KR20000067505A - Method of producing organic gel microsphere - Google Patents

Abstract

PURPOSE: A method for preparing particle-shaped organic gel by single process is provided, which uses supercritical carbon dioxide solvent as a diffusion media. CONSTITUTION: The method comprises the steps of adding 5-40 wt% of an acid catalyst (based on the weight of monomer) and 2-20 wt% (based on the weight of supercritical fluid) of a stabilizer to multifunctional monomer in a high pressure reactor to prepare the mixture solution; diffusion polymerizing the mixture solution by using supercritical carbon dioxide as a diffusion media at the pressure of 400-1200 psi and the temperature of 40-120°C for 4-24 hours; curing it for 10-72 hours; and releasing the supercritical carbon dioxide. The multifunctional monomer is one or more materials selected from the group consisting of phenolic-furfural, resorcinol-formaldehyde, melamine-formaldehyde, catechol-formaldehyde, phenol-resorcinol-formaldehyde, phloroglucinol-formaldehyde and phenol-formaldehyde.

Description

Method for producing organic gel in particle form {METHOD OF PRODUCING ORGANIC GEL MICROSPHERE}

The present invention relates to a method for preparing an organic gel in the form of particles, and more particularly, to a method for preparing an organic gel such as a phenolic-perperal gel in the form of particles in a single process using a supercritical carbon dioxide as a dispersion medium. .

Gel is a solid material having a three-dimensional continuous phase structure extending in the sol state is formed by complex bonds such as covalent bonds, ionic bonds and hydrogen bonds by chain entanglement. Gels are materials with a wide range of applications, for example as electrophoretic fields of protein mixtures, chromatography packing fields, soft lens fields and intermediates of aerogels.

Aerogels are materials made by Kisler in 1931 that have a very large inner surface area due to their low density and high porosity. These aerogels can be used as alternative materials, such as conventional CFC blown polyurethane foams or inorganic insulations, which are used as insulation, and can be used as chemical catalysts, ion exchange resins, particle accelerators, noise reduction, piezoelectric elements, insulating glass and release It has a wide range of applications, including controlled pharmaceutical materials.

Existing foam insulation can not be used for low density of less than 100kg / ㎡ because of the relatively high density, and because the pore size is limited to lower the thermal conductivity, it was difficult to use as a super insulation material. To this end, research into inorganic and organic aerogels is being conducted as a heat insulating material. Silica-based airgels in inorganic airgels are prepared by supercritical drying through hydrolysis and polycondensation of tetramethoxy silane (TMOS) or tetraethoxy silane (TEOS) under acid or base catalysts. In the case of using an acid catalyst, linear or slight crosslinked polymers are formed and gels are formed by entanglement thereof, and in the case of a base catalyst, a colloidal gel is formed by the crosslinked polymer. Such silica-based airgel has high porosity and very small pore size (100 nm or less), thereby lowering thermal conductivity.

Among the inorganic airgels, silica airgels with the highest thermal insulation effect have a total thermal conductivity of 0.013 W / m · K at a density of 120 kg / m3 at room temperature and in air. It is showing effect. However, compared with organic aerogels, the thermal insulation performance is generally poor and fragile in terms of structure. In addition, for low-density applications, atoms having an atomic number of 8 or less should be used. Silica-based airgels have an atomic number of silicon (Si) of 14, which has a higher density and higher thermal conductivity than organic airgels. On the other hand, in the case of an airgel, the atomic number of carbon constituting most of the structure is 6, and the remaining elements hydrogen and oxygen are 1 and 8, which are suitable for small cell and pore size, and have lower thermal conductivity than that of inorganic airgel. It is more suitable for application to ultra-insulating materials.

This organic airgel was only recently developed and started in 1984 at the Lawrence Livermore National Laboratory (L.L.N.L) in the United States. Dual resorcinol-formaldehyde aerogels have the structure most similar to inorganic aerogels and use carbon dioxide as a supercritical fluid to extract solvents at low temperature to form aerogels without modification of the structure.

Resorcinol-formaldehyde-based organic aerogels are described in R.W. No. 4,873,218 and US Pat. No. 4,997,804. Invented by Pekala, melamine-formaldehyde organic aerogels are also described in R.W. No. 5,081,163, 5,086,085. Invented by Pekala.

Organic gels in monolithic form prepared by sol-gel methods from phenolic-furfural-alcohol solutions are described in US Pat. Nos. 5,476,878 and 5,556,892. Invented by Pekala.

Since phenolic-perforated aerogels react with carbon dioxide and friendly alcohols, simplification of the process can be achieved by eliminating the solvent substitution process required in the resorcinol-formaldehyde or melamine-formaldehyde reactions.

However, the manufacturing of phenolic perforated aerogels in the form of particles rather than monolithic has a number of advantages, for example, in the form of particles in energy storage applications can increase the mechanical elasticity of the composite electrode, suitable binder As a result, it can be applied to a low voltage, single cell, such as a "jelly roll" cell similar to the existing "AA", "C", "D" cells. It can also be used in air filtration and medical applications. In terms of the process aspect, unlike the monolithic form produced in the batch process, the particle form can be produced through the batch and semicontinuous processes, which is advantageous for the actual process application, and the flowability is excellent due to the excellent flowability. It is easy.

Synthesis of gel particles using the sol-gel process has been largely classified into four methods. The first method is to synthesize a monolithic gel by milling and to use agglomeration of particles as a chemical method during hydrolysis, and to generate particles using aerosol, emulsification method or reverse phase emulsification. There is this. In this way, nanometer-sized particles are synthesized.

Hereinafter, a method of preparing a resorcinol-formaldehyde gel using a conventional sol-emulsion-gel method will be described.

The resorcinol-formaldehyde solution is suspended and stabilized in an organic nonpolar solvent with the appropriate surfactant. At this time, the choice of surfactant is determined by the suitability and suspension composition of the hydrophilic lipophilic balance (HLB) water of the surfactant used in the emulsion. The emulsion droplets then serve as mini reactors during the gelling step.

However, when the organic gel is manufactured through the sol-emulsion gel method, there is a problem of using a solvent harmful to the environment, and there is a problem in that the final product of the airgel cannot be manufactured in a single process, thereby reducing productivity.

Unlike the sol-emulsion-gel method using a solvent that is harmful to the environment as described above, an object of the present invention is to form organic particles in the form of particles rather than monoliths through the sol-dispersion-gel method using supercritical carbon dioxide as a solvent. It is to provide a method for preparing a gel.

1 is a scanning electron micrograph (× 5000) of organic gel particles prepared according to Example 1 of the present invention.

In order to achieve the above object, the method for preparing an organic gel in the form of particles of the present invention is to add an acid catalyst and a stabilizer to a multifunctional monomer in a high pressure reactor, and then disperse the supercritical carbon dioxide under a pressure of 40 to 120 ° C. and 1200 to 4000 psi. After the dispersion polymerization for 4 to 24 hours, after curing for 10 to 72 hours, the supercritical carbon dioxide is discharged.

The present invention will be described in more detail as follows.

In the present invention, it is characterized by using a supercritical fluid as a reaction solvent. In general, supercritical fluid is defined as a material above the critical temperature (Tc) and the critical pressure (Pc). One important advantage of using supercritical fluids in a continuous phase is the ability to control the properties of solvents such as dielectric constants simply by changing the temperature or pressure of the system. In addition, supercritical fluids have properties between liquid and gas. Supercritical fluids, in particular, have the same density as the liquid and the same viscosity as the gas. Among supercritical fluids, CO ₂ has been used as a highly effective continuous phase for many applications.

First, the sources of CO ₂ are abundant natural CO ₂ and recycled CO ₂ recovered from the emission streams of plants and power plants producing ethanol, ammonia, hydrogen and ethylene oxide. CO ₂ also has easy-to-access critical points such as Tc at 31.1 ° C. and Pc at 73.8 bar.

Another advantage of using CO ₂ as a solvent is that it is inexpensive, nonflammable, nontoxic and easily recyclable. In addition, supercritical CO ₂ can be used to effectively extract residual monomers, solvents, and catalysts from polymers. In addition, polymerization with supercritical fluids can change the density simply by changing the pressure, effectively separating polymer mixtures of different molecular weights. When the supercritical CO ₂ is adsorbed onto the polymer, the melt viscosity and the solution viscosity can be reduced, so that the form of the polymer can be controlled by supercritical drying or foaming.

In the reaction apparatus used in the present invention, since carbon dioxide is used as a supercritical solvent, a siphon tube is mounted in a carbon dioxide container to eject liquid carbon dioxide, and the liquid carbon dioxide is completely liquefied by passing it through a cooler to pressurize using a high pressure liquid pump. Allow liquid carbon dioxide to enter. The high pressure reactor is equipped with a jacketed portion of which pressure is sealed up to 4000 psi and a proportional integral derivative controller capable of temperature control from -20 ° C to 200 ° C, a stirrer capable of stirring the thermometer, heater, pressure gauge, safety valves and reactants and the following speeds. A tachometer is attached to the controller and to measure the speed.

In the present invention, in order to set the reaction conditions, a monolithic gel is first synthesized. The appropriate amount of monomer and catalyst was dissolved in alcohol and placed in an ampule and sealed by heating with a torch to prevent contact with air. At this time, by changing the content ratio of the content of the catalyst and the solid content it was intended to see the properties accordingly.

The sealed ampoules are placed in an 80 ° C. to 85 ° C. oven to gel for 7 days. At the end of the reaction, a dark brown gel is formed.

In the present invention, unlike the sol-emulsion-gel technology using a solvent that is harmful to the environment, phenolic- in the form of particles through a sol-dispersion-gel technology using supercritical carbon dioxide, which is an environmentally friendly solvent, as a solvent. Synthetic gel particles.

More specifically, first, the multifunctional monomer is placed in a high pressure reactor, and an acid catalyst and a stabilizer are added thereto.

Multifunctional monomers include phenolic-peralal, resorcinol-formaldehyde, melamine-formaldehyde, catechol-formaldehyde, phenol-resosocinol-formaldehyde, fluoroglucinol-formaldehyde (Phloroglucinol-formaldehyde) or phenol-formaldehyde is used to select one.

The stabilizer may be selected from polydimethylsiloxanes and polydihydroperfluorooctyl acrylates, and the content thereof is preferably 2 to 20% based on the supercritical fluid.

As the acid catalyst is used, one of the acid catalyst is selected from paratoluene sulfonic acid and phosphoric acid. The content of the acid catalyst is preferably 5 to 40% with respect to the phenolic novolac.

Then, dispersion polymerization is performed for 4 to 24 hours at a pressure of 1200 to 4000 psi at 40 to 120 ° C. using supercritical carbon dioxide as a dispersion medium.

If the reaction temperature is higher than the boiling point of the alcohol, a problem of boiling the reactant may occur. When the reaction pressure is low and the reaction temperature is high, the solubility of phenolic novolac in supercritical carbon dioxide deteriorates, which facilitates dispersion. On the other hand, if the reaction temperature is too low, there is a disadvantage in that it takes a long time to gel. In addition, if the reaction time is shorter than the gelling time of the reactant may cause a problem that the sol-gel reaction cannot proceed completely.

As such, when the multifunctional monomer is suspended in supercritical carbon dioxide and dispersed using a stabilizer, the resultant does not need to be washed, unlike the conventional sol-emulsion-gel method.

After the dispersion polymerization is carried out as described above, the mixture is cured for 10 to 72 hours, and the supercritical carbon dioxide is gradually discharged.

The discharge of the supercritical carbon dioxide after completion of the reaction is to prevent the prepared organic gel from breaking, and the discharge time of the supercritical fluid is preferably 0.5 to 5 hours depending on the size of the stainless steel reactor.

The present invention first synthesized phenolic-peralal gel in the form of particles, and is the first to synthesize a gel using supercritical carbon dioxide as a reaction solvent. In addition, this invention is important not only in the synthesis of organic gels but also in the synthesis of intermediates capable of producing phenolic-perforated aerogels in a single process.

The present invention provides a method for preparing solid particles for synthesizing and heat treating the desired organic gel particles in the form of a sol-dispersion-gel method in a supercritical fluid solvent, wherein the organic gel particles have a particle diameter of 500 nm to 100 μm, The distribution is characterized by having 90% or more of particles having a size of 1 to 10 µm. The organic gel particles have a density of 0.03 to 1.0 g / cc.

Looking specifically at the method for producing a phenolic-perforated gel of the organic gel according to the present invention, first, phenolic novolac, peroxide, alcohol, acid catalyst and stabilizer are mixed in the high pressure reactor to make a mixed solution.

In this case, one alcohol is selected from heptyl alcohol, octyl alcohol, normal propanol, isopropanol, ethanol and methanol. At this time, the solid content ratio of the mixed solvent is preferably 10 to 70% by weight.

Then, the reaction mixture is stirred, it is preferable that the stirring speed is 100 to 500rpm, and the average particle size, particle size distribution, and particle shape vary depending on the type of the stirrer.

After stirring, supercritical carbon dioxide was used as a dispersion medium, and the sol-gel reaction was carried out by pressing and heating. The reaction temperature was 40 to 120 ° C, the reaction pressure was preferably 1200 to 4000 psi, and the reaction time was 4 to 24. As a result, the conversion rate should be 70% or more as a result.

Then, it is cured for 10 to 72 hours, and the supercritical carbon dioxide is slowly discharged to obtain a phenolic-perforated gel according to the present invention.

On the other hand, the schematic reaction step of phenolic novolac and perperal is as follows.

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

Example 1

After dissolving 13.6 g of phenol resin and 13,6 g of perol in 70 g of heptyl alcohol solvent, the mixture was put in a high pressure reactor. 2.8 g of a catalyst for producing hydrogen chloride (paratoluene sulfonic acid, manufactured by Junsei Japan) and 20 g of polydimethylsiloxane as a stabilizer were added thereto, followed by sol-gel reaction for 12 hours using supercritical carbon dioxide at 80 ° C. as a dispersion medium. Harden (pressure 1200psi) Then, supercritical carbon dioxide was slowly discharged into the atmosphere over 1 hour.

The phenolic-perforated gel produced had a dark brown color and had a density of 0.03 to 1.0 g / cc. Other solvents may be used isopropanol, normal propanol, ethanol, methanol, octanol. However, when the solvent is different as above, the curing temperature should be different.

The average particle diameter and particle size distribution of the prepared phenolic-peral gel were measured by an electron microscope (SEM, S4200, Hitachi, Japan). The measurement result was 90% of the particle distribution with an average particle diameter of 3.5 micrometers and a particle size distribution of 3-5 micrometers.

The gelling time of the phenolic-peralal-alcohol solution was 5 hours.

Example 2

After dissolving 9.09 g of phenol resin and 9.09 g of perol in 80 g of octyl alcohol solvent, the mixture was placed in a high pressure reactor. 1.82 g of a catalyst for producing hydrogen chloride (phosphate, manufactured by Junsei, Japan) and 10 g of polydimethylsiloxane as a stabilizer were added thereto, and an organic gel particle was prepared by sol-gel reaction for 18 hours using a supercritical carbon dioxide at 80 ° C. as a dispersion medium. (Pressure 1200 psi). At this time, the process is the same as in Example 1.

Other solvents may be used isopropanol, normal propanol, ethanol, methanol, octanol. However, when the solvent is different as above, the curing temperature is different.

The particle diameter and particle size distribution of the prepared organic gel particles were measured by scanning electron microscope.

Example 3

Organic gel particles were prepared by changing the content of the stabilizer to 20% with respect to the supercritical fluid using the same process as in Example 1.

The prepared phenolic-perforated gel particle diameter and particle size distribution were measured by scanning electron microscopy. At this time, since the particle color of the phenolic peripheral gel is dark, the particle size of the phenolic peripheral gel cannot be measured using the light scattering method.

Example 4

Organic gel particles were prepared by changing the content of the acid catalyst to 30% with respect to the phenolic novolac using the same process as in Example 1.

The prepared phenolic peripheral gel particle diameter and particle size distribution were measured by an electron microscope.

Example 5

Using the same process as in Example 1, the reaction temperature was changed to 40 ° C., the reaction pressure was changed to 2500 psi, and the sol-gel reaction was carried out for 12 hours, followed by curing for one day. The prepared phenolic-perforated gel particle diameter and particle size distribution were measured by an electron microscope.

Example 6

Using the same process as in Example 1, 8g of resorcinol and 12g of formaldehyde were dissolved in 223g of propanol and then placed in a high pressure reactor. Here, 1.6 g of a catalyst for producing hydrogen chloride (paratoluene sulfonic acid, manufactured by Junsei, Japan) and 20 g of polydimethylsiloxane as a stabilizer were added thereto, followed by a sol-gel reaction at 80 ° C. and 1200 psi for 24 hours, followed by curing for one day. Formaldehyde gel particles were prepared. At this time, the prepared isosinol-formaldehyde gel particles are reddish brown.

Example 7

Using the same process as in Example 1, 21.44 g of melanin monomer and 18.86 g of formaldehyde were dissolved in 156.64 g of ethanol and then placed in a high pressure reactor. Here, 9.5 g of a catalyst for producing hydrogen chloride (paratoluenesulfonic acid, manufactured by Junsei Co., Ltd.) and 20 g of polydimethylsiloxane as a stabilizer were added thereto, followed by sol-gel reaction at 80 ° C. and 1200 psi for 24 hours, followed by curing for 2 days, followed by melamine-formaldehyde. Gel particles were prepared. The melamine-formaldehyde gel particles produced are white.

The average particle diameter and particle size distribution of the phenolic-peral gel prepared according to Examples 1 to 7 are as shown in Table 1 below.

Example Average particle diameter Particle Size Distribution (㎛) One 3.5 0.7 to 5 2 4.1 1.6 to 8 3 2.5 0.5 to 4 4 3.1 0.9 to 5 5 3.4 0.5 to 4.5 6 40 10-100 7 35 10 to 90

Meanwhile, an electron micrograph (× 5000) of phenolic-perforated gel particles prepared according to Example 1 is shown in FIG. 1.

The organic gel prepared by the sol-dispersion-gel method using supercritical carbon dioxide as a dispersion medium according to the present invention from the results of Table 1 and the attached FIG. 1 has a particle content in the form of a stabilizer for the supercritical fluid. As the mean particle size decreased, the average particle diameter of the gel was almost the same even if the acid catalyst content of phenolic novolac was changed or the reaction pressure and temperature were changed. In addition, the use of resorcinol formaldehyde or melamine-formaldehyde as the multifunctional monomer showed a larger average particle diameter than that of phenolic-peral.

As described in detail above, in the case of preparing organic gel particles such as phenolic-peripheral gel, etc. by the sol-dispersion-gel method using supercritical carbon dioxide as a dispersion medium according to the present invention, the form is in the form of a single process. It is possible to prepare an organic gel, there is no need to use a harmful solvent as in the sol-emulsion-gel method, there is an effect that does not need to wash the resultant.

Claims (9)

Preparing a mixed solution by adding an acid catalyst and a stabilizer to the multifunctional monomer in a high pressure reactor; Dispersing and polymerizing the mixed solution for 4 to 24 hours at 40 to 120 ° C. and 1200 to 400 psi pressure using supercritical carbon dioxide as a dispersion medium; Curing for 10-72 hours; And Method for producing an organic gel in the form of particles comprising the step of discharging supercritical carbon dioxide. The method of claim 1, Multifunctional monomers include phenolic-peralal, resorcinol-formaldehyde, melamine-formaldehyde, catechol-formaldehyde, phenol-resosocinol-formaldehyde, fluoroglucinol-formaldehyde and phenol-formaldehyde. Method for producing an organic gel in the form of particles, characterized in that one or more selected. The method of claim 1, As an acid catalyst, paratoluene sulfonic acid or phosphoric acid is used to produce 5 to 40% of the monomer. The method of claim 1, The stabilizer is selected from polydimethylsiloxanes or polydihydroperfluorooctyl acrylates and used in the form of organic gel in the form of particles, characterized in that it is used to 2 to 20% with respect to the supercritical fluid. The method of claim 1, Dispersion polymerization is a method for producing an organic gel in the form of particles, characterized in that the conversion is carried out to 70% or more. The method of claim 1, The organic gel has a particle size of 500nm to 100㎛, particle size distribution method of producing an organic gel in the form of particles, characterized in that 90% or more of particles having a particle size of 1-10㎛. The method of claim 1, The mixed solution is a method for producing an organic gel in the form of particles, characterized in that a mixture of phenolic novolac, peripheral, alcohol, acid catalyst and stabilizer. The method of claim 7, wherein The alcohol is a heptyl alcohol, octyl alcohol, normal propanol, isopropanol, ethanol and methanol is selected from one or more selected from among the method of producing an organic gel in the form of particles. The method of claim 1, The method for producing an organic gel in the form of particles, characterized in that the preparation of the organic gel is carried out through a single process.