Polypropylene resin melt-kneaded product, manufacturing method therefor, foam, and foam molded body

Abstract

Provided are a polypropylene resin melt-kneaded product that has better melt elasticity compared to previously, a manufacturing method therefor, and a foam and a foam molded body that are obtained using the polypropylene resin melt-kneaded product.　Used is a polypropylene resin melt-kneaded product including: an olefin copolymer (AA) that has a branch including olefin chain (a) and a main chain including olefin chain (a); an olefin copolymer (AB) that has a branch including olefin chain (a) and a main chain including olefin chain (b); an olefin copolymer (BA) that has a branch including olefin chain (b) and a main chain including olefin chain (a); and an olefin copolymer (BB) that has a branch including olefin chain (b) and a main chain including olefin chain (b), wherein the following condition (ii) is satisfied. (ii) The loss tangent tanδ0.1 at ω=0.1 rad / sec as measured by dynamic viscoelasticity measurement at 180°C is 0.4 to 2.0.

Description

Polypropylene resin melt-kneaded product, its manufacturing method, foam, and foam-molded product

[0001] The present invention relates to a polypropylene resin melt-kneaded product, a method for producing the same, a foam, and a foam-molded product.

[0002] Polypropylene resins are widely used as relatively inexpensive resin materials with excellent heat and chemical resistance. Their applications are extremely broad, including various molded products manufactured by injection molding, fibers, films, and sheets.

[0003] However, polypropylene resins generally have a linear molecular structure and are known to have poor melt elasticity. This property makes it difficult to use polypropylene resins in some processing methods. For example, in foam molding, in which cells grow in a molten state while the cell membrane undergoes elongational deformation, it is known that when a polypropylene resin with poor melt elasticity is used, the cell membrane cannot withstand the elongational deformation and breaks, resulting in open cell formation, making it difficult to obtain a satisfactory foam. To overcome this drawback, attempts have been made to increase the melt elasticity of polypropylene resins. For example, many methods have been investigated for introducing long-chain branching into polypropylene resins.

[0004] Patent Document 1 discloses that a polypropylene resin having long chain branches can be obtained by irradiating the polypropylene resin with an electron beam in a low-oxygen atmosphere, and further discloses that such a polypropylene resin has excellent melt strength. Patent Documents 2 to 4 also propose methods for introducing long chain branches into a polypropylene resin.

[0005] Japanese Patent Application Laid-Open No. 62-121704 International Publication No. 2014 / 016205 Japanese Patent Application Laid-Open No. 9-188729 International Publication No. 2016 / 126429

[0006] These methods have provided polypropylene-based resins with enhanced melt elasticity, but the methods described in Patent Documents 2 to 4 are all believed to generate long-chain branched structures by at least partially intermolecular crosslinking through the reaction of radicals generated on polymer molecules by organic peroxides or the like. However, these methods do not necessarily achieve satisfactory results, and further improvements are still required. The background to this is that polypropylene-based resins, particularly homopolymers of propylene monomers, are "radical degradable," and the methods described in Patent Documents 1 to 4 tend to generate molecular chain scission reactions simultaneously with the generation of long-chain branched structures during the reaction, which can lead to insufficient generation of long-chain branched structures based on crosslinked structures.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a polypropylene-based resin melt-kneaded product having better melt elasticity than conventional products, a method for producing the same, and a foam and foam-molded product obtained using the polypropylene-based resin melt-kneaded product.

[0008] The present inventors have found that when an olefin copolymer containing a larger amount of structural units derived from ethylene monomers than the polypropylene resin is blended and melt-kneaded together with the polypropylene resin during production of the polypropylene resin melt-kneaded product, the resulting polypropylene resin melt-kneaded product has excellent melt elasticity, and have completed the present invention.

[0009] Aspects of the present disclosure relate to the following polypropylene-based resin melt-kneaded product, its production method, foam, and foam-molded product.

[0010] [1] A polypropylene resin melt-kneaded product containing an olefin copolymer (AA) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (a), an olefin copolymer (AB) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (b), an olefin copolymer (BA) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (a), and an olefin copolymer (BB) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (b), and satisfying the following (i) to (iv): (i) The melt-kneaded product contains 1% by weight or more and 20% by weight or less of the olefin chain (a) and 80% by weight or more and 99% by weight or less of the olefin chain (b) (wherein the total of the olefin chains (a) and (b) is 100% by weight). (ii) Loss tangent tanδ at ω=0.1 rad / sec, measured by dynamic viscoelasticity measurement at 180°C ０．１is 0.4 or more and 2.0 or less. (iii) The olefinic chain (a) is an olefinic chain consisting of 5 to 20% by weight of structural units (a-1) derived from ethylene monomers and 80 to 95% by weight of structural units (a-2) derived from propylene monomers (provided that the sum of the structural units (a-1) and (a-2) is 100% by weight). (iv) The olefinic chain (b) is a polypropylene-based chain consisting of 0 to less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95 to 100% by weight of structural units (b-2) derived from propylene monomers (provided that the sum of the structural units (b-1) and (b-2) is 100% by weight). [2] The polypropylene-based resin melt-kneaded product according to [1], wherein the olefin-based chain (a) is an olefin-based chain consisting of 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers (wherein the sum of the structural units (a-1) and (a-2) is 100% by weight). [3] The polypropylene-based resin melt-kneaded product according to [1] or [2], wherein the olefin-based chain (a) is a random copolymer of ethylene monomers and propylene monomers. [4] The polypropylene-based resin melt-kneaded product according to any one of [1] to [3], wherein the olefin-based chain (b) is a polypropylene-based chain consisting of 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 99% by weight or less of structural units (b-2) derived from propylene monomers (wherein the sum of the structural units (b-1) and (b-2) is 100% by weight). [5] The polypropylene-based resin melt-kneaded product according to any one of [1] to [4], wherein the olefin-based chain (b) is a random copolymer of ethylene monomers and propylene monomers. [6] The polypropylene-based resin melt-kneaded product according to any one of [1] to [4], wherein the loss tangent tanδ at ω=0.1 rad / sec measured by dynamic viscoelasticity measurement at 180°C ０．１ [7] The polypropylene-based resin melt-kneaded product according to any one of [1] to [5], wherein the loss tangent tanδ at ω=0.1 rad / sec measured by dynamic viscoelasticity measurement at 180°C is 0.4 or more and 1.0 or less. ０．１[8] The polypropylene-based resin melt kneaded product according to any one of [1] to [5], having a melt flow rate (MFR) of 0.4 or more and 0.8 or less. [8] The polypropylene-based resin melt kneaded product according to any one of [1] to [7], having an MFR measured at 230°C of 0.01 g / 10 min or more and less than 1.0 g / 10 min. [9] The polypropylene-based resin melt kneaded product according to any one of [1] to [8], having a melt tension of 5.0 cN or more and 14 cN or less.

[10] A foamed product comprising the polypropylene-based resin melt kneaded product according to any one of [1] to [9].

[11] The foamed product according to

[10] , which is an extruded foamed bead.

[12] The foamed product according to

[11] , wherein the extruded foamed bead has an expansion ratio of 3 times or more and 50 times or less.

[13] A foamed molded product obtained by molding the extruded foamed bead according to

[11] or

[12] .

[14] The foamed molded product according to

[13] , having an open cell ratio of 30% or less.

[15] A method for producing a polypropylene-based resin melt-kneaded product, comprising melt-kneading a mixture containing 1% by weight or more and 20% by weight or less of an olefin-based copolymer (A), 80 parts by weight or more and 99% by weight or less of a polypropylene-based resin (B), one or more monomers (c) selected from the group consisting of conjugated dienes and vinyl aromatic compounds, and a radical polymerization initiator (d), wherein the total of the olefin-based copolymer (A) and the polypropylene-based resin (B) is 100% by weight, and the olefin-based copolymer (A) is an olefin-based copolymer consisting of 5% by weight or more and 20% by weight or less of a structural unit (a-1) derived from an ethylene monomer and 80% by weight or more and 95% by weight or less of a structural unit (a-2) derived from a propylene monomer, wherein the total of the structural units (a-1) and (a-2) is 100% by weight, the polypropylene-based resin (B) is a polypropylene-based resin consisting of 0% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 100% by weight or less of structural units (b-2) derived from propylene monomers (where the total of the structural units (b-1) and (b-2) is defined as 100% by weight), and the blending amount of the monomer (c) is 0.30 parts by weight to 5.00 parts by weight per 100 parts by weight of the total of the olefin-based copolymer (A) and the polypropylene-based resin (B).

[16] The method for producing a melt-kneaded polypropylene resin product according to

[15] , wherein the olefin copolymer (A) is an olefin copolymer comprising 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers (wherein the sum of the structural units (a-1) and (a-2) is 100% by weight).

[17] The method for producing a melt-kneaded polypropylene resin product according to

[15] or

[16] , wherein the olefin copolymer (A) is a random copolymer of ethylene monomers and propylene monomers.

[18] The method for producing a polypropylene-based resin melt-kneaded product according to any one of

[15] to

[17] , wherein the polypropylene-based resin (B) is a polypropylene-based chain consisting of 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and less than 99% by weight of structural units (b-2) derived from propylene monomers (wherein the sum of the structural units (b-1) and (b-2) is 100% by weight).

[19] The method for producing a polypropylene-based resin melt-kneaded product according to any one of

[15] to

[18] , wherein the conjugated diene is at least one selected from the group consisting of butadiene and isoprene.

[20] The method for producing a polypropylene-based resin melt-kneaded product according to any one of

[15] to

[19] , wherein the radical polymerization initiator (d) is at least one organic peroxide selected from the group consisting of ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters.

[21] A method for producing extruded foamed beads, comprising melt-kneading a mixture containing a polypropylene resin melt-kneaded product produced by the method according to any one of

[15] to

[20] and a blowing agent under pressure, cooling the mixture, and then extruding the mixture into a lower pressure atmosphere to foam and cut the mixture.

[22] The method for producing extruded foamed beads according to

[21] , wherein the blowing agent is at least one selected from the group consisting of normal butane, isobutane, and carbon dioxide gas.

[0011] According to the present invention, it is possible to provide a polypropylene resin melt-kneaded product having better melt elasticity than conventional products, a method for producing the same, a foam obtained by using the melt-kneaded product, and a foam-molded product.

[0012] <Polypropylene Resin Melt-Kneaded Product> The polypropylene resin melt-kneaded product of this embodiment contains: an olefin copolymer (AA) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (a); an olefin copolymer (AB) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (b); an olefin copolymer (BA) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (a); and an olefin copolymer (BB) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (b). The polypropylene resin melt-kneaded product of this embodiment also satisfies the following (i) to (iv): (i) the melt-kneaded product contains 1% by weight or more and 20% by weight or less of the olefin chain (a) and 80% by weight or more and 99% by weight or less of the olefin chain (b) (wherein the sum of the olefin chains (a) and (b) is 100% by weight). (ii) Loss tangent tanδ at ω=0.1 rad / sec, measured by dynamic viscoelasticity measurement at 180°C ０．１ is 0.4 or more and 2.0 or less. (iii) The olefinic chain (a) is an olefinic chain consisting of 5 to 20% by weight of structural units (a-1) derived from ethylene monomers and 80 to 95% by weight of structural units (a-2) derived from propylene monomers (provided that the sum of the structural units (a-1) and (a-2) is 100% by weight). (iv) The olefinic chain (b) is a polypropylene-based chain consisting of 0 to less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95 to 100% by weight of structural units (b-2) derived from propylene monomers (provided that the sum of the structural units (b-1) and (b-2) is 100% by weight).

[0013] The polypropylene resin melt-kneaded product of the present embodiment contains the olefin copolymers (AA), (AB), (BA), and (BB), and therefore has high melt elasticity.

[0014] The olefin copolymers (AA) to (BB) and the conditions (i) to (iv) will be described below.

[0015] In this specification, the term "polypropylene resin melt-kneaded product" refers to a kneaded product obtained by melt-kneading a mixture containing a polypropylene resin. As will be described later, a method for producing the melt-kneaded product includes melt-kneading a mixture containing an olefin copolymer (A) and a polypropylene resin (B). The olefin chains (a) and (b) constituting the olefin copolymers (AA), (AB), (BA), and (BB) are derived from the olefin copolymer (A) and the polypropylene resin (B), respectively.

[0016] <Olefin-based Copolymers (AA) to (BB)> The olefin-based copolymer (AA) has a branch containing an olefin-based chain (a) and a main chain containing an olefin-based chain (a). The olefin-based copolymer (AA) is produced by the recombination of a radical on the olefin-based chain (a) with a radical on the olefin-based chain (a) at a crosslinking point, or by the recombination of a radical on the olefin-based chain (a) with a radical on the olefin-based chain (a) via a monomer (c), which will be described later. In the olefin-based copolymer (AA), the chain length of one olefin-based chain (a) is compared with the chain length of the other olefin-based chain (a) from the perspective of the crosslinking point, and the longer one is defined as the main chain, and the shorter one is defined as the branch. There may be one branch or two or more branches. When there are two or more branches, in addition to the branch containing the olefin-based chain (a), there may also be a branch containing the olefin-based chain (b). When a copolymer has two or more branches of different types, and the longest branch is a branch containing an olefin chain (a), it corresponds to an olefin copolymer (AA). This definition also applies to the following olefin copolymers (AB), (BA), and (BB).

[0017] The olefin copolymer (AB) has a branch containing an olefin chain (a) and a main chain containing an olefin chain (b). The olefin copolymer (AB) is formed by the recombination of a radical on the olefin chain (a) with a radical on the olefin chain (b) at a crosslinking point, or by the recombination of a radical on the olefin chain (a) with a radical on the olefin chain (b) via a monomer (c), as described below. In the olefin copolymer (AB), the chain length of the olefin chain (b) from the crosslinking point is longer than the chain length of the olefin chain (a). Those skilled in the art generally consider the longest polymer chain to be the main chain, and in the case where the longest polymer chain is olefin chain (a)-crosslinking point-olefin chain (b), the chain length of the olefin chain (a)-crosslinking point-olefin chain (b) is considered to be the main chain. However, this application does not do so and instead compares the chain length of the olefin chain (a) alone with the chain length of the olefin chain (b) alone. The number of branches may be one or more. When there are two or more branches, in addition to the branch containing the olefinic chain (a), there may be a branch containing the olefinic chain (b). When there are two or more branches of different types, and the longest branch is a branch containing the olefinic chain (a), it corresponds to an olefinic copolymer (AB).

[0018] The olefin copolymer (BA) has a branch containing an olefin chain (b) and a main chain containing an olefin chain (a). The olefin copolymer (BA) is produced by recombining a radical on the olefin chain (a) with a radical on the olefin chain (b) at a crosslinking point, or by recombining a radical on the olefin chain (a) with a radical on the olefin chain (b) via a monomer (c) described below. In the olefin copolymer (BA), the chain length of the olefin chain (a) is longer than the chain length of the olefin chain (b) when viewed from the crosslinking point. There may be one branch or two or more branches. When there are two or more branches, in addition to the branch containing the olefin chain (b), there may be a branch containing the olefin chain (a). When there are two or more branches of different types, if the longest branch is the branch containing the olefin chain (b), it corresponds to an olefin copolymer (BA).

[0019] The olefin copolymer (BB) has a branch containing an olefin chain (b) and a main chain containing an olefin chain (b). The olefin copolymer (BB) is produced by the recombination of a radical on the olefin chain (b) with a radical on the olefin chain (b) at a crosslinking point, or by the recombination of a radical on the olefin chain (b) with a radical on the olefin chain (b) via a monomer (c) described below. In the olefin copolymer (BB), the chain length of one olefin chain (b) is compared with the other olefin chain (b) from the crosslinking point, and the longer one is defined as the main chain, and the shorter one is defined as the branch. There may be one or more branches. When there are two or more branches, in addition to the branch containing the olefin chain (b), there may also be a branch containing the olefin chain (a). When there are two or more branches of different types, if the longest branch is the branch containing the olefin chain (b), it is considered an olefin copolymer (BB).

[0020] <Condition (i)> As described above, the melt-kneaded product contains 1% by weight or more and 20% by weight or less of the olefin chain (a) and 80% by weight or more and 99% by weight or less of the olefin chain (b) (provided that the total of the olefin chains (a) and (b) is 100% by weight). Preferably, the melt-kneaded product contains 2% by weight or more and 20% by weight or less of the olefin chain (a) and 80% by weight or more and 98% by weight or less of the olefin chain (b), and more preferably, the melt-kneaded product contains 5% by weight or more and 15% by weight or less of the olefin chain (a) and 85% by weight or more and 95% by weight or less of the olefin chain (b), provided that the total of the olefin chains (a) and (b) is 100% by weight.

[0021] <Condition (ii)> As described above, the loss tangent tanδ at ω=0.1 rad / sec measured by dynamic viscoelasticity measurement at 180°C ０．１ is 0.4 or more and 2.0 or less. The loss tangent is an index of melt elasticity, and the smaller tanδ is, the more excellent the melt elasticity of the polypropylene resin melt-kneaded product is, that is, the higher the melt elasticity is. Loss tangent tanδ ０．１means the loss tangent at an angular frequency of ω=0.1 rad / sec. The loss tangent tanδ at ω=0.1 rad / sec is measured by dynamic viscoelasticity measurement at 180°C. ０．１ is preferably 0.4 or more and 1.0 or less, and more preferably 0.4 or more and 0.8 or less.

[0022] <Condition (iii)> As described above, the olefin chain (a) is an olefin chain composed of 5% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 95% by weight or less of structural units (a-2) derived from propylene monomers (where the sum of the structural units (a-1) and (a-2) is 100% by weight). The olefin chain (a) is present in the polypropylene resin melt-kneaded product either as the olefin chain (a) alone, i.e., as an unreacted olefin copolymer chain (A), or as olefin copolymers (AA), (AB), and (BA) containing the olefin chain (a). The olefinic chain (a) is preferably an olefinic chain consisting of 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers, and more preferably an olefinic chain consisting of 7% by weight or more and 17% by weight or less of structural units (a-1) derived from ethylene monomers and 83% by weight or more and 92% by weight or less of structural units (a-2) derived from propylene monomers, where the sum of the structural units (a-1) and (a-2) is taken as 100% by weight. The olefinic chain (a) is preferably a random copolymer of ethylene monomers and propylene monomers.

[0023] <Condition (iv)> As described above, the olefin chain (b) is a polypropylene chain consisting of 0% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 100% by weight or less of structural units (b-2) derived from propylene monomers (where the sum of the structural units (b-1) and (b-2) is 100% by weight). The olefin chain (b) is present in the polypropylene resin melt-kneaded product either as the olefin chain (b) alone, i.e., as unreacted polypropylene resin (B), or as olefin copolymers (AB), (BA), and (BB) containing the olefin chain (b). The olefin chain (b) has a lower content of structural units derived from ethylene monomers than the olefin chain (a). The olefinic chain (b) is preferably a polypropylene chain consisting of 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 99% by weight or less of structural units (b-2) derived from propylene monomers. The sum of the structural units (b-1) and (b-2) is 100% by weight. When the structural units (b-1) derived from ethylene monomers are 0% by weight, the olefinic chain (b) is a homopolypropylene resin. When the structural units (b-1) derived from ethylene monomers are more than 0% by weight, the olefinic chain (b) is preferably a random copolymer of ethylene monomers and propylene monomers.

[0024] <Other Conditions> The polypropylene-based resin melt-kneaded product may satisfy conditions (hereinafter also referred to as "other conditions") other than the above-mentioned conditions (i) to (iv) as long as the effects of the present invention are not impaired. Examples of the other conditions include melt flow rate (MFR) and melt tension.

[0025] (MFR) The MFR of the polypropylene-based resin melt-kneaded product measured at 230°C is not particularly limited, but from the viewpoint of the polypropylene-based resin melt-kneaded product having better melt elasticity than conventional products, it is preferably 0.01 g / 10 min or more and less than 1.0 g / 10 min, more preferably 0.05 g / 10 min or more and less than 0.8 g / 10 min, and even more preferably 0.05 g / 10 min or more and less than 0.5 g / 10 min.

[0026] (Melt Tension) The melt tension of the polypropylene-based resin melt-kneaded product is not particularly limited, but is preferably 5.0 cN or more and 14 cN or less, and more preferably 6.0 cN or more and 14 cN or less.

[0027] <<Method for Producing a Melt-Kneaded Polypropylene Resin Product>> The method for producing a melt-kneaded polypropylene resin product of this embodiment includes melt-kneading a mixture containing 1 to 20% by weight of an olefin copolymer (A), 80 to 99% by weight of a polypropylene resin (B), one or more monomers (c) selected from the group consisting of conjugated dienes and vinyl aromatic compounds, and a radical polymerization initiator (d) (wherein the total of the olefin copolymer (A) and the polypropylene resin (B) is taken as 100% by weight). The olefin copolymer (A) is an olefin copolymer comprising 5 to 20% by weight of structural units (a-1) derived from ethylene monomers and 80 to 95% by weight of structural units (a-2) derived from propylene monomers (wherein the total of the structural units (a-1) and (a-2) is taken as 100% by weight). The polypropylene resin (B) is a polypropylene resin (b) comprising 0% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 100% by weight or less of structural units (b-2) derived from propylene monomers (wherein the sum of the structural units (b-1) and (b-2) is 100% by weight).

[0028] The method for producing a polypropylene-based resin melt-kneaded product of this embodiment uses an olefin-based copolymer (A) containing a larger amount of structural units derived from ethylene monomers than the polypropylene-based resin (B), and therefore crosslinking proceeds effectively, resulting in a polypropylene-based resin melt-kneaded product with high melt elasticity.

[0029] <Olefin Copolymer (A)> As described above, the olefin copolymer (A) is an olefin copolymer consisting of 5% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 95% by weight or less of structural units (a-2) derived from propylene monomers (where the sum of the structural units (a-1) and (a-2) is 100% by weight). The olefin copolymer (A) is preferably an olefin copolymer consisting of 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers, and more preferably an olefin copolymer consisting of 7% by weight or more and 17% by weight or less of structural units (a-1) derived from ethylene monomers and 83% by weight or more and 92% by weight or less of structural units (a-2) derived from propylene monomers. However, the total of the structural units (a-1) and (a-2) is 100% by weight. The olefin copolymer (A) is preferably a random copolymer of an ethylene monomer and a propylene monomer.

[0030] <Polypropylene Resin (B)> As described above, the polypropylene resin (B) is a polypropylene resin comprising 0% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and less than 100% by weight of structural units (b-2) derived from propylene monomers (where the sum of the structural units (b-1) and (b-2) is taken as 100% by weight). The polypropylene resin (B) has a lower content of structural units derived from ethylene monomers than the olefin copolymer (A). The polypropylene resin (B) is preferably a polypropylene chain comprising 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and less than 99% by weight of structural units (b-2) derived from propylene monomers (where the sum of the structural units (b-1) and (b-2) is taken as 100% by weight). When the structural unit (b-1) derived from an ethylene monomer is 0% by weight, the polypropylene resin (B) is a homopolypropylene resin. When the structural unit (b-1) derived from an ethylene monomer is more than 0% by weight, the polypropylene resin (B) is preferably a random copolymer of an ethylene monomer and a propylene monomer.

[0031] As described above, the mixture contains 1% by weight or more and 20% by weight or less of the olefin copolymer (A) and 80% by weight or more and 99% by weight or less of the polypropylene resin (B) (provided that the total of the olefin copolymer (A) and the polypropylene resin (B) is 100% by weight). The mixture preferably contains 2% by weight or more and 20% by weight or less of the olefin copolymer (A) and 80% by weight or more and 98% by weight or less of the polypropylene resin (B), and more preferably contains 5% by weight or more and 15% by weight or less of the olefin copolymer (A) and 85% by weight or more and 95% by weight or less of the polypropylene resin (B). However, the total of the olefin copolymer (A) and the olefin copolymer (B) is 100% by weight.

[0032] <Monomer (c) Selected from Conjugated Dienes and Vinyl Aromatic Compounds> Examples of conjugated dienes include butadiene, isoprene, 1,3-heptadiene, 2,3-dimethylbutadiene, and 2,5-dimethyl-2,4-hexadiene. These conjugated diene compounds may be used alone or in combination of two or more. Among these conjugated diene compounds, butadiene and isoprene are particularly preferred because they are inexpensive, easy to handle, and the reaction proceeds uniformly.

[0033] Examples of vinyl aromatic compounds include styrene; methylstyrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, dimethylstyrene, and trimethylstyrene; chlorostyrenes such as α-chlorostyrene, β-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, dichlorostyrene, and trichlorostyrene; bromostyrenes such as o-bromostyrene, m-bromostyrene, p-bromostyrene, dibromostyrene, and tribromostyrene; o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, and difluorostyrene; Examples of the vinyl aromatic compound include fluorostyrenes such as fluorostyrene and trifluorostyrene; nitrostyrenes such as o-nitrostyrene, m-nitrostyrene, p-nitrostyrene, dinitrostyrene and trinitrostyrene; vinylphenols such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, dihydroxystyrene and trihydroxystyrene; divinylbenzenes such as o-divinylbenzene, m-divinylbenzene and p-divinylbenzene; isopropenylstyrenes such as o-diisopropenylbenzene, m-diisopropenylbenzene and p-diisopropenylbenzene, etc. Among the above-mentioned vinyl aromatic compounds, styrene and / or methylstyrene are preferred in terms of low cost, ease of handling, and the tendency for the reaction to proceed uniformly.

[0034] The amount of the conjugated diene or the like (c) to be blended is preferably 0.30 parts by weight to 5.00 parts by weight, more preferably 0.40 parts by weight to 3.00 parts by weight, and still more preferably 0.40 parts by weight to 2.00 parts by weight, per 100 parts by weight of the total of the olefin copolymer (A) and the polypropylene resin (B).

[0035] <Radical Polymerization Initiator (d)> The radical polymerization initiator (d) is an organic peroxide capable of abstracting hydrogen from the olefin copolymer (A) and the polypropylene resin (B). Examples of the radical polymerization initiator (d) include organic peroxides such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters.

[0036] As the organic peroxide, those with particularly high hydrogen abstraction ability are preferred. Examples of organic peroxides with high hydrogen abstraction ability include peroxyketals such as 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 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-dimethyl-2,5- Suitable examples of organic peroxides include dialkyl peroxides such as di(t-butylperoxy)-3-hexyne; diacyl peroxides such as benzoyl peroxide; and peroxyesters such as t-butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyisopropylcarbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate. Among these, t-butylperoxyisopropylcarbonate and / or t-butylperoxybenzoate are preferred. These organic peroxides may be used alone or in combination of two or more.

[0037] The amount of the radical polymerization initiator (d) to be blended is preferably 0.01 to 5.00 parts by weight, more preferably 0.10 to 3.00 parts by weight, more preferably 0.10 to 2.00 parts by weight, and particularly preferably 0.10 to 1.50 parts by weight, relative to 100 parts by weight of the total of the olefin copolymer (A) and the polypropylene resin (B).

[0038] In the above-mentioned production method, examples of the apparatus for melt-kneading the olefin copolymer (A), the polypropylene resin (B), the monomer (c) such as a conjugated diene, and the radical polymerization initiator (d) include kneaders such as rolls, co-kneaders, Banbury mixers, Brabenders, single-screw extruders, and twin-screw extruders; horizontal mixers such as twin-screw surface regenerators and twin-screw multi-disc devices; and vertical mixers such as double helical ribbon mixers. Among these, it is preferable to use a kneader, and extruders such as single-screw extruders and twin-screw extruders are particularly preferable from the viewpoint of productivity.

[0039] The order and method of mixing and kneading the olefin copolymer (A), polypropylene resin (B), monomer (c) such as conjugated diene, and radical polymerization initiator (d) are not particularly limited. The olefin copolymer (A), polypropylene resin (B), monomer (c) such as conjugated diene, and radical polymerization initiator (d) may be mixed and then melt-kneaded. Alternatively, the olefin copolymer (A) and polypropylene resin (B) may be melt-kneaded, and then the monomer (c) such as conjugated diene or the radical polymerization initiator (d) may be mixed simultaneously or separately, all at once, or in portions. The temperature of the kneader is preferably 130°C or higher and 300°C or lower. The melt-kneading time is generally preferably 1 minute or higher and 60 minutes or lower.

[0040] <<Foam>> The foam of the present embodiment contains the polypropylene-based resin melt-kneaded product. Examples of the foam include extruded foams, injection foams, and blown foams. As the extruded foam, extruded foam particles are preferred.

[0041] <<Method for Producing Extruded Foamed Beads>> The method for producing extruded foamed beads of the present embodiment includes melt-kneading a mixture containing the above-mentioned polypropylene-based resin melt-kneaded product and a foaming agent under pressure, cooling the mixture, and then extruding the mixture under a lower pressure atmosphere to foam and cut it.

[0042] <Blowing Agent> The blowing agent used in the production method of this embodiment is not particularly limited as long as it is a blowing agent commonly used in extrusion foaming. Examples of blowing agents include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane; alicyclic hydrocarbons such as cyclopentane and cyclobutane; ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; alcohols such as methanol and ethanol; inorganic gases such as air, nitrogen, and carbon dioxide; physical blowing agents such as water; and chemical blowing agents including thermal decomposition blowing agents such as sodium bicarbonate, azodicarbonamide, and dinitrosopentamethylenetetramine. Among these, inorganic gases and physical blowing agents are preferred from the standpoint of environmental impact.

[0043] The amount of the foaming agent used is preferably 0.5 parts by weight to 7.0 parts by weight, more preferably 1.0 parts by weight to 6.0 parts by weight, and even more preferably 1.5 parts by weight to 5.0 parts by weight, relative to 100.0 parts by weight of the polypropylene-based resin melt-kneaded product.

[0044] (Other Components) The mixture may contain components other than the polypropylene-based resin melt-kneaded product and the blowing agent (hereinafter also referred to as "other components"), as long as the effects of the present invention are not impaired. Examples of other components include bubble nucleating agents; stabilizers such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, and antacid adsorbents; and / or additives such as crosslinking agents, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, flame retardants, colorants, and antistatic agents. These other components may be used alone or in combination of two or more. The total content of the other components in the mixture is not particularly limited. For example, the total content of the other components in the mixture is preferably 0.01 to 50.00 parts by weight, and more preferably 0.05 to 30.00 parts by weight, per 100 parts by weight of the polypropylene-based resin melt-kneaded product.

[0045] (Gas nucleating agent) Examples of the gas nucleating agent include sodium bicarbonate-citric acid mixture, monosodium citrate, talc, calcium carbonate, etc. These gas nucleating agents may be used alone or in combination of two or more.

[0046] <Step of Obtaining Melt-Kneaded Product> Examples of extruders used to obtain the melt-kneaded product include single-screw extruders and twin-screw extruders. Among these, twin-screw extruders are preferred because of their excellent melt-kneading properties.

[0047] The cylinder temperature of the extruder is not particularly limited and can be appropriately set depending on the melting point of the polypropylene resin melt-kneaded product to be used, the type and amount of the blowing agent to be used, etc., from the viewpoint of sufficiently melt-kneading the polypropylene resin melt-kneaded product and the blowing agent. For example, the cylinder temperature of the extruder is preferably 150°C or higher and 250°C or lower, more preferably 170°C or higher and 230°C or lower.

[0048] <Step of cooling the melt-kneaded product and then extruding it under a lower pressure atmosphere to foam> Examples of cooling devices used to cool the obtained melt-kneaded product include a single-screw extruder, a static mixer, and a melt cooler. In the cooling device, a die for extruding the cooled melt-kneaded product is provided at the tip of the extrusion direction of the melt-kneaded product. The temperature of the cooling device is not particularly limited as long as it is a temperature suitable for foaming the obtained melt-kneaded product. For example, the temperature of the cooling device is preferably 120°C or higher and 180°C or lower, and more preferably 130°C or higher and 170°C or lower.

[0049] The cooled molten mixture is extruded through holes provided in the die into a region where the pressure is lower than the internal pressure of the cooling device (hereinafter also referred to as the "low-pressure region"). The molten mixture may be extruded into a gas phase or a liquid phase. The pressure in the low-pressure region is not particularly limited, but is preferably 5 MPa or less, and more preferably 1 MPa or less. The extruded molten mixture immediately begins to foam, and when foaming is completed, an extruded foam is obtained.

[0050] <Cutting Step> The foaming step further includes a shredding step of cutting the extruded melt-kneaded material into particles. In the shredding step, the melt-kneaded material (extruded foam) may be shredded during foaming, or the melt-kneaded material (extruded foam) may be shredded after foaming has finished. The method for shredding the extruded melt-kneaded material is not particularly limited. For example, the melt-kneaded material may be shredded along the extrusion direction using a cutter or the like provided next to the die. Through the above steps, extruded polypropylene resin foam particles are obtained.

[0051] The low-pressure region may be a gas phase or a liquid phase, but is preferably a gas phase because it is easier to obtain expanded beads with a relatively high expansion ratio. Water or the like may be sprayed onto the surface of the expanded beads cut in the gas phase to cool them.

[0052] <Physical Properties of Extruded Expanded Beads> (Expansion Ratio) The expansion ratio of the extruded expanded beads is not particularly limited, but is preferably 3 times or more and 50 times or less, and more preferably 5 times or more and 30 times or less.

[0053] (Open Cell Ratio) The lower the open cell ratio of the extruded foamed beads, the better. The open cell ratio of the extruded foamed beads is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, even more preferably 15% or less, and particularly preferably 10% or less. The lower limit of the open cell ratio of the extruded foamed beads is not particularly limited, and is, for example, 0.0% or more, preferably 2% or more.

[0054] <Effects of Monomer (c) and Radical Polymerization Initiator (d) on tan δ and MFR of the Resulting Polypropylene Resin Melt-Kneaded Product and Base Resin of Extruded Foamed Beads> Hereinafter, the effects of the monomer (c) and the radical polymerization initiator (d) on the tan δ and MFR of the Resulting Polypropylene Resin Melt-Kneaded Product and Base Resin of Extruded Foamed Beads in this production method will be described, with some speculation. Note that one embodiment of the present invention is not limited to the following description in any way.

[0055] In this production method, the radical polymerization initiator (d) is a component that initiates a reaction by abstracting hydrogen from the main chain of the polymer contained in the mixture consisting of the olefin copolymer (A) and the polypropylene resin (B). Generally, when the mixture is melt-kneaded with the radical polymerization initiator (d), the hydrogen abstraction reaction is followed by a chain-like molecular chain scission reaction of the polymer contained in the mixture, particularly the polypropylene resin (B), and therefore the tan δ and MFR of the polypropylene resin melt-kneaded product of the present invention generally become significantly large.

[0056] In this production method, the monomer (c) and the radical polymerization initiator (d) are used in combination with the mixture. As a result, in this production method, the monomer (c) adds to the polymer molecules that have undergone the hydrogen abstraction reaction, thereby suppressing the aforementioned molecular chain scission reaction. Furthermore, in this production method, the addition reaction of the monomer (c) to the polymer molecules that have undergone the hydrogen abstraction reaction proceeds, thereby forming a branched structure due to the monomer (c) in the polymer. Furthermore, in this production method, a dimerization reaction proceeds between multiple polymer molecules that have formed branched structures due to the monomer (c), and as this progresses, a crosslinked structure is formed. It is believed that the progression of these reactions allows the production of a melt-kneaded product having long chain branches based on the crosslinked structure. Furthermore, in parallel with the aforementioned series of reactions, the molecular chain scission reaction of the polymer may also proceed. Therefore, in the present production method, by appropriately adjusting the blending amount of the monomer (c) and the blending amount of the radical polymerization initiator (d) relative to the above mixture, it is possible to adjust the tan δ and MFR of the base resin of the resulting polypropylene resin melt-kneaded product and extruded foamed beads.

[0057] The radical polymerization initiator (d) can be said to be a component that determines the degree of progress of the molecular chain scission reaction of the polymer described above and the reaction of forming a branched structure and / or a crosslinked structure by the monomer (c) of the polymer. Here, the balance of the degree of progress of the molecular chain scission reaction and the reaction of forming a branched structure and / or a crosslinked structure can be adjusted by changing the ratio of the amount of the monomer (c) used to the amount of the radical polymerization initiator (d) used (amount of the monomer (c) used / amount of the radical polymerization initiator (d) used).

[0058] The higher the ratio (amount of monomer (c) used / amount of radical polymerization initiator (d) used), the more the reaction that forms the branched structure and / or crosslinked structure takes precedence over the molecular chain scission reaction. As a result, the higher the ratio, the lower the tan δ of the resulting polypropylene resin melt-kneaded product and the base resin of the extruded foam beads, and the smaller the MFR tends to be. On the other hand, the lower the ratio (amount of monomer (c) used / amount of radical polymerization initiator (d) used), the more the molecular chain scission takes precedence over the reaction that forms the branched structure and / or crosslinked structure. As a result, the lower the ratio, the higher the tan δ of the resulting polypropylene resin melt-kneaded product and the base resin of the extruded foam beads, and the larger the MFR tends to be.

[0059] The ratio (amount of monomer (c) used / amount of radical polymerization initiator (d) used) is not particularly limited, and will vary depending on the types of monomer (c) and radical polymerization initiator (d) used. As described above, by appropriately adjusting the blending amounts of the mixture consisting of the olefin copolymer (A) and the polypropylene resin (B), the monomer (c), and the radical polymerization initiator (d), the tan δ and MFR of the base resin of the resulting polypropylene resin melt-kneaded product and extruded foamed beads can be adjusted within the range of one embodiment of the present invention.

[0060] <<Foam Molded Article>> The foam molded article of this embodiment is an in-mold molded article made from the extruded foam beads described above. The foam molded article can be obtained by filling a mold that can be closed but not hermetically sealed with the extruded foam beads and then heating and molding with steam or the like. Examples of methods for producing the foam molded article include: (a) a method in which the foam beads are pressurized with an inorganic gas to impregnate the particles with the inorganic gas and impart a predetermined internal particle pressure, and then the particles are filled into a mold and heat-sealed with steam or the like (e.g., JP-B-51-22951); (b) a method in which the foam beads are compressed with gas pressure, filled into a mold, and heat-sealed with steam or the like by utilizing the recovery force of the particles (e.g., JP-B-53-33996); and (c) a method in which the foam beads are filled into a mold with an expanded gap, the mold is closed to a predetermined gap, the filled foam beads are compressed, and then heat-sealed with steam or the like.

[0061] <Physical Properties of Foam Molded Article> (Expansion Ratio) The expansion ratio of the foam molded article is not particularly limited, but is preferably 3 times or more and 50 times or less, and more preferably 5 times or more and 30 times or less.

[0062] (Open Cell Ratio) The lower the open cell ratio of the foamed molded product, the better. From the viewpoint of obtaining an extruded foamed bead molding having high compressive strength, the open cell ratio of the foamed molded product is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, and even more preferably 15% or less. The lower limit of the open cell ratio of the extruded foamed bead molding is not particularly limited, and is, for example, 0.0% or more, preferably 2% or more.

[0063] The foamed molded article is suitably used for automobile interior parts, core materials for automobile bumpers, heat insulating materials, cushioning packaging materials, etc.

[0064] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0065] [Examples 1 to 5, Comparative Examples 1 to 4] (Materials) In the examples and comparative examples, the following A1 to A3 were used as the olefin copolymer (A): A1: Versify 2200 (manufactured by Dow Chemical, an olefin copolymer consisting of 9% by weight of ethylene and 91% by weight of propylene, crystalline heat of fusion ΔH=22.7 J / g, MFR at 230°C=2 g / 10 min) A2: Versify 2300 (manufactured by Dow Chemical, an olefin copolymer consisting of 12% by weight of ethylene and 88% by weight of propylene, crystalline heat of fusion ΔH=22.7 J / g, MFR at 230°C=2 g / 10 min) A3: Engage 8100 (manufactured by Dow Chemical, an olefin copolymer consisting of 61% by weight of ethylene and 39% by weight of octene, MFR at 230°C=2.2 g / 10 min)

[0066] In the examples and comparative examples, the following B1 to B2 were used as the polypropylene resin (B): B1: F-724NPC (manufactured by Prime Polymer, random polypropylene consisting of 2.2 wt% ethylene and 97.8 wt% propylene, MFR at 230°C = 7 g / 10 min) B2: S229R (manufactured by Prime Polymer, random polypropylene consisting of 3.5 wt% ethylene and 96.5 wt% propylene, MFR at 230°C = 59 g / 10 min)

[0067] In the examples and comparative examples, the following c1 was used as the conjugated diene (c): c1: isoprene (isoprene monomer, manufactured by Kuraray Co., Ltd.)

[0068] In the examples and comparative examples, the following d1 was used as the radical polymerization initiator (d): d1: t-butylperoxyisopropyl carbonate (Perbutyl (registered trademark) I, manufactured by NOF Corp.)

[0069] [Example 1: Preparation of polypropylene resin melt-kneaded product] 100 parts by weight of a mixture of raw resins consisting of 10 parts by weight of A1 as an olefin copolymer (A) and 90 parts by weight of B1 as a polypropylene resin (B) was fed to a twin-screw extruder at 70 kg / h, and then 1.0 part by weight of d1 as a radical polymerization initiator (d) was fed to the twin-screw extruder per 100 parts by weight of the raw resin and melt-kneaded. To the obtained melt-kneaded product, c1 as a conjugated diene (c) was fed from the middle of the twin-screw extruder at a ratio of 0.53 parts by weight per 100 parts by weight of the raw resin, and further melt-kneaded. At this time, the set temperature of the twin-screw extruder cylinder was 200 ° C, and the screw rotation speed was set to 230 rpm. The finally obtained polypropylene resin melt-kneaded product was extruded from a die in the form of a strand and water-cooled, and then chopped into pellets (cylindrical) to obtain pellets of a polypropylene resin melt-kneaded product (MP-1). The properties of the obtained MP-1 were evaluated as follows. The MFR was 0.34 g / 10 min, tan δ ０．１ The viscosity was 0.71 and the melt tension was 8.4 cN.

[0070] (Melt flow rate (MFR)) In accordance with the provisions of Method B of ISO 1133 (1997), the amount of resin extruded from a die in a certain time was converted to the amount extruded in 10 minutes using a Melt Indexer S-01 (manufactured by Toyo Seiki Seisakusho) under conditions of 230°C and 2.16 kg. The certain time is 120 seconds when the melt flow rate is 1.0 g / 10 min or less; 60 seconds when the melt flow rate is greater than 1.0 g / 10 min and is 3.5 g / 10 min or less; and 30 seconds when the melt flow rate is greater than 3.5 g / 10 min.

[0071] (Loss tangent tanδ) Using a 1.5 mm thick spacer, pellets of the polypropylene resin melt-kneaded product obtained above were hot-pressed at 190°C for 5 minutes to produce a 1.5 mm thick press plate, from which a 25 mmφ punch was used to punch out a disk-shaped plate to serve as a test specimen. The measurement device used was an Anton Paar MCR viscoelasticity measuring device, and the measurement conditions were a 25 mmφ parallel plate jig, a measurement temperature of 180°C, a plate spacing of 1.0 mm, and a strain of 5%. The jig was preheated to the measurement temperature, and then the test specimen was sandwiched between the parallel plates of the jig. The plate spacing was adjusted to a predetermined value while the test specimen was melted. Furthermore, any resin that protruded from the plates was scraped off and removed, and the specimen was again preheated for 5 minutes to stabilize the temperature. After confirming that the temperature had sufficiently stabilized in air, dynamic viscoelasticity measurement was initiated. The measurement was carried out in the angular frequency ω range from 0.1 rad / s to 100 rad / s. After obtaining the storage modulus G′ and loss modulus G″ at the measured angular frequency, the loss tangent tanδ was calculated according to the following formula: ０．１ was calculated. ０．１ = G" / G' where tan δ ０．１ is tan δ at ω=0.1 rad / s.

[0072] (Melt tension) A Capillograph (manufactured by Toyo Seiki Seisakusho) equipped with a melt tension measurement attachment and having a φ10 mm cylinder with a φ1 mm and 10 mm long orifice attached to the tip was used. The pellets of the polypropylene resin melt kneaded product obtained above were filled into a cylinder set at 230 ° C., preheated for 5 minutes, and the piston was lowered at a rate of 10 mm / min. The strand discharged from the orifice was placed on a pulley with a load cell 500 mm below and taken up at a rate of 1 m / min. After stabilization, the take-up speed was increased at a rate of 200 m / min in 4 minutes. The load (unit: cN) applied to the pulley with the load cell when the strand broke was taken as the melt tension. Note that if the strand did not break, the load at which the load no longer increased even when the take-up speed was increased was taken as the melt tension.

[0073] [Preparation of Extruded Foamed Beads] The resulting polypropylene resin melt-kneaded product (MP-1) was used to prepare extruded foamed beads as follows. The equipment used consisted of a twin-screw extruder with a shaft diameter of 15 mm, a melt cooler, a diverter valve, and a die connected in series in this order. 100 parts by weight of the base resin MP-1 was dry-blended with 0.02 parts by weight of talc (Talc Powder (registered trademark) PK-S, manufactured by Hayashi Kasei Co., Ltd.) as a bubble nucleating agent to prepare a resin mixture for extrusion foaming. The resin mixture was then fed at 0.75 kg / h into a twin-screw extruder set at 200°C, and melt-kneaded at a screw rotation speed of 40 rpm. Furthermore, carbon dioxide gas, the blowing agent, was fed using a metering pump at a ratio of 4.0 parts by weight per 100 parts by weight of the resin mixture through a pressure-injection section installed midway through the extruder, and further melt-kneaded. The resulting molten mixture was cooled by passing it through a melt cooler connected to the tip of the twin-screw extruder and set at 150°C. The mixture was then extruded into the atmosphere through a die (φ0.7 mm × 2 holes) attached downstream of the melt cooler to allow foaming. The foam was then quickly cut with a cutter (four blades, 750 rpm) to obtain extruded foam particles weighing 2.1 mg / particle. The granulation method used here was a watering cut method (hereinafter also referred to as the "WRC method") in which water was poured onto the wall so that the extruded foam particles after cutting would come into contact with water and be discharged outside the system. The water temperature used in the WRC was 25-35°C. The resulting extruded foam particles were dried at 75°C for 2 hours or more, allowed to stand at 23°C for 24 hours or more, and then evaluated using the following method. The expansion ratio was 17.6 times and the open cell ratio was 7.3%.

[0074] (Expansion Ratio of Extruded Foamed Beads) The expansion ratio of extruded foamed beads was determined by measuring the mass w1 (g) of the foamed beads, then immersing the foamed beads in a measuring cylinder containing ethanol, and measuring the volume v1 (cm) by the amount of rise in the water level in the measuring cylinder (submersion method). ３) was measured, and the true specific gravity ρb = w1 / v1 of the expanded beads was calculated. Furthermore, the ratio (ρr / ρb) of this to the resin density ρr before expansion was calculated. The resin density ρr before expansion was measured using a resin obtained by melt-kneading a resin with the same composition as the expanded beads in the absence of a blowing agent. After measuring the mass w2 (g) of the resin, the resin was submerged in a measuring cylinder containing ethanol, and the volume v2 (cm) was calculated by the amount of rise in the water level in the measuring cylinder. ３ ) was measured and calculated by ρr = w2 / v2.

[0075] (Open cell ratio of extruded foam particles) This was calculated according to the method described in Procedure C of ASTM D2856-87 by carrying out the following steps (1) to (3) in order. (1) The volume Vc (cm) of the extruded foam particles was measured using an air-comparison type hydrometer. ３ (2) Next, the entire amount of the extruded foamed particles after measuring Vc was submerged in ethanol contained in a measuring cylinder. (3) After that, the apparent volume Va (cm) of the extruded foamed particles was calculated from the amount of rise in the position of the ethanol in the measuring cylinder. ３ (4) The open cell ratio of the extruded foamed beads was calculated using the following formula: Open cell ratio (%) = ((Va - Vc) x 100) / Va

[0076] [Preparation of Foam Molded Article] A polypropylene resin foam molded article was produced using the obtained extruded foam beads by the following method. The obtained extruded foam beads were placed in a pressure-resistant vessel, and the pressure was increased to 0.20 MPa·G with air at a pressure increase rate of 0.05 MPa / h and maintained at that pressure for 20 hours (internal pressure application). If necessary, the pressure of the pressure-resistant vessel was adjusted so that the internal pressure of the extruded foam beads was 0.20 MPa·G (absolute pressure). The extruded foam beads thus obtained with internal pressure application were used as the raw material for the foam molded article. Molding was performed using a commonly used foam molding machine, and a block-shaped mold (molding space: 381 mm long x 320 mm wide x variable thickness) was used. Initially, the thickness of the molding space in the mold was adjusted to 44 mm (cracking rate: 10%), and then the internally pressurized extruded foam beads were filled into the molding space. The mold was then moved so that the thickness of the molding space in the mold was 40 mm, and the molding space was compressed. The air in the mold was then expelled with steam at 0.10 MPa G, followed by heat molding for 7 seconds using steam at a vapor pressure of 0.26 MPa G to fuse the foamed particles together and produce a foamed molded article. The steam in the mold was then removed from the drain valve over 10 seconds, and the mold was cooled with water until the surface pressure gauge attached to the mold reached 0.05 MPa. The molded article was then removed from the mold to produce a foamed molded article. The resulting polypropylene resin foamed molded article was dried at 75°C for 16 hours or more, allowed to stand at 23°C for 24 hours or more, and evaluated using the methods described below. The resulting foamed molded article had an expansion ratio of 29.2 and an open cell ratio of 18.7%.

[0077] (Expansion Ratio of Foam Molded Article) A sample piece measuring 25 / 25 / 25 mm in length / width / thickness (no skin layer on the entire surface) was cut out from the obtained foam molded article. After standing at 23° C. for 24 hours or more, the weight of the sample piece was measured, and the volume of the sample piece was measured by the water immersion method in the same manner as for the expansion ratio of expanded beads, and the expansion ratio was calculated.

[0078] (Open-cell content of foamed molded article) A sample piece measuring 25 / 25 / 25 mm in length / width / thickness (no skin layer on the entire surface) was cut out from the resulting foamed molded article. After standing at 23°C for 24 hours or more, the open-cell content of the foamed molded article was measured using the same method as for measuring the open-cell content of foamed beads.

[0079] [Examples 2 to 5, Comparative Examples 1 to 4] Polypropylene resin melt-kneaded materials MP-2 to MP-9 were obtained in the same manner as in Example 1, except that the types and blending ratios of the olefin copolymer (A) and the polypropylene resin (B) and the blending ratio of c1 as the conjugated diene (c) were changed as shown in Table 1. The MFR, tanδ, and the like were also measured for each of the obtained polypropylene resin melt-kneaded materials MP-2 to MP-9. ０．１ The melt tension was evaluated. The results are shown in Table 1. Next, extruded foamed beads were obtained in the same manner as in Example 1, except that the resin composition obtained in each example was used instead of MP-1 as the base resin, and the expansion ratio and open cell ratio were evaluated. The results are shown in Table 1. Furthermore, foamed molded articles were obtained in the same manner as in Example 1, except that the extruded foamed beads obtained in each example were used, and the expansion ratio and open cell ratio were evaluated. The results are shown in Table 1.

[0080]

[0081] As can be seen from Table 1, the polypropylene resin melt-kneaded products of Examples 1 to 5, which were obtained by blending the olefin copolymer (A), have a low tan δ compared to the polypropylene resin melt-kneaded product of Comparative Example 1, which was obtained without blending the olefin copolymer (A). ０．１ It can be seen that the melt kneaded product exhibits high melt elasticity as shown by the formula (I), and the foamed molded article produced using the melt kneaded product has a small open cell ratio.

Claims

1. A polypropylene resin melt-kneaded product containing an olefin copolymer (AA) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (a), an olefin copolymer (AB) having a branch containing an olefin chain (a) and a main chain containing the olefin chain (b), an olefin copolymer (BA) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (a), and an olefin copolymer (BB) having a branch containing an olefin chain (b) and a main chain containing the olefin chain (b), and satisfying the following (i) to (iv): (i) The melt-kneaded product contains 1% by weight or more and 20% by weight or less of the olefin chain (a) and 80% by weight or more and 99% by weight or less of the olefin chain (b) (wherein the total of the olefin chains (a) and (b) is 100% by weight). (ii) Loss tangent tanδ at ω=0.1 rad / sec, measured by dynamic viscoelasticity measurement at 180°C ０．１ is 0.4 or more and 2.0 or less. (iii) The olefinic chain (a) is an olefinic chain consisting of 5 to 20% by weight of structural units (a-1) derived from ethylene monomers and 80 to 95% by weight of structural units (a-2) derived from propylene monomers (provided that the sum of the structural units (a-1) and (a-2) is 100% by weight). (iv) The olefinic chain (b) is a polypropylene-based chain consisting of 0 to less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95 to 100% by weight of structural units (b-2) derived from propylene monomers (provided that the sum of the structural units (b-1) and (b-2) is 100% by weight).

2. A polypropylene resin melt-kneaded product according to claim 1, wherein the olefin chain (a) is an olefin chain consisting of 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers (provided that the sum of the structural units (a-1) and (a-2) is 100% by weight).

3. The polypropylene resin melt-kneaded product according to claim 1, wherein the olefin chain (a) is a random copolymer of an ethylene monomer and a propylene monomer.

4. A polypropylene resin melt-kneaded product according to claim 1, wherein the olefin chain (b) is a polypropylene chain consisting of 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 99% by weight or less of structural units (b-2) derived from propylene monomers (provided that the sum of the structural units (b-1) and (b-2) is 100% by weight).

5. Loss tangent tanδ at ω = 0.1 rad / sec measured by dynamic viscoelasticity measurement at 180°C ０．１ 2. The polypropylene-based resin melt-kneaded product according to claim 1, wherein the value of [theta] is 0.4 or more and 1.0 or less.

6. Loss tangent tanδ at ω = 0.1 rad / sec measured by dynamic viscoelasticity measurement at 180°C ０．１ 2. The polypropylene-based resin melt-kneaded product according to claim 1, wherein the value of β is 0.4 or more and 0.8 or less.

7. The polypropylene resin melt-kneaded product according to claim 1, having an MFR measured at 230°C of 0.01 g / 10 min or more and less than 1.0 g / 10 min.

8. A foam comprising the polypropylene resin melt-kneaded product according to any one of claims 1 to 7.

9. The foam of claim 8, which is an extruded foam particle.

10. A foamed molded article obtained by molding the extruded foam particles according to claim 9.

11. The foamed molded article according to claim 10, having an open cell content of 30% or less.

12. A method for producing a polypropylene resin melt-kneaded product, comprising melt-kneading a mixture containing 1% by weight or more and 20% by weight or less of an olefin copolymer (A), 80 parts by weight or more and 99% by weight or less of a polypropylene resin (B), one or more monomers (c) selected from the group consisting of conjugated dienes and vinyl aromatic compounds, and a radical polymerization initiator (d) (wherein the total of the olefin copolymer (A) and the polypropylene resin (B) is 100% by weight), wherein the olefin copolymer (A) is an olefin copolymer consisting of 5% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 95% by weight or less of structural units (a-2) derived from propylene monomers (wherein the total of the structural units (a-1) and (a-2) is 100% by weight), the polypropylene-based resin (B) is a polypropylene-based resin consisting of 0% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 100% by weight or less of structural units (b-2) derived from propylene monomers (where the total of the structural units (b-1) and (b-2) is defined as 100% by weight), and the blending amount of the monomer (c) is 0.30 parts by weight to 5.00 parts by weight per 100 parts by weight of the total of the olefin-based copolymer (A) and the polypropylene-based resin (B).

13. A method for producing a polypropylene resin melt-kneaded product according to claim 12, wherein the olefin copolymer (A) is an olefin copolymer comprising 7% by weight or more and 20% by weight or less of structural units (a-1) derived from ethylene monomers and 80% by weight or more and 93% by weight or less of structural units (a-2) derived from propylene monomers (provided that the sum of the structural units (a-1) and (a-2) is 100% by weight).

14. The method for producing a melt-kneaded polypropylene resin product according to claim 12, wherein the olefin copolymer (A) is a random copolymer of ethylene monomer and propylene monomer.

15. A method for producing a polypropylene resin melt-kneaded product according to claim 12, wherein the polypropylene resin (B) is a polypropylene chain consisting of 1% by weight or more and less than 5% by weight of structural units (b-1) derived from ethylene monomers and more than 95% by weight and 99% by weight or less of structural units (b-2) derived from propylene monomers (provided that the sum of the structural units (b-1) and (b-2) is 100% by weight).

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