JPS61211342A - Production of ultrafine high-molecular material particle - Google Patents

Abstract

PURPOSE:To obtain the titled ultrafine particle which is in the form of a true sphere and has the desired average particle size and particle size distribution, by subjecting a high- molecular material soln. to a microscopic phase separation by cooling, evaporation, etc., to separate it into an amorphous high-molecular material-rich phase particle and a high- molecular material-lean dispersion medium and recovering the former. CONSTITUTION:A high-molecular material (e.g. cellulose linters) having an average degree of polymn. Dp of 500 or below is dissolved in a good solvent (e.g. cuprammonium soln.) in such a proportion as to give a high-molecular material soln. which has a concn. of 0.1wt% or above and a viscosity eta of 10cp or below at 20 deg.C and satisfies the relationship of the formula (wherein Dp is an average degree of polymn. and eta is viscosity). The high-molecular material soln. is subjected to microscopic phase separation by cooling said soln., evaporating said good solvent from said soln., mixing said soln. with a non-solvent (e.g. acetone) for said high-molecular compd. or a combination thereof to separate it into an amorphous high- molecular material-rich phase particle and a high-molecular material-lean dispersion medium. The high-molecular material-rich phase particle in the dispersed state is separated, recovered and spray-dried to obtain in the title ultrafine particle having an average particle size of 0.02-10mu.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing ultrafine particles made of polymer compounds. In this specification, "ultrafine particles" refer to particles that are approximately spherical in shape and have an average particle size of 1.0 μm or less. In addition, in this specification, "polymer compound" means
It refers to a compound with a molecular weight of 1000 or more and whose main chain is mainly made up of covalent bonds, and does not include inorganic polymer compounds whose main component is an element other than carbon atoms.

[Problems to be solved by conventional technology and invention]

Until now, fine particles made of polymer compounds have been used such as nylon, ? Those made of listyrene, polyacrylonitrile, polyethylene, polypropylene, fluorine-based polymer compounds, natural cellulose, regenerated cellulose, etc. are known. The average particle size of these fine particles is 5.0 μm or more, except for what is called latex.

There are two methods for producing fine particles: physical methods and chemical methods.

In principle, the physical method can be said to be the pulverization of fine particles. Examples include a method of grinding by mechanical force, a method of causing particles to collide and break up, and a freeze-fracture method. The shape of the fine particles obtained by these physical methods is not spherical or fixed. Furthermore, the width of the particle size distribution of the obtained fine particles is wide. In order to obtain fine particles with an average particle size of 3 μm or less using these methods, there are extremely difficult points such as the need to repeat the crushing process over a long period of time.

On the other hand, the main chemical method is based on emulsion polymerization. The shape of the obtained particles is close to spherical. However, the materials to which this method can be applied are limited.

In addition, this method has drawbacks such as difficulty in controlling particle size.

Furthermore, as a method between physical methods and chemical methods, there is a method in which crushed particles are treated with a corrosive reagent such as acid or alkali. Even with this method, it is not possible to eliminate the drawbacks of physical methods, such as non-uniformity in particle shape, non-uniformity in particle size distribution, and non-uniformity in crystalline and amorphous regions of polymer compounds. Furthermore, the difficulty in particle size control, which was a drawback of chemical methods, has not been sufficiently solved.

The purpose of the present invention is to take into consideration the drawbacks of the prior art as described above, and to obtain polymers with an average particle diameter of 0.0211 m or more and Rr1 or less by using a microphase separation method from polymer compounds that can be dissolved in a solvent. The purpose of the present invention is to provide a method for producing ultrafine particles.

[Means for solving problems]

Microphase separation in the method of the present invention refers to, in a homogeneous one-phase system consisting of a polymer compound and its good solvent, (1) cooling the system or (2) evaporating the good solvent from the thread. or (3) adding a non-solvent for the polymer compound to the system, or a combination of these operations (1) to (3), the amorphous polymer concentrated phase becomes granular. It involves phase separation into a two-phase state of a polymer-rich phase and a polymer-dilute phase to form a particle phase with a diameter of about 1 μm or less. When a solution of a highly crystalline polymer compound is subjected to phase separation, a plate-like solid phase often precipitates. In this case, if the temperature is raised to a temperature higher than the melting point of the solid phase, amorphous dense phase particles can be 'IJ'ed.

Ultrafine particles are almost perfectly spherical in shape and have an average particle size of 1
Refers to particles smaller than μm. "True spherical" means that the particle diameter observed in an electron micrograph falls within a range of ±10%.

In addition, the polymer compound used in the method of the present invention has a molecular weight of 1000 or more, the main chain is mainly made of covalent bonds, and the main target is an organic polymer compound whose main component is carbon atoms. It is.

In this specification, the particle size or grain size refers to the particle size or particle size measured by electron microscopy. However,
If the particle size is in the region of 0.1 μm or less and the particle size cannot be clearly measured by electron microscopy, the average particle size by optical quasi-elastic light scattering is also used. (9) The particle size indicated means the number average particle size.

A good solvent for the polymer compound used in the method of the present invention refers to a solvent that can dissolve the aforementioned polymer compound at a concentration of 1% by weight or more at 20°C. On the other hand, a non-solvent refers to a solvent that can be dissolved only at a concentration of 0.01% by weight or less at 20°C.

In order to transfer a polymer solution in which a polymer compound is dissolved in its good solvent to a microphase-separated state, (1) gradually cool the polymer solution, (2) evaporate the good solvent from the 11-molecule solution. or (3) adding a non-solvent of polymeric arsenic metal, any one of the three methods of <1) to (3) above may be carried out alone, or these (13 to (
You can arbitrarily combine two or three of the operations in 3) and perform them simultaneously or sequentially. There are cases in which the polymer compound forms particles, and cases in which the polymer compound forms particles.Which microphase separation state occurs depends on the type and concentration of the polymer compound, the type and concentration of the solvent used, and the microphase separation state. It cannot be generally defined because it varies depending on various conditions such as the operating method and temperature.

However, if all the above-mentioned conditions are selected appropriately, it is possible to determine the conditions for each individual case in which the polymer-rich phase is always present in the form of particles.

Generally, in the process in which a polymer solution transitions to a microphase separation state, the average particle size first becomes 0.02 μm (200 μm).
The primary particles of X) appear. These primary particles repeatedly collide with each other and have an average particle size of 1. It can grow to secondary particles of about θ μm. Average particle size is approximately 1μm
When the particle size reaches 1, the collisions between secondary particles become more frequent.) Rather than a single particle existing alone, each particle begins to form a string of beads. The mechanism by which a porous polymer body is formed by a series of secondary particles is already used as a method for manufacturing porous polymer membranes; This method has never been considered.

As a result of intensive study on the correlation between the polymer solution composition and the state of microphase separation, the present inventors found that when the viscosity of the polymer solution is 10 cP or less at 20°C, (1) the polymer solution is completely cooled. , (2) evaporating the solvent from the polymer solution, and (3) mixing the polymer solution with a non-solvent for the polymer compound. 3 of these (1) to (3)
Any one of the seed operations or these (1)
When a polymer solution is subjected to microphase separation such that the polymer-rich phase becomes a particle phase by any combination of the operations described in (3) above, the above-mentioned phenomenon in which the secondary particles are linked together in a beaded pattern occurs. It has been found that ultrafine polymer particles having an average particle diameter of 0.021 B or more and 1.0 μm or less can be produced without causing any of the following.

One factor that defines the viscosity of a polymer solution is the degree of polymerization of the polymer compound in the polymer solution. The details of how the degree of polymerization affects the process of producing ultrafine particles are unknown, but the range in which the average degree of polymerization Dp and the viscosity η of the polymer solution at 20°C satisfies the following formula (1) is unknown. It is desirable that the

Dp≦(75o/log2) (] −tagη)
(1) In the above formula (1), η is the viscosity (cP) of the polymer solution at 20° C., and Dp is the average degree of polymerization of the polymer compound.

If the viscosity of the polymer solution is the same, the average degree of polymerization D
The lower p is, the higher the yield of ultrafine particle production tends to be. It is desirable that the average degree of polymerization Dp is 500 or less.

Another factor that defines the viscosity of a polymer solution is the concentration of the polymer compound in the polymer solution. In order to reduce the probability that secondary particles collide with each other, it is effective to lower the particle density. The concentration of the polymer compound in the polymer solution is 5
．． When the amount is 0% by weight or less, the probability of existence of dispersed particles increases rapidly. However, in order to increase the production efficiency of ultrafine particles (the weight of ultrafine particles recovered from a unit solution), it is desirable that the concentration is 0.1 weight or more.

Naturally, the lower limit of the concentration needs to be at least a concentration that causes microphase separation.

In order to prevent agglomeration of dispersed particles, it is preferable to carry out the entire microphase separation method by adding a non-solvent. Furthermore, it is even more effective to add a surfactant to the polymer solution or non-solvent.

In order to obtain monodisperse ultrafine particles in a dry state, freeze drying, spray drying, critical point drying, etc. are effective. The spray drying method changes the size of ultrafine particle aggregates, which are made by agglomerating multiple ultrafine particles, from the size of monodisperse ultrafine particles by fully adjusting the ultrafine particle concentration in the ultrafine particle dispersion and the size of the sprayed droplets. This method allows dry fine particles of any size to be obtained. Although the average particle size of one ultrafine particle is up to 1.0 μm at most, ultrafine particle aggregates with an average particle size of up to about 10 μm can be produced by spray drying.

In this specification, the numerical values of viscosity, particle size, and particle size distribution are measured by the following measurement methods.

(a) Viscosity The viscosity of the polymer solution was measured at 20° C. using a B-type viscometer model BBL manufactured by Tokyo Keiki Seisakusho.

(b) Particle size and particle size distribution Scanning electron microscope [JEOL JSM-35CF model] and transmission electron microscope [JEOL JEM-1200E]
It was determined from a photograph taken with the X type. Particle size is 0.1
If the total particle size cannot be clearly measured by electron microscopy in the μm or less region, photogravielastic light scattering method (Submicron Particle Analyzer Model N manufactured by Coulter Co., Ltd.) is used.
4) Use the obtained values together.

〔Effect of the invention〕

According to the present invention, no matter what kind of polymer compound,
As long as it can be dissolved in a solvent, ultrafine particles can be produced in principle by causing a state of microphase separation.

Finally, by selecting the viscosity of the polymer solution, the concentration and degree of polymerization of the polymer compound, the type and concentration of the solvent, the method for expressing microphase separation, etc., the average particle size and particle size distribution of ultrafine particles can be easily adjusted. Can be adjusted.

This is an innovative method that can produce particles that are particularly spherical and have a narrow particle size distribution.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Cellulose linter (viscosity average molecular weight: 2.4 x 10 ) was dissolved in a cupric ammonia solution prepared by a known method at a concentration of 10% by weight to obtain a stock solution of a cellulose cupric ammonia solution.

This stock solution was diluted with 28% ammonia aqueous solution, and 8% by weight
, 5% by weight, 2% by weight, 1% by weight, 0.5% by weight and 0.1% by weight of cellulose cupric ammonia solutions. These cellulose copper ammonia solutions 25ml 1'Fr: 5
Add ON amount to 500 ml of thiacetone aqueous solution at 20℃ using a pipette. After confirming that microphase separation has occurred, immediately add concentrated sulfuric acid to coagulate and regenerate cellulose. Remove coarse floating matter. Ultrafine particles in p liquid? Collect by centrifugation for 30 minutes at 10.00 Orpm and resuspend in pure water for 5 minutes.
Circumcision 1. The ultrafine particles were washed with water.

The degree of polymerization of the cellulose regenerated from each diluted cellulose cuprammonium solution is determined from the viscosity of the solution obtained by washing the coarse cellulose suspended matter regenerated from the 5.0% by weight cellulose cuprammonium solution with water, drying it, and dissolving it in cadoxene. This is considered to be equivalent to the determined degree of polymerization of cellulose.

Table 1 As shown in Table 1, the viscosity η of the polymer solution at 20°C
is 10 cP or less, ultrafine particles are produced.

Example 2 A 10% by weight cellulose copper ammonia solution prepared in the same manner as in Example 1 was diluted with 28% aqueous ammonia to obtain diluted cellulose of 1.2% by weight, 2.4% by weight, and 6.0% by weight. It was made into a copper ammonia solution. Add 20 rnlt of 0.5% to 5% hydrogen peroxide solution to these diluted cellulose cuprammonium solutions (1/1) to lower the degree of polymerization of cellulose, and increase the cellulose a degree of each diluted cellulose cuprammonium solution by 1 0% by weight, 2.0% by weight, and 5.0% by weight. After being left at room temperature (20°C to 25°C) for more than 1 hour, the mixture was poured into a 50% by weight acetone aqueous solution in the same manner as in Example 1. Added, solidified and regenerated after micro phase separation,
I washed it with water.

The degree of cellulose polymerization was determined from the viscosity of the cadoxene solution. The complete results are shown in Table 2.

Below is a blank table. 2 Example 3 A 10% cellulose steel ammonia g solution stock solution prepared in the same manner as in Example 1 was diluted with 28% ammonia water to a concentration of 5% by weight. This 5% by weight solution was stored in a sealed T-polyethylene container at room temperature (5°C to 25°C),
When the viscosity of the solution at 20° C. reached 4 cP, it was further diluted with 28 thiammonium water to give a concentration of 1% by weight. Example 1
Washed with water in the same way. When the particle size distribution of the ultrafine particles was measured using a submicron particle analyzer manufactured by Coulter, the average particle size was 0.3 μm, the minimum particle size was 0.04 μm, and the maximum particle size was 1.0 μm.

Example 4 The concentration of the suspension of ultrafine particles obtained in Example 3 in water was adjusted to 0.2% by weight, 0.5% by weight, 1% by weight, and 3% by weight. Mother Rubis minivet)'GA-21
The mold was dried using the sysspray drying method. The obtained dry granules are aggregates of ultrafine particles, and the average particle size is 1.0 μm.
, 1.9 μm, 2.6 μm, and 4.9 μm in that order.

' Example 5 Cellulose diacetate (substitution degree 2.46) IN synthesized by a known method was dissolved in 100 I of acetone, and all undissolved matter was removed with a glass filter to form an acetone-equalized phase I solution of cellulose diacetate. (Viscosity 0.6c at 25℃
P)'i prepared as follows. 10ml of this solution 1 methanol/Ca
Mixed liquid of Ct2/2H20 (weight ratio 100:30) 10
0m7 to cause micro phase separation and form ultrafine particles?
generated. As in Example 1, centrifugation and suspension in water were repeated to perform water washing.

The average particle size of the obtained ultrafine particles was about 0.9 μm.

Example 6 Polyacrylonitrile (weight average molecular weight: 150,000) synthesized by a known method was dissolved in dimethylformamide to form a 1% by weight homogeneous phase solution. This solution] 01d was poured into 10,011 Ll of a 50% by weight aqueous dimethylformamide solution to cause complete microphase separation to produce ultrafine polyacrylonitrile particles, which were washed with water in the same manner as in Example 1. The average particle size of the obtained ultrafine particles was 0.3 μm.

Claims (1)

[Claims] 1. Prepare a polymer solution consisting of a polymer compound and its good solvent and having a viscosity η of 10 cP or less at 20°C,
Either by cooling the polymer solution, evaporating the good solvent from the polymer solution, or mixing the polymer solution with a non-solvent for the polymer compound. , or by any combination of these methods, microphase separation is performed into amorphous polymeric concentrated phase particles and a polymeric diluted phase dispersion medium, and the polymeric concentrated phase particles are separated and recovered in a dispersed state. A method for producing ultrafine polymer particles, which produces ultrafine polymer particles having an average particle diameter of 0.02 μm or more and 1.0 μm or less. 2. The method according to claim 1, wherein the viscosity η of the polymer solution at 20° C. and the average degree of polymerization Dp of the polymer compound satisfy the following formula (1). Dp≦(750/log2)(1-logη) (1) In the formula, η is the viscosity (cP) of the polymer solution at 20°C, and Dp is the average degree of polymerization of the polymer compound. 3. The method according to claim 1 or 2, wherein the polymer compound has an average degree of polymerization Dp of 500 or less. 4. The method according to any one of claims 1 to 3, wherein the concentration of the polymer solution is 0.1% by weight or more. 5. The method according to any one of claims 1 to 4, wherein a surfactant is added to the polymer solution or the nonsolvent when mixing the nonsolvent to the polymer solution. 6. The method according to any one of claims 1 to 5, wherein the ultrafine particles are dried by a spray drying method.