Polypropylene films and multilayered laminate
View Patent ↗Heat-sealing polypropylene films having specific characteristics, and being well-balanced between a tensile modulus and a heat seal temperature, less tacky, and excellent in processability, transparency and impact resistance, as well as being excellent in resistance to whitening due to peeling, softness and impact resistance. A multilayered heat-sealing polyolefin resin laminate having at least one outermost layer produced from the above heat-sealing propylene polymers exhibits excellent low-temperature heat sealability and sufficient interlaminar strength without the use of an adhesive. The heat-sealing propylene polymers are produced by polymerizing propylene or polymerizing propylene with ethylene and/or C 4 -C 20 α-olefin in the presence of a polymerization catalyst containing a transition metal compound represented by the following formula (I): wherein A 1 , A 2 , E 1 , E 2 , M, X, Y, q and r are as defined in the specification.
1. A multilayered polyolefin resin laminate, wherein at least one outermost layer is made of a heat-sealing propylene homopolymer satisfying the following requirements of:
(1) having a component soluble in a 25° C. hexane in a content (H25) of 0 to 80% by weight;
(2) having, when measured by a differential scanning calorimeter (DSC), no melting point or a melting point Tm (° C.) satisfying the following formula:
Δ H≧ 6×( Tm− 140)
wherein ΔH is a melting endotherm of 20 J/g or less,
(3) having a meso pentad fraction [mmmm] of from 20 to 60 mol %,
(4) having a tensile modulus of 100 MPa or lower, and
wherein the heat-sealing propylene homopolymer is produced by polymerizing propylene in the presence of a polymerization catalyst comprising:
(A) a transition metal compound represented by the following formula (I):
wherein M is a metal element of Groups 3 to 10 or lanthanum series of the Periodic Table;
E 1 and E 2 are the same or different and each independently is a ligand selected from the group consisting of substituted cyclopentadienyl, and substituted indenyl; and E 1 and E 2 are cross-linked via A 1 and A 2 ;
X is a σ-bonding ligand; and a plurality of X, if any, may be same or different and each X may be cross-linked with another X, E 1 , E 2 or Y;
Y is a Lewis base; and a plurality of Y, if any, may be same or different and each Y may be cross-linked with another Y, E 1 , E 2 or X;
A 1 and A 2 may be the same or different divalent silylene group for cross-linking two ligands E 1 and E 2 ;
q is an integer of 1 to 5 given by the formula, [(valence of M)−2]; and
r is an integer of 0 to 3, and
(B) at least one component selected from the group consisting of a compound (B-1) capable of forming an ionic complex by reacting with said transition metal compound (A) or a derivative thereof, and an aluminoxane (B-2).
2. The multilayered polyolefin resin laminate according to claim 1 , wherein the heat-sealing propylene homopolymer contains a fraction (W25) eluted at 25° C. or lower determined by temperature programmed chromatography in an amount of from 20 to 100% by weight.
3. The multilayered polyolefin resin laminate according to claim 1 , wherein the heat-sealing propylene homopolymer is a propylene homopolymer (A-1) having:
a racemic pentad fraction [rrrr] satisfying, together with 1−[mmmm], the following formula:
[ rrrr ]/(1 −[mmmm ])≦0.1.
4. The multilayered polyolefin resin laminate according to claim 1 , wherein the heat-sealing propylene homopolymer has a molecular weight distribution (Mw/Mn) of 4 or less as measured by gel permeation chromatography (GPC) and/or an intrinsic viscosity [η] of from 0.5 to 15.0 dL/g as measured at 135° C. in tetralin.
5. The multilayered polyolefin resin laminate according to claim 1 , having at least one layer that is made of a crystalline propylene polymer other than the heat-sealing propylene homopolymer.
6. The multilayered polyolefin resin laminate according to claim 1 , which is produced by T-die casting.
7. The multilayered polyolefin resin laminate according to claim 1 , satisfying the following formula:
TM≧12.5×HST−700
wherein TM is a tensile modulus (MPa) and HST is a heat seal temperature (° C.).
8. The multilayered polyolefin resin laminate according to claim 1 , wherein the propylene homopolymer is produced by polymerizing propylene in the presence of a polymerization catalyst comprising (1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-n-butylindenyl)zirconium dichloride, triisobutylaluminum and methylaluminoxane.
9. The multilayered polyolefin resin laminate according to claim 1 , wherein the propylene homopolymer is produced by polymerizing propylene in the presence of (1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-n-butylindenyl)zirconium dichloride and methylaluminoxane.
10. The multilayered polyolefin resin laminate according to claim 1 , wherein the silylene group is selected from the group consisting of dimethylsilylene, diphenylsilylene, methylphenylsilylene, tetramethyldisilylene and diphenyldisilylene.