|Title of Invention||
WATER BASED HEATSET OFFSET LITHOGRAPHIC INK COMPOSITIONS
|Abstract||A water based heatset offset lithographic ink composition according to the present invention comprises water; binder; a modified linseed oil; hydroxyethylethylene urea (HEEU); a dibutylated benzoguanamine; p-toluene sulfonic acid (PTSA); and pigment. In an embodiment of the water-based heat set offset lithographic ink, the binder may be a fumarated rosin resin or a polyamide resin or mixtures of polyamide resin and when the binder is a polyamide resin or mixtures of polyamide resin, the ink composition does not comprise PTSA.|
|Full Text||Field of the Invention
The invention relates to water based ink compositions for use in heat set/offset lithographic printing processes.
Background of the Invention
The heat set printing process was first introduced in the 1950's and is now well established in the printing industiy for the production of magazines, catalogues and brochures. The process yields high gloss, high quality prints and involves oven drying of the printed product.
In high speed web-offset printing presses, ink is applied to both surfaces of the web substrate simultaneously. To dry the ink before the substrate contacts a solid surface, the printed or coated web is passed through a float or floater type oven under tension and floated between cushions of hot air. Upon leaving the oven, the web must be cooled before further processing, such as sheeting, folding, or rewinding. Thus, the web is passed over one or more chill drums or rolls, i.e., internally cooled drums which reduce the web temperature from 93°C to 32°C. Thus heat set inks must fulfill exacting criteria to meet the high speed to press runs, the oven drying and required subsequent chilling and still meet the print quality standards. Further discussion of heat set inks and the heat set printing process can be found at The Printing Ink Manual, edited by R.H. Leach and R.J. Pierce, pages 571-576, 5lh edition, (Blueprint, 1993)
Generally, lithographic heat-set/offset printing inks predominantly contain petroleum distillates. The fountain solutions typically contain a desensitizer, salts, and glycols. The use of water based inks allows the printer to avoid many of these volatile organic components (VOCs) and their byproducts but requires additional equipment such as a humidity control chamber.
The offset lithographic printing process has always presented a unique challenge to ink formulators since the process utilizes a planographic printing plate i.e., the image and non-image areas are in the same plane on the image carrier, and two fluids are concurrently utilized as discussed above. Water based inks have been developed, but remain slow drying and high in tack.
U.S. Patent 5,725,646, which is incorporated herein by reference, describes a way of stabilizing a water based offset ink composition without drying up on a conventional multiple roller ink train using use a re-wetting agent, namely hydroxyethylethylene urea ("HEEU"). Since this re-wetting agent does not dry, it remains in the final film making it susceptible to poor water resistance. High levels of VOCs emanating from the oil-based ink and the aqueous fountain solution were reduced as was the difficulty in controlling the ink/water balance, while preserving the principal advantage of the conventional lithographic printing process, i.e., high surface energy differential between the image and non-image areas of the printing plate. However, the use of conventional re-wetting agents, such as glycols and glycol ethers not only imparts poor water resistance to the film, but also increases the tack of the formulations, thereby limiting its use on high speed presses.
U.S. Patent No. 6,444,021, which is incorporated by reference, describes a newspaper ink composition containing a humectant and a modified soybean oil based resin so as to eliminate the need for the humidity control (chamber) associated with water based inks while allowing the use of existing, multiple roller press set-ups. Drying problems remained however as the humectant takes longer to dry once the ink has printed on coated papers.
U.S.Patent No. 6,444,022 Bl which is incorporated by reference, describes a modified linseed oil reacted with polyglycols. In this manner, the benefits of including HEEU in the composition could be obtained without sacrificing risking water washability. However, diy times remain higher than required for heatset/offset printing.
Thus, there exists a need for a heatset/offset printing ink which can be printed at high speed and dry quicker than the prior art referenced above while still maintaining low tack for ink transfer and water resistance after printing.
Summary of the Invention
It is an object of the present invention to describe heat set ink compositions, which preserve the advantages of current water based ink systems containing HEEU, such as elimination of VOCs in the pressroom, while also eliminating the need for a humidity chamber in a manner which does not rely upon modified "soybean oil based resin. It is an additional object of this invention to allow the continued use of existing conventional multiple roller printing systems.
A water based heat set offset lithographic ink composition according to the present invention comprises; (a) water; (b) fumarated rosin resins; (c) a modified linseed oil; (d) hydroxyethylethylene urea; (e) a dibutylated benzoguanamine; (f) ptoluene sulfonic acid (PTSA); and (g) pigment. The present invention is also directed to a waterbased heatset offset lithographic ink composition comprising: (a) water (b) polyamide resins; (c) hydroxyethylethylene urea; (d) a modified linseed oil; (e) a dibutylated benzoguanamine; and (f) pigment
Detailed Description of the Invention
It has been found that the use of hydroxyethylethylene urea in conjunction with benzoguanamine resin or with certain polyamide .resins allows the formulation of a water based heatset lithographic ink which can be used in existing conventional multiple roller systems without the aid of a humidity chamber. Once printed, the ink has excellent rub and water resistance.
The water based printing inks of the present invention contain water to act as a rheology and/or a surface energy modifier of the ink composition and to ehhance the water washability of the ink. The water may be an added component or be contributed by one of the other components of the composition such as residual water from a pigment flush or press cake.
Resins for Pigment Bonding
The fumarated rosin resin in the present invention is a binder bonded to a pigment. Suggested binders to which the selected pigment may be bonded include, but are not limited to, water-soluble polymide resins, rosin resins, rosin salts, tall oil resins, methacrylic resins, styrene-acrylic resins, polystyrenesulfonic acid and its salts, and acrylic or vinyl emulsion polymers prepared from monomers selected from the group consisting of acrylic acid esters, methacrylic acid esters, acrylic acid esters of polyhydric alcohols, methyl methacrylate, styrene, vinyl styrene, and vinyl acetate, and mixtures thereof. Particularly preferred binders are polyamide resins specially developed for use in graphic arts compositions, such as those resins sold under the trademark GAX such as GAX 12-513, available from FitzChem Corporation, Elmhurst, Illinois, U.S.A., and fumarated rosin resins, available from Akzo Nobel Chemicals, Inc., Chicago, III
The composition of the present invention includes liydroxyethyl ethylene urea as a rewetting agent. The hydroxyethylethylene urea (HEEU) improves flow and increases open time on the rollers. Which not wishing to be bound by theory, it is believed that the HEEU rewetting agent serves as a plasticizer by providing surface continuity to the dry film on the substrate.
Modified Linseed Oil
The invention includes a modified linseed oil to address problems otherwise associated with the inclusion of HEEU such as poor water resistance. The modified linseed oil also helps to reduce the ink's tack. The modified linseed oil according to the present invention comprises the reaction product of polyglyocol and linseed oil.
The modified linseed oil according to the present invention may a]so include lithium ricinoleate, phthalic anhydride and triphenyl phosphate. Preferred modified linseed oils include DV 1469, manufactured by Reichold Inc., Durharii, NC.
The composition of the invention includes dibutylated benzoguanamine. The dibutylated benzoguanamine of the invention crosslinks with HEEU. The dibutylated benzoguanamine. The presence of water prevents this corsslinking reaction when the ink is being transferred.
Preferred dibutylated benzoguanamine includes but is not limited to Watersol CPC 248, manufactured by Dainippon Ink and Chemical Corp of Japan.
P-Toluene Sulfonic Acid Catalyst
The composition of the invention includes p-toluene sulfonic acid to catalyze the reaction between the HEEU and dibutylated benzoguanamine.
The pigment may be any of those which are suitable for formulating offset
lithographic printing inks such as dry power, flush, presscake or pigment
dispersions. Such pigments include CI Pigment yellows 1, 3, 4, 5, 12, 13, 14, 17, 55, 65, 73, 83, 97 and 98; CI Pigment Oranges 13, 16 and 46; CI Pigment Reds 2, 3, 4, 10, 12, 48, 48:1, 48:2, 53, 57:2, 81, 104, 146, 170 and 176; CI Pigment Greens 2, 7 and 36; CI Pigment Blues 1, 15:1, 15:2, 15:3, 15:6, 16, 29, 56 and 61; CI Pigment Violets 3, 23 and 37; CI Pigment Blacks 6 and 7; and CI Pigment Whites 6, 7, 18 and 26.
In genera, it is preferred that the ratio of pigment to fumarated rosin resin binder is in the range of 1 parts pigment to 2 parts fumarated rosin resin binder (1:2). It is preferred that the ratio be 1 parts pigment to 1 parts fumarated rosin resin binder (1:1). A person of ordinary skill in the art will recognize that the amount of fumarated rosin resin-bonded pigment present in the ink composition of the present invention will vary, depending on several factors, including the ratio of pigment to fumarated rosin resin binder, other components to be present in the specific ink composition and the desired opacity of the end product. However, particularly when the pigment: binder ratio is approximately 1;1, it is contemplated that the resin-bonded pigment is present in an amount of 10-60 wt% of the composition. It is preferred that the fumarated rosin resin-bonded pigment is present in an amount of 25-50 wt.% of the composition.
In the water based heat set/offset lithographic ink of the present invention, the water is present in amounts of 5 wt.% to 35 wt.% and more preferably in an amount of 5 wt% to 15 wt%. The resin bonded pigment may be present in the amount of 35 wt% and more preferably in an amount of 25 wt% to 50 wt%. The modified linseed oil is present in amounts of 5 wt% to 30 wt% and more preferably in an amount of 10 wt.% to 20 wt.%. The hydroxyethylethylene urea is present in amounts of 5 wt.% to 20 wt.% and more preferably in an amount of 10 wt% to 20 wt%. The dibutylated benzoguanamine is present in amounts of 5 wt% to 20 wt.% and more preferably in an amount of 10 wt.% to 20 wt.%. The p-toluene sulfonic
acid is present in an amount of 1 wt.% to 5 wt% and more preferably in an amount of 1 wt% to 2 wt%.
Printing plates for use with the printing ink of the present invention shouM have image areas hydrophilic in nature with non-image areas hydrophobic in nature. An example of a suitable printing plate is the 'waterless' Toray type. However, the image area of the plate need not contain a photo polymer. The image area of the plate may comprise, e.g. a grained aluminum surface which has no coating thereon, but is hydrophilic in nature. While the non-image area of the plate must be hydrophobic in nature, it may mearly be covered with any type of hydrophobic material, provided that such hydrophobic material adheres to the non-image .area of the plate during the printing process.
Water based material driers may also be used in printing inks of the present invention. Previously, such driers could not be added because they would destabilize the water based ink system. In the composition presented here, the ink remains stable in the presence of such driers due to the presence of amine and water.
The water washable ink compositions of the present invention are further illustrated by the following non-limiting examples in which all parts and percentages of components are by weight and based on the total weight of the composition, unless otherwise indicated.
A water based heat set/offset printing ink was prepared from the components indicated below:
The fumarated rosin resins were bonded to the dry pigment at a ratio of 1:1. This resin bonded pigment constituted 25% of the ink formulation. The ink had a pigment binder ratio 1:15.
The ink in Example 1 was measured for tack and stability. The tack was measured using an inkometer (manufactured by Thwing Albert) operating at a speed of 1200 rpm at 90 F. A tack of 17-20 was observed. Further, the ink was observed to be stable for 10 minutes in the inkometer.
A cyan ink for four color process heat set printing was formulated using the ink formula of example 1. The cyan ink was run on a Diddle web press at 1,000 fpm and printed on a 40# coated paper. No ink build up on the rollers, plate, or blanket was observed. At a 1.33 observed density, the ink was dry at a 265 F web exit temperature. The ink therefore dried as good as an oil based ink.
The print obtained from Example 3 was allowed to age for twelve hours. The print resisted 20 rubs by the Sutherland rub tester. One drop of water was placed on the dried print for 5 minutes and no ink dissolved in the water.
A waterbased ink was prepared from the components indicated below:
The polyamide resins were bonded to the dry pigment at a ratio of 1:1. The fumerated rosin resin bonded pigment constituted 25% of the ink formulation. The ink had a pigment binder ratio of 1:15
The ink in Example 5 was measured for tack and stability. The tack was measured using an inkometer (manufactured by Thwing Albert) operating at a speed of 1200 rpm at 90 F. A tack of 15-20 was observed.
The ink of Example 6 was run on a Didde web press at 1000 fps and printed on a 40# coated substrate. At a 1.33 density, the ink dried in one (1) minute at 130 C. The ink therefore dried as well as a conventional ink containing petroleum distillates.
The print obtained from Example 7 was allowed to age for 8 hours. The print resisted 20 rubs with a Sutherland rub tester. One drop of water was placed on the dried print for 5 minutes and no ink dissolved in the water.
Those skilled in the art having the benefit of the teachings of the present invention as hereinabove set forth, can effect numerous modifications thereto. These modifications are to be construed as being encompassed within the scope of the present invention as set forth in the appended claims.
1. A water based heat set A offset lithographic printing ink composition comprising:
(a) water present in an amount of 5-35 wt. %;
(c) hydroxyethylethylene urea present in an amount of 5-20 wt. %;
(d) a modified linseed oil present in an amount of 5-30 wt. %;
(e) a dibutylated benzoguanamine present in an amount of 5-20 wt. %;
(f) p-toluene sulfonic acid present in an amount of 1-5 wt. %; and
(g) pigment suitable for formulating offset lithographic printing inks,
wherein the pigment to binder ratio is 1:2; and
binder-bonded pigment is present in an amount of about 10-60 wt. % of the ink.
2. The ink as claimed in claim 1 wherein the binder is fumarated rosin resin, and said fumarated rosin resin is bonded to the dry pigment at a ratio of 1: 1.
3. The ink as claimed in claim 2 wherein the amount of fumarated rosin resin bonded pigment present is 25 wt. %.
4. A water based heat set/offset lithographic printing ink as claimed in claim 1,
wherein said binder is optionally a polyamide resin or a mixture of polyamide resins and the ink is devoid of p-toluene sulfonic acid
5. The ink as claimed in claim 4 wherein the polyamide resins are bonded to the dry pigment at a ratio of 1: 1.
6. The ink as claimed in claim 4 wherein the amount of polyamide resin bonded pigment present is about 25 wt. %.
7. The ink as claimed in claim 1 or 4 wherein the pigment is present in an amount of 12.5 wt. %.
8. The ink as claimed in claim 1 or 4 wherein the pigment is selected from the group consisting of C1 Pigment Yellows 1,3, 4,5, 12,13, 14,17, 55,65, 73,83, 97 and 98; C1 Pigment Oranges 13,16 and 46; C1 Pigment Reds 2,3, 4,10, 12,48, 48: 1,48 : 2,53, 57: 2,81, 104,146, 170 and 176; C1 Pigment Greens 2,7 and 36; C1 Pigment Blues 1, 15: 1,15 : 2,15 : 3,15 : 6,16, 29,56 and 61; C1 Pigment Violets 3,23 and 37; C1 Pigment Blacks 6 and 7; and C1 Pigment Whites 6,7, 18 and 26.
|Indian Patent Application Number||2971/DELNP/2005|
|PG Journal Number||08/2013|
|Date of Filing||04-Jul-2005|
|Name of Patentee||SUN CHEMICAL CORPORATION|
|Applicant Address||35 WATERVIEW BOULEVARD PARSIPPANY NEW JERSEY 07054-1285 U.S.A|
|PCT International Classification Number||C09D 11/02|
|PCT International Application Number||PCT/US2003/40109|
|PCT International Filing date||2003-12-16|