JPH0866963A - Heat-expandable resin pipe, manufacturing method thereof, and manufacturing method of composite pipe - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a thermally expansive resin pipe which can be firmly adhered to an inner surface of a metal pipe or the like without generation of residual stress and can be manufactured with a sufficiently short facility. [Composition] A non-foamed resin tube whose diameter expands and recovers by heating, and has a predetermined temperature T ₁ higher than the heat deformation temperature of the non-foamed resin and a predetermined temperature T ₂ lower than the extrusion molding temperature of the non-foamed resin. The change amount of the tube diameter expansion with respect to the change amount of the heating temperature is smaller than the change amount of the tube diameter expansion with respect to the change amount of the heating temperature between the thermal deformation temperature and the predetermined temperature T _1, and preferably 0. It is less than or equal to 0.05 mm / ° C. It is used for manufacturing a composite pipe, is inserted into a metal pipe, and the heat-expandable resin pipe is heated and expanded within a temperature range belonging to temperatures T _{1 to} T ₂ to coat the inner surface of the metal pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-expandable resin tube that expands and recovers by heating, a method for manufacturing the same, and a method for manufacturing a composite tube in which the inner surface of a metal tube is covered with the heat-expandable resin tube. Is.

[0002]

2. Description of the Related Art As a method for producing a composite pipe in which a resin layer is coated (lined) on the inner surface of a metal tube, a heat-expandable resin tube whose diameter expands and recovers by heating is applied on the outer surface of which an adhesive is applied. It is known to insert into a metal tube and to expand the inserted resin tube by heating from the outside of the metal tube to adhere to the inner surface of the metal tube, especially when imparting sound deadening property and dew condensation preventive property to the composite tube. It is also known to use a two-layer heat-expandable resin tube in which the inner layer is a non-foamed resin and the outer layer is a foamed resin in the heat-expandable resin tube (Japanese Patent Laid-Open No. 5-1695).
74 publication).

Conventionally, as a method for producing the above-mentioned heat-expandable resin pipe, a tubular molten resin discharged from an extrusion die is once expanded by a swelling mold immediately after the discharge and the resin extrusion speed is increased. It is known to increase the take-up speed to reduce the diameter of the expanded tubular resin by pulling, introduce the reduced diameter tubular resin into a cooling water tank, rapidly cool it, and solidify by cooling (JP-A-5-169574). Gazette).

The expansion recovery mechanism of the heat-expandable resin tube is that the molecular chain of the resin is forcibly stretched and frozen, and this freezing is released by reheating (in a crystalline resin, the crystal is However, for convenience of description, only the stretched orientation will be described below).

In the production of the above heat-expandable resin tube, however, the molecular chain of the resin is forcibly stretched by the tension received during thermal softening during the natural cooling of the tubular resin until it enters the cooling water tank. It is presumed that this extended molecular chain becomes the energy for expansion recovery. The normal state of the resin is a state in which molecular chains are randomly coiled and entangled,
Although the resin always tries to maintain this state, the resin in which the molecular chain is stretched, that is, the resin at the inlet of the forming tube, cannot be returned to the normal state because it is rapidly cooled in the water tank. Then, the molecular chain is frozen in the stretched state, cooled and solidified, and molded into a heat-expandable resin tube whose outer diameter is regulated by the forming tube. Then, it is theorized that when the frozen state of the heat-expandable resin tube is released by reheating, the extended molecular chain returns to the original coil state and expands and recovers to the tube diameter before it is almost pulled.

[0006]

When the above heat-expandable resin pipe is heated at a certain temperature T, the recovery curve of this pipe diameter is similar to the stress recovery curve in viscoelasticity theory, and the initial short term The diameter increases rapidly and then gradually increases. Assuming that the initial expansion amount is the expansion size at the heating temperature T, the heating temperature of the heat-expandable resin pipe produced by the above method (the method described in JP-A-5-169574)-
The pipe outer diameter characteristic is represented by a curve in which the expansion dimension increases proportionally as the heating temperature T approaches the processing temperature T ′ when the molecular chain of the resin is stretched by pulling.

In the above method, however, since the resin is naturally cooled and is not forcibly cooled after the resin is discharged and before reaching the forming tube, the resin is pulled by tension. Processing temperature T'when the molecular chain is stretched,
That is, the temperature between the swelling die and the forming tube is close to the discharge temperature of the resin (heating the heat-expandable resin tube to the discharge temperature of the resin or higher causes thermal expansion). This is not possible due to the shape retention of the flexible resin tube. In this case, the temperature T '
Is almost the upper limit temperature of heating), so that the heating temperature −
As shown by the curve C in FIG. 7, the pipe outer diameter characteristic is represented by a curve in which the expansion dimension increases proportionally as the heating temperature increases over the entire region between the heat distortion temperature and the resin extrusion temperature. Be touched.

In the production of the above composite pipe, since the length of the metal pipe is long, it is unavoidable that the heating of the heat-expandable resin pipe inserted inside the metal pipe varies in the longitudinal direction. Further, when the diameter of the metal tube is large, it is difficult to avoid that the heat-expandable resin tube is heated in the circumferential direction.

[0009]而Ru, when a D in FIG. 7 the inner diameter of the metal tube, when heated criteria of the heat-expandable resin tube with somewhat higher temperatures T ₀ 'than the temperature T _0, the more the temperature difference ΔT If the variation width is large, some parts of the outer surface of the heat-expandable resin pipe are hard to contact the inner surface of the metal pipe and some are excessively in contact with the inner surface of the metal pipe.

In order to avoid such a disadvantage, the heating reference temperature is increased so that the temperature of the heat-expandable resin tube can be set to the temperature T ₀ or higher in FIG. , Temperature T ₀ ″), the difference ΔD between the outer diameter of the expanded tube and the inner diameter of the metal tube becomes excessive, and the thermal expansion resin tube is adhered to the inner surface of the metal tube with residual stress. In a severe operating environment in which low temperature and high temperature are repeated for a long period of time, the residual stress easily causes interface separation between the metal pipe and the resin layer.

However, the above disadvantage can be eliminated by making the above heating temperature-tube outer diameter characteristic with a gentle gradient, but for this purpose, it is necessary to perform slow cooling instead of rapid cooling of the water tank cooling.
The gradual cooling device is long and unrealistic in terms of equipment.

An object of the present invention is to provide a heat-expandable resin pipe which can be firmly adhered to the inner surface of a metal pipe or the like without generation of residual stress, and can be produced with a sufficiently short facility, and a method for producing the same. Especially.

An object of the present invention is to provide a method of manufacturing a composite pipe using this heat-expandable resin pipe, which can easily perform corrosion protection on the inner surface.

[0014]

The heat-expandable resin tube according to the present invention is a non-foaming resin tube whose diameter expands and recovers by heating, and is a predetermined temperature T higher than the heat deformation temperature of the non-foaming resin. ₁ and the predetermined temperature T ₂ lower than the extrusion molding temperature of the non-foamed resin, the change amount of the pipe diameter expansion with respect to the change amount of the heating temperature is the change in the heating temperature between the heat deformation temperature and the predetermined temperature T _1. It is smaller than the amount of change in tube diameter expansion with respect to the amount, and preferably 0.05 mm / ° C. or less.

The heat-expandable resin pipe according to the present invention is a two-layer resin pipe in which the inner diameter is expanded and recovered by heating and the inner layer is a non-foamed resin layer and the outer layer is a foamed resin layer. Of the pipe diameter expansion with respect to the heating temperature change amount between the predetermined temperature T ₁ 'which is higher than the heat deformation temperature of the non-foamed resin and the predetermined temperature T ₂ ' which is lower than the extrusion molding temperature of the non-foamed resin. It is smaller than the amount of change in the tube diameter expansion with respect to the amount of change in the heating temperature with respect to the predetermined temperature T ₁ ′, and is preferably 0.
The configuration is characterized in that it is 05 mm / ° C. or less.

In the method for producing a heat-expandable resin tube according to the present invention, a non-foamed tubular molten resin discharged from an extrusion mold, or an inner layer discharged from the extrusion mold is a non-foamed resin layer and an outer layer is a foamed resin layer. The two-layer tubular molten resin is gradually cooled to a temperature T ₁ or T ₁ ′ with a constant inner diameter, and then, at about this temperature T ₁ or T ₁ ′, usually by pulling to a predetermined temperature. The configuration is characterized in that the diameter is reduced to the above dimension, and after this diameter reduction, it is rapidly cooled and solidified.

In the method for producing a composite pipe according to the present invention, the above-mentioned heat-expandable resin pipe is inserted into a metal pipe, and the heat-expandable resin pipe is heated to a temperature of T _{1 to} T ₂ or T ₁ 'to T ₂ '. The structure is characterized in that it is heated and expanded within the temperature range belonging to (3) to cover the inner surface of the metal tube.

The present invention will be described below with reference to the drawings. An amorphous resin such as vinyl chloride resin or a crystalline resin such as cross-linked polyethylene can be used for the heat-expandable resin pipe according to the invention of claim 1, and FIG. 1 shows the heat-expandable resin. It shows the heating temperature of the tube-outer diameter characteristics.

In FIG. 1, temperature T ₂ is a predetermined temperature lower than the extrusion molding temperature of the resin used, T ₁ is a predetermined temperature higher than the heat distortion temperature of the resin used, and the swelling dimension is
It is the outer diameter dimension that expands when heated to a certain temperature. Specifically, after the thermally expandable resin tube is put into a gear oven (heating furnace) having a predetermined heat capacity set to a predetermined temperature, the temperature outside the tube at the ultimate temperature (heating temperature) of the tube after about 15 minutes has passed. Refers to the diameter dimension. In FIG. 1, the change in the pipe diameter with respect to the change in the heating temperature at the temperatures T _{1 to} T ₂ indicates the heat deformation temperature to the temperature T.
Compared to the change in pipe diameter due to the change in heating temperature in ₁ , the change is extremely slow.

In this heat-expandable resin tube, as will be described later, the tube is inserted into a metal tube, further expanded by heating to be adhered to the inner surface of the metal tube, and the heating changes the tube diameter expansion with respect to the heating temperature change. Is small and is within a temperature range belonging to temperatures T _{1 to} T ₂ . The ratio a of the change in pipe diameter expansion / the amount of change in heating temperature within this temperature range is represented by b, the variation width of the heating temperature, and c, the variation of the allowable expansion diameter dimension (the maximum value of variation that can guarantee satisfactory adhesion). Then, it is set so as to satisfy the relationship of ab <c, and usually b is at least 10 ° C. and c is about 0.5 mm, so a is 0.05 mm.
It is set below / ° C. As will be described later, the ratio a of the pipe diameter expansion change amount / heating temperature change amount in the temperature range of T _{1 to} T ₂ indicates the resin cooling condition after the resin is discharged until it passes through the inner surface cooling mandrel. It can be adjusted by adjustment (in the case of a hard vinyl chloride resin, it is usually adjusted within the range of 85 ° C to 100 ° C of the inner surface temperature of the tubular resin at the outlet of the inner surface cooling mandrel).

The temperature T in FIG.₁~ T₂The range is
Variation of the heating temperature of the range T ₁~ T₂Inside
Is set to the temperature T₁Is almost cold, as described below.
Between the mandrel exit and the forming tube entrance
Since it matches the resin temperature of, it can be adjusted by adjusting the temperature.
it can. Temperature T₂For details, see below.
The temperature is set lower than the discharge temperature.

FIG. 2 shows an essential part of an example of a manufacturing apparatus used when manufacturing the above-mentioned heat-expandable resin pipe according to the invention of claim 3. In FIG. 2, 10 is a pipe extrusion die, 11 is a core supported by a spider in the die, 12 is a resin flow path, and 20 is a cooling mandrel connected to the tip of the core.
The 0 coil 21 is connected to the external cooling circuit via the core and the spider.

Further, in FIG. 2, 30 is a cooling water tank,
Reference numerals 25 denote forming tubes attached to the inlet of the cooling water tank 30, respectively. A take-off machine is installed outside the cooling water tank outlet, but it is not shown in the figure.

In order to manufacture the heat-expandable resin pipe according to the invention of claim 3 by using the manufacturing apparatus shown in FIG. 2, the tubular molten resin from the extrusion die 10 is cooled by the cooling mandrel 20 in FIG. Expanded diameter, coil 2 of cooling mandrel 20
In step 1, the expanded tubular resin is gradually cooled with hot water.
In this expanded diameter tubular resin, while being passed through the cooling mandrel 20, the resin (the molecular chain of the resin) is stretched by being stretched in the lengthwise direction and the circumferential direction. The proportion of the stretched tube which reaches the forming tube 25 and is rapidly cooled and frozen in the water tank 30 is small, and most of it is restored to the original coil shape before reaching the forming tube 25.

The inside diameter of the forming tube 25 is
The outer diameter of the heat-expandable resin tube to be manufactured is set to be substantially regulated, and is smaller than the outer diameter of the resin discharged. Therefore, the take-up speed is set higher than the discharge speed of the resin by that amount. Therefore, the tubular resin that has passed through the cooling mandrel 20 travels to the forming tube 25 while being reduced in diameter by tension, and during this time, the resin (the molecular chain thereof) is forcibly stretched by the tension and this elongation Cooling water tank 3 immediately (with molecular chains)
It is frozen by quenching with 0.

In the above description, assuming that the stretched resin molecular chains are completely restored to the original coil shape by the time the cooling mandrel 20 exits, the molecular chains in the resin at the inlet of the forming tube are recovered. Elongation occurs only between the cooling mandrel outlet and the forming tube inlet, and the elongation of this molecular chain is frozen by rapid cooling in a water tank and exhibits a swelling property due to reheating. If the temperature of the resin from the outlet of the cooling mandrel to the inlet of the forming tube is T ₁ , the freezing of the molecular chain is almost completely released by reheating at the temperature T ₁ , and the heat-expandable resin pipe is reduced in diameter. Even if the size is returned to and the temperature is reheated to the temperature T ₁ or higher, the expanded diameter does not occur. In addition, the temperature at which the swelling starts due to softening of the resin by reheating, that is, between the heat deformation temperature and the same temperature T ₁ , restoration of the molecular chain whose elongation has been frozen to the original coil state, Since the higher the temperature is, the higher the ratio is, the amount of expansion increases proportionally from the heat distortion temperature to the temperature T ₁ .

However, the heating temperature-outer diameter characteristic of this heat-expandable resin pipe is based on the assumption of an ideal state. In fact, as described above, the resin reaches the outlet of the cooling mandrel. molecular chain of the resin which extends in the not completely return to shape the original coil, frozen with a partially extended, because of its effect, as shown in Figure 1, at a temperature above T ₁ The heating temperature-outer diameter characteristics are slightly tilted upward.

In particular, the elongation generated in the resin in the vicinity of the discharge port of the extrusion die, that is, in the molecular chain of the resin at a temperature close to the extrusion temperature of the resin, is large, and as the cooling rate of the cooling mandrel becomes faster, the molecule having the larger elongation becomes larger. Since it becomes difficult to restore the chain to the original coil state, as shown in FIG. 3, the expansion ratio at a heating temperature close to the extrusion temperature of the resin increases depending on the cooling conditions of the cooling mandrel. Sometimes. However, even in this case, if there is a heating temperature range in which the gradient of the heating temperature-tube outer diameter characteristic is gentle and the variation of the actual heating temperature can be included in this temperature range, it can be effectively used without any trouble.

In any of the heat-expandable resin pipes having the above-mentioned heating temperature-tube outer diameter characteristic, it is used in a characteristic portion having a gentle gradient on the higher temperature side than the heating temperature T ₁ , and the gradient a is as described above. It is adjusted according to the variation width b of the actual heating temperature and the variation of the allowable expansion diameter, and the adjustment is performed by adjusting the slow cooling conditions in the cooling mandrel.

As described above, in order to manufacture the heat-expandable resin tube according to the third aspect of the present invention, the outer diameter of the heat-expandable resin tube to be manufactured is restricted by the forming tube, and the mandrel of the mandrel is controlled. Adjusting the temperature of the resin from the outlet to the inlet of the forming tube to adjust the heating temperature of the heat-expandable resin pipe-the temperature T ₁ in the outer diameter characteristic of the pipe, and a predetermined temperature range with the temperature T ₁ being the lower limit. Therefore, it is necessary to adjust the slow cooling conditions by the cooling mandrel so that the characteristic gradient becomes equal to or less than the predetermined value.

In the heat-expandable resin pipe according to the second aspect, an amorphous resin such as vinyl chloride resin or a crystalline resin such as crosslinked polyethylene can be used for the non-foamed resin layer on the inner side, and an outer resin layer on the outer side. Foamed vinyl chloride resin, foamed polyethylene resin, foamed polystyrene resin, or the like can be used for the foamed resin layer.

In this composite heat-expandable resin tube, the heating temperature-outer diameter characteristics are substantially determined by the non-foamed resin layer, and the foamed resin layer has a small influence on the characteristics (the reason therefor). Is presumed to be because the tensile force is absorbed by the deformation of the bubbles in the foamed resin layer against the tensile force under the resin melting, and the molecular chain of the resin hardly expands. Thus, even a composite of a non-foamed resin layer and a foamed resin layer has its characteristics set on the basis of the non-foamed resin layer and has a predetermined temperature T ₁ 'which is higher than the heat deformation temperature of the non-foamed resin. And the predetermined temperature T ₂ 'which is lower than the extrusion molding temperature of the non-foamed resin, the pipe diameter expansion change amount with respect to the heating temperature change amount is the heat deformation temperature and the predetermined temperature T.
It is said to be smaller than the amount of change in pipe diameter expansion with respect to the amount of change in heating temperature between ₁ 'and.

Also in this composite thermally expandable resin tube, as will be described later, the tube is inserted into a metal tube, further expanded by heating and applied to the inner surface of the metal tube, and the heating changes the heating temperature of the non-foamed layer. Temperature change T is small
It carried out within the temperature range belonging to the ₁ '~T _2'. in this case,
The non-foamed layer (inner layer) is heated from the outside of the metal tube through the foamed resin layer, and since the heat resistance of this foamed resin layer is high, it is necessary to use a heat source with a high temperature. The variation width of the temperature becomes wider than that of the heat-expandable resin tube composed of only the non-foamed resin layer.
On the other hand, the allowable variation in the outer diameter of the pipe can be made larger than the case where only the non-foamed resin layer is used, because even if the variation becomes a little too large, it can be absorbed by the cushioning effect of the foamed resin layer as the outer layer. Therefore, the variation width of the heating temperature is at least 10 ° C. in the case of only the non-foamed resin layer.
To at least 15 ° C., but the permissible variation in the outer diameter of the pipe is 0.5 mm to 0.
Since it is 75 mm, the gradient of the heating temperature-tube outer diameter characteristic to be used is at least 0.75 mm / 15 ° C (=
0.05 mm / ° C.), which is not different from the case of only the non-foamed resin layer. However, since the variation width of the heating temperature becomes wider than that in the case of only the non-foamed resin layer, the range of the temperatures T ₁ ′ to T ₂ ′ is set to the above temperatures T _{1 to} T _2.
May need to be wider than.

In order to manufacture this composite thermally expandable resin tube according to the present invention as set forth in claim 4, in the manufacturing apparatus shown in FIG. 2 above, as shown in FIG. By using a two-layer coextrusion method capable of simultaneously extruding the foamed resin layer on the outer surface of the non-emulsion resin layer, and having the same other configuration (in FIG. 4, the same reference numerals as those in FIG. Of the heat-expandable resin pipe produced by the forming tube, and the outlet of the mandrel or the forming tube. - heating temperature by adjusting the resin temperature reaches the blanking inlet thermally expandable resin pipe - 'adjusting the further temperatures T _1' the temperature T ₁ of the at extravascular size characteristics at a given temperature width of the lower limit Cooling mandator to keep the characteristic gradient below a specified value. Adjusting the annealing conditions by Le,
Etc. are required.

The heat-expandable resin pipe according to the present invention is used for the inner surface lining of various tubular bodies, and particularly preferably for the inner surface lining for corrosion protection of fluid transport metal tubes. In order to manufacture the composite pipe according to the invention of claim 5, the heat-expandable resin pipe adhered to the inner surface of the metal pipe (for example, steel pipe, aluminum pipe) is set to the inner diameter of the metal pipe or the heating condition for lining. Accordingly, it is manufactured by the invention according to claim 3 or 4.

In this case, the inner diameter of the forming tube is determined so that the outer diameter of the heat-expandable resin tube is 99% to 95% of the inner diameter of the metal tube. In addition, the reference heating temperature for lining (the reference heating temperature of the heat-expandable resin tube, in the case of a composite heat-expandable resin tube with a non-foamed resin inner layer and a foamed resin outer layer, the reference heating temperature of the non-foamed resin inner layer ) The fluctuation range of the heating temperature is set to ± ΔT under Ta (the fluctuation range is 1 in the case of a heat-expandable resin tube made of only non-foamed resin).
About 0 ° C, about 15 ° C in the case of a composite thermally expandable resin tube consisting of a non-foamed resin and a foamed resin layer), the allowable variation in the expanded diameter of the thermally expandable resin tube is b (thermal expansion consisting of only the non-foamed resin). In the case of a flexible resin tube, about 0.05 mm, and in the case of a composite thermal expansion resin tube consisting of a non-foamed resin and a foamed resin layer, 0.075
mm), the temperature range (Ta-ΔT) to (Ta
+ [Delta] T) the heating temperature was above the - to belong to the extravascular size profile of the heating temperature range (T ₁ ~T ₂₎ or within _{(T 1 '~T 2')} , and the heating temperature in the heating temperature range - extravascular Diameter characteristic gradient a
Is adjusted to satisfy 2ΔTa <b, and the slow cooling condition of the cooling mandrel is adjusted. In this case, the outer diameter of the cooling mandrel is in the temperature range (Ta-ΔT) to (Ta + ΔT).
The outer diameter of the heat-expandable resin pipe at 100% to 1% of the inner diameter of the metal pipe
It is set to be 03%.

The heat-expandable resin pipe thus obtained is coated with an adhesive and then inserted into a metal pipe, and the metal pipe having the resin pipe inserted therein is carried into a heating furnace and heated from outside the metal pipe. The heat-expandable resin pipe is heated at the above-mentioned reference temperature to expand the diameter, and is adhered to the inner surface of the metal pipe, whereby the production of the composite pipe is completed.

As the above-mentioned adhesive, not only various resin-based adhesives but also rubber-based adhesives can be used, but it is preferable to use hot-melt type adhesives, and when hot-melt type adhesives are used. The above heating reference temperature is set to the optimum bonding temperature of this adhesive. Further, for the application of the adhesive, for example, immediately after the water tank, a crosshead extrusion device having a circular discharge port surrounding the outer circumference of the heat-expandable resin tube and a mold are arranged, and the surface temperature is It is also possible to use a method in which an adhesive is applied when a heat-expandable resin tube having a certain degree of highness passes through this crosshead.

[0039]

In the production of the heat-expandable resin pipe, the tubular molten resin discharged from the extrusion die is gradually cooled when passing through the cooling mandrel, and the molecular chain of the resin stretched up to that time is almost in the original state. The cooling mandrel and fore
The molecular chains of the resin at a temperature of about T ₁ or T ₁ ′ between them and the melting tube are stretched by tension, and the molecular chains are frozen in this stretched state by rapid cooling in a water tank.

As a result, when reheated at the temperature T ₁ or T ₁ ', the freezing of the molecular chain is released, the molecular chain returns to its normal state, and the resin pipe size also returns to its original size. Completion), even if heated to T ₁ or more, swelling after that hardly occurs. Therefore, when the heating temperature exceeds T ₁ or T ₁ ′, the heating temperature-tube outer diameter characteristic becomes almost flat.

In the method for producing the composite pipe, the heat-expandable resin pipe having the above-mentioned characteristics is inserted into the metal pipe, and the heat-expandable resin pipe is within the flat heating temperature-temperature range of the pipe outer diameter characteristic portion. Be heated. As a result, even if there is heating unevenness, the expansion diameter unevenness of the heat-expandable resin pipe is kept to a minimum, and the heat-expandable resin pipe is contacted with the inner surface of the metal pipe in a sufficiently uniform state, resulting in sufficient adhesion. It is applied with strength.

[0042]

【Example】

[Example 1] This is an example of a method for producing a composite pipe, and the heat-expandable resin pipe made of a hard vinyl chloride resin produced by the invention of claim 2 was used.

The apparatus shown in FIG. 2 is used as the apparatus for producing the heat-expandable resin tube, and the inside diameter of the forming tube 25 is 5
1.1 mm and the length of the cooling mandrel 20 is 450 m
m, hot water circulation cooling, the resin was discharged at a temperature of approximately 185 ° C., and the hot water flow rate and temperature of the cooling mandrel 20 were adjusted by the temperature control unit so that the temperature of the inner surface of the tubular resin at the cooling mandrel outlet was 92 ° C. , From the cooling mandrel outlet to the forming tube from the resin pipe regulation outer diameter 53.4 mm
The take-up speed was made faster than the resin discharge speed so that the inner diameter was 51.1 mm.

The outer diameter of the produced heat-expandable resin tube is 51.0.
mm, and the heating temperature-tube outer diameter characteristics were as shown in FIG. T ₁ was 100 ° C. and T ₂ was 120 ° C., and the inclination gradient in this range was only 0.025 mm / ° C. Expanded outer diameter at a heating temperature of 100 ° C is 53.0
mm, bulging outer diameter at a heating temperature of 120 ° C is 53.5 mm
Met.

The heat distortion temperature is JIS-K-720.
The temperature is 72.5 ° C as measured by the A method (load is set to a bending stress of 18.5 N / cm ² ) according to the 7 standard hard plastic deflection temperature test method.

The heat-expandable resin pipe manufactured in this manner is uniformly applied with a thermoplastic resin hot melt adhesive and then inserted into a carbon steel pipe for piping having an inner diameter of 52.9 mm and a length of 5.5 m. Then, set the heating reference temperature of the heat-expandable resin pipe to 1
Heating was performed from the outside of the metal tube so that the temperature was 15 ° C.
For this heating, a method was used in which the tube was run in a horizontal state, and hot air was sequentially heated from above and below by a hot air heating device from the center of the tube to both ends of the tube. In this case, on the inner surface of the heat-expandable resin tube, thermocouples are attached in advance at a total of 10 locations, which are separated by approximately half a circumference in each of the 5 locations, which are spaced substantially equidistantly in the axial direction. When measured, it was 107 ° C to 120 ° C.

[Comparative Example 1] As compared with Example 1, the heat-expandable resin tube has a tube diameter substantially proportionally expanded as the heating temperature is increased from the heat distortion temperature to near the resin extrusion temperature as shown in FIG. And has a heating temperature-tube outer diameter characteristic that the gradient is 0.1 mm / ° C. in the heating temperature range 100 ° C. to 120 ° C., and the thermal expansion property is made of a hard vinyl chloride resin having an outer diameter of 51.0 mm. Same as Example 1 except that a resin tube was used.

[Comparative Example 2] In comparison with Example 1, a thermally expansive resin
For the fat tube, change the heating temperature from the heat distortion temperature to near the resin extrusion temperature.
As the pipe diameter increases, the pipe diameter expands almost proportionally, and the heating temperature
With a gradient of 0.06 mm / ° C in the range 100 ° C to 120 ° C
It has a certain heating temperature-tube outer diameter characteristic, and the outer diameter is 51.0 mm.
Using a thermally expandable resin tube made of hard vinyl chloride resin
Other than that, it was the same as in Example 1. These example products and
For the comparative example product, the interface between the metal pipe and the resin pipe immediately after manufacturing
The initial adhesion of is checked, and cold water flow at 20 ℃ for 5 minutes
Cold and hot water flow in which one cycle of hot water flow at -80 ° C for 5 minutes
When a test 3000 cycles was performed, in Comparative Example 1,
Regarding the initial adhesiveness, 4 out of 50 are defective (
Surfaces with irregularities and voids were considered as defective), cold and hot water flow test
After the test (46 samples), 5 out of 46
Poor interface adhesion was observed, and the adhesive strength (average value) was 2.1k.
g / cm ²The shrinkage amount (average value) of the resin pipe end is 1.
Residual stress of resin pipe at the beginning of manufacturing composite pipe reaching 3mm
Was found to be quite large.

In Comparative Example 2, the initial adhesion was not defective under the number of 50 samples, but after the cold water flow test (the number of samples was 49), the interface adhesion was found in 3 out of 49 samples. Poorness was observed and the adhesive strength (average value) was 2.9 kg /
As low as cm ² , the shrinkage amount (average value) of the resin pipe end is 0.9 m
It was m.

In contrast to these comparative examples, in Example 1, the poor initial adhesiveness was zero under the number of 50 samples, and after the cold water flow test (the number of samples was 50), the interface adhesion was reduced. No defective products were observed, the adhesive strength (average value) was as high as 3.8 kg / cm ^2, and the shrinkage amount (average value) of the resin tube end was only 0.7 mm. It was estimated that the residual stress of the pipe was sufficiently lower than that of the comparative example.

[Embodiment 2] This is an embodiment of a method for producing a composite pipe, in which the non-foamed resin inner layer produced by the invention according to claim 4 is a hard vinyl chloride resin The inner layer was a hard vinyl chloride resin to which a baking soda-based foaming agent was added.

As the apparatus for producing the heat-expandable resin tube, as shown in FIG. 4, the extrusion die used was a two-layer simultaneous extrusion die for simultaneously extruding the non-foamed resin inner layer and the foamed resin outer layer.
The inner diameter of the forming tube was 54.6 mm, the length of the cooling mandrel was 450 mm, and the hot water flow rate and temperature of the cooling mandrel were adjusted so that the temperature of the inner surface of the tubular resin at the cooling mandrel outlet was 94 ° C. The take-up speed was made faster than the resin discharge speed so that the outer diameter of the resin tube at the outlet of the cooling mandrel was 57.4 mm and the inner diameter of the forming tube was 54.6 mm.

The outer diameter of the produced heat-expandable resin tube is 54.5.
mm, and the heating temperature-tube outer diameter characteristics were as shown in FIG. T ₁ 'is 100 ℃, T ₂ ' is 125 ℃,
The slope gradient in this temperature range was only 0.025 mm / ° C. The expanded outer diameter at a heating temperature of 125 ° C. is 57.2.
The bulge outer diameter at a heating temperature of 100 ° C. is 56. mm.
It was 6 mm.

The two-layer heat-expandable resin pipe produced in this manner was uniformly coated with a thermoplastic resin-based hot-melt adhesive, and then a carbon steel pipe for piping having an inner diameter of 56.5 mm and a length of 5.5 m was formed. And was heated from the outside of the metal tube so that the heating reference temperature of the non-foamed resin inner layer of the thermally expandable resin tube was 115 ° C. For this heating, as in Example 1, a method was used in which the pipe was run in a horizontal state, and hot air was sequentially heated from above and below by a hot air heating device from the center of the pipe to both ends of the pipe. In this case, as in Example 1, thermocouples were previously formed on the inner surface of the heat-expandable resin tube at a total of 10 positions, which were separated by approximately half a circumference in each of the 5 positions which were separated by substantially the same distance in the axial direction. When it was attached and the variation in heating temperature was measured, it was 104 ° C to 122 ° C.

[Comparative Example 3] In comparison with Example 2, the heat-expandable resin pipe was expanded substantially proportionally as the heating temperature was increased from the heat deformation temperature to near the resin extrusion temperature as shown in FIG. And has a heating temperature-tube outer diameter characteristic in which the gradient is 0.075 mm / ° C. in the heating temperature range of 100 ° C. to 120 ° C., the inner layer is the same non-foamed rigid vinyl chloride resin as in Example 2, and the outer layer is Same as Example 2, except that the same expanded rigid vinyl chloride resin as in Example 2 was used and a two-layer thermally expandable resin tube having an outer diameter of 54.5 mm was used.

[Comparative Example 4] As compared with Example 2, the heat-expandable resin tube expanded in diameter almost proportionally as the heating temperature increased from the heat distortion temperature to near the resin extrusion temperature, and the heating temperature range was increased. Gradient at 100 ° C to 120 ° C is 0.055 mm / ° C
And the outer diameter is the same non-foamed rigid vinyl chloride resin as in Example 2, and the outer diameter is 54.5 mm.
Same as Example 1 except that the two-layer heat-expandable resin tube of 2 was used. For these Example 2 and Comparative Examples 3 and 4,
Similarly to the above, the initial adhesion of the interface between the metal pipe and the resin pipe immediately after the production was inspected, and a cold water flow test of 3000 cycles was performed. In Comparative Example 3, the initial adhesion was 50. Two out of the four were defective (those with irregularities and voids on the interface were considered defective), and after the cold water flow test (the number of samples was 48), poor interfacial adhesion was observed on 4 of the 48 The adhesive strength (average value) was as low as 1.1 kg / cm ² , the shrinkage amount (average value) of the resin pipe end reached 2.4 mm, and the residual stress of the resin pipe at the beginning of manufacturing the composite pipe was considerably large. It was confirmed that there was.

In Comparative Example 4, there was no defect in the initial adhesiveness under the number of samples of 50, but after the cold water flow test (the number of samples of 50), the interfacial adhesion was observed in 3 of 50 samples. Defects were observed, and the adhesive strength (average value) was 3.1 kg /
As low as cm ² , the shrinkage amount (average value) of the resin pipe end is 0.8 m
It was m.

In contrast to these comparative examples, in Example 2, the poor initial adhesion was zero under the number of 50 samples, and after the cold water flow test (the number of samples was 50), the interface adhesion was low. No defects were observed, the adhesive strength (average value) was as high as 3.7 kg / cm ^2, and the shrinkage amount (average value) at the end of the resin tube was only 0.6 mm. It is estimated that the residual stress of the pipe is sufficiently lower than that of the comparative example.

[0059]

According to the method for producing a composite pipe of the present invention, a non-foaming resin alone is used as a heat-expanding resin pipe or a two-layer heat-expanding resin pipe consisting of a non-foaming resin inner layer and a foaming resin outer layer is formed in a metal pipe. Inserted into the metal tube, by expanding the heat-expandable resin tube by heating from the outside of the metal tube and depositing it on the inner surface of the metal tube,
Even if the heating temperature varies, the resin pipe can be attached to the inner surface of the metal pipe with an appropriate degree of contact without excess or deficiency, and early adhesion of the inner resin coating layer due to poor adhesion due to insufficient contact or residual stress due to excessive contact Deterioration can be eliminated well, and a composite pipe with excellent quality and reliability can be manufactured. Moreover, strict control of the heating temperature is not required, and the manufacturing equipment can be simplified.

According to the method for producing a heat-expandable resin pipe according to the present invention, the heat-expandable resin pipe enabling the production of such a composite pipe is gradually cooled from the discharge of the resin to the rapid cooling of the water tank. It can be manufactured simply by adjusting the conditions and the take-up speed, and the manufacturing equipment of the heat-expandable resin pipe only needs to be added with a cooling mandrel to the existing equipment, which is also advantageous in terms of equipment.

Further, the heat-expandable resin pipe according to the present invention is characterized by the amount of change in the expansion of the pipe with respect to the amount of change in the heating temperature, as described above, so that the inner surface of the metal pipe or the like is firm and free of residual stress. Can be applied.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing heating temperature-tube outer diameter characteristics of a heat-expandable resin tube according to the present invention.

FIG. 2 is an explanatory view showing an example of a manufacturing apparatus used in the method for manufacturing a thermally expandable resin pipe according to the present invention.

FIG. 3 is an explanatory diagram showing a heating temperature-tube outer diameter characteristic of the thermally expandable resin tube according to the present invention, which is different from the above.

FIG. 4 is an explanatory view showing another example of the manufacturing apparatus used in the method for manufacturing a heat-expandable resin pipe according to the present invention.

5 is an explanatory diagram showing heating temperature-tube outer diameter characteristics of the heat-expandable resin tube used in Example 1. FIG.

FIG. 6 is an explanatory diagram showing heating temperature-tube outer diameter characteristics of the heat-expandable resin tube used in Example 2.

FIG. 7 is an explanatory diagram showing heating temperature-tube outer diameter characteristics of a heat-expandable resin tube used in manufacturing a conventional composite tube.

[Explanation of symbols]

 10 Extrusion Mold 11 Core 20 Cooling Mandrel 21 Hot Water Distribution Coil 25 Forming Tube 30 Cooling Water Tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29C 61/08 7639-4F B32B 1/08 Z 9349-4F 5/18 15/08 K // B29K 101: 00 B29L 9:00 23:00

Claims (6)

[Claims] 1. A non-foamed resin tube whose diameter expands and recovers by heating, and a predetermined temperature T ₁ higher than the heat deformation temperature of the non-foamed resin and a predetermined temperature T lower than the extrusion molding temperature of the non-foamed resin. _The amount of change in the tube diameter expansion with respect to the amount of change in the heating temperature with respect to 2 is smaller than the amount of change in the tube diameter expansion with respect to the amount of change in the heating temperature between the heat deformation temperature and the predetermined temperature T _1. And a heat-expandable resin tube. 2. A two-layer resin pipe having an inner layer made of a non-foamed resin layer and an outer layer made of a foamed resin layer, in which the pipe diameter is expanded and recovered by heating, and a predetermined temperature T higher than the heat deformation temperature of the non-foamed resin.
Tube diameter expansion change amount with respect to the heating temperature variation between the ₁ 'and the non-foamed predetermined temperature T ₂ lower than the extrusion temperature of the resin' is, between the heat deformation temperature and a predetermined temperature T ₁ ' The heat-expandable resin pipe is smaller than the change amount of the pipe diameter expansion with respect to the change amount of the heating temperature. 3. A method for producing a heat-expandable resin pipe according to claim 1, wherein the non-foamed tubular molten resin discharged from the extrusion die is gradually cooled to a temperature T ₁ under a constant inner diameter. Then
Next, a method for producing a heat-expandable resin pipe, which comprises reducing the diameter to a predetermined size at about this temperature T ₁ , and then rapidly cooling and solidifying after the diameter reduction. 4. A method for producing a heat-expandable resin pipe according to claim 2, wherein the inner layer discharged from the extrusion die is a non-foamed resin layer and the outer layer is a foamed resin layer. Slowly cool to approximately T ₁ 'under the inner diameter of
A method for producing a heat-expandable resin tube, characterized in that the diameter is reduced to a predetermined size at approximately this temperature T ₁ ', and after the diameter reduction, rapid cooling and solidification are performed. 5. The inner surface of the metal pipe, wherein the heat-expandable resin pipe according to claim 1 is inserted into a metal pipe, and the heat-expandable resin pipe is heated and expanded within a temperature range belonging to temperatures T _{1 to} T _2. A method for producing a composite pipe, which comprises coating. 6. The heat-expandable resin pipe according to claim 2 is inserted into a metal pipe, and the heat-expandable resin pipe is heated and expanded within a temperature range belonging to temperatures T ₁ 'to T ₂ ' to obtain a metal. A method for producing a composite pipe, which comprises coating the inner surface of the pipe.