Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1997-09-11
2002-11-26
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036600, C428S036900, C428S036910, C428S474400, C428S475200, C428S480000, C428S483000, C428S520000, C428S542800
Reexamination Certificate
active
06485804
ABSTRACT:
TECHNICAL FIELD
The present invention relates to novel polyesters, polyester compositions, polyester laminates and processes for producing biaxially oriented polyester bottles. More particularly, the invention relates to polyesters and polyester compositions, which have excellent high crystallization rate, gas barrier properties, transparency and heat resistance, and also relates to preforms, biaxially oriented bottles and laminates, which are produced from the polyesters, and to processes for producing biaxially oriented polyester bottles having excellent gas barrier properties, transparency and heat resistance.
BACKGROUND ART
Because of their excellent gas barrier properties, transparency and mechanical strength, saturated polyesters such as polyethylene terephthalate are widely used for containers such as bottles. Particularly, the bottles obtained by biaxial orientation blow molding of polyethylene terephthalate are excellent in transparency, mechanical strength, heat resistance and gas barrier properties, so that they have been extensively used for containers (PET bottles) to be filled with drinks such as juice, soft drinks and carbonated beverages. These bottles are generally produced by a process comprising the steps of molding saturated polyester to give a preform having a neck and a body, then inserting the preform in a mold of given shape, and subjecting the body of the preform to stretch blow molding, thereby producing bottles each having a neck and a stretched body.
The polyester bottles, particularly polyester bottles for drinks such as juice, are required to have heat resistance high enough for heat sterilization of the contents. Therefore, the bottles are generally further subjected to heat treatment (heat setting) after the blow molding to improve the heat resistance.
However, the necks of the above-obtained polyester bottles are not stretched and are inferior to the bodies in the heat resistance. In general, therefore, the necks of the preforms are heat crystallized before blow molding, or the necks of the bottles obtained by blow molding are heat crystallized, whereby the mechanical resistance and the heat resistance of the necks are improved.
In recent years, the sizes of bottles produced from the polyester resins (particularly polyethylene terephthalate) tend to be made smaller. In case of the small-sized bottles, the content has an increased area in contact with the bottle body per unit volume of content, and hence remarkable loss of gas in the content or transmission of oxygen from the outside takes place to affect the content, resulting in decrease of shelf life of the content. Accordingly, development of polyester bottles having better gas barrier properties than the conventional ones is desired.
Recently, further, the time for producing bottles of polyester resins is desired to be shortened to improve the productivity. In order to shorten the time for producing bottles, it is effective to shorten the crystallization time of the necks or the heat-setting time of the bottle bodies.
However, shortening of the crystallization time of the necks or the heat-setting time of the bottle bodies generally causes decrease of mechanical strength or heat resistance of the resulting bottles. Therefore, in order to carry out crystallization of necks or heat-setting of bottle bodies for a short period of time, it is necessary to use polyesters having a high crystallization rate. As one example of the polyester having a high crystallization rate, a polyester resin composition composed of a virgin polyester and a repro-polyester is known. The term “virgin polyester” used herein means a polyester prepared from a dicarboxylic acid and a diol and has no history of being passed through a molding machine in a molten state to give any bottle or preform. The term “repro-polyester” used herein means a polyester obtained by passing the virgin polyester in a molten state through a molding machine at least once and pulverizing the resulting polyester molded product.
Although some polyester resin compositions have a high crystallization rate and are able to be heat crystallized for a short period of time, the resulting bottles have a problem of decrease in transparency.
Accordingly, it has been desired to develop polyesters capable of producing molded articles, such as bottles having excellent transparency and gas barrier properties. Also is desired development of preforms and biaxially stretched bottles and processes for producing biaxially stretched polyester bottles made of such polyesters.
OBJECT OF THE INVENTION
The present invention has been made under such circumstances as mentioned above, and it is an object of the invention to provide a polyester and a polyester composition both having a high crystallization rate and having excellent gas barrier properties, transparency and heat resistance.
It is another object of the invention to provide a preform made of the above-mentioned polyester and a biaxially stretched bottle and a polyester laminate both having excellent gas barrier properties, transparency and heat resistance.
It is a further object of the invention to provide a process for producing biaxially stretched polyester bottles, by which bottles of excellent gas barrier properties, transparency and heat resistance can be produced, and to provide a process for producing biaxially stetched polyester bottles, by which bottles of excellent gas barrier properties, transparency and heat resistance can be produced with high productivity.
DISCLOSURE OF THE INVENTION
The novel polyester according to the invention (first polyester [A]) is a polyester comprising:
dicarboxylic acid constituent units derived from at least one dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, and
diol constituent units derived from diols comprising ethylene. glycol and a polyalkylene glycol having an alkylene chain of 2 to 10 carbon atoms,
wherein the proportion of constituent units derived from the polyalkylene glycol is in the range of 0.001 to 10% by weight based on the diol constituent units.
The polyester composition according to the invention comprises:
1 to 99% by weight of the first polyester [A]; and
1 to 99% by weight of a second polyester [B] comprising dicarboxylic acid constituent units derived from at least one dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid and diol constituent units derived from diols comprising ethylene glycol, wherein the proportion of constituent units derived from a polyalkylene glycol is less than 0.001% by weight based on the diol constituent units.
Each of the preform and the biaxially stretched bottle according to the invention comprises the first polyester [A].
The polyester laminate according to the invention has a multi-layer structure comprising:
[I] a first resin layer formed from the first polyester [A] or the polyester composition of the invention, and
[II] a second resin layer formed from at least one resin selected from the group consisting of (a) the second polyester [B], (b) a polyamide and (c) a polyolefin.
The process for producing biaxially stretched bottle according to the invention comprises the steps of producing a preform from the first polyester [A], the polyester composition or the polyester laminate, heating the preform, subjecting the preform to biaxial stretch blow molding to give a stretched bottle and holding the stretched bottle in a mold at a temperature of not lower than 100° C.
In the above process, the neck of the preform may be heat crystallized before the biaxial stretch blow molding, or the neck of the bottle may be heat crystallized after the biaxial stretch blow molding.
BEST MODE FOR CARRYING OUT THE INVENTION
The polyester (first polyester [A]), the preform and the biaxially stretched bottle made of the polyester, the polyester composition, the polyester laminate and the pro
Hiraoka Shoji
Kouya Masahiro
Nakamachi Koji
Mitsui Petrochemical Industries Ltd.
Nolan Sandra M.
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