| Résumé : |
The title of this paper contains two words which I believe to be important and topical, namely water and urethanes.
Water means water dilutable as opposed to solvent dilutable and has implications as far as cost, health and the ecology are concerned. Although water is not free, it is certainly much cheaper than solvents and is in more abundant supply. It is obtained simply by turning on a tap and can be disposed of through the sewage system. On negative factor is that more energy is required to dry water than solvent, making fuel costs higher and the capital cost of drying equipment greater.
Urethanes are a group of polymers which have been growing in importance especially during the last ten years. The unique property of urethanes is their balance of toughness and stretch. Films of urethanes which have excellent abrasion resistance retain their elasticity over a wide temperature range which other polymers do not, e.g. acrylics of comparative softness are less tough.
Since our society became conscious of the cost and ecological factors involved in the use of solvents, one of the more important finishing objectives has been to produce AWS (All Water Systems). By that I mean true solvent-free systems, i.e. those not containing significant quantities of solvent either in the base coat to aid penetration and flow, or in the top coat as part of the emulsion system as with water dilutable lacquer emulsions.
Another example of necessary change concerns the tolerance limit value of ethyl glycol, which has recently been reduced from 50 to 5 ppm. Its use is now questioned by users and, in particula, workers, their unions and the health and safety executive. I believe that theuse of urethanes in bottom and, now, in top oats is helping us to achieve true AWS finishes.
Another important area concerns, the fashionable aspect of our industry today. By fashion, I mean colour, texture, feel and handle which appeal to the senses of the buyer. Leather clothing and furniture are in fashion as are clothing accessories, belts, bags and, not the least, shoes. These are co-ordinated with clothing packages and are retailed in the new-style, trendy, high street shops. The use of the new urethane polymers can help to produce suitable new leathers for these up market goods. |
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Water urethanes in finishing in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 69 (Année 1985)
