JPH05247331A - Polyester resin composition for injection molding and its molding method - Google Patents

Abstract

PURPOSE:To provide a polyester resin composition having extremely high crystallization rate, remarkably improved moldability and excellent heat-resistance and mechanical strength. CONSTITUTION:The objective polyester resin composition for injection molding contains (A) 5-95 pts.wt. of a polyester copolymer having a heat-crystallization temperature Tc(H) of <=100 deg.C, (B) 95-5 pts.wt. of a polyethylene terephthalate resin and (C) 0-65 pts.wt. of a reinforcing filler. The composition can be molded at a mold temperature of <=100 deg.C with short molding cycle.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin composition for injection molding and a method for molding the same. More specifically, by mixing a polyester-based copolymer and a polyethylene terephthalate resin, the crystallization rate is extremely fast and the molding processability is remarkably improved, and the heat resistance and the polyester resin composition imparted with mechanical strength are excellent. The molding method is related. [0002] A high molecular weight linear polyethylene terephthalate resin obtained from a dicarboxylic acid mainly containing terephthalic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative is It has a high softening point, heat resistance, chemical resistance, light resistance, and excellent electrical properties and physical / mechanical properties, and is therefore widely used as fibers, films, and molded products. However, when such a polyethylene terephthalate resin is used as an injection-molded article, the crystallization rate is slower than that of the same crystalline polymers such as nylon and polyacetal, and the crystallization hardly progresses at 100 ° C. or lower. It has been strongly desired to improve the crystallization characteristics of polyethylene terephthalate resin, shorten the molding cycle, and expand the mold temperature range during molding. The present inventors have now surprisingly surprisingly increased the crystallization rate of the polyethylene terephthalate resin by mixing the polyester copolymer and the polyethylene terephthalate resin. In addition to shortening the molding cycle, the crystallization speed is rapid even if the mold temperature during injection molding is set to 100 ° C or lower,
It was also found that a molded product having excellent heat resistance and mechanical strength can be obtained. In the present invention, (A) heating crystallization temperature Tc
Polyester copolymer 5 having (H) of 100 ° C. or lower
To 95 parts (parts by weight, the same applies hereinafter), (B) polyethylene terephthalate resin 95 to 5 parts, and (C) reinforcing filler 0 to 65 parts, and a polyester resin composition for injection molding, and 100 parts of the composition. Mold temperature below ℃,
And a method of molding in a short molding cycle. EXAMPLES [0006] In the present invention, the heating crystallization temperature Tc (H)
First, the polyester-based copolymer (A) having a temperature of 100 ° C. or lower will be described. The heating crystallization temperature Tc (H) is 10 from the glass state resin by using a scanning differential calorimeter (DSC).
It is a crystallization temperature when heated at a temperature rising rate of ° C / min, and refers to a crystallization temperature of 100 ° C or less. The polyester copolymer is a resin obtained by copolymerizing a polymer containing ethylene terephthalate units as a main component with a modifier component that promotes crystallization. A polymer containing ethylene terephthalate units as a main component means a dicarboxylic acid component having at least 90 mol% terephthalic acid and at least 90 mol%.
From the diol component, up to which is ethylene glycol,
It is obtained by polycondensation after direct esterification or transesterification. 0 to 10 mol% of the dicarboxylic acid component is another aromatic dicarboxylic acid having 6 to 14 carbon atoms, an aliphatic dicarboxylic acid having 4 to 8 carbon atoms or an alicyclic dicarboxylic acid having 8 to 12 carbon atoms. May be. Examples of such dicarboxylic acids include phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid,
Examples thereof include diphenylethane-4,4'-dicarboxylic acid, adipic acid, sebacic acid and cyclohexanedicarboxylic acid. Further, 0 to 10 mol% of the diol component is another aliphatic diol having 3 to 10 carbon atoms, another alicyclic diol having 6 to 15 carbon atoms, or an aromatic diol having 6 to 12 carbon atoms. It may be. Examples of such diols include propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,
6-diol, cyclohexane-1,4-dimethanol, 2,2-dimethylpropane-1,3-diol,
2,2-bis- (4'-hydroxycyclohexyl)-
Examples thereof include propane, 2,2-bis- (4'-hydroxyphenyl) propane and hydroquinone. Further, an oxycarboxylic acid such as ε-oxycaproic acid or hydroxybenzoic acid in an amount of 10 mol% or less of the dicarboxylic acid component and the diol component may be copolymerized. Of course, the polyester copolymer may be branched with a trihydric or tetrahydric alcohol or a tribasic or tetrabasic acid. Examples of suitable branching agents include trimesic acid and trimellitic acid. Acid, trimethylolpropane, pentaerythritol and the like can be mentioned. Examples of the modifier component to be copolymerized include various compounds capable of keeping the above Tc (H) at 100 ° C. or lower. Specific examples will be shown below. (A) Polyalkylene glycols; examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. (B) Polyoxyalkylene compounds having an organic acid metal salt; for example, monosuccinic acid potassium salts such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide-propylene oxide copolymers, monophthalic acid sodium salt. , Calcium salt, zinc salt, aluminum salt, mono (tetrabromo) phthalate sodium salt, polyethylene glycol monotrimellitic acid sodium salt, glycerin-alkylene oxide adduct, trimethylolpropane-alkylene oxide adduct phthalate Sodium salt and mono-, di-, tri-, or tetrabromophthalic acid ester sodium salt, polyethylene glycol, polypropylene glycol , Polytetramethylene glycol,
Ethylene oxide-propylene oxide copolymer,
Examples thereof include sodium salt and calcium salt of sulfonic acid or phosphoric acid of phenyl ether such as polyhydric alcohol-alkylene oxide adduct. (C) Polyoxyalkylene compounds having an epoxy group; mono- and diglycidyl ethers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide-propylene oxide copolymers, methoxy polyethylene glycol, ethoxy polyethylene glycol. And monoglycidyl ether, glycerin-alkylene oxide adduct, trimethylolpropane-alkylene oxide adduct, pentaerythritol-alkylene oxide adduct glycidyl ether and the like. (D) Aliphatic polyester oligomer compounds; for example, butane-1,3-diol adipate oligomer, butane-1,4-diol adipate oligomer, butane-1,3-diol sebacate oligomer,
Examples thereof include butane-1,4-diol sebacate oligomer and hexane-1,6-diol adipate oligomer. In the above, an alkylene unit having usually 1 to 18 carbon atoms, preferably 2 to 6 carbon atoms can be used. Although specific examples have been shown above, the modifier is not limited to these. The modifier may be used alone or in combination of two or more kinds. As the copolymerization method of these modifiers, there are a method of adding after direct esterification or transesterification, a method of adding during the middle or end of polycondensation,
An advantageous method can be selected depending on the type of the modifier. The amount of modifier added varies from individual to
An amount that makes Tc (H) 100 ° C. or lower is added. Generally speaking, it is contained in the range of 10 to 80% (weight%, the same applies hereinafter). Among these modifiers, the molecular weight is 200 to 6
000 polyoxyalkylene compounds, especially those containing organic acid metal salts, are particularly effective. The polyethylene terephthalate resin (B) in the present invention is a polymer containing an ethylene terephthalate unit as a main component, and the modifier component to be copolymerized is excluded from the description of the polyester copolymer mentioned above. And all commercially available polyethylene terephthalate resins can be used. The polyester copolymer (A) and the polyethylene terephthalate resin (B) are used in a proportion of 5 to 5, respectively.
It is in the range of 95 parts, and generally, the higher the proportion of the polyester-based copolymer, the lower the mold temperature at the time of injection molding, so the addition amount is determined based on the quality design of the product, for example. be able to. The reinforcing filler (C) in the present invention means a fibrous, plate-like or granular inorganic filler, and by mixing these, mechanical strength, heat resistance and dimensional stability can be further enhanced. . As a specific example, glass fiber,
Mineral fiber, carbon fiber, silicon carbide fiber, boron carbide fiber, potassium titanate fiber, gypsum fiber, mica, talc, kaolin, clay, asbestos, calcium silicate, calcium sulfate, calcium carbonate, etc., but especially glass fiber, Mineral fibers, talc, mica and kaolin are preferable, and these may be used alone or in combination of two or more kinds. Further, it may be surface-treated with a silane coupling agent or the like in order to improve the affinity with the resin. The compounding amount is usually 0 to 65 parts, and considering mechanical strength, heat resistance and fluidity, 10 to 55 parts is desirable and can be determined based on quality setting. To prepare the composition of the present invention, the polyester copolymer (A), the polyethylene terephthalate resin (B) and the reinforcing filler (C) may be mixed by a known method. A method of mixing and extruding using an extruder is advantageous. In addition to other known nucleating agents, thermal oxidation stabilizers, light stabilizers, etc., the composition of the present invention may contain additives such as plasticizers, lubricants and colorants. Furthermore, other types of thermoplastic resins can be blended in a small proportion, and a small proportion of a rubber component can be introduced in order to improve impact resistance. If necessary, a flame retardant and a flame retardant aid may be added to impart flame retardancy. Thus, a polyethylene terephthalate single molded product can be obtained as a satisfactory molded product only after a mold temperature of 140 ° C. or more under a long molding cycle, whereas the composition of the present invention has a mold temperature of 100 ° C. or less, Moreover, even when a short molding cycle is used, a molded product having excellent mold releasability from the mold, surface appearance, heat resistance, and mechanical strength can be obtained. The composition of the present invention can be widely used for molding various molded parts, pipes, containers, etc.
It can be suitably used for building material parts, automobile parts, etc., and can also be used for fibers and film sheets. The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, the intrinsic viscosity of the polymer is as follows in phenol / tetrachloroethane (1: 1 (weight ratio)):
It is a value obtained from the logarithmic viscosity measured at 25 ° C. and a concentration of 0.5 g / dl. The melting point Tm of the modified polyalkylene terephthalate, the cooling crystallization temperature Tc (C) from the molten state, and the heating crystallization temperature Tc (H) from the glass state were measured by Perkin-Elmer DSC-1B type. The tensile strength of the molded product is ASTM-D638, the flexural strength and flexural modulus are ASTM-D79C, and the Izod impact resistance value is A.
STM-D256, heat distortion temperature (18.6 kg / c
m ² ) was measured by the method according to ASTM-D648. Further, at the time of injection molding, molding was performed with various molds, and the surface appearance was visually judged. The amount added in the examples is parts by weight. Example 1, Comparative Example 1 A copolymer with polyethylene terephthalate containing 40% of polyethylene glycol monotrimellitic acid disodium salt having an average molecular weight of 1740 (Tc (H) = 60).
° C, Tc (C) = 205 ° C, Tm = 225 ° C, [η] =
0.62) 100 parts, 300 parts of polyethylene terephthalate resin, and 200 parts of glass fiber having a fiber length of 3 mm were mixed using an extruder, and then injection molded at various mold temperatures. The results, as shown in Table 1, are the mechanical strength,
A molded product having excellent heat resistance and a good surface appearance was obtained even at a mold temperature of 100 ° C. [Table 1] As Comparative Example 1, when 400 parts of polyethylene terephthalate resin is mixed with 200 parts of glass fiber having a fiber length of 3 mm, the results are shown in Table 1. It can be seen that the heat resistance and the surface appearance are at a low level. Example 2 A polyester copolymer (Tc (H) = 52 ° C., Tc (C) = 162 ° C., T) obtained by copolymerizing 60% of butane-1,4-diol adipate oligomer having an average molecular weight of 3000.
m = 210 ° C., [η] = 0.58) 100 parts, polyethylene terephthalate resin 200 parts, glass fiber 150 parts with a fiber length of 3 mm were mixed using an extruder, and then injection molded at various mold temperatures. . A molded product having a good surface appearance was obtained even at a mold temperature of 90 ° C. The heat distortion temperature (1/8 ″ thickness) at a mold temperature of 90 ° C. was 212 ° C., which showed good heat resistance.Example 3 A mixture of polyethylene glycol 30% having an average molecular weight of 1000 and polyethylene terephthalate. Polymer (Tc (H)
= 72 ° C, Tc (C) = 187 ° C, Tm = 229 ° C
[Η] = 0.75) 100 parts, polyethylene terephthalate resin 200 parts, and glass fiber 150 parts with a fiber length of 3 mm were mixed using an extruder, and then injection molded at various mold temperatures. A molded product having a good surface appearance was obtained even at a mold temperature of 100 ° C. The heat distortion temperature (1/8 ″ thickness) at a mold temperature of 100 ° C. was 216 ° C., indicating good heat resistance. Effect of the Invention With the composition of the present invention, polyethylene terephthalate alone was used. Molded case, mold temperature 140
A satisfactory molded product can be obtained only after a long molding cycle at a temperature of ℃ or more, whereas the mold releasability, surface appearance, and heat resistance of the mold can be achieved even when molding at a mold temperature of 100 ° C or less and a short molding cycle. A molded product with excellent mechanical strength can be obtained.

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Claims (1)

Claims: 1- (A) 5 to 59 parts by weight of a polyester copolymer having a heating crystallization temperature Tc (H) of 100 ° C. or lower, (B) a polyethylene terephthalate resin of 95 to 5 parts by weight, and (C) ) A polyester resin composition for injection molding containing 0 to 65 parts by weight of a reinforcing filler. 2. The composition according to claim 1, wherein the polyester-based copolymer is a copolymer of a polyoxyalkylene compound and polyester. 3 (A) 5 to 59 parts by weight of a polyester copolymer having a heating crystallization temperature Tc (H) of 100 ° C. or lower, (B) 95 to 5 parts by weight of a polyethylene terephthalate resin, and (C) a reinforcing filler 0 to A polyester resin composition for injection molding containing 65 parts by weight at a mold temperature of 100 ° C. or lower,
And a method of molding in a short molding cycle.