JP7372856B2 - multilayer pipe - Google Patents

Description

The present invention relates to a multilayer tube comprising an inner layer and an outer layer.

Plastic pipes such as vinyl chloride resin pipes are often used in buildings such as condominiums, apartments, and detached houses for water supply and drainage. Moreover, as piping used outdoors, piping is used in which an inner layer and an outer layer formed of a weather-resistant material are integrated.

Patent Document 1 listed below describes a pipe having an inner layer portion formed into a tubular shape and an outer layer portion that is provided outside the inner layer portion and integrated with the inner layer portion and has higher weather resistance than the inner layer portion. ing.

Moreover, the following Patent Documents 2 and 3 disclose resin compositions having weather resistance.

Patent Document 2 below describes a method containing (A) a vinyl copolymer, (B) a compound containing two or more isocyanate groups, and (C) a hydrolyzable silicon group and an isocyanate curing catalyst. A multi-component curable resin composition for coating is disclosed. (A) The vinyl copolymer has a (meth)acrylic copolymer chain as the main chain, and has 10 or more hydrolyzable silicon groups containing a specific structure at the end of the main chain and/or side chain. and has 10 or more hydroxyl groups at the end of the main chain and/or in the side chain.

Patent Document 3 below describes a coating composition containing (I) a hydroxyl group-containing graft copolymer having a hydroxyl value of 60 to 120, (II) a modified vinyl copolymer, and (III) a polyisocyanate compound. is disclosed. (I) The hydroxyl group-containing graft copolymer contains (a) 10 to 30% by weight of a macromonomer, (b) 0 to 30% by weight of styrene, and (c) 40 to 90% by weight of other ethylenically unsaturated monomers. It can be obtained by copolymerizing. (II) The modified vinyl copolymer is obtained by copolymerizing (a) 5 to 75% by weight of cellulose acetate butyrate and (b) 95 to 25% by weight of the vinyl monomer mixture. The vinyl monomer mixture (b) is composed of 1 to 50% by weight of at least one functional vinyl monomer containing a hydroxyl group and 99 to 50% by weight of another copolymerizable vinyl monomer.

Japanese Patent Application Publication No. 2016-188696 WO2013/081022A1 Japanese Patent Application Publication No. 06-001949

If the weather resistance of plastic piping, such as vinyl chloride resin pipes, is low, the vinyl chloride resin will decompose due to ultraviolet rays, resulting in a decrease in impact resistance and a decline in design due to blackening or whitening of the outer surface. Sometimes.

Although the piping described in Patent Document 1 can improve weather resistance to some extent, depending on the shape of the piping, there may be parts of the inner layer that are not covered with the outer layer, or the adhesive strength between the inner layer and the outer layer may be low, and the outer layer may It may peel off. In this case, weather resistance may not be sufficiently improved in areas where the outer layer is not coated or where the outer layer has peeled off.

When the outer layer is formed by applying a resin composition having weather resistance as described in Patent Documents 2 and 3 to the inner layer, the weather resistance of the resulting piping can be improved.

However, the present inventor discovered that when the outer layer is formed using a conventional resin composition having weather resistance, the impact resistance performance of the resulting multilayer pipe is significantly lower than the impact resistance performance of the pipe before forming the outer layer. I found out. If the impact resistance is low, the multilayer pipe may be damaged during storage, transportation, construction, and use.

An object of the present invention is to provide a multilayer pipe that has excellent adhesiveness between an inner layer and an outer layer, and has excellent weather resistance and impact resistance.

According to a broad aspect of the present invention, the invention includes an inner layer containing a vinyl chloride resin, and an outer layer disposed on the outer surface of the inner layer and containing an acrylic urethane resin, wherein the acrylic urethane resin is an acrylic polyol compound. and an isocyanate compound, where the isocyanate compound contains a trimer isocyanate compound, and when a sample obtained by treating the outer layer with cresol was measured by gel permeation chromatography, the isocyanate A multilayer pipe is provided, in which the ratio of the peak area derived from an isocyanate compound appearing as a molecular weight of 2000 to 7000 is 10% to 90% of 100% of the peak area derived from the compound.

In a particular aspect of the multilayer pipe according to the present invention, the first tensile elongation at break of the inner layer at 0° C. and 500 mm/min is 30% or more and 80% or less, and at 0° C. and 500 mm/min. The second tensile elongation at break of the multilayer pipe under the conditions is 30% or more and 80% or less, and the absolute value of the difference between the first tensile elongation at break and the second tensile elongation at break is , 20% or less, and when an adhesion test between the inner layer and the outer layer was conducted by a cross-cut method in accordance with JIS K5600-5-6, the result of the adhesion test was classified as 0 or 0. It is 1.

In a particular aspect of the multilayer tube according to the present invention, the outer layer includes an inorganic pigment, and the inorganic pigment has an average particle size of 100 nm or more and 800 nm or less.

In a particular aspect of the multilayer tube according to the present invention, the thickness of the outer layer is 0.01 mm or more and 0.25 mm or less.

The multilayer pipe according to the present invention includes an inner layer containing a vinyl chloride resin, and an outer layer disposed on the outer surface of the inner layer and containing an acrylic urethane resin, wherein the acrylic urethane resin is an acrylic polyol compound. , is a reaction product with an isocyanate compound, and the isocyanate compound includes an isocyanate compound that is a trimer. In the multilayer tube according to the present invention, when a sample obtained by treating the outer layer with cresol is measured by gel permeation chromatography, it appears as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound. The ratio of the peak area derived from the isocyanate compound is 10% or more and 90% or less. Since the multilayer pipe according to the present invention has the above configuration, it has excellent adhesiveness between the inner layer and the outer layer, and also has excellent weather resistance and impact resistance.

FIG. 1 is a sectional view showing a multilayer pipe according to an embodiment of the present invention.

The present invention will be explained in detail below.

(Multilayer pipe)
The multilayer pipe according to the present invention includes an inner layer containing a vinyl chloride resin, and an outer layer disposed on the outer surface of the inner layer and containing an acrylic urethane resin. In the multilayer pipe according to the present invention, the acrylic urethane resin is a reaction product of an acrylic polyol compound and an isocyanate compound, and the isocyanate compound includes an isocyanate compound that is a trimer. In the multilayer tube according to the present invention, when a sample obtained by treating the outer layer with cresol is measured by gel permeation chromatography, it appears as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound. The ratio of the peak area derived from the isocyanate compound is 10% or more and 90% or less. Hereinafter, the ratio of the peak area derived from the isocyanate compound appearing as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound may be referred to as the peak area ratio (X).

Since the multilayer pipe according to the present invention has the above configuration, it has excellent adhesiveness between the inner layer and the outer layer, and also has excellent weather resistance and impact resistance. Although in the conventional multilayer pipe, the impact resistance performance of the multilayer pipe is greatly reduced compared to the impact resistance performance of the pipe before forming the outer layer, the multilayer pipe of the present invention has the impact resistance of the multilayer pipe. The performance can be maintained at the same level as the impact resistance performance before forming the outer layer. In addition, in the multilayer pipe according to the present invention, it is possible to improve the adhesion (adhesiveness) between the inner layer and the outer layer, and the weather resistance can be improved, so for example, the mechanical strength such as impact resistance of the multilayer pipe can be maintained for a long period of time.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In addition, in the following drawings, the size, thickness, shape, etc. may differ from the actual size, thickness, shape, etc. for convenience of illustration.

FIG. 1 is a sectional view showing a multilayer pipe according to an embodiment of the present invention.

The multilayer tube 11 includes an inner layer 1 and an outer layer 2. Inner layer 1 is tubular. The inner layer 1 ends on both sides of the multilayer tube 11.

The outer layer 2 is arranged on the outer surface of the inner layer 1. The outer layer 2 is disposed over the entire outer surface of the inner layer 1. Preferably, the outer layer extends to both ends of the multilayer tube. Preferably, the outer layer is arranged in a tubular manner.

(inner layer)
The inner layer includes a vinyl chloride resin. The inner layer is obtained by molding an inner layer material containing a vinyl chloride resin. The above vinyl chloride resins may be used alone or in combination of two or more.

The above-mentioned vinyl chloride resin is not particularly limited. The above-mentioned vinyl chloride resins include homopolymers of vinyl chloride monomers, copolymers of vinyl chloride monomers and monomers having unsaturated bonds that are copolymerizable with vinyl chloride monomers, and polymers and copolymers other than vinyl chloride. Examples include graft polymers in which vinyl chloride is graft-polymerized to a polymer. The vinyl chloride resin may be a hard vinyl chloride resin.

Monomers having unsaturated bonds that can be copolymerized with the vinyl chloride monomer are not particularly limited, and include α-olefin compounds such as ethylene, propylene, butylene; vinyl ester compounds such as vinyl acetate and vinyl propionate; butyl vinyl ether, cetyl Vinyl ether compounds such as vinyl ether; (meth)acrylic acid ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; N-phenylmaleimide , N-substituted maleimide compounds such as N-cyclohexylmaleimide, and the like. Only one type of monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer may be used, or two or more types may be used in combination.

Polymers and copolymers for graft copolymerizing vinyl chloride are not particularly limited, and include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, ethylene- Examples include butyl acrylate-carbon monoxide copolymer, acrylonitrile-butadiene copolymer, polyurethane, chlorinated polyethylene, and chlorinated polypropylene. Only one type of polymer and copolymer for graft copolymerizing vinyl chloride may be used, or two or more types may be used in combination.

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, preferably 98% by weight or less, more preferably 95% by weight or less. When the content of the structural unit derived from vinyl chloride is at least the above lower limit, impact resistance can be further improved. When the content of the structural units derived from vinyl chloride is below the above upper limit, moldability can be improved, thermal decomposition of vinyl chloride can be suppressed during molding, and impact resistance, flatness and water resistance can be improved. The pressure resistance can be improved, and the appearance can also be improved. Note that 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).

The degree of polymerization of the vinyl chloride resin is preferably 100 or more, and preferably 10,000 or less. When the degree of polymerization of the vinyl chloride resin is equal to or higher than the lower limit, long-term performance such as fatigue properties is unlikely to be impaired. When the degree of polymerization of the vinyl chloride resin is below the above upper limit, there is no need to use high temperature during molding, and processability becomes even better.

The above-mentioned vinyl chloride resin may be used in combination with other organic materials as long as the effects of the present invention are not impaired. For example, in order to further improve mechanical strength, an acrylic resin or the like may be used in combination with the vinyl chloride resin.

Further, the vinyl chloride resin may be a post-chlorinated vinyl chloride resin.

The content of the vinyl chloride resin in 100% by weight of the inner layer is preferably 50% by weight or more, more preferably 60% by weight or more, and preferably 80% by weight or less, more preferably 75% by weight or less. . When the content of the vinyl chloride resin is not less than the above lower limit and not more than the above upper limit, weather resistance and impact resistance can be further improved.

The inner layer and the material of the inner layer may contain various additives as necessary. The above additives include stabilizers, stabilizing aids, lubricants, processing aids, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, fillers, pigments, and plasticizers. can be mentioned. The above additives may be used alone or in combination of two or more.

The above-mentioned stabilizer is not particularly limited, and includes heat stabilizers, heat stabilization aids, and the like. The above heat stabilizer is not particularly limited, and examples thereof include organotin stabilizers, lead stabilizers, calcium-zinc stabilizers, barium-zinc stabilizers, barium-cadmium stabilizers, and the like. The organic tin stabilizers include dibutyltin mercapto, dioctyltin mercapto, dimethyltin mercapto, dibutyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, and Examples include dibutyltin laurate polymer. The thermal stabilization aid is not particularly limited, and examples thereof include epoxidized soybean oil, phosphate ester, polyol, hydrotalcite, and zeolite. The above stabilizers may be used alone or in combination of two or more.

The above-mentioned lubricants include internal lubricants and external lubricants. The internal lubricant is used for the purpose of lowering the flow viscosity of the molten resin during molding and preventing frictional heat generation. The internal lubricant is not particularly limited, and includes butyl stearate, lauryl alcohol, stearyl alcohol, epoxy soybean oil, glycerin monostearate, stearic acid, bisamide, and the like. The external lubricant is used for the purpose of increasing the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and examples include paraffin wax, polyolefin wax, ester wax, and montan acid wax. The above lubricants may be used alone or in combination of two or more.

The processing aid is not particularly limited, and examples thereof include acrylic processing aids and the like. Examples of the acrylic processing aids include alkyl acrylate-alkyl methacrylate copolymers having a weight average molecular weight of 100,000 to 2,000,000, and specifically, n-butyl acrylate-methyl methacrylate copolymers, and Examples include 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymer. The above-mentioned processing aids may be used alone or in combination of two or more.

The impact modifier is not particularly limited, and examples include methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, and acrylic rubber. The above-mentioned impact modifiers may be used alone or in combination of two or more.

The heat resistance improver is not particularly limited, and examples include α-methylstyrene resins and N-phenylmaleimide resins. Only one kind of the above-mentioned heat resistance improver may be used, or two or more kinds thereof may be used in combination.

The above-mentioned antioxidant is not particularly limited, and includes phenolic antioxidants and the like. The above antioxidants may be used alone or in combination of two or more.

The UV absorber is not particularly limited, and examples include salicylic acid ester UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, and cyanoacrylate UV absorbers. The above ultraviolet absorbers may be used alone or in combination of two or more.

The light stabilizer is not particularly limited, and examples thereof include hindered amine light stabilizers. The above light stabilizers may be used alone or in combination of two or more.

The filler is not particularly limited, and examples thereof include calcium carbonate and talc. The above-mentioned fillers may be used alone or in combination of two or more.

The above-mentioned pigment is not particularly limited, and includes organic pigments and inorganic pigments. Examples of the organic pigments include azo organic pigments, phthalocyanine organic pigments, threne organic pigments, and dye lake organic pigments. Examples of the inorganic pigments include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide/selenide-based inorganic pigments, and ferrocyanide-based inorganic pigments. The above pigments may be used alone or in combination of two or more.

The above plasticizer may be added for the purpose of improving processability during molding. The plasticizer is not particularly limited, and examples include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate. Only one type of the above plasticizer may be used, or two or more types may be used in combination.

(outer layer)
The outer layer includes an acrylic urethane resin. The acrylic urethane resin is a reaction product of an acrylic polyol compound and an isocyanate compound. The above-mentioned isocyanate compound includes a trimer isocyanate compound. An acrylic urethane resin can be obtained by reacting the acrylic polyol compound with the isocyanate compound. The above acrylic urethane resins may be used alone or in combination of two or more.

The outer layer containing the acrylic urethane resin is formed by, for example, applying an outer layer material containing an acrylic polyol compound and an isocyanate compound onto the outer surface of the inner layer, and causing the acrylic polyol compound and the isocyanate compound to react. be able to.

Acrylic polyol compound:
The acrylic polyol compound may include, for example, an ethylenically unsaturated bond-containing monomer having a hydroxyl group, alone or in a mixture, and another ethylenically unsaturated bond-containing monomer that can be copolymerized therewith, alone or in a mixture. Examples include compounds copolymerized with Examples of the ethylenically unsaturated bond-containing monomer having a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. It will be done. Only one kind of the above-mentioned acrylic polyol compound may be used, or two or more kinds thereof may be used in combination.

From the viewpoint of further improving weather resistance, the acrylic polyol compound is preferably hydroxyethyl acrylate or hydroxyethyl methacrylate.

The number average molecular weight of the acrylic polyol compound is preferably 4,000 or more, more preferably 4,500 or more, and preferably 20,000 or less, more preferably 19,000 or less. When the above-mentioned number average molecular weight is above the above-mentioned lower limit, the entanglement between molecules can be increased, the distance between crosslinking points of the obtained acrylic urethane resin can be increased, and the tensile elongation at break of the outer layer can be increased, resulting in , impact resistance can be further improved. When the above-mentioned number average molecular weight is below the above-mentioned upper limit, the viscosity of the outer layer material can be kept low, and the drying time after applying the outer layer material to the inner layer can be shortened, so production efficiency can be increased. In addition, the appearance of the multilayer pipe can be maintained in good condition.

The number average molecular weight of the acrylic polyol compound can be determined by gel permeation chromatography (GPC), molecular weight measurement between crosslinking points, solid state NMR method, or by extracting an isocyanate compound and analyzing it by ¹ H-NMR, ¹³ C-NMR, IR, It can be determined by analysis using GC, GC/MS, or GPC. When taking out the above isocyanate compound, cresol, which is the solvent of the decomposition mixture, is evaporated and removed, and the isocyanate compound precipitated as a solid is separated and recovered by centrifugation or filtration, or hexane, etc., which is a solvent in which the isocyanate compound is insoluble, is used. The polyol can be extracted and separated using The number average molecular weight of the acrylic polyol compound is preferably a number average molecular weight measured by gel permeation chromatography (GPC). When the acrylic urethane resin is hydrolyzed or decomposed with supercritical alcohol, the urethane bonds of the acrylic urethane resin are broken, so a monomer can be obtained.By identifying the obtained monomer, the molecule of the acrylic polyol compound can be obtained. The structure and number average molecular weight can be determined.

Isocyanate compound:
The above-mentioned isocyanate compound includes a trimer isocyanate compound (isocyanurate). The isocyanate compound which is a trimer has three isocyanate groups. By including the isocyanate compound which is a trimer, a three-dimensional network structure can be formed, and the adhesiveness between the inner layer and the outer layer can be further improved. The above-mentioned isocyanate compound may or may not contain an isocyanate compound (second isocyanate compound) other than the trimer isocyanate compound. The isocyanate compound may be a trimer isocyanate compound, or may be a mixture of a trimer isocyanate compound and a second isocyanate compound. The second isocyanate compound may be a diisocyanate compound having two isocyanate groups, or may be an isocyanate compound having four isocyanate groups. Only one kind of the above-mentioned isocyanate compound may be used, or two or more kinds thereof may be used in combination.

Examples of the above-mentioned isocyanate compounds include aliphatic isocyanate compounds, alicyclic isocyanate compounds, and aromatic isocyanate compounds. The above-mentioned isocyanate compound may be a diisocyanate compound or a polyisocyanate compound. Specifically, the above-mentioned isocyanate compounds include hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and bis(isocyanatomethyl). Aliphatic or alicyclic diisocyanate compounds such as cyclohexane (HXDI), tolylene diisocyanate (TDI), diphenylmethane isocyanate (MDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), diphenyl ether diisocyanate, tolidine diisocyanate, dianisidine diisocyanate, and aromatic diisocyanate compounds such as naphthalene diisocyanate (NDI), crude tolylene isocyanate (crude TDI), polymethylene polyphenylene polyisocyanate (polymeric MDI), triphenylmethane triisocyanate, and tris(phenylisocyanate) thiophosphate. Examples include aromatic polyisocyanate compounds and modified products of the above diisocyanate compounds. Examples of the above-mentioned modified products include isocyanurate modified products, Biuret modified products, carbodiimide modified products, and the like.

From the viewpoint of effectively suppressing discoloration to yellow when the multilayer pipe is installed outdoors and further improving weather resistance, the above-mentioned isocyanate compound is preferably an aliphatic isocyanate compound.

From the viewpoint of shortening the drying time after applying the outer layer material to the inner layer, the isocyanate compound is preferably an aromatic isocyanate compound.

The number average molecular weight of the isocyanate compound is not particularly limited as long as the above specific peak area ratio (X) is obtained when a sample obtained by treating the outer layer with cresol is measured by gel permeation chromatography.

The number average molecular weight of the above trimer isocyanate compound is preferably 6,000 or more, more preferably 9,000 or more, and preferably 21,000 or less, more preferably 18,000 or less. When the above-mentioned number average molecular weight is above the above-mentioned lower limit, the entanglement between molecules can be increased, the distance between crosslinking points of the obtained acrylic urethane resin can be increased, and the tensile elongation at break of the outer layer can be increased, resulting in , impact resistance can be further improved. Furthermore, when the number average molecular weight is equal to or greater than the lower limit, the adhesiveness between the inner layer and the outer layer can be improved. When the above-mentioned number average molecular weight is below the above-mentioned upper limit, the viscosity of the outer layer material can be kept low, and the drying time after applying the outer layer material to the inner layer can be shortened, so production efficiency can be increased. In addition, the appearance of the multilayer pipe can be maintained in good condition.

When the isocyanate compound contains an isocyanate compound (second isocyanate compound) other than the trimer isocyanate compound, the number average molecular weight of the trimer isocyanate compound is preferably 100 or more, more preferably It is 200 or more, preferably 1500 or less, more preferably 1000 or less. When the above-mentioned number average molecular weight is above the above-mentioned lower limit, the entanglement between molecules can be increased, the distance between crosslinking points of the obtained acrylic urethane resin can be increased, and the tensile elongation at break of the outer layer can be increased, resulting in , impact resistance can be further improved. When the above-mentioned number average molecular weight is below the above-mentioned upper limit, the viscosity of the outer layer material can be kept low, and the drying time after applying the outer layer material to the inner layer can be shortened, so production efficiency can be increased. In addition, the appearance of the multilayer pipe can be maintained in good condition.

The number average molecular weight of the above-mentioned isocyanate compound can be determined by analyzing the isocyanate compound by gel permeation chromatography (GPC), measuring the molecular weight between crosslinking points, solid-state NMR method, or by hydrolyzing the acrylic urethane resin or decomposing it with supercritical alcohol. It can be determined by extraction and analysis by ¹ H-NMR, ¹³ C-NMR, IR, GC, GC/MS, or GPC. When taking out the above isocyanate compound, cresol, which is the solvent of the decomposition mixture, is evaporated and removed, and the isocyanate compound precipitated as a solid is separated and recovered by centrifugation or filtration, or hexane, etc., which is a solvent in which the isocyanate compound is insoluble, is used. The polyol can be extracted and separated using The number average molecular weight of the isocyanate compound is preferably a number average molecular weight measured by gel permeation chromatography (GPC). In the hydrolysis or decomposition of the acrylic urethane resin with supercritical alcohol, the urethane bonds of the acrylic urethane resin are broken, so a monomer can be obtained.By identifying the obtained monomer, the molecular structure of the isocyanate compound can be determined. The number average molecular weight can be determined. However, in the hydrolysis of the acrylic urethane resin or the decomposition with supercritical alcohol, the trimeric isocyanate compound is decomposed into diisocyanate, so before measuring the molecular weight, solid-state NMR method, high-field NMR method, IR analysis, It is necessary to identify the structure by GC/MS, LC/MS, TOF-SIMS, or the like.

The molecular structure of the isocyanate compound used in the acrylic urethane resin can be analyzed by ¹ H-NMR, ¹³ C-NMR, IR measurement, and the like. Moreover, the molecular structure and number average molecular weight of the isocyanate compound can also be analyzed by analyzing the unreacted isocyanate compound contained in the acrylic urethane resin by thermal decomposition GCMS.

In the material for the outer layer, the content of the isocyanate compound is preferably 30 parts by weight or more, more preferably 40 parts by weight or more, and preferably 60 parts by weight or less, based on 100 parts by weight of the acrylic polyol compound. Preferably it is 50 parts by weight or less. When the content of the isocyanate compound is not less than the above lower limit and not more than the above upper limit, an acrylic urethane resin can be obtained satisfactorily, and the weather resistance and impact resistance of the multilayer pipe can be further improved.

In the acrylic urethane resin contained in the outer layer, the content of structural units derived from the isocyanate compound is preferably 30 parts by weight or more, more preferably The amount is 40 parts by weight or more, preferably 60 parts by weight or less, and more preferably 50 parts by weight or less. When the content of the structural unit derived from the isocyanate compound is not less than the above lower limit and not more than the above upper limit, the weather resistance and impact resistance of the multilayer pipe can be further improved.

Urethane catalyst:
The material for the outer layer preferably contains a urethanization catalyst. Examples of the urethanization catalyst include dibutyltin dilaurate, dibutyltin di(2-ethylhexoate), tin chloride, and tetra-n-butyltin.

From the viewpoint of increasing reactivity, the urethanization catalyst is preferably dibutyltin dilaurate.

With respect to 100 parts by weight of the acrylic polyol compound contained in the material of the outer layer, the content of the urethanization catalyst is preferably 0.01 parts by weight or more, and preferably 0.5 parts by weight or less. When the content of the urethanization catalyst is equal to or higher than the lower limit, the drying time after applying the outer layer material to the inner layer can be shortened. When the content of the urethanization catalyst is at most the above upper limit, manufacturing costs can be suppressed.

<Pigment>
From the viewpoint of further improving weather resistance, the outer layer and the material of the outer layer preferably contain a pigment. Examples of the pigments include colored pigments, extender pigments, aluminum flakes, and the like. The above pigments may be used alone or in combination of two or more.

From the viewpoint of further improving weather resistance, the pigment is preferably an inorganic pigment.

Examples of the inorganic pigments include zinc oxide, cobalt oxide, iron oxide, carbon black, antimony oxide, titanium oxide, chromium oxide, lead chromate, molybdate sulfate, calcium carbonate, and zinc sulfide.

The inorganic pigment preferably contains titanium oxide from the viewpoint of effectively suppressing heat generation of the pigment due to absorption of light and effectively suppressing deterioration of the outer layer.

The average particle size of the inorganic pigment is preferably 100 nm or more, more preferably 120 nm or more, and preferably 800 nm or less, more preferably 750 nm or less. When the average particle size of the inorganic pigment is equal to or larger than the lower limit, weather resistance can be further improved, and mechanical properties can be maintained favorably over a long period of time. When the average particle size of the inorganic pigment is below the above upper limit, weather resistance and impact resistance can be further improved.

The average particle size of the above-mentioned inorganic pigment indicates the number average particle size. The average particle diameter of the inorganic pigment can be determined, for example, by laser diffraction particle size distribution measurement.

<Solvent>
The material for the outer layer preferably contains a solvent from the viewpoint of increasing the adhesiveness between the inner layer and the outer layer, increasing the applicability, and disposing the outer layer favorably on the outer surface of the inner layer. For example, the outer layer can be formed by applying a material for the outer layer containing a solvent onto the outer surface of the inner layer and then volatilizing the solvent. The above solvents may be used alone or in combination of two or more.

The solvent is preferably an organic solvent from the viewpoint of further increasing the adhesiveness between the inner layer and the outer layer and from the viewpoint of further increasing the coating property.

Examples of the organic solvents include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and ester solvents such as ethyl acetate, n-butyl acetate, and cellosolve acetate. Can be mentioned.

From the viewpoint of further increasing the adhesiveness between the inner layer and the outer layer and from the viewpoint of increasing the impact resistance, the organic solvent is preferably n-butyl acetate.

<Other ingredients>
The material of the outer layer may contain, for example, a leveling agent, an anti-settling agent, etc., if necessary.

From the viewpoint of improving the applicability and disposing the outer layer well on the outer surface of the inner layer, the viscosity of the material for the outer layer at 20 ° C. is preferably 25 mPa s or more, more preferably 35 mPa s or more, and preferably is 75 mPa·s or less, more preferably 60 mPa·s or less. Furthermore, if the viscosity is within the above range, the material for the outer layer can be easily applied by spray coating.

The viscosity of the outer layer material at 20° C. is measured using an Iwata cup.

(Other details of multilayer pipe)
The multilayer pipe may have a two-layer structure of the inner layer and the outer layer, or may have a three or more layer structure. Preferably, the outer layer is the outermost layer of the multilayer tube. The inner layer may be the innermost layer of the multilayer pipe, or may be a layer other than the innermost layer.

The multilayer pipe may be a straight pipe or a pipe having a bending angle. Examples of the tube having the above bending angle include a T-shaped tube and an L-shaped tube.

The multilayer pipe may be a joint.

In the present invention, when a sample obtained by treating the outer layer with cresol is measured by gel permeation chromatography (GPC), an isocyanate compound that appears as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound. The ratio of the peak area derived from is 10% or more and 90% or less.

By treating the outer layer with cresol, the acrylic urethane resin contained in the outer layer is decomposed into an acrylic polyol compound and an isocyanate compound. Furthermore, by treating the outer layer with cresol, multimeric isocyanate compounds such as trimers are decomposed into monomeric isocyanate compounds. Therefore, when a sample obtained by treating the outer layer with cresol is measured by gel filtration chromatography, a peak of a monomeric isocyanate compound is detected as a "peak derived from an isocyanate compound."

The ratio (X) of the peak area derived from the isocyanate compound appearing as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound is preferably 20% or more, and preferably 80% or less. When the ratio (X) of the peak area is equal to or higher than the lower limit, the isocyanate compounds are well entangled with each other, and an acrylic urethane resin having a long distance between crosslinking points is obtained, thereby increasing the tensile elongation at break of the outer layer. be able to. As a result, impact resistance can be further improved. When the ratio (X) of the peak area is equal to or less than the upper limit, the appearance of the multilayer pipe can be kept good.

The peak derived from the isocyanate compound appearing as a molecular weight of 2,000 or more and 7,000 or less preferably contains a monomeric isocyanate compound obtained by decomposing the trimer isocyanate compound.

Gel permeation chromatography (GPC) can be measured, for example, by the method described in Examples.

The first tensile elongation at break of the inner layer at 0° C. and 500 mm/min is preferably 30% or more, more preferably 40% or more, even more preferably 45% or more, and preferably 80% or less, More preferably it is 70% or less, still more preferably 60% or less. When the first tensile elongation at break is not less than the lower limit and not more than the upper limit, the impact resistance can be further improved.

The second tensile elongation at break of the multilayer pipe at 0° C. and 500 mm/min is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and preferably 80% or less, More preferably it is 60% or less, still more preferably 55% or less. When the second tensile elongation at break is equal to or higher than the lower limit, the impact resistance and flatness can be improved. When the second tensile elongation at break is below the upper limit, even if the multilayer pipe is used as a joint in a place with relatively high temperatures, stress concentration on the joint due to heat shrinkage etc. can be suppressed, Cracks or cracks in multilayer pipes can be suppressed.

The first tensile elongation rate at break and the second tensile elongation rate at break are more specifically determined in accordance with JIS K6815 under conditions of 0° C. and 500 mm/min.

It is preferable that the first tensile elongation at break and the second tensile elongation at break are the same, or the first tensile elongation at break is larger than the second tensile elongation at break. In this case, even if the multilayer tube is deformed by an external impact, the outer layer can follow the deformation of the inner layer well, so that the impact resistance can be improved.

From the viewpoint of improving impact resistance and flatness, the absolute value of the difference between the first tensile elongation at break and the second tensile elongation at break is preferably 20% or less, more preferably 10% or less, More preferably, it is 5% or less. The absolute value of the difference between the first tensile elongation at break and the second tensile elongation at break is preferably small.

In order to increase the adhesion between the inner layer and the outer layer and to prevent the outer layer from peeling off after the multilayer pipe is installed, for example, the multilayer pipe has a bond between the inner layer and the above layer in accordance with JIS K5600-5-6. When an adhesion test with the outer layer is conducted by a cross-cut method, the result of the adhesion test is preferably Class 0 or Class 1, most preferably Class 0.

JIS K5600-5-6 stipulates six classifications, Class 0 to Class 5, as the results of adhesion tests. The closer the classification is to 0, the better the adhesion is.

From the viewpoint of effectively suppressing sunlight etc. from reaching the inner layer and further improving weather resistance, the total light transmittance in the thickness direction of the outer layer is preferably 50% or less, more preferably 40% or less, and Preferably it is 30% or less.

The outer layer for measuring the total light transmittance may be obtained by cutting out the outer layer from the multilayer tube, or by molding the material of the outer layer to produce a layer having the same thickness as the outer layer in the multilayer tube. It's okay.

The above-mentioned total light transmittance is measured in accordance with JIS K7361-1.

From the viewpoint of practical use, the thickness of the multilayer pipe is preferably 2 mm or more, more preferably 4 mm or more, and preferably 15 mm or less, more preferably 12 mm or less.

From the viewpoint of practical use and the viewpoint of further improving weather resistance, the thickness of the inner layer is preferably 1 mm or more, more preferably 4 mm or more, and preferably 14.5 mm or less, more preferably 13 mm or less.

From the viewpoint of practical use and the viewpoint of further improving weather resistance, the thickness of the outer layer is preferably 0.01 mm or more, more preferably 0.1 mm or more, and preferably 1 mm or less, more preferably 0.5 mm. It is as follows. In particular, when the thickness of the outer layer is equal to or greater than the lower limit, weather resistance can be improved. In particular, when the thickness of the outer layer is equal to or less than the above upper limit, the appearance can be improved.

(Manufacturing method of multilayer pipe)
Examples of the method for manufacturing the multilayer pipe include a method of forming the outer layer by applying a material for the outer layer onto the outer surface of the inner layer. An outer layer can be formed on the outer surface of the inner layer by drying the outer layer material applied on the outer surface of the inner layer. The outer layer is preferably a coating film.

Examples of the method for applying the material for the outer layer include spray application, application by brush, and the like.

The method for applying the material for the outer layer is preferably spray coating. By spray-coating the outer layer material onto the outer surface of the inner layer, the outer layer can be easily and uniformly disposed on the outer surface of the inner layer, for example, even if the inner layer has a complicated shape. As a result, a multilayer pipe with excellent weather resistance and impact resistance can be obtained. In addition, the above-mentioned spray coating can shorten the construction time and reduce the construction cost.

The coating thickness of the material for the outer layer is preferably 0.01 mm or more, more preferably 0.1 mm or more, and preferably 1 mm or less, more preferably 0.5 mm or less. When the coating thickness is not less than the lower limit and not more than the upper limit, the thickness of the outer layer can be well controlled within the preferable range, and the weather resistance can be further improved. Furthermore, when the coating thickness is below the upper limit, dripping during coating can be suppressed, the solvent can be volatilized well, and peeling of the outer layer can be effectively suppressed.

In the material for the outer layer containing the acrylic polyol compound and the isocyanate compound, the acrylic urethane resin may be synthesized before being applied to the outer surface of the inner layer or after being applied to the outer surface of the inner layer. good.

Hereinafter, the present invention will be explained in more detail with reference to Examples. The present invention is not limited only to the following examples.

The following was prepared as the inner layer.

Straight pipe 1: "Eslon normal VP pipe" manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Straight pipe 2: “Eslon normal VU pipe” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Straight pipe 3: “Eslon HI pipe” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Fitting body 1: “Eslon TS socket fitting” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Joint body 2: “Eslon TS elbow joint” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Fitting body 3: “Eslon TS cheese fitting” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Joint body 4: “Eslon DV socket joint” manufactured by Sekisui Chemical Co., Ltd., diameter 50A
Joint body 5: "Eslon TSHI socket joint" manufactured by Sekisui Chemical Co., Ltd., diameter 50A

Note that the straight pipes 1 and 2 and the joint bodies 1 to 5 contain hard vinyl chloride resin. Further, the straight pipe 3 includes an acrylic grafted hard vinyl chloride resin.

The following materials were prepared for the outer layer.

(Acrylic polyol compound)
"High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. (contains an acrylic polyol compound with a number average molecular weight of 10,000)
"Milano 2K Como Clear Hi" manufactured by Isamu Paint Co., Ltd. (contains an acrylic polyol compound with a number average molecular weight of 10,000)

Note that "High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. contains 50% by weight of titanium oxide (average particle size 600 nm) in 100% by weight of the product.

(Isocyanate compound)
"Multi Softner" manufactured by Isamu Paint Co., Ltd. (contains a trimer isocyanate compound with a number average molecular weight of 15,000)
"High Art CB Eco Hardener Standard" manufactured by Isamu Paint Co., Ltd. (contains a trimer isocyanate compound with a number average molecular weight of 300)
Hexamethylene diisocyanate (manufactured by Tokyo Kasei Kogyo Co., Ltd.), number average molecular weight 170

(Urethanization catalyst)
Tin catalyst: “Urethane drying accelerator” manufactured by Isamu Paint Co., Ltd.

(solvent)
Normal butyl acetate: “High Art CB Eco Thinner” manufactured by Isamu Paint Co., Ltd.

(Inorganic pigment)
Titanium oxide (average particle size 80 nm)
Titanium oxide (average particle size 1200nm)

(Example 1)
A joint body 1 was prepared as the inner layer.

The following components were mixed at 23° C. in the following blending ratio to obtain a material for the outer layer.

"High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. 100 parts by weight "Multi Softener" manufactured by Isamu Paint Co., Ltd. 40 parts by weight "High Art CB Eco Thinner" manufactured by Isamu Paint Co., Ltd. 35 parts by weight "Urethane drying accelerator" manufactured by Isamu Paint Co., Ltd. 0.5 parts by weight

Incidentally, "High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. contains titanium oxide (average particle size 600 nm) as described above.

The obtained outer layer material was spray applied to the entire outer surface of the joint body 1 using "TPU-65-0025-SS" manufactured by Spraying System Japan LLC under conditions of a spray pressure of 0.2 MPa and 23°C. did. After spray coating, it was dried at 60° C. for 30 minutes, n-butyl acetate (solvent) was volatilized, and the acrylic polyol compound and isocyanate compound were reacted to form an outer layer containing an acrylic urethane resin. Note that the thickness of the outer layer was 0.03 mm. In this way, a multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained.

(Examples 2 to 5)
A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1, except that the inner layer shown in Table 1 was used.

(Example 6, 7)
A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1 except that the thickness of the outer layer was changed.

(Examples 8 to 10)
A multilayer tube including an inner layer and an outer layer was obtained in the same manner as in Example 1 except that the inner layer shown in Table 2 was used.

(Example 11)
The following components were mixed at 23° C. in the following blending ratio to obtain a material for the outer layer.

"Milano 2K Como Clear Hi" manufactured by Isamu Paint Co., Ltd. 100 parts by weight "Multi Softener" manufactured by Isamu Paint Co., Ltd. 40 parts by weight "High Art CB Eco Thinner" manufactured by Isamu Paint Co., Ltd. 35 parts by weight "Urethane drying accelerator" manufactured by Isamu Paint Co., Ltd. 0 .5 parts by weight Titanium oxide (average particle size 80 nm) 20 parts by weight

A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1, except that the obtained material for the outer layer was used.

(Example 12)
The following components were mixed at 23° C. in the following blending ratio to obtain a material for the outer layer.

"Milano 2K Como Clear Hi" manufactured by Isamu Paint Co., Ltd. 100 parts by weight "Multi Softener" manufactured by Isamu Paint Co., Ltd. 40 parts by weight "High Art CB Eco Thinner" manufactured by Isamu Paint Co., Ltd. 35 parts by weight "Urethane drying accelerator" manufactured by Isamu Paint Co., Ltd. 0 .5 parts by weight Titanium oxide (average particle size 1200 nm) 20 parts by weight

A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1, except that the obtained material for the outer layer was used.

(Comparative example 1)
The joint body 1 itself was used.

(Comparative example 2)
The following components were mixed at 23° C. in the following blending ratio to obtain a material for the outer layer.

``High Art CB Eco White'' manufactured by Isamu Paint Co., Ltd. 100 parts by weight ``High Art CB Eco Hardener Standard'' manufactured by Isamu Paint Company 20 parts by weight ``High Art CB Eco Thinner'' manufactured by Isamu Paint Co., Ltd. 35 parts by weight ``Urethane drying'' manufactured by Isamu Paint Co. Accelerator” 0.5 part by weight

Incidentally, "High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. contains titanium oxide (average particle size 600 nm) as described above.

A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1, except that the obtained material for the outer layer was used.

(Comparative Examples 3 and 4)
A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as Comparative Example 2, except that the inner layer shown in Table 3 was used.

(Comparative Examples 5 to 7)
A multilayer tube including an inner layer and an outer layer was obtained in the same manner as Comparative Example 2 except that the inner layer shown in Table 3 was used.

(Comparative example 8)
The following components were mixed at 23° C. in the following blending ratio to obtain a material for the outer layer.

100 parts by weight of "Hi-Art CB Eco White" manufactured by Isamu Paints 10 parts by weight of hexamethylene diisocyanate 35 parts by weight of "Hi-Art CB Eco Thinner" manufactured by Isamu Paints 0.5 parts by weight of "Urethane drying accelerator" manufactured by Isamu Paints

Incidentally, "High Art CB Eco White" manufactured by Isamu Paint Co., Ltd. contains titanium oxide (average particle size 600 nm) as described above.

A multilayer pipe (joint) comprising an inner layer (joint body) and an outer layer was obtained in the same manner as in Example 1, except that the obtained material for the outer layer was used.

(evaluation)
(1) Ratio of peak area derived from isocyanate compounds appearing as molecular weights of 2000 to 7000 (X)

Cresol treatment:
The outer layer was cut from the obtained multilayer tube. 5 g of the obtained outer layer and 60 g of cresol were mixed, heated in a nitrogen atmosphere, heated to 204° C., and kept at 204° C. for 4 hours to react. Then, the reaction mixture was cooled to room temperature to precipitate a solid. The cresol was then evaporated at 100° C. and 0.2 mbr to obtain a solid.

Measurement by gel permeation chromatography:
The obtained solid was dissolved in tetrahydrofuran (THF) so that the content in the sample was 0.2% by weight. The obtained sample was measured by gel permeation chromatography (GPC) under the following conditions. Based on the obtained peaks, the ratio (X) of the peak area derived from the isocyanate compound appearing as a molecular weight of 2000 to 7000 in 100% of the peak area derived from the isocyanate compound was determined. Note that the molecular weight was calculated by creating a calibration curve using standard polystyrene.
Equipment: “ACQUITY APC system wasiyosi” manufactured by Waters
Column: “HSPgel HR MB-M” manufactured by Waters (particle size 3.5 μm, 6.0 mm x 150 mm)
Column temperature: 40℃
Flow rate: 0.5mL/min
Injection volume: 10.0μL

(2) Tensile elongation at break The outer layer of the obtained multilayer tube was ground with a grinder to obtain an inner layer. The tensile elongation rate at break of the inner layer (first tensile elongation rate at break) and the tensile elongation rate at break (second tensile elongation rate at break) of the multilayer pipe were measured using a tensile tester (Shimadzu Corporation's "Tabletop Precision Universal Testing Machine"). AGX-X") under the conditions of 0° C. and 500 mm/min in accordance with JIS K6815.

(3) Adhesion test between inner layer and outer layer (adhesion between inner layer and outer layer)
Regarding the obtained multilayer tube, an adhesion test between the inner layer and the outer layer was conducted by a cross-cut method in accordance with JIS K5600-5-6. Specifically, it was performed as follows. The obtained multilayer tube was cut into a size of 150 mm x 100 mm to obtain a test sample. A total of 7 cuts were made in the outer layer of the test sample at 2 mm intervals using a utility knife with a 20 degree blade and a spacer. Next, a similar operation was performed on this cut at 90 degrees to form a lattice pattern. A transparent pressure-sensitive adhesive tape with an adhesion strength of 10 N per 25 mm x 25 mm was applied to the formed grid pattern area and then pulled away at an angle of 60 degrees and in 0.5 seconds to 1.0 seconds. The number of peeled outer layers from the grid pattern was counted and classified according to the classification of test results described in JIS K5600-5-6.

[Judgment criteria for adhesion test]
○: Classification 0 or Classification 1
×: Category 2, Category 3, Category 4 or Category 5

(4) Weather resistance test (color difference)
The obtained multilayer tube was subjected to a weather resistance test for 800 hours under the following conditions. As a weather resistance tester, "METAL WEATHER" manufactured by Daipura Intes was used.

[Weather resistance test conditions]
Driving mode: L+D
L: Irradiation intensity 75 mW/cm ² , black panel temperature 50°C, humidity 50%, 4 hours D: No irradiation, black panel temperature 30°C, humidity 98%, 4 hours Shower: 30 seconds before and after D

The L, a, and b values of the multilayer tube before and after the weather resistance test were measured in accordance with JIS-Z8730 using a color difference meter "NR-300" manufactured by Nippon Denshoku Industries. The color difference was determined by the following formula from the L, a, b values of the multilayer tube before the weather resistance test and the L, a, b values of the multilayer tube after the weather resistance test. Weather resistance test (color difference) was evaluated based on the following criteria.

ΔE = [(ΔL) ² + (Δa) ² + (Δb) ² ] ^1/2

[Judgment criteria for weatherability test (color difference)]
○: ΔE is 5 or less △: ΔE is more than 5 and 12 or less ×: ΔE is more than 12

(5) Falling weight impact test (50% impact fracture height)
The inner layer used and the obtained multilayer pipe were subjected to a falling weight impact test (resistance) at 0°C using a flat-bottomed weight weighing 3 kg in accordance with JIS K6742 Annex JA and JIS K6743 Annex JA. Impact test) was conducted. From the measurement results, the 50% impact fracture height was calculated in accordance with JIS K7211. As a falling weight tester, "FALLING DART IMPACT TESTER" manufactured by Yasuda Seiki Seisakusho Co., Ltd. was used.

Furthermore, the retention rate of the 50% impact fracture height of the multilayer pipe was calculated according to the following formula.

Retention rate of 50% impact rupture height of multilayer pipe (%) = (50% impact rupture height of multilayer pipe (cm)/50% impact rupture height of inner layer (cm)) x 100

[Judgment criteria for falling weight impact test (50% impact fracture height)]
○: Retention rate of 50% impact rupture height of multilayer pipe is 70% or more ×: Retention rate of 50% impact rupture height of multilayer pipe is less than 70%

(6) Impact strength retention rate The multilayer pipe after the weather resistance test obtained in the above weather resistance test (color difference) was subjected to 50% impact fracture in the same manner as the above falling weight impact test (50% impact fracture height). I asked for height. The impact strength retention rate was determined from the 50% impact fracture height of the multilayer pipe before and after the weather resistance test, according to the following formula.

Impact strength retention rate (%) = (50% impact failure height (cm) of multilayer pipe after weather resistance test/50% impact failure height (cm) of multilayer pipe before weather resistance test) x 100

[Criteria for determining impact strength retention rate]
○: Impact strength retention rate is 50% or more △: Impact strength retention rate is 25% or more and less than 50% ×: Impact strength retention rate is less than 25%

(7) Total light transmittance in the thickness direction of the outer layer The outer layer material used was applied onto a PTFE sheet to produce coating films with thicknesses of 0.05 mm, 0.10 mm, and 0.20 mm. In addition, since the thickness of each obtained coating film varied by ±0.005 mm, the accurate thickness was measured with a micrometer.

The total light transmittance of the resulting coating film was measured using "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1. On a semi-logarithmic graph, the thickness of the coating film was plotted on the horizontal axis and the total light transmittance was plotted on the vertical axis, and the slope of the obtained approximate straight line was taken as the constant A. The total light transmittance in the thickness direction of the outer layer (the outer layer having the same thickness as the outer layer in the obtained multilayer tube) was calculated according to the following formula. Note that the smaller the total light transmittance, the better the weather resistance of the multilayer tube.

Total light transmittance (%) in the thickness direction of the outer layer = 100 x exp (-A x T)
T: Thickness of outer layer (mm)

[Judgment criteria for total light transmittance in the thickness direction of the outer layer]
○: Total light transmittance in the thickness direction of the outer layer is 50% or less △: Total light transmittance in the thickness direction of the outer layer is more than 50% and 80% or less ×: Total light transmittance in the thickness direction of the outer layer exceeds 80%

The configuration of the multilayer tube and the results are shown in Tables 1 to 3 below.

1...Inner layer 2...Outer layer 11...Multilayer pipe

Claims (4)

an inner layer containing vinyl chloride resin;
an outer layer disposed on the outer surface of the inner layer and containing an acrylic urethane resin,
The acrylic urethane resin is a reaction product of an acrylic polyol compound and an isocyanate compound,
The isocyanate compound includes a trimer isocyanate compound,
When the sample obtained by treating the outer layer with cresol is measured by gel permeation chromatography, the peak area derived from the isocyanate compound that appears as a molecular weight of 2000 to 7000 out of 100% of the peak area derived from the isocyanate compound. A multilayer pipe in which the ratio is 10% or more and 90% or less. The first tensile elongation at break of the inner layer at 0° C. and 500 mm/min is 30% or more and 80% or less,
The second tensile elongation at break of the multilayer pipe at 0° C. and 500 mm/min is 30% or more and 80% or less,
The absolute value of the difference between the first tensile elongation at break and the second tensile elongation at break is 20% or less,
Claim 1, wherein when an adhesion test between the inner layer and the outer layer is conducted by a cross-cut method in accordance with JIS K5600-5-6, the result of the adhesion test is Class 0 or Class 1. The multilayer tube described in . the outer layer contains an inorganic pigment,
The multilayer tube according to claim 1 or 2, wherein the inorganic pigment has an average particle size of 100 nm or more and 800 nm or less. The multilayer pipe according to any one of claims 1 to 3, wherein the outer layer has a thickness of 0.01 mm or more and 0.25 mm or less.

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