Hydroxyethylcellulose polymer

A derivatized hydroxyethylcellulose polymer gel exhibited excellent fluid-loss control over a wide range of conditions in most common completion fluids. This particular grated gel was compatible with the formation material and caused little or no damage to original permeability [1341]. Detailed measurements of fluid loss, injection, and regained permeability were taken to determine the polymer particulate s effectiveness in controlling fluid loss and to assess its ease of removal. Hydroxyethylcellulose can be etherified or esterified with long chain alcohols or esters. An ether bond is more stable in aqueous solution than is an ester bond [96]. 

Cationic Hydroxyethylcelluloses. These materials are manufactured by Union Carbide Corp. and National Starch and Chemical Corp., marketed under the trade names Polymer JR and Celquat, respectively (47,48). The cationic substituent on Polymer JR is presumably 2-hydroxypropyltrimethylammonium chloride (72). Celquat is presumably the reaction product of HEC with /V,/V-dia11y1-/V,/V-dimethy1ammonium chloride (73). Their primary appHcation is in shampoos and hair conditioners wherein the cationic moiety imparts substantivity to hair. Some typical properties of Celquat resins are given in Table 7. 

Carboxymethylcellulose, polyethylene glycol Combination of a cellulose ether with clay Amide-modified carboxyl-containing polysaccharide Sodium aluminate and magnesium oxide Thermally stable hydroxyethylcellulose 30% ammonium or sodium thiosulfate and 20% hydroxyethylcellulose (HEC) Acrylic acid copolymer and oxyalkylene with hydrophobic group Copolymers acrylamide-acrylate and vinyl sulfonate-vinylamide Cationic polygalactomannans and anionic xanthan gum Copolymer from vinyl urethanes and acrylic acid or alkyl acrylates 2-Nitroalkyl ether-modified starch Polymer of glucuronic acid... 

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. 

Another approach to improving the wettability of poorly soluble drugs is to treat the drug with a solution of a hydrophilic polymer. Lerk et al. [137] reported that both wettability of the powder and the rate of dissolution of hexobarbital from hard gelatin capsules could be greatly enhanced if the drug were treated with methylcellulose or hydroxyethylcellulose. In this process, called hydrophilization, a solution of the... 

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. 

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. 

Different grades of Methocel and Metolose are supplied, with nominal viscosities of 4000 mPa s (measured with a Brookfield viscometer on a 2% w/v solution). Methocel 4M types E and are different in their hydration rates, type being the quickest. Metoloses SH4000 differ in their gel temperature. Grades 60 and 90 were used. Another polymer of 4000 mPa s viscosity was used hydroxyethylcellulose, in order to observe effects on the dissolution rate. 

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). 

Within this group, the linear polymers have been most intensively studied and researched. The main area of interest lies in water-soluble polymers. However, there have also been many studies into organic solutions, although there exist problems with odor and toxicity in the case of analytical studies. Among the water-soluble additives, tests were made especially on polyethyleneoxide (PEO), polyacrylamide and the coacrylates (PAAm, PAAm/AAcNa), polyacrylic add (PAA), guar gum (GG), carboxymethylcellulose (CMC) and sodium salts, as well as hydroxyethylcellulose (HEC). From these tests, PEO proved to be the most effective flow improver, followed closely by PAAm, which is somewhat more stable than PEO in turbulent flow. 

The commercialization of new watei-soluble polymers is most often a slow process. For example, hydroxyethylcellulose (HEC) was envisaged in 1937 by... 

Tian, H.J., Landers, J.P., Hydroxyethylcellulose as an effective polymer network for DNA analysis in uncoated glass microchips optimization and application to mutation detection via heteroduplex analysis. Anal. Biochem. 2002,309,212-223. 

Figure 4.40 shows the shear-thinning behavior of an aqueous solution of ethyl hydroxyethylcellulose as a function of the concentration. The pseudoplastic behavior is observed at lower polymer concentrations as the molecular weight of the polymer increases. An aqueous solution of ethyl hydroxyethylcellulose becomes pseudoplastic at concentrations of less than 1%. Above the critical value of the shear stress the flow behavior is non-Newtonian, and viscosity decreases with the increasing shear stress. The critical stress is in the range of 0.1 N/m2 for the solution. 

Adhesive polymers used in oral patches include poly(hydroxyethylcellulose), poly (hydroxypropylcellulose), poly(sodium carboxymethylcellulose), poly(acrylic acid), poly(methacrylic acid), polyvinylpyrrolidone) and poly (vinyl alcohol). 

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 ... 

Ruhr s group studied the separation of double- and single-stranded DNA restriction fragments in capillary electrophoresis with polymer solutions under alkaline conditions in epoxy-coated capillaries and found that at pH 11 the theoretical plate numbers exceeded several millions [96], At pH 12, single-stranded DNA molecules were still well separated in entangled hydroxyethylcellulose (HEC) solutions, but the resolution decreased significantly in dilute polymer solutions. 

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). 

Over the years the other substituted cellulose ethers, particularly hydroxyethylcellulose and HPMC, have been more frequently used. They are somewhat less viscous than MC but possess cohesive and emollient properties equal or superior to those of MC. Like MC, these ethers also mix well with other polymers and substances present in artificial tear formulations and are compatible with... 

Figure 1.4 Network structure formed by an aqueous surfactant solution mixed with an associative thickening polymer hydroxyethylcellulose (HEC) with cetyl (16-carbon alkyl) side branches. (Reprinted from Clarke 1993, by courtesy of Marcel Dekker, Inc.)...

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. 

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. 

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