COMPLETELY INORGANIC, PERMANENTLY ANTI-CORROSIVE, INNOXIOUS ANTI-FOULING PAINT

Completely inorganic, permanently anti-corrosive,

innoxious anti-fouling paint

Present invention relates to a completely inorganic,

permanently anti-corrosive, innoxious anti-fouling paint.

Since it was opened up as a heat curing paint by name of

DAYMETCOAT. in 1937 (Australian patent No. 1042317), the water glass system paint has been developed through chemical curing method(US patent No. 246263, 1970) and self curing method (US patent No. 4086-616, phosphoric acid method, No. 2536-871, zinc oxide method). But, where it is used as an anti-corrosive paint, the corrosion was prevented by method of increasing the concentration of zinc without exception.

After the heat curing method appeared, water glass system paint has been considered to give an anti-corrosive effect for heavy duty, special purpose steel structure, especially in deserts and ocean environment. But, in most cases, it is used as a

primer for coating or along with organic paint.

Phosphoric acid and phosphate, such as silicon polyphosphate, titanium phosphate and metal oxides such as calcium oxide, alumina, etc. are known as curing agent of water glass paint already

reported, and glass fibre, carbon fibre etc-, are proposed as its reinforcing agent. Besides, a lot of patents are suggested. But, main defect of water glass system paint (lack of waterproofness, of bendability, of gloss etc.) have not been solved yet. Therefore, organic-inorganic complex compounds are recommended or it is replaced with alkyl silicate paint. In addition, no attempt has been made in any patent to solve anti-corrosive, anti-fouling problem by forming a special functional film of inorganic silicate.

Recently, international organizations for preventing polαtion in the world have taken legal procedures to

prohibit poisonous anti-fouling paint. However, still there is no effective innoxious paint appeared.

The object of this invention is to provide a completely inorganic, permanently anti-corrosive, innoxious anti-fouling paint based upon the study of corrosion machanism of iron and the property of adhesively inhabitating organisms in the sea environment.

Another object of this invention is to provide a paint for coating inside and outside of structures and colors for pictures which have excellent adhesiveness, waterresistance, humidity control, anti-static, anti-bacterial property and permanently unfading colors.

The latter object of the invention relates directly to a noble work for inheriting and developing more the valuable cultural heritages of our ancestors (everlasting, unfading colors) displayed in the mural of tombs and pictures of many colors and designs in the historic relics of Koguryo dinasty of our country.

According to the invention the paint is manufactured by various method in accordance with their uses.

First method

The solution of silicate I^O-SiOgof molar ratio (M₂O/ SiO₂) 0,4-0,25 is mixed with ammon chloride so that molar ratio (NH₄Cl/SiO₂) can reach 0,2-0, %where M = K,Na, Li, Rb). Then the following reaction occurs:

Na₂O-nSiO₂ + 2 NH₄Cl + H₂O = 2NaCl + 2NH₃ ↑ 4+ nSiO₂ + 2H₂O

The silicagel obtained by above mentioned reaction is matu for a certain period of time and washed to get gel-state denatu ammonia silicagel (xH₂SiO₃·NH₄OH·yH₂O) which absorbed ammonia g Its molar ratio (NH₄OH/SiO₂) is preferably 0,25-0,5. This mixtu is mixed with silicate solution of molar ratio (M₂O/SiO₂) 0,25- at the ratio of 1-50:100 by weight. The resulting solution is dispersed with MX solution so that MX/Si0₂ can reach 0,01-6,05 to get denatured silicate solution of high viscosity (vehicle) (where, M: K, Na, Li, Rb, Ba, Zn, Ca; X: Cl, P, Br).

If above-mentioned denatured silicate solution is added wi filler, dispersoid alumo silicate, metal oxides and metal powde then a paint will be obtained. (where, the alumosilicate is M(I)₂O·M(II)O·Al₂O_5·nSiO₂·mH₂O (M(I) and M(II) are monovalent a bivalent metallic cations, n is molar ratio of SiO₂/Al₂O₃, m is number of mol of water). Molar ratio (SiO₂/Al₂O₃)

is preferably in the range of 0,5-20, molar ratio (Na₂θ/CaO) is preferably in the range of 1-10, the amount of ion exchange bei 5-40 mg equivalent/100 g. The grain size of the filler is prefe ably 250-300 mesh., The vehicle is added preferably with alumosilicate, one or two_kinds of metal oxides of among ZnO, TiO₂, Fe₂O₃, BaO, Al₂O₃, one or two kinds of metallic powders of amon Zn, Pe, Al and Cu at the proportion of 30-40, 0-20, 0-20 weight respectively.

If this paint is applied, a film having a capacity of exchanging and absorbing ions is obtained.

According to the molar ratio of filler and amount of its addition, the ion absorbing capacity of film changes in the ra of 90-110 mg equivalent/100 g, iron exchanging capacity being 10-30 mg equivalent/100 g. If a paint is made in this way and applied to the bottom of a ship, inorganic film is obtained, which is prooved to have an absorbing capacity 3 times higher than natural zeolite in terms of absorption amount of cation, in particular Ca 2+ (see table 1).

It was prσoved by infrared absorption spectrum analysis, X-ray difraction analysis, X-ray photoelectron analysis, differenti thermal analysis that the film has a three dimensional reticular structure capable of performing the function of ion exchange and absorption.

Adhering to the bottom of a ship, the organism secretes an adhesive substance* amino acid calcium colloid, which becomes a strong high molecular adhesive on the surface of the object and firmly adheres thereto.

As the surface of the film comprises very active alkali metal cations, it is able to easily exchange with other metallic cations. Therefore, the film absorbos Ca²⁺ away from amino acid calcium colloid solution of adhesive secretion product of sea adhesive organisms, thus weakening the adhesive strength of the adhesive organisms and making them unable to inhabitate.

Table 2

Capacity of Ca ion absorption and exchange of fiim

Absorption Absorption Exchange Exchange Equivalent of capacity capacity capacity capacity secreting liquid per 100 g per 1 cm² per 100 g per 1 cm² of sea adhesive organism

100 mg 0,06 mg 17 mg 0,01 mg 2x10^-5 mg equiv. equiv. equiv. equiv. equiv, per 1 cm²

As is seen in the table 2, the capacity of exchange per 1 cm² of film is 0,01 mg equivalent and amount of calcium secreted by sea adhesive organism is 2x10^-5 mg equivalent, these figures show that calcium exchangeability of film is far higher.

Therefore, not only the film has the capacity to absorb any amount of calcium secreted by sea adhesive organisms, including epiphytes, but also disorption-absorption process of calcium and sodium continues due to the constant reverse reaction in the sea water. Therefore, as long as film exists, the anti-fouling capacity against sea adhesive organisms, including epiphytes is permanent.

The function of film to protect iron from corrosion is also explained by the mechanism of absorbing and fixing the ions by prohibiting the flow of iron ions due to the capacity of absorption of ion.

The X-ray photoelectron analysis of film is shown in the annexed picture. It shows that the additives bond chemically to form a passivating film. Embodyment

The vehicle is obtained according to the first method. This vehicle is mixed with filler of following composition and the resulting paint is applied to specimens and bottom of a ship and cured for a week, followed by exposure test and actual test.

Composition: (by weight %)

Vehicle 40-60

Alumosilicate 20-30

Metal oxide 5-20

Zinc powder 5-16

The result shows that anti-fouling and anti-corrosive function of film has still been maintained for 15 years until now since the beginning of the actual test.

Second method

Polyethylene glycol (n=1-2000) is added to silicate solution having molar ratio (M₂O/SiO₂)=0,4-0,25. The former causes a neutralization and polysilicate elastomer (PSE) is obtained.

H0-(CH₂CH₂O)_n-H + Na₂O·nSiO₂ +XH₂O =

= 2HO-(OH₂CH₂O)-Na + (H₂SiO₃)_n·yH₂O + (x-y)H₂O

Precipitated PSE is dispersed into silicate solution so that molar ratio (PSE/SiO₂) can be 0,1-10,0and then aluminium salt solution is added thereto so that molar ratio(Al₂O₃/SiO₂) can be 0,01-5,0 and heated at 100 º0 to get vehicle. This vehicle is mixed with barium sulphate, calcium phosphate, 1-2 kinds of metal oxides such as alumina, titanium white, zinc oxide etc. at the proportion of 5:1-10 by weight, which is made paste state, thus obtaining excellent smokeless, humidity controlling, anti-bacterial, anti-static paint needed for painting inside and outside of structures or colors for pictures.

The paint thus made is applicable to fabrics, concrete plate, glass, iron, slate and stone etc., excluding resin and oil colors, under-coating plate.

Embodyment

The vehicle obtained according to the second method is mixed with dispersoid of following composition and applied to cement plate and cured for one week:

Vehicle 40-60 % (by weight)

Titanium oxide 5-10 % " "

Zinc oxide 5-10 % " "

Barium sulphate 10-25 % " "

Actual test

When organic paint was applied as a painting material fo inside and outside decoration of building, it grew moldy in a month in the mold-growing environment(at humidity of 90 % or so, temperature of 20-30 ºC) and was contaminated within a year, which caused repainting unavoidably.

Though the paint has been used for inside-outside coatin and also for colors of pictures according to the invention, there has not been found any mold growing for 8 years since actual test commenced and the surface of the object has not contaminated yet even in the mold-growing environment.