Speed up polymerisation of formaldehyde
According to this patent, alkaline catalyst of composition sodium and potassium hydroxides, carbonates, formates, and acetates can be used to speed up formation of paraformaldehyde from formalin solution (aq. formaldehyde). 


  This invention relates to a new and improved process for the
  production of formaldehyde polymers. More particularly it relates to a
  process whereby high strength aqueous formaldehyde solutions can be
  concentrated to paraformaldehyde at a greatly accelerated rate.


Moreover, the patent describes the process of this reaction in details. Have a good read.