# US 6,723,826 B2 · Production process and production apparatus for polybutylene terephthalate

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- Number: US 6,723,826 B2
- Document ID: US6723826B2
- Status: Granted
- Kind: B2
- Application number: 10/446,075
- Filed: 2003-05-28
- Published: 2003-11-06
- Granted: 2004-04-20
- Earliest claimed: 2001-08-29
- Assignees: Hitachi, Ltd.
- Inventors: Shuji Yamaguchi; Hidekazu Nakamoto; Susumu Harada; Norifumi Maeda
- Web page: https://patentgrep.com/patent/US6723826B2

## CPC

- B01J 8/1836: {Heating and cooling the reactor (B01J8/42 takes precedence)}
- B01J 8/009: {Membranes, e.g. feeding or removing reactants or products to or from the catalyst bed through a membrane}
- B01J 8/0285: {Heating or cooling the reactor (for tubular reactors in furnaces B01J8/062)}
- B01J 8/067: {Heating or cooling the reactor (B01J8/062 takes precedence)}
- C08G 63/785: {characterised by the apparatus used}
- B01J 2208/00132: Tubes
- B01J 2208/0015: Plates; Cylinders
- B01J 2208/00522: using inert heat absorbing solids outside the bed
- C08G 63/183: Terephthalic acids
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

## Abstract

An apparatus for continuously producing polybutylene terephthalate, which comprises a first reactor for reacting an aromatic dicarboxylic acid with a glycol, thereby producing an oligomer, a second reactor for polycondensating the oligomer, thereby preparing a low polymerization product, and a third reactor for further polycondensating the low polymerization product, thereby producing a high molecular weight polyester, where the second reactor is a vertical, cylindrical polymerization vessel having a plurality of concentrical partitioned reaction compartments therein, each of the reaction compartments being provided with stirring blades and a heater, and an outlet for volatile matters being provided at the upper part of the vessel. The second reactor contributes to efficient and continuous production of polybutylene terephthalate having a good quality.

## Claims

### Claim 1

An apparatus for continuously producing polybutylene terephthalate, comprising:
a starting material conditioning vessel for mixing and stirring an aromatic dicarboxylic acid comprising terephthalic acid as a main ingredient and a glycol comprising 1,4-butanediol as a main ingredient, as the starting materials for polybutylene terephthalate;
a first reactor for reacting the aromatic dicarboxylic acid comprising terephthalic acid as a main ingredient with the glycol comprising 1,4-butanediol as a main ingredient mixed and stirred by the starting material conditioning vessel, thereby producing an oligomer with an average degree of polymerization of 2 to 5, the first reactor having a calandria heat exchanger immersed in a process solution of a vessel proper thereof, the process solution supplied into the vessel proper being stirred and mixed by spontaneous convection;
a second reactor for polycondensating the oligomer from the first reactor, thereby preparing a low polymerization product with an average degree of polymerization of 20 to 70, the second reactor being a vertical cylindrical polymerization vessel having a plurality of concentric partitioned reaction compartments therein, each of the reaction compartments being provided with stirring blades and a heater;
a third reactor for further polycondensating the low polymerization product from the second reactor, thereby producing a high molecular weight polyester with an average degree of polymerization of 70 to 180, the third reactor being a horizontal cylindrical vessel reactor in which a stirring rotor in a vessel proper thereof is provided with a plurality of stirring blade blocks in accordance with viscosity of the process solution, and the stirring blades are without any rotating shaft along a center of the stirring rotor; and
a recycle line for returning recycle 1,4-butanediol discharged from each reactor to the starting material conditioning vessel.

### Claim 2 (depends on 1)

An apparatus for continuously producing polybutylene terephthalate according to claim 1, wherein the recycle line has a line for returning the recycle 1,4-butanediol discharged from wet condensers at pressure reduction devices disposed at the third reactor to wet condensers at pressure reduction devices disposed at the second reactor, a line for returning the recycle 1,4-butanediol discharged from wet condensers at pressure reduction devices disposed at the second reactor and the third reactor to a tank, a line for returning the recycle 1,4-butanediol to a tank from a distillation column connected to the first reactor, and a line for supplying the recycle 1,4-butanediol from a tank to the starting material conditioning vessel.

### Claim 3 (depends on 2)

An apparatus for continuously producing polybutylene terephthalate according to claim 2, further comprising a line for supplying fresh 1,4-butanediol to wet condensers at pressure reduction devices disposed at the third reactor.

### Claim 4 (depends on 1)

An apparatus for continuously producing polybutylene terephthalate according to claim 1, further comprising a line for supplying fresh 1,4-butanediol to wet condensers at pressure reduction devices disposed at the third reactor.

### Claim 5

A method for continuously producing polybutylene terephthalate, comprising steps of:
mixing and stirring an aromatic dicarboxylic acid comprising terephthalic acid as a main ingredient and a glycol comprising 1,4-butanediol as a main ingredient, as starting materials for polybutylene terephthalate, by a starting material conditioning vessel;
reacting the aromatic dicarboxylic acid comprising terephthalic acid as a main ingredient with the glycol comprising 1,4-butanediol as a main ingredient mixed and stirred by the starring material conditioning vessel, in a first reactor, thereby producing an oligomer with an average degree of polymerization of 2 to 5, the first reactor having a calandria heat exchanger immersed in process solution of a vessel proper thereof, the process solution supplied into the vessel proper being stirred and mixed by spontaneous convection;
polycondensating the oligomer from the first reactor in a second reactor, thereby preparing a low polymerization product with an average degree of polymerization of 20 to 70, the second reactor being a vertical cylindrical polymerization vessel having a plurality of concentric partitioned reaction compartments therein, each of the reaction compartments being provided with stirring blades and a heater;
further polycondensating the low polymerization product from the second reactor in a third reactor, thereby producing a high molecular weight polyester with an average degree of polymerization of 70 to 180, the third reactor being a horizontal cylindrical vessel reactor in which a stirring rotor in a vessel proper thereof is provided with a plurality of stirring blade blocks in accordance with viscosity of the process solution, and the stirring blades are without any rotating shaft along a center of the stirring rotor; and
returning recycle 1,4-butanediol discharged from each reactor to the starting material conditioning vessel.

### Claim 6 (depends on 5)

A method for continuously producing polybutylene terephthalate according to claim 5, wherein the step of returning recycle 1,4-butanediol has a substep for returning the recycle 1,4-butanediol discharged from wet condensers at pressure reduction devices disposed at the third reactor to wet condensers at pressure reduction devices disposed at the second reactor, a substep for returning the recycle 1,4-butanediol discharged from wet condensers at pressure reduction devices disposed at the second reactor and the third reactor to a tank, a substep for returning the recycle 1,4-butanediol to a tank from a distillation column connected to the first reactor, and a substep for supplying the recycle 1,4-butanediol from a tank to the starting material conditioning vessel.

### Claim 7 (depends on 6)

A method for continuously producing polybutylene terephthalate according to claim 6, further comprising a step for supplying fresh 1,4-butanediol to wet condensers at pressure reduction devices disposed at the third reactor.

### Claim 8 (depends on 5)

A method for continuously producing polybutylene terephthalate according to claim 5, further comprising a step for supplying fresh 1,4-butanediol to wet condensers at pressure reduction devices disposed at the third reactor.