Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-03-13
2002-10-15
Zalukaeva, Tanya (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S319000, C526S318400, C526S320000, C526S328500, C526S328000, C526S329100, C526S210000, C526S212000, C524S504000, C524S512000, C524S533000, C524S535000, C524S536000, C524S558000, C427S407100, C427S409000
Reexamination Certificate
active
06465595
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to potentially hydrophilic resins, compositions comprising the same, and methods of their use.
b) Description of the Related Art
In recent years, plastics are used as products such as containers and wrapping bags in a variety of fields. Many of these products are printed on their surfaces or are provided with sheet-shaped prints adhered on their surfaces. From the viewpoint of low degradability of plastic products in the natural world, resource saving, economy and the like, some of plastic products are recovered by segregation and separate collection and are recycled. However, inclusion of plastic products, which are applied with prints or the like, upon regeneration results in entire or localized coloring of recycled products. Accordingly, these recycled products are substantially reduced in commercial value or may not be reused in many instances. In some instances, detrimental drawbacks may arise in connection with physical properties of recycled products. These plastic products with prints or the like applied thereon as described above are, therefore, simply disposed as are or subjected to thermal or incineration disposal. Environmental contamination by dioxin and the like, which occur upon incineration, has however become a social problem, leading to a strong demand for an advantageous method which permits recovery and reuse of plastic products having prints or the like applied thereon.
With a view to meeting the above-mentioned demand, some methods have been proposed to decolor products, which are colored by prints or the like, upon recovering and reusing plastic products having prints or the like applied thereon. For example, JP 52-26549 B discloses a method, according to which a printed product is decolored by treating it with an organic solvent capable of causing dissolution or swelling of a printed coating applied on the product and separating (peeling) the printed coating from the product. In view of the need for separation and recovery of the organic solvent in liquid waste employed in the decoloration treatment, the danger of flammability of the organic solvent, and the like, the solvent-relying method involves many problems such as the need for the installation of an explosion-proof facility and a safety management. On the other hand, a method that involves treatment of a printed product with alkaline water is simple and economical, but the treatment with alkaline water cannot easily separate printed coatings because printed coatings are often formed with hydrophobic film-forming components such as urethane resins, acrylic resins, cellulose-base resins, rosin or ethylene-vinyl acetate copolymer.
A further method is discussed in JP 58-152913 B. According to this method, an alkaline-condition-soluble resin or a hydrophilic resin is added to a printing ink to be used for printing an article, and the article printed with the printing ink is treated with alkaline water to remove a printed coating from a surface of the article. This method is an excellent method making combined use of physical properties of the printing ink and its separability under alkaline conditions. Nonetheless, this method involves a problem in that the printing ink employed in it is applicable only in a narrow range. For example, the printing ink may undergo flocculation or thickening or may lead to prints reduced in luster and transparency and may hence lack properties appropriate as a printing ink, unless the alkali-condition-soluble resin is added by taking into consideration its compatibility with resin(s) in the printing ink.
Further, when the resin in a printing ink does not have elastic property, prints cannot be readily removed even if an attempt is made to separate them by adding an alkali-condition-soluble resin or a hydrophilic resin. Moreover, fragments so separated turn to fine fragments dispersed in the treatment solution, and for the recovery of such fine fragments so dispersed, use of a costly filter or the like is needed.
SUMMARY OF THE INVENTION
To solve the above-described problems of the conventional art, the present invention therefore has as objects thereof the provision of a potentially hydrophilic resin, which makes it possible to remove a coating printed on a plastic product or the like or a sheet-shaped print adhered on the product by treatment with alkaline water, to recover and regenerate the plastic product in a colorless form and further to readily separate the removed printed coating or sheet-shaped print from a treatment solution, a composition comprising the resin, and a method of use of the composition.
The above-described objects can be achieved by the present invention to be described hereinafter. Described specifically, the present invention provides a potentially hydrophilic resin (hereinafter simply called “the resin of the present invention”) which comprises at least monomer units readily saponifiable under alkaline conditions to form carboxyl groups, carboxyl-containing monomer units, and hydroxyl-containing monomer units, a potentially hydrophilic resin composition (hereinafter simply called “the resin composition of the present invention”) comprising the resin (specifically, a printing ink, an adhesive, a primer, or the like), and a method of use of the resin composition.
A printing ink comprising the resin of the present invention has various good properties as a printing ink, because it does not contain any water-soluble resin by itself. For the removal of a printed coating applied beforehand to an article with the printing ink, it is only necessary to simply treat the article with alkaline water. As a result, methyl acrylate units in the printed coating are readily saponified with the alkaline water so that the hydrophilicity of the resin making up the printed coating is increased. The printed coating is caused to swell and is readily allowed to separate from the surface of the article. Accordingly, the printed coating is neither dissolved in the alkaline water nor formed into fine fragments but is separated as a film. The printed coating so separated can be separated with ease from the alkaline water employed for its removal.
An adhesive comprising the resin of the present invention does not contain any water-soluble resin by itself so that, when a sheet-shaped print is adhered on an article with the adhesive, the sheet-shaped print has good durability against wetness, dew or the like. For the subsequent removal of the sheet-shaped print, it is only necessary to simply treat the article with alkaline water. As a result, methyl acrylate units in the adhesive coating are readily saponified with the alkaline water so that the hydrophilicity of the adhesive coating is increased. The adhesive coating is caused to swell, and the sheet-shaped print is allowed to readily separate from the surface of the article. Accordingly, the adhesive coating is neither dissolved in the alkaline water nor formed into fine fragments but separates together with the sheet-shaped print. The separated adhesive coating and sheet-shaped print can be separated with ease from the separating treatment solution.
When an article is provided on a surface thereof with a prime coat by using a primer, which comprises the resin of the present invention, and the prime coat is printed on a surface thereof or a sheet-shaped print is adhered on the surface of the prime coat, the print applied or adhered on the prime coat has good durability against wetness, dew or the like because the primer itself does not contain any water-soluble resin. For the subsequent removal of the printed coating or the sheet-shaped print, it is only necessary to simply treat the article with alkaline water. As a result, methyl acrylate units in the prime coat are readily saponified with the alkaline water so that the hydrophilicity of the resin making up the prime coat is increased. The prime coat is caused to swell, and the printed coating or the sheet-shaped print is allowed to readily separate together with the prime coat. Accordingly,
Naganuma Hitoshi
Nakamura Michiei
Oguma Naomi
Takizawa Minoru
Dainichiseika Color & Chemicals Mfg. Co. Ltd.
Zalukaeva Tanya
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