Acrylic fiber polymer precursor and fiber

Details Acrylic fiber polymer precursor and fiber Acrylic fiber polymer precursor and fiber

1998-05-11

2001-07-31

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S292600, C526S329300, C526S330000

Reexamination Certificate

active

06268450

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an acrylic fiber polymer precursor composition. This invention also relates to an acrylic fiber having improved hot/wet properties and processes of producing such fibers.
BACKGROUND
Various acrylic fiber polymer precursors have been utilized in the production of acrylic fibers for use in outdoor applications, such as in awnings and other outdoor textiles due to certain desirable physical properties (e.g., decay resistance, UV stability weather fastness, etc.). For example, U. S. Pat. No. 4,265,970 describes an acrylic fiber that was utilized in acrylic fabric for outdoor textiles. This fiber is formed from an acrylic fiber polymer precursor having less than 93 wt. % acrylonitrile monomer and 7 wt. % or more vinyl acetate (VA). However, the fabric produced from such fibers possesses inadequate hot-wet properties such as elongation.
Large amounts of vinyl monomers (e.g., above 7 wt. %), have been included in polymer formulations for the purpose of providing the fiber with flame retardency, additional dyesites, or increased hydrophilility. However, vinyl monomer amounts below 7 wt. % have not been utilized due to problems in spinning the resulting polymer. Lower amounts of vinyl monomers have not been used due to solutioning difficulties in dimethylacetamide such as filtration prior to spinning of the solutioned polymer, poor fiber color from elevated solutioning temperatures, and low standard fiber elongation under ambient conditions.
In spite of the desirable physical properties manifested by acrylonitrile containing fibers, there are a number of difficulties encountered during the processing of fabrics made therefrom, and still provide adequate hot-wet properties. Various means have been employed in the art to improve the tensile properties of such fibers under hot-wet conditions. A number of means involve incorporating various chemical agents to modify the structural arrangement of the polymer itself. Several methods have been employed which physically modify the fiber structure. These methods and combinations thereof have met with limited success. During processing of fabrics containing polyacrylonitrile where such fabrics are exposed to heat and water or steam, deformation owing in part to a plasticity of such polyacrylonitrile materials is frequently observed. Furthermore, wrinkling or overstretching when a woven or knitted fabric thereof is subjected to tension is often exhibited. Other desirable properties for outdoor textiles include high abrasion resistance and low lint generation.
Dolan® T-65 is an outdoor textile material manufactured by Courtaulds Fibers, Inc. that is made almost entirely from a polyacrylonitrile (PAN) homopolymer (including less than about 0.8 wt. % methyl acrylate). The Dolan® T-65 acrylic fabric was made in an attempt to improve upon the hot-wet properties of previous acrylic fabrics. However, it is not possible to use a polymer, such as in the Dolan 65, which is nearly a homopolymer in all spinning solvents and provide adequate hot-wet properties. For example, using certain spinning solvents such as dimethylacetamide, to spin acrylic fiber requires a high dissolution temperature of approximately 120° C. or higher. When spinning acrylonitrile under normal residence times in solution at this elevated temperature, white base polymer color in the resulting fiber cannot be achieved.
Accordingly, there is a need for an acrylic fiber polymer precursor composition that may be economically and easily processed into acrylic fiber, which has desirable appearance, and improved hot-wet and abrasion properties.
SUMMARY OF THE INVENTION
The present invention relates to an acrylic fiber polymer precursor composition that is suitable for the economic production of acrylic fiber having desirable appearance, and improved hot-wet and abrasion resistant properties.
An acrylic fiber polymer precursor of the present invention comprises acrylonitrile in an amount from greater than 80 to 98.0 wt. %; neutral vinyl monomer in an amount from greater than 0 to 7.0 wt. %; and optionally, ionic vinyl monomer in an amount from greater than 0 to 3.0 wt. % of the polymer.
An acrylic fiber of the present invention comprises of an acrylic fiber polymer precursor having acrylonitrile in an amount from greater than 80 to 98.0 wt. %; neutral vinyl monomer in an amount from greater than 0 to 7.0 wt. %; and optionally, ionic vinyl monomer in an amount from greater than 0 to 1.0 wt. % of the fiber.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In an embodiment of the present invention, an acrylic fiber polymer precursor is produced by using continuous free radical redox aqueous dispersion polymerization, in which water is the continuous phase and the initiator is water soluble. The redox system consists of a persulfate (the oxidizing agent and initiator, sometimes called “catalyst”), sulfur dioxide or a bisulfite (reducing agent, sometimes called “activator”) and iron (the true redox catalyst). This redox system works at pH 2 to 3.5 where the bisulfite ion predominates and where both the ferric and ferrous ion are sufficiently soluble.
S
2
O
8
2−
+Fe
2+
→SO
4
2−
+SO
4
*
1−
+Fe
3+
HSO
3
1−
+Fe
3+
→HSO
3
*+Fe
2+
Salts of the initiator and activator may be used such as ammonium, sodium, or potassium. Additionally, a persulfate initiator or an azo initiator may be utilized to generate free radicals for the vinyl polymerization rather than the above-mentioned redox system. In an embodiment of the present invention, the acrylic fiber polymer precursors thus obtained may be used to form acrylic fibers by various methods, including dry and wet spinning such as those set forth in U.S. Pat. Nos. 3,088,188; 3,193,603; 3,253,880; 3,402,235; 3,426,104; 3,507,823; 3,867,499; 3,932,577; 4,067,948; 4,294,884; 4,447,384; 4,873,142; and 5,496,510, the entire subject matter of which is incorporated herein by reference. Preferably, the fibers of the present invention are formed by wet spinning.
For example, acrylic fiber polymer precursors of the present invention may be dissolved in an organic solvent or mixtures of organic solvents, which may contain 0 to 3 wt. % water. The solution may contain 10 to 40 wt. % polymer, preferably, 20 to 30 wt. %, and more preferably 22 to 27 wt. % of the solution. In inorganic solvents, the solution may contain 8 to 15 wt. % polymer and greater than 8 wt. %. The solution may be heated to a temperature of 50-150° C., preferably 70-140° C., and more preferably 80-120° C. to dissolve the polymer.
The solvent in the spin bath is normally the same solvent in which the polymer is dissolved prior to spinning. Water may also be included in the spin bath and generally that portion of the spin bath will comprise the remainder. Suitable organic spinning solvents for the present invention include N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide, and ethylene carbonate. Suitable inorganic solvents include aqueous sodium thiocyanate. Preferably, the solvent utilized in the spinning process of the present invention is DMAc.
The solution is extruded through a spinnerette (which may be of conventional design) into a coagulating bath. For DMAc solvent wet spinning the coagulating or spin bath is maintained at a temperature of from 0-600°C., preferably 10-50° C., and more preferably 20-40°C. Generally, the spin bath contains 10 to 70 wt. %, preferably 15 to 65 wt. %, and more preferably 20 to 60 wt. % of solvent by weight of the spin bath. In these ranges, all the water is associated with the solvent and the system behaves as a single phase coagulant which provides slower diffusion of solvent out of the coagulating fiber. The polymer composition and solvent concentration in the coagulation bath are correlated such that fiber density is at least 0.60, preferably at least 0.8 and most preferably 1.0 or higher. As referred to herein, the terms fiber and filament are utilized interchangeably.
The spun filaments may be subjected to je

Affiliated with

Also associated with

Rating

Acrylic fiber polymer precursor and fiber does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Acrylic fiber polymer precursor and fiber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Acrylic fiber polymer precursor and fiber will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2528896