TWI263619B - Silica aerogels with high-temperature hydrophobation synthesized by using co-precursor solutions - Google Patents

Abstract

The present invention discloses a high-temperature stable, low density and transparent silica aerogel prepared by carrying our a sol-gel process of a mixture containing a main precursor of inorganic siloxane and a high-temperature stable precursor to form a wet gel, wherein the high-temperature stable precursor and the main precursor undergo covalent-bond crosslinking; aging and supercritical drying the wet gel to form a low density, tough, hydrophobic silica aerogel of a porous network structure. The hydrophobation of the aerogel of the present invention prevails after several times of heating at 500 DEG C, and the structure of the aerogel will not collapse caused by moisture.

Description

1263619 九、發明說明： 發明所屬之技術領域 、本發明係關於一種疏水性 法’尤其有關-種高熱穩定性 二氧化矽氣凝膠的製備方法。 用作為熱絕緣材料。 一氧化石夕氣凝膠的製備方 、低密度、透光性的疏水性 此疏水性二氧化矽氣凝膠可 先前技術 、-般利用溶膠-凝膠法(sol_gel)製作玻璃或陶:免時，多 以矽烷氧化物(S1l〇xane)為最常使用的前驅物，矽烷氧化物 之化學式可表示為si(OR)4，纟中尺代表烧基。其溶凝膠製 程主要分為水解、縮合兩個步驟： 1·水解反應（Hydrolysis Reaction) 矽烷氧化物中之一 〇R基與水反應，此類物質大部分容 易水解成氫氧化物，水分子中之—〇H基取代一 〇R基而形 成含有一 0H基之矽烷氧化物，並釋出醇類，前驅物Si(〇R)4 與水攪拌後，以酸或鹼催化下進行水解，其化學反應機制 如下所示：1263619 IX. INSTRUCTIONS: The technical field to which the invention pertains, and the present invention relates to a method for preparing a hydrophobic method, in particular, a high thermal stability cerium oxide aerogel. Used as a thermal insulation material. Preparation of a oxidized stone aerobical gel, low density, light transmissive hydrophobicity The hydrophobic cerium oxide aerogel can be made by a prior art, using a sol-gel method (sol_gel) to make a glass or ceramic: In the case of decane oxide (S1l〇xane), the most frequently used precursor, the chemical formula of the decane oxide can be expressed as si(OR)4, and the ruthenium scale represents the alkyl group. The lyophilization process is mainly divided into two steps of hydrolysis and condensation: 1. Hydrolysis Reaction One of the decane oxides reacts with water, and most of these substances are easily hydrolyzed into hydroxides, water molecules. In the middle, the hydrazine H group is substituted with a fluorene group to form a decane oxide containing a OH group, and the alcohol is released. The precursor Si(〇R)4 is stirred with water and then hydrolyzed by acid or base catalysis. The chemical reaction mechanism is as follows:

(R〇)3SiOR + AH20 o HOSi(OR)3+R〇H ^Si(OH)4 -{-AROH ( 1 ) 前驅物以四乙氧基矽烷丑山 (tetraethylorthosilicate，or tetraethoxysilane，簡稱 TEOS)而(R〇)3SiOR + AH20 o HOSi(OR)3+R〇H ^Si(OH)4 -{-AROH ( 1 ) The precursor is tetraethylorthosilicate (or tetraethoxysilane, TEOS)

Si(OC2H5 )4 + 4H20 Si(OH)4 + AC2H5OH (2) 1263619 含有氫氧基的矽烷氧化物，容易與其他烷氧物中之烷 氧基或氫氧基繼續反應形成架鍵橋（bridging oxygen)而釋 放出醇或水份，例如以下反應式所示，形成二氧化矽網狀 結構之濕凝膠。Si(OC2H5 )4 + 4H20 Si(OH)4 + AC2H5OH (2) 1263619 Hydroxide-containing decane oxide, which readily reacts with alkoxy or hydroxyl groups in other alkoxides to form a bridging bridge (bridging Oxygen) releases alcohol or moisture, for example, as shown in the following reaction formula, to form a wet gel of a ceria network.

0H OH j OH HO— Si— | j 0~Si— OH 0Η | 1 o 1 0 0—Si一 OH --^ | MO****"**^ _*** 1 〇—Si—〇 —« | -η Η2〇 I | OH 1 o _ 1 OH 0H0H OH j OH HO— Si— | j 0~Si— OH 0Η | 1 o 1 0 0—Si—OH --^ | MO****"**^ _*** 1 〇—Si—〇 —« | -η Η2〇I | OH 1 o _ 1 OH 0H

OHOH

II

Si— OHSi- OH

I Ο iI Ο i

HO—Si— OHHO—Si— OH

i>H 接著利用水將濕凝膠中的鹽分洗滌去除，再以醇將水 又換出來，最後在高壓下蒸發醇移除；或者直接一超臨界 ⑽體對濕凝膠進行乾燥如此就可產生氣凝膠，避免在水或 命J瘵奄時無法承受來自液氣界面強大表面張力所導致凝 膠結構崩塌、破裂的問題。 、二氧化矽氣凝膠為輕質、低密度、高表面積之中孔洞 料（meSGp_us materials)，—般利用其低熱傳導係數特 二：用於溫度敏感的產&，以改進其能源效率。氣凝膠會 子日加而有劣化現象，這是由於在潮濕環境中，Si原 —曰义到〇Η·親核性攻擊（nucle〇phinc⑽叫造成μ—〇 2鍵結斷^導致結構„。叫針對材料仙使用觀 另一Μ膠需要提供斥水或疏水的性質來改善受潮現象。 非常由於氣凝膠化學組成是二氧切，和玻璃一樣 1263619 1992 年 Smith，Brinker，and Deshpande (Journal of Non-Crystalline Solids 142, 3，197-207，1992)首先用水/酒 精置換，使〜SiOH基團砍化（silylated)，比如：添加三甲基 氯矽烷（chlorotrimethylsilane)，如此表面反應活性就可降 低，達到疏水性的要求，此種方法可承受原來體積28%的 可逆收縮。1995類似結果Yokogawa等人（Journal of Non-Crystalline Solids 18 6, 23-29，1995)也觀察到，不過他 們的疏水性氣凝膠是以濕凝膠表面誘導衍生方法所改質， 用這種方法合成的氣凝膠也是透明的。他們所使用的疏水 劑是六甲基二矽胺（hexamethyldisilazane)。但是濕凝膠表面 誘導衍生方法的缺點是它非常耗時。2003年A. Venkateswara Rao (Journal of Sol-Gel Science and Technology 27, 103_109, 2003)提出另一種方式合成疏水氣 凝膠，包括以共同前驅物方式（C〇_precurs〇r)添加三甲基乙 氧基矽烧（trimethylethoxysilane，TMES)，水解縮合出含 -Si(CH3)3基的濕凝膠來產生疏水氣凝膠。使用共同前驅物 比表面衍生方式的主要好處是氣凝膠有較寬的透光率範圍 (93%)，且接觸角範圍可以從9〇。到13〇。。 英國專利682574 (西元1952年）揭示一種疏水性的二 氧化矽粒子，包括將具有一個或兩個C1_C4烷基的氟化矽 烷改質劑與二氧化矽凝膠（gel)反應。 一般二氧化矽氣凝膠疏水性只維持到24crc左右，超 過該溫度時氣凝膠疏水性會轉成親水性。原因是添加改質 劑於氣凝膠表面所形成的有機膜遇熱會裂解成氣體，而剩 1263619 下矽氣凝膠表面是親水性〜Si〇H。一般矽烷化處理 (S1lylatlon)的疏水二氧化矽氣凝膠其疏水性並不能維持到 高於50(TC以上，其原因可能是共前驅物的鍵結強度不足， 且沒有均勻分散於整個矽氣凝膠。 發明内容 本發明揭示一種高熱穩定性、低密度、透光性之二氧 化矽氣凝膠，其製備方法包括添加高熱穩定性前驅物與主 前驅物無機矽烷氧化物一起進行溶膠_凝膠反應合成濕凝 膠，使得高熱穩定性前驅物與主前驅物形成共價鍵結交 聯，濕凝膠經室溫時效及超臨界乾燥後，就可以合成低密 度、韌性及疏水性提升的多孔網狀結構的二氧化矽氣凝 膠。同時此氣凝膠經多次5001熱處理也不影響其疏水性， 不會因潮濕造成其結構崩潰。 本發明使用四曱氧基石夕烧（tetramethoxysilane，TMOS) 作為主前驅物，苯基三乙氧基矽烷（phenyhrieth〇xysilane， PTES)或其衍生物作為高熱穩定性共前驅物，其中ptes對 TMOS的莫耳比介於〇1至2·35。本發明的溶膠_凝膠反應 使用曱醇作為前驅物與水的共溶劑，及使用氨水（ΝΗ4〇Η) 作為觸媒。溶膠_凝膠反應所製得的濕凝膠經過超臨界乾燥 以合成尚熱穩定性、低密度、透光性之二氧化石夕氣凝膠。 於本發明的一較佳具體實施例中為了得到透明和低密度的 二氧化矽氣凝膠，使用TMOS:甲醇：η2ο··νη4οη = 1 : 11 : 5 · 3·7χ10 3 (莫耳比）。 1263619 實施方式 依本發明的一較佳具體實施例所進行的透明和低密度 的二氧化石夕氣凝膠的製備方法說明如下： 1 ·四曱氧基矽烷（TMOS)(主前驅物）、甲醇及水在氨水 (催化劑）存在下進行水解和縮合，為了可以得剡透 明和低猎度的二氧化；ε夕氣凝膠，組成分莫耳比須維 持在一定範圍内，例如TMOS:甲醇：H20:NH40H = 1:X:Y: Z，其中X介於10_15;γ介於3_6;及2 介於 2χ10·3-6χ10_3。 2.添加高熱穩定性共前驅物，苯基三乙氧基矽烷 (phenyltriethoxysilane，PTES)，PMES/TMOS 莫耳比 大於0但小於2.35 ;均勻攪拌溶膠_凝膠混合物，製 得濕凝膠。 3 ·溶膠經室溫3小時進行膠化。 4 ·濕;旋私於室溫時效兩天至十天不等。 5.最後再進行乙醇超臨界乾燥（溫度243 °C、壓力63 bars) 〇 實施例 (a)將1莫耳的四曱氧基矽烷及莫耳苯基三乙氧 基石夕烧溶於11莫耳的曱醇。將3_7χ1 (T3莫耳的氫 氧化銨與5莫耳的去離子水混合。於一反應槽内 混合上述兩種溶液，以15〇 RpM均質攪拌2〇分 1263619 鐘。 (b) 反應槽以不透氣膜隔絕外界空氣，靜置於室溫中 3小時，進行膠化（gelation)。 (c) 膠化後產物經室溫自然蒸發其中的溶劑。 (d) 再靜置於空氣中及於室溫下進行時效（aging)處理 3天後，形成濕凝膠（wet gel)。 (e) 將濕凝膠置於一密閉容器中並通入乙醇超臨界流 體，該密纳容器被維持在溫度243 °C及壓力63 bars ° (0 於1小時後，停止乙醇超臨界流體的導入，並漸 漸降壓（0.3 bars/分）至常壓，再漸漸降低溫度至室 溫，打開該密閉容器取出二氧化矽氣凝膠。 本實施例所製得的二氧化矽氣凝膠具有一密度5 g/cm ’ 一 BET 比表面積 900 m2/g，一孔隙體積 〇·2 cm3/g， 一平均孔洞大小1〇埃及熱傳導係數0.08 w/m-k。 利用真空爐在500°C，加熱300分鐘，並用接觸角量 測儀發現氣凝膠經多次500°C多次熱處理其接觸角皆高於 130度’且不會因潮濕造成其結構崩潰。i>H then use water to wash the salt in the wet gel, then replace the water with alcohol, and finally remove the alcohol under high pressure; or directly dry the wet gel with a supercritical (10) body. The aerogel is generated to avoid the problem of collapse and cracking of the gel structure caused by strong surface tension at the liquid-gas interface when water or life is lost. The cerium oxide aerogel is a lightweight, low-density, high-surface-hole material (meSGp_us materials) that generally uses its low heat transfer coefficient: for temperature-sensitive production & to improve its energy efficiency. The aerogel will be degraded and deteriorated. This is due to the fact that in the humid environment, the Si---------------------------------------------------------------------------------------------------- nucle〇phinc(10) It is necessary to provide water-repellent or hydrophobic properties to improve the moisture. It is very important because the chemical composition of aerogel is dioxo, like glass. 1263619 1992 Smith, Brinker, and Deshpande (Journal) Of Non-Crystalline Solids 142, 3, 197-207, 1992) First, water/alcohol displacement, silicifying the ~SiOH group, such as: adding chlorotrimethylsilane, so that the surface reactivity can be Reduced to meet the hydrophobicity requirements, this method can withstand the reversible shrinkage of 28% of the original volume. 1995 similar results are also observed by Yokogawa et al. (Journal of Non-Crystalline Solids 18 6, 23-29, 1995), but their Hydrophobic aerogels are modified by wet gel surface induced derivatization methods, and the aerogels synthesized by this method are also transparent. The hydrophobic agent they use is hexamethyldiamine (hexam). Ethyldisilazane). However, the disadvantage of wet gel surface induced derivatization is that it is very time consuming. In 2003 A. Venkateswara Rao (Journal of Sol-Gel Science and Technology 27, 103_109, 2003) proposed another way to synthesize hydrophobic aerogels. This includes adding a trimethylethoxysilane (TMES) in a common precursor mode (C〇_precurs〇r) to hydrolyze and condense a wet gel containing a -Si(CH3)3 group to produce a hydrophobic aerogel. The main benefit of using a common precursor than the surface derivatization method is that the aerogel has a wide range of light transmittance (93%), and the contact angle can range from 9 〇 to 13 〇. British Patent 682574 (AD 1952) Revealing a hydrophobic cerium oxide particle comprising reacting a fluorinated decane modifier having one or two C1_C4 alkyl groups with a cerium oxide gel. Generally, the hydrophobicity of the cerium oxide aerogel is maintained only When it is above 24crc, the aerogel hydrophobicity will turn into hydrophilicity when the temperature exceeds this temperature. The reason is that the organic film formed by adding the modifier on the surface of the aerogel will be cracked into gas when it is heated, and the 1263619 矽 aerogel will remain. Surface is Hydrophilic ~Si〇H. The hydrophobicity of the hydrophobic cerium oxide aerogel of S1lylatlon is not maintained above 50 (TC or more, which may be due to insufficient bonding strength of the co-precursor, and Not evenly dispersed throughout the helium gel. SUMMARY OF THE INVENTION The present invention discloses a high thermal stability, low density, light transmissive cerium oxide aerogel, which comprises a method of preparing a high thermal stability precursor together with a main precursor inorganic decane oxide for sol-gel reaction synthesis. The wet gel makes the high thermal stability precursor form a covalent bond with the main precursor. After the room temperature aging and supercritical drying, the wet gel can synthesize a porous network structure with low density, toughness and hydrophobicity. Aerated ceria aerogel. At the same time, the aerogel does not affect its hydrophobicity after repeated 5001 heat treatment, and its structure will not be collapsed due to moisture. The present invention uses tetramethoxysilane (TMOS) as a main precursor, phenyl triethoxy decane (phenehrieth 〇 silane) or a derivative thereof as a high thermal stability coprede, wherein ptes to TMOS Moerby is between 〇1 and 2.35. The sol-gel reaction of the present invention uses decyl alcohol as a co-solvent for the precursor and water, and ammonia water (ΝΗ4〇Η) as a catalyst. The wet gel obtained by the sol-gel reaction is subjected to supercritical drying to synthesize a thermodynamically stable, low-density, light-transmitting silica dioxide aerogel. In a preferred embodiment of the invention, in order to obtain a transparent and low density ceria aerogel, TMOS is used: methanol: η2ο··νη4οη = 1 : 11 : 5 · 3·7χ10 3 (Mo Erbi) . 1263619 Embodiments A method for preparing a transparent and low-density silica dioxide aerogel according to a preferred embodiment of the present invention is described as follows: 1. Tetramethoxy decane (TMOS) (main precursor), Methanol and water are hydrolyzed and condensed in the presence of ammonia (catalyst). In order to obtain a transparent and low-saturation dioxide; the oxime gas gel, the composition molar ratio must be maintained within a certain range, such as TMOS: methanol :H20:NH40H = 1:X:Y: Z, where X is between 10_15; γ is between 3_6; and 2 is between 2χ10·3-6χ10_3. 2. Add a high thermal stability co-precursor, phenyltriethoxysilane (PTES), PMES/TMOS molar ratio greater than 0 but less than 2.35; uniformly stir the sol-gel mixture to prepare a wet gel. 3. The sol was gelled at room temperature for 3 hours. 4 · Wet; Spiral tempering at room temperature for two days to ten days. 5. Finally, carry out supercritical drying of ethanol (temperature 243 ° C, pressure 63 bars). Example (a) Dissolve 1 mole of tetradecyloxydecane and molybdenum triethoxylate in 11 moles. Ear sterols. Mix 3_7χ1 (T3 molar ammonium hydroxide with 5 moles of deionized water. Mix the above two solutions in a reaction tank and homogenize with 15〇RpM for 2〇1263619 minutes. (b) The reaction tank is not The gas permeable membrane is insulated from the outside air and allowed to stand at room temperature for 3 hours for gelation. (c) The gelled product naturally evaporates the solvent at room temperature. (d) It is then placed in the air and in the chamber. After 3 days of aging treatment, a wet gel was formed. (e) The wet gel was placed in a closed container and passed through an ethanol supercritical fluid, which was maintained at temperature. 243 ° C and pressure 63 bars ° (0 after 1 hour, stop the introduction of ethanol supercritical fluid, and gradually reduce the pressure (0.3 bars / min) to normal pressure, then gradually reduce the temperature to room temperature, open the closed container to remove Cerium oxide aerogel. The cerium oxide aerogel prepared in this example has a density of 5 g/cm '- BET specific surface area of 900 m2/g, a pore volume of 2·2 cm3/g, an average pore. Size 1 〇 Egypt heat transfer coefficient 0.08 w / mk. Use a vacuum furnace at 500 ° C, heating for 300 minutes, Measuring instrument in contact with the angle amount found after numerous airgel 500 ° C heat treatment times are higher than a contact angle of 130 'without causing the collapse of the structure due to moisture.

Claims (1)

1263619 十、申請專利範圍： 1. -種疏水二氧化矽氣凝膠的製備方法，包括下列步 驟： —υ一製備濕凝膠’包含於—含有四甲氧基石夕烧主前驅物、 “ |基夕烧或其衍生物的共前驅物、甲醇、水及驗 的混合物進行中四甲氧基矽烷 及本基二乙虱基矽烷的水解 及縮合反應，而形成濕凝膠’其中甲醇對四甲氧基石夕炫的 莫耳比介於ΗΜ5;水對四甲氧基梦烧的莫耳比介於Μ; 鹼對四甲氧基錢的莫耳比介於2χ1㈣翁3;及共前驅 物對四甲氧基矽烷的莫耳比介於〇1_2 35 ; U)將該濕凝膠接觸-超臨界流體，以移除陷於該濕凝 膠中的水、醇及鹼，於是形成疏水二氧化矽氣凝膠。 2. 如申請專利範圍第1 jg & t、土 ^ j, u 囷罘1項的方法，其中步驟i)的共前 驅物為苯基三乙氧基矽烷。 3. 如申請專利範圍第…項的方法，其中步驟〇的 甲醇對四甲氧基石夕烧的莫耳比為5;水對四甲氧基石夕烧的 莫耳比為7;鹼對四甲氧基矽烷的莫耳比介為3.7χι〇_3 ;及 共前驅物對四曱氧基矽烷的莫耳比為丄。 4·如申請專利範圍第3項的方法’其中該鹼為氨水 111263619 X. Patent application scope: 1. A method for preparing a hydrophobic cerium oxide aerogel, comprising the following steps: - preparing a wet gel comprising - containing a tetramethoxy zephyr main precursor, " | The co-precursor of the base or its derivative, the mixture of methanol, water and the test, the hydrolysis and condensation reaction of the tetramethoxy decane and the benzyl diethenyl decane to form a wet gel The molar ratio of methoxy sulphur is ΗΜ5; the molar ratio of water to tetramethoxy dream is between Μ; the molar ratio of alkali to tetramethoxy is between 2χ1 (4) Weng 3; and the common precursor The molar ratio of tetramethoxy decane is between 〇1_2 35; U) contacting the wet gel with a supercritical fluid to remove water, alcohol and alkali trapped in the wet gel, thus forming hydrophobic dioxide Helium gel 2. A method of applying the patent range 1 jg & t, earth ^ j, u 囷罘1, wherein the co-precursor of step i) is phenyltriethoxydecane. A method of applying the scope of the patent item, wherein the molar ratio of methanol to tetramethoxy zebra is 5; The molar ratio of tetramethoxy zeshi was 7; the molar ratio of base to tetramethoxy decane was 3.7 χι〇_3; and the molar ratio of the co-precursor to tetramethoxy decane was 丄. · The method of claim 3, wherein the base is ammonia water 11