Blends of linear low density polyethylenes

Abstract

A polyethylene blend comprising a uniform dispersion of constituents (A) and (B): (A) a Ziegler-Natta catalyst-made linear low density polyethylene and (B) a metallocene catalyst-made linear low density polyethylene, a composition comprising the polyethylene blend and at least one additive, methods of making and using same, and manufactured articles and films comprising or made from same.

1 . A polyethylene blend comprising a uniform dispersion of constituents (A) and (B): (A) a Ziegler-Natta catalyst-made linear low density polyethylene (ZN-LLDPE) and (B) a metallocene catalyst-made linear low density polyethylene (MCN-LLDPE); wherein the (A) ZN-LLDPE is from 15 to 75 weight percent (wt %) of the total weight of (A) and (B) and the (B) MCN-LLDPE is from 85 to 25 wt % of the total weight of (A) and (B); wherein by itself (A) is independently characterized by properties (i) to (iii): (i) a melt index (“I 2 ”, 190° C., 2.16 kg) of 0.5 to 2.5 gram per 10 minutes (g/10 min.) measured according to ASTM D1238-04; (ii) a density from 0.905 to 0.930 gram per cubic centimeter (g/cm 3 ), measured according to ASTM D792-13; and (iii) η o  detectable amount of long chain branching per 1,000 carbon atoms (“LCB Index”), measured according to LCB Test Method; and wherein by itself (B) is independently characterized by properties (i) to (iii): (i) a melt index (“I 2 ”, 190° C., 2.16 kg) of 0.5 to 2.5 g/10 min. measured according to ASTM D1238-04; (ii) a density from 0.905 to 0.930 g/cm 3 , measured according to ASTM D792-13; and (iii) η o  detectable amount of long chain branching per 1,000 carbon atoms (“LCB Index”), measured according to LCB Test Method; and with the proviso that the density of constituent (B) is within ±0.003 g/cm 3  of the density of constituent (A); wherein the (A) ZN-LLDPE is made by copolymerizing ethylene and 1-butene in the presence of the Ziegler-Natta catalyst and the (B) MCN-LLDPE is made by copolymerizing ethylene and 1-butene in the presence of the metallocene catalyst. 
     
     
         2 . The polyolefin blend of  claim 1 , further characterized by one of limitations (i) to (vii): (i) each of ZN-LLDPE and MCN-LLDPE is independently characterized by a melt index of (“I 2 ”, 190° C., 2.16 kg) of 0.5 to 1.99 g/10 min.; (ii) the melt index of constituent (B) is within ±0.4 g/10 min. of the melt index of constituent (A); (iii) both (i) and (ii); (iv) each of the ZN-LLDPE and MCN-LLDPE is independently characterized by a density of 0.918±0.003 g/cm 3 ; (v) the density of constituent (B) is within ±0.001 g/cm 3  of the density of constituent (A); (vi) both (iv) and (v); or (vii) both (iii) and (vi). 
     
     
         3 . The polyolefin blend of  claim 1 , when formed as a film having a thickness of 0.0127 millimeter (0.500 mil), is further characterized by an increase in film puncture resistance, relative to film puncture resistance of (A) or (B) alone, of from 0.50% to 50%, all when tested according to ASTM D5748-95(2012). 
     
     
         4 . A method of making the polyolefin blend of  claim 1 , the method comprising: (a) contacting discrete solid particles and/or a discrete melt of constituent (A) with discrete solid particles and/or a discrete melt of constituent (B) to give an initial mixture of (A) and (B); (b) heating any solid particles of (A) and any solid particles of (B) in the initial mixture above their melting temperature to give a complete melt of constituents (A) and (B); (c) blending the complete melt to an even extent to give the polyolefin blend as a uniform melt blend of constant composition of (A) and (B) throughout. 
     
     
         5 . The method of  claim 4 , further comprising (d) cooling the uniform melt blend to a temperature below its solidification temperature, thereby giving the polyolefin blend as a solid of constant composition of (A) and (B) throughout. 
     
     
         6 . A polyolefin composition comprising the polyolefin blend of  claim 1  and at least one additive (constituent) (C) to (M): (C) a lubricant; (D) a polymer processing aid; (E) an antioxidant; (F) a metal deactivator; (G) an ultraviolet light-promoted degradation inhibitor (“UV stabilizer”); (H) a slip agent; (I) a hindered amine stabilizer; (J) an antiblock agent; (K) a colorant; (L) an antifog agent; and (M) an antistatic agent; with the proviso that the total amount of the at least one additive is from >0 to 5 wt % of the polyolefin composition and the polyolefin blend is from <100 to 80 wt % of the polyolefin composition. 
     
     
         7 . A method of making the polyolefin composition of  claim 6 , the method comprising contacting the polyolefin blend with the at least one additive (C) to (M) to give the polyolefin composition. 
     
     
         8 . A manufactured article comprising a shaped form of the polyolefin blend of  claim 1 . 
     
     
         9 . A polyethylene film of the polyolefin blend of  claim 1 . 
     
     
         10 . A method of making a polyethylene film, the method comprising restricting in one dimension the polyethylene blend of  claim 1 , thereby giving the polyethylene film.