In this work, a continuous time model for optimal planning and scheduling of the production in batch processing plants is developed. The considered plants are general in the sense the products can run through different processing stages and follow different manufacturing routes. Processing stages are represented as operations. They can be viewed as modules of operators accomplishing same tasks and sharing possibly different operational characteristics. The resulting continuous time mixed integer nonlinear program (MINLP) is capable to handle complicating situations such as batch splitting, resource allocation and equipment maintenance. By using known linearization techniques, the MINLP is reformulated as a mixed integer linear program. It is further refined by using a modified version of the reformulation linearization technique and some other equivalent reformulations. The model is also implemented on a real life case: paint production. The computation of optimal production plan and schedule takes only a few minutes for this real case.