Note: Descriptions are shown in the official language in which they were submitted.
~27i3~ 23189~6575
It is generally known that, in order to produce
adherent metallic coatings on substrate elements which
are not electroconduct;ng, an adhesion-promoting paint,
preferably based on ABS polymers, is initially applied to
S the surface. However, the disadvantage of this pretreat-
ment method is that the moulded articles coated with this
paint coat have to be treated with a pickling agent before
the actual metallization in order to roughen the surface
(cf., for example, DE-A 1,958,839)~
It has therefore already been proposed that non-
metallic substrate surfaces be treated directly, without
prior pickling, with activator solutions for currentless
me~alli~atisn which contain, as adhesion promoters, com-
plicated mixtures of acrylonitrile/bu~adiene copolymers
and, if appropriate, phenolic resins (cf., for example,
US 3,305,460 and 3,560,257).
Ho~ever, this type of process has hitherto not
been able to establish itself in industry since the adhe-
rency of the metaLlic coatings produced is inadequate and
the adhesion-promoting polymers do not meet the high
demands placed on the thermal and electrical properties,
in particulac in printed circuit board technology~
Although the process according to US 4,368,281
produces better adherency compared to this, relatively
large a~ounts of activator, namely 5-16% by ~eight, are
required for this.
Surprisingly, it has now be~n found that highly
adherent metallic coatings can be applied to plastic sur-
faces without the disadvantages mentioned if these sur-
faces are treated, without pickling, with a printingpaste formulation which contains, as essential components~
a) 0.03 - 4.00X by ~eight of an organometallic noble
metal compound as activator
b) 10 - 30 X by weight of a polyurethane elastomer
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c) 5 - 25 % by weight of a filler and
d) 40 - 90 % by ueight of a halogen free solv~nt
having a flashpoint >21C and
a boiling point >100C.
It is surprising that the formulations according
S to the invention cause adherent metallization, since
adherent metallization is not achieved on surfaces which
have been coated only with the b;nders according to the
invention. Adherent chemical metallization is caused
only by the use of the formulations according to the
invention.
Preferred printing pastes contain 0.05-3X of com-
ponent a) and 60-80~ of component d).
The binders according to the invention are known
fron polyurethane chemistry. They are prepared, for ex-
ample, by reacting esters and/or ethers with isocyanates.
For the preparation of a storage~stablQ formula-
tion~ it is advantageous to employ polyurethanes which no
longer contain free isocyanate groups.
Linear, aromatic polyurethane elastomers, as pre-
pared, for example, from butanediol polyadipate, neopentylglycol and 4,4'-diphenylmethane d;isocyanate, have proven
particularly suitable.
In order to increase the adherency of the formula-
tions according to the invention to the surfaces, it may
also be necessary to add polyisocyanates or oligourethanes
or polyurethanes which contain free isocyanate groups to
the binders according to the invention. In th;s case~
additives which contain free aliphatic isocyanate groups
have proven part;cularly su;table.
The ~ollowing may be mentioned as examples:
Organic polyisocyanates as obtained~ for example, accord-
ing to EP-A-0~160~913. These are biuret polyisocyanates
based on 1,6-diisocyanatohexane, ;socyanate group-
containing polyisocyanates based on 1-isocyanato-3~3,5-
trimethyl-5-isocyanatomethyl-cyclohexane, and ;socyanurate
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group-conta;ning poly;socyanates based on mixtures of
~,6-diisocyanatohexane and 1-isocyanato-3,3,5-trimethyl-
5-isocyanatomethylcyclohexane~ ~iuret group-containing
polyisocyanates as are accessible, for example, according
to DE-A 1,101,394 (= US 3,124~05), US 3,358,010 or
European Patent Specification 3,505 (= US 4,264,519).
Uretdione and isocyanurate group-contain;ng organic
polyisocyanates as obtained, for example, according to
the teaching of DE-A 1,954,093 (= G~ 1,244,416) or accord-
ing to EP 0,173,252.
~hen using polyurethane hav;ng free aromat;c ;so-
cyanate groups or for storage stability reasons, it may
be favourable to reversibly block the free isocyanate
groups in a known fashion. Such processes are known from
polyurethane chemistry.
Blocking agents which can be employed are, for
example, phenols, caprolactam, ~-dicarbonyl compounds
such as acetoacetic esters and malonic esters, certain
alcohols, oximes and triazoles.
ainders containing ;socyanate groups wh;ch are
not blocked should not be added to the formulations
according to the invention until just before processing.
Suitable activators in the ~ormulations according
to the invention are organometallic compounds of subgroups
1 or 8 of the periodic system (in particular Pd, Pt, Au
and Ag), as described, for example~ in EP-A 34,485, 81,438
and 131,~95. Organometallic compounds of palladium with
olefins (dienes), w;th ,~-unsaturated carbonyl compounds,
with`crown ethers and with nitriles are particularly
suitable. ~utadienepalladium dichloride, bisacetoni~rile-
palladium dichloride, (4-cyclohexene-1,2-dicarboxyl;c
anhydride)palladium dichlor;de, (mesityl oxide)palladium
chloride, 3-hepten-2-onepalladium chloride and 5-methyl-
3-hexen-2-onepalladium chloride are very particularly
suitable.
Of course, mixtures of these compounds can also
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be employed. They can be present in the formulations in
dissolved or dispersed form. In this case, a solut;on
can also be prepared by adding solubilizers, for example
quaternary ammonium salts, such as tetrabutylammonium
bromide. In the case of a dispersion of the activators,
;t must be ensured that particle sizes below 1 ~m are
achieved.
Besides the activators, fillers, binders and sol-
vents, formulations contain, if appropriate, surfactants,
Levelling agents and/or dyestuffs.
Suitable solvents in the formulations according
to the invention are substances which are kno~n in print-
ing and painting technology, such as aromatic and ali-
phatic hydrocarbons, for example toluene, xylene, benzine
and glycerol; ketones, for example methyl ethyl ketone
and cyclohexanone; esters, for example butyl acetate,
dioctyl phthalate and butyl glycolate, glycol ethers, for
example ethylene glycol mono0ethyl ether, diglyme and pro-
pylene glycol monomethyl ether; est~rs of glycol ethers,
for example ethylene glycol acetate and propylene glycol
monomethyl ether acetate; and diacetone alcohol. Of
course, mixtures of these solvents and the blends thereof
with other solvents can also be employed. Solvents hav-
ing an evaporation number >25 (diethyl ether = 1) are
preferred.
Suitable f;llers are au~;liaries wh;ch are known
from printing or painting technology, such as pigments,
disperse silica, clay minerals, carbon blacks and rheo-
logical additives.
The following may be mentioned as examples:
Aerosils, TiO2, talc, ;ron oxides, kieselghur, heavy
spars, kaol;ns, quartz po~der, smectites, colour blacks,
graphites, zinc sulphides, chromium yello~, bronzes,
organic pigments and chalk. Aerosils, heavy spars and
TiO2 are preferred.
The formulations according to the invention are
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generally prepared by m;xing the components. To this
purpose, the wet comminution machines which are conven-
tional in paint and printing technology, such as com-
pounders, attr;t;on mills, cylincler mills, dissolvers,
rotor-stator mills, ball mills and stirred ball mills
are particularly suitable, besides simple stirr;ng. Of
course, the formulation components can also be incorpora-
ted in separate steps. For example, the activator can
first be dissolved or dispersed in the binders and sol-
vents, and the f;llers only incorporated then. Previouspreparation of a paste of the fillers in the solvents
under high shear forces is also a possible process
variant.
Surfaces can be activated by apply;ng the formu-
la~ions according to the invention for the purpose ofadherent metallization by chemical plating. The applica-
tion generally takes place by processes which are kno~n
from paint or printing technology.
The following may be mentioned as examples:
spraying, brushing, rolling, offset printing, screen
printing, pelt printing and dipping.
Suitable substrates for the process according to
the invention are glass, quartz, ceramics, enamel, paper,
polyethylene, polypropylene, epoxy resins, polyesters~
polycarbonates, nylons, polyimides, polyhydantoins, ABS
plastics, silicones, polyvinyl hal;des and polyvinyldene
fluoride in the form of plates, films, paperc and mats.
Particularly preferred are substrates as are eMployed in
printed circuit board production, for example phenolic
resin papers, glass fibre-reinforced epoxide plates, poly-
ester and polyimide films and ceramics.
After application of the formulations according
to the invention to the surface, the solvents are removed.
This generally takes place by drying.
Drying can take place at different temperatures,
~or example between RT and 200C, and a~ atmospheric
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pressure or alternatively in vacuo. The drying time canof course be varied considerably.
The surfaces thus produced must subsequently be
activated by reduction. To this purpose, the reduc;ng
agents which are convent;onal in plat;ng technology, such
as, for example, formaldehyde, hypophosph;tes and boranes,
can be used preferentially.
A particularly preferred embodiment when using
the formulations accord;ng to the invention comprises
that the reduction in the metallizing bath is carried out
immediately using the reducing agent for the currentless
metallization. This embodiment is particularly suitable
for aminoborane-containing nickel baths or formalin-
con~aining copper baths.
The surfaces activated using the formulat;ons
according to the invention can be metallized ~ithout cur-
rent in a further process step. Suitable baths for ~his
are, particularly, those containing nickel, cobalt, iron,
copper, silver, gold and palladium salts, or mixtures
thereof. Such metallizing baths are known in currentless
metallization technology.
The formulations according to the invention are
particularly suitable for partial activation of surfaces,
very particularly for the preparation of printed circuits,
foil keyboards, pressure-sensitive mats and sensqrs by
printing processes, in particular screen printing pro-
cesses, and subsequent additive chemical metalli~ation.
Example 1
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An unreactive polyurethane elastomer is prepared
from butanediol polyad;pate ~MW 2,000)~ neopentyl glycol
and 4,4-diphenylme~hane d;isocyanate.
100 parts by weight of a 30% strength solut;on of this
polyurethane in ethylene ylycol ethyl
ether acetate ~viscosity at 25C
1,250 mPa.s~
" " " of a colour black ~Pr;ntex ~ V)
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2 parts by weight of 3-hepten-~2-onepalladium chloride
and
2 " " " of diethylene glycol
are carefully m;xed w;th one another or dispersed by
means of a 3-cyl;nder mill.
The paste produced is coated through a screen
onto a Tyvek paper surface, dried for 1 hour at 50C in
a water-pump vacuum, and subsequently metallized in an
aminoborane-containing nickel bath. A coherent nickel
coating is obtained. Adherency according to DIN 53 151:
code value GT 3.
Example 2
20 parts by weight of a 30% strength solution of a poly-
urethane according to Example 1 in
N-methylpyrrolidone: ethylene glycol
ethyl ether acetate = 1 : 1
4 " " " of a colour black (Printex ~ V)
2 " " " of 5-methyl-3-hexan-2-onepalladium
chloride and
2 " " " of dioctyl phthalate
are carefully mixed with one another or dispersed by
means of a 3-cylinder mill.
The paste produced is printed through a screen
onto a polyvinylidene difluoride film, and the print is
subsequen~ly dried for 2 hours at 100C in a water-pump
vacuum. The print is then metallized in an aminoborane-
containing nickel bath for 30 minutes. A coherent metal
co~ting is obtained.
Adherency according to DIN 53 151: code value GT 5.
Example 3
20 parts by weight of a 30% strength polyurethane solution
according to Example 2
4 " " " of Aerosil ~ (200 m2/g according
to BET)
" " " of ethylene glycol ethyl ether acetate
4 " " " of a commercia(ly available urethane
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3~L
stov;ng resin based on isophorons d;-
isocyanate/malonic ester blocked about
75% strength solution in ethyl glycol
acetate/xylene 1 : 1 NC0 content
blocked about 10%
1 part by weight of 5-methyl-3-hexan-2-onepalladium
chloride
are carefully mixed or dispersed in the dissolver.
The paste produced is printed onto a PES film
through a screen and the print ;s dried for 1 hour at
150C. The surface is subsequently prereduced for 5
minutes in a 1% strength alkaline aminoborane solution
rinsed and then copper-plated for 1 hour in a formalin-
containing copper bath at 60C. A coherent metal coat-
ing of thickness 2.8 ~m is obtained. Adherency accordingto DIN 53 151: code value GT 3
Example 4
60 parts by ~eight of a 30% strength polyurethane solution
according to Example 2
1 of diacetonitrilepalladium dichloride
of Aerosil ~ (380 m2/g according
to BET)
of glycol ethyl ether acetate
1 of silicone oil M 100
are carefully mixed or dispersed by means of a 3-cylinder
mill and printed according to ExampLe 3 and dried and
the surfaces are copper-plated. A coherPnt metal coating
having an adherency according to DlN 53 49~ of 36 N is
obtained.
Example 5
~100 parts by weight of a 30% strensth polyurethane solu-
tion according to Example 1
9 of Aerosil ~ ~380 m2/g according
to BET)
of glycol methyl ether acetate
16 of a uretdione and isocyanurate group-
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containing polyisocyanate based on
1,6 diisocyanatohexane having an NC0
content of 22.7%
1.5 parts by weight of ~tetrahydrophthal;c anhydride)pal-
ladium dichloride
are carefully mixed with one another in a compounder.
The paste produced is subsequently printed accord-
ing to Example 3, and the pr;nt is copper-plated. A
coherent ~etal coating ;s obtained. The adherency can no
longer be determined exactly according to DIN 53 494 since
the copper cannot be detached from the polyester f;lm
without damage.
Example 6:
. . _
650 parts by weight of a 30% strength polyurethane solu-
tion according to Example 1
330 " " " of glycol methyl ether acetate
" " " of Aerosil ~ (380 m2/g according to
~ET)
52 " " " of Helio true blue G0
13 " " " of butadienepalladium chloride
are carefully m;xed or d;spersed by means of a 3-cyl;nder
m;ll and printed according to Example 3 onto a PES film.
By currentless copper-plating of the print, a copper
coat;ng hav;ng an adherency according to DIN 53 494 of
21 N is obtained.
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