JP2002038136A - Method for producing thermal storage medium microcapsule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal storage medium microcapsule capable of rapidly and effectively removing formaldehyde remaining in a thermal storage medium microcapsule dispersion enclosed in a wall membrane of a melamine- formaldehyde resin or a urea-formaldehyde resin without causing unpleasant discoloration or emitting a malodor. SOLUTION: Hydrogen peroxide is added to a microcapsule dispersion comprising a wall membrane in which the wall membrane-forming material is composed of the wall membrane of the melamine-formaldehyde resin or the urea- formaldehyde resin and enclosing the thermal storage medium and reacted with the remaining formaldehyde. The pH during the reaction is preferably under alkaline conditions of pH >=9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a heat storage material microcapsule used for cooling or warming a substance or space or maintaining a desired temperature for a long time, and more particularly to a heat storage material microcapsule. The present invention relates to a method for producing microcapsules free of off-flavor and color from which residual formaldehyde which does not contribute to the formation of a wall film in a capsule dispersion liquid is removed.

[0002]

2. Description of the Related Art Microcapsules containing a heat storage material are disclosed in JP-A-5-163486, 5-237368, and 5-1.
It is proposed in 17642. The heat storage material microcapsule has the advantage that the heat storage and heat radiation accompanying the phase change of the heat storage material are performed in the shell of the microcapsule, so that the microcapsule dispersion liquid can always be handled as a liquid regardless of the solidification or melting of the heat storage material. Have The dispersion liquid of the heat storage material microcapsule should be stored in a heat storage tank and used as a liquid heat storage material using inexpensive midnight power, or always used as a solid latent heat storage material by removing and drying the water in the dispersion liquid. Can be.

[0003] As a technique for microencapsulating the heat storage material, a coacervation method, an interfacial polymerization method, an in-situ method, or the like can be used, and the effect of the present invention can be achieved by any of the methods. The in situ method is preferred as a method for producing chemically and physically stable microcapsules that endure long-term stability, and in particular, a polycondensation method of melamine and formalin or a microcapsule having a polymerized wall film of urea and formalin is most suitable. It is a thing.

The microcapsules produced by the in-situ method are inexpensive materials and have high robustness, which is a technique that has been put to practical use for pressure-sensitive recording paper. A microcapsule having a melamine-formaldehyde resin wall film forms a melamine-formaldehyde polymerized wall film around heat storage material particles, but requires a step of forming a film and removing excess formaldehyde not deposited in the film material. . That is, since formaldehyde has a peculiar pungent odor and strongly irritates the human body with mucous membranes and skin of eyes and respiratory organs and causes discomfort, the process of removing excess formaldehyde in a microcapsule using formaldehyde requires This is an essential operation for health and environmental hygiene.

[0005] As a method for removing excess formaldehyde in a microcapsule dispersion liquid, a method of decomposing formaldehyde by the effect of oxidation or reduction, a method of binding to a compound highly reactive with formaldehyde and changing it to a different compound, and the like are known. Specifically, urea, thiourea, hydrazine, organic amino compounds such as hydroxylamine hydrochloride and thiosulfate, ammonia,
Sulfites, persulfates, hypochlorites and the like are known as formaldehyde removing materials.

The heat storage material microcapsules of the present invention can be used not only as a refrigerant for air conditioning or as a heat storage material, but also as a building material having a high temperature buffering property by being embedded in concrete or gypsum board, or applied to fibers or foam. It can be used as a garment that has been engineered and has excellent temperature stability. When kneading or applying microcapsules to these building materials and clothing materials, the presence of excessive formalin may have an undesirable effect on the human body, so they should not be present in the microcapsules at all or should be extremely low. It is necessary to control the concentration.

In order to remove excess formalin in a microcapsule dispersion containing a heat storage material, the present inventor first prepared a compound containing no nitrogen and having two or more alcoholic hydroxyl groups in one molecule. Glucose was proposed as a specific example as a treating agent. Although the present invention certainly exhibits a high processing capacity, the isomerized saccharide mixed as a by-product is extremely dark brown, or a strong caramel odor unique to the isomerized saccharide remains, and as a heat storage material for air conditioning. It is good when used in a closed state in a heat storage tank, but it is not suitable for applications such as building materials and clothing which are used very close to or in contact with the human body.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat storage material microcapsule in which formaldehyde remaining in the heat storage material microcapsule dispersion liquid is quickly and effectively removed and which does not generate unpleasant coloring or odor. To provide.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a melamine-formaldehyde resin or urea-containing wall film.
This is achieved by reacting formaldehyde, which does not contribute to the formation of a wall film, with hydrogen peroxide in a microcapsule containing a heat storage material formed of a wall film of formaldehyde resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The heat storage material microcapsule of the present invention comprises a step of forming a melamine-formaldehyde or urea-formaldehyde polymerized wall film around a heat storage material and a step of removing excess residual formaldehyde. Hydrogen peroxide used in the latter step of treating residual formaldehyde reacts with formaldehyde and changes into formate and hydrogen. Therefore, by setting the pH at the time of the reaction to an alkali side of 9 or more, rapid reaction proceeds, and furthermore, By adding a sufficient alkali enough to neutralize the formic acid generated, the generation of acid odor due to formic acid can be suppressed. The pH of the dispersion is not limited as long as it is a compound exhibiting alkalinity, but inorganic alkali compounds containing no nitrogen, such as sodium hydroxide, potassium hydroxide, and sodium silicate, are preferred.

The amount of hydrogen peroxide to be added is adjusted depending on the thickness of the wall film and the type of resin, but is preferably added in the range of 0.1 to 10 parts based on 100 parts of the solid weight of the microcapsules. The temperature during the formaldehyde treatment step is 20 to 80
C., preferably 30 to 60.degree. After the treatment is completed, if excess hydrogen peroxide remains, it may adversely affect the tanks and containers due to the oxidation reaction, or there is a danger of ignition.Therefore, neutralization treatment using an appropriate reducing agent is required. It is preferable to apply.

The heat storage material used in the present invention is preferably physically and chemically stable, and has a heat of fusion of about 20 kcal / kg or more for the purpose of heat storage. Organic materials may be used. Calcium chloride hexahydrate, sodium sulfate decahydrate, sodium hydrogen phosphate decahydrate sodium thiosulfate pentahydrate,
Inorganic compounds containing large amounts of water of crystallization, such as nickel nitrate hexahydrate. Aliphatic hydrocarbons such as n-pentadecane and high-melting paraffin wax; aromatic hydrocarbons such as para-xylene and naphthalene; fatty acids such as stearic acid; higher alcohols such as myristyl alcohol; and ester compounds such as myristyl myristate. No. In the microencapsulation method having a melamine-formaldehyde polymer wall film of the present invention, it is preferable to use an organic heat storage material.

When microencapsulating a heat storage material,
An emulsifier or dispersant is used to disperse the heat storage material in fine droplets in a liquid that is immiscible with it. As the emulsifier for the microcapsules having a melamine-formaldehyde resin or urea-formaldehyde resin wall film of the present invention, an aqueous solution of an anionic water-soluble polymer is preferable. Specifically, ethylene maleic anhydride copolymer, styrene maleic anhydride Copolymers and sodium polyacrylate are preferred emulsifiers. In addition, an emulsifier of an alkali salt of a higher fatty acid or a monomer in which ethylene oxide is added to the higher alkyl group by several moles, or a polymer emulsifier such as gelatin, casein, polyacrylic acid, or polyvinyl alcohol may be used in combination.

The microcapsule dispersion containing the compound with a phase change thus obtained can attain the object of the present invention as it is, but if necessary, a preservative, various deterioration inhibitors, a thickener, a coloring agent Agents, dispersing aids, specific gravity adjusting materials, wetting materials, lubricants, adhesives and the like can be added.

The higher the proportion of the microcapsules in the dispersion of the heat storage material, the higher the latent heat quantity, which is preferable. However, in order to maintain good fluidity, 20 to 70 (wt / wt)%, preferably 4%
It is preferable to set in the range of 0 to 60 (wt / wt)%.
If the content is above this range, the viscosity of the heat storage material will increase, resulting in poor fluidity. If the content is below this range, the heat storage effect will be poor, which is not preferable.

[0016]

The present invention will be described below in detail with reference to examples. Note that the present invention is not limited to the embodiments.

Example 1 5% melamine powder and 37% aqueous formaldehyde solution
After adjusting the pH to 8 by adding 5 g and 10 g of water, about 70
C. to obtain an aqueous solution of a melamine-formaldehyde precondensate. Next, a 5% aqueous solution of sodium salt of a 5% styrene-maleic anhydride copolymer adjusted to pH 4.5 was prepared.
In 0 g, paraffin wax having a melting point of 60 ° C. (paraffin wax 14
0) 80 g was added to the above aqueous solution with vigorous stirring, and emulsification was performed until the particle diameter became 2.6 μm.

The whole amount of the melamine-formaldehyde precondensate aqueous solution was added to the above emulsion and stirred at 70 ° C. for 2 hours, and the pH was adjusted to 10 with a 20% (w / w) aqueous sodium hydroxide solution. Further, the temperature was set to 50 ° C.
Next, when 15 g of a 30% hydrogen peroxide solution was added and stirring was continued for 1 hour, the pungent odor of formaldehyde completely disappeared, and no unpleasant odor or liquid coloring was observed.

Example 2 5 g of urea and 0.5 g of resorcin were dissolved and the pH was adjusted to 3.0.
80 g of myristyl myristate having a melting point of 40 ° C. was added to 100 g of a 5% aqueous sodium salt solution of an ethylene-maleic anhydride copolymer adjusted with vigorous stirring, and emulsified until the average particle diameter became 10 μm. Next, 14 g of a 37% aqueous formaldehyde solution and 20
g, and the mixture was heated and stirred at 60 ° C. for 2 hours to perform an encapsulation reaction, and then the pH of the dispersion was adjusted to 20% (w / w).
The temperature was adjusted to 12.0 using an aqueous sodium hydroxide solution, and the temperature was set to 40 ° C. Next, when 45 g of a 30% aqueous hydrogen peroxide solution was added and stirring was continued for 1 hour, the pungent odor of formaldehyde completely disappeared, and no unpleasant odor or liquid coloring was observed.

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Claims (2)

[Claims] In a microcapsule containing a heat storage material comprising a wall film of a melamine-formaldehyde resin or a urea-formaldehyde resin as a wall film forming material, formaldehyde which does not contribute to the formation of the wall film is reacted with hydrogen peroxide. A method for producing heat storage material microcapsules, comprising removing excess formaldehyde in the microcapsule dispersion. 2. A method for producing heat storage material microcapsules, wherein excess formaldehyde is removed under conditions where the pH of the microcapsule dispersion is 9 or more.