RU2130516C1 - Method of manufacturing carbon fiber - Google Patents

Abstract

FIELD: artificial fibers. SUBSTANCE: invention relates to carbon fiber that can be applied as fillers in production of sports- and industrial-destination products from carbon plastics and as starting materials in production of aircraft brake systems, composite fillers, and also as heat-resistant, filtration and sorption-active materials in chemical industry, mechanical engineering, and aircraft industry. Textile-destination fibers from acrylonitrile copolymer, containing at least 93 wt % of acrylonitrile and also methacrylate and methyl sulfonate or sodium styrenesulfonate, are first oxidized at 235-260 C for 35-60 min with spindle draft 20-30% and then at 230-260 C for 85-140 min with spindle draft from -5 to 5%. Fibers are then carbonized under nitrogen atmosphere for 10 min at temperature from 350 to 1500 C in pulled state. Wet-formation polyacrylonitrile fiber can also be used. Tensile strength of fibers containing at least 94 wt % carbon is up to 210 kg/sq. mm with density 1.73-1.78 g/cu.cm. EFFECT: reduced cost and widened resource of raw materials. 2 cl, 4 ex

Description

 The present invention relates to the production of carbon fibers ("Carbon fibers", under the editorship of S. Simamura, Moscow, Mir, 1987, p. 27) from acrylonitrile copolymers.

 Carbon fiber can be used as a filler in the production of carbon fiber products for sports and industrial purposes, as a starting material in the manufacture of aircraft brake systems, as chopped and ground fillers of composite materials.

 The oxidized fiber obtained after thermal stabilization can be used as heat-resistant, heat-insulating, filtering, sorption-active materials in the chemical, engineering, aviation industries, as a raw material for the production of carbon / carbon composites and in other industries.

 Polyacrylonitrile fibers are divided into two main types: textile fibers and technical fibers (Polyacrylonitrile Fibers, Overview, NIITEKHIM, Moscow, 1984, p. 8). For the production of carbon fibers, polyacrylonitrile fibers of technical purpose, the so-called precursors, are used. In the manufacture of precursors, in order to accelerate the oxidation process, the composition of the copolymer is modified, the copolymer is further purified, and an oriented supramolecular structure of the fiber is obtained in order to improve the properties of the resulting carbon fibers. In addition, often before the process of thermal stabilization produce additional processing of the fiber.

 It is known to use fibers based on a homo- or acrylonitrile copolymer obtained by the wet spinning process (A.S. USSR N 1816819, D 01 F 9/22) from copolymers of acrylonitrile with carboxyl-containing vinyl compounds pretreated with aqueous solutions of metal salts and hydroxides (a .s. USSR, N 1816817, D 01 F 9/22), based on PAN containing stabilizers (dioxidiphenyl, diaphen NN) of thermo-oxidative degradation (a.s. USSR, N 1816821, D 01 F 9/22), based PAN and butadiene nitrile rubber (a.s. USSR, N 1821500, D 01 F 9/22), from a copolymer of acrylonitrile, meth lacrylate and itaconic acid (A.S. USSR, N 910008, D 01 F 9/22), from polyacrylic filaments, which are preliminarily subjected to gas thermal oxidation and treated with organosilicon liquid (A.S. USSR, N 1697462, D 01 F 9 / 22).

A known method of producing carbon fibers using as starting material polymer fibers from polyacrylonitrile, a copolymer of acrylonitrile with metal sulfonic acid or its salt, a copolymer of acrylonitrile with styrene sulfonic acid or its salt, a copolymer of acrylonitrile with acrylamide methyl propylene sulfonylate, acrylamidonitrile copolymer of copolyonetrionolitrile copolymer of copolyonitrile copolymer methyl acrylate and itaconic acid. The source fiber is heated in an oxidizing medium at 200-400 ^o C, providing the formation of a cyclic structure, then subjected to carbonization in nitrogen or argon at a temperature of more than 800 ^o C. In this case, in order to improve the source fiber is impregnated with ammonium sulfate, bromide or ammonium iodide (U.S. Patent No. 4,603,041 D 01 F 9/22).

 To obtain the above fibers, additional technological processes and equipment for their implementation are used. This is necessary to solve the problems associated with the dependence of the nature of the thermal decomposition of polyacrylonitrile fiber on the content of grafted monomers (Carbon fibers Ed. S. Simamura. -M .: Mir, 1987, p. 33) at a low rate of oxidative thermal stabilization of the fiber. All this is justified for high-strength carbon fibers. But at present, these carbon fibers are also used in the manufacture of sports and industrial products, in the production of aircraft brakes, where high mechanical indicators are not required. This overstates the cost of these carbon fiber products and reduces the raw material base.

 In addition, to date, there is no data in the patent literature on the production of polyacrylonitrile-based carbon fibers obtained by dry molding, since such fibers have a practically disordered supramolecular structure (Handbook of Composite Materials Edited by D. Lyubin. -M.: Mechanical Engineering , book 1, 1988, pp. 259-260).

The closest technical solution is a method for producing carbon fibers based on a copolymer of acrylonitrile (more than 90 wt.%), Methyl acrylate and sodium metallosulfonate, which consists in oxidizing the fiber in air and carbonizing in nitrogen at a temperature of 350 to 1500 ^o C under voltage (DD, 101648, CL 12 i 31/00, 12.11.73).

 This method has all the disadvantages inherent in the production of carbon fibers from textile fibers, the main of which is the low rate of thermal stabilization of the fiber, which inflates the cost of carbon fibers for use in these directions. According to this method, it is impossible to use fibers obtained by the method of "dry" molding.

 The goal is to obtain cheaper carbon fibers and expand the raw material base.

This goal is achieved by the fact that the production of carbon fibers is carried out by oxidizing textile fibers of a dry method of molding from a copolymer of acrylonitrile containing at least 93 wt.% Acrylonitrile, methyl acrylate and metal sulfonate or sodium styrene sulfonate, in air at first at a temperature of 235-260 ^o C in for 35-60 minutes with an extract of 20-30%, then at 230-260 ^o C for 85-40 minutes with an extract of 5 to + 5% and further carbonization under tension in a nitrogen medium at a temperature of 350 to 1500 ^o C within 10 minutes

 The invention is illustrated by the following examples.

 Example 1

A corrugated fiber in the form of a continuous tow of 53,000 tex from a dry bone-molded acrylonitrile copolymer with a cross section of dog bone containing at least 93 wt.% Acrylonitrile, methyl acrylate and metal sulfonate or sodium styrene sulfonate were pulled in a cold state to remove corrugation, then oxidized first at a temperature of 235 ^o C for 60 min with an extract of 30%, then at 235-250 ^o C for 140 min with an extract of 5%. The fiber thus obtained was carbonized under tension in nitrogen at a temperature of 350 to 1500 ^° C. for 10 minutes. The resulting fiber contained at least 94 wt.% Carbon, had a density of 1.73 g / cm ³ and had a tensile strength of 210 kgf / mm ² .

 Example 2

The fiber of Example 1 was pulled in a cold state to remove corrugations, then it was oxidized in air at first at a temperature of 250 ^° C for 50 minutes with a hood of 30%, then at 230-260 ^° for 120 minutes with a shrink of 5%. The fiber thus obtained was carbonized under tension in nitrogen at a temperature of 350 to 1500 ^° C. for 10 minutes. the resulting fiber contained at least 94 wt.% carbon, had a density of 1.73-1.78 g / cm ³ and had a tensile strength of 195 kgf / mm ² .

 Example 3

The fiber of Example 1 in the form of a continuous tow was pulled in a cold state to remove corrugations, then it was oxidized in air at first at a temperature of 260 ^° C for 35 minutes with a hood of 20%, then at 230-260 ^° C for 85 minutes. The oxidized fiber thus obtained had a density of 1.39 g / mm ³ , tensile strength 19.7 kgf / mm ² , elongation at elongation 18.1%.

 Example 4

The fiber obtained in paragraph 3 was carbonized under tension in a nitrogen atmosphere at a temperature of 350 to 1500 ^° C. for 10 minutes. The resulting fiber contained at least 94 wt. % carbon, had a density of 1.73-1.78 g / cm ³ and had a tensile strength of 205 kgf / mm ² .

 The data obtained show the possibility of producing carbon fibers with characteristics that meet the requirements for general-purpose carbon fibers not from a specialized precursor, but from a dry-formed textile polyacrylonitrile fiber containing acrylonitrile, methyl acrylate and metal sulfonate or sodium styrene sulfonate by appropriate temperature activation as a result of application special temperature-time regimes and hoods during thermal stabilization and carbonization, and the duration of the processes of thermal stabilization and carbonization is commensurate with the duration of thermal stabilization and carbonization upon receipt of carbon fibers from precursors (A.S. USSR, N 180744, D 01 F 9/22). The use of such an oxidation process and textile polyacrylonitrile fiber for the dry spinning process reduces the cost of carbon fibers based on PAN fibers and expands the raw material base for the production of carbon fibers.

Claims (2)

1. A method of producing carbon fibers by oxidizing textile fibers from an acrylonitrile copolymer in air and carbonizing in nitrogen at a temperature of 350 to 1500 ^° C. under tension, characterized in that the fibers from the copolymer containing at least 93 wt. % acrylonitrile, methyl acrylate and metal sulfonate or sodium styrene sulfonate, first at 235 - 260 ^o C for 35-60 minutes with a hood of 20-30%, then at 230 - 260 ^o C for 85-140 minutes with a hood from -5 to + 5%, and carbonization is carried out for 10 minutes  2. The method according to claim 1, characterized in that the fibers subjected to the dry spinning process are subjected to oxidation.