METHOD FOR PRODUCING A FLEXIBLE COMPOSITE ELASTOMERIC POLYURETHANE SKIN

摘要

The present invention relates to a method for producing a flexible elasto meric composite polyurethane skin comprising a first (1) and a second (4) fl exible polyurethane layer obtained by spraying a first and a second polyuret hane reaction mixture onto one another. The first reaction mixture is an ali phatic polyurethane reaction mixture which is free of lead and formulated to produce a polyurethane elastomer having a flexural modulus smaller than 35 MPa. The second reaction mixture is an aromatic polyurethane reaction mixtur e producing a polyurethane elastomer having a smaller flexural modulus . The thickness of the aliphatic polyurethane layer could be made so small with r espect to the thickness of the aromatic polyurethane layer that the composit e skin has an average flexural modulus smaller than 30 MPa. Notwithstanding the lower reactivity of the aliphatic polyurethane reaction mixture, especia lly when using a higher NCO-index to reduce the "rubbery feel" and the emiss ion of VOCs and/or a flexibiliser to achieve a higher flexibility, sufficien tly short cycle times can be achieved due to the accelerated curing observed when spraying the aromatic polyurethane sufficiently early against the alip hatic polyurethane layer .