Ethers mixed cellulose

Mixed alginate salts Mixed catalysts Mixed cellulose ethers... 

Over the past years considerable attention has been paid to the dispersing system since this controls the porosity of the particle. This is important both to ensure quick removal of vinyl chloride monomer after polymerisation and also to achieve easy processing and dry blendable polymers. Amongst materials quoted as protective colloids are vinyl acetate-maleic anhydride copolymers, fatty acid esters of glycerol, ethylene glycol and pentaerythritol, and, more recently, mixed cellulose ethers and partially hydrolysed polyfvinyl acetate). Much recent emphasis has been on mixed systems. 

The above mixed cellulose ethers by adjusting the D.S./M.S. balance, exhibit variations in their hydrophilic/lyophilic balance that is, their ability to dissolve in and form micelles in water. In this manner, they can function as surfactants and disperse non-polar compounds in water. 

Hydroxypropylmethylcellulose (HPMC) is one of the many mixed ethers of cellulose. It is prepared by reactions of alkali cellulose with methyl chloride and propylene oxide in a slurry process. Reaction conditions may be varied to control compositions despite the greater reactivity of methyl chloride. HPMC is an extremely effective viscosifier compared to conventional cellulose ethers. Its mi-croheterogeneous nature, phase behavior, and interaction with surfactants allow use in food, pharmaceutical, and coatings applications (72,87). 

Depending on the number of different substituents, esters and ethers of cellulose can be divided in single and mixed compounds. Table 2.2.12 lists some examples that are commercially available. Furthermore, also ether esters, cross-linked, and graft derivatives exist. 

Hydroxpropyl) Methyl Cellulose n A mixed ether of cellulose containing both hydropropyl and methyl groups. 

To 2 g of cellulose powder add 6 ml of a 5 per cent solution of arachis oil, B.P,y in redistilled ether, then add more of the ether, mix thoroughly and evaporate off the ether while still mixing. Mix the residual oleated cellulose into a thin slurry with THF-TEA solvent (a mixture of 5 volumes of triethylamine, 25 volumes of tetrahydrofuran and 70 volumes of water), transfer to the chromatographic tube and allow to drain. 

The largest volumes are represented by organic binders where - sodium alginates, - gum arable, - tragacanth, - sucrose molasses, - lignosulfo-nate, - methyl cellulose (also mixed ethers), - carboxymethyl cellulose and - starch are used. 

In context with RR, the following w. should be mentioned alginates (- sodium alginate) ->car-boxymethyl cellulose - carrageenan - guar gum - locust gum gum arabic - hydroxyethyl cellulose - hydroxypropyl cellulose - methyl-cellulose - mixed ethers of cellulose ->pectin, - starches, starch esters, - starch ethers, - oxidized starches, -+dextrins, - starch hydrolysis products, - maltodextrins and their derivatives, - dextran, - scleroglucan, - maltodextrins and - xanthan. 

The derivatives are hydroxyethyl and hydroxypropyl cellulose. AH four derivatives find numerous appHcations and there are other reactants that can be added to ceUulose, including the mixed addition of reactants lea ding to adducts of commercial significance. In the commercial production of mixed ethers there are economic factors to consider that include the efficiency of adduct additions (ca 40%), waste product disposal, and the method of product recovery and drying on a commercial scale. The products produced by equation 2 require heat and produce NaCl, a corrosive by-product, with each mole of adduct added. These products are produced by a paste process and require corrosion-resistant production units. The oxirane additions (eq. 3) are exothermic, and with the explosive nature of the oxiranes, require a dispersion diluent in their synthesis (see Cellulose ethers). 

Antiredeposition agents contribute to the appearance of washed fabrics. Sodium carboxymethylceUulose [9004-32-4], NaCMC is the most widely used, and on cotton fabrics, the most effective. With the advent of synthetic fabrics, other cellulose derivatives, eg, methylceUulose [9004-67-5], hydroxybutjiceUulose, hydroxypropyl- and mixed methyl and hydroxybutyceUulose ethers have been shown to be more effective than NaCMC (8) (see... 

HPC exhibited a notable increase in adsorption with increasing NaCl concentration. Entrapment in the interlayer of recovered sodium montmorillonite did not vary with salinity the extent of entrapment was greater with the 4 M.S. HE and HP celluloses than either of the 2.0 M.S. polymers. Mixed ethers of HEC (2 M.S.) containing an anionic (carboxymethyl) or cationic (3-0-2-hydroxypropyltrimethylaramonium chloride) group at 0.4 M.S. levels did not adsorb from fresh water. Adsorption of these polar mixed ethers increased with increasing electrolyte until electrostatic and solvation effects were negated in 0.54N NaCl solutions and the adsorbed amounts typical of a 2 M.S. HEC were observed. Interlayer entrapments comparable to the equivalent M.S. HEC were observed at lower (0.18N) electrolyte concentrations. 

Ethylhydroxyethylcellulose (EHEC) is a nonionic mixed ether available in a wide variety of substitutions with corresponding variations in aqueous and organic liquid solubilities. It is compatible with many oils, resins, and plasticizers along with other polymers such as nitrocellulose. EHEC is synthesized through a two-step process beginning with the formation of the HEC-like product through reaction between the basic cellulose and ethylene oxide. The second step involves further reaction with ethyl chloride. 

Bancroft cites cases in which disintegration is effected more readily in mixed solvents than by either solvent alone such as cellulose nitrate in ether alcohol mixtures. The interfacial surface tensions of such mixtures do not appear to have been measured. 

---