DE2343979A1 - PROCESS FOR MANUFACTURING CARBONS, PREFERABLY CARBON FOAMS - Google Patents

Description

Bayer Aktiengesellschaft

Central area of patents, trademarks and licenses

509 Leverkusen, Bayerwerk

GM / Rä

3 Aug. 0, 1973

Process for the production of carbons, preferably carbon foams.

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

One starts from polyurethane foams, it is necessary to foam at relatively low temperatures (about 150-300 ⁰ C) to anneal and to be subjected to oxidation treatment in order to prevent melting of the foam. Such lengthy procedures are described, for example, in 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 process for producing a carbon foam in which, in addition to a polyester group having carbon-containing polyurethane foam

Le A 15 212 - 1 -

509816/0387

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 carbodiimide groups used as starting material according to the invention Foams dissolved, with which particularly short carbonization times can be achieved.

The present invention relates to carbons, preferably Carbon foams, obtainable from foams containing carbodiimide groups.

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

According to the invention is preferably a method in which the foam having carbodiimide in an inert atmosphere, a temperature 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 up to 10 hours at temperatures between 600 and 3000 ⁰ C is used.

_{An argon, helium, nitrogen or CO 2} atmosphere, for example, can be used as the inert atmosphere.

Le A 15 212 - 2 -

503816/0387

The polycarbodiimide foams to be used as starting material according to the invention are known per se and can e.g., according to the teaching of American patents 2,941,966 and 2,941,983. Preferred However, such polycarbodiimide foams are used as starting material, as they are in the German Offenlegungsschrift 2 245 634 can be described. The polycarbodiimide foams that can be produced according to the teaching of this laid-open specification are produced in the presence of addition compounds, which are composed of the following components exist:

a) phospholine oxides, phospholine sulfides, phospholane oxides or phospholane sulfides and

b) Mono-, di- and / or polyalcohols with a molecular weight of 32 to 250 or protic acids, which are n / 10 aqueous Solution have a pH value between 1 and 8, or metal salts or acid chlorides.

According to this patent application, these addition compounds come in concentrations generally from 0.1 to 20, preferably from 0.5 to 10% by weight of component a), based on on the amount of isocyanate used.

Representative phospholines as component a) of the addition compounds are e.g. 1-phenyl phospholine, 3-methyl-1-

phenyl phospholine, 1-ethyl -— phospholine, 3-methyl-1-

phenyl-1-oxo-phospholine, 1-methyl-i-oxo-phospholine, 1-butyl-1-oxo-phospholine-, 1-methoxy-i-oxo-phospholine, 1-hydroxy-1-oxo-phospholine.

As component b) of the addition compounds are possible: monomeric alcohols, bi- and polyfunctional glycols, organic acids, which have a pH value in n / 10 aqueous solution have between 1 and 8 and inorganic and organic salts. Representative alcohols are e.g. methanol, ethanol, Butanol, isopropanol. Bi-, tri- and polyfunctional glycols are: ethylene glycol, di-, triethylene glycol,

Le A 15 212 - 3 -

509816/0387

Propanediol, butanediol, glycerine, trimethylolpropane, hexadiol, Hexanetriol.

Possible organic acids are, for example, formic acid, Acetic acid, propionic acid, butyric acid, mono-, di-, trichloroacetic acid, oxalic acid, fumaric acid, maleic acid and as inorganic Acids are e.g. chlorine, bromine, iodine hydrogen, ortho-phosphoric acid, boric acid. As organic and inorganic salts are, for example: sodium oxalate, potassium acetate, potassium formate, zinc chloride, Mg chloride, calcium chloride, tin chloride, phosphorus trichloride, phosphorus oxitrichloride, phosphorus pentachloride, titanium (IV) chloride, Aluminum trichloride, antimonium pentachloride.

Addition compounds are preferred

a) 1-phenyl-phospholine, 3-methyl-1-phenyl-phospholine,

1-ethyl-phospholine, 3-methyl-1-phenyl-1-oxo-phospholine, 1-methyl-1-oxo-phospholine, 1-butyl-1-oxo-phospholine, 1-methoxy-1-oxo-phospholine, 1-hydroxy-1-oxo-phospholine

b) mono-, di- or polyalcohols with a molecular weight of 32 to 250 or mono-, di- or polycarboxylic acids with a molecular weight of 46 to 250 or metal salts or acid halides or inorganic acids.

Addition compounds are particularly preferred

a) 1-methyl-1-oxo-phospholine

b) glycerine or ethylene glycol or formic acid or oxalic acid or phosphorus trichloride or phosphorus oxychloride or HCl or zinc chloride or aluminum trichloride, which are the most suitable for 1-methyl-1-oxo-phospholine Represent addition partners.

To prepare the addition compounds, component a) and component b) are mixed in a molar ratio from 1:20 to 20: 1, preferably 1: 5 to 5: 1, particularly

Le A 15 212 - 4 -

50981 6/0387

preferably 1: 2 to 3: 1.

The catalysts in the laid-open specification continue to be used as catalysts 2 102 603 mentioned catalysts.

According to this document, a mixture of 2,4,6-tris (dialkanolamino) -s-triazine and 1,3JS-TrIs- (NjN ¹ -dialkylaminoalkyl) hexahydrotriazine in amounts of 0.1-10%, based on the isocyanate , be used.

In the case of the amines to be used, all known per se are suitable. There will be primary and / or secondary aliphatic and aromatic amines with 1 to 5 primary and / or secondary amino groups are preferred. Hydrazine, ammonia or aqueous ammonia solutions can also be used. Ammonia and primary amines are preferred. As aliphatic Amines are for example:

Methyl, ethyl, propyl, butyl, dimethyl, diethyl, dipropyl, Dibutylamine; 1,2-diaminoethane, N, N'-bis (2-aminoethyl) ethylenediamine, 1,11-diamino-3 j 6,9-triaza-undecane, 1,14-diamino-3,3,9,12-tetra-aza-tetra-decane, piperazine, 1,2-diaminopropane, 1,4-diamino-butane, 1,6-diamino-hexane, N, N'-Dimethy1-1,2-diaminoethane, 3-amino-1-methylaminopropane, 2-amino-ethanol, methyl- (2-amino-ethyl) -ether, benzylamine, cyclohexylamine, 1,4-diaminocyclohexane.

The following aromatic amines may be mentioned: aniline, 2-chloroaniline, 2,4-dichloroaniline, m-toluidine, p-toluidine, p-phenylenediamine, 2,4-aminotoluene, 2,6-aminotoluene, 4j4 ^f -diaminodiphenylmethane, crude condensation products of Aniline and formaldehyde, anthranilic acid isopropyl ester, dianthranilic acid triethylene glycol ester, N-methylaniline.

Le A 15 212 - 5 -

509816/0387

As starting components for the production of polycarbodiimide foams come

aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates into consideration, as z., B. from ¥. Siefgen in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, are described, for example ethylene diisocyanate, 1 ^ -tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate and any mixtures of these isomers, i-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (DAS 1 202 785), 2,4- and 2,6- Hexahydrotolylene diisocyanate and any mixtures of these isomers, hexahydro-1,3- and / or -A , 4-phenylene diisocyanate, perhydro-2,4'- and / or -4,4'-diphenylmethane diisocyanate, 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, for example, in British patents 874 430 and 848 671 be perchlorinated aryl polyisocyanates, as described, for example, in German Auslegeschrift 1,157, polyisocyanates containing carbodiimide groups, as described in German Patent 1,092,007, and diisocyanates, as described in American Patent 3,492,330, containing allophanate groups Polyisocyanates, as described, for example, in British patent specification 994 890, Belgian patent specification 761 626 and the published Dutch patent application 7 102 524, polyisocyanates containing isocyanurate groups, as described, for example, in German patents 1,022,789, 1,222,067 and 1,027,394 and in German Offenlegungsschriften 1,929,034 and 2,004,048, polyisocyanates containing urethane groups, as described, for example, in Belgian patent specification 752 261 or in American patent specification 3,394,164, polyisocyanates containing acylated urea groups according to German P atentschrift 1 230 778, Le A 15 212 - 6 - showing biuret groups

509816/0387

Polyisocyanates, such as those in the German patent specification 1 101 394, in British patent specification 889 050 and in French patent specification 7 017 514, Polyisocyanates produced by telomerization reactions, such as those described in Belgian patent specification 723 640 are, ester group-containing polyisocyanates, such as those in British Patents 965,474 and 1,072,956, in the American patent 3,567,763 and in the German patent 1,231,688, reaction products are mentioned of the above-mentioned isocyanates with acetals according to German Patent 1,072,385.

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

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 as a rule subsequent phosgenation are produced ("crude MDI") and carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or polyisocyanates containing biuret groups ("modified polyisocyanates").

Ie A 15 212 - 7 -

S09816 / 0387

In the production of the polycarbodiimide foams, starting components which may also be used are compounds with at least two isocyanate- reactive hydrogen atoms and generally from 62-10,000 molecular weight. In addition to amino groups, thiol groups or carboxyl groups, these are preferably polyhydroxy compounds, in particular two to eight hydroxyl groups, specifically those of molecular weight from 400 to 10,000, preferably 1000 to 6000, for example at least two, usually 2 to 8, but preferably 2 to 4, hydroxyl groups polyesters, polyethers, polythioethers, polyacetals, polycarbonates, polyesteramides as they are known per se for the production of homogeneous and cellular polyurethanes.

The possible polyesters containing hydroxyl groups are, for example, reaction products of polyvalent, preferably dihydric and optionally additionally trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding Polycarboxylic acid esters of lower alcohols or mixtures thereof can be used to produce the polyesters. the Polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and, if appropriate, e.g. by halogen atoms, substituted and / or unsaturated. 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, endomethylenetetrahydrophthalic anhydride, Glutaric anhydride, maleic acid, maleic anhydride, frimaric acid, dimers and trimeric fatty acids such as oleic acid, optionally mixed with monomeric fatty acids, terephthalic acid dimethyl ester,

Le A 15 212 - 8 -

509816/0387

Terephthalic acid bis-glycol ester. As polyhydric alcohols come e.g. ethylene glycol, propylene glycol- (1,2) and - (1,3) » Butylene glycol- (1,4) and - (2,3), hexanediol- (1,6) ,. Octanediol (1,8), neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propanediol,

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

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 ,, 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), trimethylolpropane, 4,4'-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine, ethylenediamine. Sucrose polyethers, as described, for example, in German Auslegeschriften 1,176,358 and 1,064,938, are also suitable according to the invention. In many cases, those polyethers are preferred which predominantly (up to 90% by weight, based on all OH groups present in the polyether) have primary OH groups. Also through vinyl poly

Le A 15 212 - 9 -

509816/0387

merisate modified polyethers, such as those produced by the polymerization of styrene or 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.

Polythioethers include, in particular, the condensation products of thiodiglycol with itself and / or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols. Depending on the co-components, the products are polythio mixed ethers, polythioether esters, polythioether ester amides.

Suitable polyacetals are, for example, the compounds which can be prepared from glycols such as diethylene glycol, triethylene glycol, 4,4'-dioxethoxy-diphenyldimethylmethane, hexanediol and formaldehyde . Polyacetals suitable according to the invention can also be prepared by polymerizing cyclic acetals.

As hydroxyl-containing polycarbonates are those of the type known per se into consideration, for example, by reaction of diols such as propanediol- (1,3), Butandlol- (1,4) and / or hexanediol- (1,6), diethylene glycol, triethylene come , Tetraethylene glycol with diaryl carbonates, for example diphenyl carbonate or phosgene, can be produced.

The polyesteramides and polyamides include, for example, the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, diamines, polyamines and their mixtures.

Le A 15 212 -10-

509816/0387

Polyhydroxy compounds already containing urethane or urea groups and optionally modified natural poly oils, such as castor oil, carbohydrates, starch, can also be used. Addition products of alkylene oxides with phenol-formaldehyde resins or else with urea-formaldehyde resins can also be used according to the invention.

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

Le A 15 212 - 11 -

5G98 16/0387

In the production of the carbodiimide foams, water and / or volatile organic substances can be used as Propellants are also used. Organic blowing agents include acetone, ethyl acetate, and halogen-substituted ones Alkanes such as methylene chloride, chloroform, ethylidene chloride, vinylidene chloride, Monofluorotrichloromethane, chlorodifluoromethane, dichlorodifluoromethane, also butane, hexane, heptane or diethyl ether are possible. A propellant effect can also be achieved by adding at temperatures above room temperature with the elimination of gases, for example nitrogen, decomposing compounds, e.g. azo compounds such as azoisobutyronitrile will. Further examples of propellants as well as details on the use of propellants can be found in the Kunststoff-Handbuch, Volume VII, edited by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 108 and 109, 453 to 455 and 507 to 510.

There can also be those known from polyurethane chemistry Catalysts are also used. Catalysts that can also be used are those of the

known type in question, for example tertiary amines, such as triethylamine, tributylamine, N-methyl-morpholine, N-ethyl-morpholine, N-cocomorpholine, N, N, N ¹ , N'-tetramethyl-ethylenediamine, 1,4-diaza -bicyclo- (2,2,2) -octane, N-methyl-N'-dimethylaminoethyl-piperazine, Ν, Ν-dimethylbenzylamine, BiS- (N, N-diethylaminoethyl) adipate, N, N-diethylbenzylamine, pentamethyldiethylenetriamine, Ν, Ν-dimethylcyclohexylamine, N, N, N ¹ , N ¹ -tetramethyl-1,3-butanediamine, Ν, Ν-dimethyl-ß-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.

Le A 15 212 - 12 -

50981S / 0387

Silaamines with carbon-silicon bonds are also used as catalysts, as described, for example, in German patent specification 1 229 290, in question, e.g. 2,2,4-trimethyl-2-silamorpholine, 1,3-diethylaminomethyl-tetramethyl-disiloxane.

In certain cases, such as the foaming of undistilled Phosgenation mixtures of toluenediamine can be advantageous if, in addition to the polycarbodiimide catalyst addition compounds polyisocyanurate catalysts can also be used.

Any type of catalyst which forms isocyanurate groups is suitable. Preferred catalysts are those which cause the isocyanate to gel with formation of isocyanurate at a temperature of 20 ° C. in 10 minutes when they are added in an amount of 1-10 g per 100 g of organic polyisocyanate. These conditions meet eg sodium, Natriumtrichlorphenolat, 2,4,6-tri (dimethylamino-methyl) phenol, a mixture of 80 $> ortho and 20% para-Dimethylaminomethy! Phenol, potassium acetate and N, N ', N " -Tris- (dimethylaminopropyl -) - s-hexahydrotriazine.

Nitrogen-containing bases such as tetraalkylammonium hydroxides and alkali metal hydroxides such as Sodium hydroxide or alkali metal alcoholates such as sodium methylate are suitable.

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

Ie A-15 212 - 13 -

509816/0387

Preferred organotin compounds, tin (II) salts of carboxylic acids come as tin (II) acetate _f tin (II) octoate, tin (II) ethyl hexoate and tin (II) laurate, and the dialkyltin salts of carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin maleate or dioctyl tin diacetate.

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

The catalysts are generally used in an amount between about 0.001 and 10% by weight, based on the amount of compounds with at least two isocyanate-reactive hydrogen atoms with a molecular weight of

62 to 10,000 are used.

Surface-active additives can also be used in the production of polycarbodiimide foam

(Emulsifiers and foam stabilizers) can also be used. The emulsifiers used are, for example, the sodium salts of castor oil sulfonates 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 dinaphthylmethanedisulphonic acid or from 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

Le A 15 212 - 14 -

509816/0387

connected is. Such foam stabilizers are described, for example, in US Pat . No. 2,764,565.

There can also be reaction retarders, for example acidic substances such as hydrochloric acid or organic acid halides, furthermore cell regulators of the type known per se such as paraffins or fatty alcohols or dimethylpolysiloxanes, and pigments or dyes and flame retardants of the type known per se, e.g. trischloroethyl phosphate or ammonium phosphate and polyphosphate , also stabilizers against aging and weathering, plasticizers and fungistatic and bacteriostatic substances, fillers such as barium sulfate, kieselguhr, soot or whiting chalk can also be used.

Fillers can also be introduced into the foam-forming reaction mixture. Suitable fillers include Graphite, aluminum oxide and fibrous materials such as polyacrylonitrile and carbon fibers.

Further examples of surface-active additives and foam stabilizers as well as cell regulators, reaction retarders, stabilizers, flame-retardant substances, plasticizers, dyes and fillers, as well as fungistatic and bacteriostatic substances and details about the use and mode of action of these additives are published in the Kunststoff-Handbuch, Volume VI by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, for example on pages 103 to 113.

Le A 15 212 - 15 -

509816/0387

The reaction components are to carbodiimide foam manufacture brought by the known one-shot process, the prepolymer process or the semi-prepolymer for reaction, wherein one often using mechanical devices such as described in United States Patent Specification 2,764,565 such. Details about processing devices that can also be considered according to the invention are described in the Kunststoff-Handbuch, Volume VI, published by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, for example on pages 121 to 205.

Details of the procedure used in accordance with the invention can be found in the examples. It also shows that an oxidative pretreatment has no influence on the properties of the end product. According to the invention Process are lightweight and non-friable carbon foams obtain.

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.

Le A 15 212 - 16 -

09816/0387

Examples: »/ ^ _%

Production of a foam containing carbodiimide groups. 100 g of polymeric 4,4 ^I -diphenylmethane diisocyanate (obtained by aniline-formaldehyde condensation and subsequent phosgenation) was mixed with 5 g of glycerol, 2.5 g of 1-methyl-1-oxophospholine and 0.5 g of a commercially available foam stabilizer of the type the polyether polysiloxanes were mixed intensively in a beaker for 15 seconds. The mixture was placed in a mold in which the mixture foamed. The compressed foam had a density of 46 kg / m 2.
Elemental analysis: C = 74 $>; H = 5.1 1 ° ', N = 10.6 $>.

Example 1:

The foam described above was heated at a heating rate of 250 ° C / hour to 600 ⁰ C. The residence time at 600 ^° C. was 60 minutes. It was then cooled at 250 ° C. per hour.

The pyrolysis was carried out under nitrogen. The initial dimensions of the foam were 18 χ 4 x 4 cm, the final dimensions 14 x 3.1 x 3.1; that corresponds to a volume shrinkage of $ 53, the weight loss was 45% . The material was not brittle. A carbon foam was obtained. Elemental analysis: C = 78 fo; H = 3.5%; N = 11.2%.

Example 2:

The procedure was as in Example 1, 1200 ⁰ C being selected as the final temperature. The residence time at 1200 ^° C. was 60 minutes.

The volume shrinkage was $ 67; the weight loss 55%.

Elemental analysis: C = 91%; H = 1 $; N = 2.0 fo.

A carbon foam was obtained.

le A 15 212 - 17 -

509816/0 387

Physical data: density 56 kg / m

Compressive strength 4.3 kp / cm

Tensile strength 1.1 kp / cm

Tensile modulus of elasticity 1000 kp / cm ²

Elongation at break 0.4 $

Example 3:

The carbonization was carried out as in Example 2, only the residence time was increased to 5 hours ^{at 1000 ° C.} Elemental analysis: C = 91 $>', H = 0.7 #; N = 1.7 #. A carbon foam was obtained.

Example 4:

The carbonization was carried out as in Example 2; Argon was used as the inert gas instead of nitrogen. The heating rate was 600 ^° C. per hour. The properties do not change. A carbon foam was obtained.

Example 5:

The procedure is analogous to Example 1. The carbonization was only carried out after a thermo-oxidative pretreatment. The foam sample was kept in an atmosphere of 2 parts nitrogen and 1 part oxygen at 300 ^° C. for 6 hours.

Hour was then at a heating rate of 250 ° C / heated to a final temperature of 1000 ⁰ C and held for 4 hours at this temperature.

The weight loss of the sample was 65% and the volume shrinkage was 58% . A carbon foam was obtained. No differences compared to the foams according to Example 3 could be seen in the mechanical properties.

Le A 15 212 - 18 -

509816/0387

Claims (3)

Patent claims: 1. Carbons, preferably carbon foams, available from foams containing carbodiimide groups. 2. Process for the production of carbons, preferably carbon foams, characterized in that a foam containing carbodiimide groups is pyrolyzed in an inert atmosphere. 3. The method according to claim 2, characterized in that the foam containing carbodiimide groups in an inert atmosphere with a temperature increase of 100-2000 ⁰ C per hour and a residence time of 0.5 to 50 hours, preferably 0.5-10 hours, at temperatures between 600 and 300O ⁰ C is exposed. Ie A 15 212 / 509816/0387