Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-10-25
2004-07-20
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S558000, C524S556000, C524S265000
Reexamination Certificate
active
06765040
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to inks having silicone-containing water-based polymers as additives therein.
2. Description of the Related Art
Gravure is a major commercial printing process that can be used to print, on a substrate such as paper, anything from newspaper to fine art. Text and images can be printed.
Gravure is an intaglio process wherein ink is transferred to the paper as drops from very small cells that are recessed into a printing surface, e.g., a cylinder or flat plate. Web fed and high speed decorating systems are better known as Rotogravure. This is a high speed process used for large print runs. In the gravure printing process the printing area is actualy etched into the surface of a plate or metal cylinder. The etched out sections are “filled” with ink, the excess ink in the non-image area is removed with a thin stainless steel blade (doctor blade). The size and depth of the etched out areas determine how much ink is deposited on the substrate. The ink drops flow and selectively spread together to print the text or image. If the surface tension of the ink drop is too high, the ink will not spread quickly or far enough causing the print to appear rough and grainy.
Gravure inks are very fluid, solvent or co-solvent based inks that dry by evaporation to leave a film of resin and pigment on the substrate. Representative solvents and co-solvents include toluene, xylene, alcohols, acetone, aliphatic hydrocarbons, water and the like. Except for water, the solvents and co-solvents are volatile organic compounds (VOC). Due to environmental considerations, limitations are being placed on the amount of VOC emissions that occur during printing. Solvent recovery systems or incinerators, utilized to reduce the VOC emissions, treat the effect rather than the cause of the VOC problem.
Safety and environmental considerations are forcing changes in printing ink formulations. Solvent-based printing inks are now regarded as being undesirable from several points of view. This is particularly true for publication gravure printing inks that are generally based on toluene or mixtures of toluene and aliphatic hydrocarbons. Such solvents are hazardous (explosions at publication gravure printing plants have occurred) and require expensive solvent recovery units to limit air effluents (toluene and toluene/aliphatic hydrocarbon mixtures are very volatile, particularly at the temperature and air flow conditions normally present in printing press driers).
The need to reduce volatile organic compound (VOC) emission during Gravure and/or Rotogravure printing has lead to the development of various water-based gravure ink compositions, as described for example in U.S. Pat. Nos. 5,098,478 and 5,972,088. The problems in developing a water-base gravure ink composition as replacements for solvent-based gravure inks that emit VOC are well documented by the above identified patents, which are hereby incorporated by reference. Water-based inks have proven to be prone to printability problems, especially for publication gravure. Examples of such printability problems include poor transfer from the gravure cells and spreading behavior on paper. These printability problems typically manifest themselves as skipped dots in the tone areas and a generally “wormy” appearance and nonuniformity in the solids.
Water-based gravure printing processes have also been developed to avoid the environmental impact and operating expenses associated with the use of solvents. The solvent used in gravure ink is a temporary ingredient, present purely as a means of applying the vehicle solids to the substrate by way of the printing unit. A gravure ink must remain fluid during the printing process while the ink flows from the gravure cells onto the substrate. The solvent is then rapidly removed within the drying cycle. Hence, the evaporation rate of the solvent must be geared to the length of time required to remove the excess ink by the doctor blade and the elimination point of the solvent. This time span is clearly governed by press speed. In recent years, changes made to reduce the maximum concentration of solvent vapors allowable in the pressroom atmosphere have resulted in the virtual elimination of solvents such as 2-ethyloxyethanol and the corresponding acetate. These have been replaced with glycol ethers and esters and solvents based on propylene glycol. The press handling characteristics of these water-base inks are uniquely different from organic solvent base materials. Once dry, aqueous based inks may be reluctant to redissolve in water, depending upon the kind of resin system used in the ink. This could result in an increase in cylinder plugging and number of press wash-ups. Conversely, the resin system may not be sufficiently water resistant upon drying causing the ink to be easily smeared in the presence of moisture. The resin system used in water-based inks can give rise to poor dot spread and increased skipped dots. These problems have been difficult to overcome given the limited availability of resins for use in water-based systems. Water-based systems are not as readily resolubilized as solvent systems. It is therefore possible that any precipitation will not be resolubilized within the next revolution of the cylinder in the ink duct. Therefore, unless carefully controlled, fluctuations in pH can lead to packing in the etch of the gravure cylinder and ultimately to screening.
The surface tension characteristics of the water-based system must also be considered since generally they are totally different from those of solvent systems. These differences can lead to poor substrate wetting which results in ink reticulation, crawling, and non-uniform ink flow from the cells. Surface tension can be reduced, however, by careful selection of surface active agents.
In addition to the environmental concerns, ink applications have to meet several stringent requirements. For example, the ink has to have good thermal stability. The ink has to have good film forming property in order to have good smear resistance. The viscosity of the ink has to be in the right range. Other properties such as surface tension, drying rate, color density, smooth lay, high gloss and paper holdout are also very important.
For a water-based gravure ink to be considered as a suitable replacement for a solvent-based gravure ink, it must generally perform comparably to a solvent-based gravure ink in terms of various factors, such as those mentioned above. Albeit that the achievement of comparable performance of a water-based gravure ink compared to that of a solvent-based gravure ink is difficult enough, it also remains a desire in this art to find water-based gravure ink compositions that exhibit even superior performance to water-based gravure ink compositions that heretofore have been developed as suitable replacements for solvent-based gravure ink compositions.
A gravure ink may be broadly regarded as composed of four major components, namely: (1) the pigment or pigments (the colored medium that causes the print pattern); (2) a liquid vehicle that carries the pigment(s); (3) optionally, an extender (that allows for reduction in the quantity of pigment needed to achieve the desired quality of print pattern); and (4) various additives each optionally included for the achievement of a particular results (e.g., surfactants, defoaming agents, catalysts, antioxidants, corrosion inhibitors, biocides, deodorants). Primary among the concerns about the operation of a gravure printing ink are its operational/final properties of printability (clean, sharp transfer without “stringing or misting”), holdout, and final gloss.
True water-based gravure inks, i.e., inks that only use water as a solvent and do not include a co-solvent, provide a poorer print quality. The printed paper is roughened because the ink wets and swells
Avci Selcuk
Catena Robert
Krishnan Ramasamy
Persley Sidney
Shosho Callie
Sun Chemical Corporation
LandOfFree
Publication gravure printing inks based on silicone modified... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Publication gravure printing inks based on silicone modified..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Publication gravure printing inks based on silicone modified... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3223949