Polypropylene resin foam particles, polypropylene resin foam molded articles, and methods for producing polypropylene resin foam particles

Abstract

The objective is to provide polypropylene resin foam particles that can provide polypropylene resin foam molded articles containing recycled resin and exhibiting excellent blackness and flame retardancy. [Solution] A base resin containing a predetermined amount of recycled resin and carbon black, wherein the structure size per structure is 1 × 10 in relation to the total number of carbon blacks. 4 nm 2 The present invention provides polypropylene resin foam particles in which the ratio of carbon black particles less than 10% to 50%.

Description

[Technical Field]

[0001] The present invention relates to polypropylene resin foam particles, polypropylene resin foam molded articles, and a method for producing polypropylene resin foam particles. [Background technology]

[0002] Polypropylene-based foamed molded products are used in a variety of applications, including automotive interior components, core materials for automotive bumpers, as well as insulation materials, cushioning packaging materials, and reusable containers (for example, Patent Document 1).

[0003] In recent years, in order to reduce environmental impact, there has been a demand for the use of recycled resins when manufacturing resin products, and the use of recycled resins has attracted attention (for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] WO2006 / 075491 publication [Patent Document 2] Japanese Patent Publication No. 2011-173273 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when polypropylene resin foam molded articles were produced using recycled polypropylene resin, the blackness and flame retardancy of the polypropylene resin foam molded articles were not sufficient, and there was room for further improvement.

[0006] One embodiment of the present invention has been made in view of the above-mentioned problems, and its objective is to provide polypropylene resin foam particles that can provide a polypropylene resin foam molded article containing recycled resin and having excellent blackness and flame retardancy. [Means for solving the problem]

[0007] The polypropylene-based resin foam particles according to an embodiment of the present invention are polypropylene-based resin foam particles containing a base resin and carbon black, wherein the base resin includes a non-recycled polypropylene-based resin and a recycled polypropylene-based resin and / or a recycled polyethylene-based resin, and the total content of the recycled polypropylene-based resin and the recycled polyethylene-based resin is 10 parts by weight to 60 parts by weight in 100 parts by weight of the base resin, and the carbon black has a structure size per structure of 1×10 4 nm 2 Less than that, and the ratio of the number of carbon black particles is 10% to 50%.

[0008] The method for producing polypropylene-based resin foam particles according to an embodiment of the present invention includes a granulation step of melt-kneading a mixture containing a non-recycled polypropylene-based resin, a recycled material, and carbon black A having an average structure size of 0.2×10 4 nm 2 or more and 4.0×10 4 nm 2 Less than that to obtain polypropylene-based resin particles, a dispersion step of dispersing the polypropylene-based resin particles, an aqueous dispersion medium, and a foaming agent in a container, a heating step of heating the temperature in the container to a temperature not lower than the softening temperature of the polypropylene-based resin particles, a pressurization step of pressurizing the pressure in the container, and a discharging step of releasing one end of the container and discharging the dispersion liquid in the container to a region having a pressure lower than the pressure in the container. The recycled material includes a recycled polypropylene-based resin and / or a recycled polyethylene-based resin, and has an average structure size of 5.0×10 4 nm 2 or more and 9.0×10 4 nm 2The material includes carbon black B which is less than 100 parts by weight, and the amount of recycled material used is such that the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight in 100 parts by weight of a base resin which includes the non-recycled polypropylene resin and the recycled polypropylene resin and / or the recycled polyethylene resin.

[0009] One embodiment of the present invention includes the following configuration: [Effects of the Invention]

[0010] According to one embodiment of the present invention, it is possible to provide polypropylene resin foam particles that contain recycled resin and have excellent blackness and flame retardancy, thereby providing a polypropylene resin foam molded article. [Modes for carrying out the invention]

[0011] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic and patent documents mentioned herein are incorporated herein by reference. Furthermore, unless otherwise specified herein, "A to B" representing a numerical range means "A or greater (including A and greater than A) and B or less (including B and less than B)."

[0012] In this specification, a "constituent unit derived from X monomer" contained in a polymer, copolymer, or resin may be referred to as an "X unit."

[0013] Unless otherwise specified herein, the constituent units are X1 Units and X 2 Units, and... and X n A copolymer containing units (where n is an integer greater than or equal to 2) is called "X 1 / X 2 / ··· / X n It is also called a "polymer." 1 / X 2 / ··· / X n Unless otherwise specified, the polymerization mode of the copolymer is not particularly limited and may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

[0014] [1. Polypropylene resin foam particles] Polypropylene resin foam particles according to one embodiment of the present invention are polypropylene resin foam particles containing a base resin and carbon black, wherein the base resin includes a non-recycled polypropylene resin, a recycled polypropylene resin and / or a recycled polyethylene resin, the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight per 100 parts by weight of the base resin, and the carbon black has a structure size of 1 × 10 per structure relative to the total number of carbon blacks. 4 nm 2 The proportion of carbon black particles that fall below a certain threshold is between 10% and 50%.

[0015] Polypropylene-based resin foam particles according to one embodiment of the present invention can be molded by a known method to provide a polypropylene-based resin foam molded article.

[0016] In this specification, "polypropylene resin foam particles" may be referred to as "foam particles," "polypropylene resin foam particles according to one embodiment of the present invention" may be referred to as "the foam particles," and "polypropylene resin foam molded article" may be referred to as "foam molded article."

[0017] Because these foamed particles have the above-described structure, they have the advantage of providing a foamed molded article that is excellent in both blackness and flame retardancy. Furthermore, as mentioned above, these foamed particles contain recycled polypropylene resin and / or recycled polyethylene resin. Therefore, these foamed particles can be said to have a low environmental impact. In other words, because one embodiment of the present invention uses recycled polypropylene resin and / or recycled polyethylene resin, this embodiment of the present invention not only reduces environmental pollution but can also significantly reduce the amount of plastic waste generated and the amount of plastic used in its manufacture. As a result, this embodiment of the present invention can contribute to achieving, for example, Sustainable Development Goal (SDG) 12, "Ensure sustainable consumption and production patterns," and Goal 14, "Conserve and sustainably use the oceans, seas and marine resources for sustainable development."

[0018] <Ingredients> (2-1. Base resin) In this specification, the base resin refers to the resin components that substantially constitute polypropylene resin particles, polypropylene resin foam particles, and polypropylene resin foam molded articles. The base resin includes at least a non-recycled polypropylene resin and a recycled polypropylene resin and / or a recycled polyethylene resin.

[0019] In this specification, "polypropylene resin" refers to a resin that contains 50 mol% or more of propylene units out of 100 mol% of all constituent units of the resin.

[0020] In this specification, "structural units derived from propylene monomers" may also be referred to as "propylene units."

[0021] In this specification, "polyethylene resin" refers to a resin that contains 50 mol% or more of ethylene units out of 100 mol% of all constituent units of the resin.

[0022] In this specification, "structural units derived from ethylene monomers" may also be referred to as "ethylene units."

[0023] In this specification, a resin in which 100 mol% of the total structural units constituting the resin consist of 50 mol% propylene units and 50 mol% ethylene units is referred to as a "polypropylene resin."

[0024] In this specification, "recycled polypropylene resin" refers to a polypropylene resin that has gone through the form of a polypropylene resin product at least once (for example, foamed particles, foamed molded articles, films, packaging containers such as food trays and bags and bottles, miscellaneous goods such as clothing cases and clear files, etc.) and then returned to the form of a polypropylene resin (or polypropylene resin particles) by means of melting or other means. In this specification, "recycled polyethylene resin" refers to a polyethylene resin that has gone through the form of a polyethylene resin product at least once (for example, foamed particles, foamed molded articles, films, packaging containers such as food trays and bags and bottles, miscellaneous goods such as clothing cases and clear files, etc.) and then returned to the form of a polyethylene resin (or polyethylene resin particles) by means of melting or other means. In this specification, recycled polypropylene resin or recycled polyethylene resin may also be referred to as "recycled resin," and recycled polypropylene resin and recycled polyethylene resin may also be referred to collectively as "recycled resin." In this specification, "non-recycled polypropylene resin" refers to a polypropylene resin that has never gone through the form of a polypropylene resin product.

[0025] The method for producing recycled resin, in other words, the method for recycling polypropylene-based resin products and polyethylene-based resin products, is not particularly limited and any known method can be used. For example, this could include methods for crushing and melting polypropylene-based resin products or polyethylene-based resin products, or methods for shredding these products.

[0026] (Structure of polypropylene resin) In this section only, unless otherwise specified, "polypropylene resin" refers to both non-recycled and recycled polypropylene resins. The structure of polypropylene resins is described below.

[0027] The polypropylene resin may be (i) a homopolymer of propylene, (ii) a block copolymer, alternating copolymer, random copolymer or graft copolymer of propylene and a monomer other than propylene, or (iii) a mixture of two or more of these.

[0028] Polypropylene resins may contain one or more constituent units derived from monomers other than propylene monomers, in addition to propylene units, or may contain one or more of these units. Monomers other than propylene monomers used in the manufacture of polypropylene resins are sometimes referred to as "comonomers." Constituent units derived from monomers other than propylene monomers contained in polypropylene resins are sometimes referred to as "comonomer units."

[0029] Examples of comonomers include 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.

[0030] Specific examples of polypropylene resins include polypropylene homopolymers, ethylene / propylene block copolymers, 1-butene / propylene block copolymers, ethylene / 1-butene / propylene block copolymers, ethylene / propylene alternating copolymers, 1-butene / propylene alternating copolymers, ethylene / 1-butene / propylene alternating copolymers, ethylene / propylene random copolymers, 1-butene / propylene random copolymers, ethylene / 1-butene / propylene random copolymers, propylene / chlorinated vinyl copolymers, propylene / maleic anhydride copolymers, and styrene-modified polypropylene resins. These polypropylene resins may be used individually or in combination of two or more types.

[0031] From the viewpoint of moldability, it is preferable that the non-recycled polypropylene resin is (a) an alternating copolymer composed of propylene units and comonomer units, in which both units are arranged alternately, and / or (b) a random copolymer composed of propylene units and comonomer units, in which both units are arranged in a random order. Because it is readily available, it is more preferable that the non-recycled polypropylene resin contains one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer.

[0032] From the viewpoint of moldability and availability, the non-recycled polypropylene resin preferably contains 60% by weight or more of one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer, in a quantity of 100% by weight of the non-recycled polypropylene resin, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. Most preferably, the non-recycled polypropylene resin consists of only one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer.

[0033] From the viewpoint of moldability, it is preferable that the recycled polypropylene resin is (a) a block copolymer composed of propylene units and comonomer units, comprising a block structure consisting only of propylene units and a block structure consisting only of comonomer units, (b) an alternating copolymer composed of propylene units and comonomer units, in which both units are arranged alternately, and / or (c) a random copolymer composed of propylene units and comonomer units, in which both units are arranged in a random order. In the block copolymer, the arrangement order of the block structure consisting only of propylene units and the block structure consisting only of comonomer units is not particularly limited. Because it is readily available, it is more preferable that the recycled polypropylene resin contains one or more selected from the group consisting of ethylene / propylene block copolymer, ethylene / 1-butene / propylene block copolymer, ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer.

[0034] From the viewpoint of moldability and availability, recycled polypropylene resin preferably contains 60% by weight or more of one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / propylene random copolymer, in a quantity of 100% by weight of the recycled polypropylene resin, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. Most preferably, the recycled polypropylene resin consists of only one or more selected from the group consisting of ethylene / propylene block copolymer, ethylene / 1-butene / propylene block copolymer, ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer.

[0035] (Physical properties of non-recycled polypropylene resins) The melting point of the non-recycled polypropylene resin according to one embodiment of the present invention is not particularly limited, but is preferably 135°C to 160°C, more preferably 137°C to 155°C, and even more preferably 139°C to 153°C. If the melting point of the non-recycled polypropylene resin is (i) 135°C or higher, the foamed molded article obtained from the foamed particles has excellent heat resistance, and if it is 160°C or lower, it becomes easier to increase the foaming ratio of the foamed particles in the production of the foamed particles.

[0036] In this specification, the melting point of non-recycled polypropylene resin is a value obtained by measurement using differential scanning calorimetry (hereinafter referred to as the "DSC method"). The specific operating procedure is as follows: (1) The non-recycled polypropylene resin is melted by raising the temperature of 5 mg to 6 mg of non-recycled polypropylene resin from 40°C to 220°C at a heating rate of 10°C / min; (2) The molten non-recycled polypropylene resin is then crystallized by lowering the temperature of the non-recycled polypropylene resin from 220°C to 40°C at a cooling rate of 10°C / min; (3) The crystallized non-recycled polypropylene resin is then further heated 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 non-recycled polypropylene resin obtained during the second heating (i.e., at (3)) can be determined as the melting point of the non-recycled polypropylene resin. Furthermore, if multiple peaks (melting peaks) exist in the DSC curve of the non-recycled polypropylene resin obtained during the second heating cycle using the method described above, the temperature of the peak with the largest heat of fusion (melting peak) is defined as the melting point of the non-recycled polypropylene resin. As a differential scanning calorimeter, for example, the DSC7020 manufactured by Hitachi High-Tech Science Corporation can be used.

[0037] The MFR at 230°C of the non-recycled polypropylene resin used in one embodiment of the present invention is not particularly limited, but is preferably 1 g / 10 min to 40 g / 10 min, more preferably 2 g / 10 min to 35 g / 10 min, even more preferably 3 g / 10 min to 30 g / 10 min, and particularly preferably 3 g / 10 min to 10 g / 10 min. When the MFR at 230°C of the non-recycled polypropylene resin is 1 g / 10 min or more, it tends to be easier to increase the foaming ratio of the foam particles in the production of these foam particles. When the MFR at 230°C of the non-recycled polypropylene resin is 40 g / 10 min or less, there is no risk of the bubbles in the resulting foam particles becoming interconnected, and as a result, (i) the compressive strength of the foam molded article obtained from these foam particles tends to be good, or (ii) the surface quality of the foam molded article tends to be good. In this specification, the "bubbles" of the foam particles may also be referred to as "cells". In other words, in this specification, "bubble" may be read as "cell," and "cell" may be read as "bubble."

[0038] Furthermore, consider the case where the MFR of the non-recycled polypropylene resin at 230°C is in the range of 1 g / 10 min to 40 g / 10 min. In this case, it is easy to obtain polypropylene resin foam particles with a relatively large foaming ratio. Moreover, in this case, the foam molded product obtained from these foam particles has the advantage of having excellent surface quality and a small dimensional shrinkage rate.

[0039] In this specification, the MFR value of non-recycled polypropylene resin at 230°C is the value obtained by measuring using the MFR measuring instrument described in JIS K7210:1999 under the following conditions: orifice diameter of 2.0959 ± 0.005 mmφ, orifice length of 8.000 ± 0.025 mm, load of 2.16 kgf, and temperature of 230°C (230 ± 0.2°C).

[0040] (Physical properties of recycled polypropylene resin) The melting point of the recycled polypropylene resin according to one embodiment of the present invention is not particularly limited, but is preferably 135°C to 160°C, more preferably 137°C to 155°C, and even more preferably 139°C to 153°C. If the melting point of the recycled polypropylene resin is (i) 135°C or higher, the foamed molded article obtained from the foamed particles has excellent heat resistance, and if it is 160°C or lower, it becomes easier to increase the foaming ratio of the foamed particles in the production of the foamed particles.

[0041] In this specification, the melting point of recycled polypropylene resin is determined by the DSC method described above, in the same way as the melting point of non-recycled polypropylene resin, except when recycled polypropylene resin is used instead of non-recycled polypropylene resin.

[0042] The MFR at 230°C of the recycled polypropylene resin used in one embodiment of the present invention is not particularly limited, but is preferably 1 g / 10 min to 40 g / 10 min, more preferably 2 g / 10 min to 35 g / 10 min, even more preferably 3 g / 10 min to 30 g / 10 min, and particularly preferably 3 g / 10 min to 10 g / 10 min. When the MFR at 230°C of the recycled polypropylene resin is (a) 1.0 g / 10 min or more, it has the advantage that it is easy to increase the foaming ratio of the foamed particles in the production of the foamed particles, and (b) when it is 40.0 g / 10 min or less, it has the advantage that there is no risk of the bubbles of the resulting foamed particles becoming interconnected.

[0043] In this specification, the MFR value of recycled polypropylene resin at 230°C is obtained by measuring it in the same way as the MFR of non-recycled polypropylene resin at 230°C, except that recycled polypropylene resin is used instead of non-recycled polypropylene resin.

[0044] Non-recycled polypropylene resins can be obtained by known methods. There are no particular restrictions on the polymerization catalyst used when synthesizing polypropylene resins; Ziegler catalysts and the like can be used.

[0045] The base resin preferably contains 80 to 100 parts by weight, and more preferably 90 to 100 parts by weight, of polypropylene resin (non-recycled polypropylene resin and recycled polypropylene resin) per 100 parts by weight of the base resin. This configuration has the advantage of minimizing the reduction in strength of the resulting foamed molded article.

[0046] The base resin comprises at least one of recycled polypropylene resin and recycled polyethylene resin. The base resin may further comprise non-recycled polyethylene resin. In this specification, "non-recycled polyethylene resin" means polyethylene resin that has never been in the form of a polyethylene resin product.

[0047] (Structure of polyethylene resin) In this section only, unless otherwise specified, "polyethylene resin" refers to both non-recycled and recycled polyethylene resins. The structure of polyethylene resin is described below.

[0048] The polyethylene resin may be (a) a homopolymer of ethylene, (b) a block copolymer, alternating copolymer, random copolymer or graft copolymer of ethylene and monomers other than ethylene, or (c) a mixture of two or more of these.

[0049] Polyethylene resins may contain one or more structural units derived from monomers other than ethylene monomers, in addition to ethylene units, and may contain one or more of these units. The "structural units derived from monomers other than ethylene monomers" contained in polyethylene resins are sometimes referred to as "comomeron units."

[0050] Examples of comonomers include (a) α-olefins having 3 to 12 carbon atoms, such as propylene, 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, and (b) vinyl monomers such as vinyl acetate.

[0051] Specific examples of polyethylene resins include (a) polyethylene homopolymers, (b) ethylene / α-olefin copolymers such as ethylene / propylene block copolymer, 1-butene / ethylene block copolymer, ethylene / 1-butene / propylene block copolymer, ethylene / propylene alternating copolymer, 1-butene / ethylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, 1-butene / ethylene random copolymer, and ethylene / 1-butene / propylene random copolymer, (c) ethylene / vinyl unit copolymers such as ethylene / chlorinated vinyl copolymer and ethylene / maleic anhydride copolymer, (d) styrene-modified polyethylene resins, and (e) chlorinated polyethylene. These polyethylene resins may be used individually or in combination of two or more types.

[0052] Polyethylene resins can also be categorized into high-density polyethylene (HDPE or PE-HD), medium-density polyethylene (MDPE or PE-MD), and low-density polyethylene (LDPE or PE-LD), depending on their density. JIS K 6760 specifies the density ranges for HDPE, MDPE, and LDPE as follows: HDPE: 942 kg / m³ 3 Above, MDPE:930kg / m 3 More than 942kg / m 3 Less than LPDE: 910 kg / m 3 More than 930kg / m 3 It is defined as less than.

[0053] Low-density polyethylene (LPDE) can be further classified into (a) low-density polyethylene produced by a high-pressure method and having long-chain branches in addition to short-chain branches such as ethyl groups (hereinafter also referred to as branched low-density polyethylene), and (b) low-density polyethylene produced using a transition metal catalyst at medium or low pressure and having short-chain branches (hereinafter also referred to as linear low-density polyethylene (LLDPE or PE-LLD)). Branched low-density polyethylene is a homopolymer of polyethylene. Linear low-density polyethylene is a copolymer obtained by linearly polymerizing ethylene with α-olefins such as 1-butene, 1-hexene, and / or 4-methyl-1-pentene, and has short-chain branches derived from the side chains of the α-olefin. Therefore, linear low-density polyethylene can also be called an ethylene / α-olefin copolymer.

[0054] The recycled polyethylene resin may contain one or more types selected from the group consisting of high-density polyethylene, medium-density polyethylene, and low-density polyethylene.

[0055] (Physical properties of recycled polyethylene resin) In one embodiment of the present invention, the melting point of the recycled polyethylene resin is not particularly limited, but is preferably 100°C to 140°C, and more preferably 110°C to 130°C. When the melting point of the recycled polyethylene resin is (a) 100°C or higher, it has the advantage that the impact resistance of the foamed molded article does not decrease easily, and (b) when it is 140°C or lower, it has the advantage that the surface of the foamed molded article has good elongation.

[0056] In this specification, the melting point of recycled polyethylene resin is determined by the DSC method described above, in the same way as the melting point of non-recycled polypropylene resin, except when recycled polyethylene resin is used instead of non-recycled polypropylene resin.

[0057] In one embodiment of the present invention, the total content of recycled polypropylene resin and recycled polyethylene resin is 10 to 60 parts by weight, preferably 10 to 60 parts by weight, more preferably 15 to 60 parts by weight, even more preferably 18 to 60 parts by weight, and particularly preferably 20 to 60 parts by weight, per 100 parts by weight of the base resin. This configuration has the advantage of further reducing the burden on the environment.

[0058] In one embodiment of the present invention, when the total content of recycled polypropylene resin and recycled polyethylene resin is 100 parts by weight, it is preferable that (a) the recycled polypropylene resin is 60 to 100 parts by weight and the recycled polyethylene resin is 0 to 40 parts by weight; (b) the recycled polypropylene resin is 70 to 100 parts by weight and the recycled polyethylene resin is 0 to 30 parts by weight; (c) the recycled polypropylene resin is 80 to 100 parts by weight and the recycled polyethylene resin is 0 to 20 parts by weight; (d) the recycled polypropylene resin is 90 to 100 parts by weight and the recycled polyethylene resin is 0 to 10 parts by weight; and (e) the recycled polypropylene resin is 95 to 100 parts by weight and the recycled polyethylene resin is 0 to 5 parts by weight. This configuration has the advantage of providing a foamed molded article with good impact resistance and surface elongation.

[0059] The base resin preferably contains a total of 80 to 100 parts by weight of polypropylene resin (non-recycled polypropylene resin and recycled polypropylene resin) and recycled polyethylene resin per 100 parts by weight of the base resin, more preferably 90 to 100 parts by weight, and even more preferably 95 to 100 parts by weight. This configuration has the advantage of minimizing the reduction in strength of the resulting foamed molded article. The base resin may also consist only of polypropylene resin (non-recycled polypropylene resin and recycled polypropylene resin) and recycled polyethylene resin.

[0060] (Other resins, etc.) The base resin may further contain resins other than non-recycled polypropylene resin, recycled polypropylene resin, and recycled polyethylene resin (sometimes referred to as "other resins, etc.") to the extent that the effects of one embodiment of the present invention are not impaired. Examples of such other resins, etc. include (a) styrene resins such as polystyrene, styrene / maleic anhydride copolymer, and styrene / ethylene copolymer; (b) polyolefin waxes such as propylene-α-olefin wax; and (c) olefin rubbers such as ethylene / propylene rubber, ethylene / butene rubber, ethylene / hexene rubber, and ethylene / octene rubber. The content of other resins is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the total of non-recycled polypropylene resin, recycled polypropylene resin, and recycled polyethylene resin.

[0061] (2-2. Carbon Black) These foam particles contain carbon black. More specifically, these foam particles have a structure size of 1 × 10¹² per structure. 4 nm 2 Contains carbon black less than 10¹⁶. In the carbon black contained in these foam particles, the structure size per structure relative to the total number of carbon black particles is 1 × 10¹⁶. 4 nm2 The proportion of carbon black particles less than 10% is between 10% and 50%. Through diligent research, the inventors have independently discovered a novel finding: foamed particles containing carbon black of the above-mentioned structure size within the above-mentioned range can, surprisingly, provide a foamed molded article with excellent blackness and flame retardancy. Furthermore, through diligent research, the inventors have independently discovered another novel finding: foamed particles containing carbon black of the above-mentioned structure size within the above-mentioned range can, surprisingly, provide a foamed molded article with excellent color uniformity.

[0062] The method for measuring the structure size of carbon black will be explained in detail in the examples described later.

[0063] Carbon black is not particularly limited and includes channel black, roller black, disc black, gas furnace black, oil furnace black, thermal black, acetylene black, etc. One of these types of carbon black may be used alone, or two or more types may be used in combination.

[0064] The shape of the carbon black is not particularly limited and may be spherical, nearly spherical, or otherwise.

[0065] In these foamed particles, the structure size per structure relative to the total number of carbon black particles is 1 × 10⁻⁶. 4 nm 2 The ratio of carbon black particles less than 10% is preferably 15% to 30%, with a minimum of 10% to 50%. This configuration has the advantage of producing a foamed molded product with excellent color uniformity, blackness, and flame retardancy, even when using recycled resin.

[0066] In one embodiment of the present invention, with the aim of improving the blackness of foamed particles and foamed particle molded articles, the average structure size is 0.2 × 10 4 nm 2 The above 4.0 × 10 4 nm 2Carbon black A with a content of less than 10 is used. In other words, these foamed particles contain carbon black A. The average structure size of carbon black A in the foamed particles is 0.2 × 10⁻⁶. 4 nm 2 The above 4.0 × 10 4 nm 2 It is preferable that it be less than 0.2 × 10 4 nm 2 The above 3.5 × 10 4 nm 2 Less than is more preferable, 0.5 × 10 4 nm 2 The above 3.5 × 10 4 nm 2 Less than 1.0 × 10 is more preferable. 4 nm 2 The above 3.5 × 10 4 nm 2 Less than 1.5 × 10 is more preferable. 4 nm 2 The above 3.5 × 10 4 nm 2 Less than 2.0 × 10 is more preferable. 4 nm 2 The above 3.5 × 10 4 nm 2 Less than 2.5 × 10 4 nm 2 The above 3.5 × 10 4 nm 2 Less than 3.0 × 10 4 nm 2 The above 3.5 × 10 4 nm 2 A value less than this is particularly preferable. This configuration has the advantage that even when recycled resin is used, a foamed molded article with excellent color uniformity, blackness, and flame retardancy can be obtained.

[0067] These foamed particles have an average structure size of 5.0 × 10 4 nm 2 The above 9.0 x 10 4 nm 2 Contains carbon black B with a density of less than 5.0 × 10⁻¹. The average structure size of carbon black B is 5.0 × 10⁻¹. 4 nm 2 The above 9.0 x 104 nm 2 is preferably less than, and 5.0×10 4 nm 2 or more and 8.0×10 4 nm 2 is more preferably less than, and 5.0×10 4 nm 2 or more and 7.5×10 4 nm 2 is more preferably less than, and 5.0×10 4 nm 2 or more and 7.0×10 4 nm 2 is more preferably less than, and 5.0×10 4 nm 2 or more and 6.5×10 4 nm 2 is even more preferably less than, and 5.0×10 4 nm 2 or more and 6.0×10 4 nm 2 is particularly preferably less than. According to this configuration, even when a recycled resin is used, there is an advantage that a foamed molded body excellent in color unevenness, blackness, and flame retardancy can be obtained. As will be described later, the recycled material has an average structure size of 5.0×10 4 nm 2 or more and 9.0×10 4 nm 2 and may contain carbon black B having a size less than, that is, carbon black B. Therefore, the origin of carbon black B can be a recycled material. In addition to the recycled material, carbon black B may be used.

[0068] In one embodiment of the present invention, it is preferable not to use carbon black C having an average structure size of 10×10 4 nm 2 or more, or if used, the amount used is small. In other words, it is preferable that the content of carbon black C having an average structure size of 10×10 4 nm 2 or more in the foamed particles is small. For example, the foamed particles have an average structure size of 10×10 4 nm 4It is preferable that the material does not contain carbon black C, or that it contains more than 0 parts by weight and less than 0.5 parts by weight of carbon black C per 100 parts by weight of the base resin. In the course of diligent research, the inventors have surprisingly made a novel discovery that this configuration yields a foamed molded article with superior flame retardancy.

[0069] The carbon black A content in these foamed particles is preferably 0.1 to 5.0 parts by weight, more preferably 0.3 to 4.5 parts by weight, more preferably 0.5 to 4.3 parts by weight, more preferably 1.0 to 4.0 parts by weight, even more preferably 1.5 to 3.5 parts by weight, even more preferably 2.0 to 3.5 parts by weight, and particularly preferably 2.5 to 3.0 parts by weight, per 100 parts by weight of the base resin. In the course of diligent research, the inventors have surprisingly and independently obtained the novel finding that this configuration yields a foamed molded article with superior blackness.

[0070] The carbon black B content in these foamed particles is preferably 0.10 to 2.00 parts by weight, more preferably 0.10 to 1.80 parts by weight, and even more preferably 0.30 to 1.80 parts by weight, per 100 parts by weight of the base resin. In the course of diligent research, the inventors have surprisingly and independently discovered that this configuration yields a foamed molded article with superior color uniformity and flame retardancy.

[0071] (2-3. Additives) These foamed particles may contain (a) non-recycled polypropylene resin, (b) recycled polypropylene resin and / or recycled polyethylene resin, and (c) carbon black A and B, as well as optionally additional additives. Examples of additives include colorants other than carbon black, water-absorbing substances, foaming nucleating agents, antistatic agents, flame retardants, antioxidants, light stabilizers, crystal nucleating agents, conductive agents, lubricants, etc. Such additives may be added directly to the blend or polypropylene resin composition described later in the production of the polypropylene resin particles.

[0072] (Foaming agent) A foaming nucleating agent is a substance that can be used in the manufacture of these foamed particles and can act as a foaming nucleus when the resin particles foam. It is preferable to use a foaming nucleating agent in the manufacture of these foamed particles; in other words, it is preferable that these foamed particles contain a foaming nucleating agent. This configuration has the advantage of resulting in a uniform cell structure for the foamed particles.

[0073] In this specification, the foaming nucleating agent is an inorganic compound that remains as a residue after burning at 750°C for one hour or more, and may be referred to as "ash" in this specification. Examples include silica (silicon dioxide), silicates, alumina, diatomaceous earth, calcium carbonate, magnesium carbonate, calcium phosphate, feldspar apatite, barium sulfate, and zinc borate. Examples of silicates include talc, magnesium silicate, kaolin, halloysite, deckite, aluminum silicate, and zeolite. One of these foaming nucleating agents may be used alone, or two or more may be used in combination. When two or more foaming nucleating agents are used in combination, the mixing ratio may be adjusted as appropriate depending on the purpose.

[0074] In one embodiment of the present invention, the foaming nucleating agent preferably contains talc, and more preferably is talc, because the cell structure of the foamed particles becomes more uniform and the color unevenness of the foamed particles tends to decrease.

[0075] This section describes the amount of foaming agent used in the production of these foamed particles, or in other words, the foaming agent content in these foamed particles. The foaming agent content in these foamed particles refers to the total amount of foaming agent blended in these foamed particles, including the foaming agent content contained in the recycled material. From the viewpoint of uniformity of average bubble diameter, the foaming agent content in these foamed particles is preferably 0.001 to 2.00 parts by weight, more preferably 0.01 to 1.00 parts by weight, even more preferably 0.020 to 0.50 parts by weight, even more preferably 0.05 to 0.50 parts by weight, even more preferably 0.05 to 0.50 parts by weight, even more preferably 0.05 to 0.50 parts by weight, even more preferably 0.10 to 0.50 parts by weight, even more preferably 0.20 to 0.50 parts by weight, and particularly preferably 0.20 to 0.45 parts by weight per 100 parts by weight of the base resin. Conventional in-molded foamed articles made from foamed particles tend to develop color unevenness when they contain 0.20 parts by weight or more of talc. However, in-molded foamed articles made from these foamed particles exhibit no color unevenness and have good blackness even when they contain 0.20 parts by weight or more of talc.

[0076] The method for identifying the type of foaming nucleating agent is not particularly limited, and known qualitative analysis methods can be applied. Specific examples of qualitative analysis of the foaming nucleating agent include, for example, a method of analyzing ash content by infrared spectroscopy, as detailed in the following examples; a method of solvent fractionation using chloroform and analysis of chloroform-insoluble materials by infrared spectroscopy; or a method of melt fractionation using heated xylene and analysis of xylene-insoluble materials by X-ray diffraction.

[0077] Examples of flame retardants that can be used in one embodiment of the present invention include intomescent flame retardants, hindered amine flame retardants, brominated flame retardants, phosphorus-based flame retardants, and phosphate ester flame retardants. By containing a hindered amine flame retardant, the polyolefin resin foam particles of the present invention can achieve the target flame retardancy with a small amount of added flame retardant.

[0078] The foamed particles preferably contain a hindered amine-based flame retardant. This configuration has the effect of achieving the target flame retardancy with a small amount of flame retardant added.

[0079] In this specification, "hindered amine" refers to a hindered amine having an OR group directly substituted on the N atom (where R is a saturated or unsaturated monovalent hydrocarbon group) (hereinafter sometimes referred to as an N-substituted hindered amine). The hindered amine is not particularly limited as long as it has an OR group directly substituted on the N atom, and any known hindered amine may be used. One type of hindered amine may be used alone, or two or more types of hindered amines may be used in combination.

[0080] Because it can exhibit flame retardant effects over a wide temperature range, a hindered amine is preferably an N-substituted hindered amine containing a triazine component (hereinafter sometimes referred to as "triazine skeleton-containing hindered amine"). The triazine skeleton-containing hindered amine is not particularly limited, but (i) the compound of CAS number 191680-81-6 ((i-1) a product obtained by reacting the reaction product of peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidineamine with 2,4,6-trichloro-1,3,5-triazine with cyclohexane, and the reaction product with N,N'-bis(3-aminopropyl)ethylenediamine, and (i-2) 2,4-bis((1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine-4-yl)butyl It can also be said to be a reaction product of amino)-6-chloro-S-triazine and N,N'-bis(3-aminopropyl)ethylenediamine, and can also be said to be (i-3)N,N',N'''-tris{2,4-bis[(1-hydrocarbyloxy-2,2,6,6-tetramethylpiperidine-4-yl)alkylamino]-s-triazine-6-yl}-3,3'-ethylenediiminodipropylamine), and / or (ii) bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl)carbonate. In addition, isomers of the above-mentioned triazine skeleton-containing hindered amines and crosslinked derivatives of the above-mentioned triazine skeleton-containing hindered amines can also be used. More details about the triazine skeleton-containing hindered amines are disclosed on page 2, line 32 to page 4, line 6 of European Patent No. 0889085.

[0081] Commercially available hindered amines containing a triazine skeleton can also be suitably used. Examples of commercially available hindered amines containing a triazine skeleton include BASF's FLAMSTAB® NOR116 (compound with CAS number 191680-81-6), CLARIANT's HOSTAVIN® NOW XP, and ADEKA's ADEKA STAB LA-81 (bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl)carbonate).

[0082] In one embodiment of the present invention, the hindered amine may be a compound represented by the following structural formula (iv):

[0083] [ka]

[0084] In the above structural formula (iv), G 1 and G 2 Independently, C 1-8 Alkyl alkyl group, or pentamethylene; Z 1 and Z 2 These are either methyl groups or Z 1 and Z 2 They together form a bonding component, which may be additionally substituted with an ester group, ether group, amide group, amino group, carboxyl group or urethane group; and E is C 1-8 Alkoxy group, C 5-12 Cycloalkoxy group C 7-15 Aralcooxy group, -OC(O)-C 1-18 Alkyl group, or -OT-(OH) b It is a base; here T is (i)C 1-18 Alkylene chain, (ii)C 5-18 Cycloalkylene chain, (iii)C 5-18 Cycloalkenylene chain, or (iv) phenyl group or C 1-4 C substituted with alkyl-substituted phenyl groups 1-4 It is an alkylene chain; b is 1 to 3 and less than or equal to the number of carbon atoms in T; and when b is 2 or 3, each hydroxyl group is linked to a different carbon atom of T.

[0085] More details about the compound represented by the above structural formula (iv) are disclosed in European Patent No. 2225318, and more specifically, in pages 5, line 35 to page 25, line 48 of European Patent No. 2225318.

[0086] In one embodiment of the present invention, the hindered amine may be a compound represented by the following structural formula (v):

[0087] [ka]

[0088] In the above structural formula (v), R is either a hydrogen atom or a methyl group, and R 1 C 1-18 Alkyl alkyl group, C 2-18 Alkenyl group, C 2-18 Alkynyl group, C 5-12 Cycloalkyl groups, C 5-8 Cycloalkenyl group, C 6-10 Aryl group or C 7-9 It is an aralkyl group.

[0089] More details about the compound represented by the above structural formula (v) are disclosed on page 3, line 33 to page 8, line 58 of European Patent No. 0309402.

[0090] In one embodiment of the present invention, the hindered amine may be a compound represented by the following structural formula (vi):

[0091] [ka]

[0092] In the above structural formula (vi), E, ​​k, Y, W, R1-R7 and G1-G4 are as defined in U.S. Patent No. 8,598,369.

[0093] The compound represented by the above structural formula (vi) is disclosed in more detail in Examples 1 to 12 and Tables 1 to 5 of U.S. Patent No. 8,598,369.

[0094] The amount of flame retardant used in the production of these foamed particles, in other words, the content of the flame retardant in these foamed particles, will be explained. The content of the flame retardant in these foamed particles is preferably 0.05 to 1.00 parts by weight, more preferably 0.05 to 0.20 parts by weight, and even more preferably 0.05 to 0.10 parts by weight, per 100 parts by weight of the base resin. When the content of the flame retardant is (i) 0.05 parts by weight or more, a sufficient flame retardant effect can be obtained, and (ii) when it is 0.10 parts by weight or less, there is no risk that the bubble diameter of the resulting foamed particles will be uneven or fine.

[0095] <Physical properties> The following describes the physical properties of these foamed particles.

[0096] (DSC ratio of foamed particles) Preferably, these foamed particles have at least two melting peaks in the DSC curve obtained by differential scanning calorimetry, as described below. Of these melting peaks, the heat of fusion obtained from the higher temperature melting peak is defined as the "high-temperature side heat of fusion," and the heat of fusion obtained from the lower temperature melting peak is defined as the "low-temperature side heat of fusion." If there are three or more melting peaks, the heat of fusion obtained from the highest temperature melting peak is defined as the "high-temperature side heat of fusion," and the heat of fusion obtained from the other melting peaks is defined as the "low-temperature side heat of fusion."

[0097] The DSC ratio of the foamed particles is not particularly limited, but is preferably 10.0% to 50.0%, more preferably 15.0% to 40.0%, and even more preferably 20.0% to 30.0%. When the DSC ratio of the foamed particles is 10.0% or higher, the foamed particles have the advantage of being able to provide a foamed molded article with sufficient strength. On the other hand, when the DSC ratio of the foamed particles is 40% or lower, the foamed particles have the advantage of being able to be molded at a relatively low temperature (molding temperature) to provide a foamed molded article.

[0098] The method for measuring the DSC ratio of foamed particles will be explained in detail in the examples described later.

[0099] The DSC ratio of these foamed particles is also an indicator of the amount of high-melting-point crystals contained in the foamed particles. In other words, a DSC ratio of 10.0% to 50.0% indicates that the foamed particles contain a relatively large amount of high-melting-point crystals. Furthermore, the DSC ratio of the foamed particles greatly influences the viscoelasticity of the resin particles and the foamed particles during foaming and expansion. Specifically, when the DSC ratio of the foamed particles is 10.0% to 50.0%, the resin particles and the foamed particles can exhibit excellent foaming and expansion properties, respectively, during foaming and molding. As a result, the foamed particles have the advantage of producing foamed molded articles with excellent internal bonding properties at low molding pressure and excellent mechanical strength, such as compressive strength.

[0100] Methods for controlling the DSC ratio within a predetermined range in these foamed particles include adjusting the manufacturing conditions of the foamed particles (particularly the foaming temperature, foaming pressure, holding time, and the temperature of the region (space) where the dispersion is released). Because adjustments are easy, adjusting the foaming temperature, foaming pressure, and / or holding time is preferred as a method for controlling the DSC ratio within a predetermined range.

[0101] For example, increasing the foaming temperature tends to decrease the DSC ratio, while decreasing the foaming temperature tends to increase it. This is because the amount of unmelted crystals changes depending on the foaming temperature. Similarly, increasing the foaming pressure tends to decrease the DSC ratio, while decreasing the foaming pressure tends to increase it. This is because the degree of plasticization changes depending on the foaming pressure, which in turn changes the amount of unmelted crystals. Furthermore, increasing the holding time tends to increase the DSC ratio. This is because the amount of unmelted crystal growth changes depending on the holding time.

[0102] (Foaming ratio of foaming particles) The foamed particles preferably have a foaming ratio of 10 to 50 times, more preferably 15 to 40 times, and even more preferably 15 to 30 times. If the foaming ratio of the foamed particles is (i) 10 times or more, a lightweight foamed molded article can be obtained with production efficiency, and (ii) if it is 50 times or less, there is no risk of insufficient strength in the resulting foamed molded article.

[0103] The method for calculating the foaming ratio of foamed particles will be explained in detail in the examples described later.

[0104] (Average bubble diameter of foaming particles) The average bubble diameter of the foam particles is not particularly limited, but is preferably 100 μm to 500 μm, more preferably 120 μm to 400 μm, even more preferably 120 μm to 300 μm, and even more preferably 140 μm to 250 μm. When the average bubble diameter of the foam particles is (i) 100 μm or more, the foam particles can provide a polypropylene resin foam molded article that is free from color unevenness, has excellent colorability, and has excellent compressive strength, and (ii) when the average bubble diameter of the foam particles is 500 μm or less, there is no risk of the molding cycle of the in-molded foam molded article becoming long, which has the advantage of good productivity. Here, the molding cycle refers to the time from the start of in-molded foam molding to the end of molding when the obtained molded article is released from the mold, when a foam molded article is obtained by in-molded foam molding using foam particles.

[0105] The method for measuring the average bubble diameter of foamed particles will be explained in detail in the examples described later.

[0106] <Method for manufacturing polypropylene resin foam particles> A method for producing polypropylene resin foam particles according to one embodiment of the present invention comprises a non-recycled polypropylene resin, recycled material, and an average structure size of 0.2 × 10 4 nm 2 The above 4.0 × 10 4 nm 2The method for producing polypropylene resin foam particles comprises: a granulation step of melting and kneading a mixture containing carbon black A having a value of less than 5.0 × 10 to obtain polypropylene resin particles; a dispersion step of dispersing the polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container; a heating step of heating the temperature inside the container to a temperature equal to or greater than the softening temperature of the polypropylene resin particles; a pressurizing step of increasing the pressure inside the container; and a release step of releasing one end of the container and releasing the dispersion liquid inside the container into a region with a pressure lower than the pressure inside the container. In a method for producing polypropylene resin foam particles according to one embodiment of the present invention, the recycled material is recycled polypropylene resin and / or recycled polyethylene resin and has an average structure size of 5.0 × 10 4 nm 2 The above 9.0 x 10 4 nm 2 The material includes carbon black B which is less than 100 parts by weight, and the amount of recycled material used is such that the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight in 100 parts by weight of a base resin which includes the non-recycled polypropylene resin and the recycled polypropylene resin and / or the recycled polyethylene resin.

[0107] Because the method for producing these foamed particles has the above-described structure, it has the advantage of being able to provide polypropylene resin foamed particles that can provide polypropylene resin foam molded articles with excellent blackness and flame retardancy. Furthermore, as mentioned above, the method for producing these foamed particles uses recycled polypropylene resin and / or recycled polyethylene resin. Therefore, the method for producing these foamed particles can be said to have a low environmental impact.

[0108] Recycled materials currently on the market (especially recycled materials containing recycled polypropylene resin) may contain carbon black. This is because carbon black is added as a coloring agent in the original product before recycling, or because carbon black is added during the recycling process to improve the appearance of the recycled material and the color of the original product, thereby enhancing the color of the recycled material. The inventors of this invention measured the average structure size of carbon black contained in recycled polypropylene resin, an example of a recycled material, using the method described above, and found that the average structure size was, for example, 5.0 × 10⁻⁶. 4 nm 2 The above 9.0 x 10 4 nm 2 It was less than 5.0 × 10. In this specification, the average structure size is 5.0 × 10. 4 nm 2 The above 9.0 x 10 4 nm 2 Carbon black that is less than [amount missing] is designated as "carbon black B". In other words, recycled materials may contain carbon black B.

[0109] Furthermore, the inventors have found that foamed molded articles formed by molding foamed particles obtained using recycled materials (e.g., recycled polypropylene resin and / or recycled polyethylene resin) have inferior blackness. Therefore, they have diligently conducted research to provide foamed molded articles with excellent blackness, even when using foamed particles obtained using recycled materials.

[0110] In the course of diligent research, the inventors discovered that the average structure size (e.g., 0.2 × 10) is smaller than that of the carbon black contained in the recycled material. 4 nm 2 The above 4.0 × 10 4 nm 2We have independently obtained a novel finding that foamed particles obtained by further adding (using) carbon black having less than 0.2 × 10¹⁶ can remarkably provide foamed molded articles with excellent blackness. In this specification, we define foamed particles with an average structure size of 0.2 × 10¹⁶. 4 nm 2 The above 4.0 × 10 4 nm 2 Carbon black that is less than [a certain value] is referred to as "carbon black A". In other words, the inventors have independently obtained a novel finding that foamed particles obtained by using (adding) carbon black A in addition to recycled materials can provide a foamed molded product with excellent blackness.

[0111] The inventors used foamed particles obtained by adding carbon black A to recycled materials, and measured the average structure size of the carbon black in the foamed particles using the method described above. They found that at least a portion of the foamed particles had a structure size of 1 × 10¹⁶ relative to the total number of carbon black in the foamed particles. 4 nm 2 The proportion of carbon black particles with a number less than 10% to 50% was between 10% and 50%. In other words, this manufacturing method can provide foamed particles according to one embodiment of the present invention. The structure size per structure in the foamed particles is 1 × 10 4 nm 2 The carbon black that is less than [amount missing] may be carbon black B from recycled materials, or it may be carbon black A that was used (added) in addition.

[0112] Furthermore, the inventors have found that by appropriately adjusting the average structure size and amount of additional carbon black used in addition to recycled materials, the structure size per structure relative to the total number of carbon black particles in the foamed particles is 1 × 10⁻⁶. 4 nm 2We have independently obtained novel findings that by creating foamed particles in which the ratio of carbon black particles less than 10% to 50% is such that we can provide polypropylene-based resin foamed particles that contain recycled resin and provide a polypropylene-based resin foamed molded article with excellent blackness and flame retardancy.

[0113] The following describes in detail one method for manufacturing these foamed particles. For matters not described below, refer to the section [2. Polypropylene Resin Foamed Particles] above as appropriate. Note that the method for manufacturing these foamed particles is not limited to the method described below.

[0114] (granulation process) The granulation process can also be described as a process for preparing polypropylene resin particles containing (a) a base resin comprising a non-recycled polypropylene resin and recycled polypropylene resin and / or recycled polyethylene resin, and (b) carbon black. The amount of recycled material used in this manufacturing method (e.g., the granulation process) is such that the total content of recycled polypropylene resin and recycled polyethylene resin in the resulting polypropylene resin particles is 10 to 60 parts by weight per 100 parts by weight of the base resin contained in the polypropylene resin particles. In this specification, "polypropylene resin particles" may be referred to as "resin particles".

[0115] The polypropylene resin particles produced by this manufacturing method contain a base resin. It can also be said that the polypropylene resin particles obtained through the granulation process contain a base resin.

[0116] In the granulation process, it is preferable to use a foaming nucleating agent. In other words, it is preferable that the polypropylene resin particles in this manufacturing method contain a foaming nucleating agent. Specific examples of foaming nucleating agents are the same as those described in the (Foaming Nucleating Agent) section above, so that description will be used and the explanation will be omitted here. In this manufacturing method (for example, the granulation process), it is preferable that the amount of foaming nucleating agent used is such that the amount of foaming nucleating agent in the resulting polypropylene resin particles is the amount described in the (Foaming Nucleating Agent) section above, per 100 parts by weight of the base resin in the polypropylene resin particles.

[0117] In the melt-kneading of the mixture, there are no particular limitations, but for example, an extruder may be used. In the granulation process, there are no particular limitations other than melt-kneading the mixture. For example, polypropylene resin particles can be prepared by performing the following steps (1) to (3) in order on the melt-kneaded mixture: (1) Extrude the mixture through a die equipped with an extruder; (2) Solidify the extruded mixture by cooling it by passing it through water, etc.; (3) Then, cut the solidified mixture with a cutter into desired shapes such as cylindrical, elliptical, spherical, cubic, rectangular parallelepiped, hollow cylindrical, polygonal prism, etc. Alternatively, the melt-kneaded mixture may be extruded directly into water through a die equipped with an extruder, and the mixture may be cut into particle shapes immediately after extrusion, cooled, and solidified.

[0118] In the granulation process, a mixture containing non-recycled polypropylene resin, recycled material, and carbon black A is melt-kneaded. Carbon black A may be used as is, or it may be used in the form of a masterbatch that has been pre-mixed with the polypropylene resin. In the granulation process, carbon black B and carbon black C may be used in addition to carbon black A. The amounts of carbon black A, B, and C used in the granulation process will correspond to the respective carbon black content of carbon black A, B, and C in the resulting foamed particles. Therefore, it is preferable that the amounts of carbon black A, B, and C used in this manufacturing method (e.g., the granulation process) are such that the respective carbon black content of carbon black A, B, and C in the resulting polypropylene resin particles is the amount described in section (2-2. Carbon Black) per 100 parts by weight of the base resin in the polypropylene resin particles. Furthermore, the average structures of carbon blacks A, B, and C used in the granulation process are the same as those described above, so we will refer to those descriptions and omit further explanation here. Note that the amount of carbon black B used in this manufacturing method (for example, the granulation process) refers to the sum of the amount of carbon black B contained in the recycled material used and the amount of carbon black B used separately or arbitrarily, not as recycled material.

[0119] In this manufacturing method (for example, the granulation process), the total amount of non-recycled polypropylene resin and recycled material used is preferably such that the total content of the non-recycled polypropylene resin, recycled polypropylene resin, and recycled polyethylene resin in the polypropylene resin particles is the amount described in section (2-1. Base Resin).

[0120] (Dispersion process) The dispersion process can also be described as the process of preparing a dispersion in which resin particles, a foaming agent, and, if necessary, a dispersant and / or a dispersion aid are dispersed in an aqueous dispersion medium.

[0121] The container used in the dispersion process is not particularly limited, but it is preferable that it be a container that can withstand the foaming temperature and foaming pressure described later.

[0122] Examples of containers include pressure vessels and autoclave-type pressure vessels. The container may be equipped with an agitator inside.

[0123] The aqueous dispersion medium can be any medium capable of uniformly dispersing resin particles, foaming agents, etc., and is not particularly limited.

[0124] Examples of aqueous dispersion media include (a) dispersion media obtained by adding methanol, ethanol, ethylene glycol, and glycerin to water, (b) water such as tap water and industrial water, and (c) solutions (aqueous solutions) containing salts such as sodium chloride or sodium sulfate. In order to enable stable production of foaming particles, it is preferable to use pure water and ultrapure water such as RO water (water purified by reverse osmosis membrane method), distilled water, and deionized water (water purified by ion exchange resin) as the aqueous dispersion media.

[0125] Examples of blowing agents include (a) (a-1) inorganic gases such as nitrogen, carbon dioxide, and air (a mixture of oxygen, nitrogen, and carbon dioxide), and (a-2) water; and (b) (b-1) saturated hydrocarbons having 3 to 5 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; (b-2) ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; and (b-3) halogenated hydrocarbons such as monocormethane, chloroethane, and hydrofluoroolefin.

[0126] Halogenated hydrocarbons such as dichloromethane and dichlorodifluoroethane can also be used as foaming agents.

[0127] In this method for producing foamed particles, it is preferable to use a dispersant (for example, inorganic substances such as tricalcium phosphate and kaolin) and a dispersion aid (for example, an anionic surfactant such as sodium dodecylbenzenesulfonate). This configuration reduces adhesion between resin particles (sometimes referred to as blocking) and improves the stability of the dispersion in the container. As a result, it has the advantage of being able to produce foamed particles stably.

[0128] The aqueous dispersion medium and foaming agent described above may be used individually or in combination of two or more types.

[0129] This manufacturing method includes, between the dispersion step and the release step, a heating step in which the temperature inside the container is heated to a temperature above the softening temperature of the polypropylene resin particles, and a pressurizing step in which the pressure inside the container is increased to, for example, a constant pressure. The heating step and the pressurizing step may be performed in any order or simultaneously. Furthermore, this manufacturing method may further include, after the heating step and the pressurizing step, a holding step in which the temperature inside the container is maintained at a temperature above the softening temperature of the polypropylene resin particles and the pressure inside the container is maintained at a constant pressure.

[0130] (Heating process, pressurizing process, and holding process) In this specification, (a) "a temperature above the softening temperature of the polypropylene resin particles" in the heating, pressurizing, and holding steps may be referred to as the "foaming temperature," and (b) a constant pressure may be referred to as the "foaming pressure." In this specification, "a temperature above the softening temperature of the polypropylene resin particles" means a temperature above the melting point of the polypropylene resin constituting the polypropylene resin particles, which is -10°C. If two or more types of polypropylene resins are used, it means a temperature above the melting point of the polypropylene resin with the highest melting point.

[0131] The foaming temperature in the heating process cannot be specified in general terms, as it varies depending on the type of non-recycled polypropylene resin and recycled material, the type of foaming agent, the desired apparent density of the foamed particles, etc. In the heating process, as long as the temperature inside the container is heated to a temperature above the softening temperature of the polypropylene resin particles, there is no particular limit to how high the temperature inside the container is heated. In one embodiment of the present invention, the heating process preferably involves heating the temperature inside the container to (i) a temperature above the softening temperature of the polypropylene resin particles and below the softening temperature of the polypropylene resin particles + 10.0°C, more preferably to (ii) a temperature above the softening temperature of the polypropylene resin particles and below the softening temperature of the polypropylene resin particles + 8.0°C, and even more preferably to (iii) a temperature above the softening temperature of the polypropylene resin particles and below the softening temperature of the polypropylene resin particles + 6.0°C. This configuration has the advantage that there is no risk of the polypropylene resin particles sticking together inside the container.

[0132] In the pressurization process, there are no particular limitations on how high the pressure inside the container is increased. In one embodiment of the present invention, the pressurization process is preferably a process in which the pressure inside the container is increased to (i) a pressure of 1.0 MPa (gauge pressure) to 10.0 MPa (gauge pressure), more preferably a process in which the pressure is increased to 1.5 MPa (gauge pressure) to 5.0 MPa (gauge pressure), and even more preferably a process in which the pressure is increased to 1.5 MPa (gauge pressure) to 3.5 MPa (gauge pressure). When the pressurization process is a process in which the pressure inside the container is increased to a pressure of 1.0 MPa (gauge pressure) or higher, foamed particles with a suitable density can be obtained.

[0133] In the holding process, the time for which the temperature inside the container (temperature of the dispersion) is maintained at the foaming temperature and the pressure inside the container is maintained near the foaming pressure (holding time) is not particularly limited. The holding time is preferably 10 to 60 minutes, more preferably 12 to 55 minutes, and even more preferably 15 to 50 minutes. When the holding time is 10 minutes or more, a sufficient amount of unmelted crystals (crystals of the base resin) are present, which has the advantage of reducing the shrinkage of the resulting foamed particles and / or the increase in the open-cell ratio. On the other hand, when the holding time is 60 minutes or less, there is no excessive amount of unmelted crystals, which has the advantage of allowing the foamed particles to be molded at a lower molding temperature.

[0134] (Release process) The release step can be performed (a) after the heating and pressurizing steps if the holding step is not performed, or (b) after the holding step if the holding step is performed. The release step can cause the resin particles to foam, resulting in foamed particles.

[0135] In the discharge process, the "region with a pressure lower than the pressure inside the container" refers to the "region under a pressure lower than the pressure inside the container" or the "space under a pressure lower than the pressure inside the container," and can also be described as "an atmosphere with a pressure lower than the pressure inside the container." The region with a pressure lower than the pressure inside the container can also be described as a region with a pressure lower than the foaming pressure, and may, for example, be a region under atmospheric pressure.

[0136] In the discharge process, when discharging the dispersion into a region with a pressure lower than the pressure inside the container, the dispersion can also be discharged through an open orifice with a diameter of 1 mm to 5 mm for purposes such as adjusting the flow rate of the dispersion and reducing variations in the foaming ratio of the resulting foamed particles.

[0137] The low-pressure region is, for example, the gas phase. Furthermore, to improve foaming properties, the low-pressure region (space) may be filled with saturated water vapor.

[0138] As mentioned above, the process of manufacturing foamed particles from resin particles is called the "single-stage foaming process," and the resulting foamed particles are called "single-stage foamed particles."

[0139] (Two-stage foaming process) To obtain foamed particles with a high foaming ratio, the foamed particles obtained in the first foaming step may be foamed again. The step of increasing the foaming ratio of the first foamed particles is called the "second foaming step," and the polyolefin resin foamed particles obtained in the second foaming step are called "second foamed particles." The specific method for the second foaming step is not particularly limited, and known methods can be used.

[0140] [3. Polypropylene-based resin foam molded product] One embodiment of the present invention also provides a polypropylene resin foam molded article obtained by molding the polypropylene resin foam particles described in section [2. Polypropylene Resin Foam Particles] above. The polypropylene resin foam molded article according to one embodiment of the present invention can also be said to be a foam molded article containing the polypropylene resin foam particles described in section [2. Polypropylene Resin Foam Particles].

[0141] In this specification, "a polypropylene-based resin foam molded article according to one embodiment of the present invention" may be referred to as "the foam molded article."

[0142] Because of the above-described structure, this foamed molded article has the advantage of excellent blackness and flame retardancy (self-extinguishing properties). Specifically, a foamed molded article with excellent blackness can be obtained, with an L value of less than 28 measured by a spectrophotometer. This foamed molded article also has the advantage of excellent color uniformity and surface properties. Specifically, a foamed molded article with suppressed color uniformity can be obtained, with a standard deviation of less than 2 for the L value measured by a spectrophotometer. The measurement and evaluation methods for blackness, color uniformity, flame retardancy, and surface properties of the foamed molded article will be described in detail in the following examples.

[0143] The density of the foamed molded article is not particularly limited. The density is preferably 20 g / L to 90 g / L, and more preferably 20 g / L to 60 g / L. This configuration has the advantage of achieving both excellent lightness and excellent impact resistance in the molded article. The method for measuring the density of the foamed molded article will be described in detail in the following examples.

[0144] <Method for manufacturing foamed molded products> The method for manufacturing the foamed molded article is not particularly limited to any other aspect, as long as it involves molding the foamed particles (preferably by in-mold foaming) to obtain a foamed molded article, and known methods can be applied. As a method for manufacturing the foamed molded article, for example, the manufacturing method described in the section "Method for Manufacturing a Foamed Molded Article" of International Publication WO2022 / 149538 can be suitably adopted.

[0145] One embodiment of the present invention may have the following configuration.

[0146] [1] Polypropylene resin foam particles containing a base resin and carbon black, wherein the base resin includes a non-recycled polypropylene resin, a recycled polypropylene resin and / or a recycled polyethylene resin, the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight per 100 parts by weight of the base resin, and the carbon black is such that the structure size per structure is 1 × 10¹¹ relative to the total number of carbon black particles. 4 nm 2 Polypropylene resin foam particles in which the ratio of carbon black particles below a certain level is between 10% and 50%.

[0147] [2] Average structure size is 0.2 × 10 4 nm 2 The above 4.0 × 10 4 nm 2 Carbon black A is less than 5.0 × 10 4 nm 2 The above 9.0 x 10 4 nm 2 Polypropylene resin foam particles according to [1], comprising carbon black B which is less than [1].

[0148] [3] Polypropylene resin foam particles according to [1] or [2], further comprising a foaming agent.

[0149] [4] The polypropylene resin foam particles according to [3], wherein the content of the foaming nucleating agent is 0.05 to 0.50 parts by weight per 100 parts by weight of the base resin.

[0150] [5] The polypropylene resin foam particles according to [3], wherein the content of the foaming nucleating agent is 0.20 to 0.50 parts by weight per 100 parts by weight of the base resin.

[0151] [6] The foaming agent is talc, the polypropylene resin foaming particle according to any one of [3] to [5].

[0152] [7] Polypropylene resin foam particles according to any one of [1] to [6], further comprising a hindered amine flame retardant.

[0153] [8] The polypropylene resin foam particles according to [2], wherein the carbon black A content is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

[0154] [9] The polypropylene resin foam particles according to [2], wherein the carbon black B content is 0.10 parts by weight to 2.00 parts by weight per 100 parts by weight of the base resin.

[0155]

[10] The polypropylene resin foam particles according to any one of [1] to [9], wherein the base resin includes the recycled polyethylene resin, and the recycled polyethylene resin includes the recycled high-density polyethylene resin.

[0156]

[11] When the total content of the recycled polypropylene resin and the recycled polyethylene resin is 100 parts by weight, the recycled polypropylene resin is 60 to 100 parts by weight and the recycled polyethylene resin is 0 to 40 parts by weight, the polypropylene resin foam particles according to any one of [1] to

[10] .

[0157]

[12] Average structure size is 10.0 × 10 4 nm 2 Polypropylene resin foam particles according to any one of [1] to

[11] , which either do not contain carbon black C as described above, or contain less than 0.5 parts by weight of carbon black C per 100 parts by weight of the base resin.

[0158]

[13] The non-recycled polypropylene resin contains 60% by weight or more of one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer, in 100% by weight of the non-recycled polypropylene resin, polypropylene resin foam particles according to any one of [1] to

[12] .

[0159]

[14] The polypropylene resin foam particles according to any one of [1] to

[13] , wherein the base resin comprises the recycled polypropylene resin, and the recycled polypropylene resin comprises one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer and ethylene / propylene random copolymer.

[0160]

[15] The base resin is polypropylene resin foam particles according to any one of [1] to

[14] , wherein the base resin contains a total of 80 to 100 parts by weight of the non-recycled polypropylene resin, the recycled polypropylene resin, and the recycled polyethylene resin in 100 parts by weight of the base resin.

[0161]

[16] The polypropylene resin foam particles according to any one of [1] to

[15] , wherein the DSC ratio of the polypropylene resin foam particles is 10.0% to 50.0%.

[0162]

[17] The polypropylene resin foam particles according to any one of [1] to

[16] , wherein the foaming ratio of the polypropylene resin foam particles is 10 to 50 times.

[0163]

[18] The polypropylene resin foam particles according to any one of [1] to

[17] , wherein the average bubble diameter of the polypropylene resin foam particles is 100 μm to 500 μm.

[0164] A polypropylene resin foam molded article obtained by molding polypropylene resin foam particles described in any one of [1] to

[18] .

[0165]

[20] The polypropylene resin foam molded article according to

[19] , wherein the molded article density of the polypropylene resin foam molded article is 20 g / L to 90 g / L.

[0166]

[21] The polypropylene resin foam molded article is the polypropylene resin foam molded article according to

[19] or

[20] , wherein the polypropylene resin foam molded article has self-extinguishing properties.

[0167]

[22] The polypropylene-based resin foam molded article according to any one of

[19] to

[21] , wherein the L value of the polypropylene-based resin foam molded article measured by a spectrophotometer is less than 28.

[0168]

[23] The polypropylene-based resin foam molded article according to any one of

[19] to

[22] , wherein the standard deviation of the L value of the polypropylene-based resin foam molded article measured by a spectrophotometer is less than 2.

[0169]

[24] Non-recycled polypropylene resin, recycled material, and an average structure size of 0.2 × 10 4 nm 2 The above 4.0 × 10 4 nm 2The process includes: a granulation step of melting and kneading a mixture containing carbon black A, which is less than 0.50, to obtain polypropylene resin particles; a dispersion step of dispersing the polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container; a heating step of heating the temperature inside the container to a temperature above the softening temperature of the polypropylene resin particles; a pressurizing step of increasing the pressure inside the container; and a release step of releasing the dispersion liquid inside the container into a region with a pressure lower than the pressure inside the container. The recycled material comprises recycled polypropylene resin and / or recycled polyethylene resin, with an average structure size of 5.0 × 10 4 nm 2 The above 9.0 x 10 4 nm 2 A method for producing polypropylene resin foam particles, comprising carbon black B which is less than 100% of the original material, wherein the amount of recycled material used is such that the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight in 100 parts by weight of a base resin comprising the non-recycled polypropylene resin, the recycled polypropylene resin and / or the recycled polyethylene resin.

[0170]

[25] The method for producing polypropylene resin foam particles according to

[24] , wherein the heating step is a step of heating the temperature inside the container to a temperature above the softening temperature of the polypropylene resin particles and below the softening temperature of the polypropylene resin particles + 10.0°C.

[0171]

[26] The method for producing polypropylene resin foam particles according to

[24] or

[25] , wherein the pressurization step is a step of pressurizing the pressure inside the container to a pressure of 1.0 MPa (gauge pressure) to 10.0 MPa (gauge pressure).

[0172]

[27] A method for producing polypropylene resin foam particles according to any one of

[24] to

[26] , wherein the polypropylene resin particles further comprise a foaming nucleating agent.

[0173]

[28] The method for producing polypropylene resin foam particles according to

[27] , wherein the content of the foaming nucleating agent in the polypropylene resin particles is 0.05 to 0.50 parts by weight per 100 parts by weight of the base resin.

[0174]

[29] The method for producing polypropylene resin foam particles according to

[27] , wherein the content of the foaming nucleating agent in the polypropylene resin particles is 0.20 to 0.50 parts by weight per 100 parts by weight of the base resin.

[0175]

[30] The method for producing polypropylene resin foam particles according to any one of

[27] to

[29] , wherein the foaming agent is talc.

[0176]

[31] A method for producing polypropylene resin foam particles according to any one of

[24] to

[30] , wherein the polypropylene resin particles further contain a hindered amine flame retardant.

[0177]

[32] The method for producing polypropylene resin foam particles according to any one of

[24] to

[31] , wherein the amount of carbon black A used is such that the carbon black A content is 0.1 parts by weight to 5.0 parts by weight per 100 parts by weight of the base resin.

[0178]

[33] The method for producing polypropylene resin foam particles according to any one of

[24] to

[32] , wherein the amount of carbon black B used is such that the carbon black B content is 0.10 parts by weight to 2.00 parts by weight per 100 parts by weight of the base resin.

[0179]

[34] A method for producing polypropylene resin foam particles according to any one of

[24] to

[33] , wherein the recycled material includes the recycled polyethylene resin, and the recycled polyethylene resin includes the recycled high-density polyethylene resin.

[0180]

[35] A method for producing polypropylene resin foam particles according to any one of

[24] to

[34] , wherein, in the recycled material, when the total content of the recycled polypropylene resin and the recycled polyethylene resin is 100 parts by weight, the recycled polypropylene resin is 60 to 100 parts by weight and the recycled polyethylene resin is 0 to 40 parts by weight.

[0181]

[36] Average structure size is 10.0 × 10 4 nm 2 A method for producing polypropylene resin foam particles according to any one of

[24] to

[35] , wherein carbon black C is not used, or an amount is used in which the carbon black C content is less than 0.5 parts by weight per 100 parts by weight of the base resin.

[0182]

[37] The method for producing foamed polypropylene resin particles according to any one of

[24] to

[36] , wherein the non-recycled polypropylene resin contains 60% by weight or more of one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer, in 100% by weight of the non-recycled polypropylene resin.

[0183]

[38] A method for producing foamed polypropylene resin particles according to any one of

[24] to

[37] , wherein the recycled material comprises the recycled polypropylene resin, and the recycled polypropylene resin comprises one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer and ethylene / propylene random copolymer.

[0184]

[39] The method for producing polypropylene resin foam particles according to any one of

[24] to

[38] , wherein the total amount of non-recycled polypropylene resin and recycled material used is such that the total content of the non-recycled polypropylene resin, recycled polypropylene resin, and recycled polyethylene resin in the polypropylene resin particles is 80 to 100 parts by weight per 100 parts by weight of the base resin in the polypropylene resin particles.

[0185]

[40] A method for producing polypropylene resin foam particles according to any one of

[24] to

[39] , wherein the DSC ratio of the polypropylene resin foam particles is 10.0% to 50.0%.

[0186]

[41] A method for producing polypropylene resin foam particles according to any one of

[24] to

[40] , wherein the foaming ratio of the polypropylene resin foam particles is 10 to 50 times.

[0187]

[42] A method for producing polypropylene resin foam particles according to any one of

[24] to

[41] , wherein the average bubble diameter of the polypropylene resin foam particles is 100 μm to 500 μm.

[0188] A method for producing a polypropylene resin foamed molded article, comprising the step of molding polypropylene resin foamed particles obtained by any one of

[43] [1] to

[18] , or by a method for producing polypropylene resin foamed particles obtained by any one of

[24] to

[42] .

[0189]

[44] The method for producing a polypropylene-based resin foam molded article according to

[43] , wherein the density of the molded polypropylene-based resin foam molded article is 20 g / L to 90 g / L.

[0190]

[45] The method for producing the polypropylene-based resin foam molded article according to

[43] or

[44] , wherein the polypropylene-based resin foam molded article has self-extinguishing properties.

[0191]

[46] The method for producing a polypropylene-based resin foam molded article according to any one of

[43] to

[45] , wherein the L value of the polypropylene-based resin foam molded article measured by a spectrophotometer is less than 28.

[0192]

[47] The method for producing a polypropylene-based resin foam molded article according to any one of

[43] to

[46] , wherein the standard deviation of the L value of the polypropylene-based resin foam molded article measured by a spectrophotometer is less than 2. [Examples]

[0193] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The substances used in the examples and comparative examples are as follows, and were used without any particular purification or other treatment.

[0194] <Material> (Non-recycled polypropylene resin) • Ethylene / 1-butene / propylene random copolymer [ethylene content 1.0% by weight, 1-butene content 4 parts by weight, melting point 148°C] (Recycled materials) • Recycled material-1: A mixture consisting of 96.2 parts by weight of ethylene / propylene random copolymer [ethylene content 9.0% by weight and melting point 151°C], 3 parts by weight of carbon black B, and 0.8 parts by weight of talc. The average structure size of carbon black B in recycled material-1 was measured using the following method and found to be 5.8 × 10⁻⁶. 4 nm 2 The carbon black B content in recycled material-1 was obtained by the following method. The ash content in recycled material-1 was measured by the following method and was found to be 0.8 parts by weight. Furthermore, qualitative analysis of the obtained ash content by the following method revealed that it was talc. • Recycled material - 2; High-density polyethylene [Melting point 126℃] (Carbon Black) • Carbon Black A [Average structure size: 3.2 x 10 4 nm 2 (Minimum structure value: 0.01 × 10 4 nm 2 Maximum structure size: 5.0 × 10 4 nm 2 )] • Carbon Black B (Carbon Black included in Recycled Material-1) [Average Structure Size: 5.8 x 10 4 nm 2 (Minimum structure value 1.0 × 10 4 nm 2 , maximum value 9.9 × 10 4 nm 2 )] (Foaming agent) • Talc [Manufactured by Hayashi Chemical Co., Ltd., Talc Powder PK-S] (water-absorbing substance) • Glycerin [Manufactured by Lion Corporation, refined glycerin D] (Flame retardant) • Hindered amine flame retardant [BASF, NOR116] <Method for measuring melting point> The melting points of non-recycled polypropylene resin, recycled polypropylene resin, and recycled polyethylene resin were determined by DSC method using a differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Co., Ltd.). The specific operating procedure was as follows (1) to (3): (1) The temperature of 5 mg to 6 mg of the sample (non-recycled polypropylene resin, recycled polypropylene resin, or recycled polyethylene resin) was increased from 40°C to 220°C at a heating rate of 10°C / min to melt the sample; (2) The temperature of the melted sample was then decreased from 220°C to 40°C at a cooling rate of 10°C / min to crystallize the sample; (3) The temperature of the crystallized sample was then further increased 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 sample obtained during the second heating (i.e., at (3)) was taken as the melting point of the sample.

[0195] <Measuring the structural size of carbon black> The structure size of carbon black in foamed particles was determined by the following measurement method: (1) Polypropylene foamed particles were cut in half using a microtome; (2) A cross-sectional image of the cell film of the obtained polypropylene foamed particles was taken at 40,000x magnification using a transmission electron microscope; (3) Thirty carbon black structures were randomly extracted from the obtained transmission electron microscope cross-sectional images, and the area of ​​these carbon black structures was measured. Specifically, lines were drawn along the contours of the carbon black structures, and the area of ​​the region enclosed by the lines was measured using the area measurement function of PDF file editing software [Adobe Acrobat DC].

[0196] In (3) above, the structure size of carbon black in the recycled material was measured using the same method as described above, except that the image obtained by photographing the recycled material under a transmission electron microscope at 40,000x magnification was used. In addition, in (3) above, the structure size of carbon black A or B that was added (used) separately was measured using the same method as described above, except that the image obtained by photographing carbon black A or B under a transmission electron microscope at 40,000x magnification was used.

[0197] <Measurement of carbon black content in recycled materials> The carbon black content in the recycled material was measured using a differential thermogravimetric analyzer [STA200RV, manufactured by Hitachi High-Tech Science Co., Ltd.]. The specific operating procedure was as follows (1) to (3): (1) 6 to 8 mg of recycled material was weighed into a Pt measuring container; (2) The sample temperature was raised to 600°C at a rate of 10°C / min under a nitrogen atmosphere, then cooled to 400°C at a rate of 10°C / min, and then raised to 800°C at a rate of 10°C / min under a simulated air atmosphere (a mixture of oxygen and nitrogen = 21%:79%); (3) In the TG weight loss rate curve obtained in the process of (2) above, the weight ratio of carbon black [weight %] was calculated from the difference between the weight loss rate at 400°C [weight %] and the weight loss rate at 800°C [weight %] during the process of raising the temperature from 400°C to 800°C.

[0198] <Measurement of ash content in recycled materials> The amount of ash in the recycled material was determined from the weight of the recycled material and the weight of the recycled material after combustion. The specific procedure was as follows (1) to (4): (1) The recycled material was heated at 150°C for 1 hour to completely remove moisture; (2) 1 to 2 g of recycled material was placed in a crucible with a weight of W1, and the weight of the crucible containing the recycled material was measured and determined to be W2; (3) Using an electric furnace, the crucible containing the recycled material was held at 300°C for 30 minutes or more, and then held at 750°C for 1 hour or more to burn the recycled material; (4) The crucible was removed from the electric furnace and cooled in a desiccator at 23°C for 1 hour; (5) The weight of the crucible after cooling was measured and determined to be W3; (6) The amount of ash A was determined from the following formula. W1: Crucible weight W2: Weight of crucible before combustion + recycled material W3: Weight of crucible after combustion + recycled material A = (W3 - W1) × 100 / (W2 - W1).

[0199] <Qualitative analysis of ash content> The ash content in the recycled material was identified as talc using infrared spectroscopy. The specific procedure was as follows (1)-(2): (1) The ash content obtained above was pressed onto the crystal part of a total internal reflection analyzer [PerkinElmer Japan Co., Ltd., Spectrum Two], and the resolution was set to 4 cm. -1 Total internal reflection measurements were performed with 16 cumulative measurements, at 500cm. -1 ~4000cm -1 (2) The spectrum at 3700 cm was obtained; (2) The obtained spectrum included -1 Nearby, 1020cm -1 Nearby, 670cm -1 Nearby and within 550cm -1 Four peaks were observed in the vicinity. 3700cm -1 Nearby, 1020cm -1 Nearby, 670cm -1 Nearby and within 550cm -1 The spectral shape, which shows peaks in four nearby locations, is characteristic of talc, thus identifying the ash content in the recycled material as talc.

[0200] <Measurement of DSC ratio of polypropylene resin foam particles> The measurement of the DSC ratio of the foamed particles was carried out using a differential scanning calorimeter [manufactured by Hitachi High-Tech Science Corporation, DSC7020]. The specific operation procedure was as follows (1) to (5): (1) Weighed 5 mg to 6 mg of polypropylene-based resin foamed particles; (2) Raised the temperature of the foamed particles from 40 °C to 220 °C at a heating rate of 10 °C / min to melt the foamed particles; (3) In the DSC curve of the foamed particles obtained in the process of (2) (the DSC curve during the first heating of the foamed particles), (a) Connected the maximum point between the highest melting peak and the melting peak adjacent (low temperature side) to the melting peak with a straight line, and (b) Connected the maximum point and the point representing the temperature after melting with a straight line; (4) (a) (a-1) The heat quantity calculated from the region surrounded by the line segment connecting the maximum point and the point representing the temperature after melting, and (a-2) The DSC curve having the highest melting peak, was defined as the high-temperature side melting heat quantity Qh, (b) (b-1) The heat quantity calculated from the region surrounded by the line segment connecting the maximum point and the point representing the temperature before melting, and (b-2) The DSC curve having the melting peak adjacent (low temperature side) to the maximum point, was defined as the low-temperature side melting heat quantity Ql, (c) Used the high-temperature side melting heat quantity Qh; (5) Calculated the DSC ratio from the following formula: DSC ratio (%) = Qh / (Qh + Ql) × 100.

[0201] <Expansion ratio of polypropylene-based resin foamed particles> The measurement method of the expansion ratio of the foamed particles was as follows (1) to (4): (1) Measured the weight w (g) of the foamed particles; (2) Next, the foamed particles used for the weight measurement were immersed in ethanol in a graduated cylinder, and the volume v (cm 3 ) of the foamed particles was measured based on the increase in the liquid level position of the graduated cylinder; (3) Divided the weight w (g) by the volume v (cm 3 ) to calculate the density ρ1 of the foamed particles; (4) The value obtained by dividing the density ρ2 of the polypropylene-based resin particles used for the production of the foamed particles by the density ρ1 of the foamed particles (ρ2 / ρ1) was defined as the expansion ratio of the foamed particles.

[0202] <Average bubble diameter of foamed particles> The method for measuring the average bubble diameter of foamed particles was as follows (1) to (5): (1) While taking sufficient care not to destroy the bubble membrane (cell membrane) of the foamed particle, the foamed particle was cut using a razor (Feather High Stainless double-edged razor) so as to pass through the center of the foamed particle; (2) The cut surface of the obtained foamed particle was observed using a microscope [(Hyrox Co., Ltd., RH-2000)] and an image of the observed surface was obtained; (3) On the obtained image, a line segment corresponding to a length of 2000 μm was drawn in an arbitrary part of the foamed particle, excluding the surface layer; (4) The number of bubbles n that the line segment passes through was measured and the bubble diameter was calculated from the formula (bubble diameter = 2000 / n (μm)); (5) The same procedure was performed for 10 foamed particles, and the arithmetic mean of the calculated bubble diameters was taken as the average bubble diameter of the foamed particle.

[0203] <Density of foamed molded material> The weight (g) (W) of the obtained foamed molded body was measured. Next, the length, width, and thickness dimensions of the foamed molded body were measured with calipers, and the volume (in units of 1000 cm³) was measured. 3 That is, L)(let's call it V) was calculated. Next, the density of the foamed molded product (g / L) was determined using the formula (density of foamed molded product = W / V).

[0204] <Measurement of blackness and color unevenness in foamed molded products> Using a spectrophotometer [Konica Minolta Japan, Inc., CM-26dG], the L values ​​were measured at 50 arbitrary points on the surface of the foamed molded material, and the average value was defined as the blackness. Only diffuse reflected light was used during measurement. The standard deviation of the measured L values ​​was defined as color uniformity. Blackness and color uniformity were evaluated according to the following criteria. Higher values ​​indicate superior blackness and color uniformity.

[0205] (Blackness) 1 (Excellent): The average value of the measured L-values ​​is less than 28. 0 (Inferior): The average value of the measured L-values ​​is 28 or higher. (Uneven coloring) 1 (Excellent): The standard deviation of the measured L value is less than 2. 0 (Inferior): The standard deviation of the measured L value is 2 or more. <Evaluation of flame retardancy of polypropylene resin-based in-mold foamed molded products> From the obtained foamed molded body, a flame retardancy test sample measuring 350 mm in length, 100 mm in width, and 12 mm in thickness was cut out. Markings A were made at 38 mm from one end of the sample in the longitudinal direction, and B was made at 292 mm. Flame retardancy was evaluated according to the combustion test method specified in FMVSS302. Using an FMVSS flammability tester [manufactured by Suga Test Instruments Co., Ltd.], a burner flame, adjusted to a height of 38 mm with the sample end as the center of the flame, was applied to the longitudinal end of the sample for 15 seconds, and the flame retardancy was evaluated based on the combustion conditions according to the following criteria. A higher numerical value indicates superior flame retardancy. 1 (Superior): The flames are extinguished before they reach mark A, or within 60 seconds or 50 mm after passing mark A. This indicates that it has "self-extinguishing properties." 0 (Inferior): When the flame burns beyond the A mark [38 mm from the edge of the sample where the flame hits] and burns until it reaches the B mark [292 mm from the edge of the sample where the flame hits], or when the flame burns beyond the A mark and then extinguishes more than 60 seconds or more than 50 mm after passing the A mark, the burning rate is 100 mm / min or less. This is called "slow-burning". -1 (Very poor): Cannot be classified as either self-extinguishing or slow-burning. This is referred to as "easily flammable."

[0206] <Surface properties evaluation of polypropylene resin-based in-mold foamed molded products> The surface of the obtained in-molded foamed body was visually inspected, and its surface quality was determined according to the following criteria. For intergranular space (the gaps between polypropylene foam particles), one of the surface quality evaluation indicators, the number of intergranular spaces present in a 50mm square area of ​​the central surface of the molded body was visually counted. A higher number indicates superior surface quality. 2 (Good): The spacing between particles (between polypropylene foam particles) is 0 to 1, and there are no wrinkles, resulting in a beautiful finish. 1 (Acceptable): The grains are spaced 2-3 apart and have no wrinkles. 0 (Unacceptable): There are four or more spaces between grains, and wrinkles are visible.

[0207] The following describes the methods for producing polypropylene resin particles, polypropylene resin foam particles, and polypropylene resin molded foam articles in examples and comparative examples.

[0208] (Example 1) [Production of resin particles] (a) 75 parts by weight of non-recycled polypropylene resin (ethylene / 1-butene / propylene random copolymer), (b) 25 parts by weight of recycled material-1, (c) 3 parts by weight of carbon black A, (d) 0.2 parts by weight of glycerin, (e) 0.05 parts by weight of talc, and (f) 0.10 parts by weight of hindered amine flame retardant were dry blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using a twin-screw extruder [Toshiba Machine Co., Ltd., TEM26-SX], and the extruded strands were water-cooled in a 2m long water bath and then cut to produce polypropylene resin particles (1.2 mg / particle).

[0209] [Production of foamed particles and foamed molded products] In a 10L pressure-resistant autoclave, 100 parts by weight (2.4 kg) of polypropylene resin particles obtained as described above, 200 parts by weight of water, 0.3 parts by weight of kaolin [BASF, ASP170] as a dispersant, and 0.038 parts by weight of an aqueous solution of sodium dodecylbenzenesulfonate [Kao Corporation, Neoperex G-15, an aqueous solution of 16% sodium dodecylbenzenesulfonate] were charged as a dispersion aid. After stirring, 4 parts by weight of carbon dioxide was added as a foaming agent. The contents of the autoclave were heated to a foaming temperature of 155.5°C and held for 10 minutes. Then, carbon dioxide was added under pressure to increase the internal pressure of the autoclave to a foaming pressure of 2.2 MPa. After holding at the foaming temperature and pressure for 20 minutes, the valve at the bottom of the autoclave was opened and the contents were released to atmospheric pressure through a 3.6 mm diameter open orifice to obtain polypropylene resin foam particles with a foaming ratio of 17 times. During this process, carbon dioxide was injected to maintain the pressure inside the container and prevent it from dropping.

[0210] The obtained foamed particles were dried at 80°C, then impregnated with pressurized air in a pressure-resistant container to an internal pressure of 0.3 MPa (absolute pressure), and subsequently exposed to 0.07 MPa (gauge pressure) of water vapor to induce two-stage foaming. The resulting two-stage foamed particles had a foaming ratio of 25 times.

[0211] The obtained two-stage foamed particles were placed in a pressure vessel, impregnated with pressurized air, and the polypropylene resin foamed particles, pre-adjusted to an internal pressure of 0.20 MPa (absolute pressure), were filled into a mold measuring 370 mm (length) x 320 mm (width) x 50 mm (thickness). Subsequently, the mold chamber was heated with 0.30 MPa of steam to fuse the foamed particles together. After water-cooling the inside of the mold and the surface of the molded body, the molded body was removed to obtain a polypropylene resin in-molded foamed molded body. The obtained in-molded foamed molded body was left to stand at 23°C for 2 hours, and then cured at 75°C for 16 hours.

[0212] (Examples 2 and 3) Except for changing the formulation in the [Preparation of Resin Particles] step as shown in Table 1 or Table 2, and changing the foaming conditions in the [Preparation of Foamed Particles and Foamed Molded Articles] step as shown in Table 1 or Table 2, polypropylene resin particles, polypropylene resin foamed particles, and polypropylene resin in-mold foamed molded articles were prepared using the same procedure as in Example 1.

[0213] (Examples 4 and 5) (a) The non-recycled polypropylene-based resin in the amount shown in Table 1, (b) the recycled material-1 and recycled material-2 in the amounts shown in Table 1, (c) 3 parts by weight of carbon black A, (d) 0.2 parts by weight of glycerin, (e) 0.05 parts by weight of talc, and (f) 0.10 parts by weight of a hindered amine-based flame retardant were dry-blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a water tank with a length of 2 m and then cut to produce polypropylene-based resin particles (1.2 mg / particle). Except that the foaming conditions were changed as shown in Table 1 in [Production of Foamed Particles and Foamed Moldings], polypropylene-based resin foamed particles and polypropylene-based resin in-mold foamed moldings were produced by the same operations as in Example 1.

[0214] (Comparative Example 1) (a) The non-recycled polypropylene-based resin in the amount shown in Table 1, (b) the recycled material-1 and recycled material-2 in the amounts shown in Table 1, (c) 0.2 parts by weight of glycerin, (d) 0.05 parts by weight of talc, and (e) 0.10 parts by weight of a hindered amine-based flame retardant were dry-blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a water tank with a length of 2 m and then cut to produce polypropylene-based resin particles (1.2 mg / particle). Except that the foaming conditions were changed as shown in Table 2 in [Production of Foamed Particles and Foamed Moldings], polypropylene-based resin foamed particles and polypropylene-based resin in-mold foamed moldings were produced by the same operations as in Example 1.

[0215] (Comparative Example 2) (a) Recycled material-1 in the amount shown in Table 1, (b) 3 parts by weight of carbon black A, (c) 0.2 parts by weight of glycerin, (d) 0.05 parts by weight of talc, and (e) 0.10 parts by weight of hindered amine flame retardant were dry blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a 2m long water bath and then cut to produce polypropylene resin particles (1.2 mg / particle). [Preparation of foamed particles and foamed molded articles] Polypropylene resin foamed particles and polypropylene resin molded articles were produced by the same procedure as in Example 1, except that the foaming conditions were changed as shown in Table 2.

[0216] (Comparative Example 3) (a) Recycled material-1 and recycled material-2 in the amounts shown in Table 1, (b) 3 parts by weight of carbon black A, (c) 0.2 parts by weight of glycerin, (d) 0.05 parts by weight of talc, and (e) 0.10 parts by weight of hindered amine flame retardant were dry blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a 2m long water bath and then cut to produce polypropylene resin particles (1.2 mg / particle). [Preparation of foamed particles and foamed molded articles] Polypropylene resin foamed particles and polypropylene resin molded articles were produced by the same procedure as in Example 1, except that the foaming conditions were changed as shown in Table 2.

[0217] (Reference example 1) (a) 100 parts by weight of non-recycled polypropylene resin, (b) 3 parts by weight of carbon black A, (c) 0.2 parts by weight of glycerin, (d) 0.05 parts by weight of talc, and (e) 0.10 parts by weight of hindered amine flame retardant were dry-blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a 2m water bath and then cut to produce polypropylene resin particles (1.2 mg / particle). [Preparation of foamed particles and foamed molded articles] Polypropylene resin foamed particles and polypropylene resin in-molded foamed molded articles were produced by the same procedure as in Example 1, except that the foaming conditions were changed as shown in Table 2. The evaluation results of the obtained polypropylene resin foamed particles and polypropylene resin in-molded foamed molded articles are shown in Table 2.

[0218] (Reference example 2) (a) 100 parts by weight of non-recycled polypropylene resin, (b) 3 parts by weight of carbon black A, (c) 0.2 parts by weight of glycerin, (d) 0.25 parts by weight of talc, and (e) 0.10 parts by weight of hindered amine flame retardant were dry-blended using a blender to obtain a mixture. The obtained mixture was melt-kneaded at a resin temperature of 220°C using the same twin-screw extruder as in Example 1, and the extruded strands were water-cooled in a 2m long water bath and then cut to produce polypropylene resin particles (1.2 mg / particle). [Preparation of foamed particles and foamed molded articles] Polypropylene resin foamed particles and polypropylene resin molded articles were produced by the same procedure as in Example 1, except that the foaming conditions were changed as shown in Table 2.

[0219] The formulations used in the production of polypropylene resin particles in each example, comparative example, and reference example are shown in Table 1 or Table 2. In Table 1 or Table 2, (i) the amount of carbon black B is the sum of the amount of carbon black B derived from recycled materials and the amount of carbon black B added separately, and (ii) the amount of talc is the sum of the amount of talc derived from recycled materials and the amount of talc added separately.

[0220] Various measurements and evaluations were performed on the polypropylene resin foam particles and polypropylene resin molded foam articles obtained in each example, comparative example, and reference example. The results are shown in Table 1 or Table 2.

[0221] [Table 1]

[0222] [Table 2]

[0223] Reference Examples 1 and 2 show the evaluation results of conventional foamed particles that do not contain recycled materials. As can be seen from the comparison of Reference Examples 1 and 2, it has been confirmed that conventionally, when the amount of talc contained in the resin particles is increased from 0.05 parts by weight to 0.25 parts by weight, the average bubble diameter decreases and color unevenness worsens. Examples 1 to 5 show the evaluation results of polypropylene resin foamed particles and polypropylene resin in-molded foamed molded articles according to one embodiment of the present invention. As can be seen from Examples 1 to 5, in-molded foamed molded articles made of polypropylene resin foamed particles obtained by this manufacturing method have no color unevenness, excellent blackness and surface appearance, and good flame retardancy, even when talc is contained in amounts of 0.25 parts by weight or more. Comparative Examples 1 to 3 show a structure size of 1.0 × 10 4 nm 2 The results showed that reducing the carbon black content below a certain level could improve blackness and flame retardancy. [Industrial applicability]

[0224] Polypropylene foam particles according to one embodiment of the present invention have the advantage of improving blackness and flame retardancy after molding. Polypropylene foam molded articles can be suitably used in a variety of applications such as cushioning packaging materials, logistics materials, heat insulation materials, civil engineering and construction components, and automotive components.

Claims

1. Polypropylene resin foam particles containing a base resin and carbon black, The base resin comprises a non-recycled polypropylene resin and a recycled polypropylene resin and / or a recycled polyethylene resin. The total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight in 100 parts by weight of the base resin, The carbon black has a structure size of 1 × 10⁻¹⁶ per structure relative to the total number of carbon blacks. ４ nm ２ Polypropylene resin foam particles in which the proportion of carbon black particles less than 10% is between 10% and 50%.

2. The average structure size is 0.2×10 ４ nm ２ or more and 4.0×10 ４ nm ２ less than carbon black A, and an average structure size of 5.0×10 ４ nm ２ or more and 9.0×10 ４ nm ２ less than carbon black B, and the polypropylene-based resin foam particles according to claim 1.

3. Polypropylene resin foam particles according to claim 1, further comprising a foaming nucleating agent.

4. The polypropylene resin foam particles according to claim 3, wherein the content of the foaming nucleating agent is 0.05 parts by weight to 0.50 parts by weight per 100 parts by weight of the base resin.

5. The polypropylene resin foam particles according to claim 3, wherein the content of the foaming nucleating agent is 0.20 parts by weight to 0.50 parts by weight per 100 parts by weight of the base resin.

6. The polypropylene resin foam particles according to claim 3, wherein the foaming agent is talc.

7. Polypropylene resin foam particles according to claim 1, further comprising a hindered amine-based flame retardant.

8. The polypropylene resin foam particles according to claim 2, wherein the carbon black A content is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

9. The polypropylene resin foam particles according to claim 2, wherein the carbon black B content is 0.10 parts by weight to 2.00 parts by weight per 100 parts by weight of the base resin.

10. The polypropylene resin foam particles according to claim 1, wherein the base resin includes the recycled polyethylene resin, and the recycled polyethylene resin includes the recycled high-density polyethylene resin.

11. The polypropylene resin foam particles according to claim 1, wherein when the total content of the recycled polypropylene resin and the recycled polyethylene resin is 100 parts by weight, the recycled polypropylene resin is 60 to 100 parts by weight and the recycled polyethylene resin is 0 to 40 parts by weight.

12. The average structure size is 10.0 x 10 ４ nm ２ The polypropylene resin foam particles according to claim 1, which either do not contain carbon black C as described above, or contain less than 0.5 parts by weight of carbon black C per 100 parts by weight of the base resin.

13. The non-recycled polypropylene resin contains 60% by weight or more of one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer, in 100% by weight of the non-recycled polypropylene resin, according to claim 1, the polypropylene resin foam particles.

14. The polypropylene resin foam particles according to claim 1, wherein the base resin comprises the recycled polypropylene resin, and the recycled polypropylene resin comprises one or more selected from the group consisting of ethylene / propylene alternating copolymer, ethylene / 1-butene / propylene alternating copolymer, ethylene / propylene random copolymer, and ethylene / 1-butene / propylene random copolymer.

15. The polypropylene resin foam particles according to claim 1, wherein the base resin contains, in a total of 80 to 100 parts by weight of the non-recycled polypropylene resin, the recycled polypropylene resin, and the recycled polyethylene resin per 100 parts by weight of the base resin.

16. A polypropylene resin foam molded article obtained by molding polypropylene resin foam particles according to any one of claims 1 to 15.

17. Non-recycled polypropylene resin, recycled materials, and an average structure size of 0.2 x 10 ４ nm ２ The above 4.0 x 10 ４ nm ２ A granulation process involves melting and kneading a mixture containing carbon black A, which is less than [amount missing], to obtain polypropylene resin particles. A dispersion step in which the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent are dispersed in a container. A heating step in which the temperature inside the container is heated to a temperature above the softening temperature of polypropylene resin particles, A pressurization process to increase the pressure inside the container, The process includes a release step in which one end of the container is opened and the dispersion liquid inside the container is released into a region with a pressure lower than the pressure inside the container. The recycled material comprises recycled polypropylene resin and / or recycled polyethylene resin, with an average structure size of 5.0 × 10 ４ nm ２ The above 9.0 x 10 ４ nm ２ It includes carbon black B which is less than, A method for producing foamed polypropylene resin particles, wherein the amount of recycled material used is such that, in 100 parts by weight of a base resin containing the non-recycled polypropylene resin, the recycled polypropylene resin, and / or the recycled polyethylene resin, the total content of the recycled polypropylene resin and the recycled polyethylene resin is 10 to 60 parts by weight.

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