CA1255448A

CA1255448A - Flame-retardant agents stable to hydrolysis, based on ammonium polyphosphate

Info

Publication number: CA1255448A
Application number: CA000490114A
Authority: CA
Inventors: Horst Staendeke; Eduard Michels
Original assignee: Hoechst AG
Current assignee: Clariant Produkte Deutschland GmbH
Priority date: 1984-10-18
Filing date: 1985-09-06
Publication date: 1989-06-06
Also published as: EP0180790A1; KR930006474B1; DE3560398D1; ES8605559A1; ES548018A0; DE3528737A1; EP0180790B1; KR860003325A

Abstract

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

ABSTRACT OF THE DISCLOSURE

A microencapsulated flame-retardant agent stable to hydrolysis, based on free flowing, pulverulent ammonium polyphosphate of the general formula H(n-m)+2(NH4)mPnO3n+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 99.5 mass % ammonium polyphosphate and b) about 0.5 to 25 mass % of a reaction product of a polyisocyanate and water, the resulting polyurea encapsulating the individual ammonium polyphosphate particles.

Description

The present invention relates to a microencapsulated flarne-retardant agent stable to hydrolysis, based on free flowing, pulverulent arnmonium polyphosphate, and to a process for making it.
It is generally accepted that ammonium polyphos-phates can be used for imparting flame-retardant pro-perties to plastics materials. German Specification DE-AS 12 83 532, for example, discloses a process for making flame-retardant polyurethanes from high molecular weight polyhydroxyl compounds, polyisocyanates and cata-lysts, containing, as a flame-retardant additive,an 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 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 ammoniurn polyphosphates of the above general formula are known to impart good flame-retardant pro-perties to polyurethanes, the fact remains that they are not sufficiently water-insoluble and therefore liable to be washed out from ~he plastics material in tha 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-insoluble really have a considerable solubility in water;
indeed up to 5 9 ammonium po].yphosphate becomes dissolved on suspending 10 9 ammonium polyphosphate in 100 ml water at 25C; in other words, up to 50 % of the ammonium poly-,~r, ~S~

phosphate is water-soluble.
German Specifications DE-OS 29 49 537 and DE-OS
30 05 252 disclose processes for making pulverulent ammonium polyphosphates stable to hydrolysis by encap-sulating the ammonium polyphosphate particles in a mela-mine/formaldehyde-resin or phenol-formaldehyde-resin.
Ammonium polyphosphate less soluble in water than Ull-treated ammonium polyphosphate is obtained in the two cases.
The encapsulated material fails however to be an ideal flame-retardant agent as it tends to liberate formaldehyde.
A further process for making pulverulent ammonium polyphosphates stable to hydrolysis by encapsulating them with a hardened epoxide resin has been described in German Specification DE-OS 32 17 816. The epoxide resins do however not reduce the water-soluble fractions as effectively as melamine/formaldehyde-resin.
It is therefore highly desirable to have an agent and process permitting the solubility of ammonium poly-phosphate in water to be minimized, and to produce a flame-retardant agent based on ammonium polyphospha-te which is substantially not liable to be washed out From plastics materials, wood or paper under outdoor condi-tions. In addition, it is highly desirable to have encapsulating materials liberating no pollutants.
We have now unexpectedly found that polyureas should advantageously be substituted for melamine and phenol resins.

The present invention now provides a microencapsu-L~

lated flame-retardant ayent stable to hydrolysis, based on 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, 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 polyisocyanate and water, the resulting polyurea encapsulating the individual ammonium polyphosphate particles.
The agent of this invention general 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, Griffiter and McCullough" in Anal. Chem. 26, page 1755 (1954).
The agent of this invention should preferably con-tain the polyurea in a proportion of 2 to about 15 mass %.
The polyurea is a reaction product which is obtained by subjecting a polyisocyanate to a polyaddition reaction with the polyamine resulting from the reaction of the polyisocyanate with water, during which carbon dioxide is split off. The form "polyisocyanate" as used herein denotes all commercially available aromatic and aliphatic diisocyanates and poly-isocyanates as well as prepolymers based on polyisocyanates modified with a polyurethane, polyisocyanurate or polycarbodiimide, which are prepared from commercially available arornatic or aliphatic diiso-cyanates ancl polyisocyanates by subjec-t:ing these latter to partial reaction with a polyhydroxy compound, or to a partial carbodiimidization reaction or to a partial trimerization reaction, and which are used, e.g. for the manufacture of polyurethane, polyisocyanurate or poly-carbodiimide foams.
The process of this invention for making the micro-encapsulated flame-retardant agent stable to hydrolysis comprises: microencapsulating - in a polyurea - a suspen-sion consisting substantially of a diluent, a 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 about 1, a polyisocyanate and water by heating the suspension, while stirring, over a period of 0.5 to 5 hours to a tempera-ture between 30 and 200C and thereafter cooling, filtering and drying the ammonium polyphosphate microencapsulated in the polyurea.
Further preferred and optional eaturas 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 with the water, in the diluent, in the sequential order indicated;
b) for n in the above general formula of the ammonium polyphosphate to stand for an integer having an average value of 450 to 80û;

c) for the diluent to be selected from proton-inactive solvents miscible with water- or solvent mixtures such as aliphatic, aromatic and rnixed aliphatic/
aromatic ketones, preferably acetone;
d) for the polyisocyanate to be selected from commer-cially available aromatic or aliphatic di- and poly-isocyanates as well as from prepolymers based on a a polyisocyanate modified with a polyurethane or polycarbodiimide or polyisocyanurate, the prepoly-mers being made from commercially available aromatic or aliphatic di- and polyisocyanates by subjecting these latter to partial reaction with a polyhydroxy compound, to a partial carbodiimidization reaction or partial ,trimerization reaction;
e) for the polyisocyanate to be s.elected from poly-isocyanates modified with a polycarbodiimide in a partial carbodiimidization reaction, preferably to be 4,4'-diphenylmethanediisocyanate modified with a polycarbodiimids;
f) for the reactant selected for the polyisocyanates to be water;
g) for an ammonium polyphosphate/diluent/polyisocyanate/
water-ratio of 1 : 1.5-2.5 : 0.05-0.25 : 0.005-0.1 more preferably 1 : 2 : 0.1 : 0.02 to be established in the suspension;
h) for'the heating to be effecte,d over a period of 1 to 2 hours to a temperature of 50 - 100C;
i) 'for the drying to be effected at a temperature bet-ween 80 and 150C under inert gas, preferably under nitrogen;

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k) for the flame-retardant microencapsulated ammonium polyphosphate to consis-t substantially of particles having an average size between 0.01 and 0.1 mm, more preferably between 0.03 and 0.06 mm;
l) for the flame-retardant agent to contain the polyurea in a proportion of 2 to about 15 mass %.
The invantion fina.lly relates to a process using the present agent for imparting flame-retardant properties to polyurethanes and polyurethane foams, the polyurethane foams containing the agent in a proportion of about 5 to 25 mass %, based on the quantity of the polyol component of the polyurethane.
The polyurea should conveniently be applied to the ammonium polyphosphate particles in a proton-inactive solvent miscible with water, or in a solvent mixture e.y.
in an aliphatic, aromatic or mixed aliphatic/aromatic ketone; more particularly, the polyurea is applied while stirring to an ammonium polyphosphate/polyisocyanate/
water-suspension, the polyaddition reaction being carried 20 out while heating.
By encapsulating the ammonium polyphosphate particles in a polyurea in accordance with this invention, the solubility of ammonium polyphosphate in water is conside-rably reduced; this beneficially influences the encapsu-25 lated arnmonium polyphosphate for use as a flame-retardant agent in polyurethane foams, for example.
As an encapsulating material for ammonium poly-phosphates, the polyureas compare favorably with standard phenol/formaldehyde resins and epoxide resins; they 30 permit tha water-solubility to be more effectively re-duced but unlike melamine/formaldehyde resins andphenol/formaldehyde resins do not liberate formaldehyde.
The agents of this invention, the process for making them and their advantages are described in the following Examples. The experiments described in the Examples were carried out with the use of commercially available ammonium polyphosphates and various commer-cially available polyisocyanates. More particularly, the following products were used:
1. EXOLIT 422 (this is a registered Trade Mark of Hoechst Aktiengesellschaft, Frankfurt/Main). It is a fine particulate difficultly water-soluble ammo-nium polyphosphate~ (NH4P03)n, 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 various aromatic diisocyanates and tri-isocyanates with 4,4'-diphenylmethanediisocyanate as its principal component. The product is a liquid, deep brown to black. Its isocyanate content lies at 30.2 % 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. SUPRASEC 1042 (this is a registered Trade Mark of Deutsche ICI GmbH, Frankfurt/Main). It is a dark liquid free from solvent which has a density (at 25C) of 1,24 g/ml and a viscosity (at 25C) of 235 mPa.s.. Its isocyanate content lies at 28.8-30.2 % NCO.

4. DESMODUR T 80 (this is a registered Trade Mark of - , ., ,-., ~s~
Bayer Aktiengesellschaft, Leverkusen). It is an isomer mlxture of an arornatic ~iisocyanate with 80 mass % 2,4-diisocyanatotoluene and 20 mass % 2,~~
diisocyanatotoluene. The product is a colorless liquid whose isocyanate content lies at about 48 %.
Its densi.ty (at 25C) is about 1.2 g/ml.

5. Isophoronediisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate) (a product of Che-mische Werke Huls Aktiengesellschaft, Marl).
It is a liquid, colorless product whose isocyanate content lies at 37.5-37.8 % NCO. Its density (at 20C) is 1.058-1.064 g/ml and its viscosity (at 20C) is 15 mPa.s.
Example 1 250 9 EXOLIT 422 was suspended in 1000 ml acetone (water cont0nt less than 0.3 ~) in a stirring apparatus of gIass; next, a solution of 15 9 CARADATE 30 in 100 ml acetone was added dropwise. The suspension was then heated to gentle boiling and admixed dropwise with a solution of 5 9 water in 50 ml acetone. The whole was stirred for a period of 2 hours, then cooled to room temperature and filtered. The filter cake was dried at 110C under nitro-90n. 253 9 encapsulated ammonium polyphosphate containing 4.5 mass % polyurea was obtained.

To determine the water-soluble fractions, 10 9 of the product so made was suspended in 100 ml water and the suspension was stirred for 20 minutes at 25C and 60C, respectively. Next, the product fraction undissolved in the water was caused to deposit within 40 minutes by centrifugation. 5.0 ml of the supernatant solution was pipe-tted in a previously weiyhed aluminium dish and evaporated at 120C in a drying cabinet. The water-soluble fraction was calculated from the quantity of evaporation residue. The result obtained is indicated in Table 1 hereinafter.
Example 2 The procedure was as in Example 1 but a solution of 30 9 CARADATE 30 in 100 rnl acetone was used. 267 9 encapsulated ammonium polyphosphate which contained 9.7 mass % polyurea was obtained. The values determined for the water-soluble fractions are indicated in Table 1.
Example 3 The procedure was as in Example 1 but a solution of 15 9 SUPRASEC 1042 in 100 ml acetone was used. 249 9 encapsulated ammonium polyphosphate which contained 5.1 mass / polyurea was obtained. The values determined for the water-soluble fractions are indicated in Table 1.
Example 4 The procedure was as in Example 1 but a solution of 30 9 SUPRASEC 1042 in 100 ml acetone was used. 264 9 encapsulated ammonium polyphosphate which contained 10.2 mass % polyurea was obtained. The values determined for the water-soluble fractions are indicated in Table 1.
Example 5 250 9 EXOLIT 422 was suspended in 400 ml acetone in a stirring apparatus of glass; next, a solution of 15 9 DESMODUR T 80 in 100 ml acetone and a solution of 5 9 water in 50 ml acetone were added. The suspension was 30 then heated to gentle boiling. The whole was stirred _g_ , ~s~

for a period of 2 hours, cooled to room temperature and filtered. The filter cake ob-tained was dried at 100C
in a stream of nitrogen. 257 g encapsulated ammonium polyphosphate which contained 4.3 mass % polyurea was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 2.
Example 6 The procedure was as in Example 5 but a solution 10 of 30 9 DESMODUR T 80 in 100 ml acetone was used. 272 g encapsulated ammonium polyphosphate which contained 7.5 mass % polyurea was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 2.
Example 7 The procedure was as in Example 5 but a solution of 15 g isophoronediisocyanate in 100 ml acetone was used.
252 9 encapsulated ammonium polyphosphate which con-tained 5.2 mass % polyurea was obtained.
The values determined ~or the water-soluble frac-tions are indicated in Table 2.
Example 8 The proce~ure was as in Example 5 but a solution of 30 g isophoronediisocyanate in 100 ml acetone was used.
266 g encapsulated ammonium polyphosphate which con-tained 8.9 mass ~ polyurea was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 2.
Example 9 The procedure was as in Example 5 but a solution of ~s~
30 9 CARADATE 30 modified with 30 9 polycarbodiimide (prepared by heating CA~ADATE 30 with 15 ppm of a carbo-diimidization catalyst (e.g. l-methyl-l-oxo-phospholene, a product of Hoechst Aktiengesellschaft, frankfurt/Main) to 110C until establishment of an isocyanate content of 27.5 %) in 100 ml acetone was used.
272 9 encapsulated ammonium polyphosphate which con-tained 8.7 mass % ,oolyurea was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 3.
Example 10 The procedure was as in Example 9 but CARADATE 30 modified with a polycarbodiimide and containing 25.4 %
isocyanate was used.
266 9 encapsulated ammonium polyphosphate which con-tained 8.3 mass % polyurea was obtained.
The values determined for the water-solubl0 frac-tions are indicated in Table 3.
Example 11 The procedure was as in Example 9 but CARADATE 30 modified with a polycarbodiimide and containing 22.7 %
isocyanate was used.
269 9 encapsulated ammonium polyphosphate which con-tained 8.8 mass % polyurea was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 3.
Example 12 The procedure was as in Example 9 but CARADATE 30 modified with a polycarbodiimide and containing 19.8 %
isocyana~e was used.

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279 9 encapsulated ammonium polyphosphate which contained 9.1 mass % polyurea was obtained.
The values determined for the ~Jater-soluble frac-tions are indicated in Table 3.

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The values indicated in Tables 1 through 3 show that the modifying agents of this invention permit the content of water-soluble fractions to be considerably reduced (up to 90 % at 25C and up to 97 % at 60C).

Claims

The embodiments of the invention in which an exclusive properly or privilege is claimed are defined as follows:

WE CLAIM

1. A flame retardant agent based on free flowing pulveru-lent ammonium polyphosphate of the general formula H(n-m)+2(NH4)mPnO3n+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 polyisocyanate and water, the resulting polyurea 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 polyurea in a proportion of 2 to about 15 mass %.

5. Agent as claimed in claim 1 wherein the polyurea is a reaction product obtained by subjecting a polyiso-cyanate and water to a polyaddition reaction.

6. A process for making a flame-retardant agent as claimed in claim 1 which comprises: microencapsulating in a polyurea, a suspension consisting substantially of a diluent, a free flowing pulverulent ammonium polyphos-phate of the general formula H(n-m)+2(NH4)mPnO3n+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, a polyisocyanate and water by heating the suspension, while stirring, over a period of 0.5 to 5 hours to a temperature between 30 and 200°C and thereafter cooling, filtering and drying the ammonium polyphosphate micro-encapsulated in the polyurea.

7. Process as claimed in claim 6, wherein a suspension of diluent and ammonium polyphosphate is gradually ad-mixed with a solution of the polyisocyanate and with water 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 polyphos-phate.

9. Process as claimed in claim 6, wherein the solvent is a proton-inactive solvent miscible with water, or sol-vent mixture.

10. Process as claimed in claim 9, wherein the diluent is an aliphatic, aromatic or mixed aliphatic/aromatic ketone.

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

12. Process as claimed in claim 6, wherein the polyiso-cyanate is a commercially available aromatic or ali-phatic di- or polyisocyanate or a prepolymer based on a polyisocyanate with a polyurethane, polycarbodiimide or polyisocyanurate.

13. Process as claimed in claim 12, wherein the polyiso-cyanate is 4,4'-diphenylmethanediisocyanate modified with a polycarbodiimide.

14. Process as claimed in claim 6, wherein the polyisocyanate is reacted with water.

15. Process as claimed in claim 6, wherein an ammonium polyphosphate/diluent/polyisocyanate/water-ratio of 1 : 1.5-2.5 : 0.05-0.25 : 0.005-0.1 is maintained in the suspension.

16. Process as claimed in claim 15, wherein an ammonium polyphosphate/diluent/polyisocyanate/water-ratio of 1 : 2 : 0.1 : 0.02 is maintained in the suspension.

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-re-tardant microencapsulated ammonium polyphosphate substantially consists of particles having an average size between 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 particle size between 0.03 and 0.06 mm.

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

23. Polyurethanes and polyurethane foams having flame-retardant 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 polyphosphate of the general formula H(n-m)+2(NH4)mPnO3n+1 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, 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 polyisocyanate and water, the polyurea encapsula-ting the individual ammonium polyphosphate par-ticles.