Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1997-09-19
2002-07-09
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S333800, C528S50200C, C528S503000, C264S209300, C264S211120, C264S564000, C264S331170, C264SDIG004
Reexamination Certificate
active
06417289
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to compositions comprising a linear low density copolymer of ethylene and an alpha-olefin containing 4 to 10 carbon atoms (LLDPE), and to films of improved properties formed from such compositions.
BACKGROUND OF THE INVENTION
Linear low density polyethylene is ethylene copolymerized with alpha olefins of 3 to 10 carbon atoms. Improvements in impact resistance of films of linear low density polyethylene (hereinafter “LLDPE”) are desirable. Normal LLDPE resins lacks the melt strength required to blow films under high stalk extrusion conditions, often used to blow HMW-HDPE, which result in excellent film impact properties. One recent exception is a DMAC [”DMAC being an acronym for dimethylaluminum chloride] cocatalyzed LLDPE resins. A high molecular weight component of the DMAC cocatalyzed LLDPE resins is accompanied by an increased melt strength required to be blown into film under high stalk conditions used in HDPE film production.
SUMMARY OF THE INVENTION
In the present invention, the melt strength of LLDPE is increased by treatment with low levels of peroxides. Low levels of crosslinking of the LLDPE results with low levels of peroxides. This allows the LLDPE to be blown into film under high stalk conditions. The treated LLDPE can be fabricated with improved processability into blown films having improved impact properties. The impact strengths of these LLDPE films is significantly higher than that of films from uncrosslinked LLDPE films blown under non-stalk conditions.
REFERENCES:
patent: 4118453 (1978-10-01), Herrington
patent: 4578431 (1986-03-01), Shaw et al.
patent: 4606879 (1986-08-01), Cerisano
patent: 4820471 (1989-04-01), van der Molen
patent: 4832897 (1989-05-01), van der Molen
patent: 5756203 (1998-05-01), Shirodkar
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