JP3307984B2 - Heat resistant synthetic resin lining metal tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin-lined metal pipe having a synthetic resin lining layer on the inner surface of a metal pipe for preventing rust of a hot water supply pipe.

[0002]

2. Description of the Related Art Conventionally, it has been widely known to line a metal tube with a synthetic resin such as a vinyl chloride resin for the purpose of imparting corrosion resistance to the metal tube. As one of the methods, an adhesive layer is provided on the outer surface of a vinyl chloride resin tube provided with a thermal expansion property and / or the inner surface of a metal tube, and then the vinyl chloride resin tube is inserted into the metal tube and joined by heating and expanding. Methods are known.

In particular, for applications requiring heat resistance such as hot water supply, a heat-resistant vinyl chloride resin tube having a high glass transition temperature is used as a vinyl chloride resin tube, and heat resistance and durability are taken into consideration as an adhesive. A rubber-based solvent-based adhesive is mainly used.

However, in the case of such an adhesive, the use of an organic solvent causes not only the problem of deteriorating the working environment, but also the danger of fire and other disasters. However, there is a problem that a long time is required due to the necessity of a recoating process because of the inability to obtain a coating and a drying step. Further, in the case of a solvent-type adhesive, it is extremely difficult to apply it to a cylindrical article, and there is a problem that it is not easy to obtain a uniform film thickness and the defect rate is high.

In order to solve this problem, attempts have been made to provide a hot-melt type adhesive layer made of various thermoplastic resins on the outer peripheral surface of a vinyl chloride resin tube. Has been

However, in applications where a heat-resistant vinyl chloride resin tube for hot water supply is used, hot-melt type adhesives cannot provide sufficient heat resistance and durability, so that practical use has been difficult. For example, adhesives based on modified polyethylene resins such as ethylene-vinyl acetate and ethylene-acrylic acid have low peel strength at high temperatures, and can be used for a long time even with adhesives based on crystalline polyester resins that can provide peel strength at high temperatures. However, there is a problem in the durability in the case where it is performed, particularly in the durability at the interface with the metal tube.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems relating to the heat-resistant vinyl chloride resin-lined pipe, and the gist of the present invention is to form a thermoplastic adhesive layer mainly composed of a polyester resin on the outer peripheral surface. Insert the heat-expandable heat-resistant vinyl chloride resin tube into a metal tube provided with a latent-curable primer layer having a predetermined thickness and a cross-linking reaction with the polyester resin, and heat the whole to expand the heat-resistant vinyl chloride resin tube. It is a heat-resistant synthetic resin-lined metal tube characterized by being integrated with a metal tube.

Hereinafter, the present invention will be described in more detail. Examples of the polymer for the heat-expandable heat-resistant vinyl chloride resin tube used in the present invention include a polymer mainly composed of a post-chlorinated vinyl chloride resin and a blend of a polyvinyl chloride resin and a known heat-resistant improver. Those higher than vinyl chloride resin are preferred. 90 ° C as glass transition temperature
The above are particularly preferred for the use of the present invention.
If necessary, a stabilizer, a filler, a lubricant, a coloring agent and the like are added to such a polymer, and the polymer is extruded into a pipe shape and then provided with a thermal expansion property.

The adhesive applied to the outer peripheral surface of the heat-expandable heat-resistant vinyl chloride resin tube is mainly composed of a saturated polyester resin, and is formed by blending a polyolefin resin or other additives as necessary. Is done. The saturated polyester resin used in the present invention is preferably a polyester resin having excellent crystallinity with high cohesion at high temperatures because the synthetic resin lining tube is used for heat-resistant applications, and its melting point is from 120 ° C to 150 ° C. Is particularly preferred from the viewpoint of suitability for application to a heat-resistant vinyl chloride resin tube.

The melting point is measured by a differential scanning calorimeter. The temperature is raised to 200 ° C. at a scanning speed of 10 ° C./min, cooled to 0 ° C. at the same speed, and absorbed when the temperature is increased again at the same speed. It means the temperature observed as a peak. When two or more peaks corresponding to the melting point are observed, the peak observed at the highest temperature may be within the above range. If the temperature is lower than the above range, it lacks heat resistance and is not suitable for practical use, and if it is high, it is necessary to set the resin temperature excessively high when applying to the vinyl chloride resin tube, deformation of the resin tube, deformation of the adhesive. Degradation due to thermal decomposition or oxidative decomposition is likely to occur, which is inconvenient.

The saturated polyester resin referred to in the present invention means a thermoplastic copolymer polyester resin obtained by polycondensation of a glycol and a dicarboxylic acid or polycondensation of an oxycarboxylic acid.

The glycol component includes ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methylpentanediol. , 1,3-hexanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A ethylene oxide adduct and the like.

The acid component includes aromatic dibasic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, paraphenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid and azelaic acid. And dibasic aliphatic acids such as sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, hexadecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Examples of the oxycarboxylic acid include those which form an ester structure by ring-opening polymerization such as caprolactone, in addition to 3-hydroxypropionic acid and 4-hydroxyvaleric acid.

Further, tri- or higher-functional acid components such as trimellitic acid and pyromellitic acid and / or tri- or higher-functional polyol components such as trimethylolpropane and pentaerythritol were copolymerized in trace amounts for the purpose of improving physical properties such as adjustment of crystallinity. It may be something. Further, the melting point of the polyester resin may be adjusted by blending two or more kinds of polyester resins having the above composition, or a blend of the same resins having different degrees of polymerization may be used.

Next, as the component other than the polyester resin, a polyolefin resin is preferable for the purpose of improving low-temperature characteristics and water resistance for the present invention. Examples of the polyolefin resin include, but are not particularly limited to, low-density polyethylene and ethylene copolymerized or graft-modified with maleic anhydride, vinyl acetate, acrylic acid, methacrylic acid, acrylate, vinyltrimethylolsilane, and the like. Polymers can be suitably used. In the present invention, other polymers can be added according to the purpose. For example, polystyrene resins and polyurethane resin fats can be added.

The present invention further includes a compatibilizer for improving the compatibility of various polymer components, fillers such as talc, clay and silica for improving cohesion, other known stabilizers and antioxidants. Can be added in a range that does not impair the characteristics of

Next, the primer does not substantially react with the latent curing type primer provided on the inner surface of the metal tube used in the present invention at the time of primer coating, and is crosslinked in a lining step of inserting a vinyl chloride resin tube into the metal tube and expanding by heating. It has the property that a reaction occurs and the fluidity is lost at high temperatures.

Further, in the present invention, it is necessary that the latent curing type primer has a property of reacting also with the polyester resin which is the adhesive layer on the outer surface of the vinyl chloride resin tube. The interface is firmly adhered, and peeling does not occur due to the shrinkage stress of the vinyl chloride resin tube generated in the cooling process after lining.

Even when the lining tube is used for a long time at a high temperature or when used repeatedly in a cooling and heating cycle, there is no occurrence of peeling. The latent hardening type primer has good adhesiveness to the metal tube and causes a crosslinking reaction with the polyester resin on the outer surface of the vinyl chloride resin tube during the lining step as described above, and has sufficient cohesive force in a practical temperature range. Nature is required. Examples of such materials include compounds having a polyfunctional blocked isocyanate group, polymers or oligomers having a polyfunctional epoxy group, polymers having a trimethylsilanol group in which a crosslinking reaction proceeds in the presence of moisture and an accelerator, and metal ions. And the like.

Examples of the compound having a polyfunctional blocked isocyanate group include a polyester resin, a polyester polyurethane (and / or urea) resin having an average of two or more isocyanate groups per molecule, and phenol, MEK oxime, methanol, acetonate and the like. Adducts with known blocking agents such as acetates are preferred. A mixture of a low molecular weight polyisocyanate compound (for example, a trimethylolpropane-TDI adduct, a trimer of a diisocyanate compound, etc.), the adduct of the blocking agent, and a polyester resin or a polyurethane resin containing no isocyanate group; Is also good.

Examples of the polymer or oligomer having a polyfunctional epoxy group include bisphenol A type epoxy resins, novolak type epoxy resins, chain epoxy resins, alicyclic epoxy resins, and polyepoxy resins used as ordinary epoxy adhesives. other such alkylene ether epoxy resins, polyfunctional glycidyl amine resin further BF ₃ complex to the modified polyolefin resin obtained by copolymerizing a monomer and an olefin monomer having a glycidyl group, an imidazole derivative, dicyandiamide, such as a known potential ketimine compound And a mixture of curable curing agents. In this case, the polyester resin on the outer surface of the vinyl chloride resin tube preferably has a carboxyl group or an amino group at the terminal or in the middle of the molecular chain in view of reactivity.

Examples of polymers which undergo a crosslinking reaction in the presence of moisture and an accelerator include modified polyolefin resins obtained by copolymerizing or grafting vinyltrimethoxysilane with a polyolefin. As the reaction accelerator, a polycondensation catalyst of an organotin compound such as dibutyltin dilaurate or a methoxysilicone such as an organic amine can be suitably used, and can be mixed with a primer or mixed with a polyester-based adhesive for practical use. You can also.

As a polymer containing a metal ion, a polymer in which a metal ion is contained in a polyester resin or a polyurethane resin having a carboxyl group or the like at a molecular end or in a molecular chain, and a carboxyl such as ethylene-allylic acid and ethylene-methacrylic acid Polymers in which metal ions are contained in a modified polyolefin having a group are exemplified. In this case, because of the coating stability when coating the metal tube,
It is preferable to use a stabilizer such as acetylacetone, acetoacetate, or alcohol in combination. The metal ion is not particularly limited as long as a sufficient cohesive force can be obtained after crosslinking, but trivalent Al ions, tetravalent Zr ions, tetravalent Ti ions, and the like are preferable in view of crosslinking, effects, and safety. .

Further, it is also effective to add an adhesion improver such as a silane coupling agent to the metal tube to the primer layer, if necessary. The thickness of the primer layer of such composition is better to apply a range of ^{0.5g / m 2 ~5.0g / m 2} . If it does not reach this range, it is not possible to sufficiently fill the metal tube with irregularities, or the resulting coating film lacks uniformity, and does not have a sufficient primer effect. If the amount exceeds this range, it becomes difficult to dry the solvent, and as in the case of the rubber-based solvent-type bonding described above, the working environment is deteriorated and the cost is increased. Depending on the type, the peel strength is weak, and inconvenience is likely to occur.

Next, a method for manufacturing the lining metal pipe of the present invention will be described. The vinyl chloride resin tube for the lining is formed into a belt shape by a melt coating method in which the thermoplastic resin containing the above-mentioned polyester resin as the main component is extruded with a cross-head die on the outer surface of the heat-expandable heat-resistant vinyl chloride resin tube, using a T-die, etc. It is obtained by a melt winding method of extruding and winding or a film winding method of winding an adhesive formed into a film.

The formation of the primer layer on the metal pipe is carried out by applying the above-mentioned organic solvent solution of the primer onto the inner surface of a carbon steel pipe for water service, galvanized copper pipe, or the like, and then drying the solvent. You.

The vinyl chloride resin tube for lining is inserted into the metal tube having the primer layer, and usually heated from the outside of the metal tube from one end to the other end or from the center to both ends by a burner, hot air or the like. Expands and adheres the vinyl chloride resin tube. In this case, the heating condition depends on the melting point of the polyester resin as the adhesive and the reaction temperature of the latent curing type primer, but it is preferable that the metal tube surface is in the range of 140 to 200 ° C.

In the present invention, it is necessary to react the latent curing type primer after lining the vinyl chloride resin tube. If a sufficient cross-linking effect is obtained within the time required for expanding and bonding the vinyl chloride resin tube, the process can immediately proceed to the cooling step. However, if the primer does not react sufficiently within this time, the reaction temperature is maintained at the reaction temperature for a predetermined time. Is preferred.

Further, the time required for the reaction and the cooling of the lining metal tube are from 0.5 kg / cm ² to 4.0 kg.
/ Cm ² is more preferably maintained in a pressurized state.
As the pressurizing method, the inside of the vinyl chloride resin tube may be pressurized and sealed before heating, or a method may be used in which the diameter of the tube is heated, the pressurized air is sealed, and then the tube is cooled.

[0030]

Hereinafter, the present invention will be described in more detail based on embodiments of the present invention. EXAMPLE A heat-expandable heat-resistant vinyl chloride resin tube having a length of 6 m and an outer diameter of 20.1 mm (Hishi pipe HT-E20 manufactured by Mitsubishi Plastics, Inc.)
A) Polyester adhesive (Hadek A-3410 manufactured by Asahi Kasei Kogyo Co., Ltd.) using a crosshead die on the outer surface of A)
Was extrusion-coated to a thickness of 100 μm. This was placed in a carbon steel pipe for water supply having an inner diameter of 21.6 mm and a length of 5.5 m, and 100 parts by weight of a latent curing type primer solution “Vylon 300 (amorphous polyester resin manufactured by Toyobo Co., Ltd.) was used as a millionate MS-50. (Nippon Polyurethane Co., Ltd.
An MK / toluene solution containing 20% of an active ingredient blended with 10 parts by weight of an MDI-based blocked isocyanate (manufactured by MDI) is applied so as to have a film thickness of 2.5 g / m ^2, and inserted into a dried solvent. Seal both ends of the PVC resin tube,
It was passed through a lining heating furnace while being pressurized to an internal pressure of 0.5 kg / cm ² . At this time, the operating conditions of the heating furnace were adjusted so that the outer surface of the metal tube was at 170 ° C. After leaving the heating furnace having a total length of about 5.5 m, the heating operation and the forced cooling for the reaction were not particularly performed, and the mixture was naturally left to cool to room temperature. Thereafter, the internal pressure was released, and the lining portion was cut to a length of 1 m to obtain a test sample.

The performance test was performed as follows, and the results are shown in Table 1. (Initial Bonding Strength) After leaving the test sample at room temperature for 2 days, three test pieces of 2 cm in length in the axial direction were cut out from an arbitrary position of the test sample, and the test piece shown in FIG. The test piece 3 was placed horizontally on the cradle 4 at room temperature at room temperature, and a load was gradually applied by the metal plate 1 to measure the load when the adhesive surface of the inner lining portion 2 was peeled off. Calculated, and the maximum value was defined as the initial adhesive strength. F = W / S S = 3.14 d × l F: Adhesion strength (kg / cm ² ) W: Peeling load of adhesion surface (kg) S: Adhesion area (cm ² ) d: Average inner diameter of original tube (cm) L: length of test piece (cm) (Adhesive strength after cooling / heating cycle) After repeating the above test sample for 120 cycles of immersion in normal-temperature water for 1.5 hours and immersion in 95 ° C hot water for 1.5 hours, The adhesive strength was measured in the same manner as the initial adhesive strength. (Shrinkage of Tube End after Cooling / Heat Cycle) After performing the above cooling / heating cycle, the amount of misalignment between the metal tube and the vinyl chloride resin tube at the tube end was measured.

The melting point of the polyester-based adhesive used here was determined by a differential scanning calorimeter (DSC-7 manufactured by PerkinElmer).
125) at a scanning speed of 10 ° C./min.
° C. The adhesive used as the primer is a phenol block type material having terminal TDI (triresin isocyanate).

Comparative Example 1 A test sample was obtained in the same manner as in the example except that the latent curing type primer was not applied, and the same measurement was performed. Comparative Example 2 A test sample was obtained in the same manner as in the example except that the blocked isocyanate was not added to the primer layer, and the same measurement was performed. Comparative Example 3 A test sample was obtained in the same manner as in Example except that 4.2 parts by weight of Coronate L (a polyisocyanate solution manufactured by Japan Polyfretan Co., Ltd.) was used instead of the blocked isocyanate of the primer layer, and the same measurement was performed. went.

[0034]

[Table 1]

As shown in Table 1, it is clear that the lining tube of the present invention has a practically acceptable level of adhesive strength even under the condition of 120 cycles of cooling and heating, and the comparative example is not at a practical level.

[0036]

As described above, according to the method of the present invention, the latent hardening type primer layer is provided with a predetermined thickness on the inner surface of the metal tube, so that there is no problem of environmental deterioration due to the solvent and the durability at the interface with the metal tube. A heat-resistant vinyl chloride resin-lined metal tube having extremely good heat resistance is obtained, and has sufficient performance as a hot water supply piping material.

[Brief description of the drawings]

FIG. 1 shows an adhesion measuring device.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 metallization 2 inner lining part 3 test piece 4 cradle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI B29L 9:00 B29L 9:00 23:00 23:00 (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16L 58 / 10 B29C 63/34 B29C 65/40 B32B 1/08

Claims (1)

(57) [Claims] 1. A heat-expandable heat-resistant vinyl chloride resin tube having a thermoplastic resin layer mainly composed of a polyester resin formed on the outer peripheral surface thereof. A latent curing type primer layer having a crosslinking reaction with the polyester resin is provided on the inner surface of a predetermined thickness. A heat-resistant synthetic resin-lined metal tube, which is inserted into a metal tube made of, and heated to expand the heat-resistant vinyl chloride resin tube to be integrated with the metal tube.