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

Abstract

Provided is a polypropylene resin foamed particle or the like that can provide a foamed molded body in a short molding cycle. A polypropylene resin foamed particle is a foamed particle obtained by foaming a resin particle containing a polypropylene random copolymer (A) and containing a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2), the mixture of (B1) and (B2), and (A) each having a specific melting point and MFR.

Description

Technical Field

[0001] This invention relates to polypropylene resin foamed granules, polypropylene resin foamed molded articles, and methods for manufacturing polypropylene resin foamed granules. Background Technology

[0002] Polypropylene resin foamed molded parts are used in various applications such as cushioning packaging materials, turnover boxes, and automotive components (e.g., patent documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-137172

[0006] Patent Document 2: International Publication No. WO2023 / 190441 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, from the perspective of the molding cycle, the existing technology described above is insufficient in the manufacture of foamed molded articles using foamed particles, and there is room for further improvement.

[0009] One embodiment of the present invention was made in view of the above-mentioned problems, and its object is to provide a novel polypropylene resin foam granule capable of providing a polypropylene resin foamed molded body with a short molding cycle, and a polypropylene resin foamed molded body formed by molding the polypropylene resin foam granule.

[0010] Solution for solving the problem

[0011] The inventors conducted in-depth research to solve the above-mentioned problems, and as a result, completed this invention.

[0012] That is, the polypropylene resin foamed granules of one embodiment of the present invention are polypropylene resin foamed granules formed by foaming polypropylene resin granules.

[0013] The polypropylene resin particles comprise a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and also comprise a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2).

[0014] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0015] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0016] In addition, a method for manufacturing polypropylene resin foamed granules according to one embodiment of the present invention includes the following steps:

[0017] The extrusion process involves melt-blending a mixed resin comprising a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and containing a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) to obtain polypropylene resin granules; and

[0018] The foaming process involves foaming the polypropylene resin particles obtained in the extrusion process.

[0019] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0020] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0021] The effects of the invention

[0022] According to one embodiment of the present invention, the following effects are achieved: a novel polypropylene resin foam granule capable of providing polypropylene resin foamed molded articles with a short molding cycle, and a novel manufacturing method for the polypropylene resin foam granule. Detailed Implementation

[0023] The following describes one embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope shown in the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included within the technical scope of the present invention. Moreover, by combining the technical means disclosed in each embodiment, new technical features can be formed. It should be noted that all academic and patent documents described in this specification are cited as references in this specification. In addition, in this specification, unless otherwise specified, "A~B" representing a numerical range means "A or more (inclusive of A and greater than A) and B or less (inclusive of B and less than B)".

[0024] In this specification, the "structural unit derived from monomer X" contained in a polymer, copolymer or resin is sometimes referred to as "unit X".

[0025] Unless otherwise specified, X will also be included in this specification. 1 Unit, X 2 Unit, ... and X n A copolymer in which units (n is an integer greater than 2) serve as structural units is called "X". 1 / X 2 / … / X n "Copolymer". As X 1 / X 2 / … / X n Copolymers, unless otherwise specified, are not particularly limited in terms of polymerization method and can be random copolymers, alternating copolymers, block copolymers, or graft copolymers.

[0026] In this specification, "polypropylene resin particles" are sometimes referred to as "resin particles," "polypropylene resin foamed particles" are sometimes referred to as "foamed particles," "polypropylene resin foamed particles according to an embodiment of the present invention" are sometimes referred to as "this foamed particle," "polypropylene resin foamed molded body" are sometimes referred to as "foamed molded body," and "polypropylene resin foamed molded body according to an embodiment of the present invention" are sometimes referred to as "this foamed molded body." In this specification, "method of manufacturing polypropylene resin foamed particles" is sometimes referred to as "manufacturing method," and "method of manufacturing polypropylene resin foamed particles according to an embodiment of the present invention" is sometimes referred to as "this manufacturing method."

[0027] [1. Technical concept of one embodiment of the present invention]

[0028] Polypropylene random copolymers are commonly used as raw materials for polypropylene resin foams. However, polypropylene block copolymers are sometimes used as raw materials for polypropylene resin foams. For example, in cases where the impact resistance of polypropylene resin foams is improved, or when recycled resins are used from the viewpoint of reducing environmental impact.

[0029] As a recycled resin of polypropylene, polypropylene block copolymers have a much higher throughput compared to polypropylene random copolymers.

[0030] In addition, propylene homopolymers are sometimes used as raw materials for polypropylene resin foam moldings. For example, in cases where the aim is to achieve good dimensional properties in the polypropylene resin foam moldings.

[0031] Driven by the aforementioned motivation, the inventors conducted in-depth research on the following: using polypropylene random copolymers in combination with propylene homopolymers and / or polypropylene block copolymers to provide polypropylene resin foam particles as raw materials for polypropylene resin foamed molding articles.

[0032] During the in-depth research, the inventors independently obtained the following new insights: When molding foamed particles obtained by combining polypropylene random copolymers with propylene homopolymers and / or polypropylene block copolymers to obtain foamed molded bodies, the molding cycle sometimes becomes longer.

[0033] Therefore, the inventors have conducted further in-depth research with the aim of providing foamed particles that can provide foamed molded articles with a short molding cycle, even when polypropylene random copolymers are used in combination with propylene homopolymers and / or polypropylene block copolymers.

[0034] As a result, the inventors independently discovered the following new insights, thereby completing the present invention: if the foamed particles are as follows, or if the foamed particles are obtained by the following manufacturing method, it is surprisingly found that foamed molded articles can be provided with a short molding cycle.

[0035] A type of polypropylene resin foamed granules, which are formed by foaming polypropylene resin granules.

[0036] The polypropylene resin particles comprise a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and also comprise a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2).

[0037] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0038] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0039] A method for manufacturing polypropylene resin foamed granules includes the following steps:

[0040] The extrusion process involves melt-blending a mixed resin comprising a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and containing a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) to obtain polypropylene resin granules; and

[0041] The foaming process involves foaming the polypropylene resin particles obtained in the extrusion process.

[0042] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0043] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0044] [2. Polypropylene Resin Foamed Granules]

[0045] One embodiment of the present invention provides polypropylene resin foamed granules, which are polypropylene resin foamed granules formed by foaming polypropylene resin granules. The polypropylene resin granules comprise a polypropylene random copolymer (A) with a melting point of 140.0°C or higher and below 155.0°C, and comprise a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2). The mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) has a melting point of 155.0°C or higher and below 165.0°C. The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g is... B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value is 2.0~30.0. It should be noted that in this specification, the composition "the melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C" is sometimes referred to as "Composition A," and the melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g is sometimes referred to as... B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The composition with a value of 2.0~30.0 is called "Composition B".

[0046] This foamed particle has the above-described structure (especially structures A and B), and therefore has the advantage of being able to provide a foamed molded article with a short molding cycle. Furthermore, this foamed particle has the above-described structure, and therefore also has the advantage of being able to provide a foamed molded article with excellent surface aesthetics. Methods for measuring and evaluating the molding cycle and the surface aesthetics of the foamed molded article are described in detail in the following examples.

[0047] <ingredients>

[0048] (Polypropylene resin granules)

[0049] (Resin composition)

[0050] Polypropylene random copolymer (A), propylene homopolymer (B1), and polypropylene block copolymer (B2) can also be referred to as resin components in resin particles and foamed particles. In other words, the resin particles and the foamed particles, as resin components, at least contain polypropylene random copolymer (A), and contain propylene homopolymer (B1) and / or polypropylene block copolymer (B2). In this specification, both "components substantially constituting resin particles" and "components substantially constituting foamed particles" are referred to as "base resin." In other words, the resin particles contain a base resin, which contains polypropylene random copolymer (A), and contains propylene homopolymer (B1) and / or polypropylene block copolymer (B2). Furthermore, in other words, the foamed particles contain a base resin, which contains polypropylene random copolymer (A), and contains propylene homopolymer (B1) and / or polypropylene block copolymer (B2).

[0051] Polypropylene random copolymer (A), propylene homopolymer (B1), and polypropylene block copolymer (B2) are all polypropylene resins.

[0052] In this specification, "polypropylene resin" refers to a resin in which propylene units constitute the largest proportion of all structural units. For example, a polypropylene resin may contain more than 50 mol% propylene units per 100 mol% of all structural units.

[0053] (Polypropylene random copolymer (A))

[0054] In addition to propylene units, polypropylene random copolymers (A) also have one or more structural units derived from monomers other than propylene monomers.

[0055] In this specification, the "structural units other than propylene units" contained in polypropylene resins are sometimes referred to as "comonomer units". In other words, the polypropylene random copolymer (A) contains at least propylene units and comonomer units. In the polypropylene random copolymer (A), the bonding sequence of propylene units and comonomer units is random.

[0056] Examples of comonomers include α-olefins with 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.

[0057] The heating temperature at which foamed particles are molded (e.g., in-mold foaming) is sometimes referred to as the "molding temperature". From the viewpoint of being able to reduce the molding temperature, polypropylene random copolymers (A) preferably contain ethylene units as comonomer units. For example, polypropylene random copolymers (A) are preferably propylene / ethylene random copolymers containing propylene units and ethylene units.

[0058] The polypropylene-based random copolymer (A) is not limited to propylene / ethylene random copolymers. Examples of polypropylene-based random copolymers (A) other than propylene / ethylene random copolymers include propylene / 1-butene random copolymers, propylene / ethylene / 1-butene random copolymers, propylene / vinyl chloride random copolymers, and propylene / maleic anhydride random copolymers. It should be noted that 1-butene is synonymous with butene-1.

[0059] The polypropylene random copolymer (A) can be a combination of one or more of the following: propylene / ethylene random copolymer and polypropylene random copolymer other than propylene / ethylene random copolymer.

[0060] The melting point of the polypropylene-based random copolymer (A) is 140.0°C or higher and 155.0°C or lower, preferably 140.0°C or higher and 153.0°C or lower, more preferably 140.0°C or higher and 150.0°C or lower, and even more preferably 142.0°C or higher and 149.0°C or lower. Regarding the melting point of the polypropylene-based random copolymer (A), (i) when it is 140.0°C or higher, the foamed molded body obtained from the foamed particles has excellent heat resistance, and (ii) when it is below 155.0°C, it has the advantage of easily increasing the foaming ratio of the foamed particles in the manufacture of the foamed particles.

[0061] In this specification, the melting points of the polypropylene random copolymer (A), and the propylene homopolymer (B1) and polypropylene block copolymer (B2) described later, are values ​​determined by differential scanning calorimetry (hereinafter referred to as "DSC"). The specific operating procedures are as described in the examples described later. For example, a Seiko Instruments DSC7020 model differential scanning calorimeter can be used.

[0062] Melt flow rate (MFR) of polypropylene random copolymer (A) at 230°C and 2160g load A There are no special restrictions as long as the constituent B is met. The MFR of polypropylene random copolymer (A) at 230°C and a load of 2160g... APreferably, the loading rate is 3.0 g / 10 min to 30.0 g / 10 min, more preferably 3.0 g / 10 min to 25.0 g / 10 min, even more preferably 4.0 g / 10 min to 20.0 g / 10 min, and even more preferably 5.0 g / 10 min to 18.0 g / 10 min. The MFR of polypropylene random copolymer (A) at 230°C and a load of 2160 g. A When the above range is met, it has the advantage of easily obtaining foamed particles with a large expansion ratio. Furthermore, in this case, it also has the advantages of excellent surface aesthetics and reduced shrinkage rate of the foamed molded body obtained from these foamed particles.

[0063] In this specification, the MFR of polypropylene random copolymer (A), propylene homopolymer (B1), polypropylene block copolymer (B2), mixtures of propylene homopolymer (B1) and polypropylene block copolymer (B2), and polypropylene resin particles at 230°C and a load of 2160g are values ​​obtained using a melt mass flow rate tester as described in JIS-K7210. Specific operating procedures are as described in the examples described later.

[0064] The polypropylene random copolymer (A) can be a newly manufactured random copolymer (non-recycled polypropylene random copolymer) using known methods, or it can be a recycled polypropylene random copolymer derived from recycled materials. In other words, as the polypropylene random copolymer (A), recycled materials containing recycled polypropylene random copolymers can be used. The polypropylene random copolymer (A) can contain recycled polypropylene random copolymers. It should be noted that when only recycled materials are used as the polypropylene random copolymer (A), the content of polypropylene random copolymer (A) in the foamed particles is the product obtained by multiplying the amount of recycled material used (blending amount) by the content ratio of recycled polypropylene random copolymer in the recycled material. The polypropylene random copolymer (A) can be a mixture of recycled polypropylene random copolymers and non-recycled polypropylene random copolymers.

[0065] The proportion of polypropylene random copolymer (A) derived from recycled materials (i.e., recycled polypropylene random copolymer) in 100% by weight can be 50% or more, 70% or more, 80% or more, or 100%. Polypropylene random copolymer (A) can consist solely of recycled polypropylene random copolymer. The higher the proportion of polypropylene random copolymer derived from recycled materials (i.e., recycled polypropylene random copolymer) in polypropylene random copolymer (A), the greater the advantage in reducing environmental burden.

[0066] In this specification, "recycled material" refers to: (a) a resin composition that has previously been formed into the form of resin products (e.g., foamed granules; foamed molded bodies; films; food trays; packaging containers such as bags and bottles; medical containers such as IV bags and syringes; clothing cases; general merchandise such as transparent folders; home appliances; automotive parts; fishing nets, ropes, buoys, etc.) and then, through any means (e.g., crushing, shredding, melting, and combinations thereof), reprocessed resin products into a resin composition (or granules); and (b) a resin composition that reprocesses waste generated during the manufacturing process of resin products into a resin composition (or granules) through any means (e.g., crushing, shredding, melting, and combinations thereof). In the recycling of resin products, resin products are often recycled according to each use of the resin product, and / or according to each raw material of the resin product. Therefore, recycled materials may primarily consist of resins with the same or substantially the same composition (e.g., polypropylene resins and polyethylene resins). On the other hand, in the recycling of resin products, resin products for different purposes and / or resin products made from different raw materials are sometimes mixed into the resin products that are intended for recycling. Therefore, recycled materials may contain resins with compositions other than the main resin.

[0067] In this specification, the resin contained in recycled materials is sometimes referred to as "recycled resin." For example, recycled polypropylene resin may be included as a recycled resin in (a) a recycled material obtained by any means of reprocessing a resin article made primarily of polypropylene resin into a resin composition and / or (b) a recycled material obtained by any means of reprocessing waste discharged during the manufacturing process of a resin article made primarily of polypropylene resin into a resin composition. Recycled materials that primarily contain recycled polypropylene resin may sometimes contain recycled polyethylene resin as a recycled resin in a smaller amount than the amount of recycled polypropylene resin.

[0068] Recycled materials may include additives used in the manufacture of resin products (e.g., foaming nucleating agents (e.g., talc, calcium carbonate, silica, kaolin, barium sulfate, calcium hydroxide, aluminum hydroxide, alumina, titanium oxide, zinc borate, etc.) and colorants, as described in the section on (additives) below).

[0069] In this specification, the source of recycled materials is not specifically limited. Recycled materials can be derived from foamed materials such as foamed granules and foamed molded bodies. Recycled materials can also be derived from non-foamed materials (e.g., films; food trays; packaging containers such as bags and bottles; medical containers such as IV bags and syringes; clothing cases; general merchandise such as transparent folders; home appliances; automotive parts; fishing gear such as fishing nets, ropes, and buoys).

[0070] In this specification, resins that have never been used in the form of resin products are sometimes referred to as "non-recycled resins". For example, polypropylene resins that have never been used in the form of resin products are also referred to as "non-recycled polypropylene resins".

[0071] This section describes a case where the resin particles contain multiple polypropylene random copolymers with different compositions, properties, and / or sources (e.g., recycling). In this case, the mixture formed from all the polypropylene random copolymers contained in the resin particles is considered "polypropylene random copolymer (A)". Furthermore, the properties (e.g., melting point and MFR) of the mixture formed from all the polypropylene random copolymers contained in the resin particles are described. A Properties (e.g., melting point and MFR) of polypropylene-based random copolymers (A) are considered as follows: A (etc.). For example, if the resin particles contain only two types of polypropylene random copolymers, namely a polypropylene random copolymer with a melting point of 139°C and a polypropylene random copolymer with a melting point of 150°C, the melting point of the mixture formed by the total amount of the polypropylene random copolymer with a melting point of 139°C and the total amount of the polypropylene random copolymer with a melting point of 150°C contained in the resin particles shall be regarded as the melting point of the polypropylene random copolymer (A).

[0072] (propylene homopolymer (B1))

[0073] The melting point of the propylene homopolymer (B1) is not particularly limited as long as it meets the requirements of composition A. The melting point of the propylene homopolymer (B1) is preferably 155.0°C or higher and lower than 165.0°C, more preferably 155.0°C or higher and lower than 163.0°C, even more preferably 155.0°C or higher and lower than 160.0°C, and even more preferably 155.0°C or higher and lower than 158.0°C. Regarding the melting point of the propylene homopolymer (B1), (i) when it is 155.0°C or higher, it has the advantage of being able to obtain a foamed molded body with excellent heat resistance, and (ii) when it is lower than 165.0°C, it has the advantage of being able to reduce the foaming temperature and molding temperature.

[0074] The melt flow rate (MFR) of the propylene homopolymer (B1) at 230°C and a load of 2160g is not particularly limited as long as it satisfies the requirement of composition B. The MFR of the propylene homopolymer (B1) at 230°C and a load of 2160g is preferably 6g / 10min to 350g / 10min, more preferably 10g / 10min to 300g / 10min, even more preferably 15g / 10min to 280g / 10min, and particularly preferably 20g / 10min to 250g / 10min. When the MFR of the propylene homopolymer (B1) at 230°C and a load of 2160g is within the aforementioned range, it has the advantage of easily obtaining foamed particles with a large expansion ratio. Furthermore, in this case, it also has the advantages of excellent surface aesthetics and low shrinkage of the foamed molded body obtained from these foamed particles. The upper limit of the MFR of propylene homopolymer (B1) at 230°C and 2160g load can be less than 200g / 10min, less than 150g / 10min, or less than 100g / min.

[0075] When the resin particles comprise a polypropylene-based random copolymer (A) and a propylene homopolymer (B1), the content of propylene homopolymer (B1) in the resin particles, out of a total of 100 parts by weight of the polypropylene-based random copolymer (A) and the propylene homopolymer (B1), is preferably less than 95 parts by weight, more preferably 10 parts by weight or more and 50 parts by weight or less, even more preferably 10 parts by weight or more and 40 parts by weight or less, and particularly preferably 10 parts by weight or more and 30 parts by weight or less. This configuration has the advantage of reducing the foaming temperature and molding temperature.

[0076] When the resin particles contain propylene homopolymer (B1), the ratio of the content of polypropylene random copolymer (A) to the content of propylene homopolymer (B1) in the resin particles (content of polypropylene random copolymer (A) (parts by weight): content of propylene homopolymer (B1) (parts by weight)) is preferably 90:10 to 50:50, more preferably 85:15 to 50:50, even more preferably 80:20 to 60:40, and particularly preferably 75:25 to 70:30. According to this configuration, it has the advantages of (i) being able to reduce the foaming temperature and molding temperature and (ii) the excellent heat resistance of the obtained foamed molded article.

[0077] The propylene homopolymer (B1) can be a newly manufactured propylene homopolymer (non-recycled propylene homopolymer) using known methods, or it can be a recycled propylene homopolymer derived from recycled materials. In other words, as the propylene homopolymer (B1), recycled materials containing recycled propylene homopolymers can be used. The propylene homopolymer (B1) can contain recycled propylene homopolymers. It should be noted that when using recycled materials, the content of propylene homopolymer (B1) in the foamed particles is the product of the amount of recycled material used (blending amount) and the content ratio of propylene homopolymer (B1) in the recycled material. The propylene homopolymer (B1) can be a mixture of recycled propylene homopolymers and non-recycled propylene homopolymers.

[0078] From the viewpoint of reducing environmental burden, the proportion of propylene homopolymer (B1) derived from recycled materials (i.e., recycled propylene homopolymer) in 100% by weight is preferably 50% or more, more preferably 70% or more, further preferably 80% or more, and particularly preferably 100%. That is, propylene homopolymer (B1) is particularly preferably composed of only recycled propylene homopolymer.

[0079] The propylene homopolymer (B1) may contain structural units derived from isoprene and structural units derived from conjugated diene, but preferably not. In 100% by weight of the propylene homopolymer (B1), the total content of structural units derived from isoprene and structural units derived from conjugated diene is preferably 20% by weight or less, more preferably 10% by weight or less, further preferably 5% by weight or less, and most preferably 0% by weight.

[0080] This section describes a case where the resin particles contain multiple propylene homopolymers with different compositions, properties, and / or sources (whether or not they are recycled). In this case, the mixture formed from all the propylene homopolymers contained in the resin particles is considered "propylene homopolymer (B1)". Furthermore, the properties (e.g., melting point and MFR, etc.) of the mixture formed from all the propylene homopolymers contained in the resin particles are considered as the properties (e.g., melting point and MFR, etc.) of propylene homopolymer (B1).

[0081] (Polypropylene block copolymer (B2))

[0082] The polypropylene block copolymer (B2) has, in addition to propylene units, one or more structural units derived from monomers other than propylene monomers. In other words, the polypropylene block copolymer (B2) contains at least propylene units and comonomer units. More specifically, the polypropylene block copolymer (B2) contains propylene blocks formed from propylene units and comonomer blocks formed from comonomer units. Specific examples of comonomer units are the same as those described in the section on (polypropylene random copolymer (A)) above, and therefore, that description is used here without further explanation.

[0083] From the viewpoint of reducing molding temperature, polypropylene block copolymers (B2) preferably contain ethylene units as comonomer units. For example, polypropylene block copolymers (B2) are preferably propylene / ethylene block copolymers containing propylene blocks formed from propylene units and ethylene blocks formed from ethylene units.

[0084] Polypropylene block copolymers (B2) are not limited to propylene / ethylene block copolymers. Examples of polypropylene block copolymers (B2) other than propylene / ethylene block copolymers include propylene / 1-butene block copolymers, propylene / ethylene / 1-butene block copolymers, propylene / vinyl chloride block copolymers, and propylene / maleic anhydride block copolymers.

[0085] As a polypropylene block copolymer (B2), it refers to a substance that is considered a polypropylene block copolymer in the technical field of polypropylene resins. For example, a propylene / ethylene block copolymer comprises a layer of polyethylene formed by covering a homopolymer polypropylene matrix with an ethylene / propylene elastic copolymer as a domain, and is sometimes also referred to as an impact copolymer.

[0086] The polypropylene block copolymer (B2) can be a combination of a propylene / ethylene block copolymer and one or more polypropylene block copolymers (B2) other than the propylene / ethylene block copolymer.

[0087] The melting point of the polypropylene block copolymer (B2) is not particularly limited as long as it meets the requirements of composition A. The melting point of the polypropylene block copolymer (B2) is preferably 155.0°C or higher and lower than 165.0°C, more preferably 155.0°C or higher and lower than 164.0°C, more preferably 156.0°C or higher and lower than 163.0°C, more preferably 156.0°C or higher and lower than 162.0°C, and even more preferably 156.0°C or higher and lower than 161.0°C. Regarding the melting point of the polypropylene block copolymer (B2), (i) when it is 155°C or higher, it has the advantage of being able to obtain a foamed molded body with excellent heat resistance, and (ii) when it is lower than 165.0°C, it has the advantage of excellent molding processability.

[0088] The melt flow rate (MFR) of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is not particularly limited as long as the composition B is satisfied. The MFR of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is preferably 6g / 10min to 350g / 10min, more preferably 10g / 10min to 300g / 10min, even more preferably 15g / 10min to 280g / 10min, and even more preferably 20g / 10min to 250g / 10min. When the MFR of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is within the aforementioned range, it has the advantage of easily obtaining foamed particles with a large expansion ratio. Furthermore, in this case, it also has the advantages of excellent surface aesthetics and reduced shrinkage of the foamed molded body obtained from these foamed particles.

[0089] When the resin particles contain a polypropylene block copolymer (B2), the ratio of the content of the polypropylene random copolymer (A) to the content of the polypropylene block copolymer (B2) in the resin particles (content of polypropylene random copolymer (A) (parts by weight): content of polypropylene block copolymer (B2) (parts by weight)) is preferably 90:10 to 40:60, more preferably 85:15 to 55:45, even more preferably 80:20 to 60:40, and particularly preferably 75:25 to 65:35. According to this configuration, it has the advantages of (i) being able to reduce the foaming temperature and molding temperature and (ii) obtaining a foamed molded article with excellent heat resistance.

[0090] The polypropylene block copolymer (B2) can be a newly manufactured copolymer (non-recycled polypropylene block copolymer) using known methods, or it can be a recycled polypropylene block copolymer derived from recycled materials. In other words, as the polypropylene block copolymer (B2), recycled materials containing recycled polypropylene block copolymers can be used. The polypropylene block copolymer (B2) can contain recycled polypropylene block copolymers. It should be noted that when using recycled materials, the content of polypropylene block copolymer (B2) in the foamed particles is the product obtained by multiplying the amount of recycled material used (blending amount) by the content ratio of polypropylene block copolymer (B2) in the recycled material. The polypropylene block copolymer (B2) can be a mixture of recycled polypropylene block copolymers and non-recycled polypropylene block copolymers. The polypropylene block copolymer (B2) preferably contains recycled polypropylene block copolymers derived from recycled materials. As described above, as a recycled resin for polypropylene resins, the flow rate of polypropylene block copolymers is greater than that of polypropylene random copolymers. Therefore, recycled resins of polypropylene block copolymers can be obtained relatively easily.

[0091] From the viewpoint of reducing environmental burden, the proportion of recycled polypropylene block copolymer (i.e., recycled polypropylene block copolymer) derived from recycled materials in 100% by weight of the polypropylene block copolymer (B2) is preferably 50% or more, more preferably 70% or more, further preferably 80% or more, and particularly preferably 100%. That is, the polypropylene block copolymer (B2) is particularly preferably composed of only recycled polypropylene block copolymer.

[0092] The polypropylene block copolymer (B2) may contain structural units derived from isoprene and structural units derived from conjugated diene, but preferably not. In 100% by weight of the polypropylene block copolymer (B2), the total content of structural units derived from isoprene and structural units derived from conjugated diene is preferably 20% by weight or less, more preferably 10% by weight or less, further preferably 5% by weight or less, and most preferably 0% by weight.

[0093] This section describes the case where the resin particles contain multiple polypropylene block copolymers with different compositions, properties, and / or sources (whether or not they are recycled). In this case, the mixture formed from all the polypropylene block copolymers contained in the resin particles is considered "polypropylene block copolymer (B2)". Furthermore, the properties (e.g., melting point and MFR) of the mixture formed from all the polypropylene block copolymers contained in the resin particles are considered as the properties (e.g., melting point and MFR) of the polypropylene block copolymer (B2).

[0094] Preferably, at least one of the following: polypropylene random copolymer (A), propylene homopolymer (B1), and polypropylene block copolymer (B2) comprises recycled resin derived from recycled materials. Using recycled resin not only reduces environmental pollution but also significantly reduces the amount of plastic waste generated and the amount of plastic used in manufacturing. Therefore, implementations using recycled resin as all or part of the resin have the following advantages: they contribute to achieving Sustainable Development Goals (SDGs) Goal 12, "Ensuring sustainable consumption and production patterns," and Goal 14, "Conserving and sustainably using the ocean and its resources to promote sustainable development."

[0095] (A mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2))

[0096] The melting point of the mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) is 155°C or higher and lower than 165°C, more preferably 155°C or higher and lower than 164°C, more preferably 155°C or higher and lower than 163°C, more preferably 155°C or higher and lower than 162°C, more preferably 155°C or higher and lower than 161°C, more preferably 155°C or higher and lower than 160°C, and even more preferably 155°C or higher and lower than 158°C. According to this configuration, the foamed particles have the advantage of providing a foamed molded body with a short molding cycle. Furthermore, regarding the melting point of the mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2), (i) when it is above 155°C, it has the advantage of obtaining a foamed molded body with excellent heat resistance, and (ii) when it is below 165°C, it has the advantage of reducing the foaming temperature and molding temperature, as well as excellent molding processability.

[0097] Melt flow rate (MFR) of a mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) at 230°C and a load of 2160 g. B There are no special restrictions as long as the constituent B is met. The MFR of a mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) at 230°C and a load of 2160g... B Preferably, the loading is 6 g / 10 min to 350 g / 10 min, more preferably 10 g / 10 min to 300 g / 10 min, even more preferably 15 g / 10 min to 280 g / 10 min, and particularly preferably 20 g / 10 min to 250 g / 10 min. The mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) is subjected to MFR at 230°C and a loading of 2160 g. B When the aforementioned range is met, it has the advantage of easily obtaining foamed particles with a large expansion ratio. Furthermore, in this case, it also has the advantages of excellent surface aesthetics and reduced shrinkage of the foamed molded body obtained from these foamed particles.

[0098] In one embodiment of the invention, the resin particles may be (i) comprising propylene homopolymer (B1) and excluding polypropylene block copolymer (B2), (ii) comprising polypropylene block copolymer (B2) and excluding propylene homopolymer (B1), or (iii) comprising both propylene homopolymer (B1) and polypropylene block copolymer (B2). Therefore, regarding the melting point and MFR of the mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2), BSpecifically, (i) when the resin particles contain propylene homopolymer (B1) but not polypropylene block copolymer (B2), the melting point and MFR of the propylene homopolymer (B1) are used; (ii) when the resin particles contain polypropylene block copolymer (B2) but not propylene homopolymer (B1), the melting point and MFR of the polypropylene block copolymer (B2) are used; and (iii) when the resin particles contain both propylene homopolymer (B1) and polypropylene block copolymer (B2), the melting point and MFR of the mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) are used.

[0099] In the resin particles, of a total of 100 parts by weight of polypropylene random copolymer (A), propylene homopolymer (B1), and polypropylene block copolymer (B2), preferably (a) the content of polypropylene random copolymer (A) is 70 parts by weight to 95 parts by weight, and the total content of propylene homopolymer (B1) and polypropylene block copolymer (B2) is 5 parts by weight to 30 parts by weight; more preferably (b) the content of polypropylene random copolymer (A) is 70 parts by weight to 90 parts by weight, and the total content of propylene homopolymer (B1) and polypropylene block copolymer (B2) is 10 parts by weight to 30 parts by weight; and even more preferably (c) the content of polypropylene random copolymer (A) is 70 parts by weight to 80 parts by weight, and the total content of propylene homopolymer (B1) and polypropylene block copolymer (B2) is 20 parts by weight to 30 parts by weight. When the contents of polypropylene-based random copolymer (A), propylene homopolymer (B1), and polypropylene-based block copolymer (B2) in the resin particles are within the above-mentioned range, the foamed particles have the advantage of superior productivity of polypropylene-based resin foamed moldings. It should be noted that regarding the "total content of propylene homopolymer (B1) and polypropylene-based block copolymer (B2)," (i) if the resin particles contain propylene homopolymer (B1) but not polypropylene-based block copolymer (B2), it refers to the content of propylene homopolymer (B1); (ii) if the resin particles contain polypropylene-based block copolymer (B2) but not propylene homopolymer (B1), it refers to the content of polypropylene-based block copolymer (B2); and (iii) if the resin particles contain both propylene homopolymer (B1) and polypropylene-based block copolymer (B2), it refers to the total content of propylene homopolymer (B1) and polypropylene-based block copolymer (B2).

[0100] (MFR) B / MFR A )

[0101] Melt flow rate (MFR) of a mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2) at 230°C and a load of 2160 g. BThe melt flow rate (MFR) of polypropylene random copolymer (A) at 230°C and 2160g load is relative to that of polypropylene random copolymer (A). A The ratio of MFR B / MFR A The particle size is 2.0 to 30.0, preferably 4.0 to 30.0, and more preferably 5.0 to 30.0. According to this configuration, the foamed particles have the advantage of providing a foamed molded article with a short molding cycle. Furthermore, according to this configuration, it has the advantage of providing a foamed molded article with excellent surface aesthetics.

[0102] The resin particles may further include, without impairing the effects of one embodiment of the present invention, resins other than polypropylene random copolymers (A), propylene homopolymers (B1), and polypropylene block copolymers (B2) (sometimes referred to as "other resins, etc."). Examples of the aforementioned other resins, etc., include: (a) polypropylene resins other than polypropylene random copolymers, propylene homopolymers, and polypropylene block copolymers with melting points below 140.0°C or above 155.0°C; (b) ethylene resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, and ethylene / methacrylic acid copolymers; (c) styrene resins such as polystyrene, styrene / maleic anhydride copolymers, and styrene / ethylene copolymers; (d) polyolefin waxes such as propylene-α-olefin waxes; and (e) olefin rubbers such as ethylene / propylene rubber, ethylene / butene rubber, ethylene / hexene rubber, and ethylene / octene rubber. The content of other resins in the resin particles is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, relative to a total of 100 parts by weight of polypropylene random copolymer (A), propylene homopolymer (B1) and polypropylene block copolymer (B2).

[0103] (additive)

[0104] In addition to the resin components mentioned above, the resin particles may optionally contain additives. Examples of additives include colorants, water-absorbing substances (e.g., (i) polyols such as glycerol and diglycerol; (ii) polyethers such as polyethylene glycol and polyethylene oxide; and (iii) borate metal salts such as borax and zinc borate), foaming nucleating agents (e.g., inorganic substances such as talc, calcium carbonate, silica, kaolin, barium sulfate, calcium hydroxide, aluminum hydroxide, alumina, and titanium dioxide), antistatic agents (e.g., glyceryl monostearate, glyceryl monostearate / distearate), and flame retardants (e.g., hindered amine flame retardants). The additives include: flame retardants (such as brominated flame retardants, phosphate ester flame retardants, melamine flame retardants, etc.), antioxidants (such as hindered phenolic antioxidants, etc.), heat stabilizers (such as phosphorus-based heat stabilizers and sulfur-based heat stabilizers, etc.), light stabilizers (benzotriazole-based UV absorbers, triazine-based UV absorbers, HALS and / or hindered amine-based light stabilizers, etc.), nucleating agents, conductive agents (carbon, carbon nanotubes, metal fillers, etc.), lubricants, acid scavengers, anti-blocking agents, metal chelating agents (IRGANOX (registered trademark) MD1024, ADK STAB (registered trademark) CDA-1, etc.), lubricants, antibacterial agents, organic peroxides, MFR modifiers, etc. Additionally, the resin particles may contain a combination of one or more of these additives for recycling materials. "Metal chelating agents" are sometimes also referred to as "metal passivators." Such additives can be added directly to the mixed resins or polypropylene resin compositions described later during the manufacture of polypropylene resin particles.

[0105] Coloring agents include colored pigments and carbon black. Colored 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 blended with blue and yellow pigments; (v) orange pigments blended with red and yellow pigments; and (vi) purple pigments blended with cobalt violet, blue, and red pigments. Resin particles may contain carbon black.

[0106] <Physical properties>

[0107] The following describes the physical properties of the resin particles and the foamed particles.

[0108] (MFR of polypropylene resin particles)

[0109] The MFR (Mean Friction Rate) of the polypropylene resin particles at 230°C and a load of 2160g is preferably 7.0g / 10min to 30.0g / 10min, more preferably 10.0g / 10min to 28.0g / 10min, and even more preferably 13.0g / 10min to 26.0g / 10min or more. According to this configuration, the foamed particles have the advantage of providing foamed molded articles with a short molding cycle. Furthermore, according to this configuration, it also has the advantage of providing foamed molded articles with excellent internal weldability and / or surface aesthetics.

[0110] (DSC ratio of polypropylene resin foam particles)

[0111] The foamed particles preferably have at least two melting peaks in the DSC curve obtained by differential scanning calorimetry (DSC) as described later. The heat of fusion obtained from the high-temperature melting peak is taken as the "high-temperature melting heat (Q)". h The heat of fusion obtained from the melting peak on the low-temperature side is used as the "heat of fusion on the low-temperature side (Q)". l Additionally, when there are three or more melting peaks, the heat of fusion obtained from the highest melting peak is taken as the "high-temperature side heat of fusion (Q)". h The heat of fusion obtained from other melting peaks is taken as the "low-temperature side heat of fusion (Q)". l The ratio of the heat of molten metal on the high-temperature side to the total heat of molten metal, more specifically, the ratio of the heat of molten metal on the high-temperature side out of 100% of the total heat of molten metal, is also called the "DSC ratio". The DSC ratio is calculated by the following formula:

[0112] DSC ratio (%) = Q h / (Q) l +Q h )×100.

[0113] The ratio of the high-temperature side melt heat (DSC ratio) in 100% of the total melt heat of the foamed particles is not particularly limited. The DSC ratio of the foamed particles is preferably 30.0% to 50.0%, more preferably 30.0% to 40.0%, and even more preferably 30.0% to 35.0%. When the DSC ratio of the foamed particles is 30.0% or higher, the foamed particles have the advantage of providing a foamed molded body with sufficient strength. On the other hand, when the DSC ratio of the foamed particles is 50.0% or lower, it has the advantage of being able to mold the foamed particles at a lower temperature (molding temperature) to provide a foamed molded body. The method for measuring the DSC ratio of the foamed particles will be described in detail in the following examples.

[0114] The DSC ratio of these foamed granules also serves as a benchmark value for the amount of high-melting-point crystals contained in the foamed granules. That is, a DSC ratio of 30.0% to 50.0% indicates that the foamed granules contain a relatively high amount of high-melting-point crystals. Furthermore, the DSC ratio of the foamed granules is closely related to the viscoelasticity of both the resin particles and the foamed granules during foaming and expansion. In other words, when the DSC ratio of the foamed granules is between 30.0% and 50.0%, both the resin particles and the foamed granules exhibit excellent foaming and expansion properties, respectively, during both foaming and molding. As a result, the foamed granules have the advantage of providing foamed molded bodies with excellent internal weldability and superior mechanical strength, such as compressive strength, at low molding pressure.

[0115] In this foamed granule, methods for controlling the DSC ratio within a specified range include adjusting the conditions during the manufacture of the foamed granule (particularly the foaming temperature, foaming pressure, holding time, and the temperature of the area (space) where the dispersion is released). From the perspective of ease of adjustment, adjusting the foaming temperature, foaming pressure, and / or holding time is preferred as a method for controlling the DSC ratio within a specified range.

[0116] For example, increasing the foaming temperature tends to decrease the DSC ratio, while decreasing the foaming temperature tends to increase it. This is because the amount of unmelted crystals varies with the foaming temperature. Similarly, increasing the foaming pressure tends to decrease the DSC ratio, while decreasing it tends to increase it. This is because the degree of plasticization varies with the foaming pressure, thus affecting the amount of unmelted crystals. Furthermore, there is a tendency for a longer holding time to result in a larger DSC ratio. This is because the amount of unmelted crystal growth varies with the holding time.

[0117] (Expansion ratio of polypropylene resin foamed granules)

[0118] The foaming ratio of the foamed granules is preferably 10 to 50 times, more preferably 18 to 40 times, and even more preferably 18 to 30 times. Regarding the foaming ratio of the foamed granules, (i) if it is 10 times or more, lightweight foamed molded bodies can be obtained with good production efficiency, and (ii) if it is 50 times or less, the strength of the obtained foamed molded bodies will not be insufficient. The method for calculating the foaming ratio of the foamed granules is described in detail in the following embodiments.

[0119] (Average bubble diameter of polypropylene resin foam particles)

[0120] The average bubble diameter of the foamed particles is not particularly limited. The average bubble diameter of the foamed particles is preferably 80 μm to 500 μm, more preferably 85 μm to 400 μm, further preferably 90 μm to 300 μm, and particularly preferably 95 μm to 250 μm. Regarding the average bubble diameter of the foamed particles, (i) when it is 80 μm or more, the foamed particles can provide polypropylene resin foamed molded articles with excellent compressive strength, and (ii) when it is 500 μm or less, it has the advantages of not increasing the molding cycle time and having good productivity. The method for measuring the average bubble diameter of the foamed particles is described in detail in the following examples.

[0121] (Molding pressure)

[0122] This foaming granule has the following advantages: using this foaming granule, foamed molded articles with excellent weldability (e.g., weldability of 80% or more) can be obtained with low molding pressure. In other words, this foaming granule has the following advantages: it can provide foamed molded articles with excellent weldability at the same molding pressure as foaming granules obtained using only polypropylene random copolymers as the base resin.

[0123] In this specification, the lowest value among the molding pressures that can provide a foamed molded article with excellent weldability (e.g., a weldability of 80% or more) in the manufacture of foamed molded articles using foamed granules is also referred to as the "minimum molding pressure". This foamed granule also has the advantage of a low minimum molding pressure. In other words, the minimum molding pressure of this foamed granule can be equivalent to that of foamed granules obtained using only polypropylene-based random copolymers as the base resin.

[0124] The molding pressure for these foamed particles is not particularly limited, but is preferably 0.34 MPa (gauge pressure) or less, more preferably 0.32 MPa (gauge pressure) or less, and even more preferably 0.30 MPa (gauge pressure) or less. The lower limit of the molding pressure is not particularly limited, and can be, for example, 0.15 MPa (gauge pressure) or more. When the minimum molding pressure is within the above range, it has the advantage of being able to provide foamed molded articles with a small economic burden.

[0125] [3. Manufacturing method of polypropylene resin foamed granules]

[0126] A method for manufacturing polypropylene resin foamed granules according to one embodiment of the present invention includes the following steps: an extrusion step, wherein a mixed resin comprising a polypropylene random copolymer (A) having a melting point of 140.0°C or higher and lower than 155.0°C and comprising a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) is melt-blended to obtain polypropylene resin granules; and a foaming step, wherein the polypropylene resin granules obtained in the extrusion step are foamed, wherein the melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is 155.0°C or higher and lower than 165.0°C, and the melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g is... B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0127] Because this manufacturing method includes the above-described components, it has the advantage of providing foamed granules capable of producing foamed molded bodies with a short molding cycle. Furthermore, because this manufacturing method includes the above-described components, it also has the advantage of providing foamed granules that provide excellent internal weldability and / or surface aesthetics in foamed molded bodies. Additionally, because this manufacturing method includes the above-described components, it can provide foamed granules that provide excellent internal weldability and / or surface aesthetics in foamed molded bodies using less steam compared to conventional methods, even when using propylene homopolymers and / or polypropylene block copolymers. In other words, because this manufacturing method includes the above-described components, it also has the advantage of low energy consumption (energy saving). As described above, this manufacturing method also includes components A and B.

[0128] (Extrusion process)

[0129] In the extrusion process, a mixture of resins comprising a polypropylene random copolymer (A) and a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) is melt-blended.

[0130] There is no particular limitation on the specific method of the extrusion process. For example, as a method to obtain resin particles, the method of using an extruder can be listed. Specifically, for example, resin particles can be made by the following methods (1) to (5): (1) a mixed resin is prepared by blending a polypropylene random copolymer (A), a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2), and one or more of the group consisting of other resins and additives as needed; (2) the mixed resin is fed into an extruder and melt-blended to prepare a polypropylene resin composition; (3) the polypropylene resin composition is extruded from a die provided by the extruder; (4) the extruded polypropylene resin composition is cooled by passing it through water or the like, thereby solidifying it; (5) the solidified polypropylene resin composition is then cut into desired shapes such as cylinders, ellipses, spheres, cubes, cuboids, hollow cylinders, polygonal prisms, etc., using a cutter. Alternatively, in (3), the melt-blended polypropylene resin composition can be directly extruded from the die of an extruder into water, and immediately after extrusion, the polypropylene resin composition can be cut into granules, cooled, and cured. In this way, by melt-blending the mixed resin, more uniform resin granules can be obtained. In addition, the extrusion process may include a peroxide treatment process that treats the mixed resin with peroxide.

[0131] The weight of each resin particle obtained by the above operation is preferably 0.2 mg / particle to 10.0 mg / particle, more preferably 0.5 mg / particle to 6.0 mg / particle. Regarding the weight of each resin particle, (a) when it is 0.2 mg / particle or more, there is a tendency to improve the workability of the resin particles, and in addition, there is a tendency to reduce the shrinkage rate of the foamed molded body formed by molding the obtained foamed particles; (b) when it is 10.0 mg / particle or less, there is a tendency to improve the mold filling performance in the in-mold foaming molding process.

[0132] (Peroxide treatment process)

[0133] This manufacturing method preferably includes a peroxide treatment step: treating propylene homopolymer (B1') and / or polypropylene block copolymer (B2') with a peroxide to obtain said propylene homopolymer (B1) and / or said polypropylene block copolymer (B2). For example, by melt-blending an organic peroxide with (i) propylene homopolymer (B1'), (ii) polypropylene block copolymer (B2'), or (iii) a mixture of propylene homopolymer (B1') and polypropylene block copolymer (B2') in an extruder, these resins can be treated with a peroxide, and the resulting polymers can be used as (i) propylene homopolymer (B1), (ii) polypropylene block copolymer (B2), or (iii) a mixture of propylene homopolymer (B1) and polypropylene block copolymer (B2), respectively. In other words, in this manufacturing method, the propylene homopolymer (B1) and / or polypropylene block copolymer (B2) can be treated with an oxide. The mixture of propylene homopolymer and polypropylene block copolymer prepared as raw materials has a low MFR at 230°C and a load of 2160g. Even if it does not satisfy configuration B of one embodiment of the present invention, the MFR of the mixture can be improved by peroxide treatment of these propylene homopolymers and / or polypropylene block copolymers, thus satisfying configuration B. It can be said that the propylene homopolymer and polypropylene block copolymer satisfying configuration B are respectively the propylene homopolymer (B1) and polypropylene block copolymer (B2) of one embodiment of the present invention. In other words, the propylene homopolymer (B1') and polypropylene block copolymer (B2') refer to the propylene homopolymer and polypropylene block copolymer that do not satisfy configuration B. The specific method of the peroxide treatment process is not particularly limited as long as configuration B is satisfied.

[0134] In this manufacturing method, when (i) a propylene homopolymer (B1) is used and a polypropylene block copolymer (B2) is not used, the propylene homopolymer (B1') can be treated with peroxide only in the peroxide treatment step; when (ii) a polypropylene block copolymer (B2) is used and a propylene homopolymer (B1) is not used, the polypropylene block copolymer (B2') can be treated with peroxide only in the peroxide treatment step; when (iii) both a propylene homopolymer (B1) and a polypropylene block copolymer (B2) are used, in the peroxide treatment step, (iii-1) the propylene homopolymer (B1') can be treated with peroxide only; (iii-2) the polypropylene block copolymer (B2') can be treated with peroxide only; and (iii-3) both the propylene homopolymer (B1') and the polypropylene block copolymer (B2') can be treated with peroxide.

[0135] As for propylene homopolymer (B1') and polypropylene block copolymer (B2'), they can be in the same manner as propylene homopolymer (B1) and polypropylene block copolymer (B2'), except that the MFR of the mixture of propylene homopolymer (B1') and polypropylene block copolymer (B2') does not satisfy the requirement of constituting B. That is, for each manner relating to propylene homopolymer (B1') and polypropylene block copolymer (B2'), the descriptions of the above-mentioned (propylene homopolymer (B1)) and (polypropylene block copolymer (B2)) items can be appropriately referenced respectively.

[0136] In the peroxide treatment process, the amount of peroxide used is preferably 0.01 to 1.00 parts by weight, more preferably 0.05 to 0.50 parts by weight, and even more preferably 0.10 to 0.40 parts by weight, relative to a total of 100 parts by weight of propylene homopolymer (B1') and polypropylene block copolymer (B2').

[0137] Examples of peroxides that can be used include 1,1-bis(tert-butylperoxide)3,3,5-trimethylcyclohexane, tert-butyl peroxylaurate, 2,5-dimethyl-2,5-di(benzoylperoxide)hexane, tert-butyl peroxybenzoate, dicumyl peroxide, 1,3-bis(tert-butylperoxide)benzene, tert-butyl peroxyisocarbonate, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 1,1-bis(tert-butylperoxide)cyclohexane, n-butyl 4,4-di(tert-butylperoxide)valerate, α,α'-di(tert-butylperoxide)diisopropylbenzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexyn-3.

[0138] In this manufacturing method, in addition to the peroxide treatment step described above, the extrusion step may also include a step of treating the mixed resin with peroxide.

[0139] (Foaming process)

[0140] The foaming step in this manufacturing method is not particularly limited, but may include, for example, the following steps: (i) a dispersion step of dispersing polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container to obtain a dispersion; (ii) a heating step of heating the dispersion to a temperature above the softening temperature of the polypropylene resin particles; (iii) a pressurization step of pressurizing the container; and (iv) a release step of releasing one end of the container to release the dispersion into a region with a lower pressure than the container. Hereinafter, an example of a foaming step will be described, taking a case where the foaming step includes a dispersion step, a heating step, a pressurization step, and a release step.

[0141] (Dispersed processes)

[0142] There are no particular limitations on the containers used in the dispersion process. Examples of containers include pressure vessels and autoclave-type pressure vessels (pressure-resistant autoclaves). The container may contain a stirrer.

[0143] As an aqueous dispersion medium, there are no particular limitations as long as it contains water. From the viewpoint of being able to stably produce foamed particles, it is preferable to use pure water and ultrapure water such as RO water (water purified by reverse osmosis membrane method), distilled water, deionized water (water purified by ion exchange resin), etc., as an aqueous dispersion medium.

[0144] Examples of foaming agents include (a) inorganic gases such as nitrogen, carbon dioxide, and air (a mixture of oxygen, nitrogen, and carbon dioxide), and (a) inorganic foaming agents such as water; and (b) organic foaming agents. From the viewpoint of reducing environmental burden and reducing combustion hazards, inorganic foaming agents are preferred, inorganic gases and / or water are more preferred, and carbon dioxide and / or water are even more preferred. Water, used as an aqueous dispersion medium, can also be used as a foaming agent. In this case, both the aqueous dispersion medium and the foaming agent can be water in the dispersion process.

[0145] In this manufacturing method, dispersants (such as inorganic dispersants like tricalcium phosphate, trimagnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, and clay) and dispersing aids (such as sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkyl sulfonate, sodium alkyl diphenyl ether disulfonate, and sodium α-olefin sulfonate) are preferably used. This composition reduces the adhesion (sometimes referred to as sticking) between resin particles and improves the stability of the dispersion within the container. As a result, it has the advantage of being able to stably manufacture foamed particles.

[0146] (Heating process)

[0147] In this specification, "softening temperature of polypropylene resin particles" refers to the melting point of the resin with the highest melting point among the non-recycled polypropylene resin and the resin components contained in the recycled materials of the base resin constituting the polypropylene resin particles, which is -10.0℃.

[0148] In this specification, the term "temperature above the softening temperature of polypropylene resin particles" is sometimes used as "foaming temperature." In other words, the heating process can also be described as a process of heating the dispersion to the foaming temperature. There is no particular limitation on the foaming temperature in the heating process, as long as it is above the softening temperature of the polypropylene resin particles. There is no particular limitation on the upper limit of the foaming temperature, i.e., the temperature to which the dispersion is heated in the heating process. The foaming temperature is preferably below the softening temperature of the polypropylene resin particles + 20.0°C, more preferably below the softening temperature of the polypropylene resin particles + 15.0°C, and even more preferably below the softening temperature of the polypropylene resin particles + 10.0°C. With this configuration, there is the advantage that the polypropylene resin particles will not adhere to each other inside the container.

[0149] (Pressure process)

[0150] In this specification, the pressure after pressurization (constant pressure) during the pressurization process is sometimes referred to as the "foaming pressure". In other words, during the pressurization process, the pressure inside the container is increased to the foaming pressure.

[0151] In the pressurization process, there is no particular limitation on the pressure level to which the pressure inside the container is increased, i.e., the foaming pressure. The preferred foaming pressure in the pressurization process is (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 foaming pressure is 1.0 MPa (gauge pressure) or higher, foamed particles with appropriate density can be obtained.

[0152] The heating and pressurizing processes can be performed sequentially or simultaneously.

[0153] (Maintaining process)

[0154] This manufacturing method may also include the following holding process: after the heating process and the pressurizing process and before the release process, maintaining the temperature inside the container at the foaming temperature and maintaining the pressure inside the container at the foaming pressure (or near the foaming pressure).

[0155] In the holding process, the time for which the temperature of the dispersion is maintained at the foaming temperature and the pressure inside the container is maintained at the foaming pressure (near the foaming pressure) (holding time) is not particularly limited. The holding time is preferably 10 to 60 minutes, more preferably 12 to 55 minutes, and even more preferably 15 to 50 minutes. When the holding time is 10 minutes or more, a sufficient amount of unmelted crystals (crystallization of the base resin) are present, resulting in the advantage of reducing the shrinkage of the obtained foamed particles and / or the increase in the continuous bubble rate. On the other hand, when the holding time is 60 minutes or less, since there is no excessive amount of unmelted crystals, it is advantageous to mold the foamed particles at a low molding temperature.

[0156] (Release process)

[0157] Regarding the release process, (a) it can be performed after the heating and pressurizing processes if a holding process is not performed, and (b) it can be performed after the holding process if a holding process is performed. The release process enables the resin particles to foam, resulting in foamed particles.

[0158] In the release process, "the region with a pressure lower than that inside the container" refers to "the region under a pressure lower than that inside the container" or "the space under a pressure lower than that inside the container," or it can be described as "an atmosphere with a pressure lower than that inside the container." The region with a pressure lower than that inside the container can also be described as a region with a pressure lower than the foaming pressure, for example, it could be a region at atmospheric pressure. The low-pressure region is, for example, the gas phase. Furthermore, for the purpose of improving foaming properties, the aforementioned low-pressure region (space) can be filled with saturated water vapor.

[0159] In the release process, when releasing the dispersion into an area where the pressure is lower than that inside the container, the dispersion can also be released through an open throttling orifice with a diameter of 1 mm to 5 mm for purposes such as adjusting the flow rate of the dispersion and reducing the deviation of the foaming ratio of the obtained foamed particles.

[0160] As described above, the process of manufacturing foamed granules from resin particles is called the "first-stage foaming process," and the resulting foamed granules are called "first-stage foamed granules." To obtain foamed granules with a high expansion ratio, the first-stage foamed granules obtained in the first-stage foaming process can be foamed again. The process of increasing the expansion ratio of the first-stage foamed granules is called the "second-stage foaming process," and the polypropylene resin foamed granules obtained through the second-stage foaming process are called "second-stage foamed granules." The specific method for the second-stage foaming process is not particularly limited, and known methods can be used.

[0161] [4. Polypropylene Resin Foamed Molded Body]

[0162] One embodiment of the polypropylene resin foamed molded body of the present invention is a foamed molded body formed by molding the polypropylene resin foamed particles described in item [2. Polypropylene resin foamed particles]. Another embodiment of the polypropylene resin foamed molded body of the present invention may be a foamed molded body formed by molding polypropylene resin foamed particles obtained by the manufacturing method described in item [3. Method for manufacturing polypropylene resin foamed particles]. A third embodiment of the polypropylene resin foamed molded body of the present invention may include polypropylene resin foamed particles described in item [2. Polypropylene resin foamed particles], or polypropylene resin foamed particles obtained by the manufacturing method described in item [3. Method for manufacturing polypropylene resin foamed particles].

[0163] In this specification, "a polypropylene resin foamed molded article according to an embodiment of the present invention" is sometimes referred to as "the foamed molded article".

[0164] This foamed molded body has the above-described structure, and therefore has the advantages of excellent internal weldability and / or surface aesthetics.

[0165] (Internal weldability)

[0166] In this specification, the internal weldability of the foamed molded body is evaluated based on the total number of foamed particles present on the fracture surface of the foamed molded body and the number of foamed particles that break at locations other than the particle interfaces. The greater the number of foamed particles that break at locations other than the particle interfaces, in other words, the higher the internal weldability, the better the internal weldability.

[0167] The internal weld ratio of this foamed molded body is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more.

[0168] (Surface aesthetics)

[0169] In this specification, the surface aesthetics of the foamed molded body are evaluated by the degree of gaps between the foam particles on the surface of the foamed molded body (hereinafter sometimes referred to as "particle gaps") and the wrinkles on the surface of the foamed molded body. The smaller the size and the fewer the number of particle gaps on the surface of the foamed molded body, the better the surface aesthetics of the foamed molded body. Similarly, the fewer the wrinkles on the surface of the foamed molded body, the better the surface aesthetics of the foamed molded body.

[0170] (Molding cycle)

[0171] In this specification, the molding cycle of this foamed molded body is evaluated based on the time (in seconds) until the cooling (water cooling) of the molded body is completed. It should be noted that the cooling (water cooling) completion time of the molded body is set as follows: the moment when the mold is opened and demolding is completed when the surface pressure drops to 0.01 MPa (gauge pressure) using a surface pressure gauge installed on the surface of the plank.

[0172] One embodiment of the present invention may also be configured as follows.

[0173] [1] A polypropylene resin foamed granule, which is formed by foaming polypropylene resin granules.

[0174] The polypropylene resin particles comprise a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and also comprise a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2).

[0175] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0176] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0177] [2] According to the polypropylene resin foamed particles described in [1], in the polypropylene resin particles, in a total of 100 parts by weight of the polypropylene random copolymer (A), the propylene homopolymer (B1) and the polypropylene block copolymer (B2), the content of the polypropylene random copolymer (A) is 70 parts by weight to 95 parts by weight, and the total content of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is 5 parts by weight to 30 parts by weight.

[0178] [3] The polypropylene resin foamed particles according to [1] or [2] have more than two melting peaks in the DSC curve obtained by measurement based on differential scanning calorimetry.

[0179] [4] The polypropylene resin foamed particles according to any one of [1] to [3] have a DSC ratio of 30.0% to 50.0%.

[0180] [5] Polypropylene resin foamed particles according to any one of [1] to [4], wherein at least one of the polypropylene random copolymer (A), the propylene homopolymer (B1) and the polypropylene block copolymer (B2) comprises recycled resin.

[0181] [6] Polypropylene resin foamed particles according to any one of [1] to [5], wherein the melt flow rate (MFR) of the polypropylene resin particles at 230°C and a load of 2160g is 7.0g / 10min to 30.0g / 10min.

[0182] [7] Polypropylene resin foamed particles according to any one of [1] to [6], wherein the polypropylene random copolymer (A) is selected from one or more of the group consisting of propylene / ethylene random copolymer, propylene / 1-butene random copolymer, propylene / ethylene / 1-butene random copolymer, propylene / vinyl chloride random copolymer and propylene / maleic anhydride random copolymer.

[0183] [8] Polypropylene resin foamed particles according to any one of [1] to [7], wherein the melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is... A The dosage ranges from 3.0g / 10 minutes to 30.0g / 10 minutes.

[0184] [9] Polypropylene resin foamed particles according to any one of [1] to [8], wherein the polypropylene random copolymer (A) comprises recycled polypropylene random copolymer.

[0185]

[10] According to the polypropylene resin foaming particles of [9], wherein the proportion of the recycled polypropylene random copolymer in 100% by weight of the polypropylene random copolymer (A) is 50% or more.

[0186]

[11] Polypropylene resin foamed particles according to any one of [1] to

[10] , wherein the melting point of the propylene homopolymer (B1) is above 155.0°C and below 165.0°C.

[0187]

[12] Polypropylene resin foamed particles according to any one of [1] to

[11] , wherein the melt flow rate of the propylene homopolymer (B1) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min.

[0188]

[13] Polypropylene resin foamed particles according to any one of [1] to

[12] , wherein, when the polypropylene resin particles contain the propylene homopolymer (B1), the ratio of the content of the polypropylene random copolymer (A) to the content of the propylene homopolymer (B1) in the polypropylene resin particles (the content of the polypropylene random copolymer (A) (parts by weight): the content of the propylene homopolymer (B1) (parts by weight)) is 90:10 to 50:50.

[0189]

[14] Polypropylene resin foamed particles according to any one of [1] to

[13] , wherein, in 100% by weight of the propylene homopolymer (B1), the total content of structural units derived from isoprene and structural units derived from conjugated diene is 20% by weight or less.

[0190]

[15] Polypropylene resin foamed particles according to any one of [1] to

[14] , wherein the polypropylene block copolymer (B2) is selected from one or more of the group consisting of propylene / ethylene block copolymer, propylene / 1-butene block copolymer, propylene / ethylene / 1-butene block copolymer, propylene / vinyl chloride block copolymer and propylene / maleic anhydride block copolymer.

[0191]

[16] Polypropylene resin foamed particles according to any one of [1] to

[15] , wherein the polypropylene block copolymer (B2) has a melting point of 155.0°C or higher and 165.0°C or lower.

[0192]

[17] Polypropylene resin foamed particles according to any one of [1] to

[16] , wherein the melt flow rate of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min.

[0193]

[18] Polypropylene resin foamed particles according to any one of [1] to

[17] , wherein, when the polypropylene resin particles contain the polypropylene block copolymer (B2), the ratio of the content of the polypropylene random copolymer (A) to the content of the polypropylene block copolymer (B2) in the polypropylene resin particles (the content of the polypropylene random copolymer (A) (parts by weight): the content of the polypropylene block copolymer (B2) (parts by weight)) is 90:10 to 40:60.

[0194]

[19] Polypropylene resin foamed particles according to any one of [1] to

[18] , wherein the polypropylene block copolymer (B2) comprises recycled polypropylene block copolymer.

[0195]

[20] Polypropylene resin foamed particles according to any one of [1] to

[19] , wherein the proportion of the recycled polypropylene block copolymer in 100% by weight of the polypropylene block copolymer (B2) is 50% or more.

[0196]

[21] Polypropylene resin foamed particles according to any one of [1] to

[20] , wherein, in 100% by weight of the polypropylene block copolymer (B2), the total content of structural units derived from isoprene and structural units derived from conjugated diene is 20% by weight or less.

[0197]

[22] Polypropylene resin foamed particles according to any one of [1] to

[21] , wherein the melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The dosage ranges from 6g / 10 minutes to 350g / 10 minutes.

[0198]

[23] Polypropylene resin foamed particles according to any one of [1] to

[22] , wherein the polypropylene resin particles contain carbon black.

[0199]

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

[23] have a foaming ratio of 10 to 50 times.

[0200]

[25] The polypropylene resin foamed particles according to any one of [1] to

[24] have an average bubble diameter of 80 μm to 500 μm.

[0201]

[26] A polypropylene resin foamed molded body, which is formed by molding polypropylene resin foamed particles as described in any one of [1] to

[25] .

[0202]

[27] The polypropylene resin foamed molded body according to

[26] has an internal weld rate of 60% or more.

[0203]

[28] A method for manufacturing polypropylene resin foamed granules, comprising the following steps:

[0204] The extrusion process involves melt-blending a mixed resin comprising a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and containing a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) to obtain polypropylene resin granules; and

[0205] The foaming process involves foaming the polypropylene resin particles obtained in the extrusion process.

[0206] The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C.

[0207] The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.0.

[0208]

[29] The method for manufacturing polypropylene resin foamed particles according to

[28] includes the following peroxide treatment step: treating propylene homopolymer (B1') and / or polypropylene block copolymer (B2') with peroxide to obtain the propylene homopolymer (B1) and / or the polypropylene block copolymer (B2).

[0209]

[30] In the method for manufacturing polypropylene resin foamed particles according to

[28] or

[29] , the amount of peroxide used in the peroxide treatment step is 0.01 to 1.00 parts by weight relative to a total of 100 parts by weight of the propylene homopolymer (B1') and the polypropylene block copolymer (B2').

[0210]

[31] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[30] , wherein the melt flow rate (MFR) of the polypropylene resin particles at 230°C and a load of 2160g is 7.0g / 10min to 30.0g / 10min.

[0211]

[32] The method for manufacturing polypropylene resin foamed granules according to any one of

[28] to

[31] , wherein, in the extrusion step, of the total 100 parts by weight of the polypropylene random copolymer (A), the propylene homopolymer (B1) and the polypropylene block copolymer (B2), the amount of the polypropylene random copolymer (A) is 70 parts by weight to 95 parts by weight, and the total amount of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is 5 parts by weight to 30 parts by weight.

[0212]

[33] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[32] , wherein the polypropylene resin foamed particles have more than two melting peaks in the DSC curve obtained by measurement based on differential scanning calorimetry.

[0213]

[34] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[33] , wherein the DSC ratio of the polypropylene resin foamed particles is 30.0% to 50.0%.

[0214]

[35] A method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[34] , wherein at least one of the polypropylene random copolymer (A), the propylene homopolymer (B1) and the polypropylene block copolymer (B2) comprises recycled resin.

[0215]

[36] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[35] , wherein the polypropylene random copolymer (A) is selected from one or more of the group consisting of propylene / ethylene random copolymer, propylene / 1-butene random copolymer, propylene / ethylene / 1-butene random copolymer, propylene / vinyl chloride random copolymer and propylene / maleic anhydride random copolymer.

[0216]

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

[28] to

[36] , wherein the melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is... A The dosage ranges from 3.0g / 10 minutes to 30.0g / 10 minutes.

[0217]

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

[28] to

[37] , wherein the polypropylene random copolymer (A) comprises a recycled polypropylene random copolymer.

[0218]

[39] In the method for manufacturing polypropylene resin foamed particles according to

[38] , the proportion of the recycled polypropylene random copolymer in 100% by weight of the polypropylene random copolymer (A) is 50% or more.

[0219]

[40] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[39] , wherein the melting point of the propylene homopolymer (B1) is above 155.0°C and below 165.0°C.

[0220]

[41] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[40] , wherein the melt flow rate of the propylene homopolymer (B1) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min.

[0221]

[42] The method for manufacturing polypropylene resin foamed granules according to any one of

[28] to

[41] , wherein, in the extrusion step, when the propylene homopolymer (B1) is used, the ratio of the amount of the polypropylene random copolymer (A) to the amount of the propylene homopolymer (B1) in the extrusion step (the amount of the polypropylene random copolymer (A) (parts by weight): the amount of the propylene homopolymer (B1) (parts by weight)) is 90:10 to 50:50.

[0222]

[43] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[42] , wherein the total content of structural units derived from isoprene and structural units derived from conjugated diene in 100% by weight of the propylene homopolymer (B1) is 20% by weight or less.

[0223]

[44] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[43] , wherein the polypropylene block copolymer (B2) is selected from one or more of the group consisting of propylene / ethylene block copolymer, propylene / 1-butene block copolymer, propylene / ethylene / 1-butene block copolymer, propylene / vinyl chloride block copolymer and propylene / maleic anhydride block copolymer.

[0224]

[45] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[44] , wherein the polypropylene block copolymer (B2) has a melting point of 155.0°C or higher and 165.0°C or lower.

[0225]

[46] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[45] , wherein the melt flow rate of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min.

[0226]

[47] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[46] , wherein, in the extrusion step, when the polypropylene block copolymer (B2) is used, the ratio of the amount of the polypropylene random copolymer (A) to the amount of the polypropylene block copolymer (B2) in the extrusion step (the amount of the polypropylene random copolymer (A) (parts by weight): the amount of the polypropylene block copolymer (B2) (parts by weight)) is 90:10 to 40:60.

[0227]

[48] ​​A method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[47] , wherein the polypropylene block copolymer (B2) comprises a recycled polypropylene block copolymer.

[0228]

[49] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[48] , wherein the proportion of the recycled polypropylene block copolymer in 100% by weight of the polypropylene block copolymer (B2) is 50% or more.

[0229]

[50] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[49] , wherein, in 100% by weight of the polypropylene block copolymer (B2), the total content of structural units derived from isoprene and structural units derived from conjugated diene is 20% by weight or less.

[0230]

[51] A method for manufacturing polypropylene resin foamed granules according to any one of

[28] to

[50] , wherein the melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g is... B The dosage ranges from 6g / 10 minutes to 350g / 10 minutes.

[0231]

[52] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[51] , wherein the mixed resin comprises carbon black.

[0232]

[53] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

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

[0233]

[54] The method for manufacturing polypropylene resin foamed particles according to any one of

[28] to

[53] , wherein the average bubble diameter of the polypropylene resin foamed particles is 80 μm to 500 μm.

[0234]

[55] A method for manufacturing a polypropylene resin foamed molded body, comprising a step of molding polypropylene resin foamed particles manufactured by the method for manufacturing polypropylene resin foamed particles as described in any one of

[28] to

[54] .

[0235]

[56] In the manufacturing method of polypropylene resin foamed molded body according to

[55] , the internal welding rate of the polypropylene resin foamed molded body is 60% or more.

[0236] Example

[0237] The following examples and comparative examples illustrate one embodiment of the present invention in more detail. The present invention is not limited to this embodiment.

[0238] [Material]

[0239] <Base Material Resin>

[0240] (Polypropylene random copolymer (A))

[0241] • A-1, A-2 [Non-recycled resin; manufactured by Prime Polymer, propylene / ethylene random copolymer]

[0242] • A-3 [Non-recycled resin; manufactured by Prime Polymer, propylene / ethylene / 1-butene random copolymer]

[0243] • A-4 [Recyclable material; a foamed molded body containing resin as a base material (A-3) is pulverized, and the pulverized material is melt-blended to obtain a granular resin composition. The resulting granular resin composition is used as a recycling material.]

[0244] (propylene homopolymer (B1))

[0245] • B1-1 [Non-recycled resin; manufactured by Prime Polymer, propylene homopolymer]

[0246] • B1-2, B1-3 [Non-recycled resin; resin obtained by peroxide treatment of B1-1] • B1-4 [Non-recycled resin; propylene homopolymer manufactured by Prime Polymer]

[0247] • B1-5 [Non-recycled resin; resin obtained by peroxide treatment of B1-4]

[0248] (Polypropylene block copolymer (B2))

[0249] • B2-1 [Non-recycled resin; manufactured by Prime Polymer, propylene / ethylene block copolymer]

[0250] • B2-2 [Non-recycled resin; resin obtained by peroxide treatment of B2-1]

[0251] • B2-3 [Non-recycled resin; manufactured by Prime Polymer, propylene / ethylene block copolymer]

[0252] • B2-4, B2-5 [Non-recycled resin; resin obtained by peroxide treatment of B2-3] • B2-6 [Non-recycled resin; propylene / ethylene block copolymer manufactured by Prime Polymer]

[0253] • B2-7, B2-8 [Non-recycled resin; resin obtained by peroxide treatment of B2-6] • B2-9 [Recycled material; a resin composition obtained by pulverizing automotive parts containing a propylene / ethylene block copolymer as a base resin, melting and mixing the pulverized material to obtain granular resin composition. The resulting granular resin composition is used as a recycling material.]

[0254] • B2-10~B2-12 [Recycled materials; materials obtained by peroxide treatment of B2-9]

[0255] • B2-13 [Recyclable material; A foamed sheet containing a propylene / ethylene block copolymer as a base resin is pulverized, and the pulverized material is melt-blended to obtain a granular resin composition. The resulting granular resin composition is used as a recycling material.]

[0256] • B2-14, B2-15 [Recycled materials; materials obtained by peroxide treatment of B2-13]

[0257] (peroxide)

[0258] • Peroxide [manufactured by Nippon Oil Company, PERBUTYL I]

[0259] • Peroxide [Nippon Oil Company, PERHEXA 25B-40]

[0260] (MFR adjustment (peroxide treatment process) for polypropylene resins and recycled materials)

[0261] B1-2 and B1-3 were obtained as follows: B1-1 and the peroxides shown in Table 1 were dry-mixed using a blender, and then melt-mixed using a twin-screw extruder (Toshiba Machine Co., Ltd., TEM26-SX) at a resin temperature of 220°C. The extruded filament was then water-cooled in a 2m long water tank and cut to obtain approximately 5mg / particle. Similarly, B2-2 is obtained by treating B2-1 with the peroxides shown in Table 1, B1-5 is obtained by treating B1-4 with the peroxides shown in Table 1, B2-4 and B2-5 are obtained by treating B2-3 with the peroxides shown in Table 1, B2-7 and B2-8 are obtained by treating B2-6 with the peroxides shown in Table 1, B2-10 to B2-12 are obtained by treating B2-9 with the peroxides shown in Table 1, and B2-14 and B2-15 are obtained by treating B2-13 with the peroxides shown in Table 1. It should be noted that the amount (parts by weight) of peroxides in Table 1 is the amount of peroxide used relative to 100 parts by weight of non-recycled resin or recycled material.

[0262] The composition of the non-recycled resin used, the composition of the recycled polypropylene resin contained in the recycled material, and the peroxide-based treatment are shown in Table 1. Furthermore, the melting point, MFR, number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) of the non-recycled resin and the recycled material used were determined by methods described later. Additionally, the carbon black content and ash content in the recycled material used were determined by methods described later. The results are shown in Table 2. In Table 2, resins marked "-" in the "Carbon Black (wt%)" item indicate that they do not contain carbon black (0 wt%). Similarly, in Table 2, recycled materials marked "-" in the "Ash (wt%)" item indicate that they do not contain ash (more than 0.00 wt% and less than 0.05 wt%). The content of recycled polypropylene resin contained in the recycled material in Table 2 is the amount obtained by removing the carbon black content and ash content listed in Table 2 from 100 wt% of the recycled material.

[0263] [Table 1]

[0264]

[0265] [Table 2]

[0266]

[0267] <Resin Particle Additive>

[0268] Talc [Made by Lin Huacheng Company, Talcan Pawder PK-S]

[0269] • Glycerin [Lion Corporation, purified glycerol D]

[0270] • Zinc borate [manufactured by Tomita Pharmaceutical Co., Ltd., zinc borate 2335]

[0271] • Carbon black masterbatch [a mixture obtained by mixing 40 parts by weight of carbon black with 60 parts by weight of polypropylene resin (MFR=7.5g / 10min at 230℃).

[0272] [Determination Method]

[0273] The evaluation methods implemented in the embodiments and comparative examples are described below.

[0274] <Determination of Melting Point of Polypropylene Resins and Recyclable Materials>

[0275] The melting point of polypropylene resin and recycled material was determined using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science). The specific determination method is as follows (1) to (3): (1) 5-6 mg of the test sample was heated from 40°C to 220°C at a heating rate of 10°C / min to melt it; (2) thereafter, it was cooled from 220°C to 40°C at a cooling rate of 10°C / min to crystallize it; (3) then, it was heated from 40°C to 220°C at a heating rate of 10°C / min. The temperature of the peak (melting peak) of the DSC curve obtained at the second heating (i.e., at (3)) was taken as the melting point of polypropylene resin and recycled material. It should be noted that, in the case where there are multiple peaks (melting peaks) in the DSC curve of polypropylene resin and recycled material obtained at the second heating using the above method, the temperature of the peak (melting peak) with the largest heat of fusion was taken as the melting point of polypropylene resin and recycled material.

[0276] <MFR Determination of Polypropylene Resins and Recycled Materials>

[0277] For polypropylene resins and recycled materials, the melt flow rate (MFR) was measured using the melt flow rate tester described in JIS K7210 under the following conditions: orifice size of 2.0959 ± 0.005 mm φ, orifice length of 8.000 ± 0.025 mm, load of 2160 g, and temperature of 230 ± 0.2 °C.

[0278] <GPC Determination of Polypropylene Resins and Recycled Materials>

[0279] The number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) of polypropylene resins and recycled materials were determined by gel permeation chromatography (GPC) in the form of polystyrene equivalents. The GPC determination conditions for each molecular weight of polypropylene resins and recycled materials are shown below.

[0280] 20 mg of the polypropylene resin and recycled material to be tested were completely dissolved in 20 mL of o-dichlorobenzene at 145 °C. The resulting solution was then hot-filtered using a sintered filter with a pore size of 1.0 μm, and the filtrate was used as the analytical sample.

[0281] Assay apparatus: HLC-8321GPC / HT high-temperature gel permeation chromatograph (manufactured by Tosoh Corporation); Analytical apparatus: Empower3 data processing software (manufactured by Waters Corporation, Japan).

[0282] Columns: 2 TSKgel GMH6-HT, 2 TSKgel GMH6-HTL (inner diameter 7.5mm × length 300mm, manufactured by Tosoh Corporation)

[0283] Mobile phase: o-dichlorobenzene (containing 0.025% BHT)

[0284] Column temperature: 140℃

[0285] Detector: Differential refractometer

[0286] Flow rate: 1.0 mL / min

[0287] Injection volume: 1.0 mL / min.

[0288] The recycled materials used in the examples and comparative examples do not contain resins other than the polypropylene resins listed in the "Composition of Recycled Polypropylene Resin in Recycled Materials" section. They only contain carbon black and ash, in addition to the polypropylene resins. Carbon black and ash do not affect the melting point, MFR, number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz). Therefore, the melting point, MFR, number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) of the recycled materials can be considered as the melting point, MFR, number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) of the polypropylene resins listed in the "Composition of Recycled Polypropylene Resin in Recycled Materials" section, respectively.

[0289] Quantitative Analysis of Carbon Black in Recycled Materials

[0290] The carbon black content in the recycled material was determined using a differential thermogravimetric analyzer (Hitachi High-TechScience, STA200RV). The specific operating steps are as follows (1) to (3): (1) Take 6 to 8 mg of the test sample into a Pt test container; (2) In a nitrogen atmosphere, raise the temperature of the sample to 600°C at 10°C / min, then cool it to 400°C at 10°C / min, and then change to a simulated air atmosphere (a mixture of oxygen and nitrogen = 21% and 79%), and raise the temperature to 800°C at 10°C / min; (3) In the TG weight reduction curve obtained in the above (2) process, calculate the weight ratio (weight%) of carbon black based on the difference between the weight reduction rate (weight%) at 400°C and the weight reduction rate (weight%) at 800°C in the process of raising the temperature from 400°C to 800°C.

[0291] Quantitative Analysis of Ash Content in Recycled Materials

[0292] The ash content in the recycled material is determined by the weight of the recycled material and the weight of the residue after the recycled material is burned. The specific operating steps are as follows (1) to (4): (1) Heat the recycled material at 150°C for 1 hour to completely remove the moisture from the recycled material; (2) Put 1g to 2g of the recycled material into a crucible, keep it at 300°C for more than 30 minutes in an electric furnace, and then burn it at 750°C for more than 1 hour; (3) Take the crucible out of the electric furnace and cool it in a dryer at 23°C for 1 hour; (4) Calculate the ash content in the recycled material according to the following formula.

[0293] W1: Crucible weight (g)

[0294] W2: Weight of the crucible before combustion + weight of recycled material (g)

[0295] W3: Weight of the crucible after combustion + recycled material (g)

[0296] Ash content (weight %) in recycled materials = {(W3-W1)} 100} / (W2-W1)

[0297] <MFR Determination of Polypropylene Resin Particles>

[0298] The method for determining the MFR of polypropylene resin particles is the same as that described in the section on "Determination of MFR of Polypropylene Resins and Recycled Materials" above, except that the sample is polypropylene resin particles. Therefore, that description is adopted here and will not be repeated.

[0299] <Determination of DSC ratio of polypropylene resin foamed particles>

[0300] The DSC ratio was determined using a differential scanning calorimeter (Hitachi High-Tech Science, DSC7020). Specifically, the melting peak area on the low-temperature side of the DSC curve obtained when 5-6 mg of polypropylene resin foam particles were heated from 40°C to 220°C at a heating rate of 10°C / min was denoted as Q. l Set the melting peak area on the high-temperature side as Q. h The DSC ratio can be obtained using the following formula:

[0301] DSC ratio (%) = Q h / (Q) l +Q h )×100.

[0302] It should be noted that, strictly speaking, the procedure is as follows: Draw a line segment connecting the maximum point between the melting peaks on the low-temperature side and the melting peaks on the high-temperature side, and the point on the curve where the temperature reaches 100°C. LThe melting peaks and segments on the low-temperature side will be... L Let the area of ​​the enclosed region be Q. l Additionally, a line segment is drawn from the maximum point between the melting peak on the low-temperature side and the melting peak on the high-temperature side to the melting termination baseline, and is designated as line segment. H The melting peaks and segments on the high-temperature side will be... H Let the area of ​​the enclosed region be Q. h Additionally, the temperatures of the melting peaks on both the high-temperature and low-temperature sides are read.

[0303] <Determination of the foaming ratio of polypropylene resin foamed granules>

[0304] The method for determining the foaming ratio of foamed granules is as follows (1) to (4): (1) Take more than 3g and less than 10g of polypropylene resin foamed granules, dry them at 60℃ for 6 hours, and then condition them in a room at 23℃ and 50% humidity, and measure the weight w1 (g); (2) Immerse the foamed granules used for weight measurement into a graduated cylinder containing ethanol, and measure the volume v (cm³) by the rise of the water level in the graduated cylinder (water immersion method). 3 (3) Calculate the true specific gravity ρ of the polypropylene resin foam particles. b =w1 / v; (4) The density ρ of the polypropylene resin particles before foaming r Divide by the true specific gravity ρ of the polypropylene resin foam particles b The obtained value is used as the foaming ratio of the polypropylene resin foamed particles. It should be noted that in the examples and comparative examples shown below, the density ρ of the polypropylene resin particles (polypropylene resin particles) before foaming is... r Both are 0.9 g / cm³ 3 .

[0305] <Average bubble diameter of polypropylene resin foam particles>

[0306] The method for determining the average bubble diameter of polypropylene resin foamed particles is as follows (1) to (5): (1) While taking care not to damage the bubble membrane (cell membrane) of the foamed particle, use a razor (FEATHER, Hi-STAINLESS double blade) to cut the foamed particle through the center; (2) Use a microscope (HIROX, RH-2000) to observe the cut surface of the obtained foamed particle and obtain an image of the observed surface; (3) On the obtained image, draw a line segment with a length of 2000 μm in any part other than the surface part of the foamed particle; (4) Measure the number of bubbles n passing through the line segment and calculate the bubble diameter according to the formula (bubble diameter = 2000 / n (μm)); (5) Perform the same operation on 10 foamed particles and take the arithmetic mean of the calculated bubble diameters as the average bubble diameter of the polypropylene resin foamed particles.

[0307] Internal weldability of polypropylene resin foamed molded articles

[0308] The internal weldability of polypropylene resin foamed molded bodies is evaluated by determining the internal weld ratio of the molded body. The method for determining the internal weld ratio of polypropylene resin foamed molded bodies is as follows (1) to (4): (1) relative to any face of the foamed molded body, a 5 mm long cut is made from the face with a knife in a direction perpendicular to the face; (2) then, the foamed molded body is broken by hand along the cut; (3) by visually observing the area in the fracture surface other than the cut part, the number of all foamed particles in the area and the number of foamed particles that break in the area except for the particle interface (i.e., foamed particles that break themselves); (4) the internal weld ratio is calculated based on the following formula.

[0309] Internal weld rate (%) = (Number of foamed particles that break at locations other than the particle interface in the region / Total number of foamed particles in the region) × 100.

[0310] The values ​​recorded in the "Internal Weldability" column of Tables 3 to 5 are the internal weldability (%) values.

[0311] <Surface Aesthetics of Polypropylene Resin Foamed Molded Articles>

[0312] The surface aesthetics of the polypropylene resin foamed molded body (350mm x 450mm) were judged by visually inspecting the surface according to the following criteria. For particle gaps (the gaps between polypropylene resin foam particles), one of the evaluation indicators of surface aesthetics, the number of gaps present in a 50mm square area at the center of the molded body was visually counted.

[0313] 4 (Beautiful surface appearance): No wrinkles, and the gap between particles is 0~1.

[0314] 3 (Good surface appearance): No wrinkles, and 2-3 gaps between particles.

[0315] 2 (Surface appearance is acceptable): either wrinkles are observed, or there are 4 to 5 gaps between particles.

[0316] 1 (Surface appearance is not up to standard): either wrinkles are observed, or there are more than 6 gaps between particles.

[0317] Molding cycle of polypropylene resin foamed articles

[0318] The molding cycle in the manufacturing method of polypropylene resin foamed molded body is defined as the molding period from the start of molding to the demolding of the molded body. The moment when polypropylene resin foamed particles are first filled into the mold is defined as the start of molding. A mold capable of forming a molding space of 370mm in length × 320mm in width × 50mm in thickness is used. Next, with the drain valve of the molding machine's drain line open, 0.10MPa (gauge pressure) steam is introduced into the mold for 3 seconds, thereby heating the foamed particles and expelling air from the mold (preheating process). Next, steam is allowed to flow from the fixed mold side to the moving mold side for 6 seconds (one-sided heating process), and then steam is allowed to flow from the moving mold side to the fixed mold side for 3 seconds (reverse heating process), heating while expelling air. Next, with the drain valve of the molding machine's drain line closed, 0.30MPa (gauge pressure) steam is introduced into the mold for 9 seconds, thereby heating the foamed particles (double-sided heating process), causing them to fuse and form a foamed molded body. Next, the foamed molded body inside the mold is water-cooled. Then, using a surface pressure gauge installed on the mold surface, the mold is opened when the surface pressure drops to 0.01 MPa (gauge pressure), and the molding process ends when demolding is complete. The evaluation criteria for molding cycle (productivity) are as follows.

[0319] 3 (Excellent): Molding cycle is within 180 seconds.

[0320] 2 (Poor): Molding cycle is greater than 180 seconds but less than 210 seconds.

[0321] 1 (Very poor): Molding cycle greater than 210 seconds.

[0322] The following describes the manufacturing methods of the polypropylene resin particles, polypropylene resin foamed particles, and polypropylene resin foamed molded articles in the examples and comparative examples.

[0323] (Example 1)

[0324] [Preparation of Polypropylene Resin Particles]

[0325] The mixture was measured with 75 parts by weight of A-3 (a random copolymer of polypropylene (A)), 25 parts by weight of B1-2 (a homopolymer of propylene (B1)), 0.2 parts by weight of talc, and 0.2 parts by weight of glycerol. The mixture was then dry-blended using a blender to obtain a mixed resin. The resulting mixed resin was melt-blended using a twin-screw extruder (Toshiba Machine Co., Ltd., TEM26-SX) at a resin temperature of 220°C. The extruded filament was then water-cooled in a 2-m long water tank and cut to produce polypropylene resin granules (1.2 mg / granule) (extrusion process).

[0326] [Production of polypropylene resin foamed granules (foaming process)]

[0327] In a 10L pressure vessel, 100 parts by weight (2.4 kg) of polypropylene resin granules obtained as described above, 200 parts by weight of water, 0.3 parts by weight of kaolin (BASF, ASP170) as a water-insoluble inorganic compound, and 0.06 parts by weight of sodium dodecylbenzenesulfonate (Kao Corporation, NEOPELEX G-15) as a surfactant were added. Then, under stirring, 5 parts by weight of carbon dioxide as a foaming agent were added (dispersion step). The contents of the pressure vessel were heated to a foaming temperature of 160°C (heating step), and held for 10 minutes. Carbon dioxide was then added to increase the pressure inside the pressure vessel to a foaming pressure of 2.80 MPa (gauge pressure) (pressurization step). After holding at the above foaming temperature and pressure for 20 minutes (holding step), the valve at the bottom of the pressure vessel was opened, and the foamed granules were released to atmospheric pressure through a 3.6 mm diameter orifice, resulting in polypropylene resin foamed granules with a foaming ratio of 18 times (release step). At this point, carbon dioxide is injected during release to maintain pressure without reducing the pressure inside the container. It should be noted that the polypropylene resin foam particles exhibit two peaks in the DSC curve: a high-temperature melting peak at 169°C and a low-temperature melting peak at 150°C, with a DSC ratio of 30.1% and an average bubble diameter of 280 μm.

[0328] [Preparation of polypropylene resin foamed molded articles]

[0329] The obtained polypropylene resin foam granules were dried at 80°C. The dried polypropylene resin foam granules were then placed in a pressure-resistant container and impregnated with pressurized air to adjust the internal pressure of the polypropylene resin foam granules to 0.20 MPa (absolute pressure). Next, the pressurized polypropylene resin foam granules were filled into a mold measuring 370 mm (length) × 320 mm (width) × 50 mm (thickness). Then, the mold cavity was heated using steam at 0.30 MPa (gauge pressure) (molding pressure) to fuse the foam granules together. After water cooling the mold and the surface of the molded body, the molded body was demolded to obtain a polypropylene resin foam molded body. The obtained foamed molded body was allowed to stand at 23°C for 2 hours, followed by curing at 75°C for 16 hours.

[0330] (Examples 2-20, Comparative Examples 1-8)

[0331] In the [Preparation of Polypropylene Resin Particles], the formulation of the base resin was changed as shown in Tables 3 to 5. Otherwise, polypropylene resin particles were prepared by the same operation as in Example 1. For example, in Example 12, polypropylene resin particles were prepared by the same operation as in Example 1, except that A-3, as a polypropylene random copolymer (A), was measured to be 75 parts by weight, B2-12, as a propylene homopolymer (B1), was measured to be 25 parts by weight, talc was measured to be 0.2 parts by weight, glycerol was measured to be 0.2 parts by weight, and carbon black masterbatch was measured to be 7.5 parts by weight. The mixture was then dry-mixed using a blender to obtain a mixed resin. For example, in Example 13, polypropylene resin particles were prepared using the same procedure as in Example 1, except that A-3, as a polypropylene random copolymer (A), was measured to be 75 parts by weight, B2-12, as a propylene homopolymer (B1), was measured to be 25 parts by weight, zinc borate was measured to be 0.05 parts by weight, and carbon black masterbatch was measured to be 7.5 parts by weight. The mixture was then dry-mixed using a blender to obtain a mixed resin. Next, in the [Preparation of Polypropylene Resin Foamed Particles], the foaming conditions were changed as shown in Tables 3 to 5. Otherwise, polypropylene resin foamed particles and polypropylene resin foamed molded articles were prepared using the same procedure as in Example 1. The formulation conditions of the base resin, the foaming conditions, and the evaluation results of the obtained polypropylene resin foamed particles and polypropylene resin foamed molded articles are shown in Tables 3 to 5.

[0332] [Table 3]

[0333]

[0334] [Table 4]

[0335]

[0336] [Table 5]

[0337]

[0338] Regarding Examples 1 to 20, it can be seen that: if it contains a polypropylene random copolymer (A) and contains a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2), MFR B / MFR A When polypropylene resin particles with a particle size of 2.0 to 30.0 are used, even when recycled polypropylene random copolymers (A), propylene homopolymers (B1), and / or polypropylene block copolymers (B2) are used as in Examples 8 to 20, foamed molded articles can be obtained with a short molding cycle and foamed molded articles with excellent surface aesthetics.

[0339] Comparative Examples 1 to 8 show that when either configuration A or configuration B is not satisfied, the molding cycle is poor and there is room for improvement in surface aesthetics.

[0340] Industrial availability

[0341] According to one embodiment of the present invention, novel polypropylene resin granules are provided that can produce polypropylene resin foamed molded articles with a short molding cycle. Therefore, one embodiment of the present invention can be used for various applications such as automotive interior parts, core materials for automotive bumpers, as well as thermal insulation materials, cushioning packaging materials, and turnover boxes.

Claims

1. A polypropylene resin foamed granule, which is formed by foaming polypropylene resin granules. The polypropylene resin particles comprise a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and also comprise a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2). The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C. The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.

0.

2. The polypropylene resin foamed granules according to claim 1, wherein, In the polypropylene resin particles, in a total of 100 parts by weight of the polypropylene random copolymer (A), the propylene homopolymer (B1), and the polypropylene block copolymer (B2), the content of the polypropylene random copolymer (A) is 70 parts by weight to 95 parts by weight, and the total content of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is 5 parts by weight to 30 parts by weight.

3. The polypropylene resin foamed particles according to claim 1, wherein the DSC curve obtained by differential scanning calorimetry has more than two melting peaks.

4. The polypropylene resin foamed granules according to claim 1 have a DSC ratio of 30.0% to 50.0%.

5. The polypropylene resin foamed granules according to claim 1, wherein, At least one of the polypropylene random copolymer (A), the propylene homopolymer (B1), and the polypropylene block copolymer (B2) comprises recycled resin.

6. The polypropylene resin foamed granules according to claim 1, wherein, The melt flow rate (MFR) of the polypropylene resin particles at 230°C and a load of 2160g is 7.0g / 10min to 30.0g / 10min.

7. The polypropylene resin foamed granules according to claim 1, wherein, The melt flow rate of the propylene homopolymer (B1) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min. The melt flow rate of the polypropylene block copolymer (B2) at 230°C and a load of 2160g is 6g / 10min to 350g / 10min.

8. The polypropylene resin foamed granules according to claim 1, wherein, The polypropylene resin particles contain carbon black.

9. A polypropylene resin foamed molded body, which is formed by molding polypropylene resin foamed particles according to any one of claims 1 to 8.

10. A method for manufacturing polypropylene resin foamed granules, comprising the following steps: The extrusion process involves melt-blending a mixed resin comprising a polypropylene random copolymer (A) with a melting point above 140.0°C and below 155.0°C, and containing a propylene homopolymer (B1) and / or a polypropylene block copolymer (B2) to obtain polypropylene resin granules; and The foaming process involves foaming the polypropylene resin particles obtained in the extrusion process. The melting point of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) is above 155.0°C and below 165.0°C. The melt flow rate (MFR) of the mixture of the propylene homopolymer (B1) and the polypropylene block copolymer (B2) at 230°C and a load of 2160g. B The melt flow rate (MFR) of the polypropylene random copolymer (A) at 230°C and a load of 2160g is relative to the melt flow rate (MFR) of the copolymer. A The ratio of MFR B / MFR A The value ranges from 2.0 to 30.

0.

11. The method for manufacturing polypropylene resin foamed granules according to claim 10, comprising the following peroxide treatment step: treating propylene homopolymer (B1') and / or polypropylene block copolymer (B2') with peroxide to obtain said propylene homopolymer (B1) and / or said polypropylene block copolymer (B2).

12. The method for manufacturing polypropylene resin foamed granules according to claim 10 or 11, wherein, The melt flow rate (MFR) of the polypropylene resin particles at 230°C and a load of 2160g is 7.0g / 10min to 30.0g / 10min.

13. The method for manufacturing polypropylene resin foamed granules according to claim 11, wherein, In the peroxide treatment process, the amount of peroxide used is 0.01 to 1.00 parts by weight relative to a total of 100 parts by weight of the propylene homopolymer (B1') and the polypropylene block copolymer (B2').

Images