WO2015182878A9 - Method for manufacturing hollow silica particles, hollow silica particles, and composition and thermal insulation sheet comprising same - Google Patents

Abstract

The present invention provides hollow silica particles that have a refractive index of 1.2-1.4, a thermal conductivity of less than 0.1 W/ m·K, an oil absorption rate of 0.1 ml/g or below, a porosity of at least 90% when mixed with a resin, and a particle distribution coefficient of variation (CV value) of 10% or below. In addition, the present invention may provide a composition comprising the hollow silica particles, and may provide a transparent thermal insulation sheet which has a visible light transmittance of at least 70%, a thermal conductivity of less than 0.1 W/ m·K, and a filling rate of particles of 30-80%.

Description

Method for producing hollow silica particles, hollow silica particles and composition comprising same and heat insulating sheet

The present invention relates to hollow silica particles having complex properties, a method of manufacturing the same, and a composition and a heat insulating sheet including the hollow silica particles.

The annual cost for building air conditioning is over 25 trillion won. In recent years, the use of glass as an exterior material is increasing, and the heat loss to the window of the heating and cooling energy accounted for the largest portion (39% of the total heat loss). Therefore, there is an urgent need to improve the cooling and heating energy consumption, which is increasing, and there is a need for strengthening the window insulation performance. Recently, the development of insulation materials and the development of new environmentally friendly materials for the production of insulation sheets satisfying both characteristics of transparency and insulation are required. As one of such insulating materials, hollow silica particles may be used. As a method for preparing hollow silica particles, KR 101180040 describes a hollow composite in which magnesium fluoride is doped with silica, and a hollow composite having an average particle diameter of 20 to 500 nm is described. Although it is, the present invention relates to a method for producing hollow particles by a method of removing the core after preparing the core and shell of the silica particles by the sol-gel method. KR 101359848 discloses the steps of synthesizing silver nanocrystals using a polyol solvent, synthesizing silver-silica core-shell nanoparticles by coating silica on the silver nanocrystals, and the silver core of the silver-silica core-shell nanoparticles. It discloses only a method for producing hollow silica, and hollow silica prepared according to the step of etching. Therefore, the hollow silica production techniques known to date have a problem that it is difficult to manufacture hollow silica particles that exhibit high visible light transmittance, high refractive index, low thermal conductivity, monodispersity, low oil absorption, and high porosity. . In addition, there is a problem that the physical properties of the existing hollow silica is not enough to produce a transparent yet excellent heat insulating sheet.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide hollow silica particles having a combination of advantageous physical properties having a low refractive index and a low thermal conductivity. It is also an object of the present invention to provide a composition and a transparent insulating sheet containing the hollow silica particles.

The hollow silica particles of the present invention have a refractive index of 1.2 to 1.4, a thermal conductivity of less than 0.1 W / mK, an oil absorption of 0.1 ml / g or less, a porosity of 90% or more when mixed with resin, and a particle distribution variation coefficient (CV). Value) has a complex physical property of 10% or less.

It is preferable that the average diameter of the said particle | grains is 1 micrometer or less, the inner diameter of a hollow part is 10 to 90% or more of the average diameter of a particle | grain, and the thickness of a shell is 5 to 45% of an average particle diameter. More preferably, the hollow silica particles have an average diameter of 500 nm or less and an inner diameter of the hollow portion of 40 nm or more. In order to maximize the filling rate of the particles in the production of the insulating sheet, it is preferable that the average diameter of the particles is 500 nm or less and the inner diameter of the hollow portion is 40 nm or more.

In addition, it is preferable that the hollow silica particles are formed from phenyl silane, and the surface of the particles has an advantage that the -OH group and the phenyl group exist as functional groups, and thus the strength of the particles is high.

In addition, since the particles produced by the production method of the present invention have almost no pores on the surface, the oil absorption rate is 0.1 ml / g or less, and when mixed with the resin, the porosity is 90% or more. And particle characteristics such as sphericity, average particle diameter, refractive index, thermal conductivity, and the like remain stable without variation of hollow, and thus have suitable particle characteristics for high filling in binders such as resins.

The degree of sphericity of the hollow particles of the present invention is greater than or equal to 0.9 and at least 90% of the silica particles are spherical with uniform convex grain contours in which there are no flat faces, corners or recognizable recesses.

On the other hand, the hollow silica particles of the present invention is characterized by including the following steps.

(a) adding 0.1-2 mol% of silane to the aqueous solution and stirring to produce silane droplets;

(b) adding an acid to the aqueous solution to hydrate the silane droplets;

(c) adding a base aqueous solution to the reaction solution of step (b) to form primary particles by bonding between silane droplets;

(d) stirring the reaction solution to which the base aqueous solution is added to polymerize the primary particles to form a shell;

(e) etching the inside of the shell with an organic solvent to form a hollow; and

(f) filtering and drying the solution

In the above production method, the particles to be finally produced are characterized in that the average diameter is 1㎛ or less, the inner diameter of the hollow portion is 10 to 90% or more of the average diameter of the particles.

The pH of the reaction solution after the addition of the acid in step (b) is 1 ~ 5 and the hydration time in step (b) is characterized in that 1-10 minutes.

In the step (c), the basic aqueous solution is characterized in that the pH 10 or more and the polymerization reaction proceeds so that the thickness of the insoluble shell is 5 ~ 45% of the average particle diameter.

The silane is at least one selected from the group consisting of phenyl silanes, TEOS, TMOS, SiCl ₄ , and silanes having organic groups other than phenyl groups, or mixtures thereof. In the case of using a mixture of phenyl silane and other silanes, it is preferable to use a mixture of phenyl silane at least 80% by weight and other silanes at 20% by weight or less, and PTMS is preferably used as the phenyl silane.

The base solution in step (d) is characterized in that the inorganic base of the NH ₄ OH or alkylamine type, the alkylamine is NH ₄ OH, or tetramethyl ammonium hydroxide (TMAH), octylamine (octylamine, OA, CH ₃ ( CH ₂ ) ₆ CH ₂ H ₂ ), dodecylamine, DDA, CH ₃ (CH ₂ ) ₁₀ CH ₂ NH ₂ ), hexadecylamine, HDA, CH ₃ (CH ₂ ) ₁₄ CH ₂ NH ₂ ), 2-aminopropanol, 2- (methylphenylamino) ethanol, 2- (ethylphenylamino) ethanol, 2-amino-1-butanol, (diisopropylamino) ethanol, 2-diethylaminoethanol, 4-amino Phenylaminoisopropanol, N-ethylaminoethanol, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, methyldiethanolamine, dimethyl monoethanolamine, ethyl diethanolamine, diethyl Monoethanolamine is selected from the group consisting of.

The reaction temperature in the step (b) and (d) is preferably 40 ~ 80 ℃, and after the filtration in the step (f) (g) further comprising the step of sonicating the filtrate (surface) It can be produced more smoothly.

Drying after filtration is preferably performed at 250 ° C or lower, preferably at 150 ° C or lower.

After the step (f) it may further comprise the step of (i) modifying the surface of the hollow silica particles and can be expanded the use of the particles by adding a functional group of the particle surface.

On the other hand, it provides a composition comprising a hollow silica particles, a resin, and a solvent of the present invention. It is preferable that the hollow silica particles are 30 to 80 wt% and the resin is 20 to 70 wt% based on the total composition.

 In the composition, the resin preferably has a refractive index of less than 1.5, and at least one selected from acrylate polymer resin, polyimide (PI) resin, C-PVC resin, PVDF resin, ABS resin, CTFE, or a mixture thereof. It is preferable to use.

In addition, the composition may further include one or more selected from a hard coating agent, a UV blocker, or an IR blocker to impart additional functionality.

The present invention is to prepare a substrate, the composition is applied to the substrate to form a coating layer and the coating layer is cured by visible light transmittance of 70% or more, thermal conductivity of less than 0.1w / mk and hollow silica particles filling rate of 30 ~ 80% It provides a heat insulating sheet, characterized in that. The coating layer may further have a UV blocking and IR blocking function, and a sheet of a polymer material, a fiber, a film, or glass may be used as the substrate of the insulating sheet.

[Effects of the Invention]

According to the present invention, the refractive index is 1.2 to 1.4, the thermal conductivity is less than 0.1 W / mK, the oil absorption is 0.1 ml / g or less, the porosity is 90% or more when mixed with resin and the particle distribution coefficient of variation (CV value) is Hollow silica particles having a property of 10% or less can be provided by a simple and stable production method.

In addition, it is possible to provide a composition comprising the hollow silica particles having the above physical properties, so that the visible light transmittance of 70% or more, the thermal conductivity is less than 0.1w / mk, the particle filling rate of 30-80%, transparent and excellent thermal insulation function Sheets can be provided.

[Effects of the Invention]

According to the present invention, the refractive index is 1.2 to 1.4, the thermal conductivity is less than 0.1 W / mK, the oil absorption is 0.1 ml / g or less, the porosity is 90% or more when mixed with resin and the particle distribution coefficient of variation (CV value) is Hollow silica particles having a property of 10% or less can be provided by a simple and stable production method.

In addition, it is possible to provide a composition comprising the hollow silica particles having the above physical properties, so that the visible light transmittance of 70% or more, the thermal conductivity is less than 0.1w / mk, the particle filling rate of 30-80%, transparent and excellent thermal insulation function Sheets can be provided.

1 is a diagram illustrating the structure of hydrated PTMS droplets, primary particles, and particles in which a shell is formed during the manufacturing process of the present invention;

2 is a transmission electron microscope (TEM) of hollow silica particles having an average diameter of 100 nm according to an embodiment of the present invention,

3 is a TEM photograph of particles formed upon reaction at a temperature of 85 ° C. by a comparative example,

4 is a TEM photograph after etching the silica particles according to an embodiment of the present invention after hydrolysis for 60 seconds, 30 seconds,

FIG. 5 is a TEM photograph of particles after sonicating the particles of FIG. 4;

FIG. 6 is a transmission electron micrograph (TEM) of particles after polymerizing, washing, dispersing, and etching PPSQ of the present invention.

The manufacturing process and physical properties of the hollow silica particles of the present invention will be described in detail.

Preparation of Hollow Silica Particles

The hollow silica particles of the present invention are made of silane as a starting material, stirred in an aqueous solution to form a droplet, and then hydrated by adding an acid, followed by addition of a basic aqueous solution to form primary particles by bonding between the droplets, followed by polymerization and shelling. After forming the hollow inside the shell by etching with an organic solvent to form a hollow hollow silica particle powder through filtration, drying. In this case, the method may further include the step of sonicating the filtrate.

1. Raw material

As a raw material of the hollow silica particles, at least one selected from the group consisting of phenyl silane, TEOS, TMOS, SiCl ₄ , and silane having an organic group other than a phenyl group, or a mixture thereof may be used. When using a mixture of phenyl silane and other silanes, it is preferable to use a mixture of phenyl silane at least 80% by weight and other silanes at 20% by weight or less. Particularly, as the phenyl silane, the structure of Formula 1 It is preferable to use PTMS (phenyltrimethoxysilane, C ₉ H ₁₄ O ₃ Si) for the branch.

When using at least one silane selected from PTMS and a silane having an organic group other than TEOS, TMOS, SiCl ₄ , and a phenyl group, it is preferable to mix each in a weight ratio of 4: 1.

The concentration of silane should be 0.1 mol% or less in the aqueous solution to obtain small particles of 1 μm or less.

Formula 1

2. Droplet generation

When 0.1 to 2 mol% of silane is added to the aqueous solution, the silane is not mixed with the aqueous solution, and thus layer separation occurs. If the stirring is continued, silane droplets are formed and dispersed in the aqueous solution.

3. Droplet Hydration

When the acid is added to the aqueous solution, the -OR group of the silane is replaced with the -OH group by the role of the acid as shown in FIG. 1 (a). When the stirring is continued, droplets of the hydrated silane are uniformly mixed in the aqueous solution. The acid is preferably HCl, HNO _3, H ₂ SO ₄ and the like and the pH of the reaction solution is 0.5 ~ 5. In this case, the lower the pH of the reaction solution, the smaller the size of the particles due to the breakage of the chain of silane. Therefore, when the pH is strongly acidic, the amount of silane should be used in small amounts. This is because control of particle generation is difficult because no hollow is formed in the inside. In addition, when the pH is 5 or more, when a small amount of silane is used, particles and hollows are not formed.

On the other hand, after the addition of the acid, the longer the stirring time is, the smaller the final particle size is produced, but the particles are aggregated to form a gel, which is difficult to form a hollow. If the stirring time is too short, hydration of the silane droplets does not sufficiently occur to form hollow particles. It is difficult. Therefore, the stirring time is preferably between 0.5 and 10 minutes, more preferably between 1 and 5 minutes.

The droplet size is not different when the stirring speed exceeds 200rpm when the size of the stirrer is about 80% compared to the reactor, but when the stirring speed is 200rpm or less, the particle size increases, so the stirring speed is preferably 200rpm or more, and the size of the hydrated droplet is 8 to 12 It is preferable that the thickness is µm and the final particle size is determined according to the size of the droplets.

As for the temperature of reaction, 40-80 degreeC is preferable. It is difficult to produce particles at less than 40 ℃, it is easy to agglomerate particles in a high concentration to form a gel, the thickness of the shell is thickened, there is a problem that the size of the hollow is reduced, if the temperature exceeds 80 ℃ the base volatilize the reaction conditions It is difficult to control, and the inside of the shell does not melt and no hollow particles are made. The hydration scheme of PTMS is as follows.

Scheme 1

PhSi (OMt) ₃ + H ₂ O-> PhSi (OH) (OMt) ₂

PhSi (OH) (OMt) ₂ + H ₂ O-> PhSi (OH) ₂ (OMt)

PhSi (OH) ₂ (OMt) + H ₂ O-> PhSi (OH) ₃

4. Primary Particle Formation

When the base solution is added to the silane-hydrated solution, the base solution acts as a catalyst to form primary particles as shown in FIG. The base solution is a base such as NaOH, Ca (OH) ₂ , KOH, NH ₄ OH, preferably NH ₄ OH or an alkylamine type inorganic base so that the total reaction solution is at least pH 10. Alkylamines are NH ₄ OH, or tetramethyl ammonium hydroxide (TMAH), octylamine, OA, CH ₃ (CH ₂ ) ₆ CH ₂ H ₂ ), dodecylamine, DDA, CH ₃ (CH ₂ ) ₁₀ CH ₂ NH ₂ ), hexadecylamine, HDA, CH ₃ (CH ₂ ) ₁₄ CH ₂ NH ₂ ), 2-aminopropanol, 2- (methylphenylamino) ethanol, 2- (ethylphenylamino) ethanol, 2 -Amino-1-butanol, (diisopropylamino) ethanol, 2-diethylaminoethanol, 4-aminophenylaminoisopropanol, N-ethylaminoethanol, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, Diisopropanolamine, triisopropanolamine, methyldiethanolamine, dimethyl monoethanolamine, ethyl diethanolamine, diethyl monoethanolamine.

The reaction is difficult to produce hollow particles because the particles are easily aggregated together to form a gel at less than 40 ℃, the thickness of the shell is too thick, there is a problem that the size of the hollow is reduced, if the base exceeds 80 ℃ volatilized It is preferable to proceed at 40 ~ 80 ℃ because it is difficult to control the reaction conditions, the inside of the shell does not melt and hollow particles are not made.

Scheme 2

2Ph-Si (OH) ₃ → Ph-Si (OH) ₂ -O-Si (OH) ₂ -Ph

5. Shell Formation

The aqueous solution to which the base solution is added is stirred to polymerize the primary particles by siloxane bonds to form a shell insoluble in the organic solvent. The thickness of the shell is preferably 5 to 45% of the average diameter of the silica particles. When particles are formed by using PTMS as a raw material, the shell structure is a network PPSQ structure.

Scheme 3

Ph-Si (OH) ₂ -O-Si (OH) ₂ -Ph → + n [Ph-Si (OH) ₃ ] → Networked polyphenylsilsesquioxane (PPSQ)

Formula 2

6. Etching

Silane oligomer and unreacted droplets are present in the insoluble shell, and the hollow inside is etched by using an organic solvent.

To form. The organic solvent may be generally used, including ethanol or methanol.

Meanwhile, by further sonicating the filtrate using a sonicator, impurities on the surface of the particles may be removed to make the surface of the particles smoother, and the sonication may be performed within 5 seconds to 40 minutes. Do.

7. Filtration and drying

When the filtrate is dried at less than 250 ℃, more preferably less than 150 ℃ 1 to 10 hours in a vacuum oven to evaporate or sublimate moisture at a temperature corresponding to the degree of vacuum to dry.

The step of modifying the surface of the particles by a known method such as nitrification, sulfonation, amination, halogenation by treating the silane coupling agent to the resulting hollow silica particles may be further applied. A silane coupling agent can use a silane type, aluminum type, titanium type, zirconium type coupling agent. The surface modified hollow silica particles can be applied to various fields such as functional ceramics, microcapsules, nanoreactors, DDS, catalysts, sensors, and the like. In this way, the treatment with the surface treatment agent improves the dispersibility to hydrophobic dispersion mediums such as resins and organic solvents, and improves adhesion to resins, peel strength, and the like.

In addition, there is no need for a template for the production of hollow particles, and does not require a firing process requiring a lot of time and high energy costs, there is an advantage that the hollow silica particles can be obtained through a simple manufacturing process.

Hollow silica particles

Hollow silica particles prepared by the above production method has a refractive index of 1.2 to 1.4, a thermal conductivity of less than 0.1 W / m · K, an oil absorption of 0.1 ml / g or less, a porosity of 90% or more when mixed with resin, and a particle distribution variation. The coefficient (CV value) has a monodispersity of 10% or less. In addition, the average diameter of the particles is 1 µm or less, the inner diameter of the hollow portion is 10 to 90% of the average diameter of the particles, and the shell thickness is 5 to 45% of the average particle diameter and spherical particles having a sphericity of 0.9 or more.

Hereinafter, the physical properties of the hollow silica particles of the present invention and a measuring method thereof will be described together.

1) refractive index

The hollow silica is first dispersed in sorbitol syrup (70% sorbitol) / water mixture. After 1 hour of degassing, the light transmittance of the dispersion is measured using a spectrophotometer at 589 nm, and water is used as a blind sample. The refractive index of each dispersion is measured using an Abbe refractometer. From the graph of the transmittance | permeability shown with respect to a refractive index, the range of the refractive index over 70% can be seen. The maximum light transmittance of the sample and the refractive index from which this light transmittance is obtained can also be obtained from this graph.

2) thermal conductivity

The measurement of thermal conductivity first cuts out the center part of the thermal insulation sheet of 30 cm long, 30 cm wide, and 5 cm thick to square shape of 24 cm and 24 cm, and forms a frame. An aluminum foil of 30 cm in length and 30 cm in width is bonded to one side of the frame to form a concave portion, and a sample is taken. Moreover, the surface covered with aluminum foil is made into the bottom surface of a sample stand, and the other surface with respect to the thickness direction of a heat insulation sheet is made into the ceiling surface. After filling a powder-form heat insulating material into a recessed part without tapping or pressurizing, and leveling, what put the aluminum foil of 30 cm in length and 30 cm in width on the ceiling surface is used as a measurement sample. Using the measurement sample, the thermal conductivity at 30 ° C. was measured using a heat flow meter HFM 436 Lambda (trade name, manufactured by NETZSCH). The calibration is carried out in accordance with JIS A1412-2 using a standard plate for calibration of NIST SRM 1450c with a density of 163.12 kg / m 3 and thickness of 25.32 mm, on the condition that the temperature difference between the high temperature side and the low temperature side is 20 ° C., 15, 20, 24, 30 , 40, 50, 60, 65 ℃ in advance. Thermal conductivity in 800 degreeC is measured based on the method of JISA1421-1. Two sheets of a heat insulating sheet having a diameter of 30 cm and a disc shape having a thickness of 20 mm were used as measurement samples, and a protective heat plate method thermal conductivity measuring device (manufactured by Eiko Seiki Co., Ltd.) was used as the measuring device.

3) oil absorption rate

Hollow silica particles of the present invention is characterized in that the spherical surface is substantially smooth even after the separate firing and surface treatment. By "smooth" it is meant that there are very few fine pores on the surface and that the surface of the shell is free of any irregularities such as pits, gaps, nicks, cracks, protrusions, grooves and the like. Such surface properties are not seen in the hollow silica particles obtained by the conventional manufacturing method. The smoothness of the particles of the present invention can be measured by scanning electron microscopy and can be confirmed through oil absorption, porosity when mixed with resin, and the like.

Oil absorption was measured using the rub-out method (ASTM D281). This method is based on the principle of mixing linseed oil with silica by rubbing the linseed oil / silica mixture with a spatula on a smooth surface until a stiff putty-type paste is formed. By measuring the amount of oil required to have a paste mixture that is curled when sprayed, the oil absorption of silica can be calculated, indicating the volume of oil required per unit weight of silica to saturate the silica adsorption capacity. . High levels of oil absorption indicate that there are many pores on the surface or that the pores are large in size, while lower values indicate that there are few pores on the shell surface of the silica particles. Oil absorption can be determined from the equation:

Oil absorption rate = oil volume ㎖ / silica 100g

4) Porosity

When the hollow silica particles are mixed with the resin, the amount of resin permeated into the hollow interior can be confirmed. The amount of resin penetrated into the hollow is measured in the same manner as the oil absorption rate, and as the amount of the resin is smaller, the hollow inside is maintained.

That is, the structure of the particles having a smooth surface and almost no pores increases the porosity because the resin or oil constituting the binder does not penetrate into the hollow of the particles when the hollow silica particles are filled in the resin. It means that it is possible to increase the transparent heat insulating performance of the heat insulating sheet coated with the composition containing the particles and exhibiting transparent and low thermal conductivity.

5) Particle distribution variation coefficient (CV value) (monovariance)

Particles were photographed (250,000 times) using a scanning electron microscope, an average particle diameter was measured using an image analyzer for 25 particles of this image, and the coefficient of variation (CV value) related to the particle diameter distribution was calculated. It was. Specifically, each particle diameter was measured with respect to 250 particles, and the standard deviation of the average particle diameter and the particle diameter was calculated from the values, and calculated from the following equation.

Particle Distribution Variation Coefficient (CVD (%)) = (Standard Deviation (σ) / Average Particle Diameter (Dn) of Particle Diameter) × 100

6) Spherical degree

Characterization of the silica particles of the present invention as a very round shape is measured by a scanning electron microscope (SEM) photograph showing the cross-sectional structure of the particles and expressed as the ratio of the short diameter (DS) to the long diameter (DL) (DS / DL). do. Representative samples of silica particles were collected and tested by scanning electron microscopy (SEM). As understood from the electron micrograph of FIG. 2, it can be seen that the sphericity degree (S ₈₀ ) of the particles of the present invention is 0.9 or more, which is very spherical particles. As used herein, “S ₈₀ ” is defined and calculated as follows. A representative 20,000-fold magnified SEM image of the silica particle sample is loaded into photo imaging software and the contour (two-dimensional) of each particle is traced. Particles close to each other but not attached to each other should be considered as separate particles for evaluation. The contoured particles are then filled with color, and the image is taken with particle characterization software (e.g. MAGE-PRO PLUS available from Media Cybernetics, Inc. (Bethesda, Maryland)) that can determine the particle's perimeter and product. It is called. The degree of sphericity of the particles can then be calculated according to the following equation.

Roundness = Perimeter ² / 4π × area

Wherein the perimeter is the software measurement perimeter derived from the contoured tracking of the particle and the area is the software measurement area within the particle's tracked perimeter. The calculation is performed for each suitable particle as a whole in the SEM image. These values are then classified according to their values, and the lower 20% of these values are discarded. The remaining 80% of these values are averaged to obtain S ₈₀ . The sphericity coefficient S ₈₀ for the particles of FIG. 2 was found to be 0.98.

7) Average particle diameter and shell thickness

"Average diameter" is understood as the diameter averaged over all particles in a sample.

Representative samples of silica particles were collected and the diameter of the silica particles was measured by scanning electron microscopy (SEM). The inner diameter of the hollow portion was measured by transmission electron micrograph (TEM).

The average diameter of the hollow particles of the present invention is generally 1 μm or less, preferably 500 nm or less, and more preferably 100 nm or less. If the average diameter exceeds 1 μm, the filling rate may not be completely filled in the thickness of the coating layer during the production of the insulating sheet, and thus the filling rate may be lowered.

The hollow silica particles of the present invention are particles having an average diameter of 1 µm or less and an inner diameter of the hollow portion of 10 to 90% of the average diameter of the particles. In the case of particles with an average diameter of 100 nm, the inner diameter of the hollow portion was good at more than 40 nm. In addition, since the thickness of the shell is 5 to 45% of the average particle diameter and is stable during the reaction, hollow silica particles may be used as a heat insulating material.

8) functional group

In addition, when the phenyl silane is used as a raw material, the particles have -OH groups and phenyl groups as functional groups, and the phenyl group has a refractive index higher than that of other silica particles, and thus has a refractive index similar to that of resin, thereby minimizing the difference between the resin and the refractive index. Therefore, a transparent insulation sheet can be made.

Coating composition comprising hollow silica particles and resin

In still another embodiment of the present invention, a composition for forming a transparent heat insulating coating layer on a substrate is provided. The composition of the present invention may be prepared by mixing hollow silica particles having a complex physical property as described above, resin, an organic solvent and the like.

As for the hollow silica particle in the whole composition of this invention, 30 to 80 weight% is preferable. If less than 30% by weight can not sufficiently achieve the thermal insulation performance of the coating layer, if it exceeds 80% by weight because the transparency is reduced and the content of the resin is less hardening efficiency is lowered.

And the resin in the total composition of the present invention can be mixed in 20-70% by weight. The refractive index of the resin is preferably less than 1.5 to adjust the refractive index with the silica particles, and preferably, a resin similar to the refractive index with the hollow particles is selected from among UV curable resins.

Examples of UV curable resins include, but are not limited to, urethane resins, acrylic resins, polyester resins, epoxy resins, and mixtures thereof, and are resins having low thermal conductivity, such as acrylate-based polymer resins, polyimide (PI) resins, C -It can use 1 or more types or mixed from PVC resin, PVDF resin (heat-resistant temperature about 300 degreeC), ABS resin, CTFE, etc.

In addition, the composition may further include a hard coating agent, a UV blocker, or an IR blocker, and the additive may further include an additive that uses a known one and additionally provides additional functions if necessary.

As used herein, “composition” refers to any liquid, liquefiable or mastic composition comprising silica that is converted to a solid film after application to a substrate. The composition can be applied inside or outside the surface of any structure.

The composition comprises a hollow silica particle product and the silica product described herein has specific particle properties including hardness, sphericity, refractive index, oil absorption rate, thermal conductivity, and the like, which are useful for adiabatic, imparting transparency to the composition. The composition can be any coating composition and can be applied to any substrate. The compositions are useful as coatings for houses, constructions, automotive windows, and the like, such as insulation sheets, glass windows, as they exhibit excellent transparency and thermal insulation while maintaining the integrity of the polymer and pigment matrix that may be present in the coating. In addition, the compositions described herein are useful in plastic compound and masterbatch formulations, as well as exhibiting good thermal and transparent properties as well as enhancing the physical properties of the formulation.

Insulation Sheet

In another embodiment of the present invention, a heat insulating sheet may be prepared by preparing a substrate, and laminating or applying the composition of the present invention to the substrate to UV-cure to form a coating layer. The coating method may use any suitable coating method known in the art, and examples of known methods are gravure coating, offset gravure coating, two and three roll pressure coating, two and three rolleys. Roll reverse coating, immersion coating, 1 and 2 roll kiss coating, trailing balde coating, nip coating, flexographic coating, inverted knife coating ( inverted knife coating, polishing bar coating and wire wound doctor coating. After coating, the coating layer is cured with UV light and curing is usually completed in a relatively short period of time from about 1 to about 60 seconds.

Although the base material which forms a coating layer by the said composition is not specifically limited, For example, the inorganic base material represented by glass, a metal base material, a polycarbonate or polyethylene terephthalate, an acrylic resin, a fluororesin, a triacetyl cellulose, a polyimide The organic base material represented by resin is mentioned. It is preferably a sheet of a polymer material, a fiber, a film, a glass or the like, in particular the film substrate may be a film that can be commonly applied, such as PET, PE. The same base material may be independent, and the heterogeneous material may be laminated | stacked. Moreover, at least 1 layer or more of another layer may be previously formed in the base material surface. For example, an ultraviolet curable hard cord layer, an electron beam hardening type hard cord layer, and a thermosetting hard cord layer are mentioned as another layer.

The thickness of the coating layer can be arbitrarily selected and adjusted according to the product and the use, and preferably coated with a thickness of 1 ~ 500㎛, if out of the above range may increase the thermal conductivity or the visible light transmittance. The coating layer may further have a UV blocking and IR blocking function, and may be prepared by laminating a UV blocking layer and an IR blocking layer separately on the coating layer. The insulating sheet using the composition according to the present invention has a filling rate of 30-80% and a visible light transmittance of 70% or more, and exhibits a thermal conductivity of less than 0.1w / m.k, thus enabling transparent insulating properties.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only for explaining the present invention in detail, and it is obvious to those skilled in the art that the scope of the present invention is not limited, and all simple modifications and changes of the present invention are included in the scope of the present invention. It can be seen as.

Various physical properties of the hollow silica particles and the heat insulating sheet in the Example and the comparative example were measured by the method as described above.

Example 1

Water (150 ml) and phenyltrimethoxysilane (PTMS) (1 ml) were added to a 250 ml flask, and nitric acid (60%, 0.2 ml, 2.6 mmol) was added thereto and stirred at 60 ° C. for 4 minutes. Then, ammonia water (30%, 10ml, 308mmol) was added to the reaction solution, and stirred at 60 ° C. for 1 hour and 30 minutes to form a shell, and the inside of the shell was etched with ethanol. The resulting reaction was filtered and dried at 120 ° C. to obtain hollow silica particles.

As shown in the transmission electron micrograph (TEM) of FIG. 2, the generated particles are monodisperse spherical particles and hollow particles having bright hollows therein. Table 1 shows the refractive index, thermal conductivity, oil absorption rate, porosity when mixing with resin, and particle distribution variation coefficient (CV value) of the particles.

Example 2

Hollow silica particles were obtained in the same manner as in Example 1 except that the silane was used by mixing phenyltrimethoxysilane (PTMS) (0.8 ml) and TEOS (0.2 ml) in Example 1, and the physical properties of the resulting particles were obtained. Table 1 shows.

Example 3

In Example 3, particles were prepared by adding an acidic solution in Example 1 to 9 minutes of stirring time. The resulting particles formed spherical monodispersed hollow particles as shown in Figure 4, the physical properties are shown in Table 1.

Example 4

Example 4 was further subjected to the sonication in Example 1 to prepare a particle. The resulting particles formed spherical monodisperse hollow particles as shown in FIG. 5 and exhibited a smooth and spherical shape with almost no surface impurities than the particles in Example 3. Physical properties are shown in Table 1.

Comparative Examples 1 and 2

In Comparative Examples 1 and 2, the reaction proceeded in the same manner as in Example 1 except that the reaction temperature was advanced at 30 ° C. and 85 ° C., respectively.

Particles were not formed in Comparative Example 1, particles were formed in Comparative Example 2, but there was no hollow as shown in FIG.

Comparative Example 3

Comparative Example 3 was stirred for 15 minutes after the addition of the acidic solution described in Example 1 and the reaction results are shown in Table 1. The final particles gelled and did not produce hollow particles, probably due to the aggregation of small particles due to the excessively long stirring time.

Comparative Example 4

In Comparative Example 4, hollow silica particles were obtained in the same manner as in Example 1, except that the concentration of silane was 0.5 mol% in Example 1. As a result, hollow particles were produced, but the size of the particles exceeded 1 μm and did not show suitable physical properties for the insulation sheet production.

Table 1

	Hollow particle formation	Refractive index	Thermal Conductivity (W / mK)	CV (%)	Average particle diameter	Oil absorption rate (ml / g)	Porosity (%)
Example 1	formation	1.36	0.03	3	100 nm	0.018	90
Example 2	formation	1.34	0.03	3.8	180 nm	0.015	95
Example 3	formation	1.29	0.03	4	100 nm	0.018	92
Example 4	formation	1.37	0.03	3	200 nm	0.021	93
Comparative Example 1	Do not form	-	-	-	-	-	-
Comparative Example 2	Do not form	1.45	0.043	4	100 nm	-	-
Comparative Example 3	Do not form	-	-		-	-	-
Comparative Example 4	formation	1.36	0.047	-	2.4㎛	0.019	-

Example 5

The hollow silica particles prepared according to Example 1 were prepared by mixing 60% by weight of the total composition, 30% by weight of polyimide (PI) resin, and the remaining organic solvent and initiator. The prepared composition was applied to one side of the PET film by bar coating, and irradiated with UV for 20 seconds using a UV lamp to prepare a heat insulating sheet having a coating layer having a thickness of 125 μm. Table 2 shows the results of measuring physical properties of the insulation sheet.

Examples 6 and 7

Examples 6 and 7 were prepared by mixing the hollow silica particles in Example 5 at a ratio of 30% by weight and 80% by weight of the total composition, respectively, to prepare a heat insulating sheet, and the results of measuring physical properties are shown in Table 2. It was.

Comparative Examples 5 and 6

In Example 5, the composition was prepared using the mixing ratio of the hollow silica particles in 20% by weight and 90% by weight of the total composition, respectively, and when the content of the hollow particles was 50% or more, the viscosity of the crude liquid was high and the coating was difficult. Table 2 shows the results of measuring the physical properties of the insulating sheet after adjusting the viscosity by using a solvent MEK.

Comparative Example 7

Insulation sheet was prepared in the same manner as in Example 5 using hollow particles having a diameter of 200 nm and a hollow portion of 100 nm in the hollow part prepared using a conventional mold synthesis method. Shown in The insulating sheet could not be dispersed in the composition during coating and UV curing to escape from the resin to form a coating layer.

In Examples 5 to 7 and Comparative Examples 5 to 7, when the mixing ratio of the hollow particles exceeds 50%, since the viscosity of the crude liquid is too high, an organic solvent having a low BP is added to lower the viscosity, followed by coating and primary drying. The solvent was blown out and UV curing was performed.

TABLE 2

	Particle Mixing Rate (%)	Diluted solvent MEK (% of hollow particles)	Visible light transmittance (%)	Thermal Conductivity (W / mK)
Example 5	60	10	90	0.05
Example 6	30	-	92	0.08
Example 7	80	30	87	0.03
Comparative Example 5	90	40	60	0.03
Comparative Example 6	20	-	80	0.23
Comparative Example 7	60	10	-	-

As shown in Table 2, when the mixing ratio of the hollow particles is less than 30% by weight in the total composition, the visible light transmittance is high and transparent, but the air content is low, so that the thermal insulation efficiency is low. It can be seen that there is less curing efficiency.

In addition, the particles produced by Comparative Example 7 had large pores on the surface. The resin penetrated into the hollow through the pores of the particle surface when mixed with the UV curable resin, and during coating and UV curing, the particles could not be dispersed in the composition and escaped from the resin to form a coating layer. From this, it is judged that it is difficult to manufacture a transparent insulating sheet having the characteristics of the present invention with conventional hollow silica particles.

Claims (29)

1. Hollow silica having a refractive index of 1.2 to 1.4, a thermal conductivity of less than 0.1 W / mK, an oil absorption of 0.1 ml / g or less, a porosity of 90% or more when mixed with resin, and a particle distribution variation coefficient (CV value) of 10% or less. particle.
2. The hollow silica particle according to claim 1, wherein the average diameter of the particles is 1 µm or less, and the inner diameter of the hollow portion is 10 to 90% of the average diameter of the particles.
3. The hollow silica particle of claim 1, wherein the degree of sphericity of the particles is 0.9 or greater.
4. The hollow silica particle according to claim 1, wherein the surface of the particle has a -OH group and a phenyl group as functional groups.
5. The hollow silica particle of claim 1, wherein the shell has a thickness of 5 to 45% of an average particle diameter.
6. (a) adding 0.1-2 mol% of silane to the aqueous solution and stirring to produce silane droplets;

   (b) adding an acid to the aqueous solution to hydrate the silane droplets;

   (c) adding a base aqueous solution to the reaction solution of step (b) to form primary particles by bonding between silane droplets;

   (d) stirring the reaction solution to which the base aqueous solution is added to polymerize the primary particles to form a shell;

   (e) etching the inside of the shell with an organic solvent to form a hollow; and

   (f) filtering and drying the solution; Method for producing hollow silica particles comprising a.
7. The method of claim 6, wherein the primary particles have a PPSQ structure.
8. The method according to claim 6, wherein the pH of the reaction solution after addition of the acid in step (b) is 1 to 5
9. The method according to claim 6, wherein the stirring time in step (b) is 0.5 to 10 minutes.
10. 7. The method according to claim 6, wherein the pH of the reaction solution after addition of the base solution in step (c) is 10 or more.
11. The method of claim 6, wherein the insoluble shell has a thickness of 5 to 45% of an average particle diameter.
12. The method according to claim 6, wherein the silane is at least one selected from the group consisting of phenyl silane, TEOS, TMOS, SiCl ₄ , and silane having an organic group other than a phenyl group, or a mixture thereof.
13. 13. The method according to claim 12, wherein the phenyl silane is PTMS.
14. The method according to claim 12, wherein the silane mixture is 80 wt% or more of phenyl silane and 20 wt% or less of other silanes.
15. According to claim 6, The base solution is NH ₄ OH, or TMAH (Tetramethyl ammonium hydroxide), octylamine (octylamine, OA, CH ₃ (CH ₂ ) ₆ CH ₂ H ₂ ), dodecylamine (DDA, CH ₃ (CH ₂ ) ₁₀ CH ₂ NH ₂ ), hexadecylamine, HDA, CH ₃ (CH ₂ ) ₁₄ CH ₂ NH ₂ ), 2-aminopropanol, 2- (methylphenylamino) ethanol, 2- ( Ethylphenylamino) ethanol, 2-amino-1-butanol, (diisopropylamino) ethanol, 2-diethylaminoethanol, 4-aminophenylaminoisopropanol, N-ethylaminoethanol, monoethanolamine, diethanolamine, Triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, methyl diethanolamine, dimethyl monoethanolamine, ethyl diethanolamine, diethyl monoethanolamine, characterized in that the alkylamine solution selected from the group consisting of Manufacturing method.
16. The method according to claim 6, wherein the reaction temperature in the step (b) and (d) is 40 ~ 80 ℃.
17. 7. The method of claim 6, further comprising (g) sonicating the filtrate after filtration in step (f).
18. The method of claim 6, wherein the drying temperature is 250 ° C. or less.
19. 7. A method according to claim 6, further comprising (i) modifying the surface of the hollow silica particles after step (f).
20. A composition comprising the hollow silica particles of any one of claims 1 to 5, a resin, and a solvent.
21. The composition according to claim 20, wherein the hollow silica particles are 30 to 80% by weight based on the total composition.
22. The composition of claim 20 wherein the resin is 20-70% by weight relative to the total composition.
23. 21. The composition of claim 20, wherein the resin has a refractive index of less than 1.5.
24. The resin of claim 20, wherein the resin is at least one selected from acrylate-based polymer resins, polyimide (PI) resins, C-PVC resins, PVDF resins, ABS resins, CTFE, and the like, or a mixture thereof. Composition.
25. 21. The composition of claim 20, further comprising at least one selected from hard coats, UV blockers, or IR blockers.
26. An insulating sheet having a visible light transmittance of 70% or more, a thermal conductivity of less than 0.1 W / m · K and a filling rate of hollow silica particles of 30 to 80%, including a substrate and a coating layer formed by applying the composition of claim 21 to the substrate.
27.  The heat insulating sheet according to claim 26, wherein the coating layer has UV blocking and IR blocking functions.
28. 27. The thermal insulation sheet according to claim 26, wherein the substrate is a sheet of polymer material, fiber, film, or glass.
29. Preparing a substrate;

    Applying the composition of claim 20 to the substrate to form a coating layer; and

    Hardening the coating layer; Method of manufacturing a thermal insulation sheet comprising.

Images