Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
2001-04-19
2003-11-04
Webb, Gregory E. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S176000, C510S177000, C252S079200, C252S079300, C252S079400, C134S003000
Reexamination Certificate
active
06642199
ABSTRACT:
BACKGROUND OF THE INVENTION
Many different types of fabricated articles and parts are plated with nickel or a nickel alloy. For many applications, the nickel or nickel alloy is applied to the part using an electroplating process, although electroless processes have recently become widely used. Unfortunately, many of these types of parts can contain slight or gross imperfections that cause the article to be rejected by prescribed quality standards. Such imperfections can result due to defects in the plastic or metal substrate, improper cleaning of the substrate, excessive porosity of the substrate, impurities in the plating composition, etc.
In many applications, the part containing the imperfection, apart from the defective nickel or nickel alloy deposit, has considerable economic value making it cost prohibitive to scrap the rejected article. Consequently, it becomes necessary to then remove the nickel or nickel alloy coating, reclaim the base substrate, and then recoat the substrate with a nickel containing material.
In the past, various processes have been proposed for stripping defective nickel coatings from substrates. For instance, examples of such processes are disclosed in U.S. Pat. No. 3,351,556, U.S. Pat. No. 3,365,401, U.S. Pat. No. 3,856,694, U.S. Pat. No. 4,052,254, and U.S. Pat. No. 4,548,791, which are all incorporated herein by reference. In general, nickel metals can be removed from a substrate by immersing the article in a bath containing an oxidizing agent. The bath, however, must be able to remove the nickel metal without harming the underlying substrate. For example, many iron parts are nickel plated. In the past, problems have been experienced in damaging the underlying iron surface when removing nickel from the substrate.
In U.S. Pat. No. 4,720,332, which is incorporated herein by reference, a nickel strip formulation is disclosed for stripping nickel and nickel alloys from metallic and non-metallic substrates. In the '332 patent, the nickel strip formulation includes an oxidizing agent such as a suitable organic nitro compound, a sulfide ion which is utilized as a stripping rate catalyst, a pH adjusting compound to adjust the stripping solution to an operating pH range of 7 to 11 and a zwitterion. The zwitterion acts as a complexing agent for the metal being dissolved as well as a buffer to control the pH of the stripping solution.
Although the prior art has made some advances in the past in providing solutions capable of stripping nickel from substrates, the present invention is directed to further improvements in compositions for stripping nickel and nickel alloys from substrates, including stripping nickel from electroless nickel plated articles.
SUMMARY OF THE INVENTION
The present invention is generally directed to a composition for selectively removing materials containing nickel from substrates, such as metal and plastic substrates. In one embodiment, the composition contains an oxidizing agent such as a water soluble nitro substituted cyclic organic ring derivative.
In accordance with the present invention, the composition further contains an organic amine in combination with an organic acid or salt thereof. The organic amine can be a primary amine such as an alkanolamine. Particular examples of organic amines include monoethanol amine, diethanolamine, triethanolamine, isopropanolamine, 2-aminopropanol, 3-aminopropanol, and the like.
The organic acid or salt thereof can be, for instance, citric acid, a citric acid salt, boric acid or a boric acid salt. The organic acid or salt should be present within the composition in an amount sufficient to neutralize the organic amine. It has been discovered by the present inventors that the combination of an organic amine with an organic acid or salt significantly increases the nickel holding capacity of a solution containing the composition.
When present as an aqueous solution, the composition can contain the oxidizing agent in an amount from about 20 grams per liter to about 120 grams per liter and can contain the organic amine in an amount from about 4 grams per liter to about 120 grams per liter. The pH of the solution should be at least 6.5, and particularly from about 6.5 to about 12.
The nickel stripping composition of the present invention can also contain various other ingredients. For instance, the composition can contain a sulfide ion catalyst, a carboxylic acid or salt thereof, a chlorite such as a chlorate or a hypochlorite, a surfactant, and a pH adjuster. The pH adjuster can be a carbonate, a phosphate, or a hydroxide.
In an alternative embodiment of the present invention, a second type of amine can be present within the composition as an alternative to or in addition to the organic amine. The second amine can be an amine or a salt thereof which includes a substituent group containing —OH, —NH
2
, —NH, —SH, —C═O, —SO
3
, or —NO
2
. Examples include hydroxylamines and acid and alkali metal salts thereof. For example, the composition can contain hydroxylamine sulfate. Other examples include hydrazines and salts thereof, sulfamic acids and salts thereof, and urea. Urea has been found to work particularly well in a nickel stripping solution. For example, urea has been found to prevent sludge build-up, improve clarity, and provide thermal stability.
The above identified amine containing the listed substituent groups can be present in the nickel stripping composition with any of the other ingredients listed above.
The present invention is also directed to a process for removing a material containing nickel from a substrate. The process includes the steps of providing an article comprising a substrate coated with a material containing nickel. The article is contacted with an aqueous stripping solution configured to remove the nickel containing material. The aqueous stripping solution can include an oxidizing agent, an amine, and an organic acid or salt. The solution can also contain a sulfide ion catalyst, a pH adjuster, a carboxylic acid or salt thereof, a chlorite, and/or a surfactant.
The pH of the aqueous stripping solution can be from about 6.5 to about 12 when contacted with the article, and particularly can have a pH from about 8 to about 10.
The temperature of the solution can vary from about 60° F. to about 200° F., and particularly from about 150° F. to about 180° F. The article can be contacted with the solution for a time of from about one ½ hour to about 24 hours, and particularly from about one ½ hour to about 1½ hours.
Other features and aspects of the present invention are discussed in greater detail below.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.
The present invention is directed to an improved liquid or powder composition which is configured to selectively strip nickel and nickel alloy coatings from articles without attacking the underlying substrate. Of particular advantage, the composition of the present invention can remove all types of nickel coatings, including electroless nickel coatings of low, medium or high phosphorus content. In the past, these types of coatings have typically been removed with the aid of electricity or with the inclusion of an extra step of placing the article in a strongly acidic bath, such as a nitric acid bath.
The composition of the present invention contains an oxidizing agent for oxidizing the nickel
Farrell Robert
Humphreys Daniel
Dority & Manning P.A.
Hubbard-Hall, Inc.
Webb Gregory E.
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