Cellulose derivatives hydroxyethylcellulose

Cellulose derivatives, e.g. hydroxyethylcellulose, are used in the formulation of sustained release tablets and suspensions. Natrosol (hydroxyethylcellulose) is a nonionic water-soluble polymer that is extensively used as a thickener. 

These stabilizers are added to the formulation in order to stabilize the emulsion formed during particle preparation. These stabilizers, however, can also influence the properties of the particles formed. The type and concentration of the stabilizer selected may affect the particle size. Being present at the boundary layer between the water phase and the organic phase during particle formation, the stabilizer can also be incorporated on the particle surface, modifying particle properties such as particle zeta potential and mucoadhesion (203). Other polymers have also been evaluated as stabilizers in earlier studies such as cellulosic derivatives methylcellu-lose (MC), hydroxyethylcellulose ( ), hydroxypropylcellulose (HPC), and hydroxypropylmethylcellulose (HPMC), as well as gelatin type A and B, carbomer and poloxamer (203). 

Plant — Arabic gum — Tragacanth gum — Karaya gum — Ghatti gum Cellulose derivatives — Carboxymethylcellulose — Methylcellulose — Hydroxyethylcellulose — Cellulose acetate phthalate... 

Aminoethylatian of Cellulose Derivatives and of Regenerated Cellulose, Cellulose obtained by regeneration from a cuprammonium soln of cotton(in the manner described in Rept No 2,p 14) from the Wyandotte Chem Corp gave an amorphous product contg ca 23.5% N when heated with ethyieneimine in a sealed tube at 120° in the presence of toluene. The cellulose derivatives carboxy-methylcellulose and hydroxyethylcellulose (prepd in the manner described in Rept No 3, pp 14—18) gave solid products with nitrogen contents of 24.8 and 28.1% respectively, when heated with ethyieneimine in a sealed tube, in the manner described in Rept No 1, p 6... 

Figure 8. Degree of grafting for cellulose and cellulose derivatives initiated by UV light of > 280 nm. Key a, fibrous carboxymethylcellulose b, cellulose c, hydroxyethylcellulose d, ethylcellulose e, methylcellulose f, powdered carboxymethylcellulose g, acetylcellulose.

Vinyl monomers that can be grafted to cellulose to achieve adhesive properties are acrylic acid, acrylonitrile, methyl methacrylate, and many others. Graft copolymers of cellulose derivatives have also found use as adhesives. For example, vinylacetate-grafted hydroxyethylcellulose can be used as an adhesive for packaging and tile ( ). Grafting of vinyl monomers onto lignocellulosic materials can convert them into suitable adhesive materials (0). 

Cellulose derivatives Sodium carboxymethyl cellulose Methylcellulose Hydroxyethylcellulose Hydroxypropylmethyl cellulose Other derivatives Modified starches Low-Methoxyl pectins Propylene glycoalginates... 

This class of cellulose derivatives includes hydroxypropylmethylcellulose or HPMC, hydroxyethylcellulose (58), methylcellulose, HPC, and ethylcellulose. As mentioned earlier, most cellulose-based polymers except for PVP, have lower surface tension values in the range of 40-50 mN/m, thus similar adhesive and film-forming qualities will be seen. 

If processing of a substance in Carbomer gels is not possible because of incompatibilities, a gel with cellulose derivates may be prepared (Table 12.35). Hypromellose and hydroxyethylcellulose are nonionic and compatible with salts, acids and bases. 

Hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC) are prepared by nucleophilic ring opening of ethylene oxide and propylene oxide, respectively, by the hydroxyl anions on the anhydroglucose ring of cellulose. Reactions are conducted commercially in caustic aqueous slurry processes (72). Laboratory methods recently have been reported for preparation of cellulose ethers, esters, and carbamates imder homogeneous reaction conditions in organic solvents (88-91). Such solvents may lead to development of new commercial processes for cellulose derivatives with more imiform substitution. 

Chromogenlc substrates Ostazln Brilliant Red hydroxyethylcellulose (OBR-HEC), a soluble covalently dyed cellulose derivative, a substrate specific for endo-l,4-3-glucanases (cellulases) [4] Remazol Brilliant Blue xylan (RBB-X), a soluble covalently dyed beechwood 4-0-methyl-D-glucurono-D-xylan, a specific substrate for endo-l,4-B-xylanases [4]. Both substrates are available on request from Chemapol Ltd., Praha, Czechoslovakia. 

In the context with OH-radical attack of polysaccharides it is notable that cellulose derivatives bearing side groups, including carboxymethylcellulose, hydroxyethylcellulose and carboxymethyl starch (carboxymethyl amylopectin, carboxymethyl amylase), are predominantly intermolecularly crosslinked in aqueous solution (20-30 wt%), whereas they undergo predominantly... 

Cellulose is a biopolymer composed almost exclusively of glucose molecules. Some cellulose derivatives, like elhylcellulose or hydroxyethylcellulose, are used in cosmetics as thickening and fihnogenic agents. 

A popular approach to improve ocular drag bioavailability is to incorporate soluble polymers into an aqueous solution to extend the drug residence time in the cul-de-sac. It is reasoned that the solution viscosity would be increased and hence solution drainage would be reduced. The more commonly used viscolyzing agents include PVA and derivatives of cellulose. Cellulosic polymers, such as methylcellulose, hydroxyethylcellulose (HEC), hydroxypropyl-methylcellulose (HPMC) and hydroxypropylcellulose (HPC), are widely used as viscolyzers showing Newtonian properties. They have common properties ... 

Isogai and coworkers [99] recently prepared a series of tri-O-alkylcellulose ethers using a technique that was originally developed for permethylations and involves the use of alkyl halides, powdered sodium hydroxide, and non-aqueous solvents. Water-soluble phosphonomethylcellulose products have been produced by modiflcation of cellulose ethers with chloromethanephos-phonic acid derivatives [87,100]. Low levels of hydrocarbon residues can be incorporated into cellulose ethers, such as hydroxyethylcellulose, to yield high-viscosity, water-soluble products that display non-Newtonian behavior at low shear rates [ 101,102]. Small amounts of 2-(A, yV-diethylamino)ethylcel-lulose can be produced by the Williamson reaction of alkali cellulose with the hydrochloride of 2-chloroethyldiethylamine [103]. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly (vinyl acetate)—polytyinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system Poly(vinyl alcohol) is typically formed by hydrolysis of the poly (vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as well as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a colloid protection system. The protective colloids are similar to those used paint (qv) to stabilize latex. For poly (vinyl acetate), the protective colloids are isolated from natural gums and cellulosic resins (carboxymethylcellulose or hydroxyethylcellulose). The hydrolized polymer may also be used. The physical properties of the poly (vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended application. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly (vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. Applications are found mostly in the area of adhesion to paper and wood (see VlNYL POLYMERS). 

Chen R, Sekulic S, Zelesky T. Development and validation of a cost-effective, efficient, and robust liquid chromatographic method for the simultaneous determination of the acetyl and succinoyl content in hydroxypropyl methylcellulose acetate succinate polymer. J AOAC Int 2002 85(4) 824-831. Correction 85(6), 125A. Onda Y, Muto H, Maruyama K. Ether-ester derivatives of cellulose and their applications. United States Patent No. 4,226,981 1980. Final report on the safety assessment of hydroxyethylcellulose, methylcellulose, hydroxypropyl methylcellulose and cellulose gum. J Am Coll Toxicol 1986 5 1-59. 

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