KR100532693B1 - Process for Preparing Crosslinked Polystyrene Beads by Precipitation Polymerization - Google Patents

Abstract

The present invention relates to a method for preparing polystyrene particles crosslinked by precipitation polymerization, and more particularly, to preparing styrene monomer, polymerization initiator, and solvent as acetonitrile alone or in common with acetonitrile. The mixture is used in a mixture, and as the crosslinking agent, by precipitation polymerization using divinylbenzene or an acrylate system, the particles formed by crosslinking reaction in the particles have a spherical shape, and the average particle diameter is 1.0 to 8.0 μm. The present invention relates to a method for producing polystyrene particles, which has a larger particle diameter than the polymerization method, and is usefully used in various high value-added industries such as the information industry and microdevices.

Description

Process for Preparing Crosslinked Polystyrene Beads by Precipitation Polymerization

The present invention relates to a method for preparing polystyrene particles crosslinked by precipitation polymerization, and more particularly, to preparing styrene monomer, polymerization initiator, and solvent as acetonitrile alone or in common with acetonitrile. By mixing and using the medium, and the precipitation crosslinking agent using divinylbenzene or acrylate-based as a crosslinking agent, the particles formed by crosslinking reaction in the particles has a spherical shape, the average particle diameter is 1.0 ~ 8 ㎛ The present invention relates to a method for producing polystyrene particles, which has a larger particle diameter than the polymerization method, and is usefully used in various high value-added industries such as the information industry and microdevices.

In general, vinyl-based polymer particles having a diameter of 1 micron or more are prepared by a small amount of suspension polymerization, dispersion polymerization, and emulsion polymerization.

Suspension polymerization is to disperse the monomer by mechanical stirring, and then to polymerize the monomer droplets using a fat-soluble initiator, wherein the polymer prepared therefrom is prepared a crosslinked polymer particle having an average diameter of 100 μm or more. [US Patent No. 4,017,670] 4,017,670, 4,085,169, and 4,129,706. However, it is difficult to make the crosslinked polymer particles have a uniform diameter.

As a method for overcoming the limitation of the suspension polymerization, a method of preparing polymer particles having various sizes and then separating them according to the particle size using a separator has been proposed (Japanese Patent Laid-Open No. 90-261728). However, when the suspension polymerization method is used, the process is complicated, the cost of the classification apparatus is excessive, and the productivity is also very low.

Dispersion polymerization is polymerized using a vinyl monomer, an organic solvent soluble in the monomer or a mixed solvent of organic solvent and water, a steric stabilizer, and a fat-soluble initiator to prepare spherical polymer particles of 1 μm or more [Macromolecules, Vol. 23, P3104-3109 (1990); Can. J. Chem., Vol. 63, P209-216 (1985); J. Polym. Sci., Part A Polym. Chem., Vol. 31, P1393-1402 (1993); J. Polym. Sci., Part A Polym. Chem., Vol. 32, P 1087-1100 (1994)]. The organic solvent used must be soluble in monomers and insoluble in polymer particles produced by dispersion polymerization. In this dispersion polymerization, the maximum amount of crosslinking agent that can be crosslinked is not more than 5% by weight relative to the monomer, and when it is added more than that, the polymer particles are agglomerated with one another or irregularly shaped particles that are not spherical to form fully crosslinked particles. There is a difficult problem. In addition, in order to obtain spherical polymer particles, addition of steric stabilizer is essential.

Emulsion polymerization can produce crosslinked polymer particles having a uniform size of about 1 μm in a single process, and can also produce crosslinked particles up to 100 μm in diameter by swelling using seeds. (US Pat. Nos. 4.459,378, 6,228,925, and 4,996,265). However, there are many components involved in the reaction during emulsion polymerization, complicated by a multi-step process, and a long time.

The above-mentioned suspension polymerization method, dispersion polymerization method and emulsion polymerization method have various disadvantages in the production of spherical crosslinked polymer particles, and in the case of the polymer particles produced by these methods, the stabilizer adsorbed on the surface of the polymer particles It has a big influence on the final physical properties.

Therefore, in recent years, a method for producing spherical polymer particles having a crosslink of 1 μm or more by precipitation polymerization has been proposed (US Pat. No. 5,599,889). Precipitation polymerization is a polymerization method in which the basic principle is the same as that of dispersion polymerization, but without the use of a steric stabilizer that must be added during dispersion polymerization, it is possible to prepare spherical cross-linked polymer particles by crosslinking in particles.

Precipitation polymerization is a process in which spherical particles of 1 μm or more of polydivinylbenzene fully crosslinked with divinylbenzene are prepared using an acetonitrile solvent or a main solvent of acetonitrile and a cosolvent of toluene, water or propionitrile. A method for producing polymethyl methacrylate or polychloromethyl styrene spherical polymer particles has been proposed [J. Polym. Sci., Part A Polym. Chem., Vol. 37, P2295-2303 (1999); Macromolecules, Vol. 35, P9983-9989 (2002); J. Polym. Sci., Part A Polym. Chem., Vol. 37, P2899-2907 (1999)]. However, there is a limitation that the kind of monomers used in the polymerization and the solvent used as the cosolvent are extremely limited.

The present inventors have made efforts to improve the limitation of the co-solvent, which is a limitation of precipitation polymerization, among various existing polymerizations used for the polymer particles as described above. When the solvent and water having a solubility constant of 8.5 to 15 (m 3 / cm 3) ^1/2 are selected and mixed with a co-solvent, the size of the polystyrene particles can be controlled, and divinylbenzene is selected as a crosslinking agent. The present invention has been completed by discovering that the produced particles can maintain a spherical state by causing a crosslinking reaction to harden the particles to prevent them from tangling.

Therefore, an object of the present invention is a method for producing spherical polystyrene particles having a diameter of 1 μm or more excellent in heat resistance and solvent resistance by precipitation polymerization using a specific solvent and a crosslinking agent in a single process.

The present invention is a method for producing polystyrene by precipitating and polymerizing a styrene monomer, a solvent, a crosslinking agent and a polymerization initiator, wherein the solvent has a solubility constant of 8.5 to 15 / Cm 3) ^1/2 of an organic solvent or water is used, and the crosslinking agent has a thermal stability of precipitating polymerization using divinylbenzene at a temperature of 40 to 90 ° C. for 6 to 48 hours at a stirring speed of 10 to 200 rpm. It is characterized by a method for producing excellent crosslinked polystyrene particles.

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Hereinafter, the present invention will be described in more detail.

The present invention has a spherical shape by crosslinking reaction in particles during precipitation polymerization using a certain amount of a specific solvent and a crosslinking agent in the precipitation polymerization of styrene monomer, using a certain amount of a specific solvent and crosslinking agent, the average particle diameter is increased compared to the conventional polymerization method, The present invention relates to a method for producing polystyrene particles which is usefully used in various high value added industrial fields such as fine devices.

The present invention is characterized by a specific solvent and a crosslinking agent used for the precipitation polymerization of styrene monomers. The solvent may be acetonitrile alone or acetonitrile as the main solvent, and the solubility constant is 8.5 to 15 (㎈ / cm 3) ^{1 An} organic solvent of ^{/ 2} or a mixed solvent in which water is added as a cosolvent is used.

In general, the reaction mechanism of precipitation polymerization is similar to that of dispersion polymerization, but, unlike the dispersion polymerization, the co-solvent selected for use must be soluble in both styrene as a reactant and polystyrene as a product. Due to the above solubility problem, the solubility parameter (δ) of the cosolvent is preferably selected to have a value similar to that of styrene monomer and polystyrene. The solubility constants of the co-solvent, styrene monomer, and polystyrene used in the present invention are shown in Table 1, and the solubility constants of the styrene monomer and polystyrene of the present invention are 9.3 and 8.9 (8.9 / cm 3) ^1/2 , respectively. Since it has a solubility constant value, it is preferable to use the solvent which has a solubility constant value of 8.5-15 (dl / cm <3>) ^{1/2 as} a cosolvent used. For example, one or two or more selected from tetrahydrofuran, 2-propanol, 2-methoxyethanol, benzene, toluene and water may be used. Water has a high solubility constant of 23.4 (dl / cm 3) ^1/2 , but the polystyrene particles produced using it have a spherical shape. In addition, the co-solvent can control the particle size of the polystyrene produced by precipitation polymerization according to the type. The cosolvent is used in an amount of 0 to 75% by volume with respect to acetonitrile as the main solvent, and when the amount is more than 75% by volume, entanglement of the particles may occur or irregular particles may be obtained.

matter Usage Solubility Constant (㎈ / ㎠) ^1/2 Acetonitrile Main solvent 11.9 Tetrahydrofuran Common solvent 9.1 2-propanol Common solvent 11.5 2-methoxyethanol Common solvent 11.4 benzene Common solvent 9.2 toluene Common solvent 8.9 Styrene Monomer 9.3 polystyrene Polymer 8.9

The present invention has another feature that a crosslinking agent is used during precipitation polymerization in place of the steric stabilizer used in dispersion polymerization having a similar mechanism. The crosslinking agent does not get entangled with each other even if the particles hardened by the crosslinking reaction in the particles during precipitation polymerization can be kept in a spherical state. Divinylbenzene may be used as the crosslinking agent, and the crosslinking agent and the styrene monomer are preferably used in an amount of 1 to 15% by weight based on the solvent used. When the amount of use is less than 1% by weight, the efficiency of the reaction is lowered, and when the amount is more than 15% by weight, aggregation between particles occurs, so that spherical particles cannot be obtained. More preferably, it is preferable to use 2-12 weight%.

In addition, the crosslinking agent is preferably used 5 to 95% by weight of the amount of styrene monomer, when the amount is less than 5% by weight, the degree of crosslinking is low due to the low degree of crosslinking. Occurs. More preferably, it is good to use 10-50 weight%.

The present invention is the precipitation polymerization of polystyrene using a specific solvent and a crosslinking agent, a styrene monomer and a polymerization initiator as defined above, wherein the polymerization initiator to be added is lauroyl peroxide and benzoyl peroxide which are generally used in suspension polymerization. Organic peroxides, such as 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (2-methylbutyronitrile) One kind or two or more kinds selected from azo series such as) may be used. The polymerization initiator used in the present invention is oil-soluble, and has the property of initiating the addition polymerization of monomers by radical decomposition in the presence of heat and a reducing substance. The reaction initiator preferably contains 1 to 15% by weight in the total amount of the styrene monomer used and the crosslinking agent. When the amount is less than 1% by weight, the reaction rate is significantly lowered. Done.

On the other hand, the precipitation polymerization method for producing the polystyrene particles of the present invention is made by a known method.

First, the mixture is placed in a solvent reactor under a nitrogen atmosphere, and styrene monomer, a crosslinking agent, and a reaction initiator are added, followed by precipitation polymerization at 40 to 90 ° C. for 6 to 48 hours at a speed of 10 to 200 rpm. If the stirring speed is less than 10 rpm, the stirring does not occur, the size of the particles becomes uneven, and when the 200 rpm is exceeded, this kind of entanglement may occur, so it is important to control the stirring speed. More preferably, 10-150 rpm speed is good for 50-90 degreeC temperature and 12 to 24 hours.

By the above method, the styrene monomer is precipitated and polymerized to obtain polystyrene particles having a spherical shape that is completely crosslinked by crosslinking reaction in the particles. Furthermore, the average particle diameter of the polystyrene particles is 1.0-8.0 μm, which provides high added value. It can be used in various applications.

The present invention will be described in more detail based on the following examples, but the present invention is not limited to the examples.

Example 1

100 ml of acetonitrile as a main solvent was put in a nitrogen atmosphere in a three-neck round flask reactor equipped with a cooler, and styrene monomer and divinylbenzene as a crosslinking agent were fixed at 2% by weight with respect to the solvent.

The concentration of the divinylbenzene as the crosslinking agent was changed to a certain amount with respect to the styrene monomer concentration to maintain the reactor of the added mixture at 70 ° C. To the mixture was added 0.04 g of 2,2'-azobisisobutyronitrile as an initiator, followed by precipitation polymerization for 24 hours while stirring at 30 rpm to obtain a polystyrene polymer.

The yield of the obtained polystyrene polymer and centrifugal separation was analyzed by electron microscopy, and thermal stability was investigated through a differential scanning calorimeter.

As a result of the analysis and investigation, it was confirmed that the obtained polystyrene polymers were stable spherical particles having an average particle diameter of about 3 μm, and these were thermally stable, and thus the glass transition temperature was not observed in all the samples, indicating that they were completely crosslinked.

[Divinylbenzene] / [Styrene Monomer] (wt%) Form of the product yield(%) Glass transition temperature (℃) 5 rectangle 67 none 10 rectangle 68 none 20 rectangle 70 none 40 rectangle 70 none 50 rectangle 73 none 75 rectangle 75 none

Example 2

Prepared in the same manner as in Example 1, but used as a solvent to mix the main solvent acetonitrile and various types of co-solvent so that the sum of the volume is 100 ㎖, the content of the divinylbenzene crosslinking agent 50% by weight of the styrene monomer content It carried out as%.

Yield of the obtained polystyrene polymer and centrifuged it was analyzed by electron microscopy and shown in Table 3 below.

As a result of the analysis and investigation, it was confirmed that the obtained polystyrene polymer was a stable spherical particle having an average particle diameter of about 2.0 to 3.5 µm.

[Divinylbenzene] / [Styrene Monomer] (wt%) Cosolvent Type [Cosolvent] / [Main Solvent] (Volume%) Form of reaction product yield(%) 50 benzene 33 rectangle 67 50 toluene 33 rectangle 62 50 2-propanol 75 rectangle 68 50 2-methoxyethanol 75 rectangle 71 50 Tetrahydrofuran 33 rectangle 65

Example 3

In the same manner as in Example 1, the concentration of the divinylbenzene as a crosslinking agent was fixed at 50% by weight relative to the concentration of the styrene monomer, and the initiator 2,2'-azobisisobutyronitrile was used as the styrene monomer and the crosslinking agent. It was carried out by changing to 2, 4, 6, and 8% by weight relative to the total amount of divinylbenzene used.

Yield of the obtained polystyrene polymer and centrifuged and analyzed by electron microscopy are shown in Table 4 below.

As a result of the analysis and investigation, it was confirmed that the obtained polystyrene polymer was a stable spherical particle having an average particle diameter of about 2.8 to 3.8 µm, and the average particle diameter gradually increased as the concentration of the initiator increased.

[Divinylbenzene] / [Styrene Monomer] (wt%) Initiator (% by weight) Particle Diameter (㎛) yield(%) 50 2 2.80 73 50 4 2.92 74 50 6 3.24 76 50 8 3.81 78

Example 4

In the same manner as in Example 1, the concentration of the divinylbenzene as a crosslinking agent was fixed at 50% by weight relative to the styrene monomer concentration, and the sum of the styrene monomer and the divinyl benzene used was 2, 5, 8, 10, and It was added to 15% by weight.

Yield of the obtained polystyrene polymer and centrifuged it was analyzed by an electron microscope shown in Table 5 below.

As a result of the analytical investigation, it was confirmed that the obtained polystyrene polymer is a stable spherical particle having an average particle diameter of about 2.4 to 4.5 μm, and the average particle diameter gradually increased as the amount of the styrene monomer increased.

Styrene Monomer (% by weight) Form of reaction product Particle Diameter (㎛) Yield (%) 2 rectangle 2.4 61 4 rectangle 3.1 65 8 rectangle 3.7 68 10 rectangle 4.5 70 15 rectangle 5.0 75 As shown above, the amount of the initiator 2 and the reaction initiator was changed based on Example 1 and the amount of the co-solvent based on Example 1 and the amount of the divinylbenzene crosslinking agent alone and acetonitrile as the main solvent As a result of Example 3, in which the amount of styrene monomer was changed, and Example 4 in which the amount of styrene monomer was changed, all of Examples 1 to 4 produced polystyrene particles having a stable spherical shape with an average particle diameter of 1.0 to 8.0 µm. This was confirmed.

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As described in detail above, the polystyrene particles prepared by the precipitation polymerization method using a specific solvent and a crosslinking agent according to the present invention have a fully cross-linked and stabilized sphere shape, and polystyrene particles having an average particle diameter of 1.0 to 8.0 μm are prepared. High value-added materials such as standards used in instrument qualification, measurement of filter pore size and efficiency, filling of chromatography columns, supports in biochemistry, biomedical fields, coatings, inks, dry toner for information, information and microelectronics It can be used for various applications.

FIG. 1 shows electron micrographs of crosslinked polystyrene particles having an average particle size of 3.2 μm obtained by adding 50% by weight of the crosslinking agent divinylbenzene to the styrene monomer of Example 1 of the present invention.

Figure 2 is a polystyrene particles prepared by varying the amount of cross-linking agent divinylbenzene (5, 10, 20, 40, 50, and 75% by weight) for the styrene monomer of Example 1 of the present invention was analyzed through a differential scanning calorimeter The results are shown.

FIG. 3 shows an electron micrograph of polystyrene particles having an average particle diameter of 3.7 μm with 50 wt% of a crosslinking agent ethylene glycol dimethacrylate added to the styrene monomer of Example 5 of the present invention.

Claims (10)

In the method for producing polystyrene by precipitation polymerization of a styrene monomer, a solvent, a crosslinking agent and a polymerization initiator, As the solvent, acetonitrile may be used alone or in combination with acetonitrile as a main solvent, an organic solvent or water having a solubility constant of 8.5 to 15 (㎈ / cm 3) ^1/2 may be used. The crosslinking agent is a method of producing cross-linked polystyrene particles having excellent thermal stability, characterized in that the precipitation using the divinyl benzene at 40 ~ 90 ℃ temperature, 6 ~ 48 hours, 10 to 200 rpm stirring speed. The organic solvent according to claim 1, wherein the organic solvent having a solubility constant of 8.5 to 15 (dl / cm 3) ^1/2 is at least one selected from tetrahydrofuran, 2-propanol, 2-methoxyethanol, benzene, and toluene. A method for producing crosslinked polystyrene particles having excellent thermal stability. The method for preparing crosslinked polystyrene particles having excellent thermal stability according to claim 1 or 2, wherein the cosolvent is used in an amount of 0 to 75% by volume with respect to acetonitrile. delete The method of claim 1, wherein the crosslinking agent is used in an amount of 5 to 95% by weight based on the styrene monomer. The method according to claim 1, wherein the total content of the styrene monomer and the crosslinking agent is used in an amount of 1 to 15% by weight based on the solvent. The method of claim 1, wherein the polymerization initiator is one or two or more selected from organic peroxide-based or azo-based. The method of claim 7, wherein the organic peroxide polymerization initiator is lauroyl peroxide and benzoyl perdoxide, the azo polymerization initiator is 2,2'- azobisisobutyronitrile, 2,2'- azobis (2 , 4-dimethylvaleronitrile) and 2,2'-azobis (2-methylbutyronitrile). 8. The method according to claim 1 or 7, wherein the polymerization initiator is used in an amount of 1 to 15% by weight based on the total content of the styrene monomer and the crosslinking agent. The method for producing crosslinked polystyrene particles having excellent thermal stability according to claim 1, wherein the polystyrene particles have an average particle diameter of 1.0 to 8.0 mu m and are spherical.