KR100299458B1 - A forming method of thermal spray coating of thermoplastic resins having good adhesive strength and corrosion resistance - Google Patents

Abstract

PURPOSE: Provided is a method for forming a film of molten thermoplastic resin excellent in adhesion and corrosion resistance by spraying, without requiring a preheating step. CONSTITUTION: The method comprises the steps of: (i) applying adhesive primer with a thickness of 80 micrometer on substrate to be applied by spraying or brushing, and (ii) spraying a molten thermoplastic resin on the applied primer. The adhesive primer is prepared by mixing epoxy resin having an epoxy equivalent of 160-220 and viscosity of 3,000 centipoise or less at 25 deg.C with an amine hardener so that ratio of epoxy equivalent and active hydrogen equivalent is 1:0.5-1.5. The film formed by the method has adhesion strength of 80 kg/cm¬2 and more.

Description

A forming method of thermal spray coating of thermoplastic resins having good adhesive strength and corrosion resistance}

The present invention relates to a method for forming a thermal spray coating of a thermoplastic resin having excellent adhesion and corrosion resistance, and more particularly, by applying an adhesive primer to a surface of a thermal sprayed coating that is not preheated, and then forming a thermoplastic spray coating, A method for forming an excellent thermoplastic resin thermal spray coating.

Contents of various structures and plant facilities are prolonged, and a long-term maintenance-free coating method is required, and a desire for high-performance anticorrosive materials is increasing. As one method for this, a method of coating a thermoplastic resin excellent in corrosion resistance showing stable properties for a long time is performed.

The polymer spraying method is a method of thermally spraying a resin to form a film, which does not require heating equipment and has a feature that can be simply coated as compared to other powder coating methods. Methods and apparatuses for coating thermoplastics, in particular metals, by thermal spraying are shown, for example, in US Pat. Nos. 4,632,309 and 4,934,595. These methods and devices are intended to melt powdered thermoplastics and apply a guaranteed coating to a wide range of coatings, including coatings of structural steel used in bridges or other constructions, coatings of piping or vessels that resist corrosion, and coatings of ship floors and other. It is possible to handle other parts.

However, such a conventional polymer resin thermal spraying method is inevitable to preheat the workpiece. If the polymer resin is sprayed without preheating, the film of molten polymer resin is cooled and hardened on the surface of the coating, and the shrinkage stress and cohesion of the coating is greater than the adhesion between the coating and the polymer resin. A defect may occur. Therefore, there are a number of problems in the application and construction of large structures where uniform enough preheating is difficult.

Accordingly, an object of the present invention is to provide a method for forming a thermal sprayed coating of a thermoplastic resin having excellent adhesion and corrosion resistance by applying an adhesive primer to the surface of the thermally sprayed unheated coating and then forming a thermoplastic sprayed coating.

According to the invention,

On the blood

Epoxy resin with an epoxy equivalent of 160-220 and an epoxy resin having an viscosity of 3,000 centipoise or less at 25 ° C. and an amine curing agent in a ratio of 1: 0.5-1.5 equivalent ratio of epoxy equivalent and active hydrogen equivalent by spray or brush Applying the coating film within 80 μm thickness; And

Spraying the molten thermoplastic resin on the coating;

Provided is a method for forming a thermoplastic resin sprayed coating having an adhesive strength of sprayed coating strength of 80 kg / cm 2 or more.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The adhesive primer used in the thermoplastic resin spray coating method of the present invention should have good adhesion between the coating object and the thermal spray thermoplastic resin, thermal stability to the thermal spraying flame, and durability of the adhesive force. In particular, the adhesive strength of the primer should be higher than the cohesion force when the thermoplastic sprayed coating is hardened to prevent cracking and peeling.

As the adhesive primer used in the present invention, an epoxy resin and an amine curing agent are mixed and applied to the coated object.

As said epoxy resin, 1 type (s) or 2 or more types of epoxy resins of bisphenol-A diglycidyl ether, phenol novolak-type diglycidyl ether, and bisphenol F-type diglycidyl ether can be used.

The low viscosity type whose epoxy equivalent of these epoxy resins is 3,000 centipoise or less in 160-220 and 25 degreeC is preferable. This is because when the epoxy resin is applied for use as a primer, it can be applied by spraying or brushing without adding an organic solvent.

In case of applying high viscosity epoxy resin with more than 3,000 centipoise of adhesiveness, workability is inferior and should be primer-treated by adding organic solvent. In this case, there is a disadvantage in that the organic solvent contained in the primer layer is volatilized by the flame of the thermal spraying machine to generate a pinhole in the thermal spray coating of the thermoplastic resin when the thermal spray coating of the thermoplastic resin is performed in a post process.

The amine curing agent component to be mixed with the epoxy resin can be selected from polyoxypropylenediamine, cycloaliphatic modified amines, polyamideamines and aromatic modified amines, or mixtures thereof. These amine curing agents preferably have an active hydrogen equivalent weight of 80-180.

In the case of handling, when the molecular weight of an amine hardener is high, a viscosity will also become high and a pinhole will generate | occur | produce in a thermoplastic resin spray coating, since an organic solvent must be diluted and used.

The mixing ratio of the epoxy equivalent to the active hydrogen equivalent of the amine curing agent is preferably in the range of 1: 0.5 to 1.5 for mixing the epoxy resin and the amine curing agent. If the mixing ratio is less than 0.5, the adhesion and the corrosion resistance of the thermal sprayed coating are deteriorated in the long term. When the mixing ratio exceeds 1.5, excessive curing occurs, which is not preferable.

The adhesive primer is applied to the coating film thickness of 80㎛ using a spray or a brush. When the coating thickness is larger than 80 µm, the unreacted epoxy resin and the amine curing agent contained in the primer layer are volatilized by the thermal spraying flame to coat the thermoplastic resin in a subsequent step, thereby causing pinholes in the thermal spray coating.

A molten thermoplastic resin is attached to the coating object to which the primer is applied to form a thermal spray coating.

Suitable thermoplastic resins for use in the present invention include polyethylene, polypropylene, nylon, polyester resins, polybutylene resins, fluorinated resins, ethylene vinyl acetate copolymers, and the like. Polyethylene resins may be selected from maleic acid, acrylic acid, methacrylic acid, and the like. Modified polyethylene resins modified with unsaturated carboxylic acids or acid anhydrides may also be used.

The thermal spray at the time of forming the thermal spray coating is heated to a temperature higher than the melting point of the thermoplastic resin and lower than the temperature at which the thermoplastic resin is carbonized, fired or aged.

In general, excessive thermal spraying can be minimized by directing thermal spraying to a new area when the surface coating is observed by visual inspection.

The thickness of the thermoplastic sprayed coating is generally in the range of 200-3,000 μm, but this depends on the size, shape and material of the coating, the use, the use environment, and the properties required during use.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

For the method of forming the thermoplastic resin thermal spray coating of the present invention, a hot rolled steel sheet having a thickness of 2 mm without black skin was washed with an organic solvent to remove only surface contamination. As the components of the adhesive primer, the main primer and the curing agent shown in Table 1 were prepared in the compositions shown in Examples 1-2 and Comparative Examples 1-4 of Table 2, and the coatings were sprayed into the coating to within 50 µm.

Thereafter, by spraying PF111 (plastic flamecoat systems, ethylene acrylic acid copolymer having a melting point of 105 ° C.) with a thermoplastic resin on the coating object, a thermoplastic resin spray coating having a thickness of about 500 μm was formed. The fuel gases used in the Flame Spray Gun are propane and air.

The surface condition of the specimens was visually determined and the corrosion resistance test by 90 ° peel adhesion strength and salt spray test was performed. The 90 ° peel adhesion strength was averaged by measuring the adhesive strength at least 5 times with the width of the thermal spray coating being 15 mm and the cross-head speed of 25 mm / min in a universal tensile tester.

In order to measure the corrosion resistance of the thermal sprayed coating, a salt spray test was conducted by KS D 9502 to measure the time taken until the coating peeling occurred at the cross cut.

Adhesive Primer Manufacturing Ingredients Topic type Epoxy equivalent weight (g / eq) Viscosity (cps) importance Remarks R1 195-215 800-1,600 1.15 Low viscosity resin R2 184-190 11,500-13,500 1.17 Mid-density Resin R3 450-500 - 1.16-1.20 Solid resin R4 1 component urethane resin

Hardener type Active hydrogen equivalent (g / eq) Remarks C1 82-90 Polyoxypropylene diamine C2 95-110 Cycloaliphatic modified amines

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Adhesive primer subject R1 (100 g) R1 (100 g) - R4 (100 g) R2 (100 g) R3 (100 g) Hardener C1 (42 g) C2 (55 g) - - C1 (42 g) C1 (13 g) MEK - - - - 20 g 20 g Surface condition Good Good Good Good Pinhole generation Pinhole generation 90 ° Peel Adhesive Strength (g / mm) 198 139 95 88 180 69 Corrosion Resistance (Sun) 120 days or more 120 days or more 10 days 7 days 120 days or more 120 days or more

* MEK = methyl ethyl ketone

As can be seen from Table 2, Example 1-2, which satisfies the scope of the present invention, has a good surface state, adhesive strength of 139 g / mm or more, and corrosion resistance of 120 days or more. However, when the adhesive primer was not used (Comparative Example 1) or only the main material (Comparative Example 2), the adhesive strength and the corrosion resistance rapidly decreased. In addition, Comparative Examples 3 and 4 have excellent corrosion resistance, but due to the organic solvent (MEK) used for the workability of the adhesive primer, pinholes are generated in the thermal spray coating.

As described above, the thermoplastic resin thermal spray coating method of the present invention can form a thermoplastic resin thermal spray coating excellent in adhesion and corrosion resistance without preheating the coating object.

Claims (4)

On the blood Epoxy resin and amine curing agent of epoxy equivalent of 160-220 and viscosity of 3,000 centipoise or less at 25 ° C are mixed in a ratio of 1: 0.5-1.5 equivalents of epoxy equivalent and active hydrogen equivalent by spraying or brushing. Coating to a thickness of 80 μm or less; And Spraying the molten thermoplastic resin on the coating; A method of forming a thermal sprayed thermoplastic film having an adhesive strength of at least 80 kg / cm 2 of sprayed coating strength The method of claim 1, wherein the epoxy resin is selected from the group consisting of bisphenol A diglycidyl ether, phenol novolak diglycidyl ether, and bisphenol F diglycidyl ether. The method of claim 1, wherein the amine curing agent is selected from the group consisting of polyoxypropylene diamine, cycloaliphatic modified amine, polyamide amine and aromatic modified amine or mixtures thereof, characterized in that the active hydrogen equivalent weight of 80-180 Way The method of claim 1, wherein the thermoplastic resin is selected from the group consisting of polyethylene, polypropylene, nylon, polyester resin, polybutylene resin, fluorinated resin, ethylene vinyl acetate copolymer or modified polyethylene resin, The modified polyethylene resin is a method characterized in that the polyethylene resin is modified as unsaturated carboxylic acid or acid anhydride such as maleic acid, acrylic acid, methacrylic acid, etc.