MXPA00003535A

MXPA00003535A - Thermal insulating coating

Info

Publication number: MXPA00003535A
Application number: MXPA/A/2000/003535A
Authority: MX
Inventors: Karl Siemensmeyer; Peter Schuhmacher; Frank Meyer; Norbert Schneider; Hiroki Ishida
Original assignee: Basf Aktiengesellschaft 67063 Ludwigshafen De
Priority date: 1997-10-15
Filing date: 2000-04-11
Publication date: 2001-05-17

Abstract

The invention relates to a thermal insulating coating comprising one or more cholesteric IR reflecting layers. In addition, the invention relates to a method for the production and use of the inventive coating.

Description

THERMAL INSULATION COATING The invention relates to a thermal insulation coating comprising one or more cholesteric layers that reflect infrared radiation. The problem of protection against thermal radiation is important especially in relation to the insulation of residential, office or industrial buildings. Buildings with large windows heat up quickly, especially in the summer and in the southern regions, in particular, so that they must be cooled, which represents a considerable energy cost due to the operation of the air conditioning units. Common techniques for thermal insulation, especially to protect against thermal radiation within the range of wavelength between 800 nm and 2000 nm, are based on the absorption of radiation by appropriate dyes or pigments. However, a large part of the energy absorbed is transferred by conduction to the area or to the element to be isolated. The use of materials that reflect substantially the thermal radiation is also known. For this purpose, colorants or special pigments are widely used, but also graphite or gold, as absorbers or broadband reflectors. Examples of dyes used in this context are naphthalocyanines that have a broad band absorption in the infrared (IR) zone, or lacquered polymethine dyes. However, a major disadvantage of the IR absorption dyes is that they exhibit a remarkable absorption in the range of visible wavelengths also, with the result that a considerable reduction in transparency is observed. The energy of radiation absorbed is transformed into thermal energy dissipated by conduction. Graphite, gold, plate or indium-tin oxide (ITO), which are also used as absorbers or reflectors for IR radiation, have comparable disadvantages. Here too, especially in the visible region of the spectrum, there is very little transparency. Only a highly accurate and therefore extensive production of extremely thin layers ensures a sufficiently high and uniform level of transmission in the visible wavelength range. Metal layers of this type are usually applied by means of steam deposition techniques, either chemical or physical (CVD or PVD), which present high levels of complexity. It is also known that cholesteric liquid-crystalline substances can also reflect light in the IR region of the electromagnetic spectrum. Cholesteric crystals (chiral nematic) have been known for a long time. The first example of a material of this type was discovered by the Austrian botanist F. Reinitzer (Moatshefte CEIME, 9 (1988), 421). It is the chirality that determines the existence of cholesteric phases. The chiral portion may be present in either the liquid-crystalline molecule itself or it may be added as an impurity to the nematic phase, thereby inducing the chiral nematic phase. The chiral nematic phase has special optical properties: a high optical rotation and a remarkable circular dichroism that results from the selective reflection of a circularly polarized light within the nematic layer. A consequence of this situation is that no more than 50% of the incident light having the reflection wavelength is reflected. The rest passes through without interaction with the medium. The direction of rotation of the reflected light is determined by the direction of the propeller: a right propeller reflects a circularly polarized light to the right, a left propeller reflects a circularly polarized light to the left. By alternating the concentration of a chiral impurity, it is possible to vary the pitch and hence the range of wavelengths of light selectively reflected from a chiral nematic layer. There is a direct relationship here between the reciprocal of the step p observed and the concentration of the chiral compound (xch): 1 / p = http xch where HTP indicates the helical torsional power of the chiral impurity.

US-A-4,637,896 presents cholesteric crystal-crystalline compounds based on cholesterol derivatives and photopolymerized cholesteric coatings comprising these compounds in copolymerized form. The cholesteric films described have reflection maxima that are predominantly within the range of visible wavelengths. However, two examples are also offered of colorless films whose reflection maxima are at 950 and 1260 nm, respectively. Due to the narrowness of the width of reflection, however, these films are not suitable as a thermal insulation coating. US-A-5, 629, 055 discloses solid cholesteric films based on cellulose. The films can be obtained from colloidal suspensions of cellulose crystallites, said colloidal suspensions being prepared by acid hydrolysis of crystalline cellulose. Solid films have cholesteric properties and their reflection wavelength can be adjusted over the entire infrared to ultraviolet spectral range. The described materials are particularly proposed for use as optical authentication materials, since printing or photocopying techniques are incapable of reproducing the cholesteric effect. US-A-5, 352, 312 describes a method for isolating Rocket engines medium against heat and corrosive substances. The method comprises the use of an ablative insulating material comprising a thermoplastic liquid-crystalline polymer. The liquid-crystalline material, however, is not cholesteric and the insulating action is based on the ablative effect and not on the reflection of the thermal radiation. US-A-5, 016, 985 discloses an infrared radiation filter comprising a wide-band infrared radiation filter element and a cholesteric liquid-crystalline filter element. The importance of the cholesteric filter element lies particularly in its ability to block infrared wavelengths in a narrow, smooth band. The filter for infrared radiation can be used as, for example, in night vision equipment. It is an object of the present invention to provide thermal insulation means which are easy to prepare which are almost completely transparent in the visible range of the electromagnetic spectrum and which absorb very little in the vicinity of the range of infrared and visible wavelengths of the electromagnetic spectrum. We have found that this object is achieved by coatings comprising at least one layer that reflects the cholesteric radiations. The present invention therefore offers a thermal insulation coating comprising one or more cholesteric layers and reflecting at least 40%, particularly at least 45% of the incident radiation in the range of infrared wavelengths, preferably above 750 nm and, particularly, within of the wavelength range from 751 nm to approximately 2000 nm. The thermal insulation coating of the present invention has a number of surprising advantages: a) the incident radiation in the range of visible wavelengths is almost completely transmitted in such a way that the coating has a transparent appearance. b) the incident light in the region of the infrared light of the electromagnetic spectrum is reflected very widely and is not absorbed in such a way that the object to be isolated is not heated by conduction. c) there is a broadband reflection of incident thermal radiation which allows the efficient isolation of articles. d) the thickness and uniformity of the coating can vary within a wide range without significantly affecting its insulating properties, with the result that its preparation is considerably less complex than the preparation of metal-containing reflector coatings. e) the use of metals is avoided ecologically and toxicologically problematic f) the initial compounds for coating preparation are readily available in the industry; their use is therefore generally less expensive than the use of, for example, gold or silver in reflective coatings. The thermal insulation coating of the present invention preferably transmits at least 80%, particularly at least 90%, of the incident radiation in the wavelength range of visible light, i.e., approximately within the range of 390 nm at 750 nm. Especially preferred is a thermal insulation coating of the invention comprising two or more, preferably from about 2 to 20, and particularly from about 2 to 10 cholesteric layers reflecting IR light. With particular preference the layers have different reflection maxima within the range of wavelengths greater than 750 nm. The thermal insulation coating of the present invention comprising two or more cholesteric layers, preferably a number of cholesteric layers that can be divided by 2, for example 2, 4, 6, 8 or 10, is particularly preferred. of the helical superstructures of 2 layers, preferably adjacent, in each case is identical but their direction is different. Special preference is given to a thermal insulation coating of the present invention that between layers having a helical superstructure of identical pitch and of identical direction have a means which reverses the direction of rotation of the circularly transmitted polarized light, especially what is known as a lambda / 2 film or plate. The use of different direction layers, or of a medium that reverses the direction of rotation of the circularly polarized light transmitted between identical address layers, can considerably increase the reflection of the thermal insulation coating of the invention. In this way, reflection degrees of at least 75%, particularly of at least 85%, are achieved, based on the incident radiation, in the wavelength range above 750 n, particularly in the wavelength range of 751 nm at approximately 2000 nm. The only restriction regarding the composition of the thermal insulation coating of the invention is that it must include compounds that, alone or through their interaction, provide cholesteric properties of IR reflection. In principle, virtually all the known cholesteric monomers or mixtures of monomers or polymers or mixtures of polymers can be adjusted in the helical superstructure passage, by varying the chiral component, so that its maximum reflection is within GO.

A preferred thermal insulation coating of the present invention may comprise, for example, in the cured state, cholesteric compounds or mixtures of compounds selected from: a) at least one polymerizable cholesteric monomer; b) at least one achiral, nematic, polymerizable monomer and a chiral compound; c) at least one crosslinkable cholesteric polymer; d) at least one cholesteric polymer in a polymerizable diluent or a mixture of polymerizable diluents; e) at least one cholesteric polymer whose cholesteric phase can be frozen by rapid cooling below the glass transition temperature; or f) at least one liquid-crystalline achiral crosslinkable polymer and a chiral compound. For the purposes of the present invention, crosslinking refers to the covalent bonding of polymeric compounds and the term "polymerization" refers to the covalent bonding of monomeric compounds to form polymers. By curing we understand the cross-linking, polymerization or freezing of the cholesteric phase. The cure fixes the uniform orientation of the cholesteric molecules in the cholesteric layer. The preferred monomers of group a) are described in DE-A-196 02 848 and in DE-A-4 342 280, whose total content is incorporated here by reference.

Particularly, the monomers a) comprise at least one chiral, liquid-crystalline, polymerizable monomer of the formula I z? - y? -Ai- y2-Ml- y3_ (I) where Z1 is a polymerizable group or a radical bearing a polymerizable group, Y1, Y2, Y3 independently are chemical bonds, oxygen, sulfur, -co-s-, -s-co- CO N (R), -N (R) -CO. CH20 or 0CH2, A1 is a spacer, M1 is a mesogenic group, X is a chiral radical of valence n, R is hydrogen or alkyl C? -C_i, n is from 1 to 6 and radicals Z1, Y1, Y2, Y3, A1 and M1 may be identical or different if n is greater than 1. Preferred Z1 radicals are: - N = C = 0 / - N = C = S, - O- C = N, - COOH, - OH or - NH2, where each R can be identical or different and is hydrogen, or Ct.-C_ alkyl, such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl. Of the reactive polymerizable groups, the cyanates can be trimerized spontaneously in cyanurates and are therefore preferred. The polymerization of the other indicated groups requires additional compounds having complementary reactive groups. The isocyanates, for example, can be polymerized with alcohols to provide urethanes and with amines to provide urea derivatives. Similar comments apply to trirans and aziridines. Carboxyl groups can be condensed to provide polyesters and polyamides. The maleimido group is especially suitable for the copolymerization of free radicals with olefinic compounds such as styrene. Said complementary reactive groups may be present in either a second component of the invention, mixed with the first, or they may be incorporated into the polymer network through auxiliary compounds containing 2 or more such complementary groups. Particularly preferred Z1-Y1 groups are acrylate and methacrylate. Yx-Y3 may be in accordance with what is defined above, the term chemical bond meaning a single covalent bond. Suitable spacers A1 are all known groups for this purpose. The spacers generally contain from 2 to 30, preferably from 2 to 12, carbon atoms and consist of linear aliphatic groups. They may be interrupted in the chain by non-adjacent O, S, NH or NCH3, for example. Other suitable substituents for the spacer chain are fluorine, chlorine, bromine, cyano, methyl and ethyl. Examples of representative spacers are: - (CH2) p-, - (CH2CH20) mCH2CH2-, -CH2CH2SCH2CH2-, -CH2CH2NHCH2CH2-, CH 3 CH 3 CH 3 CH 3 f 1 CH 2 CH 2 N -CH 2 CH 2 - '- (CH 2 CH 0) m CH 2 CH -' - (CH 2) 6 CH - or - CH 2 CH 2 CH -. where m is from 1 to 3 and p is from 1 to 12. The mesogenic group M1 preferably has the structure (T-Y8) sT where Y8 is a bridge in accordance with one of the definitions of Y1, s is from 1 to 3 and T is identical or different in each occurrence and is an isocicloaliphatic, heterocycloaliphatic, isoaromatic or divalent heteroaromatic radical. If f is greater than 1, the bridges Y8 may be identical or different. the radicals T can also be ring systems substituted by C: -C4 alkyl, Ci-C- alkoxy, fluoro, chloro, bromo, cyano, hydroxyl or nitro. The preferred T radicals are: - The following mesogenic groups M1 are particularly preferred: Of the chiral radicals X of the compounds of the formula I, the radicals derived from sugars, binaphthyl or biphenyl derivatives and optically active glycols, dialcohols or amino acids are particularly preferred, especially because of their availability. In the case of sugars, pentoses and hexoses as well as their derivatives should be mentioned. Examples of radicals X are the following structures, the lines at the end in each case indicate free valencies.

Particular preference is given to Chiral groups that have the following structures are also suitable: Additional examples are presented in the German Application P 43 42 280.2. Preferably n is 2. Preferred monomers of group a) are further polymerizable chiral derivatives of cholesterol as described in DE-A-35 35 547 and in US-A-4, 637, 896, the entire contents of which are Incorporated here by reference. Examples of preferred monomers of group b) are described in the dissertation of H. Jonson, Department of Polymer Technology, Royal Institute of Technology (Royal Institute of Technology Technology), S-10044 Stockholm, Sweden, January 25, 1991, in DE-A-4 408 171 ', DE-A-4 408 170 and DE-A-4 405 316, the entire contents of which are incorporated herein by reference. The cholesteric mixture preferably comprises at least one polymerizable liquid-crystalline achiral monomer of the formula II Z2? 4 A2 y5 M2? 6 A3-r-? 7- (II) where Z2, Z3 are identical or different polymerizable groups or radicals containing a polymerizable group, n is 0 or 1 Y4, Y5, Y °, Y7 independently are chemical bonds, oxygen, sulfur, -co-o -, - o-co-, - co- -co-s-, -s-co- -CO N (R), - (R) -CO, CH20 or OCH2 A ", A are identical or different spacers and M is a mesogenic group.The polymerizable groups, the Y4 Y bridges, the spacers and the mesogenic group are subject to the same preferences as the corresponding variables of formula I. In addition, the mixture of group b) includes a chiral compound The chiral compound causes the torsion of the liquid-crystalline achiral phase to form a cholesteric phase In this context, the magnitude of the torsion depends on the torsional power of the chiral contaminant and its concentration. Therefore, the pitch of the helix and, in turn, the reflection wavelength depend on the concentration of the chiral contaminant, as a result, it is not possible to indicate a concentration range generally valid for the pollutant. The contaminant is added in the amount in which the desired reflection occurs. Preferred chiral compounds are the compounds of the formula I z i y? Al? 2 Ma? 3 (the), where Z1, Y1, Y2, Y3, A1, X and n are in accordance with the above defined and Ma is a divalent radical comprising at least one heterocyclic or isocyclic ring system. The M3 portion here resembles the described mesogenic groups, since in this way a particularly good compatibility with the liquid-crystalline compound is achieved. Ma, however, does not have to be mesogenic, since the compound has the purpose of causing an appropriate torsion of the liquid-crystalline phase simply by virtue of its chiral structure. Preferred ring systems present in Ma are the structures T mentioned above, preferred structures Ma are those of the aforementioned formula (T-Y8) s-T. In addition, monomers and chiral compounds of group b) are described in WO 97/00600 and its predecessor DE-A-195 324 08, the content of which is incorporated herein by reference. The preferred polymers of groups c) are derivatives of cholesteric cellulose in accordance with that described in DE-A-197 136 38, especially mixed cholesteric esters of (VI) cellulose hydroxyalkyl ethers with (VII) saturated aliphatic or aromatic carboxylic acids and (VIII) unsaturated monocarboxylic or dicarboxylic acids.

Mixed esters are particularly preferred wherein the hydroxyalkyl radicals of component VI which are attached via ether functions comprise C2-C? Or straight-chain or branched hydroxyalkyl radicals, especially hydroxypropyl and / or hydroxyethyl radicals.

Component VI of suitable mixed esters preferably has a molecular weight of from about 500 to about 1 million. Preferably, the anhydroglucose units of the cellulose are etherified with hydroxyalkyl radicals in an average molar degree of substitution of 2 to 4. The hydroxyalkyl groups in the cellulose can be identical or different, up to 50% of them can also be replaced by groups alkyl (especially Ci-Cio alkyl groups). An example of a compound of this type is hydroxypropylmethylcellulose. Compounds which can be used as component VII of the mixed esters which can be used are straight chain aliphatic Ci-Cio carboxylic acids, especially carboxylic acids C2-Ce carboxylic acids C __-C? branched aliphatics, especially C4-Cβ carboxylic acids, or straight-chain or branched halocarboxylic acids. The components VII may also comprise benzoic acid or aliphatic carboxylic acids with aromatic substituents, especially phenylacetic acid. Component VII is selected with particular preference between acetic, propionic, n-butyric, isobutyric and n-valeric acids, in particular between propionic acid, 3-chloropropionic acid, n-butyric acid and isobutyric acid. Component VIII is preferably selected from unsaturated C 3 -C 2 monocarboxylic or dicarboxylic acids or monoesters of said dicarboxylic acid, especially C 3 -C 6 alpha, betaethylenically unsaturated monocarboxylic or dicarboxylic acids or monoesters of dicarboxylic acids. With special preference, component VIII of the mixed esters that can be used is selected from acrylic, methacrylic, crotonic, vinylacetic, maleic, fumaric and undecenoic acids, especially between acrylic and methacrylic acids. Component VI is preferably esterified with component VII and with component VIII at an average degree of molar substitution of 1.5 to 3, particularly of 1.6 to 2.7 and, with particular preference, of 2.3 to 2.6. Preferably about 1 to 30%, particularly 1 to 20% or 1 to %, particularly preferably from about 5 to 7%, of the OH groups of component VI are esterified with component VIII. The ratio between component VII and component VIII determines the reflection wavelength of the polymer. Highly suitable polymers of group c), in addition, are the polyesters or polyesters or polycarbonates terminated in propargyl described in DE-A-197 17 371. Among these compounds, polyesters or polycarbonates having at least one propargyl end group are preferred. of the formula R3C-vC-CH2-, wherein R3 is H, C? -C4 alkyl / aryl or Ar-C? -C alkyl (eg, benzyl or phenethyl) attached to the polyesters or polycarbonate directly or through of a linker. The linker is preferably selected from QV X-, (the propargyl group is fixed on X), where R4 is H, C1-C alkyl. or phenyl, X is O, S or NR "and R 2 is H, C 1 -C 4 alkyl or phenyl In the polyesters, the propargyl end group is preferably fixed through The polyesters preferably comprise (IX) at least one aromatic or aliphatic dicarboxylic acid unit and / or at least one aromatic or araliphatic hydroxycarboxylic acid unit and (X) at least one diol unit. The preferred dicarboxylic acid units are the units of the formula especially the units of the formula it being possible for each of the phenyl groups or the naphthyl group to contain 1, 2 or 3 substituents selected independently from each other between C 1 -C 4 alkyl, C 1 -C 4 alkoxy / halogen and phenyl and where, in the above formulas, W is NR, S, 0, (CH3) p0 (CH2), (CH2) or a single bond, R is alkyl or hydrogen, m is an integer of a 15 and P and q independently are integers from 0 to 10. The preferred hydroxycarboxylic acid units are the units of the formula -o-foMO? 8- - wherein each phenyl group or the naphthyl group may have 1, 2 or 3 substituents independently selected from Ci-C alkyl, Ci-Cj alkoxy, halogen and phenyl. The preferred diol units are the units of the formula especially the units of the formula CH3 S-CH -CH-CH2-CH3 where in the formulas above, L is alkyl, alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, X is S, O, N, CH2 or a single bond, A is a single bond, (CH2) n, (CH2) n, S (CH2) n, NR (CH2) n, R is alkyl or hydrogen, R1 is hydrogen, halogen, alkyl or phenyl and n is an integer from 1 to 15. Polyesters comprising at least one dicarboxylic acid unit of the formula are preferred. and at least one diol unit of the formula where R 3 is H, halogen, C 1 -C 4 alkyl, especially CH 3 or C (CH 3) 3 or phenyl. Additional preferred compounds are diesters of the formula PYB-CO-OAO-CO-BYP, where P is a propargyl end group of the formula defined above, and is O, S or NR2 (R2 = C? -C4 alkyl) # B is wherein each phenyl group or naphthyl group may have 1, 2 or 3 substituents independently selected from C 1 -C 4 alkyl, C 1 -C 4 alkoxy, halogen and phenyl, and A (together with the adjacent oxygen atoms) is one of the aforementioned diol units. Particularly preferred diesters are diesters of the aforementioned formula wherein B is and especially diesters of the formula HC? CCH; 0-B-CO-0-A-0-CO-B-OCH2-CSfCH, where , A is in accordance with what is defined for XI. Additional preferred compounds are polycarbonates comprising at least one diol unit incorporated of the aforementioned formulas, especially the formulas Polycarbonates are preferred which comprise as diol units at least one mesogenic unit of the formula at least one chiral unit of the formula -or with or without a non-chiral unit of the formula R being in accordance with what is defined above and particularly H or CH3. Particularly preferred polycarbonates are polycarbonates having propargyl end groups of the formula HC = CCH20-R5-CO, where R5 is Additional suitable polymers of group c) are cholesteric polycarbonates containing photoreactive groups even in a non-terminal position. Such polycarbonates are described in DE-A-196 31 658 and are preferably of the formula XIII (XIII) where the molar ratio / x / y / z is about 1 to 2O / from about 1 to 5 / from about 0 to 10 / from about 0 to 10, particularly preferably from about 1 to 5 / from about 1 to 2 / from about 0 to 5 / from about 0 to 5. In formula XIII A is a mesogenic group of the formula B is a chiral group of the formula do), CH3 - CH2 CH CH2 S CH2 CH2 CH2 - D is a photoreactive group of the formula O well E is an additional non-chiral group of the formula where, in the above formulas, L is alkyl, alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, X is S, O, N, CH2 or a single bond, R is alkyl or hydrogen, A is a single bond, (CH2) n, 0 (CH2) n, S (Cu2) n / NR (CH2) R1 is hydrogen, halogen, alkyl or phenyl and n is an integer from 1 to 15. If R1 is alkyl or halogen and if A is a single bond, or if R1 is H or alkyl and A is 0 (CH2) n S (CH2) n NR (CH2) ", Groups are groups that improve solubility. Examples of them are isosorbide, isomanido and / oisoidido is the preferred chiral component. The proportion of the chiral diol structural units is preferably within a range of 1 to 80 mol% of the overall content of the diol structural units, with 2 to 20 mol% being particularly preferred, according to the desired reflection behavior. Examples of preferred polymers of group d) are crosslinkable cholesteric copolyisocyanates according to that described in US-A-08 834 745, the total content of which is incorporated herein by reference. Such copolyisocyanates have repeating units of the formulas and, if appropriate, the formula where R1 is a chiral aliphatic or aromatic radical, R2 is a crosslinkable radical and R3 is an achiral radical. Unless otherwise specified, in this text alkyl (including definitions such as alkoxy, dialkyl, alkylthio, etc.) refers to a branched or unbranched C1-C12 alkyl, preferably C3-C2alkyl, especially C4-C4alkyl, and particularly C2-alkyl Cio. R1 is preferably selected from alkyl radicalsalkoxyalkyl, alkylthioalkyl, cycloalkyl, alkylphenyl or C3-C9 epoxyalkyl branched or unbranched (chiral) or radicals of esters of Ci-Cß fatty acids with Ci-Cβ alkanols or C3-Cg dialkyl ketones. The ester radical can be attached to the nitrogen either through the fatty acid component or via the alkanol radical. The radical R1 may have 1, 2 or 3 identical or different substituents and are selected from alkoxy, C1-C4 dialkylamino such as CN, halogen or C1-C4 alkylthio. R1 is preferably selected from alkyl, alkoxyalkyl, Ci-Cß fatty acid ester radicals with Ci-Cβ alkanols, C3-C9 dialkyl ketones and epoxidized C3-C6 epoxyalkyl radicals, wherein R1 may be substituted by 1 or 2 identical radicals or different and selected from alkoxy, halogen, CN and CF3. Preferred substituents of branched or unbranched alkyl or alkoxy radicals are selected from alkoxy, halogen or CN atoms groups; in the case of esters of C? -Cd fatty acids with Ci-C? alkanols from alkoxy groups, halogen atoms, CN and CF3, and in the case of C3-C9 dialkyl ketones from alkoxy groups, Halogen atoms and CN. The main chain of the radical R1 has a particular length of 3 to 12, especially of 6 to 10 and preferably of 6 to 8 members (carbons, oxygens and / or sulfur atoms). R1 radicals selected from among CH3 CH3 I I 2, 6-diraethyl eptyl -CH2-CH2- i CH2) 3 CH CH3 CH3 CH3 -CH2 CH C2H5 - (CH2) - CH C2H5 2 * CH3 CH3 (CH2 > - CH C2H5 CH CH2 CH3 3 * * CH3 CN CH2- (CH2) - CH3 CH - CH2) CH3 * 5 * 5 Cl CH3 Br CH.

• CH - CH C2H5 -CH • CH C2H5 * CH3 CH3 CH3 0 I II -CH CH C2H5, CH C 0 CH3, * * CH3 OR CH3 CH3 CH O - C2H5 CH - O - CH - CH3 * * CH3 OR CH3 CH3 CH3 CH C O CH2 - CH CH3 CH C - O - CH - C2H5 * * * CF3 0 CF O CH3 C IH CH2 CI C2H5 f C IH CH2 C I - O - C iH C2HS CH3 CH3 CH - O- (C "H" 2.: H2-CH- -CH3 * CÍÍ3 ' CH3 CH3 -CH2 -C * H 0C2H5: H3 -C * H - O C3H7 CH3 CH3 ÍCH2X- 0-; H2 CH O - C2H5, - (CH2 ^ - 0 - CH2 - CH - O - C2H5, 3 * 4 * CH3 - (CH2 _0 - CH2 CH O - C2H5, CH2 - CH - CH - (CH2 - CH3 * * * 2 - CH2 - CH - CH CH3 - CH2 - CH - CH CH2 CH3 With particular preference, component III of the copolyisocyanates that can be used are derived from 2,6-dimethylheptyl isocyanate. The radical R2 of the copolyisocyanates which can be used is preferably selected from C3-Cu alkenyl radicals, C4-Cn ethervinyl radicals (= C2-Cg vinyl alkyl ethers), C3-C: ethylenically unsaturated carboxylic acid radicals and acid esters C3-C5 ethylenically unsaturated monocarboxylics with C -CO alkanols, in bond with the nitrogen atom is carried out through the alkanol radical of the ester. Particularly preferably, the radical is selected from methyl, ethyl, propyl, n-butyl, isobutyl, and 2-ethylhexyl acrylate and methyl, ethyl, propyl, n-butyl, isobutyl, and 2-ethylhexyl methacrylate, particularly acrylate. ethyl and ethyl methacrylate. The radical R 3 preferably has the same meanings as the radical R 1. However, it is achiral - in other words, it has no center of chirality, or it is present as a racemic mixture.

With particular preference, the main chain of the radical R3 has a length from 4 to 12, particularly from 6 to 10, and preferably from 6 to 8 members (carbon, oxygen and / or sulfur atoms). With very particular preference, the component V of the copolyisocyanates of the invention is derived from n-hexyl isocyanate, n-heptyl or n-octyl. Components III, IV and V are preferably present in a molar ratio III: IV: V of from about 1 to 20: 1 to 10: 50 to 98, particularly from about 5 to 15: 5 to 15: 65 to 90 and, with particular preference, of approximately 15:10:75. The units III, IV and V can be found in a random distribution within the copolyisocyanates that can be used. Suitable polymers of group e) are chiral nematic polyesters having flexible chains, comprising isosorbide, isomanido and / or isoidido units, preferably isosorbide units, and for chain flexibilization comprise at least one unit selected from (and derived from) (a) aliphatic dicarboxylic acids, (b) aromatic dicarboxylic acids with a flexible spacer, (c) alpha, omega-alkanediols, (d) diphenols with a flexible spacer and (e) condensation products of a polyalkylene terephthalate or polyalkylene naphthalate with an acylated diphenol and an acylated isosorbide, in accordance with that described in DE-A-1 97 04 506. The polyesters are non-crystalline and form stable cholesteric phases which can freeze when cooled below the glass transition temperature. The glass transition temperatures of the polyesters, in turn, despite the flexibilization, are above 80 ° C, preferably above 90 ° C and, particularly, above 100 ° C. The polyesters which can be used include as unit (a) preferably those of the formula -0C- (CH2) n -CO- where n is from 3 to 15, especially from 4 to 12, and particularly particular adipic acid; as units (b) preferably those of the formula where A is (CH2) n, 0 (CH2) r.O or (CH2) or -0- (CH2) p, n is 3 to 15, especially 4 to 12 and, with particular preference, 4 to 10, and or and p, independently, are from 1 to 7; as units (c) preferably those of the formula -0- (CH2) n-0-- or else -O- (CH2-CH2-0) m-, where n is from 3 to 15, especially from 4 to 12 and, with particular preference from 4 to 10, and is from 1 to 10; and as units (d) preferably those of the formula -or where A is (CH2) n / 0 (CH:) n0 or (CHc) or -0- (CH) pn is from 3 to 15, especially from 4 to 12 and, with particular preference from 4 to 10, yoyp , independently, they are from 1 to 7. The polyesters that can be used also comprise, as the non-flexible acid component, preferably dicarboxylic acid units of the formula Á X -X '~ - > - @? ° ^ or -MdVßy 1 / ~? and as non-flexible alcohol component diol units of the formula where in the above formulas / L is alkyl, alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, X is S, O, N, CH2 or a single bond, A is a single bond, CH2- (H) -. CH2CH2- (H) - wherein R1 is hydrogen, halogen, alkyl or phenyl and R is alkyl or hydrogen. The polyesters that may be employed may include additional flexible diol units of the formula CH, - 0- CH2- CH - CH2 - S - CH2 - CH2 - CH3"°" "O S ~ Cñ2 ~ CH - CH2 - 0 - Rl - ( where R1 is hydrogen, halogen, alkyl or phenyl, A is (CH2) n, 0 (CH2) n / S (CH2) no or NR (CH2) n, and n is 1 to 15. Examples of preferred polymers of group f) are liquid-crystalline polyorganosiloxanes crosslinkable in accordance with that described in EP-A-066 137 and in EP-A-358 208. The mixture of group f) further comprises a chiral compound. Suitable chiral compounds are, in particular, the chiral impurities of the formula described for the mixtures of group b). With particular preference, the thermal insulation coating of the invention comprises chiral compounds and nematic monomers of group b), especially chiral compounds of the formula 2: and / or of formula 5: and nematic monomers of formula 1 ? (CH2) n CH2) n 0C- (i; or of formula 3: (3; or of the formula: in the cured state, where ni and n2 in formulas 1 and 3 are, independently, 2, 4 or 6 and the monomers of formula 1 or 3 are preferably used as mixtures of compounds with n? / n2 = 2 / 4, 2/6, 4/2, 6/2, 4/4, 4/6, 6/4 or 6/6, and R in formula 4 is H, Cl or CH3. The present invention further provides a process for the production of a thermal insulation coating, comprising the application to a transparent substrate of at least one layer that reflects cholesteric IR, its cure, the application, if desired, of one or more layers which reflect additional cholesteric IR and, if desired, a medium which reverses the direction of rotation of the circularly transmitted polarized light, curing said layer (s) and thus the completion of the thermal insulation coating. The transparent substrate on which the IR reflection layer (s) is applied can be, for example, a glass unit, a window pane or a film adhered on a window pane for the purposes of isolation. The cholesteric IR reflection layer can be applied on the substrate by standard techniques: for example, by means of techniques selected from pneumatic knife coating, bar coating, squeeze coating, impregnation, reverse roll coating, transfer roller coating, engraving coating, pouring, spraying , rotating coating, or printing techniques such as letterpress printing, flexographic, sweet cut, photographic printing process or screen printing. The IR reflection layer (s) can be applied in the form of low space or high viscosity mixtures on the substrate, but preferably in the form of low viscosity mixtures. For this purpose, the cholesteric mixtures can be applied on the substrate in undiluted form or else minimally diluted at high temperature or in highly diluted form at low temperature. The cholesteric mixtures and the formulations comprising absorption pigments can be diluted with any suitable diluent before being applied to the substrate. Examples of diluents which can be used in the process of the present invention for the compounds of groups a) or b) are linear or branched esters, especially acetic esters, cyclic ethers and esters, alcohols, lactones, aliphatic and aromatic hydrocarbons, such as for example toluene, xylene and cyclohexane, as well as ketones, amides, N-alkylpyrrolidones, especially N-methylpyrrolidone, and particularly, tetrahydrofuran (THF), dioxane and methyl ethyl ketone (MEK). Examples of suitable diluents for the polymers of group c) are cyclic ethers and ethers such as tetrahydrofuran or dioxane, chlorinated hydrocarbons such as dichloromethane, 1, 1,2, 2-tetrachloroethane, 1-chloronaphthalene, chlorobenzene or 1,2-dichlorobenzene. . These diluents are especially suitable for polyesters and polycarbonates. Examples of suitable diluents for cellulose derivatives are ethers, such as dioxane, or ketones, such as acetone. When copolyisocyanates are used as group polymers d) it is advisable to use polymerizable diluents according to that described in US-A-08 834 745. Examples of such polymerizable diluents are esters of alpha, beta-unsaturated monocarboxylic or dicarboxylic acids, especially acids C3-C6 monocarboxylic or dicarboxylic acids, with C? -C? 2 alkanols, C: -C? 2 alkanols or their Ci-C? alkyl ethers and phenyl ethers, examples being acrylates and methacrylates, hydroxyethyl or hydroxypropyl acrylate or methacrylate , and 2-ethoxyethyl acrylate or methacrylate; C 1 -C 12 vinyl alkyl ethers, for example vinyl ethyl, hexyl and octyl ether; - vinyl esters of C? -C? 2 carboxylic acids, as per example vinyl acetate, vinyl propionate or vinyl laurate; C3-C9 epoxides such as, for example, 1,2-butylene oxide, styrene oxide; - N-vinylpyrrolidone, N-vinylcaprolactam, N-vini1formamide; vinylaromatic compounds such as styrene, alpha-methylstyrene, chlorostyrene, and compounds having two or more crosslinkable groups such as diolsters of diols (including polyethylene glycols) with acrylic or methacrylic acid or divinylbenzene. Examples of preferred polymerizable diluents are 2-ethoxyethyl acrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, diethylene glycol monomethyl ether acrylate, phenoxyethyl acrylate and tetraethylene glycol dimethacrylate. A particularly preferred polymerizable diluent is styrene. The mixtures of groups a), b) or c) may also include polymerizable diluents in small amounts. Preferred polymerizable solvents which may be added to a), b) or c) are acrylates, especially acrylates of relatively high functionality such as bis-, tris- or tetraacrylates and, more preferably, oligoacrylates of high boiling point. The preferred amount added is about 5% by weight, based on the total weight of the mixture. For photochemical polymerization, the cholesteric mixture may include customary commercial photoinitiators. For curing by electronic rays, such primers are not required. Examples of suitable photoinitiators are isobutylbenzoinether, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -furan-1-one, mixtures of benzophenone and 1-hydroxycyclohexylphenyl ketone. , 2, 2-dimethoxy-2-phenylacetophenone, perfluorinated diphenyl titanocenes, 2-methyl-1- (4- [methyl] phenyl) -2- (4-morpholinyl) -1-propanone, 2-hydroxy-2-methyl-1 phenylpropan-l-one, 4- (2-hydroxyethoxy) phenyl-2-hydroxy-2-propyl ketone, 2,2-diethoxyacetophenone, 4-benzoyl-4'-methyldiphenyl sulfide, ethyl 4- (dimethylamino) benzoate, mixtures of 2-isopropylthioxanthone and 4-isopropylthioxanthone, 2- (dimethylamino) ethyl benzoate, d, 1-camforquinone, ethyl-d, 1-camforquinone, mixtures of benzophenone and 4-methylbenzophenone, benzophenone, 4,4'-bisdimethylaminbenzophenone, (? 5-cyclopentadienyl) (ry-isopropylphenyl) iron (II) hexafluorophosphate, hexafluorophosphate triphenylsulfonium or mixtures of triphenylsulfonium salts, and butanediol diacrylate, dipropylene glycol diacrylate, hexanediol diacrylate, 4- (1,1-dimethylethyl) cyclohexyl acrylate, trimethylolpropane triacrylate as well as tripropylene glycol diacrylate. In order to adjust the viscosity and leveling behavior it is possible that the cholesteric mixtures are mixed with additional components. For example, it is possible to employ polymeric binders and / or monomeric compounds that can be converted to a polymeric binder by polymerization. Examples of suitable compounds of this type are polyesters soluble in organic solvent, cellulose esters, polyurethanes and silicones, including silicones modified by polyethers or polyesters. It is particularly preferred to use cellulose esters such as, for example, cellulose acetobutyrate. The addition of small amounts of suitable leveling agents can also present an advantage. It is possible to employ from about 0.005 to 1% by weight, particularly from 0.01 to 0.5% by weight, based on the amount of cholesteric employed. Examples of suitable leveling agents are glycols, silicone oils and, particularly, acrylate polymers, such as for example acrylate copolymers obtainable under the name Byk 361 or Byk 358 from Byk-Chemie and the polymers of silicone-free acrylate, modified that can be obtained under the name Tego Flow ZFS 460 from Tego. The cholesteric mixture may also include stabilizers to counteract the effects of UV rays and weathering. Examples of suitable additives of this type are 2, 4-dihydroxybenzophenone derivatives, 2-cyano-3,3-diphenyl acrylate derivatives, 2,2 ', 4,4'-tetrahydroxybenzophenone derivatives, ortho-hydroxyphenylbenzotriazole derivatives, salicylic esters, ortho-hydroxyphenyl-s-triazines or sterically hindered amines. These substances can be used alone or preferably as mixtures. The layer (s) reflecting applied IR (s) can be thermally cured, photochemically or electron beam. Curing must evidently be carried out in the cholesteric phase and with retention of the cholesteric phase. When two or more layers are applied, they can in each case be applied, dried - if desired - and individually cured. However, it is also possible to apply two or more layers or all of the layers to be applied in an application process, wet on wet, on the article to be coated, to carry out a joint drying if desired or to carry out a joint cure. A prerequisite for the simultaneous application of layers cholesteric, however, is that there is no interdifusión between the different layers that have a behavior of different reflection. Casting techniques are especially suitable for the simultaneous application of cholesteric layers, especially knife or bar emptying techniques, cast film extrusion or pour-out techniques, and the cascading process. These emptying techniques are described, for example, in DE-A-19 504 930, EP-A-431 630, DE-A-3 733 031 and EP-A-452 959, which are expressly incorporated herein by reference . The present invention further provides a multi-component coating system comprising components capable of forming cholesteric layers having mutually different reflection maxima in the range of wavelengths greater than 750 nm. Through a coating system of this type the invention, whose components can be used, for example as coating formulations, it is possible to offer any desired thermal insulation coating of the invention to any desired substrate. The thermal insulation coating of the present invention is particularly suitable for producing insulated windows or transparent thermal insulation building materials or for insulating buildings residential, office or industrial against thermal radiation. In addition, the thermal insulation coating of the present invention is also particularly suitable for use in the automotive sector, especially for the production of thermally insulated laminated glass displays. Their use for these purposes is also provided by the present invention. The following examples illustrate the invention without limiting it. Examples 1 to 3 used a nematic liquid-crystalline mixture of formula 1 which is present up to 5 ° C in the smectic phase, up to 68 ° C in the nematic phase and above 68 ° C in the isotropic phase (S 5 N 68 I). The chiral impurity used in examples 1 and 2 was the compound of formula 2 and in example 3 the compound of formula 5. Cellulose acetobutyrate was added in a concentration of 0.8% by weight based on the cholesteric mixture at the mixtures used in examples 1 to 3 in order to improve the formation of layers and the overall mixture was dissolved in butyl acetate. 2,4,6-Trimethylbenzoyldiphenylphosphine oxide was added as a photoinitiator at a concentration of 1.5% by weight, based on the cholesteric mixture. This mixture was applied with a spatula in a wet film thickness of 30 μm on a glass plate. In all three examples, a transparent layer was formed homogeneous in each case after evaporation of the solvent. This layer was photochemically crosslinked using a UV light source. Example 1: Five cholesteric layers were individually applied and cured according to what was described above. The compositions of the cholesteric layers showed differences in terms of the concentration of the ingredients, as shown in the following table 1: Layer xCh xn lambdaR 1 0.032 0.968 220 2 0.027 0.973 943 3 0.024 0.976 1085 4 0.021 0.979 1250 5 0.018 0.982 1440 In addition, all layers contained cellulose acetobutyrate and 2,4,6-trimethylbenzoyldiphenylphosphine oxide in the amounts indicated above. The concentration of the chiral component is abbreviated as Ch and is indicated as a mole fraction. The concentration of the nematic component is abbreviated as xn and is indicated in the same way as a mole fraction. LambdaR indicates the wavelength of the reflection maximum in nm. The layers applied one on top of the other provided a reflection of 47% of the incident light in the range of wavelengths between 752 and 1500 nm. The transparency in the visible wavelength range (between 400 and 700 nm) was greater than 95%. Example 2: Example 2 was carried out using the mixture present in layer 1 of example 1. As indicated above, this mixture is applied on two glass plates with a spatula that applies a wet film thickness of 30 μm, the solvent was removed, and the resulting transparent film was photochemically cured through a UV light source (Nitraphot lamp from OSRAM). A lambda / 2 (Nitto) film was then placed between the glass plates coated in such a way that the liquid-crystalline layers were in contact with the lambda / 2 film. The optical behavior of this arrangement was examined spectroscopically. It was found that the coating comprising the lambda / 2 film had a reflection degree of 89% in the wavelength range of 752 to 800 nm and a transmission in the visible wavelength range of more than 93%. Example 3: Using a doctor's blade, two layers were applied individually one on top of the other in succession with a wet film thickness of 30 μm in each case, the solvent was removed and the resulting film having a thickness of approximately 16 um and It is transparent in the range of light visible was photochemically cured with the light source indicated above. The two layers placed one on the other were identical in terms of their material composition; both contained 13 molar parts of cholesteric by 87 molar parts of the nematic compound as well as cellulose acetobutyrate and 2,4,6-trimethylbenzoyldiphenylphosphine oxide in the amounts indicated above. The wavelength of the reflection maximum for both layers was 820 nm. The layers presented differences, however, as to their meaning; the helical structure of one layer was to the right, the helical structure of the other layer was to the left. Spectroscopic investigations showed a selective reflection of 941 at a wavelength of 820 nm. The mean peak width of the reflection was 121 nm. The transmission in the visible wavelength range was greater than 93%.

Claims

CLAIMS A thermal insulation coating comprising one or more non-micellar cholesteric layers and a reflection of at least 40%, particularly at least 45%, of the incident radiation in the wavelength range of infrared light above 750 nm and, particularly, in the wavelength range from 751 nm to approximately 2000 nm. A thermal insulation coating according to claim 1, which transmits at least 80%, particularly at least 90% of the incident radiation in the wavelength range from about 390 nm to 750 nm. A thermal insulation coating according to any of the preceding claims, comprising two or more, preferably from about 2 to 20 and, particularly, from about 2 to 10 cholesteric layers of infrared radiation reflection. A thermal insulation coating according to claim 3, whose cholesteric layers have mutually different reflection maximums in the wavelength range greater than 750 nm. A thermal insulation coating according to any of the preceding claims, comprising two or more cholesteric layers, preferably a number of cholesteric layers that can be divided by 2, the pitch of the helical superstructures of 2 layers in each case is identical but their direction is different. A thermal insulation coating according to any of the preceding claims, which, between layers having a helical superstructure of identical pitch and of identical direction, has a means that reverses the direction of rotation of the circularly polarized light transmitted, especially as it is known as a film or lambda / 2 plate. A thermal insulation coating according to claim 6, which reflects at least 75%, particularly at least 85% of the incident radiation in the wavelength range greater than 750 nm, particularly in the wavelength range from 751 nm to about 2000 nm. A thermal insulation coating according to any of the preceding claims, which, in the cured state, comprises cholesteric compounds or mixtures of compounds selected from a) at least one polymerizable cholesteric monomer; b) at least one achiral, nematic, polymerizable monomer and a chiral compound; c) at least one crosslinkable cholesteric polymer; d) at least one cholesteric polymer in a diluent polymerizable or a mixture of polymerizable diluents; e) at least one cholesteric polymer whose cholesteric phase can be frozen by rapid cooling below the glass transition temperature; or f) at least one achiral liquid-crystalline crosslinkable polymer and a chiral compound. 9. A process for the production of a thermal insulation coating according to claim 1, comprising the application on a transparent substrate of at least one cholesteric layer of infrared radiation reflection, its curing, and the application, if desired, of one or more cholesteric layers of infrared radiation reflection and, if desired, a medium that reverses the direction of rotation of the circularly polarized light transmitted, curing said layer (s) and thus completing the thermal insulation coating. 10. A multi-component coating system comprising components capable of forming cholesteric layers according to the definition in any of claims 4 to 8. 1. The use of a thermal insulation coating according to any of claims 1 to 8 to produce insulating windows or transparent building materials for thermal insulation or to isolate residential, office or industrial buildings. 12. The use of a thermal insulation coating as claimed in any of claims 1 to 8 in the automotive sector, especially for producing laminated glass sheets of thermal insulation. 13. A film, particularly an adhesive film, comprising a thermal insulation coating according to claim 1 of any of claims 1 to 8.