Method of producing an aromatic polyester

Details Method of producing an aromatic polyester Method of producing an aromatic polyester

2000-01-20

2001-03-13

Acquah, Samuel A. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

C528S190000, C528S194000, C528S298000, C528S302000, C528S308600, C526S059000

Reexamination Certificate

active

06201102

ABSTRACT:

The present invention relates to a method of producing an aromatic polyester by polycondensation.
An aromatic polyester is generally obtained by acetylating raw monomers selected from aromatic hydroxycarboxylic acids, aromatic dicarboxzylic acids, aromatic diols and the like with an acetic anhydride, followed by polycondensation of them. However, this method has such a problem that low-molecular compounds such as raw monomers and acetylated monomers are adhered to distillation pipings or low-molecular compounds are contained in a recovered low-boiling fraction while low-boiling fractions such as acetic acid produced as a by-product by the acetylation reaction and polycondensation are distilled off. As a result, yield of the aromatic polyester as the product is lowered and, since the product having the same monomer formulation as that on charging is not obtained, the quality of the product does not become stable.
To solve the problem described above, JP-A-5-271398 has suggested a method in which the low-molecular compounds adhered to piping is washed and recovered by refluxing the low-boiling fraction with a partial condenser using a nitrogen gas as a coolant which is disposed before a condenser for cooling the low-boiling fraction.
However, the present inventors have found that this method is not satisfactory as an industrial production method, since the low-molecular compounds tend to be adhered to the partial condenser thereby to blockade the partial condenser due to a change in reflux amount with proceeding of the polycondensation.
An object of the present invention to provide an industrially advantageous method of producing an aromatic polyester which improve the yield of the aromatic polyester and stabilizes the product quality by preventing adhesion of low-molecular compounds to a partial condenser in a method of producing an aromatic polyester by polycondensation.
The present inventors have intensively studied about the problems described above and found that adhesion of low-molecular compounds to a partial condenser can be prevented by controlling a low-boiling fraction distilled from the partial condenser in a specific temperature range while the amount of the low-boiling fraction recovered from a polycondensation vessel is in a specific range. Thus, the present invention has been completed.
The present invention provides a method of producing an aromatic polyester by distilling a low-boiling fraction from a polycondensation vessel containing a reaction product obtained by acetylating raw monomers of the aromatic polyester with acetic anhydride, wherein
the polycondensation vessel is provided with a partial condenser, and
controlling a temperature of the low-boiling fraction distilled from the partial condenser within a range from 80 to 150° C. while the amount of the low-boiling fraction distilled from the partial condenser is within a range from 50% to 90% based on a theoretical recovery amount.
Examples of the raw monomers of the aromatic polyester used in the present invention include monomers such as aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid, and aromatic diol.
Examples of the aromatic hydroxycarboxylic acids as the raw material include those represented by the following general formula:
HO—X—CO—O—R
1
wherein R
1
represents hydrogen, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 16 carbon atoms, and X represents a divalent aromatic group. Among them, those wherein X is at least one divalent aromatic group selected from the groups represented by the following formulas (1) to (3) are preferred.
These aromatic groups represented by the formulas (1) to (3) may be optionally substituted with an alkyl, aryl, alkoxy, halogen group or the like.
Specific examples of the aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, phenyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-(4-hydroxyphenyl)benzoic acid, methyl p-(4-hydroxyphenyl)benzoate, 2-hydroxy-6-naphthoic acid, methyl 2-hydroxy-6-naphthoate, and phenyl 2-hydroxy-6-naphthoate. Among them, p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid are preferred.
Examples of the aromatic dicarboxylic acids as the raw monomer include those represented by the following general formula:
R
2
—O—CO—Y—CO—O—R
2
wherein R
2
represents hydrogen, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 16 carbon atoms, and Y represents a divalent aromatic group. Among them, those wherein Y is at least one divalent aromatic group selected from the groups represented by the following formulas (4) to (8) are preferred.
wherein A represents a direct bond, an oxygen atom, a sulfur atom, an alkyl group, a carbonyl group or a sulfonyl group. These aromatic groups represented by the formulas (4) to (8) may be optionally substituted with an alkyl, aryl, alkoxy, halogen group or the like.
Specific examples of the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4′-dicarboxydiphenyl, 1,2-bis(4-carboxyphenoxy)ethane, 2,5-dicarboxynaphthalene, 2,6-dicarboxynaphthalene, 1,4-dicarboxynaphthalene, 1,5-dicarboxynaphthalene, dimethyl terephthalate, dimethyl isophthalate, diphenyl terephthalate, diphenyl isophthalate, 4,4′-dimethoxycarbonyldiphenyl, 2,6-dimethoxycarbonylnephthalene, 1,4-dichlorocarbonylnaphthalene and 1,5-diphenoxycarbonylnaphthalene. Among them, terephthalic acid, isophthalic acid and 2,6-dicarboxynaphthalene are preferred.
Examples of the aromatic diol as the raw monomer include those represented by the following general formula:
HO—Z—OH
wherein Z represents a divalent aromatic group. Among them, those wherein Z is at least one divalent aromatic group selected from the groups represented by the following formulas (9) to (12) are preferred.
wherein A represents a direct bond, an oxygen atom, a sulfur atom, an alkyl group, a carbonyl group or a sulfonyl group. These aromatic groups may be substituted with an alkyl, aryl, alkoxy, halogen group or the like.
Specific examples of the aromatic diol include hydroquinone, resorcine, catechol, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxybenzophenone, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenylethane, 4,4′-dihydroxydiphenylether, 2,2′-bis(4-hydroxyphenyl)propane, 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfide, 2,6-dihydroxynaphthalene, and 1,5-dihydroxynaphthalene. Among them, hydroquinone, resorcine, 4,4′-dihydroxydiphenyl, 2,2′-bis(4-hydroxyphenyl)propane and 4,4′-dihydroxydiphenylsulfone are preferred.
Although the ratio among the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid and aromatic diol used in the present invention is not specifically limited, usually the amount of the aromatic hydroxycarboxylic acid is within a range from about 30 to 80% by mole, the amount of the aromatic dicarboxylic acids is within a range from about 35 to 10% by mole and the amount of the aromatic diol is within a range from about 35 to 10% by mole, based on the total amount of the aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid and aromatic diol.
In the present invention, the raw monomer is acetylated by reacting acetic anhydride with a hydroxyl group of the raw monomers, and the acetylated reaction product is polycondensed to produce the aromatic polyester.
The temperature and pressure of the acerylation reaction are not specifically limited as far as the acetylation reaction solution is refluxed, but the acetylation reaction is usually carried out at about 140 to 150° C. under normal pressure. If the reaction temperature does not reach the reflux temperature, the reaction time tends to be prolonged. The acetylation reaction is usually carried out for about 1 to 5 hours after the beginning of the reflux.
The acetylated reaction product obtained by the acetylation reaction is usually a solution containing unreacted raw monomers, acetylated raw monomers, acetic acid, and unreacted acetic anhydride.
The acetylated reaction product is usual

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