JP6595787B2 - Multilayer piping - Google Patents

Description

  The present invention relates to a multilayer tube. More specifically, the present invention relates to a pressure resistant multilayer pipe.

For various purposes, multilayer pipes in which a plurality of layers are laminated have been developed.
For example, Japanese Patent Laid-Open No. 2006-327154 (Patent Document 1) discloses a polyolefin resin main pipe as a polyolefin resin pipe buried water pipe that can reliably prevent penetration of harmful substances such as underground organic solvents and oils. A polyolefin resin tube is disclosed in which a tape-like protective layer impregnated with a compound using a non-woven fabric, woven fabric, or felt made of polyester fiber, polyamide fiber, or polypropylene fiber as a porous substrate is applied to the outer peripheral surface of .

  Japanese Patent Application Laid-Open No. 2007-216555 (Patent Document 2) discloses a fiber reinforced synthetic resin pipe excellent in strength and workability from the inner peripheral side, from an organic nonwoven fabric layer, a glass cloth layer, a transversely wound fiber layer, A fiber reinforced synthetic resin pipe provided with six fiber reinforced resin layers in the order of a directional fiber layer, a horizontally wound fiber layer, and an organic nonwoven fabric layer is disclosed.

JP 2006-327154 A JP 2007-216555 A

  However, the polyolefin resin pipe described in JP-A-2006-327154 (Patent Document 1) is inferior in pressure resistance because only a thin tape-like protective layer is applied to the outer peripheral surface of the polyolefin resin main pipe. .

  In the fiber reinforced rigid resin pipe described in Japanese Patent Application Laid-Open No. 2007-216555 (Patent Document 2), it is necessary to prepare various kinds of special fiber materials in various modes in order to configure each layer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer tube having pressure resistance 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)
The multilayer pipe of the present invention includes at least a first layer, a second layer, and a third layer in the direction from the axial center 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 that includes a polyolefin-based resin and glass fibers, and includes an alignment layer in which the glass fibers are aligned in a direction along the outer periphery of the first layer.

  Thus, by including the circumferential alignment layer in the second layer, it has pressure resistance performance. Furthermore, a special material is not required by comprising 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 are substantially free of fibers. Moreover, the glass fiber in said (1) is a short fiber, ie, a discontinuous long fiber. Furthermore, “the glass fibers are oriented in the direction along the outer periphery of the first layer” means that the cross-section when the multilayer pipe is cut in a plane perpendicular to the axial center is 10% or more of the average fiber length of the glass fibers. Of the fibers having a length, the direction of at least 10%, preferably at least 15%, more preferably at least 80% is ± 15 ° with respect to the direction perpendicular to the straight line connecting the midpoint of the fiber and the axis. It is within.

(2)
The fiber length of the glass fiber may be 0.01 mm or more and 20 mm or less.

  With this configuration, the orientation state can be easily realized by adjusting the flow of the resin composition or the like (specifically, adjusting the direction or speed of the resin composition).

(3)
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, the pressure resistance performance can be obtained more effectively.

(4)
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, the pressure resistance performance can be obtained more effectively.

It is typical sectional drawing at the time of cut | disconnecting the multilayer piping of one Embodiment of this invention in a surface perpendicular | vertical to an axial center. It is a typical expanded sectional view of the square enclosure part 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 their names and functions are also the same. Therefore, detailed description thereof 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 axis. FIG. 2 is a schematic enlarged cross-sectional view of a rectangular box portion in FIG.
A multilayer pipe 100 shown in FIG. 1 is a pipe used as a cold / hot water pipe, a cold water pipe, a hot water pipe, a water pipe such as a water and sewage pipe, and a steam pipe. In the multilayer pipe 100, the first layer 110, the second layer 120, and the third layer 130 are laminated 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 coextruded layers, for example. An adhesive layer or the like may be interposed between the respective layers. The multilayer pipe 100 may further include one or more other layers.

(Pressure resistance)
The multilayer pipe 100 has good pressure resistance because the second layer 120 is formed of an alignment layer. The pressure resistance may be measured by a fracture water pressure test. Specifically, it is, for example, 4.7 MPa or more, preferably 4.9 MPa or more, more preferably 5.0 MPa or more, and further preferably 6.8 MPa or more. The upper limit value within the allowable pressure resistance range is, for example, 10.0 MPa, and preferably 8.2 MPa. In view of compatibility with low linear expansion performance, it is more preferably 6.4 MPa.

  In addition, the destructive water pressure test can be based on PWA (Polyethylene Pipe System Study Group Standard for Building Equipment) 001 standard, and inside the test piece of the multilayer pipe 100 having a length of 1000 mm or more (for example, 1000 mm in length) The pressure resistance can be evaluated based on the water pressure at the time when the multilayer pipe 100 is ruptured.

  Further, the pressure resistance may be evaluated by a circumferential stress (MPa) derived from a pressure resistance value (for example, a pressure resistance value (MPa) obtained by a destructive hydraulic pressure test) using the following formula (1). In the formula (1), SDR indicates the ratio of the outer diameter to the minimum thickness (outer diameter / minimum thickness).

Circumferential stress is a stress applied in the circumferential direction, and is highly reliable in that it is a parameter obtained by eliminating the influence of the dimensions of the pipe from the pressure value obtained by the hydraulic test. For example, in the case of pipes having the same composition and different wall thicknesses, those having a greater wall thickness have a higher pressure value in the hydraulic pressure test, but they are the same in terms of circumferential stress values.

The circumferential stress value allowed for the multilayer pipe 100 is, for example, 35 MPa or less, preferably 33 MPa or less. From the viewpoint of compatibility with low linear expansion performance, the circumferential stress value is more preferably 30.5 MPa or less.

  The multilayer pipe 100 is particularly useful as a cold / hot water pipe because it has excellent pressure resistance as described above.

[First and third layers]
The first layer 110 and the third layer 130 are both resin layers composed of the same polyolefin resin as a main component. Therefore, the mechanical characteristics are uniform on both surfaces of the second layer 120 and the manufacturing efficiency of the multilayer pipe 100 is good. The present invention does not exclude that the first layer 110 and the third layer 130 are made of different polyolefin resins.

  The polyolefin resin is not particularly limited. Examples thereof include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. From the viewpoint of improving the strength of the molded body and the elongation percentage of the molded body at high temperature, polyethylene or polypropylene is preferable, and polyethylene is more preferable.

Furthermore, examples of polyethylene (PE) include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). Examples of polypropylene (PP) include homo PP, block PP, and random PP. Examples of polybutene include polybutene-1. The ethylene-α-olefin copolymer is about 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 the copolymer is copolymerized at a 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 like the second layer 120 described later. The first layer 110, which is the inner layer, coats the inner peripheral surface of the second layer 120 so that the water contained in the second layer 120 is not mixed into the water flowing inside the multilayer pipe 100. In addition, the third layer 130 can ensure the ease of fusion bonding with the joint when, for example, 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 compatibilizing agent and other components in the same manner as the second layer 120 described later. However, the fiber which is contained in the below-mentioned 2nd layer 120 is not included substantially.

[Second layer]
The second layer 120 is a fiber reinforced resin layer containing a matrix resin and fibers. The second layer 120 is composed of an alignment layer.

(Orientation layer)
In the second layer 120, the fibers are oriented in a direction along the outer periphery of the first layer 110. Specifically, in a cross section when the multilayer pipe 100 is cut along a plane perpendicular to the axis O, at least 10%, preferably at least 15 of the fibers having a length of 10% or more of the average fiber length of the fibers. %, More preferably at least 80% of the direction is within ± 15 ° with respect to the perpendicular direction of the straight line connecting the midpoint of the fiber and the axis O. By including such an alignment layer as the second layer 120, the multilayer pipe 100 has good pressure resistance.

  In addition, the orientation aspect of a fiber can be confirmed by observing a cross section, for example using a scanning electron microscope. Although it does not specifically limit as observation conditions, You may observe by vapor deposition thickness 10nm, acceleration voltage 15kV, and magnification 25 times using the scanning electron microscope JSM-6701F by JEOL.

(Matrix resin)
The matrix resin is a polyolefin resin. Specific examples of the polyolefin resin are the same as those exemplified as the 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 first layer 110, the second layer 120, and the third layer 130 may be different. When the same resin is used for all layers, it is preferable in that adjacent layers are easily compatible with each other, and interface peeling can be effectively suppressed.

(fiber)
As the fiber, glass fiber is used from the viewpoint of low linear expansion and the like.

  The glass fiber is a short fiber, that is, a discontinuous long fiber, and the fiber length is, for example, 0.01 mm to 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 lower limit value, a preferable pressure resistance performance can be obtained. When the fiber length is not more than the above upper limit value, the fibers are easily oriented. Furthermore, by setting the fiber length of the glass fiber within this range, the strength and dimensional stability of the molded body can be increased, 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 length of fibers included in the second layer 120 (that is, 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 not less than the above lower limit value, preferable pressure resistance performance can be obtained. When the fiber diameter is not more than the above upper limit value, the fibers are easily oriented. Furthermore, by setting the fiber diameter of the glass fiber within this range, it is possible to improve the strength, dimensional stability, and elongation at high temperature of the molded body. From the viewpoint of more effectively improving the strength, dimensional stability, and elongation at high temperature of the molded body, the fiber diameter of the glass fiber is preferably 5 μm to 20 μm, more preferably 5 μm to 15 μm. The fiber diameter means the average of the maximum diameters of the fibers included in the second layer 120.

  The glass fiber may be surface-treated. Examples of the surface treatment agent include methacryl silane, acrylic silane, amino silane, imidazole silane, vinyl silane, and epoxy silane. Of these, aminosilane is preferred.

  By including glass fiber in the second layer 120, the strength and dimensional stability of the second layer 120 can be improved. Furthermore, the amount of the glass fiber contained in the second layer 120 is 10% by weight or more and less than 60% by weight with respect to 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 pressure resistance of the multilayer pipe 100 can be obtained efficiently. In addition, 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 changed to ductile fracture. Accordingly, brittle fracture of the second layer 120 can be made difficult 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 fiber may be converged by a polyolefin sizing agent. The polyolefin sizing agent is not particularly limited as long as the glass fiber can be converged, but is specifically a polyolefin. The polyolefin may be the same as the matrix resin. That is, if the matrix resin is polyethylene, the sizing agent may also be polyethylene. Further, the polyolefin as the sizing agent includes a modified polyolefin. Specific examples of the polyolefin sizing agent 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 sizing agent is preferably a silane-modified polyolefin.

From the viewpoint of favorably converging the glass fibers, the density of the polyolefin sizing agent is preferably 0.85 g / cm ³ or more, and preferably 1.1 g / cm ³ or less.
From the viewpoint of favorably converging glass fibers, the MFR (melt mass flow rate) of the polyolefin sizing agent is preferably 0.01 g / 10 min or more, and preferably 16 g / 10 min or less. The MFR is a value measured under 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 fiber with the polyolefin sizing agent. The amount of the fiber with respect to 100 parts by weight of the total of the matrix resin and the polyolefin sizing agent 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. 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 product can be improved.

  The second layer 120 may include a compatibilizer. Examples of the compatibilizer include modified polyolefin and chlorinated polyolefin. Examples of the modified polyolefin include maleic acid-modified polyolefin and silane-modified polyolefin. 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 the fiber is preferably a glass fiber.

  The modified polyolefin as the compatibilizer is distinguished from the modified polyolefin as the sizing 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 making content of a compatibilizing agent into such a range, the intensity | strength of a molded object, dimensional stability, and the elongation rate under high temperature can be improved. From the viewpoint of more effectively increasing 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. It is.

  The second layer 120 may contain components other than those described above. When the other component is 100% by weight of the resin composition for producing the second layer 120 excluding glass fiber, the polyolefin resin content is preferably 80% by weight or more, more preferably 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-based resin may be 99.99% by weight or 99.9% by weight.

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

An antioxidant is mentioned as another component. The antioxidant can be used from the viewpoint of further enhancing the durability of the molded body at a high temperature or suppressing a decrease in durability due to a metal such as copper.
Examples of the antioxidant include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, amine antioxidants, and lactone antioxidants. One type of antioxidant may be used alone, or two or more types may be used in combination.

  The phenolic antioxidant is preferably a hindered phenolic antioxidant. Examples of hindered phenol antioxidants include 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 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, ethylenebis (oxyethylene) bis [3 -(5-tert-butyl-4-hydroxy-m-tolyl) propionate], hexamethylenebis [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 and the like.

Phosphorus antioxidants include tris (2,4-di-tert-butylphenyl) phosphite, tris [2-[[2,4,8,10-tetra-tert-butyldibenzo [d, f] [ 1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis [2,4-bis (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 the lactone antioxidant include a reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene.

  From the viewpoint of further enhancing the durability of the molded body at a high temperature or suppressing a decrease in durability due to a metal such as copper, the antioxidant is 3- (3,5-di-tert-butyl- 4-hydroxyphenyl) stearyl propionate or 2,4,6-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) mesitylene, and the polyolefin resin composition is preferably , 3- (3,5-di-tert-butyl-4-hydroxyphenyl) stearyl propionate or 2,4,6-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) Preferably it contains mesitylene.

  The content of the antioxidant is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 5% by weight or less, assuming that the resin composition for producing the second layer 120 is 100% by weight. More preferably, it is 1% by weight or less, and further preferably 0.5% by weight or less. When the content of the antioxidant is not less than the above lower limit, the durability of the molded body at a high temperature is further increased, and when the content exceeds the above upper limit, the durability of the molded body at a high temperature does not change. For this reason, by using the above upper limit or less, the use of an excessive antioxidant can be suppressed.

  The second layer 120 may contain additives such as a crosslinking agent, a copper damage inhibitor, a lubricant, a light stabilizer, and a pigment as necessary.

  Examples of the crosslinking agent include organic peroxides. Examples of the organic peroxide include dicumyl peroxide, diisopropylbenzene hydroperoxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

  The amount of 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, more preferably 1 part by weight or less with respect to 100 parts by weight of the polyolefin resin as the matrix resin.

The lubricant is not particularly limited, and examples thereof include a fluorine-based lubricant, a paraffin wax-based lubricant, and a stearic acid-based lubricant. As for the said lubricant, 1 type may be used independently and 2 or more types may be used together.
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 as the matrix resin.

  The light stabilizer is not particularly limited, and examples thereof include salicylic acid ester-based, benzophenone-based, benzotriazole-based and cyanoacrylate-based ultraviolet absorbers, hindered amine-based light stabilizers, and the like. As the light stabilizer, one type may be used alone, or two or more types may be used in combination.

  The pigment is not particularly limited, and examples thereof include organic pigments such as azo, phthalocyanine, selenium, and dye lake, and oxides, molybdenum chromate, sulfide-selenide, and ferrocyanide. An inorganic pigment etc. are mentioned. One of the above pigments may be used alone, or two or more thereof may be used in combination.

(Layer thickness)
The thickness of the second layer 120 is preferably larger than both 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 pressure resistance provided by the second layer 120. Furthermore, the thickness of the second layer 120 is preferably 50% or more and 80% or less with respect to the total thickness of the multilayer pipe 100. When the thickness is equal to or greater than the lower limit value, the multilayer pipe 100 can more effectively obtain the pressure resistance provided by the second layer 120. When the thickness is less than or equal to the above upper limit value, the inner peripheral surface coating effect by the first layer 110 and the ease of fusion bonding with the joint of the third layer 130 can be effectively obtained.

[Manufacture of multilayer piping]
As a method for manufacturing the multilayer pipe 100, a resin composition for manufacturing the first layer 110, a resin composition for manufacturing the second layer 120, and a resin composition for manufacturing the third layer 130 are prepared. The method for allowing the resin composition for producing the second layer 120 to flow in the direction corresponding to the circumferential direction of the molded tube can be used without any particular limitation. For example, the multilayer pipe 100 can be manufactured by the following method.

  When the multilayer pipe 100 is formed by the extrusion molding method, a mold in which the flow path of the middle part of the mold (the part corresponding to the thick middle part) is branched from the upstream toward the downstream is used, and the circumferential direction is even. The resin composition can be extruded from each of the outlets of the branch flow passages arranged in the pipe, and the resin compositions extruded from the outlets adjacent to each other can be joined together to produce a pipe. In this case, since the resin composition flows in the circumferential direction when the resin compositions merge, the glass fibers of the intermediate layer are oriented.

  When the multilayer pipe 100 is molded by an injection molding method, the resin composition for producing the second layer 120 can be injected in a direction corresponding to a direction perpendicular to the axial direction of the molded pipe. In this case, since the resin composition flows in the circumferential direction by setting the injection direction as described above, the glass fibers of the intermediate layer are oriented.

[Example 1] As a resin composition for producing the first layer and the third layer, high-density polyethylene (equivalent to PE100, density 0.94 g / cm ³ ), as a resin composition for producing the second layer , High density polyethylene (equivalent to PE100, density 0.94 g / cm ³ , 65% by weight), glass fiber (chopped strand shape, fiber length 3 mm, fiber diameter 13 μm, olefin sizing agent, silane surface treatment product, 30% by weight), A resin composition containing a compatibilizing agent (silane-modified polyethylene, density 0.94 to 0.96 g / cm ³ , 5% by weight) was prepared.

Using these resin compositions, extrusion molding was performed using a mold having a tournament branch (specifically, eight branches) in which the flow path of the middle part of the mold was directed from upstream to downstream. Thus, a three-layer pipe in which the first layer and the third layer were laminated on the inner and outer peripheral surfaces of the second layer was manufactured.

The cross section of the manufactured three-layer pipe cut by a plane perpendicular to the axis is visually observed using a scanning electron microscope JSM-671F manufactured by JEOL Ltd. under conditions of a deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times. It was confirmed that the glass fibers were oriented in the circumferential direction.

[Comparative Example 1] A single-layer pipe similar to Example 1 was manufactured except that glass fiber was not included. That is, a high-density polyethylene (equivalent to PE100, density 0.94 g / cm ³ ) was melted and piped to produce a single-layer pipe.

[Reference Example 1] Three-layer piping in which the orientation direction of the glass fibers in the second layer becomes axially dominant by extruding the resin composition for producing the first layer, the second layer, and the third layer. Manufactured.

A cross-section of the manufactured multilayer pipe cut along the plane including the axis is visually observed using a scanning electron microscope JSM-671F manufactured by JEOL Ltd. under conditions of a deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times. It was confirmed that the fiber orientation direction was dominant in the axial direction.

(Pressure resistance evaluation) About the pipe | tube of Example 1, the comparative example 1, and the reference example 1, destruction water pressure evaluation was performed based on PWA (polyethylene pipe system study group plan for building equipment) 001 specification. That is, a test piece of a multilayer pipe having a length of 1000 mm is cut out, filled with water at room temperature (25 ° C.) and pressurized at a constant rate, and the water pressure (MPa when the multilayer pipe bursts) )

Further, the circumferential stress (MPa) was calculated from the following formula (1). In the equation (1), SDR represents the ratio of the outer diameter to the minimum wall thickness (outer diameter / minimum wall thickness), and the pressure resistance value is the value of the water pressure obtained in the above water pressure test.

The results of pressure resistance evaluation for Example 1, Comparative Example 1 and Reference Example 1 are shown in Table 1 below.

  Preferred embodiments of the present invention are as described above, but the present invention is not limited to them, and various other embodiments are possible without departing from the spirit of the present invention.

[Correspondence Relationship Between Each Part in Embodiment and Each Component in Claim]
In this specification, the multilayer pipe 100 corresponds to the “multilayer pipe” in the claims, the first layer 110 corresponds to the “first layer”, the second layer 120 corresponds to the “second layer”, and the alignment 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 axis O corresponds to the “axis”.

100 multilayer piping 110 first layer 120 second layer 130 third layer O axis

Claims (5)

Including at least a first layer, a second layer, and a third layer in the direction from the axial center to the outer periphery;
The thickness of the second layer is 50% or more and 80% or less with respect to the total thickness of the multilayer pipe,
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-based resin and glass fibers, and the glass fibers are oriented in a direction along the outer periphery of the first layer;
The glass fiber has an orientation direction of at least 80% within ± 15 ° with respect to a perpendicular direction of a straight line connecting the midpoint of the glass fiber and the axis,
The surface of the glass fiber is subjected to silane coupling treatment,
Multi-layer piping whose circumferential stress calculated by the following formula 1 is 35 MPa or less .
The surface of the glass fibers, methacryl silanes, acrylic silanes, aminosilanes, imidazole silane, vinylsilane, or that have been treated with epoxy silane, multilayer pipe according to claim 1. Surface of the glass fibers that have been treated with an aminosilane, a multilayer pipe according to claim 1 or 2. The multilayer pipe according to any one of claims 1 to 3, wherein the second layer includes a modified polyolefin or a chlorinated polyolefin. Including at least a first layer, a second layer, and a third layer in the direction from the axial center to the outer periphery;
The thickness of the second layer is 50% or more and 80% or less with respect to the total thickness of the multilayer pipe,
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-based resin and glass fibers, and the glass fibers are oriented in a direction along the outer periphery of the first layer;
The glass fiber has an orientation direction of at least 80% within ± 15 ° with respect to a perpendicular direction of a straight line connecting the midpoint of the glass fiber and the axis,
The pressure resistance of the breaking water pressure test is 6.8 MPa or more,
On the surface of the glass fiber, a methacryl silane, acryl silane, amino silane, imidazole silane, vinyl silane, or epoxy silane surface treatment layer is formed,
Multi-layer piping whose circumferential stress calculated by the following formula 1 is 35 MPa or less.