Aliphatic polyester and process for the production thereof

Details Aliphatic polyester and process for the production thereof Aliphatic polyester and process for the production thereof

2000-03-20

2001-01-23

Acquah, Samuel A. (Department: 1711)

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

Synthetic resins

From ketone or ketene reactant

C528S225000, C528S271000

Reexamination Certificate

active

06177539

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a process for the production of a polyester and to a novel copolyester obtained by the process.
It is known to produce a polyester by ring-opening polymerization of &egr;-caprolactone using ethylene glycol as a polymerization initiator. One problem of this method is that the molecular weight of the polyester is only about 5,000. Use of an organometallic catalyst has led to a success in obtaining a polyester having a high molecular weight of 100,000 or more. In order to use the polyester thus obtained for application as a biodegradable polymer, it is important to remove the catalyst completely so that the polyester is free of the catalyst.
A method has been proposed to use boron trifluoride diethyl etherate as a catalyst for the production of a copolyester of &bgr;-propiolactone and &ggr;-butyrolactone (Urakawa et al, Polymer Preprints, Japan 42, 3721(1993)). This method, however, has a problem because the number average molecular weight of the copolyester is only 840-4,250 and because the amount of &ggr;-butyrolactone in the copolyester is 56 mole % at maximum.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a process which can produce a high molecular weight polyester without using a metal-containing catalyst.
Another object of the present invention is to provide a copolyester having a high molecular weight.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a process of producing a polyester, comprising polymerizing a cyclic lactone of the following formula (I):
wherein n is an integer of 1, 3 or 4, under a pressure of at least 200 MPa in the absence of any catalyst or in the presence of a metal-free polyesterification catalyst.
The present invention also provides a process of producing a copolyester, comprising polymerizing a mixture containing at least two different cyclic lactones of the following formula (I):
wherein n is an integer of 1-4, under a pressure of at least 200 MPa in the absence of any catalyst or in the presence of a metal-free polyesterification catalyst.
The present invention further provides a copolyester of at least one cyclic lactone of the following formula (I):
wherein n is an integer of 1-4 with a comonomer, the amount of said comonomer being 0.01 to 10 mole % based on said cyclic lactone, said comonomer being selected from the group consisting of spiculisporic acid and a spirodilactone of the following formula (II):
wherein n is an integer of 1-4.
The cyclic lactone of the above formula (I) used as a starting material for the production of polyesters may be &bgr;-propiolactone (n−1), &ggr;-butyrolactone (n=2), &dgr;-valerolactone (n=3) or &egr;-Caprolactone (n=4).
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
In one aspect of the present invention, a cyclic lactone of the formula (I) in which n is 1, 3 or 4 is polymerized under a pressure of at least 200 MPa, preferably at least 800 MPa in the absence of any catalyst or in the presence of a metal-free polyesterification catalyst. The upper limit of the reaction pressure is not specifically limited but is generally 2,000 MPa. The reaction temperature is generally 40-200° C., preferably 100-160° C. The reaction time is generally at least 10 hours, preferably at least 15 hours. The upper limit of the reaction time is not specifically limited but is generally 70 hours. By the above ring-opening polymerization, a polyester having a number average molecular weight of at least 10,000, preferably at least 30,000 can be obtained. The upper limit of the number average molecular weight is about 100,000.
The above reaction may be carried out in the presence of a metal-free or non-metal catalyst such as an organic acid, an organic base or a boron halide.
The organic acid may be an aliphatic or aromatic carboxylic acid having 1-10, preferably 1-4 carbon atoms. Illustrative of suitable organic acid catalysts are formic acid, acetic acid, propionic acid and benzoic acid. The acid catalyst is generally used in an amount of 0.01-10 mole %, preferably 0.01-1 mole %, based on the cyclic lactone.
The organic base may be an aliphatic or aromatic amine having 1-20, preferably 2-10 carbon atoms. Illustrative of suitable organic base catalysts are triethylamine, DBN (1,5-diazabicyclo[4,3,0]-5-nonene) and DBU (1,8-diazabicyclo[5,4,0]-7-undecene). The organic base catalyst is generally used in an amount of 0.01-10 mole %, preferably 0.01-1 mole %, based on the cyclic lactone.
The boron halide is preferably boron fluoride such as boron trifluoride and is generally used in an amount of 0.01-5 mole, preferably 0.01-1 mole, based on the cyclic lactone.
The non-metal polyesterification catalyst may be used in conjunction with an organic solvent such as an ether, a hydrocarbon, dichloromethane or toluene.
In another aspect of the present invention, a mixture containing at least two different cyclic lactones of the following formula (I):
wherein n is an integer of 1-4, is polymerized under a pressure of at least 200 MPa, preferably at least 800 MPa, in the absence of any catalyst or in the presence of a metal-free polyesterification catalyst. The upper limit of the reaction pressure is not specifically limited but is generally 2,000 MPa. The reaction temperature is generally 40-200° C., preferably 100-160° C. The reaction time is generally at least 10 hours, preferably at least 15 hours. The upper limit of the reaction time is not specifically limited but is generally 70 hours. By the above ring-opening polymerization, a polyester having a number average molecular weight of at least 10,000, preferably at least 30,000 can be obtained. The upper limit of the number average molecular weight is about 100,000. The above reaction may be carried out in the presence of a metal-free or non-metal catalyst. The catalyst described above in connection with the first aspect of the present invention may be used.
In the above-described first and second aspects of the present invention, a comonomer may be incorporated into the system in an amount of 0.01 to 10 mole % based on a total mole of the cyclic lactones. The comonomer may be a polycarboxylic acid having an alkyl side chain or a precursor thereof or a spirodilactone of the following formula (II):
wherein n is an integer of 1-4.
Examples of the polycarboxylic acid having an alkyl side chain or a precursor thereof include spiculisporic acid and agaricic acid. By reacting the cyclic lactone or a mixture of lactones with the polycarboxylic acid, a copolyester having a number average molecular weight of at least 5,000, preferably at least 10,000 can be obtained. The upper limit of the number average molecular weight is about 100,000.
By reacting the cyclic lactone or a mixture of lactones with the spirodilactone, a copolyester having a number average molecular weight of at least 5,000, preferably at least 10,000 can be obtained. The upper limit of the number average molecular weight is about 100,000.
The following examples will further illustrate the present invention. The melting point herein is measured by DSC (differential scanning calorimetry) method, the molecular weight is measured by GPC (gel permeation chromatography) method using polystyrene as a standard, and the absolute molecular weight is determined by the MALLLS method.


REFERENCES:
patent: 5300568 (1994-04-01), Abe et al.

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