Photocatalytic filter with fiber glass mat carrier

Details Photocatalytic filter with fiber glass mat carrier Photocatalytic filter with fiber glass mat carrier

1998-10-30

2001-05-29

Weisberger, Richard (Department: 2164)

Fabric (woven, knitted, or nonwoven textile or cloth, etc.)

Coated or impregnated woven, knit, or nonwoven fabric which...

Coated or impregnated inorganic fiber fabric

C442S331000, C442S059000, C442S071000, C442S108000, C442S111000, C442S118000, C442S081000, C442S099000, C442S172000, C442S180000, C422S186300

Reexamination Certificate

active

06239050

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention involves a structure for utilizing the known photocatalytic effect of certain metal oxides such as titanium dioxide. More particularly, it involves a combination of photocatalytic metal oxides on particular carrier surfaces of fiber glass.
The use of metal oxides such as titanium dioxide to photocatalytically decompose organic material has been extensively treated in the prior art. In addition to titanium dioxide, the photocatalytic effect has been reported to have been achieved with the oxides of zinc, tungsten, and tin. The present invention is expected to be useful with any photocatalyst that can be coated onto fiber glass. These may include some known photocatalytic non-oxide substances as well, but the ease of depositing the metallic oxides by presently known techniques makes them the preferred category for use with extended surface area substrates.
The utility of the photocatalytic compounds depends largely upon providing a solid carrier with large surface area so as to increase the contact area with the liquid or gas being treated. In U.S. Pat. No. 5,045,288 a layer of catalyst particles is loosely supported on a filter or in a granular bed. A more practical approach is to coat a solid support member with the catalyst. For example, use of porous ceramic substrates to support titanium dioxide coatings is disclosed in U.S. Pat. No. 5,035,784. Because the photocatalytic effect requires exposure of the catalyst to ultraviolet radiation, the use of a transparent substrate such as glass has been suggested. In particular, it has been recognized in U.S. Pat. Nos. 4,892,712; 4,966,759; and 5,032,241 (all to Robinson et al.) that fiberglass combines both transparency and high surface area, whereby carriers made from matrices of fiberglass are ideally suited for this purpose. The Robinson et al. patents mention both woven and non-woven fiber glass substrates, but woven meshes are preferred, and no details regarding non-woven embodiments are provided.
A non-woven fiber glass mat would be preferred over a woven mesh because substantially greater surface areas are attainable with a non-woven mat. Sizing compositions are typically applied onto fiber glass in order to reduce abrasion during processing. Additionally, when fiber glass is made into mats, it is common to apply organic binders to provide structural integrity to the mat structure. These sizings and binders, although useful to the manufacturer of the fiber glass mats, are a detriment to their use by makers of photocatalytic matrices. The organic polymer content of the sizings and binders significantly reduce adhesion of non-polymeric coatings such as the photocatalytic materials to the fiber glass mats. Attempts to use fiber glass mats as substrates for photocatalytic applications have entailed the added step of removing at least some of the organic content by heat cleaning (i.e., removing organics by combustion or volatilization at high temperature). Moreover, since it is desirable to maintain the structural integrity of the mat during processing at the user's facility, the heat cleaning step is generally carried out immediately prior to applying the photocatalytic material. Eliminating this step would be highly desirable to manufacturers of photocatalytic devices who wish to use fiber glass mat substrates.
It is also desirable for a photocatalyst support material to present a relatively low pressure drop to the flow of fluid (particularly air) therethrough. To achieve low pressure drop with an non-woven fiber glass mat would normally require maintaining the density of the mat low. But reducing the density also reduces the strength of a mat that is needed to be able to handle it in the normal processing operations involved with converting the mat to a photocatalytic matrix. Strength can be provided to a mat by organic binders, but adding such binders would be at odds with the objective of minimizing the organic content of the mat.
SUMMARY OF THE INVENTION
It has now been found that a uniquely constructed fiber glass mat can meet the objectives of providing low density and low organic material content that permit it to be used directly to manufacture a photocatalytic matrix. The fiber glass mat of the invention comprises glass fibers randomly oriented in a layer that has major dimensions in a plane and a minor thickness normal to said plane, a majority of the glass fibers being present as separate filaments, portions of said filaments extending in directions generally normal to said major dimension plane so as to interlock the mat structure. The mat contains organic material in an amount less than 1.0 weight percent as measured by loss on ignition (“LOI”), and the glass fibers and organic material in said layer have a density of 150 to 600 grams per square meter.
Preferred mat densities are 150 to 300 grams per square meter and most preferably 165 to 240 grams per square meter, which provide the desired low pressure drop when used as a catalytic air cleaner. LOI is preferably less than 0.5 weight percent, most preferably less than 0.4 weight percent. This low organic content permits applying photocatalytic material without the need for a heat cleaning step. Sizing may still be used, and the presence of some sizing is preferred, but its nature is such that heat cleaning is not necessary to attain good adhesion of the photocatalytic material. Despite the low mat density and low binder or sizing content, the mat has sufficient strength to permit the mat to be subjected to the normal handling steps associated with applying catalytic material onto the substrate.
The low organic content of the photocatalytic substrate of the present invention stems not only from the reduced reliance on organic binder and sizing materials, but also from the selection of sizing compositions that have little or no film-forming component compared to conventional sizing compositions. Instead, the sizing compositions are comprised primarily of constituents that are traditionally categorized as the lubricant and/or coupling agent components of sizing compositions. Although it is believed that some film forming may occur with some of the lubricant and/or coupling agent materials, in preferred embodiments the sizing contains no deliberate addition of a component primarily serving as a film former.
The mat of the present invention is characterized by filaments having portions extending in directions generally normal to the plane of the mat. This effect is produced by a needling operation and results in a mechanical interlocking of filaments and strands. By relying more on needling and less on organic binders to provide the required mat strength, less of the film-forming polymeric components usually included in sizings or binders need be used. Needling also results in increased mat loft due to spikes of fiber being pulled beyond the original surface of the mat. The mats of the present invention may also be characterized by relatively high loft relative to the low density.
An additional preferred feature of the mats of the present invention is that they are highly filamentized, i.e., the strands of glass fiber are separated into individual filaments. This improves surface area for a given mat density and aids in the mechanical intermeshing that permits the use of low organic content in the present invention. Preferably the glass fibers are 70 percent filamentized, and most preferably at least 80 percent filamentized.
One aspect of the present invention is the fiber glass mat substrate upon which photocatalytic material may be deposited. The mats of the present invention may have other utilities, such as for reinforcing thermoplastic or thermosetting polymeric material. Another aspect if the invention is a matrix including the fiber glass mat substrate plus photocatalytic material capable of photocatalytically decomposing organic compounds in a fluid.


REFERENCES:
patent: 4369264 (1983-01-01), Baumann et al.
patent: 4448911 (1984-05-01), Haines et al.
patent: 4892712 (1990-01-01), Robertson et al.
patent: 496675

Affiliated with

Also associated with

Rating

Photocatalytic filter with fiber glass mat carrier does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Photocatalytic filter with fiber glass mat carrier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photocatalytic filter with fiber glass mat carrier will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2447117