JPH082548B2 - Transfer molding method of thermoplastic resin and coating method of thermoplastic resin on base material - Google Patents

Description

Detailed Description of the Invention

FIELD OF THE INVENTION The present invention efficiently produces a molded product of a thermoplastic resin or a product coated with a thermoplastic resin.
The present invention relates to a transfer molding method.

2. Description of the Related Art Conventionally, a transfer molding method has been known as one of molding methods for a thermoplastic resin having a high precision and a complicated shape. In this method, for example, a molten resin is supplied into the pot by an extrusion molding machine, and then the resin is pressed into the cavity (gap) in the mold from the pot. The mold is cooled while being pressurized while the extruder and the pot are connected, and the mold is opened to mold the resin product. Further, conventionally, it has been proposed to coat the metal surface of a base material such as a T-tube with a thermoplastic resin by a transfer molding method.

However, in the above-mentioned conventional method, an extruder, a pot and a mold are connected to each other in order to produce a resin-molded product having a highly accurate and complicated shape or a resin-coated product. Since all the steps were performed in the state, there was a problem that the production efficiency was poor. That is, since it takes several times to dozens of times to complete the filling of the resin into the mold for cooling the mold, the conventional method in which the extruder is involved even while cooling the mold However, this extruder cannot be used to manufacture the next resin molded product or resin-coated product, and the productivity per unit time was extremely low. The present invention solves the above conventional problems and can efficiently produce a precise and large thermoplastic resin molded product or a product coated with a thermoplastic resin, which is suitable for mass production of small lots and a wide variety of products. Another object is to provide a suitable transfer molding method.

The molding method of the present invention is a transfer molding method of a thermoplastic resin, which cyclically uses an extruder, a plurality of pots and a plurality of molds,
In a pot connecting a preheated mold and an extruder, after supplying the molten thermoplastic resin from the extruder,
The step of separating the extruder from the pot, the step of filling the cavity in the mold with the molten thermoplastic resin from the pot, and the step of refilling the cavity in the mold with the molten thermoplastic resin from the pot under pressure. While cooling the mold. Further, the coating method of the present invention is a method for coating a base material of a thermoplastic resin that cyclically uses an extruder, a plurality of pots and a plurality of molds, and by mounting a base material for coating. In the pot that connects the preheated mold and the extruder, after supplying the molten thermoplastic resin from the extruder, separating the extruder from the pot, and the molten thermoplastic resin from the pot into the cavity The method is characterized by including a step of pressurizing and filling, and a step of cooling the base material and / or the mold while refilling the cavity with molten thermoplastic resin from the pot under pressure.
As the thermoplastic resin in the present invention, any known thermoplastic resin such as a polyolefin resin can be used, but in view of heat resistance, chemical resistance, non-deterioration, etc., a melting point of 302 to 310 ° C. A heat-meltable fluororesin such as a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA) or a copolymer of tetrafluoroethylene and hexafluoropropylene having a melting point of 253 to 282 ° C. is preferable. In the present invention, the coating base material is a T pipe, a straight pipe, a flow meter, a valve, an elbow, etc., and the base material and the lower mold are incorporated inside the outer mold, or the lower mold is provided inside the base material. By incorporating a core die, a thermoplastic resin coating can be formed on the outer or inner metal surface of the base material. In addition, throughout the specification, a mold means all molds such as an external mold, a core mold, and a lower mold used in the present invention.

In the method of the present invention, after filling the thermoplastic resin,
The extruder is separated from the pot before cooling the mold and the base material connecting the pots. The mold filled with the thermoplastic resin and the base material are cooled while the pots are connected, and the resin molded product or the product coated with the resin is taken out, and then the mold and the pot are cyclically used. On the other hand, the cooling time of the mold takes several times to several tens of times of the time until the filling of the molten thermoplastic resin into the cavity is completed. ~ Prepare a dozen or more metal molds, connect the separated extruders to another pot one after another, and use the molten thermoplastic resin cyclically to supply the molten thermoplastic resin into the pot. As a result, the loss of time spent for cooling in the conventional method can be eliminated.

Embodiments of the present invention will be described below with reference to the drawings. Example 1 FIG. 1 is a partial cross-sectional view showing a usage state of an extruder, a pot and a mold in an example of the present invention. For this example, one extruder, seven pots, seven core molds and lower molds were prepared. First, the heat block
Inject resin into pot 1 equipped with 4 and pressure cylinder 5.
Through the intermediate flange 9 having the hole 10, the coating base material 3
Connect the dies (core die 11 and lower die 12) with
did. A mold (core core mold 11 and
The lower mold 12) is separately pre-assembled and then PFA6
It has been heated to a temperature above its melting point (310 ° C).
It Further, the extruder 1 was connected to the pot 1. In the heated pot 1, a slightly larger amount of molten PFA 6 than the amount to fill and refill the cavity was supplied from the extruder 2. After the supply was completed, the extruder 2 was separated from the pot 1 and the gate 8 of the bot 1 was closed. The separation of the extruder 2 from the pot 1 is a step of cooling the coating base material 3 and the die (core die 11 and lower die 12) if the molten PFA 6 is supplied into the pot 1. At any point before. Next, the molten PFA 6 in the pot 1 is pressurized by the pressure cylinder 5, and through the resin injection hole 10, the straight pipe made of stainless steel, the core die 11 and the lower die 12 which are the base material 3 for coating are assembled. The formed cavity 7 was filled with molten PFA6. About 3.5 minutes were required for the steps up to here. Figure 2
FIG. 4 is a view showing a state in which PFA is filled in the cavity from the pot as described above. Pressure the molten PFA6
While being pressurized by the cylinder 5, it is the covering material 3
Outside stainless steel straight pipe, core mold 11 and lower mold 12
Partly or internally cooled with water. The cavity 7 was replenished with molten PFA 6 in an amount equivalent to PFA that contracts by cooling from the pot 1, and the cavity 7 was completely filled with PFA without gaps. Molten PF is used for cooling the base material and mold.
It may be carried out at the place filled with A6, or the pressure cylinder 5 is once released, the pot 1 is still connected to the die for mounting the coating base material 3, and the pot is moved to another cooling place. May be mounted and cooled while applying pressure.
When the base material and the mold are cooled at the place filled with the molten PFA 6, the extruder 2 is moved to another place and connected to the pot 1 connected to another coating base material 3 mounting die. To use. After the cooling was completed, the core mold 11 and the lower mold 12 were removed, and the product in which the PFA coating was formed inside the stainless steel straight pipe was taken out. This cooling process took about 25 minutes. The pot 1 that has been used was circulated and used in the step of supplying the molten PFA 6 from the extruder 2. Core mold 1
1, the lower mold 12, etc. were used cyclically for the next assembly.
On the other hand, after the completion of supplying the molten PFA 6 to the pot 1, the extruder 2 is again connected to another pot 1 in which another preheated coating base material 3 mounting die is connected and clamped, and the molten PF 6 is melted.
The supply process of A6 was sequentially repeated 6 more times. About 10 PFA-coated straight stainless steel tubes could be produced per hour. The manufactured PFA-coated stainless steel straight pipe is subjected to finishing such as cutting at the nozzle portion. Example 2 A PFA straight pipe was manufactured in the same manner as in the method of Example 1. However, a PFA straight pipe was manufactured in the same manner as in the method of Example 1 except that an external die for forming a straight pipe was used instead of the coating base material. Comparative Example 1 After the completion of supplying molten PFA into the pot, a PFA-coated stainless steel straight pipe was used in the same manner as in Example 1 except that the extruder was not separated from the pot.
Individually manufactured.

As described above, according to the present invention, for the first time, precise thermoplastic resin molded products of various sizes or products coated with the thermoplastic resin can be efficiently produced, and small lots and various kinds of products can be produced. It has become possible to provide a transfer molding method suitable for mass production. INDUSTRIAL APPLICABILITY The present invention is a method of great significance, which can be applied not only to thermoplastic resins but also to thermosetting resins.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a usage state of an extruder, a pot, and a mold in an embodiment of the present invention.

FIG. 2 is a view showing an example of the present invention in which a pot-to-PF is used.
It is a fragmentary sectional view showing the state where A was filled up in a cavity.

[Description of sign]

 1 pot 2 extruder 3 coating base material

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29K 105: 20

Claims (2)

[Claims] 1. A transfer molding method for a thermoplastic resin, which cyclically uses an extruder, a plurality of pots, and a plurality of molds, wherein a preheated mold and an extruder are connected to each other. , After supplying the molten thermoplastic resin from the extruder,
The step of separating the extruder from the pot, the step of filling the cavity in the mold with the molten thermoplastic resin from the pot, and the step of refilling the cavity in the mold with the molten thermoplastic resin from the pot under pressure. While cooling the mold. 2. A method for coating a base material of a thermoplastic resin, which cyclically uses an extruder, a plurality of pots and a plurality of molds, comprising a preheated base material mounting mold for coating and extrusion. In the pot connected to the molding machine, after supplying the molten thermoplastic resin from the extruder, a step of separating the extruder from the pot,
And a step of cooling the base material and / or the mold while refilling the cavity with the molten thermoplastic resin under pressure, and filling the cavity with the molten thermoplastic resin from the pot under pressure. The method as described above.