Vegetable Oil Based Printing Inks

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  Vegetable Oil Based Printing Inks S.Z. Erhan , M.O. Bagby and H.W. Cunningham 1 Oil Chemical Research, National Center for Agricultural Utilization Research, Agricultural Research Center, U.S. Department of Agriculture 2, Peoria, IL 61604 251 Nearly 75 black and 25 colored inks consisting of 100 vegetable oil-based vehicles were formulated. The physical properties of these inks met or exceeded the industry stan- dards for lithographic and letterpress newsprint appfica- tious. In addition, elimination of petroleum-based resin and reduced pigment usage, due to the fight vehicle color, pro- vided a competitively priced alternative to petroleum- based inks. KEY WORDS: Letterpress, ithography, news nk, pigments, print den- sity, rub-off, ack, vegetable oil, vehicle, viscosity. In the printing industry, the processes in current use are lithography (52%), gravure (18%), flexography (19%), lette~ press (5%) and screen printing and other miscellaneous pr~ cesses (6%) (Bassemir, R.W., private communication). Lithography and letterpress processes require paste inks. Printing inks that are conventionally used in these applica- tions are multi-component systems comprising a pigment, a hydrocarbon andbr alkyd resin, a hydrocarbon solvent and optional additives. For example, a typical petroleum-based, black lithc~news ink would be comprised of 15-20% carbon black as the pigment, 15-25% hydrocarbon or alkyd resin and 50-70% mineral oil solvent. Nearly 500 million pounds of ink for these applications are produced domestically each year (1). his volume of production represents substantial consumption of a petroleum-based fractiorL The petroleum oil shortage in the 1970's stimulated research on vegetable oil-based inks that do not require petroleum products. Inks containing vegetable otis have been formulated for various specialized applications (2-5). In the early 1980's, the American Newspaper Publishers Association (ANPA) developed a series of ink formulations comprising a blend of gilsonite and tall oil fatty acids together with carbon black pigment {6-8). he cost and availability f tall il and the difficulty of equipment clean-up caused by the gilsc~ nite has limited the acceptance of these inks by the in- dustry. A later approach by ANPA to produce a vegetable oil-based ink vehicle resulted in a lithographic news ink com- prising alkali-refined oybean oil, hydrocarbon resin and carbon black pigment (9). his black ink prints as well as the mineral off-based commercial inks, but it costs 30-50% more The color inks, formulated similarly, print well but they cost about 5% more than the petroleum-based com- mercial ~ Both the black and color inks contain 20-25% hydrocarbon resi~ Thus, the industry has continued to seek vegetable oil-based nonpetroleum ink. We describe here soy and other vegetable oil ink formulations that meet or ex- ceed industry standards in regard to rul>off resistanc~ viscosity and tackiness and are cost competitive with petrc~ leum-based inks. IPresent address: ANPA, The Newspaper Center, 11600 Sunrise Valley Drive, Reston, VA 22091. 2The mention of firm names or trade products does not imply that th y are endorsed or recommended by the U.S. Department of Agri- culture over other firms or similar roducts not mentioned. EXPERIMENTAL PROCEDURES Materials Carbon black (Elftex 8) was obtained from Cabot Co. (Boston, MA). Sunbrite Yellow AAA (Sun 273-3556), Lithol Red (Sun 210-4200), Lithol Rubine (Sun 219-0688) and Blue 15 (Sun 249-2083) were purchased from Sun Chemical Co. (Cincinnati, OH). Butylated hy- droxytoluene (BHT) was provided by Eastman Chemical Co. (Kingsport, TN). Bentone 128 was provided by NL Chemical, Inc. (Hightstown, NJ). Hydrite R was obtain- ed from Georgia Kaolin Company, Inc (Union, NJ). Vegetable oil-based vehicles were prepared by heat poly- merization of the oils (10). Black printing inks were for- mulated from these vehicles by heating the vehicle to 65-70°C and then blending with 1.0 butylated hydrox- ytoluene (BHT) and 6-20 carbon black (Elftex 8). The elevated temperature was needed to dissolve the BHT. The pigment was dispersed with a Shar High Speed Disperser, Model D-10P (Shar Ina, Fort Wayne, IN), operated at 2500-3000 rpm over a period of 5-7 hr. Color pigments, vehicles and additives were premixed with a Shar High Speed Disperser, Model D-10P, at 2500 rpm for 20-30 rain. Dispersions of the pigments were com- pleted in an Eiger Mini Mill (Eiger Machinery Inc, Bensenville, IL), loaded with 2-mm chrome steel balls, and operated at 3500 rpm for 10 min. Proper dispersion and milling were assured by checking each formulation with a NPIRI Production Grindometer (Precision Gage and Tool Company, Dayton, OH) by following ASTM 1316-87. Yellow inks were formulated with vehicles of various viscosities and yellow pigment. In some examples, a thick- ening agent (Bentone 128) was added in an amount of 0.5-2.0 as an optional agent to adjust the viscosity. Red inks were prepared by using magenta pigment with the same procedure as for the yellow inks. Blue inks were for- mulated as above with cyan pigment. In some examples, 2.0-5.0 thickening agent (Bentone 128) was added to ad- just the viscosity, and up to 20 Hydrite R was employed as an optical brightener. Viscosities of the inks were measured with a Laray Fall- ing Rod Viscometer, Model MV.01 (Testing Machines Ina, Amityville, NY). The apparent viscosity at 2500 S -1 was calculated by the Power Log method of ASTM D4040-81. The tack values of the inks were measured with an Elec- tronic Inkometer, Model 101 (Thwing-Albert Instrument Company, Philadelphia, PA). The ASTM D4361-84 meth- od was used to obtain the apparent tack values at 1200 rpm and 90.0 +-- .1°E Tack values were reported at i rain. A commercial Hamilton Beach mixer was used for the water tolerance test. Ink {50 g) was mixed with 50 g deion- ized water at 90.0 rpm, for exactly 5 rain. Water up-take of 10-18 gis an acceptable range for lithographic inks (11). A Little Joe Offset Proof Press (Little Joe Color Swat- cher, Somerville, NJ), Model HD, was used to obtain let- terpress prints. To get the proper film thickness of ink, 0.6 cc of ink (3 notches on an IPI Volumeter) was used to roll up an i~leing area of 108 square inches. A Quick Peek color proofing kit (Thwing-Albert Instrument Com- pany) was used to evaluate matching of color inks. Ab- JAOCS, VoI. 69, no. 3 March 1992)  252 S.Z. ERHAN ET AL TABLE 1 Ink Formulations with Soybean Oil Experiment Vehicle Pigment Ink tack Ink viscosity number viscosity a ( w/w) b (g-m) c (poises) d 1 e G-H 19.8 2.3-2.4 7.33 2 I-J 19.8 2.8-2.9 10.08 M-N 19.8 -- -- 4 M-N 15.0 2.8 7.40 5 M-N 12.0 2.7-2.8 6.30 6 M-N 10.0 2.5 5.26 7 T-U 19.8 4.1-4.2 16.58 8 T-U 12.0 3.4-3.5 10.36 9 T-U 10.0 2.9-3.0 7.27 10 T-U 8.0 2.9 7.06 11 T-U 6.0 2.9 6.88 12 U-V 19.8 4.5-4.6 19.04 13 U-V 9.0 3.4 11.23 14 U-V 6.0 3.0 9.79 15 V 19.8 5.0 23.38 16 V 18.0 4.8-4.9 23.71 17 V 17.0 4.6 20.95 18 V 15.0 4.2 15.55 19 V 10.0 3.5 12.37 20 V 8.0 3.5 11.77 21 W 19.8 5.3-5.4 27.65 22 W 15.0 4.7 19.46 23 W-X 19.8 6.7 33.78 24 W-X 15.0 5.4 23.38 25 W-X 12.0 4.6-4.7 18.80 26 W-X 11.0 4.3-4.4 18.37 27 W-X 10.0 3.9-4.0 14.56 28 X-Y 19.8 7.0-7.1 41.30 29 X-Y 12.0 5.2-5.3 24.85 30 X-Y 10.0 4.8-4.9 22.48 31 X-Y 8.0 4.6-4.7 21.10 32f W-X 12.0 4.5 19.56 33 X-Y 10.0 5.0 25.01 34g U-V 12.0 4.2 24.28 35 W-X 12.0 4.9 19.96 36 h M-N 19.8 3.1-3.2 12.24 37 M-N 19.8 2.7-2.8 13.14 38 M-N 19.8 3.0 14.09 39 M-N 19.8 -- 46.17 40 W-X 12.0 4.5 22.06 41 W-X 12.0 -- -- 42 M-N 12.0 2.6 6.22 43 T-U 10.0 2.9 7.44 44 W-X 12.0 4.5 20.38 45 W-X 10.0 3.9-4.0 16.60 46 X-Y 12.0 5.2-5.3 24.14 47 X-Y 10.0 4.9 21.47 ANP.A soy M-N 19.8 3.6 16.45 ink 1 z ANP.A soy M-N 12.5 2.6-2.7 6.10 ink 2/ aGardner-Holdt Viscosity Scale. bCarbon black (Elftex 8). CMeasured by Electronic Inkometer. dMeasured by Laray Falling Rod Viscometer. eVehicles in experiment 1 to 32 were prepared by Procedure 1 (ref. 10). fVehicles in experiment 32 and 33 were prepared by Procedure 2 (ref. 10). gVehicles in experiment 34 and 35 were prepared by Procedure 4 (ref. 10). hVehicles in experiment 36 to 42 were prepared by Procedure 5 (ref. 10). /Vehicles in experiment 42 and up were prepared by Procedure 3 (ref. 10). JReference 6. JAOCS, Vol. 69, no. 3 March 1992)  LITHOGRAPHIC AND LETTERPRESS INK FORMULATIONS TABLE Ink Formulations with Vegetable Oil Oil used Vehicle Pigmen t Ink tack Ink viscosity in vehicles viscosity a ( w/w) U (g-m) e (poises) ~ Cottonseed e W 15.0 4.7 21.22 Cottonseed e W-X 12.0 4.6-4.7 23.95 Cottonseed e X-Y 10.0 4.9 22.43 Cottonseed X-Y 10.0 4.7-4.8 25.72 Cottonseedg W-X 12.0 4.7 19.72 Canola e W 15.0 4.7-4.8 20.39 Canola e W-X 12.0 4.5-4.6 19.30 Canola e X-Y 10.0 4.9 20.77 Canolaf W-X 12.0 4.5-4.6 19.32 Canolag W-X 12.0 4.7 21.53 Safflower e W 15.0 4.9 20.77 Safflower e W-X 12.0 4.5-4.6 19.70 Safflower e X-Y 10.0 4.9-5.0 24.67 SafflowerJ W 15.0 4.9 20.15 Safflowerg W-X 12.0 4.5 19.11 Sunflower e W 15.0 4.9-5.0 23.13 Sunflower e W-X 12.0 4.5-4.6 18.43 Sunflower e X-Y 10.0 5.0 23.93 Sunflowerf W 15 0 4.7 -4.8 20.52 Sunflowerf W-X 12.0 4.5 18.72 Sunflowerg W-X 12.0 4.5-4.6 20.68 aGardner~Holdt Viscosity Scale. bCarbon black (Elftex 8). CMeasured by Electronic Inkometer. dMeasured by Laray Falling Rod Viscometer. eVehicles were prepared by Procedure 1 (ref. 10). fVehicles were prepared by Procedure 2 (ref. 10). gVehicles were prepared by Procedure 3 (ref. 10). 53 solute print densities were measured with an X-Rite 428 Computerized Color Reflection Densitometer (X-Rit~ In- corporated, Grandville, MI). Several formulations, con- sidered to be candidates for offset lithography, were scal- ed up and evaluated on ANPA's commercial/pilot offset web press. Rub-off resistance of these prints were evaluated by the ANPA-NAPIM Rub-off Standard Test Procedure. The amount of rub-off is reported as the percent blackness of a stain that results by pulling a tissue weighted with a 1 psi pressure over the surface of a printed sheet. Blackness densities were measured with an Applied Col- or Science Spectrometer, Model 1101 (Applied Color, Princeton, NJ) and calculated from the following:. % R (tissue) --% R (rub stain) % Blackness = X 100 % R (tissue) where % R is percent reflection at 560 nm. The percent improvement determines the rate of pigment fixation on the newsprint by either penetration into the sheet or resin hardening. Blackness of less than 6% after 2 hr is con- sidered characteristic of an ink with good rub-off resistance RESULTS AND DISCUSSION We have succeeded in formulating vegetable oil-based printing inks and have completely eliminated petroleum- based resins. Consequently, these ink formulations cost even less than petroleum oil-based ink formulations. A broad range of viscosity and tack values are possible Thus, formulations can be prepared that are suitable for both lithographic and letterpress applications. In this study, inks are prepared from the vegetable oãbased vehicles (10) by formulation with pigment and miscellane~ ous additives as required for the prospective application. These vegetable oil vehicles are compatible with the pigments for producing the four colors commonly used in the newspaper printing industry, ~g., black, cyan (blue), magenta (red) and yellow. The pigment is blended into the vehicle until a uniform dispersion is obtained. Additives that may be formulated into the inks include driers, lubricants, antioxidants and the like. The thickening ef- fect of the pigment on the base vehicle was considered in preselecting a vehicle viscosity. Formulated inks also were evaluated for rub-off resistance. Rub-off is defined as the unwanted transfer of ink from the printed page to another surface The acceptable water take-up for lithographic ink performance also was tested. Properties of inks formulated with soybean oil are sum- JAOCS, Vol. 69, no. 3 (March 1992)  254 S.Z. ERHAN ET AL TABLE 3 Ink Rub off Resistance Evaluation Rub-off values as percent Experiment blackness Improvement number Initial After 2 hr ( ) 7 10.6 6.5 39 15 8.4 5.2 38 17 7.3 7.0 5 22 7.4 7.0 5 23 6.3 10.4 -65 24 8.2 6.6 20 25 6.0 5.5 8 26 7.4 5.8 22 27 5.7 7.4 -37 29 8.6 5.9 31 30 8.4 5.6 33 31 5.3 4.6 13 44 6.6 5.2 21 45 5.1 4.4 14 46 6.8 4.5 34 47 4.3 4.2 2 ANPA soy ink 1 a 14.-1 8.4 40 aReference 6. TABLE 4 Letterpress Inks with Soybean Oil Print density absolute) Experiment One impression b Two impressions b number print print 4 1.28 1.46 42 1.20 1.44 6 1.15 1.38 8 1.19 1.44 9 1.13 1.37 10 1.03 1.27 11 0.88 1.13 13 1.06 1.32 14 0.91 1.12 19 1.11 1.38 20 1.05 1.25 5 1.20 1.41 43 1.11 1.35 ANPA soy ink 2 c 1.21 1.41 aX-Rite 428 Computerized Color Reflection Densitometer was used to obtain absolute print density. bprints are obtained by Little Joe Offset Proof Press. CReference 6. marized in Table 1. Ink formulations with cottonseed, canola, safflower and sunflower oils are shown in Table 2. These inks are characterized by viscosities in the range of about 5-46 poises and by tack values of about 2-7 gram-meter (g-m). The typical viscosity for a black litho- graphic news ink is in the range of about 13-24 poises, and about 5-12 poises for a black letterpress new ink. Tack values for lithographic inks are about 3.5 to 4.8 g-m, and about 2.6 to 3.4 g-m for letterpress. Because of the vehi- cle system we use (10), it is fairly easy to tailor the viscosi- ty and tack values of the formulated inks. These inks, with a large range of viscosities and tack values, are suitable for both letterpress and lithographic applica- tions. In water tolerance tests, the above lithographic inks demonstrated an acceptable range of 20-30 water take- up, well within the acceptable range of 20-36 (11). Inks with these properties also were characterized by accept- able or superior rub-off values. Rub-off values as percent blackness are shown in Table 3. These 17 samples were chosen to cover a wide range of viscosity and tack pro- perties. The majority showed percent blackness of less than 6 after 2 hr, thus demonstrating good rub resis- tance. The percent improvement is less important than having the minimal percent blackness after 2 hr of prin- ting. Formulations 25 and 44 in Table 1 were tested for long-term stability, and they both performed exceptionally well. Long-term stability is the ability of an ink to main- JAOCS, Vol. 69, no. 3 March 1992)
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