Method for recovering fluorine-containing solvents

Details Method for recovering fluorine-containing solvents Method for recovering fluorine-containing solvents

1999-11-22

2001-06-12

O'Sullivan, Peter (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C534S560000, C540S140000, C564S271000, C568S682000

Reexamination Certificate

active

06245953

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method for recovering fluorine-containing solvents.
BACKGROUND ART
Fluorine-containing solvents are used to dissolve dyes for producing information recording media, for example, CD-R and DVD-R, wherein writable and/or readable recording layers are provided on their substrate by means of a laser. Since fluorine-containing solvents have higher coefficients of global warming than carbon dioxide, it is desirable that the solvents are recovered after use and recycled. However, recovered fluorine-containing solvents have drawbacks for recycle because they contain dyes which are deteriorated or difficult to control their concentrations. It is therefore unfavorable to use the solvents directly after being recovered. Further, if the fluorine-containing solvents are recycled as they are after recovery, it is impossible to change the types of dyes contained therein. Therefore, impurities such as dyes have to be removed from the fluorine-containing solvents to be recycled. However, it has been considered difficult to recover fluorine-containing solvents in a purity enough for producing information recording media such as CD-R because such production requires extremely pure fluorine-containing solvents.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a method for recovering a fluorine-containing solvent which is substantially free of impurities.
The inventors of the present invention carried out extensive research on a method for removing dyes from fluorine-containing solvent. The inventors unexpectedly found that the impurities can be readily removed from the solvent by distilling the mixture, thereby recovering a fluorine-containing solvent which is substantially free of dyes and other impurities. In addition, the inventors found that the dyes can be easily separated from the fluorine-containing solvent by adding a specific second solvent to the mixture and a high-purity fluorine-containing solvent can be recovered. The present invention was accomplished based on the above findings.
The present invention provides the processes listed below:
Item 1. A method for recovering a fluorine-containing solvent from a mixture comprising a fluorine-containing solvent and a dye or dyes, wherein the fluorine-containing solvent is recovered by distillation.
Item 2. The method according to item 1, wherein the distillation is conducted under reduced pressure.
Item 3. The method according to item 1, wherein the dye is at least one member selected from the group consisting of cyanine dyes, phthalocyanine dyes, azo dyes, pyrylium dyes, thiopyrylium dyes, squarylium dyes, azulenium dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, quinone dyes, aminium dyes, diimmonium dyes and metal complex salt dyes.
Item 4. The method according to item 1, wherein the fluorine-containing solvent is capable of dissolving the dye in 1-10 mass %.
Item 5. The method according to item 1, wherein the fluorine-containing solvent is a fluoroalcohol.
Item 6. The method according to item 5, wherein the fluoroalcohol is represented by the formula (1)
H(CFR
1
CF
2
)
n
CH
2
OH  (1)
wherein n=1 or 2; when n=1, R
1
represents F or CF
3
; when n=2, R
1
represents F.
Item 7. A method for recovering a fluorine-containing solvent from a mixture comprising a fluorine-containing solvent and a dye or dyes, the method comprising the steps of adding to the mixture a second solvent which are uniformly mixed with the fluorine-containing solvent but does not dissolve the dye; separating a precipitate from the resulting mixture; and separating the second solvent.
Item 8. The method according to item 7, wherein the second solvent is at least one member selected from the group consisting of water, fluoroethers and fluoroalkanes.
Item 9. The method according to item 7, wherein the fluorine-containing solvent is capable of dissolving the dye in 1-10 mass %.
Item 10. The method according to item 7, wherein the fluorine-containing solvent is a fluoroalcohol.
Item 11. The method according to item 10, wherein the fluoroalcohol is represented by the formula (1)
H(CFR
1
CF
2
)
n
CH
2
OH  (1)
wherein n=1 or 2; when n=1, R
1
represents F or CF
3
; when n=2, R
1
represents F.
The fluorine-containing solvent is not particularly limited insofar as the solvent has at least one fluorine atom. Examples of the preferred fluorine-containing solvents include fluoroalcohols {for example, a fluoroalcohol represented by the formula (1) H(CFR
1
CF
2
)
n
CH
2
OH (wherein n=1 or 2; when n=1, R
1
represents F or CF
3
; when n=2, R
1
represents F)}; fluorine-substituted ketones (CF
3
COCF
3
, CF
3
COCH
2
COCF
3
, CF
3
COCH
2
COCH
3
, etc.); fluorine-substituted esters (CF
3
COOCH
3
, CF
3
COOC
2
H
5
, CH
3
COOCH
2
CF
3
, CF
3
COOCH
2
CF
3
, CH
3
COOCH
2
CF
2
CF
2
H, CF
3
CF
2
CF
2
CF
2
COOC
2
H
5
, etc.); fluorinated carboxylic acids {CF
3
(CF
2
)
m
COOH (m is an integer of 2-4)}, etc.; and fluorinated alkanes (CCl
2
F
2
, CCl
3
F, ClF
2
C—CClF
2
). Among them, the method of the present invention is preferably applied to the recovery of fluoroalcohols, particularly to the recovery of fluoroalcohols represented by the formula (1) H(CFR
1
CF
2
)
n
CH
2
OH (n=1 or 2; when n=1, R
1
represents F or CF
3
; when n=2, R
1
represents F).
Alternatively, preferably used are fluorine-containing solvents which is capable of dissolving the dyes contained in the mixture in 1-10 mass %.
The dyes contained in the mixture are not particularly limited but include those which are commonly used for producing information recording media comprising a laser-writable and/or a laser-readable recording layer provided on their substrate. Examples of such dyes include cyanine dyes, phthalocyanine dyes, azo dyes, pyrylium dyes, thiopyrylium dyes, squarylium dyes, azulenium dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, quinone dyes, aminium dyes, diimmonium dyes and dyes of metal (nickel, copper, cobalt, palladium, platinum, chromium, etc.) complex salt. Specific examples of these dyes are those disclosed in Japanese Examined Patent Publication No. 96333/1995, Japanese Unexamined Patent Publication No. 274732/1997, Japanese Unexamined Patent Publication No. 59529/1997 etc.
Examples of cyanine dyes are
(CH
2
)
2
N—(CH═CH)
5
—CH═
+
N(CH
3
)
1
ClO
4
−
,
(p=2 or 3) etc.
Examples of phthalocyanine dyes are as follows.
and the like.
Some of these dyes are used for producing information recording media or as quenchers for preventing deterioration or decomposition of other dyes during product storage.
Distillation of the mixture may be carried out usually by heating at a temperature of about 30-150° C. at ambient pressure or under reduced pressure, for example, about 0.0001-0.1 MPa.
When a fluorine-containing solvent is recovered after being used for producing information recording media such as CD-R and DVD-R, the recovered solvent mixture may contain not only dye(s) but also other solvent(s) (e.g., diacetone alcohol) for removing the dye(s) deposited on the periphery of the substrate. Accordingly, when the recovered fluorine-containing solvent mixture contains other solvent or solvents, the recovered solvent mixture is subjected to a fractionation step after removing impurities such as dyes, and to remove other solvent or solvents and to finally obtain the desired fluorine-containing solvent substantially free of impurities. Alternatively, by directly fractionating the recovered solvent mixture, impurities and other solvent(s) are removed simultaneously and the desired fluorine-containing solvent substantially free of impurities can be obtained.
Fractionation may be conducted under suitable conditions depending on the combination of the fluorine-containing solvents and other solvents. For instance, the fractionation may be carried out with heating to about 30-150° C. at ambient pressure or under reduced pressure, for example, about 0.0001-0.1 M

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