Cushioning materials comprising ethylene/alpha-olefin copolymer blends

Abstract

Embodiments of a cushioning net structure comprise an ethylene/α-olefin copolymer blend arranged in a three-dimensional random loop orientation, wherein a plurality of random loops are bonded together, The ethylene/α-olefin copolymer blend comprises a homogeneously branched random ethylene/α-olefin copolymer and a heterogeneously branched random ethylene/α-olefin copolymer having a molecular weight distribution (MWD) of about 2.5 to about 4.5, wherein MWD is defined as Mw/Mn with Mw being a weight average molecular weight and Mn being a number average molecular weight, a melt index (I 2 ) of about 3.0 g/10 mins to about 25.0 g/10 mins when measured according to ASTM D1238 at 190° C. and 2.16 kg load, and a density of about 0.895 to about 0.925 g/cm 3 .

What is claimed is: 
     
         1 . A cushioning net structure comprising an ethylene/α-olefin copolymer blend arranged in a three-dimensional random loop orientation, wherein a plurality of random loops are bonded together, wherein the ethylene/α-olefin copolymer blend comprises:
 a homogeneously branched random ethylene/α-olefin copolymer and a heterogeneously branched random ethylene/α-olefin copolymer, 
 wherein the ethylene/α-olefin copolymer blend has:
 a molecular weight distribution (MWD) of about 2.5 to about 4.5, wherein MWD is defined as M w /M n  with M w  being a weight average molecular weight and M n  being a number average molecular weight; 
 a melt index (I 2 ) of about 3.0 g/10 mins to about 25.0 g/10 mins when measured according to ASTM D1238 at 190° C. and 2.16 kg load; 
 a density of about 0.895 to about 0.925 g/cm 3 . 
 
 
     
     
         2 . The cushioning net structure of  claim 1  wherein the homogeneously branched random ethylene/α-olefin copolymer is a random homogeneously branched linear ethylene/α-olefin copolymer or a random homogeneously branched substantially linear ethylene/α-olefin copolymer. 
     
     
         3 . The cushioning net structure of  claim 1  wherein a Differential Scanning calorimetry (DSC) heat curve having at least two melting peaks. 
     
     
         4 . The cushioning net structure of  claim 3  wherein the highest temperature melting peak is in the range of from 120° C. to 125° C. 
     
     
         5 . The cushioning net structure of  claim 1 , wherein the homogeneously branched random ethylene/α-olefin copolymer has a density of about 0.875 to 0.905 g/cm3. 
     
     
         6 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend comprises about 10 to about 90% by weight of the homogeneously branched ethylene/α-olefin copolymer, and about 10 to about 90% by weight of the heterogeneously branched ethylene/α-olefin copolymer. 
     
     
         7 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend comprises about 40 to about 60% by weight of the homogeneously branched ethylene/α-olefin copolymer, and about 40 to about 60% by weight of the heterogeneously branched ethylene/α-olefin copolymer. 
     
     
         8 . The cushioning net structure of  claim 1  wherein each random loop of the cushioning net structure has a diameter of about 0.1 mm to about 3 mm. 
     
     
         9 . The cushioning net structure of  claim 1  wherein the cushioning net structure has an apparent density in a range of about 0.016 g/cm 3  to about 0.1 g/cm 3 . 
     
     
         10 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend comprises a melt flow ratio (I 10 /I 2 ) of about 5 to about 10, where I 10  is the melt index when measured according to ASTM D1238 at 190° C. and 10 kg load. 
     
     
         11 . The cushioning net structure of  claim 1  wherein the weight fraction of the ethylene/α-olefin copolymer blend in a temperature zone above 90° C. is above 8%, as determined by CEF. 
     
     
         12 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend has an elastic recovery at 100% strain at 1 cycle of between 50 and 80%. 
     
     
         13 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend is characterized by a ratio of storage modulus at 25° C., G′ (25° C.) to storage modulus at 100° C., G′ (100° C.) of about 20 to about 60. 
     
     
         14 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend has a weight average molecular weight of less than 75,000. 
     
     
         15 . The cushioning net structure of  claim 1  further comprising a heterogeneous linear low density polyethylene which is blended with the ethylene/α-olefin copolymer blend. 
     
     
         16 . The cushioning net structure of  claim 1  wherein the ethylene/α-olefin copolymer blend has a percent crystallinity in weight % of about 25% to about 55%. 
     
     
         17 . The cushioning net structure of  claim 1 , wherein the cushioning net structure has a height loss of less than 3% as measured in accordance with ASTM D 3574, Test B2. 
     
     
         18 . A method of making a cushioning net structure arranged in a three-dimensional random loop orientation, wherein the method comprises:
 providing an ethylene/α-olefin copolymer blend, the blend comprising a homogeneously branched random ethylene/α-olefin copolymer and a heterogeneously branched random ethylene/α-olefin copolymer,
 wherein the ethylene/α-olefin copolymer blend has:
 a molecular weight distribution (MWD) of about 2.5 to about 4.5, wherein MWD is defined as M w /M n  with M w  being a weight average molecular weight and M n  being a number average molecular weight; 
 a melt index (I 2 ) of about 3.0 g/10 mins to about 25.0 g/10 mins when measured according to ASTM D1238 at 190° C. and 2.16 kg load; and 
 a density of about 0.895 to about 0.925 g/cm 3 ; and 
 
   forming the ethylene/α-olefin copolymer blend into three-dimensional random loops which bond to form the cushioning net structure.   
     
     
         19 . The method of  claim 18  wherein the cushioning net structure has a diameter of about 0.1 mm to about 3 mm, and an apparent density in a range of about 0.016 g/cm 3  to about 0.1 g/cm 3 .