A lil Help Please

I want to have an object that is attached to the avatar detach after a timer event. I have tried to request perms on attach but it doesnt seem to work as I read it has to have perms to be able to detach. What am I doing wrong or what do I need to do to do this?

Thanks

default
{
on_rez(integer rezzed)
{
if(llGetAttached()>0)llSetTimerEvent(20);//if its attached, set the timer - that way you don't get errors when you put it on the ground
}

run_time_permissions(integer run)
{
llDetachFromAvatar();//permission granted, off it comes
}
timer()
{
llRequestPermissions(llGetOwner(),PERMISSION_ATTACH);
}
}