Hydroxyl ethyl cellulose

Some previous work is shown in Table I R. D. Smith (2) impregnated the paper in a book with acrylic resin and ethyl hydroxyl-ethyl cellulose solutions to increase fold. Salz and Skrivanek (2) patented solutions of polyvinyl butyral and formal for the purpose these materials have been supplied under the name of Regnal. Baer, Indictor, and Joel (3) compared the folding endurance of papers impregnated with Regnal,... 

The cellulose ethers constitute another important group of cellulose derivatives prepared from alkali cellulose by standard etherification reactions between the hydroxyl groups and an alkyl halide. The properties of the ethers depend on the extent of the reaction that is, the degree of etherification. In general, the ethyl celluloses are water-insoluble thermoplastic materials, whereas methyl ether, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose are soluble in cold water and are used as viscoelastic thickeners and adhesives. 

The hydrophobieally modified cellulosics consist of hydroxyethyl cellulose-based products, the first commercial associative thickeners, and more recently ethyl hydroxyethyl cellulose-based products. Relatively low molecular weight grades of the cellulosics are used, and these are modified via available hydroxyl groups on the polymer backbone. Hydrophobe substituents are one or two ethylene oxide imits terminated with an alkyl or alkylaryl group. The hydrophobe modification makes these cellulosics more Newtonian for better film build and leveling. 

On the other hand, numerous observations favour the opinion that the solvent enters into a chemical combination with nitrocellulose to form solvates. Some of those solvates are stable only at low temperatures. For instance, cellulose dinitrate does not dissolve in methyl alcohol at room temperature, though on cooling it does so. The cellulose nitric ester precipitates again when the solution is heated. Similar behaviour is observed with ethyl alcohol a lower temperature causes nitrocellulose to swell or even to dissolve more readily. The solvent seems likely to be bound to free hydroxyl radicals (Highfield [36]). The hypothesis explains why nitrocellulose is soluble in a mixture of ether and alcohol, though neither of these solvents, when used separately, is capable of dissolving it. It is assumed that first an alcohol solvate of nitrocellulose is formed which then dissolves in the ether. 

In unmodified cellulose the hydroxyl groups give a large amount of hydrogen bonding which leads to insolubility in most solvents. On the other hand if these arc changed by chemical reactions to ether or ester groups a much more tractable material results. Cellulose acetate, butyrate and nitrate methyl and ethyl ether and carboxy methyl ether are widely used modified celluloses. Starches also are modified, but much less commercial success has been had with them. 

Nature produces a tremendous amount of methyl alcohol, simply by the fermentation of wood, grass, and other materials made to some degree of cellulose. In fact, methyl alcohol is known as wood alcohol, along with names such as wood spirits and methanol (its proper name the proper names of all alcohols end in -ol). Methyl alcohol is a colorless liquid with a characteristic alcohol odor. It has a flash point of 54°F, and is highly toxic. It has too many commercial uses to list here, but among them are as a denaturant for ethyl alcohol (the addition of the toxic chemical methyl alcohol to ethyl alcohol in order to form denatured alcohol), antifreezes, gasoline additives, and solvents. No further substitution of hydroxyl radicals is performed on methyl alcohol. 

In bonding wood, the reaction of isocyanate groups with the numerous hydroxyl groups that are present in the various components of wood—cellulose, hemicellulose, and lignin—is possible. The product of this chemical reaction with wood is the urethane bond as shown in Reaction I. Methyl, ethyl, propyl, and butyl isocyanates... 

The manner in which the ethyl group is added to cellulose can be described by the degree of substitution (DS). The DS designates the average number of hydroxyl positions on the anhydroglucose unit that have been reacted with ethyl chloride. Since each anhydroglucose unit of the cellulose molecule has three hydroxyl groups, the maximum value for DS is three. 

The two main types of polymers are synthetic polymers snch as hydrolyzed polyacrylamide (HPAM) and biopolymers such as xanthan gum. Less commonly used are natural polymers and their derivatives, snch as gnar gnm, sodium carboxymethyl cellulose, and hydroxyl ethyl cellnlose (HEC). Table 5.1 summarizes the characteristics of different polymer stmctnres. 

Cellulose derivatives are formed by replacing the hydrogen of the primary and secondary hydroxyl groups of cellulose with such groups as methyl, ethyl, hydroxyethyl, carboxymethyl, etc. The resulting cellulose ethers are very stable the substituent groups are not readily removed by enzymatic means. 

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