Phthalate-free polypropylene homopolymer having high stiffness properties
Phthalate-free polypropylene homopolymers and compositions incorporating the homopolymers are described. The phthalate-free polypropylene homopolymers exhibit high molecular weight as well as low XS content. Composition incorporating the phthalate-free polypropylene homopolymer can have relatively high stiffness properties. In addition, the polypropylene compositions can have good melt flow characteristics. Phthalate-free compositions including the homopolymers can be advantageously utilized in forming containers and other articles in food contacting, medical, and personal care applications.
1 . A polypropylene homopolymer, wherein the polypropylene homopolymer has a weight average molecular weight of 150,000 or greater, a melting temperature of about 160° C. or greater, a molecular weight distribution of 5 or greater, and a xylene soluble content of 1.8% by weight or less, and wherein the polypropylene homopolymer is produced with a Ziegler-Natta catalyst and is phthalate-free.
2 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has an XS content of from 0.5% by weight to 1.5% by weight.
3 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has a weight average molecular weight of 200000 or greater.
4 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has a weight average molecular weight of 350000 or greater.
5 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has a molecular weight distribution of 5.5 or greater.
6 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has one or more of an isotactic pentad content of 95% or greater, an isotactic triad content of 97% or greater, an isotactic block length of 150 or greater, and a meso run length of 100 or greater.
7 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has a melting temperature of 164° C. or greater.
8 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer has a crystallization temperature of 120° C.
9 . The polypropylene homopolymer of claim 1 , wherein the polypropylene homopolymer is formed in a gas phase reactor.
10 . A composition comprising the phthalate-free polypropylene homopolymer of claim 1 , wherein the composition has a flexural modulus of about 1700 MPa or greater, and a melt flow rate of about 1 g/10 min or greater and about 10 g/10 min or less.
11 . The composition of claim 10 , wherein the composition has an Izod impact strength of 10 J/m or greater.
12 . The composition of claim 10 , wherein the composition has a tensile strength at yield of 20 MPa or greater.
13 . The composition of claim 10 , wherein the composition comprises a nucleating agent.
14 . The composition of claim 10 , wherein the composition does not include a nucleating agent.
15 . The composition of claim 10 , wherein the composition comprises one or more of a mold release agent, a slip agent, an antiblock, a UV stabilizer, a heat stabilizer, a clarifying agent, an antioxidant, an acid scavenger, or a colorant.
16 . The composition of claim 10 , wherein the composition comprises a second polymer.
17 . A molded article comprising the composition of claim 10 .
18 . The molded article of claim 17 , wherein the molded article is a container.
19 . The molded article of claim 17 , wherein the molded article is a food contact article, a medical care article, or a personal care article.