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US 5,028,372 AGranted
Method for producing para-aramid pulp
AssigneeE. I. Du Pont de Nemours and Company
InventorsRoland T. Brierre, Stephan C. De La Veaux, James E. Geary, Jr., Wesley Memeger, Jr., Michael L. Trancynger
Life of this patent
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Abstract
A method for producing para-aramid pulp includes forming a liquid, actively-polymerizing solution and subjecting the solution to orienting flow which produces an optically anisotropic liquid solution with polymer chains oriented in the direction of the flow. When the solution has a viscosity sufficient to maintain the orientation of the polymer chains, the solution is incubated until it gels. The gel is cut transversely at intervals and para-aramid pulp is isolated from the gel. Para-aramid pulp produced by the process can be used similarly to pulp produced from spun fiber.
Claims81
A method for producing para-aramid pulp comprising:
- forming a liquid, actively-polymerizing solution containing polymer chains of a para-aramid by contacting with agitation substantially stoichiometric amounts of aromatic diacid halide consisting essentially of a para-oriented aromatic diacid halide and aromatic diamine consisting essentially of a para-oriented aromatic diamine in a substantially anhydrous amide solvent system;
- extruding said liquid solution onto a conveyer, when the inherent viscosity of the para-aramid is between about 1 and about 4, through a die to subject the solution to a mean shear of less than about 100 sec.sup.-1 and to produce an elongated optically anisotropic liquid solution containing domains of polymer chains within which the polymer chains of para-aramid are substantially oriented in the direction of extrusion;
- incubating said anisotropic liquid solution on the conveyer for at least a duration sufficient for said anisotropic solution to become a gel, said incubating being initiated when said optically anisotropic liquid solution has a viscosity sufficient to generally maintain the orientation of said polymer chains in said anisotropic liquid solution until said liquid solution becomes a gel;
- cutting said gel with a guillotine-like cutter at selected intervals transversely with respect to the orientation of the polymer chains in said gel;
- and
- isolating para-aramid pulp from said gel.
3 more elements
A method for producing para-aramid pulp comprising:
- forming a liquid, actively-polymerizing solution containing polymer chains of poly(p-phenylene terephthalamide) by contacting with agitation generally stoichiometric amounts of terephthaloyl chloride and p-phenylene diamine in a substantially anhydrous amide solvent system containing N-methyl pyrrolidone and calcium chloride;
- extruding said liquid solution onto a conveyer, when the inherent viscosity of the para-aramid is between about 1 and about 4, through a die to subject the solution to a mean shear of less than about 100 sec.sup.-1 and to produce an elongated optically anisotropic liquid solution within which the polymer chains of poly(p-phenylene terephthalamide) are substantially oriented in the direction of extrusion;
- incubating said anisotropic liquid solution on the conveyer for at least a duration sufficient for said anisotropic solution to become a gel, said incubating being initiated when said optically anisotropic liquid solution has a viscosity sufficient to generally maintain the orientation of said polymer chains in said anisotropic liquid solution until said liquid solution becomes a gel;
- cutting said gel with a guillotine-like cutter at selected intervals transversely with respect to the orientation of the polymer chains in said gel;
- and
- isolating poly(p-phenylene terephthalamide) pulp from said gel.
3 more elements
A method for producing para-aramid pulp comprising:
- forming a liquid, actively-polymerizing solution containing polymer chains of a para-aramid by contacting with agitation substantially stoichiometric amounts of aromatic diacid halide and aromatic diamine in a substantially anhydrous amide solvent system, at least 80 mole percent of said aromatic diamine being p-phenylene diamine and at least 80 mole percent of said aromatic diacid halide being terephthaloyl halide;
- extruding said liquid solution onto a conveyer, when the inherent viscosity of the para-aramid is between about 1 and about 4, through a die to subject said solution to a mean shear of less than about 100 sec.sup.-1 and to produce an elongated optically anisotropic liquid solution mass containing domains of polymer chains within which the polymer chains of para-aramid are substantially oriented in the direction of flow;
- incubating said anisotropic liquid solution mass on the conveyer in a first incubation step to cause the polymerization to continue for at least a duration sufficient for said anisotropic solution to become a gel while conveying said mass away from said die at a velocity not less than the velocity of the mass issuing from said die, said first incubation step being initiated when said optically anisotropic liquid solution has a viscosity sufficient to generally maintain the orientation of said polymer chains in said anisotropic liquid solution until said liquid solution becomes a gel;
- cutting said gel with a guillotine-like cutter at selected intervals transversely with respect to the orientation of the polymer chains in said gel to produce discrete gel pieces;
- incubating said discrete gel pieces produced by cutting said gel in a second incubation step;
- and
- isolating para-aramid pulp from said gel pieces after said second incubation step.
4 more elements
A method for producing para-aramid pulp comprising:
- forming a liquid, actively-polymerizing solution containing polymer chains of a para-aramid by contacting with agitation substantially stoichiometric amounts of aromatic diacid halide consisting essentially of a para-oriented aromatic diacid halide and aromatic diamine consisting essentially of a para-oriented aromatic diamine in a substantially anhydrous amide solvent system;
- extruding said liquid solution, when the inherent viscosity of the para-aramid is between about 1 and about 4, through an elongational flow orientation apparatus having interior surfaces defining an elongational flow path to produce an elongated optically anisotropic liquid solution mass containing domains of polymer chains of para-aramid which are substantially oriented in the direction of extrusion;
- providing a layer of non-coagulating fluid on said interior surfaces of said elongational flow orientation apparatus during said extruding to decrease contact of said liquid solution with said interior surfaces;
- incubating said elongated anisotropic liquid solution mass for at least a duration sufficient for said anisotropic solution to become a gel;
- and
- isolating para-aramid pulp from said gel.
3 more elements
Dependencies are inferred from the claim text.