Cellulose ether table

The conversion of 2,6-di-O-TDS cellulose with an excess of alkyl halides in THF in the presence of NaH afforded the fully etherified polymers that can be desilylated with fluoride ions yielding 3-mono-O-functionalized cellulose ethers (Table 16.11) [86-89]. 

CELLULOSE ETHERS Table 8. Typical Properties of MC Ethers ... 

Extent of solvation and intrinsic viscosity are interconnected. Highly disentangled and expanded chains result in high values of conformational exponent, a, of the Mark-Houwink equation. Few literature data are available for water-soluble cellulose ethers (Table 5). 

Economic Aspects. CMC is the most widely used cellulose ether. Excluding the former Soviet Union and Eastern Bloc countries, from which httie data are available, world consumption of cmde and purified grades totaled approximately 123,000 metric tons in 1987 (Table 2). Annual growth rate is nominal at 1—2%. The total volume in the United States declined in the 1980s from —32,000 metric tons in 1981 to —19,500 in 1987 because of decreased oil well drilling activity, an important outiet. 

Typical physical properties of ethyl cellulose are compared with those of the cellulose ethers in Table 22.2. 

The phase transfer catalyzed alkylation reaction of dodecyl phenyl glycidyl ether (DPGE) with hydroxyethyl cellulose (HEC) was studied as a mechanistic model for the general PTC reaction with cellulose ethers. In this way, the most effective phase transfer catalysts and optimum reaction concentrations could be identified. As a model cellulose ether, CELLOSIZE HEC11 was chosen, and the phase transfer catalysts chosen for evaluation were aqueous solutions of choline hydroxide, tetramethyl-, tetrabutyl-, tetrahexyl-, and benzyltrimethylammonium hydroxides. The molar A/HEC ratio (molar ratio of alkali to HEC) used was 0.50, the diluent to HEC (D/HEC) weight ratio was 7.4, and the reaction diluent was aqueous /-butyl alcohol. Because some of the quaternary ammonium hydroxide charges would be accompanied by large additions of water, the initial water content of the diluent was adjusted so that the final diluent composition would be about 14.4% water in /-butyl alcohol. The results of these experiments are summarized in Table 2. 

The results of this work for gels made from different cellulose ethers at comparable levels of crosslinking are given in Fig. 6. The parameters obtained from the curve fit are given in Table 3. The quality of the curve fit depends... 

Cellulose ethers can be prepared by treating alkali cellulose with a number of various reagents including alkyl or aryl halides (or sulfates), al-kene oxides, and unsaturated compounds activated by electron-attracting groups. A variety of products of considerable commercial importance has been developed for different uses (Table 9-7). Most of the cellulose ethers are water soluble and they generally possess similar properties, but because... 

Table VI. Important Cellulose Ethers Used in Adhesive Applications...

TABLE 8 Specification Limits for Viscosity of Cellulose Ether... 

Easy-care and durable press finishes of cellulosics 59 Table 5.4 Effects of the ether modification of DMDHEU °... 

Table 6. Limiting values of [nl/ ijl and anisotropy of the segment, aj - 02 and the monomer unit, an - of cellulose ethers and esters... 

Table 7. Number of monomer units S in a segment, segment length A and hindrance parameter of cellulose ether and ester solutions according to optical data (microform effect)...

The two primary categories of cellulose derivatives, cellulose esters and cellulose ethers, which dominate the markets for cellulose derivatives (O Table 8), have somewhat different raw material requirements. Whereas both types of modification technologies prefer to start with chemical cellulose of high a-cellulose content, ethers give preference to molecular weight considerations while esters are sensitive to impurities. This is a consequence of the predom-... 

Cellulose ethers swell or are colloidally soluble. They all raise viscosity and have specific rheology profiles (seeO Fig. 18). Many cellulose ethers are surface-active, and they reduce the surface activity of water by about 20 to 25% depending on type. Cellulose ethers are generally compatible with other hydrocolloids and many other substances. The field has recently been reviewed by Majewicz et al. [95]. The primary manufacturers of industrial cellulose ethers are listed in O Table 14. 

Hydrophilic matrices are the most commonly used oral extended-release systems because of their abihty to provide desired release profiles for a wide range of drugs, robust formulation, cost-effective manufacture, and broad regulatory acceptance of the polymers. Table 11.2 shows a fist of hydrophific polymers commonly used for fabrication of matrices [17, 18]. Hydrophobic materials are also used either alone (hydrophobic matrix systems) or in conjugation with hydrophilic matrix systems (hydrophilic-hydrophobic matrix systems) and are also fisted in Table 11.2. Cellulose ethers, in particular hypromeUose (hydroxypropyl methylcellulose, HPMC), have been the polymers of choice for the formulation of hydrophilic matrix systems. 

Extended-Release Oral Drug Delivery Technologies Table 11.3 Pharmaceutical grades of Methocel cellulose ethers... 

At national level protective colloids like cellulose ether and polyvinyl alcohol are widely approved for various applications in food-contact materials (Tables 10,11). 

Table X. Chronology of Water-Soluble Cellulose Ethers...

Table XI. Cellulose Ethers DS Range for Cold-Water Solubility...

Surface tensions of 2% aqueous solutions of commercially used water-soluble cellulose ethers were determined for comparative purposes in the author s laboratory (Table 10). Five derivatives were selected, each with two different molecular weights (nominal viscosity grades). 

A general conclusion that can be drawn from Table 51.3 is that charged polymers both anionic and cationic demonstrate a better mucoadhesive capacity in comparison to non-ionic cellulose-ethers or polyvinyl alcohol (PVA). 

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