JP6497160B2 - Method for producing irregular shaped resin fine particles - Google Patents

Description

The present invention relates to a method for producing a deformed fine resin particles.

Conventionally, golf ball shape, hemispherical shape, mushroom shape, true spherical partial defect shape, biconvex lens shape, red blood cell shape, bowl for the purpose of improving light diffusion characteristics, reflection characteristics, adhesion, oil absorption, buffering properties, etc. Have been proposed (see, for example, Patent Documents 1 to 4), such as variously shaped resin fine particles such as spheres, oval spheres, short needles, and spheres having a regular wrinkle structure.
Such irregular shaped resin fine particles, for example, those with improved light diffusion characteristics are useful as matting materials in light diffusion sheets and paints, and those with improved reflection characteristics are paint and paper coatings. It is useful as a white material for agents. The irregularly shaped resin fine particles having a large specific surface area can be effectively used as a weight-reducing material, a support for a metal catalyst, and the like, and are also useful as an electromagnetic wave scattering material by coating with a metal oxide.

  However, the resin fine particles obtained by the production method disclosed in the above-mentioned patent document cannot be said to have high irregularity, and therefore cannot be said to have a sufficiently large specific surface area, for example. This is considered to be because the resin is generally flexible and has low crystallinity, so that it tends to be a thermodynamically stable true sphere.

Japanese Patent No. 4918963 JP 2011-162715 A Japanese Patent No. 5460262 Japanese Patent No. 3700997

The present invention was made based on the above circumstances, and its object is to provide a method for producing a deformed resin particles approximately spherical coronal having a large specific surface area.

The method for producing irregularly shaped resin fine particles of the present invention is a method for producing irregularly shaped resin fine particles comprising a substantially spherical crown-like film-like body made of a resin, wherein a curved portion is formed on the surface of the film-like body ,
A step of dispersing oil phase liquid in which at least a polymerizable monomer is dissolved or dispersed in a hydrophobic solvent in an aqueous medium to form oil droplets;
Polymerizing the polymerizable monomer at a temperature lower than the boiling point of the hydrophobic solvent;
By heating to a temperature higher than the boiling point of the hydrophobic solvent possess a step of foaming by vaporizing the hydrophobic solvent,
The foaming step is performed before the polymerization of the polymerizable monomer in the step of polymerizing the polymerizable monomer is completed .

  According to the irregular shaped resin fine particles of the present invention, since it has a generally spherical crown shape and a shape in which a curved portion is formed on the surface thereof, a sufficiently large specific surface area can be obtained.

  According to the method for producing irregular shaped resin fine particles of the present invention, the irregular shaped resin fine particles can be easily produced.

3 is a SEM photograph showing the surface of deformed resin fine particles according to Example 1.

  Hereinafter, the present invention will be described in detail.

[Deformed resin fine particles]
The deformed resin fine particles of the present invention are formed of a substantially spherical crown-shaped film-like body made of a resin, and have a curved portion formed on the surface of the film-like body, specifically, like a deflated beach ball. These are cap-like particles in which wrinkles are formed on the inner surface and the outer surface, respectively.

  The resin constituting the film-like body (hereinafter also referred to as “film-like resin”) is made of a polymer obtained by polymerizing a polymerizable monomer.

[Membrane resin]
Examples of the film-like resin include styrene resin, acrylic resin, vinyl chloride resin, and styrene acrylic resin.
The film-like resin preferably contains a cross-linked structure.

[Average maximum diameter of irregular shaped resin fine particles]
The average maximum diameter of the irregular shaped resin fine particles according to the present invention can be set to 1 to 100 μm, for example. This average maximum diameter can be controlled by adjusting the size of oil droplets in the production method described later.

  The average maximum diameter of the irregular shaped resin fine particles is taken by scanning image microscope "JSM-7500F" (manufactured by JEOL Ltd.). 50,000 times magnified photograph is taken, and the photograph image taken by the scanner is automatically image processing analysis Using the apparatus “LUZEX AP (software version Ver. 1.32)” (manufactured by Nireco), the irregular resin fine particles were binarized, and the substantially spherical crown-shaped irregular resin fine particles having curved portions formed on the surface thereof were used. The maximum diameter was calculated for any 100 of these, and the average value was calculated. Here, the maximum diameter refers to the maximum distance when an image of irregular shaped resin fine particles is sandwiched between two parallel lines.

[Method for producing irregular shaped resin fine particles]
The method for producing irregular shaped resin fine particles of the present invention comprises a step of dispersing oil phase liquid in which at least a polymerizable monomer is dissolved or dispersed in a hydrophobic solvent to form oil droplets in an aqueous medium, and a hydrophobic solvent. A step of polymerizing a polymerizable monomer at a temperature lower than the boiling point of the solvent, and a step of foaming by evaporating the hydrophobic solvent by raising the temperature to a temperature higher than the boiling point of the hydrophobic solvent. .

Specifically showing an example of the method for producing irregular shaped resin fine particles of the present invention,
(1) An oil phase liquid preparation step for preparing an oil phase liquid in which a polymerizable monomer for forming a film-like resin in a hydrophobic solvent and, if necessary, an oil-soluble polymerization initiator are dissolved or dispersed,
(2) an oil droplet forming step of forming an oil droplet by dispersing the oil phase liquid in an aqueous medium in which a water-soluble polymerization initiator or a surfactant is dissolved, if necessary;
(3) a polymerization step of polymerizing a polymerizable monomer to form polymer particles,
(4) A foaming step of foaming by vaporizing a hydrophobic solvent to deform the polymer particles to form deformed resin fine particles,
(5) A washing step of filtering out the irregular shaped resin fine particles from the aqueous medium and removing the surfactant from the irregular shaped resin fine particles,
(6) It comprises a drying step for drying the washed irregular shaped resin fine particles.

(1) Oil phase liquid preparation step The oil phase liquid is prepared by dissolving or dispersing a polymerizable monomer for forming a film-like resin in a hydrophobic solvent, and adding an oil-soluble polymerization initiator as necessary. To be prepared.

[Hydrophobic solvent]
As a hydrophobic solvent, the solubility in water is extremely low, so that oil droplets can be formed in an aqueous medium, and the boiling point is higher than the polymerization temperature of the polymerizable monomer for forming the film-like resin. Further, it is necessary to be higher than the boiling point of the aqueous medium, and when water is used as the aqueous medium, for example, it is preferable to use one having a boiling point lower than that of water, for example, 40 to 90 ° C. As such a hydrophobic solvent, for example, hydrocarbon compounds such as cyclohexane and hexane; chlorinated hydrocarbon compounds such as dichloromethane can be used. These can be used alone or in combination of two or more.

As a polymerizable monomer for forming a film-like resin, for example, when a vinyl resin is used as the film-like resin, examples of the polymerizable monomer that should form the film-like resin include the following. It is done.
<1> Styrene monomer Styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-phenyl styrene, p-ethyl styrene, pn-butyl styrene, p-tert -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4-dimethyl styrene and the like.
<2> (meth) acrylic acid ester-based monomers methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, Stearyl acrylate, lauryl acrylate, phenyl acrylate phenyl, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, Lauryl methacrylate, phenyl methacrylate, diethylamino Ethyl methacrylate, dimethylaminoethyl methacrylate, etc.
<3> Olefins Ethylene, propylene, isobutylene and the like.
<4> Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate and the like.
<5> Vinyl ethers Vinyl methyl ether, vinyl ethyl ether and the like.
<6> Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone and the like.
<7> N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and the like.
<8> Others Vinyl compounds such as butadiene, vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide and methacrylamide, and maleic anhydride.

As the polymerizable monomer for forming the film-like resin, one kind can be used alone, or two or more kinds can be used in combination. It is preferable to use a functional polymerizable monomer in combination.
For example, when the film-like resin is a vinyl resin, a monofunctional vinyl monomer such as the above styrene monomer or (meth) acrylic acid ester monomer is used as a polyfunctional polymerizable monomer. It is preferable to use a polyfunctional vinyl monomer.
<9> Multifunctional vinyl monomer Divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl Dimethacrylates and trimethacrylates of tertiary alcohols such as glycol diacrylate, hexylene glycol dimethacrylate, hexylene glycol diacrylate, pentaerythritol, and trimethylolpropane.
By using such a polyfunctional polymerizable monomer, it is possible to prevent the irregular shaped resin fine particles from being fused to each other during the filtration from the aqueous medium.

  The ratio (copolymerization ratio) of the polyfunctional polymerizable monomer in the entire polymerizable monomer for forming the film-like resin is, for example, 0.1 to 99% by mass, preferably 1 to 80% by mass. It is said.

  In the oil phase liquid, the content of the polymerizable monomer for forming the film-like resin is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the hydrophobic solvent.

[Oil-soluble polymerization initiator]
In the case where an oil-soluble polymerization initiator is used as the polymerization initiator, it may be anything that can exhibit the polymerization initiating ability at a temperature lower than the boiling point of the hydrophobic solvent. For example, 2,2′-azobis- ( 2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4 -Azo or diazo polymerization initiators such as dimethylvaleronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide Oxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxy Polymers having a side chain with a peroxide polymerization initiator or peroxide such as side, 2,2-bis- (4,4-t-butylperoxycyclohexyl) propane, tris- (t-butylperoxy) triazine An initiator or the like can be used.
Among these, from the viewpoint of shortening the polymerization time, it is preferable to use one having a 10-hour half-life temperature equal to or lower than the boiling point of the hydrophobic solvent.
These oil-soluble polymerization initiators can be used singly or in combination of two or more.

(2) Oil droplet formation step The oil droplet formation step is, for example, specifically a film containing an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less and further containing a water-soluble polymerization initiator. An oil phase liquid containing a polymerizable monomer for forming a resin is added, and mechanical energy is applied to form oil droplets.
The formation of oil droplets is required to be performed at a low temperature that does not generate radicals in the oil-soluble polymerization initiator and the water-soluble polymerization initiator, and is preferably performed at room temperature, for example.

[Aqueous medium]
In this invention, an aqueous medium means what consists of 50-100 mass% of water, and 0-50 mass% of water-soluble organic solvents. The water-soluble organic solvent does not dissolve the film-form resin, the polymerizable monomer for forming the film-form resin and the oil-soluble polymerization initiator when mixed with water to form an aqueous medium. If it is not limited, methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc. can be used.
As the aqueous medium, water not containing an organic solvent is preferably used because it is excellent in environmental suitability and safety.

[Surfactant]
When the surfactant is contained in the aqueous medium, it is preferable to use an anionic surfactant or a nonionic surfactant as the surfactant.

Anionic surfactants include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate, Sulfonates such as ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sulfonate sodium; dodecyl sulfate Sulfate esters such as sodium, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate; sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, And fatty acid salts such as calcium in acid.
Nonionic surfactants include polyethylene oxide, polypropylene oxide, combinations of polypropylene oxide and polyethylene oxide, esters of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide, esters of higher fatty acids and polyethylene glycol, higher fatty acids and polypropylene oxide. Examples thereof include esters and sorbitan esters.
These surfactants can be used alone or in combination of two or more.
Further, a substance having protective colloid ability such as polyvinyl alcohol or polyvinyl pyrrolidone can be used in place of the surfactant.

(Water-soluble polymerization initiator)
In the case of using a water-soluble polymerization initiator as the polymerization initiator, any one that can exhibit the polymerization initiating ability at a temperature lower than the boiling point of the hydrophobic solvent may be used, and potassium persulfate, potassium peroxodisulfate, Persulfates such as ammonium sulfate; azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide, and the like can be used.
Among these, from the viewpoint of shortening the polymerization time, it is preferable to use one having a 10-hour half-life temperature equal to or lower than the boiling point of the hydrophobic solvent.
These water-soluble polymerization initiators can be used alone or in combination of two or more.

It is preferable that the usage-amount of an aqueous medium is 50-2,000 mass parts with respect to 100 mass parts of oil phase liquids.
By making the usage-amount of an aqueous medium into said range, an oil phase liquid can be emulsified and dispersed to a desired particle size in an aqueous medium.

  Examples of the means for applying mechanical energy include means for applying strong stirring or ultrasonic vibration energy such as homomixer, ultrasonic wave, and manton gorin.

  The average particle diameter of the oil droplets obtained in this oil droplet forming step is preferably in the range of, for example, 10 nm to several hundred μm in terms of volume-based median diameter.

(3) Polymerization step In this step, an oil-soluble polymerization initiator and / or a water-soluble polymerization initiator is allowed to act on a polymerizable monomer for forming a film-like body at a temperature lower than the boiling point of the hydrophobic solvent. This is a step of polymerizing to form polymer particles.
In this step, the reaction system is heated to generate radicals in the oil-soluble polymerization initiator and / or water-soluble polymerization initiator.

(4) Foaming step In this step, the temperature is raised to a temperature higher than the boiling point of the hydrophobic solvent, and the hydrophobic solvent is vaporized to foam the polymer particles. This is a step of forming coronal deformed resin fine particles.
The foaming of the polymer particles is preferably performed before the polymerization of the polymerizable monomer in the polymerization step is completed, although it varies depending on the type of the polymerizable monomer. In that case, the polymerization is continued during and after the escape of the vaporized hydrophobic solvent.

The reason why the substantially spherical crown-shaped deformed resin fine particles having the curved portion are formed by evaporating the hydrophobic solvent and foaming the polymer particles in this way is considered as follows.
That is, first, the polymer particles are greatly expanded by a hydrophobic solvent (hereinafter also referred to as “solvent gas”) vaporized when the temperature of the reaction system is raised to a temperature exceeding the boiling point of the hydrophobic solvent. Thus, hollow particles in which a space filled with a solvent gas is formed inside the outer shell made of a polymer. Further, when the outer shell of the hollow particle is thin, or when the polymerization of the polymerizable monomer is not completed, the free volume of the polymer constituting the outer shell is large, so that the solvent gas escapes to the outside. Furthermore, the release of the solvent gas to the outside is performed in a short time due to the water pressure applied by the aqueous medium from the outside to the inside of the hollow particles, the large surface area with respect to the volume of the hollow particles, etc. The polymer constituting the outer shell is difficult to penetrate the aqueous medium, and since the water pressure is applied by the aqueous medium from the outside to the inside of the hollow particles, spherical (beach ball-shaped) hollow particles are in the shape of the outer shell. Since the polymer constituting the outer shell is not liquid, it is not crushed and shrinks into a spherical shape, and becomes a substantially spherical crown as a whole, and a curved portion is formed on the surface. Different It is assumed that reduction occurs.

(5) Washing step In this step, an aggregate formed by agglomerating the deformed resin fine particles in a wet state formed by performing solid-liquid separation treatment for solid-liquid separation of the dispersion of deformed resin fine particles and solid-liquid separation. Removes deposits such as surfactants. A typical example of the solid-liquid separation process is a filtration process, and a specific method of the filtration process is, for example, a vacuum filtration method using a centrifugal separation method or Nutsche, a filtration method using a filter press or the like. Etc. can be used.

(6) Drying process In this process, the drying process of the irregular shaped resin fine particle by which the washing process was carried out is performed. Examples of dryers that can be used in this step include known drying processors such as spray dryers, vacuum freeze dryers, and vacuum dryers, stationary shelf dryers, mobile shelf dryers, and fluidized bed dryers. Machine, rotary dryer, stirring dryer and the like. The moisture content of the dried irregular shaped resin fine particles is preferably 5% by mass or less, and more preferably 2% by mass or less.
Moreover, when the deformed resin fine particles subjected to the drying treatment are aggregated by weak interparticle attractive force to form an aggregate, it is preferable to crush the aggregate. Specific examples of the crushing treatment apparatus include mechanical crushing treatment apparatuses such as a jet mill, a Henschel mixer, a coffee mill, and a food processor.

  According to the method for producing irregular shaped resin fine particles of the present invention, the irregular shaped resin fine particles of the present invention having an extremely large specific surface area, which has a substantially spherical crown shape as a whole and further has a curved portion formed on the surface thereof, are easily produced. can do.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Example 1: Production Example 1 of resin fine particles]
106 g of styrene (St) and 5.1 g of neopentyl glycol dimethacrylate (NPG) were mixed and dissolved in 5.6 g of cyclohexane, and 420 g of water and 0.053 g of sodium lauryl sulfate were added thereto. This was dispersed for 6 minutes at 10,000 rpm in an emulsifier “Creamix” (manufactured by M Technique Co., Ltd.) to prepare an emulsion.
This emulsion is put into a separable flask in which a stirrer, a water-cooled reflux tube and a nitrogen introduction tube are set, and stirring and nitrogen introduction are continued. After stirring at room temperature for 20 minutes, the temperature is raised to 70 ° C. A solution prepared by dissolving 1.4 g of potassium sulfate (KPS) in 26.8 g of water was added, and the mixture was held at 70 ° C. for 2 hours, then heated, held at 92 ° C. for 80 minutes, and then cooled to room temperature. In addition, foaming started at around 84 ° C. during the temperature increase.
Thereafter, suction filtration and washing with ion-exchanged water were performed, spread on a vat and dried at 40 ° C. to obtain a white solid [1]. This white solid [1] was easily solved. When the undissolved white solid [1] was observed with an electron microscope, substantially spherical crown-shaped deformed resin fine particles having a curved portion formed on the surface thereof were observed. This is shown in the SEM photograph of FIG.

[Example 2: Production Example 2 of resin fine particles]
106 g of styrene and 5.1 g of divinylbenzene (DVB) were mixed and dissolved in 5.6 g of cyclohexane, and 0.9 g of α, α′-azobisisobutyronitrile (AIBN) was added thereto and mixed. To this was added 450 g of water and 0.053 g of sodium lauryl sulfate. This was dispersed for 6 minutes at 10,000 rpm in an emulsifier “Creamix” (manufactured by M Technique Co., Ltd.) to prepare an emulsion.
This emulsion is put into a separable flask in which a stirrer, a water-cooled reflux tube and a nitrogen introduction tube are set, and stirring and nitrogen introduction are continued. After stirring for 20 minutes at room temperature, the temperature is raised to 65 ° C. After holding for a period of time, the temperature was raised, held at 92 ° C. for 80 minutes, and then lowered to room temperature. In addition, foaming started at around 84 ° C. during the temperature increase.
Thereafter, suction filtration and washing with ion-exchanged water were performed, spread on a vat and dried at 40 ° C. to obtain a white solid [2]. This white solid [2] was easily solved. When the undissolved white solid [2] was observed with an electron microscope, irregular shaped resin fine particles having the same shape as the white solid [1] were observed.

[Comparative Example 1: Production Example 3 of resin fine particles]
106 g of styrene and 5.1 g of neopentyl glycol dimethacrylate were mixed and dissolved in 5.6 g of cyclohexane, and 420 g of water and 0.053 g of sodium lauryl sulfate were added thereto. This was dispersed for 6 minutes at 10,000 rpm in an emulsifier “Creamix” (manufactured by M Technique Co., Ltd.) to prepare an emulsion.
This emulsion was put into a separable flask in which a stirrer, a water-cooled reflux pipe and a nitrogen introduction pipe were set, and stirring and nitrogen introduction were continued. After stirring at room temperature for 20 minutes, the temperature was raised to 70 ° C. A solution prepared by dissolving 1.4 g of potassium disulfate in 26.8 g of water was added, and the mixture was kept at 70 ° C. for 10 hours, and then cooled to room temperature.
Thereafter, suction filtration and washing with ion-exchanged water were performed, spread on a vat and dried at 40 ° C. to obtain a white solid [3]. This white solid [3] was easily solved. When the undissolved white solid [3] was observed with an electron microscope, only spherical resin fine particles were observed, and substantially spherical crown-shaped irregular resin fine particles having curved portions formed on the surface thereof were not observed.

  Table 1 below shows the temperature of the polymerization process and the temperature of the foaming process of Examples 1 and 2 and Comparative Example 1.

Claims (1)

A method for producing deformed resin fine particles comprising a substantially spherical crown-shaped film made of a resin, wherein a curved portion is formed on the surface of the film ,
A step of dispersing oil phase liquid in which at least a polymerizable monomer is dissolved or dispersed in a hydrophobic solvent in an aqueous medium to form oil droplets;
Polymerizing the polymerizable monomer at a temperature lower than the boiling point of the hydrophobic solvent;
Foaming by evaporating the hydrophobic solvent by raising the temperature to a temperature higher than the boiling point of the hydrophobic solvent,
The method for producing deformed resin fine particles, wherein the foaming step is performed before the polymerization of the polymerizable monomer in the step of polymerizing the polymerizable monomer is completed.