JPS63185609A - Molding of plastic - Google Patents

Abstract

PURPOSE:To improve the productivity, to obtain a uniform product, to make the cleaning easy and to improve the processability, by blending a small amt. of mixed pellets and a powder at a set ratio, supplying intermittently the mixture to a hopper of an extruder and carrying out continuously a kneading and extruding treatment. CONSTITUTION:Pellets of a heat resistant polyvinyl chloride mixture are supplied from a pellet hopper 3 and e.g., 100 g thereof is measured by means of a pellet measuring machine 5 and is stored in a pellet storage 6. As a powder, a powder pigment where a polyvinyl chloride mixture is used as a binder is used and e.g. 1.0 g thereof supplied from a powder hopper 4 is measured by means of a powder measuring feeder 9 and is supplied in a mixing hopper 10. At the same time when the powder is supplied, a shutter 7 is opened and the pellets are supplied. The pellets are accelerated in a spiral-shaped spiral flow generating pipe 8 and fed in the hopper 10 at an angle close to horizontal to generate a spiral flow in the hopper 10. The pellets are supplied in such a manner that the residual amt. of the mixture in the hopper 10 is kept e.g., in the amount of 200 g or less, and the kneading amt. of the resin is e.g., 80kg/hr and is extruded to manufacture electric wires.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for molding plastics in the field of plastic processing.

(Prior art) All resins other than powdered vinyl chloride resin are generally extracted from the molten polymer in the form of pellets, and vinyl chloride is also supplied by resin manufacturers with the minimum required stabilizers, mold release agents, etc. It is often blended and supplied to the market as a pellet-like mixture. Therefore, molding manufacturers generally use a mixture obtained by blending the above-mentioned pellets with necessary additives, particularly additives such as coloring materials, and kneading them again as pellets for molding. In such cases, pellets of irregular shapes and quite different sizes, or pellets and powder, are often kneaded together.
Therefore, in such kneading, the well-known open roll or Pan Bali mixer has conventionally been used. Also, open roll and panbari mixers are
In both cases, the mixing operation is batch-type and discontinuous, so the continuous method is to mix the materials in a pre-mixer such as a Henschel mixer, and then feed this into the hopper of the extruder. A method is adopted in which extrusion processing is performed at the same time as kneading.

(Problems to be Solved by the Invention) The open roll kneading method described above has advantages such as simple equipment and easy cleaning, but the part that contributes to mixing is limited to Frixilan in the gap between the rolls, making quality control easy. However, it has disadvantages such as being highly dependent on the skill level of the worker.
Pan Bali mixers have many advantages, such as being significantly more effective at kneading than open-roll kneading systems, but they also have problems such as ungelled residue adhering to the interior falling out and mixing with the molten mass during discharge, and changes in formulation and coloring. There are disadvantages such as cleaning is troublesome and time consuming. In addition, both the open roll kneading method and the Pan Bali mixer perform batch-type discontinuous kneading operations, resulting in poor productivity.

In addition, in the method in which the premixed mixture is fed into the hopper of the extruder using a mixer such as the Henschel mixer, the mixer is used to mix pellets with different shapes and sizes, or with pellets and powder. Especially when the amount of powder added to the pellets is less than 10%, even if it is uniformly dispersed by pre-mixing, the pellets or particles that need to be removed after being put into the hopper may fall through the gaps between large pellets and become uniform. There is also the problem that the mixture loses its properties and cannot be kneaded to a uniform ratio, and it is also quite troublesome to remove the powder adhering to the premixer or hopper when changing materials.

(Means and effects for solving the problem) The present invention was made in view of the above-mentioned actual situation, and is made by mixing a small amount of admixture pellets and powder at a fixed ratio and intermittently running an extruder. The present invention provides a method of continuously kneading and extruding materials by charging them into a hopper. In other words, using a load cell or the like, the pellets and powder are automatically weighed so that the weight or volume is sufficiently small compared to the amount of extrusion and at a constant ratio, and the pellets are swirled. At the same time, the mixture is intermittently dumped into the hopper of an extruder, kneaded continuously by the screw of the extruder, and then extruded.

By controlling the interval between the intermittent dropping of pellets and powder from the hopper to a small amount so that the amount remaining in the hopper does not exceed a certain value, the gap between the pellets can be adjusted to reduce the falling speed of the powder and the amount of pellets and powder. Since the consumption rate is close to that of the hopper, separation of the pellets and powder in the hopper is significantly prevented, and since the pellets are fed in a swirling manner, they are well mixed, and are sufficiently uniform for practical use even with intermittent feeding. A homogeneous molded article is obtained since the mixture with a certain consistency is fed to the extruder. In addition, in terms of equipment, the parts where only pellets exist or pass through are easy to clean, and the parts where pellets and powder are mixed are less likely to adhere to the wall because the pellets fall in a spiral. Cleaning becomes extremely easy.

(Example) Fig. 1 is a schematic diagram showing an example in which the kneading and extrusion method of the present invention is applied to electric wire manufacturing equipment. It is an extruder equipped with a Dalmage type screw,
2 is a crosshead. 3 is a pellet 7) hopper that supplies pellets; 4 is a powder hopper that stores powder;
5 is a pellet weighing machine, 6 is a pellet clamp, 7 is a shutter, 8 is a spiral swirl generating conduit, 9 is a powder weighing feeder, and 10 is a mixing hopper, which pellets pellets of heat-resistant vinyl chloride resin mixture. The pellets are supplied from the hopper 3 and weighed to 100 g by the pellet weighing machine 5 and accumulated in the pellet retainer 6. Powdered pigment with a vinyl chloride resin mixture as a binder is used as the powder, and it is supplied from a powder hopper 3 and fed into a mixing pumper 10 in an amount of 1.0 g by a powder measuring feeder 9. At the same time as the powder is introduced, the shutter 7 opens and pellets are supplied. The pellets are accelerated in a conduit 8 generating a spiral vortex and mixed into a mixing hopper 10.
The water flows into the hopper 10 at an almost horizontal angle, generating a vortex in the hopper 10. The remaining amount of the mixture in the mixing hopper 10 is 200
The amount of resin cross-contamination is 80 kg.
The extruded electric wire was manufactured at /hr. As a result, color unevenness due to poor measurement and kneading did not occur. In addition, changing the color by exchanging the powder was easy, and there was almost no need to clean the inside of the device.

In addition, as an application example, it is applied to a 1051φ, L/D=28 vent type extrusion granulator, and contains low density polyethylene as pellets and 0.1% stabilizer (Ciba Geigy's trade name Irganox 1010) as powder. 10 so that
Although granulation was carried out at 0 kg/hr, there was no insufficient kneading. Furthermore, the method of the invention is also applicable to injection molding.

(Effects of the invention) By adopting the kneading and extrusion method of the present invention, preliminary mixing equipment is not required, continuous kneading and extrusion is possible, productivity is improved, and homogeneous products can be obtained. The method is extremely easy to apply to existing extruders, and the equipment to which this method is applied is easy to clean and has good workability.The easy cleaning prevents contamination with foreign substances, and the equipment is inexpensive. . This is particularly effective in high-mix, low-volume production that involves many mix changes and color changes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment in which the kneading and extrusion method of the present invention is applied to an electric wire manufacturing facility Oa. 1: Extrusion i, 2: Crosshead, 3: Pellet hopper, 4: Powder hopper, 5: Pellesoto weighing machine, 6: Pellesoto clamp, 7: Shutter, 8: Spiral vortex generating conduit, 9: Powder weighing Feeder, 10: Mixing hopper.

Claims (2)

[Claims] (1) Resin pellets and powder, each of which has been automatically weighed separately to the required ratio, are intermittently placed into a hopper at the same time and mixed, and then placed in a molding machine. 1. A method of molding plastics in which the pellets are guided and melted, and then molded into a predetermined shape, characterized in that the pellets are dropped into a hopper in a swirling manner. (2) Molding of the plastic according to claim 1, wherein the pellets are dropped through a spiral-shaped vortex generating conduit and merge with the powder at a substantially horizontal angle. Method.