WO2020173911A1

WO2020173911A1 - Composite aerogel material

Info

Publication number: WO2020173911A1
Application number: PCT/EP2020/054851
Authority: WO
Inventors: Elisabet TORRES CANO; Ilaria DE SANTO; Asta SAKALYTE; Belen Del Saz-Orozco; Fouad Salhi
Original assignee: Henkel Ag & Co. Kgaa; Henkel IP & Holding GmbH
Priority date: 2019-02-25
Filing date: 2020-02-25
Publication date: 2020-09-03

Abstract

The present invention is directed to a composite aerogel material comprising: i) a polymeric aerogel matrix; and, ii) a particulate aerogel component dispersed in said matrix, said particulate aerogel component being selected from inorganic aerogels. The present invention is also directed to a process for obtaining the defined composite aerogel material, said process comprising the steps of: a) dissolving the reactant monomers of the polymeric aerogel matrix in a first solvent to form a first solution; b) admixing the first solution with the particulate aerogel component to form a dispersion of said particles; c) adding a catalyst to the mixture of step ii) to initiate the reaction of said monomers and thereby form a gel; d) washing said gel with a second solvent; e) drying said gel by supercritical drying; and, optionally f) postcuring of the obtained aerogel by thermal treatment.

Description

COMPOSITE AEROGEL MATERIAL

FIELD OF THE INVENTION

The present invention is directed to a composite aerogel material comprising a particulate aerogel component dispersed within a polymeric aerogel matrix. More particularly, the present invention is directed to a composite aerogel material comprising: a dispersed, particulate aerogel component selected from inorganic aerogels; and, a polymeric aerogel matrix.

BACKGROUND OF THE INVENTION

Short supply, limited availability and increasing energy costs around the world have emphasized the need for immediate energy conservation in both oil importing and oil producing countries alike. One effective means to save energy is to improve thermal insulation in applications such as construction, transport and industry.

For many such applications, it is possible to use a thick insulating panel to reduce heat transfer. However, other applications can impose size and weight limitations on their component parts and, as such, may require thinner insulating panels or layers. For those cases, the thin insulating panels or layers must often possess mechanical properties which are not deleterious to the strength and integrity of the apparatus, device or appliance including them but importantly must possess an extremely low thermal conductivity in order to achieve the same insulating properties as thicker insulating panels or layers. Aerogels constitute a class of lightweight materials of very low thermal conductivity which have found utility in this context.

According to International Union of Pure and Applied Chemistry (lUPAC) an aerogel is defined as a gel comprised of a microporous solid in which the dispersed phase is a gas. Aegerter et al. in Aerogels Handbook, Springer, New York, NY, USA, 201 1 defined aerogels as gels in which the liquid has been replaced with gas (air) with very moderate shrinkage of the solid network. Aerogels are thus typically low density solids (0.003-0.5 g/cm³), which are further characterized by a low thermal conductivity, poor sound transmission and high specific surface area (500-1200 m²/g). Aerogels are deemed environmentally friendly because they are gas (air) filled, and furthermore, are not subject to ageing. In general, the passage of thermal energy through an insulating material occurs through three mechanisms: solid conductivity, which is an intrinsic property of a specific material; gaseous conductivity; and, radiative (infrared) transmission. The sum of these three components gives the total thermal conductivity of the material. Aerogels may have a thermal conductivity lower than that of the gas they contain: this is caused by the Knudsen effect which is a reduction of thermal conductivity in gases when the size of the cavity encompassing the gas becomes comparable to the mean free path. Effectively, the cavity restricts the movement of the gas particles, decreasing the thermal conductivity in addition to eliminating convection.

Most known aerogels are inorganic aerogels, mainly based on silica. Despite their high thermal insulating properties - with thermal conductivities commonly being in the range from 0.005-0.01 W/mK - the commercial adoption of silica aerogels has been stymied by their fragility and poor mechanical properties. The fragility of silica aerogels derives from their structure: ball-like secondary particles accumulate through neck regions, creating a“pearl necklace-like” structure with large voids; when an external load is applied, fracture occurs at the interface of secondary particles while primary particles remain intact. This fragility may be overcome by different methods including: cross-linking silica aerogels with organic polymers; and, post-gelation casting of a thin, conformal polymer coating over the entire internal porous surface of the pre-formed wet-gel, silica nanostructure.

Meador et al. in Cross-linking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials Chem. Mater., 2005, 77 (5), pp 1085-1098 describes the modification of the mesoporous surfaces of tetramethyl orthosilicate (TMOS) derived silica aerogels with amines by copolymerization of said TMOS with 3-aminopropyl triethoxy silane (APTES). The amine sites are anchors for the cross-linking of the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri-, and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than 2 orders of magnitude.

Luechinger et al. in Functionalization of silica surfaces with mixtures of 3-aminopropyl and methyl groups, Microporous and Mesoporous Materials, Volume 85, Issues 1 -2, 23 October 2005, Pages 1 1 1 -1 18 describes the functionalization of the surface of mesoporous M41 S silica material with one or both of 3-aminopropyl and methyl groups: the so-functionalized material exhibits a high stability against hydrolysis in boiling water because the siloxane bonds of the silica framework are protected by the organic moieties.

Vandenberg et al. in Structure of 3-aminopropyl triethoxy silane on silicon oxide, Journal of Colloid and Interface Science Volume 147, Issue 1 , November 1991 , Pages 103-1 18 describes the deposition of 3-aminopropyl triethoxy silane (APTES) onto silicon oxide surfaces under various conditions of solvent, heat, and time followed by exposure to different curing environments: curing was required to complete the covalent binding between APTES and the surface. Coverage equivalent to one monolayer was achieved using very mild reaction and curing conditions - such as reaction in dry toluene for 15 minutes at room temperature and curing either in air or for 15 minutes at 200°C oven - whereas thicker layers required increased reaction and curing times.

The above aside, organic aerogels have also been described in the literature as an alternative to inorganic, in particular silica aerogels. These materials are generally based on polymeric networks, formed by cross-linking of monomers in a solution to yield a gel that is subsequently dried to obtain a porous material. The organic aerogels are generally not fragile materials but their thermal insulative properties are generally inferior to silica aerogels: the thermal conductivities of organic aerogels are rarely lower than 0.016 W/mK.

WO2017/016755 (Henkel AG & Co. KGaA et al.) describes an organic aerogel having thermal insulation properties and which is obtained by reacting an isocyanate compound having a functionality of at least 2 and a cyclic ether compound having a functionality of at least 2 in the presence of a solvent.

WO2017/178548 (Henkel AG & Co. KGaA et al.) describes a benzoxazine-based copolymer aerogel obtained by reacting in the presence of a solvent and electively a catalyst: a benzoxazine monomer or oligomer; and, a comonomer selected from the group consisting of an isocyanate compound, a cyclic ether compound and an acid anhydride compound. Said catalyst is an optional ingredient when said comonomer is an acid anhydride compound or an isocyanate compound.

US2017/096548 (Korea Institute of Science & Technology) describes an aerogel-containing heat insulation composite obtained by: introducing a volatile material into the pores of the aerogel; blending the aerogel with a polymer resin, preferably a flexible polymer resin, to form a composite; and, removing the volatile material. This method is intended to prevent a decline in the the porosity of the aerogel caused by infiltration and impregnation of the pores of the aerogel with the resin.

WO2017/198658 (Henkel AG & Co. KGaA et al.) describes a hybrid aerogel having thermal insulation properties and which is obtained by reacting an aromatic or aliphatic isocyanate compound and silanol moieties on the surface of a clay and in the presence of a solvent.

WO2017/216034 (Henkel AG & Co. KGaA et al.) relates to polysiloxane-based aerogels obtained by reacting a functionalized poly(dimethylsiloxane) oligomer and an aliphatic or aromatic isocyanate compound in a presence of a catalyst and a solvent.

WO2018/077862 (Henkel AG & Co. KGaA et al.) describes an aerogel which is obtained by reacting, in the presence of at least one solvent: silanol moieties on a surface of a clay; a first isocyanate compound A; a second isocyanate compound B; and, a cyclic ether compound. WO2018/188932 (Henkel AG & Co. KGaA et al.) discloses an organic aerogel obtained by reacting an amine compound having at least two amine functionalities and a cyclic ether compound in the presence of a solvent.

PCT/EP2018/084569 (Henkel AG & Co. KGaA et al.) describes an organic aerogel obtained by reacting a thiol compound and an epoxide compound in a presence of a solvent.

PCT/EP2018/084948 (Henkel AG & Co. KGaA et al.) discloses a thiourethane based aerogels obtained by reacting an isocyanate compound having a functionality equal to or greater than 2 and a thiol compound having a functionality equal to or greater than 2 in the presence of a solvent.

There is considered to remain a need in the art to obtain an aerogel material that can possess good thermal and, optionally, acoustic insulation properties but which does not show fragility and / or exhibit deleterious mechanical properties.

STATEMENT OF THE INVENTION

In accordance with a first aspect of the invention there is provided a composite aerogel material comprising:

i) a polymeric aerogel matrix; and, ii) a particulate aerogel component dispersed in said matrix, said particulate aerogel component being selected from inorganic aerogels.

The composite aerogel material is preferably characterized by a ratio by volume of the particulate aerogel component to the polymeric aerogel matrix of from 1 : 100 to 1 : 1 , for example from 1 : 10 to 1 :1 .

The polymeric aerogel matrix is based on at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polyurea; polyimide; polyacrylates; polymethylmethacrylate; polysiloxanes; polyoxyalkylenes; polybutadiene; melamine- formaldehyde resins; phenol-furfural resins; epoxy resins; and, benzoxazine resins.

It is preferred that the polymeric aerogel matrix is based on at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polysiloxanes; and, benzoxazine resins. These polymers show fast gelation - for instance, in less than 20 hours and even less than 5 hours - which presents the benefit that the gas-filled pores of inorganic particulate aerogel component - which is dispersed in the polymer matrix - are substantially preserved.

The particulate inorganic aerogel is preferably selected from the group consisting of alumina, titania, zirconia, silica and mixtures thereof. Alternatively or additionally to this embodiment, it is preferred that the constituent particles of the particulate inorganic aerogel are characterized by at least one of the following parameters:

i) porosities of from 50 to 99.0% percent, preferably from 60 to 98%;

ii) pore diameters of from 2 nm to 500 nm, preferably from 10 to 400 nm or from 20 to 100 nm;

iii) an average volume particle size, as measured by laser diffraction / scattering methods, of from 1 to 1000 pm, preferably from 2 to 500 pm or from 5 to 200 pm;

iv) surface areas of from 400 to 1200 m²/g, preferably from 500 to 1200 m²/g and 600 to 900 m²/g;

v) a bulk density of from 20 to 500 kg/m³, preferably from 40 to 200 kg/m³; and, vi) electrical resistivities of from 0.01 W-cm to about 1 .0x10¹⁶ W-cm, preferably from 1 W- cm to 1 .0x10^s W-cm.

In a particularly preferred embodiment, the particulate inorganic aerogel component comprises, consists essentially of or consists of a particulate silica silicate aerogel having: an average particle size of 5-20 microns; a porosity of at least 90%; a bulk density of 40-100 kg/m³; and, a surface area of 600-900 m²/g.

In accordance with a second aspect of the present invention, there is provided a process for obtaining a composite aerogel material as defined hereinabove and in the appended claims, said process comprising the steps of:

i) dissolving the reactant monomers of the polymeric aerogel matrix in a first solvent to form a first solution;

ii) admixing the first solution with the particulate aerogel component to form a dispersion of said particles;

iii) adding a catalyst to the mixture of step ii) to initiate the reaction of said monomers and thereby form a gel;

iv) washing said gel with a second solvent;

v) drying said gel by supercritical drying; and, optionally

vi) postcuring of the obtained aerogel by thermal treatment.

In accordance with a final aspect of the present invention, there is provided the use of said composite as defined hereinabove and in the dependent claims as a thermal insulation panel or an acoustic insulation panel.

DEFINITIONS

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

The terms“comprising",“comprises" and“comprised of’ as used herein are synonymous with “including”,“includes",“containing” or“contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. If used, the phrase "consisting of is closed and excludes all additional elements. Further, the phrase "consisting essentially of excludes additional material elements but allows the inclusion of non-material elements that do not substantially change the nature of the invention.

When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.

The words "preferred", "preferably",“desirably” and“ particular 1/ are used frequently herein to refer to embodiments of the disclosure that may afford particular benefits, under certain circumstances. However, the recitation of one or more preferable, preferred, desirable or particular embodiments does not imply that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the disclosure.

As used throughout this application, the word“may” is used in a permissive sense - that is meaning to have the potential to - rather than in the mandatory sense.

As used herein, “ambient conditions" refers to a set of parameters that include temperature, pressure and relative humidity of the immediate surroundings of the element in question. Herein ambient conditions are: a relative humidity of from 30 to 100% percent; a temperature in the range from 20 to 40°C; and, a pressure of 0.9 to 1 .1 bar.

As used herein“room temperature" is 23°C ± 2°C.

As used herein, "supercritical" refers to a fluid medium that is at a temperature that is sufficiently high that it cannot be liquefied by pressure. With regard to the thermodynamic properties of C0₂, attention may be directed to Hyatt, J. Org. Chem. 49: 5097-5101 (1984); therein, it is stated that the critical temperature of C0₂ is about 31 °C.

The term “gelation" as used herein indicates that colloidal particles have formed a three- dimensional network with some interstitial liquid, such that the dispersion becomes essentially non-flowing and exhibits solid-like behavior at the stated temperature.

As used herein, the term“dispersion" refers to a composition that contains discrete particles that are distributed throughout a continuous liquid medium.

As used herein, the terms "monomer" and " comonomer " refer to a molecule that is capable of conversion to polymers, synthetic resins or elastomers by combination with itself or other similar molecules or compounds. The terms are not limited to small molecules but include oligomers, polymers and other large molecules capable of combining with themselves or other similar molecules or compounds.

As used herein, “polymerization conditions" are those conditions that cause the at least one monomer to form a polymer, such as temperature, pressure, atmosphere, ratio of starting components used in the polymerization mixture, reaction time, or external stimuli of the polymerization mixture. The polymerization process herein is conventionally carried out in solution. The process is operated at any of the reaction conditions appropriate to the polymerization mechanism.

The term“epoxide compound” denotes monoepoxide compounds and polyepoxide compounds: it is intended to encompass epoxide functional prepolymers. The term“polyepoxide compound” is thus intended to denote epoxide compounds having at least two epoxy groups. Further, the term“diepoxide compound” is thus intended to denote epoxide compounds having two epoxy groups.

As used herein "polyisocyanate" means a compound comprising at least two -N=C=0 functional groups, for example from 2 to 5 or from 2 to 4 -N=C=0 functional groups. Suitable polyisocyanates - for use in deriving the polymeric aerogel matrix in accordance with several embodiments of the present invention described herein below - include aliphatic, cycloaliphatic, aromatic and heterocyclic isocyanates, dimers and trimers thereof, and mixtures thereof.

Aliphatic and cycloaliphatic polyisocyanates can comprise from 6 to 100 carbon atoms linked in a straight chain or cyclized and have at least two isocyanate reactive groups. Examples of suitable aliphatic isocyanates include but are not limited to straight chain isocyanates such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, 1 ,6-hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1 ,6,1 1 -undecanetriisocyanate, 1 ,3,6-hexamethylene triisocyanate, bis(isocyanatoethyl)-carbonate, and bis (isocyanatoethyl) ether. Exemplary cycloaliphatic polyisocyanates include, but are not limited to, dicyclohexylmethane 4,4'-diisocyanate (H12MDI), 1-isocyanatomethyl-3-isocyanato-1 ,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), cyclohexane 1 ,4-diisocyanate, hydrogenated xylylene diisocyanate (H₆XDI), 1 -methyl-2,4- diisocyanato-cyclohexane, m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI) and dimer fatty acid diisocyanate. The term“aromatic polyisocyanate’’ is used herein to describe organic isocyanates in which the isocyanate groups are directly attached to the ring(s) of a mono- or polynuclear aromatic hydrocarbon group. In turn the mono- or polynuclear aromatic hydrocarbon group means an essentially planar cyclic hydrocarbon moiety of conjugated double bonds, which may be a single ring or may include multiple condensed (fused) or covalently linked rings. The term aromatic also includes alkylaryl. Typically, the hydrocarbon (main) chain includes 5, 6, 7 or 8 main chain atoms in one cycle. Examples of such planar cyclic hydrocarbon moieties include, but are not limited to, cyclopentadienyl, phenyl, napthalenyl-, [10]annulenyl-(1 ,3,5,7, 9-cyclodecapentaenyl-), [12]annulenyl-, [8]annulenyl-, phenalene (perinaphthene), 1 ,9-dihydropyrene, chrysene (1 ,2- benzophenanthrene). Examples of alkylaryl moieties are benzyl, phenethyl, 1 -phenylpropyl, 2- phenylpropyl, 3-phenylpropyl, 1 -naphthylpropyl, 2-naphthylpropyl, 3-naphthylpropyl and 3- naphthylbutyl.

Exemplary aromatic polyisocyanates include, but are not limited to: all isomers of toluene diisocyanate (TDI), either in the isomerically pure form or as a mixture of several isomers; naphthalene 1 ,5-diisocyanate; diphenylmethane 4,4'-diisocyanate (MDI); diphenylmethane 2,4'- diisocyanate and mixtures of diphenylmethane 4,4'-diisocyanate with the 2,4' isomer or mixtures thereof with oligomers of higher functionality (so-called crude MDI); xylylene diisocyanate (XDI); diphenyl-dimethylmethane 4,4'-diisocyanate; di- and tetraalkyl-diphenylmethane diisocyanates; dibenzyl 4,4'-diisocyanate; phenylene 1 ,3-diisocyanate; and, phenylene 1 ,4-diisocyanate.

It is noted that the term“ olyisocyanate’’ is intended to encompass pre-polymers formed by the partial reaction of the aforementioned aliphatic, cycloaliphatic, aromatic and heterocyclic isocyanates with polyols to give isocyanate functional oligomers, which oligomers may be used alone or in combination with free isocyanate(s).

As used herein, "Ci-C₃o alkyr group refers to a monovalent group that contains 1 to 30 carbons atoms, that is a radical of an alkane and includes straight-chain and branched organic groups. Examples of alkyl groups include, but are not limited to: methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; sec-butyl; tert-butyl; n-pentyl; n-hexyl; n-heptyl; and, 2-ethylhexyl. In the present invention, such alkyl groups may be unsubstituted or may be substituted with one or more substituents such as halo, nitro, cyano, amido, amino, sulfonyl, sulfinyl, sulfanyl, sulfoxy, urea, thiourea, sulfamoyl, sulfamide and hydroxy. The halogenated derivatives of the exemplary hydrocarbon radicals listed above might, in particular, be mentioned as examples of suitable substituted alkyl groups. In general, however, a preference for unsubstituted alkyl groups containing from 1 -18 carbon atoms (Ci-Ci₈ alkyl) - for example unsubstituted alkyl groups containing from 1 to 12 carbon atoms (C1-C12 alkyl) - should be noted.

The term “C₃ -C₃o cycloalkyt’ is understood to mean a saturated, mono-, bi- or tricyclic hydrocarbon group having from 3 to 30 carbon atoms. Examples of cycloalkyl groups include: cyclopropyl; cyclobutyl; cyclopentyl; cyclohexyl; cycloheptyl; cyclooctyl; adamantane; and, norbornane.

As used herein, an“C₆-C₁₈ aryl" group used alone or as part of a larger moiety - as in“aralkyl group" - refers to optionally substituted, monocyclic, bicyclic and tricyclic ring systems in which the monocyclic ring system is aromatic or at least one of the rings in a bicyclic or tricyclic ring system is aromatic. The bicyclic and tricyclic ring systems include benzofused 2-3 membered carbocyclic rings. Exemplary aryl groups include: phenyl; indenyl; naphthalenyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthracenyl; and, anthracenyl. And a preference for phenyl groups may be noted.

As used herein, "alkylaryf refers to alkyl-substituted aryl groups and "substituted alkylaryt' refers to alkylaryl groups further bearing one or more substituents as set forth above.

The term "hetero" as used herein refers to groups or moieties containing one or more heteroatoms, such as N, O, Si and S. Thus, for example "heterocyclic" refers to cyclic groups having, for example, N, O, Si or S as part of the ring structure. "Heteroalkyi' and "heterocycloalkyr moieties are alkyl and cycloalkyl groups as defined hereinabove, respectively, containing N, O, Si or S as part of their structure.

In accordance with established terminology, a“ rimary thiol group” is constituted by a thiol group (-SH) attached to a methylene group and a“secondary thiol group” is constituted by a thiol group (-SH) attached to a saturated carbon atom which has two other carbon atoms attached to it. Analogously, a“tertiary thiol group” is constituted by a thiol group (-SH) attached to a saturated carbon atom which has three other carbon atoms attached to it.

As used herein, the term“catalytic amount’ means a sub-stoichiometric amount of catalyst relative to a reactant. DETAILED DESCRIPTION OF THE INVENTION i) Particulate Aerogel Component

From the standpoint of chemistry, the particulate aerogels of the present invention may most broadly be selected from the group consisting of inorganic aerogels, in particular silica aerogels. For completeness, it is noted that the first component of the composite of the present invention may contain more than one type of particulate inorganic aerogel.

Particulate inorganic aerogels may conventionally be comprised of one or more of alumina, titania, zirconia or silica. They generally formed by sol-gel polycondensation of (metal) oxides to form highly cross-linked, transparent hydrogels: these hydrogels are then subjected to supercritical drying.

The present invention does not preclude the aerogel particles of this component from being modified by chemical substitution upon or within the molecular structure of the aerogel. In particular, it may be beneficial for the aerogel particles to be surface treated with a material which contains a functionality reactive to that aerogel and which modifies the surface interactions - such as the hydrophobicity, hydrophilicity or surface energy - of the aerogel. The aerogel particles may, for instance, be modified to have a surface functionality selected from the group consisting of: alkylsilane; alkylchlorosilane; alkylsiloxane; polydimethylsiloxane; aminosilane; and, methacrylsilane. In an alternative modification, surface hydroxyl groups of inorganic aerogel particles may be replaced with at least partially fluorinated organic groups.

For completeness, the use of trimethyl- and dimethylsilyl groups for permanent hydrophobization of the aerogel is described in WO 94/25149. Additionally, R. Her, The Chemistry of Silica, Wiley & Sons, 1979 describes inter alia the gas-phase reaction between an aerogel and an activated trialkylsilane derivative, such as a chlorotrialkylsilane or a hexaalkyldisilazane.

Independently of its chemistry, the component i) of the present invention is necessarily particulate. There is no particular intention to limit the shape of the particles employed: particles that are acicular, spherical, ellipsoidal, cylindrical, bead-like, cubic or platelet-like may be used alone or in combination. Moreover, it is envisaged that agglomerates of more than one particle type may be used.

That said, the particle type, porosity, pore size, and amount of the particulate aerogel component which is used for a particular embodiment may be chosen based upon the desired properties of the resultant composition and upon the properties of the polymers and solutions thereof into which the particulate aerogel is to be combined.

Desirably, the aerogel particles of the present invention should be characterized by at least one of the following parameters:

vii) porosities of from 50 to 99.0% percent, preferably from 60 to 98%;

viii) pore diameters of from 2 nm to 500 nm, preferably from 10 to 400 nm or from 20 to 100 nm;

ix) an average volume particle size, as measured by laser diffraction / scattering methods, of from 1 to 1000 pm, preferably from 2 to 500 pm or from 5 to 200 pm;

x) surface areas of from 400 to 1200 m²/g, preferably from 500 to 1200 m²/g and 600 to 900 m²/g;

xi) a bulk density of from 20 to 500 kg/m³, preferably from 40 to 200 kg/m³; and, xii) electrical resistivities of from 0.01 W-cm to about 1 .0x10¹⁶ W-cm, preferably from 1 W- cm to 1 .0x10^s W-cm.

These parameters are not intended to be mutually exclusive. An exemplary particulate aerogel may meet one, two, three, four, five or six of the defined parameters.

In an important embodiment of the present invention, the particulate aerogel component comprises, consists essentially of or consists of a particulate silica aerogel. In an illustrative but non-limiting example meeting this embodiment, that component comprises, consists essentially of or consists of a particulate silica silicate aerogel having: an average particle size of 5-20 microns; a porosity of 90% or more; a bulk density of 40-100 kg/m³; and, a surface area of 600- 900 m²/g.

The particulate aerogel component can be either formed initially at the desired particle size particles or can be formed as larger particles and then comminuted to the desired size for inclusion in the composite material. Without intention to limit the present invention, comminution of the aerogel particles may be performed by one or more of: grinding; milling; homogenization; and, sonication.

Grinding can, for instance, be effected using a planetary ball mill having a grinding chamber that includes a rotor shaft that is used to rotate grinding media. Reference may be made to: Le Caer et al. Mechanical Alloying and High-Energy Ball-Milling: Technical Simplicity and Physical Complexity for the Synthesis of New Materials www.ademe.fr/recherche/manifestations/materiaux— 2002/; and, Zoz et al. Processing of Ceramic Powder Using High Energy Milling at www.zoz.de/de/veroeff/19.htm.

Milling may be performed in any high-energy mill, of which examples include: centrifugal mills; planetary ball mills; jet mills, such as spinning air flow jet mill; and, fluid energy mills. Desirably, the high-energy mill should be able to impart an impact force of at least 0.5G, for example from 0.5 to 25G, to the milling media. Non-limiting examples of mills which may find utility in the present invention are disclosed in: US Patent No. 5,522,558; US Patent No. 5,232, 169; US Patent No. 6, 126,097; and, US Patent No. 6,145,765. Moreover, it should be noted that the present invention does not preclude milling being conducted under heat - such as described in WO 00/56486 - and / or in the presence of additives, such as lubricants, surfactants, dispersants and solvents.

A typical sonication would first comprise adding said particles to at least one solvent and optionally at least one reactant. The employed solvent(s) should comprise or consist of a non-polar solvent selected from the group consisting of: alkanes (R— H); cyclic alkanes; branched alkanes; aromatics (Ar— H); alkyl halides (R— X); and, mixtures thereof. Exemplary but non-limiting non polar solvents include n-pentane, n-hexane, cyclohexane, n-heptane, isooctane, trimethylpentane, toluene, xylene and benzene. The presence of reactants in addition to said solvents is preferred: reactants - such as silylating agents and organofunctional silanes - serve to pacify the newly generated aerogel particle surfaces created during sonication and the fragmentation of the starting aerogel particles and to thereby yield unreactive aerogel particles.

Sonic energy is then applied to the formed medium. As will be recognized by the skilled practitioner, the frequency of sonication, the time of sonication and the power used are key determinants for the end particle size distribution. For illustration only, MisoNix Sonicator® 3000 available from Cole-Parmer Instrument Company may be mentioned as an exemplary sonic probe for performing sonication.

After comminuting, any fluid present in the comminution step(s) may be separated from the particles. One or more separation process, such as air-drying, heating, filtration and evaporation, can be employed in this regard but it is preferred that the fluid is removed under heating to a sufficient temperature to prevent agglomeration of the particle during the drying thereof. ii) The Polymeric Aerogel Matrix The polymeric aerogel matrix is based on at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polyurea; polyimides; polyacrylates; polymethylmethacrylate; polysiloxanes; polyoxyalkylenes; polybutadiene; melamine- formaldehyde resins; phenol-furfural resins; resorcinol-formaldehyde resins; epoxy resins; and, benzoxazine resins. The disclosures of the following citations may be instructive in forming such matrices: US Patent No. 5,476,878; US Patent No. 5,081 ,163; US Patent No. 4,997,804; US Patent No. 4,873,218; US Patent No. 9,434,832; US 2014/0171526; and, US 2015/0141544.

It is preferred that the polymeric aerogel matrix is based on at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polysiloxanes; and, benzoxazine resins. These polymers generally show fast gelation which presents the benefit that the gas-filled pores of inorganic particulate aerogel component - dispersed in the polymer matrix - are substantially preserved.

Poly (thiourethane^')

In accordance with one embodiment of the present invention, there is provided a polymeric matrix aerogel component obtained by reacting in the presence of a catalyst and a solvent:

a) a polyisocyanate, as defined hereinabove; and,

b) a polythiol having at least one primary or secondary thiol group per molecule.

The polythiol is not precluded from having at least one tertiary thiol group. However, the polythiol is preferably characterized by having at least 2 and in particular at least 3 primary thiol groups per molecule.

The polythiols may be synthesized according to procedures known to the skilled artisan. The polythiols used in the invention are polyfunctional thiols and the skilled artisan will appreciate that monofunctional secondary thiols can be used to produce polyfunctional secondary thiols. For example, hydroxy functional secondary thiol materials - such as 1 -mercaptoethanol, 2-mercapto- 1 -propanol, 3-mercapto-1 -butanol or 4-mercapto-1 -pentanol - and carboxylic acid functional secondary thiols, such as 2-mercaptopropanoic acid, 3-mercaptobutanoic acid or 4- mercaptopentanoic acid may be converted into higher polyfunctional secondary thiol materials via esterification procedures.

Polyfunctional tertiary thiol materials may be prepared using procedures known from the literature, including the Markovnikov addition of hydrogen sulphide to a substituted olefin. Instructive disclosures for the preparation of polyfunctional tertiary thiol materials include: Fokin et al. , Organic Letters 2006 Vol. 8 No. 9 pages 1767-1770; Tetrahedron Vol. 62 (35) pages 8410-8418 (2006); Mukaiyama et al. , Chemistry Letters Vol. 30 (2001) No. 7 page 638; and, US Patent No. 5,453,544.

Exemplary polythiols which have shown positive utility in this embodiment of the present invention include: pentaerythritol tetrakis (3-mercaptobutyrate); 1 ,3,5-tris(3-mercaptobutyloxy ethyl)-1 ,3,5- triazine-2,4,6(1 H,3H,5H)-trione; and, 1 ,4-bis(3-Mercaptobutyloxy) butane. Exemplary polythiols are also commercially available from Showa Denko under the tradename Karenz® MT and from Bruno Bock under the tradenames Thiocure PETMP, Thiocure TMPMP, Thiocure Tempic, Thiocure ETTMP 700 and Thiocure GDMP.

Polyurethane

In accordance with another embodiment of the present invention, there is provided a polymeric matrix aerogel component obtained by reacting in the presence of a catalyst and a solvent: a) a polyisocyanate as defined hereinabove; and,

b) a cyclic ether compound selected from the group consisting of epoxide compounds and oxetane compounds.

The cyclic ether reacts with the polyisocyanate compound to form a urethane, which forms the matrix polymer of the aerogel according to the present invention. This reaction should desirably be performed at an equivalent ratio of epoxy or oxetane groups to isocyanate groups of from 15:1 to 1 : 15, preferably 10: 1 - 1 :10, more preferably 5:1 - 1 :5. It should of course be noted that an equivalent ratio of 1 : 1 falls within these stated ranges.

When the cyclic ether compound is an epoxide compound, it is preferably selected from the group consisting of:

wherein: R⁵ is selected from the group consisting of a C1-C30 alkyl group, a C3-C30 cycloalkyl group, a C₆-Ci₈ aryl group, a C7-C30 alkylaryl group, a C3-C30 heterocycloalkyl group and a C1 -C30 heteroalkyl group; and

n is an integer from 1 to 30;

wherein: R⁶ is selected independently from the group consisting of hydrogen, halogen, alkyl and alkenyl; and,

n is an integer from 1 to 10;

wherein: R⁷ is selected independently from the group consisting of hydrogen, hydroxyl, halogen, alkyl and alkenyl;

wherein: n is an integer from 0 to 16.

More preferably said epoxide compound is selected from the group consisting of: N, N-diglycidyl- 4-glycidyloxyaniline; sorbitol glycidyl ether-aliphatic polyfunctional epoxy resin; 4,4'- methylenebis(/V,/V-diglycidylaniline); 2-[[4-[2-[4-(oxiran-2-ylmethoxy)phenyl]propan-2- yl]phenoxy]methyl]oxirane; and, poly[(o-cresyl glycidyl ether)-co-formaldehyde].

Suitable commercially available epoxide compounds for use in this embodiment of the present invention include, but are not limited to: 1 ,4-butanediol diglycidyl ether (Erisys™ GE21 ); cyclohexandimethanol diglycidyl ether (Erisys^™ GE22); ethylene glycol diglycidyl ether (Erisys^™ EDGE); dipropylene glycol diglycidyl ether (Erisys^™ GE23); 1 ,6-hexanediol diglycidyl ether (Erisys^™ GE25); trimethylolpropane triglycidyl ether (Erisys^™ GE30); polyglycerol-3- polyglycidyl ether (Erisys^™ GE38); sorbitol glycidyl ether-aliphatic polyfunctional epoxy resin (Erisys^™ GE60); phenol novolac epoxy resins as Epalloy^™ 8220, 8230, 8240, 8250, 8280, 8330, 8350 and 8370 available from CVC Thermoset resins; tetraglycidyl ether of 1 , 1 ,2,2- tetrakis(hydroxyphenyl)ethane (Araldite® XB-4399-3); N ,N,N',N'-T etraglycidyl-4,4'- methylenebisbenzenamine (Araldite® MY720); tris-(hydroxyl phenyl) methane-based epoxy resin (Tactix® 742); triglicidyl ether of meta-aminophenol (Araldite® MY0610, MY0600); triglicidyl ether of para-aminophenol (Araldite® MY0510, MY0500); the bisphenol-A based epoxy resins Araldite® GY6004, GY6005, GY9513, GY9580, GY9613, GY9615, GT6243, GT4248, GT6097, GT7072, EPN 1 179, EPN 1 180 and Tactix® 123 available from Huntsman; the bisphenol-A based epoxy resins D.E.R.^™ 317, 330, 331 , 332, 337, 362, 383 available from Dow Chemical; polypropylene glycol epoxy, D.E.R.^™ 732, 736 available from Dow Chemical; and, the phenol novolac epoxy resins D.E.N.^™ 425, 431 , 438, 439, 440 available from Dow Chemical.

Other epoxide compounds suitable epoxide compound for use in the present invention are selected from the group consisting of

wherein e¹ , e², e³ are same or different and independently selected from 1 to 12; f , f², f³ are same or different and independently selected from 1 to 12; g¹ , g², g³ are same or different and independently selected from 1 to 26; h¹, h², h³ are same or different and independently selected from 0 to 6, provided that h¹+h²+h³ is at least 2; i¹ , i², i³ are same or different and independently selected from 0 to 25; j¹ , j², j³ are same or different and independently selected from 1 to 26; k¹ , k², k³ are same or different and independently selected from 0 to 6, provided that k¹+k²+k³ is at least 2; and I¹ , 1², I³ are same or different and independently selected from 0 to 25;

wherein R³ represents a substituent or different substituent and is selected independently from the group consisting of hydrogen, halogen and linear or branched C1-C15 alkyl or alkenyl groups, attached to their respective phenyl ring at the 3-, 4- or 5-position and their respective isomers and m is an integer from 1 to 5; wherein n and 0 are same or different and independently selected from 1 to 10;

wherein p is an integer from 1 to 5;

and mixtures thereof.

Preferably, said epoxide compound is selected from the group consisting of 2-[(3-{[2-hydroxy-3- ({2-[(2-oxiranyl)methoxy]-4-pentadecylphenyl}methyl)-4-pentadecylphenyl]methyl}-2-[(2- oxiranyl)methoxy]-4-pentadecylphenyl)methyl]-6-({2-[(2-oxiranyl)methoxy]-6- pentadecylphenyl}methyl)-3-pentadecylphenol, 2,3-bis{(E)-1 1 -[(2-oxiranyl)methoxy]-8- heptadecenylcarbonyloxy}propyl (E)-12-[(2-oxiranyl)methoxy]-9-octadecenoate, 2-{[m-(8-{p-[(2- oxiranyl)methoxy]phenyl}pentadecyl)phenoxy]methyl}oxirane, tris(2,3-epoxypropyl)isocyanurate, 2,3-bis(2-{3-[2-(3-propyl-2-oxiranyl)ethyl]-2-oxiranyl}propionoxy)propyl 3-{3-[2-(3-propyl-2- oxiranyl)ethyl]-2-oxiranyl}propionate, polymer with 2-({3-[(3-methoxy-1 - naphthyl)methyl]tolyloxy}methyl)oxirane, 7-oxabicyclo[4.1 0]hept-3-ylmethyl 7- oxabicyclo[4.1 0]heptane-3-carboxylate, phenol polymer with 3a,4,7,7a-tetrahydro-4,7-methano- 1 H-indene glycidyl ether and mixtures thereof.

Above listed preferred epoxide compounds are preferred because they provide hydrophobic aerogels. Examples of commercially available epoxide compound for use in the present invention are but not limited to Cardolite NC-547, Cardolite NC-514S and Cardolite NC-514 from Cardolite, Erisys GE35 from CVC thermosets, CER 4221 from DKSH, Vikoflex 7170 and Vikoflex 7190 from Arkema, Epiclon HP-5000, Epiclon HP-7200H and Epiclon HP-9500 from DIC Corporation, and Jagroxy-505 from Jayant Agro-Organics Ltd. KR-470, X-12-981 S, KR-517, KR-516, X-41 -1059A and X-24-9590 from Shin Etsu.

When the cyclic ether compound is an oxetane compound, it is preferably selected from the group consisting of:

wherein: R⁸ is selected from the group consisting of a C1-C30 alkyl group, a C3-C30 cycloalkyl group, a C₆-Ci₈ aryl group, a C7-C30 alkylaryl group, a C3-C30 heterocycloalkyl group and a C1-C30 heteroalkyl group; and

n is an integer from 1 to 30.

More preferably, said oxetane compound is selected from the group consisting of 1 ,4-bis[(3-ethyl- 3-oxetanylmethoxy)methyl]benzene and bis[1 -ethyl(3-oxetanyl)]methyl ether.

Suitable commercially available oxetane compound for use in this embodiment of the present invention include, but are not limited to: 1 ,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (Eternacoll OXBP); bis[(3-ethyl-3-oxetanyl)methyl]terephthalate (Eternacoll OXTP); bis[1 -ethyl(3- oxetanyl)]methyl ether (Aron OXT 221); and, 1 ,4-bis[(3-ethyl-3-oxetanylmethoxy) methyl]benzene (Aron OXT 121 ), available from Toagosei America Inc. Benzoxazine Resins

In accordance with one embodiment of the present invention, there is provided a benzoxazine matrix aerogel component obtained by reacting in the presence of a catalyst and a solvent: a) a benzoxazine monomer or oligomer; and,

b) a co-monomer selected from the group consisting of a polyisocyanate compound, a cyclic ether compound and an acid anhydride.

It is preferred that that the reactants meet at least one of the following polymerization conditions: the reactant benzoxazine monomer or oligomer has a functionality from 1 to 4, preferably of 1 or 2; the polyisocyanate compound has a functionality from 2 to 6, preferably of 2 or 3; said cyclic ether compound is an epoxide compound or an oxetane compound having a functionality from 2 to 5, preferably from 3 to 5; and, said acid anhydride compound has a functionality 1 or 2 and is derived from aliphatic or aromatic carboxylic acids.

Suitable benzoxazine monomers and oligomers are disclosed in WO2017/178548A1 (Henkel AG & Co. KGaA), the disclosure of which is incorporated by reference. Without intention to limit the present invention, said benzoxazine monomer is preferably selected from the group consisting of: 4'-bis(3,4-dihydro-2H-1 ,3-benzoxazin-3-yl)phenyl methane; 6,6'-propane-2,2-diylbis(3-phenyl- 3,4-dihydro-2H-1 ,3-benzoxazine); 6,6'-methylenebis(3-phenyl-3,4-dihydro-2H-1 ,3-benzoxazine; 3-phenyl-3,4-dihydro-2H-1 ,3-benzoxazine; and, mixtures thereof.

The aforementioned polyisocyanate compounds, epoxide compounds and oxetane compounds do find utility as reactant co-monomers in this embodiment of the invention. The disclosure of WO2017/178548A1 (Henkel AG & Co. KGaA) is also instructive on suitable anhydride co monomers. It is noted in this context that the use of di-anhydrides is preferred over mono anhydrides.

For completeness, exemplary anhydride compounds which are suitable for use in this embodiment of present invention include, but are not limited to: benzophenonetetracarboxylic dianhydride (4,4-BTDA); trimellitic anhydride; phthalic anhydride; biphenyltetracarboxylic dianhydride (S-BDPA); 4,4'-oxydiphthalicanhydride (ODPA); 4,4'-

(hexafluoroisopropylidene)diphthalic anhydride (6FDA); 4,4'-bisphenol A dianhydride (BPADA); pyromellitic dianhydride (PMDA); trimellitic anhydride (TMA); phthalic anhydride; 3, 4,5,6- tetrahydrophthalic anhydride; 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride; and, mixtures thereof. Preferably the acid anhydride compound is selected from the group consisting of: benzophenonetetracarboxylic dianhydride (4,4-BTDA); trimellitic anhydride; phthalic anhydride; biphenyltetracarboxylic dianhydride (S-BDPA); and, mixtures thereof

The benzoxazine based copolymer matrix according to the present invention should have a ratio by weight of benzoxazine monomer or oligomer to co-monomer of from 20:1 to 1 :1 , based on the total monomers in the solution: preferred weights ratios are from 10:1 to 2: 1 and from 10: 1 to 3:1 .

Polysiloxane

In accordance with one embodiment of the present invention, there is provided a polysiloxane matrix aerogel component obtained by reacting in the presence of a catalyst and a solvent: a) a functionalised poly(dimethylsiloxane) oligomer; and,

b) a polyisocyanate compound.

The reaction takes place between the terminal groups of the poly(dimethylsiloxane) (PDMS) oligomers and the isocyanate moieties. The final chemical structure of the matrix aerogel component obtained depends on the nature of the functional group of the PDMS oligomer.

A suitable poly (dimethylsiloxane) oligomer for use in the present invention is a compound having a functionality of at least 2, for example from 2 to 6. Suitable poly(dimethylsiloxane) oligomers can be functionalized with a variety of chemical compounds, such as amino, hydroxyl or epoxy groups. In the cases of either a hydroxyl-PDMS or an epoxy-PDMS being used in the reaction, a polyurethane-polysiloxane material is obtained. Where the PDMS-NH₂ oligomer is used, this yields a polyurea-polysiloxane material. Scheme 1 below illustrates the chemical reactions involved in each case with a di-functional isocyanate.

Scheme 1

Functionalised poly(dimethylsiloxane) oligomers with different molecular weights can be used in order to obtain aerogels with different properties. It is submitted that said PDMS-OH, PDMS- NH₂ or PDMS-epoxy oligomers should have a weight average molecular weight (Mw) of at least 300 g/mol. On the other hand, the weight molecular weight (Mw) of said PDMS-OH, PDMS-NH₂ and PDMS-epoxy oligomers should generally be < 12000 g/mol, preferably < 6000 g/mol and more preferably < 3000 g/mol, for example < 2000 g/mol.

Suitable functionalised poly(dimethylsiloxane) oligomers for use in the present invention are selected from the group consisting of:

wherein: R¹ is selected from the group consisting of C1-C20 alkyl or C₆-Ci₈ aryl group;

n is an integer from 0 to 200, in particular from 0 to 100; and,

p is an integer from 1 to 20, in particular from 1 to 10.

In certain embodiments, said functionalised poly(dimethylsiloxane) oligomer is selected from the group consisting of: silanol terminated polydimethylsiloxanes; aminopropyl terminated polydimethylsiloxanes; N-ethylaminoisobutyl terminated polydimethylsiloxane; epoxypropoxypropyl terminated polydimethylsiloxanes; (epoxypropoxypropyl)dimethoxysilyl terminated polydimethylsiloxanes; epoxycyclohexylethyl terminated polydimethylsiloxanes; carbinol (hydroxyl) terminated polydimethylsiloxanes; and, mixtures thereof.

Examples of commercially available functionalised poly(dimethylsiloxane) oligomer for use in his embodiment of the present invention include but are not limited to: FLUID NH 15 D, FLUID NH 40 D, FLUID NH 130 D, FLUID NH 200 D and IM 1 1 available from Wacke; poly(dimethylsiloxane) diglycidyl ether terminated, poly(dimethylsiloxane) hydroxy terminated, poly(dimethylsiloxane) bis(hydroxyalkyl) terminated and poly(dimethylsiloxane) bis(3-aminopropyl) terminated, available from Sigma-Aldrich; and, silanol terminated polydimethylsiloxanes, aminopropyl terminated polydimethylsiloxanes, N-ethylaminoisobutyl terminated polydimethylsiloxane, epoxypropoxypropyl terminated polydimethylsiloxanes, (epoxypropoxypropyl)dimethoxysilyl terminated polydimethylsiloxanes, epoxycyclohexylethyl terminated polydimethylsiloxanes and carbinol (hydroxyl) terminated polydimethylsiloxanes available from Gelest, Inc.

A polysiloxane based aerogel according to the present invention should have a functionalized poly(dimethylsiloxane) oligomer content from 5 to 80 wt.%, for example from 10 to 70 wt.%, based on the total weight of the reactant compounds. iii) Formation of the Composite Material

Broadly the composite aerogel material of the present invention is produced by a process comprising the steps of:

vii) dissolving the reactant monomers of the polymeric aerogel matrix in a first solvent to form a first solution;

viii) admixing the first solution with the particulate aerogel component to form a dispersion of said particles;

ix) adding a catalyst to the mixture of step ii) to initiate the reaction of said monomers and thereby form a gel;

x) washing said gel with a second solvent;

xi) drying said gel by supercritical drying; and, optionally

xii) postcuring of the obtained aerogel by thermal treatment.

The reaction mixture of step ii) is conventionally either prepared in or formed and transferred to a closed container or mould. That mould determines the geometry of the final composite aerogel material, for which no particular limit is intended: composite materials of both simple and complex geometries may be formed.

The first solvent - in which the polymeric aerogel matrix component is prepared - is suitably a polar solvent and preferably a polar aprotic solvent. Polar aprotic solvents do not have hydrogen atoms that can be donated into an H-bond: therefore, anions participating in a nucleophilic addition reaction are not solvate, and they are not inhibited from reaction. Without intention to limit the present invention, said compounds for use as said first solvent include: dimethylacetamide (DMAc); dimethylformamide (DMF); tetrahydrofuran (THF); 1-methyl- 2-pyrrolidinone (NMP); dimethyl sulfoxide (DMSO); acetonitrile; ethyl acetate; acetone; methyl ethyl ketone (MEK); methyl isobutyl ketone (MIBK); and, mixtures thereof.

The admixture of the particulate aerogel component with the first solution may be performed by under agitation using commonplace methods in the art: the agitation or stirring should be sufficient to ensure a homogenous dispersion of the particles in the first solution. Whilst the particulate aerogel component can be mixed directly with the first solution, it is also possible to independently disperse at least a portion of the particles in a polar aprotic solvent - which may be the same or different from said first solvent - and then mix that dispersion with the first solution.

The particulate aerogel component is conventionally admixed in an amount such that the ratio by weight of the particulate aerogel component to the total monomers is from 1 :100 to 1 : 1 , for example from 1 :10 to 1 :1 , from 1 :5 to 1 :1 or from 1 :2 to 1 :1 . This characterization is not intended to be mutually exclusive of the above mentioned characterization of the composite aerogel material by ratio by volume.

As noted above (step iii)) and to ensure fast gelation, the polymeric aerogel matrix component is obtained in the presence of a catalyst. Suitable catalysts may, in particular, be selected from the group consisting of: alkyl amines; aromatic amines; imidazole derivatives; aza compounds; guanidine derivatives; and, amidines.

For instance, the catalysts may comprise one or more of the following compounds: triethylamine; trimethylamine; benzyldimethylamine (DMBA); /V,/V-dimethyl-1-phenylmethanamine; 1 ,4- diazabicyclo[2.2.2]octane; 2-ethyl-4-methylimidazole; 2-phenylimidazole; 2-methylimidazole; 1 - methylimidazole; 4,4'-methylene-bis(2-ethyl-5-methylimidazole); 3,4,6,7,8,9-hexahydro-2H- pyrimido[1 ,2-a]pyrimidine; 2, 3, 4, 6, 7, 8, 9, 10-octahydropyrimido-[1 ,2-a]azepine; 1 ,8- diazabicyclo[5.4.0]undec-7-ene (DBU); 1 ,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD); 1 ,4- diazabicyclo[2.2.2]octane; 1 ,5-diazabicyclo[4.3.0]non-5-ene; and, 1-azabicyclo[2.2.2]octane (quinuclidine).

A particular preference for the use of benzyldimethylamine (DMBA), 1 ,5,7-triazabicyclo[4.4.0]dec- 5-ene (TBD), 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1 ,4-diazabicyclo[2.2.2]octane (DABCO), dibutyltin dilaurate (DBTDL), and triethylamine might be noted. The skilled artisan will be able to determine the appropriate catalytic amount of the given compounds and mixtures, based on inter alia the reactant monomers, the desired gelation rate, the reaction temperature of step iii) and the desired properties of the matrix. However, the catalyst will conventionally be employed in an amount up to 10 wt.%, for example from 0.5 to 5 wt.%, based on the weight of the reactant monomers.

Whilst it is not strictly precluded, the reaction or gelation step iii) should not be performed at temperatures higher than 160°C as this would necessitate the use of high boiling point solvents. As such, the reaction or gelation temperatures of step iii) should typically be from 20 to 160°C, preferably from 25 to 120°C, for example from 25 to 100°C.

Where heating is required, the container or vessel in which the mixture of step ii) is disposed may be transferred to an oven for the determined gelation time. Said gelation time is typically from 0.1 to 20 hours although gelation times of from 0.5 to 15 hours, for example from 0.5 to 12 hours would be expedient.

After complete gelation of the mixture, the gel is washed at least once and commonly several times over a period of up to 96 hours using a second solvent: the intention of the washing step is to displace the first solvent present during the gelation step with the preferred solvent for the subsequent supercritical drying process. That second solvent may, in particular, be ethanol, acetone, hexane, dimethyl sulfoxide (DMSO) or mixtures thereof and further that second solvent may be independently selected for each washing step. For illustrative purposes, the washing step iv) may be performed step-wise using the following sequence of solvents: 1 ) DMSO; 2) DMSO/acetone and a given ratio by weight; and, 3) acetone. In an alternative illustrative embodiment, the washing step iv) may be performed step-wise using the following sequence of solvents: 1) DMSO; 2) DMSO/acetone at a pre-determined weight ratio; 3) acetone; 4) acetone/hexane at an excess of acetone; 5) acetone/hexane at a weight ratio of 1 : 1 ; 6) acetone/hexane at an excess of hexane; and, 7) hexane.

After said washing step iv) - where the first solvent has been completely replaced in the wet gel by said second solvent, for example acetone or hexane in the illustrative examples - the stage of gel drying in a supercritical fluid is then performed. This supercritical drying broadly includes the following steps: a) displacement of the solvent in the wet gel by a supercritical fluid when placed in an appropriate reactor; and, b) pressure release, the transfer of the supercritical fluid in a gas and the removal of the gas phase of the sample to preserve the highly porous structure. The conditions employed throughout the supercritical drying stage must allow the gel structure of the polymeric matrix to be preserved without damage. With this in mind, but without intention to limit the present invention, the supercritical drying stage of the present invention should commonly comprise: placing the gel in the reactor and charging the reactor with additional ethanol or acetone to prevent air-drying of the gel; pressuring the reactor with C0₂ to at least 5-15 MPa under cooling to 0-10°C; flushing liquid C0₂ through the reactor to commence the extraction of said second solvent; gently heating and pressurizing the reactor over the critical temperature and pressure; flushing the reactor with C0₂ in the supercritical state at a pressure of 5-15 MPa and a temperature of from 20-60°C; permitting diffusion; and, slowly releasing the applied pressure in the reactor until ambient pressure is attained.

The high pressure reactor is desirably under computer control and should: (a) provide no stagnant zones; (b) be constructed of materials which permit isothermal conditions to be maintained without appreciable heating; (c) ideally include a transparent area to permit observation of the drying process; and, (d) possess means, such as terminal flanges, which facilitate cleaning and the loading and unloading of material.

Whilst the composite aerogel may be aged at room temperature and pressure, it may be beneficial in certain circumstances to post-cure the aerogel at an elevated temperature. Temperatures up to 250°C may be appropriate, with temperatures of from 100°C to 200 °C being preferred. iv) Adjunct Materials

In addition to the particulate aerogel component, the composite material of the present invention may contain reinforcement materials to improve the structural integrity and / or the handling of the composite. Suitable reinforcement materials include but are not limited to: glass fibers; glass mats; felt; glass wool; carbon fibers; boron fibers; ceramic fibers; rayon fibers; nylon fibers; olefin fibers; alumina fibers; asbestos fibers; clay; mica; calcium carbonate; talc; zinc oxide; barium sulfates; wood; and, polystyrene. Further suitable reinforcement materials are described in inter alia WO 95/03358, WO 96/36654 and WO 96/37539. The reinforcement material may be included in the composite material in an amount up to 100 wt.%, preferably up to 50 wt.%, for example from 10 to 50 wt.%, based on the weight of the particulate aerogel component.

If desired, the composite may further comprise at least one opacifier. Suitable opacifiers are particulate materials and include but are not limited to: carbon black; graphite; carbon nanotubes; rutile zirconium dioxide; chromium dioxide; titanium dioxide, including ilmenite; ferrosoferric oxide; iron oxide; manganese oxide; zinc oxide; magnesium oxide; antimony oxide; ilmenite; silicon carbide; and, metal silicates. The opacifier may be included in the composite material in an amount up to 100 wt.%, preferably up to 50 wt.%, for example from 10 to 50 wt.%, based on the weight of the particulate aerogel component.

The aforementioned reinforcement materials and opacifiers may be dispersed in one or more of the monomer solution of step i) above (1 ^st solution), a dispersion of the aerogel particles and / or the catalyst component, prior to the polymerization and gelation step iii). The skilled artisan would however be aware that woven fibers and mats may also be included in the composite material - as reinforcement materials - through being disposed at the bottom and / or the top of the mould in which an aerogel monolith is cast.

In an embodiment of the invention, the composite material is prepared in the presence of at least one wetting agent: that wetting agent would thereby remain in - and contribute to the overall thermal conductivity of - the composite material. Whilst that wetting agent might be added during the polymerization and gelation step iii), this is not preferred where the agent is operative to permit the wetting of the aerogel particles. Consequently, it is preferred that the wetting agent is present in the monomer solution (1 ^st solution) and / or the dispersion of the aerogel particles. The wetting agent may be added in an amount such that the composite material contains up to 100 wt.%, preferably up to 50 wt.%, for example from 10 to 50 wt.% of said wetting agent, based on the weight of the particulate aerogel component.

The wetting agent must, most broadly, be compatible with the particulate aerogel component and will conventionally be selected from the group consisting of: anionic surfactants; cationic surfactants; amphoteric surfactants; non-ionic surfactants; and, high molecular weight dispersants. Exemplary anionic surfactants include alkyl sulfates and higher alkyl ether sulfates of which groups ammonium lauryl sulfate and sodium polyoxyethylene lauryl ether sulfate may be mentioned as specific examples. Exemplary cationic surfactants include aliphatic ammonium salts and amine salts, of which groups alkyl trimethylammonium and polyoxyethylene alkyl amine may be mentioned as specific examples. Amphoteric surfactants may, for instance, be of the betaine type - such as alkyl dimethyl betaine - or of the oxido type, such as alkyl dimethyl amine oxido.

Exemplary non-ionic surfactants include: glycerol fatty acid esters; propylene glycol fatty acid esters; sorbitan fatty acid esters; polyoxyethylene sorbitan fatty acid esters; tetraoleic acid polyoxyethylene sorbitol; polyoxyethylene alkyl ether; polyoxyethylene alkyl phenyl ether; polyoxyethylene polyoxypropylene glycol; polyoxyethylene polyoxypropylene alkyl ether; polyethylene glycol fatty acid esters; higher fatty acid alcohol esters; and, polyhydric alcohol fatty acid esters.

Commercial wetting agents which may find utility in the present invention include: AEROSOL® OT, sodium di-2-ethylhexylsulfosuccinite available from Sigma Aldrich; BARLOX® 12i, a branched alkyldimethylamine oxide available from Lonza; TRITON® 100, octylphenoxypolyethoxy(9-10)ethanol available from Dow Chemical; TWEEN® surfactants such as Tween 100, available from Sigma Aldrich; Renex® surfactants, such as Renex 20, available from Croda; Hypermen polymer surfactants; and, Pluronic® surfactants, available from BASF. v) Further Embodiments of the Composite Material

It will be appreciated by the skilled artisan that the composite aerogel materials of the present invention may be utilized per se or as one element of more complex thermal and acoustic insulation constructs. For example, the composite materials may be attached to blankets of fibrous materials or utilized as one or more layers within a laminar thermal and / or acoustic insulating material.

It is also envisaged that the fine structure of the composite aerogel materials may be modified after formation to meet a particular purpose. In particular, the structure of composite aerogel material may be locally disrupted by needling or punching in which processes the following are illustrative result effective variables: needle puncture density; needle penetration depth; and, needle characteristics, such as crank, shank, blade, barb and points thereof.

The following examples are illustrative of the present invention and are not intended to limit the scope of the invention in any way.

EXAMPLES

The following compounds and materials were used in the Examples:

Karenz MT NR1 : 1 ,3,5-Tris(3-mercaptobutyloxethyl)-1 ,3,5-triazine-2,4,6(1 H,3H,5H)- trione available from Showa Denko KK PDMS-OH Polydimethylsiloxane available from Bluestar.

DMBA: L/,/V-Dimethylbenzylamine available from Sigma Aldrich

DBTDL: Dibutyltin dilaurate available from Merck.

MDI: 4,4'-Methylenebis(phenyl isocyanate) available from Sigma Aldrich

Desmodur N3300: Aliphatic polyisocyanate (HDI trimer) available from Covestro. Enova™ Aerogel IC 31 10: Particulate silica aerogel available from Worlee-Chemie GmbH

Enova™ Aerogel MT 1 100: Particulate silica aerogel available from Worlee-Chemie GmbH

The following test procedures were used in the Examples: i) Compression Modulus (MPa):

This property of the aerogels was measured in accordance with ASTM D 1261 : Standard Test Method for Compressive Properties of Rigid Cellular Plastics. Test specimens of the aerogels having a square cross section were centered between two compression platens and load was applied at a constant actuator rate. Specimen displacement and load were recorded throughout the test. Compressive strength was determined in one of two manners - peak or 10% deformation stress - depending on the characteristics of the stress-displacement curve. ii) Thermal Conductivity

This property of the aerogels was measured in accordance with ASTM C177 - 13: Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Netzsch HFM Heat Flow Meter Apparatus. A temperature gradient was set between two plates through the material to be measured. By means of two heat-flow sensors in the plates, the heat flow into the material and out of the material, respectively, was measured. Where the state of equilibrium of the system was reached, the heat flow was constant and the measurement area and thickness of the sample were known, the thermal conductivity was calculated with the aid of the Fourier equation. iii) Density

The density of the aerogels was measured in accordance with ASTM C303: Standard Test Method for Dimensions and Density of Preformed Block and Board-Type Thermal Insulation. iv) Linear Shrinkage

This property of the aerogels was measured in accordance with ASTM C356: Standard Test Method for Linear Shrinkage of Preformed High-Temperature Thermal Insulation Subjected to Soaking Heat.

Reference Example 1

A thiourethane organic aerogel was prepared as follows. A first solution was prepared by dissolving 1 .13g of Karenz MT NR1 in 10g of acetone, followed by the addition of 0.79 g of MDI thereto. A second solution was prepared by dissolving 0.193 g of DMBA in 12.20 g of acetone.

According to the above reaction scheme, the first and second solutions were then mixed at room temperature and a gel was obtained after approximately 1 minute. That resulting gel was washed three times with acetone at 24 hour intervals using a solvent volume three times that of the gel at each washing step. Subsequently the gel was dried via carbon dioxide (C0₂) supercritical drying (SCD).

The properties of the obtained gel are recorded in Table 1 herein below.

Example 1

A first solution was prepared by dissolving 1.13g of Karenz MT NR1 in 10g of acetone, followed by the addition of 0.79 g of MDI thereto. The solution was then added to a container in which 0.97g of silica aerogel particles (Enova™ Aerogel IC 31 10) had previously been disposed.

A second solution was prepared by dissolving 0.193 g of DMBA in 12.20 g of acetone.

Karenz MT NR1 R - MO! backbone structure

Silica Aerogel Particles

Silica Aerogel Particles embedded in the organic .aerogel matrix

The properties of the obtained gel are also recorded in Table 1 herein below.

Table 1

1 : Thermal conductivity measured with the C-ThermTCi.

2: Thermal conductivity measured with HFM Netzsch.

Example 2

A first solution was prepared by dissolving 0.57g of PDMS-OH in 10g acetone, followed by the addition of 1 .61 g of Desmodur N3300. The solution was then added to a container in which 1 .09 g of silica aerogel particles (Enova™ Aerogel MT1 100) had previously been disposed.

A second solution was prepared by dissolving 0.13g of DBTDL in 12.04g of acetone.

The first and second solutions were then mixed at room temperature and a gel was obtained after approximately 10 hours. That resulting gel was washed three times with acetone at 24 hour intervals using a solvent volume three times that of the gel at each washing step. Subsequently the gel was dried via carbon dioxide (C0₂) supercritical drying (SCD).

The properties of the obtained gel are also recorded in Table 2 herein below.

Table 2

1 : Thermal conductivity measured with the C-ThermTCi.

2: Thermal conductivity measured with HFM Netzsch.

In view of the foregoing description and examples, it will be apparent to those skilled in the art that equivalent modifications thereof can be made without departing from the scope of the claims.

Claims

1. A composite aerogel material comprising:

i) a polymeric aerogel matrix; and,

ii) a particulate aerogel component dispersed in said matrix, said particulate aerogel component being selected from inorganic aerogels.

2. The composite aerogel material according to claim 1 , wherein the ratio by volume of the particulate aerogel component to the polymeric aerogel matrix is from 1 : 100 to 1 :1 .

3. The composite aerogel material according to claim 1 , wherein the ratio by volume of the particulate aerogel component to the polymeric aerogel matrix is from 1 :10 to 1 : 1 .

4. The composite aerogel material according to any one of claims 1 to 3, wherein the polymeric aerogel matrix comprises at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polyurea; polyimide; polyacrylates; polymethylmethacrylate; polysiloxanes; polyoxyalkylenes; polybutadiene; melamine-formaldehyde resins; phenol-furfural resins; epoxy resins; and, benzoxazine resins.

5. The composite aerogel material according to any one of claims 1 to 3, wherein the polymeric aerogel matrix comprises at least one polymer selected from the group consisting of: polyurethanes; poly(thiourethanes); polysiloxanes; and, benzoxazine resins.

6. The composite aerogel material according to any one of claims 1 to 5 comprising a particulate inorganic aerogel selected from the group consisting of alumina, titania, zirconia, silica and mixtures thereof.

7. The composite aerogel material according to any of claims 1 to 6, wherein the constituent particles of the particulate inorganic aerogel have a surface functionality selected from the group consisting of: alkylsilane; alkylchlorosilane; alkylsiloxane; polydimethylsiloxane; aminosilane; and, methacrylsilane.

8. The composite aerogel material according to any one of claims 1 to 7, wherein the constituent particles of the particulate inorganic aerogel are characterized by at least one of the following parameters:

i) porosities of from 50 to 99.0% percent, preferably from 60 to 98%;

ii) pore diameters of from 2 nm to 500 nm, preferably from 10 to 400 nm or from 20 to

100 nm;

v) a bulk density of from 20 to 500 kg/m³, preferably from 40 to 200 kg/m³; and, vi) electrical resistivities of from 0.01 W-cm to about 1 .0x1016 W-cm, preferably from 1 W- cm to 1 .0x108 W-cm.

9. The composite aerogel material according to any one of claims 1 to 8, wherein the particulate inorganic aerogel component comprises, consists essentially of or consists of a particulate silica silicate aerogel having: an average particle size of 5-20 microns; a porosity of at least 90%; a bulk density of 40-100 kg/m³; and, a surface area of 600-900 m²/g.

10. A process for obtaining a composite aerogel material as defined in claim 1 , said process comprising the steps of:

iv) washing said gel with a second solvent;

v) drying said gel by supercritical drying; and, optionally

vi) postcuring of the obtained aerogel by thermal treatment.

1 1 . The process according to claim 10, wherein the first solvent is a polar aprotic solvent.

12. The process according to claim 10 or claim 1 1 , wherein the catalyst is selected from the group consisting of: alkyl amines; aromatic amines; imidazole derivatives; aza compounds; guanidine derivatives; and, amidines.

13. The process according to any one of claims 10 to 12, wherein the reaction of step iii) is performed at a temperature of from 20 to 160°C, preferably from 25 to 120°C.

14. The process according to any one of claims 10 to 13, wherein said gelation time of step iii) is from 0.1 to 20 hours.

15. The process according to any one of claims 10 to 14, wherein the second solvent is selected from the group consisting of: ethanol; acetone; hexane; dimethyl sulfoxide (DMSO); and, mixtures thereof.

16. Use of the composite aerogel material as defined in any one of claims 1 to 9 as a thermal insulation panel or an acoustic insulation panel.