Water-soluble cellulose ether viscosity

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). 

Fig. 13. Viscosity-temperature behavior of water-soluble cellulose ethers [11]...

Hydroxypropylmethyl cellulose (HPMC) is a water-soluble cellulose ether that is mainly used in the preparation of controlled release tablets. Viscosity is the main variable responsible for controlling the release. The hydration and gel forming abilities of HPMC can be used to prolong the drug release of the active ingredient. 

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). 

CP can also be prepared by the reaction of cellulose with phosphoms oxychloride in pyridine (37) or ether in the presence of sodium hydroxide (38). For the most part these methods yield insoluble, cross-linked, CP with a low DS. A newer method based on reaction of cellulose with molten urea—H PO is claimed to give water soluble CP (39). The action of H PO and P2 5 cellulose in an alcohol diluent gives a stable, water-soluble CP with a high DS (>5% P) (40). These esters are dame resistant and have viscosities up to 6000 mPa-s(=cP) in 5 wt % solution. Cellulose dissolved in mixtures of DMF—N2O4 can be treated with PCl to give cellulose phosphite [37264-91-8] (41) containing 11.5% P and only 0.8% Cl. Cellulose phosphinate [67357-37-5] and cellulose phosphonate [37264-91 -8] h.a.ve been prepared (42). 

Water soluble, high viscosity grade cellulose ether compositions are useful for the reduction of serum lipid levels, particularly total serum cholesterol, serum triglycerides and low density lipoprotein (LDL) levels, and/or attenuate the rise of blood glucose levels. The compositions may be in the form of a prehydrated ingestible composition, e.g. a gelatin, or a comestible, e.g. a biscuit. 

Class A. Water-soluble synthetic and natural organic polymers, which increase the viscosity of the mixing water. They include cellulose ethers, pregelatinized starches, polyethylene oxides, alginates, carrageenans, polyacrylamide, carboxyvinyl polymers and polyvinyl alcohol. 

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]. 

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. 

Class A—synthetic and natural organic polymers soluble in water, increasing the viscosity of mixing water these are the following groups of compounds cellulose ethers, poly(ethylene oxide), polyacrylamides, polyvinylalcohol and others. 

These include ethyl cellulose, hydroxy ethyl cellulose, methyl cellulose, sodium carboxy methyl cellulose, and benzyl cellulose. Ethyl and benzyl cellulose can be used as hot-melt adhesives. Methyl cellulose is a tough material, completely non-toxic, tasteless, and odorless, which makes it a suitable adhesive for food packages. It is capable of forming high-viscosity solutions at very low concentrations, so it is useful as a thickening agent in water-soluble adhesives. Hydroxy ethyl cellulose and sodium carboxy methyl cellulose can also be used as thickeners. The cellulose ethers have fair to good resistance to dry heat. Water resistance varies from excellent for benzyl cellulose to poor for methyl cellulose. ... 

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