JPH06182846A - Production of foamed polystyrene-coated heat-insulating tube - Google Patents

Abstract

PURPOSE:To produce a heat-insulating tube in one process by a method wherein a polystyrene resin containing a specific amount of liquefied hydrocarbon gas is applied to a periphery of a metal tube while being extruded at a specific expansion ratio. CONSTITUTION:An adhesive resin 7 is extruded from adhesive resin ring dies 2, 2 to be applied to a metal tube 1. The metal tube 1 is transported to heaters 3, 3. The metal tube 1 coated with the adhesive resin 7 is heated to approximately 150-200 deg.C by the heaters 3, 3, thereafter being transported to crosshead dies 4, 5. A foamable thermoplastic resin 8 and a thermoplastic resin 9 as a protective layer are coextruded in two layers from the crosshead dies 4, 5. The shape of the heat insulating material applied to the metal tube 1 is formed by a sizing device 6. The loading of a liquefied hydrocarbon gas added as a foaming agent to the polystyrene resin is suitably the order of 0.5-10%, perf. 1-6%. The expansion ratio of the foamed polystyrene layer is suitably the order of 3-20, pref. 4-8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an adiabatic pipe which can be used for heat insulation of an air conditioning pipe, a water supply pipe, a hot water supply pipe and the like and for preventing dew condensation.

[0002]

2. Description of the Related Art Conventionally, as a method for insulating a metal pipe, a heat insulating work for covering a foamed heat insulating material is performed after the pipe is installed. However, due to the increased cost of heat insulation work and the shortage of construction engineers, it has been desired to simplify heat insulation work.

Recently, as a method for solving the above problems,
A preformed pipe is heated, the foamed thermoplastic resin is extruded and coated on the outer surface of the metal pipe while inserting the metal pipe through the crosshead die, and the outer surface of the resin foamed from the crosshead die is formed by a former. A method for producing a heat-insulating pipe is disclosed, in which a foam layer is formed on the outer surface of the metal pipe while molding (Japanese Patent Laid-Open No. 62-44421). Hard vinyl chloride or polyester is used as the foam resin, and the expansion ratio is 1.5-
It is about 3.0 times.

A crosshead die is provided around the metal tube conveyed in the longitudinal direction, and an adhesive resin for the outer surface of the metal tube and a foamable thermoplastic resin for the outer ring are coextruded from the crosshead die. There is also known a method for producing a heat-insulating coated metal pipe, which comprises coating the outer surface of the metal pipe with an adhesive resin and the foamed resin while foaming the expandable thermoplastic resin in the process of extrusion (Japanese Patent Application Laid-Open No. Hei 10 (1999) -29242). 2-8161
No. 8 bulletin). The resin used in this method is polyethylene, polypropylene, or the like, and an azo compound, a nitroso compound, or the like is used as a foaming agent to foam about 1.5 to 2.8 times.

[0005]

However, in the conventional production of heat-insulating pipes by extrusion coating, about 1% of hard vinyl chloride, polyester, polyethylene resin or polypropylene resin and a thermal decomposition type foaming agent such as azo compound and nitroso compound are used. What was added was used, and the obtained product was a low foam having an expansion ratio of less than 3 times. Further, even if 1% or more of this pyrolyzable foaming agent was added, the escape of the foaming gas occurred, and the expansion ratio was still less than 3 times. Also,
Since the polyethylene resin and the polypropylene resin are not inherently high in mechanical strength when they contain bubbles, it is difficult to perform molding in which a large number of small independent bubbles remain. For this reason, the thermal conductivity was increased, and heat retention and prevention of dew condensation were insufficient. Further, in order to make these sufficient, it is necessary to make the foamed resin film thickness very large, which has been a problem in terms of economical efficiency and difficulty in handling during transportation.

The present invention has been made to solve the above-mentioned problems, and a metal pipe is extrusion-coated with a foamed resin having a high expansion ratio and having a heat insulating property necessary for keeping heat and preventing condensation,
It is an object of the present invention to provide a method for manufacturing a heat insulating pipe that can be manufactured in only one step.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems.
This object is achieved by extrusion-coating the outer periphery of a metal tube with a polystyrene resin containing 5 to 10% at a foaming ratio of 3 to 20 times.

As the liquefied hydrocarbon gas added as a foaming agent in the present invention, volatile ones such as LPG, butane, propane, pentane, isobutane, benzene and trichloroethylene are used. About 0.5 to 10% is suitable as the amount of addition to the polystyrene resin, and about 1 to 6% is preferable.

The expansion ratio of the expanded polystyrene layer is appropriately about 3 to 20 times, preferably about 4 to 8 times. The thickness of the expanded polystyrene layer is about 0.2 to 10 cm, preferably 1
About 3 cm is appropriate.

Further, in order to make the expanded polystyrene resin of the present invention a dense and rigid structure, nucleating agents such as calcium stearate, zinc stearate and calcium silicate, and reinforcing agents such as talc, alumina, kaolin, silica and calcium carbonate. It is also possible to add additives such as calcium sulfate, mica, celite, asbestos, zeolite and diatomaceous earth. About 0.01 to 1.0%, preferably about 0.05 to 0.2% is suitable for nucleating agents such as calcium stearate, and about 0.5 to 5%, preferably about 1.5 to 3% for reinforcing agents such as talc. Is appropriate.

It is preferable to provide an adhesive layer for adhering the expanded polystyrene resin on the surface of the metal tube. Adhesive resin such as thermosetting resin such as epoxy resin and urethane resin or modified polyethylene modified with unsaturated carboxylic acid such as maleic anhydride capable of extrusion coating, modified polypropylene, modified ethylene-vinyl acetate copolymer Can be used for. The thickness of the adhesive layer may be about 5 to 50 μm.

Further, in the present invention, it is preferable to coat a thermoplastic resin as a protective layer on the outer periphery of the expanded polystyrene resin. This protective layer enhances the physical strength of the surface of the expanded polystyrene layer, and is preferably one having good adhesiveness with the polystyrene resin, for example, polyolefin resin such as polyethylene, polypropylene or polystyrene.
A suitable thickness of the protective layer is about 0.5 to 3 mm.

Further, when the prevention of dew condensation is insufficient with only the expanded polystyrene resin of the present invention, the thermoplastic resin of the protective layer may contain a water absorbent resin, or the outer periphery of the protective layer may be covered with a water absorbent sheet such as a nonwoven fabric. You can also do it.

The types of metal tubes include iron tubes, steel tubes, stainless tubes, copper tubes and the like.

The polystyrene resin to be foamed may be extruded using the melt extruding device described in the above-mentioned JP-A-62-44421, JP-A-2-81618, etc., and the outer periphery of the metal tube may be coated. When the protective layer is provided, it is desirable to coextrude the resin forming the protective layer.

Furthermore, in order to maintain the shape of the expanded polystyrene resin extrusion-coated with a metal tube during the extrusion manufacturing process,
A sizing device can be installed at the exit of the extrusion die.

[0017]

In the expanded polystyrene-coated heat insulating tube of the present invention, the compatibility between the polystyrene resin and the liquefied petroleum gas is very good, so that minute closed cells are easily formed. Therefore, the mechanical strength of the expanded polystyrene resin after molding is increased, and the thermal conductivity can be lowered. Also,
By adding an additive such as talc, the bubble diameter can be made fine, which contributes to the improvement of mechanical strength.

Further, by coating the metal pipe by extrusion molding, a high-foam resin-coated pipe can be manufactured in only one step, and a heat-insulating pipe having a required heat insulating performance can be manufactured by keeping heat and preventing condensation.

[0019]

【Example】

Example 1 FIG. 1 is a diagram showing a state in which a heat insulating pipe is manufactured by the method of the present invention. In FIG. 1, ring dies 2 and 2 for adhesive resin and heating devices 3 and 3 are disposed around the longitudinal direction of the metal tube 1, and further connected to two extruders (Toshiba Machine SE65 and Nagata Seisakusho OHP45). Cross head dice 4,
5 are provided. Also, cross head dies 4, 5
A sizing device 6 is continuously provided on the outlet side of the.

The metal tube 1 is a ring die 2 or 2 for adhesive resin.
The adhesive resin 7 is extruded and applied to the heating devices 3 and 3. The metal tube 1 coated with the adhesive resin 7 heated to about 150 to 200 ° C. by the heating devices 3 and 3 is conveyed to the crosshead dies 4 and 5. Therefore, the metal tube 1 is co-extruded with the foamable thermoplastic resin 8 and the thermoplastic resin 9 as a protective layer by the crosshead dies 4 and 5, and the shape of the heat insulating material coated on the metal tube 1 is adjusted by the sizing device 6. To be

An expanded polystyrene-coated heat insulating tube was manufactured using the above apparatus. As the metal tube 1, a steel tube that had been blasted in advance was used. A thermosetting resin (“GY280” manufactured by Nippon Ciba-Geigi) was used as an adhesive resin, and a polyethylene resin (“5000S” manufactured by Mitsui Petrochemical) was used as a protective layer. The polystyrene resin used was a mixture of 3.5% butane as a foaming agent, 0.2% calcium stearate and 2% talc as additives. The extrusion temperature of polystyrene resin and polyethylene resin was about 130 to 200 ° C.

According to the above manufacturing method, the right end of FIG. 1 and FIG.
The heat-insulated pipe shown in was obtained. The expansion ratio of this expanded polystyrene resin was 5 times.

Example 2 An adiabatic tube was also produced according to Example 1 above except that 5.5% pentane was added as the blowing agent instead of butane. The expansion ratio of this expanded polystyrene resin was 10 times.

Example 3 An adiabatic tube was produced according to the above Example 1 except that 7.5% of butane was added as a foaming agent. The expansion ratio of this expanded polystyrene resin was 18 times.

Comparative Example 1 A heat insulating pipe was manufactured by extrusion coating a polyethylene resin containing 1% of an azo compound as a foaming agent onto a steel pipe at about 130 to 200 ° C. The expansion ratio of this expanded polyethylene resin was 2 times.

The results of measuring the thermal conductivity and compressive strength of Examples 1, 2, 3 and Comparative Example 1 are shown in Table 1 below.

[0027]

[Table 1]

From Table 1, Examples 1, 2 and 3 are Comparative Examples 1
The thermal conductivity was smaller than that of, and good heat insulation was exhibited. Regarding the compressive strength, a strength comparable to the conventional one was obtained despite the large expansion ratio.

Further, when the size of the cells of the foamed resin moldings used in Examples 1, 2 and 3 and Comparative Example 1 was observed, it was found that the polystyrene foam resin had an average of 30 μm and there was no continuous resin, but foaming. The polyethylene resin had an average of 60 μm and there were quite a few that were continuous.

FIG. 3 shows the result of observing the average diameter of 10 cells by thinly cutting a molded product of expanded polystyrene resin added by changing the amount of talc, making it 50 times with a magnifying glass.

[0031]

According to the method for producing a heat insulating pipe of the present invention, a heat insulating pipe coated with a foamed resin having a wide expansion ratio by covering the polystyrene resin with a foamed polystyrene resin obtained by using a liquefied hydrocarbon gas. Can be manufactured in only one step, and a coated heat insulating tube having a thermal conductivity about three times lower than that of a conventional heat insulating tube can be obtained. As a result, the construction period for on-site construction is shortened, and it is possible to manufacture an adiabatic pipe having appropriate heat retention and proper condensation prevention performance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a state in which a heat insulating pipe is manufactured by the method of the present invention.

FIG. 2 is a cross-sectional view of an example of a heat insulating tube obtained by the method of the present invention.

FIG. 3 is a diagram showing a relationship between a talc amount and a bubble diameter.

[Explanation of symbols]

 1 ... Steel pipe (metal pipe) 2 ... Adhesive resin ring die 3 ... Heating device 4, 5 ... Crosshead die 6 ... Sizing device 7 ... Adhesive resin 8 ... Foamable thermoplastic resin 9 ... Thermoplastic resin

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical indication location B29L 23:22 4F (72) Inventor Yoshiyuki Morioka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kohkan Co., Ltd. Within

Claims (2)

[Claims] 1. A method for producing a foamed polystyrene-covered heat-insulating pipe, characterized in that a polystyrene resin containing 0.5 to 10% of liquefied hydrocarbon gas is extrusion-coated on the outer periphery of a metal pipe at a foaming ratio of 3 to 20 times. 2. The method for producing a heat insulating pipe according to claim 1, wherein the polystyrene resin contains at least one of talc and calcium stearate.