(DE19709868-A1)      The production of rigid polyurethane (PUR) foam with a low bulk density (I) comprises reacting (a) polyisocyanates and/or modified polyisocyanates with (b) high-mol. wt. compound(s) with at least two reactive hydrogens and optionally (c) low-mol. wt. chain-extenders and/or crosslinkers in presence of (d) blowing agents, (e) catalysts and optionally (f) other additives etc. Component (d) consists of a mixture of (d-1) cyclopentane, (d-2) at least one 3-4C alkane and/or alkene which forms a homogeneous mixture with cyclopentane and (d-3) the carbon dioxide from the reaction of water and isocyanate. Component (b) comprises aromatic nitrogen-containing polyethers.    USE -   (I) is used as insulating material in building applications and in domestic refrigerators (claimed).    ADVANTAGE -   Enables the production of rigid PUR foam with a low bulk density, giving moulded parts or objects with a low foam density combined with good compressive strength and good long-term dimensional stability.    (JP10273549-A)      The production of rigid polyurethane (PUR) foam with a low bulk density (I) comprises reacting (a) polyisocyanates and/or modified polyisocyanates with (b) high-mol. wt. compound(s) with at least two reactive hydrogens and optionally (c) low-mol. wt. chain-extenders and/or crosslinkers in presence of (d) blowing agents, (e) catalysts and optionally (f) other additives etc. Component (d) consists of a mixture of (d-1) cyclopentane, (d-2) at least one 3-4C alkane and/or alkene which forms a homogeneous mixture with cyclopentane and (d-3) the carbon dioxide from the reaction of water and isocyanate. Component (b) comprises aromatic nitrogen-containing polyethers.    USE -   (I) is used as insulating material in building applications and in domestic refrigerators (claimed).    ADVANTAGE -   Enables the production of rigid PUR foam with a low bulk density, giving moulded parts or objects with a low foam density combined with good compressive strength and good long-term dimensional stability.    (US6040349-A)      The production of rigid polyurethane (PUR) foam with a low bulk density (I) comprises reacting (a) polyisocyanates and/or modified polyisocyanates with (b) high-mol. wt. compound(s) with at least two reactive hydrogens and optionally (c) low-mol. wt. chain-extenders and/or crosslinkers in presence of (d) blowing agents, (e) catalysts and optionally (f) other additives etc. Component (d) consists of a mixture of (d-1) cyclopentane, (d-2) at least one 3-4C alkane and/or alkene which forms a homogeneous mixture with cyclopentane and (d-3) the carbon dioxide from the reaction of water and isocyanate. Component (b) comprises aromatic nitrogen-containing polyethers.    USE -   (I) is used as insulating material in building applications and in domestic refrigerators (claimed).    ADVANTAGE -   Enables the production of rigid PUR foam with a low bulk density, giving moulded parts or objects with a low foam density combined with good compressive strength and good long-term dimensional stability.