JP6040415B2 - Microcapsule manufacturing method and microcapsule - Google Patents

Description

  The present invention relates to a method for producing a microcapsule that can be easily produced and can encapsulate a water-absorbing polymer at a high concentration, and a microcapsule obtained by the method.

  For example, sodium polyacrylate (hereinafter abbreviated as PAANA), which is a highly water-absorbing polymer, can retain water more than 100 times its own weight, but swells at the same time as water absorption, and this is dehumidified in desiccant air conditioning. When used in a honeycomb honeycomb rotor, there is a defect that the rotor is clogged. It is sufficient if PAANA is microencapsulated and can be used as a hygroscopic agent that suppresses swelling. However, PAANANa has a low solubility in water of about 5% and its viscosity is extremely high. It is impossible to do. In order to obtain a hygroscopic microcapsule, there is a demand for an immobilization technique in which high-concentration PAANA is contained in a wall material having air permeability and a tough structure.

  There is a report on the preparation method of hygroscopic microcapsules (special table 2002-511402), but there is a problem in the application to desiccant air conditioning, and there is a report on the use for desiccant rotor (Japanese Patent Laid-Open No. 2006-289258). However, there are problems in terms of high inclusion content and operability.

Special Table 2002-511402 JP 2006-289258 A

  The subject of this invention is providing the microcapsule obtained by the manufacturing method of the microcapsule which can be manufactured simply and can encapsulate a superabsorbent polymer in high concentration, and this method.

The method for producing a microcapsule according to the present invention is a method for producing a porous microcapsule that encapsulates an acrylic polymer, which is a target superabsorbent polymer, in a multinuclear manner.
A water phase in which a water-soluble acrylic monomer and a water-soluble initiator, which are intended inclusions, are dissolved, is converted into a monomer containing a crosslinkable monomer or a crosslinkable monomer, an oil-soluble initiator, and an oil-soluble dispersion. A step of mixing an organic oil phase composed of an organic solvent in which a stabilizer is dissolved, and the solution is emulsified and dispersed using a homomixer or a homogenizer to prepare a (W ₁ / O) emulsion having a droplet size of several to 10 μm. A step (primary emulsification), a step of mixing the emulsified and dispersed (W ₁ / O) emulsion solution into an aqueous phase containing an inorganic salt and a water-soluble dispersion stabilizer, and the solution being stirred or homomixer or homogenizer It was emulsified and dispersed using, consisting of water droplets suspended group _{(W 1)} of several tens to several hundreds μm size of the oil droplets group containing _{(O) ((W 1 /} O) / W 2) preparing an emulsion (Secondary emulsification) and The solution by warming, (1) oil droplets (O) suspended water droplets group in (W _1), respectively in, to form a water-absorbing acrylic polymer, polynuclear to water absorption in the oil droplets A step of enclosing an aqueous solution droplet group (W ₁ ) containing a polymer, and (2) simultaneously performing a radical polymerization reaction of a polymerizable reactant having a double bond containing a crosslinking monomer in an oil droplet (O). And a step of immobilizing the water droplet group (W ₁ ) containing these absorbent polymers and evaporating the diluted organic solvent to form microcapsules having a porous structure.

By drying after collecting the microcapsules, the water of (W ₁ ) evaporates, and the (W ₁ ) portion becomes only the water-absorbing polymer.

  In addition, the acrylic monomer of the inclusion may be a water-soluble monomer that becomes a water-absorbing polymer other than acrylic.

  As explained above, it is possible to encapsulate a high concentration of acrylic polymer by polymerizing the dissolved acrylic monomer, and this polymerization occurs within a few to 10 μm aqueous phase suspension droplets. In addition, a high-concentration acrylic polymer is contained in a dispersed state (polynuclear), and further, an organic phase suspension droplet of 10 to several hundred μm that encloses this suspension aqueous phase droplet group. Inside, cross-linking polymerization in an organic solvent occurs, and there is an effect that the microcapsules have a tough and porous skeleton structure.

2 is an SEM photograph of the microcapsule prepared in Example 1. FIG. The moisture absorption rate measurement results when the salt concentration is changed under the conditions of Example 1. The water vapor adsorption isotherm measurement result of the hygroscopic microcapsule prepared at a salt concentration of 1 M in Example 2. 4 is an SEM photograph of microcapsules prepared in Example 3. FIG. FIG. The moisture absorption and drying repeated experimental results of the microcapsule (Δ mark) prepared under the conditions of Example 3 and the microcapsule (□ mark) prepared without interfacial polymerization under the same conditions.

Hereinafter, embodiments of the present invention will be described according to the respective steps for producing microcapsules encapsulating a superabsorbent polymer according to the present invention, and the characteristics, structure and applications of the obtained microcapsules.

  Examples of the monomer that becomes the superabsorbent polymer that is the inclusion substance of the present invention include olefinic unsaturated carboxylic acids and salts thereof such as acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, etc. However, one or several of these are used in combination.

  Water-soluble initiators include persulfates such as potassium persulfate (KPS) and ammonium persulfate, perborates such as potassium perborate and sodium perborate, hydroperoxides such as t-butyl hydroperoxide, etc. Can be mentioned.

  Examples of the crosslinkable monomer include divinylbenzene, ethylene glycol dimethacrylate, triethylenedimethacrylate, and trimethylolpropane trimethacrylate. It is used alone or in combination of two or more.

  As monomers (monofunctional monomers), styrene, acrylonitrile, chlorostyrene, styrene methyl styrene, ethyl styrene, methoxy styrene, nitro styrene, amino styrene, methyl methacrylate, methyl acrylate, ethyl acrylate, phenyl acrylate, Examples include cyclohexyl acrylate, vinyl acetate, vinyl formate, vinyl phenyl ether, vinyl methyl ether, and vinyl cyclohexyl ether. It is used alone or in combination of two or more.

  Examples of the diluted organic solvent include aromatic hydrocarbons such as benzene and toluene, esters such as ethyl acetate, saturated hydrocarbons such as heptane, hexane, and octane, and chloro compounds such as dichloroethane. It is used alone or in combination of two or more.

  Oil-soluble radical polymerization initiators include azo compounds such as α, α-azobisisobutyronitrile and azobiscyclohexanecarbonitrile, and peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide and lauroyl peroxide. An oxide can be illustrated. It is used alone or in combination of two or more.

  Examples of oil-soluble dispersion stabilizers include hexaglycerin ricinoleate and sorbitan trioleate. It is used alone or in combination of two or more.

  Examples of the inorganic salt include sodium chloride, potassium chloride, sodium carbonate, and sodium sulfate. It is used alone or in combination of two or more.

  Water-soluble dispersion stabilizers include lecithin, gelatin, gum arabic, casein, dextrin, pectin, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl ether, polyacrylic acid, polyoxyethylene added tri- or distyryl phenyl ether, and polyoxyethylene. Alcohol added, tween surfactant such as sorbitan oleate added with polyoxyethylene, span surfactant such as sorbitan oleate, polyacrylate, cellulose derivative (alkali metal salt of carboxymethyl cellulose, hydroxymethyl cellulose , Hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylethylcellulose, methylcellulose, ethylcellulose), polyhydric alcohol (glycerin) , Ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, maltitol, xylitol, etc.)) are exemplified. The water-soluble dispersion stabilizer is used alone or in combination of two or more.

  Regarding the microcapsule production method, there are [primary emulsification step], [secondary emulsification step] and [temperature raising / reaction step], and each will be described below.

[Primary emulsification step] An aqueous phase (primary dispersed phase: W ₁ ) prepared by mixing and dissolving 5 to 60 wt% of a monomer that becomes a water-absorbing polymer and 0.1 to 3 wt% of a water-soluble initiator in distilled water was prepared. .
Further, 10 to 98 wt% of a monomer containing a crosslinking monomer in a diluted organic solvent, 0.05 to 3 wt% of an oil-soluble dispersion stabilizer, and 0.05 to 5 wt% of an oil-soluble polymerization initiator were mixed and dissolved. An organic phase (primary continuous phase: O) is prepared, the aqueous phase is added to the organic phase, and the mixture is emulsified and dispersed with a vibro mixer or a homogenizer, and consists of several to several tens of μm suspension droplets ( W ₁ / O) obtain an emulsion.
This is A. Solution.

Secondary emulsification step] water-soluble inorganic salt 0～30Wt%, the aqueous phase of the water-soluble dispersion stabilizer dissolved 0.02~3wt% _{(W 2)} was prepared, Vibro stirred tank with mixer and homogenizer The aqueous solution Alternatively, the A. solution was poured into the reactor while stirring to prepare an emulsion composed of a group of oil droplets (W ₁ / O) having a size of 10 to several hundred μm ((W ₁ / O) / W ₂ ). These processes were performed rapidly at approximately 0 ° C. under ice cooling so as not to cause a polymerization reaction.

  [Temperature raising / reaction step] Under a stirring speed of 100 to 500 rpm, the temperature of the reactor was increased to 50 to 80 ° C to initiate a polymerization reaction. The reaction was completed for 3 to 8 hours to complete the polymerization. During this process, the diluted organic solvent was evaporated from the reactor and recovered. The prepared microcapsules were dried at 80 ° C. after suction filtration. During this drying process, the water in the microcapsules evaporated, and microcapsules enclosing the water-absorbing polymer were obtained.

  The structure of this microcapsule is spherical in appearance as shown in FIG. 1, and has a multinuclear structure. The particle diameter can be freely controlled as 10 to 1000 μm.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

As an inner aqueous phase, a solution prepared by dissolving 1 wt% of potassium persulfate in 20 g of 4.0 M sodium acrylate aqueous solution was prepared and kept at 0 ° C.
As an outer aqueous phase (continuous phase), a solution prepared by dissolving 2% by weight of gum arabic as a dispersion stabilizer in 450 g of a 3M sodium chloride aqueous solution was prepared.
As an organic phase (dispersed phase), 90 wt% of trimethylolpropane trimethacrylate monomer, 10 wt% of toluene, 3 wt% of hexaglycerin condensed ricinoleate, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) 30 wt. Of 1 wt% was dissolved.

The inner aqueous phase was added to the organic phase solution, and stirred for 10 minutes at 5000 rpm under ice cooling to prepare a W / O emulsion.
The outer water phase was kept at 70 ° C., the prepared W / O emulsion was added thereto, and stirred at 300 rpm for 10 minutes to prepare a W / O / W emulsion.

Subsequently, a radical polymerization reaction was performed while stirring at 300 rpm at 70 ° C. to form a polymerized film, thereby obtaining a microcapsule of about 200 μm.
The surface and cross section of this capsule are shown in FIG. Spherical and porous microcapsules could be obtained.

  In Example 1 above, the other conditions were the same, and a series of experiments was performed in which only the sodium chloride concentration in the outer aqueous phase (continuous phase) was changed to 4.0M. The obtained microcapsules obtained microcapsules of about 200 μm, as in the above examples.

  The amount of moisture absorbed per gram of microcapsules at 25 ° C. and 90% humidity was measured on the microcapsules obtained in these series of experiments.

  FIG. 2 shows the change over time in the amount of moisture absorbed by the microcapsules when the concentration of the outer aqueous phase sodium chloride on the amount of water absorption is changed. From this figure, it was found that there is an optimum value for the salt concentration to be added, and the obtained microcapsules have a moisture absorption capacity about 4 times that of the silica gel commercially available as a moisture absorbent.

FIG. 3 shows the results of measurement of water vapor adsorption isotherms for the microcapsule sample marked Δ with a salt concentration of 1M in the figure. From the figure, it can be seen that the moisture absorption capacity is extremely high under high humidity and the water vapor release capacity is extremely high under drying.

As an inner aqueous phase, a solution prepared by dissolving 0.25 wt% of potassium persulfate in 6.0 g of a 3.2 M sodium acrylate aqueous solution was prepared and cooled on ice.
As an external aqueous phase (continuous phase), L-lysine 0.76 g, distilled water 600 g dissolved with 0.12 M sodium carbonate and 1.0 M sodium chloride, 1 wt% monolauric acid decaglycerin dissolved as a surfactant Prepared.
As an organic phase (dispersed phase), 90% by weight of divinylbenzene monomer, 10% by weight of toluene, 3% by weight of chloroterephthalic acid, 0.1% by weight of hexaglycerin condensed ricinoleate, 2,2′-azobis (4-methoxy-2, 26.4 g of 0.1 wt% 4-dimethylvaleronitrile) dissolved therein was prepared.

The inner aqueous phase was added to the organic phase solution, and stirred for 5 minutes at 5000 rpm under ice cooling to prepare a W / O emulsion.
The above external water phase is kept at 70 ° C., and the prepared W / O emulsion is added thereto, and stirred at 800 rpm for 10 minutes to prepare a W / O / W emulsion and simultaneously perform an interfacial polymerization reaction to form a nylon membrane. Formed.
Subsequently, a radical polymerization reaction was carried out at 70 ° C. with stirring at 100 rpm, thereby forming a polymerized film and obtaining microcapsules of about 200 μm.
The surface and cross section of the obtained microcapsule are shown in FIG.

  The maximum moisture absorption amount of the microcapsule was 0.80 g per 1 g at 30 ° C. and 90% humidity.

The microcapsules and microcapsules prepared without interfacial polymerization under the same conditions were absorbed for 1 hour at 30 ° C. and 90% humidity, and the capsule weight was measured. Subsequently, drying was performed at 110 ° C. for 1 hour, and after the capsule weight was measured, moisture absorption was repeated. The results are shown in FIG. The microcapsules subjected to interfacial polymerization had almost the same amount of moisture absorption as the microcapsules not subjected to interfacial polymerization. Even when moisture absorption and drying were repeated, the amount of moisture absorption was almost the same, and drying was also quantitative.

Claims (3)

A method of producing a microcapsule that encapsulates a target inclusion in a multinuclear manner,
A water phase composed of a water-soluble acrylic monomer and a water-soluble initiator serving as a target inclusion, a monomer containing a cross-linkable monomer or a cross-linkable monomer, a diluted organic solvent, an oil-soluble initiator and Mixing with an organic solvent phase comprising an oil-soluble dispersion stabilizer;
A step of emulsifying and dispersing the solution using a homomixer or a homogenizer to prepare a W ₁ / O emulsion (primary emulsification);
Mixing the emulsified and dispersed (W ₁ / O) emulsion solution with an aqueous phase containing a water-soluble inorganic salt and a water-soluble dispersion stabilizer;
Emulsifying and dispersing the solution using a stirrer, homomixer or homogenizer ((W ₁ / O) / W ₂ ) to prepare an emulsion (secondary emulsification);
By warming the solution,
(1) forming a water-absorbing acrylic polymer in an aqueous phase (W ₁ ) suspended in oil droplets (W ₁ / O);
(2) In the organic phase (O) in the oil droplets (W ₁ / O), a monomer containing a crosslinkable monomer or a crosslinkable monomer that is a polymerizable reactant having a double bond is radically polymerized. Reacting and simultaneously evaporating the dilute organic solvent to form porous microcapsules enclosing a water phase (W ₁ ) containing a polynuclear water-absorbing polymer;
A method for producing a water-absorbing microcapsule characterized by comprising:   The method for producing a microcapsule according to claim 1, wherein the inclusion is a water-absorbing polymer. A microcapsule produced by the method of claim 1 or claim 2 .

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