Patent ID: 8663790

Claim:
A high-strength injection-molded screw cap closure comprising: a polyethylene molding composition having a multimodal molecular mass distribution and comprising: (A) 40 to 45% by weight of a first ethylene homopolymer fraction having: (i) a first molecular weight; and (ii) a viscosity number, VN 1 , between 130 and 160 cm 3 /g; (B) 35 to 40% by weight of a second ethylene copolymer fraction comprising: (i) 96 to 99.4% by weight, based on the weight of the second ethylene copolymer, ethylene derived units; and, (ii) 0.6 to 4% by weight, based on the weight of the second ethylene copolymer, at least one additional first olefin derived units wherein the first olefin derived units are selected from first comonomers comprising 4-8 carbon atoms, wherein the second ethylene copolymer fraction has: (iii) a second molecular weight wherein the second molecular weight is higher than the first molecular weight; (iv) a molecular weight distribution (Mw/Mn) between 6 and 10; and, (v) a viscosity number, VN 2 , between 155 and 170 cm 3 /g; (C) 15 to 20% by weight of a third ethylene copolymer comprising: (i) 90 to 95% by weight, based on the weight of the third ethylene copolymer, ethylene derived units; and, (ii) 5 to 10% by weight, based on the weight of the third ethylene copolymer, at least one additional second olefin derived units wherein the second olefin derived units are selected from second comonomers comprising 4-8 carbon atoms, and wherein the third ethylene copolymer has: (iii) a third molecular weight wherein the third molecular weight is higher than the second molecular weight, and (iv) a viscosity number, VN 3 , between 200 and 250 cm 3 /g wherein the polyethylene molding composition has: (i) a density between 0.945 and 0.953 g/cm 3 at 23° C.; and, (ii) a melt flow index between 4 and 6.5 g/10 min measured at (190° C./5 kg).