Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-07-02
2003-09-30
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S035200, C428S036900, C428S036910, C428S480000, C428S034100, C528S293000, C528S294000, C528S295000, C427S140000, C427S154000, C427S155000, C427S299000, C427S307000, C427S322000, C427S372200, C427S384000, C427S385500, C427S393500
Reexamination Certificate
active
06627280
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a coated polyester hollow molded product, a regeneration method and a surface coating solution therefor. More specifically, it relates to a coated polyester hollow molded product having a coating film which can be easily removed without exerting a bad influence on the polyester hollow molded product, a regeneration method therefor and a surface coating solution for forming the coating film.
PRIOR ART
A polyethylene naphthalene dicarboxylate-based (may be abbreviated as PEN hereinafter) hollow molded product has more excellent characteristic properties than a polyethylene terephthalate-based (may be abbreviated as PET hereinafter) hollow molded product and is expected as a hollow molded product which can be salvaged and recycled.
The cleaning of a hollow molded product is necessary for recycling and generally carried out using an aqueous solution (1 to 6%) of sodium hydroxide heated at 50 to 1000° C.
However, when alkali cleaning is made on a PEN-based hollow molded product salvaged after use, the transparency of the hollow molded product reduces. The reduction of transparency is more marked as the number of times of salvaging and recycling increases.
Although water resistance can be provided simply by coating the surface of the PEN-based hollow molded product, it is difficult to remove the coating layer for recycling, for example, the coating layer can not be removed by cleaning with hot water.
When an ultraviolet light absorbing compound is blended with a material for the hollow molded product without forming a coating layer, such a problem as the contamination of contents by a bleed-out may arise.
Further, as the PEN-based hollow molded product has high surface hardness, its surface is easily scratched and the scratching of the surface must be suppressed for salvaging and recycling.
Meanwhile, the following publications are known for water-soluble polyesters.
JP-A 10-110027 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method of producing a hot water-soluble polyester by esterifying or carrying out an ester exchange reaction among terephthalic acid, alkali metal sulfonate group-containing aromatic dicarboxylic acid or lower alkyl ester thereof and ethylene glycol, and melt polycondensing and solid-phase polymerizing the esterified product or the product of the ester exchange reaction. The above publication teaches that the produced hot water-soluble polyester can be used as a material for forming a pattern by dissolving a required portion with hot water after the formation of a fabric.
JP-A 8-176284 discloses a water-soluble polyester which contains an ion dissociable group-containing dicarboxylic acid component and/or an ion dissociable group-containing glycol component in the molecular main chain of the polyester in an amount of 51 mol % or more based on the total of all the acid components, is produced at a polymerization temperature of 1800° C. or higher and lower than 2400° C. and has an intrinsic viscosity measured in orthochlorophenol at 350° C. of 0.25 or more. The above publication teaches that this water-soluble polyester is useful for the production of a low charged adherent polyester film which is useful for package materials, magnetic cards, magnetic tapes, magnetic disks, printing materials and the like.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a coated polyester hollow molded product which eliminates the possibility of contaminating its contents, retains excellent transparency even after it is salvaged and recycled and can be recycled with substantially no scratched surface.
It is another object of the present invention to provide a surface coating solution which is used for the production of the coated polyester hollow molded product of the present invention.
It is still another object of the present invention to provide a method of regenerating the coated polyester hollow molded product of the present invention for recycling.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a coated polyester hollow molded product comprising:
(A) a polyester hollow molded product, and
(B) a polyester coating layer formed on the exterior surface of the hollow molded product.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a surface coating solution for a polyester hollow molded product, which contains 1 to 40 wt % of a polyester comprising 92.99 to 60 mol % of at least one dicarboxylic acid unit selected from the group consisting of naphthalene dicarboxylic acid unit and terephthalic acid unit, 0.01 to 20 mol % of an isophthalic acid unit and 7 to 20 mol % of an isophthalic acid unit having a sulfonic acid metal salt group based on the total of all the dicarboxylic acid units as dicarboxylic acid components, and 65 to 95 mol % of an ethylene glycol unit and 35 to 5 mol % of a diethylene glycol unit based on the total of all the diol units as diol units, 0.1 to 10 wt % of a surfactant and a liquid medium.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a method of regenerating a coated polyester hollow molded product comprising the steps of preparing the salvaged coated polyester hollow molded product of the present invention, removing a polyester coating layer for the hollow molded product and forming anew polyester coating layer on the surface of the hollow molded product from which the polyester coating layer has been removed.
The present invention will be described in detail hereinbelow.
A description is first given of the coated polyester hollow molded product of the present invention. The polyester hollow molded product (A) constituting the coated polyester hollow molded product comprises preferably an aromatic polyester, more preferably an aromatic polyester which comprises a recurring unit selected from the group consisting of ethylene-2,6-naphthalene dicarboxylate unit and ethylene terephthalate unit in an amount of at least 85 mol % based on the total of all the recurring units. The aromatic polyester may be used alone or blended with two or more types of another aromatic polyester.
Polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferred as the aromatic polyester.
The intrinsic viscosity of the aromatic polyester is preferably 0.5 to 1.0, more preferably 0.55 to 0.8, particularly preferably 0.55 to 0.75. When the intrinsic viscosity is lower than 0.5, blowing properties worsen, thereby making it difficult to obtain a molded product having a uniform thickness. When the intrinsic viscosity is higher than 1.0, elongation stress becomes high, which might be the cause of hazing a molded product.
The polyester hollow molded product made from the above polyester can be produced by employing a known general molding technique. Examples of the applicable molding method include biaxial orientation blow molding techniques (cold parison method and hot parison method), injection blow molding technique and direct blow molding technique. In addition, a molding technique in which a hollow molded product is formed after the polyester is molded into a sheet form may be used. The polyester hollow molded product may be a bottle.
Preferably, the polyester coating layer (B) formed on the exterior surface of the polyester hollow molded product has a weight reduction of 3 wt % or less when it is treated with 25° C. water for 2 hours and is removed when it is treated with an alkali aqueous solution having a temperature of 750° C. and a pH of 11.6 for 9 minutes.
When the weight reduction is 3 wt % or less after 2 hours of a treatment with 250° C. water, the polyester hollow molded product is circulated in the market and used as a vessel and the coating layer is substantially retained ev
Nagano Hiroki
Suzuki Minoru
Chen Vivian
Teijin Limited
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