PROCESS FOR PRODUCING POLYMER FOAMS COMPRISING IMIDE GROUPS

Abstract

A process for producing a polymer foam including reacting components A to C in the presence of component D and optionally E or of an isocyanate-functional prepolymer of components A and B with component C in the presence of component D and optionally E. The polymer foam includes 35 to 75 wt % of at least one polyisocyanate component A, 5 to 50 wt % of at least one polyol component B, 1 to 10 wt % of water as component C, 0.01 to 3 wt % of at least one Lewis base component D, and optionally 0 to 5 wt % of at least one foam stabilizer component E. Component A is a condensation product including polyimide groups and obtained by condensing at least one polyisocyanate component with at least one polycarboxylic acid having at least 3 COOH groups per molecule or anhydride. The process is effected to release carbon dioxide.

Claims

1. A process for producing a polymer foam comprising reacting components A to C in the presence of component D and optionally E or of an isocyanate-functional prepolymer of components A and B with component C in the presence of component D and optionally E, the total amount of which is 100 wt %, (A) 35 to 75 wt % of at least one polyisocyanate component A, wherein 10 to 100 wt % of component A is a condensation product comprising polyimide groups and obtained by condensing at least one polyisocyanate component with at least one polycarboxylic acid having at least 3 COOH groups per molecule or anhydride thereof, (B) 5 to 50 wt % of at least one polyol component B, (C) 1.0 to 2.5 wt % of water as component C, and (D) 0.01 to 3 wt % of at least one Lewis base component D, (E) 0 to 5 wt % of at least one foam stabilizer component E, wherein said reacting is effected to release carbon dioxide.

2. The process according to claim 1 wherein water as component C is present in an amount of 1.3 to 2.5 wt %.

3. The process according to claim 1 wherein said polyol component B has an average molecular weight in the range from 200 g/mol to 6000 g/mol.

4. The process according to claim 1 wherein the polymer foam is a rigid polymer foam.

5. The process according to claim 1 wherein said component B has an OH number in the range from 10 mg KOH/g to 1000 mg KOH/g.

6. The process according to claim 1 wherein the polymer foam has a density in the range from 10 g/I to 250 g/I.

7. The process according to claim 1 wherein the Lewis base component D is selected from N-methylimidazole, melamine, guanidine, cyanuric acid, dicyandiamide and their derivatives or mixtures thereof.

8. The process according to claim 1 wherein said reacting is effected in the presence of a foam stabilizer component E comprising a siloxane copolymer.

9. The process according to claim 1 wherein said polyol component B is a polyether polyol or polyester polyol.

10. A polymer foam obtainable via the process according to claim 1.

11. A polymer foam deriving from polyisocyanates being to an extent of at least 10 wt %, condensation products comprising polyimide groups and obtained by condensing at least one polyisocyanate with at least one polycarboxylic acid having at least 3 COOH groups per molecule or anhydride thereof, polyols or an isocyanate-functional prepolymer thereof as monomers and water, including urethane, imide and urea groups in the polymer main chain.

12.-15. (canceled)

16. The process according to claim 7 wherein the Lewis base component D is N-methylimidazole.

17. The polymer foam of claim 11, wherein the polymer foam derives from polyisocyanates being to an extent of 100 wt %.

18. The polymer foam of claim 11, wherein the polymer foam has a foam density in the range from 10 kg/m.sup.3 to 250 kg/m.sup.3.

Description

EXAMPLES

[0093] Molecular weights in the examples which follow were determined by gel permeation chromatography (GPC). Polymethyl methacrylate (PMMA) was used as standard. The solvent used was dimethylacetamide (DMAc). The NCO content was determined by NCO titration. The syntheses were carried out under nitrogen, unless otherwise stated.

[0094] Preparation of MDI-imide

[0095] A 4 L four-neck flask equipped with dropping funnel, reflux condenser, internal thermometer and

[0096] Teflon tube was initially charged with 100 g of 1,2,4,5-benzenetetracarboxylic dianhydride (0.64 mol) dissolved in 1500 ml of acetone, and 0.1 g of water was added. This was followed at 20 C. by the dropwise addition of 465 g of polymeric 4,4-diphenylmethane diisocyanate (methylene diphenylene diisocyanate) having an average molar mass of 337 g/mol and a functionality of 2.5 (i.e., 2.5 isocyanate groups per molecule) (1.38 mol). The mixture was heated to 55 C. with stirring and refluxed at this temperature for a further 6 hours with further stirring. The mixture was then diluted with 1000 g of polymeric 4,4-diphenylmethane diisocyanate and heated to 55 C. with stirring. The mixture was refluxed at 55 C. for a further six hours with stirring. Subsequently, the acetone was distilled off at atmospheric pressure over a period of one hour. At the end of the distillation, the residue thus obtained was stripped with nitrogen at 70 C. and 200 mbar to obtain an MDI-imide having an isocyanate functionality of

[0097] 27% (measured via IR)

[0098] M.sub.n=3200 g/mol, M.sub.w=4850 g/mol

[0099] M.sub.w/M.sub.n=1.5

[0100] The MDI-imide thus obtained was used hereinbelow to produce the polymer foams.

[0101] Production of Polymer Foams

[0102] The examples hereinbelow demonstrate the production and properties of the polyimide polyurethanes of the present invention. The materials of the present invention were produced in the lab using a blender. To determine the physical properties, foam cubes having a volume of 20 I were produced and subsequently subjected to mechanical testing. The compositions of the starting substances are reported in Table 1.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 (comparative) (comparative) (inventive) (inventive) polyol 4.8 21.1 28.8 33.5 MDI-imide 90.1 75 67.9 63.5 stabilizer 0.2 0.8 1.1 1.3 Lewis base 0.1 0.2 0.2 0.2 blowing agent 4.8 2.9 2 1.4

[0103] The meanings are:

[0104] polyol: polypropylene glycol with average molecular weight (MW) 420 g/mol

[0105] blowing agent: water

[0106] MDI-imide: polyimide based on benzenetetracarboxylic dianhydride and polymeric methylenediphenylene diisocyanate having a free isocyanate content of 27%

[0107] stabilizer: polyether-polysiloxane copolymer

[0108] Lewis base: 1-methylimidazole

[0109] Example 1 (Comparative)

[0110] The components as per Table 1 with the exception of the MDI-imide were weighed in together pro rata for an overall batch size of 2.5 parts and then homogenized. This mixture was vigorously admixed with 22.5 parts of MDI-imide using a lab stirrer. No foam structure was produced. It proved impossible to produce a testable foam specimen.

[0111] Example 2 (Comparative)

[0112] The components as per Table 1 with the exception of the MDI-imide were weighed in together pro rata for an overall batch size of 12.5 parts and then homogenized. This mixture was vigorously admixed with 37.5 parts of MDI-imide using a lab stirrer. This produced an unstable foam, which collapsed to some extent. It proved impossible to produce a testable foam specimen.

[0113] Example 3 (Inventive)

[0114] The components as per Table 1 with the exception of the MDI-imide were weighed in together pro rata for an overall batch size of 256.8 parts and then homogenized. This mixture was vigorously admixed with 543.2 parts of MDI-imide using a lab stirrer and then poured into the cube mold. The foam rose in the mold and was left therein until fully cured.

[0115] Example 4 (Inventive)

[0116] The components as per Table 1 with the exception of the MDI-imide were weighed in together pro rata for an overall batch size of 200 parts and then homogenized. This mixture was vigorously admixed with 347.4 parts of MDI-imide using a lab stirrer and then poured into the cube mold. The foam rose in the mold and was left therein until fully cured.

[0117] Properties of Products Obtained

TABLE-US-00002 TABLE 2 Example 3 Example 4 (inventive) (inventive) density 29 36 compressive strength 0.12 0.16 relative deformation 8.3 3.7

[0118] density core density [kg/m.sup.3]

[0119] compressive strength in N/mm.sup.2 to DIN 53421/DIN EN ISO 604

[0120] relative deformation [%] to DIN 53421/DIN EN ISO 604

TABLE-US-00003 TABLE 3 Example 3 Example 4 (inventive) (inventive) density 29 36 closed-cell content 33 68 TGA 276 276

[0121] density core density [kg/m.sup.3]

[0122] closed-cell content [%] to DIN ISO 4590 [0123] TGA thermogravimetric analysis [ C.] to DIN EN ISO 11358, evaluation on basis of absolute value at 95% of starting sample mass