Foam materials resistant to high temperatures

Abstract

The invention relates to foam materials that are resistant to high temperatures, to the production of same from aromatic polyisocyanates and polyepoxides, and to the use of said foam materials.

Claims

1. A high-temperature resistant foam obtained by a process in which a) an aromatic polyisocyanate is mixed with b) at least one aromatic compound having at least two epoxy groups, c) at least one catalyst accelerating the isocyanate/epoxide reaction, f) chemical and optionally physical blowing agents, and e) auxiliary agents and/or additives, to form a reaction mixture, wherein the equivalent ratio of isocyanate groups to epoxy groups is from 1.2:1 to 500:1, and the reaction mixture is reacted into a foam, wherein said auxiliary agents and/or additives e) include at least one e1) phosphate liquid at 60 C. and under 1 bar, and said 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 f) consists of water and optionally one or more compounds selected from the group containing hydrocarbons, fluorocarbons, and fluorohydrocarbons; and that one or more compounds selected from the group consisting of the polyglycidyl ethers of bisphenol A, the polyglycidyl ethers of bisphenol F, novolacs and polyepoxy compounds based on aromatic amines are employed as component b); wherein said foam contains <10% by weight of carbodiimide structures.

2. The high-temperature resistant foam according to claim 1, wherein said blowing agents f) include at least one carboxylic acid selected from formic acid and acetic acid.

3. The high-temperature resistant foam according to claim 1, wherein the reaction is effected in the presence of d) a stabilizer selected from the group consisting of organic sulfonic acid esters, methyl iodide, dimethyl sulfate, benzenesulfonic acid anhydride, benzenesulfonic acid chloride, benzenesulfonic acid, trimethylsilyltrifluoromethane sulfonate, the reaction product of benzenesulfonic acid with epoxides, and mixtures thereof.

4. The high-temperature resistant foam according to claim 2, wherein said blowing agents f) consist of formic acid.

5. A process for preparing a high-temperature resistant foam by reacting a) at least one aromatic polyisocyanate with b) at least one aromatic 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, e) in the presence of auxiliary agents and additives, wherein said auxiliary agents and/or additives e) include at least one e1) phosphate liquid at 60 C. and under 1 bar, and that the reaction is performed in the presence of chemical and/or physical blowing agents f), which include at least one carboxylic acid selected from formic acid and acetic acid, or consist of water and optionally one or more compounds selected from the group containing hydrocarbons, fluorocarbons, and fluorohydrocarbons, and a catalyst accelerating the isocyanate/epoxide reaction c) with foaming; and that one or more compounds selected from the group consisting of the polyglycidyl ethers of bisphenol A, the polyglycidyl ethers of bisphenol F, novolacs and polyepoxy compounds based on aromatic amines are employed as component b); and the reaction is effected in the presence of d) a stabilizer selected from the group consisting of organic sulfonic acid esters, methyl iodide, dimethyl sulfate, benzenesulfonic acid anhydride, benzenesulfonic acid chloride, benzenesulfonic acid, trimethylsilyltrifluoromethane sulfonate, the reaction product of benzenesulfonic acid with epoxides, and mixtures thereof.

6. The process according to claim 5 comprising (i) the reaction of a) at least one aromatic polyisocyanate in the presence of c) a tertiary amine as a catalyst to form an intermediate containing isocyanurate groups; and (ii) quenching the reaction under step (i) at a conversion rate of at most 60% of the isocyanate groups of isocyanate a) by the addition of an amount that is at least equivalent to the amount of amine c) of d) a stabilizer selected from the group consisting of organic sulfonic acid esters, methyl iodide, dimethyl sulfate, benzenesulfonic acid anhydride, benzenesulfonic acid chloride, benzenesulfonic acid, trimethylsilyltrifluoromethane sulfonate, the reaction product of benzenesulfonic acid with epoxides, and mixtures thereof; and (iii) mixing the product obtained under (ii) with b) at least one aromatic compound having at least two epoxy groups in an amount that corresponds to an equivalent ratio of initially employed isocyanate groups to epoxy groups of from 1.2:1 to 500:1, e) in the presence of auxiliary agents and/or additives; wherein the mixture obtained under (iii) is converted to the foamed state under foaming by (iv) the addition of a blowing agent f), which includes at least one carboxylic acid selected from formic acid and acetic acid, or consists of water and optionally one or more compounds selected from the group containing hydrocarbons, fluorocarbons, and fluorohydrocarbons; and at least one phosphate e1) that is liquid at 60 C. and under 1 bar; and a catalyst accelerating the isocyanate/epoxide reaction c2).

7. The process according to claim 5 comprising (i) mixing of a) at least one aromatic polyisocyanate, and b) at least one aromatic 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, (ii) reacting the mixture by adding c1) a tertiary amine as a catalyst to form an intermediate product; and (iii) quenching the reaction at a conversion rate of at most 60% of the isocyanate groups of isocyanate a) by the addition of an amount that is at least equivalent to the amount of amine c) of d) a stabilizer selected from the group consisting of organic sulfonic acid esters, methyl iodide, dimethyl sulfate, benzenesulfonic acid anhydride, benzenesulfonic acid chloride, benzenesulfonic acid, trimethylsilyltrifluoromethane sulfonate, the reaction product of benzenesulfonic acid with epoxides, and mixtures thereof, to obtain an intermediate stable B state of the viscosity range of from 1500 to 20,000 mPa.Math.s at 25 C.; e) in the presence of auxiliary agents and/or additives; wherein the mixture obtained under (iii) is converted to the foamed state under foaming by the addition of a blowing agent f), which includes at least one carboxylic acid selected from formic acid and acetic acid, or consists of water and optionally one or more compounds selected from the group containing hydrocarbons, fluorocarbons, and fluorohydrocarbons; and at least one phosphate e1) that is liquid at 60 C. and under 1 bar; and a catalyst accelerating the isocyanate/epoxide reaction c2).

8. The process according to claim 5, wherein said blowing agents f) include at least one carboxylic acid selected from formic acid and acetic acid.

9. The process according to claim 5, wherein, after the foaming to the foamed state, a subsequent temperature treatment at from 70 to 250 C. is performed.

10. A method comprising utilizing the high-temperature resistant foam according to claim 1 as a 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.

11. A method comprising utilizing a foamable mixture before the end of the foaming to form the foam having high temperature resistance according to claim 1 for adhesively bonding substrates, for adhesively bonding steel, aluminum and copper plates, plastic sheets, and polybutylene terephthalate sheets.

12. 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 foam according to claim 1.

13. Bondings between substrates, bondings between steel and copper plates, plastic sheets and polybutylene terephthalate sheets, comprising the high-temperature resistant foams according to claim 1.

Description

EXAMPLES

(1) The dynamic viscosities were determined at 25 C. with a rotary viscometer (Rheoplus 32) at a shear rate of 120 s.sup.1 (DIN 53019).

(2) 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.

(3) 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.

(4) 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.

(5) The flammability and flame spread were determined according to the requirements of building material class B2 according to DIN 4102-1.

(6) The NCO conversion in the foam was measured by ATR-FTIR on a disk cut from the middle of the foams (disk of 2 cm10 cm0.5 cm). The following process was applied:

(7) The determination of the NCO conversion by infrared spectroscopy was effected with the Fourier-transform infrared spectrometer VERTEX 70 from the company Bruker, which is equipped with the ATR (attenuated total reflection) measuring unit MIRacle from the company Pike.

(8) The foam samples to be examined were prepared and pressed onto the ZnSe ATR crystal (diameter 3 mm) of the MIRacle measuring unit by means of a ratchet mechanism. For each spectrum, 32 scans were recorded at a spectral resolution of 4 cm.sup.1, and averaged. ATR absorbance spectra were evaluated with elimination of oblique or curved baselines with the elastic band method.

(9) The determination of the spectroscopic NCO conversion was effected by means of the NCO band at 2270 cm.sup.1, which is relatively isolated spectrally. The portion of the peak area between 2200 and 2320 cm.sup.1 (A.sub.NCO) that is not overlapped by other bands and is approximately proportional to the concentration of the NCO groups (C.sub.NCO) in the analyzed foam range is evaluated.

(10) With the corresponding NCO peak area (A.sub.NCO,0) at the beginning of the foaming reaction that resulted in the examined foam and is approximately proportional to the initial NCO concentration (C.sub.NCO,0), the spectroscopic NCO conversion at the time of the analysis can be determined:
NCO conversion [%]=100(1c.sub.NCO/c.sub.NCO,0)100(1A.sub.NCO/A.sub.NCO,0).

(11) Since A.sub.NCO,0 usually cannot be measured directly, this parameter is calculated from the raw material spectra recorded in advance, taking into account the respective mass proportions in the formulation, the densities of the raw materials and refractive indices (synthetic spectrum).

(12) For mixing series of isocyanate with non-reactive raw materials, it was shown that the calculated NCO peak areas of the related synthetic mixture spectra agree well with the measured NCO peak areas, so that A.sub.NCO,0 can be reasonably calculated from the synthetic mixture spectrum of the foam formulation.

(13) Materials Employed:

(14) Isocyanate

(15) MDI-1: Desmodur 85/25, isocyanate based on diisocyanatodiphenylmethane with an NCO content of 32.5% by weight and a viscosity of 20 mPa.Math.s (DIN EN ISO 11909), containing at least 85% monomeric MDI

(16) Phosphate Disflamol DPK: (diphenyl cresyl phosphate), trade name, obtainable from Lanxess, Germany, viscosity at 20 C.: 44-49 mPa.Math.s, clear colorless liquid Disflamol TKP: (tricresyl phosphate), trade name, obtainable from Lanxess, Deutschland, viscosity at 20 C.: 70-80 mPa.Math.s, clear colorless liquid Trade name Levagard TCPP (tris(2-chloropropyl) phosphate), obtainable from Lanxess, Germany, viscosity at 20 C.: <100 mPa.Math.s, clear colorless liquid

(17) Additive 1:

(18) 25% by weight polyether polysiloxane (Tegostab B8411, Evonik), 62.5% by weight polyetherpolyol (OH number 56 mg KOH/g, functionality 2, prepared by the propoxylation of propylene glycol), and 12.5% by weight N-(3-dimethylaminopropylformamide)

(19) Blowing Agent

(20) Blowing agent 1: formic acid (98-100% by weight), CAS No. 64-18-6, obtainable from KMF Laborchemie, Lohmar/Germany

(21) Blowing agent 2: Solkane 365/227 (liquid fluorohydrocarbon as a blowing agent for foams, mixture of pentafluorobutane (87% by weight) with heptafluoropropane (13% by weight), obtainable from Solvay Fluor GmbH, Hannover, Germany

(22) Epoxide:

(23) 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

(24) A) Preparation of the EPIC Resin A

(25) At 95 C., 8000 g of MDI-1 was admixed with 2000 g of EPOXIDE. Subsequently, 1.6 ml of dimethylbenzylamine was added and mixed with stirring. The slightly exothermic reaction indicated the immediate start of the isocyanurate formation.

(26) After a reaction time of 2 hours, a sample was removed from the charge. The sample had an NCO content of 21.5% by weight. The reaction was quenched by adding 40 g of p-toluenesulfonic acid methyl ester. Thereafter, the charge was stirred for another 30 min at 95 to 80 C.

(27) The product had a viscosity at 25 C. of 3900 mPa.Math.s (DIN 53019) and an NCO content of 21.0% by weight NCO (DIN EN ISO 11909:2007).

(28) B) General Description of the Preparation of Foams 1 to 4 from Table 1:

(29) For preparing the foams according to the invention, the EPIC resin from A) and the PHOSPHATE (see Table 1) were loaded with air by means of a quick stirrer for 2 minutes. With further stirring, first the ADDITIVE 1 and then the BLOWING AGENT were added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a square-shaped paper mold (20 cm20 cm14 cm) and allowed to stand for foaming. Subsequently, the foam was annealed at 200 C. for 3 hours.

(30) C) General Description of the Preparation of Foams 5 to 6 from Table 1:

(31) The EPIC resin from Example 1 was loaded with air by means of a quick stirrer for 2 minutes. With further stirring, first the ADDITIVE 1 and then the BLOWING AGENT were added, and the reaction mixture was thoroughly mixed for another 10 s. The reaction mixture was cast into a square-shaped paper mold (20 cm20 cm14 cm) and allowed to stand for foaming.

(32) Subsequently, foam 5 was annealed at 200 C. for 3 hours.

(33) Foam 6 was not annealed,

(34) TABLE-US-00001 TABLE 1 Composition and properties of foams 1-6 Foam 1 2 3 4 5 6 EPIC resin A 400 400 400 400 400 400 (weight parts) PHOS- TCPP 77 PHATE (weight parts) DPK 75 75 (weight parts) TKP 75 (weight parts) ADDITIVE-1 28.6 27.7 28.8 27.7 27.7 27.7 BLOWING Blowing 6 6 6 6 6 AGENT agent 1 (weight parts) Blowing 60 agent 2 (weight parts) Density (kg/m.sup.3) 44 39 43 31 38 39 NCO conversion (% by 98.7 98.5 98.5 97.7 95.8 90 weight) Compression strength (kPa) 277 231 255 80 246 306 MARHE (kW/m.sup.2) 101 86 92 93 104 129