To answer your question properly, we have to go fairly deep into details, but I will try my best at a short answer.
First, most valve engineers do not specify vacuum to the degree needed when qualifying a valve product.
'Valve' in this concept (including check-valves) could be anything from tiny , high-sterile instrument valves with openings down to fractions of a millimeter, up to something a meter or more in diameter.
To look at one of the used scales for vacuum we have:
Coarse vacuum:Anything from below normal pressure about 1030 millibar, down to 1,33 millibar
Fine vacuum: Down from above to 1,33*10-3millibar
High vacuum: Further down to high vacuum at 1.33*10-7 millibar
Ultra high vacuum: Down to1,33*10-8 millibar.
For 'normal valves' for 'common use' we are most often in the uppermost part of the scale for coarse vacuum. Often as small as 50 to 200 or 300 millibar below normal pressure, and not often below 500 millibar, but even here it is necessary to have best possible data.
For a very coarse vacuum and a common fluid (air?) the valve does not necessary need to differ from a standard high-quality valve in anything else than that the construction and factory test will guarantee the valve for vacuum use. Note: For vacuum use it is import to be aware of the pressure difference direction. Does it change if the positive pressure side goes down to vacuum?
Generally: A vacuum valve differs from a general valve in that it (also) keep tight for the designated vacuum, in the direction vacuum will give the pressure difference, with the designated fluid and leakrate.
For lower vacuum, construction, materials and sealing surfaces must often be 'better than normal', as vacuum keeping might be tricky, and is high-technology for the lower part of the scale.
