01. Introduction of cellulose
Cellulose is a macromolecular polysaccharide composed of glucose. Insoluble in water and general organic solvents. It is the main component of plant cell wall, and it is also the most widely distributed and most abundant polysaccharide in nature.
Cellulose is the most abundant renewable resource on the earth, and it is also the natural polymer with the largest accumulation. It has the advantages of being renewable, completely biodegradable, and good biocompatibility.
02. Reasons for modifying cellulose
Cellulose macromolecules contain a large number of -OH groups. Due to the effect of hydrogen bonds, the force between macromolecules is relatively large, which will lead to a large melting enthalpy △H; on the other hand, there are rings in cellulose macromolecules. Like structure, the rigidity of the molecular chain is greater, which will lead to a smaller melting entropy change ΔS. These two reasons make the temperature of molten cellulose (= △H / △S ) will become higher, and the decomposition temperature of cellulose is relatively low. Therefore, when the cellulose is heated to a certain temperature, fibers will appear The phenomenon that the cellulose has been decomposed before it starts to melt, therefore, the processing of cellulose materials cannot adopt the method of first melting and then molding.
03. Significance of cellulose modification
With the gradual depletion of fossil resources and the increasingly serious environmental problems caused by waste chemical fiber textiles, the development and utilization of natural renewable fiber materials has become one of the hot spots that people pay attention to. Cellulose is the most abundant renewable natural resource in nature. It has excellent properties such as good hygroscopicity, antistatic, strong air permeability, good dyeability, comfortable wearing, easy textile processing, and biodegradability. It has characteristics that are incomparable to chemical fibers. .
Cellulose molecules contain a large number of hydroxyl groups, which are easy to form intramolecular and intermolecular hydrogen bonds, and decompose at high temperatures without melting. However, cellulose has good reactivity, and its hydrogen bond can be destroyed by chemical modification or grafting reaction, which can effectively lower the melting point. As a variety of industrial products, it is widely used in textiles, membrane separation, plastics, tobacco and coatings.
04. Cellulose etherification modification
Cellulose ether is a kind of cellulose derivative obtained by etherification modification of cellulose. It is widely used due to its excellent thickening, emulsification, suspension, film formation, protective colloid, moisture retention, and adhesion properties. Used in food, medicine, paper making, paint, building materials, etc.
Etherification of cellulose is a series of derivatives produced by the reaction of hydroxyl groups on the cellulose molecular chain with alkylating agents under alkaline conditions. The consumption of hydroxyl groups reduces the number of intermolecular hydrogen bonds to reduce the intermolecular forces, thereby Improve the thermal stability of cellulose, improve the processing performance of materials, and at the same time reduce the melting point of cellulose.
Examples of effects of etherification modification on other functions of cellulose:
Using refined cotton as the basic raw material, the researchers used a one-step etherification process to prepare carboxymethyl hydroxypropyl cellulose complex ether with uniform reaction, high viscosity, good acid resistance and salt resistance through alkalization and etherification reactions. Using one-step etherification process, the produced carboxymethyl hydroxypropyl cellulose has good salt resistance, acid resistance and solubility. By changing the relative amounts of propylene oxide and chloroacetic acid, products with different carboxymethyl and hydroxypropyl contents can be prepared. The test results show that the carboxymethyl hydroxypropyl cellulose produced by one-step method has a short production cycle, low solvent consumption, and the product has excellent resistance to monovalent and divalent salts and good acid resistance.
05. Prospect of cellulose etherification modification
Cellulose is an important chemical and chemical raw material that is rich in resources, green and environmentally friendly, and renewable. The derivatives of cellulose etherification modification have excellent performance, wide range of uses and excellent use effects, and meet the needs of the national economy to a large extent. And the needs of social development, with the continuous technological progress and the realization of commercialization in the future, if the synthetic raw materials and synthetic methods of cellulose derivatives can be more industrialized, they will be more fully utilized and realize a wider range of applications. Value
Post time: Feb-20-2023