Analysis of the flow paths in a rubber internal mixer in dependency of different process parameters

对于橡胶产品的生产，混合物组分在不连续的密炼机中混炼。为了实现具有短混合时间和均匀产品的稳定和有效的过程，通常根据经验开发混合程序。这种方法很耗时，需要有经验的员工的专业知识。为了设计具有高填料分散性的时间有效的混合过程，有必要对密炼机中的流动路径有科学的了解。以前描述混合室中的流动路径的试验是基于简化的假设，例如完全填充的混合室，或者只考虑转子和混合室壁之间区域的流动行为。开发一种方法来可视化切向密炼机转子之间区域的流动行为是本研究项目的目的。研究项目完成后，将有可能首次完整地描述密炼机中的流动过程。因此，我们使用不同颜色的纤维填充化合物和多组分体系。在混炼室中硫化胶料后，将混炼室打开，从而可以分析流动行为，例如由于流动路径的不同颜色。在开发方法和识别流动路径后，可以分析不同工艺参数的影响，例如混炼室的温度、相位角或转子速度，对切向转子间流动特性的影响。通过相位角的变化，转子之间的区域中的流动条件将改变，而转子和混合室壁之间的流动条件将保持几乎恒定。例如，通过改变转子几何形状，这是不可能的。根据计算结果，推导出了不同工艺参数与流道之间的关系。因此，将有可能根据所选择的工艺参数来预测密炼机的转子之间的流动行为。此外，流路和材料的量之间的相关性，以占主导地位的混合效果将被导出。这将能够预测混合的质量。为了验证所开发的方法，在进一步的混合测试中验证了工艺参数、流路和混合效果之间的科学推导的相关性，这些混合测试在混合室尺寸和工艺参数方面有所不同。基于所获得的知识，将有可能解释和预测各种工艺参数对流动条件的影响，这使得能够更有效地设计和开发切向密炼机中的混合过程。

For the production of rubber products, the mixture components are compounded in a discontinuous internal mixer. In order to achieve a stable and efficient process with a short mixing time and a homogeneous product, the mixing procedure is usually developed empirically. This method is time consuming and requires specialised knowledge of experienced employees. To design a time efficient mixing process with high filler dispersion, it is necessary to have scientific knowledge about the flow paths in an internal mixer. Previous trials to describe the flow paths in the mixing chamber are based on simplifying assumptions, for example a fully-filled mixing chamber, or consider only the flow behaviour in the area between the rotor and the mixing chamber wall.The development of a method to visualise the flow behaviour in the area between the rotors of a tangential internal mixer is the aim of this research project. After completion the research projekt it will be possible for the first time to describe the flow process in an internal mixer completely. For this reason, different coloured as well as fibre filled compounds and multicomponent systems are used. After the compound is vulcanized in the mixing chamber, the chamber will be opened so that the flow behaviour can be analysed, for example due to the different colours of the flow paths.After the development of the method and the identification of the flow paths, the influence of different process parameters, for example the temperature of the mixing chamber, phase angle or the rotor speed, on the flow behaviour in the area between the tangential rotors is analysed. By a variation of the phase angle, the flow conditions in the area between the rotors will be varied, while the flow conditions between rotor and mixing chamber wall will remain almost constant. This would not be possible by changing rotor geometry as an example. Based on the results, a correlation between the varied process parameters and the flow paths is derived. Thus, it will be possible to predict the flow behaviour between the rotors of an internal mixer depending on the chosen process parameters. In addition, the correlation between the flow paths and the amount of material to the dominated mixing effects will be derived. This will enable to predict the quality of the mixing. To verify the developed method, the scientifically derived correlations between process parameters, flow paths and mixing effects are validated in further mixing tests, which differ regarding the mixing chamber sizes and process parameters. Based on the gained knowledge, it will be possible to explain and predict the effects of various process parameters on the flow conditions, which enables to design and develop mixing processes in tangential internal mixers more efficiently.