JPH0784912B2 - Fluid transport pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluid transport pipe in which a heat medium or a refrigerant flows.

[Prior art]

In automobiles, trains, buildings, warehouses, etc., a system for circulating and transporting a heat medium such as a refrigerant or hot water is adopted in order to lower or raise the environmental temperature. As a fluid transportation pipe used for the circulation transportation of such a refrigerant or heat medium, in order to prevent the external dissipation of the cold heat, resin foam, rubber foam, rock wool, glass wool, etc. on the outer surface of the metal pipe. The one coated with is used.

However, in the conventional method for coating the outer surface of the metal pipe with a heat insulating material such as foam, a hollow foamed molded body is previously formed using a mold or the like so as to match the outer pipe shape of the metal pipe to be applied. Since it is a method of producing and inserting a metal tube into the hollow foam molded body, it is extremely difficult to cover a metal tube having a complicated external shape such as a curved tube. Further, in such a method, if the clearance between the foam molded body and the outer surface of the metal tube is increased in order to facilitate the insertion of the metal tube into the foam molded body, it becomes extremely difficult to bond the two. Had a problem.

〔Purpose〕

The present invention aims to overcome the above-mentioned drawbacks found in the manufacture of conventional insulation coated fluid transport tubes.

〔Constitution〕

The present inventors have conceived that the drawbacks of the above-mentioned conventional techniques can be solved by a coating method using a foamable powder coating material, and as a result of earnest research to develop a foamable powder coating material for that purpose. The present invention has been completed.

That is, according to the present invention, an outer surface of a metal tube or the like is coated with a resin foam, and the foam is a thermoplastic resin containing a hydroxyl group or a mixed thermoplastic resin containing the same, and a solid at room temperature. It is formed by powder-coating an expandable powder coating material containing a cross-linking agent composed of a polyisocyanate compound exhibiting a shape and an organic peroxide and a chemical foaming agent on the outer surface of the metal tube. Is provided.

Further, there is provided the fluid transport pipe, wherein the foamable powder coating material is further mixed with a polyol compound.

BACKGROUND ART Conventionally, a foamable resin composition comprising a mixture of a polyolefin resin, a cross-linking agent composed of an organic peroxide, and a chemical foaming agent has been known. Such a foamable composition,
It is mainly applied as a molding material for producing molded products such as foam sheets, and is not considered as a powder coating material. Conventionally, as foamable powder coating materials, epoxy resin-based powder coating materials for vibration damping (vibration prevention) and sound insulation (soundproofing) are known. These epoxy resin coating materials are Including such problems, it was not satisfactory as a foamable powder coating material for coating the metal tube.

(1) When a large amount of a fibrous filler, a flake filler, etc. is used as a reinforcing material, the fluidity of the powder is lacking, and a uniform foamed coating film cannot be obtained by coating a component having a complicated shape.

(2) It is difficult for the cell diameter to be non-uniform and the cell structure to be a fine cell.

(3) The cushioning property (elasticity) and the flexibility are poor, and the foamed coating film-forming body has defects such as peeling, cracking, and cracking depending on processing conditions.

(4) The thermal conductivity is high, the heat insulating effect is small, and the adhesiveness to the metal tube surface is poor.

The foamable powder coating used in the present invention is different from the conventional ones as described above, and has excellent adhesion to the surface of the metal tube, and also has excellent heat insulation, cushioning (elasticity), and heat resistance. It gives a film.

A thermoplastic resin having a hydroxyl group is used as the base resin in the expandable powder coating material used in the present invention. The weight average molecular weight of this resin is 10,000 to 100,000, preferably 35,000 to 80,000. Examples of such a resin include polyvinyl alcohol, a partially saponified ethylene / vinyl acetate copolymer, and a butyral resin. Further, the base resin used in the present invention preferably further has a carboxyl group in addition to the above-mentioned hydroxyl group, from the viewpoint of adhesion to a metal. Resin containing such a hydroxyl group and a carboxyl group, in the polymerization for producing the hydroxyl group-containing resin,
Maleic anhydride or acrylic acid, methacrylic acid, it can be obtained by adding an unsaturated carboxylic acid such as itaconic acid as a copolymerization component, the hydroxyl group-containing resin, by graft polymerization of the unsaturated carboxylic acid Obtainable.

Examples of the base resin include other resins such as polyethylene, polypropylene, ethylene / propylene copolymer, polyolefin such as polybutene-1, ethylene / vinyl acetate copolymer, polyvinyl chloride, ethylene / ethyl acrylate. A copolymer or the like can be added and mixed. In such a mixed resin, the proportion of the hydroxyl group-containing resin is 20% by weight or more, preferably 50% by weight or more, and particularly preferably 60% by weight or more.

Further, in the powder coating material, a polyol compound which is solid (including semi-solid) at room temperature can be used as a melt viscosity modifier for the composition. As such a polyol compound, for example, a compound represented by the following general formula is used.

_{HOC m H 2m O n H (} I) ( wherein, m is a positive integer, preferably 2-6, more preferably 3 to 4, n is 2 or more, preferably an integer of 4-6) (In the formula, R represents an alkylene group having 2 to 10 carbon atoms, q represents an integer of 1 or more, preferably an integer of 3 to 4, r represents an integer of 1 or more) In addition, a molecular weight of 300 to 6,000 having a saturated hydrocarbon skeleton, Preferably, a polymer having a terminal hydroxyl group of 2,000 to 5,000 (telekeyric polymer) having 1.5 to 3 OH groups in one molecule is used.

This polyol compound lowers the viscosity of the composition in the molten state and facilitates foaming. The polyol compound is used in an amount of 5 to 100 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of the resin.

The polyisocyanate compound used as a crosslinking agent in the powder coating material of the present invention may be any polyisocyanate compound having two or more isocyanate groups (-NCO) in the molecule and showing a solid state at room temperature. In this case, the isocyanate group may be blocked by reacting with an amide compound or an active hydrogen-containing compound such as phenol, alcohol, oxime or mercaptan. Examples of such compounds include phenylene diisocyanate, tolylene diisocyanate, biphenylene diisocyanate, diphenylmethane-p, p'-diisocyanate, and compounds in which those isocyanate groups are blocked. As the polyisocyanate compound in the present invention, those whose isocyanate group is blocked by reacting with ε-caprolactam, amide, phenol, alcohol, oxime and mercaptan, for example, those represented by the following formula are preferably used.

The polyisocyanate compound acts as a crosslinking agent and reacts with the hydroxyl groups contained in the base resin to crosslink the base resin. When a polyol compound is used in combination, it also reacts with this polyol compound to increase the molecular weight.
The proportion of the polyisocyanate compound used is such that the equivalent ratio (NCO / OH) of isocyanate groups to 1 equivalent of hydroxyl groups contained in the composition is 1 or less, preferably in the range of 0.03 to 0.8.

Further, in the present invention, the polyisocyanate compound and an organic peroxide are used together as a crosslinking agent. Examples of the organic peroxide include dicumyl peroxide and bis (t
-Butylperoxy) isopropylbenzene, dimethyldi (t-butylperoxy) hexane, dimethyldi (t
-Butylperoxy) hexyne and the like. This organic peroxide reacts with the methylene bond in the resin to crosslink it. By using the organic peroxide in combination, the reactivity in curing and foaming can be improved, and the cushioning property, flexibility and heat resistance of the obtained coating film can be improved. The proportion of the organic peroxide used is 0.5 to 7.0 parts by weight, preferably 1.0 to 4.0 parts by weight, based on 100 parts by weight of the resin in the composition. This polyisocyanate usually reacts above the melting point of the thermoplastic resin.

A conventionally known chemical foaming agent is used as the foaming agent in the powder coating material of the present invention. Something like this:
Azodicarbonamide, 2,2'-azobisisobutyronitrile, dinitrosopentamethylenetetramine, 4,4 '
In addition to organic foaming agents such as -oxybisbenzene-sulfonyl hydrazide and paratoluenesulfonyl hydrazide, inorganic foaming agents such as sodium bicarbonate, ammonium carbonate, sodium boron hydride and silicon oxyhydride are used. These foaming agents are used alone or in the form of a mixture. Further, these foaming agents usually generate gas at a temperature higher than the melting point of the thermoplastic resin. Also,
By using a foaming agent having a high decomposition temperature together with a foaming aid such as zinc oxide, the decomposition temperature of the foaming agent can be lowered to a desired range. In the present invention, the foaming agent has a decomposition temperature in a range, and in order to make foaming of the composition uniform even if the temperature fluctuates, it may be in the form of a mixture of a plurality of foaming agents or a mixture with a foaming aid. Is preferably used in.

Various substances can be added to the powder coating material of the present invention as auxiliary components. As such an auxiliary component, a filler, a colorant, a fluidity imparting agent, an antioxidant or the like can be used. In this case, as the filler, organic type and / or
Alternatively, an inorganic material is used. By adjusting the particle size and the addition amount of the filler, it is possible to adjust the viscosity of the powder coating material at the time of melting, the foamed cell diameter, the strength of the foamed body and the like.

The expandable powder coating material used in the present invention can be produced by kneading the above components at the melting temperature of the thermoplastic resin, pelletizing the kneaded product, and crushing the pellets. In this case, the kneading temperature is lower than the decomposition temperature of the foaming agent, and decomposition of the foaming agent is suppressed. However, in this kneading step, although a part of the crosslinking agent may react, it is preferable to avoid the crosslinking reaction as much as possible.

The powder coating composition of the present invention is 100% by weight when passing through 40 mesh,
50% by weight or more for 00 mesh, 5 for 325 mesh
It is preferable to adjust the particle size distribution so as to be 0% by weight or less. The powder having such a particle size distribution has good fluidization characteristics, has excellent adhesion to the metal surface, and can be easily powder-coated.

In order to obtain the transport pipe of the present invention, powder coating on the outer surface of the metal pipe using the foamable powder coating material can be carried out by a conventionally known method. For example, it can be performed by fluidizing the powder coating material, immersing the heated metal tube in the flowing powder, and adhering and melting the powder on the surface thereof. In this case, the temperature of the surface of the metal tube is maintained at the decomposition temperature of the foaming agent or higher, the crosslinking reaction and the foaming reaction occur on the surface of the metal tube, and a foam film is formed on the surface of the metal tube. A commonly used metal tube is used as the metal tube, and typical examples thereof include an aluminum tube and an aluminum alloy.

〔effect〕

The expandable powder coating material used in the present invention gives a foam coating film having excellent adhesion to the surface of a metal tube. In this case, the expansion ratio of the foam coating can be adjusted by the amount of the foaming agent added and the coating temperature, and is usually 2 to 20 times, preferably 3 times.
It is better to adjust the expansion ratio to ~ 10 times. The thickness of the foam coating is usually 0.1 to 15 mm, preferably 0.5 to 8 mm.

The fluid transport pipe according to the present invention has excellent adhesion between the foam coating formed on the surface of the metal pipe and the surface of the metal pipe, and the foam coating provides heat insulation, heat resistance and cushioning (elasticity). It is also excellent in sex.

INDUSTRIAL APPLICABILITY The transport pipe of the present invention has excellent heat insulating properties, is suitable for transporting a refrigerant and a heat medium, and is applied to various fields. For example,
In air conditioners for automobiles, compressors, condensers, expanders,
It can be used as a refrigerant pipe for connecting each component such as an evaporator. In this case, the heat insulating effect can be sufficiently obtained so that the heat from the engine does not affect the refrigerant in the pipe.

〔Example〕

 Next, the present invention will be described in more detail with reference to Examples.

Example 1 100 parts by weight of a partially saponified ethylene / vinyl acetate copolymer (saponification degree: 80%) was added with calcium carbonate 30 as a filler.
Parts by weight, 5 parts by weight of azodicarbonamide as a foaming agent, and 5 parts by weight of azodicarbonamide preblended with a foaming aid, 3 parts by weight of zinc oxide as a foaming aid, and blocked isocyanate as a crosslinking agent (the above formula (III) 7.1 parts by weight (NCO / OH equivalent ratio = 0.1), 1.7 parts by weight of dicumyl peroxide, and 0.5 parts by weight of carbon black as a coloring agent, and 0.15% by weight of a fluidity imparting agent to the whole is added. Then, the entire formulation was dry-mixed, extruded from an extruder set at a temperature of 120 ° C., cooled and pelletized, and the pellets were finely pulverized.

Next, the obtained fine powder is subjected to a powder coating method at a temperature of 200 ° C.
It was applied to the surface of an aluminum tube (diameter 20 mm, length 200 mm) that was heated to 100 ° C. to perform crosslinking and foaming. Thus, an elastic foam film having a fine cell structure with an expansion ratio of 3 to 5 was obtained on the surface of the aluminum tube. The adhesion between this foam and the aluminum tube was good.

Example 2 An experiment was conducted in the same manner as in Example 1 except that 100 parts by weight of calcium carbonate was used instead of 30 parts by weight of calcium carbonate. Also in this case, an elastic foam film having a fine cell structure with a foaming ratio of 4 to 6 was obtained on the surface of the aluminum tube.

Against partially saponified 100 parts by weight of an ethylene / vinyl acetate copolymer shown in Example 3 Example 1, the compounds of the polyester polyol [the formula (II) (R = - ( CH 2) 5, r = 5 ,
q = 4)] 50 parts by weight, polytetramethylene ether glycol [compound of formula (I) (m = 4, n = 5)] 10
Parts by weight, calcium carbonate 150 parts by weight, azodicarbonamide 5 parts by weight, diazocarbonamide 5 parts by weight preblended with a foaming aid, dicumyl peroxide 3.4 parts by weight, blocked isocyanate 10 parts by weight (NCO / OH, equivalent ratio) = 0.8), 0.5 parts by weight of curing accelerator DBTL (dibutyltin dilaurate), and 0.5 parts by weight of carbon black,
The mixture was extruded from an extruder set at a temperature of 120 ° C., cooled and pelletized, and the pellets were finely pulverized.

Next, the fine powder thus obtained was applied to the surface of the aluminum tube at a coating temperature of 200 ° C. in the same manner as in Example 1,
Crosslinking and foaming were performed. Thus, an elastic foam film having a fine cell structure with a foaming ratio of 4 to 5 was obtained on the surface of the aluminum tube.

Comparative Example 1 The same experiment as in Example 1 was carried out except that only blocked isocyanate was used as the crosslinking agent without using dicumylpaoxide. In this case, a foam coating having a foaming ratio of 5 to 6 was obtained on the surface of the aluminum tube.
The foam coating had a slightly smaller cushioning property (elasticity) and flexibility as compared with that shown in Example 1.

Comparative Example 2 An experiment was carried out in the same manner as in Example 1, except that the blocked isocyanate was not used as a crosslinking agent. In this case, the properties of the foam coating obtained on the surface of the aluminum tube were as follows.

(1) Although the foaming was large, the bubbles collapsed and became a non-uniform foaming state by the time of crosslinking.

(2) The foamed cell structure was large, and the surface of the bubbles was easily broken.

(3) The surface of the foamed coating film was not smooth and lacked elasticity.

With respect to the expandable powder coating material obtained in Example 1 and the expandable powder coating material obtained in Comparative Example 1, the powder coating material characteristics and the foam material characteristics were measured by the following methods, and the results were The results are shown in Table 1.

Evaluation method (1) Powder coating properties Curing reactivity: Differential scanning calorimeter (DSC310 manufactured by Mac Science Co., Ltd.)
The residual calorific value (cal / g) was measured in (0) (sample amount 10 mg, temperature rising rate 5 ° C./min), and the degree of cure (%) was calculated from the following equation.

(2) Foam evaluation method Compression reaction force: According to JIS K6767.

The coated pipe obtained in Example 1 was used, and the length of the pipe was 5 cm.
The sample was cut into pieces, and the load when compressed to 25% and 50% before loading with respect to the total thickness of the foam coating was measured, and this was taken as the compression reaction force (cushioning property).

Flexibility: According to JIS K6767 method A.

A mold release agent is applied to the surface of an aluminum plate (50 mm x 200 mm x 2 mm), and a foamable powder coating is applied to this to a thickness of 2 mm, followed by crosslinking and foaming (crosslinking and foaming conditions: (Same as in Example 1), and peeled from the aluminum plate to prepare a sheet-shaped test piece.

The expandable powder coating material containing the organic peroxide (Example 1) of the present invention is harder and foams in a shorter time than the expandable powder coating material containing no organic peroxide (Comparative Example 1). In addition, the foam has excellent cushioning properties and flexibility.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Kitagawa 4-11-2 Ginza, Chuo-ku, Tokyo Somer Co., Ltd. (72) Inventor Tetsuo Miyake 4-11-2 Ginza, Chuo-ku, Tokyo Somer Incorporated (72) Inventor Kazusou Moriguchi 4-11-2 Ginza, Chuo-ku, Tokyo Somer Ltd. (56) Reference JP-A-60-44678 (JP, A)

Claims (2)

[Claims] 1. A metal tube comprising an outer surface coated with a resin foam, the foam comprising a thermoplastic resin containing a hydroxyl group or a mixed thermoplastic resin containing the same, and a polymorph showing a solid state at room temperature. It is characterized in that it is formed by powder coating an expandable powder coating material containing a crosslinking agent composed of an isocyanate compound and an organic peroxide and a chemical foaming agent on the outer surface of the metal tube. Fluid transport pipe. 2. The fluid transport pipe according to claim 1, wherein the expandable powder coating material is further blended with a polyol compound.