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

对于橡胶制品的生产，混合料组分在不连续的内混炼机中进行复合。为了在短的混合时间内获得稳定、高效的混合过程和均匀的产品，混合过程通常是经验制定的。这种方法耗时长，需要有经验的员工具备专业知识。为了设计一种时间效率高、填料分散度高的混合工艺，有必要对内部混合器的流动路径有科学的了解。以前描述混合腔内流动路径的试验是基于简化的假设，例如一个充满液体的混合腔，或者只考虑转子和混合腔壁之间区域的流动行为。本研究项目的目的是开发一种方法来可视化切向内混合器转子之间区域的流动行为。在完成研究项目后，将有可能首次完整地描述内部混合器中的流动过程。出于这个原因，使用了不同颜色以及纤维填充的化合物和多组分系统。在混合室中硫化后，将打开混合室，以便分析流动行为，例如由于流动路径的不同颜色。在该方法的发展和流动路径的确定之后，分析了不同工艺参数（如混合室温度、相位角或转子转速）对切向转子之间区域流动特性的影响。由于相位角的变化，转子之间的流动条件会发生变化，而转子与混合室壁面之间的流动条件基本保持不变。这将是不可能通过改变转子几何为例。在此基础上，推导了不同工艺参数与流道之间的关系。因此，根据所选的工艺参数，可以预测内部混合器转子之间的流动行为。此外，还推导了流动路径与受主导混合效应影响的物料量之间的关系。这将使我们能够预测混合的质量。为了验证所开发的方法，在进一步的混合试验中验证了科学推导的工艺参数、流动路径和混合效果之间的相关性，这些相关性随混合室尺寸和工艺参数的不同而不同。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，从而能够更有效地设计和开发切向内混合器的混合过程。

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.