WO1995007948A1

WO1995007948A1 - Fire retardant agents suitable for plastics

Info

Publication number: WO1995007948A1
Application number: PCT/AU1994/000546
Authority: WO
Inventors: Fidenciano Lopez; Christopher John Regan
Original assignee: Bains Harding Limited
Priority date: 1993-09-14
Filing date: 1994-09-14
Publication date: 1995-03-23
Also published as: AU678288B2; AU7688994A

Abstract

A fire retardant component to be incorporated in a plastic, especially polyurethane, foam which functions as a blowing agent and comprises pyrrolidone or a derivative thereof, a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea. Processes and apparatus for the production of a flexible polyurethane foam using the fire retardant component are also described.

Description

FIRE RETARDANT AGENTS SUITABLE FOR PLASTICS. Field of the Invention.

This invention relates to fire retardant agents which, when added to a material during its manufacture, provide a fire resistant or fire retardant characteristic to that material. Of special interest from the point of view of the invention are polymers, especially polyurethanes.

Background of the Invention.

It is well known to use certain chemicals and mixtures of chemicals as fire retardants for materials such as fabrics, rigid and flexible plastics foamed and non-foamed, timber, particle board and the like. The kinds of fire retardant agents employed vary with the material of interest and thus fire retardant agents considered suitable fo. application to one type of material may be completely unsuitable for another.

In the polyurethane industry, inorganic fire retardants which are soluble in nature are generally disregarded because they will leach from the polyurethane foam with deleterious results. For example, it is known from the literature the difficulties encountered with the soluble nature of ammonium monophosphate.

US Patent No. 3423343 assigned to Monsanto Company also discloses the above problem with ammonium monophosphate and ammonium orthophosphates in general and discusses the additional problem encountered with loss of physical properties such as closed cell content.

The above patent proposes the use of phosphorus and nitrogen compounds in the form of substantially water insoluble ammonium polyphosphates, having P-O-P type linkages and the general formula:

H(r-m)₊₂(NH₄)_mPnθ3n₊ι where n is an integer having an average value greater than 10 and m/n is between about 0.7 and about 1.1 and the maximum value of m is equal to n~2.

Now, this compound sold under the trade name PHOSCHEK 30 by Monsanto Company is certainly less soluble than ammonium monophosphate or ammonium diphosphate and is described by Lewin, Atlas & Pearce, Vol 1 ,

"Polyurethane Structure and Flame Resistance" to have flame spread of 36% after 7 days immersion in water, as opposed to 33% before immersion. However, Miles, C.E and Lyons, J.W report in "Properties of Rigid Urethane Foams Containing Fire Retardants based on Phosphorus", Journal of Cellular Plastics, p 539, December 1967 that polyurethane foams containing this ammonium polyphosphate require a chlorofluorinated compound (CFC) blowing agent, trichlorofluoromethane in manufacture.

Leaving aside the issue of the use of a CFC blowing agent, in itself undesirable, for the present further disadvantage may occur in that the decomposition temperature is such that a reduced amount of char is formed. This results in either reduced fire protection or the increased expense of using more material to achieve adequate protection.

Thus, present development in the art favours the use of organic fire retardants for use in polyurethane applications.

For example, US Patent No. 4623672, assigned to Bayer AG, discloses flame retardant isocyanate addition products made by reacting an isocyanate with a compound selected from the group consisting of 1 - phosphonoethane-2 -carboxylic acid-t ri-C -|-C -a lkyl esters, 1 - phosphonopropane-2-carboxylic acid-tri-Cι -C₄-alkyl esters and mixtures thereof. Blowing agents may include CFC agents, the examples particularly specify the use of trichlorofluoromethane. Australian Patent No. 591089 assigned to Ciba-Geigy Limited employs as fire retardant a salt formed by reaction between dimethyl methyl phosphonate, monomethyl methyl phosphonate and a compound of the general formula (I):

X 1

R-

R²

in which X is 0,S or NH, R is H, alkyl with 1 to 4 carbon atoms, alkenyl of up to 4 carbon atoms, CN, CONH₂ or NH₂, R² is H, alkyl with 1 to 4 carbon atoms or alkenyl of up to 4 carbon atoms or Ri and R≥ together with the nitrogen atom to which they are attached form a heterocyclic ring of up to 6 carbon atoms which may optionally contain another heteroatom and R is H, an alkyl group with 1 to 8 carbon atoms, an aryl group with 6 to 10 carbon atoms, a cycloalkyl group with 5 to 12 carbon atoms or a heterocyclic group with up to 9 ring carbon atoms or a heterocyclic group with up to 9 ring carbon atoms, or, together with Ri forms an alkylene chain of 3 to 10 carbon atoms, or R is a group NHR3 wherein R3 is H, alkyl with 1 to 4 carbon atoms, alkenyl of up to 4 carbon atoms, CN, CONH₂ or NH₂ or together with R1 forms an alkylene chain of 2 or 3 carbon atoms, or R is a group

where Ri, R2 and X are as defined above and R is a direct bond or an alkylene group having up to 8 carbon atoms or is an arylene group having 6 to 10 carbon atoms.

These flame retardants are of low volatility and allow the formation of polyol formulations which are stable on storage. Again CFC blowing agents, namely dichlorodifluoromethane or trichlorofluoromethane, are noted as being especially desirable and trichlorofluoromethane is exemplified. Tests conducted according to German Standard DIN 4102 B2 reported a burn time of 9 to 15 seconds with one of the examples burning with maximum flame height 13 cm but no burn time being recorded. In all cases, loss on ignition or oxygen index is greater than 23.5% by weight.

The burning behaviour of polyurethane foams prepared in the accordance with the above may be satisfactory for some applications but there is ? need to produce polyurethane foams with greater fire resistance, especially flexible foams which have generally lower fire retardance than rigid foams.

Further, the prior art suggests that CFC blowing agents are still very much a feature of the polyurethane manufacturing industry. However, this situation cannot continue. As a result of an International Agreement, the use of CFC agents must be phased out by the year 1997 due to the atmospheric damage apparently caused by such agents. This clearly poses a serious technical problem for the polyurethane industry since blowing agents are presently perceived as essential to the formation of commercial foams. Blowing agents are introduced to polyurethanes and other polymers during manufacture to cause gas evolution which allows the production of the cellular structure in foams commonly encountered in packaging, furniture and building products as well as other applications.

Two types of foam are employed - these being the flexible type and the rigid type. Both types of foam have a cellular structure and are made from the same basic ingredients. These ingredients are bought as a "system" from large chemical companies and are tailored to achieve individual specifications suitable for various applications. Accordingly, and as the described prior art illustrates, technical pressures exist on chemical companies to produce foams with the required properties. It is the general object of the present invention to provide a fire retardant component for plastic foams that is substantially free of the above described limitations.

It is a first specific object of the present invention to provide a fire retardant component that has reduced ignitability from prior art fire retardant agents as described above.

It is a second specific object of the present invention to provide a fire retardant agent, that through its nature, allows the use of CFC blowing agents to be avoided.

It is a third specific object of the present invention to provide a fire retardant component, formulated from compounds which are of economically ^" sustainable cost.

It is a fourth specific object of the present invention to provide a process for the manufacture of a plastic, especially polyurethane, foam which allows the attainment of good physical properties such as closed cell content and good fire retardance. Summary of the Invention.

With the above objects in view, the present invention provides, in a first aspect, a fire retardant component to be incorporated in a plastic foam which functions as a blowing agent and comprises pyrrolidone or a derivative thereof, a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea.

Preferably, the ammonium halide is ammonium bromide.

The plastic foam may be a polyurethane foam but this is not essential to the invention. The fire retardant component may equally be applied in the case of other plastic foams subject to fire retardant component compatibility with the plastic foam under consideration.

Conveniently, the fire retardant component is included within a polymerisation reaction mixture, ^' r example a polymerisation reaction mixture used in the production of a poiyurethane foam; in an amount preferably corresponding to between 15 and 50%, more preferably 20 to 30%, of the total weight of the polymerisation reaction mixture. This range is not intended to be limiting and the proportion of the component added may vary with the desired degree of fire retardance. By interaction with other constituents of the polymerisation reaction mixture, the component advantageously aids in producing the necessary gas for foam expansion without the requirement for CFC blowing agents.

A suitable fire retardant component may be produced by mixing 50 to 60, more preferably 51 to 53, percent by weight of the component ammonium halide; 5 to 15, more preferably 8 to 11 , percent by weight of the component ammonium monophosphate; 5 to 15, more preferably 8 to 11 , percent by weight of the component ammonium diphosphate; and 20 to 30, more preferably 22 to 26, percent by weight of the component urea. The pyrrolidone or derivative thereof forms between 4 and 10, preferably 5 to 8, percent by weight of the fire retardant component. Preferably, the ammonium halide selected is ammonium bromide. In a second aspect, the present invention provides a process of polyurethane foam manufacture comprising the admixture of the above described fire retardant component with an isocyanate and a polyol. Preferably, the ammonium salts and urea of the fire retardant component are mixed with the isocyanate first.

In a specific embodiment, the process comprises the steps of:

(a) mixing an isocyanate with a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea;

(b) feeding the mixture from step (a) to a mixer, to which is introduced the polyol, pyrrolidone or a derivative thereof and, optionally, a solvent; and mixing these components together; and (c) adding a polymerisation catalyst and optionally water and conducting the polymerisation reaction. The polymerisation reaction is desirably conducted in a mixer stirred with a high speed impeller. High speed intensive mixing is aimed at maintaining the above described components in suspension throughout the duration of the polymerisation reaction. It is to be understood that failure to maintain the components in suspension may lead to failure to attain a uniform homogeneous polyurethane foam.

In a third aspect, the present invention provides an apparatus for producing a polyurethane foam in accordance with the process of the second aspect of the present invention. The apparatus comprises a holding vessel to hold an isocyanate component comprising isocyanate and a mixture of soluble salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea; first means for mixing the combination of isocyanate and said mixture of soluble salts and urea; first introduction means for bringing a polyol component, comprising a pyrrolidone or a derivative thereof, a polyol and, optionally, a solvent, into contact with the isocyanate component; second means for mixing the isocyanate component with the polyol component; second introduction means for introducing a polymerisation catalyst component and, optionally, water to the mixture of the isocyanate component and the polyol component; and a high speed mixing means for further mixing of the isocyanate component with the polyol component in the presence of the polymerisation catalyst component enabling homogeneous polymerisation thereof.

The holding vessel is desirably provided with an atmosphere of inert gas, for example nitrogen or argon.

The apparatus may be provided with recycle means to allow return of the isocyanate and the mixture of soluble salts and urea to the first mixing means until the consistency of the product isocyanate component is such as to enable satisfactory contacting with the polyol component.

In a fourth aspect, the present invention provides a formulation for manufacture of a polyurethane foam comprising an isocyanate; a polyol; a catalyst system and a fire retardant component comprising pyrrolidone or a derivative thereof, a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea, each being brought into contact in a sequence to enable production of a polyurethane foam. Preferably, the ammonium halide is ammonium bromide.

Further aspects of the invention include the polyurethane foams manufactured in a process including the introduction of the above fire retardant component; foams manufactured in the above described process and apparatus. Polyurethane ^foams produced from the above described formulation and articles, for example feed material for use in the furniture industry, also form part of the invention.

The polyurethane foams prepared in accordance with the above described process and prepared with the above described fire retardant component may be flexible foams found to have reduced tendency to ignite. Solubility of the ammonium salts, without wishing to be bound by any theory, is apparently reduced by admixture with urea. The addition of pyrrolidone or a derivative thereof may have a similar effect. The fire retardant compounds are commodity chemicals, readily sourced at reasonable cost from chemical manufacturers. Therefore, a product polyurethane foam may be rendered fire retardant and more resistant to ignition by use of a fire retardant component sourced and produced at an economically sustainable cost. Indeed, the compounds used in the fire retardant component generally cost less than the base materials required to form the polyurethane foam, namely polyols and isocyanates. Detailed Description of the Invention.

The invention will be more clearly understood from the following description and reference to the appended examples and drawing in which:

Figure 1 is a schematic of the apparatus used in accordance with the invention for the manufacture of a flexible polyurethane foam.

The general reaction scheme for the formation of flexible polyurethane foams is generally understood by those skilled in the art of foam manufacture and proceeds from the reaction of isocyanates and diisocyanates with other difunctional groups such as polyols and polyesters, possibly in admixture.

Indicative of diisocyanates that can be used are liquids such as methyl diisocyanate, diphenyl methane diisocyanate, toluene diisocyanate, methylene diphenyl diisocyanate, polymeric methylene diphenyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated methylene diphenyl diisocyanate or any polyisocyanate containing two or more reactive isocyanate groups. Especially preferred in the case of the present invention is a toluene diisocyanate formulation. As suitable polyols may be mentioned, for example, those listed in

Australian Patent No. 591089 assigned to Ciba-Geigy Limited being a polyfunctional organic compound containing a plurality of hydroxyl groups. Such include, for flexible foam applications, polyether polyols such as polyoxyethylene/oxypropylene diols, polyoxyethylene/oxypropylene triols, castor oil and methylglucoside polyether glycols having average molecular weights in the range of approximately 250-6500. Any of these polyols may be employed as a flexible base polyol and, particularly preferred in the case of the present invention is a proprietary polyol formulation sourced under the trade name

Ultracell 2000 from Union Carbide.

The ammonium salts for use in the fire retardant component of the present invention are food grade ammonium monophosphate and ammonium diphosphate and an ammonium halide. Especially preferred as the ammonium halide is photographic grade 99.5% ammonium bromide, though ammonium chloride could also be used. Each of these compounds, with the exception of ammonium halide, is a bulk commodity chemical and readily obtainable. In the examples to be described, ammonium bromide was sourced from Consolidated Chemicals, Sydney. The ammonium phosphates were sourced from Albright &

Wilson, Sydney. The ammonium bromide may require to be specially ordered in commercial quantities from a chemical manufacturer.

Pyrrolidone or a derivative thereof to be used in accordance with the present invention is a ketone H derivative of pyrrolidine, ketopyrrolidine, liquid at temperatures above

has the formula:

where R may be hydrogen or, in the case of an appropriate derivative thereof for use in the present invention, an alkyl group substituted or unsubstituted. The alkyl group may have between 1 and 14 carbon ε'oms with the form having 12 carbon atoms being most preferred for use in acc^ dance with the invention.

The pyrrolidone derivative preferred for use in the invention is N-

(n-dodecyl)pyrrolidone (CAS 00002687-96-9) sourced under the trade name SURFADONE LP300® from ISP Investments Inc. The remaining component of the fire retardant component, namely industrial grade urea, was sourced from Incitec, Sydney.

Remaining components of the formulation include a suitable surfactant, catalyst and solvent. The surfactant is required to ensure that mixing of the various components is facilitated and the resulting mixture is homogeneous in physical properties and composition. Desired bubble and cell formation and a uniform distribution thereof throughout the product foam depend upon the use of a surfactant.

As a small amount of water may be introduced to the polymerisation reaction mixture to assist with foam expansion, the surfactant is desirably non-hydrolysable and, as preferred examples, may be mentioned polydimethylsiloxane and polydimethyl siloxane polyalkylene copolymers. Especially preferred in the present instance is the surfactant L6900 which is a proprietary polyalkyleneoxidemethylsiloxane copolymer sourced from OSI Specialities Inc.

As far as the catalyst system is concerned, selection of appropriate catalysts is crucial to the effective performance of the polyurethane polymerisation reaction. In the present instance, a tin compound is employed as catalyst. The tin compound may be a hydrocarbon tin alkyl carboxylate, dibutyl tin diacetate, dibutyl tin dioctoate, dibutyl tin dilaurate and stannous octoate. A suitable tin catalyst is proprietary dibutyl tin dilaurate sourced from Air Products and Chemicals, Inc. under the trade name T12®, which is especially preferred in the present instance. Other catalysts may be selected by those skilled in the art and the nature of the catalyst employed is not intended to place a restriction upon the scope of the present disclosure.

A specific blowing agent, additional to the compounds forming the fire retardant component, is not required in accordance with the present invention but the use of such an agent is not absolutely precluded. A solvent such as methylene chloride which is volatile and which consequently allows cell formation, in association with the fire retardant component described above, may be added. In the present instance, methylene chloride is employed as a solvent.

Addition of a small quantity of water at the polymerisation stage will also assist with cell formation and its use is highly recommended in the present instance.

Thus, in accordance with the above, the following formulation is most preferable for use in the present invention:

Component Proportion bv Weiαht (%)

Polyol ("Ultracell 2000") 35 - 45 Pyrrolidone Derivative

("Surfadone LP300") 1 - 2

Water 1 - 2

Surfactant ("L6900") 1 - 2

Tin Catalyst ("T12") 1 - 2 Methylene chloride 2 - 4

Stabiliser/Softener (DEAO) 1 - 2

Toluene diisocyanate (TD1 ) 15 - 30

Urea and Ammonium Salts 20 - 30 and more specifically Component Proportion bv Weiαht (%)

Polyol ("ULTRACELL 2000") 41.7

Pyrrolidone Derivative ("LP300") 1.6

Surfactant ("L6900") 1.6

Water 1.2 Tin Catalyst ("T12") 1.2

Methylene Chloride 3.2

Softener ("DEAO LF") 1.5

Urea and Ammonium Salts 26.1

Toluene diisocyanate (TDI) 21.9

100 Thus the fire retardant component forms 27.7 percent by weight of the preferred formulation.

The ammonium salts and urea of the fire retardant component are to be mixed in the proportions given below: Compound Proportion bv Weiqht (%) ammonium bromide (A) 55.1 1 ammonium diphosphate (B) 9.85 ammonium monophosphate (C) 9.85 urea (D) 25.19 The method of production of a flexible polyurethane foam in accordance with a preferred embodiment of the present invention proceeds as follows:

Preparation of Inorganic Fraction of Fire Retardant Component.

Each of the compounds (A), (B), (C), (D) is to be dried until a stable moisture content is achieved. As excessive moisture may prove detrimental to the compressive strength of the product foam, it is to be avoided at all costs.

The drying of the compounds is to occur at a temperature such that decomposition thereof does not occur. In this connection, urea melts at 132.7°C and the phosphates also decompose at low temperature. If storage after drying is required, moisture must be excluded from the storage vessel. Storage will require the vessel to be resistant to corrosion. A suitable container is a plastic drum with sealable lid inside which has been placed a poly bag and possibly vacuum sealed. As the activity of the compounds may decrease with storage time, prolonged storage is not recommended. The compounds are then to be thoroughly mixed together in a blender from which moisture is excluded and ground to a fine powder having average particle size preferably between 20 μm and 50 μm. A particle size in this range is desirable from the point of view of better dispersion within the polymerisation mixture and assists in efficient mixing. To improve flowability of the mixture, a flow promoter, such as tricalcium phosphate (TCP), may be added, in a proportion of between 1 and 3% by weight of the fire retardant agent, to improve mixing and flowability of the final powder. Preparation of Polyurethane Foam.

In accordance with a preferred embodiment of the present invention, the urea and ammonium salts in admixture are introduced and mixed with the diisocyanate, toluene diisocyanate (TDI), to form the isocyanate component.

However, this is not to place any limitation on the process of the invention. It is not intended to preclude addition of the ammonium salts or urea of the fire retardant component or the fire retardant component as a whole to the polyol as an initial step. For example, the pyrrolidone or derivative thereof could be added to the isocyanate or polyol, introduced in admixture with the remaining constituents of the fire retardant component or otherwise. In addition, the following sequence of operations is not intended to place any limitation on the foam preparation sequence. The object of the present invention is to produce polyurethane foams with acceptable fire resistance from the point of view of end users. Any mixing sequence that achieves this end is considered to fall within the scope of the invention. The following described sequence has been found beneficial but is in no way exhaustive.

Reference is now made to Figure 1 and an apparatus in which a polyurethane preparation process in accordance with a second aspect of the present invention may be performed.

The apparatus comprises a reception/storage vessel 1 in the form of a hopper to which the above described proportions of isocyanate, namely TDI, and the urea and ammonium salts of the fire retardant component being in finely divided crystalline form, are manually or automatically dosed, desirably in the absence of air. The next step is to mix these components together and this is achieved by use of mono pump 2. This pump includes a mixing means in the form of an auger or archimedes screw, the speed of rotation of which dictates the dosing rate of the isocyanate, ammonium salts and urea into the foam preparation process. Other suitable mixers allowing adequate mixing of the above components may also be employed and suitable mixers may be selected from Perry et al., Chemical Engineers Handbook, Chapter 6, 5th Edition. Valve 3 may be closed to allow recirculation of the mixture through recycle line 4 back to storage vessel 1 until a suitable consistency of the mixture has been achieved. Such consistency may be checked by appropriate sampling. If desired, a static mixer as described below may be placed in recycle line 4 to assist with further mixing. The control of water ingress and possible side reactions of the mixed isocyanate component with air commends the maintenance of an inert gas atmosphere in the headspace of vessel 1 which is sealed and blanketed with the inert gas during processing of a batch. Addition of the components to vessel 1 may take place through a port or ports in the vessel. Upon attainment of a suitable degree of mixing of the constituents constituting the isocyanate component, valve 3 is opened and first introduction means 5, which may be an injector, needle valve, dosing pump or other suitable dosing means is operated to allow bringing into contact with the isocyanate component, a polyol component which is a mixed liquid formed from Surfadone LP 300 (pyrrolidone derivative), Ultracell 2000 (polyol), L 6900 (surfactant) and methylene chloride. Premixing of these components is appropriate prior to bringing the product polyol component into contact with the isocyanate component.

In addition, manufacture of a flexible foam may require the addition of a stabiliser/softener such as diethanolamine (DEOA) or triethanolamine (TEOA) to assist in obtaining the desired foam flexibility. DEOA or TEOA are crosslinking agents which cause a chemical stabilisation of the foam during polymerisation producing a random cell size distribution within the foam. Such cell size distribution is highly desirable. This agent is conveniently added to the polyol component.

Mixing of the polyol component and isocyanate component then takes place in a mixing means such as static mixer 6. A static mixer has good mixing characteristics and a suitable mixer may be sourced from Kenics Corporation, as described in Perry et al, Chemical Engineers Handbook, 5th Edition, McGraw-Hill New York (1982). The mixer consists of twelve alternate- hand helical elements juxtaposed at an angle of 90° to one another inside a tubular housing. The fluid media mix during their passage through the mixer. Energy for the mixing is provided by mono pump 2 causing flow through the static mixer 6 and, if a pump is used to cause flow of the polyol component through the first introduction means 5, also that pump. The static mixer may also be replaced by a mixer allowing a similar degree of high intensity mixing; alternative mixers may be found in the high intensity mixers described in Perry et al, Chemical Engineering Handbook, Chapter 6, 5th Edition, the contents of which are hereby incorporated by reference.

At the end of the mixing operation in static mixer 6, water and a polymerisation catalyst component, being a tin catalyst T12®, are introduced by second introduction means 7, again a dosing pump, injector, needle valve or other suitable dosing means to the mixture of polyol and isocyanate components. It is only after the introduction of the polymerisation catalyst component to the mixture that an appreciable degree of polymerisation can occur. The polymerisation reaction is to proceed in a high speed high intensity mixer 8, a suitable type of which has been designed and built by the applicant, Bains Harding Limited. Polymerisation occurs instantaneously and residence time of less than two seconds in the mixer is envisaged.

The preferred mixer 8 is a pin mixer provided with a shaft 9 on which are provided a number of pin-like protrusions 10. The shaft is caused to rotate by a hydraulic motor driving a ram which is forced down upon the shaft to cause high speed rotation of the shaft at up to 7000 rpm, but preferably 5000 to 6000 rpm. The construction of the shaft and pin-like protrusions strictly confines the polymerisation reaction mixture within the body of pin mixer 8 and, in combination with the rapid rotation of the shaft and action of the pin-like protrusions, enables a very high degree of intensive mixing to be attained.

Following mixing, the foam may be extruded as a bun or passed to further processing stages for production of foam in a form suitable, for example, for furniture manufacture.

The above described apparatus requires a high degree of corrosion resistance and stainless steel is the recommended material of construction. Seals between items of equipment such as mono pump 2 and static mixer 6 should be of a resistant rubber, such as the fluoroelastomer supplied under the trade name VITON®.

Any valves in the apparatus, especially valve 3, should be "one¬ way" such that reflux of mixtures to preceding portions of the apparatus is avoided. The apparatus described above is capable of providing 90kg/minute of product polyurethane foam.

Curing of the product foam may be desirable to allow the solvent to permeate through, and evaporate from, the foam. A period of 24 to 48 hours may be allowed to compensate for this contingency.

Example 1.

The fire retardant performance of three flexible foams were evaluated by the Australian Department of Defence, Industry Support Office in accordance with ASTM E 1354-92, "Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter". The contents of ASTM E 1354-92 are hereby incorporated by reference.

The following properties were determined at heat fluxes of 25 and 50 kW/m2: (a) time to ignition, (b) rate of heat release (RHR), (c) effective heat of combustion (EHC), (d) smoke obscuration, and (e) mass loss. The flexible foam comparison was made with a flexible polyurethane foam supplied by another chemical manufacturer with an organic non-halogenated fire retardant agent.

Flexible Foam A Comparative Examples

(A) (B) (C) ^' Flux (kW/m2) 25 50 25 50 25 25

Time to Ignition(s) 395 29 51 6 46 43

Maximum Rate of

Heat Release

(kW/m2) 80.5 156.6 197.3 229.3 154.8 17£ Time to maximum

Rate of Heat Release(s) 420 45 245 170 155 220

Average Rate of Heat Release

(kW/rr»2) 35.6 30.0 140.7 160.2 1 14 126. Average Smoke Obscuration

(m2/kg) 1314 1469 4556 627 354 335

Loss on lgnition(%) 37.9 86.2 92.3 93.9 90.8 91.7

Comparative Examples

(A) is a flexible foam sourced from Joyce Industries, Australia under the tra name CM5 BLUE

(B) is a flexible foam sourced from Joyce Industries, Australia under the tra name CM 2 (C) is trade name CM2 is a flexible foam sourced from Joyce Industrie

Australia under the trade name CM5 YELLOW.

The flexible polyurethane foams of the comparative examples ignite at a heat flux of 25 kW/m², and in the case of comparative Example A

50kw/m2, within a shorter time than the flexible foam of the invention. Additionally, the foams of the comparative examples demonstrate a greater loss on ignition.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A fire retardant component to be incorporated in a plastic foam which functions as a blowing agent and comprises pyrrolidone or a derivative thereof a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea.

2. The component as claimed in claim 1 wherein the ammonium halide is ammonium bromide.

3. The component as claimed in claim 2 wherein the proportion by weight of the fire retardant component of each constituent are as follows:

50 to 60 weight percent ammonium bromide 5 to 15 weight percent ammonium monophosphate 5 to 15 weight percent ammonium diphosphate 20 to 30 weight percent urea.

4. The component as claimed in claim 3 wherein the proportion by weight (of the combined weight of urea and ammonium salts of the fire retardant component) of each constituent are as follows:

52 to 58 weight percent ammonium bromide 8 to 1 1 weight percent ammonium monophosphate 8 to 11 weight percent ammonium diphosphate 24 to 28 weight percent urea.

5. The component as claimed in claim 3 wherein pyrrolidone or a derivative thereof constitutes 4 to 10, preferably 6 to 8, percent by weight of the component.

6. The component as claimed in claim 1 wherein said pyrrolidone derivative is pyrrolidone substituted by an alkyl group.

7. The component as claimed in claim 6 wherein said alkyl group has 12 carbon atoms.

8. A process of polyurethane foam manufacture comprising the admixture, with an isocyanate and a polyol, of the fire retardant component as defined in any one of claims 1 to 7.

9. The process as claimed in claim 8 wherein the ammonium salts and urea are mixed with the isocyanate prior to contacting with the polyol.

10. The process as claimed in claim 9 wherein pyrrolidone or a derivative thereof is added to the polyol.

1 1. A process of polyurethane foam manufacture as claimed in claim 10 comprising the steps of

(b) feeding the mixture from step (a) to a mixer to which is introduced pyrrolidone or a derivative thereof, a polyol and, optionally, a solvent and mixing these components together; and

(c) adding a polymerisation catalyst and optionally water and conducting the polymerisation reaction.

12. The process as claimed in claim 1 1 wherein the polymerisation catalyst is a tin compound.

13. The process as claimed in claim 11 wherein step (a) is conducted in an inert atmosphere.

14. The process as claimed in claim 11 wherein the polymerisation reaction is conducted in a high intensity mixer.

15. An apparatus for the production of a polyurethane foam in accordance with the process as claimed in any one of claims 8 to 14 comprising a holding vessel to hold an isocyanate component comprising an isocyanate and a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and an ammonium halide; and urea; first mixing means for mixing the isocyanate, soluble ammonium salts and urea; first introduction means for bringing a polyol component, comprising a pyrrolidone or a derivative thereof, a polyol and, optionally, a solvent, into contact with the isocyanate component; second mixing means for mixing the isocyanate component with the polyol component; second introduction means for introducing a polymerisation catalyst component and, optionally, water to the mixture of the isocyanate component and the polyol component; and a high speed mixing means for further mixing of the isocyanate component with the polyol component in the presence of the polymerisation catalyst component enabling homogeneous polymerisation.

16. The apparatus as claimed in claim 15 including recycle means to recycle isocyanate and the soluble ammonium salts and urea to the first mixing means until the mixture attains a homogeneous consistency.

17. The apparatus as claimed in claim 15 wherein the holding vessel is provided with an inert gas atmosphere.

18. The apparatus as claimed in claim 15 wherein the second mixing means for mixing the isocyanate component with the polyol component is a static mixer.

19. The apparatus as claimed in claim 15 wherein the high speed mixing means is a pin mixer.

20. The apparatus as claimed in claim 15 wherein the ammonium halide is ammonium bromide.

21. A formulation for manufacture of a polyurethane foam comprising an isocyanate; a polyol; a polymerisation catalyst, a fire retardant component comprising pyrrolidone or a derivative thereof, a mixture of soluble ammonium salts selected from the group consisting of ammonium monophosphate, ammonium diphosphate and ammonium halide; and urea, each component to be brought into contact in a sequence to enable production of a polyurethane foam.

22. The forrr, ilation as claimed in claim 21 wherein the isocyanate comprises toluene diisocyanate.

23. The formulation as claimed in claim 21 or 22 wherein the ammonium halide is ammonium bromide.

24. The formulation as claimed in claim 22 wherein the proportions by weight (of the combined weight of urea and ammonium salts of the fire retardant component) formed by each compound are as follows:

52 to 58 weight percent ammonium bromide 8 to 11 weight percent ammonium monophosphate 8 to 11 weight percent ammonium diphosphate 24 to 28 weight percent urea.

25. The formulation as claimed in claim 21 comprising a non- hydrolysable surfactant.

26. The formulation as claimed in claim 21 wherein each soluble ammonium salt and urea is a crystalline solid ground to a size of between 20 and 50 microns.

27. The formulation as claimed in claim 21 or 22 wherein the fire retardant component forms 20 to 30 percent by weight of the product polyurethane foam.

28. The formulation as claimed in claim 21 wherein said pyrrolidone derivative is pyrrolidone substituted by an alkyl group and forms between 4 and 10, preferably between 6 and 8, percent by weight of the fire retardant component.

29. The formulation as claimed in claim 28 wherein said alkyl group has 12 carbon atoms.

30. A polyurethane foam manufactured in a process including the introduction of the fire retardant component as claimed in any one of claims 1 to 7.

31. A polyurethane foam produced in accordance with the process as claimed in any one of claims 8 to 14.

32. A polyurethane foam produced in the apparatus as claimed in any one of claims 15 to 20.

33. A polyurethane foam produced from the formulation as claimed in any one of claims 21 or 24 to 27.

34. A polyurethane foam produced from the formulation as claimed in claim 23.

35. An article manufactured from the polyurethane foam as claimed in any one of claims 30 to 34.

36. A plastic foam manufactured in a process including the introduction of the fire retardant component as claimed in any one of claims 1 to 7.

37. An article manufactured from the plastic foam as claimed in claim 36.