**4.1 Spheripol process**

A typical Spheripol II process, which is one of the most employed process owned by Basell, consists of two liquid loop reactors and a gas phase reactor for

#### **Figure 12.**

*Reactor configurations for olefin polymerization: (a) autoclave; (b) loop; (c) fluidized-bed; (d) vertical gasphase; and (e) horizontal gas-phase [107].*

**25**

*Versatile Propylene-Based Polyolefins with Tunable Molecular Structure through Tailor-Made…*

producing more than 100 types of PP brands including homopolymer and random and impact copolymers with supported catalysts. The two loop reactors are typically operated under standard conditions of 70°C and 4 MPa with liquid propene circulating round the two loop reactors. An axial flow agitator is used to maintain good flowability, ensure good heat transfer, and keep substantial polymer particles from agglomerating from the slurry in each loop [35]. Typically, the PP concentra-

HY/HS catalysts, together with triethylaluminum, and an external donor such as a dialkyldimethoxysilane are continuously fed into the reactor to produce PP with a specific stereoregularity. Morphology control of the HY/HS catalyst particles is very critical in the initial polymerization stage (the first several seconds to minutes). For this reason, a prepolymerization stage in which the catalyst particles react at lower temperature and monomer concentration is employed to prevent catalyst particles from generating fine powders due to rapid polymerization. The catalyst particles grow slowly in this prepolymerization stage and produce only small amounts of polymer (< 100 g/g) in the catalyst granules before this catalyst is fed into the loop reactor. Mean residence time of the polymer particles in a single loop is about 1–2 h. Multiple loop reactors can be operated in a tandem way to narrow residence time distributions, tune the polymer structure and properties,

The isotactic PP particles are produced in the two loop reactors bypassing the copolymerization unit. Due to the high isotactic stereoregularity, generally, the HPP obtains high rigidity and tensile strength with high melting point. By adding propylene and ethylene and hydrogen in the two loop reactors, random copolypropylene (RPP) can be prepared; generally, the ethylene content in the RPP is below 4 wt% to avoid reactor fouling. The stereoregularity of a RPP, thus, is impaired via the insertion of the ethylene molecule; therefore, the melting point and crystalline temperature decreased, and the soluble fraction in the temperature-rising elution fraction (TREF) also increased correspondingly. However, the optical properties of the RPP could be improved dramatically with very low gloss, especially when a transparent nucleating agent is added. In the 3rd gas-phase reactor, either a vertical reactor with an agitator or a fluidized-bed reactor, mixture of propylene and ethylene, is fed to generate an ethylene-propylene rubber phase which is dispersed within the isotactic polypropylene particles already formed from the loop reactors; thus, impact polypropylene can be prepared. The EP rubber consists of polyethylene and polypropylene blocks {−(CH2─CH2)x─[CH2─C(CH3)]y─}, and in an industrial production, the ethylene content of the whole impact PP could be

Mitsui Petrochemical has developed a similar process using bulk polymerization with their specific supported catalysts. In a Hypol I PP process (**Figure 14**), two conventional reactors in series are employed, with reaction heat removed by evaporation of cool liquid propylene in the reactors. The slurry containing PP particles is then fed into a heated flash vessel, in which the propylene is recovered for recycling use. One or two gas-phase reactors with stirring might be added in tandem with the two bulk polymerization reactors to produce impact polypropylene. The reactors in the 2nd Hypol process of Mitsui Chemicals are replaced with two loop reactors and gas-phase fluidized-bed. Similar with Spheripol process, Hypol processes are design with innovative HY/HS supported catalysts to be able to produce HPP, RPP and

up to 15%, or the rubber phase content could be up to 30%.

*DOI: http://dx.doi.org/10.5772/intechopen.85963*

tion content was kept around 40 wt%.

and increase productivity.

**4.2 Hypol process**

impact copolymers.

**Figure 13.** *Process of production of impact PP [107].*

### *Versatile Propylene-Based Polyolefins with Tunable Molecular Structure through Tailor-Made… DOI: http://dx.doi.org/10.5772/intechopen.85963*

producing more than 100 types of PP brands including homopolymer and random and impact copolymers with supported catalysts. The two loop reactors are typically operated under standard conditions of 70°C and 4 MPa with liquid propene circulating round the two loop reactors. An axial flow agitator is used to maintain good flowability, ensure good heat transfer, and keep substantial polymer particles from agglomerating from the slurry in each loop [35]. Typically, the PP concentration content was kept around 40 wt%.

HY/HS catalysts, together with triethylaluminum, and an external donor such as a dialkyldimethoxysilane are continuously fed into the reactor to produce PP with a specific stereoregularity. Morphology control of the HY/HS catalyst particles is very critical in the initial polymerization stage (the first several seconds to minutes). For this reason, a prepolymerization stage in which the catalyst particles react at lower temperature and monomer concentration is employed to prevent catalyst particles from generating fine powders due to rapid polymerization. The catalyst particles grow slowly in this prepolymerization stage and produce only small amounts of polymer (< 100 g/g) in the catalyst granules before this catalyst is fed into the loop reactor. Mean residence time of the polymer particles in a single loop is about 1–2 h. Multiple loop reactors can be operated in a tandem way to narrow residence time distributions, tune the polymer structure and properties, and increase productivity.

The isotactic PP particles are produced in the two loop reactors bypassing the copolymerization unit. Due to the high isotactic stereoregularity, generally, the HPP obtains high rigidity and tensile strength with high melting point. By adding propylene and ethylene and hydrogen in the two loop reactors, random copolypropylene (RPP) can be prepared; generally, the ethylene content in the RPP is below 4 wt% to avoid reactor fouling. The stereoregularity of a RPP, thus, is impaired via the insertion of the ethylene molecule; therefore, the melting point and crystalline temperature decreased, and the soluble fraction in the temperature-rising elution fraction (TREF) also increased correspondingly. However, the optical properties of the RPP could be improved dramatically with very low gloss, especially when a transparent nucleating agent is added. In the 3rd gas-phase reactor, either a vertical reactor with an agitator or a fluidized-bed reactor, mixture of propylene and ethylene, is fed to generate an ethylene-propylene rubber phase which is dispersed within the isotactic polypropylene particles already formed from the loop reactors; thus, impact polypropylene can be prepared. The EP rubber consists of polyethylene and polypropylene blocks {−(CH2─CH2)x─[CH2─C(CH3)]y─}, and in an industrial production, the ethylene content of the whole impact PP could be up to 15%, or the rubber phase content could be up to 30%.
