Resin plasticization injection device and manufacturing method for resin molded product

Abstract

To effectively remove impurities from a resin and a reinforcing fiber and to facilitate good dispersion of the reinforcing fiber.SOLUTION: A resin plasticizing injection device includes: a plasticizing cylinder with a vent opening formed on an upper surface of a middle section for introducing continuous reinforcing fibers into an interior; continuous fiber supply means arranged above the vent opening for continuously supplying the continuous reinforcing fibers; a plasma treatment part disposed between the vent opening and the continuous fiber supply means, for subjecting the continuous reinforcing fibers to a plasma treatment before they are introduced into the vent opening; an injection cylinder connected to a resin discharge port of the plasticizing cylinder via a backflow prevention mechanism; and a gas ejection nozzle coupled to a tip of the injection cylinder.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin plasticization injection device and a method for manufacturing a resin molded product. [Background technology]

[0002] There is a technique for adding reinforcing fibers such as glass fibers and carbon fibers to resin in order to increase the strength of resin molded products. For example, the following patent document describes an injection molding machine in which reinforcing fibers are supplied from a vent formed in the middle of a heating cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-166712 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the injection molding machine of the above-mentioned patent document has a problem that impurities remain in the resin or reinforcing fibers and the dispersion of the reinforcing fibers is insufficient, making it difficult to obtain high-quality molded products. In response to this, the present invention aims to provide a resin plasticization injection device and a manufacturing method for resin molded products that can effectively remove impurities from the resin or reinforcing fibers and also disperse the reinforcing fibers well. [Means for solving the problem]

[0005] The resin plasticization injection device according to the present invention is characterized in that it comprises a plasticization cylinder having a vent opening formed on the upper surface of the middle part of the peripheral wall for introducing reinforcing continuous fibers therein, a continuous fiber supplying means arranged above the vent opening and continuously supplying the reinforcing continuous fibers, a plasma treatment unit arranged between the vent opening and the continuous fiber supplying means and performing plasma treatment on the reinforcing continuous fibers before they are introduced into the vent opening, an injection cylinder connected to the resin outlet of the plasticization cylinder via a backflow prevention mechanism, and a gas emission nozzle connected to the tip of the injection cylinder.

[0006] Furthermore, the manufacturing method for resin molded products according to the present invention is a manufacturing method for resin molded products using the resin plasticization injection device, and is characterized by including the steps of: supplying a thermoplastic resin raw material containing reinforcing short fibers and having a predetermined moisture absorption state to the raw material inlet of the plasticization cylinder; supplying reinforcing continuous fibers to the vent opening; bringing the moisture in the resin to a subcritical or supercritical state in the injection cylinder; and releasing the moisture in the subcritical or supercritical state from the gas release nozzle. Effect of the Invention

[0007] According to the present invention, impurities and the like can be effectively removed from the resin and reinforcing fibers, and the reinforcing fibers can also be dispersed well. [Brief description of the drawings]

[0008] [Figure 1] 1 is a vertical sectional view of a resin plasticization injection device according to the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view of a resin raw material. [Diagram 3] FIG. 1 is a flow diagram of a method for producing a resin molded product according to the present invention. [Figure 4] FIG. 2 is a longitudinal sectional view of a resin molded product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As shown in Fig. 1, the resin plasticization injection device A according to the present invention is a so-called screw-plunger type device, and has a basic configuration in which a plasticization cylinder B with a screw 10 inside is connected to an injection cylinder C with a plunger 11 inside. The injection cylinder C and a mold D can be connected and separated.

[0010] The plasticizing cylinder B has a vent opening 12 formed on the upper surface of the middle part of the peripheral wall for introducing reinforcing continuous fibers into the interior, and an electric heating coil 13 is wound around the peripheral wall and is further covered with a heat insulating material 14. A hopper 15 for storing the resin raw material P (pellets) is provided at the base of the plasticizing cylinder B.

[0011] The screw 10 installed inside the plasticizing cylinder B transports the resin raw material P and the plasticized resin forward, and is connected to its base with a motor device 16 for rotating the screw 10 and a hydraulic device 17 for moving the screw 10 forward and backward. The shaft diameter and the shape of the helical teeth of the screw 10 differ depending on the location.

[0012] The continuous fiber supplying means 18 is disposed above the vent opening 12. In this example, a bobbin is used around which the reinforcing continuous fiber is wound, but a yarn path and the like are omitted. The reinforcing continuous fiber is, for example, carbon fiber or glass fiber, but is not limited thereto.

[0013] The plasma treatment unit 19 is disposed on the fiber transport path between the vent opening 12 and the continuous fiber supply means 18, and is composed of a treatment chamber 19a through which the reinforcing continuous fibers are passed, a gas supply unit 19b, and a power supply unit 19c. This plasma treatment can be performed at room temperature and pressure, and oxygen, hydrogen, nitrogen, argon, ammonia, etc. can be used as the gas. The plasma treatment improves hydrophilicity and has the effect of removing sizing agents (epoxy resins) that bundle the fibers of the reinforcing continuous fibers.

[0014] The backflow prevention mechanism 20 is intended to prevent the resin from flowing back into the plasticizing cylinder B when it is injected from the injection cylinder C. The backflow prevention mechanism 20 maintains a certain gap at the resin discharge port formed at the tip of the plasticizing cylinder B while the resin is being sent from the plasticizing cylinder B to the injection cylinder C, while completely closing the resin discharge port of the plasticizing cylinder B while the resin is being injected from the injection cylinder C. This makes it possible to suppress excessive breakage of the reinforcing continuous fibers.

[0015] As a specific example of this, the backflow prevention mechanism 20 may be configured so that, for example, a screw 10 installed inside the plasticizing cylinder B is moved back and forth, causing the tip of the screw 10 to close and open the resin discharge port of the plasticizing cylinder B.

[0016] The injection cylinder C is connected to the resin discharge port of the plasticizing cylinder B via a backflow prevention mechanism 20, and is provided at its tip with a gas discharge nozzle 21. An electric heating coil 13 is wound around the peripheral wall of the injection cylinder C, and is further covered with a heat insulating material 14.

[0017] The plunger 11 installed inside the injection cylinder C is used to pressurize and inject the resin inside the injection cylinder C, and a hydraulic device 17 is connected to its base for moving the plunger 11 forward and backward.

[0018] The gas emission nozzle 21 is a special nozzle configured to increase the flow rate of the resin after plasticization and to gasify and remove moisture and other substances in the resin.

[0019] Next, a method for producing a resin molded product using the plasticizing injection device A will be described. This manufacturing method is aimed at producing a resin molded product containing reinforcing long fibers and reinforcing short fibers, and has the following features. That is, the manufacturing method is characterized by including the steps of supplying a resin raw material P containing short reinforcing fibers and having a predetermined moisture absorption state to the raw material inlet of the plasticization cylinder B, supplying continuous reinforcing fibers to the vent opening 12, bringing the moisture in the resin to a subcritical or supercritical state in a portion of the injection cylinder C including the gas emission nozzle 21, and releasing the moisture from the gas emission nozzle 21.

[0020] Here, the production method will be further explained assuming that the resin raw material P is polypropylene. As shown in Fig. 2, the resin raw material P is a mixture of a base material M and short reinforcing fibers S, and is in a predetermined moisture-absorbing state. The short reinforcing fibers are assumed to be carbon fibers with an average diameter of 1μ and a length of about 10 to 100μ, and the moisture-absorbing state is assumed to be about 0.02%, which is approximately equal to the water absorption rate. If the resin raw material P is normally stored for a certain period of time or more, it will reach a moisture-absorbing state approximately equal to the water absorption rate, so in the present invention, the resin raw material P may be used as is without any special drying treatment.

[0021] In the plasticization cylinder B, the temperature and pressure are controlled for each part, and by rotating the screw 10, the resin raw material P stored in the hopper 15 is introduced into the cylinder and transported to the tip side while various processes such as plasticization, venting (gas release), and feeding of continuous reinforcing fibers are performed. The screw 10 may be rotated at the timing when the resin is transported and filled from the plasticization cylinder B into the injection cylinder C, and at that time, the backflow prevention mechanism 20 is in an open state by setting the screw 10 to the retracted position. At this time, the plunger 11 of the injection cylinder C may be gradually retracted in accordance with the filling of the resin.

[0022] To explain in more detail, in the plasticization cylinder B, in the region from the resin inlet 22 to the vent opening 12, the temperature is raised stepwise from 100°C to 240°C for plasticization and pressurization, and while plasticizing, the pressure is also raised stepwise to allow air to escape to the resin inlet 22. The temperature is controlled by controlling the electric heating coil 13, and the pressure is controlled in advance by controlling the shaft diameter and pitch of the screw 10. At the vent opening 12, the temperature is kept at 280°C, while the pressure is reduced to prevent the resin from spouting. Volatile impurities, air, moisture, etc. are exhausted from the vent opening 12, and at the same time, the reinforcing continuous fibers are introduced into the cylinder. The reinforcing continuous fibers may be made of the same material as the reinforcing short fibers or a different material. From the viewpoint of strength, the reinforcing continuous fibers are preferably made of a larger diameter than the reinforcing short fibers, for example, a diameter of 10 to 20 μm. Here, the reinforcing continuous fibers have already been subjected to plasma treatment to remove a part of the sizing agent. The reinforcing continuous fibers are repeatedly cut by the rotation of the screw 10 while being kneaded with the resin, and become long fibers with an average length of about 0.5 mm. In the region ahead of the vent opening 12, the temperature is lowered to 220° C. to prevent carbonization of the resin, while the pressure is increased to prevent air from entering through the vent opening 12. When the transport and filling of the resin from the plasticizing cylinder B to the injection cylinder C is completed, the screw 10 is advanced to close the backflow prevention mechanism 20.

[0023] On the other hand, it is preferable to control the temperature of the injection cylinder C differently between the cylinder body and the gas emission nozzle 21. That is, it is preferable to set the cylinder body at 220°C to prevent carbonization of the resin, and set the gas emission nozzle 21 at 200°C to be suitable for releasing moisture. When the resin is injected into the mold D, the plunger 11 is advanced, which strongly pressurizes the resin and causes the water in the resin to go into a subcritical state. Subcritical water exhibits higher fluidity and solubility than normal water. Specifically, it penetrates well into the gaps between the resin and the short and long reinforcing fibers, promoting dispersion, and also decomposing and dissolving the remaining sizing agent. When the sizing agent is removed, the bonding state between the resin and the short and long reinforcing fibers in the resin molded product is also improved. The resin containing the moisture in a subcritical state is accelerated and decompressed just before being injected into the mold D, that is, when passing through the gas emission nozzle 21, and the moisture is emitted from the gas emission nozzle 21 to the outside.

[0024] As shown in Figure 3, the steps of the manufacturing method can be summarized as follows: The steps shown here are a chronological order of the processing of the same resin raw material, and in reality, some steps are carried out simultaneously in parallel. Step S1 is a process of putting resin raw material into a plasticizing cylinder. Step S2 is a process of plasticizing and pressurizing the resin raw material. Step S3 is a process of decompressing and venting the resin. Step S4 is a process of subjecting the reinforcing continuous fibers to plasma treatment. Step S5 is a process of feeding the plasma-treated continuous reinforcing fibers into a plasticizing cylinder. Step S6 is a process of pressurizing the resin. Step S7 is a process of transporting and filling the resin from the plasticizing cylinder into the injection cylinder. After this process, the backflow prevention mechanism is closed. Step S8 is a process of pressurizing the resin to bring the water in the resin into a subcritical state. Step S9 is a process of discharging moisture from the gas discharging nozzle. Step S10 is a process for injecting resin into the mold.

[0025] Finally, a specific description will be given of a screw-shaped resin molded product according to the present invention. As shown in Fig. 4, the resin molded product X according to the present invention has reinforcing long fibers L and short fibers S dispersed in a base material M. More specifically, the reinforcing long fibers L are dispersed mainly in the thick parts of the molded product, whereas the reinforcing short fibers S tend to be dispersed uniformly throughout the molded product, including in its fine details. This makes the molded product extremely strong, with high resistance to bending and breaking as a whole, and with its fine details also being less likely to break.

[0026] In the above explanation, polypropylene has been used as an example of the type of resin, but the present invention can also be applied to thermoplastic resins such as polyethylene, ABS, acrylic, polyamide, polycarbonate, polyphenylene sulfide, polyether ether ketone, polybutylene terephthalate, etc. In addition, the moisture in the resin was made subcritical in the injection cylinder, but depending on the type of resin, it may be possible to make it supercritical, in which case it is believed that the sizing agent will be removed more effectively and the reinforcing fibers will be dispersed more effectively. [Explanation of symbols]

[0027] A Resin plasticization injection equipment B Plasticizing cylinder C Injection cylinder 12 Vent opening 18 Continuous fiber supply means 19 Plasma processing section 20 Backflow prevention mechanism 21 Gas discharge nozzle

Claims

1. a plasticizing cylinder having a vent opening formed on an upper surface of a middle portion of a peripheral wall thereof for introducing continuous reinforcing fibers therein; a continuous fiber supplying means arranged above the vent opening and configured to continuously supply the continuous reinforcing fibers; a plasma treatment section disposed between the vent opening and the continuous fiber supply means, which performs a plasma treatment on the reinforcing continuous fibers before they are introduced into the vent opening; an injection cylinder connected to a resin discharge port of the plasticizing cylinder via a backflow prevention mechanism; a gas ejection nozzle coupled to the tip of the injection cylinder; A resin plasticization injection device comprising:

2. In claim 1, The backflow prevention mechanism is configured so that the tip of a screw installed inside the plasticizing cylinder moves back and forth to close and open a resin discharge port formed at the tip of the plasticizing cylinder.

3. A method for producing a resin molded product using the resin plasticization injection device according to claim 1 or 2, supplying a thermoplastic resin raw material containing short reinforcing fibers and having a predetermined moisture absorption state to a raw material inlet of the plasticizing cylinder; providing continuous reinforcing fibers to the vent opening; A step of bringing the water in the resin into a subcritical or supercritical state in the injection cylinder; and releasing the water in a subcritical or supercritical state from the gas release nozzle.

4. In claim 3, A method for producing a resin molding, wherein the reinforcing continuous fibers and the reinforcing short fibers differ in at least thickness.

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