Precoating substrates before currentless wet-chemical metallising - by spraying with powder mixt. contg. non-conducting powder and (semi)precious metal cpd., and stoving to form a thin coating

摘要

Powder mixts. (I) are claimed, which are sprayed onto substrate surfaces and stoved to give a pre-coating which facilitates the deposition of adherent metal layers by a current-less wet chemical metallising process. Essential components of (I) are a non-conducting powder (II) and 0.1-10 wt.% (semi)precious metal cpd. (III), w.r.t. (I) and calcd. as metal. More specifically, (III) are complexes or inorganic salts of Cu, Au, Ag, Pt, Pd or Ru, in amts. of 0.2-8 (pref. 0.25-5) wt.%, pref. bis-(acetonitrile)-PdCl2, (Ph2P)4PD0, (Ag(NH3)2)+ complex or Ag salts such as Ag2SO4, AgNO2, AgOAc or AgMnO4. (II) is a mixt. contg. (a) a polymer, (b) 5-20 (pref. 10-15) wt.% pigment, (c) 0-70 (pref. 5-35) wt.% fillers and (d) 0-5 wt.% charge control agents (w.r.t. I). Pref. (a) is styrene/(meth)acrylaye or styrene/ethylhexyl acrylate, or a polyester from tere- or iso-phthalic acid and Bisphenol A, hexanediol or neopentyl glycol. (b) is carbon black and/or an inorganic or organic pigment, and (d) is a quat. ammonium salt. (II) has particle size 5-90 (pref. 5-50, esp. pref. 10-40) microns. USE/ADVANTAGE - (I) are useful for pretreating surfaces (e.g. of plastics) prior to metallising the surface in a current-less metallising bath. Pretreatment with (I) enables the prodn. of adherent metal coatings without pre-etching the surface with oxidising agents and without using solvents (contrast prior-art methods of pretreatment). The metallised substrates are useful, e.g. for electromagnetic screen