Patent transfer is illegal.

Article 60 of the Patent Law stipulates that the exploitation of a patent without the permission of the patentee is an act of infringement of his patent right.

Article 21 stipulates that no unit may exploit its patent without the permission of the patentee, that is, it may not manufacture, use, promise to sell, sell or import its patented products for production and business purposes, and may not use its patented methods and use, promise to sell, sell or import products directly obtained according to the patented methods.

It can be seen from the above that during the validity period of the patent, the patentee changes due to the transfer of the patent right, and you no longer have the right to exploit the patent without the permission of the new patentee.