Fiber reinforcement injection molding product and injection molding method thereof

Abstract

The invention relates to an injection molding product, in particular to a thermoplastic resin thin-wall product which has fiber content ranging from 10% to 30% and the injection molding method thereof. The product of the invention has a wall thickness ranging from 1.5mm to 2.5mm, and one or more than one surface of the product is provided with a layer of resin surface layer free from fiber, which has a thickness ranging from 5 mu to 15 mu; the product is composed of thermoplastic resin, thermoplastic fiber and nitrogen or carbon dioxide and the raw materials are calculated according to proportion by weight, wherein the content of the thermoplastic resin ranges from 69.95% to 89.95%, the content of the fiber ranges from 10% to 30%, the rest is nitrogen or carbon dioxide. The product and the method of the invention have the advantages of adopting supercritical nitrogen or carbon dioxide as plasticizer, further improving flowability by raising the surface temperature of the tool cavity before injection and obtaining lighter and thinner product by cooling the surface temperature of the tool cavity to relatively low temperature after the completion of injection; in addition, the product features fine apparent mass, high strength and high dimensional stability.

Description

technical field [0001] The invention relates to an injection molding product, in particular to a thermoplastic resin thin-walled product with a fiber content of 10-30% and an injection molding method. Background technique [0002] Thermoplastic products have been used more and more widely in various fields, especially in the fields of automobiles, electronics / electrical appliances, office equipment, and medical treatment. As a result, customers expect products to be thinner and lighter, and at the same time have higher and higher requirements for appearance quality, dimensional accuracy and stability. Adding a certain amount of fiber, such as glass fiber, plant fiber, etc., to thermoplastic resin can improve the strength, heat resistance and heat distortion temperature of the product, reduce shrinkage, etc., so that when the same strength is achieved, the product’s The wall thickness is reduced, thereby reducing the amount of thermoplastic resin used, and reducing the quali...

AI Technical Summary

Problems solved by technology

However, the fluidity of thermoplastic resin materials containing fibers is reduced when injection filling the cavity, and there are problems such as insufficient filling, fiber exposure, large warping deformation, and subsequent processing difficulties during injection molding.

Due to these problems, fiber-reinforced thermoplastic products are limited in the development of thin-walled products

In the supercritical state (nitrogen: temperature higher than -147°C and pressure higher than 3.4MPa; carbon dioxide: temperature higher than 31°C and pressure higher than 7.1MPa) a certain amount of nitrogen or carbon dioxide can be completely dissolved in the molten resin to make the molten resin Improvement of fluidity, such as the patent ZL01801653.7 "Thermoplastic Resin Injection Molding Method" authorized on February 16, 2005 discloses a thermoplastic resin injection molding method, specifically dissolving carbon dioxide that can fully improve fluidity in In the molten polymer, the fluidity of the molten polymer is thus greatly improved, and molded products are obtained at the same time. The products produced according to the patented method are non-foaming products, but the surface quality of the products is not suitable for products with high appearance requirements; and For example, the US patent application US2008 / 0226892A1 published on September 18, 2008 discloses a method of using supercritical fluid additives to reduce the viscosity of polymers to reduce damage to the formation of reinforcing fibers during injection, but this fiber reinforcement There are foam marks and floating fibers on the surface of the product

However, purely increasing the molding temperature of the mold will lead to too long molding cycle, and the uneven thermal shrinkage after demoulding will lead to deformation and warpage.

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