Methylcellulose applications

The main function of the foam stabilising agent is to reinforce the intercellular film wall by contributing rheological characteristics of viscoelasticity. The increased viscosity may also assist handling. The aim, as so often with auxiliaries, is to achieve an optimum balance. If the bubbles are too thin and wet too quickly they will collapse prematurely, whilst too stable a film could hinder uniform application. Examples of products used as foam stabilisers include thickening agents such as the polysaccharides, hydroxyethylcellulose, methylcellulose,... 

The water-soluble hydroxyethylcellulose has only a limited use as compared to water-soluble methylcellulose, principally because of the difficulty of isolating the product. Aqueous solutions of hydroxyethylcellulose do not gel on heating and the product is about as soluble in hot water as in cold, so that the method used for isolating water-soluble methylcellulose is not applicable. However, by dialyzing the reaction product the alkali and salts may be removed and the product isolated. 

Consider using methylcelluloses with high degrees of substitution (DS 2.6) and low molecular weights ( 5000) for soil removal applications, since they were found to have good antiredeposition activity while minimizing the interference with soil removal [19]. 

While reactions of low-molecular-weight compounds can sometimes be carried out in the gas phase, this technique is not applicable to macromolecular substances since they are not volatile. However, it is indeed possible to let low-molecular reagents act upon solid or dissolved polymers in gaseous form. This is done, for example, in the commercial preparation of methylcellulose by conversion of alkali cellulose with gaseous methyl chloride. 

The mechanism of separation with linear polymers is as follows. At a certain polymer concentration known as the entanglement threshold, the individual polymer strands begin to interact with each other, leading to a meshlike structure within the capillary. This allows DNA separation to take place. Many of the common polymers are cellulose derivatives, such as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and methylcellulose. Other applicable polymers include linear polyacrylamide, polyethylene oxide, agarose, polyvinyl pyrrolidone, and poly-N. Ar-dimethylacrylamide. High-resolution separation up to 12,000 bp has been reported using entangled polymer solutions. 

Fig. 27 Infiuence of the type of polymer application on film properties (top and side view). HP55 (HPMCP)-coated pellet, prepared from a micronized film dispersion (A). HP55 [hydroxypropyl methylcellulose (HPMCP)]-coated pellet, prepared from an organic solution (B).

Hlpasawa N, Ishise S, Miyata M, Danjo K. Application of nilvadipine solid dispersion to tablet formulation and manufacturing using crospovidone and methylcellulose on dispersion carriers. Chem Pharm Bull 2004 52(2) 244-247. 

Dimethyl phthalate is used in pharmaceutical applications as a solvent and plasticizer for film-coatings such as hydroxypropyl methylcellulose, cellulose acetate and cellulose acetate-butyrate mixtures. ... 

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. 

Methylcellulose is best dissolved in water by one of three methods, the most suitable being chosen for a particular application. 

Tapia Villanueva C, Sapag Hagar J. Methylcellulose its pharmaceutical applications. Acta Parm Bonaerense 1995 14(Jan—Mar) 41-47. 

In 1940, Eastman Kodak Company published a U.S. patent that provided one of the earliest de.scriptions of enteric coating of medicaments. The patent claimed the use of a cellulose derivative containing free carboxyl groups as an enteric film forming polymer. Specifically, the claimed enteric polymer was cellulose acetate phthalate (CAP) (34). Numerous enteric cellulose derivatives have been developed since this early account and these polymers remain as some of the most widely used for enteric coating applications. In addition to CAP these derivatives include cellulose acetate trimellitate (CAT), cellulose acetate succinate (CAS), hydroxypropyl methylcellulose phthalate (HPMCP), and hydroxypropyl methylcellulose acetate succinate (HPMCAS). The molecular structure of these polymers is depicted in Figure 1 with their respective substituent groups listed in the caption. 

Isoelectric focusing is a steady-state technique, and its application in capillaries requires the partial or total supression of electroosmotic flow. Capillaries used for CIEF can be derivatized with methylcellulose or linear polyacrylamide, to block the surface silanol groups, whose ionization is responsible for electroosmotic... 

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