JPS6054848B2 - Mouthpiece for manufacturing plate-shaped foams - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die for producing a plate-shaped foam.

In particular, this invention relates to a die for extrusion molding a thick foam that has been uniformly expanded at a high magnification into a desired shape without causing any undesirable bending.
Producing plate-shaped foams by extrusion has already been done.

In this case, a nozzle is attached to the tip of the extruder, a linear or annular slit is bored in the nozzle, and the foamable resin is extruded and foamed through the slit to form a plate-shaped foam. There is. Although the principle is simple as described above, it is not easy to actually produce a high-quality foam that foams uniformly and at a high magnification.
The reason why it is difficult to actually make a thick foam with high expansion ratio by extrusion is that the foaming resin starts foaming at the same time as it is extruded, and the foaming occurs in the vertical, horizontal, and front/back directions. This is due to the fact that although they try to expand equally, they cannot expand that much depending on the direction.

Specifically, a plate-shaped material can freely expand greatly in the thickness direction, but cannot expand as much in the width direction, so it bends in the width direction, creating waves and becoming distorted. It will not be able to expand evenly. Also, in terms of the foaming ratio, if the slit thickness of the mouthpiece is made smaller,
Although it is possible to obtain a low-density multifoam, the thickness of the obtained foam is thin and waves are generated in the width direction of the foam, making it impossible to obtain a flat foam. Therefore, in an attempt to obtain a foam with a large thickness, if the thickness of the pores is increased,
The foaming ratio of the resulting foam not only decreases rapidly and becomes dense, but also the size and distribution of the bubbles in the foam become uneven, resulting in a wall thickness that is uniformly foamed at a high ratio. It is not possible to obtain a plate-shaped foam. In order to improve the above-mentioned drawbacks, it has been proposed to use a cap with a straight slot, with the length of the land varied here and there.

That is, it has been proposed to provide protrusions extending along the extruded resin J at various places on the tip end surface of the die.
It is described in Japanese Patent Publication No. 47-11914. Although it was possible to obtain a somewhat thicker foam board by this method, it was still not sufficient. This inventor completely changed his way of thinking and attempted to solve this problem by devising an i-resin passage within the cap. That is, instead of making the resin passage in the cap into a flat shape that extends straight in a straight line in the cross section, a part where the cross section bends in a wavy manner is provided in the middle of the resin passage, and the resin is passed through the bent part to form a wavy shape. Then, by flattening it again and extruding it, an attempt was made to obtain a uniformly foamed thick plate without bending. This invention was completed based on this idea. This invention has a narrow slit on the outlet side, and in the middle of the passage connecting from the inlet side opening to the outlet side slit, the cross section of the passage is once bent in a wave shape near the inlet side, and as it approaches the outlet side. The present invention therefore relates to a die for manufacturing plate-shaped foams, in which the wave amplitude in the cross-section of the passage gradually decreases, resulting in a flat passage, which is connected to the exit-side slit.

An example of implementing the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of the entrance side of the cap according to the present invention. FIG. 2 is a plan view of the lower half remaining after the upper half of the mold shown in FIG. 1 is removed. FIG. 3 is a side view of FIG. 2. 4 is a front view of the exit side of the cap of FIG. 1; FIG. 1 to 4, the cap of the present invention is made of a combination of an upper half 1 and a lower half 2, with resin passages 3 to 5 formed therebetween.

At the entrance, the resin passage forms a rectangular opening with a wide cross section, as shown by the number 3 in Figure 1, but halfway through, the cross section becomes a passage 4 with a wave-shaped bend, and then becomes flat again. It is connected to the outlet side slit 5. What is bent in a wave shape is a protuberance on the upper half 1 and lower half 2 that interlock with each other. This is because they are formed facing each other. In terms of the lower half 2, the protrusions consist of approximately triangular pyramid-shaped objects located symmetrically along the resin traveling direction. A symmetrical triangular plane 7 is formed which is elongated on both sides toward the plane. The upper half 1 is made almost opposite to the lower half 2 and similarly has a roughly triangular pyramid-shaped raised part, but the raised parts of the upper half 1 are the same as the raised parts of the lower half 2. For,
The mounting position is off by a half pitch.

Therefore, when the upper half 1 and the lower half 2 are assembled facing each other, the ridges on the upper half 1 fit between the ridges on the lower half 2, and the ridges are bent in a wave-like manner between them. Since the protuberances are approximately triangular pyramid-shaped and are located symmetrically along the resin traveling direction, the above-mentioned bent passage 4 is formed as it approaches the exit side. As a result, the amplitude of the bending is reduced, and finally a flat passage is formed.The flat passage is thus connected to the outlet side slit 5.The wide rectangular entrance side opening 3 transitions to a wave-like curved passage 4. In the section, an approximately triangular plane 6 faces towards the inlet side.

That is, since the plane 6 is inclined in the direction in which the resin travels, the resin can easily enter the bent passageway 4. Therefore,
The resin progresses smoothly within this mouthpiece without stagnation. The shape of the wavy resin passage is not limited to a triangular shape, but can also be semicircular, rectangular, or trapezoidal, but triangular or semicircular are easier to manufacture and suitable for products. This is the most preferable since it does not leave any flow marks. When using the mouthpiece of this invention, the cross section of the passage bends in a wave-like manner once in the middle of the resin passage, and then returns to a flat linear slit at the exit side of the passage, so that the slit thickness at the exit side is reduced. can be increased, and the resin can be maintained at a high pressure within the exit-side slit.

For this reason, the resin exiting the exit side slit can be thickened, and can be foamed uniformly at a high magnification. Thus, by using the die of the present invention, it is possible to easily obtain a thick plate that is uniformly foamed at a high magnification. In particular, the die of this invention exhibits a remarkable effect when making a foam board with a thickness of 107 m or more. The base of the present invention can be used for all thermoplastic resins, but it is particularly suitable for making high-magnification foam boards using styrene resins or olefin resins.

Next, specific examples of the cap of the present invention will be described with reference to Examples. Example polystyrene resin (Styron #666 manufactured by Asahi Tau Co., Ltd.)
0.5 parts of finely powdered talc as a foam regulator was uniformly mixed with 10 parts of saliva, and the mixture was fed to an extruder at a rate of 70 kg for 1 hour.

As the blowing agent, a mixture of dichlorodifluoromethane and methyl chloride at a weight ratio of 1:1 was used, and this was press-injected into the extruder at a ratio of 1% by weight to the resin. .

These were mixed, the resin temperature was adjusted to 115°C, and the mixture was extruded from a die.

The cap used was as shown in FIGS. 1 to 4, and its specific dimensions were as follows. That is, the entrance side opening 3 has a thickness of 22wn1 and a width of 152wn, and therein there are 7 molds in the upper half mold, 6 molds in the lower half mold, and a height of 18T.
! A smooth approximately triangular ridge of Un was provided, and a wavy passage 4 with a length of 507 m was provided by combining the upper and lower molds.

The thickness of the wavy passage 4 is approximately 2w! n, the amplitude of the wave gradually decreases toward the exit side, and finally it gradually shrinks as it is as a flat shape, and the exit is in order of thickness and width of 100W.
rI! It was made into a slit with a flat shape of t. A molding tool was installed in close contact with this outlet.

As a molding tool, the inlet dimensions are substantially equal to the size of the outlet side slit of the mouthpiece, the total length is 120Tnfn, the exit has a thickness of 60TrrIn, and a width of 200Trr! n, the inner surface of which was coated with Teflon was used. When the foam extruded from the molding tool was taken through the guide plate, the thickness was 607!7.
7! , width 26077!77! , density 0.030fIcc
A foam of good quality was obtained.

Note that the extrusion pressure of the die at this time was 50k91cri. For comparison, the same raw material was used, and the thickness of the inlet opening without a wavy passage was 22Tm! RLl width 152? ,
When a foam with an exit side slit having a thickness of 2 mm and a width of 100 Tm was used, the extrusion pressure of the die decreased to 20 k9'd, and only a foam with a coarse bubble density of 0.038 yIcc was obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view of the inlet side of the cap according to the present invention. 2 is a plan view of the lower half of the base of FIG. 1; FIG. 3 is a side view of the lower half of the cap of FIG. 2; FIG. FIG. 4 is a front view of the outlet side of the cap shown in FIG. 1. In FIGS. 1 to 4, 1 is the upper half of the cap, 2 is the lower half of the cap, 3 is a wide rectangular opening on the inlet side, 4 is a wavy bent resin passage, 5 is a slit on the outlet side, 6 is a substantially triangular surface of the raised object, and 7 is a triangular plane on the left and right sides of the raised object.

Claims (1)

[Claims] 1. A narrow linear slit is provided on the exit side, and in the middle of the passage connecting from the inlet side opening to the above exit side slit, the cross section of the passage once curves into a wave shape near the entrance side, and then approaches the exit side. Accordingly, the amplitude of the waves in the cross section of the passage gradually decreases, forming a flat passage and connecting to the outlet side slit.