US3140188A - Bath compositions for chemical plating of metals containing boron nitrogen compounds nd an organic solubilizing compound - Google Patents

Description

United States Patent BATH COMPOSITIONS FOR CHEMICAL PLATING 'OF METALS CONTAINING BORON NITROGEN COMPOUNDS AND AN ORGANIC SOLUBILIZ- ING COMPOUND Eberhard Zirngiebl, Cologne-Flittard, and Heinz-Giinter Klein, Cologne-Deutz, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Aug. 23, 1961, Ser. No. 133,322 Claims priority, application Germany Aug. 29, 1960 9 Claims. (Cl. 106-1) The present invention relates to chemical plating; more particularly it is concerned with a process for the production of metal coatings l'y chemical means.

For chemicals plating from aqueous solutions sodium hypophosphite and alkali metal borohydride have been used until now. The hypophosphite process for plating necessitates temperatures above 90 C. This relatively high plating temperature limits the plating of plastics to a narrow range, since a great number of plastics, especially foils, are deformed already at above 90 C. This is also the reason for the unsatisfactory adhesiveness of metal coatings on plastics. Furthermore, hypophosphite baths require narrow pH ranges which have to be adjusted by the addition of suitable butler substances. On the other hand, the borohydride process is carried out at low temperatures, for example between 20 and 50 C., and at a pH range of 10-14, preferably in 2 N ammonia. The coatings thus obtained are strongly adherent to plastic surfaces and their conductivity is relatively low.

The principal object of the invention is to provide a process for the production of metal coatings by chemical means.

Further objects will become apparent from the following description.

The objects of the invention are accomplished by treatment of the objects to be coated with an aqueous metal salt solution and a reducing agent, said treatment consisting in that an aqueous metal salt solution and at least one boron-nitrogen compound which carries one to three hydrogen atoms at the boron atom and at least one organic group at the nitrogen atom to act on the objects to be metallised.

BN compounds to be considered for this process are for example N-alkyl-borazanes and N-alkylborazoles.

The following compounds are preferably used:

(a) Borozanes, R NBH (b) Borazenes, R NBH (c) Borazines, RNBH (d) Borazoles, (RNBH) Q XNQN" triethyl borazane, N isopropyl borazene, N-

f isopropyl borazine, N trimethyl borazole etc.

Alcohols or water-soluble ethers may be used as solubilizers, for example methanol, ethanol, dioxane, diethylleneglycol dimethyl ether and the like.

The concentration of the metal salts used for chemical plating such as nickel, cobalt, iron-II or zinc salts, may vary within wide limits.

Due to the great number of BN compounds the plating is possible at practically any pH value. When working in the alkaline range, the metals are kept dissolved by suitable complex formers, for example ammonia, potassium-sodium tartrate, sodium citrate, ethylene-diamine and the like. i

The plating temperatures comprise the range between 3,140,188 Patented July 7, 1964 ice 20 and 100 C. Thus, for example, chemical plating is possible at the following temperatures.

Reducing agent: Range "fi fg N-monomethylborazane 25-35 N,N-d.imethylborazane 35-60 N-isopropylborazene 30-50 N-tn'methylborazole 50-60 N,N',N"-trimethylborazane 60-80 N,N',N"-triethylborazane -95 The coating obtained according to the process for chemical plating with BN compounds on metal surfaces such as iron, steel, copper, brass, aluminium etc. or on plastic surfaces such as acetyl cellulose, polyglycol-terephthalate, polyacrylonitrile etc. are smooth, lustrous and adhesive.

The adhesiveness of these coatings to plastic surfaces is so strong that they can only be removed by destroying the plastic surface. The coatings exhibit metal conductivity. They can be reinforced galvanically Without intermediate treatment.

Compared with the known processes for chemical platting, the use of BN compounds as reducing agent for metal deposition on metal and plastic surfaces offers the following advantages:

(a) Variety in the choice of reducing agents (b) Range of plating temperature between +20 C. and

(0) pH range between 2 and 14 (d) Economy of the process The economy of the process becomes apparent when investigating the reduction equivalents. With the use of sodium hypophosphite, for example, 4-4 g. of NaH PO are required per reduction equivalent; with the use of N- monomethyl borazane there are required 7.5 g. of CH NH BH with N,N'-diethyl-borazane, 14.5 g. of (C H NHBH Since mixtures of anhydrous metal salts and B-N compounds do not react with one another, these mixtures can be marketed. The desired plating bath is obtained by introducing such a mixture into water.

The following examples are given for the purpose of illustrating the invention.

Example 1 A foil of polyglycol-terephthalate is consecutively pretreated in the following baths:

(a) 200 g. of sodium hydroxide+0.5 g. of an alkyl sulfonate of the Mersolate type+800 g. of water; duration of stay, 5 minutes; temperature, 50-60 C.

(b) 100 g./litre of zinc (II) chloride+200 cc./litre of concentrated hydrochloric acid+0.5 g./litre of an alkyl sulfonate of the Mersolate type; duration of stay, 5 minutes; temperature, 50-60 C.

(c) 0.5 g./litre of palladium chloride+10 cc./litre of concentrated hydrochloric acid; duration of stay, 5 minutes; temperature, 20-30 C.

The chemical plating is carried out in a borazane bath of. the following composition:

45 g./litre of nickel chloride 5 g./litre of cobalt chloride cc./litre of a concentrated ammonia solution 1 g./litre of N-methylborazane 50 cc./litre of methanol The bath temperature is 25-35 C., the duration of stay is .5 minutes. A silvery coating is thus obtained having a resistance of 0.2 to 0.5 ohm/cmP.

A coating of equal properties is obtained if N-methylborazane is replaced by N-ethyl-borazane.

Example 2 A foil of acetyl cellulose is subjected to a pretreatment in the baths:

(a) 100 g. of sodium hydroxide+0.5 g. of an alkyl sulfonate of the Mersolate type+900 g. of'water (b) and (c) as in Example 1 Example'j A foil of cellulose acetobutyrate is subjected to the pre-treatment of Example 2 and chemically plated in a bath of the following composition: 100 g./litre of nickel sulphate, g./litre of N,N',N"-trimethyl-borazane, 1.0 cc. of N/l hydrochloric acid, 30 cc./litre of tertiary butanol.

The bath temperature is 6080 C., the pH value is 4.5, the duration of stay is 5 minutes. coating is thus obtained with a resistance of 0.8 ohm/ cm.

Example 4 100 g. of nickel sulphate are dissolved in 500 cc. of water and 400 cc. of methyl alcohol and 3 g. of N-ethylborazane are added thereto. A strongly adhesive compact nickel coating is obtained on a copper sheet introduced 'into the solution heated to 50-60 C.

Example 5 100 g. of cobalt sulphate are dissolved in 500 cc. of water and a solution of 3 g. of N,N-diethyl-borazane in 500 cc. of methanol is added thereto. A brass sheet is suspended in this solution heated to 6070 C. A strongly'adhesive cobalt coating is formed on the brass sheet. Coatings on copper and iron can be produced in the same solution. Plastics can likewise be plated in this solution after a suitable pre-treatment.

Example 6 V 100 g. of nickel sulphate are dissolved in 500 cc. of water, and 500 cc. of methanol and 3 g. of N,N-diethy1- borazane are added thereto. After preliminary treatment as described in Example 1 or 2, iron, brass, copper and plastics can be provided at 6070 C. with a strongly adhesive nickel coating.

Example 7 50 g. of nickel sulphate are dissolved in 500 cc. of water and 250 ml. of diethylene-glycol dimethyl ether (Diglym) and 5 g. of N,N',N"-triethyl-borazane are added thereto. The pH value is adjusted to 2-4 with acid. A suspended copper sheet is coated at 85-95" C. with a strongly adhesive nickel layer.

Example 8 A polyglycol-terephthalate foil is pre-treated as described in Example 1 and chemically plated in a bath of the following composition: g./litre of iron (H) sulphate, 100 g./litre of sodium citrate, 30 g./litre of nickel sulphate, 60 gf/litre of Seignette salt, 3 g./litre of N,N- dimethyl-borazane, 50 cc./litre of methanol.

The pH value is adjusted to 89 with sodium hydroxide solution, the temperature is 6070 C. An iron-nickel coating is thus obtained which adheres strongly to the foil. Iron, brass and copper can also be chemically plated in the same bath. The coat contains about 70% of iron.

Silvery metal Example 9 An iron, copper and brass sheet having the dimensions 50 mm.x mm. is introduced, after degreasing, into a bath of the following composition: 30 g./litre of iron (II) sulphate, 10 g./litre of cobalt sulphate, 50 g./litre of Seignette salt, 2 g./litre of N,N-dimethyl-borazane, 50 cc./litre of ethanol.

The pH value is adjusted to 810 with a sodium hydroxide solution, the plating temperature is 80-90 C. An adhesive iron-cobalt coating is obtained on all plates. Plastics can also be chemically plated in the same bath after a preliminary treatment as described in Example 1.

Example 10 (a) 5 g. of nickel sulphate, 5 g. of cobalt chloride, 5 g. of ammonium chloride and 5 g. of zinc chloride are dissolved in water. 160 cc. of a concentrated ammonia solution are added thereto and the mixture is made up to l'litre with water. After the addition of 2 g. of N,N'-dimethyl-borazane and 50 cc. of dioxane, copper, iron, brass and plastics can be coated with an adhesive Ni-Co-Zn layer after preliminary treatment as described in Example 1.

(b) Nickel-zinc coatings are obtainedfrom a bath of the following composition: 5 g./litre of nickel chloride, 5 g./litre of zinc chloride, 5 g./litre of ammonium chloride, 160 cc./ litre of concentrated ammonia, l-2 g./litre of N-monoor N,N'-dimethyl-borazane, 50 cc./litre of methanol. The bath temperature is 4060 C. The coatings contain up to 20% of zinc.

Example 11 In a bath of the following composition: 50 g. of nickel sulphate, 500 ml. of water, 500ml. of methanol, 2 g. of N,N-dimethyl-borazane, plastics, copper, iron and brass can be plated adhesively at pH 5-6 and a temperature of 35-45 C. after preliminary treatment as described in Example 1. I

N,N'-dimethyl-borazene is prepared by heating dimethyl-borazane under a nitrogen stream at 400 mm. Hg and C. The analysis corresponds to dimethyl-borazane.

Example 12 .Iron, copper, brass and plastics can be chemically plated so as to be adhesive at pH 5-6 and 3040 C. in a bath of the following composition: 50 g. of nickel sulphate, 500 cc. of water, 500 cc. of methanol, 12 g. of a mixture of N-isopropyl-borazane and N-isopropylborazine.

Chemical plating with a borazene-borazine mixture can also be carried out from ammoniacal baths at a temperature between 30 and 50 C.: 25 g. of cobalt chloride, 25 g. of nickel chloride, cc. of ammonia, 750 cc. of water, 12 g. of a mixture of N-isopropyl-borazene and N-isopropyl-borazine, 100 cc. of methanol.

Example 13 100 g. of nickel sulphate are dissolved in 500 cc. of water, 500 cc. of methanol are added thereto and the mixture is heated to 50 C. After the addition of about 2-3g. of N-isopropyl-borazine, plastics, brass, iron and 7 copper can be chemically plated.

N-isopropyl-borazine is obtained by further heating of the benzene-borazine mixture used in Example 12. The analysis corresponds to a 99% N-isopropyl-borazine.

Example 14 (a) 100 g. of nickel sulphate are dissolved in 500 cc. of Water, 500 cc. of methanol are added and the mixture is heated to 5060 C. After the addition of 2 g. of N- trimethylborazol copper, iron, brass and pre-treated plastics can be chemically plated.

(b) 25 g. of cobalt chloride and 25 g. of nickel chloride are dissolved in 700 cc. of water. After the addition of 200 cc; of dioxane and 2 g. of N-trimethylborazole, pre-treated plastics, iron, brass and copper can be chemically plated at 5060 C.

N-trimethyl-borazole is obtained by heating N-monomethyl-borazane to 120 C. under a nitrogen stream at 400 mm. Hg. The analysis corresponds to N-trimethylborazole.

We claim:

1. A bath for the plating of metal and plastic surfaces by chemical deposition, comprising an aqueous solution of at least one metal salt selected from the group consisting of cobalt, nickel, iron II and zinc and at least one boron nitrogen compound selected from the group consisting of:

(a) borazanes of the formula R NBH (b) borazenes of the formula R NBH (c) borazines of the formula RNBH (d) borazoles of the formula (RNBl-D wherein R is selected from the group consisting of alkyl, aryl, hydrogen, and wherein at least one R is of the group alkyl and aryl, and organic compound solubilizing the boron nitrogen compound in the aqueous medium and selected from the group consisting of alcohols and watersoluble ethers, the said boron nitrogen compound being a reducing agent in said solution in a pH range from 2 to 14 and at a temperature range from 20 to 100 C.

2. A bath as claimed in claim 1, wherein the plating bath contains 50 grams of nickel sulfate, 500* ml. of water, 500 ml. of methanol, 1 to 2 grams of a mixture of N- isopropyl borazane and N-isopropyl-borazine, the bath having a pH value between 5 to 6 and a temperature between 30 and 40 C.

3. A bath according to claim 1, wherein the plating bath contains 25 grams of cobalt chloride, 25 grams of nickel chloride, 160 ml. of ammonia, 750 ml. of water, 100 ml. of methanol and 1 to 2 grams of a mixture of N-isopropyl borazane and N-isopropyl borazine.

4. A bath according to claim 1, wherein the plating bath contains 100 grams of nickel sulfate, 500 m1. of water, 500 ml. of methanol, 2 grams of N-trimethyl borazole.

5. A bath for the plating of iron, brass and copper which bath contains 25 grams of cobalt chloride, 25 grams of nickel chloride, 700 m1. of water, 200 ml. of

6 dioxane and 2 grams of N-trimethyl borazole, the bath having a temperature between and C.

6. A bath for the plating of brass, copper and iron which contains 100 grams of cobalt sulfate, 500 ml. of water, 500 ml. of methanol, 3 grams of N,N-diethyl borazane, the bath having a temperature between 60 and C.

7. A bath for the plating of metal and plastic surfaces by chemical deposition, comprising an aqueous solution of at least one metal salt selected from the group consisting of cobalt, nickel, iron II and zinc, and at least one boron nitrogen compound selected from the group consisting of:

(a) borazanes of the formula R N-BH (b) borazenes of the formula R N--BH (c) borazines of the formula RNBH (d) borazoles of the formula (RNBH) wherein R is selected from the group consisting of lower alkyl having at least 2 carbon atoms, aryl, and hydrogen, and wherein at least one R is of the group alkyl and aryl, and an organic compound solubilizing the boron nitrogen compound in the aqueous medium and selected from the group consisting of alcohols and water-soluble ethers, the said boron nitrogen compound being a reducing agent in said solution in a pH range of from 2 to 14 and at a temperature range of from 20l00 C.

8. A bath according to claim 1 wherein the boron nitrogen compound is a water-insoluble borazane.

9. A bath according to claim 7, wherein the boron nitrogen compound is a water-insoluble borazane.

References Cited in the file of this patent UNITED STATES PATENTS 2,461,661 Schlesinger et al. Feb. 5, 1949 2,942,990 Sullivan June 28, 1960 2,990,296 Hoke June 27, 1961 3,062,666 McLeod Nov. 6, 1962 3,063,850 Mikulski Nov. 13, 1962 OTHER REFERENCES Hurd: Chemistry of the Hydrides (1952), pub. by John Wiley and Sons, Inc. pp. 77 and 84 relied on.

o UNITED STATES PATENT OFFICE (-IERTIFICATEv OF CORRECTION July T 1964 Patent No.: 3,,l40 l88 Eberhard Zirngiebl et alg he above numbered patpears in t Patent should read as rtifi ed that error ap (1 Letters It is hereby ce tion and that the sen.

ent requiring correc corrected below.

Column 4, line 64 for "benzeneborazine" read bOIHZGDBbOIHZiDe -u Signed and sealed this 10th day of November 1964,-

(SEAL) Attest:

EDWARD J.. BRENNE ERNEST W. SWIDER' Attesting Officer Commissioner of Patent

Claims (1)

1. A BATH FOR THE PLATING OF METAL AND PLASTIC SURFACES BY CHEMICAL DEPOSITION, COMPRISING AN AQUEOUS SOLUTION OF AT LEAST ONE METAL SALT SELECTED FROM THE GROUP CONSISTING OF COBALT, NICKEL, IRON II AND ZINC AND AT LEAST ONE BORON NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF: (A) BORAZANES OF THE FORMULA R3N-BH3 (B) BORAZENES OF THE FORMULA R2N-BH2 (C) BORAZINES OF THE FORMULA RN-BH (D) BORAZOLES OF THE FORMULA (RH-BH)3 WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL, HYDROGEN, AND WHEREIN AT LEAST ONE R IS OF THE GROUP ALKYL AND ARYL, AND ORGANIC COMPOUND SOLUBILIZING THE BORON NITROGEN COMPOUND IN THE AQUEOUS MEDIUM AND SELECTED FROM THE GROUP CONSISTING OF ALCOHOLS AND WATERSOLUBLE ETHERS, THE SAID BORON NITROGEN COMPOUND BEING A REDUCING AGENT IN SAID SOLUTION IN A PH RANGE FROM 2 TO 14 AND AT A TEMPERATURE RANGE FROM 20 TO 100*C.