What You Need to Know About UNIPOL^® Polypropylene Technology

Answers to basic questions about UNIPOL^® Polypropylene Technology and Polypropylene

What is UNIPOL^® Polypropylene Process Technology?

UNIPOL^® Polypropylene (PP) process technology is a leading gas-phase process for stable and predictable, large-scale polypropylene resin production. This versatile manufacturing process provides mechanical and operational simplicity while allowing PP manufacturers to produce a broad range of products. This mechanical simplicity results in fewer capital investments, reduced operating costs and lower maintenance costs compared to other technologies. 

UNIPOL^® PP technology allows plants to consistently operate at or above capacity with the use of CONSISTA^® catalyst systems. This technology, used in conjunction with CONSISTA^® catalyst systems, delivers longer operational time and exceptional resin performance.  A single plant can produce homopolymers, random and impact copolymers and terpolymers. The ability to quickly change a plant’s production to meet the market demands is part of the flexible design of UNIPOL^® PP technology. In addition, the UNIPOL UNIPPAC^® advanced process control software can optimize plant operations, as well as efficiently manage complex product transitions.

The UNIPOL^® PP technology team helps customers with choosing technology, developing a plant design, commissioning a plant, optimize ongoing processes and expand capacity.  Customers that use UNIPOL^® PP technology receive continuous operational updates and expert support to help them lead the market, year after year.  The Plant Lifetime Performance™ commitment ensures each customer that their plant performs optimally for decades. 

What is Polypropylene?

Polypropylene is a thermoplastic made from a combination of propylene and comonomers. It is used in a variety of everyday items that most people don’t recognize, including packaging for food, plastic parts in automobiles and home appliances like washing machines. Polypropylene is one of the most produced plastics in the world!

UNIPOL^® PP technology is designed to produce polypropylene which is a synthetic resin built by the polymerization of propylene. PP is one of the important members of the polyolefin resins family. PP is molded or extruded into many polypropylene plastic products in which toughness, flexibility, lightness and heat resistance are required.

How does UNIPOL^® PP Technology produce Polypropylene?

UNIPOL^® PP process technology’s market-leading, gas-phase process provides stable and predictable operations with less equipment than competing PP process technology.

This technology enables the production of homopolymers or random copolymers in a single reactor plant regardless of the capacity being produced. The same plant can also produce impact copolymers with the addition of a second reactor of the same technology. This technology delivers the highest continuous operational time in the industry with exceptional performance, which further enhances UNIPOL^® PP technology.

What are the different types of Polypropylene?

Polypropylene is available as homopolymers, copolymers (which are further separated into impact copolymers and random copolymers) and terpolymers. The polymer type fits certain applications based on the desired purpose.

Homopolymers are general-purpose grades, usually polymerized with Ziegler-Natta catalysts. Homopolymers are the most widely used polypropylene material in the industry. Homopolymers have a high level of stiffness at room temperature and a high melting point but lower transparency and diminished impact strength. This polymer type is used for applications such as woven bags, food packaging, housewares, containers, furniture, coffee makers and bottle caps.

Random copolymers are ethylene/propylene copolymers that are produced in a single reactor by copolymerizing propylene with small amounts of ethylene. Random copolymers usually have better impact properties, decreased melting point and enhanced flexibility. Random copolymers are used in applications requiring a certain degree of softness, such as housewares, food packaging, medical devices, building and construction, etc.

Impact copolymers are physical mixtures of homopolymers and random copolymers. Impact polymers work best at low temperatures and have higher impact resistance. The random copolymer part of the mixture is called the rubber phase. The rubber-like reinforcement greatly improves impact strength, particularly at low temperatures. Typical applications are in high-end injection molding markets such as automotive and appliance applications and consumer housewares like food containers.

Terpolymer polypropylene is produced by using ethylene and butene as a comonomer in addition to propylene. It delivers better transparency compared to homopolymers and has a low melting point.  It is used as a raw material for products requiring low-temperature processing, such as thermal adhesive films for packing foods, beverages, etc.

How is Polypropylene made?

Polypropylene is made by polymerizing propylene using a catalyst system, commonly a Ziegler-Natta or metallocene catalyst system. The polymerization parameters include temperature, pressure and reactant concentrations, which are determined according to the desired polymer grade.

The two main process types are either gas-phase or liquid-phase:

Gas-phase process: The reaction can happen in a fluidized bed reactor (like UNIPOL^® PP technology) or in a stirred bed reactor at specific temperatures and pressures. The activated catalyst is injected into a gas-phase reactor along with fresh and recycled propylene and hydrogen to produce homopolymers. The homopolymer is then separated from unreacted propylene and hydrogen using separators. The fine powder produced is made into little pellets, making it ready for use in manufacturing plants to make products. When making standard impact copolymers, the powder from the first reactor is fed, along with ethylene and additional propylene, into the second gas phase reactor.

Liquid-phase process: This polymerization process combines a bulk slurry reactor for the production of homopolymers and a fluidized gas-phase reactor for impact copolymers. Homopolymerization is carried out in the liquid phase, where liquid propylene and the catalyst system are fed continuously into the bulk slurry reactor together with hydrogen, and ethylene is added to produce random copolymers. Gaseous ethylene and propylene are copolymerized on the fluid bed of polymer particles for the production of impact copolymers.

Why is Polypropylene important?

Polypropylene is an important part of production for household and industrial applications because it offers excellent chemical and temperature resistance, a high degree of stiffness and a high melting point compared to other thermoplastics. This means the PP is highly durable and tough. Another valuable characteristic of PP is that it is fully recyclable, so there is less waste in landfills. Plus, an added benefit of the recycling process is that no toxic chemicals are released.