Catalyst for curable compositions containing hexahydrotriazine structural units
A compound containing at least one hexahydrotriazine unit of formula (I) having at least one amidine or guanidine group and to the use thereof as a catalyst for the crosslinking of a functional compound, in particular a polymer including silane groups. The compound contains at least one hexahydrotriazine unit of formula (I) is producible in a simple process from readily available feedstocks, odorless at room temperature, non-volatile and largely non-toxic. The compound accelerates the crosslinking of functional polymers surprisingly well and by simple variation of the substituents is variable such that it has very good compatibility in different polymers as a result of which such compositions do not have a propensity for migration-based defects such as separation, exudation or substrate contamination.
1. A compound containing at least one hexahydrotriazine unit of the formula (I)
where
A is a divalent hydrocarbyl radical optionally containing heteroatoms, and
Z is an amidine or guanidine group bonded via a nitrogen atom,
where the hexahydrotriazine ring and the Z group are separated from one another by a chain of at least two carbon atoms.
2. A compound as claimed in claim 1 , wherein A is a divalent hydrocarbyl radical which has 2 to 50 carbon atoms and optionally contains heteroatoms in the form of ether oxygen or secondary or tertiary amine nitrogen or siloxane units.
3. A compound as claimed in claim 1 , wherein Z is
where
R 0 is a hydrogen radical or an alkyl or cycloalkyl or aralkyl radical having 1 to 8 carbon atoms,
R 1 is a hydrogen radical or an alkyl or cycloalkyl or aralkyl radical having 1 to 8 carbon atoms or together with R 2 is R 6 ,
R 2 is a hydrogen radical or an alkyl, cycloalkyl or aralkyl radical which has 1 to 18 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen, or together with R 1 is R 6 ,
R 3 is —NR 4 R 5 or a hydrogen radical or an alkyl or cycloalkyl or aralkyl radical having 1 to 12 carbon atoms,
where
R 4 and R 5 are each independently a hydrogen radical or an alkyl, cycloalkyl or aralkyl radical which has 1 to 18 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen,
R 6 is an optionally substituted 1,2-ethylene, 1,3-propylene or 1,4-butylene radical having 2 to 12 carbon atoms,
R 2 and R 0 together may also be an alkylene radical which has 3 to 6 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen,
R 2 and R 3 together may also be an alkylene radical having 3 to 6 carbon atoms,
R 4 and R 5 together may also be an alkylene radical which has 4 to 7 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen, and
R 2 and R 5 together may also be an alkylene radical having 2 to 12 carbon atoms.
4. A compound as claimed in claim 3 , wherein R 3 is a hydrogen radical or an alkyl radical having 1 to 4 carbon atoms, and R 1 and R 2 together are R 6 .
5. A compound as claimed in claim 3 , wherein R 3 is —NR 4 R 5 , R 1 , R 0 and R 4 are each a hydrogen radical, and R 2 and R 5 are each independently an alkyl, cycloalkyl or aralkyl radical which has 1 to 12 carbon atoms and optionally contains an ether oxygen or tertiary amine nitrogen.
6. A compound as claimed in claim 1 , wherein it is selected from compounds of the formula (II) and compounds of the formula (III)
where
X is -A-Z or a monovalent hydrocarbyl radical which has 1 to 30 carbon atoms and optionally contains heteroatoms,
Y is an n-valent hydrocarbyl radical which has 2 to 30 carbon atoms and optionally contains heteroatoms, and
n is 2 or 3,
where, in the case of compounds of the formula (III), the hexahydrotriazine rings are each separated from one another by a chain of at least two carbon atoms.
7. A compound as claimed in claim 6 , wherein X is a radical selected from -A-Z, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, 2-ethylhexyl, cyclohexyl, benzyl, methoxyethyl, methoxyethoxyethyl, trimethoxysilylpropyl, triethoxysilylpropyl and ω-alkoxypoly(dimethylsiloxane)prop-3-yl having an average molecular weight in the range from about 350 to 2,000 g/mol.
8. A process for preparing the compound as claimed in claim 1 , wherein at least one amine of the formula H 2 N-A-Z and at least one further primary amine are reacted with formaldehyde or a formaldehyde-releasing compound with removal of water.
9. A method comprising applying a compound as claimed in claim 1 as catalyst for the crosslinking of a functional compound.
10. The method as claimed in claim 9 , wherein the functional compound is a polyisocyanate or a polyurethane polymer having isocyanate groups or a polymer having silane groups.
11. The method as claimed in claim 10 , wherein the functional compound is a polymer having silane groups selected from the group consisting of polyorganosiloxanes having terminal silane groups and organic polymers having silane groups.
12. A curable composition comprising at least one compound as claimed in claim 1 as catalyst.
13. The curable composition as claimed in claim 12 , wherein it contains isocyanate groups and/or silane groups.
14. The curable composition as claimed in claim 12 , wherein it is an adhesive or a sealant or a coating.
15. The curable composition as claimed in claim 12 , wherein it comprises at least one further constituent selected from the group consisting of fillers, plasticizers, rheology additives, desiccants, adhesion promoters and crosslinkers.