INTRODUCTION
The Stockholm Convention in year 2019 began restricting the use of raw materials containing >25 ppb perfluorooctanoic acid (PFOA). This global restriction on PFOA and its salts as persistent organic pollutants (POPs) has impacted traditional PTFE usage for many applications. This initiated the need for PFOA compliant PTFE ≤25 ppb perfluorooctanoic acid (PFOA) or PTFE-free alternatives. Munzing started doing extensive work to develop viable alternatives to PTFE that can be used in many application areas. The newly developed products enhanced mechanical resistance properties and significantly lowered COF. These newly developed products showed excellent compatibility with various inks and coatings formulations. Incorporation to inks and coatings were made easier because of the surface morphology and chemical nature.To achieve low molecular weight and friability, irradiation process was usually required for particle size reduction. This Irradiation process used to generate small particle sizes, has demonstrated to create the PFOA content. According to EU regulations a manufacturer cannot process or have a product in the market that has more than 25 parts per billion (ppb) PFOA. To comply with the global regulatory requirements the two options are to use PFTE that has ≤25 ppb perfluorooctanoic acid (PFOA) or to make PTFE free products. For better economics and overall performance, many wax alloys contain a certain percentage of PTFE (approx. 5-20%) rather than using PTFE alone.
These PTFE containing wax additives should also need PTFE free alternatives to meet various application requirements. In essence, traditional PTFE must be replaced by low-PFOA containing PTFE or new PTFE-free alternatives that contain low PFOA PVDF or no PVDF. Besides PFOA and PVDF, linear and branched perfluoro carboxylic acids containing 9 to 14 carbon atoms in the chain are known as ‘C9-C14 PFCAs’. The groups of C9-C14 PFCAs, namely perfluorononan1-oic acid (‘PFNA’) containing 9 carbon atoms in the chain, as well as its sodium and ammonium salts, and nonadecafluorodecanoic acid (‘PFDA’) containing 10 carbon atoms in the chain, as well as its sodium and ammonium salts, were included in the Candidate List of Substances of Very High Concern (‘SVHC’).
APPLICATION
The wax additives used for the study were incorporated slowly in a mixer with a Cowles blade at around 1200 rpm. An industry standard waterbased printing ink formulation was applied on coated Algro Finess paper with Erichsen Printing Proofer gravure printing machine.TECHNICAL
LUBA-print® W 5700, WBP 2700, CERETAN® MXF 9510D, MX 3110, MBP 20220 along with a Blank sample were evaluated for gloss, coefficient of friction and rub resistance. Blank sample is an industry standard waterbased pigmented acrylic ink formulation without wax. The additives dosage was at 1% active content based on the total weight of the ink formulation. All tests were conducted at room temperature and 50% relative humidity.GLOSS ANALYSIS
BYK micro-TRI-gloss, DIN EN ISO 2813, was used to measure gloss. Gloss measurements were taken at 60° & 85° at three different parts of the printed ink panel and mean value was recorded.COEFFICIENT OF FRICTION
ZwickRoell Testexpert II, DIN EN ISO 8295 was used for COF measurements. COF measurements are important because lower COF helps with less abrasion on the ink surface that provides more slip. During these tests the dynamic and static friction was more or less at the same level, for that reason we have focused on the dynamic friction.RUB RESISTANCE
Rub resistance test was performed by using a Quartant Tester from PRÜFBAU. Panels were visually inspected to evaluate for ink transfer. Printing ink was applied using a printing proofer. Wax dosage is calculated based on wax NVM on total weight of the formulation.Rub tests carried out after a minimum of 24hr drying in a cure room. A 600 grams weight was applied, and the test was done for 200 rub cycles.
RESULTS AND DISCUSSION
GLOSS
The two dispersions have the lowest impact on gloss, because they are the finest in particle size. Coarser waxes have more impact on gloss based on dry film thickness and show lowering effect on gloss. The tested micronized waxes show very similar gloss values, there is no visual difference between synthetic & natural waxes.
COF
Lowering of coefficient of friction in printing inks has a great influence on rub resistance. Higher slip will help less abrasion to the coated surface. As expected, the PTFE modified CERETAN® MXF 9510 D is showing very low friction. The PTFE free CERETAN® MX 3110 can match the same performance.RUB RESISTANCE MEASUREMENTS
Quartant Tester from PRÜFBAU was used for evaluating rub resistance.The micronized waxes CERETAN® MXF 9510 D and CERETAN® MX 3110 provide both outstanding rub resistance, closely followed by the CERETAN® MBP 20220 which is based on a natural polar lipid which is also biodegradable wax. LUBA-print® WBP 2700 is based on the same natural, polar lipid.
Regarding mechanical resistance the waterbased dispersions are still good options and significantly better compared to the blank sample. These waterbased dispersions also have a lower impact on gloss compared to micronized waxes. For superior rub resistance micronized waxes are the best option.
CONCLUSION
CERETAN® MX 3110 works fine as an alternative to PTFE based product CERETAN®MXF 9510 D. Micronized waxes performed better in this study when compared to dispersions used here. Wax addition in the ink formulation reduced COF and improved the rub resistance property. The test results clearly indicates that PTFE free additive performed excellent as an alternative to PTFE based products. The CERETAN® MBP 20220 which is based on a natural, polar lipid shows that renewable & biodegradable additives already show a performance that is very close to the performance of synthetic waxes like Polyethylene.Royce Mathews is a Business Development Manager for Munzing. In his current role, Royce focus on promoting unique wax products and additive solutions to coatings and ink customers in NA, SA, Mexico, and Canada business territory. Royce holds a MS degree in Polymer Chemistry and Coatings Technology from De Paul University, Chicago, and an MS in Physical Chemistry.