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JP-2026075888-A - Injection foam molded article and method for manufacturing the injection foam molded article

JP2026075888AJP 2026075888 AJP2026075888 AJP 2026075888AJP-2026075888-A

Abstract

[Problem] To provide an injection foam molded article made of a polypropylene composition that has excellent dimensional accuracy, good foaming properties, and a good surface finish, and a method for manufacturing the injection foam molded article. [Solution] An injection-molded foamed article obtained using composition (X), which comprises a propylene-based resin composition (A) containing 100% by mass or less of polypropylene (A1), 0% by mass or more and 30% by mass or less of a specific polymer (A2), and 0% by mass or more and 30% by mass or less of an inorganic filler (A3) (where the total of (A1), (A2), and (A3) is 100% by mass), and a biomass material (B), wherein the MFR of the propylene-based resin composition (A) is 40 to 150 g/10 min, and the content of the propylene-based resin composition (A) is 65 to 99.5 parts by mass and the content of the biomass material (B) is 35 to 0.5 parts by mass per 100 parts by mass of the total of (A) and (B). [Selection Diagram] None

Inventors

  • 瀬田 蒼
  • 河村 達次

Assignees

  • 株式会社プライムポリマー

Dates

Publication Date
20260511
Application Date
20241023

Claims (5)

  1. Polypropylene (A1) 100% by mass or less, At least one polymer (A2) selected from the group consisting of ethylene polymers (A2-1) and vinyl aromatic block copolymer elastomers (A2-2) having a density of 850 to 970 kg/ m³ , in an amount of 0% to 30% by mass, and an inorganic filler (A3) in an amount of 0% to 30% by mass. A propylene-based resin composition (A) containing (wherein the total of polypropylene (A1), polymer (A2), and inorganic filler (A3) is 100% by mass), It includes biomass material (B), According to ASTM D1238, the MFR of the propylene resin composition (A) measured at 230°C with a 2.16 kg load was 40 to 150 g/10 min. In a total of 100 parts by mass of the propylene-based resin composition (A) and the biomass material (B), the content of the propylene-based resin composition (A) is 65 to 99.5 parts by mass, and the content of the biomass material (B) is 35 to 0.5 parts by mass. An injection-molded foam article obtained using composition (X).
  2. The injection-molded foamed article according to claim 1, characterized in that, in the composition (X), the total amount of polypropylene (A1) and polymer (A2) is 55 parts by mass or more and 99.5 parts by mass or less, with respect to 100 parts by mass of the total of polypropylene (A1), polymer (A2), and biomass material (B).
  3. The injection-molded foamed article according to claim 1, characterized in that the melting point of the propylene-based resin composition (A), as measured by DSC, is in the range of 150 to 170°C.
  4. The injection-molded foamed article according to any one of claims 1 to 3, characterized in that the biomass material (B) is at least one plant-derived filler selected from the group consisting of wood, pulp, bamboo, rice husks, rice (starch), jute, and cotton.
  5. Polypropylene (A1) 100% by mass or less, At least one polymer (A2) selected from the group consisting of ethylene polymers (A2-1) and vinyl aromatic block copolymer elastomers (A2-2) having a density of 850 to 970 kg/ m³ , in an amount of 0% to 30% by mass, and an inorganic filler (A3) in an amount of 0% to 30% by mass. A propylene-based resin composition (A) containing (wherein the total of polypropylene (A1), polymer (A2), and inorganic filler (A3) is 100% by mass), It includes biomass material (B), According to ASTM D1238, the MFR of the propylene resin composition (A) measured at 230°C with a 2.16 kg load was 40 to 150 g/10 min. In a total of 100 parts by mass of the propylene-based resin composition (A) and the biomass material (B), the content of the propylene-based resin composition (A) is 65 to 99.5 parts by mass, and the content of the biomass material (B) is 35 to 0.5 parts by mass. A method for producing an injection-molded foamed article, characterized by injecting foam a composition (X).

Description

This invention relates to an injection-molded foamed article and a method for producing the injection-molded foamed article. Polypropylene resin is widely used as a resin material in various industrial fields, including daily necessities, housing, home appliances, and automotive parts, due to its excellent moldability, balance of physical properties, recyclability, and cost-effectiveness. In recent years, there has been a strong demand for lighter automotive parts to improve fuel efficiency and reduce greenhouse gas emissions, and the use of foamed molded materials has increased, particularly in interior parts. Therefore, there is a need for injection-molded foamed materials with higher foaming ratios and superior mechanical properties. Injection foam molding is a molding method that involves an injection process in which molten resin is injected into the cavity of a mold, followed by a foaming process. Core-back injection foam molding, which involves slightly retracting the movable side of the mold after the injection process (core-back) to open the cavity and promote foaming, is one injection foam molding method that increases the foaming ratio. Here, it is known that increasing the fluidity (melt flow rate: MFR) of the resin is useful for improving the thin-wall injection moldability of molten resin, and that increasing the viscosity of the resin, in other words, decreasing its fluidity, is useful for improving foaming properties (Patent Document 1). In other words, when manufacturing relatively large foamed molded parts such as automotive interior and exterior components, if the cavity thickness is set to a high level beforehand, the amount of resin used will increase, making it impossible to meet the requirement for weight reduction. Therefore, it is desirable to fill the cavity with molten resin, and a high MFR (Metal Fluid Ratio) of the resin during filling is desirable. On the other hand, in order to obtain a stable, high-foam material to ensure sufficient rigidity of the foamed molded product, it is necessary to obtain a stable, high-foam material, and a low fluidity of the resin is desirable. Japanese Patent Application Publication No. 11-179752 The present invention will be described in detail below. <Composition (X)> Composition (X) comprises a propylene resin composition (A) and a biomass material (B). <Propylene resin composition (A)> The propylene resin composition (A) (hereinafter also referred to as "composition (A)") comprises 100% by mass or less of polypropylene (A1), 0% by mass or more and 30% by mass or less of polymer (A2), and 0% by mass or more and 30% by mass or less of inorganic filler (A3) (provided that the total of polypropylene (A1), polymer (A2), and inorganic filler (A3) is 100% by mass). The MFR of composition (A), measured at 230°C and a 2.16 kg load in accordance with ASTM D1238, is 40 to 150 g/10 min. According to ASTM D1238, the MFR of composition (A), measured at 230°C and a 2.16 kg load, is 40 to 150 g/10 min, preferably 40 to 130 g/10 min, more preferably 42 to 110 g/10 min, and even more preferably 45 to 100 g/10 min. A MFR within this range of composition (A) is preferable because it prevents defects such as short shots in the injection-molded foam, results in excellent dimensional accuracy, good foaming (stable cell moldability and no foaming defects), and a good surface finish. The MFR value of composition (A) may be a calculated value obtained by the following formula. In the above formula, [X], [Y], and [Z] each independently represent the content (mass%) of the components used in composition (A), and [x], [y], and [z] each independently represent the MFR (g/10 min) of the components used in composition (A), obtained by measurement at 230°C and a 2.16 kg load in accordance with ASTM D1238. If composition (A) contains an inorganic filler (A3), a mixture of the inorganic filler (A3) and components such as polypropylene (A1) may be prepared, and the MFR value obtained from the measurement may be used. Composition (A) may be used alone or in combination of two or more components. When using a combination of two or more components, it is preferable that the MFR (Measuring Frequency Rating) of all components, measured at 230°C and a 2.16 kg load according to ASTM D1238, be within the range of 40 to 150 g/10 min. The melting point of composition (A), as measured by DSC, is preferably 150 to 170°C, more preferably 153 to 168°C, and even more preferably 156 to 166°C. It is preferable that composition (A) does not have a melting point measured by DSC below 150°C. It is preferable that the melting point of composition (A) is within the above range because it results in good moldability of the composition. The method for measuring the melting point will be described in the examples below. <Polypropylene (A1)> Polypropylene (A1) is unmodified polypropylene and may be a homopolymer of propylene or a copolymer of propylene and other monomers. Particularly preferred are a homo