A functional paper and its use as a deodorant, filtering medium or adsorbent

Abstract: Deodorant comprising 5 to 100% by weight of a calcium phosphate compound having a molar ratio of Ca/P of 0.8 to 2.0, a deodorant sheet and filter sheet containing such calcium phosphate compound, and a functional paper containing 10 to 80% by weight of a calcium phosphate compound as well as a filtering medium for an exhaust gas which comprises a ceramic material containing 5 to 100% by weight of a calcium phosphate compound as well as a filter cartridge and exhaust gas filter containking the filtering medium. Based on excellent properties of the incorporated calcium phosphate compound, the agents and products according to the present invention exhibit a highly improved adsorptivity to an oil-soluble substance, odor substance, animal or vegetable cell, virus, biopolymeric substance or other substances and therefore can be advantageously used in various fields of technology. For example, the functional paper can be used as a deodorant, filter medium and adsorbent as well as flame-retardant paper. The filtering medium, filter cartridge and filter can be used in an exhaust system to purity an exhaust gas produced therein.

Description: The present invention relates to a functional paper used in different fields of technology, and is especially used as a deodorant, filtering medium and adsorbent. The filtering medium may be used as an exhaust gas filter disposed in an exhaust system to purify an exhaust gas. It can effectively trap soot or carbon dusts and also adsorb gaseous substances such as carbon monoxide or hydrocarbons, without causing a blocking of the pores of the filtering medium. Hitherto, to remove any odor components or substances from the surrounding atmosphere or the like, many odor removing processes have been widely used, and typical examples of the well-known deodorizing processes include (1) the use of an aromatizing agent or fragrance to mask the odor, (2) the use of a catalyst to chemically decompose odor components to thereby make them odorless, and (3) the use of an adsorbent capable of adsorbing and removing any odor components. However, each of these three processes has problems to be solved. For example, the aromatizing agent can sometimes emit an unpleasant smell to a person, because generally it must be an agent capable of give out strong fragrance in comparison with the odor components. The catalytic decomposition of the odor components is limited to only some of the odor components, because there is no catalyst which is effective for all odor components. In addition, an activated carbon which is a typical example of the well-known adsorbent-type deodorants cannot effectively adsorb any basic gases such as ammonia gas, although it can adsorb substantially all of other odor components. Further, the activated carbon must be used under the conditions of low temperature, because it can be easily removed at an elevated temperature because of a combustion thereof. It is therefore desirable to provide an improved deodorant which is effective for all types of odor components and does not restrict the conditions of the usable working temperature. In connection with the above-described adsorbents as the deodorant, it should be noted that hitherto, a fibrous substance such as filter paper or filter cloth, granular substance such as activated carbon, clay, gravel or diatomaceous earth or porous substance such as porous pottery have been used as a filtering medium. Apparently, almost of these filtering mediums are used to trap solid substances, and suitable filtering mediums are selected depending on the specific solid substances to be trapped or filtrated. However, the prior art filtering mediums suffer from some drawbacks. The activated carbon has been frequently used as the filtering medium, because it exhibits an excellent adsorptivity. However, since it has no adsorption power for any oil-soluble substances and any bad smell components such as ammonia, the activated carbon cannot be used to remove these substances and components from any gas or liquid containing the same. Recently, a membrane filtering system has been developed, but it suffers from a high production cost, because it is essential to use an ultrafiltration membrane or reverse osmosis membrane. On the other hand, a bacterial filter such as Seitz Filter has been also developed. However, the use of this filter is limited to only traping of bacteria, and if used, the filtration must be carried out under the application of the reduced pressure or centrifugal force. As is appreciated from this and above descriptions, the prior art filtering mediums can be applied to only the limited range of the substances to be filtered off, or need expensive filtering equipments. Turning the discussion of the related art to a functional paper, as is well-known in the art, in the production of conventional white-colored papers, a filler is used to improve an opacity, smoothness, ease of writing, ink-receptivity and other properties of the papers, and typical examples of such filler include clay, talc, titanium white, calcium carbonate and the like. Further, it is also well-known to produce a ceramic paper from a pulp, skeleton material and fixing material, and in accordance with a paper production technology. However, the prior art methods are not suitable for the production of ceramic papers having a high flexibility equivalent to that of the plain papers. Furthermore, JP-A-59-95931 teaches the production of papers having special functions in accordance with the specified method. The papers produced in accordance with this method contain finely divided particles of crystalline aluminum orthophosphate and is characterized by their good capability of adsorbing odor components or substances. These functional papers can effectively adsorb odor substances such as ammonia, but cannot adsorb other odor substances. Moreover, recently, developments and researches for an exhaust gas filter and a filtering medium and filter cartridge for the filter have been extensively carried out to prevent an air pollution. Exhaust gases from an internal combustion engine or the like, for example, those from automobiles, contain nitrogen oxides NO x , soot or carbon dusts, carbon monoxide CO, hydrocarbons and other gaseous substances. Since these substances cause a problem of air pollution, a discharge of the exhaust gases into an atmosphere is now controlled by an air pollution control regulation or similar act. The current regulation is generally directed to a control of the nitrogen oxides only. However, as a recent tendency, the regulation also covers the control of the soot dusts, carbon oxide and hydrocarbons discharged from a diesel engine. Hitherto, to remove fine dusts such as soot dusts from the exhaust gas discharged from the diesel engine, it is conventional to pass the exhaust gas through a porous filter such as cordierite or a fibrous filter such as quartz glass fibers or metallic fibers. The dusts are physically trapped with this porous filter or fibrous filter, and then heated to make a burning up thereof. However, the porous or fibrous filter has a drawback that back pressure can be increased due to a frequent blocking of the pores of the filter. It is also conventional to use a porous filter with a plurality of open pores in which each gas passage has a coating of the oxidation catalyst applied thereon. However, due to a complicated production process thereof, the porous filter suffers from a high production cost and a low trapping efficiency of dusts. The use of calcium phosphate compounds as deodorants, fillers and absorbents is known. JP-A-61-47401 discloses a sustained release substance prepared by adhering the release material such as a deodorant on a support composed of a calcium phosphate compound. The calcium phosphate compound itself, however, is not used as a deodorant, but as a support material to which the release material, such as a deodorant, is adhered. EP-A-274 608 and DE-A-37 22 102 disclose an adsorbent material based on a calcium phosphate compound and employed in a chromatographic system in a packed state. These documents, however, do not refer to a functional paper. WO-A-81/02 891 discloses a composition containing a deodorizing agent which produces a non-odorous ammonia salt thereby eliminating gaseous ammonia from organic waste materials. US-A-342 669 discloses a stereotype mat containing calcium aluminum phosphate and silicate. SU-A-854965 [WPI 82-45710 E] discloses a paper containing SiO 2 , TiO 2 , tricalcium phosphate and phosphogypsum. JP-A-59059999 [WPI 84-123 694] discloses aluminum phosphate as a filler. However, the absorbent capabilities, for example, of aluminum phosphate and calcium phosphate are not the same. One object of the present invention is to provide an improved functional paper which can adsorb and remove all types of bad smell components including ammonia, and can be used at both lower and higher temperatures. Another object of the present invention is also to provide a functional paper which has a wide variety of adsorption functions and therefore can be used in the adsorption of ammonia and other odor substances, in addition to general uses of the papers such as writing papers, printing papers and wrapping papers. It is also desirable to provide an improved functional paper which is useful as a multipurpose paper. Still another object of the present invention is to provide an improved functional paper which can be used as a filter medium which does not accompany blocking of the pores thereof, can be easily produced, has a high trapping efficiency of soot or carbon dusts and other dusts, and exhibits a high adsorption performance (action) with regard to gaseous substances such as carbon monoxide or hydrocarbons. The above-described objects of the present invention and other objects which will be appreciated from the following description can be accomplished by a functional paper according to claim 1. The functional paper of the present invention comprises a sheet-like support carrying powders, granules or porous granules of a calcium phosphate compound. Preferably the calcium phosphate compound is a secondary particle having a particle size of 0.1 to 30 µm. The functional paper of the present invention may be a filter sheet which comprises a sheet-like matrix of organic polymeric material having dispersed therein granules of a calcium phosphate compound having a molar ratio of Ca/P of 0.8 to 2.0. Further, the functional paper of the present invention may be used as a filtering medium for an exhaust gas. According to the present invention, as described hereinafter in detail, many advantages which could not been obtained in the prior art deodorants and other related agents and products can be obtained. First, the functional paper according to the present invention exhibits its excellent deodorizing effects at a wide working temperature of from a lower temperature to a higher temperature and accordingly can be widely used in different fields. As a deodorant it is effective for an adsorption and separation of specific gases such as carbon monoxide which could not be removed by the prior art deodorants. Further, since the calcium phosphate compound used as a principal component has a white color, it is esthetically acceptable and therefore can be used in the production of deodorant-incorporated papers such as white-colored papers or valuable papers, for example, colored papers and textured or pattern-printed papers. Second, the functional paper of the present invention is low-priced, has a simple structure, can be easily produced and handled, and can effectively trap any gaseous substances, viruses or bacteria, and animal or plant cells, in addition to the filtering off of the solid substances. Further, since it has a sheet structure, the paper can be easily inserted into and removed from filter equipment, and also can be freely and easily replaced with a new one, when its adsorptivity was reduced. Based on these advantages, the functional paper can be applied to different filter and separation apparatuses, for example, air cleaning equipments, water purifiers, deodorizing apparatuses, virus or bacteria filters, cell separators, serum filters and masks. Third, the functional paper of the present invention is easy to handle, because it has a good flexibility as in the conventional papers. In addition to its use as a writing paper, printing paper and wrapping paper, the functional paper can be used to adsorb any oil-soluble substances which could not be adsorbed with an activated carbon which is a conventional adsorbent, or any odor substances including ammonia, because it has a high adsorptivity due to specific properties of the calcium phosphate compound used as the filler. Further, since the calcium phosphate compound has a good biocompatibility, the functional paper can be used to adsorb any biological components such as animal or plant cells, virus, fractions of the cell tissue, biopolymers and other components. Furthermore, with the increased amount of the calcium phosphate compound, the resulting functional paper can be used as a flame-retardant paper. Fourth, since the functional paper of the present invention contains a calcium phosphate compound having an excellent adsorption action of the exhaust gas, it can effectively adsorb gaseous substances such as carbon monoxide or hydrocarbons, in addition to dusts such as soot dusts, and therefore ensures a notably increased purification efficiency for the exhaust gas in contrast with the prior art filtering medium. Also, it can avoid a problem of the block of the pores thereof. Further, since the filtering medium can be fabricated into a filter cartridge, the used filtering medium can be easily exchanged for a new one after a predetermined time of operation. Accordingly, it is always possible to conduct an effective purification of the exhaust gas, while the used filtering medium can be regenerated in a heat treatment or other regeneration treatments. Furthermore, the filtering medium used in an exhaust gas filter can provide a high purification efficiency due to excellent characteristics of the functional paper per se used therein, and also can significantly increase a purification efficiency of the exhaust gas due to a diffusion of the exhaust gas throughout the filtering medium thereof. In addition to these advantages, since a load is uniformly applied over the filtering medium of the filter, it becomes possible to avoid a local blocking of the pores due to incorporation of soot and other dusts in the pores. Namely, it becomes possible to notably extend a duration of life of the filtering medium and accordingly to use the filter for an extended period of time. Moreover, in this connection, since a deterioration of the functional paper in the filter is caused at a substantially same degree and speed of deterioration over a full cross section of the filter, it becomes possible to exchange all of the used functional paper for a new one at once and then regenerate the same. The invention will now be further described with reference to the drawings in which Figure 1 is a cross-sectional view of a filter device containing a functional paper according to the present invention, and Fig. 2 is a flow diagram of the deodorizing apparatus in which the functional paper of the present invention is used as a deodorant sheet. The functional paper of the present invention is characterized by containing 10 to 80% by weight of a calcium phosphate compound as a filler. In the practice of the present invention, calcium phosphate compounds are used as the filler. Useful calcium phosphate compounds include apatites such as hydroxyapatite or fluoroapatite, tricalcium phosphate and tetracalcium phosphate. These compounds may be used alone or in combination. The calcium phosphate compound is generally used as powders and the powders preferably comprise a secondary particle having a particle size of 0.1 to 30 µm. The particle size of less than 0.1 µm should be avoided, because it causes a passage of the powders together with water of the slurry through a net of the paper machine. On the other hand, the particle size of more than 30 µm will prevent an uniform dispersion of the filler powders in the resulting paper due to an excessively high weights thereof. Preferably, the secondary particle is produced from the corresponding primary particle having a particle size of 100 to 10,000Å through an aggregation or sintering thereof. In the functional paper of the present invention, it is essential that the above-described calcium phosphate compound as a filler is used in an amount of 10 to 80% by weight with regard to a total amount of the paper. The amount of the filler of less than 10% by weight is not enough to fully obtain the expected functions of the functional paper, while the amount of more than 80% by weight causes a difficulty of obtaining paper-like products. To obtain the best results, the amount of the calcium phosphate compound used may be widely varied within the above-described range of 10 to 80% by weight depending upon the specific use of the functional paper. This is because the adsorption property of the functional paper relies upon the calcium phosphate compound and also can vary depending on an amount thereof, while the calcium phosphate compound has a high, but different levels of adsorptivity for a plurality of substances including animal or plant cells, viruses, bacteria, biopolymeric materials, odor substances, tobacco tar and the like. Generally, the calcium phosphate compound is solely used as a filler in the production of the functional paper. However, if desired, it may be used together with the conventional fillers such as clay, talc, titanium white or calcium carbonate. The addition of the calcium phosphate compound as a filler to the paper can be preferably carried out in accordance with filler-in-paper method in which the calcium phosphate compound is incorporated into the paper from a slurry of pulp in water, or a filler-on-paper method in which the calcium phosphate compound is applied to the paper from a coating solution containing the same. For the filler-on-paper method, it is contemplated to coat a combination of the filler and an adhesive capable of forming a three-dimensional network structure, as a coating solution, onto a base paper. In any case, to attain a full play of the adsorption action of the calcium phosphate compound, it is preferred that the calcium phosphate compound has no coating applied onto a surface thereof. Also, it is preferred that the particles of the calcium phosphate compound as a filler have a larger surface area. Such a larger surface area of the filler particles can be obtained, if the particles are aggregated or sintered to make finely divided porous particles having a particle size of 1 µm or less and containing a plurality of fine pores. Preferably, the filler particles have a specific surface area of 1 to 150 m 2 /g and the best specific surface area can be suitably selected with the control of the pore size of the fine pores in the particles. As previously described, the filler-in-paper method can be carried out by adding a selected amount of the filler to a slurry of pulp dispersed in a much amount of water. If desired, a fixing agent may be added to the pulp slurry to inhibit a flowing out of the filler from the paper machine. Suitable fixing agents include, for example, a modified polyethyleneimine, modified polyacrylamide, sodium alginate, gum arabic, soluble starch, aluminium sulfate or potassium alum. The amount of these fixing agents used can be suitably selected depending upon factors such as the type of the fixing agent or the amount of the calcium phosphate compound used. The functional paper according to the present invention can be produced by adding powders of the calcium phosphate compound as a filler and other additives to a slurry of pulp. The pulp used herein has preferably a Canadian Standard freeness of 200 to 700cc. The additives used herein are those which are conventional in the paper making, and include, for example, a sizing agent, dye and toughening agent. After intimate mixing, the mixture is fed into a conventional paper machine. Before the mixing of the filler with the pulp slurry a surface active agent may be added to the slurry so that the filler can be effectively dispersed in the water of the slurry. The surface active agent used herein can be suitably selected from the well-known anionic, cationic and nonionic surface active agents, taking types of other additives and other factors into consideration. The functional paper shows preferably a basis weight of 20g/m 2 or more. Since the functional papers of the present invention exhibit a high adsorptivity due to the presence of the calcium phosphate compound as a filler, they can be principally utilized in the following fields of application: (a) deodorants Since the functional paper can adsorb any odor substances, it can be used as a deodorant or deodorizer or a deodorant sheet with or without release of a perfume in, for example, medical supplies such as diapers, sanitary napkins and pads for bedsores, and innersoles. (b) filter mediums Utilizing a virus adsorptivity thereof, the functional paper can be used as a mask. Further, utilizing its capability of adsorbing and separating the cells, the functional paper can be used as a filter for serum or blood. In addition, the functional paper can be used as a filter of removing proteins, filter medium for cigarettes or filter medium for air cleaners or water purifiers. (c) adsorbents Since the functional paper has a good biocompatibility and can adsorb any biopolymeric substances, it can be used as a filter paper for electrophoresis, filter paper for protein concentration or substrate for chromatography such as filter paper for paper chromatography. (d) substitute materials for biomaterials The functional paper can be used as a tape for diaplasis, artificial skin, artificial blood vessel, artificial windpipe or drug-releasing system, for example. (e) food wrapping papers (f) articles in a bioindustry The functional paper can be used as a culture medium for cells, immobilizing carrier for enzymes or microorganisms, substrate for hydroponics or bioreactor, for example. (g) articles in a medical treatment The functional paper can be used as a clinical test paper, adhesive tape or endemic preparation, for example. For the filtering medium for exhaust gas, it is enough to obtain satisfactory adsorption effects, if the calcium phosphate compound occurs in at least contact areas of the filtering medium with the exhaust gas. However, generally, it is preferred that the calcium phosphate compound is used in an amount of 50% by weight or more. The calcium phosphate compounds used in the present invention have a molar ratio of calcium to phosphorus (Ca/P) of 0.8 to 2.0. Useful calcium phosphate compounds satisfying this requirement include apatites such as hydroxyapatite or fluoroapatite, tricalcium phosphate and tetracalcium phosphate. These compounds may be used alone or as a mixture of two or more compounds. The filtering medium for the exhaust gas has a good adsorptivity because of the incorporated calcium phosphate compound and therefore can effectively adsorb not only soot dusts and other dusts but also gaseous substances such as carbon monoxide or hydrocarbons including aliphatic and aromatic hydrocarbons. Further, since the calcium phosphate compound also has a good water absorption property, the filtering medium can additionally adsorb a water vapor in the exhaust gas, thereby further improving a gas adsorption efficiency of the filtering medium. Furthermore, the filtering medium can be easily regenerated by heating and firing the used filtering medium, although an adsorption efficiency of the filtering medium is reduced with time during the purification process of the exhaust gas. To accelerate this firing of the used filtering medium, it is preferred that at least a part of the surface of the filtering medium is coated with any oxidation catalysts. Suitable oxidation catalysts include, for example, platinum catalyst or platinum-rhodium catalyst. The formation of the catalyst coating can be carried out in accordance with any conventional coating methods. As described in the above paragraphs, the functional paper can exhibit excellent performances and therefore can be widely used in different types of the filter body to make an exhaust gas filter. The inventor found that if the filtering medium is effectively disposed in the filter body, an adsorption efficiency of the resulting filter can be further increased, the exhaust gas can be diffused throughout the filter, and a load of the gas can be uniformly applied to the filter, thereby an improved exhaust gas filter which does not cause a localized blocking of the filter pores can be obtained. Figure 1 is a cross-sectional view of the filter device containing a functional paper according to the present invention. The filter device comprises a rectangular box 2 with the opened upper and lower walls. These two openings are used to introduce an ill-odored air into the filter device, and discharge the deodorized air therefrom, respectively. As is illustrated, there are four deodorant sheets 1, and one end of each deodorant sheet 1 is alternately fixed to an opposed side wall of the box 2. This alternate arrangement of the deodorant sheets 1 is intended to form a zig zag flow path 3 of the air. The filter device is used in, for example, an air conditioner to remove bad smell from an air-conditioned air. Figure 2 is a flow diagram of the deodorizing apparatus in which the functional paper of the present invention is used as a deodorant sheet. The illustrated deodorizing apparatus comprises a teddler bag 11, a filter holder 12 with the filter sheet 12a, a pump 13, a flowmeter 14 and a teddler bag 15 which connected through a tube in the recited order. Especially, the deodorizing apparatus is used to evaluate a deodorizing effect of the filter sheet. The present invention will be further described with reference to some working examples which do not restrict the scope of the present invention. Example 1: A hydroxyapatite having a Ca/P ratio of 1.67 was synthesized in accordance with the well-known production process. The hydroxyapatite was sintered at 700 °C to produce granules of hydroxyapatite having a porosity of 60% and granule size of 1 to 4mm. The thus obtained granules had an average pore size of 2 µm and specific surface area of 40 m 2 /g. Example 2: A calcium phosphate having a Ca/P ratio of 1.5 was sintered at 1100 °C to produce granules of calcium phosphate having a porosity of 30% and granule size of 1 to 4mm. The thus obtained granules had an average size of fine pores of 300mm, average size of small pores of 8 µm and specific surface area of 12 m 2 /g. Example 3: A mixture of softwood pulp and hardwood pulp in a weight ratio of 7:3 was beated to make a pulp satisfying a Canadian Standard freeness of 360cc. The pulp was dispersed in water toprepare a pulp slurry having a concentration of 0.3% by weight. A calciumphosphate (hydroxyapatite) having a Ca/P ratio of 1.67, specific surface area of 45 m 2 /g and average particle size of 2 µm was prepared in accordance with a wet process, and 0.7% by weight of the calcium phosphate was added to the pulp slurry. A paper making was made in accordance with the procedure of JIS P8209. The thus obtained functional paper had a basis weight of 85g/ m 2 and showed a calcium phosphate content of 70% by weight. Test Example 1: This example is intended to evaluate a deodorizing effect of the deodorant paper produced in Example 3. The deodorant paper of Example 3 was cut to rectangular sheets having a size of 25cm × 25cm. The deodorant sheets were disposed in a rectangular box to produce a filter device, as shown in Fig. 1. The filter device was fixed to an air outlet of the air conditioner producing an ill-smelled air. In the presence and absence of the filter device, a panel test for the presence of bad smell was carried out wit six panels. The results of the panel test are summarized in the following Table 1. evaluation A B C D panelers 3 3 0 0 A: smell completely or subst. removed B: smell reduced C: smell not changed D: smell increased Note, in Fig. 1 showing the filter device, arrows indicate a direction of air flow. Example 4: Softwood pulp was beated to make a pulp satisfying a Canadian Standard freeness of 650cc. The pulp was dispersed in water to prepare a pulp slurry having a concentration of 0.5%. A 0.5% by weight of porous tricalcium phosphate granules having an average granule size of 6.2 µm, porosity of 63%, Ca/P ratio of 1.5 and average pore size of 0.1 µm were added to the pulp slurry. A paper making was made in an experimental paper making machine in accordance with a handmade process. The thus obtained filter paper showed a tricalcium phosphate content of 50% by weight and a basis weight of 99g/ m 2 . Test Example 2: This example is intended to evaluate a remarkable excellent deodorizing effect of the filter papers or sheets of the present invention. The deodorizing apparatus of Fig. 2 was used to make this evaluation. The filter papers or sheets of Example 4 were cut to discs having a diameter of 45mm, and each disc, i.e., filter sheet 12a of Fig. 2, was set in a filter holder 12 of the deodorizing apparatus. A test gas containing 14.7ppm of ammonia (NH 4 ) in a teddler bag 11 was guided through the filter sheet 12a to a teddler bag 15. A 10 liters of the test gas was passed through the filter sheet 12a. To evaluate a deodorizing effect, i.e., removal of ammonia, of the filter sheet, a concentration of the ammonia gas remaining in the filtered test gas in the teddler bag 15 was determined in accordance with an indicator tube method. The results are summarized, together with a removal percentage of ammonia, in the following Table 2. The removal percentage of ammonia means a percentage of the ammonia gas adsorbed on the filter sheet. test gas conc. of NH 4 (ppm) removal of NH 4 (%) control (not filtered) 14.7 - filtered with filter paper of Ex. 4 1.2 91.8 The results of this table indicate that 90% or more of the ammonia gas can be adsorbed on the filter sheets depending upon a specific structure thereof, and in summary, a remarkable excellent deodorizing effect can be obtained by using the filter sheets of the present invention. Test Example 3: This example is intended to explain the usefulness of the filter sheets of Example 4 as a virus adsorbent. A floating solution of influenza virus PR8 in a physiological saline was used as a test solution. The functional paper was cut to obtain a test piece with a diameter of 5cm. The test piece was applied onto a filter funnel, and 3ml of the floating solution of influenza virus PR8 was pored into the funnel. The received virus floating solution from the funnel was tested to determine a titer thereof in accordance with the following method. The results are summarized in Table 3. Determination of Titer: When the influenza virus was adhered to red blood cells, the blood cells cause their aggregation with each other. The determination of titer is made based on this aggregation reaction. Namely, the virus floating solution as a test solution is diluted with a physiological saline (0.9% aqueous solution of sodium chloride) to make a twice (2 time, 4 time, 8 time, 16 time, ···) -increased volume, and the diluted solution each is mixed with the same amount of 0.4% floating solution of chick red blood cells. The degree of dilation at which the aggregation reaction was caused is regarded as a titer of test solution (not-diluted solution). sample titer test solution (not filtered) 128 test solution filtered through the filter sheet of Example 4 4 Note, the titer is proportional to a concentration of influenza virus in each sample solution. The results of the Table 3 indicate that in comparison with the virus concentration of the test solution (not filtered), virus concentration of the solution filtered through the filter sheet of Example 4 was reduced to 1/32. Namely, the influenza virus was effectively adsorbed by the filter sheets of the present invention Example 5: The procedure of Example 3 was repeated except that a concentration of the pulp slurry was increased to 0.5% by weight, and a concentration of the calcium phosphate added to the pulp slurry was reduced to 0.5% by weight. The obtained functional paper had a basis weight of 93g/m 2 and showed a calcium phosphate content of 50% by weight. Example 6: The procedure of Example 3 was repeated except that a concentration of the pulp slurry was increased to 0.7% by weight, and a concentration of the calcium phosphate added to the pulp slurry was reduced to 0.3% by weight. The obtained functional paper had a basis weight of 101g/ m 2 and showed a calcium phosphate content of 30% by weight. Example 7: The procedure of Example 5 was repeated except that only the softwood pulp was beated to make a pulp satisfying a Canadian Standard freeness of 650cc. The obtained functional paper had a basis weight of 103 g/ m 2 and showed a calcium phosphate content of 50% by weight. Example 8: The procedure of Example 7 was repeated except that a calcium phosphate (tricalcium phosphate) having a Ca/P ratio of 1.5, specific surface area of 1.5 m 2 /g and average particle size of 1 µm was prepared in accordance with a wet process, and 0.55 by weight of the calcium phosphate was added to the pulp slurry. The obtained functional paper had a basis weight of 105g/ m 2 and showed a calcium phosphate content of 50% by weight. Example 9: The procedure of Example 7 was repeated except that calcium phosphate (hydroxyapatite) having a Ca/P ratio of 1.67, specific surface area of 10 m 2 /g and average particle size of 8 µm was prepared in accordance with a wet process and ten sintered at 800 °C, and 0.5% by weight of the calcium phosphate was added to the pulp slurry. The obtained functional paper had a basis weight of 98g/m 2 and showed a calcium phosphate content of 50% by weight. Example 10: The procedure of Example 7 was repeated except that the pulp of Example 8 was dispersed in water to prepare a pulp slurry having a concentration of 0.3% by weight, and 0.3% by weight of the calcium phosphate was added to the pulp slurry. The obtained functional paper had a basis weight of 48g/m 2 and showed a calcium phosphate content of 50% by weight. Test Example 4: This example is intended to explain the usefulness of the functional papers of Examples 3 and 5 to 10 as a virus adsorbent. The procedure of the above-described Test Example 3 was repeated except that the filter sheets of Example 4 were replaced with the functional papers of Examples 3 and 5 to 10. The results are summarized in Table 4. sample titer test solution (not filtered) 128 test solution filtered through paper of Example 3 16 test solution filtered through paper of Example 5 32 test solution filtered through paper of Example 6 32 test solution filtered through paper of Example 7 16 test solution filtered through paper of Example 8 8 test solution filtered through paper of Example 9 32 test solution filtered through paper of Example 10 64

Claims: A functional paper containing 10 to 80 % by weight of a calcium phosphate compound having a molar ratio of calcium to phosphorus of 0.8 to 2.0 as a filler, the calcium phosphate being apatite, tricalcium phosphate, tetracalcium phosphate or a mixture thereof. A functional paper according to claim 1, in which the calcium phosphate compound is a secondary particle having a particle size of 0.1 to 30 µm. Use of a functional paper according to claim 1 or 2 as a deodorant. Use of a functional paper according to claim 1 or 2 as a filtering medium. Use of a functional paper according to claim 1 or 2 as an adsorbent.

Inventors: OGAWA TETSURO, SAKURAI TAKESHI, TSURU SUMIAKI, YOKOO AKIHIKO, OGAWA, TETSURO, SAKURAI, TAKESHI, TSURU, SUMIAKI, YOKOO, AKIHIKO, Ogawa, Tetsuro, c/o Asahi Kogaku Kogyo, K.K., Sakurai, Takeshi, c/o Yuugen Kaisha Fujimi Shoukai, Yokoo, Akihiko, c/o Asahi Kogaku Kogyo, k.k.
Applicants: ASAHI OPTICAL CO LTD, YUUGEN KAISHA FUJIMI SHOUKAI, ASAHI KOGAKU KOGYO KABUSHIKI KAISHA
Application year: 1990
Main classification: B01D53
IPC codes: B01J20, B01D53