Currently we are using open rubber mixing mill for our compound. We are looking into adding dispersion kneader to improve our productivity. Since we are using NBR rubber with silica filler will be kneader work for us.
By dispersion kneader do you mean an internal mixer such as a Banbury or Intermix type? If you are then I would recommend an Intermix type, which will give you much better dispersion and keep the batch temperatures low enough to prevent scorching.