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
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/96—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from other synthetic polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/22—Polybenzoxazoles

Definitions

• This invention is directed to a novel process for making polybenzobisoxazole containing fibers. This is accomplished by first forming a non-polybenzobisoxazole fiber and converting repeat units of the fiber polymer to a polybenzobisoxazole.
• Fibers formed from rod-like polymers are commonly used in a variety of applications including ballistics, ropes and cables, and cut resistant apparel.
• Polybenzobisoxazole polymers provide excellent physical properties due to their rod-like structure. Fibers from rod-like polymers are typically formed by extruding a polymer solution through a spinneret. Due to the limited solubility of (cis- polybenzobisoxazole polymers) (c-PBO) such as poly(benzo[1 ,2 d: 5,4- d']bisoxazole-2,6-diyl-1 ,4-phenylene), fibers produced from such polymers are typically spun from strong mineral acids such as polyphosphoric acid (PPA). Residual polyphosphoric acid present in the fiber over time can cause the physical properties of the fiber to degrade.
• PPA polyphosphoric acid
• the invention relates to a method of making polybenzobisoxazole containing fiber by first producing an aromatic polyamide fiber and subsequently converting the aromatic polyamide fiber into a polybenzobisoxazole containing fiber.
• the initial step in the reaction procedure involves forming a solution of the polymer of Structure I which is as defined in the Summary of the Invention.
• Typical solvents in forming the solution include but are not limited to sulfuric acid, polyphosphoric acid, methane sulfonic acid, n- methylpyrrolidinone, dimethylformamide, dimethylacetamide, and tetrahydrofuran.
• the solvent is sulfuric acid or n- methylpyrrolidinone.
• the solvent is sulfuric acid.
• the polymers of Structure I are known in the art and can be formed by reaction an aromatic diamine and an aromatic diacid.
• Suitable diamine monomers include but are not limited to p- phenylene diamine, m-phenylene diamine, 4,4'-diphenyldiamine, 3,3'- diphenyldiamine, 3,4'-diphenyldiamine, 4,4'-oxydiphenyldiamine, 3,3'- oxydiphenyldiamine, 3,4'-oxydiphenyldiamine, 4,4'- sulfonyldiphenyldiamine, 3,3'-sulfonyldiphenyldiamine, 4,4'- sulfonyldiphenyldiamine, 3,3'-sulfonyldiphenyldiamine, and 3,4'- sulfonyldiphenyldiamine.
• the aromatic diamine is m-phenylene diamine or p-phenylene diamine.
• Suitable diacid monomers include but are not limited to terephthalic acid, isophthalic acid, 2,6- naphthalenedicarboxylic acid, 4,4'-oxydibenzoic acid, 3,3'-oxydibenzoic acid, 3,4'-oxydibenzoic acid, 4,4'-sulfonyldibenzoic acid, 3,3'- sulfonyldibenzoic acid, 3,4'-sulfonyldibenzoic acid, 4,4'-dibenzoic acid, 3,3'-dibenzoic acid, and 3,4'-dibenzoic acid.
• the diacid monomer is terephthalic acid, isophthalic acid, or 2,6- naphthalenedicarboxylic acid, with terephthalic acid being the most preferred.
• a preferred structure I polymer has the structure:
• a further preferred structure I polymer has the structure: STRUCTURE Id
• This structure Id is commonly referenced as MPD-T.
• a further step in the reaction procedure comprises hydroxylating An groups of Structure I resulting in ortho hydroxyl groups.
• the hydroxylating step involves the use of an alkyl carboxylic acid and an oxidizing agent.
• Suitable alkyl carboxylic acids include formic acid, acetic acid, propanoic acid, butanoic acid, and the like.
• the alkyl carboxylic acid is formic acid or acetic acid.
• Most preferably the alkyl carboxylic acid is acetic acid.
• Alkyl carboxylic acids have a dissociation constant less than that of sulfuric acid and contain the oxygen necessary for the hydroxylation.
• Suitable oxidizing agents include nitrosylsulfuric acid, lead tetraacetate, and sodium nitrate.
• the oxidizing agent is nitroxylsulfuric acid.
• the oxidizing agent is added to the polymer solution containing the acid with mechanical stirring under an inert atmosphere.
• inert atmosphere it is meant an atmosphere that is essentially unreactive. Suitable inert atmospheres include but are not limited to nitrogen, helium, and noble gases.
• a further step in the method involves formation of a fiber from the polymer wherein An groups contain ortho hydroxyl groups (as well as the polymer containing unreacted A ⁇ groups).
• the step may be undertaken with known and conventional methods in formation of aromatic polyamide fibers. This step can be done by any technique that spins fibers from solution, such as wet spinning, dry-jet wet (air-gap) spinning, jet- attenuated spinning, centrifugal spinning, electro-spinning, and others.
• the hydroxylated polymer fibers can be processed by methods known in the art to reduce the amount of residual solvent and improve the mechanical properties of the fiber such as washing, pH modification, heat treatment, drying, and crystallization.
• the fibers are coagulated in a water bath, washed in a second water bath, neutralized in a neutralization bath and dried.
• the further step in the reaction procedure employs heating of the formed fiber.
• the heating step results in ring closure of a portion of the Ari groups containing orth hydroxyl groups.
• a suitable temperature range for convenience is from 170 to 280 degrees Celsius, preferably 185 to 250 degrees Celsius, with the most preferred temperature being between 200 and 240 degrees Celsius.
• Typical heating times range from 5 to 60 seconds
• an oxazole containing polymer fiber is formed.
• the fiber during heating may be subjected to tension which is known in fiber formation.
• a suitable tension is in a range from 1.0 to 18.0 grams per denier (gpd) with 2.0 to 10.0 gpd being preferred and 2.5 to 5.0 gpd being most preferred.
• the fiber will contain repeating units of the following structure:
• the final polymer in the fiber will typically contain repeating units at least of structure III and at least one of structure I and structure II. However it is within the scope of the invention that structure III is present with only one of structure I or structure II.
• Tenacity, elongation, and modulus are determined according to ASTM D 3822. Tenacity (breaking tenacity), elongation to break, and modulus of elasticity are determined by breaking test fibers on an lnstron tester. Tenacity is reported as breaking stress divided by linear density. Modulus is reported as the slope of the initial stress/strain curve converted to the same units as tenacity. Elongation is the percent increase in length at break.
• Inherent Viscosity is the ratio of the natural logarithm of the relative viscosity to the mass concentration of the polymer as measured with respect to a solution of 0.5 g of the polymer in 100 ml of concentrated sulfuric acid at 25 0 C
• Relative Viscosity is the ratio of the viscosity of the polymer in solution to that of the solvent expressed as the time of efflux of the solution divided by the time of efflux of the solvent at constant temperature.
• a reaction kettle equipped with nitrogen inlet/outlet and a basket stirrer driven by high pressure air was set-up in silicone oil bath.
• 3.0 grams of PPD-T [p-phenyleneterephthalamide] of inherent viscosity of 6.0 and 100 grams of sulfuric acid were added under nitrogen and the mixture was gradually heated to about 70 degrees Celsius to form a solution.
• To this solution was added 1.68 grams of nitrosylsulfuric acid (95%) and 1 gram of acetic acid.
• the mole % of nitrosulfuric acid (NSA) on the basis of NSA and PPD-T was 50.0%.
• the solution was stirred for 12 hours at 70 degrees Celsius under nitrogen. The color of the solution changed to bluish green from yellow as a result of the hydroxylation reaction.
• the resulting solution was precipitated in aqueous medium at room temperature, washed five times, each time with about 200 ml water, and finally neutralized to a pH of about 9 with a dilute sodium hydroxide solution.
• the yellowish brown precipitated polymer was filtered and dried in vacuum oven at 120°C overnight under nitrogen.
• a dried but not heat treated sample was sent for elemental analysis for C, H, N, and O by standard combustion method. The results are as follows:

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (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)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

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