the melt flow rate which each of a conjugated diene modified | reformed polypropylene resin (A) and a polypropylene resin (B) shows, It can be easily adjusted depending on the type, combination, blending amount, etc. of the components.

  Melt tension refers to the tension required to deform the molten resin, whereas melt flow rate is a measure of the flowability of the molten resin, so both are different concepts.

  Although the melt flow rate which the polypropylene resin composition for injection foam molding of this invention shows is not limited, It is preferable that they are 8 g / 10 minutes or more and less than 80 g / 10 minutes. The melt flow rate is measured under the conditions described above. When the melt flow rate of the polypropylene resin composition is in this range, the injection molding foam polypropylene resin composition has flowability suitable for injection foam molding and has high impact resistance after injection foam molding. A molded body can be obtained.

  The melt flow rate of the polypropylene resin composition is a numerical value measured after sufficiently melt-kneading each component, and the melt flow rate exhibited by each of the conjugated diene-modified polypropylene resin (A) and the polypropylene resin (B) And, it can be easily adjusted depending on the blending amount of each component.

<Bubbling agent (C)>
The polypropylene resin composition used for the injection foam molded article of the present invention contains a foaming agent. As a foaming agent which can be used in the present invention, any foaming agent can be used without particular limitation as long as it can be generally used for injection foam molding, and any of a chemical foaming agent and a physical foaming agent may be used.

  The chemical blowing agent is mixed in advance with the resin component and then supplied to an extruder or an injection molding machine, and is decomposed in a cylinder to generate a gas such as carbon dioxide gas. The chemical foaming agent is not particularly limited, but examples thereof include inorganic chemical foaming agents such as sodium bicarbonate and ammonium carbonate, and organic chemical foaming agents such as azodicarbonamide and N, N'-dinitrosopentamethylenetetramine. Be These may be used alone or in combination of two or more.

  A physical blowing agent is injected into the molten resin in the cylinder of an extruder or an injection molding machine as a gaseous or supercritical fluid, dispersed or dissolved, and pressure released after being injected into a mold. Function as a blowing agent. The physical blowing agent is not particularly limited, and examples thereof include aliphatic hydrocarbons such as propane and butane, alicyclic hydrocarbons such as cyclobutane and cyclopentane, halogenated hydrocarbons such as chlorodifluoromethane and dichloromethane, nitrogen And inorganic gases such as carbon dioxide gas and air. These may be used alone or in combination of two or more.

  Among these blowing agents, inorganic chemical blowing agents as chemical blowing agents and nitrogen as physical blowing agents can be used as safe ones that can be safely used in ordinary extruders and injection molding machines and uniform fine cells are easily obtained. Inorganic gases such as carbon dioxide and air are preferred. These foaming agents may be, for example, a foaming aid such as an organic acid such as citric acid, talc, lithium carbonate, etc. in order to make the cells of the injection foam molded article stable and uniform and finely divided. Such nucleating agents such as inorganic fine particles may be added. In general, the inorganic chemical foaming agent produced a masterbatch of a polyolefin resin having a concentration of the foaming agent of 10 to 75% by weight from the viewpoint of handleability, storage stability, and dispersibility in a polypropylene resin. Preferably used in

  The amount of the foaming agent used in the present invention can be appropriately set depending on the foaming ratio of the final product, the type of the foaming agent, and the resin temperature at the time of molding. For example, the inorganic chemical foaming agent is preferably in the range of 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight with respect to 100 parts by weight of the polypropylene resin composition of the present invention Used in By using an inorganic chemical foaming agent in this range, an injection molded foam having an expansion ratio of 2 or more and uniform fine cells can be obtained economically and easily. On the other hand, the physical foaming agent is preferably injected in an amount of 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polypropylene resin composition. It is used by supplying to a molding machine.

<Polyolefin wax>
The polypropylene resin composition used for the injection foam molded article of the present invention contains 0 to 2% by weight of polyolefin wax, with the total of (A) component and (B) component being 100% by weight (containing polyolefin wax Not included, including 2% by weight). The content is preferably 0 to 1% by weight, more preferably 0 to 0.5% by weight, and most preferably 0 to 0.1% by weight.

  If the content is more than 2% by weight, there is a problem that wax bleed-out, fogging and odor due to it, and heat deformation of the molded product become a problem in applications used at higher temperatures. There is.

  In the present invention, as the polyolefin wax, for example, a polymerization type polypropylene-based wax, a thermal decomposition type polypropylene-based wax, a polymerization type polyethylene-based wax, a thermal decomposition-type polyethylene-based wax, and liquid paraffin can be mentioned.

<Other additives>
The polypropylene-based resin composition used for the injection foam molded article of the present invention does not fall under any of the components (A) and (B) within the range that does not impair the effects of the present invention, as necessary. In addition to resins, high density polyethylene resins, high pressure low density polyethylene resins, linear low density polyethylene resins, ethylene-α-olefin copolymers, olefin elastomers, styrene elastomers, and other thermoplastic resins are further included. You may contain.

  In addition, the polypropylene resin composition used for the injection foam molded article of the present invention may, if necessary, be an antioxidant, a metal deactivator, a phosphorus processing stabilizer, to the extent that the effect of the present invention is not impaired. UV absorbers, UV stabilizers, fluorescent whitening agents, stabilizers such as metal soaps, antacid adsorbents, crosslinking agents, chain transfer agents, nucleating agents, plasticizers, lubricants, fillers, reinforcing materials, pigments, dyes , And may further contain additives such as flame retardants and antistatic agents (except for the polyolefin wax described above).

<Injection foam molding>
The expansion ratio of the injection foam molded article of the present invention is preferably 2.5 to 8 times, more preferably 3 to 8 times, and most preferably 4 to 6 times. If the expansion ratio is less than 2.5 times, lightness tends to be difficult to obtain, and if it exceeds 8 times, the rigidity tends to be significantly reduced.

<Injection foam molding method>
The injection foam molding method that can be used to produce the injection foam molded article of the present invention is not particularly limited, and known methods can be applied. The specific molding conditions at that time can be appropriately determined in consideration of the melt flow rate of the polypropylene resin composition, the melt tension, the type of molding machine, the shape of the mold and the like. As one example, the resin temperature is preferably 170 to 300 ° C., more preferably 190 to 270 ° C., and the mold temperature is preferably 10 to 100 ° C., more preferably 20 to 80 ° C. Moreover, it is preferable to carry out on conditions, such as a molding cycle 1 to 120 minutes, the injection speed of 10 to 300 mm / sec, the injection pressure of 10 to 200 MPa.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
The test methods and criteria used for the various evaluation methods in the examples and comparative examples are as follows.

(1) Melt flow rate (MFR)
In accordance with JIS K 7210: 1999, using Melt Indexer F-F01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.), under the conditions of 230 ° C. and a load of 2.16 kg, the amount of resin extruded from the die in a fixed time is 10 The value converted into the amount of resin extruded in one minute was taken as the melt flow rate. The converted value was calculated by MFR automatic calculation processing (method B). The calculation formula is as follows. The method was applied even if the melt flow rate exceeded 50 (g / 10 min).

MFR (g / 10 min) = (427 × L × ρ) / t
L (interval of test conditions): 3 (cm)
ρ (melt density at the test temperature): A value calculated by the following equation using the cutting method, provided that 0.75 (g / cm3) is possible if the cutting method is not possible: 不可能 = m / (0.711 x L) )
m: mass (g) of the sample that has flowed out by moving the above-mentioned interval L, which is measured by a cutting method
L: Same as the above interval t (interval moving time): actual measured value (seconds)
That is, when the clipping method can be applied, it may be calculated by the following formula.
MFR (g / 10 min) = (600 × m) / t

(2) Melt tension (MT)
A capillograph (manufactured by Toyo Seiki Seisakusho Co., Ltd.) equipped with a melt tension measurement attachment and having a cylinder with a diameter of 10 mm and an orifice with a diameter of 1 mm and a length of 10 mm attached to the tip was used. The sample was charged into a cylinder heated to 200 ° C. and preheated for 5 minutes. After the above preheating time elapses, the strand discharged from the die when it is lowered at a piston lowering speed of 10 mm / min is hung on a load cell equipped pulley under 370 mm or 520 mm and pulled off at a speed of 5 m / min. The load applied to was measured over time. About 5 minutes after the start of the measurement, the maximum value and the minimum value of the load obtained after the deflection of the load was approximately stabilized were measured, and the average value thereof was taken as the melt tension. The melt tension was set to 0 when the load applied to the load cell pulley was too low to be sensed.

(3) Dupont Impact Test Using a Dupont Impact Tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the 50% fracture height was determined by the Staircase method with a constant falling weight, and the energy value was calculated from the load at that time. The falling load was 300 g, 700 g, or 1000 g, and the energy value was calculated according to JIS K 7211.

(4) Visual Evaluation of Cell State of Foam The resin composition is completely filled in the following evaluation mold under the following molding conditions using an injection molding machine (MD 350 S-IV manufactured by NIIGATA MACHINE TECHNO) It was injection molded with minimal filling pressure.
・ Resin temperature: 200 ° C
・ Mold temperature: 40 ° C
· Injection speed: 100 mm / sec
・ Use mold: Box mold of bottom center 1 point pin gate, bottom shape: 190 mm x 190 mm, side shape (trapezoidal shape): 190 mm (bottom side) to 220 mm (anti bottom side) x 100 mm, but only bottom is core back, Do not core back the side. Cavity clearance t0: 1.5 mm (3 times foaming, 5.5 times foaming both)
・ Cavity clearance t1: 2.1 mm (both 3 times foaming and 5.5 times foaming)
Cavity clearance t2: The injection foam molding was carried out according to the following procedure for setting a foaming ratio of 3 × and 5.5 ×, respectively, for setting a high foaming ratio.

  A composition containing a foaming agent is supplied to an injection molding machine set to a predetermined cylinder temperature, and after melt-kneading with an appropriate back pressure, a mold of which the cavity clearance of the bottom portion temperature-controlled to a predetermined temperature is t0 Into it, injection filling was performed at a predetermined injection speed. Immediately after the completion of injection and filling (setting and holding time is 0 seconds), the movable mold was retracted to the cavity clearance t1 of the bottom portion to foam the resin in the cavity (first foaming step). Next, after holding for a predetermined set time (6 seconds) in the state of the clearance t1 of the mold bottom surface, the movable mold is again subjected to the cavity clearance t2 of the bottom portion so that the molded body has a desired thickness (foaming magnification). It was made to back up to perform foaming again (second foaming step). After the completion of foaming, the foamed resin was cooled and solidified to take out the injection foam molded body.

In order to ensure the stability of the injection state, four shots after the purge (material switching) were discarded, and the subsequent seven shots were collected. The appearance of the molded body was visually observed. The foaming state was evaluated based on the following criteria.
○: Among the test samples, those having good foamability ×: those for which a satisfactory foam can not be obtained at the set expansion ratio

(5) Expansion observation evaluation of the internal cell state of the foam From the point 5 cm away from the gate on the bottom of the above injection molded body, a sample for observation is cut out, and the foaming state of the cross section in the direction perpendicular to the resin flow Observed.
○: Among the test samples, the shape of the foam cell is good Δ: The shape of the foam cell is slightly stretched in the thickness direction

<Preparation of conjugated diene-modified polypropylene resin>
(Production Example 1)
According to Table 1, (a) 100 parts by weight of a propylene homopolymer (a-1) having a melt flow rate of 45 g / 10 min as a propylene polymer, 70 kg / hour from a hopper, (b) t-butyl as a radical polymerization initiator 1.1 parts by weight (0.77 kg / hour) of peroxyisopropyl carbonate was fed to a 46 mmφ twin screw extruder (L / D = 40) using a metering pump, and melt kneading was performed at a cylinder temperature of 200 ° C. And (c) isoprene monomer as a conjugated diene compound is supplied at 0.40 parts by weight (at a rate of 0.28 kg / hour) using a metering pump from the press-in portion provided on the way, in the twin-screw extruder. By melt-kneading with this, the pellet of conjugated diene modified | denatured polypropylene resin (A-1) was obtained. MFR = 60 g / 10 min. The obtained conjugated diene-modified polypropylene resin (A-1) is shown in Table 1.

(Production Example 2)
According to Table 1, 1.1 parts by weight of (b) t-butylperoxyisopropyl carbonate as a radical polymerization initiator and (c) 0.44 parts by weight of isoprene as a conjugated diene compound were changed. In the same manner as in Production Example 1, a conjugated diene-modified polypropylene-based resin (A-2) was obtained. MFR = 40 g / 10 min.

(Production Example 3)
According to Table 1, 1.1 parts by weight of (b) t-butylperoxyisopropyl carbonate as a radical polymerization initiator and (c) 0.32 parts by weight of isoprene as a conjugated diene compound were changed. In the same manner as in Production Example 1, a conjugated diene-modified polypropylene-based resin (A-3) was obtained. MFR = 100 g / 10 min.

(Production Example 4)
According to Table 1, instead of (a-1), a propylene homopolymer (a-2) having a melt flow rate of 8 g / 10 min is used as (a), and (b) t-butylperoxy as a radical polymerization initiator A conjugated diene-modified polypropylene-based resin (in the same manner as in Production Example 1) except that the amount of isopropyl carbonate was changed to 0.75 parts by weight and the supply amount of isoprene as the (c) conjugated diene compound was changed to 0.46 parts by weight A-4) was obtained. MFR = 7 g / 10 min.

(Production Example 5)
According to Table 1, instead of (a-1), a propylene homopolymer (a-3) having a melt flow rate of 1 g / 10 min is used as (a), and (b) t-butylperoxy as a radical polymerization initiator A conjugated diene-modified polypropylene-based resin (in the same manner as in Production Example 1) except that the amount of isopropyl carbonate was changed to 0.45 parts by weight and the supply amount of isoprene as the (c) conjugated diene compound was changed to 0.45 parts by weight A-5) was obtained. MFR = 0.5 g / 10 min.

<Polypropylene-based resin>
The resin used as the polypropylene resin (B) is shown in Table 2.

<Polypropylene homopolymer>
The resins used as the polypropylene homopolymer (C) are shown in Table 3.

(Examples 1-1 to 1-3, Comparative examples 1-1 to 1-3)
<Preparation of Molded Product of Polypropylene-Based Resin Composition>
The conjugated diene-modified polypropylene-based resin (A), the polypropylene-based resin (B), and the color master batch as the colorant (D) were dry-blended and used for injection molding. Table 4 shows the types of (A) and (B) and the amounts used (each of which makes the total of (A) and (B) 100 parts by weight). As (D), 3.0 parts by weight of die color PP-M77255 (black) manufactured by Dainichiseika Co., Ltd. was used.

<Evaluation of impact resistance of injection molded body>
The above injection molded articles were evaluated according to the items of the Dupont impact test described above. The obtained results are shown in Table 4.

<Preparation of composition pellet for evaluation>
The conjugated diene-modified polypropylene resin (A), the polypropylene resin (B), and the color master batch as the colorant (D) were dry-blended. Table 4 shows the types of (A) and (B) and the amounts used (each of which makes the total of (A) and (B) 100 parts by weight). As (D), 3.0 parts by weight of die color PP-M77255 (black) manufactured by Dainichiseika Co., Ltd. was used.
The dry-blended mixture was supplied from a hopper to a 32 mmφ twin-screw extruder (L / D = 25) at 9 kg / hour and melt-kneaded at a cylinder temperature of 200 ° C. to obtain pellets of the composition. The composition pellets were subjected to physical property measurement of melt flow rate (MFR) and melt tension (MT).

  Examples 1-1 to 1-3, that is, when the compounding amount of (A-1) is 5 to 15 parts by weight, the composition pellet is compared with the case of Comparative Example 1-1, that is, when not compounding (A) It is clear that melt tension can be applied to the strands discharged from the die, and the composition of Comparative Example 1-2, that is, the compounding amount of (A-1) is 30 parts by weight, It is clear that the impact resistance of the injection molded body (non-foamed) is excellent.

  The present invention relates to an impact-resistant, high-magnification injection molded foam, but in order to make it possible, the melt tension for enabling high-magnification foaming and non-foaming It is believed that both good impact resistance is required.

(Examples 2-1 to 2-10, comparative examples 2-1 to 2-7)
<Production of Injection Foam Molded Product of Polypropylene Resin Composition>
Injection blend molding by dry blending conjugated diene modified polypropylene resin (A), polypropylene resin (B), polypropylene resin (C), foaming agent (D), and color master batch as coloring agent (E) Provided for. The expansion ratio was tripled.
Table 5 shows the types of (A), (B) and (C) and the amounts used (the total of (A), (B) and (C) is 100 parts by weight). As (D), 6 parts by weight of EE25C (manufactured by Nagawa Kasei Co., Ltd.) was used, and as (E), 3 parts by weight of die color PP-M77255 (black) manufactured by Dainichi Seisei Co., Ltd. was used.

<Evaluation of foamability of injection molded foam>
The above injection molded foam was evaluated in accordance with the items of evaluation of foamability described above.

<Evaluation of impact resistance of injection molded body>
The above injection molded foam was evaluated in accordance with the item of Dupont impact test described above.
The obtained results are shown in Table 5.

When the compounding amount of Examples 2-1 to 2-4, that is, (A-1) is 5 to 20 parts by weight, three-fold foaming is possible. However, in the case of Comparative Example 2-1, that is, when (A-1) was not blended, 3 times foaming was impossible. Moreover, when it mix | blends 5-20 weight part of (C) which is the polypropylene homopolymer which is not modified | denatured instead of Comparative Example 2-4 to 2-5, ie, (A-1), (A) Even though the MFRs of -1) and (C) were almost equal, 3 times foaming was impossible.
From these comparisons, it is understood that the component (A) is essential in order to enable the foaming of high magnification of 3 times foaming which is the effect of the present invention.

  Further, Examples 2-5 to 2-7, that is, components (A-2) having a lower fluidity (A-2) and a higher fluidity (A-3) than the component (A-1) were respectively blended. Also in the case, 3 times foaming was possible.

  In addition, in the case where 20 parts by weight of (A-5) having lower fluidity than that of (A-2) was blended as Example 2-10, that is, the component (A), 3-fold foaming was possible.

  Even when (B-2) having lower fluidity than (B-1) is used as the component (B), Example 2-8, that is, the case where the compounding amount of (A-1) is 5 parts by weight Although 3 times foaming was possible, 3 times foaming was impossible in Comparative Example 2-6, that is, when (A-1) was not blended.

  Even when (B-3) having higher fluidity than (B-1) is used as the component (B), Example 2-9, that is, when the compounding amount of (A-1) is 5 parts by weight Although 3 times foaming was possible, 3 times foaming was impossible when comparative example 2-7, ie, (A-1) was not blended.

  In addition, in the case of using (B-4), which has lower fluidity than (B-2), as Example 2-10, that is, the component (B), three-fold foaming was possible.

  Example 2-4 and Comparative Example 2-2, that is, (A-1) as the component (A) and (B-1) as the component (B), and injection foam molding is performed for those which differ only in the compounding ratio In the cross section of the body, when the internal cell state was observed in an enlarged manner, Example 2-4 was in a good state, and in Comparative Example 2-2, the cell was stretched in the thickness direction and was inferior. I understood. Moreover, the result of the Dupont impact test also shows that Example 2-4 is superior to Comparative Example 2-2.

  Example 2-6 and Comparative Example 2-3, that is, (A-2) as the component (A) and (B-1) as the component (B), and injection foam molding is performed for those having different blending ratios. In the cross-section of the body, when the internal cell state is observed in an enlarged manner, Example 2-6 is in a good state, and in Comparative Example 2-3, the cell is stretched in the thickness direction and is inferior. I understood. Moreover, the result of the Dupont impact test also shows that Example 2-6 is superior to Comparative Example 2-3.

  From these comparisons, it is illustrated that (A) :( B) is 1 to 25:99 to 75 as a compounding ratio of (A) and (B), and 2.5 to 22.5: 97.5. It can be understood that 〜77.5 is preferably exemplified, and that 5 to 20:95 to 80 is more preferably exemplified.

  Next, injection foam molding was performed at a further higher foaming ratio.

<Production of Injection Foam Molded Product of Polypropylene Resin Composition>
The conjugated diene-modified polypropylene resin (A), the polypropylene resin (B), the foaming agent (D), and the color master batch as a colorant (E) were dry-blended and subjected to injection foam molding. The expansion ratio was 5.5 times.
Table 6 shows the types of (A) and (B) and the amounts used (each of which makes the total of (A) and (B) 100 parts by weight). As (D), 6 parts by weight of EE25C (manufactured by Nagawa Kasei Co., Ltd.) was used, and as (E), 3 parts by weight of die color PP-M77255 (black) manufactured by Dainichi Seisei Co., Ltd. was used.

<Evaluation of foamability of injection molded foam>
The above injection molded foam was evaluated in accordance with the items of evaluation of foamability described above.

<Evaluation of impact resistance of injection molded body>
The above injection molded foam was evaluated in accordance with the item of Dupont impact test described above.
The obtained results are shown in Table 6.

When the blending amount of Examples 3-1 to 3-2, that is, (A-1) or (A-2) is 20 parts by weight, it was possible to foam 5.5 times. However, the fluidity is higher than that of Comparative Example 3-1, that is, (A-1) (A-3), and the fluidity is lower than that of Comparative Example 3-2, that is, (A-2) (A-4) When using (5), foaming was not possible 5.5 times.
Comparative Examples 3-3 to 3-4, that is, when (A-5) having extremely low fluidity is used, the component (B) is either (B-1) or (B-4). Even, 5.5 times foaming was impossible.
Therefore, it is understood that the combination of the component (A) and the component (B) having a specific range of flowability is preferable in order to enable foaming at a further higher magnification of 5.5 times foaming.
For example, as MFR of (A) component, it can be understood that 10-80 are illustrated preferably, 20-70 are illustrated more preferably, and 30-70 are illustrated most preferably.

  Moreover, as MFR of (B) component, it can be understood that 10-80 are illustrated preferably, 20-70 are illustrated more preferably, and 20-50 are illustrated most preferably.

Claims (5)

Conjugated diene-modified polypropylene-based resin (A), which is a conjugated diene-modified propylene homopolymer having a melt flow rate of 10 g / 10 min or more and less than 80 g / 10 min measured at 230 ° C. and a 2.16 kg load ,
Containing a polypropylene-based resin (B) which is a propylene-ethylene block copolymer having a melt flow rate of 10 g / 10 minutes or more and less than 80 g / 10 minutes measured at 230 ° C. under 2.16 kg load,
The content of the component (A) is 1 to 25% by weight, and the content of the component (B) is 99 to 75% by weight with respect to a total of 100% by weight of the components (A) and (B).
About a polypropylene resin composition containing 0 to 2% by weight of polyolefin wax with respect to a total of 100% by weight of the (A) component and the (B) component,
An injection foam molded article having an expansion ratio of 2.5 to 8.0, obtained by injection foam molding it.   The injection foam molded article according to claim 1, wherein the melt tension of the polypropylene-based resin composition measured at 200 ° C and 5 m / min can take up strands and exhibits a stress significantly greater than 0 gf. The content of the component (A) is 5 to 20% by weight, and the content of the component (B) is 95 to 80% by weight with respect to a total of 100% by weight of the component (A) and the component (B)
Melt flow rate measured at 230 ° C under 2.16 kg load of component (A) is at least 20 g / 10 min and less than 70 g / 10 min, and measured at 230 ° C. under 2.16 kg load of component (B) About the said polypropylene resin composition whose melt flow rate is 20 g / 10 minutes or more and less than 50 g / 10 minutes,
The expansion ratio is 3.0 times to 6.0 times,
The injection foam molded article according to claim 1 or 2.   The material for automobile interiors which uses the injection-foaming molded object as described in any one of Claims 1-3. In a mold cavity consisting of a fixed mold and a movable mold capable of advancing and retracting and having a mold cavity clearance t0 smaller than the mold cavity clearance t2 corresponding to the final product shape position,
After injection filling the molten mixture of the polypropylene resin composition and the foaming agent,
a first foaming step of retracting the movable mold to a mold cavity clearance t1 smaller than t2 and larger than t0;
Then, after holding the clearance of t1 for a predetermined set time, the method further includes a second foaming step of retracting the movable mold to the mold cavity clearance t2 corresponding to the shape of the final product,
The manufacturing method of the injection foam molded body as described in any one of Claims 1-3.