Sandwich structure including a VIP and method for producing the same

A process for production of composite elements comprising a first and a second outer layer, a vacuum insulation panel between the first and second outer layers, rigid polyurethane foam in contact with the first outer layer and an underside of the vacuum insulation panel, and also rigid polyurethane foam in contact with the second outer layer and an upper side of the vacuum insulation panel, comprising the following steps:

• (i) applying a first unhardened reaction mixture (R1) for the production of a rigid polyurethane foam onto the first outer layer,
• (ii) bringing the underside of a vacuum insulation panel into contact with the first unhardened reaction mixture (R1),
• (iii) applying a second unhardened reaction mixture (R2) for the production of a rigid polyurethane foam to the upper side of the vacuum insulation panel,
• (iv) bringing the second outer layer into contact with the layer of the second unhardened reaction mixture (R2),
• (v) hardening of the first and second unhardened reaction mixtures (R1) and (R2) to give the composite element,
• wherein the first and second unhardened reaction mixtures (R1) and (R2) comprise the following components:
• A) at least one polvisocyanate,
• B) at least one polyfunctional compound reactive toward isocyanates,
• C) at least one blowing agent,
• D) at least one catalyst,
• E) optionally foam stabilizers and
• F) optionally further auxiliaries and/or additional substances,
• wherein the composition of the first unhardened reaction mixture (R1) and of the second unhardened reaction mixture (R2) differ in relation to at least one of the components B) to F).