JP2821695B2 - Photoreactive semiconductor supporting sheet and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photoreactive semiconductor sheet carrying a photoreactive semiconductor without impairing its performance and a method for producing the same.

More specifically, a toxic substance (a malodorous component, an irritant component, and a growth promoting component harmful to the preservation of fruits and vegetables, flowers and the like) which is gaseous or floating in the atmosphere is removed using a photooxidation reaction. And a method for producing the same.

[Conventional technology]

In recent years, with the improvement of living standards, not only bad odors and irritating components produced industrially, but also odors of waste in homes and restaurants and bad odors generated during cooking (hydrogen sulfide, ammonia, mercaptan, amines, aldehydes, etc.) ) And irritating components (formaldehyde, acrolein, etc.) have become problems.

On the other hand, along with the sophistication of food preferences, the demand for fresh fruits and vegetables and fruits and flowers in seasons outside the normal harvest season is also increasing, but in order to meet these demands, growth promotion components are required. It is important to remove some ethylene.

The present inventors have been studying the removal of these harmful components using a photo-oxidation reaction. This is because the method utilizing the photoreaction is excellent in terms of oxidation treatment efficiency, energy cost and equipment cost, safety, and the like.

However, the conventional technique is to irradiate the photoreactive semiconductor alone or in a state of being supported on a carrier and dispersed in a solution, and then irradiating the photoreactive semiconductor with ultraviolet light or visible light. It was not suitable for removing harmful components suspended in it.

Conventionally, as a method of supporting a photoreactive semiconductor on a sheet-shaped carrier such as a polymer film, metal, glass, and ceramics, the photoreactive semiconductor is suspended in water or a volatile organic solvent such as methanol, acetone, and tetrahydrofuran. Then, apply to the sheet and dry it. When the carrier is a metal or ceramics, bake the sheet carrying the photoreactive semiconductor by the above method at a higher temperature (700 ° C. or more). In the case of a polymer film or the like that is easy to immerse, it is immersed in a suspension of a photoreactive semiconductor in water or a volatile organic solvent, the semiconductor is sufficiently penetrated into the suspension, and then dried. For pre-mixing reactive semiconductors as fillers, for supporting photoreactive semiconductors using water-soluble polymers such as starch or casein, or epoxy- or urethane-based adhesives It has been carried out.

However, in the method, the amount of the photoreactive semiconductor carried is small, and the adhesive force with the sheet is small, so that the photoreactive semiconductor is easily peeled off. The type of carrier that can be used is limited, and the photoreaction is performed because most of the photoreactive semiconductors are taken into the inside of the sheet. The method of reducing the amount of photoreactive semiconductor on the sheet surface includes:
The amount of photoreactive semiconductor on the sheet surface is reduced in the same way as in the above method, and the performance of the photoreactive semiconductor deteriorates due to the reaction with other raw materials or heating during the production and processing of the sheet. The method has drawbacks such as the photoreactive semiconductor reacting with the adhesive or covering the photoreactive semiconductor surface, thereby reducing the number of active sites, and therefore, does not impair the performance of the photoreactive semiconductor. A method for uniformly supporting a required amount of a photoreactive semiconductor on the surface of a sheet-like carrier has been desired.

[Problems to be solved by the invention]

An object of the present invention is to uniformly support a required amount of a photoreactive semiconductor on the surface of a sheet-like carrier without deteriorating its performance, and to efficiently remove harmful substances that are gaseous or floating in the atmosphere using a photo-oxidation reaction. An object of the present invention is to provide a photoreactive semiconductor supporting sheet that can be removed well and a method for producing the same.

[Means for solving the problem]

The inventors of the present invention have conducted intensive studies to achieve this object, and as a result, contacted gaseous or harmful substances suspended in the atmosphere with a sheet carrying a photoreactive semiconductor using latex, It has been found that harmful substances can be efficiently removed by irradiating a conductive semiconductor with ultraviolet light, and the present invention has been completed based on this finding.

Thus, according to the present invention, in a sheet carrying a photoreactive semiconductor having a band gap of 0.5 to 5 eV on a surface, the semiconductor was carried using a latex having a minimum film formation temperature of 60 ° C. or less. A light containing 100 parts by weight of a photoreactive semiconductor supporting sheet and a photoreactive semiconductor having a band gap of 0.5 to 5 eV, and a latex of more than 1 part by weight and less than 20 parts by weight in terms of solid content. The method for producing a photoreactive semiconductor-carrying sheet is provided, wherein the reactive composition is carried on the sheet surface.

The photoreactive semiconductor used in the present invention is a semiconductor that causes a photocatalytic reaction, and 0.5 to 5 eV, preferably 1 to 3 eV.
It has a bandgap of V.

Specific examples of such a photoreactive semiconductor include metal oxides such as tin dioxide, zinc oxide, tungsten trioxide, titanium dioxide, barium titanate, and ferric oxide;
Metal chalcogenides such as zinc sulfide, cadmium sulfide, lead sulfide, zinc selenide and cadmium selenide; Group IV elements such as silicon and germanium; II such as gallium-phosphorus, gallium-arsenic and indium-phosphorus
Group IV compound; examples thereof include organic semiconductors such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polyvinylcarbazole. Among these, particularly preferred are metal oxides such as zinc oxide, tungsten trioxide, titanium dioxide, and cerium oxide, and liquid crystal materials thereof.

Further, the above-mentioned photoreactive semiconductor doped with impurities such as arsenic, phosphorus, aluminum, boron, sodium, and halogen can also be used.

In addition, by supporting a noble metal such as platinum, palladium, silver, or copper on the surface of the photoreactive semiconductor, the photocatalytic reaction efficiency can be improved.

Further, as long as the effects of the present invention are not impaired, an adsorbent such as activated carbon, clay oxide or zeolite may be used in combination with the photoreactive semiconductor.

The material of the sheet used to support the photoreactive semiconductor in the present invention is not particularly limited, and examples thereof include paper; plant fibers (cotton, linen, cannabis, etc.), and animal fibers (wool, mohair, bikuna, etc., animal hair). And silk), synthetic fibers (rayon,
Weaving, knitting, physical / chemical bonding, etc. of woven, knitted, physical, chemical, etc. acetate, triacetate, acrylic, aramid, nylon, olefin, polyester, etc.) or inorganic fibers (glass, metal, ceramics, minerals, asbestos, etc.)
Knitted fabric, non-woven fabric, etc .; acryloniloryl-butadiene-styrene copolymer (ABS), acrylonitrile-methyl acrylate copolymer, cellophane, celluloses (ethyl cellulose, cellulose acetate, etc.), fluoroplastics (ethylene-tetra Fluoroethylene copolymer (ETFE) and polytetrafluoroethylene (PTFE)
Etc.), ionomers, polyamides (nylon-6, nylon-6,6 etc.), polyesters such as polybutylene, polycarbonate, polyethylene terephthalate, polyethylene, ethylene-vinyl acetate copolymer, polyimide, polymethyl methacrylate (PMMA), polypropylene Calendering, inflation, and T-die casting of various polymers such as polystyrene, sulfone polymers such as polysulfone and polyether sulfone, polyurethane elastomers, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, and vinyl chloride-acetate copolymer. Formed by extrusion process such as coating on base material, etc .; Formed into sheet form of iron, copper, stainless steel, etc .; Extruded ceramics composed of various minerals such as clay, silica, feldspar Examples thereof include those molded into a sheet by plastic molding such as molding, dry pressure molding, and heat molding, and casting such as cast molding and melt casting.

Further, the above-mentioned various sheets may be coated or laminated with each other, or extruded together with other materials.

The thickness of the sheet depends on its mechanical strength and ease of handling.
It is preferably at least 0.25 mm, but is not particularly limited.

The surface shape of the sheet may be smooth or porous.

Further, the sheet may be subjected to secondary processing into a wire mesh, honeycomb, accordion, or more complicated shape before supporting the photoreactive semiconductor.

The latex used in the present invention has a minimum film forming temperature of 60.
It is necessary to be less than or equal to ° C. When a latex having a minimum film forming temperature exceeding 60 ° C. is used, adhesion between the photoreactive semiconductor and the sheet becomes insufficient, and the photoreactive semiconductor gradually peels off from the photoreactive semiconductor supporting sheet.

The latex used in the present invention may be either a natural rubber latex or a synthetic latex as long as it satisfies the above requirements, and there is no limitation on the synthesis method and the monomer composition constituting the latex. Specific examples of monomers that can be used in the synthesis of the latex used in the present invention, ethylene,
Olefins such as propylene and 2-methylpropene; conjugated diolefins such as butadiene, isoprene and 1,3-butadiene; aromatic vinyl compounds such as styrene, α-methylstyrene, monochlorostyrene, vinyltoluene and vinylpyridine; (Meth) methyl acrylate, (meth)
(Meth) acrylates such as ethyl acrylate and butyl (meth) acrylate; α, β-unsaturated nitrile compounds such as (meth) acrylonitrile; vinylidene halides such as vinyl chloride and vinylidene chloride; vinyl acetate; Carboxylic acid vinyl esters; vinyl isocyanate,
Urethane compounds such as vinyl urethane; and the like. The functional monomers include (meth) acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, monoethyl itaconate, monobutyl fumarate, monobutyl maleate, and sulfoacrylate. Acid group-containing monomers such as ethyl sodium, sodium sulfopropyl methacrylate, acrylamidopropanesulfonic acid, sodium acrylamidopropanesulfonate or salts thereof; hydroxyl-containing monomers such as β-hydroxyethyl acrylate; (meth) acrylamide; Amide group-containing monomers such as N-methylol acrylamide and diacetone acrylamide; epoxy group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; formyl group-containing monomers such as acrolein;
Allyl group-containing monomers such as allyl alcohol, diallyl phthalate, triallyl cyanurate and allyl acrylate;
Crosslinkable monomers such as divinylbenzene and ethylene glycol dimethacrylate can also be copolymerized.

In the present invention, a binder pigment latex or an amphoteric latex is suitably used as the latex.

The binder pigment latex is a latex composed of polymer particles having both a function as an organic pigment (improved optical properties) and a function as a binder.
As the structure of the binder / pigment / latex, there is known a two-layer structure having a core of polystyrene and a shell of a styrene / butadiene copolymer (Paper and Pulp Technical Association, Vol. 43, No. 2, No. 159-166, 1989), and the method for producing binder, pigment, and latex is described in
26692, JP-B-62-31115, JP-A-54-131013, JP-A-55
-45724, JP-A-63-303195, etc., but the binder, pigment and latex referred to in the present invention are not limited by the production method and particle structure.

The amphoteric latex refers to a latex in which the polymer particles of the latex have both a negative charge due to an anionic functional group and a positive charge due to a cationic functional group. Examples of a method for imparting both charges include a method using an anionic surfactant and a cationic surfactant in combination as an emulsifier for a latex, a method using an amphoteric surfactant in combination with these, or a method for providing a negative charge in a copolymer. There is a method of copolymerizing an unsaturated carboxylic acid or the like with an unsaturated amine imparting a positive charge, but the method is not limited thereto. As an example of the method for producing the amphoteric latex, the method disclosed in JP-B-61-39334 can be shown.

Specific examples of the anionic functional group-containing monomer that can be used for the synthesis of the amphoteric latex include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, and maleic acid; monoethyl itaconate, Monoalkyl esters of unsaturated dicarboxylic acids such as monobutyl fumarate and monobutyl maleate; unsaturated sulfonic acids such as sodium sulfoethyl acrylate and sodium sulfopropyl methacrylate; and alkali salts thereof can be given. On the other hand, as the cationic functional group-containing monomer, aminoalkyl esters of ethylenically unsaturated carboxylic acids such as methylaminoethyl (meth) acrylate, tert-butylaminoethyl (meth) acrylate, and dimethylaminoethyl (meth) acrylate An aminoalkylamide of an ethylenically unsaturated carboxylic acid such as methylaminoethyl (meth) acrylamide and dimethylaminoethyl (meth) acrylamide; an aminoalkylvinyl ether such as aminoethyl vinyl ether and methylaminoethyl vinyl ether; 2-vinylpyridine, 2-vinylpyridine Examples thereof include ethylenically unsaturated amine monomers such as vinylpyridines such as methyl-5-vinylpyridine and 2,4-diethyl-5-vinyllysine.

Furthermore, as long as the effects of the present invention are not impaired, water-soluble polymers such as starch, casein, and polyvinyl alcohol may be used in combination with the latex.

In the present invention, less than 20 parts by weight and more than 1 part by weight of latex in terms of solid content are used for 100 parts by weight of the photoreactive semiconductor having a band gap of 0.5 to 5 eV. If the weight of the latex in terms of solid content is 20 parts by weight or more, the binder covers the surface of the photoreactive semiconductor particles which are active sites of the photooxidation reaction. On the other hand, when the amount is 1 part by weight, the semiconductor is easily separated from the sheet.

In preparing the photoreactive composition, if necessary, a dispersant, a water retention agent, an antifoaming agent, and the like may be added. Further, noble metals such as platinum, palladium, silver, and copper can be mixed at this stage.

The photoreactive semiconductor supporting sheet of the present invention can be obtained by supporting a photoreactive composition obtained by adding and mixing a photoreactive semiconductor to latex on a sheet and, if necessary, heating and drying. The method of loading is not particularly limited, but a method of applying the photoreactive composition to the sheet using various coaters such as an air knife coater, a blade coater, a roll coater, a rubber doctor coater, a curtain coater, a spraying method, A method of immersing the sheet in the photoreactive composition can be exemplified. The heating and drying conditions are not particularly limited as long as volatile components can be substantially removed from the photoreactive composition.

The photoreactive semiconductor supporting sheet of the present invention can be processed into a filter structure, which is suitable for the purpose of the present invention because of its high photoreaction efficiency. Examples of the production of the filter structure include a flat membrane, a honeycomb, a wire mesh, an accordion, and a urethane foam.

〔The invention's effect〕

By using the sheet supporting the photoreactive semiconductor of the present invention, various harmful substances such as sulfur oxides, nitrogen oxides, hydrocarbon compounds, and halogen compounds can be removed quickly and efficiently at the same time. The reaction activity of the photoreactive semiconductor does not decrease.

The method of the present invention is extremely useful commercially because it is highly safe, has a wide range of applicable harmful substances, and is easy to systematize.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
In the examples, parts and percentages are by weight unless otherwise specified. "Semiconductor / latex" in the table means
The ratio of the weight of the photoreactive semiconductor to the weight of the latex in terms of solid content is shown.

Production Example 1 A photoreactive composition for preparing a sample piece used in Examples 1 to 6 was produced according to the following formulation.

Treatment Photoreactive semiconductor 100 parts Demol EP (20% aqueous solution, manufactured by Kao Corporation) 0.25〃 NaOH (10%) 0.15〃 Latex (solid content conversion) 10〃 Water 335〃 The latex used is shown in Table 1. Was. The photoreactive semiconductors used are commercially available titanium dioxide, tungsten trioxide, zinc oxide and cerium oxide.

Production Example 2 A photoreactive composition for a control example in Example 4 was produced according to the following formulation.

Treatment 1 Titanium dioxide 100 parts Urethane adhesive (Asahi Denka) 10〃 n-hexane 100〃 Treatment 2 Titanium dioxide 100 parts polyvinyl alcohol (PVA) (Nippon Synthetic Chemical Company) 10〃 n-hexane 100〃 Example 1 A photoreactive composition prepared according to Production Example 1 using latex Nos. 3 to 5 was coated on a coated base paper using an applicator bar so that the coating amount was 10 g / m ^2. , Immediately after coating
It was dried with hot air of 110 ° C. for 30 seconds. 1.5 cm of the obtained coated paper
2 pieces of sample (0.25g in weight) cut into 5cm
The mixture was placed in an Erlenmeyer flask made of Pyrex and replaced with air containing the initial concentration of ethylene shown in Table 2 and then sealed with a rubber stopper made of silicon rubber. Then 20cm from Erlenmeyer flask
A super-high pressure mercury lamp (illuminance: 10 mW / cm ² , main wavelength: 365 nm) installed at a distance of was turned on, and changes over time in the ethylene concentration in the container were tracked by gas chromatography (Experiment No. 1A ~
1D, 2A-2D).

For comparison, a similar test was performed on a system in which no sample piece was charged (Experiment Nos. 1E and 2E). Second result
It is shown in the table.

For the latex No. 5, the removal of ethylene was not measured because the photoreactive composition was severely peeled off.

From the results shown in Table 2, it can be seen that when a sheet supporting the photoreactive semiconductor of the present invention was used, ethylene could be rapidly removed under ultraviolet irradiation.

Example 2 Using Latex No. 3, the evaluation of removal performance of various harmful substances shown in Table 3 was performed in the same manner as in Example 2.

 The results are shown in Table 3.

From the results in Table 3, it can be seen that various harmful substances can be rapidly removed under ultraviolet irradiation by using the sheet supporting the photoreactive semiconductor of the present invention.

Example 3 A photoreactive composition prepared according to Production Example 1 using latex No. 3 was applied onto a nonwoven fabric and a porous urethane sheet using an applicator bar so that the loading amount was 100 g / m ^2. Immediately after coating, drying was performed with hot air at 110 ° C. for 30 seconds.

A sample piece obtained by cutting this sheet into 1.5 cm x 5 cm (weight
Table 4 shows the results obtained by performing the same ethylene removal experiment as in Example 1 using 1g).

From the results in Table 4, it can be seen that ethylene can be rapidly removed even when a nonwoven fabric or a porous urethane sheet is used as the sheet for supporting the photoreactive semiconductor.

Example 4 Example 3 using latex No. 3 and titanium dioxide
Non-woven fabric prepared in the same manner as described above, Formulation 1 shown in Production Example 2
Nonwoven fabric prepared by immersing the web in the photoreactive composition prepared according to (2) and (2) drying the sheet using PVA with hot air of 110 ° C for 2 hours, and the sheet using urethane adhesive at 60 ° C. A vacuum drying was performed for 24 hours.), And the same ethylene removal experiment as in Example 3 was performed. The weight of each nonwoven fabric sample was 1 g.

 The results are shown in Table 5.

From the results shown in Table 5, it can be seen that, when a urethane-based pressure-sensitive adhesive or PVA is used, the ethylene removal efficiency is significantly inferior to the case where the latex specified in the present invention is used as the binder.

Example 5 In the same manner as in Example 3 except that titanium dioxide was used as the photoreactive semiconductor and No. 3 was used as the latex, and the weight ratio of photoreactive semiconductor / latex (in terms of solid content) was changed to 10, 5, and 1, With respect to the obtained photoreactive semiconductor-carrying nonwoven fabric (weight 1 g), the removal performance of ethylene and methyl mercaptan was measured in the same manner as in Example 3, and the results are shown in Table 6.

From the results in Table 6, it can be seen that when the weight ratio of photoreactive semiconductor / latex (in terms of solid content) is 1 or less, the performance of removing harmful substances is poor.

Example 6 A paper on which a photoreactive semiconductor was supported by latex Nos. 1 to 3 and 5 having different minimum film forming temperatures (photoreactive semiconductor / latex weight in terms of solid content = 10) was cut into 1.5 cm × 5 cm. A cellophane tape was adhered to each sample piece (weight 0.2 g), and the amount of the photoreactive semiconductor adhered to the cellophane tape when the cellophane tape was peeled off was compared.
As shown in the table, the peeling of the photoreactive semiconductor was remarkable in the sheet using No. 5 having the minimum film forming temperature of 60 ° C. or higher.

Example 7 A titanium dioxide-supported nonwoven fabric prepared in the same manner as in Example 3 was cut into a circular shape having a diameter of approximately 5 cm so that the nonwoven fabric weight was 0.5 g and the titanium dioxide weight was 0.1 g. A filter was formed by fixing the two funnels with a spring so as to be sandwiched between upper ends.
Next, the filter was irradiated with an ultrahigh pressure mercury lamp (same as that used in Example 1) from a distance of 20 cm. In this state, the air containing the harmful component at the initial concentration shown in Table 8 was injected from the leg of one filter with a syringe, and the concentration of the harmful component in the air coming out of the leg of the other filter was measured by gas chromatography. Table 8 shows the results of the measurements by lithography.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-80833 (JP, A) JP-A-62-53657 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) A61L 9/00-9/22

Claims (2)

(57) [Claims] 1. A sheet carrying a photoreactive semiconductor having a band gap of 0.5 to 5 eV on a surface thereof, wherein the semiconductor is carried using a latex having a minimum film formation temperature of 60 ° C. or less. A photoreactive semiconductor supporting sheet. 2. A photoreactive composition comprising 100 parts by weight of a photoreactive semiconductor having a band gap of 0.5 to 5 eV and a latex of more than 1 part by weight and less than 20 parts by weight in terms of solid content is coated on a sheet surface. 3. The method for producing a photoreactive semiconductor supporting sheet according to claim 1, wherein the supporting sheet is supported on a sheet.