KR20030088670A - Method for preparing of polyethylene foam by rotational molding - Google Patents

Abstract

PURPOSE: A method for manufacturing polyethylene foam by rotational molding is provided to manufacture an insulating material and a soundproofing material with a plastic layer by using a rotational molding process and manufacturing polyethylene foam. CONSTITUTION: A method for manufacturing polyethylene foam by rotational molding comprises the steps of: injecting high-density polyethylene powder and low-density polyethylene granules in a ratio of 1 to 10 or 10 to 1 into a mold, simultaneously; rotating and heating the powder and granules at 110-160 degrees centigrade for 10-20 minutes; and rotating and heating the powder and granules at 160-200 degrees centigrade for 10-20 minutes.

Description

Method for preparing polyethylene foam by rotational molding {Method for preparing of polyethylene foam by rotational molding}

[Industrial use]

The present invention relates to a method for producing a polyethylene foam, and more particularly to a method for producing a polyethylene foam that can be used to heat insulation and sound insulation by adding foamability to existing soft and hard polyethylene plastics.

[Prior art]

In general, a two-layered plastic foam resin with a hard outer shell and a soft inner shell is called a structural foam resin. This structural foam resin is called synthetic wood because it is similar to that of natural wood.

This structural foam resin is different from the conventional foam resin in that it does not use a foam first, and has the advantages of high rigidity in physical properties, no sink mark, and material saving.

Conventionally, such a two-layered structural foam resin has been generally manufactured by injection molding by low pressure foaming and high pressure foaming.

However, the production of the structural foam resin by the injection molding process as described above has a disadvantage in that the manufacturing cost increases due to bad physical properties of the produced resin or post-treatment process.

In order to solve this disadvantage, a rotational molding process has been developed.

The conventional rotational molding process uses plastic powder, and puts it in a sealed mold and heats it with hot air while rotating in two axes, but since it is biaxial rotation, it requires a large place and is inefficient and has a significantly high temperature. Since the mold temperature is partially different, cracks are formed in the molded body, and the strength is insufficient, it is impossible to manufacture molded foams and composite molded bodies having a complicated shape and structure because the vulnerable parts are degraded by inferiority.

In U.S. Patent No. 3,814,778, powdered plastics and crosslinked foamable granules larger than 10 mesh are introduced into the mold at about 90% or less, and the rotating speed is heated at a speed of 0.1 to 1.5 m / min. And a method for producing a composite molded article filled with a foam therein. However, this method is a method for producing the manufactured composite molded product, but is limited to the production of a special composite molded product.

U.S. Patent No. 3,914,361 discloses a mold having a valve sealing a powdered plastic and a foamed granule having a particle diameter of 30 times or more, rotating the mold at a speed of 15 m / min or less and steaming at a temperature of 100 to 250 DEG C with a higher temperature than the outside. A method for producing a foamed granule is disclosed, which is heated by heating to form a skin by powdered plastic, foamed foamed granules, and gas dispersed therein by a valve. However, this patent also has a disadvantage in that the method for producing a composite molded product is limited to a method for producing a specific composite molded product.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems as described above, and an object of the present invention is to provide a method for producing polyethylene molded foam using a rotational molding process.

The present invention to achieve the above object, the present invention

Simultaneously injecting the high density polyethylene powder and the low density polyethylene granules into the mold at a ratio of 10: 1 to 1:10;

Heating and melting the powder and granules at a temperature of 110 to 160 ° C. for 10 to 20 minutes while rotating at a speed of 3.0 to 5.0 RPM; And

Heating and melting the powder and the granules at a temperature of 160 to 200 ° C. for 10 to 20 minutes while maintaining the speed;

It provides a method for producing a polyethylene foam comprising a.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

In the present invention, a polyethylene foam can be obtained by rotationally molding a powder of high density polyethylene and a low density polyethylene granule using a mixture of high density polyethylene (HDPE) and low density polyethylene (LDPE).

The polyethylene foam according to the invention is produced as follows.

First, the powder of high density polyethylene (HDPE) and the granules of low density polyethylene (LDPE) are simultaneously put into a mold and heated while rotating the mold.

The powder is melted by heat in the mold and foamed while the granules are melted later by using the one with a large difference in segregation effect and the size of the surface area of the granules while rotating the powder and the granules at the same time. It happens naturally.

Therefore, the layer of high density polyethylene and low density polyethylene can be distinguished and shape | molded.

At this time, since the high-density polyethylene is foamed at a low temperature to a high temperature at 130 to 200 ℃, low-density polyethylene is foamed at 110 to 180 ℃, it is about 10 to 40 minutes to heat to a high temperature at a low temperature from about 110 to 200 ℃ desirable. More preferably, the heating is performed at a temperature of about 110 to 160 ° C. for about 10 to 20 minutes, and then at a temperature of 160 to 200 ° C. for about 10 to 20 minutes.

In addition, the addition ratio of the high density polyethylene and the low density polyethylene is preferably from 10: 1 to 1:10, more preferably from about 3: 1.

In addition, the heating method is to heat the flame of the burner directly to the mold to heat the mold to increase the temperature, the fuel used is mainly LPG or LNG.

On the other hand, when a circular rail is made around the mold and rotated by a motor, there is no axis, but rotational rotation is possible because the center of rotation plays a role of the axis. Therefore, the entire mold is formed by receiving heat while rotating the mold at 180 to 360 °. Preferably, it is preferable to adopt a structure in which the center of the mold rotation forms an inclination angle of 45 ° left and right so that the entire mold can be molded by receiving heat.

And in order to improve the property of a molded foam, it can manufacture by adding an antioxidant, a sunscreen, an antistatic agent, a coloring agent, a filler, etc. according to a use.

0.1 to 1% of the antioxidant, 0.1 to 2% of the sunscreen, 2 to 4% of the antistatic agent, 5 to 10% of the colorant, 10 to 25% of the filler is preferably used.

In the case of employing the production method according to the present invention, it is possible to simultaneously mold the polyethylene foam of the double material. In addition, the thickness of the prepared foam skin is 1 to 10 mm, and the thickness inside the foam may be 10 to 200 mm depending on the use of the foam.

Hereinafter, a preferred embodiment of the present invention. However, the following examples are only presented to aid the understanding of the present invention, and the present invention is not limited to the following examples.

Example 1

A high density polyethylene and a low density polyethylene ratio of 3: 1 were placed in a rotary molding die having a capacity of 400 L so that the total mixing amount was 10% of the mold. Then, the inclination angle of the rotating die was set at 45 ° about the vertical axis and heated at 110 to 120 ° C. for about 20 minutes at about 5 RPM, followed by heating at 180 to 190 ° C. for 20 minutes.

Example 2

A foam was prepared in the same manner as in Example 1, except that 0.5% of a sunscreen, 0.3% of an antioxidant, and 10% of a colorant were mixed to prepare an additive mixture, and 5% of a mixture of high density polyethylene and low density polyethylene was added to the foam. Was prepared.

As described above, when the molded foam is manufactured by the foam manufacturing method according to the present invention, it is possible to manufacture a heat insulating material and a sound insulation with a plastic skin, so that the skin is not easily broken by impact, and moisture resistance, sound absorption and It is excellent in sound insulation effect, and the molding is easy according to the size of the molding, even if the structure is simple or complicated, the molding can be easily produced.

Claims (7)

Simultaneously injecting the high density polyethylene powder and the low density polyethylene granules into the mold at a ratio of 10: 1 to 1:10; Heating and melting the powder and granules at a temperature of 110 to 160 ° C. for 10 to 20 minutes while rotating at a speed of 3.0 to 5.0 RPM; And Heating and melting the powder and the granules at a temperature of 160 to 200 ° C. for 10 to 20 minutes while maintaining the speed; Method for producing a polyethylene foam, characterized in that it comprises a. The method of claim 1, Method of producing a polyethylene foam in which the heating method in the step of heat melting is direct flame. The method of claim 2, The direct fuel type fuel is LPG or LNG. The method of claim 1, The mold is a method for producing a polyethylene foam to rotate so that the center of rotation to form a tilt angle of 180 to 360 left and right. The method of claim 4, wherein A method of producing a polyethylene foam having the inclination angle of 45 degrees. The method of claim 1, Method for producing a polyethylene foam when the powder and the granules are added with an antioxidant, a sunscreen, an antistatic agent, a colorant and a filler. The method of claim 6, 0.1 to 1% of the antioxidant, 0.1 to 2% of the antistatic agent, 5 to 10% of the colorant, 10 to 25% of the filler is a method for producing a polyethylene foam.