JPH052495B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention extrudes and press-fits thermoplasticized resin into a mold at an appropriate temperature using an extruder, thereby producing stable molded products with little thermal deterioration and residual stress. The present invention relates to an extrusion press-fit molding method for synthetic resin obtained.

<Conventional technology> Conventionally, the method of in-mold molding using thermoplastic resin is to fill an injection chamber with thermoplastic resin at an appropriate temperature and inject it into a mold at high pressure from a small-diameter injection port. be. When high-pressure injection is performed through such a small injection port to generate frictional heat and the resin temperature rises to improve mold circulation and obtain a molded product, the rise in resin temperature during injection causes thermal deterioration and residual stress. As a result, only molded products with deteriorated physical properties could be obtained. In addition, in the case of reinforced resin containing glass fiber or the like, there was a problem in that the fibers were crushed when passing through a small injection port, making it impossible to obtain the desired physical properties.

As a way to prevent the generation of frictional heat as much as possible,
Improving fluidity by raising the resin temperature above the appropriate temperature will cause the aforementioned thermal deterioration from the beginning.
If this is rapidly cooled, stress will remain. If the resin temperature was adjusted to an appropriate temperature and the injection time was increased, the mold movement into the mold would be slow and this would increase the rate of defective products. Furthermore, if the above-mentioned molding conditions were adopted, and the injection speed was slowed and the cooling period was prolonged, the time required for molding would increase, resulting in inefficiency, and it was still difficult to economically obtain perfect molded products. .

<Problems to be Solved by the Invention> Recently, so-called engineered plastics with excellent physical properties have been developed as resin raw materials, and opportunities for their application are increasing. However,
The above method of injection molding this resin impairs the excellent properties of the resin.

Therefore, there is an urgent need to develop a new molding method that does not impede the properties of such resins. An object of the present invention is to provide a synthetic resin extrusion press-fit molding method that can meet the above requirements.

<Means for Solving the Problems> The present invention provides a method of filling an extrusion chamber with resin thermoplasticized by an extruder and extrusion molding, in which the extrusion path of the mold communicating with the extrusion port of the extrusion chamber has a diameter of A press-fit resin chamber is formed by making the extrusion chamber larger, and a predetermined amount of the resin in the extrusion chamber is subjected to primary extrusion into a mold, and then the remaining resin in the press-fit resin chamber, which is composed of an extrusion port and an extrusion path, is extruded into the mold. It is characterized in that it is secondly press-fitted into the mold and the excess resin is returned to the extrusion chamber.

<Effects of the Invention> The present invention is capable of suppressing the speed at which the resin is extruded in the first stage from the extrusion port and extrusion path into the mold to a low speed of 0.5 m/sec, which is about 1/16 of the conventional method. In addition to reducing the rise in resin temperature due to friction, it is also possible to reduce the possibility of breaking into small pieces even if glass fiber or the like is mixed. In addition, since a predetermined amount of resin kept at a low temperature is subtracted by the volume of the extrusion port and the extrusion path from the large-diameter extrusion path into the mold by the extrusion means, the resin inside the mold is A large amount of resin can be extruded in a short time at low pressure. Even resins with high melt viscosity and low fluidity at appropriate temperatures can be extruded in large quantities in a short period of time, allowing rapid mold turning. The residual resin stored in the press-fitting resin chamber constituted by the extrusion port and extrusion path is secondarily press-fitted into the mold by high-pressure pressing means. As a result, the inside of the mold is filled, and a perfect molded product is obtained without defects due to mid-stage solidification. The low-temperature storage resin in the extrusion chamber is more efficient than the extrusion port or extrusion path because even if a large amount of resin is extruded into the mold in a shorter time, the resin temperature does not rise much, so there is less cooling required and the molding time can be shortened. be.

The method of the present invention is not only effective for extrusion press-fit molding of extrusion grade, which is a high-density resin with high viscosity and good physical properties, but also allows the mold to be used as a bottomed parison for blow molding. By changing to a mold, it is also effective when molding a large, thick-walled parison with a bottom that is ideal for blow molding.

In addition, the present invention allows a predetermined amount of resin at an appropriate temperature in the extrusion chamber to be transferred to the mold from the large-diameter extrusion port and extrusion path (the amount after subtracting the residual resin for the volume of the press-fit resin chamber made up of the extrusion port and extrusion path). Errors may occur during primary extrusion. If this amount is small, even if the residual resin is pressed into the mold using the secondary pressing means, it will not be able to fill the mold and the product will be defective. As a result of press-fitting into the mold by secondary pressing while returning to the extrusion chamber, it is possible to prevent an excessive pressing force from being applied, and to obtain a completely molded product without forming protrusions as traces of the extrusion path.

<Example> First, I will give an overview of the molding machine used.

An extrusion chamber 3 communicating with the outlet side of the extruder 1 via an on-off valve 2 is attached to a pressure plate 4 of a mold clamping device. This extrusion chamber 3 has a diameter of 120φ excluding the tip, but the tip has an extrusion port 5 with an inner diameter of 30φ.
As a result, it communicates with an extrusion path 7 formed in the molding concave mold 6. The extrusion path 7 is continuous with the extrusion port 5, has a diameter of 30φ, and communicates with the mold space 9 formed by the molding concave mold 6 and the molding concave mold 8. A plunger 10 that can move forward and backward by sliding a portion with an inner diameter of 120φ inside the extrusion chamber 3 is an extrusion means 16.
A mandrel 11 is attached to the plunger 10 which is actuated by the plunger 10 and penetrates through the center of the plunger 10 and can be moved forward and backward by a pressing means 17. The retracted and advanced positions of the plunger 10 and mandrel 11 are shown in FIGS. 1, 2, 3, and 4. In the retracted position, the extrusion port 5 and the extrusion path 7 are not blocked; It is completely blocked in the forward position. For this reason, the tip of the mandrel 11 is shaped to tightly fit into a press-fit resin chamber composed of an extrusion port 5 and an extrusion path 7 having an inner diameter of 30φ. In FIGS. 5 and 6, a small hole is formed from the tip of the mandrel 11 fitted into the extrusion port 5 and the extrusion path 7 to form a return path 12 for the resin, and an escape path 13 is formed in the resin at the end thereof.

Since the resin A from the extruder 1 is continuously extruded even when the on-off valve 2 is closed, an auxiliary plunger 14 is provided which is pushed up by the resin pressure at that time and is temporarily stored in an auxiliary chamber 15. It's summery.

An example of forming an industrial article with a wall thickness of 3 mm and a weight of 1.5 kg using the above-mentioned molding machine using a nylon resin reinforced with glass fibers will be shown below.

Initially, as shown in Fig. 2, resin A maintained at a low temperature of 225°C is in the extrusion chamber 3 with the extrusion port 5 closed.
3 kg is stored, and by opening the on-off valve 2, the thermoplastic resin is heated to 230℃ from the extruder 1.
1.25Kg and 0.25Kg of resin are newly supplied into the extrusion chamber 3 from the auxiliary chamber 15, and when the plunger 10 moves back 100mm, the limit switch (not shown) for quantitative filling is activated and the on/off valve is opened again. 2 closed. This took 50 seconds. As a result, the resin A in the extrusion chamber 3
becomes 4.5Kg. Subsequently, as shown in FIG. 1, the mandrel 11 is retracted to open the extrusion port 5 and
is opened, and the plunger 10 is advanced to fill the mold space in 3.6 seconds with a predetermined amount of about 1.4 kg of stored resin A, which has been adjusted to a low temperature, and which has been filled in from the 30φ extrusion path 7 at a speed of 0.5 m/sec. In step 9, the first extrusion is performed. This predetermined amount is the amount obtained by subtracting 0.1 kg of the weight of the residual resin B in the volume of the press-fit resin chamber constituted by the extrusion port 5 and the extrusion path 7. plunger 1
The forward movement at zero is 100 mm, and when the amount equal to the above-mentioned filling amount of 1.5 kg is reached, the plunger 10 stops forward movement by actuation of a limit switch (not shown). Next, the mandrel 11 is advanced as shown in FIGS. 3 and 4, and high pressure is applied to the weight of 0.1 kg of residual resin B stagnant in the press-fit resin chamber in the extrusion port 5 and the extrusion path 7, and the mold is removed. A second press fit is performed into the mold space 9 to make the weight of the resin in the mold 1.5 kg. The time required for this was 10 seconds, including the first extrusion and the second press-fitting. Extrusion port 5 and extrusion path 7
Resin return path 12 and resin escape path 13 in which the remaining resin is pressed under high pressure and press-fitted into the mold interior space 9 of the mold, and excess resin is formed in the mandrel 11.
It was returned to the extrusion chamber 3 through the process. In this way, an industrial molded product of 1.5 kg made of reinforced nylon resin with sufficient cooling time could be obtained in 60 seconds.

[Brief explanation of the drawing]

The figures are for the purpose of making it easier to understand the present invention. Figure 1 is a cross-sectional view showing the state during the first extrusion into the mold, and Figure 2 is a sectional view showing the state of the mold being pressed into the mold during the second pressing. FIGS. 3 to 5 are cross-sectional views showing the inside state, with the portion near the extrusion port enlarged and showing the state of being press-fitted into the mold by primary extrusion and secondary pressing. A... Storage resin, B... Residual resin, 1... Extruder, 2... On-off valve, 3... Extrusion chamber, 5...
...extrusion port, 7...extrusion path, 10...plunger, 11...mandrel, 16...extrusion means, 1
7...Press means.

Claims (1)

[Claims] 1. In a method of filling an extrusion chamber with thermoplasticized resin in an extruder and extrusion molding, the extrusion path of the mold communicating with the extrusion port of the extrusion chamber is
A press-fit resin chamber is formed by increasing the diameter, a predetermined amount of the resin in the extrusion chamber is subjected to primary extrusion into a mold, and then the resin remaining in the press-fit resin chamber consisting of the extrusion port and extrusion path is 1. A method for extrusion press-fitting a synthetic resin, which comprises performing a second press-fitting of a synthetic resin into a mold while returning the excess resin to an extrusion chamber.