US2400785A

US2400785A - Preventing the tarnishing of

Info

Publication number: US2400785A
Authority: US
Publication date: 1946-05-21
Anticipated expiration: 1963-05-21

Description

Patented May 21, 1946 PREVENTING THE TARNISHING F SILVERWARE John B. Rust, West Orange, N.

Montclair Research Corporation,

of New Jersey 1., assig'nor to a corporation No Drawing. Application April "I, 1944,

Serial No. 530,064

7 Claims.

This invention relates to a method of retarding the tarnishing of silver with particular reference to retarding the surface staining of silverware.

The ready tendency for surfaces of silver to tarnish and stain on exposure to ordinary atmospheric conditions presents a constant cleaning problem which is annoying and labor-consuming. A solution of this problem would be of definite benefit not only to stores having silverware on exhibit but also to households where such silverware as candlesticks, bonbon dishes, trays, etc., are usually left exposed on tables, sideboards, etc., and consequently need frequent cleaning.

It has been suggested to protect silverware by applying a thincoating of collodion. It has also been suggested to protect silverware by confining it in a restricted space exposed to the vapors of a volatile amine. While this might be accomplished under certain conditions in a store, it would be impractical in a home.

I have now found a practical solution for sub stantially retarding the formation of tarnish films and stain on the surfaces of silverware without any necessity whatsoever of confining the silverware to a restricted space.

It is known that polyethylene polyamines may be partially neutralized by an aliphatic acid to give water-soluble products. I have now found that the water-soluble products of the partial neu tralization ,of polyethylene polyamines by fatty acids exert an excellent protective action on silverware. Such partial neutralization products include fatty acid salts and the amides obtained by heating these salts, the salts being formed with less fatty acid than is required completely to neutralize the polyethylene polyamine.

In practising the invention it is merely neces- 'sary to rub down the silverware with a dilute solution of a water-soluble polyethylene polyamine salt or amide. A satisfactory method of accomplishing the above is to make a 1% to 5% (preferably a 2%) solution in water, impregnate with this solution a wad of cotton, then rub this wad lightly over clean silverware, making certain that a film is left on every part of the surface which is to be protected. The film is then allowed to dry and given a slight bufiing. The solution can also be applied by dipping or spraying. silverware so treated will remain untarnished for periods over a month when left in ordinary atmospheric conditions, while an untreated piece will be badly stained and tarnished when left under similar conditions.

As polyethylene polyamine I can use diethylene triamine, triethylene tetramine, tetraethylene pentamine, and the l'ke. As fatty acid i can use aliphatic acids possessing ten or more carbon atoms in the molecule. Both saturated and un saturated acids are satisfactory, such as lauric, stearic, palmitic, oleic and the fatt acids of vegetable and animal oils and fats. Considering cost and ease of use, I find that oleic acid is excellent.

Amides are obtained by heating the polyethylene polyamine fatty acid salts. For example, heating the salt obtained from 2 moles stearic acid and 1 mole tetraethylene pentamine gives distearoamido tetraethylene triamine. Other amides suitable for use herein are monostearoamido diethylene diamine (from 1 mole stearic acid and 1 mole diethylene triamine), monolauramido triethylene triamine (from 1 mole lauric acid and 1 mole of triethylene te'tramine) etc. Where greater water-solubility is needed the solubility of the amide may be improved by means of an acid such as hydrochloric or acetic.

The description given in the following examples should not be construed as limiting, but only by way of illustration since those skilled in the art may make numerous variations in the process of this invention without departing from the scope and spirit thereof.

Example 1.--Two moles of oleic acid are mixed and warmed with 1 mole of tetraethylene pentamine. A solution of 2% tetraethylene pentamine dioleate, 30% isopropanol and 68% water is made and applied to silverware by impregnating a cotton wad with the solution, rubbing this wad lightly over clean silverware, allowing the film to dry and giving it then a, slight buiiing. After application and bufimg the silverware has a bright appearance and remains bright even after a month's exposure to ordinary atmospheric conditions.

Example 2.-One mole of diethylene triamine is mixed with '1 mole of oleic acid and warmed to form the mono-oleate. A 2% aqueous solution of the salt is then made and applied to silverware in the manner described in Example 1. Silverware so treated remains bright after one month.

Example 3.One mole of diethylene triamine and 1 mole of stearic acid are heated for 3 hours at 250 C. to form monostearamido diethylene diamine with evolution of water. A 2% aqueous solution of the monostearamide is then made and applied to silverware in the manner described in Example 1. Silverware so treated is still bright after exposure for a month.

I claim:

1. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of a watersoluble product of the partial neutralization of a polyethylene polyamine by a fatty acid of more than 10 carbon atoms.-

2. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of a. watersoluble salt of a polyethylene polyamine and a fatty acid of more than 10 carbon atoms, said salt being formed with less fatty acid than is required to completely neutralize the polyamine.

3. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of a water-soluble amide formed by heating a salt of a polyethylene polyamine and a fatty acid of more than 10 carbon atoms, said salt being formed with less fatty acid than is required to completely neutralize the polyamine.

4. A process for protecting silverware from tarnishing which comprises applying to the surface thereof a dilute aqueous solution of a water-soluble product of the partial'neutralizatlon of a polyethylene polyamine by a, fatty acid of more than 10 carbon atoms, removing the water therefrom and buffing the surface.

5. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of tetraethylene pentamine dioleate.

6. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of diethylene triamine mono-oleate.

7. A process for protecting silverware from tar nishing which comprises depositing on the surface thereof a. thin continuous film of monastearamido'diethylene diamin JOHN B. RUST.