JPH0160505B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic polyester composition that has an excellent balance between electrical properties such as antistatic properties and electromagnetic shielding properties and mechanical properties such as impact resistance and tensile properties, and has good melt extrudability. be. Thermoplastic polyesters such as polyethylene terephthalate and polybutylene terephthalate have excellent mechanical properties and heat resistance and have been used for various purposes, but they inherently have high specific volume resistivity and surface resistivity. Due to its poor electrical properties, its application is currently limited in fields such as electrical and electronic equipment parts. Generally known methods for imparting antistatic properties to thermoplastics include incorporating surfactants, antistatic agents, conductive carbon powder, etc., but in recent years, metal powders and surface metallized glass fibers have been incorporated into thermoplastics. A method of adding a conductive metal substance (for example, Japanese Patent Publication No. 54-19423) is attracting attention.
However, when making thermoplastic polyester conductive with such a conductive metal substance, although the electrical properties are improved, the affinity between the conductive metal substance and the thermoplastic polyester is poor, so the original properties of the thermoplastic polyester are Mechanical properties are reduced,
Not only are electrical and mechanical properties not balanced, but the conductive metal material is bulky.
There are problems in that it is difficult to melt-knead with thermoplastic polyester, and the stability of the gut is extremely poor when the composition is melt-extruded. Therefore, the present inventors conducted studies with the aim of obtaining a thermoplastic polyester composition that has an excellent balance between electrical and mechanical properties and also has good melt extrudability. It has been discovered that the above object can be effectively achieved by further blending a specific amount of a specific olefin copolymer, and the present invention has been achieved. That is, the present invention provides (A) thermoplastic polyester with
(B) At least one conductive material selected from aluminum or silver-coated glass fibers or glass beads, aluminum powder, silver powder, zinc white powder, aluminum flakes, aluminum ribbon, metal fibers, metal whiskers, and metal-coated powders. 50-99.5% by weight of metallic substances and (C) α-olefin
and an olefinic copolymer consisting of glycidyl ester of α,β-unsaturated carboxylic acid and/or vinyl acetate 50 to 0.5% by weight, (B) is 3 to 70% by volume based on the total composition, ( C) is 1 for (A) + (C)
Thermoplastic polyester compositions having a proportion of ˜40% by weight are provided. The specific volume resistivity of a molded product made of thermoplastic polyester alone is usually 10 ¹⁶ Ω・cm or more, but by adding a specific conductive metal substance to this, the specific volume resistivity of the molded product becomes conductive. It decreases to about 1 to 10 ⁴ Ω・cm depending on the type and amount of the metal substance mixed. Here, the specific volume resistivity is approximately 10 ² ~
10 ⁴ Ω・cm molded products already have sufficient antistatic properties, and the specific volume resistivity is approximately 1~1.
It can be said that a molded product with a resistance of 10 ² Ω·cm has sufficient electromagnetic shielding properties. However, in such a molded article, the inherent mechanical properties of the thermoplastic polyester are significantly reduced by the addition of the conductive metal substance, so that it is impossible to obtain a molded article that satisfies a balance between electrical properties and mechanical properties. However, in the present invention, by adding the olefin copolymer, the mechanical properties of the molded article are further improved compared to the original level of thermoplastic polyester.
Furthermore, not only the specific volume resistivity is further improved, but also the melt extrudability of the composition is greatly improved, making it possible to obtain stable guttation. The thermoplastic polyester (A) used in the present invention is a polymer or copolymer obtained by a condensation reaction containing dicarboxylic acid (or its ester-forming derivative) and diol (or its ester-forming derivative) as main components. be. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, bis-benzoic acid, and bis(P-carboxyphenyl).
Aromatic dicarboxylic acids such as methane, anthracene dicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dodecanedioic acid; 1,3-cyclohexane dicarboxylic acid; 1,
Alicyclic dicarboxylic acids such as 4-cyclohexanedicarboxylic acid or their ester-forming derivatives may be used alone or in mixtures, and the diol component may include aliphatic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 1 , 4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,
6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, etc., or long chain glycols with a molecular weight of 400 to 6000, such as polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, etc., and mixtures thereof. can be mentioned. Specific thermoplastic polyesters include polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polybutylene terephthalate,
Examples include polyhexamethylene terephthalate, polycyclohexane dimethylene terephthalate, and among these, particularly preferred are polybutylene terephthalate and polyethylene terephthalate, which have good mechanical properties. Further, the above thermoplastic polyester preferably has a relative viscosity of 1.15 to 2.0, particularly 1.3 to 1.8, as measured at 25° C. in a 0.5% orthochlorophenol solution. (B) Conductive metal substances used in the present invention are glass fibers or glass beads coated with aluminum or silver, aluminum powder, silver powder, zinc white powder, aluminum flakes, aluminum ribbons, metal fibers, metal whiskers, and metal coatings. At least one kind selected from powders. The glass fibers or glass beads coated with aluminum or silver herein refer to the glass fibers or glass beads coated with aluminum or silver, which can be produced by vacuum evaporation, silver mirror reaction, or by applying a paint containing aluminum powder or silver powder.
These are surface-metalized glass fibers or glass beads with aluminum or silver adhered to the surface of the glass fibers or glass beads. This surface metalized glass fiber usually has an average diameter of 50μ or less, especially
10~15μ and average fiber length less than 50mm, especially 1~30
mm is preferably used. The average diameter of the surface metallized glass beads is preferably 100μ or less, particularly 50μ or less. Further, as the aluminum powder, silver powder and zinc white powder, those having an average diameter of 500 μm or less, particularly 100 μm or less are preferably used. Aluminum flakes and aluminum ribbons have a thickness of 5~
It is a flake or ribbon shaped plate made of 100μ aluminum foil. Metal fibers are produced by cutting metal fibers manufactured by wire drawing method, dumbbell drawing method, extrusion method, etc. into appropriate lengths, or by cutting a metal block using the chatter vibration of a cutting blade. obtained aluminum fibers, steel fibers, stainless steel fibers, etc., with an average diameter of
Those having an average fiber length of 500μ or less, especially 100μ or less, and an average fiber length of 50mm or less, especially 30mm or less can be preferably used. Metal whiskers are small pieces of metal obtained by, for example, a method of reducing metal halides, and examples include chrome whiskers, copper whiskers, iron whiskers, and nickel whiskers. Metal-coated powder is applied to the surface of inorganic powder or flakes such as talc, kaolin, titanium oxide, and glass, or to the surface of organic polymer powder such as polyester resin, ABS resin, and polyphenylene sulfide resin, for example by electroless plating method. Copper, nickel, silver, etc. are deposited by
Those with a diameter of 500μ or less are preferably used. Two or more of these conductive metal substances (B) may be used in combination, and the amount thereof is selected from the range of 3 to 70% by volume, particularly 5 to 60% by volume, based on the total composition. (B) If the amount of the conductive metal substance is less than 3% by volume, sufficient conductivity cannot be obtained, and if it is more than 70% by volume,
(C) Even if an olefin copolymer is added, the mechanical properties and melt extrudability will be significantly lowered, which is not preferable. What is the (C) olefin copolymer used in the present invention?
- A copolymer consisting of 50-99.5% by weight of olefin and 50-0.5% by weight of glycidyl ester of α,β-unsaturated carboxylic acid and/or vinyl acetate. The α-olefin referred to herein includes ethylene, propylene, butene-1, etc., and ethylene is preferably used. In addition, the glycidyl ester of α,β-unsaturated carboxylic acid has the general formula (R in the formula represents a hydrogen atom or a lower alkyl group), specific examples include glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, etc.
Among them, glycidyl methacrylate is preferably used. (C) α in olefin copolymer,
The copolymerization amount of β-unsaturated carboxylic acid and/or vinyl acetate is suitably 0.5 to 50% by weight, especially 1 to 20% by weight; if it is less than 0.5% by weight, the effect of the present invention cannot be obtained; % or more is not preferable because the composition tends to gel during melt-kneading. Specific examples of the (C) olefin copolymer used in the present invention include ethylene/glycidyl methacrylate copolymer, ethylene/glycidyl methacrylate/vinyl acetate copolymer, and ethylene/vinyl acetate copolymer. These can be used in combination of two or more. The blending amount of these (C) olefin copolymers is 1 to (A) + (C).
It is preferably 40% by weight, particularly 3 to 30% by weight, and selected in proportion to the amount of the conductive metal substance (B). However, if the blending amount of (C) olefin copolymer is less than 1.0% by weight, the effect of improving mechanical properties and melt extrudability will be small, and if it is more than 40% by weight, the inherent properties of thermoplastic polyester will be inhibited, which is undesirable. . The timing of addition of the olefin copolymer (C) should be selected before or during melt mixing of the composition in order to exhibit the effect of improving melt extrudability. The thermoplastic polyester composition of the present invention may further contain other conductivity-imparting substances such as conductive carbon powder and carbon fibers, as well as various types of antistatic agents. The effect can be further enhanced. The various antistatic agents mentioned herein include nonionic, cationic, and anionic surfactants, such as polyethylene glycol, sodium dodecylbenzesulfonate, and sodium lauryl sulfate. Further, various lubricants and mold release agents that act as internal and external lubricants can be added to the thermoplastic polyester composition of the present invention, and moldability can be improved by adding these agents. Examples of these lubricants and mold release agents include aliphatic carboxylic acid metal salts, fatty acid esters, montan wax, organic siloxanes, and synthetic waxes (polyalkylene waxes). The composition of the present invention may contain conventional additives such as fibrous and powder fillers (e.g. calcium carbonate, magnesium carbonate, barium sulfate, finely divided silicic acid, wollastenite, talc, clay, mica, sericite, zeolite, bennite, dolomite, kaolin, etc.) and reinforcing agents (eg, glass fibers, glass beads, etc.). Additionally, plasticizers, flame retardants, nucleating agents, antioxidants, ultraviolet absorbers, heat stabilizers, pigments, dyes, and the like can be contained. Also small amounts of other thermoplastic resins (e.g. polyethylene, polypropylene, ABS resin, MBS resin,
Acrylic resins, fluororesins, polyamides, polyacetals, polycarbonates, polysulfones, polyphenylene oxides, etc.), thermosetting resins (e.g. phenolic resins, melamine resins, polyester resins, silicone resins, epoxy resins, etc.), soft thermoplastic resins ( For example, polyester elastomers, ethylene/propylene terpolymers, etc.) can be included. There are no particular restrictions on the method for producing the thermoplastic polyester composition of the present invention, and for example, by premixing (A) thermoplastic polyester, (B) conductive metal material, and (C) olefinic copolymer. Alternatively, a method of supplying the material to an extruder without melting and kneading may be adopted. By subjecting the composition of the present invention to conventional molding methods such as injection molding, extrusion molding, blow molding, and compression molding, molded products with an excellent balance of electrical properties and mechanical properties can be obtained, and these molded products The products are useful as parts of various electrical and electronic devices and electromagnetic shielding plates. The present invention will be further explained below with reference to Examples. Example 1 (A) polybutylene terephthalate (PBT) with a relative viscosity of 1.45, (B) flaky aluminum with average dimensions of 25 μ x 1 mm x 1.4 mm and (C) ethylene/glycidyl methacrylate (90/10 weight ratio) copolymer. The union,
(B)/(A)+(B)+(C) was mixed at 15% by volume and (C)/(A)+(B) was mixed at 10% by weight in a screw extruder set at 250℃. The mixture was melt-kneaded and pelletized. Next, the obtained pellets were dried with hot air at 130°C for 3 hours, and then subjected to a screw-on-line injection molding machine set at 250°C to produce I _ZOD impact test pieces and 3 mm thick A test piece for measuring electrical resistance with a width of 40 mm and a length of 40 mm was prepared. These test pieces will be referred to as (No. 3). In addition, the above-mentioned PBT alone (No. 1) and a mixture of PBT and 15% by volume of flaky aluminum (No.
2), each specimen was prepared in the same manner as above. The Izot impact strength of these test pieces was measured using ASTMD256, and the volume resistivity was measured using a DC resistance meter. In addition, the amount of the total composition charged to the extruder during melt-kneading by the extruder X ₁ g and the amount of pellets obtained X ₂ g
The melt extrudability was evaluated using X ₂ /X ₁ ×100 (%). These results are shown in Table 1.

[Table] As is clear from Table 1, the composition of the present invention (No. 3) has well-balanced electrical properties and mechanical properties, and has extremely improved extrusion stability. Example 2 (A) polybutylene terephthalate with a relative viscosity of 1.45, (B) a conductive metal material of the type shown in Table 2, and (C) an olefin copolymer with a copolymer composition shown in Table 2, respectively. The mechanical properties, electrical properties, and melt extrudability of test pieces obtained by blending in the ratios shown in Table 2 and molding in the same manner as in Example 1 were evaluated. The results are shown in Table 2. The details of each abbreviation or substance in Table 2 are as follows. Al flakes: Aluminum flakes with an average size of 25 μ x 1 mm x 1.4 mm Al-GF: Aluminum coated glass fiber with an average diameter of 15 μ x 6 mm coated with aluminum to an average thickness of 2.5 μ Fiber: Aluminum coated glass fiber with an average diameter of 65 μ x 6 mm Fiber-shaped aluminum Al-ribbon: Ribbon-shaped aluminum with an average size of 20 μ x 100 μ x 6 mm Al-GB: Aluminum coated glass beads with an average particle size of 28 μ coated with aluminum to an average thickness of 2 μ Ag-GB: Silver coated with an average thickness of 1 μ Coated silver coated glass beads Brass fiber with an average particle size of 28μ: Fibrous brass zinc oxide powder with an average diameter of 50μ x 3mm: Powdered zinc oxide conductive carbon powder with an average particle size of 2μ: Average particle size 50 to 60μ Carbon black Carbon fiber: Carbon fiber with an average diameter of 8.5 μ x 3 mm E/GMA/VA: Ethylene/glycidyl methacrylate/vinyl acetate copolymer

[Table] It is clear from Table 2 that the addition of the olefinic copolymer improves the electrical and mechanical properties of the composition and significantly improves the melt extrudability. Example 3 (A) Polyethylene terephthalate (PET) with a relative viscosity of 1.35, (B) flaky aluminum with average dimensions of 25 μ x 1 mm x 1.4 mm, and (C) ethylene/glycidyl methacrylate (90/10 weight ratio) copolymer. of,
(B)/(A)+(B)+(C) is mixed at 30% by volume and (C)/(A)+(C) is mixed at 10% by weight in a screw extruder set at 285℃. The mixture was melt-kneaded and pelletized. After drying the obtained pellets with hot air at 130℃ for 5 hours,
A test piece (No. 6) similar to that in Example 1 was prepared using a screw-on-line injection molding machine set at 285°C and a mold temperature of 150°C. Similarly PET
Test specimens were prepared from PET alone (No. 4) and from a mixture of PET and 30% by volume of flaky aluminum (No. 5). Table 3 shows the evaluation results for these test pieces.

[Table] As is clear from Table 3, in the case of PET,
The same effect as PBT can be obtained.

Claims (1)

[Claims] 1. From (A) thermoplastic polyester (B) glass fibers or glass beads coated with aluminum or silver, aluminum powder, silver powder, zinc white powder, aluminum flakes, aluminum ribbon, metal fibers, metal whiskers and metal coated powders. At least one selected conductive metal substance and (C)α
- an olefin copolymer consisting of 50 to 99.5% by weight of olefin and 50 to 0.5% by weight of glycidyl ester of α,β-unsaturated carboxylic acid and/or vinyl acetate, in which (B) is based on the total composition; 3～70
A thermoplastic polyester composition in which (C) is 1 to 40% by volume based on (A) + (C).