I have an object that a cloth is colliding with, and I want the collision to be disabled in the middle of the animation. However, I cannot just turn off object Collisions on the cloth, because there is another collision object that I want the cloth to continue interacting with. I cannot find an 'on/off' switch in the Collision properties. In another forum, scaling the collision object worked, but doesn't in my case because it pushes/pulls the cloth. Is there a way to animate collisions to turn off or another solution around this? (I am using Blender 2.81a)
The answer is: No
You can not directly animate the modifier so that it will be cloth-permeable, but you can easily find ways around it.
I fixed this problem by running a simple small animation myself, a cloth plane falling on a cube with collision settings, and a large plane (with collision settings to act as the floor).
I animated the cube with a LocScale keyframe at frame 1, 50, and 75.
At frame one I added a single keyframe to the cube without doing anything.
At frame 50, I did nothing to the cube, and set another keyframe.
At frame 75, I scaled the cube down to .0001 size, and moved it beneath the plane.
The final result is that the cube shrinks below the cloth, and gives the effect of the object disappearing.
I believe this is the best way to animate these kinds of simulations, so I hope this helps you.
Here is a video, too, if you don't want to have to download the .blend.