Plastic and nonmetallic article shaping or treating: processes – With step of cooling to a temperature of zero degrees c. or...
Reexamination Certificate
2000-09-19
2003-02-11
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of cooling to a temperature of zero degrees c. or...
C264S085000, C264S232000, C264S340000, C264S523000
Reexamination Certificate
active
06517752
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a surface reforming method for a plastic molded product and a surface reformed plastic molded product obtained thereby, more specifically, a new, easy, and dean surface reforming method for a plastic molded product in which, it is unnecessary to use a harmful solvent with the danger of explosion and an extremely dangerous high voltage, and in addition, generation of harmful substances and powder is prevented, and troublesome post-processing and expensive equipment for safety are not required.
Plastic molded products are molded by means of injection molding, extrusion, compression molding, and blow molding, and have been widely used for the necessities of life and industrial purposes including necessities of life such as plastic buckets and containers, electrical products such as casings for televisions and sound equipment, various parts for vehicles and car interior accessories such as seats, building materials such as wall materials and sofas, and materials for public facilities such as water pipes.
In many cases, such a plastic molded product is produced as a product by only being molded, however, depending on the purpose of use, various printing, coating with a conductor, powder-coating, adhesion of molded products, and other post-processing are applied to the plastic molded product. In the case where such post-processing must be applied, normally, in order to improve processing performance, the surface of the plastic molded product is activated and reformed.
Usually, as a method for reforming the surface of a plastic molded product, a chemical method such as rough washing before plating, following application of an anchor coating agent, or drying, an electrical method by means of discharge such as corona discharge or plasma discharge, or a physical method such as sandblasting of the surface to become rough is used.
However, in the chemical method using the anchor coating agent, use of extra compounds and disposal of the solvent are required In addition, most of the solvents to be used are harmful or explosive, so that recovery of such solvents needs considerable capital investment and maintenance cost.
Furthermore, in the electrical reforming method by means of discharge such as corona discharge or plasma discharge, expensive equipment is required, and ozone and harmful substances such as nitrogen oxides are generated due to discharge, so that a considerable cost is required for the countermeasure. In addition, the discharging section is highly dangerous, so that countermeasures against this danger are necessary.
Moreover, although the physical method in which the surface is slightly sandblasted to be rough is excellent in terms of cost, extra plastic powder is inevitably generated, and mixing with sand is inevitable.
On the other hand, among plastic molded products, plastic films have been widely used for various purposes including a purpose in the food field such as wrapping films, an industrial purpose such as photographic film bases, drawing films, magnetic disks, magnetic tapes, substrates for flexible liquid crystal panels, flexible printed circuit boards, labels, various electric insulation films, capacitor films, or surface sheets of various switches, and base films for various printing. Most of these plastic films are so-called base films, to which post-processing such as application, extrusion lamination, and printing of various functional materials are applied, and layers of the various functional materials are formed on the surfaces of the films.
For example, a heat seal layer or printing film is laminated on a wrapping film, light-sensitive layers of various colors are laminated and applied on a photographic base film, a magnetic recording material is applied on a magnetic disk and magnetic tape, and a transparent conductive layer is vapor-deposited on a substrate for a flexible liquid crystal panel. Furthermore, a copper foil is laminated or metal is vapor-deposited on a flexible printed circuit board, and screen printing and jet-printing is applied on a label. Moreover, generally, aluminum is vapor-deposited on a capacitor film, and various printing inks are screen-printed on a surface sheet for various switches, and various printing inks are offset-printed on a base film for printing.
When such post-processing is applied to plastic films, in order to increase affinity between the base film and various functional materials to be laminated thereon and maintain the excellent adhered condition between them after post-processing, as in the case of the abovementioned molded products, it is necessary that the surface of the plastic film is activated and reformed.
Usually, as a method for reforming the surface of the plastic film, a method in which the surface is cleansed by a solvent and a method in which a high voltage such as corona discharge is applied to the surface have been used
In the former method, impurities which may cause lowering in adhesion power with laminated ingredients are removed by washing the film surface to expose the active original surface of the film, whereby the adhesion power with the laminated ingredients is increased However, this method requires a solvent, so that it has the same problem as in the abovementioned chemical processing method for a plastic molded product.
On the other hand, in the latter method, an active group is introduced into the film surface by using the phenomenon of corona discharge in order to improve the adhesion power of the film surface which is originally weak. However, this method also has the same problem as in the abovementioned electric reforming method for a plastic molded product.
Recently, as introduced below, various attempts to apply a supercritical fluid to plastic molded products have been made. For example, in Japanese Laid-Open Patent Publication No. 72058 of 1996, a plastic recycling method by means of supercritical water is presented. In Japanese Laid-Open Patent Publication No. 511278 of 1994, a method for removing residual additives from an elastomer product by means of a supercritical fluid is presented. In Japanese Laid-Open Patent Publication No. 181050 of 1996, for removing a resist used for lithography, a method using supercritical carbon dioxide is presented. In Japanese Laid-Open Patent Publication No. 197021 of 1996, a cleaning device for minute processed goods such as a semiconductor device and liquid crystal display by using a supercritical fluid is presented. However, these new attempts using a supercritical fluid are not intended for post-processing for plastic molded products which is the object of the present invention.
SUMMARY OF THE INVENTION
The object of the invention is, therefore, to provide a simple, clean, and new surface reforming method for a plastic molded product in which it is unnecessary to use harmful solvents with the danger of explosion and an extremely dangerous high voltage, generation of harmful substances and powder is prevented, and troublesome post-processing and expensive equipment for safety countermeasures are not required, and a surface reformed plastic molded product which is obtained thereby.
The present inventors made earnest investigation in order to achieve the above object, and as a result, found that, when a plastic molded product was immersed in supercritical carbonate dioxide or subcritical carbonate dioxide under specific conditions and then said carbon dioxide was dried under specific conditions, an excellent surface reforming effect was obtained, whereby the present invention is completed.
That is, according to the first aspect of the invention, a surface reforming method for a plastic molded product is provided which comprises a step (a) for immersing a plastic molded product into supercritical carbon dioxide or subcritical carbon dioxide under a temperature lower than the glass transition temperature of said plastic, and a step (b) for vaporizing carbon dioxide adhered to the surface of the plastic molded product under a temperature lower than the glass transition temperature of
Hiraishi Masanori
Takahashi Hiroshi
Daicel Chemical Industries Ltd.
McDowell Suzanne E.
LandOfFree
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