[apache]

Straight Tech-Tech trades do not work from my experience. The AI does not see the point (for whatever reason) of trading one colonizing tech for another, even if you are friendly with that AI. However, most of the time, you can demand a gift from a weaker AI which they will usually send unless they hate you. Even stronger ones sometimes send you gifts. However, demanding gifts usually decreases the AI's friendliness towards you.
If you don't care about taking advantage of the AI, then you can probably trade escorts for colony ships, then analyze them. Or trading planets for tech might work too.