The invention relates to a high-pressure device for application of an expandable reaction mixture on a surface, to a method for producing expandable foams, to a device for producing sandwich composite elements, and to a method for producing expanded sandwich composite elements. The high-pressure device includes a mixing head, a distributor head fluidically connected downstream of the mixing head, at least three outlet lines attached to the distributor head, a high-pressure feed line of a component A to the mixing head, a high pressure feed line of a component B to the mixing head, at least one static mixer for mixing an inert gas to the component A, the component B or a mixture of components A and B, at least one high-pressure feed line for the inert gas, which is under increased pressure, and at least one measurement and control unit for the desired pressure of the components on the mixing head.