U.S. patent number 3,616,295 [Application Number 04/694,122] was granted by the patent office on 1971-10-26 for low-temperature transformation of nonconductive substrates to conductive substrates.
This patent grant is currently assigned to Hooker Chemical Corporation. Invention is credited to Sung K. Lee.
United States Patent |
3,616,295 |
Lee |
October 26, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
LOW-TEMPERATURE TRANSFORMATION OF NONCONDUCTIVE SUBSTRATES TO
CONDUCTIVE SUBSTRATES
Abstract
Substrates, particularly thermoplastic resins and polymers, are
plated with metals by pretreatment of the substrate with phosphorus
in an organic solvent to deposit phosphorus at the surface of the
substrate followed by subjecting the thus treated substrate with a
metal salt or complex thereof, in the presence of OH or Br.sub.3
H.sup.- or A1R.sub.3 H.sup.- or mixtures thereof, to form a
metal-phosphorus compound, wherein each R is individually selected
from the group consisting of alkyl, aryl and hydrogen. The
treatment with the metal salt solution can be accomplished at room
temperature. The resulting surface is conductive and can be readily
electroplated by conventional techniques.
Inventors: |
Lee; Sung K. (Niagara, NY) |
Assignee: |
Hooker Chemical Corporation
(Niagara Falls, NY)
|
Family
ID: |
24787486 |
Appl.
No.: |
04/694,122 |
Filed: |
December 28, 1967 |
Current U.S.
Class: |
205/166; 205/159;
205/183 |
Current CPC
Class: |
C23C
18/2066 (20130101); H05K 3/381 (20130101); H05K
3/181 (20130101) |
Current International
Class: |
C23C
18/20 (20060101); H05K 3/18 (20060101); H05K
3/38 (20060101); C23b 005/60 () |
Field of
Search: |
;204/20-22,30,38
;117/47R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mack; John H.
Assistant Examiner: Fay; R. J.
Claims
I claim:
1. A process which comprises subjecting a substrate to white
phosphorus to deposit phosphorus at the surface of the substrate
and thereafter subjecting the phosphorus-treated substrate to a
bath consisting essentially of a solution of a metal salt or
complex thereof which is capable of reacting with the phosphorus to
form a metal phosphide and stable anions, wherein said metal is
selected from Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the
Periodic Table, the anion of said metal salt is selected from the
group consisting of anions of mineral acids and anions of organic
acids, and said stable anions are selected from the group
consisting of OH.sup.- mixed with BR.sub.3 H.sup.- and OH.sup.-
mixed with A1R.sub.3 H.sup.-, and mixtures thereof, wherein each R
is individually selected from the group consisting of alkyl, aryl,
and hydrogen, and said stable anions are present in such
concentration as to avoid precipitation of the metal salts.
2. A process wherein the treated substrate resulting from the
process of claim 1 is electroplated to deposit an adherent metal
coating on the treated substrate.
3. A process which comprises subjecting a plastic to white
phosphorus to deposit phosphorus at the surface of the plastic and
thereafter subjecting the phosphorus-treated plastic to a bath
consisting essentially of a solution of a metal salt or complex
thereof which is capable of reacting with the phosphorus to form a
metal phosphide and stable anions, wherein said metal is selected
from Groups IB, IIB, IVB, VB, VIB, VIIB, and VIII of the Periodic
Table, the anion of said metal salt is selected from the group
consisting of anions of mineral acids and anions of organic acids,
and wherein said stable anions are selected from the group
consisting of OH.sup.- mixed with BR.sub.3 H.sup.- and OH.sup.-
mixed with A1R.sub.3 H.sup.-, and mixtures thereof, wherein each R
is individually selected from the group consisting of alkyl, aryl,
and hydrogen, and said stable anions are present in such
concentration as to avoid precipitation of the metal salts.
4. The process according to claim 3 wherein the plastic is
subjected to a solution of phosphorus dissolved in a solvent.
5. A process wherein the treated plastic resulting from the process
of claim 3 is electroplated to deposit an adherent metal coating on
the treated plastic.
6. The process of claim 3 wherein the BR.sub.3 H.sup.- stable anion
is introduced as sodium borohydride.
7. The process of claim 3 wherein the BR.sub.3 H.sup.- stable anion
is introduced as dimethylamine borane.
8. The process of claim 3 wherein the bath is maintained at a
temperature between about 20 degrees and about 40 degrees
centigrade.
9. The process of claim 8 wherein the metal salt complex is an
ammoniacal complex of a nickel salt.
10. The process of claim 8 wherein the plastic is polypropylene,
the phosphorus is employed as a solution of phosphorus dissolved in
trichlornethylene, the metal salt complex is an ammoniacal complex
of nickel chloride, and the stable anions are introduced into the
bath as sodium hydroxide mixed with sodium bocohydride.
11. The process of claim 8 wherein the plastic is a polyolefin.
12. The process of claim 8 wherein the plastic is polypropylene,
the phosphorus is employed as a solution of phosphorus dissolved in
trichloroethylene, and the BR.sub.3 H.sup.- stable anion is
introduced into the bath as dimethylamine borane.
13. The process of claim 8 wherein the plastic is
polyvinylchloride, the phosphorus is employed as a solution of
phosphorus dissolved in trichloroethylene, and the BR.sub.3 H.sup.-
stable anion is introduced into the bath as sodium borohydride.
14. The process of claim 8 wherein the plastic is a graft copolymer
of polybutadiene, styrene and acrylonitrile, the phosphorus is
employed as a solution of phosphorus dissolved in
trichloroethylene, and the BR.sub.3 H.sup.- stable anion is
introduced into the bath as sodium borohydride.
15. The process of claim 8 wherein the plastic is a graft copolymer
of polybutadiene, styrene and acrylonitrile, the phosphorus is
employed as a solution of phosphorus dissolved in trichloroethylene
and the BR.sub.3 H.sup.- stable anion is introduced into the bath
as dimethylamine boran.
Description
BACKGROUND OF THE INVENTION
There is a rapidly increasing demand for metal-plated articles, for
example, in the production of low-cost plastic articles that have a
simulated metal appearance. Such articles are in demand in such
industries as automotive, home appliance, radio and television and
for use in decorative containers and the like. The metal plating of
plastics and the like has required many process steps and has been
limited to either high-temperature operation or the presence of
reducing agents for low-temperature operation. Plastics with low
melting or softening points were not suited to being plated. A new
process for metal plating is described in copending application
Ser. No. 614,541, filed Feb. 8, 1967. This process also uses
relatively high temperatures for satisfactory results. Not well
suited to metal plating were substrates of minimal thickness, such
as paints.
It is an object of this invention to provide a safe, economical and
reliable low-temperature process for the metal plating of
substrates with the phosphorus system described in Ser. No.
614,541. Another object of the invention is to provide a
low-temperature bath for employment in the plating of low-heat
distortion (below 100.degree. C.) polyolefins such as
polyvinylchloride. A further objective is to provide a
low-temperature bath suitable for use when the substrate surface is
thin. A still further object of the invention is to provide a
low-temperature process for making articles having an adherent
metal coating that is resistant to peeling, temperature cycling,
and corrosion. Such coatings are electrically conductive whereby
static charges are readily dissipated from the surfaces. The metal
coatings further serve to protect the articles from abrasion,
scratching and marring, reduce their porosity and improve their
thermal conductivity. The process of this invention can be used for
making highway signs, heat exchange components, quick-freezing
frozen food containers and plastic pipes which are easy to
thaw.
SUMMARY OF THE INVENTION
This invention relates to a low-temperature bath and process for
forming a metal-phosphorus compound at the surface of a substrate
to render the surface susceptible to conventional
electroplating.
More particularly, this invention relates to a process which
comprises subjecting a substrate to phosphorus so as to deposit
phosphorus at the surface of the substrate and thereafter
subjecting the thus treated substrate with low-temperature bath
containing a metal salt or complex thereof in the presence of a
small amount of OH.sup.-, BR.sub.3 H.sup.-, A1R.sub. 3 H.sup.-, or
mixtures thereof, to form a metal-phosphorus compound, wherein each
R is individually selected from the group consisting of alkyl, aryl
and hydrogen. The resultant surface can be electroplated to deposit
an adherent metal coating of desired thickness on the surface.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process of this invention is applicable to substrates, such as
plastics and to other substantially nonmetallic substrates.
Suitable substrates include, but are not limited to, cellulosic and
ceramic materials such as cloth, paper, wood, cork, cardboard,
clay, porcelain, leather, porous glass, asbestos cement, and the
like.
Typical plastics to which the process of this invention is
applicable include the homopolymers and copolymers of ethylenically
unsaturated aliphatic, alicyclic and aromatic hydrocarbons such as
polyethylene, polypropylene, polybutene, ethylenepropylene
copolymers; copolymers of ethylene or propylene with other olefins,
polybutadiene; polymers of butadiene, polyisoprene, both natural
and synthetic, polystyrene and polymers of pentene, hexene,
heptene, octene, 2-methylpropene, 4-methylhexene-1, bicyclo-(2.2.1)
-2-heptene, pentadiene, hexadiene,
2,3-dimethylbutadiene-1,3,4-vinylcyclohexene, cyclopentadiene,
methylstyrene, and the like. Other polymers useful in the invention
include chlorinated polypropylene and methylene; polyindene,
indenecoumarone resins; polymers of acrylate esters and polymers of
methacrylate esters, acrylate and and methacrylate resins such as
ethyl acrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl
methacrylate and methyl methacrylate; alkyd resins; cellulose
derivatives such as cellulose acetate; cellulose acetate butyrate,
cellulose nitrate, ethyl cellulose, hydroxyethyl cellulose, methyl
cellulose and sodium carboxymethyl cellulose; epoxy resins; furan
resins (furfuryl alcohol or furfural ketone); hydrocarbon resins
from petroleum, isobutylene resins (polyisobutylene); isocyanate
resins (polyurethanes); melamine resins such as
melamine-formaldehyde and melamine-urea-formaldehyde; oleo-resins;
phenolic resins such as phenol-formaldehyde, phenolic-elastomer,
phenolic-epoxy, phenolic-polyamide, and phenolic-vinyl acetals;
polyamide polymers, such as polyamides, polyamide-epoxy and
particularly long chain synthetic polymeric amides containing
recurring carbonamide groups as an integral part of the main
polymer chain; polyester resins such as unsaturated polyesters of
dibasic acids and dihydroxy compounds, and polyester elastomer and
resorcinol resins such as resorcinol-formaldehyde,
resorcinol-furfural, resorcinol-phenol-formaldehyde,
resorcinol-polyamide and resorcinol-urea; rubbers such as natural
rubber, synthetic polyisoprene reclaimed rubber, chlorinated
rubber, polybutadiene, cyclized rubber, butadiene-acrylonitrile
rubber, butadiene-sytrene rubber, and butyl rubber; neoprene rubber
(polychloroprene); polysulfides (Thiokol); terpene resins; urea
resins; vinyl resins such as polymers of vinyl acetal, vinyl
acetate or vinyl alcohol-acetate copolymer, vinyl alcohol, vinyl
chloride, vinyl butyral, vinyl chloride-acetate copolymer, vinyl
pyrrolidone and vinylidene chloride copolymer; polyvinylchloride;
polyformaldehyde; polyphenylene oxide; polymers of
diallylphthalates and phthalates; polycarbonates of phosgene or
thiophosgene and dihydroxy compounds such as bisphenols,
thermoplastic polymers of bisphenols and epichlorohydrin
(tradenamed Phenoxy polymers); graft copolymers of polymers of
unsaturated hydrocarbons and an unsaturated monomer, such as graft
copolymers of polybutadiene, styrene and acrylonitrile, commonly
called ABS resin; ABS-polyvinyl chloride polymers, recently
introduced under the trade name of Cycovin; and acrylic polyvinyl
chloride polymers, known by the trade name of Kydex 100.
The polymers of the invention can be used in the unfilled
condition, or with fillers such as glass fiber, glass powder, glass
beads, asbestos, talc and other mineral fillers, wood flour and
other vegetable fillers, carbon in its various forms, dyes,
pigments, waxes and the like.
The substrates of this invention can be in various physical forms,
such as shaped articles, for example, moldings, sheets, rods, and
the like; fibers, films and fabrics, and the like and of various
thickness.
In the first step of the preferred process of the invention, the
substrate is subjected to elemental white phosphorus, which
includes the various impure or commercial grades sometimes referred
to as yellow phosphorus. The phosphorus can be utilized in the
vapor phase, as a liquid or dissolved in a solvent.
Suitable solvents or diluents for the elemental phosphorus are
solvents that dissolve elemental phosphorus and which preferably
swell the surface of a plastic without detrimentally affecting the
surface of the plastic. Such solvents include the halogenated
hydrocarbons and halocarbons such as chloroform, methyl chloroform,
phenyl chloroform, dichloroethylene, trichloroethylene,
perchloroethylene, trichloroethane, dichloropropane, ethyl
dibromide, ethyl chlorobromide, propylene dibromide,
monochlorobenzene, monochlorotoluene and the like; aromatic
hydrocarbons such as benzene, toluene, xylene, ethyl benzene,
naphthalene and the like.
When a solution of phosphorus is employed in the process, the
solution concentration is generally in the range from about 0.0001
weight percent of phosphorus based on the weight of the solution up
to a saturated solution and preferably from about 1.5 to about 2.5
percent. Prior to subjecting the substrate to the elemental
phosphorus, in gaseous, liquid or solution, the surface of the
article should be clean. When a solution is used, the solvent
generally serves to clean the surface. A solvent wash may be
desirable when gaseous or liquid phosphorus is employed. However,
it is not necessary to subject the substrate to special treatment
such as etching, polishing and the like. The phosphorus treatment
is generally conducted at a temperature below the softening point
of the substrate, and below the boiling point of the solvent, if a
solvent is used. Generally the temperature is in the range of about
10 to about 135 degrees centigrade, but preferably in the range of
about 10 to about 40 degrees centigrade. The contact time varies
depending on the nature of the substrate, the solvent and
temperature, but is generally in the range of about 1 second to 1
hour or more, preferably in the range of about one to ten
minutes.
As a result of the first treatment step, the phosphorus is
deposited or nucleated at the surface of the substrate. By this is
meant that the phosphorus can be located on the surface, embedded
in the surface and embedded beneath the surface of the substrate.
The location of the phosphorus is somewhat dependent on the action
of the solvent and reaction conditions on the surface.
Following the first treatment step, the substrate can be subjected
to water and/or aqueous solution of a surfactant, as disclosed in
my copending application Ser. No. 671,337, now abandoned filed
Sept. 28, 1967, and then can be dried by merely exposing the
substrate to the atmosphere or to inert atmospheres such as
nitrogen, carbon dioxide, and the like, or by drying the surface
with radiant heaters or in a conventional oven. Drying times can
vary considerably, for example, from one second to 30 minutes or
more, preferably 5 seconds to 10 minutes, more preferably 5 seconds
to 20 seconds. The rinsing and drying steps are optional.
In the second treatment step of the process of the invention, the
phosphorus-treated substrate is subjected to a bath containing a
solution of a metal salt or a complex of a metal salt, which is
capable of reacting with the phosphorus to form a metal phosphide,
and a stable anion. The term metal phosphide, as used herein, means
the metal-phosphorus coating which is formed at the surface of the
substrate. Without being limited to theory, the metal phosphide may
be an ionic compound or a solution (alloy). The metals generally
employed are those of Groups IB, IIB, IVB, VB, VIB, VIIB and VIII
of the Periodic Table appearing on pages 60-61 of Lange's Handbook
of Chemistry (Revised Tenth Edition). The preferred metals are
copper, silver, gold, chromium, manganese, cobalt, nickel,
palladium, titanium, zirconium, vanadium, tantalum, cadmium,
tungsten, molybdenum, and the like.
The metal salts that are used in the invention can contain a wide
variety of anions. Suitable anions include the anions of mineral
acids such as sulfate, chloride, bromide, iodide, fluoride,
nitrate, phosphate, chlorate, perchlorate, borate, carbonate,
cyanide, and the like. Also useful are the anions of organic acids
such as formate, acetate, citrate, butyrate, valerate, caproate,
heptylate, caprylate, naphthenate, 2 -ethyl caproate, cinnamate,
stearate, oleate, palmitate, dimethylglyoxime, and the like.
Generally the anions of organic acids contain one to 18 carbon
atoms.
Some useful metal salts include copper sulfate, copper chloride,
silver nitrate, nickel cyanide and nickel chloride.
The metal salts can be complexed with a complexing agent that
produces a solution having a basic pH (>7). Particularly useful
are the ammoniacal complexes of the metal salts, in which one to
six ammonia molecules are complexed with the foregoing metal salts.
Typical examples include NiSo.sub.4 .sup.. 6NH.sub.3, NiC1.sub.2
.sup.. 6NH.sub.3, Ni(C.sub.2 H.sub.3 OO).sub.2 .sup.. 6NH.sub.3,
CuSO.sub.4 .sup.. 6NH.sub.3, CuC1.sub.2 .sup.. 6NH.sub.3,
AgNO.sub.3 .sup.. 6NH.sub.3, NiSO.sub.4 .sup.. 3NH.sub.3,
CuSO.sub.4 .sup.. 4NH.sub.3, Ni(NO.sub.3).sub.2 .sup.. 4NH.sub.3,
and the like. Other useful complexing agents include quinoline,
amines and pyridine. Useful complexes include compounds of the
formula MX.sub.2 O.sub.2, wherein M is the metal ion, X is chlorine
or bromine and Q is quinoline. Typical examples include: CoC1.sub.2
Q.sub.2, CoBr.sub.2 Q.sub.2, NiC1.sub.2 Q.sub.2, NiBr.sub.2
Q.sub.2, Ni1.sub.2 Q.sub.2, MnC1.sub.2 Q.sub.2, CuC1.sub.2 Q.sub.2,
CuBr.sub.2 Q.sub.2 and ZnC1.sub.2 Q.sub.2. Also useful are the
corresponding monoquinoline complexes such as CoC1.sub.2 Q. Useful
amine complexes include the mono-(ethylenediamine)-,
bis-(ethylenediamine)-, tris-(ethylenediamine)-, bis(1,2 -propane
diamine)-, and bis-(1,3 -propanediamine)- complexes of salts such
as copper sulfate. Typical pyridine complexes include NiC1.sub.2
(py).sub.2 and CuC1.sub.2 (py).sub.2 where py is pyridine.
The foregoing metal salts and their complexes are used in ionic
media, preferably in aqueous solutions. However, nonaqueous media
can be employed such as alcohols, for example, methyl alcohol,
ethyl alcohol, butyl alcohol, hepytl alcohol, decyl alcohol, and
the like; cyclic ether, for example, tetrahydrofuran, dioxane, and
the like. Mixtures of alcohol and water can be used. Also useful
are ionic mixtures of alcohol with other miscible solvents. The
solution concentration is generally in the range from about 0.1
weight percent metal salt or complex based on the total weight of
the solution up to a saturated solution, preferably from about 1 to
about 10 weight percent metal salt or complex. The pH of the metal
salt or complex solution can range from about 4 to 14 but is
generally maintained in the basic range, i.e., greater than 7.0,
and preferably from about 10 to about 13.
The stable anion which is added to the metal salt solution is
selected from the group consisting of OH.sup.-, BR.sub.3 H.sup.-,
and A1R.sub.3 H.sup.-, wherein each R is individually selected from
the group consisting of alkyl, aryl and hydrogen. Only a small
amount is used because addition of too much stable anion will cause
the metal to precipitate. For example, the concentration of
OH.sup.- added is generally in the range of about 0.005 to about 10
percent by volume based on the volume of the solution, preferably
from about 0.05 to about 1.0 percent; and the amount of BH.sub.4
.sup.- added is generally in the range of about
1.times.10.sup.-.sup.4 to about 4.times.10.sup.-.sup.1 moles per
liter, preferably from about 2.6.times.10.sup.-.sup.4 to about 0.26
mole per liter. Instead of using these stable anions individually,
various combinations of them can be used. The compounds containing
these stable anions can contain any cation which will not react
with the ingredients of the metal salt bath. The compounds must be
soluble in the bath. Suitable cations include sodium; potassium;
hetero atom-containing species such as those containing phosphorus,
sulfur and quarternary nitrogen; and the metal to be plated.
Generally, the sodium and potassium compounds are preferred.
Typical compounds containing the stable anions include: sodium
hydroxide, potassium hydroxide, sodium borohydride, potassium
borohydride, sodium trimethyl borohydride, sodium triphenyl
borohydride, sodium diphenyl methyl borohydride, dimethyl borane,
lithium aluminum hydride, sodium trimethyl aluminum hydride, sodium
triphenyl aluminum hydride, and the like. When R is a alkyl, the
group generally contains 1 to 10 carbon atoms. When R is aryl, the
aryl group generally contains 6 to 10 carbon atoms such as in
phenyl, toluyl and benzyl.
The step of subjecting the phosphorus-treated substrate to the
solution of metal salt and stable anion is generally conducted at a
temperature below the softening point of the substrate, and below
the boiling point of the solvent, if one is used. The addition of
the small amount of stable anion allows the treating step to be
accomplished efficiently near room temperature, i.e., about 20
degrees centigrade, whereas previously presence of a reducing agent
was necessary at this temperature to produce a satisfactory treated
article. Generally the temperature is in the range of about 10 to
110 degrees centigrade, preferably from about 20 to 40 degrees
centigrade. The time of contact can vary considerably, depending on
the nature of the substrate, the characteristics of the metal salts
employed and the contact temperature. However, the time of contact
is generally in the range of about 0.1 to 30 minutes, preferably
about 5 to 10 minutes.
The process of this invention can be carried out in one continuous
operation, or the substrate can be stored after removal from the
metal salt bath and subjected to electrolytic treatment at some
later time. Subjecting the substrate to a bath containing a nickel
salt and OH.sup.- results in a black appearance. If any of the
other stable anions, or if a mixture of stable anions is employed,
the substrate acquires a metallic appearance. Both metal phosphide
coatings are generally conductive and both allow the substrate to
be stored. When a black appearance has been obtained and it is
desired to have a metallic appearance, the substrate can be
subjected to the bath a second time, said bath now containing any
of the stable anions besides OH.sup.- or a mixture of any of stable
anions.
The treated substrates of the invention are generally conductive
and can be electroplated by the processes known in the art. The
treated substrate is generally not subjected to an electroless
treatment, as is sometimes the case with the process of Ser. No.
614,541. However, if the substrate is not conductive or if it is
desired to increase the conductivity, the article can be subjected
to electroless plating prior to electroplating. The treated article
is generally used as the cathode. The metal desired to be plated is
generally dissolved in an aqueous plating bath, although other
media can be employed. Generally, a soluble metal anode of the
metal to be plated can be employed. In some instances, however, a
carbon anode or other inert anode is used. Suitable metals,
solutions and condition for electroplating are described in Metal
Finishing Guidebook Directory for 1967, published by Metals and
Plastics Publications, Inc., Westwood, N.J.
The following examples serve to illustrate the invention but are
not intended to limit it. Unless specified otherwise, all
temperatures are in degrees centigrade and parts are understood to
be expressed in parts by weight.
EXAMPLE 1
A 2 percent solution of phosphorus in trichloroethylene was
prepared by adding yellow phosphorus to trichloroethylene at 60
degrees centigrade. A polypropylene sheet was immersed in the
resulting solution for 3 minutes and then washed with a 60 percent
solution of DMF in water at 50 degrees centigrade for 30 seconds.
The sheet was then placed in a two liter nickel bath which
contained 1950 cc. of 2 percent NiCl.sub.2 in 23 percent NH.sub.4
OH and 50 cc. of 20 percent NaOH. After 10 minutes the sheet was
withdrawn and was found to have obtained a highly conductive black
coating which can be electroplated directly by conventional means.
The immersion in the nickel bath was done at room temperature.
EXAMPLE 2
A 1 percent solution of phosphorus in a mixture of
trichloroethylene and perchloroethylene was prepared as described
in example 1. An ABS plastic sample was treated as in example 1
except that the time of immersion in the phosphorus solution was 2
minutes. An excellent quality black coating was produced on the
sample.
EXAMPLE 3
A nickel bath was prepared by dissolving 0.1 gram of solid
NaBH.sub.4 in 1,000 ml. of 2 percent NiCl in 10 percent NH.sub.4
OH. A polypropylene sheet, treated with
phosphorus-trichloroethylene as described in example 1, was
subjected to this solution at room temperature for 10 minutes. A
highly conductive metallic nickel coating was produced and
satisfactory results were obtained when this was electroplated with
nickel in a conventional manner.
EXAMPLE 4
The black-coated samples of examples 1 and 2 were subjected to the
nickel bath of example 3. Upon withdrawal from the bath, the
samples had a metallic appearance.
EXAMPLE 5
A nickel bath was prepared by dissolving 8.8 grams of Ni(C.sub.2
H.sub.3 O.sub.2).sub.2 in 50 cc. of distilled water. The nickel
acetate solution was added to 500 cc. of 28 percent NH.sub.4 OH
followed by 50 cc. of 9 percent NaOH and 1 drop of p-octylphenyl
polyethylene glycol (a surfactant). The bath was heated to 30-32
degrees centigrade. A polypropylene sample, treated with phosphorus
in trichloroethylene as in example 1, was subjected to this bath
for about 20 minutes. An excellent quality, strongly adherent
nickel coating was produced on the sample.
EXAMPLE 6
A nickel bath was prepared by dissolving 10 grams of NiCl.sub.2 in
500 cc. of distilled water, followed by 50 grams of urea and 150
grams of NH.sub.4 OH. Polypropylene sheets and winged shaped knobs
were subjected to phosphorus in trichloroethylene, as in example 1,
and then to this bath at 40 degrees centigrade for 20 minutes. An
adherent coating was formed on the plastic articles.
EXAMPLE 7
Winged-shaped polypropylene knobs were given an adherent nickel
phosphide coating by subjecting them to a 2 percent solution of
phosphorus in perchloroethylene at about 20 degrees centigrade for
about 3 minutes, followed by subjection for 15 minutes to a nickel
bath. The bath contained 500 cc. of 28 percent NH.sub.4 OH, 50 cc.
of distilled water, 10 grams of NiCl.sub.2 and 50 cc. of about 10
percent BaOH, and was maintained at 30 to 35 degrees
centigrade.
EXAMPLE 8
A bath containing Cr.sub.2 O.sub.3, NiSO.sub.4, NH.sub.4 OH and a
small amount of NaOH was maintained at 30 to 37 degrees centigrade.
A metal phosphide coating was created on a polypropylene sample by
subjecting the sample to phosphorus as in example 7 and then to the
above bath for 15 minutes.
EXAMPLE 9
A polypropylene sample was treated with phosphorus as in example 7.
It was then subjected to a bath containing 5.21 grams of NiCl.sub.2
.sup.. 6H.sub.2 O, 116 grams of 28 percent NH.sub.4 OH, 128 grams
of distilled water, 0.8 gram of NaOH and 0.5 gram NaBH.sub.4,
maintained at 30 degrees centigrade. The resulting sample had a
silvery metallic appearance and was electroplated with nickel in
the conventional manner.
EXAMPLE 10
A first bath was prepared containing 4.34 grams of NiSO.sub.4
.sup.. 6H.sub.2 O, 115.47 grams of 28 percent NH.sub.4 OH, 128.29
grams of distilled water, 0.01 gram of NaOH, and 0.03 gram of a
surfactant, and maintained at 30 degrees centigrade. A second bath
was prepared containing 5.2 weight percent NiCl.sub.2, 94.3 weight
percent eater and 0.5 weight percent dimethylamine boran, and
maintained at 30 degrees centigrade. A polypropylene sample was
treated with phosphorus as in example 7 and then immersed in the
first bath for 3 minutes. The resulting black sample was immersed
in the second bath for about 2 minutes. The resulting treated
sample had a metallic appearance and was electroplated with nickel
in the conventional manner.
EXAMPLE 11
A polypropylene sample was treated as in example 10 except that
upon withdrawal from the first bath, the black appearing sample was
not subjected to the second bath. Instead, the sample was subjected
to a bath containing 2.5 weight percent dimethylamine boran, 5.1
weight percent cobalt chloride, 2.5 weight percent H.sub.3 BO.sub.3
and 89.9 weight percent water. The bath was maintained at 30
degrees centigrade and a pH of 4.2. The resulting treated sample
had a bright cobalt appearing coating.
EXAMPLES 12-29
Various polymers in various shapes were subjected to a 2 percent
solution of phosphorus in trichloroethylene. Thereafter, the
samples were subjected to the low-temperature bath containing a
small amount of OH.sup.- and BH.sub.4 .sup.-, introduced into the
bath as NaOH and NaBH.sub.4, followed by the electroplating of a
metal. The variables are reported in table I. The metals in the
bath were introduced as the chloride, sulfate or acetate salts. The
designation Ni(s) indicates the subjection to a bath of a Harshaw
Chemical Company Perflow semibright nickel plating solution, at
about 65 degrees centigrade and about 50 amperes per square foot
current density for about 30 minutes. The designation Ni(b)
indicates subjection to a bath of a Harshaw Chemical Company
Airglow bright nickel plating solution, at about 65 degrees
centigrade and a current density of about 50 amperes per square
foot for about 10 minutes. The designation Cr indicates subjection
to a Udylite K2-50 chromic acid plating bath for about 1.5 minutes
and a current density of 150 amperes per square foot. Under the
heading "Electrodeposition," the metals are listed in the order in
which they were plated on the metal phosphide. For example,
Ni(s)/Ni(b)/Cr indicate that the sample was first plated with
semibright nickel, followed by bright nickel, and finally plated
with chrome. The adhesion of the plated metal to the plastic
surface is reported in pounds per inch, which represents the
quantity of force required to pull an inch wide strip of metal away
from the plastic surface. Oleoplate is a type of polypropylene.
##SPC1##
The plated articles of each of the above examples were tested for
thermal stability by a thermocycling test. Therein, the
metal-plated articles were heated in an oven at 180 degrees
Fahrenheit for 3 hours, maintained at room temperature for 30
minutes and then placed in a freezer at -40 degrees Fahrenheit for
30 minutes. The same heating and cooling was repeated six times to
complete the test. To pass the test, the coating cannot blister,
crack or peel. All of the plated articles passed the thermocycling
test.
EXAMPLES 30-40
Various polymers in various shapes were subjected to a 3 percent
solution of phosphorus in trichloroethylene, the low-temperature
bath of this invention, and then electroplated. The variables are
reported in table II. All other conditions are as in examples
12-29. All of the plated articles were tested for thermal stability
by a thermocycling test, as described in examples 12-29, and all of
the plated articles passed the test. Adhesion is reported in pounds
per inch. ##SPC2##
EXAMPLE 41
A sample of paper was treated with phosphorus and the
low-temperature bath as in example 1. Upon withdrawal from the
bath, the paper had an adherent nickel phosphide on its
surface.
When employing the low-temperature bath of this invention,
especially when the pH is in the basic range, it is advantageous to
employ a secondary complexing agent to increase the bath life. The
secondary agents are selected from the inorganic compounds or alkyl
derivatives of Group III A and IV A metals. Examples include the
chlorides, fluorides, bromides, iodides, chromates, sulfates,
nitrates, acid phosphates, and the like; the methyl, ethyl,
isopropyl, and the like, derivatives of gallium, indium, thallium,
germanium, silicon, tin and lead.
Various changes and modifications can be made in the process of
this invention without departing from the spirit and scope of the
invention. The various embodiments of the invention disclosed
herein serve to further illustrate the invention but are not
intended to limit it.
* * * * *