Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
2001-08-13
2004-10-12
Wyrozebski, Katarzyna (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C521S048500
Reexamination Certificate
active
06803389
ABSTRACT:
This invention relates to a novel process for producing polyester resin using regenerated polyester which has been recovered from waste materials such as disused PET (polyethylene terephthalate) bottles, and also to paint compositions containing the polyester resin prepared by said process.
Disposal of wastes has been recently causing serious problems, and “3R's” (Recycle, Reduce and Reuse) are recommended. In particular, recycling of disused PET bottles is being promoted, led by the Council for PET Bottle Recycling in Japan Aided by the complete enactment of Containers and Packagings Recycling Act in April, 2000, the recovery ratio of disused PET bottles has been steadily increasing. Under the circumstances, it is essential to enlarge utility of the recovered and regenerated polyester (recycled polyester).
For example, U.S. Pat. No. 5,252,615, EP-A-558,905 and EP-A-558,906 disclose a process for producing intended polyester resin, which comprises subjecting a polyhydric alcohol component and regenerated PET to a depolymerization reaction in the presence of a catalyst to reduce the molecular weight of the PET, and adding a polybasic acid component to the system to carry out a polycondensation reaction. Those publications also teach that the resulting polyester resin is useful for both water-based and non-water-based coating compositions. However, the same process requires many hours for the depolymerization reaction of polyhydric alcohol component with regenerated PET, and the production costs are high compared to conventional processes which do not use regenerated polyester.
The Official Gazette of Hei 11 (1999)-228733A-JP discloses a process for synthesizing polyester resin through ester-interchange reaction of recycled polyester such as regenerated PET with a polyester oligomer having a molecular weight not higher than 5,000. However, this process is subject to a number of problems that it requires an extra step of advance synthesis of said polyester oligomer; its depolymerization step requires many hours because sufficient depolymerization of recycled polyester is difficult due to insufficient amount of alcohol component in the depolymerization system and also because it is a reaction between high molecular weight compounds; and the filtration residue is apt to form in large quantities.
Furthermore, Hei 8 (1996)-253596A-JP discloses a production process of binding resin for toners which comprises the two steps of adding recycled polyester such as regenerated PET to the reaction system to carry out the polymerization while depolymerizing the recycled polyester in the presence of alcohol and if necessary, water; and then of adding an acid component to carry out addition reaction and increasing the molecular weight of the product. According to this process, the first step is a reaction in the system in which a large excess (at least approximately twice) of hydroxyl groups to carboxyl groups are present, and depolymerization of recycled polyester predominantly takes place. Hence the polyester formed in the first step has a low molecular weight, and in the second step an acid component is blended to carry out the addition and polymerization reaction. Thus, the process does not enable effective one-step synthesis of high molecular weight polyester resin. The process attempts to synthesize relatively low molecular weight polyester in the first step and to increase its molecular weight in the second step by adding an acid component. Whereas, the process uses, as the acid component to be added in the second step, tri- or higher functional acid in large quantities to form branched polymers, which involve a problem that they are apt to be gentled as their molecular weight increases.
The main object of the present invention is to provide a process for producing within a short time a high molecular weight polyester resin free of any problem in respect of physical properties, which is transparent and substantially free of formation of foreign matters or filtration residues, from the polyester resin recovered from waste materials and regenerated.
We have engaged in concentrative studies with the view to accomplish the above object, and now discovered that the object can be met by concurrently reacting the polyester resin made chiefly from terephthalic acid, which has been recovered from waste materials and regenerated, with an alcoholic component and an acid component. The present invention has thus been completed.
Accordingly, therefore, the present invention provides a process for producing a polyester resin having a resin acid value not higher than 120 mg KOH/g, hydroxyl value not higher than 120 mg KOH/g and a number-average molecular weight within a range of 2,000-30,000, the process being characterized by concurrently reacting a polyester whose chief starting material is terephthalic acid and which has been recovered from waste materials and regenerated, a polyhydric alcohol component and polybasic acid component, at such ratios that the regenerated polyester occupies 10-80% by weight, based on the total weight of said regenerated polyester, polyhydric alcohol component and polybasic acid component.
The invention furthermore provides paint compositions which contain the polyester resin produced by the above-described production process.
Hereinafter the invention is explained in further details. Those polyester resins made chiefly from terephthalic acid, which have been recovered from waste materials and regenerated, and which are used in the process of this invention (hereafter the polyester resins may be abbreviated as “regenerated PES”) include polyethylene terephthalate (e.g., PET bottles) which are recovered for recycling of sources, industrial waste polyethylene terephthalate, and polyester resins regenerated from the wastes occurring in the course of production of polyester products (film, fibers, etc.) made chiefly from terephthalic acid. In particular, recycled polyethylene terephthalate and recycled polybutylene terephthalate are suitable. The regenerated PES is normally used in the form of chips or crushed pieces.
According to the process of the present invention, such regenerated PES, polyhydric alcohol component and polybasic acid component are concurrently reacted, if necessary in the presence of a depolymerization catalyst.
As said polyhydric alcohol component, those that are normally used as alcohol component for constituting polyester resins can be similarly used, examples of which including dihydric alcohols such as ethylene glycol, diethylene glycol triethylene glycol propylene glycol, 1,3-propanediol 2-methyl-1,3-propanediol 2,2-diethyl-1,3-propanediol, 2-butyl-2-diethyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,4-dimethylolcyclohexane; trihydric alcohols such as trimethylolpropane, trimethylolethane and glycerine; and tetra- and higher hydric alcohols such as diglycerine, triglycerine, pentaerythritol, dipentaerythritol and sorbitol. Of those, glycerine, trimethylolpropane, ethylene glycol, neopentyl glycol and 1,4-dimethylolcyclohexane are preferred in view of their depolymerizing ability and solubility.
As the polybasic acid component, any of those normally used as the acid component forming polyester resin can similarly be used, examples of which including dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, diphenylmethane-4,4′-dicarboxylic acid, succinic acid, fumaric acid, adipic acid, sebacic acid and maleic anhydride; tri- and higher polybasic acids such as trimellitic anhydride, pyromellitic anhydride, trimesic acid and methylcyclohexene-tri-carboxylic acid; and C
1
-C
6
alkyl esters of those dibasic acids and tri- and higher polybasic acids. Of those, dibasic acids and their C
1
-C
6
alkyl esters are preferred.
According to the process of the present invention, above-describe
Kawamura Chicara
Takabayashi Isamu
Kansai Paint Co. Ltd.
Wenderoth Lind & Ponack LLP
Wyrozebski Katarzyna
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