KR100441407B1 - Preparation of spherical poly(methylmethacrylate) powder by crystallization - Google Patents

Abstract

The present invention relates to a method for producing crystalline polymethyl methacrylate spherical powder, and more particularly, to dissolve a bulk polymethyl methacrylate (PMMA) resin in a phase separation solvent to form a uniform solution, and then at a constant rate. Cool to induce nucleation of polymer crystals through phase separation between solvent and polymethyl methacrylate, and control the growth rate of the resulting nucleus to form a heterogeneous solution in which polymethyl methacrylate is phase separated into uniform spherical particles. Only the solvent for phase separation was dissolved and washed using a washing solvent, and polymethyl methacrylate was separated and filtered as it was in a phase separated state to obtain polymethyl methacrylate powder of spherical particles having a uniform size distribution. Unlike the manufacturing method of the conventional spherical polymer powder through the separation process by the addition of emulsifier and dispersant The present invention relates to a method for producing a polymethylmethacrylate spherical powder which can improve productivity and reduce manufacturing cost by simplifying the reaction process and shortening the reaction time.

Description

Preparation method of crystalline polymethylmethacrylate spherical powder {Preparation of spherical poly (methylmethacrylate) powder by crystallization}

The present invention relates to a method for producing crystalline polymethyl methacrylate spherical powder, and more particularly, to dissolve a bulk polymethyl methacrylate (PMMA) resin in a phase separation solvent to form a uniform solution, and then at a constant rate. Cool to induce nucleation of polymer crystals through phase separation between solvent and polymethyl methacrylate, and control the growth rate of the resulting nucleus to form a heterogeneous solution in which polymethyl methacrylate is phase separated into uniform spherical particles. Only the solvent for phase separation was dissolved and washed using a washing solvent, and polymethyl methacrylate was separated and filtered as it was in a phase separated state to obtain polymethyl methacrylate powder of spherical particles having a uniform size distribution. Unlike the manufacturing method of the conventional spherical polymer powder through the separation process by the addition of emulsifier and dispersant The present invention relates to a method for producing a polymethylmethacrylate spherical powder which can improve productivity and reduce manufacturing cost by simplifying the reaction process and shortening the reaction time.

Polymer powders are used in various fields. For example, it is widely used as a copier toner, a cosmetic additive, and a filler for other products. Conventionally, in the manufacturing method of polymethyl methacrylate spherical powder, many processes such as grinding of solid polymer material, spray drying method, or evaporating solvent from polymer solution in emulsion state have been used. It is mainly manufactured by various polymerization methods such as. Well-known processes are US Pat. Nos. 2,932,629 and 4,148,741 which produce polymer powders having a narrow particle size distribution. This process is to prepare polymer powder by using solid colloidal stabilizer in suspension polymerization reaction. In the manufacturing process of polymer powder, a material such as silica was used as a solid colloidal stabilizer to give particles stability during suspension polymerization, and the disadvantage of using silica was to remove the solid colloidal stabilizer used after production of the product. . In order to remedy this disadvantage, US Pat. No. 5,133,992 improves the above-mentioned disadvantages by using a copolymer polymer stabilizer as a solid colloidal stabilizer in place of silica. Suspension polymerization is carried out under constant stirring and is generally carried out in the presence of a dispersant such as an oil-soluble polymer or an insoluble fine powder such as calcium phosphate. These dispersants aid in the dispersion of the polymerization droplets but interfere with dispersion stability. Therefore, it is necessary in this method to carry out the polymerization under continuous mechanical stirring. Otherwise phase separation occurs due to agglomeration of polymerization droplets. As a result, this process is affected by the degree of agitation in the reactor and the change in viscosity due to the polymerization. As a result, it is difficult to control the reproducibility of the reaction and the particle distribution is wide. Thus, U. S. Patent No. 5,455, 320 introduces a suspension polymerization method of minimizing entanglement to produce polymer microparticles having a very uniform and narrow particle size distribution. Unlike the existing patents, this patent establishes a process that minimizes agitation using well controlled emulsion stabilizers. In such a method, it is pointed out that the polymerization method using the emulsifier and the emulsion crystallization method include the fact that the process of removing the emulsifier after the preparation of the polymethyl methacrylate powder particles is added, and the manufacturing time is also long. By spraying. Zhou and his team dissolved polymethylmethacrylate in a solvent to produce polymer particles of uniform particle size using spray drying (Journal of materials science 36 (2001)). This method is advantageous in that it does not need to remove the emulsifier, but it is pointed out as a major factor of the increase in manufacturing cost because expensive manufacturing equipment and process control are difficult to manufacture spray particles of a certain size in the spraying process.

Accordingly, the present inventors have studied to solve the shortcomings of the manufacturing method of the polymethyl methacrylate spherical powder prepared by the polymerization and mechanical phase change, the crystallization of the polymer solution according to the concentration of the polymer solution and the cooling temperature and speed The present invention has been completed by developing a method for producing a polymethylmethacrylate spherical powder having improved productivity using the behavior.

Therefore, the present invention is different from the solvent selection and crystallization conditions in the existing crystallization method, avoiding the use of polymerization additives such as emulsifiers and dispersants through crystallization, and high efficiency and high efficiency to form crystals in solution through a simple manufacturing equipment and simple processes It is an object of the present invention to provide a method for producing a productive polymethylmethacrylate spherical powder.

1 is an electron micrograph of a polymethyl methacrylate spherical powder prepared according to the present invention.

Figure 2 is an electron micrograph of the polymethyl methacrylate spherical powder prepared according to the present invention.

Figure 3 is a graph showing the size change of the polymethyl methacrylate spherical powder with the nuclear growth time.

Figure 4 is a graph showing the size change of the polymethyl methacrylate spherical powder with the concentration of the solution.

5 is a graph showing the size change of the polymethyl methacrylate spherical powder according to the cooling rate. .

6 is a graph showing the change of the polymethyl methacrylate cloud point according to the concentration of the solution.

The present invention dissolves bulk polymethyl methacrylate (PMMA) resin in a phase separation solvent to form a transparent homogeneous solution, and then cools it at a constant rate to nucleate the polymer crystals through phase separation between the solvent and polymethyl methacrylate. Induce and control the growth rate of the resulting nucleus to form a heterogeneous solution in which polymethyl methacrylate is phase-separated into uniform spherical particles, and then use only a washing solvent to dissolve, wash and remove the phase-separating solvent. It is characterized by a method for producing polymethyl methacrylate powder of spherical particles having a uniform size distribution by separating and filtering the acrylate as it is in a phase separated state.

Referring to the present invention in more detail as follows.

The present invention is completely different from the method prepared by the conventional polymerization, and is a method of producing a powder having a uniform size distribution of spherical particles from the bulk polymethyl methacrylate resin by changing the existing crystallization method. The polymethyl methacrylate resin used in the present invention is a polymer of methyl methacrylate, a transparent plastic material generally called acrylic resin, and has excellent light transmittance, weather resistance, and the like. It is widely used in transparent windows, food containers, accessories and the like.

In general, the crystallization method is a method of obtaining a solute in which a transparent uniform solution obtained by dissolving a solute in a constant solvent is dissolved using a difference in solubility of the solute in accordance with temperature. However, in such a polymer, the solute melted by the solvent may not elute at a low temperature due to the swelling phenomenon caused by the solvent in the polymer. Therefore, in the present invention, a certain condition is used in the solvent for the polymer by using a solvent having a solubility from the boiling point of the solvent up to 15 ° C below and a solubility below 40 ° C below the boiling point of the solvent (hereinafter referred to as "compatibility solvent"). Spherical powder is prepared by inducing phase separation of homogeneous solution under. In addition, the behavior of the polymer in the solvent is a snake-like behavior in the solvent. This behavior can be observed that if agitation during phase separation causes the polymer chains to bind to each other, thereby gelling rather than forming spherical powder. For this reason, polymethylmethacrylate spherical powder is prepared through solvent selection and crystallization conditions different from those of general crystallization methods.

The phase separation solvent used in the present invention completely dissolves the polymethyl methacrylate resin from the boiling point of the solvent up to 15 ° C. to form a transparent uniform solution. On the other hand, below 40 ° C. below the boiling point of the solvent, phase separation between the solvent and the polymethyl methacrylate resin is induced to form an opaque non-uniform solution in which the polymethyl methacrylate is phase separated into spherical fine particles. Only the solvent for phase separation using a material having excellent compatibility with the solvent for phase separation but no compatibility with the polymethyl methacrylate resin (hereinafter referred to as "washing solvent") from the heterogeneous solution in which the phase separation has occurred is simply When dissolved, washed and removed, the polymethyl methacrylate is separated and precipitated as it is in the phase separated state. The precipitate is filtered and dried to obtain polymethyl methacrylate powder of spherical fine particles having a uniform size distribution. Since the size of the powder obtained is affected by the concentration of the solution, the cooling rate, and the particle growth time, the size of the separated polymethylmethacrylate phase is constantly controlled by selecting an appropriate concentration, cooling conditions, and particle growth time during phase separation. This allows a large amount of spherical powders of any size to be obtained without the addition of other processes.

In selecting a solvent for phase separation, a solvent having little solubility for polymethyl methacrylate at room temperature and having increased solubility with increasing temperature is selected from the solvent of the polymethyl methacrylate resin. Based on the boiling point temperature of the phase-separating solvent, below 40 ° C. below the boiling point, the non-solvent properties, above that, the solvent properties, the viscosity is 30 cp or less after complete dissolution to form a uniform polymer solution, Preferably it forms 15-20cp. The phase separation solvent that satisfies such conditions is selected from alcohols having 1 to 10 carbon atoms, derivatives thereof, and mixtures thereof, and preferably, propyl alcohol, normal phenyl alcohol, normal hexyl alcohol, isopropyl alcohol, and secondary butyl Alcohols, tertiary butyl alcohol, active amyl alcohol and the like are used.

Mix the polymethyl methacrylate resin with 0.1 to 30% by weight, preferably 0.5 to 20% by weight, in a phase separation solvent that satisfies the above mentioned limitations. Stir until a clear homogeneous solution is formed. The transparent homogeneous solution thus made was subjected to a rate in the range of 0.001 to 200 DEG C / min per minute, preferably 0.1 to 100 DEG C / min. Stirring and cooling are carried out simultaneously at a rate of 0 to 10000 rpm to cloud point at a speed in the range and cooled to 0 to 30 ° C. without stirring after the cloud point passes. Thereafter, when the solution reaches a cloud point, it is allowed to stand for 1 to 120 minutes at the cloud point of the solution to grow nuclei as necessary. At this time, the polymethyl methacrylate spherical powder is phase-separated during the cooling process, and the size of the separated polymer phase is determined by the concentration and cooling rate of the solution and the particle growth time. Figure 3 shows the average particle size change curve according to the nucleation time of the solution and the concentration of the solution, Figure 4 shows the average particle size change of the separated polymethyl methacrylate phase with the solution concentration and cooling rate.

The concentration of the solution affects the crystallization rate of the polymethylmethacrylate, and the larger the concentration of the solution, the larger the diameter of the polymethylmethacrylate phase is obtained, and the size of the obtained polymethylmethacrylate phase is 200 nm to 100 µm, preferably Preferably, it can adjust in the range of 100 nm-20 micrometers, and polydispersity which shows the size distribution is 1.5 or less, Preferably it is 1.1-1.4. In addition, the smaller the cooling rate, the larger the diameter of the polymethylmethacrylate phase can be obtained. In addition, if the nuclear growth time is prolonged, a larger diameter polymethylmethacrylate phase can be obtained, but if the growth time is poured for more than 2 hours, it causes a gelation phenomenon due to precipitation. If the polydispersity is greater than 1.5, there is a problem in that the application of the polymer powder shows a limit, which is undesirable.

From the mixture after the phase separation is completely mixed with the phase separation solvent, but using a washing solvent which is not compatible with the polyamide at all, only the phase separation solvent is dissolved and removed, followed by filtration and drying to form spherical polymethyl methacrylate powder. Get The size and structure of the prepared powder is the same as the size and structure of the polymethyl methacrylate phase separated in the cooling process and has a spherical shape because each powder is composed of separated single spheres.

In order to completely dissolve and remove the solvent for phase separation in the manufacturing process, the washing and filtration process should be repeated three times or more times using a washing solvent, and the washing solvent used herein is water or a mixture of water and hydrocarbon, preferably And mixtures of methanol, ethanol, propanol, ethylene glycol, and the like.

Method for producing a polymethyl methacrylate spherical powder according to the present invention provides a polymethyl methacrylate spherical powder having a uniform size distribution in a single crystal phase without other additives, unlike the conventional method using an emulsifier. Simplification improves productivity and reduces manufacturing costs.

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

Example 1

A mixture of 25% by weight of a bulk polymethyl methacrylate resin in normal propyl alcohol was dissolved in a crystallizer at 100 ° C. for about 30 minutes until the polymethyl methacrylate was completely dissolved.

The dissolved mixture was cooled to 55 ° C. while controlling the cooling rate to 0.5 ° C. per minute, and the stirring was stopped at 58 ° C. while being controlled at 400 rpm and left at 55 ° C. for 30 minutes. After standing still, the cooling rate was cooled to 25 ° C while adjusting the cooling rate to 3 ° C per minute. During this cooling, the polymethylmethacrylate phase separated into an independent monoclinic phase.

The phase separated mixture was washed with only normal propyl alcohol with water compatible with normal propyl alcohol. At this time, the complete removal of the normal propyl alcohol is very important, so washed three times or more, filtered and dried to separate the polymethyl methacrylate spherical powder.

The size and size distribution of the obtained spherical powder can be confirmed using an electron microscope, and the average diameter of the spherical powder obtained in this example was 4.8 µm, and the polydispersity representing the size distribution was 1.02.

Example 2

Except for using isopropyl alcohol instead of normal propyl alcohol as the solvent for phase separation used in Example 1 was carried out in the same manner as in Example 1. The average diameter of the spherical powders obtained in this example was 3.2 µm, and the polydispersity showing a size distribution was 1.03.

Example 3

The same method as in Example 1 was performed except that tertiary butyl alcohol was used instead of normal propyl alcohol as the phase separation solvent used in Example 1. The average diameter of the spherical powders obtained in this example was 4.3 μm, and the polydispersity showing a size distribution was 1.05.

Example 4

Except for using the polymethyl methacrylate resin in 20% by weight instead of 25% by weight in Example 1 was carried out in the same manner as in Example 1. The polydispersity of the spherical powder obtained in this example was 3.6 µm and the size distribution was 1.06.

Example 5

A mixture of 15% by weight of the bulk polymethyl methacrylate resin in normal propyl alcohol was dissolved in a crystallizer at 100 ° C. for about 30 minutes until the polymethyl methacrylate was completely dissolved.

The dissolved mixture was quenched to 25 ° C. while stopping stirring and adjusting the cooling temperature to 60 ° C. per minute. During this cooling, the polymethylmethacrylate phase separated into an independent monoclinic phase.

The phase separated mixture was washed with only normal propyl alcohol with water compatible with normal propyl alcohol. At this time, the complete removal of normal propyl alcohol is very important, so washed three times or more, filtered and dried to separate the polymethyl methacrylate spherical powder.

The size and size distribution of the obtained spherical powder can be confirmed using an electron microscope, and the average diameter of the spherical powder obtained in this example was 0.5 µm, and the polydispersity indicating the size distribution was 1.02.

Example 6

Except for using isopropyl alcohol instead of normal propyl alcohol as the phase separation solvent used in Example 5 was carried out in the same manner as in Example 5. The average diameter of the spherical powders obtained in this example was 0.7 µm, and the polydispersity showing a size distribution was 1.06.

Example 7

It was carried out in the same manner as in Example 5 except that tertiary butyl alcohol was used instead of normal propyl alcohol as the phase separation solvent used in Example 5. The average diameter of the spherical powder obtained in this example was 0.9 µm, and the polydispersity showing a size distribution was 1.2.

Example 8

In Example 5 was carried out in the same manner as in Example 5 except that the cooling temperature was adjusted to 100 ℃ per minute instead of 60 ℃ per minute. The polydispersity of the spherical powder obtained in this example was 1.02, indicating a 0.3 μm size distribution.

Comparative example

Polymethylmethacrylate particles prepared by general dispersion polymerization using azobisisobutylonitrile (AIBN) as an initiator, polyvinylpyrrolidone (PVP) as a crosslinking agent, and silica fume or colloidal silica as a dispersant Use [J. Materials Science 35 (2000) 6181-6188.

These materials and the monomer methyl methacrylate were dissolved in methanol or isopropanol well and then put into the reactor. The reaction conditions were polymerized for 24 hours while the reaction temperature was stirred at 60 ℃ in a nitrogen atmosphere. The initiator added after the polymerization was removed through a distillation process, and the polymethylmethacrylate particles obtained through the polymerization were washed and separated through centrifugation. The polydispersity of the spherical powder obtained in this comparative example was 1.0 with a 5 탆 size distribution.

As described above, the manufacturing method of the polymethyl methacrylate spherical powder according to the present invention is different from the emulsion polymerization and dispersion polymerization methods using an emulsifier and various additives, which are conventional methods, and the production of the spherical powder of polymer resin by polymerization. It provides a polymethylmethacrylate resin spherical powder having a uniform size distribution on a single crystal through polymer crystallization without using other additives, thereby simplifying the manufacturing method to improve productivity and reduce manufacturing costs. have.

The polymethyl methacrylate spherical powder thus prepared is useful for cosmetic polymer powder, polymer electronic cleaning agent, pharmaceutical drug delivery agent and the like.

Claims (7)

1) stirring the bulk polymethyl methacrylate resin in a phase separation solvent at a temperature of boiling point to below 20 ℃ to form a transparent homogeneous solution; 2) cooling the warmed homogeneous solution to 0-30 [deg.] C. at a rate of 0.001-200 [deg.] C./min. Per minute to form a nucleus with a heterogeneous solution in which polymethylmethacrylate is phase separated into an independent monolithic phase; And 3) The heterogeneous solution is dissolved in a solvent for phase separation with a washing solvent, washed and removed, and the polymethyl methacrylate is separated and filtered as it is in a phase separated state to separate polymethyl methacrylate powder having a uniform size distribution. Method for producing a crystalline polymethyl methacrylate spherical powder comprising the step of obtaining. According to claim 1, wherein 1) the phase separation solvent based on the boiling point temperature, below the boiling point 40 ℃ or less exhibits the properties of the non-solvent, above the properties of the solvent, the viscosity after the formation of a homogeneous solution 30 A method for producing a crystalline polymethyl methacrylate spherical powder, characterized in that less than cp. The method for preparing crystalline polymethylmethacrylate spherical powder according to claim 2, wherein the phase separation solvent is selected from water or alcohols having 1 to 10 carbon atoms, derivatives thereof, and mixtures thereof. The method for preparing crystalline polymethylmethacrylate spherical powder according to claim 1, wherein 0.1 to 30% by weight of the bulk crystalline polymethylmethacrylate resin is added to the phase separation solvent. The method of claim 1, wherein in step 2), the homogeneous solution is cooled to a cloud point at a stirring speed of 0 to 10000 rpm to form a nucleus, and the nucleus is grown by standing for 1 to 120 minutes at the cloud point of the solution. Method for producing a crystalline polyamide spherical powder, characterized in that. The crystalline polymethylmethacrylate of claim 1, wherein the washing solvent is mixed with a solvent for phase separation but not with polymethylmethacrylate, and is water or a mixture of water and hydrocarbons. Method for producing spherical powder. The crystalline polymethylmethacrylate spherical powder according to claim 1, wherein the polymethyl methacrylate powder has a diameter ranging from 200 nm to 100 µm and a polydispersity of 1.5 or less indicating its size distribution. Way.