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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.


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.
 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
@ Break, %
 MD 565 780 600
 TD 775 840 750
Elmendorf Tear,
 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
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