JP2003080599A - Manufacturing method of interior resin lining tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an interior resin lining tube of a thick film at a low cost by lining a base tube such as a steel tube with a resin tube such as a conventional polyethylene tube which is almost free from the property of the diameter being expanded by heating. SOLUTION: The resin tube to be applied as a lining to the base tube is drawn in the direction of the axis of the tube and thereby the diameter thereof is reduced to a dimension enabling insertion thereof into the base tube. In this state, the resin tube is cooled to a temperature of the freezing point of below to be frozen in the state of the diameter being reduced and also to be made the resin tube of which the diameter is reduced temporarily and of which the rigidity is enhanced. The operation of insertion is facilitated by inserting this resin tube into the base tube. The resin tube is restored to a state wherein the diameter is expanded and brought into closed contact with the inside of the base tube, by making it pass an appropriate time, and thus the tube is made an interior resin lining layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inner surface resin lining pipe used for water supply and sewerage.

[0002]

2. Description of the Related Art For a long time, the inner surface resin lined steel pipe has been used for various pipes including water supply and sewerage, taking advantage of its anticorrosion property, non-elution property, durability, etc., and its demand is increasing. Among them, polyethylene-lined steel pipes have attracted more attention because they have the above-mentioned characteristics remarkably and hardly cause environmental problems these days.

[0003]

However, polyethylene-lined steel pipes have a low market share compared to PVC-lined steel pipes. The main reason is the manufacturing method and cost.

[0004] The main method of manufacturing a PVC lining steel pipe is a pipe expansion method using a PVC expansion tube. In other words, a PVC expansion tube (a diameter expansion when heated) that imparts the heat expansion property by the shape memory (the function of temporarily fixing in a reduced diameter state and restoring the expanded diameter state close to the original diameter by heating) (A rate of about 20 to 50%) is inserted into a steel pipe and the PVC expansion tube is expanded in diameter by heating and is lined on the inner surface of the steel pipe. It is very easy to give the PVC tube a heat expansion property of about 20 to 50% by heat treatment and mechanical deformation, and it can be carried out at low cost.

On the other hand, in the case of a polyethylene pipe, in order to impart the same heat expansion property to that of a vinyl chloride expansion tube, it is necessary to crosslink or modify the resin. In addition to this, heat treatment and mechanical deformation are required. Since it requires processing, it is theoretically possible, but it is not economically feasible and the difficulty of manufacturing resin pipes increases. Therefore, when trying to use a polyethylene pipe for the lining of a steel pipe, it is unavoidable to use a polyethylene pipe that does not have a heat expandability or has a small heat expandability. If it is to be used, the outer diameter of the polyethylene pipe when it is inserted into the mother pipe is substantially equal to the inner diameter of the steel pipe, so that it is extremely difficult to insert it into the steel pipe. For this reason, up to now, the method of lining polyethylene pipes has not been adopted in the production of polyethylene-lined steel pipes. Conventionally, a polyethylene-lined steel pipe has been manufactured by a so-called powder fusion method in which crushed polyethylene powder is supplied into a heated steel pipe and is melted by heat to form a film. However, since powder is used in this method, the material cost is high, and it is considerably expensive as compared with a PVC lining pipe manufactured by an extrusion method from pellets. Also,
In the powder fusion method, it is technically not easy to form a thick film, and at present, the film thickness is about 0.5 mm, and there is also a tendency to give an impression that it is not robust as compared with 1.5 mm or more of PVC. In addition, the amount of expensive powdered resin used increases as the film thickness increases, which further increases the cost.

The present invention has been made in view of the above circumstances, and is a resin pipe such as a normal polyethylene pipe which is not imparted with the heat expanding property or a resin having a small heat expanding property even when imparted. It is possible to easily insert a pipe into a mother pipe made of metal such as a steel pipe and line the pipe, thereby providing a method capable of manufacturing a thick-film inner surface resin-lined pipe at low cost. To aim.

[0007]

SUMMARY OF THE INVENTION The first invention of the present application is to facilitate the operation of inserting a resin pipe having no or small diameter expansion by heating into a metal mother pipe such as a steel pipe to line the resin pipe. Is in a state of being pulled to the axial direction of the pipe and reduced in diameter to a size that can be inserted into the mother pipe, and in that state, it is cooled to a temperature below the freezing point, frozen in a reduced diameter state, and temporarily compressed with increased rigidity. A diameter resin tube is used, and the temporarily reduced diameter resin tube is inserted into the mother tube, and then restored to the expanded diameter state at least over time so as to be in close contact with the inner surface of the mother tube. In this way, the resin pipe to be inserted into the mother pipe is pulled in the pipe axial direction to be in a reduced diameter state, and frozen in that state to be a temporarily reduced diameter resin pipe. Even after releasing the tensile force, the original state is not restored immediately, but it is restored slowly. Therefore, when the work of inserting the resin pipe into the mother pipe as the temporarily reduced diameter resin pipe is performed, the resin pipe is kept in the reduced diameter state, and a clearance that can be easily inserted into the mother pipe can be secured. Moreover, since the temporary diameter-reduced resin pipe is frozen below the freezing point, it has a high rigidity, so that when it is inserted into the mother pipe, it is unlikely to be deformed and the insertion becomes easy. Furthermore, frost may form on the surface, and when frost adheres, the frost has a lubricating effect, which makes insertion into the mother tube easier. Thus, the temporarily reduced diameter resin pipe can be easily inserted into the mother pipe. After inserting the temporarily reduced diameter resin tube into the mother tube, the resin tube that has been reduced in diameter is expanded in an attempt to restore it to its original state by aging as it is or by heating if necessary, It adheres to the inner surface of the pipe. In this way, an inexpensive resin pipe can be easily lined on the inner surface of the mother pipe, and a resin lining having a desired thickness can be formed by making the resin pipe have a desired thickness. A resin lining tube for the inner surface of the membrane can be manufactured at low cost.

The second invention of the present application facilitates the operation of inserting and lining a resin pipe into a mother pipe made of metal such as a steel pipe. Therefore, the resin pipe to be inserted into the mother pipe is easily inserted into the mother pipe. Although the outer diameter of the shape-memory resin is formed so that it can be expanded beyond the inner diameter of the mother tube after restoration, the shape-memory resin tube is cooled to a temperature below the freezing point. It is configured to be inserted into the mother tube in a state where the rigidity is increased and then restored to the expanded diameter state by heating so as to be in close contact with the inner surface of the mother tube. In this way, by inserting the shape memory resin pipe into the mother pipe while cooling it to a temperature below the freezing point and increasing its rigidity, the resin pipe is less likely to deform (bend, etc.) during insertion, and is not bound to the surface. The resin pipe can be easily inserted into the mother pipe even if the clearance between the mother pipe and the resin pipe is small, because it may frost and exert a lubricating action. Thus, it becomes possible to use a shape memory resin tube having a small diameter expansion factor of about several percent, and an inexpensive shape memory resin tube can be used. After the shape-memory resin pipe is inserted into the mother pipe, the shape-memory resin pipe is expanded in diameter by heating and is brought into close contact with the inner surface of the mother pipe. In this way, an inexpensive resin pipe can be easily lined on the inner surface of the mother pipe, and a resin lining having a desired thickness can be formed by making the resin pipe have a desired thickness. A resin lining tube for the inner surface of the membrane can be manufactured at low cost.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The mother pipe used in the first and second inventions of the present application is usually a steel pipe, but may be made of other metal. Also, the resin pipe to be inserted is not particularly limited, but in consideration of corrosion resistance, non-elution property, durability, environmental problems, etc., polyolefin (polyethylene, polyethylene,
A resin tube made of polypropylene, polybutene, or a mixture thereof is preferable. In that case, the physical properties of the polyolefin are not limited, but in view of easiness of insertion into the mother tube, one having high rigidity (in polyethylene, medium density or more) is preferable.

Since the resin pipe becomes a resin lining layer after being inserted into the mother pipe, the thickness of the resin pipe should be set equal to the desired thickness of the resin lining layer to be formed on the inner surface of the mother pipe. Good. In other words, the thickness of the resin pipe is set equal to the desired thickness of the resin lining layer to be formed, and the resin pipe is inserted into the mother pipe and brought into close contact with the resin lining layer. It is possible to form a thick polyethylene lining layer, which has been difficult in the past.

The resin pipe used in the first invention of the present application may not have the heat-expanding property due to the shape memory,
It may be provided, and the size of the heat-expanding property thereof is arbitrary. When a resin pipe having a heat expandability is used, the larger the heat expandability, the smaller the outer diameter of the resin pipe at the time of insertion and the easier the insertion work into the mother pipe. On the other hand, since it costs to manufacture, it may not be a good idea depending on the material. For example, in the case of a polyethylene pipe, cross-linking or modification of the resin is required in order to impart a heat-expanding property of about 20 to 50%, which is extremely expensive and is not a good measure, but about 1 to 5%. With the heat-expandable property, the polyethylene pipe can be imparted by heat treatment and mechanical processing in which the polyethylene pipe is passed through a die in a heated state to be reduced in diameter, and immediately cooled and solidified, and the cost does not increase so much. Therefore, it is preferable to impart a heat expandability of about 1 to 5%.

The outer diameter of the resin pipe used in the first invention of the present application is selected as follows. That is, in the case of using a resin pipe having no heat-expanding property, the outer diameter of the resin pipe is reduced by pulling the resin pipe in the axial direction of the pipe, freezing it in the reduced diameter state, and inserting it into the mother pipe, After that, when the resin pipe is expanded and restored by appropriately aging, the resin pipe is selected so as to be in close contact with the inner surface of the mother pipe. Also, when using a resin tube with a heat-expanding property, the outer diameter of the resin tube is frozen by pulling the resin tube into the mother tube and then restoring it to its original state over time and heating. Select so that the resin tube will be in close contact with the inner surface of the mother tube when the diameter is expanded. In addition,
In the present specification, "close contact" means the state in which the outer surface of the resin pipe is in contact with the inner surface of the mother pipe over substantially the entire circumference thereof directly or via an adhesive layer described later, and the mother pipe It also includes the case where some gap remains between the resin pipe and the resin pipe.

The shape of the resin pipe is important in order to easily insert the resin pipe into the mother pipe. That is, if there is a variation or a bend in the outer diameter, it will be difficult to insert. Therefore, it is preferable that the variation of the outer diameter of the resin pipe is suppressed to within ± 50 μm and the resin pipe is hardly bent. Such a resin pipe can be easily manufactured due to the recent technological progress.

According to the first aspect of the present invention, when the resin pipe is inserted into the mother pipe, the resin pipe is pulled in the axial direction of the mother pipe and reduced in diameter to a size such that the resin pipe can be inserted into the mother pipe. Then, the resin pipe is frozen in the diameter-reduced state and the rigidity is increased to be a temporary diameter-reduction resin pipe. Here, the larger the diameter reduction amount, the larger the clearance with the mother tube and the easier insertion into the mother tube.However, if it is too large, the restoration amount will be small and the inner surface will be in close contact. Disappear. Therefore, usually, the diameter reduction amount is set to about 3 to 30%, and preferably,
Select about 5 to 10%. In addition, the resin pipe outer diameter when inserting the resin pipe into the mother pipe is a clearance of at least 1 to 2% of the mother pipe inner diameter between the resin pipe and the mother pipe (when the mother pipe and the resin pipe are concentrically arranged, the clearance between them is It is preferable to select them so that the gap) can be secured. The cooling temperature of the resin pipe is below the freezing point so as to ensure a frozen state in which the resin pipe can be maintained in a reduced diameter state during the insertion work into the mother pipe.
As a result of confirmation by the inventors of the present invention, after pulling the resin pipe to reduce its diameter by 5% and then cooling it to 0 ° C. to bring it into a frozen state, after releasing the tensile force of the resin pipe, 50% of the reduced diameter amount is obtained. It takes about 30 minutes to restore (reduce the diameter reduction amount to 2.5%), and during this period, the insertion work into the mother tube can be performed. The lower the cooling temperature of the resin pipe, the greater the freezing effect, the longer the time required for restoration, and the more stable the insertion work into the mother pipe. Therefore, it is preferable that the cooling temperature be lower than the freezing point. In addition, the cooling of the resin pipe not only exerts the effect of freezing the resin pipe to the reduced diameter state, but also causes the diameter reduction due to heat shrinkage, which can further increase the clearance with the mother pipe and increase the rigidity of the resin pipe. Also, it has effects such as making it difficult to deform during insertion work into the mother tube, forming frost on the surface, and expecting a lubricating action due to the frost, and these effects are further improved by lowering the cooling temperature. Because it will improve
The cooling temperature is preferably low. On the other hand, the lower the cooling temperature, the higher the cost required for cooling. Therefore, the cooling temperature of the resin pipe may be determined in consideration of these, and specifically, it is preferable to set it to about -20 to -10 ° C.

Any method may be used for cooling the resin pipe. Specifically, a method of cooling by placing it in a room kept at a low temperature such as a freezer or a method of immersing it in a liquid cooled at a low temperature by a refrigerator or the like. , Liquid cooled to low temperature with dry ice (eg dry ice + methanol solution or ethanol solution)
And a method of immersing in liquid nitrogen, liquid carbon dioxide, liquid air or the like or spraying these.

The method of inserting the cooled resin pipe into the mother pipe is either a method of pushing the resin pipe into the mother pipe to insert it, a method of pulling the resin pipe into the mother pipe, or a combination of both. Good. The method of pulling and inserting the resin pipe into the mother pipe has an advantage that the insertion can be further facilitated because the diameter is reduced by the tensile force acting on the resin pipe. Whichever method is used, the resin pipe to be inserted into the mother pipe is a temporarily reduced diameter resin pipe cooled below the freezing point, so a clearance for inserting into the mother pipe can be secured between the mother pipe and the resin pipe. In addition, the resin tube has high rigidity and is unlikely to be deformed, and moreover, the surface thereof is frosted, and the frost has a lubricating effect, so that the resin tube can be easily inserted into the mother tube.

After inserting the resin tube into the mother tube, the resin tube is allowed to stand in that state. As a result, the resin tube that has been frozen in the reduced diameter state gradually restores to its original state, and thus the diameter increases. At this time, the resin tube may be heated by an appropriate method, and the heating can accelerate the restoration of the resin tube.
In this way, the resin pipe is brought into close contact with the inner surface of the mother pipe, and an inner lining composed of the resin pipe can be formed on the inner surface of the mother pipe. If a resin pipe with a heat-expandable diameter is used, the resin pipe will not expand until it comes into close contact with the inner surface of the mother pipe by simply aging it. It is only necessary to develop the heat-expanding property of (3) and bring it into close contact with the inner surface of the mother tube. For this heating, only the resin tube may be heated by sending hot air into the resin tube or the mother tube may be heated together.

Here, the resin pipe and the mother pipe may be joined to each other only by the pressing force to the inner surface of the mother pipe due to the expansion of the diameter of the resin pipe, but in order to obtain a more reliable joining force, the resin pipe is joined. It is preferable to adhere it to the inner surface of the mother tube by a suitable means. This adhesion will be described later.

The resin pipe used in the second invention of the present application is a shape memory resin pipe having a heat-expanding property. The larger the diameter of the shape-memory resin pipe used for heat expansion is, the easier it is to insert the shape-memory resin pipe into the mother pipe. On the other hand, depending on the material, the manufacturing cost increases significantly. Further, in the present invention, by cooling the resin pipe below the freezing point, the rigidity can be increased and the surface can be frosted so that the lubricating effect can be exerted to facilitate insertion into the mother pipe. It doesn't have to be that big. For this reason, it is preferable that the heat-expanding property of the shape-memory resin pipe is about 1 to 5%. With this degree of heat expansion, even for polyethylene pipes that are difficult to impart shape memory to, heat treatment and mechanical processing to reduce the diameter of the polyethylene pipe by passing it through a die in a heated state and immediately cooling and solidifying It can be granted by the above, and does not increase the cost so much.

The outer diameter of the shape memory resin pipe used in the second invention of the present application is selected as follows. That is, in the state where the shape memory resin pipe is cooled below the freezing point, a clearance that can be easily inserted into the mother pipe can be secured, and when the diameter is heated and expanded after the insertion, the resin pipe is directly attached to the inner surface of the mother pipe or the adhesive layer. Select so that they will be in close contact with each other. The clearance between the resin pipe and the mother pipe when inserting the resin pipe into the mother pipe is preferably at least about 1 to 2% of the inner diameter of the mother pipe. The shape of the resin pipe is important in order to easily insert the resin pipe into the mother pipe when the resin pipe is inserted into the mother pipe with such a clearance. That is, if there is a variation or a bend in the outer diameter, it will be difficult to insert. Therefore,
It is preferable that the variation of the outer diameter of the resin tube is suppressed to within ± 50 μm and the resin tube is hardly bent.

In the second invention of the present application, when the shape memory resin pipe is inserted into the mother pipe, the resin pipe is cooled to a temperature below the freezing point to maintain the rigidity. As a result, the rigidity of the resin pipe is increased, deformation at the time of insertion can be prevented, frost is formed on the surface, and a lubricating action due to the frost can be expected, so that the resin pipe can be easily inserted into the mother pipe. Since these effects are further improved by lowering the cooling temperature, it is preferable to lower the cooling temperature. On the other hand, lowering the cooling temperature increases the cost required for cooling. Therefore,
The cooling temperature of the resin pipe may be determined in consideration of these,
Specifically, it is preferably about -20 to -10 ° C.

The method for cooling the resin pipe and the method for inserting the resin pipe into the mother pipe are the same as in the case of the first invention described above. In the second invention, the clearance for insertion into the mother tube can be secured more easily than in the first invention, and the resin tube cooled below the freezing point has high rigidity and is unlikely to deform, and
By forming frost on the surface and the frost having a lubricating effect,
It can be easily inserted into the mother tube. After inserting the resin pipe into the mother pipe, the resin pipe is heated to develop the heat-expanding property of the resin pipe, and is brought into close contact with the inner surface of the mother pipe. For this heating, hot air may be sent into the resin pipe to raise the temperature of only the resin pipe, or the mother pipe may be heated to heat the resin pipe with the heat from the mother pipe. Alternatively, the whole mother tube may be heated by putting it in a furnace. As described above, the resin pipe can be brought into close contact with the inner surface of the mother pipe to form the lining.

Also in this case, the resin pipe and the mother pipe may be joined only by the pressing force to the inner surface of the mother pipe due to the diameter expansion of the resin pipe, but in order to obtain a more reliable joining force, It is preferable to adhere the tube to the inner surface of the mother tube by a suitable means.

As described above, in both the first invention and the second invention of the present application, it is preferable to bond the resin pipe to the inner surface of the mother pipe. As a method of adhering the resin pipe adhered to the mother pipe, there is a method of interposing an adhesive layer that exhibits adhesiveness at room temperature between the resin pipe and the mother pipe, and bonding that exhibits adhesiveness by heating and melting. Examples thereof include a method of interposing an agent layer, a method of heating and melting the outer peripheral portion of the resin tube and adhering it to the mother tube. Among them, the method of using the heat-melting type adhesive is preferable because it has advantages such as a strong adhesive force and no hindrance to insertion of the resin pipe into the mother pipe. Hereinafter, the case of using a heat melting type adhesive will be described.

As the heat-melting type adhesive used here, a thermoplastic resin having a melting point lower than that of the resin tube is suitable. Specifically, when a polyolefin tube is used as the resin tube, a carboxylic acid-modified polyolefin or , EVA, E
AA etc. can be illustrated. The thickness of the adhesive layer interposed between the resin pipe and the mother pipe is sufficient to be 10 to 100 μm, but there is no problem due to the fact that it becomes thicker than this due to circumstances such as the two-layer extrusion described later.

In order to interpose an adhesive layer between the resin pipe and the mother pipe, an adhesive layer is formed on the outer surface of the resin pipe in advance, or an adhesive layer is formed on the inner surface of the mother pipe. The former is preferable in terms of workability and the like. As a method of forming an adhesive layer on the outer surface of the resin pipe in advance, a method of forming an adhesive layer at the same time as the production of the resin pipe by two-layer extrusion, and a method of winding an adhesive sheet on the outer surface of the resin pipe in a spiral shape or the like. The method of spraying the liquefied adhesive on the outer surface of the resin pipe can be mentioned. Of these methods, the method of forming an adhesive layer simultaneously with the production of a resin pipe by two-layer extrusion is suitable for inexpensive mass production, and can form the adhesive layer uniformly on the outer periphery, It is preferable because the adhesive layer is unlikely to be turned over at the time of insertion. On the other hand, as a method of forming the adhesive layer on the inner surface of the mother tube, a method of attaching an adhesive sheet to the inner surface of the mother tube can be mentioned. When a polyolefin tube is used as the resin tube, it is effective to pre-treat the surface of the polyolefin such as corona in advance, depending on the adhesive.

The resin pipe is inserted into the mother pipe with the adhesive layer interposed, the diameter of the resin pipe is expanded as described above and the inner face of the mother pipe is brought into close contact, and then the adhesive layer is heated and melted. .
This heating is usually performed by heating the mother tube. At the time of this heating operation, even if there is a slight gap between the inner surface of the mother tube and the adhesive layer, the resin tube begins to expand due to the heat of the mother tube when heating is started, and there is a tendency that the resin tubes adhere to each other. The adhesive layer can be heated well. However, in order to perform good heat transfer from the mother tube to the adhesive layer, it is desirable that the outer surface of the resin tube is surely in contact with the inner surface of the mother tube via the adhesive layer. Therefore, it is preferable to preheat the resin tube prior to heating the mother tube so that the resin tube is expanded to surely contact the inner surface of the mother tube via the adhesive layer. here,
The preheat temperature must, of course, be below the melting point of the adhesive. For preheating, it is possible to raise the temperature of only the resin pipe by sending hot air into the resin pipe, but it is also possible to heat the entire mother pipe by putting it in a furnace, or to heat the mother pipe by main heating (adhesive layer). The heating of the mother tube may be carried out in the same manner as in (heating for melting) and the temperature of the resin tube may be raised by heat transfer from the mother tube. In that case, the coefficient of thermal expansion of the resin pipe does not stay 10 times higher than that of the metal mother pipe, and therefore the amount of expansion of the resin pipe greatly exceeds the amount of expansion of the mother pipe even if the temperature is raised to the same temperature. The inner surface of the mother tube can be contacted with the adhesive layer.

As described above, when the resin pipe is inserted into the mother pipe, the resin pipe is cooled below the freezing point, which may cause frost on the surface of the resin pipe. Therefore, when the resin pipe is inserted, the water adhering to the surface of the resin pipe may remain at the interface with the mother pipe. Most of this moisture evaporates and dissipates during the heat welding operation, but in some cases, it may be caught in the interface. Therefore, if necessary, a drying step may be performed prior to heating so as not to involve water vapor.

The heating of the mother tube may be performed by simultaneously heating and raising the temperature of the entire mother tube using an electric furnace or the like. However, instead of heating the entire mother tube, a small section in the longitudinal direction of the mother tube is heated. However, it is preferable to perform the moving heating by moving the heating portion in the axial direction from one end of the mother tube to the other end, or from the central portion to both ends. When such moving heating is performed, the fusion-bonded portion between the resin pipe and the mother pipe sequentially moves in the axial direction, and the fusion proceeds while pushing out the gas between the resin pipe and the mother pipe. For this reason, bubbles remaining between the resin pipe and the mother pipe can be extremely reduced, and good adhesion of the resin pipe to the mother pipe becomes possible.

High frequency induction heating is the most suitable means for moving and heating the mother tube. That is, when high-frequency induction heating is used, by arranging an induction coil capable of ensuring a desired heating width on the outer periphery of the mother tube and energizing it, the mother tube portion inside thereof can be rapidly heated to a desired temperature. The heating site can be moved by moving the induction coil in the axial direction relative to the mother tube. The heating means is not limited to high-frequency induction heating, and considering the shape, quantity, and economic efficiency of the product, gas heating, heating of the electric furnace by moving in the electric furnace, or combination of them. You may use the thing.

After heating the mother pipe and adhering the resin pipe to the inner surface of the mother pipe, the mother pipe is cooled by standing cooling or water cooling. As described above, the resin pipe can be firmly adhered to the inner surface of the mother pipe, and the inner lining firmly adhered to the inner surface of the mother pipe can be formed.

Although the above description of the heating operation is for the case where an adhesive layer is interposed between the resin pipe and the mother pipe, the outer layer portion of the resin pipe is heated and melted without using the adhesive layer. The same heating operation may be performed also in the case of adhering to the inner surface of the mother tube. In this case, the heating of the mother tube causes the resin tube to be heated above its melting point, and the resin tube may melt not only the outer layer in contact with the mother tube but also the inner layer. However, polyethylene for extrusion which is generally used as a resin pipe has a poor melt flow property, and there is no particular problem unless deformation occurs. By melting the inner layer and the outer layer once,
There is also a merit that residual stress is reduced.

[0033]

[Example] [Example 1] Resin tube: high-density polyethylene tube Dimensions: outer diameter 42.0 mm, inner diameter 34.2 mm, thickness 3.
9 mm, 500 mm length Mother tube: Steel tube (SGP40A) Dimensions: Outer diameter 48.6 mm, inner diameter 41.7 mm, thickness 3.
5 mm, length 500 mm Adhesive; Maleic anhydride-modified polyethylene tape Dimensions: thickness 50 μm, width 25 mm

First, the inner surface of the steel pipe was blasted, and the modified polyethylene tape was temporarily fixed to the entire inner surface in the axial direction of the steel pipe. Next, pull the polyethylene pipe in the pipe axial direction and reduce the diameter until the outer diameter becomes 38 mm.
It was kept for 10 minutes in the freezer kept at ° C and frozen in that state. Then, the tensile force was released and the resin pipe was quickly inserted into the steel pipe. Next, when the steel pipe into which the polyethylene pipe had been inserted was left as it was for 1 hour, the diameter of the inserted polyethylene pipe expanded and it was in close contact with the inner surface of the steel pipe. After that, the steel pipe is heated to a heating width of 3
Induction heating with 0 mm induction coil, heating temperature 150
Move at a speed of 220 mm / min from one end at ° C,
The adhesive layer was heated and melted through a steel pipe. After being left to cool, it was cut, and the appearance was observed and a peel test was performed, and the following results were obtained.

Appearance: The inner surface was glossy and free from swelling, wrinkles and scratches. Adhesion: As a result of a 10 mm width peel test, it was 110 N or more, which was a sufficient value.

[Example 2] Resin tube: high-density polyethylene tube Dimensions: outer diameter 41.5 mm, inner diameter 38.0 mm, thickness 2.
However, the outer layer is 100 μm EAA resin coating layer Mother tube: Steel tube (SGP40A) Dimensions: outer diameter 48.6 mm, inner diameter 41.7 mm, thickness 3.
A material having a length of 5 mm and a length of 500 mm or more was prepared.

First, the inner surface of the steel pipe was blasted. Next, pull the polyethylene pipe in the direction of the pipe axis, and the outer diameter will be 39 m.
The diameter was reduced to m, and in that state, it was held in a refrigerating apparatus kept at −20 ° C. for 10 minutes and frozen in that state. Then, the tensile force was released and the resin pipe was quickly inserted into the steel pipe. Next, when the steel pipe into which the polyethylene pipe had been inserted was left as it was for 1 hour, the diameter of the inserted polyethylene pipe expanded and it was in close contact with the inner surface of the steel pipe. After that, the steel pipe was induction-heated by an induction coil having a heating width of 20 mm and moved at a heating temperature of 90 ° C. from one end at a speed of 110 mm / min to preheat the polyethylene pipe. Due to this preheating, the steel pipe and the polyethylene became more closely attached. Next, before the temperature cools down, induction heating is performed with an induction coil with a heating width of 30 mm,
At a heating temperature of 120 ° C., the adhesive layer was moved from one end at a speed of 220 mm / min to heat and melt the adhesive layer via a steel pipe. After being left to cool, it was cut, and the appearance was observed and a peel test was performed, and the following results were obtained.

Appearance: The inner surface was glossy and free from blisters, wrinkles and scratches. Adhesion: As a result of a 10 mm width peel test, it was 100 N or more, which was a sufficient value.

[Example 3] Resin tube: high-density polyethylene tube having a heat expandability of about 5% Dimensions: outer diameter 40 mm, inner diameter 36 mm, thickness 2.0 mm,
Length 500 mm However, the outer layer is 100 μm EAA resin coating layer Mother pipe: Steel pipe (SGP40A) Dimensions: outer diameter 48.6 mm, inner diameter 41.7 mm, thickness 3.
A material having a length of 5 mm and a length of 500 mm or more was prepared.

First, the inner surface of the steel pipe was blasted. Next, the polyethylene tube was kept in a freezing device kept at -20 ° C for 10 minutes and frozen in that state. Then, the resin pipe was taken out and inserted into the steel pipe. Next, hot air at 90 ° C. was sent into the steel pipe into which the polyethylene pipe had been inserted to heat the polyethylene pipe and restore the original expanded state. As a result, the inserted polyethylene pipe was brought into close contact with the inner surface of the steel pipe. Next, induction heating was performed using an induction coil with a heating width of 30 mm, and the adhesive layer was heated and melted through a steel pipe at a heating temperature of 150 ° C. and moved from one end at a speed of 30 mm / min. After being left to cool, it was cut, and the appearance was observed and a peel test was performed, and the following results were obtained.

Appearance: The inner surface was glossy and free of swelling, wrinkles and scratches. Adhesion: As a result of a 10 mm width peel test, it was 120 N or more, which was a sufficient value.

[0042]

As described above, according to the first aspect of the present invention, the resin pipe to be lined on the inner surface of the mother pipe is preliminarily stretched in the pipe axial direction to be reduced in size so as to be inserted into the mother pipe.
In that state, it is cooled to a temperature below the freezing point, freezes to a reduced diameter state and becomes a temporarily reduced diameter resin tube with increased rigidity, inserts the temporarily reduced diameter resin tube into the mother tube, and then expands the diameter at least with time. The resin pipe is easily inserted into the mother pipe by restoring the state and adhering to the inner surface of the mother pipe.
After that, the diameter of the resin can be increased and brought into close contact with the mother pipe, and there is an effect that an inner surface resin lining pipe provided with a resin lining having a desired thickness can be manufactured at low cost.

Further, in the second invention of the present application, the resin pipe to be inserted into the mother pipe is formed to have an outer diameter that can be easily inserted into the mother pipe. However, after restoration, the diameter can be increased beyond the inner diameter of the mother pipe. Using a shape memory resin tube having a heat-expanding property, insert the shape memory resin tube into the mother tube while cooling it to a temperature below the freezing point to increase its rigidity, and then restore the expanded state by heating. The inner surface of the resin pipe can be easily inserted into the mother pipe, and then the diameter of the resin pipe can be expanded and brought into close contact with the mother pipe. It has the effect that the tube can be manufactured at low cost.

Here, an adhesive layer having a melting point lower than that of the resin pipe is interposed between the mother pipe and the resin pipe, the resin pipe is inserted into the mother pipe, and then the adhesive layer is heated and melted. With this structure, the effect that the mother tube and the resin tube can be firmly bonded together is obtained.

The outer surface of the resin pipe to be inserted into the mother pipe is covered with an adhesive layer having a melting point lower than that of the resin pipe, the resin pipe is inserted into the mother pipe, and then the adhesive layer is heated. With the melting structure, the mother pipe and the resin pipe can be firmly adhered, and the work of arranging the adhesive layer between the mother pipe and the resin pipe becomes easy. .

Further, when the resin pipe whose outer surface is coated with the adhesive layer is manufactured by the co-extrusion method, mass production can be carried out at low cost, the adhesive layer can be uniformly formed on the outer periphery, and when the resin pipe is inserted into the mother pipe. The effect that the adhesive layer is less likely to be turned up is obtained.

Further, the heating of the mother pipe for bonding the resin pipe to the mother pipe is performed by heating a small section in the axial direction of the mother pipe to move the heating portion from one end to the other end or from the center to both ends. When configured to be performed by moving heating to move toward the direction, fusion is performed while the fusion site by heating progresses in the axial direction of the mother pipe, whereby fusion is performed while pushing out the gas between the resin pipe and the mother pipe. As a result, it is possible to obtain the effect of ensuring the adhesion between the resin pipe and the mother pipe with almost no residual air bubbles.

By using a polyolefin pipe such as a polyethylene pipe as the resin pipe used in the present invention, it is possible to inexpensively manufacture a thick film polyolefin lining pipe which is excellent in anticorrosion property, non-elution property and durability and does not cause environmental problems. The effect of being able to be obtained is obtained.

Continued front page    F-term (reference) 3H111 AA01 BA15 CA52 CB03 CB08                       CB14 DB03 DB05 EA12 EA14                 4F211 AA03 AD03 AD12 AG03 AG08                       AH43 SA13 SC03 SD04 SG01                       SH09 SH10 SH18 SJ01 SJ13                       SJ15 SJ21 SJ29 SP20 SP21                       SP39 SP40

Claims (7)

[Claims] 1. A dimension that allows a resin pipe to be inserted into the mother pipe when the resin pipe is inserted into the mother pipe to manufacture an inner resin lining pipe by pulling the resin pipe into the mother pipe by pulling in the axial direction of the pipe. To a temperature below the freezing point to freeze it to a reduced diameter state and make it a temporarily reduced diameter resin tube with increased rigidity. A method for producing an inner surface resin-lined pipe, which comprises inserting the pipe into a pipe, and then restoring the expanded diameter state at least over time so as to be in close contact with the inner surface of the mother pipe. 2. A shape memory resin pipe having a heat-expanding property is used as the resin pipe to be inserted into the mother pipe when the resin pipe is inserted into the mother pipe to manufacture an inner resin lining pipe. The inner surface is characterized in that the shape memory resin tube is cooled to a temperature below the freezing point to be inserted into the mother tube in a state where the rigidity is increased, and then restored to a diameter-expanded state by heating and adhered to the inner surface of the mother tube Manufacturing method of resin lining pipe. 3. An adhesive layer having a melting point lower than that of the resin pipe is interposed between the mother pipe and the resin pipe, the resin pipe is inserted into the mother pipe, and then the adhesive layer is heated and melted. The method for producing an inner surface resin lining pipe according to claim 1 or 2, wherein 4. An outer surface of a resin pipe to be inserted into the mother pipe,
Covered with an adhesive layer having a melting point lower than that of the resin pipe, after inserting the resin pipe into the mother pipe, heating the adhesive layer,
4. Melting, any one of Claim 1 to 3 characterized by the above-mentioned.
Item 6. A method for manufacturing an inner surface resin lining pipe according to the item. 5. The method for producing an inner resin lining pipe according to claim 4, wherein a resin pipe having an outer surface coated with an adhesive layer is manufactured by a co-extrusion method. 6. After inserting a resin pipe into the mother pipe, the mother pipe is heated in a small section in the axial direction so that the heating portion is moved from one end to the other end of the mother pipe or both ends from the central portion. 6. The adhesive layer is heated and melted by moving by moving the adhesive layer toward the surface of the adhesive layer.
The method for producing an inner resin lining pipe according to any one of 1. 7. The method for producing an inner resin lining pipe according to claim 1, wherein a polyolefin pipe is used as the resin pipe.