JPH09123350A - Polyolefin metal composite pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain interface adhesion between a coat layer and a metal layer and improve heat and water resistance of the coat layer by forming a coat layer to be formed on a surface of a metal pipe out of a resin composition in which specified quantities of specified two kinds of antioxidant are added. SOLUTION: A coat layer formed on a surface of a metal pipe is formed of a resin composition. The resin composition is formed by mixing in 100 pts.wt. of polyolefin resin, 0.05-0.3 pts.wt. of hindered amine antioxidant of poly[ 6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl} 2,2,6,6-tetramethyl-4- piperidine)imino}hexamethylene 2,2,6,6-tetramethyl-4-piperidiene)imino}] and 0.05-0.3 pts.wt. of hindered phenol antioxidant of pentaerthrityl-tetrakis [3-(3,5-di- t-butyl-4-hydroxyphenyl)propionate]. Accordingly, the coat layer is excellent in interface adhesion property and heat oxidation preventing property and can be used for heat and water resisting pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin metal composite pipe used for hot water supply / cooling / heating / chemical plants.

[0002]

2. Description of the Related Art A metal composite tube having a coating layer made of a polyolefin resin such as polyethylene, polypropylene or polybutene-1 formed on the inner surface of a metal tube has a polyolefin resin excellent in corrosion resistance and chemical resistance. Therefore, it is widely used for various pipes such as hot water supply, cooling and heating, and chemical plants.

However, if the polyolefin coating layer is in contact with a high-temperature fluid such as hot water for a long time, the polyolefin coating layer may be cracked or embrittled due to thermal oxidation to finally corrode the metal.
The tube function is lost. If such deterioration due to thermal oxidation is caused, repairing the pipes constructed in the building or in the soil,
There is a problem that it is troublesome and the cost is high.

Therefore, for example, as described in JP-A-6-143493, in order to suppress deterioration of a coating layer of a polyolefin-coated steel pipe due to thermal oxidation, a polyolefin resin used for forming the coating layer is used. , A technique of using a mixture of a specific phenolic antioxidant and a specific amine antioxidant is also disclosed.

[0005]

However, in the case of the technique described in the above publication, for example, when the coating layer is formed on the inner surface of the metal tube, each of the blended antioxidants is removed from the inside of the coating layer over time. It may migrate to the inner surface of the composite tube and dissipate in the fluid being transported within the tube. If this tendency continues for a long period of time, the concentration of the antioxidant in the coating layer will be diluted, and if it decreases to 0.001% by weight or less, thermal oxidation of the coating layer will start and long-term durability for the above-mentioned building etc. is required. There was a case that water leakage occurred in the pipes.

In order to prevent such an antioxidant from escaping into the fluid, it is considered to use a high molecular weight type antioxidant having a slow diffusion rate, but such an antioxidant is generally used. It has a poor compatibility with polyolefin and involves a problem that the interfacial adhesion between the coating layer and the metal layer is lowered.

The present invention solves the above-mentioned problems of the prior art, and maintains the interfacial adhesion between a coating layer made of a polyolefin resin and a metal layer, and at the same time, the coating layer has excellent hot water durability. It is intended to provide a composite pipe.

[0008]

The polyolefin metal composite pipe of the present invention has a structure in which "a coating layer is formed on the surface of the metal pipe, and the coating layer is added to 100 parts by weight of the polyolefin resin, poly [{6- (1 , 1,3,3-Tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {2
2,6,6-tetramethyl-4-piperidyl) imino}
Hexamethylene {2,2,6,6-tetramethyl-4-
Piperidyl) imino}] and a hindered amine antioxidant of 0.05 to 0.3 parts by weight, and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-).
Hydroxyphenyl) propionate] and a hindered phenolic antioxidant (0.05 to 0.3 parts by weight), which is formed from a resin composition. Is achieved.

The surface of the metal tube in the present invention refers to the inner surface (hereinafter simply referred to as the inner surface), the outer surface (hereinafter simply referred to as the outer surface), or both the inner and outer surfaces of the metal tube.

The hindered amine type antioxidant used in the present invention is poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-
Diyl} {2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {2,2,6,6-tetramethyl-4-piperidyl) imino}].

The above-mentioned hindered amine type antioxidants are so-called high molecular weight type ones, and commercially available products are manufactured by Ciba Geigy (trade name "CHIMASSORB 94").
4 "and a molecular weight of 2,000 to 3,300).

The hindered phenolic antioxidant used in the present invention is pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate].

The hindered phenolic antioxidant is also of high molecular weight type, and as a commercial product, a trade name "IRGANOX 10 manufactured by Ciba-Geigy" is available.
10 ", manufactured by Sumitomo Chemical Co., Ltd., product name" Sumilizer
BP-101 ”, manufactured by Asahi Denka Co., Ltd., product name“ Mark AO
-60 "and the like. All have a molecular weight of 1178.

The amount of each of the above antioxidants added is 0.05 with respect to 100 parts by weight of the polyolefin resin.
It should be in the range of 0.3 parts by weight. If the addition amount is less than 0.05 part by weight, the desired thermal oxidation resistance cannot be obtained. On the other hand, if it exceeds 0.3 parts by weight, it separates from the resin in the polyolefin-based resin coating layer and the interfacial adhesion strength between the coating layer and the metal layer decreases.

The polyolefin resin for forming the coating layer used in the present invention is not particularly limited, and includes low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, crosslinked polyethylene, polypropylene, polybutene-1, ethylene. Examples include -α-olefin copolymer, propylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, other polyolefin resins, and mixtures thereof.

The resin composition containing the above-mentioned components used in the present invention contains, in addition to the above-mentioned components, other antioxidants, metal deactivators, processing stabilizers, fillers, pigments, etc. The above additives can be optionally used within a range that does not impair the effects of the present invention.

In the present invention, the above-mentioned specific hindered amine antioxidant and the same specific hindered phenol antioxidant are used in combination with the polyolefin resin forming the coating layer and added within a specific range. By using the amounts, the effects are better than the additive effects of using each alone.

The reason for this is not clear, but by using an addition amount within a specific range, the required interfacial adhesion strength can be maintained, and by using different antioxidants in combination, any antioxidant can generate radicals. When captured and stabilized, it is presumed that the thermal oxidation resistance exhibits a synergistic effect that cannot be achieved by itself while complementing its own defects.

The polyolefin metal composite tube of the present invention is
Mainly a two-layer or three-layer structure in which a resin coating layer made of a resin composition mainly composed of a polyolefin-based resin is provided on the inner surface or outer surface of iron, aluminum, alloy steel or other metal tubes, or both surfaces thereof. However, it is optional to provide an adhesive layer between the metal layer and the resin coating layer in order to improve the interfacial adhesion, or to perform surface treatment on the surface of the metal layer. Further, a resin coating layer or another metal layer may be further laminated on the surface of the coating layer to form a multilayer structure.

[0020]

Embodiments of the present invention will be described below in detail.

Example 1 (Preparation of Resin Composition) As a polyolefin resin, a linear low density polyethylene (manufactured by Mitsubishi Petrochemical Co., Ltd., density = 0.93).
6, a resin 1 using MFR = 5.0) crosslinked polyethylene (MFR = 0.5 to 1.0) obtained by silane crosslinking
With respect to 00 parts by weight, a hindered amine antioxidant (manufactured by Ciba Geigy, trade name “CHIMASSORB”)
944 ") 0.1 part by weight, hindered phenolic antioxidant (manufactured by Ciba Geigy, trade name" IRGANOX-
1010 ") 0.2 parts by weight and phosphorus-based processing stabilizer (trade name" IRGANOX-B291 "manufactured by Ciba-Geigy)
0.15 parts by weight was added and mixed uniformly to prepare a resin composition.

(Production of metal composite pipe) An aluminum alloy sheet having a thickness of 0.18 mm is used as a metal pipe, and an inner surface coating layer made of the above resin composition having a thickness of 0.5 mm is formed on the inner surface by an extrusion molding method. Together with the outer surface 0.5
An outer surface coating layer made of only cross-linked polyethylene used for the resin composition having a diameter of 10 mm was formed to produce a polyolefin metal composite tube having an inner diameter of about 11 mm.

Example 2 A polyolefin metal composite tube was produced in the same manner as in Example 1 except that the addition amount of the hindered amine antioxidant used in Example 1 was 0.3 part by weight.

Comparative Examples 1 to 9 As a polyolefin resin, a predetermined amount shown in Table 1 was used.
Silane cross-linked polyethylene (equivalent to Example 1) resin, hindered amine antioxidant, hindered phenol antioxidant, and phosphorus-based processing stabilizer or sulfur-based processing stabilizer are added and uniformly mixed to obtain a resin. A composition was prepared. Using this resin composition, a polyolefin metal composite tube was produced in the same manner as in Example 1. In Comparative Example 2,
As the processing stabilizer, a sulfur type was used instead of the phosphorus type.

With respect to the polyolefin metal composite pipes obtained in each of the above Examples and Comparative Examples, an evaluation test of interfacial adhesion between the coating layer and the metal layer and the thermal oxidation preventive property shown below was carried out,
The results are shown in Table 1. (1) Interfacial Adhesion From a polyolefin metal composite tube, length = 60 mm, width =
Cut a test piece of 10 mm and use a tensile tester to measure 200
It was pulled at a speed of mm / min, and the peel strength between the inner coating layer and the metal layer was measured. In this case, the peel strength is generally 5 kgf / c due to many field tests and accumulated experience.
It is known that a composite pipe having a thickness of less than m may peel off during long-term use and does not have practical interfacial adhesion, and 5 kgf / cm was used as a pass / fail standard value.

(2) Thermal Oxidation Prevention Property A hot water hot water tank of 85 ° C. is used as a hot water source, a hot water source is used to continuously pump hot water through a polyolefin metal composite pipe by a pump, and the hot water source is taken out at regular intervals. More peeled off to create a piece of damppel each time, JIS K7127
According to the above, a tensile test was performed to measure the tensile breaking elongation, and the hot water passage time when the tensile breaking elongation was 3% or less was defined as the embrittlement time.

[0027]

[Table 1]

Examples 3 and 4 A polyolefin metal composite tube was produced in the same manner as in Example 1 except that polypropylene (MFR = 1.5, manufactured by Tokuyama Corporation) was used as the polyolefin resin.

Comparative Examples 10 to 15 Polypropylene (equivalent to Example 3) resin, hindered amine antioxidant, hindered phenol antioxidant, and phosphorus processing stabilizer or sulfur in the predetermined amounts shown in Table 2 A system processing stabilizer was added and mixed uniformly to prepare a resin composition. Using this resin composition, a polyolefin metal composite tube was produced in the same manner as in Example 1. still,
In Comparative Example 2, a sulfur stabilizer was used in place of the phosphorus stabilizer as the processing stabilizer.

The above Examples 3 and 4 and Comparative Examples 10 to 15
The polyolefin metal composite tube obtained in 1. was subjected to the same evaluation test of the interfacial adhesion between the coating layer and the metal layer and the thermal oxidation resistance as in Example 1, and the results are shown in Table 2.

[0031]

[Table 2]

The structure of each comparative example will be described below.
In Comparative Examples 1 to 3 and 10 to 12, when the specific antioxidant used in the present invention was not used in combination, Comparative Examples 4, 5 and 13 also used the specific antioxidant in combination. When the addition amount of one of the antioxidants is out of the specific range, Proportional Examples 6 to 9, 14 and 15 are the cases in which the specific hindered amine antioxidant used in the present invention is not used. is there.

As is clear from the results of Tables 1 and 2,
Each implementation in which a specific hindered amine-based antioxidant and a specific hindered phenol-based antioxidant were each mixed in a specific amount with respect to 100 parts by weight of a polyolefin-based resin to form a coating layer. The examples gave satisfactory results with regard to interfacial adhesion and thermal oxidation resistance.

On the other hand, in Comparative Examples 1 to 3 and 10 to 12 in which the specific antioxidant used in the present invention was not used in combination, the brittle time was short and the thermal oxidation resistance was inferior. Is. Further, in the case of Comparative Examples 4 and 13 in which the addition amount of the hindered amine-based antioxidant exceeded the upper limit, the thermal oxidation resistance was remarkably inferior without measurement, and in the case of Comparative Example 13, the peel strength was Less than 5 kgf / cm,
It was also inferior in interfacial adhesion.

Further, in the case of Comparative Example 5 in which the addition amount of the hindered amine antioxidant is below the lower limit, the embrittlement time is short,
It is apparent that the thermal oxidation resistance is inferior, and the hindered amine-based antioxidants of Comparative Examples 6 to 9, 14 and 15 in which the specific one of the present invention is not used are also short in embrittlement time. It was inferior in antioxidant property.

[0036]

The polyolefin metal composite tube of the present invention is
By using the specific hindered amine antioxidant and the specific hindered phenol antioxidant together in the polyolefin resin forming the coating layer, excellent interfacial adhesion and thermal oxidation resistance are achieved. It has excellent quality and is suitable for hot water supply, cooling and heating, chemical plants, underground pipes in hot springs, and other domestic or industrial pipes, which is suitable for pipes where hot water resistance is required. Is.

Claims (1)

[Claims] 1. A coating layer is formed on the surface of a metal tube, and the coating layer comprises 100 parts by weight of a polyolefin resin and poly [{6- (1,1,3,3-tetramethylbutyl) amino-1. , 3,5-Triazine-2,4-diyl} {2,
2,6,6-tetramethyl-4-piperidyl) imino}
Hexamethylene {2,2,6,6-tetramethyl-4-
Piperidyl) imino}] and a hindered amine antioxidant of 0.05 to 0.3 parts by weight, and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-).
Hydroxyphenyl) propionate] is used to form a polyolefin metal composite tube, which is formed from a resin composition containing 0.05 to 0.3 parts by weight of a hindered phenolic antioxidant.