Patent ID: 8318259

Claim:
A method for producing an article comprising at least a polyurethane layer, in which method a polyurethane reaction mixture is supplied under pressure to a spray nozzle, within the nozzle the reaction mixture is accelerated by passing it through one or more channels wherein the flow of reaction mixture achieves a minimum cross-sectional area measured perpendicular to the flow of the reaction mixture, the accelerated reaction mixture is injected under an angle in an outlet cavity of the nozzle to make the reaction mixture swirl in this outlet cavity, the outlet cavity forming a spray opening through which the swirling reaction mixture is sprayed, with a predetei mined amount of kinetic energy, out of the spray nozzle onto a surface to produce said polyurethane layer and the reaction mixture is allowed to cure, in which method the flow of reaction mixture achieves in said one or more channels a total minimum cross-sectional area of S mm 2 , S being a value smaller than 1.0, the reaction mixture is sprayed out of the nozzle at a flow rate of between 10×S and 80×S g/sec, and, per gram reaction mixture, an amount of 0.05 to 2.5 mmol of a pressurised gas is sprayed together with the reaction mixture through said spray opening out of the nozzle to increase the kinetic energy of the reaction mixture which is sprayed out of the nozzle, the pressurised gas being added to the reaction mixture before this reaction mixture is accelerated by said one or more channels, the reaction mixture and the pressurized gas being thus accelerated to a similar speed in said one or more channels.