KR20130051229A - Method for preparing titania microspheres with high refractive index - Google Patents

Abstract

PURPOSE: A manufacturing method of high refractivity titania fine particle is provided to effectively manufacture titania fine particle of high refractivity as crystallization without deformation of particle shape of sphere by performing thermal process after forming a shell on the surface of amorphous titania particle. CONSTITUTION: A manufacturing method of high refractivity titania fine particle comprises the following steps. (a) The amorphous titania particle including organic amine is prepared. (b) A particle of core-shell structure is formed by forming a shell on the surface of amorphous titania particle including organic amine. (c) The particle of core-shell structure is heat-treated. And (d) the shell of the heat-treated is removed. The amorphous titania particle is manufactured by using sol-gel method. The organic amine is selected more than one from propylamine, butylamine, dodecylamine, hexadecylamine, aniline and pyridine. The forming step of particle of the core shell structure and the shell is silica shell or polymer shell.

Description

Method for preparing titania microparticles {Method for preparing titania microspheres with high refractive index}

The present invention relates to a method for producing high refractive index titania microparticles. More particularly, the present invention relates to a method for producing crystalline high refractive index titania microparticles without deformation in spherical particle shape.

Titania (TiO ₂ ) depends on the crystalline phase but has a high refractive index in the absence of absorption in the visible light region. Having a refractive index of about 2.3 on anatase has a high refractive index of about 2.7 on rutile. Such high refractive index materials can be used as source materials such as paints and various optical films as light scattering phenomenon becomes prominent when manufactured in particle form.

Titania microparticles of more than 100 nanometers (nm) and several micrometers (μm), in which light scattering occurs particularly strongly, have been prepared by the sol-gel method in various literatures such as (1) to (4) below. It has been reported.

(1) Yuchuan Cheng, Jianjun Guo, Xuehui Liu, Aihua Sun, GaojieXu, Ping Cui, Journal of Materials Chemistry, 2011, 21, 5051,

(2) Hyung Kyun Yu, Gi-Ra Yi, Ji-Hwan Kang, Young-Sang Cho, Vinothan N. Manoharan, David J. Pine, Seung-Man Yang, Chem. Mater., 2008, 20, 2704-2710,

(3) Shunsuke Tanaka, Daisuke Nogami, Natsuki Tsuda, Yoshikazu Miyake, Journal of Colloid and Interface Science 2009, 334, 188-194,

(4) Tada Sugimoto, Takashi Kojima, Journal of Physical Chemistry C 2008, 112, 18760-18771.

 However, according to the method of the above documents, it is limited to amorphous particles and can be crystallized by heat treatment, but in this case, there is a problem that may cause deformation of spherical particle shape due to fusion between particles.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing high refractive index titania microparticles without deformation in spherical particle shape.

In order to solve the above problems, the present invention comprises the steps of (a) preparing amorphous titania particles comprising an organic amine; (b) forming a core-shell structured particle by forming a shell on the surface of the amorphous titania particle including the organic amine; (c) heat treating the core-shell structured particles; And (d) provides a method for producing a high refractive index titania microparticles comprising the step of removing the shell of the heat-treated particles.

The amorphous titania particles can be prepared using the sol-gel method.

The organic amine may be one or more selected from the group consisting of propylamine, butylamine, butylamine, dodecylamine, hexadecylamine, hexadecylamine, aniline, and pyridine. have.

In the forming of the core-shell structured particle, the shell may be a silica shell or a polymer shell.

The silica shell may be formed using a silicon alkoxide or a (meth) acrylate having an alkoxysilyl group as a precursor.

The polymer shell may be prepared from monomers selected from the group consisting of aromatic vinyl compounds or (meth) acrylate compounds.

The polymer shell can be prepared using a nonionic surfactant or an amphiphilic block copolymer.

The silica shell may be heat treated in an air atmosphere.

The polymer shell may be heat treated in an oxygen-free atmosphere to prepare a carbonized shell.

In the step of removing the shell of the heat-treated particles, the silica shell may be removed using hydrofluoric acid.

In the step of removing the shell of the heat-treated particles, the polymer shell may be removed by performing a heat treatment at about 300 ~ 500 ℃ in the atmosphere with oxygen.

According to the production method of the present invention, crystalline high refractive index titania microparticles can be efficiently produced without deformation in spherical particle shape.

1 is a scanning electron micrograph of amorphous titania particles comprising dodecylamine prepared according to Example 1 of the present invention.
Figure 2 is a scanning electron micrograph of amorphous titania particles comprising dodecylamine prepared according to Example 2 of the present invention.
3 is a scanning electron micrograph of a silica shell-titania-dodecylamine core composite particle prepared according to Example 5 of the present invention.
Figure 4 is a scanning electron micrograph of particles prepared according to Comparative Example 1 of the present invention.
5 is a scanning electron micrograph of a carbon shell-titania-dodecylamine core composite particle prepared according to Example 7 of the present invention.

Method for producing a high refractive index titania microparticles of the present invention comprises the steps of (a) preparing amorphous titania particles comprising an organic amine; (b) forming a shell on the surface of the amorphous titania particles including the organic amine to form particles having a core-shell structure; (c) heat treating the core-shell structured particles; And (d) removing the shell of the heat treated particles.

Specifically, each step of the manufacturing method of the high refractive index titania microparticles according to the present invention will be described in detail.

(a) Organic amines  inclusive Amorphous Titania  Steps to Prepare Particles

Amorphous titania particles containing organic amines can be prepared using the sol-gel method.

First, a solvent may be prepared, a catalyst may be mixed, a precursor may be added, and titania microparticles having a uniform size may be prepared at room temperature through reaction for 3 hours or more. The prepared titania microparticles may include an organic amine.

As the precursor, titanium alkoxide such as titanium methoxide, titanium ethoxide, titanium isopropoxide, and the like may be used. Acetonitrile (Acetonitrile) or a mixture thereof may be used, and the catalyst may be an organic amine and distilled water.

As the organic amine, propylamine, butylamine, butylamine, dodecylamine, hexadecylamine, hexadecylamine, aniline, pyridine, or the like may be used. As alcohols, methanol, ethanol, butanol, and the like may be used.

It is also possible to reduce the size of the particles formed by reducing the amount of distilled water to increase the reaction rate during titania formation.

In addition, the size of the particles can be controlled through the growth of the secondary nucleus after the primary nucleus. Through this process, titania particles having a size that cannot be obtained by primary nuclear growth can be prepared, and the refractive index can be controlled through heat treatment after primary nuclear formation, and low refractive index particles can be produced through secondary growth. Increasing the concentration of particles in the secondary growth process may cause the two particles to stick together during the growth process to obtain peanut-shaped particles.

After the reaction, the particles are centrifuged and then redispersed using alcohols to remove unreacted substances.

(b) preparing the core-shell particles

In order to solve the conventional problem of deformation in spherical particle shape due to fusion between particles when crystallized through heat treatment in step (c) described later, the titania fine particles obtained in step (a) are used as a core and a protective layer. As a result, shell particles are formed on the surface of the titania fine particles.

As the protective layer, a silica shell may be formed or a polymer shell may be formed.

The titania microparticles obtained in step (a) may be dispersed in alcohol or distilled water before the protective layer shell is formed, and a surfactant such as polyvinylpyrollidone may be used.

To prepare a silica shell, silicon alkoxides or 3-trimethoxysilylpropyl methacrylate (3) such as tetramethylorthosilicate (TMOS) tetraethylorthosilicate (TEOS), etc. (meth) acrylates having alkoxysilyl groups such as-(trimethoxysilyl) propylmethacrylate (TPM)) are used as precursors, and ammonia, sodium hydroxide, tetramethylammonium hydroxide, etc. may be used as a catalyst. . The shell thickness can be controlled by adjusting the concentration of ammonia and the concentration of the silica precursor.

The polymer shell is modified on the surface of the titania microparticles using a silane coupling agent including a polymerizable group such as 3-trimethoxysilylpropyl methacrylate, and then an aromatic vinyl compound such as styrene or methyl methacrylate (Methylmethacrylate). It can be prepared through the dispersion polymerization method using a monomer selected from the group consisting of (meth) acrylate-based compounds such as).

In the dispersion polymerization method, the polymerization inhibitor is removed through a packing column present in the monomer, and the monomer is mixed under a nitrogen stream. 2,2-azobisisobutyronitrile (2,2'-azobis (isobutyronitrile)) is used as an initiator, and polyvinyl pyrrolidone (Poly (vinyl pyrrolidone)) is used as a stabilizer.

On the other hand, a thin polymer membrane is prepared using a high molecular weight nonionic surfactant (Tween 20, Brij-based), polyvinylpyrollidone (polyvinylpyrollidone), or amphiphilic block copolymer (Pluronic F108, P123, etc.) without undergoing polymerization. You may.

(c) heat treatment

The titania microparticles obtained through the sol-gel method have an amorphous structure and organic substances contain a certain component or more, and thus the refractive index is less than 2.0. In order to obtain a high refractive index of 2.0 or more, a crystallization process through heat treatment is required. However, in this process, the particles are fused to some surface with each other to change the shape of the sphere occurs. In order to solve this problem, in step (b), a shell as a protective layer was formed.

When the silica shell is formed as a protective layer, heat treatment is performed in an air atmosphere, and when the polymer shell is formed as a protective layer, heat treatment is performed in an oxygen-free atmosphere to prepare a carbonized shell. At this time, the silica shell or the carbonized shell acts as a protective layer to prevent deformation of the spherical shape as the titania is crystallized. Crystallization is anatase phase is formed at about 500 ℃ and rutile phase is formed around 900 ℃ can be obtained the desired phase by adjusting the heat treatment temperature.

(d) Shell  Steps to remove

According to the temperature in the heat treatment process, even if the shell is partially deformed, the inner core is crystallized without deformation. By removing the shell from this, finally, spherical crystalline high refractive index titania microparticles can be obtained.

In the case where the silica shell is formed as a protective layer, the shell is removed using an acid that selectively etches silica such as hydrofluoric acid. In the case of the carbonized shell, the shell is subjected to heat treatment at about 300 to 500 ° C. in an oxygen atmosphere. The shell can be removed without fusion between livers.

Meanwhile, even in the case of core-shell titania microparticles having a silica shell, an organic shell is additionally prepared thereon and subjected to heat treatment to be carbonized, and then the carbonized layer is removed by heat treatment. It is also possible to produce microparticles of structure.

After the step (d), may further comprise the step of attaching the organic, inorganic compound or metal nanoparticles to the surface of the obtained titania microparticles, in this case may also be attached using a silane coupling agent comprising a specific reactor. .

In addition, after the step (d), it may further comprise the step of preparing a core-shell microparticles by coating a silica or a polymer material.

The high refractive index titania microparticles prepared according to the present invention may be used as a material for producing a white film having high light scattering, photonic crystal or photonic glass, or may be applied to various fields such as electronic paper and sensor particles.

Hereinafter, a method of manufacturing titania microparticles having a high refractive index according to an embodiment of the present invention will be described in detail.

≪ Example 1 >

115 g of methanol and 36 g of acetonitrile were placed in a flask, and 0.432 g of distilled water and 0.788 ml of dodecylamine were added thereto, followed by mixing at 500 rpm for 10 minutes. Next, 1.212 g of titanium tetraisopropoxide was added and stirred for 3 hours to prepare amorphous titania particles including dodecylamine.

After the reaction for 3 hours, the particles were allowed to settle by centrifugation, and water or ethanol was added thereto, followed by ultrasonic dispersion and redispersed.

The obtained particles were observed with an electron microscope as shown in FIG. 1 and uniform in size of about 800 nm.

≪ Example 2 >

115 g of methanol and 36 g of acetonitrile were put in a flask, and 0.732 g of distilled water and 0.788 ml of dodecylamine were added thereto, and the mixture was stirred at 500 rpm for 10 minutes. Next, 1.212 g of titanium tetraisopropoxide (Titanium teraisopropoxide) was added and stirred for 3 hours to prepare amorphous titania particles including dodecylamine.

After the reaction for 3 hours, the particles were allowed to settle by centrifugation, and water or ethanol was added thereto, followed by ultrasonic dispersion and redispersed.

The obtained particles were observed with an electron microscope as shown in FIG. 2 and uniform in size of about 400 nm.

<Example 3>

After the primary nucleus was prepared, the size of the particles was controlled as follows through secondary nucleus growth.

To prepare the primary nucleus, 115 g of methanol and 36 g of acetonitrile were put in a flask as described in Example 1, 0.432 g of distilled water and 0.788 ml of dodecylamine were added thereto, and the mixture was stirred and mixed at 500 rpm for 10 minutes. . 1.212 g of titanium tetraisopropoxide was added and stirred for 3 hours to prepare amorphous titania particles including dodecylamine. 30 ml of this solution was taken up by centrifugation, the particles were allowed to settle, redispersed in 30 g of methanol and 10 g of acetonitrile, 0.115 g of distilled water and 0.1 g of dodecylamine were added, and 0.1 g of titanium tetraisopropoxide was added thereto. Stirring for 3 hours yielded amorphous titania particles containing about 1.2 μm size dodecylamine.

<Example 4>

By increasing the concentration of the particles compared to Example 3 in the secondary growth process of the amorphous titania particles containing dodecylamine it was possible to obtain peanut-shaped particles formed by the two particles adhered in the growth process as follows.

To prepare the primary nucleus, 115 g of methanol and 36 g of acetonitrile were put in a flask as described in Example 1, and then 0.432 g of distilled water and 0.788 ml of dodecylamine were added and stirred at 500 rpm for 10 minutes, followed by mixing. . 1.212 g of titanium tetraisopropoxide was added and stirred for 3 hours to prepare amorphous titania particles including dodecylamine. 50 ml of the solution was collected by centrifugation, the particles were allowed to settle, redispersed in 30 g of methanol and 10 g of acetonitrile, 0.115 g of distilled water and 0.1 g of dodecylamine were added, and 0.1 g of titanium tetraisopropoxide was added thereto. After stirring for 3 hours, a solution in which a mixture of amorphous titania particles containing 1.2 μm size dodecylamine and peanut tidal particles containing two amorphous titania particles containing about 1.0 μm size dodecylamine were prepared.

<Example 5>

To form a silica shell, 30 ml of amorphous titania particles containing dodecylamine prepared in Example 1 were taken and dispersed in 50 ml of ethanol through centrifugation and redispersion. 2 ml of ammonia (28%) aqueous solution was added to the ethanol dispersion, and 4 ml of tetraethyl orthosilicate was added thereto, followed by stirring for 4 hours.

The obtained particles are amorphous titania particles including dodecylamine having a silica shell of 100 nm thickness, and titania-silica core-shell particles were prepared by heat treatment at 500 ° C. for 2 hours in an air atmosphere.

The core-shell particles were acid treated with hydrofluoric acid to remove the shell, and finally titania fine particles were prepared, and the obtained particles were observed with an electron microscope as shown in FIG. 3. It was 2.2 when the refractive index of the obtained particle | grain was measured by the laser interference method (Optics Express, 15 (26), 18275-18282 (2007)).

<Example 6>

In order to form a silica shell, 30 ml of amorphous titania particles including dodecylamine prepared in Example 1 were taken and dispersed in 50 ml of distilled water through centrifugation and redispersion. 2 ml of an aqueous ammonia (28%) solution was added to the dispersion, and 4 ml of 3-trimethoxysilylpropylmethacrylate (TPM) was added thereto, followed by stirring for 4 hours.

The particles obtained are amorphous titania particles comprising dodecylamine with a silica shell of 200 nm thickness. Titania-silica core-shell particles were prepared by heat-treating the particles at 500 ° C. for 2 hours in an air atmosphere.

The core-shell particles were acid-treated with hydrofluoric acid to remove the shell to finally prepare titania fine particles, and the refractive index of the obtained particles was determined by laser interferometry (Optics Express, 15 (26), 18275-18282 (2007)). It was 2.2 as a result.

&Lt; Example 7 >

In order to form a polymer shell, 10 ml of a solution (10 wt%) in which amorphous titania particles including dodecylamine prepared in Example 3 were dispersed in ethanol and polyvinylpyrollidone (weight average molecular weight) dissolved in ethanol: 15,000) solution (20 wt%) was mixed to form a polyvinylpyrrolidone coating film on the surface of the amorphous titania particles containing dodecylamine.

Next, a carbonized shell was prepared by heat treatment at 500 ° C. for 2 hours in a nitrogen atmosphere. Thereafter, the shell was removed by heat treatment at 500 ° C. for 2 hours in an oxygen atmosphere, and the obtained particles were shown in FIG. 5 as observed by an electron microscope.

&Lt; Comparative Example 1 &

The amorphous titania particles including dodecylamine prepared in Example 1 were heat-treated at 500 ° C. for 2 hours in an air atmosphere without forming a shell.

The obtained particles were observed by electron microscopy as shown in FIG. 4, and as a result, it was confirmed that the particles were not uniform and caused deformation of spherical particle shape due to fusion between particles.

Claims (11)

(a) preparing amorphous titania particles comprising organic amines;
(b) forming a core-shell structured particle by forming a shell on the surface of the amorphous titania particle including the organic amine;
(c) heat treating the core-shell structured particles; And
(d) a method for producing high refractive index titania microparticles, comprising the step of removing the shell of the heat-treated particles. The method of claim 1,
The amorphous titania particles are manufactured by using a sol-gel method. The method of claim 1,
The organic amine is selected from the group consisting of propylamine, butylamine, butylamine, dodecylamine, hexadecylamine, hexadecylamine, aniline, and pyridine. A method for producing high refractive index titania fine particles. The method of claim 1,
In the step of forming particles of the core-shell structure, the shell is a method for producing high refractive index titania microparticles, characterized in that the shell or silica shell. The method of claim 4, wherein
The silica shell is a method for producing high refractive index titania microparticles, characterized in that formed using alkoxide (silicon alkoxide) or (meth) acrylates having an alkoxysilyl group as a precursor. The method of claim 4, wherein
The polymer shell is a method for producing high refractive index titania microparticles, characterized in that prepared from monomers selected from the group consisting of aromatic vinyl compounds or (meth) acrylate-based compounds. The method of claim 4, wherein
The polymer shell is a method for producing high refractive index titania microparticles, characterized in that prepared using a nonionic surfactant or amphiphilic block copolymer. The method of claim 4, wherein
The silica shell is a method for producing high refractive index titania fine particles, characterized in that the heat treatment in the air atmosphere. The method of claim 4, wherein
The method of producing a high refractive index titania microparticles, characterized in that to produce a carbonized shell by heat-treating the polymer shell in an oxygen-free atmosphere. The method of claim 4, wherein
Method for producing a high refractive index titania fine particles, characterized in that for removing the silica shell using hydrofluoric acid. The method of claim 4, wherein
Method for producing a high refractive index titania microparticles, characterized in that the polymer shell is removed by performing a heat treatment at about 300 ~ 500 ℃ in the atmosphere with oxygen.

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