Development of karanja oil based offset printing ink in comparison with linseed oil.

The conventional offset lithographic printing ink is mainly based on linseed oil. But in recent years, due to stiff competition from synthetic substitutes mainly from petroleum products, the crop production shrinks down to an unsustainable level, which increases the price of linseed oil. Though soyabean oil has replaced a major portion of linseed oil, it is also necessary to develop alternate cost effective vegetable oils for printing ink industry. The present study aims to evaluate the performance of karanja oil (Pongamia glabra) as an alternative of linseed oil in the formulation of offset printing ink because karanja oil is easily available in rural India. Physical properties of raw karanja oil are measured and compared with that of alkali refined linseed oil. Rosin modified phenolic resin based varnishes were made with linseed oil as well as with karanja oil and their properties are compared. Sheetfed offset inks of process colour yellow and cyan is chosen to evaluate the effect of karanja oil in ink properties. In conclusion, karanja oil can be accepted as an alternate vegetable oil source with its noticeable effect on print and post print properties with slower drying time on paper. However, the colour and odour of the oil will restrict its usage on offset inks.

Development of mineral oil free offset printing ink using vegetable oil esters.

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 ester-based 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.