DD239215A5 - METHOD FOR PRODUCING HYDROLYSIS STABILES, PARTICULAR FLAMMIN PROTECTION AGENTS BASED ON AMMONIUM POLYPHOSPHATE - Google Patents

Abstract

The present invention relates to a process for the preparation of hydrolysis-stable, finely divided flame retardants based on free-flowing, pulverfoermigem ammonium polyphosphate of the general formula H (nm) 2 (NH4) mPn / 3n lin which n is an integer having an average value of about 20 to 800 and the ratio of m to n is about 1, by treating the ammonium polyphosphate in the presence of an organic suspending agent and stirring with a heat-resistant and hydrogenated water-insoluble synthetic resin, and separating and drying the treated ammonium polyphosphate, characterized in that at room temperature from the ammonium polyphosphate, from water and the organic suspending agent, wherein in the water-suspending agent mixture is a water content of at least 40 wt .-%, and from a melamine / formaldehyde resin and optionally a Haerter produces a suspension, this mixture under Ru Heated to 50 to 180C under normal pressure or excess pressure and to cure the resin component, the suspension for 15 to 240 minutes at this temperature belaesst.

Description

Field of application of the invention

The invention relates to a process for the preparation of hydrolysis-stable, finely divided flame retardants based on ammonium polyphosphate by microencapsulation of powdered ammonium polyphosphate with a curable, water-insoluble in the cured state synthetic resin.

Characteristic of the known technical solutions

From DE-OS 2949537 is a particulate agent based on free-flowing, powdered ammonium polyphosphates of the general formula

H (nm) +2 (NH 4) _m P _n O3n + ι

in which η is an integer having an average value of about 20 to 800 and the ratio of m.sub.n is about 1, is known for preventing flammability of combustibles which is characterized in that it consists of

a) about 75 to 99Gew .-% ammonium polyphosphate and

b) about 1 to 25% by weight of a cured, water-insoluble polycondensation product of melamine and formaldehyde enveloping the individual ammonium polyphosphate particles.

The application of the melamine / formaldehyde resin to the ammonium polyphosphate particles takes place in this case, for example, by first suspending the ammonium polyphosphate in methanol, heating the suspension to a slight reflux of the methanol, and then adding a methanolic / aqueous solution of the melamine to the suspension. Formaldehyde resin drips. After a post-reaction time of, for example, 0.5 to 2 hours, the suspension is filtered and the filter residue in the nitrogen atom at 100 ° C for 150 to 180 minutes dried. During drying, the curing of the resin coating applied from the ammonium polyphosphate particles takes place at the same time. Furthermore, a process for the microencapsulation of powdered ammonium polyphosphates has been proposed in DE-OS 3316880, which is characterized in that the ammonium polyphosphate, an aliphatic alcohol having 1-4 C atoms as a diluent and a melamine / formaldehyde resin, optionally in dissolved in a solvent, introduced in any order in a pressure vessel and intimately mixed at room temperature, the mixture heated to a temperature of about 80 ⁰ C to about 180 ° C and for curing the resin component at this temperature and the vapor pressure of the diluent corresponding pressure for 15 to Leaves 240 minutes, the mixture is cooled to room temperature, the diluent separated and the resulting product is dried.

The microencapsulation of the ammonium polyphosphate particles with cured, water-insoluble synthetic resin achieves a significantly reduced solubility and increased hydrolysis resistance of the ammonium polyphosphate. This has a favorable effect when using this agent as a flame retardant, since by weathering or cleaning processes, the water-soluble components can be washed out in the absence of microencapsulation and thus a part of the Flammschutzeffketes is lost.

The previous method for microencapsulation of ammonium polyphosphates with melamine / formaldehyde resin has the disadvantage that it comes on the inner walls of the reactor to caking of ammonium polyphosphate and hardened resin, resulting in a poor heat transfer results.

In addition, agglomerate formation in the abovementioned processes leads to an increase in the average grain diameter compared to the ammonium polyphosphate originally used. This agglomeration, and in particular the caking away from the reactor walls, necessitates milling when the microencapsulated ammonium polyphosphate is to be used as the flame retardant. The grinding process produces fracture surfaces where the ammonium polyphosphate is exposed to the hydrolysis attack and degrades to soluble, short-chain ammonium polyphosphates.

In addition, it has been found that the flame retardant prepared by the process of DE-OS 3316880 by microencapsulation with melamine / formaldehyde resins has a significant content of free formaldehyde.

Object of the invention

The aim of the invention is to provide an improved process for the preparation of hydrolysis-stable, finely divided flame retardants based on ammonium polyphosphate.

Explanation of the essence of the invention

The invention has for its object to develop a method for microencapsulation of ammonium polyphosphate, in which

1. the process of microencapsulation practically does not lead to grain coarsening of the ammonium polyphosphate used,

2. the hydrolytic stability of the microencapsulated ammonium polyphosphate is very good even at higher temperatures,

3. The content of microencapsulated ammonium polyphosphate is very low in free formaldehyde and

4. no caking on the reactor walls and the agitators. Surprisingly, it has now been found that in microencapsulation the long-chain ammonium polyphosphate is not hydrolyzed when a water-suspending agent mixture having a water content of at least 40 mass% is used.

Furthermore, there is neither agglomeration and thus grain coarsening of the ammonium polyphosphate nor caking on the reactor walls or stirrer blades. Finally, the content of free formaldehyde could be significantly reduced.

The invention is now a process for the preparation of hydrolysis-stable, finely divided flame retardants based on free-flowing, powdered ammonium polyphosphate of the general formula H ( _n _ _m ) ₊ 2 (NH 4) _m P _n O 3n + ι

in which η is an integer having an average value of about 20 to 800 and the ratio of m to η is about 1, by treating the ammonium polyphosphate in the presence of an organic suspending agent and stirring with a thermosetting and hardened water-insoluble resin, and separating and drying the treated ammonium polyphosphate, characterized in that at room temperature from the ammonium polyphosphate, from water and the organic suspending agent, wherein in the water-suspending agent mixture, a water content of at least 40 wt .-%, and from a melamine / formaldehyde Resin and optionally a hardener produces a suspension, this mixture is heated with stirring to 50 to 180 ° C under atmospheric pressure or under pressure in a pressure vessel and left to cure the resin component, the suspension for 15 to 240 minutes at this temperature.

The coating agent used may preferably be a melamine / formaldehyde resin which, in the uncured state, is a powder whose 50% strength by weight aqueous solution has a dynamic viscosity of 20 to 50 mPa s, a pH (at 20 ° C.). has from 8.8 to 10.0 and a density (at 20 ⁰ C) of 1.21 to 1.23 g / ml.

Suitable organic suspending agents may be aliphatic alcohols having 1 to 4 carbon atoms or ketones having 3 to 6 carbon atoms.

Another feature of the present invention is also that, for the preparation of the suspension, a mass ratio of water: organic suspending agent such as 100: 1 to 150, in particular from 100: 10 to 100, is maintained. Finally, there is a particularly good microencapsulation of the ammonium polyphosphate, if in the suspension, a mass ratio of ammonium polyphosphate: water-suspending agent mixture: resin component: hardener of 1: 0.5 to 5: 0.5 to 0.5: 0.0025 to 0th , 1, in particular from 1: 1 to 3: 0.05 to 0.15: 0.01, is maintained. Also, it has proved to be advantageous if the reaction time is 0.5 to 3 hours.

Suitable long-chain ammonium polyphosphates are ammonium polyphosphates having a mean particle size of 0.01 to 0.05 mm. As a flame retardant, especially the microencapsulated ammonium polyphosphate having an average particle size of 0.01 to 0.1 mm, preferably from 0.03 to 0.06 mm, has proven. Preferably, the proportion of melamine / formaldehyde resin in the flame retardant is 2 to about 15Ma .-%, in particular about 10Ma .-%. According to a further aspect of the present invention, the coating or microencapsulation of the ammonium polyphosphate by treatment with the melamine / formaldehyde resin and optionally a curing agent can also take place in several, for example two to three successive steps, wherein the reaction mixture between the individual steps before the addition is cooled by further melamine / formaldehyde resin and optionally a curing agent, for example from a reaction temperature at 80 "C to 60 ⁰ C or less.

The finely divided microencapsulated ammonium polyphosphates prepared according to the invention are particularly suitable for the flame-retardant adjustment of polyurethanes and polyurethane foams, the content of the agent in the polyurethane foam being about 5 to 25% by mass, based on the amount of the polyol component of the polyurethane.

embodiment

The process of the invention is illustrated in the following examples.

To carry out the experiments set out in the examples commercially available ammonium polyphosphates and various, also commercially available melamine / formaldehyde resins and hardeners were used. Specifically, these are the following products:

1. ®Exolit422

It is a fine-grained, sparingly soluble in water ammonium polyphosphate, (NH ₄ POa) _n , wherein the degree of condensation is η ~ 700.

2. ® Kauramine impregnating resin 700 Powder

It is a melamine / formaldehyde condensation resin which is a white powder and whose 50% by weight aqueous solution has a dynamic viscosity of 20-5OmPa.s, a pH of 8.8 to 9.0 and a density ( at 2O ⁰ C) of 1.22 g / ml.

3.MaduritMW909

It is an un-plasticized melamine / formaldehyde resin offered as a white powder. Its 50% by mass aqueous solution has a dynamic viscosity of about 3OmPa.s, a pH of 9.0 to 10.0, and a density (at 20 ° C) of 1.21 to 1.225 g / ml.

4. Hardener 527 liquid

It is a clear, yellowish liquid having a viscosity (at 20 ⁰ C) of about 17mPa · s, a pH value of 4.5 to 6.0, and a density (at 2O ⁰ C) of about 1, 2g / ml possesses.

5. ® Madurit Hardener VMH3843

It is a clear, colorless, low viscosity liquid that has a pH value of 6.2 to 7.0, and a density (at 2O ⁰ C) of 1.16 to 1.17 g / ml.

Example 1 .

In a heatable enameled pressure reactor (capacity: 161) with stirrer, temperature and pressure gauges were placed 5.61 water and 31 methanol; While stirring, a mixture of 5.2kg of Exolit 422 and 500g of Kauramine Acid Resin 700 powder was added at room temperature. The suspension was heated to 120 ⁰ C, wherein a pressure of 4 bar was established. After a reaction time of 20 minutes, the suspension was cooled and filtered. The filter cake was washed with 11 methanol and dried at 100 ⁰ C nitrogen stream.

5.5 kg of coated ammonium polyphosphate having a melamine / formaldehyde resin content of 8.4% by mass were obtained.

The filtrate contained 2.1% by weight of solid and 72% by weight of water.

To determine the water-soluble of water were suspended 10 g of the product prepared in 100 ml, and the suspension was stirred for 20 min at 25 ° C or at 60 ⁰ C. Subsequently, the undissolved in water portion of the product was sedimented by centrifugation within 40 minutes. From the supernatant clear solution, 5.0 ml were pipetted into a previously weighed aluminum dish and evaporated at 120 ⁰ C in a drying oven. From the amount of Verdanipfungsrückstandes the water-soluble fraction was calculated. The values determined for the water-soluble fractions and the other product data are listed in Tables 1 and 2.

The following methods were used to determine the other product data:

PH value

The determination of the pH was carried out with the aid of a laboratory pH meter (Knick, Berlin Type Digital pH Meter 646) in a 1% strength by weight aqueous suspension.

acid number

To determine the acid number, 10 g of product were suspended to 150 ml of water, stirred until a constant pH was established and titrated with 0.1 .mu.KOH using a laboratory pH meter (see above) to pH = 7.0.

Sieve Analysis

The sieve analyzes were carried out with a weight of 10 g of product with a laboratory air jet sieve (Alpine, Augsburg, type A 200-LS, sieve diameter 200 mm).

Example 2

In a 11-necked three-necked flask with reflux condenser, stirrer and thermometer 195g ®Exolit422 and 18.8g ®Kauramin-impregnating resin 700 powder were suspended in a mixture of 240 ml of water and 75 ml of methanol and heated with stirring to reflux the methanol. After a reaction time of 1 hour at 83 ° C, the suspension was cooled and filtered; the filter cake was washed with methanol and dried at 100 ⁰ C in a stream of nitrogen.

There were obtained 205 g of coated ammonium polyphosphate having a melamine / formaldehyde resin content of 8.3 mass%; the filtrate contained 1.9% by weight of solid and 82% by weight of water. The values determined for the water-soluble fractions and the other product data are listed in Tables 1 and 2.

Example 3

The procedure was analogous to Example 2 except that a mixture of 180 ml of water and 150 ml of acetone was used as suspending agent. After a reaction time of 1 hour at 67 ° C, the suspension was cooled and filtered; the filter cake was washed with acetone and dried at 100 ° C in a stream of nitrogen.

There were obtained 200 g of coated ammonium polyphosphate having a resin content of 8.5 mass%; the filtrate contained 1.6% by weight of solid and 65% by weight of water. The values determined for the water-soluble fractions and the other product data are listed in Tables 1 and 2.

Example 4

The procedure was analogous to Example 2, except that a mixture of 200 ml of water and 100 ml of isopropanol was used as suspending agent. After a reaction time of 1 hour at 85 ° C, the suspension was cooled and filtered; the filter cake was washed with isopropanol and dried at 100 ° C in the nitrogen stream.

There were obtained 208 g of coated ammonium polyphosphate having a resin content of 8.6 mass%; the filtrate contained 1.1 mass% solid and 74 mass% water. The values determined for the water-soluble fractions and the other product data are listed in Tables 1 and 2.

Example 5

In a heatable enamelled pressure reactor (contents: 161) 2.22 kg of water, 0.44 kg (= 550 ml) of methanol, 2.0 kg ®Exolit 422 and 0.20 kg ®Kauramin-impregnating resin 700 powder were added. With stirring, the suspension was heated to 100 ° C and kept at this temperature for 1 hour. After cooling to room temperature, the suspension was filtered; the filter cake was washed with methanol and then dried at 100 ^° C. in a stream of nitrogen. 2086 g of coated ammonium polyphosphate having a resin content of 9.3 mass% were obtained. The values determined for the water-soluble fractions and the other product data are listed in Tables 3 and 4.

Example 6

The procedure was analogous to Example 5, except that a mixture of 3.20 kg of water and 0.64 kg (= 800 ml) of methanol was used as suspending agent.

2060 g of coated ammonium polyphosphate having a resin content of 9.4 mass% were obtained. The values determined for the water-soluble fractions and the other product data are listed in Tables 3 and 4.

Example 7

The procedure was analogous to Example 6, but with a reaction temperature of 80 ° C was maintained.

2055 g of coated ammonium polyphosphate having a resin content of 9.2 mass% were obtained. The values determined for the water-soluble fractions and the other product data are listed in Tables 3 and 4.

Example 8

The procedure was analogous to Example 6, but with a reaction temperature of 60 ⁰ C was maintained.

2070 g of coated ammonium polyphosphate having a resin content of 9.3 mass% was obtained. The values determined for the water-soluble fractions and the other product data are listed in Tables 3 and 4.

Example 9

The procedure was analogous to Example 7. In this case, 2080 g of coated ammonium polyphosphate were obtained with a resin content of 9.3 Ma .-%. The values determined for the water-soluble fractions, the other product data and the content of "free formaldehyde" are listed in Tables 5,6 and 7.

Example 10

The procedure was analogous to Example 7, but with an additional 20 g of hardener 527 liquid (BASF Aktiengesellschaft, Ludwigshafen / Rhine) were used.

In this case, 2075 g of coated ammonium polyphosphate were obtained with a resin content of 9.5Ma .-%. The values determined for the water-soluble fractions, the other product data and the "free formaldehyde" content are listed in Tables 5,6 and 7.

Example 11

The procedure was analogous to Example 7, but 0.20 kg ®Madurit MW909 were used.

In this case, 2085 g of coated ammonium polyphosphate were obtained with a resin content of 9.4Ma .-%. The values determined for the water-soluble fractions, the other product data and the content of "free formaldehyde" are listed in Tables 5, 6 and 7.

Example 12

The procedure was analogous to Example 7, except that 0.20 kg ®Madurit hardener VMH3843 were used. In this case, 2095 g of coated ammonium polyphosphate were obtained with a resin content of 9.5Ma .-%. The values determined for the water-soluble fractions, the other product data and the "free formaldehyde" content are listed in Tables 5,6 and 7.

Example 13

The procedure was analogous to Example 7, except that 160 g ®Madurit MW909 and 8g ®Madurit hardener VMH 3843 were used.

In this case, 2100 g of coated ammonium polyphosphate were obtained with a resin content of 7.4 Ma .-%. The values determined for the water-soluble fractions are listed in Table 8.

Example 14

The procedure was analogous to Example 7, except that 280 g ® Madurit MW909 and 14g ®Madurit hardener VMH3843 were used.

In this case, 2140 g of coated ammonium polyphosphate were obtained with a resin content of 11.8Ma .-%. The values determined for the water-soluble fractions are listed in Table 8.

Example 15

The procedure was analogous to Example 12, except that the following changes were made: First, to the suspension medium (water / methanol) and ammonium polyphosphate only 100g ®Madurit MW909 and 10g ®Madurit hardener VMH 3843 were added. After a reaction time of 1 hour at 80 ⁰ C, the reactor contents were cooled to 6O ⁰ C; 100 g of ®Madurit MW909 and 10 g of ®Mururit hardener VMH 3843 were then charged into the pressureless reactor. Subsequently, the pressure reactor was again heated to 8O ⁰ C and maintained at 80 ⁰ C for 1 hour.

2090 g of coated ammonium polyphosphate having a resin content of 9.5 mass% were obtained. The values determined for the water-soluble fractions are listed in Table 8.

Example 16

The procedure was analogous to Example 15, but with the 2nd addition of resin (after 1 hour of reaction time at 80 ⁰ C) was dispensed with the addition of the ®Madurit hardener VMH 3843.

2085 g of coated ammonium polyphosphate having a resin content of 9.4 mass% were obtained. The values determined for the water-soluble components are listed in Table 8.

Example 17

The procedure was analogous to Example 16, except that the amount of resin was added in 3 steps. When adding the second and third third of the amount of resin (after each 1 hour reaction time at 8O ⁰ C) was dispensed with the addition of the ®Madurit hardener VMH 3843.

2090 g of coated ammonium polyphosphate having a resin content of 9.6% by mass were obtained. The values determined for the water-soluble fractions are listed in Table 8.

Table 1

Product Content of Melamine / Water Soluble (%)

Formaldehyde resin at 25 ° C change at 60 ⁰ C change

example 1 8.4 0.2 -98 0.8 Salary of melamine / PH value acid number Sieve analysis (%) <45μηη -98 <25μηη Example 2 8.3 0.2 -98 0.5 Formaldehyde resin (MgKOH / g) <75μ, ΓΠ > 99 -99 42 Example 3 8.5 0.2 -98 0.4 8.4 5.9 0.2 > 99 > 99 -99 65 Example 4 8.6 0.2 -98 0.4 8.3 5.6 0.1 > 99 97 -99 35 ®Exolit422 ¹⁾ - 8.2 - 62 8.5 5.9 0.3 > 99 99 - 76 8.6 4.8 0.7 > 99 > 99 84 - 5.6 0.5 > 99 1) For comparison, the values of the uncoated merchandise used for these experiments (®Exolit 422) were listed. Table 2 product example 1 Example 2 Example 3 Example 4 ®Exolit422 ¹¹

Table 3

product

Salary to MeI

amine / formaldehyde

hyd resin

Suspension-1) consistency

Reactivity Water soluble (%) at 25 ° C change

at 60 ^° C

Change (%)

Example 5 9.3 72 100 0.3 -96 0.7 -99 Examples 9.4 50 100 1.0 -86 1.3 -98 Example 7 9.2 50 80 0.2 -97 0.8 -99 Examples 9.3 50 60 0.4 -95 1.6 -97 ®Exolit422 ²⁾ - - - 7.4 - 61 -

1) The suspension density is given as the ratio of parts by weight of ammonium polyphosphate to parts by volume of suspending agent

2) For comparison, the values of the uncoated merchandise used for these experiments (®Exolit 422) were listed.

Table 4

product

PH value

Acid number (mgKOH / g)

Flowability 1) (cot φ)

Sieve analysis (%) <75μΓΠ <45 / xm

1) Flowability according to PFRENGLE (DIN 53916): measured value is the cotangent of the angle of repose φ

2) For the purpose of comparison, the values of the uncoated merchandise used for these tests (®Exolit 422) were listed.

<25μ, ιτι

Example 5 4.7 0.3 1.47 > 99 99 73 Examples 4.8 0.8 1.47 > 99 98 70 Example 7 5.3 0.3 1.67 > 99 99 75 Examples 5.9 0.4 1.61 99 97 77 ®Expolit422 ²¹ 6.0 0.3 > 0.7 > 99 > 99 81

Table 5

product

Melamine / formaldehyde resin type and content

Hardener Type / Hardener Concentration ¹¹

Water soluble fractions (%)

at 25 ⁰ C at 60 ° C Verände- Variegated

tion

Example 9 ®Kauramin-impregnating 0.3 -96 0.6 -99 resin 700 powder 9.3% - Example 10 ®Kauramin-impregnating Hardener 527 harz700 liquid 0.2 -97 0.5 -99 9.5% 10% Example 11 ®MaduritMW909 - 9.4% - 0.1 -99 0.4 -99 Example 12 ®MaduritMW909 "Madurit hardener VMH 3843 0.1 -99 0.3 -99 9.5% 10% ®Exolit422 ² ) - - 7.4 - 61 -

1) These figures refer to the ratio of hardener to the amount of melamine / formaldehyde resin.

2) For comparison, the values for uncoated commercial goods (®Exolit 422) used for these tests were listed.

Table 6

product

PH value

Acid number (mgKOH / g)

Flowability ¹¹ (Cot φ)

Sieve analysis (%)

<75μ.ιτι <45 / xm <25μηη

Example 9 5.8 0.3 1.20 > 99 98 70 Example 10 5.9 0.2 1.34 > 99 99 74 Example 11 6.0 0.1 1.62 > 99 99 75 Example 12 6.3 <0.1 1.74 > 99 > 99 79 ®Exolit422 ² ) 6.0 0.3 <0.7 99 > 99 81

1) Flowability according to PFRENGLE (DIN 53916): measured value is the cotangent of the angle of repose φ

2) For comparison, the values of the uncoated merchandise used for these experiments (®Exolit422) were listed.

Table 7

product

Content of melamine / formaldehyde resin (%)

Salary at "free

Formaldehyde " ¹¹

(mg CH 2 O / 100 g sample)

change

Example 9 Example 10 Example 11 Example 12 ®Exolit456 ²⁾

9.3 9.5 9.4 9.5 9.5

7.4 8.2 5.1 5.1 3.9 43.9

-83 -81 -88 -91

1) The determination of the content of "free formaldehyde" was carried out according to the WKI method (see E. Roffael, "The Formaldehyde Delivery of Particleboard and other Materials" (p.45 ff.), DRW-Verlag, Stuttgart (1982) , wherein the elimination of formaldehyde was detected at 40 ⁰ C in a period of 24 hours.

2) ®Exolit 456, It is a "Exolit 422 coated with melamine / formaldehyde resin. The microencapsulation was carried out according to DE-OS 3316880, Example 1.

Table 8

product Content of melamine / formaldehyde resin (%) Type of resin / hardener addition Water soluble fractions (%) Change at 60 ^c C (%) 0.6 Change (%) 7.4 A ¹¹ at 25 "C -97 0.5 -99 Example 13 11.8 A ¹ ' 0.2 -99 0.7 -99 Example 14 9.5 B ²¹ 0.1 -97 0.2 -99 Example 15 9.4 C ³¹ 0.2 -99 0,1, -99 Example 16 9.6 D ⁴¹ 0.1 -99 61 -99 Example 17 - - <0.1 - - ®Exolit422 ⁵⁾ 7.4

To 1) to 5) see next page To Table 8:

1) The amount of resin and hardener was added in one step.

2) The amount of resin and hardener was added in two steps. The first half was used as usual. The second half was added after a reaction time of 1 hour at 8O ⁰ C.

3) The amount of resin and hardener was added in two steps. The first half was used as usual. The second half of the resin was added without addition of curing agent after a reaction time of 1 hour at 80 ° C.

4) The amount of resin and hardener was added in three steps. The first third of resin + hardener was used as usual. The second third of the amount of resin was added without addition of hardener after a reaction time of 1 hour at 8O ⁰ C, the third third of the amount of resin (again without addition of hardener) after a further reaction time of 1 hour at 8O ⁰ C.

5) For comparison, the values of uncoated merchandise used for these tests ("Exolit 422") were listed.

Detect the values of the Tables 1,3, 5 and 8 can be that by means of the method according to the invention the content of water-soluble components in the ammonium polyphosphate can be reduced considerably (at 25 ° Cum up to 99%, at 6O ⁰ C

also by up to 99%).

In addition, the data from Tables 2, 4 and 6 show that the method of microencapsulation keeps the acid number and the pH largely unchanged and the mean values of the grain size only insignificantly (from about 12 μm to about 16 μm). be moved. In contrast, the flowability is very important (in terms of an exact Dosierbarkeit)

improved.

The data in Table 7 show that the content of "free formaldehyde" over the prior art

(DE-OS 3316880) could be reduced by more than 90%.

Claims (12)

Invention claim: 1. A process for the preparation of hydrolysis-stable, finely divided flame retardants based on free-flowing, powdered ammonium polyphosphate of the general formula in which η is an integer having an average value of about 20 to 800 and the ratio of m to η is about 1, by treating the ammonium polyphosphate in the presence of an organic suspending agent and stirring with a thermosetting and hardened water-insoluble resin, and separating and drying of the treated ammonium polyphosphate, characterized in that at room temperature from the ammonium polyphosphate, from water and the organic suspending agent, wherein in the water-suspending agent mixture, a water content of at least 40 wt .-% is present, and from a melamine / formaldehyde Resin and optionally a hardener produces a suspension, this mixture is heated with stirring to 50 to 180 ° C under atmospheric pressure or pressure and left to cure the resin component suspension for 15 to 240 minutes at this temperature. 2. A method according to item 1, characterized in that the melamine / formaldehyde resin in the uncured state is a powder whose 50 wt .-% aqueous solution has a dynamic viscosity of 20 to 50 mPa · s, a pH (at 20 ° C) of 8.8 to 10.0 and a density (at 20 ° C) of 1.21 to 1.23 g / ml. 3. The method according to item 1 or 2, characterized in that are used as organic suspending agents aliphatic alcohols having 1 to 4 carbon atoms or ketones having 3 to 6 carbon atoms. 4. The method according to any one of the preceding points, characterized in that for the preparation of the suspension, a mass ratio of water: organic suspending agent such as 100: 1 to 150, in particular from 100: 10 to 100, is maintained. 5. The method according to any one of the preceding points, characterized in that in the suspension, a mass ratio of ammonium polyphosphate water-suspending agent Gemischi resin component harder of 1: 0.5 to 5: 0.05 to 0.5: 0.0025 to 0.1, in particular from 1: 1 to 3: 0.5 to 0.15: 0.01. 6. The method according to any one of the preceding points, characterized in that the reaction time is 0.5 to 3 hours. 7. The method according to any one of the preceding points, characterized in that ammonium polyphosphate is used with an average particle size of 0.01 to 0.05 mm. 8. The method according to any one of the preceding points, characterized in that the microencapsulated ammonium polyphosphate flame retardant has an average particle size of 0.01 to 0.1 mm, preferably from 0.03 to 0.06 mm. 9. The method according to any one of the preceding points, characterized in that the proportion of the melamine / formaldehyde resin in the flame retardant is 2 to about 15JVIa .-%. 10. The method according to any one of the preceding points, characterized in that the coating of the ammonium polyphosphate takes place by treatment with the melamine / formaldehyde resin and optionally a curing agent in a plurality, for example two to three steps. 11. The method according to item 10, characterized in that the reaction mixture between the individual steps before the addition of further melamine / formaldehyde resin and optionally a curing agent is cooled. 12. Use of the flame retardant prepared by the process according to any one of items 1-11, characterized in that it is for flame-retardant adjustment of polyurethanes or polyurethane foams, wherein the content of the agent in the polyurethane foam about 5 to 25 wt .-%, based on the Amount of the polyol component of the polyurethane is used.