Bi-modal Poly-alpha-olefin Blend
AssigneeRextac LLC
InventorsJames Nicholas Fowler, Enrico Buenacosa, James Haselman
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Abstract
A low viscosity, high tensile strength polymer having a bi-modal molecular weight distribution is produced using a combination of high molecular weight polymer and low molecular weight polymer. The polymer chains have a high content of meso dyads that results in a greater amount of crystalline regions when the polymer is solidified. The low molecular weight chains provide high flow characteristics when the polymer is molten. The process for producing the high content of meso dyads includes the use of an external donor catalyst during the reaction.
Claims20
A blended polymer composition that is useful as a hot-melt adhesive consisting essentially of:
- a) a high molecular weight, high tensile strength alpha-olefin polymer;
- and;
- b) a low molecular weight, high tensile strength polymer.
A process for preparing a blended polymer composition comprising:
- preparing a first propylene/1-butene copolymer characterized by a propylene content of 25 to 50 weigh percent, a 1-butene content of 75 to 50 weight percent and a tensile strength of at least 300 psig by reacting propylene and 1-butene monomers in the presence of a catalyst system comprising:
- (a) a solid supported catalyst component is prepared by the method comprising:
- (i) co-comminuting magnesium halide support base and aluminum trihalide in a molar ratio from about 8:0.5 to about 8:3 in the absence of added electron donor;
- and
- (ii) then co-comminuting the product of step (i) in the absence of added electron donor with sufficient titanium tetrahalide to provide a molar ratio of magnesium halide to titanium tetrahalide from about 8:0.1 to about 8:1.0
- (b) a trialkylaluminum co-catalyst, having from 1 to 9 carbon atoms in each alkyl group in an amount such that the Al/Ti ratio is between about 50:1 and about 500:1
- (c) an alkoxy silane component of the formula Rn Si(OR′)4-n where n=1-3, R=aryl or alkyl and R′=C1-3 alkyl in a sufficient quantity such that the molar ratio of organoaluminum co-catalyst to alkoxy silane is in the range from about 20:1 to about 45:1
- preparing a second propylene/1-butene copolymer by feeding a portion of the first copolymer to an extruder while simultaneously feeding a peroxide to a downstream port of the extruder;
- and,
- blending the first copolymer with the second copolymer.
Dependencies are inferred from the claim text.