JPH08119619A - Surface treatment of silica particles - Google Patents

Abstract

PURPOSE: To easily, continuously and efficiently execute surface treatment without needing pretreatment and with a simple operation by allowing a specified silane alkoxide compd. to coexist. CONSTITUTION: Cylindrical, flaky or spherical silica particles having 0.1-10μm average grain size, rich in surface hydroxyl group, good in dispersibility, synthesized by sol-gel method, etc., consisting essentially of SiO2 and having an affinity with a hydrolyzed matter of the silane alkoxide compd. are diluted with a dispersing medium, and 0.05-5wt.% water is added to this dispersion, and the dispersion is kept to alkali side with aqueous ammonia, etc., then, about 0.01-10m mol silane coupling agent containing a functional group for modifying the surface and alkoxide group, amino group, etc., reactive with hydroxyl group or silane alkoxide compd. on the surface of the silica particles are added to the dispersion per 1g silica particles, then, the silane alkoxide compd. expressed by the formula ((m) is 2-4, (x) is hydroxyl group or a halogen, R<1> is an alkyl or phenyl) is added to execute hydrolysis, then the surface treated silica particles are separated and washed and added with distilled water to obtain an aq. soln. of surface treated silica particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for controlling the surface condition of silica particles in the field of using silica particles. The obtained silica particles are used as various carriers for adsorbing antigens or antibodies in the field of immunological analysis. Other,
It is used as an additive in the fields of various polymers, cosmetics, inks, greases and waxes.

[0002]

2. Description of the Related Art Conventionally, for surface modification of silica particles, a flushing method (coloring material in which the surface is made hydrophobic by a surfactant) is used.
55 [5] 300-304 1982), coating methods by adsorption of aqueous colloids and topochemical methods of reacting organic substances with functional groups on the surface of particles. Among them, focusing on the hydroxyl groups present on the surface of silica particles, there is research on the lipophilic method utilizing the reaction performed in the field of synthetic organic chemistry (Hiroshi Utsuki et al .: Surface treatment of silica gel and adsorption characteristics of treated silica gel, "Surface" 16 (9): 525,1978). In addition, a method of reacting a metal alkoxide having a desired functional group, a so-called silane coupling agent, with a hydroxyl group on the silica surface has recently been reported.
It is being actively conducted. According to this method, the surface treatment agent is immobilized by a chemical bond as compared with coating by physical adsorption, so that particles having a highly stable surface state can be produced.

[0003]

Since the above-mentioned reaction is a dehydration reaction of hydroxyl groups, in order to selectively react the hydroxyl groups on the surface of the silica particles with the hydroxyl groups of the coupling agent, unnecessary hydroxyl groups present once near the surface are removed. I have to do it. water
-In the case of silica particles synthesized in a mixed system of an organic solvent, it is common to perform a pretreatment such as drying the particle surface or replacing the dispersion medium of the particles with a non-aqueous solvent.

However, silica particles often agglomerate when they are dried or when the dispersion medium is changed. Particularly, in the case of fine particles having a size of 1 μm or less, it is very difficult to disperse them once they are aggregated. As described above, the surface treatment of the silica particles has a problem that the pretreatment is complicated and it is difficult to perform the treatment efficiently.

[0005]

As a result of intensive studies on the above problems of the surface treatment method, the present inventor has completed a method capable of easily and efficiently performing the surface treatment with a simple operation.

That is, according to the present invention, when the silica particles are surface-treated with a silane coupling agent, the following general formula (1)

[0007]

Embedded image

Silane alkoxide compound represented by the formula: wherein m is an integer of 2 to 4, X is a hydroxyl group or a halogen atom, and R ¹ is an alkyl group or a phenyl group. It is a surface treatment method.

Another invention is a surface treatment method for silica particles, characterized in that in the above surface treatment, hydrolysis is also carried out during the surface treatment.

The silica particles described in the present invention are not particularly limited in the synthetic method, and a silane alkoxide compound is hydrolyzed and condensed in a mixed solution of alcohol and water under alkaline conditions. It is possible to use silica particles by a wet method such as a method of synthesizing (sol-gel method), a method of synthesizing an aqueous solution of a soluble silicon salt and an acid, and a silica particle by a dry method of thermally decomposing tetrachlorosilane. it can. Silica particles synthesized by the sol-gel method are preferably used because the surface treatment effect is high and the dispersibility is good because the surface has abundant hydroxyl groups. The chemical composition of the silica particles is SiO ₂ as a main component, but any particles having an affinity for a silane alkoxide compound, especially a hydrolyzate thereof, may be used. Tokuyama Immunoticles HDP, etc.] or silica particles containing an alkyl group, an alkenyl group, a phenyl group, an amino group, a carbonyl group, a mercapto group, a halogen atom, or the like. A composite oxide of silica and a metal oxide other than silica such as alumina, titania, and zirconia may also be used.

The shape is not particularly limited, and may be cylindrical, scaly, or amorphous. When used as a carrier for immunological analysis, the average particle size synthesized by the sol-gel method is 0.
A spherical shape having a diameter of 1 to 10 μm is preferably used.

Specific examples of the silane alkoxide compound represented by the general formula (1) of the present invention include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, and triethoxychlorosilane. , Triethoxysilane, sodium orthosilicate, and the like. Among these silane alkoxide compounds, tetramethoxysilane, tetraethoxysilane, etc., are sodium ions in the reaction system, ions other than the components of the dispersion medium such as chlorine ions or components of an organic solvent similar thereto do not remain, and are easily available. It is preferably used.

The silane alkoxide compound may be used not only alone but also in the presence of a metal alkoxide capable of forming a metal oxide other than silica such as alumina, titania and zirconia by a hydrolysis-condensation reaction. it can. In this case, the silane alkoxide compound is usually used in an amount of 70 mol% or more based on the total amount of the silane alkoxide compound and the other metal alkoxide. Specific examples of this metal alkoxide include titanium alkoxide such as tetramethoxy titanate, tetraethoxy titanium, tetraisopropoxy titanium, and tetrabutoxy titanium, zirconium alkoxide such as tetrapropoxy zirconium, tetraisopropoxy zirconium, and tetrabutoxy zirconium, and tetraethoxy. Known alkoxides such as aluminum alkoxides such as aluminum can be mentioned.

The silane coupling agent used in the present invention is a compound having a functional group for surface modification and a moiety such as a hydroxyl group on the surface of silica particles or an alkoxide group or an amino group which reacts with the silane alkoxide compound.

To give a concrete example, the silane coupling agent having an alkyl group includes methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, phenyltrimethoxysilane, octyltrimethoxysilane, and octadecyltrimethoxysilane. ,
There are methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, octyltriethoxysilane, octadecyltriethoxysilane, etc.,
As those having other functional groups, 3-mercaptopropyltrimethoxysilane, (mercaptomethyl) methyldiethoxysilane, (mercaptomethyl) dimethylethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, methacryl Roxypropyltrimethoxysilane, vinyltriethoxysilane,
Bis (2-hydroxyethyl) -3-aminopurupyltriethoxysilane, bis {3- (triethoxysilyl) propyl} tetrasulfide, 3-isocyanatopropyltriethoxysilane, N-{(3-trimethoxysilyl) Propyl} ethylenediamine triacetic acid sodium salt, N-
(Triethoxysilylpropyl) urea, 3-chloropropyltriethoxysilane, diethylphosphateethyltriethoxysilane, trimethoxysilylpropylisothiouronium chloride, methyl {2- (3-trimethoxysilylpropylamino) ethylamine} -3 -Propionate, 3-aminopropyltriethoxysilane and the like. Generally, other metal alkoxide-based coupling agents or mixed systems of these and silane coupling agents can be used as long as they have an affinity for silica particles after hydrolysis. Examples thereof include titanate coupling agents such as isopropyl triisostearoyl titanate and isopropyl trioctanoyl titanate, zirconate coupling agents such as zirconium lactate and acetylacetone zirconium butyrate, and other zircoaluminate coupling agents.

Among the above silane coupling agents, the treatment effect is high when hydrophobicity is added to the particles, and the effect is high when proteins are adsorbed to the particles.
Mercapto group-containing silane coupling agents such as mercaptopropyltrimethoxysilane, (mercaptomethyl) methyldiethoxysilane, and (mercaptomethyl) dimethylethoxysilane are preferably used.

Next, the surface treatment method of the silica particles of the present invention will be described.

This surface treatment method is characterized in that when the silica particles are surface-treated with a silane coupling agent, the silane alkoxide compound represented by the general formula (1) is allowed to coexist. In addition, at that time, it is also characterized in that hydrolysis is also performed.

When the silica particles are surface-treated, the silica particles are usually diluted with a dispersion medium. The dispersion medium may be any one as long as the silica particles are not dissolved and the raw materials such as the silane coupling agent and the silane alkoxide compound used for the surface treatment are dissolved to some extent. In general, alcohol solvents such as methanol, ethanol, isopropanol, butanol, isoamyl alcohol, ethylene glycol and propylene glycol are preferably used because of their reactivity, operability and easy availability. Further, the other organic solvent may be partially mixed with the alcohol solvent and used.

When the hydrolysis is also carried out in the above dispersion medium, it is desirable that the silane alkoxide compound or the silane coupling agent is hydrolyzed to contain water. The water content varies depending on the alkoxide compound, the type of silane coupling agent, and the alkalinity of the solvent described later, and cannot be unconditionally limited, but generally a range of 0.05 to 5 wt% is preferable.

Further, when the dispersion medium is hydrolyzed together with the surface treatment, it may be acidified depending on the kind of the silane alkoxide compound and the silane coupling agent, but is usually neutral, particularly alkaline. It is suitable to carry out. Any means may be used for making the dispersion medium alkaline, but in general, a method of adding ammonia water or an alkali hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide, or a method of using these compounds in combination is preferable. is there. The addition amount of these compounds is not particularly limited and may be appropriately used, but generally when using aqueous ammonia, the ammonia concentration is 5 to 30 wt.
%, Preferably in the range of 5 to 25 wt%.

The concentration of the particles dispersed in the dispersion medium cannot be unconditionally limited because the reactivity varies depending on the type of the silane alkoxide compound and the silane coupling agent used as raw materials, but generally about 1 to 10 wt% is preferably used. If the concentration is too low, the efficiency of the surface treatment tends to decrease, and if it is too high, the dispersibility of the particles tends to decrease, and uniform surface treatment tends to be difficult.

When the solvent used for synthesizing silica particles by the sol-gel method is the same as the dispersion medium, the surface treatment of the present invention can be continuously performed after synthesizing the particles.

The amount of the silane coupling agent used for the surface treatment may be determined depending on the required effect of the surface treatment, and is not particularly limited, but generally 0.01 to 10 mmol per 1 g of silica particles is used.

The amount of the silane alkoxide compound used for the surface treatment cannot be unconditionally limited. Especially when simultaneously performing hydrolysis, the hydrolysis rate, the hydrolysis rate of the silane coupling agent, etc. are also taken into consideration for determination.
About 0.01 to 10 mmol is used for 1 g. If the concentration of the silane alkoxide compound is too high, it causes the generation of fine particles other than the intended particles, and if it is too low, the surface treatment effect tends to decrease. Further, the use ratio of the silane coupling agent and the silane alkoxide compound varies depending on the hydrolysis rate of both compounds, and thus is not particularly limited, but the amount of the silane alkoxide compound is usually 10 mol% to the silane coupling agent. It is used in a 4-fold molar amount.

The surface treatment is carried out by bringing the silane coupling agent and the silane alkoxide compound into contact with the silica particles. The method of adding both compounds is not particularly limited, but usually, the surface treatment is performed while adding them separately to the dispersion medium in which the particles are dispersed. In that case, when performing hydrolysis, the addition rate may be determined by the hydrolysis rate. The order of addition is not particularly limited, and may be determined by the reactivity of both compounds. When the hydrolysis rates of the silane coupling agent and the silane alkoxide compound are significantly different, they may be added at different rates. Further, both compounds may be mixed in advance and the mixture may be added to the particles, or the particles and both compounds may be mixed at the same time for the surface treatment.

The silica particle mixed solution mixed as described above is generally 10 to 3 at 0 to 50 ° C. after mixing all components.
The surface is treated by stirring for about 0 hours.

The surface-treated silica particles thus obtained can be washed and dried or redispersed in a desired dispersion liquid depending on the use.

The obtained surface-treated silica particles maintain the dispersibility before the surface treatment. Even when washed with a solvent equivalent to the dispersion medium, the added property does not change and the dispersibility is good.

By the treatment method of the present invention, more silane coupling agent can be bonded to the surface of silica particles. As a result, more functional groups in the silane coupling agent are present on the surface. For example, when a silane coupling agent having a hydrophobic group such as an alkyl group or a phenyl group is used as the functional group, the surface becomes more hydrophobic. When a silane coupling agent having a chloro group, a mercapto group or the like as a functional group is used, more properties of these functional groups can be added.

[0031]

As can be understood from the above description, according to the present invention, desired properties and desired functional groups can be efficiently provided on the surface of silica particles without complicated pretreatment operations such as particle drying and solvent replacement. It can be added, and the surface condition can be easily adjusted by changing the addition amount. The reason for this is not clear, but it is considered that the presence of the silane alkoxide compound reacts with the silane coupling agent to accelerate the surface treatment. In addition, when hydrolysis is performed, the silane coupling agent and the silane alkoxide compound are copolymerized to produce ultrafine particles, and it is thought that the surface treatment effect may be enhanced because the ultrafine particles adhere to the particle surface. To be

Thus, for example, when silica particles are used in an immunological analysis method, or when surface treatment is performed so that an antigen or antibody is easily adsorbed, the present method is used to remove silica particles by a wet method. After the synthesis, the surface treatment can be continuously performed without complicated pretreatment. Further, the surface treatment is efficiently performed as compared with the case where the silane alkoxide compound is not added. As a result, for example, when used as a carrier for immunological analysis,
High immunological sensitivity can be obtained when a protein such as an antigen or an antibody is efficiently adsorbed and an antigen-antibody reaction is carried out using the protein.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0034]

【Example】

Example 1 5 g of silica particles [1.3 μm (manufactured by Tokuyama Corp.)] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of ammonia water, and 240 ml of tetraethoxysilane 1 mmol diluted 20 times with methanol under stirring was added. 0.5 mmol of 3-mercaptopropyltrimethoxysilane diluted 10 times with methanol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 185 ml of an aqueous surface-treated silica particle solution.

The amount of mercapto groups on the surface was measured and found to be 0.89 μmol per 1 g of silica particles. The mercapto group was quantified by measuring the absorbance at 412 nm of thionitrophenolate anion (II) produced by the reaction of the mercapto group on the particle surface with 5,5-dithiobis (2-nitrobenzoic acid). In addition, the contact angle of this particle can
-When measured by the capillary ascent rate method using a permeation velocity meter (manufactured by Kyowa Interface Science Co., Ltd.), the surface-treated particles were 79.8 degrees, compared with the surface-treated particles being 71.0 degrees. It was degree.

Comparative Example 1 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of aqueous ammonia, and 3-mercaptopropyl diluted 10 times with methanol under stirring. 0.5 mmol of trimethoxysilane was added dropwise at 240 ml / h. After stirring at 20 ° C for 16 hours, centrifuge,
The supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 180 ml of an aqueous surface-treated silica particle solution. When the amount of mercapto groups on the surface was measured, relative to 1 g of silica particles
0.52 μmol was present. The contact angle of the particles was 75.8 degrees.

Comparative Example 2 Silica particles [manufactured by Tokuyama Corporation] in 200 ml of methanol
1.3 μm) 5 g were dispersed and, under stirring, 3-mercaptopropyltrimethoxysilane 0.10 diluted with methanol 10 times.
5 mmol was added dropwise at 240 ml / h. After continuing stirring at 50 ° C. for 24 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times.
Repeated washing with distilled water and finally with distilled water 2.5 wt.
% So that the surface treated silica particle aqueous solution is 180m
got l. The amount of mercapto groups on the surface was measured and found to be 0.086 μmol per 1 g of silica particles. The contact angle of the particles was 74.5 degrees.

Example 2 Silica particles in 200 ml of methanol [manufactured by Tokuyama Corporation]
1.3 μm] 5 g were dispersed and, under stirring, 1 mmol of tetramethoxysilane diluted 20 times with methanol was added dropwise at 240 ml / h, and at the same time, 240 ml of 0.5 mmol of 3-mercaptopropyltrimethoxysilane diluted 10 times with methanol was added. It was dripped at / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Repeat the washing with distilled water and finally adjust to 2.5 wt% with distilled water.
185 ml of an aqueous solution of surface-treated silica particles was obtained. When the amount of mercapto groups on the surface was measured, it was 0.66μ per 1g of silica particles.
mol was present. The contact angle of the particles was 77.5 degrees.

Example 3 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of ammonia water, and tetraethoxysilane 2.7 diluted with methanol 20 times with stirring. n-propyltrimethoxysilane 2.10 mmol of which was added dropwise at 240 ml / h and simultaneously diluted 10 times with methanol.
7 mmol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times.
Repeated washing with distilled water and finally with distilled water 2.5 wt.
%, Surface treated silica particles aqueous solution 185m
got l. The contact angle of the particles was 76.0 degrees.

Comparative Example 3 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of ammonia water, and n-propyltri was diluted 10 times with methanol with stirring. 2.7 mmol of methoxysilane was added dropwise at 240 ml / h.
After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 180 ml of an aqueous surface-treated silica particle solution. The contact angle of the particles was 73.5 degrees.

Example 4 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of ammonia water, and tetraethoxysilane 2.7 diluted with methanol 20 times with stirring. 2.7m of phenyltriethoxysilane diluted with methanol at a rate of 240ml / h and diluted 10 times with methanol.
mol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times.
Repeated washing with distilled water and finally with distilled water 2.5 wt.
%, Surface treated silica particles aqueous solution 185m
got l. The contact angle of the particles was 78.9 degrees.

Comparative Example 4 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution obtained by mixing 160 ml of methanol and 40 ml of ammonia water, and phenyltriethoxysilane diluted 10 times with methanol under stirring. 2.7 mmol was added dropwise at 240 ml / h. 20 ° C
After continuing stirring for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 180 ml of an aqueous surface-treated silica particle solution. The contact angle of the particles was 75.3 degrees.

Example 5 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution prepared by mixing 160 ml of methanol and 40 ml of ammonia water, and tetraethoxysilane 2.7 diluted with methanol 20 times with stirring. mmol was added dropwise at 240 ml / h, and at the same time, 2.7 mmol of chloropropyltrimethoxysilane diluted 10 times with methanol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Repeat washing with distilled water and finally with distilled water 2.
Adjusted to 5% wt, surface-treated silica particle aqueous solution 1
Obtained 85 ml. The amount of chloro groups on the surface was measured and found to be 0.78 μmol per 1 g of silica particles. The contact angle of the particles was 76.9 degrees.

Comparative Example 5 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution obtained by mixing 160 ml of methanol and 40 ml of ammonia water, and chloropropyltrimethoxy diluted 10 times with methanol under stirring. 2.7 mmol of silane was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Repeat the washing with distilled water and finally adjust to 2.5 wt% with distilled water.
180 ml of an aqueous solution of surface-treated silica particles was obtained. When the amount of chloro groups on the surface was measured by X-ray fluorescence analysis, 1 g of silica particles
There was 0.50 μmol. The contact angle of the particles was 73.4 degrees.

Example 6 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution obtained by mixing 160 ml of methanol and 40 ml of aqueous ammonia, and 1 mmol of tetramethoxysilane diluted 20 times with methanol under stirring. Was added dropwise at 240 ml / h, and at the same time, 0.5 mmol of 3-mercaptopropyltrimethoxysilane diluted 10 times with methanol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 185 ml of an aqueous surface-treated silica particle solution. The amount of mercapto groups on the surface was measured and found to be 0.80 μmol per 1 g of silica particles. The contact angle of this particle was 78.9 degrees.

Example 7 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution obtained by mixing 160 ml of methanol and 40 ml of aqueous ammonia, and 1 mmol of trimethoxysilane diluted 20 times with methanol was stirred. Was added dropwise at 240 ml / h, and at the same time, 0.5 mmol of 3-mercaptopropyltrimethoxysilane diluted 10 times with methanol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. The procedure of dispersing again with methanol and centrifuging was repeated and washed three times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 185 ml of an aqueous surface-treated silica particle solution. The amount of mercapto groups on the surface was measured and found to be 0.75 μmol per 1 g of silica particles. Also,
The contact angle of the particles was 78.0 degrees.

Example 8 5 g of silica particles [1.3 μm manufactured by Tokuyama Corp.] were dispersed in a solution obtained by mixing 160 ml of methanol and 40 ml of ammonia water, and 1 mmol of trimethoxychlorosilane diluted 20 times with methanol under stirring. Was added dropwise at 240 ml / h, and at the same time, 0.5 mmol of 3-mercaptopropyltrimethoxysilane diluted 10 times with methanol was added dropwise at 240 ml / h. After continuing stirring at 20 ° C. for 16 hours, the mixture was centrifuged and the supernatant was removed. Repeat the operation of dispersing again with methanol and centrifuging,
Washed 3 times. Further, washing with distilled water was repeated, and finally, with distilled water, the concentration was adjusted to 2.5 wt% to obtain 185 ml of an aqueous surface-treated silica particle solution. The amount of mercapto groups on the surface was measured and found to be 0.78 μmol per 1 g of silica particles.
The contact angle of the particles was 78.5 degrees.

Table 1 summarizes the results of Examples 1-8 and Comparative Examples 1-5.

[0049]

[Table 1]

The silica particles surface-treated with a silane coupling agent having a functional group (containing a mercapto group and a chloro group) can be treated with a silane alkoxide compound in the reaction system as compared with the case where no silane alkoxide compound is added. The amount of functional groups was large. When the surface treatment was performed with a silane coupling agent having a hydrophobic group such as an alkyl group and a phenyl group, the contact angle of the particles was measured and the hydrophobicity was compared to estimate the surface treatment effect. That is, it is considered that the higher the contact angle, the higher the surface treatment effect. The contact angle of untreated silica particles that had not been surface treated was 71.0 degrees. In the case where the silane alkoxide compound was added, the contact angle was higher than that in the case where neither was added, which shows that the hydrophobicity is high. This shows that the presence of the silane alkoxide compound increases the surface treatment efficiency.

Example 9 In the same system as in Example 1, the amount of 3-mercaptopropyltrimethoxysilane added to 1 g of silica particles in the presence of 200 μmol of tetraethoxysilane was 2,2 per 1 g of silica particles.
When the amount was changed to 0,200,2000 μmol, the amount of mercapto groups on the surface-treated silica particles was 0.053,0.825.0.792,0.908.
It changed to μmol / g.

Comparative Example 6 In the same system as in Comparative Example 1, the amount of 3-mercaptopropyltrimethoxysilane added to 1 g of silica particles was 10,100 per 1 g of silica particles without addition of tetraethoxysilane.
(Comparative Example 1) When the amount was changed to 1000 μmol, the amount of mercapto groups of the surface-treated silica particles was 0.332, 0.520, 0.558.
It changed to μmol / g.

FIG. 1 shows the results of Example 9 and Comparative Example 6 in the form of a graph. From this, it can be seen that the mercapto group on the surface of the silica particles increases as the amount of 3-mercaptopropyltrimethoxysilane added increases. The system in which the silane alkoxide compound is not added has a low mercapto group amount, which indicates that the addition of the silane alkoxide compound enhances the surface treatment effect. In the figure, SH-Pr-TMS represents 3-mercaptopropyltrimethoxysilane, and SH-group represents a mercapto group.

[Brief description of drawings]

FIG. 1 shows changes in the amount of mercapto groups on the surface of particles with respect to the amount of 3-mercaptopropyltrimethoxysilane added.

Claims (2)

[Claims] 1. When surface-treating silica particles with a silane coupling agent, the following general formula (1): (In the formula, m is an integer of 2 to 4, X is a hydroxyl group or a halogen atom, and R ¹ is an alkyl group or a phenyl group.) A silane alkoxide compound is allowed to coexist. . 2. The surface treatment method for silica particles according to claim 1, wherein hydrolysis is also performed when the surface treatment is performed.