DE2343980A1 - PROCESS FOR MANUFACTURING CARBONS, PREFERABLY CARBON FOAMS - Google Patents

Description

Bayer Aktiengesellschaft

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509 Leverkusen, Bayerwerk

GM / Rä

Process for the production of carbons, preferably carbon foams.

Process for the production of carbonized foams from synthetic resins such as phenolic resins, urethane resins are already known.

If you start with polyurethane foams, then it is necessary to temper the foam at relatively low temperatures (approx. 150 - 300 C) and an oxidation treatment subject to prevent the foam from melting. Such lengthy working methods are e.g. in the US Pat. No. 3,302,999 or in the Journal of Cellular Plastics, 1971, pages 294 ff.

Another disadvantage is the high weight loss that results from the carbonization of polyurethane foams. For example, US Pat. No. 3,302,999 mentions a weight loss of $ 70-80 .

This high weight loss can be reduced by adding fillers. For example, U.S. Patent 3 387 940 describes a method for producing a carbon foam in which, in addition to a Polyurethane foam containing carbon

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Materials such as carbon black, graphite, etc. are added. However, because of the relatively high density of the Additives no light foams.

In addition, as can be seen from DT-OS 1 911 498, synthetic Only a small number of carbons produced by carbonizing polymeric graphite dispersions Mechanic solidity.

The present invention is based on the object of reducing the disadvantages of the known methods described above. This object is achieved with the isocyanurate groups used as starting material according to the invention Foams dissolved, with which particularly short carbonation times can be achieved.

The present invention relates to carbons, preferably Carbon foam, obtainable from isocyanurate groups having foams.

The invention also relates to a process for the production of carbons, preferably carbon foam s, characterized in that a polyisocyanurate foam is pyrolyzed in an inert atmosphere.

According to the invention preferably a method, wherein the isocyanurate-containing foam in an inert atmosphere to a temperature door increase of 100-2000 ⁰ C per hour, preferably from 100 to 1000 ⁰ C per hour and a residence time of 0.5 to 50 hours, preferably 0, 5 to 10 hours, bPi temperatures between 600 ⁰ C and 3,000 ⁰ C is exposed.

For example, a nitrogen, argon, helium, neon or CO ₂ atmosphere can be used as the inert atmosphere.

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The polyisocyanurate foams to be used as starting material according to the invention are known per se and can, for example, according to the teaching of German patent specification 1 112 285 or the German Offenlegungsschrift 1 694 214, 1 769 002, 1 595 844, 1 720 953.

A typical way of working is e.g. in the German patent application P 23 01 408.6. Then work as follows:

Aromatic polyisocyanates are made in the presence of an isocyanurate polymerization catalyst and a propellant and optionally a polyhydroxy compound and an aromatic compound Amine implemented.

The aromatic polyisocyanates known per se can be used as starting components, as described, for example, by W. Siefgen in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, for example 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6 -tolylene diisocyanate and any mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4 ', 4 "triisocyanate, polyphenyl-polymethylene polyisocyanates, as obtained by aniline-formaldehyde condensation and subsequent phosgenation and described, for example, in British patents 874 430 and 848 671, perchlorinated aryl polyisocyanates, as described, for example, in German Auslegeschrift 1,157 Polyisocyanates containing carbodiimide groups, as described in German Patent 1,092,007 .

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It is also possible to use the isocyanate group-containing distillation residues obtained in the technical production of isocyanates, optionally dissolved in one or more of the aforementioned polyisocyanates to be used. It is also possible to use any desired mixtures of the aforementioned polyisocyanates to use.

The technically easily accessible polyisocyanates, for example 2,4- and 2,6-tolylene diisocyanate and any mixtures of these isomers ("TDI"), polyphenyl-polymethylene polyisocyanates, such as those produced by aniline-formaldehyde condensation and are particularly preferred subsequent phosgenation are produced ("crude MDI"), and aromatic polyisocyanates containing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"). Monoisocyanates such as phenyl or naphthyl isocyanate can also be used (up to about .50 mol .- ^).

Aromatic amines are also used in isocyanurate foam production. This is in particular to diamines and polyamines of the type known per se, although in principle the use of monoamines is not excluded. The aromatic amines to be used must have primary and / or secondary "amino groups. They generally have a molecular weight of 93 to 5000, preferably from 150 to 1200, and are used in amounts of 0.2 to 20, preferably 0.5 to 10 parts by weight, based on the Polyisocyanate, also used. As examples of such Amines are mentioned in detail:

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3,5-diamino-benzoic acid-isobutyl ester, 3,5-diaminobenzoic acid-2-ethylhexyl ester, 4-methyl-3,5-diaminobenzoic acid isobutyl ester, 4-methyl-3,5-diamino-benzoic acid-2-ethylhexyl ester, 4- Chloro-3,5-diamino-benzoic acid-isobutyl ester, 4-chloro-3,5-diamino-benzoic acid-2-ethylhexyl ester, 2,4-diamino-benzoic acid-propyl ester, 2,4-diamino-benzoic acid-stearyl ester, 4-aminoanthranilic acid isobutyl ester, 5-amino anthranilic acid 2-ethylhexyl ester, 4.4 ^! -Diamino-diphenylmethane-3,3'-dicarboxylic acid diethyl ester, 4,4'-diamino-diphenylmethane-dicarboxylic acid diisobutyl ester, 4,4'-diamino-diphenylmethane-3-carboxylic acid ethyl ester, 4,4'-Diamin.o-3,3 ', 5,5'-tetraisopropyldiphenylmethane, 4,4'-di-ß-hydroxylamino-diphenylmethane, 2,4-diamino-3,5-diethyl toluene, diethylene glycol dianthranilic acid ester, tetraethylene glycol diantrhanilic acid ester, octoethylene glycol dianthranilic acid ester, octoethylene glycol dianthranilic acid ester, Methyl diethanolamine dianthranilic acid ester, triethanolamine trianthranilic acid ester.

The amines described in German Offenlegungsschrift 2,019,432, 2,040,644, 2,040,650 are also possible, as well as the aromatic amines listed in the journal "Die Angewandte Makromolekulare Chemie (26) 1972, 29 - 45", which are diamines from the series of diaminobenzoic acid and anthranilic acid containing ester groups acts. In addition, there are mixed condensates, such as those produced by joint condensation of various anthranilic acid esters with Formaldehyde or optionally reaction of anthranil esters with aniline, o-chloroaniline, toluidine, N-ethylaniline, 2,6-dialkylanilines or ß-hydroxyethylaniline with formaldehyde are formed, particularly suitable. In addition, there are also specially ring-alkylated diamines of the 2,4-toluenediamine type and reaction products of toluenediamine with ethylene oxide and / or propylene oxide to be used as aromatic diamines for the purposes of the invention. It is preferred that those to be used according to the invention Amines completely soluble in the polyhydroxy compound are.

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Starting components to be used for the production of isocyanurate foam are also compounds with at least two hydroxyl groups, preferably of a molecular weight of 62 to 10,000. This means in particular Compounds containing two to eight hydroxyl groups, especially those with a molecular weight of 400 to 10,000, preferably 1,000 to 6,000, for example at least two, usually 2 to 8, but preferably 2 to 4, Polyesters, polyethers, polythioethers, polyacetals, polycarbonates, polyesteramides, such as those containing hydroxyl groups for the production of homogeneous and cellular Polyurethanes are known per se.

The possible polyesters containing hydroxyl groups are, for example, reaction products of polyhydric, preferably dihydric and optionally additionally trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof to produce the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and optionally substituted and / or unsaturated, for example by halogen atoms. Examples include: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, tetrachlorophthalic anhydride, a mixture of trimachlorophthalic anhydride, a mixture of tri-chlorophthalic anhydride, a mixture of oleic, maleic anhydride, and with monomeric fatty acids, terephthalic acid dimethyl ester,

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Terephthalic acid bia-glycol ester. Suitable polyhydric alcohols such as ethylene glycol, propylene glycol- (1,2) and - (1 _f 3) »~ butylene glycol (1,4) and - (2,3), hexanediol- (1, 6), octanediol- (1, 8), neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethyicyclohexane), 2-MeUJyI-1, 3-propanediol,

Glycerol, trimethyloipropane, hexanetriol (1,2,6), butanetriol (i, 2,4), trimethylolethane, pentaerythritol, quinite, mannitol and sorbitol, methyl glycoside, also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol and polybutylene glycols in question. The polyesters can have a proportion of terminal carboxyl groups. Polyesters made from lactones, for example 1-caprolactone or hydroxycarboxylic acids, for example ω-hydroxycaproic acid, can also be used.

The polyhydric alcohols mentioned here can also themselves be used as polyhydroxy compounds.

Also, the candidate, at least two, generally two to eight, preferably two to three, hydroxyl-containing polyethers are those of the type known per se and are, for example, by polymerizing epoxides such as ethylene oxide, propylene oxide, butylene oxide, tetra hydrofuran, styrene oxide or Epichlorohydrin with itself, e.g. in the presence of BF ₅ , or by adding these epoxides, optionally mixed or in succession, to starting components with reactive hydrogen atoms such as alcohols or amines, e.g. water, ethylene glycol, propylene glycol- (1,3) or - (1 , 2), Trlmethylolpropane, 4,4 ^f -dihydroxydiphenylpropane, aniline, ammonia, ethanolamine, ethylenediamine produced. Sucrose polyethers, as described, for example, in German Auslegeschriften 1,176,358 and 1,064,938, are also suitable according to the invention. Often those polyethers are preferred which predominantly (up to 90 wt .- ^, based on all OH groups present in the polyether) have primary OH groups. Also through vinyl poly

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merisate modified polyethers, such as those obtained by polymerization of styrene, acrylonitrile in the presence of polyethers (American patents 3,383,351 » 3,304,273, 3,523,093, 3,110,695, German patent specification 1,152,536) are also suitable, as are OH groups comprising polybutadienes.

Among the polythioethers are in particular the condensation products of thiodiglycol with themselves and / or with others Glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols are listed. Depending on the co-components acts the products are polythio mixed ethers, polythio ether esters, Polythioether ester amides.

As polyacetals come e.g. those from glycols, such as diethylene glycol, Triethylene glycol, 4,4'-dioxethoxy-diphenyldimethylmethane, Hexanediol and formaldehyde preparable compounds in question. Also let through the polymerization of cyclic acetals According to the invention, suitable polyacetals can be prepared.

Polycarbonates containing hydroxyl groups are those of the type known per se, which are produced, for example, by reacting Diols such as propanediol (1,3), butanediol (1,4) and / or hexanediol (1.6), diethylene glycol, triethylene glycol, tetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate or Phosgene, can be produced.

The polyester amides and polyamides include, for example, those made of polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, Predominantly linear condensates obtained from diamines, polyamines and their mixtures.

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It is also possible to use polyhydroxy compounds already containing urethane or urea groups and, if appropriate, modified natural poly oils, such as castor oil, carbohydrates, starch. Addition products of alkylene oxides with phenol-formaldehyde resins or with urea-formaldehyde resins can also be used.

The amount of polyhydroxy compounds will generally be adjusted so that a sufficient amount of free isocyanate groups is still available for the polymerization reaction. Preferably, however, the amount such that at least 50%, preferably over 70 fo _f of the total amount of isocyanate used for the polymerization reaction are available.

Representatives of these compounds to be used are, for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", written by Saunders- Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and Selten 44 - 54 and Volume II, 1964, pages 5-6 and 198-199, and in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich, 1966, for example on pages 45 to 71, are described.

In the production of isocyanurate foam, water and / or volatile organic substances are also used as blowing agents. Examples of organic blowing agents are acetone, ethyl acetate, halogen-substituted alkanes such as methylene chloride, ^ chloroform, ethylidene chloride, vinylidene chloride, monofluorotrichloromethane, chlorodifluoromethane, dichlorodifluoromethane, and also butane, hexane, heptane or diethyl ether. A propellant effect can also be achieved by adding compounds which decompose at temperatures above room temperature with the elimination of gases, for example nitrogen, for example azo compounds such as azoisobutyronitrile. Further examples of propellants and details on the use of propellants are given in Kunststoff-Le A 15 211 - 9 -

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Handbook, Volume VII, published by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 108 and 109, 453 to 455 and. 507 to 510.

Are used as catalysts in the polymerization reactions those compounds are used which initiate a polymerization reaction of the NGO group even at room temperature. Such compounds are for example in the French Patent 1 441 565, the Belgian patents 723 153 and 723 152.

Such catalysts are specifically mononuclear or polynuclear Mannich bases, optionally formed by alkyl, aryl, or Aralky! Radicals substituted condensable phenols, Oxo compounds and secondary amines, especially those where the oxo compounds are formaldehyde and the secondary Amine dimethylamine have been used. In general, according to IR spectroscopic analyzes, the foams depending on the conditions, in particular depending on the reaction temperature reached, more or less high proportions of carbodiimide structures, their proportion in the foams by using the for the production of Carbodiimides known catalysts, especially 3- to 5-valent organic phosphorus compounds, such as phospholines, Phospholine oxides, tertiary phosphines, (cyclic) esters, amides and ester amides of phosphorous and phosphoric acid, can be increased. Further details can be found, for example, in "Polyurethanes, Chemistry and Technology", Vol. I and II, Saunders-Frisch, Interscience Publishers, 1962 and 1964.

The amount of polymerization catalyst is essentially determined by the type (and, if appropriate, the basicity) of the catalyst determined, you can between 0.5 and 100 wt .-%, preferably between 1 and 25 wt .- ^ of Katäfcrsatorkomponente, based on the isocyanate component.

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In addition to the isocyanate polymerization catalysts, the catalysts known from polyurethane chemistry are also often used. Catalysts which can also be used are those of the type known per se, for example tertiary amines, such as triethylamine, tributylamine, N-methyl-morpholine, N-ethyl-morpholine, N-cocomorpholine, N, N, N ^f , N'-tetramethyl-ethylenediamine , 1,4-diaza-bicyclo- (2,2,2) -octane, N-methyl-N'-dimethylaminoethyl-piperazine, N, N-dimethylbenzylamine, BiS- (N, N-diethylaminoethyl) adipate, Ν, Ν-diethylbenzylamine, pentamethyldiethylenetriamine, Ν, Ν-dimethylcyclohexylamine, Ν, Ν, Ν ', Ν'-tetramethyl ~ 1,3-butanediamine, N, N-dimethyl-β-phenylethylamine, 1,2-dimethylimidazole, 2-methylimidazole.

Hydrogen atoms active towards isocyanate groups tertiary amines are e.g. triethanolamine, triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanolamine, N, N-dimethyl-ethanolamine, and their reaction products with alkylene oxides, such as propylene oxide and / or ethylene oxide.

Also suitable as catalysts are silaamines with carbon-silicon bonds, as described, for example, in German Patent 1,229,290, for example 2,2,4-trimethyl-2-silamorpholine, 1,3-diethylaminomethyl-tetramethyl-disiloxane .

Organic metal compounds, in particular organic tin compounds, can also be used as catalysts will.

The organic tin compounds are preferably tin (II) salts of carboxylic acids such as tin (II) acetate, tin (II) octoate, Tin (II) ethylhexoate and tin (II) laurate and the dialkyl tin salts of carboxylic acids, such as dibutyl tin acetate, dibutyl tin dilaurate, dibutyl tin maleate or dioctyl tin diacetate are possible.

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Further representatives of the catalysts to be used and details about the mode of operation of the catalysts are published in the Kunststoff-Handbuch, Volume VII by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 96 to 102.

These catalysts are usually in an amount between about 0.001 and 10 wt .- ^, based on the amount of compounds having at least two isocyanate-reactive hydrogen atoms of one molecular weight from 62 to 10,000.

Surface-active additives (emulsifiers and foam stabilizers) can also be used in isocyanurate foam production. can also be used.

The sodium salts of castor oil sulfonates, for example, are used as emulsifiers or of fatty acids or salts of fatty acids with amines such as oleic acid diethylamine or stearic acid diethanolamine in question. Also alkali or ammonium salts of Sulphonic acids such as from dodecylbenzenesulphonic acid or Dinaphthylmethanedisulfonic acid or of fatty acids such as Ricinoleic acid or polymeric fatty acids can also be used as surface-active additives.

Water-soluble polyether siloxanes are particularly suitable as foam stabilizers. These connections are in general constructed so that a copolymer of ethylene oxide and propylene oxide with a polydimethylsiloxane residue connected is. Such foam stabilizers are described, for example, in US Pat. No. 2,764,565.

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Reaction retarders can also be used, for example acidic substances such as hydrochloric acid or organic Acid halides, and also cell regulators of the type known per se, such as paraffins or fatty alcohols or dimethy / polysiloxanes as well as pigments or dyes and flame retardants of the type known per se, e.g. tris-chloroethyl phosphate or Ammonium phosphate and polyphosphate, as well as stabilizers against aging and weathering influences, plasticizers and Fungistatic and bacteriostatic substances, fillers such as barium sulfate, kieselguhr, soot or chalk can also be used.

Further examples of surface-active additives and foam stabilizers that may optionally be used with as well as cell regulators, reaction retarders, stabilizers, flame-retardant substances, plasticizers, Colorants and fillers as well as fungistatic and bacteriostatic substances as well as details on the use and the mode of action of these additives are in the Kunststoff-Handbuch, Volume VI, edited by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 103 to 113.

The reaction components are prepared according to the one-step process known per se, the prepolymer process or the semi-prepolymer process implemented, often using machines such as those described in the American patent specification 2,764,565. Details about processing devices that can also be considered according to the invention, are in the Kunststoff-Handbuch, Volume VI, edited by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. described on pages 121 to 205.

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According to the method of the invention are easy and not get friable carbon foams.

The density of the carbon foams is below 200 kg / m, preferably below 100 kg / m.

The carbon foams are used in a known manner, e.g. as thermally stable insulating materials or as supports for catalysts.

For example, carbon foams can be used for insulation at temperatures of up to 800 ^° C. with the exclusion of air. Other organic foams are already decomposed at these temperatures, while other inorganic materials usually have a higher bulk density.

The products according to the invention are not only foams, but also non-cellular products.

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Examples

Production of the polyisocyanurate foams

A) 100 parts of a prepolymer composed of 90 parts of crude 4,4'-diisocyanatodiphenylmethane (obtained by condensation of aniline and formaldehyde and subsequent phosgenation) and 10 parts of a polyether with an OH number of 250, which was made from trimethylolpropane and ethylene oxide, are mixed with 10 parts of trichlorofluoromethane mixed. The other component is a mixture of 12 parts of a Mannich base (manufactured by Condensation of 1 mole of nonylphenol, 1 mole of formaldehyde and 1 mole of dimethylamine), 2 parts of a foam stabilizer from Type of polyether-polysiloxane, 5 parts of trichlorofluoromethane and 1 part of 4-chloro-3,5-diamino-benzoic acid-2-ethyl-hexyl ester.

The two components are mixed intensively; the result is a foam with a density of 38 kg / m.

B) 100 parts of a crude 4> 4'-diisocyanate diphenylmethane (obtained by condensation of aniline and formaldehyde and subsequent phosgenation) are with a mixture of 0.5 Parts of potassium acetate in 1.5 g of diethylene glycol, 0.1 part of water, 15 parts of a polyester (made from 450 parts Trimethylolpropane, 1510 parts of adipic acid and 1670 parts of diethylene glycol) with an OH number of 350, 15 parts of trichlorofluoromethane and 1 part of a commercially available foam stabilizer based on a polyether-polysiloxane is stirred intensively.

The resulting foam has a density of 40 kg / m ^.

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Example 1 /(

The foam described under A) was ^{stored for 6 hours at 500 °} C. in an atmosphere composed of 2 parts of nitrogen and 1 part of oxygen. A mass and volume shrinkage of $ 23 > each occurred.

The mixture was then heated at a rate of 25O ° C / hour to 1000 ⁰ C and the foam stored for 4 hours at this temperature. This operation was carried out under a nitrogen atmosphere. A carbon foam is obtained. The mass loss (based on the original sample) was $ 75 and the volume shrinkage was $ 51. The density achieved was 20 kg / m 2, the compressive strength was 0.5 kp / cm and the open cell content was 95 #.

Example 2

With the exception of the thermo-oxidative pretreatment, the same procedure as in Example 1 was followed. A carbon foam is obtained. The mass loss was 65 #, the volume shrinkage was 47 #. The density was 20 kg / m.

Example 3

^{The foam described under B) was heated to 1000 °} C. in an argon atmosphere at a rate of 600 ^° C. / hour and stored at this temperature for 1 hour. Then it was cooled down again. A carbon foam is obtained.

The loss in mass was 63 #, the density 45 kg / m " ^5. The elemental analysis found 90 56 carbon, 1.5% hydrogen and 2 generally nitrogen.

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Claims (3)

234398Ü claims: "* 1. Carbons, preferably carbon foams, available from a foam containing isocyanurate groups. 2. A method for the production of carbons, preferably carbon foams, characterized in that a Isocyanurate-containing foam is pyrolyzed in an inert atmosphere. 3. The method according to claim 2, characterized in that the foam containing isocyanurate groups in an inert atmosphere, a temperature increase of 100 to 2000 ⁰ C per hour, preferably 100 to 1000 ⁰ C per hour and a residence time of 0.5 to 50 hours, preferably 0.5 to 10 hours, at temperatures between 600 and 3000 ⁰ C is exposed. A 15 211 - 17 - 509816/0388