JP2000044940A - Thermal storage material microcapsule - Google Patents

Abstract

(57) Abstract: A heat storage material microcapsule encapsulated by a melamine-formaldehyde polymer wall film is exposed for a long time not only to a low temperature condition in a cooling temperature range but also to a high temperature condition in a heating temperature range. The present invention also provides a heat storage material microcapsule having good fluidity and heat storage performance. Further, even if the heat storage material microcapsules of the present invention are circulated in various metal pipes for a long time, there is no corrosiveness to metals. A heat storage material microcapsule encapsulated by a wall film of a melamine-formaldehyde polymer has a residual formaldehyde that does not contribute to the formation of the wall film and two or more alcoholic hydroxyl groups in one molecule that do not contain nitrogen. Formaldehyde in the microcapsule dispersion is removed by reacting the compound. Glucose is preferred as the compound having an alcoholic hydroxyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat storage material microcapsule used to cool or warm a substance or space or to maintain the temperature for a long time, and more particularly to a melamine-formaldehyde polymer. The present invention relates to a microcapsule having excellent heat storage characteristics and fluidity from which residual formaldehyde which does not contribute to the formation of a wall film in a heat storage material microcapsule dispersion liquid having a united wall film is removed.

[0002]

2. Description of the Related Art Microcapsules containing a heat storage material are disclosed in JP-A-5-163486 and JP-A-5-237368.
It has been proposed in the same publication. 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 Since the dispersion liquid of the heat storage material microcapsules always has good fluidity regardless of the phase change temperature of the heat storage material, it can be used as a heat medium that can directly transfer latent heat, or it can be used in a heat storage tank. It can be stored and used as a liquid heat storage material using inexpensive midnight power.

Techniques for microencapsulating a heat storage material include coacervation, interfacial polymerization, and in-situ polymerization.
It is possible to use the tu method or the like, and the effect of the present invention can be achieved by any of the methods. However, as a method for producing microcapsules that endure long-term stability and are chemically and physically stable, in-situ A microcapsule having a melamine-formaldehyde polymerized wall film by a polycondensation method of melamine and formalin is most suitable.

[0004] Microcapsules having a melamine-formaldehyde polymer wall film are inexpensive materials and have high robustness. This is a technique that has been put to practical use for pressure-sensitive recording paper. A microcapsule having a melamine-formaldehyde polymerized 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 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, hydrogen peroxide,
Ammonia, sulfite, persulfate, hypochlorite and the like are known as formaldehyde removing materials.

The microcapsules of the heat storage material of the present invention are required to flow or store for a long period of time in a metal piping system or tank as a refrigerant or a heat storage material for air conditioning. 1. The viscosity of the microcapsule dispersion must not be increased or aggregation of the particles should not be caused. 2. The microcapsule wall membrane must not be degraded. 3. The constituent materials must not corrode the metals that make up the piping or heat exchanger. Especially 3. It is known that a basic amino compound containing ammonia or nitrogen or an inorganic metal ion significantly corrodes metals such as iron and copper.

[0007]

An object of the present invention is to provide a heat storage material microcapsule in which formaldehyde remaining in a heat storage material microcapsule dispersion liquid is quickly and effectively removed and which satisfies the above three conditions. It is in.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat storage material microcapsule encapsulated with a melamine-formaldehyde polymerized wall film, the method comprising the steps of: removing residual formaldehyde that does not contribute to wall film formation;
The object of the present invention is achieved by reacting a compound containing no nitrogen and having two or more alcoholic hydroxyl groups in one molecule.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The heat storage material microcapsule of the present invention comprises a step of forming a melamine-formaldehyde polymer wall film around a heat storage material and a step of removing excess residual formaldehyde. The compound which does not contain nitrogen and has two or more alcoholic hydroxyl groups in one molecule as described in the present invention refers to a hydroxyl group other than phenol or carboxylic acid, which does not contain a nitrogen-containing functional group such as an amino group or an imino group. A compound having two or more of Specific examples of the residual formaldehyde remover used in the present invention include particularly water-soluble polyhydric alcohols such as ethylene glycol, glycerin, and trimethylol-furopan, sugars such as glucose, fructose, sorbose, and mannose, dihydroxyacetone, and polyvinyl. Alcohol and the like can be mentioned, and glucose is particularly preferable.

These compounds are added in the range of 0.1% to 20.0% based on 100 parts by weight of the microcapsules. Since the pH during the reaction varies depending on the residual formaldehyde treating agent to be used, it is necessary to set an optimum pH. In the case of glucose, the reaction is preferably performed under alkaline conditions of pH 7 or more, preferably pH 9 or more. Since the residual formaldehyde remover used in the present invention is added in an equivalent amount in excess of the residual formaldehyde, some of the microcapsule dispersions are dissolved without being reacted even in the microcapsule dispersion liquid. But it does not cause any corrosive effects.

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 in view of the purpose of heat storage. Organic materials may be used. Inorganic compounds containing large amounts of water of crystallization, such as calcium chloride hexahydrate, sodium sulfate decahydrate, sodium hydrogen phosphate decahydrate, sodium thiosulfate pentahydrate, nickel nitrate hexahydrate, and the like. 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 the melamine-formaldehyde polymer 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 copolymer, poly Sodium acrylate and the like 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. However, if necessary, a preservative, various kinds of deterioration inhibitors, thickeners, coloring 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 heat storage material dispersion liquid, 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.

[0015]

The present invention will be described below in detail with reference to examples. Note that the present invention is not limited to the embodiments. still,
The melting point, freezing point and heat of fusion shown in the examples were measured using a differential calorimeter (DSC-7, manufactured by Perkin Elmer, USA).

Example 1 5% melamine powder and 37% formaldehyde aqueous 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.

5% styrene adjusted to pH 4.5
100g of sodium salt aqueous solution of maleic anhydride copolymer
A paraffin wax having a melting point of 60 ° C. (Nippon Seisaku's paraffin wax 140) 8 is a compound having a phase change therein.
0 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 the mixture was stirred at 70 ° C. for 2 hours, and the pH was adjusted to 10 with a 20% (w / w) aqueous sodium hydroxide solution. . Next, when 40 g of a 10% glucose aqueous solution was added and stirring was continued at 70 ° C. for 1 hour, the pungent odor of formaldehyde had completely disappeared.

Example 2 A microcapsule dispersion of paraffin wax was prepared in the same manner as in Example 1, and then 40 g of a 10% (w / w) aqueous solution of 1,3-dihydroxyacetone was used in place of glucose to remove residual formaldehyde. Was added and stirring was continued for 1 hour under conditions of pH 10 and a temperature of 70 ° C., and then the pH was adjusted to 8.0.
To obtain a microcapsule dispersion. The irritating odor of formaldehyde had completely disappeared from the obtained microcapsule dispersion liquid.

Example 3 A microcapsule dispersion of paraffin wax was prepared in the same manner as in Example 1, and then 5% (w / w) polyvinyl alcohol (Kuraray Co., Ltd.) was used instead of glucose to remove residual formaldehyde. PVA117) 40 g of aqueous solution
Was added and stirring was continued for 1 hour under conditions of pH 10 and a temperature of 70 ° C., and then the pH was adjusted to 8.0 to obtain a microcapsule dispersion. The irritating odor of formaldehyde was considerably reduced in the obtained microcapsule dispersion liquid.

Comparative Example 1 A microcapsule dispersion of paraffin wax was prepared in the same manner as in Example 1, and then 40 g of a 10% (w / w) aqueous urea solution was added in place of glucose to remove residual formaldehyde. After stirring for 1 hour, the pH was adjusted to 8.0 to obtain a microcapsule dispersion. The irritating odor of formaldehyde had completely disappeared from the obtained microcapsule dispersion liquid.

Comparative Example 2 A microcapsule dispersion of paraffin wax was prepared in the same manner as in Example 1, and then 40 g of a 10% (w / w) aqueous solution of sodium sulfite was added in place of glucose to remove residual formaldehyde. After stirring for 1 hour, the pH was adjusted to 8.0 to obtain a microcapsule dispersion. The irritating odor of formaldehyde had completely disappeared from the obtained microcapsule dispersion liquid.

The following evaluations were performed on the heat storage material microcapsule dispersions obtained in Examples and Comparative Examples. Extracted amount of residual formaldehyde (F): Extracted amount of water per microcapsule solid by the acetylacetone method. Corrosion to metal pieces: Change of copper pieces and microcapsule dispersion liquid after infiltrating copper pieces into microcapsule dispersion liquid and leaving it to stand at 70 ° C. for one month. Viscosity after F treatment: viscosity at 20 ° C. measured by a B-type viscometer. Destruction degree of microcapsule by electron microscope.

[0024]

[Table 1]

Claims (2)

[Claims] In a heat storage material microcapsule encapsulated in a wall film of a melamine-formaldehyde polymer, a compound with a phase change contains residual formaldehyde not contributing to the formation of the wall film and nitrogen-free and 2% per molecule. Heat storage material microcapsules in which formaldehyde in microcapsule dispersion liquid is removed by reacting a compound having at least two alcoholic hydroxyl groups 2. The heat storage material microcapsule according to claim 1, wherein the compound having an alcoholic hydroxyl group is glucose.