Heat sealable films from propylene and α-olefin units
AssigneeExxonMobil Chemical Patents Inc.
InventorsMichael Glenn Williams, Hans Joachim Pip
Life of this patent
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Abstract
A film structure having a base layer comprising a film-forming thermoplastic polymer; and a heat-seal layer having a seal-initiation temperature less than or about 130° C. and comprising from about 50 to about 98 wt % of a first polymer component and about 2 to about 50 wt % of a second polymer component. The first polymer component comprising propylene-derived units and, optionally, up to about 20 wt % of comonomer units derived from a C2 and/or C4-C20 α-olefin, and having a heat of fusion greater than 75 J/g and a melting point greater than or equal to 105° C. The second polymer component comprising at least 75 wt % propylene-derived units, and having a melting point less than 105° C. and a heat of fusion less than 75 J/g.
Claims14
A heat sealable film structure comprising:
- (a) an unoriented or uniaxially oriented base layer comprising a metallocene-catalyzed isotactic polypropylene homopolymer having an isotacticity of from about 80 to 99%, a melting point from about 155° C. to about 165° C., and a melt flow rate (2.16 kg @ 230° C., ASTM D-1238) of from 0.5 g/10 min to about 15 g/10 min;
- and
- (b) a heat-seal layer having:
- a seal-initiation temperature ≦130° C.;
- and
- comprising from 80 wt % to 90 wt % of a first polymer component (FPC) and 10 wt % to 20 wt % of a second polymer component (SPC), based on the total weight of FPC and SPC, wherein:
- (i) the FPC comprises a polypropylene copolymer with 2 to 5 wt % comonomer and has a heat of fusion >75 J/g and a melting point ≧105° C.;
- and
- (ii) the SPC comprises from about 75 wt % to about 95 wt % propylene and from about 8 wt % to about 16 wt % ethylene, the SPC having a melting point of about 25° C. to about 65° C. and a heat of fusion <75 J/g,
- wherein 50 to 99 percent of the heat sealable film thickness is the base layer, and wherein the base layer further comprises a slip agent, and
- the heat seal layer further comprises a slip agent and an anti-blocking agent.
A heat sealable film structure consisting essentially of:
- (a) an unoriented or uniaxially oriented base layer comprising a metallocene-catalyzed isotactic polypropylene homopolymer having an isotacticity of from about 80 to 99%, a melting point from about 155° C. to about 165° C., and a melt flow rate (2.16 kg @ 230° C., ASTM D-1238) of from 0.5 g/10 min to about 15 g/10 min;
- and
- (b) a heat-seal layer having:
- a seal-initiation temperature ≦130° C.;
- and comprising a first polymer component (FPC) and a second polymer component (SPC), wherein:
- (i) the FPC comprises a polypropylene copolymer with 2 to 5 wt % comonomer, the FPC having a heat of fusion >75 J/g and a melting point ≧105° C.;
- and
- (ii) the SPC consists essentially of from about 75 wt % to about 94 wt % propylene and from about 6 wt % to about 25 wt % ethylene, the SPC having a melting point of about 30° C. to about 60° C. and a heat of fusion <50 J/g,
- wherein the heat seal layer comprises 80 wt % or 90 wt % FPC and 10 wt % or 20 wt % SPC, and
- 50 to 99 percent of the heat sealable film thickness is the base layer, and
- wherein the base layer further comprises a slip agent and the heat seal layer further comprises a slip agent and an anti-blocking agent.
Dependencies are inferred from the claim text.