JP2563155B2 - Flame-retardant coated heat-insulating pipe, heat-insulating coated pipe used therefor, and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant coated heat-insulating pipe, a heat-insulating coated pipe used therefor, and a method for producing the heat-insulating coated pipe. More specifically, it is excellent in flame retardancy. Since the heat-insulating layer has low hygroscopicity, a high degree of heat-insulating property is ensured for a long period of time, and the outer periphery is covered with a heat-insulating cladding tube that is easy and economical to manufacture, and has excellent dimensional stability. The present invention relates to a coated heat-insulating pipe, the heat-insulated sheathed pipe used for the same, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Pipes for supplying water and hot water, pipes for hot water heating, refrigerant pipes for air conditioners, etc. are generally made of plastic such that the outer peripheral surfaces of various metal pipes such as copper pipes and various resin pipes are made of plastic. It is covered with a foam to form a heat-insulating sponge layer, and the surface of this heat-insulating layer is extrusion-coated with a polyolefin resin such as polyethylene, polypropylene or ethylene-vinyl acetate copolymer, or a polyvinyl chloride film or A structure having a sheath layer formed by covering with a polyethylene film is widely used.

On the other hand, at the construction site, the outer peripheral surface of the above-mentioned tubular body is usually covered with an inorganic heat insulating material such as glass wool, rock wool or calcium silicate, and the glass cloth tape or the like is used to prevent it from being scattered. Then, it is finished as a coated heat insulation pipe. Of these two types of insulated heat pipes, the former one is subjected to the above-mentioned heat treatment at the factory beforehand, so there is no need to perform heat treatment again at the pipe construction site.
It has excellent on-site workability. However, most of the heat-insulating sponge layers and the like are made of polyolefin resin, so they have a difficulty in flame retardancy. For example, when a fire occurs, the heat-insulating sponge layers and sheath layers spread and easily burn out. There's a problem.

On the other hand, the latter does not cause the problem of burnout of the heat insulating material, but has a problem in workability in a narrow place, and the finished state may vary depending on the operator, and the appearance may be impaired. In order to solve such a problem in the conventional coated heat insulating pipe, a flame-retardant coated heat insulating pipe having a structure in which a heat insulating sponge layer is formed by using a tubular silicone foam as a heat insulating material has been proposed (actually, See Kaihei 2-30600).

This heat-insulating pipe has excellent flame retardancy, and since it can be integrally manufactured in a factory, the work of covering the heat-insulating material at the construction site can be made unnecessary.

[0006]

However, in the case of the above heat insulating tube, the silicone foam forming the heat insulating sponge layer has excellent flame retardancy, but its water vapor permeability is large, so that Problems arise. For example, when the heat insulating pipe is exposed to a harsh environment such as high temperature and high humidity, dew condensation occurs on the outer surface of the heat insulating sponge layer made of the silicone foam. Then, the water vapor in the atmosphere permeates from the surface of the heat-insulating sponge layer to the inside through the dew condensation, and the water vapor is condensed as time passes. As a result, many pores of the heat insulating sponge layer are filled with condensed water, so that the heat insulating efficiency of the heat insulating sponge layer is significantly reduced.

[0007] In order to solve this problem, it is conceivable to increase the thickness of the outer cover of the heat insulating sponge layer to suppress the permeation of water vapor into the layer. However, in the silicone-based foam, it is extremely difficult as a practical problem to selectively foam and cure only the inner layer portion while leaving the outer skin portion in a thick unfoamed cured state. It is also possible to form a heat-insulating sponge layer with a silicone-based foam in advance, and then apply a non-foamed and cured silicone-based polymer sheet to the outer peripheral surface of the heat-insulating sponge layer to cover it. Has been. However, in order to carry out this method, a complicated work that requires a long time is required, and since a high degree of skill is required for sticking the silicone-based sheet, this measure cannot be said to be practical.

Further, a tube body having a laminated structure in which the inner layer tube is made of a foamable silicone type composition, and the outer layer tube made of a non-foaming silicone type composition is laminated on the outer side of the inner layer tube to be integrated. After molding, the tube is heated, for example, in a hot air oven to foam and harden the inner layer into a heat-insulating sponge layer, and the outer layer to non-foam-harden into a solid sheath layer to form a covered heat-insulating tube, and its hollow portion. At the same time, attempts have been made to insert a tube for flowing a heat medium.

However, in this method, since heat acts from the outside, the outer layer tube first starts to cure in the non-foamed state. Therefore, when the inner layer tube is heated next to foam and harden to be converted into the heat-insulating sponge layer, the outer layer is in a dense solid state, which suppresses the foaming of the inner layer and is thus a good heat-insulating sponge. Not only the layer is not formed, but in some cases, large deformation or bubble rupture occurs. As a result, the geometry of the resulting coated insulation tube may not be the target geometry,
In addition, there arises a problem that the dimensional accuracy becomes poor.

This problem can be dealt with by making the curing rate of the silicone composition used for the outer layer slower than the foaming curing rate of the silicone composition used for the inner layer. For example, 2,4-dichlorobenzoyl peroxide having a low decomposition temperature is used as the curing agent for the silicone-based composition forming the inner layer, and benzoylperoxide is used as the curing agent for the silicone-based composition forming the outer layer. A temperature near the decomposition temperature of the curing agent compounded in the silicone composition for the inner layer is used in the initial stage of heating by using a material having a higher decomposition temperature than the 2,4-dichlorobenzoyl peroxide such as oxide or dicumyl peroxide. Is applied to selectively foam the inner layer, and then the outer layer is non-foamed and cured by raising the temperature to a temperature around the decomposition temperature of the curing agent blended in the outer layer silicone composition.

However, in the sheathed heat-insulated pipe manufactured under such a countermeasure, a sheath layer in a good cured state is not formed, its surface is sticky, and air bubbles are present in the sheath layer. May occur. Furthermore, since the heating is performed in stages, there is a problem that the dimensional variation of the heat insulating sponge layer and the sheath layer becomes large, and a heat insulating cladding tube having a constant shape cannot be stably and reproducibly manufactured.

The present invention solves the above-mentioned problems in the above-mentioned heat-insulating pipe in which the heat-insulating sponge layer is made of a silicone-based foam, and the above-mentioned heat-insulating coated pipe used for the same, and it is clear that it is excellent in flame retardancy, and that it absorbs moisture. An object of the present invention is to provide a flame-retardant coated heat-insulating pipe that does not cause a decrease in heat-insulating efficiency, a heat-insulating coated pipe used for the same, and a method for manufacturing the same.

[0013]

In order to achieve the above object, in the present invention, first, a tubular body, a heat-insulating sponge layer of a silicone-based foam covering an outer peripheral surface of the tubular body, and the heat-insulating layer. There is provided a flame-retardant coated heat-insulating pipe comprising a silicone-based non-foamed sheath layer coating the outer peripheral surface of a sponge layer.

Further, in the present invention, there is provided a heat insulating coated tube having a laminated structure in which the inner layer is made of a silicone type foam and the outer layer is made of a silicone type non-foamed body. , 900-5000M
A non-foaming material that is composed of a foamable silicone composition that foams and cures by microwave irradiation of Hz, and the outer layer laminated on the outside of the inner layer does not foam and cure by the microwave irradiation but only cures by heating. A resin tube having a laminated structure made of a conductive silicone composition, and converting the resin tube into a heat-insulating sponge layer by irradiating the resin tube with a microwave of 900 to 5000 MHz to foam and cure the inner layer, and then heating the whole. Then, there is provided a method for manufacturing a heat insulating coating tube, which comprises non-foaming and curing the outer layer to form a sheath layer.

The flame-retardant coated heat insulating pipe and the heat insulating coated pipe of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a heat insulating tube of the present invention. In the figure, the outer peripheral surface of the tubular body 1 through which a heat medium such as water, hot water, gas, or liquid gas flows is integrated with the heat-insulating sponge layer 2a made of a silicone-based foam and outside the heat-insulating sponge layer 2a. And a sheath layer 2b composed of a silicone-based non-foamed body and a heat insulating coating layer 2 having a two-layer structure.

Here, the tube body 1 is not particularly limited, for example, a metal tube made of copper, copper alloy, iron, stainless steel, aluminum, etc .; ceramics, glass, FRP.
And a non-metal pipe made of, for example, a polyolefin such as polyethylene or polypropylene, or a cross-linked product thereof, or a resin pipe made of polyamide or the like.

Thermal insulation layer sponge layer 2 for covering this tubular body 1
The silicone-based foam of a has a chemically stable Si-O bond as a main chain. For example, a method of foaming a liquid silicone rubber as a main raw material or a foamable molding of a millable silicone rubber as a main raw material. Can be formed by the method. As a method of forming the heat-insulating sponge layer 2a by coating the tubular body 1 with this silicone-based foam, for example, a silicone-based foam is molded into a tubular body in advance and the tubular body 1 is inserted into the hollow portion. Alternatively, it is possible to employ a method in which the foamed silicone rubber is extrusion-coated directly on the outer peripheral surface of the tubular body 1.

The outer peripheral surface of the heat-insulating sponge layer 2a is covered with a silicone-based non-foaming material described later to form a sheath layer 3. Since this sheath layer 3 is made of a silicone-based non-foamed material, its hygroscopicity is remarkably smaller than that of a silicone-based foamed material having a thin cell wall, and therefore water vapor in the atmosphere serves as a heat insulating layer. It works to prevent penetration into the body.

Examples of the silicone-based non-foamed material used for forming the sheath layer 3 include silicone-based polymers such as silicone rubber, silicone resin, and silicone oil. The silicone-based polymer may be ethylene propylene. Examples thereof include polymers modified by blending one kind or two or more kinds of a diene copolymer, polyacryl, polystyrene, m-carborane, poly α-methylstyrene, polyurethane, and polycarbonate.

Since all of these silicone-based polymers are mainly composed of silicone having Si--O as the main chain, they are chemically stable and have good heat resistance, weather resistance and flame retardancy, and none. It is pollution. For example, as a method for forming a sheath layer with silicone rubber, a millable rubber compound or a liquid rubber compound is directly extrusion-coated on a silicone foam, and the rubber compound is formed into a sheet (film). It is possible to adopt a method of taping or adhering to the outer peripheral surface of the heat-insulating sponge layer, or a method of molding a heat-shrinkable tube from the rubber compound and externally fitting it to the heat-insulating sponge layer and then heating to cover it. it can.

In particular, the sheath layer formed by the above-mentioned double extrusion coating method is made of the same material as the heat-insulating sponge layer of the silicone foam and is integrally formed on the heat-insulating sponge layer. In addition, since it is unnecessary to form the sheath layer in a separate step, it is extremely effective in terms of both quality and economy. As a method of forming a sheath layer with a silicone resin such as varnish or paint, a method of spray coating the above silicone resin on the heat-insulating sponge layer or brush coating, or molding a sheet with the above resin Then, a method of taping or sticking it on the outer peripheral surface of the heat insulating sponge layer can be adopted.

Further, as the silicone oil, for example,
Oil solutions, oil emulsions, oil compounds, greases and waxes can be used, and the sheath layer is usually formed by coating the outer surface of the heat insulating sponge layer at the construction site. In this case, dust or the like may adhere to the coating surface, but in general, these heat insulating tubes protect the outer circumference with a cover made of metal or resin to prevent crows and maintain aesthetics. Adherence does not cause any inconvenience.

The thickness of the sheath layer is preferably 0.01 to 2 mm. When the thickness is less than 0.01 mm, the water vapor permeability becomes large, so that the function of suppressing the hygroscopicity of the heat insulating sponge layer 2 is reduced, and the thickness is 2
If it is thicker than mm, wrinkles due to bending will occur during piping construction, which will impair aesthetics and increase costs.

The shape of the outer peripheral surface of the sheath layer 3 is shown in FIG.
Without being limited to the smooth type as shown in, for example,
As shown in FIG. 2, the outer surface may be embossed 2c, or, as shown in FIG. 3, the outer surface may be corrugated 2d. When the sheath layer 3 is subjected to such embossing 2c and corrugation 2d, it is possible to prevent wrinkles from being generated at the bent portion when the bending is performed at the construction site, and it is possible to obtain beautiful piping. It is preferable because the state can be obtained.

Next, the heat insulating coated tube provided in the present invention is used by inserting the tube body 1 through which the heat medium flows into the hollow portion, and the inner layer is a heat insulating sponge layer made of silicone foam. The outer layer has a laminated structure of a sheath layer made of non-foamed silicone. Here, the silicone-based foam of the heat-insulating sponge layer is preferably obtained by foaming and curing a foamable silicone-based composition described below, and the silicone-based non-foamed body of the sheath layer is formed of the non-foamable silicone-based composition described below. Those that have been heat-cured are preferred.

A heat-insulating sponge layer made of this silicone-based foam is added to the following foamable silicone-based composition in an amount of 900-5.
It is formed by irradiating a microwave of 000 MHz to foam and simultaneously curing. The foamable silicone composition used at this time is composed of polyorganosiloxane, a curing agent, a foaming agent, and an inorganic compound and / or an organic compound that self-heats by microwave irradiation of 900 to 5000 MHz as essential components.

First, the first essential component, polyorganosiloxane, is a base component of the foamable silicone composition, and a polymer having a linear structure having a siloxane bond as a main chain is used. A part thereof may have a branched structure. Although various organic groups are bonded to the silicon atom, examples of the organic group include the same or different monovalent substituted or unsubstituted hydrocarbon groups. Examples of the unsubstituted hydrocarbon group include methyl group, ethyl group, propyl group, butyl group, hexyl group,
Alkyl group such as dodecyl group; aryl group such as phenyl group; aralkyl group such as β-phenylethyl group and β-phenylpropyl group; vinyl group, propenyl group,
Examples thereof include alkenyl groups such as butenyl group and hexenyl group. Further, some or all of the hydrogen atoms of the above-mentioned unsubstituted hydrocarbon group are substituted with, for example, a halogen atom or a cyano group, a chloromethyl group, a chloropropyl group, a 3,3,3-trifluoropropyl group, 2 It may be a substituted hydrocarbon group such as a -cyanoethyl group.

The end of the molecular chain of this polyorganosiloxane is blocked with a hydroxyl group or a triorganosilyl group such as a trimethylsilyl group or a dimethylvinylsilyl group. The polyorganosiloxane used here is preferably one having an alkenyl group as an organic group, and in this case, the ratio of the alkenyl group to all the organic groups depends on the characteristics of the obtained silicone rubber sponge, particularly strength and compression. From the viewpoint of permanent set, it is preferably 0.01 to 0.3 mol%, and particularly preferably 0.025 to 0.2 mol%.

The polyorganosiloxane used is
From the viewpoint of shape retention and dimensional stability during extrusion molding, the viscosity at 25 ° C is preferably 100,000 cSt or more. The second essential component, the curing agent, may be any that is commonly used when curing a silicone composition. Specifically, an organic peroxide or an organohydrogenosiloxane and a platinum catalyst may be used. It is a combination.

Examples of the organic peroxide include benzoyl peroxide, monochlorobenzoyl peroxide, p-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butylperbenzoate, dicumyl peroxide, 2, and the like. 5-bis (t
-Butylperoxy) -2,5-dimethylhexane,
2,5-bis (t-butylperoxy) -2,5-dimethylhexyne, dimyristyl peroxycarbonate,
Dicyclododecyl peroxydicarbonate, t-butyl monoperoxycarbonate, the following formula:

[0031]

Embedded image

(In the formula, R ¹ represents a monovalent hydrocarbon group having 3 to 10 carbon atoms) and the like. These may be used alone or in combination of two or more kinds as appropriate. The organic peroxide is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of polyorganosiloxane. If the compounding amount is less than 0.1 part by weight, the polyorganosiloxane will be insufficiently crosslinked, resulting in poor compression set and rubber strength.
This is because if the amount is more than the amount by weight, the crosslinking becomes excessive and the sponge rubber strength decreases, and it is also economically disadvantageous.

When the polyorganosiloxane contains an alkenyl group, one silicon-bonded hydrogen atom that undergoes an addition reaction with the alkenyl group is used as a curing agent.
It is also possible to use an organohydrogenosiloxane having two or more molecules in the molecule and a platinum-based addition reaction catalyst.
Examples of the organohydrogenosiloxane include:
The following formula: R ² _b HcSiO _{(4-bc) / 2} (In the formula, R ² represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and b and c are 1. And a compound represented by a positive number satisfying 0 ≦ b + c ≦ 3.0. Of these compounds, R ² is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group; a phenyl group,
An aryl group such as a tolyl group is preferable, and a polymerization degree of 300 or less is preferable. The above-mentioned organohydrogenosiloxane may have any of the conventionally known linear structure, cyclic structure, and branched chain structure. The amount of the organohydrogenosiloxane blended depends on the alkenyl group content (mole) of the polyorganosiloxane. Number), the Si-H bond is
The amount is set to 0.5 to 10 mol%.

Examples of the other platinum-based addition reaction catalyst include chloroplatinic acid, a solution of chloroplatinic acid and an olefin or vinylsiloxane, an alcohol solution of chloroplatinic acid, and the like. The amount of these catalysts to be added is 5 to 5,000 as platinum based on the polyorganosiloxane.
ppm, preferably 2-200 ppm. The foaming agent which is the third essential component of the foamable silicone composition may be one that is stable at room temperature and releases a foaming gas at high temperatures. The effervescent gas is usually nitrogen gas, but may be carbon dioxide or other gas.

Examples of the foaming agent include azobisisobutyronitrile, dinitrosopentamethylenetetramine, benzenesulfon hydrazide, N, N'-dinitroso-N, N'-dimethylterephthalamide and azodicarbondiamide. be able to. This foaming agent is 0.5 per 100 parts by weight of polyorganosiloxane.
10 to 10 parts by weight, preferably 3 to 7 parts by weight. If the blending amount is less than 0.5 parts by weight, the foaming ratio of the sponge layer obtained is small and the heat insulating properties are poor.
On the other hand, if the amount is more than 10 parts by weight, not only the expansion ratio does not substantially increase, but also the formed cells (cells) are destroyed, resulting in a sponge layer having many open cells, resulting in poor heat insulating properties. is there.

The fourth essential component of the foamable silicone composition is an inorganic compound and / or an organic compound that self-heats when irradiated with a microwave of 900 to 5000 MHz. These compounds enhance the microwave absorptivity of the silicone composition by being dispersed in the silicone composition, so that the silicone composition has 900 to 5%.
The silicone composition is heated when irradiated with a microwave of 000 MHz, whereby the foaming agent is foamed and simultaneously cured to form a sponge-like composition.

Examples of such compounds include powders of inorganic compounds such as carbon black, iron oxide powder, ferrite powder, titanium oxide powder, zinc oxide powder, glycols such as diethylene glycol, triethanol. Examples thereof include organic compounds such as amines such as amines. These compounds are blended in an amount of 1 to 200 parts by weight based on 100 parts by weight of polyorganosiloxane. If the amount is less than 1 part by weight, 900-5
The amount of heat generation is small even when microwave irradiation of 00 MHz is performed, and the silicone composition does not generate sufficient heat, so that it is difficult to realize sufficient foaming and curing.
This is because when the amount is more than 0 parts by weight, excessive heat generation causes excessive foaming, which causes a decrease in mechanical strength of the obtained heat-insulating sponge layer. A preferred blending amount is 5 to 150 parts by weight with respect to 100 parts by weight of polyorganosiloxane.

In this heat-insulating coated tube, the silicone-based non-foaming body which constitutes the sheath layer integrally laminated on the outside of the heat-insulating sponge layer is formed by heating and curing the non-foaming silicone-based composition described later. Formed. This non-foaming silicone composition is obtained by removing the blowing agent and the inorganic compound and / or organic compound self-heating at 900 to 5000 MHz from the main components of the above-mentioned foaming silicone composition, It contains siloxane and a curing agent as essential components. Moreover, for example, the above-mentioned ethylene propylene diene copolymer, polyacryl, polystyrene, m-carborane, poly α-methylstyrene,
A modified silicone polymer modified by blending one or more of polyurethane and polycarbonate may be used. Furthermore, oil solution, oil emulsion,
It may be a silicone oil used in the form of an oil compound, grease, wax or the like.

In the above-mentioned foamable silicone composition and non-foamable silicone composition, if necessary, fumed silica, precipitated silica, calcined silica, diatomaceous earth, silica aerosol, alumina, mica, clay, Reinforcing fillers such as zinc carbonate, glass beads, polydimethylsiloxane, and alkenyl group-containing polysiloxane, and known additives such as various heat resistance improvers and flame retardants may be added in appropriate amounts.

The reinforcing filler may be surface-treated at the time of compounding with an organosilicon compound such as organochlorosilane, polydiorganosiloxane, and hexaorganodisilazane. When the reinforcing filler is compounded, the compounding amount is 5 to 100 parts by weight, preferably 20 to 70 parts by weight, based on 100 parts by weight of the polyorganosiloxane as the base of the composition. This is because if the blending amount is too small, the reinforcing effect does not appear, and if it is too large, the strength is decreased.

This heat insulation cladding tube is manufactured as follows. That is, by using the above-mentioned foamable silicone composition and non-foamable silicone composition, a silicone having a laminated structure in which the inner layer is composed of the foamable silicone composition and the outer layer is composed of the non-foamable silicone composition in advance. The resin tube is extruded by, for example, a twin-screw extruder, irradiated with microwaves from the outside, first, the inner layer is foam-cured to form a heat-insulating sponge layer, and then the whole is heated to heat-cure the outer layer. As a sheath layer.

In this case, the resin pipe is, for example, 2450
It is transferred batchwise or continuously to a UHF vulcanization tank of MHz, where it is irradiated with microwaves of said frequency. The outer layer does not generate heat and maintains an uncured state, but the inner layer generates heat due to self-heating of the dispersed inorganic compound and / or organic compound, the foaming agent foams, and the curing agent acts to foam. It cures and transforms into a heat-insulating sponge layer.

After the foaming and hardening of the inner layer is completed, it is subsequently transferred batchwise or continuously to a normal temperature hot air vulcanization tank at, for example, 200 ° C., where it is heated to the above temperature. Only the outer layer is cured, where the heat-insulating sponge layer is the inner layer,
The heat-insulated cladding tube of the present invention having a sheath layer closely adhered and integrated with it as an outer layer can be obtained. In addition, the resin pipe of the laminated structure,
If it is sent to the next heating step before the foaming and hardening of the inner layer is completed,
Since the heat curing of the outer layer proceeds and the foam curing of the inner layer also proceeds, the expansion ratio, cell structure, cell shape, etc. in the formed heat-insulating sponge layer become unstable, and the heat-insulating sponge layer bursts. It is inconvenient because it may happen.

[0044]

【Example】

Examples 1 to 10 and Comparative Example 1 As shown in FIG. 1, foamed silicone rubber (foaming ratio 4.8 was used) on the outer circumference of a copper tube 1 having an outer diameter of 15.88 mm and a wall thickness of 1.02 mm.
2 times) and extrusion-cover the heat-insulating sponge layer 2a with a thickness of 10 mm,
Further, the sheath layer 2b shown by the method shown in Table 1 was formed on the outer peripheral surface of the heat insulating sponge layer 2a.

The water absorption, flame retardancy, and workability of each of the obtained heat insulating tubes were measured according to the following specifications. Water absorption: R-22 Freon gas was enclosed in a copper tube in a room having a temperature of 35 ° C. and a relative humidity of 90%, and a water flow test was conducted at a refrigerant temperature of −17 ° C. for 17 days. When the weight of the heat insulating pipe before the water flow test is A and the weight after the test is B, (B−A) ×
100 / A (%) was calculated, and this value was defined as the water absorption rate. The smaller this value, the smaller the water absorption capacity and the greater the adiabatic efficiency.

Flame retardancy: An evaluation test was carried out according to the method specified in JIS C3521. That is, the flame height and the amount of smoke generated during the combustion of the gas burner for 20 minutes were measured, and the extinguishing situation and the state of the heat insulating sponge layer after the combustion of the gas burner was stopped were observed. Workability: When bending with a bending radius of 100R,
Observe the occurrence of wrinkles on the surface of the sheath layer.

The above results are shown in Table 1. For comparison, the same water absorption rate, flame retardancy, and workability were also measured for the heat insulating tube without the sheath layer 2b, and the results are also shown in Table 1.

[0048]

[Table 1]

Example 11, Comparative Examples 2 to 6 The ends were blocked with dimethylvinylsilyl groups, contained 0.2 mol% of methylvinylsiloxane units, and had an average degree of polymerization of 6
100 parts by weight of polydimethylsiloxane of 000 was charged into a kneader, and 40 parts by weight of fumed silica having a specific surface area of 200 m ² / g and a terminal end blocked with a dimethylmethoxysilyl group were added thereto, and the viscosity at 25 ° C. was 20 cSt. 5 parts by weight of chain-like polydimethylsiloxane was blended, and the whole was kneaded until uniform. 1 more of the obtained kneaded product
The mixture was kneaded at 50 ° C. for 2 hours and then cooled to prepare a base polyorganosiloxane.

To 100 parts by weight of this polyorganosiloxane, the components shown in Table 2 were mixed in the indicated proportions (parts by weight), and the whole mixture was kneaded with a two-roll mill until uniform and various foamable silicones were obtained. A rubber composition and a specific foaming silicone rubber composition were prepared.

[0051]

[Table 2]

The respective compositions were combined as shown in Table 3 and then, using a twin-screw continuous extruder, an inner diameter of 13 mm, an outer diameter of 27 mm,
Non-foaming outer layer 2m thick resin pipe with a laminated structure of 2m /
It was continuously extruded at the linear speed of minutes. Next, a belt type UHF vulcanization tank (microwave frequency: 2450M) with a tank length of 4 m, which operates the resin pipe at the above-mentioned extrusion speed and at the output shown.
After irradiation with microwaves (irradiation time of 2 minutes), it was continuously passed through a belt-type hot air vulcanization tank having a length of 40 cm at the indicated temperature.

The presence or absence of deformation of the obtained tubular body was observed, and the outer diameter and the inner diameter of the tubular body were measured at three places with an interval of 10 m to examine the dimensional stability and the cured state of the surface sheath layer. It was The above results are collectively shown in Table 3.

[0054]

[Table 3]

Example 12 The outer diameter of the hollow portion of the heat insulation coating tube of Example 11 was 14.0 mm and the wall thickness was
A 1.0 mm copper tube was inserted into the heat insulating tube of the embodiment. For comparison, composition A was used to form a tube, which was used in Example 1
Foam and cure under the same conditions as No. 1, and the average inner diameter is 13.7 mm,
A sheath layer-free insulation cladding having an average outer diameter of 37.6 mm was produced. A copper tube having the above dimensions was inserted into this tube to give a heat insulating tube for comparison.

In a room at a temperature of 35 ° C. and a relative humidity of 90%, R-22 Freon gas was caused to flow through these adiabatic tubes, and a moisture absorption test was carried out at a refrigerant temperature of −10 ° C. for 14 days. From the heat-insulated pipe weight B after the test, the following formula: (B-
The moisture absorption rate (%) was measured based on A) × 100 / A.
In addition, after the above test, each coating tube was sliced into rings and the state inside the heat insulating sponge layer was visually observed.

The moisture absorption rate of the heat insulating tube of the example was 3.1%, and no dew condensation was observed in the heat insulating sponge layer. On the other hand, in the case of the heat insulating pipe of Comparative Example, the moisture absorption rate was 87.1%, and a large amount of water was condensed on the heat insulating sponge layer.

[0058]

As is clear from the above description, in the flame-retardant coated heat-insulating pipe of the present invention, the heat-insulating sponge layer and the sheath layer are composed of silicone-based foam and silicone-based non-foam, respectively. A high degree of flame retardancy is ensured without inconveniences such as fire spread of the heat-insulating sponge layer and sheath layer and melting and dropping.

Further, since the outermost sheath layer has almost no hygroscopic ability even in a high temperature and high humidity environment, the heat insulating sponge layer of the silicone type foam located inside thereof has a high heat insulating property for a long period of time. Secured. Further, in the heat insulating sponge tube of the present invention, both the heat insulating layer and the sheath layer can be continuously formed on the outer peripheral surface of the pipe body at the factory,
Unlike the conventional case, the work of covering the heat-insulating sponge layer at the construction site is unnecessary, and the construction cost can be greatly reduced.

Further, in the heat-insulating coated tube provided by the present invention, when the heat-insulating sponge layer to be the inner layer is formed, the non-foaming silicone-based composition to be the outer layer does not cure, and the non-foaming material is formed after the heat-insulating sponge layer is formed. Since it is manufactured so that the sheath layer is formed, the overall dimensional stability is good.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a heat insulating tube of the present invention.

FIG. 2 is a cross-sectional view of a heat insulating tube in which a sheath layer is embossed.

FIG. 3 is a perspective view of a heat insulating tube in which a sheath layer is corrugated.

[Explanation of symbols]

 1 Tubular body 2a Insulation sponge layer of silicone foam 2b Sheath layer of silicone non-foam 2c Embossing 2d Corrugation

 ─────────────────────────────────────────────────── ─── Continuation of front page (73) Patent holder 591147683 Jabico 1-2-1, Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Yuji Nishikawa 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. In-house (72) Inventor Takeyuki Nemoto 1-6, Uchiyuki-cho, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (72) Inventor Hideo Sato 6-2-1, Roppongi, Minato-ku, Tokyo Within Toshiba Silicone Co. ( 72) Inventor Hirofumi Yoshida 6-23-1, Roppongi, Minato-ku, Tokyo Toshiba Silicone Co., Ltd. (72) Inventor Naoya Kurata, 3-10-19 Nishikamakura, Kamakura-shi, Kanagawa (72) Hideo Asano, Kanagawa 665-17 Hirokawa, Hiratsuka-shi (72) Inventor Chiman Nakamura 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Jabico Co., Ltd. ( 56) References JP-A-61-256095 (JP, A) Actually open 3-130991 (JP, U) Actually open 47-13753 (JP, U) Actually open 2-30600 (JP, U)

Claims (3)

(57) [Claims] 1. A tubular body, a heat-insulating sponge layer of silicone-based foam covering the outer peripheral surface of the tubular body, and a sheath layer of silicone-based non-foam covering the outer peripheral surface of the heat-insulating sponge layer. Flame-retardant coated heat-insulating pipe characterized by. 2. A heat-insulating coated tube having a laminated structure comprising an inner layer enclosing a tubular body and an outer layer integrally covering the outer periphery of the inner layer, wherein the inner layer is made of a silicone-based foam and the outer layer is made of a non-silicone-based material. A heat insulation cladding tube, which is made of foam. 3. The inner layer is made of a foamable silicone composition that is foamed and cured by irradiation with microwaves of 900 to 5000 MHz, and the outer layer laminated outside the inner layer is foamed and cured by the irradiation of microwaves. First, a resin tube having a laminated structure made of a non-foaming silicone-based composition that is cured only by heating is molded, and
It is characterized in that it is converted into a heat-insulating sponge layer by first foaming and curing the inner layer by irradiating it with a microwave of 5000 MHz, and then heating the whole to non-foam and cure the outer layer into a sheath layer. A method for manufacturing a heat insulating cladding.