Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Patent
1995-05-17
1997-07-15
Pyon, Harold
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
134 26, 134 40, 134 42, B08B 308, B08B 314
Patent
active
056479140
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a nonaqueous solvent regenerating method in which a hydrophilic solvent, such as an alcohol, introduced in the previous step is separated from a nonaqueous solvent, such as a silicone compound, employed in cleaning of a metal part or an optical part, such as a lens or a prism. The present invention also relates to an apparatus suitable for use in the above method.
2. Background Art
Fluorocarbons have widely been used as a dehydrating or drying agent in the final step of cleaning of optical parts such as a glass lens and plastic items and other parts such as semiconductors and mount substrates. However, the fluorocarbons have a grave drawback in that they destroy the ozonosphere. Various studies have been made to provide substitutes for the fluorocarbons. In recent years, the drying with the use of IPA (isopropyl alcohol) vapor have been carried out as described in the "Report on the results of cleaning of lenses and resins" (published by the Environmental Group of Japan Camera Industry Association in December, 1989). In the process involving the drying with the use of IPA vapor, first, a material to be cleaned is washed with a solvent, secondly with an aqueous surfactant, thirdly with clean water and fourthly with demineralized water, and thereafter washing for dehydration is carried out with the use of IPA fluid, which is evaporated off in the final drying step to thereby dry the material.
However, the IPA vapor is not only inflammable and explosible but also toxic to human health, so that not only are precautions required in handling but also recovery facilities must inevitably be of a large scale. In contrast, the inventors found that the drying of the hydrophilic solvent such as IPA could be accomplished by replacing the same caused to adhere to the material in the dehydrating step with a silicone compound, thereby rendering the evaporation of the hydrophilic solvent such as IPA unnecessary. Examples of the silicone compounds include low molecular weight silicone compounds such as octamethylcyclotetrasiloxane and octamethyltrisiloxane.
In the cleaning process in which the above silicone compound is employed in the final drying step, however, stain and unevenness are likely to occur in the cleaned material with the repetitions of the cleaning operation. The reason is that the silicone compound dissolves the hydrophilic solvent such as IPA to remove the same, so that the concentration of the hydrophilic solvent in the silicone compound increases with the repetitions of the cleaning operation to thereby lower the purity of the silicone compound. This purity lowering leads to bringing of the hydrophilic solvent into the nonaqueous solvent to thereby increase the water content of the nonaqueous solvent with the result that stain and unevenness occur in the cleaned material.
The present invention has been made taking the above situation into account. Thus, an object of the present invention is to provide a nonaqueous solvent regenerating method in which regeneration is carried out to maintain the purity of not only a silicone compound for use in removing hydrophilic solvents for drying but also other nonaqueous solvents for use in similar drying, so that recycling of the nonaqueous solvent while maintaining the drying power thereof is achieved. Another object of the present invention is to provide a regenerating apparatus suitable for use in the above regeneration of the nonaqueous solvent.
DISCLOSURE OF THE INVENTION
In the present invention, a hydrophilic solvent mixed in a nonaqueous solvent, whose compatibility with water is so low that it is substantially immiscible with water, is contacted with a separation fluid to thereby cause the separation fluid to absorb the hydrophilic solvent, so that the nonaqueous solvent is regenerated. Therefore, use is made of a separation fluid having low compatibility with the nonaqueous solvent and high compatibility with the hydrophilic solvent. The absorption of the hydrophilic solvent in the separati
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Goto Mitsuo
Hijino Masamichi
Itakura Masahiro
Uzawa Kunihiko
Olympus Optical Co,. Ltd.
Pyon Harold
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