I would imagine that there would be no benefit to use for water cooling your pc, it be even yield in a loss in performance. Essentially, I believe that if you use that, then you'll get less than or equal to the cooling ability of normal water cooling for pc.
The purpose of antifreeze is so that the water in you car will be harder to freeze or boil. If the water freezes in your car, then you risk your car components being cracked, like the engine block, because water expands when it changes to ice. If the water boils, then the water turns to gas and pressure goes up in the loop then it blows something.
There should be no reason to use antifreeze for pc water cooling because that is not what antifreeze/car coolant is designed for.