3501.90 - Other:

This HTS category, 3501.90, encompasses caseinates and other derivatives of casein, as well as casein glues. Caseinates are salts or esters of casein, often produced by reacting casein with alkalis. This category serves as a residual category for casein-based products that do not fit the specific classification of pure casein.

It is important to distinguish this category from its sibling, 3501.10, which is exclusively for casein in its primary form, whether curdled or in other unprocessed states. While 3501.90 also includes casein-derived glues, the primary distinction lies in the processing and modification of casein into derivatives or formulated adhesive products.

The subcategories within 3501.90 further refine the classification. 3501.90.20.00 specifically covers casein glues, which are ready-to-use adhesive formulations where casein is the principal binding agent. The remaining products, such as caseinates and other processed casein derivatives not specifically designated as glues, fall under 3501.90.60.00, serving as a catch-all for these specialized casein-based materials.