JP-7857132-B2 - Expanded polystyrene resin particles, pre-expanded particles thereof, and foamed molded articles

Inventors

• 鈴木 基理人
• 小林 剛
• 落越 忍
• 木口 太郎

Assignees

• 株式会社カネカ

Dates

Publication Date

20260512

Application Date

20220328

Claims (10)

1. These are foamed polystyrene resin particles containing a resin composition comprising a base resin, a brominated flame retardant, and graphite. The base resin includes a styrene copolymer resin containing styrene monomer units as constituent units. The resin composition has a glass transition temperature of 105°C or higher and 125°C or lower. The styrene monomer content is less than 0.03% by weight. The styrene copolymer resin comprises styrene monomer units and acrylic monomer units as constituent units. Expandable polystyrene resin particles in the resin composition wherein the content of styrene resin, which consists solely of styrene monomer units as constituent units, is less than 20 parts by weight per 100 parts by weight of the resin composition .
2. The foamed polystyrene resin particle according to claim 1 , wherein the ratio (L/D) of the length in the long axis direction (L) to the length in the short axis direction (D) of the particle shape is 0.8 or more.
3. Expandable polystyrene resin particles according to claim 1 or claim 2 , wherein the weight-average molecular weight is 180,000 or more and 250,000 or less.
4. The foamed polystyrene resin particles according to any one of claims 1 to 3 , wherein the content of the brominated flame retardant is 2 parts by weight or more and 4 parts by weight or less per 100 parts by weight of the base resin.
5. The foamed polystyrene resin particles according to any one of claims 1 to 4 , wherein the graphite content is 2 parts by weight or more and 8 parts by weight or less per 100 parts by weight of the base resin.
6. The foamed polystyrene resin particles according to any one of claims 1 to 5 , wherein the foamed polystyrene resin particles are pre-foamed 50 times, and the average chord length of the bubbles in the molded foamed product is 20 μm or more and 150 μm or less.
7. The foamed polystyrene resin particles according to any one of claims 1 to 6 , wherein when foamed polystyrene resin particles are pre-foamed 50 times and molded to form a foamed molded article, the following conditions (a), (b), and (c) are met. (a) The dimensional change rate after heating at 95°C for 168 hours is less than 2%. (b) The thermal conductivity is 0.033 W/mK or less. (c) The minimum oxygen index is 26 or higher.
8. Pre-foamed particles obtained by pre-foaming the foamable polystyrene resin particles described in any one of claims 1 to 7 .
9. A foamed molded body obtained by molding the pre-foamed particles described in claim 8 .
10. An insulating material for a hot water storage tank comprising the foamed molded body described in claim 9 .

Description

This invention relates to foamed polystyrene resin particles, pre-foamed particles, and foamed molded articles. Polystyrene foam molded materials are sometimes used as insulation materials for hot water storage tanks, roof insulation, and pipe insulation due to their lightweight nature and ease of assembly. These applications require high thermal insulation performance and dimensional stability during long-term use in high-temperature environments; therefore, polystyrene foam molded materials with enhanced heat resistance through copolymerization are used. Furthermore, flame retardancy is required to prevent fires, and low emissions of organic volatile components (VOCs) such as styrene monomers are required for environmental reasons. For example, Patent Document 1 provides foamed polystyrene resin particles obtained by kneading a styrene-methacrylic acid copolymer resin with a flame retardant and a foaming agent in an extruder and then granulating it, thereby producing a foamed molded article with excellent heat resistance and flame retardancy. Patent Document 2 provides foamed polystyrene resin particles obtained using a styrene-alphamethylstyrene-acrylonitrile copolymer, which yields a foamed molded article with dimensional stability at 95°C and flame retardancy, and which have a low styrene monomer content. These foamed molded materials possess excellent heat resistance, but in recent years, the demand for thermal insulation performance in heat-insulating materials has increased, necessitating further improvements in thermal insulation performance. On the other hand, as shown in Patent Document 3, it is known that foamed polystyrene resin particles with improved thermal insulation can be obtained by introducing carbon-based radiation suppressants such as graphite. While introducing carbon-based radiation suppressants improves thermal insulation, the heat resistance of the base resin is insufficient. Therefore, foamed polystyrene resin particles that achieve both high-temperature dimensional stability and excellent thermal insulation have not existed until now. Japanese Patent Publication No. 2011-93952Japanese Patent Publication No. 2015-151486Japanese Patent Publication No. 2020-33481 Embodiments of the present invention will be described in detail below. However, the present invention is not limited thereto, and various modifications are possible within the scope described. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included within the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or greater (including A and greater than A), B or less (including B and less than B)." The foamed polystyrene resin particles of the present invention are foamed polystyrene resin particles comprising a resin composition containing a base resin, a brominated flame retardant, and graphite. The base resin contains a styrene copolymer resin containing styrene monomer units as constituent units, the glass transition temperature of the resin composition is 105°C to 125°C, and it contains less than 0.03% by weight of styrene monomers. Because the foamed polystyrene resin particles of the present invention have the above configuration, they provide a novel foamed molded article with excellent dimensional stability at 95°C, high heat insulation and flame retardancy, and low VOC content. The base resin constituting the foamed polystyrene resin particles of the present invention mainly consists of styrene monomers and includes a styrene copolymer resin containing styrene monomer units as constituent units. In this specification, "styrene monomer unit" refers to a constituent unit derived from a styrene monomer. Examples of styrene monomers include styrene (sometimes referred to as styrene monomer), α-methylstyrene, para-methylstyrene, t-butylstyrene, and chlorostyrene. The resin composition contained in the foamed polystyrene resin particles of the present invention has a glass transition temperature of 105°C to 125°C. To achieve both foam moldability and dimensional stability as a heat-insulating material, a glass transition temperature of 105°C to 120°C is preferred, and more preferably 108°C to 118°C. If the glass transition temperature of the resin composition is below 105°C, sufficient dimensional stability cannot be obtained when used at high temperatures, and if it exceeds 125°C, the heat resistance becomes too high, making it difficult to obtain the required foaming ratio during pre-foaming. Furthermore, the foamed polystyrene resin particles of the present invention contain less than 0.03% by weight of styrene monomers. The contained monomer components tend to volatilize from the foamed molded article obtained by foaming the foamed polystyrene resin particles. Therefore, by keeping the amount of styrene monomers remaining in the foamed polystyrene resi