KR100885469B1 - Double-layer coating method of steel pipe and double coated steel pipe - Google Patents

Abstract

The present invention is to coat the polyurethane-based resin coating paint to form a first, second coating layer on the outer surface of the steel pipe, the first coating layer is directly coated on the outer surface of the steel pipe is an inexpensive aromatic polyurethane resin Coating coating and coating on the outside of the first coating layer is coated with a weather-resistant aliphatic polyurethane resin coating coating to reduce corrosion or shorten the life of steel pipe caused by infrared rays or ultraviolet rays An object of the present invention is to provide a double coated coating method of a steel pipe and a double coated coated steel pipe which can prevent the phenomenon in advance.

To this end, the present invention, the foreign matter removal step of the steel pipe to cleanly remove the foreign matter on the surface of the steel pipe; A first coating layer coating coating step in which a main body and a curing agent are respectively contained in a two-component coating machine, heated at 70 ° C., and sprayed at a high pressure with an aromatic paint having a viscosity of 100 cps to 200 cps; A second coating layer coating coating step of coating an aliphatic paint having a viscosity of 150 cps to 300 cps on the outside of the first coating layer coated on the outer surface of the steel pipe by the first coating layer coating coating step; And a double coating coating method of the steel pipe, characterized in that it comprises a finishing step of coating the peeled off part after peeling off both sides of the second coating layer coated on the outer surface of the steel pipe by the coating step of the second coating layer,

A steel pipe having a coating layer formed on an outer surface thereof, wherein the coating layer comprises: a first coating layer formed by coating and coating a polyurethane resin directly on an outer surface of the steel pipe; It is made of a double coated coated steel pipe comprising a second coating layer formed by coating a polyurethane resin coating on the outside of the first coating layer.

In the present invention, the double coating coating method of the steel pipe and the double coating coating steel pipe are primarily coated with an aromatic polyurethane resin coating material and secondly with an aliphatic polyurethane resin coating material for coating coating on the outer surface of the steel pipe. By improving the adhesion of the primary and secondary paints with the same quality paint, the coating coating work is easy, and the external weather resistant aliphatic polyurethane resin coating material is coated on the outside of the steel pipe for a long time. Even if it is constructed, various problems caused by infrared rays or ultraviolet rays of sunlight can be solved to maintain the anticorrosive effect of steel pipe for a long time.

Steel pipe, painted coating, steel pipe coating, double coating, double coating

Description

Double-layer coating method of steel pipe and double coated steel pipe}

1 is a process chart showing the process of the double coating coating method of the present invention steel pipe.

Figure 2 is a partially cutaway perspective view showing the configuration of a double coated coating steel pipe by the method of double coating coating of the present invention steel pipe.

Figure 3 is a schematic diagram showing a part of the configuration of the double-coated coated steel pipe by the double-coated coating method of the present invention steel pipe.

<Description of the symbols for the main parts of the drawings>

S1: foreign material removal step S2: first coating layer coating coating step

S3: coating step of the second coating layer S4: finishing step

10: steel pipe 20: first coating layer

30: second coating layer

The present invention relates to a steel pipe, and more particularly, by coating a double layer of polyurethane coating on the outer surface of the steel pipe to improve the weather resistance of the steel pipe is buried underground, the corrosion of the steel pipe generated by moisture, as well as ultraviolet rays of sunlight The present invention relates to a double coated coating method of a steel pipe and a double coated coated steel pipe to prevent the performance degradation of the coating layer generated during long-term exposure, to prolong the life of the steel pipe installed outside and to prevent corrosion of the steel pipe.

In general, a pipe or pipe is a guide member for transporting a fluid, and these pipes are classified into steel pipes, copper pipes, cast iron pipes, and resin pipes according to materials, and fluids sensitive to temperature changes such as cold water, hot water, steam, oil, etc. When transporting, it is necessary to use a pipe made of materials having excellent performance such as rust prevention, anticorrosion, heat insulation, and cold storage to increase durability and preserve physical properties of the fluid to be transported.

Among these pipes, steel pipes are used in many places. If they are used for pipes or for structural purposes, there are some differences depending on the environmental conditions, but most of the steel pipes are corroded and shorten their lifespan. There are problems such as rebuilding the whole steel pipe.

In view of these problems, the anticorrosive treatment is performed on the inner and outer surfaces of the steel pipe, and a representative example of the anticorrosive treatment is a coating method for coating anticorrosive paint.

In the case of coating the steel pipe by coating the paint in this way, the corrosion of the steel pipe can be prevented to some extent, but especially in the case of the steel pipe which is naturally exposed to direct sunlight, the method may be applied by infrared rays or ultraviolet rays by direct sunlight ( Anti, anticorrosion (effective) is reduced, there is a problem to re-paint the anticorrosive coating on the outer surface of the constructed steel pipe or to replace the steel pipe.

The conventional method of coating the paint on the outer surface of the most commonly used steel pipe is a method of coating the outer surface of the steel pipe with polyethylene or coating coating with coal-tal enamel or asphalt, and with a high molecular compound recognized as a relatively new anticorrosive material. As a coating method, there is a method of coating an epoxy resin or a polyurethane resin.

Among them, polyethylene, coal enamel, and asphalt are prohibitively used in steel pipes which are constructed in an exposed environment because the above-mentioned degradation of coating performance is very severe when exposed to sunlight (sunlight). Epoxy resins have relatively good weather resistance, but the impact resistance, abrasion resistance, and adhesive strength of the coating film are lowered, so that it is not easy to coat the coating layer coated on the steel pipe with a thickness of 1 mm or more. As a result, the workability is deteriorated, and the cost burden caused by the mixing of other resins is increased, resulting in an economic disadvantage.

On the other hand, in the coating method using polyurethane resin, polyurethane resin has a weather resistance of more than epoxy resin and most of them are 100% solids and can be coated with a thickness of 1mm or more. According to the various physical and chemical properties, workability and economics, there are various differences, it is not easy to apply as a coating coating on the outer surface of the steel pipe.

Polyurethane can be applied to various industrial products by combining various isocyanates with polyols or amine resins, but it can be used as an anticorrosive material for coating and coating the outer surface of steel pipes. There are three types of elastic polyurea.

Since these polyurethanes have a characteristic of easily reacting with moisture to generate carbon dioxide, in the early days, industrialization began with the development of relatively moisture-insensitive elastic polyurethanes. Increasingly, it is increasingly used as a coating material for concrete structures.

In addition, the rigid polyurethane using the foaming characteristics are also mainly used as industrial foaming material, but a hard polyurethane resin that satisfies the requirements of coating coating method of steel pipes such as wear resistance and adhesiveness is being developed recently, and elastic polyurea is The company invented the so-called Jeffamine Polyether Amines (Jeffamine Polyether Amines) as a raw material, recently used as a coating coating anticorrosive coating for steel pipes.

These polyurethane resins are composed of two kinds of liquids, which are divided into a main agent and a hardener, and the two liquids are mixed and sprayed onto the steel pipe by a mechanical method immediately before coating, thereby coating the steel pipe. At room temperature, high viscosity of the paint is difficult to spray, lower the viscosity at approximately 70 ℃ and then spray at a high pressure of 150 ~ 200kg / ㎠ to proceed with the coating coating.

However, although the outer coating layer of the steel pipe coated with the polyurethane-based resin has a certain degree of weather resistance, when exposed to sunlight for a long time, the performance of the coating layer is deteriorated by ultraviolet rays or infrared rays, and various problems appear. In addition, in order to solve this problem, the coating can be made using a coating made using an aliphatic material resistant to ultraviolet rays, but with the use of expensive aliphatic raw materials, there is an economic burden. In addition, there is a method of coating more, but there is a problem that the workability due to the delay of curing of the fluorine resin coating film as well as the increase of the cost due to the high cost of the fluorine watch paint, it is possible to additionally apply other paint, This is due to the fact that the weatherability of the additionally applied paint is not very good or that it is a coating coating with a primary coating. The adhesion of the Li-based resin is held by this lowered.

The present invention was devised to solve the problems of steel pipes coated with a coating layer on the outer surface of the prior art, and the first and second coating layers are formed on the outer surface of the steel pipe by double coating and coating the polyurethane resin, but the outer surface of the steel pipe The first coating layer coated directly on the coating material coats an inexpensive aromatic polyurethane resin coating material, and the second coating layer coated on the outside of the first coating layer uses an aliphatic polyurethane resin material having high weather resistance. The purpose of the present invention is to provide a double coated coating method of a steel pipe and a double coated coated steel pipe which can be prevented in advance due to corrosion or shortened life of steel pipes generated by infrared rays or ultraviolet rays of sunlight by coating coating.

Double coated coating method and double coated coated steel pipe of the present invention as a means for achieving the above object, the foreign material removal step of the steel pipe to cleanly remove the foreign matter on the surface of the steel pipe; A first coating layer coating coating step in which a main body and a curing agent are respectively contained in a two-component coating machine, heated at 70 ° C., and sprayed at a high pressure with an aromatic paint having a viscosity of 100 cps to 200 cps; A second coating layer coating coating step of coating an aliphatic paint having a viscosity of 150 cps to 300 cps on the outside of the first coating layer coated on the outer surface of the steel pipe by the first coating layer coating coating step; And a double coating coating method of the steel pipe, characterized in that it comprises a finishing step of coating the peeled off part after peeling off both sides of the second coating layer coated on the outer surface of the steel pipe by the coating step of the second coating layer,

A steel pipe having a coating layer formed on an outer surface thereof, wherein the coating layer comprises: a first coating layer formed by coating and coating a polyurethane resin directly on an outer surface of the steel pipe; It is made of a double coated coated steel pipe comprising a second coating layer formed by coating a polyurethane resin coating on the outside of the first coating layer.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings, and the terminology or words used in the specification and claims are used to explain the invention in its best way. Based on the principle that the concept of can be properly defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

1 is a process chart showing a process of the double coating coating method of the present invention steel pipe, Figure 2 is a partially cutaway perspective view showing the configuration of a double coated coating steel pipe by the double coating coating method of the present invention, Figure 3 is the present inventor It is a partially omitted configuration diagram showing the configuration of a double coated coating steel pipe by the double coating coating method of the steel pipe.

As shown in the present invention, the double coating coating method and the double coating coating steel pipe of the present invention, the foreign matter removing step (S1), the first coating layer coating coating step (S2), the second coating layer coating coating step (S3) and the finish The double coated coating method of the steel pipe made of the process of step (S4), and is made by a double coated coated steel pipe manufactured by such a process.

The foreign material removal step (S1) is to remove the foreign matter on the surface of the steel pipe by using a blasting and a power tool, the roughness of the steel pipe surface after cleaning should be about 40㎛ ~ 80㎛, foreign matter removal degree Preference is given to Sa2.5 or higher of KS / ISO 8501-1.

If the roughness is lower than 40 microns, the size of the unevenness is small, so the adhesive strength of the paint may be lowered. On the contrary, the adhesive strength of the paint is increased when the roughness is higher than 80 microns. Since there is a problem of deterioration, the roughness of the steel pipe surface is preferably about 40 µm to 80 µm.

In addition, the foreign material removal degree Sa 2.5 in the foreign material removal step (S1) is the state that most of the rust is removed when cleaning through the blasting (blasting) to remove the rust and foreign matter adhering to the surface before coating the steel pipe In some cases, depending on the quality and characteristics of the paint and the importance of the painted steel pipe, Sa 2 may be required to have a degree of rust, or Sa 3 may be completely removed from rust. Most polymer paints and pipe steel pipes used for general water and oil transport use Sa 2.5 as a standard for surface cleaning.

In addition, the steel pipe from which the foreign matter is removed by the foreign matter removing step (S1) is preferably maintained so that foreign matter does not adhere to the surface again.

In the first coating layer coating coating step (S2), the main body and the hardener are each contained in a two-component coating machine, heated to 70 ° C., and coated by spraying an aromatic paint having a viscosity of 100 cps to 200 cps at a high pressure.

The reason why the paint is heated to 70 ° C is that the higher the viscosity of the paint is, the more uneven the mixing of the paint is, and the higher the resistance at the outlet of the nozzle tip located at the end of the spray gun, thus facilitating atomization and spraying of the paint. As a result, the paint is heated to keep the viscosity low so that the mixing of the paint is uniform and the spray gun is easily sprayed. At this time, when the temperature of the paint is overheated to 90 ° C. or higher, the viscosity is lowered, but the paint is easily vaporized. Since there is a risk of evaporation or bubbles in the coating film is to be heated to 70 ℃ from the stable side, even if heated up to about 80 ℃ is not a big burden, but there is a high risk of overheating.

In addition, the viscosity of the paint is 100cps ~ 200cps, the polyurethane paint applied to the present invention uses a device that is mixed immediately before the spray gun in a state where the two liquids are separated in a separate container, wherein The paint contained in the container has a different viscosity at each room temperature before heating, and if the paints have different viscosity, friction loss occurs in the supply hose until the spray gun reaches the spray gun. Differences can occur depending on the amount of paint reached, and it may be difficult to maintain the correct mixing ratio even during the mixing process just before the spray gun, so that the two paints maintain similar viscosity when heating the paint to 70 ° C. This is because the viscosity is 100cps ~ 200cps so that it can flow smoothly through the supply hose.

The two-component coating machine is provided with a container containing a main material and a hardener, which are the constituent materials of the polyurethane resin coating material, and a pressure feeding part for feeding the contained main material and the hardener to the spraying part at a constant ratio, and the pressure feeding part by the pressure feeding part. It is composed of an injection part (spray gun, etc.) to be sprayed and is a super-speed reaction type in which the reaction is initiated between several seconds to several tens of seconds when the main body and the curing agent are mixed, and the viscosity of the main body and the curing agent is very different. As it is high, each container and mixing device are required, and the spray pressure of the mixed paint should be about 150kg / ㎠ ~ 200kg / ㎠.

The reason for spraying the mixed paint at a pressure of 150kg / cm2 to 200kg / cm2 is that the hot-mixed paint is sprayed at high speed through the nozzle hole in the spray tip of the spray gun, and the coating coating is applied to the surface of the steel pipe in the form of fine particles. Bar and spray pressure is very important to maintain a constant spray pattern (the spreading width and spraying amount of sprayed paint) while the paint passes through the fine nozzle hole, 150kg / ㎠ ~ 200kg for heat-mixed viscosity 100cps ~ 200cps Spraying at a pressure of / cm2 maintains a consistent spray pattern.

Of course, the spray pattern can be maintained even at higher or lower pressures depending on the paint, and the pressure range may not be increased or limited unless the paint is specifically defined.

What is necessary is to coat and coat the 1st coating layer on the outer surface of a steel pipe using the 2-component sprayer comprised in this way, The main body and the hardening | curing agent compressed by high pressure in the inside of a sprayer are supplied along the separate passage to the mixing part just before an injection part, The high-pressure main body and the hardening agent reached to the mixing part were mixed at a high speed, and then applied to the outer surface of the steel pipe at high pressure through the spraying part to coat the first coating layer. As the curing proceeds between about several tens of minutes, a hard first coating layer is formed.

The second coating layer coating coating step (S3), Aliphatic polyurethane resin having a viscosity of 150cps ~ 300cps on the outside of the first coating layer coated on the outer surface of the steel pipe by the first coating layer coating coating step (S1). Coat the paint.

The aliphatic polyurethane resin may be used by selecting any one of two kinds, one of which is the amount of the catalyst in the raw material added to the main material or the curing agent to the minimum amount necessary for the reaction and a small amount of solvent The reaction rate was delayed (up to 30 minutes) by adding an aliphatic polyurethane resin which sufficiently lowered the viscosity from 150 cps to 300 cps at room temperature. The main body and the curing agent were poured into one container immediately before the coating operation and mixed. Then, low pressure spraying at 5 kg / cm 2 or less with a one-component air spray gun or low pressure spray coating at around 100 kg / cm 2 with a one-component airless spray sprayer.

At this time, the reason why the low-pressure spraying to less than 5kg / ㎠ with the one-component air spray gun is that the air spray gun uses compressed air produced using a compressed air generator such as an air compressor, supplying compressed air to the air spray gun When the supply hose is connected, the mixed paint is put into the container attached to the air spray gun, and the nozzle is opened, and when the compressed air is ejected, the paint is sprayed by using the generated airflow to store the compressed air. This is because the container is used at a low pressure of 10 kg / cm 2 or less in view of the risk of explosion, and therefore, it is preferable to spray at a low pressure of 5 kg / cm 2 or less.

In addition, the reason why the low-pressure spray coating to 100kg / ㎠ around the one-component airless spray sprayer, the second coating layer coating coating step (S3) even if the coating coating using a one-component airless spray painter so as to form a thin coating layer as possible as possible. In order to spray the spraying pressure of the one-component airless spray painter as low as possible around 100kg / ㎠.

The other is to use aliphatic polyurethane resin paint prepared in a one-component water reaction type, which is contained in a sealed container in a state in which a main agent and a curing agent are mixed, and then the container is opened and painted. As a coating material which gradually reacts and hardens with moisture, a water reaction type containing a raw material containing free isocyanate and a triol polymer is suitable.

The reason why the aliphatic polyurethane resin in the second coating layer coating coating step S3 has a viscosity of 150 cps to 300 cps is that the second coating layer coating coating step S3 is different from the first coating layer coating step S2. Otherwise, the two paints must be premixed in one container at room temperature and then sprayed to form a coating layer at a relatively low pressure using a one-part spray painter to form a coating layer as thin as possible. Since the viscosity of the paint should not be high so as to limit the viscosity of the paint to 150cps ~ 300cps, the viscosity of the paint may vary beyond the viscosity range of the paint manufacturer, of course.

In addition, in the second coating layer coating coating step (S3), the paint is sprayed by a one-component coating machine, but is not limited to this, just like the first coating layer coating coating step (S1), the coating material immediately before the spray gun inside the mechanical device. It is also possible to use an internal mixed two-component sprayer which is automatically mixed in the.

The finishing support system (S4), by partially peeling off both sides of the second coating layer coated on the outer surface of the steel pipe by the second coating layer coating coating step (S3), and finish coating the peeled portion, temporarily rust prevent the peeled portion We paint with shop primer.

Peel off the polyurethane coating film coated on both ends of the coated steel pipe in the finishing step (S4) by a certain distance (usually around 100mm) from both ends of the steel pipe, and then by coating the portion with a shop primer for temporary rust prevention Is complete.

The peeling of the anticorrosive coating film at both ends of the steel pipe is to prevent the coating film from being damaged by heat effect when welding the steel pipe in the field, and to prevent the welding work. Before coating the first coating layer in the first coating layer coating coating step (S2), cover the tape or paper by a certain distance before uncoating, and after completing the first coating layer and the second coating layer coating coating step, It is desirable to peel off the paper.

The coating material applied in the first coating layer coating coating step of the double coating coating method of the steel pipe of the present invention refers to a polyurethane resin coating material, specifically, a solvent-free hard polyurethane resin coating material of 100% solids, or 100 It may be a solvent-free elastic polyurethane-based resin material of% solids, or a solvent-free elastic polyurea resin of 100% solids, and should be considered to include all such resins even if the present invention is described separately.

The steel pipe applied to the double coated coated steel pipe by the double coating coating method of such a steel pipe can be made of various steel pipes such as shapes such as straight pipes and shaped pipes as well as its inner diameter, outer diameter and length thickness.

Double coated coated steel pipe of the present invention, in the steel pipe 10 having a coating layer formed on the outer surface, as shown in Figure 2 and 3, the first formed by coating the polyurethane resin coating directly on the outer surface of the steel pipe 10 The coating layer 20 and the second coating layer 30 formed by coating a polyurethane resin on the outside of the first coating layer 20.

The polyurethane resin coating material forming the first coating layer 20 is made of an aromatic polyurethane resin material, and the polyurethane resin coating material forming the second coating layer 30 is aliphatic having excellent weather resistance. ) It consists of polyurethane resin.

Therefore, although the first coating layer 20 is different depending on the external corrosion environment, it protects the steel pipe 10 from external impact and preserves a predetermined anticorrosive effect, and the thickness of the first coating layer 20 is 0.6 mm to It is good to form 3.0mm.

In addition, the second coating layer 30 is preferably coated as thin as possible, but in order to form a good adhesion with the first coating layer 20, and to be protected from direct sunlight of the second coating layer 30 ), The thickness is preferably 0.05mm to 0.10mm.

The reason why the thickness of the first coating layer 20 is 0.6 to 3.0 mm is that the first coating layer 20 functions as a pivotal function of the protective coating protecting the steel pipe, and a minimum value of 0.5 mm with respect to the coating film thickness of the similar polymer coating. Or it is specified as about 0.6mm and the maximum value may vary depending on the corrosive environment around the steel pipe, but 3.0mm is suitable in terms of paint quality, maintenance life and economics.

The reason why the thickness of the second coating layer 30 is 0.05 to 0.10 mm is to prevent the second coating layer 30 from deteriorating the first coating layer 20 due to ultraviolet rays, and the first coating layer 20. The thickness of the second coating layer 30 is preferably formed to a suitable thickness of 0.05 ~ 0.10mm in order to maintain the adhesion to the) and the minimum coating thickness required for the UV blocking effect, and to avoid excessive coating thickness in terms of economics. Because.

In the double-coated coated steel pipe of the present invention, the first coating layer 20, which is an aromatic polyurethane resin coating coating, is coated on the outer surface of the steel pipe 10, and is further aliphatic on the outside of the first coating layer 20. As the second coating layer 30, which is a polyurethane resin, is coated and coated, it prevents corrosion of the steel pipe as well as protecting against external impact of the steel pipe 10, and in particular, an aliphatic polyurethane resin coating material having excellent weather resistance. The second coating layer 30 may solve various problems caused by infrared rays or ultraviolet rays of the sunlight, so that no problem occurs even when installed outdoors for a long time.

The double coated coating method and the double coated coated steel pipe of the present invention is capable of various modifications in addition to those shown and described as long as it does not depart from the scope of the present invention, all the embodiments to be modified are within the scope of the present invention. It should be included and interpreted.

As described above, the double coated coating method and the double coated coated steel pipe of the present invention, when coating the coating on the outer surface of the steel pipe, firstly coating an aromatic polyurethane resin coating material, and secondly aliphatic polyurethane resin By painting the paint, the adhesion of the first and second paints is improved by the same quality paint, so that the coating coating work is easily performed, and the external weather resistant aliphatic polyurethane resin coating material is coated on the outside of the steel pipe. Therefore, even if the construction for a long time to the outside, various problems caused by infrared rays or ultraviolet rays of the sun light is solved can maintain the anticorrosive effect of the steel pipe for a long time.

Claims (7)

Removing foreign substances in the steel pipe to cleanly remove foreign substances on the surface of the steel pipe; A first coating layer coating coating step in which a main body and a curing agent are respectively contained in a two-component coating machine, heated at 70 ° C., and sprayed at a high pressure with an aromatic paint having a viscosity of 100 cps to 200 cps; A second coating layer coating coating step of coating an aliphatic paint having a viscosity of 150 cps to 300 cps on the outside of the first coating layer coated on the outer surface of the steel pipe by the first coating layer coating coating step; The coating method of the double coating coating of the steel pipe, characterized in that it comprises a finishing step of coating the peeled part after peeling off both sides of the second coating layer coated on the outer surface of the steel pipe by the coating step of the second coating layer. The method of claim 1, The coating applied in the coating step of coating the first coating layer is a double coating coating method of a steel pipe, characterized in that the non-solvent-type hard polyurethane resin coating material of 100% solids. The method of claim 1, The coating applied in the coating step of coating the first coating layer is a double coating coating method of a steel pipe, characterized in that the solvent-free elastic polyurethane resin coating material of 100% solids. The method of claim 1, The coating applied in the coating step of coating the first coating layer is a double coating coating method of a steel pipe, characterized in that the solvent-free elastic polyurea resin of 100% solids. Double coated coated steel pipe manufactured by the method of claim 1. delete delete

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