WO2008091131A1

WO2008091131A1 - Fire-proof covering agent composition and nonflammable method for flammable material

Info

Publication number: WO2008091131A1
Application number: PCT/KR2008/000477
Authority: WO
Inventors: Jong-Won Park
Original assignee: Jungmac Ind R & D Ltd
Priority date: 2007-01-25
Filing date: 2008-01-25
Publication date: 2008-07-31
Also published as: WO2008091129A1

Abstract

Provided is a liquid alkali metal silicate based fire-proof covering agent composition coated on a flammable material to provide superior flame retardance thereto, which comprises a liquid modified alkali metal silicate substrate and a siloxane reactive denaturant.

Description

FIRE-PROOF COVERING AGENT COMPOSITION AND NONFLAMMABLE

METHOD FOR FLAMMABLE MATERIAL

[Technical Field] The present invention relates to a fire-proof covering agent, more particularly to a liquid alkali metal silicate based fire-proof covering agent coated on a flammable material to provide flame retardance to the flammable material.

[Background Art] In general, methods of coating a fire-proof covering agent on a flammable material to provide flame retardance to the flammable material are well known in the art.

The requirements for a good fire-proof covering agent are as follows. First, the fire-proof covering agent should be coated uniformly. Second, the fire-proof covering agent should not affect the function or shape of the material on which it is coated. Third, the coated fire-proof covering agent should not be peeled off or removed in operation environment. Fourth, the coating density should be above a predetermined level in order to provide sufficient flame retardance. In addition to the aforesaid basic requirements, good operability is required. For instance, during the coating of the fire-proof covering agent or the processing following the coating, less generation of dusts is required. Further, the fire-proof covering agent should be able to provide superior flame retardance with a small coating amount. And, the fire-proof covering agent needs to be unharmful to humans and animals.

At present, a fire-proof covering agent requiring all the requirements does not exist.

The use of alkali metal silicates unharmful to the human body, e.g., sodium silicate, which form foamed films at high temperature, as flame retardant material is widely known. However, alkali silicates are hydrophilic and there is difficulty in coating them on organic flammable materials. Even when coating is possible, it is difficult to obtain a stable film, and good water resistence is not attained. Besides, an outstanding flame retardancy is not attained although they are inorganic materials. In addition, alkali silicates easily react with carbon dioxide in the air, resulting in increased viscosity or hardness. Therefore, storage property is not good, and the film formed on the bead surface may form dusts by reacting with carbon dioxide in the air.

Various flame retardant inorganic particles are included in the sodium silicate solution to improve flame retardance. However, because of low adhesion strength to sodium silicates and weak film strength, the inorganic particles tend to be detached from the film, thereby resulting in dust generation. To prevent this, the film thickness has to be increased.

Modified alkali metal silicates with increased silicon dioxide content have improved water resistance and increased foaming density inside the foam film formed at high temperature. However, as with general alkali metal silicates, modified alkali metal silicates are also associated with the problems of insufficient flexibility of dry film, dust generation, and curing upon contact with air.

[Disclosure]

[Technical Problem]

The present invention has been made in an effort to solve the above-described problems associated with the prior art. An object of the present invention is to provide an economical, high-density coating type liquid alkali metal silicate based fire-proof covering agent composition, which is advantageous in coatability, stability, adhesion, dust generation, water resistence, storage property, film strength and film flexibility and is capable of providing high-level flame retardance to a flammable material with a small coating amount, and a method for providing flame retardance using the same. [Technical Solution]

In one aspect, the present invention provides a liquid alkali metal silicate based fire-proof covering agent composition comprising: a liquid modified alkali metal silicate substrate; and a siloxane reactive denaturant.

In another aspect, the present invention provides a method for providing flame retardance to a flammable material comprising the steps of: providing a flammable material; and coating the aforesaid liquid alkali metal silicate based fire-proof covering agent on the flammable material.

[Advantageous Effects]

The composition of the present invention is superior in coatability, stability, adhesion, dust generation, water resistence and storage property, and is able to form strong but flexible film. From the composition of the present invention, an economical, high-density coating type liquid alkali metal silicate based fire-proof covering agent composition capable of providing high-level flame retardance to a flammable material even with a small coating amount can be attained.

[Best Mode]

The present invention provides a liquid fire-proof covering agent comprising liquid modified alkali metal silicate with increased silicon dioxide content and capable of improving water resistence and coating density as substrate and a siloxane reactive denaturant for making up for the function of the silicate film.

The fire-proof covering agent of the present invention is coated on a flammable material such as organic fiber, organic fabric, organic nonwoven fabric, paper, wood, plywood, organic mold, plastic, organic foam, expandable resin, foam resin, synthetic resin, etc. to form a film at room temperature and provide flame retardance. In the fire-proof covering agent of the present invention, the modified alkali metal silicate, which is synthesized from the reaction of liquid alkali metal silicate and silica powder, has increased silicon dioxide content and serves at once as flame retardant base, binder and solvent. Cured alkali silicate prevents the cured film from transferring oxygen to polystyrene foams, when the cured film is subject to extreme heat such as flame. At 150 ⁰C or higher, crystal water is liberated from, causing the cured film to expand and form a cell-type foamed film. The foamed film blocks oxygen transfer and prevents the polystyrene foams from burning due to its insulating property.

The modified alkali silicate of the present invention, which serves as flame retardant base, has better insulation and fire resistance, when compared with general alkali metal silicates, because more foams are formed per unit area. That is, the increased silicon dioxide density results in increased film strength and formation of more foams per unit area. Further, the increased film strength reduces the generation of dusts, significantly reduces efflorescence caused by carbon dioxide included in the air, and makes the cured film less soluble even in hot water (80-100 ⁰C). Further, the increased silicon dioxide density results in increased solid content, thereby improving the rate of drying, increasing the solid density of the film, and preventing the supply of air to the flammable material. As a result, superior flame retardance is attained.

Further, the fire-proof covering agent of the present invention has superior coatability. Coatability also affects the flame retardance. When alkali-soluble silica powder is added to liquid alkali silicate, viscosity of the liquid alkali silicate increases without increase in stickiness. The high viscosity accompanied by low stickiness allows uniform and adequate coating on the surface of a flammable material over a large area even with a small amount, provides superior flame retardance with high silicon dioxide density, and improves the rate of drying. Further, the siloxane groups of the silicate allow uniform and thin coating on the hydrophobic surface of a flammable material, along with the siloxane reactive denaturant, thereby resulting in flexible coat film. The fire-proof coating agent of the present invention is a liquid with low thixotropy. Because solid particulate materials are not included, there is no problem of dust generation upon drying or curing of film. The low thixotropy is due to the absence of hydrogen bonding between hydrophilic particles and water molecules of alkali silicate. Thus, the coating agent can be coated on a flammable material evenly and uniformly, without aggregation.

Along with the liquid modified alkali silicate, the fire-proof coating agent of the present invention further comprises denaturants such as silicone oil, organosilane and sugar or modified starch, to provide advantages in cost, flame retardance, coatability, water resistence, dust generation, adhesion, etc.

To this end, the liquid alkali metal silicate used the present invention is preferably at least one selected from sodium silicate, potassium silicate, lithium silicate and a combination thereof. Considering flame retardance, coatability and manufacturing productivity, sodium silicate, particularly commercially available Water Glass No. 2, is more preferred. Meta-sodium silicate in powder form or Water Glass No. 1 with little fluidity may be used as dissolved in water. In that case, a dry solid content of 30 to 50 weight % is preferred for appropriate fire resistance and coatability.

The silica powder may be either amorphous silica or crystalline silica. One with a small particle size is preferred for fast dissolution in the liquid alkali silicate. A particle size of 325-mesh all pass will be sufficient. Preferred amorphous silica is one that can be silicated by alkali, such as white carbon, silica gel, fumed silica, fused silica, diatomaceous earth, etc. And, preferred crystalline silica is α-quartz comprising at least 50 % of soluble silicon dioxide (SiO₂). For example, the quartzite mined at the quartzite mine located at Gaegok-ri, Gapyeong-eup, Gapyeong-gun, Gyeonggi-do, Korea may be used.

Although variable depending on the particular silica and liquid alkali silicate, a preferred proportion of the liquid alkali silicate to the silica powder is from 80 : 20 to 99 : 1 , based on weight, in case Water Glass No. 2 is used. When the addition amount of the silica is less than 1 , improvement of fire resistance and water resistence may be insufficient due to low silicon dioxide content. Particularly, flame retardance becomes deteriorated since the coating composition may be lost upon exposure to raindrops, etc. When the addition amount of the silica exceeds 20, the silica may not be dissolved, or gelation may occur even if it is dissolved. And, undissolved silica powder may precipitate. For amorphous silica, when the addition amount of the silica powder is up to 4 parts by weight, dissolution can be completed by stirring at room temperature. When the addition amount exceeds 4 parts by weight, gelation or curing may occur. Therefore, after dissolving by heating, boric acid or borax may be added for stabilization, before cooling. Alternatively, boric acid or borax may be added before the addition of the silica powder, and dissolution may be performed at room temperature. Here, the boric acid or borax serves as flux or stabilizer. Preferably, boric acid or borax is added in an amount from 0.5 to 10 parts by weight, based on 100 parts by weight of the liquid alkali metal silicate. When the addition amount is less than 0.5 part by weight, the effect of stabilizing the silicate may not be attained. And, when the addition amount exceeds 10 parts by weight, a better stabilizing effect is not attained, and water resistence may decrease.

Thus prepared liquid modified alkali metal silicate has a significantly increased silicon dioxide content, as compared with conventional sodium silicate (23-38 weight %).

The viscosity of the liquid modified alkali metal silicate increases as the addition amount of the silica powder, and is sensitive to temperature change. When the viscosity is too high, a small amount of water or alkali silicate solution may be added to reduce viscosity, considering operability and coatability. In the present invention, a siloxane reactive denaturant is added to the liquid modified alkali metal silicate, which is obtained from the reaction of the liquid alkali metal silicate and the silica powder, in order to complement insufficient physical properties. Particularly, differently from a cured film comprising the modified alkali metal silicate only, a flexible cured film with decreased brittleness may be attained.

The siloxane reactive denaturant refers to a substance that can react with the siloxane groups of the alkali metal silicate to change the physical properties of the fire-proof covering agent. The substance may be at least one selected from silicone oil, organosilane, sugar and modified starch, and a variety of combinations thereof may be used depending on the particular flammable material. The siloxane reactive denaturant is added in an amount from 0.1 to 100 parts by weight, preferably from 0.1 to 10 parts by weight, based on 100 parts by weight of the liquid modified alkali metal silicate. When the addition amount is less than 0.1 part by weight, the effect of addition may not be attained. And, when the addition amount exceeds 100 parts by weight, a further effect is not attained.

The silicone oil is added to the liquid modified alkali metal silicate in liquid form. The siloxane groups of the silicone oil allow chemical or physical adsorption with the siloxane groups of the silicate, thereby improving fire resistance, coatability, storage property, film flexibility, efflorescence resistance, dust resistance, water repellency and water resistance. The siloxane groups of increased silicon dioxide and the silicate make the hydrophobic silicone oil miscible with the liquid modified alkali silicate.

The silicone oil used in the present invention is a straight-chain oil consisting of dimethylpolysiloxane. Modified oils with various organic groups introduced in part of the methyl groups of the dimethylpolysiloxane, e.g., amino-modified, epoxy-modified, carboxyl-modified, carbinol-modified, methacryl-modified, mercapto-modified, phenol-modified, single-end modified, heterofunctional group-modified, polyether-modified, methylstyrene-modified, alkyl-modified, higher fatty acid ester-modified, fluorine-modified oils, may also be used alone or in combination. Preferably, the silicone oil has a viscosity in the range from 50 to 5000 cs (centi-stokes). When the viscosity is below 50 cs, the silicone oil is not mixed with the liquid modified alkali silicate, but remains separated. Consequently, a larger amount of silicone oil is required to attain the wanted properties. And, when the viscosity exceeds 5000 cs, the process of mixing becomes difficult.

The organosilane is added to the liquid modified alkali metal silicate in liquid form. The siloxane groups or other functional groups of the organosilane bind with the siloxane groups of the silicate, thereby providing fire resistance, coatability, adhesion, film flexibility, efflorescence resistance and water resistence to the fire-proof covering agent. The organosilane used in the present invention, also commonly called as silane or silane coupling agent, refers to an organosilicon compound in which an alkoxy, chloro or alkyl group is bonded to a silicon atom. It may form hydrogen bonding with moisture in the air. Preferred organosilanes are alkoxy silane, aminosilane, epoxysilane, acrylic silane, vinylic silane, mercaptosilane, etc. The organosilane may be used alone or in combination. Among them, alkoxysilane, particularly methyltrimethoxysilane, is preferred.

Gel is formed when the addition amount of the organosilane exceeds 1 part by weight based on 100 parts by weight of the liquid modified alkali silicate. The gel results from the reaction with the silicate, and may function as another binder at high temperature, in addition to the silicate. However, when the addition amount of the organosilane exceeds 1 part by weight, the gel is formed accompanied by abrupt exothermic reaction. The addition of boric acid or borax in advance may prevent the gel formation. Further, the addition of the boric acid or borax results in improved flame retardance of the fire-proof covering agent. The silicone oil and the organosilane, which are used as the siloxane reactive denaturant in the present invention, has siloxane groups and other various functional groups offering good fire resistance and, thus, provides heating control and self-extinguishing properties to the fire-proof covering agent.

The sugar is added to the liquid modified alkali metal silicate in liquid form. Glucose, dextrose, malto-dextrine, fructose, sucrose, syrup with low dextrose, oligosaccharide or a combination may be used. The hydroxyl groups of the sugar are chemically bonded to the siloxane groups of the silicate, thereby resulting in improved coatability, adhesion, storage property, film flexibility, and water resistence of the fire-proof covering agent. The modified starch is added to the liquid modified alkali metal silicate in powder form, and then dissolved or dispersed. The hydroxyl groups of the starch are chemically bonded to the siloxane groups of the silicate, thereby resulting in improved coatability, adhesion, storage property and water resistence. Starch basically consists of glucose. It is a mixture of amylase (unbranched fraction) and amylopectin (branched fraction). Through gelatinization into α-form, thickening effect is improved and film formation upon drying becomes possible. The modified starch used in the present invention refers to a starch modified by physical or enzymatic treatment. The modified starch may be gelatinized in advance and dissolved or dispersed in alkali. Upon drying, the modified starch may form film (retrogradation to β-form). Examples of the modified starch that can be used include refined starch, bleached starch obtained by bleaching refined starch using an oxidizing agent, refined tapioca starch obtained by removing crude fiber, crude protein, crude ash, etc. from cassava powder, modified starch obtained by substituting hydroxyl groups of starch molecules with sodium hypochlorite, cationic starch obtained by substituting hydroxyl groups of starch molecules with a quaternary ammonium compound, acetylated starch obtained by substituting hydroxyl groups of starch molecules with ester, phosphate-crosslinked starch obtained by linking two hydroxyl groups of two starch molecules, and epichlorohydrin-crosslinked starch. These may be used alone or in combination. Since the concomitant addition of the sugar and modified starch is not so effective due to the hydrolysis by the alkali, it is preferable that they are added independently to the liquid modified alkali metal silicate.

When the siloxane reactive denaturants are added concomitantly, they may result in a synergic effect. For example, in one embodiment, sugar or modified starch and silicone oil are added to the liquid modified alkali metal silicate. The concomitant addition of sugar or modified starch and silicone oil results in improved adhesion, in addition to the effects attained by the addition of each of the sugar or modified starch and the silicone oil described above. That is, the sugar or modified starch reacts with the silicone oil to form a new binder, thereby improving adhesion of the fire-proof covering agent to a flammable material. It is considered that the new binder is attained from the reaction of the functional group of the sugar or modified starch with the siloxane group of the silicone oil. Actually, the reaction product resulting from the addition of the silicone oil in an aqueous solution of the sugar or modified starch while stirring forms soft but strong white film upon drying, like an emulsion-type binder.

In another embodiment, silicone oil and organosilane are added to the liquid modified alkali metal silicate. In addition to the effects attained by the addition of each of the silicone oil and the organosilane, the concomitant addition of silicone oil and organosilane further provides the advantage of improved adhesion and film strength. This seems to be due to the coupling effect of the organosilane.

In another embodiment, sugar or modified starch and organosilane are added to the liquid modified alkali metal silicate. In addition to the effects attained by the addition of each of the sugar or modified starch and the organosilane, the concomitant addition of sugar or modified starch and organosilane further provides the advantage of improved adhesion. This seems to be due to the coupling effect of the organosilane, accompanied by the effect of the functional groups of the sugar or modified starch and the organosilane.

In another embodiment, sugar or modified starch, silicone oil and organosilane are added to the liquid modified alkali metal silicate. In addition to the effects attained by the addition of each of the sugar or modified starch, the silicone oil and the organosilane, the concomitant addition of sugar or modified starch, silicone oil and organosilane further provides the advantage of improved adhesion, film strength, etc. This seems to be due to the coupling effect of the organosilane, as well as the functional groups of the sugar or modified starch and the organosilane, and the formation of binder by the silicone oil and the sugar or modified starch.

The compositions of the liquid fire-proof covering agents comprising the liquid modified alkali metal silicate as substrate described above can be summarized as follows. However, the present invention is not limited thereto.

A first embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; and ii) 0.1 to 10 parts by weight of silicone oil.

A second embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; and ii) 0.1 to 1 parts by weight of organosilane.

A third embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 1 to 10 parts by weight of organosilane; and iii) 0.5 to 10 parts by weight of boric acid or borax.

A fourth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; and ii) 0.1 to 10 parts by weight of sugar or modified starch.

A fifth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 10 parts by weight of silicone oil; and iii) 0.1 to 1 parts by weight of organosilane. A sixth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 10 parts by weight of silicone oil; iii) 1 to 10 parts by weight of organosilane; and iv) 0.5 to 10 parts by weight of boric acid or borax. A seventh embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 10 parts by weight of silicone oil; and iii) 1 to 10 parts by weight of sugar or modified starch.

An eighth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 1 parts by weight of organosilane; and iii) 1 to 10 parts by weight of sugar or modified starch.

A ninth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 1 to 10 parts by weight of organosilane; iii) 0.5 to 10 parts by weight of boric acid or borax; and iv) 1 to 10 parts by weight of sugar or modified starch.

A tenth embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 10 parts by weight of silicone oil; iii) 0.1 to 1 parts by weight of organosilane; and iv) 0.1 to 10 parts by weight of sugar or modified starch.

An eleventh embodiment comprises i) 100 parts by weight of liquid modified alkali metal silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80 : 20 to 99 : 1 ; ii) 0.1 to 10 parts by weight of silicone oil; iii) 1 to 10 parts by weight of organosilane; iv) 0.5 to 10 parts by weight of boric acid or borax; and v) 0.1 to 10 parts by weight of sugar or modified starch.

The fire-proof covering agent of the present invention may further comprise 0.01 to 3 parts by weight of a pigment based on 100 parts by weight of the liquid modified alkali silicate, in order to provide color. When the pigment is added in an amount less than 0.01 part by weight, it is difficult to provide color.

And, an amount exceeding 3 parts by weight does not provide a richer color.

In addition, the fire-proof covering agent of the present invention may further comprise 0.01 to 2 parts by weight of a liquid flame retardant based on 100 parts by weight of the liquid modified alkali silicate, in order to further improve flame retardance. When the liquid flame retardant is added in an amount less than 0.01 part by weight, further improvement of flame retardance may not be attained. And, when the liquid flame retardant is added in an amount exceeding 2 parts by weight, flame retardance is not improved further, and precipitation may occur. The liquid flame retardant is added to the flame retardant coating composition of the present invention to provide self-distinguishing property. Compounds soluble in water and alkali, e.g., phosphor compounds or dicyandiamides, are preferred.

Previously known inorganic particles may be added as flame retardant.

But, in that case, a small amount is preferred considering the possibility of dust generation during drying, deterioration of storage characteristics caused by precipitation, and flexibility and transparency of cured film, and the like.

The fire-proof covering agent of the present invention may be directly coated on a flammable material such as organic fiber, organic fabric, organic nonwoven fabric, paper, wood, plywood, organic mold, plastic, organic foam, expandable resin, foam resin, organic resin, etc., and then formed into film, for example, by drying.

The coating amount is preferably from 50 to 500 parts by weight, more preferably 100 parts by weight, based on 100 parts by weight of the flammable material. The larger the coating amount, the higher is the flame retardance. When the coating amount is less than 50 parts by weight, it is difficult to attain wanted flame retardance. And, when the coating amount exceeds 500 parts by weight, further improvement of flame retardance is not attained, and the cost increases. Good flame retardance and coatability are attained when the wet coating thickness ranges from 0.1 to 100 mil. The coating method is not particularly limited. Any of dip coating, spray coating, beat coating, screw coating, injection coating, etc. may be used.

Following the coating, a cured film is formed as moisture other than crystal water evaporates. Drying may be performed to accelerate the formation.

The drying may be performed by natural drying, hot air drying, microwave drying, or CO₂ curing drying using the reaction of alkali silicate with carbon dioxide.

The flammable material coated with the fire-proof covering agent of the present invention exhibits flame retardance corresponding to or better than KS

F2271 3rd grade or 2nd grade flame retardance, depending on the source materials of the flame retardant coating composition, proportions thereof and coating amount. [Mode for Invention]

The following examples are intended to illustrate the present invention and should not be construed as limiting the scope of the present invention.

Examples Preparation Example 1

Preparation of liquid modified alkali metal silicate from liquid sodium silicate and amorphous silica

96 kg of sodium silicate Water Glass No. 2 was put in a plastic drum. While stirring at 500 rpm with a paddle stirrer, 4 kg of 400-mesh all pass white carbon (TIXOSIL 38 AB, Rhodia Silica Korea) was put as amorphous silica. Stirring was further performed for 10 minutes to obtain a modified sodium silicate solution. In water resistence test (90 ⁰C hot water), loss of the coating composition was 13 weight %. In adhesion strength test (cellophane tape test), the loss ratio of the coating composition was 8/25. Preparation Example 2

90 kg of sodium silicate Water Glass No. 2 was put in a plastic drum. While stirring at 500 rpm with a paddle stirrer, 5 kg of borax was added and dissolved. Then, 10 kg of silica gel (ss-sil230, S-ChemTech) with an average particle size of 3.4 μm was added. Stirring was further performed for 10 minutes to obtain a modified sodium silicate solution. In water resistence test (90 ⁰C hot water), loss of the coating composition was 5 weight %. In adhesion strength test (cellophane tape test), the loss ratio of the coating composition was 3/25. Preparation Example 3

Preparation of liquid modified alkali metal silicate from liquid sodium silicate and crystalline silica

90 kg of sodium silicate Water Glass No. 2 was put in a plastic drum.

While stirring at 500 rpm with a paddle stirrer, 5 kg of borax was added and dissolved. Then, 10 kg of quartzite (SiO₂ 82-89 weight %, AI₂O₃ 3-7 weight %,

Fe₂O₃ 0.5-5.0 weight %, CaO 0.0.5-1.5 weight %, MgO 0.1-1.0 weight %, Na₂O 0.01-1.5 weight %, K₂O 0.1-3.0 weight %, TiO₂ 0.05-0.5 weight %, Ig 0.5-2.5 weight %, major crystal phase = α-quart, minor crystal phase = kaolin, halloysite, illite, sericite, muscovite and mica, particle size = 4-25 μm, apparent specific gravity = 0.3-0.7 ) was added. Stirring was further performed for 10 minutes to obtain a modified sodium silicate solution. In water resistence test (90 ⁰C hot water), loss of the coating composition was 1.5 weight %. In adhesion strength test (cellophane tape test), the loss ratio of the coating composition was 1/25.

Comparative Example 1

Commercially available Water Glass No. 2 was prepared.

Examples 1 to 15 and Comparative Example 2

Fire-proof covering agent were prepared by adding the components listed in Tables 1 and 2 below to the modified sodium silicate solutions prepared in Preparation Examples 1 to 3 and Comparative Example 1.

Table 1

Table 2

In Tables 1 and 2, the numbers in parentheses refer to the quantity included in the substrate.

Physical properties were measured as follows, and the result is given in Tables 3 and 4 below. Test Example

Water resistance

Each of the solutions was coated on polystyrene foams with a thickness of 4 mil and an area of 200 cm² using a square applicator. After drying, the polystyrene foams were immersed in 90 ⁰C of hot water for 10 minutes. Then, the polystyrene foams were dried and the loss of the coating composition was calculated

Adhesion force

Each of the solutions was coated on an acyl plate with a thickness of 2 mil and an area of 200 cm² using a square applicator. After drying, lines were drawn on the resultant film to result in 5 x 5 squares of size 2 mm x 2 mm. A cellophane tape was attached and then detached with an angle of 90 °.

Water repellencv

Water repellency was evaluated by observing water drops sprayed on the board. O means that water drops roll on the surface, and X means that they do not.

Precipitation

Precipitation was observed with eyes after allowing a sealed beaker containing each solution to stand for 28 days.

Storage property Storage property was observed with eyes after allowing a sealed beaker containing each solution to stand for 28 days by determining whether viscosity increased, and/or gelation or curing had occurred.

Polystyrene foams Each 76 g of the coating agents was dip coated on 76 g of expandable polystyrene beads. After drying with hot air of 70 ⁰C while stirring, the beads were loaded in a mold equipped with a 22 cm x 22 cm x 10 cm wire gauze, and foamed in a chamber for 20 seconds at a water vapor pressure of 0.8 kgf/cm² to obtain flame retardant polystyrene foams.

While drying, the beads were loaded in a mold equipped with a 22 cm x

22 cm x 10 cm wire gauze, and foamed in a chamber for 20 seconds at a water vapor pressure of 0.8 kgf/cm² to obtain flame retardant polystyrene foams.

Physical properties and flame retardance test result are given in Tables 3 and 4 below.

Flexibility was evaluated by touching with fingers. © means superior, O means good, Δ means moderate, and X means hard. Heat fusion property was evaluated by observing the fracture surface. © means that 80 % or more of bead particles were broken, O means 65 % or more of bead particles were broken, and X means less than 65 % of bead particles were broken. Flame retardance was evaluated by flame retardance test according to KS F 2271-1998. O means pass, and X means fail.

Polystyrene plate

Each 190 g of the coating agents was spray coated on a 22 cm x 22 cm x 10 cm polyester fiber plate, and dried with hot air of 70 ⁰C while stirring. Physical properties and flame retardance test result are given in Tables 3 and 4 below.

Flexibility was evaluated by touching with fingers. © means superior,

O means good, Δ means moderate, and X means hard. Flame retardance was evaluated by flame retardance test according to KS F 2271-1998. O means pass, and X means fail. Newspaper

Each 100 g of the fire-proof covering agents was put in a vat. A 10 cm x

10 cm newspaper was immersed in the solution for 1 minute. After drying for 1 hour in a 100 ⁰C dryer, the newspaper was folded in half, and the breakage of the film was observed with eyes. Then, flame was applied at a distance of 30 cm using a gas torch. O means that large foam film was formed, © means that small foam film was formed, and X means that foam film was not formed. Table 3

Table 4

Test Example 2

The coating compositions were coated on a polyester fiber plate, a polyethylene extrusion foam plate and a polypropylene extrusion foam plate, and flame retardance was measured.

Polyester fiber plate

The coating agent prepared in Preparation Example 2 was uniformly coated on a polyester fiber plate (average fiber diameter = 4 μm, apparent specific gravity = 0.02, 5T x 1,000 mm x 20,000 mm) by repeatedly pressing. Remaining coating agent was removed using a squeeze roller (4 kgf/cm²), followed by drying with hot air.

Upon squeezing, the fiber plate exhibited superior thickness restoration property. Upon drying with hot air of 100 ⁰C, the physical properties (flexibility, thermal conductivity, restoration) did not change, except that the apparent specific gravity was 0.025-0.04. The fiber plate was rolled by applying a pressure of 5 kgf/cm² from one direction. When the fiber plate was unrolled 1 week later, it was unfolded within 10 seconds, and thickness restoration was completed within 30 minutes, without dust generation.

The fiber plate passed the flame retardance 3rd grade test according to KS F 2271-1998.

Polyethylene extrusion foam plate

A polyethylene extrusion foam plate (5OT x 10,000 mm x 10,000 mm) with an expansion ratio of 50 was immersed in the coating agent of Preparation Example 2, while needling using a needling puncher. Remaining coating agent was removed using a press (4 kgf/cm²), followed by drying with hot air of 100 ⁰C.

Weight increase was 0.6 times on average, and no deformation was observed.

A laminate plate prepared by bonding 0.2 mm-thick galvanized plates on both sides of the foam plate passed the flame retardance 2nd grade test according to KS F 2271-1998.

Polypropylene extrusion foam plate

A polyethylene extrusion foam plate (5OT x 10,000 mm x 10,000 mm) with an expansion ratio of 70 was coated with the coating agent of Preparation Example 2, under 5 cycles of pressing and release using a press. Remaining coating agent was removed using a squeeze roller (4 kgf/cm²), followed by drying with hot air of 100 ⁰C. Weight increase was 0.8 times on average, and no deformation was observed.

As will be apparent to those skilled in the art, various modifications and adaptations of the present invention above described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

Claims

[CLAIMS]

[Claim 1 ]

A liquid alkali metal silicate based fire-proof covering agent composition comprising: a liquid modified alkali metal silicate substrate; and a siloxane reactive denaturant.

[Claim 2]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1 , which comprises 0.1 to 100 parts by weight of the siloxane reactive denaturant, based on 100 parts by weight of the liquid modified alkali metal silicate.

[Claim 3] The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1 , wherein the liquid modified alkali metal silicate is silicate synthesized from liquid alkali silicate and silica powder with a weight proportion ranging from 80:20 to 99:1.

[Claim 4]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 3, wherein the liquid alkali metal silicate is at least one selected from sodium silicate, potassium silicate, lithium silicate and a combination thereof.

[Claim 5]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 3, wherein the silica powder is at least one selected from white carbon, silica gel, fumed silica, fused silica, diatomaceous earth, α-quartz comprising at least 50 % of soluble silicon dioxide (SiO₂) and a combination thereof .

[Claim 6]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1 , wherein the siloxane reactive denaturant is at least one selected from silicone oil, organosilane, sugar or modified starch and a combination thereof.

[Claim 7]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1 , which comprises 0.1 to 100 parts by weight of at least one siloxane reactive denaturant selected from silicone oil, organosilane, sugar or modified starch and a combination thereof, based on 100 parts by weight of the liquid modified alkali metal silicate.

[Claim 8]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 6, wherein the silicone oil is at least one selected from dimethylpolysiloxane, amino-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with amino groups, epoxy-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with epoxy groups, carboxyl-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with carboxyl groups, carbinol-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with carbinol groups, methacryl-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with methacryl groups, mercapto-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with mercapto groups, phenol-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with phenol groups, single-end modified silicone oil, heterofunctional group-modified silicone oil, polyether-modified silicone oil, methylstyrene-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with methylstyrene groups, alkyl-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with alkyl groups, higher fatty acid-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with higher fatty acid esters, fluorine-modified oil obtained by substituting some methyl groups of dimethylpolysiloxane with fluorine and a combination thereof, and has a viscosity in the range from 50 to 5000 centi-stokes.

[Claim 9]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 6, wherein the organosilane is at least one selected from alkoxysilane, aminosilane, epoxysilane, acrylic silane, vinylic silane, mercaptosilane and a combination thereof.

[Claim 10] The liquid alkali metal silicate based fire-proof covering agent composition according to claim 6, wherein the sugar is at least one selected from glucose, dextrose, malto-dextrine, fructose, sucrose, syrup with low dextrose, oligosaccharide and a combination thereof.

[Claim 11 ]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 6, wherein the modified starch is at least one selected from refined starch, bleached starch obtained by bleaching refined starch using an oxidizing agent, refined tapioca starch obtained by removing crude fiber, crude protein and crude ash from cassava powder, starch ether obtained by substituting hydroxyl groups of starch molecules with carboxyl or carbonyl groups using sodium hypochlorite, cationic starch obtained by substituting hydroxyl groups of starch molecules with a quaternary ammonium compound, acetylated starch obtained by substituting hydroxyl groups of starch molecules with ester, phosphate-crosslinked starch obtained by linking two hydroxyl groups of two starch molecules, epichlorohydrin-crosslinked starch and a combination thereof.

[Claim 12]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1, which further comprises 0.5 to 10 parts by weight of boric acid or borax, based on 100 parts by weight of the liquid modified alkali metal silicate.

[Claim 13] The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1, which further comprises 0.01 to 3 parts by weight of a pigment, based on 100 parts by weight of the liquid modified alkali metal silicate.

[Claim 14]

The liquid alkali metal silicate based fire-proof covering agent composition according to claim 1 , which further comprises 0.01 to 2 parts by weight of a liquid flame retardant, based on 100 parts by weight of the liquid modified alkali metal silicate.

[Claim 15]

An organic fiber, organic fabric, organic nonwoven fabric, paper, wood, plywood, organic mold, plastic, organic foam, expandable resin, foam resin or synthetic resin coated with the liquid alkali metal silicate based fire-proof covering agent according to claim 1.

[Claim 16]

A method for providing flame retardance to a flammable material comprising the steps of: providing a flammable material; and coating the flammable material with the liquid alkali metal silicate based fire-proof covering agent according to claim 1.

[Claim 17]

The method for providing flame retardance to a flammable material according to claim 16, wherein the coating is performed by spray coating, screw coating, injection coating or dip coating.

[Claim 18]

The method for providing flame retardance according to claim 16, wherein the coating is performed such that the wet coating thickness ranges from 0.1 to 100 mil.

[Claim 19]

The method for providing flame retardance according to claim 16, which further comprises the step of drying the fire-proof covering agent.

[Claim 20]

The method for providing flame retardance according to claim 19, wherein the drying is performed by a method selected from natural drying, hot air drying, microwave drying and CO₂ curing drying.