JP3103927B2 - Thermal storage material composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a latent heat storage material used for heating buildings and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conditions to be provided as a heat storage material include: a large amount of heat storage, operation at a predetermined temperature level, stability over a long period of time, low cost, no toxicity,
And non-corrosiveness. Phase change hydrate salts are most often studied as satisfying these conditions, and sodium sulfate decahydrate is a typical example.

[0003] Since sodium sulfate decahydrate has a melting point of 32 ° C and a latent heat of 60 cal / g, an attempt to use it as a heat storage material was made in 1952 as a four-borane as a supercooling prevention material used in combination therewith. Sodium acid decahydrate (Na
Since been found to be _{2 B 4 O 7 · 10H 2} O) is in effect, it has been a number considered until today. A problem encountered in practical applications is that sodium sulfate decahydrate exhibits anharmonic melting. That is, anhydrous sodium sulfate is generated during melting and settles at the liquid bottom. When this is cooled, the deposited surface layer of anhydrous salt is condensed to dehydrate, but the inside remains as anhydrous salt. Since the remaining anhydrous salt does not participate in the phase change, the amount of stored heat is reduced.
In order to solve this, various methods have been studied for dispersing and retaining the anhydrous salt in the liquid without causing the anhydrous salt to settle to the liquid bottom. These are methods for preventing sedimentation by thickening with an organic or inorganic additive.

For example, a method using an inorganic compound (Japanese Patent Publication No. 55-501180, Japanese Patent Application Laid-Open No. 53-34687) has been attempted, but sufficient prevention of sedimentation has not always been achieved.

As the organic polymer, a water-soluble polymer such as sodium polyacrylate, a cross-linkable polymer (Japanese Patent Publication No.
No. -30873, Japanese Patent Publication No. 57-48027,
JP-A-58-132075, JP-A-59-1029
No. 77) has been proposed, but is not always sufficient in terms of long-term stability.

[0006] In a sodium sulfate-based heat storage agent composition, a method is known in which water containing a silicon-based antifoaming agent and a chelating agent is added to sodium sulfate to suppress deterioration of heat storage.
(JP-A-60-203687) In this method,
It is essential that a silicon-based antifoaming agent and a chelating agent coexist, and when both are absent, a decrease in heat storage is seen after 500 cycles.

[0007]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems of the prior art. That is, the present invention uses sodium sulfate and water as main materials,
The present invention relates to a heat storage material composition in which the amount of heat storage does not decrease over a long period of time even if a cycle of melting and solidification is repeated, and a method for producing the same.

[0008]

The present invention provides (1) sodium sulfate and / or a eutectic salt thereof, (2) water, and
(3) a crosslinked polymer obtained by polymerizing a polyfunctional monomer with at least one monomer selected from unsaturated carboxylic acids, organic unsaturated sulfonic acids and salts thereof,
The present invention relates to a heat storage material composition containing 16 to 24 mol of water per 1 mol of sodium sulfate.

[0009] The present invention also relates to anhydrous sodium sulfate and / or
Or its eutectic salt and anhydrous sodium sulfate per mole
Using at least one monomer selected from unsaturated carboxylic acids, organic unsaturated sulfonic acids and salts thereof, a polyfunctional monomer, and a polymerization initiator in the presence of 16 to 24 mol of water The present invention relates to a method for producing a heat storage material composition characterized by being polymerized. Hereinafter, these inventions will be described in detail.

In the present invention, the raw material sodium sulfate may be anhydrous sodium sulfate itself or a eutectic salt thereof. Also, sodium sulfate decahydrate can be used. As a substance which forms a eutectic salt with sodium sulfate, known substances such as sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, magnesium sulfate, and urea can be used. The amount of these compounds to be used is 0.2 to 1 mol of sodium sulfate.
1.0 mole. Eutectic salts have the effect of lowering the melting point compared to sodium sulfate alone, and can be used for adjusting the melting point.

The first feature of the present invention resides in the molar ratio of sodium sulfate and water in the heat storage material composition. In the present invention, sodium sulfate (anhydrous basis) per mole of 1
6 to 24 moles are blended. By adjusting the amount of water per mole of sodium sulfate to the range of 16 to 24 moles, even in the repetition (cycle) of the temperature history of melting and solidification,
There is almost no decrease in the amount of latent heat over a long period of time.Therefore, heat load calculation is ready, and it is not necessary to overload the heat storage material composition in anticipation of the decrease in the amount of latent heat. This provides an excellent effect that the thickness can be reduced and the load can be reduced.

When the amount of water is less than 16 moles, the initial latent heat amount is large, but the latent heat amount is significantly reduced due to the temperature history, which is a serious problem in terms of facilities and control in contrast to the above. There is.

On the other hand, when the amount of water exceeds 24 moles, the change in the amount of latent heat is controlled by repeating the temperature history, but the amount of latent heat is small and a large amount of heat storage material is required. It is disadvantageous in terms of load and the like.

In particular, when the blending amount of water is 16 to 24 mol, the residual ratio of latent heat after 5,000 cycles is 95%.
As described above, there is almost no change, and the absolute value is more than the practical level. The critical significance of the characteristic range of the water content of the present invention will be quantitatively clarified in Examples and Comparative Examples described below.

Next, the crosslinked polymer used in the present invention and components constituting the polymer will be described. As the unsaturated carboxylic acid used in the present invention, an unsaturated carboxylic acid soluble in water is suitable. Examples of these unsaturated carboxylic acids include acrylic acid, methacrylic acid and itaconic acid. More preferably, acrylic acid can be used. Methacrylic acid, itaconic acid and hydroxyethyl acrylate can also be used in combination with acrylic acid.

Examples of the organic unsaturated sulfonic acid include 2-acrylamido-2-methylpropanesulfonic acid, p-styrenesulfonic acid, sulfoethylmethacrylate, allylsulfonic acid, and methallylsulfonic acid.

As the salts of unsaturated carboxylic acids and organic unsaturated sulfonic acids, those which are easily soluble in water such as alkali metal salts or ammonium salts thereof are used. Preferably, a sodium salt can be used. Sodium acrylate or sodium methacrylate are the most preferred.

It is also possible to use an unsaturated amide copolymerizable with these monomers in combination. Acrylamide or methacrylamide is used as the unsaturated amide.

The amount (polymer amount) of these monomers used is
It is 1 to 10% by weight, preferably 2 to 5% by weight, based on the whole heat storage material composition. If the amount is less than 1% by weight, the viscosity is low, and the effect of preventing precipitation of anhydrous sodium sulfate caused by the phase change is reduced. If the concentration is higher than necessary, such as exceeding 10% by weight, the amount of stored heat decreases.

Polyfunctional monomers are used to crosslink the polymer. Preferably, a water-soluble polyfunctional monomer is used. Specifically, N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide,
N'-dimethylenebisacrylamide, N, N'-dimethylenebismethacrylamide and the like are exemplified. Preferably N, N'-methylenebisacrylamide or N, N '
N'-methylenebismethacrylamide can be used. The amount used is also 0.0% based on the entire heat storage material composition.
It is in the range of 1 to 1% by weight, preferably 0.05 to 0.5% by weight.
If it exceeds 1% by weight, the effect corresponding to the added amount cannot be obtained, so that it is not preferable.

The above-mentioned monomer and polyfunctional monomer form a crosslinked polymer as a result of a polymerization reaction described below. The proportion of the crosslinked polymer in the heat storage material composition is the sum of the amounts of the above-mentioned monomer and polyfunctional monomer, and is 1 to 11% by weight,
Preferably it is 2-5.5% by weight.

As the polymerization initiator used in the polymerization,
Acetyl peroxide, diacyl peroxides such as lauroyl peroxide and benzoyl peroxide, hydroperoxides such as cumene hydroperoxide, alkyl peroxides such as di-tert-butyl peroxide, ammonium or potassium peroxydisulfate, hydrogen peroxide, 2,2 -A generally known radical polymerization initiator such as azobisisobutyronitrile is used in a usual amount. Among them, a redox polymerization initiator is preferable because it is active at a relatively low temperature.

The redox polymerization initiator suitably used in the present invention is a water-soluble one among commonly known ones. Examples of the oxidizing agent include ammonium or potassium peroxydisulfate and hydrogen peroxide, and examples of the reducing agent include sodium thiosulfate, sodium sulfite, and ferrous sulfate. The temperature for crosslinking polymerization is sodium sulfate 1
The temperature is not lower than the melting point of 0-hydrate or its eutectic salt, and is usually, but not necessarily, 20 to 50 ° C.

The redox polymerization initiator exhibits polymerization activity in a relatively short time when the constituent oxidizing agent and reducing agent are mixed. It deactivates when it comes into contact with oxygen in the air after the polymerization activity is developed. Therefore, after the two are mixed, it is necessary to transfer the mixture to a polymerization vessel as quickly as possible so as not to come into contact with air.

There are various embodiments for implementing the method of the present invention. For example, there is a method in which polymerization is performed in a relatively large container, and the generated heat storage material is subdivided into a container constituting a heat storage portion of a heating device. A large vessel to be polymerized is replaced with nitrogen gas in advance, and the raw material components are mixed to perform polymerization.

In the present invention, the mixing operation is easy because the monomer is used without using a crosslinked polymer or the like as a raw material.

There is also a method in which polymerization is carried out in a heat storage vessel such as a heating device. The features of the present invention are particularly well demonstrated in this method.

In the present invention, since a monomer is used as a starting material instead of a crosslinked polymer or the like, the mixed material before polymerization is a liquid composition having a low viscosity. Therefore, the mixed material can be easily injected even if the containers have many and complicated shapes. By performing polymerization in a container, a heat storage material that is a viscous liquid or a jelly-like solid can be easily stored in a container having a complicated shape. When polymerization is performed by filling a mixed material in a container, it is not always necessary to perform nitrogen replacement in the container.

As a method for injecting the liquid composition before polymerization into a container for storing the heat storage material, for example, when a redox initiator is used as a polymerization initiator, an oxidizing agent and a reducing agent are added in a flow system of the composition. It is desirable to inject while mixing continuously.

For example, a method in which an oxidizing agent and a reducing agent are separately added during the injection of a liquid composition of anhydrous sodium sulfate or a eutectic salt thereof, water, etc., and a monomer into a container; A method in which one of an agent or a reducing agent is dissolved, and the other is added during injection into a container, the liquid composition is divided, an oxidizing agent is dissolved in one, and a reducing agent is dissolved in the other, and A method in which the two liquids are caused to collide with each other in the injection path, mixed, and injected into a container. It is also possible to put an in-line mixer in the flow path of the liquid in order to perform the mixing more sufficiently.

In the method of the present invention, anhydrous sodium sulfate and other additives are settled and separated in the container after the mixed raw material is injected into the container and before the polymerization reaction of the monomer proceeds and the viscosity increases. In order to prevent this, it is also a preferable method to add a thickener in advance to increase the viscosity of the aqueous medium. As the thickener used for this purpose, various well-known thickeners are used, for example, fumed silica, finely divided silica, inorganic substances such as various clays, and water-soluble polymers such as sodium polyacrylate. And hydrogels. The amount to be used is about 0.1 to 7% by weight, and in the case of a monomer, it is sufficient to provide a viscosity that prevents the precipitation of anhydrous sodium sulfate in a short time until the crosslinking reaction proceeds and the viscosity increases. I just need.

[0032] A supercooling inhibitor is generally added to the heat storage material. In the method of the present invention, a supercooling inhibitor may be added to the mixed solution before the polymerization, or may be added after the polymerization. However, when the polymerization is carried out in a container in which the heat storage material is finally stored, it is necessary to add the heat storage material to the mixed solution before the polymerization.

It is well known that sodium tetraborate decahydrate is generally effective as a supercooling inhibitor. The amount used is about 2-5% by weight of the whole heat storage material,
It is sufficient that the amount of addition is equal to or higher than the saturation solubility in the aqueous medium in the operating temperature range. Since the pH range in which sodium tetraborate decahydrate is stably present in an aqueous medium is neutral to basic, it is desirable to neutralize with an alkali beforehand when the monomer or polymer becomes acidic.

[0034]

Next, the present invention will be described in more detail by way of examples.

COMPARATIVE EXAMPLE 1 A 10% by weight aqueous solution of sodium acrylate obtained by neutralizing acrylic acid to pH 7.5 with an aqueous sodium hydroxide solution
To 0 g, 135 g of water was further added, and while stirring at 30 ° C., 0.75 g of N, N′-methylenebisacrylamide was added.
Then, 142 g of anhydrous sodium sulfate and 20 g of sodium tetraborate decahydrate were added to obtain a uniform mixture without sedimentation. The molar ratio of sodium sulfate (in terms of anhydride) and water of this mixture was as shown in Table 1.

This mixture was divided into two parts, and 0.5 g of ammonium peroxydisulfate and 0.5 g of sodium thiosulfate pentahydrate were added to one side and 0.5 g of sodium thiosulfate pentahydrate, respectively, and mixed. The two liquid streams were injected into a polyethylene bag having a width of 40 mm and a length of 600 m while being subjected to collision mixing.

This is suspended in an atmosphere of 40 ° C.
When observed after 1 hour, the crosslinking reaction proceeded, and the content was a composition containing a uniform jelly-like elastic polymer. It undergoes a phase change at about 32 ° C.

The obtained polymer-containing composition (50 g) was treated with a diameter of 3
0mm x 100mm length in a glass cylinder, 40 ℃
When a temperature history of repeating a temperature increase and a temperature decrease between 10 ° C. and 10 ° C. was given, the temperature was stable even after a temperature history test of 5000 cycles, and no phase separation phenomenon was observed. The latent heat amount in the first cycle was 44.5 cal / g, and the relative value of the latent heat amount after lapse of 5000 cycles with this value being 100 was 91 (40.5 cal / g). It was kept stable.

[0039] In Examples 1, 2, 3, and Comparative Examples 2 and 3 Comparative Example 1 with the same method to prepare the heat storage material compositions shown in Table 1. In Example 3 , sodium chloride forms a eutectic salt with sodium sulfate below the melting point. Table 1 shows the results of the temperature history test performed in the same manner as in the example.
A change in the amount of heat as shown in FIG.

[0040]

[Table 1]

[0041]

According to the present invention, by controlling the molar ratio of sodium sulfate / water to 16 to 24 , the amount of latent heat per unit weight of the heat storage material is large, and even after 5,000 cycles of repeated melting and solidification. An excellent heat storage material composition can be obtained while maintaining the initial amount of latent heat.

[Brief description of the drawings]

FIG. 1 is a temperature history test 500 for repeated melting and solidification.
It represents the change in the amount of latent heat up to 0 cycles.

FIG. 2 shows the relationship (A) between the amount of water (mol per mole of sodium sulfate) and the amount of latent heat per unit weight of the heat storage material (cal / g (after 5000 cycles)), and the amount of water and 5000 cycles. The residual rate of latent heat after ((5000
Latent heat after cycle / initial latent heat) x 100
(%)).

[Explanation of symbols]

1 . Comparative Example 1 2. Example 1 3. Comparative Example 2 4. Example 2 5. Example 3 6. Comparative Example 3

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09K 5/00 C09K 5/06 C09K 5/08-5/14

Claims (3)

(57) [Claims] (1) at least one kind selected from (1) sodium sulfate and / or a eutectic salt thereof, (2) water, and (3) unsaturated carboxylic acid, organic unsaturated sulfonic acid and salts thereof. A heat storage material composition comprising a crosslinked polymer obtained by polymerizing a monomer and a polyfunctional monomer, wherein the heat storage material composition contains 16 to 24 mol of water per 1 mol of sodium sulfate. 2. The heat storage material composition according to claim 1, comprising 1 to 11% by weight of the crosslinked polymer. 3. An unsaturated carboxylic acid, an organic unsaturated sulfonic acid or a salt thereof in the presence of sodium sulfate and / or its eutectic salt and 16 to 24 moles of water per mole of sodium sulfate. A method for producing a heat storage material composition, comprising polymerizing one kind of monomer and a polyfunctional monomer using a polymerization initiator.