Continuous method for producing a thermally stabilized multifilament thread, multifilament thread, and fiber

Patent metadata

Field	Value
Publication number	US-11242623-B2
Application number	US-201716476739-A
Country	US
Kind code	B2
Filing date	Jan 10, 2017
Priority date	Jan 10, 2017
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

The invention relates to a method for thermally stabilizing melt-spun PAN precursors. For this purpose, the invention provides a continuous method for producing a thermally stabilized multifilament thread made of a meltable copolymer of polyacrylonitrile (PAN), wherein a pre-stabilized multifilament thread is thermally stabilized and in the process at least temporarily stretched. The invention additionally relates to a thermally stabilized multifilament thread which can be obtained according to a corresponding method and to a carbon fiber which is made of the correspondingly thermally stabilized multifilament thread.

First claim

The invention claimed is:

1. A continuous method for the production of a thermally stabilised multifilament yarn made of a meltable copolymer of polyacrylonitrile (PAN), in which
a prestabilised multifilament yarn or a non-prestabilised multifilament yarn is fed continuously,
in the case of a non-prestabilised multifilament yarn, a prestabilisation and subsequently a neutralisation are implemented, and subsequently
the prestabilised multifilament yarn is thermally stabilised at a temperature greater than 0° C., wherein the thermal stabilisation is implemented by feeding the multi-filament yarn through at least two ovens which are connected subsequently,
in at least a first oven, no stretching or stretching <10% and, in at least one further oven, stretching of at least 30% is effected,
in the at least a first oven, temperatures of 80 to 200° C. being set, and, in the at least one further oven, temperatures of 130 to 270° C. being set, and
stretching of the multifilament yarn is implemented, at least at times, during, before and/or after the thermal stabilisation.

2. The method according to claim 1 , wherein the strength of the thermally stabilised multifilament yarn standardised to the filament diameter is at least 50 MPa.

3. The method according to claim 1 , wherein the multifilament yarn is stretched by 10 to 300%.

4. The method according to claim 1 , wherein the thermal stabilisation is effected by feeding the multifilament yarn through at least one oven or at least two ovens connected subsequently.

5. The method according to claim 1 , wherein the thermal stabilisation is implemented in two stages, the multifilament yarn not being stretched or to a lower degree in the first stage than in the second stage and/or being stabilised, in the first stage, at lower temperatures on average than in the second stage.

6. The method according to claim 1 , wherein the thermal stabilisation is implemented with rising or constant temperatures in the feeding direction of the multifilament yarn.

7. The method according to claim 1 , wherein the thermal stabilisation is implemented such that a stabilisation degree (DOS) of the copolymer of polyacrylonitrile of 20 to 75% results.

8. The method according to claim 1 , wherein the thermal stabilisation is implemented in an oxidising atmosphere.

9. The method according to claim 1 , wherein the thermal stabilisation is effected with application of tensile stress to the multifilament.

10. The method according to claim 1 , wherein the thermal stabilisation is implemented over a period of 10 to 180 min.

11. The method according to claim 1 , wherein the copolymer of polyacrylonitrile (PAN) is produced by copolymerisation of 99.9 to 70% by mol of acrylonitrile with at least one comonomer selected from
a) 0.1 to 20% by mol of at least one alkoxyalkylacrylate of the general formula I,

with R=C n H 2n+1 and n=1-8 and m=1-8,

b) 0 to 10% by mol of at least one alkylacrylate of the general formula II

with R′=C n H 2n+1 and n=1-18, and

c) 0 to 10% by mol of at least one vinyl ester of the general formula III

with R=C n H 2n+1 and n=1-18.

12. The method according to claim 1 , wherein the multifilament yarn is produced by melting and extrusion of the copolymer of polyacrylonitrile through at least one spinning nozzle and spinning to form multifilaments.

13. The method according to claim 1 , wherein the prestabilisation of the non-prestabilised multifilament yarn is implemented
i) by treatment with a mixture comprising at least one solvent for polyacrylonitrile and an aqueous alkaline solution or consisting thereof, and subsequent neutralisation of the treated multifilament yarn, and/or
ii) by electron beam crosslinking of the meltable copolymers of polyacrylonitrile (PAN), and/or
iii) by removing any residual plasticiser contained in the meltable copolymer of polyacrylonitrile (PAN).

14. The method according to claim 13 , wherein the prestabilisation is effected by guiding the non-prestabilised multifilament yarn through a modifying bath, comprising the mixture at a temperature of 20 to 80° C., within a dwell time of 5 s to 2 min, or the non-prestabilised multifilament yarn is sprayed with the mixture.

15. The method according to claim 13 , wherein the aqueous alkaline solution comprises from 3 to 15 mol/l of at least one alkaline earth- or alkali salt.

16. The method according to claim 1 , wherein the neutralisation is effected by guiding the prestabilised multifilament yarn through a neutralisation bath, comprising an aqueous acidic solution with a pH value of less than 3, and at a temperature of 5 to 95° C., within a dwell time of 5 s to 2 min.

17. The method according to claim 1 , wherein a further temperature treatment under inert gas, at temperatures of 300 to 3,000° C., follows the thermal stabilisation, resulting in the production of a carbon fibre.

Assignees

• Fraunhofer Ges Forschung

Inventors

• Erdmann Jens
• Ganster Johannes

Classifications

• D02J13/00

  Heating or cooling the yarn, thread, cord, rope, or the like, not specific to any one of the processes provided for in this subclass (heating, cooling or drying during spinning or twisting D01H; drying of yarns or the like, in general F26B) · CPC title

• D01F6/38

  comprising unsaturated nitriles as the major constituent · CPC title

• D01F9/225 Primary

  from stabilised polyacrylonitriles · CPC title

• D01D5/08

  Melt spinning methods {(D01D5/0023 takes precedence)} · CPC title

• D02J1/228

  Stretching in two or more steps, with or without intermediate steps · CPC title