JP7179304B1 - FOAMED RESIN MOLDED PRODUCT AND METHOD FOR MANUFACTURING SAME - Google Patents

Abstract

Kind Code: A1 A thermoplastic resin foam which has a beautiful appearance and whose deformation after molding is suppressed, and a method for producing the same are provided. A foamed resin molded article contains biomass particles and a thermoplastic resin, the content of the biomass particles in the foamed resin molded article is in the range of 1 to 70% by mass, and the surface is rippled or tree-like. It has a ring-shaped appearance, and the amount of deformation of this foamed resin molded article is 5% or less of this foamed resin molded article immediately after foam molding. A method for producing a foamed resin molded article containing biomass particles and a thermoplastic resin comprises a step of melt-kneading a thermoplastic resin composition containing biomass particles, and mixing the melt-kneaded thermoplastic resin composition and a supercritical fluid. process and injection molding process, and the dimensions of the mold gate and foamed resin molding meet specific requirements. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a foamed resin molded article and a method for producing the same.

A method for producing a biodegradable resin foam has been studied in which a thermoplastic resin such as a biodegradable resin is foamed using a supercritical fluid, which is easy to handle, as a foaming agent. For example, Patent Document 1 discloses a foam obtained by foaming a biodegradable resin composition using a supercritical fluid.

Further, in Patent Document 2, a wood powder-containing thermoplastic resin composition is impregnated with a fluid in a supercritical state, and injection molding is performed while expanding the volume of a cavity to form a plurality of foamed layers having different average pore diameters. Disclosed is a method for producing a containing resin molding.

Japanese Patent Application Laid-Open No. 2006-131703 Japanese Patent Application Laid-Open No. 2011-5811

Conventionally, no consideration has been given to the appearance of thermoplastic resin foams such as biodegradable resin foams. Further, the thermoplastic resin foam may shrink and deform after being foam-molded.

In recent years, there has been a demand for a thermoplastic resin foam that has a beautiful appearance and is suppressed in deformation after molding, but such a thermoplastic resin foam has not been provided. The problem to be solved by the present invention is to provide a thermoplastic resin foam which has a beautiful appearance and whose deformation after molding is suppressed, and a method for producing the same.

The inventors of the present invention have made extensive studies in view of the above problems, and obtained a heat produced by injection molding a mixture of a thermoplastic resin composition containing biomass particles and a supercritical fluid using a mold equipped with a gate that satisfies specific conditions. We have found that a plastic resin foam can solve the above problems of the present invention. The present invention has been completed based on these findings.

The present invention provides a foamed resin injection molded article containing biomass particles and a thermoplastic resin, wherein the content of the biomass particles with respect to the foamed resin injection molded article is in the range of 1 to 70% by mass, and the surface is rippled or The foamed resin injection -molded article has an appearance like annual rings of a tree, the amount of deformation of the foamed resin injection-molded article is 5% or less of the foamed resin injection -molded article immediately after foam molding, and the thickness of the foamed resin injection-molded article is t. It is a foamed resin injection molded article of ≧2.5 mm .
The thermoplastic resin preferably contains a biodegradable resin.
The thermoplastic resin preferably contains polylactic acid.
Said biomass particles preferably comprise cellulose flour.

Further, the present invention provides a method for producing a foamed resin injection molded article containing biomass particles and a thermoplastic resin, wherein a thermoplastic resin composition having a biomass particle content of 1 to 70% by mass is melt-kneaded. A melt-kneading step, a mixing step of mixing the melt-kneaded thermoplastic resin composition with a supercritical fluid in the range of 0.01 to 0.2% by mass of the thermoplastic resin composition, and the mixing step A foamed resin injection -molded article which includes an injection molding step of injection molding the thermoplastic resin composition containing the supercritical fluid, wherein the injection molding step satisfies the conditions represented by the following formulas (1) and (2). manufacturing method.
Mold gate width X1/molded body width X≧17.4% (1)
Mold gate thickness t1/molding body thickness t ≤ 20% and t ≥ 2.5 mm (2)
The supercritical fluid is preferably nitrogen in a supercritical state.
The molten thermoplastic composition preferably forms a vortex within the mold cavity.

INDUSTRIAL APPLICABILITY The foamed resin molded article of the present invention can provide a thermoplastic resin foam that has a beautiful appearance and whose deformation after molding is suppressed. Further, the method for producing a foamed resin molded article of the present invention can provide a method for producing a thermoplastic resin foam that has a beautiful appearance and is suppressed from being deformed after molding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory cross-sectional view showing one embodiment of an injection molding apparatus used for manufacturing a foamed resin molded article of the present invention;

The present invention will be described in more detail.
[Foamed resin molding]
The foamed resin molded article of the present invention contains biomass particles and a thermoplastic resin.
<Biomass particles>
In the present invention, biomass is a renewable organic resource of biological origin, excluding fossil resources. Examples of biomass used in the present invention include the following.
(1) Resource crops Resource crops are biomass cultivated for the purpose of utilization as resources. Examples of resource crops include starch derived from rice, corn, potatoes, etc., and carbohydrates derived from sugarcane, sugar beet, etc.
(2) Unused biomass Unused biomass is biomass discarded without being used as a resource. Examples of unused biomass include forestry resources such as forest residue and wood flour, and agricultural resources such as rice straw, rice husks, and wheat straw.
(3) Waste biomass Waste biomass is biomass generated as waste. Waste-based biomass includes, for example, livestock resources such as livestock excrement, food resources such as processing residue, garbage, animal and plant residues, industrial resources such as pulp waste liquid, sawmill leftovers, paper mill leftovers, construction waste, etc. Examples include forestry resources and sewage sludge.

The biomass particles of the present invention are obtained by pulverizing the biomass into particles. Said biomass particles preferably comprise cellulose flour. The cellulose powder is obtained by pulverizing biomass containing cellulose such as forest residue, rice straw, rice husk, wheat straw, and paper pieces into particles, such as wood powder, rice straw powder, rice husk powder, and wheat straw powder. is mentioned.

The average particle size of the biomass particles is preferably in the range of 1-1000 μm, more preferably in the range of 10-500 μm.

The content of the biomass particles in the foamed resin molded article of the present invention is in the range of 1 to 70% by mass. When the content is less than 1% by mass, ripples are not formed on the surface of the foamed resin molded article. On the other hand, if the content is more than 70% by mass, the melt viscosity of the thermoplastic resin composition is too high, making foam molding difficult.

<Thermoplastic resin>
The thermoplastic resin used in the present invention is not limited to any specific thermoplastic resin. Examples of thermoplastic resins used in the present invention include the following thermoplastic resins.
(1) Biodegradable resins such as polylactic acid, polyhydroxyalkanoate, polybutylene succinate, cellulose acetate, polyvinyl alcohol, polyglycolic acid, polybutylene succinate-co-adipate, polybutylene adipate terephthalate, and polyethylene terephthalate succinate ,
(2) various polyolefin resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-high-density polyethylene, polypropylene, polymethylpentene, and copolymers thereof;
(3) chlorine-containing resins such as polyvinyl chloride (PVC) and polyvinylidene chloride (PVdC);
(4) fluorine-containing resins such as tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer resin, perfluoroethylene propene copolymer resin, polychlorotrifluoroethylene resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin;
(5) Addition thermoplastic resins other than the addition thermoplastic resins shown in (1) to (4), such as ethylene vinyl acetate resin, polymethyl methacrylate (PMMA) resin, polystyrene resin, ABS resin, and AS resin ,
(6) various polyamide resins such as nylon 6, nylon 66, nylon 12, nylon 11, metaxylylene adipamide (mXD6), hexamethylene terephthalamide (6T), and copolymers thereof;
(7) polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polymethylene terephthalate (PMT), polypropylene terephthalate (PPT), polyethylene-p-oxybenzoate (PEOB), Poly-1,4-cyclohexylene dimethylene terephthalate (PCT) and copolymer components such as diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, Various polyester resins such as polyesters (excluding biodegradable polyesters) copolymerized with dicarboxylic acid components such as 2,6-naphthalene dicarboxylic acid, liquid crystal polyesters,
(8) Polyamideimide resin, thermoplastic polyimide, thermoplastic polyurethane, polycarbonate resin, polyacetal (POM) resin, polyetherimide (PEI) resin, polyphenylene ether (PPE) resin, polyetheretherketone (PEEK) resin, polyphenylene sulfide Condensed thermoplastic resins other than the condensed thermoplastic resins shown in (6) and (7), such as (PPS) resins.
At least one of these thermoplastic resins may be used.

The thermoplastic resin preferably contains a biodegradable resin, more preferably polylactic acid.

<Other additives>
The foamed resin molded article of the present invention comprises a resin composition containing the biomass particles and the thermoplastic resin, and optionally a filler, a flame retardant, an antioxidant, a clarifying agent, a plasticizer, an antistatic agent, and a phase. Solubilizer, Nucleating agent, UV absorber, Weathering agent, Heat stabilizer, Light stabilizer, Binder, Anti-blocking agent, Lubricant, Neutralizer, Crystallization accelerator, Colorant, Waterproof agent, Water repellent, Antibacterial Additives usually added to resin compositions for foam molding, such as agents, anti-fogging agents, and impact-resistant reinforcing agents, are added and molded by injection molding, which will be described later.

Examples of the filler include glass fiber, carbon fiber, potassium titanate, carbon black, graphite, carbon fiber, metal powder, metal fiber, metal foil, Al ₂ O ₃ , mica, graphite, carbon fiber, ferrite, iron powder, Lead powder, barium sulfate, graphite, hexagonal BN, molybdenum sulfide, talc, titanium oxide, glass beads, calcium carbonate, aluminum powder, antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc borate, titanium oxide, zinc oxide, oxide Iron etc. are mentioned.

Examples of the flame retardant include chlorine-based flame retardants, phosphorus-based flame retardants, bromine-based flame retardants, and inorganic flame retardants.
Examples of the antioxidant include phenol antioxidants, phosphorus antioxidants, amine antioxidants, and the like.

The surface of the foamed resin molded product of the present invention exhibits a ripple-like or tree-ring-like appearance. Since the appearance differs for each foamed resin molded article and the same pattern cannot be reproduced, the foamed resin molded article of the present invention presents various aesthetic appearances, and its economic value is further increased. Furthermore, the appearance of the foamed resin molded article of the present invention provides a relaxing effect through visual perception.

<Deformation amount of foamed resin molding>
The amount of deformation of the foamed resin molded article of the present invention is 5% or less of the thickness of the foamed resin molded article immediately after foam molding. Here, the amount of deformation of the foamed resin molded article of the present invention is calculated by measuring the foamed resin molded article immediately after molding and the foamed resin molded article 24 hours after molding with a three-dimensional measuring machine. be. A commercially available three-dimensional measuring machine can be used.

[Method for manufacturing foamed resin molding]
The method for producing a foamed resin molded article of the present invention includes a melt-kneading step of melt-kneading a thermoplastic resin composition containing the biomass particles and the thermoplastic resin. Examples of devices used in the melt-kneading step include Banbury mixers, kneaders, and extruders. Further, the method for producing a foamed resin molded article of the present invention includes a mixing step of mixing the melt-kneaded thermoplastic resin composition and the supercritical fluid.

<Supercritical Fluid>
The supercritical fluid preferably contains at least one of supercritical nitrogen and supercritical carbon dioxide, more preferably supercritical nitrogen. The content of the supercritical fluid mixed with the thermoplastic resin composition is in the range of 0.01 to 0.2% by mass of the thermoplastic resin composition. When the content is less than 0.01% by mass, the foaming ratio of the molded product is small, and there is a risk that the surface of the molded product will not have a pattern of ripples or tree rings. On the other hand, when the content exceeds 0.2% by mass, the foaming ratio of the molded product increases, and the cells in the foam do not become uniform.

The method for producing a foamed resin molded article of the present invention includes an injection molding step of injection molding the thermoplastic resin composition containing the supercritical fluid obtained in the mixing step. The conditions represented by the following formulas (1) and (2) are satisfied in the injection molding process.

Mold gate width X ₁ / compact width X≧17.4% (1)
Mold gate thickness t ₁ / compact thickness t≦20% and t>1.2 mm (2)
Here, X, X ₁ , t, and t ₁ are measured with a three-dimensional measuring machine immediately after foam molding.

The method for producing a foamed resin molded article of the present invention may be carried out using, for example, an injection molding apparatus 11 shown in FIG.

An injection molding apparatus 11 shown in FIG. 1 includes a cylinder 12 and a mold 13 into which thermoplastic resin is injected by the cylinder 12 . The cylinder 12 includes a rotating shaft 15 that is rotationally driven by a motor 14, a hopper 16 that supplies thermoplastic resin and biomass particles, and a supercritical fluid supply unit 17 that supplies supercritical fluid. I have.

A hopper 16 is provided near the end of the cylinder 12 opposite to the mold 13 , and a supercritical fluid supply section 17 is provided downstream of the hopper 16 and near the center of the cylinder 12 . The supercritical fluid supply unit 17 includes a supercritical fluid generator 18 that generates a supercritical fluid, and a fluid conduit 19 that conveys the supercritical fluid generated by the supercritical fluid generator 18 toward the cylinder 12. and a metering device 20 interposed in the fluid conduit 19 . Fluid conduit 19 is connected to cylinder 12 via isolation valve 21 .

In addition, the cylinder 12 has a nozzle 22 at the tip on the die 13 side and a plurality of heating devices 23a on the outer peripheral surface. The nozzle 22 has a heating device 23 b on its outer peripheral surface and is connected to the mold 13 via a cutoff valve 24 .

The rotating shaft 15 is connected to the motor 14 at the end opposite to the mold 13, and has a helical screw 25 provided on the outer peripheral surface and a screw head provided at the tip of the mold 13 side. 26. The screw 25 consists of a proximal side continuous screw 25a, a discontinuous screw 25b, and a distal side continuous screw 25c.

The proximal-side continuous screw 25a is provided in a portion extending from the end on the motor 14 side through the lower portion of the hopper 16 to just before the lower portion of the supercritical fluid supply portion 17 . The discontinuous screw 25 b is provided in the lower portion of the supercritical fluid supply section 17 and has a plurality of discontinuous sections along the circumferential direction of the rotating shaft 15 . The distal continuous screw 25 c is provided between the discontinuous screw 25 b and the screw head 26 .

The mold 13 includes a fixed mold 28 having a shape that follows the outer shape of the foamed resin molded article 1 and a movable mold 31 that is fitted to the fixed mold 28 to form a cavity 29 . The fixed mold 28 includes a sprue 32 communicating with the cylinder 12 and a runner 34 communicating with the sprue 32 and with the cavity 29 via a gate 33 .

In the injection molding apparatus 11 , first, the thermoplastic resin is charged from the hopper 16 into the cylinder 12 . The thermoplastic resin is melted in the cylinder 12 by being stirred by the continuous screw 25a while being heated by the heating device 23a, thereby forming a molten resin.

Next, the biomass particles are charged from the hopper 16 into the cylinder 12 . The input amount of the biomass particles is in the range that the content of the biomass particles with respect to the thermoplastic resin composition is 1 to 70% by mass. The biomass particles may be mixed with the thermoplastic resin in advance to form pellets, and the pellets may be charged from the hopper 16 into the cylinder 12 .

The biomass particles are stirred in the cylinder 12 by the continuous screw 25a while being heated by the heating device 23a, thereby being uniformly mixed with the molten resin to form a molten thermoplastic resin composition. The molten thermoplastic resin composition containing the biomass particles formed as described above is conveyed toward the mold 13 by the continuous screw 25a.

Next, from the supercritical fluid supply unit 17, supercritical fluid in the range of 0.01 to 0.2% by mass of the thermoplastic resin composition is supplied, and the thermoplastic resin composition is impregnated under pressure. do. Carbon dioxide or nitrogen can be used as the supercritical fluid. Said supercritical fluid is preferably nitrogen in a supercritical state.

The fluid in the supercritical state is agitated by the discontinuous screw 25b provided in the lower portion of the supercritical fluid supply section 17, and sufficiently mixed with the thermoplastic resin composition to impregnate the fluid. As a result, the thermoplastic resin composition is impregnated with the supercritical fluid in the cylinder 12 between the screw head 26 and the nozzle 22 . At this time, the thermoplastic resin composition is in a state in which nuclei for foaming have not yet been formed.

Next, an injection molding step is performed in which the thermoplastic resin composition impregnated with the supercritical fluid is injected from the nozzle 22 into the cavity 29 via the sprue 32, the runner 34 and the gate 33.

In the injection molding process, the conditions represented by the following formulas (1) and (2) are satisfied.
Mold gate width X ₁ / compact width X≧17.4% (1)
Mold gate thickness t ₁ / compact thickness t≦20% and t>1.2 mm (2)
Here, X, X ₁ , t, and t ₁ are measured by measuring the foamed resin molding with a three-dimensional measuring machine immediately after injection molding.

In the injection molding process, the molten thermoplastic resin composition is preferably injected through the gate 33 to form a vortex within the cavity 29 . In order for the vortex to be formed, for example, the flow direction of the molten thermoplastic resin composition at the gate 33 and the flow direction of the molten thermoplastic resin composition in the cavity 29 near the gate 33 Make the flow directions parallel (see arrows in Figure 1).

When the flow direction of the molten thermoplastic resin composition at the gate 33 and the flow direction of the molten thermoplastic resin composition in the cavity 29 near the gate 33 are parallel, the thermoplastic A vortex is formed in the cavity 29 by the resin composition through the gate 33, and the ripple-like or tree ring-like appearance peculiar to the foamed resin molding of the present invention is likely to be formed.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.

Example 1
A raw material consisting of 30% by mass of paper powder (particle size 25 to 200 μm) made of pulp and 70% by mass of polylactic acid (TERRAMAC TE-2000 manufactured by Unitika Ltd.) is pelletized with an extruder (TEX440αIII manufactured by Japan Steel Works, Ltd.), Next, an injection molding machine (NEX360 manufactured by Nissei Plastic Industry Co., Ltd., mold clamping force 360t), a supercritical fluid supply device (MuCell Series-II-trj-10 manufactured by Trexel Inc.) and a mold (pre-hardened by Daido Steel Co., Ltd.) Using steel NAK80), mold temperature 30 ° C., heating cylinder temperature 210 ° C., filling pressure 80 MPa, injection speed 50 mm / sec, molding cycle 70 sec, nitrogen content in the supercritical state in the thermoplastic resin composition Injection molding was performed under the conditions of .2% by mass. Ripples were formed on the surface of the injection molded foamed resin plate. The foamed resin flat plate immediately after molding is measured with a three-dimensional measuring machine (CRYSTA-Apex V500 manufactured by Mitutoyo Co., Ltd.), and the molded body width X, the molded body thickness t, the mold gate width X ₁ , and _A gate thickness t1 of the mold was measured. The amount of deformation of the foamed resin molding was measured by the three-dimensional measuring machine 24 hours after the molding. Table 1 shows the results.

Example 2
The same operation as in Example 1 was performed except that the thickness t of the molded body was changed as shown in Table 1 and a flat plate having ripples formed on the surface was injection molded. Table 1 shows the results.

Example 3
A raw material consisting of 70% by mass of cedar wood powder (particle size 1 to 1000 μm) and 30% by mass of polylactic acid (TERRAMAC TE-2000 manufactured by Unitika Ltd.) is pelletized with an extruder (TEX440αIII manufactured by Japan Steel Works, Ltd.) and then injection molded. machine (NEX360 manufactured by Nissei Plastic Industry Co., Ltd., clamping force 360t), supercritical fluid supply device (MuCell Series-II-trj-10 manufactured by Trexel Inc.) and mold (pre-hardened steel NAK80 manufactured by Daido Steel Co., Ltd.) using, mold temperature 30 ° C., heating cylinder temperature 210 ° C., filling pressure 100 MPa, injection speed 70 mm / sec, molding cycle 90 sec, supercritical nitrogen content in the thermoplastic resin composition 0.2 mass % conditions. Ripples were formed on the surface of the injection-molded foamed resin housing. The foamed resin casing immediately after molding is measured with a three-dimensional measuring machine (CRYSTA-Apex V500 manufactured by Mitutoyo Co., Ltd.), and the width of the molded body X of the foamed resin casing, the thickness of the molded body t, and the gate width of the mold X ₁ , and the gate thickness _t1 of the mold were measured. The amount of deformation of the foamed resin molding was measured by the three-dimensional measuring machine 24 hours after the molding. Table 1 shows the results.

Comparative example 1
The same operation as in Example 1 was performed except that the thickness t of the molded body was changed as shown in Table 1 and the foamed resin flat plate was injection molded. Table 1 shows the results. No ripples were formed on the surface of the flat plate.

Comparative example 2
A raw material consisting of 70% by mass of cedar wood powder (particle size 1 to 1000 μm) and 30% by mass of polylactic acid (TERRAMAC TE-2000 manufactured by Unitika Ltd.) is pelletized with an extruder (TEX440αIII manufactured by Japan Steel Works, Ltd.) and then injection molded. machine (NEX360 manufactured by Nissei Plastic Industry Co., Ltd., clamping force 360t), supercritical fluid supply device (MuCell Series-II-trj-10 manufactured by Trexel Inc.) and mold (pre-hardened steel NAK80 manufactured by Daido Steel Co., Ltd.) using, mold temperature 30 ° C., heating cylinder temperature 210 ° C., filling pressure 50 MPa, injection speed 50 mm / sec, molding cycle 60 sec, supercritical nitrogen content in the thermoplastic resin composition 0.2 mass % conditions. No ripples were formed on the surface of the injection-molded foamed resin casing. The foamed resin casing immediately after molding is measured with a three-dimensional measuring machine (CRYSTA-Apex V500 manufactured by Mitutoyo Co., Ltd.), and the width of the molded body X of the foamed resin casing, the thickness of the molded body t, and the gate width of the mold X ₁ , and the gate thickness _t1 of the mold were measured. The amount of deformation of the foamed resin casing was measured by the three-dimensional measuring machine 24 hours after molding. Table 1 shows the results.

Mold gate thickness t ₁ /molded body thickness t is too large Foamed resin molded article of Comparative Example 1, mold gate thickness t ₁ /molded body thickness t is too large and mold gate width The foamed resin molded article of Comparative Example 2, in which X ₁ /width X of the molded article was too small, did not have ripples formed on the surface, and the amount of deformation thereof was large.
On the other hand, the foamed resin moldings of Examples 1 to 3, which satisfy the conditions represented by the above formulas (1) and (2), have a beautiful rippled appearance and are suppressed in deformation after molding. Met.

DESCRIPTION OF SYMBOLS 11... Injection molding apparatus, 13... Mold, 29... Cavity, 32... Sprue,
33... Gate, 34... Runner.

Claims (7)

Foamed resin containing biomass particles and thermoplastic resininjectionA molded body,
The foamed resininjectionThe content of the biomass particles with respect to the compact is in the range of 1 to 70% by mass,
The surface has a rippled or tree-ring-like appearance,
The foamed resininjectionThe amount of deformation of the molded product is the foamed resin immediately after foaming.injection5% or less of the compactthe law of nature,
When the molded body thickness t≧2.5 mm of the foamed resin injection molded body A foamed resin characterized byinjectionmolding. 2. The foamed resin injection molded article according to claim 1, wherein said thermoplastic resin contains a biodegradable resin. 3. The foamed resin injection molded article according to claim 1, wherein said thermoplastic resin contains polylactic acid. The foamed resin injection molded article according to any one of claims 1 to 3, wherein said biomass particles contain cellulose powder. A method for producing a foamed resin injection molded article containing biomass particles and a thermoplastic resin,
A melt-kneading step of melt-kneading a thermoplastic resin composition in which the content of the biomass particles is in the range of 1 to 70% by mass;
A mixing step of mixing the melt-kneaded thermoplastic resin composition with a supercritical fluid in the range of 0.01 to 0.2% by mass of the thermoplastic resin composition;
An injection molding step of injection molding the thermoplastic resin composition containing the supercritical fluid obtained in the mixing step,
A method for producing a foamed resin injection molded article, wherein the conditions represented by the following formulas (1) and (2) are satisfied in the injection molding step.
Mold gate width X ₁ / compact width X≧17.4% (1)
Mold gate thickness t ₁ / molded product thickness t ≤ 20% and t ≥ 2.5 mm (2) 6. The method for producing a foamed resin injection molded article according to claim 5, wherein said supercritical fluid is nitrogen in a supercritical state. 7. The method for producing a foamed resin injection molded article according to claim 5 or 6, wherein the molten thermoplastic resin composition forms a vortex in the mold cavity. .

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