Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1998-12-01
2001-03-13
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S035800, C428S036400, C528S285000, C528S286000, C528S274000
Reexamination Certificate
active
06200659
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyester containing antimony metallic particles, a stretch blow molded product formed thereof, and a method for producing a polyester containing antimony metallic particles.
BACKGROUND OF THE INVENTION
Polyesters including polyethylene terephthalate are excellent in mechanical strength, chemical stability, gas barrier properties and hygienic properties, and relatively inexpensive and lightweight. They have been therefore widely used as packaging containers for various foods and drinks.
When these packaging containers are produced, methods are used in which preformed articles are first formed and then heated again to soften them, followed by reforming to desired shapes. For example, when stretch blow molded products are produced, closed-end tubular preforms are first produced by injection molding, and these preforms are usually heated again with near infrared heaters to soften them. Thereafter, the softened preforms are allowed to come into contact with metal molds having specified shapes, thereby producing the blow molded products. However, these methods have the problem that productivity is poor because it takes time to heat the preforms again.
For solving such a problem, U.S. Pat. No. 5,419,936 proposes a packaging material comprising a thermoplastic polymer composition comprising a polymer which contains metal particles intrinsically absorbing radiation in the wavelength region 500 nm to 2000 nm in such an amount that the reheat time of the polymer is less than the reheat time of the polymer in the absence of the particles. Here, the radiation in the wavelength region 500 nm to 2000 nm is a radiation generated by a general near infrared heater. The above U.S. patent further discloses in the working examples a method of adding a trivalent phosphorus compound to a polyethylene terephthalate prepolymer as a reducing agent, 10 minutes after that, adding antimony trioxide as a reducible metal compound, followed by polymerization, and reacting the metal compound with the reducing agent to generate fine metal particles. However, a result of detailed studies by the present inventors has revealed that this method shows a large variation in size of particles generated and gives a considerably large number of coarse particles. The coarse particles are smaller in surface area than fine particles having the same volume, so that the radiation absorption efficiency is insufficient. Accordingly, when this composition is formed into a packaging material, the transparency thereof is poor. Further, when this composition is formed into a packaging material, the coarse particles raise the color tone and external problems that the packaging material strongly inclines to black, and that the coarse particles are observed as black foreign matter, because the coarse particles are metal particles, which are tinged with black. Furthermore, it is necessary to add a large amount of a relatively expensive trivalent phosphorus compound, because of the insufficient radiation absorption efficiency.
On the other hand, JP-B-49-20638 (the term “JP-B” as used herein means an “examined Japanese patent publication”) discloses a method for producing a polyester which comprises using a reaction solution in which metallic antimony is precipitated by allowing phosphorous acid, hypophosphorous acid, or an ester or salt thereof to act on a solution or suspension of an antimony compound as a polycondensation catalyst. However, as a result of detailed studies in this method by the present inventors, the ratio of coarse particles to precipitated particles contained in a polyester obtained by this method is high, and the radiation absorption efficiency is insufficient. Accordingly, when this polyester is formed into a packaging material, problems are encountered with regard to transparency and color tone.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polyester used as a raw material for various molded products and packaging materials, which is very high in temperature elevating speed at the time when heated, can be heated to a processing temperature for a short period of time, is excellent in transparency and color tone after processing, and is also excellent in productivity and moldability.
Another object of the present invention is to provide a stretch blow molded product excellent in transparency.
A further object of the present invention is to provide a method by which a polyester having excellent characteristics as described above can be produced efficiently at low cost.
As a result of intensive studies for achieving the above-mentioned objects, the present inventors have completed this invention.
The present invention provides:
A polyester mainly composed of an aromatic dicarboxylic acid as an acid component and an aliphatic diol as a diol component, wherein the content of an antimony element in said polyester is from 50 to 350 ppm, the number of metallic antimony particles having a diameter of 0.5 &mgr;m or more is 30,000 or more per 100 mg of polyester, the ratio of the number of fine particles having a diameter of 0.5 &mgr;m to less than 0.6 &mgr;m is 70% or more, and the L value based on Hunter Color Space (hereinafter “Hunter L value”) is 80 or more;
A stretch blow molded product formed of said polyester; and
A method for producing a polyester mainly composed of an aromatic dicarboxylic acid as an acid component and ethylene glycol as a diol component which comprises adding a preliminary mixed catalyst solution of an antimony compound and a trivalent phosphorus compound as a catalyst, said catalyst solution having a haze of 10% or less, at a stage showing an acid value of 1,000 eq/ton or less before initiation of melt polymerization.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below in detail.
The polyester of the present invention is a polyester mainly composed of an aromatic dicarboxylic acid as an acid component and an aliphatic diol as a diol component. As the aromatic dicarboxylic acid, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferably used. The amount thereof is preferably 90 mol % or more, more preferably 95 mol % or more, and most preferably 97 mol % or more, based on the total acid component. As the aliphatic diol, ethylene glycol is preferably used. The amount thereof is preferably 90 mol % or more, and more preferably 95 mol % or more, based on the total diol component. Examples of the other dicarboxylic acid components include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, cyclohexanedicarboxylic acid, dibromoisophthalic acid, sodium sulfoisophthalate, biphenyldicarboxylic acid, biphenyletherdicarboxylic acid, biphenylsulfondicarboxylic acid, biphenylketonedicarboxylic acid, biphenoxyethanedicarboxylic acid and phenylenedioxydicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, undecanedicarboxylic acid and dodecanedicarboxylic acid. In particular, isophthalic acid is preferred as a copolymerization component with terephthalic acid, and the amount of isophthalic acid is more preferably 3 mol % or less based on the total acid component.
The other diol components include, for example, aliphatic glycols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol and polyoxytetramethylene glycol; alicyclic glycols such as 1,4-cyclohexanedimethanol and 1,4-cyclohexanediol; branched aliphatic glycols such as neopentyl glycol and 2-butyl-2-ethyl-1,3-propanediol; aromatic glycols such as xylylene glycol; and ethylene oxide addition products and propylene oxide addition products of 2,2-bis(4-hydroxyphenyl)propane. Of these, diethylene glycol may be added as a raw material from the beginning, but it is generally produced as a by-product component when polyethylene terephthalate is produced.
In addition to
Fujimori Yoshihiro
Hamano Toshiyuki
Matsumoto Hitoshi
Mino Kazuyoshi
Tanaka Katsuji
Dye Rena L.
Hon Sow-Fun
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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