GB2118834A - Powder for fire extinguishers - Google Patents

Abstract

A method for producing a powdery fire extinguishant comprising monoammonium phosphate and/or ammonium sulphate as main raw materials, in which method a polysiloxane having an active hydrogen and a solvent are included with the raw materials which are then subjected to the steps consisting of mixing; a solvent-vaporization and removal; and heating in the presence of an oxygen-containing gas. An organotin compound is for preference also included with the raw materials. The method is best effected in apparatus provided by the invention and having a mixing and kneading chamber 1; a solvent-vaporizing chamber 2; a heating reaction chamber 3; a raw material-feeding port 4; a solvent-vaporizing pipe 5; a port 6 for discharging powdery fire extinguishant; a rotating shaft 7; stirring blades (rotor) 8; partition walls 9 and 10; partition plates 11; heaters (jacket) 12; and 13 and a transfer opening 14. <IMAGE>

Description

1 GB 2.118 834 A 1

SPECIFICATION Apparatus for continuously producing powdery fire extinguishants

The present invention relates to powder for fire extinguishers, and in particular to such powders which are prepared using monoammonium phosphate and/or ammonium sulphate.

Extinguishant powders, particularly the so-called ABC powders prepared from monoammonium 5 phosphate, can be used effectively against most fires, electric or otherwise, and have met with broad acceptance in recent years. In order to maintain their effectiveness, it is important that such powders should have good moisture resitance so that they do not deteriorate with time. Additionally, the powders should possess good particle flui.dity.in -order that they can be discharged from an extinguisher without difficulty. To these ends, the conventional powders for fire extinguishers have been made by 10 mixing finely powdered silicic anhydride (otherwise known as white carbon), a silicone resin and/or other ingredients, with the main raw material, monoammonium phosphate and/or ammonium sulphate.

However the products from there simple mixing methods are not entirely satisfactory.

According to the present invention there is provided a method for producing a powdery fire extinguishant comprising monoammonium phosphate and/or ammonium sulphate as main raw 15 materials, in which method a polysUoxane having an active hydrogen and a solvent are included in the raw materials which are then subjected to the steps consisting of mixing; solvent-vaporization and removal; and heating in the presence of an oxygen-containing gas.

The method can be carried out as a batch process using a batch mixer, or, more preferably, the method is carried out as a continuous process. In this latter respect, a continuous process preferably 20 comprises feeding the ingredients in fixed amounts to a mixing step where mixing and kneading are carried out at room temperature, thereafter continuously feeding the resulting material to a solvent vaporizing and removal step where the material is heated with stirring and the solvent is removed by vaporization, and finally feeding the resultant material to a heating step where a heat treatment is carried out in the presence of the oxygen-containing gas.

Continuous processes in accordance with the present invention are conveniently effected in sectional apparatus providing respective sections in which the steps of mixing, evaporating, and heating can be independently and continuously performed on material passing through the apparatus.

In a particularly preferred embodiment, the method of the invention is carried out using apparatus also forming the subject of this invention, this apparatus comprising a mixing and kneading part having 30.

a feed port for raw materials; a solvent-vaporizing part with heater and vaporization pipe; and a heating reaction part with a heater and fire extinguishant discharging port.

It is preferable to employ an apparatus of high efficiency, making the retention time shorter yet allowing a sufficient time for the various steps.

The ingredients employed by the present invention for preparing extinguishant powders comprise 35 monoammonium phosphate and/or ammonium sulphate as the main raw material, together with a polysiloxane and other optional ingredients. The polysiloxane has an active hydrogen and is, for example, a poly(alkyihydrogensiloxane) such as poly(m ethyl hyd rogensi loxa ne) or a copolymer of an alkylhydrogensiloxane with a copolymerizable monomeric siloxane, such as the copolymer formed by copolymerization of dimethylsiloxane with methyihydrogensiloxane. While the amount is not critical it is 40 preferred to use 0.2 to 3% polysiloxane, based on the main raw material (quoted percentages of raw materials are by weight).

In order to improve the particle fluidity of the product, it is greatly preferred to include as an ingredient an organotin compound. Suitable organotin compounds include those of the general formula R' R 3 Sin 45 R 2 R 4 (where R' and R 2 are the same or different and each represent an alkyl group, usually the same alkyl group, and R' and R' are the same or different and each represent an oxycarbonylalkyl group derived from a monocarboxylic fatty acid, usually the same group, or R' and R' together represent a di (oxycarbonylalkylene group derived from a dicarboxylic fatty acid). R' and R 2 are suitably each buty], and R' and R' can for example each be stearate or octoate groups or together form a maleate group. Thus, 50 typical organotin compounds (1) include dibutyltin distearate, dibutyltin dioctoate and dibutyltin maleate. Conveniently from 0 to 0.5% organotin compound based on the main raw material is added, with 0.005 to 0.5% being preferred.

Further ingredients which may be employed include silicic anhydride and/or pigment. 0 to 5% silicic anhydride based on the main raw material is a particularly suitable amount, more particularly 0.5 55 to 5%. Trace amounts, if any, of pigment are normally appropriate.

It is preferred that each ingredient is in powdered form with a size of 80 mesh or less.

In the present method, the ingredients are intimately mixed with an organic solvent. Solvents with 2 GB 2 118 834 A 2 a relatively low boiling point are preferred, especially halogenated hydrocarbons. Examples of the preferred solvents are perch loroethylene and trichloroethylene. The amount of solvent is variable, but is conveniently from 5 to 20% based on the main raw materials (monoammonium phosphate and/or ammonium sulphate).

For the mixing step, it is preferable to mix the ingredients together while compressing them at room temperature, usually employing a mixer or a kneader. Machines capable of uniformly mixing a small amount of liquid with fine powder are preferable, particularly those having blades such as of the oar, paddle or ribbon type fixed on to a twin worm and c apable of applying a high compression force tothe mixture.

Solvent is evaporated from the intimate mixture, preferably using a relatively low temperature. In particular, it is preferable to carry out the vaporization step with stirring at 701C or lower. As for the kind of machine employed, a kiln type and a paddle type- is preferable in which heat transfer is possible from stirring blades in addition to transfer to the wall of the machine.

Subsequent to the solvent evaporation, the resultant residue is heated in an oxygen-containing gas, typically air or oxygen itself.

Heating when the ingredients do not include an organotin compound is preferably carried out at a temperature of 70-2001C, for an average retention time of 2 hours or longer, preferably at 70-1450C for 3-20 hours, with stirring, in a flow method manner. When the ingredients do include an organotin compound the heating treatment is preferably carried out at a temperature of 40-2001C, preferably 70-1451C, for 0.5-2 hours ' with stirring. In the cases where the main raw material is monoammonium phosphate, the temperature is 1 501C or lower, preferably, 70-1451'C.

As mentioned, in a production method of the present invention, the mixing, vaporization and heating treatments may be carried out in a batch mixer. As one alternative, mixing, vaporization and heating may be compartmentalized and independently and continuously carried out., For continuous production, apparatus of the present invention consists, for example, of a mixing 25 and kneading chamber, a solvent-vaporizing chamber and a heating reaction chamber. Each of these chambers is furnished with at least two mixing rotors and partition plates for partitioning the mixing rotors. The mixing and kneading chamber, the solvent-vaporizing chamber and the heating raction chamber are independent, and they communicate with the succeeding chamber by way of an opening or pipe. Thus, as examples, one can have an apparatus wherein the respective chambers are indepentent from each other, such as a mixer, a solvent-vaporizer and a heating reactor independent from each other; an apparatus wherein a mixing and kneading chamber and a solvent-vaporizing chamber as well as a solvent-vaporizing chamber and a heating reaction chamber are contacted with each other by way of a partition wall, respectively and are so integrated that the rotors of the respective chambers are rotated by a common shaft; or an apparatus wherein a solventvaporizing chamber is 35 contacted with a heating reaction chamber by way of a partition wall, and the two chambers are so integrated that the rotors of the respective chambers are rotated by a common shaft and the mixing and kneading chamber is separate.

The location of the opening or pipe through which the mixing and kneading chamber communicates to the solvent-vaporizing chamber is not particularly critical, but the opening or,pipe is preferably arranged to be where the raw materials are retained, i.e. at the lower part of the rotating shaft. The shape of the rotors in the apparatus of the present invention- has no particular limitation. For example, ribbon oar and paddle type blades, etc., are mentioned. The number of the rotors of the respective chambers may be decided in accordance with necessity. The partition plates provided between the rotors prevent the short pass of raw materials and increase the kneading effect, and may be furnished as appropriate with openings, if necessary. The mixing and kneading chamber is furnished with a raw material-feeding port, the solvent-vaporizing chamber with a heater and a vaporizing pipe for removing the vapour of solvent and the heating reaction chamber with a heater and a discharging port of the product, the powdery fire extinguishant. As for the heater, any type maybe employed, but a jacket is preferable. For the heating reaction, an air-blowing-in port may be provided, and its location may be 50 anywhere in the apparatus of the present invention.

By adoption of the preferred forms of the present invention in which the mixing of the raw materials with a solvent, the solvent-vaporizing:treatment and the heating treatment are sectioned and separately carried out, a balance of the times of the respective treatments can be maintained; particularly the time of the heating reaction can be varied as desired, whereby it is possible continuously 55 to produce a product having a constant quality. Furthermore, the solvent vaporization and the heating reaction can be carried out by separate steps and the reaction time made longer, whereby the reaction of the polysiloxane with oxygen in the heating reaction step, or the reaction of the raw material mixture with the polysiloxane, can be uniformly carried out, thereby to be able to impart moisture resistance and free-flow properties at a lower temperature and with unifor m_lty, and thus stabilize the quality of product. Still further, the preferred methods of the present invention have the great advantages that larger hoppers for containing either raw materials after milling or fire extinguishant prior to sieving are unnecessary, thereby allowing smaller apparatus. As for the heating equipment, supply of only the heat quantity sufficient for the raw materials fed is usually needed and hence a small capacity may be sufficient, 1 1 11 r r 1 3 GB 2 118 834 A 3 The resulting extinguishant typically has a superior emission property and does not change in performance even after lengthy storage. These advantages are particularly attainable when an organotin compound is included into the raw materials. A further advantage of this invention attainable when using an organotin compound is that moisture resistance and flec-flow properties can be imparted to the powder in a short time, thus representing a saving in the volume capacity of the reactor used for the_ 5 continuous production process of the invention.

The present invention is illustrated by the following non-limiting examples.

Example 1

A 500 1 capacity batch mixer having a heating jacket heated by way of a heating medium and a main shaft having ribbon type stirring blades fixed thereonto was employed. With the mixer rotating at 10 40 rpm, the raw materials given in Table 1 were introduced and then mixed together for one hour. Thereafter the temperature was elevated and perch loroethylene was vaporized at 601C, followed by further elevating the temperature and carrying out baking at 1 001C to prepare a powdery fire extinguishant.

TABLE 1

Ingredient Weight (Kg) Monoammonium phosphate 200 Fine powder of silicic anhydride 6 Methyl hydropolysil oxa ne 4 Perchloroethylene 30 Red pigment trace Dibutyltin dioctoate 0.01 The relationship between the baking time and the properties of the resulting powdery fire extinguishant were as shown in Table 2.

EXAMPLE 2

Example 1 was repeated except the amount of clibutyltin dioctoate was changed t o 0. 1 Kg. The 20 results were as shown in Table 2.

EXAMPLE 3

Example 1 was repeated except that dibutyltin dioctoate was not employed. The results were as shown in Table 2.

4 GB 2 118 834 A 4 TABLE2

Baking Example time:' (min.) Property 1 2 3 Rate of moisture absorption" 0.31 0.13 0 Angle of repose (1) 38 34 Light-duty bulk density' 0.82 0.90 Residual amount of emission (g)2 168 88 Rate of moisture absorption" 0.28 0.10 Angle of repose (1) 34 32 Light-duty bulk density' 0.86 0.91 Residual amount of emission (g)2 62 39 Rate of moisture absorption" 0.22 0.10 Angle of repose (1) 33 33 Light-duty bulk density' 0.92 0.93 Residual amount of emission (g)2 34 34 Rate of moisture absorption" 0.16 0.08 0.20 120- Angle of repose (1) 33 33 38 Light-duty bulk density' 0.93 0.93 0.79 Residual amount of emission (q)2 33 32 183 Rate of moisture absorption" 0.16 0.08 0.24 Angle of repose (1) 33 32 36 Light-duty bulk density' 0.93 0.93 0.82 Residual amount of emission (g)2 36 32 162 Rate of moisture absorption' 0.12 0.08 0.19 240 Angle of repose (0) 32 32 36 Light-duty bulk density' 0.93 0.93 0.84 Residual amount of emission (g)2 33 36 165 According to Japanese minor regulations for inspection of fire- extinguishant agents of fire extinguisher 1.5 Kg vessel employed 3 Time after arrival at 1 OOOC EXAMPLE 4

Example 1 was repeated except that the baking temperature was changed to 1401C. The results were as shown in Table 3.

EXAMPLE 5

Example 4 was repeated except that the amount of dibuty[tin dioctoate was changed to 0. 1 kg. The results were as shown in Table 3.

EXAMPLE 6

Example 4 was repeated except that dibutyltin dioxtoate was not employed. The results were as 10 showninTableI GB 2 118 834 A TABLE 3

Baking Example time4 Property 4 5 6 (min.) Rate of moisture absorption' 0.27 0.10 0 Angle of repose (0) 36 31 Light-duty bulk density' 0.89 0.92 Residual amount of emission (g)' 77 36 Rate of moisture absorption" 0.22 0.08 Angle of repose (1) 36 32 Light-duty bulk density' 0.90 0.93 Residual amount of emission (g)2 62 39 Rate of moisture absorption" 0.20 0.07 0.30 Angle of repose (0) 34 31 39 Light-duty bulk density' 0.91 0.94 0.85 Residual amount of emission (g)2 38 31 114 Rate of moisture absorption" 0.15 0.08 0.22 Angle of repose (0) 34 30 38 Light-duty bulk density' 0.90 0.93 0.88 Residual amount of emission (9) 2 32 32 93 Rate of moisture absorption" 0.11 0.06 0.12 Angle of repose (0) 35 30 34 Light-duty bulk density' 0.92 0.95 0.91 Residual amount of emission g 2 34 33 48 4 Time after arrival at 1401C EXAMPLE 7

A powdery extinguishant was produced employing a continuous production apparatus separated into a mixer (100 1 capacity), a solvent vaporizer (250 1 capacity) and a baking chamber (a mixer of 1 M 3 volume, having ribbon-type stirring blades fixed onto its rotating main shaft and having partition plates provided therebetween, and also having two chambers inside it; rpm, 40). At a temperature for the mixer of room temperature, for the solvent vaporizer of 500C and for the baking chamber of 1401'C, raw materials were fed at the rates shown in Table 4 and production was continuously carried out for 3 weeks:

TABLE 4

Raw Material Rate (kg/hr) Monoammonium phosphate 300 Fine powder of silicic anhydride 9 Methyl hydropolysil oxa ne 6 Perch loroethylene 50 Red pigment trace Dibutyltin octoate 0.1 6 GB 2 118 834 A 6 A powdery extinguishant was obtaihed at a rate of 315 kg/hr. Its properties after one., two and three weeks were as shown in Table 5.

TABLE5

Example 7

After - After After one week 2 weeks 3 weeks Rate of moisture absorption" 0.04 0.06 0.06 Angle of repose (0) 31 29 -305 Light-duty bulk density" 0.935 0.93 -0.93 Residual amount of emission (g)2 32 30 32 For the remaining examples an apparatus in accordance with the invention was employed. This 5 apparatus is shown in the accompanying drawing, in which:

The figure is a cross-secflon of an apparatus for producing a powdery fire extinguishant. The inside of a 4 m' capcity mixer having a rotatable main shaft 7 with stirring blades 8 fixed thereonto was sectioned into three chambers, viz a mixing and kneading chamber 1, a solventvaporizing chamber 2 and a heating reaction chamber 3 ' -Sectioning was by means of partition walls 9 and 10, with partition plates 11 were provided between the stirring blades of the respective chambers.10 An opening 15 for transferring raw material was provided above the partition wall 10, between the mixing and kneading chamber 1 and the solvent-vaporizing chamber 1. An opening 14 was also provided at the lower part of the partition wail, between the. solvent-vaporizing chamber 2 and the heating reaction chamber 3. A feed port 4 was fixed on to the mixing and kneading chamber 1, a.

vaporization pipe 5 for removing vapor was fixed to t ' he solventvapo'rtzing chamber 2, and a discharge is port 6 was fixed on the heating reaction chamber. Furthermore, on the outer walls of the solventvaporizing chamber 2 and the heating reaction chamber 3 were fixed-heating jackets 12 and'13capable of feeding heat at 15000 Kcal/hr.

EXAMPLE 8

A powdery fire extinguishaAt was produced employing the described apparatus, t'he.tdmperatures, 20 of the solvent-vaporizing chamber and the 'heating reaction, chamber being set to'SOIC-'and 1400C, respectively, and the stirring blades being r otated at a rate of 40 times per minute. Raw m- aterials were supplied through the raw material feeding port at the rates shown in Table 6 and the extinguishant was produced continuously for 3 weeks. Perchlor-oethylene was quantitatively removed at a rate of 50 Kg/hr.

TABLE 6

Raw Material Rate (Kg/hr) Monoammonium phosphate 300 Fine powder of-silicic anhydride 9 Methyl hydropolysi 1 oxane 6 Perchloroethylene 50 Red pigment trace The resulting powdery fire extinguishant was obtained at a rate of 315 Kg/hr. Test results after 1, 2 and 3 weeks were as shown in the following Table 8.

EXAMPLE 11 A jacket was fixed also to the outer wall of the mixing and kneading chamber of the apparatus; the f 7 GB 2 118 834 A 7 partition walls and the partition plates were removed; The discharge port for fire extinguishant was closed; the stirring blades were rotated at a rat of 40 times/min; and the raw materials of Table 7 were introduced:

TABLE 7

Raw Material Amount (Kg) Monoammonium phosphate 2,000 Fine powder of silicic anhydride 60 Methyihydropolysiloxane 40 Perchloroethylene 333 Red pigment trace Mixing was carried out for one hour, and then the same heat quantity as in Example 8 was supplied. Perchloroethylene was vaporized over 5 hours and then heat treatment was carried out for 3 hours. This procedure was repeated 3 times. The results were as shown in the Table 8. After initiation of temperature elevation, the amount of solvent vaporized varied to a large extent, and at the time of the most violent vaporization, the amount was about 300 kg per hour.

TABLE 8

Example 9 Example 10 After After After After After one week 2 weeks 3 weeks twice thrice Mixing and kneading 3.5 3.5 3.5 1 1 Time of Solvent removal 3.5.3.5 3.5 5 5_ Steps (h r) Reating reaction 7 7 7 3 3 Tota 1 14 14 14 9 Kg/batch 2,100 2,100 Produc tion Kg/hr 315 315 315 capacity Kg/day 7,560 7,560 7,560 5,600 5,600 Number of steps required (per day) 3 3 3 6 6 Rate of moisture absorption' 0.05 0.04 0.05 0.10 0.08 Powdery fire Angle of repose (0) 31 30 31 36 34 extin- guishant Light-duty bulk density' 0.93 0.93 0.93 0.90 0.93 Residual amount of emission (g)2 32 35 30 48 44

Claims (7)

1. An apparatus for continuously producing a powdery fire extinguishant, the apparatus comprising a mixing and kneading part having a feed port for raw materials; a solvent-vaporizing part with a heater and vaporization pipe; and a heating reaction part with a heater and fire extinguishant 15 discharge port.

8 GB

2 118 834 A 8 2. Apparatus according to Claim 1 comprising a mixing and kneading chamber, a solventvaporizing chamber and a heating reaction chamber, each of these chambers being furnished with at least two mixing rotors and partition plates between the mixing rotors, and said mixing and kneading chamber and said solvent vaporizing chamber and also said solvent- vaporizing chamber and said heating reaction chamber communicating through a respective opening.

3. Apparatus according to Claim 2, wherein the respective rotors of said solvent-vaporizing chamber and said heating reaction chamber are rotated by means of a common shaft.

4. Apparatus according to Claim 2 or Claim 3, wherein said solventvaporizing chamber shares with said reaction chamber a common partition wall through which extends an opening from the solverit-vaporizing chamber to the heating reaction chamber, the opening being located where material 10 will be retained.

5. Apparatus according to Claim 2,3 or 4, wherein the mixing and kneading chamber and the solvent-vaporizing chamber, and also the solve ntvaporizing chamber and the heating reaction chamber each share a respective partition wall and form a unified structure so that the rotors of the respective - chambers can be rotated by means of a common shaft.

6. Apparatus according to any one of Claims 2 to 5, wherein the partition plates have a throughopening.

li:

7. Apparatus according to any one of claims 1 to 6, wherein an opening is provided for blowing in of air in to the apparatus.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office, Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

E A.

7. Apparatus according to any one of Claims 1 to 6, wherein an opening is provided for blowing in of air in to the apparatus.

New claims or amendments to claims filed on 14 June 1983. Superseded claims 1 to 7. New or amended claims:- 1 to 7.

1. An apparatus for continuously producing a powdery fire extinguishant, the apparatus comprising a mixing and kneading chamber with a feed port for raw materials; a solvent-vaporizing chamber with heater and vapour outlet; and a reaction chamber with a heater and a product discharge 25 port, the chambers being in communication for passage of material from the feed port through the mixing chamber to the solvent-vaporizing chamber and then to the reaction chamber and out through the discharge port.

2. Apparatus according to claim 1, wherein each of the chambers is furnished with at least two rotatable mixing blades partitioned by partition plates between the blades.

3. Apparatus according to claim 2, wherein the respective blades of said solvent-vaporizirig chamber and said reaction chamber are rotated by means of a common shaft.

4. Apparatus according to claim 2 or 3, wherein said solvent-vaporizing chamber shares with said reaction chamber a common partition wall through which extends an opening from the solvent vaporizing chamber to the reaction chamber, the opening being located where materials will be 35 retained.

5. Apparatus according to claim 2, 3 or 4, wherein the mixing and kneading chamber and the solvent-vaporizing chamber, and also the solvent-vaporizing chamber and the reaction chamber each share a resepective partition wall and form a unified structure so that the blades of the respective chambers can be rotated by means of a common shaft.

6. Apparatus according to any one of claims 2 to 5, wherein the partition plates have a through opening.