Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2000-10-20
2003-01-21
Anthony, Joseph D. (Department: 1714)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S670000, C210S685000, C252S184000
Reexamination Certificate
active
06508940
ABSTRACT:
TECHNICAL FIELD
This invention relates to processes for regenerating onium hydroxides from solutions containing onium compounds. In particular, the invention relates to processes for recovering onium hydroxides from solutions containing onium hydroxides and/or onium salts using a cation exchange material and a base.
BACKGROUND OF THE INVENTION
Onium hydroxides, such as quaternary ammonium hydroxides including tetramethylammonium hydroxide (TMAH) and tetraethylammonium hydroxide (TEAH), are strong organic bases that have been known for many years. Quaternary ammonium hydroxides have found a variety of uses including use in zeolite manufacture and polymer manufacture. Aqueous solutions of quaternary ammonium hydroxides, particularly TMAH solutions, have also been used extensively as a developer for photoresists in printed circuit board and microelectronic chip fabrication. For a variety of reasons, it is desirable to minimize the overall amount of developer used in printed circuit board and microelectronic chip fabrication. One way to minimize the overall amount of hydroxide developer is to reuse the waste developer. Reusing developer reduces the amount lost and decreases disposal problems.
Waste developer contains impurities including ionic impurities and nonionic impurities. Ionic impurities include various metal cations such as sodium, potassium, zinc, nickel, aluminum, copper and calcium; and anions such as halides, nitrates, nitrites, carbonates, carboxylates, sulfates. Nonionic impurities include photoresists, surfactants, amines and numerous other organic molecules. Waste developer also contains relatively low concentrations of the hydroxide developer. Accordingly, there remains a continuing need to effectively recover hydroxide developer in a useable form so that it may be reused thereby minimize the overall amount of developer used in printed circuit board and microelectronic chip fabrication.
U.S. Pat. No. 4,714,530 (Hale et al) describes an electrolytic process for preparing high purity quaternary ammonium hydroxides which utilizes a cell containing a catholyte compartment and an anolyte compartment separated by a cation-exchange membrane. The process comprises charging an aqueous solution of a quaternary ammonium hydroxide to the anolyte compartment, adding water to the catholyte compartment, and passing a direct current through the electrolysis cell to produce a higher purity quaternary ammonium hydroxide in the catholyte compartment which is subsequently recovered. The '530 patent also describes an improvement which comprises heating the quaternary ammonium hydroxide at an elevated temperature prior to charging the hydroxide to the anolyte compartment of the electrolytic cell.
U.S. Pat. No. 4,938,854 (Sharifian et al) also describes an electrolytic process for purifying quaternary ammonium hydroxides by lowering the latent halide content. The electrolytic cell may be divided into an anolyte compartment and a catholyte compartment by a divider which may be an anion or cation selective membrane. The cathode in the catholyte compartment comprises zinc, cadmium, tin, lead, copper or titanium, or alloys thereof, mercury or mercury amalgam.
Japanese Kokai Patent No.60-131985 (1985) (Takahashi et al) describes a method of manufacturing a high purity quaternary ammonium hydroxide in an electrolysis cell which is divided into an anode chamber and a cathode chamber by a cation exchange membrane. A quaternary ammonium hydroxide solution containing impurities is charged to the anode chamber and a direct current is supplied between two electrodes after water has been charged to the cathode chamber. Purified quaternary ammonium hydroxide is obtained from the cathode chamber. The purified quaternary ammonium hydroxide contains reduced amounts of alkali metals, alkaline earth metals, anions, etc.
U.S. Pat. Nos. 5,439,564 and 5,545,309 (Shimizu et al) relate to methods of processing waste liquid containing an organic quaternary ammonium hydroxide by contacting the waste liquid with a cation-exchanging material, eluting organic quaternary ammonium cations from the cation-exchanging material, and electrolyzing the eluate in a two chamber electrolytic cell equipped with an anode, cathode and cation-exchanging membrane. Organic quaternary ammonium hydroxide is obtained from the cathode chamber of the electrolytic cell.
U.S. Pat. No. 5,968,338 (Hulme et al) describes a process for regenerating onium hydroxides from solutions containing onium compounds such as hydroxides and salts using a cation exchange material, an acid to form a salt, and an electrochemical cell comprising at least three compartments to regenerate the onium hydroxide.
SUMMARY OF THE INVENTION
In one embodiment the present invention is a process for recovering an onium hydroxide from a cation exchange material having onium cations adsorbed thereto which comprises
(A) contacting said cation exchange material with an aqueous solution of a base selected from alkali metal hydroxides and ammonium hydroxide to form an onium hydroxide, and
(B) recovering an aqueous solution of the onium hydroxide.
In another embodiment, the present invention relates to a process for recovering an onium hydroxide from a solution containing an onium compound such as an onium hydroxide and/or onium salt, including contacting the solution with a cation exchange material so that at least a portion of onium cations from the onium compound are adsorbed by the cation exchange material; contacting the cation exchange material having the onium cations adsorbed thereto with an aqueous solution of an inorganic base to form an onium hydroxide; and recovering the onium hydroxide solution. The onium hydroxides that can be recovered in this manner include quaternary ammonium hydroxides, quaternary phosphonium hydroxides, and tertiary sulfonium hydroxides.
In another embodiment, the present invention relates to a process for recovering tetraalkylammonium hydroxides from waste solutions containing a tetraalkylammonium compound, including contacting the waste solution with a cation exchange material so that at least a portion of the tetraalkylammonium cations from the tetraalkylammonium compound are adsorbed by the cation exchange material; contacting an inorganic base with the cation exchange material whereby a tetraalkylammonium hydroxide is formed; and recovering tetraalkylammonium hydroxide solution.
As a result of the process of the present invention, recycled solutions of onium hydroxides can be obtained in which the concentration and purity is increased. Recycling spent solutions of onium hydroxides provides not only cost savings, but also environmental benefits by eliminating or reducing the need for synthesizing new hydroxide compound solutions, the associated expensive purification processes, and the toxicity of waste solution effluents. Additionally, it is not necessary to store large amounts of chemicals. The relatively high concentration and purity of onium hydroxide solutions obtainable via the present invention can effectively be used in numerous applications where onium hydroxide solutions are required.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In one embodiment of the invention, onium hydroxides are recovered from a cation exchange material having onium cations adsorbed thereto which comprises
(A) contacting said cation exchange material with an aqueous solution of a base selected from alkali metal hydroxides and ammonium hydroxide to form an onium hydroxide, and
(B) recovering an aqueous solution of the onium hydroxide.
This process is described in more detail below.
In another embodiment of the present invention, onium hydroxides are regenerated (produced, purified or recycled) from solutions containing an onium compound such as onium hydroxides and/or onium salts. In one embodiment, the solution containing an onium compound is a waste solution of an onium hydroxide after it has been used in a process, such as a developing processes associated with printed circuit board and microelectronic chip fabrication. As a result of such processes,
Anthony Joseph D.
Renner , Otto, Boisselle & Sklar, LLP
Sachem, Inc.
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