Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
1998-07-28
2001-04-10
Weisberger, Richard (Department: 1774)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C264S177100, C264S288400
Reexamination Certificate
active
06214269
ABSTRACT:
The present invention relates to a band-shaped article and to a production process therefor. More specifically, it relates to a band-shaped article made from a polyester and used for packing or binding and to a production process therefor. The present invention also relates to a series of technologies for utilizing recovered polyester molded articles for the production of a band-shaped article having excellent characteristic properties.
PRIOR ART
Aromatic polyesters, especially polyethylene terephthalate, have excellent characteristic properties and are widely used as fibers, films and plastics. Since mechanical properties out of the physical properties of such a polyester are greatly dependent on the polymerization degree of the polyester, a polyester having, within limits that moldability related to melt viscosity and the like permits, a high degree of polymerization is desired. Therefore, various processes for producing a polyester having a high degree of polymerization are now being studied and proposed.
A solid-phase polymerization process is known as a means of further increasing the polymerization degree of a polyester obtained by melt polymerization. The solid-phase polymerization process is a method for increasing the degree of polymerization by heating a polyester at a temperature below its melting point. However, this process gives priority to the suppression of a secondary reaction caused by thermal decomposition over the reaction rate and has such a defect that an extremely long-time reaction is required and productivity is low.
A process is known in which a polymerization promoting agent such as diphenyl carbonate or diphenyl terephthalate is added during the melt polymerization of a polyester. Although a polyester having a high degree of polymerization can be obtained by the addition of the polymerization promoting agents in a short period of time, this process has such a defect that it cannot be used without reducing the pressure of a reaction system because a phenol formed as a by-product must be distilled out of the reaction system.
Since a polyester is readily thermally decomposed and hydrolyzed at a high temperature, dry heat resistance and wet heat resistance are required for the polyester. As the dry heat resistance and wet heat resistance of a polyester is greatly dependent upon the amount of terminal carboxyl groups of the polyester, a polyester having a small amount of terminal carboxyl groups is desired.
Although a polyester having a small amount of terminal carboxyl groups can be obtained by the above solid-phase polymerization process, the process has, as described above, a defect that it has a low productivity.
As a means of reducing the amount of terminal carboxyl groups of a polyester, there has been proposed a method for reacting a compound having a glycidyl group, such as phenyl glycidyl ether, N-glycidyl phthalimide or glycidyl carboxylate, with a molten polyester. However, a satisfactory effect still cannot be obtained without a catalyst. Therefore, use of a catalyst is proposed (for example, in JP-A 57-143524 (the term “JP-A” as used herein mean an “unexamined published Japanese patent application”) and the like). However, while it is possible to greatly reduce the amount of terminal carboxyl groups, it is impossible to produce a polyester resin having a high degree of polymerization required as a saturated polyester resin.
In recent years, the necessity for the recovery and reuse of plastics has been globally recognized in view of resource saving and environmental preservation, and the recovery and reuse of used polyester films and bottles are vigorously in progress.
The Container and Package Recycling Law has recently been enforced in Japan and obliges users to recover and recycle PET bottles. The development of a technology for recycling recovered PET bottles is under way.
However, since recovered polyester molded articles have repeatedly experienced heat hysteresis that they have been molten by heating at the time of molding, the polymerization degree thereof is low and the amount of terminal carboxyl groups thereof is increased. Hence, when they are directly re-molten and molded, a molded product having good physical properties cannot be obtained. Therefore, a process capable of increasing the polymerization degree and at the same time reducing the amount of terminal carboxyl groups of a recovered polyester having deteriorated physical properties in a short period of time is desired.
Technologies for improving the physical properties and moldability of a polyester, mainly a polyester molded article, have been proposed for the purpose of recycling it. Some of them will be described below.
JP-A 2-311554 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a composition having the increased crystallization rate of a polyester and improved productivity, prepared by melt-kneading a polyester resin with a higher paraffin having 40 to 100 carbon atoms on the average. This technology is worthy of notice also for the recovery and recycling of polyester molded articles. However, it cannot be said that a molded product from the obtained composition has particularly improved physical properties as compared with the raw material resin.
JP-A 6-298991 discloses a method for recovering a resin having improved impact properties by melt-kneading an epoxy group-containing ethylene copolymer into a molded and processed product made of a thermoplastic resin such as a polyester resin or a polycarbonate resin. This method is intended for restoring the deteriorated impact properties of the recovered resin to increase the recycling value of the resin. Since this method is aimed primarily at restoration of impact properties, other properties such as heat resistance and physical strength are not improved by the method.
JP-A 8-508776 proposes a process for heat-melting a bifunctional epoxy resin and a steric hindering hydroxyphenyl alkyl phosphonate or half-ester by heating so as to recover and recycle polyester molded articles. Using this method, a polyester having a higher intrinsic viscosity and higher physical properties than a recovered polyester is regenerated in a relatively short period of time. However, it cannot be said that this process is satisfactory as a technology for recycling recovered molded articles which requires a low cost because the steric hindering phenol used is very expensive.
Under the circumstances, the inventors of the present invention have conducted studies on a process for obtaining a band-shaped article having improved physical properties from a polyester, especially recovered polyester molded articles, advantageously from an industrial point of view.
Heretofore, many proposals for a polyester band- shaped article and a production process therefor have been made. For example, JP-A 55-100138 discloses a rolled band obtained by stretching in a longitudinal direction and an axial direction at predetermined ratios to have a plane orientation degree of 2.5 or more, and JP-B 62-34624 (the term “JP-B” as used herein means an “examined Japanese patent publication”) discloses a stretched band made from a polyester having a relatively high degree of polymerization and an intrinsic viscosity of 0.9 to 1.2. In general, these are bands made from a polyester obtained by polymerization or a polyester having a specified high degree of polymerization as a raw material, and these technologies are not suitable for the production of a band from recovered polyester molded articles having a low degree of polymerization and low physical properties.
It is therefore the first object of the present invention to provide a band-shaped article having improved physical properties, particularly a band for binding, using an ordinary polyester, particularly recovered polyester molded articles; as well as a production process therefor.
It is the second object of the present invention to provide a band-shaped article which is stretched in a longitudinal direction, has excellent physical strength and does not cause s
Fujita Kuniaki
Nagano Shozaburo
Yamana Takashi
Sekisui Jushi Corporation
Weisberger Richard
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