DE2718308A1 - Powdered glassy carbon prodn. - by pyrolysing a mixt. of a (meth)acrylamide! (co)polymer and a water soluble salt - Google Patents

Abstract

Powdered glassy carbon is made by pyrolysing non-ionic cationic or anionic (meth) acrylamide (co)polymers in admixture with water soluble salts at 40-1600 degrees C, opt. after pre-hardening teh resin. Process is simple to operate and gives powdered glassy carbon, which is normally difficult to obtain due to the hardness of the glassy carbon (microhardness 150-200 Vickers). The prods. are useful for the prodn. of ceramic bodies; as abrasives; as fillers in tyres to increase the skid resistance; and as fillers in polyacrylonitrile fibres or viscose fibres which on pyrolysis give carbon fibres with increased rigidity.

Description

Process for the production of powdery, glass

like carbon The invention relates to a method of production of powdered, vitreous carbon and the use of this material for Manufacture of ceramic moldings.

The production of vitreous carbon is described in Vitreous Carbon ", Chemie-Ing.-Techn. 42nd Volume, 1970, No. 9/10, pp. 659 to 669, and in GB-PS 1 o33 277 and in DT-OS 2 400 9o9. The manufacture of vitreous Carbon is very expensive and complicated. The production of powdered, vitreous carbon is not described. Vitreous carbon itself is very hard and has a microhardness of 150 to 200 Vickers, i.e. vitreous carbon can only be pulverized with some effort.

The object of the invention is to powdery, vitreous carbon in a simple way, and pulverizing this material as well is largely simplified.

The invention relates to a process for the production of powdery, vitreous carbon, which is characterized by the fact that it is nonionic, cationic or anionic acrylic acid amide, methacrylic acid amide polymers and / or copolymers the same in a mixture with water-soluble salts at temperatures between 400 to 16000C are pyrolyzed.

The process is preferably carried out in a non-oxidizing atmosphere, e.g. carried out under nitrogen, optionally under pressure.

In the process according to the invention, a mixture of acrylic acid amide, Methacrylic acid amide polymers and / or copolymers of the same with water-soluble ones Salts pyrolyzed, with 2 to 2ovo% of the water-soluble salts, based on the Amide polymer, can be used. As water-soluble salts are used in pyrolysis water-soluble salts of alkali and alkaline earth metals, aluminum, titanium, chromium, Manganese, iron, cobalt and / or nickel used, such as sodium chloride, Potassium chloride, lithium chloride, sodium sulfate, potassium sulfate, sodium or potassium phosphate, Aluminum chloride or aluminum sulfate, titanyl sulfate, chromium (III) chloride, chromium (III) sulfate, chrome alum, aluminum alum, manganese sulfate and manganese chloride, iron (II) - and iron (III) chloride and sulfate, cobalt and nickel chloride or

Sulfate.

In a mixture with the water-soluble salts according to the invention water soluble, nonionic, cationic or anionic Acrylic acid amide and / or methacrylic acid amide polymers and / or copolymers thereof are pyrolyzed. Suitable polymers are described in Houben-Weyl "Methods of Organic Chemistry ", 4th edition, 1961, Volume XIV / 1, Macromolecular Materials, Part 1, G.Thieme Verlag, Stuttgart, p. 1029, the DT-AS 1068 013; Polymethacrylic acid amide, in which about 5% Methacrylic acid were polymerized, according to DT-PS 697 481; the copolymer of methacrylic acid amide with at least 6% vinylpyrrolidone, according to the DT-PS 954 197; water-soluble copolymers of acrylic acid amide and methacrylic acid amide, which contain 6 to 95% acrylic acid amide and 94 to 5% methacrylic acid amide, accordingly DT-PS 964 902; Polymers corresponding to US Pat. No. 2,504,074 and US Pat. No. 2 486 191; substituted acrylic and methacrylic acid amides according to US Pat. No. 2,680 11o; N-methoxymethylacrylamide, corresponding to DT-AS 1 o35 363 etc. The invention Acrylic acid amide, methacrylic acid amide polymers and / or the copolymers used the same can also be mixed with other pulverulent polymers, such as Polyacrylonitrile powder, powdered phenol-formaldehyde resins, novolaks, etc. together Pyrolyzed with water-soluble salts at temperatures between 700 and 18000C will.

After pyrolysis, the water-soluble salts are mixed with water or leached from the vitreous carbon with dilute acids, and the resulting Glass-like, powdery carbon is possibly again after drying pulverized.

The pulverulent, vitreous carbon produced according to the invention Can be used as an abrasive, as a filler in tire treads to increase slip resistance of tires or used for the production of ceramic moldings will.

The pulverulent, vitreous carbon produced according to the invention has a grain size of less than 50 microns (.mu.m). For the manufacture of ceramic Shaped bodies is a powdery, vitreous carbon with a grain size of below 10 microns (/ µm) used. The powdery, Vitreous carbon can be used along with silicon carbide and glass-ceramic particles according to DT-OS 25 12 549 or according to DT-OS 24 49 662 together with silicon carbide, a boron-containing compound, 0.1 to 1% by weight powdery, vitreous carbon can be processed into a ceramic molded body. Of the Powdery, vitreous carbon according to the invention can also be used in sintered hard metals are used, which consist of 70 to 97% of a hard phase, and the at least 73% cubic tantalum nitride and possibly at least one more, likewise cubic carbide or nitride of the metals of groups IVA and VA of the periodic System of elements, as well as from 3 to 30% of a binding phase, the iron, Nickel, cobalt and optionally chromium molybdenum or tungsten, the Sintered carbide, for example, in accordance with DT-OS 24 39 924 or DT-OS 20 43 411 is made. With the vitreous carbon produced according to the invention With the smallest possible grain size, i.e. below lo microns, ceramic bodies can also be used for gas turbine jet engines are manufactured in accordance with DT-AS 22 56 326, all or part of the colloidal graphite used in the manufacture is replaced by the powdery vitreous carbon. Vitreous carbon molded bodies can be produced in accordance with DT-OS 24 oo 9o9 in that part of the phenol-formaldehyde and furan resins used for production and pyrolysis the pulverulent, vitreous carbon according to the invention are replaced, with the powdery, vitreous carbon with the resins before shaping and pyrolysis be thoroughly mixed. The use of powdered, vitreous carbon brings in the pyrolysis of the plastics mentioned or in the pyrolysis of ceramic Moldings have the advantage that the powdery, vitreous carbon gives the molding high hardness and no further shrinkage during pyrolysis is subject.

The pulverulent, vitreous carbon produced according to the invention very small grain size is also suitable as a filler for filling polyacrylonitrile fibers or viscous fibers prior to spinning these fibers, with pyrolysis too Carbon fibers from this material carbon fibers are made, the stiffness can be increased in this way, and that in pyrolysis, as opposed to not having glass-like carbon-filled material, are subject to less shrinkage.

The method according to the invention is carried out at temperatures between 400 carried out to 16000C, the nonionic, cationic or anionic acrylic acid amide, methacrylic acid amide polymers and / or copolymers the same in a mixture with the water-soluble salts hardened under nitrogen from 4000C can be, the pyrolysis temperature preferably following this hardening is increased to looo to 12000C. The curing of the amide polymers mentioned is optionally carried out under pressure.

Example 1 In an annealing furnace, a mixture of 21 g of a non-ionic, powdered acrylamide homopolymer with 2.8 g FeCl3.6H2O in a porcelain crucible cured for 8 hours at 4000C, during which a gentle stream of nitrogen flows through the annealing furnace.

Then the temperature in the annealing furnace is gradually increased by 50 ° C / 30 minutes to 900 ° C and the product is pyrolyzed at 900 ° C for 2 hours. After cooling, the pyrolyzed product is finely ground in a mortar and treated cold for 15 minutes with 2N hydrochloric acid and washed with water until the product is neutral. Then the product is dried in a drying cabinet at So0C and pulverized again.

Example 2 A porcelain crucible is made with 12 g of a commercially available cationic acrylamide polymer (copolymer of acrylamide and diallylamine), which has been thoroughly mixed with 5 g of potassium chloride and 2 g of chromium (III) chloride, filled, and pyrolyzed at 11000C in the annealing furnace for 35 minutes, whereby through the annealing furnace a weak stream of nitrogen is passed during the glow. After cooling down the pyrolyzed product is crushed in a mortar and treated with dilute hydrochloric acid leached for 10 minutes. It is then filtered off, with water until the reaction is neutral washed out, dried and then pulverized again.

Example 3 A mixture of 10 g of a powdery acrylic acid amide and methacrylic acid amide polymer, 12 g sodium sulfate and 5 g aluminum alum pyrolyzed in a porcelain crucible at 14000C for 15 minutes in an annealing furnace. After pulverization, the pyrolyzed product is heated to 80 ° C. for 15 minutes treated with warm water, filtered off, dried and then pulverized again.

Example 4 A mixture of lo g of an anionic acrylamide polymer, 5 g of powdered polyacrylonitrile and 3 g of potassium sulfate in a porcelain crucible are cured in the annealing furnace 0 for 45 minutes at 42o C and then pyrolyzed at 900 ° C. for 25 minutes. Then the mixture is pulverized, leached with 60 ° C warm water, dried and pulverized again.

Example 5 A mixture of 21 g of a nonionic, powdered acrylamide homopolymer with 2.8 g FeCl3.6H20 in a porcelain crucible pyrolyzed at 520 ° C. for 12 hours.

After cooling, the pyrolysed product is finely ground in a mortar and cold-treated for 30 minutes with 1N hydrochloric acid, and washed with water until until the product reacts neutrally. The product is then placed in a drying cabinet at 40 ° C dried and pulverized again.

Claims (5)

Claims method for the production of pulverulent, vitreous Carbon, noting that it is nonionic, cationic or anionic acrylic acid amide, methacrylic acid amide polymers and / or copolymers the same in a mixture with water-soluble salts at temperatures between 400 to 16000C, if necessary after the resins have been pre-hardened, pyrolyzed. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that the pyrolysis is carried out in a non-oxidizing atmosphere. 3. The method according to claim 1 and 2, characterized in that g e -k e n n z e i c h n e t that the mixture of acrylic acid amide, methacrylic acid amide polymer and / or Copolymers of the same with water-soluble salts that are subjected to pyrolysis is, contains 2 to 200% water-soluble salts, based on the amide polymer. 4. The method according to claim 1 to 3, characterized in that g e -k e n n z e i c h n e t that ah water-soluble salt in pyrolysis water-soluble salts of the alkali, Alkaline earth metals, aluminum, titanium, chromium, manganese, iron, cobalt and / or of nickel can be used. 5. Use of the powdery, vitreous produced according to claim 1 Carbon with a grain size of less than 50 microns for the manufacture of ceramic Moldings.