thank, there aren't mode for long exposure with dayligth?
The sx230 has an adjustable diaphragm but it can only be stopped down to f8. What you can try is to manually over-riding the camera's internal ND filter from the CHDK menu to be on, set the ISO to 50, and the experiment with how slow you can set the shutter manually and still get an acceptable exposure.
Or even better, put a darker ND filter in front of the lens and set the exposure manually with CHDK.
Why do you want to make long exposures in bright light ? A differnt approach might be to make many short exposures and combine them using stacking software on your PC?