JP2001191391A - Device and method for manufacturing foamed thermoplastic resin sheet, and foamed thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing device which can manufacture a thermoplastic resin foamed body wherein the homogeneity of the overall foamed state is high at a higher expansion ratio, and a manufacturing method for the thermoplastic resin foamed body. SOLUTION: This manufacturing device for a foamed thermoplastic resin sheet is equipped with at least one unit of an extruder 3, a circular die 7, and a pressure-reducing chamber 10. In this case, the extruder 3 is equipped with a foaming agent-feeding device 6, melts a thermoplastic resin, and forms a foaming composition by mixing the molten thermoplastic resin and the foaming agent. The circular die 7 is fitted on the extruder, and extrudes the thermoplastic resin as a cylindrical sheet body. The pressure-reducing chamber 10 forms the foaming composition into a foamed body. Then, the pressure-reducing chamber 10 is arranged in a manner to be connected to the circular die 7, and is constituted of an internal cylindrical section 9 and an external cylindrical section 8 which covers the internal cylindrical section 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a thermoplastic resin foam sheet, particularly a foam having a high expansion ratio, and a method for producing a thermoplastic resin foam.

[0002]

2. Description of the Related Art A production apparatus for producing a thermoplastic resin foam having a higher expansion ratio by using a foaming agent which does not cause environmental health problems such as carbon dioxide as a foaming agent is disclosed in JP-A-11-240063. It is known in the publication.

According to the above-mentioned known technique, a molten mixture obtained by mixing a foaming agent with a thermoplastic resin is once extruded into the atmosphere to form a primary foam, and a flat sheet is left as it is. It is formed into a sheet and further foamed in a decompression chamber to form a secondary foam.

[0004]

However, Japanese Patent Application Laid-Open No.
The technique described in Japanese Patent No. 240063 has the following problems.

[0005] (1) Since the resin once undergoes a process of forming a primary foam at atmospheric pressure, the temperature of the resin, particularly the surface temperature, decreases at this stage, and the increase in the expansion ratio in the secondary foaming in the decompression chamber is limited. In particular, a foam having a high expansion ratio cannot be obtained. In order to increase the expansion ratio, it is necessary to provide a separate heating means, which increases the cost of equipment and is disadvantageous in terms of energy. (2) The decompression chamber has a shape applicable only to flat sheets,
If an attempt is made to obtain a wide sheet, the size of the apparatus becomes large, and a difference tends to occur between the foamed state at the end and the center.

An object of the present invention is to provide a manufacturing apparatus and a method for manufacturing a thermoplastic resin foam sheet capable of manufacturing a thermoplastic resin foam sheet having a higher expansion ratio and high uniformity of the entire foaming state. Is to do.

[0007]

The apparatus for producing a foamed thermoplastic resin sheet according to the present invention includes a foaming agent supply device for supplying a foaming agent, and melts the thermoplastic resin. At least one extruder that is mixed with a foaming agent to form a foamable composition, a circular die that is mounted on the extruder and extrudes the thermoplastic resin as a tubular sheet, and a foam that is formed by foaming the foamable composition. Wherein the decompression chamber is arranged so as to be connected to the circular die, and is constituted by an inner cylinder portion and an outer cylinder portion covering the inner cylinder portion.

Since the foaming composition is placed in a reduced pressure state immediately after extrusion by the manufacturing apparatus having such a configuration, the foaming composition is not once cooled, and is foamed in a state in which the foaming composition is uniformly heated. It is possible to produce a foam having a uniform magnification and a uniform foam state. In addition, there is no need to provide a separate heating means, which reduces the cost of the equipment and is advantageous in terms of energy.

[0009] The use of a circular die enables the production of a wide sheet in a relatively small space, and the production of a highly uniform foam sheet.

In the above manufacturing apparatus, at least one extruder for extruding a non-foamed thermoplastic resin is mounted on the circular die, and the circular die is provided with the foamable composition and the non-foamed thermoplastic resin. A multilayer molded circular die capable of coextruding a resin in a molten state and producing a multilayer foamed thermoplastic resin sheet having at least one foamed layer and at least one non-foamed layer. Is preferred.

By forming the non-foamed layer as a surface layer, a foamed sheet having a high surface smoothness can be manufactured, and the vacuum formability of the foamed sheet is also improved. By co-extrusion, the foamed layer and the non-foamed layer can be bonded and laminated without using an adhesive.

Since the foamed sheet is formed into a cylindrical shape by using a circular die, a foamed sheet having a uniform and high expansion ratio can be formed as a whole, and a foamed sheet having a wide width can be formed by using a relatively small-diameter die. Can be manufactured. Since the width is small immediately after the extrusion, the decompression chamber can be manufactured with a relatively simple structure.

In the above-mentioned manufacturing apparatus, it is preferable that the inner cylindrical portion is a mandrel capable of expanding the diameter of the extruded cylindrical sheet member.

This is a simple apparatus, and it is possible to produce a foamed thermoplastic resin sheet according to the required thickness and width by changing the shape of the mandrel.

The mandrel has an outer diameter close to the diameter of the extruded tubular sheet at a portion near the resin discharge port of the circular die, and the diameter increases toward the downstream side of the flow of the foamed resin sheet. At an appropriate position up to the outlet of the decompression chamber, it is formed so as to have a predetermined diameter corresponding to the dimensions of the foamed thermoplastic resin sheet to be manufactured.

In the above manufacturing apparatus, it is preferable that a seal member for sealing the decompression chamber is provided on at least one of the outer periphery of the inner cylinder and the inner periphery of the outer cylinder.

The foamed thermoplastic resin sheet is continuously produced and sent out of the apparatus through a gap between the outer periphery of the inner cylinder and the inner periphery of the outer cylinder. Therefore, if the seal of the gap depends only on the foam sheet, which is a product, the gap must be large enough to allow the thermoplastic resin sheet to pass without resistance after foaming, and if the gap is too large, the pressure in the decompression chamber is reduced. In order to stably maintain the degree, it is necessary to use a pressure reducing means having a large displacement, and the apparatus becomes expensive. With the above configuration,
Sealing for vacuum in the decompression chamber can be effectively performed, and at the same time, the foamed thermoplastic resin sheet easily passes. The seal member is preferably provided on the outlet side of the decompression chamber, that is, on the downstream side of the flow of the foamed thermoplastic resin sheet.

In a preferred embodiment, at least one of the inner cylinder and the outer cylinder is provided with a temperature adjusting means. The temperature adjusting means is appropriately selected and used according to the properties of the resin used by the cooling device or the heating device, the thickness of the foam sheet to be produced, the expansion ratio, and the like. It is also a preferred embodiment to use a cooling device and a heating device together as necessary.

With this configuration, the foaming state can be controlled to a favorable state according to the required characteristics. More preferably, the temperature adjusting means is provided on both the inner cylinder and the outer cylinder. As the temperature adjusting means, a method of passing a heat medium or a refrigerant through a space formed inside the inner cylinder or the outer cylinder, a method of blowing hot air or cold air from the outside to the inner cylinder or the outer cylinder, and the like are exemplified. However, it is not limited.

Since a large number of fine irregularities are formed on at least one of the outer surface of the inner cylindrical portion and the inner surface of the outer cylindrical portion, the contact area between these and the foam sheet is reduced, and the foam is in contact with the foam sheet. This is preferable because the frictional resistance when passing through is reduced. The fine irregularities are irregularities that allow the thermoplastic resin sheet after foaming to pass with a small resistance, specifically, irregularities formed by etching, irregularities formed by sand blast, shot blast, etc., formed by cutting. And the like.

In the above-mentioned apparatus for producing a foamed thermoplastic resin sheet, it is a preferred embodiment that a gear pump is provided between at least one of the extruders and the circular die.

By providing the gear pump, the uniformity of the extrusion speed of the resin is increased, and the variation in the thickness of the foamed sheet is reduced. In particular, since the variation in the resin thickness at the time of extrusion is amplified by foaming, it is effective and preferable to provide the gear pump in an extruder that extrudes the foamed resin in order to increase the uniformity of the sheet thickness.

In the apparatus for producing a foamed thermoplastic resin sheet according to the present invention, there is provided a winding device for winding the foamed sheet, and at least one cutting device for cutting the tubular foamed sheet if necessary. A crimping device or the like for crimping the foamed sheet into a two-layer laminated sheet is provided.

[0024] The method for producing a foamed thermoplastic resin sheet of the present invention comprises the steps of: melting a thermoplastic resin; and mixing a foaming agent with the melted thermoplastic resin to form a foamable composition.
An extruding step of extruding the foamable composition as a tubular sheet from a circular die, and foaming the foamable composition constituting the extruded tubular sheet under reduced pressure in a vacuum chamber connected to the die. It is characterized by having a reduced-pressure foaming step for forming a body.

In the above-mentioned production method, the foamed thermoplastic resin sheet has a multi-layered foamed thermoplastic resin comprising at least one foamed layer and at least one non-foamed layer formed of a non-foamed thermoplastic resin. Preferably, the extrusion step is a co-extrusion step in which the foamable composition and the non-foamed thermoplastic resin are co-extruded in a molten state to form a multilayer tubular sheet body. .

In the above-mentioned manufacturing method, claims 1 to 7
It is preferable to use the manufacturing apparatus described in any of the above.

Since the foamable composition is placed in a reduced pressure state immediately after extrusion, the foamable composition is not once cooled, and is foamed in a state where the foaming composition is uniformly heated, so that the foaming composition has a high foaming ratio and a uniform foaming state. A suitable foam can be manufactured. Moreover, there is no need to provide a separate heating means, and the equipment becomes low cost.
Also, energy consumption is low and a low cost foam sheet can be obtained.

The present invention is a foamed thermoplastic resin sheet having a high foaming ratio and a uniform foamed state, characterized by being produced by the above-mentioned production method. The resin constituting the thermoplastic resin sheet in the present invention is preferably a thermoplastic polyolefin, especially a crystalline polypropylene, and the use of carbon dioxide as a foaming agent is preferred.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. In this example, polypropylene using carbon dioxide as a foaming agent is used as the foaming layer, long-chain branched polypropylene is used as the non-foaming layer, and a three-layer structure of non-foaming layer / foaming layer / non-foaming layer is used. The case where a foamed polypropylene sheet is manufactured is shown as an example.

FIG. 1 shows an example of an apparatus for producing a multilayer polyolefin foam sheet according to the present invention. Manufacturing equipment 1
Are a first extruder 3 for extruding a foamed layer, a second extruder 5 for extruding a non-foamed layer, a circular die 7 as an extrusion die (hereinafter sometimes simply referred to as a die), a decompression chamber 1
0, and a take-up roll 11 as an example of a take-up device. The decompression chamber 10 includes a mandrel 9 as an inner cylinder and an outer cylinder 8.

The first extruder 3 is provided with a pump 6 which is an example of a foaming agent supply device for supplying carbon dioxide as a foaming agent. The polypropylene resin charged into a hopper (not shown) of the first extruder 3 is melted in a melting step in a cylinder, and sent to a circular die 7 by a screw. The carbon dioxide gas is supplied to the molten resin when the resin is sufficiently melted, further dispersed uniformly and sent to the die 7 (mixing step), and extruded from the resin discharge port of the die 7 as a tubular sheet ( Extrusion process).

If the resin supplied as pellets is not sufficiently melted, the foaming agent leaks from the hopper through the voids in the pellets, and the die 7
If it is too close, it will be extruded before the mixing of the blowing agent is sufficient. Therefore, the supply position of the foaming agent is preferably at the center of the cylinder. A configuration in which a well-known vent-type extruder is used as the first extruder 3 and carbon dioxide gas is supplied under pressure from a vent hole is not particularly necessary to improve the extruder, and is a preferable embodiment. When a gas is used as the foaming agent, it is also a preferable embodiment to use an extruder including a screw having a mechanism for partially reducing the resin feeding speed, such as a reverse spiral portion.

In each of the above examples, a single-screw extruder is used, but a twin-screw extruder or the like can be used as an extruder for extruding at least one, and preferably, a foam layer constituent material. is there.

The multilayer tubular sheet 12 extruded from the circular die 7 into the decompression chamber 10 connected thereto is immediately formed into a foam (decompression foaming step). At this time, the tubular sheet body 12 is not once cooled as in the case of being extruded into the atmosphere, and the entire foamable composition foams under a reduced pressure at a uniform temperature. Is formed.

In the example of FIG. 1, since the mandrel 9 is used as the inner cylindrical portion, the diameter of the tubular sheet body 12 having the foamed layer is enlarged in the direction perpendicular to the extrusion direction, and It is formed into a tubular foamed thermoplastic resin sheet 15, cut open at the outlet of the decompression chamber by a cutter 30, and taken up by a take-off roller 11 as a wide foamed thermoplastic resin sheet. When two cutters 30 are used to make incisions at two opposite locations of the tube 15, two three-layer foam sheets are obtained.

FIG. 2 shows a cross section of a preferred embodiment of the structure of the die. The dice used in this example is a circular dice. The die 7 is formed with resin flow paths 23a, 23b forming a foamed layer and resin flow paths 24, 24a, 24b, 24c, 24d forming a non-foamed layer.

The head 21 of the first extruder 3 is connected to the end of the die 7 on the source flow side in the resin flow direction, and the head 22 of the second extruder 5 is connected to the source flow side. Head 2
The molten resin forming the foam layer supplied from 1 first enters the flow path 23a and is sent toward the die exit. On the way, it is branched by passing through the path P and sent to the flow path 23b.

On the other hand, the molten resin forming the non-foamed layer is the second resin.
It is supplied from the head 22 of the extruder 5 and
a and 24b, are supplied so as to adhere to both sides of the flow path 23b so as to cover both sides of the foam layer, and are multi-layered at 25a. The molten resin supplied to the flow paths 24a and 24b passes through a divided flow path (not shown) similar to the path P so as to cover both surfaces of the foam layer of the flow path 23a.
c, 24d, and are multi-layered at 25b.

The molten resin having a three-layer cylindrical shape at 25a and 25b is extruded from a die outlet 26. By the extrusion into the decompression chamber, the carbon dioxide gas in the foamable composition expands, and bubbles are formed to form a foamed layer.

A decompression chamber 1 comprising an outer cylinder 8 and a mandrel 9
0 to 0 are shown in FIGS. The example shown in FIG.
The mandrel 9 and the outer cylinder 8 are formed separately, and the outer cylinder 8 is composed of a flange 8F mounted on the circular die 7 and a cylinder 8T provided on the carriage 31. It is fixed to the resin discharge port of the circular die 7. The cylinder 8T is abutted and fixed to the flange 8F, is configured to be movable to a position apart from a position where the pressure reducing chamber 10 is formed by covering the mandrel 9, and is replaceable with a cylinder having a different inner diameter. In this example, by using the cylindrical body 8 having a different inner diameter, it is possible to easily cope with a change in the thickness of the foamed thermoplastic resin sheet to be manufactured.

FIGS. 4A and 4B show an example in which the mandrel 9 and the cylindrical body 8T are fixed to the same carriage 31, and can be integrally moved in a combined state.
In FIG. 4 (A), the outer cylinder portion is composed of a flange 8F mounted on the circular die 7 and a cylinder 8T, and the ends thereof are abutted and fixed to each other to reduce the pressure in the decompression chamber 1.
0 is formed.

FIG. 4B shows that the outer cylinder portion 8 is integrally formed, and the decompression chamber 10 is formed by fitting a hole 8H provided at the tip to the tip of the die. FIG.

In the example shown in FIG. 5, the tubular body 8T constituting the outer tubular portion 8 is independently attached to the carriage 31, and the mandrel 9 is independently attached to another carriage 32.
The mandrel 9 and the mandrel 9 can move with a coaxial core.
Is formed. In this example, by changing the combination of the outer diameters of the cylindrical body 8T and the mandrel 9, it is possible to easily produce foamed thermoplastic resin sheets having different widths and thicknesses.

FIG. 6A shows a seal member and an example of mounting the seal member.
(B). In the example shown in FIG. 6A, the seal member 33 is attached to the mandrel 9 on the downstream side of the flow of the foamed thermoplastic resin sheet, that is, at the end of the expansion of the tubular sheet body. The seal member 33 may be mounted with a groove provided on the outer cylinder portion 8 side.

FIG. 6B shows an example of the structure of the seal member 33. The seal member may be entirely formed of a rubber-like elastic material such as silicon rubber or fluoro rubber like a commonly used O-ring, and may be a hollow member as shown in the example of FIG. You may. The example shown in FIG.
The outer side is formed of a resin layer 41 such as polytetrafluoroethylene or silicon rubber, and the inner layer is formed by bonding a high rigidity layer 42 such as a glass fiber cloth or a resin film. By sending pressurized air to the hollow portion 43, the hollow portion 43 can be expanded to a predetermined outer diameter and sealed. A plurality of seal members may be provided. If a plurality of expandable seal members having different outer diameters as shown in FIG.
By expanding the sealing member having an outer diameter selected according to the target thickness and contracting the other, it is possible to easily manufacture products having different thicknesses, which is preferable.

FIG. 7 shows an example of the structure of the decompression chamber 10 and an example of the state of production of the foamed thermoplastic resin sheet 15. Outer cylinder part 8 is formed with outer cylinder part decompression holes V1 and V2,
They are connected to exhaust pipes 51 and 52, respectively. Only one of V1 and V2 may be provided in the outer cylinder pressure reducing hole. A mandrel 9, which is an inner cylinder, is provided with an inner cylinder pressure reducing hole V3, an exhaust pipe 56 for connecting the same to a pressure reducing device, and a jacket 53 for temperature control. It is configured to be able to circulate through the flow pipes 54 and 55 connected to the same, and can cope with cooling and heating. A pipe may be brought into contact with the inner wall of the mandrel 9 instead of the jacket. The jacket and the pipe do not have to be formed on the entire surface, and a heating part and a cooling part may be provided. The same applies to the temperature adjustment of the outer cylinder portion 8.

FIG. 8 shows a pump 6 as a blowing agent supply device.
An example of an apparatus for manufacturing a foamed thermoplastic resin sheet in which a gear pump 60 is provided between the first extruder 3 having the above-described structure and the circular die 7 is shown. A second extruder 5 for extruding a thermoplastic resin forming a non-foamed layer is connected to the circular die 7.

When two sheets of the obtained foamed thermoplastic resin sheet having a three-layer structure are laminated and bonded, a non-foamed layer having a structure of non-foamed layer / foamed layer / non-foamed layer / foamed layer / non-foamed layer is formed. A foamed sheet having three layers is obtained.

The raw materials used in the present invention will be described.
As the polyolefin resin constituting the foamed layer, ethylene, propylene, a homopolymer such as butene or a copolymer using two or more of these monomers, and furthermore, a copolymer of at least one of these monomers and another monomer And copolymers. Examples of the copolymer include ethylene-
α-olefin copolymer, propylene-α-olefin copolymer and the like are exemplified.

Polyethylene (PE) or a copolymer of ethylene and another monomer, that is, as the ethylene resin, for example, polyethylene such as low-density polyethylene and high-density polyethylene; ethylene-propylene copolymer, ethylene-butene-1 copolymer Polymer, ethylene-4-methyl-1
Ethylene-α such as pentene copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, etc.
An olefin copolymer; an ethylene copolymer comprising a repeating unit derived from at least one vinyl monomer and a repeating unit derived from ethylene, such as an ethylene-methyl methacrylate copolymer and an ethylene-vinyl acetate copolymer. Coalescence, and mixtures thereof.

The propylene-α-olefin copolymer includes a propylene-α-olefin block copolymer,
Examples include propylene-based polymers such as propylene-α-olefin random copolymers and mixtures thereof. Examples of the α-olefin of the propylene-α-olefin block copolymer and the propylene-α-olefin random copolymer include ethylene, butene-1, and octene-1.
And α-olefins having 2 to 4 carbon atoms, such as

Among the polyolefins exemplified above, (a) long-chain branched polypropylene, because the uniformity of the foam is high and the multi-layer polyolefin foam sheet of the present invention is particularly excellent in vacuum moldability. (P
P), (b) In the first step, a crystalline PP having an intrinsic viscosity of 5 dl / g or more is synthesized, and in a second step, a crystalline PP having an intrinsic viscosity of less than 3 dl / g is continuously synthesized. Has a PP of 0.05 to 25 wt% and an intrinsic viscosity of 3 dl as a whole.
A suitable raw material is polypropylene having an Mw / Mg of less than 10 and Mw / Mn of less than 10. As a commercially available product (a), there is a polypropylene PF814 (manufactured by Montell).
The above (b) can also be suitably used.

The foaming agent used for forming the foamed layer is preferably an inert substance such as water or carbon dioxide gas in consideration of the influence on the environment. In particular, when polypropylene is used as the resin constituting the foam layer, the use of carbon dioxide is preferred.

As the thermoplastic resin forming the non-foamed layer, use of a long-chain branched polypropylene or a polyolefin-based adhesive resin having a long-chain branch is preferred. As the long-chain branched polypropylene, for example, the above-mentioned product of Montell is available as a commercial product, and can be suitably used. The thickness of the non-foamed layer is appropriately set according to the thickness of the entire multi-layer polyolefin foam sheet, applications, etc., and is not particularly limited as long as the surface smoothness, that is, the appearance is good, but is preferably 1 μm or more. Yes, more preferably 10 μm or more, even more preferably 50 μm or more. If the thickness of the non-foamed layer is too large, the properties of the foamed layer will not be sufficiently exhibited.

Examples of the polyolefin adhesive resin having a long chain branch which forms a non-foamed layer include: 1) unsaturated carboxylic acid, unsaturated carboxylic anhydride, epoxy group-containing vinyl monomer, unsaturated carboxylic acid ester, vinyl Examples thereof include a copolymer of one or more monomers selected from a group of monomers composed of esters and an olefin monomer, and 2) an acid-modified olefin polymer obtained by grafting an unsaturated carboxylic acid or an acid anhydride thereof. .

1) at least one monomer selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic anhydrides, epoxy group-containing vinyl monomers, unsaturated carboxylic acid esters and vinyl esters, and olefin monomers; Examples of the copolymers of ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer metal crosslinked product, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer Polymer, ethylene-glycidyl methacrylate-methyl (meth) acrylate copolymer, ethylene- (meth) acrylate copolymer, ethylene- (meth)
Acrylic ester-maleic anhydride copolymer, ethylene-vinyl acetate copolymer and the like are exemplified.

Examples of the above 2) acid-modified olefin polymers grafted with unsaturated carboxylic acids or their anhydrides include maleic anhydride-grafted ethylene polymers and maleic anhydride-grafted propylene polymers. Coalescence is exemplified.

In the present invention, the non-foamed layer is defined as having a foaming ratio of 1.0 to 1.5 times, preferably 1.0 to 1.1 times.
It is a double layer, and the expansion ratio exceeds 1.5 times with the foam layer,
It is preferably a 2.5 to 40 times layer. The expansion ratio is 2.
If it is less than 5 times, the properties as a foam, specifically, lightness and heat insulation, will not be sufficient, and if it exceeds 40 times, it will be difficult to manufacture, and it will not be possible to suppress foam breakage during vacuum forming. The expansion ratio can be adjusted by the amount of the foaming agent to be used, the pressure reduction after forming the foam sheet, and the like.

The multi-layer polyolefin foam sheet obtained by the production method of the present invention can be used for various purposes, and specifically, food containers including microwave-compatible containers (HMR), heat insulating materials, sports equipment and packaging. Cushioning material such as wood
Automotive parts such as insulating materials, vehicle ceiling materials, sealing materials, building materials,
Examples of the use of a resin in the aerospace industry in which lightness, heat insulation, and the like are required are used.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. Using polypropylene (manufactured by Sumitomo Chemical Co., Ltd.) as the foam layer constituent material and long-chain branched polypropylene PF814 (manufactured by Montell) as the non-foam layer constituent material, using the manufacturing apparatus schematically shown in FIG. A multilayer polypropylene foam sheet was produced.

The extruder used was a 50 mmΦ twin-screw extruder as the first extruder for extruding the constituent material of the foamed layer, and 90 mm as the second extruder for extruding the non-foamed layer constituent material.
Φ single screw extruders were each used. As the extrusion die, a circular die shown in FIG. 2 capable of extruding two kinds of materials into a three-layer tube shape is used.
A mandrel having a maximum diameter of 210 mm for expanding the extruded tubular multilayer foam sheet was connected to the extrusion die.

To the polypropylene constituting the foamed layer, 1 part by weight of hydrocerol (manufactured by Beilinger Ingelheim Chemicals Co., Ltd.) is blended as a nucleating agent with respect to 100 parts by weight of the resin, and charged into the hopper of the first extruder. Then, 1 part by weight of carbon dioxide as a foaming agent was injected at a high pressure in the vicinity of the center of the cylinder where the melting of the resin had progressed, and the mixture was fed to an extrusion die in a state where the raw material and carbon dioxide were sufficiently kneaded. The foamed material and the non-foamed material are stacked in a molten state in an extrusion die, extruded in a tube, introduced into a decompression chamber, and cooled and expanded (blow-up) along the mandrel that is the inner cylinder of the decompression chamber. ) And foaming. Next, the formed tubular multi-layer polypropylene foam sheet was cut at one place with a cutter, and the tube was opened to form a flat sheet and wound by a winder.

The obtained multilayer polypropylene foam sheet has a three-layer structure of a non-foam layer / foam layer / non-foam layer, a width of 650 mm, a thickness of 1 mm, an expansion ratio of 12 times, and an expansion ratio of 2 in the width direction. And the magnification in the length direction was 1.2 times. This multilayer polypropylene foam sheet had good surface smoothness.

For comparison, a laminated tube in a molten state comprising a foamed layer constituent material and a non-foamed layer constituent material is once extruded into the atmosphere to form a foam, and the surface is further heated and introduced into a decompression chamber. As a result, the expansion ratio was limited to 8 times, and the surface condition of the expanded thermoplastic resin sheet was inferior to that of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus for manufacturing a foamed thermoplastic resin sheet in which a decompression chamber is directly connected to a die.

FIG. 2 is a diagram showing a structural example of a circular die suitable for manufacturing a multilayer foamed thermoplastic resin sheet.

FIG. 3 is a diagram showing a structural example of an outer cylinder portion and an inner cylinder portion constituting a decompression chamber.

FIG. 4 is a diagram showing a structural example of an outer cylinder portion and an inner cylinder portion constituting a decompression chamber.

FIG. 5 is a diagram showing a structural example of an outer cylinder portion and an inner cylinder portion constituting a decompression chamber.

FIG. 6 is a diagram showing a structure of a seal member and a mounting example.

FIG. 7 is a diagram showing an example of the structure of a decompression chamber and an example of a production state of a foamed thermoplastic resin sheet.

FIG. 8 is a diagram showing an example of a configuration in which a gear pump is provided in an extruder of a thermoplastic resin constituting a foamed layer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 foamed thermoplastic resin production apparatus 3 first extruder 7 circular die 8 outer cylinder part 9 inner cylinder part 10 decompression chamber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // B29K 23:00 B29K 23:00 105: 04 105: 04 B29L 9:00 B29L 9:00 23:00 23:00 (72) Inventor Tatsuma Kuroda 2-10-1, Tsukahara, Takatsuki-shi, Osaka Sumitomo Chemical Industries Co., Ltd. (72) Inventor Takeo Kitayama 2-1-1 Tsukahara, Takatsuki-shi, Osaka Sumitomo Chemical Industrial Co., Ltd. F term (reference) 4F207 AA03 AB02 AG01 AG03 AG08 AG20 AM03 AR06 KA01 KA12 KA17 KB26 KF04 KK51 KL88 KL92 KM15 KM16

Claims (12)

[Claims] 1. A foaming agent supplying device for supplying a foaming agent, wherein at least one foaming composition is formed by melting a thermoplastic resin and mixing the molten thermoplastic resin and the foaming agent. An extruder, a circular die mounted on the extruder and extruding the thermoplastic resin as a tubular sheet body, and a decompression chamber including the foamable composition as a foam, wherein the decompression chamber is connected to the circular die. An apparatus for manufacturing a foamed thermoplastic resin sheet, comprising: an inner cylinder portion; and an outer cylinder portion covering the inner cylinder portion. 2. The method according to claim 1, wherein at least one extruder for extruding the non-foamed thermoplastic resin is mounted on the circular die, and the circular dice melts the foamable composition and the non-foamed thermoplastic resin. The foamed thermoplastic die according to claim 1, which is a multilayer molded circular die capable of producing a multilayer foamed thermoplastic resin sheet having at least one foamed layer and at least one non-foamed layer. Equipment for manufacturing resin sheets. 3. The apparatus for manufacturing a foamed thermoplastic resin sheet according to claim 1, wherein the inner cylindrical portion is a mandrel capable of expanding the diameter of the extruded tubular sheet body. 4. The heat of foaming according to claim 1, wherein a seal member for sealing the decompression chamber is provided on at least one of an outer periphery of the inner cylinder portion and an inner periphery of the outer cylinder portion. Equipment for manufacturing plastic resin sheets. 5. The heat of foaming according to claim 1, wherein fine irregularities are formed on at least one of an outer periphery of the inner cylinder and a surface of the outer cylinder facing the foamed thermoplastic resin. Equipment for manufacturing plastic resin sheets. 6. The apparatus for producing a foamed thermoplastic resin sheet according to claim 1, wherein at least one of the inner cylinder part and the outer cylinder part is provided with a temperature adjusting means. 7. The apparatus for producing a foamed thermoplastic resin sheet according to claim 1, wherein a gear pump is provided between at least one of the extruders and the circular die. 8. A mixing step of melting a thermoplastic resin, mixing a foaming agent with the melted thermoplastic resin to form a foamable composition, and extruding the foamable composition from a circular die as a cylindrical sheet. Production of a foamed thermoplastic resin sheet having an extrusion step and a reduced-pressure foaming step of forming a foam under reduced pressure in a reduced-pressure chamber arranged and connected to the die, the foamable composition constituting the extruded tubular sheet body. Method. 9. The foamed thermoplastic resin sheet is a multilayer foamed thermoplastic resin sheet having at least one foamed layer and at least one non-foamed layer formed of a non-foamed thermoplastic resin. The foamed thermoplastic resin according to claim 8, wherein the extrusion step is a coextrusion step of coextruding the foamable composition and the non-foamed thermoplastic resin in a molten state to form a multilayer tubular sheet body. Sheet manufacturing method. 10. The method for producing a foamed thermoplastic resin sheet according to claim 8, wherein the production apparatus according to claim 1 is used. 11. A thermoplastic resin foam sheet produced by the production method according to claim 8. Description: 12. The thermoplastic resin foam sheet according to claim 11, wherein the thermoplastic resin is a thermoplastic polyolefin.