Epoxy coating composition for dry, wet, and underwater applications

Abstract

The aim of this invention relates to underwater paint which can be used on dry, wet, or underwater surfaces. An epoxy resin, barium sulfate and talcum as filler, and amine curing agent are major compositions. UV absorber, light stabilizer and leveling agent are also added to improve the coating properties. This epoxy paint in this invention provides good adhesion, corrosion protection and chemical resistance on steel surface.

Description

[0001] EPOXY COATING COMPOSITION FOR DRY, WET AND UNDERWATER APPLICATIONS

[0002] Technical Field

[0003] This invention presents an underwater epoxy paint which can be used with steel or concrete structures. This epoxy can be applied on dry, wet, or underwater surfaces and is suitable for protecting structures from corrosion. The paint composition consists of epoxy resin, filler and curing agent as the main component.

[0004] Background Art

[0005] Many structures are exposed to both dry and wet conditions or even submerged into water. Maintenance is difficult because of some limitations such as surface preparation without blasting or damp surface during operation. Plants shut down for maintenance or repair are too expensive. Underwater paint will be the solution to this problem. It is designed to work on dry, wet, or underwater surfaces.

[0006] In US Patent 5,320,871 by Susan et al., underwater coating for submerged substrates comprises of base resin selected from the group consisting of epoxidized polysulfide resin and mixtures of an epoxidized polysulfide resin and an epoxy resin, a barrier pigment, and a curing agent for curing the coating compositions while submerged in aqueous fluid.

[0007] In US Patent 6,037,435 by Toshiharu Hayashi, underwater curable coating composition is revealed. The underwater curable coating composition consists essentially of an epoxy resin component and its curing agent, wherein the epoxy resin component is a mixture comprising a liquid hydrophobic epoxy resin and a self-emulsifiable liquid epoxy resin. The curing agent is composed partly or solely of ketimine.

[0008] Disclosure of Invention

[0009] In this invention, epoxy resin is the main component to act as a binder to adhere on the surface. Silica, calcium carbonate, barium sulfate, clay, talcum, or bentonite can be used as a filler, but barium sulfate is preferable. Barium sulfate in coating will improve its thickness, surface hardness, water resistance and abrasion resistance. Talcum helps to increase coverage and weather resistance of the coating. The barrier effect from Talcum will limit the penetration of water and corrosive which lead to a reduction in bubble formation, corrosion, and peeling. The appropriate curing agent for underwater paint will be amine types such as aromatic polyamine, modified aliphatic polyamine, amine amide dimer acids or phenalkamine. Each amine type will give different properties to the coating. In this invention, low viscosity modified aliphatic polyamine is chosen because of fast curing. UV absorber, light stabilizer and leveling agent are also added to improve the properties of the underwater paint.

[0010] The solvent-free and low VOC epoxy coating composition for dry, wet, and underwater uses is prepared by mixing the following raw materials together.

[0011] Part A: i Epoxy resin 50.0 - 65.0 weight % ii Barium sulfate 20.0 - 30.0 weight % iii Talcum 10.0 - 15.0 weight % iv Hydroxyphenyl benzotriazole-type UV absorber 0.5 - 2.0 weight % v Hindered secondary or tertiary amine type stabilizer 1.0 - 3.0 weight % vi Polyacrylate I.0 -2.0 weight %

[0012] Part B: Low viscosity modified aliphatic polyamine 100.0 weight %

[0013] If the pigments are needed, the solvent-free and low VOC epoxy coating composition will be the following:

[0014] Part A: i Epoxy resin 46.0 — 60.0 weight % ii Barium sulfate 18.0 - 30.0 weight % iii Talcum 9.0 - 15.0 weight % iv Hydroxyphenyl benzotriazole-type UV absorber 0.5 - 2.0 weight % v Hindered secondary or tertiary amine type stabilizer 1.0 - 3.0 weight % vi Polyacrylate 1.0 - 2.0 weight % vii Pigment 3.0 - 10.0 weight %

[0015] Part B: Low viscosity modified aliphatic polyamine 100.0 weight %

[0016] The mixing ratio between part A and part B for both is 5:1 by weight.

[0017] Performance Test

[0018] The test specimens were prepared using steel plates with dimension 100x150x0.7 mm.

[0019] All test specimens were sand blasted and painted by brush. The specimens were painted in 3 different surface conditions, dry, wet, and underwater. The dry film thickness of all specimens was 12 mils or 300 microns minimum approximately. Then, 500 hours salt spray (fog) test conformed to ASTM Bl 17, X-cut adhesion test conformed to Thai Industrial Standard, TIS.285 Vol.47 or ASTM D3359, 10 wt.% sulfuric acid and 5 wt.% sodium hydroxide solution resistance test conformed to TIS.285 Vol.25 or ISO 2812 were performed. The results show that all specimens can pass all tests as shown in the figures 4 to 7.

[0020] Description of the Drawing

[0021] Figure 1 is a photograph showing the sample coating using brush in dry condition.

[0022] Figure 2 is a photograph showing the sample coating using brush in wet condition.

[0023] Figure 3 is a photograph showing the sample coating using brush in underwater condition.

[0024] Figure 4 shows the results of 500 hours salt spray (fog) test (a) applying underwater coating on samples in fresh water and (b) applying underwater coating on samples in seawater.

[0025] Figure 5 shows the results of X-cut adhesion test of underwater coating: al, a2 and a3 are the results of X-cut adhesion test of underwater coating in dry, wet, and underwater conditions after 1 day of coating finished respectively. bl, b2 and b3 are the results of X-cut adhesion test of underwater coating in dry, wet, and underwater conditions after 2 days of coating finished respectively.

[0026] Figure 6 show's (a) before and (b) after 24 hours of 10 wt.% sulfuric acid solution resistance test.

[0027] Figure 7 shows (a) before and (b) after 24 hours of 5 wt.% sodium hydroxide solution resistance test.

Claims

Claims1. The composition of solvent-free and low VOC epoxy coating for dry, wet, and underwater applications, comprising:Part A: i Epoxy resin 50.0 - 65.0 weight % ii Barium sulfate 20.0 - 30.0 weight % iii Talcum 10.0 - 15.0 weight % iv Hydroxyphenyl benzotriazole-type UV absorber 0.5 - 2.0 weight % v Hindered secondary or tertiary' amine type stabilizer 1.0 - 3.0 weight % vi Polyacrylate 1.0 - 2.0 weight %Part B: Low viscosity modified aliphatic polyamine 100.0 weight %2. The composition of solvent-free and low VOC epoxy coating with pigment for dry, wet, and underwater applications, comprising:Part A: i Epoxy resin 46.0 — 60.0 weight % ii Barium sulfate 18.0 - 30.0 weight % iii Talcum 9.0 - 15.0 weight % iv Hydroxyphenyl benzotriazole-type UV absorber 0.5 -2.0 weight % v Hindered secondary or tertiary amine type stabilizer 1.0 — 3.0 weight % vi Polyacrylate 1.0 -2.0 weight % vii Pigment 3.0 - 10.0 weight %Part B: Low viscosity modified aliphatic polyamine 100.0 weight %3. The assembly as claimed in claim 1 and 2 wherein the mixing ratio between part A and part B for both claims is 5:1 by weight.

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