JPH072391B2 - Hollow body made of thermoplastic resin and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a hollow body made of a thermoplastic resin, which is preferably used as an air intake duct of an engine of an automobile or the like, a duct or a pipe connected to an air conditioner, or the like. The manufacturing method is related.

[Problems to be Solved by Conventional Techniques and Inventions] In ducts and the like connected to air conditioners and the like, heat insulation for reducing heat loss, mechanical strength capable of withstanding mechanical shock, cushioning, However, it is required to have a sound absorbing property for suppressing the transmission of noise. In order to satisfy these characteristics,
A blow-molded hollow body composed of an outer layer made of a non-foamed resin and an inner layer made of a foamed resin has been proposed. For example, JP-A-58-126122 discloses a non-foamable thermoplastic resin outer layer and a foamable thermoplastic resin inner layer, the inner layer,
A method for producing a double-walled tubular body has been proposed in which the expandable resin powder and the non-expandable resin powder are used in a specific ratio and the apparent expansion ratio is set to 2 to 10 times. Further, Japanese Patent Application Laid-Open No. 63-236620 proposes a hollow body composed of an outer layer made of a non-foamed resin and an inner layer made of a foamed resin, and a method for producing the same, by blow molding. The inner layers of these hollow bodies are each composed of one foam layer.

In these blow molding methods, a thermoplastic resin and a thermoplastic resin containing a foaming agent are respectively melt-extruded by an extruder and supplied to an annular resin flow channel in a die, respectively, and extruded in a laminated state from an extrusion port of the die. , Forming a tubular parison. Next, a hollow body is manufactured by sucking compressed air into the parison while sandwiching the parison with a mold.

However, when the inner layer made of a foamed resin is formed by this blow molding method, there is a problem that the mechanical strength is lowered and the integrity is insufficient. That is, in the blow molding method, generally, the molten resin melt-extruded by the extruder is supplied to the annular resin flow channel of the die from the direction orthogonal to the extrusion direction, so the molten resin is in the circumferential direction of the annular resin flow channel. The merging is performed while moving to, and a line formed at the merging portion of the molten resin, that is, a streak weld line along the extrusion direction is generated in the parison. This weld line functions as a weakened portion and reduces the mechanical strength of the parison and hollow body. In particular, a hollow body having a foamed inner layer has insufficient mechanical strength in the foamed layer, and further has poor mechanical strength due to a weld line, resulting in lack of integrity.

Further, since the inner layer is composed of one foam layer, when the expansion ratio is increased, the bubbles in the surface layer portion are easily broken. Then, when the bubbles are broken, the broken portion becomes bulged, the surface smoothness and the inner diameter dimensional accuracy are deteriorated, and it is difficult to form a uniform inner layer. In particular, when the thickness of the foam layer is made small and the expansion ratio is made large, or the pressure of the air supplied to the parison is made large, the above-mentioned problem appears remarkably.

Further, in the above manufacturing method, the surface of the foam layer is cooled at the time of forming the parison or in the process of pressurizing air, and a non-foaming skin layer is formed on the surface. This skin layer reduces the cushioning property, the heat insulating property and the sound absorbing property.

The present invention has been made in view of the above points, and provides a thermoplastic resin hollow body having a foamed layer excellent in not only cushioning properties and heat insulating properties but also uniformity, sound absorption properties, and integrity. With the goal.

It is another object of the present invention to provide a method for producing a thermoplastic resin hollow body having the above-mentioned excellent properties.

Furthermore, the present invention does not have a skin layer on the surface of the foam layer,
It is an object of the present invention to provide a thermoplastic resin hollow body having excellent properties as described above.

An object of the present invention is to provide a method for producing the above thermoplastic resin hollow body in which a skin layer does not exist on the surface of an inner layer which is a foam layer.

[Means and Actions for Solving the Problem] The present invention is a blow-molded hollow body having an outer layer made of a non-foamed thermoplastic resin and an inner layer made of a foamed thermoplastic resin, wherein the inner layer has a plurality of layers. The above problem is solved by a thermoplastic resin hollow body formed of a foam layer.

According to the thermoplastic resin hollow body having the above configuration, since the inner layer is composed of a plurality of foam layers, even if the thermoplastic resin containing the foaming agent merges in the annular resin flow path, the weld line of each foam layer The positions are displaced from each other. Therefore, the weld line generated in one foam layer can be reinforced with the other foam layer, and the damage due to the weld line does not occur at the time of gas blowing, and the mechanical strength due to the weld line is not lowered as a whole. Can be prevented.

Further, since the inner layer is composed of a plurality of foam layers, it is possible to prevent the bubbles of the foam layer interposed between the outer layer and the foam layer on the inner surface side of the plurality of foam layers from breaking. Therefore, even if the thickness of each foam layer is thin, it is possible to form an inner layer having excellent uniformity as a whole.

The present invention supplies a molten thermoplastic resin to an annular resin flow channel in a die, includes a foaming agent, and forms a plurality of molten thermoplastic resins formed inward of the annular resin flow channel in the die. To the annular resin flow path, melted thermoplastic resins are combined in a laminated state and extruded from a die, and a compressed gas is supplied to the parison produced, and a method for producing a thermoplastic resin hollow body which is molded by a die The above problems are solved by.

Furthermore, the present invention is a blow-molded hollow body having an outer layer made of a non-foamed thermoplastic resin and a foamed layer made of a foamed thermoplastic resin, the thermoplastic resin having no skin layer on the surface of the foamed layer. The above-mentioned problems are solved by the hollow body.

The present invention also provides a hollow structure obtained by laminating an outer layer made of a non-foamed thermoplastic resin and a non-adhesive layer having a non-adhesiveness with respect to the foamed layer through a foamed layer made of a thermoplastic resin by a blow molding method. The above problem is solved by a method for producing a hollow body made of a thermoplastic resin in which the non-adhesive layer is peeled off after the body is produced.

According to this manufacturing method, since the positions of the weld lines of the foam layer and the non-adhesive layer are displaced from each other, the hollow body is not damaged during the blow molding process, as described above. Further, since the non-adhesive layer laminated on the foam layer is peeled off, no skin layer is formed on the exposed foam layer. Further, since the foamed layer is exposed by peeling off the non-adhesive layer, the foamed layer is smooth and has excellent dimensional accuracy and is uniform, regardless of its thickness and foaming ratio, and has excellent buffering properties, heat insulating properties and sound absorbing properties. . Furthermore, since the foamed layer and the outer layer have excellent adhesiveness, they are well integrated.

As described above, the thermoplastic resin hollow body in which the skin layer does not exist on the surface of the foam layer is excellent in cushioning property, heat insulating property, uniformity, sound absorbing property, and integrity.

The thermoplastic resin hollow body of the present invention and the method for producing the same will be described below with reference to the accompanying drawings.

FIG. 1 is a partially cutaway sectional perspective view showing an embodiment of the thermoplastic resin hollow body of the present invention. In this example, the hollow body is
It is composed of an outer layer (1) made of a non-foamed thermoplastic resin and an inner layer (2) made of a foamed thermoplastic resin.

The thermoplastic resin forming the outer layer (1) of the hollow body is not particularly limited as long as it can form a non-foamed layer by blow molding. As such a thermoplastic resin, for example,
Olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, ionomer; polystyrene, styrene-acrylic copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer , Styrene polymers such as high-impact polystyrene; acrylonitrile-butadiene copolymers; polyvinyl chloride; ethylene-vinyl acetate copolymers; acrylic resins, methacrylic resins; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polycarbonates; 6- Examples thereof include polyamides such as nylon, 66-nylon, 6,10-nylon, and 12-nylon; polyacetal; polysulfone; polyvinylidene chloride; polyphenylene oxide. Among these thermoplastic resins, polyethylene, polypropylene and the like, which have excellent blow moldability, are preferable. These thermoplastic resins are used alone or in combination of two or more. The thickness of the outer layer (1) can be appropriately set depending on the application etc., but when it is used for ducts, pipes, etc., it is usually
It is about 0.1 to 5 mm, preferably about 0.5 to 3 mm.

As the thermoplastic resin forming the inner layer (2), any thermoplastic resin can be used as long as it can be foamed by a foaming agent. Examples of such a thermoplastic resin include olefin polymers such as polyethylene, polypropylene, ethylene-propylene-diene copolymer; polystyrene, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-polymer. Styrene-based resin such as styrene copolymer; polyvinyl chloride; ethylene-vinyl acetate copolymer; acrylic resin, methacrylic resin; styrene-based thermoplastic elastomer such as block-type styrene-butadiene copolymer, olefin-based thermoplastic elastomer, Examples thereof include urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and the like, and thermoplastic elastomers composed of hard segments and soft segments. Among these thermoplastic resins, thermoplastic elastomers having excellent elasticity and cushioning properties are particularly preferable. Further, as the thermoplastic resin forming the inner layer (2), a resin having excellent adhesiveness to the thermoplastic resin forming the outer layer (1) is used in order to enhance the integrity. The thermoplastic resin having excellent adhesiveness can be selected according to the type of the thermoplastic resin forming the outer layer (1), and a resin of the same system as the resin forming the outer layer (1) is usually used. More specifically, when the thermoplastic resin forming the outer layer (1) is an olefin polymer such as polyethylene or polypropylene, a polyolefin polymer can be used as the thermoplastic resin forming the inner layer (2).
These thermoplastic resins are used alone or in combination of two or more.

Further, as the foaming agent for foaming the thermoplastic resin of the inner layer (2), a conventionally used volatile foaming agent, decomposable foaming agent or the like can be used. Examples of the volatile foaming agent include carbon dioxide gas; aliphatic hydrocarbons such as propane, butane, pentane and hexane; ethers such as methyl ether and ethyl ether;
Examples thereof include ketones such as acetone; alcohols; halogenated hydrocarbons such as freon-11, freon-12, freon-22 and the like. As the volatile foaming agent, a liquid having a boiling point of 100 ° C. or lower is usually used. Examples of the decomposable foaming agent include inorganic compounds such as ammonium carbonate, ammonium hydrogen carbonate and sodium bicarbonate; azo compounds such as azobisisobutyronitrile, azodicarbonamide, diazoaminobenzene and azobisformamide, N, N'-dimethyl-N, N'-
Ninitroso compounds such as dinitrosoterephthalamide, N, N'-dinitrosopentamethylenetetramine, benzenesulfonylhydrazide, p-toluylenesulfonylcarbazide, 4,4'-oxybis (benzenesulfonylhydrazide), trihydrazinotriazine, Sulfonyl hydrazide compounds such as disulfo hydrazine of diphenyl sulfone-3,3 ′, triazole compounds such as 5-morpholyl-1,2,3,4, -thiatriazole, terephthal azide, p-tert-butyl benz azide, etc. Examples thereof include organic compounds such as azide compounds. These foaming agents may be of the same kind or of different kinds, and one kind or two or more kinds are used. The amount of the foaming agent used can be appropriately set according to the desired expansion ratio and the like, but is usually 0.5 to 10 with respect to the thermoplastic resin.
It is about% by weight. The thermoplastic resin forming the inner layer (2) is preferably in the form of beads or pellets containing the above-mentioned foaming agent, and a foaming masterbatch made of the thermoplastic resin containing the foaming agent and a non-foaming resin. Mixtures with powders are also preferred.

The inner layer (2) is composed of two foam layers (2a) and (2b). The foam layers (2a) and (2b) can be made of the same or different thermoplastic resins. The expansion ratio and thickness of each foam layer (2a) (2b) can be appropriately set according to the desired heat insulating property, cushioning property, sound absorbing property, etc., and are not particularly limited. The expansion ratio of each of the foam layers (2a) and (2b) is usually 2 to 25 times, preferably 2.5 to 10 times, and the thickness thereof is usually 0.1 to 10 mm, preferably 0.2 to 5 mm. The bubbles in the foam layers (2a) and (2b) may be closed cells or open cells. Closed cells are useful for increasing heat insulation and open cells are useful for increasing sound absorption. Therefore, in the application such as an air intake duct that requires sound absorption, it is preferable that the cells are open cells. The closed cells and the open cells may be mixed.

As described above, the inner layer (2) is replaced by two foam layers (2a) (2b)
When the parison is formed by the blow molding method, the weld line (3) formed on one foam layer (2a)
Since the position of a) and the weld line (3b) generated in the other foam layer (2b) are displaced from each other, the mechanical strength due to the weld lines (3a) and (3b) is reduced.
They can be reinforced by (2b). Further, since the foam layer (2a) is interposed between the outer layer (1) and the inner foam layer (2b), the entire inner layer (2) can be adjusted by adjusting the thickness of each foam layer (2a) (2b). The thickness of can be easily controlled. Furthermore, even if the thickness of the meat layer (2) is reduced or the expansion ratio is increased, the bubbles in the foam layer (2a) interposed at least between the outer layer (1) and the inner foam layer (2b) are eliminated. Since the bubbles are not broken, the uniform inner layer (2) can be accurately formed. At that time, if the foaming ratio of the inner foaming layer (2b) is made smaller than the foaming ratio of the other foaming layer (2a), the number of foam breaks is reduced, so that the inner layer (2) having excellent surface smoothness is further improved. It can be formed accurately and evenly.

In addition, in the above example, the inner layer (2) is formed in two layers, but the inner layer (2) may be formed by a plurality of three or more foam layers. Further, the plurality of foam layers may be formed with the same or different expansion ratios and thicknesses. Furthermore, in order to increase the adhesive strength, a foam layer having excellent adhesiveness may be interposed between the plurality of foam layers.

The thermoplastic resin hollow body may have not only a linear shape and a curved shape, but also a three-dimensional shape, and the cross-sectional shape thereof may be a triangular shape, a polygonal shape such as a square shape, a cylindrical shape, an oval shape, or the like. Well, it is not particularly limited. The size of the hollow body can be appropriately selected according to the application etc., but in the case of an air conditioning duct or pipe, the outer diameter is usually about 50 to 200 mm, and the length is 300 to
It is about 2000 mm.

In the outer layer (1) and / or the inner layer (2), deterioration inhibitors such as antioxidants and ultraviolet absorbers; plasticizers; coloring agents such as dyes and pigments; calcium carbonate, barium sulfate, silica, talc. Inorganic fillers such as, antistatic agents; various additives such as flame retardants may be contained. These additives can be added within a range that does not deteriorate the properties of the hollow body, and usually can be contained in an amount of about 0.1 to 25% by weight.

The thermoplastic resin hollow body having the above structure can be manufactured by a blow molding method.

FIG. 2 is a vertical cross-sectional view of a main part showing a manufacturing apparatus for a thermoplastic resin hollow body. This manufacturing apparatus is provided according to the number of the extruder (11a) that melts and extrudes the thermoplastic resin and the number of foam layers that form the inner layer (2), and melts and pushes the thermoplastic resin containing the foaming agent. Extruder (11b) (11c) for discharging, die (12) for forming parison (P) in a laminated state from molten resin extruded from each extruder (11a) (11b) (11c), and parison (P) The split mold (16
a) and (16b). Further, the die (12) is provided with annular resin flow passages (13a) (13b) (13c) which are passages for the molten resin extruded from the extruders (11a) (11b) (11c), respectively. , This annular resin flow path (13a) (13
b) (13c) joins in a predetermined part in sequence. Further, a compressed gas supply port (15) for supplying compressed gas to the parison (P) to inflate it is extended from the center of the die (12) to the extrusion port (14).

In the above apparatus, the thermoplastic resin containing no foaming agent is extruded from the extruder (11a), and the thermoplastic resin containing the foaming agent is extruded from each of the extruders (11b) and (11c) and supplied to the die (12). Then, each molten resin joins in a laminated state in the middle of each resin flow path (13a) (13b) (13c),
Extruded from the extrusion port (14) of the die (12) in a laminated state,
A parison (P) is formed.

At that time, the inner layer (2) made of a thermoplastic resin containing a foaming agent
Foam to form foam layers (2a) and (2b). Then, by supplying compressed gas such as compressed air from the compressed gas supply port (14) in a state where the parison (P) is sandwiched by the split molds (16a) (16b), each foam layer of the inner layer (2). (2a)
A hollow body having a predetermined shape obtained by foaming (2b) is obtained. At that time, in the illustrated example, each extruder (11a) (11b) (11
c) are provided at different positions of the die (12), and since each molten resin is extruded under pressure, the position where the molten resin merges in each annular resin flow path (13a) (13b) (13c) different. That is, the parison (P) is formed in which the positions of the weld lines are offset from each other. Therefore, the inner layer (2) of the obtained hollow body is composed of the foam layers (2a) and (2b) in which the positions of the weld lines are different, and the decrease in mechanical strength due to the weld lines can be prevented.

Since the molten resin is extruded under pressure, even if each extruder (11a) (11b) (11c) is provided on the same line along the extrusion of the molten resin on the outer periphery of the die (12), Usually, a slight deviation occurs in the position of the weld line of each foam layer (2a) (2b). Therefore, each extruder (11a) (11b) (11c)
Can be provided at any suitable position on the die (12). In addition, when the foam layers (2a) and (2b) may have the same composition, foaming ratio, etc., the extruder (11b) is connected to the plurality of annular resin channels (13b) of the die (12). A thermoplastic resin containing a foaming agent having the same composition may be extruded into (13c). The extruders (11a) (11b) (11c) may be extruders equipped with an in-line screw that compensates for the load generated due to the accumulation of the molten resin. In addition, the parison (P) extruded from the extrusion port (14) of the die (12) is prevented from hanging down, that is, drawdown due to its own weight, and the extruder (11a) (11b) is manufactured in order to accurately manufacture the hollow body. )
Between the (11c) and the extrusion port (14) of the die (12), there is provided an accumulator composed of a storage part for storing the molten resin and a plunger for extruding the molten resin at a predetermined pressure. Good. With this accumulator, the amount of each molten resin extruded can be accurately adjusted, and each foam layer (2a) constituting the outer layer (1) and the inner layer (2) of the hollow body.
The thickness of (2b) can be controlled.

Further, the mold is not limited to the split molds (16a) and (16b) having a structure in which the hanging parison (P) is sandwiched from the side, but one mold supports the parison from below and the other mold is used. It may be a pair of upper and lower molds sandwiching the parison from above. For example, by moving the die and / or the lower mold, the suspended parison is guided and accommodated in the cavity of the lower mold, and the cavity of the upper mold sandwiches the parison and compressed air is applied to the parison. To produce a hollow body. In this case, the pair of upper and lower molds and dies are horizontal to each other,
It may be configured to be relatively movable in the vertical direction.
Further, the cavity of the mold is not limited to a linear shape, but may be formed in a curved shape or a three-dimensional shape.

The thermoplastic resin hollow body of the present invention, as described above, comprises a thermoplastic resin containing no foaming agent forming the outer layer, and a thermoplastic resin containing a foaming agent forming an inner layer composed of a plurality of foam layers. It can be formed by melt extrusion in a laminated state and supplying compressed gas into the parison. that time,
As described above, during parison formation and compressed gas supply process,
A non-foamed skin layer is likely to be formed on the inner layer surface.

The thermoplastic resin hollow body having no skin layer can be manufactured as follows. That is, by the blow molding method similar to the above, an outer layer made of a non-foamed thermoplastic resin and a non-adhesive layer not adhered to the foamed layer were laminated with a foamed layer made of a thermoplastic resin interposed therebetween. After producing the hollow body, the non-adhesive layer is peeled off to form a foam layer having no skin layer.

The thermoplastic resin forming the non-adhesive layer is not particularly limited as long as it is a resin having an adhesive property capable of being peeled from the foam layer. Such a thermoplastic resin can be appropriately selected from the above-exemplified thermoplastic resins according to the type of the thermoplastic resin forming the foam layer, but a thermoplastic elastomer is preferable. More specifically, when the thermoplastic resin constituting the foam layer is an olefin polymer, a polyester thermoplastic elastomer can be used as the non-adhesive layer. The non-adhesive layer can be formed to have an appropriate film thickness,
It is about 0.05 to 5 mm, preferably about 0.1 to 2.5 mm. Incidentally, the non-adhesive layer, in order to ensure the tensile strength at the time of peeling,
It is preferably non-foamed.

Below, the manufacturing method of the thermoplastic resin hollow body will be explained based on FIG. 2 and FIG. Note that FIG. 3 is a partially cutaway perspective view showing the outline of the peeling process.

In the above apparatus, a thermoplastic resin containing no foaming agent is melted and extruded from the extruder (11a), a thermoplastic resin containing foaming agent is melted and extruded from the extruder (11b), and the foaming agent is not contained. When the non-adhesive thermoplastic resin is melted and extruded from the extruder (11c), each molten resin is melted in the die (12) in the respective annular resin flow paths (13a) (13b) (13).
After passing through c), join together in a laminated state in the middle. The molten resin in the laminated state is extruded from the extrusion port (14) of the die (12), and the parison (P) is sandwiched by the split molds (16a) (16b) to deliver compressed gas from the compressed gas supply port (14). By supplying, as shown in FIG. 3, an outer layer (21) formed of a thermoplastic resin containing no foaming agent and a non-adhesive layer formed of a non-adhesive thermoplastic resin containing no foaming agent. (23) and
A hollow body laminated with the foam layer (22) interposed therebetween is obtained. At this time, each molten resin is pressed and the thermoplastic resin forming the foam layer (22) is crushed by the non-foaming thermoplastic resin layer forming the outer layer (21) and the non-adhesive layer (23). Since the foamed layer (22) is extruded in this state, the generation of weld lines is significantly suppressed even if the foam layer (22) is composed of one layer. Further, even if a weld line is formed in the foam layer (22) when the parison (P) is formed, the weld line and the weld line of the non-adhesive layer (23) are different in position, as described above. Therefore, the hollow body can be prevented from being damaged during the blow molding process, and the parison (P) and the hollow body having excellent mechanical strength can be obtained.

The hollow body thus obtained has the non-adhesive layer (23).
Is subjected to a peeling step of peeling from the foam layer (22). When the non-adhesive layer (23) is peeled in this peeling step, the foam layer (22)
However, since the outer layer (21) and the non-adhesive layer (23) are pressed together, the surface of the foam layer (22) is smooth and uniform, regardless of the thickness of the foam layer (22). The layerless foam layer (22) is exposed. Therefore, it is possible to obtain a hollow body in which the foam layer (23) having excellent cushioning properties, heat insulating properties and sound absorbing properties and the outer layer (21) are integrated.

In the above example, the case where the foaming layer (22) is composed of one layer has been described. However, in the manufacturing apparatus shown in FIG. The layer may be composed of a plurality of layers. Further, the bubbles existing near the surface of the foam layer may be opened when exposing the foam layer. The open cells can be easily formed by using, as the thermoplastic resin forming the non-adhesive layer, a resin that can be peeled from the foam layer and has an adhesive property that can break the cell wall of the foam layer at the time of peeling. it can.
In this way, even if the bubbles are opened, the surface of the foamed layer before exposure is smooth, so that the surface smoothness, the inner diameter dimensional accuracy, etc. are not impaired.

EFFECTS OF THE INVENTION As described above, the thermoplastic resin hollow body of the present invention has the inner layer composed of a plurality of foam layers, so that not only the cushioning property and the heat insulating property but also the uniformity, the sound absorbing property and the integral property are obtained. It has excellent properties.

According to the method for producing a thermoplastic resin hollow body of the present invention, the molten thermoplastic resin forming the outer layer and the molten thermoplastic resin forming a plurality of foam layers containing a foaming agent are laminated. It is merged and extruded from the die, and the generated parison is supplied with compressed gas and molded with a mold, so the position of the weld line does not shift, and the hollow body is not damaged during the blow molding process. It is possible to efficiently manufacture a hollow body composed of a foam layer and an outer layer.

Furthermore, according to the thermoplastic resin hollow body of the present invention, the skin layer does not exist on the surface of the foamed layer, and is excellent in cushioning property, heat insulating property, sound absorbing property, uniformity and integrity.

Further, according to the method for producing a thermoplastic resin hollow body of the present invention, a blow molding method is used to produce a hollow body in which an outer layer and a non-adhesive layer are laminated via a foam layer. The position of the weld line is displaced, and the hollow body can be prevented from being damaged during the blow molding process. Further, since the non-adhesive layer is peeled off after the hollow body is produced, the skin layer is not formed in the foam layer. Therefore, it is possible to easily manufacture a hollow body made of a thermoplastic resin having a foamed layer excellent in cushioning property, heat insulating property, sound absorbing property, uniformity and integrity.

[Brief description of drawings]

FIG. 1 is a partially cutaway cross-sectional perspective view showing an embodiment of a thermoplastic resin hollow body of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a principal part showing a thermoplastic resin hollow body manufacturing apparatus. The figure is a partially cutaway cross-sectional perspective view showing the peeling step of the method for producing a thermoplastic resin hollow body of the present invention. (1) (21) …… Outer layer, (2) …… Inner layer, (2a) (2b)
(22) …… foam layer, (23) …… non-adhesive layer

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Claims (4)

[Claims] 1. A blow-molded hollow body having an outer layer made of a non-foamed thermoplastic resin and an inner layer made of a foamed thermoplastic resin, wherein the inner layer is composed of a plurality of foam layers. A hollow body made of a thermoplastic resin. 2. A molten thermoplastic resin is supplied to an annular resin flow channel in a die, and a molten thermoplastic resin containing a foaming agent is formed inward of the annular resin flow channel in the die. A thermoplastic resin which is supplied to a plurality of annular resin flow paths, melted thermoplastic resins are merged in a laminated state and extruded from a die, and compressed gas is supplied to the parison that is generated and is molded by a mold. A method for producing a resin hollow body. 3. A blow-molded hollow body having an outer layer made of a non-foamed thermoplastic resin and a foamed layer made of a foamed thermoplastic resin, wherein a skin layer does not exist on the surface of the foamed layer. A hollow body made of thermoplastic resin. 4. A hollow obtained by laminating an outer layer made of a non-foamed thermoplastic resin and a non-adhesive layer not adhering to the foamed layer via a foamed layer made of a thermoplastic resin by a blow molding method. A method for producing a hollow body made of a thermoplastic resin, characterized in that the non-adhesive layer is peeled off after the body is produced.