WO2005019135A1

WO2005019135A1 - Method and composition for coloring stone

Info

Publication number: WO2005019135A1
Application number: PCT/KR2004/001249
Authority: WO
Inventors: Hakjae Lee
Original assignee: Diamond Marble Co., Ltd.
Priority date: 2003-08-26
Filing date: 2004-05-27
Publication date: 2005-03-03

Abstract

Disclosed herein is a method for coloring stone. The method comprises electrolyzing an oily colorant composition, immersing a stone in the electrolyzed colorant composition to colorize a desired color on the stone surface and coating the stone surface with a fluorinated resin. According to the method, there is less danger of discoloration during use of the colored stone for a long period of time. Since the colored stone has a desired color and texture, simple colors and textures of conventional stone are diversified. Accordingly, the method is expected to extend the applications of the colored stone to decorative materials as well as construction materials for interior and exterior decoration. Further disclosed is a colorant composition for coloring stone.

Description

METHOD AND COMPOSITION FOR COLORING STONE

Technical Field The present invention relates to a method for coloring stone, and more particularly to a method for coloring stone which can improve the physical properties, surface colors and textures of stone used as a construction material for interior and exterior decoration. Background Art

Generally, various construction materials for interior and exterior decoration are used in such a manner that they are suitable for use in the interior and exterior spaces of buildings in terms of functions and aesthetics. Such construction materials for interior and exterior decoration also serve to protect buildings against ambient environments, such as wind, rain, cold and warm weather, sunlight, fire, heat, noise and the like. They are largely divided into timber, synthetic resins and stone in terms of materials used. Among these construction materials for interior and exterior decoration, stone has been frequently used as a highly durable and environmentally friendly material. However, since natural stone has an inherent texture and color of its own, it cannot satisfy consumers' diverse needs for color. For this reason, a stone-textured construction material for interior and exterior decoration has been developed in which a mixture of an artificial stone powder, a colorant and an adhesive in a certain ratio is adhered to the surface of stone. However, this construction material has problems that the surface color is likely to fade or be discolored due to exposure to UV light with the passage of time, and dust and the colorant particles used are scattered during processing. For example, marble must be mechanically surface processed by polishing several times in order to be usable as a construction material. However, such a polishing process not only takes a great deal of time and cost, but also generates a large quantity of stone powder. With recent development of nanotechnologies, it has been found that silver nanoparticles have potent antibacterial properties. However, there has been made no attempt to apply silver nanoparticles to surface processing of stone. Disclosure of the Invention

Technical tasks to be solved by the invention Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for coloring stone wherein the surface of stone is colored so as to have a desired color and texture, thereby diversifying simple colors and textures of conventional stone and extending the application of the colored stone to decorative materials as well as construction materials for interior and exterior decoration. It is another object of the present invention to provide a method for coloring stone which can realize various surface textures and colors of stone, and provide a glossy surface to the stone, without the risk of oxidation in air nor the necessity of polishing several times. It is another object of the present invention to provide an environmentally friendly method for coloring stone which does not require the use of a stone powder and a powdery colorant, so that dust is not scattered during coloring. It is yet another object of the present invention to provide a method for coloring stone wherein a nano-sized silver powder is coated on the surface of stone to impart antibacterial properties to the stone.

Technical solution In order to accomplish the above objects of the present invention, there is provided a method for coloring stone, comprising the steps of: cutting a selected stone into a predetermined size, and trimming the surface of the stone; washing and drying the surface-trimmed stone; preparing a colorant composition comprising 15-70% by weight of an organic solvent, 1-5% by weight of a dye soluble in the organic solvent, 2-10% by weight of a pigment and 5-30% by weight of a thermosetting resin for adhering the dye and the pigment to the stone surface; applying an electric current to the colorant composition; immersing the stone in the electrolyzed colorant composition to colorize the stone surface; and washing and drying the colored stone. According to the method of the present invention, since the dye and the pigment dissolved or dispersed in the organic solvent is adhered to the surface of stone by the thermosetting resin, the stone has desired colors and textures depending on the type of dye and pigment used. In one embodiment of the present invention, a UV-blocking agent is coated on the surface of the colored stone in order to prevent the surface discoloration caused by UV light. The UV-blocking agent used herein consists of 5-20% by weight of a silver powder having an average size of 20nm or less, 5-20% by weight of titanium oxide, 30-50% by weight of polyvinylidene fluoride (PVDF) and 10-50% by weight of a diluent. As the diluent, toluene is preferably used. The organic solvent is preferably a mixture of methylethyl ketone and toluene. The thermosetting resin is preferably a silicone resin. The pigment is preferably an inorganic-based pigment. The resin used to adhere particles of the dye and pigment to the stone surface includes 5-30% by weight of a silicone resin and 0.1-5% by weight of a silane coupling agent as an auxiliary resin for improving the adhesive strength of the silicone resin to the stone surface, based on the total weight of the colorant composition.

Advantageous effects According to the method of the present invention, since the surface of stone is colored so as to have a desired color and texture, simple colors and textures of conventional stone are diversified and the applications of the colored stone are extended to decorative materials as well as construction materials for interior and exterior decoration. In addition, since a UV-blocking agent is coated on the stone surface, there is less danger of discoloration during use of the colored stone for a long period of time. Furthermore, since a nano-sized silver powder is coated on the stone surface, superior antibacterial properties are imparted to the stone.

Best Mode for Carrying Out the Invention

The present invention will now be described in more detail. First, a natural stone is selected and cut into a desired size. The cut stone is surface-treated using a polishing machine (step S1). Stones usable in the present invention include all rocks found in nature. Granite is particularly preferred. Since granite is composed of crystals of quartz, mica and feldspar particles, it has many fine pores formed between the particles. In particular, since granite from Korea has a high strength and is finely-grained, it is widely used as decorative materials and construction materials for interior and exterior decoration. The polished stone is completely washed with water to remove impurities from the surface, and is then dried for subsequent processing (i.e. adherence of colorants to the stone surface) (step S2). A colorant composition is used in order to adhere colorants to the stone surface. The colorant composition consists of 15-70% by weight of an organic solvent, 1-5% by weight of a dye soluble in the organic solvent, 2-10% by weight of a pigment, and 5-30% by weight of a thermosetting resin for adhering the dye and the pigment to the stone surface. The dye used herein is soluble in the organic solvent (i.e., an organic solvent-soluble dye), and is commercially available. Examples of commercially available dyes include ORICO (manufactured by Orico Corp., Korea), NEOJAPON (manufactured by BASF, Germany), etc. The pigment may be an organic pigment and/or an inorganic pigment, depending on intended functions such as coverage properties. These pigments may be used alone or in combination as a mixture. Where light resistance is required, an inorganic pigment is favorable. Depending on the amount of the dye and pigment used, colors of the stone surface and coverage strength are controlled. Examples of organic solvents that can be used to dissolve the organic dye include aliphatic hydrocarbon solvents such as methylethyl ketone (MEK), acetone, diethyleneglycol monobutyl monoether and diethyleneglycol monoethyl monoether, and aromatic hydrocarbon solvents such as toluene, xylene and benzene. A mixture of methyletheyl ketone and toluene is preferred. Preferred mixing ratio of methylethyl ketone to toluene is 20-70%: 15-40%, based on the total weight of the colorant composition. The thermosetting resin functions as a binder for adhering the dye and the pigment to the stone surface. As specific examples, melamine, phenol, alkyd, silicone resins, etc. may be mentioned. These resins may be used alone or in combination. Silicone resins are preferred. A commercially available silicon resin is manufactured under the trade name of DC-806 by Dow Corning, U.S.A. For better adhesive strength of the silicone resins, a silane coupling agent may be further added. The silane coupling agent is commercially available, for example, DC Z-6032 manufactured by Dow Corning, U.S.A. The silicone resin and the silane coupling agent are present in an amount of 5-30% and 0.1-5%, respectively, based on the total weight of the colorant composition (step S3). On the other hand, in order to make the color of the stone surface clear, the colorant composition may further comprise 1-10% by weight of glacial acetic acid and 1-5% by weight of alum (MIAI(SO₄)i₂H₂O), based on the total weight of the colorant composition. Next, prior to application of the colorant composition to the stone surface, an electric current is applied to the colorant composition (step S4) to electrolyze the colorant composition. This electrolysis of the colorant composition homogenizes the distribution of the dye and the pigment so that the colorant composition is easily adhered to the stone surface and uniform coloring is accomplished. When an electric current is supplied to an electrolytic bath containing the colorant composition, positive ions present in the colorant composition are shifted toward a cathode and negative ions are shifted toward an anode, causing a partial chemical reaction on the electrode surface. At this time, since the colorants contained in the electrolytic bath are finely ionized, the penetration of the ions into the stone is greatly improved. The conditions for penetration, such as amount of current, are properly varied according to the kind of stone to be colorized. Next, the washed stone is immersed in the colorant composition for a certain period of time (step S5). Specifically, after the stone is placed in a predetermined arrangement in a sedimentation tank, the colorant composition is fed into the sedimentation tank. The stone is immersed for about 30 minutes. The immersion time is appropriately controlled depending on the kind of the stone and the roughness of the stone surface. The surface of the colored stone is washed with a suitable cleaner. The cleaner used herein consists of 50-90% by weight of toluene, 5-20% by weight of acetic acid and 5-10% by weight of alcohol. Finally, the washed stone is dried

(step S6). The drying is carried out using high-temperature heat, which is generated when a temporary short-circuit is caused by applying electricity. This high-temperature drying evaporates moisture present even inside the stone. If necessary, the method of the present invention further comprises the step of coating the colored stone with a UV-blocking agent (step S7). The UV- blocking agent is mainly coated on stone for exterior decoration. The UV- blocking agent includes a fluorinated resin as a main component. Specifically, the UV-blocking agent consists of 5-20% by weight of a silver powder having an average size of 20nm or less, 5-20% by weight of a titanium oxide powder, 30-50% by weight of polyvinylidene fluoride (PVDF) and 10-50% by weight of toluene as a diluent. The silver powder is excellent in antibacterial properties and durability. A commercially available silver powder is manufactured under the trade name of Nanosilver by Global Life Tech Co., Ltd., Korea. Fine titanium oxide particles are metallic organic materials, and serve to block UV light to protect the color of the colored stone against UV light. The polyvinylidene fluoride (PVDF) resin acts to adhere the silver powder and the titanium oxide powder to the stone surface and to protect the stone due to its superior durability. The coating is accomplished by using a sprayer or brush. The coated stone is naturally cured by allowing it to stand for about 8 hours, or is thermally cured at 250°C for about 10 minutes. The present invention will now be described in more detail with reference to the following examples.

Granite was cut to a dimension of 30mm x 500mm x 1 ,000mm, washed and dried. A colorant composition was prepared to have the composition indicated below. After the colorant composition was fed into a sedimentation tank equipped with an electrolytic apparatus, electrolysis was performed at 380V and 25A for 20 minutes.

* Colorant composition Methylethyl ketone: 50 wt% Toluene: 15 wt% Dye (ORICO YELLOW 210): 3 wt% Pigment (PANAX PY-1000R): 4 wt% Silicone resin (DC 806): 15 wt% Silane coupling agent (DC Z - 6032): 3 wt% Acetic acid: 6 wt% Alum: 4 wt%

The granite was settled in the sedimentation tank to colorize the stone, washed and dried. The colored stone was coated with a UV-blocking agent mixture having the composition indicated below. Finally, the coated stone was cured at high temperature. * Composition of UV-blocking agent mixture Silver powder (NANOSILVER): 15 wt% Titanium oxide: 12 wt% Polyvinylidene fluoride (PVDF): 38 wt% Toluene: 35 wt% The weather resistance, light fastness, water resistance and chemical resistance of the colored stone were evaluated in accordance with the following procedures: (1) Weather resistance test

The colored stone was allowed to stand at a) 20±2°C and 90±5%RH for 1

hour, b) 60±2°C and 90+5%RH for 6 hours, and c) - 30+2 °C for 6 hours,

sequentially. The procedure was repeated five times. As a result, there

was no change in the gloss and color of the stone.

(2) Water resistance test The water resistance of the colored stone was evaluated in accordance with the KS F 4061 :2001 standard method. The water resistance was expressed by the water absorption rate, as calculated by the following equations: Water absorption rate = Dry weight of stone/(Wet weight of stone - Dry weight of stone) x 100 The result was shown to be 0.1 %.

(3) Chemical resistance test - Spot test was performed for 1 hour using a liquid detergent (Yuhan lax,

Yuhanclorox, Korea) to observe the gloss and color. As a result, there was no change in the gloss and color of the stone. - A powdery detergent (Super-Ti, LG Household & Health Care, Korea) was diluted to 50%, and then the subsequent procedure was carried out in the same manner as in the liquid detergent. As a result, there was no change in the gloss and color of the stone. - The procedure was carried out in the same manner as in the liquid detergent, except that hydrochloric acid (pH 2) was used. As a result, there was no change in the gloss and color of the stone.

(4) UV resistance test The UV resistance of the colored stone was evaluated in accordance with the KS F 2274:2002 standard method (WS-A, 200 hours). As a result, there was no change in the discoloration of the stone.

Industrial Applicability

From these test results, it was confirmed that the gloss and color of the colored stone were protected against chemicals and UV light. Accordingly, the colored stone is expected to be a very useful construction material for interior and exterior decoration. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

Claims:

1. A method for coloring stone, comprising the steps of: cutting a selected stone into a predetermined size, and trimming the surface of the stone (S1 ); washing and drying the surface-trimmed stone (S2); preparing a colorant composition comprising 15-70% by weight of an organic solvent, 1-5% by weight of a dye soluble in the organic solvent, 2-10% by weight of a pigment and 5-30% by weight of a thermosetting resin for adhering the dye and the pigment to the stone surface (S3); applying an electric current to the colorant composition prepared in step (S3) (S4); immersing the stone of step (S2) in the electrolyzed colorant composition for a certain period of time to colorize the stone surface (S5); and washing and drying the colored stone (S6).

2. The method according to claim 1 , wherein, after step (S6), the colored stone is coated with a UV-blocking agent (S7).

3. The method according to claim 2, wherein the UV-blocking agent consists of 5-20% by weight of a silver powder having an average size of 20nm or less, 5-20% by weight of titanium oxide, 30-50% by weight of polyvinylidene fluoride (PVDF) and 10-50% by weight of a diluent.

4. The method according to claim 3, wherein the diluent is toluene.

5. The method according to claim 1 , wherein the organic solvent is a mixture of methylethyl ketone and toluene, the thermosetting resin is a silicone resin, and the pigment is an inorganic-based pigment.

6. The method according to claim 5, wherein the thermosetting resin includes 5-30% by weight of a silicone resin and 0.1-5% by weight of a silane coupling agent, based on the total weight of the colorant composition.

7. The method according to claim 1 , wherein the washing of step (S6) is carried out using a cleaner comprising 50-90% by weight of toluene, 5-20% by weight of acetic acid and 5-10% by weight of alcohol.

8. The method according to claim 1 , wherein the drying of step (S6) is carried out by connecting an anode and a cathode to the stone and applying electricity to cause a temporary short-circuit.

9. The method according to any one of claims 1 to 8, wherein the colorant composition further comprises 1-10% by weight of acetic acid and 1-5% by weight of alum (MIAI(S0₄)i₂H₂0).

10. The method according to any one of claims 1 to 8, wherein the stone is granite.

11. A colorant composition for coloring the surface of stone, comprising

20-70% by weight of methylethyl ketone and 15-40% by weight of toluene as organic solvents, 1-5% by weight of a dye soluble in the organic solvent, 2-10% by weight of a pigment, 5-30% by weight of a silicone resin as a thermosetting resin for adhering the dye and the pigment to the stone surface, and 0.1-5% by weight of a silane coupling agent as an auxiliary resin for improving the adhesive strength of the silicone resin.

12. The colorant composition according to claim 11 , wherein the colorant composition further comprises 1-10% by weight of acetic acid and 1-5% by weight of alum (MIAI(SO₄)i₂H₂O), based on the total weight of the colorant composition.