US3342330A - New product and process - Google Patents

Description

United States fPatent C) 3,342,330 NEW PRODUCT AND PROCESS Harry W. Buchanan, Milford, Pa, assiguor to M & T Chemicals Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed May 5, 1964, Ser. No. 365,174 Claims. (Cl. 206-84) This invention relates to a method of preparing novel collapsible tubular metal containers.

As is well known to those skilled in the art, collapsible tubular metal containers such as aluminum metal containers may be used in connection with a wide variety of products. These containers have been found to have widespread use in the packaging of chemically inert materials, such as tooth paste, shaving cream, hand lotion, etc. It has been observed however, that certain compositions may be sufiiciently reactive to a degree which prevents packaging in aluminum tubes. For example, although many tooth pastes have heretofore been packaged in aluminum metal tubes, it has been found that those tooth pastes containing certain active ingredients such as stannous tin or fluorides, including stannous fluoride, may be sufliciently reactive to corrode the container.

For example, a typical aluminum tooth paste tube containing no corrosively active materials may have an indefinitely long shelf life under normal shelf conditions. In order to estimate shelf life under normal conditions an accelerated storage test may be employed. Under accelerated shelf life tests at 43 C., such a tube may be free of perforation for at least several months. By comparison, an aluminum tube containing tooth paste, identical to the standard but additionally containing 1.52% stannous fluoride would last only about three days at which time it may be preforated.

As a result, it has heretofore been the practice to market fluoride-containing tooth paste in lead tooth paste tubes. This is undesirable because the lead tubes cost more to fabricate and contain an uneconomically large amount of leadthis results inter alia from the required increased wall thickness of lead. Furthermore the use of lead metal raises the possibility of problems arising because of the well known toxicity of lead. This factor requires e.g. the use of a plastic spout because the action of the air with the contents in the presence of lead may discolor the tooth paste.

It is an object of this invention to prepare a novel collapsible tubular aluminum container. Other objects will be apparent to those skilled in the art on inspection of the following description.

In accordance with certain of its aspects the method of this invention for preparing a collapsible tubular aluminum container comprises forming an aluminum container from an aluminum blank; cleaning said aluminum container; and contacting at least the interior surface of said cleaned aluminum container with an aqueous alkaline bath containing a stannate salt selected from the group consisting of sodium stannate and potassium stannate; maintaining said aluminum container in contact with said bath for time sufiicient to deposit a surface layer of tin thereon; and separating from said bath said aluminum container bearing said surface layer of tin.

In accordance with certain of its other aspects, the novel composition of this invention comprises a collapsible tubular aluminum container having a surface layer of tin on the interior surface thereof.

Preparation of the aluminum con-tainer of this invention may include the extrusion of a slug or coin of aluminum metal, which may be substantially pure aluminum, in an impact extrusion press. During extrusion, the slug on impacting may follow the die to form an openended aluminum metal tube.

The so-formed metal tube may then be trimmed to uniform length, and cleaned as by immersion in a cleaning solution. Typically such a cleaning solution may be an aqueous solution containing 15 g./l.60 g./l., say 30 g./l. of sodium carbonate and 15 g./l.60 g./l., say 30 g./l. of trisodium phosphate. During this cleaning, the aluminum tube may be degreased and mildly etched. The tube may then be rinsed and immersed in l0%-50%, say 25% nitric acid thereby neutralizing the alkali and removing any smut which may be present on the surface of the aluminum.

The so-treated aluminum tube may then be further treated by contacting at least the inner surface thereof with an aqueous alkaline bath containing a Iongkindchelating agent, and a stannate salt selected from the group consisting of sodium stannate and potassium stannate, maintaining said aluminum in said bath for time suflicient to deposit a surface layer of tin thereon; and withdrawing said aluminum from said bath.

Preferably the aluminum tube may be treated by contacting said aluminum in an aqueous bath consisting essentially of water, and a stannate salt selected from the group consisting of sodium stannate and potassium stannate; maintaining said aluminum in said bath for time sufiicient to deposit a surface layer of tin thereon; and withdrawing said aluminum from said bath.

The immersion baths which may be used in practice of this invention may be typicallymade up by dissolving potassium stannate and/or sodium stannate in water to form a bath containing from about 15 g./l. (grams per liter) to saturation, typically about 70 g./l. of the stannate salt, the resulting solution containing about 30 g./l. of tin. Sufficient potassium hydroxide and/or sodium hydroxide may be initially added to form a bath containing about 4 g./l. of the metal hydroxide to prevent precipitation of tin due to low pH during make up. During operation, the free alkali metal hydroxide may be maintained between about 0.5 g./l. and about 12 g./l., preferably between 1 g.l. and 8 g./l., say 4 g./l. Proper operation of the bath may normally be carried out at a pH sufliciently high to keep the stannate in solution. Since tin may precipitate from these baths at pH below about 11.5, normal operation of these baths may be at pH above this point and preferably at pH of at least 12. This pH may normally be maintained automatically by the hydroxide generated and it may not normally be necessary to add hydroxide to the baths. The required free hydroxide concentration may be initially attained by addition of potassium hydroxide or sodium hydroxide. During operation the bath may generate sufiicient hydroxide to maintain the desired concentration.

The Jongkind-chelating agent which may be used in practice of this invention may be a chelating agent which is characterized by the ability to complex or chelate at at least one metal selected from the group consisting of: copper in solutions containing at least 1.2 Normal hydroxide ion, and magnesium in solutions containing at least 0.7 Normal hydroxide ion, the chelating ability being present when the agent is present in amount of one and one-half moles per mole of copper or magnesium metal present.

In a preferred embodiment, the Jongkind-chelating agent may typically be an anion of an aminocarboxylic acid such as ethylene diamine tetraacetic acid; water soluble salts of this compound, typically alkali metal salts such as the disodium salt of ethylene diamine tetraacetate; the monosodium salt of N,N-dihydroxyethyl glycine, the trisodium salt of N-hydroxyethyl ethylene diamine triacetic acid, etc.

In accordance with certain other preferred aspects of this invention, the Jongkind-chelatingagent added to the solution may be in the form of an anion of a polyhydroxy carboxylic acid. In a highly preferred embodiment, this anion may be an anion having less than about 8 carbon atoms. The preferred anion maybe an anion of a polyhydroxy monocarboxylic acid, typified by the gluconate ion, the glucoheptonate ion, the glycerate ion, or of a polyhydroxy polycarboxylic acid typified by the saccharate ion or the tartrate ion. The preferred anions which may be employed may be gluconate, glucoheptonate, glycerate, and saccharate.

The anions may be added as sodium or potassium salts e.g. sodium gluconate, potassium gluconate, sodium saccharate, potassium saccharate, sodium glucoheptonate, potassium glucoheptonate, sodium glycerate, potassium glycerate, sodium tartrate, and potassium tartrate. The anion may alternatively be added as acid, typically gluconic acid, saccharic acid, etc. or as lactone, typically glucono-delta-lactone, the delta-lactone of glucoheptonic acid, etc.; etc. Mixtures of these compounds maybe employed. The Jongkind-chelating agent may be added, preferably with agitation, to the aqueous stannate bath independently or jointly with the stannates which are used to make up and also to maintain the baths. Presence of the Jongkindchelating agent is desirable to improve the characteristics of the tin deposit, reduce sludging, and maintain stable pH.

Preferably, the Jongkind-chelating agent may be employed as the salt in amounts of 0.01 mole to 0.25 mole, say 0.1 mole/ 1. When the agent is the anion of the polyhydroxy carboxylic acid, equivalent amounts of acid or lactone may be employed. Smaller amounts may be employed, but they do not substantially control the thickness of the immersion plate or the formation of the sludge. Greater amounts may be employed but no substantial additional improvement may be obtained thereby.

In accordance with the process of this invention, the surface of the collapsible aluminum container may be contacted with an aqueous bath containing stannate. Contacting may be by immersion of the tube in the bath, by spraying or brushing the bath onto the surface of the container, etc. For the sake of convenience, reference will hereinafter be made to contact by immersion. Immersion plating in accordance with this invention may be carried out between room temperature of e.g. 20 C. and 90 C., and preferably between 40 C. and 80 C., say 60 C. Immersion time may be as little as 30 seconds, but it is usually between 1-6 minutes, say 4 minutes. During this time, aluminum may be coated with a layer of tin of desired thickness.

For make up and maintenance of the baths, preferred compositions may contain 80%99% by weight of potassiurn stannate and/ or sodium stannate and 1%20% of at least one compound containing the Jongkind-chelating agent, typically an anion of a polyhydroxy carboxylic acid. Preferred compositions of matter may contain 90%-98% of the stannate and 10%2.% of at least one Jongkind-chelating agent, e.g. a compound containing an anion of a polyhydroxy carboxylic acid. The compositions containing lower percentage of the agent e.g. 2%- 5% may be preferred for replenishment or maintenance while the compositions with the higher agent content e.g. 5%20% may be preferred for the make up of new baths. Illustrative of these are the following compositions:

tetrasodiurn salt of ethylene diamine tetraacetic acid 1 4. sodium stannate 86 tetrasodium salt of ethylene diamine tetraacetic acid 14 4 5. potassium stannate 98 monosodium salt of N,N-dihydroxyethyl glycine 2 6. sodium stannate 97 monosodium salt of N,N-dihydroxyethyl glycine 3 7. potassium stannate 95 potassium gluconate 5 8. sodium stannate 96 sodium gluconate 4 9. potassium stannate 98 sodium gluconate 2 10. sodium stannate sodium gluconate 15 11. potassium stannate 97 potassium glucoheptonate 3 12. sodium stannate 96 sodium glucoheptonate 4 13. potassium stannate 97 sodium gluconate 3 The novel tubular aluminum containers which have been coated with tin by contact with the bath may be found to have a coating of 0.5-1.5, say 1 micron on the inner surface, if the contacting has been by spraying, and on both the inner and outer surface if the contact has been by immersion. These tubes are particularly characterized by their resistance to the corrosive effect of active compositions such as fluorides including stannous fluoride in tooth paste. As a further advantage, the tin coating on the interior of the tooth paste tube may serve as a means for reducing stannic tin ion to stannous tin. This is desirable because tin in the stannic form possesses little or no activity as an anti-caries agent.

The novel collapsible tubes of this invention may comprise a collapsible tubular aluminum container having a surface layer of tin on the interior surface thereof. These novel containers are highly useful containers for any substance which is corrosive in nature and which is therefore not capable of being stored for prolonged periods.

The containers of this invention are particularly useful in combination with tooth pastes containing stannous tin or fluoride as an active ingredient. A preferred combination is a novel collapsible tubular aluminum container having a surface layer of tin on the interior surface thereof; and, within said container, tooth paste containing at least one active ingredient selected from the group consisting of stannous tin and fluoride. In accordance with certain preferred aspects of this invention, the active ingredient in said novel combination may be stannous fluoride.

In one series of comparative illustrative examples, pairs of tooth paste tubes which had been impact extruded from 99.7+% aluminum metal were tested. One series of tubes was tin plated on the inside and the outside by immersion plating in a bath containing 60 g./1. of potassium stannate K Sn(OI-I) 11.25 g./l. of sodium gluconate, and 3.75 g./l. of potassium hydroxide. The tubes were immersed for one minute at 48 C. to form a coating of tin having a thickness of one micron on the inside and the outside of the tubes. The tubes were filled with a typical tooth paste formulation which may be made up as follows:

Component: Parts by weight CaHPO -2H O 41.6 Synthetic detergent (Na lauryl sulfate) 1.4 Glycerine 25.0 Water 28.0 Irish moss extract 1.5 Stannous fluoride 1.6

Flavoring 0.9

Total 100.0

The Irish moss extract was wet out in part of the glycerine and the calcium phosphate (dibasic) was wet out in part of the water, in which the synthetic detergent had been dissolved. These slurries were then mixed together with heating until a uniform temperature of 70 C. was reached. The thickened paste mixture was then cooled to a temperature of 35 C. and the flavoring, the remaining glycerine and the remaining water containing the stannous fluoride were all added and mixed in thoroughly to give a homogeneous paste of suitable consistency.

Aluminum tubes were filled with equal amounts of the above composition. The tubes, both untreated and treated, were stored at 43 C. The tubes were inspected daily. It was apparent from inspection that the tubes had become perforated after a certain time because of the appearance of white spots on a substantial portion of the surface.

It was apparent after only three days of this accelerated testing that the aluminum tubes which had not been treated by practice of this invention were substantially entirely perforated. The tubes which had been treated as indicated by application thereto of a tin coating were found to be substantially free of perforation up to about the twenty-third day under the very severe conditions of the accelerated test.

Thus it is apparent that the practice of this invention permits attainment of tubes which have a shelf life under accelerated storage (which correlates readily with normal storage conditions) which may be eight times as long as the standard aluminum tube normally employed.

Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.

I claim:

1. A novel collapsible tubular aluminum container having a surface layer of tin on the interior surface thereof.

2. A novel container as claimed in claim 1 wherein said layer of tin has a thickness of 0.5-1.5 microns.

3. A novel collapsible tubular aluminum container having a surface layer of tin on the interior surface thereof; and, within said container, tooth paste containing at least one active ingredient selected from the group consisting of stannous tin and fluoride.

4. A novel container as claimed in claim 3 wherein said layer of tin has a thickness of 0.5-1.5 microns.

5. A novel collapsible tubular aluminum container having a 0.5-1.5 micron surface layer of tin on the interior surface thereof; and, within said container, tooth paste containing stannous fluoride.

References Cited UNITED STATES PATENTS THERON E. CONDON, Primary Examiner.

I. M. CASKIE, Assistant Examiner.

Claims (1)

1. 5. A NOVEL COLLAPSIBLE TUBULAR ALUMINUM CONTAINER HAVING A 0.5-1.5 MICRON SURFACE LAYER OF TIN ON THE INTERIOR SURFACE THEREOF; AND, WITHIN SAID CONTAINER, TOOTH PASTE CONTAINING STANNOUS FLUORIDE.