The nature and use of cellulose derivatives
Starch can be used as a diluent, binder, disintegrant, and can be used to prepare dextrin and starch pulp. Chemical experiments with amylose test iodine. Of course, as a plant energy storage material can also eat. Organic derivatives such as rayon, cellophane and nitrates, acetate and the like, and ether derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose and polyanionic cellulose are prepared on the basis of textile and papermaking. Raw material is used as a dietary fiber.
The basic rules of esterification and etherification of cellulose In the cellulose molecule, the position of the three hydroxyl groups in the glucose group is different, and the influence of the adjacent substituents and the spatial blocking effect are different. The relative acidity and dissociation of the three hydroxyl groups are: C> C> C When the etherification reaction is carried out in the alkaline medium, the C hydroxyl group first reacts, then the C hydroxyl group, and finally the C primary hydroxyl group. In the acidic medium for esterification reaction, the reaction of the hydroxyl reaction is difficult and etherification reaction in the opposite order. When reacted with a larger amount of substituted reagents, the spatial hindrance has an important effect, and the space hindering the smaller C hydroxyl groups is easier to react than C and C hydroxyl groups.
By replacing the reagent selection and process design, the product can be dissolved in water, dilute alkali solution or organic solvent, or have thermoplastic properties such as chemical fiber, film, film, plastic, insulating material, coating, slurry , Polymeric dispersants, food additives and household chemical products. The nature of the cellulose derivative and the nature of the substituent, the degree of substitution of the three hydroxyl groups on the glucose group, and the distribution of the substituents along the macromolecular chain. Due to the randomness of the reaction, the following three substitutions are different in other cases (homogeneous or heterogeneous reactions) except that the three hydroxyl groups are substituted (DS = 3) And non-substituted glucose groups: (1) monosubstituted (DS is 1, C, C or C position is substituted, the structural formula see cellulose); ② disubstituted (DS is 2, C, C, C, C Or C, C position is replaced); ③ total substitution (DS is 3). Thus, the properties of the same cellulose derivative having the same substitution value may also be quite different. For example, the cellulose diacetate which is directly esterified to DS of 2 is insoluble in acetone, but the cellulose diacetate obtained by saponification of the fully esterified cellulose triacetate can be completely dissolved in acetone. The irreducibility of this substitution is related to the basic rule of cellulose ester and etherification.
