Surfȳnol Surfactants: Superior Substrate Wetting Agents in Water-Based Printing Inks

Transcription

1 Surfȳnol Surfactants: Superior Substrate Wetting Agents in Water-Based Printing Inks Introduction The performance benefits of Surfȳnol surfactants have been evaluated in water-based inks to assess their effectiveness in providing substrate wetting while reducing or eliminating the need for alcohols. The substrates evaluated were difficult-to-wet polypropylene and polyethylene films as well as flexible paper and coated stock. The results demonstrate that Surfȳnol SE-F, Surfȳnol 420, Surfȳnol 440 and Surfȳnol 04 surfactants provide important benefits, including: excellent substrate wetting and improved flow and leveling; VOC reduction through solvent reduction or elimination; antifoam/low foam; and broad FDA compliances (for specific information, call ). Additionally, the study results indicate that Surfȳnol surfactants have no adverse effect on gloss, water sensitivity, blocking or flexographic plate swell. A summary of surfactant recommendations and use-levels for typical printing ink applications is provided in Table. Typical physical properties of Surfȳnol SE-F, Surfȳnol 420, Surfȳnol 440 and Surfȳnol 04 surfactants are presented in Table 2. Table Surfȳnol Surfactant Starting-Point Recommendations Surfȳnol Surfȳnol Surfȳnol Surfȳnol 04 IPA Substrate SE-F % Blends Comparison Polypropylene % + 3 5% % + 3 5% % + 3 5% % + 3 5% 0% Film alcohol alcohol alcohol alcohol Polyethylene % + 3% % + 3% % + 3% % + 3% 0% Film alcohol alcohol alcohol alcohol Coated Stock % % % % 2% Flexible Paper % % % % 2% Other Selection Criteria VOC, wt% % Foam Control Excellent Excellent Good Excellent Excellent Water Resistance Excellent Excellent Good Excellent Excellent Excellent Table 2 Typical Properties Good Surfȳnol 04 surfactant is available as a 50% solution in isopropanol, n-propanol, dipropylene glycol monomethyl ether (DPM), propylene glycol, ethylene glycol, 2-butoxy ethanol (EB) and 2-ethylhexanol. Surfȳnol Surfȳnol Surfȳnol Surfȳnol 04 SE-F % Blends Specific 25 C Density, lb/gal C, cps <200 <200 <200 <200 (Brookfield, Spindle #3) HLB (Hydrophile Lipophile Balance) Surfȳnol 04 surfactant is available as a 50% solution in isopropanol, n-propanol, dipropylene glycol monomethyl ether (DPM), propylene glycol, ethylene glycol, 2-butoxy ethanol (EB) and 2-ethylhexanol.

2 Surface Tension and VOC Reduction Water-based printing inks have inherently high surface tensions due to the surface tension of water (72 dynes/cm). To reduce surface tension and achieve good surface wetting with defect-free printing, solvents such as isopropanol (IPA) are often incorporated. Increasing concerns about Volatile Organic Compound (VOC) levels, however, require many formulators to reduce their use of solvents. Surfactants, as a result, have become an even more important component in water-based ink formulations. Typical surface tension values, such as those obtained with a DuNouy ring instrument, are equilibrium measurements that characterize a system at rest. These values, however, are not indicative of an ink s ability to wet out a substrate under dynamic or high-speed printing conditions. Indications of high-speed printing performance can more accurately be predicted by measuring dynamic surface tension with an instrument such as a maximum bubble pressure tensiometer. Low dynamic surface tension occurs when a surfactant has the ability to migrate rapidly to the newly created ink/substrate interface. Typical surfactants, however, generally provide good equilibrium values, but poor dynamic performance. Most commercial surfactants also tend to stabilize foam. Surfȳnol surfactants, in contrast, provide high performance under both equilibrium and dynamic conditions while minimizing foam. These properties make Surfȳnol surfactants excellent alternatives to solvents used in water-based inks for substrate wetting and improved printability. Substrates Surfȳnol surfactants were evaluated in the following flexographic and gravure printing ink applications: Polymer film substrates for flexible packaging Polypropylene Polyethylene Paper substrates suitable for flexible packaging, folding cartons, food containers and preprint linerboard Flexible paper (CS) Coated stock The ink systems were evaluated for equilibrium and dynamic surface tension, ink printability, foam control, gloss, water sensitivity, blocking, film adhesion and flexographic photopolymer plate swell. Formulating Notes Use-levels that include combinations of Surfȳnol surfactants with reduced levels of alcohol were selected as starting point recommendations for the polymeric film applications. However, Surfȳnol surfactants allow the formulating latitude required to balance the competing needs of performance, cost containment and VOC reduction. For instance, Surfȳnol surfactants can be utilized at less than % use levels as a co-surfactant with the remaining alcohol. Alternatively, Surfȳnol surfactants can be used as a total replacement for alcohol at 2 3% for polymeric film applications and % or less for paper substrates. A common problem with many surfactants is that they cause the ink viscosity to rise. If a rise in viscosity occurs with the use of a Surfȳnol surfactant, introducing the surfactant at an early stage of the letdown with good mixing is recommended. Summary and Recommendations Surfȳnol surfactants demonstrate the ability to provide excellent substrate wetting and overall system VOC reduction in water-based ink formulations. These results are due to their unique combination of low dynamic surface tension and defoaming characteristics. In addition, Surfȳnol surfactants have no deleterious impact on the other ink properties tested. The results reported in this study with isopropanol have been observed with other common solvents, such as n-propanol. Please refer to Table for assistance in selecting Surfȳnol surfactants. The starting point recommendations in Table are based on the printability results discussed in this brochure. In addition, various performance criteria are listed in the table to further aid formulators in selecting appropriate Surfȳnol surfactants for their particular ink systems. Performance Results The data and results from the study are presented on the following pages. Experimental procedures for all systems tested are outlined in the Appendix of this brochure. Flexible Polypropylene Film Inks Two model water-based flexographic ink formulations, suitable for printing polypropylene flexible packaging films, are provided in Figures and 2. Figure provides the equilibrium and dynamic surface tension results of ink formulation, with and without Surfȳnol surfactants. A strong correlation can be seen between dynamic surface tension reduction and the printability of the inks on polypropylene. This is demonstrated both photographically and through a rating system. Here, Surfȳnol surfactants (with Surfȳnol SE-F and Surfȳnol 420 the most noteworthy) provide equal or superior printability at a 70% reduced alcohol level compared to the isopropanol-containing control. Ink formulation 2 (Figure 2) was evaluated on an alternative polypropylene to demonstrate the broad-based performance of the Surfȳnol surfactants. Surface tensions were again determined on the inks, both without surfactant and with combinations of surfactant and 50% reduced alcohol. Printability, as with the earlier system, improves as dynamic surface tension is reduced. Surfȳnol SE-F and Surfȳnol 420 surfactants, followed closely by Surfȳnol 04 and Surfȳnol 440, again demonstrate outstanding wetting properties. Figures and 2 also demonstrate foam control performance for the ink systems. The 0% alcohol control acts as an antifoam, preventing foam formation, which results in higher ink foam densities. This performance is readily achieved with the Surfȳnol surfactant systems without the use of defoamers required with typical surfactants. Surfȳnol surfactants are unique in this balance of surface tension reduction and low foam, making them ideally suited for water-based printing inks. Other ink performance properties such as gloss, water sensitivity, blocking, adhesion and plate swell were evaluated with and without Surfȳnol surfactants. The results, provided in Table 3, clearly demonstrate that the addition of Surfȳnol additives does not adversely impact other ink properties.

3 Figure Flexographic Ink for Polypropylene Flexible Film Formulation No Alcohol With With Surfȳnol Model Formulation No Surfactant Isopropanol Surfactant Acrylic Polymer Emulsion 44% 40% 40% Acrylic Resin Solution Flexiverse Phthalo Blue GS :3 Dispersion Isopropanol 0 3 Surfȳnol Surfactant (actives) Water All inks adjusted to 25 seconds (#2 Zahn cup). Polypropylene Film: LBW 240 (ICI Americas Film Division); dynes/cm (critical surface tension estimate). Excellent Wetting and VOC Reduction with Surfȳnol Surfactants 3 00% 00% 00% No IPA 0% IPA 3% IPA + % 3% IPA + % 3% IPA + % 3% IPA + % No Surfactant Control Surfȳnol SE-F Surfȳnol 420 Surfȳnol 440 Surfȳnol 04 Printability Rating ( = Poor; 0 = Excellent) Alcohol Replacement (wt %) 0% 70% 70% 70% 70% Surface Tension 69.7 Equilibrium Dynamic Dynes/cm Excellent Foam Control with Surfȳnol Surfactants Ink Density (g/ml) Unagitated Ink No IPA No Surfactant 0% IPA Control 3% IPA + % 3% IPA + % 3% IPA + % 3% IPA + % Surfynol - SE-F Surfynol Surfynol Surfynol - 04 Vancryl 954 (Air Products and Chemicals, Inc., Polymer Chemicals Division). Other choices include Joncryl 74 (S.C. Johnson Polymer) and Lucidene 603 (Morton International). 2 Vancryl 68S. Other choices include Joncryl 6 and Morcryl 34 (Morton International). 3 Photos taken at 3.7x magnification.

4 Figure 2 Flexographic Ink for Polypropylene Flexible Film Formulation 2 No Alcohol With With Surfȳnol Model Formulation No Surfactant Isopropanol Surfactant Acrylic Polymer Emulsion 47% 42% 42% Flexiverse Diarylide AAOT Yellow 4 Dispersion PE Wax Emulsion Isopropanol 0 5 Surfȳnol Surfactant (actives) Water All inks adjusted to 25 seconds (#2 Zahn cup). Polypropylene Film: Bicor BSR-ONE (Mobil); dynes/cm (critical surface tension estimate). Excellent Wetting and VOC Reduction with Surfȳnol Surfactants 3 00% 00% 00% No IPA 0% IPA 5% IPA + % 5% IPA + % 5% IPA + % 5% IPA + % No Surfactant Control Surfȳnol SE-F Surfȳnol 420 Surfȳnol 440 Surfȳnol 04 Printability Rating ( = Poor; 0 = Excellent) Alcohol Replacement (wt %) 0% 50% 50% 50% 50% Surface Tension Dynes/cm Equilibrium Dynamic Excellent Foam Control with Surfȳnol Surfactants Ink Density (g/ml) Unagitated Ink No IPA No Surfactant 0% IPA Control 5% IPA + % 5% IPA + % 5% IPA + % 5% IPA + % Surfynol - SE-F Surfynol Surfynol Surfynol - 04 Joncryl 624. Other choices include Lucidene Jonwax 26 (S.C. Johnson Polymers). 3 Photos taken at 3.7x magnification.

5 Flexible Polyethylene Film Inks A model flexographic ink suitable for printing polyethylene flexible packaging films is provided in Figure 3. The experimental results (Figure 3) again indicate a strong correlation between the dynamic surface tension of the ink and printability on the polyethylene substrate. In addition, the photographs and subjective printability ratings clearly demonstrate that a 70% reduction in alcohol in combination with % Surfȳnol SE-F, Surfȳnol 420 or Surfȳnol 440 surfactant provides superior wetting performance compared to the 0% isopropanol-containing control. Foam control performance is also presented in Figure 3. Low foam is obtained with the control ink containing 0% alcohol. Yet, similar foam control performance is obtained in the formulation with a 70% alcohol reduction and the addition of % Surfȳnol surfactant. Here again, Surfȳnol surfactants demonstrate their defoaming and outstanding surface tension reducing capabilities, making them an excellent choice when formulating inks for polyethylene and other nonporous, difficult-to-wet surfaces. Other ink performance properties, such as gloss, water sensitivity, blocking, adhesion and plate swell, were investigated with and without Surfȳnol surfactants. As seen with the polypropylene inks, the results provided in Table 3 clearly demonstrate that there are no deleterious effects with the addition of Surfȳnol surfactants. Table 3 No Detrimental Effects with Surfȳnol Surfactants (Results for All Ink Formulations) Gloss Water Sensitivity Blocking Substrate Adhesion Flexographic Plate Swell Coated Stock and Flexible Paper Inks Inks formulated for porous substrates occasionally require wetting agents to assure wetout and defect-free coverage. Surface defects that may require wetting agents include mottling and snowflakes, both of which are related to poor flow and leveling. Surfȳnol surfactants can solve these problems, while allowing the removal of alcohol and their VOCs. A model formulation suited for flexographic coated stock ink and gravure flexible paper ink applications is presented in Figure 4, along with test results. As with the flexographic film ink systems, a strong correlation can be seen between the dynamic surface tension values of the ink and printability on the substrates. The addition of 2% isopropanol reduces the dynamic surface tension enough to allow moderate printability. However, when the isopropanol is replaced by % Surfȳnol surfactant, the surface tension reduction and printability improves significantly. Surfȳnol 420 and Surfȳnol 04 provide the best results on the coated stock, while Surfȳnol SE-F, Surfȳnol 420 and Surfȳnol 04 perform best on the flexible paper substrate. <.5% variance with the IPA-containing control No difference from the IPA-containing control No difference from the IPA-containing control No difference from the IPA-containing control <.5% weight gain over the IPA-containing control The foam control data in Figure 4 indicates that the Surfȳnol surfactants provided similar or superior defoaming performance when compared to the isopropanol-containing control. As illustrated in the polymeric film application areas, the unique combination of dynamic surface tension reduction and defoaming capabilities also makes Surfȳnol surfactants ideally suited for water-based inks for porous substrates. Gloss, water sensitivity, blocking, adhesion and plate swell were also evaluated with and without Surfȳnol surfactants. The results in Table 3 indicate there are no adverse effects on ink performance with the addition of Surfȳnol surfactants.

6 Figure 3 Flexographic Ink for Polyethylene Flexible Film No Alcohol With With Surfynol Model Formulation No Surfactant Isopropanol Surfactant Acrylic Polymer Emulsion 47% 42% 42% Flexiverse Diarylide AAOT Yellow 4 Dispersion PE Wax Emulsion Isopropanol 0 3 Surfȳnol Surfactant (actives) Water All inks adjusted to 25 seconds (#2 Zahn cup). Polyethylene Film: High Density, Corona Treated (Mobil); dynes/cm (critical surface tension estimate). 00% 00% 00% Excellent Wetting and VOC Reduction with Surfȳnol Surfactants 3 No IPA 0% IPA 3% IPA + % 3% IPA + % 3% IPA + % 3% IPA + % No Surfactant Control Surfȳnol SE-F Surfȳnol 420 Surfȳnol 440 Surfȳnol 04 Printability Rating ( = Poor; 0 = Excellent) Alcohol Replacement (wt %) 0% 70% 70% 70% 70% Surface Tension Equilibrium Dynamic Dynes/cm Excellent Foam Control with Surfȳnol Surfactants Ink Density (g/ml) No IPA No Surfactant % IPA Control 0.79 Unagitated Ink % IPA + % 3% IPA + % 3% IPA + % 3% IPA + % Surfynol - SE-F Surfynol Surfynol Surfynol - 04 Joncryl 624. Other choices include Lucidene Jonwax Photos taken at 3.7x magnification.

7 Figure 4 Ink for Coated Stock and Flexible Paper No Alcohol With With Surfȳnol Model Formulation No Surfactant Isopropanol Surfactant Acrylic Polymer Emulsion 45% 45% 45% Acrylic Resin Solution Flexiverse BFD Isopropanol 2 Surfȳnol Surfactant (actives) Water % 00% 00% All inks adjusted to 25 seconds (#2 Zahn cup). Coated Stock: Clay-coated Linerboard (Riverwood), Flexographic Printed; Flexible Paper: Coated One-Side, CS (James River Corp.), Gravure Printed. Excellent Wetting and VOC Reduction with Surfȳnol Surfactants 3 Printability Rating ( = Poor; 0 = Excellent) No IPA 2% IPA % % % % No Surfactant Surfȳnol SE-F Surfȳnol 420 Surfȳnol 440 Surfȳnol 04 Coated Stock (shown above) Flexible Paper Alcohol Replacement (wt %) 0% 00% 00% 00% 00% Surface Tension Dynes/cm Equilibrium Dynamic Excellent Foam Control with Surfȳnol Surfactants.0 Unagitated Ink Ink Density (g/ml) No IPA No Surfactant 2% IPA Control % % % % Surfynol - SE-F Surfynol Surfynol Surfynol - 04 Joncryl 89. Other choices include Lucidene 370 and Vancryl Joncryl 6. Other choices include Morcryl 34 and Vancryl 68S. 3 Photos taken at 3.7x magnification.

8 Appendix Experimental Procedures Sample Preparation Ink bases for each formulation listed in Figures 4 were prepared both with and without alcohol or surfactant. For each flexible film ink, 90 parts of the base were mixed with 0 parts of a combination of surfactant, alcohol and water. For the paper substrate inks, 98 parts of the ink base were combined with 2 parts alcohol or surfactant and water. All formulations were adjusted to a viscosity of 25 seconds on a #2 Zahn cup. Surface Tension Measurements Surface tension values were determined on a SensaDyne TM 6000 Tensiometer (Chem-Dyne Research Corporation). Samples were diluted 50/50 with water to reduce viscosity to within the operating range of the instrument; therefore, the values are relative. Both equilibrium ( bubble/second) and dynamic (5 bubbles/ second) surface tensions were evaluated. The critical surface tensions of the substrates were determined via surface tension fluids from Diversified Enterprises, Inc. Printability Flexographic printing (flexible films and coated stock) was performed using a Pamarco hand proofer equipped with a #65 anilox. A Geiger press was utilized for gravure printing (flexible paper). Printability was visually evaluated on a qualitative scale of 0, with 0 being an excellent film. Dewetting and pinholing were the major defects on the nonporous substrates, and mottling was the major defect on the porous substrates. Foam Test Ink samples (50 grams) were agitated at 2,000 rpm for minute utilizing a Waring Blender. Densities were measured before and after agitation. Blocking Blocking was evaluated via ASTM D Adhesion Adhesion was evaluated via the 60 Scotch tape test. Water Resistance Water droplets were placed on the cured films and wiped off at the following intervals: 0.5,, 2 and 5 minutes. Gloss Gloss values were determined at 60 degrees with a Dr. Lange Reflectometer. Plate Swell One-inch squares of Letterflex Photopolymer flexographic printing plate on a steel backing (WR Grace) were cut and then pre-weighed on an analytical balance. The plates were placed in the formulated inks for 24 hours, then removed, cleaned and re-weighed to determine plate swelling via weight increase. These values were then compared with those of the control containing no surfactant. Raw Material Suppliers Air Products and Chemicals, Inc.: Vancryl 954, Vancryl 68S; Sun Chemical Corporation: Flexiverse Phthalo Blue GS Dispersion, Flexiverse Diarylide AAOT Yellow Dispersion; S.C. Johnson Polymer: Joncryl 624, Joncryl 89, Joncryl 6, Jonwax 26 PE Wax Emulsion. For More Information If you d like additional information, write or call Air Products and Chemicals, Inc., at the following locations. Air Products and Chemicals, Inc. Performance Chemicals 720 Hamilton Boulevard Allentown, PA Telephone: (Outside U.S./Canada ) Fax: Latin America Air Products and Chemicals, Inc. Latin American Region 720 Hamilton Boulevard Allentown, PA Telephone: Fax: Air Products and Chemicals de Mexico S.A. de C.V. Suite 26, Piso 2 World Trade Center Avenida de las Naciones No Col. Napoles, México D.F Mexico Telephone: Fax: Air Products Gases Industriais Ltda. (APGIL) Praca Radialista Manoel de Nobrega, 65 Casa Verde São Paulo, SP Brazil Telephone: Fax: Europe Air Products Nederland B.V. Kanaalweg 5, Box GD Utrecht Netherlands Telephone: Fax: Asia Air Products Japan, Inc , Toranomon, Minato-Ku Tokyo 05 Japan Telephone: Fax: Air Products Asia, Inc. Rm Hopewell Centre 83 Queen s Road East Wanchai Hong Kong Telephone: Fax: The information in this literature is offered without charge for use by technically qualified personnel at their discretion and risk. All statements, technical information and recommendations are based on tests and data which we believe to be reliable, but their accuracy or completeness is not guaranteed and no warranty of any kind is made. Air Products and Chemicals, Inc., 999 (20000) Printed in USA