JPS5918785A - Manufacture of heat storage composition - Google Patents

Abstract

PURPOSE:To obtain titled composition free from supercooling and solid-liquid separation over along period, by applying,as a thickening agent, a specifically- prepared jelly-like hydrous silicic acid to a mixture consisting of a hydrous salt having potential to reveal latent heat due to solid-liquid phase transformation and an antisupercooling agent. CONSTITUTION:The objective composition can be obtained by incorporating a mixture consisting of (A) a hydrous salt with potential to reveal latent heat due to solid-liquid phase transformation (e.g., Na2SO4.10H2O) and (B) an antisupercooling agent (e.g., Na2B4O7.10H2O) with (C) as a thickening agent, 2-10 (pref. 2.5-8.0)wt% (as SiO2) of a jelly-like hydrous silicic acid. The component (C) can be prepared through the following process: preferably, water glass containing 2-20wt% of an alkali silicate and 2-50% H2SO4 are mixed at 0-10 deg.C to obtain a clear salution of a pH 5-9, which is then left to stand, or heated 40-100 deg.C for continuous dehydration.

Description

[Detailed description of the invention] The present invention relates to a method for producing a heat storage composition.

In particular, the present invention relates to a method for producing a heat storage composition using jelly-like hydrous silicic acid produced by a specific method as a thickening agent in the heat storage composition.

The idea of storing thermal energy by utilizing a hydrous salt compound having latent heat due to phase changes of melting and solidification has been known for a long time. According to the study results reported so far, in many cases this method does not occur at the same point, and a so-called supercooling phenomenon occurs. Therefore, it is necessary to prevent supercooling in order to cause a phase change with a certain width. In addition, as a method for preventing supercooling of the cartilage, for example, N
#ll as a supercooling inhibitor for a25o4” 10H20
A method is described in which I sand (Na2B4O7.10H20) is used as an additive. This Na2B407-10H
The crystal of 2O is in an epitaxial relationship with the crystal of Na25o4"l0H20, and the crystal of Na2B4O7'l0
There is a report that the presence of H20 crystals in a supersaturated solution of Na2SO4''lOH2O promotes crystal precipitation of Na25o, 10H20 and is effective in preventing supercooling (Industrial and Engineering Chemistry).
ng chemistry Vol 1141, 73K
~/3/θpage/wa3'2) oAlso, Ba(OH)2. Ba
(OH)2-8H20 etc. (Tokuko Sho J
J-93; Publication No. 96), same < BaI2. Ba
A method using SO4 etc. (%Kaisho 33; -10.2
47j) is also known. These methods are eac
There are some substances that do not have an epitaxial relationship with h2.6H20, and the relationship between crystal form and nucleation is not necessarily clear.

The problem with the third method is that the anhydrous salt produced during the phase change sediments, causing a phenomenon of solid separation. For example, Na2504-10H20 is 3.2. It decomposes at 'l''C to produce 2jξ(hydrated salt, but this anhydrous salt settles to the bottom of the liquid. When this is cooled to below Jlj,/l''C, the anhydrous salt in the surface layer condenses and becomes Na2SO4・10H,,O, but since these crystals cover the surface, condensation of anhydrous salt at the bottom is suppressed.Therefore, it is necessary to prevent sedimentation of anhydrous salt.Generally, to prevent sedimentation, However, as a heat storage material, long-term stability must be satisfied.Organic materials such as natural rubber and synthetic polymers are gradually hydrolyzed, or are absorbed into living organisms. There is a possibility that
I don't like it.

For inorganic materials, a method using a porous support (Tokuko Sho! 3)
-/S/θg4-3 Publication), a method of using a clay-type substance having Thess-like particles as a thixotropic agent (Japanese Patent Application Laid-Open No. 53-3μ
G7 Publication), method using ultrafine silicic anhydride (S10□) powder (Chemical Week Chemical Co'ee
k J month/day issue 3g page, /ng) etc. have been proposed. However, these are 1. They are either natural products that cannot be produced or are expensive, and there are problems in putting them into practical use economically from the point of view of energy conservation, which is the original purpose of heat storage materials.

Therefore, an object of the present invention is to provide a heat storage composition that does not cause supercooling phenomenon and does not cause solid-liquid separation phenomenon during the period.

In view of the above-mentioned problems, the present inventors have conducted intensive studies to achieve the first object of the present invention in a method for producing a latent heat-utilizing heat storage composition. It has been found that these problems can be solved by using the first compound as a thickening agent. By the way, there have been attempts to use hydrous silicic acid, and for example, in the above-mentioned Japanese Unexamined Patent Application Publication No. 53-3-3GAg7, the formation of silicic acid gel was so rapid that it became an obstacle when transferring the composition to a container. It is stated that this is the case, but it has not been put into practical use. The present inventors have studied various methods for producing hydrated silicic acid,
It was discovered that only hydrated silicic acid jelly produced by a specific method is effective as a thickening agent, leading to the completion of the present invention.

That is, the present invention provides a method for producing a heat storage composition comprising a hydrated salt compound having latent heat due to solid/liquid phase change, a supercooling inhibitor, and a thickening agent, which includes mixing an alkali silicate and an acid as the thickening agent. This is a method for producing a heat storage composition, which comprises using a jelly-like hydrated silicic acid obtained by producing a transparent solution with a pH of ~ - and turning it into a jelly.

Since hydrated silicic acid is an inorganic substance, it is an excellent thickening agent for microorganisms and the like.

As for the production method of hydrous silicic acid, for example, a method of mixing an aqueous sodium silicate solution and an inorganic acid has been known for a long time. Water glass is the most commonly used sodium silicate aqueous solution, but sodium silicate in the aqueous solution is dissolved as a long chain molecule with a main chain of 18i-0-8i-0- bonds. So, the sodium ion is ei -0
It is ionically dissociated in the form of eNa■. When sodium silicate aqueous solution and acid are mixed, Na■ is replaced by ■1■ and 5
It becomes i-OH, and a condensation reaction between long chain molecules occurs to generate a three-dimensional network structure. This phenomenon is called gelation.

If the concentration of sodium silicate or citric acid is high, a gel will form almost simultaneously when both solutions are mixed, and will settle to the bottom of the solution.If the concentration of the solution is low, it will take an hour after both solutions are mixed. A gel will later form. When the liquid concentration is appropriate, a network structure spreads throughout the liquid9, producing an elastic gel containing a large amount of water, which is called jelly. The gelation time depends on the liquid concentration,
pH1 varies significantly depending on temperature, mixing order of liquids, etc. Journal of Physical Chemistry (Jaurna)
l of physica fl che uistry)
vol,! ;'I gθg page /wajθ According to the diagram, pH = 7. (E3'xO2 at /
/ ~ 3, the gelation time when ゛j weight it % is 3θ minutes ~
/min, and the higher the S10□ concentration, the shorter the gelation time.

In addition, at 5i023% by weight, the gelation time is θθ, 30, s, /, respectively when −=ri, jS6.7, and ri.
A, /, Ge, 70 minutes, and there is a minimum value of the gelation time around pH 7-g. Therefore, controlling these conditions is important for gel production. On the other hand, the rate of condensation reaction of long-chain molecules is not extremely high at pH 7 to g, as reported in Japan Chemical Journal Vol. 77, 937-9j? It is described on page (/separate 1).

According to this, the condensation reaction rate increases as the pH increases. Si
Considering that the degree of dissolved M of O□ is higher in the higher pH range,
Since the condensation reaction is slow in the low pH range, 5 in.
2 It can be understood that because the solubility is low, the gelation time becomes minimum near neutrality.

In addition, Bulletin e of the Chemical Society
Bulletin of the C
Chemical Society of Jap8. n
) magazine Vol 3/, /39~/IIθ pages (/light g
), it is suggested that the particle size of hydrated silicic acid depends on the PTR produced, with independent fine particles produced in an acidic region, fine polymer particles produced in a weakly acidic region, and relatively large independent particles produced in a weakly alkaline region. Jelly with a network structure developed throughout the liquid contains a large amount of water, but when left for a long time or heated, the network gradually contracts and separates the water.

This is called syneresis. Water in jelly is classified into bound water bound to the gel as monohydration water or crystallization water, and free water as a solvent.

According to "Handbook of Water and Moisture", pages 9 to 9 (Kyoritsu Shuppan), bound water and free water can be distinguished by freezing at a temperature below 0°C, and free water Freezes, but bound water does not freeze easily. As a result of measurement by freezing method, the solid content/Kf/Kf is θ0%.
Ky, fruits and vegetables are said to have unfrozen water of θ, θA Ky. In addition, free water is strongly influenced by the gel network structure; for example, the water retention capacity of proteins (the ratio of free water to the total water content) reaches a minimum value in the case of bamboo and electricity, and increases in acidic and alkaline regions. are doing. Kneading reflects the pH dependence of the gel network structure.

Based on the above-mentioned conventional knowledge, the inventors of the present invention have repeatedly investigated the method for producing a hydrous silicic acid jelly that is effective as a thickening agent, and have discovered the following fact.

(1) Mixing an aqueous solution of sodium silicate and an acid with a relatively low concentration to obtain a clear solution and then making a jelly is effective as a thickening agent, but mixing a solution with a relatively high concentration If the conditions are such that a white gel is produced during mixing, the gel produced is not effective as a thickening agent.

(,2) When using solutions of the same concentration, it is easier to obtain a clear solution at a lower temperature.

(3) Those that form jelly on the acidic side have a certain effect as a clarifying agent, but there is a change over time.

Jelly produced under weakly acidic or neutral conditions is stable.

(lI) The produced jelly is left to stand for a long time, but when heated, water is released by the syneresis phenomenon. The effect as a thickening agent is greater if this separated water is removed, but 510
If the concentration of 2 is high, it is not necessarily necessary to remove it. On the other hand, if water is completely removed and the product is kept completely dry, it loses its effectiveness as a thickening agent. Furthermore, the effect is weakened even if 3A of extractable crab water is added after removing some of the water.

(J) The effective addition percentage as a thickening agent depends on the properties of the suspended matter and the degree of ♂λ, but it is usually 5in2 conversion'J,'? :, and requires a double M person or more.

The alkali silicate used in the present invention includes water glass,
Examples include sodium metasilicate and potassium metasilicate, but water glass is particularly often used industrially. The concentration of alkali silicate is 7 to 50% by weight, preferably β to −0%. As the acid, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as acetic acid can be used, but there are no particular limitations as long as the acidic substance can neutralize the alkali silicate. Sulfuric acid is particularly used industrially. The appropriate acid concentration is 7 to 760% by weight, preferably 2 to jθ weight ratio.

Although the order of mixing the alkali silicate and acid is not limited, it is easier to obtain a transparent solution by mixing by adding the alkali silicate to the acid. The mixing ratio of alkali silicate and acid must be within the range of pH=J to 2 after mixing. At this time, if the pH is below pHs, the condensation reaction rate of silicic acid is slow, resulting in insufficient particle growth and low effectiveness as a thickening agent, as well as the need for neutralization to form a composition. A pH of 9 or above is unsuitable because the condensation reaction rate of silicic acid is high, the particles become coarse, and the effect as a thickening agent is low.

The mixing temperature may be room temperature, but it is preferably 0 to 70°C because it is easier to obtain a transparent solution at a low temperature.

In order to turn a transparent solution into a jelly, it is sufficient to leave it at room temperature, and the temperature is not limited, but it may be heated to about θ~/θθ°C in order to continue the dehydration process. Alternatively, the clear solution may be stirred to form a jelly, or the clear solution may be allowed to stand still to form a jelly and then stirred (r ratio).

If the jelly is left to stand or heated, it will reach 100%.
It needs to be below ℃. /θθ°C or higher, there is a possibility that not only the free water in the jelly but also the bound water can be removed. Further, the amount of water removed must be greater than the amount of water separated from the jelly, and the residual H20/5102 molar ratio must be in the range of 80 or more. If the water is less than the mercury separated from the jelly, the separated water that was not removed will remain.
This is undesirable because it reduces its effectiveness as a thickening agent. The amount of water Nh removed from the jelly is determined by the degree of maturation of the jelly, for example, SiO□6.3
The amount of water separated when a jelly of 1 wt. [My φ
It is. Therefore, it cannot be fixed uniformly.

In addition, if the residual (120/5102 molar ratio) is less than 80, even the bound water of the hemihydrate silicic acid will be removed, which will destroy the gel network structure and lose its effectiveness as a thickening agent. Nice and cheap.

In order to use the dehydrated jelly as a thickening agent, it may be mixed with an anhydride of a hydrated salt compound and an anti-supercooling agent that absorbs latent heat due to solid/liquid phase change.

At this time, the moisture in the jelly and the above-mentioned anhydride produce a water utilization reaction in an appropriate temperature range. The effective addition amount as a thickening agent is solid/
Although it depends on the properties of the compound that has latent heat due to liquid phase change, it is 3 to 70 weight M% in terms of 5in2, preferably 3.5
~g% by weight is required. At this time, if the amount of the thickening agent is less than 2% by weight in terms of E (io. Unfavorable. The mixing with the above anhydride must be carried out at a temperature above the melting point of the hydrating agent of the compound. Below the melting point, a water utilization reaction will occur - the composition will solidify;
This is because mixing is not done sufficiently. The hydrated salt having latent heat due to solid/liquid phase change used in the present invention has a phase change temperature in the range of 0 to 700°C, and free water in the jelly freezes below θ°C. I don't like it, /
Exceeding θθ゛C is not preferable because bound water in the jelly may be removed. Such compounds include:
Na2SO4" 10H20, + 11a2S203", which has been known to be used for this type of purpose
5H20, CaCf12"6H20, etc. and their combination with Na0fl, xap, NH40A, MgO, Mg8
This includes mixtures with 04, etc.

Also, as a supercooling inhibitor, Na2SO4・10H2
For 0, Na2B4O711io H2O is triplet, for CaCf12-6H20, Ba, (OH)
An amount effective for each phase-change compound, such as 0.3 weight of 2.8H2Cl, is selected and used.

According to the present invention, by using hydrous silicic acid jelly as a thickening agent, it has become possible to inexpensively produce a heat storage material that is free from decomposition by microorganisms and has long-term stability. .

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example / 3.2% by weight H2SO into a /θθml glass beaker
4, 2/, 9? The mixture was cooled to 5°C, and a water glass solution containing commercially available water glass No. 3/3.777 and water 6'1.33 Y was added dropwise under stirring. The point at the end of dropping the water glass solution is 7. It was a clear solution.

After about 7 minutes, it became jelly-like.

Next, this jelly-like material was placed in a constant temperature dryer (go'c) and dehydrated and dried until it became 7θ1 (dehydration rate 6.g% by weight), and anhydrous Na28043A-31s S', Na0
fi Otsu θ62, Na2B4O7”1OH203-ooW
was added and mixed in a bath at 0°C. 5 in this composition
1o2 concentration is 3. It is the S heavy darkness.

The composition thus obtained is very viscous and q
O゛C: Floating ice after 0 cycles of joC,
No sedimentation of anhydrous No2So crystals was observed, and no change was observed in the melting and solidification subroutes.

Comparative Example / No. 3 water glass / 3.7 sol and water 3/, 33? in a 700 ml glass beaker. 1) at room temperature (26°C)
A portion of (/, 2.g2) is added dropwise to pH/θ,! At this point, the solution became jelly-like and no clear solution was obtained. Take over the upper Ncj RFJQ, I-, < 4 (i
ff 1 flight was dropped by 3j.

The obtained jelly-like material was placed in a dryer at a temperature of 11≦θ゛C, and dehydrated and dried until the temperature reached 7θ1 (dehydration rate/7./section).

Next, add anhydrous Na2SO43A to Shiro'htA example/dowa)
-3t El 5NaOnδ, 071, l+a2134
07-101120 J 9- was added to the jelly and mixed in a bath at θ°C.

The resulting composition was 1 in 11″J, 5 in 2J, j wc
%, there was no viscosity and the formation of floating ice was observed.

Example J /θθrnl 3% by weight Hal, u
Add JV, cool to 3°C, and stir for 3 minutes in a water glass/j
, 79y and water glass solution 7 are dropped into water 3, and sieved (j
, I got a transparent line. If you leave this liquid for about 7 minutes, it will turn into a jelly-like substance.

Next, add this jelly-like substance to 9! ;Put in a constant temperature dryer at 'C3
! ;, 9 ii' (dehydration rate 1./, 1 weight) 6%) Anhydrous Na2SO439,-'J y
%””p.

3-. 7tI? , Na2B4O7"1OH2037 was added and mixed in a bath at θ°C. The resulting composition was viscous and contained 51°C and 50%, and no phenomena such as the formation of floating ice or precipitation of anhydrous Na2SO4 were observed. I couldn't.

Example 3 /θθml Amount of disturbance θjM into the glass beaker HOI −? 4
．． Add moth 1, cool to s 'c, and add No. 3 water glass, No. 6 water glass 7, and water glass 3 while stirring. Drop the water glass solution of J1, p
A clear liquid of II A-g/θθ1 was obtained. If you leave this liquid for 70 seconds, it will turn into a jelly-like substance. Place in qsc constant temperature dryer; 7. // Dehydrate and dry until it becomes (dehydration rate/1.7.l1 weight-w%),
Anhydrous OaO/z 'I Og g and Byt (01()
2-gH,,OO,,3g was mixed in a bath at t toC.

The resulting composition was viscous and contained heavy IC, S, and tA, and even when cooled, floating ice was generated and CaCl2.zI (2
0 and 13n (OH)2 ・j? H20 sedimentation 1
: Couldn't see it.

Example q 100ml glass beaker JJ Nj? t%1(2B
O4, j+, 2. Add 28 pieces, cool to JC, and pour into a No. 3 water glass with stirring. 7./♂g was added dropwise to a water glass solution containing 9 g of At and u9 g of water, and the pH was adjusted to 7.7.
100g of clear liquid was obtained. If this liquid is left to stand for about 5 seconds, it will become jelly-like. Next, put this jelly-like material in a constant temperature dryer and dehydrate and dry it until it becomes VC (dehydration rate,!:
/, 4 heavy'r-A゛%) L, anhydrous Na2S2O3
, /, /, /J' g and Sr'504o, s g
1 and mixed in a bath of zOC. The resulting composition is S
It was viscous and contained % iO□j,t, and no floating ice was observed even during cooling, and precipitation of Na2S2O3., 5H20, and SrSO4 was not observed.

Comparative Example Jelly f prepared in the same manner as in Example/1 was dehydrated and dried in a 100C constant temperature dryer at a constant weight of 1.

4. Grind the whole thing in a mortar and use anhydrous N8□So4. ?
JJ&g1 water tI9. '73 g, Nap/g, 0
Otsuz, ! Ja2B407@10 H2O, 3,001
Add r and mix in a toc bath.

This composition contains 5 of J, gJTCk as in Example/.
Contains io2'6, but has almost no viscosity and is anhydrous N when cooled.
a Sedimentation of 2SO4 crystals was observed.

(/9 completed)

Claims (1)

[Claims] /) A method for producing a heat storage composition comprising a hydrated salt compound having latent heat due to solid/liquid phase change, an anti-supercooling agent, and a thickening agent, comprising an alkali silicate and an acid as the thickening agent. A clear solution of pH 3-2 is prepared by mixing the
A method for producing a heat storage composition, comprising using a jelly-like hydrous silicic acid obtained by jelly-forming the same. The method according to claim 1.