JP4851799B2 - Method for producing polymer fine particles - Google Patents

Description

  The present invention relates to a method for producing polymer fine particles having a uniform particle size, and more particularly, to a production method capable of synthesizing a large amount of polymer fine particles having a high degree of crosslinking without requiring a large-scale and special equipment.

  Polymer fine particles of micron size (0.01 to several tens of μm diameter) are organic pigments, toner particles, liquid crystal panel spacers, separation materials, biochemical carriers, standard particles, cosmetic fillers, various additives or compounding agents, etc. Widely used in various applications. These polymer fine particles are required to have as uniform a particle size as possible from the viewpoint of ensuring fluidity.

  Various production methods such as suspension polymerization, emulsion polymerization, and dispersion polymerization have been conventionally known as methods for producing such micron-sized polymer fine particles (see Patent Documents 1 and 2). However, when producing fine polymer particles with a uniform particle diameter by these production methods, it is necessary to delicately prepare the composition of the reaction solution, such as the amount of surfactant and stabilizer added to the reaction solution. It was. Therefore, it is difficult to produce polymer fine particles in which a secondary reactive functional group capable of surface modification is left for fixing a chemical substance or a biological substance and using it as a carrier for biochemistry. It was.

  As a method for eliminating such drawbacks and producing polymer fine particles capable of surface modification, conventionally, an organic solvent containing diethylene glycol dimethacrylate, which is a crosslinkable monomer, is irradiated with radiation (gamma rays) to increase the size. Methods for producing molecular fine particles have been studied (see Non-Patent Documents 1 to 3).

  This radiation-based polymerization method uses a uniform system of only a crosslinkable monomer and an organic solvent without adding a surfactant or a stabilizer to a polymer particle having a uniform particle size in which secondary reactive functional groups remain on the surface. The solution can be produced without stirring. However, since a radiation irradiation facility is required, there is a problem that it is difficult to manufacture easily and at a low cost.

On the other hand, thermal polymerization is generally used as a method for producing a large amount of polymer fine particles from a monomer / solvent system by radical polymerization. Fine particle synthesis by thermal polymerization uses monomers, solvents that do not dissolve polymer particles, surfactants that stabilize heterogeneous solutions or stabilizers that prevent polymer particles from binding, polymerization initiators that generate radicals, etc. These are put in a reaction vessel, oxygen that reacts with radicals to stop the chain reaction is removed by nitrogen bubbling or the like, and heated with stirring to perform radical polymerization reaction. Thus, production of polymer fine particles by thermal polymerization requires preparation of a complicated solution composition and stirring operation during the synthesis reaction, and it is difficult to produce polymer fine particles with a uniform particle size. There was a problem.
JP 59-181301 JP-A-63-3316766 Yoshida et al., “Character of polymer microspheres prepared by radiation-induced polymerization in the presence of organic solvents”, Radiation physics and chemistry (Radiat Phys. Chem.), Elsevier, 1987, Vol. 30, No. 1, p. 39-45 Y. Naka et al. “Preparation of Microspheres by Radiation-Induced Polymerization. 1.Mechanism for the Formation of Monodisperse Poly (diethylene glycol dimethacrylate) Microspheres), Polymer Science Journal Part A (J. Polym. Sci., Part A, Polym. Chem. Ed.), USA, Jone Wily & Sons, Inc., 1991, Vol. 29, No. 8, p. 1197-1202 Y. Naka et al., “Preparation of Microspheres by Radiation-Induced Polymerization. 2. Mechanism of Microsphere Growth.”, Journal of Polymer Science, A (J. Polym. Sci., Part A, Polym. Chem. Ed.), USA, Jone Wily & Sons, Inc., 1992, Volume 30, No. 7, p. 1287-1298

  The present invention eliminates the drawbacks of conventional polymer fine particle production methods, has secondary reactive functional groups that can be modified on the surface, and specially produces polymer fine particles with a uniform particle size. An object of the present invention is to provide a method that can be easily and mass-produced without using a large-scale facility.

  As a result of diligent research, the inventors have found that the polymer fine particles can be produced by thermal polymerization of the crosslinkable monomer under certain conditions without using special equipment such as radiation irradiation equipment. .

  That is, the present invention includes a step of dissolving a crosslinkable monomer in an organic solvent to obtain a raw material solution, a step of adding a polymerization initiator or a polymerization initiator solution to the raw material solution to obtain a reaction solution, and a polymerization to the raw material solution. A method for producing polymer fine particles, comprising: adding an initiator or a solution of a polymerization initiator and stirring during an induction period to obtain a reaction solution; and heating and reacting the reaction solution in a stationary state It is.

  Since the method for producing polymer fine particles of the present invention does not use special equipment such as radiation irradiation equipment, it is easy to increase the synthetic scale. Therefore, the surface-modified polymer fine particles can be produced easily and in large quantities, and the production cost can be reduced. In addition, the polymer fine particles produced according to the present invention can be surface-modified with a chemical substance or a biological substance that adds various functional groups to the surface and reacts with these functional groups.

  The present invention includes a step of dissolving a crosslinkable monomer in an organic solvent to obtain a raw material solution, a step of adding a polymerization initiator or a polymerization initiator solution to the raw material solution to obtain a reaction solution, a polymerization initiator or a polymerization of the raw material solution Each step includes a step of adding a solution of an initiator and stirring to obtain a reaction solution during the induction period, and a step of performing a polymerization reaction by heating the reaction solution while standing.

(Crosslinkable monomer)
Examples of the crosslinkable monomer used in the present invention include diethylene glycol dimethacrylate.

  In addition to the crosslinkable monomer, as a monomer, non-crosslinkable monomers such as styrene monomers, acrylamide, acrylic acid esters such as acrylic acid and methyl acrylate, and methacrylic acid esters such as methacrylic acid and methyl methacrylate are used. May be added. Further, a non-crosslinkable monomer having secondary reactive reactivity such as maleic anhydride, glycidyl methacrylate, hydroxylethyl methacrylate, methacryloyloxyethyl isocyanate, acryloyloxyethyl isocyanate may be added.

(Organic solvent)
The organic solvent used in the present invention is particularly limited as long as it dissolves monomers including a crosslinkable monomer, a polymerization initiator, and other necessary auxiliary agents, and does not dissolve polymer fine particles after polymerization. Can be used without Specific examples of such an organic solvent include good solvents for the crosslinkable monomer, and preferable examples include esters such as ethyl acetate and propyl acetate, and ketones such as acetone, acetonitrile, and diethyl ketone. it can.

  The amount of the organic solvent used is about 300 to 5000 parts by weight, preferably about 500 to 2000 parts by weight, based on 100 parts by weight of the total amount of monomers. When the amount of the organic solvent used is less than 300 parts by weight, the shape deteriorates and the entire solution gels. When the amount exceeds 5000 parts by weight, fine particles are not formed, and a sufficient yield cannot be obtained. Such problems arise.

(Polymerization initiator)
The polymerization initiator used in the present invention is not particularly limited as long as it is an oil-soluble known radical polymerization initiator. Such polymerization initiators include cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, o-chlorobenzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide, t-butyl peroxide. Organic peroxides such as acetate, t-butylperoxyisobutyrate, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis (2 -Methylbutyronitrile), azobiscyclohexanecarbonitrile, etc. Azo compounds, and the like derivatives of these polymerization initiators may be exemplified.

  Moreover, the usage-amount of a polymerization initiator is about 0.1-5 weight part with respect to 100 weight part of raw material solutions, and it is preferable to set it as 0.1-1 weight part. When the amount of the polymerization initiator used is less than 0.1 parts by weight, problems such as insufficient polymerization reaction and a long time for polymerization occur, and when it exceeds 5 parts by weight, the yield does not change. Such a problem arises that particles having a bad shape are formed due to the rapid progress of the reaction. Since the polymerization initiator is dissolved in the raw material solution in a short time, a method in which the polymerization initiator is dissolved in an organic solvent separately from the raw material solution is also possible. And as an organic solvent used for melt | dissolution, the same thing as what was used for the raw material solution is preferable.

(Manufacture of polymer fine particles)
The polymer fine particles are produced from monomers such as the above-mentioned crosslinkable monomer, an organic solvent, a polymerization initiator and the like by the following procedure.

(1) Preparation of raw material solution, etc. Monomers are dissolved in an organic solvent to form a reaction solution, and this reaction solution is put into a reaction vessel, and the temperature rises for each reaction vessel up to the temperature at which the polymerization initiator used generates radicals (polymerization temperature). Warm up. On the other hand, the polymerization initiator and the solution in which the polymerization initiator is dissolved are stored at a temperature slightly lower than the temperature at which the polymerization initiator generates radicals, specifically, about 40 to 120 ° C.

(2) Preparation of reaction solution A polymerization initiator or a solution of a polymerization initiator is added to a reaction vessel containing a raw material solution and stirred to obtain a reaction solution. The reaction solution is stirred only during the induction period (period from the addition of the polymerization initiator to the start of the polymerization reaction). Here, unlike the usual thermal polymerization, the stirring is stopped during the polymerization reaction in order to prevent the produced polymer fine particles from adhering to each other and obtain uniform polymer fine particles.

(3) Polymerization reaction The reaction vessel containing the reaction solution homogenized in (2) is immersed in a thermostatic bath set at the polymerization temperature and allowed to stand without stirring for a certain period of time. After a certain period of time, the reaction vessel is cooled to stop the synthesis reaction, the polymer fine particles are filtered with a membrane filter or the like, and the filtered polymer fine particles are washed with a solvent.

  The particle diameter of the polymer fine particles thus produced can be measured by observing the polymer fine particles with a known method, for example, a scanning electron microscope. The variation in the particle size of the polymer fine particles can be evaluated by, for example, the CV value (%) {(standard deviation / average particle size) × 100}, and the value is preferably 10% or less, More preferably, it is 5% or less.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope of the invention described in the claims.

  For example, the raw material solution may be bubbled with an inert gas such as nitrogen gas after the step of obtaining the raw material solution. In addition, by bubbling, oxygen contained in the raw material solution is driven out, the oxygen concentration in the raw material solution is adjusted, and the time (induction period) until the polymerization reaction starts can be adjusted. Specifically, the induction period is shortened by bubbling for a long time, and conversely, the induction period is lengthened by bubbling for a short time.

  Therefore, in comparison with the case of producing polymer fine particles by a conventional thermal polymerization method, if the bubbling is performed for a shorter time, the induction period becomes longer, the temperature of the reaction solution at the start of polymerization, the concentration distribution of the polymerization initiator The polymer fine particles having a more uniform shape and particle size distribution can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the claims of the present invention is not limited by the following examples in any way.

(1) Preparation of raw material solution After putting 50.0 g of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) into a 500 ml glass container (reaction container) and pouring 400 g of ethyl acetate (manufactured by Aldrich) as a solvent, The reaction vessel was closed and heated to 60 ° C.

(2) Polymerization reaction After the temperature of the raw material solution reached 60 ° C, the reaction container was opened and 1.5 g of 2,2'-azobisisobutyronitrile (manufactured by Aldrich) was added. After the addition, the reaction solution was promptly stirred to dissolve the polymerization initiator to obtain a reaction solution. The reaction vessel was sealed and the reaction vessel was placed in a constant temperature bath (60 ° C.) and allowed to stand to allow the polymerization reaction to proceed. After 2 hours and 10 minutes, the reaction vessel was gently removed from the thermostat, the lid was opened, air was introduced, the reaction vessel was placed in a freezer (−10 ° C.) and cooled to stop the polymerization reaction. Finally, the reaction solution was filtered with a membrane filter to separate the polymer particles, and the polymer particles were washed with ethyl acetate and dried.

  From the observation of the progress of the polymerization reaction, the time from the end of the induction period to the start of generation of fine particles is about 10 to 20 minutes, and this time depends on the amount of air remaining in the space portion of the reaction vessel Specifically, it has been found that the polymerization reaction is promoted when the amount of air is large, and the polymerization reaction is suppressed when the amount of air is small.

(3) Evaluation Thereafter, reaction yield and reaction yield were measured from the weight of the polymer fine particles. In addition, the polymer fine particles were observed with a scanning electron microscope (Hitachi S-2250N) to measure the particle size. As a result, the reaction yield was 38.2 g, the reaction yield was 76.4%, and the particle size was 1.13 ± 0.10 μm. The CV value (%) was 8.8%.

(1) Preparation of raw material solution and catalyst solution 50.0 g of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 2.0 g of styrene monomer (manufactured by Aldrich) are placed in a 500 ml glass container (reaction container), and acetic acid as a solvent is added thereto. After 350 g of ethyl (manufactured by Aldrich) was poured and dissolved, the reaction vessel was closed and heated to 60 ° C. to obtain a raw material solution (hereinafter abbreviated as “A solution”). Also, add 2.5 g of 2,2'-azobisisobutyronitrile (manufactured by Aldrich) into another container, pour 25 ml of ethyl acetate solution (manufactured by Aldrich), dissolve, and dissolve the catalyst solution (hereinafter abbreviated as B solution). .) In addition, B liquid was stored at room temperature.
(2) Polymerization reaction
After the reaction vessel containing solution A was heated to around 60 ° C., solution B was poured into the reaction vessel and mixed, and the reaction vessel was left in a constant temperature bath (60 ° C.) for 120 minutes. After 120 minutes, the synthesis reaction was stopped by cooling the reaction vessel with ice. Finally, the reaction solution was filtered through a membrane filter to separate the polymer particles, and the polymer particles were washed with ethyl acetate and dried.

(3) Evaluation Thereafter, the reaction yield, reaction yield, and particle size of the polymer fine particles were measured in the same manner as in Example 1. As a result, the reaction yield was 42.6 g, the reaction yield was 81.9%, and the particle size was 1.67 ± 0.13 μm. The CV value (%) was 7.8%.

(1) Preparation of raw material solution and catalyst solution Diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) 10.2 g and methacryloyloxyethyl isocyanate (manufactured by Showa Denko) 4.2 g are placed in a 100 ml glass container (reaction container). After 78 g of ethyl acetate (manufactured by Aldrich) as a solvent was poured and dissolved, the reaction vessel was closed and heated to 60 ° C. to obtain a raw material solution (hereinafter abbreviated as “A solution”). Also, add 0.3 g of 2,2'-azobisisobutyronitrile (manufactured by Aldrich) into another container, pour 6 ml of ethyl acetate solution (manufactured by Aldrich) and dissolve to dissolve the catalyst solution (hereinafter abbreviated as solution B). .) In addition, B liquid was stored at room temperature.

(2) Polymerization reaction
After the reaction vessel containing solution A was heated to around 60 ° C., solution B was poured into the reaction vessel and mixed, and the reaction vessel was left in a constant temperature bath (60 ° C.) for 120 minutes. After 120 minutes, the synthesis reaction was stopped by cooling the reaction vessel with ice. Finally, the reaction solution was filtered with a membrane filter to separate the polymer particles, and the polymer particles were washed with a solvent and dried.

(3) Evaluation Thereafter, the reaction yield, reaction yield, and particle size of the polymer fine particles were measured in the same manner as in Example 1. As a result, the reaction yield was 10.5 g, the reaction yield was 73%, and the particle size was 1.93 ± 0.15 μm. The CV value (%) was 7.8%.

Claims (4)

Particle size is a method for producing the polymer fine particles is 0.01 to 2 [mu] m,
A step of dissolving a crosslinkable monomer in an organic solvent to obtain a raw material solution;
Adding a polymerization initiator or a solution of the polymerization initiator to the raw material solution and stirring during the induction period to obtain a reaction solution;
Heating the reaction solution in a standing state to cause a polymerization reaction;
A method for producing polymer fine particles comprising   The method for producing polymer fine particles according to claim 1, comprising a step of bubbling the raw material solution with an inert gas after the step of obtaining the raw material solution.   The method for producing polymer fine particles according to claim 1, wherein the raw material solution contains a non-crosslinkable monomer in addition to the crosslinkable monomer.   The method for producing fine polymer particles according to any one of claims 1 to 3, wherein the crosslinkable monomer is diethylene glycol dimethacrylate.