Method for the production of a polyurethane sandwich element

An isocyanate-reactive composition B comprising:

• B1) at least one isocyanate-reactive component having at least two reactive hydrogen atoms;
• B2) more than 5.0 to less than 9.0 wt % of an internal mold release, based on the amount of isocyanate-reactive composition B;
• and
• B3) at least one blowing agent,
• wherein the internal mold release comprises:
• B2a) a first internal mold release agent;
• and
• B2b) a second internal mold release agent which is a fatty acid and different from B2a,
• wherein the second internal mold release agent B2b is present in an amount of 1.0-4.0 wt %, based on total weight of the isocyanate-reactive composition B, and
• wherein the at least one isocyanate-reactive component having at least two reactive hydrogen atoms B1 comprises:
• B1a) a polyether polyol with an OH number of 700-1000 mg KOH/g and a functionality of 2.0-4.0, obtained by addition of an alkylene oxide to an alcohol;
• B1b) a polyether polyol with an OH number of 300-600 mg KOH/g and a functionality of 3.0-6.0, obtained by addition of an alkylene oxide to a starter compound, wherein the starter compound comprises at least one of a carbohydrate, a bifunctional alcohol that is not a carbohydrate, or a mixture of the foregoing;
• and
• B1c) a polyether polyol different from B1b with an OH number of 250-550 mg KOH/g and a functionality of 2.0-4.0, obtained by addition of an alkylene oxide to an alcohol.