JP6934384B2 - Manufacturing method of foam molded products - Google Patents

Description

The present invention relates to a method for producing a foam molded product.

When injecting resin, simply pouring the molten resin into the mold at normal pressure will result in insufficient filling of the resin into the mold, resulting in molding defects such as sink marks and voids and variations in quality between molding shots. May cause. In order to prevent this, pressure is applied when the molten resin is injected into the mold to fill the mold with a sufficient amount of resin. However, when injection molding a resin with high fluidity to some extent, the molten resin leaks from the gap between the degassing vent of the mold and the parting line, which is the mating surface of the mold, due to the pressure applied during molding. May cause burrs. As a method of suppressing such burrs, a method of reducing the parting line of the mold as much as possible (for example, a method of forcing the mold corresponding to the undercut portion of the molded product to have a punched structure instead of a slide structure). ) Or a method of adding a burr inhibitor to the resin, but forcible punching may not be applicable due to product design restrictions, and adding a burr inhibitor may impair the fluidity of the resin. There is. Further, there is a method of reducing burrs by injecting a supercritical fluid into a thermoplastic resin composition having a specific viscosity and injection foam molding (Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-276574

When a resin injected with a supercritical fluid is injection foam molded, the pressure at the time of injecting the supercritical fluid should theoretically be equal to or higher than the critical pressure of the fluid, but in reality, the supercritical fluid should be equal to or higher than the critical pressure of the fluid. For the purpose of accurately measuring the amount of the fluid introduced, the pressure is usually much higher than the critical pressure (for example, a pressure exceeding 10 MPa). However, if a high pressure exceeding 10 MPa is applied during the injection of the fluid, the surface of the obtained molded product may have a rough appearance, or fine bubble-like bulges called blister may be formed on the surface after the heat treatment. As a result, the appearance of the molded product may deteriorate. On the contrary, if the pressure at the time of injecting the fluid is too low, the filling of the resin into the mold becomes insufficient, and the quality varies between shots in short shots or continuous molding, which makes molding difficult. The appearance is poor due to the occurrence of sink marks.

An object of the present invention is to provide a method for producing a foam molded product capable of suppressing burrs while maintaining good appearance.

The present invention relates to the following.
[1] In the step of injection-foaming a resin composition containing a thermoplastic resin, the resin composition contains 20% by mass or more of an inorganic filler in the total resin composition, and the injection-foaming is performed. , The weight loss rate of the foam molded product obtained in the injection foam molding step of injecting a gas having a pressure of 1 MPa or more and 10 MPa or less into the resin composition with respect to the reference weight calculated from the mold dimensions is 3% or more and 12%. A method for producing a foam molded product, in which the following amounts are brought into contact with each other.
[2] The method for producing an effervescent molded product according to [1], wherein the melt viscosity of the resin composition is 100 Pa · s or more and 600 Pa · s or less.
[3] The method for producing a foam molded product according to [1] or [2], wherein the resin composition contains 1 part by mass or more and 50 parts by mass or less of the thermoplastic elastomer with respect to 100 parts by mass of the thermoplastic resin.
[4] The production of the foam molded product according to any one of [1] to [3], wherein the thermoplastic resin contains at least one selected from a polyarylene sulfide resin, a polyethylene terephthalate resin, and a polybutylene terephthalate resin. Method.
[5] One of [1] to [4], which obtains a foam molded product having a bending strength retention rate of 80% or more measured in accordance with ISO178 with respect to a standard molded product having a weight loss rate of 0%. The method for producing a foam molded product according to the above.
[6] The foam-molded product according to any one of [1] to [5], which comprises a step of heat-treating the foam-molded product obtained in the injection foam molding step at 100 to 350 ° C. for 1 to 120 minutes. Production method.
[7] The method for producing an effervescent molded product according to [6], wherein a bulging portion is not formed on the surface of the foam molded product after the heat treatment step.
[8] The method for producing an effervescent molded product according to any one of [1] to [7], which obtains an effervescent molded product for piping parts.

According to the present invention, it is possible to provide a method for producing an effervescent molded product capable of suppressing burrs while maintaining good appearance.

Hereinafter, one embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications as long as the effects of the present invention are not impaired.

[Manufacturing method of foam molded products]
The method for producing a foam molded product (hereinafter, also simply referred to as “molded product”) according to the present embodiment is a step of injection foam molding a resin composition containing a thermoplastic resin (hereinafter, simply “injection foam molding step”). Also referred to as). The foam molded product is a molded product that is molded by injection foam molding and has a bubble structure inside.

(Resin composition)
The resin composition contains a thermoplastic resin. The thermoplastic resin may be any thermoplastic resin that can be used for injection molding, and is not particularly limited. Thermoplastic resins include polyamide, polyester, polyethylene terephthalate (PET), acrylic, polyolefin, aramid, polyethylene naphthalate, polybutylene terephthalate, polyarylensulfide, polyacetal, liquid crystal polymer (aromatic polyester, aromatic polyesteramide, etc.), Examples thereof include polyimide, polyarylate, polyetherimide, and polyether ether ketone. These can be used alone or in combination of two or more. Among them, it is selected from polyamide, polyethylene terephthalate, polybutylene terephthalate, polyallylensulfide, polyacetal, liquid crystal polymer, polyarylate, polyetherimide, and polyetheretherketone because of its excellent mechanical properties, heat resistance, and chemical resistance. It is preferable to contain one or more kinds of resins, and it is possible to contain one or more kinds of resins selected from polyallylensulfide, polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polymer in that it is excellent in moldability. Polyethylene terephthalate and / or polyallylensulfide is more preferable, and particularly excellent in appearance.

The content of the thermoplastic resin is preferably 30% by mass or more, more preferably 50% by mass or more, and 60% by mass or more in the total resin composition in terms of sufficiently exhibiting the characteristics of the resin. Is even more preferable.

The melt viscosity of the resin composition is based on the thermoplastic resin constituting the resin composition having the largest amount of addition, and if the thermoplastic resin is a crystalline resin, the melting point is + 30 ° C. and the amorphous resin. If this is the case, the melt viscosity measured at a glass transition temperature of + 120 ° C. and a shear rate of 1216 sec ^-1 is preferably 100 Pa · s or more and 600 Pa · s or less, and more preferably 150 Pa · s or more and 500 Pa · s or less. , 200 Pa · s or more and 400 Pa · s or less is more preferable. Within this range, it is possible to obtain a molded product having an excellent appearance and suppressing burrs while ensuring good moldability. The resin composition may contain one or more resins having a melt viscosity in the above range.

The resin composition contains an inorganic filler in an amount of 20% by mass or more, preferably 25% by mass or more, based on the entire resin composition. When the amount of the inorganic filler is less than 20% by mass, fine irregularities called lumps and fine sink marks called avatars are formed on the surface of the obtained molded product, and burrs are formed, resulting in good appearance and burrs. It becomes difficult to achieve both suppression and suppression. The upper limit of the content of the inorganic filler is preferably 70% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less in terms of ensuring the fluidity of the resin. ..

As the inorganic filler, for example, a fibrous, powdery or plate-shaped inorganic filler can be used. Fibrous inorganic fillers include glass fibers, asbestos fibers, silica fibers, silica / alumina fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and stainless steel, aluminum, and titanium. Examples thereof include metal fibrous materials such as copper and brass. Examples of the powdery granular filler include silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, silicates such as wollastonite, and iron oxide. , Titanium oxide, zinc oxide, antimony trioxide, metal oxides such as alumina, carbonates of metals such as calcium carbonate and magnesium carbonate, sulfates of metals such as calcium sulfate and barium sulfate, other ferrites, silicon carbide, nitrided Examples thereof include silicon, boron nitride, and various metal powders. Moreover, as the plate-shaped filler, mica, glass flakes, various metal foils and the like can be exemplified. These inorganic fillers can be used alone or in combination of two or more.

The size of the inorganic filler is not particularly limited as long as it does not impair the effects of the present invention. For example, the average diameter of the fibrous filler can be about 1 μm to 30 μm (preferably 3 μm to 20 μm), and the average length is, for example, 100 μm to 5 mm (preferably 300 μm to 4 mm, more preferably 500 μm to 3. It can be about 5 mm). The average primary particle size of the plate-shaped or powder-granular filler can be, for example, about 1 μm to 500 μm, preferably about 10 μm to 100 μm. The average diameter and average length of the fibrous filler and the average primary particle diameter of the plate-like or powder-like filler are determined by the CCD camera for the fibrous filler, plate-like or powder-like filler before being blended in the resin composition. It is a value calculated by analyzing the image taken in 1 and using a weighted average.

The resin composition may contain an elastomer in order to suppress a decrease in strength (particularly impact resistance) of the foam molded product. The type of elastomer is not particularly limited, and examples thereof include olefin-based elastomers, styrene-based elastomers, polyester-based elastomers, polyamide-based elastomers, urethane-based elastomers, and core-shell-based elastomers.

Preferred olefin-based elastomers are copolymers containing ethylene and / or propylene as main components, and specifically, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, and ethylene. Examples thereof include, but are limited to, -propylene-butene copolymer, ethylene-propylene-diene copolymer, ethylene-ethylacrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-glycidyl methacrylate copolymer and the like. It's not a thing.

Examples of the styrene-based elastomer include block copolymers composed of a polymer block mainly composed of a vinyl aromatic compound such as styrene and a polymer block mainly composed of an unhydrogenated and / or hydrogenated conjugated diene compound. However, it is not limited to this.

Examples of polyester-based elastomers include aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate as hard segments, and polyethers such as polyethylene glycol and polytetramethylene glycol, or aliphatic polyesters such as polyethylene adipate, polybutylene adipate, and polycaprolactone. Examples include, but are not limited to, block copolymers as segments.

Examples of polyamide-based elastomers include, but are limited to, block copolymers having nylon 6, nylon 66, nylon 11, nylon 12 and the like as hard segments and polyether or aliphatic polyester as soft segments. It's not a thing.

Examples of urethane-based elastomers include reacting diisocyanates such as 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate with glycols such as ethylene glycol and tetramethylene glycol. Examples thereof include block copolymers in which the polyurethane obtained by the above is used as a hard segment and a polyether such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol or an aliphatic polyester such as polyethylene adipate, polybutylene adipate or polycaprolactone is used as a soft segment. However, it is not limited to this.

The core-shell elastomer is a polymer having a multilayer structure composed of a core layer (core portion) and a shell layer covering a part or all of the core layer (surface of the core portion). The core layer of the core-shell elastomer is composed of a rubber component (soft component), and an acrylic rubber component (acrylic rubber) is particularly desirable. The glass transition temperature of the rubber component is, for example, less than 0 ° C. (for example, −10 ° C. or lower), preferably −20 ° C. or lower (for example, about −180 to −25 ° C.), and more preferably −30 ° C. or lower (for example, −30 ° C. or lower). It may be about −150 to −40 ° C.).

The acrylic rubber as a rubber component is an acrylic monomer [particularly, an alkyl acrylate (acrylic acid C1-12 alkyl ester such as butyl acrylate, preferably acrylic acid C1-8 alkyl, more preferably acrylic acid C2-6 alkyl ester). Acrylic acid ester such as] is the main component of the polymer. The acrylic rubber may be an acrylic monomer alone or a copolymer (a copolymer of acrylic monomers, a copolymer of an acrylic monomer and another unsaturated bond-containing monomer, etc.), and may be an acrylic monomer. It may be a copolymer of a monomer (and other unsaturated bond-containing monomer) and a crosslinkable monomer.

The content of the elastomer is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, and further preferably 5 parts by mass or more and 15 parts by mass with respect to 100 parts by mass of the thermoplastic resin. It is less than a part by mass.

The resin composition may be used as an antioxidant, a weather-resistant stabilizer, a molecular weight adjuster, a fluidity adjuster, an ultraviolet absorber, a near-infrared absorber, an antistatic agent, a colorant such as a dye / pigment, and a lubricant, if necessary. , Mold release agent, crystallization accelerator, crystal nucleating agent, flame retardant, flame retardant aid and the like can be contained.

The form of the resin composition may be a powder or granular material mixture or a melt mixture such as pellets (melt kneaded product). The method for producing the resin composition is not particularly limited, and the resin composition can be produced using equipment and methods known in the art. For example, the required components can be mixed and kneaded using a single-screw or twin-screw extruder or other melt-kneading device to prepare pellets for molding. Multiple extruders or other melt kneaders may be used. Further, all the components may be input from the hopper at the same time, or some components may be input from the side feed port.

(Injection foam molding process)
In the injection foam molding step, the resin composition is injection foam molded. Injection foam molding is performed by contacting the resin composition with a gas having a pressure of 1 MPa or more and 10 MPa or less, preferably 3 MPa or more and 8 MPa or less. If the pressure is less than 1 MPa, the filling of the resin into the mold becomes insufficient and molding becomes difficult, or burrs are generated by increasing the resin pressure to fill the mold with the resin. It may be chilly. When the pressure exceeds 10 MPa, the surface of the obtained molded product has a rough appearance, and blisters are likely to be formed after the heat treatment.

As the gas, a pressurized gas can be used, and examples thereof include nitrogen, carbon dioxide, compressed air, chlorofluorocarbons, and hydrocarbons. Depending on the type of these gases, phase changes may occur in the above-mentioned pressure range, but in the description of the present embodiment, these are included in the term “gas”.

The amount of gas dissolved in the resin composition correlates with the weight reduction rate with respect to the reference weight calculated from the mold size of the obtained molded product. Regarding the amount of gas used in the present embodiment, the weight loss rate of the molded product obtained in the injection foam molding step with respect to the reference weight calculated from the mold dimensions is 3% or more and 12% or less, preferably 5% or more and 10%. The amount is as follows. By setting the amount of gas used within the above range, it is possible to achieve both good appearance and a burr suppressing effect. The amount of gas used can be adjusted by adjusting the amount of molten resin injected into the mold. For example, if the amount of molten resin injected into the mold is reduced, the amount of gas used can be increased.

The "reference weight calculated from the mold dimensions" means the weight of the molded product obtained by filling the mold with 100% of the resin composition by ordinary injection molding other than foam molding. .. Here, in the resin composition containing the crystalline thermoplastic resin, "100% filling" means that the filling amount of the resin composition in the cavity is stable by ensuring an injection time equal to or longer than the so-called gate sealing time. Means.

The method of bringing the gas into contact with the resin composition can be carried out in the same manner as in ordinary injection foam molding. For example, it can be carried out by using an injection molding machine provided with a cylinder provided with a screw for melting the thermoplastic resin and a container for supplying gas into the cylinder. The gas supply method is not particularly limited, and the gas may be supplied from a cylinder such as a nitrogen cylinder, a carbon dioxide cylinder, or a compressed air cylinder to the injection foam molding machine through a supply valve, and at that time, the pressure is reduced through the pressure reducing valve. May be supplied. When compressed air is used, air in the atmosphere may be compressed by a compressor or the like and supplied.

(Heat treatment process)
The method for producing a foam molded product according to the present embodiment includes a step of heat-treating the molded product obtained in the injection foam molding step at 100 to 350 ° C. for 1 to 120 minutes after the injection foam molding step. May be good. By heat treatment, the crystallinity can be increased, and the mechanical properties and dimensional stability can be improved. In the conventional method for manufacturing an effervescent molded product, even if the appearance of the surface of the molded product after injection foam molding is good, when heat treatment is performed, fine bubble-like bulges (blisters) are formed on the surface. There is. In particular, in a reflow soldering process in which heat treatment is performed at a high temperature of 200 to 320 ° C. for about 1 to 10 minutes, a problem of blisters may occur in the conventional foam molded product, but the production of the foam molded product of the present embodiment. According to the method, even when heat treatment is performed after the injection foam molding step, it is possible to prevent the formation of blisters on the surface and maintain good appearance.

(Other processes)
The method for producing a foam molded product according to the present embodiment can include a dry blending step of a resin pellet and an organic foaming agent and / or an inorganic foaming agent or microcapsules, which is performed by ordinary injection molding.

[Effervescent molded product]
The foam-molded product obtained by the method for producing a foam-molded product according to the present embodiment has a flexural strength measured in accordance with ISO178 of 80% or more as a retention rate with respect to a standard molded product having a weight loss rate of 0%. It is preferably 90% or more, and more preferably 90% or more. "Standard molded product with a weight loss rate of 0%" means that 100% of the resin composition is filled in the mold by ordinary injection molding, not foam molding (for crystalline resin, the gate seal time is secured. It means a molded product obtained by molding (with the weight stabilized). By setting the retention rate of bending strength with respect to the standard molded product to 80% or more, it is possible to use the product without significantly impairing its mechanical properties.

Blister is unlikely to be formed in this foam molded product even after heat treatment. Therefore, it is preferable that no bulging portion is formed on the surface of the foam molded product after the heat treatment step. The "bulging portion" refers to a fine bubble-like bulge protruding from the surface of the foam molded product. In the case of a bulging portion called a blister, the maximum diameter is usually about 2 mm to 5 mm and the height is about 0.2 mm to 1 mm.

(Use)
The foam-molded product obtained by the method for producing the foam-molded product according to the present embodiment can be used for various purposes. In particular, since this foam molded product has excellent good appearance and suppresses burrs, it can be suitably used for applications in which it is preferable to use a molded product with few burrs. For example, for piping parts, it is preferable to use a molded product having few burrs because the presence of burrs in the joint portion causes liquid leakage. Therefore, the foam-molded product obtained by the method for manufacturing the foam-molded product according to the present embodiment can be suitably used for fluid piping parts applications (fluid piping joint parts applications, fluid piping port parts applications) and the like. Examples of fluid piping component applications include cold / hot water piping component applications.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[material]
The resin composition used is as follows. The melt viscosity of the polyarylene sulfide resin composition (melting point of about 280 ° C.) is a value measured at ^{310 ° C. and a shear rate of 1216 sec -1.}
PPS1: Polyarylene sulfide resin manufactured by Polyplastics Co., Ltd., containing 30% by mass of glass fiber (manufactured by Owens Corning Japan GK, average length 3 mm, average diameter 10 μm) with a melt viscosity of 220 Pa · s. Composition PPS2: Polyarylene sulfide resin manufactured by Polyplastics Co., Ltd. containing 40% by mass of glass fiber (manufactured by Owens Corning Japan GK, average length 3 mm, average diameter 10 μm), polyarylene with a melt viscosity of 160 Pa · s. Sulfide resin composition PPS3: Polyarylene sulfide resin manufactured by Polyplastics Co., Ltd., 40% by mass of glass fiber (manufactured by Nippon Denki Glass Co., Ltd., average length 3 mm, average diameter 13 μm), talc (manufactured by Matsumura Sangyo Co., Ltd., average) Polyarylene sulfide resin composition having a melt viscosity of 200 Pa · s, containing 13% by mass (diameter 2.3 μm) and 7% by mass of glass beads (manufactured by Potters Barotini Co., Ltd., average diameter 20 μm) PPS4: Polyplastics stock For 100 parts by mass of polyarylene sulfide resin manufactured by the company, 5 parts by mass each of "Modiper A4300" manufactured by Nichiyu Co., Ltd. and "Engage 8440" manufactured by Dow Chemical Japan Co., Ltd. are contained as olefin-based elastomers, and glass fibers (glass fibers ( A polyarylene sulfide resin composition having a melt viscosity of 400 Pa · s, which is manufactured by Nippon Denki Glass Co., Ltd. and contains 30% by mass of the entire resin composition (with an average length of 3 mm and an average diameter of 13 μm).
PPS5: Polyarylene sulfide resin composition of 300 Pa · s melt viscosity containing 40% by mass of glass fiber (Nippon Electric Glass Co., Ltd., average length 3 mm, average diameter 13 μm) in a polyarylene sulfide resin manufactured by Polyplastics Co., Ltd. In addition to the above, each of the resin compositions of PPS1 to PPS5 contains about 0.2% by mass of pentaerythritol tetrastearate as a release agent.

[Examples 1 to 17, Comparative Examples 1 to 16]
Gas injection mechanism in the cylinder of an injection molding machine (mold clamping force 40 tons) manufactured by Nippon Steel Works (a mechanism equipped with a foaming agent supply mechanism connected to a nitrogen bomb and an introduction speed adjusting container to inject gas at a predetermined pressure) Using an injection foam molding machine installed in the above, nitrogen gas injected directly into the starvation zone of the cylinder while being controlled to a constant pressure at all times, and an appropriate amount of pellets were supplied from the hopper by starvation supply for metrological plasticization. After kneading the molten resin of each material (thermoplastic resin composition) shown in Table 1, injection foam molding is performed in an injection pressure holding process (however, the holding pressure is set to zero) equivalent to that of normal injection molding. rice field. The weight reduction rate of the foam molded product was adjusted by changing the VP injection switching position. As a result, a flat plate-shaped foam molded product having a size of 60 mm × 60 mm × thickness 2 mm (a side gate having a width of 4 mm × a thickness of 2 mm at the center of one side) was obtained.
Here, a molded product was also produced in which each molding condition such as the pressure of the injected gas (gas pressure) and the resin temperature at the time of molding (cylinder temperature) was changed as shown in Table 1. The mold temperature in the injection foam molding of PPS1 to PPS5 was 140 ° C.
Further, as a "standard molded product (weight reduction rate 0%)", the same method is applied by a normal injection molding method (same as above except that nitrogen gas is not injected and filling is performed by holding pressure after switching VP injection). A flat plate-shaped molded product was produced.

[evaluation]
(Bari)
The length of burrs on the surface of the obtained foam molded product was measured and evaluated according to the following criteria. The results are shown in Table 1. In the case of the mold used above, the burr is formed so that one end surface of the foam molded product projects toward one of the main surfaces.
4: Less than 0.05 mm 3: 0.05 mm or more, less than 0.1 mm 2: 0.1 mm or more, less than 0.2 mm 1: 0.2 mm or more

(Surface appearance)
Using SURFTEST EXTREME SV-3000 manufactured by Mitutoyo Co., Ltd., the surface (fixed mold surface side) of the flat foam molded product obtained without protruding pin marks is 10 mm inside from the gate side, in the direction perpendicular to the flow. The arithmetic mean roughness Ra at 12.5 mm near the center of the line along the line was measured according to JIS B 0601. The ratio of the arithmetic average roughness Ra of the foam molded product to the arithmetic average roughness Ra of the standard molded product (ratio to the standard Ra: Ra of the foam molded product ÷ Ra of the standard molded product) was determined and evaluated according to the following criteria. The results are shown in Table 1.
Less than 4: 1 3: 1 or more and less than 2 2: 2 or more and less than 3 1: 3 or more

(Blister)
The obtained foam molded product was heat-treated at 150 ° C. for 1 hour using a heated hot air constant temperature bath device (VTEC-75 manufactured by Isuzu Seisakusho Co., Ltd.). The surface of the foam molded product after the heat treatment was visually observed to evaluate the presence or absence of blisters. The results are shown in Table 1.
2: Blister does not occur at all or hardly occurs.
1: Remarkably blister occurs.

(Retention rate of flexural strength)
For the foam molded products and the standard molded products of Examples and Comparative Examples, a 60 × 12.6 × 2 mm test piece was cut out from a 60 × 60 × 2 mm flat plate-shaped molded product, and was manufactured by A & D Co., Ltd. Using the testing machine RTC-1325A, measure the bending strength by the 3-point bending center load method at a test speed of 1 mm / min, load point R = 5 mm, support span 32 mm, and fulcrum R = 2 mm in accordance with ISO178. bottom. From the obtained numerical values, the retention rate of the bending strength of the foam molded products of Examples and Comparative Examples with respect to the reference molded product was calculated and judged according to the following criteria. The results are shown in Table 1.
3: Retention rate is 90% or more 2: Retention rate is 80% or more and less than 90% 1: Retention rate is less than 80%

Claims (8)

It has a step of injection foam molding of a resin composition containing a thermoplastic resin, and has a step of injection foam molding.
The resin composition contains an inorganic filler in an amount of 20% by mass or more in the total resin composition.
In the step of injection foam molding, the pressure on the resin composition is 1 MPa or more and 10 MP.
The gas of a or less is brought into contact with the foam molded product obtained in the injection foam molding step in an amount such that the weight reduction rate with respect to the reference weight calculated from the mold dimensions is 3% or more and 12% or less.
The melt viscosity of the resin composition is more than 100 Pa · s and 600 Pa · s or less.
The melt viscosity is
When the thermoplastic resin with the largest amount added among the thermoplastic resins is a crystalline resin, it is the melt viscosity measured at a ^{shear rate of 1216 sec -1 at a temperature 30 ° C. higher than the melting point.}
When the thermoplastic resin with the largest amount added among the thermoplastic resins is an amorphous resin, it has a melt viscosity measured at a ^{shear rate of 1216 sec -1 at a temperature 120 ° C. higher than the glass transition temperature.} Method. The method for producing an effervescent molded product according to claim 1, wherein the melt viscosity of the resin composition is 150 Pa · s or more and 600 Pa · s or less.
A method for manufacturing an effervescent molded product. The method for producing a foam molded product according to claim 1 or 2, wherein the resin composition contains 1 part by mass or more and 50 parts by mass or less of the thermoplastic elastomer with respect to 100 parts by mass of the thermoplastic resin. The method for producing a foam molded product according to any one of claims 1 to 3, wherein the thermoplastic resin contains at least one selected from a polyarylene sulfide resin, a polyethylene terephthalate resin, and a polybutylene terephthalate resin. The foam according to any one of claims 1 to 4, wherein a foam molded product having a bending strength retention rate of 80% or more measured in accordance with ISO178 with respect to a standard molded product having a weight loss rate of 0% is obtained. Manufacturing method of molded products. The method for producing a foam molded product according to any one of claims 1 to 5, further comprising a step of heat-treating the foam molded product obtained in the injection foam molding step at 100 to 350 ° C. for 1 to 120 minutes. The foam-molded product according to claim 6, wherein a bulge having a maximum diameter of 2 mm to 5 mm and a height of 0.2 mm to 1 mm is not formed on the surface of the foam-molded product after the heat treatment step. Production method. The method for producing an effervescent molded article according to any one of claims 1 to 7, wherein an effervescent molded article for a piping part is obtained.