Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-06-26
2001-10-16
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S271000, C524S522000, C524S576000, C525S054440
Reexamination Certificate
active
06303676
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for preparing superior water-based resin binders useful in the formulation of laminating inks. The present invention particularly relates to a novel method for the production of styrenated acrylic modified rosin ester resins useful in laminating printing inks. The method of the invention provides rosin ester resins that are water soluble and suitable for flexible packaging ink formulation while conferring important improvements in the properties of those printing inks.
BACKGROUND OF THE INVENTION
The formulation of printing inks is dominated by the application for which the ink is to be used. Inks for gravure printing of paper or paperboard present a comparatively mild challenge to the artisan to formulate an appropriate ink but other applications can escalate that challenge beyond the scope of the state of the art. The required presentation of the printed article, the composition of the substrate on which the ink is to be printed and the post-printing process and use to which the article is to be exposed readily conspire to complicate the formulation process, often creating a need to formulate well beyond the state of the art. Metallized substrates, food packages and the packing process, laminates and the laminating process are just a few examples of specific end-uses or post-printing processes offering continuing challenges to the ink formulation artisan.
Known ink formulations are confronted constantly with the test to meet the needs of an ever changing mix of consumer products with ever changing print demands. Now, a fundamentally new constraint is being imposed upon many ink formulations by environmental regulations that urge a reduction in the use of organic solvents in ink formulations. For the more exacting applications such as inks suitable for laminates and the lamination process, the need to produce water based ink formulations which meet or preferably exceed the performance of formulations of laminating inks known in the art represents a prodigious challenge to the artisan. To this challenge, the present applicants have bent their efforts and provided the instant invention of a water based laminating ink formulation with performance properties that exceed those of the prior art.
Inks for lamination comprise a wide range of formulations depending upon the type of lamination process—adhesive, extrusion lamination or extrusion coating—the many substrates used, adhesive type and end-use of the laminate. In the foregoing laminates the printing ink is within the interface of the two substrates and the performance of the ink formulation must take into account and be compatible with the stresses of the lamination process. Key ink requirements are bond strength to the substrate and compatibility with the adhesive. Acrylic-based resins, among others, have been found to be useful as binders in meeting the formulation requirements of laminating inks. The physical mixture of styrenated acrylics and rosin esters as binders in flexible packaging inks is known to be particularly useful, but with limitations. They usually impart gloss and heat resistance to systems formulated with them. However, problems such as crinkle resistance, alcohol tolerance, bond strength and rheology can arise with their use.
U.S. Pat. No. 5,164,262 to Boswell, et al. discloses a method for the production of an acrylic polymer modified rosin ester binder for gravure printing ink formulations for paper. The binder is soluble in organic solvents such as toluene. U.S. Pat. No. 5,166,446 also to Boswell, et al. claims the acrylic polymer modified rosin ester. The Boswell, et al. patent is described hereinafter in greater detail with respect to the pertinency to the instant invention
U.S. Pat. No. 5,026,755 to Kveglis, et al. teaches a water-dispersable graft copolymer of a polyamide and an acrylic monomer produced by free radical polymerization.
U.S. Pat. No. 5,183,847 to El-Hefnawi, et al. discloses alkali soluble resins of carboxylated polyamide/acrylic resin prepared by a fusion process.
U.S. Pat. No. 5,216,064 to Rivera, et al. teaches rosin-based resin-fortified emulsion polymer compositions and the method for their preparation. The emulsions are prepared by polymerization of vinyl monomers and are used to prepare water based inks.
It is an objective of the present invention to provide a method for the production of a water soluble modified rosin-acrylic vehicle for laminating ink formulation.
Another objective of the invention is to provide a laminating ink exhibiting superior properties and containing the water soluble modified rosin-acrylic vehicle.
SUMMARY OF THE INVENTION
Through the application of the discoveries of the present invention novel water based laminating inks have been formulated that exhibit uniquely superior properties in crinkle resistance, bond strength and alcohol resistance. These achievements have been realized by employing as a vehicle for the laminating inks esterified carboxylated Diels Alder adducts of rosins plus acrylic copolymers. It has been discovered that when these components are reacted under the conditions of the invention a product of higher molecular weight is produced having a high acid number. The product can be used as a vehicle for water based laminating inks to overcome problems common to the use of conventional laminating ink formulations.
More particularly, a method for the production of an improved water soluble resin binder for laminating printing inks has been discovered. The method comprises esterifying the carboxylated Diels Alder adduct produced from the reaction of rosin and at least one carboxylated dienophile with a sufficient amount of at least one polyol to produce a modified rosin having an acid number greater than 156. The modified rosin is reacted with a sufficient amount of a styrenated acrylic copolymer having an acid number greater than 180 under esterification conditions between 175° C. and 185° C. for a time from fifteen minutes to forty five minutes to produce a resin binder having an acid number between 157 and 175.
The invention includes a method for the production of an improved aqueous varnish solution for laminating printing ink comprising esterifying fumarated gum rosin with a sufficient amount of pentaerythritol to produce a modified rosin having an acid number of 157-175. At a weight ratio of 1 to 1, the modified rosin is reacted with styrenated acrylic copolymer having an acid number of about 202 under esterification conditions at about 180° C. for about 1 hour whereby a resin is produced having an acid value of 160-173, melting point of 155-165° C. and molecular weight of about 14,400. The resin is dissolved in dilute ammonium hydroxide to provide an aqueous varnish solution having a pH of 8.5 and viscosity of 0.5-2.0 poises.
A laminating ink formulation of the invention comprises water, pigment, styrene-acrylic varnish, shellac varnish, alkanol and the improved water soluble resin binder of the invention as described above.
DETAILED DESCRIPTION OF THE INVENTION
The use of acrylic copolymers and modified rosin esters as resin binders in flexible packaging inks has been known for some time. These materials are the precursors employed in the novel process of the present invention to produce the modified resin product whose unique properties are responsible for the improved laminating ink formulations described herein.
The rosins used in the present invention include tall oil rosin, gum rosin and wood rosin. However, gum rosin is the preferred rosin. The selected rosin is converted to a carboxylated Diels Alder adduct by reaction with a carboxy Diels Alder dienophile under conditions well known in the art, preferably between the melting point of the rosin and the boiling point of the dienophile. The preferred carboxy dienophiles for reaction with the rosin component are fumaric acid, maleic acid, acrylic acid, methacrylic acid, itaconic acid, citraconic acid and maleic anhydride.
Upon completion of the Diels Alder reaction, the carboxylated rosin adduct is reacted with a po
Catena Robert J.
Kveglis Albert A.
Mathew Mathew C.
Persley Sidney
Reddick Judy M.
Sun Chemical Corporation
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