JP2002248707A - Steel pipe with inside surface lined with resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel pipe with its inside surface lined with a resin which is made of materials containing no halogen and causing no environmental problem and is free from deformation, etc., even under negative pressure environment such as a water hammer phenomenon and in which the lining resin is adhered sufficiently to its inside surface. SOLUTION: The lining resin layer of the steel pipe is composed of at least two layers of a polyolefin resin and of a polar olefin resin with polarity having functional groups comprising elements other than carbon and hydrogen. The innermost surface is the polyolefin resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner resin-lined steel pipe used for piping such as water supply, hot water supply, air conditioning, and drainage.

[0002]

2. Description of the Related Art Conventionally, pipes used for water supply and drainage are made of steel pipe or chromate treated with powder of adhesive polyethylene resin or polyethylene resin modified with vinyl chloride resin, maleic anhydride or the like in order to improve corrosion resistance and the like. A resin-lined steel pipe lined on the inner surface of a galvanized steel pipe is used.

[0003]

However, vinyl chloride resin causes acid rain and the generation of toxic dioxin by incineration after use.
It is becoming more difficult to use it due to recycling and environmental issues. In addition, when manufacturing an inner resin-lined steel pipe, an adhesive polyethylene resin powder modified with maleic anhydride is used to form a lining layer on the inner surface of the steel pipe by applying powder coating to the heated steel pipe. It is used, but in the case of this powder, the production process is complicated, such as the need to apply a primer treatment because the adhesiveness is insufficient,
Furthermore, the coating equipment is expensive. In addition, it is difficult to uniformly adsorb the resin powder to the inner surface of the steel pipe, and pinholes and the like are easily generated. As a result, when used as a water supply pipe or the like for a long time, there is a problem that the anticorrosion performance is reduced. Polyethylene is excellent in moldability, chemical resistance and hygiene, but does not have adhesiveness to steel pipes by itself, and it is very difficult to adhere to various adhesives. In this case, it was very difficult to maintain the initial and secondary adhesion performance.

[0004] In addition, when a resin that is easy to adhere is used, the resin is subjected to rigidity. Therefore, when a negative pressure is applied to the inside of the steel pipe due to a water hammer phenomenon or the like, there is a problem that blockage occurs due to deformation or crushing.

The present invention has been made to solve the above problems,
It is made of a material that does not contain halogen elements and does not cause environmental problems.It can be lined on the inner surface of the steel pipe, and the steel pipe and the inner lining resin are sufficiently bonded to be deformed even in a negative pressure environment such as a water hammer phenomenon. It is an object of the present invention to provide an inner resin-lined steel pipe which does not cause problems such as the above.

[0006]

As a result of intensive studies to solve the above problems, the present inventors have found that an olefin polar resin having adhesiveness is interposed on the polyolefin resin surface, and the inner layer is made of polyolefin. By using a resin lining layer, the adhesion between the polyolefin and the steel pipe is good, and there is no problem such as denaturation even under a negative pressure environment such as a water hammer phenomenon. An inner resin-lined steel pipe using a material that has no possibility of causing it was found.

[0007] That is, at least two layers of a polyolefin resin and a polar olefin-based polar resin layer having a functional group consisting of an element other than carbon and hydrogen on the inner surface of the steel pipe.
The present invention relates to an inner surface resin-lined steel pipe having a resin lining layer composed of a layer, and an innermost surface being a polyolefin resin layer.

The reason why the inner resin-lined steel pipe of the present invention has good performance is presumed as follows.

Since the polyolefin in the innermost layer does not have a polar group, it is extremely stable, and has excellent water resistance, chlorine water resistance, and rigidity. Since the olefin-based polar resin has a skeleton similar to that of polyolefin, it is partially compatible with each other and has good adhesion to polyolefin. In addition, since there are many polar parts in the resin, this interacts with a polar group such as a hydroxyl group on the surface of a steel pipe or a general adhesive, such as electrostatic attraction, resulting in good adhesion. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show an example of a laminated state of an inner resin-lined steel pipe according to the present invention. The inner resin-lined steel pipe shown in FIG.
And the polyolefin resin layer 3 are laminated in this order,
The inner resin-lined steel pipe shown in FIG. 2 is further provided with an adhesive layer 4 between the olefin-based polar resin layer 2 and the steel pipe 1.

An olefinic polar resin having a functional group having an element other than carbon and hydrogen and having polarity is a copolymer of ethylene with one or several kinds of vinyl acetate, acrylate, methacrylate and the like. Or a homopolymer or a copolymer of the above monomers excluding ethylene. Specific examples include an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, an ethylene-methacrylic acid ester copolymer, an ethylene-acrylic acid copolymer, and an ethylene-methacrylic acid copolymer. Further, a modified polyolefin resin obtained by grafting maleic anhydride or the like to such a resin may also be used.
The ratio of ethylene to comonomer is 0.1 to 0.1%.
It is about 50 mol%, preferably about 1 to 25 mol%.

In the invention according to claim 2, the olefin-based polar resin layer comprises an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic ester copolymer, an ethylene-methacrylic acid copolymer, The inner resin-lined steel pipe according to claim 1, which is made of any one of an ethylene-methacrylic acid ester copolymer, satisfies the problem, and has a higher adhesive strength than when another polar resin is used. Although the reason for this is unknown, it is thought that the adhesion strength is increased because the compatibility with the polyolefin is increased and the resin strength is higher than other polar resins. Also, it has a sufficient adhesive strength with general adhesives.

According to the third aspect of the present invention, the inner resin-lined steel pipe according to the first aspect, wherein the olefin-based polar resin layer is made of an ionomer resin, satisfies the above-mentioned problems. In, metal ions contained in the resin may be eluted.

The ionomer resin is a resin having a structure in which the molecules of the resin are cross-linked with metal ions. In particular, the ionomer resin is obtained by cross-linking the molecules of ethylene-methacrylic acid copolymer or ethylene-acrylic acid copolymer with metal ions. It is a resin with a structure. That is, an ethylene-methacrylic acid copolymer having ethylene and methacrylic acid components or an ethylene-acrylic acid copolymer having ethylene and acrylic acid components, and a part or all of the carboxyl groups contained in the resin are neutralized. Is a salt with metal ions.
Kinds of metals are zinc, sodium, magnesium, lithium, potassium, calcium and the like. The density is 0.87 or more and 0.99 or less, preferably 0.93 or more and 0.97 or less, and the melting point is preferably 80 ° C to 15 ° C.
0 ° C, more preferably 85 ° C to 120 ° C. The MFR is 0.01 or more and 20 or less, more preferably 0.1 or more and 10 or less.

The thickness of the olefinic polar resin is 0.0
About 1 to 5 mm, preferably about 0.1 to 3 mm is appropriate.

The polyolefin resin may be any resin having an olefin skeleton, such as polyethylene, polypropylene and polybutene. For example, in the case of polyethylene, more specific examples include low density, medium density, high density, and linear low density polyethylene. In the case of polypropylene, a homopolymer, a random or block copolymer and the like can be mentioned. Among the polyolefin resins, polyethylene and polypropylene resins are preferred. By using polyethylene or polypropylene as the polyolefin resin layer, the adhesive strength of the resin lining layer after forming the coated steel pipe is superior to that using polybutene. It is considered that this is because the compatibility with the olefin-based polar resin is high. In addition, in recent years, the impact resistance at low temperatures has been improved by the addition of a polyethylene component or a rubber component, but in general, polypropylene is inferior in impact resistance at low temperatures and is not suitable for use in cold regions. .

The thickness of the polyolefin resin layer is from 0.01 to
About 5 mm, preferably about 0.1 to 3 mm is appropriate.

The thickness of the resin lining layer having a polyolefin resin layer and an olefin polar resin layer is usually 0.3 m.
m and 5 mm or less. Two or more polyolefin resin layers or olefinic polar resins may be used, or three or more resin lining layers may be formed by incorporating another layer.

The resin used in the present invention may contain, if necessary, an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an antistatic agent as long as the performance of the present invention is not impaired.
Additives such as colorants can be added.

As the adhesive for bonding the pipe comprising the polyolefin resin layer and the olefin polar resin layer used in the present invention to the inner surface of the steel pipe, a general adhesive can be used. For example, hot-melt adhesives containing olefin-based, rubber-based, polyester-based, and polyamide-based resins as main components, solvent-based adhesives thereof, and adhesives mainly containing epoxy resin are used. The thickness of the adhesive layer is usually 0.0
It is 03 mm or less and 1 mm or less.

The steel pipe used in the present invention may be one whose surface is plated or the like. If necessary, the inner or outer surface is subjected to a pretreatment such as a blast treatment or an acid washing treatment, and further,
Surface treatment such as chemical conversion treatment and primer treatment can be performed.

The method for producing a resin tube comprising a polyolefin resin layer and an olefin-based polar resin layer according to the present invention includes a method in which a resin is co-extruded from a round die at a temperature not lower than the melting point, for example, at 180 ° C. to 250 ° C. After forming the resin layer into a pipe shape, a method of obtaining a resin tube by laminating an olefin-based polar resin with a round die is used. At that time, a method of imparting heating duality to the pipe may be used according to a conventional method performed with a vinyl chloride pipe or the like. A coated steel pipe made from a resin pipe manufactured by a co-extrusion method has excellent adhesiveness of the resin lining layer. It is considered that the reason is that the degree of compatibility between the two resin layer tubes is high. Then, apply the adhesive to the outer surface of the obtained resin pipe by a general method such as coating the adhesive with a round die or extruding it into a sheet with a T die and winding it around the outer surface of the resin pipe. Thus, a resin tube with an adhesive can be obtained.

As a lining method, a general method used for an inner surface vinyl chloride lining steel pipe may be used. For example, a resin pipe having an outer diameter larger than the inner diameter of the steel pipe is extruded in advance, and the diameter is reduced to a pipe smaller than the inner diameter of the steel pipe. If necessary, after pretreatment such as blasting and pickling on the inner surface, and further, if necessary, surface treatment such as chemical conversion treatment and primer application, the outer surface of the steel pipe manufactured by the above method, smaller than the inner diameter of the steel pipe The resin pipe having a diameter and 5 to 30% longer than the length of the steel pipe is inserted. The steel pipe surface temperature is 80
Heat to ~ 250 ° C. Heat transfer from steel pipe,
Alternatively, the resin pipe inside the steel pipe is heated by the hot air, whereby a force for restoring the shape works and the resin pipe comes into close contact with the inner surface of the steel pipe. Alternatively, there is a method in which a resin pipe is inserted into a steel pipe, then softened by heating, and the inside is pressurized and expanded with air or the like to perform lining. After cooling, the resin pipe protruding from the end of the steel pipe is cut to obtain an inner resin lining steel pipe.

It goes without saying that the steel pipe of the present invention may be provided with a coating layer on the outer surface if necessary.

[0025]

EXAMPLES Examples 1 to 18 The polyolefin resins shown in Table 1 were extruded at a die temperature of 200 ° C. into a pipe having an outer diameter of 30.0 mm. After appropriately cooling the pipe, the pipe was stretched to an outer diameter of 26.1 mm, and further cooled in a cooling water tank to produce a pipe having an outer diameter of 26.1 mm and a wall thickness of about 1.3 mm. The pipe was lined with the olefin polar resin shown in Table 1 with a round die at a die temperature of 160 ° C. to a thickness of 0.2 mm, and then an adhesive was applied to a thickness of 0.1 mm.

A resin pipe having a length of 4 m and 50 cm produced by the above method was blasted to a steel pipe (inner diameter 27.6 mmφ,
The outer diameter of the steel pipe is 34 mmφ × 4 m), and then the steel pipe is heated to a temperature of 200 ° C. by a high-frequency heating device to restore the shape of the resin pipe. Further, the resin portion protruding from the end of the steel pipe was cut to obtain a sample, which was evaluated.

Examples 19 to 36 The polyolefin resins and olefinic polar resins shown in Table 2 were used at a die temperature of 2
It was coextruded at 00 ° C. into a pipe shape having an outer diameter of 30.0 mm.
After appropriately cooling the pipe, the pipe was stretched to an outer diameter of 26.1 mm, and further cooled in a cooling water bath to obtain an outer diameter of 26.1 mm.
A pipe having a thickness of 1.5 mm and a wall thickness of about 1.5 mm (polyolefin resin layer 1.3 mm, olefin polar resin layer 0.2 mm) was prepared. Thereafter, an adhesive was applied to a thickness of 0.1 mm.

A resin pipe having a length of 4 m and 50 cm produced by the above method was blasted to a steel pipe (inner diameter 27.6 mmφ,
(With an outer diameter of 34 mmφ x 4 m). Thereafter, the steel pipe surface was heated to 200 ° C. by a high frequency heating device to restore the shape of the two-layer resin pipe. Further, the resin portion protruding from the end of the steel pipe was cut.

The evaluation method of the inner resin-lined steel pipe obtained in the above embodiment is shown below.

Initial adhesive strength The initial adhesive strength was measured in terms of shear adhesive strength. The inner surface resin-lined steel pipe manufactured under the conditions described above is cut to a length of 20 mm, only the outer steel pipe portion is supported using a jig, and only the inner lining layer is punched at a speed of 10 mm / min. The force was the shear bond strength. 5 samples each
Individuals were taken and averaged. The unit of the adhesive strength is N / cm ²
It is. The temperature during the measurement test was uniformly 23 ° C.
After the sample was prepared and before the test, the sample to which the resin layer tube was not adhered was evaluated as x.

Low-Temperature Impact Resistance The low-temperature impact resistance test method is as follows: a resin-lined steel pipe is halved, the inner surface of the lining steel pipe is cooled down to −10 ° C., and a 1.5 kg drop weight is applied to a 1.0-meter drop. Dropped from the height onto the lining layer of the resin-lined steel pipe and the inner lining layer that failed, such as peeling or cracking, was rejected (×)
And

[0032]

[Table 1]

[0033]

[Table 2]

The comonomer content of each of the above olefinic polar resins is 15 mol%.

Comparative Examples 1 to 9 The polyolefin resins shown in Table 3 were extruded at a die temperature of 200 ° C. into a pipe having an outer diameter of 30.0 mm. After appropriately cooling the pipe, the pipe was stretched to an outer diameter of 26.1 mm, and further cooled in a cooling water tank to produce a pipe having an outer diameter of 26.1 mm and a wall thickness of about 1.5 mm. Thereafter, the adhesive was lined using a round die.

4 m long with adhesive prepared by the above method
50 cm resin pipe blasted steel pipe (27.
6φ, outer diameter 34mmφ × 4m). After that, the steel pipe was heated to a temperature of 200 ° C. by a high-frequency heating device to restore the shape of the resin pipe. Further, the resin portion protruding from the end of the steel pipe was cut.

[0037]

[Table 3]

[0038]

The inner resin-lined steel pipe of the present invention has at least two layers of an inner resin lining layer consisting of a polyolefin resin layer and an olefin polar resin layer having a polarity having a functional group consisting of elements other than carbon and hydrogen. It is an inner resin-lined steel pipe having a lining layer, which has a high adhesive strength between the lining layer and the steel pipe and has a sufficient anticorrosion performance, so that it can be used as a sufficiently satisfactory water supply pipe or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of an inner resin-lined steel pipe of the present invention.

FIG. 2 is a cut surface of another example of the inner resin-lined steel pipe of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel pipe 2 ... Olefin polar resin layer 3 ... Polyolefin resin layer 4 ... Adhesive layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/08 C08L 23/08 23/26 23/26 F16L 9/04 F16L 9/04 9/14 9 / 14 // B29K 23:00 B29K 23:00 B29L 9:00 B29L 9:00 23:00 23:00 (72) Inventor Yasuhiro Harada 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. 72) Inventor Akihiko Furuta 1-2-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3H111 AA01 BA02 BA34 CA52 CB08 CB22 DA20 DB03 DB05 EA14 4F100 AB03A AK03B AK03C AK04C AK07C AK70 BA68BAK BA10C CB00 DA11 EH202 4F211 AA03 AA03E AA04 AA10 AA11 AA21E AA22 AD03 AD12 AG03 AG08 AH43 SA13 SC03 SD04 SD11 SG01 SH06 SN01 SP20 SP25 SP28 SW23 4J002 BB031 BB062 BB072 BB082 BB121 BB171 BB171 BG042 BG052 BP021

Claims (7)

[Claims] 1. A polyolefin resin on an inner surface of a steel pipe;
It has a resin lining layer composed of at least two layers of an olefin-based polar resin layer having a functional group composed of elements other than carbon and hydrogen and having polarity, and the innermost surface is a polyolefin resin layer. Internal resin lining steel pipe 2. An olefin-based polar resin layer comprising an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic ester copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-methacrylic ester. The inner resin-lined steel pipe according to claim 1, which is made of a polymer. 3. The inner resin-lined steel pipe according to claim 1, wherein the olefin-based polar resin layer is made of an ionomer resin. 4. The inner resin-lined steel pipe according to claim 1, wherein the polyolefin resin layer is made of polyethylene or polypropylene resin. 5. The inner resin-lined steel pipe according to claim 1, wherein the polyolefin resin layer is made of polyethylene or polypropylene resin, and the olefin-based polar resin layer is made of ionomer resin. 6. An inner resin-lined steel pipe, wherein the resin lining layer according to claim 1, 2, 3, 4, or 5 is produced by co-extrusion of two resins at a melting point or higher. 7. The inner resin-lined steel pipe according to claim 5, wherein the resin lining layer according to claim 1, 2, 3, 4, and 5 is formed by co-extrusion of two resins at a melting point or higher. Resin tube used for