JP6156868B2 - Thermal storage microcapsule and manufacturing method thereof - Google Patents

Description

  The present invention relates to a microcapsule having a size of 200 to 1000 μm that can be easily produced and can contain a PCM heat storage material at a high concentration, and a method for producing and using the same.

  The thermal storage microcapsules preferably have a size as small as several microns when used as a water slurry, but when immersed in a water storage tank in an ice thermal storage air conditioning system, a size of 200 to 1000 microns, which is two orders of magnitude larger, is desirable.

A major problem in the case of immersing in the water storage tank by the ice heat storage air conditioning system described above is that a tough, leak-free microcapsule with suppressed supercooling is not provided.

  Conventionally, a microcapsule having no leakage has been proposed in which the outer wall film is a melamine resin film, a nylon film, a polyurethane film, a cross-linked polymer film or the like, or a combination thereof to form a double film or a triple film.

Any of these methods have the problem of unstable droplets when preparing large size microcapsules, and the problem of stable and mass production of tough microcapsules of 200 to 1000 micron size is It has not been solved.

That is, it is difficult to stably maintain a large number of large droplets without breaking them, and it is also difficult to solve the problem of coalescence between droplets when the polymerization of the outer wall monomer proceeds and the viscosity increases. It remains as an issue. Even if a microcapsule of a large size is prepared by these methods, there remains a problem to be solved for its strength.

In addition, by coating solid particle outer wall, tough microcapsule preparation technology is provided, but since there is no stable solid particle of 100 microns or more, technology to provide microcapsules of larger size It is currently not provided.

JP-A-4-82036 JP-A-5-163486 JP-A-7-213890 JP 2001-247855 A JP 2009-19857 A JP 2011-213750 A

   As described in Patent Document 5, when a cold heat storage microcapsule is immersed in a water storage tank of an ice storage air conditioning system, an effective size is 200 to 2000 microns in terms of handling and heat transfer characteristics. About the 200-1000 micron size cold thermal storage microcapsule which corresponds to this range, since the preparation technique is not completed for the above-mentioned reason, it has become a bottleneck of practical use and is a problem to be solved.

  Such a problem is tough, leak-proof by stably bonding several to several hundred heat storage microcapsules of 10 to 50 micron size that can be stably prepared by the above-mentioned patent-pending technology. This can be solved by using microcapsules of 200 to 1000 micron size with suppressed supercooling.

  The method for producing microcapsules according to the present invention is as follows.

This method is a slurry (S / W) system in which microcapsule particles having a stable size of about 10 to 50 μm are dispersed in an aqueous phase as described in the above-mentioned prior art documents. Prepare the emulsion (first step),
On the other hand, a system emulsion solution containing a polymerization initiator and having a double bond is prepared (O / W) in a suspension of several to several tens of microns (O / W) (second step),
By adding this (O / W) emulsion to the above-prepared slurry, forming an (O + S) / W emulsion solution, stirring and polymerizing at 40-80 ° C., the microcapsules Are bonded together (third process),
It is characterized by having.

  In the manufacturing method described above, the degree of adhesion between microcapsules, that is, the size of the obtained microcapsules is the solid content in the slurry in the first step, the monomer content and the droplet diameter in the second step, the third It can be adjusted by the stirring speed and reaction temperature in the process.

4 is a scanning electron micrograph of the microcapsule prepared in Example 3. FIG. 3 shows DSC measurement results of the microcapsules prepared in Example 3.

The reagents and prescriptions used in the first step are described in each patent document, and the details thereof will be omitted here, but will be described in Examples described later. However, water-soluble dispersion stabilizers are styrene-maleic anhydride copolymer hydrolyzate, sodium dodecylbenzenesulfonate, lecithin, gelatin, gum arabic, casein, dextrin, pectin, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl ether, poly Acrylic acid, tri- or distyryl phenyl ether added with polyoxyethylene, alcohol ether added with polyoxyethylene, tween surfactant such as sorbitan oleate added with polyoxyethylene, spanned interface such as sorbitan oleate Activators, polyacrylates, cellulose derivatives (alkali metal salts of carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxy Propylethylcellulose, methylcellulose, ethylcellulose), polyhydric alcohols (glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, maltitol, xylitol Etc.)). The water-soluble dispersion stabilizer is used alone or in combination of two or more.

As oil-soluble radical polymerization initiator used in the second step, azo compounds such as α, α-azobisisobutyronitrile and azobiscyclohexanecarbonitrile, cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, peroxide A peroxide such as lauroyl can be exemplified. It is used alone or in combination of two or more.

  Monomers used in the second step include monofunctional or crosslinkable monomers, such as styrene, acrylonitrile, chlorostyrene, styrene methylstyrene, ethylstyrene, methoxystyrene, nitrostyrene, aminostyrene, methyl methacrylate, acrylic Methyl acid, ethyl acrylate, phenyl acrylate, cyclohexyl acrylate, vinyl acetate, vinyl formate, vinyl phenyl ether, vinyl methyl ether, vinyl cyclohexyl ether, divinyl benzene, ethylene glycol dimethacrylate, triethylene dimethacrylate, trimethylol Examples include propane trimethacrylate. It is used alone or in combination of two or more.

  Hereinafter, embodiments of the present invention will be described according to each step of manufacturing a 200 to 1000 μm microcapsule containing a PCM heat storage material according to the present invention, and the characteristics and applications of the obtained microcapsule.

(First Step) Preparation of (S / O) emulsion solution. In the method according to Patent Document 2, melamine resin-coated heat storage microcapsules having a size of 20 to 50 microns can be obtained by adjusting the stirring speed at the initial stage of the reaction. Alternatively, in the method according to Patent Document 3, a double-coating heat storage microcapsule having an outer coating of 20 to 50 microns in size as a nylon film and an inner coating as a polymethylmethacrylic film can be obtained by adjusting the stirring speed and the like. . Or in the case of patent document 6, if the solid particle of a 50 micron size is chosen as a raw material, the thermal storage microcapsule of a polyurethane film of a 50 micron size will be obtained.

The microcapsules obtained in this way can be said to be heat storage microcapsules in which supercooling is suppressed because they are relatively small in size, and this was put into the aqueous phase to obtain a heat storage microcapsule slurry. Alternatively, the slurry after completion of the reaction without recovery may be used as the heat storage microcapsule slurry.

(Second step) Preparation of (O / W) emulsion solution. A monomer in which 0.02 to 5 wt% of an oil-soluble initiator is dissolved is charged into an aqueous phase in which 0.02 to 3 wt% of a water-soluble dispersion stabilizer is dissolved, and emulsified and dispersed with a vibro mixer or a homogenizer. An (O / W) emulsion solution composed of suspension droplets of several to several tens of microns was obtained. This step was performed under ice cooling so as not to cause a polymerization reaction.

(Third step) The (O / W) emulsion solution obtained in the second step is added to the heat storage microcapsule slurry (obtained in the first step) in the stirred tank reactor, and the stirring speed is 100 to 300 rpm. Polymerization was carried out at a temperature of 40 to 80 ° C. for 3 to 8 hours.

In this process, a group of monomer droplets adheres to the heat storage microcapsule particles and is polymerized to increase the adhesiveness. As a result, coalescence of the particles occurs, and the size of the solid particles gradually increases. As a result, it was possible to obtain a microcapsule having a toughness of several hundred microns, leak-free and suppressed supercooling.

  The structure of this microcapsule can be said to be a multisphere type in which a large number of mononuclear structure spherical particles are bonded, and is a multinuclear structure type microcapsule. The particle size is freely controlled to 100 to 2000 μm by changing the solid content in the slurry in the first step, the monomer content and droplet size in the second step, the stirring speed and the reaction temperature in the third step. Is possible.

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

(First step) Styrene / maleic anhydride copolymer 1.46 g and distilled water 300 g
Was added, and the pH was adjusted to 12 with a 10% aqueous sodium hydroxide solution and dissolved by heating. Then, the pH was adjusted to 8 with 10% citric acid. This is called (Aqueous solution 1).
120 g of distilled water was mixed with 13.8 g of 35% aqueous formalin solution and 2.52 g of melamine, adjusted to pH 12 with 10% aqueous sodium hydroxide solution, and stirred at 60 ° C. for 30 minutes to prepare a prepolymer aqueous solution. This is designated as (Aqueous solution 2).

20 g of cold medium tetradecane was added to (Aqueous solution 1) and mixed with a homogenizer to prepare an (O / W) emulsion composed of a group of suspended oil droplets having a size of 20 to 50 microns. This is designated as (O / W) -based solution 1.
To this (O / W) -based solution 1, (aqueous solution 2) was added, 10% citric acid was added, and the pH was set to 4.85. 1 hour at 80 ° C and 200 rpm
By stirring, tetradecane-encapsulated melamine resin-coated microcapsules having a size of 20 to 50 microns could be prepared. After filtration, washing and drying, 22.8 g of microcapsules were obtained.

(Second Step) Under a temperature of 5 ° C., 7.5 g of methyl methacrylate in which 1.0% of benzoyl peroxide was dissolved was added to 100 g of 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution, and the mixture was mixed with a Vibro mixer. Hertz was allowed to flow and mix for 10 minutes to prepare an (O / W) emulsion composed of a group of suspended oil droplets of several microns in size. This is designated as (O / W) -based solution 2.

(Third step) To 250 g of a 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution, 20.0 g of the microcapsules obtained in (First step) was added, and stirred and dispersed. To this solution, the (O / W) system solution 2 obtained in the (second step) was added, and the polymerization reaction was carried out at a stirring speed of 300 rpm, 70 ° C. for 5 hours. Could get.

(First Step) Under ice cooling, 10.8 g of methyl methacrylate and 2.03 g of isophthaloyl dichloride were dissolved in 20.0 g of heat storage medium tetradecane, and 0.54 g of azobisisobutyronitrile was further added and dissolved. This organic phase (O) is put into 200 g of a 1 wt% aqueous polyvinyl alcohol solution (W), and mixed and stirred at 2000 rpm for 1 minute by a homogenizer (O / W) system consisting of a group of 20 to 50 micron-sized organic droplets. An emulsion was prepared.

This emulsion was transferred to a reactor equipped with a stirrer and subjected to radical polymerization at 100 ° C. for 3 h at 100 rpm. Maintaining the reactor at 70 ° C., 50 g of 4.32 wt% p-phenylenediamine aqueous solution and 50 g of 4.24 wt% sodium carbonate aqueous solution were added, and the interface polycondensation reaction was performed for 3 h at a stirring speed of 200 rpm. A double membrane microcapsule having a nylon membrane as the outer wall was prepared. After filtration, washing and drying, 30.3 g of microcapsules were obtained.

(Second step) At a temperature of 5 ° C., add 100 g of 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution with 7.5 g of triethylene dimethacrylate in which 1.0% benzoyl peroxide is dissolved. An emulsion (O / W) composed of a group of suspended oil droplets of several microns was prepared by flowing and mixing at 20 Hz for 10 minutes. This is designated as (O / W) -based solution 2.

(Third step) To 250 g of a 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution, 20.0 g of the microcapsules obtained in (First step) was added, and stirred and dispersed. To this solution, the (O / W) system solution 2 obtained in the (second step) was added, and the polymerization reaction was carried out at a stirring speed of 300 rpm, 70 ° C. for 5 hours. Could get.

(First step) An aqueous solution in which 1.0 g of a styrene / maleic anhydride copolymer acting as a surfactant is dissolved in 500 g of distilled water together with 1.5 g of a 10% aqueous sodium hydroxide solution in a reactor equipped with a stirrer. Injected.
Next, under ice cooling, 2.0 g of tolylene diisocyanate as a wall material was dissolved in 20.0 g of tetradecane as a heat storage material, and a slurry organic phase in which 5.0 g of solid particles were impregnated with this solution was prepared.

This slurry organic phase was charged into the stirred tank reactor and stirred at 70 ° C. and 200 rpm for 10 minutes to form a ((O + S) / W) emulsion. Thereafter, 70 ° C., allowed to 4h reaction under 150rpm stirring speed in real-particle skeleton, was prepared Poriu Reamaku coated microcapsules. Next, the pH of the reaction solution is adjusted to about 4.8 using a 17% aqueous citric acid solution, to which 0.62 g of melamine, 1.80 g of tap water, 1.60 g of 35% formalin, 0.1% aqueous solution of 10% caustic soda. An additional phase composed of 10 g was added and reacted for 1.5 h at 70 ° C. and 200 rpm to form a melamine resin film. The obtained double membrane microcapsule was recovered by filtration, washing and drying to recover 22.3 g of microcapsule.

(Second step) At a temperature of 5 ° C., add 100 g of 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution with 7.5 g of triethylene dimethacrylate in which 1.0% benzoyl peroxide is dissolved. An emulsion (O / W) composed of a group of suspended oil droplets of several microns was prepared by flowing and mixing at 20 Hz for 10 minutes. This is designated as (O / W) -based solution 2.

(Third step) To 250 g of a 0.1 wt% sodium dodecylbenzenesulfonate aqueous solution, 20.0 g of the microcapsules obtained in (First step) was added, and stirred and dispersed. To this solution, the (O / W) system solution 2 obtained in the (second step) was added, and the polymerization reaction was carried out at a stirring rotational speed of 300 rpm, 70 ° C. for 5 hours. Could get.

Claims (2)

Thermal storage microcapsules of small particle size 20 to 50 micron size is a polynuclear structure microcapsules made by assembling a plurality adhered 200-1000 micron size via an acrylic resin,
The heat storage microcapsule is impregnated with tetradecane as a heat storage material in solid particles, and the surface of the solid particles is provided with a double film composed of a melamine resin upper layer coating and a polyurea resin lower layer coating. polynuclear structure supercooling is inhibited, wherein type microswitch capsules. Solid particles are added to a tetradecane solution as a heat storage material in which tolylene diisocyanate as a wall material is dissolved under ice cooling, and a slurry organic phase is prepared while impregnating the tetradecane solution into the solid particles, and a stirrer is provided. The slurry organic phase is added to an aqueous solution containing a styrene-maleic anhydride copolymer hydrolyzate previously contained in a reaction vessel and stirred at 70 ° C. to obtain a ((O + S) / W) emulsion. And then react with stirring at 70 ° C. to prepare a precursor microcapsule with a polyurea membrane coating with solid particles as a skeleton, and then add citric acid to adjust the pH of the reaction solution to about 4.8. Then, an additional phase composed of melamine, water, formalin and caustic soda was added thereto and reacted while stirring at 70 ° C. to form a melamine resin film on the surface of the precursor microcapsule. A heavy film microcapsules, a first step of filtered, washed, to recover the heat storage microcapsules with small particle size of the dried 20-50 micron size,
Triethylene dimethacrylate in which benzoyl peroxide is dissolved is added to an aqueous sodium dodecylbenzenesulfonate solution at a temperature of 5 ° C., and is supplied to a mixer to form a group of suspended oil droplets of several to several tens of microns in size (O / W) a second step of preparing an emulsion solution;
The heat storage microcapsules collected in the first step are added to an aqueous sodium dodecylbenzenesulfonate solution to form a slurry by stirring and dispersing, and then the (O / W) emulsion solution prepared in the second step is added to the slurry. And a third step of obtaining a 200-1000 micron-sized multinuclear structure microcapsule by performing a polymerization reaction at 70 ° C. with stirring to obtain a multinuclear structure type microcapsule having a size of 200 to 1000 microns. the method of preparation.

Images