JP2012215300A - Multilayered resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered resin pipe in which a coating layer can be peeled certainly and easily.SOLUTION: The multilayered resin pipe is obtained by integrally forming a major layer of a polyethylene resin, that is a main pipe, and the coating layer of a polypropylene resin peelably laminated on an outer peripheral surface of the major layer, by co-extrusion molding, wherein the coating layer is formed using the polypropylene resin having an elastic modulus of 1,000 MPa or more and a molecular weight of 5.0×10or less.

Description

  The present invention relates to a multilayer resin pipe to be joined using an electric fusion joint.

  Conventionally, a synthetic resin pipe such as a polyethylene pipe is frequently used for water pipes, gas pipes and the like because they are excellent in durability, corrosion resistance and flexibility, and are lightweight and excellent in workability (workability). In addition, as a joint for sockets, elbows, cheeses, saddles, etc., for joining this type of pipe material, it is possible to simply perform the joining work without using expensive tools, and there is no variation in joining quality and high reliability. Therefore, EF joints (electric fusion joints) are frequently used.

  The EF joint is formed using a synthetic resin such as polyethylene, and is formed by embedding a heating wire such as a nichrome wire in a spiral shape on the inner peripheral surface side of the joint body. The EF joint is formed by providing a pair of terminal pins (terminal pins) projecting radially outward from the outer peripheral surface of the joint body, and connecting both ends of the heating wire to the terminal pins.

  And when joining pipe materials using an EF joint, the cable connector of a controller (electric conduction apparatus) is attached to a pair of terminal pins in the state which fitted the end part of each pipe material to the joint main body, and it is attached to a heating wire. Energize to generate heat. Due to the heat generated by the heating wire, the inner peripheral surface side of the joint body and the outer peripheral surface side of the pipe material are fused, and the pipe materials can be joined to each other through the EF joint.

  Here, a foreign material such as dust may adhere to the pipe material of the synthetic resin pipe at a piping site or the like. In addition, an oxide layer may be formed on the outer peripheral surface due to exposure to the atmosphere at a high temperature during processing by extrusion molding, which may cause oxidative degradation. Furthermore, the outer peripheral surface may be photodegraded by ultraviolet rays. For this reason, conventionally, when joining pipe materials using EF joints, a scraping operation is performed to scrape off the outer peripheral surface of the portion to be a fusion surface on the end side of the pipe material before fusion, and further acetone or the like is used. It is used to clean the outer peripheral surface.

  On the other hand, since the scraping work requires a special tool and is a laborious work, it is desired to improve the workability by allowing the pipe materials to be joined with an EF joint without performing the scraping work. It was.

  On the other hand, Patent Document 1 discloses a multilayer resin pipe in which a coating layer such as a polyolefin resin is integrally provided on the outside of a main layer (main pipe) of a polyolefin resin by coextrusion molding so as to be peeled off. ing. In this multilayer resin pipe, the coating layer is quickly and integrally formed on the main layer by coextrusion molding, so that no oxidative deterioration occurs on the outer peripheral surface of the main layer which is the main pipe. Further, since the main layer is covered with the coating layer, the light deterioration does not occur. Also, in the stage of joining using the EF joint, the coating layer is peeled off from the main layer of the main pipe to expose the main pipe's fused surface, so that no foreign matter such as dust adheres to the fused surface. It is possible to perform the joining work with ensuring. Thereby, by using the multilayer resin pipe disclosed in Patent Document 1, it is possible to perform the joining work without using the scraping work and to improve the workability.

JP 2004-225821 A

  However, in the above-mentioned conventional multilayer resin pipe, the coating layer such as polyolefin resin provided outside the main layer (main pipe) of the polyolefin resin has a difference in peelability due to differences in resin physical properties such as molecular weight and elastic modulus. It will occur. For this reason, in a multilayer resin pipe in which the coating layer is simply formed integrally with the main layer, there is a possibility that the coating layer may not be suitably peeled off during the joining operation, and a method for reliably and easily peeling the coating layer Development of was strongly desired.

  In order to solve the above problems, the present invention provides the following means.

The multilayer resin pipe according to claim 1 is formed by integrally forming a main layer of polyethylene resin as a main pipe and a coating layer of polypropylene resin laminated on the outer peripheral surface of the main layer so as to be peelable. The covering layer is formed of a polypropylene resin having an elastic modulus of 1000 MPa or more and a molecular weight of 5.0 × 10 ⁵ or less.

  The multilayer resin pipe according to claim 2 is the multilayer resin pipe according to claim 1, wherein the coating layer is formed of a homopolymer of propylene.

  The multilayer resin pipe according to claim 3 is the multilayer resin pipe according to claim 1 or 2, wherein the ratio X / Y between the fluidity index X of the coating layer and the fluidity index Y of the main layer is from 8 to The range is 12.

  In the multilayer resin pipe according to claim 1, by forming a coating layer using a polypropylene resin having an elastic modulus of 1000 MPa or more, no tearing occurs when peeling from the main layer of the main pipe. Thus, the multilayer resin tube can be formed in such a manner that the coating layer can be peeled off reliably and easily.

Further, by forming a coating layer using a polypropylene resin having a molecular weight of 5.0 × 10 ⁵ or less, the viscosity at the time of coextrusion molding is maintained in a suitable state with respect to the polyethylene resin of the main layer which is the main pipe. Therefore, it is possible to form the coating layer with high accuracy without generating wrinkles or the like. As a result, the adhesion strength (peeling strength) to the main layer becomes too high, the adhesion strength becomes too low, and the coating layer cannot be easily peeled off when peeling the coating layer from the main layer of the main pipe, It is possible to prevent the coating layer from being peeled off from the main layer before the peeling operation, and it is possible to form the coating layer and the multilayer resin tube with suitable peelability that can be peeled more reliably and easily.

  3. The multilayer resin pipe according to claim 2, wherein the coating layer is peeled off from the main layer of the main pipe by being formed of a homopolymer of propylene (homo PP) having a crystal structure that is largely different from the polyethylene resin of the main layer. The releasability at the time can be kept good.

  In the multilayer resin pipe according to claim 3, the ratio X / Y between the fluidity index (MFR) X of the coating layer and the fluidity index Y of the main layer is in the range of 8 to 12 so that the post-peeling The surface roughness can be kept small, and the appearance can be kept good.

It is a figure which shows the multilayer resin pipe which concerns on one Embodiment of this invention. It is the X1-X1 arrow view figure of FIG. It is a figure which shows an example of the extrusion molding apparatus used when manufacturing the multilayer resin pipe which concerns on one Embodiment of this invention by coextrusion molding.

  Hereinafter, a multilayer resin tube according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  The multilayer resin pipe 1 of this embodiment is a pipe material joined by an EF joint (electric fusion joint) as a water pipe, a gas pipe, etc. As shown in FIG. 1 and FIG. A main layer (inner layer) 2 and a polypropylene resin coating layer (outer layer) 3 detachably laminated on the outer peripheral surface 2a of the main layer 2 are integrally formed.

Moreover, in this embodiment, when joining the multilayer resin pipe 1 using an EF joint, in order to peel off the coating layer 3 suitably, the coating layer 3 is a polypropylene having a molecular weight of 5.0 × 10 ⁵ or less. It is formed using resin. Furthermore, the coating layer 3 is formed using a polypropylene resin having an elastic modulus of 1000 MPa or more.

  Furthermore, in this embodiment, the coating layer 3 is formed of a propylene homopolymer (homo PP). And it selected so that ratio X / Y of the fluidity index X of the coating layer 3 and the fluidity index Y of the main layer 2 might be in the range of 8-12.

  On the other hand, the multilayer resin tube 1 of this embodiment is manufactured using, for example, an extrusion molding apparatus 4 as shown in FIG. In this extrusion molding apparatus 4, a cylindrical cavity 7 is formed by providing an inner mold (core mold) 6 inside a cylindrical outer mold (cavity mold) 5, and around the outer mold 5, Two extruders 8 and 9 are provided to melt and plasticize the resin and feed it into the cavity 7. One extruder 8 is arranged to supply polyethylene resin forming the main layer 2 of the main pipe into the cavity 7 upstream in the extrusion direction T of the molded product, and the other extruder 9 is coated. The polypropylene resin forming the layer 3 is arranged to be fed into the cavity 7 on the downstream side in the extrusion direction T.

  And the multilayer resin tube 1 of this embodiment is manufactured by coextrusion molding using the above extrusion molding apparatuses 4. FIG. Specifically, when the multilayer resin tube 1 is formed, the polyethylene resin (2) extruded from one extruder 8 flows through the cavity 7 between the inner mold 6 and the outer mold 5 in the extrusion direction T. To form a main layer 2 of the main pipe. At the same time, the polypropylene resin (3) extruded from the other extruder 9 is extruded between the polyethylene resin of the main layer 2 flowing through the cavity 7 and the inner surface of the outer mold 5. This polypropylene resin (3) flows in the extrusion direction T in the cavity 7 and is formed into a cylindrical shape so as to cover the outer periphery of the main layer 2, and is integrally laminated so as to cover the outer peripheral surface 2a of the main layer 2 of the main pipe. The covering layer 3 is formed.

  Further, an uncured multilayer resin tube 1 in which a coating layer 3 of polypropylene resin is laminated on the outer peripheral surface 2a of the main tube 2 of polyethylene resin is extruded outward from the molds of the outer mold 5 and the inner mold 6 and formed. 10 and sent to the water tank 11 from the forming 10 to be cooled and solidified. As a result, the multilayer resin tube 1 is manufactured, in which the coating layer 3 is integrally laminated on the outer peripheral surface 2a of the main layer 2.

  At this time, the uncured multilayer resin tube 1 is exposed to the atmosphere when it is sent from the molds 5 and 6 to the forming 10 (part S in FIG. 3), but the outer periphery of the main layer 2 Since the surface 2a is covered with the coating layer 3, the outer peripheral surface 2a of the main layer 2 is not oxidized and deteriorated. Also, the multilayer resin tube 1 completed by cooling and solidification is such that the outer peripheral surface 2a of the main layer 2 is covered with the coating layer 3, so that the outer peripheral surface 2a of the main layer 2 is photodegraded by ultraviolet rays, or the outer peripheral surface No foreign matter such as dust adheres to 2a.

  Thereby, the multilayer resin pipe 1 is the outer peripheral surface of the main layer 2 in which foreign matter such as oxidation deterioration, light deterioration, and dust does not occur by peeling the coating layer 3 from the main layer 2 at the time of joining the EF joint. The EF joint can be joined to 2a (fused surface), and the joining work can be performed without a scraping work.

On the other hand, in the multilayer resin tube 1 of the present embodiment, the coating layer 3 is formed using a polypropylene resin having a molecular weight of 5.0 × 10 ⁵ or less. When the coating layer 3 is formed using a polypropylene resin having a molecular weight larger than 5.0 × 10 ⁵ , the viscosity at the time of co-extrusion molding becomes too large for the polyethylene resin of the main layer 2 which is a main pipe, and wrinkles and the like are generated As a result, the dimensional accuracy of the coating layer 3 (multilayer resin tube 1) is reduced, and the coating layer 3 is greatly contracted during curing.

On the other hand, when the coating layer 3 is formed using a polypropylene resin having a molecular weight of 5.0 × 10 ⁵ or less as in the multilayer resin tube 1 of the present embodiment, coextrusion molding is performed on the polyethylene resin of the main layer 2. The viscosity of the time is maintained in a suitable state, and the coating layer 3 is formed with high accuracy without causing wrinkles or the like. As a result, the covering layer 3 and thus the multilayer resin tube 1 are formed so as to be surely and easily peeled, that is, with suitable peelability.

  Moreover, the multilayer resin tube 1 of this embodiment forms the coating layer 3 using the polypropylene resin from which an elasticity modulus becomes 1000 Mpa or more. For this reason, when the covering layer 3 is peeled off from the main layer 2 at the time of joining the EF joint, the covering layer 3 is not elastic enough to be broken off. In addition, the coating layer 3 and thus the multilayer resin tube 1 is formed.

  Further, in the multilayer resin tube 1 of the present embodiment, the coating layer 3 is formed of a propylene homopolymer (homo PP). In this way, the coating layer 3 is formed of a propylene homopolymer (homo PP) having a crystal structure that is significantly different from that of the polyethylene resin of the main layer 2, so that the coating layer 3 is peeled off from the main layer 2. The property can be kept good.

  And since the multilayer resin pipe 1 of this embodiment was made so that ratio X / Y of the fluidity index X of the coating layer 3 and the fluidity index Y of the main layer 2 might be in the range of 8-12, The surface roughness of the main layer 2 can be kept small, and the appearance can be kept good.

  Here, the test results obtained by forming the coating layer 3 using a plurality of types of polypropylene resins having different molecular weights and elastic moduli and confirming the peelability of the multilayer resin tube 1 provided with these types of the coating layers 3 are shown in Table 1 and It shows in Table 2.

Further, in this test, when the peel strength was 3.0 to 5.0 kg / cm, it was determined that the film was suitably peelable, and the determination was “◯: Peelability (good)”. When the peel strength deviated from the peel strength of 3.0 to 5.0 kg / cm, the judgment was “x: peelability (defect)”.
Furthermore, in this test, when the surface roughness after peeling was 50 μm or less, the determination was “◯: good appearance”, and when it exceeded 50 μm, the determination was “x: poor appearance”.
In this test, when the ratio (X / Y) between the fluidity index (MFR) X of the coating layer 3 and the fluidity index Y of the main layer 2 is in the range of 8 to 12, the determination is “◯ If the result is out of the range, the determination is “x”.

  “Homo PP” in Tables 1 and 2 is a homopolymer of propylene, and “Block PP” is a block copolymer of polypropylene, ethylene-propylene rubber, and polyethylene (exactly, ethylene-propylene rubber). , And a two-phase resin in which polyethylene islands exist), and “random PP” is obtained by randomly incorporating a small amount of ethylene into a propylene chain.

From the results shown in Table 1 and Table 2, when the coating layer 3 is formed using a polypropylene resin having a molecular weight of 5.0 × 10 ⁵ or less, the coating layer 3 is formed using a polypropylene resin having an elastic modulus of 1000 MPa or more. It has been demonstrated that the coating layer 3 and thus the multilayer resin tube 1 can be formed with suitable peelability by reliably and easily peeling.

  Furthermore, when the coating layer 3 is a homo-PP and the coating layer 3 is formed so that the ratio X / Y between the fluidity index X of the coating layer 3 and the fluidity index Y of the main layer 2 is in the range of 8-12. Thus, it was proved that the peeling performance can be kept better, the surface roughness of the main layer 2 after peeling can be reduced, and the appearance can be kept good.

Therefore, in the multilayer resin tube 1 of the present embodiment, by forming the coating layer 3 using a polypropylene resin having a molecular weight of 5.0 × 10 ⁵ or less, the polyethylene resin of the main layer 2 which is the main tube, The viscosity at the time of coextrusion molding can be maintained in a suitable state, and the coating layer 3 can be accurately formed without generating wrinkles or the like.

  As a result, the adhesion strength (peeling strength) to the main layer 2 becomes too high, or the adhesion strength becomes too low, and the coating layer 3 cannot be easily peeled off when the coating layer 3 is peeled off from the main layer 2. The covering layer 3 can be prevented from being peeled off from the main layer 2 before the peeling work, and the covering layer 3 and the multilayer resin tube 1 can be formed with suitable peeling properties that can be peeled off reliably and easily.

  Further, by forming the coating layer 3 using a polypropylene resin having an elastic modulus of 1000 MPa or more, when peeling from the main layer 2, no tearing occurs, and the coating layer 3 can be more reliably and easily formed. It becomes possible to form the multilayer resin tube 1 so that it can peel.

  Furthermore, by forming the coating layer 3 from a homopolymer of propylene (homo PP), the releasability when peeling the coating layer 3 from the main layer 2 can be kept good.

  And the surface roughness of the main layer 2 after peeling is made such that the ratio X / Y of the fluidity index X of the coating layer 3 and the fluidity index Y of the main layer 2 is in the range of 8-12. Can be kept small, and the appearance can be kept good.

  As mentioned above, although one embodiment of the multilayer resin pipe concerning the present invention was described, the present invention is not limited to the above-mentioned one embodiment, and can be suitably changed in the range which does not deviate from the meaning.

  DESCRIPTION OF SYMBOLS 1 ... Multilayer resin pipe 2 ... Main layer 2a ... Outer peripheral surface (fusion surface) 3 ... Coating layer 4 ... Extrusion molding device 5 ... Outer mold (cavity mold) 6 ... Inner mold (core mold) 7 ... Cavity 8 ... Extruder 9 ... Extruder 10 ... Forming 11 ... Water tank T ... Extrusion direction

Claims (3)

A multilayer resin pipe formed integrally by coextrusion with a main layer of polyethylene resin as a main pipe and a coating layer of polypropylene resin laminated on the outer peripheral surface of the main layer in a peelable manner,
The multi-layered resin pipe, wherein the coating layer is formed using a polypropylene resin having an elastic modulus of 1000 MPa or more and a molecular weight of 5.0 × 10 ⁵ or less. In the multilayer resin pipe according to claim 1,
The multi-layered resin pipe, wherein the coating layer is formed of a propylene homopolymer. In the multilayer resin pipe according to claim 1 or 2,
A multilayer resin pipe, wherein the ratio X / Y of the fluidity index X of the coating layer and the fluidity index Y of the main layer is in the range of 8-12.

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