Process for making rigid polyurethane or urethane-modified polyisocyanurate foams

Abstract

Process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams from polyisocyanates and polyfunctional isocyanate-reactive compounds in the presence of blowing agents wherein the polyfunctional isocyanate-reactive compounds comprise a polyether polyol having a hydroxyl number of between 50 and 650 mg KOH/g obtained by reacting a polyfunctional initiator first with ethylene oxide and subsequently with propylene oxide wherein the propoxylation degree is between 0.33 and 2 mole propylene oxide per active hydrogen atom in the initiator and wherein the molar ratio of ethylene oxide to propylene oxide in said polyether polyol is at least 2.

Claims

1. A process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams comprising reacting polyisocyanates and polyfunctional isocyanate-reactive compounds in the presence of blowing agents wherein the polyfunctional isocyanate-reactive compounds comprise a polyether polyol having a hydroxyl number of between 50 and 650 mg KOH/g obtained by reacting a polyfunctional initiator first with ethylene oxide and subsequently with propylene oxide such that the propoxylation degree of said polyether polyol is between 0.33 and 2 moles propylene oxide per active hydrogen atom in the polyfunctional initiator and the molar amount of ethylene oxide is from 2 to 15 moles per active hydrogen in the polyfunctional initiator; and wherein the molar ratio of ethylene oxide to propylene oxide in said polyether polyol is at least 2.

2. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the propoxylation degree of said polyether polyol is between 0.66 and 1 mole of propylene oxide per active hydrogen atom in the initiator.

3. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the molar ratio of ethylene oxide to propylene oxide is between 2 and 10.

4. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the hydroxyl number of said polyether polyol is between 50 and 400 mg KOH/g.

5. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the polyfunctional initiator used to obtain said polyether polyol is selected from glycerol, diaminodiphenylmethane and polymethylene polyphenylene polyamines.

6. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein said polyether polyol is present in an amount ranging from 5 to 80 pbw per 100 parts by weight of the polyfunctional isocyanate-reactive compounds.

7. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the blowing agents are selected from the group consisting of hydrocarbons, hydrofluorocarbons, hydrochlorofluoroolefins, hydrofluoroolefins and any mixture thereof.

8. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the reacting is carried out at an isocyanate index of up to 240% in order to prepare rigid polyurethane foam.

9. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the reacting is carried out at an isocyanate index of from 250 to 1000% in order to prepare rigid urethane-modified polyisocyanurate foam.

10. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, wherein the reacting is carried out in the presence of flame retardants in an amount of 10 to 60 pbw per 100 parts by weight of the polyfunctional isocyanate-reactive compounds.

11. A rigid polyurethane or urethane-modified polyisocyanurate foam obtained by the process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams as defined in claim 1.

12. The rigid polyurethane or urethane-modified foam according to claim 11 wherein said rigid polyurethane or urethane-modified polyisocyanurate foam satisfies the requirements of fire class B2 according to DIN 4102 test.

13. The rigid polyurethane or urethane-modified foam as defined in claim 11 wherein said rigid polyurethane or urethane-modified polyisocyanurate foam is a layer in a sandwich panel.

14. The process for preparing rigid polyurethane or urethane-modified polyisocyanurate foams according to claim 1, where the amount of ethylene oxide is 2.5 to 8.5 moles per active hydrogen atom in the polyfunctional initiator.

Description

EXAMPLE 1

(1) Rigid polyurethane foams were prepared from the ingredients listed below in Table 1 (amounts are indicated in pbw) using a Cannon S10 High Pressure PU mixing machine. The apparatus is designed to perform high pressure (up to 170 bar) mixing of two liquid streams at lab scale. The polyol blend and isocyanate tanks require 2 kg of material and are kept at 23? C. All additives including pentane were added to the polyol blend by mechanical stirring prior to loading it into the polyol blend tank.

(2) A curve of foam height versus time was recorded with an in-house designed dynamic flow tube equipment, which is commonly used in the industry. The parameter % height at string time was noted for each of the curves. The typical reactivity data (cream time, string time, free rise density) were also noted.

(3) A mould of 40 cm?40 cm?10 cm was used to measure post-expansion after demoulding. The mould was left open at one side (40 cm?10 cm) and tilted under an angle of 6 degrees in order to simulate the conditions of overpack and flow present on an industrial laminator. Metal facings were present at the bottom and top of the mould at a temperature similar to an industrial laminator process. At a given point in time (demould time), the panel was removed from the mould and the maximum post expansion in the central 20 cm?20 cm area of the panel was measured. After 24 hours, the panel was cut to pieces to examine the occurrence of foam splits. The overall experiment was typically repeated for a number of demould times (e.g. 5 minutes, 6 minutes, etc. . . . ). Overall this demould test has proven to correlate well with an industrial laminator process.

(4) The reaction to fire was measured by the B2 flame spread test according to standard DIN 4102.

(5) The results are reported in Table 2.

(6) TABLE-US-00002 TABLE 1 Comparative 1 Inventive 1 Polyether A 39.40 39.40 Polyether C 19.00 Polyether D 19.00 Polyester A 15.00 15.00 Jeffcat PMDETA 0.25 0.25 Catalyst LB 0.36 0.33 Jeffcat DMCHA 0.05 0.20 TCPP 18.85 18.85 TEP 5.00 5.00 Surfactant 2.00 2.00 Water 2.00 2.00 n-pentane 5.00 5.00 Total polyol blend 106.91 107.03 Suprasec 2085 123.4 123.3 Isocyanate Index 130 130

(7) TABLE-US-00003 TABLE 2 Comparative 1 Inventive 1 Reactivity test with Cannon S10 Cream time s 7 6 String time s 52 50 Free rise density g/L 36.1 35.6 Dynamic flow tube test with Cannon S10 Foam height at string time % 70 78 Demould test with Cannon S10 Post-expansion after 4 min mm 7.3 6.4 Post-expansion after 5 min mm 6.1 5.3 Post-expansion after 6 min mm 5.5 4.6 Presence of foam splits after yes/no yes no 6 min demoulding DIN 4102 result (average) cm 14.0 14.5 DIN 4102 classification B2/B3 B2 B2

EXAMPLE 2

(8) Foams were prepared from the ingredients listed in Table 3 and tested in the same way as in Example 1 above. The results are listed in Table 4.

(9) TABLE-US-00004 TABLE 3 Comparative Comparative Inventive Inventive 2 3 2 3 Polyether B 33.00 33.00 33.00 33.00 Polyether E 25.00 Polyether F 25.00 Polyether G 25.00 Polyether H 25.00 Polyester A 15.00 15.00 15.00 15.00 Jeffcat PMDETA 0.25 0.25 0.25 0.25 Catalyst LB 0.50 0.50 0.50 0.50 Jeffcat DMCHA 0.05 0.25 0.10 0.15 TCPP 19.00 19.00 19.00 19.00 TEP 5.00 5.00 5.00 5.00 Surfactant 2.00 2.00 2.00 2.00 Water 2.20 2.20 2.20 2.20 n-pentane 4.00 4.00 4.00 4.00 Total polyol blend 106.00 106.20 106.05 106.10 Suprasec 2085 124.3 124.2 124.0 123.8 Isocyanate Index 130 130 130 130

(10) TABLE-US-00005 TABLE 4 Comparative 2 Comparative 3 Inventive 2 Inventive 3 Reactivity test Cream time s 8 6 8 6 String time s 46 51 48 50 Free rise density g/L 36.0 36.8 35.8 36.8 Dynamic flow tube test Foam height at string time % 70 77 74 76 Demould test Post-expansion after 5 min mm 6.4 4.2 5.4 4.8 Post-expansion after 6 min mm 5.5 3.4 4.7 4.1 Presence of foam splits yes/no yes no no no after 6 min demoulding DIN 4102 result (average) cm 13.0 17.0 14.0 14.5 DIN 4102 classification B2/B3 B2 B3 B2 B2

EXAMPLE 3

(11) Foams were prepared from the ingredients listed in Table 5 and tested in the same way as in Example 1 above. The results are listed in Table 6.

(12) TABLE-US-00006 TABLE 5 Comparative 4 Comparative 5 Inventive 5 Polyether A 39.40 39.40 39.40 Polyether I 19.00 Polyether J 19.00 Polyether K 19.00 Polyester A 15.00 15.00 15.00 Jeffcat PMDETA 0.25 0.25 0.25 Catalyst LB 0.50 0.50 0.50 Jeffcat DMCHA 0.05 0.30 0.15 TCPP 18.85 18.85 18.85 TEP 5.00 5.00 5.00 Silicone surfactant 2.00 2.00 2.00 Water 2.00 2.00 2.00 n-pentane 5.00 5.00 5.00 Total polyol blend 107.05 107.30 107.15 Suprasec 2085 123.8 123.8 123.8 Isocyanate Index 130 130 130

(13) TABLE-US-00007 TABLE 6 Compar- Compar- Inven- ative 4 ative 5 tive 5 Reactivity test Cream time s 9 6 8 String time s 51 47 50 Free rise density g/L 34.6 35.5 35.1 Dynamic flow tube test Foam height at string time % 72 76 76 Demould test Post-expansion after 6 min mm 6.2 4.4 4.7 Post-expansion after 7 min mm 5.1 4.0 4.2 Presence of foam splits after yes/no yes no no 7 min demoulding DIN 4102 result (average) cm 13.5 19.0 13.5 DIN 4102 classification B2/B3 B2 B3 B2

EXAMPLE 4

(14) Rigid urethane-modified polyisocyanurate foams were prepared from the ingredients listed in Table 7 and tested in the same way as in Example 1 above. The amount of catalyst was adjusted so as to keep the string time in all samples the same. The results are listed in Table 8.

(15) TABLE-US-00008 TABLE 7 Comparative 6 Comparative 7 Inventive 6 Polyether C 60.00 Polyether D 60.00 Polyether L 60.00 Polyether M 15.00 15.00 15.00 Jeffcat TR 90 0.05 1.10 0.60 NIAX Kzero 3000 1.30 1.30 1.30 Catalyst LB 0.40 0.40 0.40 Lactic Acid (90 wt % 1.20 1.20 1.20 in water) TCPP 6.50 6.50 6.50 TEP 9.50 9.50 9.50 Jeffsol PC 3.00 3.00 3.00 Silicone surfactant 3.10 3.10 3.10 Water 0.60 0.60 0.60 n-pentane 11.50 11.50 11.50 Total polyol blend 112.15 113.20 112.70 Suprasec 2085 175 175 175 Isocyanate Index 330 330 330

(16) TABLE-US-00009 TABLE 8 Compar- Compar- Inven- ative 6 ative 7 tive 6 Reactivity test Cream time s 5 3 4 String time s 47 46 48 Free rise density g/L 34.2 34.5 34.6 Panel Density Density 40 ? 40 ? 10 cm g/L 43.8 41.1 40.6 panels (average) Demould test Post-expansion after 3 min mm 4.3 5.3 3.6 Post-expansion after 4 min mm 3.8 3.8 2.5 Presence of foam splits after yes/no yes no no 3 min demoulding DIN 4102 result (average) cm 9.5 15.3 11.3 DIN 4102 classification B2/B3 B2 B3 B2

(17) In the examples above it can each time be seen that the comparative examples with ethoxylated polyols are able to pass the DIN 4102 test but have a number of processing weaknesses such as low height at string time, high post expansion in the demould test and the occurrence of foam splits at critical demould times. The other comparative examples with propoxylated polyethers do not have these processing limitations seen with ethoxylated polyethers but they fail to pass the DIN4102 test.

(18) It is seen in all 4 examples that the use of ethoxylated polyethers with a propylene oxide tip according to the invention have processing characteristics very close to propoxylated polyethers (low post expansion, high height at string time, no foam splits at demoulding) but surprisingly, they still pass the DIN4102 test in all of the above examples.

(19) On the basis of state of the art literature, this result was not to be expected since the urethane bond formed with a propylene oxide tip is generally thought to be weak in a test such as DIN4102. The Handbook Chemistry and Technology of Polyols for Polyurethanes (Dr. Mihail Ionescu) says on page 547 that Polyurethanes based on oligo-polyols with primary hydroxyl groups are more thermostable than the polyurethanes derived from polyols with secondary groups.