JP6484771B2 - Substrate-silica sol dry matter composite and method for producing the same - Google Patents

Description

  The present invention relates to a substrate-silica sol dry matter composite that retains an OH radical precursor even in the absence of light and has the function of decomposing harmful substances in the air. The present invention also relates to an applied article of the above-mentioned substrate-silica sol dry matter composite and a method for producing the same. In addition, OH radical precursor points out having a function which produces | generates OH radical, when it contacts with water. In the case of semiconductors, positive charges generated in the dried silica of the present invention generate OH radicals upon contact with water as well as holes generated in the valence band generate OH radicals upon contact with water. Since the holes present in the insulator have no name, they were referred to as OH radical precursors.

Hazardous gases contained in the atmosphere, for example, ammonia which is mentioned as a causative agent of malodor, VOC (volatile organic compound) which causes sick house syndrome such as toluene and formaldehyde, ethylene which is a plant hormone which promotes aging and aging of pollen and fruits and vegetables There is a need for means of actively removing the air and purifying the atmosphere.

  Many proposals have been made as means for removing these harmful gases. However, what has been put to practical use is a means of adsorbing and removing harmful gases mainly using activated carbon.

On the other hand, for example, Patent Document 1 proposes that the harmful gas should be removed by utilizing the photocatalytic activity of titanium oxide which does not need to be discarded or replaced.
Patent Document 2 proposes that a titanium oxide powder is spray-coated on an artificial flower and dried at 200 ° C. or less. Patent Document 3 proposes a fruit and vegetable freshness holding device provided with a photocatalyst and an ultraviolet lamp on the surface of activated carbon for the purpose of preventing ripening and aging of fruits and vegetables during storage and transportation.

While these methods require high energy irradiation of ultraviolet light, Patent Document 4 proposes a method for producing a photocatalyst that generates superoxide anion with visible light of wavelength 470 nm.
Patent Document 5 shows a substrate-silica sol dry matter composite characterized in that holes are held even in a state where there is no light irradiation, and only after coating and drying silica sol on a substrate, It has been shown that influenza virus is inactivated even in the absence of light.

  Further, in Patent Document 6, a base material-silica sol dry matter complex obtained by applying a silica sol having a content of NaOH to 1 mol of silica limited to a ratio of less than 1.9 mmol on a base material and drying is immersed in an aqueous solution of coumarin A fluorescence at a wavelength of 460 nm, which is known to show the formation of 7OH coumarin indicating the presence of a radical, has been observed, and has been shown to exhibit the effect of inactivating harmful viruses in the air under no light.

Unexamined-Japanese-Patent No. 2-280818 JP, 2006-37305, A Unexamined-Japanese-Patent No. 5-103588 JP 2005-272259 A JP, 2016-68543, A JP, 2017-172068, A G. Louit et al .: The reaction of coumarin with the OH radically revisited: hydroxylation product analysis determined by fluorescence and chromatography Radiation Physics and Chemistry 72 (2005) 119-124) Zhang Jie, Nosaka Yoshio OH radical formation of H2O2 and visible light responsive photocatalyst suspension 2011.12.12 Optical functional materials research meeting Kasuya Kazutoshi Determination of coumarins in wastes associated with illegal gas oil production BUNSEKIKAGAKU vol. 59, No. 5.2010, 405-409 Ralph K. Iler, THECHEMISTRY OF SILICA Solubility, Polymerization, Colloid and Surface Properties, and Biochemistry JOHN & WILEYS 1978, p116 Satoshi Horikiri High-performance liquid chromatography and mass spectrometric analysis of methylene blue's porous photocatalytic decomposition and decomposition products BUNSEKIKAGAKU vol. 52 No. 10, pp 881-885 (2003)

Activated carbon is eliminated and replaced when its adsorption is saturated and loses its function. For example, there is a problem that it can be effectively implemented only in a relatively narrow space such as deodorizing in a refrigerator or deodorizing a toilet bowl in a toilet . Patent Document 1 and Patent Document 2 propose that TiO ₂ which does not need to be discarded or replaced function as a photocatalyst. However, to make titanium oxide function as a photocatalyst at night or indoors, it is necessary to prepare a separate ultraviolet light source, and fluorescent lamps containing ultraviolet light have been used as indoor light sources, but the life is longer In addition, since it has been replaced by LEDs with lower power consumption, an air purification catalyst that functions with visible light is desired.

Freshness preservation method of vegetables and fruits that have been proposed in Patent Document 3 installed undesirable conflicting function object that installing a light source that generates heat to be within the container refrigerated as the basic storage. Although the superoxide anion generated from the visible light photocatalyst proposed in Patent Document 4 is active oxygen, it does not contain the OH radical which is said to be the most active. Although much effort has been devoted to develop high-performance visible light photocatalysts including this modification, even visible light requires illumination and it works even at night after extinguishing, ie under no light The demand for air purification catalysts is increasing.

  Although the means described in Patent Document 5 mentions the possibility of decomposition, detoxification and purification of harmful substances in the air under no light as its effect, it mentions a specific composition range and a deodorizing effect. Not. Among the fibers, the production amount is overwhelmingly large, and utilization as a silica sol dry matter composite based on polyester fibers is also excellent in terms of wrinkling, quick drying, strength, dimensional stability, etc. It is requested.

  The means described in Patent Document 6 is a composite obtained by applying and drying a silica sol that brings OH radicals when the content of NaOH is 1.9 mmol or less with respect to 1 mol of silica, when the compound is dipped in an aqueous solution of coumarin and OH radicals Although the fluorescence of the wavelength of 7OH coumarin which proves the presence of is observed to inactivate the virus under no light, the influence of NaOH on the deodorizing function is not clear. An object of the present invention is to provide a substrate-silica sol dry matter composite which holds an OH radical precursor equivalent to a valence band hole capable of generating an OH radical without requiring light irradiation as a means for purifying air. It is in.

In the present invention, when the alkali content of the silica sol applied to the substrate is adjusted to a specific range in the substrate-silica sol dried product complex, particularly, the substrate-silica sol dried material composite is not present. Elucidating the effect of NaOH on the formation of OH radical precursor identified by the coumarin test described later even under light, and decomposing harmful organic substances such as VOC that cause sick odor and sick house syndrome in the atmosphere Obtained quantitative knowledge with the content of a water-soluble alkali metal salt exhibiting an action and the like, and completed the present invention.

  That is, according to the present invention, light irradiation is carried out by applying and drying a silica sol having a water-soluble alkali metal selected from 2.5 to 7.1 mmol of Na, K, or Li with respect to 1 mol of silica. The present invention is to provide an inexpensive substrate-silica sol dry matter composite which efficiently retains an OH radical precursor even in the absence of light without the need for

  The OH radical precursor which brings about the decomposition, detoxification and purification of harmful substances in the air is equivalent to the holes. This is due to the fluorescence spectroscopy that occurs when OH radicals coexist with NaOH in coumarin liquid Newly found that it generates a spectrum with the same wavelength as that of cinnamic acid, which is observed when only C is present, but its peak light intensity is less than about one-tenth, indicating the presence of OH radical in the presence of NaOH. I clarified that I would get it.

That is, the present invention is a composite comprising a substrate and a dried silica sol, which comprises the silica 1 on the substrate.
Silica sol containing 2.5 to 7.1 millimoles of one or more water-soluble alkali metal salts selected from Na, K and Li per mole in terms of alkali metal hydroxides Provided is a substrate-silica sol dried composite excellent in air purification function characterized by being dried after application. Also, this complex does not degrade the solid organic substrate.

A base material-silica sol dry matter composite characterized by retaining OH radical precursor even in absence of light, wherein the coating amount of silica sol to the base material is the mass per unit surface area of the base material in the dry state. It adjusts to the range of 1 mg-1.5 g per (g / m < ² >). When the base material-silica sol dry matter complex according to the present invention is immersed in a coumarin aqueous solution with a molar concentration of 0.1 to 0.2 mM, it emits fluorescence having a peak of 500 to 510 nm when excited by light of 330 to 370 nm It can be proved that this complex possesses an OH radical precursor.

The base material-silica sol dry matter complex according to the present invention generates OH radicals when in contact with water even in the absence of light, and decomposes VOC and malodor in the atmosphere. The silica sol of the present invention is applied and dried on the inner surface of a storage container without the need to install a TiO ₂ and an ultraviolet light source for irradiation because ethylene decomposes to bring about ripening and aging of fruits and vegetables during storage and transportation of fruits and vegetables. Just do it. In addition, if the spray is applied to the inner wall, ceiling, curtain, artificial flower, and artificial foliage plant of the building, the silica sol dry matter complex is formed by natural drying, and the air purification is continued even at night.

  As the substrate of the present invention, natural fibers, regenerated fibers, woven or non-woven fabrics of chemical fibers, single materials selected from wood, paper, wallpaper, or composites thereof can be used, and the above non-woven substrates are used as air filters It is more preferable that meshing is performed from the viewpoint of air permeability in the case where the pressure loss is small.

  The base material-silica sol dry matter composite according to the present invention is a filter for shoji paper, deodorizer, air purifier, air conditioner, in addition to partitions, clothes, white coats / hats of doctors / nurses, hygiene masks and deodorant masks. Can be incorporated into the exhalation passage of the

The base material-silica sol dry matter complex of the present invention retains OH radical precursors equivalent to holes even in the absence of light, and decomposes harmful gases such as VOC and malodor, but additionally paper, natural fiber, regenerated fiber The reason for having the ground-breaking feature of not decomposing a solid organic substance base consisting of woven and non-woven fabrics of chemical fibers is presumed as follows.
First, in the solution of silica sol, when the silica particles collide with each other in water, they are negatively charged so that the silica particles repel each other in order to prevent them from bonding, coarsening and settling, and how to be negative According to Non-Patent Document 4, it is proposed that the silica particles in the silica sol liquid have a form such as (OH) ₂ SiO ^{2 2-} as a mechanism for determining whether or not they are charged.

  If the silica sol is directly dried, OH groups of the silica particles bond to each other to obtain a dried silica in which the charge is lost. However, if it is dried on the substrate, the bonding of the OH groups is prevented, and the chemical formula remains negative even after drying. The charge should be maintained to generate a positive charge equal to the negative charge. Since the behavior of the spectrum that would not be generated if the substrate-silica sol dry matter complex was immersed in the coumarin solution was observed without the presence of OH radicals, this base material-silica sol dry matter complex provides OH radicals Since this has been proved, this positive charge is called an OH radical precursor equivalent to the valence electron hole of the semiconductor.

If such (OH) group-containing << (OH) ₂ SiO ₂ ^2- >> is a source of OH radical precursor, OH of negatively charged OH even if the OH radical precursor is once lost by deelectron reaction such as deodorization As long as a group is present, the corresponding positively charged OH radical precursor regenerates many times. However, the OH radical precursor is lost during the time of being wet in contact with water, but it regenerates when it is dry.
The photocatalyst TiO ₂ is a semiconductor, and it is considered that the holes generated in the trace where the electrons in the charge band are excited and moved by the irradiation of the ultraviolet light are deprived of the electrons from the organic base material to be decomposed. On the other hand, since this positively charged OH radical precursor is attached to silica, which is an insulator, and can not move itself, if it is a fluid such as a gas or a liquid, it will collide and it will deprive the electrons and decompose it, That is, gases such as malodor are not in microscopic contact with positively charged OH radical precursors equivalent to the holes generated in the dried silica sol applied to a solid organic substance, although they decompose. It is thought that it does not disassemble.

FIG. 1 is the spectrum of the fluorescence spectroscopy test of sample 1. FIG. 2 is the spectrum of the fluorescence spectroscopy test of sample 2. FIG. 3 is the spectrum of the fluorescence spectroscopy test of sample 3. FIG. 4 is the spectrum of the fluorescence spectroscopy test of sample 8.

A complex comprising a substrate and a dried silica sol, comprising one or more water-soluble alkali metal salts selected from Na, K and Li per mole of silica on the substrate and an alkali metal water When a silica sol containing 2.5 to 7.1 millimoles in terms of oxides is coated and then dried, a substrate-silica sol dry matter composite having excellent air purification function is formed.
Besides natural fibers, regenerated fibers or synthetic fibers and their woven or non-woven fabrics, wood and paper can also be used as the substrate. Natural fibers of the substrate are cotton, silk and hemp, regenerated fibers are rayon and lyocell, and synthetic fibers are preferably polyester and nylon. If a silica sol containing an OH radical precursor that exerts an air purification function is applied to these substrates, the drying temperature can be an atmosphere from normal temperature to 230 ° C. Curtains, wall materials, flooring materials, ceiling materials, Shoji paper, It can be dried by spray application to artificial flowers and artificial foliage plants and left as it is.

The silica sol to be applied is 2.5 to 7.1 millimoles of one or more water-soluble alkali metal salts selected from Na, K and Li in terms of alkali metal hydroxide per mole of silica. Is preferable, and the ratio of 4.3 to 7.1 mmol is particularly preferable.

The silica sol preferably has a particle size of 4 nm to 0.7 μm of silica particles in the silica sol. Specifically, a sol of spherical silica particles having a normal particle diameter of 4 to 25 nm or a sol of silica particles having a particle diameter of 0.3 to 0.7 μm of porous spherical particles having mesopores of 2 to 50 nm in diameter , Can be used. The adhesion to the substrate depends mainly on the particle size, and the smaller one is excellent, but if it is 0.7 μm or less, practically sufficient adhesion can be obtained. Within this range, sufficient adhesion can be obtained without peeling of the silica particles from the substrate during handling of the substrate-silica sol dry product complex. In addition, the particle size of the said silica particle means the particle size measured by BET method (nitrogen adsorption method) and the Sears method.
Usually, the BET method is used to measure the particle size of the silica sol. In this method, a dry powder is prepared, nitrogen is adsorbed on the surface of the dry powder, and the surface area is measured from the amount of adsorption, and the particle diameter is calculated on the basis of the spherical shape on the basis of calculation.

In the present invention, the adhesion amount of silica sol to the substrate varies depending on the application, and in the case of an air filter for the purpose of purifying the air to be passed, it is dry and 0.3 per unit surface area of the substrate.
~1.5g / ^{m 2,} wall, ceiling, artificial flowers, 0.1~0.8g / ^{m 2} in the case of applications that do not touch the people as such as a partition, clothing, in the case of applications that touch the person, such as curtain 0.001 ~ 0.3 g / m ² is a standard.

The concentration of silica sol is selected to be 0.001 to 20% by mass because it is necessary and easy to select depending on the thickness and mass of the substrate in order to achieve the above-mentioned adhesion amount, and drying is required for productivity Depending on temperature, room temperature to 230 ° C., preferably 10 to 200 ° C. may be selected. That increases the cleaning rate of the air passing through as the air filter, and as large as 3-20% of the concentration of the silica sol in the case of increasing the productivity may be selected to a high temperature atmosphere more than 100 ° C., interior conversely The low concentration of 0.03 to 1% may be selected for applications such as building materials and curtains where application area is wide and purification time is long and feeling is not felt by touch.

In order to evaluate the catalytic performance of decomposing harmful substances in the air, the concentration may be measured directly using a detector tube or a gas chromatograph, but as a simple method, methylene blue dye (chemical formula C ₁₆ H ₁₈ N ₃ S · · A method of evaluating the decomposing ability of a photocatalyst product using Cl, abbreviation: MB) is established as JIS R 1703-2. However, as it is stipulated that it does not apply to water-permeable substrates that can penetrate water, we have developed the MB color resistance test method to evaluate various materials including substrates for textiles as in the present invention. .

According to reference 5 in which the ground of the fading of methylene blue is described, TiO ₂ immersed in methylene blue solution is irradiated with black light of wavelength 369 nm for 1 to 4 hours, and methylene blue is generated after 0 h, 2 h, 4 h When the derivatives Azul A and B are determined by liquid chromatography, the methylene blue molecule has N (CH ₃ ) at two locations, but Azole A at one location is NHCH ₃ and Azole B at NH ₂ And the CH ₃ group are lost, that is, the N-CH ₃ bond is broken. It is believed that the holes generated from the photocatalyst generate OH radicals and thereby this bond is broken, and that the base material-silica sol dry matter complex has the same function as the holes when it fades under no light. It shows that it possesses the OH radical precursor.
The spin trap method used to detect OH radicals is difficult to use because ESR equipment and coumarin fluorescence spectrophotometers are both difficult to use because of the small number of units present, while the spectrophotometer used to measure the concentration of methylene blue has many studies In the present invention, the catalyst activity was evaluated mainly by methylene blue color fading.
The specific test method prepares MB solution with high concentration of 1.0.1 mM to 3 mM. (Hereinafter, “mM” represents millimoles / liter.)
Place a 2.3 x 3 cm sample into a 50 mm シ ャ ー petri dish and determine the amount of water that will stain the entire surface of the sample.
3. Next, select the MB solution at a concentration at which the sample to be measured changes its color appropriately, and drop it on the actual sample.
4. The film was covered with a pp film and peeled off after 2 minutes, 2 mL of purified water was added dropwise to shake the petri dish, the washing solution was stored in a microtube, the color was compared with the naked eye, and the concentration at a wavelength of 664 nm was measured with a spectrophotometer (SP-1 manufactured by As One Corporation) Measure at 300).

In order to investigate the influence of the alkali concentration in the silica sol on the catalytic activity, the deodorizing performance of the sheet coated with the silica sol to which the alkali concentration was changed by adding a concentrated alkali solution was evaluated.
Base material: 40 mass% (The following% are all mass%) Polyester blended cotton non-woven fabric mesh processing Escott 40 (trade name) Unitika Co., Ltd. product basis 40 g / m ² (A mass is the number of mass g per 1 m ² ) 10 × 15 cm
Silica sol: A Particle size: 4 to 6 nm (SiO ₂ : 20.5% 3.42 M NaOH: 0.58
_{% = 14.5mM, NaOH / SiO 2} : 4.2 / M) concentration 10% (NaOH: 4.68 mM) dilution (NaOH / SiO ₂ of mM / M ratio: 2.81), 1 to the 10mL 0.01 mL of .9 M lithium silicate (Nissan Chemical Industries, Ltd. Li ₂ O: SiO ₂ molar ratio 3.50, Li ₂ O = 2.89%), 0.25 M NaOH, 0.20 M 0.02 mL each of an aqueous solution of KOH was added, and 3 ml of them was applied to a 10 × 15 cm substrate, and dried at 90 ° C. for 10 minutes in a forced convection constant temperature drying oven OF-450B (manufactured by As One Co., Ltd.).
Deodorizing property: 10x15cm base material is folded into two 10x7.5cm sheets and sandwiched between a commercially available pleated mask (made by Amway with nose pad) to smell the smell of 1% ammonia water, 2 sheets The smells of the samples were relatively compared and evaluated. The test is for sample no. 1 to 4 and 5 to 8, 9 to 11 were separately prepared, and the deodorizing test was collectively performed and the results are shown in Table 1.
In addition, since all the silicas of lithium silicate were melt | dissolved, it did not calculate to an alkali / silica ratio.

*: Converted from the lithium silicate Li2O content of 2.89%

Regardless of the type of alkali, when two or three types are mixed and added, the deodorizing performance reaches its maximum value at an alkali / silica ratio of 5.06, and the deodorizing performance does not improve even if Na or K is further added. Sample No. When an alkali is added to 13 or more, gelation (solidification) occurs in a short time, and thus the alkali concentration in the silica sol of 10% silica is limited.

As a method of evaluating the catalytic activity of the OH radical precursor generated when a high concentration of alkali is present, the relationship between the deodorizing performance and the fading of the methylene blue aqueous solution was investigated. : Four kinds of silica sols E, B, M, A, M having different NaOH concentrations were adjusted to a silica concentration of 8%, and 2 mL of the sol was coated with 100 cm ² and dried at 90 ° C. for 10 minutes. The deodorizing test method was the same as in Example 1.

  Methylene blue fading test: Three samples of 3 × 3 cm were prepared for each condition. The sample was placed in a 50 mm シ ャ ー petri dish, measured with 0.25 mL of a 3 mM aqueous MB solution, and an average value of 3 sheets was adopted. The results of these tests are shown in Table 2.

  It can be seen that the higher the NaOH concentration of the silica sol, the greater the decrease in the concentration of MB, and the higher the decomposing ability. Since the rank of deodorizing performance is also in line with the rank of the fading performance of the MB dye, it was recognized that the MB fading performance can be an index of the deodorizing performance, that is, the catalyst activity of the OH radical precursor.

We examined how much deodorization can be expected with the amount of silica sol adhesion that is not felt even by human touch such as clothing. In preliminary tests, in the case of polyester fabric with a basis weight of 140 g / m ² , for a sample of 3 × 3 cm, the silica sol concentration is 0.3% at 0.12 mL, 0.4 g / m ² is the limit and feels more than this I understood it.
According to Example 1, in the case of silica sol having a high silica concentration of 10%, the deodorizing performance is maximized when the alkali metal hydroxide is added from 4.2 mM to 5.1 mM with respect to the molar concentration of SiO ₂ Although it is known to reach, improvement in deodorizing performance by addition of alkali is observed even in the case of the low concentration of 0.3% which is the limit of the hand feeling as described above, or conversely, the same deodorizing performance is lower than silica adhesion The methylene blue fading test was performed to see if it can be achieved.
Silica sol type M: particle size 4 to 6 nm NaOH / SiO ₂ mM / M ratio 5.2
A: Particle size 4 to 6 nm NaOH / SiO ₂ mM / M ratio 4.2
0.003 g / 120 g / m ^{2 in} the case of 0.12 mL / 3 x 3 cm 0.3% of liquid coating amount
NaOH was added by adding 0.02 mL of 10% = 2.5 M aqueous NaOH solution to 10 mL of 0.31% silica sol solution, and the mM / M ratio of NaOH / SiO _{2 changed} from 5.17 to 6.11
. The addition of 04 mL increases to 7.05 each and drying 70 ° C x 20 min
MB test concentration 0.3mM solution volume 0.3mL
The methylene blue test results are shown in Table 3.

The addition effect of 0.02 mL of 10% NaOH slightly improves the MB color fading to 2.5% in the case of silica sol M, while it significantly improves to 37% in the case of silica sol A, whereas the addition of 0.04 mL It is found that the MB fadeability is significantly degraded or the improvement rate is lowered. Similar to Example 1 with a high concentration of 10%, it was demonstrated that the optimum alkali concentration was present in the activity. In particular, the optimum value of 5.01 in the case of silica sol A agrees with the optimum value of 5.06 in the silica sol solution with a high concentration of 10% silica.
According to the experimental results, the upper limit of the mM / M concentration of the alkali metal hydroxide containing NaOH in the silica sol is 6.10 when the silica concentration is 10%, but the gelation limit is 6.90, but the gelation occurs when the concentration is low. The upper limit is 7.05, that is 7.1.

The influence of the ambient temperature on the catalyst activity when applying a silica sol to a substrate and drying was evaluated by examining the fading of methylene blue.
As the substrate 40% polyester blend cotton, using polyester woven fabric having a mass per unit area of 40 g / m ² of non-woven fabric and basis weight 140 g / m ^2, the silica sol and silica sol M of NaOH / SiO ₂ mM / M ratio of 5.2 1.0 It adjusted to%, applied 0.2 mL / application to base material 3x3 cm, mounted on a stainless steel wire mesh, and inserted into a drier adjusted to predetermined temperature, and dried.
The MB test was performed by dropping 0.25 mL of 1 mM MB solution onto a 3 × 3 cm sample. The results are shown in Table 4.

Methylene blue test results

There is also an influence of the residence time, but at 70 ° C. or higher, no influence of the drying temperature on the MB fading is observed. The silica sol used in the example of Patent Document 3 has a Na / SiO ₂ mM / M ratio of 1.4 or less, which is considerably lower than 5.2 of the present invention, in which case the drying temperature is preferably 150 ° C. It was revealed that the heat resistance is greatly improved by the inclusion of a trace amount of NaOH as compared with that of 50 ° C. or less, and the catalyst activity is maintained up to 230 ° C. where the polyester fiber decomposes.

The effect of the alkali content in the silica sol applied to a polyester non-woven fabric as a substrate on the catalyst activity was examined by methylene blue fading.
Base material: 100% polyester (spunbond nonwoven fabric) 70450 WTO (trademark)
Weight: 45 g / m ² manufactured by Unitika Co., Ltd.
Silica sol: 5 types of H, D, B, A, M 10% silica
Coating amount: 0.1 mL / base 3 x 3 cm
Drying conditions: 70 ° C. × 10 minutes MB test: Measurement was performed in the same manner as in Example 2 except that 0.2 ml of 3 mM MB solution was used. The results are shown in Table 5

The silica sols H and D of the comparative example in which the Na / SiO ₂ mM / M ratio of the silica sol is lower than 2.5 have high MB concentrations, whereas the Na / SiO ₂ mM / M ratio is higher than 2.5 in the inventive example B, A, and M were found to be excellent in methylene blue color fading, that is, having high catalytic activity, although the particle size was also affected.

In order to evaluate catalytic activity such as deodorizing property when treated with silica sol of different alkali concentration using silk, paper, rayon, lyocell, and wood board as a substrate, methylene blue color fading was examined. Each sample was cut into 3 × 3 cm, 0.1 mL of silica sol with 8% silica concentration, 0.3 mL of rayon, and 0.2 mL of lyocell were coated on a substrate and dried at 70 ° C. for 10 minutes to obtain a sample.
The paper was a sample of natural wood pulp, dry air-laid non-woven fabric KS40 (trade name) manufactured by Oji Kinocross Co., Ltd. and 5% rayon 95% pulp shoji paper. The rayon non-woven fabric used a sample obtained from Naniwa Silk Cotton Co., Ltd. The wood board was processed to a board of about 0.05 mm on a front surface of a 5.4 mm thick plywood.
The test was conducted in the same manner as in Example 2 except that depending on the basis weight of the substrate, 0.2 to 0.5 ml of 1 mM MB solution and 0.1 ml of wood plate were used. The results are shown in Table 6.

Methylene blue fading (relative concentration)

Since the amount of silica sol coating liquid and the amount of methylene blue liquid differ depending on the base material, comparison between the base materials is not appropriate, but the comparative example 1.4 of Na / SiO ₂ mM / M ratio of the used silica sol is 2.5 or less In the case of using a silica sol of It was confirmed that when silica sols having a mM / M ratio of 4.2 or 5.2 and 2.5 or more were used, the activity was better than that of the comparative example when compared between the same substrates.
As a base material, the color fading of wood board and two kinds of paper is excellent, and the paper may be evaluated as the same as cotton since cellulose produced from wood pulp is a raw material. The same results were obtained for hemp as for silk.

Removal of VOC by artificial foliage plant A 14-mass% silica and a silica sol of NaOH / SiO ₂ mM / M ratio were spray-applied to an ornamental artificial branch attached with 18 Momiji leaves as a substrate, and dried at 70 ° C. for 10 minutes. A portion of a 10 L volume of the cocked Tedlar bag was cut by 10 cm, a treated branch was inserted, and the cut end was sealed with a tape.
As a VOC, 10 L of air having a toluene concentration of 15 ppm was injected. The concentration was measured by 124SB and found to be 6 ppm after 20 minutes and 1 ppm or less after 2 hours. The untreated branch was similarly measured and found to be 14 ppm after 2 hours. No discoloration due to silica sol treatment was observed compared to untreated maple leaves.
Thus, it was confirmed that the 5.2 silica sol having a NaOH / SiO ₂ mM / M ratio higher than 2.5 exhibited excellent VOC decomposition performance even by spray coating.

Ethylene removal experiment contributing to maintaining freshness of fruits and vegetables
Non-woven fabric of 40 mass% polyester blended cotton as a base material, fabric weight: 35 x 40 cm of 40 g / m ² , ethylene removal performance depends on alkali / silica ratio in preliminary test; Silica sol with 14.3% silica, 0.38% Na ₂ O, 5.2 mM NaOH / SiO ₂ mM / M ratio 2. Silica 30.3% Na ₂ O: 0.30% NaOH / SiO ₂ mM / M ratio silica with purified water Diluted to 10%, coated with 28 mL and dried with circulating air at 90 ° C. for 10 minutes. This base material-three pieces of silica sol dry matter complex is folded, and the end of the 5 L Tedlar bag (250 x 400 mm) with a cock is cut open about 20 cm and stored, and after sealing the cut with a transparent adhesive tape, 50 ppm ethylene gas The sample / bag was stored in 500 mL and stored in a refrigerator at 3 ° C. for 1, 2, 3 hours, and the ethylene concentration was measured with a detection tube.
Detector tube: No. 127 L 0.2 to 50 ppm 100 mL 4 times) Gastec Co., Ltd. The results are shown in Table 7.

Sample No. 1 coated with 1.9 silica sol of Comparative Example in which the mM / M ratio of Na / SiO ₂ is lower than 2.5. Sample No. 1 of the Inventive Example with a mM / M ratio of 5.2 decreased to only 10 ppm, 5 ppm, while 2 decreased only 45 ppm and only 5 ppm 3 hours after ethylene gas filling. It turned out that the decomposition ability of is great.

The air purification function of the photocatalyst is said to be mainly due to valence band holes, but its short life and its detection require advanced technology at a low temperature of 77 K deaerated. If OH radicals, which are strong active oxygen generated by holes in water, can be detected, it can be proved that holes, ie OH radical precursors, were present before being immersed in water. The method of fluorescence spectroscopy of the reaction product with coumarin was applied to prove the presence of holes before immersion in water for the case where the concentration of oxide is 1.9 mmol or less per mole of silica.
It has already been shown by many examples that the higher the concentration of the alkali metal hydroxide is 2.4 millimoles or more per 1 mol of silica, the greater the deodorizing property and the ability to decompose organic substances such as VOCs. The effects of NaOH concentration on the formation of OH radical precursor in the base material-silica sol dry matter complex are shown below as the result of investigation by coumarin fluorescence spectroscopy.

According to Non-Patent Document 1, when coumarin (the following chemical formula 1) in an aqueous solution encounters an OH radical, an OH group is added at the 3 to 8 positions, but a 7 OH coumarin (alias umbellii) having an OH group added at the 7 position. It has been shown that only feron (chemical formula 2 below) generates fluorescence having a peak at 455 nm, and detection of fluorescence of a specific wavelength by a fluorescence spectroscopy test can demonstrate the presence of OH radicals.
Non-Patent Document 2 describes that when irradiated with ultraviolet light, TiO ₂ powder suspended in a coumarin aqueous solution is recognized as 7OH coumarin, and the existence of valence band holes can be proved, and Non-Patent Document 3 coumarin It is shown that when NaOH coexists in the liquid, a fluorescence spectrum of cinnamic acid (chemical formula 3 below) having a wavelength of 510 nm is generated.

  That is, it has been known that coumarin of formula 1 reacts with OH radical to form 7OH coumarin of formula 2 and coumarin reacts with NaOH to form cinnamic acid of formula 3, but coumarin It was unknown about the spectrum when NaOH and OH radical coexist.

The inventors of the present invention have obtained a fluorescence spectrum having a peak of 455 nm having the same wavelength as that of Non-Patent Document 1 from experimental sample 1 shown in Table 1 in which ultraviolet light is irradiated to coumarin aqueous solution in which TiO ₂ powder is dispersed. Therefore, it can be proved that valence band holes are generated.

Next, when the solution of sample 3 prepared by dispersing the same amount of titanium oxide powder as that of FIG. 1 in the 25 mM aqueous solution of sodium hydroxide sample 2 (FIG. 2) and 25 mM alkaline solution was excited with ultraviolet light, As shown in FIG. 2, a peak height of 42 and a peak about one tenth the height of Sample 2 appear at 510 nm of the same wavelength as FIG. 2, and a peak of wavelength 455 nm in FIG.
In other words, the peak of 7OH coumarin does not appear in the presence of OH radical because 25 mM NaOH is present and titanium oxide is also irradiated with ultraviolet light, and instead the peak height of NaOH alone is about 1/10 A new finding was obtained that a peak of cinnamic acid occurs.

Fig. 4 shows the spectrum of the fluorescence spectroscopy test of sample liquid 8 in which a sheet of the composite obtained by applying and drying a silica sol containing 2.8 mM NaOH and 20% by mass of silica to a cotton substrate is immersed in the same 0.1 mM coumarin liquid. Indicated.
This spectrum shows that a low peak having a half intensity of Sample 3 at a wavelength of 510 nm as in FIG. 3 indicates that a high concentration of NaOH and OH radicals coexist, this substrate-silica sol drying It can be said that the compound complex possesses an OH radical precursor equivalent to holes.

According to Table 8 that summarizes the above experimental results,
1. A spectrum of 7OH coumarin appears in samples 1 and 5 in which the NaOH concentration is as low as 0 mM and 0.25 mM, and contains TiO ₂ and OH radicals coexist, which proves that holes are generated.
2. A low peak cinnamic acid spectrum appeared in sample 3 in which the NaOH concentration was as high as 2.5 mM and TiO ₂ was contained and OH radicals were generated by holes, and a substrate in which the same low peak cinnamic acid spectrum appeared It has been proved that the silica sol dry matter composite 8 has an OH radical precursor equivalent to a hole.

In addition, Hitachi spectrofluorimeter F-7000 was used for the measurement of these fluorescence spectroscopy.

Claims (10)

The OH radical precursor is retained even in the absence of light , and one or two or more water-soluble alkali metal salts selected from Na, K and Li are used as hydroxides of alkali metals per one mole of silica on a substrate. What is claimed is: 1. A base material-silica sol dry matter composite having an excellent air purification function characterized by retaining a silica sol dry matter containing 2.5 to 7.1 millimoles in terms of conversion. The step of applying the silica sol to the substrate and the subsequent step of drying are sequentially carried out , and the amount of the silica sol applied to the substrate is 1 mg to 1 mg per unit area of the substrate (g / m ² ) in the dry state. the substrate according to claim 1, characterized in Rukoto such a range of .5G - method for producing silica sol dry matrix composite. The substrate-silica sol dry matter composite according to claim 1 , wherein volatile organic compound VOC, malodor and ethylene are decomposed. Is less than one tenth of the intensity of the fluorescence coumarin liquid emitted containing a wavelength to be generated only the intensity of the fluorescence is an alkali metal salt not a free or a silica sol of 500~520nm when excited by immersion in an aqueous solution of coumarin The base material-silica sol dry matter composite according to any one of claims 1 to 3 , characterized in that. The particle diameter of the silica particle in a silica sol is 4 nm-0.7 micrometer, The base material-silica sol dry matter complex in any one of Claim 1 , 3 or 4 characterized by the above-mentioned. The substrate according to any one of claims 1 or 3 , wherein the substrate is a natural fiber, a regenerated fiber or a synthetic fiber and their woven or non-woven fabric, wood, paper or wallpaper. Complex. The base material-silica sol dry matter composite according to claim 6 , wherein natural fibers of the base material are cotton, silk, hemp, regenerated fibers are rayon, lyocell, and synthetic fibers are polyester, nylon. . Substrates were prepared by the method described in claim 2 - sol dried product hygiene mask the complex and set the air passage section write No This and characterized as an air filter, air cleaner, deodorizer, or air conditioning of the manufacturing method. The substrate according to any one of claims 1 to 3 , wherein the substrate is a curtain comprising a fiber and its woven or non-woven fabric, wall material, floor material, ceiling material, artificial flower, artificial foliage plant. Silica sol dry matter complex. The substrate according to claim 2 ambient temperature after application of the sol to a substrate is characterized that you dried at 0 to 230 ° C. - method for producing silica sol dry matrix composite.