KR101507999B1 - The preparation of monodisperse spheric particles via solution re-crystallization with RITP technique - Google Patents

Abstract

The present invention relates to a method for producing spherical polymer particles having high stability through RITP polymerization and solution recrystallization. More particularly, the present invention relates to a process for producing polymer latex particles having a certain molecular weight range through RITP polymerization, And dissolving it in a compatible solvent to obtain spherical stabilized polymer particles by recrystallization in a solvent using the difference in solubility.

Description

[0001] The present invention relates to a method for preparing stabilized monodisperse spherical polymer particles by RITP polymerization and solution recrystallization,

The present invention relates to a method for producing spherical polymer particles having high stability through RITP polymerization and solution recrystallization. More particularly, the present invention relates to a process for producing polymer latex particles having a certain molecular weight range through RITP polymerization, And dissolving it in a compatible solvent to obtain spherical stabilized polymer particles by recrystallization in a solvent using the difference in solubility.

The spherical polymer particles have higher elasticity, optical characteristics and processability than other inorganic materials and metals, and can be used as various industrial core materials because of their large size and monodispersity and various polymers. Such polymer particles have been applied to a wide variety of fields such as optical diffusing materials of various films, LCD spatter, conductive balls, optical and electrical and electronic fields as well as medicine delivery capsule particles and MRI molding materials. In addition, it can be used as a catalyst by introducing various inorganic substances into the surface and inside of particles. Since it is spherical, it can be applied not only to organic pigments, paints, inks, and cosmetics with high hiding power but also to military electric apparatuses.

The suspension polymerization method and the emulsion polymerization method are known as the methods by the polymerization method. The method of producing the polymer particles by suspension polymerization is a method of dispersing monomers by mechanical stirring and then polymerizing the monomer droplets by using a fat-soluble initiator , And polymer particles having an average diameter of 100 micrometers or more are prepared (U.S. Patent Nos. 4,017,670, 4,071,670, 4,085,169, and 4,129,706). However, with this method, it is difficult to make the polymer particles have a uniform diameter. As a method for overcoming the limitations of such suspension polymerization, various sizes of polymer particles are prepared, and then a method of separating the particles according to their sizes by using a classification device has been proposed (Japanese Patent Laid-Open No. 90-261728). However, when such a separation method is used, there is a problem in that the process is complicated, the cost for the classifier is excessively high, and the productivity is very low.

In addition, emulsion polymerization is widely used as a useful method for producing particles with extremely uniform particle size distribution. However, the polymer produced by this method does not exceed 1 μm in diameter, and the surfactant used for imparting particle stability is a particle Which is adsorbed on the surface, resulting in bubbles or deterioration of the physical properties of the polymer.

The non-emulsion emulsion polymerization method, which is one of the emulsion polymerization methods, is a method in which polymer particles are obtained by ionization of a water-soluble initiator only without using a surfactant used for imparting particle stability in general emulsion polymerization, There is a problem that the diameter of the obtained particles can not exceed 1 탆. In order to solve this problem, an oil-free emulsion polymerization method may be carried out in a mixed solvent of water and alcohol, or a small amount of a cationic surfactant or an electrolyte may be added at the beginning of the reaction, Have been prepared [J. Appl. Polym. Sci., Vol. 19,3077 (1975); J. Colloid Interf Sci., Vol. 230, 210-212 (2000); J. Appl. Polym. Sci., Vol. 71, 2259-2229 (1999); U.S. Patent No. 6,552,115; U.S. Patent 6,252,004; Macromol. Res., Vol, 12, 240-245 (2004)]. However, in the oil-free emulsion polymerization, since the stabilization of the polymer particles is obtained only by ionization by the initiator, the maximum diameter of the vinyl-based polymer obtained by this method does not exceed 2.5 μm and the particle size distribution is reduced to 20 to 30% there is a problem.

Various methods for preparing spherical particles by solution recrystallization have been proposed. Japanese Patent Publication No. 2,723,200 and Japanese Patent Publication No. 3,423,922 disclose a reprecipitation method by a method of preparing organic fine particles. In the reprecipitation method, an organic compound is dissolved in a good solvent, and the solution is injected into a poor solvent (usually distilled water) using a syringe or the like to produce fine particles of the organic compound. However, the process can only use polar solvents in which both solvents are infinitely dilutable to poor solvents. Therefore, the organic compound is limited to a part of the polar solvent.

On the other hand, there is no known method for preparing stable polymer particles of desired size through the process of preparing polymer particles by introducing the RITP method into suspension polymerization and emulsion polymerization, dissolving them in a solvent for compatibility and re-precipitating them.

The inventors of the present invention have made efforts to produce stable spherical polymer particles, and as a result, they have found that polymer latex particles are prepared through RITP polymerization and then dissolved in a compatible solvent, and then distilled deionized water The present invention has been accomplished based on the discovery that stable polymer particles can be produced by recrystallizing stable spherical polymer particles by adding the polymer particles to the polymer particles in the form of spherical particles effectively.

Accordingly, it is an object of the present invention to provide a method for producing stable spherical polymer particles by applying the RITP polymerization method and the particle recrystallization method.

According to the present invention,

(a) dissolving an unsaturated vinyl monomer, a water-soluble polymerization initiator, a peroxide-based catalyst, and a chain transfer agent in a reaction solvent and stirring to prepare polymer latex particles; And

(b) dissolving the polymer latex particles in a compatible solvent and adding distilled deionized water to disperse and recrystallize the polymer latex particles

The method for producing spherical polymer particles according to claim 1,

The polymer particle manufacturing method of the present invention is advantageous in that the monodisperse distribution of the particles produced and the stability of the particles are superior to the conventional method of performing the recrystallization through dispersion polymerization. In addition, it is possible to manufacture particles having a low average molecular weight while having a narrow molecular weight distribution at the same time by introducing RITP technology in the first step of producing a polymer latex used in a recrystallization process, and a high effect can be obtained even when a small amount of chain transfer agent is used The stability of the process and the manufacturing cost are low. The sphericity of the particles is increased by the recrystallization process using the solvent of the second step and monodispersed particles having a desired size can be produced.

1 is an electron microscope photograph of a polymer latex particle prepared by the RITP method in the step (a) of Example 1. Fig.
2 is an electron micrograph of polymer particles recrystallized in step (b) of Example 1. Fig.

The present invention provides a process for producing a polymer latex, comprising: (a) dissolving an unsaturated vinyl monomer, a water-soluble polymerization initiator, a peroxide-based catalyst and a chain transfer agent in a reaction solvent and stirring the polymer latex particles; And (b) dissolving the polymer latex particles in a compatible solvent and adding distilled deionized water to disperse and recrystallize the polymer latex particles.

The term "unsaturated vinyl monomer" in the present invention means any unsaturated vinyl monomer capable of radical initiation used in general dispersion polymerization, emulsion polymerization or suspension polymerization.

In the present invention, the term "polymerization initiator" means that both the ionic functional group and the hydrophilic terminal group are dissociated into free radicals, thereby initiating the polymeric polymerization reaction and electrostatically preventing the entanglement of the generated polymeric particles. do.

The term "catalyst" in the present invention means all the peroxide-based catalysts capable of accelerating the reaction rate by increasing the rate at which the polymerization initiator dissociates into free radicals.

In the present invention, the term "chain transfer agent" means a substance used in polymerization for the purpose of controlling the molecular weight and molecular weight distribution of the polymer to be produced.

In the present invention, "compatible solvent" means a material which is used as a dispersing solvent in the recrystallization process to dissolve the polymer latex.

The present invention relates to a process for preparing polymer latex particles having a weight average molecular weight and PDI (polymer dispity index) controlled by a non-emulsified emulsion polymerization method after completely dissolving an unsaturated vinyl monomer, a chain transfer agent, And dispersing and dissolving the latex polymer particles in a compatible solvent, and dispersing the latex polymer particles in an aqueous solution to recrystallize them to prepare stabilized polymer particles having a spherical shape and exhibiting monodisperse.

In particular, the present invention relates to a RITP polymerization method based on the principle that the water-soluble polymerization initiator forms a radical to initiate polymerization of an unsaturated vinyl-based monomer, and then the chain transfer agent reacts with the radical to control the molecular weight of the polymer by the continuous reversible reaction A method of recrystallizing polymeric latexes into a spherical polymer particle having a desired size by solubilizing the polymer latex by first obtaining polymer latex, dissolving it in a solvent and then applying it to a recrystallization process It is based on.

In the present invention, the unsaturated vinyl monomer may be any unsaturated vinyl monomer as long as it can initiate a radical used for general dispersion polymerization, emulsion polymerization or suspension polymerization, and preferably styrene, divinylbenzene, ethylvinylbenzene, alphamethylstyrene, fluoro Acrylates such as styrene, vinylpyridine, vinyl chloride, acrylonitrile, methacrylonitrile, butyl acrylate, 2-ethylhexyl ethyl acrylate, glycidyl acrylate, N, N'-dimethylaminoethyl acrylate, butyl methacrylate Butyl methacrylate, 2-ethylhexyl ethyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, Hexane diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethyl It is preferable to use one or two or more selected from the group consisting of ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate and 1,3-butylene glycol dimethacrylate.

The unsaturated vinyl monomer is preferably used in an amount of 2 to 40 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the reaction solvent. When the amount of the unsaturated vinyl-based monomer is less than 2 parts by weight, the reaction efficiency is lowered. When the amount of the unsaturated vinyl-based monomer is more than 40 parts by weight, aggregation of particles occurs and spherical particles can not be obtained.

The water-soluble polymerization initiator of the present invention is not limited in its use as long as it can be used in free radical polymerization, but is preferably 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4 One or two selected from the group consisting of dimethylvaleronitrile, 2,2'-azobis-2-methylisobutyronitrile, ammonium persulfate, potassium persulfate, sodium persulfate, ammonium bisulfate and sodium bisulfate It is better to use more than species.

The polymerization initiator is preferably used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the unsaturated vinyl monomer. When the amount is less than 0.01 part by weight, the rate of polymerization reaction is remarkably reduced. When the amount is more than 10 parts by weight, gelation occurs due to auto-acceleration.

Also, the peroxide-based catalyst is used for the purpose of promoting the reaction rate of the RITP process, and hydroperoxide, cumene hydroperoxide, butyl hydroperoxide, hydro-methyl hydroperoxide, or acetyl hydroperoxide can be used.

The catalyst is preferably used in an amount of 0.001 to 5 parts by weight, particularly preferably 0.01 to 0.5 parts by weight, based on 100 parts by weight of the unsaturated vinyl monomer. If the amount of the catalyst used is too small, the reaction rate is too slow to cause aggregation of the particles, and if the amount is too large, the molecular weight of the polymer particles can not be controlled.

Examples of the chain transfer agent used in the RITP method include a group consisting of iodine, potassium iodide, sodium iodide, lithium iodide, bromine iodide, iodine monochloride, magnesium iodide, phosphorus triiodide and alkyl iodide May be used alone or in combination.

The molecular weight and the molecular weight distribution of the polymer can be controlled according to the amount of the chain transfer agent. Preferably, the water-soluble polymerization initiator and the chain transfer agent are used in a weight ratio of 1: 5 to 2: 1.

The non-emulsified emulsion polymerization in the first step is carried out by stirring the above components, and stirring is preferably performed at 60 to 90 ° C at a stirring speed of 100 to 300 rpm for 5 to 10 hours.

On the other hand, known nonionic emulsion polymerization reaction may be used in the non-emulsified emulsion polymerization reaction in addition to usual uses and methods. A polymerization regulator such as butyl aldehyde, trichlorethylene, perchlorethylene, acetaldehyde or mercaptan, a pH adjuster, a crosslinking agent, an anti-scale agent and a dispersion stabilizer may be added as needed.

The polymer latex has a weight average molecular weight ranging from 25,000 to 60,000 g / mol, and the prepared polymer latex preferably has a poly dispersity index (PDI) in the range of 1.5 to 1.8.

The prepared polymer latex is dissolved in a compatible solvent, and distilled deionized water is added to disperse and recrystallize to prepare final spherical polymer particles.

In this case, the compatible solvent may be a solvent which completely dissolves the polymer latex. Specific examples of the solvent include toluene, benzene, ethyl acetate, butyl acetate, chloroform, dichloromethane, tetrahydrofuran (THF), methyl ethyl ketone, But are not limited to, acetonitrile, acetone, and C ₁ to C ₆ alcohols. Preferably, a solvent containing tetrahydrofuran or ethanol can be used. The compatible solvent is preferably used in an amount of 300 to 10000 parts by weight, preferably 500 to 1000 parts by weight, based on 100 parts by weight of the produced polymer latex.

Through the recrystallization process, nano-micron sized polymer particles recrystallized in a stable spherical form can be produced.

The polymer particles produced according to the above manufacturing process can be used in a variety of fields such as optical diffusion and diffusion films of various films, LCD SPACER, conductive balls, etc., as well as in medical fields such as drug delivery capsule particles and MRI molding materials And so on. In addition, it can be applied to various industrial fields such as organic pigments, paints, inks, polymerized toners for photocopying, cosmetics, and military equipment for radio wave shielding because of their spherical shape. Do.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, it should be understood that the scope of the present invention is not limited by the following embodiments, and that those skilled in the art will readily understand that the technical idea of the present invention and the equivalents of the claims It goes without saying that various modifications and variations are possible.

Example 1

(a) Production process of polymer latex by RITP method

100 g of distilled deionized water was poured into the three-neck round plast reactor equipped with a condenser, and the mixture was stirred and heated at 200 rpm. When the internal temperature of the reactor reached 80 ° C, 10 g of styrene and 0.260 g of iodine Lt; / RTI > 0.1 g of potassium persulfate (KPS) as a reaction initiator was dissolved in 10 g of deionized water and injected into the reactor. 1 ml of hydroperoxide as a catalyst was added dropwise into the reactor, and the reaction was carried out in the absence of light in the reactor.

The reactor of the mixture was maintained at 80 ° C and polymerized for 7 hours while stirring at 200 rpm to obtain a polymer latex. The weight average molecular weight was analyzed by GPC and it was confirmed that the polymer had a molecular weight of 50,000 g / mol and a PDI of 1.7 Respectively. 1 shows an electron micrograph of the polymer latex particles prepared through the above process.

(b) Recrystallization process

100 g of tetrahydrofuran and 10 g of dried polymer latex prepared through the polymerization process of step (a) were added to a three-necked round flask equipped with a condenser, and the mixture was stirred at 200 rpm for 2 hours at 30 ° C. 50 g of deionized water in which 0.5 g of polyvinyl alcohol was dispersed as a dispersion stabilizer was added and stirred at 250 rpm to finally obtain polystyrene particles.

The thus-obtained polystyrene particles were centrifuged and observed with an electron microscope. The photographs of the particles are shown in Fig. 2, and the results of GPC analysis are shown in Table 1. As shown in FIG. 2, it was confirmed that the polystyrene particles were prepared as spherical particles having a uniform size and an average particle diameter of about 2 to 3 micrometers.

Example 2

The procedure of Example 1 was repeated except that methylmethacrylate was used instead of styrene as a monomer to be introduced during the polymer latex production process through the RITP method in the step (a).

Example 3

The procedure of Example 1 was repeated except that butylmethacrylate was used instead of styrene in the polymer latex preparation process through the RITP method in the step (a).

Example 4

The procedure of Example 1 was repeated except that 0.220 g of iodine was used in the polymer latex preparation process through the RITP method in the step (a).

Example 5

The procedure of Example 1 was repeated except that 0.280 g of iodine was used in the polymer latex preparation process through the RITP method in the step (a).

Example 6

The procedure of Example 1 was repeated except that acetone was used instead of tetrahydrofuran in the recrystallization step of step (b).

Example 7

The procedure of Example 1 was repeated except that polyvinyl alcohol was not used in the recrystallization step of step (b).

Example 8

The procedure of Example 1 was repeated except that 1 g of polyvinyl alcohol was used during the recrystallization process in the step (b).

Comparative Example 1

The procedure of Example 1 was repeated except that the polymer latex was prepared without using iodine in the process of producing polymer latex by the RITP method in the step (a).

Comparative Example 2

except that iodine was not used in the polymer latex production process through the RITP method in the step (a), and the polymer latex was prepared by performing emulsion polymerization using mercaptan to prepare a polymer latex.

Experimental Example: Measurement of molecular weight distribution by GPC measurement

The molecular weight distribution of the polymer particles was measured by GPC measurement of the particles prepared in the examples and comparative examples. In order to measure the molecular weight, the unreacted monomers added during the reaction in the polymer particles were completely removed through a washing process and then analyzed. The analysis was carried out by completely dissolving the washed particles in tetrahydrofuran and measuring the molecular weight distribution according to various conditions. The measurement results are shown in Table 1 below.

Monomer Iodine content (g) Molecular Weight
(g / mol) PDI
(Mw / Mn) Compatible solvent PVA
Content (g) particle
Size (μm) Example 1 Styrene 0.260 50,000 1.7 THF 0.5 2.7 Example 2 MMA 0.260 35,000 1.55 THF 0.5 5.5 Example 3 BMA 0.260 45,000 1.63 THF 0.5 4.1 Example 4 Styrene 0.220 50,000 1.7 THF 0.5 2.7 Example 5 Styrene 0.280 50,000 1.7 THF 0.5 2.7 Example 6 Styrene 0.260 50,000 1.7 Acetone 0.5 1.8 Example 7 Styrene 0.260 50,000 1.7 THF 0 4.8 Example 8 Styrene 0.260 50,000 1.7 THF One 1.2 Comparative Example 1 Styrene 0 200,000 3.7 THF 0.5 Cohesion Comparative Example 2 Styrene 0 45,000 2.5 THF 0.5 Cohesion

As shown in Table 1, when a RITP method using a chain transfer agent is introduced into a polymerization process, a polymer latex having a low molecular weight and a narrow molecular weight distribution can be synthesized. When the polymer latex is dissolved in a compatible solvent and recrystallized, a stable spherical polymer It was confirmed that the particles can be produced.

Particularly, the polymer latex prepared without using a chain transfer agent has a large molecular weight and a broad molecular weight distribution, which makes it difficult to obtain a polymer having a spherical particle state even after a recrystallization process, resulting in the aggregation of the polymer during the recrystallization process.

Thus, it was confirmed that spherical particles having a mass average molecular weight of 25,000 to 60,000 (g / mol) and a PDI range of less than 1.8 and having a size of 2 to 3 microns can be produced by the production method of the present invention.

Claims (11)

(a) dissolving an unsaturated vinyl monomer, a water-soluble polymerization initiator, a peroxide-based catalyst, and a chain transfer agent in a reaction solvent and stirring to prepare polymer latex particles; And
(b) dissolving the polymer latex particles in a compatible solvent and adding distilled deionized water to disperse and recrystallize the polymer latex particles
Wherein the PDI of the polymer latex prepared in the step (a) is in the range of 1.5 to 1.8. The method of manufacturing a spherical polymer particle according to claim 1, wherein the polymer latex has a PDI of 1.5 to 1.8.
The method of claim 1, wherein the stirring is performed at 60 to 90 ° C at a stirring speed of 100 to 300 rpm for 5 to 10 hours.
2. The composition of claim 1, wherein the unsaturated vinyl monomer is selected from the group consisting of styrene, divinylbenzene, ethylvinylbenzene, alphamethylstyrene, fluorostyrene, vinylpyridine, vinyl chloride, acrylonitrile, methacrylonitrile, butyl acrylate, Methyl ethyl acrylate, ethylhexyl ethyl acrylate, glycidyl acrylate, N, N'-dimethyl amino ethyl acrylate, butyl methacrylate, 2-ethylhexyl ethyl methacrylate, methyl methacrylate, Butylene glycol diacrylate, 1,6-hexane diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diethylene glycol dimethacrylate, Triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and 1,3-butylene glycol dimethacrylate, and one or more selected from the group consisting of The method of spherical polymer particles as ranging.
The method of claim 1, wherein the unsaturated vinyl monomer is used in an amount of 2 to 40 parts by weight based on 100 parts by weight of the reaction solvent.
The method of claim 1, wherein the water-soluble polymerization initiator is selected from the group consisting of 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'- Wherein the polymer is at least one selected from the group consisting of methyl isobutyronitrile, ammonium persulfate, potassium persulfate, sodium persulfate, ammonium bisulfate and sodium bisulfate.
The method for producing spherical polymer particles according to claim 1, wherein the water-soluble polymerization initiator is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the unsaturated vinyl monomer.
The peroxide-based catalyst according to claim 1, wherein the peroxide-based catalyst is at least one selected from the group consisting of hydroperoxide, cumene hydroperoxide, butyl hydroperoxide, hydro-methyl hydroperoxide and acetyl hydroperoxide. By weight based on the total weight of the polymer particles.
The method of claim 1, wherein the chain transfer agent is selected from the group consisting of iodine, potassium iodide, sodium iodide, lithium iodide, bromoiodide, iodine monochloride, magnesium iodide, phosphorus triiodide, and alkyl iodide And at least one selected from the group consisting of at least one selected from the group consisting of water,
The method of claim 1, wherein the water-soluble polymerization initiator and the chain transfer agent are mixed at a weight ratio of 1: 5 to 2: 1.
The method of claim 1, wherein the polymer latex prepared in step (a) has a mass average molecular weight of 25,000 to 60,000 g / mol.
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