JPS6225188A - Production of heat storage material - Google Patents

Abstract

PURPOSE:A heat storage material for heating of construction, etc., having improved long-term stability, by polymerizing a monomer such as unsaturated carboxylic acid, organic unsaturated sulfonic acid, etc., with a polyfunctional monomer in the presence of sodium sulfate, water and a polymerization initiator. CONSTITUTION:In the presence of (A) sodium sulfate or its eutectic crystal salt (e.g., eutectic crystal with sodium chloride), (B) water and (C) a polymerization initiator (preferably redox polymerization initiator such as ammonium peroxydisulfate-sodium thiosulfate, etc.,), (D) preferably 2-5wt% one or more monomers selected from an unsaturated carboxylic acid (e.g., acrylic acid, etc.,), an organic unsaturated sulfonic acid (e.g., 2-acrylamido-2-methylpropanesulfonic acid, etc.,) and its salt is polymeized with (E) preferably 0.05-0.5wt% polyfunctional monomer (e.g., N,N'-methylenebisacrylamide, etc.,), to give the aimed heat storage material consisting of a composition of the component A and a crosslinked polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a heat storage material used for heating buildings, etc.

(Conventional technology) The conditions that must be met for a heat storage material are a large amount of heat storage;
These include operating at a given temperature level, being stable for long periods of time, being inexpensive, being non-toxic, and being non-corrosive. Phase changeable hydrated salts have been most frequently studied as substances that satisfy these conditions, and sodium sulfate decahydrate is a typical example thereof.

Sodium sulfate decahydrate has a melting point of 32°C and 60°C
Since it has a latent heat of al/7, attempts to use it as a heat storage material began in 1952 when sodium tetraborate decahydrate (N1
Since it was discovered that 3"40?・10H20) is effective, many studies have been conducted to date.The problem encountered in practical studies is that sodium sulfate decahydrate exhibits anharmonic melting. be.

That is, upon melting, anhydrous sodium sulfate is generated and settles to the bottom of the liquid. When this is cooled, the surface layer of deposited anhydrous salt condenses to decahydrate, but the interior remains as anhydrous salt.

The remaining anhydrous salt does not participate in the phase change, resulting in a decrease in the amount of heat storage. In order to solve this problem, various methods have been studied to disperse and retain the anhydrous salt in the liquid without allowing it to settle to the bottom of the liquid. These methods prevent sedimentation by increasing the viscosity with organic or inorganic additives. For example, natural organic polymers such as carboxymethyl cellulose and starch (US Pat. No. 3,986,969, etc.)
has been proposed, but there are concerns about long-term use because natural products are easily decomposed. Fumed silica (Special Publication 1986-501)
．． 180), attapulgite clay (Japanese Unexamined Patent Publication No. 1983-
Inorganic substances such as 34,687) have been proposed, but melting,
As the viscosity gradually decreases through the coagulation cycle, prevention of precipitation of anhydrous sodium sulfate becomes insufficient. For synthetic organic polymers, thickening with water-soluble polymers such as sodium polyacrylate has been proposed, but since these have fluidity, they flow during the growth and disappearance of hydrated salt crystals during the melting and solidification cycle. However, as a result, the crystals become coarser and eventually the anhydrous salt settles. In this case, sedimentation is not necessarily sedimentation to the bottom of the liquid, but also sedimentation within a minute portion (hereinafter referred to as water pool) consisting only of the aqueous phase within the network structure formed in the liquid by water-soluble polymers. gradually expanded. Crosslinked polymers have been proposed to solve these problems with water-soluble polymers. For example, a method in which a water-soluble polymer having a carboxyl group or a sulfonic acid group is reacted with a polyvalent metal ion in a solution containing sodium sulfate to produce an ionically crosslinked polymer (Japanese Patent Publication No. 57-30873), Water-soluble polymers with functional groups (e.g. polyacrylamide)
and other crosslinking agents (e.g., aldehydes) in a solution containing sodium sulfate etc. to produce a covalently crosslinked polymer (Japanese Patent Publication No. 57-48027), water-swellable polymers produced outside the system Method of adding crosslinked polymer to hydrated salt melt (JP-A-58-132075, JP-A-59-1029)
77) etc. These have a considerable effect of preventing sedimentation of anhydrous salt during the melting and solidification cycle, and therefore the decrease in heat storage amount is relatively small.

(Problems to be Solved by the Invention) In the method using the crosslinked polymer described above, a mixture of a crosslinkable, water-soluble polymer and sodium sulfate, etc. is mixed with water, or a crosslinkable, water-soluble polymer or a water-soluble polymer is mixed with water. Operations such as dissolving or dispersing the swellable crosslinked polymer in a melt of hydrated salt of sodium sulfate, etc. are performed. At this time, if a large amount of polymer is brought into contact with water at once, only the surface will become hydrated and become water impermeable, so-called mako, so it is necessary to bring the polymer into contact with water little by little while stirring vigorously. There is. This makes the above-mentioned mixing operation complicated; and requires special equipment, which is industrially disadvantageous.

In addition, the liquid obtained by the above mixing operation is extremely viscous or jelly-like solid, and in order to divide it and fill it into containers, a special filling machine that applies pressure is required, making filling and cleaning operations complicated. It is.

The present invention provides a method for producing a heat storage material that uses sodium sulfate decahydrate as a main material, does not deteriorate in performance even after repeated cycles of melting and solidification, and does not have the above-mentioned problems in the production process.

(Means for Solving the Problems) The present invention provides a method for solving the problems in the presence of sodium sulfate or its eutectic salt, water, and a polymerization initiator (a small amount selected from unsaturated carboxylic acids, organic unsaturated sulfonic acids, and salts thereof). A heat storage material comprising a composition of a hydrate of sodium sulfate or its eutectic salt and a crosslinked polymer, characterized by polymerizing one type of monomer and two types of polyfunctional monomers. This is the manufacturing method.

Sodium sulfate or its eutectic salt and water serve as a phase change heat storage medium. Substances that form eutectic salts with sodium sulfate are sodium chloride, potassium chloride, sodium nitrate,
Known materials such as potassium nitrate, magnesium sulfate, and urea can be used. These ratios are 0.2 to 1.0 mol per mol of sodium sulfate.

The eutectic salt has the effect of lowering the melting point compared to sodium sulfate alone.

The amount of water is 10 to 1 mole of sodium sulfate, including crystal water.
It is about 15 moles. 10 moles is the theoretical amount of sodium sulfate decahydrate, and if it exceeds 15 moles, it will simply be excessive and the performance of the heat storage medium will deteriorate.

Unsaturated carboxylic acids include acrylic acid, methacrylic acid,
Examples include hydroxyethyl acrylic acid and itaconic acid.

As the organic unsaturated sulfonic acid, 2-acrylamide-2
Examples include -methylpropanesulfonic acid, P-styrenesulfonic acid, sulfoethyl methacrylate, allylsulfonic acid, metaallylsulfonic acid, and the like.

Salts of unsaturated carboxylic acids and organic unsaturated sulfonic acids include those easily soluble in water, such as their alkali metal salts or ammonium salts.

It is also possible to use unsaturated amides copolymerizable with these monomers.

Acrylamide or methacrylamide is used as the unsaturated amide.

The amount of these monomers used is 1 chill 1 for the entire heat storage material.
0%, preferably 2% to 5%. If it is less than 1 ml, the viscosity will be low and the effect of preventing the precipitation of anhydrous sodium sulfate caused by phase change will be reduced. Also, if the concentration is higher than necessary, the amount of heat storage will decrease.

Polyfunctional monomers are used to crosslink the polymer.

Specifically, N,N'-methylenebisacrylamide, N
, N'-methylenebismethacrylamide, N, N'-
Examples include dimethylenebisacrylamide and N,N'-dimethylenebismethacrylamide. The amount used is in the range of 0.1% to 1%, preferably 0.05 to 0.5%. If it is less than 0.01%, the crosslinking effect will be poor, and if it is more than 1%, the effect commensurate with the added wind will not be obtained, so it is preferable. do not have.

Examples of polymerization initiators include diacyl peroxides such as acetyl peroxide, lauroyl peroxide, and benzoyl peroxide; hydroperoxides such as cumene hydroperoxide;
Commonly known radical polymerization initiators such as alkyl peroxides such as ert-butylheroxide; ammonium or potassium beroxonisulfate, hydrogen peroxide, and 2,2-azobisisobutyronitrile are used. Among these, redox polymerization initiators are preferred because they are active at relatively low temperatures.

Among the commonly known redox polymerization initiators preferably used in the present invention, water-soluble ones are used.

Oxidizing agents include ammonium or potassium peroxonisulfate, hydrogen peroxide, etc., and reducing agents include sodium thiosulfate, sodium sulfite, ferrous sulfate, and the like.

The crosslinking polymerization temperature is higher than the melting point of sodium sulfate decahydrate or its eutectic salt, and is usually carried out at 20 to 50°C.

A redox polymerization initiator exhibits polymerization activity in a relatively short time when the constituent oxidizing agent and reducing agent are mixed. After the polymerization activity is developed, it is deactivated when it comes into contact with oxygen in the air.

Therefore, after mixing the two, it is necessary to quickly deliver the mixture to a container for polymerization while avoiding contact with air as much as possible.

There are many ways to implement the method of the invention. For example, there is a method in which polymerization is carried out in a relatively large container, and a small amount of the produced heat storage material is filled into a container that constitutes a heat storage portion of a heating device.

A large container to be polymerized is replaced with nitrogen gas in advance, and the raw materials are mixed and polymerized.

In the present invention, since a cross-linked polymer or the like is not used as a raw material and its monomer is used, the mixing operation is easy.

There is also a method in which polymerization is carried out in a heat storage container such as a heating device.

The features of the invention are particularly well demonstrated in this method.

In the present invention, since a monomer rather than a crosslinked polymer is used as a starting material, the mixed material before polymerization is a liquid composition with low viscosity.

Therefore, mixed materials can be easily poured into containers even if the containers have a large number of complicated shapes. By polymerizing inside the container, the heat storage material, which is a viscous liquid or a jelly-like solid, can be easily stored in a complicated-shaped container.

Furthermore, since a crosslinked polymer or the like is not used as a starting material, the mixing operation of the materials is easy.

When a container is filled with a mixed material and polymerization is carried out, it is not necessarily necessary to replace the inside of the container with nitrogen.

In order to inject the liquid composition before polymerization into the container containing the heat storage material, if a redox initiator, for example, is used as a polymerization initiator, the oxidizing agent and the reducing agent are continuously injected in the distribution system of the composition. It is preferable to pour while mixing.

For example, a method in which an oxidizing agent and a reducing agent are separately added to a liquid composition of sodium sulfate or its eutectic salt, water, etc., and monomers during injection into a container, and a method in which an oxidizing agent or a reducing agent is added to the liquid composition. A method in which one of the two is dissolved and the other is added during injection into a container; a method in which the liquid composition is divided, an oxidizing agent is dissolved in one and a reducing agent is dissolved in the other, and the injection route into the container is There is a method in which the two liquids are mixed by colliding with each other, and then poured into a container.

In order to achieve more thorough mixing, it is also conceivable to insert an in-line mixer into the liquid flow path.

In the method of the present invention, after the mixed raw materials are poured into the container, the anhydrous sodium sulfate and other additives are prevented from settling and separating in the container until the polymerization reaction of the monomers progresses and the viscosity increases. It is also a preferable method to increase the viscosity of the aqueous medium by adding a binder in advance. As the thickening agent used for this purpose, various well-known thickening agents are used, such as fumed silica, wet fine powder silica,
These include inorganic materials such as various clays, and water-soluble polymers such as sodium polyacrylate. The amount used is about 0.1 to 7%, and the amount is such that the viscosity is reduced by 49% to prevent precipitation of anhydrous sodium sulfate in a short period of time until monomer polymerization and crosslinking reaction progress and the viscosity increases. Good to have.

A supercooling inhibitor is generally added to the heat storage material.

In the method of the present invention, the supercooling inhibitor may be added in advance to the liquid mixture before polymerization, or may be added after polymerization. However, if polymerization is carried out in a container that will ultimately house the heat storage material, it is necessary to add it to the mixed solution before polymerization.

It is well known that sodium tetraborate decahydrate is effective as a supercooling inhibitor. The amount used is about 2 to 5% of the total heat storage material, and the amount added is sufficient as long as it is at least the saturation solubility in the aqueous medium within the operating temperature range. pH at which sodium tetraborate decahydrate exists stably in an aqueous medium
Since the range is neutral to basic, if the monomer or polymer becomes acidic, it is desirable to neutralize it with an alkali in advance.

(Example) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the same extent by these Examples.

Example 1 A solution of acrylic acid neutralized to pH 7.5 with an aqueous solution of caustic soda (sodium acrylate lQw
t%") 150, add 150.8% water to F, add 3
N,N-methylenebisacrylamide 0 under stirring at 0°C.
．． 7511 and anhydrous sodium sulfate 177.41,
Sodium chloride 2'1.9. F.

15 I of sodium tetraborate decahydrate and 251 fine silica powder (Tokusil ■-P manufactured by Tokuyama Soda Co., Ltd.) were added to obtain a homogeneous mixture without sedimentation. This mixture was divided into two parts, one containing ammonium beroxonisulfate o, s, p.

After adding and mixing 0.5 F of sodium thiosulfate pentahydrate to the other side, each was flowed out from a separate flow path, and in the middle, both liquid streams were collided and mixed to form a 40 x 800 rtr.
It was poured into a polyethylene bag of 1.5 m. When this product was suspended in an atmosphere at 40°C and observed after 1 hour, it was found that crosslinking polymerization had progressed and it had become a uniform jelly-like elastic polymer.

This polymer 50I was placed in a glass cylinder of izf 30 x 100 wm, and a temperature history was given by repeating a cycle of increasing and decreasing the temperature between 40°C and 10°C. This product underwent a phase change at about 28°C. This material remained stable even after a thermal history of 100 cycles, and no phase separation phenomenon was observed.

Example 2 500 parts by weight of the mixture prepared in the same manner as in Example 1 was divided into two parts, and one part was mixed with 0.5 parts of ammonium beloxonisulfate. F,
Add 0.51 sodium sulfite to the other, 30
After stirring and mixing for a minute, each liquid flowed out from a separate flow path, and the two liquid streams were collided and mixed in the middle.
injected into a polyethylene bag. When this product was suspended in an atmosphere at 40°C, it became a uniform jelly-like elastic crosslinked polymer within 10 minutes. The obtained polymer was treated in the same manner as in Example 1.
No phase separation was observed even after a temperature history of 00 cycles was given.

Example 3 A solution of acrylic acid neutralized to pH 7.5 with an aqueous solution of caustic soda (sodium acrylate iowt s > i
Add 195.8 F of water and F to OO #, and while stirring at 30°C in the atmosphere, add 5 Jl of acrylamide, 0.75 F of N,N-methylenebisacrylamide, O of sodium sulfite,
s Ii was dissolved. To this solution, add 1 anhydrous sodium sulfate 17'1.4 / 1 sodium chloride 21.9 Jr 1 sodium tetraborate decahydrate 15 JI and silica fine powder (Tokusil ■-P Tokuyama Soda ■) 25, F to form a non-sedimentable solution. A homogeneous mixture was obtained. Divide this into two parts, and divide one half into 0.5% ammonium beroxonisulfate. f. Add and mix 0.5 F of sodium thiosulfate pentahydrate to the other, let each flow out from a separate flow path, collide and mix both liquid streams in the middle, pour into a polyethylene bag, and store at 40°C. I put it under the atmosphere. When observed after about 10 minutes, it was found to be a uniform jelly-like elastic polymer.

Even when this polymer was subjected to a temperature history of 100 cycles in the same manner as in Example 1, no phase separation was observed.

Example 4 Take 10% sodium acrylate solution 3 (1) in a 100-cm beaker, add 1.321 ml of 2-acrylamido-2-methylpropanesulfonic acid, dissolve it, and dilute with caustic soda.
H7.37 and water was added to bring the total volume to 61.6F.

Add 0.1 N,N-methylenebisacrylamide to this solution.
5 F and 0.1 g of sodium sulfite were dissolved, and 35.5 F of anhydrous sodium sulfate, 4.41 sodium chloride, and 3 I of sodium tetraborate decahydrate were added to the suspension under stirring in the air at 30°C, and 0.0 g of ammonium beroxonisulfate was added to the suspension. .1F,
When 0.11 of sodium thiosulfate pentahydrate was added, it rapidly polymerized after 15 seconds to form a uniform jelly-like elastic polymer.

This polymer was subjected to a temperature history of 100 cycles in the same manner as in Example 1, but no phase separation was observed.

Comparative Example 1 10% sodium acrylate prepared in the same manner as Example 1
Solution 30. 30.2 Ii of water was added to F and N2 was blown into it. This solution was heated to 30°C and heated to 35.5°F of anhydrous sodium sulfate while stirring.

4.4 J' of sodium chloride and 31 I of sodium tetraborate decahydrate were mixed. Add N to this solution.

Under a stream of air, 0.11 ji of ammonium beroxonisulfate and 0.1 ji of sodium thiosulfate pentahydrate were added and stirred. After about 3 minutes, the viscosity increased by one degree, but no increase in viscosity was observed even after continued stirring, and a phase separation phenomenon was observed when stirring was stopped.

(This example is an example in which a polyfunctional monomer as a crosslinking agent is not used.) Comparative Example 2 100 - Water 57.2. Add 0.2% of N,N-methylenebisacrylamide while stirring at 30°C. F,
Acrylamide 3.011, sodium sulfite 0.1
1 was added and dissolved to obtain a clear solution. Add 35% of anhydrous sodium sulfate to this solution. ! After adding Ml, 4.4 g of sodium chloride and 3 g of sodium tetraborate decahydrate, 0.11 g of ammonium beloxonisulfate and 0.1 g of sodium thiosulfate pentahydrate were added. After about 10 seconds, the inside of the system became cloudy and polymerized, but an elastic polymer was not formed, and separation of the polymer and aqueous phase was observed.

(This example is an example where the cross-linked polymer is different from that of the present invention.) (Effects of the invention) According to the method for producing a heat storage material of the present invention, the mixed material before polymerization is in the state of a monomer solution. It has the advantage that it does not require anything to handle. This significantly improves the productivity of the heat storage material. Moreover, the polymerization product is a water-swellable crosslinked polymer, which suppresses a decrease in the amount of heat storage during the melting and solidification cycles, and has excellent long-term stability as a heat storage material.

The heat storage material produced by the method of the present invention can be combined with a solar collector or a heating element that uses late-night electricity,
Used in heat storage parts, etc. that make up energy-saving derooming systems.

Claims (2)

[Claims] (1) At least one monomer selected from unsaturated carboxylic acids, organic unsaturated sulfonic acids, and salts thereof in the presence of sodium sulfate or its eutectic salt, water, and a polymerization initiator;
A method for producing a heat storage material comprising a composition of a hydrate of sodium sulfate or a eutectic salt thereof and a crosslinked polymer, the method comprising polymerizing the composition with a polyfunctional monomer. (2) The method according to claim 1, wherein the polymerization initiator is a redox polymerization initiator.