Biodegradable recycled polyester resin and production...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...

Reexamination Certificate

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C521S048500

Reexamination Certificate

active

06730709

ABSTRACT:

BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a biodegradable polyester resin and a production process therefor, wherein the polyester resin is obtained by utilizing a recycled aromatic polyester. More specifically, the invention relates to a biodegradable polyester resin and a production process therefore, wherein the polyester resin is obtained by a reaction of a recycled aromatic polyester with a specific aliphatic polyester.
B. Background Art
Aromatic polyesters have good mechanical strength, thermal properties, humidity properties, transparency, and many other excellent properties. Therefore, they are used in wide fields such as fibers, molding materials, wrapping materials, and magnetic recording materials. In addition, a demand for the aromatic polyesters is more and more increasing due to their excellent characteristics in recent years, and with this increase of the demand, the amount of waste aromatic polyesters increases so sharply as to cause social problems.
However, because the aromatic polyesters generally have no biodegradability and therefore do not putrefy, disposition thereof by embedding them into lands wants places therefor, and further, disposition of the aromatic polyesters by incineration has such as problems of doing damage to incinerators due to high heat of combustion. As means to solve these problems, attempts are made to recover and recycle used aromatic polyesters. However, the number of times of the recycling is naturally limited, and the disposition must be carried out sooner or later, therefore the fundamental solution of the problems has not been attained yet.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide a biodegradable recycled polyester resin and a production process therefor, wherein the polyester resin is inexpensive and economical due to use of recycled aromatic polyesters, and further, can solve problems of wastes by affording biodegradability to the aromatic polyester which has so far been assumed to have no biodegradability.
B. Disclosure of the Invention
Thus, to solve the above-mentioned problems, the present inventors diligently studied about whether or not the aromatic polyester itself, which has so far been assumed to generally have no biodegradability, could be caused to biodegrade.
First of all, the inventors made an attempt to blend the aromatic polyester with a biodegradable aliphatic polyester. However, in this case, only the aliphatic polyester portions biodegraded, and the aromatic polyester did not, therefore the fundamental solution of the problems was not attained.
Thus, instead of the above simple blending, the inventors caused the aromatic polyester to react with the aliphatic polyester by a specific method and to thereby constitute a molecular structure such that the aromatic polyester and the aliphatic polyester were arranged in a block form. As a result, the inventors have found out that, surprisingly, even the aromatic polyester portions, which have so far been assumed not to biodegrade, do biodegrade.
That is to say, a biodegradable recycled polyester resin, according to the present invention, is obtained by a process including the step of carrying out a reaction of a recycled aromatic polyester (A) with an aliphatic polyester (B) having a number-average molecular weight of 3,000 to 300,000 in a reaction ratio (weight ratio) of (A)/(B)=95/5 to 5/95, thereby affording biodegradability to the recycled aromatic polyester (A).
In addition, a production process for a biodegradable recycled polyester resin, according to the present invention, comprises the step of carrying out a melting reaction of a recycled aromatic polyester (A) with an aliphatic polyester (B) in a heated state in a reaction ratio (weight ratio) of (A)/(B)=95/5 to 5/95, wherein the aliphatic polyester (B) has a number-average molecular weight of 3,000 to 300,000.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the recycled aromatic polyester (A) as used in the present invention include: a material with a hysteresis of having been passed through a molding machine or spinning apparatus in a heat-melted state; and a recovered (recycled) product formed from a virgin raw material in such as polyester production facilities; and further a product obtained by a process including the step of causing the above recovered (recycled) product to further react with a multifunctional acid anhydride, such as pyromellitic dianhydride, or a multifunctional epoxy compound. The above recovered (recycled) product is favorably used in the form pulverized into the size of 0.1 to 20 mm.
A polyester comprising such a recycled aromatic polyester (A) is obtained mainly from terephthalic acid and a glycol having at least two carbon atoms by conventional methods. Examples of polybasic acids other than terephthalic acid include isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, and diphenyl ether dicarboxylic acid. These polybasic acids may be copolymerized with the above raw materials in small ratios. Examples of the glycol having at least two carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and decamethylene glycol. Of these, a combination of terephthalic acid with ethylene glycol or 1,4-butanediol is favorable in consideration of the melting point of the resulting aromatic polyester and the economical advantages.
The above aromatic polyesters may be polyesters obtained by further copolymerization with a small quantity of at least one kind of trifunctional or more multifunctional compound such as pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, trimethylolpropane, and pentaerythritol, if necessary.
If necessary, the polyester as obtained in the above way may be converted into a high-molecular one by a further reaction with various chain-extending agents.
The method involving the above reaction with the chain-extending agent has industrial disadvantages in that: the process involves many steps; unreacted chain-extending agents have an bad influence on safety or cause changes of properties with the passage of time; and the used chain-extending agents cause fisheyes in films. Examples of the chain-extending agents include the below-mentioned ones such as isocyanates, epoxides, aziridines, oxazolines, multivalent metal compounds, multifunctional acid anhydrides, phosphate esters, and phosphite esters. These can be used either alone respectively or in combinations with each other.
The specific process for producing the aliphatic polyester (B) as used in the present invention is not especially limited, but, usually, examples of the process for obtaining the aliphatic polyester resin include:
(i) a process which involves polycondensation of a polybasic acid (or its ester) with a glycol;
(ii) a process which involves polycondensation of a hydroxycarboxylic acid (or its ester);
(iii) a process which involves ring-opening polymerization of a cyclic acid anhydride with a cyclic ether; and
(iv) a process which involves ring-opening polymerization of a cyclic ester.
Examples of the polybasic acid as used in the above process (i) include succinic acid, adipic acid, suberic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, octadecanedicarboxylic acid, dimer acid, and their esters. Examples of the glycol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and decamethylene glycol. In addition, it is also possible to use polyoxyalkylene glycol as a part of the glycol component. Examples of this polyoxyalkylene glycol include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, and their copolymers. Of these, a combi

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