Cellulose acetate

=Cellulose acetate= Cellulose acetate is a polyester of glucose with acetate so as to replace the glucose's hydroxyl (OH) groups. Ideally all three hydroxyl groups (C2, C3, C6) are replaced with acetate resulting in cellulose triacetate. Cellulose acetate can be made by reacting cellulose biomass with acetic anhydride and an acid catalyst. Cellulose acetate has good optical and packaging characteristics but is not very durable.

Process for obtaining cellulose acetate from agricultural by-products by Biswas et al 2006 demonstrated yields of cellulose acetate from hemicellulose sugar depleted biomass. The study utilized a pretreatment to remove sugars and then an acetylation step followed by filtration to gather cellulose acetate. Feedstocks utilized were rice straw, wheat hull, and corn fibers and untreated and pretreated biomass were compared. The yield of the pretreated samples increase from 0.5, 1.8, 13.5% respectively to all around 25%. The value of cellulose acetate ~$2.00 is used to compare the cost of reagents. The pretreatment consists of milling followed by a hot hexane wash to remove oils. Corn fibers were then slurried 0.5% H2SO4 and pretreated in an autoclave at 121 C for 15 min, while rice hulls (15%, w/v) and wheat straw (8.6%, w/v) were slurried in 1% (v/v) H2SO4 separately and pretreated in an autoclave at 121 C for 1 h. Pretreated fibers were neutralized to pH 5.0 using 10 M NaOH. The solids were separated from the liquid, washed with water, and dried at 60 C for 24 hr for use in acetylation. Acetylation consisted of combining 2 grams of sample along with 0.5 g of acetic acid, 5.0 g of acetic anhydride, 30 ml of methylene chloride, and 0.04 g of sulfuric acid in a 100 ml round bottom ﬂask. The mixture was heated to 80 C with stirring for 4 hr under a reflux condensor. The mixture was cooled and sieved through a #60 filter. The remaining cellulose acetate was recovered from the residue with 60 ml chloroform and stirred for 30 minutes. The sample was filtered through Tyler #60 filter and the filtrate combined with the first filtrate.

http://www.mpri.lsu.edu/Integrating_Biomass_Feedstocks_into_Chemical_Production_Complexes_-_a_White_Paper.pdf

http://www.google.com/patents/US4162359

http://www.google.com/patents/US2129052

http://www.google.com/patents/US5142034

http://www.google.com/patents/US2487892 describes a method to acetylate cellulose sheets by passing them over a suction machine. The sheet is soaked by overhead spray and suction from below. The pretreatment is water followed by glacial acetic acid, and then treatment with catalyst and acetate anhydride.