JP6546433B2 - Multilayer piping - Google Patents

Description

  The present invention relates to multilayer tubes. More specifically, the present invention relates to low linear expansion multilayer piping.

For various purposes, multilayer tubes have been developed in which multiple layers are stacked.
For example, Japanese Patent Application Laid-Open No. 2006-327154 (Patent Document 1) is a polyolefin resin main pipe as a polyolefin resin pipe embedded water pipe which can reliably prevent the penetration of harmful substances such as organic solvents and oils in the ground. Discloses a polyolefin resin pipe coated with a non-woven fabric made of polyester fiber, polyamide fiber, polypropylene fiber fiber, woven fabric, and a tape-like protective layer impregnated with a compound using felt as a porous base on the outer surface of .

  Further, in JP 2007-216555 A (patent document 2), as a fiber-reinforced synthetic resin pipe excellent in strength and workability, an organic non-woven fabric layer, a glass cloth layer, a horizontally wound fiber layer, a longitudinal direction from the inner peripheral side There is disclosed a fiber reinforced synthetic resin pipe provided with a fiber reinforced resin layer of six layers in the order of a direction fiber layer, a transverse wound fiber layer and an organic non-woven layer.

JP, 2006-327154, A JP 2007-216555 A

  However, the polyolefin resin pipe described in JP-A-2006-327154 (Patent Document 1) only has a thin tape-like protective layer applied to the outer peripheral surface of the polyolefin resin main pipe, so low linear expansion performance It is inferior to. Furthermore, it is necessary to prepare a compound impregnated base tape for applying a protective layer separately from the production of the polyolefin resin main.

  In the fiber-reinforced rigid resin pipe described in JP-A-2007-216555 (Patent Document 2), it is necessary to prepare various types of special fiber materials of various aspects in order to constitute each layer.

  Therefore, an object of the present invention is to provide a multilayer tube having low linear expansion performance and configured without requiring a special material.

In order to achieve the above object of the present invention, the present invention includes the following inventions.
(1)
In the multilayer piping of the present invention, at least a first layer, a second layer and a third layer are stacked in the direction from the axis to the outer periphery. The first layer and the third layer are resin layers composed mainly of a polyolefin resin. The second layer is a fiber reinforced resin layer containing a polyolefin resin and glass fibers, and an alignment layer in which the glass fibers are oriented in the direction along the axis.

  Thus, by including the axial orientation layer in the second layer, it has low linear expansion performance. Furthermore, a special material is not required by being comprised by the 1st layer and 3rd layer which have polyolefin resin as a main component, and the 2nd layer of a fiber reinforced resin layer.

  In the above (1), the first layer and the third layer substantially do not contain fibers. In addition, “the glass fibers are oriented in the direction along the axis” is a direction of at least 50%, preferably at least 70%, of the fibers having a length of 10% or more of the average fiber length of the glass fibers Is within ± 15 ° with respect to the axial direction.

(2)
The ratio of the cross-sectional area occupied by the alignment layer to the cross-sectional area occupied by the entire second layer may be 20% or more and 100% or less in the cross section when the multilayer pipe is cut at a plane including the axial center.

This configuration provides more preferable low linear expansion performance.
In the present specification, the ratio of the cross-sectional area occupied by the alignment layer to the cross-sectional area occupied by the entire second layer may be described as the ratio of the alignment area.

(3)
The second layer may further include a non-oriented layer in which glass fibers are not oriented.

  By this configuration, low linear expansion performance and pressure resistance performance are compatible.

(4)
The fiber length of the glass fiber may be 0.01 mm or more and 10.0 mm or less.

  This configuration facilitates the manufacture of a laminated structure. For example, coextrusion is easy. Furthermore, in the embodiment having the non-oriented layer, it is easy to prevent the fibers from being in the axial direction, so the production of the non-oriented layer is also facilitated.

(5)
The thickness of the second layer may be greater than the thickness of the first layer and the thickness of the third layer.

  With this configuration, low linear expansion performance can be obtained more effectively. In addition, when the second layer includes a non-orientation layer, low linear expansion performance and pressure resistance performance can be more effectively obtained.

(6)
The ratio of the thickness of the second layer to the total thickness of the multilayer pipe may be 50% or more and 80% or less.

  With this configuration, low linear expansion performance can be obtained more effectively. In addition, when the second layer includes a non-orientation layer, low linear expansion performance and pressure resistance performance can be more effectively obtained.

It is a typical sectional view at the time of cutting a multilayer piping of one embodiment of the present invention by a field perpendicular to an axial center. It is a typical expanded sectional view at the time of cut | disconnecting to an axial center direction with the AA of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same elements are denoted by the same reference numerals, and the names and functions thereof are also the same. Therefore, detailed description about them will not be repeated.

[Multilayer piping]
(Basic configuration)
FIG. 1 is a schematic cross-sectional view of a multilayer pipe according to an embodiment of the present invention cut along a plane perpendicular to the axial center. FIG. 2 is a schematic enlarged cross-sectional view in the case of cutting in the axial direction along the line A-A in FIG. 1 (that is, in the case of cutting in a plane including the axial center).
A multilayer pipe 100 shown in FIG. 1 is a pipe used as a hot and cold water pipe, a cold water pipe, a hot water pipe, a water distribution pipe such as a water and sewage pipe, and a steam pipe. In the multilayer pipe 100, a first layer 110, a second layer 120, and a third layer 130 are stacked in the direction from the axis O to the outer periphery. The first layer 110, the second layer 120 and the third layer 130 may be, for example, co-extruded layers. An adhesive layer or the like may be interposed between the respective layers. The multilayer piping 100 may further include one or more other layers. The second layer 120 includes an alignment layer 121 and a non-alignment layer 122.

(Low linear expansion performance)
The multilayer pipe 100 has low linear expansion performance by including the orientation layer 121 in the second layer 120. Specifically, the linear expansion coefficient of the entire multilayer piping 100 is, for example, less than 10 × 10 ⁻⁵ / ° C., preferably 8.0 × 10 ⁻⁵ / ° C. or less, more preferably 5.5 × 10 ^−5. / ° C. or less, more preferably 4.0 × 10 ⁻⁵ / ° C. or less. The lower limit value in the allowable linear expansion coefficient range is not particularly limited, but may be, for example, 2.0 × 10 ⁻⁵ / ° C., or 2.7 × in view of compatibility with pressure resistance. 10 ⁻⁵ / ° C. is preferred.

  The linear expansion coefficient is determined by the following method. The tube molded body is cut into an arbitrary length and aged for 24 hours in a thermostatic bath set to an arbitrary temperature (Thot). After curing, the length of the tube is measured (Lhot). Thereafter, the same formed tube is aged for 24 hours in a constant temperature bath set to an arbitrary temperature (Tcool) lower than Thot, and the length of the formed tube is measured (Lcool). The obtained value is substituted into the following equation 1 to determine the linear expansion coefficient.

(Pressure resistance)
The multilayer pipe 100 is provided with pressure resistance as well as the low linear expansion performance described above by combining the non-alignment layer 122 with the alignment layer 121. The pressure resistance may be measured by a breaking water pressure test. Specifically, for example, it is 4.7 MPa or more, preferably 4.9 MPa or more, more preferably 5.0 MPa or more. The upper limit value in the allowable pressure resistance range is, for example, 6.5 MPa, preferably 6 MPa, but in view of compatibility with low linear expansion performance, it is more preferably 5.8 MPa.

  In addition, the fracture water pressure test can conform to the PWA (polyethylene pipe system study group standard for building equipment) 001 standard, and the inside temperature of the test piece of the multilayer pipe 100 having a length of 1000 mm or more (for example, a length of 1000 mm) The pressure resistance can be evaluated by the water pressure when the multilayer piping 100 is ruptured by filling the water at 25 ° C. and continuously adding water at a constant rate.

  The multilayer piping 100 is particularly useful as a hot and cold water pipe because the low linear expansion performance and the pressure resistance are compatible as described above.

[Layer 1 and layer 3]
The first layer 110 and the third layer 130 are resin layers mainly composed of the same polyolefin resin. Therefore, mechanical properties are uniform on both sides of the second layer 120, and the manufacturing efficiency of the multilayer pipe 100 is also good. The present invention does not exclude that the first layer 110 and the third layer 130 are made of different polyolefin resins.

  It does not specifically limit as polyolefin resin. For example, polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer and the like can be mentioned. From the viewpoint of improving the strength of the molded article and the elongation of the molded article at high temperature, polyethylene or polypropylene is preferable, and polyethylene is more preferable.

Furthermore, as polyethylene (PE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and the like can be mentioned. Examples of polypropylene (PP) include homoPP, block PP and random PP. As polybutene, polybutene-1 etc. are mentioned. The ethylene-α-olefin copolymer is composed of several mol% of α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene with respect to ethylene. It is preferable that it is a copolymer copolymerized in the ratio of
One of these polyolefin resins may be used alone, or two or more thereof may be used in combination.

  The first layer 110 and the third layer 130 do not contain fibers as in the second layer 120 described later. The first layer 110, which is the inner layer, coats the inner circumferential surface of the second layer 120 so that the water contained in the second layer 120 does not mix with the water flowing inside the multilayer piping 100. In addition, the third layer 130 can ensure the ease of fusion bonding with the joint, for example, when the multilayer pipe 100 is fusion-bonded with the joint by electrofusion bonding or the like.

  In addition to the above, the first layer 110 and the third layer 130 may contain a compatibilizer and other components in the same manner as the second layer 120 described later. However, the fibers contained in the second layer 120 described later are not substantially contained.

[The second layer]
The second layer 120 is a fiber reinforced resin layer containing a matrix resin and fibers. In the present embodiment, the second layer 120 is composed of the laminated alignment layer 121 and non-alignment layer 122.

(Alignment layer)
In the orientation layer 121, the fibers are oriented in the direction along the axis O. Therefore, it is easy to visually distinguish from the non-alignment layer. Specifically, among fibers having a length of 10% or more of the average fiber length of the fibers, the direction of at least 50%, preferably at least 70% is within ± 15 ° with respect to the axial O direction. It fits. By including such an orientation layer 121, the multilayer piping 100 has good low linear expansion performance.

The alignment layer 121 may be configured to occupy a cross-sectional area of 20% or more and less than 100% of the cross-sectional area of the entire second layer 120 in the cross section of FIG. When the orientation area ratio is 20% or more, preferable low linear expansion performance can be obtained. From the viewpoint of obtaining the low linear expansion performance more effectively, the orientation area ratio is preferably 35% or more.
When the alignment layer 121 is combined with the non-alignment layer 122 as in the present embodiment, the upper limit within the cross-sectional area range of the alignment layer 121 to the cross-sectional area of the entire second layer 120 is the pressure resistance. In consideration of coexistence, for example, 90% is preferable.

  In addition, the orientation aspect of a fiber can be confirmed by observing a cross section, for example using a scanning electron microscope. The observation conditions are not particularly limited, but observation may be conducted at a deposition thickness of 10 nm, an acceleration voltage of 15 kV and a magnification of 25 using a scanning electron microscope JSM-6701F manufactured by JEOL.

(Non-alignment layer)
In the non-alignment layer 122, there is no orientation of glass fibers as in the orientation layer 121. It is preferable that the number of fibers in the non-oriented layer 122 be such that the fiber direction is the axial O direction. Specifically, the fiber directions of the glass fibers in the non-oriented layer 122 are random and arbitrary. For this reason, the number of fibers in which the fiber direction is in the axial center O direction is significantly smaller than that of the alignment layer 121. By combining such non-oriented layers 122, the multilayer piping 100 is provided with pressure resistance as well as low linear expansion performance.

  The boundary between the non-alignment layer 122 and the alignment layer 121 can be visually confirmed when the cross section is observed using, for example, a scanning electron microscope.

(Matrix resin)
The matrix resin is a polyolefin resin. Specific examples of the polyolefin-based resin are the same as those listed as constituent resins of the first layer 110 and the third layer 130. The matrix resin of the second layer 120 may be the same as or different from the resin constituting the first layer 110 and the second layer 120, but the matrix resin of the first layer 110, the second layer 120 and the third layer 130 When the same resin is used for all the layers, adjacent layers are preferable because they can easily conform to each other and interface peeling can be effectively suppressed.

(fiber)
Glass fibers are used as fibers from the viewpoint of low linear expansion and the like.

  The glass fibers are short fibers, that is, discontinuous long fibers, and the fiber length is, for example, 0.01 mm or more and 20 mm or less, preferably 0.05 mm or more and 10 mm or less. When the fiber length is equal to or more than the above lower limit, preferable low linear expansion performance can be obtained, and when the non-alignment layer 122 is combined as in this embodiment, preferable pressure resistance can also be obtained. When the fiber length is less than or equal to the above upper limit value, control of fiber orientation and non-orientation is easy. Furthermore, by setting the fiber length of the glass fiber within this range, the strength and dimensional stability of the molded body can be enhanced, and the elongation at high temperature can be improved. From the viewpoint of further enhancing the above effects, the fiber length of the glass fiber is preferably 0.1 mm or more and 3 mm or less. The fiber length means the average of the lengths of the fibers contained in the second layer 120 (that is, the average fiber length).

  The fiber diameter of the glass fiber is 1 μm or more and 30 μm or less. When the fiber diameter is equal to or more than the above lower limit, preferable low linear expansion performance can be obtained, and preferable pressure resistance can also be obtained when the non-orienting layer 122 is combined as in the present embodiment. When the fiber diameter is less than or equal to the above upper limit value, control of fiber orientation and non-orientation is easy. Furthermore, by setting the fiber diameter of the glass fiber within this range, the strength, dimensional stability and elongation at high temperature of the molded body can be improved. The fiber diameter of the glass fiber is preferably 5 μm or more and 20 μm or less, more preferably 5 μm or more and 15 μm or less, from the viewpoint of more effectively improving the strength, dimensional stability and the elongation at high temperature of the molded body. The fiber diameter means the average of the maximum diameters of the fibers contained in the second layer 120.

  The glass fiber may be surface treated. The surface treatment agent may, for example, be methacrylsilane, acrylsilane, aminosilane, imidazolesilane, vinylsilane or epoxysilane. Among these, aminosilane is preferable.

  By including glass fibers in the second layer 120, the strength and dimensional stability of the second layer 120 can be improved. Furthermore, the amount of glass fibers contained in the second layer 120 is 10% by weight or more and less than 60% by weight based on 100% by weight of the entire resin composition for producing the second layer 120. By setting the lower limit of the amount of glass fiber as described above, good dimensional stability of the multilayer pipe 100 can be efficiently obtained. Further, by setting the upper limit of the amount of glass fiber as described above, the fracture mode of the second layer 120 can be easily transitioned to ductile fracture. Therefore, brittle fracture of the second layer 120 can be less likely to occur. From the viewpoint of enhancing such effects more effectively, the amount of fibers contained in the second layer 120 is preferably 20% by weight or more and 50% by weight or less.

  The glass fibers may be converged by a polyolefin binder. The polyolefin sizing agent is not particularly limited as long as glass fibers can be converged, but is specifically a polyolefin. The polyolefin may be similar to the matrix resin. That is, if the matrix resin is polyethylene, the focusing agent may also be polyethylene. Furthermore, the said polyolefin as a convergence agent contains modified polyolefin. Examples of the polyolefin binder include maleic acid-modified polyolefin and silane-modified polyolefin. From the viewpoint of providing the second layer 120 with a low linear expansion coefficient, the polyolefin binder is preferably a silane-modified polyolefin.

From the viewpoint of making the glass fibers converge well, the density of the polyolefin binder is preferably 0.85 g / cm ³ or more, and preferably 1.1 g / cm ³ or less.
From the viewpoint of causing the glass fibers to converge well, the MFR (melt mass flow rate) of the polyolefin binder is preferably 0.01 g / 10 min or more, and preferably 16 g / 10 min or less. The MFR is a value measured under the conditions of a temperature of 190 ° C. and a load of 2.16 kgf based on JIS K7210.

  Any method may be used to converge the glass fibers with the polyolefin binder. The amount of fibers is preferably 6 parts by weight or more, more preferably 12 parts by weight or more, still more preferably 19 parts by weight or more, preferably 533 parts by weight or less, based on 100 parts by weight of the matrix resin and the polyolefin binder. Is 171 parts by weight or less, more preferably 138 parts by weight or less. By setting the amount of fibers in the above range, the strength, dimensional stability and elongation at high temperature of the molded article can be improved.

  The second layer 120 may contain a compatibilizer. Examples of the compatibilizer include modified polyolefins and chlorinated polyolefins. Examples of modified polyolefins include maleic acid-modified polyolefins and silane-modified polyolefins. One type of compatibilizer may be used alone, or two or more types may be used in combination. From the viewpoint of providing the second layer 120 with a low linear expansion coefficient, the compatibilizer is preferably a silane-modified polyolefin, and more preferably the fiber is glass fiber.

  In addition, the modified polyolefin as a compatibilizer is distinguished from the above-mentioned modified polyolefin as a convergence agent. The amount of the compatibilizer contained in the second layer 120 is, for example, 1% by weight or more and 10% by weight or less based on 100% by weight of the entire resin composition for producing the second layer 120. By setting the content of the compatibilizer in such a range, it is possible to improve the strength, dimensional stability and elongation at high temperature of the molded body. The amount of the compatibilizer contained in the second layer 120 is preferably 2% by weight or more and 9% by weight or less from the viewpoint of more effectively enhancing the strength, dimensional stability and the elongation at high temperature of the molded body. It is.

  The second layer 120 may contain other components other than those described above. The content of the polyolefin resin is preferably 80% by weight or more, more preferably 100% by weight of the other components excluding the glass fiber from the resin composition for producing the second layer 120. It may be used in an amount of 90% by weight or more, more preferably 95% by weight or more. The upper limit value included in the range of the content of the polyolefin resin may be 99.99% by weight, or 99.9% by weight.

  Other components include thermoplastic resins other than polyolefin resins as matrix resins. However, in this case, the thermoplastic resin is a secondary component, and the content thereof is less than the content of the polyolefin resin.

Other ingredients include antioxidants. The antioxidant can be used from the viewpoint of further enhancing the durability of the molded body at high temperature or suppressing the reduction of the durability due to a metal such as copper.
As said antioxidant, a phenolic antioxidant, phosphorus type antioxidant, sulfur type antioxidant, amine type antioxidant, lactone type antioxidant etc. are mentioned. One of the antioxidants may be used alone, or two or more thereof may be used in combination.

  The phenolic antioxidant is preferably a hindered phenolic antioxidant. As a hindered phenolic antioxidant, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5-di-tert-) Butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexane-1,6-diylbis [3- (3, (3) 5-di-tert-butyl-4-hydroxyphenyl) propionamide], benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy, C7-C9 side chain alkyl ester, 3,3 ', 3' ', 5, 5', 5 ''-hexa-tert-butyl-a, a ', a' '-(mesitylene-2, , 6-Triyl) tri-p-cresol, 4,6-bis (dodecylthiomethyl) -o-cresol, 4,6-bis (octylthiomethyl) -o-cresol, ethylene bis (oxyethylene) bis [3 -(5-tert-butyl-4-hydroxy-m-tolyl) propionate], hexamethylene bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5- Tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tris [( 4-tert-Butyl-3-hydroxy-2,6-xylyl) methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-ter -Butyl-4- [4,6-bis (octylthio) -1,3,5-triazin-2-ylamino] phenol and diethyl [{3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] } Methyl] phosphonate etc. are mentioned.

As a phosphorus antioxidant, tris (2,4-di-tert-butylphenyl) phosphite, tris [2-[[2,4,8,10-tetra-tert-butyl dibenzo [d, f] [ [1,3,2] dioxaphosphefin-6-yl] oxy] ethyl] amine, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis [2,4-bis (1) 1,1-Dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid, and tetrakis (2,4-di-tert-butylphenyl) (1,1-biphenyl) -4,4′-diylbisphosphonite Etc.
Examples of lactone antioxidants include reaction products of 3-hydroxy-5,7-di-tert-butyl-furan-2-one with o-xylene and the like.

  From the viewpoint of further enhancing the durability of the molded body at high temperatures or suppressing the decrease in durability due to metals such as copper, the above-mentioned antioxidant is 3- (3,5-di-tert-butyl-). The sterolyl 4-hydroxyphenyl) propionate or 2,4,6-tris (3 ', 5'-di-tert-butyl-4'-hydroxybenzyl) mesitylene is preferred, and the above-mentioned polyolefin resin composition is preferably Stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate or 2,4,6-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) It is preferred to include mesitylene.

  The content of the antioxidant is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and preferably 5% by weight or less, based on 100% by weight of the resin composition for producing the second layer 120. More preferably, it is 1% by weight or less, still more preferably 0.5% by weight or less. When the content of the antioxidant is at least the above lower limit, the durability of the molded article at high temperatures is further enhanced, and at a content exceeding the above upper limit, the durability of the molded article at high temperatures does not change. Therefore, use of excess antioxidant can be suppressed by setting it to the above-mentioned upper limit or less.

  The second layer 120 may contain, if necessary, additives such as a crosslinking agent, an anti-copper agent, a lubricant, a light stabilizer, and a pigment.

  An organic peroxide etc. are mentioned as a crosslinking agent. Examples of the organic peroxide include dicumyl peroxide, diisopropylbenzene hydroperoxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexine. As the crosslinking agent, one type may be used alone, or two or more types may be used in combination.

  The amount of the organic peroxide used is not particularly limited. For example, the amount is preferably 0.01 parts by weight or more, preferably 2 parts by weight or less, and more preferably 1 part by weight or less, based on 100 parts by weight of the polyolefin resin which is a matrix resin.

The lubricant is not particularly limited, and examples thereof include fluorine-based lubricants, paraffin wax-based lubricants and stearic acid-based lubricants. The lubricant may be used alone or in combination of two or more.
The amount of lubricant used is not particularly limited. For example, the amount is preferably 0.01 parts by weight or more, and preferably 3 parts by weight or less, with respect to 100 parts by weight of the polyolefin resin which is a matrix resin.

  The light stabilizer is not particularly limited, and examples thereof include ultraviolet absorbers such as salicylic acid ester type, benzophenone type, benzotriazole type and cyanoacrylate type, and light stabilizer of hindered amine type and the like. A light stabilizer may be used individually by 1 type, and 2 or more types may be used together.

  The pigment is not particularly limited, and, for example, organic pigments such as azo, phthalocyanine, srene and dye lakes, and oxides, molybdenum chromate, sulfide-selenide and ferrocyanide etc. Inorganic pigments and the like can be mentioned. The said pigment may be used individually by 1 type, and 2 or more types may be used together.

(Layer thickness)
The thickness of the second layer 120 is preferably greater than any of the thickness of the first layer 110 and the thickness of the third layer 130. Thereby, the multilayer piping 100 can more effectively obtain the performance (low linear expansion performance and pressure resistance in the case of the present embodiment) provided by the second layer 120. Furthermore, the thickness of the second layer 120 is preferably 50% to 80% of the total thickness of the multilayer pipe 100. When the thickness is equal to or more than the above lower limit value, the performance (low linear expansion performance and pressure resistance in the case of the present embodiment) provided by the second layer 120 can be more effectively obtained by the multilayer piping 100. When the thickness is equal to or less than the upper limit, the inner surface coating effect by the first layer 110 and the fusion bonding easiness of the third layer 130 to the joint can be effectively obtained.

[Manufacture of multilayer piping]
Although the manufacturing method in particular of multilayer piping 100 is not limited, it is manufactured, for example by coextrusion. Therefore, a resin composition for producing the first layer 110, a resin composition for producing the second layer 120, a resin composition for producing the third layer 130 are prepared, and an extruder is used. To mold. Since the glass fibers contained in the second layer 120 are short fibers, extrusion is easy. And besides the process of extrusion molding, the process of preparing a separate fiber base is unnecessary.

  The orientation layer 121 in the second layer 120 is manufactured by shaping the resin composition containing glass fibers while orienting the glass fibers in the axial direction by passing a channel of an arbitrary shape in the mold that promotes orientation. can do. The flow path that promotes orientation can be appropriately determined by one skilled in the art.

  In addition, it does not specifically limit as a molding machine, A single-screw extruder, a biaxial opposite direction parallel extruder, a biaxial opposite direction conical extruder, a biaxial simultaneous direction extruder, etc. are mentioned. Furthermore, the resin temperature to be shaped is not particularly limited.

[Other example]
The multilayer piping of the present invention may have no non-alignment layer and the second layer may be composed of only the alignment layer, in addition to the first embodiment. That is, in the cross section corresponding to FIG. 2, the alignment layer may occupy 100% of the cross-sectional area of the entire second layer. In this case, the multilayer pipe is particularly excellent in low linear expansion.

Alternatively, in the multilayer piping of the present invention, the number of alignment layers and non-alignment layers constituting the second layer is not particularly limited. That is, the second layer may include a plurality of either or both of the alignment layer and the non-alignment layer, and the alignment layer and the non-alignment layer may be alternately stacked. When a plurality of alignment layers are included, the total cross-sectional area of the alignment layers may be configured to occupy 20% or more and less than 100% of the cross-sectional area of the entire second layer in the cross section corresponding to FIG. Also in this case, as in the first embodiment, the upper limit within the range of the total of the cross sectional area of the alignment layer to the cross sectional area of the entire second layer is, for example, 90%, preferably 70%, more preferably 50 %.
Furthermore, whether the layer in contact with the first layer is an alignment layer or a non-alignment layer, and
It is optional as to whether the layer in contact with the layer is an alignment layer or a non-alignment layer.

Example 1 As a resin composition for producing the first layer and the third layer, high density polyethylene (equivalent to PE 100, density 0.94 g / cm ³ ), a resin composition for producing the second layer High-density polyethylene (PE 100 equivalent, density 0.94 g / cm ³ ) 65% by weight, glass fiber (chopped strand shape, fiber length 3 mm, fiber diameter 13 μm, olefin binder, silane surface-treated product) 30% by weight, compatibilization A resin composition containing 5% by weight of an agent (silane-modified polyethylene, density 0.94 to 0.96 g / cm ³ ) was prepared. Using these resin compositions, a multilayer pipe including, as an intermediate layer, a second layer composed of an alignment layer and a non-alignment layer was manufactured using a mold including an optional flow path promoting alignment. The average fiber length was 0.252 mm. The molding temperature was 200.degree.

(Orientation area ratio) A cross section of the manufactured multilayer piping with a thick section cut along a plane including the axial center, using a scanning electron microscope JSM-671F manufactured by Nippon Denshi Co., deposited thickness 10 nm, accelerating voltage 15 kV, magnification 25 times Visual observation was conducted under the conditions of (1), and the ratio of the total cross sectional area of the alignment layer to the cross sectional area of the second layer was determined. As a result, the alignment area ratio was 21%.

(Measurement of pressure resistance) Evaluation of fracture water pressure was performed in accordance with PWA (Planned by Research Group for Polyethylene Pipe System for Building Equipment) 001 standard. That is, a test piece of a multilayer pipe with a length of 1000 mm is cut out, water is filled at normal temperature (25 ° C.) inside and water is continuously added at a constant speed to pressurize, and the water pressure when the multilayer pipe ruptures is determined The

(Linear expansion measurement)
The linear expansion coefficient of the manufactured multilayer piping was determined as follows. The multilayer pipe was cut to a length of 1000 mm and aged for 24 hours in a thermostatic bath set at 60 ° C. (Thot). After curing, the length of the multilayer piping (Lhot) was measured. Thereafter, the same multilayer pipe was aged for 24 hours in a thermostatic bath set at 5 ° C. (Tcool), and the length (Lcool) of the multilayer pipe was measured. The obtained value was substituted into the following equation 1 to determine the linear expansion coefficient.

[Examples 2 to 6] A multilayer pipe was manufactured in the same manner as Example 1 except that the orientation area ratio was changed to the ratio shown in Table 1 described later, and the pressure resistance measurement and the linear expansion measurement were carried out. went.

Example 7 A multilayer pipe including a second layer constituted only of an alignment layer was produced, and in the same manner as in Example 1, the pressure resistance measurement and the linear expansion measurement were performed.

Comparative Example 1 A multilayer pipe was manufactured in the same manner as in Example 1 except that the orientation area ratio was changed to 15%, and pressure resistance measurement and linear expansion measurement were performed.

The results of Examples 1 to 7 and Comparative Example 1 are shown in Table 1 below.

  Although the preferred embodiments of the present invention are as described above, the present invention is not limited to them alone, and various other embodiments can be made without departing from the spirit of the present invention.

[Correspondence between each part in the embodiment and each component of the claims]
In the present specification, the multilayer piping 100 corresponds to the “multilayer piping” in the claims, the first layer 110 corresponds to the “first layer”, the second layer 120 corresponds to the “second layer”, and the orientation layer 121 corresponds to the “alignment layer”, the non-alignment layer 122 corresponds to the “non-alignment layer”, the third layer 130 corresponds to the “third layer”, and the axial center O corresponds to the “axial center”.

100 Multilayer piping 110 First layer 120 Second layer 121 Alignment layer 122 Non-alignment layer 130 Third layer O axis

Claims (3)

Including at least a first layer, a second layer and a third layer in the direction from the axis to the outer periphery,
The first layer and the third layer are resin layers composed mainly of a polyolefin resin,
The second layer is a fiber-reinforced resin layer containing a polyolefin resin, glass fibers, and a compatibilizer , and includes an alignment layer in which the glass fibers are oriented in a direction along the axis.
The amount of the glass fiber is 20% by weight or more and 50% by weight or less based on 100% by weight of the resin composition constituting the second layer,
The amount of the compatibilizer is 1% by weight or more and 10% by weight or less based on 100% by weight of the resin composition constituting the second layer,
In cross section in the case of cutting the multilayer pipe with a plane including the axis state, and are percentage 90% or less than 20% of the cross-sectional area of the alignment layer occupies to the cross-sectional area which is entirely occupied by the second layer,
Linear expansion coefficient is 8.0 × 10 ⁻⁵ / ° C. or less,
The breaking water pressure by the breaking water pressure test based on the PWA (polyethylene pipe system study group standard for building equipment) 001 standard is 4.7 MPa or more,
The multilayer piping whose ratio of the thickness of the said 2nd layer to the total thickness of the said multilayer piping is 50% or more and 80% or less . Including at least a first layer, a second layer and a third layer in the direction from the axis to the outer periphery,
The first layer and the third layer are resin layers composed mainly of a polyolefin resin,
The second layer is a fiber reinforced resin layer containing a polyolefin resin and glass fibers, and the glass fibers include an alignment layer oriented in a direction along the axis.
The ratio of the cross-sectional area occupied by the alignment layer to the cross-sectional area occupied by the entire second layer is 20% or more and 90% or less in the cross section when the multilayer pipe is cut at a plane including the axial center
Multilayer piping in which the second layer further includes a non-oriented layer in which the glass fiber is not oriented. The multilayer piping of Claim 1 or 2 whose fiber length of the said glass fiber is 0.01 mm or more and 20.0 mm or less.

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