JP4436209B2 - Foamed silica gel and method for producing the same - Google Patents
Foamed silica gel and method for producing the same Download PDFInfo
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Description
本発明は、発泡シリカゲルに関し、特に断熱性コーティング材用硬化性組成物などに配合するフィラーとして適した発泡シリカゲル及びその製造方法に関する。 The present invention relates to a foamed silica gel, and more particularly to a foamed silica gel suitable as a filler to be blended in a curable composition for a heat-insulating coating material and a method for producing the same.
従来、多孔質物質であるシリカゲルを中空体とした中空シリカゲルとしては、シリカゲル粒子を原料としてこれを発泡させて中空シリカ球状体とすることが公知である。
これは、粉砕した粒径が300〜590μmのシリカゲルに、発泡助剤としてアルミナ粉末を10%添加して、電気炉において1100℃の温度で30分熱処理して中空シリカ発泡体を形成するものである(特許文献1参照。)。
Conventionally, as a hollow silica gel in which a silica gel, which is a porous material, is a hollow body, it is known that a silica gel particle is used as a raw material to foam it into a hollow silica sphere.
This is a method in which 10% alumina powder is added as a foaming aid to silica gel having a pulverized particle size of 300 to 590 μm and heat-treated at a temperature of 1100 ° C. for 30 minutes in an electric furnace to form a hollow silica foam. Yes (see Patent Document 1).
しかしながら、本発明者らが詳細に検討したところ、このように発泡剤としてアルミナ粉末を使用して得られる中空シリカ発泡体は、水に投入した場合、いったんは水に浮くものの、長時間は浮遊することができず、すぐに沈降してしまうものであることを確認した。すなわち、アルミナを発泡剤とした中空シリカ粒子の外側被膜(シェル)は、無孔質ではなく、実質的には多孔質である。また、その内部は中空とされているだけで、具体的な構造は不明である。 However, when the present inventors examined in detail, the hollow silica foam obtained by using alumina powder as a foaming agent in this way floats once in water, but floats for a long time. It was not possible to do so, and it was confirmed that it would settle immediately. That is, the outer coating (shell) of hollow silica particles using alumina as a foaming agent is not nonporous but substantially porous. Moreover, the inside is only made hollow and the specific structure is unknown.
本発明は、その粒子内部が単なる中空ではなく多孔質であって、これが緻密な被膜で覆われている新規な形態を有する発泡シリカゲル粒子を提供しようとするものである。 The present invention intends to provide expanded silica gel particles having a novel form in which the inside of the particles is not hollow but porous and is covered with a dense coating.
本発明者らは、かかる観点から鋭意検討した結果、シリカゲル粒子に微少量のナトリウム塩を存在させた状態で加熱することにより、意外なことに、当該ナトリウムが発泡助剤として作用し、このシリカゲルを効果的に発泡せしめることができること、及び、得られた発泡シリカゲルは、内部は中空ではなく、連続気泡からなる多孔質の状態であり、しかも、外壁は、完全に無孔質なシェルを有するものであることを見出した。本発明は、かかる知見に基づいてなされたものである。 As a result of intensive investigations from such a viewpoint, the present inventors surprisingly, by heating in a state where a small amount of sodium salt is present in the silica gel particles, the sodium acts as a foaming aid, and this silica gel And the obtained foamed silica gel is not hollow inside but in a porous state composed of open cells , and the outer wall has a completely non-porous shell. I found out that it was. The present invention has been made based on such knowledge.
A)本発明に従えば、以下の発泡シリカゲルが提供される。
〔1〕
その粒子内部は連続気泡からなる多孔質に形成され、粒子外表面全体が緻密な外被膜により覆われていることを特徴とする発泡シリカゲル。
A) According to the present invention, the following foamed silica gel is provided.
[1]
A foamed silica gel characterized in that the inside of the particle is formed into a porous body composed of open cells, and the entire outer surface of the particle is covered with a dense outer coating.
〔2〕
粒子中にナトリウムを0.003〜0.65質量%含有する〔1〕項に記載の発泡シリカゲル。
[2]
The foamed silica gel according to item [1], wherein the particles contain 0.003 to 0.65% by mass of sodium.
〔3〕
前記発泡シリカゲルが粒子径1.0〜10.0mmのものである〔1〕項又は〔2〕項に記載の発泡シリカゲル。
[3]
The foamed silica gel according to [1] or [2], wherein the foamed silica gel has a particle diameter of 1.0 to 10.0 mm.
〔4〕
前記発泡シリカゲルにおいて当該粒子の比重の平均値が0.05〜0.50である〔1〕項〜〔3〕項のいずれかに記載の発泡シリカゲル。
[4]
The foamed silica gel according to any one of [1] to [3], wherein an average value of specific gravity of the particles in the foamed silica gel is 0.05 to 0.50.
〔5〕
断熱性コーティング材用硬化性組成物又は断熱性硬化体に配合して使用する〔1〕項〜〔4〕項のいずれかに記載の発泡シリカゲル。
B)また本発明に従えば、以下の発泡シリカゲルの製造方法が提供される。
[5]
The foamed silica gel according to any one of [1] to [4], which is used by blending with a curable composition for a heat insulating coating material or a heat insulating cured body.
B) Moreover, according to this invention, the manufacturing method of the following foamed silica gel is provided.
〔6〕
硫酸ナトリウムを0.01〜2.00質量%含有した、粒子径0.5〜10.0mmのシリカゲルを焼成することを特徴とする〔1〕項〜〔5〕項のいずれかに記載の発泡シリカゲルの製造方法。
[6]
The foam according to any one of [1] to [5], wherein silica gel containing 0.01 to 2.00% by mass of sodium sulfate and having a particle diameter of 0.5 to 10.0 mm is fired. A method for producing silica gel.
〔7〕
前記シリカゲルが硫酸ナトリウムを0.01〜1.00質量%含有するものである〔6〕項に記載の発泡シリカゲルの製造方法。
[7]
Method for producing a foamed silica gel according to the sheet Rikageru is one containing 1.00 wt% 0.01 Sodium sulfate [6] Section.
〔8〕
前記シリカゲルを950〜1150℃で、0.05〜5時間焼成する〔6〕項又は〔7〕項に記載の発泡シリカゲルの製造方法。
C)さらに本発明に従えば、以下の断熱性コーティング材用硬化性組成物又は断熱性硬化体が提供される。
[8]
The method for producing foamed silica gel according to [6] or [7], wherein the silica gel is baked at 950 to 1150 ° C. for 0.05 to 5 hours.
C) Further, according to the present invention, the following curable composition for a heat insulating coating material or a heat insulating cured body is provided.
〔9〕
〔1〕項〜〔5〕項のいずれかに記載の発泡シリカゲル又は〔6〕項〜〔8〕項のいずれかの方法で得られた発泡シリカゲルを含有することを特徴とする断熱性コーティング材用硬化性組成物又は断熱性硬化体。
[9]
A heat-insulating coating material comprising the foamed silica gel according to any one of [1] to [5] or the foamed silica gel obtained by any one of the methods [6] to [8] Curable composition or heat-insulating cured product.
以下、本発明の好ましい実施の形態を詳細に説明する。
(発泡シリカゲル粒子)
本発明の発泡シリカゲル粒子は、その粒子内部は多孔質に形成され、また、粒子外表面全体が緻密な外被膜により覆われていることを特徴とする特異な形態を有する発泡シリカゲルである。
Hereinafter, preferred embodiments of the present invention will be described in detail.
(Foamed silica gel particles)
The foamed silica gel particle of the present invention is a foamed silica gel having a unique form characterized in that the inside of the particle is formed to be porous and the entire outer surface of the particle is covered with a dense outer coating.
すなわち、後に詳述するように、当該発泡シリカゲルは、粒子内部が単なる中空ではなく、発生ガスにより連続気泡に形成されている多孔質である点で、従来の内部が中空な中空シリカゲルと異なり、また、その外表面が、実質的に水等を通さない緻密な被膜に覆われている点で、アルミナ粉末を添加して発泡させたいわゆる中空シリカ球状体とも異なるものである。 That is, as will be described in detail later, the foamed silica gel is different from a hollow silica gel in which the interior is hollow in that the inside of the particles is not simply hollow, but is porous formed into open cells by the generated gas . Further, it is different from so-called hollow silica spheres, which are foamed by adding alumina powder, in that the outer surface is covered with a dense film that is substantially impermeable to water or the like.
このような、特異な形態を有する本発明の発泡シリカゲルは、発泡剤として硫酸ナトリウムを特定量含有せしめたシリカゲル粒子を焼成して、発泡せしめることにより製造されるものである。 The foamed silica gel of the present invention having such a specific form is produced by firing and foaming silica gel particles containing a specific amount of sodium sulfate as a foaming agent.
(原体シリカゲル)
本発明においては、発泡させる原体シリカゲルとしては、特に限定するものではないが、通常、平均粒径0.5〜10.0mm、好ましくは1.0〜5.0mmであって、粒子比重約1.0〜2.0、好ましくは1.3程度の乾燥用に使用されるものが望ましい。
(Original silica gel)
In the present invention, the active silica gel to be foamed is not particularly limited, but usually has an average particle diameter of 0.5 to 10.0 mm, preferably 1.0 to 5.0 mm, and has a particle specific gravity of about Those used for drying of 1.0 to 2.0, preferably about 1.3 are desirable.
粒子形状は、後記実施例に示すように、不定形のもの(実施例1)でもよいし、球状のもの(実施例2)でもよい。例えば破砕した不定形のものでもよいが、球状のものがより好ましい。かかる原体としてのシリカゲルは、市販のものが容易に入手可能であり、また、所望のものを、公知の手段により、合成することも可能である。 The particle shape may be indefinite (Example 1) or spherical (Example 2), as shown in Examples below. For example, a crushed amorphous shape may be used, but a spherical shape is more preferable. A commercially available silica gel is easily available as such a raw material, and a desired silica gel can be synthesized by a known means.
(硫酸ナトリウム含有量)
本発明においては、このようなシリカゲル粒子に、硫酸ナトリウムを0.01〜2.00質量%、好ましくは0.01〜1.00質量%含有せしめて加熱、発泡させる。
(Sodium sulfate content)
In the present invention, such silica gel particles contain 0.01 to 2.00% by mass of sodium sulfate, preferably 0.01 to 1.00% by mass, and are heated and foamed.
本発明者らが見出したところによれば、硫酸ナトリウム由来のナトリウムの存在は、シリカゲルの融点を低下させて、シリカゲル内部の吸着水その他の発泡ガスにより当該シリカゲルを内部から外方へ塑性変形せしめて連続気泡を形成するために必須のものであって、その量が少なすぎると、実質的に発泡が起こらず、一方その量がこれより過剰であると、シリカゲル内部も溶解、収縮して発泡体を形成できず、また、ガラス化が起こるため、やはり発泡の程度がきわめて低くなる。 The present inventors have found that the presence of sodium sulfate-derived sodium lowers the melting point of the silica gel and causes the silica gel to be plastically deformed from the inside to the outside by adsorbed water or other foaming gas inside the silica gel. If the amount is too small, foaming does not occur substantially. On the other hand, if the amount is excessive, the inside of the silica gel also dissolves and contracts to foam. Since the body cannot be formed and vitrification occurs, the degree of foaming is still very low.
このように、ナトリウムの範囲が上記規定外のシリカゲルは、水に投入された場合、長時間浮遊することはなく、短時間で沈んでしまうのである。 Thus, silica gel whose sodium range is not defined above does not float for a long time and sinks in a short time when poured into water.
すなわち、シリカゲルに含有させる硫酸ナトリウムの量を上記規定された範囲とすることにより、その表面に無孔質に近い緻密な外被膜を有し、粒子内部は連続気泡の多孔質であるような発泡シリカゲルが形成される。 That is, by setting the amount of sodium sulfate to be contained in the silica gel within the specified range, the surface has a dense outer coating close to non-porous, and the inside of the particle is a foam that is porous with open cells. Silica gel is formed.
(焼成)
硫酸ナトリウム含有シリカゲルの焼成は、空気又は空気以外のガス雰囲気下で、950〜1150℃、好ましくは980〜1100℃の温度で、0.05〜5時間、好ましくは0.1〜2時間焼成することにより得られる。この条件で焼成することにより、原体シリカゲルは適度に発泡し、粒子形状が球形で、より小さい比重の発泡シリカゲル粒子が得られる。
(Baking)
Firing of the sodium sulfate-containing silica gel is performed at a temperature of 950 to 1150 ° C., preferably 980 to 1100 ° C., for 0.05 to 5 hours, preferably 0.1 to 2 hours in air or a gas atmosphere other than air. Can be obtained. By firing under these conditions, the base silica gel is appropriately foamed, and the foamed silica gel particles having a spherical particle shape and a smaller specific gravity are obtained.
焼成を実施するための焼成装置としては、硫酸ナトリウム含有原体シリカゲルを収容し、上記規定する温度で焼成しうるものであれば、如何なる形式の炉であってもよい。 The baking apparatus for carrying out the calcination, houses a sodium-containing drug substance silica gel sulfate, as long as it is capable of firing at the prescribed temperature, but it may also be a furnace of any type.
このようにして、硫酸ナトリウム含有シリカゲルを焼成することにより、焼成時に離脱するシリカゲル中の結合水や、反応分解して発生するSO3 ガスなどが発泡ガスとなって、当該シリカゲル粒子を内部から発泡膨張せしめ、比重の小さな球形シリカ粒子が形成されると推定される。 In this way, by firing the sodium sulfate-containing silica gel, the bound water in the silica gel that is released during firing or the SO 3 gas generated by reaction decomposition becomes a foaming gas, and the silica gel particles are foamed from the inside. It is estimated that spherical silica particles having a small specific gravity are formed.
(発泡シリカゲルの形態的特徴)
図1はかくして形成された本発明の発泡シリカゲル粒子を示す光学顕微鏡写真である。その外観は球状であることが認められる。
(Morphological features of foamed silica gel)
FIG. 1 is an optical micrograph showing the foamed silica gel particles of the present invention thus formed. It is recognized that the appearance is spherical.
このように本発明の発泡シリカゲル粒子は、従来のいわゆる中空シリカゲルと異なり、粒子内部は、発生ガスにより多孔質(連続気泡)に形成されているが、粒子外表面全体は、無孔質に近い極めて緻密な外被膜により覆われているため、内部の連続気泡は、当該外被膜により遮断され、粒子表面までは到達しないという特異な形態を有しているものである。当該緻密な外被膜の存在により、外気や水分は、粒子内には進入しないため、特に断熱性コーティング材用硬化性組成物に用いる多孔質粒子として望ましいものである。 Thus, unlike the conventional so-called hollow silica gel, the foamed silica gel particles of the present invention are porous (open cells) inside the particles by the generated gas, but the entire outer surface of the particles is almost nonporous. Since it is covered with a very dense outer coating, the internal open cells are blocked by the outer coating and have a unique form that does not reach the particle surface. Due to the presence of the dense outer coating, the outside air and moisture do not enter the particles, and are particularly desirable as porous particles used in the curable composition for heat insulating coating materials.
本発明の発泡シリカゲル中のナトリウムの含有量は、0.003〜0.65質量%、さらに好ましくは0.015〜0.15質量%、最も好ましくは0.015〜0.10質量%のものである。このように、ナトリウム含有量を上記規定された範囲とすることは、その表面に無孔質に近い緻密な被膜を有し、粒子内部は連続気泡の多孔質であるような発泡シリカゲルを形成するのに極めて重要な要件である。 The content of sodium in the foamed silica gel of the present invention is 0.003 to 0.65% by mass, more preferably 0.015 to 0.15% by mass, most preferably 0.015 to 0.10% by mass. It is. Thus, setting the sodium content within the range specified above forms a foamed silica gel having a dense coating close to non-porous on the surface and the inside of the particle being open-celled porous. This is an extremely important requirement.
本発明の発泡シリカゲルは、その粒子径が、1.0〜10.0mm、粒子の比重の平均値(20粒の平均値)が0.05〜0.50のものであり、さらに好ましくは、粒子径が、1.0〜8.0mm、粒子の比重の平均値(20粒の平均値)が0.07〜0.30のものである。この数値は、当該発泡シリカゲルが、断熱性コーティング材用硬化性組成物における断熱機能材料として使用する場合において、特に好ましいものである。 The foamed silica gel of the present invention has a particle diameter of 1.0 to 10.0 mm, an average particle specific gravity (average value of 20 particles) of 0.05 to 0.50, and more preferably, The particle diameter is 1.0 to 8.0 mm, and the average value of specific gravity of particles (average value of 20 grains) is 0.07 to 0.30. This numerical value is particularly preferable when the foamed silica gel is used as a heat insulating functional material in the curable composition for a heat insulating coating material.
なお、発泡シリカゲルと、一件類似に見える発泡シリカゲル粒子に、すでに述べた、アルミナを10%添加して発泡させた、特許文献1で提案されている、いわゆる「中空シリカ球状体」があるが、かかる「中空シリカ球状体」は、水に投入すると、一旦は浮くものの、当該被膜は、緻密なものではなく、開口部が多数あって、粒子内に水が進入するため、長時間浮遊状態を維持出来ないことから、本発明の発泡シリカゲルとは、本質的に差異があるものである。 In addition, there is a so-called “hollow silica sphere” proposed in Patent Document 1 in which 10% of alumina is added to foamed silica gel particles that look similar to the foamed silica gel and foamed. Such “hollow silica spheres” float once when put into water, but the coating is not dense and has a large number of openings, so that water enters the particles, so that it floats for a long time. Therefore, it is essentially different from the foamed silica gel of the present invention.
(用途)
本発明の発泡シリカゲルは、このように内部が連続気泡であって、軽量であるとともに、かつ、その外表面は緻密な被膜で被覆されているため、水中に投入して長時間経過(例えば100時間以上)しても沈むことはない。このように、当該発泡シリカゲルは、水などの液体に接触しても、液体の粒子内部への浸入を防止できるものであるため、断熱性コーティング材用硬化性組成物に用いる多孔質粒子として、特に望ましい。
(Use)
Since the foamed silica gel of the present invention is open-celled inside and light in weight as described above, and its outer surface is covered with a dense film, it is poured into water for a long time (for example, 100 It will not sink even if it is over time). Thus, since the foamed silica gel can prevent the liquid from entering the inside of the particles even in contact with a liquid such as water, as the porous particles used in the curable composition for heat-insulating coating materials, Particularly desirable.
さらにまた、本発明の発泡シリカゲルは、断熱性コーティング材用硬化性組成物以外の用途として、軽量かつ液が粒子内に進入しないため安定的に浮く特性を利用して、断熱用充填材、液面浮上断熱材、樹脂やセメント硬化体用の軽量化用中空充填材、浮材、包装用の軽量クッション材料、燃焼する油面の消火剤、触媒担体など広い用途範囲に好適に使用できるものである。 Furthermore, the foamed silica gel of the present invention can be used for applications other than the curable composition for heat-insulating coating materials by utilizing the characteristics of being light and stably floating because the liquid does not enter the particles, It can be suitably used in a wide range of applications such as surface-floating insulation, lightweight hollow fillers for resin and hardened cement, floating materials, lightweight cushioning materials for packaging, fire extinguishing agents for burning oil, and catalyst carriers. is there.
以下、実施例をあげて本発明を具体的に説明するが、本発明の技術的範囲がこれに限定されるものではない。また、単に部とあるのは、とくに断りなき限り質量部を示す。 Hereinafter, the present invention will be specifically described with reference to examples, but the technical scope of the present invention is not limited thereto. The term “parts” means parts by mass unless otherwise specified.
〔実施例1〕(発泡シリカゲルの製造)
硫酸ナトリウムを0.15質量%含有する粒子径2.5mmの乾燥されたシリカゲル(洞海化学工業社製シリカゲル、商品名Sゲル、粒子形状は不定形、粒子の平均比重1.32)200gを原体として、白金製ルツボに入れ、空気雰囲気下で、1100℃で、0.5時間焼成した。放出されるシリカゲル中の結合水等が発泡ガスとなって、シリカゲル粒子が発泡膨張して、比重の小さな球形シリカ粒子(発泡シリカゲル)が得られた。この発泡シリカゲルの平均粒子径は、4.0mmであり、粒子の平均比重(20粒の平均値)は、0.14であった。この発泡シリカゲル中のナトリウム含有量は、0.047質量%であった。
[Example 1] (Production of foamed silica gel)
200 g of dried silica gel containing 0.15% by mass of sodium sulfate and having a particle diameter of 2.5 mm (silica gel manufactured by Dokai Chemical Industry Co., Ltd., trade name S gel, particle shape is irregular, average specific gravity of particles 1.32) The raw material was placed in a platinum crucible and baked at 1100 ° C. for 0.5 hours in an air atmosphere. Bonded water or the like in the released silica gel became foaming gas, and the silica gel particles expanded and expanded to obtain spherical silica particles (foamed silica gel) having a small specific gravity. The average particle diameter of the foamed silica gel was 4.0 mm, and the average specific gravity (average value of 20 particles) of the particles was 0.14. The sodium content in the foamed silica gel was 0.047% by mass.
得られた発泡シリカゲルを水中に投入して100時間経過しても、水に沈むことはなかった。このように、本発明の発泡シリカゲルは、緻密な外被膜に覆われているため、水などの液体に接触しても、液体の粒子内部への浸入を防止できるものであった。 The foamed silica gel thus obtained was not submerged in water even after 100 hours had passed. As described above, since the foamed silica gel of the present invention is covered with a dense outer coating, even when it comes into contact with a liquid such as water, the infiltration of the liquid into the particles can be prevented.
〔実施例2〕(発泡シリカゲルの製造)
硫酸ナトリウムを0.20質量%含有する粒子径3.0mmの乾燥されたシリカゲル(洞海化学工業社製シリカゲル、商品名パール、粒子形状は球形、粒子の平均比重1.31(20粒の平均値))200gを、白金製ルツボに入れ、空気雰囲気下で、1050℃で、0.5時間焼成した。放出されるシリカゲル中の結合水等が発泡ガスとなって、シリカゲル粒子が発泡膨張して、比重の小さな球形シリカ粒子が得られた。この発泡シリカゲルの平均粒子径は、4.7mmであり、粒子の平均比重(20粒の平均値)は、0.13であった。この発泡シリカゲル中のナトリウム含有量は、0.061質量%であった。
[Example 2] (Production of foamed silica gel)
Dry silica gel containing 0.20% by mass of sodium sulfate and having a particle size of 3.0 mm (silica gel manufactured by Dokai Chemical Industries, trade name pearl, particle shape is spherical, average specific gravity of particles 1.31 (average of 20 particles) Value)) 200 g was placed in a platinum crucible and baked in an air atmosphere at 1050 ° C. for 0.5 hour. Bonded water or the like in the released silica gel became a foaming gas, and the silica gel particles expanded and expanded to obtain spherical silica particles having a small specific gravity. The average particle diameter of the foamed silica gel was 4.7 mm, and the average specific gravity (average value of 20 particles) of the particles was 0.13. The sodium content in the foamed silica gel was 0.061% by mass.
得られた発泡シリカゲルを水中に投入して100時間経過しても、水に沈むことはなく、水などの液体に接触しても、液体の粒子内部への浸入を防止できるものであることが確認された。 Even if 100 hours have passed after the obtained silica gel foam is poured into water, it does not sink into water, and even if it comes into contact with a liquid such as water, it can prevent the liquid from entering the particles. confirmed.
〔実施例3〕(発泡シリカゲルを含有する断熱コーティング材用硬化性組成物及び断熱性硬化体)
(1)SiO2 /Na2 O=3.0(モル比)、SiO2 濃度21.0質量%であるケイ酸ナトリウム水溶液2000ml/minと、硫酸濃度20.0質量%の硫酸水溶液とを、瞬間的に均一混合、空中に放出し、空中でゲルせしめ、水を張った熟成槽中でpHを6に調整、粗粉砕しシリカヒドロゲルを得た。
[Example 3] (Curable composition for heat-insulating coating material containing foamed silica gel and heat-insulating hardened body)
(1) SiO 2 / Na 2 O = 3.0 (molar ratio), a sodium silicate aqueous solution 2000 ml / min having a SiO 2 concentration of 21.0% by mass, and a sulfuric acid aqueous solution having a sulfuric acid concentration of 20.0% by mass, The mixture was instantaneously and uniformly mixed, released into the air, gelled in the air, adjusted to pH 6 in a ripening tank filled with water, and coarsely pulverized to obtain a silica hydrogel.
容量50000mlのオートクレーブ(電気加熱式、アンカ−型撹拌羽根付き)に、系内の総SiO2 /Na2 Oモル比が12.0になるように、上記シリカヒドロゲル23.7kg及びケイ酸ナトリウム水溶液(SiO2 28.75質量%、Na2 O9.3質量%、SiO2 /Na2 O=3.17(モル比))5.5kgを仕込み、これにイオン交換水を10.7kgを加え、185℃で8時間水熱処理を行った。系内の総シリカ濃度は、SiO2 として15質量%であった。 In an autoclave with a capacity of 50000 ml (electrically heated, with anchor-type stirring blades), 23.7 kg of the above silica hydrogel and aqueous sodium silicate solution so that the total SiO 2 / Na 2 O molar ratio in the system is 12.0 (SiO 2 28.75% by mass, Na 2 O 9.3% by mass, SiO 2 / Na 2 O = 3.17 (molar ratio)) 5.5 kg was charged, and 10.7 kg of ion-exchanged water was added thereto, Hydrothermal treatment was performed at 185 ° C. for 8 hours. The total silica concentration in the system was 15% by mass as SiO 2 .
水熱処理後のスラリーは、濾布式竪型遠心分離機(東興機械社製、TU−18型)を用いて濾過水洗を行い、有姿含水率69.7質量%(固形分濃度30.3質量%)の葉状シリカ3次凝集体粒子の湿ケーキを得た。 The slurry after the hydrothermal treatment was washed with filtered water using a filter cloth type vertical centrifuge (manufactured by Toko Machine Co., Ltd., TU-18 type), and the solid water content was 69.7% by mass (solid content concentration: 30.3). (Mass%) wet cake of leafy silica tertiary aggregate particles was obtained.
(2)当該シリカ3次凝集体粒子の湿ケーキ1000g( 固形分濃度:30.3質量%) に水1020gを加えてリパルプし、 固形分15質量%のシリカスラリーを調製し、当該スラリーを媒体撹拌ビーズミル(シンマルエンタープライゼズ社製、ダイノーミルKDL−PILOT A型 (ベッセル容量1.4L、直径0.5mmジルコニアビーズ80%充填) )でシャフト回転数3400rpm、流量30L/hで1回通過し、シリカ3次凝集体粒子の解砕・分散化を行い、自己造膜性のある葉状シリカ2次粒子スラリー(固形分15%、平均粒子径:1.6μm)を得た。 (2) 1020 g of water is added to 1000 g of wet cake of the silica tertiary aggregate particles (solid content concentration: 30.3% by mass) and repulped to prepare a silica slurry having a solid content of 15% by mass. Passed once with a stirring bead mill (Shinmaru Enterprises Co., Ltd., Dynomill KDL-PILOT A type (Bessel capacity 1.4L, 0.5mm diameter zirconia beads 80% filled)) at a shaft speed of 3400 rpm and a flow rate of 30 L / h. The tertiary aggregate particles were crushed and dispersed to obtain self-film-forming foliar silica secondary particle slurry (solid content 15%, average particle size: 1.6 μm).
(3)当該葉状シリカ2次粒子からなるスラリーを40g、実施例1に記載した平均粒子径4.0mm、粒子の平均比重0.14の球状の発泡シリカゲル粒子を8g、及び水15gをビーカーに入れ、撹拌混合し、スラリー状の断熱性コーティング材用硬化性組成物とした。 (3) 40 g of the slurry composed of the secondary silica particles, 8 g of spherical foamed silica gel particles having an average particle diameter of 4.0 mm and an average specific gravity of 0.14 described in Example 1, and 15 g of water in a beaker. The mixture was stirred and mixed to obtain a slurry-like curable composition for a heat insulating coating material.
(4)ステンレス製板(100mm×100mm×1mm厚)を用意し、コテを使って、ステンレス板上に、当該断熱性コーティング材用硬化性組成物のスラリーを塗布し、室温で乾燥し試験片とした。 (4) Prepare a stainless steel plate (100 mm x 100 mm x 1 mm thick), apply a slurry of the curable composition for a heat insulating coating material on the stainless steel plate using a trowel, dry at room temperature, and test piece It was.
塗装量は、固形分換算で約1400g/m2 であり、塗層厚みは約6.5mmであった。塗膜の外観は、発泡シリカゲルを粒とするオコシ状であった。
ここで、発泡シリカゲルと葉状シリカ2次粒子との固形分での質量比は、57:43である。
The coating amount was about 1400 g / m 2 in terms of solid content, and the coating layer thickness was about 6.5 mm. The appearance of the coating film was a scouring shape with foamed silica gel.
Here, the mass ratio in the solid content of the foamed silica gel and the leaf-like silica secondary particles is 57:43.
次に上記の塗布乾燥された試験片を、塗層側を上にして、165℃に保持したホットプレート上に乗せ、1時間後の塗層側表面温度を、表面温度計(TLV社製、PK1型)で測定したところ65℃であった。 Next, the coated and dried test piece was placed on a hot plate maintained at 165 ° C. with the coating layer side up, and the coating layer side surface temperature after 1 hour was measured with a surface thermometer (manufactured by TLV, It was 65 degreeC when measured by PK1 type | mold.
〔比較例1〕
実施例3に記載したものと同じステンレス板で、塗装を施してないものを、100℃に保持したホットプレート上に乗せ、1時間後の板表面温度を表面温度計(TLV社製、PK1型)で測定したところ100℃であった。
[Comparative Example 1]
The same stainless steel plate as described in Example 3, which was not coated, was placed on a hot plate maintained at 100 ° C., and the plate surface temperature after 1 hour was measured with a surface thermometer (manufactured by TLV, model PK1) ) And measured 100 ° C.
本発明の発泡シリカゲルは、内部が連続気泡であって、軽量であり、かつ、その外表面は緻密な被膜で被覆されるという新規な形態をしているため、水中に投入して長時間沈むことはない。すなわち、外気や水分が粒子内には浸入しないので、断熱性コーティング材用硬化性組成物に用いる多孔質粒子として好適に使用されるものである。 The foamed silica gel of the present invention has a novel form in which the inside is open-celled, lightweight, and the outer surface is covered with a dense coating, so it will sink into water for a long time. There is nothing. That is, since outside air and moisture do not enter into the particles, they are suitably used as porous particles used in the curable composition for heat insulating coating materials.
さらにまた、本発明の発泡シリカゲルは、軽量であり、かつ液が粒子内に進入せず安定的に浮遊する特性を利用して、断熱用充填材、液面浮上断熱材、樹脂やセメント硬化体用の軽量化用中空充填材、浮材、包装用の軽量クッション材料、燃焼する油面の消火剤、触媒担体用など広い分野において好適に使用できるものである。 Furthermore, the foamed silica gel of the present invention is lightweight and utilizes the property that the liquid does not enter the particles and stably floats, so that the heat-insulating filler, liquid surface-floating heat insulating material, resin or cement cured body is used. It can be suitably used in a wide range of fields such as a hollow filler for weight reduction, a floating material, a lightweight cushioning material for packaging, a fire extinguishing agent for burning oil, and a catalyst carrier.
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