WO2002061004A1

WO2002061004A1 - Coating paint being dried speedly for rust proofing

Info

Publication number: WO2002061004A1
Application number: PCT/KR2001/000600
Authority: WO
Inventors: Hyung Dong Chung
Original assignee: Hyung Dong Chung
Priority date: 2001-02-01
Filing date: 2001-04-10
Publication date: 2002-08-08
Also published as: KR20010035294A

Abstract

A fast rust-preventive coating composition obtained by mixing a basis and a curing agent with a urethane-bond containing resin in a ratio of 10 : 1, respectively and then adding thereto a thinner, anti-foaming agent, and drying accelerator in a predetermined ratio. The rust-preventive coating agent of the present invention, when sprayed onto a substance to be coated, can be rapidly dried in a state where the MEK-resistance, acid-resistance, abrasion-resistance, adhesion property, etc. are supplemented, which in turn improves operability. Because the subject rust-preventive coating agent can be dried immediately after coating on speedily processed item such as a press, in the state wherein the adhesion, MEK-resistance, chemical-resistance, harness, acid-resistance, etc. are supplemented, it enables easy and rapid handling of the subsequent operations.

Description

COATING PAINT BEING DRIED SPEEDLY FOR RUST PROOFING

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fast drying rust-preventive coating agent.

More particularly, the rust-preventive coating agent of the present invention is prepared by mixing a basis and a curing agent with a urethane-bond containing resin in a ratio of 10 : 1, respectively and then adding thereto a thinner, anti-foaming agent, and drying accelerator in a predetermined ratio.

2. Description of the Background Art

It is well known that a film formed on a coil, steel sheet, etc. by a curing system of a coating agent has a macrorholecular dense structure due to a chemical reaction.

Such dense structure allows a good solvent-resistance, high blocking property against a foreign material such as a moisture or a gas, etc., which in turn provides a more extended durability compared to that of a thermoplastic resin.

However, there have been several problems with such coating agents. For example, bisphenol A-type epoxy resin which is the one of the most widely used paint resin has many advantages such as a good adhesion, good chemical-resistance, high mechanical strength, reasonable price as well as an easy curing at a room temperature.

But, this resin has a problem of unpleasant odor and high toxicity when amine is used as a curing agent. Because of such problem, polyamide resin has been tried as a curing agent, but in this case, it is difficult to obtain a cross-linking degree as high as in the case of amine, which leads to the disadvantages such as slow drying and deterioration of physicochemical properties. Further, bisphenol A-type epoxy resin is generally suffered from poor weatherability due to its unique structure and because of the yellowing resulted from amine curing, it is difficult to apply the same on an outside part of a stove. Lots of measures have been suggested to solve the above-mentioned prior art problems. US Patent No. 4,525,521 describes a method for preparing coating composition comprising reacting carboxyl group containing acrylic resin with an alkylene amine, or glycidyl group containing acrylic resin with an ammonia to obtain an acrylic resin having pendent primary amine and then curing the same with an epoxy resin. Japanese Laid-Open Patent Publication No. 63-30521 discloses a method for preparing a resin having a pendant ketimine by reacting the said acrylic resin with a ketone.

Although the above referenced techniques are characterized by the introduction of acrylic resin that has a good weatherability while maintaining the speedy drying property, it is difficult to commercialize these methods due to the excessive costs for handling and the toxicity of the raw materials, etc.

SUMMARY OF THE INVENTION The present invention solves the aforementioned prior art problems by providing a rust-preventive coating agent, which is prepared by mixing a basis and a curing agent with a urethane-bond containing resin in a ratio of 10 : 1, respectively and then adding thereto a thinner, anti-foaming agent, and drying accelerator in a predetermined ratio. The thusly-obtained anti-rust coating agent, when sprayed onto a substance to be coated, can be rapidly dried in a state where the MEK-resistance, acid- resistance, abrasion-resistance, adhesion property, etc. are supplemented, which in turn improves operability.

Therefore, it is an object of the present invention to provide a fast-drying rust- preventive coating agent that enables improving operability as aforementioned. Any further objects of the present invention will be clearly understood in view of the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

In order to achieve the above objects, a preferred embodiment of the present invention provides a rust-preventive coating agent as a urethane bond-containing polyurethane type resin, obtained by reacting isocyanate group-containing compound with a hydroxyl group-containing compound. More particularly, the coating agent of the present invention is prepared by mixing a polyol basis solution and polyisocyanate curing agent solution with a urethane-bond containing resin in a ratio of 10 : 1, respectively and then adding thereto a thinner, anti-foaming agent, and drying accelerator in a predetermined ratio. The obtained fast drying rust-preventive coating agent of the present invention, when sprayed on the subject to be coated and dried, forms a glossy film.

The above basis is preferably selected from the group consisting of a fatty acid modified polyester, vinyl modified polyester, acryl polyol, and oil-free polyester. It is also preferred to use a curing agent selected from the group consisting of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate (MDI), and p-phenylene diisocyanate.

As thinner, it is preferable to use a low-b.p. solvent having a boiling point of not more than 100^°C which can dissolve the resin by itself. As anti-foaming agent, it can be mentioned silicones and acryl resin. A drying accelerator can be a tertiary amine or a metal salt (Co, Pb, Mn).

The solid content of the coating agent of the present invention is 20 ~ 30% and the drying condition of the coating subject to be coated with the present coating agent is for 30 seconds at a room temperature, or 5 ~ 10 seconds in an oven at 60 ^°C .

Hereinafter, the present invention is explained in more detail.

Generally 50 ~ 90% of paint loss is occurred because the paint is attached on a subject to be coated in an impactive manner by a spray-coating which uses a pressed air to inject paints with no flames. Considering that the air-spraying amounts to about 70% of spraying method, it will be preferable to employ lift type method to coat the coating agent of the present invention. Depending upon the supplying manner of the paints, the coating method can be categorized into lift type, forced delivery type and gravity type. Among them, the lift type method is advantageous as long as it is possible to obtain fine particles, to control the patterns as one wish, and the paint is of a low viscosity. Further, in the case of air-spray, the spray gun should be of small caliber (1 ~

1.3 mm), and the spraying distance is suitable at 10 ~ 20 cm. However, the distance can be decreased in the case of local coating. Normally, the spray gun is operated at a rate of 20 ~ 50 cm/sec.

On the other hand, it is also appropriate to use an airless process that enables a homogeneous coating with decreased scattering of paint for spraying the coating agent of the present invention. It is the principle of the airless spray that the highly pressed paint is delivered without flames into a small hole on the spray nozzle. The nozzle is used at 0.381 m/m and the coating angle will be 60°. The air pressure is adjusted to 3.0 ~ 4.5 kg/cm while the paint pressure is adjusted to 60 ~ 90 kg/cm. The maximum pressure of pump is normally around 3,000 psig. The thickness of the hose is usually 6 ~ 9 m/m which thickness endures even at 8,000 ~ 10,000 psig.

In the case of a spray coating, high viscosity of coating results in a poor smoothness and the discharging property also decreases. On the other hand, if the viscosity of the coating is low, non- volatile components decrease and swelling becomes poor, which can influence an adverse effect on rust-proofing.

Preferably, the viscosity of the fast drying rust-preventive coating agent of the present invention is 20-30 seconds with a Ford cup 4 and normally, the optimal temperature of the coating room is 20±5 ^°C .

The fast drying rust-preventive coating agent of the present invention can also be used for preventing corrosion of a cutting area of a tin plate, TFS sheet, and coil. Further, the fast drying rust-preventive coating agent of the present invention has been greatly improved in the aspect of the instant drying ability (wherein the drying refers to a surface track free drying), adhesion to the matrix, retort property, MEK-resistance, bath hardness as well as acid-resistance. In addition, a specified kind of thinner should be used in order to reduce sagging of the present coating agent. The pressed air must be free of moisture, oil, or dust because such impurities deteriorate the mechanical function of the accessories such as compressor, cylinder, etc. Further, the air should not be excessively hot or cold.

The following examples are set forth to illustrate more clearly the principles and practice of the present invention to a person skilled in the art. As such, they are not intended to limit the invention, but are illustrative f certain preferred embodiments. Examples The composition of the fast drying rust-preventive coating agent

The rust-preventive coating agent of the present invention comprises a urethane bond-containing polyurethane resin, as a reaction product of isocyanate group- containing compound and a hydroxyl group-containing compound.

With the aforementioned urethane paint, it is possible to obtain a glossy film of high density. It also renders good physical properties such as high abrasion-, chemical-, and shock-resistance, good adhesion, hardness, excellent bending and retort property, etc.

The urethane bond containing resin, polyol basis, and polyisocyanate solution as a curing agent is stored separately in different containers until mixed altogether with thinner to obtain the rust-prevent coating agent of the present invention.

The reaction mechanism of the coating agent of the present invention can be summarized as in the following reaction scheme 1.

Reaction scheme 1

R-N=C=O+R'-HO(Polyisocyanate)→ R-N-C-O-R'(Polyurethane)

The basis can be selected from the group consisting of a fatty acid modified polyester, vinyl modified polyester, acryl polyol, and oil-free polyester.

Acryl polyol dries fast, and has excellent transparency and yellowing-resistance. Polyester polyol has superior flexibility and solvent-resistance as well as good abrasion, toughness and luster. While polyester polyol is flexible, it dries slowly. On the other hand, alkyd polyol dries fast and is cheap.

The reaction between the curing agent, i.e. isocyanate and the basis which is an active hydrogen compound is an addition reaction of active hydrogen compound to an isocyanate. More basic the active hydrogen compound, the higher the reaction rate. Thus, the reaction rate is slower in an acidic atmosphere than in a moderate atmosphere. But, when OH% of basis increases, the stickiness, chemical-resistance, hardness and drying property, etc. are improved while the flexibility is decreased.

The curing agent is selected from the group consisting of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate (MDI), and p-phenylene diisocyanate. The coating agent of the present invention is obtained by mixing basis and curing agent in a 10:1 ratio and diluting the same with a thinner appropriately depending on the particular operational need. , Thinner is used at 50-100% dilution. Thinner is a true solvent which can dissolve resin by itself and it influences on operation efficiency, storability, and physical properties of film obtained. A Low boiling point-solvent of b.p. of not more than 100^°C is used as a thinner.

However, it should be noted that a thinner having a hydroxyl group might result in extended suspending time, poor dryness, air bubble, etc. It can be mentioned isobutyl acetate, cyclohexane, ethyl acetate, β-butanol, isopropyl acetate, etc. as a hydroxyl group containing thinner. Further, an appropriate amount of additive can be added in order to prevent film deficiency such as orange peel, cratering, seeding, brushing, pinhole, etc.

The above additive may contain anti-foaming agent and drying accelerator. As anti-foaming agent, it can be mentioned silicones, acryl resin and as drying accelerator, tertiary amine or metal salt (Co, Pb, Mn) can be used. Further, silicon, N.C., vinyle can be preferably used as a leveling agent.

The solid content of the coating agent of the present invention is 20 ~ 30% and the drying condition (in terms of surface track free) is 30 seconds at a room temperature and 5 - 10 seconds in an oven at 60 ^°C .

Moreover, the rust-preventive coating agent of the present invention is designed to be adhered not only on the subject to be coated such as tin plate, TFS sheet, and coil itself, but also on sizer coating or white coating. Thus, there is no problem of rust peeling during post-processing or on storage.

Sizer coating material can be thermosetting epoxy, vinyl material, and as white coating, it can be mentioned polyester resin type , epoxy-urea resin type, vinyl resin type, acryl resin type, etc.

It must be assured that any dust or foreign material should not flow into the coating agent and after finishing work, nozzle and filter must be washed. A fine dry weather is best for operation. In a rainy season of high humidity, the surface becomes white as if it frosts. Careful attention should be made on the generation of foam, pin hole, etc. and even the coating is finished, dust or foreign material must be kept away.

As discussed heretofore, the fast drying rust-preventive coating agent of the present invention can be dried immediately after coating on speedily processed item such as a press, in the state wherein the adhesion, MEK-resistance, chemical-resistance, harness, acid-resistance, etc. are supplemented. Thus, the coating agent of the present invention enables easy and rapid handling of the subsequent operations.

Claims

What is claimed is:

1. A fast drying rust-preventive coating agent in the form of a urethane bond- containing polyurethane resin as a reaction product of a isocyanate group containing compound and a hydroxyl group containing compound, which coating agent is obtained by mixing a polyol basis solution and a polyisocyanate curing agent solution with a urethane-bond containing resin in a ratio of 10 : 1, respectively and then adding thereto a thinner, anti-foaming agent, and drying accelerator in a predetermined ratio.

2. The coating agent according to claim 1 wherein said basis is selected from the group consisting of fatty acid modified polyester, vinyl modified polyester, acryl polyol, and oil free polyester.

3. The coating agent according to claim 1 wherein the said curing agent is selected from the group consisting of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and p-phenylene diisocyanate.

4. The coating agent according to claim 1 wherein the said thinner is a low-b.p. solvent having the boiling point of not more than 100^°C which can dissolve the resin by itself and used at 50-100% dilution.

5. The coating agent according to claim 1 wherein the said anti-foaming agent is silicones or acryl resin.

6. The coating agent according to claim 1 wherein the said drying accelerator is a tertiary amine or a metal salt (Co, Pb, Mn).

7. The coating agent according to claim 1 which has the solid content of 20 - 30%.

8. The coating agent according to claim 1 wherein the drying is performed for 30 seconds at a room temperature or 5 - 10 seconds in an oven of 60 ^°C .