PROCESS FOR PRODUCING RIGID, FLAME-RETARDANT PU/PIR FOAM

Abstract

The present invention relates to flame-retarded rigid polyurethane and/or polyurethane/polyisocyanurate foams (hereinafter individually or jointly also termed “rigid PUR/PIR foams”), and also to a process for producing rigid PUR/PIR foams that comprises reacting a reaction mixture comprising A1 an isocyanate-reactive component, A2 blowing agent A3 catalyst, A4 optionally additive, A5 flame retardant, and B an isocyanate component, and that is characterized in that the flame retardant A5 comprises at least two phosphorus-containing compounds, with one of the two compounds having the general formula R.sup.1R.sup.2(O)P—[O—R.sup.5—R.sup.6—O—P(O)R.sup.3].sub.nR.sup.4 (I) or R.sup.1R.sup.2(O)P—[O—R.sup.5—X—R.sup.6—O—P(O)R.sup.3].sub.nR.sup.4 (II), where X=an alkylene group, N—R.sup.7, O, CO, S, SO, SO.sub.2 OR P—R.sup.7, n=an integer from 0 to 4, preferably 1 or 2, R.sup.1, R.sup.2, R.sup.3, R.sup.4=in each case an aryl-O—, aryl- or alkyl groups, R.sup.5, R.sup.6=in each case an arylene group, R.sup.7=an aryl-O—, aryl- or alkyl group, where the at least one compound having the general formula (I) or (II) is used in an oligomer mixture and on average the value (aa) of n is 0.80 to 4.00, preferably 0.90 to 2.00, more preferably 1.25 to 1.75.

Claims

1. A process for producing a rigid PUR/PIR foam comprising reacting a reaction mixture comprising: A1 an isocyanate-reactive component; A2 blowing agent; A3 catalyst; A4 optionally additive; A5 flame retardant; and B an isocyanate component, wherein the flame retardant A5 comprises at least two phosphorus-containing compounds, wherein at least one of the two compounds has the general formula
R.sup.1R.sup.2(O)P—[O—R.sup.5—R.sup.6—O—P(O)R.sup.3].sub.nR.sup.4   (I) or
R.sup.1R.sup.2(O)P—[O—R.sup.5—X—R.sup.6—O—P(O)R.sup.3].sub.nR.sup.4   (II) wherein X represents an alkylene group, N—R.sup.7, O, CO, S, SO, SO.sub.2, or P—R.sup.7, n represents an integer having a value from 0 to 4, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each represent an aryl-O, aryl or alkyl group, R.sup.5 and R.sup.6 each represent an arylene group, R.sup.7 represents an aryl-O, aryl or alkyl group, and wherein the at least one compound having the general formula (I) or (II) is employed in an oligomer mixture and n on average has a value n;.sup.− of 0.80 to 4.00.

2. The process as claimed in claim 1, wherein the isocyanate-reactive component A1 comprises a polyester polyol.

3. The process as claimed in claim 2, wherein the isocyanate-reactive component A1 comprises a polyester polyol and a polyether polyol each having a molecular weight of 50 g/mol to 2000 g/mol.

4. The process as claimed in claim 2, wherein the isocyanate-reactive component A1 comprises a polyester polyol and a polyether polyol each having a functionality of 1.0 to 6.0.

5. The process as claimed in claim 1, wherein the blowing agent A2 comprises a halogen-free chemical blowing agent, a halogen-free physical blowing agent, a (hydro)fluorinated olefins, or a mixture of any two or more thereof.

6. The process as claimed in claim 1, wherein the compound having the general formula (I) or (II) is present in an amount of 45.0% by weight to 95.0% by weight, based on the total mass of the flame retardant A5.

7. The process as claimed in claim 1, wherein the compound having the general formula (I) or (II) is present in an amount of 5.0% by weight to 40.0% by weight, based on the total mass of the components A1 to A5.

8. The process as claimed in claim 1, wherein the flame retardant A5 contains no halogen-containing flame retardant.

9. The process as claimed in claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each represent an aryl-O group.

10. The process as claimed in claim 9, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each represent a phenoxy group.

11. The process as claimed in claim 10, wherein the compound having the general formula (I) or (II) comprises bisphenol A bis(diphenylphosphate).

12. The process as claimed in claim 1 to 11, wherein the flame retardant A5 further comprises at least one of diphenylcresyl phosphate, triethyl phosphate and red phosphorus.

13. The process as claimed in claim 1, wherein the isocyanate component B comprises at least one of MDI, polymeric MDI and TDI.

14. A rigid PUR/PIR foam obtained by the process as claimed in claim 1.

15. An insulation material comprising the rigid PUR/PIR foams as claimed in claim 14.

Description

EXAMPLES

1. Reactants

[0150] A1-1 polyester polyol composed of glutaric acid, succinic acid, adipic acid, ethylene glycol and diethylene glycol having a functionality of 2 and a molecular weight of 520 g/mol

[0151] A1-2 polyester polyol composed of phthalic acid, adipic acid, ethylene glycol and diethylene glycol having a functionality of 2 and a molecular weight of 460 g/mol

[0152] A1-3 polyether polyol on 1,2-propylene glycol started with 70% by weight of propylene oxide and 29% by weight of ethylene oxide, functionality of 2 and a molecular weight of 4000 g/mol

[0153] A1-4 polyether polyol composed of propylene oxide with a starting mixture of sorbitol and glycerol, functionality of 4.5 and a molecular weight of 600 g/mol

[0154] A1-5 triethanolamine

[0155] A2-1 n-pentane

[0156] A2-2 water

[0157] A3-1 25% by weight of potassium acetate in diethylene glycol (catalyst)

[0158] A3-2 dimethylcyclohexylamine (catalyst)

[0159] A4-1 polyether-modified polydimethylsiloxane (foam stabilizer)

[0160] A5-1 bisphenol A bis(diphenyl phosphate) (Fyroflex® BDP, ICL Industrial Products) having an average value of n;.sup.−=1.50

[0161] A5-2 red phosphorus (Acros)

[0162] A5-3 diphenylcresyl phosphate DPC

[0163] A5-4 resorcinyl diphenyl phosphate RDP (Fyrolflex RDP, ICL)

[0164] A5-5 triethyl phosphate (disflammol TEP, Lanxess)

[0165] B-1 polymeric MDI comprising 31.5% by weight of NCO groups and a viscosity of 700 mPa.Math.s at 25° C.

Production and Testing of Rigid PUR/PIR Foams

[0166] The flame spread of the rigid PUR/PIR foams was measured by edge flaming with the small burner test according to DIN 4102-1 (May 1998) on a sample having dimensions of 18 cm×9 cm×2 cm. The destroyed sample length is a measure for the fire safety properties of the employed flame retardant, wherein a shorter destroyed sample length represents better flame retardancy.

[0167] The compressive strength of the rigid PUR/PIR foams was determined according to DIN EN 826 (May 2013) on test specimens having dimensions of 50 mm×50 mm×50 mm. The compressive strength of the test specimens was measured in the foaming direction and perpendicular to the foaming direction.

[0168] Measurement of apparent density was performed according to DIN EN ISO 845 (October 2009).

[0169] To measure the dimensional stability of the rigid PUR/PIR foams test specimens having dimensions of 5 cm×5 cm×5 cm were measured centrally in the three directions. The test specimens were stored for 22 hours at 100° C. in a circulating air drying cabinet and after cooling of the test specimens to 20° C. measured once again. The dimensional stability @100° C. corresponds to the geometric quadratic average of the changes in side lengths in three directions at 100° C. over 22 hours.

[0170] The open-cell content of the rigid PUR/PIR foams was measured with an Accupyk-1330 instrument on test specimens having dimensions of 5 cm×3 cm×3 cm according to DIN EN ISO 4590 (August 2003).

[0171] To determine the phosphorus proportion of the obtained rigid PUR/PIR foams the weight fraction of phosphorus in phosphorus-containing compounds in the reaction mixture is calculated and related to the total mass of the reaction mixture.

[0172] Based on the polyol components rigid PUR/PIR foams were produced in the laboratory by mixing 0.3 dm.sup.3 of a reaction mixture in a paper cup. To this end the flame retardant, the foam stabilizer, catalysts and n-pentane as the blowing agent were added to the respective polyol component and the mixture was briefly stirred. The obtained mixture was mixed with the isocyanate and the reaction mixture was poured into a paper mold (3×3×1 dm.sup.3) and reacted therein. The precise formulations of the individual experiments are reported in table 1 and table 2 (composition of the reaction mixtures), likewise the results of the physical measurements on the obtained samples (table 1/2, physical properties).

TABLE-US-00001 TABLE 1 Composition of the reaction mixtures (examples 1-4) Examples 1* 2 3* 4 A1-1 parts by wt. 23.8 23.8 22.8 22.8 A1-2 parts by wt. 21.5 21.5 20.6 20.6 A1-3 parts by wt. 6.3 6.3 6 6 A1-4 parts by wt. 32.6 32.6 31.1 31.1 A1-5 parts by wt. 5.0 5.0 4.8 4.8 A2-1 parts by wt. 3.6 3.6 4.2 4.2 A2-2 parts by wt. 3.1 3.1 3 3 A3-1 parts by wt. 1.0 1.0 1 1 A3-2 parts by wt. 1.0 1.0 1 1 A4-1 parts by wt. 3.1 3.1 3 3 Flame retardant A5-1 parts by wt. 18.0 27.8 A5-2 parts by wt. 2.5 2.5 2.5 2.5 A5-3 parts by wt. 19.3 27.8 Isocyanate B-1 parts by wt. 181.9 181.9 174 174 Index 148.5 148.5 148.5 148.5 Physical properties Cream time s 17 15 16 15 Fiber time to s 37 35 36 35 Tack-free time s 98 78 78 65 Apparent core density kg/m.sup.3 37.3 38.0 38.3 38.9 Dimensional % 1.1 0.6 5.1 0.6 stability@100° C. Open-cell content % 6 6 6.5 6.1 Compressive strength kPa 333 354 328 350 in foaming direction Compressive strength kPa 155 184 145 181 perpendicular to foaming Phosphorus content in g/kg.sup.1) 19.5 18.5 18.1 16.5 foam (calculated) Destroyed sample length mm 88 89 97 94 according to DIN 4102 *Comparative example .sup.1)mass of phosphorus in grams (g) based on the sum of the masses of A1 to A5 and B = 1 kilogram (kg).

[0173] Tables 1 and 2 show the use of inventive flame retardant mixtures compared to flame retardant mixtures representative of the prior art. Comparative examples 1 and 3 in each case employ polycyclic phosphate esters having benzene rings as substituents (DPC, A5-3) but which are not compounds of general formula (I) oder (II) in combination with red phosphorus. The use of an inventive flame retardant mixture containing a compound of general formula (I) or (II) in the inventive example 2 affords a rigid PUR/PIR foam having a comparable flame retardancy to the rigid PUR/PIR foam of comparative example 1. However, the compressive strength of the inventive rigid PUR/PIR foam perpendicular to the foaming direction and in the foaming direction is increased and the dimensional stability of the rigid PUR/PIR foam is improved. The same effect is apparent upon comparison of the rigid PUR/PIR foam of comparative example 3 and that of inventive example 4, wherein the flame retardancy of the rigid PUR/PIR foam of inventive example 4 is improved compared to the rigid PUR/PIR foam of comparative example 3.

Comparison of Inventive Flame Retardant Mixture vs. Resorcinyl Diphenylphosphate

[0174] In the following examples 5-8 inventive formulations containing the flame retardant mixture A5-1 [bisphenol-A bis(diphenylphosphate) (BDP)]/A5-3 [diphenylcresyl phosphate (DPC)] or A5-1 (BDP)/A5-5 [triethylphosphate (TEP)] are compared with noninventive formulations containing A5-5 [resorcinyldiphenyl phosphate (RDP)] or an RDP/DPC mixture as the flame retardant.

[0175] The formulations according to table 2 were processed into polyurethane foams having an index of 148.5 and tested analogously to the examples 1-4.

TABLE-US-00002 TABLE 2 Composition of the reaction mixtures and properties of the foams (examples 5-8) Examples 5* 6* 7 8 A1-1 parts by weight 26.92 26.92 26.79 26.79 A1-2 parts by weight 24.23 24.23 24.11 24.11 A1-3 parts by weight 7.08 7.08 7.05 7.05 A1-4 parts by weight 36.84 36.84 36.67 36.67 A1-5 parts by weight 5.67 5.67 5.64 5.64 A2-1 parts by weight 4.11 4.11 4.19 4.19 A2-2 parts by weight 3.54 3.54 3.53 3.53 A4-2 parts by weight 3.54 3.54 3.53 3.53 A3-2 parts by weight 1.13 1.13 1.13 1.13 A3-1 parts by weight 1.13 1.13 1.13 1.13 Flame retardant A5-3 (DPC) parts by weight 10.14 10.85 A5-1 (BDP) parts by weight 10.85 16.27 A5-4 (RDP) parts by weight 10.14 20.27 A5-5 (TEP) parts by weight 5.42 Isocyanate B-1 parts by weight 205.52 205.52 204.54 204.54 Index 148.5 148.5 148.5 148.5 Reaction parameters Cream time seconds 17 18 17 18 Fiber time seconds 35 36 35 36 Rise time seconds 60 58 58 60 Tack-free time seconds 85 80 80 76 Physical properties of the foams Apparent density 41.3 42.2 40.0 40.0 Open-cell content % 6.8 7.1 7.4 7.6 Compressive kPa 0.37 0.37 0.39 0.38 strength in rise direction Compressive kPa 0.16 0.18 0.18 0.16 strength perpendicular to rise direction Compressive 1000 m.sup.2/s.sup.2 5.1 5.3 5.8 5.4 strength/apparent density Dimensional % 1.3 0.9 0.3 0.5 stability @100° C.

[0176] Compared to the examples 5 and 6 the inventive foams 7 and 8 have more advantageous apparent densities at identical open-cell content and comparable strength. This results in a more advantageous ratio of strength to density when mixtures of BDP are employed.

[0177] Fire characteristics were tested according to ISO 5660-1:2015 (cone calorimeter test with 50 kW/m.sup.2 output, table 3). All values shown are average values from two measurements. The results show that the inventive BDP-based mixtures are the equals of noninventive RDP and RDP/DPC mixtures or achieve better results. This was not expected on the basis of US 2014/0066532.

TABLE-US-00003 TABLE 3 Fire characteristics for examples 5-8 Examples 5* 6* 7 8 Time to ignition, tti seconds 4.5 3.5 4.5 5.0 Maximum heat release kW/m.sup.2 262 282 235 248 rate, HRR.sub.peak Total heat release, THR MJ/m.sup.2 22 23 22 21 Effective heat of combustion, EHC MJ/m.sup.2g 2.6 2.2 2.1 2.0