Hydroxyethylcellulose preparation

Fluidized aqueous suspensions of 15% by weight or more of hydroxyethyl-cellulose, hydrophobically modified cellulose ether, hydrophobically modified hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and polyethylene oxide are prepared by adding the polymer to a concentrated sodium formate solution containing xanthan gum as a stabilizer [278]. The xanthan gum is dissolved in water before sodium formate is added. Then the polymer is added to the solution to form a fluid suspension of the polymers. The polymer suspension can serve as an aqueous concentrate for further use. 

The low-substituted hydroxyethylcellulose which, like methyl- and ethylcellulose, is soluble in alkali, particularly when cooled, has much to recommend it from an industrial point of view. It can be formed by the action of only small quantities (0.25 to 0.5 moles) of ethylene oxide on alkali cellulose.47 The reaction product need not be isolated since there are no salts formed, but may be diluted with water or weak alkali to give a spinning solution. The product should therefore be quite cheap. Preparation and properties of hydroxyethylcellulose have been discussed by Schorger and Shoemaker.47... 

Another interesting system containing a surface active betaine ester is the dilute aqueous mixture of dodecyl betainate and hydrophobically modified hydroxyethylcellulose (HM-HEC) that has been studied by Karlberg et al. [33]. It is well known that the viscosity of mixtures of HM polymers and surfactants is strongly dependent on the concentration of the amphiphile. By preparing a mixture of a surface active betaine ester and HM-HEC in a solution buffered at a pH where the surfactant is hydrolyzed, it is possible to make a gel with a time-dependent viscosity. 

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). 

Hydroxyalkyl celluloses are obtained in the reaction of cellulose with alkene oxides or their corresponding chlorohydrins. The reaction is a base-catalyzed SN2-type substitution, and the reaction rate is proportional to the product [epoxide][CelI—O3]. The commercial preparations include hy-droxyethyl- and hydroxypropylcellulose for which ethylene oxide and propylene oxide are used as reagents. Hydroxyethylcellulose is formed according to the following equation ... 

Hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC) are prepared by reacting cotton linter or woodpulp with aqueous sodium hydroxide, and the resulting alkali cellulose is reacted with ethylene oxide and propylene oxide, respectively. 

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]. 

Nongel sieving media have been applied to problems of forensic interest by McCord et al. (1993a), who used the following procedure for buffer preparation 0.1 mAf EDTA was added to 100 mAf Trisma base and 100 mAf boric acid pH was adjusted to 8.7 with cesium hydroxide. Hydroxyethylcellulose was dissolved in this buffer at a concentration of 0.5% (w/v), and the solution was filtered through a 0.45 mm cellulose acetate filter. Prior to analysis, ethid-ium bromide was added to a concentration of 1.27 mAf. Phenylmethyl-coated... 

Substituted Cellulose Ethers. Since their introduction for ophthalmic use, MC and other substituted cellulose ethers such as hydroxyethylcellulose, hydroxypropylcel-lulose, hydroxypropyl methylcellulose (HPMC), and carboxymethylcellulose (CMC) have been used in artificial tear formulations.These colloids dissolve in water to produce colorless solutions of varying viscosity. They have the proper optical clarity, a refractive index similar to the cornea, and are nearly inert chemically. Their relative lack of toxicity, their viscous properties, and their beneficial effects on tear film stability have made cellulose ethers useful components of artificial tear preparations. Historically, the most frequently used representative of this group was MC. 

Name Methyl hydroxyethylcellulose Sample preparation Solid film, sodium chloride cell... 

Immediately after the moisture content has been determined, portions of the same undried hydroxyethylcellulose should be taken for the viscosity solution preparations. Transfer 500 mL of distilled water (4°C) into a beaker. The... 

Cellulose ethers can be prepared by various methods, as by using the common Williamson ether synthesis, with alkyl halides in the presence of a strong base (Fig. 32). This procedure is most often used to introduce carboxyl functions [O-carboxymethylcellulose (CMC)] or hydroxyl groups [3-hydroxypropylcellulose (HPC) and 2-hydroxyethylcellulose (HEC)]. 

Poly(vinylidene fluoride) (PVDF) porous supports coated with cellulose [92] were commercialized by Dow (ETNA membranes). PVDF is soluble only in a few organic solvents such as dimethyl acetamide. Cellulose is very stable in organic and aqueous solvents. However, because of its low solubility, preparing cellulose membranes is not a trivial task. Stengaard [72] proposed the preparation of composite membranes by coating chlorotrifluoroethylene/vinylidene fluoride (CTFE/VF) or PVDF supports with hydroxyethylcellulose and hydroxypropylcel-... 

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. 

Semi-IPNs prepared from chitosan and acrylamide-grafted-hydroxyethylcellulose Semi-IPNs showed pH-dependent in-vitro drug release. [27]... 

Cohen SG, Haas HC, Eamey L, Valle C Jr (1953) Preparation and properties of some ether and ester derivatives of hydroxyethylcellulose. Ind Eng Chem 45 200-203 Debeaufort E, Voilley A (1995) Methyl cellulose-based edible films and coatings I. Effect of plasticizer content on water and l-octen-3-ol sorption and transport Cellulose 2 205-213 Debeaufort E, Quezada-Gallo JA, Voilley A (1998) Edible films and coatings tomorrow s packagings a review. Crit Rev Food Sci Nutr 38(4) 299-313 de Souza Lima MM, Borsali R (2004) Rod like cellulose microcrystals Stmcture, properties and applications. Macromol Rapid Comm 25 771-787 Eitan A, Eisher FT, Andrews R, Brinson LC, Schadler LS (2006) Reinforcement mechanisms in MWCNT-filled polycarbonate. Compos Sci Technol 66 1159-1170 George J, Bawa AS, Siddaramaiah (2010) Synthesis and characterization of bacterial cellulose nanocrystals and their PVA nanocomposites. Adv Mater Res 123 383-386... 

Hydroxyethylcellulose is prepared from alkali cellulose and ethylene oxide. A segment of the product might be represented as follows ... 

Finally, a rather unusual technique was developed in Japan (25) for the identification of several drugs in pharmaceutical preparations. The technique is called thin-layer slick chromatography (TLSC) and is described as an advanced version of thin-layer chromatography in a cylindrical form. The adsorbent on the stick is a mixture of silica gel, microciystalline cellulose (proportions, 5 2) and 3% of a binder, hydroxyethylcellulose. One to ten microliters of the sample are spotted on the thin-layer stick 2 cm from the lower end and similarly, standard samples are applied on the reverse side, to ensure precise detection. For the identification of retinyl palmitate or retinyl acetate, pure benzene (200 pi) was used as developer. 

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