【発明の詳細な説明】
本発明は硫酸ナトリウム10水塩を主体とする蓄
熱材組成物に関するもので凝固・放熱時に際して
の相分離現象を防止し、長期に亘つて寿命を保持
するなど、蓄熱性能を改善したものである。
従来、太陽熱冷暖房や給湯用に使用されている
蓄熱には主として水の顕熱を利用した方法が用い
られているが、この方法では、蓄熱装置の大型化
が必要であり、また熱の放出と共に蓄熱材自体の
温度が低下してしまう欠点がある。これに対し潜
熱を利用する方法には、有機の結晶性物質や無機
水和温を用いるものが例として挙げられている。
この方法は原理的には、物質の固・液相間の相変
化現象を利用するため、その物質に固有の一定温
度で熱の放出が可能でこれに伴う蓄熱材の温度変
化が程んど無く、また顕熱に比して体積（重量）
当りの熱量が大きいので蓄熱装置の小型化が可能
である等の利点がある。
本発明は、無機水和塩物質の融解潜熱を利用し
て蓄熱する技術、特に安価で融解温度域が太陽熱
空調システムや給湯用に適しており、蓄熱量も約
60cal／grと大きい硫酸ナトリウム10水塩を蓄熱
材として長期間使用可能のように改質する技術に
関するものである。
硫酸ナトリウム10水塩（以下、Na2SO4・
10H2Oと記す）は、石油脱硫時の副産物として
大量かつ安価に得られ、保有蓄熱量も相対的に大
きいが、その融点は包晶点であり、蓄放熱のくり
返しと共に次第に２相に分離し、未満解結晶が器
底に沈降する相分離現象を起すため潜熱蓄熱材と
しての機能を果し得ない欠点がある。
本発明は、相分離防止剤として酸性白土とＯ／
Ｗ型エマルジヨンラテツクスの混合物を用いるこ
とにより、従来の粘度類物質を使用したものより
も更に相分離防止効果を向上させたもので以下に
本発明の詳細を記す。
一般に相分離現象は、包晶点系物質に特有な現
象で、このため潜熱型熱材への応用が著るしく制
約されて来た。その代表的なNa2SO4・10H2O
は、吸熱融解時に全体の約30％弱がNa2SO4（無
水物結晶）となり、残りのNa2SO4を含む水溶液
と２相に分離する。放熱・凝固時では分離した２
時間で反応させて、Na2SO4・10H2Oを生成せね
ばならないが、この逆反応は水和反応のため極め
て遅く、更に凝固時の過冷却現象のため一層遅延
してしまう。このため凝固時の放熱量は大巾に減
少して蓄熱材としての機能は全く失われてしま
う。これまで相分離現象を防止するために、チキ
ントロピツクな物質を混ぜて全体を均一に保持す
るなどの方法が採られて来た。例として、白土類
の一種であるアタパルジヤイトを添加する方法が
ある。この物質は吸水性が極めて大きくNaイオ
ンに配位した水分子を吸着してNa2SO4×10H2O
を包み込み相分離の防止に寄与しているものと思
われる。しかしアタパルジヤイトは、同時に脱水
現象も起すので蓄放熱サイクルの繰返しと共に吸
着した水分子を次第に離脱する。このため条件に
もよるが、一般は数10回のサイクル繰返し後に相
分離による沈澱物が生成して放熱量が低下する。
即ちアタパルジヤイトの相分離防止能力は短期間
に限られたものと見做すことが出来る。太陽熱空
間システムや給湯用に用いられる蓄熱材は少くと
も10年以上の使用に耐えるものが要求され、途中
で交換するにしても数年の寿命が必要でありアタ
パルジヤイトによる相分離防止策はこの要求に答
えられない。
本発明者らは、長期に亘る蓄放熱のくり返しで
も相分離現象を発生せず、従つて寿命の長い相分
離防止剤の検索を行つて来たが、安価で入手容易
の酸性白土と乳化重合した合成樹脂エマルジヨン
ラテツクスの混合物が極めて有効であることを見
出した。
酸性白土は３層構造を有するモンモリロナイト
系粘度を主成分とする吸着性の極めて強い多孔性
の微粉末物質でNa2SO4分子周辺に配位した水分
子と層間のH+イオンが強固に結合・吸着する。
また、Ｏ／Ｗ型合成樹脂エマルジヨンは水分子を
吸着結合した酸性白土粒子とその親水性基部分で
結合して酸性白土粒子間の結合剤として働き、全
体として弱いゲル構造を構成する。このことは酸
性白土がエマルジヨンラテツクスの増粘作用を有
することからもうなずける。使用するエマルジヨ
ンラテツクスの乳化剤はノニオン系またはアニオ
ン系のもの何れでもよいが酸性白土ではアニオン
系のものが好ましい。また合成樹脂は種類は問わ
ないがエマルジヨン粒子径は数ミクロン以下のも
のがよい。つまり、酸性白土とエマルジヨンラテ
ツクスは、Na2SO4・10H2Oの相分離、沈降現象
を弱いゲル構造を構成することにより２重に防止
する作用を有する。
次に本発明の実施例を記す。
実施例
Na2SO4・10H2O45grに硼砂1.5gr、酸性白土
（200メツシユ通過85％以上のもの）6gr、スチレ
ンアクリル共重合エマルジヨン（昭和高分子(株)製
ポリゾールCA−Ｆ、アニオン系濃度45％）4grを
加え本試料を調整した。別に比較試料として、(A)
Na2SO4・10H2O50grに硼砂2grを加えたもの。
(B)(A)試料に更にアタパルジヤイト5grを加えたも
の２種を調整した。これらをCC熱電対を挿入し
たガラス製試験管に入れて密栓し、50℃の湯浴中
に浸漬して一様に融解・吸熱させた後、1000mlの
水れ入れたジユワーびん中に浸漬して放熱させ、
蓄熱材と水温変化を記録・測定し放熱量を求め
た。この蓄・放熱サイクルをくり返して放熱の低
下率、凝固開始温度および目視による相分離現象
の進行度を測定追跡した。
結果を表−１に示す。本試料は蓄熱材含有率が
小さいので初回の放熱量は少ないが60サイクルで
も90％を維持しているが比較試料は共に初回放熱
量は大きいがサイクル数の増加共に低下率が大と
なり、また、相分離現象の発生が見られた。ま
た、40サイクル時の凝固開始温度（発核温度）
は、(A)のNa2SO4・10H2Oの約30℃に対して他試
料共大差ない。この事は使用した相分離防止剤
は、過冷現象に大きく関与しないことを示してい
る。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage material composition mainly composed of sodium sulfate decahydrate. It has improved performance. Conventionally, methods that utilize the sensible heat of water have been mainly used for heat storage used for solar heating and cooling and hot water supply, but this method requires a larger heat storage device and also increases energy consumption while releasing heat. There is a drawback that the temperature of the heat storage material itself decreases. On the other hand, examples of methods using latent heat include methods using organic crystalline substances and inorganic hydration temperatures.
In principle, this method utilizes the phase change phenomenon between the solid and liquid phases of a substance, so it is possible to release heat at a constant temperature unique to the substance, and the accompanying temperature change in the heat storage material is moderate. There is no volume (weight) compared to sensible heat.
Since the amount of heat per unit is large, there are advantages such as the ability to downsize the heat storage device. The present invention is a technology for storing heat using the latent heat of fusion of an inorganic hydrated salt substance, which is particularly inexpensive, has a melting temperature range suitable for solar air conditioning systems and hot water supply, and has a heat storage capacity of approximately
This relates to technology for modifying sodium sulfate decahydrate, which has a large capacity of 60 cal/gr, so that it can be used as a heat storage material for a long period of time. Sodium sulfate decahydrate (hereinafter referred to as Na 2 SO 4
10H 2 O) is obtained in large quantities and at low cost as a by-product during petroleum desulfurization, and has a relatively large amount of heat storage, but its melting point is the peritectic point, and it gradually separates into two phases with repeated heat storage and release. However, it has the disadvantage that it cannot function as a latent heat storage material because it causes a phase separation phenomenon in which undissolved crystals settle to the bottom of the vessel. The present invention uses acid clay and O/O as a phase separation inhibitor.
By using a mixture of W-type emulsion latexes, the effect of preventing phase separation is further improved than that using conventional viscous substances.The details of the present invention will be described below. In general, phase separation is a phenomenon unique to peritectic point-based materials, and for this reason, its application to latent heat type heating materials has been severely restricted. The typical Na 2 SO 4・10H 2 O
During endothermic melting, approximately 30% of the total becomes Na 2 SO 4 (anhydride crystals) and separates into two phases with the remaining aqueous solution containing Na 2 SO 4 . During heat dissipation and solidification, the two separated
Na 2 SO 4 .10H 2 O must be produced by the reaction over a period of time, but this reverse reaction is extremely slow due to the hydration reaction, and further delayed due to the supercooling phenomenon during solidification. For this reason, the amount of heat released during solidification is greatly reduced, and the function as a heat storage material is completely lost. In order to prevent the phase separation phenomenon, methods such as mixing chicken tropic substances to maintain uniformity as a whole have been used so far. For example, there is a method of adding attapulgite, which is a type of white earth. This substance has extremely high water absorption and adsorbs water molecules coordinated to Na ions to form Na 2 SO 4 ×10H 2 O.
It is thought that this contributes to the prevention of phase separation by enveloping the However, since attapulgite also causes a dehydration phenomenon, the adsorbed water molecules are gradually released as the heat storage/release cycle is repeated. For this reason, although it depends on the conditions, in general, after several dozen cycles, a precipitate is formed due to phase separation, and the amount of heat dissipated decreases.
That is, it can be considered that attapulgite's ability to prevent phase separation is limited to a short period of time. Heat storage materials used in solar thermal space systems and hot water supply systems are required to withstand use for at least 10 years, and even if they are replaced midway through, they require a lifespan of several years, and attapulgite's phase separation prevention measure meets this requirement. I can't answer. The present inventors have been searching for a phase separation inhibitor that does not cause phase separation even after repeated heat storage and release over a long period of time and has a long lifespan. It has been found that a mixture of synthetic resin emulsion latexes prepared by the present invention is extremely effective. Acid clay is a highly adsorbent porous fine powder material whose main component is montmorillonite viscosity with a three-layer structure. Water molecules coordinated around Na 2 SO 4 molecules and H + ions between the layers are tightly bound together.・Adsorbs.
Further, the O/W type synthetic resin emulsion binds the acid clay particles to which water molecules are adsorbed and bonded through their hydrophilic group portions, acts as a binder between the acid clay particles, and forms a weak gel structure as a whole. This can be understood from the fact that acid clay has a thickening effect on emulsion latex. The emulsifier used in the emulsion latex may be either nonionic or anionic, but for acid clay, anionic emulsifiers are preferred. Although the synthetic resin may be of any type, it is preferable that the emulsion particle size be several microns or less. In other words, acid clay and emulsion latex have a double effect of preventing phase separation and sedimentation of Na 2 SO 4 .10H 2 O by forming a weak gel structure. Next, examples of the present invention will be described. Example Na2SO4・10H2O45gr , borax 1.5gr , acid clay (200 mesh passing 85% or more) 6gr, styrene-acrylic copolymer emulsion (Showa Kobunshi Co., Ltd. Polysol CA-F, anionic concentration) This sample was prepared by adding 4gr (45%). Separately, as a comparison sample, (A)
Na 2 SO 4・10H 2 O 50gr with borax 2gr added.
(B) Two types of samples were prepared by adding 5 gr of attapulgite to the sample of (A). These were placed in a glass test tube into which a CC thermocouple was inserted, sealed tightly, and immersed in a 50℃ water bath to uniformly melt and absorb heat, and then immersed in a Juwar bottle containing 1000ml of water. to dissipate heat,
Changes in heat storage material and water temperature were recorded and measured to determine the amount of heat released. This heat storage/radiation cycle was repeated to measure and track the rate of decrease in heat radiation, solidification initiation temperature, and visual observation of the progress of the phase separation phenomenon. The results are shown in Table-1. This sample has a small heat storage material content, so the initial heat release amount is small, but it maintains 90% even after 60 cycles, whereas the comparison samples both have a large initial heat release amount, but the rate of decrease becomes larger as the number of cycles increases. , the occurrence of a phase separation phenomenon was observed. Also, solidification start temperature (nucleation temperature) at 40 cycles
is about 30°C for Na 2 SO 4 .10H 2 O in (A), but there is no big difference between the other samples. This indicates that the phase separation inhibitor used does not significantly contribute to the supercooling phenomenon. 【table】