PROCESS FOR THE PREPARATION OF A POLYURETHANE FOAM

Abstract

The present invention relates to processes for the preparation of polyurethane foams comprising a step wherein a chemical compound with a low particle size releases a chemical and/or physical blowing agent by decomposition, polyurethane foams prepared by such processes as well as compositions comprising at least one polyol and a chemical compound with a low particle size capable of releasing a chemical and/or physical blowing agent by thermally- and/or chemically-induced degradation and uses of such compositions.

Claims

1. A process for the preparation of a polyurethane foam or a modified polyurethane foam, the process comprising a step wherein a chemical compound releases a chemical and/or physical blowing agent by thermally- and/or chemically-induced decomposition wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μm.

2. The process according to claim 1 wherein the chemical compound releases the chemical and/or physical blowing agent by thermally-induced decomposition.

3. The process according to claim 1 wherein the chemical compound releases the chemical and/or physical blowing agent by chemically-induced decomposition.

4. The process according to claim 1 wherein the chemical compound is an inorganic carbonate.

5. The process according to claim 1 wherein the chemical compound is a hydrate of an inorganic salt.

6. The process according to claim 1 wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or above 10 nm.

7. The process according to claim 1, wherein the process comprises the steps of a) preparing a suspension comprising the chemical compound and at least one polyol, and b) contacting the suspension formed in step a) with a composition comprising at least one isocyanate to prepare a polyurethane foam wherein a chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μm.

8. The process of claim 7, wherein the process comprises the steps of a.sub.1) preparing a suspension comprising the chemical compound and at least one polyol, a.sub.2) subjecting the suspension formed in step a.sub.1) to a treatment to reduce the particle size distribution of the chemical compound, and b) contacting the suspension formed in step a.sub.2) with a composition comprising at least one isocyanate to prepare a polyurethane foam wherein a chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μm.

9. The process according to claim 8 wherein the treatment to reduce the particle size distribution comprises a milling step.

10. The process according to claim 1, wherein the process comprises the steps of m1) preparing a suspension comprising the chemical compound and a milling solvent, m2) subjecting the suspension formed in step m1) to a treatment to reduce the particle size distribution of the chemical compound, m3) removing the milling solvent by evaporation m4) preparing a suspension of the chemical compound formed in step m3) in the A-side or in one or several components of the A-side, and m5) contacting the suspension formed in step m4) with a composition comprising at least one isocyanate to prepare a polyurethane foam wherein a chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μm.

11. The process according to claim 10 wherein the treatment to reduce the particle size distribution comprises a milling step.

12. A polyurethane foam or a modified polyurethane foam obtainable obtained by the process of claim 1.

13. The foam of claim 12 comprising cells with an average cell size measured according to ASTM D 3576 from 10 nm to 1 μm.

14. A composition comprising at least one polyol and a chemical compound capable of releasing a chemical and/or physical blowing agent by thermally- and/or chemically-induced degradation wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μm.

15. (canceled)

16. The process according to claim 2 wherein the chemical compound releases the chemical and/or physical blowing agent by thermally-induced decomposition in the absence of an acidic activator.

17. The process according to claim 3 wherein the chemical compound releases the chemical and/or physical blowing agent by chemically-induced decomposition in the presence of an acidic activator.

18. The process according to claim 17 wherein the acidic activator is citric acid and/or formic acid.

19. The process according to claim 4 wherein the inorganic carbonate is NaHCO.sub.3.

20. The process according to claim 5 wherein the hydrate of an inorganic salt is a hydrate of sodium sulphate.

21. The process according to claim 9 wherein the treatment to reduce the particle size distribution comprises a milling step using a ball mill.

Description

EXAMPLES

Example 1: Preparation of Polyol Mixture

[0062] 13.5 wt % NaHCO.sub.3 (Bicar® from Solvay) was dispersed in a polyol mixture comprising 16.7 g IXOL® B251, 50.0 g Stepanol® 2412 and 33.3 g Voranol® RN 490 by using a PENDRAULIK overhead dissolver at 10000 rpm for 30 min. Subsequently, the resulting mixture was subjected to a milling step in a bead mill DISPERMAT® SL-C 25 (manufacturer: VMA-Getzmann GmbH) using ZrO2 beads (diameter: 0.5 mm) at 200 rpm for 12.5 h. Subsequently, the mixture was subjected to a sonication step for 1 h.

[0063] The particle size distribution of the NaHCO.sub.3 in the resulting suspension was measured as described above and showed a D50 of 0.85 μm.

[0064] Table 1 shows the D50 values achieved with various milling times and optional sonication (1 h).

TABLE-US-00001 TABLE 1 Conditions D50 (μm) Bicar ®, initial 10.5 Milling 5.5 h 4.1 Milling 5.5 h 2.4 & sonication Milling 12.5 h 1.8 Milling 12.5 h 0.85 & sonication

Example 1b: Preparation of the A-Side with Milling Solvent

[0065] NaHCO.sub.3 (Bicar® from Solvay) is dispersed in Galden® HT55 by using a PENDRAULIK overhead dissolver at 3000 rpm for 1 hour to give 10 kg of a slurry containing 40 wt % NaHCO.sub.3. The suspension is grinded by ball milling (Netzsch Zeta® RS) with ZrO.sub.2 beads for 4 h. The particle size distribution expressed as a D50 achieved in this step is from 50 to 150 nm depending on the total milling time. The slurry is then evaporated on a rotary evaporator and the solid obtained is re-dispersed in a polyol mixture comprising 16.7 g IXOL® B251, 50.0 g Stepanol® 2412 and 33.3 g Voranol® RN 490 by using a PENDRAULIK overhead dissolver at 10000 rpm for 30 min. Afterwards other components of the A-side are added to this polyol/NaHCO.sub.3 mixture.

Example 2: Manufacture of Polyurethane Foams (PU Panel)

[0066] The polyol suspensions from Examples 1 and 1b are used to prepare a polyurethane foam using the components as shown in the table below:

TABLE-US-00002 Part by Compound Type weight Stepanpol ® 3152 Aromatic Polyester polyol 100 Trichloropropylphosphate Flame retardant 18.7 (TCPP) NaHCO.sub.3 Chemical compound 8 Methylendiphenyldiisocyanat Isocyanate 190 (MDI)

[0067] 100 g of the polyol mixture prepared in example 1 and the flame retardant were stirred using a PENDRAULIK overhead dissolver in a 500 mL paper cup.

[0068] Subsequently, MDI was added and stirring continued at 2500 rpm for 10 s after which the mixture looked uniform and bubbles start to appear. After the stirrer was stopped, the mixture was poured into a 1 L paper cup to allow the foam to expand and cure for at least one day. The foam obtained can be used to prepare discontinuous panels.

Example 3: Spray Foaming

[0069] A polyurethane foam (spray foam) was prepared by conventional means using the components as shown in the table below. The

TABLE-US-00003 Type Compound pbw* Polyester polyol Stepanpol ® PS 2412 80 Chemical NaHCO.sub.3 5 compound Flame retardant TCPP 38 Surfactant Tegostab ® B8444 1.5 Catalyst PMDETA 1.5 Isocyanate Methylendiphenyldiisocyanat (MDI) 103 *represents as parts per hundred of polyols by weight

Example 4: Manufacture of Polyisocyanurate Foams (PIR Panel)

[0070] The polyol suspensions from Examples 1 and 1b are used to prepare a polyisocyanurate foam using the components as shown in the table below:

TABLE-US-00004 Part by Compound Type weight Stepanpol ® 3152 Aromatic Polyester polyol 80 Trichloropropylphosphate Flame retardant 22 (TCPP) N,N,N′,N″,N″- Amine based catalyst 1.5 Pentamethyldiethylenetriamine (PMDETA) Tegostab B 8444 Surfactant 1.5 NaHCO.sub.3 Chemical compound 7.5 Water Coblowing agent 1.5 Methylendiphenyldiisocyanat Isocyanate 191 (MDI) An MDI index of 200 was applied to prepare the polyisocyanurate foams.

[0071] 80 g of the polyol mixture prepared in example 1 or 1b, the catalyst, the flame retardant and the surfactant are stirred using a PENDRAULIK overhead dissolver in a 500 mL paper cup. Subsequently, MDI is added and stirring continues at 2500 rpm for 10 s after which the mixture looks uniform and bubbles start to appear. After the stirrer was stopped, the mixture is poured into a 1 L paper cup to allow the foam to expand and cure for at least one day. The foam obtained can be used to prepare discontinuous panels.