CA1258010A

CA1258010A - Flame - retardant agents stable to hydrolysis, based on ammonium polyphosphate

Info

Publication number: CA1258010A
Application number: CA000489250A
Authority: CA
Inventors: Horst Staendeke; Eduard Michels
Original assignee: Hoechst AG
Current assignee: Clariant Produkte Deutschland GmbH
Priority date: 1984-10-18
Filing date: 1985-08-22
Publication date: 1989-08-01
Also published as: KR930006472B1; KR860003323A; ES8605562A1; ES547874A0; EP0178554A1; EP0178554B1; DE3560455D1; DE3526965A1

Abstract

FLAME-RETARDANT AGENTS STABLE TO HYDROLYSIS, BASED ON AMMONIUM POLYPHOSPHATE

ABSTRACT OF THE DISCLOSURE
A flame-retardant agent based on free flowing, pul-verulent ammonium polyphosphate of the general formula H(n-m)+2(NH4)mPn03n+1 in which n stands for an integer with an average value of about 20 to 800 and the ratio of m/n is about 1, consists substantially of a) about 75 to 94.5 mass %, ammonium polyphosphate and b) about 0.5 to 25 mass % of a reaction product of a polyisocyanate and a polyhydroxy compound, the re-sulting polyurethane encapsulating the individual am-monium polyphosphate particles.

Description

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The present invention relates to a microencapsulated flame-retardant agent stable to hydrolysis, based on free flowing, pulverulent ammonium polyphosphate, and to a process for making it.
It is generally acceptecl that ammonium polyphospha-tes can be used for imparting flame-retardant properties to plastics materials. German Specification DE-AS
12 83 532 9 for example 7 discloses a process for making flame-retardant polyurethanes from high molecular weight polyhydroxyl compounds, polyisocyanates and catalysts, containing, as a flame-retardant additive, an ammonium polyphosphate of the general formula H(n m)~2(NH4)mPnO3n+l in which n stands for an integer having an average value of more than 10, m stands for an integer of at most n+2 ; and the ratio of m/n is between about 0.7 and 1.1.
While ammonium polyphosphates of the above general formula are known to impart good flame-retardant properties to polyurethanes, the ract remains that they are not sufficiently water-insoluble and therefore liable to be washed out from the plastics material in the course of time under outdoor conditions. As can be inferred from the statements made in column 3 of DE-AS 12 83 532, the ammonium polyphosphates said to be practically water-in-soluble really have a considerable solubility in water;indeed up to 5 9 ammonium polyphosphate becomes dissolved on suspending 10 9 ammonium polyphosphate in 100 ml water at 25~C; in other words, up to 50 O of the ammonium poly-phosphate is water-soluble.

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~ erman Specifications DE-OS 29 49 537 and DE-OS
30 05 252 disclose pracesses for making pulverulent ammo-nium polyphosphates stable to hydrolysis by encapsulating the ammonium polyphosphate particles in a melamine/form-aldehyde-resin or phenol/formaldehyde-resin. Ammonium po-lyphosphate distinctly less soluble in water than un-treated ammonium polyphosphate is obtained in the two ca-ses.
The encapsulated material fails however to be an ideal flame-retardant agent as it tends to liberate form-aldehyde.
A further process for making pulverulent ammonium polyphosphates stable to hydrolysis by encapsulating them with a hardened epoxide resin has been described in Ger-man Specification DE-OS 32 17 816~ The epoxide resins do however not reduce the water-soluble fractions as effec-tively as melamine/formaldehyde-resins.
It is therefore highly desirable to have an agent and process permitting the solubility of ammonium poly-phosphate in water to be minimized and produce aflame-retardant agent based on ammonium polyphosphate which is substantially not liable to be washed out from plastics materials, wood or paper under outdoor conditi-ons. In addition, it is highly desirable to have encapsu-lating materials liberating no pollutants.
We have now unexpectedly found that polyurethanesshould advantaneously be substituted for melamine and phe-nol resins.

The present invention now provides a microencapsu-lated flame-retardant agent stable to hydrolysis, based on free flowing pulverulent ammonium polyphosphate of the general formula H(n m)+2(NH4)mPn3n+1 in which n stands for an integer having an average value of about 20 to 800 and the ratio of m/n is abou-t 1, con-sisting substantially of a) about 75 to 99.5 mass O ammonium polyphosphate and b) about 0.5 to 25 mass O of a reaction product of a polyisocyanate and a polyhydroxy compound, the re-sulting polyurethane encapsulating the individual ammonium polyphosphate part:icles.
The agent of this invention generally consists sub--stantially of particles having an average size oF about 0.01 to 0.1 mm, and the degree of condensation n of the ammonium polyphosphate preferably is an integer having an average value of 450 to 800, determined by the terminal group titration process described by "van Wazer, Griffi-ter and McCullough" in Anal. Chem. 26, page 1755 (1954).
The agent of this invention should preferably con-tain the polyurethane in a proportion of 2 to about 15 mass O.
The polyurethane is a reaction product which is ob-tained on subjecting a polyisocyanate and a polyhydroxy compound to a polyaddition reaction. The term "polyiso-cyanate" as used herein denotes all commercially availab-le aromatic and aliphatic diisocyanates and poly-iso-cya-nates which are customarily used for making polyurethane, polyisocyanurate or polycarbodiimide foams, For example.

The term "polyhydroxy compound" as used herein deno-tes all commercially available polyether and polyester polyols of the kind used for example, for making polyure-thane foams or polyurethane elastomers, and also alipha-tic, aromatic and heterocyclic di- and polyhydroxy com-pounds.
The process of this invention for making the micro-encapsulated flame-retardant agent stable to hydrolysis comprises: microencapsulating - in a polyurethane - a lû suspension consisting substantially of a diluent, a free-flowing pulverulent ammonium polyphosphate of the general formula H ( n m ) -~-2 ( NH4 ) mPnO3n~l in which n stands for an integer having an average value of about 20 to 800 and the ratio of m/n is about 1, a po-lyisocyanate and a polyhydroxy compound by heating the suspension, while stirring, over a period of 0.5 to 5 hours to a temperature between 30 and 200~C and thereaf-ter cooling, filtering and drying the ammonium polyphos-2û phate microencapsulated in the polyurethane.
Further preferred and optional features of the pre-sent process provide:
a) for the suspension of diluent and ammonium polyphos-phate to be gradually admixed with a solution of -the polyisocyanate and a solution of the polyhydroxy compound in the diluent, in the sequential order in-dicated;
b) for n in the above general formula of the ammonium polyphosphate to stand for an integer having an ave-rage value of 450 to 800;

~ 25~

c) for the d~.luent to be selected from solvents based on aromatic, aliphatic or cycloaliphatic hydrocarbons or on aliphatic, aromatic and mixed aliphatic/aromatic ke-tones or ketone/water-mixtures or preferably to be ace-tone;
d) - for the polyisocyanate to be selected from commercially available aromatic or aliphatic diisocyanates and po-lyisocyanates, or preferably to be commercial 4,4'-di-phenylmethanediisocyanate (MDI);
lû e) for the polyhydroxy compound to be selected from commer-cially available polyether or polyester polyols or from aliphatic, aromatic and heterocyclic polyhydroxy com-pounds, preferably From melamine/formaldehyde resins;
f) for an ammonium polyphosphate to diluent to polyisocya-nate/polyhydroxy compound-ratio of 1 : 1.5 - 2.5 : 0.05 -0.25, more preferably 1 : 2 : 0.1, to be established in the suspension;
g) for the heating to be effected over a period of 1 to 2 hours to a temperature of 50 - 100C;
h) for the drying to be effected at a temperature between 80 and 150C under inert gas, preferably under nitrogen;
i) for the flame-retardant microencapsulated ammonium poly-phosphate to consist substantially of particles having an average size between 0.01 and û.l mm, more preferably : 25 between 0.03 and 0.06 mm;
k) for the flame-retardant agent to contain the polyurethane in a proportion of 2 to about 15 mass O.
The invention finally relates to a process using the present agent for imparting flame-retardant properties to ~.25~

polyurethanes and polyurethane foams, the polyurethane foams containing the agent in a proportion of about 5 to 25 mass O~
based on the quantity of the polyol component of the polyure-thane.
The polyurethane should conveniently be applied to the am-monium polyphosphate particles in a solvent based on an aroma-tic, aliphatic or cycloaliphatic hydrocarbon or in an alipha-tic, aromatic or mixed aliphatic/aromatic ketone or a ketone/
water-mixture; more particularly, the polyurethane is applied while stirring the ammonium polyphosphate/polyisocyanate/poly-hydroxy compound-suspension, the polyaddition reaction being carried out while heating.
By encapsulating the ammonium polyphosphate particles with a polyurethane in accordance with this invention9 the solubili-ty of ammonium polyphosphate in water is considerably reduced;
this benefically influences the encapsulated ammonium polyphos ; phate for use as a flame-retardant agent in polyurethane foams, for example.
As an encapsulating material for ammonium polyphosphates, the polyurethanes compare favorably with standard phenol/formaldehy-de resins and epoxide resins; they permit the water-solubility to be more effectively reduced but unlike melamine/formaldehyde-resins and phenol/formaldehyde resins they do not liberate form-aldehyde.
In addi-tion, material encapsulated in a polyurethane has a greater thermal stability than material encapsulated in a mel-amine/formaldehyde-resin; this is of particular interest for incorporation into thermoplastic materials which are processed at high temperatures.
The agents of this invention, the process for making them ~586~

and their advantages are described in the following Examples.
The experiments described in the Examples were carried out with the use of ccmmercially available ammonium polyphospha-tes and various commercially available polyisocyanates and 5 polyhydroxy compounds. More particularly, the following pro-ducts were used:
1. EXOLIT 422 (this is a registered Trade Mark of Hoechst Ak-tiengesellschaft, Frankfurt/Main). It is a fine particula-te difficultly water-soluble ammonium polyphosphate with a degree of condensation n of about 700.

2. CARADATE 30 (this is a registered Trade Mark of Deutsche Shell Chemie GmbH, Frankfurt/Main). It is a blend of va-rious aromatic diisocyanates and triisocyanates with 4,4'-diphenylmethanediisocyanate as its principal component. The product is a liquid, deep brown to black. Its isocyanate content lies at 30.2 c NCO. It has a density (at 23C) of 1.22-1.24 g/ml and a viscosity (at 25C) of 160-240 mPa-s.

3. DESMODUR T 80 (this is a registered Trade Mark of Bayer Ak-tiengesellschaft, Leverkusen). It is an isomer mixture of an aromatic diisocyanate with 80 weight O 2,4-toluenediiso-cyanate and 20 weight O 2,6-toluenediisocyanate. The pro-duct is a colorless liquid containing about 48 O isocyana-te. It has a density (at 25C) of about 1.2 g/ml.

4. Isophoronediisocyanate (3-isocyanatomethyl-3,5,5-tri-~ methylcyclohexyl isocyanate) (a product of Chemische Werke Huls, Marl). It is a liquid colorless product with an isocyanate content of 37.5 - 37.8 O NCO. Its density (at 20C) is 1.058 - 1.064 g/ml and its viscosity (at 20C) is 15 mPa s. ~

5. CARADOL 585-8 (this is a registered Trade Mark of Deutsche Shell Chem~e GmbH, Frankfurt/Main). It is a polyetherpoly-ol which has an ûH-number of 580 mg KOH/g, a density (at 20C) of 1~10 g/ml and a viscosity (at 20C) of 7500 mPa-s.

6. UGIPOL 1004 (this is a registered Trade Mark of Arco Chemi-cal Europe, Inc., Dusseldorf). It is a polyetherpolyol whi~h has an OH-number of 235 - 295 mg KOH/g, a density (at 20C) of 1.01 g/ml and a viscosity (at 25C) of 50 mPa s.

7. UGIPOL 1020 (this is a registered Trade Mark of Arco Chemi-cal Europe, Inc., Dusseldorf). It i9 a polyetherpolyol which has an OH-number of 54 - 60 mg KOH/g~ a density (at 25C) of 1.00 g/ml and a viscosity (at 25C) of 300 mPa-s.

8. Polyol GOO PU (a product of Hoechst Aktiengesellschaft, Frankfurt/Main). It is a polyethylene glycol which has an OH-number of 178 - 197 mg KOH/g, a viscosity (at 25C) of 150 mPa-s and a density (at 25C) of 1.12 g/ml.
; 9. ALVONOL PN 320 (this is a registered Trade Mark of Hoechst Aktiengesellschaft, Frankfurt/Main). It is a bright unhar-denable phenol resin of the kind of novolac which has an OH-number of about 530 mg KOH/g, a melting point of 83 -88C and a density (at ZOC) of 1.25 g/ml.
10. PHENODUR PR 373 (this is a registered Trade Mark of Hoechst Aktiengesellschaft, Frankfurt/Main). It is a bright harde-; nable phenol resin. The product has an OH-number of about 600 - 610 mg KOH/g and a density (at 20C) of 1.26 g/ml.
11. KAURAMIN-impregnating resin 700, powder (this is a regi-stered Trade Mark of BASF Aktiengesellschaft, Ludwigsha-fen). It is a white pulverulent melamine/formaldehyde-con-densation resin. In a 50 cO aqueous solution, the product has a viscosity (at 20C) of 20 - 50 mPa-s, a density (at 20C) of l.Z2 g/ml and a pH-value of 8.8 - 9.
12. MADURIT MW 9û9 (this is a registered Trade Mark of Hoechst Aktiengesellschaft, Frankfurt/Main). It is a white pulver-ulant melamine/formaldehyde-condensation resin. In a 50 O
aqueous solution, the product has a viscosity (at 20C) of about 30 mPa-s, a density (at 20C) of 1.21 - 1.22 9/
ml and a pH-value of 9.0 - 10Ø
Example 1 250 9 'XOLIT 422 was suspended in lnOO ml xylene in a 10 stirring apparatus of glass; next, 9.8 9 CARADOL 585-8 and 15.2 9 CARADATE 30 were added dropwise. The suspension was then heated to gentle boiling, stirred for 2 hours, cooled to room temperature and Filtered. The filter cake was dried at 110C under nitrogen. 264 9 encapsulated ammonium polyphosphate containing 7.9 mass ~ polyurethane was ob-tained.
To determine the water-soluble fraction, lû g of the product so made was suspended in lnO ml water and the sus-pension was stirred for 20 ~lnutes at 25C. Next, the pro-duct fraction undissolved in the water was caused to depo-sit within 40 minutes by centrifugation. 5.0 ml of the su-pernatant solution was pipetted into a previously weighed aluminum dish and evaporated at 12nC in a drying cabinet.
The water-soluble fraction was calculated from the quanti-ty of evaporated residue. The result obtained is indicated in Table 1 hereinafter.

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Example 2 The procedure was as in Example 1 but 14.7 q UGIPOL1004 and 10.3 9 CARADATE 3n were used. 266 9 encapsulated ammonium polyphosphate which contained 8.7 mass O polyure-S thane was obtained. The values determined for the wa-ter-soluble fractions are indicated in Table 1.
Exsmple 3 The procedure was as in Example 1 but 26.3 ~ UGIPOL
ln20 and 3.79 CARADATE 30 were used. 271 9 encapsulated ammonium polyphosphate which contained 10.1 mass O poly-urethane was obtained. The values determined for the wa-ter-soluble fractions are indicated in Table 1.
Example 4 The procedure was as ln Example 1 but 16.6 q Polyol 600 PU and 8.4 cl CARADATE 30 were used.
269 9 encapsulated ammonium polyphosphate which con-tained 8.3 mass cO polyurethane was obtained. The values determined for the water-soluble fractions are indicated in Table 1.

Example 5 250 9 EXOLIT ~22 was suspended in 400 ml acetone in a stirring apparatus of glass; nex-t, a solution of 4.75 q CARADATE 30 in lOO ml acetone and a solution of 1.5 q KAIJ-ramin - impregnating resin 700 powder in 4n ml acetone/20 ml water were added. The suspension was then heated to gentle boiling. The whole was stirrecl for a period of 1 hour, cooled to room temperature and filtered. The filter cake obtained was dried at 100C in a stream of nitrogen.

246 9 encapsulated ammonium polyphosphate which contained 1.9 mass ~ polyurethane was obtained.

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The values determined for the water-soluble fractions are indicated in Table 2.
Example 6 The procedure was as in Example 5 but a solution of

9.5 9 CARADATE 30 in 100 ml acetone and a solution of 3 9 KAURAMIN - impregnating resin 70n powder in 40 ml aceto-ne/20ml water were used. 251 9 encapsulated ammonium ooly-phosphate which contained 4.2 mass iO polyurethane was ob-tained.
The values determined for the water-soluble fractions are indicated in Table 2.
Example 7 The procedure was as in Examp.le ~ but a solution of 1~.25 9 CARADATE 3Q in 100 ml acetone and a solution of 4.5 9 KAURAMIN - impregnatin4 resin 700 powder in 40 ml acetone/2Q ml water were used. 263 4 encapsulated ammonium polyphosphate which contained 6.6 mass ~O polyurethane was obtained.
The values determined for the water-soluble fractions are indicated in Table 2.
Example ~
The procedure was as in Example 5 but a solution of 19 9 CARADATE 3n in 100 ml acetone and a solution of 6.0 9 KAURAMIN - impregnating resin 700 powder in 40 ml aceto-25 ne/20 ml water were used. 271 9 polyphosphate which con-tained 8.7 mass ~O polyurethane was obtained.
The values determined for the water-soluble fractions are indicated in Table 2.
Example ~
The procedure was as in Example 5 but a solution of ~2~

28.5 9 CARADATE 30 in 100 ml acetone and a solution of 9.0 g KAURAMIN - impregnating resin 700 powder in 40 ml ace-tone/20 ml water were used. 274 9 encapsulated ammonium polyphosphate which contained 13.4 mass O polyurethane was obtained.
The values determined for the water-soluble fractions are indicated in Table 2.
Example 10 The procedure was as in Example 8 but a solution of 6 9 MADURIT MW gn9 in 40 ml acetone/2Q ml water was used.
273 9 encapsulated ammonium polyphosphate which contained 8.3 mass 6 polyurethane was obtained.
The values determined for the INater-solub]e fractions are indicated in Table 3.
Example 11 The procedure was as in Example 5 but a solution of 20 9 CARADATE 30 in 100 ml acetone and a solution of 5 9 ALNOVOL PN 320 in 50 ml acetone were used. 263 q encapsu-lated ammonium polyphosphate which contained 7.9 mass O
polyurethane was obtained.
The values determined for the water-soluble fractions are indicated in Table 3.
Example 12 The procedure was as in Exarriple 5 bu-t a solution oF
]7.5 9 CARADATE 30 in 100 ml acetone and a solution of 7.5 9 PHENODUR PR 373 in 50 ml acetone were used. 261 q encapsulated ammonium polyphosphat.e which contained 7.6 mass ~0 polyurethane was obtained.
The values determined for the water-soluble Fractions are indicated in Table 3.

Example 13 The procedure was as in Example 5 but a solution of 17.5 9 DESMODUR T 80 in 100 ml acetone and a solution of 7.5 9 KAURAMIN-impregnating resin 700 powder in 40 ml ace-tone/20 ml water were used. 275 9 encapsulated ammonium polyphosphate which contained 8.1 mass O polyurethane was obtained.
The values determined for the water-soluble fractions are indicated in Table 3.
ln Example 14 The procedure was as in Example 5 but a solution of 20 9 isophoronediisocyanate in lnO ml acetone and a solu-tion of 5 9 KAlJRAMIN-impregnatlng resin 70n powder in 4n ml acetone/20 ml water were usecl. 266 q encapsulated ammo-nium polyphosphate which contained 7.3 mass ~ polyurethane was ootained.
- The values determined for the water-soluble fractions are indicated in Table 3.
Example 15 60 kg EXOLIT 422 was suspended in 100 1 acetone in a heatable enamelled reactor (capacity = 300 1) provided with a stirrer. Next7 a solution of 4.5 kg CARADATE 30 in 15 1 acetone and a solution of 1.4 kq KAURAMIN-impregnat-ing resin 700 powcder in 10 1 acetone/5 1 water were added.
The suspension was then heated to boiling and maintained at boiling temperature over a period of 3 hours. The whole was cooled to room temperature and filtered, and the filter cake was dried at lOO~C in a stream of nitrogen. 65.1 k9 encapsulated ammonium polyphosphate which contained 8.7 mass , polyurethane was obtained. n . 2 1 was water-soluble s~

at 25C and 0.7 O was water-soluble at 60C. This meant a reduction of the water-soluble fractions of 98 O and 99 30, respectively, compared with uncoated EXOLIT 42~.
The values determined by thermogravimetrical analysis are indicated in Table 4.

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The values indicated in Tables 1 through 3 indicate that the modifying agents of this invention permit the content of water soluble matter to be considerably reduced (uo to 98 O at 25C and up to 99 O at 60C).
The values indi.cated in Table 4 show that the nodi-fied ammonium polyphosphate, i.e. encapsulated in a poly-urethane, has a distinctly improved thermal stability.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flame-retardant agent based on free flowing pulverulent ammonium polyphosphate of the general formula H(n-m)+2(NH4)mPn03n+1 in which n stands for an integer having an average value of about 20 to 800 and the ratio m/n is about 1, consisting substantially of a) about 75 to 99.5 mass % ammonium polyphosphate and b) about 0.5 to 25 mass % of a reaction product of a polyhydroxy compound and a polyisocyanate, the resulting polyurethane encapsulating the individual ammonium polyphosphate particles.

2. Agent as claimed in claim 1 consisting substantially of particles having an average size of about 0.01 to 0.1 mm.

3. Agent as claimed in claim 1, wherein n stands for a whole number having an average value of 450 to 800.

4. Agent as claimed in claim 1 containing the poly-urethane in a proportion of 2 to 15 mass %.

5. Agent as claimed in claim 1 wherein the polyurethane is a reaction product obtained by subjecting a polyisocyanate and a polyhydroxy compound to a polyaddition reaction.

6. A process for making a flame-retardant agent as claimed in claim 1 which comprises: microencapsulating, in a polyurethane, a suspension consisting substantially of a diluent, a free flowing pulverulent ammonium polyphosphate of the general formula - 20a -H(n-m)+2(NH4)mPn03n+1 in which n stands for an integer having an average va-lue of about 20 to 800 and the ratio m/n is about 1, a polyisocyanate and a polyhdroxy compound by heating the suspension, while stirring, over a period of 0.5 to 5 hours to a temperature between 30 and 200°C and there-after cooling, filtering and drying the ammonium poly-phosphate microencapsulated in the polyurethane.

7. Process as claimed in claim 6, wherein a suspension of diluent and ammonium polyphosphate is gradually admixed with a solution of the polyisocyanate and with a solu-tion of the polyhydroxy compound in the diluent in the sequential order indicated.

8. Process as claimed in claim 6, wherein n stands for an integer having an average value of 450 to 800, in the general formula indicated for the ammonium polyphospha-te.

9. Process as claimed in claim 6, wherein the diluent is a solvent based on an aromatic, aliphatic or cycloalipha-tic hydrocarbon or on an aliphatic, aromatic or mixed aliphatic/aromatic ketone, or ketone/water-mixture.

10. Process as claimed in claim 9, wherein the diluent is acetone.

11. Process as claimed in claim 6, wherein the polyisocya-nate is a commercially available aromatic or aliphatic di- or polyisocyanate.

12. Process as claimed in claim 11, wherein the polyisocya-nate is commercial 4,4'-diphenylmethanediisocyanate (MDI).

13. Process as claimed in claim 6, wherein the polyhydroxy compound is a commercially available polyether or poly-ester polyol or an aliphatic, aromatic or heterocyclic polyhydroxy compound.

14. Process as claimed in claim 13, wherein the polyhydroxy compound is a melamine/formaldehyde-resin.

15. Process as claimed in claim 6, wherein an ammonium po-lyphosphate to diluent to polyisocyanate/polyhydroxy compound-ratio of 1 : 1.5 - 2.5 : 0.05 - 0.25 is main-tained in the suspension.

16. Process as claimed in claim 15, wherein an ammonium po-lyphosphate to diluent to polyisocyanate/polyhydroxy compound-ratio of 1 : 2 : 0.1 is maintained in the sus-pension.

17. Process as claimed in claim 6, wherein the suspension is heated to temperatures between 50 and 100°C over a period of 1 to 2 hours.

18. Process as claimed in claim 6, wherein the drying is effected at temperatures between 80 and 150°C under inert gas.

19. Process as claimed in claim 18, wherein the drying is effected under nitrogen.

20. Process as claimed in claim 6, wherein the flame-retar-dant microencapsulated ammonium polyphosphate substan-tially consists of particles having an average size be-tween 0.01 and 0.1 mm.

21. Process as claimed in claim 20, wherein the flame-re-tardant microencapsulated ammonium polyphosphate sub-stantially consists of particles having an average par-ticle size between 0.03 and 0.06 mm.

22. Process as claimed in claim 6, wherein the flame-re-tardant agent contains the polyurethane in a proportion of 2 to about 15 mass %.

23. Polyurethanes and polyurethane foams having flame-re-tardants properties, containing - in the polyurethane foam - from about 5 to 25 mass %, based on the polyol component of the polyurethane, of a flame-retardant agent based on a free flowing, pulverulent ammonium po-lyphosphate of the general formula H(n-m)+2(NH4)mPn03n+1 in which n stands for an integer having an average va-lue of about 20 to 800 and the ratio of m/n is about 1, the flame-retardant agent consisting substantially of a) about 75 to 99.5 mass % of an ammonium polyphosphate and b) about 0.5 to 25 mass % of a reaction product of a polyhydroxy compound and a polyisocyanate, the re-sulting polyurethane encapsulating the individual am-monium polyphosphate particles.