Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-12-11
2004-03-30
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C524S141000, C524S145000, C524S601000
Reexamination Certificate
active
06713595
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to copolyester resin composition which has good physical properties and biodegradability and a process for preparing and/or producing the same which is suitable for various applications, such as films, moldings, and fiber. More particularly, the present invention have solved a problem of poor physical properties, especially tensile strength and tear strength, so it can be used in many practical uses including packaging film and trash bags.
DESCRIPTION OF THE RELATED ARTS
Many aliphatic polyester resin compositions have been published in the literature, and they completely biodegrade in the environment. But they have difficulty in commercializing because of high cost, poor physical properties and inferior processability comparing to the conventional polymers such as polyethylene, polypropylene and polystyrene.
The typical polyester resin used for various products including textures, fibers, moldings, formings, films, etc, is a high molecular weight aromatic polyester resin produced by the polycondensation reaction of terephthalic acid with ethylene glycol, or terephthalic acid with 1,4-butanediol. The high molecular weight polyester resin is a polymer having a number average molecular weight of over 10,000. Such aromatic polyester resins are not degradable naturally so it is a serious, worldwide of environmental concern.
Otherwise, the aliphatic polyester resins are known as being biodegradable (J.Macromol. Sci.-Chem., A23(3), pp.393-409 (1986)). They have a variety of usage in the medical and agricultural fields, and other applications are being developed.
However, the conventional aliphatic polyester resin has a low melting point and a high melt index, because of the structure of the main chain and the crystallinity thereof, and having low heat resistance and unsatisfactory mechanical properties, the usage of this polymer material has been limited. In order to utilize this aliphatic polyester resin, it should have a number average molecular weight of more than 30,000. However, it is difficult to manufacture the aliphatic polyester resins having a number average molecular weight of more than 15,000 using the conventional polycondensation reaction system because further growth reaction is surpassed by decomposition reaction due to the poor heat stability of aliphatic polyesters.
In order to solve this problem, Korean Laid-Open Patent No. 95-758 discloses the process of preparing high molecular weighted aliphatic polyester resin having a number average molecular weight of more than 30,000, by controlling the reaction temperature, the degree of vacuum and the amount of catalyst. However, this aliphatic polyester resin has poor processability because of its low weight average molecular weight and low heat stability.
In another method, Korean Laid-Open Patent No. 95-114171 discloses the process of preparing the high molecular weighted aliphatic polyester resin by introducing monomer which containing poly(at least three)-functional groups, where the recommended functional group is hydroxy group(—OH) or carboxylic group(—COOH). According to this process, by introducing the monomer, the reaction time can be reduced and the processability of the resin can be enhanced by broadening molecular weight distribution. However, the utilization of the polyester resin thereof is very difficult because the physical property such as a tensile strength is poor due to the increased amount of low molecular weight portions. Furthermore, it is difficult to control the reaction for preparing the polyester resin, because the polyester resin easily becomes a gel type.
In yet another process for increasing the molecular weight of the aliphatic polyester resin, Korean Laid-Open Patent No. 95-25072 discloses the high molecular weighted aliphatic polyester resin produced by using isocyanate as a coupling agent reacting to an aliphatic polyester resin having a number average molecular weight of from 15,000 to 20,000, which is produced by de-hydration reaction or de-glycol reaction of (1) an aliphatic (including cyclic type), and (2) an aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof), and a little of (3) monomer of polyhydric alcohol or polyhydric carboxylic acid (or acid anhydride thereof). According to the application, the aliphatic polyester resin has a number average molecular weight of from 20,000 to 70,000. However, this process requires more time for the reaction which leads to the poor production yield. And the isocyanate used as a coupling agent to increase the molecular weight is harmful to the human body so it needs to be handled carefully.
In yet another process for increasing the molecular weight of the aliphatic polyester resin, U.S. Pat. No. 5,843,573 discloses the high molecular weighted aliphatic polyester resin produced by using twin-screw extruder. However this process is very complicated and requires more time for the reaction.
In yet another process for increasing the molecular weight of the aliphatic polyester resin, World Patent WO9503347A1 discloses the high molecular weighted aliphatic polyester resin produced by using diethylene glycol as a glycol ingredient. However this process requires more time for the reaction, and the product is not desirable for practical use because of its low melting point and poor physical properties.
In the conventional process as mentioned above, it has been used to introduce a coupling agent like an isocyanate or a monomer such as a polyhydric alcohol or polyhydric carboxylic acid. These conventional processes have many problems such as low production yields, poor physical properties and/or poor processability.
SUMMARY OF THE INVENTION
The present invention provides a copolyester resin composition which has good physical properties, biodegradability and processability and a process for preparing and/or producing the same. To improve the biodegradability and physical properties of the copolyester, the present invention applied multi-stage reaction step, and copolyester resin having number average molecular weight of from 30,000 to 70,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 55° C. to 120° C., and melt index of from 0.1 to 30 g/10 minute (190° C., 2,160 g) is obtained. The processability and physical properties of the copolyester resin of the present invention has been greatly enhanced by incorporating (i) an “aromatic-aliphatic prepolymers” having number average molecular weight of from 300 to 30,000 and the contiguous repeating unit of aromatic group in the dicarboxylic acid position of “aromatic-aliphatic prepolymers” is less than 5. Thus it can be processed by using the conventional processing equipment for polyethylene and polypropylene without any modification.
To solve the above mentioned problems, the present inventors applied multi-stage reaction step. The copolyester resin composition according to the present invention would be described in detail hereinafter.
In the first reaction step, the oligomer-like substances (hereinafter, referred to as “aromatic-aliphatic prepolymers”) having number average molecular weights of from 300 to 30,000 and the contiguous repeating unit of aromatic group in the dicarboxylic acid position of “aromatic-aliphatic prepolymers” is less than 5, is obtained through one or a plurality of condensation, esterification and ester-exchange reaction with three ingredients;
(a) one or a plurality of aromatic dicarboxylic acid (or an acid anhydride thereof) which containing aromatic group in the molecule, selected from dimethyl terephthalate, terephthalic acid, phthalic acid, phthalic anhydride, isophthalic acid, 4-methylphthalic acid, 4-methylphthalic anhydride, dimethyl phthalate;
(b) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid; and
(c) one or a plurality
Chung Hyun Soo
Kim Do Youn
Kim Dong Hoon
Lee Jae Wang
Lee Suok Woo
IRE Chemical Ltd.
Shanks & Herbert
LandOfFree
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