Resin composition, foam molded product, and multilayer pipe

Abstract

To provide a resin composition that can suppress the adhering of the resin composition to a die and can improve a closed-cell ratio of a resultant foam molded body.SOLUTION: A resin composition according to the present invention contains a vinyl chloride resin, an acrylic polymer, a foaming agent, and a zinc-phosphate compound, the vinyl chloride resin having an average degree of polymerization of 600 or more and 1,000 or less, the foaming agent containing sodium bicarbonate, and the content of the zinc-phosphate compound being 0.3 pts.wt. or more and 1.7 pts.wt or less relative to 100 pts.wt. of the vinyl chloride resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing a vinyl chloride resin and a foaming agent, and also to a foam-molded article and a multi-layer pipe using the resin composition. [Background technology]

[0002] Foamed molded articles obtained by foam molding a resin composition containing a vinyl chloride resin and a foaming agent, or molded articles including such foamed molded articles, are widely used. For example, Patent Document 1 listed below discloses an air conditioning drain pipe including a foam layer obtained by foam molding a composition containing a vinyl chloride resin and a foaming agent.

[0003] The foamed molded article is generally produced by molding a resin composition in a mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-059707 Summary of the Invention [Problem to be solved by the invention]

[0005] When a resin composition containing a vinyl chloride resin and a foaming agent is molded in a mold, the resin composition may adhere to the mold, which may result in a decrease in moldability and production efficiency.

[0006] Furthermore, if a large amount of lubricant is added to the resin composition to prevent the resin composition from adhering to the mold, kneading during molding becomes difficult, and the resulting foamed molded article may have open or dense cells (a decrease in the closed cell content). If the closed cell content of the foamed molded article decreases, the water permeability increases, and when the foamed molded article is used to produce a multi-layer pipe, water easily penetrates into the foamed molded article, resulting in an increase in the heat exchange rate of the multi-layer pipe and a decrease in its thermal insulation properties.

[0007] An object of the present invention is to provide a resin composition that can suppress adhesion of the resin composition to a mold and increase the closed cell content of the resulting foam-molded article. Another object of the present invention is to provide a foam-molded article and a multi-layer pipe using the resin composition. [Means for solving the problem]

[0008] According to a broad aspect of the present invention, there is provided a resin composition comprising a vinyl chloride resin, an acrylic polymer, a foaming agent, and a zinc-phosphate compound, wherein the vinyl chloride resin has an average degree of polymerization of 600 or more and 1000 or less, the foaming agent comprises sodium bicarbonate, and the content of the zinc-phosphate compound is 0.3 parts by weight or more and 1.7 parts by weight or less per 100 parts by weight of the vinyl chloride resin.

[0009] In a specific aspect of the resin composition according to the present invention, the blowing agent includes azodicarbonamide.

[0010] In a specific aspect of the resin composition according to the present invention, the weight ratio of the content of the zinc-phosphate compound to the content of the sodium hydrogen carbonate is 0.14 or more and 0.78 or less.

[0011] In a specific aspect of the resin composition according to the present invention, the content of the acrylic polymer is 10 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the vinyl chloride resin.

[0012] According to a broad aspect of the present invention, there is provided a foamed molded article obtained by foam-molding the above-described resin composition.

[0013] In a specific aspect of the foamed molded article according to the present invention, the foamed molded article is in the form of a sheet, a tube, or a rod.

[0014] According to a broad aspect of the present invention, there is provided a multi-layer pipe comprising a foam layer, an inner layer disposed inside the foam layer, and an outer layer disposed outside the foam layer, wherein the foam layer is a foam-molded body obtained by foam-molding the above-mentioned resin composition.

[0015] In a specific aspect of the multi-layer pipe according to the present invention, the multi-layer pipe is an air conditioning drain pipe. [Effects of the Invention]

[0016] The resin composition according to the present invention contains a vinyl chloride resin, an acrylic polymer, a foaming agent, and a zinc-phosphate compound. In the resin composition according to the present invention, the vinyl chloride resin has an average degree of polymerization of 600 or more and 1000 or less, and the foaming agent contains sodium bicarbonate. In the resin composition according to the present invention, the content of the zinc-phosphate compound is 0.3 parts by weight or more and 1.7 parts by weight or less per 100 parts by weight of the vinyl chloride resin. Because the resin composition according to the present invention has the above overall configuration, it is possible to suppress adhesion of the resin composition to a mold and increase the closed cell content of the resulting foam molded article. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below.

[0018] (Resin composition) The resin composition according to the present invention contains a vinyl chloride resin, an acrylic polymer, a foaming agent, and a zinc-phosphate compound. In the resin composition according to the present invention, the vinyl chloride resin has an average degree of polymerization of 600 or more and 1000 or less, and the foaming agent contains sodium bicarbonate. In the resin composition according to the present invention, the content of the zinc-phosphate compound is 0.3 parts by weight or more and 1.7 parts by weight or less per 100 parts by weight of the vinyl chloride resin.

[0019] When a conventional resin composition is molded using a mold, the resin composition may adhere to the mold, which may result in a decrease in moldability and production efficiency.

[0020] Furthermore, when the resin composition contains a foaming agent containing sodium bicarbonate, the vinyl chloride resin and the sodium carbonate generated by the foaming reaction are more likely to adhere to the mold. If the vinyl chloride resin or the like adheres to the surface of the mold, the vinyl chloride resin is thermally decomposed to generate gas, which may corrode the metal (plating, etc.) of the mold.

[0021] Furthermore, if a large amount of lubricant is added to the resin composition to prevent the resin composition from adhering to the mold, kneading during molding becomes difficult, and the resulting foamed molded article may have open or dense cells (a decrease in the closed cell content). If the closed cell content of the foamed molded article decreases, the water permeability increases, and when the foamed molded article is used to produce a multi-layer pipe, water easily penetrates into the foamed molded article, resulting in an increase in the heat exchange rate of the multi-layer pipe and a decrease in its thermal insulation properties.

[0022] The resin composition according to the present invention has the above-described features, and therefore, adhesion of the resin composition to a mold can be suppressed, thereby improving moldability and production efficiency.

[0023] Furthermore, since the resin composition according to the present invention has the above-mentioned constitution, it is possible to suppress adhesion of sodium carbonate and vinyl chloride resin to a mold, and as a result, it is possible to suppress corrosion of the metal (plating, etc.) of the mold.

[0024] Furthermore, since the resin composition according to the present invention has the above-described features, the closed cell content of the resulting foam molded article can be increased. Furthermore, the resin composition according to the present invention can reduce the cell diameter of the resulting foam molded article. As a result, the water permeability of the resulting foam molded article can be reduced. Therefore, when the foam molded article is used to produce a multi-layer pipe, the heat exchange rate of the multi-layer pipe can be reduced, thereby improving the heat insulation.

[0025] [Vinyl chloride resin] The resin composition contains a vinyl chloride resin.

[0026] As the vinyl chloride resin, conventionally known vinyl chloride resins can be used. Examples of the vinyl chloride resin include (1) a homopolymer of a vinyl chloride monomer, (2) a copolymer of a vinyl chloride monomer and a monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer, and (3) a graft polymer in which a vinyl chloride monomer is graft-polymerized onto a polymer other than a homopolymer of a vinyl chloride monomer. The vinyl chloride resins may be used alone or in combination of two or more.

[0027] The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer is not particularly limited, and examples thereof include ethylene, propylene, allyl chloride, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, vinyl acetate, maleic anhydride, acrylonitrile, etc. The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer may be used alone or in combination of two or more.

[0028] The polymer other than the homopolymer of vinyl chloride monomer may be a homopolymer or a copolymer. Examples of the polymer other than the homopolymer of vinyl chloride monomer include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate-carbon monoxide copolymer. The polymer other than the homopolymer of vinyl chloride monomer may be used alone or in combination of two or more.

[0029] The vinyl chloride resin may be a chlorinated vinyl chloride resin.

[0030] The content of structural units derived from vinyl chloride in 100% by weight of the vinyl chloride resin is preferably 70% by weight or more, more preferably 75% by weight or more, even more preferably 80% by weight or more, particularly preferably 90% by weight or more, and preferably 98% by weight or less, more preferably 95% by weight or less. When the content of structural units derived from vinyl chloride is equal to or greater than the lower limit, flame retardancy can be further improved. When the content of structural units derived from vinyl chloride is equal to or less than the upper limit, moldability can be improved. Furthermore, when the content of structural units derived from vinyl chloride is equal to or less than the upper limit, thermal decomposition of the vinyl chloride resin during molding can be suppressed, thereby suppressing gas generation due to thermal decomposition and corrosion of the metal of the mold. The content of structural units derived from vinyl chloride in 100% by weight of the vinyl chloride resin may be 100% by weight (total amount).

[0031] The weight average molecular weight of the vinyl chloride resin is preferably 37,500 or more, more preferably 43,750 or more, and preferably 62,500 or less, more preferably 56,250 or less.

[0032] The weight average molecular weight of the vinyl chloride resin means the weight average molecular weight measured by GPC (gel permeation chromatography) using polyethylene glycol as a standard substance.

[0033] From the viewpoint of achieving the effects of the present invention, the average degree of polymerization of the vinyl chloride resin is 600 or more and 1000 or less. The average degree of polymerization of the vinyl chloride resin is preferably 700 or more and preferably 900 or less. When the average degree of polymerization is equal to or more than the above lower limit and equal to or less than the above upper limit, the effects of the present invention can be achieved more effectively. Furthermore, when the average degree of polymerization is equal to or more than the above lower limit, long-term performance such as thermal stability and fatigue properties is less likely to be impaired. When the average degree of polymerization is equal to or less than the above upper limit, there is no need for a high-temperature environment during molding, and moldability and production efficiency are further improved.

[0034] The average degree of polymerization of the vinyl chloride resin can be calculated by dividing the weight average molecular weight by the molecular weight of chloroethylene.

[0035] From the viewpoint of more effectively suppressing adhesion of the resin composition to the mold, the content of the vinyl chloride resin in 100% by weight of the resin composition is preferably 65% ​​by weight or more, more preferably 75% by weight or more, and is preferably 85% by weight or less, more preferably 80% by weight or less.

[0036] As will be described later, the resin composition may or may not contain a thermoplastic resin other than the vinyl chloride resin.

[0037] Of the total 100% by weight of all thermoplastic resins contained in the resin composition, the content of the vinyl chloride resin is preferably 65% ​​by weight or more, more preferably 75% by weight or more, and preferably 90% by weight or less, more preferably 85% by weight or less.

[0038] [Acrylic polymer] The resin composition contains an acrylic polymer. By using the acrylic polymer, the closed cell content of the resulting foamed molded article can be increased. In addition, the cell diameter can be reduced. As a result, the water permeability of the resulting foamed molded article can be reduced.

[0039] As the acrylic polymer, a conventionally known acrylic polymer can be used. Examples of the acrylic polymer include (1) a homopolymer of an acrylic monomer, and (2) a copolymer of an acrylic monomer and a monomer copolymerizable with the acrylic monomer. The acrylic polymer may be used alone or in combination of two or more.

[0040] Examples of the acrylic monomer include acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters.

[0041] In 100% by weight of the acrylic polymer, the content of structural units derived from acrylic monomers is preferably 85% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 98.5% by weight or more.

[0042] The weight average molecular weight of the acrylic polymer is preferably 3 million or more, more preferably 4 million or more, and preferably 6 million or less, more preferably 5 million or less.

[0043] The weight average molecular weight of the acrylic polymer refers to the weight average molecular weight measured by GPC (gel permeation chromatography) using polyethylene glycol as a standard substance.

[0044] The content of the acrylic polymer is preferably 10 parts by weight or more, more preferably 12 parts by weight or more, even more preferably 18 parts by weight or more, and preferably 50 parts by weight or less, more preferably 36 parts by weight or less, and even more preferably 24 parts by weight or less, relative to 100 parts by weight of the vinyl chloride resin. When the content of the acrylic polymer is equal to or more than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the closed cell content of the obtained foamed molded article can be further increased, and the cell diameter can be reduced. As a result, the water permeability of the obtained foamed molded article can be reduced.

[0045] [Foaming agent] The resin composition contains a foaming agent.

[0046] The foaming agent contains sodium bicarbonate. By including sodium bicarbonate in the foaming agent, the foaming ratio can be increased.

[0047] The foaming agent may or may not contain azodicarbonamide. When azodicarbonamide is used, the azodicarbonamide acts as a nucleating agent, making it possible to foam the sodium bicarbonate more uniformly. The foaming agent preferably contains sodium bicarbonate and azodicarbonamide.

[0048] The foaming agent may or may not contain a foaming agent different from both sodium hydrogen carbonate and azodicarbonamide (hereinafter, sometimes referred to as foaming agent X). Only one type of foaming agent X may be used, or two or more types may be used in combination.

[0049] The foaming agent X may be a volatile foaming agent or a decomposition type foaming agent.

[0050] Examples of the blowing agent X, which is a volatile blowing agent, include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, and ketones. Examples of the aliphatic hydrocarbons include propane, butane (normal butane, isobutane), and pentane (normal pentane, isopentane, etc.). Examples of the alicyclic hydrocarbons include cyclopentane and cyclohexane. Examples of the halogenated hydrocarbons include trichlorofluoromethane, trichlorotrifluoroethane, tetrafluoroethane, chlorodifluoroethane, and difluoroethane. Examples of the ethers include dimethyl ether and diethyl ether. Examples of the ketones include acetone and methyl ethyl ketone.

[0051] The decomposition-type blowing agent X may be an inorganic blowing agent or an organic blowing agent. Examples of the inorganic blowing agent include sodium carbonate, ammonium bicarbonate, ammonium nitrite, azide compounds, and sodium borohydride. Examples of the organic blowing agent include barium azodicarboxylate and dinitrosopentamethylenetetramine.

[0052] Examples of the blowing agent X include thermally expandable microcapsules and gases such as carbon dioxide, nitrogen, and air. The thermally expandable microcapsules are preferably thermally expandable microcapsules encapsulating a hydrocarbon. The thermally expandable microcapsules are preferably thermally expandable microcapsules in which a hydrocarbon is encapsulated in a shell formed of a thermoplastic resin.

[0053] The content of the foaming agent is preferably 1.0 part by weight or more, more preferably 2.0 parts by weight or more, and preferably 8.0 parts by weight or less, more preferably 5.0 parts by weight or less, relative to 100 parts by weight of the vinyl chloride resin. When the content of the foaming agent is equal to or more than the lower limit and equal to or less than the upper limit, the expansion ratio can be increased.

[0054] The content of sodium bicarbonate is preferably 1.0 part by weight or more, more preferably 2.0 parts by weight or more, and preferably 3.0 parts by weight or less, more preferably 2.5 parts by weight or less, relative to 100 parts by weight of the vinyl chloride resin. When the content of sodium bicarbonate is equal to or more than the above lower limit and equal to or less than the above upper limit, the expansion ratio can be increased.

[0055] [Zinc-phosphate compound] The resin composition contains a zinc-phosphate compound. The zinc-phosphate compound is a compound having a zinc atom and a phosphoric acid structure. By using the zinc-phosphate compound, adhesion of the resin composition to a mold can be suppressed. Furthermore, by using the zinc-phosphate compound, adhesion of vinyl chloride resin, sodium carbonate generated by foaming of sodium bicarbonate, and other inorganic components in the resin composition to a mold can be suppressed.

[0056] Examples of the zinc-phosphate compound include zinc phosphate ester. .superior The zinc-phosphate compounds may be used alone or in combination of two or more.

[0057] The content of the zinc-phosphate compound is 0.3 parts by weight or more and 1.7 parts by weight or less per 100 parts by weight of the vinyl chloride resin. The content of the zinc-phosphate compound is preferably 0.4 parts by weight or more, more preferably 0.6 parts by weight or more, and preferably 1.5 parts by weight or less, more preferably 1.0 part by weight or less per 100 parts by weight of the vinyl chloride resin. When the content of the zinc-phosphate compound is equal to or more than the lower limit and equal to or less than the upper limit, adhesion of the resin composition to the mold can be more effectively suppressed. Furthermore, adhesion of the vinyl chloride resin, sodium carbonate generated by foaming of sodium bicarbonate, and other inorganic components in the resin composition to the mold can be more effectively suppressed.

[0058] The weight ratio of the zinc-phosphate compound content to the sodium bicarbonate content (zinc-phosphate compound content / sodium bicarbonate content) is preferably 0.14 or more, more preferably 0.20 or more, and preferably 0.78 or less, more preferably 0.58 or less, and even more preferably 0.39 or less. When the weight ratio (zinc-phosphate compound content / sodium bicarbonate content) is equal to or greater than the lower limit and equal to or less than the upper limit, adhesion of the resin composition to the mold can be more effectively suppressed. Furthermore, adhesion of the vinyl chloride resin, sodium carbonate generated by foaming of sodium bicarbonate, and other inorganic components in the resin composition to the mold can be more effectively suppressed.

[0059] [Other ingredients] The resin composition may contain other components in addition to the above-mentioned components. Examples of the other components include lubricants, heat stabilizers, compatibilizers, heat stabilization aids, impact modifiers, impact resistance modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, fillers, pigments, plasticizers, and thermoplastic resins (thermoplastic resins other than vinyl chloride resins). One type of the other components may be used alone, or two or more types may be used in combination.

[0060] <Lubricant> The resin composition preferably contains a lubricant. Use of the lubricant can improve the sliding properties between the mold and the resin composition and between the resins contained in the resin composition.

[0061] Examples of the lubricant include internal lubricants and external lubricants. The internal lubricant is used to reduce the flow viscosity of the molten resin during molding and to prevent frictional heat generation. The internal lubricant is not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl alcohol, epoxy soybean oil, glycerin monostearate, stearic acid, and bisamide. The external lubricant is used to improve the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and examples thereof include paraffin wax, polyolefin wax, ester wax, and montanic acid wax. The lubricants may be used alone or in combination of two or more.

[0062] The total content of the zinc-phosphate compound and lubricant is preferably 0.4 parts by weight or more, more preferably 0.6 parts by weight or more, and preferably 2.0 parts by weight or less, more preferably 1.5 parts by weight or less, and even more preferably 1.0 parts by weight or less, per 100 parts by weight of the vinyl chloride resin. When the total content is above the lower limit and below the upper limit, adhesion of the resin composition to the mold can be more effectively suppressed. Furthermore, adhesion of sodium carbonate generated by foaming of the vinyl chloride resin and sodium bicarbonate, and other inorganic components in the resin composition to the mold can be more effectively suppressed. Furthermore, when the total content is below the upper limit, the resin composition can be well kneaded, thereby improving the dispersibility of the acrylic polymer and increasing the expansion ratio and closed cell ratio of the resulting foamed molded article.

[0063] <Heat stabilizer> The resin composition preferably contains a heat stabilizer. By using the heat stabilizer, the thermal stability of the resin composition can be improved.

[0064] Examples of the heat stabilizer include organotin-based stabilizers, lead-based stabilizers, calcium-zinc-based stabilizers, barium-zinc-based stabilizers, and barium-cadmium-based stabilizers. From the viewpoint of improving the thermal stability of the resin composition, the stabilizer is preferably an organotin-based stabilizer. Examples of the organotin-based stabilizer include dibutyltin mercapto, dioctyltin mercapto, dimethyltin mercapto, dibutyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, and dibutyltin laurate polymer. The heat stabilizers may be used alone or in combination of two or more.

[0065] <Heat stabilization aid> The resin composition may or may not contain a heat stabilizing aid. Examples of the heat stabilizing aid include epoxidized soybean oil, phosphate ester, polyol, hydrotalcite, and zeolite. The heat stabilizing aid may be used alone or in combination of two or more.

[0066] <Impact modifier> The resin composition may or may not contain an impact modifier. Examples of the impact modifier include methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, and acrylic rubber. The impact modifier may be used alone or in combination of two or more.

[0067] <Heat resistance improver> The resin composition may or may not contain a heat resistance improver. Examples of the heat resistance improver include α-methylstyrene-based and N-phenylmaleimide-based resins. The heat resistance improver may be used alone or in combination of two or more.

[0068] <Antioxidants> The resin composition may or may not contain an antioxidant. Examples of the antioxidant include phenolic antioxidants. The antioxidants may be used alone or in combination of two or more.

[0069] <UV absorber> The resin composition may or may not contain an ultraviolet absorber. Examples of the ultraviolet absorber include salicylic acid ester-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. The ultraviolet absorbers may be used alone or in combination of two or more.

[0070] <Light stabilizer> The resin composition may or may not contain a light stabilizer. Examples of the light stabilizer include hindered amine light stabilizers. The light stabilizers may be used alone or in combination of two or more.

[0071] <Filler> The resin composition may or may not contain a filler. Examples of the filler include calcium carbonate and talc. The filler may be used alone or in combination of two or more.

[0072] <Pigments> The resin composition may or may not contain a pigment. Examples of the pigment include organic pigments and inorganic pigments. Examples of the organic pigment include azo-based organic pigments, phthalocyanine-based organic pigments, threne-based organic pigments, and dye lake-based organic pigments. Examples of the inorganic pigment include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide-selenide-based inorganic pigments, and ferrocyanide-based inorganic pigments. The pigments may be used alone or in combination of two or more.

[0073] <Plasticizer> The resin composition may or may not contain a plasticizer. Examples of the plasticizer include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate. The plasticizer may be used alone or in combination of two or more.

[0074] <Thermoplastic resins other than vinyl chloride resins> The resin composition may or may not contain a thermoplastic resin other than a vinyl chloride resin. Examples of the thermoplastic resin other than a vinyl chloride resin include polyethylene, polypropylene, polystyrene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, polyethylene terephthalate, and ABS resin. The thermoplastic resin other than a vinyl chloride resin may be used alone or in combination of two or more.

[0075] The presence or absence of the other components in the resin composition and their contents can be measured by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), gas chromatography mass spectrometry (GC-MS), etc. However, other methods can also be used to confirm. In the case of ICP-AES, the measurement can be performed in accordance with EN ISO17353:2004.

[0076] (Molded foam and multi-layer pipes) The foam molded article according to the present invention is a foam molded article obtained by foam molding the resin composition described above. The foam molded article can be obtained by foam molding the resin composition.

[0077] The shape of the foamed molded article is not particularly limited. The foamed molded article may be in the form of a sheet, a tube, or a rod. The foamed molded article is preferably in the form of a sheet, a tube, or a rod, more preferably in the form of a sheet or a tube, and even more preferably in the form of a tube.

[0078] The multi-layer pipe according to the present invention comprises a foam layer, an inner layer disposed inside the foam layer, and an outer layer disposed outside the foam layer, and the foam layer is a foam-molded body obtained by foam-molding the resin composition described above. The multi-layer pipe comprises, from the center to the outside in the radial direction, the inner layer, the foam layer, and the outer layer, in this order. The inner layer is preferably a non-foamed layer, and the outer layer is preferably a non-foamed layer. The multi-layer pipe may have a three-layer structure consisting of the inner layer, the foam layer, and the outer layer, or may have a structure of three or more layers.

[0079] The materials for the inner layer and the outer layer are not particularly limited, and any conventionally known material for multilayer pipes can be used as the materials for the inner layer and the outer layer.

[0080] The tubular foam molded article is preferably used as a pipe for an air conditioning drain. The multi-layer pipe is preferably used as a pipe for an air conditioning drain. The tubular foam molded article is preferably used as a pipe for an air conditioning drain, and the multi-layer pipe is preferably used as a pipe for an air conditioning drain.

[0081] The expansion ratio of the foam molded product and the expansion ratio of the foam layer in the multi-layer pipe are each preferably 3.5 times or more, more preferably 4.5 times or more, and preferably 10 times or less, more preferably 6.5 times or less. When the expansion ratio is below the upper limit, the closed cell structure can be further improved and the cell diameter can be made uniform. When the expansion ratio is above the lower limit and below the upper limit, the heat insulating properties can be improved and the foam molded product and multi-layer pipe can be made lighter.

[0082] The expansion ratio of the foamed molded article and the expansion ratio of the foam layer in the multi-layer pipe are measured as follows.

[0083] The foamed molded article or foam layer is cut into a 15mm x 40mm test piece. The apparent density of the test piece obtained is measured to three decimal places using a water displacement hydrometer at 23°C ± 2°C in accordance with JIS K7112:1999. The expansion ratio is calculated using the following formula (1):

[0084] m=γc / γ' (1)

[0085] In the above formula (1), m represents the expansion ratio, and γ' represents the apparent density (g / cm 3 ) and γc represents the density (g / cm 3 )

[0086] The expansion ratio of the foamed molded article and the expansion ratio of the foamed layer in the multi-layer pipe can be appropriately adjusted by the type and content of the vinyl chloride resin, the type and content of the foaming agent, the production conditions, and the like.

[0087] The closed cell ratio of the foamed molded article and the closed cell ratio of the foamed layer in the multi-layer pipe are each preferably 45% or more, more preferably 50% or more, and even more preferably 60% or more. When the closed cell ratio is equal to or greater than the lower limit, the water permeability can be reduced, thereby reducing the heat exchange rate of the resulting multi-layer pipe and improving its thermal insulation. There is no particular upper limit to the closed cell ratio. The closed cell ratio may be 100%.

[0088] The closed cell content of the foamed molded article and the closed cell content of the foamed layer in the multi-layer pipe are measured in accordance with JIS K 7138:2006 as follows.

[0089] The foamed molded article or foam layer is cut into a 20 mm circumference x 30 mm width test piece. The volume of the obtained test piece is measured using an air comparison hydrometer at 23°C ± 2°C in accordance with JIS K 7138:2006 (air comparison volume), and the volume is measured using a water displacement hydrometer at 23°C ± 2°C in accordance with JIS K 7112:1999 (water displacement volume). The closed cell ratio is calculated using the following formula (2):

[0090] Cc=(Va / Vaq)×100 (2)

[0091] In the above formula (2), Cc represents the closed cell rate (%), Va represents the air relative volume (cm 3), and Vaq is the water displacement volume (cm 3 )

[0092] The closed cell content of the foamed molded article and the closed cell content of the foamed layer in the multi-layer pipe can be appropriately adjusted by changing the type and content of the vinyl chloride resin, the type and content of the foaming agent, the type and content of the acrylic polymer, the production conditions, etc.

[0093] The foamed molded body and the foam layer preferably have a water permeability of 0.1% or less when subjected to the following water permeability test. If the water permeability is below the upper limit, water is less likely to penetrate into the foamed molded body and the foam layer, thereby reducing the heat exchange rate of the resulting multi-layer pipe and improving its thermal insulation.

[0094] The water permeability of the foamed molded article and the water permeability of the foamed layer in the multi-layer pipe are measured as follows.

[0095] The foamed molded article or foam layer is cut into a piece measuring 200 mm in length and 4 mm in width to obtain a test piece. The test piece is placed in a resin pipe equipped with a water pressure test jig, and water is passed through the resin pipe at a water pressure of 0.06 MPa for 1 minute.

[0096] The water permeability of the test piece is calculated by the following formula (3) and is defined as the water permeability of the foamed molded article or the foamed layer. Note that the water permeability is preferably calculated by averaging the water permeabilities of two test pieces.

[0097] Water permeability (%) = weight of test piece after water flow / weight of test piece before water flow × 100 (3)

[0098] If the "temperature of the resin composition during molding" at which the water permeability is 0.1% or less is defined as the "water flow test passing temperature," the water flow test passing temperature is preferably 200° C. or less, more preferably 180° C. or less. When the water flow test passing temperature is equal to or less than the upper limit, deterioration of the mold due to adhesion or decomposition of the vinyl chloride resin is unlikely to occur.

[0099] The thickness of the foam layer in the foam molded product and the multi-layer pipe is preferably 3.0 mm or more, more preferably 4.8 mm or more. When the thickness of the foam layer is equal to or greater than the above-mentioned lower limit, the heat insulating properties can be further improved. There is no particular upper limit to the thickness of the foam layer in the foam molded product and the multi-layer pipe. The thickness of the foam layer in the foam molded product and the multi-layer pipe may be 10 mm or less, or may be 8 mm or less.

[0100] The foamed molded article and the multi-layer pipe can be produced by a conventionally known method. For example, the foamed molded article and the multi-layer pipe can be produced by a method of extruding the resin composition. The temperature during extrusion molding is preferably 5°C or more, and more preferably 10°C or more, higher than the temperature at which the water flow test is passed.

[0101] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0102] The following materials were prepared:

[0103] PVC resin: Vinyl chloride resin (A1) (Tokuyama Sekisui Kogyo Co., Ltd. "TS-800E", average degree of polymerization 800) Vinyl chloride resin (A2) (Tokuyama Sekisui Kogyo Co., Ltd. "TS-640M", average degree of polymerization 640)

[0104] Acrylic polymers: Acrylic polymer (B) (Kaneka "PA-40", weight-average molecular weight 5 million)

[0105] Zinc-phosphate compounds: Zinc-phosphate compound mixture (C) (a mixture of 75-85% by weight of zinc-phosphate compound (C') and 15-25% by weight of a lubricant-based organic substance ("NPO-3" manufactured by ADEKA Corporation))

[0106] Foaming Agent: Sodium bicarbonate (D1) (Eiwa Chemical Industry Co., Ltd. "Celbon SC-855") Azodicarbonamide (D2) ("Vinihall AC#3" manufactured by Eiwa Chemical Industry Co., Ltd.)

[0107] Example 1 Preparation of resin composition: The following components were mixed to prepare a resin composition.

[0108] Vinyl chloride resin (A1) 100 parts by weight Acrylic polymer (B) 20 parts by weight Zinc-phosphate compound mixture (C) 0.4 parts by weight Sodium bicarbonate (D1) 2.2 parts by weight Azodicarbonamide (D2) 0.3 parts by weight

[0109] Preparation of foam molding: The resulting resin composition was kneaded using a twin-screw extruder and pelletized into 5 mm x 5 mm pellets. The pelletized resin composition was then extrusion-molded at 177°C to 180°C using a twin-screw extruder ("USV30 Extruder" manufactured by Union Plastics Co., Ltd.) and a slit mold (exit dimensions 20 mm x 2 mm) to obtain a sheet-like foamed molded product.

[0110] (Examples 2 and 3 and Comparative Examples 1 and 2) Resin compositions and foam-molded articles were obtained in the same manner as in Example 1, except that the formulation of the resin composition and the temperature of the resin composition during molding were changed as shown in Table 1.

[0111] (evaluation) (1) Expansion Ratio The obtained sheet-like foamed molded article was cut into a size of 15 mm length x 40 mm width to prepare a test piece. The apparent density of this test piece was measured to three decimal places using a water displacement hydrometer at 23°C ± 2°C in accordance with JIS K7112:1999, and the expansion ratio was calculated using the following formula (1).

[0112] m=γc / γ' (1)

[0113] In the above formula (1), m represents the expansion ratio, and γ' represents the apparent density (g / cm 3) and γc is the density (g / cm 3 )

[0114] (2) Water flow test (water flow test passing temperature) The obtained sheet-like foam molded product was cut into a piece measuring 200 mm in length and 4 mm in width to obtain two test pieces. The two test pieces were placed in a resin pipe equipped with a water pressure test jig, and water was passed through the resin pipe at a water pressure of 0.06 MPa for one minute.

[0115] The water permeability of each of the two test pieces was calculated using the following formula (3), and the average value was taken as the water permeability of the foam-molded article.

[0116] Water permeability (%) = weight of test piece after water flow / weight of test piece before water flow × 100 (3)

[0117] The "temperature of the resin composition during molding" at which the water permeability of the foamed molded article was 0.1% or less was defined as the "water permeability test passing temperature." The water permeability test was evaluated according to the following criteria.

[0118] [Water flow test criteria] ○: Water flow test pass temperature is 180℃ or less ×: The temperature at which the water flow test is passed exceeds 180°C

[0119] (3) Adhesion of resin composition to mold After the foamed molded article was produced, the mold was disassembled, and it was visually confirmed whether or not the resin composition had adhered to the mold, and the adhesion was judged according to the following criteria.

[0120] [Criteria for determining adhesion of resin composition to mold] ○○: The resin composition does not adhere to the mold surface ○: The resin composition adheres to less than 50% of the surface area of ​​the mold (100%). ×: The resin composition adheres to 50% or more of the surface area of ​​the mold (100%).

[0121] The constitution of the resin composition, the temperature of the resin composition during molding, and the results are shown in Table 1 below.

[0122] [Table 1]

[0123] As shown in Table 1, adhesion of the resin composition to the mold could be suppressed in Examples 1 to 3. In Comparative Examples 1 and 2, the resin composition adhered to 100% (total surface area) of the surface area of ​​the mold.

Claims

1. The composition includes a vinyl chloride resin, an acrylic polymer, a foaming agent, and a zinc-phosphate compound, the vinyl chloride resin has an average degree of polymerization of 600 or more and 1000 or less; the effervescent agent comprises sodium bicarbonate; The resin composition has a content of the zinc-phosphate compound of 0.3 parts by weight or more and 1.7 parts by weight or less relative to 100 parts by weight of the vinyl chloride resin.

2. The resin composition according to claim 1 , wherein the blowing agent comprises azodicarbonamide.

3. 3. The resin composition according to claim 1, wherein a weight ratio of the content of the zinc-phosphate compound to the content of the sodium hydrogen carbonate is 0.14 or more and 0.78 or less.

4. The resin composition according to any one of claims 1 to 3, wherein the content of the acrylic polymer is 10 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the vinyl chloride resin.

5. A foam-molded article obtained by foam-molding the resin composition according to any one of claims 1 to 4.

6. The foamed molded article according to claim 5 , which is in the form of a sheet, a tube or a rod.

7. a foam layer, an inner layer disposed inside the foam layer, and an outer layer disposed outside the foam layer; A multilayer pipe, wherein the foam layer is a foam-molded article obtained by foam-molding the resin composition according to any one of claims 1 to 4.

8. The multilayer pipe according to claim 7, which is an air conditioning drain pipe.

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