PROCESS FOR PRODUCING POLYURETHANE/POLYISOCYANURATE (PUR/PIR) RIGID FOAMS

Abstract

The invention relates to a process for producing polyurethane/polyisocyanurate rigid foams by reacting a specific reaction mixture in the presence of a catalyst component containing potassium formate and to the polyurethane/polyisocyanurate rigid foams produced according to said method.

Claims

1. A process for producing a rigid polyurethane/polyisocyanurate (PUR/PIR) foam comprising reacting a reaction mixture comprising: A) a polyisocyanate component; B) an isocyanate-reactive component comprising: B1) a polyol component, B2) a catalyst component, and B3) optionally auxiliary and additive substances; and C) a physical blowing agent wherein: (1) the polyol component B1) comprises at least 40% by weight, based on the total weight of the polyol component B1), of a polyol B1.a) comprising one or more of a polyester polyol, and a polyether ester polyol, (2) the catalyst component comprises potassium formate B2.a), (3) the reaction mixture contains less than 0.3% by weight of water and less than 0.2% by weight of formic acid, and (4) the reaction mixture has an isocyanate index of ≥150.

2. The process as claimed in claim 1, wherein the reaction mixture further contains less than 0.20% by weight of naphthenic acids.

3. The process as claimed in claim 1, wherein the reaction mixture comprises at least 55% by weight, based on the total weight of the polyol component B1), of a polyol B1.a) comprising one or more of a polyester polyol, and a polyether ester polyol.

4. The process as claimed in claim 3, wherein the polyol B1.a) is present in a proportion of 55.0-98.0% by weight based on the total weight of the component B1).

5. The process as claimed in claim 1, wherein the component B) of the reaction mixture comprises: 50.0% to 90.0% by weight of at least one polyester polyol and/or polyether ester polyol B1.a) having a hydroxyl number in the range from 80 mg KOH/g to 290 mg KOH/g determined according to DIN 53240, 1.0% to 10.0% by weight of at least one polyol component B1.b) comprising one or more of a polyether polyol, a polycarbonate polyol, and a polyether-polycarbonate polyol, in each case having a hydroxyl number in the range from 300 mg KOH/g to 600 mg KOH/g determined according to DIN 53240, and optionally further isocyanate-reactive components B1.c), wherein the reported % by weight values are in each case based on the total weight of the composition B).

6. The process as claimed in claim 1, wherein the potassium formate is present in an amount of 0.1%-4.0% by weight, based on the total weight of component B).

7. The process as claimed in claim 1, wherein the component B) of the reaction mixture comprises: 50.0% to 90.0% by weight of at least one polyester polyol and/or polyether ester polyol B1.a) having a hydroxyl number in the range from 80 mg KOH/g to 290 mg KOH/g determined according to DIN 53240, 1.0% to 10.0% by weight of at least one polyether polyol B1.b) having a hydroxyl number in the range from 300 mg KOH/g to 600 mg KOH/g determined according to DIN 53240, 0.0% to 5.0% by weight of at least one low molecular weight isocyanate-reactive compound B1.c) having a molar mass M.sub.n of less than 400 g/mol, 1.0% to 30.0% by weight of at least one flame retardant B.3), and 0.1% to 4.0% by weight of potassium formate B.2a), wherein the reported % by weight values are in each case based on all components of the isocyanate-reactive composition B), wherein component A) comprises a mixture of diphenylmethane-4,4′-diisocyanate with isomeric and higher-functional homologs, and wherein the reaction mixture has an isocyanate index of ≥150 to ≤450.

8. The process as claimed in claim 1, wherein the catalyst component B2) comprises, based on the total weight of the catalyst component B2), 15-100% by weight of potassium formate and 0-85% by weight of an aminic catalyst B2.b).

9. The process as claimed in claim 1, wherein the reaction mixture further comprises a carbamate.

10. The process as claimed in claim 1, wherein the reaction mixture comprises a flame retardant comprising tris(chloro-2-propyl) phosphate (TCPP), triethyl phosphate (TEP), or a mixture thereof.

11. The process as claimed in claim 1, wherein the blowing agent C) is a physical blowing agent comprising one or more of a hydrocarbon, a halogenated ether, and a (per)fluorinated hydrocarbon.

12. The process as claimed in claim 1, further comprising applying the reaction mixture onto a moving outerlayer using a curtain coater.

13. A rigid polyurethane/polyisocyanurate foam obtained by the process of claim 1.

14. A composite element comprising one or two outerlayers and the rigid polyurethane/polyisocyanurate foam as claimed in claim 13.

15. The composite element as claimed in claim 14, wherein at least one outerlayer is made of metal.

16. A wall element, profiled roof element, industrial door, truck body, or transport container comprising the composite element of claim 15.

Description

EXAMPLES

[0137] The following compounds are employed for production of the rigid PUR/PIR foams:

TABLE-US-00001 B1.a-P1 Polyester polyol produced from phthalic anhydride, adipic acid, monoethylene glycol and diethylene glycol, OH number 240 mg KOH/g, from Covestro Deutschland AG, B1.a-P2 Stepanpol PS 2412, aromatic polyester polyol based on phthalic anhydride and diethylene glycol, containing 3-10% by weight of TCPP, OH number 240 mg KOH/g, from Stepan, B1.a-P3 Aliphatic polyester polyol produced by reacting a mixture of adipic acid, succinic acid and glutaric acid with ethylene glycol, OH number 216 mg KOH/g, from Covestro Deutschland AG, B1.b-P4 Polyether polyol based on ortho-toluenediamine, ethylene oxide and propylene oxide having an OH number of 415 mg KOH/g, from Covestro Deutschland AG, B1.b-P5 Polyether polyol based on propylene glycol, propylene oxide and ethylene oxide having 90% primary OH groups and an OH number of 28 mg KOH/g, from Covestro Deutschland AG, B3.b-1 Tris(1-chloro-2-propyl) phosphate (TCPP) from Lanxess GmbH B3.b-2 Triethyl phosphate (TEP) from Lanxess GmbH B3.a-1 Polyether polysiloxane copolymer Tegostab ® B8443 from Evonik. B1.c-P6 Half ester of phthalic anhydride and diethylene glycol, OH number 795 mg KOH/g, from Covestro Deutschland AG, A-1 Desmodur ® 44V70L polymeric PolyA-1 based on 4,4- diphenylmethane diisocyanate having an NCO content of about 31.5% by weight from Covestro Deutschland AG Carbamate 2-Hydroxypropylcarbamate, 40-60% in ethanediol, carbon dioxide- liberating additive from Covestro Deutschland AG B2.b-1 Dimethylbenzylamine, Covestro Deutschland AG B2.c-1 Potassium acetate (IUPAC name: potassium ethanoate), 25% by weight in diethylene glycol (DEG) B2.c-2 12.5% by weight of potassium acetate (IUPAC name: potassium ethanoate) and 25% by weight of potassium 2-ethylhexanoate in diethylene glycol (DEG) B2.c-3 Potassium 2-ethylhexanoate, 50% by weight in DEG:NMP (=1:2) B2.a-1 Potassium formate (IUPAC name: potassium methanoate), 36% by weight in monoethylene glycol C-1 n-Pentane [F+; Xn; N]

[0138] Measurement of Reaction and Product Properties of Produced Rigid PUR/PIR Foams:

[0139] The foam pressure and the flow properties during the foaming reaction may be determined in a rigid foam tube by processes known to those skilled in the art. To this end the reaction mixture is produced in a paper cup as per the description hereinabove and the filled paper cup is introduced from below into a temperature-controlled tube. The rise profile and the exerted foam pressure are continuously captured during the reaction.

[0140] Measurement of apparent density was performed according to DIN EN ISO 845 (October 2009).

[0141] Measuring Fiber Time:

[0142] The fiber time is generally the time after which for example in the polyaddition between polyol and polyisocyanate a theoretically infinitely extended polymer has formed (transition from the liquid into the solid state). The fiber time may be determined experimentally by dipping a thin wooden stick into the foaming reaction mixture, produced here in a test package having a base area of 20×20 cm.sup.2, at short intervals. The time from the mixing of the components until the time at which threads remain hanging off the rod when removed is the fiber time.

[0143] Measurement of Tack-Free Time:

[0144] Once dispensing was complete the tack-free time of the foam surface was determined according to TM 1014:2013 (FEICA).

[0145] Measurement of Impression Depth:

[0146] The impression depth was determined on freshly produced laboratory foams in test packages having a base area of 20×20 cm.sup.2 by measurement of the penetration depth of a piston with a defined piston pressure after the reported times during the curing phase.

Examples 1-4): Production of Pentane-Blown Foams, with Potassium Carboxylate Catalysts, without Amine Catalyst

[0147] All foams are produced by hand mixing on the laboratory scale in test packages having a base area of 20×20 cm.sup.2 (for formulations and reaction properties see table 1). The polyol component containing the polyols, additives and catalysts are initially charged. Shortly before mixing, the polyol component is temperature-controlled to 23-25° C., whereas the polyisocyanate component is brought to a constant temperature of 30-35° C. Subsequently, with stirring, the polyisocyanate component is added to the polyol mixture, to which the amount of pentane necessary to achieve an apparent core density of 37-38 kg/m.sup.3 has previously been added. The mixing time is 6 seconds and the mixing speed of the Pendraulik stirrer is 4200 min-1. After 2.5 or 5 minutes the foam hardness is determined using an indentation method and after 8-10 minutes the maximum core temperature is determined. The foam is then stored for a further 24 hours 20 at 23° C. to allow postreaction.

TABLE-US-00002 TABLE 1 Production and properties of pentane-blown foams, with potassium carboxylate catalysts, without amine catalyst. Formulation, Exam- Exam- reaction Exam- ple ple Exam- properties Unit ple 1* 2* 3* ple 4 B1.a-P1 pbw 66.5 66.5 66.5 66.5 B1.b-P4 pbw 5.2 5.2 5.2 5.2 B3.b-1 pbw 20.8 20.8 20.8 20.8 B3.b-2 pbw 5.2 5.2 5.2 5.2 B1.c-P6 pbw 2.3 2.3 2.3 2.3 B3.a-1 pbw 3.0 3.0 3.0 3.0 B2.c-1 pbw 4.300 B2.c-2 pbw 4.300 B2.c-3 pbw 3.800 B2.a-1 pbw 2.900 A-1 pbw 189.2 189.0 167.4 190.8 C-1 pbw 14.6 14.6 13.5 13.7 C-1 % by 4.7 4.7 4.7 4.4 Index 330.0 330.0 330.0 330.0 Cream time s 16 15 12 14 Fiber time s 46 46 45 46 Tack-free time s 65 69 92 55 Apparent core kg/m.sup.3 37.0 37.3 37.7 37.5 density Foam pressure hPa 266.0 248.0 192.0 382.0 Maximum ° C. 170.1 170.3 166.0 175.3 core temperature Impression mm 9.0 9.5 13.0 7.0 depth after 2.5 min Impression mm 10.0 10.5 13.5 7.5 depth after 5 min

[0148] It is apparent from table 1 that less pentane as blowing agent is required to achieve the target density of about 37 kg/m.sup.3 when using potassium formate. At the same time inventive example 4 with potassium formate as the PIR catalyst features higher foam pressures and higher core temperatures at the time of the foaming reaction. Itis further apparent that the flow behavior can be optimized compared to potassium acetate in the presence of potassium formate as the catalyst. This is reflected by shorter cream times at otherwise identical fiber times (comparative examples 1* and 2* vs. inventive example 4).

[0149] Only when potassium formate is used can higher foam pressures and better flow behavior be simultaneously achieved. Shorter cream times are also recorded in the case of potassium 2-ethylhexanoate (comparative example 3*) but the foams exhibit lower foam pressures. Foams produced with potassium formate also feature improved curing (quantified by impression depth of a weight after 2.5 and 5 min).

Examples 5-12): Production of Pentane-Blown Foams, with Potassium Carboxylate Catalysts, with Amine Catalyst

[0150] The production of these foams was carried out as per examples 1-4) by manual mixing on a laboratory scale (for formulations and reaction properties see table 2).

[0151] Examples 5-9) are adjusted to approximately the same apparent core density of about 38 kg/m.sup.3 via the pentane amount. Examples 9) and 10) and examples 11) and 12) employed other polyol formulations which differ in the composition of the main polyol (polyol P2=aromatic polyester, polyol P3 aliphatic polyester). It is apparent in each case that at a constant blowing agent amount the use of potassium formate (examples 10) and 12)) instead of potassium acetate causes the bulk density of the rigid foam to drop by 1.5 to 2.1 kg/m.sup.3 while at the same time the foam pressure increases by about 35 or about 70 hPa. It is further apparent that, in addition simultaneously to lower densities, foams produced using potassium formate exhibit improved curing properties (see impression depth) compared to those of the potassium acetate-catalyzed PUR/PIR foams.

TABLE-US-00003 TABLE 2 Production and properties of pentane-blown foams, with potassium carboxylate catalysts, with amine catalyst Example Example Example Example Example Example Example Example Formulation Unit 5* 6* 7* 8 9* 10* 11* 12* B1.a-P1 pbw 66.5 66.5 66.5 66.5 B1.a-P2 pbw 83.0 83.0 B1.a-P3 pbw 83.0 83.0 B1.b-P4 pbw 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 B3.b-1 pbw 20.8 20.8 20.8 20.8 9.5 9.5 9.5 9.5 B3.b-2 pbw 5.2 5.2 5.2 5.2 Bl.c-P6 pbw 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 B3.a-1 pbw 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 B2.b-1 pbw 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 B2.c-1 pbw 3.5 4.20 4.60 B2.c-2 pbw 3.6 B2.c-3 pbw 3.5 B2.a-1 pbw 1.9 2.50 3.00 A-1 pbw 184.1 184.6 167.0 180.9 200.0 200.0 200.0 200.0 C-1 pbw 14.4 14.4 13.6 13.3 14.9 14.9 14.9 14.9 C-1 % by wt. 4.7 4.7 4.7 4.4 4.6 4.6 4.6 4.6 Index 330.0 330.0 330.0 330.0 305.6 310.5 325.9 328.0 Cream time s 13 13 11 12 13 11 14 12 Fiber time s 46 47 47 46 37 36 37 38 Tack-free time s 90 92 126 84 48 44 47 45 Apparent kg/ 38.5 37.6 38.4 38.3 39.8 38.2 38.9 36.8 core density m.sup.∧3 Foam pressure hPa 228.0 188 173 247 242 278 286 355 Maximum core ° C. 166.2 166.3 165 167.2 175.4 177.7 171 174.2 Impression depth mm 13.5 16.5 18 11.5 4.2 3.9 6.0 5.8 after Impression depth mm 14.5 17.5 19.5 12.0 5.0 4.8 7.0 6.3 after 5

Examples 13-15): Production of Pentane-Blown Foams, with Potassium Carboxylate Catalysts, without Amine Catalyst and Carbamate

[0152] The production of these foams was carried out as per examples 1-4) by manual mixing on a laboratory scale (for formulations and reaction properties see table 3). Itis apparent that the positive effect both on foam pressure and on curing is particularly great in the presence of carbamate.

TABLE-US-00004 TABLE 3 Production and properties of pentane-blown foams, with potassium carboxylate catalysts, with 2-hydroxyethyl carbamate Formulation, reaction Example Example Example Example properties Unit 13* 14* 15* 16 B1.a-P1 pbw 66.5 66.5 66.5 66.5 B1.b-P4 pbw 5.2 5.2 5.2 5.2 B3.b-1 pbw 20.8 20.8 20.8 20.8 B3.b-2 pbw 5.2 5.2 5.2 5.2 B1.c-P6 pbw 2.3 2.3 2.3 2.3 B3.a-1 pbw 3.0 3.0 3.0 3.0 Carbamate pbw 1.5 1.5 1.5 1.5 B2.c-1 pbw 4.800 B2.c-2 pbw 4.800 B2.c-3 pbw 4.200 B2.a-1 pbw 3.400 A-1 pbw 211.2 211.0 186.9 214.7 C-1 pbw 15.5 15.5 14.3 14.7 C-1 % by 4.6 4.6 4.6 4.4 Index 330.0 330.0 330.0 330.0 Cream time s 14 12 11 13 Fiber time s 47 46 46 45 Tack-free time s 62 67 88 54 Apparent core density kg/m{circumflex over ( )}3 36.7 36.3 36.8 37.2 Foam pressure hPa 308 287 237 392 Maximum core ° C. 173.9 174.4 169.8 179.4 Impression depth after 2.5 mm 9.5 10.5 12.0 6.0 Impression depth after 5 mm 10.5 11.5 13.0 6.5

[0153] Compared to other potassium carboxylate-catalyzed foams all inventive examples exhibit a shortening of tack-free time. This is surprisingly observable only for foams blown in the absence or virtual absence of water as demonstrated by the following comparative examples 17* and 18* (table 4).

Examples 17-18): Production of Pentane-Blown Foams, with Potassium Carboxylate Catalysts, Water-Containing (not According to the Invention)

[0154] The production of these foams was carried out as per examples 1-4) by manual mixing on a laboratory scale (for formulations and reaction properties see table 4).

TABLE-US-00005 TABLE 4 Production and properties of pentane-blown foams, with potassium carboxylate catalysts, water-containing Formulation, Example Example reaction properties Unit 17* 18* B1.a-P3 pbw 73.0 73 B1.b-P5 pbw 12.0 12 B3.b-1 pbw 15 15 Water pbw 0.80 0.80 B3.a-1 pbw 3.00 3.00 B2.b-1 pbw 1.20 1.20 B2.c-1 pbw 3.50 B2.a-1 pbw 2.3 A-1 pbw 202.75 201.87 C-1 pbw 13.30 12.30 C-1 % by 4.10 3.80 Index 350.0 350.0 Cream time s 13 13 Fiber time s 38 38 Tack-free time s 43 45 Apparent core density kg/m{circumflex over ( )}3 40.2 40.7

[0155] In comparative examples 17* and 18* (water-containing) the use of potassium formate does result in an elevated foam pressure but not in a shortening of the tack-free time.