CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application, filed under 35 U.S.C. § 371, of International Application No. PCT/EP2018/084469, which was filed on Dec. 12, 2018, and which claims priority to European Patent Application No. 17207922.0, which was filed on Dec. 18, 2017. The contents of each are incorporated by reference into this specification.

FIELD

The present invention relates to flame-retardant rigid polyurethane foams and rigid polyurethane/polyisocyanurate foams (hereafter also referred to individually or collectively as “rigid PUR/PIR foams”) with diurethane diols (hereafter also referred to as “DUD”), and also to processes for producing same and to the use of diurethane diols in systems for producing rigid PUR/PIR foams and to mixtures containing a diurethane diol and a compound selected from the group consisting of polyether polyol, polyester polyol, polyether carbonate polyol and polyether ester polyol.

BACKGROUND

The preparation of polyether carbonate polyols by catalytic reaction of alkylene oxides (epoxides) and carbon dioxide in the presence of H-functional starter substances (“starters”) has been the subject of intensive study for more than 40 years (e.g. Inoue et al., Copolymerization of Carbon Dioxide and Epoxide with Organometallic Compounds; Die Makromolekulare Chemie [Macromolecular Chemistry] 130, 210-220, 1969). This reaction is shown schematically in the scheme (I), where R is an organic radical such as alkyl, alkylaryl or aryl, which in each case can also contain heteroatoms such as O, S, Si, etc., and where e, f and g are each an integer, and where the polyether carbonate polyol product shown here in scheme (I) should be interpreted merely as meaning that blocks having the structure shown can in principle be present in the polyether carbonate polyol obtained, but with the order, number and length of the blocks and also the OH functionality of the starter being able to vary and not being restricted to the polyether carbonate polyol shown in scheme (I). This reaction (see scheme (I)) is highly advantageous from an environmental standpoint since this reaction is the conversion of a greenhouse gas such as CO2to a polymer and hence replaces, i.e. saves, a corresponding amount of alkylene oxide. The by-product formed is the cyclic carbonate shown in scheme (I) (by way of example propylene carbonate for R═CH3, also referred to as cPC hereafter, or ethylene carbonate for R═H, also referred to as cEC hereafter).



Double metal cyanide (DMC) catalysts have proven to be particularly advantageous for preparing polyether carbonate polyols of this kind.

EP 3 098 251 A1 discloses a process for preparing diurethane diols from cyclic carbonates and diamines. The diurethane diols obtained are used as H-functional starter compound for preparing polyether polyols. Furthermore, a process for producing flexible polyurethane foams from the polyether polyols obtained is disclosed. However, neither the use of a diurethane diol as isocyanate-reactive component nor the production of a rigid polyurethane foam is disclosed. An effect of the diurethane diol on the flame retardancy of the flexible polyurethane foam is likewise not disclosed.

SUMMARY

It was therefore an object of the present invention to utilize the cyclic carbonate, obtained as a by-product in the preparation of polyether carbonate polyols, as a material for producing flame-retardant rigid polyurethane foams.

A further object was to improve the flame retardancy of rigid polyurethane foams and reduce the proportion of halogenated flame retardants in the production of rigid polyurethane foams.

According to the invention, this object is achieved by a process for producing rigid PUR/PIR foams via the reaction of a reaction mixture containingA1 an isocyanate-reactive componentA2 flame retardantA3 blowing agentA4 catalystA5 optionally auxiliaries and additiveswithB an organic polyisocyanate componentcharacterized in thatisocyanate-reactive component A1 contains a diurethane diol A1.1 and a compound A1.2 selected from the group consisting of polyether polyol, polyester polyol, polyether carbonate polyol and polyether ester polyol.

It has surprisingly been found that a mixture containing a diurethane diol A1.1 and a component A1.2, characterized in that component A1.2 is selected from the group consisting of polyether polyol, polyester polyol, polyether carbonate polyol and polyether polyol, in a process for producing rigid PUR/PIR foams increases the flame retardancy of the rigid PUR/PIR foams obtained.

