Abstract
An antibacterial ceramic contains an antibacterial material produced by loading an antibacterial metal such as silver on a calcium ceramic carrier and an inorganic material such as cordierite, and has a bulk density of 0.6-1.2 g/cm.sup.3. An antibacterial ceramic filter contains an antibacterial material produced by loading an antibacterial metal such as silver on a calcium ceramic carrier, an aggregate such as mullite, and a binder such as frit, and has a porosity of 20% or more. The light-weight antibacterial ceramic is suitably applicable to a roof garden or the like. The antibacterial ceramic filter can remove and extirpate various bacteria and suspensions.
Claims
What is claimed is:
1. A lightweight antibacterial ceramic comprising:
an antibacterial material of 0.01-20 wt % in which an antibacterial metal or metallic ion is loaded on a carrier; and an inorganic material of 99.9-80 wt %, said inorganic material being selected from the group consisting of an oxide inorganic material, a non-oxide inorganic material, and mixtures thereof; wherein said antibacterial ceramic has a particle bulk density of 0.6-2.0 g/cm.sup.3.
2. A lightweight antibacterial ceramic according to claim 1, wherein said antibacterial material comprises an antibacterial metal or metallic ion of 0.01-20 wt % and a carrier of 99.9-80 wt %.
3. A lightweight antibacterial ceramic according to claim 1, wherein said antibacterial metal or metallic ion comprises at least one component selected from the group consisting of silver, copper, zinc, platinum, tin, arsenic, lead, cadmium, and chromium.
4. A lightweight antibacterial ceramic according to claim 1, wherein said carrier comprises at least one component selected from the group consisting of phosphate, silica, and zeolite.
5. A lightweight antibacterial ceramic according to claim 4, wherein said phosphate comprises at least one component selected from the group consisting of calcium phosphate, zinc phosphate, zirconium phosphate, and aluminum phosphate.
6. A lightweight antibacterial ceramic according to claim 5, wherein said calcium phosphate comprises at least one component selected from the group consisting of tricalcium phosphate, calcium hydrogenphosphate, calcium pyrophosphate, calcium metaphosphate, hydroxy apatite, and apatite halide.
7. A lightweight antibacterial ceramic according to claim 1, wherein said inorganic material is insoluble in water and substantially harmless to humans, animals, and plants.
8. A method for producing a lightweight antibacterial ceramic comprising the steps of: preparing an antibacterial ceramic material by loading an antibacterial metal or metallic ion on a carrier; mixing the obtained antibacterial ceramic material of 0.01-20 wt % with an inorganic material selected from the group consisting of an oxide inorganic material, a non-oxide inorganic material, and mixtures thereof of 99.9-80 wt % to obtain a first mixture; mixing a combustible material of 5-50 weight parts with 100 weight parts of the first mixture to obtain a second mixture; and firing the second mixture at a temperature of 500.degree.-1300.degree. C.
9. A method for producing a lightweight antibacterial ceramic according to claim 8, wherein said combustible material is selected from the group consisting of a carbon powder, a grain powder, and sawdust.
10. A method for producing a lightweight antibacterial ceramic according to claim 9, wherein the grain powder is wheat flour or rice flour.
11. An antibacterial ceramic filter comprising: a base material phase of 99.9-80 wt % comprising an aggregate phase and an inorganic binder phase, said aggregate phase comprising a material selected from the group consisting of an oxide inorganic material, a non-oxide inorganic material, and mixtures thereof; and an antibacterial material of 0.01-20 wt % comprising a carrier and an antibacterial metal or metallic ion loaded on said carrier, wherein said antibacterial ceramic filter has a porosity of 20% or more.
12. An antibacterial ceramic filter according to claim 11, wherein said filter has a pore diameter ranging from 20 .mu.m to 8000 .mu.m.
Description
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an antibacterial ceramic and an antibacterial ceramic filter. More particularly, the present invention relates to a lightweight antibacterial ceramic, a method for producing the lightweight antibacterial ceramic, and an antibacterial ceramic filter which can remove and extirpate various bacteria.
There has conventionally been known antibacterial ceramics having an antibacterial metal such as silver, copper, and zinc loaded on a ceramic. Such antibacterial ceramics are used as soil conditioners and water conditioners because of their antibacterial property, anti-mildew property, and water-holding property. An antibacterial ceramic having the shape of a ball has been used for cultivation of chicks, prawns, or the like. An antibacterial ceramic having the shape of a pellet with enlarged specific surface area or the shape of a Rasching ring has been used for treating water to improve its quality.
Incidentally, the aforementioned antibacterial ceramic is formed to be relatively porous so as to enhance its antibacterial property. However, many of such conventional antibacterial ceramics have been dense and heavy. There has also been known antibacterial materials made by adding an antibacterial metal to a plastic or a glass. However, such antibacterial materials have a low antibacterial property because of low porosity.
There also has been known a ceramic filter used as a precise filtering film. This filter can remove mildew and various bacteria in a liquid.
In the construction of a garden, either in or on the roof of a building, both the soil and the soil conditioners used in the garden must be lightweight to avoid exceeding the structural strength of the building. However, there has been a problem that the aforementioned antibacterial ceramics are not suitable for a roof garden or the like since they are relatively heavy. On the other hand, there has been another problem that roots of plants in roof gardens are liable to rot because roof gardens suffer from poor drainage, and as a result, such plants have short lives.
There has been still another problem that conventional ceramic filters are not always effective to completely remove various bacteria from a liquid because of the diameters of the pores in such filters.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of such conventional problems. An object of the present invention is to provide a lightweight antibacterial ceramic which is suitably applicable to, for example, a roof garden, and a method for producing the lightweight antibacterial ceramic.
Another object of the invention is to provide an antibacterial ceramic filter which has an antibacterial property which can remove and extirpate various bacteria and floats.
As a result of energetic studies to achieve the aforementioned objects, the present inventors found that the objects can be achieved by firing a mixture of an antibacterial metal and a specific material and controlling the bulk density and the porosity of the sintered body, which led to the completion of the present invention.
Therefore, the lightweight antibacterial ceramic of the present invention includes: an antibacterial material of 0.01-20 wt % in which an antibacterial metal or metallic ion is loaded on a carrier; and an oxide inorganic material and/or a non-oxide inorganic material of 99.9-80 wt %; wherein the antibacterial ceramic has a particle bulk density of 0.6-2.0 g/cm.sup.3.
The method for producing the lightweight antibacterial ceramic of the present invention includes the steps of: preparing an antibacterial ceramic material by loading an antibacterial metal or metallic ion on a carrier; mixing the obtained antibacterial ceramic material of 0.01-20 wt % with an oxide inorganic material and/or a non-oxide inorganic material of 99.9-80 wt % to obtain a first mixture; mixing a combustible of 5-50 weight parts with the mixture of 100 weight parts to obtain a second mixture; and firing the second mixture at a temperature of 500.degree.-1300.degree. C.
The antibacterial ceramic filter of the present invention includes: an aggregate phase comprising an oxide inorganic material and/or a non-oxide inorganic material; and an inorganic binder phase; wherein the antibacterial ceramic filter has: a base material phase of 99.9-80 wt % including the aggregate and the inorganic binder phase; and an antibacterial material of 0.01-20 wt % comprising a carrier and an antibacterial metal or metallic ion loaded on the carrier; and the antibacterial ceramic filter has a porosity of 20% or more.
In the antibacterial ceramic of the present invention, the ceramic can be lightened and the surface area can be enlarged because the bulk density of the ceramic particles is appropriately controlled. Therefore, the antibacterial ceramic can be suitably used for applications such as a roof garden and the probability that the ceramic will come in contact with bacteria is increased, which improves its antibacterial property.
On the other hand, the antibacterial ceramic filter of the present invention can not only remove but also extirpate bacteria and further improve the clearness of a liquid. It is also possible to make the diameter of pores a little larger than in conventional filters so that the filtering time is shortened without decreasing the clearness of the liquid because the antibacterial ceramic of the present invention can extirpate the bacteria which passes through the pores and can not be removed.
DETAILED DESCRIPTION OF THE INVENTION
The antibacterial ceramic of the present invention is hereinbelow described in more detail.
The antibacterial ceramic of the present invention contains an antibacterial material made by loading an antibacterial metal or metallic ion on a carrier. The antibacterial material preferably has a composition of an antibacterial metal or metallic ion of 0.01-20 wt % and a carrier of 99.9-80 wt %.
When the aforementioned antibacterial metal or metallic ion is present in an amount less than 0.01 wt %, the antibacterial ceramic has a low antibacterial property. When the antibacterial metal or metallic ion is present in an amount more than 20 wt %, the cost of the antibacterial ceramic becomes high because the cost of such a metal or metallic ion is high.
The antibacterial metal or metallic ion may be silver, copper, zinc, platinum, tin, arsenic, lead, cadmium, chromium, or any mixture of these components.
The aforementioned carrier may be phosphate, silica, zeolite, or any mixture of these components. Phosphate for the carrier may be calcium phosphate, zinc phosphate, zirconium phosphate, aluminum phosphate, or any mixture of these components. Calcium phosphate for the carrier may be tricalcium phosphate, calcium hydrogenphosphate, calcium pyrophosphate, calcium metaphosphate, hydroxy apatite, apatite halide, or any mixture of these components.
The methods for loading the antibacterial metal or metallic ion on the aforementioned carrier are not limited. Suitable methods include, for example, ion exchange, a firing treatment at 800.degree. C. or higher after ion exchange, or firing at about 80.degree. C. or higher an aqueous solution containing a water-soluble salt having an antibacterial component and then collecting the precipitate. Among these methods, the preferred method is the one in which a water-soluble salt having an antibacterial component is used because this method prevents elusion of the antibacterial metallic component and reduces the production cost.
Incidentally, each of the aforementioned calcium ceramics to be used for the carrier is highly safe for a human body. Further, such calcium ceramics readily absorb a water-soluble salt of an antibacterial metal and metallic ion when an antibacterial metal is loaded. Therefore, the calcium ceramics are suitably applicable to the present invention.
The antibacterial ceramic of the present invention includes 1) the aforementioned antibacterial material of 0.01-20 wt % and 2) an oxide inorganic material and/or a non-oxide inorganic material of 99.9-80 wt %.
It is not preferred that the antibacterial material be less than 0.01 wt % or more than 20 wt % because the antibacterial property decreases or the production cost is high, respectively.
The aforementioned oxide inorganic material or non-oxide inorganic material may be any material which is water-insoluble and harmless to human bodies, animals and plants. The oxide inorganic material may be alumina, cordierite, mullite, silica, clay, or the like. The non-oxide inorganic material may be silicon carbide, silicon nitride, or aluminum nitride. Note that a self-sintering material such as clay or an inorganic binder such as a frit can be mixed with these inorganic materials.
Further, the antibacterial ceramic of the present invention is light because it has a particle bulk density of 0.6-2.0 g/cm.sup.3, preferably 0.6-1.2 g/cm.sup.3. Therefore, the antibacterial ceramic of the present invention can be used as a soil conditioner, particularly for a garden on the roof, or the like, and its conveyability is excellent. It is not preferred that the antibacterial ceramic has a bulk density of less than 0.6 g/cm.sup.3 because it is then so light that it can be scattered in the wind. It is not preferred either that the antibacterial ceramic has a bulk density of more than 2.0 g/cm.sup.3 because it is then too heavy and the antibacterial property decreases because the porosity of the ceramic is low.
Since the aforementioned antibacterial ceramic of the present invention has an excellent antibacterial property and is safe for human bodies, the ceramic can be used not only as a soil conditioner for a garden on the roof or the like but also applied to soil for home gardening. Further, the ceramic can be used as sand for evacuation by a pet such as a dog or a cat. The antibacterial ceramic of the present invention can prevent various bacteria from generating and make animals' and plants' lives longer while satisfying the proof load on a building.
The method for producing an antibacterial ceramic of the present invention is hereinbelow explained.
The antibacterial ceramic of the present invention is produced by a method including the steps of: preparing an antibacterial ceramic material by loading an antibacterial metal or metallic ion on a carrier; mixing the obtained antibacterial ceramic material of 0.01-20 wt % with an oxide inorganic material and/or a non-oxide inorganic material of 99.9-80 wt % to obtain a first mixture; mixing a combustible of 5-50 weight parts with the mixture of 100 weight parts to obtain a second mixture; and firing the second mixture at a temperature of 500.degree.-1300.degree. C.
The aforementioned combustible may be a carbon powder, a grain powder such as wheat flour or rice flour, a sawdust, or the like. These combustibles are consumed by the aforementioned firing and have the function of making the resultant antibacterial ceramic light and porous. It is not preferred that the combustible be added in an amount of less than 5 weight parts or more than 50 weight parts because the effect of lowering the bulk specific gravity is small or the resultant ceramic is liable to be crushed, respectively. Note that the order in which the antibacterial material, the inorganic material, and the combustible are added is not limited, and any order is acceptable if the aforementioned powder for firing having a predetermined composition can be obtained.
The antibacterial ceramic filter of the present invention is now described in detail.
The antibacterial ceramic filter of the present invention includes: the aforementioned antibacterial material of 0.01-20 wt %; and a base material phase of 99.9-80 wt % having 1) an aggregate phase containing an oxide inorganic material and/or a non-oxide inorganic material and 2) an inorganic binder phase.
The oxide inorganic material and the non-oxide inorganic material to be used for forming an aggregate phase by firing are not limited, and any water-insoluble material which is harmless to human bodies, animals, and plants can be employed. The oxide inorganic material may be alumina, mullite, zirconia, andalusite, silica ceramic material, glass, or the like. The non-oxide inorganic material may be silicon carbide, silicon nitride, and aluminum nitride.
The aforementioned inorganic binder may be an inert self-sintering material such as clay or inorganic binding material such as a frit. The ratio of the inorganic binder to the aforementioned aggregate is preferably within the range of 1-50 wt %. When the ratio is less than 1 wt %, the resultant filter does not have sufficient strength. When the ratio is more than 50 wt %, the resultant filter has a low porosity, which lowers water permeability.
Each of the pores of the ceramic filter of the present invention preferably has a diameter ranging 20 to 8000 .mu.m. When the diameter of a pore is less than 20 .mu.m, the pore is prone to be clogged up with impurities, which lowers water-permeability of the filter in the early stages. When the diameter of a pore is more than 800 .mu.m, the filter has a low antibacterial property.
Incidentally, the configuration of the antibacterial ceramic filter of the present invention is not particularly limited, and various kinds of configurations such as the shape of a plate, a cylinder, or the like can be employed. The use of the ceramic filter is not limited, and it can be suitably used for purifying water in a Japanese traditional bath tub and water for a large bathing place such as a swimming pool.
When the antibacterial ceramic filter of the present invention is in use, a particular tank or the like is not necessary, and the flow passage or the like is directly equipped with the ceramic filter.
The method for producing the antibacterial ceramic filter of the present invention is hereinafter described.
The method for producing the ceramic filter of the present invention includes the steps of: mixing the aforementioned antibacterial material of 0.01-20 wt % with the aforementioned mixture of 99.9-80 wt % containing an aggregate and an inorganic binder phase; adding a combustible of 0-30 weight parts to the obtained mixture of 100 weight parts to prepare another mixture for forming a compact; preparing a compact having a predetermined shape by the mixture for forming a compact; and firing the compact at 1300.degree. C. or less, preferably at 700.degree.-1000.degree. C.
Incidentally, the order of adding the antibacterial material, the aggregate, the inorganic binder, and the combustible is not limited in the aforementioned method, and any order is acceptable if the aforementioned mixture having a predetermined composition for forming a compact can be obtained.
In this method, the 50% average particle diameter of the aggregate is preferably 0.1-20 mm. When the diameter is less than 0.1 mm, water-permeability becomes low because of clogging in the early stages though the discriminating ability of the filter is high. When the diameter is more than 20 mm, the filter has a low antibacterial property, and the discriminating ability of the filter is lowered.
The aforementioned inorganic binding material has a particle diameter of 100 .mu.m or less, preferably 44 .mu.m or less, and the blending ratio of the inorganic binding material to the aforementioned aggregate is preferably about 1-50%.
Further, the porosity and the pore diameter of the ceramic filter can be adjusted as necessary by adding the aforementioned combustible. For example, the combustible may have a particle diameter of 1-100 .mu.m.
The present invention is hereinbelow described in more detail with reference to the following Examples. However, the present invention is not limited to these Examples.
EXAMPLES 1-6
There were kneaded by a kneader a mixture of an oxide inorganic material (base material A) mainly consisting of cordierite, an antibacterial material produced by loading Ag on hydroxy apatite, an appropriate amount of a binder, and a combustible of 10-50 weight parts to the base material A of 100 weight parts in the ratio shown in Table 1. The obtained mixture was dried at 110.degree. C. and then fired at 1100.degree. C. in ambient air. Then, it was crushed by a roll crusher so as to obtain a lightweight antibacterial ceramic. Incidentally, in Tables 1-9, "amount of metal" refers to the total amount of Ag or the like contained in each lightweight antibacterial ceramic.
The obtained lightweight antibacterial ceramic was dried and then measured for dry weight. The dried ceramic was treated for three hours under a reduced pressure of 730 mmHg and then measured for weight in water. Then the ceramic saturated with water was measured for weight. The particle bulk density of the ceramic was calculated from the obtained three kinds of weights. The results are shown in Table 1.
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