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 an amine, 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, and 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 catalyst component B2) comprises potassium formate B2.a) and an amine B2.b), and (2) the reaction mixture contains less than 0.2% by weight of formic acid and has an isocyanate index ≥150, the proviso that the reaction mixture contains no aminic compounds having the formula (I)
R.sup.1N(CH.sub.3)(CH.sub.2CH.sub.2OR.sup.2)   (I) wherein R.sup.1 represents CH.sub.3, CH.sub.2—CH.sub.2—N(CH.sub.3).sub.2 or CH.sub.2—CH.sub.2OH, and R.sup.2 represents H, CH.sub.2—CH.sub.2OH or CH.sub.2—CH.sub.2N(CH.sub.3).sub.2.

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 isocyanate-reactive component B) comprises B1.a) at least one polyester polyol, at least one polyether ester polyol, or a combination thereof.

4. The process as claimed in claim 2, wherein the at least one polyester polyol, at least one polyether ester polyol, or a combination thereof is present in an amount of at least 55% by weight, based on the total weight of the isocyanate-reactive component.

5. The process as claimed in claim 1, wherein the component B2.b) comprises dimethylbenzylamine or dimethylcyclohexylamine.

6. The process as claimed in claim 1 the potassium formate B2.a) is present in an amount of 0.2% to 4.0% by weight, based on the total weight of component B).

7. The process as claimed in claim 1, wherein the amine B2.b) is present in an amount of 0.1% to 3.0% by weight, based on the total weight of component B).

8. The process as claimed in claim 1, wherein the potassium formate is present in an amount of 15.0% to 90.0% by weight of potassium formate and the amine is present in an amount of 10.0% to 85.0% by weight, each based on the total weight of the catalyst component B2).

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

10. The process as claimed in claim 1, wherein the reaction mixture further comprises water.

11. The process as claimed in claim 1, wherein component B) 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 20.0% 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 low molecular weight isocyanate-reactive compounds 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), 0.1% to 4.0% by weight of potassium formate B.2a), and 0.1% to 3.0% by weight of amine B2.b) 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 its isomers and higher-functional homologs and wherein the reaction mixture has an isocyanate index of ≥150 to ≤450.

12. The process as claimed in claim 1, wherein the reaction mixture comprises tris(chloro-2-propyl) phosphate (TCPP), triethyl phosphate (TEP) and mixturcsor a mixture thereof.

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

14. A rigid polyurethane/polyisocyanurate foam obtained by the process as claimed in claim 1.

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

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

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

Description

EXAMPLES

[0140] The following compounds are employed for production of the rigid foams: [0141] B1.a-P1 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 [0142] 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 [0143] B1.b-P3 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. [0144] B1.b-P4 Polyether polyol based on ethylene glycol, saccharose and propylene oxide having an OH number of 440 mg KOH/g, from Covestro Deutschland AG. [0145] B1.b-P5 Polyether polyol based on saccharose, propylene glycol, ethylene glycol and propylene oxide having an OH number of 380 mg KOH/g, from Covestro Deutschland AG. [0146] B1.b-P6 Polyether polyol based on ethylenediamine and propylene oxide having an OH number of 620 mg KOH/g, from Covestro Deutschland AG. [0147] B3.b-1 Tris(1-chloro-2-propyl) phosphate from Lanxess GmbH (component B3.b) [0148] B3.b-2 Triethyl phosphate from Lanxess GmbH [0149] B3.a-1 Polyether polysiloxane copolymer Tegostab® B8443 from Evonik [0150] B1-P7 Castor oil [0151] A-1 Desmodur® 44V70L polymeric polyisocyanate based on 4,4-diphenylmethane diisocyanate having an NCO content of about 31.5% by weight from Covestro Deutschland AG [0152] B2.c-1 Potassium acetate (potassium ethanoate IUPAC name), 25% by weight in diethylene glycol [0153] B2.a-1 Potassium formate (potassium methanoate IUPAC name), 36% by weight in monoethylene glycol [0154] B2.b-1 Dimethylbenzylamine (N,N-dimethyl-1-phenylmethanamine IUPAC name) [0155] B2.b-2 Dimethylcyclohexylamine (N,N-dimethylcyclohexanamine IUPAC name) [0156] B2.d-1 Bis(2-dimethylaminoethyl)ether (Niax® A1, 70% in dipropylene glycol, Momentive Performance Materials) (aminic compound having structural formula of formula (I)) [0157] B2.d-2 2,T-dimorpholinyl diethyl ether (DMDEE aminic compound having structural formula of formula (I)) [0158] C-1 n-Pentane [F+;Xn;N] [0159] D-1 Water

[0160] Measurement of reaction and product properties of produced rigid PUR/PIR foams:

[0161] 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.

[0162] Measurement of apparent density was performed according to DIN EN ISO 845 (October 2009).

[0163] Measuring fiber time:

[0164] 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.

[0165] Measurement of tack-free time:

[0166] Once dispensing was complete the tack-free time of the foam surface was determined according to TM 1014:2013 (FEICA).

[0167] Measurement of impression depth:

[0168] 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 1-12

Production of Pentane-Blown Foams

[0169] 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 and table 3). 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-00001 TABLE 1 Formulation of rigid PUR/PIR foams Example Example Example Example Example Example Example Example Example Example 1* 2 3 4* 5* 6* 7* 8 9* 10 B1.a-P1 pbw 73 73 73 73 73 73 83 83 B1.a-P2 83 83 B1.b-P3 pbw 12 12 12 12 12 12 5 5 5 5 B3.b-1 pbw 15 15 15 15 15 15 B3.b-2 10.5 10.5 10.5 10.5 D-1 pbw 0.80 0.80 0.80 0.80 0.80 0.80 0.50 0.50 0.50 0.50 B3.a-1 pbw 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 B2.b-1 pbw 1.20 1.20 1.50 1.20 1.50 1.20 B2.c-1 pbw 3.50 3.50 3.00 3.00 B2.b-2 pbw 0.30 0.30 B2.a-1 pbw 2.30 2.30 2.30 2.30 2.00 2.10 B2.d-1 pbw 0.40 B2.d-2 pbw 3.60 C-1 pbw 13.30 12.30 12.20 12.40 12.30 13.20 13.20 12.80 13.20 12.80 C-1 wt-% 4.10 3.80 3.80 3.80 3.80 4.10 4.10 4.00 4.10 4.00 A-1 pbw 202.75 201.87 201.87 201.87 202.72 202.75 200.00 200.00 200.00 200.00 Index 350.0 350.0 350.0 350.0 350.0 350.0 311.6 312.3 337.0 336.13

TABLE-US-00002 TABLE 2 Reaction and product properties of produced rigid PUR/PIR foams Example Example Example Example Example Example Example Example Example Example 1* 2 3 4* 5* 6* 7* 8 9* 10 Cream time s 13 13 14 9 9 13 13 12 14 13 Fiber time s 38 38 37 39 38 36 39 38 39 38 Tack-free time s 43 45 42 45 45 42 49 49 48 45 Apparent core density kg/m3 40.2 40.7 40.8 41 39.8 41.2 39.7 37.9 38.6 37.9 Water absorption g 9.3 9.2 8.7 10.8 10.6 8.7 10.8 11.1 8.6 10.9 (486 cm.sup.3 foam) Foam pressure hPa 282 328 345 353 338 316 214 321 279 357 Surface defects 1-2 1-2 1-2 4 4 1-2 (flip-top mold) Impression depth 8.0 5.0 8.5 4.0 after 2.5 min Impression depth fiqs 9.0 5.5 9.5 4.5 after 5 min Fire class E E E E E E E E E E SBT (ISO 11925-2) Average flame height mm 115 113 102 112 105 108 132 120 128 100 Min-max flame height mm 110-120 110-115 100-105 110-115 100-110 105-115 130-135 120-120 125-130 100-100

[0170] It is apparent that when using potassium formate less of the physical blowing agent pentane is required to achieve a target apparent density of 40-41 kg/m.sup.3. Furthermore, all examples containing potassium formate as PIR catalyst feature higher foam pressures. This is even more pronounced when using dimethyl cyclohexylamine (DMCHA) as the aminic catalyst than when using dimethylbenzylamine (DMBA).

[0171] However, marked surface defects in the finished foam are observed when the polyol formulation contains a diaminoether (Niax, DMDEE) as in comparative examples 4* and 5*.

[0172] In addition, the foams produced with potassium formate exhibit improved curing (quantified by the impression depth of a weight after 2.5 and 5 min) compared to the foams catalyzed with potassium acetate (comparative example 7* vs 8, comparative example 9* vs 10).

[0173] Surprisingly, improved fire characteristics in the small burner test (SBT) compared to the potassium acetate-catalyzed foams are observed even in the case of foams which contain the halogen-free flame retardant TEP and potassium formate. This is all the more surprising since in the foams protected with the flame retardant TCPP this effect was only observable—and even then less pronounced—for the combination of potassium formate and dimethylcyclohexylamine.

[0174] Substitution of B1.a-P2 (aromatic polyester polyol) for B1.a-P1 (aliphatic polyester polyol) (example 8 vs example 10) likewise brings marked advantages in respect of foam pressures, impression depth and fire characteristics.

[0175] However, the use of potassium formate in rigid polyurethane foams having an index of 120 does not show the same positive effect as in PUR/PIR foams (comparative examples 11 and 12, table 3). For identical employed pentane amounts polyurethane foams catalyzed with potassium formate instead of potassium acetate exhibit virtually identical foam pressure and identical apparent densities as well as only small differences in curing.

TABLE-US-00003 TABLE 3 Formulation and properties of rigid polyurethane foams (noninventive) Example Example 11* 12* B1.b-P4 pbw 40.00 40.00 B1.b-P5 pbw 23.50 23.50 B1.b-P6 pbw 9.90 9.90 B1-P7 pbw 15.50 15.50 B3.b-1 6.10 6.10 D-1 pbw 1.80 1.80 B3.a-1 pbw 3.20 3.20 B2.b-2 pbw 2.13 2.14 B2.C-1 pbw 2.02 B2.a-1 pbw 1.17 C-1 pbw 5.32 5.34 C-1 wt-% 2.01 2.02 A-1 pbw 149.06 149.54 Index 119.3 119.8 Cream time s 13 13 Fiber time s 46 47 Tack-free time s 43 45 Apparent core density kg/m 62 64 Foam pressure hPa 256 267 Impression depth after 2.5 8.3 7.6 min Impression depth after 5 min 9.2 8.4