Cellulose 0- -, preparation

Starting cellulose, prepared by deacetylation of commercial, medium viscosity cellulose acetate (40.4% acetyl content). 

Ethylcellulose is made commercially by the action of ethyl chloride on an alkali cellulose prepared by steeping cotton linters or wood pulp... 

The N,N -dimethyl-l,3-propanediamine complex of cellulose, prepared from ramie, requires a large unit-cell, with a - 3.364 nm, b (chain axis) = 1.026 nm, c = 3.040 nm, and /3 = 32.74°. One diamine molecule per two /3-D-Glcp residues exists in the complex. 

Cellulose powder is a mechanically shortened cellulosic fiber, whereby the degree of polymerization remains almost intact. Microcrystalline cellulose is a partially purified and depolymerized cellulose, prepared by treating a-cellulose obtained from fibrous plant material with mineral acids. It occurs as a fine white odorless and... 

The recent systematic investigations carried out by Newman et al. [37] were devoted to the viscosity, sedimentation, diffusion and osmotic pressure of nitro-celluloses prepared by nitrating non-purified cotton, purified cotton, and viscose fibres with mixed add containing phosphoric acid and phosphoric anhydride. 

In Great Britain, according to the patents of Picton [6] small flakes of sheet wood-cellulose have been nitrated, while in the United States shredded cellulose prepared by the Stem method [7] was most widely used (shreds made of loosely felted cellulose fibres in a special machine). This last form of cellulose is especially suitable for uniform penetration and imbibition of the nitrating acid. Normal nitrators, as used for linters, are also suitable for nitrating this type of cellulose. 

Another cheap and readily available source of cellulose is the straw of annual plants. This raw material usually contains exceptionally large quantities of mineral matter. In order to separate cellulose the chlorine process is often used. It consists in treating the cellulosic raw material (previously boiled in a 10% sodium hydroxide solution and then in water) with chlorine. The decomposition of lignin, pentosans and other substances takes place and at the same time the cellulose is bleached. Crude cellulose prepared in this way contained 80-92% of a-cellulose and about 1% of mineral matter. 

The sodium alcoholate of cellulose prepared from a sodium alkoxide is probably similar to, if not identical with, that prepared from sodium hydroxide. Monomethylation of the alcoholate prepared with either sodium methoxide or sodium l-butoxide140 occurs preferentially at the hydroxyl groups on C-2 and C-6. Very little methylation occurs at the hydroxyl group on C-3. 

Dialysis is a simple clean-up or purification process to remove unwanted low-molecular-weight compounds from solutions. The dialysis membrane consists of regenerated cellulose prepared from cotton linters by the viscose process. In addition to water, the membrane also contains glycerol and small amounts of sulfur compounds, which are removed during preparation of the tubing prior to use. 

Figure 4. Poly acrylamide-disc gel electrophoretic patterns obtained for forms of CBH I from Trichoderma (2). The protein samples applied to these gels were, from left to right 20 fxg CBH I (A), 15 fig CBH I (B), 33 jig CBH I (C), and 40 fig CBH 1 (D). Forms A, B, and C were purified from a commercial T. viride cellulose preparation and Form D was purified from a culture of T. reesei QM 9123 grown on purified cellulose.

In the past, BCME was used for crosslinking of cellulose, preparation of styrene and other polymers, surface treatment of vulcanized rubber to increase adhesion, and in the manufacture of flameretardant fabrics (EPA 1980a). These applications have been discontinued, and no uses of BCME other than as a nonisolated intermediate were identified. 

Reduced and neutralized cellulose preparations were assayed using the BC A assay as described for insoluble reducing ends using glucose as the calibration standard. 

Cellulose preparation Amount (mg) Reducing ends (pmol/g) SE BCA" DNS6 ... 

Cellulose preparation" Solvent-accessible reducing ends (mmol/g) Solvent accessibility (% of total)biC... 

The average molecular weight of a cellulose preparation may be found by a number of techniques, but it is most conveniently evaluated by determination of the viscosity in a suitable solvent. Detailed procedures are given in TAPPI standards T206 and T230 and in ASTM standard D1795, Intrinsic Viscosity of Cellulose. The distribution of molecular weights can be determined for additional evaluation of the material, but the fractionation procedures required prohibit use of the necessary operations as a routine characterization. 

Cellulose Gel occurs as a fine, white or almost white powder. It is purified, partially depolymerized cellulose prepared by treating a// /za-ccllulose, obtained as a pulp from fibrous plant material, with mineral acids. It consists of free-flowing, nonfi-brous particles that may be compressed into self-binding tablets that disintegrate rapidly in water. It is insoluble in water, in dilute acids, in dilute sodium hydroxide solutions, and in most organic solvents. 

Microcrystalline cellulose (Avicel) is purified partially depolymerized cellulose, prepared by treating a-cellulose with mineral acids. In addition to being used as a filler, it is also used as dry binder and disintegrant in tablet formulations. Depending on the preparation conditions, it can be produced with a variety of technical specifications depending on particle size and crystallinity. It is often used as an excipient in direct compression formulations but can also be incorporated as a diluent for tablets prepared by wet granulation, as a filler for capsules and for the production of spheres. 

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