Alexban
The possibility of encountering icing conditions after take-off is not a consideration of an anti-ice treatment. Most guidance on de-icing/anti-icing will contain warnings on this. See the AEA document: numerous notes along the lines of "De-icing/anti-icing fluids used during ground de-icing/anti-icing are not intended for - and do not provide - protection during flight."
I think someone has already commented on the fact that much of that fluid will have come unstuck by lift-off. Also a good reason not to sit too close behind another aircraft prior to take-off due to the jet blast effect on fluid.
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Edit: think the comment on fluid separation must have been in another, similar thread.