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POLYMER BLENDS AND FILMS MADE THEREFROM

IP.com Disclosure Number: IPCOM000202517D
Publication Date: 2010-Dec-20

Publishing Venue

The IP.com Prior Art Database

Abstract

Polymer blends and films made therefrom are provided. The polymer blend can include a low density polyethylene having a Mw(absolute)/Mw(RI) ratio of about 1.9 or greater and a melt index (I2) of about 0.2 to about 20. The polymer blend can also include a linear polyethylene comprising ethylene and at least one C3 to C20 α-olefin comonomer. The linear polyethylene can have a molecular weight distribution (MWD) of about 3 to about 5 and a line obtained by regressing a linear line to a plot of molecular weight (Mw) in Daltons as ordinate and Temperature Rising Elution Fractionation (TREF) temperature from about 40°C to about 110°C has a slope that is greater than -15,000 and equal to less than zero. The plot of molecular weight (Mw) and Temperature Rising Elution Fractionation (TREF) temperature can include at least 10 data points acquired at equal intervals between about 40°C and about 110°C.

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POLYMER BLENDS AND FILMS MADE THEREFROM

BACKGROUND

[0001]      Sheet or film extrusion of polyethylene is used to produce a wide variety of products.  Conventional polyethylenes used for such applications include branched high pressure low density polyethylenes (LDPE), which are typically produced via high pressure autoclave polymerization.  Low density polyethylenes provide excellent extrusion characteristics such as low motor load, low neck-in, and high take-off speeds with web stability; however, the physical properties of the extruded resin are limited by the possible density range of low density polyethylene and the poor tensile properties exhibited by low density polyethylene.  On the other hand, conventional linear polyethylenes (LPE) provide acceptable properties over a wide density range, but linear polyethylenes require high motor load and frequently exhibit low draw-down rates during extrusion, often due to web instabilities. 

[0002]      Blends of low density polyethylene (LDPE) and linear polyethylene (LPE) have been made in an attempt to combine the processability of low density polyethylene and the physical attributes of linear polyethylene.  When conventional linear polyethylenes are blended with low density polyethylene to produce a polymer blend having a particular physical property such as low heat seal, toughness, or low wax content, such blends, however, also require high motor load for extrusion due to the narrow weight distribution of the conventional linear polyethylenes.  There is a need, therefore, for improved polymer blends comprising low density polyethylene and linear polyethylene that exhibit improved processability for film extrusion applications such as reduced motor load.

SUMMARY

[0003]      The polymer blend may comprise a low density polyethylene having a Mw(absolute)/Mw(RI) ratio of about 1.9 or greater and a melt index (I2) of about 0.2 to about 20, or about 0.2 to 10 g/10 min.  The polymer blend can also include a linear polyethylene comprising ethylene and at least one C3 to C20 α-olefin comonomer, wherein the linear polyethylene may have a molecular weight distribution (MWD) of about 3 to about 5 and a line obtained by regressing a linear line to a plot of molecular weight (Mw) in Daltons as ordinate and Temperature Rising Elution Fractionation (TREF) temperature from about 40°C to about 110°C as abscissa has a slope that is greater than -15,000 and equal to less than zero, wherein the plot of molecular weight (Mw) and Temperature Rising Elution Fractionation (TREF) temperature includes at least 10 data points acquired at equal intervals between about 40°C and about 110°C.  The linear polyethylene may be present in the polymer blend in an amount ranging from about 60 wt% to about 95 wt% based on the combined weight of the low density polyethylene and the linear polyethylene

[0004]      The low density polyethylene may have a Mw(absolute)/Mw(RI) ratio of about 2.7 or more. 

[0005]      The low density polyethylene...