Polypropylene-based foamed resin particle, polypropylene-based foamed resin molded body, and method for producing polypropylene-based foamed resin particles

Abstract

The present invention addresses the problem of providing polypropylene-based foamed resin particles which contain a recycled polypropylene-based resin and with which it is possible to provide a polypropylene-based foamed resin molded body having excellent internal fusion properties. The polypropylene-based foamed resin particles contain a base material resin containing a non-recycled polypropylene-based resin and a specific amount of a recycled material that contains a recycled polypropylene-based resin. The crystallization temperature of the recycled material is higher than the crystallization temperature of the non-recycled polypropylene-based resin.

Description

Polypropylene-based resin expanded beads, polypropylene-based resin expanded molded article, and method for producing polypropylene-based resin expanded beads

[0001] The present invention relates to expanded polypropylene resin beads, expanded molded polypropylene resin articles, and a method for producing expanded polypropylene resin beads.

[0002] Polypropylene resin foam molded articles are used in a variety of applications, including automotive interior components, core materials for automotive bumpers, heat insulating materials, cushioning packaging materials, and returnable containers.

[0003] In recent years, in order to reduce the environmental load, there has been a demand for using recycled resins when producing resin products, and the use of recycled resins has been attracting attention (for example, Patent Document 1).

[0004] Japanese Patent Application Publication No. 2023-049877

[0005] However, the above-mentioned conventional techniques using recycled polypropylene resins are not sufficient from the viewpoint of internal fusion properties of foamed molded articles, and there is room for further improvement.

[0006] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its object is to provide novel expanded polypropylene-based resin beads that contain recycled polypropylene-based resin and can provide a polypropylene-based resin foamed molded article with excellent internal fusion properties.

[0007] As a result of intensive research into solving the above-mentioned problems, the present inventors independently discovered the following new findings, which led to the completion of the present invention: Surprisingly, polypropylene-based resin foamed particles containing a non-recycled polypropylene-based resin and a specific amount of recycled material having a crystallization temperature higher than that of the non-recycled polypropylene-based resin can provide a polypropylene-based resin foamed molded article having excellent internal fusion properties.

[0008] That is, the expanded polypropylene-based resin beads according to one embodiment of the present invention are expanded polypropylene-based resin beads containing a base resin, the base resin containing a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin, the content of the recycled material in the base resin being 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material being higher than the crystallization temperature of the non-recycled polypropylene-based resin.

[0009] Furthermore, a method for producing expanded polypropylene-based resin beads according to one embodiment of the present invention includes a granulation step of melt-kneading a base resin containing a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin to obtain polypropylene-based resin particles; a dispersion step of dispersing the polypropylene-based resin particles, an aqueous dispersion medium, and a blowing agent in a container to obtain a dispersion; a heating step of heating the dispersion to a temperature equal to or higher than the softening temperature of the polypropylene-based resin particles; a pressurizing step of increasing the pressure inside the container; and a discharging step of releasing one end of the container to discharge the dispersion inside the container into a region with a pressure lower than the pressure inside the container, wherein the amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material is higher than the crystallization temperature of the non-recycled polypropylene-based resin.

[0010] According to one embodiment of the present invention, it is possible to provide novel expanded polypropylene-based resin beads that contain recycled polypropylene-based resin and that can provide expanded polypropylene-based resin molded articles with excellent internal fusion properties.

[0011] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective 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. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the term "A to B" representing a numerical range means "greater than or equal to A (including and greater than A) and less than or equal to B (including and less than B)."

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

[0013] Unless otherwise specified in this specification, the structural unit is X １ Units and X ２ Units, ... and X ｎ A copolymer containing units (n is an integer of 2 or more) is referred to as "X １ / X ２ / ・・・ / X ｎ Also referred to as "copolymer". X １ / X ２ / ・・・ / X ｎ Unless otherwise specified, the polymerization mode of the copolymer is not particularly limited, and the copolymer may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

[0014] In this specification, "polypropylene-based resin particles" may be referred to as "resin particles," "expanded polypropylene-based resin particles" may be referred to as "expanded particles," "expanded polypropylene-based resin particles according to one embodiment of the present invention" may be referred to as "the present expanded particles," "polypropylene-based resin foam molded body" may be referred to as "foam molded body," and "polypropylene-based resin foam molded body according to one embodiment of the present invention" may be referred to as "the present foam molded body." In this specification, "method for producing expanded polypropylene-based resin particles" may be referred to as "production method," and "method for producing expanded polypropylene-based resin particles according to one embodiment of the present invention" may be referred to as "the present production method."

[0015] 1. Expanded Polypropylene Resin Beads Expanded polypropylene resin beads according to one embodiment of the present invention include a base resin, which includes a non-recycled polypropylene resin and a recycled material including a recycled polypropylene resin, the content of the recycled material in the base resin being 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material being higher than the crystallization temperature of the non-recycled polypropylene resin.

[0016] The present expanded beads can be molded by a known method to provide a foamed molded article (the present expanded molded article).

[0017] The present expanded beads contain recycled materials, including recycled polypropylene-based resins. Furthermore, because the present expanded beads have the above-described structure, they have the advantage of being able to provide polypropylene-based resin foam molded articles with excellent internal fusion. Foam molded articles produced by molding expanded beads containing recycled materials, including recycled polypropylene-based resins, also contain recycled materials, including recycled polypropylene-based resins. That is, the present expanded beads and the present expanded molded articles contain recycled materials (recycled polypropylene-based resins), as described above. Therefore, the present expanded beads and the present expanded molded articles can be said to have a low environmental impact. In other words, one embodiment of the present invention uses recycled materials (recycled polypropylene-based resins). Therefore, one embodiment of the present invention not only reduces environmental pollution, but also significantly reduces the amount of plastic waste generated and the amount of plastic used in manufacturing. As a result, one embodiment of the present invention can contribute to the achievement of the Sustainable Development Goals (SDGs), for example, Goal 12, "Ensure sustainable consumption and production patterns," and Goal 14, "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0018] The expanded polypropylene resin beads according to a preferred embodiment of the present invention surprisingly have an advantage in that the molding cycle required for producing a foamed molded article from the expanded beads is short.

[0019] The expanded polypropylene resin particles according to a preferred embodiment of the present invention can also be said to be expanded polypropylene resin particles obtained by expanding polypropylene resin particles containing a base resin.

[0020] <Components> (2-1. Base Resin) In this specification, the base resin refers to a resin component that substantially constitutes the polypropylene-based resin foam particles and the polypropylene-based resin foam molded article. The base resin includes non-recycled polypropylene-based resin and recycled material.

[0021] As used herein, the term "recycled material" refers to (a) a resin composition (or pellets) obtained by reusing a resin product (e.g., foam particles; foam molded products; films; food trays; packaging containers such as bags and bottles; medical containers such as IV packs and syringes; clothing cases; miscellaneous goods such as clear files; home appliances; automobile parts; etc.) that has been used and / or discarded, and then reusing the resin composition (or pellets) by any means (e.g., crushing, shredding, melting, and combinations thereof); and (b) a resin composition obtained by reusing waste generated during the manufacturing process of a resin product by any means (e.g., crushing, shredding, melting, and combinations thereof). Resin product recovery is often performed by collecting resin products for each intended use and / or by collecting the raw materials used for the resin product. Therefore, recycled materials may primarily contain resins of the same or substantially the same composition (e.g., polypropylene-based resins, polyethylene-based resins, etc.). On the other hand, in the recovery of resin products, the resin product to be recovered may be mixed with other resin products for different purposes and / or made from different raw materials. Therefore, the recycled material may contain, in addition to the resin that is the main component, resins with compositions other than the resin in question.

[0022] In this specification, the resin contained in the recycled material may be referred to as a "recycled resin." For example, a recycled material obtained by (a) converting a resin product obtained primarily from a polypropylene-based resin into a resin composition by any means, and / or (b) converting waste generated during the production process of a resin product using a polypropylene-based resin as a primary raw material into a resin composition by any means, contains recycled polypropylene-based resin as the recycled resin. A recycled material containing mainly recycled polypropylene-based resin as the resin may contain recycled polyethylene-based resin as the recycled resin in an amount less than the amount of recycled polypropylene-based resin.

[0023] The recycled material may contain additives used in the manufacturing process of the resin product (for example, various additives described below in the section (2-3. Additives), such as foam nucleating agents (e.g., talc, calcium carbonate, silica, kaolin, barium sulfate, calcium hydroxide, aluminum hydroxide, aluminum oxide, titanium oxide, zinc borate, etc.) and colorants).

[0024] In this specification, the origin of the recycled material is not particularly limited. The recycled material may be derived from a foam such as foam particles and foam molded products. The recycled material may also be derived from a non-foamed material (for example, films; food trays; packaging containers such as bags and bottle containers; medical containers such as intravenous packs and syringes; clothing cases; miscellaneous goods such as clear files; home appliances; automobile parts; fishing gear such as fishing nets, ropes, and floats).

[0025] In this specification, a polypropylene-based resin that has never been in the form of a resin product is referred to as a "non-recycled polypropylene-based resin."

[0026] (Polypropylene-based resin) In this section only, unless otherwise specified, the term "polypropylene-based resin" refers to both non-recycled polypropylene-based resin and recycled polypropylene-based resin.

[0027] In this specification, the term "polypropylene resin" refers to a resin having the highest content of propylene units among all structural units constituting the resin. For example, the polypropylene resin contains 50 mol % or more of propylene units in 100 mol % of all structural units.

[0028] The polypropylene-based 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. Block copolymers are sometimes called impact copolymers. Propylene homopolymers, block copolymers, alternating copolymers, and random copolymers of propylene and a monomer other than propylene are all linear polymers. It is preferable that the polypropylene-based resin is a linear polymer.

[0029] A polypropylene-based resin may have, in addition to a propylene unit, one or more units, or may have one or more types, of structural units derived from a monomer other than a propylene monomer. A "monomer other than a propylene monomer" used in the production of a polypropylene-based resin may be referred to as a "comonomer," and a "structural unit derived from a monomer other than a propylene monomer" contained in a polypropylene-based resin may be referred to as a "comonomer unit."

[0030] Comonomers used in the production of polypropylene-based resins 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.

[0031] Specific examples of polypropylene-based 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, styrene-modified polypropylene-based resins, etc. As the polypropylene-based resin, one of these may be used alone, or two or more may be used in combination.

[0032] Polypropylene-based resins can be obtained by known methods. The polymerization catalyst used to synthesize the polypropylene-based resin is not particularly limited, and Ziegler-Natta catalysts, metallocene catalysts, and the like can be used. From the viewpoints of availability, production cost, production stability, and the expandability of the resulting resin particles, the polypropylene-based resin (i.e., non-recycled polypropylene-based resin and / or recycled polypropylene-based resin) is preferably a resin polymerized using a Ziegler-Natta catalyst as the polymerization catalyst. Resins polymerized using a Ziegler-Natta catalyst as the polymerization catalyst may contain a Ziegler-Natta catalyst. In other words, the polypropylene-based resin preferably contains a Ziegler-Natta catalyst. It is extremely difficult to determine by analyzing the polypropylene-based resin itself whether it is a polypropylene-based resin polymerized using a Ziegler-Natta catalyst or a polypropylene-based resin polymerized using a metallocene catalyst.

[0033] (Non-recycled polypropylene-based resin) In the following, non-recycled polypropylene-based resin will be described.

[0034] From the viewpoint of moldability, the non-recycled polypropylene-based resin is preferably (a) an alternating copolymer composed of propylene units and comonomer units (e.g., ethylene units and 1-butene units) arranged alternately, and / or (b) a random copolymer composed of propylene units and comonomer units (e.g., ethylene units and 1-butene units) arranged in a random order. Because of their easy availability, the non-recycled polypropylene-based resin more preferably contains one or more copolymers selected from the group consisting of ethylene / propylene alternating copolymers, ethylene / 1-butene / propylene alternating copolymers, ethylene / propylene random copolymers, and ethylene / 1-butene / propylene random copolymers.

[0035] From the viewpoints of moldability and availability, the non-recycled polypropylene resin preferably contains at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 90 wt%, and particularly preferably at least 95 wt%, 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, based on 100 wt% of the non-recycled polypropylene resin. The upper limit of the content of one or more selected from the above group based on 100 wt% of the non-recycled polypropylene resin is not particularly limited, and may be, for example, 100 wt%. Most preferably, the non-recycled polypropylene resin is composed solely of at least one 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.

[0036] The crystallization temperature of the non-recycled polypropylene resin is not particularly limited. The crystallization temperature of the non-recycled polypropylene resin is preferably 95°C to 120°C, more preferably 98°C to 117°C, more preferably 100°C to 115°C, even more preferably 103°C to 112°C, and particularly preferably 105°C to 110°C. This configuration has the advantage that the cell diameter of the expanded polypropylene resin particles is less likely to become fine. The method for measuring the crystallization temperature of the non-recycled polypropylene resin will be described in detail in the Examples below.

[0037] The melt flow rate (sometimes referred to as "MFR") of the non-recycled polypropylene resin at 230°C is not particularly limited. The MFR of the non-recycled polypropylene resin at 230°C is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more, more preferably 3 g / 10 min or more, even more preferably 4 g / 10 min or more, and particularly preferably 5 g / 10 min or more. When the MFR of the non-recycled polypropylene resin at 230°C is 1 g / 10 min or more, it tends to be easier to increase the expansion ratio of the expanded beads in the production of the expanded beads. The MFR of the non-recycled polypropylene resin at 230°C is preferably 30 g / 10 min or less, more preferably 25 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 15 g / 10 min or less, and particularly preferably 10 g / 10 min or less. When the MFR of the non-recycled polypropylene resin at 230°C is 30 g / 10 min or less, there is no risk of the cells of the resulting expanded beads becoming interconnected, and as a result, (i) the compressive strength of the expanded molded article obtained from the expanded beads tends to be good, (ii) the surface properties of the expanded molded article tends to be good, and / or (iii) the molding cycle of the expanded molded article tends to be short. The "bubbles" of the expanded beads are sometimes referred to as "cells." That is, in this specification, "bubbles" can be read as "cells," and vice versa. The method for measuring the MFR of the non-recycled polypropylene resin at 230°C will be described in detail in the Examples below.

[0038] The melting point of the non-recycled polypropylene resin is not particularly limited. The melting point of the non-recycled polypropylene resin is preferably 160°C or lower, more preferably 158°C or lower, more preferably 155°C or lower, even more preferably 153°C or lower, and particularly preferably 152°C or lower. When the melting point of the non-recycled polypropylene resin is 160°C or lower, it is easy to increase the expansion ratio of the expanded beads in the production of the expanded beads. The melting point of the non-recycled polypropylene resin is preferably 125°C or higher, more preferably 127°C or higher, more preferably 130°C or higher, even more preferably 132°C or higher, and particularly preferably 135°C or higher. When the melting point of the non-recycled polypropylene resin is 125°C or higher, the expanded molded article obtained from the expanded beads has excellent heat resistance. The method for measuring the melting point of the non-recycled polypropylene resin will be explained in detail in the Examples below.

[0039] (2-2. Recycled Material) In one embodiment of the present invention, the recycled material includes a recycled polypropylene-based resin, that is, the base resin includes at least a non-recycled polypropylene-based resin and a recycled polypropylene-based resin.

[0040] (Recycled Polypropylene Resin) Hereinafter, recycled polypropylene resin will be described.

[0041] From the viewpoint of moldability, the recycled polypropylene resin is preferably (a) a block copolymer composed of propylene units and comonomer units (e.g., ethylene units and 1-butene units) and composed of a block structure composed only of propylene units and a block structure composed only of comonomer units, (b) an alternating copolymer composed of propylene units and comonomer units (e.g., ethylene units and 1-butene units) in which the two units are arranged alternately, and / or (c) a random copolymer composed of propylene units and comonomer units (e.g., ethylene units and 1-butene units) in which the two units are arranged in random order. In the block copolymer, the arrangement order of the block structure composed only of propylene units and the block structure composed only of comonomer units is not particularly limited. Because they are easily available, the recycled polypropylene-based resin more preferably contains one or more selected from the group consisting of ethylene / propylene block copolymers, ethylene / 1-butene / propylene block copolymers, ethylene / propylene alternating copolymers, ethylene / 1-butene / propylene alternating copolymers, ethylene / propylene random copolymers, and ethylene / 1-butene / propylene random copolymers.

[0042] From the viewpoints of moldability and availability, the recycled polypropylene resin preferably contains at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 90 wt%, and particularly preferably at least 95 wt%, of one or more copolymers selected from the group consisting of ethylene / propylene alternating copolymers, ethylene / 1-butene / propylene alternating copolymers, ethylene / propylene random copolymers, and ethylene / propylene random copolymers, based on 100 wt% of the recycled polypropylene resin. Most preferably, the recycled polypropylene resin is composed solely of at least one copolymer selected from the group consisting of ethylene / propylene block copolymers, ethylene / 1-butene / propylene block copolymers, ethylene / propylene alternating copolymers, ethylene / 1-butene / propylene alternating copolymers, ethylene / propylene random copolymers, and ethylene / 1-butene / propylene random copolymers.

[0043] Because of its excellent recyclability and moldability, the recycled material preferably contains mainly recycled polypropylene-based resin as the recycled resin. Because of its excellent recyclability and moldability, the recycled material preferably contains 50 parts by weight or more of recycled polypropylene-based resin per 100 parts by weight of the recycled material, more preferably 60 parts by weight or more, even more preferably 70 parts by weight or more, and particularly preferably 80 parts by weight or more. The upper limit of the content of recycled polypropylene-based resin in the recycled material is not particularly limited, and may be, for example, 100 parts by weight or less per 100 parts by weight of the recycled material.

[0044] The base resin preferably contains 60 to 100 parts by weight, more preferably 70 to 100 parts by weight, and even more preferably 80 to 100 parts by weight of non-recycled polypropylene-based resin and recycled polypropylene-based resin in total, per 100 parts by weight of the base resin. This configuration has the advantage of minimizing the decrease in strength of the resulting foamed molded article.

[0045] (Recycled Polyethylene Resin) The recycled material may contain a recycled polyethylene resin. In other words, the base resin may further contain a recycled polyethylene resin in addition to the non-recycled polypropylene resin and the recycled polypropylene resin.

[0046] In this specification, the term "recycled polyethylene resin" refers to a recycled resin having the highest content of ethylene units among all structural units constituting the resin. The recycled polyethylene resin contains, for example, 50 mol % or more of ethylene units out of 100 mol % of all structural units.

[0047] In this specification, a resin that is composed of equal amounts of propylene units and ethylene units is referred to as a "polypropylene-based resin."

[0048] Because of excellent recyclability and moldability, the smaller the amount of recycled polyethylene resin in the recycled material, the more preferable. The recycled material preferably contains 20 parts by weight or less of recycled polyethylene resin per 100 parts by weight of the recycled material, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, and particularly preferably 1 part by weight or less. The amount of recycled polyethylene resin in the recycled material may be more than 0 parts by weight, or even 0 parts by weight. In other words, the recycled material may not contain recycled polyethylene resin.

[0049] The crystallization temperature of the recycled material is not particularly limited as long as it is higher than the crystallization temperature of the non-recycled polypropylene-based resin. The crystallization temperature of the recycled material is preferably 100°C to 130°C, more preferably 103°C to 125°C, more preferably 105°C to 120°C, even more preferably 107°C to 115°C, and particularly preferably 108°C to 113°C. This configuration has the advantage that the cell diameter of the expanded polypropylene-based resin particles is less likely to become fine. Furthermore, the crystallization temperature of the recycled material may vary depending on the ash content (residue that remains unburned when burned at 750°C for one hour or more) contained in the recycled material. The method for measuring the crystallization temperature of the recycled material will be described in detail in the Examples below.

[0050] The difference between the crystallization temperature of the recycled material and the crystallization temperature of the non-recycled polypropylene resin is not particularly limited. Since a foamed molded article having excellent internal fusion properties can be provided, the difference between the crystallization temperature of the recycled material and the crystallization temperature of the non-recycled polypropylene resin is preferably 1°C or more. Through extensive research, the present inventors have discovered the novel finding that a difference between the crystallization temperature of the recycled material and the crystallization temperature of the non-recycled polypropylene resin of 17°C or less has the advantage that the bubble diameter of the expanded polypropylene resin beads is less likely to become fine. Therefore, the difference between the crystallization temperature of the recycled material and the crystallization temperature of the non-recycled polypropylene resin is preferably 17°C or less, and more preferably 15°C or less.

[0051] The MFR of the recycled material at 230°C is not particularly limited. The MFR of the recycled material at 230°C is preferably 1 g / 10 min to 30 g / 10 min, more preferably 1 g / 10 min to 25 g / 10 min, even more preferably 2 g / 10 min to 20 g / 10 min, and particularly preferably 3 g / 10 min to 18 g / 10 min. This configuration eliminates the risk of interconnected cells in the resulting expanded beads, resulting in (i) a tendency for the present expanded molded article obtained from the expanded beads to have good compressive strength, (ii) a tendency for the surface properties of the expanded molded article to be good, and / or (iii) a tendency for the molding cycle of the expanded molded article to be shortened. Furthermore, when the MFR of the recycled material at 230°C is within the above-mentioned range, the compatibility between the non-recycled polypropylene resin and the recycled material tends to be good, and / or it tends to be easier to increase the expansion ratio of the expanded beads during production. The method for measuring the MFR of the recycled material at 230° C. will be explained in detail in the Examples below.

[0052] The melting point of the recycled material is not particularly limited. The melting point of the recycled material is preferably 135°C to 170°C, more preferably 140°C to 165°C, even more preferably 143°C to 160°C, and particularly preferably 145°C to 158°C. This configuration has the following advantages: (i) it is easy to increase the expansion ratio of the expanded beads in the production of the expanded beads; (ii) the expanded molded article obtained from the expanded beads has excellent heat resistance; and / or (iii) the compatibility between the non-recycled polypropylene resin and the recycled material is good. The method for measuring the melting point of the recycled material will be described in detail in the Examples below.

[0053] The content of the recycled material in the base resin is 10 to 90 parts by weight, preferably 15 to 90 parts by weight, more preferably 20 to 90 parts by weight, even more preferably 23 to 90 parts by weight, and particularly preferably 25 to 87 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.

[0054] As mentioned above, the recycled material may contain additives used in the manufacturing process of the resin product. In this specification, even if the recycled material contains additives that are not resin components, the amount of recycled material used is defined as the content of the recycled material in the base resin of the obtained expanded beads.

[0055] (Other Resins, etc.) The base resin may further contain resins other than the non-recycled polypropylene-based resin and the recycled materials described above (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 include: (a) non-recycled polyethylene-based resins; (b) recycled materials that do not contain recycled polypropylene-based resins; (c) styrene-based resins such as polystyrene, styrene / maleic anhydride copolymers, and styrene / ethylene copolymers; (d) polyolefin-based waxes such as propylene-α-olefin-based waxes; and (e) olefin-based rubbers such as ethylene / propylene rubber, ethylene / butene rubber, ethylene / hexene rubber, and ethylene / octene rubber. The content of such 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 the non-recycled polypropylene-based resin and the recycled material containing the recycled polypropylene-based resin.

[0056] (2-3. Additives) The present expanded particles may further contain optional additives in addition to the base resin containing a non-recycled polypropylene-based resin and a recycled material including a recycled polypropylene-based resin. Examples of additives include colorants, water-absorbing substances (e.g., (i) polyols such as glycerin and diglycerin, (ii) polyethers such as polyethylene glycol and polyethylene oxide, and (iii) metal borates such as borax and zinc borate), foam nucleating agents (e.g., inorganic substances such as talc, calcium carbonate, silica, kaolin, barium sulfate, calcium hydroxide, aluminum hydroxide, aluminum oxide, titanium oxide, and zinc borate), antistatic agents (e.g., glycerin monostearate, glycerin monodistearate, and the like), and flame retardants. Examples of suitable flame retardants include flame retardants (e.g., hindered amine flame retardants, bromine flame retardants, phosphate ester flame retardants, melamine flame retardants, etc.), antioxidants (e.g., hindered phenol antioxidants, etc.), heat stabilizers (e.g., phosphorus-based heat stabilizers and sulfur-based heat stabilizers, etc.), light stabilizers (benzotriazole UV absorbers, triazine UV absorbers, HALS and / or hindered amine light stabilizers, etc.), nucleating agents, conductive agents (carbon, carbon nanotubes, metal fillers, etc.), lubricants, acid scavengers, antiblocking agents, metal chelating agents (IRGANOX MD1024, ADK STAB CDA-1, etc.), lubricants, antibacterial agents, etc. The expanded beads may also contain an additive for recycled materials containing any one or a combination of two or more of these additives.

[0057] (Colorant) Examples of colorants include chromatic pigments and carbon black. In this specification, the term "chromatic pigment" refers to a pigment that can produce a color other than white, gray, and black. In this specification, the term "chromatic pigment" does not include carbon black. Examples of chromatic pigments include (i) blue pigments such as copper phthalocyanine blue, ultramarine, cobalt blue, and Prussian blue; (ii) red pigments such as perylene red, quinacridone red, and cadmium red; (iii) yellow pigments such as condensed azo yellow, cadmium yellow, and barium chromate; (iv) green pigments obtained by blending blue and yellow pigments; (v) orange pigments obtained by blending red and yellow pigments; and (vi) purple pigments such as cobalt violet and pigments obtained by blending blue and red pigments.

[0058] Since the color and / or stains derived from the recycled material are less noticeable, it is preferable that the present expanded beads further contain carbon black in addition to the base resin, even if the recycled material contained in the base resin already contains carbon black.

[0059] It is preferable that the recycled material contains carbon black because (i) the amount of carbon black added separately from the base resin in the granulation process can be reduced, thereby increasing the proportion of recycled material in the base resin, and (ii) the color tone of the expanded beads tends to be more uniform.

[0060] In one embodiment of the present invention, the carbon black content in the expanded polypropylene resin particles is not particularly limited. In this specification, the "carbon black content in the expanded polypropylene resin particles" refers to the total amount of carbon black contained in the recycled material in the base resin and the amount of carbon black contained (blended) separately from the base resin. The carbon black content in the expanded particles is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin. This configuration has the advantage of making colors and / or stains derived from recycled materials less noticeable.

[0061] Since the color and / or stains derived from the recycled material are less noticeable, it is preferable that the present expanded particles further contain a chromatic pigment in addition to the base resin, even if the recycled material contained in the base resin already contains a chromatic pigment.

[0062] It is preferable that the recycled material contains a chromatic pigment because (i) the amount of chromatic pigment added separately from the base resin in the granulation process can be reduced, thereby increasing the proportion of recycled material in the base resin, and (ii) the color tone of the expanded beads tends to be uniform.

[0063] <Physical Properties> (DSC Ratio of Expanded Beads) The expanded beads preferably have at least two melting peaks in a DSC curve obtained by differential scanning calorimetry, which will be described later. Of the melting peaks, the heat of fusion determined from the melting peak on the higher temperature side is referred to as the "higher temperature side heat of fusion," and the heat of fusion determined from the melting peak on the lower temperature side is referred to as the "lower temperature side heat of fusion." When there are three or more melting peaks, the heat of fusion determined from the highest temperature melting peak is referred to as the "higher temperature side heat of fusion," and the heat of fusion determined from the other melting peaks is referred to as the "lower temperature side heat of fusion."

[0064] The DSC ratio of the expanded beads is not particularly limited. The DSC ratio of the expanded beads is preferably 10.0% to 50.0%, more preferably 15.0% to 40.0%, even more preferably 18.0% to 30.0%, and particularly preferably 20.0% to 28.0%. When the DSC ratio of the expanded beads is 10.0% or more, the expanded beads 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 expanded beads is 40% or less, the expanded beads have the advantage of being able to be molded at a relatively low temperature (molding temperature) to provide a foamed molded article. The method for measuring the DSC ratio of the expanded beads will be described in detail in the Examples below.

[0065] The DSC ratio of the expanded beads is also a measure of the amount of high-melting-point crystals contained in the expanded beads. That is, a DSC ratio of 10.0% to 50.0% indicates that the expanded beads contain a relatively large amount of high-melting-point crystals. Furthermore, the DSC ratio of the expanded beads is significantly related to the viscoelasticity of the resin beads and the expanded beads when they are foamed and expanded. That is, when the DSC ratio of the expanded beads is 10.0% to 50.0%, the resin beads and the expanded beads can exhibit excellent foamability and expansion properties, respectively, when they are foamed and when they are molded. As a result, the expanded beads have the advantage that they can produce foamed molded articles with excellent internal fusion properties and excellent mechanical strength, such as compressive strength, even at low molding pressures.

[0066] In the present expanded beads, examples of a method for controlling the DSC ratio within a predetermined range include a method for adjusting the conditions during production of the present expanded beads (particularly, the foaming temperature, foaming pressure, holding time, and the temperature of the region (space) from which the dispersion is released, etc.) In terms of ease of adjustment, a method for controlling the DSC ratio within a predetermined range by adjusting the foaming temperature, foaming pressure, and / or holding time is preferred.

[0067] For example, increasing the foaming temperature tends to decrease the DSC ratio, while decreasing the foaming temperature tends to increase the DSC ratio. This is because the amount of unmelted crystals varies depending on the foaming temperature. Increasing the foaming pressure also tends to decrease the DSC ratio, while decreasing the foaming pressure also tends to increase the DSC ratio. This is because the degree of plasticization varies depending on the foaming pressure, thereby changing the amount of unmelted crystals. In addition, the DSC ratio tends to increase as the holding time increases. This is because the amount of growth of unmelted crystals varies depending on the holding time.

[0068] (Expansion Ratio of Expanded Beads) The expansion ratio of the expanded beads is not particularly limited. The expansion ratio of the expanded beads is preferably greater than 1.0, more preferably 1.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more. A higher expansion ratio of the expanded beads has the advantage of enabling a lighter foamed molded article to be produced more efficiently. Since a lighter foamed molded article can be produced more efficiently, the expansion ratio of the expanded beads is more preferably 5.0 or more, more preferably 10.0 or more, even more preferably 13.0 or more, and particularly preferably 15.0 or more. The expansion ratio of the expanded beads is preferably 50.0 or less. A lower expansion ratio of the expanded beads has the advantage of enabling a foamed molded article with excellent strength to be produced. The expansion ratio of the expanded beads is more preferably 45.0 or less, more preferably 40.0 or less, even more preferably 35.0 or less, and particularly preferably 30.0 or less. The method for calculating the expansion ratio of the expanded beads will be explained in detail in the Examples below.

[0069] (Average Cell Diameter of Expanded Beads) The average cell diameter of the expanded beads is not particularly limited. The average cell diameter of the expanded beads is preferably 80 μm to 500 μm, more preferably 85 μm to 400 μm, even more preferably 90 μm to 300 μm, and particularly preferably 95 μm to 250 μm. When the average cell diameter of the expanded beads is (i) 80 μm or more, the expanded beads can provide a polypropylene resin foam molded article having excellent compressive strength, and (ii) when the average cell diameter is 500 μm or less, there is an advantage that the molding cycle is not likely to be extended and productivity is improved. The smaller the cell diameter, the less the molding cycle is likely to be extended and productivity is improved. The method for measuring the average cell diameter of the expanded beads, and the method for measuring and evaluating the molding cycle will be described in detail in the Examples below.

[0070] 2. Method for producing expanded polypropylene-based resin beads A method for producing expanded polypropylene-based resin beads according to one embodiment of the present invention comprises: a granulation step of melt-kneading a base resin containing a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin to obtain polypropylene-based resin particles; a dispersion step of dispersing the polypropylene-based resin particles, an aqueous dispersion medium, and a blowing agent in a container to obtain a dispersion; a heating step of heating the dispersion to a temperature equal to or higher than the softening temperature of the polypropylene-based resin particles; a pressurizing step of increasing the pressure in the container; and a discharging step of releasing one end of the container to release the dispersion in the container into a region having a pressure lower than the pressure in the container, wherein the amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material is higher than the crystallization temperature of the non-recycled polypropylene-based resin.

[0071] The present manufacturing method, having the above-described configuration, has the advantage of being able to provide expanded polypropylene resin particles containing recycled polypropylene resin, which can produce expanded polypropylene resin molded articles with excellent internal fusion. Furthermore, the present manufacturing method uses recycled materials (recycled polypropylene resin). Therefore, the present manufacturing method not only reduces environmental pollution but also significantly reduces the amount of plastic waste generated and the amount of plastic used in manufacturing. This can contribute to achieving, for example, Sustainable Development Goals (SDGs) Goal 12, "Ensure sustainable consumption and production patterns," and Goal 14, "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0072] The method for producing expanded polypropylene-based resin beads according to a preferred embodiment of the present invention surprisingly has the advantage of being able to provide expanded polypropylene-based resin beads that can provide expanded molded articles in a short molding cycle.

[0073] Each step and each aspect of the present production method will be described in detail below, but for matters other than those described in detail below, the description in the above section [1. Expanded polypropylene resin particles] will be used as appropriate.

[0074] (Granulation Process) In the granulation process, a mixture containing a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin is melt-kneaded. The non-recycled polypropylene resin and the recycled material containing a recycled polypropylene resin used in the granulation process constitute the base resin in the finally obtained expanded polypropylene resin beads. Therefore, the granulation process can also be said to be a process of melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. Furthermore, the amount of non-recycled polypropylene resin used in the granulation process can be the content of non-recycled polypropylene resin in the base resin of the finally obtained expanded polypropylene resin beads. Furthermore, the amount of recycled material containing a recycled polypropylene resin used in the granulation process can be the content of recycled material containing a recycled polypropylene resin in the base resin of the finally obtained expanded polypropylene resin beads. Furthermore, the amount of recycled polypropylene resin in the recycled material used in the granulation process, in other words, the amount of recycled polypropylene resin used in the granulation process can be the content of recycled polypropylene resin in the base resin of the finally obtained expanded polypropylene resin beads. The granulation step can also be said to be a step of preparing polypropylene-based resin particles containing a base resin that includes a non-recycled polypropylene-based resin and a recycled material that includes a recycled polypropylene-based resin.

[0075] The device used for melt-kneading the base resin (mixture) is not particularly limited, but for example, an extruder equipped with a die can be used. The extruder is not particularly limited, and a single-screw extruder or a twin-screw extruder can be suitably used.

[0076] In the granulation step, the mode other than melt-kneading the base resin (mixture) is not particularly limited. For example, polypropylene-based resin particles can be prepared by sequentially performing the following steps (1) to (3) on the melt-kneaded base resin: (1) extruding the base resin through a die provided in an extruder; (2) solidifying the extruded base resin by cooling it, for example, by passing it through water; (3) then shredding the solidified base resin with a cutter into a desired shape such as a cylindrical, elliptical, spherical, cubic, rectangular, hollow cylinder, polygonal prism, etc. Alternatively, the melt-kneaded base resin may be directly extruded through a die provided in an extruder into water, shredding the base resin into particles immediately after extrusion, and cooling and solidifying the shredded particles.

[0077] In the granulation step, the above-mentioned additives (e.g., colorants and foam nucleating agents) may be further used. In other words, the granulation step may be a step of melt-kneading (i) a base resin containing a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin, and (ii) an additive to obtain polypropylene-based resin particles. When an additive is used in the granulation step, the finally obtained expanded particles may contain the additive in an amount equal to the amount used.

[0078] In the granulation step of this production method, the non-recycled polypropylene resin and the recycled material are melt-kneaded. Therefore, in the final expanded beads, the non-recycled polypropylene resin and the recycled material are uniformly or substantially uniformly mixed. In other words, the expanded beads do not need to have a core-sheath structure.

[0079] (Dispersion step) The container used in the dispersion step is not particularly limited. Examples of the container include a pressure-resistant container and an autoclave-type pressure-resistant container (pressure-resistant autoclave). The container may be equipped with a stirrer inside the container.

[0080] The aqueous dispersion medium is not particularly limited as long as it contains water. In terms of enabling stable production of expanded beads, it is preferable to use pure water such as RO water (water purified by a reverse osmosis membrane method), distilled water, deionized water (water purified by an ion exchange resin), or ultrapure water as the aqueous dispersion medium.

[0081] Examples of blowing agents include (a) (a-1) inorganic blowing agents such as inorganic gases such as nitrogen, carbon dioxide, and air (a mixture of oxygen, nitrogen, and carbon dioxide), and (a-2) water; and (b) organic blowing agents. From the viewpoint of reducing the environmental load and reducing the risk of combustion, the blowing agent is preferably an inorganic blowing agent, more preferably an inorganic gas and / or water, and even more preferably carbon dioxide and / or water. The water used as the aqueous dispersion medium can also be used as the blowing agent. In this case, both the aqueous dispersion medium and the blowing agent in the dispersion step can be water.

[0082] In this production method, it is preferable to use a dispersant (e.g., inorganic dispersant such as tricalcium phosphate, trimagnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, etc.) and a dispersing aid (e.g., sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylsulfonate, sodium alkyldiphenyletherdisulfonate, sodium α-olefinsulfonate, etc.). This configuration can reduce adhesion of resin particles (sometimes referred to as blocking) and improve the stability of the dispersion in the container. As a result, it has the advantage of enabling stable production of expanded beads.

[0083] (Heating step) In this specification, the "softening temperature of the polypropylene-based resin particles" means the melting point of the resin with the highest melting point among the non-recycled polypropylene-based resin contained in the base resin constituting the polypropylene-based resin particles and the resin components contained in the recycled material, minus 10°C.

[0084] In this specification, "a temperature equal to or higher than the softening temperature of the polypropylene-based resin particles" may be referred to as "foaming temperature." In other words, the heating step can be said to be a step of heating the temperature of the dispersion to the foaming temperature. The foaming temperature in the heating step is not particularly limited as long as it is equal to or higher than the softening temperature of the polypropylene-based resin particles. In the heating step, the temperature to which the dispersion is heated, i.e., the upper limit of the foaming temperature, is not particularly limited. The foaming temperature is preferably equal to or lower than the softening temperature of the polypropylene-based resin particles + 20.0°C, more preferably equal to or lower than the softening temperature of the polypropylene-based resin particles + 17.0°C, and even more preferably equal to or lower than the softening temperature of the polypropylene-based resin particles + 16.0°C. This configuration has the advantage that there is no risk of the polypropylene-based resin particles adhering to each other in the container.

[0085] (Pressurizing Step) In this specification, the pressure (constant pressure) after being pressurized in the pressurizing step may be referred to as the “foaming pressure.” In other words, in the pressurizing step, the pressure inside the container is increased to the foaming pressure.

[0086] In the pressurizing step, the pressure inside the container, i.e., the expansion pressure, is not particularly limited. The expansion pressure in the pressurizing step is preferably (i) 1.0 MPa (gauge pressure) to 10.0 MPa (gauge pressure), more preferably (ii) 1.5 MPa (gauge pressure) to 5.0 MPa (gauge pressure), and even more preferably (iii) 1.5 MPa (gauge pressure) to 3.5 MPa (gauge pressure). When the expansion pressure is 1.0 MPa (gauge pressure) or more, expanded beads with a suitable density can be obtained.

[0087] The heating step and the pressure application step may be carried out in any order, or may be carried out simultaneously.

[0088] (Holding Step) The present production method may further include a holding step, after the heating step and the pressurizing step and before the releasing step, of holding the temperature inside the container at the foaming temperature and the pressure inside the container at (or near) the foaming pressure.

[0089] In the holding step, the time (holding time) for holding the temperature of the dispersion at the foaming temperature and the pressure inside the container at (near) the foaming pressure 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. A holding time of 10 minutes or longer has the advantage that a sufficient amount of unmelted crystals (crystals of the base resin) are present, thereby reducing shrinkage and / or an increase in the open cell ratio of the resulting expanded beads. On the other hand, a holding time of 60 minutes or shorter has the advantage that an excessive amount of unmelted crystals are not present, allowing the expanded beads to be molded at a low molding temperature.

[0090] (Releasing Step) The releasing step can be carried out (a) after the heating step and the pressurizing step when the holding step is not carried out, or (b) after the holding step when the holding step is carried out. The releasing step can expand the resin particles, resulting in expanded particles.

[0091] In the releasing step, the "region under a pressure lower than the pressure inside the container" refers to a "region under a pressure lower than the pressure inside the container" or a "space under a pressure lower than the pressure inside the container", and can also be referred to as "an atmosphere under a pressure lower than the pressure inside the container". The region under a pressure lower than the pressure inside the container can also be referred to as a region under a pressure lower than the foaming pressure, and may be, for example, a region under atmospheric pressure. The low-pressure region is, for example, a gas phase. Furthermore, in order to improve foaming properties, the low-pressure region (space) may be filled with saturated water vapor.

[0092] In the discharging step, when the dispersion is discharged into a region having a pressure lower than the pressure inside the container, the dispersion can also be discharged through an orifice having a diameter of 1 mm to 5 mm for the purposes of adjusting the flow rate of the dispersion and reducing variation in the expansion ratio of the resulting expanded beads.

[0093] As described above, the process of producing expanded beads from resin beads is called the "first-stage expansion process," and the resulting expanded beads are called "first-stage expanded beads." In order to obtain expanded beads with a high expansion ratio, the first-stage expanded beads obtained in the first-stage expansion process may be expanded again. The process of increasing the expansion ratio of the first-stage expanded beads is called the "second-stage expansion process," and the expanded polyolefin resin beads obtained by the second-stage expansion process are called "second-stage expanded beads." The specific method for the second-stage expansion process is not particularly limited, and any known method can be used.

[0094] [3. Polypropylene-based resin foam molded article] One embodiment of the present invention also provides a polypropylene-based resin foam molded article obtained by molding the expanded polypropylene-based resin beads described in the above section [1. Expanded polypropylene-based resin beads]. The polypropylene-based resin foam molded article according to one embodiment of the present invention can also be said to be a foam molded article containing the expanded polypropylene-based resin beads described in the section [1. Expanded polypropylene-based resin beads].

[0095] The foamed molded article has the above-described structure and thus has the advantage of excellent internal fusion. The foamed molded article has the advantage that the internal fusion rate, as measured by the measurement method described in detail in the Examples below, is, for example, 75% or more. The internal fusion rate of the foamed molded article is more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more.

[0096] <Method for producing foamed molded article> The method for producing the foamed molded article is not particularly limited as long as it is possible to produce a foamed molded article by molding the foamed beads (preferably in-mold foam molding), and any known method can be used. As a method for producing the foamed molded article, for example, the method described in the section <Method for producing foamed molded article> of International Publication WO2022 / 149538 can be suitably used.

[0097] An embodiment of the present invention may have the following configuration.

[0098] [1] Expanded polypropylene-based resin particles containing a base resin, wherein the base resin contains a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin, the content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material is higher than the crystallization temperature of the non-recycled polypropylene-based resin.

[0099] [2] The expanded polypropylene resin particles according to [1], wherein the melt flow rate of the non-recycled polypropylene resin at 230°C is 5 g / 10 min or more.

[0100] [3] The expanded polypropylene resin particles according to [1] or [2], wherein the melting point of the non-recycled polypropylene resin is 152°C or less.

[0101] [4] The expanded polypropylene resin particles according to any one of [1] to [3], wherein the crystallization temperature of the recycled material is 100°C to 130°C.

[0102] [5] The expanded polypropylene resin particles according to any one of [1] to [4], wherein the non-recycled polypropylene resin and the recycled polypropylene resin are both resins polymerized using a Ziegler-Natta catalyst as a polymerization catalyst.

[0103] [6] The expanded polypropylene resin beads according to any one of [1] to [5], wherein the expanded polypropylene resin beads further contain carbon black in addition to the base resin.

[0104] [7] The expanded polypropylene resin particles according to [6], wherein the content of carbon black in the expanded polypropylene resin particles is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

[0105] [8] The expanded polypropylene resin beads according to any one of [1] to [7], further comprising a chromatic pigment in addition to the base resin.

[0106] [9] The expanded polypropylene resin particles according to any one of [1] to [8], wherein the recycled material contains a chromatic pigment.

[0107]

[10] The expanded polypropylene resin particles according to any one of [1] to [9], wherein the recycled material is derived from a foam.

[0108]

[11] The expanded polypropylene resin particles according to any one of [1] to

[10] , wherein the recycled material is derived from a non-foamed material.

[0109]

[12] The expanded polypropylene resin particles according to any one of [1] to

[11] , wherein the recycled material contains carbon black.

[0110]

[13] The expanded polypropylene resin particles according to any one of [1] to

[12] , wherein the non-recycled polypropylene resin and the recycled polypropylene resin both contain a Ziegler-Natta catalyst.

[0111]

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

[13] , wherein the non-recycled polypropylene resin comprises at least one selected from the group consisting of an ethylene / propylene alternating copolymer, an ethylene / 1-butene / propylene alternating copolymer, an ethylene / propylene random copolymer, and an ethylene / 1-butene / propylene random copolymer.

[0112]

[15] Expanded polypropylene resin particles according to any one of [1] to

[14] , wherein the crystallization temperature of the non-recycled polypropylene resin is 95°C to 120°C.

[0113]

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

[15] , wherein the melt flow rate of the non-recycled polypropylene resin at 230°C is 30 g / 10 min or less.

[0114]

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

[16] , wherein the melting point of the non-recycled polypropylene resin is 125°C or higher.

[0115]

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

[17] , wherein the recycled polypropylene resin comprises at least one selected from the group consisting of an ethylene / propylene block copolymer, an ethylene / 1-butene / propylene block copolymer, an ethylene / propylene alternating copolymer, an ethylene / 1-butene / propylene alternating copolymer, an ethylene / propylene random copolymer, and an ethylene / 1-butene / propylene random copolymer.

[0116]

[19] The polypropylene-based resin expanded particles according to any one of [1] to

[18] , wherein the recycled material contains more than 0 parts by weight and not more than 20 parts by weight of recycled polyethylene-based resin per 100 parts by weight of the recycled material.

[0117]

[20] The expanded polypropylene resin particles according to any one of [1] to

[18] , wherein the recycled material does not contain recycled polyethylene resin.

[0118]

[21] The polypropylene-based resin expanded particles according to any one of [1] to

[20] , wherein the difference between the crystallization temperature of the non-recycled polypropylene-based resin and the crystallization temperature of the recycled material is 1°C or more.

[0119]

[22] The polypropylene-based resin expanded particles according to any one of [1] to

[21] , wherein the difference between the crystallization temperature of the non-recycled polypropylene-based resin and the crystallization temperature of the recycled material is 17°C or less.

[0120]

[23] The expanded polypropylene resin particles according to any one of [1] to

[22] , wherein the melt flow rate of the recycled material at 230°C is 1 g / 10 min to 30 g / 10 min.

[0121]

[24] Expanded polypropylene resin particles according to any one of [1] to

[23] , wherein the melting point of the recycled material is 135°C to 170°C.

[0122]

[25] The expanded polypropylene resin beads according to any one of [1] to

[24] , wherein the DSC ratio of the expanded polypropylene resin beads is 10.0% to 50.0%.

[0123]

[26] The expanded polypropylene resin beads according to any one of [1] to

[25] , wherein the expansion ratio of the expanded polypropylene resin beads is greater than 1.0.

[0124]

[27] The expanded polypropylene resin beads according to any one of [1] to

[26] , wherein the expansion ratio of the expanded polypropylene resin beads is 50.0 times or less.

[0125]

[28] The expanded polypropylene resin beads according to any one of [1] to

[27] , wherein the expanded polypropylene resin beads have an average cell diameter of 80 μm to 500 μm.

[0126]

[29] The expanded polypropylene resin particles according to any one of [1] to

[28] , wherein the expanded polypropylene resin particles do not have a core-sheath structure.

[0127]

[30] A polypropylene resin foam molded article obtained by molding the expanded polypropylene resin beads according to any one of [1] to

[29] .

[0128]

[31] The polypropylene resin foam molded article according to

[30] , wherein the internal fusion rate is 75% or more.

[0129]

[32] A method for producing expanded polypropylene-based resin beads, comprising: a granulation step of melt-kneading a base resin containing a non-recycled polypropylene-based resin and a recycled material containing a recycled polypropylene-based resin to obtain polypropylene-based resin particles; a dispersion step of dispersing the polypropylene-based resin particles, an aqueous dispersion medium, and a blowing agent in a container to obtain a dispersion; a heating step of heating the dispersion to a temperature equal to or higher than the softening temperature of the polypropylene-based resin particles; a pressurizing step of increasing the pressure inside the container; and a release step of opening one end of the container and releasing the dispersion inside the container into a region with a lower pressure than the pressure inside the container, wherein the amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin, and the crystallization temperature of the recycled material is higher than the crystallization temperature of the non-recycled polypropylene-based resin.

[0130]

[33] The method for producing expanded polypropylene resin beads according to

[32] , wherein the melt flow rate of the non-recycled polypropylene resin at 230°C is 5 g / 10 min or more.

[0131]

[34] The method for producing expanded polypropylene resin beads according to

[32] or

[33] , wherein the melting point of the non-recycled polypropylene resin is 152°C or less.

[0132]

[35] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[34] , wherein the crystallization temperature of the recycled material is 100°C to 130°C.

[0133]

[36] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[35] , wherein the non-recycled polypropylene resin and the recycled polypropylene resin are both resins polymerized using a Ziegler-Natta catalyst as a polymerization catalyst.

[0134]

[37] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[36] , wherein the expanded polypropylene resin beads further contain carbon black in addition to the base resin.

[0135]

[38] The method for producing expanded polypropylene resin beads according to

[37] , wherein the content of carbon black in the expanded polypropylene resin beads is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

[0136]

[39] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[38] , wherein the expanded polypropylene resin beads further contain a chromatic pigment in addition to the base resin.

[0137]

[40] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[39] , wherein the recycled material contains a chromatic pigment.

[0138]

[41] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[40] , wherein the recycled material is derived from a foam.

[0139]

[42] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[41] , wherein the recycled material is derived from a non-foamed material.

[0140]

[43] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[42] , wherein the recycled material contains carbon black.

[0141]

[44] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[43] , wherein both the non-recycled polypropylene resin and the recycled polypropylene resin contain a Ziegler-Natta catalyst.

[0142]

[45] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[44] , wherein the non-recycled polypropylene resin comprises at least one selected from the group consisting of an ethylene / propylene alternating copolymer, an ethylene / 1-butene / propylene alternating copolymer, an ethylene / propylene random copolymer, and an ethylene / 1-butene / propylene random copolymer.

[0143]

[46] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[45] , wherein the crystallization temperature of the non-recycled polypropylene resin is 95°C to 120°C.

[0144]

[47] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[46] , wherein the melt flow rate at 230°C of the non-recycled polypropylene resin is 30 g / 10 min or less.

[0145]

[48] ​​The method for producing expanded polypropylene resin beads according to any one of

[32] to

[47] , wherein the melting point of the non-recycled polypropylene resin is 125°C or higher.

[0146]

[49] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[48] , wherein the recycled polypropylene resin comprises at least one selected from the group consisting of an ethylene / propylene block copolymer, an ethylene / 1-butene / propylene block copolymer, an ethylene / propylene alternating copolymer, an ethylene / 1-butene / propylene alternating copolymer, an ethylene / propylene random copolymer, and an ethylene / 1-butene / propylene random copolymer.

[0147]

[50] The method for producing expanded polypropylene-based resin particles according to any one of

[32] to

[49] , wherein the recycled material contains more than 0 parts by weight and not more than 20 parts by weight of recycled polyethylene-based resin per 100 parts by weight of the recycled material.

[0148]

[51] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[49] , wherein the recycled material does not contain recycled polyethylene resin.

[0149]

[52] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[51] , wherein the difference between the crystallization temperature of the non-recycled polypropylene resin and the crystallization temperature of the recycled material is 1°C or more.

[0150]

[53] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[52] , wherein the difference between the crystallization temperature of the non-recycled polypropylene resin and the crystallization temperature of the recycled material is 17°C or less.

[0151]

[54] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[53] , wherein the melt flow rate of the recycled material at 230°C is 1 g / 10 min to 30 g / 10 min.

[0152]

[55] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[54] , wherein the melting point of the recycled material is 135°C to 170°C.

[0153]

[56] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[55] , wherein the DSC ratio of the expanded polypropylene resin beads is 10.0% to 50.0%.

[0154]

[57] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[56] , wherein the expansion ratio of the expanded polypropylene resin beads is greater than 1.0.

[0155]

[58] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[57] , wherein the expansion ratio of the expanded polypropylene resin beads is 50.0 times or less.

[0156]

[59] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[58] , wherein the expanded polypropylene resin beads have an average cell diameter of 80 μm to 500 μm.

[0157]

[60] The method for producing expanded polypropylene resin beads according to any one of

[32] to

[59] , wherein the expanded polypropylene resin beads do not have a core-sheath structure.

[0158]

[61] A method for producing a polypropylene-based resin foamed molded article, comprising a step of molding the expanded polypropylene-based resin beads according to any one of [1] to

[29] , or the expanded polypropylene-based resin beads produced by the method for producing expanded polypropylene-based resin beads according to any one of

[32] to

[60] .

[0159]

[62] The method for producing a polypropylene resin foam molded article according to

[30] , wherein the polypropylene resin foam molded article has an internal fusion rate of 75% or more.

[0160] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0161] <Materials> The substances used in the examples and comparative examples are as follows, and were used without any particular purification.

[0162] (Non-recycled polypropylene resins and recycled materials) Table 1 shows the non-recycled polypropylene resins used, and Table 2 shows the recycled materials used. Non-recycled polypropylenes 1 to 4 are resins polymerized using a Ziegler-Natta catalyst. Non-recycled polypropylene 5 is a mixture of non-recycled polypropylenes 3 and 4, so it can also be said that non-recycled polypropylene 5 is a resin polymerized using a Ziegler-Natta catalyst. The recycled polypropylene resins contained in recycled materials 1 to 12 are each resins polymerized using a Ziegler-Natta catalyst. In Table 2, recycled materials marked with "-" in the "Carbon black content (wt%) in 100 wt% recycled material" column indicate that they do not contain carbon black (0 wt%). Similarly, recycled materials marked with "-" in the "Polyethylene resin content (wt%) in 100 wt% recycled material" column indicate that they do not contain polyethylene resin (0 wt%). In Table 2, the content of recycled polypropylene resin contained in the recycled material is the amount obtained by subtracting the content of carbon black, the content of polyethylene resin, and the amount of ash from 100% by weight of the recycled material.

[0163] (Carbon Black) Carbon Black Masterbatch A 40 parts by weight of carbon black and 60 parts by weight of a non-recycled polypropylene resin [MFR at 230°C = 7.5 g / 10 min] were mixed together to obtain a mixture designated as carbon black masterbatch A.

[0164] Carbon Black Masterbatch B 3 parts by weight of carbon black and 97 parts by weight of non-recycled polypropylene resin 2 shown in Table 1 were mixed together to obtain a mixture designated as carbon black masterbatch B.

[0165] (Chromatic pigment masterbatch) Green pigment masterbatch (containing a total of 25% by weight of copper phthalocyanine blue and condensed azo yellow) Blue pigment masterbatch (containing a total of 21% by weight of phthalocyanine blue and ultramarine) Red pigment masterbatch (containing 1% by weight of perylene red) (Foam nucleating agent) Talc [Talc Powder PK-S, manufactured by Hayashi Kasei Co., Ltd.] (Water absorbing substance) Glycerin [Purified glycerin D, manufactured by Lion Corporation] Polyethylene glycol [PEG #300, manufactured by Lion Corporation] (Flame retardant) Hindered amine flame retardant [NOR116, manufactured by BASF] <Method for measuring melting point and crystallization temperature> The melting point and crystallization temperature of the non-recycled polypropylene resin and the recycled material were measured using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation). The specific operating procedures were as follows (1) to (3): (1) 4.5 mg to 5.5 mg of a sample (non-recycled polypropylene resin or recycled material) was melted by increasing the temperature from 40°C to 220°C at a heating rate of 10°C / min; (2) The temperature of the melted sample was then decreased from 220°C to 40°C at a heating rate of 10°C / min to crystallize the sample; (3) The temperature of the crystallized sample was then increased from 40°C to 220°C at a heating rate of 10°C / min. The temperature of the peak (crystallization peak) of the DSC curve of the sample obtained during cooling (i.e., during (2)) was taken as the crystallization temperature of the sample. When multiple peaks (crystallization peaks) were observed in the DSC curve of the sample obtained during cooling, the highest peak was taken as the crystallization temperature of the sample. The temperature of the peak (melting peak) of the DSC curve of the sample obtained during the second heating (i.e., during (3)) was taken as the melting point of the sample. If multiple peaks (melting peaks) were obtained during the second heating, the peak with the highest temperature was taken as the melting point of the sample.

[0166] <Method for measuring melt flow rate at 230°C> The melt flow rates of the non-recycled polypropylene resin and the recycled material were measured using an MFR measuring device described in JIS K7210-1: 2014. The measurement conditions were an orifice diameter of 2.0959±0.005 mmφ, an orifice length of 8.000±0.025 mm, a load of 2160 g, and a temperature of 230±0.2°C.

[0167] <Method for Quantifying Carbon Black in Recycled Material> The carbon black content in the recycled material was measured using a simultaneous differential thermal and thermogravimetric analyzer (STA200RV, manufactured by Hitachi High-Tech Science Corporation). The specific operating procedures were as follows (1) to (3): (1) 6 mg to 8 mg of the recycled material was weighed into a platinum (Pt) measuring container and used as a sample; (2) The temperature of the sample was increased to 600°C at 10°C / min under a nitrogen atmosphere, and then cooled to 400°C at 10°C / min; (3) The sample was then changed to a simulated air (a mixed gas of oxygen and nitrogen in a ratio of 21% and 79%) atmosphere, and the temperature of the sample was increased to 800°C at 10°C / min and maintained at 800°C for 20 minutes; (4) In the TG weight loss rate curve obtained in the process (3), the weight loss rate [wt%] at 400°C in the step of increasing the temperature from 400°C to 800°C and the weight loss rate [wt%] after maintaining the temperature at 800°C for 20 minutes were used to calculate the weight ratio [wt%] of the carbon black in the recycled material.

[0168] <Method for Quantifying Ash Content in Recycled Materials> The ash content in recycled materials was determined from the weight of the recycled materials and the weight of the residue after burning the recycled materials. The specific operating procedures were as follows: (1) The recycled materials were heated at 150°C for 1 hour to completely remove moisture from the recycled materials; (2) 1 g to 2 g of recycled materials were placed in a crucible and held at 300°C in an electric furnace for 30 minutes or more, and then burned at 750°C for 1 hour or more; (3) The crucible was removed from the electric furnace and cooled in a desiccator at 23°C for 1 hour; (4) The ash content in the recycled materials was calculated using the following formula: W1: weight of crucible (g); W2: weight of crucible + recycled materials before burning (g); W3: weight of crucible + recycled materials after burning (g); Ash content in recycled materials (wt%) = {(W3 - W1) * 100} / (W2 - W1).

[0169] <Measurement of DSC Ratio of Expanded Polypropylene Resin Beads> The DSC ratio of the expanded beads was measured using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation). The specific operating procedures were as follows (1) to (5): (1) 4.5 mg to 5.5 mg of expanded polypropylene resin beads were weighed; (2) The temperature of the expanded beads was increased from 40°C to 220°C at a heating rate of 10°C / min to melt the expanded beads; (3) In the DSC curve of the expanded beads obtained in the process (2) (DSC curve during the first heating of the expanded beads), (a) a line was drawn connecting the maximum point between the highest melting peak and the melting peak adjacent to the highest melting peak (on the low-temperature side) and the point at 100°C, and (b) a line was drawn connecting the maximum point and the point at 100°C. A straight line was drawn between the point representing the temperature after the end of melting and the line segment connecting the maximum point and the point representing the temperature after the end of melting; (4) (a) (a-1) The heat quantity calculated from the area surrounded by (a-2) the DSC curve having the highest temperature melting peak was designated as the high-temperature heat of fusion Qh, and (b) (b-1) The heat quantity calculated from the area surrounded by (b-2) the line segment connecting the maximum point and the point representing the temperature before the start of melting and the DSC curve having the melting peak next to the maximum point (low-temperature side) was designated as the low-temperature heat of fusion Ql; (5) The DSC ratio was calculated using the following formula. The obtained DSC ratio was rounded to one decimal place to obtain a value up to one decimal place: DSC ratio (%) = (Qh / (Qh+Ql)) x 100.

[0170] <Expansion Ratio of Expanded Polypropylene Resin Beads> The expansion ratio of expanded beads was measured by the following methods (1) to (4): (1) The weight w (g) of the expanded beads was measured; (2) Next, the expanded beads used for the weight measurement were submerged in ethanol contained in a measuring cylinder, and the volume v (cm) of the expanded beads was calculated based on the rise in the liquid level in the measuring cylinder. ３ (3) The weight w (g) was measured, and the volume v (cm ３ ) and the density of the foamed particles ρ １ (4) The density ρ of the polypropylene resin particles used in the production of the expanded beads was calculated. ２ is the density of the foam particles ρ １ Divide by (ρ ２ / ρ １The value obtained was taken as the expansion ratio of the expanded beads. ２ In the following examples and comparative examples, the density ρ of the polypropylene resin particles was measured in the same manner as above except that resin particles were used instead of the expanded particles. ２ are all 0.9 g / cm ３ It was.

[0171] <Average Cell Diameter of Expanded Polypropylene Resin Beads> The average cell diameter of expanded beads was measured by the following methods (1) to (5): (1) Using a razor (high-stainless steel double-edged blade manufactured by Feather Co., Ltd.), the expanded beads were cut so as to pass through the center of the expanded beads, while being careful not to destroy the cell membranes (cell membranes) of the expanded beads; (2) The cut surface of the expanded beads obtained was observed using a microscope [manufactured by Hirox Co., Ltd., RH-2000], and an image of the observed surface was taken; (3) On the obtained image, a line segment corresponding to a length of 2000 μm was drawn at any part of the expanded beads except for the surface layer part; (4) The number n of cells through which the line segment passed was measured, and the cell diameter was calculated from the formula (cell diameter = 2000 / n (μm)); (5) The same procedure was performed on 10 expanded beads, and the arithmetic mean value of the calculated cell diameters was taken as the average cell diameter of the expanded beads.

[0172] <Internal fusion rate of polypropylene-based resin foam molded article> The internal fusion rate of a foam molded article was measured by the following methods (1) to (4): (1) a cutter was used to make a 5 mm long incision on any one surface of the foam molded article in a direction perpendicular to the surface; (2) the foam molded article was then manually broken along the incision; (3) the region of the resulting fracture surface excluding the incision was visually observed to count the number of all expanded beads present in that region and the number of expanded beads that had broken in that region other than at the particle interfaces (i.e., expanded beads in which the expanded beads themselves had broken); (4) the internal fusion rate was calculated according to the following formula: internal fusion rate (%) = (number of expanded beads that had broken in that region other than at the particle interfaces / total number of expanded beads present in that region) × 100.

[0173] <Molding cycle of polypropylene-based resin foam molded article> The molding cycle for the foam molded article was defined as the period from the start of molding to the end of molding when the molded article was released from the mold. A more detailed explanation follows. The start of molding was defined as the point at which the polypropylene-based resin foam beads began to be filled into the mold. A mold capable of forming a molding space measuring 370 mm in length, 320 mm in width, and 50 mm in thickness was used. Next, with the drain valve of the drain line of the molding machine open, the foam beads were heated with steam at 0.10 MPa (gauge pressure) for 3 seconds to expel air from the mold (preheating step). Next, steam was flowed from the fixed mold side to the movable mold side for 6 seconds (one-way heating step), and then steam was flowed from the movable mold side to the fixed mold side for 3 seconds (reverse one-way heating step) to expel air and heat the molded article. Next, with the drain valve of the drain line of the molding machine closed, steam at 0.30 MPa (gauge pressure) was sent into the mold for 9 seconds to heat the foam particles (double-sided heating process) and fuse them to form a foam-molded product. The foam-molded product in the mold was then water-cooled. Next, the mold was opened and the foam-molded product was released when the surface pressure measured by a surface pressure gauge attached to the surface of the Planck mold had dropped to 0.01 MPa (gauge pressure). Molding was completed when the foam-molded product was released. The evaluation criteria for molding cycle (productivity) were as follows: 3 (very excellent): Molding cycle was within 180 seconds. 2 (excellent): Molding cycle was longer than 180 seconds and shorter than 210 seconds. 1 (poor): Molding cycle was longer than 210 seconds.

[0174] The methods for producing polypropylene resin particles, expanded polypropylene resin particles, and in-mold foamed polypropylene resin articles in Examples and Comparative Examples will be described below.

[0175] (Example 1) [Preparation of Resin Particles] (Granulation Step) 70 parts by weight of non-recycled polypropylene-based resin 2 (ethylene / 1-butene / propylene random copolymer), 30 parts by weight of recycled material 1, 0.20 parts by weight of talc, and 0.5 parts by weight of polyethylene glycol 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 melt-kneaded mixture was extruded in the form of a strand from a die equipped in the extruder. The extruded mixture (strand) was water-cooled in a 2 m long water tank and solidified. The solidified mixture was then cut to produce polypropylene-based resin particles (1.2 mg / particle).

[0176] [Preparation of Expanded Beads] (Dispersion Step) A 10 L pressure-resistant autoclave (autoclave-type pressure-resistant container) was charged with 100 parts by weight (2.4 kg) of the polypropylene-based resin particles obtained as described above, 200 parts by weight of water as an aqueous dispersion medium, 0.3 parts by weight of kaolin [ASP170, manufactured by BASF] as a dispersant, and 0.38 parts by weight of an aqueous solution of sodium dodecylbenzenesulfonate [Neopelex G-15, manufactured by Kao Corporation, an aqueous solution of 16% by weight of sodium dodecylbenzenesulfonate] as a dispersion aid. Stirring of the mixture was initiated. Thereafter, the mixture (dispersion) was continuously stirred until the release step was completed. 4 parts by weight of carbon dioxide was added to the mixture as a blowing agent. Through this operation, the polypropylene-based resin particles, the aqueous dispersion medium, the blowing agent, the dispersant, and the dispersion aid were dispersed in the container to obtain a dispersion.

[0177] (Heating step, pressurizing step, and maintaining step) The temperature of the dispersion was raised (heated) to a foaming temperature of 153.3°C, and the temperature of the dispersion was maintained at the foaming temperature for 10 minutes. Thereafter, carbon dioxide was additionally injected into the container, and the internal pressure of the autoclave was pressurized (increased) to a foaming pressure of 2.0 MPa (gauge pressure). The temperature of the dispersion was maintained at the foaming temperature, and the internal pressure of the autoclave was maintained at the foaming pressure for 20 minutes.

[0178] (Discharge step) Thereafter, the valve at the bottom of the autoclave was opened, and the dispersion was discharged under atmospheric pressure through an orifice having a diameter of 3.6 mm to obtain expanded polypropylene resin beads having an expansion ratio of 15.7. During this discharge, the pressure in the container was maintained by injecting carbon dioxide to prevent a decrease in the pressure in the container.

[0179] [Preparation of Foam Molded Article] The resulting foamed beads were dried at 80°C. The foamed beads were then placed in a pressure-resistant container, and pressurized air was impregnated into the foamed beads, adjusting the internal pressure of the foamed beads to 0.20 MPa (absolute pressure). The pressurized foamed beads were then filled into a mold measuring 370 mm long x 320 mm wide x 50 mm thick. The mold chamber was then heated with steam at 0.30 MPa (gauge pressure) (molding pressure) to fuse the foamed beads together. After water-cooling the interior of the mold and the surface of the molded article, the molded article was released from the mold to obtain a polypropylene resin foam molded article. The resulting foam molded article was left to stand at 23°C for 2 hours and then aged at 75°C for 16 hours.

[0180] Example 2 The expanded beads obtained in Example 1 were dried at 80°C. The expanded beads were then placed in a pressure-resistant container, and pressurized air was impregnated into the expanded beads, adjusting the internal pressure of the expanded beads to 0.30 MPa (absolute pressure). The pressurized expanded beads were then brought into contact with water vapor at 0.07 MPa (gauge pressure) to cause second-stage expansion, yielding second-stage expanded beads. The resulting second-stage expanded beads had an expansion ratio of 26.2 times. A polypropylene resin expanded molded article was then produced using the same procedures as those described in the section "Preparation of Expanded Molded Article" of Example 1.

[0181] (Examples 3 to 11, Examples 13 to 18 and Comparative Examples 1 to 3) Polypropylene-based resin particles, expanded polypropylene-based resin particles and expanded polypropylene-based resin molded articles were prepared by the same procedures as those described in the sections [Preparation of resin particles], [Preparation of expanded beads] and [Preparation of expanded molded articles] of Example 1, except that in [Preparation of resin particles] the formulation was changed as shown in Table 3 or 4 and in [Preparation of expanded beads] the expansion conditions were changed as shown in Table 3 or 4.

[0182] Example 12 In the step of [Preparation of Resin Particles], the formulation was changed as shown in Table 4 to obtain polypropylene-based resin particles.

[0183] [Preparation of Expanded Beads] (Dispersion Step) Into a 10 L pressure-resistant autoclave (autoclave-type pressure-resistant container), 100 parts by weight (2.4 kg) of the obtained polypropylene-based resin particles, 200 parts by weight of water as an aqueous dispersion medium, 0.46 parts by weight of tribasic calcium phosphate [manufactured by Taihei Chemical Industry Co., Ltd.] as a dispersant, and 0.04 parts by weight of sodium alkylsulfonate [manufactured by Kao Corporation, Latemul PS] as a dispersion aid were charged. Stirring of the mixture was started. Thereafter, the mixture (dispersion) was continuously stirred until the release step was completed. By this operation, the polypropylene-based resin particles, the aqueous dispersion medium, the dispersant, and the dispersion aid were dispersed in the container to obtain a dispersion.

[0184] (Heating step, pressurizing step, and maintaining step) The temperature of the dispersion was increased (heated) to a foaming temperature of 154.2°C. Compressed air was additionally injected into the container to increase (pressurize) the internal pressure of the autoclave to a foaming pressure of 2.3 MPa (gauge pressure). The temperature of the dispersion was maintained at the foaming temperature, and the internal pressure of the autoclave was maintained at the foaming pressure for 20 minutes.

[0185] (Discharge step) Thereafter, the valve at the bottom of the autoclave was opened, and the dispersion was discharged under atmospheric pressure through an orifice having a diameter of 4.4 mm to obtain expanded polypropylene resin beads having an expansion ratio of 2.9. During this discharge, the pressure in the container was maintained by injecting air to prevent a decrease in the pressure in the container.

[0186] [Preparation of foamed molded article] The obtained foamed beads were dried at 80°C. Subsequently, the foamed beads were filled into a mold measuring 370 mm in length, 320 mm in width, and 50 mm in thickness. The interior of the mold chamber was then heated with steam at 0.30 MPa (gauge pressure) (molding pressure) to fuse the foamed beads together. After cooling the interior of the mold and the surface of the molded article with water, the molded article was released from the mold to obtain a polypropylene resin foamed molded article. The obtained foamed molded article was left to stand at 23°C for 2 hours and then aged at 75°C for 16 hours.

[0187] (Examples 19 to 26) Polypropylene-based resin particles and expanded polypropylene-based resin particles were prepared by the same procedures as those described in the sections [Preparation of Resin Particles] and [Preparation of Expanded Particles] of Example 1, except that in [Preparation of Resin Particles] the formulation was changed as shown in Table 5, and in [Preparation of Expanded Particles] the expansion conditions were changed as shown in Table 4.

[0188] [Preparation of Foam Molded Article] The obtained foamed beads were placed in a pressure vessel and compressed by air pressure. The compressed foamed beads were then filled into a mold measuring 370 mm long x 320 mm wide x 50 mm thick. The mold chamber was then heated with steam at 0.30 MPa (gauge pressure) (molding pressure) to fuse the foamed beads together. After cooling the interior of the mold and the surface of the molded article with water, the molded article was released from the mold to obtain a polypropylene resin foam molded article. The obtained foam molded article was left to stand at 23°C for 2 hours and then aged at 75°C for 16 hours.

[0189] The expanded polypropylene resin beads and in-mold foamed polypropylene resin articles obtained in each of the Examples and Comparative Examples were subjected to various measurements and evaluations. The results are shown in Tables 3 to 5.

[0190] One embodiment of the present invention has the advantage of being able to provide a polypropylene-based resin foam molded article having excellent internal fusion properties and a polypropylene-based resin foam particle containing recycled polypropylene-based resin, which can be suitably used for various applications such as cushioning packaging materials, logistics materials, heat insulating materials, civil engineering and construction materials, and automotive components.

Claims

1. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The recycled material comprises polypropylene resin foam particles containing 0 to 20 parts by weight of recycled polyethylene resin per 100 parts by weight of the recycled material (excluding the non-recycled polypropylene resin and the recycled material where the melting point difference is 10°C or more and 30°C or less).

2. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The aforementioned recycled material has a melting point of 135°C to 151°C and is polypropylene resin foam particles.

3. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The recycled material contains, in 100 parts by weight, 0 to 20 parts by weight of recycled polyethylene resin. Polypropylene resin foam particles, wherein the melting point of the non-recycled polypropylene resin is 143°C or higher and 160°C or lower.

4. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The polypropylene resin foam particles have an average bubble diameter of 121 μm to 500 μm.

5. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The polypropylene resin foam particles are single-stage foam particles. The polypropylene resin foam particles have a foaming ratio of 13.0 times or more.

6. The polypropylene resin foamed particle according to claim 5, obtained by foaming the first-stage foamed particle again.

7. Polypropylene resin foam particles containing a base resin, The aforementioned base resin includes a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin. The content of the recycled material in the base resin is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The aforementioned polypropylene resin foam particles further contain carbon black, The polypropylene resin foam particles wherein the carbon black content in the polypropylene resin foam particles is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

8. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the melt flow rate of the non-recycled polypropylene resin at 230°C is 5 g / 10 min or more.

9. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the melting point of the non-recycled polypropylene resin is 152°C or lower.

10. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the crystallization temperature of the recycled material is 100°C to 130°C.

11. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein both the non-recycled polypropylene resin and the recycled polypropylene resin are resins polymerized using a Ziegler-Natta catalyst as the polymerization catalyst.

12. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the polypropylene resin foam particles further contain carbon black in addition to the base resin.

13. The polypropylene resin foam particles according to claim 12, wherein the carbon black content in the polypropylene resin foam particles is 0.1 parts by weight to 5.0 parts by weight per 100 parts by weight of the base resin.

14. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the polypropylene resin foam particles further contain a chromatic pigment in addition to the base resin.

15. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the recycled material contains a chromatic pigment.

16. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the recycled material is derived from foam.

17. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the recycled material is derived from a non-foamed material.

18. The polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7, wherein the recycled material contains carbon black.

19. A polypropylene resin foam molded article obtained by molding polypropylene resin foam particles according to claim 1, 2, 3, 4, 5, or 7.

20. A granulation process to obtain polypropylene resin particles by melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing recycled polypropylene resin, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The recycled material comprises 0 to 20 parts by weight of recycled polyethylene resin in 100 parts by weight of the recycled material, and is a method for producing polypropylene resin foam particles (excluding cases where the melting point difference between the non-recycled polypropylene resin and the recycled material is 10°C or more and 30°C or less).

21. A granulation step of melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin to obtain polypropylene resin particles, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. A method for producing polypropylene resin foam particles, wherein the melting point of the recycled material is 135°C to 151°C.

22. A granulation step of melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing a recycled polypropylene resin to obtain polypropylene resin particles, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The recycled material contains, in 100 parts by weight, 0 to 20 parts by weight of recycled polyethylene resin. A method for producing foamed polypropylene resin particles, wherein the melting point of the non-recycled polypropylene resin is 143°C or higher and 160°C or lower.

23. A method for producing polypropylene resin foam particles, A granulation process to obtain polypropylene resin particles by melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing recycled polypropylene resin, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. A method for producing polypropylene resin foam particles, wherein the average bubble diameter of the polypropylene resin foam particles is 121 μm to 500 μm.

24. A method for producing polypropylene resin foam particles, A granulation process to obtain polypropylene resin particles by melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing recycled polypropylene resin, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The polypropylene resin foam particles are single-stage foam particles. A method for producing polypropylene resin foam particles, wherein the foaming ratio of the polypropylene resin foam particles is 13.0 times or more.

25. A method for producing polypropylene resin foamed particles according to claim 24, wherein the first-stage foamed particles are foamed again.

26. A method for producing polypropylene resin foam particles, A granulation process to obtain polypropylene resin particles by melt-kneading a base resin containing a non-recycled polypropylene resin and a recycled material containing recycled polypropylene resin, A dispersion step is to disperse the aforementioned polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion liquid. A heating step in which the temperature of the dispersion is heated to a temperature above the softening temperature of the 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 amount of recycled material used is 10 to 90 parts by weight per 100 parts by weight of the base resin. The crystallization temperature of the recycled material is higher than that of the non-recycled polypropylene resin. The aforementioned non-recycled polypropylene resin is a random copolymer. The recycled polypropylene resin is a random copolymer. The aforementioned polypropylene resin foam particles further contain carbon black, A method for producing polypropylene resin foam particles, wherein the carbon black content in the polypropylene resin foam particles is 0.1 to 5.0 parts by weight per 100 parts by weight of the base resin.

Images