Low Polymerization Degree Cellulose Ether Depolymerization

The patent applies preliminary action by adding ultraviolet absorbers (such as titanium dioxide, zinc oxide, or organic UV absorbers) to the cellulose ether mixture before or during the acid depolymerization process. This preliminary protection prevents yellowing from occurring during the depolymerization and subsequent storage, allowing the product to maintain its white appearance and stability without requiring post-treatment steps.

The patent uses ultraviolet absorbers as intermediary substances that absorb UV radiation and convert it to harmless heat energy, preventing the UV-induced yellowing of cellulose ether. These absorbers (titanium dioxide, zinc oxide, or organic compounds) act as mediators between the UV environment and the cellulose ether, protecting the product without generating harmful sulfur-containing by-products, thus maintaining pharmaceutical suitability.

The patent applies preliminary action by incorporating ultraviolet absorbers into the cellulose ether formulation before storage. This preliminary protection mechanism prevents yellowing during long-term storage by continuously absorbing UV radiation that penetrates the stored material, maintaining the white appearance over extended periods without requiring re-irradiation or additional treatments.

The patent uses ultraviolet absorbers as intermediary protective agents that can be added directly to the depolymerization system without requiring diluents like alcohol. This approach suppresses yellowing while avoiding the need for additional separation steps, as the absorbers remain integrated in the final product or can be easily removed through standard filtration, thereby maintaining high production efficiency.