JPS588333B2 - Method for manufacturing patterned thermoplastic synthetic resin molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a patterned thermoplastic synthetic resin molded article;
In particular, the present invention relates to a method of manufacturing a molded article with a pattern using different thermoplastic synthetic resins with different molding temperatures and different colors using a blow molding apparatus equipped with a screw extruder.

The molding temperature here refers to the temperature required to plasticize the molding material.

In blow molding, the molding material is melted in an extruder and a crosshead connected to the extruder, and then a tube-shaped parison is extruded from the crosshead die, immediately sandwiched between molds, and air is blown inside to form the material. It's a method.

In general, there are two types of extruders for blow molding equipment: plunger type, which extrudes the molding material with a plunger, and screw type, which extrudes the molding material with a screw.In plunger type extruders, the molding material in contact with the cylinder wall of the extruder is subject to thermal decomposition. On the other hand, the internal material has the disadvantage that it is delayed in melting.
It is difficult to obtain homogeneous molded products.

On the other hand, in the screw type, kneading is carried out completely, so thermal decomposition of the molding material is less likely to occur, and since shear force is applied to the molding material by kneading, the melt viscosity is lowered, making molding easier.

Therefore, most of the extruders currently in use are screw type.

Conventionally, several methods for producing patterned thermoplastic synthetic resin molded products are known, but in blow molding, the molding equipment is equipped with a plunger-type extruder that does not involve a kneading process. During the melting process, molding materials colored in two or more colors are mixed non-uniformly to create a pattern, making it easy to produce patterned molded products.

On the other hand, in blow molding equipment equipped with a screw extruder, the molding material is melted in the heated cylinder of the extruder, but at the same time it is kneaded by the screw, so the molding material is colored in two or more colors. However, it was completely mixed into a single color, making it almost impossible to obtain patterned molded articles.

However, in spite of this, the plunger type extruder has the above-mentioned drawbacks, so it is hardly used at present.For this reason, patterned molded products are manufactured using a blow molding device equipped with a screw type extruder. Development of a method was desired.

Of course, even in blow molding equipment equipped with a screw type extruder, multiple cylinders are connected to one crosshead, and a differently colored molding material is charged into each cylinder and melted and kneaded. A method was considered in which the colored molten resin extruded from each cylinder is led to a crosshead and mixed to create a pattern, extruded, and blow molded, but this method requires a cylinder for each color, so The drawback is that it requires a large amount of equipment and labor, and is extremely expensive.

Therefore, as a result of intensive research, the present inventor found that (1) The melting process of thermoplastic synthetic resin molding material in a blow molding device equipped with a screw extruder is strictly speaking a melt-kneading process carried out within the cylinder of the extruder. The process can be divided into two stages: a melting process that does not involve a kneading process, which is carried out in a crosshead connected to the extruder, and the set temperature of each process can be freely controlled. (2) The molding temperature, that is, the temperature required to plasticize, differs depending on the type of thermoplastic synthetic resin, and thermoplastic synthetic resins that have different colors and have a high molding temperature (hereinafter referred to as high molding temperature resin) and molding We focused on two points: Even if a low-temperature thermoplastic synthetic resin (hereinafter referred to as a low-molding-temperature resin) is plasticized and mixed unevenly under the molding temperature of a high-molding-temperature resin, an irregular pattern will appear. did.

The present invention was established against the above background, and proposes a method that allows thermoplastic synthetic resin molded products with beautiful patterns to be easily manufactured using a blow molding device equipped with an ordinary screw extruder. This is what I am trying to do.

That is, the present invention provides a blow molding apparatus that includes a screw extruder and a crosshead connected to the extruder after loading thermoplastic synthetic resin molding materials that have different molding temperature ranges and are colored in different colors. , a thermoplastic synthetic resin with a low molding temperature is melt-kneaded in the cylinder of the extruder heated to match the molding temperature of the low molding temperature resin, and then a thermoplastic synthetic resin with a high molding temperature is mixed with the high molding temperature. The gist is that the resin is melted in the crosshead heated to match the molding temperature of the resin, and then blow-molded into a desired shape to create an irregular pattern on the molded product.
The present invention is characterized by the melting process of the molding material, which will be explained below in sequence.

First, in the present invention, different types of thermoplastic synthetic resins having different molding temperature ranges are used as molding materials.

As shown in the table below, the molding temperature of thermoplastic synthetic resins varies depending on the type.

However, the above table does not indicate exact numerical values; they vary depending on the structure and performance of the molding equipment, and the degree of plasticization of the molding material also varies depending on the size of the molding material. For example, powder is better than granular. Any combination of molding materials may be selected, except in cases where there is an extreme difference in molding temperature, which is also affected by the length of the melting time, but some types may not be compatible with each other. In this case, the strength of the molded product will be affected, so when selecting such a combination, it is preferable to reduce the mixing ratio.

Different types of molding materials must have different colors from each other.

For coloring, dry colors and masterbatches are added to low molding temperature resins.

However, since the high molding temperature resin is melted after the low molding temperature resin is melted and kneaded as described later, it must be colored in advance.

In this case, high molding temperature resin is sprinkled with dry color and melted and kneaded in an extruder, then cut with a cutter or pelletizer, or molded products made of colored high molding temperature resin are crushed with burrs, etc. Can be used.

One of the different molding materials may be uncolored.

Also, if you want to create a multicolored pattern, you can use high molding temperature resins of various colors.

Next, the colored molding material is thoroughly stirred in a tumbler, etc., then loaded into a blow molding device equipped with a screw extruder, and then melted and extruded. This will be explained using drawings.

The figure is a schematic diagram of a conventional blow molding apparatus equipped with a screw extruder. First, a well-stirred molding material 1 is loaded into a hopper 2, and then fed into a screw extruder 3.

At this time, the temperature of the cylinder 4 of the extruder 3 is set by the heating device 5 in accordance with the molding temperature of the low molding temperature resin of the molding material 1.

In this way, only the low molding temperature resin of the molding material 1 is melted and colored, and at the same time, it is completely kneaded by the screw 6.

At this stage, the high molding temperature resin remains unmelted.

Subsequently, the molding material 1 is fed from the extruder 3 to the crosshead 7 by the screw 6, but at this time, the temperature of the crosshead 7 is set by the heating device 8 to match the molding temperature of the high molding temperature resin.

In this case, the high molding temperature resin is also melted here, but since there is no kneading process in this crosshead 7, the melted low molding temperature resin is already mixed unevenly, and the crosshead die 9 A tubular parison 10 with an irregular pattern is extruded.

Finally, the parison is placed in a mold (not shown) and blow molded into the desired shape to produce a patterned molded product.

In addition, blow molding equipment equipped with a screw extruder includes:
There is also a system in which an accumulator rake is provided between the extruder and the crosshead, but even with this type, patterned thermoplastic synthetic resin molded products can be manufactured by appropriately controlling the temperature of the accumulator.

Next, an example will be described.

Example 1 Screw type blow molding equipment Kautex V-8 manufactured by Japan Steel Works Molding material and low molding temperature resin coloring treatment Addition of ivory dry color to low density polyethylene (Ube F-022).

High molding temperature resin high density polyethylene (Asahi Kasei Suntec B-170) It was colored brown and made into pellets.

Temperature conditions: Cylinder temperature: 120°C Crosshead temperature: 140°C Results: A molded product with an irregular pattern in which ivory and brown were intricately intertwined was produced.

Example 2 Screw type blow molding equipment Kautex V-8 manufactured by Japan Steel Works Molding material and low molding temperature resin coloring treatment Low density polyethylene (Ube F-022) Uncolored high molding temperature resin polypropylene (Mitsubishi Noblen BC-8) Blue color It was colored and made into pellets.

Temperature conditions: Cylinder temperature: 120°C Crosshead temperature: 150°C Results: A beautiful blue irregular pattern appeared in the resin of the translucent molded product.

From the above, the effects of the present invention can be summarized as follows.

(1) Molded products with beautiful patterns can be easily obtained by simply controlling the heating temperature using a blow molding apparatus equipped with a conventional screw extruder without the need for special equipment.

(2) Molded products with multicolored patterns can be easily manufactured.

[Brief explanation of the drawing]

The figure is a schematic diagram, partially in section, of a blow molding apparatus equipped with a conventional screw extruder. 1... Molding material, 3... Extruder, 6...
...Screw, 7...Cross head.

Claims (1)

[Claims] 1. After loading thermoplastic synthetic resin molding materials that have different molding temperature ranges and are colored in different colors into a blow molding device equipped with a screw extruder and a crosshead connected to the extruder, A low thermoplastic synthetic resin is melt-kneaded in the cylinder of the extruder heated to the molding temperature of this low molding temperature resin, and then a thermoplastic synthetic resin with a high molding temperature is melted and kneaded at a molding temperature of this high molding temperature resin. 1. A method for producing a patterned thermoplastic synthetic resin molded article, which comprises melting the molded article in the crosshead heated according to the temperature, and then blow-molding it into a desired shape to create an irregular pattern on the molded article.