JP3611736B2 - Manufacturing method of resin fine particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing resin fine particles, and relates to a method for producing resin fine particles having an average particle size of 0.5 to 5 μm by a simple operation without using a special additive.
[0002]
[Prior art]
In recent years, resin fine particles have been used in various applications such as matting agents for paints, light diffusing agents, slipperiness imparting agents for cosmetics, and anti-blocking agents for toners or plastic films.
[0003]
[Problems to be solved by the invention]
In general, emulsion polymerization, seed polymerization, suspension polymerization and the like are known as methods for producing resin fine particles.
In emulsion polymerization, resin particles having a uniform particle size distribution can be obtained, but it is usually difficult to produce resin particles having a particle diameter of 0.5 μm or more.
In seed polymerization, resin particles having a relatively uniform particle size distribution and a particle size of several μm can be obtained, but the operation is complicated and the number of manufacturing steps is increased.
[0004]
In suspension polymerization, it is usually difficult to obtain fine particles having a particle size of 5 μm or less. However, if the amount of surfactant added in the suspension system is increased, the droplet size can be reduced, and the resin is reduced accordingly. The particle diameter of the particles can also be reduced. However, when the amount of the surfactant in the suspension system exceeds the critical micelle concentration, emulsion polymerization occurs, so that there is a disadvantage that many particles smaller than the target particle size are generated.
In suspension polymerization, a special dispersion machine may be used as a method for reducing the droplet diameter to 5 μm or less, but the manufacturing process becomes complicated.
[0005]
In order to solve this problem, Japanese Patent Application Laid-Open No. 10-87710 discloses a resin fine particle having a relatively uniform particle size of 2 to 15 μm by adding a hardly water-soluble substance to the suspension system. Is disclosed. However, since the resin fine particles produced by such a method have poorly water-soluble substances remaining in the resin fine particles, when molding is performed using the resin fine particles, gas may be generated or the moldability may deteriorate. There are concerns about adverse effects such as
[0006]
[Means for Solving the Problems]
As a result of earnest research, the present inventor has solved the problems of the conventional production method as described above, and the average particle size is 0.5 to 5 μm by a simple operation without using a special additive. The present inventors have found a method for producing the resin particles and have completed the present invention.
According to the present invention, a liquid mixture composed of a polymerizable monomer component containing a polymerizable monomer and a polymerization initiator and an aqueous solution containing a surfactant having a critical micelle concentration or higher is stirred to have a droplet diameter of 5 μm or less. Provided is a method for producing resin fine particles, comprising preparing an o / w emulsion, adding an aqueous solution containing a dispersion stabilizer to the emulsion to make the concentration of the surfactant less than the critical micelle concentration, and then performing suspension polymerization. Is done.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the production method of the present invention, first, a polymerizable monomer component containing a polymerizable monomer and a polymerization initiator and an aqueous solution containing a surfactant having a critical micelle concentration or more are mixed, and this mixed solution is stirred. To prepare an emulsion having a droplet diameter of 5 μm or less.
[0008]
Examples of the polymerizable monomer used in the method of the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. Examples include (meth) acrylic acid ester monomers such as 2-ethylhexyl, aromatic vinyl monomers such as styrene and α-methylstyrene, and monomers having a vinyl group such as acrylonitrile and vinyl acetate. These polymerizable monomers can be used alone or in combination of two or more.
In order to obtain resin fine particles having a crosslinked structure, a crosslinkable monomer having a plurality of polymerizable double bond groups in the molecule is used as the polymerizable monomer.
[0009]
Examples of the crosslinkable monomer include trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, decaethylene glycol dimethacrylate, pentadecaethylene glycol dimethacrylate, dimethacrylate. (Meth) acrylic acid-based monomers such as pentaglyceride ethylene glycol, 1,3-butylene dimethacrylate, allyl methacrylate, pentaerythritol tetramethacrylate, diethylene glycol dimethacrylate, divinylbenzene, divinylnaphthalene and Examples thereof include aromatic divinyl compounds which are derivatives thereof. These crosslinkable monomers can be used alone or in combination of two or more thereof, or in combination with the polymerizable monomer as described above.
[0010]
As the polymerization initiator used in the method of the present invention, an oil-soluble peroxide-based or azo-based one generally used for suspension polymerization can be used. Examples of the peroxide-based polymerization initiator include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, t-butyl hydroperoxide, and the like. Examples of the azo polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2). , 4-dimethylvaleronitrile, 2,2′-azobis (2-methylbutyronitrile), and the like.
The ratio of the polymerizable monomer and the polymerization initiator in the polymerizable monomer component is suitably about 0.01 to 5 parts by weight of the polymerization initiator with respect to 100 parts by weight of the polymerizable monomer.
[0011]
The surfactant in the surfactant-containing aqueous solution added to the polymerizable monomer component comprising the polymerizable monomer and the polymerization initiator as described above is not particularly limited, but examples thereof include sodium oleate and lauryl sulfate. Anionic surfactants such as sodium and sodium dodecylbenzenesulfonate, cationic surfactants such as laurylamine acetate and lauryltrimethylammonium chloride, and nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether Etc.
[0012]
The concentration of the surfactant in the aqueous solution is not less than the critical micelle concentration (the surfactant is the lowest concentration capable of forming micelles in the aqueous solution), preferably 1.0 to 10 times the critical micelle concentration, More preferably, it is -3.0 times. When the concentration of the surfactant in the aqueous solution does not reach the critical micelle concentration, it is difficult to obtain resin particles having an average particle diameter of 0.5 to 5 μm, and the concentration exceeds 10 times the critical micelle concentration. No further effect of reducing the particle size can be obtained.
The ratio of the polymerizable monomer component to the aqueous solution containing the surfactant is suitably about 100 to 500 parts by weight of the surfactant aqueous solution with respect to 100 parts by weight of the polymerizable monomer component.
[0013]
It is preferable to stir the mixed liquid thus obtained while applying shearing. For example, a known stirring device such as a high-pressure homogenizer, a homomixer, an ultrasonic dispersion device, or a high-pressure jet dispersion device is preferably used. Can be used. By stirring while applying shear, an emulsion having a droplet diameter of 5 μm or less, preferably 1 to 3 μm can be easily prepared.
[0014]
In the method of the present invention, an aqueous solution containing a dispersion stabilizer is added to the emulsion obtained as described above, and the concentration of the surfactant in the emulsion is less than the critical micelle concentration, preferably 0.01 times the critical micelle concentration. Resin fine particles having an average particle diameter of 0.5 to 5 μm are obtained by suspension polymerization after preparing a dispersion of less than ˜1.0 times.
[0015]
The dispersion stabilizer is not particularly limited, and examples thereof include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, and hydroxyethyl cellulose, and anionic interfaces such as sodium oleate, sodium lauryl sulfate, and sodium dodecylbenzenesulfonate. Examples thereof include cationic surfactants such as activators, laurylamine acetate and lauryltrimethylammonium chloride, and nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether. These dispersion stabilizers can be used alone or in combination of two or more.
[0016]
The amount of the dispersion stabilizer in the dispersion stabilizer-containing aqueous solution added to the emulsion is not particularly limited, but usually 0.5 to 5 parts by weight is appropriate for 100 parts by weight of water. The amount of the dispersion stabilizer-containing aqueous solution added to the emulsion varies depending on the concentration of the surfactant in the emulsion and the concentration of the dispersion stabilizer in the aqueous solution, but is usually 100 to 500 parts by weight with respect to 100 parts by weight of the emulsion. The degree is appropriate.
[0017]
An aqueous solution containing a dispersion stabilizer is added to the emulsion so that the concentration of the surfactant in the dispersion is less than the critical micelle concentration, and then the polymerization reaction is started. If the polymerization reaction is carried out while the concentration of the surfactant in the dispersion is not less than the critical micelle concentration, emulsion polymerization occurs, and a large amount of resin fine particles having a particle diameter outside the target range is not preferable. The polymerization reaction is carried out by stirring the dispersion obtained as described above at 40 to 90 ° C. Even if the concentration of the surfactant in the dispersion is less than the critical micelle concentration, the polymerization reaction may proceed in the aqueous phase, and undesirable new particles may be produced as a by-product. A water-soluble polymerization inhibitor such as hydroquinone may be added to the reaction system.
[0018]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but these examples do not limit the present invention.
In addition, the average particle diameter of the resin fine particles in Examples and Comparative Examples is a weight average particle diameter measured by a Coulter Multisizer manufactured by Coulter Co., Ltd.
[0019]
Example 1
0.5 g of benzoyl peroxide was dissolved in a mixed solution composed of 90 g of methyl methacrylate and 10 g of trimethylolpropane trimethacrylate to obtain a polymerizable monomer component. Separately, 0.3 g of sodium dodecylbenzenesulfonate [critical micelle concentration (CMC) 0.08%] was dissolved in 200 g of water. The above polymerizable monomer component is mixed with this aqueous solution. K. The mixture was stirred for 10 minutes at a rotational speed of 7000 rpm using a Homomixer (manufactured by Special Machine Industries Co., Ltd.). The droplet diameter in the obtained o / w emulsion was about 3 μm.
[0020]
The obtained emulsion was put in a reaction vessel having a capacity of 1 L equipped with a stirrer and a thermometer. The aqueous solution dissolved in was further added, and polymerization was carried out at 65 ° C. with stirring in a nitrogen stream. The concentration of the sodium dodecylbenzenesulfonate aqueous solution at the time of preparing the emulsion in this example is 0.15%, the concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system is 0.06%, and the average resin fine particles obtained are The particle size was 3.3 μm.
[0021]
Example 2
0.5 g of 2,2′-azobis (2,4-dimethylvaleronitrile) is dissolved in a mixed solution of 50 g of methyl methacrylate, 40 g of butyl methacrylate and 10 g of ethylene glycol dimethacrylate, did. Separately, 0.4 g of sodium lauryl sulfate (CMC 0.23%) was dissolved in 100 g of water. The above polymerizable monomer component is mixed with this aqueous solution. K. The mixture was stirred for 10 minutes at a rotational speed of 8000 rpm using a Homomixer. The droplet diameter in the obtained o / w emulsion was about 1 μm.
[0022]
This emulsion was put in a reaction vessel having a capacity of 1 L equipped with a stirrer and a thermometer, and an aqueous solution in which 8 g of polyvinylpyrrolidone (PVP K-90, manufactured by GAF Corporation) and 0.03 g of sodium nitrite were dissolved in 500 g of water was added. Polymerization was carried out at 50 ° C. with stirring in a nitrogen stream. In this example, the concentration of the sodium lauryl sulfate aqueous solution at the time of preparing the emulsion was 0.4%, the concentration of sodium lauryl sulfate in the polymerization reaction system was 0.067%, and the average particle size of the obtained resin fine particles was 0. .9 μm.
[0023]
Example 3
0.5 g of 2,2′-azobisisobutyronitrile was dissolved in a mixed solution composed of 90 g of styrene and 10 g of divinylbenzene to obtain a polymerizable monomer component. Separately, 0.2 g of sodium dodecylbenzenesulfonate (CMC 0.08%) was dissolved in 100 g of water. The above polymerizable monomer component is mixed with this aqueous solution. K. The mixture was stirred for 10 minutes at 6000 rpm using a Homomixer. The droplet diameter in the obtained o / w emulsion was about 4 μm.
[0024]
This emulsion was put in a reaction vessel having a capacity of 1 L equipped with a stirrer and a thermometer, and an aqueous solution obtained by dissolving 10 g of polyvinyl alcohol [GL-05, manufactured by Nippon Synthetic Chemical Co., Ltd.] and 0.03 g of sodium nitrite in 400 g of water. In addition, polymerization was carried out at 60 ° C. with stirring in a nitrogen stream. The concentration of the sodium dodecylbenzenesulfonate aqueous solution at the time of emulsion preparation in this example is 0.2%, the concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system is 0.04%, and the average resin fine particles obtained are The particle size was 4.3 μm.
[0025]
Comparative Example 1
An o / w emulsion was prepared in the same manner as in Example 1 except that 0.5 g of sodium dodecylbenzenesulfonate was used. The droplet diameter in the obtained emulsion was 2 μm. This emulsion was put in a 1 L reaction vessel equipped with a stirrer and a thermometer, and 4 g of polyvinyl alcohol [Gosenol GH-23, manufactured by Nippon Synthetic Chemical Co., Ltd.] and 0.03 g of sodium nitrite were dissolved in 300 g of water. An aqueous solution was added, and polymerization was performed at 65 ° C. with stirring in a nitrogen stream. In this comparative example, the concentration of the aqueous sodium dodecylbenzenesulfonate at the time of preparing the emulsion was 0.25%, and the concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system was 0.10%. In this comparative example, the concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system exceeded the critical micelle concentration, and a large amount of submicron-sized particles other than the intended particle size were generated.
[0026]
Comparative Example 2
0.5 g of benzoyl peroxide was dissolved in a mixed solution composed of 90 g of methyl methacrylate and 10 g of trimethylolpropane trimethacrylate to obtain a polymerizable monomer component. Separately, 0.3 g of sodium dodecylbenzenesulfonate, 4 g of polyvinyl alcohol [Gosenol GH-23, manufactured by Nippon Synthetic Chemical Co., Ltd.] and 0.03 g of sodium nitrite were dissolved in 500 g of water. The above polymerizable monomer component is mixed with this aqueous solution. K. The mixture was stirred for 10 minutes at a rotational speed of 7000 rpm using a Homomixer. The droplet diameter in the obtained o / w emulsion was about 7 μm.
[0027]
This emulsion was put in a reaction vessel having a volume of 1 L, and polymerization was carried out at 65 ° C. with stirring in a nitrogen stream. The concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system of this comparative example was 0.06%, and the obtained resin particles were observed with an electron microscope. As a result, the average particle size of the resin particles was about 7 μm, and the particles Was agglomerated.
[0028]
Comparative Example 3
0.5 g of 2,2′-azobisisobutyronitrile was dissolved in a mixed solution composed of 90 g of styrene and 10 g of divinylbenzene to obtain a polymerizable monomer component. Separately, 0.07 g of sodium dodecylbenzenesulfonate (CMC 0.08%) was dissolved in 100 g of water. The above polymerizable monomer component is mixed with this aqueous solution. K. The mixture was stirred for 10 minutes at a rotational speed of 8000 rpm using a Homomixer. The droplet diameter in the obtained o / w emulsion was about 6 μm.
[0029]
This emulsion was put in a reaction vessel having a capacity of 1 L equipped with a stirrer and a thermometer, and a solution obtained by dissolving 10 g of polyvinyl alcohol [GL-05, manufactured by Nippon Synthetic Chemical Co., Ltd.] and 0.03 g of sodium nitrite in 400 g of water. In addition, polymerization was carried out at 60 ° C. with stirring in a nitrogen stream. In this comparative example, the concentration of the sodium dodecylbenzenesulfonate aqueous solution at the time of emulsion preparation was 0.07%, the concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system was 0.014%, and the average resin fine particles obtained were The particle diameter was 6.1 μm.
[0030]
Comparative Example 4
1 g of hexadecane and 1 g of lauroyl peroxide were dissolved in a mixed solution composed of 97.5 g of styrene and 2.5 g of divinylbenzene to obtain a polymerizable monomer component. Separately, 1.0 g of sodium dodecylbenzenesulfonate and 0.015 g of sodium nitrite were dissolved in 250 g of water. The above polymerizable monomer component was mixed with this aqueous solution and allowed to pass through a centrifugal pump at 1,750 rpm for 2 hours to obtain an o / w emulsion having a droplet diameter of 6.0 μm.
[0031]
This emulsion was polymerized by stirring at 65 ° C. for 7 hours in a nitrogen stream. The concentration of sodium dodecylbenzenesulfonate in the polymerization reaction system of this comparative example was 0.4%, and the average particle size of the obtained resin fine particles was 5.9 μm.
Characteristics of the resin fine particles obtained in Example 1 and Comparative Example 4 during high-temperature melt processing and the produced resin molded plates were evaluated under the following conditions.
[0032]
Reference example 1
10 parts by weight of the resin fine particles obtained in Example 1 were added to 90 parts by weight of a polymethyl methacrylate resin (Sumitomo Chemical Co., Ltd. Sumipex MG-5) and mixed by stirring with a Henschel mixer. This mixture was extruded with a twin screw extruder at 280 ° C. while melting the polymethyl methacrylate resin to produce pellets. The pellets were injection molded using an injection molding machine under conditions of a molding temperature of 200 ° C. and a mold temperature of 50 ° C. to obtain a resin molded plate having a thickness of 1 mm.
[0033]
Reference example 2
A resin molded plate was produced in the same manner as in Reference Example 1 using the resin fine particles obtained in Comparative Example 4.
Each molded plate obtained in Reference Example 1 and Reference Example 2 was visually evaluated for coloring and appearance.
As a result, foaming was observed in the molded plate obtained in Reference Example 2, whereas no appearance defects such as foaming and silver streaks were observed in the molded plate obtained in Reference Example 1.
From this, the resin fine particles obtained by the method of the present invention are not colored when melted at a high temperature as compared with the resin fine particles obtained by the conventional method, and the molded product obtained using the resin fine particles of the present invention has It turned out that there was no appearance defect.
[0034]
【The invention's effect】
According to the method of the present invention, resin fine particles having an average particle diameter of 0.5 to 5 μm can be produced by a simple operation without using a special additive. The resin fine particles obtained by the method of the present invention can be used for applications such as a matting agent for paints, a light diffusing agent, a slipperiness imparting agent for cosmetics, and a toner.

Claims (2)

An emulsion having a droplet diameter of 5 μm or less is prepared by stirring a mixed solution composed of a polymerizable monomer component containing a polymerizable monomer and a polymerization initiator and an aqueous solution containing a surfactant having a critical micelle concentration or higher. A method for producing resin fine particles, characterized in that an aqueous solution containing a dispersion stabilizer is added to an emulsion so that the concentration of the surfactant is less than the critical micelle concentration, followed by suspension polymerization. The production method according to claim 1, wherein the resin particles to be produced have a weight average particle diameter of 0.5 to 5 μm.