Enhanced Purification of Organic Solutions for Use in Electronics
Publication Date: 2003-Oct-07
The IP.com Prior Art Database
We have discovered that organic solutions or dispersions of monomers, pre-polymers, and polymers, can be reliably purified to the levels required by the electronics industry using a combination of microfiltration and ion exchange. The combination of both separation techniques is necessary in order to ensure removal of a broad spectrum of elemental impurities.
The electronic industry requires ultra-high ionic purity for all raw material and solvents that are used in the production of integrated circuits. Ionic purity requirements of less than 10 ppb/individual element are not uncommon for this industry. For solvents and other volatile materials, these purity levels are commonly achieved through distillation. However, for non-volatile or thermally sensitive materials, pre-polymers, and polymers, other means must be employed to achieve the desired ionic purity.
A New Approach Combining Microfiltration and Ion Exchange
We have discovered that organic solutions or dispersions of monomers, pre-polymers, and polymers, can reliably purified to the levels required by the electronics industry using a combination of microfiltration and ion exchange. The combination of both separation techniques is necessary in order to ensure removal of a broad spectrum of elemental impurities.
Microfiltration, or ultrafiltration, effectively removes elements that are present in the solution as particles of insoluble compounds. Typically, these elements include calcium, aluminum, iron, and titanium, which are present in the form of dust particles or other environmental contamination. These particles can easily be removed by sufficiently rigorous filtration. However, filtration is not effective on those elements that are truly soluble in the organic solution and present as ionic species.
A cation exchange resin can be used to remove the elements that are truly soluble in the system and are present as ionic species, most commonly sodium and potassium. The ion exchange resin is not effective on metals that are present as insoluble particles.
Following purification, the solute present in the solvent can optionally be isolated by precipitation, or other methods, to yield a product free of ionic impurities.
Examples of monomers for which this process may be useful include phenylethynylated aliphatic and aromatic compounds such as described in WO 03/059984A1 and WO 03/0606979A1, and aryl-substituted cyclopentadienones including tetracyclones, substituted tolanes. Examples of polymers or oligomers for which this process may be useful include the reaction products of phenylethynylated aromatics such as 1,3,5-tris phenylethynylbenzene, 1,3,5-tris(4-phenylethynlphenyl)benzene and aryl-substituted cyclopentadienones, polymers of styrenic monomers such as styrene, alpha-methylstyrene, t-butylstyrene; of acrylate monomers such as t-butyl acrylate, methyl acrylate and methyl methacrylate; of vinyl aromatics such as vinyl biphenyl, vinyl naphthalene and vinyl anthracene.
Solvents in which the above materials may be dispersed to run the process include glycol ethers, alcohols, ethers, cyclic ethers, ketones, esters, DMF, DMSO and aromatic hydrocarbons.
Microfiltration is preferably done to remove particles larger than approximately 0.05 micron. Preferred filter medi...