Merkon P-210 is described as a butyl methacrylate methyl methacrylate copolymer (CAS # 25608-33-7). It is said to consist of 78.6 percent polymethyl methacrylate, 19.6 percent polybutyl methacrylate and less than 2 percent additives. The product will be imported as a white powder. You state that the product will be used as a process aid in the production of polyvinyl compounds.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N319987