Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-13
2002-06-04
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S275000, C528S276000, C528S281000, C528S283000, C528S285000, C528S286000, C528S300000, C528S301000, C528S302000, C528S307000, C528S308000, C528S308600, C524S115000, C524S127000, C524S135000, C524S136000
Reexamination Certificate
active
06399716
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a copolyester resin composition which has good biodegradability and physical properties, and a process for preparing and/or producing the same. More particularly, the present invention have solved a problem of poor biodegradability of aromatic containing copolyester resin wherein the aromatic ingredients are incorporated to increase the physical properties of the copolyester.
DESCRIPTION OF THE BACKGROUND ART
The present invention relates to a copolyester resin composition and a process of preparation thereof which has good biodegradability and physical properties. The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability. To improve the physical properties and inferior processability, the aromatic group is incorporated to the aliphatic polyester, but the rate of biodegradation is greatly decreased because of the aromatic group.
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 poly-condensation 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 is a coupling agent reacting to an aliphaltic 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, by incorporating aromatic group to the aliphatic polyester, the physical properties have been greatly improved, but the rate of biodegradation gets very slow.
SUMMARY OF THE INVENTION
The present invention provides a copolyester resin composition which has good biodegradability and a process for preparing and/or producing the same. To improve the biodegradability and physical properties of the copolyester, the present invention applied multistage reaction step, and copolyester resin having number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70° C. to 150° C., and melt index of from 0.1 to 50 g/10 minute (190° C., 2,160 g) is obtained. The biodegradability and physical properties of the copolyester resin of present invention has been greatly enhanced by incorporating (i) an “aliphatic prepolymers” having number average molecular weight of from 300 to 30,000, thus the aromatic components distribute randomly and not contiguously more than 8 aromatic components in a row in the dicarboxylic acid positions of the copolyester chain. So it can be used in many practical uses including packaging film. trash bags and agricultural Film.
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 “aliphatic prepolymers”) having number average molecular weights of from 300 to 30,000 is obtained through one or a plurality of condensation, esterification and ester-exchange reaction with;
(a) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof), 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
(b) one or a plurality of aliphatic (including cyclic type) glycols, selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 1,9-nonanediol, 1,2-decanediol, 1,10-decanediol, decamethylene glycol.
Next, in the second reaction step, with the existence of (i) an “aliphatic prepolymers” which was produced in the first reaction step, from 0.1 wt % to 30 wt %, (ii) 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; and (iv) one or a plurality of aliphatic (including cyclic type) glycol selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 1,9-nonanediol, 1,2-decanediol, 1,10-decanediol, decamethylene glycol, are added, one or a p
Chung Hyun Soo
Kim Do Youn
Kim Dong Hoon
Lee Jae Wang
Lee Suok Woo
Acquah Samuel A.
IRE Chemical Ltd.
Shanks & Herbert
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