Method for producing a moulded article comprising a sprayed polyurethane layer

Abstract

For producing a polyurethane layer by spraying a polyurethane reaction mixture, this 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 having a reduced cross-sectional area, and the accelerated reaction mixture is sprayed, with a predetermined amount of kinetic energy, through a spray opening out of the spray nozzle onto a surface. The channels wherein the reaction mixture is accelerated have a total minimum cross-sectional area of Smm<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 x S and 80 x 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. By the addition of a pressurised gas to the reaction mixture, a same or even a better spray pattern can be achieved and the reaction mixture can be sprayed at a smaller flow rate.

Description

technical field [0001] The invention relates to a method for producing at least a layer comprising polyurethane, in which method a polyurethane reaction mixture is conveyed under pressure into a nozzle in which the reaction mixture passes through one or more A channel in which the flow of the reaction mixture acquires the smallest cross-sectional area measured perpendicular to the flow of the reaction mixture, the accelerated reaction mixture is ejected from the nozzle through the nozzle with a predetermined kinetic energy, the injection onto the surface to produce the polyurethane layer and process the reaction mixture. Background technique [0002] Such methods are disclosed in EP-B-0 303 305 and EP-B-0 389 014. In the known method, a light-stable polyurethane reaction mixture is sprayed according to a predetermined spray pattern by using an airless two-component nozzle, so that an elastic polyurethane skin layer is produced, exhibiting a thickness greater than 0.3 mm , ...

AI Technical Summary

Problems solved by technology

[0003] A disadvantage of the known method, in particular of the nozzles used, is that in practice the minimum injection flow rate of the reaction mixture has a lower limit

It is obvious: the risk of clogging will increase in such narrow slots, and the use of only two slots has a negative effect on the uniformity of the spray pattern

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