In a cooperation agreement (R&D agreement) it is a good idea to record who contributes what knowledge, what it may be used for, and how any jointly developed knowledge is handled. You may also want to include agreements on possible patent applications, the name or names under which the invention will be registered, the cost sharing of the patent application, portfolio management, possible licensing, enforcement, and transfer.
If you don't have an agreement in case of a joint innovation, the Dutch Patents Act determines that the cooperating parties are jointly entitled to a patent (50/50). In addition, joint owners are not allowed to independently grant licenses to other parties. You may, however, transfer your own share in the patent without permission. Other than that, not much is regulated by law and that can cause difficult situations. For example, both owners will have to agree on every decision during and after the creation of the patent. Consider, for example, the choice of country or the interests in patent infringement. Make sure to take a good look at the various interests in advance to determine an appropriate agreement.