WO2008105595A1

WO2008105595A1 - Method for manufacturing flame-retardant expanded polystyrene blocks and molded products

Info

Publication number: WO2008105595A1
Application number: PCT/KR2008/000990
Authority: WO
Inventors: Young-Joon Moon
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-02-28
Filing date: 2008-02-20
Publication date: 2008-09-04
Anticipated expiration: 2009-08-28
Also published as: KR100799282B1

Abstract

Disclosed is a method for manufacturing flame-retardant expanded polystyrene blocks and molded products. More specifically, the method comprises the steps of: coating a silicon dioxide-containing silicate flame retardant on expanded polystyrene beads in a pre-expander and drying the coated beads to make first coated beads; coating the first coated beads with a water-resistant coating material containing one or more selected from the group consisting of ethylene acrylic acid in the form of a solution of acrylic resin in ethyl alcohol, methyl alcohol or water, an acrylate-based aqueous solution, an aqueous solution of a melamine-, phenol- or urea-containing organic resin in acetic formaldehyde, a mixed aqueous solution of acrylate and silicon, polyvinyl alcohol, a solution of acetic acid vinyl resin, industrial casein, and casein sodium, and drying the coated water-resistant coating material, thus making second coated beads; and manufacturing expanded polystyrene blocks and molded products from the second coated beads. According to the method, a first coating material coated on expanded polystyrene beads in order to impart flame retardancy is prevented from being dissolved and removed by steam and cooling water during the manufacture of the flame-retardant expanded polystyrene block and molded product, thus ensuring flame retardancy.

Description

METHOD FOR MANUFACTURING FLAME-RET ARD ANT EXPANDED POLYSTYRENE BLOCKS AND MOLDED

PRODUCTS

Technical Field

[1] The present invention relates to a method for manufacturing flame -retardant expanded polystyrene blocks and molded products, and more particularly to a method for manufacturing flame-retardant expanded polystyrene blocks and molded products, in which a first coating material coated on expanded polystyrene beads in order to impart flame retardancy is prevented from being dissolved and removed by steam and cooling water during the manufacture of the flame-retardant expanded polystyrene block and molded product, thus ensuring flame retardancy. Background Art

[2] A general process for manufacturing expanded polystyrene beads, molded products and blocks is as follows.

[3] Expanded polystyrene (EPS) beads are composed of a resin prepared by impregnating about 5-7 wt% of a foaming agent, such as pentane or butane, into polystyrene resin. The expanded polystyrene beads are charged in a pre-expander and set to a foaming magnitude of about 30-80 times, and then steam having a temperature of about 100 ⁰C is applied to the beads for a given period of time to form pre-expanded polystyrene bead particles (hereinafter, referred to as "expanded polystyrene beads") having the set foaming magnitude.

[4] The expanded polystyrene beads are aged in a reservoir, which is well ventilated, for

2-12 hours. The aged expanded polystyrene beads are filled in an aluminum mold having a large number of small holes perforated therethrough, and steam having a temperature of 105-118 ⁰C, and cooling water having a temperature of about 60 ⁰C, are sequentially injected through the holes for about 1-5 minutes, thus manufacturing expanded polystyrene blocks and molded products (hereinafter, referred to as "post-expansion"). Then, the post-expanded polystyrene blocks and molded products are dried in a drying chamber for about 1 hour or longer, thus completing the manufacture of expanded polystyrene blocks and molded products.

[5] In the process in which the expanded polystyrene beads are filled in the mold after aging, the beads apparently seems to be closely filled in the mold, but the empty space between the expanded polystyrene bead particles accounts for about 40% of the total volume of the filled expanded polystyrene bead particles. The empty space is almost filled with the expanded polystyrene beads, which are post-expanded by the heat of steam injected into the mold. At this time, the surfaces of the expanded polystyrene bead particles are melted by heat and bonded with each other. During the process in which the beads are dried in a drying chamber using hot air having a temperature of about 30-60 ⁰C, steam evaporates and the surfaces of the expanded polystyrene beads are bonded with each other, thus forming expanded polystyrene blocks and molded products.

[6] The expanded polystyrene blocks manufactured according to the above process are cut mainly with an electrical heating wire to the desired thickness to make boards, which are used as insulation materials for the floor, wall and roof of buildings, and internal core materials for panels having steel sheets attached to both surfaces thereof. The expanded polystyrene molded products are used for the manufacture of containers for fruits and fishes, circular or rectangular insulating ducts, devices, such as air blowers or filters, total heat exchangers for electrical parts, etc.

[7] However, the expanded polystyrene blocks and molded products manufactured according to the above general method have a shortcoming in that they do not resist a temperature higher than 80 ⁰C and heat. R>r example, when they are used as equipment and structural materials for buildings, they are readily burned by fire, and in addition, the expanded polystyrene resins quickly melt or run down due to the heat of fire in a state in which they catch fire, so that they spread fire, thus increasing property damage. Also, a large amount of hazardous gases, such as carbon dioxide and carbon monoxide, are generated during the burning process, thus causing casualties.

[8] In order to solve the above-described problems, Korean Patent Registration No.

10-0479218 discloses a method for manufacturing flame-retardant polystyrene blocks and molded products. In the disclosed method, acetic acid vinyl resin, which is condensable adhesive resin, is dissolved in methanol, and a large amount of fine aluninun hydroxide powder as a flame retardant is added to the solution, thus making a mixed liquid solution. The mixed solution is coated on pre-expanded polystyrene beads, and a small amount of a surfactant such as ethylene glycol is used as a release agent in order to prevent the expanded polystyrene beads coated with adhesive resin from agglomerating with each other.

[9] In said method, there is a phenomenon in which the flame retardant aluminum hydroxide coated on the surface of the expanded polystyrene bead particles are readily removed from the expanded polystyrene beads due to a decrease in the adhesion thereof. To enhance the adhesion, the acetic acid vinyl resin, which is condensable resin having the property of readily adhering to other materials at room temperature, is used as an adhesive.

[10] The acetic acid vinyl resin has the property of readily adhering to other materials at a low temperature of 30-40 ⁰C, but tends to become soft or gelled at that temperature. Also, when the expanded polystyrene beads coated with aluninum hydroxide are post- expanded in a mold, the coated aluminun hydroxide is mostly dissolved and removed by steam, having a temperature of 104-118 ⁰C, and cooling water, having a temperature of about 60 ⁰C, which are injected to the entire surface of the flame-retardant polystyrene bead particles from the outside of the mold and the molding machine. Thus, the manufactured flame-retardant expanded polystyrene blocks and molded products have a reduced flame retardant function. Disclosure of Invention Technical Problem

[11] The present invention has been made in order to solve the above-described problems occurring in the prior art, and it is an object of the present invention to provide a method for manufacturing flame-retardant expanded polystyrene blocks and molded products from expanded polystyrene beads, in which a silicate flame retardant is coated on the surface of expanded polystyrene beads two times or more in order to impart flame retardancy to expanded polystyrene blocks and molded products, thus making flame-retardant expanded polystyrene beads, and the flame-retardant polystyrene beads are coated with a water-resistant coating material so as to have resistance to high-temperature steam and cooling water, before they are post-expanded.

[12] The water-resistant coating material should cover the expanded polystyrene beads, such that it swells together with the expanded polystyrene beads, even when the expanded polystyrene beads swell by 40% due to a large amount high-temperature steam and cooling water during post-expansion in a mold, while the silicate flame retardant coated inside thereof is not dissolved or washed out. Also, the water-resistant coating material should have ensured water resistance to prevent the dissolution and removal of the silicate flame retardant, even when it comes into contact with steam, having a temperature of 104-118 ⁰C, for 5 minutes. Moreover, the water-resistant coating material should be rapidly dried and cured below 70-80 ⁰C at which the expanded polystyrene beads are post-expanded. [13] Another object of the present invention is to provide a method for manufacturing flame-retardant expanded polystyrene blocks and molded products, which make it possible to prevent the polystyrene resin from being melted or hazardous gases from being generated, in a state in which the resin catches fire, even when the blocks and molded products come into contact with high-temperature heat and flame, having a temperature higher than 750 ⁰C, due to the occurrence of fire, during the use of the blocks and molded products as interior and exterior materials for building or equipment materials. Technical Solution

[14] Meanwhile, the step of making the expanded polystyrene blocks and molded products from the second coated beads may comprise the steps of: supplying steam into a mold by an injection unit so as to expand the second coated beads received in the mold, in a state in which injection pipes are positioned at an insertion position, wherein the mold has insertion holes formed therein and receives therein the second coated beads to be injected with steam and cooling water, and the injection unit has the injection pipes, which are inserted into the insertion holes, serve to inject the water- resistant coating material on the second coated beads, and reciprocally move between the insertion position, positioned in the mold, and a withdrawing position apart from the inside of the mold; injecting the water-resistant coating material onto the surface of the second coated beads through the injection pipes while moving the injection pipes from the insertion position to the withdrawing position; and supplying cooling water into the mold, after the movement of the injection pipes to the withdrawing position is completed.

Advantageous Effects

[15] As described above, according to the present invention, it is possible to manufacture flame-retardant expanded polystyrene blocks and molded products, which are not burned at a temperature higher than 750 ⁰C and prevent the expanded polystyrene resin from being melted down by the flame and heat of fire to spread the fire to other materials or sites.

[16] Also, the present invention allows the manufacture of flame-retardant polystyrene blocks and molded products, which serve as an insulation barrier against the heat and flame of flame and, at the same time, block the supply of oxygen, which assists in burning, so as to minimize the generation of hazardous gases, such as carbon monoxide and carbon dioxide, caused by burning. [17] Moreover, in the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention, there is an advantage in that the cost for producing the polystyrene blocks and molded products is low, because silicate flame retardants, including liquid sodium silicate and potassiun silicate, which are expensive and have excellent flame retardancy, are used.

[18] Furthermore, in the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention, expanded polystyrene beads are coated with the water-resistant coating material for imparting both water resistance and flame retardancy. Thus, it is possible to prevent the sodiun or potassium component of the flame retardant being readily dissolved and removed by the water or moisture of rain or snow during the use of the polystyrene blocks and molded products as structural materials or insulation materials for buildings. Accordingly, the flame retardancy of the polystyrene blocks and molded products is ensured.

[19] In addition, in the flame-retardant expanded polyester blocks and molded products manufactured according to the present invention, the silicate flame retardant is provided on the surface of the polyester blocks and molded products. Thus, the flame- retardant expanded polystyrene blocks and molded products according to the present invention can be attached to cement or concrete without using a separate adhesive material such as mortar, and thus they can be used as building materials.

[20] Also, the flame-retardant expanded polyester blocks and molded products manufactured according to the present invention have heat resistance, antibacterial properties, insecticidal properties, and far infrared ray-emitting functions, because one or more selected from among charcoal, zeoilte and yellow earth are added to the water- resistant coating material. Brief Description of the Drawings

[21] FIG. 1 is a flow chart showing a method for manufacturing flame-retardant expanded polypropylene blocks and molded products according to the present invention.

[22] FIG. 2 is a flow chart showing a method for manufacturing flame-retardant expanded polypropylene blocks and molded products, which comprises, in addition to the steps shown in FIG. 1, a step of coating expanded polypropylene beads with an organic coating material.

[23] FIG. 3 is a cross-sectional view showing a mold in a state in which injection pipes are positioned at an insertion position.

[24] FIG. 4 is a cross-sectional view showing a mold in a state in which injection pipes are positioned at a withdrawing position.

[25] HG. 5 is a photograph of flame-retardant expanded polystyrene molded products manufactured according to the present invention.

[26] HG. 6 is a photograph showing a flame retardancy test for an expanded polystyrene molded product manufactured according to the prior art.

[27] HGS. 7 and 8 are photographs showing flame retardancy tests for flame-retardant expanded polystyrene molded products manufactured according to the present invention.

[28] HG. 9 is a photograph showing the results of flame retardancy tests for the flame- retardant polystyrene molded products manufactured according to the present invention and the expanded polystyrene molded product manufactured according to the prior art. Mode for the Invention

[29] Hereinafter, the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention will be described in detail with reference to the accompanying drawings.

[30] As shown in HG. 1, the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention comprises a step (Sl) of making first coated beads.

[31] The first coated beads 20 are produced by primarily coating expanded polystyrene beads 10 with a silicate flame retardant.

[32] The silicate flame retardant contains, as a main material, silicon dioxide (SiO ₂), which is an inorganic noninflammable material resisting high heat having a temperature higher than 1200 ⁰C. Also, the silicate flame retardant may be composed of sodiun silicate, modified sodiun silicate, potassiun silicate, modified colloidal silica, colloidal silica or lithiun silicate.

[33] Herein, sodium silicate is also generally called "water soluble glass'Or "soda silicate"and is represented by a molecular formula of Na ₂O-nSiO₂-xH₂O. Although sodiun silicate can be provided in various forms having a sodium dioxide content of 10-40%, it is preferable in the present invention to use sodium silicate having a sodiun dioxide content of 30-40%.

[34] Also, the silicate flame retardant can be provided with potassiun silicate. Potassiun silicate is represented by a molecular formula of K ₂OnSi0_{2 x}H₂0 and can be provided in various forms having a silicon dioxide content of 10-45%. However, in the present invention, potassium silicate having a silicon dioxide content of 30-40% is preferably used, because it is inexpensive and, at the same time, exhibits the functionality and action of the present invention.

[35] It is to be understood that, as the silicate flame retardant, a mixture of 1-99 wt% of sodiun silicate and 1-99 wt% of potassiun silicate can be used depending on the intended purpose and use, such as the prevention of whitening events.

[36] When sodiun silicate is used as the silicate flame retardant, the sodiun component can be dissolved in water or moisture. In order to the dissolution of the sodiun component, modified sodiun silicate, from which sodiun has been removed through ion exchange, can be used as the silicate flame retardant in the present invention.

[37] Also, as the silicate flame retardant in the present invention, colloidal silica, which contains silicon dioxide (SiO₂) and a hydroxyl (OH-) compound in an amount of 10-50% and has a cluster structure, can be used.

[38] Herein, colloidal silica is a colloidal material, which has a particle size of 1-100 nm and contains silica as a solute. The colloidal silica has a number of hydroxyl groups (OH) on the surface thereof and contains siloxane bonds (Si-O-Si) therein, and thus it has characteristics, such as bonding ability and heat resistance.

[39] Also, as the silicate flame retardant in the present invention, modified colloidal silica obtained by adding pure colloidal silica to the modified sodiun silicate may be used.

[40] Moreover, as the silicate flame retardant in the present invention, liquid lithium silicate, in which lithiun having the lightest specific gravity (about 0.543) among solid elements is dispersed in colloidal silica, may also be used. Herein, the lithiun silicate is characterized in that it has high water resistance compared to those of other inorganic silicate flame retardants, has high heat resistance and is stable even at low temperatures, such as room temperature (about 25 ⁰C).

[41] The process of coating the expanded polystyrene beads 10 with the silicate flame retardant are repeated two times or more, such that the silicate flame retardant can be uniformly coated on the surface of the expanded polystyrene beads 10. Also, the number of coating with the silicate flame retardant can be controlled to adjust the thickness of the coating layer. Herein, coating the expanded polystyrene beads 10 with the silicate flame retardant can be performed by mixing the expanded polystyrene beads 10 with the silicate flame retardant in a ribbon mixer and drying the mixture with hot air. The construction and function of the ribbon mixer are obvious to those skilled in the art, and thus the detailed description thereof will be emitted herein.

[42] Although sodiun silicate, potassiun silicate, modified sodiun silicate, colloidal silica, modified colloidal silica or lithiun silicate, which are provided as the silicate flame retardant in the present invention, may be used alone, additives can be added to thereto to enhance the flame retardant properties of the silicate flame retardant.

[43] That is, in order to further enhance the flame retardant properties of the silicate flame retardant in the present invention, a mixture of 50-99.99 wt% of the silicate flame retardant with 0.01-50 wt% of any one selected from among flame-retardant ammoniun phosphate, aluninun hydroxide, magnesium hydroxide, antimony pentoxide, calciun carbonate, sodium carbonate and az^dicarbonamide may be used as the silicate flame retardant.

[44] As shown in HG. 2, the step of making the first coated beads 20 may further comprise a step (SIa) of coating the silicate flame retardant-coated expanded polystyrene beads 10 with an organic coating material, such as acrylate, polyvinyl alcohol, melamine, phenol or urea, thus making first coated beads. Herein, the organic coating material is provided in order to enhance water resistance to steam and cooling water, which are supplied in a post-expansion process to be described later. Although the organic coating material can be coated on the first coated beads 20 by itself, it is to be understood that a mixture of 50-99.9 wt% of the silicate flame retardant with 0.01-50 wt% of the organic coating material may be coated on the expanded polystyrene beads 10.

[45] The first coated beads can be post-expanded in a mold 40, but the silicate flame retardant can be dissolved and removed by steam and cooling water, which are supplied into the mold 40 during the post-expansion.

[46] R>r this reason, as shown in HGS. 1 and 2, the inventive method comprises, after making the first coated beads 20 and 21 as described above, a step (S2) of coating the first coated beads 20 and 21 with the water-resistant coating material in order to impart water resistance properties to the first coated beads 20 and 21, thus making second coated beads 30.

[47] Herein, coating the first coated beads 20 and 21 with the water-resistant material is performed in order to prevent the coated silicate flame retardant from dissolved and removed by steam, having a temperature of 105-118 ⁰C, and cooling water, having a temperature of 60 ⁰C, which are supplied during post-expansion in the mold 40.

[48] Also, coating the first coated beads with the water-resistant coating material can be performed in the above -described ribbon mixer.

[49] The water-resistant coating material can be provided as a liquid coating material having heat resistance and water resistance. Specifically, the water resistant coating material can be provided as ethylene acrylic acid in the form of a solution of an acrylic resin, having an acrylate solid content of 10-75%, in ethyl alcohol, methyl alcohol or water. Alternatively, the water-resistant coating material can be provided as an aqueous solution of polyester or acrylate such as acryl. Alternatively, it can be provided as an solution of a melamine-, phenol- or urea-containing organic resin in acetic formaldehyde, a mixed solution of said acrylate and inorganic silicon (6:4 w/w), polyvinyl alcohol (PVA), acetic acid vinyl resin solution, industrial casein, or casein sodiun.

[50] In order to impart flame retardant properties to the water-resistant coating material, a mixture of 90-99.9 wt% of the water-resistant coating material with 0.1-10 wt% of a flame-retardant material, such as ammoniun phosphate, aluninum hydroxide, magnesiun hydroxide, antimony pentoxide, calciun carbonate, sodium carbonate, potassium bicarbonate or a2)dicarbonamide, may be used as the water-resistant coating material in the present invention.

[51] Also, in order to impart antibacterial, insecticidal and far infrared ray-emitting functions and heat resistance properties to the water-resistant coating material and to increase the flame retardant properties, a mixture of 80-99 wt% of the water-resistant coating material with 1-20 wt% of one or more selected from among charcoal, zeolite, talc, calciun carbonate, expanded vermiculite, expanded perlite, yellow earth and magnesiun hydroxide may be used as the water-resistant coating material in the present invention.

[52] Moreover, it is to be understood that the silicate flame retardant can be added to the water-resistant coating material to increase the water resistance of the second coated beads 30 and at the same time, increase the flame retardant properties of the beads.

[53] As shown in HGS. 1 and 2, as the second coated beads 30, a step (S3) of pre- expanding the second coated beads 30 to make flame-retardant expanded polystyrene blocks and molded products is carried out.

[54] In another embodiment of the present invention, even though the water-resistant coating material is coated on the expanded polystyrene beads to increase the water resistance of the beads, the flame-retardant expanded polystyrene blocks or molded products can also be manufactured while the pressure of steam supplied into the mold 40 during post-expansion is maintained higher than the conventional pressure of steam supplied during post-expansion. R>r example, when flame-retardant expanded polystyrene blocks having a high density of 45-75 kg/m³ are to be manufactured, the temperature and pressure of steam should be increased, and the time required for the second coated beads to come into contact with steam and cooling water will increase. R>r this reason, the water-resistant coating material of the second coated beads can be partially dissolved and removed by high-temperature and high-pressure steam, and then the silicate flame retardant can be dissolved and removed.

[55] Accordingly, as shown in HGS. 3 and 4, in the step (S3) of making the flame- retardant expanded polystyrene blocks and molded products according to the present invention, steam can be supplied by an insertion unit to the second coated beads 30 received in the mold 40, which has insertion holes formed therein and receives the second coated beads 30 therein, the injection unit 50 serving to inject the second coating material and comprising one or more injection pipes having a plurality of holes formed therethrough. Then the water-resistant coating material can be injected and coated again on the second coated beads.

[56] The mold 40 comprises an outer mold 41 and an inner mold 42. The outer mold 41 receives the inner mold 42 therein and comprises a first inlet 44 through which steam or cooling water is introduced, and a first insertion hole 41b into which the injection pipe 51 is inserted. The inner mold 42 receives and post-expands the second coated beads 30 therein. In the inner mold 42, a plurality of second inlets 43 for supplying steam or cooling water from the outer mold 41 to the second coated beads 30 are formed, and second insertion holes 42b to be inserted with the injection pipes 51 are formed.

[57] The injection unit 50 comprises a plurality of injection pipes 51. Although two injection pipes 51 are illustrated by way of example in HGS. 3 and 4, it is to be understood that one or two or more injection pipes 51 can be provided.

[58] The injection pipes 51 are reciprocally movable between an insertion position A, to which the injection pipes 51 are inserted into the mold 40 through the insertion holes of the mold 40, and a withdrawing position B, to which the injection pipes 51 are withdrawn from the inside of the mold 40. Also, Pluralities of injection holes 52 for injecting the water-resistant coating material to the second coated beads 30 are formed.

[59] Accordingly, the step (S3) of making the flame-retardant expanded polystyrene blocks and molded products according to the present invention comprises: supplying steam into the mold 40 so as to expand the second coated beads 30 received in the mold, in a state in which the injection pipes 51 are positioned at the insertion position A, as shown in HG. 3; injecting the water-resistant coating material onto the surface of the second coated beads 30 through the injection pipes 51 while moving the injection pipes 51 from the insertion position A to the withdrawing position B, as shown in HG. 4; and supplying cooling water into the mold 40, after the movement of the injection pipes 51 to the withdrawing position B is completed.

[60] Specifically, before the second coated beads 30 coated with the water-resistant coating material are filled in the mold 40, the injection pipes 51 are positioned at the insertion position A close to the bottom of the inside of the inner mold 42. Then, the second coated beads 30 are filled in the inner mold 42, and immediately after high- temperature steam is injected into the inner mold 42, the injection pipes 51 move to the withdrawing position B, while the water-resistant coating material, heated to 80 ⁰C or higher, is injected between the second coated beads uniformly through the injection pipes. After the movement of the injection pipes 51 to the withdrawing position B is completed, cooling water is introduced into the inner mold 42 to cool the expanded second coated beads 30, thus manufacturing flame-retardant expanded polystyrene blocks and molded products. Herein, the water-resistant coating material injected through the injection pipes 51 are positioned between the expanded second coated beads 30, such that it also functions to bond the expanded second coated beads 30 with each other.

[61] Also, the surface of molded products, obtained by processing the above-produced flame-retardant expanded polystyrene blocks and molded products according to the intended use, can also be coated with the silicate flame retardant one time or more through a spray injection process and dried, thus increasing the flame retardancy of the molded products.

[62] Hereinafter, a process for manufacturing flame-retardant expanded polystyrene molded products and a flame retardancy test conducted using the prepared flame- retardant expanded polystyrene molded products will be described with reference to HGS. 5 to 9.

[63] Erst, in a ribbon mixer, 500 g of expanded polystyrene beads 10 having a density of

15.3 kg/m³ were mixed with 750 g of a potassiun silicate solution (silicate flame retardant), having a silicon dioxide content of 20%, for 5 minutes, and then the mixture was dried with hot air, having a temperature of 60-70 ⁰C, for about 5 minutes. Then, in the ribbon mixer, a mixture of 150 g of potassiun silicate solution and 100 g of lithiun silicate solution, and the flame-retardant expanded polystyrene coated with the silicate flame retardant, were stirred for about 10 minutes and dried with hot air having a temperature of 60-70 ⁰C, thus obtaining 1,200 g of first coated beads 20 and 21.

[64] Meanwhile, 80 wt% of ethylene acrylic acid having an acryl solid content of 45%, 10 wt% of a material containing charcoal, zeolite or yellow earth, having a particle size of 7-10 /M, and about 10 wt% of ammonium phosphate, were stirred in a ribbon mixer for 1 minute, thus producing 250 g of a water-resistant coating material. Then, 250 g of the water-resistant coating material and 600 g of the first coated beads 20 and 21 were mixed with each other in the ribbon mixer for about 5 minutes and dried with hot air having a temperature of 70 ⁰C. Then, the dried material was taken out of the mixer, and then aged and dried in a drying chamber at a hot air temperature of 80 ⁰C for more than

2 hours, thus obtaining 750 g of gray-colored second coated beads 30.

[65] Also, 300 g of a water-resistant coating material consisting of 60 wt% of ethylene acrylic acid, having an acryl solid content of 75%, 10 wt% of ammoniun phosphate, and 30 wt% of lithiun silicate, was mixed with 600 g of the first coated beads 20 and 21 in the ribbon mixer. The mixture was dried with hot air, having a temperature of 70 0C, for 5 minutes, and then aged and dried in a drying chamber at a hot air temperature of 80 ⁰C for more than 2 hours, thus obtaining 780 g of white second coated beads 30.

[66] As shown in HG. 5, the gray and white second coated beads 30 were placed in a mold and a steam molding machine and applied with steam at a pressure of about 0.75 kg/m² for 20 seconds and with cooling water for 1 minute. Then, the second coated beads 30 are dried, thus obtaining white and gray flame -retardant expanded polystyrene molded products.

[67] Also, a general white expanded polystyrene molded product, which was 150 mm in width, 250 mm in length and 25 mm in thickness, was prepared.

[68] Also, a torch lamp emitting a 10-cm length flame having a temperature of 1200-1300

⁰C was prepared. As shown in HG. 6, the general expanded polystyrene molded product was placed at a distance of 10 cm (flame length) from the torch lamp and brought into contact with the flame of the torch lamp for 2-3 seconds.

[69] As shown in HG. 6, the general expanded polystyrene molded product caught fire in a moment, so that the central portion was destroyed and melted by fire, and the expanded polystyrene resin was melted with the generation of smoke and dropped down in the form of small jelly drops which caught fire. As a result, as can be seen in HG. 9, a large hole having a diameter of about 8-12 cm was formed in the central portion of the general expanded polystyrene molded product (the middle of HG. 9).

[70] Also, as shown in HG. 7, the deep-gray -colored, flame -retardant expanded polystyrene molded product coated with the water-resistant coating material, containing the silicate flame retardant, charcoal and zeolite, was placed at a distance of 10 cm (flame length) from the torch lamp as described above and was brought into contact with the flame of the torch lamp for about 8-10 seconds.

[71] As shown in HG. 9, in the gray flame -retardant polystyrene molded product (the left side of HG. 9), a flame mark in the form of a circular shallow groove, having a diameter of about 10-30 mm and a depth of about 3-5 mm, occurred in the central portion of the molded product, but the molded product did not catch fire, and the resin was not melted down in the form of jelly.

[72] As shown in HG. 8, the white flame-retardant polystyrene molded product was brought into contact with the flame of the torch lamp for about 8-10 seconds in the above-described conditions. As a result, as shown in HG. 9, in the white flame- retardant expanded polystyrene molded product (the right side of HG. 9), a flame mark having a size smaller than that in the gray flame-retardant expanded polystyrene molded product remained, little or no smoke was generated, and a burning reaction was slow.

[73] As a result, as shown in HG. 9, it can be seen that the flame-retardant polystyrene molded product manufactured according to the present invention has excellent flame retardancy compared to that of the general expanded polystyrene molded product and can achieve the objects of the present invention.

[74] Although the preferred embodiment of the present invention has been described 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. Industrial Applicability

[75] As described above, according to the present invention, it is possible to manufacture flame-retardant expanded polystyrene blocks and molded products, which are not burned at a temperature higher than 750 ⁰C and prevent the expanded polystyrene resin from being melted down by the flame and heat of fire to spread the fire to other materials or sites.

[76] Also, the present invention allows the manufacture of flame-retardant polystyrene blocks and molded products, which serve as an insulation barrier against the heat and flame of flame and, at the same time, block the supply of oxygen, which assists in burning, so as to minimize the generation of hazardous gases, such as carbon monoxide and carbon dioxide, caused by burning.

[77] Moreover, in the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention, there is an advantage in that the cost for producing the polystyrene blocks and molded products is low, because silicate flame retardants, including liquid sodium silicate and potassiun silicate, which are expensive and have excellent flame retardancy, are used. [78] Furthermore, in the method for manufacturing flame-retardant expanded polystyrene blocks and molded products according to the present invention, expanded polystyrene beads are coated with the water-resistant coating material for imparting both water resistance and flame retardancy. Thus, it is possible to prevent the sodiun or potassium component of the flame retardant being readily dissolved and removed by the water or moisture of rain or snow during the use of the polystyrene blocks and molded products as structural materials or insulation materials for buildings. Accordingly, the flame retardancy of the polystyrene blocks and molded products is ensured.

[79] In addition, in the flame-retardant expanded polyester blocks and molded products manufactured according to the present invention, the silicate flame retardant is provided on the surface of the polyester blocks and molded products. Thus, the flame- retardant expanded polystyrene blocks and molded products according to the present invention can be attached to cement or concrete without using a separate adhesive material such as mortar, and thus they can be used as building materials.

[80] Also, the flame-retardant expanded polyester blocks and molded products manufactured according to the present invention have heat resistance, antibacterial properties, insecticidal properties, and far infrared ray-emitting functions, because one or more selected from among charcoal, zeoilte and yellow earth are added to the water- resistant coating material.

Claims

[1] A method for manufacturing flame-re tardant expanded polystyrene blocks and molded products, the method comprising the steps of: coating a silicon dioxide-containing silicate flame retardant on expanded polystyrene beads and drying the coated beads to make first coated beads; coating the first coated beads with a water-resistant coating material containing one or more selected from the group consisting of ethylene acrylic acid in the form of a solution of acrylic resin in ethyl alcohol, methyl alcohol or water, an acrylate-based aqueous solution, an aqueous solution of a melamine-, phenol- or urea-containing organic resin in acetic formaldehyde, a mixed aqueous solution of acrylate and silicon, polyvinyl alcohol, a solution of acetic acid vinyl resin, industrial casein, and casein sodium, and drying the coated water-resistant coating material, thus making second coated beads; and manufacturing expanded polystyrene blocks and molded products from the second coated beads.

[2] The method of Claim 1, wherein the step of making the first coated beads further comprises a step of coating the silicate flame retardant-coated expanded polystyrene beads with an organic coating material containing one or more selected from among acrylate, polyvinyl alcohol, melamine, phenol and urea.

[3] The method of Claim 1, wherein the water-resistant coating material may further contain one or more selected from among charcoal, zeolite, talc, calcium carbonate, expanded vermiculite, expanded perlite, yellow earth and magnesium hydroxide.

[4] The method of any one of Claims 1 to 3, wherein the step of making the expanded polystyrene blocks and molded products from the second coated beads comprises the steps of: supplying steam into a mold by an injection unit so as to expand the second coated beads received in the mold, in a state in which injection pipes are positioned at an insertion position, wherein the mold has insertion holes formed therein and receives therein the second coated beads to be injected with steam and cooling water, and the injection unit has the injection pipes, which are inserted into the insertion holes, serve to inject the water-resistant coating material on the second coated beads, and reciprocally move between the insertion position, positioned in the mold, and a withdrawing position apart from the inside of the mold; injecting the water-resistant coating material onto the surface of the second coated beads through the injection pipes while moving the injection pipes from the insertion position to the withdrawing position; and supplying cooling water into the mold, after the movement of the injection pipes to the withdrawing position is completed.