Polypropylene resin extruded foam particles, method for producing the same, and foamed molded articles

Abstract

The present invention addresses the problem of providing a modified polypropylene resin having high melt tension that can obtain polypropylene resin foam particles having a low open-cell ratio. The present invention is a modified polypropylene resin obtained by reacting a polypropylene resin having a specific peak in the DSC curve with a conjugated diene compound and a radical polymerization initiator. The present invention is also a resin composition including a modified polypropylene resin, obtained by reacting a polypropylene resin with a specific ethylene polymer, a conjugated diene compound, and a radical polymerization initiator.

Description

[Technical Field]

[0001] This invention relates to polypropylene resin extruded foam particles, a method for producing the same, and a foamed molded article. [Background technology]

[0002] Polypropylene resin in-mold foamed molded articles obtained using polypropylene resin foam particles are characterized by their excellent flexibility in shape, cushioning properties, light weight, and heat insulation properties.

[0003] Methods for producing polypropylene resin foam particles include the discontinuous depressurization foaming method and the continuous extrusion foaming method. The extrusion foaming method has many advantages in terms of efficiency and environmental impact. For example, the extrusion foaming method allows for continuous production and does not require the wastewater treatment facilities necessary for the depressurization foaming method.

[0004] In the extrusion foaming method, resins obtained by modifying or multi-stage polymerization of linear general-purpose polypropylene can be used. For example, Patent Document 1 discloses a modified polypropylene resin composition obtained by melt-kneading a polypropylene resin, a polyethylene resin, at least one monomer selected from isoprene monomer and 1,3-butadiene monomer, and a radical polymerization initiator. Patent Document 1 also discloses a method for producing a foam made from a modified polypropylene resin composition, characterized by extruding a mixture of the modified polypropylene resin composition and a foaming agent in a molten state. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 11-035723 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the conventional technologies described above were insufficient from the standpoint of providing polypropylene-based resin foam particles with a low open-cell ratio, and there was room for further improvement.

[0007] One aspect of the present invention has been made in view of the above-mentioned problems, and its objective is to provide polypropylene resin foam particles with a low open-cell ratio. [Means for solving the problem]

[0008] Polypropylene resin extruded foam particles according to one embodiment of the present invention are polypropylene resin extruded foam particles obtained by extruding a modified polypropylene resin (B1), wherein the modified polypropylene resin (B1) is obtained by the reaction of a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%).

[0009] Polypropylene resin extruded foam particles according to another embodiment of the present invention are polypropylene resin extruded foam particles obtained by extruding a resin composition containing a modified polypropylene resin (B), wherein the resin composition is obtained by the reaction of 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) includes at least one of an ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering.

[0010] A method for producing polypropylene resin extruded foam particles according to one embodiment of the present invention includes a melt-kneading step to obtain a modified polypropylene resin (B1) by melt-kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, and an extrusion foaming step to extrude and foam the modified polypropylene resin (B1), wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%), and the extrusion foaming step includes a first step of melt-kneading the modified polypropylene resin (B1) and a foaming agent in a manufacturing apparatus, and a second step of extruding the composition obtained in the first step through a die to a region with a pressure lower than the internal pressure of the manufacturing apparatus.

[0011] A method for producing polypropylene resin extruded foam particles according to another embodiment of the present invention includes a melt-kneading step to obtain a resin composition containing a modified polypropylene resin (B) by melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, and an extrusion foaming step to extrude and foam the resin composition, wherein the ethylene polymer (C) includes at least one of an ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering, and the extrusion foaming step includes a first step of melt-kneading the resin composition and a foaming agent in a manufacturing apparatus, and a second step of extruding the composition obtained in the first step through a die to a region with a pressure lower than the internal pressure of the manufacturing apparatus. [Effects of the Invention]

[0012] According to one aspect of the present invention, polypropylene resin foam particles with a low open-cell ratio can be provided. [Brief explanation of the drawing]

[0013] [Figure 1] It is a schematic diagram for explaining a method of calculating the area of a peak in a DSC curve.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims. Also, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, by combining the technical means disclosed in each embodiment, new technical features can be formed. All academic documents and patent documents described in this specification are incorporated herein by reference as references. Also, unless otherwise specified in this specification, "A to B" representing a numerical range is intended to mean "A or more (including A and greater than A) and B or less (including B and less than B)".

[0015] 〔1. Modified polypropylene-based resin or resin composition〕 As a result of intensive studies to solve the above problems, the present inventors have found that, by the following means, it is possible to provide a modified polypropylene-based resin or resin composition having a high melt tension while reducing the amount of radical polymerization initiator used, and polypropylene-based resin foam particles having a low closed cell ratio, and have completed the present invention: Reacting a polypropylene-based resin (A1) having a specific peak in a DSC curve with a conjugated diene compound; or, Reacting a specific ethylene-based polymer (C) with a polypropylene-based resin (A) via a conjugated diene compound.

[0016] A modified polypropylene resin (B1) according to one embodiment of the present invention is a modified polypropylene resin (B1) obtained by the reaction of a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%).

[0017] In this specification, "modified polypropylene resin according to one embodiment of the present invention" may also be referred to as "this modified polypropylene resin." A modified polypropylene resin obtained using polypropylene resin (A1) is referred to as modified polypropylene resin (B1). When simply referred to as "modified polypropylene resin" or "this modified polypropylene resin," it encompasses both modified polypropylene resin (B1) and modified polypropylene resin (B) described later.

[0018] Modified polypropylene resin (B1) has the advantage of exhibiting high melt tension due to its aforementioned structure. Furthermore, modified polypropylene resin (B1) has the advantage of producing polypropylene resin extruded foam particles with a low open-cell ratio. In addition, modified polypropylene resin (B1) has the advantage of being obtainable using a manufacturing method that requires less radical polymerization initiator than conventional methods. Radical polymerization initiators are often expensive. Therefore, modified polypropylene resin (B1) is more cost-effective than conventional resins and also exhibits high melt tension.

[0019] Modified polypropylene resin (B1) contains structural units derived from polypropylene resin (A1) and structural units derived from conjugated diene compounds. Furthermore, modified polypropylene resin (B1) may contain the aforementioned ethylene homopolymer units within the structural units derived from polypropylene resin (A1). If other resins are used in the production of modified polypropylene resin (B1), modified polypropylene resin (B1) contains components derived from the other resins and / or other resins. Furthermore, modified polypropylene resin (B1) may contain structural units derived from radical polymerization initiators. Here, "structural units derived from radical polymerization initiators" refers to structural units derived from various substances produced by the decomposition of radical polymerization initiators in the production of modified polypropylene resin (B1). If other components are used in the production of modified polypropylene resin (B1), modified polypropylene resin (B1) contains the other components.

[0020] Furthermore, a resin composition according to one embodiment of the present invention is a resin composition containing a modified polypropylene resin (B) obtained by reacting 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) may contain at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering. The polypropylene resin (A) to be reacted with this ethylene polymer (C) may be the polypropylene resin (A1) containing ethylene homopolymer units in its molecule as described above, or it may be any other polypropylene resin.

[0021] The "resin composition according to one embodiment of the present invention" may also be referred to as "this resin composition." The modified polypropylene resin contained in this resin composition, i.e., the modified polypropylene resin obtained using polypropylene resin (A), is referred to as modified polypropylene resin (B). Since this resin composition also has the configuration described above, it has the same advantages as modified polypropylene resin (B1).

[0022] Modified polypropylene resin (B) contains structural units derived from polypropylene resin (A) and structural units derived from conjugated diene compounds. Furthermore, like modified polypropylene resin (B1), modified polypropylene resin (B) may contain structural units derived from radical polymerization initiators, other resins and / or other resin-derived components, and other components. Modified polypropylene resin (B) may also contain structural units derived from at least one of ethylene-α-olefin elastomer (C1) and ethylene polymer (C2), in addition to structural units derived from polypropylene resin (A).

[0023] The modified polypropylene resin (B) may have a structure in which polypropylene resins (A) are crosslinked with each other, or a structure in which polypropylene resin (A) and an ethylene polymer (C) are crosslinked, or it may have both. This resin composition may contain a resin having a structure in which polypropylene resin (A) and an ethylene polymer (C) are crosslinked, a resin having a structure in which polypropylene resins (A) are crosslinked with each other, and / or a resin having a structure in which ethylene polymers (C) are crosslinked with each other. The modified polypropylene resin (B) may be modified polypropylene resin (B1), or any other modified polypropylene resin.

[0024] (Polypropylene resin (A)) In this specification, polypropylene resin (A) refers to a resin containing 50% by weight or more of structural units derived from propylene monomers out of 100% by weight of all structural units contained in the resin. In this specification, "structural units derived from propylene monomers" may also be referred to as "propylene units."

[0025] The polypropylene resin (A) used in this manufacturing method may be (a) a propylene homopolymer, (b) a block copolymer, random copolymer, or graft copolymer of propylene and a monomer other than propylene, or (c) a mixture thereof. The random copolymer is preferably a copolymer containing propylene units and structural units (ethylene units) derived from ethylene monomers (propylene-ethylene random copolymer). The amount of ethylene units contained in 100% by weight of the random copolymer (ethylene content) is preferably 0 to 5.5% by weight, more preferably 0 to 3.0% by weight, and even more preferably 0 to 2.5% by weight. Alternatively, the polypropylene resin (A) may be a polypropylene resin (A1) containing ethylene homopolymer units in its molecule, as described later.

[0026] The polypropylene resin (A) may be (a) an unmodified polypropylene resin, or (b) a mixture of an unmodified polypropylene resin and a modified polypropylene resin. The modified polypropylene resin used in (b) a mixture with an unmodified polypropylene resin may be (i) a modified polypropylene resin obtained by the present manufacturing method, (ii) a graft copolymer of propylene and a monomer other than propylene, (iii) a modified polypropylene resin obtained by introducing a branched structure into an unmodified polypropylene resin by irradiating the unmodified polypropylene resin with radiation, or (iv) a mixture thereof.

[0027] Polypropylene resin (A) may have one or more structural units derived from monomers other than propylene monomers, in addition to propylene units, or may have one or more of these units. Monomers other than propylene monomers used in the manufacture of polypropylene resin (A) are sometimes referred to as "comonomers," and the "structural units derived from monomers other than propylene monomers" contained in polypropylene resin (A) are sometimes referred to as "comonomer units."

[0028] Examples of comonomers include the following monomers: (a) α-olefins having 2 or 4 to 12 carbon atoms, such as ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, and 1-decene; (b) cyclic olefins such as cyclopentene, norbornene, and tetracyclo[6,2,11,8,13,6]-4-dodecene; (c (d) Dienes such as 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, and (d) vinyl monomers such as vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, maleic acid, maleic anhydride, styrene monomers, vinyltoluene, divinylbenzene, etc.

[0029] Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and glycidyl acrylate.

[0030] Examples of methacrylate esters include methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and glycidyl methacrylate.

[0031] Examples of styrene monomers include styrene, methylstyrene, dimethylstyrene, alpha-methylstyrene, para-methylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, t-butylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and trichlorostyrene.

[0032] The polypropylene resin (A) preferably has structural units derived from α-olefins having 2 or 4 to 12 carbon atoms as comonomer units, more preferably has structural units derived from ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene and / or 1-decene, more preferably has structural units derived from ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene and / or 4-methyl-1-pentene, even more preferably has structural units derived from ethylene, 1-butene, isobutene and / or 1-pentene, and most preferably has structural units derived from ethylene and / or 1-butene. This configuration has the advantages of (a) obtaining a modified polypropylene resin or resin composition having high melt tension and low gel fraction, and (b) providing polypropylene resin extruded foam particles with excellent moldability from the obtained modified polypropylene resin or resin composition.

[0033] The polypropylene resin (A) preferably contains 90% by weight or more of propylene units, more preferably 93% by weight or more, even more preferably 95% by weight or more, and particularly preferably 97% by weight or more, of the total structural units contained in the polypropylene resin (A). This configuration has the advantage of yielding a modified polypropylene resin or resin composition having high melt tension and low gel fraction.

[0034] The melting point of the polypropylene resin (A) is not particularly limited. The melting point of the polypropylene resin (A) is preferably 130°C to 165°C, more preferably 135°C to 164°C, even more preferably 138°C to 163°C, and particularly preferably 140°C to 162°C. When the melting point of the polypropylene resin (A) is (a) 130°C or higher, there is no risk of reduced dimensional stability of the in-molded foamed molded article, there is no risk of insufficient heat resistance of the in-molded foamed molded article, and the compressive strength of the in-molded foamed molded article tends to be increased. When the melting point is 165°C or lower, it is possible to mold the extruded foamed particles at a relatively low vapor pressure, which has the advantage of allowing the extruded foamed particles to be molded using a general-purpose molding machine for polypropylene resin foamed particles.

[0035] In this specification, the melting point of polypropylene resin (A) is measured by differential scanning calorimetry (hereinafter referred to as the "DSC method"). The specific procedure is as follows: (1) Melt the polypropylene resin (A) by raising the temperature of 5-6 mg of polypropylene resin (A) from 40°C to 220°C at a heating rate of 10°C / min; (2) Then, crystallize the polypropylene resin (A) by lowering the temperature of the molten polypropylene resin (A) from 220°C to 40°C at a cooling rate of 10°C / min; (3) Then, further raise the temperature of the crystallized polypropylene resin (A) from 40°C to 220°C at a heating rate of 10°C / min. The temperature of the peak (melting peak) of the DSC curve of the polypropylene resin (A) obtained during the second heating (i.e., at (3)) can be determined as the melting point of the polypropylene resin (A). As a differential scanning calorimeter, for example, the DSC6200 model manufactured by Seiko Instruments Inc. can be used.

[0036] The melt flow rate (MFR) of the polypropylene resin (A) is not particularly limited, but is preferably 0.5 g / 10 min to 20.0 g / 10 min, more preferably 0.5 g / 10 min to 15.0 g / 10 min, even more preferably 0.5 g / 10 min to 12.0 g / 10 min, and particularly preferably 0.5 g / 10 min to 10.0 g / 10 min. When the MFR of the polypropylene resin (A) is (a) 0.5 g / 10 min or more, the resulting modified polypropylene resin or resin composition has the advantage of providing an in-molded foamed molded article with less deformation and good (beautiful) surface properties, and (b) when it is 20.0 g / 10 min or less, it has the advantage of obtaining polypropylene resin foamed particles with a lower open-cell ratio.

[0037] In this specification, the MFR value of polypropylene resin (A) is the value measured using an MFR measuring instrument described in JIS K7210, under conditions of an orifice diameter of 2.0959±0.0050 mmφ, an orifice length of 8.000±0.025 mm, a load of 2160 g, and a temperature of 230±0.2°C.

[0038] In one embodiment of the present invention, the polypropylene resin (A) may contain ethylene homopolymer units within its molecule (i.e., it may be polypropylene resin (A1)). In this specification, an ethylene homopolymer unit means a structural unit containing multiple ethylene units in a sequence. The number of consecutive ethylene units is not limited, but may be, for example, 2 to 3,000 or 10 to 2,500. When ethylene units are consecutively contained in the polypropylene resin (A1), it is presumed that the molecule appears to contain structural units derived from an ethylene homopolymer; therefore, in this specification, the term ethylene homopolymer unit is used. Furthermore, the polypropylene resin (A1) may be a resin obtained by actually polymerizing an ethylene homopolymer and the polypropylene resin (A).

[0039] Furthermore, in the polypropylene resin (A1) described above, structural units other than ethylene homopolymer units may be (i) propylene homopolymer units (structural units containing multiple propylene units in succession), or (ii) propylene random copolymer units (structural units in which multiple propylene units and comonomer units are randomly bonded together). These structural units other than ethylene homopolymer units are collectively referred to as polypropylene polymer units.

[0040] Polypropylene resin (A1) exhibits a peak originating from ethylene homopolymer units in the DSC curve obtained by the DSC method described above. That is, this polypropylene resin (A1) may have at least two peaks in the DSC curve: one originating from polypropylene polymer units and another from ethylene homopolymer units. Of these, the temperature of the peak originating from ethylene homopolymer units is preferably 120-140°C, more preferably 125-140°C, and even more preferably 130-140°C. Ethylene homopolymer units exhibiting such peak temperatures have a density of 0.925 g / cm³. 3 It is presumed that these correspond to the ethylene homopolymers described above. Examples of such ethylene homopolymers include high-density polyethylene (HDPE).

[0041] The area of ​​the peak originating from the ethylene homopolymer unit is preferably 1-40%, more preferably 2-35%, and even more preferably 2-30% of the total area of ​​the DSC curve. The area of ​​the peak is calculated as follows. Figure 1 is a schematic diagram illustrating the method for calculating the area of ​​the peak in the DSC curve. The DSC curve is obtained by the method described above. The DSC curve in Figure 1 is an example of a DSC curve obtained when the polypropylene resin (A1) is heated for the second time. A straight line (tangent) is drawn connecting the temperature before melting begins and the temperature after melting is completed in the DSC curve. The area enclosed by this tangent line and the DSC curve is taken as the total area of ​​the DSC curve. The DSC curve contains peaks originating from the ethylene homopolymer and peaks originating from the polypropylene polymer. The maximum value between the peak originating from the ethylene homopolymer and the peak originating from the polypropylene polymer is taken as the dividing point. The total area of ​​the DSC curve is divided by drawing a straight line that is the shortest distance from the dividing point to the tangent line. Of the divided areas, the area containing peaks originating from ethylene homopolymers is defined as the area of ​​peaks originating from ethylene homopolymer units.

[0042] (Ethylene-based polymer (C)) To obtain a modified polypropylene resin (B) or resin composition, an ethylene polymer (C) having an ethylene content exceeding 50% by weight may be used. In this specification, the ethylene content of the ethylene polymer (C) refers to the content of ethylene units in 100% by weight of the ethylene polymer (C). The ethylene content can be calculated by the method described in the examples below. Since the ethylene polymer (C) has an ethylene content exceeding 50% by weight, it can be distinguished from a polypropylene resin (A) containing 50% by weight or more of propylene units.

[0043] The ethylene polymer (C) may or may not contain structural units derived from monomers other than ethylene monomers. The ethylene content is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. There is no particular upper limit to the ethylene content, but it may be, for example, 100% by weight or less, or 95% by weight or less.

[0044] If the amount of ethylene polymer (C) used per 100 parts by weight of polypropylene resin (A) is 0.1 parts by weight or more, it has the advantage that a modified polypropylene resin (B) or resin composition with sufficient melt tension can be obtained even if the amount of radical polymerization initiator used is reduced. If the amount used is 13.0 parts by weight or less, it has the advantage that the excessive generation of gel due to crosslinking can be suppressed. The amount used is preferably 0.1 to 10.0 parts by weight, more preferably 0.1 to 5.0 parts by weight, even more preferably 0.1 to 4.0 parts by weight, particularly preferably 0.5 to 3.5 parts by weight, and most preferably 0.5 to 3.0 parts by weight.

[0045] Specifically, the ethylene polymer (C) includes at least one of ethylene-α-olefin elastomer (C1) and ethylene polymer (C2) having a peak at 120-140°C in the DSC curve obtained by the DSC method. As a result, the modified polypropylene resin (B) or resin composition has the advantage of exhibiting high melt tension. Furthermore, foamed particles with a low open-cell ratio can be obtained from the modified polypropylene resin (B) or resin composition.

[0046] In this specification, "elastomer" refers to a resin having a surface hardness (Shore A) of 70 to 95 as defined in ASTM D2240.

[0047] Examples of ethylene-α-olefin elastomers (C1) include (i) ethylene-α-olefin copolymers; (ii) ethylene-α-olefin-non-conjugated diene copolymers; and (iii) graft copolymers consisting of a main chain and side chains. Here, the (iii) graft copolymer is a vinyl polymer in which the main component constituting the main chain is an ethylene-α-olefin copolymer and / or an ethylene-α-olefin-non-conjugated diene copolymer, etc., and the main component constituting the side chain is at least one structural unit derived from at least one vinyl monomer. In (iii), the vinyl polymer may be a homopolymer or a copolymer. These may be used individually or in combination of two or more.

[0048] Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene. These α-olefins may be used individually or in combination of two or more. Examples of the non-conjugated dienes (non-conjugated diene compounds) include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene, ethylidenenorbornene, and vinylnorbornene. These non-conjugated dienes may be used individually or in combination of two or more.

[0049] Examples of ethylene-α-olefin copolymers include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer. Examples of ethylene-α-olefin-non-conjugated diene copolymers include ethylene-1-butene-non-conjugated diene copolymer and ethylene-propylene-non-conjugated diene copolymer.

[0050] The vinyl monomer is preferably at least one monomer selected from the group consisting of alkyl (meth)acrylate esters having an alkyl chain length of 1 to 20 carbon atoms, vinyl monomers having an acid group, vinyl monomers having a hydroxyl group, vinyl monomers having an epoxy group, vinyl monomers having a cyano group, and styrene. Specifically, examples of the vinyl monomer include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, meth)acrylic acid, maleic acid, maleic anhydride, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, meth)acrylonitrile, styrene, propylene, octene, and the like.

[0051] The ethylene content in the ethylene-α-olefin elastomer (C1) is preferably 80% by weight or more, and more preferably 90% by weight or more. The upper limit of the ethylene content in the ethylene-α-olefin elastomer (C1) is not particularly limited, but may be, for example, 99% by weight or less, or 95% by weight or less.

[0052] Ethylene-based polymers (C2) that have a peak at 120-140°C in the DSC curve obtained by the DSC method have a density of 0.925 g / cm³. 3 More than 0.97g / cm 3 The following ethylene-based polymers are preferred, with a density of 0.942 g / cm³. 3 More than 0.97g / cm 3The following ethylene-based polymers are more preferable. Furthermore, the peak temperature is more preferably 125-140°C, and even more preferably 130-140°C. The ethylene-based polymer (C2) may also be an ethylene homopolymer. Examples of such ethylene-based polymers (C2) include high-density polyethylene (HDPE). As raw materials for the modified polypropylene resin (B) or resin composition, low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), and linear low-density polyethylene (LLDPE) with a density of 0.925 g / cm³ are preferred. 3 It is preferable not to use resins with a density of less than 0.925 g / cm³. 3 For resins below a certain threshold, the peak temperature in the DSC curve may be outside the range of 120-140°C (e.g., 90-115°C).

[0053] The following describes the case where the above DSC method is performed using a mixture of polypropylene resin (A) and ethylene polymer (C2) instead of polypropylene resin (A1). In this case, a peak originating from the ethylene polymer (C2) may be present in the resulting DSC curve. That is, the mixture of polypropylene resin (A) and ethylene polymer (C2) may have at least two peaks in the DSC curve obtained during the second heating: one originating from polypropylene resin (A) and one originating from the ethylene polymer (C2). Of these, the temperature of the peak originating from the ethylene polymer (C2) may be between 120 and 140°C, or it may be between 125 and 140°C, or it may be between 130 and 140°C. The ethylene polymer (C2) exhibiting such a peak temperature has a density of 0.925 g / cm³. 3This is presumed to correspond to the ethylene homopolymer described above. In the DSC curve of a mixture of polypropylene resin (A) and ethylene polymer (C2), the area of ​​the peak originating from the ethylene polymer (C2) is preferably 1-40%, more preferably 2-35%, and even more preferably 2-30%, relative to 100% of the total area of ​​the DSC curve. The area of ​​this peak can be calculated in the same manner as the area of ​​the peak originating from the ethylene homopolymer unit in the DSC curve of the polypropylene resin (A1) described above. The area of ​​the peak originating from the ethylene polymer (C2) in the DSC curve of a mixture of polypropylene resin (A) and ethylene polymer (C2) has a high correlation with the content (ratio) of ethylene polymer (C2) in the mixture. If the area of ​​the peak originating from the ethylene polymer (C2) in the DSC curve of a mixture of polypropylene resin (A) and ethylene polymer (C2) is 1 to 40% of the total area of ​​the DSC curve, then it is highly probable that the amount of ethylene polymer (C2) in the mixture is 0.1 to 13.0 parts by weight per 100 parts by weight of polypropylene resin (A).

[0054] (Conjugated diene compounds) Examples of conjugated diene compounds that can be used in one embodiment of the present invention include butadiene, isoprene, 1,3-heptadiene, 2,3-dimethylbutadiene, and 2,5-dimethyl-2,4-hexadiene. These conjugated diene compounds may be used individually or in combination of two or more. Among these conjugated diene compounds, butadiene and isoprene are particularly preferred due to (a) their low cost and ease of handling, and (b) the fact that the reaction proceeds uniformly.

[0055] The amount of conjugated diene compound used is preferably 0.20 to 1.50 parts by weight, more preferably 0.25 to 0.80 parts by weight, and even more preferably 0.25 to 0.60 parts by weight, per 100 parts by weight of polypropylene resin (A). When the amount of conjugated diene compound used is 0.20 parts by weight or more per 100 parts by weight of polypropylene resin (A), the number of crosslinks introduced into the polypropylene resin (A) becomes sufficient, and as a result, the melt tension of the resulting modified polypropylene resin or resin composition can be sufficiently increased (for example, to 8 cN or more). When the amount of conjugated diene compound used is 1.50 parts by weight or less per 100 parts by weight of polypropylene resin (A), the crosslinking between polypropylene resins (A) by the conjugated diene compound is appropriate, and the viscosity of the resulting modified polypropylene resin or resin composition can be suppressed. As a result, it becomes easy to obtain high-magnification polypropylene resin extruded foam particles from the resulting modified polypropylene resin or resin composition. If the amount of conjugated diene compound used exceeds 1.50 parts by weight, a large amount of gel may be generated, which may cause the cells to rupture during foaming. As mentioned above, when using ethylene polymers (C), crosslinking can be performed between ethylene polymers (C) themselves, or between polypropylene resin (A) and ethylene polymers (C).

[0056] Within the limits of not impairing the effects of one embodiment of the present invention, in addition to the polypropylene resin (A), ethylene polymer (C), conjugated diene compound, and radical polymerization initiator, monomers copolymerizable with the conjugated diene compound may be used in combination. In other words, the resin mixture described later may further contain monomers copolymerizable with the conjugated diene compound. Examples of monomers copolymerizable with the conjugated diene compound include (a) acrylic acid esters such as vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, metal acrylate salts, metal methacrylate salts, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and stearyl acrylate, and (b) methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and stearyl methacrylate.

[0057] (Radical polymerization initiator) The radical polymerization initiator according to one embodiment of the present invention is preferably an organic peroxide having the ability to abstract hydrogen from a polypropylene resin (A), an ethylene polymer (C), and a conjugated diene compound. Suitable radical polymerization initiators used in one embodiment of the present invention include organic peroxides such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters.

[0058] As for organic peroxides, 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-butyl4,4-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, and 2,5-dimethyl-2,5- Suitable examples include dialkyl peroxides such as di(t-butylperoxy)-3-hexine; diacyl peroxides such as benzoyl peroxide; and peroxyesters such as t-butyl peroxyoctate, t-butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butyl peroxy 3,5,5-trimethylhexanoate, t-butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxyacetate, t-butyl peroxybenzoate, and di-t-butyl peroxyisophthalate. Among these, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, and 2,2-bis(t-butylperoxy)butane are preferred. These organic peroxides may be used individually or in combination of two or more.

[0059] The amount of radical polymerization initiator used is preferably 0.40 to 1.00 parts by weight, more preferably 0.50 to 1.00 parts by weight, and even more preferably 0.50 to 0.90 parts by weight, per 100 parts by weight of polypropylene resin (A). When the amount of radical polymerization initiator used is 0.40 parts by weight or more per 100 parts by weight of polypropylene resin (A), the number of crosslinks introduced into the polypropylene resin (A) can be sufficient. As a result, when the resulting modified polypropylene resin or resin composition is extruded and foamed, the modified polypropylene resin or resin composition exhibits sufficient strain hardening properties, and extruded foamed particles with a low open-cell ratio tend to be obtained. When the amount of radical polymerization initiator used is 1.00 part by weight or less per 100 parts by weight of polypropylene resin (A), the molecular weight of the resulting modified polypropylene resin does not decrease due to the appropriate abstraction of hydrogen from the polypropylene resin (A) by the radical polymerization initiator, and the modified polypropylene resin or resin composition can be obtained at low cost. As a result, when extruding foamed using the modified polypropylene resin or resin composition, there is a tendency to obtain extruded foamed particles with a high foaming ratio and a low open-cell ratio.

[0060] (resin mixture) In the method for producing the modified polyethylene resin or the resin composition, a mixture containing at least a polypropylene resin (A), a conjugated diene compound, and a radical polymerization initiator (and in one embodiment, an ethylene polymer (C)) is referred to as the resin mixture.

[0061] (Other ingredients) In the method for producing the modified polyethylene resin or the resin composition described herein, in addition to the polypropylene resin (A), ethylene polymer (C), conjugated diene compound, and radical polymerization initiator described above, other components may be used as needed. In other words, the resin mixture may further contain other components as needed. Examples of other components include (a) resins other than the polypropylene resin (A) and ethylene polymer (C) (sometimes referred to as "other resins"), (b) stabilizers such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, ultraviolet absorbers, ultraviolet stabilizers, fluorescent whitening agents, metal soaps, and antacid adsorbents, and / or (c) additives such as foam regulators, colorants, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, flame retardants, water-containing agents, and antistatic agents. Other resins include (a) polyolefin resins other than polypropylene resins (A) and ethylene polymers (C), (b) ethylene resins such as ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, and ethylene / methacrylic acid copolymers, and (c) styrene resins such as polystyrene, styrene / maleic anhydride copolymers, and styrene / ethylene copolymers. These other components may be used individually or in combination of two or more.

[0062] (Physical properties of modified polypropylene resins or resin compositions) The melt tension of the modified polypropylene resin or the resin composition is preferably 8.0 to 12.0 cN. When the melt tension of the modified polypropylene resin is as described above, the melt tension of the modified polypropylene resin during foaming is sufficiently high when polypropylene resin extruded foam particles are produced by an extrusion foaming method using the modified polypropylene resin. As a result, the obtained polypropylene resin extruded foam particles have the advantage of being able to sufficiently retain the cell film. The same advantages are obtained when the resin composition is used instead of the modified polypropylene resin. The lower limit of the melt tension is preferably 8.0 cN or higher, more preferably 8.2 cN or higher, more preferably 8.4 cN or higher, more preferably 8.6 cN or higher, more preferably 8.8 cN or higher, and even more preferably 9.0 cN or higher. The upper limit of the melt tension may be 11.8 cN or less, 11.6 cN or less, 11.4 cN or less, 11.2 cN or less, 11.0 cN or less, 10.5 cN or less, or 10.0 cN or less.

[0063] The break-down take-up rate of the modified polypropylene resin or the resin composition is preferably 7.0 m / min or less. According to the above configuration, when polypropylene resin extruded foam particles are produced by an extrusion foaming method using the modified polypropylene resin, there is an advantage that the degree of elongation of the modified polypropylene resin during foaming is sufficient to maintain the cell film, but not excessive. The same advantages are obtained when the resin composition is used instead of the modified polypropylene resin. The break-down take-up rate is more preferably 6.5 m / min or less, even more preferably 6.0 m / min or less, even more preferably 5.8 m / min or less, and particularly preferably 5.5 m / min or less. The break-down take-up rate may be 5.0 m / min or less, 4.8 m / min or less, 4.5 m / min or less, 4.3 m / min or less, or 4.0 m / min or less. The lower limit of the break-up rate may be 3.5 m / min or more, 3.8 m / min or more, 4.0 m / min or more, 4.2 m / min or more, 4.5 m / min or more, 4.7 m / min or more, 5.0 m / min or more, 5.2 m / min or more, or 5.5 m / min or more. The modified polypropylene resin or resin composition preferably has a melt tension of 8.0 to 12.0 cN and a break-up rate of 7.0 m / min or less.

[0064] The methods for measuring fusion tension and fracture take-up rate in this specification are described below. In this specification, fusion tension is measured using a Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd., Japan). Specifically, the procedure is as follows (1) to (5): (1) A 9.55 mm diameter barrel heated to the test temperature (200°C) is filled with the sample resin for measurement (this modified polypropylene resin or this resin composition); (2) The sample resin is then heated for 10 minutes in the barrel heated to the test temperature (200°C); (3) The sample resin is then dispensed in a string-like form from a capillary die (1.0 mm diameter, 10 mm length) at a constant piston descent speed (10 mm / min), and this string-like material is passed through a tension-detecting pulley located 350 mm below the capillary die, after which winding using a winding roll is started; (4) After the winding of the string-like material stabilizes, the winding speed of the string-like material is increased at a constant rate from an initial speed of 1.0 m / min to a speed of 200 m / min in 4 minutes; (5) The load on the load cell pulley when the string-like material breaks is measured as the melt tension. Furthermore, the winding speed at the time of breakage is measured as the breakage pull-up speed.

[0065] The MFR of the modified polypropylene resin or resin composition is not particularly limited, but is preferably 0.5 g / 10 min to 20.0 g / 10 min, more preferably 1.0 g / 10 min to 15.0 g / 10 min, more preferably 1.5 g / 10 min to 10.0 g / 10 min, even more preferably 1.5 g / 10 min to 6.0 g / 10 min, even more preferably 1.5 g / 10 min to 5.5 g / 10 min, and particularly preferably 2.0 g / 10 min to 5.0 g / 10 min. The MFR of the modified polypropylene resin or resin composition may be 2.2 g / 10 min or more, 2.4 g / 10 min or more, 2.6 g / 10 min or more, 2.8 g / 10 min or more, or 3.0 g / 10 min or more. The MFR of the modified polypropylene resin or the resin composition may be 4.8 g / 10 min or less, 4.6 g / 10 min or less, 4.4 g / 10 min or less, 4.2 g / 10 min or less, or 4.0 g / 10 min or less. When the MFR of the modified polypropylene resin is (a) 0.5 g / 10 min or more, the modified polypropylene resin has the advantage of being able to provide an in-molded foamed molded article with little deformation and good (beautiful) surface properties, and (b) when the MFR is 20.0 g / 10 min or less, the composition containing the modified polypropylene resin has the advantage of having good foaming properties when extruded foamed. The same advantages are obtained when the resin composition is used instead of the modified polypropylene resin. The modified polypropylene resin or resin composition preferably has a melt tension of 8.0 to 12.0 cN, a break-up rate of 7.0 m / min or less, and an MFR of 0.5 g / 10 min to 20.0 g / 10 min.

[0066] In this specification, the MFR of the modified polypropylene resin or the resin composition can be measured in the same manner as the MFR value of polypropylene resin (A), except that the modified polypropylene resin or the resin composition is used in place of polypropylene resin (A).

[0067] The shape and size of the modified polypropylene resin or the resin composition are not particularly limited and may be, for example, pellets. In this specification, pellets refer to small, granular molding materials having approximately constant length and thickness, such as cylindrical, spherical, elliptical, or polygonal prisms (e.g., triangular, square, pentagonal, or hexagonal prisms). The size of the pellets is not particularly limited as long as they can be handled, but examples include those with a length of approximately 2.5 mm to 3.5 mm and a thickness of approximately 2.5 mm to 3.5 mm.

[0068] (Application) Applications of this modified polypropylene resin or resin composition include extruded foam particles and extruded foam sheets. Extruded foam particles or extruded foam sheets can be obtained by extruding a composition containing this modified polypropylene resin and a foaming agent. This modified polypropylene resin can be used in injection foam molding, such as core-back molding, by using this modified polypropylene resin and a foaming agent. Because this modified polypropylene resin has high melt tension, the film obtained by molding this modified polypropylene resin into a film has the advantage of being difficult to tear. Therefore, this modified polypropylene resin can also be used for non-foamed films and surface coatings of paper. Furthermore, this modified polypropylene resin can also be used in ordinary injection molding (non-foamed). This resin composition can be used in the same way as this modified polypropylene resin.

[0069] [2. Method for producing modified polypropylene resin or resin composition] A method for producing a modified polypropylene resin (B1) according to one embodiment of the present invention comprises a melt-kneading step of melt-kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%).

[0070] A method for producing a resin composition according to one embodiment of the present invention includes a melt-kneading step of melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) may contain at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in the DSC curve obtained by differential scanning calorimetering. As described above, the polypropylene resin (A) to be reacted with this ethylene polymer (C) may be a polypropylene resin (A1) containing ethylene homopolymer units in its molecule, or it may be any other polypropylene resin.

[0071] In this specification, "Method for producing a modified polypropylene resin according to one embodiment of the present invention" and "Method for producing a resin composition according to one embodiment of the present invention" may be collectively referred to as "this manufacturing method."

[0072] This manufacturing method makes it possible to obtain a modified polypropylene resin or resin composition having high melt tension. In other words, this manufacturing method can provide the modified polypropylene resin or resin composition described in the section [1. Modified Polypropylene Resin or Resin Composition] above. Furthermore, the modified polypropylene resin obtained by this manufacturing method has the advantage of being able to provide polypropylene resin extruded foam particles with a low open-cell ratio. In addition, this manufacturing method has the advantage of being able to provide a modified polypropylene resin having high melt tension even when the amount of radical polymerization initiator used is reduced compared to conventional methods. In other words, this manufacturing method has the advantage of being able to obtain a modified polypropylene resin having high melt tension at a lower cost than conventional methods. The same advantages are obtained when obtaining a resin composition by this manufacturing method. In the following, "modified polypropylene resin" may be read as "resin composition".

[0073] (manufacturing equipment) The manufacturing apparatus used in this manufacturing method comprises, for example, a melt-mixing section having a screw and a die. Examples of the melt-mixing section include a single-screw extruder having a single screw and a multi-screw extruder having multiple screws (for example, a twin-screw extruder having two screws). Of these, a multi-screw extruder is preferred as the melt-mixing section, and a twin-screw extruder is more preferred, due to its ability to perform continuous mixing and its ease of scaling up.

[0074] The die of the manufacturing apparatus used in this manufacturing method is located at the end of the extrusion direction of the manufacturing apparatus and has at least one hole (sometimes referred to as an extrusion hole) for discharging the modified polypropylene resin. The number and diameter of the holes in the die, as well as the thickness of the die (length of the holes in the extrusion direction), are not particularly limited.

[0075] (Melting and mixing process) The melt-kneading process involves supplying "raw materials for modified polypropylene resin," which include a polypropylene resin (A), a conjugated diene compound, and a radical polymerization initiator, to a melt-kneading section and melt-kneading the resin mixture containing these raw materials within the melt-kneading section. Melt-kneading in the melt-kneading process means kneading the polypropylene resin (A), the resin mixture containing the conjugated diene compound, and the radical polymerization initiator within the melt-kneading section at a temperature at which the polypropylene resin (A) can melt. In one embodiment, the raw materials and resin mixture include the aforementioned ethylene polymer (C). The melt-kneading process can also be described as a process of preparing (obtaining) a modified polypropylene resin by reacting the polypropylene resin (A) (and the ethylene polymer (C)) with the conjugated diene compound and the radical polymerization initiator. As mentioned above, the ethylene polymer (C) may be polymerized with the polypropylene resin (A) beforehand. The descriptions in section 1. Modified Polypropylene Resins or Resin Compositions above may be appropriately applied to the embodiments of the polypropylene resin (A), ethylene polymer (C), conjugated diene compound, radical polymerization initiator, and other components.

[0076] The melt-mixing process refers to the period from when the unmelted polypropylene resin (A) and / or ethylene polymer (C) are introduced into the melt-mixing section until the modified polypropylene resin is introduced from the melt-mixing section into the die.

[0077] In the melt-mixing process, it is sufficient that a modified polypropylene resin is ultimately prepared. The specific methods for preparing the modified polypropylene resin by supplying the polypropylene resin (A), a conjugated diene compound, and a radical polymerization initiator to the raw material supply port of the melt-mixing section and melt-mixing these raw materials are not particularly limited, and examples include the following methods (a1) to (a4) (in one embodiment, an ethylene polymer (C) is supplied together with the polypropylene resin (A): (a1) A method for preparing a resin mixture by simultaneously or in any order mixing an unmelted polypropylene resin (A), a conjugated diene compound, and a radical polymerization initiator. Then, supplying the resin mixture to a melt-kneading section and melt-kneading the resin mixture to prepare a modified polypropylene resin; (a2) A method for preparing a modified polypropylene resin by supplying unmelted polypropylene resin (A) to a melt-kneading section and melt-kneading the polypropylene resin (A). Subsequently, a conjugated diene compound and a radical polymerization initiator are supplied to the melt-kneaded polypropylene resin (A) from the same or separate raw material supply ports located in the middle of the melt-kneading section, and the resulting resin mixture is further melt-kneaded; (a3) A method for preparing a modified polypropylene resin by supplying unmelted polypropylene resin (A) and a radical polymerization initiator to the melt-mixing section from the same or separate raw material supply ports, and melt-mixing the polypropylene resin (A) and the radical polymerization initiator. Subsequently, a conjugated diene compound is supplied to the melt-mixed mixture of polypropylene resin (A) and radical polymerization initiator from a raw material supply port located in the middle of the melt-mixing section, and the resulting resin mixture is further melt-mixed; (a4) A method for preparing a modified polypropylene resin by supplying unmelted polypropylene resin (A) and a conjugated diene compound to the melt-kneading section from the same or separate raw material supply ports, and melt-kneading the polypropylene resin (A) and the conjugated diene compound. Subsequently, a radical polymerization initiator is supplied to the melt-kneaded mixture of polypropylene resin (A) and conjugated diene compound from a raw material supply port located in the middle of the melt-kneading section, and the resulting resin mixture is further melt-kneaded.

[0078] In this manufacturing method, if other components are used as needed, the timing of supplying the other components to the melt-mixing section is not particularly limited. The other components may be added to the pre-prepared resin mixture in (i)(a1), and in (ii)(a2) to (a4), they may be supplied to the melt-mixing section together with or separately from the unmelted polypropylene resin (A), ethylene polymer (C), conjugated diene compound, or radical polymerization initiator from the same or separate raw material supply port.

[0079] Since the polypropylene resin (A) in the resin mixture becomes molten at the start of the reaction with the radical polymerization initiator, methods (a2) to (a4) are preferred. Depending on the properties of the radical polymerization initiator and conjugated diene compound used, method (a3) ​​is more preferred for raw material supply from a safety standpoint.

[0080] (Discharge process) This manufacturing method may include a dispensing step in which a modified polypropylene resin obtained by melt-kneading a resin mixture is extruded from a die. The dispensing step refers to the period from when the modified polypropylene resin enters the die from the melt-kneading section until the modified polypropylene resin is extruded from the die.

[0081] In the extrusion process, the modified polypropylene resin is extruded from the die in strand form at a temperature at which it can be extruded from the die's pores. By cooling and shredding the extruded strand-shaped modified polypropylene resin (also simply called "strand"), a modified polypropylene resin of the desired shape and size can be obtained. The method of cooling the strand is not particularly limited and includes water cooling using water. The strand may be shredded after cooling, or cooling and shredding may be performed simultaneously.

[0082] [3. Polypropylene resin extruded foam particles] Polypropylene resin extruded foam particles according to one embodiment of the present invention are obtained by extruding and foaming a modified polypropylene resin or resin composition described in section [1. Modified polypropylene resin or resin composition]. Polypropylene resin extruded foam particles according to one embodiment of the present invention can also be said to include a modified polypropylene resin or resin composition described in section [1. Modified polypropylene resin or resin composition].

[0083] Polypropylene resin extruded foam particles according to one embodiment of the present invention may have the following configuration: Polypropylene resin extruded foam particles obtained by extruding and foaming a modified polypropylene resin (B1), wherein the modified polypropylene resin (B1) is obtained by the reaction of a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, and the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) has a peak originating from the ethylene homopolymer units in a DSC curve obtained by differential scanning calorimetering, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%).

[0084] Furthermore, polypropylene resin extruded foam particles according to another embodiment of the present invention may have the following configuration: polypropylene resin extruded foam particles obtained by extruding foam a resin composition containing a modified polypropylene resin (B), wherein the resin composition is obtained by the reaction of 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) comprises at least one of an ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering, wherein the polypropylene resin extruded foam particles.

[0085] In this specification, "polypropylene-based resin extruded foam particles" may also be referred to as "extruded foam particles", and "polypropylene-based resin extruded foam particles produced by the production method described in the section of [4. Production method of polypropylene-based resin extruded foam particles]", that is, "polypropylene-based resin extruded foam particles according to an embodiment of the present invention" may also be referred to as "the present extruded foam particles".

[0086] Since the present extruded foam particles have the above-described configuration, they have the advantage of a low closed cell ratio.

[0087] (Closed cell ratio) The lower the closed cell ratio of the present extruded foam particles, the more preferable. The closed cell ratio of the present extruded foam particles is preferably 28.0% or less, more preferably 27.0% or less, still more preferably 26.0% or less, and particularly preferably 25.0% or less. The lower limit value of the closed cell ratio of the present extruded foam particles is not particularly limited, and is, for example, 0.0% or more. According to this configuration, (a) when the extruded foam particles are molded, the cells are hardly broken and shrunk, so that the extruded foam particles have the advantage of excellent moldability, and (b) in the foam molded body obtained by using the extruded foam particles, features such as shape arbitrariness, cushioning property, light weight, compressive strength, and heat insulation property are more exhibited.

[0088] In this specification, the closed cell ratio of polypropylene-based resin extruded foam particles is a value obtained by measuring according to the method described in PROCEDURE C of ASTM D2856-87 using an air comparison pycnometer [manufactured by Tokyo Science Co., Ltd., model 1000]. The closed cell ratio of the extruded foam particles is specifically calculated by performing the following (1) to (4) in order: (1) Measure the volume Vc (cm 3 ) of the extruded foam particles using an air comparison pycnometer; (2) Then, immerse the entire amount of the extruded foam particles after measuring Vc in ethanol contained in a graduated cylinder; (3) Thereafter, from the increase amount of the position of ethanol in the graduated cylinder, the apparent volume Va (cm 3(4) Determine the open-cell ratio of the extruded foamed particles using the following formula: Open cell percentage (%) = ((Va - Vc) × 100) / Va The method for measuring volume Va is also known as the immersion method.

[0089] (Expansion ratio) The foaming ratio of the extruded foam particles is preferably 2 to 45 times, more preferably 3 to 40 times, even more preferably 3 to 30 times, and particularly preferably 3 to 25 times. The above configuration has the advantage that the polypropylene resin molded foam article obtained using the extruded foam particles exhibits characteristics such as arbitrary shape, cushioning, lightness, and heat insulation. If the foaming ratio of the extruded foam particles obtained by the production of the extruded foam particles does not reach the above range, a method of increasing the foaming ratio by pressurizing the inside of the extruded foam particles with an inert gas and then heating the extruded foam particles is also available (for example, the method described in Japanese Patent Publication No. 10-237212).

[0090] In this specification, the foaming ratio of polypropylene resin extruded foam particles is calculated by the following method: (1) measure the weight w (g) of the extruded foam particles; (2) then immerse the extruded foam particles used for weight measurement in ethanol contained in a graduated cylinder, and calculate the volume v (cm³) of the extruded foam particles based on the rise in the liquid level in the graduated cylinder. 3 (3) measure the weight w (g) and the volume v (cm³). 3 (4) Divide by (ρ2 / ρ1) to calculate the density ρ1 of the extruded foam particles; (5) Divide the density ρ2 of the base resin of the extruded foam particles by the density ρ1 of the extruded foam particles (ρ2 / ρ1) and the resulting value is taken as the foaming ratio. In this specification, the base resin can also be said to be the resin component that substantially constitutes the extruded foam particles. The density ρ2 of the base resin is the density of a typical polypropylene resin, which is 0.9 g / cm³. 3 It is possible to adopt this.

[0091] [4. Method for producing polypropylene resin extruded foam particles] A method for producing polypropylene resin extruded foam particles according to one embodiment of the present invention includes an extrusion foaming step of extruding and foaming the modified polypropylene resin or resin composition described above. Specifically, a method for producing polypropylene resin extruded foam particles according to one embodiment of the present invention includes a first step of melting and kneading (a) a modified polypropylene resin or resin composition obtained by the manufacturing method described in section [2. Method for producing modified polypropylene resin or resin composition], or a modified polypropylene resin or resin composition described in section [1. Modified polypropylene resin or resin composition], and (b) a foaming agent in a manufacturing apparatus, and a second step of discharging the composition obtained in the first step through a die to a region where the pressure is lower than the internal pressure of the manufacturing apparatus. In the following, the modified polypropylene resin may be read as a resin composition.

[0092] A method for producing polypropylene resin extruded foam particles according to one embodiment of the present invention may have the following configuration: a melt kneading step to obtain a modified polypropylene resin (B1) by melt kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, and an extrusion foaming step to extrude and foam the modified polypropylene resin (B1), wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%), and the extrusion foaming step comprises a first step of melt kneading the modified polypropylene resin (B1) and a foaming agent in a manufacturing apparatus, and a second step of extruding the composition obtained in the first step through a die into a region with a pressure lower than the internal pressure of the manufacturing apparatus.

[0093] Furthermore, a method for producing polypropylene resin extruded foam particles according to another embodiment of the present invention may have the following configuration: a method for producing polypropylene resin extruded foam particles comprising: a melt-kneading step to obtain a resin composition containing a modified polypropylene resin (B) by melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator; and an extrusion foaming step to extrude and foam the resin composition, wherein the ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering, and the extrusion foaming step comprising: a first step of melt-kneading the resin composition and a foaming agent in a manufacturing apparatus; and a second step of extruding the composition obtained in the first step through a die into a region with a pressure lower than the internal pressure of the manufacturing apparatus.

[0094] (First step) The first step will now be explained in detail. A specific example of the first step is the process of melting the modified polypropylene resin in a manufacturing apparatus and dissolving the foaming agent into the modified polypropylene resin. The first step can also be described as the process of preparing a molten and kneaded mixture of the modified polypropylene resin and the foaming agent.

[0095] The blowing agent used in one embodiment of the present invention is not particularly limited, and known organic and inorganic blowing agents can be used. Examples of organic blowing agents include aliphatic hydrocarbons such as propane and butane, and fluorinated hydrocarbons such as difluoroethane. Examples of inorganic blowing agents include carbon dioxide, air, nitrogen and other inorganic gases, and water. The blowing agents described above may be used individually or in combination of two or more. The amount of blowing agent used in the first step may be appropriately adjusted according to the type of blowing agent and the target foaming ratio of the polypropylene resin extruded foam particles.

[0096] In the first step, if necessary, further nucleating agents, stabilizers (e.g., antioxidants, metal deactivators, phosphorus-based processing stabilizers, UV absorbers, UV stabilizers, fluorescent whitening agents, metal soaps, and antacid adsorbents) and additives (e.g., colorants, crosslinking agents, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants, and antistatic agents) may be used.

[0097] In the first step, the modified polypropylene resin and the blowing agent, as well as any other components that may be used, may be mixed before being supplied to the manufacturing apparatus, or they may be mixed within the manufacturing apparatus. In other words, in the first step, the composition may be supplied to the manufacturing apparatus, or the composition may be prepared (completed) within the manufacturing apparatus. In the first step, (i) the method and sequence of mixing the modified polypropylene resin and the blowing agent, as well as any other components that may be used, or (ii) the method and sequence of supplying the modified polypropylene resin and the blowing agent, as well as any other components that may be used, to the manufacturing apparatus is not particularly limited.

[0098] The composition obtained in the first step may be cooled before being extruded into a low-pressure region.

[0099] (Second step) The second step involves extruding the composition obtained in the first step, i.e., the melted and kneaded composition, through a die into a region with a pressure lower than the internal pressure of the manufacturing equipment, and then shredding the extruded composition. The second step yields extruded foam particles. Therefore, the second step can also be described as a granulation step for granulating polypropylene resin extruded foam particles.

[0100] In the second step, the region in which the composition obtained in the first step is extruded is not particularly limited, as long as the pressure is lower than the internal pressure of the manufacturing apparatus. For example, in the second step, the composition obtained in the first step may be extruded into the gas phase or into the liquid phase.

[0101] In the second step, the composition extruded into a region with a pressure lower than the internal pressure of the manufacturing apparatus immediately begins to foam. In the second step, the foaming composition may be shredded, or the foamed composition may be shredded. If the foaming composition is shredded, the shredded composition may complete foaming in the region to which it was extruded.

[0102] Depending on the region in which the composition obtained in the first step is extruded and the method of shredding the composition, the second step (granulation step) can be broadly classified into two types: the cold cut method and the die face cut method. An example of the cold cut method is a method in which the composition containing a foaming agent extruded from the die is foamed, and the strand-shaped foam is taken up while being cooled through a water tank and then shredded (strand cut method). The die face cut method is a method in which the composition extruded from the holes of the die is cut by a cutter that rotates while in contact with the surface of the die or while maintaining a small gap.

[0103] The die face cutting method can be further divided into the following three types based on differences in cooling methods: the underwater cut (sometimes referred to as UWC), the watering cut (sometimes referred to as WRC), and the hot cut (sometimes referred to as HC). The UWC method involves filling a chamber attached to the tip of the die with cooling water adjusted to a predetermined pressure so that it is in contact with the resin discharge surface of the die, and cutting the composition extruded from the hole in the die underwater. The WRC method involves placing a cooling drum downstream of the die through which cooling water flows along the inner circumference of the cooling drum connected to the die, and cooling the composition cut by the cutter in the air while foaming, or after foaming, in the cooling water. The HC method involves cutting the composition in the air with a cutter, and cooling the cut composition in the air while foaming, or after foaming. The HC method may also include the mist cut method, which further includes a step of spraying a mixed mist of water and air. The granulation method in the second step is preferably one or more selected from the group consisting of the HC method, the WRC method, and the UWC method.

[0104] [5. Polypropylene-based foamed molded articles] A polypropylene resin foam molded article according to one embodiment of the present invention is formed by molding polypropylene resin extruded foam particles as described in section [3. Polypropylene resin extruded foam particles].

[0105] In this specification, "polypropylene-based resin foamed molded article" may also be referred to as "foamed molded article," and "polypropylene-based resin foamed molded article according to one embodiment of the present invention" may also be referred to as "this foamed molded article." Furthermore, a foamed molded article obtained by manufacturing using a mold may also be referred to as an in-mold foamed molded article.

[0106] The polypropylene-based resin foam molded article according to one embodiment of the present invention has the above-described structure, and therefore has a high foaming ratio and excellent fusion properties.

[0107] [6. Method for manufacturing polypropylene resin foam molded articles] A method for producing a polypropylene resin foam molded article according to one embodiment of the present invention includes a heating step of filling a molding space formed from at least two molds of a mold with polypropylene resin extruded foam particles obtained by the manufacturing method described in section [4. Method for producing polypropylene resin extruded foam particles] or polypropylene resin extruded foam particles described in section [3. Polypropylene resin extruded foam particles], and then heating the polypropylene resin extruded foam particles in the molding space.

[0108] In a method for manufacturing a polypropylene resin foam molded article according to one embodiment of the present invention, the mold used is not particularly limited. The mold may consist of at least two molds, for example, a fixed mold that cannot be driven and a movable mold that can be driven. As the movable mold approaches the fixed mold, a molding space is formed inside the fixed mold and the movable mold. When the extruded foam particles in the molding space are heated, the mold frame of the fixed mold and the mold frame of the movable mold may come into contact (i.e., the mold may be closed but not airtight). On the other hand, when filling the molding space with extruded foam particles, the mold frame of the fixed mold and the mold frame of the movable mold do not need to come into contact, and a small gap (also called cracking) may be formed between the mold frame of the fixed mold and the mold frame of the movable mold.

[0109] In the method for manufacturing a polypropylene resin foam molded article according to one embodiment of the present invention, the method for filling the molding space with polypropylene resin extruded foam particles and the method for heating the polypropylene resin extruded foam particles in the mold are not particularly limited. Examples of these methods include the following (c1) to (c4).

[0110] (c1) A method in which extruded foam particles are pressurized with an inorganic gas in a container to impregnate the extruded foam particles with the inorganic gas and apply a predetermined internal pressure to the extruded foam particles. Subsequently, the extruded foam particles are filled into the molding space of a mold, and the extruded foam particles in the molding space are heated with steam; (c2) Fill the molding space of the mold with extruded foam particles. Then, compress the extruded foam particles in the molding space so that the volume of the molding space is reduced by 10% to 75%, and then heat the extruded foam particles in the molding space with steam; (c3) A method in which extruded foam particles are compressed with gas pressure and filled into the molding space of a mold. Subsequently, the extruded foam particles in the molding space are heated with steam, utilizing the recovery force of the extruded foam particles in the molding space; (c4) A method in which extruded foam particles are filled into the molding space of a mold without any special pretreatment, and then the extruded foam particles in the molding space are heated with steam.

[0111] In the manufacturing of this foamed molded product, the pressure of the steam used to heat the extruded foam particles (hereinafter sometimes referred to as the molding pressure) varies depending on the characteristics of the extruded foam particles used and cannot be specified in general terms.

[0112] In the method described in (c1) above, at least one inorganic gas selected from the group consisting of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, etc., can be used. Among these inorganic gases, air and / or carbon dioxide are preferred.

[0113] In the method (c1) described above, the internal pressure of the foamed particles is preferably 0.05 MPa to 0.30 MPa (gauge pressure), and preferably 0.06 MPa to 0.25 MPa (gauge pressure).

[0114] In the method (c1) described above, the temperature inside the container when impregnating the foamed particles with inorganic gas is preferably 10°C to 90°C, and more preferably 40°C to 90°C.

[0115] One embodiment of the present invention may have the following configuration: [1-1] Polypropylene resin extruded foam particles obtained by extruding and foaming a modified polypropylene resin (B1), wherein the modified polypropylene resin (B1) is obtained by the reaction of a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, and the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) has a peak originating from the ethylene homopolymer units in a DSC curve obtained by differential scanning calorimetering, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%). [1-2] The polypropylene resin extruded foam particles according to [1-1], wherein the modified polypropylene resin (B1) has a melt tension of 8.0 to 12.0 cN and a break-up rate of 3.5 m / min or more and 7.0 m / min or less. [1-3] Polypropylene resin extruded foam particles according to [1-1] or [1-2], wherein the melt flow rate of the modified polypropylene resin (B1) is 0.5 g / 10 min to 20.0 g / 10 min. [1-4] Polypropylene resin extruded foam particles obtained by extruding and foaming a resin composition containing a modified polypropylene resin (B), wherein the resin composition is obtained by the reaction of 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering, the polypropylene resin extruded foam particles. [1-5] Polypropylene resin extruded foam particles according to [1-4], wherein the melt tension of the resin composition is 8.0 to 12.0 cN and the break-up rate is 3.5 m / min or more and 7.0 m / min or less. [1-6] Polypropylene resin extruded foam particles according to [1-4] or [1-5], wherein the melt flow rate of the resin composition is 0.5 g / 10 min to 20.0 g / 10 min. [1-7] The polypropylene resin (A) is one or more selected from the group consisting of a homopolymer of propylene, and block polymers and random copolymers of propylene and monomers other than propylene, as described in any one of [1-4] to [1-6], the polypropylene resin extruded foam particles. [1-8] The polypropylene resin (A) has a melting point of 130°C to 165°C, as described in any one of [1-4] to [1-7], the polypropylene resin extruded foam particle. [1-9] Polypropylene resin extruded foam particles according to any one of [1-4] to [1-8], wherein the ethylene-α-olefin elastomer (C1) is one or more selected from the group consisting of (i) ethylene-α-olefin copolymer, (ii) ethylene-α-olefin-non-conjugated diene copolymer, and (iii) graft copolymer consisting of a main chain and side chains. [1-10] The ethylene-based polymer (C2) having a peak at 120-140°C in the DSC curve has a density of 0.925 g / cm³. 3 More than 0.97g / cm 3 Polypropylene resin extruded foam particles as described in any one of the following [1-4] to [1-9]. [1-11] Polypropylene resin extruded foam particles as described in any one of [1-1] to [1-10], wherein the open-cell ratio is 28.0% or less. [1-12] The polypropylene resin extruded foam particles according to any one of [1-1] to [1-11], wherein the radical polymerization initiator is an organic peroxide. [1-13] The polypropylene resin extruded foam particles according to [1-12], wherein the organic peroxide is one or more selected from the group consisting of ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, and peroxyester. [1-14] Polypropylene resin extruded foam particles as described in any one of [1-1] to [1-13], having an expansion ratio of 2 to 45 times. A polypropylene resin foam molded article obtained by molding polypropylene resin extruded foam particles described in any one of [1-15], [1-1], to [1-14]. [1-16] A method for producing polypropylene resin extruded foam particles, comprising: a melt-kneading step to obtain a modified polypropylene resin (B1) by melt-kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator; and an extrusion foaming step to extrude and foam the modified polypropylene resin (B1), wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, it has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%), and the extrusion foaming step comprises: a first step of melt-kneading the modified polypropylene resin (B1) and a foaming agent in a manufacturing apparatus; and a second step of extruding the composition obtained in the first step through a die into a region with a pressure lower than the internal pressure of the manufacturing apparatus. [1-17] The method for producing polypropylene resin extruded foam particles according to [1-16], wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A1). [1-18] The method for producing polypropylene resin extruded foam particles according to [1-16] or [1-17], wherein the amount of the conjugated diene compound used is 0.20 to 1.50 parts by weight per 100 parts by weight of the polypropylene resin (A1). [1-19] A method for producing polypropylene resin extruded foam particles, comprising: a melt-kneading step to obtain a resin composition containing a modified polypropylene resin (B) by melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator; and an extrusion foaming step to extrude and foam the resin composition, wherein the ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering, and the extrusion foaming step comprises a first step of melt-kneading the resin composition and a foaming agent in a manufacturing apparatus, and a second step of extruding the composition obtained in the first step through a die into a region with a pressure lower than the internal pressure of the manufacturing apparatus. [1-20] The method for producing polypropylene resin extruded foam particles according to [1-19], wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A). [1-21] The method for producing polypropylene resin extruded foam particles according to [1-19] or [1-20], wherein the amount of the conjugated diene compound used is 0.20 to 1.50 parts by weight per 100 parts by weight of the polypropylene resin (A). [1-22] The method for producing polypropylene resin extruded foam particles according to any one of [1-16] to [1-21], wherein the blowing agent is one or more selected from the group consisting of aliphatic hydrocarbons, fluorinated hydrocarbons, carbon dioxide, air, nitrogen, and water. [1-23] A method for producing polypropylene resin extruded foam particles according to any one of [1-16] to [1-22], wherein the granulation method in the second step is one or more selected from the group consisting of the hot cut method, the watering cut method, and the underwater cut method.

[0116] Furthermore, one embodiment of the present invention may have the following configuration. [2-1] Modified polypropylene resin (B1) obtained by reaction of a polypropylene resin (A1) with a conjugated diene compound and a radical polymerization initiator, wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) in a DSC curve obtained by differential scanning calorimetering, the peak has a peak originating from the ethylene homopolymer units, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%). [2-2] A modified polypropylene resin (B1) as described in [2-1], having a melt tension of 8.0 to 12.0 cN and a break-up rate of 7.0 m / min or less. [2-3] A resin composition comprising a modified polypropylene resin (B) obtained by the reaction of 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering. [2-4] The resin composition according to [2-3], wherein the melt tension is 8.0 to 12.0 cN and the break-up rate is 7.0 m / min or less. [2-5] A method for producing a modified polypropylene resin (B1), comprising a melt-kneading step of melt-kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, wherein the polypropylene resin (A1) (i) contains ethylene homopolymer units in its molecule, and (ii) has a peak originating from the ethylene homopolymer units in a DSC curve obtained by differential scanning calorimetering, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%). [2-6] The method for producing the modified polypropylene resin (B1) according to [2-5], wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A1). [2-7] A method for producing a resin composition containing a modified polypropylene resin (B), comprising a melt-kneading step of melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, wherein the ethylene polymer (C) includes at least one of ethylene-α-olefin elastomer (C1) and an ethylene polymer (C2) having a peak at 120 to 140°C in a DSC curve obtained by differential scanning calorimetering. [2-8] The method for producing the resin composition according to [2-7], wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A). Polypropylene resin extruded foam particles obtained by extruding and foaming a modified polypropylene resin (B1) described in [2-9], [2-1], or [2-2], or a resin composition described in [2-3] or [2-4]. A polypropylene resin foam molded article obtained by molding polypropylene resin extruded foam particles as described in [2-10] and [2-9]. [Examples]

[0117] One embodiment of the present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the following examples.

[0118] [Raw materials] <Polypropylene resin (A)> • RD265CF (manufactured by Borouge, ethylene content in polypropylene polymer units (ethylene content other than ethylene homopolymer units): 5.1% by weight, melting peaks: 128°C and 152°C, peak area in the range of 120-140°C: 3-30%) • F724NPC (manufactured by Prime Polymer, random polypropylene resin, ethylene content: 2.0 wt%, melting peak: 148°C) • E228 (Prime Polymer Co., Ltd., random polypropylene resin, ethylene content: 2.8% by weight, melting peak: 144°C) For convenience, RD265CF is listed under the category of polypropylene resin (A), but it is presumed that RD265CF is either a random polypropylene resin (polypropylene resin (A1)) containing ethylene homopolymer units in its molecule, or a mixture of random polypropylene resin (polypropylene resin (A)) and ethylene polymer (C2). Therefore, the 128°C melting peak observed in the DSC curve obtained by differential scanning calorimetering for RD265CF is either a peak originating from the ethylene homopolymer units contained in the molecule of RD265CF, or a peak originating from the ethylene polymer (C2) contained in the mixture RD265CF.

[0119] The methods for measuring the melting peak and peak area will be described later.

[0120] <Ethylene-based polymer (C)> • Tuffmer DF7350 (manufactured by Mitsui Chemicals, ethylene-1-butene copolymer, density: 0.870 g / cm³) 3 Shore A:70) • Tuffmer DF840 (manufactured by Mitsui Chemicals, ethylene-1-butene copolymer, density: 0.885 g / cm³) 3 Shore A:86) • Toughmer DF9200 (manufactured by Mitsui Chemicals, ethylene-1-butene copolymer, density: 0.893 g / cm³) 3 Shore A:92) • Novatec HD HJ490 (manufactured by Nippon Polyethylene Co., Ltd., HDPE, density: 0.958 g / cm³) 3 (Melting peak: 133℃) • Yumerit 613A (manufactured by Ube Maruzen Polyethylene Co., Ltd., LLDPE, density: 0.913 g / cm³) 3 (Melting peak: 113℃) • UBE Polyethylene J3524 (manufactured by Ube Maruzen Polyethylene Co., Ltd., LDPE, density: 0.924 g / cm³) 3 (Melting peak: 112℃) Ethylene-1-butene copolymers are classified as ethylene-α-olefin elastomers (C1). HDPE, LLDPE, and LDPE are classified as ethylene homopolymers. HDPE is classified as an ethylene-based polymer (C2) with a peak in the DSC curve between 120 and 140°C. The method for measuring the melting peak of ethylene homopolymers will be described later.

[0121] <Radical polymerization initiator> • Perbutyl I (manufactured by NOF Corporation) <Conjugated diene compounds> Isoprene [Measurement and evaluation methods] <Ethylene content in ethylene polymer (C)> The ethylene content in the Tuffmer series of ethylene-1-butene copolymers manufactured by Mitsui Chemicals was determined based on an approximate formula derived from the relationship between the butene content and density of Tuffmer DF640 and Tuffmer DF840. Based on its physical properties, Tuffmer DF640 is an ethylene-butene 1 copolymer (density 0.864 g / cm³) as described in the examples of Japanese Patent Publication No. 2019-172961. 3 Since it is presumed to be equivalent to ), the ethylene content was set to 80% by weight and the butene content to 20% by weight. Based on its physical properties, Tuffmer DF840 is the ethylene-butene 1 copolymer described in the examples of Japanese Patent Publication No. 2019-172961 (density 0.885 g / cm³). 3 Since it is presumed to be equivalent to ), the ethylene content was set to 90% by weight and the butene content to 10% by weight.

[0122] Here, Engage manufactured by Dow Chemical, which is an ethylene-octene copolymer, is known to have a correlation between the octene content and the density. The Toughmer series is an ethylene-1-butene copolymer and, like Engage, is an ethylene-α-olefin elastomer. Therefore, it is considered that there is a correlation between the butene content and the density in Toughmer. Thus, an approximate formula for the correlation between the butene content and the density in the Toughmer series was calculated from the values of the aforementioned Toughmer DF640 and Toughmer DF840. The approximate formula was as follows. Butene content [wt%] = -476.19 × density [g / cm 3 + 431.43 Based on this approximate formula, the butene content was calculated from the density in Toughmer DF9200 and Toughmer DF7350. Also, the ethylene content was calculated from this butene content.

[0123] Since Novatec HD HJ490, Umerit 613A, and UBE polyethylene J3524 are ethylene homopolymers, the ethylene content is 100 wt%.

[0124] <Melting peak and peak area in DSC curve> For RD265CF, the melting peak of the DSC curve was determined by the following procedure using a differential scanning calorimeter (DSC6200 type manufactured by Seiko Instruments Inc.): (1) RD265CF of 5 to 6 mg was melted by raising the temperature from 40°C to 220°C at a heating rate of 10°C / min; (2) thereafter, the melted RD265CF was crystallized by lowering the temperature from 220°C to 40°C at a cooling rate of 10°C / min; (3) thereafter, the temperature of the further crystallized RD265CF was raised from 40°C to 220°C at a heating rate of 10°C / min. The temperature of the peak (melting peak) of the DSC curve of the said RD265CF obtained during the second heating (i.e., in (3)) was determined. The melting peak temperatures of F724NPC and E228, as well as those of the ethylene homopolymer, were also determined in the same manner.

[0125] Furthermore, for RD265CF, the area of ​​the melting peak was determined by the following procedure. A straight line (tangent) was drawn connecting the temperature before the start of melting and the temperature after the end of melting in the DSC curve obtained during the second heating of RD265CF using the method described above. The area enclosed by this tangent line and the DSC curve was defined as the total area of ​​the DSC curve. The point of maximum value, which lies between the peak originating from the ethylene homopolymer and the peak originating from the polypropylene polymer in the DSC curve, was defined as the division point. The total area of ​​the DSC curve was divided by drawing a straight line that was the shortest distance from the division point to the tangent line. Of the divided area, the area containing the peak originating from the ethylene homopolymer was defined as the area of ​​the peak originating from the ethylene homopolymer unit.

[0126] <Melting tension and break-out rate> The melt tension was measured using a Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd., Japan). In the following, "modified polypropylene resin" may be read as "resin composition." Specifically, the procedure was as follows (1) to (5): (1) A 9.55 mm diameter barrel heated to 200°C was filled with the modified polypropylene resin obtained in each example or comparative example; (2) The modified polypropylene resin was then heated for 10 minutes in the barrel heated to the test temperature (200°C); (3) The modified polypropylene resin was then dispensed in a string-like form from a capillary die (1.0 mm diameter, 10 mm length) at a constant piston descent speed (10 mm / min), and this string-like material was passed through a tension-sensing pulley located 350 mm below the capillary die, after which winding using a winding roll was started; (4) After the winding of the string-like material stabilized, the winding speed of the string-like material was increased at a constant rate from an initial speed of 1.0 m / min to a speed of 200 m / min in 4 minutes; (5) The load on the load cell pulley when the string-like material broke was measured as the melt tension. Furthermore, the winding speed at the time of breakage was measured as the breakage pull-up speed.

[0127] <Foaming ratio> The expansion ratio of polypropylene resin extruded foam particles was calculated using the following method: (1) The weight w (g) of the extruded foam particles was measured; (2) Next, the extruded foam particles used for weight measurement were submerged in ethanol contained in a graduated cylinder, and the volume v (cm³) of the extruded foam particles was calculated based on the rise in the liquid level in the graduated cylinder. 3 (3) measured the weight w (g) and the volume v (cm³). 3 (4) The density ρ1 of the extruded foam particles was calculated by dividing by (ρ2 / ρ1) the density ρ2 of the base resin of the extruded foam particles by the density ρ1 of the extruded foam particles to obtain the foaming ratio. The density ρ2 of the base resin was set to the density of a typical polypropylene resin, which is 0.9 g / cm³. 3 We adopted it.

[0128] <Open cell ratio> The open-cell ratio of extruded foam particles was measured using an air-comparison hydrometer [Tokyo Science Co., Ltd., Model 1000] according to the method described in Procedure C of ASTM D2856-87. Specifically, the open-cell ratio of extruded foam particles was calculated by performing the following steps (1) to (3) in order: (1) Using an air-comparison hydrometer, the volume Vc (cm³) of the extruded foam particles was measured. 3 (1) The volume of the extruded foam particles after measuring Vc was measured; (2) Then, the entire volume of the extruded foam particles after measuring Vc was submerged in ethanol in a graduated cylinder; (3) After that, the apparent volume of the extruded foam particles Va (cm³) was determined from the amount of rise in the position of the ethanol in the graduated cylinder. 3 (4) The open-cell ratio of the extruded foamed particles was calculated using the following formula: Open cell percentage (%) = ((Va - Vc) × 100) / Va.

[0129] [Example 1] <Manufacturing of modified polypropylene resins or resin compositions> The modified polypropylene resin or resin composition of Example 1 (Modified PP-1) was produced by the following method. RD265CF was supplied to a twin-screw extruder, and then the amount of radical polymerization initiator shown in Table 1 per 100 parts by weight of RD265CF was supplied to the twin-screw extruder. Subsequently, the conjugated diene compound shown in Table 1 per 100 parts by weight of RD265CF was supplied to the melt-kneaded RD265CF and radical polymerization initiator to the twin-screw extruder, and the resin mixture was prepared in the twin-screw extruder. The supply rate of the resin mixture to the twin-screw extruder was 70 kg / h. Note that the supply rate of the resin mixture refers to the amount of resin mixture prepared per unit time in the twin-screw extruder at the time the conjugated diene compound is supplied to the twin-screw extruder.

[0130] The prepared resin mixture was melt-kneaded in a twin-screw extruder at a cylinder temperature of 180°C and a screw rotation speed of 230 rpm to obtain a modified polypropylene resin or resin composition (melt-kneading step). The obtained modified polypropylene resin or resin composition was extruded from a die in strand form at a discharge rate of 70 kg / h (extrusion step). The extruded modified polypropylene resin or resin composition (strands) was (a) water-cooled and then (b) shredded into pellets (cylindrical shapes).

[0131] <Manufacturing of extruded foamed particles> A resin mixture was prepared by blending 100 parts by weight of modified polypropylene resin or resin composition with 0.02 parts by weight of talc as a bubble nucleating agent. The resin mixture was then supplied from the raw material supply unit to a twin-screw extruder (melt-mixing unit), and melt-mixing of the resin mixture was started at a cylinder temperature of 180°C and a screw rotation speed of 80 rpm. The supply rate of the resin mixture to the twin-screw extruder was 0.75 kg / h. During the melt-mixing of the resin mixture, carbon dioxide was injected into the twin-screw extruder from the foaming agent supply unit as a foaming agent, and the resulting composition was further melt-mixed. The supply rate of the foaming agent to the twin-screw extruder was 0.0375 kg / h.

[0132] The melt-kneaded composition obtained through the melt-kneading process was passed through a die in the granulation section and discharged at a discharge rate of 0.75 kg / h into an air phase with a pressure lower than the internal pressure of the manufacturing apparatus. The extruded composition was shredded with a cutter in the air phase to obtain spherical or nearly spherical polypropylene resin extruded foam particles. The obtained polypropylene resin extruded foam particles were placed on the water surface flowing along the wall of the manufacturing apparatus and recovered by the water flow.

[0133] [Examples 2 and 3] The resin compositions of Examples 2 and 3 (Modified PP-2, Modified PP-3) were prepared by the following method. RD265CF and the ethylene polymer (C) shown in Table 1 were supplied to a twin-screw extruder. The amount of ethylene polymer (C) supplied was as shown in Table 1 per 100 parts by weight of RD265CF. Next, the radical polymerization initiator in the amount shown in Table 1 per 100 parts by weight of RD265CF was supplied to the twin-screw extruder. Subsequently, the conjugated diene compound in the amount shown in Table 1 per 100 parts by weight of RD265CF was supplied to the melt-kneaded RD265CF, ethylene polymer (C), and radical polymerization initiator to the twin-screw extruder. The resin compositions and polypropylene resin extruded foam particles were obtained in the same manner as in Example 1, except for the above steps.

[0134] [Examples 4-9, Comparative Examples 1-2] The resin compositions of Examples 4-9 (Modified PP-4-9) and Comparative Examples 1-2 (Modified PP-10-11) were prepared by the following method. Specifically, the resin compositions and polypropylene resin extruded foam particles were obtained in the same manner as in Examples 2 and 3, except that the polypropylene resin (A) shown in Table 1 was used instead of RD265CF, and the type and amount of ethylene polymer (C), as well as the amounts of radical polymerization initiator and conjugated diene compound, were changed as shown in Table 1.

[0135] [Reference Example 1, Comparative Examples 3-5] Modified polypropylene resins for Reference Example 1 (Modified PP-12) and Comparative Examples 3-5 (Modified PP-13-Modified PP-15) were produced by the following method. Specifically, modified polypropylene resins and polypropylene resin extruded foam particles were obtained in the same manner as in Example 1, except that polypropylene resin (A) shown in Table 1 was used instead of RD265CF, and the amounts of radical polymerization initiator and conjugated diene compound added were changed as shown in Table 1.

[0136] [Evaluation Results] Table 1 shows the composition and physical properties of modified PP-1 to modified PP-15.

[0137] [Table 1]

[0138] The foaming ratio and open-cell ratio of the polypropylene resin extruded foam particles obtained in Examples 1-9, Reference Example 1, and Comparative Examples 1-5 were measured using the method described above. The results are shown in Table 2.

[0139] [Table 2]

[0140] Modified PP-1 corresponds to a modified polypropylene resin (B1) obtained using a polypropylene resin (A1), or a resin composition obtained using a polypropylene resin (A) and an ethylene polymer (C2). Modified PP-2 and Modified PP-3 correspond to a resin composition obtained using a polypropylene resin (A1) and an ethylene-α-olefin elastomer (C1), or a resin composition obtained using a polypropylene resin (A), an ethylene polymer (C2), and an ethylene-α-olefin elastomer (C1). Modified PP-4 to Modified PP-9 correspond to a resin composition obtained using a polypropylene resin (A) and an ethylene-α-olefin elastomer (C1) or an ethylene polymer (C2). Therefore, Modified PP-1 to Modified PP-9 have high melt tension and low break-out rate even with a relatively small amount of radical polymerization initiator used. Furthermore, in Examples 1 to 9, foamed particles with a low open-cell ratio were obtained by using these modified polypropylene resins or resin compositions.

[0141] On the other hand, in Comparative Examples 1 and 2, modified PP-10 and modified PP-11 obtained using an ethylene-based polymer (C) that does not fall under either ethylene-α-olefin elastomer (C1) or ethylene-based polymer (C2) yielded foamed particles with a high open-cell ratio. In Comparative Examples 3 to 5, which did not use an ethylene-based polymer (C), modified polypropylene resins with high break-up rates were obtained, as well as foamed particles with a high open-cell ratio. When an ethylene-based polymer (C) was not used, it was not possible to suppress the open-cell ratio without using a large amount of radical polymerization initiator, as in Reference Example 1. [Industrial applicability]

[0142] According to one embodiment of the present invention, a novel modified polypropylene resin or resin composition with improved melt tension can be provided. Therefore, one embodiment of the present invention can be suitably used to obtain polypropylene resin extruded foam particles with a low open-cell ratio. Therefore, one embodiment of the present invention can be suitably used in fields such as automotive interior components, cushioning materials, packaging materials, and heat insulating materials.

Claims

1. Polypropylene resin extruded foam particles obtained by extruding and foaming a modified polypropylene resin (B1), The modified polypropylene resin (B1) is obtained by the reaction of a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator. The aforementioned polypropylene resin (A1) is (i) Contains ethylene homopolymer units within the molecule, (ii) Polypropylene resin extruded foam particles having a peak originating from the ethylene homopolymer unit in the DSC curve obtained by differential scanning calorimetering, the temperature of the peak being 120 to 140°C, and the area of ​​the peak being 1 to 40% of the total area of ​​the DSC curve (100%).

2. The polypropylene resin extruded foam particles according to claim 1, wherein the modified polypropylene resin (B1) has a melt tension of 8.0 to 12.0 cN and a break-taking rate of 7.0 m / min or less.

3. The polypropylene resin extruded foam particles according to claim 1 or 2, wherein the melt flow rate of the modified polypropylene resin (B1) is 0.5 g / 10 min to 20.0 g / 10 min.

4. Polypropylene resin extruded foam particles obtained by extruding and foaming a resin composition containing a modified polypropylene resin (B), The resin composition is obtained by the reaction of 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator. The ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and ethylene polymer (C2) having a peak at 120-140°C in the DSC curve obtained by differential scanning calorimetering, wherein the polypropylene resin extruded foam particles are provided.

5. The polypropylene resin extruded foam particles according to claim 4, wherein the melt tension of the resin composition is 8.0 to 12.0 cN and the break-up rate is 7.0 m / min or less.

6. The polypropylene resin extruded foam particles according to claim 4 or 5, wherein the melt flow rate of the resin composition is 0.5 g / 10 min to 20.0 g / 10 min.

7. Polypropylene resin extruded foam particles according to any one of claims 1 to 6, wherein the foaming ratio is 2 to 45 times.

8. A polypropylene resin foam molded article obtained by molding polypropylene resin extruded foam particles according to any one of claims 1 to 7.

9. A melt-kneading step to obtain a modified polypropylene resin (B1) by melt-kneading a polypropylene resin (A1), a conjugated diene compound, and a radical polymerization initiator, The process includes an extrusion foaming step of extruding and foaming the modified polypropylene resin (B1), The aforementioned polypropylene resin (A1) is (i) Contains ethylene homopolymer units within the molecule, (ii) In the DSC curve obtained by differential scanning calorimetering, there is a peak originating from the ethylene homopolymer unit, the temperature of the peak is 120 to 140°C, and the area of ​​the peak is 1 to 40% of the total area of ​​the DSC curve (100%). A method for producing polypropylene resin extruded foam particles, comprising: a first step of melting and kneading the modified polypropylene resin (B1) and a foaming agent in a manufacturing apparatus; and a second step of extruding the composition obtained in the first step through a die into a region where the pressure is lower than the internal pressure of the manufacturing apparatus.

10. The method for producing polypropylene resin extruded foam particles according to claim 9, wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A1).

11. The method for producing polypropylene resin extruded foam particles according to claim 9 or 10, wherein the amount of the conjugated diene compound used is 0.20 to 1.50 parts by weight per 100 parts by weight of the polypropylene resin (A1).

12. A melt-kneading step to obtain a resin composition containing a modified polypropylene resin (B) by melt-kneading 100 parts by weight of a polypropylene resin (A), 0.1 to 13.0 parts by weight of an ethylene polymer (C) having an ethylene content of more than 50% by weight, a conjugated diene compound, and a radical polymerization initiator, The process includes an extrusion foaming step of extruding and foaming the resin composition, The ethylene polymer (C) comprises at least one of ethylene-α-olefin elastomer (C1) and ethylene polymer (C2) having a peak at 120-140°C in the DSC curve obtained by differential scanning calorimetering. A method for producing polypropylene resin extruded foam particles, comprising: a first step of melting and kneading the resin composition and a foaming agent in a manufacturing apparatus; and a second step of extruding the composition obtained in the first step through a die into a region where the pressure is lower than the internal pressure of the manufacturing apparatus.

13. The method for producing polypropylene resin extruded foam particles according to claim 12, wherein the amount of radical polymerization initiator used is 0.40 to 1.00 parts by weight per 100 parts by weight of the polypropylene resin (A).

14. The method for producing polypropylene resin extruded foam particles according to claim 12 or 13, wherein the amount of the conjugated diene compound used is 0.20 to 1.50 parts by weight per 100 parts by weight of the polypropylene resin (A).

15. The method for producing polypropylene resin extruded foam particles according to any one of claims 9 to 14, wherein the foaming agent is one or more selected from the group consisting of aliphatic hydrocarbons, fluorinated hydrocarbons, carbon dioxide, air, nitrogen, and water.

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