JPH0698664B2 - Insulation pipe manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a heat insulating pipe in which a metal polyethylene pipe is provided with a covering layer made of expanded polyethylene.

(Prior art and its problems) When manufacturing this type of heat-insulating pipe, the metal pipe is run from the upstream side, and while the coating layer is coated on the outer peripheral surface of the metal pipe by the extruder, heat insulation is performed by the caterpillar mechanism from the downstream side. It is designed to pull a pipe.

However, since the caterpillar mechanism grasps the outer peripheral surface of the coating layer and pulls the heat insulating pipe, if the adhesive force between the coating layer and the metal pipe is weak, only the coating layer is peeled off from the metal pipe. In particular, when the foaming degree of the foamed polyethylene forming the coating layer is increased in order to reduce the weight of the heat insulating pipe, the above-mentioned problem remarkably occurs.

The foamed polyethylene of the coating layer tends to have a higher degree of foaming, and it is desired to improve the adhesive force between the coating layer and the metal tube.

(Object of the invention) An object of the present invention is to provide a method for manufacturing a heat insulating pipe capable of improving the adhesive force between a coating layer and a metal pipe and preventing only the coating layer from peeling off from the metal pipe.

(Structure of the Invention) (1) Technical Means The present invention is a method for manufacturing a heat insulating pipe in which a covering layer 12 made of foamed polyethylene is provided around a metal pipe made of copper or aluminum, and is delivered from a delivery reel 20. The metal tube thus drawn is stretched straight by the metering mechanism 24, the metal tube is preheated to 50 ° C to 60 ° C by the preheating mechanism 26, and then the first-stage screw 28a is used.
The extruder 28 having a second-stage screw 28b is followed by a foaming degree of 5
The outer peripheral surface 10a of the metal tube is directly coated with 0% to 85% high-foaming polyethylene foam, and immediately sizing die 30 and water tank 3
2 is passed in this order, and the outer peripheral surface 56 is gripped between the two take-up belts 36a and pulled by the pulling machine 36 for pulling.

(2) Function Since the metal pipe is preheated to a temperature at which the high-expansion polyethylene foam will firmly adhere to the metal pipe, even if the metal pipe is directly coated on the outer peripheral surface, the adhesive force of the polyethylene foam becomes strong. .

(Example) In FIG. 1 showing a heat insulating pipe manufactured by adopting the present invention, 10 is, for example, a copper pipe (metal pipe) through which water for supplying hot water is supplied.
Is. The outer peripheral surface 10a of the copper tube 10 is directly coated with a coating layer 12 described later in detail. The coating layer 12 is made of water-tight closed-cell polyethylene, and the coating layer 12 has a high degree of foaming of about 80%.

The coating layer 12 has a weak adhesion to the outer peripheral surface 10a of the copper tube 10, and the coating layer 12 is peeled off from the outer peripheral surface 10a in a normal coating process, so that the coating layer 12 is manufactured by a manufacturing facility as shown in FIG.

In FIG. 2, 20 is a delivery reel, and the copper tube 10 is traveling from the delivery reel 20 in the direction of arrow A toward the take-up reel 22 at a predetermined speed. A metering mechanism 24 and a preheating mechanism are provided between the delivery reel 20 and the take-up reel 22.
26, extruder 28, sizing die 30, water tank 32, counter 3
5, the take-up machine 36 is arranged in sequence.

The metering mechanism 24 is a mechanism for straightly stretching the copper tube 10 wound around the delivery reel 20. The preheating mechanism 26 preheats the copper tube 10 to a predetermined temperature described later in detail so that the outer peripheral surface 10a (FIG. 1) of the copper tube 10 can be directly coated with the coating layer 12.

The extruder 28 coats the outer peripheral surface 10a with a high-foaming polyethylene resin, and the extruder 28 is a so-called two-stage screw type having a first stage screw 28a and a second stage screw 28b. 2nd stage screw 2 from 1st stage screw 28a
8b has a large diameter so that the resin can be coated in a constant and stable state.

The sizing die 30 is a mechanism for maintaining the diameter of the coating layer 12 (FIG. 1) after coating the outer peripheral surface 10a (FIG. 1) with high accuracy. The water tank 32 is provided to cool the coating layer 12. The outer diameter measuring instrument 34 is a measuring instrument for measuring the diameter of the coating layer 12 after cooling. The take-up machine 36 is a drive source that holds the outer peripheral surface of the coating layer 12 between the two take-up belts 36a and pulls the entire heat insulating pipe in the direction of arrow A.

In FIG. 3 showing the coating process of the coating layer 12 in the extruder 28, the copper tube 10 is preheated to a temperature of 50 to 60 ° C. by the preheating mechanism 26 (FIG. 2). A well-known nipple 40 and a die 42 are arranged on the outer side of the copper pipe 10 in the radial direction. The first-stage screw 28a and the second-stage screw 28b (Fig. 2) are provided in an annular passage between the nipple 40 and the die 42. Foamed polyethylene resin 44 is supplied. Foaming degree of foamed polyethylene resin 44 is 80%
Is set to.

The expanded polyethylene resin 44 extruded onto the outer peripheral surface of the outer peripheral surface 10a at about 140 ° C. comes into contact with the outer peripheral surface 10a, and the inner peripheral surface 46 of the expanded polyethylene resin 44 is once cooled, and A peripheral layer 48 is formed. Inner layer 48 is a bubble layer in the center
As it solidifies faster than 50, air bubbles in the inner layer 48
52 does not mix.

The outer peripheral layer 54 of the foamed polyethylene resin 44 is passed through the cooled sizing die 30 to form a smooth outer peripheral surface 56. Bubbles 52 are substantially uniformly distributed in the bubble layer 50 between the inner peripheral layer 48 and the outer peripheral layer 54, and the bubble layer 50 has a large heat insulating effect.

Each of the above steps will be described below in the order of steps.

Step 1: The copper tube 10 is stretched straight by the metering mechanism 24.

Step 2: The preheating mechanism 26 preheats the copper tube 10 to 50 to 60 ° C.

Step 3: The extruder 28 coats the outer peripheral surface 10a of the copper tube 10 with the foamed polyethylene resin 44.

Step 4: Increase the accuracy of the outer diameter of the expanded polyethylene resin 44 with the sizing die 30.

Step 5: The expanded polyethylene resin 44 is cooled in the water tank 32 to form the coating layer 12.

Step 5: The outer diameter of the coating layer 12 is measured by the outer diameter measuring device 34.

Step 6: Measure the length with the counter 35.

Process 7: The heat insulating pipe is sent to the take-up reel 22 by the take-up machine 36.

Next, the operation will be described. In FIG. 4, an inner peripheral layer 48 is formed on the inner peripheral surface 46 of the inner peripheral layer 48, and the inner peripheral layer 48 strongly grips the outer peripheral surface 10a, and the take-up machine 36 (FIG. 2) removes the cover layer 12 from the inner peripheral layer 48. Even if the outer peripheral surface is grasped and pulled in the direction of arrow A, the coating layer 12 does not peel off from the outer peripheral surface 10a.

Therefore, as in the conventional case shown in FIG.
After coating the polyethylene layer 60 (non-foamed) on 10a, it becomes unnecessary to coat the outer peripheral surface of the polyethylene layer 60 with the coating layer 12. Therefore, it is not necessary to provide the first stage extruder 62 (phantom diagram in FIG. 2) between the preheating mechanism 26 and the extruder 28 in FIG.

Further, since the outer peripheral surface 56 of the outer peripheral layer 53 in FIG. 4 is smooth, water does not permeate from the outer peripheral surface of the coating layer 12 into the coating layer 12.

In FIGS. 3 and 4, when each data is set as follows, the optimum preheating temperature of the copper tube 10 is 54 ° C. In this case, the inner peripheral layer 48 has a thickness δ1 of 0.15 mm, and the outer peripheral layer 54 has a thickness δ1.
2 becomes 2.0 mm.

Diameter of copper tube 10 D1 = 9.52 mm Thickness of copper tube 10 T1 = 0.5 mm Feed rate of copper tube 10 S = 10 m / min. Thickness of coating layer 12 T2 = 2.0 mm Supply amount of expanded polyethylene resin 44 W = 300cc / min. (Effect of the invention) As described above, in the method for manufacturing an adiabatic pipe according to the present invention, the metering mechanism 24 stretches the copper pipe 10 straight and the preheating mechanism 26 brings the copper pipe 10 to a predetermined temperature. After preheating, the expanded polyethylene resin 44 is directly applied to the outer peripheral surface 10 by the extruder 28.
Since the inner peripheral layer 48 shown in FIG. 4 is used to firmly adhere the outer peripheral surface 10a to the outer peripheral surface 10a, the take-up machine 36 covers the outer peripheral layer 10a.
Even if the outer peripheral surface is grasped and the heat insulating pipe is pulled in the direction of arrow A, the coating layer 12 will not be peeled off from the outer peripheral surface 10a, and the polyethylene layer 60 in FIG. 5 can be omitted.

Therefore, it is not necessary to provide the first-stage extruder 62 between the preheating mechanism 26 and the extruder 28 shown in FIG. 2, and the facility for manufacturing the heat insulating pipe can be simplified.

Foamed polyethylene resin extruded on the outer peripheral surface 10a at about 140 ° C
The outer peripheral surface 10a is in contact with the outer peripheral surface 10a (Fig. 4) which has been preheated to a relatively low temperature of 50 ° C to 60 ° C.
The inner peripheral surface 44 of 4 is once cooled, and the inner peripheral layer 48 is formed.
Since the inner peripheral layer 48 solidifies faster than the central bubble layer 50, the bubbles 52 are not mixed in the inner peripheral layer 48 and the bond with the outer peripheral surface 10a becomes strong. Since the coating layer 12 exiting the extruder 28 immediately passes through the sizing die 30 having a relatively low temperature, the outer peripheral surface 56 is cooled, and a durable outer peripheral layer 54 containing no bubbles 52 is formed, and subsequently cooled in the water tank 32. To be done. And the outer surface 56
Since the take-up machine 36, which holds and pulls between the take-up belts 36a, pulls the coating layer 12 from the outer peripheral surface 10a during the take-up due to the action of the durable inner peripheral layer 48 and the outer peripheral layer 54.
Since the metering mechanism 24 is arranged in front of the preheating mechanism 26,
The thickness of the coating layer 12 can be made uniform in combination with the improvement of the linearity by preheating. Since the second-stage screw 28b is arranged after the first-stage screw 28a, the resin can be coated in a constant and stable state. When the copper tube 10 is preheated at a temperature lower than 50 ° C., it becomes difficult to smoothly form the inner peripheral layer 48,
When preheated to a temperature higher than 60 ° C, bubbles 52 will be generated in the inner layer 48.
And the strength of the inner peripheral layer 48 decreases. If the degree of foaming of the foamed polyethylene resin 44 is lower than 50%, the desired heat insulation cannot be obtained. If it exceeds 85%, it becomes difficult to secure sufficient strength.

(Other Examples) (1) The present invention is not limited to the above examples, but can be applied to the ranges of the following items.

Polyethylene foam material: Low-density polyethylene, high-density polyethylene, blend type Foaming agent (Freon): Yes, Nucleating agent: 0.5-10.0% Metal tube material: Copper, aluminum Metal tube outer diameter: 7.0-55mm Metal Tube wall thickness T1: 0.5 to 3.0 mm Foaming degree of coating layer 12: 50 to 85% Effective electric conductivity of coating layer 12: 1.195 to 1.65 Outer diameter of coating layer 12: 12 to 80 mm

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heat insulating pipe adopting the present invention, and FIG.
Fig. 3 is a structural schematic diagram showing the heat insulation pipe manufacturing equipment, Fig. 3 is a vertical cross-sectional view showing the process of coating the foamed polyethylene resin, Fig. 4 is an enlarged view of IV part of Fig. 3, and Fig. 5 is a conventional heat insulation pipe. FIG. 10 …… Copper tube, 12 …… Coating layer, 26 …… Preheating mechanism, 28 …… Extruder, 36 …… Drawer, 44 …… Polyethylene foam resin, 48
…… Inner layer, 54 …… Outer layer

Claims (1)

[Claims] 1. A method of manufacturing a heat insulating pipe in which a covering layer (12) made of foamed polyethylene is provided around a metal tube made of copper or aluminum, and the metal tube sent from a sending reel (20) is metered. The mechanism (24) stretches straightly, and the preheating mechanism (26) preheats the metal tube to 50 ° C to 60 ° C, then the 1st stage screw (28a) followed by the 2nd stage screw (28b).
The outer peripheral surface (10a) of the metal tube is directly coated with high-expansion polyethylene having a foaming degree of 50% to 85% by an extruder (28) having a sizing die (30) and a water tank (32) in this order. A method for producing a heat-insulated pipe, characterized in that the outer peripheral surface (56) is passed between two take-up belts (36a) and pulled by a take-up machine (36).