Puyang Yifan New Material Co.,Ltd.--Tetrahydrophthalic anhydride|transformed tetrahydrophthalic anhydride|tetrahydroimine|transformed tetrahydroimine|hexahydrophthalic anhydride|methyl hexahydrophthalic anhydride|methyl tetrahydrophthalic anhydride|maleic anhydride|fumaric acid|phthalic anhydride