Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
2001-07-23
2002-08-06
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C528S272000, C528S495000, C528S501000, C528S503000, C525S437000, C525S444000, C521S048000
Reexamination Certificate
active
06429233
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of recycling a polyester chip derived from the used containers or industrial wastes recovered for resource recycling and to a reconstituted polyester resin as obtainable by the method.
BACKGROUND ART
Heretofore, polyester resins, particularly polyester resins produced by copolymerizing terephthalic acid with diols, have been used in quantities in the manufacture of fiber, film and other shaped articles.
Usually, in various stages of manufacture of polyester fiber, film or other shaped articles, varying amounts of rejects and scraps are inevitably formed. For efficient uses of resources, it is assuming more and more importance to reuse not only said rejects and wastes but also used polyester articles as such. Moreover, the recent upsurge in the recycling movement has caused a dramatic increase in the quantity of poly (ethylene terephthalate) (PET) articles recovered from the domestic refuse and, therefore, the recovery and reuse of them is also getting more and more important.
Several technologies have already been reported on the reuse of said rejects, scraps, and used polyester articles recovered (these will hereinafter be referred to collectively as “recovered polyester”), and Japanese Kokai Publication Hei-6-166747, for instance, discloses a method of producing a reconstituted PET through depolymerization of PET.
The PET reconstituted by the above method tends to have been discolored by the heat applied for depolymerization under high-viscosity condition so that the reconstituted PET can be used only in the manufactured of ordinary fiber and film.
Japanese Kokoku Publication Sho-62-56893 discloses a method of producing a reconstituted polyester resin for the manufacture of medical fibers which comprises utilizing a reconstituted material containing not more than 20 mole % of the polyethylene terephthalate repeating unit for the purpose of overcoming the disadvantage of poor dyeability of polyethylene terephthalate. However, this PET-containing reconstituted polyester resin, which is intended for use as fiber, is not only large in molecular weight and sparingly soluble in solvents but also shows no fluidity over the temperature range from room temperature to at least 190° C., with the result that it is not capable of forming thin films (20 to 60 &mgr;m).
Thus, the use for reconstituted resins obtained from recovered polyesters is limited to fiber and film and substantially none of recycled resins can be used as binders for coatings, adhesives, inks and the like.
DISCLOSURE OF THE INVENTION
The object of the invention is to provide a method for recycling a polyester which comprises reusing recovered polyesters to produce a reconstituted polyester resin suitable for use as a binder in coatings, adhesives and inks, among other products.
The inventors of the present invention made extensive investigations for solving the above problem and found a method for producing a reconstituted polyester resin having satisfactory thin-film-forming properties, good fluidity over a broad temperature range from room temperature to 140° C., and a sufficient amount of functional groups to react with a crosslinking agent.
The present invention, therefore, provides a method for recycling a polyester chip
which comprises providing a polyester chip (a) whose principal component of polybasic acid is terephthalic acid, a polyol (b) and a polybasic acid (c), with the total of (a), (b) and (c) being taken as 100 weight parts,
subjecting 5 to 60 weight parts of said polyester chip (a) and 5 to 40 weight parts of said polyol (b) to transesterification reaction
and reacting it with 10 to 60 weight parts of said polybasic acid (c) to give a reconstituted polyester resin having a number average molecular weight of 1000 to 10000, an acid value of 1 to 100, and a hydroxyl value of 30 to 200,
the total number of moles of hydroxyl group being not less than 1.03 times the total number of moles of carboxyl group in the material for the production of said reconstituted polyester resin.
The invention further provides a method for recycling a polyester chip
which comprises providing a polyester chip (a) whose principal component of polybasic acid is terephthalic acid, a polyol (b) and a polybasic acid (c), with the total of (a), (b) and (c) being taken as 100 weight parts,
subjecting 5 to 60 weight parts of said polyester chip (a) and 10 to 60 weight parts of said polybasic acid (c) to transesterification reaction
and reacting it with 5 to 40 weight parts of said polyol (b) to give a reconstituted polyester resin having a number average molecular weight of 1000 to 3000, an acid value of 3 to 100, and a hydroxyl value of 30 to 200,
the total number of moles of hydroxyl group being not less than 1.03 times the total number of moles of carboxyl group in the material for the production of said reconstituted polyester resin.
The invention further provides a reconstituted polyester resin as obtainable by the above method for recycling a polyester chip.
In the context of the present invention, the terms “polyester chip”, “recovered poly(ethylene terephthalate); recovered PET”, and “recovered poly(butylene terephthalate)” means the poly(ethylene terephthalate) or poly(butylene terephthalate) derived from containers recovered for recycling and the poly(ethylene terephthalate) or poly(butylene terephthalate) derived from industrial wastes, including crushings of the rejects or scraps formed in various stages of manufacture of polyester products (for example, fiber, film and other shaped articles).
Further, in the context of the invention, the term “reconstituted polyester resin” means the polyester resin synthesized by reusing said “polyester chip”.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is now described in detail.
The first aspect of the present invention relates to a method for recycling a polyester chip
which comprises providing a polyester chip (a) whose principal component of polybasic acid is terephthalic acid, a polyol (b) and a polybasic acid (c), with the total of (a), (b) and (c) being taken as 100 weight parts,
subjecting 5 to 60 weight parts of said polyester chip (a) and 10 to 60 weight parts of said polybasic acid (c) to transesterification reaction
and reacting the reaction product further with 5 to 40 weight parts of said polyol (b) to give a reconstituted polyester resin having a number average molecular weight of 1000 to 10000, an acid value of 1 to 100, and a hydroxyl value of 30 to 200,
the total number of moles of hydroxyl group being not less than 1.03 times the total number of moles of carboxyl group in the material for the production of said reconstituted polyester resin.
Referring to the amounts of said polyester chip (a), polyol (b) and polybasic acid (c), the values mentioned above are formulating amounts of the respective materials, with the total amount thereof being taken as 100 weight parts.
The subject of recycling in the present invention is said polyester chip (a) containing terephthalic acid as a predominant polybasic acid component. While polyesters are generally prepared from a polybasic acid and a diol, the polyester chip (a) mentioned above is produced by using terephthalic acid as a principal polybasic acid component. The polyester chip (a) may comprise poly(ethylene terephthalate) and/or poly(butylene terephthalate). As will be mentioned later herein, the kinds and proportions of starting materials for said polyester chip (a) must be known in order that the amounts of hydroxyl and carboxyl groups that will be available on hydrolysis may be ascertained.
The polyester chip (a) mentioned above is derived from used fiber, film and other shaped articles and/or the rejects and scraps formed in the manufacture of such articles and is preferably in the form of pellets, chips or crushings not larger than 20 mm square. When the size of polyester chip (a) is not greater than 20 mm, the melting time can be curtailed in the course of production and, moreover, when said pellet or the like form is used, the apparent specif
Matsumoto Masahiro
Oguri Hiroyuki
Umemoto Hirotoshi
Acquah Samuel A.
Connolly Bove Lodge & Hutz
Nippon Paint Co. Ltd.
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