JP2004270852A - Multilayer polyolefin tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-layer polyolefin tube capable of coping with solvent penetration, applying to pipe jacking methods, improving workability and reducing cost on material, and being usable for exposed piping. <P>SOLUTION: This multilayer polyolefin tube 10 includes a main tube 12 formed of polyolefin resin and a covering layer 14. The covering layer 14 includes a covering inner layer 16 having resistance to solvent penetration formed of polyamide, for example. On the covering inner layer 16, a covering outer layer 20 formed of polypropylene, for example, and having moisture resistance is laminated through a covering bonding layer 18. The covering layer 14 has prescribed thickness to be applicable to pipe jacking methods, while it can be easily peeled from the main tube 12, so that the main tube 12 is prevented from being damaged. The covering layer 14 only can be easily eliminated without scraping work at the time of junction. By adding coloring agent to the covering outer layer 20, the main tube 12 can be uncolored. By adding weather resisting agent to the covering outer layer 20, deterioration due to light can be prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a multi-layer polyolefin pipe, and more particularly to a multi-layer polyolefin pipe having a main pipe formed of, for example, a polyolefin-based resin and a coating layer covering an outer peripheral surface of the main pipe.
[0002]
[Prior art]
Examples of pipes in which a coating layer is formed on a main pipe made of a polyolefin-based resin are disclosed in Patent Documents 1 to 5, for example. In Patent Literature 1, an aluminum tape as a coating layer (outer layer) is wound around the outer periphery of a main pipe (pipe main body) with a margin for joining at both ends, in order to prevent solvent penetration. In Patent Literature 2, the coating layer (outer layer) is made of, for example, a material based on LDPE (low-density polyethylene) to which an inorganic filler has been added in order to easily remove the coating from the main pipe (core pipe). Also disclosed is one in which this coating layer is used as the outermost layer and a thin aluminum layer is provided between the outermost layer and the core pipe. In Patent Document 3, the coating layer (surface layer) is made of a resin having a light shielding property such as a soft polyvinyl chloride resin having a thickness of, for example, 0.3 mm or more and 3 mm or less for an exposed pipe, The main pipe (pipe main body layer) and its interface are in a non-adhered state. In Patent Document 4, the coating layer is made of a thermoplastic polymer having resistance to permeation of hydrocarbons and oxygen to prevent solvent penetration, and is fused to the main pipe (base pipe) without an adhesive layer. Is done. In Patent Document 5, in order to omit the canning during fusion bonding, the resin forming the main pipe (pipe body) is made of a resin having a thickness of 0.01 to 0.5 mm which is incompatible and non-foamed. The coating layer (protective layer) is formed integrally with the main pipe by multiple extrusion.
[0003]
Japanese Patent Application No. 2002-111855 previously filed by the present applicant (hereinafter referred to as “prior art 1”) also shows such an outer-layer-coated polyolefin tube. In this prior art 1, the coating layer (outer layer) is made of polyolefin, vinyl chloride, polyamide, ethylene vinyl alcohol, or the like, and is provided so that the main pipe (inner layer) can be easily peeled off without being damaged. Have been.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-2462 [Patent Document 2]
Japanese Patent Application Laid-Open No. Hei 7-1542 [Patent Document 3]
JP-A-10-267172 [Patent Document 4]
JP 2001-330179 A [Patent Document 5]
Japanese Patent No. 2868018 [0005]
[Problems to be solved by the invention]
However, in Patent Literature 1, if the aluminum tape is torn during transportation or construction, the solvent permeation resistance will be extremely reduced. Therefore, there is a problem that it cannot be used for the propulsion method. In addition, since a welding margin is left at the end of the pipe, when performing electrofusion bonding, etc., in order to obtain a new and clean bonding surface, complicated and troublesome scraping (cutting) work is performed using a special tool. It is necessary and the workability is poor.
[0006]
In Patent Literature 2, LDPE to which an inorganic filler is added does not have sufficient solvent penetration resistance, and therefore cannot be used as a pipe for preventing solvent penetration. In addition, since the coating is removed by hitting and breaking the coating layer, there is a problem that the main pipe is likely to be damaged and workability is poor. On the other hand, when the aluminum layer is provided, the aluminum layer has solvent resistance, but it is difficult to remove the aluminum layer at the time of joining, and the workability is also poor. Further, there is a problem that manufacturing equipment for providing the aluminum layer is extremely expensive and costly.
[0007]
In Patent Literature 3, the soft polyvinyl chloride resin does not have sufficient solvent permeation resistance, and thus cannot be used as a pipe for preventing solvent permeation. Further, when the thickness of the coating layer is set to about 0.3 mm, when used in the propulsion method, there is a strong possibility that a scratch on the pipe surface at the time of construction penetrates the coating layer and reaches the main pipe.
[0008]
In Patent Document 4, since the coating layer is fused to the main pipe, the scraping work at the time of fusion joining cannot be omitted, but the cutting allowance increases, and the work requires more time than before, and the workability is reduced. There is a problem of bad.
[0009]
In Patent Document 5, although the constituent material of the coating layer is a resin different from the constituent material (polyolefin) of the main pipe, it is not particularly disclosed. Therefore, even if the scraping operation can be omitted, it cannot be used as a solvent penetration prevention pipe. That is, even if a resin having a solvent permeation resistance, such as polyamide or ethylene vinyl alcohol, is used for the coating layer, the solvent permeation resistance may be significantly reduced by ambient moisture because the coating layer is located on the outermost layer. . When a material other than those described above is used, solvent penetration resistance cannot be obtained.
[0010]
Further, the prior art 1 also has a problem similar to that of Patent Document 5 described above. That is, when the coating layer is formed of polyolefin or vinyl chloride, sufficient solvent penetration resistance cannot be obtained. On the other hand, polyamide and ethylene vinyl alcohol are excellent in solvent permeation resistance, but there is a problem that if the surrounding humidity is high, moisture or water is absorbed, and the solvent permeation resistance is extremely reduced.
[0011]
Therefore, a main object of the present invention is to provide a multilayer polyolefin pipe that can be used as a pipe for preventing solvent penetration and a pipe for preventing a propulsion method and that can improve workability.
[0012]
Another object of the present invention is to provide a multi-layer polyolefin pipe which can further cope with an exposed pipe.
[0013]
It is another object of the present invention to provide a multi-layer polyolefin tube that can further reduce material costs.
[0014]
[Means for Solving the Problems]
The present invention relates to a multi-layer polyolefin pipe having a main pipe formed of a polyolefin-based resin and a coating layer covering an outer peripheral surface of the main pipe, wherein the coating layer has a coating inner layer having resistance to solvent penetration, a moisture-proof property and coloring. Includes a coating outer layer to which pigment is added, and a coating adhesive layer for bonding the coating inner layer and the coating outer layer, and has a predetermined thickness capable of propulsion work, and can be easily peeled off from the main pipe. It is a multilayer polyolefin pipe characterized by being overlapped as follows.
[0015]
[Action]
The coating inner layer has resistance to solvent penetration, and can be formed of, for example, a polyamide resin. The outer coating layer is moisture-proof and may be formed, for example, of polypropylene. As described above, since the outer coating layer having moisture resistance is provided outside the inner coating layer, even if the inner coating layer has hygroscopicity, it is possible to prevent a decrease in solvent permeation performance due to water absorption. Therefore, it can be used as a pipe for preventing solvent penetration. In addition, since the coating layer has a predetermined thickness capable of being propelled and constructed, it is possible to prevent a flaw from penetrating the covering layer at the time of construction by the propulsion method, so that the main pipe is not damaged. Furthermore, the coating layer is provided so that it can be easily peeled off from the main pipe. For example, since the coating layer is not adhered to the main pipe, even if the coating layer is damaged, the damage propagates to the main pipe. It won't hurt you. Therefore, it can be used as a propulsion method countermeasure pipe. In addition, the coating layer is firmly integrated by bonding with the coating adhesive layer, but the main pipe and the coating layer are in a state that can be easily peeled off. Instead, only the coating layer can be easily peeled off from the main pipe and removed. Therefore, a clean surface for joining can be easily obtained without damaging the surface of the main pipe, and workability can be improved. Further, since a coloring pigment is added to the outer coating layer, the main pipe can be made non-colored. That is, the main tube may be colored or uncolored, but if the main tube is not colored, the material cost can be reduced.
[0016]
Further, a weathering agent may be further added to the outer coating layer. In this case, combined with the fact that the outer coating layer is colored and not transparent, it is possible to prevent the main pipe from being irradiated with light (ultraviolet rays), and to prevent deterioration of the main pipe surface due to light. Therefore, it can be used for an exposed pipe.
[0017]
Further, a coloring pigment may be added to the inner coating layer. In this case, since the coating inner layer is also colored, it can be easily confirmed that the coating layer was surely removed at the time of joining. Therefore, the workability can be further improved.
[0018]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can be used as a solvent penetration prevention pipe and a propulsion method countermeasure pipe, and can also improve workability. Further, the material cost can be reduced. Also, if a weathering agent is added to the outer coating layer, it can be used for exposed piping.
[0019]
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0020]
【Example】
The multilayer polyolefin pipe 10 of this embodiment shown in FIG. 1 can be used for, for example, a water pipe or a gas pipe, and includes a main pipe 12 and a coating layer 14 that coats an outer peripheral surface of the main pipe 12. .
[0021]
FIG. 1A is a cross-sectional view orthogonal to the tube axis, and FIG. 1B is an enlarged view of a part (broken line) of the tube wall in FIG. 1A for easy understanding. ing.
[0022]
The main pipe 12 has a predetermined diameter and thickness, and its constituent material is, for example, a polyolefin resin such as polyethylene (low density, medium density, high density, ultra high density, etc.), polybutene or polypropylene. Further, the main pipe 12 may be colored by adding a coloring pigment for use identification, or may be uncolored without adding a coloring pigment. If the main pipe 12 is made uncolored, the material cost can be reduced.
[0023]
In addition, in this specification, each resin as a constituent material of the tube 10 includes its resin composition.
[0024]
The coating layer 14 includes a coating inner layer 16, a coating adhesive layer 18, and a coating outer layer 20, and has a three-layer structure laminated in this order from the inside.
[0025]
The coating inner layer 16 has excellent solvent penetration resistance. The coating inner layer 16 is formed of, for example, a polyamide resin. Further, the constituent material of the coating inner layer 16 is not limited to a polyamide resin, but in another embodiment, a resin having a higher resistance to solvent permeation than the polyolefin resin of the main pipe 12, for example, ethylene vinyl alcohol, etc. Good. Although it is very expensive, a fluororesin (tetrafluoroethylene-ethylene copolymer or the like) may be used in some cases.
[0026]
Further, since the coating layer 14 is superimposed on the outer peripheral surface of the main pipe 12 by multilayer coating extrusion molding as described later, the coating inner layer 16 is in close contact with the main pipe 12 but is not adhered thereto. Accordingly, the coating inner layer 16 is provided in a non-adhered state to the main pipe 12, that is, in a state where it can be easily peeled off. In this sense, the coating inner layer 16 is easily peeled from the main pipe 12 with respect to the main pipe 12. It can be said that it is provided with the property.
[0027]
The coating adhesive layer 18 is for bonding the coating inner layer 16 and the coating outer layer 20. The constituent material of the coating adhesive layer 18 is, for example, an adhesive polyolefin or the like, and as a product, for example, “Admer (registered trademark)” manufactured by Mitsui Chemicals, Inc. or the like can be used. The coating layer 14 is firmly integrated by the coating adhesive layer 18.
[0028]
The coating outer layer 20 has excellent moisture-proof properties. This coating outer layer 20 is formed of, for example, polypropylene. Polypropylene is also relatively hard, and has a higher hardness than, for example, polyethylene (Rockwell hardness (representative value) of block PP is R85, and Rockwell hardness (representative value) of high-density polyethylene is R70). If it is made of polypropylene, it can be hardly damaged.
[0029]
A coloring pigment (colorant) is added to the coating outer layer 20 for identifying the use of the multilayer polyolefin tube 10. Specifically, it is colored blue for water use and yellow for gas use. It is preferable that the coloring pigment has a high light blocking property.
[0030]
In this embodiment, a sufficient amount of a weathering agent is added to the outer coating layer 20 to provide excellent weather resistance. The weathering agent is an ultraviolet absorber or the like, and for example, a salicylic acid ester type, a benzotriazole type, a hydroxybenzophenone type or the like can be used.
[0031]
The constituent material of the coating outer layer 20 is not limited to polypropylene, and in another embodiment, for example, a soft vinyl chloride resin or the like may be used. However, according to experiments by the inventors, when the outer coating layer 20 was formed of polypropylene, the outer coating layer 20 was most easily torn and the coating layer 14 was most easily removed from the main pipe 12. Further, among homo PP, random PP and block PP classified according to the structure of polypropylene, etc., the result that the block PP is most easily removed is obtained.
[0032]
The thickness of each of the layers 16, 18, and 20 of the coating layer 14 is appropriately set, but is set to a predetermined thickness that can prevent penetration of a scratch during the propulsion work, and the hardness that can be propelled is provided. According to the experiments and experiences of the inventors, the thickness of the coating inner layer 16 is desirably set to 0.01 mm or more and 0.3 mm or less, the thickness of the coating outer layer 20 is set to 0.3 mm or more, and Is set to about 0.5 mm or more. In this way, by setting the thickness of the entire coating layer 14 to about 0.5 mm or more, it is possible to prevent the flaws from penetrating the coating layer 14 at the time of construction by the propulsion method, and to prevent the main pipe 12 from being damaged. Therefore, this multilayer polyolefin pipe 10 can be used for the propulsion method. If the coating inner layer 16 is too thick, the work of removing the coating layer 14 becomes difficult. Therefore, it is desirable to set the thickness to about the above numerical value. Further, in a case where both a measure against solvent penetration and a measure against the propulsion method are required, and further high humidity is assumed in the surrounding area, the thickness of the coating outer layer 20 may include a scratch within the thickness. It is desirable to set the thickness to a predetermined value.
[0033]
The multilayer polyolefin pipe 10 is formed, for example, by extruding a coating layer 14 in a multilayer coating extrusion step on the outer pipe of the main pipe 12 by extruding the main pipe 12 previously extruded alone and cooled and solidified. Can be manufactured. Specifically, in the production line of the extrusion molding, as the equipment for the coating extrusion process as shown in FIG. 2, the second mold 22, the second extruder 24, the third extruder 26, and the fourth extruder are provided. 28 etc. are incorporated. For example, a first extruder and a first mold for extruding the main pipe 12, first to third vacuum water tanks for sizing and cooling, a printing machine, a take-off machine, an annealing device, a cooling water tank and a cutting machine, and the like. In a well-known extruder manufacturing apparatus (not shown) which is provided in order with, for example, between the third vacuum water tank and the printing machine, together with the coating extrusion equipment of FIG. A water tank (not shown) and the like are provided.
[0034]
The second mold 22 is a crosshead die for multi-layer (three-layer) extrusion, and the tip of a second extruder 24, a third extruder 26, and a fourth extruder 28 for extruding the molten material of each layer. Are connected respectively. The second extruder 24, the third extruder 26, and the fourth extruder 28 heat and melt the raw materials of the coating inner layer 16, the coating adhesive layer 18, and the coating outer layer 20 and supply the raw materials to the second mold 22. In the second mold 22, the molten materials of the respective layers are sequentially merged and stacked as they progress in the traveling direction. Then, the coating layer 14 is extruded from the outlet as the coating layer 14 in a laminated state.
[0035]
The extruded coating layer 14 is brought into close contact with the outer peripheral surface of the main pipe 12 that has been inserted through the second mold 22 and sent. The close contact may be achieved by, for example, providing a tapered sleeve at the front of the opening, providing a sleeve or the like defining the outer diameter at the entrance of the next cooling water tank, or providing the main pipe 12 at the front of the second mold 22. This can be performed by placing the space between the resin layer and the coating layer 14 under reduced pressure, or by forming the resin flow path in a tapered shape at the tip of the second mold 22. In this manner, the main pipe 12 and the coating layer 14 are adhered to each other, but the main pipe 12 is already cooled and solidified at the time of coating and is not in a molten state, and the coating inner layer 16 and the main pipe 12 are made of different materials. Therefore, the main pipe 12 and the coating layer 14 do not fuse or adhere to each other, and the two are not completely integrated. On the other hand, the intermediate layer of the covering layer 14 is an adhesive layer, and the covering inner layer 16 and the covering adhesive layer 18 are adhered to each other by the covering adhesive layer 18 to form the strongly integrated covering layer 14.
[0036]
Incorporating the above-described coating extrusion process for forming the coating layer 14 into an existing extrusion molding facility is because, for example, an aluminum layer as described in Patent Document 2 is formed between the main pipe and the outermost layer. This can be carried out at extremely low cost as compared with preparing such equipment.
[0037]
When this multilayer polyolefin pipe 10 is used, it is transported to the construction site while the main pipe 12 is covered with the coating layer 14. Then, when the pipes are fusion-bonded to each other, for example, as shown in FIG. At this time, for example, a notch that does not penetrate the coating layer 14 may be made using a cutter knife or the like, and the coating layer 14 may be torn off from that portion.
[0038]
In this embodiment, since the outer coating layer 20 is formed of a material (such as polypropylene) having a small tear resistance or tear strength, that is, an easily tearable material, the outer coating layer 20 can be easily torn when removed. . According to experiments by the inventors and the like, it was possible to tear easily enough if a cut having a depth of about 50% of the thickness of the coating outer layer 20 was made. Since the outer coating layer 20 and the inner coating layer 16 are integrated by the coating adhesive layer 18, the entire coating layer 14 can be easily torn by tearing the outer coating layer 20. Further, the coating layer 14 is integrated by the coating adhesive layer 18, but since the main pipe 12 and the coating layer 14 are not bonded as described above, only the coating layer 14 is easily peeled off from the main pipe 12. Can be removed.
[0039]
In this way, a new clean fused surface 30 can be obtained at the end of the multi-layer polyolefin tube 10 as shown in FIG. 3B without performing a complicated scraping operation. Then, after performing the cleaning operation of the fusion surface 30, as shown in FIG. 3C, the fusion surface 30 and the inner surface of the socket of the electrofusion joint 32 are joined by electrofusion. The fusion surface 30 is an intact and clean surface protected by the coating layer 14 until immediately before, so that good bonding can be performed. Thereafter, it is desirable to secure the solvent permeation resistance at the joint by coating the outside of the joint with a sleeve having a polyamide layer or an aluminum layer, for example.
[0040]
The joint to be joined is not limited to the electric fusion joint 32, and may be a heat fusion joint or the like. In addition, not only the joining of the pipe ends, but also, for example, when a saddle or the like for connecting a branch pipe is provided, it is possible to cope with the same by peeling off the coating layer 14 at the portion forming the branch portion. In addition, the present invention can be similarly applied to a case where the fixed-sized multilayer polyolefin tube 10 is cut into a predetermined length and used as an adjusting tube.
[0041]
According to this embodiment, the coating inner layer 16 is formed of a material having excellent solvent permeation resistance, and the coating outer layer 20 is formed of a material having excellent moisture resistance. Even if it is formed of a material having a hygroscopic property such as ethylene vinyl alcohol, etc., the permeation of moisture to the inner coating layer 16 is prevented by the outer coating outer layer 20, and the solvent permeation resistance of the inner coating layer 16 is reduced due to water absorption. Can be prevented. Therefore, since the coating inner layer 16 sufficiently exhibits its solvent permeation resistance and prevents the penetration of contaminants such as organic solvents into the main pipe 12, the multilayer polyolefin pipe 10 is used as a pipe for preventing solvent permeation. be able to.
[0042]
Further, since the coating layer 14 is set to a predetermined thickness, it is possible to prevent the main pipe 12 from being damaged even when used in the propulsion method. In addition, in this embodiment, the coating outer layer 20 is formed of a relatively hard material such as polypropylene, so that the coating outer layer 20 itself can be prevented from being scratched, and the coating outer layer 20 can be more reliably connected to the main pipe 12. Scratches can be prevented. Further, since the main pipe 12 and the coating layer 14 are not bonded and fused, even if the coating layer 14 is damaged, the damage does not propagate to the main pipe 12 and the main pipe 12 is damaged. Is prevented. Therefore, the multilayer polyolefin pipe 10 can be used as a pipe for a propulsion method.
[0043]
Furthermore, as described above, the coating layer 14 can be easily torn and easily peeled off from the main pipe 12, so that a troublesome scraping operation is not required. it can. Therefore, it is possible to easily obtain a clean surface for joining without damaging the surface of the main pipe 12, and to improve workability.
[0044]
Further, since a coloring pigment for use identification is added to the coating outer layer 20, the main pipe 12 can be made non-colored. Therefore, when the main pipe 12 is made uncolored, the overall material cost can be reduced even if the coating layer 14 is formed.
[0045]
Further, in this embodiment, since a weathering agent is further added to the coating outer layer 20, it is possible to prevent the main pipe 12 from being irradiated with light (ultraviolet light), and to prevent deterioration due to the irradiation. In addition, light can be more effectively shielded because the outer coating layer 20 is colored and not transparent. Therefore, for example, the surface of the main pipe 12 can be prevented from being oxidized during storage, and the multilayer polyolefin pipe 10 can be used as an exposed pipe.
[0046]
In the above-described embodiment, the coloring pigment is added only to the outer coating layer 20, but in other embodiments, the coloring pigment may be further added to the inner coating layer 16. In this case, since the coating inner layer 16 is also colored, it can be easily confirmed that the coating layer 14 has been reliably removed at the time of joining. Therefore, the workability can be further improved.
[0047]
Further, in each of the above-described embodiments, a cut is made with a cutter knife or the like when removing the coating layer 14, but in other embodiments, the coating layer 14 is removed from the coating outer layer 20. May be formed. As the guide, for example, a groove-shaped thin portion, perforation, or the like may be formed to extend linearly or spirally. However, it is necessary that the depth of the guide does not reach the inner coating layer 16, and it is desirable that the depth of the guide be within the thickness of the outer coating layer 20. When the guide is formed in this manner, the tearing of the coating layer 14 can be easily started using the guide as a clue without using a cutter knife or the like, so that the coating layer 14 can be more easily removed. And the workability can be further improved. It should be noted that such a guide formation for removing the coating layer is described in detail in the above-mentioned prior art 1, that is, Japanese Patent Application No. 2002-111855 previously filed by the present applicant, and therefore, please refer to it.
[Brief description of the drawings]
FIG. 1 is an illustrative view showing a multilayer polyolefin pipe of one embodiment of the present invention, (A) is a cross-sectional view, and (B) is a partially enlarged view in (A).
FIG. 2 is an illustrative view showing one portion of a manufacturing process of the embodiment in FIG. 1 and showing an example of a process of coating and extruding a coating layer on a main pipe;
FIG. 3 is an illustrative view schematically showing a state of a joining step in the embodiment of FIG. 1, wherein (A) shows a state of removing a coating layer, and (B) shows a pipe end from which the coating layer has been removed; (C) shows the joint part which was fusion-bonded.
[Explanation of symbols]
10 Multilayer polyolefin pipe 12 Main pipe 14 Coating layer 16 Coating inner layer 18 Coating adhesive layer 20 Coating outer layer

Claims (4)

A multi-layer polyolefin pipe comprising a main pipe formed of a polyolefin-based resin and a coating layer covering an outer peripheral surface of the main pipe,
The coating layer,
Coating inner layer having solvent penetration resistance,
The main pipe includes a coating outer layer having moisture resistance and to which a coloring pigment is added, and a coating adhesive layer for bonding the coating inner layer and the coating outer layer, and having a predetermined thickness capable of being propelled and constructed, and A multi-layer polyolefin pipe characterized by being stacked so that it can be easily peeled off. The multilayer polyolefin tube according to claim 1, wherein a weathering agent is further added to the outer coating layer. The multilayer polyolefin pipe according to claim 1 or 2, wherein a coloring pigment is added to the coating inner layer. The multilayer polyolefin pipe according to any one of claims 1 to 3, wherein the inner coating layer is formed of a polyamide resin, and the outer coating layer is formed of polypropylene.

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