Synthesis and application of carboxymethyl cellulose salts
Carboxymethyl cellulose is a kind of cellulose ethers obtained by etherification of natural cellulose, and generally refers to its sodium salt. In recent years, sodium carboxymethyl cellulose (CMC-Na) has been widely used in food and dairy products, petroleum drilling, mineral processing papermaking, ceramic construction, printing and sizing, chemical separation, and other fields, providing adhesion, thickening, and filtration loss. , Suspension and improving rheology, etc., showing a broad application prospects. However, the application of carboxymethyl cellulose sodium salt also shows some limitations. Therefore, the development of other carboxymethyl cellulose salts to replace CMC-Na has important theoretical and application values.
The common carboxymethyl cellulose salts include lithium, potassium, calcium, and ammonium salts in addition to sodium salts. This article briefly introduces the functions and synthesis methods of several cellulose salts.
1. Lithium carboxymethyl cellulose (CMC-Li):
Lithium-ion batteries currently produced in China contain heavy metal substances that seriously damage the environment. In order to solve the problem of environmental pollution, a new electrolyte needs to be found to replace the heavy metal electrolyte or polymer electrolyte to reduce pollution.
CMC-Li is a product neutralized with lithium hydroxide after CMC-Na acidification. It is easy to prepare and has a large volume of anions. If it is applied to the electrolyte of a lithium ion battery, it will be compared with other lithium salts with a smaller anion volume ( Such as LiFePO4, Li2FePO4F, etc.), CMC-Li has the advantages of reducing the association of positive and negative ions; meanwhile, CMC-Li is an ionic cellulose derivative. In addition to the general properties of lithium battery electrolyte, it also has the ability to The advantages of natural degradation, renewable and excellent conductivity, and a wide range of sources, is very suitable for large-scale applications.
2. Potassium carboxymethyl cellulose (CMC-K):
CMC-K is a water-soluble cellulose derivative made by refining cotton with potassium hydroxide and chloroacetic acid under alkaline conditions. CMC-K is used to replace CMC-Na as a common food additive in the food industry. Studies have found that excessive intake of sodium ions can cause diseases such as diabetes, hypertension, and cardiovascular disease, so it is necessary to reduce the sodium consumption in daily life and use some potassium salts instead of sodium salts. In the petroleum industry, the effect of CMC-K in inhibiting the expansion of rock and soil hydration is significantly better than that of CMC-Na. It can control the drilling fluid medium into the formation and inhibit the expansion and dispersion of mud shale hydration.
Carboxymethyl cellulose potassium can also be prepared by acidifying CMC-Na, letting H + replace Na + in CMC-Na, and then reacting the acidified material with KOH liquid or K2CO3 powder.
3. Carboxymethyl cellulose calcium (CMC-Ca)
CMC-Ca is insoluble in water and swells with water absorption. It is the only calcium-containing disintegrant in the world. CMC-Ca is mainly used in tablets, as a binder at 5% to 15%, as a disintegrant at 1% to 15%, and the maximum concentration is 15wt%. Because the presence of calcium will cause it to react with some phosphate and sulfate-containing drugs, it has good compressibility and disintegration.
There are two main methods for preparing CMC-Ca as a pharmaceutical excipient: one is called the salt exchange method, that is, treating alkaline cellulose with chloroacetic acid (or its sodium salt), and then replacing the sodium in the product with CaCl2; For the neutralization method, acidic CMC-Na is acidified to obtain acidic carboxymethyl cellulose, and then reacted with calcium hydroxide or calcium carbonate to form CMC-Ca.
4.Carboxymethyl cellulose ammonium (CMC-NH4)
Carboxymethylcellulose ammonium is a common binder. Compared with other carboxymethylcellulose salts, it has the characteristics of good cohesiveness and small residue after roasting. It is suitable for certain requirements on metal ions. Or sensitive operating conditions. For example, in the current selective catalytic reduction denitrification (SCR) process preparation for nitrogen oxides, it is necessary to build a high-performance catalyst into a uniform shaped paste with a certain mechanical strength and pore structure through various molding aids. Therefore, there are higher requirements for adhesives. The presence of potassium, sodium and other metal ions can cause catalyst poisoning or affect catalytic efficiency, so conventional carboxymethyl cellulose salts cannot be used. Since there is no residual metal ion after the carboxymethyl cellulose ammonium is roasted, it can well meet the requirements for the preparation of SCR. In addition, carboxymethyl cellulose ammonium is also suitable for phosphor spraying requirements. It can be used as a suspension stabilizer for phosphors. After drying, it avoids the influence of alkali metal ions on the luminous center ions and sensitizer ions of the phosphor.
Similar to other carboxymethyl cellulose salts, carboxymethyl cellulose ammonium is also mainly obtained by acidifying sodium carboxymethyl cellulose and then adding the corresponding cationic component (such as ammonia ethanol solution) to react.
Due to the increasingly serious environmental pollution and energy crisis, the development of natural renewable resources has attracted great attention from countries around the world. With the continuous development of application fields, cellulose and its derivatives are one of the most promising resources, with research value unmatched by other materials. Such renewable natural macromolecular compound resources will remain the focus of research in many fields in the coming decades.
Post time: Aug-01-2020