JPH0153164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves mixing propylene polymer resin powder with a uniform particle size with glass fibers and specific additives, and directly injection molding the mixture.
This invention relates to a method for producing an injection molded article, which provides improvements in terms of resin deterioration and plasticization time, as well as significantly improved dispersion of glass fibers in the resin, resulting in a significantly reduced variation in product weight. Propylene polymer resins are widely used in various fields because they are light, have excellent mechanical strength and appearance, are easily molded, and are readily available. Particularly in the fields of automobile parts, building materials, and mechanical parts, parts are increasingly being made of plastic for reasons such as weight reduction, cost reduction, and aesthetics. Fiber-reinforced resins are commonly used. In general, the method for manufacturing injection molded articles made of propylene polymer resin reinforced with glass fibers is to blend glass fibers into resin pellets or powder, melt-knead them, and then add glass fibers with a particle size of about 1 to 3 mm. A method has been adopted in which the pellets are made into pellets and then injection molded. However, this method has the disadvantage that it undergoes thermal history at least twice before obtaining a molded product, which causes a decrease in mechanical strength and poor appearance due to thermal deterioration, and also complicates the manufacturing process. There is. In order to improve this drawback, studies have been made to improve the stabilizer, the length of the glass fibers, the sizing agent, etc., but this has not resulted in a fully satisfactory result. In addition, some methods involve direct injection molding of propylene polymer resin powder together with glass fiber, but conventional resin powder has a particle size of several micrometers.
It is wide at ~1500μ, has poor biting from the molding machine's hopper to the screw, requires a pushing machine (for example, a screw type), and has the disadvantages of large variations in the weight of the molded product. It was hot. The present invention has been made with the aim of eliminating these drawbacks, and takes advantage of the advantages of direct injection molding of powder, and also solves the problem of the dispersion in product weight caused by the inconsistency in the resin of glass fibers. This was reached as a result of extensive research, based on the idea that this is due to poor dispersion. That is, in the present invention, (a) the particle size is substantially 50~
100 parts by weight of a propylene polymer resin powder having a particle size of 800 μ and 70% by weight of the powder is from 200 to 500 μ;
(b) 5 to 100 parts by weight of glass fiber and (c) carbon number of 8 to 100 parts by weight
This is a method for producing an injection molded article, which comprises blending 0.01 to 1 part by weight of a fatty acid or a derivative thereof, mixing the powder in an unmolten state, and then injection molding. According to the method of the present invention, not only the above-mentioned drawbacks are solved, but also other effects such as shortening the plasticization time of the resin powder are achieved, and it is possible to obtain a molded article of high quality in a very rational manner. can. The propylene polymer resin powder, which is the component (a) used in the present invention, has a particle size of substantially 50 to 800 μm.
, and 70% by weight of it is from 200 to 500μ, consisting of propylene homopolymer, majority of the weight propylene and other α-olefins (ethylene, butene-1, hexene-1,4-methylpentene- 1
etc.), or these polymers are graft-modified with unsaturated aromatic monomers, unsaturated organic acids or their derivatives, unsaturated halogenated monomers, etc., or combinations of these polymers. A mixture etc. is suitable. Among these, those having an average particle size of 300 to 400 μ are preferable. Since such resin powder has a uniform particle size, it can be easily bited into the screw from the hopper of the molding machine, making a pusher unnecessary. In addition, as the glass fiber used in the present invention as the component (b), commercially available products can be used as appropriate, but the length is suitably about 1 to 10 mm, especially 5 mm.
It is best to have a uniform diameter of ~7mm. Furthermore, the fatty acid or derivative thereof which is the component (c) used in the present invention has 8 to 30 carbon atoms, and specifically includes capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Acids, fatty acids of cerotic acid, or their esters, metal salts, amides, etc. Among these, mono- to trivalent metal salts are preferred. The blending ratio of these three components is 5 to 100 parts by weight, preferably 10 parts by weight of component (b) to 100 parts by weight of component (a).
~50 parts by weight and component (c) 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weight. In the present invention, adhesive components, stabilizers, colorants, inorganic fillers, etc. can also be blended in addition to these components. In particular, the mechanical strength of the molded article can be significantly improved by incorporating a small amount of a polymer containing a polar group such as a glycidyl group, a carbonyl group, or a silanol group as an adhesive component. Next, these components are blended, and while the component (a) is not melted, they are mixed using an existing method such as a V-blender or tumbler, but the order in which the components are blended is not particularly limited. For example, component (c) may be added while mixing components (a) and (b). This is then injection molded. Molding conditions are not particularly limited, but preferably the screw back pressure is increased and the molding temperature is also raised. Example: As polypropylene powder, manufactured by Mitsubishi Yuka Co., Ltd.
BC4Q (substantive particle size 50-800μ, 70% by weight of 200-500μ, average particle size 350μ, melt flow rate 5.5g/10 min) and BC4P (substantive particle size 1 ~1500μ, and 70% by weight of it is 70~1000μ, average particle size 500μ, melt flow rate 5.5g/10 min). Glass fiber (length 6mm, number of bundles 1000) is added to 100 parts by weight of each of two types of resin. 25 parts by weight of each of MA411 (manufactured by Asahi Fiber Glass Co., Ltd.) were added and mixed for 5 minutes in a V-tumbler. During this mixing, 0.25 parts by weight of calcium stearate was added and mixed without being added. This mixture was molded using an inline screw injection molding machine (N100B) manufactured by Japan Steel Works, at a molding temperature of 260°C, an injection pressure of 500 kg/cm ² , and an injection time of 15 seconds.
Injection molding was performed with a cooling time of 20 seconds and a screw back pressure of 50 kg/cm ² to form test pieces with a wall thickness of 2 mm and a length x width of 125 x 35 mm. In this molding, when plasticizing the resin before injection, an amount corresponding to the amount of injected resin (50g) is
The limit switch was set so that the screw would move back by a certain amount, and the time required for the screw to move back from the position before plasticization to this limit switch was measured and evaluated as the plasticization time. However, the screw rotation speed is 70rpm
It is. The shorter the plasticization time, the faster the next injection process can be carried out. In addition, BC4P, which is one of the polypropylene powders used above, is mixed with glass fiber and calcium stearate in the same amount as above,
Pellets obtained by granulation at 240°C using a 100 mm diameter single screw extruder were also injection molded in the same manner. The test piece thus obtained was evaluated in the following items. (1) Dispersion state of glass fibers The state of dispersion of glass fibers was visually determined by looking at both the front and back surfaces of the test piece. The criteria for evaluation was to count the number of cases in which the bundled glass fibers remained completely white without unraveling, and the following four ranks were determined. Excellent: 0 pieces Good: 1 piece acceptable: 2 to 3 pieces Impossible: 4 pieces or more (2) Weight variation of molded products As described above, 20 test pieces were molded for each sample, and the standard deviation of their weights was calculated. I asked for it. (3) Melt flow rate (MFR) Measured at 230℃ and a load of 2.16Kg in accordance with JIS-K7210. These results are shown in Table 1. 【table】

[Brief explanation of drawings]

FIG. 1 is a photographic drawing showing the surface state of glass fibers in the mixture in an unmolten state in Example 1, and FIGS. 2 and 3 are similar photographs in Comparative Example 3 and Comparative Example 2, respectively. The drawings are photographs, and the magnification is 10x.

Claims (1)

[Claims] 1 (a) The particle size is substantially 50 to 800μ, and 70μ
To 100 parts by weight of propylene polymer resin powder whose weight percentage is 200 to 500μ, (b) 5 to 50% of glass fiber is added.
100 parts by weight and (c) 0.01 to 1 part by weight of a fatty acid having 8 to 30 carbon atoms or a derivative thereof are mixed in an unmolten state of the powder, and then injection molded. Method.