JP2000119430A - Foamed sheet and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a formed sheet having smooth surface and rectangular cross-section that is continuously extruded from an extrusion molder in the form of sheeted foamed composition. SOLUTION: To obtain a foamed sheet of a rectangular section by kneading/ heating/pressurizing a foaming composition composed of water, etc., as a foaming agent using a extrusion molder, when extruding and swelling in air from a die pore having a prescribed shape opening, the formed sheet of the rectangular section composed of a smoothing surface resistant to tearing is continuously obtained by designing the die shape to prevent swelling from one long side of the rectangular section opening in swelling to a three-dimensional direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foamed sheet having a rectangular cross section composed of smooth surfaces, from a sheet-shaped foamable composition produced by continuous discharge by an extruder.

[0002]

2. Description of the Related Art When a foam of the prior art is kneaded, heated and pressurized by an extruder and discharged, water and other foaming agents expand to obtain a foam. The foaming composition is kneaded, heated and pressurized by a machine, and discharged into the atmosphere from a die hole provided at the tip, the foaming agent evaporates and expands into a foam, but in this case, in a three-dimensional direction. Free foaming occurs and the product tends to be spherical. In the case of discharging continuously, the foam is connected to form a round cord-like foam.

[0003] In the above, a round string-shaped foam can be easily obtained by making a die hole provided at a tip end into a round hole, and a foam having an elliptical or rectangular cross section can be obtained. May be provided with a jig that deforms a foam that is discharged and generated in the form of a round string into a rectangle from the outside.

In this case, since the size of a round cord-like foam obtained from a single die hole is limited, a plurality of die holes are provided at appropriate intervals if it is desired to enlarge the dimension. For example, the size can be increased in both the vertical and horizontal directions.
At this time, it is a precondition that the die holes are provided at intervals such that the foamable compositions discharged from the plurality of die holes are pressed and fused to each other.

In order to obtain a foam having an elliptical or rectangular cross section, when a die having an elliptical or rectangular opening manufactured in proportion to the expansion ratio is used, the ratio of the short dimension to the long dimension is obtained. Exceeds a certain limit, the ink is discharged in a shape folded in the longitudinal direction. This phenomenon is explained as a result of the fact that the expansion in the longitudinal direction is prevented, and as a result, a strain pressure is generated in the short direction, and this strain is absorbed by the folding phenomenon.

A foam discharged from a plurality of die holes and bonded to each other or a foam sheet discharged from a die hole having an elliptical or rectangular cross section has an uneven surface, so that a smoother surface can be obtained. In some cases, a jig that is forcibly deformed from the outside is provided, but there is a disadvantage that the pressed and fused joints are not sufficiently adhered and are easily peeled off.

[0007]

In order to obtain a smooth surface, the sheet-like foam obtained by the prior art is discharged and formed in a round string shape and then is forcibly deformed and joined from the outside.
The product discharged from the die hole having a rectangular cross section and folded in the longitudinal direction must be forcibly deformed and joined from the outside to ensure a predetermined shape and a smooth surface.

[0008] In addition, when the foam of the prior art is kneaded, heated and pressurized by an extruder and discharged, water and other foaming agents expand to obtain a foam. This is due to the vaporization and expansion of water and other foaming agents, and expands while depriving the heat of vaporization from the surroundings, causing a sudden temperature drop.If a thermoplastic resin is used as the binder, the The fluidity of the resin will be significantly impaired. Therefore, after forming a discharge from a plurality of die holes in the form of a round string, a sheet-shaped foam obtained by forcibly deforming and joining from the outside, and a folded foam obtained by discharging from a die hole having a rectangular cross section are obtained. The foamed sheet obtained by forcibly deforming and joining the thermoplastic composition from the outside is cooled when the thermoplastic resin used as the binder is discharged and expanded, and the original fluidity is significantly reduced. Due to the pressure bonding, there is a problem that the adhesive strength is insufficient and the film is weak against tearing.

[0009]

In order to solve the above-mentioned problems, the present invention provides a structure in which a long side of a rectangular die hole cross section is extended in the discharge direction from the other side. Since the expansion to one side is hindered, and free foaming is possible only in the remaining three sides, the foamed composition in which the expansion is hindered is absorbed in the remaining three sides, without causing the conventional folding phenomenon. It has become possible to obtain a sheet-like foam which is smooth on all four sides.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The foamed sheet of the present invention is obtained by kneading, heating and pressurizing a foamable composition using water or other foaming agent with an extruder and discharging it into the atmosphere from a die having a predetermined shape into the atmosphere. With a rectangular cross-section foam sheet that is continuously generated,
Provided is a method for producing a foamed sheet having a smooth surface without forcibly deforming and joining after foaming.

In the structure for extending one side of a dice hole having a rectangular cross section used in the present invention in the discharge direction, even if it is an integral type, it is made separately by joining with a fastener such as a bolt. You may.

In addition to the method of providing one extending side on one side of the long side of the rectangular cross section, it is also fixed at the center of the rectangular opening with an opening as the core of the rectangular cross section. By doing so, two rectangular cross-section foam sheets can be simultaneously formed on both sides of the core.

Further, by forming the core into a circular shape and providing an opening outside thereof, a tubular foamed sheet can be obtained.

[0014] The production method of the present invention is characterized by providing a production method in which a foamed sheet having a rectangular cross section composed of smooth surfaces can be easily obtained and a foamed sheet having excellent tear strength can be obtained.

[0015]

EXAMPLE A mixture of 30 kg of polypropylene, 70 kg of corn starch and 3 kg of calcium carbonate was fed to a twin screw extruder having a screw diameter of 47 mm. Water was supplied at a rate of 3-5 liters / hour together with the mixture, and a sheet-like mixture was discharged and expanded from a discharge section maintained at 160-180 degrees Celsius at an extrusion rate of 50 kg / hour. At this time, the temperature of the heater of the extruder and the temperature of the discharge die were adjusted so that the temperature of the mixture immediately before discharge was maintained at 170-190 degrees Celsius accurately.

The opening of the discharge section is 0.7 mm × 70 mm
70m wide where a rectangular die was attached and discharged.
m, a foamed sheet having a cross section with an average thickness of 5 mm was obtained. In this foamed sheet, about 12 grooves were formed on both front and back sides in the width direction, and a folding phenomenon was observed because expansion in the width direction was prevented. Was done.

One side of the opening of the die (width 70 m)
A jig was attached along m), and a foam sheet having a cross section having a width of 90 mm and a thickness of 5 mm was obtained when a discharge was performed by devising the expansion in the side direction.
No trace of the folding phenomenon was observed because the expansion in the width direction was prevented, and a smooth surface was formed on both sides.

[0018]

When the foamed sheet obtained by the example of the present invention and the foamed sheet produced by the conventional method are compared, the product of the present invention is superior in smoothness in appearance, and in strength, The tear strength of the conventional product is so low that it cannot be used, but the product of the present invention has a strength comparable to that of corrugated cardboard. Also, in terms of manufacturing equipment, in the prior art, a jig for forcibly deforming the foam from the outside after being discharged is provided, and the discharge of the sheet is hindered by the frictional resistance of the jig. However, in the case of the product of the present invention, a frictional resistance that hinders discharge does not occur, so that a special take-up device or the like is not required. As described above, according to the present invention, not only the quality is improved but also the production equipment is simple and the handling is easy, so that the production cost can be reduced as compared with the conventional technology.

Claims (4)

[Claims] 1. A smooth surface obtained by kneading, heating and pressurizing a foaming composition using water and other foaming agents in an extruder and discharging and expanding it into the atmosphere. A foam sheet characterized by the following. 2. A method for producing a foamed sheet by kneading, heating and pressurizing a foaming composition using water or another foaming agent with an extruder, and discharging and expanding the composition in the atmosphere. Characterized in that the opening has a rectangular shape, and a long side of the four sides constituting the rectangle has a structure extending in the ejection direction. 3. In the structure of the above-mentioned discharge die, a core having a rectangular cross section is provided at the center of the rectangular opening so as to protrude in the discharge direction, and the opening is provided around the core. A method for producing a foamed sheet characterized by the following structure. 4. A structure of the above-mentioned discharge die, wherein a core having a circular cross section protrudes in the discharge direction at the center of the circular opening and is fixed, and the opening is provided outside the core. Method for producing a foam sheet.