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

为了生产橡胶产品，混合组分在不连续的密炼机中混合。为了获得稳定、高效、混合时间短、产物均匀的过程，混合过程通常是由经验开发的。这种方法很耗时，而且需要有经验的员工的专业知识。为了设计一种高效、高填料分散度的混合工艺，必须对密炼机内的流动路径有科学的了解。以前描述混合室内流动路径的试验都是基于简化的假设，例如完全填充的混合室，或者只考虑转子和混合室壁面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，将首次有可能完全描述密炼机内的流动过程。为此，使用不同颜色以及纤维填充的化合物和多组分系统。胶料在密炼室中硫化后，由于流动路径的颜色不同，密炼室将被打开，以便分析流动行为。在开发了方法和确定流动路径后，分析了不同的工艺参数，如密炼室温度、相角或转子速度，对切向转子之间区域流动行为的影响。随着相角的变化，转子间的流动状况会发生变化，而转子与混合室壁面之间的流动状况几乎保持不变。以改变转子几何形状为例，这是不可能的。在此基础上，建立了不同工艺参数与流道之间的关联式。因此，可以根据所选择的工艺参数来预测密炼机转子之间的流动行为。此外，还将推导出流动路径和物料数量与主要混合效果之间的关系。这将使得能够预测混合的质量。为了验证所开发的方法，在不同混合室尺寸和工艺参数的进一步混合试验中，验证了工艺参数、流道和混合效果之间的科学推导关系。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，从而能够更有效地设计和开发切向密炼机内的混合过程。

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.