Compounding technology for Bitumen

From a chemical point of view, bitumen comprises the semi-solid to spring hard, fusible, high molecular weight hydrocarbon mixture obtained by fractional distillation of petroleum, and the carbon disulfide soluble components of natural asphalts and paraffin and montan waxes. Bitumen belongs to the thermoplastic materials, i.e. its viscosity is temperature-dependent: When heated, it passes seamlessly through all states from solid through viscous until it becomes thinly liquid between 150 °C and 200 °C.

Finds in the Middle East have revealed pre-antiquity applications. And in the 19th century, the continuous production of bitumen became possible. Today, it is mainly procured as a residue from the vacuum distillation of petroleum. Depending on the desired quality, a specific property profile is set by mixing with heavy vacuum gas oil.

Typical applications

Bitumen plays an important role as a carrier matrix in many applications. Characteristics such as sealing properties, weather resistance, wettability and adhesion to dry surfaces are of great importance in a wide range of applications. They include backing layers of carpets and floor coverings, heavy-duty sound and vibration-insulating foils, components in vehicles and technical equipment, as well as various applications in the construction industry.

Compounding requirements

The traditional production methods for highly filled bitumen compounds are by processing on batch internal mixers. These established methods offer advantages such as flexibility, easy offline dosing of even small ingredients, as well as variable dwell times and mixing times. However, limitations such as interim storage times and variations in characteristics between individual batches allow continuous processes to exploit their advantages: Uniform process conditions, narrow residence time distribution and the integration of process steps are part of the typical strength profile. The BUSS Kneader can also score with precise temperature control, the handling of large differences in viscosity between bitumen and polymers/elastomers, and the possibility to perfectly mix even the highest filler proportions.

Recently, a wide range of extended application fields has been added, thanks largely to the integration of process steps such as inline processing on carrier substrates and the use of alternative recipe components. In the Buss technical centre, the sophisticated procedures used to accommodate and implement these high standards can be developed and optimized. The first plants with a throughput factor of 10 have been realized industrially and are successfully in operation. In a throughput range of 1:6, the products are directly processed in line. The split barrel of the BUSS Kneader furthermore ensures fast access and high system availability. Together with broadly based Buss process expertise, the modular and thus adaptable design of the entire system make the Buss Kneader system an excellent choice and sound investment for compounding highly filled bitumen compounds and their future substitution materials.

Bitumen used for heavy duty vehicle surfaces due to high durablility

Typical plant layout for bitumen

BUSS compounding systems for Bitumen offer the following specific benefits

  • Precise temperature control
    The Buss Kneader technology has been widely recognized for precise temperature control since more than 6 decades. This is achieved via controlled energy input due to uniform, moderate shear rates and precise temperature monitoring by thermocouples mounted in pins at any position along the process section.

  • High filler loadings
    Filler loadings up to 90% are possible with Buss technology thanks to additional inlet openings, split feed of fillers, removal of trapped air by back venting, and excellent conveying efficiency. Moderate shear rates allow perfect handling of the highest viscosities at such high loadings.

  • Easy to access to process parts
    Easy access to process parts is guaranteed because Buss Kneaders feature a split-barrel design with a uniquely wide opening angle of 120°. This allows fast and easy screw adaptations within minutes, without removing the screw or barrel, thus assuring fast product changes and higher yields.

  • Narrow residence time distribution
    The residence time of the material and the associated exposure to shear, pressure, temperature and other components have an influence on the properties of the product. While the residence time can be shorter or longer depending on the application, the distribution of the residence time is generally advantageous if it is narrow in order to obtain homogeneous and reproducible products. Due to the intensive but homogeneous material mixing, the BUSS Kneader offers defined material streams with little dead volume. This results in unique advantages in terms of residence time distribution compared to other systems.

  • Continuous process
    The BUSS Kneader offers a continuous process with all the advantages of a system for continuous, uninterrupted production. Highly accurate metering systems ensure exact recipe specifications, and are realized in low to high throughputs. High product homogeneity and more efficient production are the advantages of continuous production processes such as the BUSS Kneader.

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