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 an unmodified or modified novolac polyol and 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 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 such that the propoxylation degree of said polyether polyol is between 0.33 and 2 mole propylene oxide per active hydrogen atom in the initiator and the molar ratio of ethylene oxide to propylene oxide in said polyether polyol is at least 2 characterised in that the polyfunctional isocyanate-reactive compounds further comprise an unmodified or modified novolac polyol.

2. The process according to claim 1, wherein the unmodified novolac polyol has a general chemical structure as follows: ##STR00005## wherein R is an alkylene group and the novolac polyol has an average hydroxyl functionality of from 2 to 30 calculated by dividing the weight average molecular weight of the novolac polyol by the equivalent weight of the novolac polyol.

3. The process according to claim 1, wherein the novolac polyol is the reaction product of a phenolic compound and an aldehyde.

4. The process according to claim 3, wherein the phenolic compound is selected from the group consisting of phenol, o-cresol, m-cresol, p-cresol, bisphenol A, bisphenol F, bisphenol S, alkylphenols like p-tert. butylphenol, p-tert. amylphenol, p-isopropylphenol, p-tert. octylphenol, nonylphenol, dodecylphenol, p-cumylphenol, xylenols (dimethylphenols), ethylphenols, p-phenylphenol, alpha and beta naphthols, resorcinol, methylresorcinols, cashew nut shell liquid (CNSL) such as C15 alkylphenol, halogenated phenols like p-chlorophenol, o-bromophenol, or combination of two or more thereof and wherein the aldehyde is selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, furfuryl aldehyde, glyoxal, or combinations of two or more thereof.

5. The process according to claim 1 wherein the modified novolac polyol is obtained by alkylating the phenolic hydroxyl groups of an unmodified novolac polyol with an alkylene oxide or alkylene carbonate.

6. The process according to claim 1 wherein the unmodified or modified novolac polyol is present in an amount ranging from 1 to 65 parts by weight per 100 pbw of polyfunctional isocyanate-reactive compounds.

7. The process according to claim 1, wherein the propoxylation degree of the polyether polyol is between 0.66 and 1 mole of propylene oxide per active hydrogen atom in the initiator.

8. The process according to claim 1, wherein the molar ratio of ethylene oxide to propylene oxide in said polyether polyol is between 2 and 10.

9. The process according to claim 1, wherein the hydroxyl number of said polyether polyol is between 50 and 400 mg KOH/g.

10. The process according to claim 1, wherein the polyfunctional initiator used to obtain said polyether polyol is selected from glycerol, diaminodiphenylmethane, and polymethylene polyphenylene polyamines.

11. The process according to claim 1, wherein said polyether polyol is present in amounts ranging from 5 to 80 pbw of total polyfunctional isocyanate-reactive compounds.

12. The process according to claim 1, wherein the blowing agent is selected from the group consisting of hydrocarbons, hydrofluorocarbons, hydrochlorofluoroolefins, hydrofluoroolefins, or mixtures thereof.

13. The process according to claim 1, wherein the reaction is carried out at an isocyanate index of up to 180% in order to prepare rigid polyurethane foam.

14. The process according to claim 1, wherein the reaction is carried out at an isocyanate index ranging from 180 to 1000% in order to prepare rigid urethane-modified polyisocyanurate foam.

15. A rigid polyurethane or urethane-modified polyisocyanurate foam obtained by the process as defined in claim 1.

16. A foam as defined in claim 15, wherein said foam is a layer in a sandwich panel.

17. A polyfunctional isocyanate-reactive composition containing an unmodified or modified novolac polyol as defined in claim 2 and a polyether polyol as defined in claim 1 and further auxiliaries.

18. A reaction system for preparing rigid polyurethane or urethane-modified polyisocyanurate foam comprising a) an organic polyisocyanate, b) a polyfunctional isocyanate-reactive component, c) a blowing agent and optionally d) further auxiliaries characterized in that the polyfunctional isocyanate-reactive component comprises an unmodified or modified novolac polyol as defined in claim 2 and a polyether polyol as defined in claim 1.

Description

EXAMPLES 1-6 AND COMPARATIVE EXAMPLES 1-6 AND 11

[0115] Rigid urethane-modified polyisocyanurate foams were prepared from the ingredients listed below in Table 1 (amounts are indicated in pbw).

[0116] The typical reactivity data (cream time (CT), string time (ST), free rise density (FRD), closed cell content (ccc)) were noted.

[0117] Free rise density (FRD) refers to density measured on foam samples made under atmospheric conditions (in the presence of blowing agents) according to ISO 845.

[0118] Cream time (CT) refers to the time required for the reaction mixture to change from the liquid state to a creamy state and starts to foam (expand) subsequently.

[0119] The reaction to fire was measured by the B2 flame spread test according to standard DIN 4102.

[0120] Friability was measured according to normative reference ISO C421.

[0121] The results are reported in Table 1.

TABLE-US-00002 TABLE 1 Comp Comp Comp Comp Comp Comp Comp Ex 1 Ex 2 Ex 3 Ex 4 1 2 3 4 5 6 Ex 5 Ex 6 11 Polyether A pbw 66.6 66.6 66.6 66.6 66.6 66.6 66.6 66.6 66.6 66.6 66.6 Novolac 1 pbw 13.8 13.8 10.5 13.8 Novolac 2 pbw 13.8 Novolac 3 pbw 13.8 Novolac 4 pbw 13.8 Polyether B pbw 13.8 Polyether C pbw 13.8 Polyether D pbw 13.8 Polyether E pbw 13.8 Polyether G pbw 66.6 Polyester A pbw 13.8 Polyester B pbw 66.6 Novolac 5 pbw 19.7 TEP pbw 9.2 9.2 9.2 9.2 9.2 9.2 9.2 9.2 9.2 9.2 12.5 3.2 9.2 Catalyst LB pbw 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Niax Kzero pbw 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 3000 Lactic acid pbw 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Jeffsol PC pbw 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Surfactant pbw 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 BDMA pbw 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Jeffcat pbw 0.5 0.5 0.5 0.6 0.1 0.5 0.5 0.3 0.2 0.8 0.5 0.3 1.4 TR90 water pbw 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 n-pentane pbw 12.0 12.0 12.0 12.7 10.5 11.0 11.0 11.0 9.0 12.0 12.0 11.5 12.0 Total pbw 113.5 113.5 113.5 114.2 111.5 112.4 112.5 112.2 110.1 113.8 113.5 112.7 113.5 OHv-Pol. mg 250 253 257 256 258 256 253 252 258 256 236 237 250 Blend KOH/g Required % 256 256 256 256 256 256 256 256 256 256 256 256 256 Index Suprasec pbw 181 183 185 186 183 183 181 180 181 185 170 170 181 2085 CT/ST sec/sec 12/97 12/98 12/96 12/99 14/97 10/96 10/100 10/99 13/99 15/100 11/89 10/88 12/97 FRD kg/m.sup.3 31.2 31.5 31.6 31.5 31.2 31.2 31.6 31.3 31.3 31.9 29.0 29.1 32.8 B2 cm 14.1 14.1 13.8 14.3 13.4 16.2 16.8 16.4 13.0 12.0 13.6 13.4 >17 ccc % 88.6 88.3 88.2 90.1 87.2 85.2 86.1 86.0 88.5 89.6 88.6 86.6 86.2 friability % 13.2 16.4 16.3 16.9 26.7 26.9 26.1 26.0 26.4 22.1 14.0 19.5 30.1

[0122] 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. 4 minutes, 5 minutes, etc. . . . ). Overall this demould test has proven to correlate well with an industrial laminator process.

[0123] The post expansion results are presented in FIG. 1 and the shrinkage results in FIG. 2.

[0124] These examples show that the addition of novolac polyol leads to B2 fire rated foam with low exothermicity (examples 1-4) while addition of other types of polyols either do not provide B2 rated foam (comparative example 2-4) or give high exothermicity (comparative example 1, comparative example 5). Also lower friability is obtained when novolac polyols are used. Further better pentane emulsification and foam aspect are obtained.

[0125] FIG. 1 shows that the higher exothermicity of Comparative example 1 and Comparative example 5 leads to a much worse post expansion and also in a higher shrinkage the following day (see FIG. 4).

[0126] The examples in Table 1 show that: [0127] 1) The addition of unmodified novolac to the ethoxylated polyol with PO tip leads to B2 fire rated foams (examples 1-4) while the addition of other types of polyols either do not provide B2 rated foam (comparative example 2, comparative example 3 and comparative example 4) or give high friability (comparative example 1 and comparative example 5). [0128] 2) Much higher foam friability is obtained if Novolac is added to a polyester rather than to the ethoxylated polyol with PO tip (comparative example 6) although in this case the fire rating is conserved. [0129] 3) Higher friability is also obtained if a Novolac polyol is used in combination with the ethoxylated polyol with PO tip instead of unmodified Novolac (Example 6 relative to Example 5), although B2 fire rating remains conserved. [0130] 4) When polyether A is replaced by polyether G (Comparative example 11), the resulting foam is not B2 fire rated although the composition of the Primary/Secondary of groups of the two polyols is the same (85/15 secondary/primary OH for polyol A and G), as well as the OHv=165 and the initiator used (glycerol). This shows that the OH terminal group composition is not relevant to achieve the goal of the current invention, differently from what is described in US 2013/059934. Furthermore in Comparative example 11 the friability is much higher compared to the examples according to the invention.

[0131] FIGS. 1,2,3,4,5 and 6 show post expansion and shrinkage figures. [0132] 1) FIGS. 1 and 4 show the higher post expansion and the higher shrinkage (after 1 day) of Comparative example 1 and Comparative example 5 relative to the inventive examples (Example 1, Example 2, Example 3 and Example 4). [0133] 2) FIGS. 2 and 5 show the much higher post expansion of comparative example 6 relative to Example 1, with comparable shrinkage. This shows that the beneficial effect of Novolac described in US2012/009407 are not sufficient to pursue the target of this invention. This is also continued by Comparative example 11 and comparative example 12 formerly discussed. [0134] 3) FIGS. 3 and 6 show that post expansion of Example 5 and Example 6 are similar and shrinkage as well. This suggests that both unmodified Novolac and Novolac polyols could be used in combination to the ethoxylated polyol with PO tip to achieve low post expansion, although the disadvantage of the higher friability with the Novolac polyol makes the use of the unmodified Novolac the preferred choice to exploit in full the benefits of the concept.

EXAMPLE 7 AND COMPARATIVE EXAMPLES 7-10 AND 12

[0135] A series of B2 fire rated rigid PUR foams were prepared from the ingredients listed below in Table 2 (amounts are indicated in pbw).

[0136] The typical reactivity data (cream time (CT), string time (ST), free rise density (FRD), closed cell content (ccc)) were noted.

[0137] The reaction to fire was measured by the B2 flame spread test according to standard DIN

[0138] Results are reported in Table 2.

TABLE-US-00003 TABLE 2 Ex 7 Comp 7 Comp 8 Comp 9 Comp 10 Comp 12 Polyether A pbw 20.0 Novolac 1 pbw 6.0 6.0 6.0 Glycerol pbw 5.5 5.5 5.5 5.5 5.5 5.5 Polyester C pbw 26.0 TCPP pbw 20.5 20.5 20.5 20.5 20.5 20.5 Polyether F pbw 26.0 Novolac 5 pbw 26.0 Polyether D pbw 30.0 30.0 30.0 30.0 30.0 Polyether G 20 Polyether H TEP pbw 11.6 11.6 11.6 11.6 11.6 11.6 Polyester B pbw 20.0 PMDETA pbw 0.2 0.2 0.2 0.2 0.2 0.2 Catalyst LB pbw 0.3 0.3 0.3 0.3 0.3 0.3 Jeffcat TR 52 pbw 0.5 0.5 0.5 0.5 0.5 0.5 Surfactant pbw 2.8 2.8 2.8 2.8 2.8 2.8 DMCHA pbw 0.25 0.10 0.15 0.20 0.20 0.25 water pbw 2.5 2.5 2.5 2.5 2.5 2.5 n-pentane pbw 4.7 4.0 4.0 5.0 5.3 4.7 Total pbw 104.80 103.95 104.00 105.05 105.35 104.80 OHv-Pol. mg 460 464 464 465 460 460 Blend KOH/g Required Index % 130 130 130 130 130 130 Suprasec 2085 pbw 156 156 156 158 156 156 CT/ST sec/sec 14/78 15/79 16/78 17/78 15/77 15/80 FRD kg/m.sup.3 33.5 33.7 33.3 34.0 33.3 34.0 B2 cm 14.0 12.1 13.0 14.4 14.5 >19 ccc % 88.7 90.1 86.0 89.7 85.4 88.1

[0139] In the case of PUR formulations, a given combination of unmodified Novolac and an EO polyol with PO tip having 77% EO and 23% PO and an OHv=240 (see Example 7 according to the invention) was systematically replaced by other polyols with similar OHv, all expected to provide fire rated B2 foams (see Comparative examples 7, 8, 9, 10) and to be compared in terms of demolding performance.

[0140] FIGS. 7 and 8 show post expansion and shrinkage figures.

[0141] The combination of unmodified Novolac and the ethoxylated polyol with PO tip shows lower post expansion and lower shrinkage compared to the use of other polyols having the same OHv level, such as a polyester, an ethoxylated polyether and even Novolac initiated polyol.

[0142] In particular Comparative example 9, relative to Example 7 according to the invention, shows that in the case of PUR the choice of unmodified Novolac over the Novolac polyol is preferred if compared to the examples described in table 1 (PIR formulations).

[0143] Furthermore, in the case of Comparative example 8, splits were observed in the foam core of panels.

[0144] Finally comparative example 12 confirms that also in the case of PUR formulations, when the polyether A is replaced by polyether G, the resulting foam is not anymore B2 fire rated although the composition of the Primary/Secondary of groups of the two polyols is the same (85/15 secondary/primary OH for polyol A and G) or similar (nearly 100% secondary OH for polyol H), as well as the OHv=165 and the initiator used (glycerol). Therefore the OH terminal group composition is not relevant to pursue the target of this invention, differently from what described in US 2013/059934. Furthermore Comparative example 12 confirms that the beneficial effect of Novolac described in US2012/009407 is not sufficient to pursue the target of this invention, if not combined with the EO polyol with PO tip (inventive Example 7).