Polyester resins such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) have excellent mechanical properties, heat resistance, moldability, recyclability, and chemical resistance, and can be made into molded articles, films, fibers and the like by melt processing. In particular, PBT is widely used as a material for industrial molded articles such as connectors, relays, and switches for automobiles and electrical/electronic devices. In general, PBT is produced from terephthalic acid (TPA) or an ester-forming derivative thereof, and 1,4-butanediol (BDO).
In JP 2014-129513 A, a small amount of a monomethoxy endcapped poly(ethylene glycol) is added to a thermoplastic resin, and they are reacted during polymerization to improve flowability.
In JP 63-35824 A, a monomethoxy endcapped poly(ethylene glycol) having a high molecular weight is reacted with polyethylene terephthalate (PET) during polymerization to impart an antifouling property and wash durability.
In JP 2001-247681 A, a PBT master batch containing polytetramethylene glycol is prepared to impart thermal shock resistance to PBT.
“Synthesis and characterization of poly(ethylene glycol) methyl ether endcapped poly(ethylene terephthalate)” written by Timothy E. Long, published by Macromolecular Symposia, October 2003, volume 199, issue 1, pp. 163-172 discloses a PET resin obtained by adding a monomethoxy endcapped poly(ethylene glycol) during PET polymerization.
PBT is known to have a higher melt viscosity as its molecular weight increases. Reducing the melt viscosity reduces the shear heating during melt processing, which enables reduced thermal decomposition, lower melt-processing temperatures, and the production of molded articles of complex shape.
However, in the technique in JP 2014-129513 A, the amount of the compound having a (poly)oxyalkylene group is small since a decrease in mechanical properties should be suppressed so that the reduction effect of melt viscosity is small, which is problematic.
In the technique of JP 63-35824 A, the molecular weight of the compound having a (poly)oxyalkylene group is high so that the molecular weight decreases in a molten state, and the reduction effect of melt viscosity is small, which is problematic.
In the technique of JP 2001-247681 A, a compound having a (poly)oxyalkylene group is bound to the backbone rather than to a polymer end to prepare a block copolymer. Therefore, the reduction effect of melt viscosity is hardly obtained, which is problematic.
In the technique of “Synthesis and characterization of poly(ethylene glycol) methyl ether endcapped poly(ethylene terephthalate)” written by Timothy E. Long, published by Macromolecular Symposia, October 2003, volume 199, issue 1, pp. 163-172, the obtained PET resin is a low molecular weight polymer and has a low melting point and low mechanical properties. In addition, the PET resin disadvantageously gels through the introduction of a branched backbone.
It could therefore be helpful to provide a terminal modified polybutylene terephthalate resin having a very low melt viscosity, high melt stability, and a high melting point.