JP2988765B2 - Cool storage material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerator material used for cooling a substance, and more particularly, to an aqueous liquid regenerator having good fluidity even at a low temperature and capable of maintaining a high density latent heat. About materials. The cold storage material according to the present invention can be used as a portable cold insulation material or a freshness holding material such as fresh food by holding it in a refrigerant for air conditioning, or various packaging materials or containers.

[0002]

2. Description of the Related Art Ice is the most commonly used regenerative material in daily life, and when water undergoes a phase change to ice, about 80 kcal / cm.
It can store cold latent heat of kg and can be said to be the most inexpensive and inexpensive cold storage material that is used in various fields in daily life such as maintaining freshness of fresh foods and using it for ice pillows.

In general, a method of storing heat using latent heat due to a phase change of a substance has a large amount of heat energy in a narrow temperature range including a melting point compared to a method using only sensible heat without a phase change. In this case, the heat storage material capacity can be reduced, and the heat loss can be suppressed to a small amount because a large temperature difference does not occur when the heat storage amount is large.

[0004] The following materials have conventionally been known as latent heat utilizing heat storage materials accompanying a phase change, particularly a phase change between a liquid and a solid. (1) Inorganic water containing a large amount of water of crystallization such as calcium chloride hexahydrate, sodium sulfate decahydrate, sodium hydrogen phosphate decahydrate, sodium thiosulfate pentahydrate, nickel nitrate hexahydrate, etc. Japanese (2) Hydrocarbon compounds such as petroleum paraffins and waxes, fatty acids such as caprylic acid, lauric acid and stearic acid

[0005] In order to enhance the heat exchange efficiency of these various heat storage materials, means for microencapsulating the heat storage materials has been proposed (for example, JP-A-62-1452 and JP-A-62-1452).
Nos. 45680, 62-149334, 62-225241, 63-115718, 63-217196, and JP-A-2-2580.
No. 52).

[0006] Among the microencapsulation methods disclosed in the above publication, the microencapsulation method generally called an interfacial polymerization method is capable of encapsulating both an aqueous substance and a substance immiscible with water. However, when water or an inorganic hydrate of (1) is used as the core substance (for example, JP-A-61-192785), the dispersion medium of the capsule is a water-immiscible organic solvent (for example, cyclohexane, toluene, four for carbon tetrachloride, chloroform, various plastic materials, such as butyl phthalate) is usually used, obtained only water-in-microcapsule dispersion oil, in order to obtain a cold accumulating material of aqueous some A desolvation step is required.

[0007] In addition, a technique generally called a submerged drying method has an advantage that microcapsules containing a water-soluble substance can be directly obtained in an aqueous dispersion system, but has a low boiling point, which is a solvent for a polymer compound to be a film material. Of removing the organic solvent (for example, benzene, ether, chloroform, etc.), and the stability of the microcapsule coating often needs to be improved.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the encapsulation method for storing heat and to obtain a regenerative material having the following effects.

First, there is a need to obtain an aqueous regenerative material mainly composed of durable microcapsules which can be freely mixed with an aqueous antifreeze or various inorganic salts and which will not break even after long-term use. . This is difficult to produce by the microcapsules of an aqueous substance by the interfacial polymerization method or the in-liquid drying method.

Secondly, even if the regenerator material is cooled to a temperature lower than the melting point of the compound with phase change contained in the microcapsules, if the temperature is higher than the melting point of the dispersion medium of the microcapsules, the fluidity of the regenerator material itself is reduced. An object of the present invention is to obtain a cold storage material which does not change at all and which is always in a liquid state. This is a characteristic that cannot be obtained with the inorganic and organic heat storage materials alone.

[0011]

Means for Solving the Problems The present inventor studied to achieve the above object, and found that a compound having a phase change immiscible with water having a melting point of 0 to 15 ° C. was coated with an aminoplast resin film. By using the microcapsules thus obtained as a main component of the cold storage material, it has become possible to obtain a cold storage material that can achieve the above object. Next, the details will be described.

In general, the temperature range in which the effect of the cold storage material is felt as real is different depending on the temperature of the outside air and the form and amount of the cold storage material, but it is determined that a temperature of about 20 ° C. or less is necessary. In order to realize the effect, it is judged that about 15 ° C. or less is preferable. In addition, in consideration of maintaining freshness of fresh foods and the like, preventing freezing, appropriate skin feel, and the like, it is determined that setting the temperature to be cooled to 0 to 15 ° C. is most effective.

Compounds having a melting point in this temperature range and having a phase change immiscible with water include tetradecane, p-chlorotoluene, 1-ethoxynaphthalene, o-anisidine,
Iodonaphthalene, o-dibromobenzene, cyclohexane, benzene, o-bromophenol, d-fencon,
Dimethyl carbonate, dibutyl sebacate, diethyl cinnamate, oleic acid, 3,3-dimethylbiphenyl, dibromoethane, and the like can be used. Especially, tetradecane having a purity of 98% or more has a heat of fusion of about 50 kcal / kg. The compound having a phase change is the most preferable. These compounds with a phase change can be used alone or in combination of two or more kinds. If necessary, metal powder and various pigments are added to the compound for heat conductivity and specific gravity.
Can also be adjusted .

The compound with a phase change used in the present invention is encapsulated using a suitable microencapsulation method. Microencapsulation of a liquid immiscible with water includes a coacervation method using gelatin and an anionic polymer, an interfacial polymerization method, an in-situ method, and a method using yeast (Japanese Patent Application Laid-Open No. 63-163). 88033) can be used, but in order to be able to be used as a cold storage material for a long period of time, a more robust microcapsule is required. For that purpose, an aminoplast resin obtained by an in-situ method is used. It is most desirable to use microcapsules as a film.

The aminoplast resin used in the present invention refers to a resin obtained by a polymerization reaction between an amino compound and formaldehyde, and specifically, a urea-formalin resin, a melamine-formalin resin, a benzoguanamine-formalin resin. Melamine-
Formalin resin is mentioned as the most preferred aminoplast resin. Microencapsulation with these aminoplast resins is generally obtained by the following procedure. 1. A step of preparing an aminoplast resin precondensate. 2. A step of emulsifying and dispersing a compound with a phase change in an aqueous dispersant solution. After adding the initial condensate of 3.1 to the emulsified dispersion of 2.
A step of forming a film around compound particles accompanied by a phase change by heating and stirring.

1. As a method for producing the aminoplast resin precondensate, a specific example in the case of a melamine resin is as follows. Melamine powder and formalin (37% aqueous formaldehyde solution) are mixed at a molar ratio of 1: 1 to 1: 4, By heating to a temperature of about 60 ° C. or more in a weak alkali, a water-soluble melamine-formalin precondensate can be obtained.

The aminoplast resin is added in an amount of about 1 to 30 (wt / wt)%, preferably 5 to 20%, based on the weight of the compound having a phase change. If the amount is less than this, the strength as a microcapsule is insufficient, and if it is more than this range, the proportion of the film material in the regenerator material increases, and the regenerative efficiency decreases, which is not preferable.

2. Specific examples of the dispersant include acrylic acid copolymer, ethylene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride copolymer, butadiene-maleic anhydride copolymer. Copolymers, vinyl acetate-maleic anhydride copolymers, and their sodium salts are used. These dispersants are added in the range of 1.0 to 20.0 (wt / wt)% based on the aqueous solution of the dispersant.

The pH of the aqueous solution of the dispersant is set to a value at which the film-forming reaction of the aminoplast resin proceeds most efficiently.
It is adjusted in the range of 3 to 6.

In the step of emulsifying a compound with a phase change, the compound with a phase change is added to an aqueous solution of a dispersant, and the mixture is stirred using a commercially available emulsifying and dispersing apparatus until the emulsified particle size becomes about 1 to 50 μm. It is done by doing.

Next, the aminoplast resin precondensate previously prepared is mixed with an emulsion of a compound which undergoes a phase change.
By heating and stirring to polymerize the initial condensate around the emulsified particles, a water-insoluble resin is formed to obtain microcapsules containing a compound with a phase change. The heating temperature during encapsulation is 40 to 100 ° C, preferably 60 to 80 ° C.
Stirring is performed at a temperature in the range of 30 ° C. for a period of 30 minutes to 4 hours.

The microcapsule dispersion containing the compound with a phase change thus obtained can achieve the object of the present invention as it is. However, if necessary, ethylene glycol, propylene glycol, various inorganic salts, preservatives, etc. Agents, various deterioration inhibitors, thickeners, coloring agents, dispersing aids,
An aqueous liquid cold storage material is obtained by adding a specific gravity adjusting material, a wetting material and the like.

The higher the proportion of the microcapsules in the regenerator material, the higher the latent heat quantity, which is preferable. However, in order to maintain good fluidity, 20 to 70 (wt / wt)%, preferably 40 to 6%.
It is preferably set in the range of 0 (wt / wt)%. If the content is above this range, the viscosity of the cold storage material will increase, resulting in poor fluidity. If the content is below this range, the cold storage effect will be poor, which is not preferable.

[0024]

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 Preparation of Initial Condensate 6.5 g of 37% aqueous formaldehyde solution and 10 g of water were added to 5 g of melamine powder, and the pH was adjusted to 8
After heating to about 70 ° C., an aqueous melamine-formaldehyde precondensate solution was obtained.

[Emulsification step] 5% of which pH was adjusted to 4.5
N-tetradecane (melting point: about 5 ° C., heat of fusion: 50.8 kcal / kg) as a compound with a phase change in 100 g of a sodium salt aqueous solution of styrene-maleic anhydride copolymer
80 g was added with vigorous stirring, and the particle size was 10 μm
The emulsification was carried out until.

[Encapsulation Step] 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 then the pH was adjusted to 9 to complete the encapsulation.

[Preparation of Cold Storage Material] A mixture of 100 parts of the obtained microcapsule dispersion liquid and 30 parts of ethylene glycol was filled in a hard polyethylene bag to obtain a portable cold storage material. When this cold storage material was left in a home freezer for about 1 hour, the cold storage material did not solidify and the cold storage effect was maintained for a long time.

[Measurement of heat of fusion] The heat of fusion of this cold storage material was measured by a differential scanning calorimeter (DSC7, manufactured by PerkinElmer, USA).
As a result, a heat of fusion of 18 kcal / kg was observed in a range sandwiching the melting point of n-tetradecane.
The heat of fusion of the cold storage material was measured at -20 to 30 ° C.
In this range, good fluidity was always maintained.

Example 2 [Preparation of Initial Condensate] To 10 g of melamine powder, 12.9 g of a 37% aqueous formaldehyde solution and 10 g of water were added.
Was adjusted to 8, and then heated to about 70 ° C. to obtain an aqueous solution of a melamine-formaldehyde precondensate.

[Emulsification step] 5% of which pH was adjusted to 3.5
N-pentadecane (melting point: about 10 ° C., heat of fusion: 40 kcal / kg) as a compound accompanied by a phase change in 100 g of an aqueous solution of a sodium salt of an ethylene-maleic anhydride copolymer
0 g was added with vigorous stirring, and emulsification was performed until the particle diameter became 5 μm.

Then, the initial condensate and the emulsion were mixed and encapsulated in the same manner as in Example 1, and 30 parts of ethylene glycol was added to 100 parts of the obtained microcapsule dispersion to obtain a regenerator material. Was.

[Measurement of heat of fusion] The heat of fusion of this regenerator material was measured using a differential scanning calorimeter of the same type as in Example 1. The heat of fusion was 14 kcal / m2 within the range sandwiching the melting point of n-pentadecane.
A heat of fusion of kg was observed. Also, in the range of -20 to 30 ° C. where the heat of fusion of the cold storage material was measured, good fluidity was always maintained.

[0034]

As is clear from the examples, the regenerator material according to the present invention is capable of accumulating a large amount of cold heat in a range sandwiching the freezing point of a compound with a phase change, It is possible to obtain an aqueous liquid regenerator material having a high fluidity even at a temperature lower than the melting point, and it is useful as a regenerator material.

Claims (2)

(57) [Claims] 1. A regenerative material mainly comprising microcapsules containing a compound with a phase change, wherein the compound with a phase change is a compound that is immiscible with water and has a melting point in the range of 0 to 15 ° C. A regenerator material, wherein the coating of the microcapsules is made of aminoplast resin. 2. The regenerative material according to claim 1, wherein the compound with a phase change is tetradecane.