Injection molding method, screw, and injection molding machine

Abstract

Provided is an injection molding method that can resolve uneven reinforcing fiber distribution without applying an excessive shearing force on the reinforcing fibers. In the injection molding method for fiber-reinforced resin according to the present invention: a resin-accumulating area is provided on the downstream side of the injection completion position inside a heating cylinder (201); in the injection step of a preceding cycle, an injection pressure is applied on molten resin (Mr) occupying the resin-accumulating area; and in the plasticizing step of the following cycle, a shearing force is applied on the molten resin (Mr) that is occupying the resin-accumulating area. Applying a high injection pressure on the molten resin (Mr) occupying the resin-accumulating area impregnates molten resin (Mr) into clumped reinforcing fibers (F). Subsequently applying a shearing force in the plasticizing step of the following cycle promotes dispersion of the reinforcing fibers (F).

Description

technical field [0001] The present invention relates to injection molding of resin containing reinforcing fibers. Background technique [0002] Molded articles of fiber-reinforced resins whose strength is increased by containing reinforcing fibers are used in various applications. As a method of obtaining the molded product by injection molding, there is known a method of melting a thermoplastic resin by rotation of a screw in a cylinder constituting a plasticizing device, mixing or kneading fibers therein, and then injecting it into a mold of an injection molding machine . [0003] In order to obtain the effect of improving the strength by the reinforcing fibers, it is desirable that the reinforcing fibers be uniformly dispersed in the resin. In order to achieve uniform dispersion, it is sufficient to increase the shearing force applied to the reinforcing fibers by making the mixing conditions strict, but too strong a shearing force may cause cutting of the reinforcing fi...

AI Technical Summary

Problems solved by technology

In order to achieve uniform dispersion, it is sufficient to increase the shearing force applied to the reinforcing fibers by making the mixing conditions strict, but excessive shearing force will lead to cutting of the reinforcing fibers

In this way, the fiber length after molding is greatly shortened compared with the original fiber length, and there is a possibility that the obtained molded product cannot satisfy desired properties (Patent Document 1)

Therefore, it is necessary to select injection molding conditions that weaken the shear force to prevent fiber breakage during mixing, but in this way, the reinforcing fibers cannot be uniformly dispersed in the fiber-reinforced resin, resulting in uneven distribution.

In addition, in order to contribute to the uniform dispersion of reinforcing fibers, there are also cases where a mechanism (feeder) for forcibly supplying reinforcing fibers into the cylinder is provided (for example, Patent Document 2), but this is not enough to dissipate the mass of reinforcing fibers eliminate

In particular, when the content of reinforcing fibers is as high as 10% or more, it becomes difficult to uniformly disperse the reinforcing fibers in the resin

Images