Background Art More than 200 kinds of invisible noxious material are generated in a dwelling space constructed with cement. More particularly, wallpapers and construction finishing materials used for a house generate noxious materials such as formaldehyde, radon gas and volatile organic compounds (VOC), and severely threaten the health of dwellers. Therefore, Korean Government established "The Act of Indoor Air Quality Control for Multiplex Facilities" and indoor contamination of apartments has been measured since May 2004. The indoor contamination and environmental deterioration of apartments recently constructed have been regarded as an important social problem. As a method to solve the above problems, wallpapers, construction finishing materials and exterior materials containing such as silver particles (nanosilver) or silver yarns have been introduced. Although the nanosilver has an excellent antimicrobial property, it has a disadvantage of difficulty to remove the volatile organic compounds in the air. Further, nanosilver is an expensive material, and its antimicrobial property is reduced because nanosilver particles are buried by a material such as adhesive. Therefore, the nanosilver is not suitable for removing the indoor noxious materials, and is limited in actual applications. Zeolite has widely been used for water purification, radioactive waste treatment, washing, drying, and heat insulation, and attempts have been made to apply it to the removal of indoor noxious materials. The zeolite has an adsorption property and can remove the noxious materials to a certain extent, and removal ability may be recognized significantly, if it is directly contacted with volatile organic compounds in a test environment. However, the targeted noxious materials of organic compounds that are not directly contacting with the zeolite may not practically be removed only with the zeolite, because the volatile organic materials themselves do not move towards the zeolite to be removed in a dwelling environment. In order to solve the above problems, a method of utilizing materials emitting anions and/or far infrared rays has been recently disclosed (Korea Utility Model No. 20-328609, Korea Patent Publication No. 10-2004-34625 and Korea Patent Publication No. 2003-78841). Typical materials are tourmaline, monazite, kiyoseki, evlan, iouseki, kisinseki, quartz, and monzonite. Although a few patents were applied, activity and usage of the minerals are not identified clearly, and most applications were made under the inventors' own option or arbitrary interpretation. It is frequently said that anions are good for human health because they help expansion of the blood vessel, control of a normal blood pressure, alkalization of the blood, recovery from fatigue, and stabilization of autonomic nerves. The above minerals have almost no effect on the health, because the minerals emit very weak anions or far infrared rays. However, most of the inventors exaggerate the effect, or insist that the minerals can remove noxious materials, without considering that anions and/or far infrared rays are excessively emitted more than an amount required for the removal of the noxious materials, and thereby may give a bad influence to the health. The tourmaline is mainly produced in Brazil, India, China, and Africa. In 1880, Pierre Curie, the husband of Marie Curie, and his elder brother who is a mineralogist have discovered that electric charge is formed on the surface of the tourmaline crystal if heat or pressure is applied to the tourmaline crystal, and named this phenomenon piezoelectricity. Tourmaline has been also called "electric quartz" since then. The tourmaline emits 200 ~ 600 anions/cc and far infrared rays in the natural state. Particularly, the anions and far infrared rays remove noxious materials, exhaust gases, and chemical compounds used in interior construction materials, which have cations in the air, and have good effect in the prevention and treatment of atopic dermatitis. However, the above amount of generated anions is not enough to remove the noxious materials in the air. The anion emission is further decreased and the effect of the tourmaline is doubtful, when the tourmaline is mixed with adhesive and is used inside a material, not on the surface of the material. Additionally, monazite is recently known as a mineral containing rare-earth elements, and used as an anion-emitting material. Monazite is a mineral containing a lanthanide element, and its composition varies according to the mining location. Its anion emission also varies in the range of about 20,000 ~ 100,000 ions/cc. It has been identified that this mineral emits low-dose radioactive rays, but does not emit far infrared rays. As described above, trials have been carried out for removing volatile organic compounds in the air with a large amount of generated anions. Although such a large amount of anions may remove noxious materials in the air by reacting with them, excessive anions left after the reaction may activate oxygen in the air and may cause various cancers such as skin cancer. About 1,000 ~ 3,000 anions/cc are emitted from the natural condition of waterfall, forest, or water stream, and it is desirable to remove noxious materials by the above amount of anions. Effect of the anion may not be expected if the amount of anion is less than the above range, and excessive amounts of anion may be harmful to the health.

Disclosure of the Invention Technical Problem As described above, removal of indoor noxious materials by using minerals currently known is not satisfactory. Additionally, there is a problem that use of materials emitting excessive anions to remove noxious materials may be harmful to the human health, or the noxious materials in the air may not be removed if the anions emission is insufficient.

Technical Solution Accordingly, the inventor carried out researches to solve the above problem, and completed the present invention by discovering that anion emission may be controlled in the range of 1,000 ~ 2,200 anions/cc by properly mixing tourmaline, monazite, zeolite, and precious serpentine, and thereby indoor volatile organic compounds including formaldehyde are effectively removed and emission of far infrared rays is increased. An object of the present invention is to provide an adhesive composition by mixing tourmaline, monazite, zeolite, and precious serpentine with a conventional water-based adhesive. Another object of the present invention is to provide a plywood floor covering manufactured by using the adhesive composition.

Advantageous Effects In the compositions according to the present invention, emission of anions and far infrared rays from tourmaline may be controlled in a predetermined range by properly mixing with monazite, because the monazite significantly increases the emission of anions and far infrared rays from the tourmaline. Additionally, moisture content is controlled and various organic compounds are removed by adding zeolite thereto. By further adding precious serpentine, indoor volatile organic compounds and various noxious materials are removed, and atopic dermatitis recently regarded as a problem may be prevented or treated, because the precious serpentine has an antimicrobial property. Therefore a comfortable dwelling environment may be maintained. Description of the Drawings Fig. 1 is a sectional view of a plywood floor covering using a composition according to the present invention.

Best Mode Firstly, the present invention will describe tourmaline, monazite, zeolite, and precious serpentine, which are blended with a water-based adhesive. The composition, anion emission number and anion emission rate of tourmaline differs according to the suppliers. In the present invention, tourmaline imported from ChangXing Tourmaline Co., Ltd., China was used, and the following description is based on this tourmaline. According to the analysis result tested by Korea Basic Science Institute, the tourmaline contains SiO2 of 64.37%, Al2O3 of 15.04%, Fe2O3 of 5.08%, MnO of 0.05%, CaO of 2.16%, MgO of 2.88%, K2O of 1.90%, Na2O of 2.01%, P2O5 of 0.13%, and TiO2 of 0.63%. According to the test result of Korea Far Infrared Association, anion emission number was 412 anions/cc; emissivity (5 ~ 20 μm) was 0.928 at 40°C; and emissive energy was 364 W/irf. It has been disclosed that tourmaline is good for human health and removes noxious materials in the air, because the tourmaline continuously generates minute electrostatic and far infrared rays. However, as described above, about 200 ~ 600 anions/cc are emitted from tourmaline according to the kind and origin of the tourmaline. This amount is not sufficient for the removal of indoor noxious materials such as ammonia and volatile organic compounds, and it takes undesirably too long time for the treatment of the noxious materials. The content of tourmaline is preferably 20 - 30 wt% of the total composition excluding adhesive. Monazite used as a component of the composition according to the present invention is a mineral having a chemical composition of (Ce5La, Nd5Th)PO4 and containing cerium as Ce2O3 of40~70%. This material has a light-brown color, Mohs hardness of 5 ~ 5.5, specific gravity of about 5.2. The material emits low-dose radioactive rays. About 20,000 ~ 100,000 anions/cc are emitted according to the kinds of monazite, and monazite emitting about 30,000 ions/cc is commercially used. The present invention used a monazite imported from Brazil by Keumyoung Academy Mine Korea. In the meantime, it has been disclosed that low-dose radioactive rays are not harmful to the health [K. Yamaoka, Biochim, Biophys. Acta., 1381, 265(1998)]. The amount of anions emitted from the monazite is excessively high, and may be harmful to the human body, because the excessive anions activate oxygen in the air. Electrostatic charge and anions emitted from the tourmaline may be increased to a predetermined level by properly mixing this material in tourmaline. The content of the monazite may be controlled in the range of 1,000 ~ 2,200 ions/cc by analyzing anion emission in a tourmaline mixture. According to test results, the addition of monazite is preferably about 22 ~ 45 wt% of the total composition excluding adhesive to have anion emission of the above range. Zeolite is used as another component of the composition according to the present invention, and natural zeolite and synthetic zeolite are available. A natural zeolite mined from Kyungju, Korea, may not be used, because it is not effective for the adsorption of ammonia and volatile organic compounds. A zeolite having Mohs hardness higher than 3.5 and ammonia exchangeability of about 1.7 - 2.1 milliequiv./g is preferable. As an example of zeolite having such performances, Ecosorb M (U. S. Zeolites, Inc.) is available. This zeolite is suitable for removing ammonia and volatile organic compounds in the air. Although the content of zeolite is not particularly limited, it is preferably prepared with the weight ratio of 0.2 ~ 0.4 to the total weight of the composition by considering the anion emission rate change according to the blend ratio of tourmaline and monazite. The addition of zeolite is preferably 10 - 20 wt% of the total composition excluding the adhesive. Additionally, precious serpentine is another component of the composition according to the present invention. It has been reported that a precious serpentine mined from Buyeo, Korea, has an emission rate of far infrared ray higher than 93%, antimicrobial effect of 86%, anti-mildew effect of 100%, and excellent deodorizing property. The content of precious serpentine is preferably 15 - 20 wt% of the total composition excluding adhesive. Removal rate of organic compounds such as formaldehyde is significantly reduced, if the content of precious serpentine is less than 10 wt%. Organic compounds are not detected at all, if the content is greater than 20 wt%. Therefore, the addition of the precious serpentine more than 20 wt% is meaningless and causes a problem of reducing the adhesive strength. Among the above components, the particle size of zeolite is preferably 0.8~1.5g/cin3, and the particle sizes of tourmaline, monazite, and precious serpentine are preferably 400 ~ 1,000 mesh for good homogenizing effect with the adhesive. The kinds of adhesive are not particularly limited, and conventional adhesives may be used. As examples of the adhesives, phenol resin, resorcinol resin, urea resin, polyester resin, epoxy resin, polyvinyl alcohol resin, polyacrylate resin, silicon resin, polyurethane resin, and melamine resin may be used. Particularly among these adhesives, a commercialized acrylic resin of an emulsion type as a water-based adhesive is preferably used. The weight ratio of the adhesive is preferably 0.6 ~ 0.7 to the composition of tourmaline, monazite, zeolite, and precious serpentine. The anion emission and removal effect of noxious materials are undesirably decreased, if the content of the mineral composition is mixed with less than the weight ratio of 0.3 to the adhesive. The adhesion property is undesirably decreased, if the content of the mineral composition is greater than the weight ratio of 0.4. An adhesive composition is prepared by mixing the minerals and adhesive in a conventional method. A floor covering according to the present invention may be manufactured by using the adhesive composition in a manufacturing process of conventional floor coverings and includes a timber plywood 10, a first adhesive layer 20, a plywood 30, a second adhesive layer 40 formed of the adhesive composition according to the present invention, and a decorative laminate 50. According to the requirements, a floor covering may be manufactured by further coating the upper or lower surface of the decorative laminate with nanosilver in a conventional method.

Mode for carrying out the Invention Hereinafter, example embodiments of the present invention will be described in more detail.

Examples 1—10 and Comparative Examples 1-6 Mineral components shown in table 1 were mixed with an adhesive of emulsion type (main component: EVA, brand name: 175HY, Okong Adhesives Co., Ltd.) in the ratio of 4:6 by weight, and floor coverings were manufactured by using the adhesive compositions. Trials were made at a floor covering manufacturer located in Kwangju-city, Kyunggi-do, Korea, without modification of the existing production facilities. The floor coverings were manufactured in a conventional method by applying mixtures of the adhesive (175HY, emulsion type, Okong Adhesives Co., Ltd.) and compositions of Examples 1 ~ 10 and Comparative Examples 1 ~ 6 in the ratio of 6:4 as shown in table 1.

Table 1

l)Supplier: ChangXing Tourmaline Co., Ltd., China, 600 mesh

2)Supplier: Keumyoung Academy Mine Korea, 600 mesh,

imported from Brazil

3)Supplier: U. S. Zeolites, Inc, U.S.A., Brand Name: Ecosorb M 4)Supplier: SamunokNara Co., Ltd., Korea, 500 mesh *) Tested by KCIM-FIR- 1042 method. **) Tested by KS F 3111-01 method.

Referring to the above table, 16.4% and 10.4% of formaldehyde were detected respectively from Comparative Examples 1 and 2. Therefore, it has been identified that an effect of removing organic compounds is decreased in the cases that adhesive compositions include the amount of precious serpentine in 1/3 compared to Examples 1 to 10. Test was carried out by using a measuring equipment of electrically charged particles in the condition of room temperature of 27°C, humidity of 47%, and anions of 96 ions/cc in the air (tested by Korea Institute of Far Infrared Applied Estimation). According to the result of measuring anion emission rates for the compositions of Examples 1 to 10, the number of anions per unit volume was 1,100 ~ 2,200 ions/cc. In the case of Comparative Example 3 containing no monazite, the number of anions per unit volume from the adhesive composition was decreased to about 700 ~ 800 ions/cc. Therefore, it has been identified that the monazite activates the anion emission of tourmaline. Additionally, it has been identified that precious serpentine is an important factor to remove the volatile organic compounds, because the removal rates of formaldehyde were decreased in the cases of Comparative Examples 1,2, 5 and 6.

Experiment 1 Various floor covering were manufactured by changing the ratio between the adhesive and compositions according to the method of Example 1, and the adhesion strengths of the adhesive compositions were tested. The results are shown in the following Table 2.

Table 2

As shown in the above table, the best result was obtained when the mineral and adhesive

were mixed with the mixing ratio of 40:60.

Experiment 2

Anti-mildew tests were carried out according to ASTM G-21 test method; by using a

mixed strain of Aspergillus niger ATCC 9642, Penicillium pinophilum ATCC 11797, and

Chaetomium globosum ATCC 6205. The results are shown in the following Table 3.

Table 3

Referring to' the above test result, a growth of fungi in the sample has not been detected.

Experiment 3 Samples according to the example embodiments of the present invention were submitted to Korea Environment & Merchandise Testing Institute to test volatile organic compounds of the samples. According to the test result, all the volatile organic compounds such as acetone, methanol, methylethylketone, ethanol, benzene, 2-propanol, methylisobutylketone, isobutanol, toluene, butylacetate, 1-butylalcohol, cellosolve, o-xylene, m-xylene, p-xylene, sterene, and butylcellosolve were not detected. The test results are shown in the following Table 4.

Table 4

* TVOCs: VOC detected in the range of n-hexane to n-hexadecane by the GC analysis.

While this invention has been described in connection with what is presently considered to be practical example embodiments, it should be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Industrial Applicability As described above, in a composition according to the present invention, emission of anions and far infrared rays from tourmaline may be controlled by properly mixing monazite, because the monazite significantly improves the emission of anions and far infrared rays from the tourmaline. Various organic compounds may be removed in addition to moisture control by mixing zeolite. Additionally, various indoor volatile organic compounds and noxious materials may be removed by mixing precious serpentine. Since the composition has also antimicrobial property, it may be used for prevention or treatment of atopic dermatitis by maintaining a comfortable dwelling environment.