Foamable polyolefin compositions and methods thereof
Foamed reactor made thermoplastic polyolefins (rTPOs), and articles made therefrom, are described. The compositions have an rTPO combined with a foaming agent. The foaming agent can be a physical blowing agent and/or a chemical foaming agent, and may include optional nucleating agents. Some compositions utilize a masterbatch having one or more chemical foaming agents to foam the rTPOs. The rTPOs have a large melt flow rate range and flexural modulus range that translate into a broad scope of potential applications and foamed architecture. This allows the combination of rTPOs and foaming agents to be fine-tuned for selected foaming application.
1. An article comprising:
a foamed reactor made thermoplastic polyolefin composition comprising:
a) from 8 to 25% by weight of a crystalline polymer comprising:
a copolymer of propylene and at least one alpha-olefin of formula H 2 C═CHR, where R is H or a C 2 -C 6 linear or branched alkyl, containing at least 85% by weight of propylene, having solubility in xylene at room temperature lower than 15% by weight; and
b) from 75 to 92% by weight of an elastomeric fraction comprising
i) a first elastomeric copolymer of propylene with at least one alpha-olefin of formula H 2 C═CHR, where R is H, optionally containing 0.5 to 5% by weight of a diene, the first elastomeric copolymer containing from 15 to 32% by weight alpha-olefin, and having solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction ranging from 3.0 to 5.0 dl/g; and
ii) a second elastomeric copolymer of propylene with at least one alpha-olefin of formula H 2 C═CHR, where R is H, optionally containing 0.5 to 5% by weight of a diene, the second elastomeric copolymer containing more than 32% up to 45% by weight alpha-olefin, and having solubility in xylene at room temperature greater than 80% by weight, the intrinsic viscosity of the xylene soluble fraction ranging from 4.0 to 6.5 dl/g
wherein the bi)/bii) weight ratio ranges from 1:5 to 5:1, and,
wherein said reactor made thermoplastic polyolefin composition has a flexural modulus lower than 60 MPa, a Shore A hardness lower than 90, a tension set at 100% lower than 35%, and a melt flow rate between 0.1 and 10 g/10 min.
2. The article of claim 1 , wherein said foamed reactor made thermoplastic polyolefin composition is foamed using at least one physical blowing agent (PBA) or at least one chemical foaming agent (CFA).
3. The article of claim 2 , wherein said foamed reactor made thermoplastic polyolefin composition is combined with a masterbatch comprising at least one nucleating agent.
4. The article of claim 3 , wherein said chemical foaming agent is in the same masterbatch as at least one nucleating agent, or in a different masterbatch as at least one nucleating agent.
5. The article of claim 4 , wherein the total amount of masterbatch in the foamable composition is 5% by weight or less.
6. The article of claim 2 , wherein said chemical foaming agent is endothermic or exothermic.
7. The article of claim 2 , wherein said chemical foaming agent acts as a nucleating agent.