Process for producing polyisocyanurate plastics by means of phosphine catalysis
The present invention relates to process for producing polyisocyanurate plastics, comprising the following steps: a) providing a polyisocyanate composition A) which comprises oligomeric polyisocyanates and is low in monomeric diisocyanates, “low in monomeric diisocyanates” meaning that the polyisocyanate composition A) has a content of monomeric diisocyanates of not more than 20% by weight, b) catalytically trimerizing the polyisocyanate composition A) using at least one tertiary organic phosphine catalyst B). The invention further relates to polyisocyanurate plastics obtainable by the process according to the invention, to coatings, films, semifinished products and mouldings comprising or consisting of the polyisocyanurate plastic according to the invention, and to the use of the polyisocyanurate plastics according to the invention for production of coatings, films, semifinished products and mouldings.
1. A process for producing a polyisocyanurate plastic, comprising the following steps:
a) providing a polyisocyanate composition A) which comprises oligomeric polyisocyanates and is low in monomeric diisocyanates, “low in monomeric diisocyanates” meaning that the polyisocyanate composition A) has a content of monomeric diisocyanates of not more than 20% by weight, mixing A) with at least one tertiary organic phosphine catalyst B) of formula (I)
in which
R1, R2 and R3 are identical or different radicals and are each an alkyl or cycloalkyl group having up to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, or an aryl group which has 6 to 10 carbon atoms, optionally substituted by alkyl radicals having up to 10 carbon atoms, with the proviso that not more than one of the radicals is an aryl group and at least one of the radicals is an alkyl or cycloalkyl group, or in which
R1 and R2 are aliphatic and, joined to one another, together with the phosphorus atom form a heterocyclic ring having 4 to 6 ring members, where R3 is an alkyl group having up to 4 carbon atoms, forming a mixture,
and
b) catalytically trimerizing, at a relative air humidity of at least 20%, the polyisocyanate composition A) using the at least one tertiary organic phosphine catalyst B)
and wherein the mixture does not comprise a tin compound.
2. The process according to claim 1 , wherein the tertiary organic phosphine catalyst B) is selected from the group consisting of trimethylphosphine, triethylphosphine, tri-n-propylphosphine, tripropylphosphine, dibutylethylphosphine, tri-n-butylphosphine, triisobutylphosphine, tri-tert-butylphosphine, pentyldimethylphosphine, pentyldiethylphosphine, pentyldipropylphosphine, pentyldibutylphosphine, pentyldihexylphosphine, dipentylmethylphosphine, dipentylethylphosphine, dipentylpropylphosphine, dipentylbutylphosphine, dipentylhexylphosphine, dipentyloctylphosphine, tripentylphosphine, hexyldimethylphosphine, hexyldiethylphosphine, hexyldipropylphosphine, hexyldibutylphosphine, dihexylmethylphosphine, dihexylethylphosphine, dihexylpropylphosphine, dihexylbutylphosphine, trihexylphosphine, trioctylphosphine, tribenzylphosphine, benzyldimethylphosphine, dimethylphenylphosphine and butylphosphacyclopentane and mixtures of these.
3. The process according to claim 1 , wherein the tertiary organic phosphine catalyst is tri-n-butylphosphine and/or trioctylphosphine.
4. The process according to claim 1 , characterized in that the catalytic trimerization is conducted at least up to a conversion level at which there are only at most 20% of the isocyanate groups originally present in the polyisocyanate composition A).
5. The process according to claim 1 , characterized in that the polyisocyanate composition A) consists to an extent of at least 80%, 85%, 90%, 95%, 98%, 99% or 100% by weight, based in each case on the weight of the polyisocyanate composition A), of polyisocyanates having exclusively aliphatically and/or cycloaliphatically bonded isocyanate groups.
6. The process according to claim 1 , characterized in that the oligomeric polyisocyanates comprise one or more oligomeric polyisocyanates which are composed of or consist of 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, isophorone diisocyanate or 4,4′-diisocyanatodicyclohexylmethane or mixtures thereof.
7. The process according to claim 1 , characterized in that the polyisocyanate composition A) and/or the oligomeric polyisocyanates have a mean NCO functionality of 2.0 to 5.0.
8. The process according to claim 1 , characterized in that the polyisocyanate composition A) has a content of isocyanate groups of 8.0% to 28.0% by weight, based on the weight of the polyisocyanate composition A).
9. The process according to claim 1 , wherein the polyisocyanate composition A) has a content of monomeric diisocyanates of not more than 15% by weight, not more than 10% by weight or not more than 5% by weight, based in each case on the weight of the polyisocyanate composition A).