All the weapons are not patented I think. And China is always a low tech country, we begain to industrialize in the mid of 1950's, with the soveit help, but the good time only last less then 10years, we get big trouble with the soveit in the year of 1961,and as you know, China is enemy of the whole west world, from 1949 untill the beginning of the 1980's, no any technic cooperation with any westen country since funding of the PRC, in the 1980's, China are partner of the west in the plot to contain the soviet, during this time, get some access to the west technic,especially the Franch, but after the 1989 incident, this assistance suspended, again the Russia became the supplier of the know how to China, but since then, all the countries use the soviet weapon system was beaten hands down by the USA, China already lost the confidence in the soviet system and the war fair doctrine behand it.now China are looking to the west. After the collaps of the soviet, the defence industry were in a shamble, many talents went to other countries for a carrer, some of them came to China.
Now we can see China buy less Russia weapons, because Russia is depend on mostly soveit heritage, not too much new develop, China are turning to the USA and Europ system, China now are geting some ability to develop towards this system.