JPS589746B2 - Method for manufacturing a foamed resin laminated sheet with a striped pattern and a die for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a foamed resin laminated sheet with a striped pattern, and a die used for manufacturing the same.

A method of imparting a striped pattern to the surface of a foam produced by extrusion is already known from Japanese Patent Publication No. 51-38340.

This method uses an extrusion die with protrusions provided at intervals on the inner surface of the extrusion die, and extrudes thermoplastic resin containing a foaming agent through the die, thereby creating grooves on the surface. This method involves extruding a certain foamed molded product, introducing the molded product into a straightening mold before hardening, closing the grooves, and forming a striped pattern there.

This method has some difficulties in implementation.

That is, when trying to form a uniform striped pattern, it is difficult to do so uniformly.

There are various possible causes for this, but since the cause is not clear, it has not been easy to eliminate the problem.

The inventor assumed various causes for the above-mentioned difficulties.

As a result, it was concluded that the above-mentioned difficulties were caused by the following factors.

That is, in the above method, after forming grooves on the outer surface of the extruded product, in order to foam the extruded product sufficiently, the molded product is once exposed to the atmosphere from the die, and then introduced into the straightening mold. There is.

In this method, since the molded product is once exposed to the atmosphere, it is difficult to uniformly foam and cool the molded product, which makes it difficult to form a uniform pattern.

Therefore, the inventor attempted to implement the above in one base.

As a result, we confirmed that the striped pattern could be expressed well.

Thus, the applicant has provided a method for manufacturing a foamed resin sheet having a striped pattern, and a die used for manufacturing the same.

Although the method described therein was initially described for products with a single composition, it has now become clear that this method can also be applied to products with different compositions.

This is how this invention was born.

This invention involves impregnating at least one of two or more thermoplastic resins with different compositions with a foaming agent, extruding each resin in a molten state from an extruder, and introducing the resin into a single die. Spread each resin into a wide sheet or cylindrical shape halfway inside the mouthpiece, and overlap each other to form a laminate,
After that, a large number of protrusions facing the extrusion direction are formed on the surface of a resin sheet or cylinder containing a foaming agent in the same die, and then the protrusions are crushed in the same die to form a flat laminate. This invention provides a method for manufacturing a foamed resin laminated sheet with a striped pattern, which is characterized by extrusion and foaming from the tip of a die.

Further, the present invention provides a cap used in the above-described manufacturing method.

The invention related to the nozzle is a sheet forming nozzle that is attached to the tip of an extruder, and the resin inlet is divided into a plurality of parts, and the resin passage from the inlet first spreads separately into sheets or cylinders, and then mutually. Overlapping in parallel, then merging in a layered manner, forming a number of grooves extending along the resin flow direction on the wall surface of the slit-like passage after merging, and then disappearing the grooves,
The object is a die for manufacturing a laminated sheet of foamed resin with a striped pattern, which is opened as a narrow channel with a certain thickness at the resin discharge end.

The method of this invention presupposes the use of a special cap, so the cap will be explained first.

FIG. 1 schematically shows a cap according to the present invention.

In FIG. 1, 1 is a base, 2 is a resin passage, and within the passage 2, resin is extruded in the direction of arrow X.

In the cap 1, the shape of the passage 2 therein is particularly important, so the shape of the passage 2 is shown in FIG.

That is, FIG. 2 can be considered to be a case in which the resin passage 2 of the cap shown in FIG. 1 is filled with resin, and then the cap is removed, leaving only the resin.

1 and 2, planes B, C, D, E and F parallel to the end surface A are shown to further clarify the shape of the passage 2.
This shows the shape when cut.

First, in the end surface A of FIG. 1, the passage 2 is a narrow gap with a small width.

At surface B, which is slightly inward from end surface A, end surface A
Similarly, the passage 2 is a narrow gap.

At a plane C, which is further advanced from the plane B in the direction of the arrow X, the passage 2 is in the form of a slit as a whole, but an extra groove 3 is formed in a part of its inner wall.

If we talk about this with the resin passage 2 shown in FIG. 2 as the center,
The passage 2 has a shape in which protrusions 4 extending in the extrusion direction are protruded here and there on its surface.

In the plane D, which is further advanced from the plane C in the opposite direction of the arrow do not have.

In the plane E that goes further in the direction of the arrow X, the passage 2 is
It is divided into two parallel passages E1 and E2.

On the plane F that goes further in the opposite direction of the arrow X direction, there are two passages F.
1 and F2 are both narrow in the width direction and have a shape close to an ellipse.

Although FIGS. 1 and 2 show the case where the grooves 3 are provided only on one side of the sheet-like passage, the grooves 3 may be provided on both sides of the sheet-like passage.

Furthermore, in FIGS. 1 and 2, the passage 2 is shown to be planar, but the invention is not limited thereto.

For example, as shown in FIG. 3, after two resin passages 21 and 22 are joined in a cylindrical shape to form a cylindrical passage 2, protrusions 4 extending in the extrusion direction are provided here and there. It may be a shaped shape.

In the nozzle shown in FIG. 1, when a section near the end face A of the nozzle is taken longitudinally along the flow direction of the resin, an enlarged cross-section is shown in FIG. 4.

That is, the resin flows in the direction of arrow X, and the resin, which was initially divided into two passages 21 and 22, merges into one passage 2 and flows in a stacked state.

The thickness of the resin passage 2 is gradually reduced at a point 5 close to the end surface A, and then the resin passage 2 advances while maintaining the reduced thickness T and opens at the end surface A.

At this time, the deepest part of the groove 3 has a shape as shown by the dotted line.

That is, the groove 3 exists at a height H over a part of the decreasing thickness part 5 and a part of the decreasing thickness part 6.

In addition, at the place where groove 3 disappears, the deepest part of the groove is indicated by dotted line 3.
As shown in 1, it becomes diagonal and gradually disappears.

The dimensional relationship near the extrusion end of the die is as follows.

In FIG. 4, let L be the length of the portion 6 where the thickness has been reduced, and let M be the length of the portion where the notch 3 is provided.

At this time, it is desirable that M be larger than L.

Moreover, it is desirable that the thickness T be larger than the height H.

In the method of this invention, two types of thermoplastic resins with different compositions are used.

Here, "different compositions" includes two resin compositions that have the same composition except for the colorant, that is, two resin compositions that differ only in color.

Furthermore, the term "different compositions" also includes two resin compositions that differ only in whether or not they contain a blowing agent.

Needless to say, this also includes cases where the resin itself is different.

The resins having different compositions are heated and kneaded in separate extruders to become plastic, and then put into the passages 21 and 22 in the mouthpiece 1 of the present invention, where they are formed into a thin sheet and merged. , and proceed in the direction of the arrow X in a laminated state 6 Therefore, in the method of this invention, two extruders are used.

Various thermoplastic resins can be used in the method of this invention.

For example, polyethylene, polypropylene, polystyrene, polybutine, polyamide, polyether, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-acrylic nitrile copolymer, etc. can be used.

As the resins to be laminated together, it is desirable to use resins that are highly compatible with each other, in other words, resins that have similar values of solubility parameters.

Various blowing agents can be used in the method of this invention.

For example, carbon dioxide, ammonia, methane, ethane, propane, butane, isobutane, penkune, hexane, isohexane, cyclohexane, ethylene, propylene, and gaseous halogenated hydrocarbons can be used.

In addition, solid compounds that decompose to generate gas at the softening temperature of the thermoplastic resin can also be used as blowing agents.

Examples of solid compounds are azoisobutyrogenyl, α, α
- azo compounds such as azopisisobutyronitrile, and sodium bicarbonate, ammonium carbonate, sodium nitrite, and the like.

The above-mentioned blowing agent may be impregnated into the thermoplastic resin before the thermoplastic resin is put into the extruder, or it may be mixed into the thermoplastic resin and impregnated in the extruder. It may be anything that comes to mind.

In this invention method, as shown in FIG. 5, the nozzle 1 of the invention is attached to the tips of two mutually orthogonal extruders P and P2, and resins with different compositions are extruded from each extruder. .

One of the resins needs to be a foamable resin.

FIG. 5 shows a case in which the base 1 is provided with a resin passage 2 as shown in FIG. 3 therein.

To be more specific, the foamable resin extruded from the extruder P1 is
The foamable resin passes through the passage 21 in the mouthpiece 1 and is extruded from the extruder P2. The foamable resin passes through the passage 22 in the mouthpiece 1, and the two resins merge and advance in the passageway 2.

FIG. 5 shows an embodiment in which a blowing agent is press-injected through pipes Q1 and Q2 and impregnated into a thermoplastic resin in an extruder.

The resin extruded from the extruder P1 advances through the resin passage 21 within the nozzle 1, and initially takes a cylindrical shape with a circular cross section, but then collides with the inner mold within the nozzle 1, and the resin travels around it. It develops into a cylindrical shape and then expands into a cylindrical shape.

On the other hand, the resin extruded from the extruder P2 advances within the passage 22 within the die 1.

The passage 22 is located outside the passage 21 and is arranged so as to surround the passage 21.

After becoming cylindrical, the resin passage 22 changes its flow direction and proceeds along the resin passage 21, gradually decreasing in inner diameter and approaching the resin passage 21.

In this way, the resin passage 22 merges with the resin passage 21,
One cylindrical passage 2 is formed here.

This cylindrical passage 2 is provided with a groove corresponding to the protrusion 4 shown in FIG. 3 in the middle thereof.

This groove disappears as it approaches the extrusion end, forming a flat cylindrical channel and opening.

Therefore, when a foamable resin is supplied to the resin passage 22 in this nozzle and extruded from this nozzle, the extruded resin will foam and the foamed resin will have a striped pattern along the position where the groove was present within the nozzle. A cylindrical laminated sheet is obtained.

When this cylindrical sheet is cut along the axial direction and unfolded,
There, a laminated sheet is obtained.

The reason for the striped pattern is thought to be as follows.

The resin laminated at the base and containing a foaming agent advances along the resin path 2 in a molten state.

By the way, the resin passage 2 has a groove 3 as shown in FIG.
3, the resin advances to fill the groove 3, and as shown in FIG. 3, the resin is provided with the protrusion 4.

However, since groove 3 disappears by the time it reaches the tip of the cap,
The protrusion 4 must be pressed and disappear at the tip of the cap. Therefore, once formed, the protrusion 4 is pressed by the tip of the no-groove base to form an apparently flat cylindrical plane, that is, without any irregularities.

However, the protrusions 4 still remain as stress strain within the time required for the stress received by the suppression to relax.

For this reason, the portion where the protrusion 4 was present becomes foamed in a different state than other portions after coming out of the slit 6 of the mouthpiece.

That is, the resin that comes out of the cap immediately foams in the atmosphere, but the portion where the protrusion 4 was present exhibits a different foaming state because the stress received inside the cap is different.

It is thought that a striped pattern is formed in this way.

According to the method of this invention, one foamable resin is laminated with another resin having a different composition while it travels through one die, and at the same time a striped pattern is formed on the foamable resin, so it is easy to A laminated sheet with a striped pattern is obtained.

Also, since the striped pattern is formed within one cap, the striped pattern is more uniform and more uniform compared to when the striped pattern is formed outside the cap.
Moreover, it appears reliably according to the shape of the groove, and therefore there is little variation in the pattern.

Therefore, it has the advantage that high quality products can be easily obtained.

Moreover, since the obtained product is a laminated sheet, it has the great advantage that by appropriately selecting the material of each layer, and especially by changing the color, it is possible to obtain foam sheets with different tastes. .

In that sense, the base of this invention is also highly useful.

Next, examples will be described to further explain the details of the method of the present invention.

This example was carried out using a cap having a cylindrical passage 2 as shown in FIG.

As for the cap, the inner mold of the outer mold is 60mm at the tip of the cap.
The outer diameter of the inner diameter was 58.5 mm, and a cylindrical slit with a thickness T=0.75 mm as shown in FIG. 4 was formed therebetween.

The cylindrical slit is 5m from the tip, as shown in Figure 4.
It has a uniform thickness T up to the point where it enters m, but
Then, towards the back, there are 1
It had 20 grooves 3.

The groove 3 had a height H of 0.5 mm, a regular triangular cross section, and a length M along the resin flow of 10 mm.

Polystyrene was used as the resin.

A foamable resin containing 100 parts by weight of polystyrene, 1 part by weight of curcum, and 27 parts by weight of butane was extruded from an extruder P1, and 1 part by weight of a yellow pigment was further added to this foamable resin. The materials were extruded from the extruder P2 and merged in the mouthpiece 1.

When extruded from the die, a cylindrical foam with a thickness of about 2 mm was obtained.

This foam was immediately cut along the axis and opened into sheets, which had a width of about 640 mm and a density of about 0.09 g/CC.

This sheet had 120 stripes over its entire surface, and the stripes were uniformly formed and beautiful.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the structure of the base of the present invention. 2 is a schematic perspective view showing the shape of the resin passage in the base of FIG. 1. FIG. FIG. 3 is a schematic perspective view showing the shape of another resin passage of the base according to the present invention. FIG. 4 is a sectional view showing the structure of the tip portion of the resin passage in the base of the present invention. FIG. 5 shows an example of an apparatus used in the method of this invention.

Claims (1)

[Claims] 1. At least one of two or more thermoplastic resins having different compositions is impregnated with a foaming agent, each resin is extruded in a molten state from an extruder, and the resin is extruded into one die. Each resin is spread into a wide sheet or cylindrical shape in the middle of the nozzle, and stacked on top of each other to form a laminate, and then a protrusion extending in the extrusion direction is placed on the resin sheet or cylinder containing the foaming agent. A foamed resin with a striped pattern, which is characterized by forming a large number of ridges in the same nozzle, and then crushing the protrusions within the same nozzle to form a flat laminate, which is then extruded from the tip of the nozzle and foamed. Method for manufacturing laminated sheets. 2. A sheet forming die attached to the tip of an extruder, the resin inlet is divided into multiple parts, and the resin passage from the inlet first spreads out separately into sheets or cylinders, then overlaps in parallel to each other, The resin then merges into layers, and after merging, many grooves are formed on the walls of the slit-like channels that extend along the flow direction of the resin, and then these grooves disappear, leaving a narrow slit with a constant thickness at the resin discharge end. It opens as a gap-like passage. Foam resin laminated sheet with striped pattern, manufacturing cap.