JP2006083015A - Dispersion of silica ultrafine particles, its producing method, and resin formed article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide dispersions of silica ultrafine particles; a method for producing the same, and resin formed articles using the dispersions. <P>SOLUTION: A dispersion of silica ultrafine particles is characterized in that the silica ultrafine particles are each expressed by following rational formula (I): SiOa(OR1)b (wherein, 1.60≤a≤1.95; 0.10≤b≤0.80; 2a+b=4.0; and R1 is hydrogen atom or/and 1-6C alkyl group) and have a number average particle diameter within a range of 0.5-10 nm, and the contact angle of water on the surface of a coating film is ≤30° when it is made into the film. Further, a dispersion of silica ultrafine particles is characterized in that the silica ultrafine particles are each expressed by following rational formula (II): SiOa(OR1)b(R2)c (wherein, 1.60≤a≤1.95; 0≤b≤0.70; 0.02≤c≤0.80; 2a+b+c=4.0; R1 is a hydrogen atom or/and 1-6C alkyl group; and R2 is an organic group) and have a number average particle diameter within a range of 0.5-30 nm. The method for producing them and resin formed articles using them are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrafine silica particle dispersion, a method for producing the same, and a resin molded body using the same, and includes, for example, additives for surface treatment agents such as paints and coating agents, inorganic binders, and various resin molded bodies. The present invention relates to a silica ultrafine particle dispersion suitably used as a filler and the like, a production method thereof, and a resin molded body using the same.

  Conventionally, ultrafine particulate silica such as ultrafine anhydrous silica produced by a dry method such as a thermal decomposition method of a silicon compound, and colloidal silica produced by a wet method from water glass, etc., are resistant to contamination and weather. For the purpose of imparting functions specific to inorganic compounds such as properties, hardness, rigidity, scratch resistance, chemical resistance, heat resistance, etc., for example, as an additive to surface treatment agents such as paints and coating agents, or It is used in various fields as an inorganic binder or as a filler for various resin moldings.

  However, these ultrafine anhydrous silica and colloidal silica are mainly composed of silicon oxide as an inorganic component and have almost no reactive functional group, so that they are additives for paints and coating agents. In addition, when used as a filler or a filler for a resin molded body, the affinity of the base material for the organic compound component is not always sufficient, and the particle size is as large as several tens of nm. It was not effective.

  On the other hand, polyalkoxy obtained by partial hydrolytic condensation of tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane in order to impart affinity to the organic compound component of the base material and effectively express the intended purpose Siloxane compounds have also been proposed (see, for example, Patent Document 1 and Patent Document 2), and are also used in various fields.

However, these polyalkoxysiloxane compounds are imparted with reactivity and are likely to be gelled. For example, when stored as a paint, coating agent or the like to which the polyalkoxysiloxane compound is added, the viscosity is increased. Precipitation of solids is likely to occur, and it is difficult to say that the intended purpose can be effectively expressed like the above-mentioned ultrafine anhydrous silica and colloidal silica.
JP-A-8-27419. JP-A-9-12583.

  The present invention has been made in view of the above-mentioned present situation in ultrafine silica, etc. Therefore, the present invention can effectively express the intended purpose in applying ultrafine silica in various applications. An object is to provide a silica ultrafine particle dispersion, a method for producing the same, and a resin molded body using the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have produced a specific characteristic formula produced by a specific production method, having a particle size smaller than that of conventional silica ultrafine particles and having a reactive functional group. The inventors have found that a dispersion of ultrafine silica particles can achieve the above-mentioned object, and have reached the present invention, that is, the present invention is a dispersion of ultrafine silica particles represented by the following formula (I). A silica ultrafine particle dispersion in which the number average particle diameter of the silica ultrafine particles is in the range of 0.5 to 10 nm and the contact angle of water on the film surface when it is used as a coating film is 30 degrees or less. This is the first gist. SiO _a (OR ¹ ) _b (I)
[In the formula (I), a and b are 1.60 ≦ a ≦ 1.95, 0.10 ≦ b ≦ 0.80, 2a + b = 4.0, and R ¹ is a hydrogen atom or / and carbon. The alkyl group of number 1-6 is shown. ]

The present invention also provides a dispersion of ultrafine silica particles represented by the following formula (II), wherein the ultrafine silica particles have a number average particle size in the range of 0.5 to 30 nm. The fine particle dispersion is a second gist.
SiO _a (OR ¹ ) _b (R ² ) _c (II)
[In the formula (II), a, b and c are 1.60 ≦ a ≦ 1.95, 0 ≦ b ≦ 0.70, 0.02 ≦ c ≦ 0.80, 2a + b + c = 4.0 , R ¹ represents a hydrogen atom or / and an alkyl group having 1 to 6 carbon atoms, and R ² represents an organic group. ]

  Further, the present invention is a dispersion of ultrafine silica particles represented by the formula (II), wherein the silica ultrafine particles are represented by the formula (I) and the number average particle size is A silica ultrafine particle dispersion obtained by reacting a modifier with silica ultrafine particles in the range of 0.5 to 10 nm is a third gist.

Further, the present invention provides tetraalkoxysilane in water having a basic catalyst in a pH of 9 to 11 or in a water / alcohol mixed solution with a final concentration of 10% by weight or less in terms of SiO ₂ and the total amount within 30 minutes. The method for producing a silica ultrafine particle dispersion according to the first aspect, wherein the silica ultrafine particles represented by the above formula (I) are formed by addition and hydrolysis condensation reaction of the first aspect, The gist of

In the present invention, tetraalkoxysilane is added in water of a pH 9 to 11 containing a basic catalyst or in a water / alcohol mixed solution with a final concentration of 10% by weight or less in terms of SiO ₂ , and the total amount is within 30 minutes. Is added for a period of time of addition and hydrolysis condensation reaction is performed to form silica ultrafine particles represented by the above-mentioned formula (I), followed by addition of a silane coupling agent and reaction to the formed silica ultrafine particles. The fifth aspect of the method for producing the silica ultrafine particle dispersion according to the second or third aspect, wherein the silica ultrafine particles represented by the formula (II) are obtained.

  Furthermore, the present invention provides, as a sixth gist, a resin molded product having a coating film containing silica ultrafine particles on its surface, and a resin molded product comprising a resin containing the silica ultrafine particles, To do.

  The present invention provides a silica ultrafine particle dispersion capable of effectively expressing the intended purpose in applying ultrafine silica in various applications, a method for producing the same, and a resin molded body using the same. Can do.

The silica ultrafine particle dispersion according to the first aspect of the present invention is a dispersion of silica ultrafine particles represented by the following formula (I), wherein the number average particle diameter of the silica ultrafine particles is 0. In the range of 5 to 10 nm, the contact angle of water on the film surface when it is used as a coating film is 30 degrees or less.
SiO _a (OR ¹ ) _b (I)
[In the formula (I), a and b are 1.60 ≦ a ≦ 1.95, 0.10 ≦ b ≦ 0.80, 2a + b = 4.0, and R ¹ is a hydrogen atom or / and carbon. The alkyl group of number 1-6 is shown. ]

In the formula (I), a indicating the degree of siloxane condensation for forming silica particles must be 1.60 ≦ a ≦ 1.95, and 1.80 ≦ a ≦ 1.92. Preferably there is. When a <1.60, formation of silica particles becomes difficult and the amount of OR ¹ groups as functional groups is too large, so that it is effective as a form in which functional groups are included in the siloxane network or silica particles. Therefore, it cannot be arranged on the surface of the silica particles. Moreover, if the amount of functional groups increases, the storage stability of the dispersion also decreases. On the other hand, when a> 1.95, silica particles are formed. However, since the OR ¹ group as the functional group is reduced, the reactivity is poor, resulting in a decrease in dispersibility in the base material and a decrease in the inorganic binder function. It becomes.

  On the other hand, b indicating the functional group amount is linked to the degree of siloxane condensation a as shown by 2a + b = 4.0, and it is essential that 0.10 ≦ b ≦ 0.80, and 0.16 ≦ It is preferable that b ≦ 0.40. When b <0.10, the amount of functional groups is small, so that the reactivity is poor, resulting in a decrease in dispersibility in the base material and a decrease in the inorganic binder function. On the other hand, when b> 0.80, the silica particles are difficult to form because the functional group is included in the siloxane network or the silica particles. In addition, the storage stability of the dispersion also decreases.

R ¹ is a hydrogen atom or / and an alkyl group having 1 to 6 carbon atoms. When R ¹ is a hydrogen atom, it forms a hydrophilic silanol group (Si—OH), has self-crosslinking properties and is polar. It becomes excellent in compatibility and dispersibility with a hydrophilic base material having a group. In addition, since the silica ultrafine particle-containing coating film obtained therefrom has a silanol group, the water contact angle from the initial stage after curing is characterized by a high hydrophilicity of several degrees to 30 degrees, such as contamination resistance, scratch resistance, etc. It will be excellent. On the other hand, when R ¹ is an alkyl group, it becomes a hydrolyzable alkoxy group (—OR ¹ ), exhibits hydrophobicity, and has excellent compatibility and dispersibility with a hydrophobic base material having no polar group. It becomes. Here, as the alkyl group, an alkyl group having 1 to 6 carbon atoms as a hydrophobic alkyl group that can improve the affinity for the base material and can suppress hydrolysis of the alkoxy group residue after the crosslinking reaction. The group is appropriately selected from the group, and a methyl group and an ethyl group are particularly preferable because of high reactivity.

In the above formula (I), the a indicating the degree of siloxane condensation is determined by ²⁹ Si-NMR analysis under the following conditions.
Measuring device: JEOL nuclear magnetic resonance apparatus “AL-400”
Measurement mode: Non-decoupling (NNE)
Measurement temperature: 25 ° C
Pulse width: 18.0 μs
Data capture time: 2.245s
Wait time: 5.750 s
Observation frequency: 78.5 MHz
Accumulation count: 800 times Reference material: tetramethylsilane Diluent: heavy acetone Relaxant: Cr (acac) ₃
When the measurement is performed under the above conditions, the information regarding the siloxane bond of the tetraalkoxysilane gives peaks of 5 groups of Q0 to Q4 from about -75 ppm to -130 ppm. From these peak area ratios, the degree of siloxane formation of silicon atoms can be known, and in the present invention, this value is defined as the degree of siloxane condensation a in the above formula (I).

In the above formula (I), b indicating the functional group amount is determined by ¹ H-NMR analysis or ¹³ C-NMR analysis under the following conditions. However, since direct quantification is not possible when R ¹ is a hydrogen atom, it was confirmed by ¹³ C-NMR that no methoxy group was present, and the degree of siloxane condensation a was determined from the relationship of 2a + b = 4.
¹ H-NMR measurement conditions Measuring apparatus: JEOL nuclear magnetic resonance apparatus “AL-400”
Measurement temperature: 23-26 ° C
Pulse width: 4.8 μs
Data capture time: 2.04s
Wait time: 4.95s
Observation frequency: 400 MHz
Accumulation count: 32 times Reference substance: Tetramethylsilane Diluent solvent: Heavy water Relaxant: None When measured under the above conditions, a peak derived from methanol is observed at 3.3 ppm, and a peak due to methoxy is observed at 3.4 ppm.

¹³ C-NMR measurement conditions Measuring apparatus: JEOL nuclear magnetic resonance apparatus “AL-400”
Measurement mode: Non-decoupling (NNE)
Measurement temperature: 23-26 ° C
Pulse width: 3.3 μs
Data acquisition time: 2.62s
Wait time: 27.4s
Observation frequency: 99.45MHz
Cumulative number: 2048 times Reference substance: dioxane Diluent solvent: heavy water Relaxant: none When measured under the above conditions, a peak derived from methanol is observed at 49.5 ppm, and a peak derived from methoxy group is observed at 51 ppm.

  The ultrafine silica particle in the ultrafine silica particle dispersion according to the first aspect of the present invention has a sodium component content of usually 10 ppm or less, preferably 1 ppm or less, and does not substantially contain a sodium component. It is.

  In addition, the silica ultrafine particle dispersion according to the first aspect of the present invention has a number average particle diameter of silica ultrafine particles in the range of 0.5 to 10 nm. Conventional colloidal silica, organosols, etc. have an average particle diameter of several tens of nanometers to several hundreds of nanometers and are translucent or milky white liquid dispersed in water, alcohol or organic solvent. The silica ultrafine particle dispersion is a silica ultrafine particle having a reactive functional group as described above having a smaller particle size and a number average particle size in the range of 0.1 to 10 nm. In addition to being colorless and transparent, the intended purpose of imparting a function specific to an inorganic compound can be sufficiently achieved.

  In addition, the said number average particle diameter of a silica ultrafine particle is the measurement data of 90 degree | times scattering intensity using Ar laser by "Photo-DLS-7000" by Otsuka Electronics Co., Ltd. here by a dynamic light scattering method. Was obtained by fitting using a cumulant analysis method.

  And the silica ultrafine particle dispersion as the first gist of the present invention has a water surface contact angle of 30 degrees or less as a coating film, preferably 20 degrees or less, It is particularly preferably 15 degrees or less. With this water contact angle, the silica ultrafine particle dispersion of the present invention can sufficiently achieve the intended purpose of imparting a function specific to an inorganic compound.

  Here, the contact angle of water on the film surface is determined by dipping the slide glass with a silica ultrafine particle dispersion at a pulling rate of 2 mm / second, drying at room temperature, and then heat-curing in an oven at 150 ° C. for 1 hour. The contact angle when a water droplet having a diameter of 2 mm was dropped on the surface of the coating film formed by using a microscopic contact angle meter (“CA-QI type” manufactured by Kyowa Interface Science Co., Ltd.) was measured.

  The silica ultrafine particle dispersion according to the first gist of the present invention has a viscosity at 25 ° C. of usually 1 to 100 mPa as a value measured with an E-type viscometer (“DV-1” manufactured by Brookfield).・ It is of sec.

The silica ultrafine particle dispersion according to the second aspect of the present invention is an aqueous dispersion of silica ultrafine particles represented by the following formula (II), wherein the number average particle size of the silica ultrafine particles is The diameter is in the range of 0.5 to 30 nm.
SiO _a (OR ¹ ) _b (R ² ) _c (II)
[In the formula (II), a, b and c are 1.60 ≦ a ≦ 1.95, 0 ≦ b ≦ 0.70, 0.02 ≦ c ≦ 0.80, 2a + b + c = 4.0 , R ¹ represents a hydrogen atom or / and an alkyl group having 1 to 6 carbon atoms, and R ² represents an organic group. ]

In the formula (II), a indicating the degree of siloxane condensation for forming silica particles is essential to be 1.60 ≦ a ≦ 1.95 as in the formula (I). And 1.80 ≦ a ≦ 1.92 is preferable. When a <1.60, formation of silica particles becomes difficult, and the amount of OR ¹ groups or / and organic groups R ² as functional groups becomes too large. Therefore, it becomes a form including an organic group and cannot be effectively arranged on the surface of the silica particles. On the other hand, when a> 1.95, silica particles are formed. However, since the amount of OR ¹ group or / and organic group R ² as a functional group is small, the reactivity is poor, and the dispersibility to the base material is reduced. The inorganic binder function will be reduced.

  On the other hand, b indicating the functional group amount and c indicating the organic group amount are linked to the siloxane condensation degree a as indicated by 2a + b + c = 4.0, and 0 ≦ b ≦ 0.70 and 0.02 It is essential that ≦ c ≦ 0.80. Here, since 2a + b + c = 4.0 and 1.60 ≦ a ≦ 1.95, 0.02 ≦ b + c ≦ 0.80 and 0.04 ≦ b + c ≦ 0.40. Is preferred. When b + c <0.02, the reactivity is poor due to the small amount of functional groups, or the compatibility with the hydrophobic base material and the dispersibility are lowered due to the small amount of organic groups. On the other hand, when b + c> 0.80 and b is too large, it becomes difficult to form silica particles because the functional groups or / and organic groups are included in the siloxane network or silica particles, and c is large. When the amount is too large, since there are many non-hydrolyzable organic groups, the formation of siloxane is inhibited and the formation of silica particles becomes difficult.

R ¹ is the same as in the formula (I), and examples of the organic group R ² include an alkyl group such as a methyl group and an ethyl group; an aryl group such as a phenyl group; and a vinyl group. Unsaturated hydrocarbon groups such as allyl groups; (meth) acryloyloxyalkyl groups such as (meth) acryloyloxypropyl groups; glycidyloxyalkyl groups such as glycidyloxypropyl groups; aminoalkyl groups such as aminopropyl groups; mercaptopropyl A mercaptoalkyl group such as a group; a haloalkyl group such as a chloropropyl group; and the like, among which a vinyl group, a glycidyloxyalkyl group, an aminoalkyl group and the like are particularly preferable.

In the formula (II), the a indicating the degree of siloxane condensation is the same as in the formula (I) by ²⁹ Si-NMR analysis, and b indicating the functional group amount, and Said c which shows the amount of organic groups was calculated | required by the < ¹ > H-NMR analysis method or the < ¹³ > C-NMR analysis method similarly to said characteristic formula (I), respectively. However, depending on the type of R ² , if it is not soluble in heavy water as a deuterated solvent, it is necessary to appropriately select heavy methanol, heavy acetone, or the like.

  The ultrafine silica particles in the ultrafine silica particle dispersion according to the second aspect of the present invention also have a sodium component content of usually 10 ppm or less, preferably 1 ppm or less, and substantially no sodium component. It is.

  In addition, the silica ultrafine particle dispersion according to the second aspect of the present invention is one in which the number average particle diameter of the silica ultrafine particles is in the range of 0.5 to 30 nm. Conventional colloidal silica, organosols, etc. have an average particle diameter of several tens of nanometers to several hundreds of nanometers and are translucent or milky white liquid dispersed in water, alcohol or organic solvent. In the silica ultrafine particle dispersion, the silica ultrafine particles having a reactive functional group and / or an organic group as described above have a particle size smaller than those and a number average particle size in the range of 0.1 to 30 nm. In addition, the dispersion is colorless and transparent and can sufficiently achieve the intended purpose of imparting a function specific to the inorganic compound.

In addition, the silica ultrafine particle dispersion according to the second gist of the present invention has a contact angle of water on the surface of the film when it is used as a coating film, depending on the type of the organic group R ^2. For example, when R ² is a methyl group or an ethyl group, it is preferably 40 degrees or less, more preferably 30 degrees or less. Depending on the selection of the organic group R ² , the intended purpose of imparting a function specific to an inorganic compound may be achieved. It can be fully achieved.

In the silica ultrafine particle dispersion according to the first aspect of the present invention, the final concentration of tetraalkoxysilane is 10% by weight in terms of SiO _{2 in} water or a water / alcohol mixture having a basic catalyst and a pH of 9 to 11. The following amount can be produced by a method in which the total amount is added within an addition time of 30 minutes or less and hydrolytic condensation reaction is performed to form ultrafine particles of silica represented by the above-mentioned formula (I). .

  Here, as the tetraalkoxysilane used as a raw material, those having 1 to 6 carbon atoms of the alkoxy group are usually used, but the hydrolysis reactivity and condensation reactivity of the alkoxysilane are generally the number of carbon atoms of the alkoxy group. Therefore, the number of carbon atoms in the alkoxy group is preferably small, and tetramethoxysilane and tetraethoxysilane are preferred, and the most reactive among the alkoxysilanes. Tetramethoxysilane having high properties is particularly preferable.

  As the basic catalyst, any water-soluble basic compound can be used. For example, inorganic hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide; ammonia; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, Amines such as diisopropylamine and n-butylamine; ethanolamines such as monoethanolamine, diethanolamine and triethanolamine; N, N-dimethylethanolamine, N, N-diethylethanolamine, N-methylethanolamine, N- Amino alcohols such as methyldiethanolamine; other organic compounds having an amino group such as pyridine, polyvinylamine, polyallylamine; γ-aminopropyltriethoxysilane, N Silicon compounds having an amino group such as β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, etc. Can be mentioned. These basic catalysts are appropriately selected from the viewpoints of the particle size, particle size distribution, and amount of functional groups of the silica ultrafine particles in the silica ultrafine particle dispersion of the present invention.

  As the reaction solvent, water or a water / alcohol mixed solution is used. These solvents are appropriately selected from the viewpoints of particle size, particle size distribution, type of functional group, and the like of the silica ultrafine particles in the silica ultrafine particle dispersion of the present invention. When water is used as the solvent, the hydrolysis and condensation reaction of the raw material tetraalkoxysilane is the fastest, and it becomes easy to obtain silica particles having a smaller particle diameter. In this case, the alcohol concentration in the reaction solution is only the alcohol content generated by hydrolysis of the raw material tetraalkoxysilane. On the other hand, in the case of a water / alcohol mixed solution, it is sufficient that the raw material tetraalkoxysilane and water are compatible with each other, and the alcohol has a carbon number that does not inhibit the hydrolysis condensation reaction for the purpose of obtaining ultrafine silica particles. A lower alcohol with a small amount is preferable, and examples thereof include methanol, ethanol, n-propyl alcohol, and isopropyl alcohol. The selection of these alcohols and the alcohol concentration in the water / alcohol mixture are appropriately selected from the viewpoints of the particle size, particle size distribution, type of functional groups, etc. of the silica ultrafine particles in the silica ultrafine particle dispersion of the present invention.

In addition, the hydrolysis and condensation reaction of the raw material tetraalkoxysilane needs to be performed in a reaction solvent containing a basic catalyst in a pH range of 9 to 11 in the reaction solvent. At that time, the basic catalyst is used after being dissolved in water or a water / alcohol mixture of the reaction solvent, and the amount used is determined by the degree of basicity (pK _b ) of the catalyst and the pH of the reaction solvent. In the range of 9-11.

  In the hydrolysis condensation reaction of the raw material tetraalkoxysilane described above, the particle size and particle size distribution of the silica ultrafine particles in the obtained silica ultrafine particle dispersion are the type of raw material tetraalkoxysilane, the type and amount of basic catalyst, Depending on the type of reaction solvent, etc., under conditions where the hydrolysis and condensation reaction of the raw material tetraalkoxysilane is fast, it is easy to become a silica ultrafine particle having a small particle size and a sharp particle size distribution within the range of the number average particle size. In the range of the number average particle diameter, it becomes easy to become a silica ultrafine particle having a large particle diameter and a broad particle size distribution.

  And the manufacturing method of the silica ultrafine particle dispersion of the present invention is as follows. The raw material tetraalkoxysilane is added to water or water / alcohol mixed solution of pH 9-11 containing a basic catalyst within 30 minutes. It is essential to add. When the addition time exceeds 30 minutes, the average particle diameter of the obtained silica ultrafine particles exceeds the above range and the particle size distribution becomes broad. In this case, the raw material tetraalkoxysilane is added within 30 minutes, and the whole amount can be divided at a time, even if the whole amount is added all at once or a small amount is added continuously. May be added. In order to sharpen the particle size distribution of the obtained ultrafine silica particles, it is preferable to add in small portions, and from the viewpoint of productivity, it is preferable to add all at once.

The addition amount of the raw material tetraalkoxysilane must be such that the final concentration is 10% by weight or less in terms of SiO ₂ at the end of the reaction. If the concentration exceeds this, the particle size of the resulting silica ultrafine particles becomes large and the particle size distribution becomes broad.

  Moreover, the reaction temperature at the time of addition of raw material tetraalkoxysilane will not be specifically limited if it is the range of 0-100 degreeC. Within this range, if the temperature is low, the hydrolytic condensation reaction will be slow, so the particle size of the ultrafine silica particles will be large, and if the temperature is high, the reaction will be fast and the particle size will be small. What is necessary is just to select suitably from the surface of the particle size and particle size distribution of a silica ultrafine particle. In addition, the reaction time is about 20 ° C. at ΔT due to the heat of hydrolysis reaction with the addition of the raw material tetraalkoxysilane, but gradually decreases with the end of the reaction. The reaction time is sufficient if the time to return to the temperature is taken. From this, as reaction time, 1-2 hours are enough from the start of addition of raw material tetraalkoxysilane.

  The silica ultrafine particle dispersion liquid according to the second aspect of the present invention and the silica ultrafine particle dispersion liquid according to the third aspect are the same as the production method of the silica ultrafine particle dispersion liquid according to the first aspect. Subsequently, a modifier is added to the obtained silica ultrafine particle dispersion, and the resulting silica is reacted with the ultrafine silica particles represented by the formula (I) formed by the production method. It can be produced by using ultrafine silica particles represented by II).

  Here, the silica ultrafine particles represented by the formula (I) are reacted with a modifier to form the ultrafine silica particles represented by the formula (II). This partially sacrifices the reactivity, hydrophilicity, etc. of the silica ultrafine particles represented by the above formula (I), while improving the compatibility, dispersibility, etc. with respect to the hydrophobic matrix as silica ultrafine particles. In addition, in the case of replacing the solvent as the dispersion, gelation hardly occurs, and it can be easily replaced with a hydrophobic solvent.

As the modifier used in that case, a siloxane bond can be formed by a condensation reaction with the OR ¹ group in the above-mentioned formula (I), and the organic group R ² in the above-mentioned formula (II) For example, represented by the general formula R ² _n SiX _4-n (where R ² represents an organic group, X represents a hydrolyzable group, and n is an integer of 1 to 3). A typical example is a silane coupling agent. Specific examples of the silane coupling agent include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, triphenylmonomethoxysilane, vinyltrimethoxysilane, and vinyl. Triethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 2 -(3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3-aminopropyl Limethoxysilane, 3-aminopropyltriethoxysilane, 3- [N- (2-aminoethyl) amino] propyltrimethoxysilane, 3- [N- (2-aminoethyl) amino] propyltriethoxysilane, 3- [N- (2-aminoethyl) amino] propylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and the like, and N-glycidyl-N, N-bis [3- (trimethoxysilyl) propyl] amine, N-glycidyl-N, N-bis [3- (triethoxysilyl) propyl] amine, N-glycidyl-N, N -Bis [3- (methyldimethoxysilyl) propyl] amine, N-glycidyl -N, N-bis [3- (methyl-diethoxy silyl) propyl] amine. In addition, resins having a hydrolyzable silyl group such as acrylic resin, epoxy resin, polyester resin, urethane resin, silicon resin, fluorine resin and the like can also be mentioned.

The addition amount of the modifying agent is the upper limit of the maximum amount that can modify the ultrafine silica particle surface represented by the above-mentioned formula (I) with R ² having the modifying agent. The amount, or the amount that does not produce the modifier self-condensate, is the upper limit of use. However, the addition amount of the modifier should be determined in consideration of the compatibility and dispersibility of the ultrafine silica particles represented by the formula (II) with respect to the intended base material.

Further, the temperature and time of the modification reaction by addition of the modifier may be any conditions as long as the condensation reaction between the hydrolyzable group possessed by the modifier and the surface functional group OR ¹ of the silica ultrafine particles is completed. In order to accelerate the reaction within the range of -100 ° C, it is possible to heat, and a reaction time of 1-2 hours is sufficient.

The silica ultrafine particle dispersion according to the first aspect of the present invention produced by the method described above, the silica ultrafine particle dispersion according to the second aspect, and the silica superfine particle according to the third aspect of the present invention. The fine particle dispersion can be further changed in form as a dispersion by, for example, being subjected to the following post-treatment process.
(1) Dispersion concentration step The solvent component of the water or water / alcohol mixture in the silica ultrafine particle dispersion produced by the above-described method is concentrated by distilling it out of the system by heating or decompression. And a step of making the silica concentration higher than that.
(2) Basic catalyst neutralization or removal step The basic catalyst residue in the silica ultrafine particle dispersion produced by the method described above is neutralized with acid to pH 6-9, or more than water. After synthesizing ultrafine silica particles using a basic catalyst having a low boiling point, the basic catalyst is removed from the system by heating above the boiling point of the basic catalyst, or a cation exchange resin (H type), etc. Removing the basic catalyst out of the system using
(3) Solvent removal or replacement step The alcohol solvent in the silica ultrafine particle dispersion produced by the method described above is removed out of the system by heating above the boiling point of the alcohol, or by evaporation under reduced pressure, or Adding a new solvent component that can be replaced with a solvent, and removing the solvent originally used by heating or evaporation under reduced pressure to replace the solvent.

The silica ultrafine particle dispersion according to the first aspect of the present invention described above, the silica ultrafine particle dispersion according to the second aspect, and the silica ultrafine particle dispersion according to the third aspect are added to a paint, for example. In addition, it is suitably used as an additive for imparting stain resistance, weather resistance, scratch resistance, water resistance, chemical resistance, heat resistance, adhesion to a substrate, and the like to the coating film. In this case, the paint is used for water-based paints such as water-soluble resin paints, water-dispersed resin paints, and water-based emulsion resin paints, and may be either a room temperature drying type or a baking drying type. Further, as the resin, pigment, solvent and the like in the paint used, conventionally known ones are used, and the addition amount of the silica ultrafine particle dispersion of the present invention is 100 parts by weight of the non-volatile content of the paint. is preferably 1 to 100 parts by weight in terms of SiO _2, particularly preferably 2 to 50 parts by weight.

The silica ultrafine particle dispersion according to the first aspect of the present invention, the silica ultrafine particle dispersion according to the second aspect, and the silica ultrafine particle dispersion according to the third aspect are, for example, a coating material, a representative Specifically, it is added to a top coat resin material of a sizing material as a building material for an outer wall, and is suitably used as an additive for imparting stain resistance, scratch resistance, weather resistance, adhesion and the like to the coating film. As the resin in the coating material used at that time, a conventionally known resin is used, and the addition amount of the silica ultrafine particle dispersion of the present invention is SiO ₂ equivalent to 100 parts by weight of the non-volatile content of the coating material. 1 to 100 parts by weight is preferable, and 2 to 30 parts by weight is particularly preferable.

  The silica ultrafine particle dispersion according to the first aspect of the present invention, the silica ultrafine particle dispersion according to the second aspect, and the silica ultrafine particle dispersion according to the third aspect are prepared by silanol in the presence of water. A cross-linked structure can be formed by a condensation reaction. For example, coating for forming various function-imparting agent layers for the purpose of imparting various functions to various base materials such as resin, glass, metal, and existing coating films. By being used as an inorganic binder in the agent, it can be cured at room temperature or under heating, and can impart heat resistance, weather resistance, stain resistance, chemical resistance, water resistance, adhesion, etc. to the function-imparting layer. Are preferably used.

  The silica ultrafine particle dispersion according to the first aspect of the present invention, the silica ultrafine particle dispersion according to the second aspect, and the silica ultrafine particle dispersion according to the third aspect are filled in various resin moldings. It is also suitably used as a material. For example, it can be used as a surface treatment agent in using various conventionally known fillers after surface treatment with the silica ultrafine particle dispersion of the present invention, or as a filler together with various conventionally known fillers. The amount used is preferably 1 to 100 parts by weight, particularly preferably 2 to 50 parts by weight with respect to 100 parts by weight of the filler when used as a surface treatment agent for various fillers. When used as a material, the amount is preferably 1 to 100 parts by weight, particularly preferably 2 to 50 parts by weight with respect to 100 parts by weight of the resin.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
To a 1 L jacketed separable flask equipped with a stirrer and a condenser, 835.9 g of water and 12.2 g of monoethanolamine as a basic catalyst were added and mixed. The pH of this solution was 10.5. Cooling water adjusted to 25 ° C. was passed through the jacket. When the temperature of the water and monoethanolamine mixed solution in the jacket reached 25 ° C. ± 1 ° C., 152 minutes of tetramethoxysilane (Na component content: 3 ppb as Na atom) was stirred over 2 minutes 30 seconds. It was dripped at. Initially, the whole became cloudy but soon became transparent. When all the tetramethoxysilane was added dropwise, the liquid temperature rose temporarily to about 45 ° C. Stirring was continued for 1 hour while maintaining the jacket temperature at 25 ° C., and then the reaction solution was filtered through a 150-mesh nylon filter to obtain a colorless and transparent ultrafine silica particle dispersion “A-0”.

The concentration of the silica ultrafine particles in the obtained silica ultrafine particle dispersion “A-0” A was 6% by weight in terms of SiO ₂ , and the viscosity of the dispersion was 2.9 mPa · s at 25 ° C. . In addition, the number average particle diameter obtained by the dynamic light scattering method under the above-mentioned conditions is 1.1 nm, and the characteristic formula is obtained by ²⁹ Si-NMR analysis method and ¹³ C-NMR analysis method under the above-mentioned conditions. , SiO _1.83 (OH) _0.34 was confirmed. Using this dispersion, the slide glass was dipped at a pulling rate of 2 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to obtain a transparent film. The water contact angle was determined to be 5 degrees.

Furthermore, as an index of the adhesion of the coating film to the glass substrate, cellophane tape is attached to the coating film surface according to JIS Z1522, and the tape is adhered by rubbing with an eraser (JIS S6050). After observing the peeling state of the coating film when holding the tape one side at a time and peeling it off at a stroke, the coating film peels off from the glass substrate only when the tape remains on the coating surface. The adhesion of the coating film to the glass substrate was very good. In addition, as an indicator of solvent resistance, the appearance after rubbing the coating film 100 times with a load of 500 g / cm ² using absorbent cotton impregnated with xylene was visually observed. I couldn't see it. Furthermore, when the appearance after the coating film was immersed in boiling water for 1 hour was visually observed as an index of boiling water resistance, no particular change was found in the coating film.

Example 2
A silica ultrafine particle dispersion “B-0” was obtained in the same manner as in Example 1 except that 12.2 g of monoethanolamine as a basic catalyst was changed to 12.1 g of 20% ammonia. The concentration of the ultrafine silica particles in the obtained ultrafine silica particle dispersion “B-0” was 6% by weight in terms of SiO ₂ , and the viscosity of the dispersion was 2.9 mPa · s at 25 ° C. The number average particle diameter determined by the dynamic light scattering method under the above-mentioned conditions is 1.0 nm, and the formula obtained by the ²⁹ Si-NMR analysis method and ¹³ C-NMR analysis method under the above-mentioned conditions is It was SiO _1.83 (OH) _0.34 . Further, the water contact angle of the coating film surface obtained in the same manner was 5 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was performed in the same manner as in Example 1. As the tape paste remained on the coating film surface, peeling of the coating film from the glass substrate was not recognized, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 3
To 200 g of the silica ultrafine particle dispersion “A-0” obtained in Example 1, 2.56 g of a 50 wt% methanol solution of vinyltrimethoxysilane (“S210” manufactured by Chisso) as a modifier is taken over 1 minute. The solution was dropped intermittently with stirring. Cooling water adjusted to 25 ° C. was continuously passed through the jacket and stirred for 1 hour, and then the reaction solution was filtered through a 150-mesh nylon filter to obtain an ultrafine silica particle dispersion “A-1”.

In the obtained silica ultrafine particle dispersion “A-1”, the concentration of silica ultrafine particles having a number average particle size in the range of 0.5 to 30 nm is 6.2% by weight in terms of SiO _2. The viscosity of the liquid was 3.1 mPa · s at 25 ° C. The characteristic formula obtained by ²⁹ Si-NMR analysis method and ¹³ C-NMR analysis method under the above-mentioned conditions was SiO _1.85 (OH) _0.25 (C = C) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle of this coating film surface was determined to be 33 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

  Separately, 1.5 g of vinyltrimethoxysilane (“KBM1003” manufactured by Shin-Etsu Chemical Co., Ltd.) as a modifier was added to 90 g of the ultrafine silica particle dispersion “A-0” obtained in Example 1, and then 1 at room temperature. After standing for a day, it was concentrated with an evaporator under conditions of a temperature of 40 ° C. and a degree of vacuum of 20 Torr. Finally, 35 g of a fine milky white liquid concentrate of silica ultrafine particle dispersion (concentration ratio 2.6 times) could be obtained.

Example 4
Example 3 except that 2.56 g of a 50 wt% methanol solution of vinyltrimethoxysilane as a modifier was changed to 4.72 g of γ-glycidyloxypropyltrimethoxysilane (“A187” manufactured by Nihon Unicar). Thus, a silica ultrafine particle dispersion “A-2” was obtained. In the obtained silica ultrafine particle dispersion “A-2”, the concentration of silica ultrafine particles having a number average particle size in the range of 0.5 to 30 nm is 6.2% by weight in terms of SiO _2. The viscosity of the liquid was 3.2 mPa · s at 25 ° C. In addition, the formula for the production obtained by ²⁹ Si-NMR analysis and ¹³ C-NMR analysis under the above-mentioned conditions was SiO _1.85 (OH) _0.25 (γ-glycidyloxypropyl) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle on the surface of the coating film was determined to be 22 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 5
Silica in the same manner as in Example 3 except that 2.56 g of a 50 wt% methanol solution of vinyltrimethoxysilane as a modifier was changed to 4.42 g of aminopropyltriethoxysilane (“A1100” manufactured by Nihon Unicar). An ultrafine particle dispersion “A-3” was obtained. In the obtained silica ultrafine particle dispersion “A-3”, the concentration of the silica ultrafine particles having a number average particle diameter in the range of 0.5 to 30 nm is 6.5% by weight in terms of SiO _2. The viscosity of the liquid was 88.2 mPa · s at 25 ° C. In addition, the formula for production obtained by ²⁹ Si-NMR analysis and ¹³ C-NMR analysis under the above-described conditions was SiO _1.85 (OH) _0.25 (C ₃ H ₆ NH ₂ ) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle on the surface of the coating film was determined to be 6 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 6
The silica ultrafine particle dispersion “B-” was changed in the same manner as in Example 3 except that the silica ultrafine particle dispersion “A-0” was changed to the silica ultrafine particle dispersion “B-0” obtained in Example 2. 1 "was obtained. In the obtained silica ultrafine particle dispersion “B-1”, the concentration of ultrafine silica particles having a number average particle diameter in the range of 0.5 to 30 nm is 6.2% by weight in terms of SiO _2. The viscosity of the liquid was 3.2 mPa · s at 25 ° C. In addition, the formula for production obtained by ²⁹ Si-NMR analysis and ¹³ C-NMR analysis under the above-mentioned conditions was SiO _1.85 (OH) _0.25 (C = C) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle on the surface of this coating film was determined to be 32 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 7
Example 6 except that 2.56 g of a 50 wt% methanol solution of vinyltrimethoxysilane as a modifying agent was changed to 4.72 g of γ-glycidyloxypropyltrimethoxysilane (“A187” manufactured by Nihon Unicar). Thus, a silica ultrafine particle dispersion “B-2” was obtained. In the obtained silica ultrafine particle dispersion “B-2”, the concentration of ultrafine silica particles having a number average particle size in the range of 0.5 to 30 nm is 6.2% by weight in terms of SiO _2. The viscosity of the liquid was 3.2 mPa · s at 25 ° C. The characteristic formula obtained by ²⁹ Si-NMR analysis and ¹³ C-NMR analysis under the above-mentioned conditions was SiO _1.85 (OH) _0.25 (γ-glycidyloxypropyl) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle on the surface of the coating film was determined to be 20 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 8
Silica in the same manner as in Example 6 except that 2.56 g of a 50 wt% methanol solution of vinyltrimethoxysilane as a modifying agent was changed to 4.42 g of aminopropyltriethoxysilane (“A1100” manufactured by Nihon Unicar). An ultrafine particle dispersion “B-3” was obtained. In the obtained silica ultrafine particle dispersion “B-3”, the concentration of ultrafine silica particles having a number average particle diameter in the range of 0.5 to 30 nm is 6.5% by weight in terms of SiO ₂ , and the dispersion The viscosity of the liquid was 89 mPa · s at 25 ° C. The characteristic formula obtained by ²⁹ Si-NMR analysis and ¹³ C-NMR analysis under the above-mentioned conditions was SiO _1.85 (OH) _0.25 (C ₃ H ₆ NH ₂ ) _0.05 . The dispersion is diluted twice with ion-exchanged water, then the slide glass is dipped at a pulling rate of 3 mm / sec, dried at room temperature, and then cured in an oven at 150 ° C. for 1 hour to form a transparent film. The water contact angle of this coating film surface was determined to be 7 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Example 9
Cooling water adjusted to 45 ° C. was passed through the jacket, tetramethoxysilane was dropped when the temperature of the water in the jacket and the monoethanolamine mixed solution reached 45 ± 1 ° C., and the jacket temperature was 45 A silica ultrafine particle dispersion “C-0” was obtained in the same manner as in Example 1 except that the reaction was continued for 1 hour while maintaining the temperature. The concentration of the ultrafine silica particles in the obtained ultrafine silica particle dispersion “C-0” was 6% by weight in terms of SiO ₂ , and the viscosity of the dispersion was 2.2 mPa · s at 25 ° C. The number average particle diameter determined by the dynamic light scattering method under the above-mentioned conditions is 1.1 nm, and the formula obtained by the ²⁹ Si-NMR analysis method and ¹³ C-NMR analysis method under the above-mentioned conditions is It was SiO _1.83 (OH) _0.34 . Further, the water contact angle of the coating film surface obtained in the same manner was 8 degrees.

  Furthermore, for the obtained coating film, a cellophane tape peel test was conducted in the same manner as in Example 1. As the tape paste remained on the coating film surface, no peeling of the coating film from the glass substrate was observed, The adhesion of the coating film to the glass substrate was very good. Further, when the solvent resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film. Furthermore, when the boiling water resistance was evaluated in the same manner as in Example 1, no particular change was observed in the coating film.

Comparative Example 1
Commercially available colloidal silica (“Cataloid SI-30” manufactured by Catalyst Kasei Kogyo Co., Ltd., appearance is translucent) is diluted with ion-exchanged water so that the silica concentration becomes 6% by weight. When the number average particle diameter was determined by fitting the measurement data obtained by the dynamic light scattering method using the human sgram analysis method, it was 5.2 nm, and the presence of particles of 3.5 nm or less could not be confirmed. Further, the water contact angle of the coating film surface obtained in the same manner as described above was 50 degrees.

Comparative Example 2
Commercially available colloidal silica (“Cataloid SI-40” manufactured by Catalyst Kasei Kogyo Co., Ltd., appearance is translucent) is diluted with ion-exchanged water so that the silica concentration becomes 6% by weight. The number average particle diameter was determined by fitting the measurement data obtained by the dynamic light scattering method using the human sgram analysis method, which was 10.1 nm, and the presence of particles of 6.6 nm or less could not be confirmed. Further, the water contact angle of the coating film surface obtained in the same manner as described above was 55 degrees.

  The silica ultrafine particle dispersion according to the first aspect of the present invention and the silica ultrafine particle dispersion according to the second aspect include additives for surface treatment agents such as paints and coating agents, inorganic binders, and various resins. By using it as a filler for moldings, etc., it is possible to impart functions specific to inorganic compounds such as contamination resistance, weather resistance, hardness, rigidity, scratch resistance, chemical resistance, and heat resistance to the base material for those uses. Can be effectively expressed, and application as nanoparticulate silica in these fields can be expected.

Claims (8)

A dispersion of ultrafine silica particles represented by the following formula (I), wherein the number average particle diameter of the ultrafine silica particles is in the range of 0.5 to 10 nm, and a coating film is obtained. A silica ultrafine particle dispersion having a water contact angle of 30 degrees or less on the surface of the film.
SiO _a (OR ¹ ) _b (I)
[In the formula (I), a and b are 1.60 ≦ a ≦ 1.95, 0.10 ≦ b ≦ 0.80, 2a + b = 4.0, and R ¹ is a hydrogen atom or / and carbon. The alkyl group of number 1-6 is shown. ] A dispersion of ultrafine silica particles represented by the following formula (II), wherein the number average particle diameter of the ultrafine silica particles is in the range of 0.5 to 30 nm. Dispersion.
SiO _a (OR ¹ ) _b (R ² ) _c (II)
[In the formula (II), a, b and c are 1.60 ≦ a ≦ 1.95, 0 ≦ b ≦ 0.70, 0.02 ≦ c ≦ 0.80, 2a + b + c = 4.0 , R ¹ represents a hydrogen atom or / and an alkyl group having 1 to 6 carbon atoms, and R ² represents an organic group. ]   A dispersion of ultrafine silica particles represented by the formula (II), wherein the ultrafine silica particles are represented by the formula (I) and have a number average particle size of 0.5 to 10 nm. A silica ultrafine particle dispersion obtained by reacting a modifier with silica ultrafine particles in the range.   The silica ultrafine particle dispersion according to any one of claims 1 to 3, wherein the silica contains substantially no sodium component. The tetraalkoxysilane, in an amount final concentration of 10 wt% or less in terms of SiO ₂ in water or a water / alcohol mixture of pH9~11 containing basic catalyst, the total amount was added at addition time of 30 minutes 5. The method for producing a silica ultrafine particle dispersion according to claim 1, wherein the silica ultrafine particles represented by the formula (I) are formed by hydrolysis and condensation reaction. 5. The tetraalkoxysilane, in an amount final concentration of 10 wt% or less in terms of SiO ₂ in water or a water / alcohol mixture of pH9~11 containing basic catalyst, the total amount was added at addition time of 30 minutes Then, a hydrolytic condensation reaction is performed to form ultrafine particles of silica represented by the above-mentioned formula (I), a modifier is subsequently added, and the resulting ultrafine particles of silica are reacted to form the aforementioned formula (II). 5. The method for producing a silica ultrafine particle dispersion according to claim 2, wherein the silica ultrafine particles are represented by the following formula.   A resin molded article having a coating film containing the ultrafine silica particles according to claim 1 on the surface.   A resin molded body comprising a resin containing the ultrafine silica particles according to any one of claims 1 to 4.