	US 7,550,552 B2
	Process for producing polybutylene terephthalate
Masanori Yamamoto, Yokkaichi (Japan); Toshiyuki Hamano, Yokkaichi (Japan); and Shinichiro Matsuzono, Yokkaichi (Japan)
Assigned to Mitsubishi Chemical Corporation, Tokyo (Japan)
Appl. No. 10/594,676 PCT Filed Apr. 28, 2005, PCT No. PCT/JP2005/008209 § 371(c)(1), (2), (4) Date Aug. 01, 2007, PCT Pub. No. WO2005/108462, PCT Pub. Date Nov. 17, 2005.
Claims priority of application No. 2004-140366 (JP), filed on May 10, 2004.
Prior Publication US 2008/0081886 A1, Apr. 03, 2008
Int. Cl. C08G 63/00 (2006.01)

U.S. Cl. 528—271

15 Claims

1. A continuous process for producing polybutylene terephthalate, comprising: continuously subjecting terephthalic acid and 1,4-butanediol to an esterification reaction in the presence of a titanium compound catalyst using one-stage or plural-stage esterification reaction vessels, and then subjecting the resultant reaction product to a polycondensation reaction, said process satisfying the following requirements (A) to (C):

(A) a pressure (P) in at least one of said esterification reaction vessels being in the range of 20 to 90 kPa;

(B) a concentration of the titanium compound catalyst used in the esterification reaction being not more than 90 ppm, calculated as a concentration (α) by weight of titanium atom, based on the weight of the polybutylene terephthalate finally produced; and

β=BM/TM−0.03×α+0.045×P (I)

β=4.0 to 7.0 (II)

wherein TM is the number of moles of terephthalic acid supplied to the esterification reaction vessels per unit time; BM is the number of moles of whole 1,4-butanediol supplied continuously to the esterification reaction vessels per unit time; α is a concentration (unit: ppm) of the titanium catalyst used in the esterification reaction (calculated a concentration by weight of titanium atom based on the finally produced PBT); and P is a pressure (unit: kPa) in at least one of the esterification reaction vessels, and wherein BM/TM represented by formula (I) is not less than 2.1.