Photodegradable cellulose ester tow

#This invention is directed to a photodegradable cellulose ester tow.

#Cellulose ester tow is known. Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Edition, Vol. 5, John Wiley & Sons, New York, N.Y., 1993, p. 496-529. Cellulose acetate tow is known. Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Vol. 5, John Wiley & Sons, New York, N.Y., 1979, p. 89-117. Cellulose acetate tow impregnated with titanium dioxide pigments, either anatase or rutile, as a delustrant is known. See: Kirk-Othmer, Ibid, 3rd Edition, p. 90; and U.S. Pat. No. 4,022,632. The ideal delustering titanium dioxide pigment has a particle size ranging from 200 to 350 nm (0.2 to 0.35 microns). See: Undated publication of Kemira, Inc. entitled "The Savannah Story". These pigments are typically coated to retard their photocatalytic effect. Rabek, J. F., Mechanisms of Photophysical Processes and Photochemical Reactions in Polymers, John Wiley & Sons, New York City, N.Y., 1987, p. 585-587.

#It has been proposed that anatase-type titanium dioxides can be used to accelerate the photodegradation of cellulose ester tows. See: EPO Publication No. 597,478; WO 93/24685; and U.S. Pat. No. 5,242,880. These photodegradable cellulose ester tows utilize uncoated anatases. Ibid. As a photodegradability accelerator, anatase-type titanium dioxide is better than rutile-type titanium dioxide. In EPO Publication No. 597,478, the cellulose ester tow has about 0-5% by weight of an anatase-type titanium dioxide having an average particle diameter of about 300 nm (0.3 microns), a particle size distribution of 10-1000 nm (0.01-1 micron), and specific surface area of 3 to 30 m.sup.2 /g. In WO 93/24685, the average particle size is given by reference to the exemplary photoactive anatase titanium dioxides set forth in Table 1 at page 48. Therein, three commercially available pigments are disclosed. Each is believed to have an average particle size of about 350 nm (0.35 microns). In U.S. Pat. No. 5,242,880, an oxidizable polymer such as cellulose acetate or polypropylene, is impregnated with a photoactive catalyst to increase biodegradability. The photoactive catalyst comprises an anatase-type titanium dioxide containing or coated with a salt. The salt comprises between 2-30 weight percent of the catalyst.

#All yarn were prepared in a conventional manner. See: Cellulose Chemistry And Its Applications, Ellis Harwood Ltd., Chichester, England, 1985, p. 474-476, incorporated herein by reference. Cellulose acetate polymer is dissolved in a solvent of 96% acetone and 4% water. In all cases, 100 lbs of total solution prepared which contained 27 lbs of cellulose acetate polymer in 73 pounds of a 96%/4% acetone/water solvent. If titanium dioxide is added, it is done so after the polymer is dissolved in the solvent. The mixture is stirred until homogenous, and filtered. After filtering, yarn is extruded through a 190 hole spinnerette with a hole diameter of 52 .mu.m. This results in a fiber with 2.9 denier/filament.

#The yarns are evaluated according to the procedures of the American Association of Textile Chemist and Colorists (AATCC). AATCC Test Method 169-1990 "Weather Resistance of Textiles: Xenon Lamp Exposure", Option 1 is used. Yarns are prepared for evaluation according to AATCC Test Method 177-1993 "Colorfastness to Light at Elevated Temperature and Humidity: Water Cooled Xenon Lamp Apparatus".

#The yarns are wrapped around a paper card and placed in a metal holder. The holder with the yarn is placed in an Atlas model C65 WeatherOmeter and subjected to alternating conditions of Xenon light exposure and water spray. Conditions (option 1) have been predetermined to equate to environmental conditions of South Florida. At 100 hours intervals, which roughly relate to one month outdoors exposure, yarns are removed, conditioned to ambient conditions and then breaking strength is measured.