JPH0375335B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an extrusion die device for molding synthetic resins, and more specifically, it easily molds molded bodies of various shapes from highly crystalline thermoplastic resin pellets such as nylon 6, polyacetal, polybutylene terephthalate, polyethylene terephthalate, etc. This invention relates to an extrusion die device for molding synthetic resin. Screw extrusion equipment, which is generally used to extrude highly crystalline thermoplastic resin pellets into rods, plates, or irregular shapes, consists of a material feeding hopper, a cylinder equipped with a heating device, and a cylinder that is inserted into the cylinder and rotated. An extrusion die device with a heating device is attached to the tip of a screw extruder consisting of a moving screw, and a sizing former portion with a water cooling jacket is attached to the tip of the die device. The extrusion device is also equipped with a water tank for water-cooling the extruded product to maintain its shape, and a back pressure take-up rubber roll for eliminating sink marks in the center of the extruded product. However, when extruding high-crystalline resin pellets using the above-mentioned extrusion equipment, the pressing pressure of the extrusion molded product is increased using a take-up rubber roll in order to eliminate the gap that occurs in the center of the extrusion molded product. It is necessary to increase the extrusion resin pressure, but especially when high back pressure is used during high-speed extrusion, the extruded product expands in the diametrical direction at the sizing former neck part of the extrusion die device and adheres to the inner surface of the same part. However, it was difficult to extrude it. The present invention improves these drawbacks, and when screw extruding highly crystalline resins such as nylon 6, nylon 6.6, polyacetal, polybutylene terephthalate, and polyethylene terephthalate, the molten resin is The purpose of the present invention is to provide an extrusion die device for synthetic resin molding that can smoothly extrude extruded products by suppressing the sticking phenomenon that occurs due to high back pressure, and can continuously mold molded products without gaps. The extrusion die device is connected to the screw extruder, and the extrusion die device has a heating device on the outside and a mold having a passageway for the extruded product inside, and a cooling jacket connected to the mold. A water-cooling jacket divided into at least two parts is arranged at a position away from the inlet of the sizing former, and the volume of the water-cooling jacket near the inlet is divided into other water-cooling jackets. For synthetic resin molding, which is smaller than that of the jacket, exposes the outer surface of the sizing former neck part corresponding to the inlet part of the sizing former part to the water cooling jacket, and has a surface adhesion layer only on the inner surface. Located in extrusion die equipment. Next, the present invention will be explained using the drawings. FIG. 1 is a longitudinal cross-sectional view of a synthetic resin molding extrusion die device according to the present invention. The mold 1 is equipped with a heating device 4 on its outer surface, and has a passage 5 for the extruded product inside, and the passage 5 has a region with a narrower diameter in the middle and a region with a larger diameter. 3
On the other hand, the sizing former part 3 has a passage 6 with a constant diameter and is provided with water cooling jackets 7 and 8 on the outside. The water cooling jackets 7 and 8 are installed at a position away from the inlet of the sizing former section 3,
And it is divided into two. The volume of the water cooling jacket 7 on the side closer to the mold 2 is smaller than that of the other water cooling jackets 8, reducing the cooling capacity of the inlet portion of the sizing former section 3. A sizing former neck part 9 is formed between the entrance part of the sizing former part 3 and the water cooling jacket 7, and the outer surface of the neck part 9 is exposed to provide natural heat dissipation. Therefore,
The surface temperature gradually decreases from the inlet to the outlet of the sizing former part 3, and the semi-molten extruded resin extruded from the mold 2 gradually cools and the marble pattern that tends to occur on the surface disappears, resulting in an appearance. becomes better. Note that it is preferable that the water temperature of the water cooling jacket 7 near the mold 2 be slightly higher than that of the water cooling jacket 8. Therefore, on the inner surface of the sizing former neck part 9 which is located in the passage 6 of the sizing former part 3 and is close to the entrance, there is a surface slipping layer 10 in order to prevent the semi-molten extruded resin from sticking. For example, such an adhesion layer 10 is made by first applying hard chrome plating to the surface, chemically creating bag-shaped minute cracks in the plating layer, and further heating to enlarge the cracks.
Thereafter, the surface may be coated by embedding a tetrafluoride resin, or the surface may be simply coated with hard comb plating or a tetrafluoride resin by baking. The thickness of the surface smoothing layer 10 obtained in this manner is 0.01 to 0.1 mm, and the inner surface of the sizing former neck portion 9 is a flat surface with no steps. Although the sizing former neck portion 9 is within 1/3 of the total length of the sizing former portion 3, the distance between the tip of the sizing former portion 3 and the water cooling jacket 7 is longer than the sizing former portion 3.
This is within 1/3 of the total length, and this is because the extruded product becomes semi-molten and tends to stick during this period. As shown in FIG. 2, the extrusion die device 1 has a screw 16 in a cylindrical cylinder 15 which has heating devices 11, 12, 13 on its surface and a hopper 14 at the end into which raw materials are introduced. Insert the bolt into the outlet of the screw extruder 17,
A breaker plate 18 connected with a nut and having a plurality of holes is inserted into the inlet of the extrusion die device 1 to adjust the flow of the molten resin. In addition, a water tank 19 is provided in front of the outlet of the extrusion die device 1 connected to the screw extruder 17 to cool and solidify the extrusion molded product 20, and rubber rolls 21 and 22 are further provided in front of the extrusion molded product 20 to suit the extrusion molded product 20. The molded body is continuously extruded by applying a certain amount of back pressure. When such an extrusion die device 1 is used in conjunction with the screw extruder 17, the semi-molten molded product extruded from the mold 2 of the extrusion die device 1 does not stick at all at the sizing former neck portion 9. It is extruded smoothly, and even if back pressure is applied to the extruded product, this is not affected in any way. Next, in order to confirm the effects of using the extrusion die device according to the present invention, specific examples will be described in detail below. Example 1 P-65-22AB manufactured by Japan Steel Works, Ltd. with a screw inserted into a cylinder with an inner diameter of 65 mm and a length of 2000 mm
This screw extruder is equipped with an extrusion die according to the present invention in which the inner surface of the sizing former neck part has been subjected to a trough process (manufactured by Omori Chrome Plating Co., Ltd.), and a water tank and two rubber rolls are arranged in front of the extrusion die. When a polyacetal copolymer pellet (trade name: Ultraform H2320; manufactured by BASF) was extruded into a round bar using an extrusion molding apparatus (shown in Figure 2) under the extrusion conditions shown in Table 1, Even if high resin pressure is 30~50
Even at Kg/cm ² , the extruded product did not adhere to the inner surface of the sizing former neck, and a round bar with an outer diameter of 100 mm could be continuously extruded as shown in FIG. The extruded product had good appearance and roundness, and had no voids in the center.

[Table] Comparative Example 1 An attempt was made to mold a round bar by screw extrusion molding a polyacetal copolymer pellet under the same conditions as in Example 1 except that the inner surface of the sizing former neck part was not subjected to Teflock processing. At 30 kg/cm ² or more, the extruded resin stuck to the sizing former neck, making continuous extrusion impossible (see Figure 4). Continuous extrusion was possible by lowering the back pressure by adjusting the take-up roll pressure so that the resin pressure was 30 kg/cm ² ) or less, but the center of the extruded round bar had a diameter of about 5 mm. A riot occurred. Example 2 When 6 nylon pellets recycled from monomer cast nylon (manufactured by Mitsuboshi Belting Co., Ltd.; Mitsuboshi Cast Nylon NA) were extruded into round bars using the same screw extrusion molding apparatus as in Example 1, the inner surface of the sizing former neck part There is no sticking phenomenon to the resin pressure ^range of 15 to 35 kg/cm
mm round bars could be continuously extruded. The external appearance and roundness of the extruded product were good, and there was no hole in the center of the cross section of the round bar. Table 2 shows the extrusion conditions.

[Table] Comparative Example 2 A round bar was formed by screw extrusion molding monomer cast nylon recycled 6 nylon pellets under the same conditions as in Example 2 except that the inner surface of the sizing former neck part was not subjected to Teflock processing. However, when the resin pressure exceeded 15 kg/cm ² , the extruded resin stuck to the sizing former neck, making continuous extrusion impossible. In addition, the resin pressure is 10Kg/cm ²
Continuous extrusion was possible if the back pressure was lowered by adjusting the transaction roll pressure as follows, but a gap with a diameter of about 10 mm occurred in the center of the extruded round bar cross section. As described above, the extrusion die device of the present invention can perform continuous extrusion molding under high back pressure regardless of the type of resin, and has the effect of preventing the formation of cracks inside the molded product. are doing.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an extrusion die device for molding synthetic resin according to the present invention, FIG. 2 is a cross-sectional view of a screw extrusion molding device using the extrusion die device shown in FIG. 1, and FIG. Relationship between extrusion time and resin pressure when using the extrusion die device according to the invention, and the fourth
The figure shows the relationship between extrusion time and resin pressure when a conventional extrusion die device is used. 1... Extrusion die device, 2... Mold, 3... Sizing former section, 4... Heating device, 5, 6...
...Passage, 7, 8...Water cooling jacket, 9...Sizing former network portion, 10...Surface adhesion layer.

Claims (1)

[Claims] 1 An extrusion die device connected to a screw extruder, the extrusion die device comprising a mold having a heating device on the outside and a passage for the extruded product inside, and a water cooling jacket connected to the mold. A water cooling jacket divided into at least two parts is disposed at a position away from an inlet part of the sizing former part, and the volume of the water cooling jacket near the inlet part is divided by that of the other water cooling jacket. Furthermore, the outer surface of the sizing former neck part corresponding to the area from the inlet part of the sizing former part to the water cooling jacket is exposed, and a surface slipping layer is provided only on the inner surface thereof. Extrusion die equipment for synthetic resin molding.