Diol-phosphonates as flame-retardants in polyurethane foam

The present invention relates to certain novel diol-phosphonates, and to their use in flameproofing polyurethane foams.
It is known that phosphorus-containing derivatives reduce the inflammability of products into which they are introduced. Phosphorus can be added in the form of unreactive compounds to polymers or copolymers; however, in this case, the phosphorus-containing compounds tend to exude from the polymer. It is therefore preferable to introduce phosphorus into a polymeric material, by employing a phosphorus-containing monomer in the copolymerization or copolycondensation reactions used to form the polymeric material.
In order to flameproof polyurethane foams, it has already been proposed to use diol-phosphonates of the formula ##STR3## in which R and R.sup.1 are alkyl, R.sup.2 and R.sup.3 are alkylene and R.sup.4 is methylene. These compounds may be prepared by a Mannich reaction between a dialkyl phosphite, a dialkanolamine and an aldehyde or a ketone (U.S. Pat. No. 3,076,010). A compound of this type is commercially available under the trade name "Fyrol 6". It is prepared by means of a Mannich reaction between diethyl phosphite, formaldehyde and diethanolamine, and has the formula ##STR4##
Compounds of this type, however, possess the disadvantage of undergoing a reverse Mannich reaction, a so-called "retro Mannich reaction", when in monomeric form or when incorporated into a polymer. This manifests itself in storage and processing difficulties and in a deterioration of the mechanical properties of polyurethane foams prepared with these compounds.
We have now developed certain novel diolphosphonates which do not possess this disadvantage and which enable a better flameproofing effect to be obtained.
The novel compounds according to the present invention have the following general formula: ##STR5## in which R.sub.1 is an alkyl group with 1 to 4 carbon atoms, R.sub.2 is hydrogen, methyl, or ethyl, and A is --CH.sub.2 --CH.sub.2 --CH.sub.2 -- or ##STR6##
A compound which has proved particularly valuable is diethyl 3-[bis-(2-hydroxy-ethyl)-amino]-propyl-phosphonate, and another preferred compound is diethyl 2-[bis-(2-hydroxy-ethyl)-amino-]-2-methylethyl phosphonate.
The compounds of the formula I in which A is a trimethylene radical, --(CH.sub.2).sub.3 --, can be prepared in accordance with the following reaction schemes (a), (b) and (c). ##STR7## In this scheme X is a chlorine or bromine atom, and R.sub.1 and R.sub.2 have the meanings given above.
The phosphonates II used in process (a) may be prepared by the reaction of a trialkyl phosphite with a dihalogeno-alkane, in accordance with known methods (Parfentjew and Schafiew, Trudy Usbekak Univ. Sbornik Rabot Chim., 1939, 15, 87; C.A., 1941, 3963; and T. R. Fukuto and R. L. Metcalf, J. Amer. Chem. Soc., 1959, 81, 372-7). These methods possess the disadvantage of giving only average yields, even in the presence of an excess of the halogenated derivative, the halogen being only slightly activated in this type of compound. The action of a dialkanolamine III, preferably in the presence of triethylamine, on the phosphonates II leads to the diol-phosphonates I.sub.a as shown in scheme (a). ##STR8## In this scheme X is a chlorine or bromine atom and R.sub.1 and R.sub.2 have the meanings given above.
The .beta.-ethylenic-.gamma.-halogenated-phosphonates IV have been described by Laviolle, Sturtz and Normant (Bull.Soc.Chim., 1967, 4186).
The dialkanolamine III reacts with the phosphonates IV, preferably in the presence of triethylamine, in a manner analogous to the reaction that occurs with phosphonates II, forming derivatives V, which are thereafter catalytically reduced to form diolphosphonates I.sub.a. This hydrogenation is preferably carried out using Pd/C at atmospheric pressure, or in an autoclave under a few atmospheres and at ambient temperature. ##STR9## In this scheme R.sub.1 and R.sub.2 have the meanings given above.
The compounds of formula I in which A is ##STR10## can be prepared in accordance with the following scheme: ##STR11##
The phosphonates VI are described in U.S. Pat. No. 2,827,475. The reaction of the dialkanolamine III with the phosphonate VI is advantageously carried out in the presence of triethylamine. The compounds VII are then reduced by catalytic hydrogenation to form diol-phosphonates I.sub.b under fairly vigorous conditions (preferably using a pressure of at least 70 bars and a temperature of about 70.degree. C.).
The following Examples describing the preparation of compounds of the invention are given by way of illustration only.

EXAMPLES 1 to 8
In Examples 1 to 8, diol-phosphonates of formula I.sub.a were prepared in accordance with general reaction procedure (1) or (2) described below. The starting materials, reaction procedure, product and yield obtained are summarised in Table 1 below. (1) 100 cm.sup.3 of an alcohol R.sub.1 OH, 0.1 mole of a phosphonate II, 0.2 mole of triethylamine and 0.2 mole of a dialkanolamine III were heated under reflux. The mixture was left under reflux for 6 to 7 hours in the case of brominated derivatives II and for 24 hours in the case of chlorinated derivatives II. (2) The same procedure as described under (1) was employed but a phosphonate IV was used in place of the phosphonate II.
Thereafter, after filtering off the triethylammonium halide precipitate, the crude product was hydrogenated in the alcoholic solution in which it was prepared (using 5% by weight of 10% Pd/C, at 25.degree. C. for 2 hours under a pressure of 10 bars, or at atmospheric pressure).
TABLE 1__________________________________________________________________________(Diol-phosphonates I.sub.a)Ex- Reac-am- tion Com-ple pro- Starting pound YieldNo. cedure phosphonate Amine Product obtained No. %__________________________________________________________________________1 (1) ##STR12## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR13## 1 822 (1) ##STR14## HN(CHOHCH.sub.3).sub.2 ##STR15## 2 883 (1) ##STR16## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR17## 3 914 (1) ##STR18## HN(CH.sub.2 CHOHCH.sub.3).sub.2 ##STR19## 4 885 (1) ##STR20## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR21## 1 566 (1) ##STR22## HN(CH.sub.2 CHOHCH.sub.3).sub.2 ##STR23## 2 637 (2) ##STR24## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR25## 1 728 (2) ##STR26## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR27## 3 69__________________________________________________________________________
EXAMPLES 9 to 15
Diol-phosphonates of formula I.sub.b were prepared in accordance with the following general reaction procedure. The starting materials, product and yield are summarised in Table 2 below.
100 cm.sup.3 of an alcohol R.sub.1 OH, 0.1 mole of a phosphonate VI, 0.2 mole of triethylamine and 0.2 mole of a dialkanolamine III were heated under reflux. The mixture was left under reflux for 6 to 7 hours in the case of brominated derivatives VI and for 24 hours in the case of chlorinated derivatives VI.
After cooling and filtering off the triethylammonium halide precipitate, the excess alcohol and triethylamine were driven off under reduced pressure. The residue was hydrogenated over Pd/C in the alcohol R.sub.1 OH at 70.degree. C. for 14 hours under 80 bars. After filtering off the Pd/C and evaporating the alcohol, the residue was taken up in water and in CHCl.sub.3. The residual starting products were extracted at pH 1 and the diol-phosphonate was extracted at pH 10.
Table 2__________________________________________________________________________(Diol-phosphonates I.sub.b) Com-Example pound YieldNo. Starting phosphonate Amine Product obtained No. %__________________________________________________________________________ ##STR28## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR29## 5 8110 ##STR30## HN(CH.sub.2 CHOHCH.sub.3).sub.2 ##STR31## 6 9111 ##STR32## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR33## 7 8812 ##STR34## HN(CH.sub.2 CHOHCH.sub.3).sub.2 ##STR35## 8 8313 ##STR36## HN(CH.sub.2 CH.sub.2 OH).sub.2 ##STR37## 5 7214 ##STR38## HN(CH.sub.2 CHOHCH.sub.3).sub.2 ##STR39## 6 7515 ##STR40## HN(CH.sub.3 CH.sub.2 OH).sub.2 ##STR41## 9 63__________________________________________________________________________
Certain characteristics of the products obtained are given below, together with some spectral data.
Diethyl 3-[bis-(2-hydroxy-ethyl)-amine]-propyl-phosphonate (1)
Empirical formula C.sub.11 H.sub.26 NO.sub.5 P: Oil n.sub.D.sup.22 = 1.4642.
IR = .nu..sub.OH = 3,382 cm.sup.-1 : .nu..sub.P=O = 1,225 cm.sup.-1. NMR (CCl.sub.4, .delta. in ppm). ##STR42## 6H.sub.a at 1.3 (triplet); 4H.sub.b at 4.05 (quintuplet); 2H.sub.c + 2H.sub.d
at 1.7 (hump); 2H.sub.e + 4H.sub.f at 2.56 (triplet); 4H.sub.g at 3.05 (triplet); and 2H.sub.h at 4.5 (singlet).
Diethyl 3-[bis-(2-hydroxy-propyl)-amino]-propyl-phosphonate (2)
Empirical formula C.sub.13 H.sub.30 NO.sub.5 P: Oil n.sub.D.sup.22 = 1.4583.
IR = .nu..sub.OH = 3,340 cm.sup.-1 : .nu..sub.P=o = 1,220 cm.sup.-1. NMR (CCl.sub.4, .delta. in ppm). ##STR43## 6H.sub.a at 1.3 (triplet); 4H.sub.b at 4.02 (quintuplet); 2H.sub.c + 2H.sub.d at 1.7 (hump); 2H.sub.e + 4H.sub.f at 2.38 (multiplet); 2H.sub.g at 3.65 (hump); 2H.sub.h at 4.26 (singlet); and 6H.sub.i at 1.02 (doublet).
Diisopropyl 3-[bis-(2-hydroxy-ethyl)-amino]-propyl-phosphonate (3)
Oil n.sub.D.sup.22 = 1.4608.
IR = .nu..sub.OH = 3,380 cm.sup.-1 : .nu..sub.P=O = 1,221 cm.sup.-1. NMR (CCl.sub.4, .delta. in ppm). ##STR44## 12H.sub.a at 1.35 (doublet); 2H.sub.b + 2H.sub.h at 4.8 (hump); 2H.sub.c + 2H.sub.d at 1.7 (hump); 2H.sub.e + 4H.sub.f at 2.58 (triplet); and 4H.sub.g at 3.51 (triplet).
Diisopropyl 3-[bis-(2-hydroxy-propyl)-amino]-propyl-phosphonate (4)
Oil n.sub.D.sup.22 = 1.4542.
IR: .nu..sub.OH = 3,390 cm.sup.-1 : .nu..sub.P=O = 1,230 cm.sup.-1.
NMR (CCl.sub.4, .delta. in ppm) = ##STR45## 12H.sub.a at 1.33 (doublet); 2H.sub.b + 2H.sub.h at 4.5 (hump); 2H.sub.e + 4H.sub.f at 2.40 (multiplet); 2H.sub.g at 3.70 (hump); and 6H.sub.i at 1.03 (doublet).
Diethyl 2-[bis-(2-hydroxy-ethyl)-amino]-2-methyl-ethyl-phosphonate (5)
Empirical formula C.sub.11 H.sub.26 NO.sub.5 P Oil n.sub.D.sup.22 = 1.4627.
IR: .nu..sub.OH = 3,390 cm.sup.-1 : .nu..sub.P=O = 1,215 cm.sup.-1.
NMR (CCl.sub.4, .delta. in ppm) = ##STR46## 6H.sub.a at 1.4 (triplet); 4H.sub.b at 4.12 (quintuplet); 2H.sub.c at 1.8 (multiplet); 4H.sub.b at 2.56 (multiplet); 4H.sub.g + H.sub.d at 3.48 (multiplet); 2H.sub.h at 4.26 (singlet); and 3H.sub.c at 1.1 (doublet).
Diethyl 2-[bis-(2-hydroxy-propyl)-amino]-2-methyl-ethyl-phosphonate (6)
Oil n.sub.D.sup.22 = 1.4562.
IR: .nu..sub.OH = 3,400 cm.sup.-1 : .nu..sub.P=O = 1,221 cm.sup.-1.
NMR (CCl.sub.4, .delta. in ppm) = ##STR47## 6H.sub.a at 1.32 (triplet); 4H.sub.b + H.sub.d + 2H.sub.g at 4.08 (multiplet); 2H.sub.c at 2.8 (multiplet); 3H.sub.c + 6H.sub.i at 1.05 (appearance of doublet); 4H.sub.f at 2.35 (multiplet); and 2H.sub.h at 4.2 (singlet).
Diisopropyl 2-[bis-(2-hydroxy-ethyl)-amino]-2-methyl-ethyl-phosphonate (7)
Empirical formula: C.sub.13 H.sub.30 NO.sub.5 P: Oil n.sub.D.sup.23 = 1.4576.
IR = .nu..sub.OH = 3,350 cm.sup.-1 : .nu..sub.P=O = 1,205 cm.sup.-1.
NMR (CCl.sub.4, .delta. in ppm) ##STR48## 12H.sub.a at 1.35 (doublet); 2H.sub.b at 4.6 (septet); 2H.sub.c at 1.8 (hump); 3H.sub.c at 1.08 (doublet); 4H.sub.f at 2.5 (multiplet); 4H.sub.g + H.sub.d at 3.38 (hump); and 2H.sub.h at 4.25 (singlet).
Diisopropyl 2-[bis-(2-hydroxy-propyl)-amino]-2-methyl-ethyl-phosphonate (8)
Empirical formula C.sub.15 H.sub.34 NO.sub.5 P: Oil n.sub.D.sup.22 = 1.4539.
IR = .nu..sub.OH = 3,400 cm.sup.-1 : .nu..sub.P=O = 1,225 cm.sup.-1.
NMR (CCl.sub.4, .delta. in ppm) ##STR49## 12H.sub.a at 1.28 (doublet); 2H.sub.b at 4.60 (septet); 2H.sub.c at 1.8 (hump); 3H.sub.e + 6H.sub.i at 1.09 (hump); 4H.sub.f at 2.3 (multiplet); 2H.sub.g + H.sub.d at 3.6 (hump); and 2H.sub.h at 4.2 (singlet).
Dibutyl 2-[bis-(2-hydroxy-ethyl)-amino]-2-methyl-ethyl-phosphonate (9)
Oil n.sub.D.sup.22 = 1.4531.
IR = .nu..sub.OH = 3,370 cm.sup.-1 : .nu..sub.P=O = 1,220 cm.sup.-1.
NMR (CCl.sub.4, in ppm) ##STR50## 14H.sub.a + 3H.sub.e + 2H.sub.c at 1 and 1.6 (humps); 4H.sub.b at 4 (multiplet); H.sub.d + 4H.sub.g at 3.48 (appearance of triplet); 4H.sub.f at 2.57 (triplet); and 2H.sub.h at 4.32 (singlet).
The flameproofing action of the compounds according to the invention in polyurethane foams has been demonstrated by means of the following tests:
Rigid polyurethane foams were prepared by polycondensation of diol-phosphonates with diisocyanates under the usual conditions for the preparation of these foams. Toluene diisocyanate (TDI) in the form of a mixture of the 2,4- (80%) and 2,6-(20%) isomers, and 4,4'-diisocyanatodiphenylmethane (MDI) were used as the diisocyanates. The foams were prepared in accordance with the so-called "one-shot process" which consists of reacting the diisocyanate with the diol containing the catalysts (tertiary amines and tin derivatives) and the pore-forming agent.
The procedure was as follows:
0.05 mole of the diol-phosphonate containing 0.1 g of diazabicyclooctane, 0.2 g of "Silicone 9193", approximately 2 g of Freon 11 (in the case of diol-phosphonates derived from diisopropanolamine, 0.1 g of dibutyl-tin dilaurate was also added) were cooled slightly, and then 0.05 mole of the diisocyanate was added whilst stirring vigorously. The foam was then left "to rise". The "cream" times were of the order of 5 to 10 seconds.
The results obtained when the foams thus obtained were brought into contact with a flame are given in Tables 3 and 4 below. In these Tables S.E. denotes self-extinguishing and S.C. denotes slightly combustible. It can be seen that the foams prepared using TDI (Table 3) are more self-extinguishing than those prepared using MDI (Table 4).
TABLE 3__________________________________________________________________________POLYCONDENSATIONS WITH TDI__________________________________________________________________________Diol-phosphonate No. Polyurethane obtained %P__________________________________________________________________________ Type ##STR51## ##STR52## 6.8 S.E. ##STR53## ##STR54## 6.4 S.E. ##STR55## ##STR56## 6.4 S.E. ##STR57## ##STR58## 6 S.E. ##STR59## ##STR60## 6.8 S.E. ##STR61## ##STR62## 6.4 S.E. ##STR63## ##STR64## 6.4 S.E. ##STR65## ##STR66## 6 S.E.__________________________________________________________________________
TABLE 4__________________________________________________________________________POLYCONDENSATIONS WITH MDIDiol-phos-phonates No. Polyurethane obtained % P Type__________________________________________________________________________ ##STR67## 5.8 S.E.2 ##STR68## 5.5 S.E.3 ##STR69## 5.5 S.E.4 ##STR70## 5.2 S.C.5 ##STR71## 5.8 S.E.6 ##STR72## 5.5 S.E.7 ##STR73## 5.5 S.C.8 ##STR74## 5.2 S.C.__________________________________________________________________________
Experiments were also carried out using diol-phosphonates as additives in rigid polyurethane foams. The results obtained are given below, compound No. 1 being used as an example of the diol-phosphonate according to the invention, and the results obtained are compared with those obtained using Fyrol 6, that is to say diethyl [bis-(2-hydroxy-ethyl)-amino]-methyl-phosphonate.
Polyurethane foams were prepared, using the following mixture:
Alcohol: 80 g of TP 440 (trimethylolpropane epoxidised by means of propylene oxide),
isocyanate: 105.5 g of MDI,
blowing agent: 30 g of Forane (Freon II),
catalysts: 0.10 g of DBTL (dibutyl-tin dilaurate) and 1 g of NMM (N-methylmorpholine),
silicone: 1 g of Si 9193 supplied by Messrs. Rhodorsil; and flameproofing agent: a phosphonate in an amount to provide the P contents indicated in Table 5. The density of the foam thus obtained was approximately 34 g/l.
TABLE 5______________________________________ Phosphorus-containing P content inComposition additive %______________________________________R None 01 Fyrol 6 0.512 " 0.963 " 1.674 " 2.195 Compound No. 1 0.506 " 0.707 " 0.998 " 1.42______________________________________
The flameproof properties of the foams thus prepared were determined by means of the LOI (limiting oxygen index) combustion test.
The mechanical properties, as well as the effect of aging on the mechanical properties, were determined by measuring the corresponding critical pressures of foams of identical density which had been flameproofed by means of 1% of phosphorus.
The tests used were as follows:
LOI: ASTM 2863 test
This test consists of burning a sample of specific dimensions (0.3 .times. 0.3 .times. 13 cm) in an atmosphere possessing a defined and adjustable oxygen concentration. The minimum oxygen concentration necessary to cause and maintain combustion is measured. The Limiting Oxygen Index is given by the formula: ##EQU1##
Compressive Strength: Standard Specification NFT 56,101
This test consists of subjecting a test specimen (5 .times. 5 .times. 5 cm) to an increasing pressure between two platens and of determining the corresponding force/crushing diagram. The critical pressure Pc, that is to say the value of the pressure for which the deformation of the sample becomes irreversible, is measured. This value was determined in the expansion direction.
Aging
Two types of aging were carried out:
(a) Aging in a wet atmosphere, by immersion in water for 144 hours at ordinary temperature.
(b) Aging in a dry atmosphere for 22 hours at 140.degree. C.
Results
(a) Flameproof properties
Table 6 gives the LOI values measured.
TABLE 6______________________________________Polyurethanefoam %P LOI______________________________________R 0 0.1721 0.51 0.1882 0.96 0.1963 1.67 0.2074 2.19 0.2165 0.50 0.1936 0.70 0.1977 0.99 0.2028 1.42 0.207______________________________________
This Table shows that the foams which were flameproofed by means of the phosphonate according to the invention possess, for an identical phosphorus content, a better LOI, and thus improved fire-resistance, then the foams which were flameproofed by means of the known phosphonate.
(b) Mechanical properties
The mechanical properties were determined by means of the compressive strength. The critical pressures Pc of the reference foams R and those of the flameproofed foams A and B containing 1% of phosphorus, added respectively in the form of Fyrol 6 and of compound No. 1, were compared. Since the critical pressure Pc depends on the density of the foams, the measurements were made on foams of a particular and identical density. Table 7 gives the values for the critical pressures of the polyurethane foams investigated. Samples of each of the foams R, A and B having two different densities were employed. Table 7 also lists the % variation in the critical pressure of the flameproofed foams A and B compared with the reference foam R, this percentage being defined for foams A and B respectively by the formulae; ##EQU2##
TABLE 7______________________________________CRITICAL PRESSURES Variation in Pc Density Critical pressure in % relativeFoam g/l Po in bars to PcR______________________________________R 35 2.2 --A 35 1.5 -33B 35 2.2 0R 45 3.3 --A 45 2.0 -37B 45 3.25 -1.5______________________________________
Table 7 shows clearly that, for the same density, the critical pressures of the foams R and B are substantially the same, whilst they are considerably less (by approximately 36%) in the case of the foams A. These measurements show that the introduction of compound No. 1 of the invention, which leads to the foam B, does not significantly affect the mechanical properties of the foam.
(c) Aging experiments
In order to investigate the dry and wet aging characteristics of the foams R, A and B, the critical pressures Pc were measured before and after aging, and this made it possible to determine the percentage deterioration in the mechanical properties of the foams which had undergone aging, using the formula: ##EQU3##
Table 8 gives the deteriorations in the mechanical properties of the foams caused by the aging procedures. The measurements were made on foams of density 45 g/l, having a 1% phosphorus content (foams A and B).
TABLE 8______________________________________AGING EXPERIMENTS Deterioration in the mechanical properties, in %Foam Wet aging Dry aging______________________________________R +5 -6A -11 -8B -16 -9______________________________________
Notes
After wet aging, the reference foam R possessed better mechanical properties. This could arise from the excess isocyanate groups in these formulations, leading to crosslinking reactions under the action of water. In contrast, the mechanical properties of the foams A and B underwent slight deterioration during the 2 types of aging processes.
The deterioration was more marked in the case of wet aging because of the partial hydrolysis of the ester-phosphonate groups leading to phosphonic acids, which in their turn promoted hydrolysis reactions.
Other experiments were carried out which further demonstrated the advantages possessed by the foams flameproofed by means of a phosphonate according to the invention.
(b) Delay in self-ignition
______________________________________Epiradiator: 300.degree. C.Foam R Foam A Foam B (according to the invention)(Reference foam) (Containing 1% (Containing 1% of of Fyrol 6) compound No. 1)5.2 seconds 4.7 seconds 5.6 seconds______________________________________
It is seen that the foam according to the invention ignites after a longer period than the reference foam and after a considerably longer period than the foam containing Fyrol.
(e) Fume density
Maximum specific optical density above the sample set alight, as measured in the NBS fume chamber. ##EQU4## I = light transmitted at the maximum evolution of fumes Io = light transmitted before setting alight
V/al = factor characteristic of the chamber: V/AL = 132 for the NBS chamber.
The results obtained were as follows:
______________________________________Foam R Foam A Foam B______________________________________175 689 400______________________________________
Thus it may be seen that a markedly lower fume density was observed in the case of the foam according to the invention than in the case of the foam containing Fyrol.
(f) Toxic products (ppm) evolved during combustion
______________________________________ Foam R Foam A Foam B______________________________________CO 1,000 900 320HCN 20 20 12______________________________________
The toxic products evolved were, in the case of the foam of the invention, markedly less than in the case of the reference foam or even in the case of the foam containing Fyrol.
Experiments were also carried out using compound No. 5.
The composition used to prepare the polyurethane foam was as follows:
Alcohol: 80% of TP 440 (trimethylolpropane epoxidised by means g propylene oxide),
isocyanate: 61.6g of TDI (toluene diisocyanate),
blowing agent: 18.8 g of Forane (Freon II),
catalysts: 0.38 g of DBTL (dibutyl-tin dilaurate) and 0.12 g of DABCO (diazabicyclooctane),
silicone: 1.13 g of Si 9193 supplied by Messrs. Rhodorsil; and
flameproofing agent; a phosphonate used in an amount to provide a P content of 0.98%.
The following LOI values were obtained
Reference foam: LOI 0.167
Flameproofed foam: LOI 0.189
It is apparent from all these experiments that the compounds according to the invention can be used as copolycondensed flameproofing additives in rigid polyurethane foams, advantageously in proportions corresponding to phosphorus contents of up to 2%, and preferably of 0.5 to 1.5%, and in particular of approximately 1%.

Number	Name	Date
3076010	Beck	Jan 1963
3235517	Beck	Feb 1966
3294710	Rosenberg	Dec 1966
3674748	Iliopulos	Jul 1972
4052487	Sturtz	Oct 1977

Diol-phosphonates as flame-retardants in polyurethane foam

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