Compounding systems for Luxury Vinyl Tiles (LVT)

Luxury Vinyl Tiles, known as LVT, are floor tiles on a vinyl or PVC basis.

They consist of several layers – one of these is the so-called decorative layer, which is printed and enables almost unlimited design and colour options. This means that wood or ceramic and stone decors can hardly be distinguished visually from the original.

Special embossing techniques also ensure a realistic surface touch. LVT have an installation height of just a few millimetres, can be laid directly on a prepared substrate, and are regarded as particularly easy to clean. Due to their vinyl base and the possibility of incorporating appreciable recycling fractions, these tiles have a low CO2 footprint as well as a good energy balance.

Typical applications

Thanks to their outstanding properties, Luxury Vinyl Tiles are now a highly esteemed floor covering in residential, commercial and public buildings alike. This goes hand in hand with exceptionally steep market growth rates and, as a result, continuously optimised manufacturing methods.

Production requirements

In order to attain their special characteristics, LVT are composed of several specific layers as mentioned. This is classically achieved by separately compounding each layer on a Buss Kneader and calendering inline. The individual layers are subsequently pressed together.

In this optimized process, the three-layer core of LVT flooring is produced with two extruders and two calenders. In the first Buss Kneader a PVC compound, to which high proportions of mineral fillers and other additives are introduced through side feeders and split-feed, is plasticized and homogenized. The pressure build-up for feeding a fishtail nozzle is realized by a flanged-on discharge extruder to ensure decoupling of the compounding stage. Subsequently in the first calender, the compound is applied to fibreglass matting. This is then fed into the second calender, where the PVC compound prepared in the second Buss Kneader is applied to the other side of the fibreglass matting.

The great advantage of this inline processing, compounding and sheet production, all at the same temperature, is that the thermally sensitive PVC material is treated gently without any intermediate cooling/heating steps. After the second calendering stage, the decorative and wear-protection layers are laminated onto the triplex core. This 5-layer laminate then passes through an embossing station and a tempering section to ensure dimensional stability, and is finally cut to size.

Thus, with Buss process expertise and the continuously enhanced strengths of the Buss Kneader, specific requirements are being met as always. Product characteristics are optimized with uniformly moderate shear rates that can be adjusted, if necessary, as well as intensive mixing processes. And layering through a fishtail nozzle enables cost-effective inline calendering. It is these advances that exemplify why Buss has always been the technological and market leader in compounding vinyl-based materials.

Flooring with luxury vinyl tiles

Typical plant layout for compounding LVT materials

BUSS compounding lines for LVT offer the following specific benefits

  • Degassing of volatiles
    Volatiles are typically removed by a vacuum degassing opening at the end of the barrel or optionally in the discharge unit. Continual highlevel compound surface renewal is achieved with the large number of mixing cycles, striations and foldings created by the Buss Kneader, thus enabling entrapped air or volatiles to be removed completely.

  • Intensive distributive mixing
    The Buss Kneader achieves intensive distributive mixing because the combined rotation and axial motion of the Kneader screw generates extensional flow, a large number of shear interfaces, and cross channel mixing.

  • Narrow temperature range
    A narrow temperature range can be maintained with a Buss Kneader due to consistent and moderate shear rates. Therefore, the typically excessive temperature peaks of alternative systems are eliminated. This enables precise temperature control. Temperatures are monitored by thermocouples inserted in the mixing pins, which are surrounded by polymer along the barrel.

  • Compounding and pressure build-up optimized in two independent steps
    Mixing on the Buss Kneader and pressure build-up in the discharge unit are separated to enable the efficient optimization of both steps. This allows mixing at low pressure and temperature as well as optimized pelletizing, while maintaining temperature control at all times.

  • Flexible configuration of process section
    Screw elements, barrel liners and kneading pins are easily exchangeable components quickly accessed by opening the Buss Kneader’s split barrel. They can all be changed without removing the barrel or screw shaft.

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