JPS6111189B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing plastic wood suitable for food packaging.

Traditionally, wood for packaging has generally been manufactured by slicing wood into thin pieces and cutting them into predetermined lengths. However, such wooden logs contain an anthelmintic agent to prevent pests from entering the wood, and are therefore unfavorable in terms of food hygiene.

Therefore, in recent years, paper-made wood has been used, which is made from pulp bleached with a special bleaching agent, impregnated with wax, and embossed. However, since the manufacturing process for this paper-made wood is complicated, attempts have been made to manufacture a plastic-made wood that can be manufactured using a simple process.

However, traditional plastic wood
It is known that a single-layer plastic film is embossed to increase its rigidity, but it does not have sufficient stiffness for practical use. On the other hand, films using highly rigid resins such as polycarbonate resin, polystyrene, ABS resin, etc. lack film strength and are easily damaged by bending, etc., and have the disadvantages of poor oil resistance.

The object of the present invention is to produce plastic wood that has sufficient stiffness as wood, is resistant to bending and tearing, and has excellent chemical and oil resistance.

The present invention uses a two-layer inflation molding method to form a two-layer cylindrical film with an inner layer of 70% of the total thickness of the film.
Form a polystyrene layer with a wall thickness of ~90%,
A biaxially stretched two-layer cylindrical film with a high-density polyethylene layer having a thickness of 10 to 30% of the total film thickness as the outer layer is folded flat and the inner layers are pressed together by embossing to form a fixed length. The present invention provides a method for manufacturing plastic warped wood, which is characterized by cutting into pieces.

In carrying out the method of the present invention, a two-layer cylindrical film is first formed. As the raw material resin for this film, polystyrene is used for the inner layer and high density polyethylene is used for the outer layer.

Polystyrene gives strength to the wood, and the thickness of the polystyrene layer is equal to the total thickness of the film.
A range of 70 to 90% is appropriate. On the other hand,
The high-density polyethylene used in the outer layer provides the wood with tensile strength, tear strength, chemical resistance, oil resistance, etc., and serves to compensate for the insufficient mechanical strength of the polystyrene layer. The thickness of the high-density polyethylene layer is suitably in the range of 10 to 30% of the total thickness of the film.

If the ratio of the wall thicknesses of these inner and outer layers is other than the above, it will not be possible to obtain appropriate stiffness and mechanical strength for packaging wood. In addition, if the combination of resins used for the inner and outer layers is reversed to the above case, or if they are combined with other resins, it is possible to obtain a material that has a good balance of stiffness and mechanical strength required for wood. I can't.

Molding of a two-layer cylindrical film is carried out by a normal two-layer inflation molding method, in which both resins forming the inner and outer layers are molded at a molding temperature by, for example, an in-die contact co-extrusion method.
It is extruded at 180-220°C and expanded at an expansion ratio of 3.0-6.0 to obtain a biaxially stretched two-layer cylindrical film with a wall thickness of 40-150μ. Next, this film is flattened using pinch rolls and embossed in the folded state. In embossing, for example, the inner layers are pressed together by passing between 22 heated rolls having uneven surfaces. In this case, if you use an embossing roll with uneven surfaces so that protrusions and grooves are alternately formed in the circumferential direction on one or both of the front and back surfaces of the film, the rigidity of the wood will be further increased. be able to. The embossed film is cut into lengths of, for example, about 10 cm, so as to have the necessary width for the warp. Cutting is usually done by thermal cutting.

The wood obtained in this way can be used as is for packaging foods, etc., but if necessary, a recess for storing food can be provided in the center of the wood, which is very convenient for use as wood. Become something. This recess can be formed using, for example, a vacuum forming machine, and a rectangular, square, circular, or other shallow-bottomed recess is formed in the center of the wood. In this case, the dimensions of the recess can be determined by considering the purpose of use, but generally speaking, if it is about 1/3 to 1/2 of the total length of the tree, both pieces can be used as a lid for the food storage area. Therefore, it is convenient.

The wood obtained by the method of the present invention has appropriate stiffness and mechanical strength (tensile strength, tear strength, etc.), and has excellent chemical resistance and oil resistance, which poses food hygiene problems. There is no In addition, this warp wood does not cause curling due to differences in film shrinkage that tends to occur in laminated films, so it has excellent packaging workability.

Next, the present invention will be explained in detail using examples.

Example 1 General-purpose polystyrene (product name: Idemitsu Styrene HH-30, manufactured by Idemitsu Petrochemical Co., Ltd.) was used as the inner layer resin, and a high-density polyethylene layer (product name: Idemitsu Polyethylene 640UF, manufactured by Idemitsu Petrochemical Co., Ltd.) was used as the outer layer resin.
The inner layer resin was supplied at a rate of 32 kg/hour and the outer layer resin was supplied at a rate of 8 kg/hour to a 60 mm diameter two-layer inflation molding die, using a die temperature of 210°C.
The two-layer film was extruded and expanded at an expansion ratio of 4.8 to obtain a biaxially stretched two-layer cylindrical film with a wall thickness of 100 μm and a folded diameter of 45 cm. In this film, the thickness of the inner layer is 8.0% of the total thickness of the film, and the thickness of the outer layer is 20% of the total thickness of the film.

Next, this two-layer film was folded flat with pinch rolls and embossed with two uneven rolls heated to about 90°C. The resulting film, which has an uneven surface, is thermally cut into 10 cm width sections to create lengths.
A piece of wood was obtained which had a rectangular shape of 45 cm and a width of 10 cm, and had striations formed by convex striations along its long sides.

Example 2 The film having an uneven surface obtained in Example 1 was supplied to a vacuum forming machine heated to about 170°C using an infrared heater, and a film was formed in the center of the film according to a normal vacuum forming method. Width 8.5cm in longitudinal direction, length 15cm in film width direction, depth 1.5cm
Recesses for food storage were formed at intervals of 10 cm, and then the center lines of adjacent recesses were cut to obtain a wood having recesses for food storage.

Claims (1)

[Claims] 1. 70 to 90% of the total thickness of the film as the inner layer of a two-layer cylindrical film by the two-layer inflation molding method.
A biaxially stretched two-layer cylindrical film, which has a polystyrene layer with a wall thickness of A method for manufacturing plastic warp wood, which is characterized by pressing the inner layers together by embossing and cutting them into predetermined lengths. 2. The method according to claim 1, wherein the expansion ratio during two-layer inflation molding is 3 to 6. 3. The method according to claim 1, wherein protrusions and grooves are alternately formed in the circumferential direction of the cylindrical film by embossing. 4. Claim 1, in which a recessed portion for storing food is formed on an embossed cylindrical film by a vacuum forming method.
or the method described in Section 3.