JPH05156016A - Production of hybrid silica gel - Google Patents

Abstract

(57) [Summary] [Structure] A tetraalkoxysilane such as tetraethoxysilane, an organoalkoxysilane such as phenyltriethoxysilane, and a photochromic compound having an alkoxysilyl group in the molecule are reacted to perform cohydrolysis,
Photochromic hybrid silica gel is produced by condensation. [Effect] By using the organoalkoxysilane in combination, the number of acid sites in the produced silica gel is reduced, or the acid strength is reduced. As a result, deterioration of the photochromic compound portion chemically fixed in silica gel can be prevented, and light durability is improved. Further, since the photochromic compound portion is chemically bonded to silica gel, the photochromic compound does not elute in the solvent. Furthermore, because tetraalkoxysilane is used as one of the raw materials,
Excellent strength, solvent resistance, and heat resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hybrid silica gel having photochromic properties by a sol-gel method, and more particularly to a method for producing a hybrid silica gel having a remarkably improved durability as a photochromic material.

[0002]

2. Description of the Related Art Conventionally, the sol-gel method has been known as a low temperature synthesis method of silica glass, and a siloxane bond is formed from a raw material in a solution state by hydrolysis and polycondensation reaction to obtain a silicon oxide. .. In the case of producing a binary or higher oxide, the raw materials can be mixed on a molecular order, so that a uniform copolymerized oxide can be produced. Further, in the synthesis of silica glass by the melting method, a substance that decomposes at a high temperature such as an organic substance cannot be doped into silica glass, but the sol-gel method of solution mixing can synthesize glass at a relatively low temperature. It is possible to dope organic substances into silica glass. Studies of doping various dyes into silica gel using this method have been performed, for example, Makishima et al. (J. Am. Ceram. Soc, 69 (4) 198).
6), Tani et al. (J. Appl. Phys, 58 (9) 1.Nov. 1985), David AVNI
L et al. (J. Non. Cry. Solids, 74, 1985, 395).

We have been conducting research on doping functional organic substances into silica gel for a long time. So far, we have succeeded in doping the functional dyes such as photochromic compounds into silica gel and expressing the function in silica gel. Further, they have found that the photochromic compound having an alkoxysilyl group can be chemically immobilized in silica gel to prevent the photochromic compound from being eluted from the silica gel.

[0004]

However, it has been newly found that the photochromic compound fixed in silica gel may have low durability by the above method. As a result of examination, the cause of this is presumed as follows. When organic matter is contained, heat treatment cannot be performed at a high temperature, so many hydroxyl groups remain in the silica gel, and the amount of acid sites in the silica gel is considerably large.
Equivalent to ~ 4. Therefore, the doped photochromic compound is prone to deterioration, and particularly in the case of the photochromic compound, deterioration reaction is promoted by light irradiation and oxidative deterioration is remarkable. Therefore, conventional silica gels exhibiting photochromic properties are not yet practically sufficient in terms of durability, and it has been extremely important to solve these problems.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have found that a silica gel doped with a compound exhibiting photochromic properties is chemically fixed. We succeeded in improving the durability of photochromic properties by controlling the acid strength of silica gel.

That is, the present invention provides a tetraalkoxysilane represented by the general formula (1), Si (OR ¹ ) ₄ (1) (wherein R ¹ represents an alkyl group) represented by the general formula (2) Organoalkoxysilane and an alkoxysilyl group R ² _n Si (OR ³ ) _4-n (2) (wherein R ² is an alkyl group, an alkenyl group or a phenyl group, R ³ is an alkyl group, n Is a photochromic compound having an integer of 1 or 2).

Still another invention is a photochromic compound having a tetraalkoxysilane represented by the general formula (1) and Si (OR ¹ ) ₄ (1) (in the formula, R ¹ represents an alkyl group) alkoxysilyl group. Silica gel is synthesized by reacting with a compound, and the silica gel is then treated with an organoalkoxysilane represented by the general formula (2) to R ² _n Si (OR ³ ) _4-n (2) (wherein R ² is an alkyl group). Group, an alkenyl group, or a phenyl group, R ³ is an alkyl group, and n is an integer of 1 or 2).

The present invention will be described in detail below.

The object of the present invention is to reduce the acid sites or the acid strength of silica gel as a method for suppressing the deterioration of the photochromic compound immobilized in hybrid silica gel.

The photochromic hybrid silica gel of the present invention is a so-called sol-gel method for chemically imparting photochromic compounds to silica gel for the purpose of imparting photochromic properties to the silica gel with an organic compound exhibiting photochromic properties. It refers to those dispersed and contained in molecular units or clusters. The shape of the silica gel is not limited at all, and may take any form such as a thin film, bulk gel, fiber and particles.

As the tetraalkoxysilane represented by the general formula (1) used in the production method of the present invention, tetramethoxysilane, tetraethoxysilane, etc., in which R ¹ is a methyl group, an ethyl group, a propyl group, a butyl group or the like, Examples thereof include tetrapropoxysilane and tetrabutoxysilane.

In the organoalkoxysilane represented by the general formula (2), which is also used in the production, R ² is an alkyl group, an alkenyl group or a phenyl group. Examples of the alkyl group include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, butyl group, octyl group, decyl group and octadecyl group. Examples of the alkenyl group include linear or branched alkenyl groups such as an ethenyl group, a propenyl group, a butenyl group and a hexenyl group. R ³ represents an alkyl group, and preferably the same substituents as those exemplified for R ¹ can be mentioned.

Specific examples of the organoalkoxysilane of the general formula (2) include phenyltrimethoxysilane,
Phenyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane,
n-octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, n-octyltriethoxysilane, n-
Octadecyltriethoxysilane, n-dodecyltriethoxysilane, methyltributoxysilane, ethyltributoxysilane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane,
Examples thereof include vinylmethyldiethoxysilane.

The photochromic compound having an alkoxysilyl group used in the present invention (hereinafter referred to as a silyl group-containing photochromic compound) may be one having an alkoxysilyl group which can be cohydrolyzed with the above silicon alkoxide or organoalkoxysilane in the molecule. If there is no particular limitation, various organic photochromic compounds can be used. For example, a compound obtained by introducing an alkoxy group into a photochromic compound such as azobenzenes, spiropyrans, and spiroxazines is preferably used. Specific examples of the compound group are shown below, but the compound group is not limited thereto.

[0015]

[Chemical 1]

[0016]

[Chemical 2]

Since these photochromic compounds have an alkoxysilyl group in the molecule, they are hydrolyzed to cause polycondensation with tetraalkoxysilanes and / or organoalkoxysilanes to form Si--O--Si bonds, and silica gel and Can be chemically bound.

There are the following two methods for producing the photochromic hybrid silica gel of the present invention.

In the first method, a tetraalkoxysilane represented by the general formula (1), an organoalkoxysilane represented by the general formula (2), and a silyl group-containing photochromic compound are reacted with each other to co-hydrolyze, And a method of producing by condensation reaction. This method is a so-called sol-gel method, and known methods can be adopted without any limitation.

For example, co-hydrolysis and condensation are carried out by reacting in an acidic alcohol aqueous solution having a pH of 2-3 and a molar ratio of 10-40. Specifically, a method in which an organoalkoxysilane having a slow hydrolysis rate and a silyl group-containing photochromic compound are first reacted in the above solution, and tetraalkoxysilane is added during the reaction, or tetraalkoxysilane is added in the same aqueous solution. A method of reacting a silyl group-containing photochromic compound to form an oligomer and then reacting with an organoalkoxysilane to form a hybrid silica gel can be mentioned.

The latter method of passing through an oligomer is preferably adopted because hybrid silica gel of various forms can be produced as described in detail below.

For example, in the case of producing particulate silica gel, a mixed solution of the above-mentioned oligomer and organoalkoxysilane is added dropwise to a 10-20 times volume ammonia water-alcohol solution having a pH of 10-13 to form an emulsion. And a method of collecting the obtained solid by centrifugation or the like is preferably used. In the case of producing bulk silica gel, for example, a method in which the oligomer solution and the organoalkoxysilane are placed in a container having a small hole and allowed to stand still to gradually evaporate the solvent is suitable. Further, a thin film hybrid silica gel can be produced by dip-coating or spin-coating a mixed solution of the above-mentioned oligomer and organoalkoxysilane on a substrate.

Regarding the reaction amount ratio of the tetraalkoxysilane and the organoalkoxysilane, it is possible to react at any ratio by adjusting the hydrolysis reaction time.

The amount of the silyl group-containing photochromic compound used is not particularly limited and may be used in any ratio. Usually, it is used in an amount of 0.2 to 1 times the molar amount of the tetraalkoxysilane and the organoalkoxysilane. To be done.

The hydrolysis temperature is not particularly limited as long as it does not decompose the added silyl group-containing photochromic compound. The higher the temperature is, the faster the hydrolysis proceeds, but when an acidic catalyst is added during the hydrolysis, high temperature promotes oxidative deterioration, so about 10 to 60 ° C. is preferable.

The heat treatment temperature for removing water and alcohol remaining in the gel after hydrolysis varies depending on the intended product, but is not particularly limited as long as the function of the photochromic compound is not lost. Absent. Usually, it is processed at 100 to 200 ° C.

A reaction solvent is usually used for the purpose of allowing the hydrolysis and condensation reaction to proceed uniformly, but alcohol is preferably used. As this alcohol, methanol,
Examples include ethanol, propanol, and butanol.

As mentioned above, in order to accelerate the hydrolysis and condensation reactions, it is a preferred embodiment to use an acidic catalyst such as hydrochloric acid, sulfuric acid, acetic acid or citric acid, or a basic catalyst such as sodium hydroxide or ammonia. .. Water is a component necessary for the hydrolysis reaction, and the amount used is appropriately selected depending on the amount of the substance to be hydrolyzed, the form of the resulting silica gel and the like.

Another method for producing the photochromic hybrid silica gel of the present invention is to carry out a co-hydrolysis and condensation reaction to react a tetraalkoxysilane represented by the general formula (1) and a photochromic compound containing a silyl group, and carry out a one-part hybrid silica gel. After the production of the general formula (2)
Is a method of performing a reaction treatment with an organoalkoxysilane represented by.

For example, the tetraalkoxysilane represented by the general formula (1) and the silyl group-containing photochromic compound are hydrolyzed with an aqueous acidic alcohol solution having a pH of 2 to 3, and the resulting oligomer is further reacted to produce a hybrid silica gel. And then reacted with the organoalkoxysilane represented by the general formula (2).

Usually, both are reacted in an organic solvent such as alcohol, and then the solvent is removed. The shape of the hybrid silica gel is not particularly limited, such as a thin film and particles. In the case of particles, it is preferable to disperse the particles to be treated in advance in a solvent and then mix with the solution of the organoalkoxysilane.
A method of performing ultrasonic treatment for a certain period of time is also suitable for sufficiently dispersing.

Also in this second production method, the production conditions such as the solvent, the catalyst, the hydrolysis temperature and the heat treatment temperature in the previous production method are also adopted. However, the reaction amount of the organoalkoxysilane with respect to the tetraalkoxysilane is usually 5 to 40 mol% with respect to the tetraalkoxysilane because the particles of the organoalkoxysilane tend to be generated when the amount of the organoalkoxysilane is large. To do.

[0033]

[Functions and Effects] The photochromic hybrid silica gel produced according to the present invention is subjected to a reaction treatment in the presence of an organoalkoxysilane during or after the production of the silica gel to reduce the acid points in the silica gel and reduce the acid strength. It was made. That is, an organoalkoxysilane having a small number of alkoxy groups which can be converted into hydroxyl groups by hydrolysis is used to react with the hydroxyl groups remaining in the gel to reduce the acid strength. As a result, it is possible to prevent deterioration of the compound portion exhibiting photochromic characteristics that easily cause deterioration, and improve the durability of the photochromic characteristics.

Of course, since the photochromic compound part is chemically bonded and fixed to silica gel, the photochromic compound is not eluted with an organic solvent or the like.

Further, since the tetraalkoxysilane is used as the silica gel raw material, the gel itself has sufficient strength and is excellent in solvent resistance and heat resistance. For example, photochromic hybrid silica gel particles produced using only organoalkoxysilane without using tetraalkoxysilane swell in ethanol, dissolve in tetrahydrofuran, and have a melting point near 160 ° C. On the other hand, the hybrid silica gel particles produced by using tetraalkoxysilane in combination with 10 mol% do not dissolve in ethanol and do not have a melting point until the organic group burns. Again 3
When it is used in an amount of 0 mol%, it also becomes insoluble in tetrahydrofuran.

[0036]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 To a solution prepared by dissolving 2.1 g of phenyltriethoxysilane and 0.24 g of spirooxazine (a) in 20 ml of ethanol, 4.5 ml of hydrochloric acid aqueous solution having a pH of 3 was added, and the mixture was added at 25 ° C.
It was stirred for 15 hours. 0.8 g of tetraethoxysilane was added to the reaction liquid, and the mixture was further stirred for 5 hours. Aqueous ammonia (25% aqueous ammonia 11.2 ml, water 5
6 ml) with stirring. The produced solid was separated by centrifugation, washed with water and ethanol, and then dried at 120 ° C. for 4 hours to give a particle size of 0.
Hybrid silica gel particles of 2 to 0.4 μm were obtained.

When the surface acid strength of the silica gel particles was measured by an indicator method, the pKa was 5 to 6 and the acid strength was low.

Polymethylmethacrylate (PMMA) 2
g in 40 ml of dioxane and a dispersion of 0.02 g of the hybrid silica gel particles prepared in the above method in 2 ml of dioxane were mixed and then sonicated, and 1 ml of this preparation was placed in a Petri dish. A cast film was prepared by evaporating the cast dioxane. This PMMA film is continuously irradiated with a Xe lamp,
The PMMA film was taken out every 30 minutes and the absorbance based on the photochromic reaction was measured. The results are shown in FIG. In this figure, the absorbance was plotted based on the absorbance immediately after the start of irradiation, and the ratio to the initial absorbance was plotted. In the figure, by comparison with Comparative Example 1 described later, the hybrid silica gel of the present invention has an increased half-life of absorbance (time at which the absorbance reaches 50% of the initial absorbance) by about 1.8 times, and the light durability is improved. It is recognized that they are doing.

The hybrid silica gel thus obtained was subjected to Soxhlet extraction with ethanol.
After extraction, it showed the same photochromic properties as before extraction.

Comparative Example 1 2 g of tetraethoxysilane and spirooxazine (a)
To a solution prepared by dissolving 0.24 g in 20 ml of ethanol, p
H3 hydrochloric acid-ethanol aqueous solution 3.6 ml (water 0.2 m
1) was added, and the mixture was stirred at 25 ° C. for 5 hours. The reaction solution was treated with an ammonia-ethanol aqueous solution (25% ammonia water 1
1.2 ml, ethanol 56 ml) was added dropwise with stirring. The produced solid was separated from the reaction solution by centrifugation, washed with water and ethanol, and then dried at 120 ° C. for 4 hours to obtain silica gel particles having photochromic properties.

When the surface acid strength of the silica gel particles was measured in the same manner as in Example 1, the pKa was 3-4. or,
A cast film was prepared in the same manner as in Example 1, and the change in absorbance with time was measured. Figure 1 together with the results
It was shown to.

Example 2 To a solution of 21 g of phenyltriethoxysilane and 0.24 g of spirooxazine (a) in 20 ml of ethanol was added 45 ml of a hydrochloric acid aqueous solution of pH 3 (2.5 ml of water), and the mixture was stirred at 25 ° C. for 15 hours. did. 8 g of tetraethoxysilane was added to the reaction solution, and the mixture was further stirred for 5 hours. The reaction solution was allowed to stand, a lid with small holes was placed, and the solvent was gradually evaporated. It was sufficiently dried to form a xerogel and then dried at 120 ° C. for 4 hours to prepare a hybrid silica gel.

The pKa of this hybrid silica gel is 6
Met. This hybrid silica gel was once crushed, then molded into pellets and subjected to continuous irradiation in the same manner as in Example 1, and compared with the silica gel of Comparative Example 2 produced using only tetraethoxysilane described below, The half-life of absorbance was increased by 1.5 times.

Comparative Example 2 20 g of tetraethoxysilane and spirooxazine (a)
To a solution of 2.4 g dissolved in 20 ml of ethanol, pH
45 ml of hydrochloric acid aqueous solution of 3 (2.5 ml of water) was added, and 2
The mixture was stirred at 5 ° C for 15 hours. The reaction solution was allowed to stand, a lid with small holes was placed, and the solvent was gradually evaporated. It was sufficiently dried to form a xerogel and then dried at 120 ° C. for 4 hours to produce silica gel.

Pellets were prepared from this silica gel in the same manner as in Example 2, and the change in absorbance with time was examined.

Example 3 To a solution prepared by dissolving 2.1 g of phenyltriethoxysilane and 0.24 g of spirooxazine (b) in 20 ml of ethanol, 4.5 ml of hydrochloric acid aqueous solution having a pH of 3 was added, and the mixture was added at 25 ° C.
It was stirred for 15 hours. 0.8 g of tetraethoxysilane was added to the reaction liquid, and the mixture was further stirred for 5 hours. The reaction solution was dip-coated on a clean glass substrate. After the solvent was volatilized, heat treatment was performed at 120 ° C. for 10 minutes, cooling was performed, and then dip coating was performed again. Do this operation 10
After repeating the process twice, heat treatment was performed at 120 ° C. for 4 hours to obtain a gel film.

The pKa of this gel film was 5-6. Further, when continuous irradiation with a Xe lamp was performed in the same manner as in Example 1, the absorbance half-life was 1.7 times that of the film of Comparative Example 3 produced using only tetraethoxysilane described below. there were.

Comparative Example 3 Tetraethoxysilane 2 g and spirooxazine (b)
To a solution prepared by dissolving 0.24 g in 20 ml of ethanol, p
4.5 ml of H3 aqueous hydrochloric acid solution was added, and the mixture was stirred at 25 ° C for 15 hours. The reaction solution was dip-coated on a clean glass substrate. After the solvent was volatilized, heat treatment was performed at 120 ° C. for 10 minutes, cooling was performed, and then dip coating was performed again. After repeating this operation 10 times, 4 at 120 ℃
A heat treatment was performed for an hour to obtain a gel film.

The temporal change of the absorbance of this film based on the photochromic reaction was examined in the same manner as in Example 3.

Example 4 2 g of tetraethoxysilane and spirooxazine (a)
To a solution prepared by dissolving 0.24 g in 20 ml of ethanol, p
H3 hydrochloric acid ethanol-water solution 3.6 ml (water 0.2 m
1) was added, and the mixture was stirred at 25 ° C. for 5 hours. The reaction solution was treated with an ammonia-ethanol aqueous solution (25% ammonia water 1
1.2 ml, ethanol 56 ml), the mixture was added dropwise with stirring, separated, washed and dried to prepare hybrid silica gel particles. An ethanol solution 20 containing 0.6 g of the silica gel particles and 1 g of methyltriethoxysilane.
It was dispersed in ml and sonicated for 1 hour. After collecting the particles by centrifugation and washing with water and ethanol,
Hybrid silica gel particles were obtained by heat treatment at 120 ° C. for 4 hours.

The pKa of the silica gel particles was 5.
Further, a PMMA film was prepared in the same manner as in Example 1,
When the light durability was examined, the half-life of the absorbance was 1 as compared with the PMMA film prepared from silica gel particles (pKa = 3 to 4) produced in the same manner as in this example except that it was not treated with methylethoxysilane. It was found to be 0.6 times, and the light durability was improved.

Example 5 2 g of tetramethoxysilane, 2 g of allyltrimethoxysilane and 0.45 g of spiropyran (e) were added to 2 parts of methanol.
To a solution dissolved in 0 ml, 3.6 ml of a hydrochloric acid-methanol aqueous solution having a pH of 2 (0.2 ml of water) was added, and the mixture was added at
Stir for hours. The reaction solution was dip-coated on a clean glass substrate. 10 at 120 ° C after the solvent evaporates
After heat treatment for 1 minute and cooling, dip coating was performed again, and this operation was repeated 10 times. Finally 120 ℃
After heat treatment for 4 hours, a silica gel film was obtained. The film exhibited photochromic activity which was colored by irradiation with ultraviolet rays and was erased by irradiation with visible light. Further, it showed the same light durability as that of Example 3.

Example 6 2 g of tetraethoxysilane and 0.2 of azobenzene (g)
To a solution of 4 g dissolved in 20 ml of ethanol, 3.6 ml of a hydrochloric acid-ethanol aqueous solution having a pH of 3 (0.2 ml of water) was added, and the mixture was stirred at 25 ° C for 5 hours. A solution obtained by mixing the reaction solution and 10 ml of an ethanol solution of 2 g of ethyltriethoxysilane was added dropwise to an ammonia-ethanol aqueous solution (25% ammonia water 11.2 ml, ethanol 56 ml) with stirring. The produced solid was separated by centrifugation, washed with ethanol and water, and heat-treated at 100 ° C. for 4 hours to obtain hybrid silica gel particles having photochromic activity.

When the silica gel particles were alternately irradiated with ultraviolet rays and visible light, it was observed that the photochromic properties due to cis-trans photoisomerization were rapidly obtained.

Furthermore, a PMMA film was prepared from the silica gel particles in the same manner as in Example 1 and the change in absorbance with time was examined. In the case of the silica gel of Comparative Example 6 prepared using only tetraethoxysilane described below, The half-life was 1.3 times longer than that of the other products.

Comparative Example 6 Tetraethoxysilane 2 g and azobenzene (g) 0.2
To a solution of 4 g dissolved in 20 ml of ethanol, 3.6 ml of a hydrochloric acid-ethanol aqueous solution having a pH of 3 (0.2 ml of water) was added, and the mixture was stirred at 25 ° C for 5 hours. The reaction solution was treated with an ammonia-ethanol aqueous solution (25% ammonia water 11.2 m).
1 and 56 ml of ethanol) was added dropwise with stirring.
The produced solid was separated by centrifugation, washed with ethanol and water, and heat-treated at 100 ° C. for 4 hours to obtain hybrid silica gel particles having photochromic activity.

A PMMA film was prepared from the silica gel particles in the same manner as in Example 1, and then the change in absorbance with time was determined.

[Brief description of drawings]

FIG. 1 is a diagram showing a time-dependent change in absorbance based on a photochromic reaction of a PMMA film containing (hybrid) silica gel particles produced in Example 1 and Comparative Example 1.

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Claims (2)

[Claims] 1. A tetraalkoxysilane represented by the general formula (1), Si (OR ¹ ) ₄ (1) (in the formula, R ¹ represents an alkyl group) An organoalkoxy represented by the general formula (2) Silane, R ² _n Si (OR ³ ) _4-n (2) (wherein R ² represents an alkyl group, an alkenyl group, or a phenyl group, R ³ represents an alkyl group, and n represents an integer of 1 or 2). ) And a photochromic compound having an alkoxysilyl group are reacted with each other to produce a photochromic hybrid silica gel. 2. A reaction between a tetraalkoxysilane represented by the general formula (1) and Si (OR ¹ ) ₄ (1) (wherein R ¹ represents an alkyl group) with a photochromic compound having an alkoxysilyl group. To synthesize silica gel, and then the silica gel is treated with an organoalkoxysilane represented by the general formula (2) to obtain R ² _n Si (OR ³ ) _4-n (2) (wherein R ² is an alkyl group or an alkenyl group). Group or phenyl group, R ³ represents an alkyl group, and n represents an integer of 1 or 2).