WO2021185716A1

WO2021185716A1 - Thin and flexible thermal insulation material based on a monolithic organic aerogel

Info

Publication number: WO2021185716A1
Application number: PCT/EP2021/056447
Authority: WO
Inventors: Dirk Weinrich; Marc Fricke; Volker VOGELSANG; Fabian LIED; Sabrina ENGEL
Original assignee: Basf Se
Priority date: 2020-03-17
Filing date: 2021-03-15
Publication date: 2021-09-23
Also published as: EP4121469A1

Abstract

A thermal insulation material with a thickness in the range from 0.1 mm to 5 mm comprising at least one layer A) consisting essentially of a monolithic organic aerogel and at least one cover layer C), a process for preparing such a thermal insulation material and the use of the thermal insulation material in building and construction, refrigeration appliance, electronic devices, aerospace and batteries.

Description

Thin and flexible thermal insulation material based on a monolithic organic aerogel Description

The present invention relates to a thermal insulation material with a thickness in the range from 0.1 mm to 5 mm comprising at least one layer A) consisting essentially of a monolithic organic aerogel and at least one cover layer C), a process for preparing such a thermal insulation mate- rial and its use.

Flexible polyurethane foams and melamine-formaldehyde foams have a thermal conductivity above about 30 milliwatt per m K, which is significantly higher compared to insulating sheets based on aerogels. Because of the higher thermal conductivity, the thermal insulation properties are inferior.

DE 102005021 994 discloses a process for producing vacuum insulation panels by envelop- ment of a shaped body comprising open-celled foam, preferably a rigid polyurethane foam, with a gastight film and subsequent evacuation and gastight welding shut of the films wherein the shaped body comprising open-celled foam is compressed after curing and before evacuation.

Aerogel und xerogel based on polyisocyanate, which may be obtained by supercritical and non- supercritical drying, are disclosed in WO 95/02009 and WO 95/03358.

WO 96/37539 relates to polyisocyanate-based aerogels and their method of preparation. The aerogels are produced by mixing an organic polyisocyanate, carbon black and catalyst in a sol- vent and enables preparation of filled polyisocyanate-based organic aerogels of lower density than aerogels which do not include a filler.

US 2006/211840 A discloses polyurea aerogels as well as methods for preparing the same by mixing a polyisocyanate with a polyamine in a solvent and supercritically drying the resultant gel. Polyoxyalkyleneamine are a preferred type of the polyamines.

WO 2008/138978 discloses xerogels which comprise from 30 to 90 % by weight of at least one polyfunctional isocyanate and from 10 to 70 % by weight of at least one polyfunctional aromatic amine and have a volume average pore diameter of not more than 5 micrometer and their use for vacuum insulation panels. The thermal conductivity for a xerogel material with a density of 170 kg/m³ is above 37 mW/m^*K at a pressure of 1004 mbar. WO 2014/068105 relates to composite elements comprising a profile and an insulating core at least partially enclosed by the profile, wherein the insulating core consists of an organic porous material which has a thermal conductivity ranging from 13 to 30 mW/m^*K, determined in ac- cordance with DIN 12667, and a compressive strength of greater than 0.20 N/mm², determined in accordance with DIN 53421 , to methods for producing such composite elements and to the use of such a composite element for producing windows, doors, refrigerating and/or freezing units and cabinets or facade-structure elements. The porous materials in the examples show thermal conductivities between 20 and 21 mW/m^*K and densities of 110 to 153 g/l.

WO 2017/125414 and WO 2017/125415 relate to a process for producing isocyanate-based aerogels and xerogels with low density, sufficient mechanical stability and low thermal conduc- tivity at ambient pressure and their use as thermal insulation material or for vacuum insulation panels.

Lee et al. describe in J Sol-Gel Sci Technol (2009) 49 page 209 - 220 lightweight polyurea- based organic aerogels via sol-gel processing and supercritical drying and their thermal conduc- tivity depending on the final density.

The mechanical stability and thermal conductivity of the matrix material of uniaxially com- pressed polyurea aerogel was determined as a function of density in Journal of Non-Crystalline Solids, 2014, 406, 73-78. Solid thermal conductivity rises as a function of density.

EP 2 615 132 and US 2005/100728 disclose a material comprising aerogel particles and a poly- tetrafluoroethylene (PTFE) binder having a thermal conductivity of less than or equal to 25 mW/m K at atmospheric conditions. The material is moldable or formable, having little or no shedding or filler particles, and may be formed into structures such as tapes or composites, for example, by bonding the material between two outer layers. Advantageously, composites may be flexed, stretched, or bent without significant dusting or loss of insulating properties. Varying uniformity of the mixture components in the material may have influence on the performance of the structures, such as lower mechanical strength or higher thermal conductivity. In order to create an intimate blend of the PTFE and the aerogel particles specific processes, such as co- coagulation of aqueous colloidal dispersions or dry blending of fine powders at higher shearing rates and lower temperatures and in some cases further milling, mixing, drying and extrusion steps are necessary. US 2014/0287641 discloses layered composites of aerogel materials and non-aerogel materi- als, such as fibrous sheet or laminated plies, including mechanically strong composites with multifunctional properties for various applications, such as insulation for garments, ballistic ma- terials, space applications, lightweight structures for aircraft and automotive parts or sport equipment. Properties, such as flexibility and thermal conductivity of the layered composites depend strongly on the type, amount and thickness of the non-aerogel material in the layered composite.

CN 108576360 A relates to a flexible hydrophobic aerogel compound heat insulation film and a preparation method thereof. The heat insulation film is prepared from a hydroxyapatite thin film and polysiloxane aerogel, wherein the content of the polysiloxane aerogel is 10 to 90 weight percent.

WO 2016/053399 discloses the production of highly durable, flexible fiber-reinforced aerogels with a thickness of less than 10 mm, which can be used as insulation in thermal battery applica- tions. Preferably inorganic silica aerogels are applied to non-woven fiber reinforcement materi- als. Insulation materials based on inorganic silica generally show problems with dusting. Since the fiber diameter is much larger than the cells of the aerogel the resulting fiber-reinforced aero- gel generally forms a non-uniform network structure.

US 2017/0210092 discloses an insulating structure comprising at least one microporous layer and at least one a monolithic aerogel structure extending through a plurality of micropores of a microporous layer. The microporous layer is preferably an expanded fluoropolymerfilm, such as ePTFE film. Optionally the microporous facing layer is adjacent to a porous base layer, such as an open cell foam or a textile layer. Both layers function as reinforcing material for the aerogel.

It was therefore an object of the invention to avoid the abovementioned disadvantages and to provide a thin, flexible, non-dusting and uniform thermal insulation material with low thermal conductivity, as well as an easy process for its preparation and application.

According to the present invention, this object was achieved by a thermal insulation material with a thickness in the range from 0.1 mm to 5 mm comprising at least one layer A) consisting essentially of a monolithic organic aerogel and at least one cover layer C). Most preferably the at least one layer A) consists of a monolithic organic aerogel. Further functional layers F) may be included between layers A) and between layers A) and C). The functional layers F) are preferably selected from an electrically insulating or conducting lay- er, a flame-retardant layer or a heat spreader layer. Several functions can be integrated into one layer F).

The layers may be attached to each other by heat, pressure or chemical bonding. Preferably the layers are connected by adhesives. The adhesive may be applied as spots, stripes or other pat- terns or as a separate adhesive layer (B). Preferably the thermal insulation material consists of one layer A) and one or two layers C), which are attached by an adhesive layer B) resulting in the layer structure A-B-C and C-B-A-B-C respectively.

To facilitate the application of the thermal insulation material a further adhesive layer B) may be applied to the outside of the cover layer C) resulting in the structures A-B-C-B and C-B-A-B-C-B.

In the thermal insulation material each layer A), B), C) and F) have different chemical composi- tions but may have similar functionalities, such as flame retardancy beside their main function.

Preferably the thickness of the thermal insulation material is in the range from 0.3 to 2.5 mm.

For applications where a very thin thermal insulation material in form of tape or foil is desired, preferably only layers A), B) and C) are present. A thermal insulation material consisting of one layer A), one layer B) and one cover layer C) is particularly preferred for very thin thermal insu- lation tapes or foils.

A thermal insulation material consisting of one layer A) and two cover layers C) attached by adhesive layers B) with the layer structure C-B-A-B-C is preferred, if thermal insulation tapes with higher flexibility are advantageous.

Preferably the at least one layer A has a thickness in the range from 0.09 to 4.49 mm, more preferably in the range from 0.25 to 2.45 mm.

The at least one cover layer C) preferably has a thickness in the range from 0.01 to 2.5 mm, more preferably in the range from 0.05 to 1.0 mm, most preferably in the range from 0.05 to 0.5 mm.

Preferably the thickness of the sum of all layers A) is 50% to 99.9%, more preferably 90% to 99% of the total thickness of the thermal insulation material. Preferably the thermal insulation material has a density in the range from 100 to 300 kg/m³ and a thermal conductivity in the range from 12 to 23 mW/m^*K, more preferably in the range from 17 to 22 mW/m^*K.

The flexural strength of the thermal insulation material is preferably in the range from 1000 - 12000 kPa, more preferably in the range from 2000 to 6000 kPa. Flexural strength is deter - mined with a three-point bending test according to DIN EN ISO 178:2013-09.

The aerogel layer A) consists essentially, more preferably consists of a monolithic organic aero- gel and does not comprise any binder or reinforcement structure, which can lead to thermal conductivity through the binder around the aerogel particles or through the fibers or cell struts of the reinforcement surrounding the aerogel.

The monolithic organic aerogel of the aerogel layer A) preferably contains less than 5 wt.-% silica. More preferably the monolithic organic aerogel is not prepared from metal oxide gel pre- cursors, such as modified or unmodified silica aerogels. Most preferably the monolithic organic aerogel consists essentially of the elements C, H, N and O.

Preferably the monolithic organic aerogel in layer A) is a monolithic aerogel based on polyure- thane (PU) and/or polyurea (PUR) with less than 80% of polyisocyanurate (PIR) structures. Layer A)

Layer A) is preferably obtained from a molding based on a monolithic organic aerogel, which may be cut and/or compressed into thinner sheets.

The molding based on an organic aerogel according to the invention has a density in the range from 100 to 300 kg/m³, preferable in the range from 140 to 240 kg/m³. The thermal conductivity is in the range from 12 to 19 mW/m^*K, preferable in the range from 13 to 18 mW/m^*K, meas- ured according to DIN EN 12667:2001-05 at 10°C and 101325 Pa. Most preferably the molding according to the invention has a density is in the range from 140 to 240 kg/m³ and the thermal conductivity is in the range from 14 to 17 mW/m^*K.

The molding according to the invention preferably has an average pore size in the range be- tween 1 to 150 nm. The molding according to the invention preferably has a compression strength in the range from 300 - 1200 kPa. The flexural strength is preferable in the range from 300 - 5000 kPa, more preferable in the range from 1000 - 2500 kPa, as determined according to DIN EN 12089:2013- 06. The bending is preferably in the range from 10 - 20 mm.

The molding according to the present invention may have various sizes and shapes depending on the molding tools selected. The molding may be in the form of blocks or sheets. Preferable the molding is in the form of a sheet with a thickness in the range from 100 pm to 10 mm, more preferably in the range from 0.5 to 5 mm.

The molding according to the present invention may have a certain surface texture depending on the molding tools selected.

Aerogels are porous materials, which are obtainable by pouring a sol in a molding followed by drying through solvent exchange with supercritical carbon dioxide (scC02). Preferred aerogels are based on polyurethanes (PU) or polyurea (PUR). The organic aerogel is preferable a mono- lithic aerogel based on polyurethane (PU), polyurea (PUR), polyisocyanurate (PIR) or mixtures thereof. Preferably the organic aerogel has less than 80%, more preferably less than 50% of polyisocyanurate (PIR) structures, based on the total of PU-, PUR- and PIR- structures. The amount of PU-, PUR- and PIR- structures may be determined by infrared (IR) spectroscopy. Preferred aerogels may be produced by reacting a mixture (M) comprising at least one poly- functional isocyanate (a1), at least one aromatic amine (a2), and at least a catalyst (a3) in the presence of a solvent (S) to form a gel and drying the gel obtained under supercritical condi- tions, as described in more detail below.

Further aerogels suitable as layer A) are aerogels based on polyimides (PI), polyamides, resor- cinol-formaldehyde, melamine-formaldehyde, polycyclopentadiene, polybenzoxazine, polysty- rene, or bio-based polymers, such as polysaccharides, pectin, cellulose, nanocellulose, pectin, chitosan, starch, lignin, proteins or any mixtures of the aerogels described above. Preferably the organic aerogel does not contain carbon-based aerogels, such as graphene, pyrolyzed organic aerogels or metal-containing aerogels or organic-inorganic hybrid aerogels, such as silica, alu- mosilicates, clays and metal oxides of titanium, zinc, aluminium, magnesium iron or zirconium. Preferably, alginate-containing porous materials as described in WO 2015/17708 or polyimide- based aerogels may be used. Sheet or moldings of highly crosslinked organic aerogels and xerogels are generally non- flexible. They can be converted to thinner sheets or moldings by non-destructive compression without lateral deformation performed in a hydraulic or pneumatic press. Due to higher density the compressed sheets or moldings show better mechanical properties. Surprisingly the thermal conductivity is additionally significantly lower compared with sheets or moldings with compara- ble density, which were not compressed.

One embodiment of the process for preparing a molding as described above comprises com- pressing a molding based on an organic aerogel with a density in the range from 80 to 140 kg/m³ with a compression factor in the range from 5 to 70 Vol.-%.

A preferred process comprises compressing a molding based on an organic aerogel in the form of a sheet unidirectional in the direction of the thickness of the sheet.

The compression may be performed in a hydraulic or pneumatic press. Preferably the tempera- ture of the molding is between 10 and 80°C. The pressure applied is preferably in the range from 0.12 - 10 MPa. During compression a tool, i.e. a tool with a logo, may be used to emboss the logo on the surface of the sheet.

Before compression the organic aerogel sheet or molding has a homogeneous nanoporous structure with an average pore size in the range from 10 to 1000 nm and shows a thermal con- ductivity in the range from 17 to 20 mW/m^*K and a density from 70 to 140 kg/m³. Such aerogel sheets or moldings can be produced e.g. as described in WO 2017/125414.

After compression the aerogel sheet or molding is more flexible and has a lower thermal con- ductivity. The thermal conductivity of the sheet or molding is preferably 17 mW/m^*K or below, more preferably in the range from 14 to 17 mW/m^*K at a density between 100 - 300 kg/m³, preferably between 140 and 240 kg/m³. The average pore size after compression is preferably in the range between 1 to 100 nm.

A further preferred process for preparing a molding as described above, comprises the steps of a) reacting a mixture (M) comprising at least one polyfunctional isocyanate (a1), at least one aromatic amine (a2), and at least a catalyst (a3) in the presence of a solvent (S) to form a gel, b) drying the gel obtained in step b) under supercritical conditions, and c) optionally cutting the dried gel into sheets with a thickness in the range from 0.1 to 10 mm, and d) compressing the dried gel to a density in the range from 100 to 300 kg/m³.

Possible polyfunctional isocyanates are aromatic, aliphatic, cycloaliphatic and/or araliphatic iso- cyanates with two or more isocyanate groups per molecule.

As polyfunctional isocyanates (a1), preference is given to aromatic isocyanates. Particularly preferred polyfunctional isocyanates of the component (a1) are the following embodiments:

(i) polyfunctional isocyanates based on tolylene diisocyanate (TDI), in particular 2,4-TDI or 2,6-TDI or mixtures of 2,4- and 2,6-TDI;

(ii) polyfunctional isocyanates based on diphenylmethane diisocyanate (MDI), in particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI or oligomeric MDI, also referred to as polyphe- nylpolymethylene isocyanate, or mixtures of two or three of the abovementioned diphe- nylmethane diisocyanates or crude MDI which is obtained in the production of MDI or mixtures of at least one oligomer of MDI and at least one of the abovementioned low molecular weight MDI derivatives;

(iii) mixtures of at least one aromatic isocyanate according to embodiment i) and at least one aromatic isocyanate according to embodiment ii).

Preferably, the aromatic amine (a2) is a polyfunctional aromatic amine.

The amines (a2) are preferably selected from the group consisting of 3,3’,5,5’-tetraalkyl-4,4’- diaminodiphenylmethane, 3,3’,5,5’-tetraalkyl-2,2’-diaminodiphenylmethane and 3, 3’, 5,5’- tetraalkyl-2,4’-diaminodiphenylmethane, where the alkyl groups in the 3, 3’, 5 and 5’ positions can be identical or different and are each selected independently from among linear or branched alkyl groups which have from 1 to 12 carbon atoms and can bear further functional groups. The abovementioned alkyl groups are preferably methyl, ethyl, n-propyl, i-propyl, n- butyl, sec-butyl or t-butyl (in each case unsubstituted).

Composition (M) preferably further comprises at least one monool (am). In principle, any monool can be used in the context of the present invention. It is also possible according to the present invention that the composition (M) comprises two or more monools. The monool can be branched or linear. Primary, secondary or tertiary alcohols are suitable according to the present invention. Preferably, the monool (am) is a linear alcohol, more preferred a linear primary alco- hol. The monool can be an aliphatic monool or an aromatic monool in the context of the present invention. Furthermore, the monool can also contain further functional groups as long as these do not react with the other components under the conditions of the process according to the present invention. The monool may for example contain C-C- double bonds or C-C triple bonds. The monool can for example be a halogenated monool, in particular a fluorinated monool such as a polyfluorinated monool or a perfluorinated monool.

According to a further embodiment, the present invention therefore is directed to the process for preparing a porous material as disclosed above, wherein the composition (M) comprises at least one monool (am).

The catalyst (a3) is preferably selected from the group consisting of dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N,N,N-pentamethyldiethylenetriamine, methylimidazole, dimethylimidazole, aminopropylimidazole, dimethylbenzylamine, 1 ,6-diazabicyclo[5.4.0]undec- 7-ene, trisdimethylaminopropylhexahydrotriazine, triethylamine, tris(dimethylaminomethyl)phenol, triethylenediamine (diazabicyclo[2.2.2]octane), dimethylami- noethanolamine, dimethylaminopropylamine, N,N-dimethylaminoethoxyethanol, N,N,N- trimethylaminoethylethanolamine, triethanolamine, diethanolamine, triisopropanolamine, diiso- propanolamine, methyldiethanolamine, butyldiethanolamine, metal acetylacetonates, ammoni- um, alkylammonium or other substituted ammonium carboxylates, and metal carboxylates such as acetates, propionates, sorbates, ethyl hexanoates, octanoates, benzoates and citrates, am- monium, alkylammonium or other substituted ammonium phosphates and metal phosphates.

Composition (M) can further comprise at least one flame retardant (af). According to the present invention, compound (af) comprises phosphorous and at least one functional group which is reactive towards isocyanates. According to the present invention, the phosphorous can be pre- sent in the compound (af) in the form of a functional group comprising phosphorous or in any other part of the molecule, for example in the backbone of the molecule. The compound (af) further comprises at least one functional group which is reactive towards isocyanates. Com- pound (af) may also comprise two or more functional groups which are reactive towards isocya- nates, in particular two groups which are reactive towards isocyanates. Typically, according to the present invention compound (af) is used in an amount which results in a phosphorous con- tent in the porous material in a range of from 0.1 to 5 % by weight.

Suitable functional groups which are reactive towards isocyanates are for example hydroxyl or amine groups. It is also possible in the context of the present invention, that composition (M) comprises two or more different compounds (af). Composition (M) may for example comprise one compound (af) which comprises phosphorous and at least one functional group which is reactive towards isocyanates and a second compound (af) which comprises phosphorous and at least two functional groups which are reactive towards isocyanates.

Suitable functional groups comprising phosphorous are known to the person skilled in the art. The functional group comprising phosphorous may for example be selected from the group consisting of phosphates, phosphonates, phosphinates, phosphites, phosphonites, phos- phinites, and phosphine oxides. Thus, according to a further embodiment, the present invention is directed to the process for preparing a porous material as disclosed above, wherein the com- pound (af) comprises at least one functional group comprising phosphorous selected from the group consisting of phosphates, phosphonates, phosphinates, phosphites, phosphonites, phos- phinites, and phosphine oxides.

Composition (M) preferably further comprises at least one polyol (ap). In principle, any polyol can be used in the context of the present invention. It is also possible according to the present invention that the composition (M) comprises two or more polyols. The polyol can be branched or linear. Primary, secondary or tertiary alcohols are suitable according to the present invention. Preferably, the polyol (ap) is a linear diol, more preferred a linear primary diol. The polyol can be an aliphatic polyol or an aromatic polyol in the context of the present invention. Furthermore, the polyol can also contain further functional groups as long as these do not react with the other components under the conditions of the process according to the present invention. The polyol may for example contain C-C- double bonds or C-C triple bonds. The polyol can for example be a halogenated polyol, in particular a fluorinated polyol such as a polyfluorinated polyol.

In the context of the present invention, the polyol may also be chosen from allyl alcohols, al- kylphenols, or propargyl alcohols. Furthermore, alkoxylates can be used in the context of the present invention such as fatty alcohol alkoxylates, oxo alcohol alkoxylates, or alkyl phenol alkoxylates.

According to a further preferred embodiment, the polyol is selected from aliphatic or aromatic polyols with 1 to 20 carbon atoms. Suitable primary polyols are for example linear alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propanediols, bu- tanediols, pentanediols, hexanediols, heptanediols or octanediols. Other examples are a poly- oxyalkylene, a polyoxyalkenyl, a polyester diol, a polyesterol, a polyether glycol, especially a polypropylene glycol, a polyethylene glycol, a polypropylene glycol, a polypropylene ethylene glycol. Suitable branched primary polyols are for example glycerol and trimethylolpropane.

Mixtures of polyols can be used. A mixture can be understood as meaning for example a copol- ymer, but also a mixture of polymeric or non-polymeric polyols.

Generally, the amount of polyol present in the composition (M) can vary in wide ranges. Prefer- ably, the polyol is present in the composition (M) in an amount of from 0.1 to 30 % by weight based on the composition (M), more preferable in an amount of from 0.5 to 25 % by weight based on the composition (M), in particular in an amount of from 1.0 to 22 % by weight based on the composition (M), for example in an amount of from 1.5 to 20 % by weight based on the composition (M).

Possible solvents (S) are, for example, ketones, aldehydes, alkyl alkanoates, amides such as formamide, N-methylpyrollidone, N-ethylpyrollidone, sulfoxides such as dimethyl sulfoxide, ali- phatic and cycloaliphatic halogenated hydrocarbons, halogenated aromatic compounds and fluorine-containing ethers. Mixtures of two or more of the abovementioned compounds are like- wise possible. Aldehydes and/or ketones are particularly preferred as solvent (S). Suitable al- dehydes or ketones are, in particular, acetaldehyde, propionaldehyde, n-butyraldehyde, isobu- tyraldehyde, 2-ethyl butyraldehyde, valeraldehyde, isopentaldehyde, 2-methylpentaldehyde, 2- ethylhexaldehyde, acrolein, methacrolein, crotonaldehyde, furfural, acrolein dimer, methacrolein dimer, 1 ,2,3,6-tetrahydrobenzaldehyde, 6-methyl-3-cyclohexenaldehyde, cyanoacetaldehyde, ethyl glyoxylate, benzaldehyde, acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-butyl ketone, methyl pentyl ketone, dipropyl ketone, ethyl isopropyl ketone, ethyl butyl ketone, diisobutyl ketone, 5-methyl-2-acetyl furan, 2-acetylfuran, 2-methoxy-4- methylpentan-2-one, 5-methylheptan-3-one, 2-heptanone, octanone, cyclohexanone, cyclopen- tanone, and acetophenone. The abovementioned aldehydes and ketones can also be used in the form of mixtures. Ketones and aldehydes having alkyl groups having up to 3 carbon atoms per substituent are preferred as solvent (S).

The components of mixture (M), for example the components (a1) and (a2) are preferably pro- vided separately from one another, each in a suitable partial amount of the solvent (S). The separate provision makes it possible for the gelling reaction to be optimally monitored or con- trolled before and during mixing.

The gelling formation in step a) is a polyaddition reaction, in particular a polyaddition of isocya- nate groups and amino groups. For the purposes of the present invention, a gel is a crosslinked system based on a polymer which is present in contact with a liquid (known as solvogel or lyo- gel, or with water as liquid: aquagel or hydrogel). Here, the polymer phase forms a continuous three-dimensional network.

Drying of the gel in step b) is carried out under supercritical conditions, preferably after re- placement of the solvent by CO₂ or other solvents suitable for the purposes of supercritical dry- ing. Such drying is known per se to a person skilled in the art. Supercritical conditions charac- terize a temperature and a pressure at which CO₂ or any solvent used for removal of the gela- tion solvent is present in the supercritical state. In this way, shrinkage of the gel body on remov- al of the solvent can be reduced.

In step c) the dried gel obtained in step b) may be cut into sheets with a thickness in the range from 0.1 to 10 mm with a saw or a diamond-coated wire.

The compression in step d) may be performed in a hydraulic, mechanical or pneumatic press. Preferably the temperature of the molding is between 10 and 80°C. The pressure applied is preferably in the range from 0.12 - 10 MPa/1000 cm².

The process according to the present invention allows to produce moldings or sheets of organic aerogels with different shapes and thickness, i.e. wedges, by using different tools and/or pres- sure.

A coating or laminate may be applied to the sheet or molding before, during or after compres- sion. The sheet or molding may be embossed during compression by using embossing tools. Logos, ornaments or patters may thus be applied to the surface of the sheet or molding.

Layer B)

For the adhesive layer any suitable adhesive, such as polyurethanes, acrylates, epoxy, silicate or silicone may be used. The adhesive layer B) may comprise additives, such as carbon pow- der, glass fiber or powder or flame retardants.

The adhesive layer may be applied directly onto one or both sides of any layer, preferably to the cover layer C) or functional layer F). Preferably layer C) is used in form of a hybrid tape CB) consisting of a cover layer C) and an adhesive layer B) or a hybride tape CFB consisting of a cover layer C), a functional layer F) and an adhesive layer B). The hybrid layer can then be at- tached to one or both sides of an aerogel layer A) to build the thermal insulation material Layer C) Layer C) is chemically different from layer A) and/or has different mechanical properties. Layer C) preferably has a higher mechanical flexibility compared with aerogel layer A). Flexible prod- ucts may be obtained by applying a coating or flexible cover layer C) on the surface of the mold- ing based on a monolithic organic aerogel as described above. The flexible cover layer C) may be a thermoplastic polymer, or a thermoplastic polymer reinforced with organic or inorganic fi- bers or woven or non-woven fabrics. Further materials suitable as flexible cover layer are a graphite or graphene film, a metal film, or a ceramic film, such as a hydroxyapatite film or glass fiber paper. The coating or flexible layer C) may be modified with additives to impart functionali- ties, such as electrical conductivity or insulation or flame retardancy. Preferably the cover layer C) is a polymer film, a graphite or graphene film, a metal film, or a ceramic film, such as a hy- droxyapatite film or a mineral fleece. More preferably a thermoplastic polymer film, such as transparent polyethylene, polypropylene or polyterephthalate film or a mineral fleece.

Layer F)

The functional Layer F) is optionally used in the thermal insulation material and is preferably an electrically conducting or insulating layer, a flame-retardant layer, a heat spreader layer. The functional layer F) may be applied as separate layer, preferably between layer A) and C) or as a hybrid tape CF or CBF comprising a layer C) attached to a functional layer F), optionally by an adhesive layer B).

A further subject of the present invention is therefore a thermal insulation material comprising a molding based on a monolithic organic aerogel in form of a sheet as layer A) and at least one coating or cover layer C). Preferably the thickness of the layer A) is in the range from 0.09 to 4.49 mm, more preferably in the range from 0.25 to 2.45 mm. The thickness of the at least one coating or cover layer C) is in the range from 0.01 to 2.5 mm, more preferably in the range from 0.05 to 1 .0 mm.

Preferably the laminated sheet comprises an adhesive tape attached on all or part of the sur- face of a layer A) of a monolithic aerogel, based on polyurethanes (PU), polyurea (PUR), polyi- socyanurate (PIR) or mixtures thereof. Preferably, layers C comprises an adhesive layer facing the outside for facile attachment to other parts.

The thermal insulation material may be adapted to various forms by thermoforming or rolling to cylinders with diameter as low as 3 mm. The thermal insulation material may be cut to the de- sired shape easily with common tools such as scissors or saws. A further subject of the present invention is a process for preparing a thermal insulation material as defined above, comprising the steps of

(a) reacting a mixture (M) comprising at least one polyfunctional isocyanate (a1), at least one aromatic amine (a2), and at least a catalyst (a3) in the presence of a solvent (S) to form a gel, b) drying the gel obtained in step b) under supercritical conditions to form a monolithic aerogel as layer A), c) optionally cutting the monolithic aerogel obtained in step b) into sheets with a thickness in the range from 0.09 to 4.49 mm as layer A), d) optionally compressing the monolithic aerogel obtained in step b) or step c) to a layer A) with a density in the range from 100 to 300 kg/m³, e) applying at least one cover layer C) optionally by an adhesive layer B) to the layer A) obtained in step b) or c).

In step c) the monolithic aerogel sheet is preferably compressed with a compression factor in the range from 5 to 70 Vol.-%.

The thermal insulation material according to the invention show a low thermal conductivity and therefore good thermal insulation properties at high densities. At the same time the molding is non-dusting, flexible, mechanically stable and shows a high compression and bending strength.

The thermal insulation material according to the invention is suitable for use in construction and refrigeration appliance industry or for the use in electronic devices as well as batteries or aero- space applications, preferably as thermal insulation material for interior insulation, shutter box, window fanning, refrigerators, electronic devices, smart phones, tablets, notebooks or re- chargeable batteries.

Examples

Test Methods:

The thermal conductivity was measured according to DIN EN 12667:2001-05 with a heat flow meter from Hesto (Lambda Control A50) at 10°C. Laminated and non-laminated sheets of 1 - 2 mm thickness were measured as stacks of 4 to 10 sheets (15 cm ^* 15 cm) depending on their thickness. Flexural strength was determined with a three-point bending test based on DIN EN ISO 178:2013-09 and reported as bending strength at different bending displacements. Holding points were spaced between support span of 50 mm apart. The maximum bending radius was 90°. Sample dimension was about 100 x 20 mm. Settings for preload and test speed were 0.1 N / 2 mm/min. Samples laminated on one side were pressed on the laminated side.

Materials:

M200 oligomeric MDI (Lupranat M200) having an NCO content of 30.9 g per100 g accordance with ASTM D-5155-96 A, a functionality in the region of three and a viscosity of 2100 mPa. s at 25 °C in ac- cordance with DIN 53018.

MDEA 3, 3’ ,5,5’-Tetraethyl-4,4’-diaminodiphenylmethane

MEK Methyl ethyl ketone

Ksorbate solution Potassium sorbate dissolved in monoethylene glycol (MEG) as 5 wt.-% solution

Exolit OP560 Phosphorous polyol

Transparent tape (CB1):

Ca. 0.06 mm thick transparent PP tape (width 5 cm) with contact adhesive (Enviropack® e- Tape)

Textile-reinforced tape (CB2):

Ca. 0.3 mm thick polymer tape (width 5 cm) with textile reinforcement and contact adhesive (Tesa® 4651 white)

Paper (CB3):

Office paper 80 g/m2 with a manually applied layer of glue-stick adhesive (Pritt® original glue stick)

Graphite foil (CFB4):

Ca. 25 μm thick graphite foil with 10 μm electrically isolating polymer layer and contact adhesive (heat-spreader foil from ProGraphite)

Aluminum-coated paper (CFB5):

Ca. 0.3 mm thick aluminum-coated paper with contact adhesive Mineral fleece (CFB6):

Ca. 0.6 mm thick, fire-resistant mineral fleece (Innobra MIV 520 P) with a manually applied layer of glue-stick adhesive (Pritt® original glue stick)

Preparation of monolithic aerogel layer A1 :

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20 °C leading to a clear solution. Similarly, 6 g MDEA, 2 g Ksorbate solution, 2 g Exolit OP560 and 6 g 1 -butanol were dissolved in 220 g MEK to obtain a second solution. The solutions were combined in a rectan- gular container (20 cm x 20 cm x 5 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with sc CO₂ in a 25 I autoclave leading to a porous material.

A slab of the porous material of 15 x 15 x 1.5 cm was cut to sheets of 15 x 15 cm and 1 - 3 mm thickness using a band saw.

Preparation of compressed monolithic aerogel layer A2:

Porous plates obtained as described above for the monolithic aerogel layer A1 were com- pressed for 2 seconds using a hydraulic press (Schmidt Maschinentechnik) with press plates (30x30 cm) at 25°C with a pressure in the range of 30 - 60 kN/900 cm² and a press speed of 20 - 25 cm/min. In Table 1 the thickness reduction is listed as compression in %.

Examples 1 to 11

Pre-cut strips of adhesive tape (CB1), textile tape (CB2), paper with a layer of glue-stick adhe- sive (CB3), graphite foil (CFB4), aluminum coated paper (CFB5) or mineral fleece with a layer of glue-stick adhesive (CFB6) were pressed manually with the adhesive layer onto a sheet of monolithic aerogel layer A1 and A2. In the case of CB1 and CB2, for samples of 5 cm width or less, one layer of tape was used per side. In case of samples with more than 5 cm width, tape layers were applied in such a way as to cause an overlap of ca. 5-10 mm between layers. The laminate structure, thickness and mechanical properties of the thermal insulation material are summarized in Table 1.

Examples 3 to 7, 8, 10 and 11 show no delamination in three-point-bending test, if bent with tape layer on outside no delamination occurs. Minimum diameter is the diameter without visible damage when bent or rolled. In case of sheets with lamination on one side the sheet was bent over the side without cover layer. Sheets are considered not reusable, if the material breaks and/or partial delamination occurs after bending to minimum rolling diameter.

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Claims

1. A thermal insulation material with a thickness in the range from 0.1 mm to 5 mm com- prising at least one aerogel layer A) consisting essentially of a monolithic organic aero- gel and at least one cover layer C).

2. A thermal insulation material as defined in claim 1 comprising one layer A) and two cov- er layers C).

3. A thermal insulation material as defined in claim 1 or 2, wherein the at least on layer A) has a thickness in the range from 0.09 to 4.49 mm.

4. A thermal insulation material as defined in any of claims 1 to 3, wherein the at least one cover layer C) has a thickness in the range from 0.01 to 1 mm.

5. A thermal insulation material as defined in any of claims 1 to 4, which has a density in the range from 100 to 300 kg/m³ and a thermal conductivity in the range from 12 to 22 mW/m*K, measured at 10°C according to DIN EN 12667:2001-05

6. A thermal insulation material as defined in any of claims 1 to 5, which has a flexural strength according to DIN EN ISO 178:2013-09 in the range from 1000 - 12000 kPa.

7. A thermal insulation material as defined in any of claims 1 to 6, wherein the monolithic organic Aerogel in layer A) is a monolithic aerogel based on polyurethane (PU) and/or polyurea (PUR) with less than 80% of polyisocyanurate (PIR) structures.

8. A thermal insulation material as defined in any of claims 1 to 7, wherein the at least one cover layer C) comprises a polymer film, a graphite or graphene film, a metal film or mineral fleece.

9. A thermal insulation material as defined in any of claims 1 to 8, wherein one layer A) and one or two layers C), are attached by an adhesive layer B) with a layer structure A-B-C and C-B- A-B-C.

10. A thermal insulation material as defined in any of claim 9, wherein a further adhesive layer B) is applied to the outside of the cover layer C) wit the structure A-B-C-B or C-B- A-B-C-B.

11. A thermal insulation material as defined in any of claims 1 to 10, comprising one or more functional layers F), selected from an electrically insulating or conducting layer, a flame- retardant layer or a heat spreader layer.

12. A process for preparing a thermal insulation material as defined in any of claims 1 to 11, comprising the steps of a) reacting a mixture (M) comprising at least one polyfunctional isocyanate (a1), at least one aromatic amine (a2), and at least a catalyst (a3) in the presence of a solvent (S) to form a gel, b) drying the gel obtained in step b) under supercritical conditions to form a mono- lithic aerogel as layer A), c) optionally cutting the monolithic aerogel obtained in step b) into sheets with a thickness in the range from 0.09 to 4.9 mm as layer A), d) optionally compressing the monolithic aerogel obtained in step b) or step c) to a layer A) with a density in the range from 100 to 300 kg/m³, e) applying at least one cover layer C) optionally by an adhesive layer B) to the lay- er A) obtained in step b) or c).

13. A process as defined in claim 12, wherein in step c) the monolithic aerogel sheet is compressed with a compression factor in the range from 5 to 70 Vol.-%.

14. Use of the thermal insulation material as defined in any of claims 1 to 11 in building and construction, refrigeration appliance, electronic devices, aerospace and batteries.