Cellulose acetate/Research Development
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.
U.S. Patent 5,288,318 issued to Mayer et al on Feb 22 1994 details a biodegradable bioplastic made with 30-70% cellulose acetate (28-62 kDa, >2.2 degree of substitution), 10-60% raw starch, and 5-35% plasticizer (glycerol and its modified forms). High substitution numbers create a less biodegradable product and other anhydrides (besides acetate) may be used to increase durability. Starch can be formed into bioplastic polymers but is relatively high cost and unstable with water, mixing cellulose acetate and starch creates a biodegradable bioplastic with good strength and optical properties that is desirable for many applications. In this method a dry mixture of the cellulose acetate and starch bioplastic in pellet form is combined and the plasticizers added and mixed before extrusion at 100-170 C. Water content must be kept >4%. A number of other compounds can be included to improve certain product properties including shellac for water resistance, boric acid for fire resistance, and agricultural or mineral waste for fillers.
http://www.google.com/patents/US2090809
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC187130/pdf/applmicro00025-0143.pdf
http://128.104.77.228/documnts/pdf1989/barka89a.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.