Liquid purification or separation – Filter – Material
Reexamination Certificate
2002-09-26
2004-11-23
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Filter
Material
C055S514000, C055S523000, C055S524000, C210S509000, C156S073600, C156S219000
Reexamination Certificate
active
06820751
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-transmittable linear photocatalytic filter material having a long and narrow light-transmittable linear material and a number of particulate materials provided on an outer surface of the linear material, and further having a photocatalytic layer formed on or above an outer surface of the linear material and the number of particulate materials; a filter formed of such light-transmittable linear photocatalytic filter materials; and a process for producing the above filter material.
2. Prior Art
A photocatalyst is a material that exhibits functions of sterilization, antimicrobial activity, decomposition, deodorization, non-soiling, non-fogging, and the like when exposed to light. When titanium dioxide, a typical example of the photocatalyst, is exposed to light, the titanium dioxide causes an intense redox reaction on its surface to decompose a substance that is in contact with the surface. For example, when the above substance is an organic substance, the organic substance is decomposed into carbon dioxide gas and water. The photocatalyst decomposes, for example, environmental pollutants such as microorganisms, virus, malodorous substances, dioxin, trichloroethylene, etc., and endocrine-disturbing chemicals that may cause a sick building syndrome.
Attempts are being made to utilize the above photocatalysis for a filter and apply the filter to disposing of various liquids, disposing of various gases and environmental cleaning.
For providing a high-performance photocatalytic filter at a less expensive price, there is proposed a photocatalytic filter material having a filter base material formed by bonding particulate materials to a surface of a long and narrow light-transmittable linear material to form projections and a photocatalyst layer formed on the filter base material (JP-A-10-71312).
When a large number of such photocatalytic filter materials are bundled with aligning their ends on each side to constitute a photocatalytic filter, gaps are formed among the filter materials adjacent side by side owing to the presence of the above projections, so that a fluid to be disposed of can be allowed to flow through the above gaps. Further, passage spaces forming the above gaps do not easily change with the passage of time or are stabilized, so that the photocatalytic filter can maintain performances as a filter for a long period of time.
In the above photocatalytic filter, one end surface or each end surface of a bundle formed of a number of photocatalytic filter materials is provided with a light incidence portion, and light such as ultraviolet ray is allowed to enter the light incidence portion and is propagated inside the photocatalytic filter materials. Since the photocatalyst layer (e.g., titanium dioxide) has a higher refractive index than the linear material (e.g., glass fiber), the propagated light above has no components that undergo total reflection, so that it leaks into the photocatalyst layer.
When an inorganic adhesive containing silica as a main component is used as an adhesive for bonding particulate materials as projections to outer side surfaces of the light-transmittable linear materials, the refractive index of the adhesive satisfies the condition of total reflection since it is equivalent to, or slightly lower than, the refractive index of the light-transmittable linear materials, so that no light leaks into the photocatalyst layer. Since, however, microscopic pores are formed in an interface between the light-transmittable linear materials and the adhesive after the adhesive is baked, there occurs light that leaks into the photocatalyst layer through the pores as base points. Therefore, the light that enters the light incidence portion is not propagated far but gradually leaks into the photocatalyst layer, and the photocatalyst layer is irradiated with the light that has leaked into it.
On the other hand, a fluid to be disposed of is allowed to flow “uniformly” through the passage of gaps of a bundle of a number of the photocatalytic filter materials, whereby the photocatalytic filter traps contaminants contained in the fluid to be disposed of, with the surface of the photocatalyst layer. The photocatalyst layer is irradiated with the above light that leaks into it, whereby the trapped contaminants are decomposed by photocatalysis.
It is expected that the efficiency of the photocatalysis is increased with an increase in the number of photocatalytic filter materials bundled. In reality, however, when the number of the photocatalytic filter materials bundled comes to be thousands, tens of thousands or more, there is caused another new problems.
For example, as shown in
FIG. 11
, a number of quartz glass spheres
2
(average particle diameter; 50 &mgr;m) as particulate materials are bonded to an outer surface of a fiber
1
made of glass as a long and narrow light-transmittable linear material with an adhesive. Further, a titanium dioxide layer
4
(thickness; 2 &mgr;m) is formed on the above number of quartz glass spheres
2
and an outer surface of the fiber
1
made of quartz glass by a known dipping method, to prepare a glass fiber photocatalytic filter material
90
. About 70,000 photocatalytic filter materials
90
are bundled to obtain a photocatalytic filter. In the thus-obtained photocatalytic filter, the following abnormal phenomenon takes place.
As shown in
FIG. 12
, when such photocatalytic filter materials
90
are bundled with their ends on each side aligned, and housed in a cylindrical case
5
made of aluminum (internal diameter; 70 mm&phgr;, a length; 200 mm) to constitute a photocatalytic filter
91
, the photocatalytic filter
91
has the form of a barrel as shown in FIG.
12
. The above “form of a barrel” means that photocatalytic filter materials
90
positioned on outer side surface of central portion of the photocatalytic filter
91
swell outwardly in a convex form. As shown in
FIG. 12
, the middle portions of the photocatalytic filter materials
90
are in close contact with the internal side surface of the cylindrical case
5
, and a space portion
7
occurs near an opening on each side of the photocatalytic filter.
The photocatalytic filter
91
sufficiently performs as a filter only when a fluid to be disposed of is allowed to flow “uniformly” through the passage of gaps formed by particulate materials
2
among the photocatalytic filter materials
90
of the photocatalytic filter
91
formed by bundling a number of the photocatalytic filter materials
90
with aligning their ends on each side. In the above space portion
7
, however, the flow of the fluid abnormally increases in amount, and the flow comes to be non-uniform, so that the photocatalytic filter cannot sufficiently work as a filter.
As shown in
FIG. 13
, when an overflow state of a water stream
8
is observed in a test in which a photocatalytic filter formed of a number of photocatalytic filter materials
90
is allowed to stand upright and the water is allowed to flow upwardly in a stream
8
(flow rate: 2 liters/minute), water stream
8
above the above space portion
7
rapidly flows to cause a standing portion
6
. The above test result shows the above abnormal phenomenon of a fluid caused by the space portion
7
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide light-transmittable linear photocatalytic filter materials that can be arranged in parallel in the longitudinal direction without causing a filter to have the form of a barrel when the filter is made of a bundle of a number of such photocatalytic filter materials; a filter made of the above photocatalytic filter materials, and a process for the production of the above photocatalytic filter materials.
According to a first aspect of the present invention for achieving the above object, there is provided a light-transmittable linear photocatalytic filter material comprising a light-transmittable linear material, a number of particulate materials bonded to an outer side surface o
Arai Souji
Nishii Yoshikazu
Drodge Joseph
Hoya Candeo Optronics Corporation
Nixon & Vanderhye P.C.
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