JPS6348693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pattern, particularly a cloud or marble pattern, on a synthetic resin foam.

Synthetic resin foams are often made by extrusion foaming. In extrusion foaming, thermoplastic resin is melted and kneaded in an extruder to create a resin melt containing a foaming agent, and the molten resin is directly introduced into a die and extruded from the die to cause foaming. In this method, the aim was exclusively to produce a homogeneous foam, and therefore only attention was paid to producing a homogeneous resin melt.

In molding a foam, in order to make a uniform resin melt, it is necessary to heat the resin to a high temperature and melt it well. However, in order to guide the resin into the mouthpiece, mold it, and maintain a certain shape, it is necessary to maintain the resin at a slightly softened level.
For this reason, in extrusion foaming, resin heated to a high temperature is cooled at the tip of the extruder or in a resin passage between the extruder and the die before being introduced into the die.
A resin cooling device for this purpose has also been proposed.
Conventionally, even during such cooling, attention has been paid only to uniformly cooling the resin to form a uniform resin melt.

This inventor first created a high-temperature foamable melt in an extruder, then intentionally created a partial temperature difference in the melt when cooling it, and then tried to extrude it from a die. . To this end, the inventor provided a cylindrical resin passage between the extruder and the die, forcedly cooled the cylinder by blowing air from the outside, and controlled the temperature of the molten resin flowing inside the cylinder around the outer circumference of the circular cross section. I made it lower in the lower part and higher in the center, and pushed it out of the mouthpiece. In the foamed molded article thus obtained, in the cross section, the diameter of the bubbles formed on the outside was small, and the diameter of the bubbles formed inside was large, and the difference was remarkable.

Next, in addition to the above device, the inventor added a partition wall extending obliquely to the extrusion direction at the tip of the cylinder, so that the relatively low temperature molten material on the outside was diagonally crossed. This was extruded with the low-temperature melt being scattered inside as lumps.
As a result, the inventor found that the part where the low-temperature melt existed became a group of microbubbles, and the other part became a group of coarse bubbles, and a unique pattern appeared here. It has also been found that when the above-mentioned partition walls are appropriately present, the low-temperature portions are appropriately dispersed, and a cloud shape or a marble pattern appears there.

A type of mixed mixer (or static mixer) has a partition wall that extends diagonally inside the cylinder, divides the fluid by the partition wall, causes the divided fluid parts to proceed in different directions, and then collects them. mixer)
known as. A complex mixer is used to create a homogeneous composition. To achieve this, in a complex mixer, the above-mentioned partition walls are attached over a long distance inside the cylinder, and the partition walls are cut in the middle, so that the partition walls intersect in a complicated manner at the cut point, and the fluid moves in a zigzag pattern. In need of.

However, when the partition wall is attached only at a short distance within the cylinder and the fluid is simply allowed to advance diagonally, sufficient mixing is not achieved.
In particular, when something with high viscosity and only a small temperature difference, such as molten resin, is passed between short diagonal partition walls, an uneven composition is created there, and areas with temperature differences are It was found that the unexpected result was that the particles were present in clusters here and there. This invention was made based on such knowledge.

This invention involves melting and kneading thermoplastic resin in an extruder to create a molten resin containing a blowing agent, passing this from the outside through a cooled resin passage, and then inserting a partition wall extending diagonally to the resin passage. The molten resin is divided by the molten resin, the divided resin parts are made to proceed in different directions, and then the resin parts are brought together, and parts with different temperatures are locally present in the whole molten resin, and in this state, the resin is transferred to the base. guidance,
The present invention relates to a method of expressing a pattern on a synthetic resin foam, which is characterized by extrusion and foaming from a die.

The gist of this invention is to locally create portions with different temperatures throughout the molten resin. To this end, this invention cools the molten resin containing a foaming agent from the outside to create a temperature difference between the inside and outside of the resin, and then provides a partition wall that extends obliquely to the resin passage, and divides the molten resin by this partition wall. However, a method is used in which the divided resin parts are advanced in different directions and then brought together. Therefore, the invention requires the use of specific equipment. First, we will begin with a description of the apparatus used in the method of this invention.

In the drawings, FIG. 1 is a partially cut away longitudinal sectional view of the apparatus used in the method of the present invention. FIG. 2 shows an example of the material for forming partition walls used in the method of the present invention. FIG. 3 shows other materials for constructing partition walls that can be used in the method of this invention. FIG. 4 shows yet another partition wall construction material used in the method of the present invention.

In FIG. 1, 1 is an extruder, 2 is a screw,
3 is a breaker plate, 4 is a cylinder, 5 is a partition wall, 6
7 is a base, and 7 is a molding frame. The extruder 1 has a screw 2 rotatably attached within a barrel, a breaker plate 3 attached to the tip thereof, and a cylinder 4 further attached to the tip of the screw 2. The cylinder 4 forms a resin passage. At least the extruder side of the tube 4 is cooled from the outside, a partition wall 5 is fixed inside the nozzle side, and a nozzle 6 is attached to the tip of the partition wall 5.

In the method shown in FIG. 1, the foamable resin is melted by heating in an extruder 1, kneaded by a screw, passes through a breaker plate 3, enters a cylinder 4, is first cooled on the outside, and then passes through a partition wall 5. It is divided accordingly. Inside the partition wall 5, the divided resin is made to advance in different directions. After passing through the partition wall 5, the resin is collected in a die 6, extruded from the die 6, foamed, and shaped by a molding frame 7 to form a foamed body 8.

As the partition wall 5, it is convenient to use one constructed as an assembly of partition walls, such as those shown in FIGS. 2 to 4. Of these, the one shown in Figure 2 is a collection of many corrugated plates.
The one shown in FIG. 3 has a large number of small flat plates intersecting each other, and the one shown in FIG. 4 has a large number of holes drilled in a metal block. Some of these partitions, as already mentioned, are known as mixer elements for obtaining a homogeneous composition.

The bulkhead assembly 51 shown in Fig. 2 consists of a large number of corrugated metal sheets 511, 512, etc., which are stacked on top of each other, and the corrugated sheets are fixed to each other so that the bent portions of the corrugated sheets intersect with each other in different directions. It was made by Specifically, for example, if the corrugated sheet 511 is arranged with its valleys and peaks extending in the direction of arrow a, the metal corrugated sheet 512 located immediately below it will be arranged in the direction in which its valleys and peaks extend. The corrugated plates are arranged so that they face in the direction of arrow b, and the contact points of these corrugated plates are welded to fix them in a crossed state. Furthermore, a metal corrugated plate 52 located immediately below the metal corrugated plate 512
3 is arranged so that the extending direction of its valleys and peaks are in the direction of arrow a, and similarly welded to form an assembly 51 of inclined partition walls. In the assembly 51 of inclined partition walls, passages are formed between each corrugated plate, but the passages are oriented in different directions between adjacent corrugated plates, and the thickness of the passages varies in various ways.

In the method of this invention, simply by inserting the above-mentioned inclined partition wall assembly 51 into the cylinder 4, that is, the resin passage, a large number of partition walls can be provided to extend diagonally. When inserting, only one assembly 51 may be used, but a small number, for example, two or three partition wall assemblies 51 and 52 may be inserted in series.

When using a plurality of aggregates 51, one aggregate is insufficient for dispersion, so it is preferable to arrange the plurality of aggregates 51 so that the dispersion is even more sufficient. . For that, 1
Two assemblies are arranged side by side and connected so that a plane parallel to arrows a and b in one assemblage 51 is orthogonal to a plane parallel to arrows a and b in another assemblage 52 adjacent thereto. The ends of the corrugated plates in the assemblies 51 and 52 are brought into contact with each other in a state of crossing each other, and the contact points are welded to integrate these partition wall assemblies in a perpendicular state. In the same way, further aggregates are connected in an orthogonal manner. Aggregate 51 or 52
In order to insert the tube into the tube 4, insert it so that the direction of the arrow X in FIG. 2 coincides with the axial direction of the tube 4.

Inside the cylinder 4 thus formed, the small plates 511,
The directions a and b in which the peaks or valleys such as 512, etc. extend are oblique to the axial direction X of the cylinder 4. Moreover, inside the assembly 51, there are small plates 511, 5.
A large number of resin passages partitioned by 12, etc. are formed. The resin passage is often obstructed due to bending of the platelets. Therefore, the resin passing through the aggregate 51 forms a turbulent flow.

The apparatus shown in FIG. 1 is constructed as described above. Therefore, the method of the invention will be explained with reference to FIG. Inside the extruder 1, a thermoplastic resin containing a foaming agent is fed in a molten state through a breaker plate 3 into a resin passage formed by a cylinder 4. Up to the cylinder 4, the resin uniformly contains the blowing agent and is thoroughly kneaded to form a composition having approximately the same temperature throughout. The outer surface of the tube 4 is exposed to the atmosphere. Therefore, while the resin passes through the tube 4, the outer part becomes lower in temperature than the inner part. When such resin is passed through the partition wall 5, the resin is divided by the partition wall and advances obliquely along the partition wall. As a result, the low-temperature resin moves from the outside to the inside and is dispersed here and there.

As mentioned above, since the resin passing through the aggregate 51 forms a turbulent flow, the resins are mixed while passing through the partition wall 5. In the method of this invention, what flows through the cylinder 4 is a viscous molten resin, and since the partition wall 5 is only provided within a short range of the tip of the cylinder 4, the above-mentioned mixing is not possible. It is not possible to make the whole thing uniform. Moreover, since cylinder 4 is exposed to the atmosphere,
The resin is cooled from the exposed surface. Therefore, while passing through the partition wall 5, the resin becomes in a state in which the low-temperature portion thereof is dispersed as lumps here and there inside.

In the method of this invention, attaching the partition wall 5 within a short range of the tip of the cylinder 4 means that the area where the partition wall 5 is attached is D in the axial direction of the cylinder 4 with reference to the inner diameter D of the cylinder 4. This means that the length ranges from 5×D to 5×D.

The resin exiting the partition wall 5 then enters the cap 6. At this time, as described above, the resin is in a state where the low-temperature resin is scattered here and there in the form of lumps. Therefore, inside the cap 6, the lump of low-temperature resin is
The cross-sectional shape will be arranged in a scattered state as it is. The shaped resin foams at the same time as it exits the cap 6, but at this time it is in a molding frame 7 and its outer shape is regulated by the frame 7. During foaming, low-temperature lumps are scattered in the resin, so the low-temperature parts generate small bubbles and foam at a low magnification, while the remaining high-temperature areas generate large bubbles and foam at a high magnification. This will result in foaming.

The foam obtained as described above has a mixture of a portion foamed at a high magnification and a portion foamed at a low magnification. Therefore, when this foam is cut and viewed, the low magnification part of the cut surface is dark colored.
The high magnification area is light colored, and dark and light colors are mixed irregularly, creating a cloud-like or marble-like pattern. In this way, a resin foam with a cloud-shaped or marble-like pattern is obtained.

As already mentioned, the partition wall assembly 9 of FIG. 3 can be used instead of the partition wall assembly 51 of FIG. 2. The partition wall 9 in FIG.
It is made by combining 92, 93, etc.
To be more specific, a set of small plates 911, 912, 9
13, 914, etc. are arranged in parallel at equal intervals on one plane, and another set of small plates 916, 9
17,918,919, etc. are equally spaced,
They are arranged in parallel in different planes, and the latter set is interposed between the former set and the intersections are welded, thus forming a small plate intersection 91. Similarly, a set of small plates 921, 922, 923, etc. are arranged at equal intervals and intersect with small plates 926, 927, 928, etc. to form an intersection 92. Furthermore, the crossing object 93 is constructed in the same manner. Thereupon, these intersecting objects 91, 92 and 93 are further intersected, for example, the platelet 926 of intersecting object 92 is intersected by intersecting object 91.
The contact points are welded together to form an assembly 9. In this case, pay attention to the arrangement of each intersection so that the ends of each intersection are in a straight line. In the assembly 9 of FIG. 3, the gaps between the small plates 911 to 928, etc., form resin passages.

In the method of this invention, a foam can be produced by inserting the partition wall assembly 9 shown in FIG. 3 into the resin passage constituted by the cylinder 4 instead of the partition wall 5. At this time, the assembly 9 is positioned so that the direction of the arrow X in FIG. 3 coincides with the axis of the cylinder 4. In this way, when the molten resin is passed into the cylinder 4, the resin is passed through the small flat plate 911.
etc., and are guided and advance diagonally inside the cylinder 4. Since the small plates intersect and exist in multiple layers, the resin repeats division, diagonal progression, and aggregation. Moreover, the resin on the outer periphery is cooled and at a low temperature. Therefore, while moving through the resin passage formed by the cylinder 4, the low-temperature resin on the outer periphery is transferred to the inside, and becomes scattered inside in the form of lumps. Therefore, when this resin is extruded from the die, it foams, and as described above, a foam is obtained in which low-foaming areas and high-foaming areas appear in an irregular pattern.

The partition wall assembly 100 in FIG.
01 with a large number of through holes 103 to 106. The through holes 103 to 106 are all oriented obliquely to the cylindrical axis of the metal lump 101. Furthermore, the inclinations of the through holes 103 to 106 with respect to the cylinder axis differ between adjacent through holes. For example, if the through hole 103 represented by cross section c in Figure 4a is inclined to the left as it goes up as shown in Figure c, the adjacent through hole 104 represented by cross section b is As shown in the figure, the slope slopes to the right as it goes up. Therefore, when the resin is divided into these through-holes 103 to 106 and collected when it exits the through-holes, the resin that was on the outer periphery is divided and moves diagonally to come to the center. Conversely, the resin that was in the center will be on the outer periphery. In this way, the low-temperature resin on the outer periphery is scattered here and there inside.

In addition, in the method of this invention, it is desirable that the molten resin immediately before the partition wall assembly 5 has a temperature distribution in as wide a range as possible. This is because the larger the temperature difference between the high-temperature part and the low-temperature part, the more pronounced the pattern appears on the foam. Therefore, it is preferable that the cylinder 4 is not only exposed to the atmosphere, but also of a jacket type, and that a cooling medium such as water or oil is passed therethrough.

According to the method of this invention, it is easy to obtain a resin foam that includes a foamed portion with a low magnification inside and in which the low magnification portion is irregularly dispersed in the high magnification portion. Therefore, when this foam is cut to expose the cut surface, a resin foam is obtained in which the cut surface exhibits a unique cloud-shaped or marble-like pattern in the lower magnification portion. Since the pattern is beautiful, this foam can be cut to expose the cross section and used as a foam with a beautiful appearance. In addition, this foam has excellent heat insulation properties, so when sliced and used for shoji screens, sliding doors, etc., beautiful products with high commercial value can be obtained. In this respect, the method of this invention has great practical effects.

Next, the details of the method of this invention will be explained with reference to Examples.

Example 1 In this example, in the embodiment shown in FIG.
A jacket type tube was used as the cylinder 4, and a structure shown in FIG. 2 was used as the partition wall assembly.

Polystyrene resin is used as the resin.
After adding 0.5 parts by weight of finely powdered talc to 100 parts by weight and mixing well, the mixture was transferred to an extruder with two connected units, one with a diameter of 40 mm and one with a diameter of 50 mm, for one hour.
It was supplied at a rate of 15Kg. Then, trichloromonofluoromethane was supplied from the middle of an extruder with a diameter of 40 mm at a ratio of about 15% by weight to the resin, and was uniformly mixed to obtain a foamable resin.

The cylinder 4 provided at the tip of the extruder has an inner diameter of 60 mmφ and a length of 300 mm in the axial direction, and a partition wall assembly 51 shown in FIG.
and partition wall assemblies 52 having the same structure were inserted in series. Corrugated plate 51 in this partition wall assembly 51, 52
1,512...... is composed of seven pieces each with a thickness of 1.5 mm, and the connecting part of both assemblies is in contact with the edges of the corrugated plates crossing each other, and the contact points are welded and integrated. It was something I did. Next, the cap 6 has an opening at the tip with a narrow passage having a thickness of 2 mm and a width of 100 mm, the molding frame 7 contacts the resin discharge surface of the cap, surrounds the resin discharge passage, and the opening widens toward the exit. The ends were 25 mm thick and 200 mm wide. Moreover, the length in the axial direction was 100 mm.

For extrusion, the resin supply part of the extruder with a diameter of 40 mm was set at 170 °C, the melting part was set at 200 °C, and the extruder with a diameter of 50 mm was set at 100 to 160 °C, and the molten resin discharged from the extruder was The oil is guided into the cylinder 4, and a temperature-controlled oil of 90°C is circulated inside the jacket on the outside of the cylinder, passed through the partition wall assembly 51, 52 provided in the cylinder 4, and then extruded from the die, followed by foaming in the forming frame 7. The external shape was regulated. Thereafter, the foam was continuously taken off with a take-off machine to obtain a foamed molded article.

This foamed molded product has a density of 0.07 g/ ^cm3 , a maximum thickness of 40 mm, and a maximum width of 240 mm, with an oblate circular cross section, and when viewed from all angles, micro bubbles and coarse bubbles are mixed together, making it look like marble. It was a reflection of the pattern.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of one embodiment of the method of this invention. FIGS. 2 and 3 are perspective views showing materials for forming partition walls used in the method of the present invention. FIG. 4 is a plan view and a sectional view showing another partition wall forming material used in the method of the present invention.

Claims (1)

[Claims] 1 In an extruder, a thermoplastic resin is melted and kneaded to create a high-temperature molten resin containing a blowing agent, which is passed through a cooled resin passage from the outside, and then a partition wall that extends obliquely to the resin passage. The molten resin is divided by the molten resin, the divided resin parts are made to proceed in different directions, and then the resin parts are brought together, and parts with different temperatures are locally present in the whole molten resin, and in this state, the resin is transferred to the base. guidance,
A method of expressing a pattern on a synthetic resin foam, which is characterized by extrusion and foaming from a die.