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Publication numberUS3607351 A
Publication typeGrant
Publication dateSep 21, 1971
Filing dateAug 2, 1968
Priority dateAug 2, 1968
Publication numberUS 3607351 A, US 3607351A, US-A-3607351, US3607351 A, US3607351A
InventorsLee Sung Ki
Original AssigneeHooker Chemical Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for metal plating of substrates
US 3607351 A
Abstract  available in
Images(1)
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Claims  available in
Description  (OCR text may contain errors)

Unite States atent Continuation-impart of application Ser. No. 7 071 337, Sept. 28, now abandoned.

PROCESS FOR METAL PLATING ()lF SUBSTRATES 34 Claims, 3 Drawing Figs.

11.5. C1 117/417 A, 117/71 R, 117/160 R,23/223, 106/287 R, 204/30 Int. Cl 154M 11/092 C23c 3/02 Field of Search 1 17/47 R References Cited OTHER REFERENCES Wcin, S. Metallizing Non-Conductors NY., Metal Industry Publ. Co., 1945. p. 39 Copy in Op 160 ABSTRACT: Substrates, including plastics, are plated with metals by pretreatment of the substrate surfaces with phosphorus in an organic solvent and subjecting the phosphorus-treated surface to water and/or a surfactant to impregnate the surface with phosphorus. The resulting treated surface is contacted with a metal salt or complex thereof, to form a metal-phosphorus compound. The step of contacting with water and/or a surfactant can be accomplished by providing a layer of water or a layer of surfactant on the surface of the phosphorus-organic solvent contacting bath. The resulting treated surface is either conductive or is capable of catalyzing the reduction of a metal salt to produce a conductive surface. Such conductive surfaces are readily electroplated by conventional techniques.

P ATENTED SEP21 1911 m uwmmwm & mml llhlll;

mwuqomhuudm PROCESS FOR METAL PLATING OF SUBSTRATIES REFERENCE TO PRIOR APPLICATION This is a continuation-in-part of application Ser. No. 671,337, filed Sept. 28, I967 now abandoned.

BACKGROUND OF THE INVENTION A new process has recently been developed wherein substrates, particularly thermoplastic resins and polymers, are plated with metals by pretreatment of the surface with phosphorus to deposit phosphorus at the surface of the substrate, followed by contacting the treated surface with a metal salt or complex thereof, to form a metal-phosphorus compound. This process is capable of producing, at low cost, plastic articles that have a metallic 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. This invention relates to improvements in the process for pretreatment of substrate surfaces prior to electroplating by conventional techniques.

It is an object of this invention to provide an improved process for the metal plating of substrates. Another object of the invention is provide a process for producing articles having an adherent metal coating that is especially resistant to peeling, temperature cycling, and has good corrosion-resistant properties. Such metal coatings are electrically conductive, whereby static charges are readily dissipated from the plastic surfaces, and are useful in printed circuits. The metal coatings further serve to protect articles from abrasion, scratching and marring, reduce their porosity and improve their thermal conductivity. A further object of the invention is to stabilize the phosphorus-organic solvent treating bath used for the pretreatment of substrates by suppressing the evaporation of the organic solvent and by reducing the oxygen absorption in the treating bath. Still a further object of the invention is to provide improved preplating baths for use in the process of metal plating of substrates. Another object of the invention is to provide a process for the conditioning of the surfaces of articles in the process of pretreating them prior to conventional plating processes. Still another object of the invention is to provide safer operation of preplating baths which utilize organic solvents in the pretreatment of substrates prior to conventional plating processes. A further object is to improve the hydrophilic properties of phosphorus-treated substrate surfaces.

SUMMARY OF THE INVENTION This invention provides a process which comprises contacting a substrate with phosphorus to deposit phosphorus at the surface of the substrate, and additionally contacting the substrate with a medium comprising water and/or a surfactant, and thereafter contacting the thus-treated surface with a solution of a metal salt or complex thereof to form a metalphosphorus composition, generally a metal phosphide alloy, at the plastic surface.

In one aspect of the invention, the medium comprises water per se, and the contacting step can be carried out (a) by providing an emulsion of water in the organic solvent which contains phosphorus, (b) by contacting the plastic surface by a separate water phase located on the surface of the organic solvent, or (c) by providing a separate water contact zone in which the plastic surface is immersed subsequent to its removal from contact with the phosphorus-organic solvent treatment zone.

In another aspect of the invention, the medium comprises a surfactant or an aqueous solution thereof, and the contacting step can be conducted by (a) providing a separate phase or layer of the surfactant on the surface of the organic solvent, or (b) providing a separate treatment zone for the surfactant for contacting the plastic surface subsequent to its removal from the phosphorus-organic solvent contact zone for any desired duration. When used in this specification, the term surfactant shall include aqueous solutions thereof.

In a further aspect of the invention, contact with the medium comprises sequentially contacting the substrate with water and with a surfactant, which can be conducted by (a) providing an emulsion of water in the phosphorus-organic treating zone and a separate phase or layer of the surfactant on the surface of the emulsion, (b) providing an emulsion of water in the phosphorus-solvent solution and providing the surfactant in a separate contact zone for contacting the substrate subsequent to its removal from the phosphorus-organic solvent solution, (c) providing a water phase or layer on the surface of the phosphorus-organic solvent solution and providing a separate contact zone which contains the surfactant, or (d) providing distinct zones for treatment of the substrate with water and with the surfactant subsequent to the removal of the plastic surface from the phosphorus-organic solvent solution.

Also in accordance with the invention, there are provided the following novel treating or contacting baths: I) an emulsion of water as the dispersed phase and a phosphorus-organic solvent solution as the continuous phase, (2) a two-phase system comprised of (a) an upper layer of water and (b) a lower layer of a solution of phosphorus in an organic solvent, (3) a two-phase system comprised of (a) an upper layer of a surfactant and (b) a lower layer of a solution of phosphorus in an organic solvent, and (4) a two-phase system comprised of (a) an upper layer of a surfactant and (b) a lower layer of an emulsion comprised of water as the dispersed phase and a solution of phosphorus in an organic solvent as the continuous phase.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to a preferred embodiment of the invention illustrated in FIG. 1 of the drawing, a molded, polypropylene article 10 is passed sequentially through contacting baths 112, I4, 116, 18 and 20, following the route designated by lines 11, 113, 15, 17, 19 and 21 or 22. Contacting bath 12 comprises a layer of water 25 which is about I inch in depth on the surface of a solution of 2 weight percent of commercial yellow phosphorus dissolved in trichloroethylene. The phosphorusorganic solvent solution is at a temperature of about 70 C. The plastic article is immersed. in the phosphorustrichloroethylene solution for about 5 minutes, and then is withdrawn from the solution such that the surface of the treated plastic article is washed by water layer 25 for about 5 minutes. Next, the plastic article is immersed for about 1 minute in treating vessel 14 which contains a solution of a surfactant, dimethyl formamide, in water. This treating solution is at a temperature of about 60 C. Upon withdrawal of the plastic article from vessel 14 it is introduced to vessel 16 which contains water at a temperature of about 60 C. Contacting vessel 16 serves to wash the extraneous dimethyl formamide solution from the surface of the treated plastic article. Thereafter, the treated plastic article is immersed in an ammoniacal solution of nickel sulfate 29' contained in treating vessel 18 for a period of about 15 minutes. Treating bath 29 is prepared by dissolving about 5 weight percent of nickel sulfate hexahydrate in about equal parts of water and a 30 percent by weight solution of ammonium hydroxide. This treating bath is maintained at a temperature of about 60) C. and the ammonia concentration is maintained at a level of at least about 0.5 percent by weight. The nickel-phosphide-coated polypropylene article is withdrawn from treating bath 29 and washed in contacting vessel 20 with water 30. The treating baths or vessels 112, l4, l6 and 11% are equipped with heating means represented in the figure by pairs of inlet and outlet conduits or coils 44-45, 464148-49 and 50-51, respectively.

The nickelphosphidecoated polypropylene article emerging from water wash 30 can be passed by route 21 directly to a conventional electroplating process, designated schematically by 32 wherein metals such as chromium, nickel, copper and noble metals can be plated on the nickel-phosphide-coated plastic article to provide adherent metal-coated plastics. Alternatively, the nickel-phosphide-coated polypropylene article can be passed by route 22 to a conventional alkaline or acidic electroless chemical plating process wherein the polypropylene article can be coated with metals such as nickel and copper. The thus-coated article can then be passed by route 23 to the conventional electroplating process described before.

In another embodiment of the invention, the phosphorustreated polypropylene article emerging from contacting bath 28 can be passed directly by route 24 to an alkaline electroless chemical plating process 34 wherein the metal salt present in the electroless chemical plating bath reacts with the phosphorus coated article to form a metal phosphide coating and electroless metal is chemically plated on the surface of the polypropylene article. The resulting coated article can be passed by route 23 to the conventional electroplating process 32.

FIG. 2 shows a treating vessel 36 which contains a twophase preplating system comprised of an upper layer 37 of a 60 percent by weight of dimethyl formamide in water and a lower layer or phase 38 comprised of a solution of 2 weight percent commercial yellow phosphorus dissolved in trichloroethylene. Treating vessel 36 is equipped with heating means designated 52-53.

FIG. 3 illustrates a treating vessel 40 which is useful in the foregoing process instead of treating vessel 12. Treating vessel 40 contains an upper layer 41 comprised of a solution of 6 weight percent dimethyl formamide in water and a lower layer 42 comprised of an emulsion wherein water is the dispersed phase and the continuous phase is a solution of 2 weight percent of commercial yellow phosphorus dissolved in trichloroethylene. Treating vessel 40 is equipped with heating means designated 54-55.

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, ethylene-propylene copolymers; copolymers of ethylene or propylene with other olefins, polybutadiene; polymers of butadiene, polyisoprene, both natural and synthetic, polystyrene and polymers of l-pentene, l-hexene, l-heptene, l-octene, 2-methylpropene, 4-methylhexene-l, bicyclo- (2.2.1 )-2-heptene, pentadiene, hexadiene, 2,3-dimethylbutadienel,3,4-vinylcyclohexene, cyclopentadiene, methylstyrene, and the like.

Other polymers in addition to the above-described polyolefins that are useful in the invention include polyindene, polymers of acrylate esters and polymers of methacrylate esters, acrylate and methacrylate resins such as ethyl acrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl methacrylate and methyl methacrylate; alkyd resins and paint vehicles, such as bodied linseed oil; 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-ureaformaldehyde; oleo-resins; phenolic resins such as phenol-formaldehyde, phenolic-elastomer, phenolic-epoxy, phenolicpolyamide, and phenolic-vinyl acetals; polyamide polymers, such as polyamides, polyamideepoxy 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-phenolformaldehyde, resorcinol-polyamide and resorcinol-urea; rubbers such as natural rubber, synthetic polyisoprene, reclaimed rubber, chlorinated rubber, polybutadienc, cyclized rubber, butadiene-acrylonitrile rubber, butadiene-styrene 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; polyformaldehyde; polyphenylene oxide; polymers of diallyl phthalates and phthalates; polycarbonates of phosgene or thiophosgene and dihydroxy compounds such as bisphenols, phosgene, 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 polybutadienc, styrene and acrylonitrile, commonly called ABS resins; 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 polymers of the invention can be in various physical forms, such as shaped articles, for example, moldings, sheets, rods, tubes, and the like; fibers, coatings, films and fabrics, and the like.

In the first step of the preferred process of the invention, the substrate is treated with 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 or increase the diffusibility of 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. Mixtures of any of the foregoing solvents can be employed.

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 at the operating temperature. At least 1 weight percent phosphorus is preferred. Prior to contacting the substrate with the phosphorus solution, the surface of the article should be clean. The solvent generally serves to clean the surface. However, it is not necessary to subject the surface 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 30 to 135 C., but preferably in the range of about 50 to C. 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 l to 20 minutes.

In the embodiments of the invention that utilize an emulsion of water dispersed in a phosphorus-organic solvent solution, the water is present in the emulsion in a proportion from about 40 to 70 parts by weight of water per 100 parts of emulsion. The phosphorus-organic solvent concentrations and conditions are the same as described hereinbefore. Suitable emulsifying agents for maintaining the emulsion include anionic, cationic and nonionic dispersing agents or surfactants. Suitable nonionic surfactants include the alkylphenoxypoly(ethyleneoxy)ethanols, and the dialkylphenoxypoly(ethyleneoxy)ethanols preferably those wherein the alkyl substituent has 5 to 12 carbon atoms and which have 1 to 20 ethyleneoxy groups. Typical members are octylphenoxypoly(ethyleneoxy)ethanol, nonylphenoxypoly(ethyleneoxy)ethanol and dodecylphenoxypoly(ethyleneoxy)ethanol. Also useful are the fatty acid esters of polyhydric alcohols of ether alcohols, for example, glycerol mono-sterate; esters of ethylene glycol, diethylene glycol, triethylene glycol and polyethylene glycol, for example, the condensation product of oleic acid with ethylene oxide; and fatty esters of sugar alcohols. Suitable anionic surfactants include the alkali metal alkylbenzene sulfonates, particularly those wherein the alkali metal is sodium or potassium and the alkyl group has 8 to 20 carbon atoms. Typical members are sodium dodecylbenzene sulfonate and potassium dodecylbenzene sulfonate. Another suitable group of anionic surfactants is the alkali metal alkyl sulfates, particularly those wherein the alkali metal is sodium or potassium and the alkyl group has 8 to 20 carbon atoms. A typical member is sodium lauryl sulfate. Also useful are the sulfonated aliphatic polyesters, free acids of complex phosphate esters, sodium salts of complex phosphate esters and sodium salt of disproportionated wood rosin. Another suitable group of anionic surfactants is the alkali metal lignin sulfonates, such as sodium lignin sulfonate and potassium lignin sulfonate. Suitable cationic surfactants include the fatty amides of monoethanolamines; fatty nitriles and fatty acid amides, such as olein morpholide. Also useful are cationic agents such as N-coco-B-amino buteric acid, dicoco dimethyl ammonium chloride and polyoxyethylated alkylamines.

in embodiments of the invention wherein the phosphorustreatment step is conducted in a vessel containing two liquid phases with an upper phase of water or a surfactant the thickness of the upper layer is generally at least about 0.25 inch, and is preferably at least about 1 inch. The thickness of the aqueous layer can be as great as 1.5, 2, 5 inches, as thick as the phosphorus-organic solvent layer, or an even greater depth. The temperature of the aqueous phase is generally maintained in the range of about 30 to 100 Centigrade, preferably in the range of about 30 to 80 Centigrade. These temperatures are generally maintained by contact with the organic solvent phase beneath the aqueous phase. Many advantages result from maintaining the water or surfactant phase on the surface of the solution of phosphorus and the organic solvent. The evaporation of the organic solvent is suppressed. The penetration or absorption of oxygen into the organic phase is reduced, thereby preventing deterioration of the organic phase. Safer working conditions result from the blanket effect of the phase covering the solution of phosphorus in the organic solvent. Moreover, instantaneous prewashing and postwashing action of the substrate is obtained.

In embodiments of the invention wherein water or a surfactant are utilized in separate contacting zones, the temperature of these contacting zones are normally maintained in the range of about 30 to 100 C. preferably about 30 to 80 Centigrade. Time of contact is generally in the range of 1 second to 30 minutes, preferably 0.25 to 5 minutes. Moderate agita tion is generally employed. The liquid surfactant is generally used in a nondiluted form, however, an aqueous solution in a concentration in the range of about one to about 99 parts by weight of surfactant per 100 parts of total solution, preferably in the range from about l0 to 90 parts by weight of surfactant per 100 parts of total solution, can also be employed.

The surfactants employed in this aspect of the invention in clude the anionic, cationic and nonionic surfactants. Typical of useful compounds are alcohols such as the monohydric aliphatic alcohols, for example, ethanol, butanol, hexanol, decanol, and the like; dihydric aliphatic alcohols, for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and other alkylene glycols. Higher alcohols, such as glycerol are also useful. Other suitable surfactants include the phosphate, carbonate, bicarbonate, hydroxide, sulfate and acid sulfate salts of alkali metals and quaternary nitrogen. Thus, the corresponding compounds of lithium, sodium, potassium, rubidium, cesium, francium and NH, can be employed. Other suitable surfactants are such nonionic, anionic and cationic surfactants as enumerated hereinbefore. Especially preferred surfactants for use in this aspect of the invention are the alkyl amides of the formula:

wherein R, and R are independently selected from the group consisting of hydrogen and alkyl, and R is selected from the group consisting of hydrogen, alkyl and NR,R The alkyl groups can have one to about 12 carbon atoms, preferably one to about six carbon atoms. Typical amides that can be used in the practice of the invention include: formamide, ethylformamide, propylformamide, hexylforma'mide, dimethylforma mide, diethylformamide, dipropylformamide, acetamide, ethylacctamide, isopropylacetamide, hexylacetamide, dimethylacetamide, diethylacetamide, and the like. Mixtures of any of the foregoing surfactants can also be employed.

As a result of the phosphorus treatment step, the phosphorus is deposited at the surface of the substrate, that is, the phosphorus is located on the surface of the substrate and embedded or impregnated in or beneath the surface of the substrate. [t is believed that contacting the phosphorus-treated surface with water and/or a surfactant, removes the excess phosphorus on the surface and leaves phosphorus embedded or impregnated in (including beneath) the plastic surface.

Many advantages result from contact of the phosphorustreated article with water and/or a surfactant in the foregoing embodiments of the invention. The contact with water conditions the surface by washing off the excess phosphorus-organic solvent solution, thereby preventing an uneven buildup of phosphorus at the surface of the article. This advantage also results when the phosphorus-treated article is first contacted with the surfactant following withdrawal from the phosphorusorganic solvent solution. Moreover, treatment of the phosphorus-treated surface with the surfactant efficiently removes the organic solvent from the surface and the pores of the substrate surface to facilitate more effective reaction of the phosphorus with the metal salt or complex thereof in subsequent treatment steps. The treatment with the surfactant also improves the wettability of the substrate surface, and neutralizes acidic materials that may have formed around the surface prior to introduction of the substrate into the alkaline metal-salt-treating bath. Such neutralization of oxidized phosphorus acids and anhydrides prevents damage to the sur face.

The foregoing treatment steps can be followed by a water washing or rinse step. The treated article is immersed in a water bath maintained at 30 to 100 Centigrade, preferably 40 to Centigrade for a period from 1 second to 5 minutes, preferably 0.5 to 3 minutes. Moderate agitation is generally employed. Washing can also be accomplished by other methods such as by subjecting the article to water sprays, and the like.

In the next step of the process of the invention, the phosphorus'treated substrate is contacted with 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. The term metal phosphide, as used herein, means the metalphosphorus 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 lB, MB, NB, VB, VlB, VllB and VIII of the Periodic Table. 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 eaproate, cinnamate, stearate, oleate, palmitate, dimethylglyoxime, and the like. Generally the anions of organic acids contain 1 to 18 carbon atoms.

Some useful metal salts include copper sulfate, copper chloride, silver nitrate, nickel cyanide and nickel sulfate. Mixtures of salts can be employed.

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 I to 6 ammonia molecules are complexed with the foregoing metal salts. Typical examples include NiSo,-6NH NiCl -6NH Ni(C H,00) -6NH CuSo -6NH CuCl -6NH AgNO -6NH NiSO -3NH CuSO -4NH Ni(NO -4NH and the like. Other useful complexing agents include quinoline, amines and pyridine. Useful complexes include compounds of the formula MX Q wherein M is the metal ion, X is chlorine or bromine and Q is quinoline. Typical examples include: CoCl Q CoBr Q NiCl Q NiBr Q Nil Q MnCl.,Q,, CuCl Q CuBr Q and ZnCl Q Also useful are the corresponding monoquinoline complexes such as CoCl O. Useful amine complexes include the mono(ethylenediamine)- bis-(cthylenediamine)-, tris-(ethylenediamine)-, bis-(1,2- propane diamine)-, and bis-( l,3-propane diamine)- complexes of salts such as copper sulfate. Typical pyridine complexes include NiCl (py) and CuCl (py) 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, heptyl alcohol, decyl alcohol, and the like. Mixtures of alcohol and water can be used. Also useful are mixtures of alcohol with other miscible solvents of the types disclosed hereinbcfore. 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 I to about 10 weight percent metal salt or complex. The pH of the metal salt or complex solution is generally maintained in the range from about 4 to 14, but is generally maintained in the basic range, i.e., greater than 7, and preferably from about 10 to about 13.

The step of contacting the phosphorus-treated substrate with the solution of metal salt 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. Generally the temperature is in the range of about 30 to 1 10 Centigrade, preferably from about 50 to 100 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 10 to minutes.

The metal salt treatment step can be followed by a water washing or rinse step such as described hereinbcfore. The treated articles can then be dried, for example, in a forced draft oven for 0.25 to 1 hour, at 50 to l35Centigrade.

Depending on the conditions employed in the treatment steps, the duration of the treatments, and the nature of the substrate treated, the resulting treated substrate may be either (1) conductive, such that the surface can be readily electroplated by conventional techniques, or (2) nonconductive.

The treated substrates that result from contacting the phosphorus-treated article with a metal salt solution can be subjected to a process that has become known in the art as electroless plating or chemical plating. In a typical electroless plating process, a catalytic surface is contacted with a solution of a metal salt under conditions in which the metallic ion of the metal salt is reduced to the metallic state and deposited on the catalytic surface. The use of this process with the products of this invention relies upon the catalytic metal sites deposited in the surface as a result of the treatment with the solution of metal salt or complex of this invention. A suitable chemical treating bath for the deposition of a nickel coating on a catalytic surface produced in accordance with the process of the invention can comprise, for example, a solution of a nickel salt in an aqueous hypophosphite or borohydride solution. Suitable hypophosphites include the alkali metal hypophosphites such as sodium hypophosphite and potassium hypophosphite, and the alkaline earth metal hypophosphites such as calcium hypophosphite and barium hypophosphite. Suitable borohydrides include the alkali metal borohydrides such as sodium borohydride and potassium borohydride, and the alkaline earth metal borohydrides, such as calcium borohydride and barium borohydride. Other suitable metal salts for use in the chemical treating bath include the metal salts described hereinbefore with respect to the metal salt treatment of the phosphorus-treated plastic surface of the invention. Other reducing media include formaldehyde, hydroquinone and hydrazine. Other agents, such as buffering agents, complexing agents, and other additives are included in the chemical plating solution or baths.

The treated substrates of the invention that are conductive can be electroplated by the processes known in the art. The conductive plastic 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. Suitable metals, solutions and conditions for electroplating are described in Metal Finishing Guidebook Directory for 1967, published by Metals and Plastics Publications, lnc. Westwood, NJ.

The following examples serve to illustrate the invention but are not intended to limit it. Unless specified otherwise in this specification and claims, all temperatures are in degrees Centigrade and parts are understood to be expressed in parts by weight. The adhesion of the plated metal of the substrate is reported in pounds per inch, which represents the quantity of force required to pull an inch-wide strip of metal away from the surface. ASTM test 8-368-65 was employed to measure the corrosion resistance of the metal plated articles. Thermal stability of the plated articles was measured by a thermo cycling" test, wherein the metal-plated article was subjected to the following conditions. The article was heated in an oven at Fahrenheit for 3 hours, maintained at room temperature for 30 minutes and then placed in a freezer at -40 Fahrenheit for 30 minutes. The same heating and cooling cycle was repeated five times to complete the test. To pass the test, the coating can not blister, crack or peel. Example l A sheet of polypropylene was immersed in trichloroethylene to degrease the surface. The polypropylene sheet was then immersed in a solution of 2 weight percent yellow phosphorus dissolved in trichloroethylene, maintained at 70 Centigrade for 2 minutes. The plastic sheet was removed from the solution and washed with cold water, and was then immersed for 10 minutes in an ammoniacal solution of 5 percent nickel sulfate dissolved in water. The solution temperature was maintained at 65. The resulting coated plastic article was washed with cold water and dried in air. The treated plastic surface had a dull, black appearance, and the preplate coating could be removed by scratching the surface.

The preplated polypropylene article was then plated as follows: About 0.8 mil of semibright nickel was applied to the preplated plastic surface by employing the plastic sheet as the cathode, and using a nickel anode, in a bath of a Harshaw Chemical Company Perflow semibright nickel plating solution, at 65 Centigrade and a current density of 4 amperes per square foot for 2 minutes, and 50 amperes per square foot for about 30 minutes. Then about 0.3 mil of bright nickel was applied to the plated surface by employing the plastic sheet as the cathode, and using a nickel anode, in a bath of Harshaw Chemical Company Airglow bright nickel plating solution, at 65 Centigrade and a current density of50 amperes per square foot for minutes. Then the nickel-plated article was coated with 0.002 mil of chrome by using the plastic article as a cathode and an inert anode in a Udylite l(2-50 chromic acid plating bath. A current density of 150 amperes per square foot was employed for 1.5 minutes. The resulting coated article i had an adhesion of 1 to 10 pounds per inch, and passed the thermocycling test and ASTM 8-368-65 corrosion test. Example 2 A polypropylene sheet of the same type utilized in example 1 was degreased by immersing the sheet in trichloroethylene. Thereafter, the polypropylene sheet was immersed in a treating bath comprised of a 2 weight percent solution of yellow phosphorus dissolved in trichloroethylene and maintained at a temperature of 68 Centigrade, and having on the surface of the solution a l-inch'deep layer of water. The plastic article was immersed in the solution for 2 minutes and then withdrawn from the solution through the water phase. The phosphorus-treated article was then immersed in a solution of 60 weight percent dimethyl formamide in water at a tempera ture of 60 centigrade for l minute. The thus-treated polypropylene sheet was thereafter rinsed in a hot water bath. The resulting phosphorus-treated polypropylene sheet was then immersed for 10 minutes in an ammoniacal solution of 5 weight percent nickel sulfate dissolved in water and main tained at a temperature of 65 Centigrade. The resulting plastic article coated with a nickel phosphide was dried in an oven, washed with trichloroethylene and found to have a shiny, strongly adherent nickel phosphide coating that could not be scratched from the surface of the plastic. The thustreated plastic article was then plated as in example 1. The plated plastic article was found to have an adhesion of 25 to 40 pounds per inch. It passed the thermocycle test and the ASTM B- 368-65 test for corrosion.

Similar results are obtained when white phosphorus is employed in place of the commercially available yellow phosphorus.

Other ammoniacal metal salts are readily employed in the foregoing process such as copper sulfate, copper chloride, and silver nitrate.

Example 3 The procedure of example 2 was repeated utilizing polypropylene sheets of the same type utilized in example 1. However, in this example, the degreasing step by immersion in trichloroethylene was omitted, the time of contact of the phosphorus-treated plastic sheet in the nickel sulfate bath was increased to minutes and the step of washing the nickel phosphide coated article with trichloroethylene was omitted. Plated plastic articles resulting from the process were found to have adhesion values of 25 to 40 pounds per inch. The articles passed the thermocyclic and the ASTM corrosion test.

Similar results are obtained when perchloroethylene is employed as the solvent for the phosphorus.

Example! The procedure of example 3 was repeated utilizing polypropylene sheets of the same type utilized in example 1. However, in this example, the step of immersing the phosphorus-treated plastic article in an aqueous solution of dimethyl formamide was omitted. The temperature of the phosphorus-trichloroethylene solution was 70 Centigrade, the temperature of the ammoniacal solution of nickel sulfate was 60 Centigrade and the immersion time therein was 10 minutes. The plated plastic articles resulting from the process were found to have adhesion values of to 30 pounds per inch. The metal plated polypropylene sheet passed the ASTM 5-368-65 corrosion test, and the thermocycle test.

Example 5 The procedure of example 3 was repeated utilizing polypropylene sheets of the type employed in example 1. However, in this example, no water layer was employed on the surface of the phosphorus-trichloroethylene solution. The long term stability of this solution was not good as evidenced by discoloration of the solution, formation of orange insoluble material, decrease in active phosphorus content of the solution, and evaporation of the trichloroethylene solvent. Moreover, it was found the surface of the metal-phosphidecoated article was inferior as compared to the products of examples 3 and 4 as evidenced by pitting of the surface coating. However, the metal articles had good adhesion and passed the thermocycle and ASTM B36865 corrosion test. Example 6 A polypropylene molded disc was immersed in a treating bath comprised of a 2 weight percent solution of yellow phosphorus dissolved in trichloroethylene and maintained at a temperature of 68 Centigrade, and having on the surface of the solution a l-inch-deep layer of water. The plastic article was immersed in the solution for 2 minutes and was then withdrawn from the solution through the water phase, and thereafter immersed in a solution of 60 weight percent dimethyl formamide in water at a temperature of 60 Centigrade for 2 minutes. The thus-treated polypropylene disc was thereafter rinsed in a hot water bath. The resulting phosphorus-treated polypropylene disc was then immersed for IS minutes in an ammoniacal solution of 5 weight percent nickel chloride dissolved in water and maintained at a temperature of 35 Centigrade. The resulting plastic article coated with a nickel phosphide alloy was rinsed with cold water and dried in an oven. The coated plastic article had a shiny, strongly adherent nickel phosphide alloy coating which could not be scratched from the surface of the plastic. The thustreated plastic article was then plated as in example I. The plated plastic article was found to have an adhesion of 20 to 30 pounds per inch and passed the ASTM 8-368-65 corrosion test, and thermocycle test. Example 7 Polypropylene molded discs were immersed in a treating bath comprised of trichloroethylene having 2 weight percent of yellow phosphorus dissolved therein, and an equal weight of water emulsified therein with the aid of 1 weight percent (based on weight of emulsion) of octylphenoxy poly(ethyleneoxy)ethanol containing about 10 ethyleneoxy groups per molecule. (In this aspect of the invention, the emulsifying agent or surfactant is employed in a proportion of about 1 to 5 weight percent of the emulsion.) The phosphoruswater-trichloroethylene treating bath was maintained at 65 Centigrade, and the plastic discs were immersed for about 2 minutes. Then the plastic discs were washed in a separate cold water bath, and immersed for 10 minutes in an ammoniacal solution of 5 weight percent nickel chloride dissolved in water and maintained at a temperature of 35 C. The resulting plastic article coated with a nickel phosphide alloy was rinsed with cold water and dried in an oven. The polypropylene discs were plated as in example 1. The plated discs exhibited adhesion values from 3 to 15 pounds per inch and passed the thermocycle and ASTM B36865 corrosion test. Example 8 Polyvinylchloride sheets were immersed for 3 minutes in a treating bath comprised of a 2 weight percent solution of yellow phosphorus dissolved in a mixture of 25 volume percent trichloroethylene and 75 volume percent perchloroethylene and maintained at 60 Centigrade, and having a l'inch-deep layer of water on the surface. The plastic sheets were withdrawn through the water layer and then immersed in a solution of 60 weight percent dimethyl formamide in water at a temperature of 60 Centigrade for 1 minute. The treated plastic sheets were rinsed with water and then immersed for 10 minutes in an ammoniacal solution of 5 weight percent nickel sulfate dissolved in water and maintained at 65 Centigrade. The resulting nickelphosphide-coated sheets were water washed, dried in an oven and then metal plated as in example l. The metal-plated plastic sheets had adhesion values of l 1.6 to 12.8 pounds per inch and passed the ASTM B-368-65 corrosion test. Example 9 Articles molded from Cycolae EP-3510 ABS resin, a graft eopolymer of polybutadiene, styrene and acrylonitrile were subjected to the process of example 8. The metal-plated articles passed the ASTM B368-65 corrosion test. Example 10 A molded polypropylene article was immersed in 1,1-' difluorotetrachoroethane to degrease the surface and then immersed in a bath containing about 2.5 percent phosphorus in trichloroethylene at about 55 Centigrade as a lower phase and an equal volume of water at 65 Centigrade as the upper phase. The article remained in the phosphorus layer for 8 minutes and then in the water layer for minutes. Thereafter, the plastic was transferred to a 100 percent dimethyl formamide bath at room temperature for 2 minutes, followed by a 20-minute subjection to an ammoniaeal nickel sulfate bath. The resulting metal-phosphide-coated polypropylene was washed with water and dried in an oven at 80 Centigrade for 30 minutes. The article was then electroplated as described in example 1. Examples ll-l7 Following the procedure of example 10, additional substrates were provided with adherent metal phosphide coatings which can be plated as described in example 1.

Time in Nickel Sulfate Sol. (Min.)

Time in Phosphorus Example No. Substrate Solution (Minutes)' Wood Cardboard Porous Clay Asbestos Cement Leather 3 Porcelain (Unglazed) l Example Surfactant KOH 1% KOH 2% Nupu 2% Mp0, 2% NaHCO, 2% m so, 2% Nauso, 2% NaOH When the plastic was removed from the metal salt solution, there was an adherent metal phosphide on the surface of the plastic in all cases. Example 26 Poylypropylene was immersed in a bath containing 2 weight percent solution of yellow phosphorus in trichloroethylene maintained at a temperature of 55 Centigrade, and having a layer of 1.5 M NH OH on the surface of the solution. After remaining 8 minutes in the phosphorus solution, the plastic was withdrawn into the NH OH solution for 1 minute. Then the plastic was immersed in 7M NH OH at 25 Centigrade for 1 minute and in an ammoniaeal nickel sulfate solution at 70, (entigrudc for IS minutes. The resulting polypropylene had an adherent nickel phosphide coating. Example 27 The procedure of example 26 was repeated except that a 2 weight percent aqueous Na CO was substituted for the NH OH layer on the surface of the phosphorus solution and the plastic remained for 4 minutes in this layer. The resulting polypropylene had an adherent metal phosphide coating.

Various changes and modifications can be made in the process and treating baths 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.

Iclaim:

l. A process which comprises contacting a nonconductive substrate with a solution of white phosphorus dissolved in an organic solvent, and at least one medium of the group of water, a surfactant or aqueous solutions thereof, and thereafter contacting the thus-treated substrate with a solution of a metal salt or complex thereof which is capable of reacting with the phosphorus to form a metal phosphide, wherein said metal is selected form the Groups I8, I18, lVB, VB, VlB, VllB and VIII of the Periodic Table.

2. The process of claim 1 wherein the substrate is contacted with an emulsion comprised of water as the dispersed phase and a solution of white phosphorus dissolved in an organic solvent as the continuous phase.

3. The process of claim 1 wherein the substrate is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, and with water.

4. The process of claim 3 wherein said water is provided as an upper phase on the surface of said solution of white phosphorus.

5. The process of claim 1 wherein the substrate is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, and with a surfactant or aqueous solution thereof, wherein said surfactant is selected from the group consisting of alkyl and dialkylphenoxypoly(ethyleneoxy)et hanols; fatty acid esters of alcohols; alkali metal alkylbenzene sulfonates, alkyl sulfates and lignin sulfonates; sulfonated aliphatic polyesters; free acids of complex phosphate esters and the sodium salts thereof; sodium salts of disproportionated wood rosin; fatty amides of monoethanol amines; fatty nitriles; fatty acid amides; N-coco-B-amino buteric acid; dicoco dimethyl ammonium chloride; polyoxyethylated alkyl amines; aliphatic alcohols; alkyl amides; phosphate, carbonate, bicarbonate, hydroxide, sulfate, and acid sulfate salts of alkali metals and of quaternary nitrogen; and mixtures thereof.

6. The process of claim 5 wherein the surfactant is dimethyl formamide.

7. The process of claim 5 wherein the surfactant is sodium carbonate.

8. The process of claim 4 wherein said surfactant or aqueous solution thereof is provided as an upper phase on the surface of said solution of white phosphorus.

9. The process of claim 1 wherein the substrate is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, with water, and then with a surfactant or aqueous solution thereof, wherein said surfactant is selected from the group consisting of alkyl and dialkylphenoxypoly(ethyleneoxy)ethanols; fatty acid esters of alcohols; alkali metal alkylbenzene sulfonates, alkyl sulfates and lignin sulfonates; sulfonated aliphatic polyesters; free acids of complex phosphate esters and the sodium salts thereof; sodium salts of disproportionated wood rosin; fatty amides of monoethanolamines; fatty nitriles; fatty acid amides; N-coco- B-amino buteric acid; dicoco dimethyl ammonium chloride; polyoxyethylated alkylamines; aliphatic alcohols; alkyl amides; phosphate, carbonate, bicarbonate, hydroxide, sulfate, and acid sulfate salts of alkali metals and of quaternary nitrogen; and mixtures thereof.

10. The process of claim 9 wherein the surfactant is dimethyl formamide.

ll. The process of claim 9 wherein the surfactant is sodium carbonate.

12. The process of claim 9 wherein said water is provided as an upper phase on the surface of said solution of white phosphorus.

13. The process of claim 1 wherein the metal salt complex is an ammoniaeal complex of nickel sulfate.

14. The process of claim 1 wherein the metal salt complex is an ammoniaeal complex ofnickel chloride.

15. 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.

16. A process which comprises contacting a plastic with a solution of white phosphorus dissolved in an organic solvent, and at least one medium of the group of water, a surfactant or aqueous solutions thereof, and thereafter contacting the thustreated substrate with a solution of a metal salt or complex thereof which is capable of reacting with the phosphorus to form a metal phosphide, wherein said metal is selected from the lB, NB, NB, VB, VlB, VllB, and Vlll of the Periodic Table.

17. The process of claim 16 wherein the plastic is contacted with an emulsion comprised of water as the dispersed phase and a solution of white phosphorus dissolved in an organic sol vent as the continuous phase.

18. The process of claim 16 wherein the plastic is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, and with water.

19. The process of claim 16 wherein the plastic is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, and with a surfactant or aqueous solution thereof, wherein said surfactant is selected from the group consisting of alkyl and dialkylphenoxypoly(ethyleneoxy)et hanols; fatty acid esters of alcohols; alkali metal alkylbenzene sulfonates, alkyl sulfates and lignin sulfonates; sulfonated aliphatic polyesters; free acids of complex phosphate esters and the sodium salts thereof; sodium salts of disproportionated wood rosin; fatty amides of mono-ethanolamines; fatty nitriles, fatty acid amides, N-coco-B-amino buteric acid; dicoco dimethyl ammonium chloride; polyoxyethylated alkylamines; aliphatic alcohols; alkyl amides; phosphate, carbonate, bicarbonate, hydroxide, sulfate, and acid sulfate salts of alkali metals and of quaternary nitrogen; and mixtures thereof.

20. The process of claim 19 wherein the surfactant is dimethyl formamide.

21. The process of claim 19 wherein the surfactant is sodium carbonate.

22. The process of claim 16 wherein the plastic is treated in sequential steps with a solution of phosphorus dissolved in an organic solvent, with water, and then with a surfactant or aqueous solution thereof, wherein said surfactant is selected from the group consisting of alkyl and dialkylphenoxypoly(ethyleneoxy)ethanols; fatty acid esters of alcohols; alkali metal alkylbenzene sulfonates, alkyl sulfates and lignin sulfonates; sulfonated aliphatic polyesters; free acids of complex phosphate esters and the sodium salts thereof; sodium salts of disproportionated wood rosin; fatty amides of monoethanolamines; fatty nitriles; fatty acid amides; N-coco-B- amino buteric acid; dicoco dimethyl ammonium chloride, polyoxyethylated alkylamines; aliphatic alcohols; alkyl amides; phosphate, carbonate, bicarbonate, hydroxide, sulfate, and acid sulfate salts of alkali metals and of quaternary nitrogen; and mixtures thereof.

23. The process of claim 22 wherein the surfactant is dimethyl formamide.

24. The process of claim 22 wherein the surfactant is sodium carbonate.

25. The process of claim 22 wherein the solvent is trichloroethylene, and the plastic is a polyolefin.

26. The process of claim 22 wherein the solvent is a mixture of trichloroethylene and perchloroethylene, and the plastic is a graft copolymer of polybutadiene and an unsaturated monomer.

27. The process of claim 22 wherein the solvent is a mixture of trichloroethylene and perchloroethylene, and the plastic is polyvinylchloride.

28. A process wherein the treated plastic resulting from the process of claim 16 is electroplated to deposit an adherent metal coating on the treated plastic.

29. The process of claim 28 wherein the plastic is polypropylene, the phosphorus is em loyed as a solution of phosphorus dissolved in trlchloroethy one, and the metal salt complex is an ammoniacal complex of nickel sulfate.

30. The process of claim 28 wherein the plastic is polyvinylchloride, the phosphorus is employed as a solution of phosphorus dissolved in a mixture of trichloroethylene and perchloroethylene, and the metal salt complex is an ammoniacal complex of nickel sulfate.

31. The process of claim 28 wherein the plastic is a graft copolymer of polybutadiene and an unsaturated monomer, the phosphorus is employed as a solution of phosphorus dissolved in a mixture of trichloroethylene and perchloroethylene, and the metal salt complex is an ammoniacal complex of nickel sulfate.

32. A bath for treating substrates which comprises an emulsion of water as the dispersed phase and a solution of white phosphorus in an organic solvent as the continuous phase.

33. A two-phase bath for the treating of substrates which comprises an upper layer of at least one medium of the group of water, a surfactant or aqueous solutions thereof, and a lower layer of a solution of white phosphorus dissolved in an organic solvent, wherein said surfactant is selected from the group consisting of alkyl and dialkylphenoxypoly(ethyleneoxy)ethanols, fatty acid esters of alcohols; alkali metal alkylbenzene sulfonates, alkyl sulfates and lignin sulfonates; sulfonated aliphatic polyesters; free acids of complex phosphate esters and the sodium salts thereof; sodium salts of disproportionated wood rosin; fatty amides of monoethanol amines; fatty nitriles; fatty acid amides; N-coco-lB-amino buteric acid; dicoco dimethyl ammonium chloride; polyoxyethylated alkylamines; aliphatic alcohols; alkyl amides; phosphate, carbonate, bicarbonate, hydroxide, sulfate, and acid sulfate salts of alkali metals and of quaternary nitrogen; and mixtures thereof.

34. The bath in claim 33 wherein the medium is water.

Non-Patent Citations
Reference
1 *Wein, S. Metallizing Non-Conductors NY., Metal Industry Publ. Co., 1945. p. 39 Copy in Gp 160
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6743380Dec 28, 2001Jun 1, 2004Caterpillar IncSilver particles dispersed in phosphate glass
Classifications
U.S. Classification427/306, 205/166, 106/287.29, 106/287.19, 106/287.28, 106/287.3, 205/169, 106/287.32, 106/287.18, 106/287.24, 427/404, 106/287.25
International ClassificationC23C18/20, H05K3/18
Cooperative ClassificationC23C18/2006, H05K3/188, H05K3/181
European ClassificationC23C18/20B
Legal Events
DateCodeEventDescription
Jun 28, 1982ASAssignment
Owner name: OCCIDENTAL CHEMICAL CORPORATION
Free format text: CHANGE OF NAME;ASSIGNOR:HOOKER CHEMICALS & PLASTICS CORP.;REEL/FRAME:004109/0487
Effective date: 19820330