If you're no longer employeed by the selling company, it would seem that you have nothing to gain by signing.
I guess my angle isn't: What is there to gain for me. Even though I was made redundant, the employer is nice and I'd have no problems signing it. But it's the first time I'm asked to sign one of these things and some of the things I'd be agreeing to doesn't even sound like it's in english. I don't want to inadvertently sign over any side project I was working on in that time or IP for the industry I was working in or…
Turn it around and tell them your needs: you don't want to lose rights to your own work. Leave at that at first, and see if they come back with anything, such as a list of the specific works they want you to disclaim prior to their acquisition.
You get the open end, not them.
And charge them for laying you off, I assume you don't have equity that will act as any kind of redemption in the sale.