US3345295A - Copper cleaning compositions - Google Patents

Description

United States Patent 3,345,295 COPPER CLEANING COMPOSITIONS Morton Schwarcz, Watchung, N.J., and Myron Barchas, New York, N.Y., assignors to Shulton, Inc., Clifton, N.J., a corporation of New Jersey No Drawing. Filed Mar. 3, 1966, Ser. No. 531,365 5 Claims. (Cl. 252-90) This application is a continuation-in-part of the copending applications Serial Nos. 331,388 and 331,389, both filed on February 13, 1963, both now abandoned.

This invention relates to copper cleaning preparations including self-dispensing copper cleaning and polishing preparations, such as may be dispensed from a pressurized container as a liquid stream, spray or foam. The reference herein to copper means copper and copper alloys, including brass and bronze.

Copper cleaning preparations, including such preparations which both clean and polish the copper surface heretofore known, are objectionable for a number of reasons. Many of such presently available preparations are strongly acid and are therefore highly irritating to the user and corrosive to the copper in that, in addition to removing copper oxides, they also corrode the copper base. Strongly acid preparations, of course, cannot be packaged in inexpensive metal containers. Other such presently available preparations are highly toxic and have an objectionable odor. To our knowledge, no copper cleaner was available prior to our invention which could be dispensed from a valve controlled pressurized container such as the well known aerosol type containers, had good shelf life, low toxicity, non-irritating, rapid cleaning action, little or no odor, and was substantially non-corrosive to the copper base. The expression selfdispensing is used herein to mean such aerosol type preparations! The compositions of this invention substantially alleviate the above-cited difficulties of previously known copper cleaning compositions.

The aqueous copper cleaning compositions described and claimed herein are substantially free of oxyboron compounds such as sodium or potassium tetraborate and are formulated to contain as essential active constituents at least one dissolved te co und such as an alkali metal thiosulfateor ammonium thiosulfate, and at least o -alk 1 me a tan having a normal alkyl group containing from 12 to 22 carbon atoms. The mercaptan group is on the number one carbon atom in the alkyl chain. The mercaptan constituent is emulsified with the aqueous thiosulfate solution. The compositions may be prepared as free flowing liquids, as pastes or, in admixture with a suitable propellant, as self-dispensing compositions. Other ingredients such as abrasives, surface active agents, grease solvents, thickeners, perfumes and the like may be mixed with the basic compositions for special purposes. If desired the compositions can be impregnated or otherwise absorbed on paper, cloth or natural or synthetic sponges. In this application of the invention it is preferred to drive off the water to provide dry products which can be again wetted when ready for use to reconstitute the aqueous compositions of the invention. The aqueous compositions can be used as in dips, sprays or other conventional applications.

Surface active agents are a well-known class of chemical compounds having the property of altering the surface tension of liquids in which they are dissolved or dispersed. Specific types of surface active agents, depending upon the purpose for which they are employed may be identified as emulsifiers, detergents, soaps, dispersing agents, fiocculating agents, etc. In the compositions of this invention surface active agents are employed to emulsify the alkyl mercaptan in the aqueous solution of the thiosulfate.

The preferred alkali metal thiosulfates are sodium and potassium thiosulfate because of their ready availability. Ammonium thiosulfate is especially preferred because of its high solubility. The selected thiosulfate or thiosulfates may be employed in any concentration from about 5% by weight up to the solubility limit in the composition. (All concentrations in this disclosure and in the appended claims are given on a by weight basis, based on the total weight of the composition.)

While the action of these thiosulfates in effecting the cleaning of copper and copper alloys is not fully understood, it is believed that the thiosulfates reduce the cupric oxide to the cuprous state; the cuprous compounds thus produced form water-soluble, copper-ammonium or alkali metal thiosulfate complexes. When the copper article treated with the cleaning and polishing preparation is wiped off with a cloth, paper or other absorbent member the complexes in solution are thus removed from the copper article leaving a clean surface.

As aforesaid, ammonium thiosulfate is preferred. It is highly soluble and the most effective of the thiosulfates. Sodium and potassium thiosulfates have lower activity toward copper oxides than ammonium thiosulfate and hence must be used at higher concentrations to attain equivalent cleaning action. Anhydrous ammonium thiosulfate is soluble in water at F. up to about 63% whereas the anhydrous sodium thiosulfate is soluble in water at 70 F. up to to about 33%. Anhydrous potassium thiosulfate is more soluble than the sodium salt but less soluble than the ammonium salt, being soluble in water at 70 F. up to about 49%. The preparation can contain from about 5% up to the solubility limit of the thiosulfate salt in water at room temperature, i.e., about 63% in the case of the ammonium salt, about 35% in the case of the sodium salt, and about 50% in the case of the potassium salt. Room temperature for the purposes of this disclosure may be considered as from 68 F. to 86 F. The preferred concentration of the thiosulfate in the preparation is from 10% to 20%.

These thiosulfates are rapid-acting under neutral and alkaline conditions to effect removal of copper oxides so as to produce a clean surface; they are substantially non-toxic, non-irritating and non-corrosive to the copper base. In the case of self-dispensing preparations, valve and actuator stoppage, due to deposition of crystals within the passageway through which the preparation is dispensed, are minimized by the strongly hygroscopic nagure of the thiosulfates, particularly ammonium thiosulate.

The alkyl mercaptans employed in the compositions impart tarnish-resistance to the cleaned copper surface. The property of the alkyl mercaptan to impart tarnish-resistance is believed to be due to bonding of the alkyl groups with the copper through the sulfur of the mercaptan to form a metallo-organic compound wherever the metallic substratum is exposed by the cleaning action of the thiosulfate. A mono-molecular layer of copper-sulfur-alkyl reaction product is thus produced on the surface, forming a protective barrier for the copper surface. The alkyl mercaptan also behaves as a fiocculating agent, aiding in the flocculation of such abrasive particles as may be employed, to prevent them from settling to form a hard dilatant layer which would clog the dip tube of a pressurized container for the preparation. The concentration of the mercaptan will vary with the molecular weight of the mercaptan employed, the higher the molecular weight the higher the concentration. In general, from 0.1% to 10% mercaptan is incorporated in the product; preferred concentration is from 0.1% to 4%. Low molecular weight meiiiii'n.

mercaptans are not suitable for use in the compositions of this invention because of their relatively high solubility in water. They would tend to be washed away when the composition is rinsed from the copper surface, rather than form the metallo-organic compound discussed above. Additionally, they have a most noxious odor.

Liquid tarnish-resistant copper cleaners of this type contain the selected thiosulfate, preferably at a range of from 10% to 20%, mixed with at least one n-alkyl mercaptan at a preferred range of 0.1% to 4%, with water as the carrier. The quantity of the latter will thus range from about 76% (where both ingredients are at their maximums) to about 90%. The order of mixing is not important. The mixing can be done at room temperature. The water content can be reduced by an amount equal to the amount of additional ingredients which may be employed.

It is preferred to adjust the pH of the preparation to within the range of 5 to 11, preferably from about 7 to about 8. Above 11, the preparation can be irritating to the eyes. Below 5, the thiosulfate decomposes and hence the preparation will have an unsatisfactory shelf life. Adjustment of the pH can be effected by the addition of alkali such as ammonium hydroxide where the preparation is too acidic and the addition of an acid such as sulfuric acid where the preparation is too basic.

As aforesaid, the thiosulfates react with the copper oxide to remove it and the mercaptans react with the exposed copper to inhibit tarnishing. If the copper object being treated is, for example, a decorative object such as a wall plaque, these are usually the only actions required. However if the object is a cooking utensil or other heavy duty wear it may be necessary to remove grease, oil or food deposits. For this purpose the basic compositions of this invention may be fortified by the inclusion of surfactants of the class generally identified by the term detergents. Heavy duty phosphate detergents, for example from about 1% to about 25% trior tetra-alkali metal detergents such as trisodium, tripotassium, tetrasodium or tetrapotassium phosphates are especially effective, although other detergents in substantially the same concentration range can also be employed.

It may also be desirable to add grease solvents such as butyl Cellosolve, methylene chloride and the like to the compositions to enhance their cleaning power. Where the grease solvent is not water soluble, additional surfactant may be required to emulsify it with the thiosulfate solution. The amount of such grease solvent may vary widely, forexample from about 1% to about 50%.

For cleaning cooking utensils and in the production generally of the preparations within the scope of the invention for imparting a shine or polish to the copper surface, conventional abrasive particles, that is grinding or polishing materials such as bentonite, anhydrous aluminum silicates, hydrous aluminum silicates and other abrasives having a particle size not exceeding about 50 microns may be employed. The preferred abrasives are anhydrous aluminum silicates of a particle size not exceeding 5 microns. An especially preferred abrasive is the hydrous aluminum silicate sold under the trade name Kaopolite SF. The amount of abrasive incorporated is specific; preparations may vary from about 1% to about 50%. For ease of manipulation, both in preparation and use, the preferred concentration is from 10% to 20% except that in self-dispensing preparations, the preferred concentration is from 1% to 10%.

The compositions may, if desired, be formulated as viscous pastes or slurries, with or without abrasives. Such products may be prepared by adding one or more thickeuers to increase the viscosity of the compositions. Any of a number of thickening agents generally employed for decreasing the fluidity of liquid compositions may be employed. Natural or synthetic gums such as acrylate polymers, guar or karaya are useful. Hydroxyethyl cellulose and sodium carboxymethyl cellulose may be mentioned by way of specific example. Paste compositions of this invention will ordinarily contain, in addition to the thiosulfate and mercaptans, one or more of the excipients mentioned above. Normally the non-aqueous ingredients are employed in concentrations at the high end of the ranges stated above, although not necessarily so. The water content of pastes within the purview of this invention rarely exceeds 40% Self dispensing products are preferred embodiments of this invention. As such the compositions may be compounded with a suitable propellant and stored in valve actuated pressurized containers of the usual type until ready for use. For this embodiment of the invention, the compositions are formulated wit-h the propellant in accodance with the usual practices of the aerosol art to produce two phase or three phase systems containing at least the thiosulfate and the mercaptan, to be ejected from the container as streams, sprays or foams. Foams are especially preferred since foaming acts to immobilize the preparation where it contacts the surface to be cleaned thereby permitting verticals surfaces to be cleaned.

Self dispensing compositions containing abrasives present a particular problem since the fined particles, which are employed in the same particle size and concentration described above, tend to settle out on standing and to form a dense, dilatant layer which tends to clog the dip tube and often cannot be redispersed even with the most vigorous shaking. Occasionally instead of settling the dilatant layer will form at the interface of the aqueous and propellant layer, and sometimes it will rise to the liquid propellant-gas propellant interface. In any event, the dense layer seriously affects the efiiciency with which the compositions may be dispensed. We have found that this problem can be substantially overcome by employing a mixture of two surfactant materials, flocculating surfactant and a dispersing surfactant. The paired surfactants will be referred to herein as complementary surfactants.

Each member of a complementary surfactant pair will have properties different from the other member of the pair. Effective complementary pairs may be selected from the usual classes of anionic, cationic, non-ionic and amphoteric surfactants. Often a particular surfactant will function as a flocculating agent in one system and a dispersing agent in another system.

The dispersing agent functions to distribute the abrasive particles throughout the medium, the flocculating agent to agglomerate the particles into soft masses comprising 'groups of particles loosely held together. Such agglomerates either remain dispersed or if they form into layers either at the bottom or at an inter-face, such layers are not dilatant layers, i.e. they are not so dense and closely packed that they cannot be readily redispersed by shaking. The phenomena can be readily observed by compounding the formulations in a bottle and observing the effect of the addition of various surfactants. Suitable self-dispensing compositions containing abrasives will also contain from about 0.05% to 10% of a dispersing surfactant and from about 0.05 to about 10% of a fiocculating surfactant, not necessarily in equal quantities.

As aforesaid, the dispersing and flocculating agents will have opposite properties. Thus a suitable complementary pair would be an anionic, a cationic surfactant or an anionic and an amphoteric surfactant with the pH of the composition adjusted so that the amphoteric surfactant is cationically charged. Pairs of nonionic surfactants can be employed provided one is hydrophobic and the other hydrophilic. Thus a suitable nonionic pair would be a polyoxyethylene (hydrophilic) surfactant and a copolymer of ethylene oxide and propylene oxide rendered hydrophobic by the presence of the latter.

In addition to their function as dispersing or flocculating agents, one or both of the surfactants may also aid in emulsifying the mercaptan and in forming a water-out emulsion of the class in which the propellant is dispersed in the aqueous phase. Such emulsions are especially preferred for the production of foams.

While the exact mechanism by which complementary pairs of surfacants function is not understood a possible explanation may be offered by considering the effect of a pair of cationic and anionic surfactants on the aluminum silicate abrasives. These abrasive particles have both. negative and positive charges unequally distributed on their surfaces, with the negative charges predominating so that the particles have a net negative charge. The addition of an anionic material results in neutralization of the positive charge sites thereby increasing the net negative charge and thereby improving dispersion. The addition of excess anionic material does not cause reversal of the dispersion.

The addition of a small amount of a cationic material causes neutralization of some of the negative charge sites giving some of the particles a net positive charge. These positive particles attract those particles with a remaining net negative charge, resulting in flocculation. Cationic materials, when added in such small amounts are classified, for purposes of the present invention, as fiocculating agents.

Further addition of the cationic material neutralizes the remaining negative particles, producing a system in which all of the abrasive particles have a net positive charge. The particles are therefore repelled by one another causing dispersion of the abrasive particles. When added in such amounts, the cationic materials are considered dispersing agents.

Anionic surfactants are, for purposes of this invention, classified as dispersing agents, not as flocculating agents. Examples of anionic materials which can be used are: (1) Alkyl aryl sulfonates (2) Alkyl sulfates (3) Sulfated amides (4) Sulfated amides (5) Sulfonated amides (6). Sulfonated amines (7) Sulfated'esters (8) Sulfated ethers (9) Sulfonated esters (10) Sulfonated ethers (l1) Alkylsulfonates (12) Soap (such as sodium and potassium salts of various fatty acids having at least 8 carbon atoms).

Examples of cationic materials which can be employed in the production of the preparations of this invention are: (1) Salts of simple primary and tertiary amines.

(2) Quaternary ammonium salts.

(3) Salts and quaternary derivatives of amino amides. (4) Salts and quaternary derivatives of imidazolines. (5) Salts and quaternary derivatives of amino esters.

Examples of non-ionic materials which can be used in preparing the copper cleaner and polisher embodying this invention are:

(1) Ethoxylated propylene oxide-propylene glycol condensates (Pluronics). (2) Fatty or rosin acid esters of polyoxyethylene glycols (Ethofats).

(3) Alkyl aryl polyglycol ethers such as alkyl phenyl polyethylene glycol ether (Tergitols and Igepols).

(4) Fatty alcohols ethers such as polyoxyethylated fatty alcohols (Emulphor and Renex).

(5) Fatty acid amides (Ninols).

(6) Ethoxylated fatty amides (7 Ester ethers (8) Ethylene and propylene oxide addition products of ethylenediamine (T etronics) Amphoteric surfactants, having both acidic and basic properties, act as dispersants in alkaline solution where the amphoteric material reacts more anionically and as fiocculants in acidic solution where the amphoteric reacts more cationically. At or near the isoelectric point the RiN in which R is an alkyl group containing from 8 to 18 carbon atoms; n is an integer from 1 to 2; M is sodium, potassium, ammonium, monoethanolamine, diethanolamine or triethanolamine; and X is hydrogen or an ethoxylated group having from 1 to 20 carbon atoms.

These detergents are sold under the trade name Deriphat. An example of such compounds is sodium N- lauryl fl-aminopropionate.

The alkali metal salts of the ethoxylated acyl alkyl amines, in which the ethoxylated groups have from 1 to 20 carbon atoms, preferably 10 to 15, are sold under the trade name Triton QS-15.

(2) Compounds having the formula in which R is an alkyl group having from 8 to 18 carbon atoms; n is an integer from 1 to 2', M is sodium, potassium, ammonium, monoethanolamine, diethanolamine or triethanolamine; and X is hydrogen or an alkyl group having from 1 to 20 carbon atoms.

Such amphoteric detergents are sold under the trade name Miranol.

It is generally desirable to determine the action of the surfactants used in any particular formulation by testing same in a sample of the formulation. By so doing surfactant combinations can be chosen having the desired properties of (l) flocculating the abrasive particles, (2) dispersing the fiocculated particles sothat the preparation upon standing in the pressured containers will not form hard dilatant layers which clog the dip tube, and (3) imparting foaming properties to the preparation when dispensed.

When a self-dispensing composition of the invention is desired, the propellant can be any known propellant compatible with the constituents of the formulation such, for example, as hydrocarbon propellants, e.g., propane, butane, pentane, isobutane, hexane, etc., halogenated hydrocarbons, such as trichloro-monofiuoro methane (Freon 11), dichloro-difluoro methane (Freon 12), tetrafluorodichloro ethane (Freon 114), pentafiuoro-monochloro ethane (Freon 115), trifiuoro-trichloro ethane (Freon 113), cyclic hexafiuoro-dichloro butane (Freon C 316), octafluoropropane (Freon 218), and cyclic octafiuorobutane (Freon C 318); liquefied gases; insoluble compressed gases such as nitrogen or soluble compressed gases such as carbon dioxide.

Where the abrasive particles are flocculated by a hydrophobic surfactant, being thus termed lipophilic flocs, they are compatible with the propellant phase and incompatible with the aqueous phase. When a propellant forming an upper layer above the aqueous phase is used, the abrasive particles fiocculated with a hydrophobic surfactant rise with the separating propellant. This is advantageous because a more stable non-clogging system is thus obtained; the dip tube remains open and the valve controlling flow unobstructed.

Abrasive particles which are dispersed by a hydrophilic surfactant provide a surface which is compatible with the aqueous phase and exhibit no tendency or at least limited tendency to separate with the propellant phase. The

abrasive particles stay in the water phase and upon long standing will settle to the bottom. Upon shaking of the container, however, the abrasive particles are readily redispersed.

The constituents, other than the propellant, can be mixed in any desired order and preferably at room temperature (2025 C.). The composition thus produced is introduced into the container and thereafter the propellant introduced either under pressure or as a refrigerated liquid in accordance with conventional techniques for producing pressurized packages such as aerosols.

The compositions of this invention are applied directly on the copper surface to be cleaned. In the case of the preferred foaming self-dispensing preparation the foam thus produced shows the area covered. After application the coating thus produced can be wiped off, rubbed into the surface or rinsed off, desirably with water. Wiping or rubbing can be effected using paper or cloth. Where a highly polished surface is desired, it is preferred to remove the coating by first rubbing it into the copper surface and thereafter rinsing the surface thus treated with water.

This invention includes copper cleaners and/or copper polishers constituted of an absorbent base or substrate such as cloth, including flannel cloth, paper toweling, high wet-strength papers, woven, knitted or felted, and sponges, including synthetic sponges, impregnated with the copper cleaner or copper cleaner and polisher preparations herein disclosed, both liquid and paste preparations with and without abrasive particles. The base or substrate can be impregnated with from to 125%, preferably 75% to 100%, of the selected copper cleaning composition. The thus impregnated base is then dried to form the product in the form of a pad or impregnated cloth, paper or sponge effective for cleaning copper surfaces and in the preferred embodiment containing the nalkyl mercaptan, imparting a tarnish-resistant surface thereto.

In use the pad, cloth, paper or sponge is moistened with water to reconstitute the copper cleaning composition with which the substrate or base is impregnated. The surface to be cleaned is then rubbed with the moistened pad, cloth or paper. This treatment can be followed with a wiping or rubbing treatment with a dry cloth or paper where a more highly polished surface is desired.

The following examples are given for illustrative purposes. It will be appreciated the invention is not limited 1 to these examp es EXAMPLE I A liquid copper cleaning composition is prepared by mixing the following ingredients:

Constituents: Percent Ammonium thiosulfate 15 Lauryl mercaptan 3 Water 80.5 Emulsifier (Miranol SM conc.) 1.0

Constituents: Percent Ammonium thiosulfate 15 Lauryl mercaptan 0.25 Carbowax polyethylene glycol 1500 35 Alkyl phenyl ether of polyethylene glycol (Tergitol Nonionic NPX) 3 Abrasive (bentonite) 27 Water 19.75 Total 100.00

EXAMPLE III A self-dispensing composition is prepared by mixing the ingredients listed below in a pressurized container and then adding 8.00% of isobutane under pressure:

Percent 3.60

Constituents:

Anhydrous aluminum silicate Dispersing and foaming agent (Tole Terge 332anionic) 1.30 Plocculating agent (Miranol SM conc.) 1.60 Ammonium thiosulfate 14.50 Lauryl mercaptan 0.25 Water 69.75 Thickener (Thycorthyn LV) 1 0.75 Perfume .25

Total 92.00

1 Magnesium calcium aluminate complex.

This example involves impregnating a cotton flannel cloth with the emulsion of Example I. The pick-up is 100% of the emulsion, i.e., the weight of the cloth is increased about 100%. The impregnated cloth is then heated to drive off the moisture and produce an impregnated cloth dry to the touch.

The dry cloth is moistened with water and used to clean a copper surface by rubbing same to provied a clean, tarnish-resistant surface.

EXAMPLE V This example involved impregnating a high wetstrength paper with the formulation of Example H. The amount of the paste of Example II thus applied to the paper is about The impregnated paper is then heated to drive off the moisture and produce an impregnated paper dry to the touch.

The dry paper may be moistened with water and used to clean a copper surface by rubbing same to provide a clean, tarnish-resistant surface.

Since certain changes can be made in copper cleaning and polishing preparations without departing from the scope of this invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A substantially oxyboron free aqueous copper cleaning composition containing as essential ingredients; (1) from about 5% to the solubility limit of a thiosulfate compound selected from the group consisting of alkali metal thiosulfates and ammonium thiosulfate and (2) from about 0.1% to about 10% of an n-alkyl mercaptan containing from 12 to 22 carbon atoms; all percentages being by weight based on the total weight of the composition.

2. A composition as in claim 1 in which the thiosulfate concentration is from 10% to 20% by weight and the mercaptan concentration is from 0.1% to 4% by weight.

3. A composition as in claim 1 containing from about 1% to about 50% by weight of an abrasive in particulate form having a particle size less than 50 microns.

4. A composition as in claim 1 in a valve actuated, pressurized container in admixture with from 0.1% to 75 by weight of a propellant.

5, A composition as in claim 1 absorbed on a substrate 9 selected from the group consisting of paper, cloth and 2,955,047 natural and synthetic sponge substrates. 3,014,844 3,031,408 References Cited 3,248,235 UNITED STATES PATENTS 6 2,403,821 7/1946 Morgan et a1. 252-91 2,550,434 4/1951 Viles et a1 252395 X 2,726,970 12/1955 Toth 255105X Terry 106-3 Thiel et a1 106--3 X Perlman et a1 252154X Pryor et a1. 106-3 LEON D. ROSDOL, Primary Examiner.

SAMUEL H. BLECH, Examiner.

M. WEINBLATT, Absistant Examiner.

Dedicatidn 3,345,295.M0rt0n Schwarcz, Watchung, N.J., and Myron Barchas, New York, N.Y. COPPER CLEANING COMPOSITIONS. Patent dated Oct. 3, 1967. Dedication filed Feb. 6, 1980, by the assignee, Sterling Drug Inc. Hereby dedicates to the Public the remainder of the term of said patent.

[Official Gazette, April 8, 1.980.]

Claims (1)

1. A SUBSTANTIALLY OXYBORON FREE AQUEOUS COPPER CLEANING COMPOSITION CONTAINING AS ESSENTIAL INGREDIENTS; (1) FROM ABOUT 5% TO THE SOLUBILITY LIMIT OF A THIOSULFATE COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL THIOSULFATES AND AMMONIUM THIOSULFATE AND (2) FROM ABOUT 0.1% TO ABOUT 10% OF AN N-ALKYL MERCAPTAN CONTAINING FROM 12 TO 22 CARBON ATOMS; ALL PERCENTAGES BEING BY WEIGHT BASED ON THE TOTAL WEIGHT OF THE COMPOSITION.