Anti-block compounds for extrusion of transition metal catalyzed resins
AssigneeUnion Carbide Corporation
InventorsMichael A. Corwin, George N. Foster
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Abstract
A non-volatile, anti-gel compound having a chain of at least about 5 repeat units of an alkylene oxide and which is soluble in olefin polymers, and an inorganic anti-block agent having a substantially neutral pH are added to a film grade transition metal catalyzed resin containing halide residues such as Ziegler-Natta catalyzed olefin polymer compositions to prevent: (1) gel streaking/pinstriping during film extrusion processes; (2) blocking of the extruded film; and (3) discoloration of the extruded film upon aging. The anti-gel compound has a molecular weight between about 200 and about 4,000,000 Daltons.
Claims2
An improved process for extruding a film forming olefin polymer based composition into film which is essentially free from gel streaking and pinstriping and which does not discolor upon aging at 60.degree. C. for 4 weeks, said composition comprising a Ziegler-Natta catalyzed film grade olefin polymer containing a chloride catalyst residue having a concentration between about 5 and about 500 ppm and at least one hindered phenolic anti-oxidant having a concentration between about 20 and about 5000 ppm, which composition is susceptible to gel streaking/pinstriping during the formation of said film, the improvement which comprises:
- Extruding said composition into said film in the presence of at least one anti-gel compound and at least one inorganic anti-block compound, said anti-gel compound being characterized by having at least about 5 repeat units of an alkylene oxide and being present in a concentration sufficient to neutralize said chloride catalyst residue in said composition, said concentration of said anti-gel compound being at least about 0.8 times the concentration of said hindered phenolic anti-oxidant, said anti-gel compound having a molecular weight between about 200 and about 4,000,000 Daltons;
- said inorganic anti-block compound having a concentration between about 500 ppm and about 5% by weight and having a pH of between 6 and 8.
An improved process for extruding a film forming olefin polymer based composition into film, which film is essentially devoid of gel streaking and pinstriping and which does not discolor upon aging at 60.degree. C. for 4 weeks, which process comprises:
- extruding, under an extrusion temperature of at least 135.degree. C. to 345.degree. C. and a throughput time for said olefin polymer based composition in the extruding equipment of about 0.2 to 10 minutes, an extrudable composition which comprises,
- film grade olefin polymer containing a chloride catalyst residue in the range of between about 5 and about 500 ppm, based on the olefin polymer, and, based upon said olefin polymer, at least one anti-oxidant in a concentration between about 20 and about 5000 ppm, an inorganic anti-block compound in the range of between about 500 ppm and about 5% by weight, said inorganic anti-block compound having a pH of between 6 and 8, and an anti-gel compound containing at least about 5 moles of alkylene oxide in a concentration sufficient to neutralize said catalyst residue, said concentration of anti-gel compound being at least about 0.8 times the concentration of said anti-oxidant, said anti-gel compound having a molecular weight between about 200 and about 4,000,000 Daltons,
- the anti-oxidant stabilized film grade olefin polymer being a material which is susceptible to gel streaking and pinstriping under said extrusion conditions and which is susceptible to discoloration after extrusion upon aging at 60.degree. C. for four weeks in the absence of said anti-gel compound.
Dependencies are inferred from the claim text.