JPH0369698B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an extrusion molding method for synthetic resin moldings, and more specifically, thermoplastic resin pellets such as nylon 6, nylon 6.6, polyacetal, polybutylene terephthalate, polyethylene terephthalate, etc. are molded into round bars, plates, etc. using a screw extrusion device. The present invention relates to an extrusion molding method for easily forming a molded article. Screw extrusion equipment, which is generally used to extrude thermoplastic resin pellets into rods, plates, or irregular shapes, consists of a material feeding hopper, a cylinder equipped with a heating device, and a rotating screw inserted into the cylinder. At the tip of the extruder,
An extrusion die device equipped with a heating device and a resin pressure gauge for measuring molten resin pressure is installed, and a sizing former section with a water cooling jacket is attached to the tip of the die device. The extrusion device is equipped with a water tank for water-cooling the extruded product to maintain its shape, and a back pressure take-up rubber roll or caterpillar for eliminating the gap in the center of the extruded product. However, when extruding high-crystalline resin pellets using the above-mentioned extrusion equipment, the extrusion molded product is held down by a take-up rubber roll or a caterpillar and the pressure is increased to eliminate the gap that occurs in the center of the extrusion molded product. High back pressure (high resin pressure) on the pressed body
It was necessary to apply However, when high back pressure is applied during high-speed extrusion, the extruded product tends to expand in the diametrical direction in the sizing armor part of the extrusion die device and stick to the inner surface of the part, making continuous extrusion molding difficult. It was hot. Therefore, in order to improve this problem, the inventors of the present invention first developed a method of lubricating the inner surface of the sizing former neck part, or by making the inner surface of the sizing former neck part a tapered surface. We proposed a method to prevent molded bodies from sticking. Although these methods have achieved their intended purpose, they still have drawbacks such as large fluctuations in resin pressure of ±25%, lack of stability, and fluctuations in the dimensions and weight of extruded products. 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 in the sizing former part of the extrusion die has a high height. This invention provides an extrusion molding method for synthetic resin moldings that suppresses the sticking phenomenon that occurs due to pressure, allows extrusion molded products to be smoothly extruded, and can continuously mold molded products with no gaps. This is done by adding 0.001 to 0.1 part by weight of silicone oil to 100 parts by weight of the synthetic resin as a raw material for the molded product in advance in a method of extruding a synthetic resin molded body using an extrusion device in which an extrusion die device is connected to a screw extruder. A method of extrusion molding a synthetic resin molded article by extruding a mixture while applying back pressure. Synthetic resins in the present invention include powders of nylon 6, nylon 6.6, polyacetal, polybutylene terephthalate, polyethylene terephthalate, etc.
It is a highly crystalline resin in the form of granules or flakes, and is supplemented with inorganic and organic fillers such as talc, silica, calcium carbonate, and carbon black, glass fiber,
In addition to reinforcing agents such as carbon fibers, pigments, flame retardants, antistatic agents, stabilizers, etc., reinforcing agents, extenders, and additives that are commonly mixed into resins may also be used in combination. The silicone oil used in the method of the present invention is oily at room temperature, and includes methyl silicone oil (dimethylpolysiloxane), methyl chlorinated phenyl silicone oil, fatty acid-modified silicone oil, and polyoxyalkylene-modified silicone oil. , methylhydrogen silicone oil and the like. The viscosity of the silicone oil used may be one having a kinematic viscosity of 5 to 10 ^-6 centistokes at 25°C. Silicone oil is used by adding 0.001 to 0.1 parts by weight to 100 parts by weight of synthetic resin.
If the amount added is less than 0.001 part by weight, the lubricant effect will be lost and a sticking phenomenon will occur inside the sizing former, while if it is more than 0.1 part by weight, silicone oil will overflow onto the surface of the molding resin more than necessary.
It slips on the screw surface of the screw extruder and the inner surface of the cylinder, resulting in poor biting and making it difficult to consistently feed the material. Silicone oil can be added to synthetic resin by mixing a predetermined amount during pellet molding, or by pre-molding silicone masterbatch pellets containing high-concentration silicone oil, and using a tumbler or Henschel mixer immediately before molding the molded product. An example of this method is to mix it with synthetic resin pellets that serve as a matrix. An example of the screw extrusion molding apparatus used in the method of the present invention is shown in FIG. This extrusion molding apparatus 1 consists of a screw extruder 2 and an extrusion die device 3 connected thereto. First, the screw extruder 2 is equipped with heating devices 4, 5, and 6 on its surface, and a hopper 7 at the end for feeding raw materials. It consists of a cylindrical cylinder 8 with a diameter and a screw 9 inserted into the cylinder. On the other hand, the extrusion die device 3 is composed of two parts: a mold 10 and a sizing former part 11 connected to the mold 10.
0 is equipped with a heating device 12 on its outer surface and has an extrusion channel 13 in its interior. This passage 13 has three stages of circular diameters, including a region where the diameter is narrowed in the middle and a region where the diameter is increased. Further, the sizing former part 11 has a passage 14 having a constant diameter and a sizing former neck part 15 in contact with the mold 10, and is provided with a water cooling jacket 16 on the outside. Further, a breaker plate 17 having a plurality of holes for adjusting the flow of molten resin is inserted into the connecting portion between the screw extruder 2 and the mold 10, and a pressure gauge 18 for measuring the resin pressure is attached. .
A water tank 19 is provided in front of the exit of the extrusion die device 3 to cool and solidify the extruded body 20. Furthermore, there are rubber rolls 21 and 22 in front of the extruded body 20, and there are rubber rolls 21 and 22 in front of the extruded body 20, which apply appropriate back pressure to the molded body 20 to continuously form the molded body. It is designed to push out. Using such a screw extrusion molding apparatus 1, a raw material consisting of a synthetic resin mixed with silicone oil is introduced from the hopper 7, and then the screw extruder 2 is used to mold the mold 10.
When extruded, the semi-molten molded product extruded from the mold 10 is smoothly extruded without any sticking in the sizing former part 11, and the variation in resin pressure is small, and there is nothing inside the molded product. You can get something without any problems. Next, specific examples of the method of the present invention will be described. Example 1 A P65-22AB type screw extruder manufactured by Japan Steel Works Co., Ltd. was connected to an extrusion die (a die for four round bars of φ60), and in front of it was a water tank and two sets of rubber rolls (two air rollers per set). Using a screw extrusion molding apparatus (Figure 1) equipped with a cylinder (with siloxane) [Product name Torre Silicone]
SH200: Manufactured by Toray Silicone Co., Ltd. When a round bar was extruded from raw material pellets containing 0.05 parts by weight under the extrusion conditions shown in Table 1, the resin pressure was 23 to 25.
Kg/cm ² (see Figure 2), and the extrusion molded product does not stick to the inner surface of the sizing former and has an outer diameter of 60 mm.
mm round bars could be continuously extruded. The extruded product had good appearance and roundness, and had no voids in the center.

[Table] Comparative Example 1 When molding a round bar was attempted under the same extrusion conditions as in Example 1 except that raw material pellets without silicone oil added to the polyacetal copolymer pellets were used, the resin pressure was 25 kg/cm. ² or more, the extruded resin stuck to the inner surface of the sizing former several times, and the extrusion operation was stopped again and again. (Indicated by the arrow in Figure 3) Continuous extrusion was possible by adjusting the take-up roll pressure and lowering the back pressure so that the resin pressure was 25 kg/cm ² or less, but A hole with a diameter of about 3 to 4 mm was generated in the center of the rod cross section. Example 2 Nylon 6 pellets were recycled from monomer cast nylon (Mitsuboshi Cast Nylon NA, manufactured by Mitsuboshi Belting Co., Ltd.) using the same screw extrusion molding apparatus as in Example 1 except for the single die for 100φ round bar. Silicone oil (dimethylpolysiloxane) of 10,000 centistokes per 100 parts by weight [Product name: Toray Silicone SH200: Toray Silicone Co., Ltd.
When a round bar was extruded from raw material pellets to which 0.05 parts by weight was added under the extrusion conditions shown in Table 2, the resin pressure was stable at 10 to 15 kg/cm ² (see Figure 4), and the extruded product was A round bar with an outer diameter of 100 mm could be continuously extruded without sticking to the inner surface of the sizing former. The extruded product had good appearance and roundness, and had no hole in the center. Comparative Example 2 When molding a round bar was attempted under the same extrusion conditions as in Example 2, except that raw material pellets without silicone oil were used for monomer cast nylon regenerated 6 nylon pellets, the resin pressure was 10 kg/
At cm ² or more, the extruded resin stuck to the inner surface of the sizing former several times, and the extrusion movement was stopped again and again.
(Indicated by the arrow in Figure 5) Continuous extrusion was possible by adjusting the take-up roll pressure and lowering the back pressure so that the resin pressure was 10 kg/cm ² or less, but extrusion molding The diameter at the center of the round bar cross section is approx.
A gap of about 10 mm occurred.

[Table] As described above, the method of the present invention allows raw materials to which silicone oil is added to be continuously extruded under high back pressure and with stable resin pressure. This has the effect of preventing the occurrence of

[Brief explanation of drawings]

Figure 1 is an example of a screw extrusion molding apparatus used in the method of the present invention, and is a sectional view thereof;
Figures 3 and 4 show the relationship between extrusion time and resin pressure in Example 1 and Example of the present invention, respectively, and Figures 3 and 5 show the relationship between extrusion time and resin pressure in Comparative Example 1 and Comparative Example 2, respectively. shows. 1... Screw extrusion molding device, 10... Mold, 2... Screw extruder, 19... Water tank, 3
...Extrusion die device, 21...Rubber roll, 4,
5, 6, 12... heating device, 22... rubber roll, 11... sizing former section.

Claims (1)

[Claims] 1. In a method of extruding a synthetic resin molded body using an extrusion device in which an extrusion die device is connected to a screw extruder, 0.001 to 0.1 part by weight of silicone oil is mixed in advance with 100 parts by weight of the synthetic resin as a raw material for the synthetic resin molded body. A method for extrusion molding a synthetic resin molded article, characterized by extrusion molding the product while applying back pressure.