Process for producing flame-retardant porous materials based on polyurea

Abstract

The present invention relates to a process for producing flame-retardant porous materials comprising the following steps: (a) reacting at least one polyfunctional isocyanate (a1) and at least one polyfunctional aromatic amine (a2) in an organic solvent optionally in the presence of water as component (a3) and optionally in the presence of at least one catalyst (a5); and then (b) removing the organic solvent to obtain the organic porous material,
where step (a) is carried out in the presence of at least one organic flame retardant as component (a4), where this flame retardant is soluble in the solvent. The invention further relates to the porous materials thus obtainable, and also to the use of the porous materials for thermal insulation.

Claims

1. A process for producing a porous xerogel, comprising: a) reacting at least one polyfunctional isocyanate (a1) and at least one polyfunctional aromatic amine (a2) in an organic solvent in the presence of water (a3) and in the presence of at least one catalyst (a5); and then b) removing the organic solvent under subcritical conditions to obtain the porous xerogel, wherein (1) a) is carried out in the presence of at least one organic flame retardant (a4), and wherein the at least one organic flame retardant (a4) is soluble in the organic solvent, (2) the at least one polyfunctional isocyanate (a1) consists of at least one member selected from the group consisting of diphenylmethane 4,4-diisocyanate, diphenylmethane 2,4-diisocyanate, diphenylmethane 2,2-diisocyanate, and oligomeric diphenylmethane diisocyanate, (3) the at least one polyfunctional aromatic amine (a2) comprises at least one polyfunctional aromatic amine of the general formula I: ##STR00005## wherein R.sup.1 and R.sup.2 can be identical or different and are selected mutually independently from hydrogen and optionally substituted linear or branched alkyl groups having from 1 to 6 carbon atoms, and Q.sup.1 to Q.sup.5 and Q.sup.1 to Q.sup.5 are identical or different and are selected mutually independently from hydrogen, a primary amino group, and an optionally substituted linear or branched alkyl group having from 1 to 12 carbon atoms, with the proviso that the at least one polyfunctional aromatic amine of the general formula I comprises at least two primary amino groups, wherein at least one of Q.sup.1, Q.sup.3, and Q.sup.5 is a primary amino group, and at least one of Q.sup.1, Q.sup.3, and Q.sup.5 is a primary amino group, (4) the organic solvent comprises acetone, and (5) the at least one organic flame retardant (a4) comprises at least one member selected from the group consisting of polybrominated compounds and organophosphorus compounds, wherein in said reacting step a) the amount of the at least one polyfunctional isocyanate (a1) is from 76 to 97.5% by weight, the amount of the at least one polyfunctional aromatic amine (a2) is from 2 to 12% by weight, and the amount of the water (a3) is from 0.5 to 12% by weight, all of said amounts based on the total combined weight of the at least one polyfunctional isocyanate (a1), the at least one polyfunctional aromatic amine (a2) and the water (a3), which is 100% by weight, and wherein the amount of the at least one catalyst (a5) is from 0.2 to 2.5 parts by weight based on a total of 100 parts by weight of (a1), (a2), (a3) and (a4).

2. The process according to claim 1, wherein Q.sup.2, Q.sup.4, Q.sup.2, and Q.sup.4 are selected in such a way that the at least one polyfunctional aromatic amine of the general formula I has at least one linear or branched alkyl group which can bear further functional groups and which has from 1 to 12 carbon atoms in -position with respect to at least one primary amino group bonded to the aromatic ring.

3. The process according to claim 1, wherein the at least one organic flame retardant (a4) comprises at least one organophosphoric acid derivative.

4. The process according to claim 1, wherein the at least one organic flame retardant (a4) comprises at least one organophosphonic acid derivative.

5. The process according to claim 1, wherein the at least one organic flame retardant (a4) comprises at least one organophosphinic acid derivative.

6. The process according to claim 5, wherein the at least one organic flame retardant (a4) further comprises at least one polybrominated compound.

7. The process according to claim 1, wherein the at least one organic flame retardant (a4) comprises at least one compound which comprises a functional group reactive toward isocyanates.

8. The process according to claim 7, wherein the at least one compound which comprises a functional group reactive toward isocyanates comprises at least 2 functional groups reactive toward isocyanates.

9. The process according to claim 1, wherein the at least one polyfunctional isocyanate (a1) comprises an oligomeric diphenylmethane diisocyanate.

10. The process according to claim 1, wherein the at least one polyfunctional isocyanate (a1) comprises an oligomeric diphenylmethane diisocyanate having a functionality of at least 2.4.

11. The process according to claim 1, wherein the at least one polyfunctional aromatic amine (a2) comprises an oligomeric diaminodiphenylmethane having a functionality of at least 2.4.

12. A porous xerogel obtained by the process according to claim 1.

13. The porous material according to claim 12, wherein the volume-average pore diameter of the xerogel is at most 5 micrometers.

14. The process according to claim 1, wherein the organic solvent consists of acetone.

15. A process for producing a porous xerogel, comprising: a) reacting at least one polyfunctional isocyanate (a1) and at least one polyfunctional aromatic amine (a2) in an organic solvent in the presence of water (a3) and without the presence of catalyst; and then b) removing the organic solvent under subcritical conditions to obtain the porous xerogel, wherein (1) a) is carried out in the presence of at least one organic flame retardant (a4), and wherein the at least one organic flame retardant (a4) is soluble in the organic solvent, (2) the at least one polyfunctional isocyanate (a1) consists of at least one member selected from the group consisting of diphenylmethane 4,4-diisocyanate, diphenylmethane 2,4-diisocyanate, diphenylmethane 2,2-diisocyanate, and oligomeric diphenylmethane diisocyanate, (3) the at least one polyfunctional aromatic amine (a2) comprises at least one polyfunctional aromatic amine of the general formula I: ##STR00006## wherein R.sup.1 and R.sup.2 can be identical or different and are selected mutually independently from hydrogen optionally substituted and linear or branched alkyl groups having from 1 to 6 carbon atoms, and Q.sup.1 to Q.sup.5 and Q.sup.1 to R.sup.5 are identical or different and are selected mutually independently from hydrogen, a primary amino group, and an optionally substituted linear or branched alkyl group having from 1 to 12 carbon atoms, with the proviso that the at least one polyfunctional aromatic amine of the general formula I comprises at least two primary amino groups, wherein at least one of Q.sup.1, Q.sup.3, and Q.sup.5 is a primary amino group, and at least one of Q.sup.1, Q.sup.3, and Q.sup.5 is a primary amino group, (4) the organic solvent comprises acetone, and (5) the at least one organic flame retardant (a4) comprises at least one member selected from the group consisting of polybrominated compounds and organophosphorus compounds, wherein in said reacting step a) the amount of the at least one polyfunctional isocyanate (a1) is from 68 to 90% by weight, the amount of the at least one polyfunctional aromatic amine (a2) is from 2 to 12% by weight, and the amount of the water (a3) is from 8 to 20% by weight, all of said amounts based on the total combined weight of the at least one polyfunctional isocyanate (a1), the at least one polyfunctional aromatic amine (a2) and the water (a3), which is 100% by weight.

16. The process according to claim 15, wherein Q.sup.2, Q.sup.4, Q.sup.2, and Q.sup.4 are selected in such a way that the compound at least one polyfunctional aromatic amine of the general formula I has at least one linear or branched alkyl group which can bear further functional groups and which has from 1 to 12 carbon atoms in -position with respect to at least one primary amino group bonded to the aromatic ring.

Description

EXAMPLES

(1) Pore volume in ml per g of sample and average pore size of the materials were determined by means of mercury porosimetry to DIN 66133 (1993) at room temperature. For the purposes of this invention, average pore size is equivalent to average pore diameter. Volume-average pore diameter is determined here by calculation from the pore size distribution determined to the abovementioned standard.

(2) Porosity in % by volume was calculated from the formula P=(V.sub.i/(V.sub.i+V.sub.s))*100% by volume, where P is the porosity, V.sub.i is the Hg intrusion volume to DIN 66133 in ml/g, and V.sub.s is the specific volume in ml/g of the test specimen.

(3) Density of the porous gel in g/ml was calculated from the formula =m/(*r.sup.2)*h, where m is the mass of the porous gel, r is the radius (half diameter) of the porous gel, and h is the height of porous gel.

(4) Shrinkage during step (b) of the process of the invention was determined by comparing the height of a cylindrical gel and the diameter in cm prior to and after removal of the solvent. The values stated are based on the relative volume of the cylinder after shrinkage in comparison with the gel product prior to removal of the solvent, and this means that shrinkage is stated as % loss of volume. Prior to shrinkage, the height of the cylinders was 4.9 cm and the diameter of the cylinders was 2.7 cm.

(5) Flame retardancy properties were determined by the BKZ test as described above. To the extent that the maximum flame height stated for the purposes of combustibility class 5, 15 cm, was not achieved, the flame height observed in the BKZ test has instead been stated.

(6) The following compounds were used:

(7) Component a1:

(8) Oligomeric MDI (Lupranat M50) having NCO content of 31.5 g per 100 g to ASTM D5155-96 A, functionality in the range from 2.8 to 2.9, and viscosity of 550 mPa.Math.s at 25 C. to DIN 53018 (hereinafter compound M50).

(9) Component a2:

(10) Oligomeric diaminodiphenylmethane with viscosity of 2710 mPa.Math.s at 50 C. to DIN 53018, functionality in the region of 2.4, and amino group content of 9.93 mmol/g (hereinafter PMDA).

(11) Component a3:

(12) ##STR00002##
PHT-4-Diol from Chemtura:

(13) ##STR00003##
Antiblaze V490 from Albemarle:

(14) ##STR00004##

Example 1

(15) 2.0 g of compound M50 were dissolved in 10.5 g of acetone in a glass beaker at 20 C., with stirring. 1.3 g of PMDA and 0.5 g of Exolit OP560 were dissolved in 11 g of acetone in a second glass beaker. The two solutions of step (a) were mixed. This gave a clear mixture of low viscosity. The mixture was allowed to stand at room temperature for 24 hours for hardening. The gel was then removed from the glass beaker, and the liquid (acetone) was removed by drying at 20 C. for 7 days.

(16) The average pore diameter of the resultant material was 4.0 m. Porosity was 86% by volume, with corresponding density of 233 g/l. Shrinkage was 42%. The flame height measured in the BKZ test was 5 cm.

Example 2

(17) 2.0 g of compound M50 were dissolved in 10.5 g of acetone in a glass beaker at 20 C., with stirring. 1.3 g of PMDA and 0.5 g of PHT-4-Diol were dissolved in 11 g of acetone in a second glass beaker. The two solutions of step (a) were mixed. This gave a clear mixture of low viscosity. The mixture was allowed to stand at room temperature for 24 hours for hardening. The gel was then removed from the glass beaker, and the liquid (acetone) was removed by drying at 20 C. for 7 days.

(18) The average pore diameter of the resultant material was 5.0 m. Porosity was 85% by volume, with corresponding density of 235 g/l. Shrinkage was 43%. The flame height measured in the BKZ test was 9 cm.

Example 3

(19) 2.0 g of compound M50 were dissolved in 10.5 g of acetone in a glass beaker at 20 C., with stirring. 1.3 g of PMDA and 0.5 g of Antiblaze V490 from Albemarle were dissolved in 11 g of acetone in a second glass beaker. The two solutions of step (a) were mixed. This gave a clear mixture of low viscosity. The mixture was allowed to stand at room temperature for 24 hours for hardening. The gel was then removed from the glass beaker, and the liquid (acetone) was removed by drying at 20 C. for 7 days.

(20) The average pore diameter of the resultant material was 3.0 m. Porosity was 86% by volume, with corresponding density of 226 g/l. Shrinkage was 42%. The flame height measured in the BKZ test was 5 cm.

Example 4 Comp

(21) 2.4 g of compound M50 were dissolved in 10.5 g of acetone in a glass beaker at 20 C., with stirring. 1.3 g of compound PMDA were dissolved in 11 g of acetone in a second glass beaker. The two solutions of step (a) were mixed. This gave a clear mixture of low viscosity. The mixture was allowed to stand at room temperature for 24 hours for hardening. The gel was then removed from the glass beaker, and the liquid (acetone) was removed by drying at 20 C. for 7 days.

(22) When the resultant material was compared with example 1, it had a markedly shrunk shape. Shrinkage was 70%. Porosity was 71% by volume, with corresponding density of 390 g/l. The flame height measured in the BKZ test was 7 cm, and it should be noted here that combustibility is reduced by the high density of the material.