JPS641493B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polybutylene terephthalate molding material. Polybutylene terephthalate has been widely used in mechanical parts in recent years because of its excellent mechanical properties, electrical properties, and heat resistance. However, by injection molding from polybutylene terephthalate,
At present, improvements are still needed for applications in molding precision mechanical parts. In other words, when injection molding precision mechanical parts, it is possible to shorten the molding cycle and increase productivity, while at the same time achieving dimensional uniformity and weight uniformity of each individual molded product between and within injection molding shots. However, polybutylene terephthalate alone cannot fully satisfy all such requirements. Therefore, conventionally known methods for improving the moldability of polyester resin include using a mold release agent to make it easier to release a molded product, and using a nucleating agent to increase the crystallinity of polyester. This method cannot sufficiently improve moldability. For example, Japanese Patent Publication No. 47-48894 describes a technique for blending fatty acid esters and metal soaps into polybutylene terephthalate to improve mold release properties, but the fatty acid esters used here are injection molded. It is susceptible to deterioration due to the molten state (time and temperature) inside the machine, and is not effective enough to improve the dimensional accuracy of precision parts, and when the residence time in the injection molding machine is long, or when recycled products are used. There is a large decrease in physical properties. In addition, Special Publication No. 47-32435 and Special Publication No. 48-
Publication No. 4907 describes a method of uniformly sprinkling polyester chips with aliphatic metal salts and/or inorganic solid powders, but in this method, the uniformly sprinkled salt re-separates due to the generation of static electricity or other reasons. The disadvantage is that the quality of the molded product varies from injection molding shot to injection molding shot. Furthermore, JP-A-51-39756 describes a technique for attaching paraffin to the surface of polyester particles in order to improve mold releasability, but the paraffin used here is either liquid at room temperature or has a melting point. Because the solid content is relatively low, the coefficient of friction between the chips changes within the pots of the injection molding machine, causing uneven chip transfer, making the plasticization state unstable, and making it difficult to obtain molded products of stable quality. There are some drawbacks. As described above, the conventional methods have their own problems, and even when applied to polybutylene terephthalate, the moldability, quality of the molded product, and uniformity of molded product dimensions, weight, and other properties are sufficiently satisfactory. can't get results. Therefore, the present inventors have improved the molding cycle and
As a result of intensive studies aimed at obtaining a polybutylene terephthalate molding material that also has good dimensional stability and quality stability for molded products, it was discovered that the above object could be effectively achieved by adopting the following means, and the present invention was achieved. did. That is, a polyethylene wax having a molecular weight of 500 to 12,000 is added to the reaction product mixture of the raw materials for forming polybutylene terephthalate at any stage until the polymerization of the raw materials for forming polybutylene terephthalate is completed, at a concentration of 0.01% based on the polybutylene terephthalate finally obtained. ~
The object of the present invention is achieved by adding 2.0% by weight. The polyester molding material produced by the production method of the present invention has an extremely short molding cycle, small variations in molded product dimensions and weight between and within molded product shots, and little deterioration in the molten state. This greatly improves the long-term residence at high temperatures in injection molding machines and the deterioration of physical properties when recycled products are used, making it particularly useful for injection molding applications such as precision mechanical parts. The method of the present invention will be specifically explained in detail. First, polybutylene terephthalate in the present invention is substantially obtained by condensation polymerization of terephthalic acid or a terephthalic acid derivative and butanediol, but some of the acid components are replaced with isophthalic acid, adipic acid, sebacic acid, etc. with other dicarboxylic acids, and also those in which a part of the diol component is replaced with other diol components such as ethylene glycol, hexamethylene glycol, decamethylene glycol, polymethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, etc. include. Such polybutylene terephthalate was added at a concentration of 0.5 gr per 100 ml of orthochlorophenol solution at 25°C.
It is appropriate that the relative viscosity when measured is 1.30 to 1.75, preferably 1.3 to 1.65. If the relative viscosity of polybutylene terephthalate is less than 1.30, the mechanical strength will be too low, and if it is more than 1.75, the dimensional stability will be significantly reduced, which is not preferable. The polyethylene wax used in the present invention is an ethylene homopolymer or ethylene with a molecular weight of 500 to 12,000, preferably 1,000 to 8,000 and up to 30% by weight of other monomers such as propylene, 1-butene, butadiene, maleic anhydride, acrylic esters. copolymers and oxidatively modified products, and their metal salts. Among these, the most preferred are ethylene homopolymer and polyethylene oxide. If the molecular weight of the polyethylene wax is less than 500, the mold releasability will decrease and the molded product will be denatured upon release. On the other hand, if the molecular weight exceeds 12,000, the dispersibility of the polyethylene wax itself deteriorates, resulting in poor dimensional stability of the molded product, which is not preferable. Here, the molecular weight refers to a value obtained by converting the intrinsic viscosity of a 135° C. decalin solution of wax using M=2.51×10 ⁴ [η] ^1.235 . However, in the above formula, M=molecular weight and [η]=intrinsic viscosity. The appropriate amount of polyethylene wax to be added is 0.01 to 2.0% by weight, preferably 0.05 to 1.0% by weight, based on polybutylene terephthalate. The amount added
If it is less than 0.01% by weight, no improvement in moldability, dimensional stability, etc. can be expected, and if it is more than 2% by weight, the moldability improvement effect is saturated, and the heat resistance and mechanical properties of polybutylene terephthalate itself are reduced. It is not preferable because it deteriorates the properties. In the present invention, the polyethylene wax must be added to the reaction system before the polymerization reaction of polybutylene terephthalate is completed. By adding it at this stage, the dispersion of the above-mentioned additives in the molded product becomes extremely good, resulting in excellent physical properties and dimensional accuracy that cannot be obtained by adding it after polymerization is complete or adding it using an extruder. , dimensional stability, and weight stability. There are no particular restrictions on the method of adding the additives, but for example, a mixture of 1,4-butanediol and polyethylene wax mixed and dispersed at a temperature higher than the melting point of 1,4-butanediol may be mixed and dispersed into polybutylene. An example of this method is to add it to the reaction system during the polymerization reaction of terephthalate. In the present invention, an inorganic solid powder can be added at the same time as the polyethylene wax during polymerization. Examples of the inorganic solid powder include talc, clay, wollastenite, mica, asbestos, kaolin, siloid, alumina, etc.
Particularly preferred are talc and wollastenite, which have excellent nucleating effects. These inorganic solid powders have a particle size of
Desirably, it is 0.5 to 10μ, and the amount added is 0.01 to 5.0% by weight based on polybutylene terephthalate.
is appropriate. In addition to the above-mentioned polybutylene terephthalate, polyethylene wax added during polymerization, and inorganic solid powder, the polyester molding material of the present invention may optionally contain glass fiber, inorganic powder such as titanium oxide, metal soap, plasticizer such as fatty acid ester, etc. ,Flame retardants,
Antistatic agents, heat stabilizers, ultraviolet absorbers, pigments, dyes, etc., or known resins other than polybutylene terephthalate, such as polyethylene, polypropylene, ethylene vinyl acetate copolymer (EVA),
Polyolefin resins such as EVA modified products, polyamide resins, polyester resins, etc. can be mixed and used in a range of 50% by weight or less. The polyester molding material of the present invention is particularly suitable for producing precision molded products and thin-walled molded products by injection molding, and can stably produce molded products with excellent dimensional accuracy in a short molding cycle. It is also possible to apply to other methods such as extrusion molding and blow molding. The present invention will be explained below with reference to Examples. Example 1 1.8 times the mole of 1,4- to 100 parts by weight of terephthalic acid
Butanediol was added, and then tetra-n-butyl titanate was added as a catalyst, and under a nitrogen atmosphere.
The esterification reaction is carried out at 220℃, and after the start of the reaction approximately 2.5
Esterification was completed in a few hours. Subsequently, polyethylene wax with a molecular weight of 2000 (trade name Mitsui Hiwax 210P, manufactured by Mitsui Petrochemicals) is added to the obtained product.
was added to the resulting polymer to a concentration of 0.5%, then the system was gradually depressurized and the final temperature was 0.5mm at 245°C.
Polycondensation was carried out under Hg for 3 hours and 10 minutes to obtain polyester (relative viscosity 1.46). Next, the polyester was chipped, dried at 130°C, and then injection molded at 240°C. Dimensional stability and weight fluctuation stability are determined by continuously molding 100 shots using a mold with four gears with a diameter of 37 mm, and determining the maximum outer diameter of the outermost gear where the dimensional fluctuation is the largest for the molded product of each shot, The weight was measured and the standard deviation value based on normal distribution was determined from the measurement results. In addition, the thin wall formability is 0.8 mm thick (with a 3 mm thick rib in the center), and the diameter
Using an 80 mm disc mold, 50 shots were continuously molded, and the amount of deformation of each molded product was measured. In addition, tensile strength was measured by molding ASTA No. 1 dumbbell test pieces. The results are shown in Table 1. Example 2 Example 1 except that polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) was used instead of the polyethylene wax with a molecular weight of 2000 in Example 1.
I did the same thing. The results are shown in Table 1. Example 3 The same procedure as in Example 1 was carried out except that oxidized polyethylene wax (Mitsui Hiwax 4202E) with a molecular weight of 2,400 and an acid value of 16 was used instead of the polyethylene wax with a molecular weight of 2,000 in Example 1. The results are shown in Table 1. Example 4 Same as Example 1 except that instead of the polyethylene wax with a molecular weight of 2000 in Example 1, polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) and powdered talc were added to each amount to 0.5% of the produced polymer. I did the same thing. The results are shown in Table 2. Example 5 Same as Example 1 except that instead of the polyethylene wax with a molecular weight of 2000 in Example 1, polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) and powdered wollastenite were each added at 0.5% to the produced polymer. I did the same thing. Second result
Shown in the table. Example 6 Instead of the polyethylene wax with a molecular weight of 2,000 in Example 1, oxidized polyethylene wax (Mitsui Hiwax 4202E) with a molecular weight of 2,400 and an acid value of 16 and powdered talc were each added to the resulting polymer at a concentration of 0.5%. The same procedure as in Example 1 was carried out. The results are shown in Table 2. Comparative Example 1 Polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) was used instead of the polyethylene wax with a molecular weight of 2000 in Example 1 for the produced polymer.
The same procedure as in Example 1 was carried out except that the amount was added to 0.005%. The results are shown in Table 1. Comparative Example 2 Polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) was used instead of the polyethylene wax with a molecular weight of 2000 in Example 1.
The same procedure as in Example 1 was carried out except that the amount of addition was adjusted to %. The results are shown in Table 1. Comparative Example 3 Polybutylene terephthalate with a relative viscosity of 1.47 was blended with 0.5% polyethylene wax (Mitsui Hiwax 310MP) with a molecular weight of 3000, and the mixture was melt-mixed using a 65 mmφ extruder set at 240°C to form chips. Next, injection molding and performance tests were conducted under the same conditions as in Example 1. The results are shown in Table 1. Comparative Example 4 0.5% polyethylene wax (Mitsui Hiwax 310MP) with a molecular weight of 3000 was added to polybutylene terephthalate chips with a relative viscosity of 1.47, mixed at room temperature using a Henschel mixer, and then injected under the same conditions as in Example 1. Molding and performance tests were conducted. The results are shown in Table 1. Comparative Example 5 Polybutylene terephthalate chips having a relative viscosity of 1.47 were injection molded and performance tested under the same conditions as in Example 1. The results are shown in Table 1. Comparative Example 6 Polybutylene terephthalate with a relative viscosity of 1.47, polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) and powdered talc were blended at 0.5% each, and the mixture was melt-mixed using a 65mmφ extruder set at 240°C to form chips. . Next, injection molding and performance tests were conducted under the same conditions as in Example 1. The results are shown in Table 2. Comparative Example 7 0.5% each of polyethylene wax with a molecular weight of 3000 (Mitsui Hiwax 310MP) and powdered talc were added to polybutylene terephthalate chips with a relative viscosity of 1.47.
and mixed at room temperature using a Henschel mixer, and then injection molded and performance tested under the same conditions as in Example 1. The results are shown in Table 2.

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Claims (1)

[Claims] 1. Polyethylene wax with a molecular weight of 500 to 12,000 is added to the reaction product mixture of the materials at any stage until the polymerization of the polybutylene terephthalate forming raw material is completed, with a molecular weight of 0.01 to 2.0 based on the polybutylene terephthalate finally obtained. A method for producing a polybutylene terephthalate molding material having a relative viscosity of 1.3 to 1.75, which comprises adding % by weight.