JPS5845033A - Manufacture of thermoplastic resin foamed item bent helically - Google Patents

Abstract

PURPOSE:To produce a helical foamed item, by cutting a part of a thermoplastic foamed sheet, the orientations of the surface and undersurface of which are different from each other, into sheets rectangular in shape, and heating the sheets to be softened. CONSTITUTION:Foamed sheet 1 is extruded in a direction shown by an arrow (a). At this time, an outer mold 21 is rotated in a direction shown by an arrow (d) while an inner mold 22 is rotated in a direction shown by an arrow (e). Thus the foamed sheet cylindrical in shape is obtained, the directions of orientations of the outer surface and the inner surface thereof being differed from each other. The cylindrical sheet is cut open along the length to obtain flat sheet. Rectangular pieces 5, 6 are cut out from the flat sheet. The pieces 5, 6 are heated to cause twisting so that helically bent foamed items can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermoplastic resin foam having a spiral shape, and in particular, to heating a thermoplastic resin foam to relieve internal stress existing within the foam. This method is based on the principle of spirally bending.

When a thermoplastic compound is kept at a relatively low temperature above its softening temperature and an external force is applied to cause strain, stress is generated inside the resin. When a resin having such internal stress is heated again to a temperature above its softening point, the resin deforms to relieve the stress. It is already known that resin molded bodies have such properties.

This inventor has developed a foam sheet made of styrene resin,
A foam sheet is made in which the air bubbles are stretched and oriented in a certain direction on the front and back sides, and the orientation direction is different between the front and back sides, and a small rectangular piece is cut from this sheet. Just in case you try heating it up. At that time, the rectangle was cut so that both the long side and the short side were different from the orientation direction of the bubbles on the front and back surfaces. When such a rectangular or short Wf-shaped piece is heated to a relatively low temperature above the softening point of tar fat, the piece twists due to the difference in internal stress on the front and back sides.
It was found that as a result, the material was bent in a spiral shape. Moreover, my friend discovered that since the product obtained in this way is a foam, it is bulkier and has a unique W construction. This invention was made based on such knowledge.

In this invention, a thermoplastic foam sheet in which the air bubbles are stretched and oriented in a certain direction on both the front and back surfaces, and the orientation direction is different between the front and back surfaces, is cut into a rectangle, and the long sides of the rectangle are A method for producing a helically bent resin foam, characterized by heating the thus obtained rectangular small pieces of T-resin in a direction different from the orientation direction, above the softening temperature and below the flow temperature. 0, which is related to
In this invention method, a foam sheet is formed from a single foamed sheet of thermoplastic resin, and the air bubbles are stretched and oriented in a certain direction on both the front and back sides, and the foam sheet has different orientation directions between the front and back sides. The material is

The seat is as shown in FIG.

In FIG. 1, on the surface of the foam sheet, the bubbles are elongated in the direction of the arrow C to form an elongated circle, and the long axis of the circle is oriented in the direction of the arrow C. That is, on the surface, the bubbles are oriented in the direction of the arrow. However, on the back surface of the foam sheet, the air bubbles are oriented in the direction of arrow C. In addition,
The arrow & indicates the longitudinal direction of the foam sheet, or in other words, the extrusion direction.

Foamed sheets such as those shown in factor 1 can be made by extrusion methods. That is, when a foam sheet is made by an extrusion method, this can be made by moving the opposite wall surface of the resin passage located at the tip of the 10-karat gold in a direction perpendicular to the extrusion direction.

FIG. 2 is a perspective view of essential parts showing an example of a method for manufacturing a foam sheet used in the method of the present invention. In FIG. 2, 1 indicates a cap, of which 1 is an outer mold, and 1 is an inner mold, and a Kll-shaped space is formed between the outer mold and the inner mold. /li foam sheet, the above ring l! It is molded by extruding resin containing a foaming agent into a sheet from 1 m long. Accordingly, the foam sheet / is extruded in the direction of arrow a and in the size of arrow a. At this time, rotate the outer mold, 2/, in the direction of arrow d, and rotate the inner mold, here, in the direction of arrow . Then, the outer surface of the foam sheet / is rubbed in the direction of the combination of the arrow d and the push B1 speed a. Therefore, on the outer surface of the foamed sheet/Ω, the bubbles are elongated in the above synthetic direction and are oriented in the above synthetic direction. However, since M here in Fi1 is rotated in the direction of arrow .on the inner surface of 1 foam sheet/, the bubbles are oriented in the composite direction of arrow a and arrow . In this way, a tube of foamed sheet is obtained in which the directions of cell orientation differ between the outer and inner surfaces. The thus obtained cylindrical sheet is cut along the longitudinal direction and flattened to obtain a foamed sheet.

In the method of this invention, a strip or string-shaped rectangular piece is cut from a foamed heat whose bubbles are oriented in different directions on the front and back sides. That is, as shown in FIG. 3, small rectangular pieces j and g are cut out from the foam sheet. When forming the bubbles, the edges of the pieces 5 and 1, for example, the long sides J/ and 1, are arranged in a direction KI that is not aligned with either the direction of bubble orientation or -C.

Furthermore, the relationship between the long sides and the short sides of the pieces j and g is such that the long sides are significantly longer than the short sides. In this case, the direction in which the short side extends does not need to be different from either the bubble orientation direction (S) or zero. Next, this small piece is movably placed on a flat plate, and the small piece is heated to a temperature above the softening point of the resin and below the pour point. Then, the small piece undergoes one twist and deforms because the direction in which the internal stress acts is oriented between the front surface and the back surface.

Seventhly, the deformation in the above case differs depending on the orientation state of the cells in the foamed material K. That is, when the orientation directions on both the front and back surfaces are perpendicular to each other, the deformation becomes most noticeable, and the greater the degree of orientation, the more remarkable the deformation becomes. f1g2 to 1 The deformation in the above case is the direction in which the long side of the small piece cut from the foam sheet extends;
It also varies depending on the relationship with the above-mentioned orientation direction. That is, when the extending direction of the long side intersects the orientation direction at a large angle, the 1 deformation becomes more significant.

Polystyrene was used as the resin, and a foam sheet was used in which the orientation directions of the bubbles on both the front and back sides of the sheet were oriented almost perpendicular to each other.The angle β between the orientation direction of the bubbles and the long side of the small piece was varied. In case 1, we confirmed the shape of the teleflexible object obtained by heating it. The results were as shown in Table 7 below. In the table, the tens and minus numbers attached to the angle β are 1'. When looking at the long side from the orientation and direction of the bubble, 1 is the direction opposite to the direction of rotation of the clock's hands, and vice versa. was set as -.

Items marked with × in the summary column of the table are not spirals, but are △, ○.
, ◎ indicates that in this order, one pitch becomes a short spiral.If we combine these results, β
When the angle was within the range of ±5 to ±1j degrees, some helically curved foams were obtained. Among these, when β was within the range of 2 to 4 degrees, a good spirally bent foam as shown in FIG. 2 was obtained. More specifically, when β is less than ±j degrees, the bending foams do not overlap and form a spiral; conversely, when β is greater than ±1j degrees, the bending foams become elongated and become rod-like rather than spirals. become.

As for the resin, it is better to use hard resin than soft resin.
Good bending foams are obtained, and among these, the use of styrenic resins produces the best bending bodies. The styrene resin is not limited to a styrene homopolymer, but may be a copolymer of styrene and another monomer copolymerizable with the styrene. In addition, the styrene resin may be a mixture of homopolymers or copolymers containing styrene. When a styrene resin is used, a suitable heating temperature afterward is θ to 720°C.

A spirally bent foam Fi obtained by the method of this invention,
It is suitable for use as packaging filler for various products and as a cushioning material.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a foam sheet used as a material in the method of this invention. Figure ＠J is a perspective view of a main part showing a method for manufacturing a foam sheet used as a material in the method of this invention. FIG. 3 is a perspective view of the super-foamed sheet showing how it is cut into rectangles. Figure D is a perspective view of a resin foam bent in a spiral shape. Figure 2

Claims (1)

[Claims] 79 A thermoplastic foam sheet in which the air bubbles are stretched and oriented in a certain direction on both the front and back sides, and the orientation direction is different between the front and back sides, is cut into a rectangle, and the long sides of the rectangle are cut out. of a spiral K11 curved resin foam, which is characterized in that the rectangular pieces obtained in this way are heated above the softening temperature of the resin and below the flow temperature. Production method. 2. The method according to claim 1, wherein the orientation direction of the bubbles has an angular difference of 0 degrees between the front and back surfaces of the foam sheet. J, the longitudinal direction of the small piece is ±5 to ±1 with respect to the bubble orientation direction.
The method according to claim 81187 or Fi 2, which has a third degree angular difference. The method according to any one of claims 1 to 3, wherein the lubricant is a styrene resin and the heating temperature is θ to /o”c.