Toxic gas treatment sheet and method of manufacturing the same

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention uses a photocatalyst to nitrogen oxides (NO) in gas._X), Hazardous gas treatment sheet for decomposing and removing harmful components such as malodorous substances such as ammonia and hydrogen sulfide, and its manufacturing method.

【0002】

[Conventional technology]

In metropolitan areas, many areas that cannot meet environmental standards are emerging due to the increase in the number of automobiles and the deterioration of traffic conditions such as traffic jams. For this reason, in order to reduce the load on the surrounding area, in addition to measures against the source, NO after discharge_XVarious studies have been conducted on how to remove.

【0003】

In homes and offices, there are problems with tobacco odor, pet odor, and formaldehyde, which is released from building materials and is a causative substance of chemical substance hypersensitivity, and harmful gas in exhaust gas generated from incinerators becomes a problem. Therefore, efficient removal of these harmful substances is desired.

【0004】

As a method for removing harmful components such as nitrogen oxides and malodorous substances, an adsorption method using activated carbon, zeolite or the like is known. This adsorption method has a problem that if a malodorous substance or the like exceeds the saturated adsorption amount of the adsorbent, it cannot be removed, and the adsorbent must be regenerated or replaced.

【0005】

Recently, titanium dioxide (TiO) has been recently used as a method for eliminating the troublesome work.₂), ZnO, Fe₂O₃, CdS, CdSe, SrTiO₃A photocatalytic decomposition method containing the above as the main component has been attracting attention. In particular, titanium dioxide (TiO₂) Is attracting attention.

【0006】

The titanium dioxide is excited by ultraviolet light of about 400 nm or less to generate electron-hole pairs. Holes react with hydroxyl groups (OH groups) on the surface of titanium dioxide to generate OH radicals, and electrons are oxygen (O).₂), Superoxide anion (O)₂^-) Is generated. These reactive oxygen species have a very strong oxidizing power and decompose and detoxify the above-mentioned malodorous substances. Therefore, malodorous substances and the like do not accumulate on the surface of titanium dioxide, and work such as replacement of the adsorbent becomes unnecessary.

【0007】

Titanium dioxide is a powder, and in practical use, it is necessary to immobilize and use it without lowering the photocatalytic activity. As the immobilization method, a method of mixing with an inorganic paint or a coating agent and applying it on a plastic film, a method of mixing with a PTFE (polytetrafluoroethylene) resin, rolling and forming a sheet, and the like are known.

【0008】

In this method of forming a sheet with a PTFE resin, the amount of titanium dioxide supported can be increased, and since the material is porous, titanium dioxide inside the sheet can also contribute to the reaction, and the photocatalytic activity is high. The photocatalyst sheet in which titanium dioxide is supported on the sheeted photocatalyst or plastic film with a coating agent is suitable for mass production and is easy to handle as a part. Conventionally, when such a photocatalyst sheet is applied to a harmful gas removing device including a deodorizing device, an exhaust gas treatment device, a sterilizing device, an oxidative decomposition wall, etc., it is applied to a wall or a support of a container constituting the harmful gas removing device. It is used with a photocatalyst sheet attached.

【0009】

By the way, in the decomposition of harmful gas by a photocatalyst, there are several factors that determine the decomposition efficiency, but one of the major factors is how efficiently the harmful gas component and the photocatalyst are brought into contact with each other. Conventionally, as a means for improving the contact efficiency, a material in which titanium dioxide is supported on a wavy ceramic paper is used (see JP-A-3-94813), or a mesh in which titanium dioxide is supported on a borosilicate glass cloth. (See Japanese Patent Application Laid-Open No. 3-106420) is known. In these materials, the corrugated or net-like material used as the base material is impregnated with titania sol in which titanium dioxide particles are dispersed in water, alcohol, etc., dried, and then heat-treated at 400 to 700 ° C to obtain titanium dioxide. It is supported.

【0010】

[Problems to be Solved by the Invention]

A material on which titanium dioxide is supported by the above impregnation can be a material on which titanium dioxide is supported and contact efficiency is good as long as the base material is impregnated with titania sol regardless of the shape of the base material.

【0011】

However, a material in which titanium dioxide is supported on a plastic film, or a photocatalyst sheet as described above, which is formed by mixing fluororesin powder and titanium dioxide and then rolling them into a sheet shape, is corrugated in order to improve contact efficiency. It is difficult to use in combination with a base material or a network base material. This is because it takes too much time and effort to attach the corrugated sheet in close contact with the corrugated sheet, and in the case of a reticulated base material, it covers the pores of the reticulated base material.

【0012】

On the other hand, in order to improve the mechanical strength of the photocatalyst sheet itself and improve mass productivity and handleability as a part in the photocatalyst sheet using, for example, PTFE resin and titanium dioxide particles without using the base material. It is desirable to select the thickness of the photocatalyst sheet appropriately and then fire it at the melting temperature of PTFE (320 to 330 ° C). In this case, the PTFE resin in which titanium dioxide particles are melted is coated. As a result, the contact surface area between the titanium dioxide particles and the harmful gas is reduced, which leads to a decrease in the oxidation / decomposition performance of the photocatalyst sheet.

【0013】

Japanese Patent Application Laid-Open No. 10-44346 states that mechanical strength and adhesive strength are improved by forming a titanium oxide-free fluorine resin (PTFE) layer on one side of a fluorine resin (PTFE) layer containing titanium oxide particles. However, even in this case, the problem of reduction in contact surface area with harmful gas due to the PTFE resin coating cannot be solved.

【0014】

The subject of the present invention has been made in view of the above points, and the harmful gas treatment sheet has a large contact area between the photocatalyst particles and the harmful gas, and has improved mechanical strength and mass productivity. The purpose is to provide the manufacturing method.

【0015】

[Means for solving problems]

In order to solve the above-mentioned problems, in the present invention, it is a harmful gas treatment sheet for decomposing and removing harmful substances such as nitrogen oxides and malodorous substances in the gas to be treated, and is a fluorine resin as a binder. A) is formed by laminating a first layer containing metal compound particles having a photocatalytic function in A) and a second layer containing ceramic particles in a fluororesin (A) as a binder, and further, the first layer. The layer 2 contains a second fluororesin (B) having a lower melting point than the fluororesin (A) (the invention of claim 1).

【0016】

According to the above configuration, in the first layer, for example, by a production method described later, it is possible to make the unmelted fluororesin (A) fibrously bonded to the photocatalyst particles, and the photocatalyst particles and harmful gas. In the second layer, the molten second fluorine resin (B) binds the ceramic particles and the fluorine resin (A) to improve the mechanical strength, thereby ensuring a large contact area with the ceramic particles. As a result, this laminated sheet becomes a sheet having a large contact area and high mechanical strength as a whole.

【0017】

As an embodiment of the invention of claim 1, the inventions of claims 2 to 7 below are preferable. That is, in the harmful gas treatment sheet according to claim 1, the metal compound is TiO.₂, ZnO, Fe₂O₃, CdS, CdSe and SrTiO₃(Invention of claim 2).

【0018】

Further, in the harmful gas treatment sheet according to claim 1, the ceramic is at least one of silicon oxide, zinc oxide, titanium carbide, silicon carbide, and tungsten carbide (invention of claim 3). Among them, as in the invention of claim 6, the metal compound is TiO.₂The ceramic is preferably silicon carbide.

【0019】

Further, in the harmful gas treatment sheet according to claim 1, the fluorine resin (A) is polytetrafluoroethylene (PTFE), and the second fluorine resin (B) is a tetrafluoroethylene / hexafluoropropylene copolymer. It shall be coalesced (FEP) (invention of claim 4), and the thickness of the first layer and the second layer shall be at least 50 μm each (invention of claim 5). If it is 50 μm or less, pinholes may occur during roll molding.

【0020】

Further, in the harmful gas treatment sheet according to claim 4, the composition ratio of PTFE in the first layer is 5% to 70%, and the component ratios of PTFE and FEP in the second layer are at least, respectively. 5% and 10% (invention of claim 7). When the component ratio of PTFE is 5% or less, it becomes difficult to form a sheet. Further, if the proportion of the PTFE component in the first layer exceeds 70%, there is a problem that the activity of the photocatalyst particles decreases. There is no clear upper limit on the proportion of PTFE and FEP components in the second layer, but if there is too much, the material is wasted, and as a guideline for the upper limit, PTFE is 20% and FEP is 50%.

【0021】

Next, the invention of claim 8 is preferable as a method for producing a harmful gas treatment sheet. That is, the following steps are included in the method for producing a harmful gas treatment sheet according to claim 1. 1) A step of kneading a liquid dispersion of a fluorine resin (A) and metal compound particles, kneading the coagulated precipitate, and then pre-rolling to form the first layer into a sheet. 2) The liquid dispersion of the fluorine resin (A), the second fluorine resin (B), and the metal compound particles is kneaded, the coagulated precipitate is kneaded, and then pre-rolled to form a sheet of the second layer. The process of forming into. 3) After the sheet-like first layer and the second layer are overlapped and rolled to prepare a sheet having a two-layer structure, the second fluorine resin (B) is melted and the fluorine resin (A) is formed. ) Is the process of firing at a temperature within the temperature range where it does not melt.

【0022】

By the above manufacturing method, as described above, it is possible to form a harmful gas treatment sheet having a large contact area as a whole and high mechanical strength, and mass productivity is also good.

【0023】

Further, as an embodiment of the invention of claim 8, the inventions of claims 9 to 10 below are preferable from the viewpoint of improving the dispersibility of various materials. That is, in the production method according to claim 8, the liquid of the liquid dispersion liquid is made by adding a surfactant to pure water (invention of claim 9). Further, in the production method according to claim 8, an organic solvent such as methanol, ethanol, 2-propanol, ethylene glycol, and glycerin is mixed with the liquid dispersion before forming the coagulated precipitate (invention of claim 10). ).

【0024】

Further, the invention of claim 11 below is preferable from the viewpoint of the combination of suitable fluorine resin materials and the selection of the firing temperature. That is, in the production method according to claim 8, the fluorine resin (A) is polytetrafluoroethylene (PTFE), and the second fluorine resin (B) is a tetrafluoroethylene / hexafluoropropylene copolymer. (FEP), and the firing temperature is approximately 300 ° C.

【0025】

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are described below with reference to the drawings.

【0026】

FIG. 1 shows a conceptual schematic diagram of the configuration of a harmful gas treatment sheet according to the present invention, and FIG. 2 shows an example of a method for manufacturing the harmful gas treatment sheet. Further, in FIGS. 1 and 2, the metal compound having a photocatalytic function is TiO.₂An example is shown in which the ceramic used for the second layer is silicon carbide, the fluororesin (A) is PTFE, and the second fluororesin (B) is FEP.

【0027】

In FIG. 1, the hazardous gas treatment sheets are PTFE3 and TiO as binders.₂It consists of a first layer 5 containing particles 1 and a second layer 6 containing PTFE3 as a binder, silicon carbide (SiC) particles 2 and FEP4 as a second fluororesin. In the first layer 5 or the second layer 6, PTFE3 is composed of PTFE particles (black circles in FIG. 1) and fibrous ones, and is TiO.₂It is entangled and bonded to particle 1 or silicon carbide (SiC) particle 2. FEP4 also melts in the second layer 6 and entangles and bonds with the silicon carbide (SiC) particles 2 and PTFE3 to increase the mechanical strength of the second layer 6 and the second layer 6 It serves as a supporting base material for the first layer 5.

【0028】

Since the melting temperature of FEP4 is 290 to 305 ° C and the melting temperature of PTFE3 is 320 to 330 ° C, by setting the firing temperature of the sheet to approximately 300 ° C, PTFE3 does not melt. , Only FEP4 can be melted. As a result, TiO in the first layer 5₂The surface of the particle 1 is not covered with the molten resin, but effectively contacts the harmful gas and contributes to the oxidation reaction. Further, in the second layer 6, the molten FEP4 is evenly bonded to other materials and contributes to the improvement of mechanical strength.

【0029】

Next, the manufacturing procedure of the harmful gas treatment sheet is described below with reference to FIG.

【0030】

First, titanium dioxide (TiO₂), A liquid dispersion of PTFE is added to the dispersion (a solution in which a surfactant is added to pure water) and mixed, and then methanol is mixed to prepare a coagulated precipitate. This coagulated precipitate is kneaded to generate a fibrous bond of PTFE, which is pre-rolled by a roll rolling mill to prepare a sheet having a thickness of several mm.

【0031】

Next, a liquid dispersion of PTFE and FEP is added to and mixed with a dispersion of silicon carbide (SiC), and methanol is further mixed to prepare a coagulated precipitate. This coagulated precipitate is kneaded to generate a fibrous bond of PTFE, which is pre-rolled by a roll rolling mill to prepare a sheet having a thickness of several mm.

【0032】

The above two pre-rolled sheets are superposed and rolled again by a roll rolling machine with a roll gap set to a predetermined thickness to prepare a sheet having a two-layer structure. This sheet is washed with pure water, dried, and then fired at 300 ° C.

【0033】

By the above step, the problem of decrease in contact surface area with harmful gas due to the PTFE resin coating can be solved, and a harmful gas treatment sheet having high mechanical strength can be prepared.

【0034】

[Effect of the invention]

As described above, according to the present invention, it is a harmful gas treatment sheet for decomposing and removing harmful substances such as nitrogen oxides and malodorous substances in the gas to be treated, and is a fluorine resin (A) as a binder. A first layer containing metal compound particles having a photocatalytic function therein and a second layer containing ceramic particles in a fluororesin (A) as a binder are laminated, and further, the second layer is formed. The layer contains a second fluororesin (B) having a melting point lower than that of the fluororesin (A), and as a method for producing a harmful gas-treated sheet, 1) A step of kneading a liquid dispersion of fluorine resin (A) and metal compound particles, kneading this coagulated precipitate, and then pre-rolling to form a first layer in the form of a sheet. 2) The liquid dispersion of the fluororesin (A), the second fluororesin (B) and the metal compound particles is kneaded, the coagulated precipitate is kneaded, and then pre-rolled to form a sheet of the second layer. The process of forming. 3) After the sheet-like first layer and the second layer are overlapped and rolled to prepare a sheet having a two-layer structure, the second fluorine resin (B) is melted and the fluorine resin (A) is formed. ) Is the process of firing at a temperature within the temperature range where it does not melt. As described above, it is possible to form a harmful gas treatment sheet having a large contact area and high mechanical strength as a whole, and it is possible to provide a harmful gas treatment sheet having high mass productivity and a method for manufacturing the same. ..

[Simple explanation of drawings]

[Figure 1]

Conceptual schematic diagram of the structure of the hazardous gas treatment sheet according to the present invention [Figure 2]

The figure which shows an example of the manufacturing method of the harmful gas treatment sheet of this invention. [Explanation of symbols]

1: Titanium dioxide particles, 2: Silicon carbide particles, 3: PTFE, 4: FEP, 5: 1st layer, 6: 2nd layer.