keyboard - xmodmap how to remap keys and disable the original ones?

I'm considering getting a 60% keyboard and want to try out working with that layout before buying the actual keyboard.

I'm trying to map arrow keys to caps lock + ijkl and disable the real arrow keys. I've found out how to remap it, but when I try to disable the real arrow keys, the remapped ones break. Here's a working map:

keycode 66 = Mode_switch
keycode 31 = i I Up
keycode 44 = j J Left
keycode 45 = k K Down
keycode 46 = l L Right

To disable arrow up I add

keycode 111 =

And as soon as I do that, ijkl don't work as characters anymore, but act as arrows even without pressing the modifier(caps lock). How do I disable the arrow keys without breaking my previous mapping?