Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-06-13
2002-09-10
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C528S270000, C528S300000, C528S307000, C528S308600, C528S403000, C528S406000, C528S425000, C521S050000, C428S036500
Reexamination Certificate
active
06447859
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyester resin, and more particularly to a polyester resin for films, sheets or hollow containers having excellent heat resistance, transparency, mechanical properties, moldability and fabrication qualities, and a molded article produced from the polyester resin.
2. Description of the Prior Art
As well-known in the arts, PET (polyethylene terephthalate) is an industrially valuable polyester because of its superiority in mechanical properties such as tensile strength, elongation and Young's modulus, physical properties such as heat resistance and dimensional stability and chemical properties such as chemical resistance and water resistance, and low costs. For example, PET has been widely used in various applications such as fibers, tire cords, bottles and films. However, when PET is formed into thick sheets, i.e., plates, its high crystallization rate is likely to cause whitening of the plates due to crystallization in the fabrication step, thereby failing to provide transparent plates. To avoid this disadvantage, PET modified with cyclohexane dimethanol, etc. has been used. Also, in the production of PET bottles, expensive germanium oxide has been used as a catalyst to reduce the crystallization rate, or PET modified by copolymerizing a modifying component such as isophthalic acid and cyclohexane dimethanol has been used.
However, the modified PET is less heat-resistant, and therefore, its use in the application requiring a high heat resistance, for example, illumination plates, carports and heat-resistant food containers, is limited.
U.S. Pat. No. 2,945,008 discloses, in Examples 9 and 10, that a diol component (glycol component) comprising ethylene glycol and 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane (hereinafter occasionally referred to merely as “SPG”) represented by Formula I:
is polymerized with a dicarboxylic acid component comprising dimethyl terephthalate in the presence of a titanium compound catalyst to produce a polyester which melts at 180 to 220° C. The modified PET disclosed therein is expected to show a high heat resistance as compared with non-modified PET because the modified PET contains SPG component having a rigid structure. However, the U.S. Patent does not specify properties of the modified PET such as intrinsic viscosity, molecular weight distribution, melt viscosity, mechanical characteristics and heat resistance. In addition, the modified PET fails to stably show effective moldability and heat resistance or suffers from drastic deterioration in impact resistance, depending upon its chemical composition and properties. Therefore, the modified PET is not necessarily a practically usable molding material.
Japanese Patent Application Laid-Open No. 3-130425 and Japanese Patent Publication Nos. 5-69151 and 6-29396 have proposed to use a polyester produced from a glycol component containing SPG as high shrinkage filament of combined filament yarn composed of different shrinkage filaments, coating agent and adhesive. However, in these prior arts, there is no description concerning molecular weight distribution, melt viscosity and mechanical properties of the modified PET. Since the modified PET fails to stably show an effective heat resistance or suffers from drastic deterioration in impact resistance depending upon its composition and properties, the proposed modified PET is not necessarily a practically usable molding material.
Further, it is extremely difficult to produce a good foamed article by foam-extruding a linear aromatic polyester resin such as polyethylene terephthalate, because the melt thereof is less elasticity and viscous.
To solve the above problems, Japanese Patent Publication No. 5-15736 proposes to foam-extrude a mixture of a linear aromatic polyester resin and a compound having two or more acid anhydride groups per one molecule, and Japanese Patent Publication No. 5-47575 proposes to foam-extrude a mixture of a linear aromatic polyester resin, a compound having two or more acid anhydride groups and a specific metal compound. In addition, Japanese Patent Application Laid-open No. 7-33899 proposes to foam-extrude a polyester having a molecular weight distribution (weight-average molecular weight
umber-average molecular weight) of 5.0 to 21.0, and Japanese Patent Application Laid-open No. 11-166067 proposes to foam-extrude a polyester having a Z-average molecular weight of 1×10
6
or higher and a branching parameter of 0.8 or lower.
In any of the above-described methods, a polyfunctional carboxylic anhydride or a polyfunctional glycidyl compound is added to the polyester resin. If such a polyfunctional compound is added during the production of the polyester resin, the resultant product becomes three-dimensional to make it difficult to take out the product from a reaction vessel. Therefore, the polyfunctional compound or a branched aromatic copolyester resin obtained by copolymerizing the polyfunctional compound with the linear polyester resin must be added during the later extrusion step.
Japanese Patent Application Laid-open No. 8-231751 discloses a foamed article made of an aromatic polyester resin which is produced using a glycol component comprising cyclohexanedimethanol and ethylene glycol. In this method, the crystallization during the foaming process is delayed by the use of the aromatic polyester resin made of two kinds of glycol components, so that the resultant foamed article has uniform, fine closed cells, a high foaming ratio, an excellent heat-insulating property, a high cushioning property, and a good recycling ability. However, the foamed article is still insufficient in the heat resistance and the mechanical strength.
Further, Japanese Patent Application Laid-open No. 11-147969 proposes a foamed article made of an aromatic polyester resin which is produced using a dicarboxylic acid component comprising 2,6-naphthalene dicarboxylic add and terephthalic acid. In the production of the foamed article, when the amount of 2,6-naphthalene dicarboxylic acid is increased to enhance the heat resistance, the production of a satisfactory foamed article having a high closed cell content becomes difficult because of the increased crystallization rate.
SUMMARY OF THE INVENTION
In view of the above problems in the prior art, an object of the present invention is to provide a polyester resin for films, sheets and hollow containers having excellent heat resistance, transparency, mechanical properties, moldability and fabrication qualities. Another object of the present invention is to provide a polyester resin having a high melt viscosity even when produced without any branching agent, and further exhibiting a low intrinsic viscosity, i.e., various excellent properties for producing foamed articles even when polymerized in a short period of time.
As a result of extensive researches in view of the above objects, the inventors have found that a copolyester which is produced by using a limited amount of a specific glycol comonomer and exhibits a specific solution viscosity, melt viscosity and molecular weight distribution is excellent in heat resistance, transparency, mechanical properties and fabrication qualities. The inventors have further found that such a copolyester is excellent suitable as a material for producing foamed articles.
Thus, the present invention provides a polyester resin produced by polymerizing a monomer mixture comprising a glycol component containing 5 to 60 mol % of a glycol (SPG) represented by Formula I:
and 30 to 95 mol % of ethylene glycol, and a dicarboxylic acid component containing 80 to 100 mol % of terephthalic acid and/or an ester thereof; the polyester resin satisfying the following requirements (1) to (4):
(1) an intrinsic viscosity of 0.4 to 1.5 dL/g when measured at 25° C. in a 6/4 by mass mixed solvent of phenol/1,1,2,2-tetrachloroethane;
(2) a melt viscosity of 700 to 5,000 Pa·s when measured at 240° C. under a shear rate of 100 s
−1
;
(3) a molecular weig
Hayashi Takeo
Hirokane Takeshi
Kurokawa Masahiro
Oguro Dai
Yamamoto Koji
Acquah Samuel A.
Antonelli Terry Stout & Kraus LLP
Mitsubishi Gas Chemical Company Inc.
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