Thermal Insulation Materials

Abstract

A thermal insulation material comprising a flame retardant coating applied on a surface of said thermal insulation material, characterized in that the flame retardant coating comprises nano-filaments obtained by a polymerisation reaction of one or more silane compounds in the presence of water.

Claims

1. A thermal insulation material comprising: a surface of the thermal insulation material; a flame retardant coating applied on the surface of the thermal insulation material, wherein the flame retardant coating comprises nano-filaments obtained by a polymerisation reaction of one or more silane compounds in the presence of water.

2. The thermal insulation material according to claim 1, wherein the one or more silane compounds have the formula I:
R.sub.aSi(R.sup.1).sub.n(X.sup.1).sub.3n I wherein R.sub.a is a straight-chain or branched C.sub.1-24 alkyl group or an aromatic group which is linked by a single covalent bond or a spacer unit to the Si atom, R.sup.1 is a lower alkyl group, X.sup.1 is a hydrolysable group, and n is 0 or 1, wherein X.sup.1 represents the same or different groups.

3. The thermal insulation material according to claim 14, wherein the polymerisation reaction of one or more silane compounds in the presence of water is carried out in the gas phase and the relative humidity is in the range of 20% to 80%.

4. The thermal insulation material according to claim 1, wherein the polymerisation reaction of one or more silane compounds in the presence of water is carried out in the liquid phase in an aprotic solvent in the presence of 5 to 500 ppm of water.

5. The thermal insulation material according to claim 1, wherein the thermal insulation material is a fibrous material.

6. The thermal insulation material according to claim 1, wherein it has a density of from 10 to 350 kg/m3.

7. The thermal insulation material according to claim 1, wherein the thermal insulation material is obtained from a renewable raw material.

8. The thermal insulation material according to claim 1, wherein the thermal insulation material is obtained from an inorganic raw material.

9. The thermal insulation material according to claim 1, wherein the thermal insulation material is obtained from synthetic polymer raw materials.

10. A method comprising: performing a polymerisation reaction of one or more silane compounds in the presence of water to produce a coating comprising nano-filaments; applying the coating comprising the nano-filaments as a flame retardant coating on a surface of a material.

11. The method according to claim 10, wherein the one or more silane compounds have the formula I:
R.sub.aSi(R.sup.1).sub.n(X.sup.1).sub.3n I wherein R.sub.a is a straight-chain or branched C.sub.1-24 alkyl group or an aromatic group which is linked by a single covalent bond or a spacer unit to the Si atom, R.sup.1 is a lower alkyl group, X.sup.1 is a hydrolysable group, and n is 0 or 1, wherein X.sup.1 represents the same or different groups.

12. The method according to claim 10, wherein the polymerisation reaction of one or more silane compounds in the presence of water is carried out in the gas phase and the relative humidity is in the range of 20% to 80% or is carried out in the liquid phase in an aprotic solvent in the presence of 5 to 500 ppm of water.

13. The method according to claim 10, wherein the material is a thermal insulation material.

14. The method according to claim 10, wherein the material is one of a textile, a medical dressing, and a medical bandage.

15. (canceled)

16. The thermal insulation material according to claim 1, wherein the one or more silane compounds is chosen from alkylsilanes, alkenylsilanes, arylsilanes, or derivatives thereof.

17. The thermal insulation material according to claim 3, wherein the relative humidity is in the range of 30% to 60% or 30% to 50%.

18. The thermal insulation material according to claim 4, wherein the polymerisation reaction of one or more silane compounds in the presence of water is carried out in the liquid phase in an aprotic solvent in the presence of 75 to 150 ppm or 130 to 150 ppm, of water.

19. The thermal insulation material according to claim 5, wherein the fibrous material has the form of one of a non-woven fibre batt, a non-woven fabric, or a flashspun non-woven fabric.

20. The thermal insulation material according to claim 6, wherein the density is from 25 to 250 kg/m3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

[0033] FIG. 1 shows on the left, a sequence of photographs of a virgin wood wool sample after being exposed to a source of ignition, from top to bottom, as well as a sequence of photographs of a wood wool sample having a flame retardant coating according to the present invention, on the right, after being exposed to a source of ignition, from top to bottom.

[0034] FIG. 1 shows a scanning electron microscope 1.24 K magnification of a polyester filament having a flame retardant coating of nano-filaments obtained by gas phase polymerisation attached to its surface.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0035] The thermal insulation material according to the present invention comprises a flame retardant coating applied on a surface thereof, characterized in that the flame retardant coating comprises nano-filaments obtained by a polymerisation reaction of one or more silane compounds in the presence of water.

[0036] The flame retardant coatings resulting from the polymerisation reaction of one or more silane compounds in the presence of water exhibit a special nanofilament morphology, which the inventors believe to be at the root of the conferred flame resistance. The nanofilaments formed have a diameter of about 10 to 160 nm and a length of about 2, 3 or more micrometres. While the morphology is in general that of nanofilaments, it has also been observed that they can have a beads-on-a-string type morphology, depending on the type of silane and water concentration used.

[0037] The one or more silane compounds suitable in the production of the coatings can be any type of silane, provided the silane includes at least one hydrolysable group and preferably at least one hydrolysable group and at least two non-hydrolysable groups such as alkyl, alkylene, alkylaryl and aryl groups. The hydrolysable group can preferably be a halide such as chlorine or bromine, or an alkoxy group such as for example methoxy or ethoxy groups.

[0038] The coatings may be exclusively obtained by polymerisation reaction of one or more silane compounds in the presence of water without the addition of further flame retardants and may further be free from phosphorus- and/or nitrogen-containing compounds.

[0039] In general, the thermal insulation material is in a fibrous form such as filaments, fibres or shavings and is then further processed into all sorts of webs such as slivers, batts, blankets, loose-fill fibre, felts, spun-bond or flash spun non-wovens and fibre panels. The flame retardant coating can be applied either to the unprocessed or to the processed thermal insulation material such as for example fibre batts.

[0040] Spun-laid, also called spun-bond, nonwovens are made in one continuous process. Fibers are spun and then directly dispersed into a web by deflectors or can be directed with air streams. The can generally be made from polyolefins such as PP or polycondensates such as polyester or polyamide.

[0041] In a preferred embodiment the thermal insulation material is a spun-bond non-woven that has been combined with melt-blown non-woven, conforming them into a layered product called SMS (spun-melt-spun). Melt-blown nonwovens have extremely fine fiber diameters but are not strong fabrics which are then bonded to spun-bonded non-wovens by either resin or thermally.

[0042] In general, the thermal insulation material can be sourced from a renewable material such as plant material or animal material. Suitable plant material can be softwood or hardwood, grass, straw, cotton whereas suitable animal material can be wool such as sheep wool. While in some cases, the source is already in fibrous form, such as with wool, in other cases the source must be brought into fibrous form to provide the adequate low density for use as a thermal insulation material. For instance, in the case of wood, the wood can be cut into wood wool or the wood may be chemically transformed into a cellulosic or lingo-cellulosic fibre such as viscose.

[0043] In general, the thermal insulation material can also be sourced from materials which are usually used in the manufacture of thermal insulation material such as inorganic materials. Such inorganic materials can be chosen from glass, silicate, rock and other minerals.

[0044] The one or more silane compounds useful for obtaining the flame retardant coating can in general be chosen from compounds of formula I when using one silane

R.sub.aSi(R.sup.1).sub.n(X.sup.1).sub.3n I

[0045] wherein

[0046] R.sub.a is a straight-chain or branched C.sub.1-24 alkyl group or an aromatic group which is linked by a single covalent bond or a spacer unit to the Si atom,

[0047] R.sup.1 is a lower alkyl group,

[0048] X.sup.1 is a hydrolysable group, and

[0049] n is 0 or 1, with the proviso that X.sup.1 may represent the same or different groups.

[0050] Alternatively, when using two or more silanes, the compounds useful for obtaining the flame retardant coating can in general be chosen from compounds of formula I and at least one compound of formula II

R.sup.aSi(R.sup.1).sub.n(X.sup.1).sub.3n I

R.sup.bSi(R.sup.2).sub.m(X.sup.2).sub.3m II

[0051] wherein

[0052] R.sup.a is a straight-chain or branched C.sub.(1-24) alkyl group,

[0053] R.sup.b is an aromatic group which is linked by a single covalent bond or a spacer unit to the Si atom,

[0054] R.sup.1 and R.sup.2 are independently of each other a lower alkyl group,

[0055] X.sup.1 and X.sup.2 are independently of each other a hydrolysable group, and

[0056] n, m are independently of each other 0 or 1,

[0057] with the proviso that if n and m are independently of each other 0 or 1, X may represent the same or different groups.

[0058] It is understood that the term straight-chain or branched C.sub.(1-24) alkyl group includes preferably straight chain and branched hydrocarbon radicals having 1 to 16, more preferably 1 to 12, more preferably 1 to 8 carbon atoms and most preferred 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl groups.

[0059] It is understood that the term aromatic includes optionally substituted carbocyclic and heterocyclic groups comprising five-, six-or ten-membered ring systems, such as furan, phenyl, pyridine, pyrimidine, or naphthalene, preferably phenyl, which are unsubstituted or substituted by an optionally substituted lower alkyl group, such as methyl, ethyl or trifluoromethyl, a halogen, such as fluoro, chloro, bromo, preferably chloro, a cyano or nitro group.

[0060] It is understood that the term spacer unit includes a straight-chain or branched alkyl residue, having 1 to 8 carbon atoms, preferably 1 to 6, more preferably 1, 2 or 3 carbon atoms.

[0061] It is understood that the term lower alkyl includes straight chain and branched hydrocarbon radicals having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Methyl, ethyl, propyl and isopropyl groups are especially preferred.

[0062] It is understood that the term hydrolysable group includes a halogen, such as fluoro or chloro, preferably chloro, or an alkoxy group, such as a straight chain and branched hydrocarbonoxy radical having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, wherein methoxy, ethoxy, propoxy and isopropoxy groups are especially preferred.

[0063] In both cases, particularly preferred examples of compounds of formula I include trichloromethylsilane (TCMS), trichloroethylsilane, trichloro(n-propyl)silane, trimethoxymethylsilane and triethoxymethylsilane and when using two or more silanes, particularly preferred examples of compounds of formula II include (3-phenylpropyl)-methyldichlorosilane (PMDS), benzyltrichlorosilane, methylbenzyltrichlorosilane and trifluoromethylbenzyltrichlorosilane.

[0064] In case of acid-sensitive substrates it is preferred to use alkoxysilanes, such as methyltriethoxysilane, (3-phenylpropyl)-methyldimethoxysilane or (3-phenylpropyl)-methyldiethoxysilane, to avoid the formation of hydrochloric acid during hydrolysis of the silanes with the water molecules in the reaction volume or at the substrate surface.

[0065] If the flame retardant coating comprises a compound of formula II, the volume ratio of compound of formula I to compound of formula II ranges from 1:100 to 100:1, preferably from 1:50 to 50:1, more preferably from 1:10 to 10:1, most preferably from 1:1 to 5:1 depending on the nature of the compounds and the nature of the substrate. For example, on inorganic thermal insulation materials such as glass wool, a composition comprising TCMS and PMDS in a volume ratio of 3:1 is preferred.

[0066] The flame retardant coating is preferably applied in the gas phase, since in the gas phase the silanization mixture of one or more silanes and water can penetrate into the thermal insulation material easily and more in-depth silanization can be achieved. On a smaller scale, a simple desiccator may be used as reaction vessel for the silanization. The one or more silane is placed in a closed Eppendorf tube, which is fixed in a special holder. The holder comprises a mechanism for opening the Eppendorf tube which can be triggered from outside by a magnet. The desiccator holding the Eppendorf tube and the uncoated thermal insulation material is closed and flushed by a suitable carrier gas, e.g. a nitrogen/water gas mixture. The relative humidity of the gas mixture needed in the desiccator can be set by independently adjusting the flow rates of dry and wet gas stream by two valves combined with rotameters. The gas streams are mixed in a mixing chamber where the relative humidity is controlled by a hygrometer, and may for example be set in general to about 30 to 60% to form filaments. The desiccator is then flushed until the relative humidity measured by a second hygrometer at the outlet of the desiccator remains constant and corresponds to the set value. The inlet and outlet cocks at the desiccator are then closed and the coating reaction is started by opening the Eppendorf tube. Depending on the volatility of the silanes, the reaction may be run at atmospheric pressure or lower pressures if necessary. The reaction is completed within 0 to 24 hours and typically after twelve hours. After rinsing with an aqueous solvent, such as water, the coated insulation material is ready for use.

[0067] As a final step the coated material may optionally be submitted to a curing step to complete the condensation reaction of remaining free hydroxyl groups at the surface of the material and the coating, thereby further increasing the mechanical stability of the flame retardant coating by forming additional cross-linking SiOSi bonds within the coating or from the material to the coating.

[0068] Alternatively, the silanization may be achieved in solution, either by direct contact with the material in solution or by first polymerizing the one or more silane in solution in the absence of the material and applying the resulting dispersion of nanofilaments onto the material. In the former case, the material is placed at room temperature under stirring in a previously prepared solution comprising the one or more silanes dissolved or suspended in an aprotic solvent, such as toluene in the presence of 5 to 500 ppm, preferably 60 to 250 ppm, more preferably 75 to 150 ppm and most preferably 130 to 150 ppm, of water. After 3 to 4 hours the material is removed, rinsed with for example ethanol and subsequently water and finally dried. In the case of first polymerizing the one or more silane in solution in the absence of the material, a liquid coating composition comprising a solvent and dispersed silicone nanofilaments, preferably in an amount of from 0.01% to 40% by weight based on the total weight of the liquid coating composition, is formed and then applied as a layer of the liquid coating composition on the surface of the material on which the flame retardant coating is to be formed, and the solvent from the liquid coating composition is evaporated to form the flame retardant coating and impart said property on said surface of the material. The dispersed silicone nanofilaments are formed by introducing total one or more silanes in an aprotic solvent such as toluene comprising 5 to 500 ppm, preferably 60 to 250 ppm, more preferably 75 to 150 ppm and most preferably 130 to 150 ppm, of water.

[0069] Characterization of the surface coatings of the invention by scanning electron microscopy, transmission electron microscopy and scanning force microscopy demonstrated the formation of distinct geometrical forms, such as nanofilaments giving rise to the required surface roughness. The fibres are solid and ranged from very short, nearly spherical bases of at least 200 nm in length up to several, i.e 2, 3 or more m in length with diameters ranging from approximately 10 nm to 160 nm and up to 200 nm.

[0070] Such unexpected formation of the surface roughness during condensation reaction as a consequence of self-organisation, i.e. self-arrangement, or self-assembly of the silanes of the present invention is a great advantage over many other coating methods, which do not yield the nano-filamentous morphology as in the present invention.

EXAMPLES

[0071] Fibres were positioned on the surface of the glass slides and anchored with glue, in order to obtain a fibre layer as homogeneous as much as possible. The glass slides, on which are positioned the three materials on three circular tapes (12 mm, 113 mm.sup.2) are placed into the desiccator and exposed to gaseous phase silanization to form silicone nanofilaments on the surface thereof. The same procedure was used on fibre wads.

[0072] The gaseous phase silanization is realized under a controlled atmosphere with the relative humidity set to 360.5%, at room temperature and pressure and left to proceed overnight. For glass fibre based materials, the reaction carried out using 300 l TCMS (trichloromethylsilane)/339 mm.sup.2 for glass fibres and for wood fibre based materials, the reaction was carried out using 500 l TCMS/339 mm.sup.2. When silanizing the fibre wads, the amount of silane used was increased 600 l and 1 ml, respectively, because the surface area was approximately double that of the glued fibre.

[0073] As can be seen from the photograph sequence in the FIG. 1, the virgin wood wool wad continues burning after being ignited until essentially all of the wood wool was combusted. On the other hand, the wood wool wad that had been treated with TCMS at relative humidity set to 360.5% did not ignite even after prolonged exposure to the flame and did therefore not sustain combustion of the wood wool.