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EP-3926004-B1 - POLYBUTYLENE TEREPHTHALATE RESIN COMPOSITION

EP3926004B1EP 3926004 B1EP3926004 B1EP 3926004B1EP-3926004-B1

Inventors

  • KAMIYA, MOTONOBU
  • FUJII, YASUTO
  • SHIMOHARAI, Takuya

Dates

Publication Date
20260506
Application Date
20200205

Claims (4)

  1. A polybutylene terephthalate resin composition comprising: 80 to 95 parts by mass of a polybutylene terephthalate resin (A) having an intrinsic viscosity (IV) of 0.60 to 0.95 dl/g, 3 to 9 parts by mass of a modified olefin resin (B), and 1 to 15 parts by mass of a polyester elastomer (C), based on 100 parts by mass of components (A), (B) and (C) in total, and further comprising 0.1 to 1.2 parts by mass of a carbodiimide compound (D) based on 100 parts by mass of the components (A), (B) and (C) in total, and the intrinsic viscosity (IV) is determined by dissolving 0.1g of a sample in 25 ml of a mixed solvent of phenol/tetrachloroethane (mass ratio: 6/4), and measuring at 30°C using an Ubbelohde viscosity tube.
  2. The polybutylene terephthalate resin composition according to claim 1, wherein the polybutylene terephthalate resin composition has a flow length obtained by injection molding (measurement conditions: cylinder temperature at 250°C, mold temperature at 50°C, and an injection pressure at 80 MPa) of 155 mm or more.
  3. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein a molding obtained by injection molding of the polybutylene terephthalate resin composition has a Charpy impact strength of 4.5 kJ/m 2 or more, and the Charpy impact strength is determined according to the method outlined in the description.
  4. The polybutylene terephthalate resin composition according to any one of claims 1 to 3, wherein the modified olefin resin (B) is an ethylene copolymer obtained by copolymerization with maleic anhydride and/or glycidyl methacrylate in a total amount of 0.01 to 15 mass%.

Description

TECHNICAL FIELD The present invention relates to a polybutylene terephthalate resin composition. More specifically, the present invention provides a polybutylene terephthalate resin composition having excellent impact properties, high fluidity, and excellent in mold releasability in molding and t melt stability, and thus suitable for thin-wall molding. BACKGROUND ART Due to excellence in mechanical properties, electrical properties, other physical and chemical properties and due to good processability, polybutylene terephthalate resins have been used as an engineering plastic in a wide range of applications for automobiles, electric and electronic parts, etc. In particular, due to the excellent electrical properties, their applications for home appliances, office automation equipment, and automobiles, etc., have a tendency to increase. The growing tendency to make these products lighter, thinner, shorter and smaller is remarkable, and, for example, the outer shell parts thereof are extremely thin. A polybutylene terephthalate resin, however, has poor Charpy impact properties, resulting in a drawback that a thin-wall molding is particularly easily broken. In addition, a material having higher fluidity than conventional one is required. A polybutylene terephthalate resin composition having excellent Charpy impact properties is, therefore, strongly required. As a method for improving the Charpy impact properties of a polybutylene terephthalate resin, addition of rubber is generally known. In Patent Literature 1, enhancement of compatibility and improvement in impact resistance are performed by addition of a core-shell rubber having a glycidyl group to a polybutylene terephthalate resin. However, no attention is paid to fluidity, so that the fluidity is expected to be low. In Patent Literature 2, it is shown that addition of an ethylene-alkyl acrylate-glycidyl methacrylate copolymer to a polybutylene terephthalate resin enables modification of the resin while maintaining a comparative tracking index. However, it is easily presumed that the fluidity decreases due to the reaction between the polybutylene terephthalate resin and a glycidyl group. In Patent Literature 3, addition of a rubber and a core-shell elastomer to a polybutylene terephthalate resin improves impact resistance and enhances low warpage properties and weld strength. However, addition of a large amount of rubber and core-shell elastomer is required to improve the impact resistance, and so presumed to decrease the fluidity. In Patent Literature 4, a core-shell polymer and glass fibers are used in combination in a polybutylene terephthalate resin to improve the impact resistance and rigidity. However, significant decrease in fluidity is expected due to increase in the flow resistance resulting from the combined use of glass fibers. As shown in these literature, although various researches have been conducted on the improvement in impact properties, no studies for improvement in compatibility with high fluidity have been made. As a result, thin-wall molding of a material with improved impact properties has been difficult. On the other hand, in Patent Literature 5, an attempt has been made to achieve compatibility between impact properties and high fluidity by blending an elastomer having a glycidyl group and/or a carboxylic acid derivative terminal and a chain polyester oligomer into a polybutylene terephthalate resin. However, since a chain polyester oligomer is easily gasified, there have been fundamental problems such as a cause of mold stains in injection molding and contamination of the internal part of a product. PTL 6 describes a flexible polyester resin composition hardly causing dirt adhesion. CITATION LIST PATENT LITERATURE PTL 1: Japanese Patent Laying-Open No. 10-36645PTL 2: Japanese Patent Laying-Open No. 2017-27906PTL 3: Japanese Patent Laying-Open No. 2016-183294PTL 4: Japanese Patent Laying-Open No. 10-95907PTL 5: Japanese Patent Laying-Open No. 2012-201857PTL 6: JP 2016 108378 A SUMMARY OF INVENTION TECHNICAL PROBLEM The present invention is intended to solve the problems described above, and an object thereof is to provide a polybutylene terephthalate resin composition having excellent impact properties and high fluidity. SOLUTION TO PROBLEM The present inventors have completed the present invention as a result of extensive studies on the constitution and properties of a polybutylene terephthalate resin composition in order to solve the problem described above. The present invention is defined in the appended claims. ADVANTAGEOUS EFFECTS OF INVENTION According to the present invention, compatibility between excellent Charpy impact strength and high fluidity is achieved even for a polybutylene terephthalate resin by addition of a modified olefin resin and a polyester elastomer at a specific compounding ratio. DESCRIPTION OF EMBODIMENTS The present invention is specifically described as follows. Unless otherwise specified, the conten