HIGH-TEMPERATURE-RESISTANT FOAMS HAVING HIGH FLAME RETARDANCY

Abstract

The invention relates to high-temperature-resistant foams having excellent flame retardancy, to the production thereof from organic polyisocyanates and polyepoxides, and to the use of said foams.

Claims

1.-15. (canceled)

16. A process for preparing a high-temperature resistant foam, comprising the reaction of a) at least one mixture of organic polyisocyanates, and b) at least one organic compound having at least two epoxy groups in an amount that corresponds to an equivalent ratio of isocyanate groups to epoxy groups of from 1.2:1 to 500:1, in the presence of c) optionally at least one catalyst accelerating the isocyanate/epoxide reaction, e) optionally in the presence of auxiliary agents and additives, f) chemical and/or physical blowing agents, wherein said polyisocyanate a) contains more than 50% by weight of polyphenyl polymethylene polyisocyanates having a functionality f>2 and the structural formula C.sub.15H.sub.10N.sub.2O.sub.2 [C.sub.8H.sub.5NO].sub.n, where n=integer >0, and that the organic compound b) contains one or more polyglycidyl ethers selected from the group consisting of the polyglycidyl ethers of bisphenol A, bisphenol F and novolac, that the chemical and/or physical blowing agents f) include at least one carboxylic acid selected from formic acid and acetic acid, or that said blowing agent consists of water and optionally one or more compounds selected from the group containing hydrocarbons, fluorocarbons, and fluorohydrocarbons, and that the reaction proceeds in the absence of a component d) acting as a stopper.

17. The process according to claim 16, wherein said mixture of organic polyisocyanates a) contains more than 55% by weight polyphenyl polymethylene polyisocyanates with f>2 and the structural formula C.sub.15H.sub.10N.sub.2O.sub.2 [C.sub.8H.sub.5NO].sub.n, where n=integer >0.

18. The process according to claim 16, wherein the organic compound b) contains a polyglycidyl ether of bisphenol F.

19. The process according to claim 16, wherein said catalyst is employed in an amount of from 0 to <2.0% by weight, based on the total weight of components (a) and (b).

20. The process according to claim 16, wherein said foam contains <0.8% by weight of urethane groups and/or urea groups derived from the reaction of the polyisocyanate a) with e1) multifunctional compounds containing hydroxy groups and/or amino groups, based on the total weight of the components.

21. The process according to claim 16, wherein said further auxiliary agents and additives e) are included in such a maximum amount that the ratio of the weight of all compounds containing hydroxy and/or amino groups e1) to the weight of epoxy component b) is smaller than 30:70 and preferably at most 28:72, more preferably at most 25:75, and even more preferably at most 20:80.

22. The process according to claim 16, wherein said further auxiliary agents and additives e) are included in such a maximum amount that less than 28% by weight, preferably less than 25% by weight, of component e1) is employed, based on the total weight of components b) and e1), and said EPIC foam contains 0.01 to 1% by weight, preferably 0.01 to <0.8% by weight, of urethane and/or urea groups derived from the reaction of polyisocyanate a) with component e), based on the total weight of the foam.

23. The process for preparing high-temperature resistant foams according to claim 16, containing the steps of (i) mixing the components a) to f), (ii) reacting the components a) to f) in a one-shot process.

24. The process according to claim 16, wherein, after said foaming to the foamed state, a subsequent temperature treatment is performed at from 70 to 250 C., or no temperature treatment is performed.

25. The process for preparing a foam according to claim 24, wherein an aminic compound selected from the group consisting of boron trichloride tert. amine adducts, N,N-dimethylbenzylamine, N,N-methyldibenzylamine, a compound with at least two isocyanate-reactive hydrogen atoms and a molecular weight of less than 500 g/mol, wherein at least one of said isocyanate-reactive hydrogen atoms belongs to a primary or secondary amino group, and mixtures thereof, is added.

26. A high-temperature resistant foam obtainable by a process according to claim 16.

27. A method comprising utilizing the high-temperature resistant foams according to claim 26 as a filling foam for hollow spaces, as a filling foam for electric insulation, as a core of sandwich constructions, for the preparation of construction materials for all kinds of interior and exterior applications, for the preparation of construction materials for vehicle, ship, airplane and rocket construction, for the preparation of airplane interior and exterior construction parts, for the preparation of all kinds of insulation materials, for the preparation of insulation plates, tube and container insulations, for the preparation of sound-absorbing materials, for use in engine compartments, for the preparation of grinding wheels, and for the preparation of high-temperature insulations and hardly flammable insulations.

28. A method comprising utilizing a foamable mixture before the foaming to the high-temperature resistant foam according to claim 26 is complete for adhesively bonding substrates, for adhesively bonding steel, aluminum and copper plates, plastic sheets, and polybutylene terephthalate sheets.

29. Hollow spaces, electric insulations, cores of sandwich constructions, sandwich constructions, construction materials for all kinds of interior and exterior applications, construction materials for vehicle, ship, airplane and rocket construction, airplane interior and exterior construction parts, all kinds of insulation materials, insulation plates, tube and container insulations, sound-absorbing materials, damping and insulation materials in engine compartments, grinding wheels, high-temperature insulations, and hardly flammable insulations, comprising the high-temperature resistant foams according to claim 26.

30. Bondings between substrates, e.g., steel, aluminum and copper plates, plastic sheets, e.g., polybutylene terephthalate sheets, comprising the high-temperature resistant foams according to claim 26.

Description

EXAMPLES

[0091] In the following Examples, all percentages are by weight.

[0092] The measurement of the bulk densities was effected according to DIN 53 420 on foam cubes (5 cm5 cm5 cm) that were cut from the middle of the foams.

[0093] The measurement of the compressive strengths was effected according to DIN EN 826 on foam cubes (5 cm5 cm5 cm) that were cut from the middle of the foams.

[0094] The measurement of the maximum average rate of heat emission (MARHE) was effected according to ISO 5660-1. The measurement of the total smoke production per occupied surface (TSP) was effected according to ISO 5660-2. All tests were performed with a radiant heat flux density of 50 kW/m.sup.2 on test specimens having dimensions of 100 mm100 mm20 mm.

[0095] The flammability and flame spread were determined according to the requirements of building material class B2 according to DIN 4102-1.

[0096] Isocyanate:

[0097] MDI-1: Desmodur 44 V 70 L, mixture of about 35% by weight monomeric MDI and 65% by weight polymeric MDI, f=3.19, isocyanate content 30.5 to 32%, viscosity at 20 C. is 1100 mPa.Math.s according to DIN 53 019; commercial product of the Bayer MaterialScience AG, Leverkusen/Germany

[0098] MDI-2: mixture of about 30% by weight monomeric MDI and 70% by weight polymeric MDI, functionality of about 2.8, isocyanate content 31.5 g/100 g according to ASTM D 5199-96 A, viscosity at 25 C. is 550 mPa.Math.s according to DIN 53 018

[0099] Epoxide:

[0100] BADGE1: Ruetapox 0162, diglycidyl ether of bisphenol A, commercial product from Bakelite AG; Duisburg/Germany, epoxide index: 5.8-6.1 eq/kg and an epoxy equivalent of 167-171 g/eq, viscosity at 25 C.: 4000-5000 mPas

[0101] BADGE2: Araldite GY250, diglycidyl ether of bisphenol A, commercial product from Huntsman, Basel/Switzerland, epoxide index: 5.3-5.45 eq/kg and an epoxy equivalent of 182-192 g/eq, viscosity at 25 C.: 10,000-12,000 mPas according to DIN/ISO 9371 B

[0102] BADGE3: Leuna Epilox A 18-00, diglycidyl ether of bisphenol A, commercial product of LEUNA-Harze GmbH, Leuna/Germany, epoxy equivalent of 175-185 g/eq according to DIN 16 945, viscosity at 25 C. from 8000 to 10,000 mPa.Math.s according to DIN 53 015

[0103] BFDGE: Araldite GY281, diglycidyl ether of bisphenol F, commercial product from Huntsman, Basel/Switzerland, epoxide index: 5.8-6.3 eq/kg and an epoxy equivalent of 158-172 g/eq, viscosity at 25 C.: 5000-7000 mPas

[0104] EPN: Araldit GY289, epoxyphenol of novolac, commercial product from Huntsman, Basel/Switzerland, epoxide index: 5.7-6.0 eq/kg and an epoxy equivalent of 167-175 g/eq, viscosity at 25 C. 7000-11000 mPas

[0105] Further Components:

[0106] POLYOL-1: Desmophen 3600Z, polyether polyol, OH number 56 mg KOH/g, f=2, prepared by propoxylation of 1,2-propylene glycol: commercial product from Bayer MaterialScience AG, Leverkusen/Germany

[0107] Tegostab B 8411: polyether polysiloxane, commercial product from Evonik, Essen/Germany

[0108] Tegostab B 8485: polyether polysiloxane, commercial product from Evonik, Essen/Germany

[0109] Accelerator DY 9577: boron trichloride/amine complex, thermolatent catalyst, commercial product from Huntsman, Bad Sckingen, Germany

[0110] Addocat 3144: N-[3-(dimethylamino)propyl]formamide, commercial product from Rheinchemie, Mannheim/Germany

[0111] FA: formic acid (98-100%), CAS No. 64-18-6, obtainable from KMF Laborchemie, Lohmar/Germany

[0112] Amasil 85%, 85% by weight formic acid in water

[0113] Disflamol DPK: diphenyl cresyl phosphate, commercial product from Lanxess, Kln/Germany

[0114] Solkane 365/227: liquid hydrofluorocarbon as a blowing agent for foams, obtainable from Solvay Fluor GmbH, Hannover, Germany

[0115] N,N-Dimethylbenzylamine, 98% CAS No. 103-83-3, obtainable from Sigma-Aldrich/Germany

[0116] N,N-Methyldibenzylamine, CAS No. 102-05-06, obtainable from Sigma-Aldrich/Germany

[0117] DETDA 80, diethyltoluenediamine, CAS No. 68479-98-1, obtainable from Lonza, Basel/Switzerland

[0118] DABCO T: (2-(2-dimethylamino)ethyl)methylamino)ethanol), commercial product of the Air Products and Chemicals, Inc.

[0119] p-Toluenesulfonic acid methyl ester: CAS No. 80-48-8, obtainable from Merck KGaA Darmstadt/Germany

[0120] Exolit RP6520: thixotropic dispersion containing red phosphorus, flame retardant from the company Clariant SE/Germany

[0121] Additive mixture 1 (AM-1): Mixture of POLYOL-1, Tegostab B 8411, N-[3-(dimethylamino)propyl]formamide, as used in Examples 1 to 11

[0122] Additive mixture 2 (AM-2): Mixture of Tegostab B 8485, diethyltoluenediamine, accelerator DY 9577, N,N-dimethylbenzylamine, and N,N-methyldibenzylamine, as used in Examples 12 and 13

Example 1

[0123] 320 g of MDI-1 was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0124] Bulk density: 40 kg/m.sup.3

Example 2

[0125] 320 g of MDI-1 was admixed with 80 g of BFDGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0126] Bulk density: 42 kg/m.sup.3

Example 3

[0127] 320 g of MDI-1 was admixed with 80 g of BADGE and 93.6 g of Disflamoll DPK and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 10 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box.

[0128] Bulk density: 42 kg/m.sup.3

Example 4

[0129] 320 g of MDI-1 was admixed with 80 g of BADGE and 93.6 g of Disflamoll DPK and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 8.8 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0130] Bulk density: 42 kg/m.sup.3

Example 5

[0131] 320 g of MDI-1 was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The reaction mixture was allowed to foam in said cardboard cup.

[0132] Bulk density: 43 kg/m.sup.3

Example 6

[0133] 320 g of MDI-1 was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. The reaction mixture is cooled down to 10 C. in a refrigerator. With stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) and 19.6 g of Solkane 365/227 87/13 were added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0134] Bulk density: 35 kg/m.sup.3

Example 7

[0135] 320 g of MDI-1 was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. The reaction mixture is cooled down to 10 C. in a refrigerator. With stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) and 18.0 g of HFC-245fa were added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The reaction mixture was allowed to foam in said cardboard cup. The foam was annealed at 200 C. for 3 hours.

[0136] Bulk density: 35 kg/m.sup.3

Example 8* (Comparison, Preparation of EPIC Reaction Resin, Pretrimerization to Intermediate)

[0137] At 50 C., 800 g of a mixture of 60% 2,4-diisocyanatodiphenylmethane and 40% 4,4-diisocyanatodiphenylmethane (NCO content=33.6%) was mixed with 200 g of BADGE1 and 0.1 ml of N,N-dimethylbenzylamine, and subsequently heated to 120 C. The slightly exothermic reaction indicated the immediate start of the isocyanurate formation. After a reaction time of 2 hours without external heating, the charge was cooled. This resulted in an interior temperature of about 90 C. A sample was taken from the charge. The sample has an NCO content of 23%. The reaction was quenched by adding 4.28 g of p-toluenesulfonic acid methyl ester. Subsequently, the charge was stirred at 120 C. for another 30 min. A clear yellow storage-stable resin that is liquid at 20 C. and has a viscosity at 25 C. of 2080 mPa.Math.s and an NCO content of 21.4% (B state) was formed.

Example 9a* (Comparison with Annealing)

[0138] 400 g of the resin from Example 8 was loaded with air using a quick stirrer for 2 minutes. With stirring, 17.6 g of POLYOL-1, 7.0 g of Tegostab B 8411 and 3.5 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0139] Bulk density: 39 kg/m.sup.3

Example 9b* (Comparison without Annealing)

[0140] 400 g of the resin from Example 8 was loaded with air using a quick stirrer for 2 minutes. With stirring, 17.6 g of POLYOL-1, 7.0 g of Tegostab B 8411 and 3.5 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box.

[0141] Bulk density: 39 kg/m.sup.3

Example 10

[0142] 320 g of MDI-1 was admixed with 80 g of BFDGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411, 3.0 g of N-[3-(dimethylamino)propyl]formamide and 4 g of Exolit RP6520 were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box.

[0143] Bulk density: 42 kg/m.sup.3

Example 11

[0144] 320 g of MDI-1 was admixed with 80 g of EPN and loaded with air using a quick stirrer for 2 minutes. With further stirring, 15.0 g of POLYOL-1, 6.0 g of Tegostab B 8411 and 3.0 g of N-[3-(dimethylamino)propyl]formamide were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box.

[0145] Bulk density: 42 kg/m.sup.3

Example 12

[0146] 320 g of Desmodur 44 V 70 L was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 6.3 g of Tegostab B 8485, 4.4 g of diethyltoluenediamine, 3.3 g of accelerator DY 9577, 2.4 g of N,N-dimethylbenzylamine and 1.6 g of N,N-methyldibenzylamine were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box.

[0147] Bulk density: 40 kg/m.sup.3

Example 13

[0148] 320 g of MDI-1 was admixed with 80 g of BADGE and loaded with air using a quick stirrer for 2 minutes. With further stirring, 6.3 g of Tegostab B 8485, 4.4 g of diethyltoluenediamine, 3.3 g of accelerator DY 9577, 2.4 g of N,N-dimethylbenzylamine, 1.6 g of N,N-methyldibenzylamine and 16.0 g of Exolit RP6520 were added. Immediately thereafter, 6.0 g of formic acid (98-100%) was added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a cardboard box of 20 cm20 cm24 cm, and the reaction mixture was allowed to foam in said cardboard box. The foam was annealed at 200 C. for 3 hours.

[0149] Bulk density: 42 kg/m.sup.3

Example 14

[0150] 340.75 g of MDI-2 and 113.1 g of BADGE3 were mixed together using a quick stirrer at 1000 rpm for 20 s to 30 s. 6.8 g of 1.36 w/w water was added and mixed at 1000 rpm for 10 s. Immediately thereafter, the additive package consisting of 12.35 g of Tegostab B 8485, 8.6 g of diethyltoluenediamine, 6.5 g of accelerator DY 9577, 4.7 g of N,N-dimethylbenzylamine and 3.1 g of N,N-methyldibenzylamine (corresponding to AM-2) and 0.81 g of Dabco T was added and mixed at 2000 rpm for 3 s. The reaction mixture was subsequently allowed to foam.

[0151] Bulk density: 28.1 kg/m.sup.3

Example 15

[0152] 340.75 g of MDI-2 and 112.5 g of BADGE3 were mixed together using a quick stirrer at 1000 rpm for 20 s to 30 s. Amasil 85% was added and mixed at 1000 rpm for 10 s. Immediately thereafter, the additive package consisting of 12.3 g of Tegostab B 8485, 7.4 g of diethyltoluenediamine, 5.6 g of accelerator DY 9577, 4.1 g of N,N-dimethylbenzylamine and 2.7 g of N,N-methyldibenzylamine (corresponding to AM-2) and 0.81 g of Dabco T was added and mixed at 2000 rpm for 3 s. The reaction mixture was subsequently allowed to foam.

[0153] Bulk density: 36.4 kg/m.sup.3

TABLE-US-00001 TABLE 1 1 2 3 4 5 10 11 6 7 9a* 9b* Epoxy component BADGE2 BFDGE BADGE2 BADGE2 BADGE2 BFDGE EPN BADGE2 BADGE2 BADGE1 BADGE1 Blowing agent FA FA FA FA FA FA FA Solkane HFC-245fa FA FA 365/227 and FA and FA Flame retardant DPK DPK Exolit RP6520 Additive mixture AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 AM-1 Annealing for 3 yes yes no yes no yes yes yes yes yes no hours at 200 C. (yes/no) NCO index 452 427 387 416 453 444 314 451 451 453 453 Functionality of 3.19 3.19 3.19 3.19 3.19 3.19 3.19 3.19 3.19 2 2 the MDI employed Density [kg/m.sup.3] 40 42 42 42 43 42 42 35 35 39 39 B2 small burner passed passed passed passed passed passed passed passed passed passed failed test (DIN 4102-1 B2) MARHE 84.3 81.8 76.5 62.1 98.0 63.9 82.5 87.6 88.1 120.2 132 [kW/m.sup.2] TSP [m.sup.2/m.sup.2] 271.6 554.5 984.6 746.9 848.8 860.1 346.3 543.2 486.6 912.2 761 Compressive 278 270 257 227 289 256 302 192 180 246 296 strength F 10% [kPa] 12 13 14 15 Epoxy component BADGE2 BADGE2 BADGE3 BADGE3 Blowing agent FA FA water FA + water Flame retardant Exolit RP6520 Additive mixture AM-2 AM-2 AM-2 AM-2 Annealing for 3 yes yes no no hours at 200 C. (yes/no) NCO index 445 445 Functionality of 3.19 3.19 2.8 2.8 the MDI employed Density [kg/m.sup.2] 40 42 28.1 36.4 B2 small burner passed passed passed passed test (DIN 4102-1 B2) MARHE [kW/m.sup.2] 76 48 75 74 TSP [m.sup.2/m.sup.2] 571.5 339.5 588.5 565.9 Compressive 250 205 131 198 strength F 10% [kPa]

[0154] Examples 1 and 2 according to the invention both have excellent mechanical properties with compressive strengths of from 270 to 280 kPa at densities around 40 kg/m.sup.3. In a Cone Calorimeter Test, very low MARHE and TSP (total smoke production) values were achieved, which demonstrate the excellent flame-retardant properties of the foams. With a MARHE value of 84.3 kW/m.sup.2, Example 1 also has a very low TSP of 2.4 m.sup.2. A similar case is seen in Example 2 with a MARHE value of 81.8 kW/m.sup.2 and a TSP of 4.9 m.sup.2.

[0155] In each of Examples 3 and 4 according to the invention, DPKs were added as flame retardants. In contrast to the foam from Example 4, the resulting foam of Example 3 was not annealed. For the same bulk density, both foams showed excellent Cone Calorimeter Test results. The MARHE values with 76.5 kW/m.sup.2 (Example 3, not annealed) and 62.1 kW/m.sup.2 (Example 4, annealed) are very low, the flue gas density with 8.7 m.sup.2 (Example 3) and 6.6 m.sup.2 (Example 4) being in the expected range. As can be seen from the Cone Calorimeter Test results, the annealing of the foams has only a little influence on the fire properties. As can be seen from Table 1, the compressive strengths are also very good.

[0156] In Example 5 according to the invention, a foam was also prepared with formic acid as the blowing agent, which was not annealed, however. In this Example 5 according to the invention, the compressive strength is also very high with 289 kPa. A very good MARHE value of 98 kW/m.sup.2 is achieved even without an annealing process.

[0157] In Example 10 according to the invention, red phosphorus was added as a flame retardant. In the Cone Calorimeter Test, a very low MARHE value of 63.9 kW/m.sup.2 and a TSP value of 7.6 m.sup.2 were achieved, which demonstrates the excellent flame retarding properties of the foams.

[0158] In Example 11 according to the invention, EPN was employed as an epoxide component. The resulting foam has excellent mechanical properties with a compressive strength of 302 kPa. In the Cone Calorimeter Test, very low MARHE (82.5 kW/m.sup.2) and TSP (3.06 m.sup.2) values were achieved, demonstrating the excellent flame retarding properties of the foams.

[0159] In Examples 12 (without flame retardant) and 13 (with red phosphorus as the flame retardant), alternative additive mixtures were employed, which also achieved very good MARHE and TSP values.

[0160] In Examples 6 and 7 according to the invention, a mixture of Solkane 365/227 and formic acid (Example 6) and a mixture of HFC-245fa and formic acid (Example 7) were used instead of formic acid. The polymeric MDI employed had a functionality of f=3.19. The resulting foams have a good compressive strength of 192 kPa (Example 6) and 180 kPa (Example 7) with a bulk density of 35 kg/m.sup.3. The MARHE values, being 87.6 (Example 6) and 88.1 kW/m.sup.2 (Example 7), are very low and comparable with those of foams that were foamed only with formic acid. The flue gas densities, being 4.8 m.sup.2 (Example 6) or 4.3 m.sup.2 (Example 7), are also in a comparable range.

[0161] Also, the use of water or mixtures of water/formic acid as blowing agents yield foams with better properties than those of the prior art foams.

[0162] The foam from Comparative Example 9a* and b* (formic acid as blowing agent) was prepared in a two-step process. At first, as described in Comparative Example 8, monomeric MDI was subjected to preliminary trimerization to a particular NCO value, and the thus obtained prepolymer was converted to a foam only thereafter. The functionality of the MDI employed was f=2. The foam from Comparative Example 9a* was annealed at 200 C. for 3 hours. The Cone Calorimeter results with a MARHE value of 120.2 kW/m.sup.2 and a TSP of 8 m.sup.2 are significantly worse than the values from the Examples according to the invention, but the small burner test was passed. In contrast, the foam from Comparative Example 9b* was not annealed, and in this case, the small burner test was failed.