High-molecular weight polymers and methods of manufacture

Details High-molecular weight polymers and methods of manufacture High-molecular weight polymers and methods of manufacture

2002-10-08

2004-09-21

Robertson, Jeffrey B. (Department: 1712)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S437000

Reexamination Certificate

active

06794462

ABSTRACT:

FIELD OF THE INVENTION
The field of the invention is high-molecular weight polymers.
BACKGROUND OF THE INVENTION
Many known copolymers comprising an aromatic polyester and caprolactone are known in the art and used in numerous applications as thermoplastic elastomers. For example, Japanese Patent Publication 4115 (published Feb. 5, 1973) describes copolymers in which the aromatic polyester is poly(ethylene terephthalate) (PET) or poly(butylene terephthalate) (PBT). The average molecular weight of some of these copolymers is within a range of about 500-5,000, which corresponds to an intrinsic viscosity (IV) of less than 0.3 (as measured in a 60/40 by weight mixture of phenol and tetrachloroethane solvents according to William L. Hergenrother and Charles Jay Nelson, “Viscosity-Molecular Weight Relationship for Fractionated Poly(ethylene Terephthalate)”, Journal of Polymer Science (1974),12, 2905-2915). Unfortunately, copolymers having such relatively low IV are generally insufficient for spinning high-performance fibers.
The molecular weight can be extended to at least some degree by reacting the aromatic polyester and caprolactone in the presence of a polyfunctional acylation agent, thereby forming a multiblock copolymer as also described in the Japanese Patent Publication 4115. Although such a copolymerization generally increases the molecular weight and intrinsic viscosity of the resulting product, various disadvantages still remain. For example, the intrinsic viscosity of the aromatic polyesters used in such copolymerizations is relatively low. Consequently, the resulting copolymers and multiblock copolymers will exhibit comparably low molecular weight, intrinsic viscosity, and relatively short block lengths. Moreover, due to the conditions employed during the polymerization process (particularly temperature and residence time in the reactor), the rate of transesterification may be undesirably high.
To circumvent or at least alleviate most of the aforementioned problems with block copolymers comprising an aromatic polyester and caprolactone, copolymerization may be carried out under conditions as described in U.S. Pat. No. 5,869,582 to Tang et al. Tang's co-polymer is formed from an aromatic polyesters with relatively high intrinsic viscosity (IV of about 0.9) and lactone monomers. Furthermore, the copolymerization is performed in a reactor having a configuration that significantly reduces residence time, and wherein the melt in the process of polymerization is under continuous agitation of intermeshing turbulators and homogenization of advancing/combining mixers. However, numerous advanced applications and fibers demand block copolymers with even higher molecular weight and intrinsic viscosity.
While it is known for certain polymers to increase the molecular weight after polymerization in the solid state, solid-stating block copolymers comprising an aromatic polyester and caprolactone using known protocols typically results in an increased molecular weight, but in significant loss of caprolactone concurrent with a substantial increase in transesterification. For example, when temperatures normally employed for PET solid-stating are used in solid stating of a PET-caprolactone copolymer, numerous significant and often undesirable changes may occur. Among other things, at temperatures of about 200° C., the percent esterification can increase by a factor of two, and at temperatures of about 210-215° C., the loss of caprolactone can be as much as 10% of the total amount present.
Although various methods and compositions are known in the art to produce block copolymers from an aromatic polyester and caprolactone, all, or almost all of them suffer from one or more problems. Thus, there is still a need to provide compositions and methods for production of such block copolymers, especially block copolymers with improved intrinsic viscosity.
SUMMARY OF THE INVENTION
The present invention is directed to solid-stated block copolymers from aromatic polyester and caprolactone. Such copolymers have been solid state polymerized under a protocol to increase the intrinsic viscosity at least 20%, while decreasing the caprolactone content no more than 1.2% absolute and increasing the transesterification no more than 3.5% absolute. Preferred solid-stated copolymers have an intrinsic viscosity of at least 0.82.
In one aspect of the inventive subject matter, the protocol includes heating of the copolymer to a temperature of no more than 175° C., more preferably to a temperature of no more than 165° C., wherein the heating is preferably performed under a nitrogen sweep. It is further contemplated that especially where the aromatic polyester comprises poly(ethylene terephthalate), the decrease in caprolactone content is no more than 0.1% absolute, and the increase in transesterification is no more than 0.2% absolute. In further alternative aspects, the increase in intrinsic viscosity of such polymers is at least 35% and the increase in transesterification is no more than 0.6% absolute.
In another aspect of the inventive subject matter, the aromatic polyester in preferred copolymers is a poly(alkylene terephthalate) such as poly(ethylene terephthalate) and poly(butylene terephthalate), a poly(alkylene naphthalate) such as poly(ethylene naphthalate) and poly(butylene naphthalate), or a poly(cycloalkylene naphthalate).
In a still further aspect of the inventive subject matter, a method of producing a fiber comprises a step in which contemplated block copolymers are provided. In a further step, the copolymer is solid-stated to achieve an increase in intrinsic viscosity of at least 20%, a decrease in caprolactone content of no more than 1.2% absolute, and an increase in transesterification of no more than 3.5% absolute, wherein the solid-stated copolymer has an intrinsic viscosity of no less than 0.82. In a still further step, the solid-state polymerized copolymer is spun to a fiber. Consequently, it is contemplated that yarns may be spun from contemplated block copolymers.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention.
DETAILED DESCRIPTION
The inventors discovered that a block copolymer of an aromatic polyester and a caprolactone can be solid-stated (i.e., the molecular weight of the polymer can be increased while the polymer is in the solid state) to significantly advance the IV while substantially maintaining caprolactone content and transesterification. More particularly, the inventors surprisingly observed that conditions similar to conditions employed for drying are sufficient for such solid stating.
In a particularly preferred aspect of the inventive subject matter, the block copolymer is a block copolymer of polyethylene terephthalate and caprolactone with IV of about 0.76, a caprolactone content of about 13.2 wt %, and a transesterification of approximately 5.2%, which is commercially available from Honeywell under the trade name SECURUS™ material, and which is solid-stated using the following protocol: Crystallization cycle at 120° C. under vacuum at 15 mm Hg for 8 hrs, followed by incubation at 152° C. under nitrogen sweep for 24 hrs.
However, it should be appreciated that while a block copolymer of polyethylene terephthalate and caprolactone with an IV of about 0.76, a caprolactone content of about 13.2 wt %, and a transesterification of approximately 5.2% may be used, numerous alternative copolymers are also considered suitable for use in conjunction with the teachings presented herein. For example, the aromatic polyester in alternative copolymers need not be restricted to polyethylene terephthalate, but may also include other poly(alkylene terephthalates), poly(alkylene naphthalates), and poly(cycloalkylene naphthalates), wherein the alkylene unit in such polymers may have between 2 to 10 carbon atoms, and more preferably between 2 and 6 carbon atoms. Further preferred copolymers have a caprolactone content of no more than 30 mol %, and more prefera

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