In Europe, Kautex is regarded as the inventor of blow molding technology. The first machine for the production of plastic bottles was developed back in 1949.
In blow molding technology, continuous extrusion is the basic process for the production of blow molded articles from a parison. In this manufacturing process that is still used today, the extrusion speed depends on the screw r.p.m.
Characteristics for continuous extrusion:
Materials with high viscosity
High melt stiffness
Short, light parisons
Coextrusion, especially with thin layers
The interest in large, shallow plastic components has grown world-wide. Kautex Maschinenbau has recognized this market demand and developed a process that has attracted attention because of its cost-effective manufacturing and levels of quality that are unprecedented in this segment.
Compared to conventional processes, where the extruded parison is infalted to the required diameter using support air, this patented process uses special spreader pins to spread the parison over its entire length before molding. Before the mold is released, the parison is cut open laterally by "flying knives" so that the spreader pins can retract to release the article.
The coextrusion process has been offered by Kautex Maschinenbau since the early 1980s. It was developed to meet new requirements in agricultural chemicals packaging.
The term "coextrusion" stands for the simultaneous processing of diverse materials that are bonded in the extrusion head into a multi-layer parison by means of an adhesive promoter. For particularly challenging applications, Kautex Maschinenbau offers equipment for the production of up to seven layers.
Low requirements for master batches in the outer decorative layer reduce the costs of Deco/Reco produced parts and additionally allows regrind or recycled material to be embedded into the middle layer. This process, with the inclusion of a suitable barrier layer, can be used toprotect food products from environmental influences and prevent chemicals from being discharged into the environment.
As early as the 1960s, blow molded articles were starting to exceed the critical limit of between 80 and 100 liters and were therefore too large for the continuous extrusion process that had been used up to then.
So Kautex developed this process in order to maximize the output rate for the production of larger products.
In contrast to continuous extrusion, in this process the melt is transported into a storage chamber and, after the previous part has been released from the mold, it is ejected all at once at high speed. This means that the extrusion speed is much higher and is no longer dependent on the screw r.p.m. The storage chamber can be refilled again during the cooling and mold release stages.
Discontinuous extrusion necessitates the use of accumulator heads.
Characteristics for discontinuous extrusion:
Materials with low viscosity
Low melt stiffness
Long, heavy parisons
e.g. barrels, IBC (Intermediate Bulk Containers), fuel tanks (Mono, Selar)
High rate of output
Low draw-down of the parison
Less cooling of the parison lower end
High temperature extrusion
Towards the end of the 1990s, plastics manufacturers developed new materials for different requirements, such as fiberglass-reinforced polyamides capable of being blow molded. Some polymers have to be processed at melt temperatures of up to 360 °C, so Kautex developed a high temperature extrusion process in the early 2000s.
This specialist sector needs supplementary parts that have been specially developed by Kautex Maschinenbau. These include:
- Extruder and head made of special steels that are resistant to high temperatures
- Specially designed electrical components
- Heat separation for feed zone, transmission, mold/clamping plate
- Special die heating
- Special screws developed for this use
- Special oil temperature control for feed zone and mold
- High-quality head insulation
- Facility for support air and preblowing air with heating
- Automatic lowering of the extruder temperature after extended downtime