Increased rubber content in high impact polypropylene via a sirius ziegler‐natta catalyst containing nanoparticles

Abstract

High impact polypropylene was produced in a tworeactor polymerization process operating in series using two different Ziegler-Natta catalysts (referred to as catalysts A and B) that had been prepared by Sirius emulsion technology in the absence and presence of SiO 2 nanoparticles, respectively. The homo polypropylene matrix was produced in liquid bulk and the ethylene/propylene rubber in gas phase under industrial conditions. Catalyst B was prepared with the same emulsion technology as catalyst A, except that SiO 2 nanoparticles (average particles size 80 nm) were added during catalyst preparation. Scanning electron microscopy studies showed that the nanoparticles were fairly evenly distributed within catalyst B particles, although there was some agglomeration. It was shown that the nanoparticles in catalyst B increased the internal porosity in the homo polypropylene matrix particles and this enabled a significant increase in the rubber content. Maximum rubber content, before running into stickiness problems, was approximately 25 wt % for catalyst A without nanoparticles, whereas the maximum rubber content for catalyst B was almost doubled to 45 wt % due to the beneficial transformation of the internal catalyst morphology by the nanoparticles. In addition, it was also found that the reaction was not mass transfer limited during the ethylene/propylene rubber polymerization stage, even at very high rubber contents where all pores and cavities were filled with rubber.

Heterophasic copolymers of polypropylene: Development, design principles, and future challenges

“…The development of traditional ZN catalysts is also moving forward, both on the support side and in the area of internal and external donors . For the former, the legal requirements for developing largely phthalate‐free catalyst systems will change the scene very soon and will probably also cause major product adaptation needs.…”

The Effect of Reactor Conditions on High‐Impact Polypropylene Properties and Gas Phase Polymerization Kinetics

“…Their stickiness is due to two factors: 1) the rubber present on the surface and 2) the degree of stickiness of the rubber. This last point depends on the molar mass (lower molar mass rubber is stickier) and on the ethylene content of the rubber . The flowability of the powder can be used as a measurement of the stickiness of the particles, which in practice has been found to be one of the key reasons for process disturbances.…”

Reducing the Surface Stickiness of Multiphase Polypropylene Particles: An Environmentally Friendly and Scalable Method

“…However, the introduced inert inorganic particles impair the mechanical properties and optical properties of the polyolefin material. − On the other hand, the addition of ultrafine powders to the reactor also increases the difficulty of reactor operation . In addition, Vestberg increased the rubber content in high-impact polypropylene to 45 wt % by preparing a high-porosity catalyst containing SiO 2 nanoparticles before the polymer encountered stickiness problems, but the polymer also suffered from a high ash content. In summary, for the polypropylene industry, the existing particle surface stickiness reduction techniques are deficient in terms of copolymerization activity damage and product heterogeneity and still lack a green and efficient strategy for regulating rubber distribution within polypropylene particles …”