US20160122925A1

US20160122925A1 - Cushioning materials comprising ethylene/alpha-olefin copolymer blends

Info

Publication number: US20160122925A1
Application number: US14/927,958
Authority: US
Inventors: Viraj K. Shah; Rajen M. Patel
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2014-10-31
Filing date: 2015-10-30
Publication date: 2016-05-05

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 (I₂) 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/cm³.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application 62/073,708 filed Oct. 31, 2014, which is incorporated by reference herein in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure are generally related to cushioning net structures comprising a 3D random loop orientation, and are specifically related to cushioning net structures wherein the random loops are fibers or filaments comprising ethylene/α-olefin copolymer blends with a homogeneously branched random ethylene/α-olefin copolymer and a heterogeneously branched random ethylene/α-olefin copolymer.

BACKGROUND

Polyurethane foam is used cushioning material for furniture, beds, train seats, automobiles seats, etc. Despite its durability and cushioning function, polyurethane may have many detrimental properties. For instance, polyurethane foam can retain water and moisture, which may lead to bacterial growth. It may also absorb heat and lacks suitable breathability, and thus can make the upper surface of the polyurethane foam warm, which may be uncomfortable to a person, especially during hotter months. Further, polyurethane foam may not be easy to reuse or recycle, thus discarded polyurethane foam is generally incinerated or buried, which are undesirable options from an environmental and cost standpoint
Accordingly, there may be a continual need for cushioning net structures which yield durability and cushioning function, while also providing breathability, recyclability, and good processability.

SUMMARY

Embodiments of the present disclosure are directed to cushioning net structures comprising a 3D random loop orientation, wherein the random loops are fibers or filaments comprising ethylene/α-olefin copolymer blends having a homogeneously branched random ethylene/α-olefin copolymer and a heterogeneously branched random ethylene/α-olefin copolymer. The present embodiments of the cushioning net structure may provide cushioning and durability as well as air permeability, which, in turn, may prevent the cushioning net structure from becoming too hot or too cold at the surface. Moreover, the present cushioning net structure may reduce the retention of water, thereby reducing bacterial growth in the cushioning net structure. Further, the present cushioning net structure may be recyclable and demonstrate good processability.
According to one embodiment, a cushioning net structure is provided. The cushioning net structure is 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. 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 Mw/Mn with Mw being a weight average molecular weight and Mn being a number average molecular weight; a melt index (I₂) 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/cm³.
According to another embodiment, a method of making a cushioning net structure comprising an ethylene/α-olefin copolymer blend arranged in a three-dimensional random loop orientation is provided. 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 Mw/Mn with Mw being a weight average molecular weight and Mn being a number average molecular weight; a melt index (I₂) 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/cm3. The method further comprises forming the ethylene/α-olefin copolymer blend into three-dimensional random loops which bond to form the cushioning net structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the drawings enclosed herewith.

FIG. 1 is a schematic view depicting the looping of the ethylene/α-olefin copolymer blend fibers in a water cooling unit disposed downstream of an extruder in accordance with one or more embodiments of the present disclosure.

FIG. 2 is a schematic view depicting the bonding of the fibers loops inside the water cooling unit.

FIG. 3 is a Different Scanning calorimetry (DSC) curve of an ethylene/α-olefin copolymer blend in accordance with one or more embodiments of the present disclosure.

The embodiments set forth in the drawings are illustrative in nature and not intended to be limiting of the embodiments defined by the claims. Moreover, individual features of the drawings will be more fully apparent and understood in view of the detailed description.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to a cushioning net structure comprising fibers or filaments arranged in a three-dimensional random loop orientation, wherein the fiber or filament loops comprise an ethylene/α-olefin copolymer blend. As used herein, “copolymer” means a polymer prepared by the polymerization of at least two different types of monomers. As used herein, “random copolymer” means a copolymer wherein the at least two different monomers arranged in a non-uniform order. The “random copolymer” specifically excludes block copolymers.

Ethylene/α-Olefin Copolymer Blend

The ethylene/α-olefin copolymer blend comprises at least one homogeneously branched random ethylene/α-olefin copolymer and at least one heterogeneously branched random ethylene/α-olefin copolymer. In some embodiments, the ethylene/α-olefin copolymer blend is an in situ ethylene/α-olefin copolymer blend.
As stated above, the ethylene/α-olefin copolymer blend has properties which make it suitable for processing into a cushioning net structure. In one embodiment, 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 Mw/Mn with Mw being a weight average molecular weight and Mn being a number average molecular weight. In further embodiments, the MWD is from about 2.5 to about 3.8, or from about 2.7 to about 3.8, or from about 2.5 to about 3.5, or from about 2.7 to about 3.0.
Here, the ethylene/α-olefin copolymer blend may also have a melt index (I₂) 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, or about 5.0 g/10 mins to about 25.0 g/10 mins, or from about 10 to about or about 25.0 g/10 mins, or about 5.0 g/10 mins to about 20.0 g/10 mins, or about 10.0 g/10 mins to about 20.0 g/10 mins, or about 12.0 g/10 mins to about 18.0 g/10 mins, or about or about 14.0 g/10 mins to about 16.0 g/10 mins. Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear. Without being bound by theory, it is believed that the combination of melt index (I2) and MWD may aid in the processability of the ethylene/α-olefin copolymer blend.
The density of the ethylene/α-olefin copolymer blend may be between about 0.895 to about 0.925 g/cm³, or about 0.900 to about 0.920 g/cm³, or about 0.900 to about 0.915 g/cm³, or from about 0.905 to about 0.915 g/cm³. Density is measured in accordance with ASTM D 792.
In addition to melt index, the ethylene/α-olefin copolymer blend may have a melt flow ratio (I10/I2) of about 5 to about 15, where I10 is the melt index of when measured according to ASTM D1238 at 190° C. and 10 kg load, and I2 is defined above. In further embodiments, the ethylene/α-olefin copolymer blend has a melt flow ratio (I10/I2) of about 5 to about 12, or about 5 to about 10, or about 6 to about 10, or 6 to about 9, or about 6 to about 8.
According to Crystallization Elution Fractionation (CEF), the ethylene/α-olefin copolymer blend may have a weight fraction in a temperature zone from 90° C. to 115° C. of about 5% to about 15% by wt., or about 6% to about 12%, or about 8% to about 12%, or greater than about 8%, or greater than about 9%. Additionally, as detailed below, the copolymer blend may have a Comonomer Distribution Constant (CDC) of at least about 100, or at least about 110.
Referring to FIG. 3, the present ethylene/α-olefin copolymer blend may have at least two, or three melting peaks when measured using Differential Scanning calorimetry (DSC) below a temperature of 130° C. In one or more embodiments, the ethylene/α-olefin copolymer blend may include a highest temperature melting peak of at least 115° C., or at least 120° C., or from about 120° C. to about 125° C., or from about from 122 to about 124° C. Without being bound by theory, the heterogeneously branched ethylene/α-olefin copolymer is characterized by two melting peaks, and the homogeneously branched ethylene/α-olefin copolymer is characterized by one melting peak, thus making up the three melting peaks. Further without being bound by theory, it is believed that 3D cushioning net structures having an ethylene/α-olefin copolymer blend with a highest DSC melting peak of at least 115° C. can demonstrate effective heat resistance when subjected to high temperature sterilization processes. Specifically, heat and/or steam sterilization of a cushioning net structure may degrade the structural integrity of a structure having a DSC highest melting peak below 115° C., (for example, via compression of the structure), whereas 3D cushioning net structures having an ethylene/α-olefin copolymer blend with a highest DSC melting peak of at least 115° C. can be heat resistant and retain their structure. Further, the ethylene/α-olefin copolymer blend may have an enthalpy of fusion value AH of at least 120 J/g, or at least 125 J/g when measured via DSC.
Additionally, the ethylene/α-olefin copolymer blend may also have a percent crystallinity in weight percent of about 25% to about 55%, or about 25% to about 45%, or about 30% to about 40%. Percent crystallinity may be computed via DSC or may be calculated from the density of the copolymer blend as shown below.
Various molecular weights and compositional amounts are considered suitable for the ethylene/α-olefin copolymer blend. For example, and not by way of limitation, the ethylene/α-olefin copolymer blend may have a weight average molecular weight of less than 75,000 g/mol, or less than about 70,000 g/mol.
Additionally, the ethylene/α-olefin copolymer blend may comprise about 10 to about 90% by weight, or about 30 to about 70% by weight, or about 40 to about 60% by weight of the homogeneously branched ethylene/α-olefin copolymer. Similarly, the ethylene/α-olefin copolymer blend may comprise about 10 to about 90% by weight, about 30 to about 70% by weight, or about 40 to about 60% by weight of the heterogeneously branched ethylene/α-olefin copolymer. In a specific embodiment, the ethylene/α-olefin copolymer blend may comprise about 50% to about 60% by weight of the homogeneously branched ethylene/α-olefin copolymer, and 40% to about 50% of the heterogeneously branched ethylene/α-olefin copolymer.
Moreover, the strength of the ethylene/α-olefin copolymer blend may be characterized one or more of the following metrics. One such metric is elastic recovery. Here, the ethylene/α-olefin copolymer blend has an elastic recovery, Re, in percent at 100 percent strain at 1 cycle of between 50-80%. Additional details regarding elastic recovery are provided in U.S. Pat. No. 7,803,728, which is incorporated by reference herein in its entirety.
The ethylene/α-olefin copolymer blend may also be characterized by its storage modulus. In some embodiments, the ethylene/α-olefin copolymer blend may have 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, or from about 20 to about 50, or about 30 to about 50, or about 30 to about 40.
Moreover, the ethylene/α-olefin copolymer blend may also be characterized by a bending stiffness of at least about 1.15 Nmm at 6 s, or at least about 1.20 Nmm at 6 s, or at least about 1.25 Nmm at 6 s, or at least about 1.35 Nmm at 6 s. Without being bound by theory, it is believed that these stiffness values demonstrate how the ethylene/α-olefin copolymer blend will provide cushioning support when incorporated into 3D random fibers bonded to form a cushioning net structure.

Homogeneously Branched Random Ethylene/Alpha-Olefin Copolymer

The homogeneously branched random ethylene/α-olefin copolymer may be a random homogeneously branched linear ethylene/α-olefin copolymer or a random homogeneously branched substantially linear ethylene/α-olefin copolymer. The term “substantially linear ethylene/α-olefin copolymer” means that the polymer backbone is substituted with from 0.01 long chain branches/1000 carbons to 3 long chain branches/1000 carbons, or from 0.01 long chain branches/1000 carbons to 1 long chain branches/1000 carbons, or from 0.05 long chain branches/1000 carbons to 1 long chain branches/1000 carbons. In contrast, the term “linear ethylene/α-olefin copolymer” means that the polymer backbone has no long chain branching.
The homogeneously branched random ethylene/α-olefin copolymers may have the same ethylene/α-olefin comonomer ratio within all copolymer molecules. The homogeneity of the copolymers may be described by the SCBDI (Short Chain Branch Distribution Index) or CDBI (Composition Distribution Branch Index) and is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content. The CDBI of a polymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation (abbreviated herein as “TREF”) as described in U.S. Pat. No. 4,798,081 (Hazlitt et al.), or in U.S. Pat. No. 5,089,321 (Chum et al.) the disclosures of all of which are incorporated herein by reference. The SCBDI or CDBI for the homogeneously branched random ethylene/α-olefin copolymers is preferably greater than about 30 percent, or greater than about 50 percent.
The homogeneously branched random ethylene/α-olefin copolymer may include at least one ethylene comonomer and at least one C₃-C₂₀α-olefin comonomer. For example and not by way of limitation, the C₃-C₂₀α-olefins may include but are not limited to propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene, or, in some embodiments, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene.
The homogeneously branched random ethylene/α-olefin copolymer may comprise a melt index (I₂) of about 1 g/10 mins to about 50 g/10 mins, or about 5 g/10 mins to about 25 g/10 mins, or about 10 g/10 mins to about 25 g/10 mins, or about 5 g/10 mins to about 20 g/10 mins, or about 10 g/10 mins to about 25 g/10 mins, or about 10 g/10 mins to about 20 g/10 mins, or about 12 g/10 mins to about 18 g/10 mins, or about 13 g/10 mins to about 17 g/10 mins. The homogeneously branched random ethylene/α-olefin copolymer may include a melt flow ratio (I₁₀/I₂) of about 5 to about 15, or about 5 to about 10, or about 6 to about 12, or about 6 to about 10, or about 7 to about 10, or about 6 to about 9, or about 7 to about 9.
The homogeneously branched random ethylene/α-olefin copolymer may have a density of about 0.875 to about 0.925 g/cm³, or about 0.875 to 0.905 g/cm³, or about 0.900 to about 0.920 g/cm³, or about 0.900 to about 0.910 g/cm³, about 0.900 to about 0.905 g/cm³. The homogeneously branched random ethylene/α-olefin copolymer may have a molecular weight distribution (Mw/Mn) of about 2.0 to about 4.0, or about 2.0 to about 3.8, or about 2.5 to about 3.8, or about 2.5 to about 3.5.
While various mechanisms for producing the homogeneously branched random ethylene/α-olefin copolymer are contemplated, the homogeneously branched random ethylene/α-olefin copolymer may be produced, for example, using metallocene catalysts. This includes homogeneous-branched, substantially linear ethylene polymers (“SLEP”) which are prepared using constrained geometry catalysts (“CGC Catalyst”), such as disclosed in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 6,812,289, and WO 93/08221, which are incorporated herein by reference, as well as the homogeneous linear ethylene polymers (“LEP”) which are prepared using other metallocene (called “bis-CP catalysts”). Other catalyst systems that may be used to form the homogeneously branched random ethylene/α-olefin copolymer include those comprising a metal complex of a polyvalent aryloxyether, which is further described in U.S. Pat. No. 8,450,438, and is incorporated herein by reference.

Heterogeneously Branched Random Ethylene/Alpha-Olefin Copolymer

The heterogeneously branched random ethylene/α-olefin copolymers differ from the homogeneously branched random ethylene/α-olefin copolymers primarily in their branching distribution. For example, heterogeneously branched random ethylene/α-olefin copolymers have a distribution of branching, including a highly branched portion (similar to a very low density polyethylene), a medium branched portion (similar to a medium branched polyethylene) and an essentially linear portion (similar to linear homopolymer polyethylene).
Like the homogeneously branched random ethylene/α-olefin copolymer, the heterogeneously branched random ethylene/α-olefin copolymer may include at least one ethylene comonomer and at least one C₃-C₂₀α-olefin comonomer. For example and not by way of limitation, the C₃-C₂₀α-olefins may include but are not limited to propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene, or, in some embodiments, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene. In one embodiment, the heterogeneously branched ethylene/α-olefin copolymer may comprise greater than about 50% by wt ethylene comonomer, or greater than about 60% by wt., or greater than about 70% by wt. Similarly, the heterogeneously branched ethylene/α-olefin copolymer may comprise less than about 50% by wt α-olefin monomer, or less than about 40% by wt., or less than about 30% by wt.
The heterogeneously branched random ethylene/α-olefin copolymer may have a density from about 0.900 g/cm³to about 0.950 g/cm³, or from about 0.910 g/cm³to about 0.940 g/cm³, or from about 0.905 g/cm³to about 0.930 g/cm³, or from about 0.910 g/cm³to about 0.930 g/cm³or from about 0.915 g/cm³to about 0.925 g/cm³. The density may be calculated as follows:
1/density blend=wt. % A/density A+wt. % B/Density B,
where A, is the homogeneously branched random ethylene/α-olefin polymer component and B is the heterogeneously branched random ethylene/α-olefin polymer component of the ethylene/α-olefin copolymer blend.
The heterogeneously branched random ethylene/α-olefin copolymer may also include a melt index (I2) from about 1 g/10 min to about 50 g/10 min, or about 5 to about 25 g/10 min, or from about 10 g/10 min to about 25 g/10 min, or from about 5 to about 20 g/10 min, or from about 10 g/10 min to about 20 g/10 min, or from about 15 g/10 min to about 20 g/10 min. The heterogeneously branched random ethylene/α-olefin copolymer may have a melt flow ratio (I10/I2) of about 5 to about 15, or about 5 to about 10, or about 6 to about 9, or about 6 to about 8. To calculate the melt index of the copolymer blend or, in this case, the heterogeneously branched random ethylene/α-olefin polymer component, the following equation may be used:
MI^−0.277 =w ₁MI^−0.277 +w ₂MI₂ ^−0.277
wherein w₁is the weight fraction of the homogeneously branched random ethylene/α-olefin polymer component; w₂is the weight fraction of the heterogeneously branched random ethylene/α-olefin polymer component; MI₁is the melt index of the homogeneously branched random ethylene/α-olefin polymer component; and MI₂is the melt index of the heterogeneously branched random ethylene/α-olefin polymer component; and MI is overall blend melt index.
The heterogeneously branched random ethylene/α-olefin copolymer may have a molecular weight distribution (Mw/Mn) of about 3.0 to about 4.5, or about 3 to about 4.
The heterogeneously branched random ethylene/α-olefin copolymer can be prepared via the polymerization of ethylene and one or more α-olefin comonomers in the presence of a Ziegler Natta catalyst as disclosed in U.S. Pat. Nos. 4,076,698 and 5,844,045, which are incorporated by reference herein in their entirety. For example and not by way of limitation, these Ziegler-Natta catalysts may include Group 4 metal halides supported on Group 2 metal halides or mixed halides and alkoxides and chromium or vanadium based catalysts. In specific embodiments, the Ziegler-Natta catalyst composition may be a multi-constituent catalyst system including a magnesium and titanium containing procatalyst and a cocatalyst. The procatalyst may, for example, may comprise the reaction product of magnesium dichloride, an alkylaluminum dihalide, and a titanium alkoxide.

3D Cushioning Net Structure and Method of Making

Various conventional polymerization processes are contemplated to produce the ethylene/α-olefin copolymer blend. Such conventional polymerization processes include, but are not limited to, a solution polymerization process, using one or more conventional reactors e.g. loop reactors, isothermal reactors, stirred tank reactors, batch reactors in parallel, series, and/or any combinations thereof.
In one embodiment, the ethylene/α-olefin copolymer blend may be produced via a solution polymerization process in a dual reactor system, for example a dual loop reactor system, wherein ethylene and one or more α-olefins are polymerized in the presence of one or more catalyst systems. In the first reactor, the homogeneously branched random ethylene/α-olefin copolymer is produced by contacting ethylene and at least one other α-olefin in the presence of a homogeneous catalyst (e.g., a metallocene catalyst) at a temperature of at least 100° C., or at least 150° C. In a second reactor, the heterogeneously branched random ethylene/α-olefin copolymer is produced by contacting ethylene and at least one other α-olefin in the presence of a Ziegler-Natta catalyst at a temperature of at least 180° C. The first and second reactors may be connected in series or in parallel.
Subsequently, the homogeneously branched random ethylene/α-olefin copolymer is mixed with the heterogeneously branched random ethylene/α-olefin copolymer to produce an ethylene/α-olefin copolymer blend. Various mechanisms for blending the homogeneously branched random ethylene/α-olefin copolymer with the heterogeneously branched random ethylene/α-olefin copolymer are contemplated. For example, the homogeneously branched random ethylene/α-olefin copolymer may be injected into the second reactor to yield an in situ blend. After blending, additional processing steps, such as separation, devolatilization, and pelletization of the blend may be conducted. For discussion of the dual reactor polymerization and these post-blending steps, PCT Publication WO 2014/159844 is incorporated by reference herein in its entirety.
Referring to FIGS. 1 and 2, when delivering molten ethylene/α-olefin copolymer blend 2 to a water cooling unit 4, the cooling of the molten ethylene/α-olefin copolymer blend 2 facilitates the formation of 3D random loops 3. Additional description regarding the making of cushioning structures is provided in U.S. Pat. Nos. 5,639,543, 7,622,179, and 7,625,629, which are incorporated by reference herein in their entirety.
In specific embodiments as shown in FIG. 2, the ethylene/α-olefin copolymer blend 2 in a molten state is delivered to a water cooling unit 4 via a drive mechanism 7 at least partially submerged, or for example, fully submerged, within the water cooling unit 4. It is contemplated that the ethylene/α-olefin copolymer blend 2 is in a molten or melted state upon delivery to the water cooling unit 4.
In one or more embodiments as depicted in FIG. 2, the ethylene/α-olefin copolymer blend 2 may be melted from a pelletized form. These ethylene/α-olefin copolymer blend pellets are heated and melted in an extruder 10. In a specific embodiment, the extruder 10 may include a hopper, screw and barrel, motor to turn the screw and heaters to heat the barrel. The ethylene/α-olefin copolymer blend pellets enter the hopper and get melted in the heated barrel due to heat and shear. As the flight clearance between the screw and barrel reduce going from the hopper to the die end, the solid pellets get softer and melt from the feed zone to the transition zone and finally at the end near the die, the metering of the melt happens, like a pump, thus generating positive extrusion pressure as the melt exits the die 5.
The molten ethylene/α-olefin copolymer blend exiting the die, which is now under positive pressure, is transferred through a heated transfer pipe into the die 5. The die consists of several rows of holes in series. The melt, which enters the die from a round transfer pipe, is uniformly distributed so it can exit the die from each of the individual holes uniformly. The die is in a horizontal arrangement such that the melt exiting the die, which is now in form of fibers, travels downward vertically before breaking the surface of the water in the water tank. The air gap or the distance between the die surface and the surface of water is adjustable.
As shown in FIG. 1, the water cooling of the molten ethylene/α-olefin copolymer blend 2 facilitates formation of three-dimensional random loops 3 which bond to form the cushioning net structure. In one or more embodiment, the drive mechanism 7 comprises at least one belt, a plurality of rollers, at least one conveyor, or combinations thereof. The drive mechanism 7 is typically an underwater mechanism which constrains a thickness of the cushioning net structure. Considering the significant number of fibers being delivered to the water cooling unit 4, there is significant bonding of the fibers during looping thereby creating a net structure. Without being bound by theory, it is believed that the cooling or solidifying of the 3D loop structure increases with the increasing depth into the water cooling unit 4.
Upon leaving the water cooling unit 4, the three-dimensional random loops 3 are sufficiently bonded together to form the cushioning net structure. Excess water may be removed by various mechanisms. Moreover, there is a mechanism to cut the continuously forming structure into a desired length.

Cushioning Net Structure

As stated above, the cushioning net structure provided herein may be used in various cushioning applications known in the art, including, but not limited to wadding for a surface layer, a middle layer cushioning material, for use in vehicle seats, seacraft seats, beds, sofas, chairs, and furniture.
Further as stated above, the random looped structures of the cushioning net structures, specifically, the three dimensional looped structures, are bonded with one another. The loop size of the random loops may vary based on industrial application, and specifically may be dictated by the diameter of the holes in the die. The loop size of the random loops may also be dictated by the polymer, melt temperature of the fibers or filaments coming out of the die, the distance between the die and water, the speed of the belts or rollers or other mechanism under water etc. In one or more embodiments, the random loop may have a diameter of about 0.1 mm to about 3 mm, or a diameter of about 0.6 mm to about 1.6 mm. The apparent density may range from about 0.016 to about 0.1 g/cm³, or about 0.024 to about 0.1 g/cm³and can be achieved by adjusting various factors.
As stated above, the cushioning net structures using the present copolymer blend have excellent durability. As an example of this durability, the cushioning net structures may demonstrate a height loss of less than 4% as measured in accordance with ASTM D 3574, Test B2. In further embodiments, the cushioning net structures may demonstrate a height loss of less than 3%, or less than 2.5% as measured in accordance with ASTM D 3574, Test B2.

Optional Blends and Additives

The ethylene/α-olefin copolymer blend may further comprise additional components or additives. Such additives include, but are not limited to, antistatic agents, color enhancers, dyes, lubricants, fillers such as TiO₂or CaCO₃, opacifiers, nucleators, processing aids, pigments, primary anti-oxidants, secondary anti-oxidants, processing aids, UV stabilizers, anti-blocks, slip agents, tackifiers, fire retardants, anti-microbial agents, odor reducer agents, anti-fungal agents, and combinations thereof. Various amounts are contemplated for these additional optional additives. In one or more embodiments, the ethylene/α-olefin copolymer blend may comprise about 0.01 to about 10% by wt, or about 1 to about 10% by wt. of the additional additives.
The ethylene/α-olefin copolymer blend may further be blended with one or more polymeric materials, e.g. a low density polyethylene (LDPE) or another linear low density polyethylene (LLDPE). Such LDPEs or LLDPEs are commercially available under the tradenames DOWLEX™, DNDA, and ATTANE™, all of which are available from The Dow Chemical Company (Midland, Mich.). Additionally, other LLDPE products may also be blended with the ethylene/α-olefin copolymer blend.
It is also possible to use the structure together with other cushioning materials to achieve a desired property or desired use.

Testing Methods

Melt index (I₂), is measured in accordance with ASTM D 1238-10, Condition, 190° C./2.16 kg, and is reported in grams eluted per 10 minutes.
Melt index (I₁₀) is measured in accordance with ASTM D 1238-10, Condition 190° C./10 kg, and is reported in grams eluted per 10 minutes.
Density
Density is measured in accordance with ASTM D792.
Gel Permeation Chromatography (GPC)
GPC Chromatographic Conditions
The chromatographic system consists of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with a 4-capillary differential viscometer detector and IR5 fixed wavelength infra-red detector (measurement channel) or equivalent high temperature chromatograph equipped with IR4 detection. Data collection is performed using GPCOne software from PolymerChar. The system is equipped with an on-line solvent degas device from Agilent Technologies (Santa Clara, Calif., USA). Polyethylene samples are prepared at a 2 mg/mL concentration in 1,2,4-trichlorobenzene solvent by slowly shaking or stirring the sample in TCB at 150° C. for 3 hours. Both the autosampler compartment and the column compartment are operated at 150° C. The columns are 4 Polymer Laboratories (Now Agilent Technologies) Olexis 30 cm 13-micron columns and a 13-um pre-column. The chromatographic solvent is 1,2,4 trichlorobenzene and contains 200 ppm of butylated hydroxytoluene (BHT). The solvent source is nitrogen sparged. The injection volume is 200 microliters and the flow rate is 1.0 milliliters/minute.
Conventional GPC Molecular Weight Measurements
For conventional molecular weight measurements, the GPC column set is calibrated with 21 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 and are arranged in 6 “cocktail” mixtures with at least a decade of separation between individual molecular weights. The standards are purchased from Polymer Laboratories (now Agilent Technologies). The polystyrene standards are prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000, and 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000,000. The polystyrene standards are dissolved at 80 degrees Celsius with gentle agitation for 30 minutes. The polystyrene standard peak molecular weights are converted to polyethylene molecular weights using the following equation (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)):
M _polyethylene =A×(M _polystyrene)^B
where M is the molecular weight, A has a value of approximately 0.41 which is determined by the weight-average molecular weight of NIST NBS1475 being equivalent to 52,000 and B is equal to 1.0.
A 3^rdorder polynomial is used to fit the respective polyethylene-equivalent calibration points. PolymerChar GPC One software is used to calculate the polyethylene-equivalent weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer and to determine the molecular weight distribution, MWD or Mw/Mn. The z-average molecular weight, Mz, is also determined. Data was processed using PolymerChar GPC One software. A flowrate marker (decane) is placed in the calibration standards vials as well as the sample vials prior to injection so that flow rate deviations (<1%) could be compensated for.
Crystallization Elution Fractionation (CEF) Method
Comonomer distribution analysis is performed with Crystallization Elution Fractionation (CEF) (PolymerChar in Spain) (B Monrabal et al, Macromol. Symp. 257, 71-79 (2007)). Ortho-dichlorobenzene (ODCB) with 600 ppm antioxidant butylated hydroxytoluene (BHT) is used as solvent. Sample preparation is done with autosampler at 160° C. for 2 hours under shaking at 4 mg/ml (unless otherwise specified). The injection volume is 300 μm. The temperature profile of CEF is: crystallization at 3° C./min from 110° C. to 30° C., the thermal equilibrium at 30° C. for 5 minutes, elution at 3° C./min from 30° C. to 140° C. The flow rate during crystallization is at 0.052 ml/min. The flow rate during elution is at 0.50 ml/min. The data is collected at one data point/second. CEF column is packed by the Dow Chemical Company with glass beads at 125 μm+6% (MO-SCI Specialty Products) with ⅛ inch stainless tubing. Glass beads are acid washed by MO-SCI Specialty with the request from the Dow Chemical Company. Column volume is 2.06 ml. Column temperature calibration is performed by using a mixture of NIST Standard Reference Material Linear polyethylene 1475a (1.0 mg/ml) and Eicosane (2 mg/ml) in ODCB. Temperature is calibrated by adjusting elution heating rate so that NIST linear polyethylene 1475a has a peak temperature at 101.0° C., and Eicosane has a peak temperature of 30.0° C. The CEF column resolution is calculated with a mixture of NIST linear polyethylene 1475a (1.0 mg/ml) and hexacontane (Fluka, purum, >97.0, 1 mg/ml). A baseline separation of hexacontane and NIST polyethylene 1475a is achieved. The area of hexacontane (from 35.0 to 67.0° C.) to the area of NIST 1475a from 67.0 to 110.0° C. is 50 to 50, the amount of soluble fraction below 35.0° C. is <1.8 wt %. The CEF column resolution is defined in the following equation:
$Resolution = \frac{\begin{matrix} Peak temperature of NIST 1475 a - \\ Peak Temperature of Hexacontane \end{matrix}}{\begin{matrix} Half - height Width of NIST 1475 a + Half - \\ height Width of Hexacontane \end{matrix}}$
where the column resolution is 6.0.
Differential Scanning Calorimetry (DSC)
Differential Scanning calorimetry (DSC) is used to measure the melting and crystallization behavior of a polymer over a wide range of temperatures. For example, the TA Instruments Q1000 DSC, equipped with an RCS (refrigerated cooling system) and an autosampler is used to perform this analysis. During testing, a nitrogen purge gas flow of 50 ml/min is used. Each sample is melt pressed into a thin film at about 175° C.; the melted sample is then air-cooled to room temperature (approx. 25° C.). The film sample is formed by pressing a “0.1 to 0.2 gram” sample at 175° C. at 1,500 psi, and 30 seconds, to form a “0.1 to 0.2 mil thick” film. A 3-10 mg, 6 mm diameter specimen is extracted from the cooled polymer, weighed, placed in a light aluminum pan (ca 50 mg), and crimped shut. Analysis is then performed to determine its thermal properties. The thermal behavior of the sample is determined by ramping the sample temperature up and down to create a heat flow versus temperature profile. First, the sample is rapidly heated to 180° C., and held isothermal for five minutes, in order to remove its thermal history. Next, the sample is cooled to −40° C., at a 10° C./minute cooling rate, and held isothermal at −40° C. for five minutes. The sample is then heated to 150° C. (this is the “second heat” ramp) at a 10° C./minute heating rate. The cooling and second heating curves are recorded. The cool curve is analyzed by setting baseline endpoints from the beginning of crystallization to −20° C. The heat curve is analyzed by setting baseline endpoints from −20° C. to the end of melt. The values determined are peak melting temperature (Tm), peak crystallization temperature (Tc), heat of fusion (Hf) (in Joules per gram), and the calculated % crystallinity for polyethylene samples using: % Crystallinity=((Hf)/(292 J/g))×100. The heat of fusion (Hf) and the peak melting temperature are reported from the second heat curve. Peak crystallization temperature is determined from the cooling curve.
Apparent Density
A sample material is cut into a square piece of 15 cm×15 cm in size. The volume of this piece is calculated from the thickness measured at four points. The division of the weight by the volume gives the apparent density (an average of four measurements is taken).
Storage Modulus
Storage modulus is measured according to ASTM D 5026-01.
Elastic Recovery
Cyclic loading to 100% strain using ASTM D 1708 microtensile specimens with an Instron™ instrument. The sample is loaded and unloaded at 267% min⁻¹for 3 cycles at 21° C. Elastic recovery is calculated from the first unloading cycle using the strain at which the load returned to the base line. The elastic recovery is defined as:
% Elastic Recovery=εf−(εs)(εf)×100%,
where εf is the strain taken for cyclic loading and εS is the strain where the load returns to the baseline during the 1st unloading cycle.
Weight Percent Crystallinity
Weight Percent crystallinity may be calculated from the density ρ of the polymer.
$W t % Crystallinity = \frac{ρ_{c} (ρ - ρ_{a})}{ρ (ρ_{c} - ρ_{a})}$
where ρ_c=1 (the density at 100% crystallinity), ρ_a=the density of the polymer in amorphous state, and ρ=the density of the polymer. The amorphous density of polyethylene is known to be approximately 0.855.
Comonomer Distribution Constant (CDC) Method
Comonomer distribution constant (CDC) is calculated from comonomer distribution profile by CEF. CDC is defined as Comonomer Distribution Index divided by Comonomer Distribution Shape Factor multiplying by 100 as shown in the following equation:
$CDC = \frac{Comonomer Distribution Index}{Comonomer Distribution Shape Factor} = \frac{Comonomer Distribution Index}{Half Width / Stdev} * 100$
Comonomer distribution index stands for the total weight fraction of polymer chains with the comonomer content ranging from 0.5 of median comonomer content (C_median) and 1.5 of C_medianfrom 35.0 to 119.0° C. Comonomer Distribution Shape Factor is defined as a ratio of the half width of comonomer distribution profile divided by the standard deviation of comonomer distribution profile from the peak temperature (T_p).
CDC is calculated from comonomer distribution profile by CEF, and CDC is defined as Comonomer Distribution Index divided by Comonomer Distribution Shape Factor multiplying by 100 as shown in the following Equation:
$CDC = \frac{Comonomer Distribution Index}{Comonomer Distribution Shape Factor} = \frac{Comonomer Distribution Index}{Half Width / Stdev} * 100$
wherein Comonomer distribution index stands for the total weight fraction of polymer chains with the comonomer content ranging from 0.5 of median comonomer content (C_median) and 1.5 of C_medianfrom 35.0 to 119.0° C., and wherein Comonomer Distribution Shape Factor is defined as a ratio of the half width of comonomer distribution profile divided by the standard deviation of comonomer distribution profile from the peak temperature (Tp).
CDC is calculated according to the following steps:
(A) Obtain a weight fraction at each temperature (T) (w_T(T)) from 35.0° C. to 119.0° C. with a temperature step increase of 0.200° C. from CEF according to the following Equation:
$\int_{35}^{119.0} W_{T} (T) \partial T = 1$
(B) Calculate the median temperature (T_median) at cumulative weight fraction of 0.500, according to the following Equation:
$\int_{35}^{T_{median}} w_{T} (T) \partial T = 0.5$
(C) Calculate the corresponding median comonomer content in mole % (C_median) at the median temperature (T_median) by using comonomer content calibration curve according to the following Equation:
$\ln (1 - comonomercontent) * - \frac{207.26}{273.12 + T} + 0.5533$ $R^{1} = 0.997$
(D) Construct a comonomer content calibration curve by using a series of reference materials with known amount of comonomer content, i.e., eleven reference materials with narrow comonomer distribution (mono-modal comonomer distribution in CEF from 35.0 to 119.0° C.) with weight average M_wof 35,000 to 115,000 (measured via conventional GPC) at a comonomer content ranging from 0.0 mole % to 7.0 mole % are analyzed with CEF at the same experimental conditions specified in CEF experimental sections;
(E) Calculate comonomer content calibration by using the peak temperature (T_p) of each reference material and its comonomer content; The calibration is calculated from each reference material according to the following Equation:
$\ln (1 - comonomercontent) * - \frac{207.26}{273.12 + T} + 0.5533$ $R^{2} = 0.997$
wherein: R²is the correlation constant;
(F) Calculate Comonomer Distribution Index from the total weight fraction with a comonomer content ranging from 0.5*C_methanto 1.5*C_median, and if T_medianis higher than 98.0° C., Comonomer Distribution Index is defined as 0.95;
(G) Obtain Maximum peak height from CEF comonomer distribution profile by searching each data point for the highest peak from 35.0° C. to 119.0° C. (if the two peaks are identical, then the lower temperature peak is selected); half width is defined as the temperature difference between the front temperature and the rear temperature at the half of the maximum peak height, the front temperature at the half of the maximum peak is searched forward from 35.0° C., while the rear temperature at the half of the maximum peak is searched backward from 119.0° C., in the case of a well defined bimodal distribution where the difference in the peak temperatures is equal to or greater than the 1.1 times of the sum of half width of each peak, the half width of the inventive ethylene-based polymer composition is calculated as the arithmetic average of the half width of each peak;
(H) Calculate the standard deviation of temperature (Stdev) according the following Equation:
$Stdev = \sqrt{\sum_{35.0}^{119.0} {(T - T_{p})}^{2} * w_{T} (T)}$
Bending Stiffness
The bending stiffness is measured per DIN 53121 standard, with compression molded plaques of 550 μm thickness, using a Frank-PTI Bending Tester. The samples are prepared by compression molding of resin granules per ISO 293 standard. Conditions for compression molding are chosen per ISO 1872-2007 standard. The average cooling rate of the melt is 15° C./min. Bending stiffness is measured in 2-point bending configuration at room temperature with a span of 20 mm, a sample width of 15 mm, and a bending angle of 40°. Bending is applied at 6°/s and the force readings were obtained from 6 to 600 s, after the bending is complete. Each material is evaluated four times.
Height Loss
The cushioning net structure is tested for height loss in accordance with ASTM D 3574, Test B2. After the initial measurement of height, the cushioning net structure is subjected to constant force pounding of 10,000 cycles, where the fatigue tester is calibrated to 220N and the pounder has a rate of 80 cycles/min. After waiting for 24 hours once pounding is completed, the cushioning net structure is tested for height again. Loss in height is measured in percent.

Examples

The following Tables 1-3 lists properties of an instant embodiment as well as comparative compositions:

TABLE 1

		Instant	Comparative
	Comparative	Embodiment	Example 2 -
Physical	Example 1 -	(Ethylene/1-octene	KERNEL ™
Properties	INFUSE 9817 ™¹	copolymer blend)	KS 571²

Melt Index	15	15	12
(I2)
Density	0.877	0.910	0.907
I10/I2	7.294	6.750	5.650
Mw/Mn	2.340	2.813	2.325
DSC Melt	120.0	123.4	96.7
Temp
ΔH (J/g)	50.42	129.30	115.40
Elastic	78	63	72
recovery(%)
100% strain
G′ (25 c.)/G′	5.87	38.67	1084.96
(100 C.)
Bending	0.27 ± 0.04	1.38 ± 0.20	1.00 ± 0.15
Stiffness
(Nmm) at 6 s

¹INFUSE 9817 ™ is available by Dow Chemical Company (Midland, Michigan)
²KERNEL ™ KS 571 is supplied by the Japan Polychem Corporation.

TABLE 2

Comparative CEF Data

Wt % in Each Temperature Zone

MW of Each Temperature Zone

	25° C.-	35° C.-	90° C.-	25° C.-	35° C.-	90° C.-
Sample ID	35° C.	90° C.	115° C.	35° C.	90° C.	115° C.

KERNEL ™ KS	4.20%	95.80%	0.00%	10,186	65,598	ND
571
INFUSE ™ 9817	42.35%	43.11%	14.54%	94,012	91,428	48,962
INSTANT	6.52%	83.92%	9.56%	29,248	60,048	123,874
EMBODIMENT

TABLE 3

Comparative Comonomer Distribution Constant (CDC) Data

	Comonomer		Half
	Distribution	Stdev,	Width,	Halfwidth/
Sample	Index	° C.	° C.	Sigma	CDC

KERNEL ™	0.962	7.393	11.058	1.496	64.3
KS 571
INFUSE ™	0.604	17.507	25.027	1.43	42.2
9817
INSTANT	0.78	12.756	8.91	0.698	111.7
EMBODIMENT

The following table (Table 4) lists specific properties and fabrication parameters for producing the above ethylene/1-octene copolymer blend embodiment in a dual reactor system as described above. As shown, the homogeneously branched random ethylene/1-octene copolymer is produced in the first reactor via and the heterogeneously branched random ethylene/1-octene copolymer of the ethylene/1-octene copolymer blend is produced in the second reactor and is also blended with the homogeneously branched random ethylene/1-octene copolymer in the second reactor.

TABLE 4

Operating Parameters

1. CATALYST

First Reactor Catalyst	Constrained geometry catalyst -
	Titanium, [N-(1,1-dimethylethyl)-
	1,1-dimethyl-1-[(1,2,3,3a,8a-.eta.)-
	1,5,6,7-tetrahydro-2-methyl-s-indacen-
	1-yl]silanaminato(2-)-.kappa.N][(1,2,3,4-
	.eta.)-1,3-pentadiene]-
First Reactor Co-Catalyst	Amine, bis(hydrogenated tallow alkyl)methyl,
	tetrakis(pentafluorophenyl)borate(1-)
Second Reactor Catalyst	Heterogeneous Ziegler-Natta catalyst
	prepared substantially according to the
	examples of U.S. Pub. No. 2012/0041148.

2. PRODUCT DATA
First Reactor Product	%	58.19
Split
Second Reactor Product	%	41.81
Split
First Reactor Product	g/10 mins	15
Melt Index (I₂)
Second Reactor Product	g/10 mins	16.7
Melt Index (I₂)
First Reactor Product		6.5
Melt Flow Ratio (I₁₀/I₂)
Second Reactor Product		8
Melt Flow Ratio (I₁₀/I₂)
Overall Product	g/10 mins	15
Melt Index (I₂)
First Reactor Product	g/cm³	0.902
Density
Second Reactor Product	g/cm³	0.921
Density
Overall Product Density	g/cm³	0.910

Referring to Table 4 above, the instant embodiment (ethylene/α-olefin copolymer blend) comprises 58.19% homogeneously branched random ethylene/α-olefin copolymer and 41.81% heterogeneously branched random ethylene/α-olefin copolymer, where the homogenously branched random ethylene/α-olefin copolymer has melt index (I₂) of 15 g/10 min, a density of 0.902 g/cm³and an I₁₀/I₂of 6.5, and the heterogeneously branched random ethylene/α-olefin copolymer has a melt index (I₂) of 16.7, a density of 0.921 g/cm³and an I₁₀/I₂of 8. This embodiment and the KERNEL™ KS 571 composition were used to create cushioning net structures.
The method of making the cushioning net structures was similar to the procedure described in U.S. Pat. No. 7,625,629, which is incorporated by reference herein in its entirety. As shown in Table 5 below, the cushioning net structures were tested using the height loss calculation as defined above. As shown, the instant embodiment demonstrates significantly less height loss after indentation than the KERNEL™KS 571.

TABLE 5

	Instant
Properties of	Embodiment	Comparative
Cushioning net	(Ethylene/1-octene	Example
structure	copolymer blend)	KERNEL ™KS 571

Apparent Density	2.4	2.3
(lb/ft³)
Height Loss (%)	2.4	4.3

It is further noted that terms like “preferably,” “generally,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure.
It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

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_nwith M_wbeing a weight average molecular weight and M_nbeing a number average molecular weight;

a melt index (I₂) 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/cm³.

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/cm³to about 0.1 g/cm³.

10. The cushioning net structure of claim 1 wherein the ethylene/α-olefin copolymer blend comprises a melt flow ratio (I₁₀/I₂) of about 5 to about 10, where I₁₀is 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 melt index (I₂) 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/cm³; 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/cm³to about 0.1 g/cm³.