CA1262500A

CA1262500A - Flame-retardant agents stable to hydrolysis, based on ammonium polyphosphate

Info

Publication number: CA1262500A
Application number: CA000489466A
Authority: CA
Inventors: Horst Staendeke; Eduard Michels
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1984-10-18
Filing date: 1985-08-27
Publication date: 1989-10-24
Also published as: EP0178564B1; ES547875A0; KR930006473B1; EP0178564A1; KR860003324A; DE3560413D1; DE3528034A1; ES8605563A1

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)mPnO3m+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 a trimerization catalyst, the resulting polyisocyanurate encapsulating the indivi-dual ammonium polyphosphate particles.

Description

~25~0 The present invention relates to a microencapsulated flame-retardant agent s-table to hydrolysis, based on ; free flowing, pulverulent ammonium polyphosphate, and to a process for making it.
It is generally accepted that ammonium polyphosphates can be used for imparting flame-retardant properties to plastics materials. German Specification DE-AS 12 83 532, for example, discloses a process for making flame-re-tardant polyurethanes from high molecular weight poly-hydroxyl compounds, polyisocyanates and catalysts, con-taining, as a flame-retardant additive an ammonium poly-: phosphate of the general formula : :
~, :
(n m)+2(NH4)m:pno3n+l in which n stands for an lnteger havlng an a~erage value :of more than 10j m stands fo~r an integer of at;most n+2 : and;the~ratio of m/n is between about 0.7 and 1.1.
While ammonlum polyphosphates of the above genaral formula~are known to impart good:1ame-retardant pro-: pertiea to polyurethanes, the fa~ct remains:that thay : 20:~are~not: sufficiently~water-insoluble and therefore~
liable to be was~hed ~ou~:from the~plastics~matarial in : ~ : the course of time under:outdoor conditions. As can be : , , ~
nferred from tha statements made:in column 3 of DE-AS
12 83~532,:th~e ammonium polyphospha~es sai:d to ba prac-tically water-insoluble really have a considerable solu-~,.,: ~ :
:~: : bility in watar; indaed up to 5 g ammonium polyphosphate : ~ ~ b0comas`dissolved on suspending 10 9 ammonium polyphos-: phate in 100 ml water at 25C; in other words, up ko 50 %

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of the arnmonium polyphosphate is water-soluble.
German Specifications DE-OS 29 49 537 and DE-OS
30 05 252 disclose processes 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 polyphospha-te significantly less soluble in water than untreated 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 encapsulatlng them in 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 effec-tively as melamine/for~maldehyde-resins.
It is therefore highly desirable to have an agent ; 20 and process permitting the solubility of ammonium poly-phosphate ln water to be m1nimized and pro~duce a flame-retardant agent based~ Dn ammonium:polyphosphate whlch is substantially not liabl~e to :be washed out from plastics materials, wood~or pape~ under outdoor conditlons. In addltion, it ls~highl`y des1rable;to have encapsulating materials liberating no pollutants.`
We have now unexpectedly found that polylsocyanu-~, .
rates shouId advantageously be substituted for melamine and phenol resins.
:~
`~ 30 The present invention now provides a microencapsu-

-2-' :

~6~56~

-3 23343-788 lated flame-retardant agent stable to hydrolysis, based on free flowing pulverulent ammoniurn polyphosphate of the general formula H(n_,n~*2(~H4)mPn 3n-~1 ln which n stands for an in~eger having an averag~ value of about 20 to 800 and the ratio of ~n is about 1, consistlng substantially of a) about 75 to 99.5 mass '~ ammonium polyphosphate and b) about 0.5 to 25 ~ass % of a reaction product of a polyisocyana~e and 2,4,6-tris-(dimethylaminomethyl)phenol as a trimerization catalyst, the resulting polycarbopolyisocyanurate encapsulating the indiviclual ammonium polyphosphate particles.
The agent of this invention generally consists substantially o~ particles havin~ an average size of about 0.01 to 0.1 mm, and the degree of condensativn n of the ammonium polyphosphate preferably is an integer ~aving an average value ~ of 450 ~o 800, determined by the terminal group titration -`~ pxocess described by "van ~azerr Griffiter and McCullough" in Anal. Chem. 26, page 1755 (1954j.
~` 20 The agent of this invention should preferably contain ~ the polyisoayanura~e in a proportion of 2 to about 15 mass %.
;~ The polyisocyanurate is a reaction product which is obtained ~y subjecting a polyisocyanate to a catalyzed ; trimerization reaction. The term "polyisocyanate" as used `herein denotes all commercially available aromatic and aliphatic diisocyana~es and polyisocyanates whlch are customarily used for ~aking polyurethane, polyisocyanurate or polycarbodiimide foamsr ~or example.
The process of thl~s inventlon for making the microencapsulated ~lame-retardant agent stable ~o hydrolysis comprises, microencapsulating - in a polyisoayanurate - a su9pension consis~in0 substantlally of a dlluent, a ~ree-5~

-4- 23343-78 flowing pulverulent ammonium polyphosphate of the general formula H(n-m~+2(N~4)mYnO3n+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 2,4,6-tris (dimethylaminome~hyl~phenol as a trimerlzation catalyst by heating ~he suspension, while stirring, over a period of O.S to 5 hours to a temperature between 3Q and 200C and thereafter cooling, filtering and drying the ammonium polyphosphate microencapsulated in the polyisocyanurate.
Further p.referred and optional features of the present process provide~
a) for the suspension of diluent and ammonium polyphosphate to be gradually admixed with a solution of the polylsoeyanate and a solution of the trimerization catalyst in the diluent, in the sequential order indicated;
b) for n in the above yeneral formula of ammonium . : polyphosphat~ to stand for an integer having an average value of 450 to ~00;
: c) for the diluent to be selec~ed from solvents based on : aromatic, aliphatic or cycloaliphatic hydrocarbons or from aliphatic, aromatic and mixed aliphatic/aromatic ketones, .:~
~ preferably acetone;
.~ .
d) for the polyisocyanate to be selected from commercially avallable arQmatic;or aliphatic diiso~yanates ;~"`'` ~' ~
,~ ~

:'~ ~ ' :~;26;~

and polyisocyanates, preferably to be commercial 4,4'-diphenylmethanediisocyanate (MDI);
e) for the agent accelsrating the trimerization reaction to be selected from standard trimerizatlon catalysts, preferably to be 2,4,6-tris/dimethylaminomethyl/
phenol;
f) for an ammonium polyphosphate/diluent/polyisocyanate/
: trimerization catalyst-ratio of 1 : 1.5-2.5 :
0.05-0.25 : û.00025-0.025, more preferably 1 : 2 :
;~ 10 0.1 : 0.005 to be established in the suspension;
g) for the heating to be effected over a period of 1 to 3 hours to a temperature of 50 - 150C;
h) for the drying to be effected at a temperature bet-: ween 80 and 150C under inert gas, preferably under ~ nltrogen; :
j for the flame-retardant microencapsulated ammonium ;
polyp:ho:sphate to consist substantially of particl;es ~ :
having~an average size between 0.01 anq 0.1 mm, ;: : more preferably between 0.03 and 0.06 mm;
k) for the flame-retardant~agent to contain the poly-isocyan:urate l~n a proportion of 2:to about 15 mass ~.
The~lnvention flnal:ly relates t~o a process usin~g the;~
present egent ror impertlng ~fleme-retardant properties to polyurethanes and polyurethane foams, the polyurethane 25~foam~s cont~alnlng the agent~:in a proportion o~about 5 to;25~mass %,~bassd~on~the~quantity of the polyol compo-nent of the poly~urethan;e.~
: The polylsocye~nurates should conveniently be applied to the ammon:ium polyphosphate:particles in a solvent ; 30 based on an aromatic, aliphatic or cycloaliphatic hydro-~; ~5-: :

, . - , :, , :.

~6~5~3 carbon or in an aliphatic, aromat.ie or mixed aliphatic/
aromatic ketone; more particularly, the polyisocyanurate is applied while stirring to an ammonium polyphosphate/
polyisocyanate-suspension, the cata].yzad trimerization reaction being carried out while heating.
By encapsulating the ammonium polyphosphate par-ticles with a polyisocyanurate in accordance with this invention, the solubility of ammonium polyphosphate in water is considerably reduced; this beneficially influen-ces the encapsulated ammonium polyphosphate for use as a ~ flame-retardant agent in polyurethane foams, for example.
; As an encapsulatlng matarial for ammonium polyphos-phates, the polyisocyanurates compare favorably with standard phenollormaldehyde resins and epoxide resins;
they permit the water-solubllity to be more effectively reduced but unlike melamine/formaldehyde-resins and :.
phenol/formaldehyde resins they do not liberate formal-dehyde.
The agents of this invention, the process for making :~:
~ 20 them and their advantages are described in the following . ~ .
Examples. The experiments described in the Examples were carried out with the use of commercia~lly available ammo-ni~um polyphosphates and~vsriou~s commercislly svsllsble~
polyisocysnates. More~ psrticularly, the foll~wing pro-~25 ducts were used-1. EXOLIT~422 (th1s ls s registered Trade Msrk of Hoechst Aktiengesellscha~t, Frankfurt/Main). It is~a fine particulate difficultly water-solubls ammonium poly-.
phosphate with a degree of condensation n of about 3û 700.

, - - -2. CARADATE 30 (this is a registered Trade Mark of Deut-sche Shell Chemie GmbH, Frankfurt/Main). It is a blend of various aromatic diisocyanatPs and triiso-cyanates with 4,4'-diphenylmethanediisocyanate as its principal component. The product is a liquid, deep brown to black. Its isocyanate content lies at 30.2 YO NCO. It has a density (at 23C) of 1.22-l.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 Aktiengesellschaft, Leverkusen). It is an isomer mixture of an aromatic diisocyanate containing 80 mass % 2,4-toluenediisocyanate and 20 mass % 2,~-toluenediisocyanate. The product is a colorless liquid and its isocyanate conten-t lies at about 48 % N50. Its density (at 25C) is about 1.2~g/ml.
4. Isophoronediisocyanate (3-isocyanotomethyl-3,5,5-trimethyl-cyclohexylisocyanate) (a product of Chemische~
Werke Huls Ak~tiengesellschaft, Marl). It is a liquid ~` colorless product with an isocyanate content of .
~20 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 25~0 g~EXOLIT ~22 was ~suspsnd~ed in~lOOO ml acstone in~
a~stirring apparatus~of~glas~s;~next, a solution of 15 9 25~CARAOATE 30 ln lOO~ml~acetone was added dropwlse. The~
suspension~was thsn~heated to gentle~boiling and~admlx d dropwise~with a solution~of 0.3 9~ DABOO TMR trimerization catalyst (this lS a registered Trade Mark of Katalysatoren-werke Houdry-Huls GmbH, Marl.) in 50 ml acetone. The whole 30 was stirred for a period of 2 hours, then cooled to room ~. : . .:

s~

temperature and filtered. The filter cake was dried at 100C under nitrogen. 252 9 Pncapsulated ammonium poly-phosphate contalning 3.9 mass % polyisocyanurate was obtained.
To determine the water-soluble fraction, 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 pipetted into a previously weighed aluminium dish and evaporated at 120C in a drying cabinet. The water-soluble fraction was calculated from khe quantity of evaporation residue. The result obtained is indicated in ; 15 Table 1 hereinafter Example 2 ~; The procedure was as in Example l but a solution of :
30 9 CARADATE 30 in 100 ml acetone was used. The trimerl-; ~ ~zation catalyst was a solution of 0.6 9 DABC0 TMR in 50 ml acet:ne, which was added dropwise. 268 9 encap-sulated ammonium polyphosphate which contained 9.8 mass %

; p:lyisocyanurate~ W85 :btalned. The values determlned~for the water~soluble fractions are indicated in Table 1.

Example 3 ~ ~

25~The~procedure was~as ln Example 1 but a solution of 0.75 g DABC0 TMR in 50 ml acetone was~added dropwise.

254 9 encapsulated ammonium polyphosphate which contained

5.7 mass % polyisocyanurate was obtained. The values ~; determined for the water-solubIe fractions are indicated in Table 1.

::

~2~25~)~

Example 4 The procedure was as in Example 2 but a solution of 1.5 9 DABCO TMR in 50 ml acetone was added dropwise.
270 9 encapsulated ammonium polyphosphate which contained 10.9 mass % polyis~cyanurate 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 xylene in a stirring apparatus of glass; next, a solution of 25 9 DESMODUR T 80 in 100 ml xylene and a solution of 0.25 9 DMP--30 (this is a registered Trade Mark of Rohm und Haas GmbH, Frankfurt/Main) (2,4,6-tris/dimethylaminomethyl) phenol - a trimerization catalyst - in 50 ml xylene were added. The suspension was then heated to gentle boiling.
The whole was stirred for a period of 2 hours, cooled to room temperature and filtered. The filter cake was dried at 100C in a stream of ni~rogen. 267 9 encapsulated ammonium polyphosphate which contalned 6.8 mass % poly-isocyanurate 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 of 1.25~g;DMP-30 in 50~ml xylene was used. 272 9 encapsula-ted ammonium polyphosphate which contained 8.3 mass %
:
~ polyisocyanurate was~ obtained.~

E~ The values~determined for the water-soluble frac-:::
tions are indicated in Table 2 :;
~9~

: .
i : :

12625~

Example 7 The procedure was as in Example 5 but a solution of 25 9 isophoronediisocyanate in 100 ml xylene was used.
260 9 encapsulated ammonium polyphosphate which contained 5.9 mass % polyisocyanurate was obtained.
The values determined for the water-soluble frac-tions are indicated in Table 2.
Example 8 The procedure was as in Example 5 but a solution of lû 25 9 isophoronediisocyanate in 100 ml xylene and a solu-. tion of 1.25 9 ûMP-30 in 50 ml xylene were used. 27S g encapsulated ammonium polyphosphate which contained ` 7.7 mass % polyisocyanurate was obtained.
, - The values determined for the water-soluble frac-tions are indicated in Table 2.
Example 9 250 9 EXOLIT 422 was suspended in 400 ml acetona in a glass vessel; next, a solution of 25 g CARADATE 30 in lOO~ml acetone and a solution of 0.125 9 DMP-30 (2,4,6-tris(dimethylaminomethyl~phenol1 a trimerization , .
catalyst of Rohm und Haas GmbH, Frankfurt/Main) in 50 ml acetone were added. The suspension was heated to gentle ; boiling and kept at that temperature over a period of 3.;5 hours. The whole was th~en worked up as described in 25 ~Example~5.;251 9 encapsulat~ed ammonium polyphosphate which contained 3.9 mass %~polylsocyanurate was obta;lned~
The values determined for the water-soluble ~rac-tions are indicated in Table 3.
Example 10 The procedure was as in Example 9 but a solution of ~' :
:
, s~

0.25 9 DMP-30 ln 50 ml acetone was used. 257 9 encapsu-lated ammonium polyphosphate which contained 5.1 mass %
polyisocyanurate was obtained.
The values determined for the water-soluble frac-~; 5 tions are indicated in Table 3.
Example 11 The procedure was as in Example 9 but a solution of0.5 9 DMP-30 in 50 ml acetone was used. 254 g encapsulated ~ ammonium polyphosphate which contained 6.5 mass % poly-- 10 isocyanurate 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 a solution of 1.25 9 DMP-30 in S0 ml acetone was used. 266 9 encapsulated ammonium polyphosphate which contained J~2 mass % poly-isocyanurate was obtained.
The values determlned for~the water-soluble frac-..~: : :
~ tions are indicated in Table 3.
.
~; 20 Example 13 . ,~
The procedure was as in Example 9 but a solutiun of 2.5 9 DMP-30 in 50 ml acetone was used. 268 9 encap-~
sulated ammonlum polyphosphate w~hich contalned 9.2 mass %
polyisocyanura~te was obtalned.
The values determined for the water-soluble frac-tions are~lndicated in Table 3.

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The values indicated in Tables 1 through 3 indicate that the modifying agent of this invention permits the content of water-soluble fractions to be considerably reduced (up to 95 % at 25C and up to 97 % at 60C1.

: : 15 .' ~

.

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)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 2,4,6-tris-(dimethylaminomethyl)phenol as a trimerization catalyst, the resulting polyisocyanurate 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 polyisocyanurate in a proportion of 2 to about 15 mass %.

5. Agent as claimed in claim 1 wherein the polyisocyanurate is a reaction product obtained by subjecting a polyisocyanate to a catalyzed trimerization reaction.

6. A process for making a flame-retardant agent as claimed in claim 1 which comprises: microencapsulating, in a polyisocyanurate, a suspension consisting substantially of a diluent, 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 m/n is about 1, a polyisocyanate and 2,4,6-tris-(dimethylaminomethyl)phenol as a trimerization catalyst by heating the suspension, while stirring, over a period of 0.5 to 5 hour to a temperature between 30 and 200°C
and thereafter cooling, filtering and drying the ammonium polyphosphate microencapsulated in the polyisocyanurate.

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 solution of the trimerization catalyst 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 polyphosphate.

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

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

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

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

13. Process as claimed in claim 6, wherein an ammonium polyphosphate/diluent/polyisocyanate/trimerization catalyst-ratio of 1 : 1.5-2.5 : 0.05-0.25 : 0.00025-0.025 is maintained in the suspension.

14. Process as claimed in claim 13, wherein an ammonium polyphosphate/diluent/polyisocyanate/trimerization catalyst-ratio of 1 : 2 : 0.1 : 0.005 is maintained in the suspension.

15. Process as claimed in claim 6, wherein the suspension is heated to temperatures between 50 and 150°C over a period of 1 to 3 hours.

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

17. Process as claimed in claim 16, wherein the drying is effected under nitrogen.

18. Process as claimed in claim 6, wherein the flame-retardant microencapsulated ammonium polyphosphate substantially consists of particles having an average size between 0.01 and 0.1 mm.

19. Process as claimed in claim 18, wherein the flame retardant microencapsulated ammonium polyphosphate substantially consists of particles having an average particle size between 0.03 and 0.06 mm.

20. Process as claimed in claim 6, wherein the flame-retardant agent contains the polyisocyanurate in a proportion of 2 to about 15 mass %.

21. 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 2,4,6-tris-(dimethylaminomethyl)phenol as a trimerization catalyst, the resulting polyisocyanurate encapsulating the individual ammonium polyphosphate particles.