Xerogels made from aromatic polyureas

Abstract

The invention relates to a xerogel comprising from 30 to 90% by weight of a monomer component (a1) composed of at least one polyfunctional isocyanate and from 10 to 70% by weight of a monomer component (a2) composed of at least one polyfunctional aromatic amine, at least one of which is selected from 4,4′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 2,2′-diaminodiphenylmethane and oligomeric diaminodiphenylmethane, where the sum of the % by weight of monomer components (a1) and (a2) adds up to 100% by weight and where the monomer components are present in polymeric form in the xerogel and the volume-weighted mean pore diameter of the xerogel is at most 5 μm, The invention further relates to a process for preparing xerogels, to the xerogels thus obtainable and to the use of the xerogels as an insulating material and in vacuum insulation panels.

1 .- 15 . (canceled) 
   
   
       16 . A xerogel comprising:
 from 30 to 90% by weight of a first monomer component comprising at least one polyfunctional isocyanate and   from 10 to 70% by weight of a second monomer component comprising at least one polyfunctional aromatic amine;   wherein at least one of the at least one polyfunctional aromatic amine is selected from the group consisting of 4,4′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 2,2′-diaminodiphenylmethane and oligomeric diaminodiphenylmethane;   wherein a sum of the % by weight of the first and second monomer components is about 100% by weight; and   wherein the first and second monomer components are present in polymeric form in the xerogel and a volume-weighted mean pore diameter of the xerogel is at most 5 μm.   
   
   
       17 . The xerogel of claim  1 , wherein the xerogel comprises from 40 to 80% by weight of the first monomer component and from 20 to 60% by weight of the second monomer component. 
   
   
       18 . The xerogel of claim  1 , wherein the first monomer component consists of at least one polyfunctional aromatic amine selected from the group consisting of: 4,4’-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 2,2′-diaminodiphenylmethane and oligomeric diaminodiphenylmethane. 
   
   
       19 . The xerogel of claim  1 , wherein the first monomer component comprises from 50 to 70% by weight of the first monomer component and from 30 to 50% by weight of the second monomer component. 
   
   
       20 . The xerogel of claim  1 , wherein the second monomer component comprises oligomeric diaminodiphenylmethane and has a functionality of at least 2.5. 
   
   
       21 . The xerogel of claim  1 , wherein the first monomer component comprises at least one polyfunctional isocyanate selected from the group consisting of: diphenylmethane 4,4′-diisocyanate, diphenylmethane 2,4′-diisocyanate, diphenylmethane 2,2′-diisocyanate and oligomeric diphenylmethane diisocyanate. 
   
   
       22 . The xerogel of claim  1 , wherein the first monomer component comprises oligomeric diphenylmethane diisocyanate and has a functionality of at least 2.5. 
   
   
       23 . The xerogel of claim  1 , wherein the first monomer component comprises an oligomeric diphenylmethane diisocyanate and the second monomer component comprises an oligomeric diaminodiphenylmethane; and wherein a sum of functionalities of the first monomer component and the second monomer component is at least 5.5. 
   
   
       24 . The xerogel of claim  1 , wherein the volume-weighted mean pore diameter of the xerogel no more than 3 μm. 
   
   
       25 . A process for preparing xerogels, comprising
 providing a gel precursor comprising first and second monomer components in a solvent, wherein
 from 30 to 90% by weight of a first monomer component comprises at least one polyfunctional isocyanate and 
 from 10 to 70% by weight of a second monomer component comprises at least one polyfunctional aromatic amine, wherein at least one of the at least one polyfunctional aromatic amine is selected from the group consisting of 4,4′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 2,2′-diaminodiphenylmethane and oligomeric diaminodiphenylmethane; 
 wherein a sum of the % by weight of the first and second monomer components is about 100% by weight; and 
 wherein the first and second monomer components are present in polymeric form in the xerogel and a volume-weighted mean pore diameter of the xerogel is at most 5 μm; 
   converting the gel precursor in the presence of the solvent to a gel; and   drying the resulting gel by converting the liquid present in the gel to the gaseous state at a temperature and a pressure below a critical temperature and a critical pressure of the liquid present in the gel.   
   
   
       26 . The process for preparing xerogels of  claim 25 , further comprising
 modifying the gel by means of at least one organic compound which was present neither in the providing step nor the converting step;   wherein the steps are performed in the order recited.   
   
   
       27 . The process for preparing xerogels of  claim 25 , wherein the resulting gel is dried by converting the solvent to the gaseous state at a temperature and a pressure below a critical temperature and a critical pressure of the solvent. 
   
   
       28 . A xerogel obtainable from the process of  claims 25 . 
   
   
       29 . The use of xerogels of claim  1  as an insulating material. 
   
   
       30 . The use of xerogels of claim  1  for vacuum insulation panels.