JPH0143607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin foam. More specifically, the present invention manufactures a foam by extruding a foamable resin through a plurality of holes to form a foam, and then fusing the extrudates together while the extruded foam is still softened. This relates to improvements in methods for

The hole mentioned here, ie, the hole from which the foamable resin is to be extracted, refers to the hole drilled at the tip of the cap. The hole is not meant to be a hole in a breaker plate as disclosed in Japanese Patent Application Laid-open No. 146668/1983. The breaker plate is a perforated plate that must be installed between the extruder and the die. The breaker plate is used to apply back pressure to the resin to remove air bubbles from the resin, and is also equipped with a screen to remove foreign matter from the resin. Therefore, the breaker plate is separate from the cap and has a completely different function from the cap. In particular, since the resin that has passed through the breaker plate is immediately put into the mouthpiece, it is maintained under pressure. The resin will not foam immediately after passing through. that's why,
The holes in the breaker plate cannot be discussed in the same way as the extrusion holes in the base.

A method of extruding foamable resin through multiple holes drilled in one die, foaming the extruded resin in a low-pressure region, and fusing the extrudates together while still softening to form a foam. is already known.
However, only by using such a method, it is not possible to obtain a foam having a particularly high-density skin layer over the entire surface of the foam. Without a dense skin layer, the foam becomes susceptible to scratches on its surface.

Therefore, it has been proposed to provide a high-density skin layer on the surface of the foam as described above. The main idea of this proposal is to attach a frame surrounding the extrusion hole to the extrusion end face of the die, pass the extrudate through the frame, and foam the extracts within the frame and fuse them together. This frame is completely separate from the base. This is because the resin passage in the cap must be kept under high pressure, whereas the resin passage in the frame must be kept under low pressure. In addition, in order for the resin inside the cap to flow, the inner surface of the resin passage must be kept above the softening temperature of the resin, but the inner surface of the frame is usually kept below the softening temperature of the resin. be. If such a frame is attached and the extract is passed through the frame while a cooling medium is passed inside the frame, the resulting foam will have a dense skin layer over its entire surface. .

The above-mentioned proposal is described in, for example, Japanese Patent Application Laid-open No. 123777/1982 and Japanese Patent Publication No. 35231/1983.
The frame used here has an inner surface facing the extrudate.
It is a plane extending parallel to the extrusion direction. More precisely, the inner surface of the frame is composed of straight lines perpendicular to the extruded end surface. As a result of further testing based on this publication, the inventor found that using such a frame, it is possible to form a high-density skin layer on the surface of the molded product, but when it comes to fusing a large number of extrudates, the internal It was noticed that large cavities were formed in the foam, making it difficult to obtain good quality foam. This inventor is
As a result of investigating the cause of this, it was found that when the cross-sectional area of the molded body becomes large, when a large number of extrudates are fused together, the gas generated from the blowing agent cannot escape from between the extrudates and accumulates between them. I thought that.
Therefore, the inventor felt that further improvement in this point was necessary.

It has also been proposed to use a frame with a widened end in the method of molding a foam as described above. For example, Japanese Patent Publication No. 51-33585 proposes using a frame with an inner surface that widens as it goes forward. The inner surface of the frame used here has an arcuate cross-section in the extrusion direction and expands in a so-called trumpet shape. Such an inner surface is insufficient to form a dense skin layer over the entire foam. It was therefore necessary to devise a convenient method for uniformly applying a high density skin layer over the entire foam. This invention is
It was born in response to this need.

The inventor focused on the fact that, as mentioned above, the inner surface of conventional frames had been extended parallel to the extrusion direction, or had been vaguely widened toward the tip,
We investigated the relationship between the inclination of the inner surface of the frame and the structure or properties of the resulting foam. As a result, the inventor found that in order to prevent the formation of cavities within the foam and to provide a high-density skin layer on the surface of the foam, it was not sufficient to simply slope the inner surface of the frame so that it flared out. , the angle of inclination is between 5 degrees and 30 degrees with respect to the extrusion direction.
We have found that it is necessary to hold it at a degree angle. The inventor also confirmed that it is necessary to cool the inner surface of the frame tilted in this way and to allow the extrudate to advance while coming into contact with this inner surface. This invention was made based on such knowledge.

The first invention in this application extrudes foamable resin through a plurality of holes drilled in one die, and provides a frame surrounding these holes in close proximity to the extrusion end surface of the die, so that the extruded material from the holes is extruded. In a method of producing a foam by fusing the extrudates together while they are foamed and still softened, the inner surface of the frame facing the extrudate is made into the widening slope, and the angle of inclination of the slope is perpendicular to the extrusion end surface. The temperature is within the range of 5 degrees to 30 degrees with respect to the curve, the slope is kept below the softening temperature of the resin, and the extrudates are brought into contact with the slope and fused to each other before being taken off. The present invention relates to a method for producing a plastic resin foam.

Further, when the above-mentioned frame was provided close to the extrusion end surface of the die, the inventor also considered the mounting position of the frame on the extrusion end surface. That is, when attaching the frame to the extruded end surface, we considered whether to position the inner surface of the frame at an equal distance from the outer periphery of the hole on the extruded end surface, or whether to position it biased toward a part of the hole. As a result, if the inner surface of the frame is positioned partially toward the hole on the outer periphery on the extruded end surface,
It was confirmed that a particularly thick epidermis layer could be obtained in the uneven areas. Based on this confirmation, when attaching the frame, the distance from the hole on the outer periphery to the inner surface of the frame on the extruded end surface is varied, thereby varying the timing at which the extrudate comes into contact with the inclined surface, The second invention of this application is to freely adjust the thickness of the epidermal layer in this way.

That is, the second invention extrudes foamable resin from a plurality of holes drilled in one die, and provides a frame surrounding these holes adjacent to the extrusion end surface of the die,
While the extrudate from the hole is foaming and still softening,
In a method of manufacturing a foam by fusing extrudates together, the inner surface of the frame facing the extrudate is made into a widening slope, and the angle of inclination of the slope is 5 degrees to 30 degrees with respect to a line perpendicular to the extrusion end surface. The slope is kept within the range of The present invention relates to a method for producing a thermoplastic resin foam, which is characterized in that it is fused and then taken off. The softening temperature here refers to the Vicat softening point according to the test method specified in ASTM D1525.

The embodiment of the method of this invention and the cap, frame and other accessories used in the method are shown in the drawings, of which FIG. 1 is a sectional view showing one embodiment of the method of this invention. . Figure 2 shows the first
It is a front view of the frame 4 in a figure. FIG. 3 is a cross-sectional view of a foam obtained using the frame of FIG. FIG. 4 is a model diagram for explaining the pore distribution area. 5, 7, 9, and 11 are front views of the frame used in the method of this invention. Figures 6, 8, 10, and 12 are equivalent to Figures 5, 7, 9, and 11, respectively.
FIG. 3 is a cross-sectional view of the foam obtained using the figure frame.

In FIG. 1, 1 is an extruder, 2 is a die, 3 is a resin extrusion end plate in the die 2, 4 is a frame, 5 is a sizing die, 6 is a water tank, and 7 is a foam. Further, 31 is a hole through which the resin is extruded, 41 is a void, 4
2 is a medium passage, and 71 to 73 are extrudates.

In the method of the present invention, a foamable resin containing a foaming agent is press-fitted from an extruder 1 into a die 2, and a large number of extrudates 71 to 73 are formed into a frame 4 through holes 31 of an extrusion end plate 3.
Push inward. Then, the extrudates 71 to 73 foam inside the frame 4 and expand in volume. Among the extrusions 71 to 73, the extrusions 71 and 73 located on the outside come into contact with the inner surface of the frame 4 and are pressed. As a result, extrudates 71 to 73 are fused together.

The frame 4 has a front structure as shown in FIG. 2, and a cooling medium is circulated in a medium passage 42 to cool its inner surface. The frame 4 has an entrance side opening 4
3 and an exit side opening 44, between which an upper surface 45, a left surface 46, a right surface 47 and a lower surface 4 are provided.
8 is formed. The upper surface 45 to the lower surface 48 are
It constitutes the inner surface of the frame 4, and is inclined to widen at an angle of 5 to 30 degrees with respect to a straight line perpendicular to the extrusion end surface of the extrusion end plate 3.

A more detailed explanation of frame 4 in FIG. 2 is as follows. Both the inlet side opening 43 and the outlet side opening 44 form a right angled quadrilateral, and are perpendicular to a line connecting their axes. Therefore, the upper surface 45, the left surface 46, the right surface 47 and the lower surface 48
The ridge lines formed therebetween are located in a relationship such that they intersect on the above-mentioned axis. Further, the upper surface 45 and the lower surface 48 have a symmetrical relationship and are inclined at an angle of 6 degrees with respect to the axis. In addition, the left side 46 and the right side 4
7 is also axially symmetrical and is inclined at an angle of 20 degrees with respect to the axis. Generally, the angle of inclination is increased between inner surfaces facing each other with a large interval, and conversely, the angle of inclination is decreased between inner surfaces facing each other with a small interval. However, in any case, the slope angle is 5
The slope is wide open at an angle of 30 degrees to 30 degrees.

A frame 4 as shown in FIG. 2 is attached to the extrusion end plate 3, the extrusion end plate 3 is attached to the base 2, and the medium passage 42
The foamable resin is extruded from the extruder 1 while circulating cooling oil inside. Then, the foamable resin becomes extrudates 71 to 73 and foams while traveling inside the frame 4. The extrudate 71 contacts the upper surface 45 of the frame 4 and is cooled, and the extrudate 73 forms the extrudates 71 to 73 on the lower surface of the frame 4. 48, thereby inhibiting foaming, resulting in a dense or low foaming skin layer therein. However, the extrudates 72 located inwardly are not given the opportunity to contact the inner surface of the frame 4 and therefore do not produce a dense skin layer.

Moreover, in the frame 4 shown in FIG.
Both are allowed to foam and expand. Therefore, even if the epidermal layer is produced, the extrudate 7 for the epidermal layer
Progression from 1 to 73 will not be difficult. Therefore, operations can be performed smoothly. Also, frame 4
Since the angle of inclination of the inner surface is in the range of 5 degrees to 30 degrees with respect to the axis, the speed at which the foamable resin foams and expands is easily balanced with the speed at which the foamable resin is extruded. Therefore, a desired high-density skin layer can be easily provided on the surface of the foam. Moreover, since the extrusions 71 and 73 on the outside are pressed by the inner surface of the frame 4, the extrusions 71 and 73 are well fused with the extrusions 72 on the inside, so that the overall structure is strong. A foam 7 is obtained. Moreover, during this process, gas does not accumulate between the extrudates 71 to 73, etc., thereby preventing fusion bonding.

The foam 7 thus obtained is shown in FIG. The foam 7 in FIG. 3 is an extrudate 71
73 are made by being firmly fused together without any gaps. Furthermore, a high-density skin layer 7H is uniformly formed on the surface of the foam 7. As a result, the surface of the foam 7 is less likely to be damaged. Further, the foam 7 does not generate large cavities on the fused surface formed by the fused extracts 71 to 73. For this reason, this foam 7 is a high quality foam.

The holes 31 formed in the extruded end plate 3 have the following relationship with the cross section of the foam. That is, the pore distribution area is 70% or less, preferably 50% or less of the foam cross-sectional area. The hole distribution area here is the area of a polygon obtained by connecting the centers of the holes 31 located on the outer periphery. For example, as shown in Figure 4,
When the holes 31 are formed in three rows vertically and in five rows horizontally, the hole distribution area is the area of the shaded portion. The fact that this pore distribution area is less than 70% of the cross-sectional area of the foam indicates that the foam has been expanded to a large extent because it fills the foam strip spaces and also expands to the outside. There is. In conventional foaming methods, especially methods that add a high-density skin layer, the ratio of the pore distribution area to the cross section of the foam is more than 70%, leaving voids inside the molded product and causing wrinkles on the surface. However, in the method of this invention, the ratio is less than 70%, preferably less than 50%. This value is generally increased when molding a material with a lower density.

Further, the length of the frame 4 in the direction perpendicular to the extrusion end surface is 10 to 50 mm. This is because if the length of the frame 4 in the above direction is longer than 50 mm, the inner surface of the frame in the extrusion direction will be longer, and therefore the length of the inner surface over which the extrudate will come in contact with and advance will be longer, so it will take longer to take off. This is because a large amount of force is required, resulting in inconveniences such as the foam being cut or damaged. On the other hand, if it is shorter than 10 mm, the length of the inner surface on which the extrudate comes into contact and progresses will be insufficient, and the effect of forming a high-density skin layer will be lost.

In this invention method, various thermoplastic resins can be used. For example, polymers or copolymers of polystyrene, polymethyl methacrylate, polycarbonate, polypropylene, polyethylene, polyvinyl chloride, polyamide, etc. can be used. Particularly preferred among these are polystyrene and styrene copolymers. In order to foam these resins, a foaming agent is mixed therein, and various types of foaming agents can be used. For example, solid compounds such as azodicarbonamide that decompose to produce gas when heated, or resins such as propane, butane, pentane, and various fluorinated hydrocarbons, can be dissolved or swollen to lower the softening point of the resin. Organic compounds with low boiling points can be used. Among these, for styrene-based or olefin-based resins, it is preferable to use a halogenated aliphatic hydrocarbon such as trichloromonofluoromethane or dichlorodifluoromethane together with finely powdered talc.

FIG. 5 is a front view of the frame 4 similar to FIG. 2. However, in the frame 4 in FIG. 5, the bottom surface 48 is the top surface 45.
It is not symmetrical with the upper surface 45, and is inclined at a larger angle of inclination than the upper surface 45. That is, the upper surface 45 is inclined at 6 degrees with respect to the straight line perpendicular to the extruded end surface, the left surface 46 and the right surface 47 are inclined at 20 degrees with respect to the straight line perpendicular to the extruded end surface, and the lower surface 48 is inclined at 6 degrees with respect to the straight line perpendicular to the extruded end surface. It is inclined at 11 degrees to the straight line. Therefore, when the inner surface of the frame 4 is viewed from the front, the upper surface 45 appears to be the narrowest, the lower surface 48 appears to be the second narrowest, and the left and right surfaces 46 and 47 appear to be the widest.

When the frame 4 of FIG. 5 is used to extrude the foamable resin in the same manner as described above, the resulting foam will have a cross-sectional structure as shown in FIG. 6.
That is, in the foam 7 of FIG. 6, the surfaces formed in contact with the top surface 45, left surface 46, and right surface 47 are uniformly provided with a high-density skin layer 7H having the same thickness as described above. However, the surface formed in contact with the lower surface 48 is provided with a high-density skin layer 7S that is thinner than the skin layer 7H.

Although FIGS. 2 to 6 show the case of molding a typical foam with a rectangular cross section, it is also possible to mold a foam with a complex cross section.
The method of the invention can be applied in the same way. FIG. 7 shows a case where a foam having a complicated cross section, that is, a irregularly shaped foam is produced.

In FIG. 7, the extruded end plate 3 has a large number of holes 31 in an irregular shape. The hole 31 is so thin that there is only one hole 31a in the vertical direction at the right end, but there are three holes in the vertical direction at the left end.
The thickness is so thick that two holes 31c overlap each other, and the thickness is such that two holes 31b overlap in the vertical direction in the middle. The entrance side opening 43 of the frame 4 has a shape surrounding these many holes 31. The inner surface of the frame 4 is constituted by a generatrix that passes through the inlet side opening 43 and is inclined at 6 degrees at any position with respect to a straight line perpendicular to the extrusion end surface. The inner surface is, to put it simply, the top surface 45, the left surface 46,
Although it can be divided into a right side 47 and a bottom side 48,
The boundaries between these surfaces are not clear. These surfaces have the same inclination angle, and the frame 4 in the extrusion direction
Since the thicknesses of 45 and 45 are the same, in FIG.
The widths of the left surface 46, right surface 47, and lower surface 48 appear to be the same, so the outlet opening 44 does not have a shape strictly similar to the entrance opening 43.

The foam 7 obtained using the frame shown in FIG. 7 has a shape as shown in FIG. 8, and is provided with a high-density skin layer 7H over its entire surface.

FIG. 9 shows the frame 4 used in the second invention of this application. In FIG. 9, the extruded end plate 3 is provided with holes 31 distributed in a U-shape.
The inlet opening 43 of the frame 4 is shaped to surround these holes 31, similar to the frame shown in FIG. Moreover, the inner surfaces 45 to 48 of the frame 4 are
A constant angle of inclination with respect to a straight line perpendicular to the extrusion end surface,
For example, the frame is composed of a group of generatrix lines having an inclination angle of 6 degrees, which is similar to the frame in FIG. 7.

The frame 4 in Fig. 9 differs from the frame in Fig. 7 in that the hole 3
1 is not located at the center of the entrance side opening 43 in the width direction, but is biased towards the inside. Specifically, the hole 31 consists of an inner hole 311 and an outer hole 312, of which the inner hole 311 is close to the inner edge of the inlet opening 43. However, the outer hole 312 is provided at a distance from the outer edge of the inlet opening 43. Therefore, the upper surface 45 connected to the inner edge is located close to the hole 311, and the left surface 46 and the right surface 4
7 and the lower surface 48 are both located away from the hole 312.

Using frame 4 of FIG. 9, a foam as shown in FIG. 10 is obtained. The foam 7 shown in FIG. 10 has a U-shaped cross section and has a thick high-density skin layer 7H on the inner surface, and a thin high-density skin layer 7S on the outside surface. It is equipped with the following. The reason why there is such a difference in wall thickness in the epidermal layer is considered to be due to the following reasons. That is, since the hole 311 is close to the inner surface 45, the hole 311
Immediately after being extruded, the extrudate comes into contact with the inner surface 45 and is cooled to control foaming.
On the other hand, since the holes 312 are moving away from the left surface 46, right surface 47, and bottom surface 48, the extruded material pushed out from the holes 312 will be exposed to the left surface 46, right surface 47, and bottom surface 48 after a while. This is because the foams come into contact with each other and are therefore foamed to a certain extent before being cooled, resulting in less suppression of foaming.

The second method of the invention is particularly effective when attempting to provide a highly dense skin layer on only one surface. In particular, in the second method of the invention, if the angle of inclination of the inner surface of the frame 4 is further changed, the formation of a high-density skin layer can be achieved even more as desired.

According to the method of this invention, foamable resin is extruded through a plurality of holes drilled in one die, the extrudate is fused to form a foam, and these holes are formed in the vicinity of the extrusion end surface of the die. Since a surrounding frame is provided and the extrudate is fused into a foam, the desired high density skin layer can be provided over the foam.
This is especially true when compared to foams extruded through a single large hole drilled in one die. This is because foam extruded through a single large hole will undergo unexpected deformation due to foaming after it leaves the die, so if a skin layer is to be provided on it, it is impossible to provide a uniform skin layer. I can't. However, according to the method of the present invention, it is possible to extrude through a plurality of holes and position the extrudate at a desired location, so that a desired skin layer can be provided. Furthermore, in the method of this invention, the inner surface of the frame is made into an inclined surface that widens toward the tip, and the inclination angle of the inclined surface is set to 5.
Since the temperature is between 30° and 30°, it is possible to sufficiently foam the inside of the frame and prevent the formation of cavities between the extrudates, thereby making it possible to obtain a high-quality foam with no internal cavities.

Further, according to the method of the present invention, by partially changing the inclination angle of the inner surface of the frame within the range of 5 degrees to 30 degrees, high-density skin layers with different thicknesses can be provided at desired locations.

In addition, by partially varying the distance from the hole on the outer periphery to the inner surface of the frame, specifically, by decreasing the distance from the hole to the inner surface, it is possible to increase the thickness of the skin layer. On the other hand, by increasing the distance from the hole to the inner surface,
The thickness of the epidermal layer can be reduced. The inventive method provides these advantages.

Next, further details of the method of the present invention will be explained with reference to Examples. In the following, parts simply mean parts by weight.

Example 1 In this example, polystyrene was used as the material, a device as shown in FIG. 1 was used, a frame as shown in FIG. 2 was used, and a foam as shown in FIG. I got it. Specifically, it was carried out as follows.

To 100 parts of polystyrene, 1.5 parts of finely powdered talc as a bubble control agent and 0.1 part of brown pigment were added, and this was fed to an extruder connected to two machines, one with a diameter of 40 mm and one with a diameter of 50 mm. The mixture was heated to 190 to 220°C, a foaming agent was press-fitted into an extruder with a diameter of 40 mm, and the mixture was extruded at a rate of 15 kg per hour. As blowing agents, trichloromonofluoromethane (Freon-11) and dichlorodifluoromethane (Freon-12) are used.
A mixture of 1:1 and 1:1 was used, and this was press-fitted at a ratio of about 1.5 times to 100 parts of resin.

The base 2 is 150 or more depending on the plate heater.
It was heated to 160°C, and 60°C oil was circulated in the medium passage 42 of the frame 4, and a gap 41 was provided in order to avoid heat transfer from the mouthpiece 2.

The extruded end plate 3 had the following structure.
The hole 31 had a diameter of 1.6 mm and a length in the advancing direction of 10 mm. 4 vertically with such a hole 31
17 holes were formed in a rectangular shape on the extruded end plate 3 at equal intervals of 2 mm in each row. As a result, the extruded end plate 3 had a total of 68 holes 31. The hole distribution area of this extruded end plate is
It was ^1.92cm2 .

The frame 4 had a thickness of 20 mm in the direction perpendicular to the extrusion end surface, and a rectangular inlet opening 43 measuring 8 mm in length and 34 mm in width was provided therein. As for the inner surface of the frame 4, an upper surface 45 and a lower surface 48 are both inclined at an angle of 6 degrees with respect to the direction perpendicular to the extrusion end surface, and are also inclined so as to widen toward the other side, and a left surface 46 and a right surface 47 Both were inclined at an angle of 20 degrees with respect to the above direction, and were also inclined so as to widen at the front. An exit side opening 44 was located beyond that. The inner surface of the frame 4 was coated with Teflon.

The extrudate from the hole 31 is foamed, and the extrudate is formed into the frame 4.
The extrudate is melted so as to contact the inner surfaces 45 to 48 of the sizing die 5.
The foam was passed through to adjust the outer shape, and then placed in a water tank 6 to be cooled to obtain a foam 7.

The foam 7 has a rectangular cross section as shown in ^FIG . The ratio to the area was 32%.

Furthermore, although the fused surface of the extrudate appeared in a straight-grained manner on the surface of the foam 7, the fused surface was not concave, and a high-density skin layer 7H was formed on the entire surface of the foam. It was formed uniformly throughout. As a result, the surface was scratch-resistant and beautiful. This foam had an average density of 0.35 g/cm ³ , and the surface was hard, with a hardness of 50 to 60 on the Shore D hardness scale, even though it was foamed.

Example 2 This example was carried out in the same manner as in Example 1, except that the extruded end plate 3 and the frame 4 were changed, and the same as shown in FIG. 5 was used.

In the extrusion end plate 3, 17 holes 31 with a diameter of 1.6 mm and a length in the extrusion direction of 10 mm are formed in 3 rows vertically and horizontally at equal intervals of 2 mm.
It has a total of 51 holes 31. The pore distribution area of this plate 3 was 1.28 cm ² .

The frame 4 had a thickness of 20 mm in the extrusion direction, and had a rectangular inlet opening 43 with a long side of 34 mm and a short side of 6 mm. The inner surface of the frame is such that the upper surface 45 is inclined at 6 degrees, the left surface 46 and the right surface 47 are inclined at 20 degrees, and the lower surface 48 is inclined at 11 degrees with respect to a straight line perpendicular to the extrusion end surface. The tip was tilted to widen.
As a result, the outlet opening 44 of the frame 4 had the same size as the outlet opening of the frame 4 used in Example 1.

The same resin compound was put into the same extruder as in Example 1 and extruded from the extrusion end plate 3 to the frame 4 to obtain a foam 7 as shown in FIG. 6. This foam was similar to the foam of Example 1 and had a cross-sectional area of 6 cm ² . Therefore, in this case, the ratio of the pore distribution area to the cross-sectional area of the compact was 21.3%.

However, the foam obtained in this example was significantly different from the foam obtained in Example 1 in the following points. That is, the foam 7 of this example is
As shown in FIG. 6, the biggest difference was that only one surface had a thin, high-density skin layer 7S, and the surface hardness of this surface was not very large. More specifically, the top surface 45, the left surface 46,
The foam surface 7H obtained by contacting the right side 47 is
The foam surface 7S obtained by contacting the lower surface 48 has a hardness of 45 to 50 on Shore D hardness.
had a hardness of 30 to 35 on the Shore D scale. The average density of this foam was 0.33 g/cm ³ . In other respects, the foam of this example was of good quality, similar to the foam of Example 1.

Example 3 In this example, the extruded end plate 3 and frame 4 as shown in FIG. 7 were used, and the details were carried out as follows.

The resin used was a mixture of 90 parts of polystyrene and 10 parts of high-impact polystyrene, to which 1.0 part of finely powdered talc and 0.1 part of brown pigment were added. The product was supplied to a connected extruder, and about 2.0 parts of Freon-12 as a blowing agent was press-injected into the extruder, and extrusion was carried out at a rate of 20 kg per hour. Base 2 is 145-150
℃, and 50℃ oil was circulated in frame 4.

The extruded end plate 3 has a diameter as shown in FIG.
1.6 mm holes 31 are distributed at approximately equal intervals in an irregular shape,
The total number of holes 31 was set to 60. To be more specific, the holes 31 are arranged in three rows up and down at the left end, only one at the right end, and three or two rows in the middle, and the length in the up and down direction increases from left to right. It gradually decreased and was distributed in a shape with the left end sloping upward to the left.

The inlet openings 43 of the frame 4 are located at different distances from the holes 31 in the outer periphery. Specifically, the left edge and right edge of the opening 43 are located away from the hole 31c and the hole 31a, respectively, but the upper edge and the lower edge of the opening 43 are located away from the hole 31b.
was located near. This is because it was anticipated that when the extrudate foams, it will spread widely in the horizontal direction, but not so much in the vertical direction.

As a result of extrusion using the extrusion end plate 3 and frame 4 described above, a foam as shown in FIG. 8 was obtained. The cross-sectional area of this foam was 5.5 cm ² . Therefore, the ratio of the foam cross-sectional area to the pore distribution area was about 33%. Further, the average density of this foam was 0.30 g/cm ³ , and a high-density skin layer 7H was formed on the entire surface thereof. Its surface hardness was 45 to 50 on Shore D hardness.

Example 4 In this example, the extruded end plate 3 and frame 4 as shown in FIG. 11 were used.

Polypropylene is used as the resin, 100 parts of polypropylene is mixed with 2.0 parts of finely powdered talc, this mixture is fed to an extruder with a diameter of 40 mm, and about 3 parts of butane as a blowing agent is press-injected into the extruder to generate a volume of 10 kg per hour. It was extruded at a rate of The base 2 was maintained at 160 to 170°C, and oil at 80°C was circulated in the frame 4.

As shown in FIG. 11, in the extruded end plate 3, 48 holes 31 each having a diameter of 1.8 mm were bored in two rows, upper and lower, with equal intervals of 2.5 mm. Therefore, a total of 96 holes 31 were provided, and the hole distribution area was 2.93 cm ² .

The frame 4 has a thickness of 30 mm in the extrusion direction, has a rectangular inlet opening 43, and has a rectangular length of 6.5 mm and a width of 6.5 mm.
It was set to 120mm. The inner surface of the frame 4 has an upper surface 45 and a lower surface 48 inclined at 6 degrees with respect to a straight line perpendicular to the extrusion end surface, a left surface 46 and a right surface 47 inclined at 20 degrees with respect to the above straight line, and an inclined surface that widens toward the tip. And so.

As a result of extrusion using the above-mentioned device, the first
A foam 7 as shown in FIG. 2 was obtained. The cross section of the foam 7 had a rectangular shape with a long side of 140 mm and a short side of 10 mm. The cross-sectional area was therefore 14 cm ² and the ratio of the pore distribution area to the foam cross-sectional area was 20.9%.
In addition, the foam 7 has an average density of 0.19 g/cm ³ ,
A high-density epidermal layer was formed all around the surface, and the interior was clean and of good quality with no cavities.

Example 5 This example was implemented in the same manner as Example 1, except that the extrusion end plate 3, frame 4, and sizing die 5 were
The experiment was conducted so that the ratio of the pore distribution area of the plate 3 to the cross-sectional area of the foam was larger than that of the other examples.

In the extruded end plate 3, holes 31 with a diameter of 1.6 mm and a length of 10 mm in the extrusion direction are bored in 5 rows vertically and 25 horizontally at equal intervals of 2 mm, for a total of 125 holes. It has a hole 31. The pore distribution area of this plate 3 was 3.84 cm ² .

The frame 4 had a thickness of 20 mm in the extrusion direction, and had a rectangular inlet opening 43 with a long side of 59 mm and a short side of 12 mm. On the inner surface of the frame, all the surfaces of the upper surface 45, left surface 46, right surface 47, and lower surface 48 were inclined at 8 degrees with respect to a straight line perpendicular to the extruded end surface, and were also inclined so as to widen toward the front. Exit side opening 4 beyond that
4 was located. Note that the inner surface of the frame 4 is nickel plated.

The same resin compound was put into the same extruder as in Example 1, extruded from the extrusion end plate 3 to the frame 4 at a rate of 7 kg per hour, and taken through the sizing die 5 to obtain a foam 7.

Foam 7 had a rectangular cross section with a long side of 60 mm and a short side of 10 mm, so the cross-sectional area was 6 cm ² , and the ratio of the pore distribution area to the cross-sectional area of the foam was 64%.

The foam obtained in this example had an average density of
0.4 g/cm ³ , and similar to that obtained in Example 1, a high-density skin layer 7 was formed over the entire surface of the foam.
H was formed.

However, when the extrusion rate was increased to 15 kg or more per hour using the apparatus of this example, a sufficiently high-density skin layer was not formed on the surface of the foam 7, and a good product could not be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the method of this invention. FIG. 2 is a front view of the frame 4 in FIG. 1. FIG. 3 is a cross-sectional view of a foam obtained using the frame of FIG. 2; FIG. 4 is a model diagram for explaining the pore distribution area. Fifth
7, 9 and 11 are front views of the frame used in the method of this invention. 6th
Figures 8, 10 and 12 are cross-sectional views of foams obtained using the frames of Figures 5, 7, 9 and 11, respectively.

Claims (1)

[Claims] 1. A foamable resin is extruded through a plurality of holes drilled in one die, a frame is provided close to the extrusion end face of the die and surrounding these holes, and the extruded material from the holes is foamed. In a method of manufacturing a foam by fusing the extrudates together while they are still softened, the inner surface of the frame facing the extrudate is the widening slope, and the angle of inclination of the slope is a line perpendicular to the extrusion end surface. 5 degrees against
A method for producing a thermoplastic resin foam, which comprises: maintaining the slope within a range of 30 degrees, keeping the slope below the softening temperature of the resin, and bringing the extrudate into contact with the slope, fusing the extrudate with each other, and then taking it off. 2 The slope is at least 10 in the direction perpendicular to the extrusion end surface.
mm to 50 mm, the first claim
The method described in section. 3. Claim 1 or 2, in which the angle of inclination of the inclined surface is made different in each part of the inner surface of the frame.
The method described in section. 4. Extrude foamable resin through multiple holes drilled in one die, provide a frame surrounding these holes close to the extrusion end face of the die, and extrude from the holes while foaming and still softening. In a method for manufacturing a foam by fusing extrudates together, the inner surface of the frame facing the extrudate is made into a widening slope, and the angle of inclination of the slope is 5 degrees or more with respect to a line perpendicular to the extrusion end surface.
30 degrees, keeping the slope below the softening temperature of the resin, partially varying the distance from the hole on the outer periphery to the inner surface of the frame on the extrusion end surface, and keeping the extrudate in contact with the slope. A method for producing a thermoplastic resin foam, the method comprising: fusing the foam to each other and then taking it off. 5 At least 10 slopes in the direction perpendicular to the extrusion end surface
mm to 50 mm, claim 4
The method described in section. 6. Claim 4 or 5, in which the angle of inclination of the inclined surface is made different in each part of the inner surface of the frame.
The method described in section.