US2051697A - Liquid cleaner for silverware - Google Patents

Description

Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE LIQUID CLEANER FOR SILVERWARE Ohio No Drawing. Application December 31, 1934, Serial No. 760,047

'7 Claims.

The present invention relates to a liquid cleaner for silverware and has for an object the provision of a new type of cleaner that is more rapid in its action than the usual paste preparations for cleaning silver.

Another object of the invention is to provide a cleaner that removes tarnish from both flat and scroll work without laborious effort and which does not destroy the plate when used a large number of times.

A further object is to provide such a cleaner that will not dull or scratch the surface finish of the wares cleaned and which does not render the surface immune to repeated cleanings.

Another object is to provide a silver cleaner which is much milder in its action as to the amount of silver removed than the usual heretofore known silver cleaners or polishes and which furthermore produces a cleaned surface that appears to resist subsequent tarnish eight to ten times as long as when cleaned with other known and popularly accepted silver cleaners and polishes.

Another object of the invention is to provide a product that can be made and sold at prices favorably comparable with presently used cleaners and which at the same time can be stated to save 200% to 300% in labor required compared with the various popular creams and pastes, etc. These and other objects are attained by the means and in the manner hereinafter described.

Products made according to the present invention represent a true liquid silver cleaner, not a so-called plating compound and furthermore, are not of the abrasive type mixture which is known to be messy and to entail considerable labor.

Silverware tarnish is due principally to the accumulation of coatings of silver sulfide and oxide. Since even sterling silverware contains 7% of copper there is always a possibility of the con comitant formation of copper sulfide and oxide. Most silverware plating consists of very thin films and hence any abrasive action rapidly cuts down the plate and exposes the base metal. Paste, powder and the so-called cream silver polishes are all of the messy abrasive type and a great deal of time is usually consumed on each piece of ware that is cleaned. Scroll work is particularly difficult because the relief portion thereof is often abraded bare of plating in attempts to thoroughly clean the deeper set surfaces.

The commonly known electrolytic scheme using aluminum and a sodium bicarbonate solution 55, avoids the labors of the abrasive methods but is The classes of amines, and types of nitrogen 15 bearing compounds which can be classed as amines or amine compounds that have been found useful in products of the invention are first, those wherein two NHz groups attach to the same carbon atom; second, amines of the polyhydroxy alcohol type; and third, the addition products of the latter such as those attained by their treatment with carbon dioxide which upon heating regenerate the amine.

Any of the foregoing may be prepared as a water solution with a salt of the alkali metals or alkaline earth metals such as the sulphates, carbonates and chlorides of ammonia, the chlorides of sodium and potassium etc. and used in the presence of a piece of metal electropositive to silver, such as aluminum. The product of the Percent 1-3 diaminopropanol 2 NH4C1 0.5 Water 97.5

The manner of use is to maintain the solution of the above named ingredients at a temperature of Gil-95 C. The entire lot of silverware to be cleaned after having been washed in soapy water to remove superficial grease and dirt, is immersed in an aluminum pan of the solution at the temperature indicated, or in any other suitable vessel in contact with a piece of aluminum metal. The aluminum piece or vessel should be scoured clean and free of black deposit when different successive batches of silverware are cleaned therein. In a very short time after immersion. in the heated solution the tarnish is freed from the silverware and the more tenacious particles of dirt and grease in the scroll work is also released. The ware is then removed from the solution, washed in soapy water, rinsed in clear warm water and dried by rubbing with a soft cloth.

The solution may be used repeatedly upon successive articles or batches of silverware. When the solution has been used long enough to saturate it with sulfide so that an equilibrium point is reached, a brownish stain remains on the silver plate. This stain, however, is removable by a subsequent washing with soap and water and drying with a soft cloth. In some cases, the dirt and tarnish is best removed from scroll Workwith a brush and warm water and soap to insure separation of all the easily removed stains from the silverware after treatment as aforesaid. This is not a laborious task because the stain is soft and not tenacious and therefore requires no real abrasion for its removal. It is to be noted, however, that the appearance of the ware after re- .moval from the solution depends upon two factors, namely, first, the cleanliness of the aluminum pan, and second, the number of previous uses to which the solution has been put. This latter saturation or weakened condition can be overcome by adding approximately 1.25% of NH4C1 after the weakening has become apparent, but the cost of the solution is so relatively small as to permit of its disposal after each treatment of a batch of silverware. If the latter is to be advocated in the merchandising a water solution of only 1% of diaminopropanol with 0.25% NH4C1 may be used.

The surface of the plate is not altered by the use of the liquid cleaner of the invention, i. e. it is not scratched, nor does it become dull and gray. By a series of laboratory tests, it was determined that the plate on identical wares should last at least four times as long when cleaned by the herein described means and methods than it would if cleaned by other known means and methods. Additionally, and of further importance, is the fact that wares cleaned by the compound of the invention resist subsequent tarnish from eight to ten times longer than when otherwise cleaned.

While the 1-3 diaminopropanol product is of the more desirable nature in its action with NHlCl for the removal of tarnish it is to be understood that other amines may be useful.

The specific formula given may be varied in keeping with the foregoing explanation, i. e., a 1% to 3% aqueous solution of 1-3 diaminopropanol used in an aluminum pan with an electrolyte such as NH'lC]. or NaCl added to make from 0.01N to 0.5N solution.

While various concentrations of diaminopropanol and NaCl or NHqCl were found to be of some value, the former (NaCl) caused some frothing and clouding of the solution and was not deemed as satisfactory for household use as the solution containing ammonium chloride. The use of soap in this solution has not been considered entirely satisfactory because while assisting in the removal of grease and dirt from the silverware, it appears to retard the tarnish removing action of the solution.

The use of NH401 alone, while operative leaves a grayish coating and removes some free metallic silver and thus entails the use of mild abrasive paste as a subsequent operation which is not considered desirable technic. When ammonium chloride is used with an amine, the amine forms an addition product with I-ICl thus preventing the formation of silver chloride.

There must always be another metal that is electro-positive to silver in contact with the silverware during the cleaning operation, and while aluminum and its alloys are considered the best and are generally available in the household in some form, it is to be expected that other metals such as tin, zinc and iron are usable but not as eflicient as aluminum.

The reaction temperature is variable with the amount of use of the solution. When newly prepared, good results obtain at 149 F. and this temperature may be increased, as the solution ages with use, up to about 194 F.

The product of this invention with 1-3 diaminopropanol is very successfully used as a liquid silver cleaner. It has not been finally determined whether its successful operation is. dependent on its liberation of nascent ammonia or its solvent action or on a combination of both. It appears probable that the latter is the most plausible. The formula of this compound-is:

Another highly efficient formula which is to be understood to be within the scope of the invention is om-on-om NH: NHZ NH:

This compound can be made by the interaction of PC13 on glycerol under pressure. The mono-, di-, and trichlorohydrin formed are changed to the amines by treatment with an aqueous solution of ammonium hydroxide. The salts formed as byproducts in this method are desirable as catalysts in the tarnish removal bath. It is to be understood that the use of other amines such as aliphatic and aromatic amines and so also of the quaternary ammonium bases are comprehended within the scope of this invention.

The following represent products within the broad scope of the invention and are of notable efiiciency. All are to be used in the presence of aluminum or other metal electropositive to silver.

1. A dilute Water solution of diaminopropanol and NHILCI.

2. A dilute water solution of acetone diamine and NH4C1.

3. A dilute water solution of 1,3 diaminopropanol and (NH4)2CO3.

4. A dilute water solution of diaminopropanol carbon dioxide addition compound plus (NHi) 2CO3 plus NH4C1.

5. A dry powder soluble in watera. 1,3 diaminopropanol and (NH-QCOs b. Diaminopropanol carbon dioxide addition compound, (NH4)2CO3 and NHrCl.

a. Solid product derived from chlorinating isopropyl alcohol and treating with ammonia or ammonium hydroxide d. 1,6 diaminomannitol and NH4C1.

The manufacture of the product entails merely the mixing of the amine and the selected chloride with water.

The use of the product as previously explained consists merely in placing the solution in a container and heating it to from 149 F. to 194 F. and immersing all of the silverware to be cleaned therein in contact with a piece of metal electropositive to silver such as aluminum. The action is almost immediate, the sulphides or tarnish on the wares leaving them and depositing on the aluminum. A subsequent washing in soapy water and drying with a soft cloth completes the operation, leaving the finish on the wares the same as before they became tarnished. No immunity to subsequent rapid and successful cleaning by the same process is built up in this operation, as in the electrolytic NalCO3aluminum pan method, and the resistance to subsequent tarnish is notably increased.

From the foregoing it will be noted that the formula may be Varied considerably within the limits of the disclosure herein for various conditions under which it is to be used. Obviously the products of the invention that are most stable would be selected for merchandising, while under circumstances that permit of their immediate use, the formulas producing less stable compounds or mixtures may be desirable.

Other important factors in determining the,

formula selected is that of the Working temperature of the solution, the appearance ofcthe solution (whether clear or colored and cloudy) and the rate of tarnish removal.

1,3 diaminopropanol and 1,6 diaminornannitol are both useful but the former in a 1.5% solution containing 0.5% NH4C1 will successfully remove tarnish at C., while the latter is slower and works at higher temperatures and is furthermore apt to decompose and polymerize to produce colored solutions of cloudy appearance.

1,3 diaminopropanol carbon dioxide addition product in a 3% solution with 0.5% NH4C1 removes tarnish at 50-60 C. In this case the carbon dioxide functions to bring about the desired activity at a lower temperature and the ammonium chloride functions as an electrolyte and not to furnish nascent ammonia as it would at higher temperatures of say 85-90 C.

Ammonium carbonate is considered to be an excellent adjunct to a preparation of the character of this invention.

Ammonium carbonate in a 34% solution with an electrolyte salt such as KCI, NaCl or NH4C1 constitutes a formula applicable to silver tarnish removal at from 35-40 C. and in the presence of a metal electropositive to silver.

Urea in a 2% solution in the presence of an electrolyte and a metal electropositive to silver will also remove tarnish from silver and it is also a valuable addition to preparations such as previously set forth.

In summary, it will be noted that only a few classes of amines are applicable to silver tarnish removal. The amines of polyhydroxy alcohols are notable among these and amines containing two NI-Iz groups to the same carbon atom are useful.

Silver tarnish removal preparations can be made with these amines, the first group being active with or without the addition of other compounds such as electrolytes or ammonia producing salts. These may be divided into two groups classified as first, efiicient but too unstable as solutions for commercial distribution; and second, products that are efficient and stable over long periods of time that permit of retail distribution and domestic use.

Those of the first group would be acceptable in those environments wherein they could be used immediately or shortly after making. This group includes products comprising acetone diamine and the chlorinated products of isopropyl alcohol neutralized with ammonia gas, aqueous ammonia or.

given. Parts 1,3 diaminopropanol carbonate Ammonium carbonate -1 2 Ammonium chloride Urea (optional) 1 This formula produced as'white powder is readily made into a 3% solution in the home and effectively removes silver tarnish at 30 10 C. in the presence of a metal electropositive to silver, such as aluminum.

Wares cleaned with the preparations made according to the teachings herein do not tarnish again as quickly as those not treated.

What is claimed is:

1. An immersion solution for cleaning silver tarnish in the presence of a metal electropositive to silver comprising diaminopropanol, NI-IiCl and. water to form a 1% to 3% solution.

2. An immersion solution for cleaning silver tarnish in the presence of a metal electropositive to silver comprising 1,3 diaminopropanol, (NI-I4) 2CO3 and water.

3. An immersion solution for cleaning silver tarnish in the presence of a metal electropositive to silver comprising diaminopropanol carbondioxide addition compound, (NH4)2CO3, NH4C1 and water.

4. A composition of matter of the class de-v scribed comprising a dry powder for solution in water and for use in the presence of a metal electropositive to silver for silver tarnish removal comprising 1,3 diaminopropanol, and (NI-l4) 2CO3.

5. A composition of matter of the class described comprising a dry powder for solution in 7 water and for use in the presence of a metal electropositive to silver for silver tarnish removal i comprising diaminopropanol carbondioxide addi tion compound. (NI-14) 200s and NH4C1.

6. A composition of matter of the class described comprising a dry powder for solution in water and for use in the presence of a metal electropositive to silver for silver tarnish removal comprising: Parts 1,3 diaminopropanol carbondioxide addition compounds approximately 3 Ammonium carbonate do 2 Ammonium chloride do Urea do 1 7. An immersion solution for cleaning silver in the presence of a metal electropositive to silver comprising a substance selected from the group consisting of diaminopropanol, and diamino propanol carbon dioxide addition compound.

WILMER C. GANGLOFF. RUSSELL H. HIERONYMUS.