ADDITIVES FOR PRINTING INKS THAT PROVIDE RELEASE

Abstract: A releasable lithographic ink composition comprising: (a) an ultraviolet-curable or air-curable printing ink and (b) a methacrylate-terminated poly(dimethylsiloxane) having a number average molecular weight in the range of 5,000 to 50,000 or mercaptopolydiorganosiloxane copolymer additive having general formula (I), wherein y ranges from 0.5 to about 80 % of (x+y); R1, R2 and R3 are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fluoroalkyl, divalent linking groups; R4, R5 and R6 are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fluoroalkyl; z can range from 1 to about 16; x and y are integers of at least one and the sum of x+y is an integer of 10 or greater and further articles printed with printing inks blended with additives having releasable characteristics.

Description: Additives for Printing Inks That Provide Release Field of the Invention This invention relates to printing inks, particularly to additives for printing inks that provide a low energy surface and articles using printing inks with additives. Background of Invention Repositionable note pads, tapes and linerless labels typically consist of sheets of stock (paper, films, etc.) coated with pressure sensitive adhesive ("PSA") (and optionally a primer) on one side of the sheet and a release coating (also referred to as "low adhesion backsize" or "LAB") on the other side. In either pad (stacked sheets) or roll form, the release coating is in contact with the adhesive. In pad form, the release coating is used to lower the force required to remove the adhesive from the adjacent sheet in order to facilitate dispensing and minimize stock deformation or curl. In roll form, the release coating is used to ensure easy unwind during processing and dispensing. Lithographic, flexographic, or gravure printing processes are often used to prepare printed repositionable notes, tapes and linerless labels. Often, the printing process is separate from and subsequent to the process that applies the adhesive and release coating. In such situations, a roll of stock that has been pre-coated with adhesive and a release material is routed through a printing press, ink is printed on top of the release coating, and the printed material is immediately either rolled back up or cut into a stack of discrete sheets. Printing of ink over the release coating renders the release coating ineffective. Undesirable adhesive-ink interactions are also formed which results in poor release (high unwind, tear outs, poor dispensing) and transfer of ink from the printed stock to the adhesive. Such "ink transfer" damages the printed image and contaminates the adhesive. Common release materials that are used with pressure sensitive adhesives (PSAs) are typically based on moieties that have low surface energies such as aliphatic compounds, silicones and fluorochemicals. Traditional ink additives that are used to lower the "tack" of printed inks include polyethylene, polypropylene or polytetrafluoroehtylene (such as Teflon®) particles or waxes. These have been found to be relatively ineffective at reducing PSA/ink interactions. Silicone additives are generally avoided as they can cause ink-wetting problems on the print rollers or plates and adversely affect transfer of ink from the printing plate to the substrate and print quality. Recently, the addition of organopolysiloxanes that contain mercapto groups to ultraviolet (UV)-curable lithographic inks has been reported (Japanese Kokai: J.P. Sho. 56- 118472) for use in the printing of polyethylene or polypropylene coated papers. The addition of the mercapto containing silicone reduces the tendency of printed sheets to fuse together after exposure to excessive heat and pressure. In contrast, no desired improvements are observed when mercapto-containing silicones are added to air-curable lithographic inks. To date, it is believed that no references describe the addition of organopolysiloxanes that contain mercapto groups to lithographic inks in order to improve the properties of printed PSA products such as repositionable notes, tapes and linerless labels. It would be advantageous to have ink that would not form undesirable adhesive-ink interactions, and, preferably, would act as a release material. Such ink would eliminate the aforementioned problems of poor release and high "ink transfer" and allow for the manufacture of improved (better release, less ink transfer) printed repositionable notes, tapes and linerless labels. Summary of Invention Briefly in one aspect of the present invention, releasable lithographic inks that provide release characteristics to printed inks are provided comprising (a) UV-curable or air-curable printing inks and (b) a release additive. The preferred additives to the UV- curable or air-curable inks are mercaptopolydiorganosiloxane copolymers. Inks containing additives such as mercaptopolydiorganosiloxane copolymers can be advantageously used in products that have pressure sensitive adhesives (PSAs) in contact with the printed inks in order to reduce undesirable PSA/ink interactions. Undesirable PSA/ink interactions that are avoided by this invention include "ink transfer" from the printed image to the adhesive which results in damage to the printed image and adhesive contamination, and high release forces during unwind or sheet removal which can cause damage to the backing or render the product unusable. Another class of additives that provide good properties for UV-curable inks are acrylate terminated silicones ("silicone macromers"). An example of such materials is Silicone "Plus" HG-10 Siloxane, which is commercially available from 3M Company , St. Paul, MN. Silicone "Puls" HG-10 is a methacrylate terminated poly(dimethylsilicone) polymer having a number average molecular weight of 10,000. In another aspect of the present invention, adhesive coated articles are provided comprising (a) a backing substrate having a front and back surface, (b) a layer of pressure sensitive adhesive on at least one portion of the back surface of the backing substrate, and (c) indicia on the front surface of the backing substrate, wherein the indicia is printed using lithographic inks having release characteristics. Furthermore, in yet another aspect of the present invention, a pad assembly is provided comprising a multiplicity of flexible sheets each having similarly sized body portion that have pressure sensitive adhesive on the back surface and indicia printed on the front surface, wherein the indicia is printed with lithographic inks having release characteristics, such that when a sheet is removed from the pad assembly, the sheet is easily removable and the lithographic ink is not transferred from the front of the sheet of a first sheet to the back of the sheet of second sheet overlaying the first sheet. The multiplicity of sheets have pressure sensitive adhesive coated onto the back surface of the sheets and the sheets are disposed in a stack with the corresponding peripheral edges of the body portions of the sheets aligned and the pressure sensitive adhesive of each sheet adhering that sheet to the adjacent sheet in the stack. Such products include printed repositionable note pads (such as 3M Post-it® Notes), linerless labels, printed pressure sensitive tapes, adhesive coupons, and the like. Advantageously, using lithographic inks having release characteristics provides a construction that eliminates the need of providing a release coating on sheets having indicia printed on the front of them. In a further aspect of the present invention, a method of using lithographic inks having release characteristics are providing comprising the steps of: (a) blending a UV-curable or air-curable printing ink with an appropriate weight percent of an additive that functions as a release coating; (b) printing the blended ink onto a substrate having a front and back surface, such that the printing is positioned on the front surface of the substrate coincident with the adhesive coating applied on the back surface of the substrate; (c) stacking the printed substrates into a pad or winding the printed substrate onto a roll core. Description of the Preferred Embodiment(s) In this invention, ink additives have been discovered that eliminate the aforementioned problems of poor release and high "ink transfer". The additives can be blended with commercially available UV or air-curable lithographic inks and the resultant inks printed on standard lithographic printing presses. While not to be bound by theory, it is believed that the mercapto group of the additive enters into the curing processes of both air-curable and UV-curable lithographic inks and becomes covalently bound to the cured ink. The bound additive will not transfer to and contaminate pressure sensitive adhesives that may come in contact with the ink. Additive Types Preferred additives are mercaptopolydiorganosiloxane copolymers that are described by the following general formula wherein: y can range from 0.5 to about 80% of (x + y); preferably from 1-20% of (x + y) and most preferably from 3.5 - 14% of (x + y); Ri, R 2 and R 3 , are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, divalent linking groups and are most preferably alkyl moieties; R 4 , R 5 , and Re are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, and are most preferably alkyl moieties; z can range from 1 to about 16, preferably from 1 to 5 and is most preferably 3. x and y are integers of at least one and the sum of x + y is an integer of 10 or greater. The molecular weight of the additive can range from about 1000 to about 200,000. The preferable range is from about 5000 to about 50,000. In these preferred ranges the additive has a viscosity which is desirable for blending into inks. The molecular weight can also affect additive effectiveness. Optimal molecular weights will be dependent on additive and ink type. A most preferred additive is commercially available from Shin-Etsu, Inc. (1150 Darner Drive, Akron, OH 44305 under the commercial designation of "X-22-980") wherein Ri, R 2 , R 3 , R4, R 5 , and R 6 = CH 3 , y = 3.5 - 4.5% of (x + y), z = 3, and the number average molecular weight (Mn) = 8000. Most preferably, any cyclic material that may be present is removed prior to use by such methods as evaporation under vacuum at elevated temperatures (for example, 150°C, 200 mm Hg). Additional most preferred additives of varying values of R, x, y and z are available from Huls America Inc. (Piscataway, NJ). The additive is added to the ink in amounts ranging from 0.1 to 15% by weight of the ink and most preferably between 1 and 5%. The optimum additive amount will be dependent on the strength of the pressure sensitive adhesive and desired release value in the printed product. Addition of too much additive can cause wetting problems on the print rollers and blankets and adversely affect the printing process. The upper limit of additive ranges between about 5 and 15% depending on the printing press type, roller and blanket materials, and ink formulation. The mercapto content (weight percent SH moieties based on weight of additive) in the additive can range from about 0.1 to about 20 weight percent. Most preferable mercapto contents range from 0.35 to about 4 weight %. Additive effectiveness appears to decrease at very high levels of SH. For example, poly(mercaptopropylmethylsiloxane) (26 wt% SH) is not a very effective additive. Another class of additives that provide good properties for UV-curable inks are acrylate terminated silicones ("silicone macromers"). An example of such materials is Silicone "Plus" HG-10 Siloxane, which is commercially available from 3M Company , St. Paul, MN. Silicone "Puls" HG-10 is a mefhacrylate terminated poly(dimethylsilicone) polymer having a number average molecular weight of 10,000. Traditional ink additives such as polyolefin and polytetrofluoroethylene (such as Teflon®) waxes and particles have been found to be ineffective. Also ineffective are fluoroacrylate compounds such as Fluorad™ FX-189, Fluorad™ FX-13 and Fluorad™ FX-14 that are commercially available from 3M Company, St. Paul, MN. Ink Types Preferable lithographic inks are curable by UV irradiation although lithographic inks that are curable by air-oxidation may also be used. Typical lithographic inks that are commercially available from common ink suppliers can be used. Suitable UV-curable lithographic inks include UV 1/D process inks from Kohl and Madden Corporation (Minneapolis, MN), and UVALUX process inks from Zeller Interchem Corporation (2205 Tomlynn Street, Richmond, VA 23230). Suitable air-curable lithographic inks include soy-based process inks from Kohl and Madden Corporation such as Lithographic Soy ABDT Black MSP-42200-D-STG-5 (tack = 16), PMS-185-ABD (OFF-ABD-STD-RED), and MSP-42200-D-STG-S (OFF- SOY- ABDT-BLACK). Additional examples of suitable inks include Note Pad Process Black K52-3444-22 commercially available from Central Ink Corporation (Plymouth, MN). Printing Process Standard lithographic printing presses can be used. Such presses for air-curable inks include: Didde's (Emporia, Kansas) Webcom and Apollo presses and printing presses available from Stevens International (Fort Worth, Texas). Laboratory presses include the Little Joe Proving Press (Little Joe Color Swatcher, Somerville, NJ). UV Presses include those available from Sanden (Cambridge, Ontario) and Mueller Martini (New York). This invention is further illustrated by the following examples that are not intended to limit the scope of the invention. In the examples, all parts, ratios and percentages are by weight unless otherwise indicated. The following test methods were used to evaluate and characterize the printing ink with additives compositions produced in the examples. All materials are commercially available, for example from Aldrich Chemicals (Milwaukee, WI), unless otherwise indicated or described. Examples Test Methods Compounding of Additives with the Inks Additives were added to the base ink and mixed with a wood applicator until uniform. The amount of additive is reported as weight % based on the mass of base ink used. Printing Procedure using a Little Joe Lithographic Proving Press Printing was carried out using a Little Joe Lithographic Proving Press (Little Joe Color Swatcher, Somerville, NJ) according to the following procedure. Brayers and print blankets designed specifically for either air-curable or UV-curable inks were used. 1) A 0.6 cc portion of ink was applied to the 28 x 25 cm stainless steel "inking plate". 2) The ink was then distributed uniformly across the plate via the use of a hand brayer (rubber roller). 3) The brayer, which was saturated with ink, was then rolled once across the 10 x 15 cm "printing plate" in order to transfer ink to the printing plate. 4) The brayer was used, once again, to uniformly redistribute the ink over the inking plate. 5) Another coat of ink was applied to the printing plate with the ink saturated brayer. 6) The printing "blanket" was rolled across the printing plate and then across the non-adhesive side of Post-it® Note paper (yellow Ashdown paper) in order to make print #1. 7) Print #1 was discarded. 8) Repeating steps 4-6 made prints #2-6. 9) Print #2 was discarded. Prints 3-6 were retained and evaluated. 10a) For air-curable inks, the prints were hung on a wall and allowed to dry for at least 24 hours prior to testing. 10b) For UV-curable inks, each printed sample was immediately attached to a piece of cardboard and passed through an ultraviolet curing unit (Fusion UV Curing Systems, Rockville, MD, F300 ultraviolet lamp system, MC-6R conveyor) at a speed of approximately 15 feet (4.57 meters) per minute. The proving press was thoroughly cleaned prior to the printing of another sample. Samples were tested after equilibration in a controlled temperature and humidity room for at least 24 hours. "Peel Adhesion'Of 3M 810 Magic™ Tape to a Substrate This test is similar to TAPPI test method UM-504. A 25 mm wide strip of 3M 810 Magic™ Tape was applied to a substrate. A 2 kg roller was rolled over the tape on the substrate (two passes) in order to adhere the tape to the substrate. One end of the tape was attached to a tensile tester. The tape was peeled from the surface at a 90 degree angle at 12" (30.48 cm)/min. The force in g/1" (2.54 cm) was recorded. The tape was saved and used in the re-adhesion test. The test was carried out on prints 3-6. The average of these tests was reported and is referred to as "peel adhesion" in the Examples. Re-Adhesion Re-adhesion is a qualitative measure of the amount of adhesive contamination that occurs when 3M 810 Magic™ Tape is peeled from a substrate. In this test, the tape that was used in the Peel Adhesion test is applied to the non-adhesive side of unprinted Post- it® Note paper (yellow Ashdown paper). Peel Adhesion was measured and the tape strip was retained for evaluation of ink transfer. The test was carried out on prints 3-6. The average of these tests is reported. The "re-adhesion value" was compared to the Peel Adhesion of fresh 3M 810 Magic™ Tape to the non-adhesive side of unprinted Post-it® Note paper (yellow Ashdown paper) (Table 1, Cl). A value that was similar to that of Cl indicated little or no contamination, whereas a value significantly less than Cl indicated a reduction in adhesion due to contamination of the adhesive with the ink or ink additive. Ink Transfer Ink transfer is the amount of ink that transfers to the 3M 810 Magic™ Tape that is used in the Peel Adhesion test. The amount of ink transfer was evaluated visually after lamination of the tape to white bond paper. Ratings were made on a scale of 0 to 3 where 0 = "no ink transfer", 1 = "very little", 2 = "some" and 3 = "a lot" were used. Print Quality Print quality was evaluated visually. Ratings of "good" (uniform image of desired color density) and "poor" (non-uniform image or low color density) were used Sheet Removal Force Sheet removal force is the force required to remove the top sheet from a pad of repositionable notes such as Post-it® Notes. This test was carried out by cutting a one inch (2.54 cm) wide strip across the top sheet of the note pad such that the strip was perpendicular to the adhesive stripe. The adhesive-free end of the strip was attached to a tensile tester. The strip was peeled from the surface at a 90 degree angle at 12" (30.48 cm)/min. The force in g/1" (2.54 cm) was recorded. The test was repeated and the average of the trials was reported. Examples with Air-Curable Inks The following examples illustrate the improved properties that are obtained with this invention when using air-curable inks. Comparative Examples C1-C3 Comparative examples C1-C3 showed the detrimental effect of printing a typical air-curable lithographic ink onto a paper coated with a release coating. In examples C1-C3, peel adhesion of 3M 810 Magic™ Tape to printed and unprinted standard Post-it® Note paper (coated with adhesive, primer and release coating) was measured. In addition, "re-adhesion" of the 810 Magic™ Tape was measured in order to detect any contamination of the adhesive by the printed surface. Print quality and amount of ink transferred to the Magic™ Tape were noted. Results (Table 1) for C1-C2 show that peel adhesion increased from 140 to 242 g/1.25" (3.175 cm) when red ink was printed on top of Post-it® Note paper. A peel adhesion value of 317 g 1.25" (3.175 cm) was observed when black ink was used (C3). Re-adhesion values were significantly lower (117 and 105 g/1.25" (3.175 cm)) than 140 g/1.25" (3.175 cm), which indicates that contamination of the adhesive with ink was significant. Ink transfer was high (2.5) for both C2 and C3. Comparative Examples C4-C12 Comparative examples C4-C6 (Table 1) showed that use of typical ink additives such as polyethylene and polytetrafluoroethylene (such as Teflon®) waxes did not improve release and cause adhesive contamination as indicated by the high peel adhesion and low re-adhesion values. Comparative examples C7-C12 showed that stearic acid, fluorine containing monomers, a methacrylate terminated silicone "silicone macromer", and polyethylene glycol monomethacrylate also provided poor results. JM410-9, 410-8, and 413-3 are typical waxes that are used in lithographic inks. They were obtained from Kohl & Madden Corporation, Minneapolis, MN. JM410-9 is commercially available as "Super Poly 4" from Lawter International, Pleasant, WI. JM410-8 is commercially available as "CC5510-D" and JM413-3 is commercially available as "PROTECH 200" both materials are available from Carrol Scientific, Countryside, LL. Stearic Acid was obtained from Aldrich Chemical Co. Fluorad™ FX-13, Fluorad™ FX-189 and Fluorad™ FX-14 were obtained from 3M Company (Industrial Chemical Products Division, St. Paul, MN). CW-750 is polyethylene glycol monomethacrylate 10 moles, EO obtained from Polysciences, Inc., Warrington, PA (Cat. #16713). Comparative Examples C13-C14 Comparative examples C13 and C14 showed that using mercaptan-free polydimethylsiloxanes that did not have mercaptan functionality did not provide improved properties. In these examples, polydimethylsiloxane (trimethylsiloxy terminated, CAS No. [63148-62-9]) of varying molecular weight were evaluated. They were obtained from Huls America as PS041.2 (MW = 9430, viscosity = 200) and PS042 (MW = 17,250, viscosity = 500). High peel adhesion, high ink transfer and low re-adhesion values were observed. Examples 1-10 Examples 1-8 (Table 1) showed that the addition of 1-3 wt % of the mercaptopolydiorganosiloxane ("X-22-980" where Ri, R 2 , R 3 , *, R 5 , and R 6 = CH 3 , z = 3, y = 3.5-4.5% of (x + y), Mn = 8000, commercially available from Shin-Etsu, Inc.) reduced ink/adhesive interactions, as indicated by the decrease in peel adhesion of Magic™ Tape to the printed ink. Very little adhesive contamination was observed and re-adhesion values were high. Ink transfer was greatly reduced as well and essentially eliminated at X-22-980 levels of 2.5%. Examples 9 and 10 showed that poor print quality was obtained if 3.75% or 5% of X-22-980 was used. This indicated that print quality could be affected on certain printing presses if relatively high levels of X-22-980 were used. It should be noted, however, that Didde Webcom lithographic printing presses were found to successfully print ink containing 5% X-22-980 and that an upper limit for X-22-980 level was dependent on press type. Table 1 Air-curable Lithographic Inks (Little Joe Proving Press) Ink % Additive Peel Re-adhesion Print Ink Transfer in Ink Adhesion g/2.54 cm Quality to Magic™ g/2.54 cm Tape Cl none — 147 144 - - C2 Red — 242 117 good 2.5 C3 Black — 317 105 good 2.5 1 Black 2.5% X-22-980 56 132 good 1 2 Red 2.5% X-22-980 34 141 good 0 3 Red 2.5% X-22-980 27 136 good 0 4 Red 2.5% X-22-980 24 133 good 0 5 Red 1% X-22-980 129 130 good 1.5 6 Red 1.75% X-22-980 70 125 good 1.5 7 Red 2% X-22-980 45 130 good 1 8 Red 3% X-22-980 25 130 good 0 9 Red 3.75% X-22-980 34 135 poor 0 10 Red 5% X-22-980 did not " print a C4 Red 2.5% JM410-8 259 80 good 3 C5 Red 2.5% JM410-9 239 77 good 3 C6 Red 2.5% JM413-3 215 87 good 3 C7 Red 2.5% Stearic 243 86 good 3 Acid C8 Red 2.5% Fluorad 280 78 good 3 FX-13 C9 Red 2.5% Fluorad 262 80 good 3 FX-14 CIO Red 2.5% Fluorad 300 103 good 3 FX-189 Cl l Red 2.5% Silicone 212 120 good 2 Macromer C12 Red 2.5% CW-750 248 89 good 3 C13 Red 2.5% PS041.2 226 80 good 3 C14 Red 2.5% PS042 218 76 good 3 a Ink did not wet out the inking plate or printing plate very well. Inks were obtained from Kohl & Madden Printing Ink Corp (Minneapolis, MN). Red ink was labeled PMS-185-ABD (OFF-ABD-STD-RED). Black Ink was labeled MSP-42200-D-STG-S (OFF-SOY-ABDT-BLACK). Examples with UV- Curable Inks The following examples illustrate the improved properties that were obtained with this invention when using UV-curable inks. Comparative Examples C100-C101 Comparative examples C100-C101 were carried out in a similar fashion as examples C1-C3. The high peel adhesion value in CIO 1 illustrated the detrimental PSA ink interactions that resulted when printing a typical UV-curable lithographic ink onto a paper coated with a release coating. In contrast to air-curable inks, low ink transfer and low adhesive contamination were observed when using UV-curable inks and proper curing conditions. Comparative Examples C103-C109 Comparative examples C107-C109 (Table 2) showed that typical ink additives, such as polyethylene and polytetrofluoroethylene (such as Telfon®) waxes did not improve release. Comparative examples C103-C106 showed that fluorine-containing monomers and polyethylene glycol monomethacrylate were also ineffective at reducing PSA/ink interactions. JM410-9, 410-8, and 413-3 are typical waxes that are used in lithographic inks. They were obtained from Kohl & Madden Corporation, Minneapolis, MN. JM410-9 is commercially available as "Super Poly 4" from Lawter International, Pleasant, WI. JM410-8 is commercially available as "CC5510-D" from Carrol Scientific, Countryside, IL. JM413-3 is commercially available as "PROTECH 200" from Carrol Scientific. Countryside, LL. Fluorad™ FX- 13 , Fluorad™ FX- 189 and Fluorad™ FX- 14 were obtained from 3M Company (Industrial Chemical Products Division, St. Paul, MN). CW-750 is polyethylene glycol monomethacrylate 10 moles, EO obtained from Polysciences, Inc., Warrington, PA (Cat. #16713). Comparative Examples C110 and Clll Comparative examples C 110 and Cl l l show that the use of mercaptan-free polydimethylsiloxanes that do not have the mercaptan functionality do not provide improved properties. In these examples, polydimethylsiloxane (trimethylsiloxy terminated, CAS No. [63148-62-9]) of varying molecular weight were evaluated. They were obtained from Huls America as PS041.2 (MW = 9430, viscosity = 200) and PS042 (MW = 17,250, viscosity = 500). High peel adhesion values were observed which indicate that poor release results when no mercaptan functionality is present. Examples 100-108 The peel adhesion values for Examples 100-108 (Table 2) show that X-22-980 reduces PSA / ink interactions. Peel adhesion decreases as X-22-980 levels are increased from 1 to 6 wt%. The high re-adhesion values indicate that adhesive contamination is low. Examples 109 and 110 show that poor print quality is obtained if 7.5% or 10% X- 22-980 is used. This indicates that print quality can be affected on certain printing presses if relatively high levels of X-22-980 are used. Examples 109-116 Examples 109-116 (Table 2) illustrate the positive affects of additives with various amounts of mercapto content and variations in polymer structure. Except for PS 927 and PS405, the additives are dimethylsiloxy / 3-mercaptopropylmethylsiloxy copolymers of varying comonomer ratios and molecular weights. PS927 is the homopolymer based on a 3-mercaptopropylmethylsiloxy repeat unit. PS405 is described as "polydimethylsiloxane, mercaptopropyl t-structure with branch points" by Huls America. The additives are described in detail in Table 3. Table 3 Ex. Additive z 100*y/ R^o wt% SH Molecular Relative (x + y) 6 in weight Viscosity polymer Mn 109 PS850.5 3 14 CH 3 3.6 na 75 110 PS850 3 5-10 CH 3 100-200 111 GP-71- 3 4 CH 3 1 6600 na SS 112 PS849 3 2 CH 3 na 200 113 PS405 NA NA NA na na 100-200 114 PS848 2 CH 3 0.5 na 25 115 GP-72- 1.4 CH 3 0.38 13,000 na SS 116 PS927 100 CH 3 26 na na Example 117 Example 117 illustrated that methacrylate-terminated poly(dimethylsiloxane) of a number average molecular weight of 10,000 (Silicone PLUS HG-10, commercially available from 3M) was an effective additive. Table 2. Results with UV-curable lithographic inks using Little Joe Proving Press. Ex. Ink wt %, additive in Peel Re- Print Ink ink Adhesion adhesion Quality Transfer to g/1" (2.54 g/1" (2.54 Magic™ cm) cm) Tape C100 none — 147 144 — C101 red None 264 139 good 0 100 red 1% X-22-980 105 132 good 0 101 red 2% X-22-980 48 135 good 0 102 red 2.5% X-22-980 39 138 good 0 103 red 3% X-22-980 32 143 good 0 104 red 4% X-22-980 24 134 good 0 105 red 5% X-22-980 20 139 good 0 106 red 6% X-22-980 16 132 good 0 107 red 7.5% X-22-980 — — did not ~ print a 108 red 10% X-22-980 — — did not — print a 109 red 2.5% PS850.5 30 137 good 0 110 red 2.5% PS850 34 127 good 0 111 red 2.5% GP-71-SS 49 147 good 0 112 red 2.5% PS849 67 131 good 0 113 red 2.5% PS405 75 131 good 0 114 red 2.5% PS848 133 137 good 0 115 red 2.5% GP-72-SS 178 143 good 0 116 red 2.5% PS927 237 139 good 0 117 red 2.5% Silicone 160 140 good 0 PLUS HG-10 C103 red 2.5% Fluorad 283 148 good 0 FX-189 C104 red 2.5% Fluorad 274 149 good 0 FX-14 C105 red 2.5% Fluorad 266 146 good 0 FX-13 CIO red 2.5% PEG 260 151 good 0 C107 red 2.5% JM 410-8 251 146 good 0 C108 red 2.5% JM 410-9 254 145 good 0 C109 red 2.5% JM 413-3 228 152 good 0 C110 Red 2.5% PS041.2 220 160 good 0 Cl l l Red 2.5% PS042 197 160 good 0 Ink did not wet out the inking plate or printing plate very well. Inks were obtained from Zeller and Gmelin. Red Ink was labeled UVALUX US423185 LD UN RED. Comparative Example C200 and Examples 130-135 These examples were carried out on a Sanden Varicom printing press equipped with five ultra-violet curing stations. Rolls of adhesive (coated in 1.25 inch (3.175 cm) wide stripes) and release coated (coated over entire paper surface) Post-it® Note paper was routed through the press at 500 feet (152.4 meters) per minute, printed on (printing pattern was a 2 x 9 inch (5.08 x 22.86 cm) rectangle, 100% ink coverage), routed through the UV curing stations (UV light intensity = 600 watts/inch (2.54 cm) for each light), cut into 12 x 18 inch (30.48 x 45.72 cm) sheets and stacked, individual 3 x 5 inch (7.62 x 12.70 cm) Post-it® Note pads were prepared by cutting stacks of 12 inch x 18 inch (30.48 x 45.72 cm) sheets with a guillotine. Samples were tested for peel adhesion, re-adhesion, sheet removal force and ink transfer. Inks used in these examples were obtained from Zeller Interchem Corporation. Black ink was labeled UVALUX US4826LD; yellow ink was labeled UVALUX US4825LD. Ink additive "X-22-980" was added to the inks at 1, 3 and 5 weight percent based on the weight of the ink. Black ink was cured with 4 lights whereas the yellow ink was cured with one UV light. Results in Table 4 show that addition of X-22-980 lowered both peel adhesion and sheet removal force (SRF) for both the black and yellow inks. The improvements were more pronounced with the black inks that illustrated that ink type can be important. The reduction of SRF in repositionable notes was a significant quality improvement as lower SRF values reduce paper deformation (curl) that was caused during removal of the top sheet. Print quality was good for all samples. No ink transfer was observed in these examples. Table 4. Results with UV-curable lithographic inks using a Sanden press. Ex. Ink wt %, Peel SRF X-22-980 Adhesion g i" ' (2.54 cm) Added g/1" (2.54 cm) C200 None — 192 48 130 Black 1 102 25 131 Black 3 24 13 132 Black 5 13 6 133 Yellow 1 204 37 134 Yellow 3 113 37 135 Yellow 5 71 33 Examples with Products Other Than Repositionable Notes Examples C200-C203 and 201-202 Examples C200-C203 and 201-202 demonstrate that the additives described in this invention can be used to make printed tapes that have good release characteristics. Printing was carried out on the non-adhesive side of several strips of 1" (2.54 cm) wide Scotch™ Magic™ Tape (810 tape, commercially available from 3M company, St. Paul, MN) in a similar manner as C 1 and C 100. The several strips of Scotch™ Magic™ Tape were laminated next to each other onto bond paper prior to printing in order to create a large area for printing. Results in Table 5 show that addition of 2.5% of X-22-980 results in low ink transfer and low peel adhesion for both UV and air-curable inks. Table 5. Results when printing on the non-adhesive side of Scotch™ Magic™ Tape. Ex. Ink Wt %, Peel Re- Print Ink X-22-980 Adhesion adhesion Quality Transfer In ink g/1" (2.54 g/1" (2.54 to cm) cm) Magic™ Tape C200 none — 121 — good - C201 UV 0 273 159 good 0 201 UV 2.5 21 133 good 0 C202 Air-curable 0 [24]* 0 good 3+ 202 Air-curable 2.5 24 133 good 1 [24]* = the value was very low due to complete ink transfer during the peel adhesion test. UV-curable ink = UVALUX US423185 LD UN RED obtained from Zeller and Gmelin. Air-curable ink = PMS-185-ABD (OFF-ABD-STD-RED) obtained from Kohl and Madden Corp. Examples C210-C213 and 211-212 Examples C210-C213 and 211-212 demonstrate that the additives described in this invention can be used to make printed labels that have good release characteristics. Printing was carried out on the non-adhesive side of 1" x 2 5/8" (2.54 x 6.66 cm) address labels that were on an 8.5" x 11" (21.59 x 2.54 cm) liner in a similar manner as Cl and CIOO. The labels are commercially available as "Laser Labels" product #5160 from Avery Dennison Office Products (Diamond Bar, CA). Results in Table 6 show that addition of 2.5% of X-22-980 results in low ink transfer and low peel adhesion for both UV and air- curable inks. Table 6. Results when printing on the non-adhesive side of Avery Laser Labels. Ex. Ink Wt %, Peel Re- Print Ink X-22-980 Adhesion adhesion Quality Transfer to In ink g/1" (2.54 g 1" (2.54 Magic™ cm) cm) Tape C210 none NA 343 133 NA NA C211 UV 0 310 147 good 0 211 UV 2.5 45 132 good 0 C212 Air-curable 0 287 139 good 0 212 Air-curable 2.5 62 159 good 0 UV-curable ink = UVALUX US423185 LD UN RED obtained from Zeller and Gmelin. Air-curable ink = PMS- 185-ABD (OFF-ABD-STD-RED) obtained from Kohl and Madden Corp. Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and principles of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth hereinabove. All publications and patents are incorporated herein by reference to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference.

Claims: What is Claimed: 1. A releasable lithographic ink composition comprising (a) an air-curable printing ink and (b) mercaptopolydiorganosiloxane copolymer additive having the following general formula: wherein: y ranges from 0.5 to about 80% of (x + y); Ri, R 2 and R 3 , are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, divalent linking groups; R , R 5 , and R 6 are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl; z can range from 1 to about 16; x and y are integers of at least one and the sum of x + y is an integer of 10 or greater. 2. The releasable lithographic ink composition according to claim 1 wherein y ranges from 1 -20% of (x + y). 3. The releasable lithographic ink composition according to claim 1 wherein y ranges from 3.5 - 14% of (x + y). 4. The releasable lithographic ink composition according to claim 1 wherein the molecular weight of the additive is in the range from about 1000 to about 200,000. 5. The releasable lithographic ink composition according to claim 1 wherein the additive is present in the composition in amounts ranging from 0.1 to 15 % by weight of the ink. 6. The releasable lithographic ink composition according to claim 1 wherein Ri, R , R 3 , R , R5, and Re = CH 3 , y = 3.5 to 4.5 % of (x + y), z = 3 and the number average molecular weight (Mn) = 8000. 7. An adhesive coated article comprising (a) a backing substrate having a front and back surface, (b) a layer of pressure sensitive adhesive on at least one portion of the back surface of the backing substrate, and (c) indicia on the front surface of the backing substrate, wherein the indicia is printed using a releasable lithographic ink comprising (a) an ultraviolet curable printing ink or an air-curable printing ink and (b) mercaptopolydiorganosiloxane copolymer additive having the following general formula: wherein: y ranges from 0.5 to about 80% of (x + y); Ri, R 2 and R 3 , are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, divalent linking groups; R 4 , R 5 , and Re are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl; z can range from 1 to about 16; x and y are integers of at least one and the sum of x + y is an integer of 10 or greater. 8. The adhesive coated article according to claim 7 wherein the molecular weight of the additive is in the range from about 1000 to about 200,000. 9. The adhesive coated article according to claim 7 wherein the molecular weight of the additive is in the range from about 1000 to about 200,000. 10. The adhesive coated article according to claim 7 wherein the additive is present in the composition in amounts ranging from 0.1 to 15 % by weight of the ink. 11. The adhesive coated article according to claim 7 wherein Ri, R 2 , R 3 , R^ R 5 , and Re = CH 3 , y = 3.5 to 4.5 % of (x + y), z = 3 and the number average molecular weight (Mn) = 8000. 12. A pad assembly comprising a multiplicity of flexible sheets each having similarly sized body portion that have pressure sensitive adhesive on a back surface and indicia printed on a front surface, wherein the indicia is printed with lithographic inks having release characteristics, such that when a sheet is removed from the pad assembly, the sheet is easily removable and the lithographic ink is not transferred from the front of the sheet of a first sheet to the back of the sheet of second sheet overlaying the first sheet, wherein the lithographic ink comprises (a) an ultraviolet curable printing ink or an air- curable printing ink and (b) mercaptopolydiorganosiloxane copolymer having the following general formula: wherein: y ranges from 0.5 to about 80% of (x + y); Ri, R 2 and R 3 , are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, divalent linking groups; R 4 , R s , and Rg are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl; z can range from 1 to about 16; x and y are integers of at least one and the sum of x + y is an integer of 10 or greater. 13. The pad assembly according to claim 12 wherein the molecular weight of the additive is in the range from about 1000 to about 200,000. 14. The pad assembly according to claim 12 wherein the molecular weight of the additive is in the range from about 1000 to about 200,000. 15. The pad assembly according to claim 12 wherein the additive is present in the composition in amounts ranging from 0.1 to 15 % by weight of the ink. 16. The pad assembly according to claim 12 wherein Ri, R 2 , R , R 4 , R 5 , and R 6 = CH 3 , y = 3.5 to 4.5 % of (x + y), z = 3 and the number average molecular weight (Mn) = 8000. 17. A roll of adhesive coated material comprising a substrate having at least one portion that has a pressure sensitive adhesive on a back surface and indicia printed on a front surface, wherein the indicia is printed with lithographic inks having release characteristics, such that when the material is unrolled from the roll, the material is easily removable and the lithographic ink is not transferred from the front of the substrate, wherein the lithographic ink comprises (a) an ultraviolet curable printing ink or an air- curable printing ink and (b) mercaptopolydiorganosiloxane copolymer having the following general formula: wherein: y ranges from 0.5 to about 80% of (x + y); Ri, R 2 and R 3 , are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl, divalent linking groups; R4, R5, and Re are monovalent moieties that can independently be the same or different and are selected from the group consisting of alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, fiuoroalkyl; z can range from 1 to about 16; x and y are integers of at least one and the sum of x + y is an integer of 10 or greater. 18. A releasable lithographic ink composition comprising (a) an ultraviolet- curable printing ink and (b) a methacrylate-terminated poly(dimethylsiloxane) having a number average molecular weight in the range of 5,000 to 50,000. 19. A pad assembly comprising a multiplicity of flexible sheets each having similarly sized body portion that have pressure sensitive adhesive on a back surface and indicia printed on a front surface, wherein the indicia is printed with lithographic inks having release characteristics, such that when a sheet is removed from the pad assembly, the sheet is easily removable and the lithographic ink is not transferred from the front of the sheet of a first sheet to the back of the sheet of second sheet overlaying the first sheet, wherein the lithographic ink comprises (a) an ultraviolet curable printing ink and (b) a methacrylate-terminated poly(dimethylsiloxane) having a number average molecular weight in the range of 5,000 to 50,000. 20. A roll of adhesive coated material comprising a substrate having at least one portion that has a pressure sensitive adhesive on a back surface and indicia printed on a front surface, wherein the indicia is printed with lithographic inks having release characteristics, such that when the material is unrolled from the roll, the material is easily removable and the lithographic ink is not transferred from the front of the substrate, wherein the lithographic ink comprises (a) an ultraviolet curable printing ink or an air- curable printing ink and (b) a methacrylate-terminated poly(dimethylsiloxane) having a number average molecular weight in the range of 5,000 to 50,000.

Inventors: KESTI MICHAEL R, MATHNA CHARLES A, ROMSOS JASON D, KESTI, MICHAEL, R., MATHNA, CHARLES, A., ROMSOS, JASON, D.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1999
Main classification: C09D11
IPC codes: C09D11, C09J7, C09J201