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Tough new hexene copolymer LLDPE.

New "super-strong" hexene copolymer LLDPE, said to match the strength of octene copolymers, has been developed by Mobil Chemical Co.'s R&D labs in Edison, N.J. This is the first such resin made by a Unipol gas-phase reactor. Mobil has been sampling the first grades of the new resin to customers since late last year for blown films that can be up to 30% thinner and have the same properties as standard hexene resins, Mobil says.

Because Mobil is passing its catalyst development on to Union Carbide Chemicals & Plastics Co., Inc., Danbury, Conn., as part of Carbide's Unipol licensing agreement, such high-strength film resins could become widely available to processors for the first time. Previous Unipol technology made only hexene copolymers of lower properties. The only high-strength LLDPE blown film resins have been octene-based Dowlex resins from Dow Plastics in Midland, Mich., which enjoys a dominant position in a market that has grown to about 750 million lb/yr.

TOUGHER THAN OCTENE

Mobil's new resin is initially available in three grades--NTX-101, NTX-104 (with antiblock added), and NTX-095 (with slip and antiblock)--for blown film gauges of 0.3 to 5 mil. All have significantly higher dart impact and tear strengths (see table) than standard hexene copolymers because of more homogeneous short-chain branching distribution and narrower molecular-weight distribution, Mobil says. While strength properties are generally similar to octene LLDPE, dart impact substantially exceeds that of octene copolymers.
PROPERTIES OF MOBIL'S 'SUPER-STRENGTH' LLDPE
 Mobil's Mobil's Dow Chemical
Properties (Hexene) (Hexene) (Octene)
(1.0 mil) NTX-095 NTA-261 Dowlex 2045
Melt Index,
 g/10 min 0.9 0.9 1
Density, g/cc 0.918 0.917 0.920
Tens. Break, kpsi
 MD 8.16 5.5 8.4
 TD 5.8 4.8 5.8
Tens. Yield, kpsi
 MD 1.485 1.69 1.5
 TD 1.51 1.76 1.6
Dart Impact,
 |F.sub.50~, g 480 180 275
Elong.
@ Break, %
 MD 565 780 600
 TD 775 840 750
Elmendorf Tear,
 g/mil
 MD 430 350 375
 TD 750 750 750
Haze, % 28(a) 9 8
aContains slip and antiblock.


NTX resins process on standard equipment at 420-450 F melt temperature, at a blow-up ratio of 2.0-3.0, with a recommended die gap of 80-100 mils, according to Mobil's preliminary data sheet.

Using the same new, patented catalyst system, Mobil is also developing grades for injection molding and roto-molding. Mobil's manager of commercial development, Ino Hassid, says these grades will be available for customer sampling "in a matter of months." (CIRCLE 12)
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Title Annotation:Materials; Technology News; light low density polyethylene
Author:Schut, Jan H.
Publication:Plastics Technology
Date:May 1, 1992
Words:424
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