The answer is at :
1) Choose the method corresponding to your ubuntu version
2) Check which programs from the KDE environment you would like to keep because you need it and a) remove it from the removal list (with dependencies) or b) leave it in the list and reinstall it later.
3) Copy/past the command
The command is as stated in this webpage and depends on your version, but generally looks like :
sudo apt-get remove akonadi-backend-mysql akonadi-server akregator amarok amarok-common amarok-utils apport-kde apturl-kde ark bluedevil cdparanoia cdrdao
.... and a lot of packages
The command will not remove configuration files anyway, only the programs. If you want to also remove the config files, you will add the --purge option to the command.
Warning: The list of packages below is for a plain default install of Ubuntu with Kubuntu. You may want to keep some of the below packages and you should review what apt is going to remove before accepting.
These removal commands were created based on what Kubuntu, Xubuntu, etc. packages were added to a default Ubuntu installation. It's possible that the commands might remove some other packages you have since added to the default and want to keep. If that's the case, keep track of which packages those are and reinstall them. Your settings should still be there.
As always,backup your partition before modifying it.