CA1327258C - Method of manufacturing carbon fiber using preliminary stretch - Google Patents
Method of manufacturing carbon fiber using preliminary stretchInfo
- Publication number
- CA1327258C CA1327258C CA000590558A CA590558A CA1327258C CA 1327258 C CA1327258 C CA 1327258C CA 000590558 A CA000590558 A CA 000590558A CA 590558 A CA590558 A CA 590558A CA 1327258 C CA1327258 C CA 1327258C
- Authority
- CA
- Canada
- Prior art keywords
- precursor
- stretching
- temperature
- tow
- precursor tow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
- D01F9/225—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles from stabilised polyacrylonitriles
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D10/00—Physical treatment of artificial filaments or the like during manufacture, i.e. during a continuous production process before the filaments have been collected
- D01D10/02—Heat treatment
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/12—Stretch-spinning methods
Abstract
NOVEL METHOD OF MANUFACTURING CARBON FIBER
USING PRELIMINARY STRETCH
Abstract of the Disclosure Process of carbon fiber manufacture wherein the polyacrylonitrile precursor is stretched prior to oxidation in limited temperature range. Process permits greater throughput in precursor manufacture and reduces flaws in the precursor because significant stretching is at lower line speeds typically used for oxidation and carbonization in making carbon fiber.
USING PRELIMINARY STRETCH
Abstract of the Disclosure Process of carbon fiber manufacture wherein the polyacrylonitrile precursor is stretched prior to oxidation in limited temperature range. Process permits greater throughput in precursor manufacture and reduces flaws in the precursor because significant stretching is at lower line speeds typically used for oxidation and carbonization in making carbon fiber.
Description
~3~72~
0796p This invention relates to improvements in the manufacture of carbon fiber from polyacrylonitrile polymers. This inven-~tion, more particularly, relates to producing high quality andperformance carbon fiber at significant cost savings through enhancing throughputs of precursor materials used in making such carbon fiber. This inventicn, still more particularly, relates to the discovery and exploitation of a limited temperature range wherein a multitude of filaments of the polyacrylonitrile polymer, such multitude often called "carbon fiber (polyacrylonitrile) precursor" or "precursor"
for short, may be safely stretched up to four or more times its original length after formation but prior to the oxida-tion used in making the carbon fiber. -PA~-based carbon fiber (for purposes of describing thiC
invention hereafter called "carbon fiber") is a well-known material that is over 85~ by wei~ht elemental carbon. Such carbon fiber is notable for enabling manufacture of light weight composite materials and other articles of manufacture of exceptional tensile strength and modulus.
Increased useage coupled with incremental improvements in the processes which manufacture carbon fiber have dramatically reduced its cost compared to when it was first ~ ~2~2~8 ~, c.3 ~
introduced several years ago. Moreover, the attractiveness of light weight structures comprising carbon fiber has increased significantly due to recent marked improvements in the material properties of the carbon fibel and resin materials used in making the structures.
Of late, however, despite even wider potential useage of carbon fiber through advances in material properties, con-tinued significant decreases in its price, at one time dramatic and routine, have not proceeded as expected. One reason is that reliable manufacture of high quality carbon fiber remains an art: skillful control of process conditions used in making it and repeated testing for assuring quality remain a manufacturing requisite. Furthermore, recent advances in material property performance have been achieved through use of finer denier precursor, i.e., small diameter filaments, and such finer denier precursor requires the same or greater amount of precursor process control in making it but at generally lower throughputs. Accordingly, while the processing quality and performance characteristics of carbon fiber have been maintained and even improved over the years, the cost of making such high quality carbon fiber has not been reduced to the degree possi~ly anticipated, particularly with respect to newer carbon fibl~rs made with finer denier precursor.
It is evident that increases in the line speeds of the precursor and carbon fiber manufacturing processes reduce cost per weight of the final carbon fiber. However, further increases in line speeds, especially in precursor manufactur-ing speeds, increase the risk of lowering the quality of the resultant carbon fiber, particularly since precursor line speeds have generally approached their maximum limits with conventional equipment.
The cost of making carbon fiber under current procedures can be divided into two categories. First, there is the cost of making the precursor, e.g. material costs o~ acrylonitrile, other monomer~ and solvent used in making the polyacryloni-~, : , ,, : -, 132~2~8 trile polymer, C05tS associated with spinning the precursor,costs associated with treating the spun filaments such as stretching in cold and hot water and steam, and costs associated with process control and testing. Other costs in making carbon fiber include the costs of oxidizing and then carbonizing the precursor, costs associated with the process control o~ such oxidation and carbonization and testing costs.
Since only about half by weight of the precursor becomes carbon fiber, it can be seen that reduction per pound of precursor manufacturing costs results in about twice that reduction per pound in carbon fiber.
Exemplary description of making precursors useful for producing carbon fiber appear in UK 1,324,772, U.S. Patents 4,100,004; 4,001,382; 4,009,24B; 4,113,847: 4,397,831;
4,448,740; 4,452,860 and ~apanese Applications 53-24427 published March 7, 1978 (Nippon Exlan Kogyo K.K.) and 61-~, 152826 published November 7, 1986 (Mitsubishi Rayon Co. Ltd.).
These publications describe making precursors wherein polyacrylonitrile filaments are stretched in hot water, steam and air prior to oxidation. For example, in the "Example of Application 1" of Japanese Application 61-152826 wet spun polyacrylonitrile filaments are said to have been stretched over five (5) times over a hot water bath, washed and dried and then drawn 1.3 times at 170C using dry heat prior to oxidation. U.S~ Patent 4,104,004, on the other hand, discloses stretching up to 75~ between 100C and 160C, e.g., 130C.
Now, in accordance with this invention, a limited temperature range has been discovered whereby the precursor may be stretched to four or more times its original length in air, steam or other fluid medium. As a result, greater throughput of precursor can be achieved under the same process c~ntrol procedures used at less than half the throughputs while at the same time, only marginally increa~ing the cost of producing carbon fiber through such stretching. Furthermore, since the stretching achieved in this limited temperature range can be quite high, certain stretching during manu~acture of the precursor may be reduced or even eliminated "
~;
~. . . ",.
.:. : , 13272~8 '-thereby allowing still further increases in throughputs and reductions in precursor manufacturing costs.
This invention, in a broad aspect, relates to an improvement in the process of manufacturing carbon fiber, the process comprising (a~ forming a polyacrylonitrile polymer in a solvent for such polymer, (b) extruding the polymer through a die to provide a multitude of continuous fil~ments, (c) drawing these filaments to a longer length in making a precursor tow and (d) oxidizing and then carbonizing the precursor tow in a series of ovens ~nd furnaces to provide the carbon fiber, the improvement comprising: (i) selecting for the polyacrylonitrile polymer a material that stretches in filamentary form as the precursor tow to a length that is at least two times its original length at a temperature in a range above about 140C and below that temperature (e.g. 200C) causing oxidation of the precursor tow, the original length being measured at a temperature below 142C prior to stretching; 5ii) heating said precursor tow to a temperature within the limited temperature range; and (iii) stretching the precursor tow heated to the aforementioned temperature so that its length after stretching is longer. Pre~erably, the precursor i5 stretched in the limited temperature range at least about two times its original `Length prior to such stretching and the stretching is done in air. Moreover! after the polyacrylonitrile polymer is extruded through the die, stretching prior to oxidation preferably consists essentially of stretching in the limited temperature range preceded by stretching at temperatures below boiling water temperature.
Also, such stretching prior to stretching in the limited temperature ranga preferably comprises stretching under circumstances that plasticize the filaments.
In a further broad aspect, the pr~sent invention relates to a process for making carbon fibre in the form of a tow or bundle comprising a multitude of high strength carbon fibre filaments, said process comprising: (a) forming a polyacryl-onitrile polymer in a solvent for such polymer; (b) extruding :
. ,..~ :. .
.
, :,:, :
L3272~8 4(a) said polymer through a die to provide a multitude of ~ontinuous filaments; (c) drawing the filaments to a longer leng~h in making a precursor tow; and (d) oxidizing and then carbonizing said precursor tow in a series of ovens and furnaces to provide said carbon fibre, the improvement which comprises: (i) selecting for said polyacrylonitrile polymer a material that stretches in filamentary form as said precursor tow to a length that is greater than twice its original length 1~ before stretching in a limited temperature range above about 140C and below that temperature causing oxidation of said precursor tow; (ii) heating said precursor tow to a temperature within said limited temperature range; and (iii) stretching said precursor tow heated to said temperature so that its length after said stretching is longer than its lèngth prior to said stretching; wherein said heating step tiii) is selected from the group consisting of heating in a gaseous medium and heating through contact with heated rollers.
In another broad aspect, the present invention relates to a method of making a precursor suitable for manufacture of high quality carbon fiber, said method comprising polymerizing acrylonitrile and one or more other monomers in a solvent for the resultant polymer, extruding sald polymer through a spinneret comprising a multitude of apertures to provide a precursor tow comprising a multitude of filaments and stretching said precursor tow wherein said stretchin~ consists essentially of first and second stretching operations wherein said first stretching operation is at a temperature below about 100C and said second stretching operation consists of stretching at a temperature between 142C and a temperature wherein said filaments begin to oxidizeO
Figure 1 illustrates the thermal response curve for a preferred precursor of this invention.
Figure 2 illustrates diagrammatically a device that is useful in practice of this invention.
, . ...... ;
. . . . ;
` _ 5 _ ~327~
Figures 3, 4 and 5 illustrate properties of precursors heated to a temperature in a range useful for practice of this invention.
The polyacrylonitrile precursor use~ul ln making carbon fiber in accordance with this invention comprises a poly~er made by addition polymerization, either in solution or other-wise, of ethenic monomers (i.e. monome~s that are ethyleni-cally unsaturated), at Least about 80 ~ole percent of which comprise acrylonitrile. The preferred polyacryLonitrile precursor polymers are copolymers of acrylonitrile and one or more other monofunctional ethenic monomers. Available ethenic monomers are diverse and include, for example, acrylates and methacrylates; unsaturated ketones; and acrylic and meth-acrylic acid, maleic acid, itaconic acid and their salts.
,15 Preferred comonomers comprise acrylic or methacrylic acids or their salts, and the preferred molar amounts o~ the comonomer ranges between about 1.5 and 3.5%. (See U.S. Patent ~,001,382 and U.S. Patent 4,397,831, The polyacrylonitrile precursor polymers suitable for making carbon fiber hereof are soluble in organic and/or inorganic solvents such as di~ethylsul~oxide, dimethyl formamide, zinc chloride or sodium thiocyanate solutions In a preferred practice of making a polyacrylonitrile precursor 2S for use in making the carbon fibers hereo~, a solution is formed rom water, polyacrylonitrile polymer and sodium thiocyanate at exe~plary respective weight ratios of about 60:10:30. This solution is concentrated through evaporation and filtered to provide a spinning solution. The spinning solution preferably comprises about 15~ by weight of the polyacrylonitrile polymer.
The spinning solution is passed through spinnerets using dry, dry/wet or wet spinning to orm the polyacrylonitrile precursor. The preferred polyacrylonitrile precursor is made u~ing a dry/wet spinning wherein a multitude of filaments are formed ~rom the spinning solution and pass from the ~pinneret .~, . . .
, . ' ' , ~ , ' .
13272~
through an air gap or other gap between the spinneret and a coagulant preferably comprising aqueous sodium thiocyanate.
After exiting from the coagulant bath, the spun fila~ents are washed and then stretched again to several times their original length in hot water and steam. (See U.S.- Patent 4,452,860 and Japanese ~pplication 53-24427 [1918].) In addition, the polyacrylonitrile precursor is treated with sizing agents such as silane compounds (see U.S. Patent 4,009,248.
The polyacrylonitrile precursc~r (preferably silane sized) is in the form of tows in bundles comprising a multi-tude of fiLaments ~e.g. l,000, lO,000 or more). The tows or bundles may be a combination of two or more tow3 or bundLes, l$ each ormed in a separate spinning operation.
A thermal response curve in air o~ a preferred poly-acrylonitrile pre~ursor suitable for use in making the carbon fibers o~ thi~ invention i5 shown in Figure l. Thi9 precursor is made from a monomer composition comprising about ninety eight mole percent ~98~) acrylonitrile and about two mole percent (2%) methacrylic acid.
The denier per filament of the polyacrylonitrile precursors desirably ranges between 0.6 and 6.0 or higher.
The particular denier of the polyacrylonitrile precursor chosen influences subsequent processing of the precursor into carbon fiber hereof. For exa~ple, larger denier precursor, e.g. 1033 denier per filament or above precursor is preferably tretched at temperatures below 200C ~e.g. about 150 - l60DC) to reduce-its denier to less than 0.8 prior to significant oxidation. Greater stretching in the limited temperature range reduce~ the need for such stretching in later, e.g., during oxidation, manufacturing steps in making the carbon fiber.
Through ~tretching at temperatures between 145 and 165C, the resultant precursor i~ up to 4.0 times or more it~ orig-inal length; and due to the minimal reaction at temperatures . ,,~; ,..~
' ., ' : , , . . .
-within this range may be in amounts selectively calculated in advance to provide the denier desir~d for subsequent oxidation and stabiliæation. For example, a 2.2 denier per filament precursor may be stretched to twice its origina} length to yield a l.l denier per filament material by a Str~tch Ratio (S.R.) of 2 according to the following formula:
dn = ds where S.R. equals Lo S.R. Li where Lo is length out, Li is length in (i.e. original length), dS is original denier and dN is new denier.
Desired stretch ratio (S.R.) may be achieved by drawing the precursor faster through the desired heated zone ~e.g.
temperature between 150C and 160C) that it is permitted to enter this zone.
Figure 2 illustrates in schematic form the design of stretching device 20 useful in practice of this invention.
Device 20 of Figure 2 comprises supports 22 which carry platform 24 on which inlet roll stack 26, steam heated roll stack 28, steam heated tube 30 and outlet roll stacks 32 and 34 are mounted.
Steam heated tube 30 is heated by steam passing through a jacket surrounding the tube walls. In addition, ga~ inlet tube 36 is mounted to the downstream end of steam heated tube 30 and provides for entry oE heated air or other gas when countercurrent gas heating is used in heat-up of the precursor traveling between about inlet and outlet roll stacks 26, 34. Control 38 monitors inlet and outlet counter-roll~ 40, 42 which can also measure tension and line speed as read out in control 38. Access port 44 permits stringing precursor through steam heated roll stack 28.
Steam heated roll stack 28 is optionally used in provid-ing preliminary heat transfer to the precursor as it travels around the steam heated rolls 28. This preliminary heat ` tran3fer permits shorter heated lengths of steam heated tube 30, if desired.
: ~ , - . ~,, , , . , - . . , .: . .. . .
,,, : ~ , , , , .: ' .. :.. ~
.
- 8 _ ~ ~ 2 7~ ~ ~
Features of the Device 20 of Figure 2 such as length of steam heated tube 30, use or non-use of steam heated roll stacX 28 and gas flow velocity, direction and placement of inlet tube 36 as well as temperatures used for heating thereof are selected as a matter of design choice so as to provide rapid heat-up of the precursor as well as compatibil-ity with the oxidation and carbonization line speeds in the carbon fiber process. Initial tow spacing that ranges preferably between about 2 and 4.5 tows per 2.54 centimeter for 12000 filament tows are preferred for flow of heat transfer medium, such spacing advantageously inherently increasing as stretching proceeds.
The polyacrylonitrile precursor after stretching in the limited temperature range according to this invention, is oxidized in one or more ovens preferably maintained at temperatures between 200C and 300C. A variety of oven geometries are known to provide appropriate oxidation in making carbon fiber and any of these ovens may be suitably employed in accordance with this invention. Preferably, however, a series of ovens (or series of passes through a single oven) are employed according to this invention with the precursor that is undergoing oxidation optionally stretched to a longer length than the length it has upon entering the oxidation oven. After exit from the oxidation oven or ovens, the oxidized (ancl stabilized) precursor is pas ed to one or more furnaces for carbonization in an inert atmosphere. Preferably, at least two furnaces are employed - respectively at temperatures between 400C and 800C and between 1000C and 1400C. Still higher modulus carbon fiber is made through using still another furnace having tempera-tures above 1800C, e.g. between 2000C and 2800C. The fiber undergoing carbonization is desirably stretched or at least not allowed to shrink in the temperature range between - 400C and 800C and 2000C and 2800C.
After exi~ from the high temperature furnace the carbonized fiber is surface treated. A variety of surface - ~32~2~
g treatments are known in the art. Pre~erred surface treatment is an electrolytic surface treatment and the degree of surface treatment is ordinarily a function of the carbonization temperatures used in making the fiber. The preferred electrolytic surface treatment comprises passing the fiber through a bath containing an aqueous ammonium bicarbonate or sodium`hydroxide solution ~e.g. O~S - 3% by weight). The current i~ applied to the fiber at between about 0.1 and 5 columbs/inch of fiber per 12,000 filaments. The resulting surface treated fiber is then prefèrably ~ized with an epoxy compatible siziny agent such as Shell epoxy Epon 834.
The following e~amples are intended to illustra~e this invention and not to limit its broader scope as set forth in the appended claims. In these examples, all temperatures are in degrees Centrigade and all parts are parts by weight unless otherwise noted.
Example 1 Polyacrylonitrile precursors were made using an air gap wet spinning process. The polymer of the precursor had an intrinsic viscosity between about 1.9 and 2.1 deciLiters per gram using a concentrated sodiu~ thiocyanate solution as the solvent. The spinning solution an~ coagulants comprised an aqueous solution of sodium thiocyanate. The polymer was made from a monomer composition that was about 98 mole ~ acrylo-nitrile and 2 mole % methacrylic acid. The precursors werestretched so that their length in tow form was about six times greater after steam stretching compared to their length after extrusion from the spinnerets. Table A shows the character-istics of the resulting precursor which were nominal 1.3 and 0.8 dpf (denier per filament).
~, 7 ~
TABLE A
Precursor Properties DPF (~OMI~AL) 1.3 0.8 Precursor Properties Tow Denier tg/9OOOm) 16,053 9,570 Tow Tenacity (g/d) 4.9 5.6 Tow Modulus (g/d) 96 102 D~T (g/d) 0.142 0.166 Boil-off Shrinkage (%) 5.5 5.7 US Content (~) 0.60 0.88 Sodium Content (ppm) 580 568 Residual Solvent (~) - 0.0073 Moisture Content (%) 0.92 0.60 Filament Dia~eter Cv (%) 4.1 4.4 Monster Filaments O O
The precursors were then stretched at a temperature of 158C with a residence time of about six (6) minutes at that temperature. After stretching, the stretched precursor was oxidized in stages generally at 234C and then 249C. The oxidized fiber was then passed through a low temperature furnace with a non-oxidi~.ing atmosphere (nitrogen) at a temperature between 600C and 800C (tar removal) and then passed to a high-temperature furnace having a temperature between 1200C and 1400~C and a non-oxidi~lng atmosphere (nitrogen). During passage through the low and high temperature furnaces the fiber undergoing carbonization in these furnaces was either allowed to shrink or was stretched across the length of the furnaces.
Tables B and C, set forth below, show the stretch of the fiber undergoing carboniæation a~ it passes through the tar removal (TR) and high temperature (Cl) furnaces along with the calculated dpf of the filament based on the stretch imparted at 158C. Under each level of stretch in these tables the ten~ile s~rength and modulus properties are li~ted for the fiber having the calculated dpf and stretch during passage ~ Ll -through the TR and Cl furnaces. (Tables B and C show results fro~ using the 1.3 dpf precursor of Table A; Table D shows the result of using the 0.8 dpf precursor of Table A.) The first value in columns 4 through 9 of Table A is tensile strength of the resultant carbon fiber in psi times 1000 and the second value is modulus in psi times 1,000,000. Modulus and tensile strength measurements were made using strand and tow test (Impregnated Strand~ procedures.
.
.
- 12~
O .~1 N ~ --I
a~ ~ o ~
_ ~ N ~ \o C
~ o o~
o 1~ ~
0796p This invention relates to improvements in the manufacture of carbon fiber from polyacrylonitrile polymers. This inven-~tion, more particularly, relates to producing high quality andperformance carbon fiber at significant cost savings through enhancing throughputs of precursor materials used in making such carbon fiber. This inventicn, still more particularly, relates to the discovery and exploitation of a limited temperature range wherein a multitude of filaments of the polyacrylonitrile polymer, such multitude often called "carbon fiber (polyacrylonitrile) precursor" or "precursor"
for short, may be safely stretched up to four or more times its original length after formation but prior to the oxida-tion used in making the carbon fiber. -PA~-based carbon fiber (for purposes of describing thiC
invention hereafter called "carbon fiber") is a well-known material that is over 85~ by wei~ht elemental carbon. Such carbon fiber is notable for enabling manufacture of light weight composite materials and other articles of manufacture of exceptional tensile strength and modulus.
Increased useage coupled with incremental improvements in the processes which manufacture carbon fiber have dramatically reduced its cost compared to when it was first ~ ~2~2~8 ~, c.3 ~
introduced several years ago. Moreover, the attractiveness of light weight structures comprising carbon fiber has increased significantly due to recent marked improvements in the material properties of the carbon fibel and resin materials used in making the structures.
Of late, however, despite even wider potential useage of carbon fiber through advances in material properties, con-tinued significant decreases in its price, at one time dramatic and routine, have not proceeded as expected. One reason is that reliable manufacture of high quality carbon fiber remains an art: skillful control of process conditions used in making it and repeated testing for assuring quality remain a manufacturing requisite. Furthermore, recent advances in material property performance have been achieved through use of finer denier precursor, i.e., small diameter filaments, and such finer denier precursor requires the same or greater amount of precursor process control in making it but at generally lower throughputs. Accordingly, while the processing quality and performance characteristics of carbon fiber have been maintained and even improved over the years, the cost of making such high quality carbon fiber has not been reduced to the degree possi~ly anticipated, particularly with respect to newer carbon fibl~rs made with finer denier precursor.
It is evident that increases in the line speeds of the precursor and carbon fiber manufacturing processes reduce cost per weight of the final carbon fiber. However, further increases in line speeds, especially in precursor manufactur-ing speeds, increase the risk of lowering the quality of the resultant carbon fiber, particularly since precursor line speeds have generally approached their maximum limits with conventional equipment.
The cost of making carbon fiber under current procedures can be divided into two categories. First, there is the cost of making the precursor, e.g. material costs o~ acrylonitrile, other monomer~ and solvent used in making the polyacryloni-~, : , ,, : -, 132~2~8 trile polymer, C05tS associated with spinning the precursor,costs associated with treating the spun filaments such as stretching in cold and hot water and steam, and costs associated with process control and testing. Other costs in making carbon fiber include the costs of oxidizing and then carbonizing the precursor, costs associated with the process control o~ such oxidation and carbonization and testing costs.
Since only about half by weight of the precursor becomes carbon fiber, it can be seen that reduction per pound of precursor manufacturing costs results in about twice that reduction per pound in carbon fiber.
Exemplary description of making precursors useful for producing carbon fiber appear in UK 1,324,772, U.S. Patents 4,100,004; 4,001,382; 4,009,24B; 4,113,847: 4,397,831;
4,448,740; 4,452,860 and ~apanese Applications 53-24427 published March 7, 1978 (Nippon Exlan Kogyo K.K.) and 61-~, 152826 published November 7, 1986 (Mitsubishi Rayon Co. Ltd.).
These publications describe making precursors wherein polyacrylonitrile filaments are stretched in hot water, steam and air prior to oxidation. For example, in the "Example of Application 1" of Japanese Application 61-152826 wet spun polyacrylonitrile filaments are said to have been stretched over five (5) times over a hot water bath, washed and dried and then drawn 1.3 times at 170C using dry heat prior to oxidation. U.S~ Patent 4,104,004, on the other hand, discloses stretching up to 75~ between 100C and 160C, e.g., 130C.
Now, in accordance with this invention, a limited temperature range has been discovered whereby the precursor may be stretched to four or more times its original length in air, steam or other fluid medium. As a result, greater throughput of precursor can be achieved under the same process c~ntrol procedures used at less than half the throughputs while at the same time, only marginally increa~ing the cost of producing carbon fiber through such stretching. Furthermore, since the stretching achieved in this limited temperature range can be quite high, certain stretching during manu~acture of the precursor may be reduced or even eliminated "
~;
~. . . ",.
.:. : , 13272~8 '-thereby allowing still further increases in throughputs and reductions in precursor manufacturing costs.
This invention, in a broad aspect, relates to an improvement in the process of manufacturing carbon fiber, the process comprising (a~ forming a polyacrylonitrile polymer in a solvent for such polymer, (b) extruding the polymer through a die to provide a multitude of continuous fil~ments, (c) drawing these filaments to a longer length in making a precursor tow and (d) oxidizing and then carbonizing the precursor tow in a series of ovens ~nd furnaces to provide the carbon fiber, the improvement comprising: (i) selecting for the polyacrylonitrile polymer a material that stretches in filamentary form as the precursor tow to a length that is at least two times its original length at a temperature in a range above about 140C and below that temperature (e.g. 200C) causing oxidation of the precursor tow, the original length being measured at a temperature below 142C prior to stretching; 5ii) heating said precursor tow to a temperature within the limited temperature range; and (iii) stretching the precursor tow heated to the aforementioned temperature so that its length after stretching is longer. Pre~erably, the precursor i5 stretched in the limited temperature range at least about two times its original `Length prior to such stretching and the stretching is done in air. Moreover! after the polyacrylonitrile polymer is extruded through the die, stretching prior to oxidation preferably consists essentially of stretching in the limited temperature range preceded by stretching at temperatures below boiling water temperature.
Also, such stretching prior to stretching in the limited temperature ranga preferably comprises stretching under circumstances that plasticize the filaments.
In a further broad aspect, the pr~sent invention relates to a process for making carbon fibre in the form of a tow or bundle comprising a multitude of high strength carbon fibre filaments, said process comprising: (a) forming a polyacryl-onitrile polymer in a solvent for such polymer; (b) extruding :
. ,..~ :. .
.
, :,:, :
L3272~8 4(a) said polymer through a die to provide a multitude of ~ontinuous filaments; (c) drawing the filaments to a longer leng~h in making a precursor tow; and (d) oxidizing and then carbonizing said precursor tow in a series of ovens and furnaces to provide said carbon fibre, the improvement which comprises: (i) selecting for said polyacrylonitrile polymer a material that stretches in filamentary form as said precursor tow to a length that is greater than twice its original length 1~ before stretching in a limited temperature range above about 140C and below that temperature causing oxidation of said precursor tow; (ii) heating said precursor tow to a temperature within said limited temperature range; and (iii) stretching said precursor tow heated to said temperature so that its length after said stretching is longer than its lèngth prior to said stretching; wherein said heating step tiii) is selected from the group consisting of heating in a gaseous medium and heating through contact with heated rollers.
In another broad aspect, the present invention relates to a method of making a precursor suitable for manufacture of high quality carbon fiber, said method comprising polymerizing acrylonitrile and one or more other monomers in a solvent for the resultant polymer, extruding sald polymer through a spinneret comprising a multitude of apertures to provide a precursor tow comprising a multitude of filaments and stretching said precursor tow wherein said stretchin~ consists essentially of first and second stretching operations wherein said first stretching operation is at a temperature below about 100C and said second stretching operation consists of stretching at a temperature between 142C and a temperature wherein said filaments begin to oxidizeO
Figure 1 illustrates the thermal response curve for a preferred precursor of this invention.
Figure 2 illustrates diagrammatically a device that is useful in practice of this invention.
, . ...... ;
. . . . ;
` _ 5 _ ~327~
Figures 3, 4 and 5 illustrate properties of precursors heated to a temperature in a range useful for practice of this invention.
The polyacrylonitrile precursor use~ul ln making carbon fiber in accordance with this invention comprises a poly~er made by addition polymerization, either in solution or other-wise, of ethenic monomers (i.e. monome~s that are ethyleni-cally unsaturated), at Least about 80 ~ole percent of which comprise acrylonitrile. The preferred polyacryLonitrile precursor polymers are copolymers of acrylonitrile and one or more other monofunctional ethenic monomers. Available ethenic monomers are diverse and include, for example, acrylates and methacrylates; unsaturated ketones; and acrylic and meth-acrylic acid, maleic acid, itaconic acid and their salts.
,15 Preferred comonomers comprise acrylic or methacrylic acids or their salts, and the preferred molar amounts o~ the comonomer ranges between about 1.5 and 3.5%. (See U.S. Patent ~,001,382 and U.S. Patent 4,397,831, The polyacrylonitrile precursor polymers suitable for making carbon fiber hereof are soluble in organic and/or inorganic solvents such as di~ethylsul~oxide, dimethyl formamide, zinc chloride or sodium thiocyanate solutions In a preferred practice of making a polyacrylonitrile precursor 2S for use in making the carbon fibers hereo~, a solution is formed rom water, polyacrylonitrile polymer and sodium thiocyanate at exe~plary respective weight ratios of about 60:10:30. This solution is concentrated through evaporation and filtered to provide a spinning solution. The spinning solution preferably comprises about 15~ by weight of the polyacrylonitrile polymer.
The spinning solution is passed through spinnerets using dry, dry/wet or wet spinning to orm the polyacrylonitrile precursor. The preferred polyacrylonitrile precursor is made u~ing a dry/wet spinning wherein a multitude of filaments are formed ~rom the spinning solution and pass from the ~pinneret .~, . . .
, . ' ' , ~ , ' .
13272~
through an air gap or other gap between the spinneret and a coagulant preferably comprising aqueous sodium thiocyanate.
After exiting from the coagulant bath, the spun fila~ents are washed and then stretched again to several times their original length in hot water and steam. (See U.S.- Patent 4,452,860 and Japanese ~pplication 53-24427 [1918].) In addition, the polyacrylonitrile precursor is treated with sizing agents such as silane compounds (see U.S. Patent 4,009,248.
The polyacrylonitrile precursc~r (preferably silane sized) is in the form of tows in bundles comprising a multi-tude of fiLaments ~e.g. l,000, lO,000 or more). The tows or bundles may be a combination of two or more tow3 or bundLes, l$ each ormed in a separate spinning operation.
A thermal response curve in air o~ a preferred poly-acrylonitrile pre~ursor suitable for use in making the carbon fibers o~ thi~ invention i5 shown in Figure l. Thi9 precursor is made from a monomer composition comprising about ninety eight mole percent ~98~) acrylonitrile and about two mole percent (2%) methacrylic acid.
The denier per filament of the polyacrylonitrile precursors desirably ranges between 0.6 and 6.0 or higher.
The particular denier of the polyacrylonitrile precursor chosen influences subsequent processing of the precursor into carbon fiber hereof. For exa~ple, larger denier precursor, e.g. 1033 denier per filament or above precursor is preferably tretched at temperatures below 200C ~e.g. about 150 - l60DC) to reduce-its denier to less than 0.8 prior to significant oxidation. Greater stretching in the limited temperature range reduce~ the need for such stretching in later, e.g., during oxidation, manufacturing steps in making the carbon fiber.
Through ~tretching at temperatures between 145 and 165C, the resultant precursor i~ up to 4.0 times or more it~ orig-inal length; and due to the minimal reaction at temperatures . ,,~; ,..~
' ., ' : , , . . .
-within this range may be in amounts selectively calculated in advance to provide the denier desir~d for subsequent oxidation and stabiliæation. For example, a 2.2 denier per filament precursor may be stretched to twice its origina} length to yield a l.l denier per filament material by a Str~tch Ratio (S.R.) of 2 according to the following formula:
dn = ds where S.R. equals Lo S.R. Li where Lo is length out, Li is length in (i.e. original length), dS is original denier and dN is new denier.
Desired stretch ratio (S.R.) may be achieved by drawing the precursor faster through the desired heated zone ~e.g.
temperature between 150C and 160C) that it is permitted to enter this zone.
Figure 2 illustrates in schematic form the design of stretching device 20 useful in practice of this invention.
Device 20 of Figure 2 comprises supports 22 which carry platform 24 on which inlet roll stack 26, steam heated roll stack 28, steam heated tube 30 and outlet roll stacks 32 and 34 are mounted.
Steam heated tube 30 is heated by steam passing through a jacket surrounding the tube walls. In addition, ga~ inlet tube 36 is mounted to the downstream end of steam heated tube 30 and provides for entry oE heated air or other gas when countercurrent gas heating is used in heat-up of the precursor traveling between about inlet and outlet roll stacks 26, 34. Control 38 monitors inlet and outlet counter-roll~ 40, 42 which can also measure tension and line speed as read out in control 38. Access port 44 permits stringing precursor through steam heated roll stack 28.
Steam heated roll stack 28 is optionally used in provid-ing preliminary heat transfer to the precursor as it travels around the steam heated rolls 28. This preliminary heat ` tran3fer permits shorter heated lengths of steam heated tube 30, if desired.
: ~ , - . ~,, , , . , - . . , .: . .. . .
,,, : ~ , , , , .: ' .. :.. ~
.
- 8 _ ~ ~ 2 7~ ~ ~
Features of the Device 20 of Figure 2 such as length of steam heated tube 30, use or non-use of steam heated roll stacX 28 and gas flow velocity, direction and placement of inlet tube 36 as well as temperatures used for heating thereof are selected as a matter of design choice so as to provide rapid heat-up of the precursor as well as compatibil-ity with the oxidation and carbonization line speeds in the carbon fiber process. Initial tow spacing that ranges preferably between about 2 and 4.5 tows per 2.54 centimeter for 12000 filament tows are preferred for flow of heat transfer medium, such spacing advantageously inherently increasing as stretching proceeds.
The polyacrylonitrile precursor after stretching in the limited temperature range according to this invention, is oxidized in one or more ovens preferably maintained at temperatures between 200C and 300C. A variety of oven geometries are known to provide appropriate oxidation in making carbon fiber and any of these ovens may be suitably employed in accordance with this invention. Preferably, however, a series of ovens (or series of passes through a single oven) are employed according to this invention with the precursor that is undergoing oxidation optionally stretched to a longer length than the length it has upon entering the oxidation oven. After exit from the oxidation oven or ovens, the oxidized (ancl stabilized) precursor is pas ed to one or more furnaces for carbonization in an inert atmosphere. Preferably, at least two furnaces are employed - respectively at temperatures between 400C and 800C and between 1000C and 1400C. Still higher modulus carbon fiber is made through using still another furnace having tempera-tures above 1800C, e.g. between 2000C and 2800C. The fiber undergoing carbonization is desirably stretched or at least not allowed to shrink in the temperature range between - 400C and 800C and 2000C and 2800C.
After exi~ from the high temperature furnace the carbonized fiber is surface treated. A variety of surface - ~32~2~
g treatments are known in the art. Pre~erred surface treatment is an electrolytic surface treatment and the degree of surface treatment is ordinarily a function of the carbonization temperatures used in making the fiber. The preferred electrolytic surface treatment comprises passing the fiber through a bath containing an aqueous ammonium bicarbonate or sodium`hydroxide solution ~e.g. O~S - 3% by weight). The current i~ applied to the fiber at between about 0.1 and 5 columbs/inch of fiber per 12,000 filaments. The resulting surface treated fiber is then prefèrably ~ized with an epoxy compatible siziny agent such as Shell epoxy Epon 834.
The following e~amples are intended to illustra~e this invention and not to limit its broader scope as set forth in the appended claims. In these examples, all temperatures are in degrees Centrigade and all parts are parts by weight unless otherwise noted.
Example 1 Polyacrylonitrile precursors were made using an air gap wet spinning process. The polymer of the precursor had an intrinsic viscosity between about 1.9 and 2.1 deciLiters per gram using a concentrated sodiu~ thiocyanate solution as the solvent. The spinning solution an~ coagulants comprised an aqueous solution of sodium thiocyanate. The polymer was made from a monomer composition that was about 98 mole ~ acrylo-nitrile and 2 mole % methacrylic acid. The precursors werestretched so that their length in tow form was about six times greater after steam stretching compared to their length after extrusion from the spinnerets. Table A shows the character-istics of the resulting precursor which were nominal 1.3 and 0.8 dpf (denier per filament).
~, 7 ~
TABLE A
Precursor Properties DPF (~OMI~AL) 1.3 0.8 Precursor Properties Tow Denier tg/9OOOm) 16,053 9,570 Tow Tenacity (g/d) 4.9 5.6 Tow Modulus (g/d) 96 102 D~T (g/d) 0.142 0.166 Boil-off Shrinkage (%) 5.5 5.7 US Content (~) 0.60 0.88 Sodium Content (ppm) 580 568 Residual Solvent (~) - 0.0073 Moisture Content (%) 0.92 0.60 Filament Dia~eter Cv (%) 4.1 4.4 Monster Filaments O O
The precursors were then stretched at a temperature of 158C with a residence time of about six (6) minutes at that temperature. After stretching, the stretched precursor was oxidized in stages generally at 234C and then 249C. The oxidized fiber was then passed through a low temperature furnace with a non-oxidi~.ing atmosphere (nitrogen) at a temperature between 600C and 800C (tar removal) and then passed to a high-temperature furnace having a temperature between 1200C and 1400~C and a non-oxidi~lng atmosphere (nitrogen). During passage through the low and high temperature furnaces the fiber undergoing carbonization in these furnaces was either allowed to shrink or was stretched across the length of the furnaces.
Tables B and C, set forth below, show the stretch of the fiber undergoing carboniæation a~ it passes through the tar removal (TR) and high temperature (Cl) furnaces along with the calculated dpf of the filament based on the stretch imparted at 158C. Under each level of stretch in these tables the ten~ile s~rength and modulus properties are li~ted for the fiber having the calculated dpf and stretch during passage ~ Ll -through the TR and Cl furnaces. (Tables B and C show results fro~ using the 1.3 dpf precursor of Table A; Table D shows the result of using the 0.8 dpf precursor of Table A.) The first value in columns 4 through 9 of Table A is tensile strength of the resultant carbon fiber in psi times 1000 and the second value is modulus in psi times 1,000,000. Modulus and tensile strength measurements were made using strand and tow test (Impregnated Strand~ procedures.
.
.
- 12~
O .~1 N ~ --I
a~ ~ o ~
_ ~ N ~ \o C
~ o o~
o 1~ ~
2~
a~ l u~
~ I I !~~
Y~ ~ ~ ~ ~ N C
~_ ~ a~e æ~ a~ O O ~
~ 8 ,~ I a~
U~ o - 13 - ~3~
~ IIo~
~5 I ~ 1~ I t ~ r~ .
,~ ,~ ~
W 1~ If~ O N 0~
~ ~ ~ r ~ ~
~ N ¦ O ~ ~ N ~
c~
O~ N
O, ~ 0~ ~--1 N O N
~! ~¦ ~ ~ ~ N O
_~
a~ ~ ~ ~ o O~ N
aS~ 1~ O
~-,1 r` 2 ~1 ¦ a) N 1~ N r~
~æl o O O O O
O
~zl U~
.. . .
~ 3 ~
Example 2 Polyacrylonitrile precursor was made generally according to the conditions previously described except that it had no steam stretching and its denier was 1.2 dpf. The 1.2 dpf polyacrylonitrile precursor fiber was stretched to twice its original length (i.e. s. r. equals 2) at a temperature of 158C and wound around a spool and stored.
The precursor was then oxidized by passing it through air circulation ovens at temperatures for the times shown in the following Table D.
TABLE D
Temperatures Time (minutes) 158C 2.05 240C 17.73 245C 14.43 248C 17.72 250C 17.72 250C 4.43 The oxidized precursor passed from the last oxidation oven through a low temperature (tar removal) furnace. Then the partially carbonized fiber passed through a first low temperature furnace held at 142$C and then a second high temperature furnace held at 2500C.
The stretch in each of the low temperature, first high and second high temperature furnaces are shown below (values are %~ for four distinct runs in Table E below.
TABLE E
Run Overall TR Cl C2 135-1 0.1 4.5 ~5.3 0.9 135-2 2.4 6.9 -S.l 0.9 5135-3 4.9 9.3 -5.0 1.0 135-4 6.9 11.3 ~4.1 0.2 . . :
, . ..
.
- : . ~, - ' ~ , ' .
..
~ 3 ~ 7 ,~
Table F, below, shows the properties of carbon fiber made according to the procedures of this Example.
TABLE F
Tensile Strengthb 5 Run Modulusa Density 135.1 58.2 606 135.2 60.1 615 135-3 61.5 628 135-~ 61.4 558 a 106 psi b 103 psi In this Example, precursor was made under conditions generally described heretofore. The precursor had a 1.67 dpf (12,000 filaments per tow) and had not been s~retched under steam. The preeursor was passed through a device like that shown in Figure 2 and stretched four (4) times its original length (i.e. S.R. equals 4) after a residence of 0.8 minutes at about 158C. In similar studies, a precursor run at the same temperature but at a residen,ce time of 0.25 minutes broke prior to achieving a stretch that was equivalent to making it 2.3 times longer than its original length. When the r~sidence time was increased to 0.33 minutes at 158C, the tows broke unacceptably after a stretch that made them 3O3 their original length. However, the precursor had reduced cosmetics at stretch ratios (S.R.) which equaled 2.0 ~, and 2.3 at these respective 0.25 minutes and 0.33 minutes residences at 158C.
E~ample 4 In this ~xample the precursor used was made from a polyacrylonitrile polymer using sodium thiocyanate as solvent and coagulant and an air gap spinning process, as descri'bed heretofore. The fiber was only ~tretched in water and had a ... . ...
:: : . .. .
. .:
~ 3~7~
2.67 dpf and 12,000 filaments p0r tow. Methacrylic acid was used in making the polyacrylonitrile poiymer.
The 2.67 dpf precursor was stretched in a prototype device like that shown in Figure 2, also described herein-before. Hot air at 158C was circulated in counter-current flow in tube 30 around the tows which were spaced about l.8 toss per centimeter. Steam at 71 psig was passed into the jacket of tube 30 and into the rolls of roll stack 28. The line speed was gradually increased with the stretch ratio held at 3.9 (i.e. precursor was 3.9 times as long after stretching as compared to length prior to stretching).
Tensions of the precursor were measured in the rolls stacks 26, 34.
Results of this Example are shown in Table G, below.
TABI,E G
Effect of Increasing Speed on Break Stretch RatlO
Stretch Line No. of Tension (gpd) at Pin Position Ratio Speed Tows 1 4 lO
a~ l u~
~ I I !~~
Y~ ~ ~ ~ ~ N C
~_ ~ a~e æ~ a~ O O ~
~ 8 ,~ I a~
U~ o - 13 - ~3~
~ IIo~
~5 I ~ 1~ I t ~ r~ .
,~ ,~ ~
W 1~ If~ O N 0~
~ ~ ~ r ~ ~
~ N ¦ O ~ ~ N ~
c~
O~ N
O, ~ 0~ ~--1 N O N
~! ~¦ ~ ~ ~ N O
_~
a~ ~ ~ ~ o O~ N
aS~ 1~ O
~-,1 r` 2 ~1 ¦ a) N 1~ N r~
~æl o O O O O
O
~zl U~
.. . .
~ 3 ~
Example 2 Polyacrylonitrile precursor was made generally according to the conditions previously described except that it had no steam stretching and its denier was 1.2 dpf. The 1.2 dpf polyacrylonitrile precursor fiber was stretched to twice its original length (i.e. s. r. equals 2) at a temperature of 158C and wound around a spool and stored.
The precursor was then oxidized by passing it through air circulation ovens at temperatures for the times shown in the following Table D.
TABLE D
Temperatures Time (minutes) 158C 2.05 240C 17.73 245C 14.43 248C 17.72 250C 17.72 250C 4.43 The oxidized precursor passed from the last oxidation oven through a low temperature (tar removal) furnace. Then the partially carbonized fiber passed through a first low temperature furnace held at 142$C and then a second high temperature furnace held at 2500C.
The stretch in each of the low temperature, first high and second high temperature furnaces are shown below (values are %~ for four distinct runs in Table E below.
TABLE E
Run Overall TR Cl C2 135-1 0.1 4.5 ~5.3 0.9 135-2 2.4 6.9 -S.l 0.9 5135-3 4.9 9.3 -5.0 1.0 135-4 6.9 11.3 ~4.1 0.2 . . :
, . ..
.
- : . ~, - ' ~ , ' .
..
~ 3 ~ 7 ,~
Table F, below, shows the properties of carbon fiber made according to the procedures of this Example.
TABLE F
Tensile Strengthb 5 Run Modulusa Density 135.1 58.2 606 135.2 60.1 615 135-3 61.5 628 135-~ 61.4 558 a 106 psi b 103 psi In this Example, precursor was made under conditions generally described heretofore. The precursor had a 1.67 dpf (12,000 filaments per tow) and had not been s~retched under steam. The preeursor was passed through a device like that shown in Figure 2 and stretched four (4) times its original length (i.e. S.R. equals 4) after a residence of 0.8 minutes at about 158C. In similar studies, a precursor run at the same temperature but at a residen,ce time of 0.25 minutes broke prior to achieving a stretch that was equivalent to making it 2.3 times longer than its original length. When the r~sidence time was increased to 0.33 minutes at 158C, the tows broke unacceptably after a stretch that made them 3O3 their original length. However, the precursor had reduced cosmetics at stretch ratios (S.R.) which equaled 2.0 ~, and 2.3 at these respective 0.25 minutes and 0.33 minutes residences at 158C.
E~ample 4 In this ~xample the precursor used was made from a polyacrylonitrile polymer using sodium thiocyanate as solvent and coagulant and an air gap spinning process, as descri'bed heretofore. The fiber was only ~tretched in water and had a ... . ...
:: : . .. .
. .:
~ 3~7~
2.67 dpf and 12,000 filaments p0r tow. Methacrylic acid was used in making the polyacrylonitrile poiymer.
The 2.67 dpf precursor was stretched in a prototype device like that shown in Figure 2, also described herein-before. Hot air at 158C was circulated in counter-current flow in tube 30 around the tows which were spaced about l.8 toss per centimeter. Steam at 71 psig was passed into the jacket of tube 30 and into the rolls of roll stack 28. The line speed was gradually increased with the stretch ratio held at 3.9 (i.e. precursor was 3.9 times as long after stretching as compared to length prior to stretching).
Tensions of the precursor were measured in the rolls stacks 26, 34.
Results of this Example are shown in Table G, below.
TABI,E G
Effect of Increasing Speed on Break Stretch RatlO
Stretch Line No. of Tension (gpd) at Pin Position Ratio Speed Tows 1 4 lO
3.9X 25 ft/min. lO 0.347 0.335 0.333 3.9X 25.8 lO 0.347 0.335 0.333 3.9X 26.6 10 0.347 0.335 0.333 3.9X 27.5 10 0,347 0.335 0.333 3.9X 28.3 10 0.349 0.335 ~.335 3.9X 29.1 10 0.349 0.335 0.335 3.9X 30.0 10 0.349 0.335 0.335 .
Fiber broke during 30 ft/min. run.
Run used 2.67 dpf/12K precursor, hot air at 158C, steam tube and rolls at 71 psig.
Table H below shows the results of making a nominal 0.8 dpf precursor from the aforedescribed 2.67 precursor described above using the procedures of this invsntion.
' .
~L3~J~
~ ~o ol N N
C O ~>
'CL
~ ~ U~
N N
--' ~1 ~ ~
~ O O
O) O
.,1 ~ C~l c ;r ~ ~1 1 ~ r~
~ O O
Q
r X X r~
a~ ~ ~
f-l ~'O . N
~ r~
I
a~ . I~
tO
,C ' U~
o ~ Il~
O (r1N N C
~ ~a ~ ~ U~
U u~ Ul 3~ o ~ o o ct,C~ _l ~ U~ f~
zq_31 0 .~0) a: zl ~ o N
A standard steam stretched precursor ~team (See Table A) having a 0.8 dpf was used as a control in making carbon fiber and compared against carbon fiber made from a 0.8 dpf (calculated) precursor which was made using the procedures of S this invention. The results are shown in Table I below. As can be een, nearly equivalent properties are obtained using the procedures of this invention even though the amount of stretching in oxidàtion is less.
::
.: . .: ., ~7~
: O O O O 0 3 00 0 ~n ~ U ~ t~ ~ N ~ I~ It \ a:l a~ ~ ~ I~ ~ I` ct~
'~ C ~ I` I` I` I` r~ I~ I` I` ~`
c~ a Q) ~ . a O C~ O
~ ~ ~ ~ o D ~ .~`:t N V
.-1 . ~\ ;~O~ N ~
LL 10 :E .-i C~
O O ~ .
h 11 O ~l,~ 0 ;~ ~ O ~0 N ~0~ O C C o Q
. Ul r~ I r` N
If~
~ . ~a ~ o ~o U
XXXXX X C ~0--1 LLI C~ c m N C ~
N ~ O O
.. ~ (1 ~ X X X X ~ 'l o o ~ ~
^ o 3 o .,1 0 ~ a~
U ~_~
Q I Q C~ Q ~- O o o o o ~.) o N
~ ~ ~ v~ O ~ ~ v~ ~ u~~ C a LL O OO O ~ O ~O ~ ~ c V V ~0 h h ~ ~ , O
o c . o f-~ h '.-1 n o C
~`J .-1~1 --I N N N (~ C~J ~ I-- - 1~ D h u~ N
_I ~1 ,- .~
.,,, :~ :; ~
-ll 3 ~., 7 2 Dr~ $
Example 5 The tension developed at increasing temperatures and 0 stretch (i.e. constant length) for various precursors was measured. The tension measured versus the temperature to which each precursor was heated at this 0% stretch is shown in Figure 3 for four polyacrylonitrile materials. The monomer compositio~ for the precursor of Curve A in Figure 3 included acrylonitrile, methacrylic acid and methylacrylate. The monomer composition used in making the precursor of Curve B
in Figure 3 included acrylonitrile and methacrylic acid. The monomer composition used in making the precursor of Curve C
included acrylonitrile, itaconic acid and methylacrylate.
Precursors oE various compositions were heated to various temperatures and the break stretch ratio (i.e. stretch ratio (SR) when the precursor filaments broke) determine for that temperature for each precursor composition. Curve A, Figure 4, shows a plot of break stretch ratio, or stretch ratio at the time the filaments of the precursor broke, for a precursor made from ingredients noted above in connection with Figure 3. Likewise, Curves B and C of Figure 4 show result~ for precursors having compositions indicated above with respect to Figure 3.
Figure 5 shows the results of stretching different denier precursors until breaking at various temperatures.
The monomer composition used in making each of the precursors in Figure 5 was 98 mole % acrylonitrile and 2 mole ~ meth-acrylic acid. Precursors D, E and F were not stretched in steam and have therefore somewhat less previous stretch imparted than precursors G and H (which were steam stretched).
:
Fiber broke during 30 ft/min. run.
Run used 2.67 dpf/12K precursor, hot air at 158C, steam tube and rolls at 71 psig.
Table H below shows the results of making a nominal 0.8 dpf precursor from the aforedescribed 2.67 precursor described above using the procedures of this invsntion.
' .
~L3~J~
~ ~o ol N N
C O ~>
'CL
~ ~ U~
N N
--' ~1 ~ ~
~ O O
O) O
.,1 ~ C~l c ;r ~ ~1 1 ~ r~
~ O O
Q
r X X r~
a~ ~ ~
f-l ~'O . N
~ r~
I
a~ . I~
tO
,C ' U~
o ~ Il~
O (r1N N C
~ ~a ~ ~ U~
U u~ Ul 3~ o ~ o o ct,C~ _l ~ U~ f~
zq_31 0 .~0) a: zl ~ o N
A standard steam stretched precursor ~team (See Table A) having a 0.8 dpf was used as a control in making carbon fiber and compared against carbon fiber made from a 0.8 dpf (calculated) precursor which was made using the procedures of S this invention. The results are shown in Table I below. As can be een, nearly equivalent properties are obtained using the procedures of this invention even though the amount of stretching in oxidàtion is less.
::
.: . .: ., ~7~
: O O O O 0 3 00 0 ~n ~ U ~ t~ ~ N ~ I~ It \ a:l a~ ~ ~ I~ ~ I` ct~
'~ C ~ I` I` I` I` r~ I~ I` I` ~`
c~ a Q) ~ . a O C~ O
~ ~ ~ ~ o D ~ .~`:t N V
.-1 . ~\ ;~O~ N ~
LL 10 :E .-i C~
O O ~ .
h 11 O ~l,~ 0 ;~ ~ O ~0 N ~0~ O C C o Q
. Ul r~ I r` N
If~
~ . ~a ~ o ~o U
XXXXX X C ~0--1 LLI C~ c m N C ~
N ~ O O
.. ~ (1 ~ X X X X ~ 'l o o ~ ~
^ o 3 o .,1 0 ~ a~
U ~_~
Q I Q C~ Q ~- O o o o o ~.) o N
~ ~ ~ v~ O ~ ~ v~ ~ u~~ C a LL O OO O ~ O ~O ~ ~ c V V ~0 h h ~ ~ , O
o c . o f-~ h '.-1 n o C
~`J .-1~1 --I N N N (~ C~J ~ I-- - 1~ D h u~ N
_I ~1 ,- .~
.,,, :~ :; ~
-ll 3 ~., 7 2 Dr~ $
Example 5 The tension developed at increasing temperatures and 0 stretch (i.e. constant length) for various precursors was measured. The tension measured versus the temperature to which each precursor was heated at this 0% stretch is shown in Figure 3 for four polyacrylonitrile materials. The monomer compositio~ for the precursor of Curve A in Figure 3 included acrylonitrile, methacrylic acid and methylacrylate. The monomer composition used in making the precursor of Curve B
in Figure 3 included acrylonitrile and methacrylic acid. The monomer composition used in making the precursor of Curve C
included acrylonitrile, itaconic acid and methylacrylate.
Precursors oE various compositions were heated to various temperatures and the break stretch ratio (i.e. stretch ratio (SR) when the precursor filaments broke) determine for that temperature for each precursor composition. Curve A, Figure 4, shows a plot of break stretch ratio, or stretch ratio at the time the filaments of the precursor broke, for a precursor made from ingredients noted above in connection with Figure 3. Likewise, Curves B and C of Figure 4 show result~ for precursors having compositions indicated above with respect to Figure 3.
Figure 5 shows the results of stretching different denier precursors until breaking at various temperatures.
The monomer composition used in making each of the precursors in Figure 5 was 98 mole % acrylonitrile and 2 mole ~ meth-acrylic acid. Precursors D, E and F were not stretched in steam and have therefore somewhat less previous stretch imparted than precursors G and H (which were steam stretched).
:
Claims (9)
1. In a process for making carbon fibre in the form of a tow or bundle comprising a multitude of high strength carbon fibre filaments, said process comprising:
(a) forming a polyacrylonitrile polymer in a solvent for such polymer;
(b) extruding said polymer through a die to provide a multitude of continuous filaments;
(c) drawing the filaments to a longer length in making a precursor tow; and (d) oxidizing and then carbonizing said precursor tow in a series of ovens and furnaces to provide said carbon fibre, the improvement which comprises:
i) selecting for said polyacrylonitrile polymer a material that stretches in filamentary form as said precursor tow to a length that is greater than twice its original length before stretching in a limited temperature range above about 140°C
and below that temperature causing oxidation of said precursor tow.
ii) heating said precursor tow to a temperature within said limited temperature range; and iii) stretching said precursor tow heated to said temperature so that its length after said stretching is longer than its length prior to said stretching;
wherein said heating step (iii) is selected from the group consisting of heating in a gaseous medium and heating through contact with heated rollers.
(a) forming a polyacrylonitrile polymer in a solvent for such polymer;
(b) extruding said polymer through a die to provide a multitude of continuous filaments;
(c) drawing the filaments to a longer length in making a precursor tow; and (d) oxidizing and then carbonizing said precursor tow in a series of ovens and furnaces to provide said carbon fibre, the improvement which comprises:
i) selecting for said polyacrylonitrile polymer a material that stretches in filamentary form as said precursor tow to a length that is greater than twice its original length before stretching in a limited temperature range above about 140°C
and below that temperature causing oxidation of said precursor tow.
ii) heating said precursor tow to a temperature within said limited temperature range; and iii) stretching said precursor tow heated to said temperature so that its length after said stretching is longer than its length prior to said stretching;
wherein said heating step (iii) is selected from the group consisting of heating in a gaseous medium and heating through contact with heated rollers.
2. The process in accordance with Claim 1, wherein said heating of step (iii) comprises heating in a gaseous medium.
3. The process in accordance with Claim 1, wherein said heating of step (iii) comprises heating through contact with heated rollers.
4. The process in accordance with Claim 1, wherein said limited temperature range is between about 150°C and 160°C.
5. The process in accordance with Claim 1, wherein said polyacrylonitrile is made from a monomer composition comprising 98 mole % acrylonitrile and 2 mole % methacrylic acid.
6. The process in accordance with Claim 1, wherein said precursor tow that is stretched in step (iii) is passed in a heated condition to an oxidation oven.
7. The process in accordance with Claim 1, wherein said drawing of step (c) consists essentially of drawing at a temperature below 100°C.
8. In a process for making carbon fibre comprising oxidizing and then carbonizing a precursor tow comprising a multitude of continuous filaments consisting essentially of a polyacrylonitrile polymer, the improvement which comprises heating said polyacrylonitrile to a temperature between 142°C and 180°C so as to permit said precursor tow to be stretched at least to a length that is three times its original length prior to said stretching and then stretching said precursor tow at said temperature so it would be longer after said stretching than prior to said stretching at said temperature.
9. A method of making a precursor suitable for manufacture of high quality carbon fibre, said method comprising polymerizing acrylonitrile and one or more other monomers in a solvent for the resultant polymer, extruding said polymer through a spinneret comprising a multitude of apertures to provide a precursor tow comprising a multitude of filaments and stretching said precursor tow wherein said stretching consists essentially of first and second stretching operations wherein said first stretching operation is at a temperature below about 130°C and said second stretching operation consists of stretching at a temperature between 142°C and a temperature wherein said filaments begin to oxidize.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US15638988A | 1988-02-16 | 1988-02-16 | |
| US156,389 | 1988-02-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1327258C true CA1327258C (en) | 1994-03-01 |
Family
ID=22559371
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000590558A Expired - Fee Related CA1327258C (en) | 1988-02-16 | 1989-02-09 | Method of manufacturing carbon fiber using preliminary stretch |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0329128B1 (en) |
| JP (1) | JP3033960B2 (en) |
| AT (1) | ATE176012T1 (en) |
| CA (1) | CA1327258C (en) |
| DE (1) | DE68928911T2 (en) |
| ES (1) | ES2128296T3 (en) |
| IL (1) | IL89271A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2770233B1 (en) * | 1997-10-27 | 2000-01-14 | Messier Bugatti | PROCESS FOR MANUFACTURING CARBON FIBER PREFORMS |
| WO2012073852A1 (en) | 2010-11-30 | 2012-06-07 | 東レ株式会社 | Polyacrylonitrile fiber manufacturing method and carbon fiber manufacturing method |
| CN108431310A (en) | 2015-12-31 | 2018-08-21 | Ut-巴特勒有限公司 | The method for producing carbon fiber from multipurpose commercial fibres |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1324041A (en) * | 1969-10-31 | 1973-07-18 | Nippon Carbon Co Ltd | Method of producing carbon fibres |
| DE2211639C3 (en) * | 1972-03-10 | 1978-12-14 | Bayer Ag, 5090 Leverkusen | Process for the production of carbon threads |
| JPS6039763A (en) * | 1983-08-11 | 1985-03-01 | Japan Storage Battery Co Ltd | Lead storage battery with eletrolyte circulating device |
| JPS6156327A (en) * | 1984-08-28 | 1986-03-22 | Canon Inc | Driving method of display panel |
| JPH0742605B2 (en) * | 1987-09-16 | 1995-05-10 | 日機装株式会社 | Method for producing acrylic fiber |
-
1989
- 1989-02-09 CA CA000590558A patent/CA1327258C/en not_active Expired - Fee Related
- 1989-02-13 IL IL89271A patent/IL89271A/en not_active IP Right Cessation
- 1989-02-16 DE DE68928911T patent/DE68928911T2/en not_active Expired - Fee Related
- 1989-02-16 EP EP89102638A patent/EP0329128B1/en not_active Revoked
- 1989-02-16 JP JP1037316A patent/JP3033960B2/en not_active Expired - Lifetime
- 1989-02-16 AT AT89102638T patent/ATE176012T1/en not_active IP Right Cessation
- 1989-02-16 ES ES89102638T patent/ES2128296T3/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| IL89271A0 (en) | 1989-09-10 |
| JP3033960B2 (en) | 2000-04-17 |
| JPH026627A (en) | 1990-01-10 |
| ES2128296T3 (en) | 1999-05-16 |
| IL89271A (en) | 1992-12-01 |
| DE68928911D1 (en) | 1999-03-04 |
| ATE176012T1 (en) | 1999-02-15 |
| EP0329128B1 (en) | 1999-01-20 |
| EP0329128A3 (en) | 1991-03-13 |
| EP0329128A2 (en) | 1989-08-23 |
| DE68928911T2 (en) | 1999-05-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1095206A (en) | Process for producing carbon fibers | |
| US3529934A (en) | Process for the preparation of carbon fibers | |
| EP1130140B1 (en) | Acrylonitril-based precursor fiber for carbon fiber and method for production thereof | |
| US5066433A (en) | Method of manufacturing carbon fiber using preliminary stretch | |
| US4113847A (en) | Process for producing carbon fibers | |
| US4917836A (en) | Process for producing high-strength, high-modulus carbon fibers | |
| US5051216A (en) | Process for producing carbon fibers of high tenacity and modulus of elasticity | |
| US4452860A (en) | Carbon fibers and process for producing the same | |
| US4186179A (en) | Process for producing oxidized or carbon fibers | |
| CA1327258C (en) | Method of manufacturing carbon fiber using preliminary stretch | |
| CN111945251A (en) | Ultrahigh-strength medium-modulus polyacrylonitrile-based carbon fiber and preparation method thereof | |
| US3867499A (en) | Process for wet-spinning fibers derived from acrylic polymers | |
| CA1199763A (en) | Process for the production of high-strength filaments from dry-spun polyacrylonitrile | |
| GB2064498A (en) | Acrylonitrile based fibres and their use in the production of oxidized or flame resistant fibres | |
| US3993719A (en) | Process for producing carbon fibers | |
| US3838562A (en) | Acrylonitrile yarn | |
| EP0378381A2 (en) | Metal-loaded carbon fibres | |
| US5413858A (en) | Acrylic fiber and process for production thereof | |
| US4869856A (en) | Method for producing carbon fibers from acrylonitrile fiber strands | |
| US5281477A (en) | Carbon fibers having high tenacity and high modulus of elasticity and process for producing the same | |
| CN115584573A (en) | T700-grade wet large-tow carbon fiber and preparation method and application thereof | |
| CN112708969B (en) | Preparation method of polyacrylonitrile pre-oxidized fiber | |
| US4237109A (en) | Process for producing carbon fabric | |
| JP3562115B2 (en) | Carbon fiber precursor acrylic yarn package and method for winding carbon fiber precursor acrylic yarn | |
| JP2002003081A (en) | Carbon fiber precursor acrylic thick filament yarn package and its manufacturing method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |