CMC is usually an anionic polymer compound prepared by reacting natural cellulose with caustic alkali and monochloroacetic acid, with a molecular weight of 6400 (±1 000). The main by-products are sodium chloride and sodium glycolate. CMC belongs to natural cellulose modification. It has been officially called “modified cellulose” by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

quality

The main indicators to measure the quality of CMC are the degree of substitution (DS) and purity. Generally, the properties of CMC are different when the DS is different; the higher the degree of substitution, the better the solubility, and the better the transparency and stability of the solution. According to reports, the transparency of CMC is better when the degree of substitution is 0.7-1.2, and the viscosity of its aqueous solution is the largest when the pH value is 6-9. In order to ensure its quality, in addition to the choice of etherifying agent, some factors that affect the degree of substitution and purity must also be considered, such as the dosage relationship between alkali and etherifying agent, etherification time, system water content, temperature, pH value, solution concentration and salts.

Analysis of the advantages and disadvantages of sodium carboxymethyl cellulose

The development of sodium carboxymethyl cellulose is indeed unprecedented. Especially in recent years, the expansion of application fields and the reduction of production costs have made the manufacture of carboxymethyl cellulose more and more popular. The products on sale are mixed.

Then, how to determine the quality of sodium carboxymethyl cellulose, we analyze from some physical and chemical perspectives:

First of all, it can be distinguished from its carbonization temperature. The general carbonization temperature of sodium carboxymethyl cellulose is 280-300 ° C. When it is carbonized before this temperature is reached, then this product has problems. (Generally carbonization uses muffle furnace)

Secondly, it is distinguished by its discoloration temperature. Generally, sodium carboxymethyl cellulose will change color when it reaches a certain temperature. The temperature range is 190-200 °C.

Thirdly, it can be identified from its appearance. The appearance of most products is white powder, and its particle size is generally 100 mesh, and the probability of passing through is 98.5%.

Sodium carboxymethyl cellulose is a very widely used cellulose product and has a wide range of applications, so there may be some imitations on the market. So how to identify whether it is a product required by users can pass the following identification test.

Choose 0.5g of sodium carboxymethyl cellulose, which is not sure whether it is a product of sodium carboxymethylcellulose, dissolve it in 50mL of water and stir, add a small amount each time, stir at 60 ~ 70 ℃, and heat for 20 minutes to make a uniform solution, cool After the liquid detection, the following tests were carried out.

1. Add water to the test solution to dilute 5 times, add 0.5mL of chromotropic acid test solution to 1 drop of it, and heat it in a water bath for 10 minutes to appear red-purple.

2. Add 10 mL of acetone to 5 mL of the test solution, shake and mix thoroughly to produce a white flocculent precipitate.

3. Add 1mL of ketone sulfate test solution to 5mL of test solution, mix and shake to produce light blue flocculent precipitate.

4. The residue obtained by ashing of this product shows the conventional reaction of sodium salt, that is, sodium carboxymethyl cellulose.

Through these steps, you can identify whether the purchased product is sodium carboxymethyl cellulose and its purity, which provides a relatively simple and practical method for users to correctly select products