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)