JPH0310461Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a composite pipe with excellent heat resistance and adhesive properties.

(Prior art) Composite pipes that are flexible and have excellent heat resistance and corrosion resistance are made by preventing moisture from forming on the inner and outer surfaces of the aluminum intermediate layer, as disclosed in, for example, Japanese Patent Application Laid-Open No. 58-92539. It has a structure in which synthetic resins, such as silane-modified polyethylene, are laminated together to form a network bond through the action of silane-modified polyethylene. An adhesive layer made of another material is provided between the aluminum intermediate layer and the silane-modified polyethylene layer.

These conventional composite pipes are used, for example, as piping material for water heaters such as instantaneous water heaters. but,
Abnormally high temperature (120~
When hot water (140°C) flowed through the pipe, the adhesive layer or the silane-modified polyethylene layer softened and flowed, separating from the aluminum intermediate layer and potentially clogging the pipe.

(Problems to be solved by the invention) The present invention solves the above-mentioned conventional problems, and its purpose is to provide a composite pipe that has excellent heat resistance and adhesive properties, and does not cause blockage inside the pipe. There is a particular thing.

(Means for solving the problem) The present invention improves the heat resistance and adhesiveness of the composite pipe by coating the inner surface of the aluminum intermediate layer formed into a tubular shape with water-crosslinkable silane-modified polyolefin. It was completed based on the inventor's knowledge of .

The composite pipe of the present invention includes (1) an aluminum intermediate layer;
(2) It is formed of a water-crosslinkable silane-modified polyolefin that directly coats the inner surface of the aluminum intermediate layer, a silane compound, a free radical generator, and a condensation catalyst. a first inner layer having a proportion of 0.001 part by weight or more and 0.01 part by weight or less; (3) coating the inner surface of the first inner layer and containing a larger amount of condensation catalyst than the first inner layer but not more than 0.1 part by weight; (4) a second inner layer formed of a water-crosslinkable silane-modified polyolefin comprising a polyolefin, a silane compound, a free radical generator, and a condensation catalyst; and an outer layer made of another synthetic resin, thereby achieving the above object.

Here, the water-crosslinkable silane-modified polyolefin is a polyolefin that forms crosslinks between molecules when brought into contact with water, preferably hot water. This water-crosslinkable silane-modified polyolefin is
Contains polyolefin, silane compound, free radical generator and condensation catalyst.

The above polyolefins include polyethylene,
Examples include ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, and the like. Further, as the silane compound, a compound having a hydrolyzable organic functional group and an unsaturated hydrocarbon group is preferable. Hydrolyzable organic functional groups include, for example, alkoxy groups such as methoxy, ethoxy, and butoxy groups; acyloxy groups such as formyloxy, acetoxy, and propionoxy groups;
Substituted amino groups such as alkylamino groups and arylamino groups; oxime groups. The unsaturated hydrocarbon groups are reactive with free radical sites generated in the polyolefin. Examples of the unsaturated hydrocarbon group include a vinyl group, an allyl group, a butenyl group, a cyclohexenyl group, and a cyclopentadienyl group. Suitable examples of the silane compound include vinyltrimethoxysilane and vinyltriethoxysilane. Examples of free radical generators include organic peroxides such as dicumyl peroxide and t-butyl peroxide. Furthermore, examples of condensation catalysts include organic tin compounds such as dibutyltin diurarate, dibutyltin diacetate, and dibutyltin dioctate; carboxylates such as lead naphthenate and cobalt naphthenate; titanate esters; ethylamine, hexylamine, Examples include organic bases such as dibutylamine and pyridine; inorganic acids and fatty acids; dibutyltin diurarate and dibutyltin diacetate are preferred.

The water-crosslinkable silane-modified polyolefin used in the composite pipe of the present invention is synthesized as follows: The polyolefin is synthesized using a free radical generator.
Hydrogen atoms are extracted. An unsaturated hydrocarbon group in a silane compound is added to the radical generated in the polyolefin, and a conventional silane-modified polyolefin is synthesized. The above-mentioned silane-modified polyolefin undergoes a hydrolysis reaction with an organic functional group in the silane compound under the action of a condensation catalyst, and becomes a water-crosslinkable silane-modified polyolefin.

The above-mentioned water-crosslinkable silane-modified polyolefin has the following physical properties: (1) extremely high resistance to cracking, (2) resistance to organic solvents, and (3) moderate tensile strength above the crystalline melting temperature. It is characterized by having tensile strength. Therefore, water-crosslinkable silane-modified polyolefins are useful as piping materials for water heaters and the like that require heat resistance. However, if the amount of condensation catalyst in the polyolefin is too large, the adhesion to the aluminum intermediate layer may be reduced.

Based on these findings, the first inner layer that directly coats the inner surface of the aluminum intermediate layer needs to contain less condensation catalyst than the second inner layer in order to maintain adhesion to the intermediate layer.

The ratio of condensation catalyst to 100 parts by weight of water-crosslinkable silane-modified polyolefin is as follows:
0.001 parts by weight or more and 0.01 parts by weight or less, the second inner layer contains more than the first inner layer, but at most
The amount shall be 0.1 part by weight or less.

(Example) The present invention will be described below with reference to embodiments.

Example 1 As shown in FIG. 1, the composite pipe A of the present invention includes an aluminum intermediate layer 3, this aluminum intermediate layer 3
, a second inner layer 2 covers the inner surface of the inner layer 1 , and an outer layer 4 covers the outer surface of the aluminum intermediate layer 3 .
Both the first inner layer 1 and the second inner layer 2 are made of the water-crosslinkable silane-modified polyolefin. For the outer layer 4, in addition to the same water-crosslinkable silane-modified polyolefin as the first inner layer 1 and the second inner layer 2, known synthetic resins such as polyolefin and polyamide are also used. When the outer layer 4 is made of the water-crosslinkable silane-modified polyolefin, two layers 41 and 4 with different condensation catalyst contents are used as shown in FIG.
It is also possible to set it to 2. For the aluminum intermediate layer 3, an aluminum alloy can be used in addition to pure aluminum.

The thickness of the inner and outer layers is determined in the range of 500-5000 μm depending on the diameter of the composite tube. The first inner layer 1 can achieve the purpose of adhesion with a thickness of 50-300 μm.
Further, the thickness of the aluminum intermediate layer 3 is also determined depending on the required pressure resistance. For example, when imparting flexibility to a composite tube, the thickness is preferably in the range of 100 to 500 μm.

FIG. 3 shows an example of the composite pipe manufacturing apparatus of the present invention. A coiled aluminum plate 5 is sequentially supplied to a mold 6 having a U-shaped cross section and a mold 7 having an O-shaped cross section to form a tubular aluminum intermediate layer 3. At the same time, water-crosslinkable silane-modified polyolefin is extruded and coated on the inner surface of this aluminum intermediate layer 3 using an inner surface coating mold 8 to form the first inner layer 1.
and form the second inner layer 2. Next, the outer surface of the aluminum intermediate layer 3 is coated with, for example, a water-crosslinkable silane-modified polyolefin extruded using an extrusion mold 9 to form the outer layer 4 . The composite tube thus obtained is coiled and immersed in hot water for a certain period of time to obtain the desired flexible composite tube having inner and outer layers 1, 2 and 4 of water-crosslinkable silane-modified polyolefin.

Experimental Example A composite pipe was manufactured in the same manner as in Example 1 using the manufacturing apparatus shown in FIG. First, an aluminum plate 5 having a width of 52 mm and a thickness of 0.25 mm was supplied to a U-shaped mold 6 and an O-shaped mold 7, and formed into a tubular shape. At the same time, the inner coating mold 8 extrudes water-crosslinkable silane-modified polyethylene containing different amounts of condensation catalyst into two layers to coat the inner surface of the aluminum intermediate layer, forming a first inner layer with a thickness of 0.15 mm and a first inner layer with a thickness of 1.0 mm.
A second inner layer of mm thickness was formed. Next, silane-modified polyethylene containing no condensation catalyst was extruded using the outer surface coating mold 9 to cover the outer surface of the aluminum intermediate layer to form an outer layer having a thickness of 0.6 mm. The composite tube thus obtained was wound into a coil shape and soaked in hot water at 95°C for 24 hours to obtain a composite tube with a gel fraction of 75%. The inner diameter of the composite tube is 13.0mm, and the outer diameter is 17.0mm.
It was warm in mm.

The water-crosslinkable silane-modified polyethylene used in this experiment was 100 parts by weight of medium-density polyethylene (density
0.936gr/cm ³ , melt index 5.0), 1.0 parts by weight of vinyltrimethoxysilane, 0.03 parts by weight of dicumyl peroxide, and 0.005 parts by weight of dibutyltin diuralate (first inner layer) and 0.05 parts by weight (second inner layer). ).

The above composite pipe was cut to a length of 3m and continuously piped into the steam piping line, and 100% of steam at 140°C was
The heat resistance was evaluated by passing water through it for a period of time. As a result, the first inner layer of the composite tube did not separate from the aluminum intermediate layer, and no blockage occurred in the tube.

Comparative Example The same procedure as in the experimental example was used, except that adhesive polyethylene (ADMER NE060, manufactured by Mitsui Petrochemicals, Inc.) was used instead of the water-crosslinkable silane-modified polyethylene for the first inner layer of the composite pipe in the experimental example. In an experiment, foaming occurred in the first inner layer of the composite tube, and the entire inner layer separated from the aluminum intermediate layer, resulting in blockage in the tube.

(Effects of the invention) As described above, the composite pipe of the present invention has aluminum because the first inner layer that covers the inner surface of the aluminum intermediate layer is formed of water-crosslinkable silane-modified polyolefin having a specific content. The intermediate layer and the first inner layer directly coated on the aluminum intermediate layer are firmly bonded, and the second inner layer is
Since the first inner layer is made of water-crosslinkable silane-modified polyolefin having a specific content, it firmly adheres to the first inner layer and forms an inner layer with excellent heat resistance. The inner layer and the second inner layer form an inner layer with excellent heat resistance and adhesive properties. For example, when this composite pipe is used as a piping material for a water heater, even if a medium with a temperature of 120 to 140°C passes through the pipe due to trouble with the water heater, the aluminum intermediate layer The inner layer will not separate from the tube and cause intraductal blockage.

Therefore, the composite pipe of the present invention is suitable as a water heater piping material that requires heat resistance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the composite pipe of the present invention, FIG. 2 is a cross-sectional view showing another embodiment of the present invention,
FIG. 3 is an explanatory diagram showing an example of the apparatus used for manufacturing the composite pipe of the present invention. A... Composite pipe, 1... First inner layer, 2... Second
3... Aluminum intermediate layer, 4... Outer layer, 41... First outer layer, 42... Second outer layer.

Claims (1)

[Claims for Utility Model Registration] (1) An aluminum intermediate layer; (2) A water-crosslinkable silane-modified polyolefin comprising a polyolefin, a silane compound, a free radical generator, and a condensation catalyst that directly coats the inner surface of the aluminum intermediate layer. a first inner layer formed in which the ratio of the condensation catalyst to 100 parts by weight of water-crosslinkable silane-modified polyolefin is 0.001 parts by weight or more and 0.01 parts by weight or less; (3) coating the inner surface of the first inner layer; The first inner layer is made of a water-crosslinkable silane-modified polyolefin, which contains a polyolefin containing a larger amount of condensation catalyst than the first inner layer, but not more than 0.1 part by weight, a silane compound, a free radical generator, and a condensation catalyst. (4) an outer layer made of the water-crosslinkable silane-modified polyolefin or other synthetic resin on the outer surface of the aluminum intermediate layer.