JP2002307538A - Extruder for molding synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a process in which a molding is heat-treated to remedy warpage by preventing the generation of warpage by making the entire circumference of a sizing former contact a cooling medium in a cooling part substantially simultaneously. SOLUTION: In an extruder 1 for molding a synthetic resin, the sizing former 7 is covered with an insulating layer 14, and a surface 15 which forms the end of the insulating layer 14 is arranged to be substantially parallel to the perpendicular cross section of the sizing former 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruding apparatus for molding a synthetic resin, and more particularly to a method for extruding a molded article having various shapes from a thermoplastic resin to prevent warping of the molded article. The present invention relates to an extruder for molding a synthetic resin.

[0002]

2. Description of the Related Art Conventionally, a screw extruder used for extruding a thermoplastic resin into a rod or a plate has been known.
A cylinder having a material supply hopper and a heating device, a screw extruder and an extrusion die comprising a screw inserted into the cylinder and rotating, and a sizing former having a cooling layer is attached to the tip of the extrusion die. I have.

[0003] For example, thermoplastic resin pellets supplied from a hopper when manufacturing a resin round bar are melted by a heating device, and the molten resin extruded by a screw becomes a predetermined shape such as a round bar in an extrusion die. Is formed into a round bar by passing through a sizing former attached to the tip of the extrusion die. Then, the molded product from the sizing former is completely cooled by being cooled in a cooling section containing a cooling medium such as water.

[0004] Usually, the cooling section contains water as a cooling medium, and the sizing former penetrates the holes provided in the cooling layer and protrudes into the cooling section. The molded product is extruded into
It is cooled by water.

[0005]

When a water-cooled jacket is used to cool the sizing former in the above-mentioned synthetic resin molding extrusion molding apparatus, a jacket must be made for each size of the sizing former. No. In particular, it is difficult to process the inlet / outlet of the cooling water with a small-sized sizing former, so that the cost is relatively high, and there is a concern that there may be a problem with the piping or a leak of water.

Therefore, when extruding a small-sized molded product, a method of using a water tank as a cooling unit and cooling the sizing former is adopted. Specifically, a hole larger than the diameter of the sizing former is provided on the wall of the cooling unit that is a water tank, and the sizing former is inserted through packing made of an elastic material such as rubber to prevent water leakage. The method has been adopted.

[0007] A rubber packing is attached as a seal member to a hole provided in the cooling unit through which the sizing former penetrates so that water in the cooling unit does not leak out. Because it consists of a body,
Depending on the degree of insertion of the sizing former, the packing is inclined with respect to the sizing former, for example, as shown in FIG.

On the other hand, since the sizing former is made of metal and has good heat conductivity, it can be said that rapid cooling has already started from the part where the former comes into contact with the cooling water in the cooling tank. When the sealing member is inclined as described above, a portion where cooling starts early and a portion where cooling starts slightly later occur in the entire circumference of the extruded round bar.

[0009] The molten resin shrinks by cooling, but if the timing of the start of cooling differs as described above, the degree of shrinkage will change because the cooling will also be different in some parts. Then, it appears as a sled of the molded product. When warpage occurs, heat treatment is performed after molding in order to forcibly remove the warp, so that extra steps are required, which is disadvantageous in terms of cost.

Accordingly, an object of the present invention is to provide a resin extruder in which cooling of a molded product is started simultaneously over the entire circumference so that warpage does not occur.

[0011]

In order to achieve the above-mentioned object, the present invention provides an extruding unit having a raw material supply unit and a heating device for melting and extruding a raw resin, In a synthetic resin molding extrusion apparatus including a mold having a passage and a sizing former connected to the mold and having a cooling unit, at least the mold side of the sizing former in the cooling unit is covered with a heat insulating layer. In this case, the surface forming the end of the heat insulating layer is a surface substantially parallel to the orthogonal cross section of the sizing former.

[0012] The sizing former is covered with a heat insulating layer, and the surface formed by the end of the heat insulating tank is made substantially parallel to the orthogonal cross section of the sizing former. Since contact can be made substantially simultaneously around the entire circumference of the sizing former, cooling of the molded product passing through the inside of the sizing former also starts at the same time on the entire circumference, eliminating the problem of warpage. it can.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic side view of an extrusion apparatus for molding a synthetic resin according to the present invention, and FIG. 2 is an enlarged view near a sizing former. Extrusion apparatus 1 for resin molding of the present invention
Is a hopper 2 which is a resin raw material supply unit such as pellets,
It comprises a screw extruding section 3 for melting and extruding the charged resin raw material by a heating apparatus, an extruding apparatus main body having a mold 4, and a cooling section 6 in which a cooling medium 5 is stored.
Further, a sizing former 7 is attached to a tip of the mold 4 so as to extend to a cooling section. Further, although not shown,
A take-up machine for the molded body extruded by the resin extruder 1,
A cutting machine or the like for cutting to a predetermined length is added.

The pellets 8, which are raw materials of the resin, are placed in the hopper 2.
And the inside of the screw extruding section 3 is heated by a heater to the melting temperature of the resin. In a state where the pellets are sufficiently melted, the melted resin 9 is fed in the direction of the mold by cutting into the screw. In the case of molding a round bar, the molten resin is fed into a mold 4 having a cylindrical cavity, and is shaped into a round bar. Next, the resin 10 formed into a round bar shape by the mold 4 is further passed through a sizing former 7 to be shaped into a round bar having a desired diameter and a very smooth cylindrical surface. 11 is extruded.

The molding 11, which has been shaped into the final round bar by the sizing former 7, is
And cooled by the cooling medium 5. The sizing former 7 is attached to the tip of the mold 4, but extends from the extruded portion to extend the side wall 6 of the cooling portion 6.
a, and extends into the cooling unit through the hole provided in the cooling unit. The sizing former 7 has at least the mold 4 side covered with a heat insulating layer 14.

FIG. 2 is a sectional view of the vicinity of a sizing former 7 which is a characteristic part of the extrusion apparatus for molding a synthetic resin according to the present invention. The mold 4 having an external heating device is connected to the tip thereof. A sizing former 7 is arranged. The mold 4 has a passage (cavity) for molten resin therein, and is configured to send the resin to the sizing former 7.

On the other hand, the sizing former 7 is inserted into a hole 12 provided in a wall 6a of a water tank as the cooling unit 6 and extends into the cooling unit 6. The water layer serving as the cooling section 6 is filled with cooling water at a predetermined temperature as a cooling medium 5 so that the sizing former 7 and the resin molded body 11 coming out of the sizing former can be cooled.

The hole 12 provided on the side wall of the water tank as the cooling unit 6
Is provided with a packing 13. The mold 4 in the cooling section of the sizing former 7 is covered with a pipe-shaped heat insulating layer 14, and the sizing former 7 is inserted into the packing 13 via the heat insulating layer 14. . The surface 15 formed by the end of the heat insulating layer 14 is a surface substantially parallel to the orthogonal cross section of the sizing former 7.

The resin in the sizing former 7 is cooled by the cooling unit 6. However, if the cooling start position is different at the entire circumference of the molded body 11, a difference occurs in the degree of cooling. Warping occurs due to the difference in resin shrinkage.

In the present invention, since the surface 15 formed by the end of the heat insulating layer 14 is a surface substantially parallel to the orthogonal cross section of the sizing former 7, the extruded molded body 11 is formed.
Since cooling can be started at the same time in the entire circumference, it is possible to prevent the occurrence of warpage of the resin molded body due to the displacement of the cooling start position.

In the present invention, the heat insulating layer 14 can be used as, but is not particularly limited to, such that even when the packing 13 is tilted, its influence appears on the resin molding and no warping occurs. It has heat insulating properties, and is made of a material such as silicone, fluororesin, or fluororubber, and preferably has a thickness of 0.2 mm or more.

Next, the effect of the present invention was confirmed by conducting a comparative test between the example and the comparative example.

[0023]

(Example) As an example, a polyacetal 1-piece extruder was used by using an extruder for a resin molded product as shown in FIG.
A round bar of 0 mmφ was extruded. As the sizing former, a heat-insulating layer made of silicone and having a thickness of 2 mm and a length of 24 mm was coated on the extrusion die side. The extruded round bar was cut into 1 m to make 10 samples, and the amount of warpage per 1 m was measured. As for the amount of warping, as shown in FIG.
A round bar 22 cut to 1 m was placed thereon, and both ends of the round bar were set on an L ruler to measure a maximum value D at a curved portion. Table 1 shows the range of the amount of warpage.

(Comparative Example) As a comparative example, a 10 mmφ round bar made of polyacetal was extruded in exactly the same manner as in Example except that the heat insulating layer made of silicone was not covered and attached to the sizing former. 1 as in the embodiment
Zero samples were prepared and the amount of warpage per meter was measured. Table 1 shows the range of the amount of warpage.

[0025]

[Table 1]

As can be seen from the results shown in Table 1, the round bar produced by the apparatus of the present invention in which a sizing former was provided with a heat insulating layer had a significantly lower amount of warpage than the comparative example in which no heat insulating layer was provided. It was confirmed that the effect of the present invention was obtained.

[0027]

As described above, according to the present invention, in the extrusion apparatus for molding synthetic resin, at least the mold side of the sizing former in the cooling section is covered with the heat insulating layer, and the surface forming the end of the heat insulating layer is This is a synthetic resin molding extruder characterized by having a surface substantially parallel to an orthogonal cross section of the sizing former.

By covering the sizing former with a heat insulating layer and making the surface formed by the end of the heat insulating tank substantially parallel to the orthogonal cross section of the sizing former, the sizing former can be used as a cooling medium in the cooling part. Since contact can be made substantially simultaneously around the entire circumference of the sizing former, cooling of the molded product passing through the inside of the sizing former also starts at the same time on the entire circumference, eliminating the problem of warpage. it can. Therefore, the step of correcting the warp by heat-treating the molded body can be eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of an extrusion apparatus for molding a synthetic resin according to the present invention.

FIG. 2 is an enlarged side sectional view near a sizing former.

FIG. 3 is a front view showing a state where a warp of a round bar is measured.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extrusion apparatus for synthetic resin molding 2 Hopper 3 Screw extrusion part 4 Die 5 Cooling medium 6 Cooling part 7 Sizing former 8 Pellet 12 Hole 13 Packing 14 Heat insulation layer

Claims (1)

[Claims] 1. A sizing unit having a raw material supply unit and a heating device for melting and extruding a raw material resin, a mold having a molten resin passage therein, and a cooling unit connected to the mold. In a synthetic resin molding extruder comprising a former, at least the mold side of the sizing former in the cooling unit is covered with a heat insulating layer, and the surface forming the end of the heat insulating layer is perpendicular to the cross section of the sizing former. An extruder for molding a synthetic resin, wherein the extruder has substantially parallel surfaces.