JPH08229971A - Resin foam sheet and molding method thereof - Google Patents

Abstract

PURPOSE: To provide a resin foam sheet and a molding method having adequate satisfaction in its rigidity and cushioning property even in the case being used in a large-sized vessel. CONSTITUTION: An original foamed sheet 1 subjected to a primary foaming process is heated, and the molding gap t2 is set twice or more as larger as the thickness t0 of the original foamed sheet 1 to subsequently be held by a pair of molds 2, 3 heated to a temperature or higher being lower by 10 deg.C than the softening temperature of the original foam sheet 1. The original foam sheet 1 is vacuum sucked alternately or at the same time from the side of each mold 2, 3 for subjecting the original foamed sheet to a secondary foaming process and forming a high-order foamed sheet 5. Thus, molding a foamed resin sheet having the cell configuration dimensions longer in its wall thickness direction (Z direction) than in its width direction (X direction) and flowing direction (Y direction).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed resin sheet excellent in rigidity and cushioning property, and a method for molding the same.

[0002]

2. Description of the Related Art Conventionally, a foamed resin sheet made of a thermoplastic resin such as polystyrene (PS) or polypropylene (PP) having a wall thickness of about 1 to 3 mm is widely used after being molded into containers such as food trays and donburi. Has been done.

In the case of small containers such as food trays and dongbris as described above, the conventional foamed resin sheet is almost satisfactory in both rigidity and cushioning property. For example, in a large container such as a fish box. In this case, if the conventional foamed resin sheet is used as it is, the rigidity and the cushioning property are insufficient.

In order to solve such a problem, therefore, the thickness of the foamed resin sheet is increased, or water-resistant treated high-rigidity wood, corrugated paper, paperboard or the like is attached to the foamed resin sheet. I was using it.

[0005]

However, when the thickness of the foamed resin sheet is increased, it takes a long time to cool the foamed resin sheet after extrusion molding, and there is a problem that the surface of the foamed resin sheet is wavy. there were. Further, when sticking wood or the like to the foamed resin sheet, the work of sticking the wood or the like takes time and labor, and the weight of the foamed resin sheet also increases.
The appearance was poor and there was a problem with recyclability.

The present invention has been made in view of the above conventional problems, and has various problems in increasing the thickness of the foamed resin sheet or when attaching wood or the like to the foamed resin sheet. It is an object of the present invention to provide a foamed resin sheet that sufficiently satisfies rigidity and cushioning property even when used in a large container such as a fish box, and a molding method thereof.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies and researches to solve the above-mentioned problems, and as a result, the shape and size of the cells are determined from the width direction (X direction) and the flow direction (Y direction). Further, they have found that a foamed resin sheet long in the thickness direction (Z direction) is excellent in both rigidity and cushioning property, and arrived at the present invention.

That is, the foamed resin sheet of the present invention is characterized in that the shape and size of the cells are longer in the thickness direction (Z direction) than in the width direction (X direction) and the flow direction (Y direction). . Here, the shape dimension in the thickness direction (Z direction) is 1.2 times or more the shape dimension in the width direction (X direction) and the flow direction (Y direction) in the region excluding the 10% internal region from the surface of the foamed resin sheet. It is preferable that 30% or more of the cells are present.

As the raw material resin for the foamed resin sheet, polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PE) is used.
T), acrylonitrile butadiene styrene copolymer (ABS), ethylene vinyl acetate copolymer (EVA) and other thermoplastic resins can be applied. The foamed resin sheet has a thickness (t _f ) of 2 to 10 mm, particularly 3 to 8 m.
m, the expansion ratio is 15 to 100 times, and particularly preferably 20 to 40 times.

In the method of molding a foamed resin sheet of the present invention, the primary foamed raw fabric foamed sheet is heated, and the molding gap is set to be at least twice the thickness of the raw fabric foamed sheet to soften the raw fabric foamed sheet. It is sandwiched by a pair of molds heated to a temperature 10 ° C. lower than the temperature, preferably to a melting point temperature or higher, and vacuum suction is alternately or simultaneously applied from each mold side to secondary foam the raw fabric foam sheet to obtain a higher order. It is characterized by molding a foamed sheet.

The raw fabric foam sheet has a thickness (t _O ) of 1 to
It is preferably 2.5 mm and the expansion ratio is 5 to 15 times. The content of the foaming agent is preferably 0.6 to 3% by weight,
It is more preferably 1 to 3% by weight.

[0012]

EXAMPLES Specific examples of the foamed resin sheet and the method for molding the same according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the raw fabric foam sheet 1 has
Inorganic filler, plasticizer, as an additive to polystyrene resin,
A foaming agent (content: 2.5% by weight), a colorant, etc. are blended, melted and kneaded in an extruder, and then a molten resin is extruded from a circular die connected to the tip end, and the resulting foamed molded article is cut. Use a sheet.

The original fabric foam sheet 1 is, as shown in FIG.
Width 1000 mm, length 200 m, thickness (t _O ) 2.5 m
m, a foaming ratio of 10 times, a basis weight of 240 g / m ² , and the cross-sectional cell structures in the width direction (X direction) and the flow direction (Y direction) are as shown in FIGS. 2 (A) and 3 (A). there were.

This raw fabric foam sheet 1 is placed on a conveying table of a thermoforming machine (vacuum forming machine) with both ends fixed by needle pins, and is set by a roller chain into a heating zone, a forming zone and a cutting zone. Carry in sequence.

A heater is provided in the heating zone,
The raw fabric foam sheet 1 is heated by the heater to 80 ° C. to 120 ° C., which is 80 ° C. or higher which is the softening temperature of the polystyrene resin.

A pair of molds 2 and 3 are arranged in the molding zone. As shown in FIG. 4, the molds 2 and 3 are pressed with a pressing gap (t ₁ ) and a molding gap (t). ₂ ) is defined. Here, the pressing gap (t ₁ ) is 2.3 mm, which is less than the thickness (t ₀ ) of the raw sheet 1, and the molding gap (t ₂ ) is about 2.8 of the thickness (t ₀ ) of the raw sheet 1. Doubled to 7 mm.

A large number of through holes 4 are formed in the molding walls 2a and 3a of the molds 2 and 3, and the air in the molding gap (t ₂ ) is sucked through these through holes 4 by a vacuum suction device. , Can be eliminated. Further, the molds 2 and 3 can be set to an arbitrary temperature by a temperature adjusting device, and the temperature is 70 ° C. to 1 ° C. which is 10 ° C. lower than the softening temperature of the polystyrene resin.
It has been heated to 20 ° C.

Each mold 2, on the upper and lower surfaces of the original fabric foam sheet 1,
3 are brought into contact with each other and the original fabric foam sheet 1 is sandwiched in the pressing gap (t ₁ ). Then, vacuum suction is alternately or simultaneously applied from the mold sides 2 and 3 by a vacuum suction device to secondary-foam the original fabric foam sheet 1 to form a high-order foam sheet 5.

A cutter is provided in the cutting zone,
The high-order foamed sheet 5 secondary-foamed by this cutter is cut from the remaining portion of the original fabric foamed sheet 1. The high-order foam sheet 5 has a width of 1000 mm and a thickness (t _f ) of 7 m.
m, the expansion ratio is 25 times, the basis weight is 240 g / m ² , and the cross-sectional cell structures in the width direction (X direction) and the flow direction (Y direction) are as shown in FIGS. 2 (D) and 3 (D). there were.

The high-order foamed sheet 5 thus obtained has a cell shape dimension longer in the thickness direction (Z direction) than in the width direction (X direction) and the flow direction (Y direction), and is very lightweight, Since it is thicker than the original fabric foam sheet 1, the bending rigidity is high, and since the expansion ratio is 2 times or more, the surface and the inside are soft, and the cushioning property was sufficient.

The high-order foam sheet 5 was molded under various molding conditions by the above-described molding method. The molding conditions are shown in Table 1 and the evaluation results are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

From Table 2, it is seen that 30% or more of the cells have a shape dimension in the thickness direction (Z direction) that is 1.2 times or more the shape dimension in the width direction (X direction) and the flow direction (Y direction). It has been found that a resin sheet can sufficiently satisfy both bending rigidity and cushioning property. The 10% inner region from the surface of the foamed resin sheet is a non-foamed skin layer, and is therefore excluded from the calculation of the cell number ratio.

The higher the set temperature of the molds 2 and 3, the higher the foaming ratio, and the higher-order foamed sheet 5 excellent in buffering property can be obtained. Further, when the mold is closed, the gap between the lower surface of the molding wall portion 2a of the mold 2 and the upper surface of the original sheet 1 is set to 0.1 to 1 mm, and a large vacuum suction is applied to the mold 3 side, the flatness of one side surface is improved. A higher foamed sheet 5 having a higher appearance and excellent appearance is obtained.

As shown in FIG. 5, one or both surfaces of the high-order foamed sheet 5 may be laminated with a thermoplastic film 7 on which printing, aluminum vapor deposition or the like is applied via an adhesive resin 6.

Here, for example, ethylene-vinyl acetate resin 15 to 30 μm is used as the adhesive resin 6, and polystyrene (PS), high impact polystyrene (HIPS), polypropylene (P) is used as the thermoplastic film 7.
P) and polyethylene (PE) 20 to 50 μm can be laminated well.

As a laminating method, a generally known appropriate method such as an extrusion laminating method and a dry laminating method can be adopted.

The high-order foamed sheet 5 thus obtained is punched into a predetermined shape by a press machine equipped with a punching blade to obtain a final product as a container lid. In addition, if a bending curve portion forming bar is attached to the molds 2 and 3 for molding,
As shown in (C), the high-order foam sheet 5 has a fold line portion 5
It is possible to obtain a final product as a lid or a body of a container in which a is formed and which can be bent into a predetermined shape. In this way, as shown in FIGS. 6A and 6B, the lid 9 or the main body 10 of the fish box 8 having excellent rigidity and cushioning properties can be manufactured.

[0031]

EFFECT OF THE INVENTION The foamed resin sheet of the present invention is one in which the shape dimension of the cross-section cell is made longer in the thickness direction (Z direction) than in the width direction (X direction) and the flow direction (Y direction). Compared to a foamed resin sheet of the same size, it is lighter in weight, yet has sufficient rigidity and cushioning properties, as well as excellent recyclability.

Further, according to the method for molding a foamed resin sheet of the present invention, this foamed resin sheet can be easily molded and a foamed resin sheet having a good appearance can be molded.

[Brief description of drawings]

FIG. 1 is an external perspective view of a raw fabric foam sheet.

2A and 2B are explanatory views showing a cross-sectional cell structure in the width direction (X direction), in which (A) is a raw foam sheet, (B) is a high-order foam sheet that is secondary foamed without vacuum suction, ( C) is a high-order foamed sheet that is secondarily foamed while vacuum suction is performed from one mold side, and (D) is a high-order foamed sheet that is secondarily foamed while vacuum suction is performed from both mold sides. .

3A and 3B are explanatory views showing a cross-sectional cell structure in the flow direction (Y direction), in which (A) is a raw fabric foam sheet, (B) is a high-order foam sheet that is secondarily foamed without vacuum suction, ( C) is a high-order foamed sheet that is secondarily foamed while vacuum suction is performed from one mold side, and (D) is a high-order foamed sheet that is secondarily foamed while vacuum suction is performed from both mold sides. .

FIG. 4 is an explanatory view showing a method for molding a foamed resin sheet of the present invention.

FIG. 5 is a cross-sectional view of a foamed resin sheet laminated with a thermoplastic film.

6A is an external perspective view of a fish box having a foamed resin sheet of the present invention as a lid, FIG. 6B is an external perspective view of the lid, FIG.
(C) is an enlarged cross-sectional view of a folding curve portion of the foamed resin sheet.

[Explanation of symbols]

 1 original fabric foam sheet 2 mold 3 mold 5 high-order foam sheet 5a folding curve part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Kawamura 1000 Kawajiri-cho, Yokkaichi-shi, Mie Prefecture Mitsubishi Chemical BSF Corporation

Claims (6)

[Claims] 1. A foamed resin sheet characterized in that the shape and size of the cell are longer in the thickness direction (Z direction) than in the width direction (X direction) and the flow direction (Y direction). 2. The shape dimension in the thickness direction (Z direction) is 1.2 of the shape dimension in the width direction (X direction) and the flow direction (Y direction) in the region excluding the 10% internal region from the surface of the foamed resin sheet. The foamed resin sheet according to claim 1, wherein 30% or more of the cells are double or more. 3. The foamed resin sheet according to claim 1, wherein polystyrene resin is used as a raw material resin, and the expansion ratio is 20 times or more and the thickness is 3 mm or more. 4. The foamed resin sheet according to claim 1, wherein a bent curve portion is formed. 5. The foamed resin sheet according to any one of claims 1 to 4, which is used as a lid or a main body of a fish box. 6. The primary foamed raw fabric foamed sheet is heated, and the molding gap is set to be at least twice the thickness of the raw fabric foamed sheet and heated to a temperature 10 ° C. lower than the softening temperature of the raw fabric foamed sheet. A method for molding a foamed resin sheet, characterized in that it is sandwiched by a pair of molds, and vacuum suction is performed alternately or simultaneously from each mold side to secondary foam the raw fabric foamed sheet to form a high-ordered foamed sheet. .