JPS5829221B2 - Hatsuposhi - Tonoseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a foamed synthetic resin sheet, and its purpose is to freely obtain a wide sheet with high strength and no difference between the front and back, from thin to thick sheets. It's about to try.

Conventionally, the standard method for producing foamed synthetic resin sheets is to extrude a thermoplastic resin melt containing a blowing agent through a circular die to form a tubular foam, which is then cut open to form the foamed synthetic resin sheet. There are known ways to obtain it.

However, in this method, there is a limit to the thickness of the foamed synthetic resin sheet, and it is difficult to make the foaming and cooling conditions on the inner and outer surfaces of the tubular body the same, so it is necessary to cut it open and make it into a sheet. In this case, the properties of the front and back surfaces are not equal and warpage tends to occur.

In order to improve the above-mentioned drawbacks, a method has been proposed in which the tubular body is immediately compressed after extrusion to form a single plate.
No. 368 exemplifies blowing solvent vapor into the tubular body while dropping liquid adhesive;
The working environment is deteriorated due to solvents, etc., and the product sheet deteriorates due to solvent cranking.

Furthermore, Japanese Patent Publication No. 49-5749 exemplifies a method in which after extruding the inner surface of a tubular body at a temperature that causes foaming, the inner surface is compressed between pinch rolls while the inner surface is still above the softening temperature of the resin. In this method, if the distance of narrowing the foam sheet with pinch rolls is long enough to prevent deflection of wide sheets or thin sheets, the heat will be absorbed and the inner resin temperature will rise above the softening temperature at the time of narrowing with the pinch rolls. It is difficult to hold the foamed sheet, and the resulting foamed sheet tends to easily peel off partially or completely after cooling.

Furthermore, in Japanese Patent Publication No. 46-40789, as a method to improve this drawback, water vapor is injected into the tubular body to maintain the resin temperature above the softening temperature. It is also difficult to balance the drainage of the condensed water.

If condensed water entrained on the inner surface of the sheet is present, there are drawbacks such as the sheets not being fused together in some places.

The inventors of the present invention have solved this drawback and have improved the thickness from 2 to 15 mm.
In manufacturing a sheet with a width of 700 mm or more and a width of 1 ft. By heating the inside of the sheet again, thermally melting it, and fusing it with pinch rolls, the foam sheet can be sufficiently foamed by the first pinch roll, and there is no deflection, and the temperature can be easily adjusted by heating again. Moreover, since the distance for the heat-fused foam sheet to be compressed by the next pinch roll is short, the present invention provides a method for manufacturing a foam sheet with a width of 700 mm or more that can be uniformly fused.

That is, the present invention extrudes a foamed synthetic resin into a tubular shape by a circular die extrusion method, and the temperature of the inner surface of the tubular body is such that the inner surface of the tubular body does not fuse with each other due to pressure bonding, and the temperature is 1500 m from the die surface.
A sheet with a width of 700 m is compressed between pinch rolls of 50 m or more to make a flat plate, cut into pieces, heated again to melt the inner surface of the sheet, and then compressed again between pinch rolls to fuse the inner surface.
It is characterized by producing a foam sheet of rn or more.

Since the sheet obtained by the present invention is made by pressing together two sheets having a symmetrical structure in the thickness direction, there is no difference in density or cell diameter between the front and back sides of the foam sheet, and warping of the sheet is prevented. .

Furthermore, the foamed sheet obtained by the method of the present invention has a structure in which the surface cells are small and relatively high density, and the inner layer cells are large and relatively low density, so compared to a sheet with a small difference in density between the inner and outer layers, Strength for the same average density, especially bending strength,
It can be made into a sheet with a high bending modulus.

In the method of the present invention, suitable raw material synthetic resins include polystyrene and styrene-based copolymers, such as copolymers of styrene and acrylonitrile, methyl methacrylate, or butadiene, and compounding agents include appropriate amounts of blowing agents, such as An organic compound having a boiling point lower than the softening temperature of the resin composition or a chemical blowing agent that generates gas by thermal decomposition is used.

The former method involves supplying a polymer pellet pre-soaked with a low-boiling substance such as propane, pentane, vinyl chloride, methyl chloride, dichlorotetrafluoroethane, or dichlorodifluoromethane to an extruder;
Foaming can be achieved by press-feeding the low-boiling point material from the middle part of the extruder and extruding it while kneading.

A method belonging to the latter category involves foaming by subjecting a chemical blowing agent such as sodium bicarbonate, abbisisobutyronitrile, or para-toluenesulfonyl hydrazide to an extruder together with a resin and causing the chemical blowing agent to decompose in the extruder. will be held.

EXAMPLE A polystyrene resin containing 3% pentane as a blowing agent was applied to the extruder 1 shown in FIG. 1, and extruded at 120 DEG C. through a circular die 2 having a slit of 150 ml in diameter and 1 ml in thickness.

Air is pressurized into this from air pipe 3 and the diameter is 500m/
A tubular foam 4 having a diameter of m was formed, and the tubular foam was compressed and folded between pinch rolls 5 at a position 1.500 m 1 m from the circular die surface to form an envelope-shaped flat plate.

Further, both ends of the sheet were cut with a knife 6 and the sheet was divided into two parts with a roll 7. After that, the inner surface of the sheet was heated and melted with an infrared heater 8, and the sheet was again compressed with a pinch roll 9.

As a result, the inner surface is firmly bonded to a thickness of 5 m/m and a width of 760 mm.
A foamed sheet with a foaming ratio of 11 times was obtained at m/m2.

At this time, the temperature of the tubular foam at the position of the pinch roll 5 is:
Even when the surfaces were heated at 60° C. and the inner surfaces were heated at 80° C., the sheets did not fuse together even when compressed with pinch rolls 5, and after cutting both ends, the sheets could be easily peeled off when divided into two with rolls 7.

[Brief explanation of drawings]

The figure shows a cross-sectional view illustrating the process of the invention. 1... Extruder, 2... Circular die, 3... Air pipe, 4... Tubular foam, 5... Pinch Roll 6...Knife, 7...Roll 8...Heater 9...Pinch roll.

Claims (1)

[Claims] 1 A foamed synthetic resin was extruded into a tubular shape using the circular die extrusion method, and the temperature of the inner surface of the tubular body was such that it would not fuse with each other due to pressure bonding, and it was compressed between pinch rolls at a distance of 1,500 degrees or more from the goose surface to form a flat plate. Width 7001 characterized in that the sheet is then incised, the inner surface of the sheet is heated again to melt it, and the inner surface is again compressed between pinch rolls to fuse the inner surface.
A method for producing a foam sheet with a t1rL or higher.