Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
1999-10-06
2001-05-01
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06225492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for purifying a cyanate, which is useful for a sealant, laminate, composite material, molding material and adhesive of electronic parts, efficiently and at high purity from a cyanate crude product solution containing an unsubstituted phenol.
2. Description of the Related Art
As a method for producing a cyanate industrially, there is a well known method in which a cyanogen halide and a phenol are reacted in the presence of a tertiary aliphatic amine (A. W. Snow in “Chemistry and Technology of Cyanate Ester Resins”, Chap. 2 (Ed. T. Hamerton), Blackie Academic and Professional, Glasgow, 1994, pp. 7 to 57). However, a cyanate obtained in this method can not avoid remaining of unreacted phenols and the like. Further, when a cyanate is stored for a long period of time, it is easily hydrolyzed to give a phenol. If such a phenol contained in the cyanate, there occurs a problem that the phenol functions as a polymerization catalyst of cyanate and makes difficult the control of thermo-setting reaction using the cyanate.
As a method for purifying a cyanate in a crude product solution containing an unsubstituted phenol, there is reported a distillation method. However, some cyanates have sublimation property under reduced pressure or polymerization property catalyzed by the unsubstituted phenol as a catalyst when heated, therefore, distillation is not satisfactory method for safely obtaining a cyanate of high purity in high yield.
Also reported is a method in which purification is conducted by crystallizing or precipitating a crude product solution of a cyanate. However, a conventionally suggested method in which crystallization is conducted by cooling using only a good solvent gives low yield, and a conventionally suggested method in which crystallization is conducted by contacting a crude product solution of a cyanate with a poor solvent such as hexane, 2-propanol and the like has a problem that the isolation yield is low since removal of a raw material phenol is difficult and further a part of a cyanate is dissolved in the poor solvent.
Moreover, a filtrate obtained in this operation contains alcohol and non-alcoholic solvent, and disposal thereof is complicated, causing obstruction in efficiency of production of a cyanate itself in practice.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a safe and simple method for purifying a cyanate having high purity at high yield from a cyanate crude product solution containing unsubstituted phenol.
According to the present invention, there is provided a method for purifying a cyanate wherein a cyanate crude product solution comprising a cyanate represented by the general formula (1), unsubstituted phenol and non-alcoholic solvent is allowed to contact with a poor solvent containing an alcohol and water, to crystallize or precipitate said cyanate represented by the general formula (1):
in the formula (1), A
1
to A
3
each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; X represents a single bond, an organic group having 1 to 20 carbon atoms, a carbonyl group, a sulfone group, a divalent sulfur atom or oxygen atom; n represents an integer of 0 to 3; and i
1
to i
3
each independently represents an integer of 0 to 4.
DETAILED DESCRIPTION OF THE INVENTION
The purification method of the present invention includes a step in which a cyanate crude product solution is allowed to contact with a specific poor solvent to crystallize or precipitate the cyanate.
The cyanate crude product solution used in the present invention comprises a cyanate represented by the above-described general formula (1) as a desired material, and unsubstituted phenols.
The cyanate which is contained in the above-described crude product solution may be any compound providing it satisfies the above-described general formula (1). In the formula, x represents a single bond, an organic group having 1 to 20 carbon atoms, a carbonyl group, a sulfone group, a divalent sulfur atom or oxygen atom. Examples of the organic group having 1 to 20 carbon atoms include linear or branched alkylene groups, such as —(CH
2
)m—, —CH((CH
2
)mH)—, —C((CH
2
)mH)
2
— and —C(CF
3
)
2
— (here, m represents an integer of 1 to 20). The symbol n represents preferably an integer of from 0 to 20, and more preferably 0.
Examples of the cyanate include: 4,4′-dicyanatediphenyl, 3,3′, 5,5′-tetramethyl-4,4′-dicyanatediphenyl, bis(4-cyanatephenyl)methane, bis(4-cyanate-3-methylphenyl)methane, bis(4-cyanate-3-t-butylphenyl)methane, bis(4-cyanate-3-i-propylphenyl)methane, bis(4-cyanate-3,5-dimethylphenyl)methane, bis(2-cyanate-3-t-butyl-5-methylphenyl)methane, bis(4-cyanatephenyl)ethane, bis(4-cyanate-3-methylphenyl)ethane, bis(4-cyanate-3-t-butylphenyl)ethane, bis(4-cyanate-3-iso-propyphenyl)ethane, bis(4-cyanate-3,5-dimethylphenyl)ethane, bis(2-cyanate-3-t-butyl-5-methylphenyl)ethane, 2,2-bis(4-cyanatephenyl)propane, 2,2-bis(4-cyanate-3-methylphenyl)propane, 2,2-bis(4-cyanate-3-t-butylphenyl)propane, 2,2-bis(4-cyanate-3-iso-propylphenyl)propane, 2,2-bis(4-cyanate-3,5-dimethylphenyl)propane, 2,2-bis(2-cyanate-3-t-butyl-5-methylphenyl)propane, 2,2-bis(4-cyanate-3-t-butyl-6-methylphenyl)propane, 2,2-bis(3-allyl-4-cyanatephenyl)propane, 1,1-bis(4-cyanatephenyl)butane, 1,1-bis(4-cyanate-3-methylphenyl)butane, 1,1-bis(4-cyanate-3-t-butylphenyl)butane, 1,1-bis(4-cyanate-3-iso-propylphenyl)butane, 1,1-bis(4-cyanate-3,5-dimethylphenyl)butane, 1,1-bis(2-cyanate-3-t-butyl-5-methylphenyl)butane, 1,1-bis(4-cyanate-3-t-butyl-6-methylphenyl)butane, 2,2-bis(3-allyl-4-cyanatephenyl)propane, 1,1-bis(3-allyl-4-cyanatephenyl)butane, 1,1-bis(4-cyanatephenyl)cyclohexane, 1,1-bis(4-cyanate-3-methylphenyl)cyclohexane, bis(4-cyanatephenyl) sulfide, bis(4-cyanate-3-methylphenyl) sulfide, bis(4-cyanate-3-t-butylphenyl) sulfide, bis(4-cyanate-3-iso-propylphenyl) sulfide, bis(4-cyanate-3,5-dimethylphenyl) sulfide, bis(2-cyanate-3-t-butyl-5-methylphenyl) sulfide, bis(4-cyanatephenyl)sulfone, bis(4-cyanate-3-methylphenyl)sulfone, bis(4-cyanate-3-t-butylphenyl)sulfone, bis(4-cyanate-3-iso-propylphenyl)sulfone, bis(4-cyanate-3,5-dimethylphenyl)sulfone, bis(2-cyanate-3-t-butyl-5-methylphenyl)sulfone, bis(4-cyanatephenyl) ether, bis(4-cyanate-3-methylphenyl) ether, bis(4-cyanate-3-t-butylphenyl) ether, bis(4-cyanate-3-iso-propylphenyl) ether, bis(4-cyanate-3,5-dimethylphenyl) ether, bis(2-cyanate-3-t-butyl-5-methylphenyl) ether, bis(4-cyanatephenyl)carbonyl, bis(4-cyanate-3-methylphenyl)carbonyl, bis(4-cyanate-3-t-butylphenyl) sulfide, bis(4-cyanate-3-iso-propylphenyl)carbonyl, bis(4-cyanate-3,5-dimethylphenyl)carbonyl, bis(2-cyanate-3-t-butyl-5-methylphenyl)carbonyl and the like. Among them, bis(4-cyanatephenyl)methane, bis(4-cyanate-3,5-dimethylphenyl)methane, 2,2-bis(4-cyanatephenyl)propane and 2,2-bis(4-cyanate-3,5-dimethylphenyl)propane are preferable, and 2,2-bis(4-cyanatephenyl)propane represented by the general formula (2) is more preferable.
The cyanate crude product solution which comprises a cyanate represented by the general formula (1), a non-alcoholic solvent, and an unsubstituted phenol is obtained by reacting a phenol represented by the above-described general formula (1) with a cyanogen halide in a non-alcoholic solvent immiscible with water using a tertiary amine.
The unsubstituted phenol usually includes a raw material phenol and a phenol compound having an unsubstituted phenolic hydroxy group such as a mono-cyanated phenol, remaining in the cyanate crude product solution. The content of the unsubstituted phenol in the crude production solution is not particularly restricted, and usually 10% by weight or less, preferably from 0.5 to 5% by weight. When the content of the unsubstituted phenol in a cyanate crude product solution is in the range as described above, the cyanate crude product solution can be subjected in the step of contacting with a specific poor solvent. However, it is also permissible that the crude product solution is concentrated
Okamoto Satoshi
Watabu Hisashi
Calve John N
Killos Paul J.
Pillsbury & Winthrop LLP
Sumitomo Chemical Co,. Ltd.
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