JP7074421B2 - Polyolefin resin multilayer tube - Google Patents

Description

The present invention relates to a polyolefin-based resin multilayer tube. More specifically, the present invention relates to a polyolefin-based resin multilayer tube having an excellent balance of performance and particularly having a good balance between strength and earthquake resistance.

In recent years, polyolefin-based resin pipes have been developed mainly for gas pipes and water distribution pipes. Such a trend is that polyolefin resin pipes are lightweight, workability is much better than metal pipes, and excellent pipe performance and flexibility make them excellent in earthquake resistance when burying pipes. It is considered that this feature is the result of being accepted by the market.

However, since the olefin-based resin tube has a limit in functioning as a single layer, a multi-layer tube in which a plurality of layers are laminated has been developed so far in order to achieve various purposes.

For example, Japanese Patent Application Laid-Open No. 2006-327154 (Patent Document 1) describes a water pipe for burying a polyolefin resin pipe for the purpose of reliably preventing harmful substances such as organic solvents and oils from infiltrating into the ground. Polyester resin A polyolefin resin tube with a tape-shaped protective layer impregnated with a compound using polyester fiber, polyamide fiber, polypropylene fiber non-woven fabric, woven cloth, and felt as a porous base material on the outer peripheral surface of this pipe. It has been disclosed.

Further, Japanese Patent Application Laid-Open No. 2007-216555 (Patent Document 2) describes a fiber-reinforced synthetic resin pipe for the purpose of excellent strength and workability, from the inner peripheral side, an organic non-woven fabric layer, a glass cloth layer, and horizontal winding. A fiber-reinforced synthetic resin pipe provided with six fiber-reinforced resin layers in the order of a fiber layer, a longitudinal fiber layer, a horizontal winding fiber layer, and an organic non-woven fabric layer is disclosed.

Japanese Unexamined Patent Publication No. 2006-327154 Japanese Unexamined Patent Publication No. 2007-216555

However, although it is possible to improve the strength of conventional polyolefin-based multilayer tubes, the flexibility (particularly tensile elongation) is greatly impaired by forming multiple layers. Therefore, it was difficult to ensure earthquake resistance.

Therefore, an object of the present invention is to provide a polyolefin-based multilayer tube having excellent earthquake resistance by having an excellent performance balance that exhibits high strength and good tensile elongation.

In order to achieve the above object of the present invention, the present invention includes the following inventions.
(1)
The polyolefin-based resin multilayer tube of the present invention includes a first layer, a second layer, and a third layer in this order in the direction from the axis to the outer periphery.
The first layer and the third layer contain a polyolefin resin as a main component.
The second layer contains a polyolefin resin and glass fiber. The blending amount of the glass fiber contained in the second layer is 5% by weight or more and 18% by weight or less. The average fiber length of the glass fibers contained in the second layer after molding is 150 μm or more and 700 μm or less. The second layer includes an oriented layer in which the glass fibers are oriented along the axis. In this case, the ratio of the oriented area occupied by the oriented layer in the second layer is 5% or more and less than 40%.

The "alignment layer in which the glass fibers are oriented in the direction along the axis" is preferably at least 50% (based on the number of fibers) of the fibers having a length of 10% or more of the average fiber length after molding of the glass fibers. Refers to a layer in which the direction of at least 70% is within ± 15 ° with respect to the axial direction.
The "alignment area ratio" means the ratio of the cross-sectional area occupied by the oriented layer to the cross-sectional area occupied by the entire second layer in the cross section when the multilayer pipe is cut on the surface including the axis.

As described above, in the polyolefin resin multilayer tube of the present invention, the second layer is formed as a fiber reinforced resin layer, and the average fiber length (after molding) of the glass fiber and the blending amount of the glass fiber are set within a specific range. The performance balance of the multi-layer tube is good. A good balance of performance means that at least both strength and tensile elongation are well expressed.
Further, when the second layer includes an axially oriented layer, it is possible to obtain an effect of improving low linear expansion and rigidity as an effect of orientation, and the ratio of the oriented area occupied by the oriented layer is set to a specific range. By doing so, tensile elongation can be well developed.

(2)
In the polyolefin-based resin multilayer tube of (1) above, the second layer may further contain an acid-modified polyolefin-based resin as a compatibilizer.

As a result, for example, the pressure resistance in a normal temperature environment is improved, and the performance balance is further improved.

(3)
In the polyolefin-based resin multilayer tube of (2) above, the content of the acid-modified polyolefin-based resin in the second layer may be 0.3% by weight or more and 10% by weight or less.

As a result, the effect of improving the pressure resistance in a normal temperature environment can be obtained more effectively.

(4)
In the polyolefin-based resin multilayer tube according to any one of (1) to (3) above, when the relative thickness of the first layer is 1, the relative thickness of the second layer is 0.5 or more and 2 or less, and the third layer. The relative thickness of may be 0.5 or more and 1.5 or less.

As a result, the surface smoothness, pressure resistance and tensile elongation of the first and third layers are satisfactorily obtained, and the strength improving effect of the glass fiber reinforced layer of the second layer is also satisfactorily obtained, including creep resistance. The performance balance is further improved.

According to the present invention, a polyolefin-based multilayer tube having excellent earthquake resistance is provided by having an excellent performance balance that exhibits high strength and good tensile elongation.

It is a schematic cross-sectional view when the multilayer tube of one Embodiment of this invention is cut in the plane perpendicular to the axis. It is a schematic enlarged sectional view in the case of cutting in the axial direction along the line AA of FIG. 1.

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

[1. Multi-layer tube]
[1-1. Basic configuration]
FIG. 1 is a schematic cross-sectional view of a multilayer tube 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 in the case of cutting in the axial direction along the line AA of FIG. 1 (that is, when cutting in the plane including the axial center).

The multilayer pipe 100 shown in FIG. 1 is a pipe used as a water distribution pipe such as a cold / hot medium pipe, a cold / hot water pipe, a cold water pipe, a hot water pipe, a water / sewage pipe, and a fire extinguishing pipe. In the multilayer tube 100, the first layer 110, the second layer 120, and the third layer 130 are laminated in the direction of the outer periphery from the axis O. The first layer 110, the second layer 120 and the third layer 130 may be, for example, a coextruded layer. The multilayer tube 100 may further include 1 or 2 or more, preferably 1 or 2 other layers. An adhesive layer may intervene as another layer between the first layer 110 and the second layer 120, and one or both between the second layer 120 and the third layer 130.

[1-2. 1st layer and 3rd layer]
The first layer 110 and the third layer 130 are both resin layers composed of the same polyolefin-based resin as a main component. Therefore, the mechanical properties are uniform on both sides of the second layer 120, and the manufacturing efficiency of the multilayer tube 100 is also good. However, the present invention does not exclude that the first layer 110 and the third layer 130 are composed of different polyolefin resins.

The polyolefin-based resin is not particularly limited. 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 product and the tensile elongation, polyethylene or polypropylene is preferable.

Further, as the 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 homo PP, block PP, random PP and the like. Among these, random PP is preferable from the viewpoint of developing the rigidity, strength, tensile elongation, etc. of the molded product in a well-balanced manner. Examples of polybutene include polybutene-1 and the like. The ethylene-α-olefin copolymer contains 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 the above ratio.
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 are substantially made of resin and therefore are substantially free of fibers such as the second layer 120 described below. It is preferable that the fiber is not substantially contained, but it is preferable that the fiber is not contained at all. ) Means to allow fibers that can be mixed. The first layer 110, which is an inner layer, coats the inner peripheral surface of the second layer 120 so that the fibers contained in the second layer 120 are not mixed with a medium such as water flowing inside the multilayer tube 100. Further, the third layer 130 can smooth the outer surface of the multilayer tube 100.

In addition to the above, the first layer 110 and the third layer 130 may contain a compatibilizer and other components (excluding fibers) as in the second layer 120 described later.

[1-3. Second layer]
The second layer 120 is a fiber reinforced resin layer containing a matrix resin and fibers. The second layer 120 includes an oriented layer 121 and an unoriented layer 122.

[1-3-1. Matrix resin]
The matrix resin of the second layer 120 is a polyolefin resin. Specific examples of the polyolefin-based resin are the same as those mentioned 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 of the first layer 110, the second layer 120, and the third layer 130. When the same resin is used for all the layers, it is preferable in that adjacent layers are easily compatible with each other and interface peeling can be effectively suppressed.

The second layer 120 improves the tensile strength and rigidity of the matrix resin by reinforcing the matrix resin with fibers. More specifically, glass fiber is used from the viewpoint of pressure resistance and initial fracture water pressure.

[1-3-2. Glass fiber content]
The content of the glass fiber in the second layer 120 is 5% or more, preferably 10% or more, from the viewpoint of obtaining good strength, rigidity and tensile elongation. The upper limit value within the range of the content is 18%, preferably 15% from the viewpoint of obtaining good tensile elongation.

[1-3-3. Orientation of glass fiber]
In the alignment layer 121, the fibers are oriented in the direction along the axis O. Specifically, among the 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 axis O direction. It fits. By orienting the glass fibers in this way, the effect of improving low linear expansion and rigidity is imparted to the multilayer tube 100.

Further, the orientation area ratio in the second layer 120 (the ratio of the area of the alignment layer 121 to the cross section of the entire second layer 120 in the cross section of FIG. 2) is 5% or more from the viewpoint of imparting tensile elongation to the multilayer tube 100. Less than 40%. From the viewpoint of obtaining better tensile elongation of the multilayer tube 100, it is preferably 5% or more and 35% or less. From the viewpoint of obtaining better pressure resistance, it is preferably 5% or more and 20% or less.

The portion corresponding to 60% or more, preferably the portion corresponding to more than 65%, outside the range of the above-mentioned oriented area ratio forms the non-oriented layer 122. Although the non-oriented layer 122 exists on the first layer 110 side in this embodiment, it may exist on both sides of the first layer 110 and the third layer 130.
In the non-oriented layer 122, the glass fibers are not oriented as in the oriented layer 121. Specifically, the fiber direction of the glass fiber in the non-oriented layer 122 is random and arbitrary. Therefore, the number of fibers whose fiber direction is relatively the axial center O direction is significantly smaller than that of the oriented layer 121. The presence of such a non-oriented layer 122 is preferable in terms of imparting pressure resistance to the multilayer tube 100.

The orientation of the fibers can be confirmed by observing the cross section using, for example, a scanning electron microscope. The observation conditions are not particularly limited, but observation may be performed using a scanning electron microscope JSM-6701F manufactured by JEOL Ltd. at a vapor deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times. Thereby, the boundary of the oriented layer 121, for example, the boundary between the oriented layer 121 and the non-aligned layer 122 can be visually confirmed.

[1-3-4. Average fiber length of glass fiber (after molding)]
The glass fiber is a short fiber, that is, a discontinuous long fiber. The average fiber length of the glass fibers actually contained in the second layer 120 after molding is 150 μm or more from the viewpoint of efficiently obtaining the effect of orientation (effect of improving low linear expansion and rigidity), and the effect of orientation. It is preferably 200 μm or more from the viewpoint of more efficiently obtaining. The upper limit value within the range of the average fiber length is 700 μm from the viewpoint of moldability, and preferably 650 μm from the viewpoint of obtaining better moldability.

The average fiber length of the glass fiber contained in the second layer 120 after molding was measured by cutting out a part of the second layer 120 after molding, collecting the resin portion, and measuring the length of the remaining glass fiber. , Derived by finding the average value. More specifically, it may be an average value of 500 glass fibers arbitrarily selected. The means for removing the resin portion is not particularly limited, and the resin portion may be burned or dissolved in a liquid having corrosiveness to the resin such as an organic solvent. A microscope can be used in the selection of glass fibers.

[1-3-5. Average fiber diameter of glass fiber]
The average fiber diameter of the glass fiber may be, for example, 1 μm or more and 30 μm or less. It is preferable that the fiber diameter is at least the above lower limit value in terms of strength. When the fiber diameter is not more than the above upper limit value, it is preferable in that the orientation of the fibers can be easily controlled. From the viewpoint of more effectively obtaining these effects, the fiber diameter of the glass fiber is preferably 5 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. The average fiber diameter is an average value of the maximum diameters of each of the plurality of (for example, 500) fibers contained in the second layer 120.

[1-3-6. Glass fiber surface treatment and converging agent]
The glass fiber may be surface-treated. Examples of the surface treatment agent include methacrylsilane, acrylicsilane, aminosilane, imidazolesilane, vinylsilane, and epoxysilane. Of these, aminosilane is preferred.

The glass fiber may be converged by a polyolefin converging agent. The polyolefin converging agent is not particularly limited as long as it can converge the glass fiber, but specifically, it is a polyolefin. The polyolefin may be the same as the matrix resin. That is, if the matrix resin is polyethylene, the converging agent may also be polyethylene. Further, the polyolefin as a converging agent includes a modified polyolefin. Specific examples of the polyolefin converging agent include maleic anhydride-modified polyolefin and silane-modified polyolefin. From the viewpoint of providing the second layer 120 with good strength, the polyolefin converging agent is preferably maleic anhydride-modified polyolefin.

From the viewpoint of satisfactorily converging the glass fiber, the density of the polyolefin converging agent is preferably 0.85 g / cm ³ or more, preferably 1.1 g / cm ³ or less.
From the viewpoint of satisfactorily converging the glass fiber, the MFR (melt mass flow rate) of the polyolefin converging agent is preferably 0.01 g / 10 minutes or more, preferably 16 g / 10 minutes or less. The above MFR is a value measured based on JIS K7210 under the conditions of a temperature of 190 ° C. and a load of 2.16 kgf (the same applies hereinafter).

Any method may be used for converging the glass fiber with the polyolefin converging agent. The amount of fiber with respect to a total of 100 parts by weight of the matrix resin and the polyolefin converging 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, more preferably. Is 171 parts by weight or less, more preferably 138 parts by weight or less. It is preferable to set the amount of fibers in the above range from the viewpoint of obtaining good strength and dimensional stability of the molded product.

[1-3-7. Compatibility agent]
The second layer 120 may contain a compatibilizer. Examples of the compatibilizer include modified polyolefins and chlorinated polyolefins. Examples of the modified polyolefin include acid-modified polyolefin and silane-modified polyolefin. Modifications of the modified polyolefin include modification by grafting and copolymerization. The acid-modified polyolefin is a polyolefin-based resin modified with an unsaturated carboxylic acid or a derivative thereof. The unsaturated carboxylic acid includes, for example, unsaturated dicarboxylic acids such as maleic acid, nadic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid, as well as acrylic acid, methacrylic acid, crotonic acid, sorbic acid, and angelic acid. , And phthalic acid and the like. Examples of the derivative include acid anhydrides, esters, amides, imides, metal salts and the like. Examples thereof include methyl metacurate, ethyl acrylate, butyl acrylate, monoethyl maleate ester, acrylamide, monoamide maleic acid, maleimide, N-butylmaleimide, sodium acrylate, sodium methacrylate and the like. Among these, unsaturated dicarboxylic acids and derivatives thereof are preferable, and maleic anhydride and phthalic anhydride are particularly preferable.
From the viewpoint of imparting strength to the second layer 120, the compatibilizer is preferably maleic anhydride-modified polyolefin. As the compatibilizer, one type may be used alone, or two or more types may be used in combination.

In the present invention, the modified polyolefin as a compatibilizer is structurally distinguished from the above-mentioned modified polyolefin as a converging agent. The amount of the compatibilizer contained in the second layer 120 is, for example, 0.3% by weight or more and 10% by weight or less, preferably 0.5, with 100% by weight of the entire resin composition for producing the second layer 120. It is 0% by weight or more and 8% by weight or less. It is preferable that the amount of the compatibilizer is not less than the above lower limit value in terms of improving the strength (particularly the tensile strength at room temperature) while maintaining the low linear expansion performance and rigidity, and it is not more than the above upper limit value. It is preferable in that the effect of improving the strength is efficiently obtained.

[1-3-8. Oriented layer and non-oriented layer]
In the multilayer tube 100, the number of the oriented layer 121 and the non-oriented layer 122 constituting the second layer 120 is not particularly limited. That is, the second layer 120 may include a plurality of one or both of the oriented layer 121 and the unaligned layer 122, and the oriented layer 121 and the unaligned layer 122 may be alternately laminated. When a plurality of oriented layers 121 are included, in the cross section corresponding to FIG. 2, the total cross-sectional area of the oriented layers 121 is 5% or more and less than 40% of the cross-sectional area of the entire second layer 120. It may be preferably configured to occupy 5% or more and 35% or less.

Further, regarding whether the layer closest to the first layer 110 is the oriented layer 121 or the unaligned layer 122, and the layer closest to the third layer 130 is the oriented layer 121 or the unoriented layer 122. Is also optional.

[1-3-9. others]
The second layer 120 may contain components other than those described above as long as the strength, rigidity and tensile elongation performance are ensured. As for the other components, the content of the polyolefin resin is preferably 80 parts by weight or more, more preferably 80 parts by weight or more, assuming that the component excluding the glass fiber from the resin composition for producing the second layer 120 is 100 parts by weight. It may be used in an amount of 90 parts by weight or more, more preferably 95 parts by weight or more. The upper limit value included in the content range of the polyolefin resin may be 99.99% by weight or 99.9% by weight.

Examples of other components include thermoplastic resins other than polyolefin resins as matrix resins. However, in this case, the thermoplastic resin is a sub-component, and its content is smaller than the content of the polyolefin-based resin.

Other examples of other components include antioxidants. The antioxidant can be used from the viewpoint of further enhancing the durability of the molded product under high temperature and suppressing the decrease in durability due to a metal such as copper.
Examples of the antioxidant include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, lactone-based antioxidants, and the like. 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 the hindered phenolic antioxidant include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and 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''-(methicylene-2,4,6-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-) Trill) 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-tert-butyl-4- [4,6-bis (octylthio)- Examples thereof include 1,3,5-triazin2-ylamino] phenol, diethyl [{3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl} methyl] phosphonate and the like.

As phosphorus-based antioxidants, tris (2,4-di-tert-butylphenyl) phosphite, tris [2-[[2,4,8,10-tetra-tert-butyldibenzo [d, f]] [ 1,3,2] dioxaphosfefin-6-yl] oxy] ethyl] amine, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis [2,4-bis (1) , 1-dimethylethyl) -6-methylphenyl] ethyl ester phosphite, and tetrakis (2,4-di-tert-butylphenyl) (1,1-biphenyl) -4,4'-diylbisphosphonite And so on.
Examples of the lactone-based 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 product at high temperatures and suppressing the decrease in durability due to metals 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 is preferable, and the above-mentioned polyolefin resin composition is , 3- (3,5-di-tert-butyl-4-hydroxyphenyl) stearyl propionate or 2,4,6-tris (3', 5'-di-tert-butyl-4'-hydroxybenzyl) It preferably contains mesitylen.

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, assuming that the resin composition for producing the second layer 120 is 100% by weight. , More preferably 1% by weight or less, still more preferably 0.5% by weight or less. When the content of the antioxidant is equal to or higher than the above lower limit, the durability of the molded product under high temperature is further increased, and when the content exceeds the above upper limit, the durability of the molded product under high temperature does not change. Therefore, by setting the content to the above upper limit or less, the use of an excessive amount of the antioxidant can be suppressed.

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

Examples of the cross-linking agent include organic peroxides and the like. Examples of the organic peroxide include dicumyl peroxide, diisopropylbenzene hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexine and the like. As the cross-linking 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, it 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 with respect to 100 parts by weight of the polyolefin resin which is a 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. The lubricant may be used alone or in combination of two or more.
The amount of lubricant used is not particularly limited. For example, it is preferably 0.01 parts by weight or more, 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 hindered amine type light stabilizers. One type of light stabilizer may be used alone, or two or more types may be used in combination.

The pigment is not particularly limited, and for example, organic pigments such as azo-based, phthalocyanine-based, slene-based and dye lake-based, and oxide-based, molybdenum chromate-based, sulfide-selenium-based and ferrocyanide-based pigments are used. Examples include inorganic pigments. One of the above pigments may be used alone, or two or more of them may be used in combination.

[1-4. Layer thickness ratio]
The ratio of the layer thicknesses of the first layer 110, the second layer 120 and the third layer 130 of the multilayer tube 100 is such that the thickness of the second layer is 0.5 or more and 2 or less when the relative thickness of the first layer is 1. It can be designed so that the relative thickness of the third layer is preferably 0.5 or more and 1.5 or less, preferably 0.7 or more and 1.2 or less. By setting the thickness of each layer to such a ratio, good surface smoothness and pressure resistance due to the first layer and the third layer can be obtained, and at the same time, the effect of the orientation of the second layer and the earthquake resistance based on the good tensile elongation can be obtained. Good properties can be obtained, and a more preferable performance balance including good creep resistance can be obtained.

The layer thickness of the second layer 120 varies depending on the pipe diameter, but as an example, it may be in the range of 0.5 mm or more and 20 mm or less. However, in the present invention, the layer thickness of the second layer 120 may exceed this range.

[2. Production method]
The multilayer tube 100 is formed by preparing a resin composition for producing the first layer 110 and the third layer 130, respectively, and a resin composition for producing the second layer 120, and molding the multilayer tube 100 using a molding machine. Can be done. The molding machine is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw different-direction parallel extruder, a twin-screw different-direction conical extruder, and a twin-screw same-direction extruder.

In the preparation of the resin composition for producing the second layer 120, the polyolefin resin which is a matrix resin and the glass fiber are kneaded. The MFR of the polyolefin resin to be the matrix resin is 0.1 g / 10 minutes or more and 10 g / 10 minutes or less, preferably 0.3 g / 10 minutes or more and 5 g / 10 minutes or less (condition: 230 ° C., load 2) at the time of kneading. It may be .16 kg). It is preferable that the MFR of the matrix resin is at least the above lower limit value because it is easy to obtain a glass fiber having an average fiber length of 150 μm or more after molding, and that the MFR is at least the above upper limit value is the shape after molding. It is preferable in terms of ease of holding and molding.

In order to bring the average fiber length of the molded glass fiber closer to 700 μm (that is, to adjust the length), it is preferable to add the glass fiber by the side feed method.
In order to bring the average fiber length of the molded glass fiber closer to (that is, adjusted to be shorter) to 150 μm, the MFR of the matrix resin can be adjusted to be smaller.

The average fiber length of the glass fiber (before molding) to be added may be, for example, 1.0 mm or more and 5.0 mm or less. It is preferable that the average fiber length is not less than the above lower limit value because it is easy to obtain an average fiber length of 150 μm or more after molding, and it is preferable that the average fiber length is not more than the above upper limit value is the average of the glass fibers after molding. It is preferable because it is easy to obtain a fiber having a fiber length of 700 μm or less.

The average fiber diameter of the glass fiber to be added may be, for example, 1 μm or more and 30 μm or less. It is preferable that the fiber diameter is at least the above lower limit value from the viewpoint of developing strength. When the fiber diameter is not more than the above upper limit value, it is preferable in that the orientation of the fibers can be easily controlled. From the viewpoint of more effectively obtaining these effects, the fiber diameter of the glass fiber is preferably 5 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. The average fiber diameter is an average value of the maximum diameters of each of the plurality of (for example, 500) fibers contained in the second layer 120.

In the kneading of the polyolefin resin and the glass fiber, the glass fiber is cut to produce a glass fiber fragment having an average fiber length of 150 μm or more, preferably 200 μm or more, 700 μm or less, preferably 650 μm or less.

When molding using a molding machine, the mold to be shaped, the resin temperature, and the like are not particularly limited. The second layer is formed by shaping the glass fiber so as not to be too axially oriented by temporarily narrowing the flow path and further expanding the resin composition containing the glass fiber immediately before making the resin composition into multiple layers in the mold. Can be manufactured.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following inventions.

[Example 1]
(Manufacturing of multi-layer pipe)
The multilayer tube 100 was manufactured as follows.
High-density polyethylene (equivalent to PE100, density 0.94 g / cm ³ ) was prepared as a resin composition for producing the first layer 110 and the third layer 130. As a resin composition for producing the second layer 120, a glass fiber (chopped strand shape, average fiber length 3 mm, average fiber diameter 13 μm, olefin converging agent, silane surface treatment) is added to the same high-density polyethylene resin resin composition as described above. Product) 10% by weight (amount with respect to the entire resin composition for producing the second layer 120) and compatibilizer (maleic anhydride-modified polyethylene, melting point 130 ° C., density 0.96 g / cm ³ ) 1% by weight. A blended resin composition was prepared. The resin composition was kneaded using a twin-screw codirectional extruder to prepare a compound.

Molding was performed by coextrusion using the resin composition for producing the first layer 110 and the third layer 130 and the resin composition for producing the second layer 120. Specifically, three single extruders (the screw diameter of the single extruder for the first layer 110 and the third layer 130 is 40 mm, and the screw diameter of the single extruder for the second layer is 75 mm) are used. It was extruded at an extrusion temperature of 200 ° C. and shaped using a three-layer tube mold. However, the flow path of the second layer of the three-layer tube type is configured to pass through a portion expanded from 2 mm to 6 mm before the first layer and the third layer merge.

The inner diameter of the obtained multilayer tube 100 was 51 mm, the outer diameter was 63 mm, and the thickness ratio of the first layer 110, the second layer 120, and the third layer 130 was 1: 1: 1.

(Measurement of fiber length of glass fiber after molding)
About 0.3 g of a test piece was taken from the second layer 120 of the multilayer tube 100 and burned at 500 ° C. for 1 hour. As a result of measuring the length of the remaining 500 glass fibers using a KEYENCE microscope, the average fiber length was 243 μm.

[Example 2]
A multilayer tube was produced in the same manner as in Example 1 except that the blend amount of the glass fiber in the resin composition for producing the second layer 120 was 15% by weight, and the fiber length of the glass fiber after molding was obtained. Was measured. As a result, the average fiber length was 221 μm.

[Example 3]
A multilayer tube was produced in the same manner as in Example 1 except that the blend amount of the compatibilizer in the resin composition for producing the second layer 120 was 5% by weight, and the fiberglass fibers after molding were produced. The length was measured. As a result, the average fiber length was 240 μm.

[Example 4]
A multilayer tube was manufactured in the same manner as in Example 1 except that the thickness ratio of the first layer 110, the second layer 120, and the third layer 130 of the multilayer tube was 1: 0.5: 1, and after molding. The fiber length of the glass fiber was measured. As a result, the average fiber length was 238 μm.

[Example 5]
A multilayer tube was produced in the same manner as in Example 1 except that the blend amount of the compatibilizer in the resin composition for producing the second layer 120 was 10% by weight, and the fiberglass fibers after molding were produced. The length was measured. As a result, the average fiber length was 233 μm.

[Example 6]
The blend amount of the glass fiber in the resin composition for producing the second layer 120 is 5% by weight, and the thickness ratio of the first layer 110, the second layer 120, and the third layer 130 of the multilayer tube is 1. A multilayer tube was produced in the same manner as in Example 1 except that the ratio was 3: 1, and the fiber length of the glass fiber after molding was measured. As a result, the average fiber length was 240 μm as in Example 1.

[Example 7]
A multilayer tube was produced in the same manner as in Example 1 except that the blend amount of the compatibilizer in the resin composition for producing the second layer 120 was 15% by weight, and the fiberglass fibers after molding were produced. The length was measured. As a result, the average fiber length was 240 μm.

[Comparative Example 1]
A multilayer tube was produced in the same manner as in Example 1 except that the blend amount of the glass fiber in the resin composition for producing the second layer 120 was 25% by weight, and the fiber length of the glass fiber after molding was obtained. Was measured. As a result, the average fiber length was 208 μm.

[Comparative Example 2]
The flow path of the second layer of the three-layer tube type was carried out except that the flow path of the second layer was formed by a mold not composed of a portion expanded from 2 mm to 6 mm before the first layer and the third layer merged. A multilayer tube was manufactured in the same manner as in Example 1, and the fiber length of the glass fiber after molding was measured. As a result, the average fiber length was 248 μm as in Example 1.

[Comparative Example 3]
The tube was produced in the same manner as in Example 1 except that the resin composition for producing the second layer 120 did not contain glass fiber. That is, both the first layer to the third layer were composed of the same resin composition, and a single-layer tube was substantially manufactured.

[Comparative Example 4]
A multi-layer tube was manufactured in the same manner as in Example 1 except that the resin composition was kneaded using a twin-screw codirectional extruder and the screw rotation speed was increased up to 3 times to prepare a compound. Fiber length was measured. As a result, the average fiber length was 120 μm.

[performance test]
The following performance tests were performed on the tubes obtained in Examples 1 to 7 and Comparative Examples 1 to 4.

[A. Tensile strength / elongation]
The tensile yield strength and the tensile elongation at break were tested under the following conditions based on JIS K7161 (1994).
Specimen: JIS K7162 (1994) type 1B type (punching)
Test temperature: 23 ° C
Test speed: 50 mm / min
Testing machine: Tensilon (UCT-5T Orientec)
However, the test piece was measured by punching in the axial direction and the circumferential direction. When punching in the circumferential direction, the prototype tube was heated at 200 ° C. for 10 minutes, pressed with a hand press to form a flat plate, and then punched after cooling.

[B. Orientation area ratio]
A cross section of the multilayer tube obtained by cutting a thick wall on the surface including the axis was visually observed using a scanning electron microscope JSM-671F manufactured by JEOL Ltd. under the conditions of a vapor deposition thickness of 10 nm, an acceleration voltage of 15 kV, and a magnification of 25 times. The ratio of the total cross-sectional area of the oriented layer to the cross-sectional area of the two layers was determined.

[C. Pressure resistance measurement]
Destructive water pressure evaluation was performed in accordance with PWA (Polyethylene Pipe System Study Group for Building Equipment) 001 standard. That is, a test piece of a multi-layer pipe having a length of 1000 mm is cut out, filled with water at room temperature (25 ° C), and pressurized by continuously pouring water at a constant speed to obtain the water pressure when the multi-layer pipe bursts. rice field.

[D. Linear expansion coefficient measurement]
The coefficient of linear expansion of the multilayer tube was obtained as follows. The multi-layer tube was cut to a length of 1000 mm and cured in a constant temperature bath set at 60 ° C. (Thot) for 24 hours. After curing, the length of the multi-layer tube (Lhot) was measured. Then, the same multi-layer pipe was cured in a constant temperature bath set at 5 ° C (Tcool) for 24 hours, and the length (Lcool) of the multi-layer pipe was measured. The obtained value was substituted into Equation 1 below to determine the coefficient of linear expansion.

The above test results are shown in Tables 1 and 2 below together with the components of each Example and each Comparative Example. As shown in these tables, in Examples 1 to 7, multi-layer tubes having an excellent performance balance exhibiting high strength and good tensile elongation were obtained. In order to improve the pressure resistance, it was effective to improve the tensile yield strength in the circumferential direction, and in order to improve the seismic resistance, it was effective to improve the tensile elongation at break in the axial direction.

Preferred embodiments of the present invention are as described above, but the present invention is not limited thereto, and various embodiments that do not deviate from the gist of the present invention are made elsewhere.

100 Multi-layer pipe 110 1st layer 120 2nd layer 121 Orientation layer 130 3rd layer

Claims (4)

The first layer, the second layer and the third layer are included in this order in the direction from the axis to the outer circumference.
The first layer and the third layer contain a polyolefin resin as a main component, and the first layer and the third layer contain a polyolefin resin as a main component.
The second layer contains a polyolefin resin and glass fibers, and the blending amount of the glass fibers is 5% by weight or more and 18% by weight or less, and the average of the glass fibers contained in the second layer after molding. The fiber length is 150 μm or more and 700 μm or less, and
The second layer has a continuous alignment layer in which the glass fiber is oriented in a direction along the axis, and has an orientation area of 5% or more and less than 40% in a cross section when cut at a surface including the axis. It is a ratio,
In the glass fiber of the alignment layer, the direction of at least 50% of the fibers having a length of 10% or more of the average fiber length of the glass fiber is within ± 15 ° with respect to the axial direction. Polyformic resin multilayer tube. The polyolefin-based resin multilayer tube according to claim 1, wherein the second layer further contains an acid-modified polyolefin-based resin as a compatibilizer. The polyolefin resin multilayer tube according to claim 2, wherein the content of the acid-modified polyolefin resin in the second layer is 0.3% by weight or more and 10% by weight or less. When the relative thickness of the first layer is 1, the relative thickness of the second layer is 0.5 or more and 2 or less, and the relative thickness of the third layer is 0.5 or more and 1.5 or less. Item 2. The polyolefin-based resin multilayer tube according to any one of Items 1 to 3.

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