Views: 10 Author: Site Editor Publish Time: 2022-11-04 Origin: Site
Carboxymethyl cellulose is the most representative ionic cellulose ether, and its sodium salt is usually used, so it is also called sodium carboxymethyl cellulose. In addition, it can also have its ammonium salt, aluminum salt and so on.
Pure CMC is a white or slightly yellow fibrous powder or granular solid, odorless and tasteless. CMC is easily dispersed in water to form a colloidal solution with a certain viscosity. The equilibrium moisture of CMC increases with the increase of air humidity and decreases with the increase of temperature. At room temperature and average humidity of 80% to 85%, the equilibrium moisture is above 26%, while the moisture in the product is about 10%, which is lower than the equilibrium moisture. The solution viscosity of CMC is related to factors such as concentration, temperature, pH value, storage time and salts. The carboxymethyl group in CMC can have bridging reaction with polyvalent metal ions; it can react with iodic acid, nitrogen dioxide, hypochlorite, hydrogen peroxide, other chlorinating agents and ultraviolet rays, etc., in the presence of alkali, The oxidation reaction causes the scission of the main chain, resulting in the decrease of the degree of polymerization, that is, the decrease of the viscosity; in the presence of an acid catalyst, it is easy to hydrolyze, so that the main chain is broken and the degree of polymerization decreases; CMC can form salts with alkali metals and amines, monovalent salts They are soluble, the most common being sodium salts, and salts with more than two valences, such as zinc, barium, aluminum, and copper, become insoluble. Although CMC solution is more difficult to spoil than natural rubber, under certain conditions, especially the action of cellulase and amylase will cause it to spoil, resulting in a decrease in viscosity. Digestive enzymes in the human body do not decompose CMC, which is why CMC can be used in the food industry.
In the process of manufacturing CMC, the main chemical reactions are: (1) alkali cellulose and alkali aqueous solution undergo alkalization reaction to generate alkali cellulose; (2) alkali cellulose undergoes etherification reaction with sodium monochloroacetate (or monochloroacetic acid). The production methods of CMC can be divided into two types: the water-based method using water as the reaction medium and the solvent-based method using an organic solvent as the medium.
1. The water-based method is the most classic method in CMC production and is still used by some factories. It is characterized by simple equipment, low investment and low cost, and it can manufacture medium and low-grade CMC products, which are used in the fields of detergent, textile sizing, adhesive and petroleum industry.
2. The solvent method is characterized by short production cycle, high product quality and wide application range, but high material consumption, high equipment investment and high cost.
1. Used in synthetic detergents and soap making industry CMC has the functions of emulsifying and protective colloid, and is the best active auxiliary agent for synthetic detergents. Generally, the amount of CMC added to the detergent is 0.5% to 2.0%. It has been determined that the detergent added with 2% CMC can keep the whiteness of white fabrics above 90% after washing.
2. It is used in oil and natural gas drilling, well drilling and other projects. Adding CMC to the mud can form a thin and firm filter cake with low permeability on the well wall, so as to reduce the water loss, thereby reducing the penetration of the mud into the formation due to anhydrous mud. Caused by shrinkage, collapse, block drop and other phenomena.
3. It is used in the textile and printing and dyeing industries as warp sizing for cotton, wool, silk, chemical fiber and other fabrics, which can not only save a lot of grain and edible oil, but also have good stability, high yarn strength, smoothness, wear resistance and other effects; As a printing color paste, it can also improve the printing brilliance, the fabric feels soft after dyeing, and has the effect of preventing moth and mildew.
4. It is used in the paper industry as a smoothing agent and an acid applicator in the paper industry. After adding 0.1%～0.3% CMC to the pulp, the tension of the paper can be increased by 40%～so%, and the paper quality is uniform at the same time, which is convenient for the infiltration of printing ink.
5. It can be used in the silicate industry as an adhesive, plasticizer, and color-fixing agent for blanks. Adding CMC during concrete construction can reduce water loss, retard setting, and improve building strength and service life.
6. Used in the food industry CMC is odorless, tasteless, non-toxic, easy to dissolve, can be stored for a long time without spoilage, has high viscosity and strong shape retention, so it is widely used in the food industry, such as thickeners for jams, ice creams. Stabilizer, molding agent for jelly, surface coating preservative for vegetables and fruits, etc.
7. It is used as an emulsion stabilizer for various injections in the pharmaceutical industry, as a base material for ointments, as an adhesive for tablets, etc.
8. It is used in daily industrial products such as forming agent of toothpaste, stabilizer of skin care cream, adhesive of mosquito coil, etc. In addition, it is also used as glazing agent, colorant for leather, stabilizer for foam fire extinguishing agent, dispersant for pesticide, sizing agent in coating industry, polymerization inhibitor during formaldehyde production and storage, surface of film film and photographic negative. treatment agent, etc. Toxicity and Protection This product is non-toxic and non-dangerous.
Because CMC is easy to absorb water, it should be protected from sun and rain during transportation. When storing, it should be placed in a clean, dry and ventilated warehouse, protected from direct sunlight, away from heat sources, and should not be mixed or transported with toxic substances.
Most of them are processed into colloidal thickeners, emulsifiers, dispersants, oil drilling muds and fabric sizing agents, treatment agents and ceramic adhesives by using their water-soluble properties.