What insturies in Hong Kong relocated to South China??

You'll know that Hong Kong has many type of industries before, and some of them had been allocated to china in respect to lower land price and fewer limits on legislation.

Some of the examples were:
Textile:
Textile is an industry which has a low profit margin. However, the land rent in Hong Kong is rising due to improve in transportation and facilities as well as industrial taxes. Therefore in the 90th century the textile industry in several industrial estates , e.g. Yuen Long, Kwuen Tong. They're mainly move to the Industrial estate near the Jujiang delta, they thus enjoy industrial agglomeation. However, the industrial sectors were diminishing at that time.

Plastic production and electronics
They were being move due to the same reason, the plastic industry may sub-divided into several categories like Toys, Household tools, Containers, Furnitures etc.
While the electronics production included television, radio, players, phones, watches, toys, etc.