JP2001260173A - Sandwich molded article and method for producing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sandwich molded article wherein a core material is not exposed on the surface and the quality of appearance can be prevented from being lowered and a method for producing it. SOLUTION: In an apparatus 11 for injection molding of the sandwich molded article, after injection of a skin material 16 and a core material 14 is completed, a screw 24 of a core material feeding part 15 is retreated. Then, the core material 14 is drawn into a core material flow path 21 from a nozzle 19 and a skin material flow path 22. As the result, it is possible to prevent a core layer with a different color from a skin layer from being exposed on the surface of the sandwich molded article obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has prevented the exposure of a core material on the surface of a skin layer in a sandwich molded article molded by an injection molding method so as to have a core layer and a skin layer covering the core layer. The present invention relates to a sandwich molded product and a method for producing the same.

[0002]

2. Description of the Related Art In general, a sandwich molded product is formed into a sandwich by a core layer and a skin layer covering the core layer. An injection molding apparatus used for molding a sandwich molded article includes a cylinder having a heater, and a nozzle is provided at a tip of the cylinder. A plunger is provided in the cylinder, and the plunger is provided so as to be able to advance and retreat in the cylinder.

[0003] Outside the cylinder, a core material heated and melted with a thermoplastic resin is accommodated, and a core material supply section for supplying the core material into the cylinder is provided. And a skin material supply unit that accommodates different skin materials and supplies the skin material into the cylinder.

[0004] A molding die is provided in front of the cylinder. The molding die includes a fixed die and a movable die. The fixed die has a cavity formed therein, and a gate communicates with the cavity. The movable mold moves relative to the fixed mold so that the opening of the cavity can be opened and closed.

[0005] In order to form a sandwich molded product using the above-mentioned injection molding apparatus, first, a closed molding die is arranged in front of a cylinder. Next, the skin material is supplied from the skin material supply unit into the cylinder, the plunger is retracted to open the nozzle, and the skin material is injected from the nozzle into the cavity through the gate.
Next, the core material is supplied from the core material supply unit into the cylinder. Then, the core material is injected from the nozzle into the cavity through the gate. Then, the core material is injected so as to be included in the skin material.

[0006] Subsequently, after the injection of the skin material and the core material is completed, the skin material and the core material are weighed and each of them is supplied into the cylinder in order to perform the molding operation of the next sandwich molded product. The plunger is advanced to close the nozzle with the plunger. At this time, for example, when the core material remains in the nozzle, when the skin material is injected into the cavity at the time of molding the next sandwich molded product, the core material leaks into the cavity and is obtained by the molding. The core material different in color from the skin material is exposed on the surface of the sandwich molded product.

For this reason, the following method has been adopted to prevent the core material from leaking. As a method,
First, before the injection of the skin material is completed, the injection holding timer of the core material is artificially turned off to complete the injection of the core material. Then, the core material flows backward in the cylinder from the nozzle by the holding pressure of the skin material during injection. As a result, the core material remains in the nozzle and is prevented from leaking into the cavity at the time of forming the next sandwich molded product.

[0008] Finally, after the skin material and the core material in the molding die are cured, the mold is opened to form a sandwich molded product in which the core layer is covered with the skin layer.

[0009]

However, in the conventional method of manufacturing a sandwich molded product, the timing of cutting off the core material injection holding timer and completing the injection is left to the discretion of the operator of the injection molding apparatus. It was done artificially. For this reason, the timing at which the core material injection holding timer is turned off differs for each operator, and the reverse flow rate of the core material cannot be constantly and accurately controlled. As a result, the core material cannot be reliably backflowed so that the core material does not remain in the nozzle, and the core material is exposed on the surface of the sandwich molded product, particularly near the gate, and the appearance quality is reduced. There was a problem.

The present invention has been made by paying attention to such problems existing in the prior art. It is an object of the present invention to provide a sandwich molded product that does not expose a core material on the surface and can prevent a deterioration in appearance quality, and a method for manufacturing the same.

[0011]

In order to achieve the above object, a method for producing a sandwich molded article according to the present invention is characterized in that a core layer obtained by curing a core material obtained by heating and melting a thermoplastic resin is used. A method for producing a sandwich molded product in which a skin material obtained by heating and melting a thermoplastic resin is covered with a cured skin layer and molded into a cross-section sandwich, wherein the core material and the skin material are formed in a concave portion of a molding die. Provided with a nozzle for injecting the skin material by an extruding member, a skin material supplying section having a skin material extruding member for accommodating the skin material and supplying the skin material into the cylinder, and the core material And a core material supply unit having a core material pushing member for supplying or drawing the core material into or from the cylinder. The skin material and the core material to a core material is coated by injection into molding the recess by the skin material,
After the injection of the skin material and the core material into the molding recess is completed, the core material extruding member of the core material supply unit is retracted to make the inside of the core material supply unit a negative pressure, and a predetermined amount of the nozzle material enters the cylinder from the nozzle. The core material is drawn in.

[0012] A sandwich molded article according to the second aspect of the present invention is obtained by the method for producing a sandwich molded article according to the first aspect.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention embodied in a sandwich molded product and a method for manufacturing the same will be described in detail with reference to the drawings.

[0014] The sandwich molded product is obtained by curing a core material prepared by heating and melting a thermoplastic resin, and covering the core layer with a cured skin layer prepared by heating and melting the thermoplastic resin. It is formed in a sandwich shape in cross section.

By changing the material constituting the core layer, the sandwich molded article can be molded according to its use. For example, by using a material (for example, calcium carbonate, metal powder, or the like) having a higher specific gravity than the thermoplastic resin for the core layer, a sense of mass can be imparted to the sandwich molded product. By using a material containing a thermoplastic resin and a reinforcing material (for example, a resin containing glass fiber) for the core layer, the rigidity of the sandwich molded product can be improved.

By foaming the core layer with a foaming agent, it is possible to obtain a sandwich molded product having a sound absorbing effect, a soft feeling, and a cushioning property. It is possible to reduce the thickness and prevent sinking of the thick part. In addition, by using a recycled material for the core layer, it is possible to contribute to a reduction in manufacturing cost and industrial waste, and to use an electromagnetic wave shielding material for the core layer, it is possible to impart electromagnetic wave shielding properties.

Next, the injection molding apparatus 11 for molding the sandwich molded product will be described. As shown in FIG. 1, the injection molding device 11 is installed horizontally. The injection molding apparatus 11 includes a cylindrical cylinder 12, a plunger 13 as an extruding member disposed so as to be able to advance and retreat inside the cylinder 12, and a core material 14.
And a skin material supply unit 17 for supplying the skin material 16 into the cylinder 12.

First, the cylinder 12 will be described.
A band heater (not shown) is wound around the outer periphery of the cylinder 12, and the inside of the cylinder 12 is heated by the heater. The tip of the cylinder 12 (FIG. 1)
(A left end), a cylinder head 18 is provided, and a nozzle 19 communicating with the inside of the cylinder 12 is formed through the cylinder head 18.

The plunger 13 disposed in the cylinder 12 is connected to plunger driving means (not shown) for moving the plunger 13 forward and backward. The plunger 13 has a substantially cylindrical outer plunger 13a.
And an inner plunger 13b provided in the outer plunger 13a. A discharge port 20 communicating with the inside of the outer plunger 13a is formed through the center of the distal end portion of the outer plunger 13a. The inner plunger 13b is connected to the plunger driving means, and the plunger driving means can move in and out of the outer plunger 13a. The outer plunger 13a moves forward and backward in conjunction with the movement of the inner plunger 13b.

A core material flow path 21 is formed between the inner peripheral surface at the distal end of the outer plunger 13a and the outer peripheral surface at the distal end of the inner plunger 13b. A skin material flow path 22 is formed between the jar 13a and the outer peripheral surface of the tip.

When the inner plunger 13b advances inside the outer plunger 13a, the discharge port 20 of the outer plunger 13a can be closed by the tip of the inner plunger 13b. Further, the inner plunger 13b
When the outer plunger 13a moves forward in the cylinder 12 with the discharge port 20 closed, the nozzle 19 can be closed by the tip of the outer plunger 13a.

Next, the core material supply unit 15 will be described.
Has a substantially cylindrical shape, and is connected to the cylinder 12 via a first connecting portion 23 having a cylindrical shape. A band heater (not shown) is wound around the outer periphery of the core material supply unit 15 and the first connection unit 23. A core material 14 is accommodated in the core material supply unit 15, and a recycled material is used as the core material 14 in this embodiment.

Further, a screw 24 as a core material pushing member is disposed in the core material supply section 15, and the screw 24 is connected to a screw driving mechanism (not shown), and the screw 24 is driven by the screw driving mechanism. The inside of the material supply unit 15 can be moved forward and backward.
A core material supply path 25 is formed in the first connection part 23, and the core material supply path 25 communicates with the core material flow path 21 in the cylinder 12.

When the screw 24 is advanced,
The core material 14 accommodated in the core material supply unit 15 is extruded from the core material supply unit 15, passes through the core material supply path 25, and is supplied into the core material flow path 21.

Next, the skin material supply section 17 will be described. The skin material supply section 17 disposed on the rear side of the cylinder 12 has a substantially cylindrical shape, and is provided with a cylinder through a second connecting portion 26 having a cylindrical shape. 12 is connected. Skin material supply unit 1
A band heater (not shown) is wound around the outer periphery of the seventh connection portion 26 and the second connection portion 26. A skin material 16 is accommodated in the skin material supply unit 17, and in this embodiment, a polypropylene resin is used as the skin material 16 having a different color from the core material 14.

Further, a screw 24 as a skin material pushing member is provided in the skin material supply section 17, and the screw 24 is connected to the screw driving mechanism.
Numeral 4 allows the skin material supply unit 17 to move forward and backward. A skin material supply path 27 is formed in the second connection part 26, and the skin material supply path 27 communicates with the skin material flow path 22 in the cylinder 12.

When the screw 24 is advanced,
The skin material 16 accommodated in the skin material supply unit 17 is extruded from the skin material supply unit 17 to form a skin material supply path 27.
And is supplied into the skin material flow path 22.

A molding die 28 is provided in front of the cylinder 12. This molding die 28
It comprises a fixed mold 28a and a movable mold 28b movably provided with respect to the fixed mold 28a. Fixed type 2
8a, a cavity 30 is formed as a molding concave portion corresponding to the shape of the sandwich molded product, and a gate 31 communicating with the cavity 30 is formed.
The movable mold 28b opens and closes the cavity 30.

When a sandwich molded article is molded by using the injection molding apparatus 11 having the above configuration, first, as shown in FIG. 2, the movable mold 28b is moved in the direction of the fixed mold 28a to close the mold. Next, the outer plunger 13a and the inner plunger 13b are respectively advanced,
The nozzle 19 and the discharge port 20 are each closed.

Next, the core material 14 is placed in the core material supply section 15.
The skin material 16 is measured and supplied into the skin material supply unit 17 by a predetermined amount, and the core material 14 and the skin material 16 are heated and melted by a band heater. Subsequently, as shown in FIG. 3, the outer plunger 13a and the inner plunger 13b are retracted to make the nozzle 19 communicate with the skin material flow path 22 and the nozzle 19. At this time, the outer plunger 1 is moved by the inner plunger 13b.
The discharge port 3a is closed. Then, the screw 24 of the skin material supply unit 17 is advanced from the position indicated by the two-dot chain line to the position indicated by the solid line in FIG. 3 to extrude the skin material 16, and the skin material 16 is moved from the skin material supply path 27 to the skin material flow path 22. To supply. Then, the skin material 16 is injected into the cavity 30 from the skin material channel 22 through the nozzle 19 and then through the gate 31.

Next, as shown in FIG. 4, the inner plunger 1
3b is retracted to open the discharge port 20 of the outer plunger 13a. Then, the screw 24 of the core material supply unit 15 is advanced from the position shown by the two-dot chain line in FIG. 4 to the position shown by the solid line, and the core material 14 is extruded. To supply. Then, the core material 14 passes through the discharge port 20 from the core material flow path 21 and passes through the skin material 16 to the nozzle 19 and then to the gate 31.
And is injected into the cavity 30. The core material 14 and the skin material 16 are such that the core material 14 is the skin material 1.
6 and filled in the cavity 30.

After the screw 24 of the core material supply unit 15 and the screw 24 of the skin material supply unit 17 are advanced from the position shown by the two-dot chain line to the position shown by the solid line in FIG. 5, the injection of the core material 14 is completed. The injection of the skin material 16 is completed. Next, the screw 24 of the core material supply unit 15 is retracted from the position indicated by the two-dot chain line in FIG. 6 to the position indicated by the solid line. Then, the inside of the core material supply unit 15 is in a negative pressure state due to the retreat of the screw 24, and the core material 14 is drawn into the core material supply unit 15. Accordingly, the skin material 16 in the nozzle 19 is drawn into the discharge port 20 and further into the core material flow path 21.

The retracting amount of the skin material 16, that is, the retreat distance of the screw 24 in the core material supply section 15, is determined by the following. When the outer plunger 13a and the inner plunger 13b are advanced forward, the core material 14 19
It is set so that the amount does not leak into the inside. Specifically, in FIG. 6, the amount of retraction is 10 to 15 times the sum of the volume of the discharge port 20 of the outer plunger 13 a and the volume of the tapered portion of the core material flow path 21. It is preferable to set the retreat distance of the screw 24 so as to be as follows. Further, the retreat distance of the screw 24 in the core material supply unit 15 can be adjusted according to the volume of the gate 31 and the like.

Subsequently, the outer plunger 13a and the inner plunger 13b are advanced to close the nozzle 19 with the outer plunger 13a and the discharge port 20 with the inner plunger 13b. At this time, only the skin material 16 remaining in the nozzle 19 and the skin material flow path 22 is extruded into the cavity 30. Then, the core material 14 for the next sandwich molded product is measured and supplied to the core material supply unit 15 and the skin material 16 is measured and supplied to the skin material supply unit 17 respectively. Finally, core material 14
After the skin material 16 is cured, the mold is opened and the cavity 30 is opened.
Take out the sandwich molding from inside. As a result, a sandwich molded product in which the core material 14 is not exposed on the surface is obtained.

Also, when the skin material 16 is injected into the cavity 30 at the time of molding the next sandwich molded product, the surface of the sandwich molded product obtained without leaving the core material 14 in the skin material 16 can be obtained. The exposure of the core material 14 different in color from the skin material 16 is prevented.

The effects exerted by the above embodiment will be described below. After the injection of the skin material 16 and the core material 14 is completed, the screw 24 of the core material supply unit 15 is retracted to remove the core material 14.
Was drawn into the core material supply unit 15, and the skin material 16 in the nozzle 19 was drawn into the core material flow path 21. Therefore, it is possible to prevent the core material 14 remaining in the skin material 16 in the nozzle 19 and exposing the core layer different in color from the skin layer on the surface of the obtained sandwich molded product. Therefore, it is possible to prevent the appearance quality of the sandwich molded product from being deteriorated.

The amount of retraction of the core material 14 into the core material supply unit 15 can be adjusted by adjusting the amount of retreat of the screw 24 of the core material supply unit 15. Also,
After the injection of the skin material 16 and the core material 14 is completed, the screw 24 of the core material supply unit 15 is retracted. For this reason, it is possible to eliminate the variation in the amount of retraction without the amount of retraction of the core material 14 into the core material supply unit 15 being different for each operator of the injection molding apparatus 11. Therefore, it is possible to reliably prevent the core member 14 from remaining in the skin member 16 in the nozzle 19.

By changing the material used for the core layer, a sandwich molded product corresponding to a desired purpose can be formed. In particular, by using a recycled material for the core layer, it is possible to contribute to a reduction in manufacturing cost and a reduction in industrial waste.

The present embodiment can be embodied with the following modifications. The plunger 13 is used in place of the screw 24 as the core material extruding member and the skin material extruding member, and each plunger 13 is advanced in the core material supply unit 15 or the skin material supply unit 17 to make the core material 14 or the skin. Lumber 1
6 may be extruded. Further, a screw 24 may be used instead of the plunger 13 as an extruding member.

The colors of the skin material 16 and the core material 14 may be the same. Sandwich molded products include floor boards, buckets, troughs, transport containers, medical collection containers, pallets,
When molding a resin product such as a personal computer case, the injection molding apparatus 11 of the present embodiment may be used. Injection molding equipment 1
1 may be used as a vertical type.

Only the outer plunger 13a is provided as a plunger 13 in the cylinder 12, and a plunger driving means is connected to the outer plunger 13a so that the outer plunger 13a can advance and retreat in the cylinder 12. I do. Further, the inside of the outer plunger 13a is used as a core material flow path 21, and a skin material flow path 22 is formed between the outer peripheral surface of the outer plunger 13a and the inner peripheral surface of the cylinder 12. Then, the core material 14 and the skin material 16 may be injected into the cavity 30 by the reciprocation of the outer plunger 13a in the cylinder 12 to manufacture a sandwich molded product.

Further, the technical ideas that can be grasped from the above embodiment will be described below. The push-out member has a cylindrical shape, and comprises an outer plunger disposed so as to be able to advance and retreat inside the cylinder, and an inner plunger arranged so as to be able to advance and retreat inside the outer plunger. By allowing the skin material to be injected to the nozzle by retracting, the core material can be injected to the nozzle from within the outer plunger by retracting the inner plunger so that the skin material covers the core material at the nozzle. The method for producing a sandwich molded product according to claim 1. With this configuration, the sandwich layer can be reliably manufactured by covering the core layer with the skin layer.

[0043]

As described above in detail, according to the present invention, the following effects can be obtained. According to the method for manufacturing a sandwich molded product according to the first aspect of the present invention, it is possible to produce a sandwich molded product in which the core material is not exposed on the surface and a deterioration in appearance quality can be prevented.

According to the sandwich molded product of the second aspect of the present invention, the core material does not remain on the surface, and the appearance quality can be prevented from lowering.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing an injection molding apparatus according to an embodiment.

FIG. 2 is a plan sectional view showing a state where a plunger is advanced.

FIG. 3 is a plan sectional view showing a state in which an outer plunger is retracted.

FIG. 4 is a plan sectional view showing a state in which an inner plunger is retracted.

FIG. 5 is a plan sectional view showing a state where injection of the skin material and the core material is completed.

FIG. 6 is a plan sectional view showing a state in which a screw in a core material supply unit is retracted.

[Description of Signs] 11 ... Injection molding device, 12 ... Cylinder, 13 ... Plunger as extrusion member, 13a ... Outer plunger, 13b ... Inner plunger, 14 ... Core material,
15: Core material supply unit, 16: Skin material, 17: Skin material supply unit, 19: Nozzle, 24: Screw as a skin material extruding member and a core material extruding member, 28: Mold for molding as a mold, 30 ... cavities as molding recesses.

Claims (2)

[Claims] 1. A sandwich molding in which a core layer obtained by curing a core material obtained by heating and melting a thermoplastic resin is covered with a skin layer obtained by curing a skin material obtained by heating and melting a thermoplastic resin, and is formed into a cross-sectional sandwich shape. A method of manufacturing an article, comprising: a cylinder provided with a nozzle for injecting the core material and the skin material into a molding recess of a molding die by an extruding member; and accommodating the skin material, and placing the skin material inside the cylinder. Material supply unit having a skin material pushing member for supplying the core material, and a core material supplying unit having a core material pushing member for accommodating the core material and supplying or pulling the core material into the cylinder. Injecting the skin material and the core material into the molding concave portion so that the core material is covered with the skin material, using an injection molding apparatus comprising: And after the injection of the core material into the molding recess is completed, the core material pushing member of the core material supply unit is retracted to make the inside of the core material supply unit a negative pressure, and a predetermined amount of the core material from the nozzle into the cylinder. A method for producing a sandwich molded product, comprising: 2. A sandwich molded article obtained by the method for producing a sandwich molded article according to claim 1.