Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Patent
1986-12-12
1987-12-15
Page, Thurman K.
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
4273935, 4274071, 428 35, B05D 302
Patent
active
047132663
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of producing a polyester structure with improved gas barrier property which comprises coating a polyester substrate structure with a solution of a vinyl alcohol resin having a high gas barrier property.
BACKGROUND ART
(Prior Art)
Polyesters such as polyethylene terephthalate are excellent in moldability and biaxially-stretchable and give structures which excel in clarity, mechanical strength, heat resistance and impact resistance and are moderately good in gas barrier property. Therefore, such structures have found broad application as containers for foods such as carbonated beverages. However, being moderately good, the gas barrier property of polyester structures is not as good as desired, so that foods in polyester containers cannot keep long. Improvements, therefore, have been awaited.
For the purpose of improving the gas barrier property of polyester articles, attempts have been made to provide a multi-layer structure consisting of at least one polyester layer and at least one gas-impermeable ethylene-vinyl alcohol copolymer layer by utilizing the multi-layer extrusion, extrusion coating, or other technique but as the mutual adhesive affinity of the polyester and ethylene-vinyl alcohol copolymer is low, improvements in this interlayer adhesive bond strength are desired.
For the purpose of improving the above-mentioned interlayer bond strength, there has recently been proposed a method in which a defined thermoplastic polyester, i.e. a polyester consisting of terephthalic acid and isophthalic acid in the proportions of 95 to 40 mol percent and 5 to 60 mol percent, respectively, based on the total dibasic acid component, is interposed as an adhesive layer between the above-mentioned two heterogenous layers and the two layers are intimately welded together in the molten state of the adhesive (Japanese Patent Application Kokai 59-143637) or a method in which a thermoplastic polyester comprising terephthalic acid in a proportion of at least 40 mol percent of the total dibasic acid component and containing ether bonds in a proportion of 17 millimols per 100 grams of the resin within its backbone chain (Japanese Patent Application Kokai 59-143638) is interposed as an adhesive layer between said two heterogenous layers and the two layers are then intimately welded together in the molten state of the adhesive.
(Problems that the Invention to Solve)
However, when the lamination of said polyester layer, adhesive layer and ethylene-vinyl alcohol copolymer layer is carried out in molten state by multi-layer extruction, extrusion coating, multi injection molding or the like technique in accordance with the prior art described in the above-mentioned Japanese Patent Application Kokai 59-143637 or 59-143638, the thicknesses of the adhesive layer and the ethylene-vinyl alcohol copolymer layer are unnecessarily thicker so that the product structure suffers a substantial loss of clarity in comparison with the single layer polyester structure. Furthermore, the application of a lamination process involving a molten state of the materials, such as multi-layer extrusion, extrusion coating or multi injection molding is disadvantageous, from the standpoint of commercial scale production, in that a large capital investiment is required for the production equipment, the molding conditions are difficult to set, and the manufacture of laminates with intricate shapes is difficult.
(Objects of the Invention)
An object of the present invention is to provide a method of producing polyester structures with excellent gas barrier property which comprises coating a polyester substrate structure with a solution of a vinyl alcohol resin having a high gas barrier performance instead of relying on a lamination process involving a molten state of the materials.
Another object of the present invention is to provide a method of forming a dry anchor coating layer on the surface of a polyester substrate structure from a solvent solution of a defined polyester prior to coating o
REFERENCES:
patent: T103002 (1983-05-01), Petke
patent: 3326742 (1967-06-01), Shepherd
patent: 4564541 (1986-01-01), Taira et al.
patent: 4576918 (1986-03-01), Hilger et al.
Hasegawa Kenji
Iwanami Teruo
Sato Tetsuo
Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha
Page Thurman K.
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