Photocatalytic filter with fiber glass mat carrier

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

(Background of invention) The present invention relates to structures for utilizing the known photocatalytic effects of certain metal oxides such as titanium dioxide. More specifically, the present invention relates to a combination of photocatalytic metal oxides on a particular carrier surface of fiberglass.

【0002】

The use of metal oxides such as titanium dioxide to photocatalytically decompose organic substances has been extensively addressed in the prior art. In addition to titanium dioxide, its photocatalytic effect has been reported to be achieved with oxides of zinc, tungsten, and tin. The present invention is expected to be useful by using any photocatalyst that can be coated on fiberglass. They may also contain some known photocatalytic non-oxide materials, but due to the ease of depositing metal oxides by currently known techniques, they are for use with expanded surface area substrates. This is a preferred category.

【0003】

The usefulness of the photocatalytic compound depends largely on providing a solid support with a large surface area to increase the contact area with the liquid or gas being treated. In U.S. Pat. No. 5,045,288, the layer of catalytic particles is on a filter or granular. Loosely supported in bed). A more practical approach is to catalyze the solid support members. For example, the use of a porous ceramic substrate to support a titanium dioxide coating is disclosed in US Pat. No. 5,035,784. Since the photocatalytic effect requires exposure of the catalyst to UV irradiation, the use of transparent substrates such as glass has been advocated. In particular, in U.S. Pat. Nos. 4,892,712; 4,966,759; and 5,032,241 (all Robinson et al.), Fiberglass has both transparency and high surface area, thereby being made from a fiberglass matrix. It has been recognized that carriers are ideally suitable for this purpose. Although Robinson et al.'S patent refers to fiberglass substrates for both woven and non-woven fabrics, woven mesh is preferred and does not provide any details regarding embodiments of the non-woven fabric.

【0004】

Non-woven fiberglass mats are preferred over woven meshes. This is because a substantially larger surface area can be obtained with the non-woven mat. To reduce wear during processing, sizing compositions are typically applied on fiberglass. In addition, when fiberglass is made in a mat, it is common to apply an organic binder to provide structural integrity to the mat structure. While these sizing and binders are useful for fiberglass mat manufacturers, they are disadvantageous for their use by photocatalytic matrix manufacturers. The organic polymer contents of the sizing and binder significantly reduce the adhesion of non-polymeric coatings such as photocatalytic materials to fiberglass mats. Attempts to use fiberglass mats as substrates for photocatalytic applications include an additional step of removing at least some organic content by thermal cleaning (ie, removal of organic matter by burning or volatilizing at high temperatures). In addition, the thermal cleaning step is generally performed immediately prior to application of the photocatalytic material, as it is desired to maintain the structural integrity of the mat during processing in the user's facility. Eliminating this step is highly desired by manufacturers of photocatalytic devices who desire to use fiberglass matte substrates.

【0005】

It is also desired that the photocatalytic support material provide a relatively low pressure drop in the flow of fluid (particularly air) through it. Achieving a low pressure drop in a non-woven fiberglass mat usually requires keeping the density of the mat low. However, lowering this density also reduces the strength of the mat required to allow it to be processed in the normal processing operations for the process of converting the mat to a photocatalytic matrix. Although strength can be provided to the mat by an organic binder, the addition of such a binder defeats the purpose of minimizing the organic content of the mat.

【0006】

(Gist of the invention) Here, it is found that the uniquely constructed fiberglass mats can meet the objectives of providing low density, low organic material content, which allows the fiberglass mats to be used directly in the manufacture of photocatalytic matrices. It was issued. The fiberglass mats of the present invention include randomly oriented glass fibers in the layers, which have a major amount of dimensions in a plane and a small thickness perpendicular to this plane, the majority of the glass fibers. Exists as a separate filament, a portion of this filament extending approximately perpendicular to the plane of the major quantity of dimensions and interlocking this mat structure. This mat contains less than 1.0% by weight of organic material as measured by ignition loss (LOI), and the fiberglass and organic material in this layer is 150-600 g / m.²Has a density of.

【0007】

The preferred mat density is 150-300 g / m²And most preferably 165 ~ 240g / m²This provides the desired low pressure drop when used as a contact air purifier. The LOI is preferably less than 0.5% by weight, most preferably less than 0.4% by weight. This low organic content allows the application of photocatalytic material without the need for a heat cleaning step. Sizing can be used further, and it is preferred that some sizing be present, but its properties are such that thermal cleaning is not required to achieve good adhesion of the photocatalytic material. Despite the low mat density and low binder or sizing content, the mat is strong enough to allow the mat to be subjected to normal operating steps associated with the application of catalytic material to the substrate.

【0008】

The low organic content of the photocatalytic substrates of the present invention results not only from the reduced dependence on organic binders and sizing materials, but also with little or no film-forming components compared to conventional sizing compositions. It also results from the selection of no sizing composition. Instead, the sizing composition is predominantly composed of components traditionally classified as lubricant and / or coupling agent components of the sizing composition. Some film formation can occur with some lubricant and / or coupling material, but in preferred embodiments, the sizing comprises a deliberate additional component that primarily acts as a film-forming agent. Absent.

【0009】

The mat of the present invention is characterized by a filament having a portion extending in a direction substantially perpendicular to the plane of the mat. This effect is caused by the needling operation and results in mechanical interlocking of filaments and strands. By being more dependent on needling and less dependent on organic binders to provide the required matt strength, the sizing or binder that needs to be used usually contains very little film-forming polymer component. Needling also results in increased matte bulkiness due to fiber spikes that are pulled over the original surface of the mat. The mats of the present invention can also be characterized by a relatively high bulkiness associated with low density.

【0010】

A further preferred feature of the mats of the present invention is that they are highly filamentized. That is, the strands of glass fiber are separated into individual filaments. This improves the surface area of a given mat density and aids in mechanical engagement that allows the use of low organic content in the present invention. Preferably, the glass fiber is 70% filamentized, and most preferably at least 80% filamentized.

【0011】

One aspect of the present invention is a fiberglass matte substrate on which the photocatalytic material can be deposited. The mats of the present invention may have other usefulness, for example, for reinforced thermoplastic materials or thermosetting polymer materials. Another aspect in the case of the present invention is a matrix containing a fiberglass matte substrate and a photocatalytic material capable of photocatalytically decomposing organic compounds in a fluid.

【0012】

(Detailed explanation) The present invention uses a fiberglass mat as a substrate on which the photocatalytic material is supported. The process of producing fiberglass and forming the fiberglass into a mat is well known in the art and is not itself a part of the present invention. Therefore, any conventional method for carrying out these steps can be used and does not need to be described in detail. The description of the fiber forming step and the mat forming step herein does not limit the types of processes that can be used, but is merely an embodiment included to disclose the best mode of practice of the present invention. It is intended to be. If desired, further details of these conventional aspects of the invention can be found in K. Loewenstein, The Manufacturing Technology of Continuous Glass Fibers, 3rd Edition (1993).

【0013】

The mat may consist of fibers of a known glass composition based on silicon oxide that is selectively modified with other oxidizing or non-oxidizing compounds. Useful glass fibers can be formed from any type of fibrogenic glass composition known to those skilled in the art, including "E-glass", "A-glass", "C-glass", "D-". Examples thereof include glass fibers prepared from commonly known fibrogenic glass compositions such as "glass", "R-glass" and "S-glass". Preferred glass fibers are formed from E-glass. Methods for making such compositions and glass filaments from them are described in Loewenstein (supra), pages 30-44, 47-60, 115-122, and 126-135 (these are herein). It is well known to those skilled in the art as shown in (incorporated as a reference in the document).

【0014】

Glass fibers are made with nominal filament diameters in the range of about 3.5 to about 35.0 micrometers, and any filament diameter can theoretically be used in the present invention. Although smaller filament diameters are possible, especially for spun fiberglass, it is preferable to use filaments above 3.5 to avoid the presence of respirable fibers. Moreover, filament diameters less than 7 micrometers are not readily available commercially. Certain embodiments of the invention use fibers with a nominal filament diameter of 10 micrometers. Larger diameters on the order of 17 micrometers or more may also be considered for use with the present invention and may have the advantage of being easy to process. However, the filament diameter is not definitive for the present invention. See Loewnstein (supra), page 25 (these are incorporated herein by reference) for further information on the designation of nominal filament diameters and glass fibers. Individual filaments are usually collected to form strands. The number of filaments per strand can range from about 100 to about 15,000, typically from about 200 to about 7000. See Loewnstein, supra, p. 27 (these are incorporated herein by reference) for further information on the designation of fiberglass strands.

【0015】

To prevent destructive wear between the filaments during the process, glass fibers are commonly used on at least some of their surfaces with sizing compositions that help lubricate the fibers and bond the filaments to the strands. Be coated. Conventionally, most sizing compositions include a polymeric film-forming material as their largest organic component. The most conventional sizing compositions also include coupling agents, lubricants, and surfactants. Other small amounts of additives (eg, antistatic agents) may also be present. To minimize the organic content of fiberglass, the present invention uses sizing compositions that contain little or no material that is usually considered for primary film formation. This does not mean that film formation does not occur with the remaining components. If present, especially the coupling agent is thought to produce some film formation, but conventional film formers (film). former) is not of the type of elastomer selected. In the present invention, relatively friable films are not considered to be disadvantageous. This is because such films serve individual filaments at the openings of the strands, which is done in the subsequent matting process. Filamentization has advantages as it increases the surface area of the mat and increases the chances of mechanical intertwining of the filament. In the present invention, the sizing components are selected primarily for their lubricity function, and thus preferably include conventional lubricants. Coupling agents can also serve a lubricating function, so the sizing composition of the present invention may include a coupling agent in place of or in addition to a conventional lubricant.

【0016】

Glass fiber lubricants, at least one of which is included in the sizing of the present invention, differ from those conventionally considered polymeric film-forming materials. Fiberglass lubricants may have some glass film forming ability, but otherwise they are not selected for that purpose. Useful glass fiber lubricants include cationic, nonionic or anionic lubricants and mixtures thereof. The fibrous lubricant may contain 0-100% by weight of the sizing composition based on the total amount of solids. Preferably, a combination of lubricant and coupling agent is used, in which case the lubricant may be present in an amount of 1-20% by weight based on the total solids of the sizing composition. Some examples of many known fiber lubricants include amine salts of fatty acids (eg, 1-22 atoms attached to fatty acid moieties with 12-22 carbon atoms and / or nitrogen atoms. Alkyl imidazoline derivatives (eg, which can be formed by the reaction of fatty acids with polyalkylene polyamines), acid solubilized fatty acid amides (eg, 4-24 such as stearic acid amides). Saturated or unsaturated fatty acid amides with acid groups of carbon atoms), fatty acid and condensates of polyethyleneimines and amide-substituted polyethyleneimines, such as EMERY® 6717, partially amidated polyethyleneimines (commercially available from Henkel Corporation). ).

【0017】

Useful alkyl imidazoline derivatives include CATION X (manufactured by Rhone Poulenc (Princeton, New Jersey)) and LUBRIL CAT-X / VC (manufactured by Rhodia (Cranbury, New Jersey)). Other useful lubricants include RD-1135B epoxidized polyester (commercially available from Borden Chemical (Louisville, Kentucky)), CIRRASOL 185A fatty acid amide, KETJENLUBE 522 partially carboxylated polyester (Akzo Chemicals, Inc. (Chicago,) (Commercially available from Illinois), and PROTOLUBE HD high density polyethylene emulsion (commercially available from Symbron Chemicals (Birmingham, New Jersey)).

【0018】

The coupling agents that may be included in the sizing composition of the present invention are organosilane coupling agents, transition metal coupling agents (eg, titanium, zirconium and chromium coupling agents), amino-containing Werner coupling agents, and mixtures thereof. Can be selected from the group consisting of. These coupling agents typically have bifunctionality. Each metal or silicon atom can react with the surface of the glass fiber or otherwise be chemically attached (but not necessarily bonded) to the surface of the glass fiber. To this atom. By convention, other functional groups contained in the coupling agent provide reactivity or compatibility with the film-forming polymer. This functional group is not important as conventional film-forming polymers are independent in the present invention. However, some self-crosslinking ability with some coupling agents may be provided by additional functional groups.

【0019】

The organosilane compound is the preferred coupling agent in the present invention. Examples of suitable organosilane coupling agents are Z-6040γ-glycidoxypropyltrimethoxysilane (commercially available from Dow Corning), A-187γ-glycidoxypropyltrimethoxysilane, A-174γ-methacryloxy. Propyltrimethoxysilane and A-1100γ-aminopropyltriethoxysilane, each of which is commercially available from OSi Specialties, Inc. (Tarrytown, New York). The amount of coupling agent can be 0-80% by weight of the sizing composition on an all-solid basis basis. In a preferred embodiment, the coupling agent content is at least 10%, most preferably at least 30%. This organosilane coupling agent can be hydrolyzed with water, at least partially, before being applied to the glass fibers.

【0020】

The sizing composition may contain one or more surfactants to stabilize the other components of the sizing composition in the aqueous medium. When the sizing composition is applied onto glass fibers, the sizing composition is preferably diluted with water to a weight several times its weight. Examples of suitable surfactants are polyoxyalkylene block copolymers (eg, PLURONIC).^TMF-108 polyoxypropylene-polyoxyethylene copolymer (commercially available from BASF Corporation (Parsippany, New Jersey)), ethoxylated alkylphenols (eg, IGEPAL CA-630 ethoxylated octylphenoxyethanol (GAF Corporation (Wayne, New Jersey)) )), Polyoxyethylene octylphenyl glycol ethers, ethylene oxide derivatives of sorbitol esters and polyoxyethylated vegetable oils (eg, EMULPHOR EL-719 (commercially available from GAF Corp.)). In general, the amount of surfactant can be 0-40% by weight of the sizing composition on an all-solid basis basis.

【0021】

Trace amounts of various additives may also be present in sizing such as antistatics, fungicides, fungicides, and defoamers. Also included in the sizing composition are sufficient amounts of organic acids or bases and / or inorganic acids or bases to provide an aqueous sizing composition with a suitable pH (typically 2-10). obtain. Water (preferably deionized water) is included in the sizing composition in an amount sufficient to facilitate the application of a nearly uniform coating onto the fiberglass. The solid weight% of the sizing composition is generally in the range of about 5% to about 20% by weight, but the dilution of the sizing is highly dependent on factors such as the type of applicator used. Can change.

【0022】

The sizing composition used in the preferred embodiment of the present invention was made as follows: Ingredient amount (part by weight) 1 water 3632.00 2 acetic acid 45.40 3 silane¹ 169.50 4 Cationic softener² 18.16 5 Hot water 484.20 6 Surfactant³ 84.80 7 Hot water 484.20¹A-1100γ Aminopropyltriethoxysilane (OSi Specialities, Inc. (Tarrytown, New York))²LUBRIL CAT-X / VC, imidazoline (Rhodia, Inc., Cranbury, New Jersey)³IGEPAL CA-630 (GAF Corporation, Wayne, New Jersey).

【0023】

Ingredients 4 and 5 were premixed by stirring for 20 minutes and then added to the other ingredients. Ingredients 6 and 7 were premixed by stirring for 20 minutes and then added to the other ingredients.

【0024】

The sum of all the organic components of the sizing composition described above was minimized in the present invention to avoid the need for a heat cleaning step. Generally, the LOI of this fiberglass mat is less than 1.0% by weight, preferably less than 0.5% by weight, most preferably less than 0.4% by weight. Although some sizing is preferably present, its components are selected to minimize LOI, as described above. In a preferred embodiment where some sizing is present, the LOI of this mat is at least 0.1% by weight.

【0025】

This sizing can be done by any of the various modes known in the art, eg, by contacting the filament with a static or dynamic applicator (eg, a roller or belt applicator), or by spraying, or otherwise. It can be applied on the filament by the means of. See Loewenstein (supra), pp. 165-172, for a discussion of suitable applicators (which is incorporated herein by reference). The sized filaments can be gathered together in the strands. The number of filaments per strand can range from about 100 to about 15,000, more typically from about 200 to about 7000. See page 27 of Loewenstein (supra) for more information on fiberglass strand designation (which is incorporated herein by reference).

【0026】

The sizing strands are dried at room temperature or high temperature to remove moisture content and cure any curable sizing or possible second coating composition. Drying of the glass fibers that form the package or cake is common in the art, and further details are incorporated herein by Loewenstein, pp. 219-222 (which is incorporated herein by reference). Can be seen in

【0027】

Although not a preferred practice of the present invention, a second coating may be applied to the strands. This second coating composition is preferably aqueous based and may contain components similar to the sizing composition described above. This second coating composition may be applied in an amount effective for coating or impregnating a portion of the strand with at least a portion of the surface of the strand. The second coating is, for example, by immersing the strands in a bath containing the composition, by spraying the composition onto the strands, or by a static or dynamic applicator (eg, a roller or belt applicator). ) And the strands, which can be customarily applied. The coated strands can pass through the mold to remove excess coating from the strands and / or dry for at least a sufficient amount of time for the second coating to dry and cure as described above. Can be done. The second coating, when used, has a composition similar to the sizing composition described above. After drying, roving by winding several nearly parallel strands together Gathering into a package) is a common practice for strands intended for mats.

【0028】

Preferably, the mat is formed from strands cut to discontinuous length by a chopper. To facilitate the manufacture of mats and interlocking of filaments, these cut lengths are generally provided in average lengths greater than 2 centimeters and generally less than 10 centimeters. To. Shorter lengths are generally difficult to convert to structurally integrated mats, and longer lengths are difficult to handle in the mat forming process. A cut length of 5 centimeters is used successfully, and some strength benefits can be achieved with slightly longer lengths on the order of 7-8 centimeters. Commercially available choppers such as the Model 90 chopper (Finn and Fram, Inc.) are suitable. Devices and processes useful for forming layers of cut strands are disclosed in Loewenstein (supra), pp. 293-303, which is incorporated herein by reference.

【0029】

In order to provide a high surface area in the catalyst substrate of the present invention, the fiberglass stran is at least partially filamentized, i.e., the bundle of filaments containing the strands is at least partially split into the respective filaments. The glass fibers in the mat of the present invention are preferably filamentized at least 70% by weight, more preferably at least 80% filamentized, and most preferably at least 90% filamentized. 100% filamentation is optimal, but this is rarely achieved. Filamentization itself is known in the art and can typically be achieved by mechanical or pneumatic mean associated with the mat forming apparatus. An example of a device that favorably imparts a high degree of fragmentation to a strand is RANDO-OPENER BLENDER (which is a MODEL B commercially available from Rando Machine Corporation of Macedon, NY, NY). It is part of the RANDO-WEB® processor). Alternatively, the strand opener may be a card machine (such as one commercially available from Hollingsworth on Wheels, Inc. (Grrenville, South Carolina) or N. Schlumberger (USA) Inc. (Charlotte, North Carolina)). The opening action of the Rando model is the agitation that occurs by passing through the strands between a series of rolls that rotate in opposite directions. The proportion of filamentized strands can be adjusted by adjusting the space between the opposing rolls of the strand opener and the speed of rotation of the rolls.

【0030】

After the opening process, the fiberglass can be transported to the mat forming apparatus. A preferred mat forming machine is the RANDO-WEBBER® (which is part of the MODEL B RANDO-WEB® processor described below). In the Rando process, the glass fibers are carried by an air stream. In this type of mat forming machine, fibers are deposited on the surface of a rotating cylindrical feed mat capacitor screen maintained at a pressure below atmospheric pressure to form a feed mat. The feed mat is stripped from this feed mat capacitor and then fed from the feed mat carried by the other air stream to the lickerin combing each strand and monofilament, and below atmospheric pressure. It is deposited as a mat on the surface of the other rotating cylindrical capacitor screen that is maintained at pressure. The mat thus formed is transported from the mat forming machine to the needling station.

【0031】

Traditional mats are occasionally combined with small amounts of unidirectional glass fiber, plastic fiber and / or fabric. The purpose of these additional fibers is to provide the mat with temporary strength during the manufacturing process prior to the laminating process. These reinforcing strands and / or fabrics can be placed between layers of the mat or on one side of the mat and then subjected to needling operations. Although not excluded by the present invention, these reinforcing layers have not been found to be required for preferred embodiments of the present invention. It is valuable that the mechanical strength of the mats of the present invention can be obtained without such reinforced strands or fabrics.

【0032】

The glass filaments and fiberglass (and any reinforcing fibers) of the mat are meshed with each other by subjecting the mat to a needling process. This needling can be achieved using conventional needling devices such as those used in the reinforced fiberglass industry, where the mat is passed between the spaced needling boards. An example of such a device is described in US Pat. No. 4,277,531 (Picone) assigned to the same person, which is incorporated herein by reference. One example of a suitable needling machine is Model NL9 (Textilmaschinenfabric Dr. Ernest) (Commercially available from Fehrer AG (Germany)). In the needling operation, an array of barbed needles is used to entangle or entangle the monofilaments and strands of the mat to give the mat mechanical strength and integrity. The effect of needling is to displace the filament and / or strand portions from the mat of a nearly flat array in a direction substantially perpendicular to the mat surface. The extent to which this displacement occurs depends on factors such as the type of needle used, the depth of penetration of the needle into the mat, and the density of the needle punch.

【0033】

The needling operation may use a needle configured with a hook angled towards the needle tip, which entangles the fibers in the mat as the needle passes through the mat. In the pull-in stroke, this needle type generally releases the fiber. Needles with a downwardly pointed hook are preferred, but the use of reverse hook needles (ie, having an angle away from the needle tip) is not excluded in the present invention. Due to the low density of the mats of the present invention, it has been found that it is advantageous to use relatively fine needles. Needles with gauges heavier than 25 gauge (ie, having a smaller gauge number) tend to break an excessive number of filaments, thereby failing to achieve the intended strength improvement. Lighter 30 gauge needles, preferably 32 gauge and lighter needles, are recommended for the low density mats of the invention. A particularly useful commercial needle type is the "star" type needle, which has six hooks spaced in a triangular arrangement around the shaft of the needle, with a pair of hooks on top of each other. Align vertically to. It has also been found that it is desirable to limit the punch depth of the needle, so it is advantageous for a "star" type needle to place the hook near the tip of the needle. Suppliers of these types of needles include Foster Needle Company, Manitowoc, Wisconsin, and Groz-Beckert USA, Charlotte, and North Carolina.

【0034】

As used herein in the description of needling operations, the term "horizontal" or "horizontally" means that a plane is approximately parallel to the main plane of the mat, which is typical. In addition, it is almost parallel to the ground. As used herein, the terms "vertical" or "vertically", "downward", and "upward" refer to directions that are approximately perpendicular to "horizontal". These specific directional terms are, for convenience, used to describe the needling operation, to reflect the normal orientation of the needling device, and to define directions relative to each other. However, it should be understood that these orientations are not restricted during the process.

【0035】

As soon as the needling stroke is entered, the needle carried on the needle board passes through the mat and enters the nearly cylindrical orifice in the backer board supporting the mat. Depending on the needling depth, one or more layers of hooks pass through the mat completely and enter the backerboard orifice. When a two-layer needle design is used for the purposes of the present invention, it is preferred that both layers of the hook pass through this mat. The distance these needles cross this mat into the backer board orifice is called the "kneading depth". The needling depth of the preferred embodiment is in the range of 0.45 to 0.65 inches (1 cm to 1.7 cm).

【0036】

After the needles exit the mat during the pull-in stroke, these needles pass through multiple nearly cylindrical orifices in a metal stripper plate spaced from the mat during the needling process. The filaments and strands are pulled from the hook by this stripper plate, and then the mat is advanced after a complete stroke of inserting and pulling in the needle. The needle board can be reciprocated at a frequency of about 80 to about 3000 strokes per minute. Needlers typically include rolls to propel the mat horizontally during the needling. At a lower frequency, advancing occurs intermittently in the interval between needle punches. At a higher frequency, advancing approaches continuous movement.

【0037】

Punch density can also be varied to affect the reinforcement of the mat. Needle punch density depends on the particular type of needle used, the thickness of the mat, and other factors. With respect to other preferred needling parameters disclosed herein, the needle punch density is preferably in the range of 100 to about 160 punches per square inch (15 to 25 punches per square centimeter). Lower punch densities are possible, but the desired mat strength may not be achieved without the binder. Larger punch densities at some point tend to result in reduced return and actually reduce mat strength. A preferred embodiment utilized approximately 140 punches per square inch (23 punches per square centimeter).

【0038】

The needling process is described in more detail in the assignee's US Pat. No. 4,335,176 (Bauman), which is incorporated herein by reference.

【0039】

In a typical needling process, the mat entering the needler can have an overall average thickness of about 5 to about 30 millimeters. After passing through the needler, the mat can have a compression average thickness of about 2.5 to about 7 millimeters. The thickness of this mat, or "loft," is affected by the extent to which the fiber spikes extend from the surface of the mat due to the needling process. In the mat of the present invention, the loft is relatively high at low densities. The loft in a preferred embodiment of the mat of the present invention exceeds 0.25 inches (6.3 mm), and preferably exceeds 0.35 inches (8.9 mm). Maximizing loft is generally desirable in the present invention, but achieving loft greater than about 0.5 inch using the types of mats included herein may require excessive needling. , May have a detrimental effect on tensile strength. Lofts were measured by placing an ounce weight on an area of 1 square foot and measuring the thickness of the compressed mat.

【0040】

Tensile strength was measured using the Instron Series IX Materials Testing System, using a 3 inch (7.6 cm) x 9 inch (22.9 cm) sample of mats drawn to its large size. A preferred embodiment of the invention showed a tensile strength greater than 8.0 lbs per foot of the mat width line, and in the best embodiment showed a tensile strength greater than 10.0 lbs.

【0041】

There is extensive literature describing the application of photocatalytic materials to glass substrates. The present invention is not limited to any particular technique for producing a photocatalytic coating, but the use of these photocatalytic materials which can be applied from a liquid medium to impregnate a large surface area substrate such as a fiberglass mat is possible. , Is an advantage. By immersing the mat in the liquid coating composition, a large surface area can be coated with the photocatalytic material. Metal oxide photocatalysts are useful for the immersion coating process. This is because the metal alkoxide can be dissolved in a liquid solvent (usually an alcohol) into which the mat can be immersed. Subsequently, the deposited alkoxide can be hydrolyzed to form a metal oxide film that is well bonded to the glass substrate. This type of preferred process is described in US Pat. No. 4,966, Disclosure in issue 759 (Robertson et al.). More specifically, the process of this patent involves using a metal alkoxide as a starting material, which can be, for example, titanium ethoxyoxide in the preferred case of titanium dioxide photocatalyst. This titanium ethoxydo is dissolved in an organic solvent such as absolute ethanol and reacts with a controlled amount of acid (eg, nitric acid) and water to form a coating solution. The fiberglass mat can be immersed in this coating solution under dry conditions for a time on the order of 1 minute. Subsequently, the coating mat is dried in air at room temperature to hydrolyze the alkoxide, thereby forming an amorphous polymeric titanate layer on the mat. After the coating has dried for 1-2 hours, the coating mat is heated to a temperature sufficient to transform the amorphous layer into a photocatalytically active crystalline form (anatase in the case of titanium dioxide). The heating cycle for producing anatase titanium dioxide can include a slow warming period on the order of 2-5 hours, holding at about 400 ° C for 1 hour, and a cooling period on the order of 5 hours or more. It should be understood that coating and heat treatment conditions vary depending on the particular material used, as known to those skilled in the art.

【0042】

It is also known to apply the catalytic metal oxide onto the substrate using an aqueous medium. These may use aqueous solutions or slurries of titanate products, especially chelated versions, or similar products from Degussa, available from DuPont under the name TYZOR.

【0043】

A further advantage that may be attributed to the presence of the coupling agent in the preferred embodiments of the present invention is that improved coating of the wet photocatalytic material on the fiberglass substrate is achieved. In the conventional practice of thermal cleaning of the substrate, this advantage is lost due to the thermal decomposition of any coupling agent present.

【0044】

It is known that metal oxides are doped with other materials (eg platinum) to enhance the photocatalytic activity of the catalyst, and the photocatalytic matrix of the present invention may contain such dopants.

【0045】

The present invention has been described in the context of a particular embodiment for the purpose of providing the best mode of the invention. It should be understood that other changes and modifications known to those skilled in the art can be used within the scope of the invention as defined in the claims.