JP-2026075965-A - Alkali-resistant polyester resin composition and resin molded article

Abstract

[Problem] To provide a polyester resin composition with excellent alkali resistance and mold release properties. [Solution] An alkali-resistant polyester resin composition comprising a polybutylene terephthalate resin (A), a recycled polyethylene terephthalate resin (B), a transesterification inhibitor (C), a silicone compound (D), an elastomer (E), and an inorganic filler (F), wherein the amount of terminal hydroxyl groups of the polybutylene terephthalate resin (A) is 30 to 70 mmol/kg relative to the total amount of the polybutylene terephthalate resin (A) and the recycled polyethylene terephthalate resin (B), and the amount of the elastomer (E) is 8 to 17% by mass relative to the total amount of the alkali-resistant polyester resin composition. [Selection Diagram] None

Inventors

• 斎藤 樹

Assignees

• ポリプラスチックス株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (6)

1. An alkali-resistant polyester resin composition comprising polybutylene terephthalate resin (A), recycled polyethylene terephthalate resin (B), transesterification inhibitor (C), silicone compound (D), elastomer (E), and inorganic filler (F), With respect to the total amount of the polybutylene terephthalate resin (A) and the recycled polyethylene terephthalate resin (B), the amount of terminal hydroxyl groups of the polybutylene terephthalate resin (A) is 30 to 70 mmol/kg. An alkali-resistant polyester resin composition in which the amount of the elastomer (E) is 8 to 17% by mass relative to the total amount of the alkali-resistant polyester resin composition.
2. The alkali-resistant polyester resin composition according to claim 1, wherein the sum of the terminal hydroxyl groups of the polybutylene terephthalate resin (A) and the recycled polyethylene terephthalate resin (B) is 60 to 90 mmol/kg, relative to the total amount of the polybutylene terephthalate resin (A) and the recycled polyethylene terephthalate resin (B).
3. The alkali-resistant polyester resin composition according to claim 1 or 2, wherein the transesterification inhibitor (C) comprises a phosphorus-based compound containing a sodium atom or a calcium atom.
4. The alkali-resistant polyester resin composition according to claim 1 or 2, further comprising a crystal nucleating agent (G).
5. The alkali-resistant polyester resin composition according to claim 1 or 2, wherein the amount of the inorganic filler (F) is 5 to 50% by mass relative to the total amount of the alkali-resistant polyester resin composition.
6. A resin molded article obtained using the alkali-resistant polyester resin composition described in claim 1 or 2.

Description

Embodiments of the present invention relate to alkali-resistant polyester resin compositions and resin molded articles. In recent years, highly recyclable resins have been in demand for the realization of a sustainable society. Resins such as polyethylene, polystyrene, polypropylene, and polyethylene terephthalate, used in packaging and containers, have a high polymer ratio in packaging containers. Therefore, waste collected from the market is crushed, washed, and repelled for use as recycled products. On the other hand, polybutylene terephthalate resin (hereinafter also referred to as PBT resin) is often used with various additives such as inorganic fillers, impact absorbing agents, and flame retardants added according to market requirements. Because the polymer ratio of polybutylene terephthalate resin itself is low, it is difficult to obtain stable quality through the aforementioned processes. Therefore, methods such as recovering energy through thermal recycling or decomposing the polymer through chemical recycling, and then polymerizing the recovered monomers or using them as raw materials for other substances, are being considered. However, these methods consume a lot of energy and have not been widely adopted. Therefore, studies are underway to increase the proportion of recycled plastics used in polybutylene terephthalate resin compositions by blending readily available recycled resins, such as recycled polyethylene terephthalate resin (hereinafter also referred to as recycled PET resin) and recycled polystyrene resin, with polybutylene terephthalate resin. The compounding of polybutylene terephthalate resin with polyethylene terephthalate resin (hereinafter also referred to as PET resin) or polystyrene resin is commonly used for purposes such as improving dimensional accuracy, reducing warping, and improving appearance. However, since polystyrene resin reduces heat resistance, polyethylene terephthalate resin, which has a high melting point, is used in automotive parts and electrical equipment such as induction cooktops where heat resistance is required. However, polyethylene terephthalate resin inhibits the crystallization of polybutylene terephthalate resin, resulting in problems with moldability. For example, Patent Document 1 describes a resin composition containing PBT resin, PET resin, thermoplastic polyester elastomer, and an inorganic filler, wherein the inorganic filler consists of calcined kaolin and a non-fibrous inorganic filler, and exhibits excellent mold release properties. Furthermore, when polybutylene terephthalate resin is used in applications such as automobiles, it tends to have low long-term durability against alkaline solutions. When used in parts that come into contact with alkaline cleaning agents or de-icing agents, exposure to these agents, which contain components such as sodium hypochlorite, sodium percarbonate, calcium chloride, and sodium hydroxide, while under strain, can cause environmental stress cracking, resulting in cracks in the molded product, which has been a problem. For example, Patent Document 2 describes that a composition containing PBT resin, PET resin as an amorphous alloy resin for improving dimensional accuracy, a filler for improving dimensional accuracy, and an aromatic polycarboxylic acid ester exhibits excellent alkali resistance. Japanese Patent Publication No. 2006-265331Japanese Patent Publication No. 2022-057306 This is a schematic perspective view showing the molded product used to evaluate the release properties in the example. The following describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments. <Alkali-resistant polyester resin composition> The alkali-resistant polyester resin composition of this embodiment comprises a PBT resin (A), a recycled PET resin (B), a transesterification inhibitor (C), a silicone compound (D), an elastomer (E), and an inorganic filler (F), wherein the amount of terminal hydroxyl groups of the PBT resin (A) is 30 to 70 mmol/kg relative to the total amount of the PBT resin (A) and recycled PET resin (B), and the amount of elastomer (E) is 8 to 17% by mass relative to the total amount of the alkali-resistant polyester resin composition. In resin compositions containing PBT resin and PET resin, transesterification reactions tend to occur easily between the PBT resin and PET resin under high-temperature conditions such as during melting. If the transesterification reaction proceeds too far, the melting point and crystallization temperature of the resin composition change, and temperature characteristics such as the temperature of deflection under load, as well as tensile strength and elastic modulus, may decrease, making it impossible to obtain the expected physical properties. Furthermore, if the crystallization temperature changes and crystallization becomes difficult, the amount of shrinkage during injection molding decreases, the solidification rate