WO2010128294A1 - Matériau solide de faible masse volumique dérivé de riz - Google Patents

Matériau solide de faible masse volumique dérivé de riz Download PDF

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Publication number
WO2010128294A1
WO2010128294A1 PCT/GB2010/000903 GB2010000903W WO2010128294A1 WO 2010128294 A1 WO2010128294 A1 WO 2010128294A1 GB 2010000903 W GB2010000903 W GB 2010000903W WO 2010128294 A1 WO2010128294 A1 WO 2010128294A1
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Prior art keywords
rice
solid layer
solid
gel
low density
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PCT/GB2010/000903
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English (en)
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Fortunato Cardenas
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Palmer, Jonathan, Richard
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Publication of WO2010128294A1 publication Critical patent/WO2010128294A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/08—Interconnection of layers by mechanical means
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • C01B33/1585—Dehydration into aerogels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/14—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by a layer differing constitutionally or physically in different parts, e.g. denser near its faces
    • B32B5/147—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by a layer differing constitutionally or physically in different parts, e.g. denser near its faces by treatment of the layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/10—Interconnection of layers at least one layer having inter-reactive properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/005—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising one layer of ceramic material, e.g. porcelain, ceramic tile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/02—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising animal or vegetable substances, e.g. cork, bamboo, starch
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B32B9/04—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
    • B32B2307/102—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/206—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/304—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/72—Density
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/73—Hydrophobic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2419/00—Buildings or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2551/00—Optical elements

Definitions

  • the present invention relates to a method for producing a rice-derived low density solid material, and in particular a method for producing a rice-derived aerogel, and the low density solid material obtained by the method.
  • Aerogels are solid materials having low density and high porosity. Such materials are formed by replacing the liquid or solvent of a gel with a gas. Aerogels typically have large open pores and high specific surface areas. These provide aerogels with useful physical properties, for example low thermal conductivity and low sound velocity. Aerogels are the best insulation known to man to date, however existing industrial production is not economically viable due to expensive raw materials and complex processes involved.
  • WO 2005/044727 describes a method for producing a silica aerogel, which comprises combustion of rice husk until the white ash is obtained, dissolving rice husk ash in aqueous sodium hydroxide, heating and stirring the resultant gel mixture to produce a sodium silicate solution, adding concentrated sulphuric acid to the resulting water glass solution to convert the sodium silicate to silica and produce a silica hydrogel, aging the hydrogel to allow the gel structure to develop, displacing the water with a Cl to C4 alcohol, to produce an alcogel, and subjecting the alcogel, to super critical drying to form an aerogel.
  • the method of producing a silica aerogel described in WO 2005/044727 only provides a method of using rice husks.
  • the present invention aims to address at least some of the disadvantages of the prior art methods.
  • One of the aims of the present method is to provide a more economically viable, more environmentally friendly, and/or cheaper process than known methods of producing rice-derived low density solid material and/or aerogels.
  • a method for producing a rice-derived low density solid material comprising: providing a first solid layer, preferably an aerogel, formed from a rice hull derived gel; providing a second solid layer, , preferably an aerogel, derived from rice flour; and laminating the first and second layers together to form the low density solid material.
  • One advantage of the present invention is that the method of making the rice-derived low density solid material as described herein uses both the rice hull (otherwise known as rice husk) and rice flour. This is unlike prior art methods which only describe the use of rice hulls in the formation of aerogels. Previously there has been no disclosure or suggestion that rice grain and/or rice flour itself may be used in the formation of rice-derived low density solid materials and/or aerogels.
  • rice-derived solid material means a solid material which is formed from material derived from rice.
  • the term "rice-flour” means ground rice grain.
  • the rice is processed to remove substantially all of the husk (otherwise known as rice hull) .
  • the grains of rice are ground into a powder.
  • it will be ground to the finest possible grain size to provide ultra fine powder.
  • the rice flour will be filtered prior to use to ensure that the particles sizes in the flour are small enough.
  • the powder will have a mean particle diameter of from 1 to 40 microns.
  • the mean particle diameter of the rice flour is from 5 to 10 microns, more preferably it is approximately 5 microns.
  • Particle size may be measured by any suitable means, for example by the use of sieves having holes of suitable sizes.
  • rice soup means a solution provided by boiling rice flour in water.
  • low density solid material means a solid material which has a bulk density of less than 5 grams per cubic centimetre, preferably less than 2 grams per cubic centimetre, more preferably less than 1 gram per cubic centimetre, more preferably still less than 0.75 grams per cubic centimetre, more preferably still less than 0.5 grams per cubic centimetre.
  • the bulk density of the solid material may be measured as follows: the dimension of the material is measured to compute its volume. The material is then weighed. The weight divided by the volume provides the density. For measurement of the density of the powder, a sample of powder is weighed. The sample of powder is then placed in a beaker of solvent, for example, water. The volume of solvent displaced by the powder is equal to the volume of the powder. The density is then calculated by dividing the weight of the powder by its volume.
  • the first solid layer is an aerogel.
  • the second solid layer is an aerogel.
  • the term "aerogel” means a porous solid formed by replacing the liquid or solvent of a gel with a gas.
  • the aerogel has a low density.
  • the aerogel has a bulk density of less than 5 grams per cubic centimetre, preferably less than 2 grams per cubic centimetre, more preferably less than 1 gram per cubic centimetre, more preferably still less than 0.75 grams per cubic centimetre, more preferably still less than 0.5 grams per cubic centimetre.
  • the term "laminating the first and second layers together" includes contacting and/or joining the first and second layers.
  • the first and second layer may be laminated together by chemical and/or physical means.
  • the first and second layer may be glued together with any suitable glue, for example, sodium silicate.
  • Sodium silicate is the same slurry which may be used in making the first solid layer (or aerogel) .
  • Sodium silicate is a common adhesive used in metal to wood and metal to glass and glass to wood and glass to glass adhesion.
  • the first and second layers may be laminated together by a clamping or holding means .
  • the two layers may be placed in a retaining means , for example a holder or container.
  • the surface of the first and/or second layer may be chemically treated such that a chemical bond may form between the first and second layer.
  • the chemical bond may comprise Van-der-Waals interactions, hydrogen bonds, covalent bonds and/or ionic bonds .
  • the first and second layer may be laminated together with one or more intermediate layers between the first and second layer.
  • the intermediate layer (s) may be formed of any suitable material, and the methods of laminating the intermediate layers with the first and/or second layer may be the same or different to those described above.
  • Both methods of forming the first and second solid layers require ash formed by the thermal pyrolysis of rice hulls .
  • Rice straw may also undergo thermal pyrolsis to form ash for use in the present invention.
  • Rice hull ash may be produced by gasification and/or by combustion and/or by incineration of rice hulls in a furnace.
  • Gasification is the conversion of the hydrocarbon or carbohydrate components in a solid fuel into gases through the application of heat.
  • Combustion is the act or process of burning or a chemical change, especially oxidation, accompanied by the production of heat and light.
  • Incineration is the act of consuming by burning to ashes.
  • Thermal pyrolysis is a chemical change that occurs in a substance through the application of heat.
  • the term "thermal pyrolysis" includes gasification, combustion, incineration, and any and all forms of heat which produces rice hull ash and amorphous carbon from rice hulls.
  • thermal pyrolysis is used to produce rice hull ash and amorphous carbon from rice hulls
  • the thermal pyrolysis is gasification.
  • heat and/or energy is produced. This heat and/or energy may be used in the subsequent processes for forming the rice-derived low density solid material and/or the first solid layer and/or second solid layer. For example, this heat and/or energy may be used to grind the rice grain to a powder to produce rice flour, and/or to heat the rice soup .
  • the ashes obtained from the thermal pyrolysis of the rice hull are preferably collected and ground to fine powder.
  • the particles in the fine powder have a mean diameter of from 1 to 40 microns, or from 5 to 20 microns.
  • the mean diameter of the particles is approximately 5 microns .
  • a base and water are added to the ash and heated to form a solution.
  • the water is boiled for from 10 minutes to 2 hours, more preferably from 30 minutes to 1 hour.
  • the water is heated at over 100 0 C, more preferably it is heated at approximately 200 0 C.
  • the resulting solution preferably comprises a water-soluble silicate.
  • any suitable base may be used to form a water soluble silicate when heated with the rice hull ash and water.
  • base is added until the pH of the solution is in the range of from 11 to 13.
  • the pH of the solution formed is from 12 to 12.5, and more preferably it is approximately 12.3.
  • potassium silicate is formed by the addition of base, preferably the pH of the solution formed is from 11.5 to 12, and more preferably it is approximately 11.7.
  • the pH of the solution may be measured by any suitable means, for example using pH indicator paper.
  • the base may be selected from one or more alkali, or alkaline earth metal salts.
  • base is selected from NaOH, KOH, Mg(OH) 2 , Na 2 CO 3 and mixtures of two or more thereof. Most preferably the base is NaOH. This is because NaOH is easily and cheaply commercially available.
  • the ratio of base to rice hull ash by weight is in the range of from 5: 1 to 1.5 to 1, more preferably it is from 3:1 to 1.5 :1, more preferably still the ratio is 2:1.
  • the ratio of water to rice hull ash by weight is in the range of from 50: 1 to 10 to 1, more preferably it is from 25:1 to 10:1, more preferably still the ratio is 22:1.
  • the solution comprising water soluble silicate is filtered to provide a permeate and a retentate.
  • Any suitable filtering means may be used.
  • Suitable filters for use in the present invention have the following characteristics.
  • the permeate comprises water-soluble silicate.
  • the retentate contains a high amount of amorphous carbon which is dried and may be then added to the rice flour to form the second solid layer.
  • a method for forming a first solid layer, preferably an aerogel, for use in a rice-derived low density solid material comprising: providing ash formed from thermal pyrolysis of rice hulls; adding a base and water to the ash and heating to form a solution; filtering the solution to provide a permeate and a retentate ; heating at least a portion of the permeate, adding an inorganic salt and an acid to form a gel; removing solvent from the gel to form the first solid layer, preferably an aerogel.
  • the permeate is concentrated by boiling to attain a viscous solution, preferably comprising from 1 to 1.5 kg of metal silicate (preferably sodium silicate) per litre of water. More preferably the permeate will be concentrated to provide a solution comprising from 1.2 to 1.4 kg of metal silicate (preferably sodium silicate) per litre of water. Most preferably, the permeate will be concentrated to provide a solution comprising approximately 1.365kg of metal silicate (preferably sodium silicate) per litre of water. The level of silicate in the permeate may be measured by titration.
  • enough water is removed by heating the permeate to form a slurry, or viscous solution.
  • An inorganic salt is added to the permeate and acid is added to neutralise the solution. It will be understood that these steps may be carried out in any order.
  • the inorganic salt may be added before, whilst or after the acid is added.
  • the permeate may be heated before, during and/or after the inorganic salt is added.
  • the permeate may be heated before, during and after the acid is added.
  • the inorganic salt is added to the permeate to further thicken it before acid addition.
  • slurry and inorganic salt are blended so that it has a substantially homogenous consistency.
  • the mixture may be blended using any suitable means, for example by hand, and/or using a mechanical blender.
  • the inorganic salt is added to the permeate after the permeate has been concentrated to provide a solution comprising from 1.2 to 1.4 kg of metal silicate (preferably sodium silicate) per litre of water.
  • metal silicate preferably sodium silicate
  • the volume of the permeate is increased by from 20% to 70% by addition of the inorganic salt based on the total volume of the permeate prior to addition of the inorganic salt .
  • volume of the permeate is increased by from 40% to 60%, more preferably still by approximately 50% by addition of the inorganic salt based on the total volume of the permeate prior to addition of the inorganic salt.
  • Addition of the inorganic salt to the permeate typically results in the formation of a semi-solid paste.
  • This paste is preferably thoroughly mixed.
  • Acid is added to the permeate to neutralise it.
  • acid is added until the pH of the permeate is from 6 to 8, more preferably from 6.5 to 7.5, more preferably still it is approximately pH 7.
  • the acid may be acetic acid, sulphuric acid, hydrochloric acid, phosphoric acid, nitric acid and mixtures of two or more thereof.
  • Other suitable acids include tartaric acid and citric acid.
  • the acid is acetic acid.
  • Acetic acid has been found to be particularly advantageous, because when it is used in the presence of sodium ions in the permeate, sodium acetate is formed which has a lower melting point than silicate, and thus can easily be removed from the structure once it has served its purpose as structural supports.
  • rice may be used to form acetic acid for use in the described method of making the first solid layer.
  • rice flour preferably in the form of a powder, may be mixed with water, and heated to form a rice soup.
  • the rice soup may them be fermented to produce acetic acid.
  • Bacteria for example, acetobacter
  • Bacteria may be used to aide the fermentation process .
  • the concentration of the acid is from IM to 2M.
  • the amount of acid added to the silicate is calculated by titration. Adding too much acid typically causes the aerogel to be dark because the acid may burn during the heat treatment of melting the salt and might trap some soot in the process.
  • the structure of the gel may be controlled.
  • the volume of first solid layer (which is preferably an aerogel) may be changed, for example, by varying the amount or altering which inorganic salt, acid and/or base is used. This allows the properties of the resulting first solid layer (which is preferably an aerogel) to be controlled, and/or tailored to suit its desired application.
  • an inorganic salt into the permeate results in the presence of the salt in the subsequent gel, which helps the gel to keep its shape and form intact when the solid is formed. It is thought that a salt matrix is formed within the gel structure. Preferably, once the gel structure has been strengthened, the inorganic salt is removed.
  • the presence of the inorganic salt, and preferably a salt matrix, in the gel helps to make the first solid layer, preferably an aerogel, porous and keeps the volume substantially stable during gelatinisation. By maintaining, or helping to stabilise the gel structure prior to removal of the solvent therefrom, allows the formation of a high porous, low density layer without the need for solvent removal to be carried out by supercritical drying.
  • the inorganic salt is an inorganic salt of one or more alkali, and/or alkaline earth metal.
  • the inorganic salt is selected from NaCl, KCl, CaCl 2 , Na 2 SO 4 and mixtures of two or more thereof .
  • the inorganic salt is NaCl.
  • the inorganic salt will be a sodium salt .
  • the inorganic salt has mean particle diameter of from 1 to 40 microns.
  • the mean particle diameter is from 5 to 10 microns, more preferably it is approximately 5 microns .
  • the inorganic salt may comprise up to 1% or up to 2% by weight of sodium bicarbonate based on the total weight of the inorganic salt .
  • the inorganic salt present in the gel structure has a lower melting point than silicon dioxide. This is advantageous so that these salts may be melted away during the heating process in which solvent is removed from the gel to form the first solid layer (which is preferably an aerogel) .
  • the silicon dioxide does not melt . Any remaining salts which are no longer required in the first solid layer may be washed away.
  • the salts may be washed away and/or dissolved either before the gel has completely solidified, and/or afterwards.
  • the process comprises an optional washing step. Any suitable solvent may be used to wash away the salts, for example water and/or methanol. Preferably boiling water is used.
  • the structure may be at least partially or fully submerged in the solvent to wash away the solvent. Additionally and/or alternatively, the solvent may be poured or sprayed on the structure.
  • the gel may be heated via microwave, using an oven and/or furnace. Typically the gel will be heated from 0.5 to 5 hours, or from 1 to 2 hours, more preferably for approximately 1 hour. Preferably the gel is heated at from 300 0 C to 1000 0 C, from 500 0 C to 800 0 C, and most preferably at approximately 700 0 C. Preferably the gel is placed in a mould and is heated in the mould. Heating the gel strengthens it structure.
  • the mould is preferably made of aluminium and/or a metal plated with aluminium.
  • the mould and/or container prevents or substantially reduces oxygen, and/or air, entering the container, but allows moisture and gas out of the mould and/or container.
  • the gel may be removed from the mould and/or container after the gel has been strengthened by heating, and before solvent is removed from the gel. However, preferably, the strengthened gel will be maintained in the mould and/or container (which allows liquids and/or gases to be released) whilst solvent is removed.
  • the strengthened gel may then be submerged in water to remove or at least partially remove the salt matrix, preferably leaving the silicate framework in place.
  • the strengthened gel may be at least partially dried by spinning.
  • Solvent is removed from the gel to form the first solid layer, which is preferably an aerogel.
  • the solvent is removed by conventional heating means.
  • the solvent is not removed by supercritical drying (which is expensive) .
  • solvent is removed from the gel by heating.
  • the solvent is removed from the gel, by heating at from 100 0 C to from 300 0 C for from 12 hours to 24 hours.
  • the gel is kept out of contact with oxygen and/or air.
  • the gel is kept in a container and/or mould which prevents oxygen, and/or air, entering the container, but which allows moisture and gas out of the container.
  • the container used in the method of producing the first solid layer may be the same or different to that used to produce the second solid layer.
  • the pore solvent in the gel is replaced by gas without substantially altering the network structure or the volume of the gel body.
  • the change in volume of the wet gel to the dry solid gel (first solid layer) is no more than 30% by volume, preferably no more than 20%, or 10 % by volume, based on the total volume of the wet gel.
  • a method for forming a second solid layer for use in a rice-derived low density solid material comprising: providing ash formed from the thermal pyrolysis of rice hulls; mixing a base and water with the ash and heating to form a solution; filtering the solution to provide a permeate and a retentate; blending at least a portion of the retentate with rice flour and an inorganic salt to form a mixture; compacting the mixture; heating the mixture to form a consolidated material ; washing the consolidated material to at least partially remove the inorganic salt drying the washed consolidated material to form the second solid layer.
  • the retentate is dried to remove at least some of the water present.
  • the retentate is dried in an oven.
  • substantially all of the water present in the retentate is removed by drying.
  • the retenate is dried at a temperature in the range of from 40 to 50 degree Celsius until the total density of the material approaches that of coal ⁇ 613-913 (kg/m3) .
  • the dried retentate has less than 5% by weight, more preferably less than 2%, or less than 1% by weight of water based on the total weight of the dried retenate.
  • the rententate is preferably prevented from being exposed to air by covering it at all times during the drying process.
  • Rice flour is then added to at least a portion of the
  • rice flour is added in an amount of from 1/20 to 1/5 of the volume of volume of the retentate. More preferably rice flour is added in an amount of from 1/10 of the volume of volume of the retentate .
  • the silica content in the dried retentate may be as high as 10% by weight of the total weight of the dried retentate.
  • the percentage silica content of the retentate may be measured by obtaining a sample and oxidizing it further by combustion and weighing the ash content .
  • the rice flour has a high portion of amorphous carbon.
  • the rice flour comprises from 40 to 50 % by weight of amorphous carbon.
  • the rice flour and retentate is then preferably mixed by grinding. Any suitable means of grinding the mixture may be used. Typically the rice flour and retentate will be ground together to provide a powder having a mean particle diameter of from 1 to 40 microns. Preferably the mean particle diameter will be from 5 to 10 microns, more preferably it is approximately 5 microns .
  • An inorganic salt is added to the mixture of rice flour and (preferably dried) retentate.
  • the inorganic salt is added as a fine powder.
  • the inorganic salt has mean particle diameter of from 1 to 40 microns.
  • the mean particle diameter is from 5 to 10 microns, more preferably it is approximately 5 microns.
  • the inorganic salt may comprise up to 1% or up to 2% by weight of sodium bicarbonate based on the total weight of the inorganic salt.
  • inorganic salt is added to the rice flour and retentate in an amount of from 2 to 30 times, or from 5 to 20 times, by weight of the total weight of the rice flour and retentate mixture. More preferably inorganic salt is added to the mixture of rice flour and retentate in an amount approximately ten times by weight of total weight of rice flour and dried retentate mixture.
  • the inorganic salt used in the method of making the first solid layer may be the same or different to the inorganic salt used in making the second solid layer.
  • the inorganic salt is an inorganic salt of one or more alkali, and/or alkaline earth metal.
  • the inorganic salt is selected from NaCl, KCl, CaCl 2 , Na 2 SO 4 and mixtures of two or more thereof. Most preferably the inorganic salt is NaCl.
  • the inorganic salt will be a sodium salt.
  • the at least a portion of the retentate, rice flour and an inorganic salt are blended together to form a mixture . Any- suitable means of blending these components may be used.
  • a substantially homogenous mixture is formed.
  • the mixture is filtered in order to obtain a mixture having a mean particle size of from 1 to 40 microns.
  • the mean particle diameter is from 5 to 10 microns, more preferably it is approximately 5 microns.
  • the mixture comprising the at least a portion of the retentate, rice flour and an inorganic salt are compacted together.
  • the mixture is compacted together using a substantially flat, solid heavy block.
  • the compacted mixture has a density approaching the density of the inorganic salt used.
  • the compacted mixture has a density similar to or substantially the same as the density of the inorganic salt used.
  • the compacted mixture is then preferably placed inside a container, which is then sealed.
  • the container is designed such that gases and solvents may escape, but air cannot enter the container to oxidise the components of the mixture. It is not necessary for a vacuum to be formed in the container. However, it is desirable to keep oxygen and/or air out.
  • Such containers are available by special fabrication from metal shops and ceramic fabricators.
  • the mould is preferably made of aluminium and/or a metal plated with aluminium.
  • the compacted mixture preferably inside a container, is heated to form a consolidated material.
  • the compacted mixture is heated at from 500 0 C to 1000 0 C, more preferably from 600 0 C to 800 0 C, or at approximately 700 0 C.
  • the compacted mixture is heated for from 10 minutes to 2 hours, more preferably from 20 minutes to 1 hour, more preferably still for approximately 30 minutes. Moisture and/or gases are released from the mixture during heating to form the consolidated material.
  • the consolidated material is then allowed to cool.
  • the material is allowed to cool to ambient temperature (from 15 0 C to from 35°C, or to 40 0 C) .
  • the consolidated material is then washed to at least partially remove the inorganic salt. Preferably washing removes substantially all, or all of the inorganic salt.
  • a gel is formed during the washing step. It is thought that a carbon comprising hydrogel is formed during the washing process .
  • the inorganic salt is thought to provide a salt matrix which helps to support the formation of a hardened low-density, highly porous structure. After washing, solvent is thought to fill the gaps formed in the structure by removal of the inorganic salt.
  • Any suitable solvent may be used to wash away the inorganic salt, for example water and/or methanol. Preferably boiling water is used.
  • the structure may be at least partially or fully submerged in the solvent to wash away the solvent.
  • the solvent may be poured or sprayed on the structure . If the Consolidated material was held in a container while it was heated, optionally the container may be removed before washing. Optionally, the consolidated material may be placed in a further container, for example a further liquid-gas permeable container prior to washing. The consolidated material may be kept in the same container for washing .
  • the washed consolidated material preferably in the form of a carbon comprising hydrogel, is then dried to form the second solid layer.
  • solvent present in the gel structure is replaced by gas, thus an aerogel is formed.
  • the pore solvent in the gel is replaced by gas without substantially altering the network structure or the volume of the gel body.
  • the change in volume of the wet gel to the dry solid gel (second solid layer) is no more than 30% by volume, preferably no more than 20%, or 10 % by volume, based on the total volume of the wet gel.
  • the consolidated material may be removed from the container before, or after it is dried to remove the solvent from the structure.
  • Drying the consolidated material removes solvent to form the second solid layer, which is preferably an aerogel.
  • substantially all the solvent is removed from the consolidated material to form the second solid layer, which is preferably an aerogel.
  • the solvent is removed by heating, more preferably by conventional heating means.
  • the solvent is not removed by supercritical drying (which is expensive) .
  • the solvent is removed from the consolidated material, by heating at from 100 0 C to from 300 0 C for from 12 hours to 24 hours.
  • the consolidated material is kept out of contact with oxygen and/or air.
  • the consolidated material is kept in a container which prevents or substantially reduces oxygen, and/or air, entering the container, but allows moisture and gas out of the container.
  • the first and/or second solid layer may be treated to alter their properties, and in particular to alter their surface properties.
  • the first and/or second solid layer obtained by the methods outlined herein have hydrophilic surfaces.
  • the surfaces may be altered by, for example, submerging the gel and/or consolidated material in 1:1 methanol-silanol with an optional Tetra Ethyl Ortho-Silicate (TEOS) solution (preferably 10 percent by weight) to modify the surface of the gel and/or consolidated material. This may also served to further strengthen the skeleton.
  • TEOS Tetra Ethyl Ortho-Silicate
  • the gels and/or consolidated material may be submerged for approximately 24 hours at approximately 40 degrees Celsius. After submerging the structures may be spin dried at the boiling temperature of the methanol-silanol solution until completely dried.
  • the first and/or second solid layer may undergo surface treatment after they have been formed.
  • the first solid layer has a bulk density of from 0.1 to 0.8 grams per cubic centimetre, more preferably, it has a bulk density of from 0.2 to 0.7 grams per cubic centimetre, more preferably still, it has a bulk density of from 0.3 to 0.6 grams per cubic centimetre.
  • the second solid layer has a bulk density of from 0.1 to 0.8 grams per cubic centimetre, more preferably, it has a bulk density of from 0.15 to 0.6 grams per cubic centimetre, more preferably still, it has a bulk density of from 0.2 to 0.5 grams per cubic centimetre.
  • the density of the first solid layer may be the same or different to the density of the second solid layer.
  • the first and/or solid layer will have a depth of less than 1 cm. This has been found to be advantageous in order to aid the drying process.
  • the first and/or solid layer will have a depth of from 0.2 to 1 cm, or from 0.5 to 0.75cm.
  • a rice-derived low density solid material obtainable by the method described herein.
  • first and/or second solid layer for use in a rice-derived low density solid material obtainable by the method described herein.
  • the insulation may be thermal insulation, soundproofing insulation, electrical insulation and/or building insulation. Such insulation also has applications in cryogenics and superheated steam insulation and the likes.
  • the rice-derived low density solid material described herein and/or the first and/or solid layers described herein may also be used as filters, for example in purification methods .
  • the present invention also provides insulation comprising the first solid layer obtainable by the method described herein, the second solid layer obtainable by the method described herein and/or the rice-derived low density solid material obtainable by the method described herein.
  • the gasification of the rice hull may be used to produce methanol or be directly used for the production of aerogels.
  • Methanol which may be used in the process of the present invention may be produced by the gasification of rice hulls.
  • the rice hulls are gasified and compressed while allowing them to react with water vapours using copper as a catalyst (see US Patent No. 3689575) .
  • Figure 1 A schematic diagram of the rice-derived low density solid material of the present invention.
  • Figure 2a A photograph of the first solid layer, which is preferably an aerogel, produced by the method of the present invention.
  • Figure 2b A photograph of the second solid layer, which is preferably an aerogel, produced by the method of the present invention.
  • Figure 3a A scanning electron microscope (SEM) image showing the porosity of a first solid layer produced by the method of the present invention.
  • Figure 3b A scanning electron microscope (SEM) image showing sodium acetate in the matrix of a first solid layer produced by the method of the present invention.
  • Figure 4a A scanning electron microscope (SEM) image showing the porosity of a second solid layer produced by the method of the present invention.
  • Figure 4b A scanning electron microscope (SEM) image showing the porosity of a second solid layer produced by the method of the present invention.
  • Figure 1 show a schematic diagram of a rice-derived low density solid material (1) of the present invention.
  • the first solid layer (2) and the second solid layer (3) are laminated together to form the low density solid material (1) .
  • laminated the first and second layers together includes contacting and/or joining the first and second layers.
  • the first and second layer may be laminated together by chemical and/or physical means.
  • the first and second layer may be glued together which any suitable glue (4) as depicted in Figure 1.
  • Method of making the first solid layer preferably an aerogel .
  • Rice hulls are gasified to form rice hull ash.
  • the gasification process produces methanol and/or releases energy which may be used in the subsequent process .
  • the ashes are collected.
  • the energy released in the gasification of the rice hulls is used in the process of first solid layer (aerogel) production.
  • the ashes are then passed to a grinder to be pulverized and filtered into fine powder.
  • the fine powders are mixed with 2 parts of NaOH and 22 parts of H 2 O for each part of Rice hull ash by weight.
  • the mixture is boiled in distilled water at 200 degrees Celsius for one hour to produce a sodium silicate solution.
  • the boiling solution is then filtered to remove the un- dissolved residues, the filtered solution is then concentrated by boiling futher to attain a viscous solution having a molar concentration of 1-1.365kg or lkg ⁇ 0.7331 Na 2 SiO 3 per H 2 O determined via titration based on the following chemical reaction.
  • the viscous solution is further thickened by adding sodium chloride with a volume half of the sodium silicate solution to attain a semi solid paste viscosity almost solidified.
  • the solution is thoroughly mixed.
  • the sodium silicate is turned into gel by adding 1 mole acetic acid to the solution while continuous heating until a gel is formed based on the equation:
  • the gel is then heated to attain a solidified form via microwave or oven heater.
  • the resulting silica gel has a salt matrix of sodium acetate and sodium chloride.
  • the gel is strengthened by heating for 1 hour at 700° Celsius to solidify in a mould which substantially prevents oxygen and/or entering the mould, but allows gas and liquid to drain from the mould.
  • the mould full of solidified gel with salt is then submerged in boiling water and rotated in a spinner for 1 hour. Excess water is removed by filtration using a synthetic, non absorbing, liquid permeable fabric. Water is partially removed from the gel by slight compression using the filtering fabric without destroying the solidified hydrogel structure. This is done twice using boiling water to wash away and remove the acetate matrix and sodium chloride in the solidified gel.
  • the solidified gel is dried at 100° Celsius until completely dried to produce hydrophilic first solid layer (aerogel) .
  • Method of making the second solid layer preferably an aerogel .
  • the amorphous carbon obtained in the filtration of the sodium silicate is dried and rice flour is added to thicken and act as a binder of the solid mixture.
  • Ultra fine salt of sodium chloride is added to the thickened mixture and is thoroughly mixed via filtration to obtain a homogenous and uniform mixture. The mixture is then compacted, sealed and is heated to react and release moisture based on the following decomposition reaction:
  • Both the gels are strengthened by heating for 1 hour at 700° Celsius to solidify in a mould which substantially prevents oxygen entering the mould, but allows gas and liquid to drain from the mould.
  • the mould full of solidified gel with salt is removed from the mould and placed in a liquid permeable container and is then submerged in boiling water and rotated in a spinner for 1 hour. Excess water is removed by filtration using a synthetic, non absorbing, liquid permeable fabric. Water is partially removed from the gel by slight compression using the filtered fabric without destroying the solidified hydrogel structure. This is done twice using boiling water to wash, away and remove the salt sodium acetate and sodium chloride matrix in the solidified gel. The solidified gel is dried at 100° Celsius until completely dried to produce hydrophilic second solid layer (aerogel) .
  • the hydrophilic first and second solid layers are submerged in 1:1 methanol-silanol with an optional 10 percent 4 Tetra Ethyl Ortho-Silicate (TEOS) solution to modify the surface area of the gel and to further strengthen the skeleton of the silicon dioxide structure for 24 hours at 40 degrees Celsius.
  • TEOS Tetra Ethyl Ortho-Silicate
  • the alcogel can be spin dried at the boiling temperature of the methanol-silanol solution until completely dried. Alternatively, it can also be dried using microwave heating via evaporation.
  • the aerogels 5 are then removed from the mould for characterization and may be used for the purpose of insulation.
  • the filtered residue containing carbon is oven dried by spreading the residue in a tray at 90 degrees Celsius until completely dried.
  • Rice flour is added in the amount of 1/10 of the volume of the dried carbon residue, and is mixed by- grinding and is weighed.
  • An amount of ultra fine sodium chloride is added equal to 10 times the total weight of the carbon residue mixture.
  • the mixture is thoroughly mixed by filtration until a uniform homogenous mixture is obtained.
  • the resulting mixture is then compacted and sealed in a metal container to be heated at 700 degrees for 30 minutes to release the moisture and gases in the compacted mixture. It is the cooled by submerging in water and unpacked and is washed in boiling water twice.
  • a solution of 1:1 methanol and silanol is added modify the surface of the aerogel .
  • the alcogels are then dried via evaporation.
  • the aerogels obtain are then joined together to form a composite insulation material.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Dispersion Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

La présente invention concerne un procédé pour produire un matériau solide de faible masse volumique dérivé de riz, comprenant : la production d'une première couche solide formée d'un gel dérivé de cosse de riz ; la production d'une deuxième couche dérivée de farine de riz ; et le laminage des première et deuxième couches conjointement pour former le matériau solide de faible masse volumique.
PCT/GB2010/000903 2009-05-04 2010-05-04 Matériau solide de faible masse volumique dérivé de riz WO2010128294A1 (fr)

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ITTO20121170A1 (it) * 2012-12-28 2014-06-29 Gerardo Forgione Pasta a bassa densita¿ di rivestimento superficiale per intonaco
ITTO20121171A1 (it) * 2012-12-28 2014-06-29 Gerardo Forgione Pasta a bassa densita¿ di rivestimento superficiale per intonaco

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Publication number Priority date Publication date Assignee Title
ITTO20121170A1 (it) * 2012-12-28 2014-06-29 Gerardo Forgione Pasta a bassa densita¿ di rivestimento superficiale per intonaco
ITTO20121171A1 (it) * 2012-12-28 2014-06-29 Gerardo Forgione Pasta a bassa densita¿ di rivestimento superficiale per intonaco
EP2749548A2 (fr) 2012-12-28 2014-07-02 Gerardo Forgione Pâte à densité baisse de revêtement superficiel pour enduit

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