What kind of dangerous process is etherification of cellulose?

The etherification reaction of cellulose is different because of the different substituents introduced, and the etherification process is also different, so it cannot be generalized. The specific analysis is as follows.

Cellulose is a macromolecular polysaccharide composed of glucose, and its structural formula is as follows:

Cellulose etherification is to make cellulose into a polymer compound with ether structure. Each monomer (glucosyl ring) in cellulose macromolecules contains three hydroxyl groups, the primary hydroxyl group on the sixth carbon atom and the secondary hydroxyl groups on the second and third carbon atoms, and the hydrogen in the hydroxyl groups is replaced by hydrocarbon groups to generate cellulose ether derivatives. Cellulose is a kind of polyhydroxy polymer compound, which neither dissolves nor melts. Cellulose can be dissolved in water, dilute alkali solution and organic solvent after etherification, which is thermoplastic, so it is used in many fields.

According to different etherification reagents, methyl cellulose, hydroxyethyl cellulose, ethyl cellulose, benzyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and phenyl cellulose are used. Although the general process of etherification process is similar, the toxicity and danger of etherification reagents are different due to different kinds of etherification reagents and different reaction conditions, so the danger of etherification process of various varieties of cellulose is also different.

(1) preparation of alkali cellulose: that is, natural cellulose reacts with sodium hydroxide under certain conditions to produce alkali cellulose. (Generally speaking, this is the boiling of cellulose in alkaline solution, which is not flammable, explosive and toxic. Please be careful not to let lye stick to the skin, the risk factor is extremely small. )

(2) etherification. Some etherification reagents are nontoxic, such as sodium chloroacetate; Some etherifying agents are very toxic, such as methyl bromide, ethyl bromide, methyl chloride, ethylene oxide, etc., all of which are highly toxic gases. If the ventilation equipment in the production workshop or laboratory is not good, it is often difficult to prevent toxic gases. I made hydroxyethyl starch. The structure of starch and cellulose is similar, and the etherification process is similar. The etherification reagent used is ethylene oxide. When I do it carefully, I operate in a fume hood without any accident.

(3) neutralization. Neutralize unreacted alkali with appropriate acid.

(4) product separation and post-treatment. (These are not dangerous. )

For example, the etherification process of polyanionic cellulose (PAC) is as follows.