CA2089737A1 - Methods for synthesizing pulps and short fibers containing polybenzazole polymers - Google Patents
Methods for synthesizing pulps and short fibers containing polybenzazole polymersInfo
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- CA2089737A1 CA2089737A1 CA002089737A CA2089737A CA2089737A1 CA 2089737 A1 CA2089737 A1 CA 2089737A1 CA 002089737 A CA002089737 A CA 002089737A CA 2089737 A CA2089737 A CA 2089737A CA 2089737 A1 CA2089737 A1 CA 2089737A1
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- average
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- polybenzoxazole
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- 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
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/74—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polycondensates of cyclic compounds, e.g. polyimides, polybenzimidazoles
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- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Artificial Filaments (AREA)
- Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
- Paper (AREA)
Abstract
Pulps and short fibers containing polybenzoxazole and/or polybenzothiazole or copolymers thereof can be synthesized by freezing the wet fiber straight from the coagulation bath without drying, and chopping or grinding the frozen fiber to the desired size and degree of fibrillation.
Description
20~737 j W092/05300 PCT/US91/0599~
_ 1 _ METHODS FOR SYNTHESIZING PULPS AND SHORT FIBERS
CONTAINING POLYBENZAZOLE POLYMERS
This invention relates to polybenzoxazole and polybenzothiazole fibers.
Polybenzoxazole ~nd polybenzothiazole polymers are known polymers which are noted for their high tensile strength and modulus. The polymers, methods to syntheqize them and methods to ~pin them into fibers are de~cribed in detail in numerous references, such as the following: Wolfe et al., Liauid_CrYstalline Polymer Com~ositions. Process and Products, U.S. Patent 4,703,103 (October 27, 1987); Wolfe et al., Liquid Crvstalline PolYmer Compositions2 Process and Products, U.S. Patent 4,533,692 (Auguqt 6, 1985); ~olfe et al., Liquid Crvi~talline PolY(2.6-Benzothiazole) Compositions2 Proces~ and Products, U.S. Patent 4,533,724 (August 6~
1985); Wolfe, Liquid Crystalline PolYmer Com~ositions, Process and Products, U.S. Patent 4,533,693 (August 6, 1985); Evers, Thermoxadativelv Stable Articulated D-Benzobisoxazole and ~-~enzobisthiazole Polvmers, U.S.
Patent 4,359,567 (November 16, 1982) t Tsai et al., Method for Makin~ Heterocvclic Block Co~olymer, U.S.
Patent 4,578,432 (March 25, 1986); 11 Ency. Poly. Sci.
208~7~7 W092/05300 PCTIUS91/05~5 & Eng., Polvbenzothiazoles and Polvbenzoxazoles, 601 (J. Niley & Sons 1988) and W.W. Adams et al., The Materials Science and En~ineerin~ of Ri~id-Rod Polvmers (Material~ Re~earch Society 1989).
It i~ kno~ that the polymers can be made into fibers and films which are useful in composites and laminates. It wo~ld be useful to make other forms of ~haped articles cc-.taining polybenzazole polymer that are useful for other purposes.
A process of (a) spinning a dope fiber from a spinnable dope containing a polybenzoxazole or polybenzothiazole polymer or copolymer and a solvent acid and (b) coagulating the dope fiber in a freezable liquid that is not a ~olvent for the polymer or copolymer to form a coagulated fiber; characterized in that the process further comprises the steps of:
1) freezing the coagulated fiber which contains the polymer or copolymer and the freezable non-solvent liquid;
_ 1 _ METHODS FOR SYNTHESIZING PULPS AND SHORT FIBERS
CONTAINING POLYBENZAZOLE POLYMERS
This invention relates to polybenzoxazole and polybenzothiazole fibers.
Polybenzoxazole ~nd polybenzothiazole polymers are known polymers which are noted for their high tensile strength and modulus. The polymers, methods to syntheqize them and methods to ~pin them into fibers are de~cribed in detail in numerous references, such as the following: Wolfe et al., Liauid_CrYstalline Polymer Com~ositions. Process and Products, U.S. Patent 4,703,103 (October 27, 1987); Wolfe et al., Liquid Crvstalline PolYmer Compositions2 Process and Products, U.S. Patent 4,533,692 (Auguqt 6, 1985); ~olfe et al., Liquid Crvi~talline PolY(2.6-Benzothiazole) Compositions2 Proces~ and Products, U.S. Patent 4,533,724 (August 6~
1985); Wolfe, Liquid Crystalline PolYmer Com~ositions, Process and Products, U.S. Patent 4,533,693 (August 6, 1985); Evers, Thermoxadativelv Stable Articulated D-Benzobisoxazole and ~-~enzobisthiazole Polvmers, U.S.
Patent 4,359,567 (November 16, 1982) t Tsai et al., Method for Makin~ Heterocvclic Block Co~olymer, U.S.
Patent 4,578,432 (March 25, 1986); 11 Ency. Poly. Sci.
208~7~7 W092/05300 PCTIUS91/05~5 & Eng., Polvbenzothiazoles and Polvbenzoxazoles, 601 (J. Niley & Sons 1988) and W.W. Adams et al., The Materials Science and En~ineerin~ of Ri~id-Rod Polvmers (Material~ Re~earch Society 1989).
It i~ kno~ that the polymers can be made into fibers and films which are useful in composites and laminates. It wo~ld be useful to make other forms of ~haped articles cc-.taining polybenzazole polymer that are useful for other purposes.
A process of (a) spinning a dope fiber from a spinnable dope containing a polybenzoxazole or polybenzothiazole polymer or copolymer and a solvent acid and (b) coagulating the dope fiber in a freezable liquid that is not a ~olvent for the polymer or copolymer to form a coagulated fiber; characterized in that the process further comprises the steps of:
1) freezing the coagulated fiber which contains the polymer or copolymer and the freezable non-solvent liquid;
2) mechanically reducing the frozen fiber to a chosen average length and level of fibrillation; and 3) warming the frozen fibers to aitemperature at which they can be used or dried, such that a cut fiber or pulp containing the polybenzoxazole or polybenzothiazole polymer or 3 copolymer is formed.
A second aspect of the present invention is a pulp containing polybenzoxazole or polybenzothiazole or a copolymer thereof having an average fibrillar length .
.
. . .~ . .
2~9737 W092/05300 PCT/US91/05~5 of at most about l/2 inch and an average fibrillar diameter of at most 10 ~m.
A third aspect of the present invention i~ a short fiber, containing polybenzoxazole or polybenzo-thiazole or a copolymer thereof, that has an averagefiber length of no more than about 1/2 inch and is e~sentially unfibrillated, except at the ends.
The process of the present invention can be u~ed to make short fibers and pulps of the present invention, which are useful in composites, papers and abrasion resistant materials.
The present invention uses fibers that contain polybenzoxazole (PBO) or polybenzothiazole (PBT) or copolymers thereof. PB0, PBT and random, sequential and block copolymers of PBO and P8T are described in references such as Wolfe et al., Liquid Crvstalline Polvmer ComDositions. Process and Products, U.S. Patent 4,703,103 (October 27, 1987); Wolfe et al., Liauid CrYstalline Polvmer ComDoqitions. Process and Products, U.S. Patent 4,533,692 (August 6, 1985); Wolfe et al., Liauid Crvstalline Polv(2.6-Benzothiazole) comPo~ition Process and Products, U.S. Patent 4,533,724 (August 6, 1985); Wolfe, Liauid Crvstalline Polvmer ComDositions, Process and Product~, U.S. Patent 4,533,693 (August 6, 1985); Evers, ThermoxadativelY Stable Articulated D-Benzobisoxazole and D-Benzobisthiazole Polvmers, U.S.
3 Patent 4,359,567 (November 16,.1982); Tsai et al., - Method for Makin~ Heterocvclic 81Ock CoDolvmer, U.S.
Patent 4,578,432 (March 25, 1986); 11 Ency. Poly. Sci.
& Eng., Polvbenzothiazoles and Polvbenzoxaæoles, 601 (J. Wiley ~ Sons 1988) and W.W. Adams et al., The . ; ' ,~ ' , :
. " .` : .
2~897~7 W O 92/05300 PC~r/US91/05995 Materials Science and En~ineerin~,of Ri~id-Rod Polvmers (Materials Research Society 1989).
The polymer may contain AB-mer units, as represented in Formula 1(a), and/or AA/BB-mer units, a~
repreqented in Formula l(b) o 4 < z~
l(a) AB
~ / ~ Ar1 ~ ~ DX
1(b) AA/BB
' wherein: , Each Ar repre~ents an aromatic group. The aromatic group may be heterocyclic, quch as a pyridinylene group, but it i~ preferably carbocyclio. The aromatic group may be a fused or unfu~ed polycyclic qyqtem, but is preferably a 3 qingle six-membered ring. Size is not critical, but the aromatic group preferably contain~ no more than about 18 carbon atom~, more preferably no more than about 12 carbon atomq and most preferably no more than about 6 oarbon atoms. Ex-mpleq of suitable .
,... , .. ., -~
: :. , - . . - .
.
.
W092/05300 2 ~ 3 7 PCT/US91/05995 aromatic groups include phenylene moieties, tolylene moieties, biphenylene moieties and bis-phenylene ether moieties.
Each Z is independently an oxygen or a sulfur atom.
Each DM is independently a bond or a divalent organic moiety that does not interfere with the synthesis, fabrication or use of the polymer. The divalent organic moiety may contain an aliphatic group, which preferably has no more than about 12 carbon atoms, but the divalent organic moiety is preferably an aromatic group (Ar) as previously descrlbed.
The nitrogen atom and the Z moiety in each azole ring are bonded to adjacent carbon atoms in the aromatic group, such that a five-membered azole ring fused with the aromatic group is formed.
The azole rings in AA~BB-mer units may be in cis- or tran~-position with respect to each other, as illustrated in 11 Ency. Poly. Sci. & Eng., suora, at 602.
The polymer preferably consists essentially of either AB-PBZ mer units or AA/BB-PBZ mer units, and more preferably consists essentially of AA/8B-PBZ mer units.
The polybenzazole polymer may be rigid rod, semi-rigid rod or flexible coil. It i~ preferably rigid rod in the case of an AA/B8-PBZ polymer or semirigid in the case of an AB-PBZ polymer. Azole ringQ within the polymer are 3 preferably oxazole rings (Z = 0). Preferred mer unitq are illustrated in Formulae 2 (a)-(e).
... . .
"
WO 92/05300 2 0 8 9 7 r~ ~ PCI'/US91/05995 ~/
~ (b) t~o ~N >{~
(c) ~5 ~N >{~3~
(d) ~ ~_ , and ,,~ N~_ 2~97~7 W092/OS3~0 PCT/US91/05~5 Each polymer preferably contains on average at least about 25 mer units, more preferably at least about 50 mer units and most preferably at least about 100 mer units.
The polymer may also be a random, sequential or block copolymer containing PBO or PBT mer units and mer units of other polymers, such as polyamide, polyimide, polyquinoxaline, polyquinoline or poly(aromatic ether ketone or sulfone) such copolymers are described in Harris et al., Copolymers Containing Polybenzoxazole, Polybenzothiazole and Polybenzimidazole Moieties, International Application No. PCT/US89/04464 (filed October 6, 1989), International Publication No.
WO gO/03995 (published April 19, 1990).
The polymers are spun into fibers from spinnable dopes containing polymer dissolved in.a solvent acid, which is preferably polyphosphoric acid and/or.methanesulfonic acid. The dope should contain a ~ufficient amount of fiber to be spinnable to form fibers. The optimum concentration may vary widely depending upon the polymer in the dope and its average . molecular weight. In most ca-~es, the dope preferably contains at least about 2 percent polymer and more preferably at least about 4 percent polymer.
When the dope contains a rigid rod polybenzoxazole or polybenzothiazole having an intrinsic 3 viscosity of at least 20 dL/g at about 25C in methanesul~onic acid (preferably saturated with methane-sulfonic acid anhydride), the concentration of polymer in the dope is highly preferably at least about 10 weight percent, more highly preferably at least about 12 .
, ~' ' ' . ' ' ' W092/05300 2 ~ 8 9 7 3 7 PCT/US91/05~5 weight percent and mo~t preferably at least about 15 weight percent. When the dope contains a rigid rod polybenzoxazole or polybenzothiazole having an intrin~ic viqc03ity in methane~ulfonic acid of at least 20 dL/g, the maximum c,oncentration of polymer in the dope i limited primarily by practical considerations, such as solubility and viscosity. The concentration is ordinarily less than about 20 percent and preferably no more than about 17 percent.
The dope is spun to form a fiber by a dry jet--wet spinning process. Such processes are described in Chenevey et al, "Formation and Properties of Fiber and Film from PBZT," The Materials Science and En~ineerin~
of Ri~id-Rod Pol~mers 245 (Materials Research Society 1989); and Ledbetter et al., "An Integrated Laboratory Proces~ for Preparing Rigid Rod Fibers from Monomers,"
The Materials Science and EnRineerin~ of Ri~id-Rod Polvmers 253 ~Materials Research Society 1989). The spun and drawn dope fiber i9 coagulated in a freezable liquid which dilutes the solvent acid and is a non-solvent for the polymer. The freezable non-solvent liquid may be organic, but it is preferably aqueous.
Aqueou~ coagulant~ may be basic or mildly acidic, but are preferably about neutral, at lea~t at the commencement of coagulation. The most preferred freezable non-~olvent liquid is water.
It is important that the non-solvent u~ed for 3 coagulation be a freezable liquid that is suitable to freeze with the fibers for the next ~tep of the process.
The coagulated fiber has a relatively open structure containing the coagulant liquid. Once the fiber has been dried, it ha~ very little water regain and can not .
I W092/05300 2 ~ 8 ~ 7 3 7 PCT/US91/05~5 _g_ be effectively rewetted, so that grinding of a fiber which has been dried and rewetted is much les~
effective. From the stand point of both convenience and effectivenes~, it i~ important to keep the coagulated fiber wet and free7e it with the coagulating non-solvent without drying.
The wet fiber suitable for freezing contains the polymer or copolymer and the freezable liquid, as previously described. The weight ratio of freezable liquid to polymer is preferably at least about 10:90 and more preferably at least about 50:50. It ls preferably at most about 95:5.
The wet fiber is frozen to a temperature at which it becomes brittle. For the purposes of this application, the term "freezing" refers broadly to any solidification by reduction in temperature, without regard to whether a crystalline structure or a glassy solid is formed. For fibers containing aqueous liquid, the temperature is preferably le~s than 0C, more preferably at most about -100~C and most preferably at most about -190C. A convenient temperature iq at about liquid nitrogen temperatures.
Once frozen, the fiber is mechanically reduced to a de~ired length and degree of fibrillation, such as by grinding, crushing, tearing, cutting and/or chopping.
The preferred techniques vary depending upon whether 3 short ~ber~ or pulps are desired. To obtain a pulp, it is preferred to grind, tear or crush the fiber, so that extensive fibrillation occurs. Cryogenic grinding equip~ent i~ known and described in numerous references, such a~ U.S. Patents 2,347,464; 3,480,456; 3,921,874;
W092/05300 2 ~ (~ 9 7 3 7 PC~/US91/05~5 4,846,408 and 4,884,753. To obtain a short fiber, it is preferred to scisqor, chop or otherwise cut the fiber by a mean~ ~uch that little or no fibrillation occurs.
The short fiber or pulp may be returned to warmer temperatures, dried and used, for instance by impregnating with a matrix resin and curing to provide a composite.
The length of short fibers and fibrils within pulps is preferably no more than about l/2 inoh, more preferably no more than about 1/~ inch and most prefer-ably no more than about 1/8 inch. Pulps are preferably highly fibrillated. They preferably have an average fibrillar diameter of no more than lO ym, more prefer-ably no more than about 5 ~m and most preferably of nomore than 1 ~m. Short fiber~ preferably have a diameter about the ~ame as that of the original fiber. Their average diameter is preferably more than lO ~m and more preferably at least about 15 ~m. Segments of the short fiber may be partially fibrillated, but the short fiber i~ preferably not sub~tantially fibrillated and most preferably essentially unfibrillated, except at the end Q -The short fibers and pulp~ of the pre~entinvention are preferably sub tantially uniform. When the average length or width of a pulp or short fiber i~
limited as previously de~cribed, then preferably no more 3 than about 20 percent of the ~hort fibers or pulp fall out~ide that limit, more preferably no more than about 10 percent fall outside that limit, and mo~t preferably no more than about 5 percent fall outside that limit.
Among pulps, preferably no more than about 20 percent of .
.. : .
~~ W092/05300 2 0 ~ ~ 7 3 ~ PCT/US91/05g95 the pulp i~ unfibrillated, more preferably no more than about 10 percent, and most preferably no more than about 5 percent. Among short fiber~, preferably no more than about 20 percent of the fiber is fibrillated, more preferably no more than about 10 percent, and most preferably no more than about 5 percent.
The process and resulting fibers and pulps o~
the present invention have several advantages over processes and resulting pulp~ from ~imply chopping or grinding a dried fiber. Dried fibers are very difficult to cut or fibrillate. Therefore, attempts to cut them cause excessive wear on grinding and cutting equip~ent and ordinarily yield to very inconsistent quality cut - fibers or pulp, containing irregular lengths of fiber, ~ome of which is highly fibrillated and some of which is essentially unfibrillated. On the other hand, frozen wet fibers are more brittle. They cut, grind, crush and tear more easily without excessive wear to the equipment, and the resulting short fiber or pulp product is much more uniform. The degree of fibrillation can easily be ~elected from uniformly highly fibrillated to essentially unfibrillated or degrees of fibrillation inbetween by proper selection of the cutting or grinding or other technique.
The short fibers may be used in random fiber compo-~ite-~, as described in U.S. Patents 4,426,470 and 4,5~0,131. Pulps may be used in non-woven sheet~ and 3 abrasive materials, as described in U.S. Patent 4,324,706.
Illustrative ExamDle~
- - . .
.,' - . , - - .
W O 92/05300 2 0 8 9 7 3 7 - PC~r/US91/05995 The following examples are given to illustrate the invention and should not be interpreted aq limiting the Specification or the Claims. Unless stated otherwise, all parts and percentages are given by weight.
Example 1 - Preparation of PB0 Pulp A dope is obtained containing 87 percent polyphosphoric acid and 13 percent cis-polybenzoxazole (as illustrated in Formula 2(a)) having an inherent viscosity of about 34 dLtg at 25C and 0.05 g/dl concentration in methanesulfonic acid saturated with methanequlfonic acid anhydride. The dope is spun at 150C from a 10 mil 35 hole spindle with a spin-draw ratio of about 30 into a coagulation bath contain_ng water. The fibers are kept immersed in water for about 24 hourq and then scissored to lengths of l to 2 nches while wet. The wet fibers are immersed in liquid nitrogen for about 1 minute. The frozen fiber is ground in a Retsch centrifugal grinder at 10,000 rpm using a ~.0 mesh screen (having openings of 1.8mm x 1.2mm). A
small amount of liquid nitrogen is fed into the grinding chamber before and during grinding to keep the grinding chamber at an appropriate temperature. The ground fibers are warmed to room temperature and dried. They are pulps with a fibrillar diameter of about 1-5~m.
Examole 2 - Preparation of Random Short PB0 Fibers A dope as described in Example 1 is spun at 150C through a 3 mil spin die at a s?in-draw ratio of 20 into a coagulation bath. The fibers are washed for 24 hour3 in running water and then kept under water until used further. The wet fibers are scissored into .
~ W092/05300 2 0 ~ 9 ~ ~ 7 PCT/US91/05~5 segments about 2 inches long and mixed with 50cc of water. The mixture of water and fiber is frozen with liquid nitrogen and crushed with a hammer, stopping periodically to refreeze with liquid nitrogen. The cru~hed frozen product is heated to room temperature and dried. It is made up of short partially fibrlllated fiber~ having a length of about 3~16 inch.
ComDarative ExamPle A
A fiber iq spun as described in Example 1. The spun fiber is heat treated at 500C under tension and then dried in air for 7 days.
Sample A-1 is ground as described in Example 1 without further processing. The fiber neither breaks nor fibrillates.
Sample A-2 is immersed in liquid nitrogen for one minute, then ground as described in Example 1.
The fiber does not break but fibrillates a little.
Sample A-3 is immersed in water for 2 hours and immersed in liquid nitrogen for two minutes, then ground as described in Example 1. The resulting fiber is broken into qectionq with irregular lengthq and extensively fibrillated.
A second aspect of the present invention is a pulp containing polybenzoxazole or polybenzothiazole or a copolymer thereof having an average fibrillar length .
.
. . .~ . .
2~9737 W092/05300 PCT/US91/05~5 of at most about l/2 inch and an average fibrillar diameter of at most 10 ~m.
A third aspect of the present invention i~ a short fiber, containing polybenzoxazole or polybenzo-thiazole or a copolymer thereof, that has an averagefiber length of no more than about 1/2 inch and is e~sentially unfibrillated, except at the ends.
The process of the present invention can be u~ed to make short fibers and pulps of the present invention, which are useful in composites, papers and abrasion resistant materials.
The present invention uses fibers that contain polybenzoxazole (PBO) or polybenzothiazole (PBT) or copolymers thereof. PB0, PBT and random, sequential and block copolymers of PBO and P8T are described in references such as Wolfe et al., Liquid Crvstalline Polvmer ComDositions. Process and Products, U.S. Patent 4,703,103 (October 27, 1987); Wolfe et al., Liauid CrYstalline Polvmer ComDoqitions. Process and Products, U.S. Patent 4,533,692 (August 6, 1985); Wolfe et al., Liauid Crvstalline Polv(2.6-Benzothiazole) comPo~ition Process and Products, U.S. Patent 4,533,724 (August 6, 1985); Wolfe, Liauid Crvstalline Polvmer ComDositions, Process and Product~, U.S. Patent 4,533,693 (August 6, 1985); Evers, ThermoxadativelY Stable Articulated D-Benzobisoxazole and D-Benzobisthiazole Polvmers, U.S.
3 Patent 4,359,567 (November 16,.1982); Tsai et al., - Method for Makin~ Heterocvclic 81Ock CoDolvmer, U.S.
Patent 4,578,432 (March 25, 1986); 11 Ency. Poly. Sci.
& Eng., Polvbenzothiazoles and Polvbenzoxaæoles, 601 (J. Wiley ~ Sons 1988) and W.W. Adams et al., The . ; ' ,~ ' , :
. " .` : .
2~897~7 W O 92/05300 PC~r/US91/05995 Materials Science and En~ineerin~,of Ri~id-Rod Polvmers (Materials Research Society 1989).
The polymer may contain AB-mer units, as represented in Formula 1(a), and/or AA/BB-mer units, a~
repreqented in Formula l(b) o 4 < z~
l(a) AB
~ / ~ Ar1 ~ ~ DX
1(b) AA/BB
' wherein: , Each Ar repre~ents an aromatic group. The aromatic group may be heterocyclic, quch as a pyridinylene group, but it i~ preferably carbocyclio. The aromatic group may be a fused or unfu~ed polycyclic qyqtem, but is preferably a 3 qingle six-membered ring. Size is not critical, but the aromatic group preferably contain~ no more than about 18 carbon atom~, more preferably no more than about 12 carbon atomq and most preferably no more than about 6 oarbon atoms. Ex-mpleq of suitable .
,... , .. ., -~
: :. , - . . - .
.
.
W092/05300 2 ~ 3 7 PCT/US91/05995 aromatic groups include phenylene moieties, tolylene moieties, biphenylene moieties and bis-phenylene ether moieties.
Each Z is independently an oxygen or a sulfur atom.
Each DM is independently a bond or a divalent organic moiety that does not interfere with the synthesis, fabrication or use of the polymer. The divalent organic moiety may contain an aliphatic group, which preferably has no more than about 12 carbon atoms, but the divalent organic moiety is preferably an aromatic group (Ar) as previously descrlbed.
The nitrogen atom and the Z moiety in each azole ring are bonded to adjacent carbon atoms in the aromatic group, such that a five-membered azole ring fused with the aromatic group is formed.
The azole rings in AA~BB-mer units may be in cis- or tran~-position with respect to each other, as illustrated in 11 Ency. Poly. Sci. & Eng., suora, at 602.
The polymer preferably consists essentially of either AB-PBZ mer units or AA/BB-PBZ mer units, and more preferably consists essentially of AA/8B-PBZ mer units.
The polybenzazole polymer may be rigid rod, semi-rigid rod or flexible coil. It i~ preferably rigid rod in the case of an AA/B8-PBZ polymer or semirigid in the case of an AB-PBZ polymer. Azole ringQ within the polymer are 3 preferably oxazole rings (Z = 0). Preferred mer unitq are illustrated in Formulae 2 (a)-(e).
... . .
"
WO 92/05300 2 0 8 9 7 r~ ~ PCI'/US91/05995 ~/
~ (b) t~o ~N >{~
(c) ~5 ~N >{~3~
(d) ~ ~_ , and ,,~ N~_ 2~97~7 W092/OS3~0 PCT/US91/05~5 Each polymer preferably contains on average at least about 25 mer units, more preferably at least about 50 mer units and most preferably at least about 100 mer units.
The polymer may also be a random, sequential or block copolymer containing PBO or PBT mer units and mer units of other polymers, such as polyamide, polyimide, polyquinoxaline, polyquinoline or poly(aromatic ether ketone or sulfone) such copolymers are described in Harris et al., Copolymers Containing Polybenzoxazole, Polybenzothiazole and Polybenzimidazole Moieties, International Application No. PCT/US89/04464 (filed October 6, 1989), International Publication No.
WO gO/03995 (published April 19, 1990).
The polymers are spun into fibers from spinnable dopes containing polymer dissolved in.a solvent acid, which is preferably polyphosphoric acid and/or.methanesulfonic acid. The dope should contain a ~ufficient amount of fiber to be spinnable to form fibers. The optimum concentration may vary widely depending upon the polymer in the dope and its average . molecular weight. In most ca-~es, the dope preferably contains at least about 2 percent polymer and more preferably at least about 4 percent polymer.
When the dope contains a rigid rod polybenzoxazole or polybenzothiazole having an intrinsic 3 viscosity of at least 20 dL/g at about 25C in methanesul~onic acid (preferably saturated with methane-sulfonic acid anhydride), the concentration of polymer in the dope is highly preferably at least about 10 weight percent, more highly preferably at least about 12 .
, ~' ' ' . ' ' ' W092/05300 2 ~ 8 9 7 3 7 PCT/US91/05~5 weight percent and mo~t preferably at least about 15 weight percent. When the dope contains a rigid rod polybenzoxazole or polybenzothiazole having an intrin~ic viqc03ity in methane~ulfonic acid of at least 20 dL/g, the maximum c,oncentration of polymer in the dope i limited primarily by practical considerations, such as solubility and viscosity. The concentration is ordinarily less than about 20 percent and preferably no more than about 17 percent.
The dope is spun to form a fiber by a dry jet--wet spinning process. Such processes are described in Chenevey et al, "Formation and Properties of Fiber and Film from PBZT," The Materials Science and En~ineerin~
of Ri~id-Rod Pol~mers 245 (Materials Research Society 1989); and Ledbetter et al., "An Integrated Laboratory Proces~ for Preparing Rigid Rod Fibers from Monomers,"
The Materials Science and EnRineerin~ of Ri~id-Rod Polvmers 253 ~Materials Research Society 1989). The spun and drawn dope fiber i9 coagulated in a freezable liquid which dilutes the solvent acid and is a non-solvent for the polymer. The freezable non-solvent liquid may be organic, but it is preferably aqueous.
Aqueou~ coagulant~ may be basic or mildly acidic, but are preferably about neutral, at lea~t at the commencement of coagulation. The most preferred freezable non-~olvent liquid is water.
It is important that the non-solvent u~ed for 3 coagulation be a freezable liquid that is suitable to freeze with the fibers for the next ~tep of the process.
The coagulated fiber has a relatively open structure containing the coagulant liquid. Once the fiber has been dried, it ha~ very little water regain and can not .
I W092/05300 2 ~ 8 ~ 7 3 7 PCT/US91/05~5 _g_ be effectively rewetted, so that grinding of a fiber which has been dried and rewetted is much les~
effective. From the stand point of both convenience and effectivenes~, it i~ important to keep the coagulated fiber wet and free7e it with the coagulating non-solvent without drying.
The wet fiber suitable for freezing contains the polymer or copolymer and the freezable liquid, as previously described. The weight ratio of freezable liquid to polymer is preferably at least about 10:90 and more preferably at least about 50:50. It ls preferably at most about 95:5.
The wet fiber is frozen to a temperature at which it becomes brittle. For the purposes of this application, the term "freezing" refers broadly to any solidification by reduction in temperature, without regard to whether a crystalline structure or a glassy solid is formed. For fibers containing aqueous liquid, the temperature is preferably le~s than 0C, more preferably at most about -100~C and most preferably at most about -190C. A convenient temperature iq at about liquid nitrogen temperatures.
Once frozen, the fiber is mechanically reduced to a de~ired length and degree of fibrillation, such as by grinding, crushing, tearing, cutting and/or chopping.
The preferred techniques vary depending upon whether 3 short ~ber~ or pulps are desired. To obtain a pulp, it is preferred to grind, tear or crush the fiber, so that extensive fibrillation occurs. Cryogenic grinding equip~ent i~ known and described in numerous references, such a~ U.S. Patents 2,347,464; 3,480,456; 3,921,874;
W092/05300 2 ~ (~ 9 7 3 7 PC~/US91/05~5 4,846,408 and 4,884,753. To obtain a short fiber, it is preferred to scisqor, chop or otherwise cut the fiber by a mean~ ~uch that little or no fibrillation occurs.
The short fiber or pulp may be returned to warmer temperatures, dried and used, for instance by impregnating with a matrix resin and curing to provide a composite.
The length of short fibers and fibrils within pulps is preferably no more than about l/2 inoh, more preferably no more than about 1/~ inch and most prefer-ably no more than about 1/8 inch. Pulps are preferably highly fibrillated. They preferably have an average fibrillar diameter of no more than lO ym, more prefer-ably no more than about 5 ~m and most preferably of nomore than 1 ~m. Short fiber~ preferably have a diameter about the ~ame as that of the original fiber. Their average diameter is preferably more than lO ~m and more preferably at least about 15 ~m. Segments of the short fiber may be partially fibrillated, but the short fiber i~ preferably not sub~tantially fibrillated and most preferably essentially unfibrillated, except at the end Q -The short fibers and pulp~ of the pre~entinvention are preferably sub tantially uniform. When the average length or width of a pulp or short fiber i~
limited as previously de~cribed, then preferably no more 3 than about 20 percent of the ~hort fibers or pulp fall out~ide that limit, more preferably no more than about 10 percent fall outside that limit, and mo~t preferably no more than about 5 percent fall outside that limit.
Among pulps, preferably no more than about 20 percent of .
.. : .
~~ W092/05300 2 0 ~ ~ 7 3 ~ PCT/US91/05g95 the pulp i~ unfibrillated, more preferably no more than about 10 percent, and most preferably no more than about 5 percent. Among short fiber~, preferably no more than about 20 percent of the fiber is fibrillated, more preferably no more than about 10 percent, and most preferably no more than about 5 percent.
The process and resulting fibers and pulps o~
the present invention have several advantages over processes and resulting pulp~ from ~imply chopping or grinding a dried fiber. Dried fibers are very difficult to cut or fibrillate. Therefore, attempts to cut them cause excessive wear on grinding and cutting equip~ent and ordinarily yield to very inconsistent quality cut - fibers or pulp, containing irregular lengths of fiber, ~ome of which is highly fibrillated and some of which is essentially unfibrillated. On the other hand, frozen wet fibers are more brittle. They cut, grind, crush and tear more easily without excessive wear to the equipment, and the resulting short fiber or pulp product is much more uniform. The degree of fibrillation can easily be ~elected from uniformly highly fibrillated to essentially unfibrillated or degrees of fibrillation inbetween by proper selection of the cutting or grinding or other technique.
The short fibers may be used in random fiber compo-~ite-~, as described in U.S. Patents 4,426,470 and 4,5~0,131. Pulps may be used in non-woven sheet~ and 3 abrasive materials, as described in U.S. Patent 4,324,706.
Illustrative ExamDle~
- - . .
.,' - . , - - .
W O 92/05300 2 0 8 9 7 3 7 - PC~r/US91/05995 The following examples are given to illustrate the invention and should not be interpreted aq limiting the Specification or the Claims. Unless stated otherwise, all parts and percentages are given by weight.
Example 1 - Preparation of PB0 Pulp A dope is obtained containing 87 percent polyphosphoric acid and 13 percent cis-polybenzoxazole (as illustrated in Formula 2(a)) having an inherent viscosity of about 34 dLtg at 25C and 0.05 g/dl concentration in methanesulfonic acid saturated with methanequlfonic acid anhydride. The dope is spun at 150C from a 10 mil 35 hole spindle with a spin-draw ratio of about 30 into a coagulation bath contain_ng water. The fibers are kept immersed in water for about 24 hourq and then scissored to lengths of l to 2 nches while wet. The wet fibers are immersed in liquid nitrogen for about 1 minute. The frozen fiber is ground in a Retsch centrifugal grinder at 10,000 rpm using a ~.0 mesh screen (having openings of 1.8mm x 1.2mm). A
small amount of liquid nitrogen is fed into the grinding chamber before and during grinding to keep the grinding chamber at an appropriate temperature. The ground fibers are warmed to room temperature and dried. They are pulps with a fibrillar diameter of about 1-5~m.
Examole 2 - Preparation of Random Short PB0 Fibers A dope as described in Example 1 is spun at 150C through a 3 mil spin die at a s?in-draw ratio of 20 into a coagulation bath. The fibers are washed for 24 hour3 in running water and then kept under water until used further. The wet fibers are scissored into .
~ W092/05300 2 0 ~ 9 ~ ~ 7 PCT/US91/05~5 segments about 2 inches long and mixed with 50cc of water. The mixture of water and fiber is frozen with liquid nitrogen and crushed with a hammer, stopping periodically to refreeze with liquid nitrogen. The cru~hed frozen product is heated to room temperature and dried. It is made up of short partially fibrlllated fiber~ having a length of about 3~16 inch.
ComDarative ExamPle A
A fiber iq spun as described in Example 1. The spun fiber is heat treated at 500C under tension and then dried in air for 7 days.
Sample A-1 is ground as described in Example 1 without further processing. The fiber neither breaks nor fibrillates.
Sample A-2 is immersed in liquid nitrogen for one minute, then ground as described in Example 1.
The fiber does not break but fibrillates a little.
Sample A-3 is immersed in water for 2 hours and immersed in liquid nitrogen for two minutes, then ground as described in Example 1. The resulting fiber is broken into qectionq with irregular lengthq and extensively fibrillated.
Claims (10)
1) freezing the coagulated fiber which contains the polymer or copolymer and the freezable non-solvent liquid;
2) mechanically reducing the frozen fiber to a chosen average length and level of fibrillation; and 3) warming the frozen fibers to a temperature at which they can be used or dried, such that a cut fiber or pulp containing the polybenzoxazole or polybenzothiazole polymer or copolymer is formed.
2) mechanically reducing the frozen fiber to a chosen average length and level of fibrillation; and 3) warming the frozen fibers to a temperature at which they can be used or dried, such that a cut fiber or pulp containing the polybenzoxazole or polybenzothiazole polymer or copolymer is formed.
2. The process as described in Claim 1 wherein the freezable non-solvent liquid contains water.
3. The process as described in any one of the previous claims wherein the weight ratio of freezable non-solvent liquid to polymer in the coagulated fiber is at least 10:90 and at most 95:5.
4. The process as describes in any one of the previous claims wherein coagulated fiber containing non--solvent liquid is frozen at a temperature of no higher than -100°C.
5. The process as described in any one of Claims 1-4 wherein the frozen fiber is converted to a short fiber having an average length of no greater than 1/2 inch and an average diameter of at least 10 µm.
6. The process as described in any one of Claims 1-4 wherein the frozen fiber is converted to a pulp having an average fibrillar diameter of no greater than 10 µm and an average fibrillar length of no greater than about 1/2 inch.
7. A pulp containing polybenzoxazole or polybenzothiazole or a copolymer thereof which has an average fibrillar diameter of no greater than about 10 µm and an average fibrillar length of no greater than about 1/2 inch.
8. The pulp as described in Claim 7 which has an average fibrillar diameter of no greater than about 1 µm.
9. A short fiber, containing polybenzoxazole or polybenzothiazole or a copolymer thereof, that has an average fiber length of no more than about 1/2 inch and is essentially unfibrillated, except at the ends.
10. The invention as described in any one of Claims 1-9 wherein the polybenzoxazole or polybenzothiazole polymer or copolymer is made up of repeating units that are represented by one or more of the Formulae:
(a) , , (b) , (C) (d) , and (e) ,
(a) , , (b) , (C) (d) , and (e) ,
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/584,813 | 1990-09-19 | ||
| US07/584,813 US5164131A (en) | 1990-09-19 | 1990-09-19 | Methods for synthesizing pulps and short fibers containing polybenzazole polymers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2089737A1 true CA2089737A1 (en) | 1992-03-20 |
Family
ID=24338899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002089737A Abandoned CA2089737A1 (en) | 1990-09-19 | 1991-08-22 | Methods for synthesizing pulps and short fibers containing polybenzazole polymers |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US5164131A (en) |
| EP (1) | EP0549609A4 (en) |
| JP (1) | JP3047469B2 (en) |
| KR (1) | KR100203964B1 (en) |
| CN (1) | CN1040894C (en) |
| AU (1) | AU8428891A (en) |
| CA (1) | CA2089737A1 (en) |
| IE (1) | IE913284A1 (en) |
| IL (1) | IL99514A0 (en) |
| WO (1) | WO1992005300A1 (en) |
| ZA (1) | ZA917433B (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5292470A (en) * | 1993-01-05 | 1994-03-08 | The Dow Chemical Company | Convective leaching of polybenzazole films |
| US5292469A (en) * | 1993-01-05 | 1994-03-08 | The Dow Chemical Company | Process for coagulation, washing and leaching of shaped polybenzazole articles |
| US5527609A (en) * | 1994-04-20 | 1996-06-18 | Toyo Boseki Kabushiki Kaisha | Crimped polybenzazole staple fiber and manufacture thereof |
| JP3541966B2 (en) * | 1994-08-03 | 2004-07-14 | 東洋紡績株式会社 | Method for producing nonwoven fabric of polybenzazole fiber |
| US5756040A (en) * | 1994-08-03 | 1998-05-26 | Toyobo Co., Ltd. | Process of making polybenzazole nonwoven fabric |
| US5585052A (en) * | 1994-08-10 | 1996-12-17 | The Dow Chemical Company | Process for the preparation of polybenzazole staple fiber |
| US5756031A (en) * | 1994-08-12 | 1998-05-26 | Toyobo Co., Ltd. | Process for preparing polybenzazole filaments and fiber |
| DE19509410A1 (en) * | 1995-03-15 | 1996-09-19 | Merck Patent Gmbh | Electro-optical liquid crystal display |
| AT405847B (en) * | 1996-09-16 | 1999-11-25 | Zellform Ges M B H | METHOD FOR PRODUCING BLANKS OR SHAPED BODIES FROM CELLULOSE FIBERS |
| CN1098392C (en) * | 1997-06-10 | 2003-01-08 | 帝人株式会社 | Heat resistant fiber paper |
| US6485828B2 (en) | 2000-12-01 | 2002-11-26 | Oji Paper Co., Ltd. | Flat synthetic fiber, method for preparing the same and non-woven fabric prepared using the same |
| US7744724B2 (en) * | 2005-12-21 | 2010-06-29 | E.I. Du Pont De Nemours And Company | Polyareneazole/thermoplastic pulp and methods of making same |
| JP2007177113A (en) * | 2005-12-28 | 2007-07-12 | Teijin Techno Products Ltd | Organic macromolecular polymer fine particle and method for producing the same |
| CN106067970B (en) * | 2009-05-28 | 2019-01-22 | 皇家飞利浦电子股份有限公司 | Auto-stereoscopic display device |
| JP6424518B2 (en) * | 2014-09-01 | 2018-11-21 | 東洋紡株式会社 | Polybenzazole pulp |
| US20170306563A1 (en) | 2016-04-20 | 2017-10-26 | Clarcor Inc. | Fine fiber pulp from spinning and wet laid filter media |
| US10676614B2 (en) | 2016-04-20 | 2020-06-09 | Clarcor Inc. | High molecular and low molecular weight fine fibers and TPU fine fibers |
| CN111621859A (en) * | 2019-02-27 | 2020-09-04 | 中蓝晨光化工有限公司 | Preparation method of polybenzazole short fiber |
Family Cites Families (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2347464A (en) * | 1939-12-08 | 1944-04-25 | Lehon Co | Method of pulverizing resinous and thermoplastic materials |
| NL295570A (en) * | 1962-07-20 | |||
| US3921874A (en) * | 1973-09-04 | 1975-11-25 | Raymond G Spain | Method of preparing short fibers of fine diameters |
| US4127625A (en) * | 1975-03-27 | 1978-11-28 | Daicel Ltd. | Process for preparing hollow fiber having selective gas permeability |
| US4278623A (en) * | 1977-01-11 | 1981-07-14 | Union Carbide Corporation | Ultra-fine fibers and method for making same |
| JPS56103270A (en) * | 1980-01-22 | 1981-08-18 | Teijin Ltd | Friction material |
| US4426470A (en) * | 1981-07-27 | 1984-01-17 | The Dow Chemical Company | Aqueous method of making reinforced composite material from latex, solid polymer and reinforcing material |
| US4359567A (en) * | 1981-10-02 | 1982-11-16 | The United States Of America As Represented By The Secretary Of The Air Force | Thermooxidatively stable articulated p-benzobisoxazole and p-benzobisthiazole polymers |
| US4533693A (en) * | 1982-09-17 | 1985-08-06 | Sri International | Liquid crystalline polymer compositions, process, and products |
| WO1984001161A1 (en) * | 1982-09-17 | 1984-03-29 | Stanford Res Inst Int | Liquid crystalline poly(2,6-benzothiazole) compositions, process and products |
| US4533692A (en) * | 1982-09-17 | 1985-08-06 | Sri International | Liquid crystalline polymer compositions, process, and products |
| US4703103A (en) * | 1984-03-16 | 1987-10-27 | Commtech International | Liquid crystalline polymer compositions, process and products |
| US4578432A (en) * | 1984-05-16 | 1986-03-25 | The United States Of America As Represented By The Secretary Of The Air Force | Method for making heterocyclic block copolymer |
| US4550131A (en) * | 1984-10-30 | 1985-10-29 | The Dow Chemical Company | Aqueous slurry process for preparing reinforced polymeric composites |
| US4836507A (en) * | 1987-08-10 | 1989-06-06 | E. I. Du Pont De Nemours And Company | Aramid staple and pulp prepared by spinning |
| US4846408A (en) * | 1988-01-21 | 1989-07-11 | Gentex Corporation | Method for making a friction material |
| DE3868515D1 (en) * | 1988-11-21 | 1992-03-26 | Okayama Jonan Denki K K | METHOD FOR POWDERING. |
| JPH03104921A (en) * | 1989-09-14 | 1991-05-01 | Mitsui Petrochem Ind Ltd | Production of fiber of polybenzothiazoles, polybenzoxazoles or polybenzimidazoles |
-
1990
- 1990-09-19 US US07/584,813 patent/US5164131A/en not_active Expired - Fee Related
-
1991
- 1991-08-22 WO PCT/US1991/005995 patent/WO1992005300A1/en not_active Application Discontinuation
- 1991-08-22 KR KR1019930700792A patent/KR100203964B1/en not_active IP Right Cessation
- 1991-08-22 CA CA002089737A patent/CA2089737A1/en not_active Abandoned
- 1991-08-22 JP JP3514552A patent/JP3047469B2/en not_active Expired - Fee Related
- 1991-08-22 EP EP19910915088 patent/EP0549609A4/en not_active Withdrawn
- 1991-08-22 AU AU84288/91A patent/AU8428891A/en not_active Abandoned
- 1991-09-17 IL IL99514A patent/IL99514A0/en unknown
- 1991-09-18 IE IE328491A patent/IE913284A1/en unknown
- 1991-09-18 ZA ZA917433A patent/ZA917433B/en unknown
- 1991-09-18 CN CN91109008A patent/CN1040894C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US5164131A (en) | 1992-11-17 |
| EP0549609A1 (en) | 1993-07-07 |
| IE913284A1 (en) | 1992-02-25 |
| KR930702565A (en) | 1993-09-09 |
| JP3047469B2 (en) | 2000-05-29 |
| CN1061227A (en) | 1992-05-20 |
| IL99514A0 (en) | 1992-08-18 |
| AU8428891A (en) | 1992-04-15 |
| EP0549609A4 (en) | 1993-09-15 |
| ZA917433B (en) | 1993-03-18 |
| WO1992005300A1 (en) | 1992-04-02 |
| KR100203964B1 (en) | 1999-06-15 |
| JPH06500830A (en) | 1994-01-27 |
| CN1040894C (en) | 1998-11-25 |
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