The piratini republic declared their independence in 1836, before Pedro II become legit emperor (because of his age).
"A justificativa original centrava-se no conflito político entre os liberais que propugnavam modelo de estado com maior autonomia às províncias, e o modelo imposto pela constituição de D. Pedro I de caráter unitário."
basically its saying that the independence was declared because of the conflict between the interests of the liberals in the province, who demanded more autonomy to the provinces, different from what the Pedro's I constitution said, which was a centralized government, who deemed autonomy to provinces. Even today, there is a separatist feeling in the south of Brazil, because they feel they are much better and much more white than us, the rest.