KR101937346B1 - Coated steel pipe for water works and Method thereof - Google Patents

Abstract

According to the present invention, an inner coating steel pipe for a waterworks includes a steel pipe, an inner paint film coated on the inner surface of the steel pipe, and an outer paint film coated on the outside of the steel pipe. The inner paint film features to be coated on the inner surface of the steel pipe as two fluid type of organic-inorganic hybrid paint comprising: a first reformed siloxane formed by reforming mesoporous silica to r-glycidoxy propyl trimethoxy silane; a second reformed siloxane formed by reforming mesoporous silica to r-aminopropyl trimethoxy silane; an A-agent of isocyanate prepolymer formed by mixing the first reformed siloxane and diphenylmethane-4,4-diisocyanate (MDI); and a B-agent of a polyol group mixed with the second reformed siloxane.

Description

Technical Field [0001] The present invention relates to an inner surface-coated steel pipe for waterworks using an organic-inorganic hybrid coating material containing modified silica,

The present invention relates to an inner surface-coated steel pipe for a water supply using an organic-inorganic hybrid coating material containing modified silica and a method for producing the same, and more particularly, to a method for coating an inner surface of a steel pipe with a modified siloxane, an isocyanate prepolymer, Friendly, high-strength paint to meet the drinking water standards.

Generally, the water pipe is coated with inner and outer surfaces to prevent corrosion of steel pipes.

Corrosion resistant inner coatings used in drinking steel pipes are demanding not only for excellent performance, but also for environmentally friendly coatings that are harmless to humans and conform to drinking water standards.

In the case of epoxy-based coatings used as inner coatings, bisphenols, which are known as hormone-disintegrating substances, are a major component of the risk-raising controversy.

As a substitute, polyurea or polyurethane resin which has no risk to the human body and has high hardness and excellent workability has started to attract attention.

Solvent-free two-part polyurea coatings are prepared from polyether compound A composed of polyisocyanate group and polyether compound B composed of polyamine group, respectively, and polyurea reaction (-NCO + -NH ₂ → -NHCONH-) occurs when mixed. The polyamines have low water adsorption, so there is no generation of carbon dioxide during the application, but the strong initial reactivity of the polyamines is poor in workability because the pot life (time available for coating before gelation) is only about 10 seconds or even a few seconds and the wetting time Is lacking. Therefore, insufficient penetration of the coating paint on the surface of the steel pipe causes a problem of adhesion failure, so that the reliability on the quality of the coated steel pipe is lowered, which is very limited in use.

Solvent-free two-pack type polyurethane is prepared from polyisocyanate group (A) and polyol group (B), respectively, and polyurethane reaction (-NCO + -OH → -OCONH-) occurs by mixed injection. Since the polyurethane is used as the polyol as the B agent, the wetting time for the steel plate is about 5 to 30 minutes, and the adhesion and the workability are excellent. On the other hand, since the polyol has the water adsorption characteristic, the adsorbed water and the isocyanate The reaction (NCO + H ₂ O → -NHCONH + CO ₂ ) causes carbon dioxide to generate bubbles.

Therefore, in polyurethane coating materials, it is important to secure safety against moisture.

Polyurea and polyurethane are polymers having repeating groups in common and composed mainly of isocyanate having two or more functional groups. A and polyurea are composed of polyamine group B, polyurethane Is composed of a polyol group B compound, and a coating film is formed by a polymer curing reaction by mixing the components A and B, respectively.

Polymer formation of polyurea and polyurethane is a structure formed by intertwining with a segmented block copolymer. Each segment has a soft segment having a flexible molecular structure and a polymer having a strong molecular structure It is composed of hard segment and it is possible to control the degree of each segment content and fine phase separation. Therefore, it is theoretically possible to control a wide range of properties. Especially, in case of polyurethane, excellent adhesive properties and excellent mechanical properties, It can be widely applied.

The coating performance of the coating material required for the steel pipe for water supply is required to be high quality and strong. In order to satisfy these requirements, polyurea or polyurethane should have a high hard segment ratio as mentioned above. As the hard segment fraction increases, the average molecular weight decreases and the viscosity decreases. As a result, the mobility between the molecular chains improves, so that the coating workability is improved. However, in the case of polyurea, the curing reaction time is too short, In the case of polyurethane, the water adsorption of the polyol group is increased, and a large amount of carbon dioxide is generated as in the above-mentioned reaction. Thus, the problem of making paint work and forming a good film is difficult.

As a result of the above problems, there is a technical limitation in increasing the hard segment fraction. Therefore, the soft segment fraction is set to a high level as long as the above problems do not occur. The formed coating is a high elastic material and has a low heat resistance ~ 90 ° C), it is not possible to satisfy the physical properties required for the interior coating paint for water pipes.

1. Korean Patent No. 10-1681251

Disclosure of the Invention The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a viscous organic-inorganic hybrid coating material capable of effectively suppressing the generation of bubbles by effectively adsorbing and removing moisture at the time of coating using a modified siloxane, Is applied to the inner surface of the steel pipe to form an environmentally friendly and high-strength coating, thereby providing a steel pipe for waterworks meeting the drinking water standard.

The present invention is to provide a solvent-free two-component type organic-inorganic hybrid coating material by modifying an inorganic mesoporous silica to provide a method of manufacturing an inner surface-coated steel pipe for waterworks having a high heat resistance and a strong inner surface coating.

According to an aspect of the present invention, there is provided an inner surface coated steel pipe for a water supply system, comprising: a steel pipe; An inner coating film coated on the inner surface of the steel pipe, and an outer coating film coated on the outer surface of the steel pipe, wherein the inner coating film comprises: a first modified siloxane modified with mesoporous silica with r-glycidoxypropyltrimethoxysilane; a second modified siloxane modified with mesoporous silica with r-aminopropyltrimethoxysilane; A two component liquid organic / inorganic composite coating composed of an A component of an isocyanate prepolymer mixed with the first modified siloxane and diphenylmethane-4,4-diisocyanate (MDI) and a B component of a polyol group mixed with the second modified siloxane, And is coated on the inner surface of the steel pipe.

The polyol group is characterized by being a mixture of a trifunctional polyol having a molecular weight of 600, a bifunctional polyol having a molecular weight of 1000, a trifunctional polyol having a molecular weight of 1200, and a hydrogenated castor polyol.

And the oxazolidine compound is contained in the agent B.

As another embodiment of the present invention, a method of manufacturing an inner surface-coated steel pipe for a water supply includes the steps of: preparing a steel pipe for a water supply; Pretreating the outer surface of the steel pipe; Heating the steel pipe; Coating an outer surface of the steel pipe; Cooling the steel pipe; Pretreating the inner surface of the steel pipe; Coating the inner surface of the steel pipe and inspecting the surface after completion of the coating, wherein coating the outer surface comprises: forming a primary coating by thermal fusion coating using a powdered epoxy; Forming a second conductive film by thermally fusing coating using a modified polyethylene adhesive, and forming a third conductive film by thermally fusing and coating the polyethylene, wherein the step of coating the inner surface comprises the steps of: And a two-component organic-inorganic hybrid coating material is applied while applying a predetermined positive voltage while being connected to the anode of the direct current electricity generating device.

The two-component organic-inorganic hybrid coating material may include: a first modified siloxane modified with mesoporous silica with r-glycidoxypropyltrimethoxysilane; a second modified siloxane modified with mesoporous silica with r-aminopropyltrimethoxysilane; An A component of an isocyanate prepolymer obtained by mixing the first modified siloxane and diphenylmethane-4,4-diisocyanate (MDI), and a B component of a polyol group mixed with the second modified siloxane.

The present invention can apply the organic or inorganic composite paint using the modified siloxane, isocyanate prepolymer and polyol group to the inner surface of the steel pipe to form an environmentally friendly and harmless high strength paint and use it as a steel pipe for water supply meeting the drinking water standard.

Further, the present invention forms a high heat resistance and strong inner surface coating film by using a two-component non-solvent type inorganic / organic hybrid polyurethane resin paint.

1 is a sectional view of an inner surface-coated steel pipe for a water supply according to the present invention.
Fig. 2 is a production process diagram of an organic-inorganic hybrid coating material using a modified siloxane, an isocyanate prepolymer and a polyol group.
3 is a view illustrating a manufacturing process of the inner surface-coated steel pipe for water supply according to the present invention.

In the present invention, the weight ratio (weight ratio) is expressed in wt%, and in the case where the relative weight is expressed based on a certain substance, the weight is expressed in parts by weight. The terms "A-form" and "B-form" used in the present invention have no particular significance. For convenience, the terms "A" and "B" Also, there is no meaning of numbers in 'first, second' or 'A 1st, A 2nd', etc., and it is a convenience expression to distinguish each other.

FIG. 1 is a longitudinal sectional view of an environmentally friendly inner surface-coated steel pipe for a water supply according to the present invention, which is a steel pipe for a water pipe coated with a coating material harmless to the human body, An inner coating film 20 and an outer coating film 30.

The steel pipe 10 is a carbon steel pipe for piping that is formed by cutting a steel plate and welding it, and includes an inner pipe and an outer pipe.

The inner coat 20 is coated on the inner surface of a steel pipe and requires mechanical strength and physical and chemical performance such as water resistance, corrosion resistance, durability, flexural resistance, abrasion resistance, heat resistance, cold resistance, weather resistance, acid resistance, environment friendliness and biocompatibility.

The outer coating 30 is coated on the outer surface of the steel pipe and formed into a three-layer coating. The primary coating 31 is coated with a thermal epoxy coating using a powder epoxy and the secondary coating 32 is coated with a modified polyethylene adhesive , And the tertiary coating film (33) is thermally fused and coated with polyethylene.

In the present invention, polyurethane which is a conventional inner coating film absorbs moisture and bubbles are generated, and low strength and heat resistance are improved.

Since the polyurea is formed by the reaction of the polyisocyanate with the polyamine, it is practically difficult to exclude the rapid reaction. Therefore, it is insufficient to fundamentally improve the problem and is unsuitable for application as a coating material for steel pipes for tap water.

Polyurethane is used as a diluent for applying a viscosity of about 5,000 ~ 50,000 cP because of its high molecular weight. The reaction product formed by this reaction forms a rubber-like elastic urethane, so it is practically limited to use in steel pipes and other structures. There is a limit to replacing paints.

Therefore, in order to form a high-strength polyurethane coating film which is not an elastic body and to facilitate injection without a solvent, it is necessary to make the number-average molecular weight of the reactant be low to be in the range of about 100 to 1,000, preferably about 300 to 800, It is possible to form a coating film which is dense and strong by low molecular weight and crosslinking.

As a method for lowering the viscosity of the coating material, there is a method in which a diluent is added, or a polyol having a low number-average molecular weight and a high hydroxyl value and a low-viscosity active hydroxyl group is used. In the former case, And deterioration of physical properties are insufficient to replace epoxy coating material. In the latter case, instead of lowering the number average molecular weight and lowering the viscosity, hydroxyl groups per molecule unit rapidly increase the water adsorption property of the reactants, which makes it difficult to obtain a good coating film.

In the present invention, alkoxysilanes, mesoporous silica, oxazolidine compounds, and aldimine compounds are used as a method for suppressing moisture adsorption, which is a problem to be solved in the two-component solventless polyurethane coating.

The main compositions used in the present invention are as follows.

1. A

The polyisocyanate having two or more functional groups usable in the present invention may be at least one selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4-diisocyanate (MDI) There are various kinds of isocyanate (TDI), 1,5-naphthalene diisocyanate, tolidine isocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, etc. In the present invention, An MDI having an equivalent weight of 120 - 200 is suitable.

The MDI used constitutes the main skeleton of the hardsegment as a constituent of the two-pack type polyurethane-coated paint A zein main subject, and is an aromatic toluene diisocyanate (TDI), aliphatic or alicyclic hexamethylene diisocyanate, Isophorone diisocyanate and xylylene diisocyanate. However, since the reactivity thereof is much lower than that of MDI, the reaction time is somewhat effective for controlling the reaction time, but the formation of the hard segment is insufficient and the curability is poor and the physical properties are unsatisfactory. The polyisocyanate used in the present invention is preferably MDI because of the health and osmotic problems of workers due to the generation of toxic vapors and the high price in the case of aliphatic and alicyclic groups. However, MDI has the disadvantages of providing high reactivity and excellent hard segmentation, but it is the most sensitive to moisture.

2. B

In order to constitute a coating film having a strong polyol system which is a constituent of a curing agent which is a part of the two-pack type polyurethane coating material of the present invention (referred to as a 'curing agent' and about 50% of the total composition ratio of the coating material), the ratio of polyols having short molecular chains However, as the ratio of the short molecular chain polyol increases, there is a problem that the adsorptivity to moisture increases.

A polyol refers to an alcohol in which a number of hydrogen atoms in the hydrocarbon are replaced by hydroxyl groups, for example, one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide and tetrahydrofuran, All kinds of alcohols obtained by an addition reaction with a compound having a hydrogen atom.

Compounds having two or more active hydrogen atoms include, for example, polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethyl glycol, glycerin, hexanetriol, trimethylolpropane and pentaerythritol, Ethylenediamine and hexamethylenediamine), alkanolamines (e.g., ethanolamine and propanolamine), and polyhydric phenols.

Examples of the polyol used in the present invention include polyolefin-based polyols such as polytetramethylene glycol, polyethylene glycol, polypropylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polyether polyol, polybutadiene polyol and polyisoprene polyol. , A polyester-based polyol (for example, an adipate-based polyol, a lactone-based polyol and a castor oil). These polyols have a number average molecular weight of 100 to 10,000, more preferably 300 to 5,000.

The polyol group used in the present invention may be a mixture of a trifunctional polyol having a molecular weight of 600, a bifunctional polyol having a molecular weight of 1,000, a trifunctional polyol having a molecular weight of 1,200 and a hydrogenated caster polyol having a short molecular chain.

3. Mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSN) having pores of the order of 2 to 50 nm have many applications in catalysts, adsorbents, polymeric brighteners, optical devices, bio-imaging materials, drug delivery systems and biomedical applications It is one of the nanomaterials. In the present invention, in order to improve the adhesion, the heat resistance and the mechanical strength, the A and B components are mixed to adsorb moisture in the air before the polyol or isocyanate in the urethane reaction to function as a molecular sieve of water molecules, Structure mesoporous silica is used.

Mesoporous silica is a high surface area silica with a mesoporous, open structure that contains zeolites and has high adsorptivity to water molecules. The specific surface area of silica is about 8.0 x 10 ² m ² / g, the pore size of the pores is about 4.2 x 10 ^-1 cc / g, the pore size is about 1 to 50 nm, A size of 1 to 3 nm is preferable.

Mesoporous silica not only improves the heat resistance of the coating film but also improves the mechanical properties as well as the moisture adsorption, and also provides the important polyanion in the coating process to increase the adhesion. However, since the mesoporous silica powder is difficult to be chemically bonded with an organic polyurethane component, mesoporous silica powder can not be chemically bonded to a liquid compound, so that heat resistance, mechanical properties, and adhesive strength are expected to be improved It is difficult and difficult to disperse, which lowers the gloss of the cured coating and raises the viscosity.

In order to solve these problems, polydimethylsiloxane which has an organic reactor and an inorganic reactor simultaneously in a molecular structure and can induce chemical bonding between silica and an organic group was used.

The effect of modifying silica with polydimethylsiloxane is not only improved in water adsorption, but also improved in heat resistance, mechanical properties and adhesion, as compared with silica alone. Particularly, heat resistance is known to be increased by the formation of a modified ladder-type or kage-type network of modified silica.

The reactive polydimethylsiloxane is specifically exemplified by r-aminopropyl trimethoxy silane, n-β (aminoethyl) r-aminopropyl trimethoxy silane (n-β (amino ethyl) silane, 3-mercaptopropyl trimethoxy silane, r-glycidoxy propyl trimethoxy silane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl trimethoxy silane), which may be used alone or in combination of two or more. Silanes with amino groups can be used for B agents because of their high reactivity.

4. Oxazolidine

As the latent curing agent used in the present invention, an oxazolidine compound having an oxazolidine ring (a saturated ring containing oxygen and nitrogen) and an aldimine are subjected to ring opening reaction with water before the isocyanate to change a water molecule into a hydroxyl group To suppress the formation of bubbles in the coating film.

The oxazolidine compound can be prepared by reacting N- (2-hydroxyethyl) -tetrahydrooxazole with an organic carbonate or by reacting N- (2-hydroxyethyl) -tetrahydrooxazole with 1,6-hexane diisocyanate (Hardener OZ manufactured by Bayer), Zoldine (registered trademark) RD-4 (manufactured by Angus Chemical), and Incozol (manufactured by Mitsubishi Chemical Corporation) (Registered trademark) LV, INCOSOL (registered trademark) 4, INCOSOL (registered trademark) HP, INCOSOL (registered trademark) NC, INCOSOL (registered trademark) CF, INCOSOL (registered trademark) EH and INCOSOL ) K (manufactured by Incorez).

In the present invention, a filler, a plasticizer, a pigment, an antistatic agent, a flame retardant, a thixotropic agent, a silane coupling agent, a dispersant, an oxidation inhibitor, a polymerization inhibitor, and a chain extender may be added in addition to the above-mentioned composition.

The filler can be calcium carbonate, carbon black, clay, talc, titanium oxide, quicklime, kaolin, zeolite, diatomaceous earth, vinyl chloride paste resin, glass balloon and vinylidene chloride resin balloon. They may be used alone or in combination

The pigments may be organic pigments (such as azo pigments and copper-phthalocyanine pigments) or other inorganic pigments.

The thixotropic agent may be an aerosol distearate or the like.

The antistatic agent may be an ionic compound such as a quaternary ammonium salt and an amine or a hydrophilic compound such as a polyethylene glycol and an ethylene oxide derivative.

As the adhesion modifier, a terpene resin, a phenolic resin, a terpene phenol resin, a rosin resin and a xylene resin can be used.

The flame retardant may be chloroalkyl phosphate, dimethyl methylphosphonate, bromine, phosphorus compound, ammonium polyphosphate, diethylbishydroxyethylaminophosphate, etc.

In the present invention, an organic metal or other catalyst known to be harmful to human body is not used.

The modified siloxane is modified with an organic solvent by mixing and dispersing 100 parts by weight of the polydimethylsiloxane with mesoporous silica in an amount of 25 to 75 parts by weight. The siloxane 1 is used as the siloxane 1 for the A agent and the siloxane 2 is used for the B agent.

5. Manufacture of Modified Siloxane 1.

100 parts by weight of r-glycidoxy propyl trimethoxy silane, which is an isocyanate-reactive polydimethylsiloxane, was added to a five-necked separable flask equipped with a stirrer, a condenser and a nitrogen gas injector, and the temperature was raised to 70 ° C 50 parts by weight of well-dried mesoporous silica nanoparticles (trade name: Baylith L powder) was added thereto over 10 minutes while stirring to stir the silica powder until the silica powder was sufficiently dispersed, and then the temperature was elevated to 110 DEG C and the supply of nitrogen was stopped The temperature was maintained for about 30 minutes. The temperature was adjusted to room temperature and cooled to prepare siloxane 1 modified with silica dispersed therein.

6. Manufacture of Modified Siloxane 2

 was prepared in the same manner as the 'modified siloxane 1' except that r-glycidoxypropyltrimethoxysilane was replaced with r-aminopropyl trimethoxy silane.

7. Preparation of A (isocyanate-terminated prepolymer)

In the present invention, in order to form a high-strength polyurethane coating film which is not an elastic body and to facilitate injection without a solvent (solvent), an isocyanate prepolymer (for example, prepolymer.

A polymer is a molecule with repeating molecular weights of 10,000 or more, and a prepolymer is a form of several monomers attached, which means that the molecular weight is smaller than the polymer and longer than the monomer.

Monomers in polyurethane are isocyanate compounds such as MDI and TDI, and have molecular weights of several hundreds. Polyols have hydroxyl groups and molecular weights of several hundreds to 5,000.

The composition A is prepared by mixing 30 to 95 parts by weight of MDI, 5 to 40 parts by weight of the modified siloxane 1, 0.5 to 2 parts by weight of aminopropyltrimethoxysilane as a silane coupling agent, and 2.5 to 10 parts by weight of a hydrogenated castor oil Mix.

1) A 1st

In a five-necked separable flask equipped with a stirrer, a condenser and a nitrogen injector, 75 parts by weight of diphenylmethane-4,4-diisocyanate (MDI), 19 parts by weight of the modified siloxane 1 prepared above, 1 part by weight of aminopropyltrimethoxysilane and 5 parts by weight of hydrogenated castor oil were mixed and stirred at 80 rpm for 2 hours at 150 rpm in a nitrogen atmosphere to prepare a prepolymer liquid resin composition 'A No. 1'.

2) A second

Is the same as the 'A-1' except that the liquid resin composition is formed using 'modified siloxane 2' instead of 'modified siloxane 1' in 'A-1'.

3) A third

The same as in the 'A-1' except that the amount of the modified siloxane 1 is changed to 15 parts by weight in 'A-1' to form the liquid resin composition.

4) A Fourth

The same as in the above 'A' except that the amount of the modified siloxane 1 is changed to 10 parts by weight in 'A' to form the liquid resin composition.

5) A fifth

A 'is the same as the' A-1 'except that the amount of the modified siloxane 1 is changed to 5 parts by weight to form the liquid resin composition.

6) A 6th

'A No. 1' except that the liquid resin composition is formed from 15 parts by weight of mesoporous silica instead of 'modified siloxane 1' in 'A 1'.

7) A seventh

'A No. 1' except that the liquid resin composition is formed from 10 parts by weight of mesoporous silica instead of 'modified siloxane 1' in 'A 1'.

8. Manufacture of B (polyol group)

The B agent of the polyol group has a molecular weight of 600, 10 to 40 parts by weight of a trifunctional polyol, 5 to 20 parts by weight of a bifunctional polyol having a molecular weight of 1,000, a molecular weight of 1,200, 5 to 20 parts by weight of a trifunctional polyol, 10 to 40 parts by weight of a polyol and 10 to 50 parts by weight of a modified siloxane 1 are mixed, and 2 to 5 parts by weight of oxazolidine, 0.1 to 2 parts by weight of a pigment, a thixotropic agent, an antioxidant, More parts can be added.

1) B 1st

In a five-necked separable flask equipped with a stirrer, a condenser and a nitrogen gas injector, 20 parts by weight of a trifunctional polyol having a molecular weight of 600 and a molecular weight of 1,000, 10 parts by weight of a bifunctional polyol, a molecular weight of 1,200 and 10 parts by weight of a trifunctional polyol, 20 parts by weight of hydrotreated caster polyol, 30 parts by weight of modified siloxane 1, 3 parts by weight of oxazolidine, 0.1 to 2 parts by weight of pigments, thixotropic agents, antioxidants, dispersants and other fillers, Was heated to 120 占 폚 and stirred for about 1 hour to confirm that the mixing reaction had been completed, followed by vacuum degassing for 2 hours to prepare a liquid resin composition B agent.

2) B second

Is the same as the 'B No. 1' except that the modified resin composition is formed from the 'modified siloxane 1' and the 'modified siloxane 2' in an amount of 30 parts by weight in 'B No. 1'.

3) B third

And the liquid resin composition was prepared by changing the amount of the modified siloxane 2 from 20 parts by weight to 30 parts by weight in the 'B No. 2' to the 'B No. 2'.

4) B Fourth

And the liquid resin composition was prepared by changing 30 parts by weight of 'modified siloxane 2' to 10 parts by weight in 'B' to '2'.

5) B 5th

And 2 parts by weight of N-hydroxyalkyloxazolidine in 2 parts by weight of 'B No. 2' to form a liquid resin composition.

6) B 6th

And the liquid resin composition was prepared by using 4 parts by weight of N-hydroxyalkyloxazolidine in 4 parts by weight of 'B No. 2' to form the liquid resin composition.

7) B Seventh

The same as in 'B No. 2' except that 25 parts by weight of 'modified siloxane 1' and 3.5 parts by weight of oxazolidine were used in 'B No. 1' to form a liquid resin composition.

8) B Section 8

And the liquid resin composition was formed by changing the amount of the modified siloxane 2 to 25 parts by weight and the amount of the oxazolidine to 3.5 parts by weight in the 'B No. 2', the same as the 'B No. 2'.

The composition A and the composition B prepared above were mixed and sprayed at a ratio of 1: 1 on the inner surface of a steel pipe using a two-pack type high-pressure sprayer to form a coating film, and a pot life (tack free time) .

[Example 1]

[Example 2]

[Example 3]

[Example 4]

[Example 5]

[Example 6]

[Example 7]

[Example 8]

As shown in the above examples, when the mesoporous silica mixture modified with polydimethylsiloxane and the oxazolidine derivative were appropriately used, it was found that the formation of bubbles in the polyurethane coating was suppressed, and the presence or absence of the polydimethylsiloxane and the mesoporous silica The composite effect increases the adhesive strength, mechanical strength and heat resistance. The quality of the coating film by the second composition of Example 2 was measured to be the best.

Also, the coatings in the liquid state prior to the reaction form a negative electrode "polyanion ".

According to another embodiment of the present invention, there is provided a method of manufacturing an inner surface-coated steel pipe for a water supply, comprising the steps of: preparing a water pipe for a water supply; Pretreating the outer surface of the steel pipe; Heating the steel pipe; Coating an outer surface of the steel pipe; Cooling the steel pipe; Pretreating the inner surface of the steel pipe; Coating the inner surface of the steel pipe, and inspecting the coating after completion of the painting.

The step of coating the outer surface may include a step of forming a primary coating by thermal fusion coating using a powder epoxy; A step of forming a second conductive film by a thermal fusion coating using a modified polyethylene adhesive, and a step of forming a third conductive film by thermally fusing and coating the polyethylene.

The coating of the inner surface is performed by applying a positive voltage to the positive electrode of a DC generator capable of controlling the voltage of the steel pipe while applying a two-component type organic or inorganic composite paint.

The two-component organic-inorganic hybrid coating material may include: a first modified siloxane modified with mesoporous silica with r-glycidoxypropyltrimethoxysilane; a second modified siloxane modified with mesoporous silica with r-aminopropyltrimethoxysilane; An A component of an isocyanate prepolymer obtained by mixing the first modified siloxane and diphenylmethane-4,4-diisocyanate (MDI), and a B component of a polyol group mixed with the second modified siloxane.

The present invention relates to a method for increasing the quality of a steel pipe. When a steel pipe is applied with a positive electricity during the coating process of a steel pipe coating, the coating material of "polyanion" is increased in adhesion to the surface of the steel pipe by +/- bonding, The effect of discharging fine bubbles to be discharged to the outside and the penetration of the coating paint by the fine pores or gaps of the surface of the steel pipe plate become more effective.

Since the curing reaction is completed and the coating film is formed in this state, the coating film has an advantage of maintaining an improved high adhesion strength to the steel pipe, so that the inorganic or organic composite polyurethane steel pipe is superior to the adhesion force required by the KWWA quality standard

[Example 9]

In the coated steel pipe manufacturing equipment including the steel pipe rotating device and the coating gun conveying device, the second composition A and the B component of Example 1 were adjusted to a temperature of 65 캜 and a spraying pressure of 160 / kg using the two-component type high- And the bonding strength was measured by applying voltage to each electrode at the positive side of the voltage-adjustable direct current generator. In addition, there was no abnormality as a result of the elution test for water.

As a result, fine bubbles were not captured on the surface of the coating film even though the voltage was not applied. However, there was a slight decrease in gloss as compared with the third-order voltage of 10V.

Adhesion was improved in the 3rd order voltage 10V range even in the adhesive force. The surface condition was good even in the 4th and 5th times that the higher voltage was applied, but the adhesion increase was insignificant. Considering the risk of electric shock during operation, .

[Comparative Example]

A comparative experiment was conducted using a non-solvent reinforced polyurethane composition of the prior art (M Company, USA) in the same manner as in Example 9 above.

In the comparative example, many fine bubbles were observed on the surface of the coating film, and the gloss deteriorated considerably. This phenomenon appears to be insufficient in safety against moisture, and even when voltage is applied, there is no improvement in micro-bubbles or gloss reduction adhesion, which indicates that the liquid coating material of Dion is not polarized.

As a result, in the present invention, the polarity imparting property by the polydimethylsiloxane-modified mesoporous silica mixture and the oxazolidine derivative gives strong polarity, and the bubble formation is suppressed due to the water absorption property, thereby remarkably improving the inner coat property .

Claims (5)

Steel pipe; An inner coating film coated on an inner surface of the steel pipe and an outer coating film coated on an outer surface of the steel pipe,
The inner coating film
a first modified siloxane modified with an organic solvent by mixing and dispersing mesoporous silica with r-glycidoxypropyltrimethoxysilane;
a second modified siloxane modified with an organic solvent by mixing and dispersing mesoporous silica with r-aminopropyltrimethoxysilane;
The A-form of an isocyanate prepolymer obtained by mixing the first modified siloxane and diphenylmethane-4,4-diisocyanate (MDI)
Wherein the inner surface of the steel pipe is coated with a two-component organic-inorganic hybrid coating composed of the B component of a polyol group mixed with the second modified siloxane. The method according to claim 1,
Wherein the polyol group is a mixture of a trifunctional polyol having a molecular weight of 600, a bifunctional polyol having a molecular weight of 1,000, a trifunctional polyol having a molecular weight of 1,200, and a hydrogenated castor polyol. The method according to claim 1,
And the oxazolidine compound is contained in the B-form. Preparing a steel pipe for a water supply; Pretreating the outer surface of the steel pipe; Heating the steel pipe; Coating an outer surface of the steel pipe; Cooling the steel pipe; Pretreating the inner surface of the steel pipe; Coating the inner surface of the steel pipe and inspecting the inner surface of the steel pipe after completion of the coating,
The step of coating the outer surface comprises:
Forming a primary coating by thermal spray coating using powdered epoxy;
Forming a second conductive film by a thermal fusion coating using a modified polyethylene adhesive, and
And forming a tertiary film by thermally fusing and coating polyethylene,
Wherein coating the inner surface comprises:
The two-component type organic-inorganic hybrid coating material is applied while the voltage is applied to the steel pipe by connecting it to the anode of a direct current generator capable of voltage control,
The two-liquid type organic or inorganic composite coating material,
a first modified siloxane modified with an organic solvent by mixing and dispersing dried mesoporous silica with r-glycidoxypropyltrimethoxysilane;
a second modified siloxane modified with an organic solvent by mixing and dispersing mesoporous silica dried with r-aminopropyltrimethoxysilane;
The A-form of an isocyanate prepolymer obtained by mixing the first modified siloxane and diphenylmethane-4,4-diisocyanate (MDI)
And a B component of a polyol group mixed with the second modified siloxane. delete

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