CN100386260C - Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material - Google Patents
Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material Download PDFInfo
- Publication number
- CN100386260C CN100386260C CNB2005101245882A CN200510124588A CN100386260C CN 100386260 C CN100386260 C CN 100386260C CN B2005101245882 A CNB2005101245882 A CN B2005101245882A CN 200510124588 A CN200510124588 A CN 200510124588A CN 100386260 C CN100386260 C CN 100386260C
- Authority
- CN
- China
- Prior art keywords
- brucite fiber
- materials
- glue
- brucite
- insulating material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Silicon Compounds (AREA)
Abstract
The present invention discloses a preparation method for brucite fiber reinforced SiO2 aerogel heat-insulating materials. Industrial general-purpose water glass or silicasol and short fibers of natural brucite are used as preparation raw materials, inorganic opacifier grain size refinement is realized through high energy ball milling work and a chemical dispersion method before sol is solidified, and the raw materials are evenly dispersed in glue solution. Natural brucite fibers are split into nanometer level diameter through the chemical dispersion method and are used as reinforcing materials, the volume contraction problem in materials in a normal pressure drying state is overcome through solvent replacement, hydrophobic treatment and a fiber reinforcing method, and a kind of solid aerogel material without volume contraction in the normal pressure drying state is obtained. The materials have good hydrophobicity, the density of the materials is 0.20 to 0.50 g/cm<3>, and the thermal conductivity of the materials is 0.010 to 0.030 w/m. k.
Description
Technical field
The present invention relates to a kind of preparation method of inorganic non-metallic based composites, the fibre-reinforced SiO of particularly a kind of natural brucite
2The preparation method of inorganic aerogels lagging material.
Background technology
Compare with traditional thermal insulation inorganic material, inorganic aerogels is a kind of novel super insulating material, it is by the mutual coalescent nanoporous network structure that forms of colloidal inorganic particle, and in hole, be full of a kind of lightweight amorphous solid-state material of gaseous state dispersion medium, have that density is low, specific surface area is big, porosity is high, the aperture is little and characteristics such as narrow distribution.Because the thermal conduction and the thermal convection of lagging material are all relevant with the material structure yardstick, when the hole in the material and structure dimension reach nanometer scale, when particularly the yardstick of material mesoporosity is less than the mean free path (about 70nm) of air molecule, the thermal motion of molecule is subjected to very big constraint, thermal conduction and thermal convection effect descend significantly, and the heat-proof quality of material has greatly improved.Therefore, the nanoporous network structure of aerogel can suppress solid-state and gaseous state thermal conduction effectively, be at present known to the minimum a kind of solid material of thermal conductivity in the inorganic materials.Aerogel particular structure characteristic makes it have many peculiar physicalies, have great application potential and tempting application prospect in fields such as the energy, information, environmental protection, medicine, agricultural chemicals, metallurgy, catalysis, building and scientific experiments, cause the great attention of countries in the world, begun to be applied to many key areas such as space flight, military affairs, high energy physics, catalyzer.
The shortcoming of inorganic aerogels maximum is that intensity is low, fragility is big; Under very little stress, inorganic aerogels will destroy.In recent years, many progress have been obtained round problems such as improving aerogel intensity.One of comparison effective means that wherein improves aerogel intensity is to add inorganic fibre or web material before gel formation, solidifies the back and forms fibre reinforced composites.This method strengthens aerogel with inorganic/organic composite structure aerogel or organic fibre to be compared, and the use temperature of material is higher; Compare with the method that improves the intensity of inorganic aerogels by thermal treatment, the toughness of material improves obviously; With the inorganic aerogels particulate add tackiness agent and fiber again the preparation method of compacting sintering compare, fiber is distribution uniform in aerogel, heat-proof quality is good.But inorganic reinforcing fiber commonly used in this method moulding mainly is a glass fibre, and not only price height, and fiber is thicker, and Fibre diameter generally reaches micron order, and heat-proof quality is bad.Also have in the progress and mention mineral fibre, but the length that requires fiber is greater than 1 centimetre, such mineral fibre price is also high.In addition, natural mineral fiber generally is the form output of fibrous bundle, tight bond between fiber, the commodity mineral fibre that adopts in the application is only split branch by machinery, it is used diameter and is generally micron order, and not only heat-proof quality is bad, and enhancement also is difficult to effectively be brought into play.
The another one shortcoming of inorganic aerogels is lower to the blocking capability of high temperature heat radiation.In order to solve the high temperature heat radiation heat transfer problem, conventional practice is to add opalizer in the aerogel matrix.The granularity of opalizer is generally also bigger, and is difficult to realize homodisperse in the aerogel matrix, therefore, influences the heat-proof quality of aerogel nanostructure.
At present, the preparation of China's aerogel is many to be the silicon source with silicoorganic compound, expensive raw material price; Carry out the product drying with supercritical drying in the preparation, the equipment requirements height, energy consumption is big, and processing condition are complicated harsh, make the preparation cost of aerogel very high.All of these factors taken together has all hindered the large-scale promotion application of aerogel.
Summary of the invention
The purpose of this invention is to provide a kind of brucite fiber and strengthen SiO
2The preparation method of aerogel heat-insulating material can guarantee the heat-proof quality of material when improving aerogel material intensity, reduce the preparation cost of material, gives full play to the advantage of material nano structure.
Technical scheme of the present invention is achieved in that the present invention is undertaken by following step:
At first, adopting the service water glass glue of industry silicasol liquid or process ion exchange treatment is siliceous glue, add tap water, add-on is the 10-30% of siliceous glue quality, add chemical dispersant then, the chemical dispersant consumption is inorganic sunscreen and brucite fiber total amount quality 10%-25%, adds inorganic sunscreen again, and the inorganic sunscreen consumption is the 2%-20% of siliceous glue quality;
Secondly, the siliceous glue that adds chemical dispersant and inorganic sunscreen is carried out ball milling, the high-energy ball milling time is 0.5-2 hour, makes inorganic sunscreen levigate and be dispersed in the siliceous glue;
Then, add brucite fiber, the brucite fiber consumption is the 5%-10% of siliceous glue quality, with brucite fiber making beating stirring in turbine mixer in siliceous glue, time is 0.5-1.0 hour, makes brucite fiber obtain splitting branch and dispersion after making beating is stirred;
At last, glue after the making beating is carried out injection molding and is heating and curing, the temperature that is heating and curing is 30-50 ℃, solidifying the back is washed to neutrality, soaked 24-48 hour with inorganic ethanol liquid subsequently cured product with distilled water, flood through organic silicon solution again, dipping time 10-30 minute, 50-65 ℃ of drying obtained brucite fiber enhancing SiO under normal pressure at last
2Aerogel heat-insulating material.
The brucite fiber fiber is the staple fibre of length less than 5mm.
Chemical dispersant is meant sodium stearate, sodium lauryl sulphate, Sodium dodecylbenzene sulfonate, sodium diethylhexyl sulfosuccinate or 1,2-dibutyl naphthalene-6-sodium sulfonate.
Inorganic sunscreen is meant TiO
2, Fe
3O
4, carbon black or ZrO
2
With inorganic siliceous glue and natural brucite staple fibre is the main preparation raw material of aerogel, to reduce raw materials cost; By the inorganic sunscreen granularity refinement and in material structure homodisperse, to reduce the influence of thermal radiation to the material heat-proof quality; By the natural brucite fibrous bundle split be divided into nanometer grade diameter and with it as strongthener, to improve the intensity of aerogel material; By the volumetric shrinkage problem in solvent exchange, hydrophobic processing and the fibre-reinforced method solution material normal pressure drying, to simplify preparation technology and equipment.
The inorganic siliceous glue that the present invention adopts is the commercially available industry silicasol liquid or the service water glass glue of process ion exchange treatment, compares with organosilicon raw materials such as tetraethoxy commonly used, and wide material sources, cheap.
Brucite fiber is a kind of harmless mineral fibre, and main component is Mg (OH)
2, be the advantage Mineral resources of China.Brucite fiber has excellent mechanical property and water-dispersion performance, has good consistency and bonding strength with silicate material.Brucite fiber is the form output of mineral aggregate, though the commodity brucite fiber through the mining machinery shredding, but still is the state of fibrous bundle, diameter is generally micron order.As strongthener, the long value height of fiber in the brucite fiber commercial grade, staple fibre then using value is lower.The present invention adopts the staple fibre of staple length less than 5mm, and is cheap.In application, the present invention is by splitting branch with the making beating of brucite staple fibre in containing the inorganic siliceous glue of chemical dispersant, make the Fibre diameter refinement reach nano level, improved the length-to-diameter ratio of staple fibre, and realized its homodisperse in siliceous glue, not only do not influence the heat-proof quality of material, and can bring into play the enhancement of fiber effectively.In addition, in siliceous glue was heating and curing process, the oligodynamical of brucite fiber can also promote the gelling of colloidal sol to solidify.
In order to realize the constant pressure and dry of aerogel, the present invention, carries out surperficial hydrophobic with organosilicon moisture repellent to the gelling solid and handles as the strongthener of aerogel, replace the bigger aqueous solvent of surface tension in the siliceous glue porous cured body hole with the less anhydrous ethanol solvent of surface tension with the nano level brucite fiber.Like this, not only strengthen the mechanical property of product, and solved contraction, cracking and avalanche problem, technology and the simplified equipment of product in the constant pressure and dry process well.The aerogel material that finally makes has excellent hydrophobic property, and density is 0.20～0.50g/cm
3, thermal conductivity is 0.010～0.030w/mk.
Embodiment
Embodiment one
At industrial TiO through adding water glass glue quality 10% in the water glass glue of ion-exchange
2Powder, 30% tap water, and chemical dispersant is brucite fiber and TiO
2The Sodium dodecylbenzene sulfonate of quality summation 15%, is poured in the stirrer ball milling 1.5 hours, adds the brucite fiber of the length of water glass glue quality 6% less than 5mm, after half hour is stirred in making beating, injects metal die, 40 ℃ down heating until curing.With distilled water cured body is washed to neutrality then, used soaked in absolute ethyl alcohol again 48 hours, then flooded 10 minutes in commercially available organic silicon solution, 55 ℃ of dryings obtain product under normal pressure at last.Product does not have volumetric shrinkage, and hydrophobicity is good, and density is 0.21g/cm
3, thermal conductivity is 0.012W/M.K.
Embodiment two
The industrial Fe that in the commercially available industry silicasol liquid of solid content 25%, adds silica sol liquid quality 5%
3O
4Powder, 10% tap water, and brucite fiber and Fe
3O
4The sodium diethylhexyl sulfosuccinate of quality summation 20%, ball milling 2 hours is poured in the stirrer, adds the brucite fiber of the length of silica sol liquid quality 9% less than 5mm, and making beating was stirred after 1 hour, injected mould, and heating is until curing under 50 ℃.Be washed to neutrality with distilled water then, used soaked in absolute ethyl alcohol again 36 hours, then flooded 20 minutes with organosilicon, last 65 ℃ of following constant pressure and dries obtain product.Product does not have volumetric shrinkage, and hydrophobicity is good, and density is 0.43g/cm
3, thermal conductivity is 0.025W/M.K.
Embodiment three
At industrial TiO through adding water glass glue quality 15% in the water glass glue of ion-exchange
2Powder, 20% tap water, and brucite fiber and TiO
2The sodium lauryl sulphate of quality summation 25%, is poured in the stirrer ball milling 1 hour, adds the brucite fiber of the length of water glass glue quality 7.5% less than 5mm, and making beating was stirred after 1 hour, injected mould, 35 ℃ down heating until curing.With distilled water cured body is washed to neutrality then, used soaked in absolute ethyl alcohol again 48 hours, then flooded 30 minutes, obtain product at 60 ℃ of following constant pressure and dries at last with commercially available organic silicon solution.Product does not have volumetric shrinkage, and hydrophobicity is good, and density is 0.40g/cm
3, thermal conductivity is 0.020W/M.K.
Embodiment four
In the process water glass glue of ion-exchange, add the industrial carbon black powder of water glass glue quality 20%, 25% tap water, and the sodium stearate of brucite fiber and carbon black quality summation 20%, ball milling 2 hours, pour in the stirrer, add the brucite fiber of the length of water glass glue liquid quality 10% less than 5mm, injection molding after 0.5 hour is stirred in making beating, heats until curing down at 45 ℃.With distilled water cured body is washed to neutrality then, used soaked in absolute ethyl alcohol again 48 hours, then flooded 30 minutes, obtain product at 60 ℃ of following constant pressure and dries at last with commercially available organic silicon solution.Product does not have volumetric shrinkage, and hydrophobicity is good, and density is 0.47g/cm
3, thermal conductivity is 0.028W/M.K.
Embodiment five
The industrial ZrO that in the silicon sol glue of commercially available solid content 25%, adds silicon sol glue quality 3%
2Powder, 15% tap water, and brucite fiber and ZrO
21 of quality summation 10%, 2-dibutyl naphthalene-6-sodium sulfonate, is poured in the stirrer ball milling 0.5 hour, adds the brucite fiber of the length of glue liquid quality 5% less than 5mm, making beating was stirred after 1 hour, injected mould, 30 ℃ down heating until curing.With distilled water cured body is washed to neutrality then, used soaked in absolute ethyl alcohol again 24 hours, then flooded 20 minutes, obtain product at 50 ℃ of following constant pressure and dries at last with commercially available organic silicon solution.Product does not have volumetric shrinkage, and hydrophobicity is good, and density is 0.25g/cm
3, thermal conductivity is 0.018W/M.K.
Claims (4)
1. brucite fiber strengthens SiO
2The preparation method of aerogel heat-insulating material is characterized in that, is undertaken by following step:
At first, adopting the service water glass glue of industry silicasol liquid or process ion exchange treatment is siliceous glue, add tap water, add-on is the 10-30% of siliceous glue quality, add chemical dispersant then, the chemical dispersant consumption is inorganic sunscreen and brucite fiber total amount quality 10%-25%, adds inorganic sunscreen again, and the inorganic sunscreen consumption is the 2%-20% of siliceous glue quality;
Secondly, the siliceous glue that adds chemical dispersant and inorganic sunscreen is carried out ball milling, 0.5-2 hour ball milling time, make inorganic sunscreen levigate and be dispersed in the siliceous glue;
Then, add brucite fiber, the brucite fiber consumption is the 5%-10% of siliceous glue quality, with the brucite fiber stirring of in siliceous glue, pulling an oar, making beating is stirred in the turbine mixer to be carried out, time is 0.5-1.0 hour, and brucite fiber diameter nano level makes brucite fiber obtain splitting branch and dispersion after making beating is stirred;
At last, the glue after the making beating is carried out injection molding and is heating and curing, the temperature that is heating and curing is 30-50 ℃, solidifies the back and with distilled water cured product is washed to neutrality, soaked 24-48 hour with anhydrous alcohol solution subsequently, floods through organic silicon solution again; Dipping time 10-30 minute, 50-65 ℃ of drying obtained brucite fiber enhancing SiO under normal pressure at last
2Aerogel heat-insulating material.
2. brucite fiber according to claim 1 strengthens SiO
2The preparation method of aerogel heat-insulating material is characterized in that, brucite fiber is the staple fibre of length less than 5mm.
3. brucite fiber according to claim 1 strengthens SiO
2The preparation method of aerogel heat-insulating material is characterized in that, chemical dispersant is meant sodium stearate, sodium lauryl sulphate, Sodium dodecylbenzene sulfonate, sodium diethylhexyl sulfosuccinate or 1,2-dibutyl naphthalene-6-sodium sulfonate.
4. brucite fiber according to claim 1 strengthens SiO
2The preparation method of aerogel heat-insulating material is characterized in that inorganic sunscreen is meant TiO
2, Fe
3O
4, carbon black or ZrO
2
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005101245882A CN100386260C (en) | 2005-12-20 | 2005-12-20 | Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005101245882A CN100386260C (en) | 2005-12-20 | 2005-12-20 | Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1803602A CN1803602A (en) | 2006-07-19 |
| CN100386260C true CN100386260C (en) | 2008-05-07 |
Family
ID=36865785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2005101245882A Expired - Fee Related CN100386260C (en) | 2005-12-20 | 2005-12-20 | Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100386260C (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20120023707A (en) * | 2009-04-27 | 2012-03-13 | 캐보트 코포레이션 | Aerogel compositions and methods of making and using them |
| CN101654349B (en) * | 2009-09-11 | 2012-02-22 | 长春理工大学 | Method for preparing silica aerogel by doped brucite fiber and titanium dioxide powder |
| CN101696101B (en) * | 2009-10-30 | 2012-06-20 | 广东埃力生高新科技有限公司 | Heat-insulating material and preparation method thereof |
| EP2606102A1 (en) * | 2010-08-16 | 2013-06-26 | Basf Se | Fire protection elements and production of fire protection elements based on silicate- containing intumescent masses |
| CN102351507B (en) * | 2011-07-18 | 2013-04-10 | 南京工业大学 | Preparation of fiber-reinforced SiO by using rice hull ash as raw material2Method for producing aerogels |
| CN103910516A (en) * | 2012-12-31 | 2014-07-09 | 上海新安纳电子科技有限公司 | Method for recovering waste silica sol for reutilization |
| CN104478395A (en) * | 2014-11-14 | 2015-04-01 | 刘吉海 | Composite SiO2 aerogel heat insulation material and preparation method thereof |
| CN107438588B (en) * | 2015-09-10 | 2018-12-11 | 株式会社Lg化学 | Felt and preparation method thereof containing aerosil |
| CN105797694B (en) * | 2016-05-28 | 2019-02-12 | 南京兰庭绿色建筑技术有限公司 | A kind of preparation method of recyclable water quality cleansing agent |
| CN106565266B (en) * | 2016-10-25 | 2019-05-31 | 北京派诺蒙能源科技有限公司 | A kind of method that low cost prepares aerosil |
| CN108641361B (en) * | 2018-04-23 | 2020-12-01 | 华东理工大学 | Fiber-reinforced organic silicon aerogel heat-insulation composite material and preparation method thereof |
| CN109231219A (en) * | 2018-10-27 | 2019-01-18 | 上海永丰热镀锌有限公司 | A kind of aeroge and its aeroge fibrofelt |
| CN111302827A (en) * | 2020-04-10 | 2020-06-19 | 中国人民解放军国防科技大学 | Preparation method of high-temperature-resistant fiber-reinforced silica aerogel heat-insulation composite material |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4221672A (en) * | 1978-02-13 | 1980-09-09 | Micropore International Limited | Thermal insulation containing silica aerogel and alumina |
| GB1580909A (en) * | 1977-02-10 | 1980-12-10 | Micropore Internatioonal Ltd | Thermal insulation material |
| CN1177993A (en) * | 1995-03-07 | 1998-04-01 | 赫彻斯特股份公司 | Transparent component containing at least one fibre-reinforced aerogel plate and/or mat |
| CN1214319A (en) * | 1997-10-10 | 1999-04-21 | 同济大学 | Modified nanometer heat insulating material and its production process |
| EP1340729A1 (en) * | 2002-02-28 | 2003-09-03 | E.G.O. ELEKTRO-GERÄTEBAU GmbH | Heat-insulating body |
| CN1544324A (en) * | 2003-11-20 | 2004-11-10 | 中国科学院上海技术物理研究所 | Silica dioxide aerogel membrane material preparation method |
-
2005
- 2005-12-20 CN CNB2005101245882A patent/CN100386260C/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1580909A (en) * | 1977-02-10 | 1980-12-10 | Micropore Internatioonal Ltd | Thermal insulation material |
| US4221672A (en) * | 1978-02-13 | 1980-09-09 | Micropore International Limited | Thermal insulation containing silica aerogel and alumina |
| CN1177993A (en) * | 1995-03-07 | 1998-04-01 | 赫彻斯特股份公司 | Transparent component containing at least one fibre-reinforced aerogel plate and/or mat |
| CN1214319A (en) * | 1997-10-10 | 1999-04-21 | 同济大学 | Modified nanometer heat insulating material and its production process |
| EP1340729A1 (en) * | 2002-02-28 | 2003-09-03 | E.G.O. ELEKTRO-GERÄTEBAU GmbH | Heat-insulating body |
| CN1544324A (en) * | 2003-11-20 | 2004-11-10 | 中国科学院上海技术物理研究所 | Silica dioxide aerogel membrane material preparation method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1803602A (en) | 2006-07-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN100386260C (en) | Method for preparing brucite fiber reinforced SiO2 aerogel heat-insulating material | |
| CN101823867B (en) | Preparation method of SiO2 aerogel composite material doped with aramid fibre | |
| CN103524140B (en) | Oxide ceramic fiber board | |
| CN103755302B (en) | Fiber reinforced TiO2-SiO2 aerogel composite material preparation method | |
| CN101450852A (en) | Nano-pore SiO2 aerogel thermal insulation composite material and preparation method thereof | |
| CN102351507B (en) | Preparation of fiber-reinforced SiO by using rice hull ash as raw material2Method for producing aerogels | |
| CN104446306A (en) | Submicron inorganic whisker aerogel thermal insulation composite and preparation method thereof | |
| CN102464468B (en) | Nano composite heat-insulating material and preparation method thereof | |
| CN101445356A (en) | Nano-hole aerogel heat-insulating composite material and preparation method thereof | |
| CN104312105A (en) | Carbon-modified resin/fiber composite material and preparation method thereof | |
| CN101439957A (en) | Aerogel heat insulation composite material containing nano semiconductor infrared light screening agent and preparation thereof | |
| CN104446305A (en) | Calcium sulphate whisker aerogel heat-insulating composite material and preparation method thereof | |
| CN109608783A (en) | A method of with nano silica reinforced plastics waste residue-stalk fibre wood plastic composite | |
| CN101591192B (en) | Reinforcement method for fibre-quartz ceramic-base composite material | |
| CN109081673A (en) | A kind of fiber reinforcement alumina aerogels composite material and preparation method | |
| CN101941046B (en) | Composite sodium silicate binder for sand mold and preparing method thereof | |
| CN106565266A (en) | Method for preparing silicon dioxide aerogel with low cost | |
| CN111500022B (en) | Preparation method of reticular basalt fiber reinforced ceramic-based material | |
| CN105238072A (en) | Preparation method for inorganic powder enhanced carbon cloth/resin composite material | |
| CN108929072B (en) | Method for preparing ferric oxide and nano composite heat insulation material from iron tailings | |
| CN107880483A (en) | A kind of preparation method of graphene phenol-formaldehyde resin modified | |
| CN101439958A (en) | Silica aerogel heat insulation composite material containing nano semiconductor particle and preparation thereof | |
| CN114506128B (en) | Light heat insulation material and preparation method thereof | |
| CN109457826A (en) | A kind of three-decker cement base suction wave plate and preparation method thereof for mixing EP and NGPs wave absorbing agent again | |
| CN107200581A (en) | A kind of preparation method of stalk wood ceramics composite |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080507 Termination date: 20101220 |