BG66058B1 - Universal silicate paint with air-cleaning effect - Google Patents

Abstract

The invention relates to the composition and method of producing one-component all-purpose silicate paint with photocatalytic, air-cleaning effect. The paint serves for protective decorative coatingson concrete, bricks, plaster, putties, stone facings, and other surfaces. It is environment friendly, and its main components, such as film-forming substances pigments, fillers, are of an inorganic origin and do not pollute the environment. Under the influence of ultraviolet rays the paint coatings create ozone and oxygen emissions, which clean the air and have antibacterial and fungicidal action.

Description

Technical field

The invention relates to paint for protective coatings, in which the use of potassium silicate in the form of modified potassium water glass, and as the main pigment titanium dioxide having high photocatalytic properties, is used as a film-forming substance.

BACKGROUND OF THE INVENTION

Silicate interior and facade paints are known, which, according to European and American technical literature, retain their protective and decorative qualities for decades. Silicate paint coatings are highly weather resistant. They have high strengths, good air and vapor permeability, flame retardant properties and are environmentally friendly. They are also characterized by a slight dusting. These specific properties of silicate paints make them particularly suitable for painting facades of buildings.

Silicate paints are produced in the USA and in most European countries. Russia also produces silicate paints for exterior and interior dyeing, which typically consist of two ingredients: a) a liquid ingredient in a plastic package - potassium water glass; (b) a dry ingredient in a paper package consisting of zinc (ZnO), mineral pigments and fillers (finely ground quartz, talc, chalk, etc.). The preparation of the paint is carried out just before the beginning of its application. The finished paint is suitable for 10-12 hours.

Often, silicate paints are paints in which water glass is present in small quantities only as a modifier.

Over the last two decades, there has been an increasing interest in the development of photocatalytic materials for the transformation, decomposition and deactivation of various hazardous environmental pollutants.

There are dozens of patents for materials related to the photocatalytic action of TiO ₂ - en tibacterial ceramics, photocatalytic silica gel, photocatalytic filter, photocatalysts for water purification, etc.

Known scientific communications and patents for so-called environmental dyes for "passive" purification of the ambient air, using organosilicon compounds or special fluorocarbon polymers as a film-forming substance, and as a pigment and photocatalyst TY ₂ . Many of the patents claim that a special TiO ₂ with very fine particle size obtained using low temperature plasma (NTP) is used. It should be borne in mind that this is a routine technology, 70% of titanium dioxide in the US is obtained using NTP to give TiO ₂ with a particle size of 0.2 - 0.3 µm.

Problems with the use of the photocatalytic properties of titanium dioxide are related to the properties of the film-forming substance and the strength of the resulting film.

The use of organic-based polymeric materials as a film-forming substance in photocatalytic coatings has the following disadvantages: the resulting film is not sufficiently light-fast; the solvents and thinners used pollute the environment; the raw materials used are scarce.

The use of organosilicon compounds (organosilicon lacquers) seems promising, but it also has disadvantages: the coatings obtained, which have high strength and hydrophobic properties, are not sufficiently breathable; to reduce the curing temperature and accelerate the drying of organosilicon lacquers, they are usually modified with alkyd, polyether, epoxy and other resins. Aromatic hydrocarbons are used as solvents for organosilicon lacquers, while simple or complex ethers, ketones and chlorine derivatives of hydrocarbons are used as diluents; due to the formation of large internal stresses in the coatings of their bases, the coating must be applied to several successive layers with intermediate drying; moreover, organosilicon compounds are expensive materials.

The basic requirements for a photocatalytic film are: to have an open porous structure;

66058 Bl to be breathable; be resistant to strong oxidizing agents (ozone, oxygen); be transparent and resistant to ultraviolet radiation. In our opinion, films obtained by use as a film-forming agent - aqueous solutions of alkaline silicates (water glasses) are best met by these requirements.

From the existing silicate paints with photocatalytic air-purifying effect, it is worth mentioning the Italian silicate paint (EP 1559753 A2-03.08.2005) based on potassium water glass and the Bulgarian silicate paint (BG 108908A1 - 30.04.2006) based on sodium water glass. Despite their good performance, they are not free from some disadvantages. The first of them has low photocatalytic activity of the film due to the insufficient air permeability of the film and the optimum penetration of UV radiation into the depth of the coating due to the composition of the paint. The second paint has some problems with the hydrophobization of the coating and is not universal and has three options: interior, facade and with a pronounced air-purifying effect. The burden of this development, as can be seen from the patent itself, is to replace the expensive and deficient potassium water glass with sodium water glass.

It is an object of the invention to provide a composition for silicate paint based on potassium water glass providing a coating having high mechanical, protective and decorative properties. The film formed must be breathable, stable and permeable to ultraviolet radiation, possess photocatalytic properties, providing antibacterial and fungicidal action and purifying the air from harmful pollutants and enriching it with oxygen.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a silicate paint composition comprising the following components:

1. Film-forming agent - Potassium water glass - K ₂ O.mSiO ₂ .nH ₂ O m = 3-3,6, ρ = 1,40-1,42 g / cm ³ , modified from 10-50 vol. % sodium water glass with a silicate modulus of m = 2.0-2.5 and a density of 1,451.50 g / cm ³ and of 0.5-2 vol. % lithium water glass with a density of 1.20-1.25 g / cm ³ .

Potassium water glass with a density of 1,121.28 g / cm ³ is used in the preparation of the silicate paint. Dilution of the potassium water glass to this density is carried out with deionized water to ensure a long shelf life of the paint. When used in practice, silicate paint can be diluted to working density with plain water.

The amount of film-forming substance is 50-70% by weight of paint.

For the preparation of one-component paint with a long shelf life, dry components (pigments and fillers) are selected which will not dissolve and hydrolyze in the film-forming substance.

Dry components

2. Pigments

- Titanium dioxide - TU ₂ .

Due to the effective scattering of visible light and the high value of the refractive index, it gives the coating whiteness, brightness and high roofing ability. Titanium dioxide is insoluble in water. It is chemically completely inert and can be used with any binder.

TiO ₂ is a chemically stable compound, but its titanium atom has a coordination number which is coordination unsaturated and can firmly attach two water molecules to form a peroxide group in the form of a tense triangular ring. Compounds with such a ring, under the influence of ultraviolet radiation, easily break the ring and release ozone and oxygen. Titanium dioxide exists in the form of two crystallographic modifications - rutile (R) and anatase (A). Both modifications have a very high light refractive index - n _D , for rutile n _D = 2.73 and for analysis n _D = 2.56. The covering capacity (at equal mass) at Rec is 30% greater than that of anatase. The photocatalytic activity at A is much higher than that of rutile. By changing the ratio between the two modifications in the composition, the photocatalytic activity of the paint can be altered.

The amount of titanium dioxide is 4562% by weight of the dry components.

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3. Fillers:

- Barium sulphate - BaSO ₄ - natural or synthetic

By the magnitude of the refractive index of light, it is located at the boundary between the pigments and the fillers, with n _D = 1,64.

A white barite having a particle size distribution of 10-20 micrometer is used in an amount of 4-6% by weight of the dry components. Barium sulphate is practically insoluble in water (lg. BaSO ₄ dissolves in 200,000 g. H ₂ O), the pH of the aqueous extract is 7. It is resistant to acids and bases and sulfur-containing gases, it is thermally stable (m. mp 1580 ° C). It is easily wetted and dispersed.

The combination of TiO ₂ - BaSO ₄ ensures faster drying of the coating by silicate paint.

- Talc - White talc, 9297% whiteness, n _D = 1,58 and 10-20 micrometer granulometry are used. It is distinguished by its softness and oiliness, which is not peculiar to other minerals.

It is chemically inert, insoluble in water and acids. Due to the specific shape of the particles, it has a reinforcing effect on the coating, increasing its hydrophobicity and weather resistance.

Its amount is from 4 to 6% by weight of the dry components.

- Magnesium carbonate (magnesite) - MgCO ₃ . Fine-milled natural magnesite, 10-20 microns in white, acts as a filler (n _D = 1.51 1.7). Improves the ability of the silicate paint to be applied with a brush. Its amount is from 4 to 6% by weight of the dry components.

- Mica (potassium or lithium free of Fe) obtained by wet milling of muscovite with a luminance ratio greater than 68%.

Granulometry: particle content <20 micrometer - 90%, <10 micrometer - 60% and below 5 micrometer - 30%. The amount of mica is 3 to 5% by weight of the dry components.

Mica improves the elasticity and weather resistance of the coating and also reduces the tendency to form dense sludge while storing paint.

- Aerosil (SiO ₂ > 99.9%): artificial silica crystalline with a particle size of 0.003-0.04 micrometer, bulk mass of 40-60 kg / m ³ , specific surface area over 175 m ² / g, in the amount of 1- 3% by weight of the dry mixture;

- Quartz - SiO ₂ - ground natural quartz with a content of SiO ₂ above 92% with different particle size of 10-75 micrometer, in the amount of 6-10% of the dry mixture.

This filler provides high mechanical strength of the coating and transparency for UVB.

- Wolastonite - CaSiO ₃ . Volastonite is a natural mineral. It has high brightness and whiteness - a reflectance of 94%. The particles of milled volastonite have a needle-like shape. Increases the stability of the emulsions, prevents corrosion of metal containers and reduces air entrainment. Amount from 2.5 to 3% of the dry mixture.

- CaF ₂ fluoride - a finely ground mineral with a minimum CaF ₂ content of 80%. It transmits UV light and promotes the photocatalytic action of titanium dioxide. Amount of 3-5% by weight of dry components.

- Bentonite (colloidal clay, montmorillonite) - a finely ground natural product that improves the rheological structure of silicate paints and gives them textotropic and anti-precipitation properties and stabilizes them. Add 4-5% by weight of dry components. Bentonite can also be replaced with Bentone (dimethyloctadecylammonium montmorillonite) - a finely ground natural bentonite, additionally aminated. Bentone possesses higher bentonite properties and is hydrophobic.

- Zeolite - skeletal aluminosilicates with a three-dimensional skeleton of tetrahedrons of [SiOJ ⁴ · and [A1OJ ⁵ 'firmly fixed to the angles forming channels and cavities with dimensions 0.2-1.5 nm throughout the crystal structure; Si ratio: Al = 1.7-2.9; cation exchange capacity - min 100 mg eqv / 100 g. The zeolites adsorb potassium ions from the water glass, which balances the negative charge of the zeolite structure. Improves film elasticity. Amount of 2-3% by weight of dry components.

4. Modifiers:

- Methylcellulose or other cationic surfactants in an amount of 0.5 to 1.5% by weight of the dry components.

- Alkaline soaps of fatty acids in

66058 Bl amount of 0.5-1.5% by weight of the dry components.

The inventive composition has all the advantages of the known silicate paints, and also has the following advantages:

- silicate paint is universal, combines the qualities of interior, facade and air-purifying paint;

- the silicate paint has a low surface tension and a good wetting of the surfaces to be applied. It has high adhesion to concrete, bricks, lime and lime-cement plasters, stone other coatings. The viscosity of the paint is low, close to that of the water and penetrates well into the substrate on which it is applied by strengthening it;

- the coating of the inventive composition has a strong photocatalytic action and is a kind of ecological machine for the production of oxygen and ozone, the raw material being the moisture from the atmosphere and the energy for its action is provided by UV radiation in the sun or artificial sources of UV;

- the required thickness of the coating can be achieved by a single application;

- no internal stresses are formed in the coating and no cracks are observed during operation.

Examples of carrying out the invention

The invention is illustrated by the following examples

Example 1

Components % of the dry mixture % of the silicate paint TY2 (A) 53.5 20,00 BaSO4 5,6 2.11 Aerosil 1.4 0.53 SiO2 <20 pm 4.9 1.84 SiO2 <75pm '4,9 ---- П84 ---- MgCO3 4.2 1.58 Talc 4.2 1.58 Mica 4.2 1.58 CaF2 fluoride 4.2 1.58 Wollastonite 2.8 1,05 Bentonite 4.2 1.58 Zeolite 2.8 1,05 -, Λ Methylcellulose 1.4 0.52 Alkaline Soap (Na) 1.4 0.52 Dry mixture 100 5737

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K 50% water glass, mod. with: 10 vol. % Na water glass and 2 vol. % Li water glass 62.63

Impurity 2

Components % of the dry mixture % of the silicate paint TiO2 (A) - anatase 40,0 14.95 TiO2 (R) - rutile 13.5 5.05 BaSO4 5,6 2.09 Aerosil 1.4 0.52 SiO2 <20 pm 4.9 1.83 SiO2 <75pm 4.9 1.83 MgCO3 4.2 1.57 Talc 4.2 1.57 Mica 4.2 1.57 Ca2 fluoride 4.2 1.57 Wollastonite 2.8 1,05 Bentonite 4.2 1.57 Zeolite 2.8 1,05 Methylcellulose 1.4 0.52 Alkaline soaps 0.7 0.26 Dry mixture 100 37.00 50% water glass, mod. with: 10 vol. % Na water glass and 2 vol. % Li water glass “Mr. 63.00

Claims (2)

1. Universal air purifying silicate paint based on water glass, titanium dioxide, fillers, pigments and modifying additives, characterized in that the water glass is in the amount of 50-70% by weight of paint and has a silicate module m = 3-3 , 6, diluted with deionized water to a density of 1.4-1.42 g / cm ³ , wherein it is modified by 10-50 vol. % sodium water glass and 0.5-2 vol. % lithium water glass, pigments are titanium dioxide - anatase and / or rutile in an amount of 45-62% by weight of dry components, fillers are barium sulphate in an amount of 4-6% by weight of dry components, talc in an amount of 4-6% by weight of the dry components, magnesium carbonate in the amount of 4-6% by weight of the dry components, mica in the amount of 3-5% by weight of the dry components, quartz with a particle size distribution 105 75 micrometer in the amount of 6-10% by weight of the dry components, volastonite in the amount of 2.53% by weight of the dry components, calcium fluoride in the amount o 3-5% by weight of the dry components bentonite in an amount of 4-5% by ma10 measure of the dry components, zeolite in a quantity 2-3% by weight of dry components and modifying additives are methylcellulose or other cationic surfactants in an amount of 0.5-1.5% by weight of dry 15 components or alkaline soaps in an amount of 0.5-1.5% by weight of dry components.