JPS62941B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester molding materials with improved moldability. More specifically, the present invention is a polyester which is particularly useful for injection molding small precision mechanical parts, and which is formed by forming a bonded layer of aliphatic carboxylic acid metal salt containing inorganic solid powder on the surface of polybutylene terephthalate granules. It relates to molding materials. Polybutylene terephthalate has excellent mechanical properties, electrical properties, and heat resistance, so it is widely used for medium to large molded products such as electrical parts and automobile parts. In addition, polybutylene terephthalate itself has excellent moldability, and if we pay attention to these characteristics, we can expect it to be used for small precision mechanical parts, but no matter how good it is, However, the current situation is that improvements are still needed for this application. In other words, when injection molding small precision mechanical parts, it is possible to improve the molding cycle and increase productivity, while at the same time achieving dimensional uniformity and weight uniformity of each molded product between and within injection molding shots. However, polybutylene terephthalate alone cannot fully satisfy these requirements. Conventionally, many methods have been proposed to improve the moldability of polyester, as typified by the molding cycle, such as increasing the crystallinity of polyester with a nucleating agent, and making mold release easier with a mold release agent. Representative examples of these include the following methods. (1) Stearic acid metal salt and/or polyester
or a method of melt-mixing inorganic solid powders. (Japanese Patent Publication No. 47-10532, Japanese Patent Publication No. 48-48894) (2) A method of uniformly coating polyester chips with fatty metal salts and/or inorganic solid powder. (Special Publication No. 45-19392, Publication No. 32435-1970,
(3) Polyester chips containing fatty acid metal salts and/or
Or a method of using a liquid spreading agent such as liquid paraffin when uniformly sprinkling inorganic solid powder.
(JP-A-50-78647) (4) A method of coating montanate on polyester chips with or without inorganic solid powder by melt-mixing. (Japanese Patent Publication No. 47-13137) However, although the molding cycle of the molded product by method (1) above is certainly faster, the homogeneity of the molded product is greatly affected by the chip shape and the type of injection molding machine. , is not satisfactory. Furthermore, according to the method (2) above, there is a drawback that the uniformly sprinkled salt re-separates due to the generation of static electricity or other reasons, and the quality of the molded product fluctuates from injection molding shot to molding cycle. Method (3) above clearly improves the drawbacks of method (2), but on the other hand, since the spreading agent is generally a sticky liquid, the coefficient of friction between the chips changes.
Since the chips are not transferred uniformly, the plasticized state becomes unstable, making it difficult to obtain molded products of stable quality, and there is also the drawback that dirt and dust may be attracted to the hopper. In method (4) above, the surface of the polyester chips is coated with molten salt, so it is uniform over the entire surface, but the slip between the chips is poor, and the chips may become brittle in the hopper of the molding machine, causing problems in the supply of chips. The plasticization is not uniform and the plasticization state is also unstable, making it difficult to obtain molded products of stable quality. As described above, each of the conventional methods has its own problems, and even when applied to polybutylene terephthalate, the molding cycle is shortened due to the addition of aliphatic carboxylic acid metal salts and/or inorganic solid powders as crystallization nucleating agents. Although this effect can be obtained,
At the same time, the plasticized state during molding becomes unstable, making it impossible to obtain sufficiently satisfactory results in uniformity of dimensions, weight, and other properties of the molded product. Therefore, the present inventors conducted intensive studies to obtain a polybutylene terephthalate molding material with improved molding cycles and good quality stability of molded products. By simultaneously adding high melting point inorganic solid powder when melt coating,
The inventors have discovered that the above object can be effectively achieved and have arrived at the present invention. That is, the present invention adds 0.01 to 5.0 parts by weight of an aliphatic carboxylic acid metal salt having a melting point of 60 to 200°C and 0.01 to 5 parts by weight of an inorganic solid powder to 100 parts by weight of polybutylene terephthalate granules. The object of the present invention is to provide a polyester molding material obtained by heating and mixing at a temperature above the melting point of the group carboxylic acid metal salt and below the melting point of polybutylene terephthalate. In the polyester molding material of the present invention, the surface of polybutylene terephthalate granules is coated with a layer formed from a melt of an aliphatic carboxylic acid metal salt containing an inorganic solid powder, and the molding cycle is extremely shortened. , shape of molding material, molding machine,
A stable plasticized state can be obtained almost unaffected by molding conditions, and fluctuations between shots and within shots of molded products are significantly improved, making it particularly useful for injection molding applications such as small precision mechanical parts. be. Polybutylene terephthalate in the present invention means a linear polyester obtained by condensing 1,4-butadiol and terephthalic acid, and a polyester obtained by replacing a part of the alcohol component and acid component with other copolymerizable components. Even if it is a copolymer mainly composed of butylene phthalate or a mixture of polybutylene terephthalate or a copolymer mainly composed of polybutylene terephthalate with 50% by weight or more and less than 50% by weight of other organic polymer substances, the present invention applies. Can be applied. In this case, copolymerization components include diols such as ethylene glycol and diethylene glycol as alcohol components, and isophthalic acid, adipic acid, etc. as acid components. The organic polymer substances to be mixed with the polybutylene terephthalate include polyethylene-acrylic acid ester copolymer, polypropylene, ethylene-propylene copolymer, polyamide, polypropylene terephthalate, polyoxymethylene, polystyrene, styrene-butadiene-acrylonitrile resin. , styrene-acrylonitrile resin, polycarbonate,
Examples include polyphenylene oxide, polybutadiene, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, and butyl rubber. In addition, these linear polyesters can be used even if they have added organic or inorganic substances such as flame retardants, pigments, and fillers, including those reinforced with reinforcing agents such as glass fiber. do. The polybutylene terephthalate including these used in the present invention is used in the form of small particles of any arbitrary shape such as prismatic, cylindrical, spherical, etc. It is desirable that the small particles have an average diameter in the range of 1 to 10 mm. Particularly preferred is a range of 2 to 5 mm. Examples of aliphatic carboxylic acid metal salts with a melting point of 60 to 200°C used in the present invention include potassium stearate, sodium stearate, magnesium stearate, aluminum stearate, magnesium palmitate, calcium palmitylate, magnesium oleate, and montanic acid. These include sodium and calcium montanate. These salts may coexist with aliphatic carboxylic acid esters, especially glycerols. In some cases, this may even be preferable in order to provide an excellent coating effect.
The amount of these aliphatic carboxylic acid metal salts added is 0.01 to 100 parts by weight of polybutylene terephthalate.
5.0 parts by weight, preferably 0.05 to 1.0 parts by weight, is suitable. If the amount of aliphatic carboxylic acid metal salt added is less than 0.01 part by weight, no improvement in moldability can be expected, and if it is more than 5.0 parts by weight, the moldability improvement effect is saturated, and on the contrary, the effect of improving moldability is This is not preferable because it deteriorates physical properties. The inorganic solid powder used in the present invention generally preferably has a melting point higher than the melting point of polybutylene terephthalate, and examples thereof include talc, clay, wollastenite, mica, asbestos, silica, kaolin, zirconium oxide, calcium carbonate, alumina, and gypsum. , thyroid, fluorite, glass powder, ore powder, metal powder, etc. These inorganic solid powders are required to be in the form of fine powder with a particle size of 0.5 to 10 microns, particularly preferably 1 to 5 microns, in order to improve the plasticizing properties of the molding material. The amount of inorganic solid powder added is required to be 0.01 to 5.0 parts by weight per 100 parts by weight of polybutylene terephthalate; if it is less than 0.01 parts by weight or more than 5.0 parts by weight, the plasticization of the molding material will become unstable and a stable molded product will not be obtained. This is not preferable because it does not provide The method for preparing the molding material of the present invention is not particularly limited as long as it forms a coating layer made of aliphatic carboxylic acid metal salt containing inorganic solid powder on the surface of granular polybutylene terephthalate. For example, a method in which granular polybutylene terephthalate inorganic solid powder and aliphatic carboxylic acid metal salt are sequentially or simultaneously supplied to a predetermined mixer and mixed while heating to a predetermined temperature, and a method in which preheated granular polybutylene terephthalate Examples include a method of adding and mixing an inorganic solid powder and an aliphatic dicarboxylic acid or a preliminary mixture thereof. Here, preheated granular polybutylene terephthalate means, for example, discharged after melt polymerization, immediately after granulation, during or immediately after solid phase polymerization, discharged from an extruder, immediately after granulation, and still after drying. It also includes the state before cooling. In this way, the mixing is carried out at a temperature above the melting point of the aliphatic carboxylic acid metal salt and below the melting point of polybutylene terephthalate,
Conditions are adopted in which a coating layer made of an aliphatic carboxylic acid metal salt containing an inorganic solid powder is uniformly formed on the surface of the polybutylene terephthalate. Although this mixing temperature is usually below the melting point of polybutylene terephthalate, it may be possible to adopt a range near or slightly higher than the melting point of the polymer as long as the particulate polymers do not fuse together. However, when preparing the molding material of the present invention, it is important to uniformly fuse the aliphatic carboxylic acid metal salt containing inorganic solid powder to the surface of the polybutylene terephthalate granules. If one or both of the metal salt and the inorganic solid powder are simply attached to the surface of the polybutylene terephthalate particles, the desired effect cannot be obtained. The polyester molding material of the present invention is particularly suitable for producing small, thin-walled molded products by injection molding, and can produce stable molded products at high speed and with little variation between and within shots. Of course, excellent effects can be expected when producing medium- to large-sized injection molded products from the polyester molding material of the present invention, and it can also be applied to other injection molding, blow molding, etc. The effects of the present invention will be further explained below with reference to Examples. The relative viscosity of polybutylene terephthalate in the examples is a value measured in a 0.5 g/100 ml 0-chlorophenol solution at 25°C. In addition, all parts by weight added in the examples mean values per 100 parts by weight of polybutylene terephthalate. Example 1 Polybutylene terephthalate chips (3 mm x 3 mm x 4 mm) with a relative viscosity of 1.46 were placed in a tumbler at 150° C.
After drying at 100°C for 1 hour, magnesium stearate (melting point: 145°C) or magnesium stearate and talc powder were added thereto according to methods A to E below to obtain molding materials A to E. A. Cool the chips to 100℃, add and mix 0.2 parts by weight of magnesium stearate. B. Cool the chips to 100°C, and add and mix 0.2 parts by weight of magnesium stearate and 0.1 parts by weight of liquid paraffin. C Chips were cooled to 100°C, and 0.2 parts by weight of magnesium stearate and 0.2 parts by weight of talc were added and mixed. D Magnesium stearate in chips at 150℃
Add 0.2 parts by weight and mix. E Magnesium stearate in chips at 150℃
Addition and mixing of 0.2 parts by weight and 0.2 parts by weight of talc (invention) From each of the molding materials A to E thus obtained, 16 small gears (outer diameter 20 mm) were prepared under the following molding conditions.
φ, each piece weighing 0.80 to 0.85 g) was injection molded. Molding machine Toshiba IS-50 Molding temperature 240℃ (setting) Mold temperature 80℃ (setting) Molding cycle Injection/cooling 3 seconds/7 seconds or 5 seconds/10 seconds Number of molding shots 100 shots (40 shots after cleaning) Molding Speed Maximum (approximately 1 second) Molding pressure Lower limit pressure x 1.5 Kg/cm ² Evaluate moldability (mold releasability) and stability of molded products (weight and dimensional variations between and within shots) during molding of each molding material The results are shown in Table 1. As is clear from the results in Table 1, each method of ABCD has the effect of improving mold release properties during molding or shortening the molding cycle, but the weight and dimension variations of the obtained molded products are large. On the other hand, with the dimension E (invention), it is possible to improve mold releasability and shorten the molding cycle, and at the same time, the dimensional stability of the obtained molded product is also extremely good.

【table】

[Table] Example 2 A polybutylene terephthalate chip (cylindrical shape of 3 mmφ x 3 mm) with a relative viscosity of 1.25 was placed in a rotary solid phase polymerization apparatus, and solid phase polymerization was performed at 200°C under a reduced pressure of 0.5 mmHg. By changing the time, three types of chips with relative viscosities of 1.30, 1.50, and 1.90 were obtained, respectively. After each solid phase polymerization is completed, the inside of the rotary solid phase polymerization apparatus is returned to normal pressure with an inert gas, and 0.3 parts by weight of magnesium stearate and 0.3 parts by weight of clay powder are added to each chip that is still heated at 200°C. were added and mixed to obtain three types of molding materials F, G, and H. For comparison, each chip was incubated at 25℃ after solid phase polymerization.
Magnesium stearate
Add and mix 0.3 parts by weight to make three types of molding materials F′,
G′ and H′ were obtained. From these chips, 1/8" dumbbell test pieces and 1/2" impact test pieces were injection molded under the following molding conditions. Molding machine Toshiba IS-50AM Molding temperature 240℃ (setting) Mold temperature 40℃ (setting) Molding cycle Injection/cooling 10 seconds/20 seconds Molding pressure Lower limit pressure + 5Kg/cm ² Fluctuations in plasticizing torque during each molding are As shown in Table 2, the molding materials F to H of the present invention exhibit a more stable plasticized state than the conventional molding materials F' to H' (comparative examples). For reference, the physical properties of the test pieces obtained are also shown in Table 2.

[Table] Example 3 A polybutylene terephthalate chip with a relative viscosity of 1.40 was uniformly sprinkled with 0.2 parts by weight of silica powder, and 250
The mixture was kneaded in an extruder at ℃ and turned into chips. Next, this chip was heated to 200°C, and 0.2 parts by weight of sodium montanate (melting point 180°C) was added to uniformly coat the chip surface to obtain molding material I. On the other hand, according to the method of the present invention, powder and 0.2 parts by weight of sodium montanate were directly added to polybutylene terephthalate chips having a relative viscosity of 1.40 and welded to the surface of the chips to obtain molding material J. Using each chip, six S-shaped 1/8" test pieces were molded using a Toshiba IS-50AM molding machine under the following conditions. Molding temperature: 240℃ (setting) Mold temperature: 80℃ Molding cycle: Injection/cooling/ Intermediate / 74 seconds / 6 seconds / 6 seconds Injection pressure Injection speed shown in Table 3 Maximum injection shot 100 consecutive shots For the molded product, the weight of one S-shaped test piece is shown in Table 3. Compared to the conventional molding material I, the molding material J could be molded in a very stable plasticized state, and the weight fluctuation of the molded product was small. A similar experiment was conducted on ``Tux-OP'' and almost the same results were obtained.

【table】

【table】

Claims (1)

[Claims] 1. 0.01 to 5.0 parts by weight of aliphatic carboxylic acid metal salt with a melting point of 60 to 200°C and 0.01 to 0.01 parts by weight of inorganic solid powder per 100 parts by weight of polybutylene terephthalate granules.
A polyester molding material prepared by adding 5.0 parts by weight of the aliphatic carboxylic acid metal salt and heating and mixing at a temperature above the melting point of the aliphatic carboxylic acid metal salt and below the melting point of polybutylene terephthalate.