KR101070365B1 - Process for preparing polymer particles by dispersion polymerization - Google Patents

Abstract

The present invention relates to a method for producing polymer particles by the dispersion polymerization method, and more particularly, to a solution mixture of an oligomer, an unreacted monomer and an initiator by performing solution polymerization in an organic solvent or an aqueous solution without directly adding a monomer. After the preparation, it is injected into a dispersion medium in which a dispersion stabilizer is dissolved or in a dispersion medium in which an organic solvent is used alone or as a co-solvent to perform dispersion polymerization to prepare stable polymer particles having a uniform particle size of several tens of nanometers to several micrometers. It is about.

The manufacturing method according to the present invention is uniform because it has a short nucleation cycle by preparing some of the monomers in an oligomer form through solution polymerization without directly adding the monomer, and then introducing the monomer into a dispersion medium containing a dispersion stabilizer of dispersion polymerization. Particles of the size can be prepared, and the reaction time to reach the final reaction yield can be reduced, so that high economic and high value-added effects can be expected.

Dispersion polymerization, oligomer, solution polymerization, polymer particles

Description

Process for preparing polymer particles by dispersion polymerization

The present invention relates to a method for producing polymer particles by the dispersion polymerization method, and more particularly, to a solution mixture of an oligomer, an unreacted monomer and an initiator by performing solution polymerization in an organic solvent or an aqueous solution without directly adding a monomer. After the preparation, it is injected into a dispersion medium in which a dispersion stabilizer is dissolved or in a dispersion medium in which an organic solvent is used alone or as a co-solvent to perform dispersion polymerization to prepare stable polymer particles having a uniform particle size of several tens of nanometers to several micrometers. It is about.

Generally, polymerization methods for producing spherical polymer particles include suspension polymerization, emulsion polymerization, seed polymerization, precipitation polymerization, dispersion polymerization, and the like. Each polymerization method has advantages and disadvantages.

Suspension polymerization is a method of preparing a polymer particle by adding a hydrophobic monomer in the presence of a dispersion stabilizer, dispersing it in an aqueous solution using a mechanical force, and then polymerizing the dispersed monomer droplets using a fat-soluble initiator. The advantage is that the particles can be obtained by the process, but because the monomer must be dispersed by physical force, the polymer produced has a very wide particle size distribution range of 0.1 to 1000 microns (US Pat. Nos. 4,017,670, 4,017,670, 4,085,169, and 4,129,706). In order to lower the particle size distribution, a method of using separate mechanical devices and separating particles formed in various sizes has been studied (Japanese Patent No. 90-261628), but it requires excessive cost and effort for a complex classification device, The problem is that the productivity is very low.

Emulsion polymerization can produce polymer particles of uniform size ranging from tens to hundreds of nanometers in a single process, but it is difficult to produce particles with diameters larger than that. Adsorption to the foam is not easy to remove or there is a disadvantage in that the resulting physical properties of the polymer formed. The emulsion-free polymerization method, which is one of the emulsion polymerization methods, is a method of obtaining polymer particles by ionization of a water-soluble initiator instead of a surfactant used for imparting stability to particles, unlike a general emulsion polymerization method [J. Appl. Polym. Sci., Vol. 19, 3077 (1975); J. Colloid Interf. Sci., Vol. 230, 210 (2000)].

Seed polymerization is a method for preparing polymer particles having a uniform particle size distribution in microns by re-dispersing the particles of uniform size prepared by emulsion polymerization or dispersion polymerization in a dispersion medium (US patent) Nos. 4.459,378, 6,228,925, and 4,996,265; European Patents 326,383; Japanese Patents 62273215 and 05222204). While the seed polymerization is easy to control the particle size, the polymerization procedure is very difficult, and the long time is required because the polymerization process of two or three steps is required.

Precipitation polymerization is a relatively uniform method of preparing cross-linked spherical polymer particles, but the basic principle is similar to dispersion polymerization, but without the use of steric stabilizer, the particles are themselves maintained in the form of spheres by crosslinking in the particles ( U.S. Patent No. 5,599,889), which is characterized by high purity of the particles produced because there is no unreactive material. However, precipitation polymerization has a limitation in that the types of monomers available and the solvents used as cosolvents are extremely limited.

Finally, dispersion polymerization uses an organic solvent, water or a mixed solvent of water or an organic solvent and water, a steric stabilizer, and a fat-soluble initiator that are soluble in the vinyl monomer and the monomer, and are insoluble in the polymer particles produced by the dispersion polymerization. At the beginning of the reaction, all the reaction components are dissolved in the reaction solvent, and a single phase in a transparent state, or a polymer whose molecular weight increases as the polymerization proceeds, no longer dissolves in the reaction solvent, and precipitates. It is a polymerization method in which particles are obtained in sizes from hundreds of nanometers to tens of microns (KEJ Barrett, Dispersion Polymerization in Organic Media, Wiley, Chichester, England, 1975). The spherical polymer particles formed by the dispersion polymerization method have high uniformity, and are used as standard materials for measuring the device, measuring the efficiency of the size of the filter pores, packing materials for the chromatography column, support in biochemistry, biomedical field, It can be applied to various fields of high value added such as information electronics such as coating, ink, polymerized toner for radiation, anisotropic conductive balls and microelectronic devices. However, this method also has a disadvantage in that the change in particle distribution and the reproducibility of the process are not good because it is sensitive to the reaction environment such as the change in the content ratio of the reaction composition and the presence of oxygen as compared to other polymerization methods. Particle formation begins at the nucleation stage, which causes precipitation of oligomers that are no longer soluble in the reaction solvent, so short nucleation cycles and uniform growth of their initial particles are of utmost importance in obtaining final polymer particles of uniform size. Do.

Accordingly, the present inventors have made efforts to solve the above problems and to produce uniform and stable polymer particles within a shorter reaction time than the conventional dispersion polymerization method. As a result, the present inventors have precipitated the reaction solvent in the dispersion polymerization through the solution polymerization method. The addition of the step of forming an oligomer having a low molecular weight as low as possible to shorten the nucleation time in the particle formation process of the dispersion polymerization to confirm that more uniform and stable particles can be produced, and completed the present invention.

After all, the present invention is to provide a method for producing spherical polymer particles having a uniform particle size of several tens of nanometers to several micrometers by the dispersion polymerization method.

In order to achieve the above object, the present invention prepares a part of the monomer in oligomer form through solution polymerization method without directly inputting the monomer, and then adds it to the dispersion medium containing the dispersion stabilizer of dispersion polymerization to proceed with the dispersion polymerization and dozens of nanometers. In the present invention, there is provided a method for producing polymer particles by dispersion polymerization to produce stable polymer particles having a uniform particle size of several micrometers.

Specifically, in the present invention to prepare the polymer particles by dispersion polymerization method,

(1) mixing a vinyl monomer, an initiator and a reaction solvent and performing solution polymerization to obtain a solution polymer in which an unreacted monomer, an initiator and an oligomer are dissolved in the reaction solvent;

(2) adding the solution polymer to the dispersion medium to which the dispersion stabilizer is added and polymerizing; And

(3) recovering the synthesized polymer particles by dissolving an unreacted stabilizer by adding an excess of water or alcohol to the solution after polymerization, thereby providing a method for producing polymer particles by dispersion polymerization.

In the present invention, the solvent that can be used for the solution polymerization may be used in general, any solvent that can be mixed with the dispersion medium used in the dispersion polymerization while dissolving the organic solvent or aqueous solution used in solution polymerization, especially monomers and initiators, Preferably, one or two or more selected from organic solvents such as alcohols, ethers, ketones, furans, or water may be used and mixed, and are not particularly limited or limited.

In addition, in the present invention, the vinyl monomers may be used as long as the radical initiation used in general dispersion polymerization, emulsion polymerization or suspension polymerization may be used, and all of them may be used in single or multiple kinds. Preferably aromatic vinyl compounds; Cyan vinyl compound; Acrylate compound; Methacrylate type compounds; Diacrylate-based compound, dimethacrylate-based compound and the like can be used together with one kind or two or more kinds, more preferably styrene; Divinylbenzene; Ethyl vinyl benzene; Alphamethylstyrene; Fluorostyrenes; Vinylpyridine; Vinyl chloride; Acrylonitrile; Methacrylonitrile; Methyl acrylate; Butyl acrylate; 2-ethylhexylethyl acrylate; Glycidyl acrylate; N, N'-dimethylaminoethyl acrylate; Butyl methacrylate; 2-ethylhexylethyl methacrylate; Methyl methacrylate; 2-hydroxyethyl methacrylate; Glycidyl methacrylate; Polyethylene glycol diacrylate; 1,3-butylene glycol diacrylate; 1,6-hexanediacrylate; Ethylene glycol dimethacrylate; Diethylene glycol dimethacrylate; Triethylene glycol dimethacrylate; Polyethylene glycol dimethacrylate; 1,3-butylene glycol dimethacrylate and the like may be used together with one kind or two or more kinds, and most preferably one kind or two kinds are used together in acrylonitrile or methyl acrylate.

In addition, the (polymerization) initiator of the present invention has a characteristic of initiating the addition polymerization of monomers by radical decomposition in the presence of heat and a reducing substance. The free radical initiator is preferably used 0.01 to 5.0% by weight of the total weight of the unsaturated vinyl monomer used, more preferably 0.05 to 3.0% by weight. If the amount is less than 0.01% by weight, there is a problem that the rate of the polymerization reaction is significantly reduced, when the amount exceeds 5.0% by weight, very small particles are formed to make the distribution of the particles even wider. As the radical initiator used in the present invention is known, one or a mixture of two or more selected from a peroxide, an azo compound, a percarbonate compound, and a perester compound may be used, and preferably, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, benzoyl peroxide, 2,2'-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis (4- Methoxy-2,4-dimethylvaleronitrile), di-isopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, dioctoxyethyl peroxydicarbonate, α-cumyl peroxyneodecanate, t-butyl It can be selected and used among peroxy neodecanate.

In addition, the dispersion stabilizer of the present invention can be adsorbed or chemically bonded to the surface of the particles when the polymer produced during the reaction is precipitated into the particles to form the shape of the particles into a sphere, to prevent the impulse between the particles to maintain the sphere Play a role.

The dispersion stabilizer used in the present invention is selected from polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, polyethyleneamine, polyacrylic acid, polyvinylacetate, polyvinylacetate copolymer, polyethylcellulose and polyhydroxypropylcellulose. One or two or more selected ones may be mixed and used, and preferably selected from polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyhydroxy and polypropyl cellulose.

At this time, the stabilizer is preferably used in 0.1 to 30% by weight of the total weight of the vinyl monomer used, more preferably 1.0 to 20% by weight. If the amount of the stabilizer is used too much, it may affect the physical properties of the polymer itself or may make the size of the formed particles too small. On the contrary, when the amount of the stabilizer is used too little, the particles may not be maintained in a stable form, resulting in agglomeration of particles.

In addition, the dispersion medium used in carrying out the dispersion polymerization of the present invention should be able to dissolve all the components and to precipitate the vinyl polymer produced as a result of the polymerization. Therefore, considering that the polymerization temperature of the present invention is in the range of 50 ~ 120 ℃ should be selected and used that the boiling point of the dispersion medium is more than the polymerization temperature. Preferably, the dispersion medium of the present invention may be used by mixing one or two or more selected from an organic dispersion medium, for example, alcohols, ketones, more preferably methanol; ethanol; Isopropane alcohol; Butyl alcohol; Pentyl alcohol; Benzyl alcohol; Cyclohexanol; Ethylene glycol; Glycerol; Diethylene glycol; Methyl cellosolve; Cellosolves; Butyl cellosolve; Isopropyl cellosolve; Ethylene glycol monomethyl ether; Ethylene glycol monoethyl ether; Diethylene glycol monomethyl ether; Diethylene glycol monoethyl ether; Acetone; Methyl ethyl ketone; Methyl isobutyl ketone and the like may be used alone or in combination of two or more.

In addition, in carrying out the dispersion polymerization according to the present invention, it is possible to further use various known additives to impart the required physical properties within the scope without departing from the object of the present invention. As the additive, a polymerization regulator, a pH regulator, a crosslinking agent, a crosslinking agent, an anti-scaling agent, a dye and a pigment may be used, and the amount used is preferably in the range of 0.01 to 50 parts by weight based on 100 parts by weight of the monomer.

 In addition, the time and temperature for solution polymerization and dispersion polymerization of the present invention may vary depending on monomers, dispersion stabilizers, initiators, and other reaction conditions, and oligomers formed as a result of solution polymerization are dissolved in a reaction solvent when added to the dispersion polymerization step. It is preferable that the molecular weight is low enough to prevent precipitation.

The polymer particles prepared as described above may have various sizes of particles having an average particle diameter in the range of 0.05 to 10 micrometers, and may have a uniform spherical particle having a uniform particle size distribution.

In addition, the present invention provides a polymer particle having an average particle diameter of 0.05 ~ 10 micrometer range prepared by the above method.

In the method for preparing polymer particles by dispersion polymerization according to the present invention, a short nucleation cycle is performed by preparing some of the monomers in an oligomer form through solution polymerization without directly adding a monomer, and then introducing the dispersion into a dispersion medium containing a dispersion stabilizer of dispersion polymerization. Since it can be produced particles of uniform size, and can reduce the reaction time to reach the final reaction yield can be expected a high economic effect and high value-added effect.

In addition, the polymer particles prepared according to the present invention may be usefully used in various industrial purposes because of their uniform size.

In addition, the polyacrylonitrile-based polymer particles prepared according to an embodiment of the present invention can be produced by an environmentally friendly and economical method using an excess of water as a solvent, a variety of carbon materials such as precursors of carbon fiber It can be used as a composite material.

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

However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

Example 1 Solution Polymerization Step

1-1 .:

9 g of acrylonitrile washed with polymerization inhibitor with caustic soda solution diluted to 10% (wt / wt), 1 g of methyl acrylate, 0.01 g of 2,2'-azobisisobutyronitrile as an initiator and N as a reaction solvent 10 g of, N'-dimethylsulfoxide was stirred for 20 minutes in a nitrogen atmosphere, and then transferred to a completely closed reactor. The reaction was carried out by heating the temperature to 70 ° C to react unreacted acrylonitrile, methyl acrylate monomer, initiator and oligomer. A solution polymer dissolved in was prepared.

1-2 .:

Tetrahydrofuran (THF) with 10 g of methyl methacrylate washed with polymerization inhibitor with 10% (wt / wt) solution of polymerization inhibitor, 0.01 g of initiator 2,2'-azobisisobutyronitrile and reaction solvent Using 10g to prepare a solution polymer in the same manner as in Example 1-1.

Example 2 Dispersion Polymerization Step

2-1 .:

In a three-neck round bottom flask reactor equipped with a cooler, 1 g of polyvinyl alcohol as a stabilizer was dissolved in 100 ml of distilled water as a reaction solvent, and 0.01 g of 2,2'-azobisisobutyronitrile was added. 89.2 polymer particles comprising a copolymer of polyacrylonitrile and polymethyl acrylate having a size of about 100 nm were polymerized by adding the solution polymer prepared in Example 1-1 while maintaining an over temperature of 70 ° C. for 2 hours. Obtained in% yield.

The polymer obtained above was washed with the addition of excess water, and the resultant was analyzed by scanning electron microscopy (SEM; S4200, Hitach, Japan) by centrifugation to remove unreacted monomer, reaction solvent, etc., as shown in FIG. Similarly, stable spherical particles having a constant size could be identified.

2-2 to 2-7 .:

In the present invention, in order to determine the effect of the stabilizer on the formation of polymer particles, it is prepared in the same manner as in Example 2-1, the content of the polyvinyl alcohol stabilizer is the total weight of the acrylonitrile and methyl acrylate monomers The polymerization was carried out with constant change as reference.

The obtained polymer was washed and separated, and the size of the polymer particles was confirmed by a particle size analyzer (COULTER, L230, Beckman Coulter, USA) and a scanning electron microscope (SEM) and the results are shown in Table 1 below.

As shown in the following table, in all cases except Example 2-2 and 2-7, the spherical stable particle shape was observed, it was confirmed that the particle size decreases as the amount of stabilizer is increased.

In the case of Examples 2-2 and 2-7 no spherical stable particle morphology was observed, which means that the particles formed due to insufficient amount of stabilizer could not maintain their morphology (Example 2-2), or conversely in too much If the stabilizer is present (Example 2-7), it is believed that the particles formed and the stabilizers are entangled and agglomerated.

Example Stabilizer (g) Dispersion medium (g)
(Water: DMSO) Acrylonitrile: Methyl acrylate (g) Initiator (g) Average particle diameter
(Nm) 2-2 0.2 100: 10 9: 1 0.01 Not measurable 2-3 0.3 100: 10 9: 1 0.01 783 2-4 1.2 100: 10 9: 1 0.01 112 2-5 15 100: 10 9: 1 0.01 71 2-6 50 100: 10 9: 1 0.01 50 2-7 60 100: 10 9: 1 0.01 Not measurable

2-8 .:

Prepared in the same manner as in Example 2-1, but stabilized polyvinyl alcohol (1 g) in a mixed medium of the reaction solvent N.N'- dimethyl sulfoxide (10 g) and water (100 g) without going through a solution polymerization step Dissolved and polymerized by adding a mixture of 0.01 g of 2,2'-azobisisobutyronitrile, acrylonitrile (9 g) and methyl acrylate (1 g), and comparing the yield with the shape of the prepared polymer particles. It was.

As a result, the yield was very low (31%) compared with Example 1, and the particle shape also obtained spherical particles and some resin-type polymer (see Fig. 2).

2-9 to 2-11 .:

In the present invention, in order to determine the effect according to the reaction time of the dispersion polymerization, it was prepared in the same manner as in Example 2-1, the polymerization time while changing the reaction time to 30 minutes, 1 hour, and 2 hours 30 minutes, the reaction time Yield according to the size and the size of the prepared polymer particles are shown in Table 2 below.

Example Response time (hr) yield(%) Average particle diameter (nm) 2-9 0.5 26.9 61.5 2-10 One 72.4 89.4 2-11 2.5 90.1 113

2-12 to 2-14 .:

In the present invention, in order to determine the effect according to the amount of the (reaction) initiator, it was carried out in the same manner as in Example 2-1, it was polymerized while changing the content of the initiator based on the total weight of the monomers.

As a result, when the content of the initiator is 0.001g, the yield during the reaction time of 2 hours is 50% or less, which is economically inefficient, on the contrary, when the amount of the initiator is used in excess of 1.2g, the excess oligomer and polymer The yield was reduced due to precipitation due to aggregation and formation of limited spherical polymer particles (see Table 3).

Example Initiator (g)  Acrylonitrile: Methyl acrylate (g) Response time (hr) yield(%) 2-12 0.001 9: 1 2 46 2-13 0.5 9: 1 2 93 2-14 1.2 9: 1 2 67

2-15 .:

In a three-neck round bottom flask reactor equipped with a cooler, 1 g of polyvinyl alcohol as a stabilizer was dissolved in 100 ml of ethanol as a reaction solvent, and 0.01 g of 2,2'-azobisisobutyronitrile was added and stirred under a nitrogen atmosphere. The solution polymer prepared in Example 1-2 was added while maintaining a speed of 100 rpm and a temperature of 70 ° C., followed by polymerization for 2 hours to obtain polymer particles composed of 9.7 micron-sized polymethylmethacrylate in a yield of 83%.

The polymer obtained above was washed with the addition of excess water, and analyzed by scanning electron microscopy by removing unreacted monomers, reaction solvents, etc. using centrifugation, and found that stable spherical particles were formed (see Table 4). ).

Example Stabilizer (g) Methyl methacrylate (g) Average particle size (㎛) yield(%) 2-15 One 10 9.7 83

1 is an electron micrograph (SEM) of the polymer particles prepared in Example 2-1 of the present invention.

Figure 2 is an electron micrograph of the polymer particles with or without the solution polymerization step prepared in Examples 2-1 and 2-8 of the present invention.

Figure 3 is a result showing the size distribution of the polymer particles according to the reaction time of the dispersion polymerization prepared in Examples 2-9 to Example 2-11 of the present invention.

Claims (10)

In preparing the polymer particles by dispersion polymerization method, (1) As the vinyl monomer, one or more selected from acrylonitrile or methyl acrylate is used, and an initiator and a reaction solvent are mixed and solution polymerization is carried out so that unreacted monomer, initiator and oligomer are added to the reaction solvent. Obtaining a dissolved solution polymer; (2) a dispersion medium to which a dispersion stabilizer is added, wherein the solution polymer is added to dimethyl sulfoxide to which polyvinyl alcohol is added and polymerized; And (3) recovering the synthesized polymer particles by dissolving an unreacted stabilizer by adding excess water or alcohol to the solution after the polymerization is completed; polymer particles produced by the dispersion polymerization method. The method of claim 1, The solvent used for the solution polymerization of the step (1) is a production method characterized in that it is used by mixing one or two or more selected from an organic solvent or water consisting of alcohols, ethers, ketones, furans. delete The method of claim 1, The initiator of step (1) is acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, benzoyl peroxide, 2,2'-azobisisobutyronitrile, azo Bis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4-dimethylvaleronitrile), di-isopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, dioctoxyethyl A production method characterized by using a mixture of one or two or more selected from peroxydicarbonate, α-cumyl peroxy neodecanate, t-butyl peroxy neodecanate. The method according to claim 1 or 4, The initiator of step (1) is characterized in that the use of 0.01 to 5.0% by weight of the total weight of the vinyl monomer. delete The method of claim 1, The dispersion stabilizer of step (2) is characterized in that the production method using 0.1 to 30% by weight of the total weight of the vinyl monomer. delete The method of claim 1, The polymer particles synthesized in the step (3) is characterized in that the average particle diameter ranges from 0.05 to 10 micrometers. Polymer particles having an average particle diameter of 0.05 to 10 micrometers prepared by the method of claim 1.

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