JP2002257264A - Manufacturing method of multilayer resin pipe, and manufacturing method of inner surface resin lining steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a multi-layer resin pipe of which shape is restored by heating. SOLUTION: A multilayer resin having two or more layers formed of two or more kinds of resins is deformed and kept in shape temporarily, in a state in which residual stress is applied to at least two layers, thereby providing the property of restoring the shape for at least one layer and providing a property of keeping the shape at a room temperature for at least one layer. Thereafter, the shape is restored by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape-restoring multilayer resin pipe and a method for producing an inner resin-lined steel pipe for water supply and hot water supply. The shape restoring multilayer resin pipe manufactured by this method can also be used for repairing and renewing old pipes that have deteriorated.

[0002]

2. Description of the Related Art In recent years, an inner resin-lined steel pipe having a resin layer on the inner surface of a steel pipe or the like has been used for the purpose of corrosion prevention or the like. In addition, when existing pipes such as gas pipes and water pipes are deteriorated and need to be replaced, a method of lining and renewing the existing pipes with a resin lining has been adopted.

[0003] These linings methods, reduced diameter resin tube having an outer diameter greater than the inner diameter of the steel pipe and the existing pipe, after the shape recovery resin tube having a slightly smaller outer diameter than the inner diameter of the steel pipe and the existing pipe, There is a method of inserting it into a steel pipe or existing pipe, expanding it by heating, and attaching it to the inner surface of the steel pipe or existing pipe. This shape-restoring resin tube exhibits the ability to recover to the stored outer diameter by heating.

[0004]

A method using a shape memory resin is proposed in Japanese Patent Application Laid-Open No. 2-57323. However, in general, the shape memory resin is expensive and the product cost is high. In addition, there were problems in hygiene and moldability.

Also, a method using a general-purpose resin is disclosed in
033 and JP-A-2-48928.
However, since the resin is a viscoelastic material, the shape of the resin tube is not stable especially when the glass transition point is below room temperature, and the shape is restored immediately after the resin tube is made, or when the resin tube is left near room temperature, it does not heat. The shape of the resin pipe began to gradually recover, and the outer diameter of the resin pipe became larger than the inner diameter of the steel pipe or existing pipe. There was a restriction that it had to be.

[0006] How to solve this problem is proposed in JP-A 5-162199 JP. What this method of fixing the shape by cooling the resin tube diameter to 30 ° C. temperature lower than the condensation 径温 degree in a temperature range below the melting temperature of the resin at 60 ° C. or more and a resin softening temperature or higher It is. But,
For this to be the diameter of a solid in the temperature range, completely it is difficult to fix the resin tube shape, the shape is a problem also depends ambient temperature.

[0007] characteristic required for shape recovery resin tube is not only the shape recovery property at high temperature is also important shape maintainability at around room temperature. However, in the prior art, it was not possible to satisfy both characteristics with a general-purpose resin.

An object of the present invention is to provide a method for manufacturing an inner resin-lined steel pipe and a multilayer resin pipe, which can solve the above-mentioned problems.

[0009]

According to the first aspect of the present invention,
In a method for manufacturing a multilayer resin tube that recovers its shape by heating, a resin having two or more layers composed of two or more resins is deformed and temporarily treated while different residual stresses are applied to at least two layers. By maintaining the shape, at least one layer is given a property of restoring the shape, and at least one layer is given a property of keeping the shape near room temperature.

[0010] According to a second aspect of the invention, in the method for manufacturing a multilayer resin pipe for shape recovery by heating, the resin melting temperature is the melting point or glass transition point of Tm1 1
And the melting temperature, which is the melting point or glass transition point, is Tm2,
However, a multilayer resin having two or more layers composed of two or more resins including Tm2 <Tm1 and a resin 2 having a Tm2 <Tm1 within a temperature range of the Vicat softening point of the resin 2 and Tm1 or less, preferably Tm2 or more and Tm1 or less. By deforming and temporarily maintaining the shape while applying different residual stresses to at least two layers, at least one layer is given a shape restoring property, and at least one layer is maintained at a temperature around room temperature. It is characterized by giving properties.

According to a third aspect of the present invention, there is provided a method for manufacturing a multilayer resin tube which recovers its shape by heating, wherein the melting temperature or the glass transition point of the resin 3 is Tm3.
And a melting temperature Tm4, which is the melting point or glass transition point,
However, when manufacturing a multi-layered resin tube of two or more layers made of two or more kinds of resin including resin 4 satisfying Tm4 <Tm3, the resin tube made of resin 3 is deformed at Tm3 or less to give residual stress. in state, lined on the surface of the resin tube made of resin 4 from the resin 3, by temporarily maintaining the shape in a state where given different residual stresses in at least two layers, at least one layer shape reconstruction Give the nature,
It is characterized in that at least one layer has a property of maintaining the shape near room temperature.

[0012] The invention of claim 4, wherein, using the claim 1, 2 or 3 multilayer resin pipe according, inner diameter, before deformation the a not more than the outside diameter of the multilayer resin pipe, further shrinkage 径後After being inserted into a steel pipe having an outer diameter equal to or larger than the outer diameter of the multilayer resin pipe, the inner diameter of the steel pipe is lined by heating to expand the diameter of the multilayer resin pipe.

In order to solve the above problems, the present inventors have made a resin into a multilayer structure, and have at least one layer exhibiting shape restoring property (hereinafter referred to as restoring layer) and at least one layer exhibiting shape maintaining property (hereinafter referred to as "maintaining layer"). It invented a new shape recovery of the mechanisms provided.

That is, the resin of the restoration layer restores its shape even at a temperature lower than the temperature at which the shape of the single layer is to be restored, but the resin of the maintenance layer does not substantially change its shape at a temperature lower than the temperature at which the shape is to be restored. a property of softening or melting at a temperature around you want to restore. By these resins and multilayer structure, maintaining shape for strong nature of sustaining layer at around room temperature, whereas, by heating, to express the properties of the restored layer by weakening the properties of sustaining layer, the molded article Has invented a mechanism to restore the shape.

In order to obtain such properties, a multi-layer resin tube of two or more layers made of two or more kinds of resins is temporarily maintained while different residual stresses are applied to at least two layers. In a state where a large residual stress is generated in the restoration layer and a state where only a small residual stress that does not cause a residual stress or a shape change is generated in the maintenance layer is maintained at room temperature for a long time. It has also been found that a shape-restoring resin tube or a shape-restoring resin product whose shape does not substantially change can be obtained. In short, the restoration layer and the maintenance layer can be formed by controlling the degree of the residual stress generated during the molding process for each layer.

[0016]

While DETAILED DESCRIPTION OF THE INVENTION Possible resins used in the present invention is not particularly limited, styrene excellent shape resilient restoring layer - butadiene copolymer, polyurethane, and polynorbornene course, in a normal molding method Polyolefin resins such as polyethylene, cross-linked polyethylene, polypropylene, polymethylpentene, and polybutene, which exhibit little heat restorability or leave a large residual stress and are not excellent in stability, are particularly preferred. These resins have high water resistance and are suitable as a lining material. Further, it ionomer, polystyrene, polyethylene terephthalate, polycarbonate, other engineering plastics applications. The maintenance layer, ionomer, ethylene - vinyl acetate copolymer resin, ethylene - acrylic acid copolymer resin, an ethylene - methacrylic acid copolymer resin, ethylene - acrylic acid ester copolymer resin, ethylene - such as methacrylic acid ester copolymer resin Copolymerized polyolefins are particularly preferred. These resins are typically the melting point, a low softening point, favoring also the adhesion between the lining material because rich in adhesiveness. For example, in the case of polyethylene, more specific examples include low density, medium density, high density, and linear low density polyethylene. In the case of polypropylene, a homopolymer,
Examples include random or block copolymers. As for the crosslinked polyethylene, the base resin may be any of low density, medium density, high density, linear low density polyethylene and the like. Further, a blend resin obtained by mixing different kinds of resins may be used.

In the present invention, there is no problem even if characteristics such as density, MFR and molecular weight are not particularly limited. If necessary, additives such as a plasticizer, a colorant, a pigment, a filler, a flame retardant, an antioxidant, an ultraviolet absorber, a charging material, a lubricant, and a tackifier can be added.

Here, a two-layer resin tube will be described in detail as an example. Tm1, Tm2 resin 1 and resin 2 having a melting point of (Tm2 <Tm1), {resin 1 (melting temperature Tm1: melting point or glass transition point), the resin 2 (melting temperature Tm2: melting point or glass transition point)} is composed of The two-layer resin is extruded
The two-layer resin tube is obtained by extruding in a molten state and fixing the outer diameter while cooling using a sizing die or the like.

Next, the resin 2 has a Vicat softening point or higher and a Tm
When the two-layer resin tube is stretched and reduced in diameter while being reheated within a temperature range of 1 or less, the resin 1 is reduced in diameter in a solid state, so a large stress is generated. Only a small stress is generated. When this two-layer resin tube is cooled, a large residual stress remains in the resin 1,
The resin 2 so that the residual stress is not generated only or small residual stress occurs. The residual stress of the resin 1 becomes a driving force for restoring the shape of the two-layer resin tube, and the resin 1 has a force for restoring the shape, but the resin 2 has substantially no force for restoring the shape and keeps maintaining the shape. . Since the resin 1 and the resin 2 are in contact with each other, the resin 2 at room temperature suppresses the shape restoration of the resin 1. Therefore, the shape of the two-layer resin tube can be maintained for a long time. On the other hand, when the two-layer resin tube is heated, the resin 2 is softened or melted, so that the shape restoration of the resin 1 can no longer be suppressed, and the two-layer resin tube expands and recovers its shape. Here, the resin 1 layer serves as a restoration layer, and the resin 2 layer serves as a maintenance layer. The above-described reheating stretching of the two-layer resin pipe can be performed by using a line in which a superheating furnace and a cooling tank are arranged between the two take-off machines and utilizing the speed ratio of the take-off machine. .

In the case of this example, since the shape restoration is in the direction of increasing the diameter, it is more effective to maintain the shape by using the resin 2 as the outer layer and the resin 1 as the inner layer. However, in the direction in which the diameter decreases, it is more effective to maintain the shape by using the resin 2 as the inner layer and the resin 1 as the outer layer.

Here, a two-layer resin tube made of two kinds of resins has been described as an example, but a multi-layered resin tube made of more kinds of resins may be used as long as this property is not impaired. The may be an adhesive layer provided in order to increase the adhesion between the steel pipe after lining.

The method of manufacturing this manner the two or more layers of the multi-layer resinous tube having a different residual stress in each layer may be less.

When manufacturing a multilayer resin tube of two or more layers composed of two or more resins including resin 3 (melting temperature Tm3: melting point or glass transition point) and resin 4 (melting temperature Tm4: melting point or glass transition point) in the single or multi-layer resin pipe made of a resin 3 in a state that gave deformation and residual stress in Tm3 following, a method of lining the resin 4 in a molten state on the surface of the resin tube. Here, the layer of the resin 3 in the restorer layer, the layer of the resin 4 is in the maintenance layer.

Further, by using a shape restoring multilayer resin pipe produced by the method described above, and heated to insert and more Vicat softening point of the sustaining layer within the steel pipe or existing piping, thereby expanded the multilayer resin pipe Accordingly, also found that stably lined steel pipe or the inner surface of the existing piping.

Further, the product shape is not limited to pipes,
By using this method, a multi-layer resin molded product that recovers its shape by heating can be obtained for multi-layer products having two or more layers such as rods, sheets, films, and tubes.

[0026]

EXAMPLES will now be described in detail of the present invention through examples. 1 and 2 are perspective views showing an embodiment of a die.

[Examples 1 to 21] Tables 1 and 2 show material properties and constitutions of the shape restoring multilayer resin tube employed in the examples. 2 following the method for producing a shape restoring multilayer resin pipe
Kind adopted.

[0028] "A method" circular die extruder with using an extrusion resin of all the layers in a molten state, then, to prepare a multi-layer resin pipe by sizing with cooling (outer diameter of about φ
30mm, thickness about 1.5mm). Subsequently, using an infrared heating furnace and a cooling water tank installed between the two take-off machines, the multilayer resin tube is heated and stretched to a predetermined temperature, and then cooled and fixed in shape to obtain a shape-restoring multilayer. Obtain a resin tube (when manufacturing a two-layer resin tube: outer diameter is about φ26mm, wall thickness is about 1.45mm
(Inner / outer layer ratio = 8/2), when manufacturing a three-layer resin tube: outer diameter is about φ26 mm, wall thickness is about 1.45 mm (inner / outer / outermost layer ratio = 7.5 / 1.5 / 1). At this time, the temperature of the outer surface of the resin tube at the outlet of the infrared heating furnace was taken as the stretching temperature.

[Method B] A resin tube excluding the outermost layer is extruded in a molten state using an extruder equipped with an annular die, and then sized while cooling to produce a resin tube (a two-layer resin tube is manufactured). Case: Outer diameter is about φ29.4mm, wall thickness is about 1.
(When manufacturing 3mm, three-layer resin pipe: outer diameter is about φ29.7mm, wall thickness is about 1.35mm).

Subsequently, the resin pipe is heated to a predetermined temperature by using an infrared heating furnace and a cooling water tank installed between the two take-off machines, and a predetermined outer diameter (when a two-layer resin pipe is manufactured: (When manufacturing a three-layer resin tube with a diameter of about φ25.4mm: external total 25.7mm)
After stretching, the resin is applied to the outer surface of the resin tube that has been cooled and fixed in shape to obtain a shape-recoverable multilayer resin tube. (When manufacturing a two-layer resin tube: outer diameter is about φ26mm, wall thickness is about 1.45
mm (inner / outer ratio = 8/2), when producing a three-layer resin pipe: outer diameter of approximately Fai26mm, wall thickness of about 1.45 mm (inner / outer / outermost ratio = 7.5 / 1.5 / 1). At this time, the temperature of the outer surface of the resin tube at the outlet of the infrared heating furnace was taken as the stretching temperature.

In order to investigate the shape retention, the reduced-diameter resin tube was left immediately after stretching and left at room temperature for 20 days.
Performed outside diameter measurement of the resin pipe was examined shape maintainability at around room temperature. Immediately after stretching, those whose outer diameter has already expanded by ± 1% or more are rejected (XX). After leaving at room temperature for 20 days,
Those having an outer diameter change rate of less than ± 1% were judged as acceptable (〇), and others were judged as unacceptable (×). Next, in order to examine the shape restoring property of the shape restoring resin tube that passed the above test, the shape restoring resin tube was put into silicon oil heated to a temperature lower by 10 ° C. than the deformation temperature of the resin tube. Restoration rate A is,
After measuring the outer diameter of the resin tube two minutes after heating, A =
(DA-d) / (D-d). Here, DA is the measured outer diameter of the resin tube 1 minute and 30 seconds later, D is the outer diameter of the resin tube before stretching and contraction, and d is the outer diameter of the resin tube before being poured into silicone oil. Determination tests restoration rate A is passed (〇) those inflated to 0.8 or more, and those otherwise judged as failure (×).

Next, an inner lining test on a steel pipe was performed. The shape recovery resin tube, blasted steel pipe (steel pipe inner diameter 1~4mm larger size # than the outer diameter of the shape recovery resin tube length 4m) inserted within a.

[0033] Then, the maximum temperature of the steel pipe surface by high-frequency heating apparatus, a resin pipe deformation temperature than 10 ° C. lower temperatures or higher, causing the heated resin pipe in a range of less than higher deformation temperature than 30 ° C. Temperature is shape recovery . Further, the resin portion protruding from the end of the steel pipe is cut. Thereafter, by cutting the steel pipe central portion was observed lining condition. Lack resin pipe is restored, and if there is a gap between the steel pipe inner diameter and the resin lining layer, the resin tube is excessively inflated, unacceptable and if unevenness is observed in the resin layer (×), pass the others (○ ).

[0034]

[Table 1]

[0035]

[Table 2]

Comparative Examples Comparative Examples 1 to 18 Tables 3 and 4
Shows the material properties and configuration of the shape-restoring multilayer resin tube employed in the examples. The same resin and the same line as those in the above example were adopted, and an attempt was made to produce a shape-recoverable resin tube of the same size. However, the stretching temperature was controlled to be equal to or higher than the melting temperature of the resin in the restoration layer or equal to or lower than the melting temperature of the resin in the shape maintaining layer.

In the same manner as in the examples, examinations were made on the shape maintaining properties, shape restoring properties, and lining properties, but none of the examples passed all the tests.

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

Effect of the Invention] The shape recovery multilayer resin pipe of the present invention,
Inexpensive resin that is not excellent in shape recovery can be used, and the inner resin lining steel pipe manufactured by the method of the present invention can be manufactured by an efficient method using shape recovery and has sufficient anticorrosion performance. It can be used as a water supply / hot water supply pipe that is satisfactory.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a die used for forming a solid product according to the invention method.

FIG. 2 is a schematic view showing an embodiment of a die used for molding a hollow product.

[Explanation of symbols]

 1 restoration layer 2 maintenance layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiko Furuta 1-2-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3H111 AA01 BA02 BA15 BA34 CA52 CA53 CB04 CB05 CB08 DA08 DA26 DB03 EA04 4F210 AA04 AA10 AA21 AA22 AD03 AD05 AD12 AG03 AG08 QC01 QD36 QD43 QG02 QG15 4F211 AA04 AA10 AA21 AA22 AD03 AD05 AD12 AG03 AG08 SA13 SC03 SD11 SG04 SH06 SN01 SP28 SW23

Claims (4)

[The claims] In a method for manufacturing a multilayer resin pipe which recovers its shape by heating, a resin having two or more layers composed of two or more resins is deformed to give different residual stresses to at least two layers. A method for producing a multilayer resin tube, characterized in that at least one layer is given a property of restoring its shape by temporarily maintaining its shape in a state, and at least one layer is given a property of maintaining its shape near room temperature. 2. A method for producing a multilayer resin tube which recovers its shape by heating, wherein a resin 1 having a melting point or a glass transition point of Tm1 and a melting point of a melting point or a glass transition point of Tm2, , Tm2 <Tm1
Two or more layers a resin composed of two or more resins including the resins 2, or Vicat softening point of the resin 2 and Tm is
By performing deformation processing within a temperature range of not more than 1, preferably not less than Tm2 and not more than Tm1, and temporarily maintaining the shape while giving different residual stresses to at least two layers,
A method for manufacturing a multilayer resin tube, wherein at least one layer has a property of restoring shape, and at least one layer has a property of maintaining shape near room temperature. 3. A method for producing a multilayer resin tube which recovers its shape by heating, comprising: a resin 3 having a melting point or a glass transition point of Tm3; and a melting point of a melting point or a glass transition point of Tm4. , Tm4 <Tm3
When manufacturing a multi-layered resin tube of two or more layers made of two or more types of resins including the resin 4, the resin tube made of the resin 3 is deformed at Tm3 or less to give a residual stress.
By lining the resin 4 on the surface of the resin tube made of the resin 3 and temporarily maintaining the shape while applying different residual stresses to at least two layers, at least one layer is given a shape restoring property, A method for producing a multilayer resin tube, wherein at least one layer has a property of maintaining a shape near room temperature. 4. Using the multilayer resin pipe produced by the method of claim 1, wherein an inner diameter of not more than the outside diameter of the multilayer resin pipe before deformation, and the multilayer contraction 径後A method of manufacturing an inner resin-lined steel pipe, comprising: inserting a steel pipe having a diameter equal to or larger than the outer diameter of a resin pipe, and then heating the pipe to expand the diameter of the multilayer resin pipe to line the inner surface of the steel pipe.