JP3344003B2 - Method for producing spherical particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example,
The present invention relates to a method for producing optimal spherical particles used for producing monodispersed spherical particles of about m to several mm.

[0002]

2. Description of the Related Art Monodispersed polymer spherical particles are widely used as spacers for liquid crystal display devices (LCDs), matting materials for paints, fillers such as lubricating materials, carriers for diagnostic agents, and standard particles. I have. However, it is generally very difficult to produce monodisperse polymer particles having a specific particle size.

For example, in emulsion polymerization, monodispersed polymer particles can be produced relatively easily, but usually only polymer particles having a particle size of about 1 μm or less are obtained.
It is said that the production of polymer particles having a particle size of about 3 μm is the limit even under special conditions.

On the other hand, in suspension polymerization, the particle size is 1 to 100 μm.
Although it is possible to produce polymer spherical particles over a relatively wide range of about m, it is difficult to control the particle size, so that the obtained polymer particles have a considerably wide particle size distribution. Therefore, in order to obtain polymer particles in a monodispersed state having a certain particle size by suspension polymerization, it is necessary to classify the polymer particles produced in suspension polymerization, and therefore, the number of steps is increased. There are problems that the operation is complicated and the yield is low.

As a method for producing polymer particles having a relatively large particle size in a monodispersed state, JP-A-54-975 discloses a method.
A technique disclosed in Japanese Patent Application Publication No. 82 or Japanese Patent Application Laid-Open No. 54-126288 is known.

In Japanese Patent Application Laid-Open No. 54-97582, a polymer having a molecular weight much lower than that of a normal polymer latex is produced by adding a chain transfer agent during emulsion polymerization, and this is used as seed particles. A method for producing polymer particles by absorbing unsaturated monomers which are somewhat soluble in water into the seed particles is disclosed.

However, in this method, when an oil-soluble initiator or a water-soluble initiator is used as a polymerization initiator, problems such as aggregation of polymer particles or generation of new polymer particles occur. It is considered that it is difficult to reliably obtain polymer particles having a large particle size in a monodispersed state with a high yield.

In Japanese Patent Application Laid-Open No. 54-126288, in the first stage, the solubility in water is 10 ^-2 g /
An organic compound as a swelling aid, smaller than 1 liter H ₂ O, is absorbed by the seed particles. In the second step, a polymerizable monomer which is somewhat soluble in water of about 100 times the volume of the seed particles is removed. Absorbed by seed particles to form swollen particles, and then use a water-soluble polymerization initiator such as potassium peroxide or an oil-soluble polymerization initiator such as azoisobutyronitrile as a polymerization initiator to maintain the shape of the seed particles A method for producing polymer particles by growing seed particles as it is is disclosed.

However, in this method, when an oil-soluble polymerization initiator is used as a polymerization initiator, even polymerizable monomers dispersed in water are polymerized, and polymer particles having a small particle size are newly formed. When a large amount is produced, a polymer particle having a single particle size cannot be obtained, and when a water-soluble polymerization initiator is used as a polymerization initiator, even if the emulsifier concentration is equal to or less than the critical micelle concentration, water is not obtained. The growth radicals in the phase act as an emulsifier, so that the so-called soap-free emulsion polymerization proceeds partially or entirely, so that the form of swollen particles cannot be maintained. Further, according to this method, in the first step of the process, the polymer particles obtained are distorted due to the action of the low water-soluble organic compound as a swelling aid to be absorbed by the seed particles, and it is considered that true spherical particles cannot be obtained. Can be

As a method for solving such a problem,
A method of growing seed particles without using a swelling aid is described in J. Polym. Sei., Polym. Lett. Ed., 21 , 937-943 (198
3) (by JHJansson, MCWellons, GWPoehlein).

According to this method, the polymerizable monomer and the oil-soluble polymerization initiator are mixed in advance, and this mixture is finely dispersed to form an emulsion of the polymerizable monomer. By adding to the dispersion (latex),
Seed particles can be grown with a high swelling ratio of 14: 1.

However, the polymer particles obtained by this method are considered to have a problem that the uniformity of the particle diameter is inferior to that of the method described in JP-A-54-126288.

The nonuniform particle size of the polymer particles obtained by the above method is considered to be due to the following phenomenon. That is, after mixing the polymerizable monomer and the oil-soluble polymerization initiator, the polymerizable monomer mixture is dispersed in an aqueous dispersion medium, and in this dispersion step, heat is applied due to high shear energy applied to the system. Is generated, and a part of the polymerizable monomer is polymerized by the heat, so that a new polymer is generated in the droplet of the polymerizable monomer mixture. Then, since the surrounding polymerizable monomer mixture is absorbed by the polymer, the polymerizable monomer is not sufficiently absorbed by the seed particles. Thus, while the growth of the seed particles becomes insufficient, a large number of new polymer particles are generated,
The particle size distribution of the obtained polymer particles becomes wider.

On the other hand, Japanese Utility Model Application Laid-Open No. 61-190504
JP, JP-A-61-215604, JP-A-61-215604
JP-A-215605 and JP-A-62-63856 disclose that the solubility in water is 0.001% by weight or less.
Methods for producing polymer particles using 0.02% by weight of an organic substance as a swelling aid are disclosed. However, in these methods, it is necessary to disperse the swelling aid in a smaller size than the seed particles. When the fine dispersion of the swelling aid is insufficient, it is considered that monodispersed polymer particles having a uniform particle size cannot be obtained.

[0015]

As described above, in the conventional example, not only can the monodisperse polymer particles having a relatively wide particle size distribution and a uniform particle diameter be obtained, but also a wide range can be obtained. At present, it is difficult to control the particle size over a range of temperatures, and it is difficult to impart functions such as coloring, magnetism, and conductivity in the polymerization process.

In view of the above, the present invention provides a method for controlling monodisperse polymer particles having a relatively narrow particle size distribution and a more uniform particle size, in which the particle size can be controlled over a wide range. It is an object of the present invention to provide a product which not only can be obtained by a simple process but also can easily impart functions such as coloring, magnetism, and conductivity.

[0017]

In order to achieve the above object, a method for producing spherical particles according to the present invention comprises a vibrating orifice obtained by adding a radiation-curable substance to a vibrating means.
The droplets are used to form droplets and float in a fluid, and the droplets of the radiation-curable substance in suspension are irradiated with light to be cured in suspension.

[0018]

In general, when a liquid is formed into droplets and suspended in a fluid such as air or water, the droplets have the most stable spherical shape due to the surface tension. For example, by using a vibrating orifice or impactor, the droplets can be granulated. Spherical particles having a substantially uniform diameter can be relatively easily produced, and the particle diameter can be relatively easily controlled over a wide range. Therefore, radiation-curable substances are used for orifices.
Use a vibrating orifice with vibration means
By applying vibrating liquid to form droplets and suspend in the fluid, irradiate light in this state to cure the suspended radiation-curable substance to produce spherical particles, thereby narrowing the particle size distribution to a true spherical shape. The particle size can be controlled over a wide range while maintaining it, and by adding additives such as a coloring agent and a magnetic substance to the radiation-curable substance before being formed into droplets, the function of the additive can be obtained. Can be easily provided.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus used in the first embodiment. This apparatus uses an aerosol sprayer as a droplet preparation means to produce relatively small spherical particles having a particle size of about 1 to 20 μm. It is something to do.

That is, in FIG. 1, reference numeral 1 denotes an aerosol sprayer. The aerosol sprayer 1 comprises a flask-shaped closed container 2 and a double container extending upward through the mouth of the closed container 2. A gas inlet pipe 4 for introducing compressed gas is connected to the double pipe nozzle 3.

The double pipe nozzle 3 has two flow paths, that is, a first flow path 3a extending vertically along a center line.
And a second concentrically surrounding and bending the periphery of the first flow path 3a.
A flow path 3b is provided, and the second flow path 3b and the gas introduction pipe 4 are configured to communicate with each other, and an opening for communicating the inside of the sealed container 2 with the second flow path 3b. A hole 3c is provided.

Then, in a state where the radiation-curable substance 5 is filled in the closed vessel 2, a compressed gas is introduced from the gas introduction pipe 4 into the second flow path 3 b of the double-tube nozzle 3, By pressurizing the inside, the radiation-curable substance 5
Is ejected from the tip of the double-tube nozzle 3 to the outside as an aerosol, that is, as an ultrafine powder (droplet) 5a in the form of droplets.

On the other hand, there is provided a reaction tank 7 having an impactor 6 formed by bending a pipe upward at a right angle.
The aerosol sprayer 1 is arranged so that the tip of the double tube nozzle 3 faces the impactor 6.

As a result, the relatively large droplet 5a ejected from the tip of the double tube nozzle 3 collides with the impactor 6 and falls downward, and only the droplet 5a having a substantially constant particle size passes through the impactor 6. After passing through, it reaches the inside of the reaction tank 7, where it floats in the air with a stable spherical shape.

A quartz glass plate 8 is provided above the reaction tank 7.
A light source 10 having an ultraviolet lamp 9 is disposed above the quartz glass plate 8, and the inner peripheral surface of the reaction tank 7 is almost entirely covered with, for example, a mirror-finished surface or aluminum. A reflection film 11 such as a lining is formed.

As a result, the ultraviolet light from the ultraviolet lamp 9 that has passed through the quartz glass plate 8 is reflected multiple times by the reflection film 11, and all around the droplet 5 a floating in the reaction tank 7. And irradiate the droplet 5a
Is hardened while spontaneously settling in the reaction tank 7, and the resulting spherical particles 5 b are deposited on the bottom of the reaction tank 7.

The production of spherical particles using the apparatus constructed as described above is performed as follows. The radiation curable substance 5 is filled in the closed container 2 of the aerosol sprayer 1 in this state.
The inside of the closed vessel 2 is pressurized by introducing a high-pressure gas into the second flow path 3b, and at the same time, the ultraviolet lamp 9 is turned on. Then, the radiation-curable substance 5 in the sealed container 2 is formed into droplets from the tip of the double-tube nozzle 3 of the aerosol sprayer 1, is formed into a stable spherical shape, and is jetted toward the impactor 6. The droplets 5a having a relatively large diameter are excluded, and only the droplets 5a having a substantially constant particle diameter pass through the impactor 6 and reach the inside of the reaction tank 7, where they float. Then, ultraviolet rays are irradiated during this floating to be cured, whereby spherical particles 5 b are generated and deposited on the bottom of the reaction tank 7.

By placing the substrate 12 on the bottom of the reaction tank 7, the cured droplets 5a, that is, the generated spherical particles 5b can be deposited on the upper surface of the substrate 12. .

The droplet 5a, and thus the spherical particle 5b
Can be easily controlled by adjusting the concentration of the radiation-curable substance 5, the pressure of the high-pressure gas introduced from the gas introduction pipe 4, and the inner and outer diameters of the double pipe nozzle 3. Can be.

For example, a radiation-curable substance 5 is a urethane acrylate radiation-curable resin SCR300 (manufactured by Nippon Synthetic Rubber Co., Ltd.), and a double-tube nozzle 3 having an inner diameter of 0.2 mm and an outer diameter of 1 mm. By using each of them and setting the pressure of the high-pressure gas introduced from the gas introduction pipe 4 to 2 kg / cm ² and the flow rate to 1 liter / min, the droplets 5a having an average particle diameter of 10 μm can be produced. .

At this time, the curing time when irradiating with a light source of 100 mJ / cm ² is about 0.1 second, and by setting the height of the reaction tank 7 to 50 cm or more, the droplet 5 a This can be surely hardened while floating inside.

If the curing time is long and the droplets 5a do not cure while spontaneously settling in the reaction tank 7, the N ₂ gas, hot air or the like is sent from below the reaction tank 7 so that the natural The settling time can also be controlled, thereby ensuring that it sets during suspension.

As described above, by using the impactor 6, spherical particles made of the radiation-curable substance 5 having a substantially uniform particle diameter can be relatively easily produced, and the spherical particles can be formed by floating in the air. It can be held stably, and the particle size can be controlled relatively easily over a wide range. Therefore, by irradiating light in this state to cure the floating radiation-curable substance to produce spherical particles, it is possible to control the particle size over a wide range while maintaining a true spherical shape and a narrow particle size distribution. Can be.

The radiation-curable substance 5 includes reduced polyisoprene, reduced polybutadiene, poly (meth) acrylate of polyether, and poly (meth) acrylate of polyvinyl alcohol which are generally known as radiation-sensitive resin or radiation-curable resin. Examples include cinnamic acid esters, novolak resins, polyglycidyl methacrylate, and chlorinated polymethylstyrene.

These radiation curable substances are diluted with a solvent or a polymerizable monomer, and a radiation crosslinking agent or a radiation polymerization initiator is added. As the solvent, for example, xylene or methylcellosolve acetate is used, but the use of a radiation-curable substance diluted with a polymerizable monomer enhances the particle strength and facilitates control of the particle size. This is preferable in terms of realization.

As the polymerizable monomer, styrene, α
-Methylstyrene, vinyltoluene, chlorostyrene,
Vinyl aromatic monomers such as divinylbenzene, (meth) acrylic acid, methyl (meth) acrylate, n-butyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol di (meth) acrylate , Acrylic monomers such as (meth) acrylonitrile,
Vinyl ester monomers such as vinyl formate and vinyl acetate,
Examples thereof include vinyl halide monomers such as vinyl chloride and vinylidene chloride, and diallyl phthalate and triallyl cyanurate.

These polymerizable monomers may be used alone or in a combination of two or more. Preferred polymerizable monomers are styrene, (meth) acrylate and divinylbenzene. If the polymerized monomer having two or more vinyl groups is used in an amount of 30% by weight or more based on the total weight of the monomer, the additive no longer migrates and elutes even when the produced particles are brought into contact with an organic substance, and Since the particles are not deformed by heat, they can be suitably used, for example, as liquid crystal spacer particles for LCD.

Examples of the radiation crosslinking agent or radiation polymerization initiator include azide compounds such as aromatic azides and trichloromethyltriazide, silver halides, bisimidazole derivatives, cyanine dyes and ketocoumarin dyes. In addition, an azo radical polymerization initiator such as azobisisobutyronitrile and azobisvaleronitrile can be used.

The radiation-curable substance 5 before the above-mentioned curing is used.
In addition, oil-soluble dyes, carbon black, iron oxide, coloring agents such as titanium oxide, ferrite, magnetic substances such as magnetite,
By adding a metal fine powder such as a nickel powder and an aluminum powder, functions such as conductivity, mechanical properties, and coloring properties can be imparted. The addition amount is, for example, 0.1 to 50 parts by weight based on 100 parts by weight of the radiation-curable substance.

At this time, by disposing a stirrer (not shown) inside the closed vessel 2, these additives can be more uniformly dispersed in the solution of the radiation-curable substance 5.

The wavelength of light for curing the droplets 5a of the radiation-curable substance 5 during the floating is from ultraviolet to 480.
nm, particularly 250 to 410 nm, and a high-pressure or low-pressure mercury lamp can be used as a light source. The energy required for this curing is several mJ / cm ² to several J / cm.
² is preferred.

By using a vibrating orifice in which vibration is applied to the orifice as a means for producing droplets, the particle size is controlled while keeping the particle size distribution narrow, so that the particle size is 1-2.
Spherical particles of about 00 μm can be produced. This is because if the particle size exceeds 200 μm, the curing reaction does not proceed sufficiently, and the particles may aggregate, and if the particle size is less than 1 μm, the particle size distribution becomes wide.

The vibrating orifice has an inner diameter of 10
Preferably, the vibration frequency is adjusted to, for example, several hundred to several million Hz. As means for vibrating the orifice, for example, a vibrator or a piezo element that vibrates when a voltage is applied can be used. The direction of vibration may be vertical or horizontal with respect to the orifice.

FIG. 2 shows a monodisperse aerosol generator MODEL as a means for producing droplets using the vibrating orifice.
3450 (manufactured by TSI, USA) 15 and the droplets 5 of the radiation-curable substance generated by the aerosol generator 15 are used.
This shows an apparatus in which a is introduced into a reaction tank 7 having substantially the same configuration as the apparatus shown in FIG.

That is, this aeizorol generator 15
Controlling the ejection of a cylindrical molten jet by means of a vibrating orifice, utilizing the principle that if a suitable vibration is applied to the droplet, the formation of the droplet will be stable and uniform particles can be obtained. Aerosol particles.

Then, one droplet is formed in one cycle, and the flow rate passing through the orifice is Q,
If the frequency of vibration is f, the volume of the droplet is represented by Q / f, and if the volume concentration of the solution is C, the particle size can be calculated as DP = (6CQ / πf) ^1/3. ing.

In this apparatus, the above-mentioned SCR 300 is used as a radiation-curable substance.
2 parts by weight of black oil-soluble dye oil black G and 10 parts by weight of acetone were added to the
pressure of 2kg / using a micrometer vibration orifice (nozzle)
When droplets were generated and cured at a frequency of 1 MHz and cm ² , black particles having an average particle size of 8 μm were obtained, and the standard deviation of the particle size was 0.2 μm.

The particles are useful, for example, as an LCD spacer. FIG. 3 shows an apparatus used in the second embodiment. This apparatus uses an orifice as a droplet producing means, and hardens the droplet in a state of being suspended in water, thereby forming a particle. This is to produce relatively large spherical particles having a diameter of 10 μm or more. When this apparatus is used, particles having a particle size of several mm can be produced.

This device is provided with a syringe 20 and a micro feeder 22 for moving a piston 21 of the syringe 20, and is configured such that the volume in the syringe 20 decreases with the operation of the micro feeder 22. At the same time, a thin tube 23 is connected to the tip of the syringe 20, and an orifice 24 is connected to the thin tube 23. Further, a water pipe 25 for flowing water is laid horizontally, and the tip of the orifice 24 reaches almost the center of the water pipe 25.

In this way, with the syringe 20 filled with the radiation curable substance 5, the micro feeder 22
Is operated to reduce the volume in the syringe 20, and at the same time, water is caused to flow in the water pipe 25, so that the radiation-curable substance 5 flows out from the tip of the orifice 24 and is turned into ultrafine powder (droplets). It is configured to float the water flowing through the water pipe 25 by 5a.

A quartz tube 26 is fitted into the water tube 25 on the downstream side of the position where the orifice 24 is arranged. The quartz tube 26 is surrounded by a reflecting plate 27 and bent around the reflecting plate 27. A light source 10 having an ultraviolet lamp 9 is arranged outside. A window 27a is provided at a position of the reflection plate 27 corresponding to the ultraviolet lamp 9.

As a result, the ultraviolet light from the ultraviolet lamp 9 that has passed through the quartz tube 26 is reflected multiple times by the reflection plate 27, and all around the droplet 5 a floating in the water in the water tube 25. And irradiate the droplet 5
is hardened while passing through the quartz tube 26, and the resulting spherical particles 5b are sequentially sent out together with water.

The production of spherical particles using the above-configured apparatus is performed as follows. While filling the radiation curable substance 5 in the syringe 20,
Water is allowed to flow in the water channel 25. In this state, the micro feeder 22 is operated at a constant speed to gradually reduce the volume in the syringe 20 and simultaneously turn on the ultraviolet lamp 9. Then, the radiation-curable substance 5 in the syringe 20
Flows out from the tip of the orifice 24 through the thin tube 23. At this time, when the droplet gradually grows and reaches a predetermined size, the droplet separates from the orifice 24 and separates from the water tube 25.
It floats in a stable spherical shape in the water flowing inside. And
Ultraviolet rays are irradiated during this floating to be cured, whereby spherical particles 5b are generated and sequentially sent out.

The droplets 5a and thus the spherical particles 5b
Is the concentration of the radiation-curable substance 5, the orifice 24
Can be easily controlled by adjusting the inner diameter of the sample, the amount of the radiation-curable substance extruded by the microfeeder 22, and the like.

For example, the SCR 300 is used as the radiation-curable substance 5, 20 parts by weight of magnetite having a major axis length of 10 nm is added to 100 parts by weight of the SCR 300, and the orifice 24 having an inner diameter of 25 μm is used. When the amount of the radiation-curable substance 5 extruded by the microfeeder 22 is 0.5 g / min, magnetic particles having an average particle diameter of 55 μm and a standard deviation of the particle diameter of 3 μm can be obtained.

At this time, the flow of water near the orifice 24 was set at 5 cm per minute, and a quartz tube 26 having an inner diameter of 1 cm and a length of 30 cm was used. Curing is complete.

The particles are useful, for example, as a carrier for a diagnostic agent. In the case of this embodiment, as shown in FIG. 4, a double pipe nozzle including an inner pipe 30 extending substantially vertically upward and an outer pipe 31 surrounding and surrounding the inner pipe 30 is used.
A radiation curable substance may flow through the inner tube 30 and water may flow through the outer tube 31, and the radiation curable substance and water may be mixed at the tip of the inner tube 30. .

In this case, when the radiation-curable resin droplet 5a ejected from the tip (upper end) of the inner tube 30 mixes with the water flowing inside the outer tube 31, it is necessary to adjust the droplets 5a so that they do not collide with each other. The particle diameter can be controlled by adjusting the concentration of the radiation-curable substance 5, the inner diameter of the inner tube 30, the discharge pressure of the radiation-curable substance, the discharge pressure of water, and the like.

Here, in order to improve the dispersibility of the radiation-curable substance in the aqueous medium, a dispersion stabilizer can be used by melting it in the aqueous medium. Examples of the dispersion stabilizer include polymer dispersion stabilizers such as polyvinyl alcohol, polyvinyl porolidone, polyacrylic acid, polyacrylamide, and polyethylene oxide, anionic surfactants, cationic surfactants, and nonionic surfactants. .

The droplets made of the radiation-curable substance may be partially cured in the air to complete the curing reaction in an aqueous medium. In addition, an organic medium that is easily volatilized or an organic medium having high solubility in water, for example, a substance such as ether, acetone, or ethanol is dissolved in a radiation-curable substance, and the particles are evaporated as the substance evaporates or moves to water. It is also possible to adjust the diameter to a smaller one.

[0061]

Since the present invention has the above configuration,
Vibration of radiation-curable substance added to the orifice
By applying appropriate vibrations to the droplets using an orifice and suspending them in a fluid with the most stable droplets in the fluid, and curing in this state, spherical spherical particles can be formed into a relatively simple process. Can be produced. Moreover, the particle size of the droplets is made more uniform, the particle size distribution is narrowed, the particle size can be easily controlled over a wide range, and functions such as coloring, magnetism, and conductivity can be easily provided. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an apparatus used in a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an outline of another device.

FIG. 3 is a schematic diagram showing an outline of an apparatus used in a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing an outline of another device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 aerosol sprayer 2 closed container 3 double tube nozzle 5 radiation curable substance 5 a droplet 5 b spherical particle 6 impactor 7 reaction tank 9 ultraviolet lamp 11 reflective film 15 aerosol generator 20 syringe 22 microfeeder 24 orifice 25 water pipe 27 reflector

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-56-62803 (JP, A) JP-A-56-112966 (JP, A) JP-A-56-62804 (JP, A) JP-A-1- 234230 (JP, A) JP-A-60-7931 (JP, A) JP-A-6-248107 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 2/46 -2 / 50

Claims (1)

(57) [Claims] An orifice is provided with a radiation-curable substance at an orifice.
Using a vibrating orifice with a step, it is formed into droplets and floats in a fluid, and the droplet-forming floating radiation-curable substance is irradiated with light and cured during floating. A method for producing spherical particles.