It's been a while since I used CATIA v4 but if I remember correctly...
From the command line type in
catutil -XM -l catdxf
If you have the proper licenses you can batch out all of your CATIA v4 2D models to DXF. Depending upon what level of CATIA you are on and how your declaration files are set up you will get a DXF in a Autodesk v12 or v13 format.