Medium density polyethylene compositions for film applications
First Claim
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1. A coextruded film consisting of:
- (i) a first layer of a composition comprising a low density polyethylene (LDPE) prepared with a non-metallocene catalyst and/or a linear low density polyethylene (LLDPE) prepared with either a non-metallocene or a metallocene catalyst;
(ii) a second layer of a homogeneous blend of a low density polyethylene (LDPE) with a metallocene catalyzed medium density polyethylene (mMDPE), this blend essentially consisting of from 0.5 to 99.5% by weight of mMDPE and from 99.5 to 0.5% by weight of LDPE, based on the total weight of the blend, and having a density of from 0.925 to 0.955 g/cm3, and the metallocene catalyst system essentially consisting of a bridged metallocene compound, alone or in combination with another metallocene catalyst which contributes less than 80% by weight of said metallocene;
(iii) a third layer of a composition comprising a low density polyethylene (LDPE) prepared with a non-metallocene catalyst and/or a linear low density polyethylene (LLDPE) prepared either with a non-metallocene or a metallocene catalyst, said third layer being the same as or different from the first layer.
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Abstract
Use of a homogeneous blend of a metallocene-catalysed medium density polyethylene (mMDPE) with low density polyethylene (LDPE), to produce blown films, this composition essentially consisting of from 0.5 to 99.5 % by weight of mMDPE and from 99.5 to 0.5 % by weight of LDPE, based on the total weight of the blend. The blend is optionally coextruded between layers of LDPE. The compositions of this invention have good processability and are used to make blown films which have the good optical properties of LDPE and the good mechancial and processing properties of MDPE.
10 Citations
14 Claims
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1. A coextruded film consisting of:
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(i) a first layer of a composition comprising a low density polyethylene (LDPE) prepared with a non-metallocene catalyst and/or a linear low density polyethylene (LLDPE) prepared with either a non-metallocene or a metallocene catalyst;
(ii) a second layer of a homogeneous blend of a low density polyethylene (LDPE) with a metallocene catalyzed medium density polyethylene (mMDPE), this blend essentially consisting of from 0.5 to 99.5% by weight of mMDPE and from 99.5 to 0.5% by weight of LDPE, based on the total weight of the blend, and having a density of from 0.925 to 0.955 g/cm3, and the metallocene catalyst system essentially consisting of a bridged metallocene compound, alone or in combination with another metallocene catalyst which contributes less than 80% by weight of said metallocene;
(iii) a third layer of a composition comprising a low density polyethylene (LDPE) prepared with a non-metallocene catalyst and/or a linear low density polyethylene (LLDPE) prepared either with a non-metallocene or a metallocene catalyst, said third layer being the same as or different from the first layer. - View Dependent Claims (2, 3, 4, 5, 6, 11, 12, 13)
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7. A process for preparing a blow film:
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a) preparing a blend of 0.5 to 99.5% by weight of a metallocene-catalyzed medium density polyethylene (mMDPE) with 99.5 to 0.5% by weight of a low density polyethylene prepared with a non-metallocene catalyst (LDPE), based on the total weight of the blend, said blend having a density of from 0.93 to 0.955 g/cm3 and a melt index MI2 of from 0.2 to 10 g/10 min, and the metallocene catalyst system essentially consisting of a bridged metallocene compound, alone or in combination with another metallocene catalyst which contributes less than 80% by weight of said metallocene;
b) preparing a second composition of a LDPE prepared with a non-metallocene catalyst, and/or a LLDPE prepared with either a non-metallocene or a metallocene catalyst;
c) preparing a third composition of a LDPE prepared with a non-metallocene catalyst, and/or a LLDPE prepared with either a non-metallocene or a metallocene catalyst, said composition being the same or different from the composition of step b);
d) coextruding the blend of step a) between a layer prepared from the composition of step b) and a layer prepared from the composition of step c), said blend of step a) representing from 33 to 100% by weight of the total weight of the film;
e) blowing the coextrudate of step d) to prepare a blown film with improved optical properties. - View Dependent Claims (8, 9, 10, 14)
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Specification