JP2004143405A - Method for producing resin fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing resin particles capable of obtaining the resin particles having a high sphericity and uniform particle diameter easily. <P>SOLUTION: The method for producing resin particles is provided by heating and/or pressurizing a mixture of the resin with a fluid not dissolving the resin at a normal temperature and pressure, and having a process 1 of making at least one component of the liquid state fluid as a supercritical state or semi-supercritical state and a process 2 of lowering the temperature of the liquid state fluid and releasing the pressure. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing fine resin particles that can easily obtain fine resin particles having a high sphericity and a uniform particle diameter.
[0002]
[Prior art]
BACKGROUND ART Resin fine particles are widely used in applications such as a lubricity-imparting agent, a toner, a matting agent for paint, an additive for light diffusion, a filler for chromatography, and a carrier for immunodiagnostic reagents. Particularly in recent years, applications in the IT field, such as spacers for liquid crystal panels and base particles of conductive fine particles, have been expanding. It is required that resin fine particles used in the IT field and the like, such as spacers for liquid crystal panels and base particles of conductive fine particles, be spherical and have a narrow particle size distribution.
[0003]
Conventionally, as a method of producing resin fine particles, a method of physically pulverizing using a pulverizer or the like has been used. According to this method, resin fine particles can be easily obtained at low cost for many resins. However, in this method, the shape of the obtained resin fine particles is indefinite, the particle size is large, and a process such as classification is required to obtain a narrow particle size distribution, and the strength of the obtained resin fine particles is also high. There is a problem that it tends to be weak.
[0004]
On the other hand, a method for producing resin fine particles by a polymerization method such as emulsion polymerization, dispersion polymerization, seed polymerization, or suspension polymerization has been proposed. For example, Patent Document 1 discloses a resin obtained by preparing a monomer dispersion containing droplets of a desired size in advance, and then introducing the dispersion into a polymerization tank and performing polymerization under ordinary stirring. Methods for controlling the particle size and particle size distribution of fine particles have been proposed. According to this method, spherical resin particles having a narrow particle size distribution can be produced. However, these methods are not only applicable to resins that can be polymerized by these polymerization methods, but also require the polymerization conditions and the like to be extremely strictly adjusted in order to produce resin fine particles having a target particle diameter. was there.
[0005]
[Patent Document 1]
JP-A-3-131603
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and has as its object to provide a method for producing resin fine particles capable of easily obtaining resin fine particles having a high sphericity and a uniform particle diameter.
[0007]
[Means for Solving the Problems]
The present invention provides a step 1 of heating and / or pressurizing a mixture of a resin and a fluid that does not dissolve the resin at normal temperature and pressure to bring at least one component of the fluid into a supercritical state or a subcritical state; And a step of depressurizing the fluid by depressurizing the fluid.
Hereinafter, the present invention will be described in detail.
[0008]
The present inventors have as a result of intensive studies, heating and / or pressurizing a mixture of a resin and a fluid that does not dissolve the resin at normal temperature and normal pressure to bring at least one component of the fluid into a supercritical state or a subcritical state, After that, it was found that by lowering the temperature and decompressing, a resin fine particle suspension in which resin fine particles having a high sphericity and a uniform particle diameter were suspended in a fluid was obtained, and the present invention was completed.
A fluid in a supercritical or subcritical state has both the diffusivity of a gas and the solubility of a liquid. Therefore, at normal temperature and normal pressure, even if a poor solvent is used for the resin, a supercritical state or a subcritical state becomes a good solvent, and the resin can be dissolved and dispersed. After that, if the temperature is reduced and the pressure is released, the fluid becomes a poor solvent again, so that the dissolved resin is deposited. Since the resin was in a very high dispersion state in a fluid in a supercritical state or a subcritical state, it is considered that the precipitated resin is extremely small and almost completely spherical due to its surface tension.
[0009]
In this specification, a supercritical fluid refers to a fluid that is at or above a critical pressure (hereinafter, also referred to as Pc) and at or above a critical temperature (hereinafter, also referred to as Tc). The subcritical fluid is a state other than the supercritical state, and when the pressure and temperature during the reaction are P and T, respectively, 0.5 <P / Pc <1.0 and 0.5 < It means T / Tc or a fluid satisfying the condition of 0.5 <P / Pc and 0.5 <T / Tc <1.0. The preferred pressure and temperature ranges of the subcritical fluid are 0.6 <P / Pc <1.0 and 0.6 <T / Tc, or 0.6 <P / Pc and 0.6 <T / Tc. <1.0. However, when the fluid is water, the range of temperature and pressure at which the fluid becomes a subcritical fluid is 0.5 <P / Pc <1.0 and 0.5 <T / Tc, or 0.5 <P / Pc. / Pc and 0.5 <T / Tc <1.0. Here, the temperature represents Celsius, but when either Tc or T is minus in Celsius, the above expression for the subcritical state is not limited to this.
[0010]
In the method for producing resin fine particles of the present invention, first, a resin is mixed with a fluid that does not melt at normal temperature and normal pressure.
The resin to which the method for producing resin fine particles of the present invention can be applied is not particularly limited, and examples thereof include a polyester resin such as polyethylene terephthalate; a polyphenylene ether resin; an alicyclic hydrocarbon resin; a thermoplastic polyimide resin; a polyamide imide resin; Resin; polyolefin resin; polystyrene resin; polyamide resin; polyvinyl acetal resin; polyvinyl alcohol resin; polyvinyl acetate resin; poly (meth) acrylate resin such as polyvinyl chloride resin and polymethyl methacrylate; polyetherimide resin; And a plastic polybenzimidazole resin.
Also, for example, epoxy resin, curable modified polyphenylene ether resin, curable polyimide resin, silicon resin, benzoxazine resin, melanin resin, urea resin, allyl resin, phenol resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin Curable resin such as furan resin, polyurethane resin, aniline resin and the like can also be used.
[0011]
In producing the resin fine particles in the method for producing resin fine particles of the present invention, it is preferable that the shape of the resin be such that the specific surface area (surface area per unit volume) is large. By increasing the specific surface area, the contact between the fluid and the resin can be performed with high efficiency, and the processing time can be reduced. By shortening the processing time, energy efficiency can be increased, and decomposition and deterioration of the resin can be suppressed. The method for increasing the specific surface area is not particularly limited, and examples thereof include a method using a powdery resin having a diameter of about 1 to 5 mm, and a method using a resin previously formed into a film of 1 mm or less.
[0012]
The fluid is not particularly limited as long as it does not dissolve the resin at normal temperature and normal pressure, but may be a liquid that is liquid at normal temperature and normal pressure such as an organic medium such as water or alcohol, or carbon dioxide, It may be a gas at normal temperature and normal pressure such as nitrogen, oxygen, helium, argon, and air, or a mixed fluid thereof. However, it is preferable to contain at least one kind that is liquid at normal temperature and normal pressure. When the fluid is only a gas that is a gas at normal temperature and normal pressure, an extremely high pressure and temperature may be required to dissolve the resin in the fluid.
When a mixed fluid is used as the fluid, at least one component of the fluid constituting the mixed fluid may be in a supercritical state or a subcritical state.
[0013]
As the fluid which is liquid at normal temperature and normal pressure, water and / or alcohol are preferable. Water is an easy-to-use medium, is economical because it is inexpensive, and is preferable in terms of its effect on the environment. Alcohols such as methanol are also preferred for similar reasons. Furthermore, if isopropanol, which is a secondary alcohol, is used, hydrolysis of the hydrolyzable resin can be suppressed.
Unless the resin is dissolved at normal temperature and normal pressure, saturated, unsaturated, linear, branched, and cyclic saturated hydrocarbons such as hexane, heptane, isobutane, isopentane, neopentane, cyclohexane, and butene; toluene, benzene, styrene, xylene Organic solvents such as acetone, isobutyl methyl ketone, isopropyl methyl ketone, and methyl ethyl ketone; carboxylic acid compounds such as isovaleric acid and acetic acid; diethyl ether, dibutyl ether, tetrahydrofuran, dioxane, etc. Ether organic solvents; ester organic solvents such as ethyl acetate and butyl acetate; amine organic solvents such as hexamethylene diamine; acrylic organic solvents such as methyl (meth) acrylate and ethyl (meth) acrylate; dimethyl sulfoxide , N, N Dimethylformamide, N, N- dimethylacetamide can be used also N- methyl-2-pyrrolidone. These organic solvents may be partially or entirely modified by halogenation or the like.
[0014]
An optimal combination of the resin and the fluid is selected within a range satisfying the above-described conditions. For example, when the resin is polyethylene terephthalate, methanol is preferable as the liquid fluid, and when the resin is polymethyl methacrylate, water is preferable as the liquid fluid, and the resin is a polyolefin resin. In such a case, a mixed fluid of water and alcohol is suitable as the liquid fluid.
[0015]
In the method for producing resin fine particles of the present invention, the mixture of the resin and the fluid is heated and / or pressurized to make the fluid a supercritical state or a subcritical fluid. When the fluid is a mixed fluid, at least one component may be in a supercritical state or a subcritical fluid. For example, it is known that water becomes a supercritical state at a temperature of about 374 ° C. or more and a pressure of about 22 MPa or more, and methanol becomes a supercritical state at a temperature of about 240 ° C. or more and a pressure of about 8 MPa or more.
If the mixture is sealed in a pressure vessel, a supercritical state or a subcritical state can be easily achieved by heating. The heat-resistant container is not particularly limited, and a conventionally known one can be used. For example, an autoclave or the like can be used.
[0016]
The supercritical state or subcritical state is an environment with extremely high activity, and the chemical reaction is greatly accelerated, so if the resin is kept in the supercritical state for a long time, reactions such as esterification and acetalization may occur and decomposition may occur. Reaction may occur. Therefore, it is preferable that the time during which the resin is placed in the supercritical state or the subcritical state is within a short time such that the resin does not react. For example, in the case of a combination of polyethylene terephthalate and methanol, the temperature is preferably set to 250 ° C. within 5 minutes.
[0017]
Further, it is preferable to stir the mixture of the resin and the fluid in a supercritical state or a subcritical state. By stirring and applying a shearing force, the resin is more uniformly diffused in the fluid, and the particle diameter of the obtained resin fine particles can be made more uniform.
The stirring method is not particularly limited, and a conventionally known method can be used. For example, a method using a stirring motor for an autoclave, or a hard sphere that is stable in a supercritical state or a subcritical state in advance (for example, A method of placing at least one steel ball or the like in a pressure vessel and shaking the pressure vessel in a supercritical state or a subcritical state.
[0018]
After maintaining the supercritical state or subcritical state for a predetermined time, it is preferable that the temperature of the fluid is rapidly lowered to decompress the fluid. If the resin is left in the supercritical state or subcritical state for a long time as described above, the resin may react. After a predetermined time has elapsed, the reaction of the resin can be prevented by rapidly cooling in a sealed state and returning to normal temperature and normal pressure. The method of quenching is not particularly limited, and includes, for example, a method of air-cooling or water-cooling the pressure-resistant container.
Through the above steps, a suspension of fine resin particles is obtained. The resin fine particles in the obtained suspension are almost perfectly spherical, and the particle size distribution is extremely narrow.
[0019]
The method for recovering the resin fine particles from the resin fine particle suspension is not particularly limited, and a conventionally known method can be used. However, depending on the combination of the resin and the fluid, the obtained resin fine particle suspension may have a sticky feeling. In this case, it is necessary to prevent the resin fine particles from coalescing when collecting the resin fine particles. is there. For example, a method in which the resin fine particle suspension is dried while being heated in the air using a heat source such as hot air or far infrared rays, or a method in which the resin fine particle suspension is once washed with a non-polar solvent and then dried. FIG. 1 shows an example of an apparatus for thermally drying in the air while dropping the resin fine particle suspension.
[0020]
In the method for producing resin fine particles of the present invention, a mixture of a resin and a fluid that does not dissolve the resin at normal temperature and normal pressure is heated and / or pressurized so that at least one component of the fluid is in a supercritical state or a subcritical state, and then the temperature is lowered. By releasing the pressure, it is possible to obtain a suspension of resin fine particles which are almost perfectly spherical and have a narrow particle size distribution. In the present invention, a series of steps can be performed by controlling only the temperature by using a sealed pressure-resistant container.
Furthermore, if the production conditions are adjusted, the thermal decomposition of the resin hardly occurs. Therefore, when a high-molecular-weight resin is used as a raw material, high-molecular-weight resin fine particles can be obtained as they are. In addition, even if the molecular weight of the raw material resin varies, by performing the operation to remove the relatively low molecular weight resin dissolved in the fluid in the process until the supercritical state or subcritical state, high molecular weight and Resin fine particles having a narrow molecular weight distribution can also be obtained.
According to the method for producing resin fine particles of the present invention, spherical resin fine particles having a uniform particle diameter can be obtained very easily for most resins.
[0021]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0022]
(Example 1)
4 g of methanol and 0.2 g of polyethylene terephthalate pellets having a diameter of about 3 mm were placed in a pressure-resistant container having an internal volume of 10 mL, and sealed. Note that one SUS ball was put in the heat-resistant container in advance. The pressure vessel was vibrated to mix methanol and polyethylene terephthalate, and then heated to 250 ° C. in an oil bath to bring the methanol to a supercritical state. In this state, the pressure vessel was vibrated, and rapidly cooled after 5 minutes to return to normal temperature and normal pressure.
As a result, a resin fine particle suspension in which fine particles of polyethylene terephthalate were suspended in methanol was obtained.
Observation of the resin fine particles in the obtained resin fine particle suspension revealed that the resin fine particles were almost completely spherical and the average particle diameter was 8.6 μm. FIG. 2 shows the particle size distribution of the obtained resin fine particles.
[0023]
(Example 2)
4 g of water and 0.2 g of pelletized polymethyl methacrylate having a diameter of about 3 mm were placed in a pressure-resistant container having an internal volume of 10 mL, and sealed. In addition, one SUS ball was previously placed in the thick container. After the water and polymethyl methacrylate were mixed by vibrating the pressure vessel, the mixture was heated to 400 ° C. in a sand bath to bring the water to a supercritical state. After 5 minutes, the mixture was rapidly cooled and returned to normal temperature and normal pressure.
As a result, a resin fine particle suspension in which fine particles of poly (methyl methacrylate) were suspended in water was obtained.
[0024]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the sphericity is high and the manufacturing method of the resin fine particle which can easily obtain the resin fine particle with a uniform particle diameter can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an apparatus for thermally drying in the air while dropping a resin particle suspension.
FIG. 2 is a view showing a distribution of particle diameters of resin fine particles obtained in Example 1.

Claims (4)

Heating and / or pressurizing a mixture of a resin and a fluid that does not dissolve the resin at normal temperature and pressure to bring at least one component of the fluid into a supercritical state or a subcritical state;
And 2. depressurizing the fluid by depressurizing the fluid. Resin and a mixture of a fluid that does not dissolve the resin at normal temperature and normal pressure is sealed in a pressure vessel, and heating the pressure vessel to bring at least one component of the fluid into a supercritical state or a subcritical state; and ,
And 2. depressurizing the pressure-resistant container by rapidly cooling the pressure-resistant container. 3. The method for producing resin fine particles according to claim 1, wherein the fluid contains a liquid that is liquid at normal temperature and normal pressure. The method for producing resin fine particles according to claim 1, wherein the fluid contains water and / or alcohol.

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