Cellulose producers

Of somewhat greater technical interest are the addition compounds and the cellulose esters and ethers. Of the apparent addition compounds the most important is alkali cellulose produced by steeping cellulose in caustic soda and considered to be of general form (CgHioOs), (NaOH) ) rather than a sodium alcoholate compound. Alkali cellulose is a particularly important starting point in the manufacture of cellulose ethers. The ability of aqueous cuprammonium hydroxide solutions to dissolve cellulose appears to be dependent on addition compound formation. 

Hydroxyethyl cellulose, produced by reacting alkali cellulose with ethylene oxide, is employed for similar purposes. 

Eastman uses acetic anhydride primarily for esterification of cellulose, producing acetic acid as a byproduct. This acetic acid is used to convert the methanol into methyl acetate in a reactor-distillation column in which acetic acid and methanol flow countercurrently. 

Attention was first directed toward the dextrans about the middle of the last century as these slimes were at times a serious problem in the wine and beet sugar industries. In the latter, jelly-like masses blocked the filters and interfered with the refining processes by retarding crystallization. Dextran, at various times, was regarded as a protoplasmic constituent of the beet cell,22 a product of sucrose fermentation, and as cellulose produced by fermentation.22 The empirical formula, (CeHioOs)n, for dextran was obtained2422 at an early date (about 1875) on hydrolysis, the substance was found to yield only D-glucose.1422-24 A tribenzoate and a triacetate of dextran were prepared by Daumichen.24... 

In 1857, Schweizer discovered that ammoniacal solutions of copper hydroxide could dissolve cellulose. Cellulose is a versatile polymer which is found in plenty in nature in the form of cotton, hemp, jute, flax, etc. In 1891, first attempts were made to spin a solution of cellulose. The cellulose produced like this is known as Bemberg Rayon and is still being produced commercially in Germany, Italy, Japan and USA. 

CIEF analysis of rtPA in the presence of urea was also carried out in an uncoated capillary using pressure mobilization.114 The final urea concentration used was 4 M, and EOF was reduced by adding polymers to the reagents and sample (0.4% hydroxypropylmethyl cellulose produced better results than polyethylene glycol). A one-step CIEF method described by Moorhouse et al.115 for the analysis of rtPA produced a constant residual EOF in a neutral capillary. The sample was prepared by dilution to 125 to 250 pg of protein per milliliter in 3% ampholytes 3 to 10 and 5 to 8 (1 1) containing 7.5% TEMED and 4 M urea. Results obtained by CIEF correlated well with those generated by IEF, and the analysis was completed in less than 10 min. 

Strong basic solutions, such as sodium hydroxide, penetrate the crystalline lattice of a-cellulose producing an alkoxide called alkali or soda cellulose. Mercerized cotton is produced by aqueous extraction of the sodium hydroxide. 

Consider also that almost every plastic raw material is made by more than one producer. For example there are now about seven producers of ABS, five producers of methyl methacrylate, eight producers of polypropylene, four producers of fluorocarbons, fifteen producers of polyesters, five producers of nylon, twenty-one producers of polystyrene, thirteen producers of low density polyethylene, eleven producers of high density polyethylene, two polycarbonate producers, twenty-four PVC producers, three epoxy producers, two acetal producers, three cellulosics producers, and thirteen producers of phenolics. 

Herzog and Londberg [20] have examined the X-ray diagrams of cellulose produced by denitration of a carefully nitrated product. The picture of the regenerated cellulose was in principle identical with that of cellulose before nitration. This observation suggests that a cautious nitration of cellulose that proceeds without oxidation or hydrolysis does not change the microcrystalline structure of the cellulose, i.e. this is a topochemical reaction, in which the product preserves the same... 

Murine epidermal growth factor is a polypeptide containing 53 residues. Its molar mass is 6040 g/mol. Chromatography on diethylaminoethyl cellulose produced a single peak. The isocratic RPC of this seemingly homogeneous material on a C 18 column (300 x 7.8 mm) yielded two clearly separated peaks (Fig. 19)77). The eluent was water — acetonitrile (74 26), 0.04 M in triethylamine acetate, pH = 5.6. The structure of the p component is identical with that of the a component but does not possess the Asn residue at chain position 1. 

Exercise 20-14 Explain how the /3-D-glucoside units of cellulose produce a polymer with a stronger, more compact physical structure than the a-D-glucose units of starch. Models will be helpful. 

A major problem in the commercialization of this potential is the inherent resistance of lignocellulosic materials toward conversion to fermentable sugars (4). To improve the efficiency of enzymatic hydrolysis, a pretreatment step is necessary to make the cellulose fraction accessible to cellulase enzymes. Delignification, removal of hemicellulose, and decreasing the crystallinity of cellulose produce more accessible surface area for cellulase enzymes to react with cellulose (5). 

It is thus very likely that at least cellulose produced by Acetobacter xylinum is synthesized by simultaneous polymerization and crystallization. Especially interesting remaining problems in this system are the questions of nucleation of new fibrils, the reasons for the limiting diameter of the fibrils, and the defect structure of the only partially crystalline cellulose which is not uniform across the fibril. 

Hemicellulose produces acetic acid, lurlurat, fiiran Cellulose produces levoglucosan,... 

Nordin S.B., Nyren J.O. and Back E.L. (1974) An Indication of Molten Cellulose Produced in a Laser Beam. Textil Research J., 152-154... 

The formation of crystalline microfibrils has been elucidated using the bacterium Acefol acter xylinum as cellulose producing model. It appears that individual cellulose chains are extruded at multiple cellulose-synthesizing sites located in the cytoplasmatic membrane of the organism. Cellulose synthesis produces 12 to 16 cellulose chains into the surrounding medium... 

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