Development of Mineral Oil Free Offset Printing Ink Using Vegetable Oil Esters

Size: px

Start display at page:

Download "Development of Mineral Oil Free Offset Printing Ink Using Vegetable Oil Esters"

Leo Harris
5 years ago
Views:

1 Journal of Oleo Science Copyright 2007 by Japan Oil Chemists Society Development of Mineral Oil Free Offset Printing Ink Using Vegetable Oil Esters Ananda Sankar Roy 1, Moumita Bhattacharjee 1, Rabindranath Mondal 1 and Santinath Ghosh 1 DIC India Limited (Transport Depot Road, Taratola, Kolkata-0 088) 2 Department of Chemical Technology, Oil Technology Division, University of Calcutta (92, A.P.C. Road, Kolkata west Bengal, INDIA) Abstract: Until the middle of this century, fats and oils are the major raw material source for paints, coating and lubricating applications. These markets are completely taken over by petroleum based stocks due to their abundance and versatility. However, recent public awareness to use environmentally acceptable products that minimize pollution, are compatible to human health and readily biodegradable created opportunities for vegetable oils for application in paints and printing inks. The formulation of vegetable oil methyl ester based green offset printing ink that reduces the volatile organic compounds (VOC) has been discussed in the present study. Methyl esters of rapeseed, soybean, rice bran and palm oil have been prepared and their physical properties have been measured and compared with standard petroleum feed stock. Varnishes were prepared with these esters and their properties are also compared with that of the petroleum based products. Rheological properties of the inks are also evaluated and compared with standard printing ink using petroleum based solvent. In general performance of the esterbased printing inks are comparable with that of the mineral oil based product. On the basis of tack stability and gloss, ester based inks are much superior than the mineral oil based products. In conclusion, a new non-volatile diluent for printing ink has been developed. The diluent is made from common vegetable oils like rapeseed, soybean, rice bran and palm oil, a renewable source that is environmental friendly. Vegetable oil esters offer a cost effective solution for mineral oil based printing ink to meet VOCs regulations. Key words: diluent, printing ink, volatile organic compounds (VOC) 1 INTRODUCTION Current environmental concerns and legislation principally targeted to reduce and ultimately eliminate solvent emissions, expressed as volatile organic content (VOC) from paints and printing inks 1). There is now consumer pressure to use renewable rather than petroleum based resources. The coating manufacturers will be forced to reduce VOCs from solvent based coatings in order to comply with air quality regulations 2). Therefore, the reduction of VOCs in petroleum solvent based industrial coatings and printing inks to meet environmental regulations without sacrificing functional properties presents a technical challenge 3). One of the major alternatives is to use vegetable oil based products as bio-renewable raw materials. On cost grounds, oils can compete well with the petrochemically derived ingredients normally used to form polymers. Particularly in the field of printing ink industry, a pressure is created in the last few years for the replacement of mineral oil in inks with vegetable oils and their derivatives 4-7). On the above ground our objective is to formulate vegetable oil based 'green' offset printing ink with the complete substitution of mineral oil i.e. to produce VOC free printing ink. 2 MATERIALS AND METHODS 2 1 Vegetable Oil - Linseed oil (Viscous Oils, India) Correspondence to: Santinath Ghosh, Department of Chemical Technology, Oil Technology Division, University of Calcutta, 92, A.P.C. Road, Kolkata-0 009, West Bengal, INDIA santinathghosh@yahoo.com.hk Accepted September 14, 2007 (recieved for review May 21, 2007) Journal of Oleo Science ISSN print / ISSN online 623

2 A.S. Roy, M. Bhattacharjee, R. Mondal and S. Ghosh Resins - Rosin-modified phenolic resins: high viscosity (HV) and medium viscosity (MV), Long oil linseed isophthalic alkyd resin (all from DIC India Ltd., India). Solvents - Mineral distillate PKWF28/31 AP (boiling range : 2-310, aniline point :, Haltermann, Germany). Methyl esters of Rapeseed (RSO Ester), Soya (SO Ester), Rice Bran (RBO Ester) and Palm olein (PO Ester) oils - made in the laboratory by standard method. Pigment - Phthalocyanine Beta Blue (CI Pigment Blue 15:3, J 500, Francolor, France). Additives - Aluminium chelate (Manalox 820, Rhone Poulenc, USA), Butylated hydoxy toluene (BHT, Camlin, India), Polyethylene (PE) wax paste & Polytetrafluoroethylene (PTFE) wax paste (Micro Powders, USA), Fumed silica antiset off paste (Degussa, Germany) Litho paste based on silica (Lawter International, USA), Mixed drier (Co, Mn & Zr octoate, DURA Chemicals, India) Linseed oil was charged in a five-necked one litre glass kettle fitted with a mechanical stirrer, a nitrogen inlet, a thermometer and a condenser, and heated to 150. Resins were added and heated to 1/200, cooked for 30/60 minutes. Vegetable oil ester / distillate was added, then gelled by adding Al-chelate at 160. BHT was added and finally varnish was filtered off. Raw Materials Linseed oil Rosin resin (MV) Rosin resin (HV) Alkyd Resin Mineral distillate Oil Ester Al-chelate BHT Cooking Process Temp / time Varnish Formulation Varnish A (Based on Distillate) /60min Varnish B (Based on Oil Ester) / 30 min Ingredients for inks were mixed in a stainless steel container and then milled with the help of a Laboratory 3-roll mill (Buhler, Switzerland). Raw Materials Varnish A Varnish B Additive Varnish (Oil based) Pigment Blue 15:3 Antiset off paste PTFE Wax PE Wax Litho Paste BHT Mixed Drier Oil Ester Distillate Ink Formulation INK A (Based on Distillate) INK B (Based on Oil Ester) Colour - Measured by Lovibond 2000 Tintometer (U.K.) Cloud Point - Measured by Chemotronic Cloud Point Tester (Novamatics, Germany); Composition 2g resin (RL 58, Arizona Chemicals, Belgium) + 6 g vegetable oil ester + 12 g distillate (PKWF 6/9 AF, Haltermann, USA) Heptane Tolerance - 2 g of varnish was mixed with 2 g of toluene and the mixture was titrated with n-heptane at 25 till the mixture becomes cloudy. Volume of n-heptane required was expressed as heptane tolerance Rheology - Viscosity and yield value of varnish and ink were measured by Laray Viscometer at 30. Variation of viscosity with temperature was measured with a Carrimed Rheometer (CSL2 500, TA Instruments, U. K) at a fixed shear rate of 50 S Tack & Tack Stability - Tack was measured at 90 F with an Inkometer (Thwing Albert, USA) by taking 1 c.c. of sample. Tack Stability of ink was measured by Tack-o-mat (Prufbau, Germany) at Laboratory prints and setoff on art paper were taken with the help of a Prufbau printing machine (Prufbau, Germany) at Optical Density of the prints was measured with a Densitometer (D 19C Gretag, Switzerland) Gloss of the prints was measured with Glossometer (BYK Gardner, Sheen Instruments, U.K.) at reflections Rub Resistance of the prints was checked with Rub Tester (TMI, USA) after 90 minutes and 24 hours (Weight- 10 gms, No of rubs - 20) Emulsification Behavior of inks was studied with Lithotronic Emulsification Tester (Novamatics, Germany). (Stirrer speed rpm, Fount Dose rate - 8%). 624

3 Mineral Oil Free offset Ink Using Vegetable Oil Esters 3 RESULTS AND DISCUSSION Comparative properties of the mineral oil distillate and vegetable oil esters are presented in. Printing ink quality is dependent on the wax point of vegetable oil, which helps mainly to control the ink flow. Offset inks made with higher quantity of wax present in the mineral oil distillate or in the vegetable oil, will be shorter in flow specially when the ambient temperature of the environment is less. The offset inks performance on the machine will be disrupted as offset inks with shorter flow will transfer less on the paper creating poor image quality. From the, it has been found that wax points of the rice barn and palm olein esters are higher than the mineral oil distillate as well as the soybean and rapeseed oil esters due to presence of saturated fatty acids in these two esters at higher level. So, the difference of wax point among vegetable oil esters is mainly due to the difference in fatty acid composition. Varnish properties are presented in. Heptane tolerance of varnishes prepared from esters is slightly lower than the mineral oil based varnish. It implies that the compatibility of resin is slightly better with mineral oil than ester oil. But viscosity of the ester based varnishes is lower than the mineral oil based varnish. Yield value of the ester based varnishes are higher than the mineral oil based product implies that the ester based varnish has better structure so that it can withstand more shearing force generated between the inking rollers of a printing machine during the printing process than mineral oil based product. Tack of varnishes based on ester oil is slightly lower than standard mineral oil based varnish. It is beneficial to some extent for the offset printing inks as less tack imparts better transferability of inks between the rollers and getting the similar depth of the image to be printed with less ink release in the printing machine. Properties of the inks are presented in. Rheological (i.e. viscosity, yield value, tack and flow) properties of all the inks are comparable. A balanced combination of rheological properties helps in getting good printing image without causing any problem in ink transfer. It also helps in the proper dot reproduction thus creating more clear and sharp image. Emulsification properties i.e. the water uptake value of the ink as well as stability of the ink - water emulsion of all the inks are almost comparable. Results of the stability measurements of the inks are presented in. In terms of tack stability vegetable oil based inks are better than the mineral oil based printing ink as their tack rise per minute is lower. If there is a tendency of tack rise, then there is a chance of paper fluffs coming out of the substrate along with the ink during printing causing printing defect. Among the vegetable oils, rice bran oil (RBO) and palm olein (PO) based products show better result in terms of more stability with less tack rise. Print stability (measurement of density loss with time) of vegetable oil ester based inks is much better than the min- Table 1 Properties of Mineral Distillate and Vegetable Oil Esters. Properties Mineral Distillate PKWF 28/33 RSO Ester SO Ester RBO Ester PO Ester Appearance Sp. Gravity Wax Point ( ) Cloud Point ( ) Boiling Range ( ) ± ± 2-320± ± ± 95± ± ± ± 89± ± ± ± 90± ± ± ± 99± ±4 Measured by Chemotronic; composition - 2g resin (RL 58) + 6g ester + 12g distillate (Halterman PKWF 6/9 AF) RSO: Rapeseed oil, SO: Soybean oil, RBO : Rice bran oil, PO: Palm Olein Table 2 Properties of Varnishes. Properties Varnish A Varnish B/RSO Varnish B/SO Varnish B/RBO Varnish B/PO Heptane Tolerance, ml Laray Viscosity, Poise Yield Value, dynes/cm 2 Tack, GM 10.2± ±15 00± ± ± ± ± ± ± ± ± ± ± 240± ± ± ± ± ± ±

4 A.S. Roy, M. Bhattacharjee, R. Mondal and S. Ghosh Table 3 Properties of Inks Produced With Vegetable oil Esters. Dispersion, micron Laray Viscosity, Poise Yield Value, dynes/cm 2 Tack, GM Flow, cm Lithotronic Properties Tq Start (mnm) D Tq EC (%) 1±5 9000± ±0.1 1± ±30 15±5 58±2 1± ± ±0.2 1± 624±50 2±7 61±1 6±1 160± ± ± ± ±25 1±7 58±2 165± ± ±0.2 1± ±30 3±8 51±3 185± ± ±0.2 1± ± ±2 Table 4 Stability of the Inks. Tack Stability Initial Tack Max. Tack (40 min) Avg Tack Rise/min Print Stability Optical Density 30 sec Optical Density 20 min Avg Loss in O.D. (%) Duct Stability (Applicator, 37m) Opening Time (hrs.) Skinning Time (hrs) 192±2 241± ± ± ± ± ± ± ±2 201±5 220± ± ± ±2 192±4 201± ± ± ± 32±1 191±3 204± ± ± ±3 eral oil based ink. That means vegetable oil ester based inks will give better runnability in press compared to mineral oil based ink. Drying time i.e. the time taken to make a hard dried ink film is higher in case of oil ester based ink than mineral oil based ink. Skinning times of the vegetable oil ester based inks are also higher than standard mineral oil based ink which indicates that vegetable oil ester based ink will remain open (i.e. skin free) for a longer period of time without forming any skin in ink duct. Variation of viscosity of the ink with temperature is an important parameter from application point of view. Variation of ink viscosity with temperature (23-50 ) is studied by Carrimed Rheometer and results are reported in. In case of mineral oil based ink the drop in viscosity is 726 unit when it is heater from 23 to 50, where as in case of vegetable oil based inks the viscosity drop is less than 0 units. So ester based inks will be advantageous at high temperature application. Print and post print properties of the ester based inks along with the standard mineral oil based inks are presented in. Optical density of all the inks is comparable. Gloss of the ester based inks is higher than the mineral oil based ink. Among the vegetable oil esters, gloss of soybean oil (SO) based ink is higher than other inks, but its density is less. This is mainly due to the presence of higher amount of unsaturated fatty acids in soybean ester. Setting of the vegetable oil ester based inks is inferior than those of the mineral oil based ink, which is significant due to presence of high amount of vegetable oil in the formulation. Rub resistance (both instant and overnight) of vegetable oil based inks is better than mineral oil based ink which means that the ink surface is dried at much faster rate. 4 CONCLUSION Considering overall performance of the vegetable oil ester based inks in comparison with the standard mineral 626

5 Mineral Oil Free offset Ink Using Vegetable Oil Esters Table 5 Variation of Viscosity of the Final Inks with Temperature (Carrimed, Shear 50S -1 ). Viscosity (Poise) at ± ±1 26± ± ±1 96.8± ± ± ± ± ± ±1 815± ± ± ± ± ±1 820± ± ± ± ± ±1 830± ± ± ± ± ±15.0 Table 6 Print and Post-Print Properties of the Printing Inks (Prufbau/Gloss Art Paper/30 ). Gloss (Glossometer/ ) Optical Density (Gretag) Setting (100 - Best; 0-worst) Rub Resistance 90 mins 24 hrs (100 - Best, 0-worst) 86.8± ± ± ± ± ± ± ± ± ±0.02 oil based product, ester based products are superior than the mineral oil based product in terms of better stability of the offset inks on the machine creating good image quality on the substrate with minimum wastage of the paper. Moreover ester based products will be able to reduce the volatile organic compounds (VOC) from the printing ink that deteriorate the air quality and contribute to the formation of smog and causing health hazards to the people working in the printing press. So, a new non-volatile diluents for printing ink has been developed. The diluents are made from common vegetable oils like rapeseed, soybean, rice bran and palm olein, renewable source that is environmental friendly. Vegetable oil esters offer a cost effective solution for mineral oil based printing ink to meet VOCs regulations. Acknowledgement The authors would like to thank for the cooperation, support and guidance received from the Department of Oil Technology, University of Calcutta and Dr. P. K. Dutt (CMD, DIC India Ltd). The authors also gratefully acknowledge Mr. A. D. Chatterjee (COO, DIC India Ltd), Mr. S. K. Gupta (Retd GM - Paste Inks, DIC India Ltd) and Mr. P Sengupta (Production Manager Resin, DIC India Ltd) for getting the kind help and support to fulfill this project work successfully. 1. Barrends, J. Results in resins : Past, present and future American ink maker., (1997). 2. Nielsen, P.K.; Hanson, J.H. Paint and pollution a question of solids. Farg Lack Scand. 6, (1992). 3. Bentley, J. The use of oil and fatty acids in paints and surface coatings. in Lipid Technologies and Application (Gunstone, F.D.; Padley, J.B. ed.), Marcel Dekker, Inc. pp (1997). 4. Industrial markets for U.K. produced oil seeds, home grown cereals authority. U.K. Research Review No. OS9, January (1995). 5. Mispreuve, J. Oil Fats Int. 10, 3 (1994). 6. Use of fatty acid esters based on branched fatty acids as solvents for printing inks. European Patent Application, Patent No Fatty acid esters based on branched fatty acids and their use as printing ink solvents. US Patent Application, Patent No Scarlatti, A.N. Am. Ink Maker. 71, (1993). 9. The Printing Ink Manual, 5 th ed. (Pierce, R.J. et al ed.) pp , pp (1999). 10. Baldassare, J. Am. Ink Maker. 73, (1995). 627

6 A.S. Roy, M. Bhattacharjee, R. Mondal and S. Ghosh 11. The Printing Ink Manual, 5 th ed. (Pierce, R.J. et al. ed.) Ch 14 &15 (1999). 12. Schmidt, U. Am. Ink Maker. 84, (2006). 628

Awadhoot Shendye Western Michigan University LITHO VARNISH MAKING

Awadhoot Shendye Western Michigan University LITHO VARNISH MAKING LAB SCALE ASSEMBLY COMPONENTS OTHER EQUIPMENTS Weighing balance to weight material Thermometer- To measure temperature Hot plate- To supply