A PROCESS FOR MANUFACTURING OF FIRE SUPPRESSING CRYSTALS

Abstract

A process for the manufacturing of fire suppressing crystals having a high Q-factor particle size distribution, said fire suppression crystals being intended for use as a fire suppressing additive in polymer compositions, the process comprising the steps; a) Preparing a mother liquor comprising water and a salt composition obtained in step c) or d), the temperature of said mother liquor being adjusted to 10-50 C. and comprising said salt composition to a level of at least 90% of saturation. Calcium hydroxide is added to the mother liquor to a level of at least 90% of saturation. b) Preparing an acid solution comprising water and two or more acids selected from the group consisting of; C.sub.2-C.sub.6 mono-, di- and/or tri-carboxylic acids, and optionally a phosphorous compound. The temperature of said acid solution is adjusted to 20-90 C. 31 and comprising acids to a level of at least 50% of saturation. c) The mother liquor, comprising calcium hydroxide, obtained from step a) is subjected to intense agitation under which the acid solution obtained from step b) is slowly added to said mother liquor allowing reaction to form salt until supersaturation is achieved while maintaining PH at a level securing that no unreacted acids remains after reaction, d) Crystals formed in the reaction of step c) is continuously or discontinuously removed from the reaction product of step c).

Claims

1. A process for the manufacturing of fire suppressing crystals having a high Q-factor particle size distribution, the process comprising: a) preparing a mother liquor comprising water and a salt composition obtained in c) or d), the temperature of said mother liquor being adjusted to a selected temperature in the range 10-50 C. and comprising said salt composition at a level of at least 90% of saturation at the selected mother liquor temperature, and calcium hydroxide is added to the mother liquor to a level of at least 90% of saturation, b) preparing an acid solution comprising water and two or more acids selected from the group consisting of: C.sub.2-C.sub.6 mono-, di- and tri-carboxylic acids, or a combination thereof, and optionally a phosphorous compound selected from the group consisting of: polyphosphoric, pyrophosphoric, and phosphoric acid or a combination thereof, wherein the temperature of said acid solution is adjusted to a level in the range 20-90 C. and comprises acids at a level of at least 50% of saturation at the selected acid solution temperature, whereupon, c) the mother liquor, comprising calcium hydroxide, obtained from a) is subjected to intense agitation under which the acid solution obtained from b) is slowly added to said mother liquor allowing reaction to form salt until supersaturation is achieved while maintaining PH at a level ensuring that no unreacted acids remains after reaction and, d) crystals formed in the reaction of c) are continuously or discontinuously removed from the reaction product of c).

2. A process according to claim 1, wherein fire suppressant synergist particles have an average particle size in the range 0.3-1 m and are suspended in the mother liquor at a level of 1-25% by weight of the calcium hydroxide added.

3. A process according to claim 2, wherein said suspended fire suppressant synergist particles act as seeding particles for crystallization of said salt, and the fire suppressant synergist particles are selected from the group consisting of: calcium carbonate, aluminum trihydroxide magnesium dihydroxide, huntite, dolomite, magnesite, hydromagnesite, tricalciumphosphate, hydroxylapatite, and combinations thereof.

4. A process according to claim 1, wherein the reaction performed in c) is achieved in a reactor that maintains temperature in the range of 10-60 C. and pressure in the range of 0.5-5 Bar.

5. A process according to claim 1, wherein the acid solution obtained in b) added in c) is finely distributed into small droplets.

6. A process according to claim 5, wherein the process comprises ejection of surplus water.

7. A process according to claim 5, wherein crystallization is controlled by lowering temperature and/or lowering pressure in the reactor.

8. A process according to claim 5 wherein crystallization is performed outside the reactor by of lowering temperature, by lowering pressure and/or by evaporation of water.

9. A process according to claim 5, wherein crystallization is performed outside the reactor by pumping a controlled stream from the reactor into a precipitation chamber, wherein, the temperature and/or pressure is guided in said precipitation chamber to control crystal growth and size, and crystals above a desired size are separated from the controlled stream which then are fed back to the reactor and/or the mother liquor of claim 1 a).

10. A process according to claim 1, wherein the obtained crystals are dried at a temperature not exceeding 140 C., optionally after rinsing with fresh water.

11. A process according to claim 10, wherein the obtained crystals have an average particle size in the range of 0.2-50 m.

12. A process according to claim 10, wherein the obtained crystals have an average particle size in the range of 0.2-20 m.

13. A process according to claim 5, wherein the PH in the reactor is kept above 8.

14. A process according to claim 5, wherein the crystal size is guided by controlling concentration levels of salt in the reactor, temperature in the reactor, flow in the reactor and pressure in the reactor.

15. A process according to claim 9, wherein the crystal size is guided by controlling parameters in the reactor selected from the group consisting of: concentration levels of salt in the reactor, temperature in the reactor, pressure in the reactor, flow speed in the reactor, concentration levels of salt in the precipitation chamber, residence time in the precipitation chamber, temperature in the precipitation chamber and a combination thereof.

16. A process according to claim 11, wherein the crystal size deviation from average crystal particle size for a produced batch is <10% by weight having half the average particle size and <5% by weight having twice the average particle size.

17. A process according to claim 1, wherein said at least two acids are selected from the group consisting of: ethanoic acid, ethanedioic acid, oxoethanoic acid, 2-hydroxyethanoic acid, propanoic acid, prop-2-enoic acid, propanedioic acid, 2-oxopropanoic acid, 2-hydroxypropanoic acid, butanoic acid, 2-methylpropanoic acid, butanedioic acid, 3-oxobutanoic acid, butenedioic acid, oxobutanedioic acid, hydroxybutanedioic acid, 2,3-dihydroxybutanedioic acid, but-2-enoic acid, pentanoic acid, pentanedioic acid, 2-oxopentanedioic acid, hexanoic acid, hexanedioic acid, 2-hydroxypropane-1,2,3-tricarboxylic acid, prop-1-ene-1,2,3-tricarboxylic acid, 1-hydroxypropane-1,2,3-tricarboxylic acid, propane-1,2,3-tribarboxylic acid and hexa-2,4-dienoic acid, and at least one of said at least two acids is a di- or tricarboxylic acid.

18. A process according to claim 10, wherein the process further comprises adding calcium carbonate particles having an average particle size of 0.3-2 m before or after drying so that said calcium carbonate is present at a level of 1-30% by weight of the crystals.

Description

[0033] The invention is further described together with FIG. 1.

[0034] FIG. 1 shows a process for manufacturing the fire suppressing crystals comprising the steps; [0035] a) A mother liquor comprising water and a salt composition obtained in step c) as a depleted mother liquor from step d), is prepared in a mother liquor vessel 1. The temperature of said mother liquor is adjusted to 15 C. and comprising said salt composition to a level of at least 90% of saturation. Calcium hydroxide is added to the mother liquor to a level of at least 90% of saturation. [0036] b) An acid solution comprising water, ethanedioic acid, 2,3-dihydroxybutanedioic acid and phosphoric acid is prepared in an acid solution vessel 2. The temperature of said acid solution is adjusted to 50 C. and comprises acids to a level of at least 50% of saturation. The ratio between the acids are per weight of each of the above listed. [0037] c) The mother liquor, comprising calcium hydroxide, obtained from step a) is subjected to intense agitation by being propelled through a tube reactor 3. The mother liquor is made essentially free from solid particles by means of filtration. The acid solution obtained from step b) is slowly and steadily added to said mother liquor, allowing reaction to form salt so that supersaturation is achieved while maintaining PH at a level securing that no unreacted acids remains after reaction. The adding of the acid solution is accordingly guided by a guiding means 31. The reactor is also provided with cooling to remove exothermal energy from the reaction. [0038] d) The crystals formed in the reaction of step c) are continuously removed from the reaction product of step c) by means of a decanter centrifuge 4. The remaining reaction product, now free from crystals of the desired size, is then, in its depleted form, pumped back to the mother liquor vessel 1 via an overflow vessel 5 where excess water is removed. The crystals having an average particle size of 4 m is then de-agglomerated and dried. Each individual crystal produced comprises the components of step a) and b).

[0039] The embodiment described shall not be perceived as a limitation of the scope of the present invention. It is for example possible to select other combination of acids within the scope of the invention. Temperatures and ratios between acids selected are, depending on the properties desired in the fire suppression crystals, possible to adjust within the scope of the invention. It is accordingly also possible to add calcium carbonate particles to the mother liquor within the scope of the invention.