FIELD OF THE INVENTION The present invention relates to an iron containing composition, its method of manufacture and use as a fire retardant. More particularly, the invention relates to a fire resistant composition comprising a flammable host material and a fire retardant selected from the group consisting of an iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide, iron (III) hydroxide or a combination thereof. More particularly, the invention relates to the use of the composition as a sound suppressant. Still more particularly, the invention relates to a method for making an iron containing composition from a metal chloride stream, especially from a by product stream.

BACKGROUND OF THE INVENTION Fire retardant materials are commonly incorporated into polymer composites, such as for use in plastics, rubbers, adhesive, wire and cable industries. Fire retardant materials typically are those compositions that have high endothermic decomposition enthalpies that absorb energy during a fire to keep the host cool and result in the formation of a char at the surface of the polymer composite during burning to retard vapor phase fuel release, total heat release and time to peak heat release. In addition, these materials also release water or carbon dioxide during the decomposition that functions to smother the flame. Well-known fire retardant materials include aluminum trihydrate, magnesium hydroxide, antimony oxide, organophosphorous compounds and organic halogen containing compounds. In cases where the fire retardant is less expensive than the polymer in which it is compounded, the fire retardant can function as a polymer extender, provided that it does not degrade the properties of the polymer.

Each fire retardant has its limits of utility. Aluminum trihydrate decomposes in the range of 200°C and cannot be compounded into materials that require compounding temperatures above this range.

Magnesium hydroxide decomposes at a temperature above 300°C, but is

expensive. Halides and antimony compounds are not only expensive, but are viewed as environmental hazards in Europe and Japan. It seems clear that alternative fire retardant compositions are needed that provide the functionality without the inherent problems associated with many of the commercial products.

SUMMARY OF INVEIXTIObI The fire resistant composition of the present invention comprises a flammable host material and a fire retardant amount of an iron containing composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (11) hydroxide, and iron (III) hydroxide alone or in combination as a mixture or solid solution.

The iron containing composition of this invention or a mixture or solution made from the iron containing composition can be dried to compositions and morphologies fine tuned to have specific decomposition temperatures, compounding characteristics and fire retardancy features appropriate for use with various polymers for commercial plastic, textile and wood product applications. The composition, because of its high density, may also be used as a sound suppressant or to retard the electrical breakdown of a variety of host materials. Used as a sound suppressant, the composition of the present invention may be used to replace calcium carbonate, barium sulfate, magnetite and other known materials used for this purpose.

Thus, the present invention also relates to a sound suppressant material comprising a polymer and an iron containing composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide, iron (III) hydroxide and combination thereof.

The present invention further provides a process of making an iron containing composition from a metal chloride containing stream rich in ferrous chloride, the process comprising: (a) adjusting the pH of the metal chloride containing stream to about 6 to about 8 by contacting the metal chloride containing stream with a base to produce a brine and precipitate a mixture comprising an iron containing composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide and a combination thereof ; (b) separating the mixture from the brine to produce a wet solid composition essentially free of the brine ; and

(c) drying, and preferably, deagglomerating or grinding the wet solid composition to form the iron containing composition.

In a further embodiment of the process of this invention, useful for waste streams containing amounts of cationic impurities having a valence state above 2, the metal chloride-containing stream is first contacted with a base to increase the pH of the stream to from about 3. 5 to about 5. 5 and to form a precipitate of the cationic impurities having a valence state above 2 present as hydroxides and separating the precipitate from the by-product stream to produce a liquor rich in ferrous chloride having a pH of from about 3.5 to about 5.5 ; the pH of the liquor is then adjusted to about 6 to about 8 by contacting the liquor with a base to produce a brine and precipitate the mixture comprising an iron containing composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide, and a combination thereof.

The conditions and manner of drying the wet solid composition may be selected to produce desired compositions and morphologies for specific applications for both making fire retardant compositions and sound suppressant materials.

If desired, one or more modifiers may be added at any time during the process including without limit prior to, during or after the pH adjusting and/or drying steps. Examples of modifiers include without limit any metal (II) compound, especially a compound selected from the group consisting of Mg (II), Mn (II), Ca (II) and a mixture thereof.

The iron containing composition of this invention may be produced from an industrial by-product of the chlorination of ores for the recovery of metals such as titanium and zirconium and other processes that produce an iron (II) containing by-product such as from hydrochloric acid leaching of ores and hydrochloric acid pickling of steel products. The iron containing composition may also be produced from a carbonate resulting from other processes or naturally occurring carbonates.

Thus, the present invention further provides a process of converting a by-product metal chloride-containing stream into an iron containing composition, comprising: (a) contacting the metal chloride containing by-product with a base to increase the pH of the by-product to from about 3. 5 to about 5. 5 and to form a precipitate of any cations with a valence state above 2, typically 3+ and 4+ metais which are usuaiiy present as hydroxides ;

(b) separating the precipitate from the by-product to produce a liquor rich in ferrous chloride having a pH of from about 3.5 to about 5.5 ; (c) adjusting the pH of the liquor to about 6 to about 8 by contacting the liquor with a base to produce a brine and precipitate a mixture comprising a composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide, and a combination thereof ; (d) separating the mixture from the brine to produce a wet solid composition essentially free of the brine ; and (e) drying, and preferably, deagglomerating or grinding of the wet solid composition to form the iron containing composition.

DETAILED DESCRIPTION In one embodiment, the invention relates to use of an iron containing composition selected from the group consisting of iron (II) carbonate, iron carbonate hydroxide, iron (II) hydroxide, iron (III) hydroxide and a combination thereof, particularly, iron carbonate, as a fire retardant, sound suppressant and electrical insulator. Thus, any naturally occurring iron containing composition can be used, such as iron (II) carbonate and iron (II) hydroxide carbonate. These compositions may be processed by drying or heating to convert them into desired mineral crystal states or they may be mixed (as can the compositions made according to the present invention) with other materials to provide compositions having precisely selected thermal properties, or densities, or cost efficiencies, or electrical properties for a particular application. When the source of the iron containing composition is an iron-containing solid or ore, for example, siderite, the compound can be rendered suitable for use as a fire retardant by grinding.

The iron containing composition of this invention can have a lattice structure containing species other than iron. Iron (II) carbonate, iron (II) carbonate hydroxide, iron (II) hydroxide and iron (III) hydroxide can have other metals substituted for some of the iron in the iron (II) carbonate, iron (II) carbonate hydroxide, and iron (II) hydroxide, and iron (III) hydroxide.

As an example, the iron atoms of iron (II) carbonate can be substituted by manganese or magnesium. Alternatively, in the iron containing composition there can be a metal other than iron by simple addition wherein at least one other metal species, such as calcium, fits within the lattice structure. Such other metal species can change the decomposition temperature of the iron containing composition over a range of 200°C.

The composition of the present invention may be added to any flammable host material including without limit polymers and wood products as fire retardants to form a fire resistant composition. By"fire retardant"it is meant a composition having high endothermic decomposition enthalpies that absorb energy during a fire to keep the host cool and result in the formation of a char at the surface of the potymer composite during burning to retard vapor phase fuel release, total heat release and time to peak heat release. In addition these materials can also release water or carbon dioxide during the decomposition that functions to smother the flame. Also, the composition can act as a diluent in the host, typically a polymer, thereby reducing the concentration of fuel for the fire.

The composition of this invention, because of its high density, may also be used as a sound suppressant. The density of the composition is sufficiently high for application as a high density filler for suppressing sound. The composition of the present invention may be employed at least as a partial replacement for calcium carbonate, barium sulfate, magnetite and other similar materials. The density of iron (II) carbonate is 3.8 g/cc, the density of iron (II) hydroxide is 3.4 g/cc, and the density of siderite is in the range of 3. 83-3. 88 g/cc.

Further because of the high dielectric breakdown voltages and low conductivity, the iron containing composition of this invention may be used to retard the electrical breakdown of a variety of host materials.

There are many sources, industrial or natural, that can provide a metal chloride starting material for the iron containing composition of the invention. A mixed metal chloride containing stream is an example of a suitable source.

Thus, in another embodiment, the invention relates to methods of making the iron containing compositions described herein.

In a typical process of making the iron containing composition of this invention, the process comprises a"first neutralization"step of contacting a metal chloride stream with a base to increase the pH of the stream to about 3.5 to about 5.5 and form a first precipitate of the 3+ and 4+ metals present in the stream as hydroxides and/or carbonates, and thereby produce a liquor rich in iron (II). The first precipitate is separated from the liquor using any conventional separation means, such as filtration, centrifugation, decanting, and the like.

Then the liquor is treated again with a base in a"second neutralization"step to produce a brine and a second precipitate containing among other metal compositions, iron (II) carbonate, iron (II) carbonate hydroxide, iron (11) hydroxide and combination thereof and a brine solution.

In the second neutralization step, the base is used to adjust the pH to about 6 to about 8. The second precipitate is separated from the brine to provide a wet solid, which is then dried. Optionally, the wet solid is deagglomerated or ground.

When the source of the metal chloride starting material is rich in ferrous chloride, typically a highly pure ferrous chloride stream containing a relatively small amount of other compounds especially cations with a valence state above 2, the first neutralization step can be omitted.

In one particular embodiment of the present invention, the source of metal chlorides is an aqueous metal chloride solution such as is produced by hydrochloric acid pickling of metals. A particular example is. hydrochloric acid pickling of steel to remove oxides from the surface in order to make further treatment such as galvanizing possible. Such solutions, conventionally known as pickle liquor, typically comprise 10-26% iron chloride, mainly as ferrous chloride, with some ferric chloride and 0.5- 10% HCI. Metal chloride sources such as pickle liquor exemplify a highly pure ferrous chloride stream. In processing a pickle liquor in accordance with this invention, because of its purity, the first neutralization step can be omitted.

In another process of making the iron containing composition a by- product material generated in the reduction of metal ores by carbochlorination is employed. Ores containing titanium and zirconium values are typically rich in iron. The titanium and zirconium are usually recovered from such ores as metal chlorides via carbochlorination leaving as by-product mixtures of iron and other metal chlorides. The composition of the other metal chlorides typically comprises higher valent metals, that is +3 and higher, typically +3 and +4 metal ions and associated anions.

The exact composition of higher valent metals present in a by-product stream will depend on the source and processing history of the stream prior to the processing by the present method.

The by-product of the carbochlorination of titanium containing ores may be processed using the first and second neutralization steps described herein.

The base employed in the processes of this invention can be any alkaline material, including without limit alkali or alkaline earth carbonate or hydroxide, or combination thereof. Examples of suitable bases include sodium carbonate, sodium bicarbonate, sodium hydroxide, calcium carbonate, calcium hydroxide, hydrated lime, limestone, and mixtures thereof. Preferably, the base is selected from the group consisting of sodium carbonate, sodium bicarbonate and calcium carbonate or combination thereof.

Preferably, the base in the second neutralization step is a combination of sodium carbonate and sodium hydroxide.

The second precipitate, that is, iron (II) carbonate, iron (11) carbonate hydroxide, iron (II) hydroxide, optional other metals substituted for some of the iron is separated using conventional methods, such as filtration, centrifugation, and the like, from the liquid to produce a wet solid and subsequently dried. The drying process may also be controlled as to drying rate, gas environment and temperature to develop specific properties in the resulting composition. The gas environment may be nitrogen, vacuum, or both. The precipitate may be dried at room temperature or at elevated temperature. Preferably, the precipitate is dried at elevated temperature, such as at a temperature of about 100°C.

Optionally, after separation of the wet solid from the brine, the wet solid is deagglomerated or ground. Methods of deagglomerating or grinding include, milling, such as media milling, and fluid energy milling.

Modifiers, inorganic or organic, may also be added prior to, during, or after each step of neutralization, drying and deagglomerating or grinding.

Examples of inorganic modifiers include metal (II) compounds, especially compounds selected from the group consisting of Mg (II), Mn (li), Ca (II) and mixtures thereof.

An example of a suitable organic modifier is ascorbic acid. Organic compounds known for their ability to stabilize ferrous may also be useful.

Such organic compounds include erythorbic acid compounds, hydroxycarboxylic acid compounds and oxocarboxylic acid compounds which are further described in U. S. Patent No. 4, 652, 435.

Erythorbic acid compounds are known as an antioxidant for foods, etc. Such compounds may include erythorbic acid itself and its salts such as sodium and potassium salts.

Hydroxycarboxylic acid compounds that may be useful are hydroxycarboxylic acids containing at least one hydroxyl group and at least one carboxyl group in the molecule, or salts of these acids. Specific examples include aliphatic or aromatic compounds having about 2 to about 8 carbon atoms, such as lactic acid, hydroxyacetic acid, hydroxybutyric acid, malic acid, tartaric acid, glyceric acid, citric acid, alpha-me1 : hylmalic acid, beta-hydroxy-glutaric acid, desoxalic acid, monoethyl tartrate, monoethyl citrate, gluconic acid, galactaric acid, glucronic acid, ketogluconic acid, salicylic acid, p-hydroxybenzoic acid, 2, 4-dihydroxybenzoic acid, gallic acid and hya'roaQyphthalic acid, and salts of these acids such as sodium, potassium and ammonium salts.

The oxocarboxylic acid compounds that may be useful are oxocarboxylic acids containing at least one aldehyde or keto group and at least one carboxyl group in the molecule. Specific examples include compounds having 2 to 8 carbon atoms, such as glyoxylic acid, malonaldehydic acid, succinaldehydic acid, pyruvic acid, 2-ketobutyric acid, 4-acetylbutyric acid, 2-ketoglutaric acid, 4-keto-n-valeric acid, acetoacetic acid, oxomalonic acid, oxaloacetic acid and acetonedicarboxylic acid and their salts such as sodium, potassium and ammonium salts.

The modifiers act as iron oxidation suppressants and modify the decomposition temperature of the fire retardant compositions of this invention. For example, a pure FeC03 decomposes at 250°C whereas a synthetic Fe (Mn), (Mg), C03 composition prepared in the presence of ascorbic acid decomposes at 400°C. It is believed that isoascorbic acid can stabilize the ferrous species on the particle surface, which can provide a composition having a light color.

Different product properties in the fire retardant composition of iron (II) carbonate, iron (II) carbonate hydroxide, iron (II) hydroxide, other metals substituted for some of the iron in the iron (II) carbonate, iron (II) carbonate hydroxide, and iron (II) hydroxide, and combination thereof, can be achieved by varying the ratio of sodium carbonate to sodium hydroxide in the second neutralization step. By adjusting the ratio of sodium carbonate concentration to that of sodium hydroxide a fire retardant composition having specific fire retarding properties can be produced.

Particle size may be controlled and/or modified Iby varying the concentration of reactants, both metal chloride, carbonate or bicarbonate, for example the ratio of sodium carbonate to that of sodium hydroxide

used in the second neutralization step. Particle size may also be controlled by the method of contacting the reactants, the temperature of the reaction, temperature and time of aging after the reaction, the kind of base used in the neutralization steps (e. g. carbonate or bicarbonate) and any other metal species that may be present (e. g., magnesium, manganese or calcium).

By"method of contacting the reactants,"it is meant whether base is added to the metal chloride or whether metal chloride is added to the base to adjust pH to about 6 to about 8. For example it has been found that if metal chloride is added to base it stabilizes ferrous better than if the base is added to the metal chloride. The order of contacting the reactants can be important for producing iron (II) containing products, and can impact color and oxidizability of the ferrous ion.

Desired particle size of the iron containing composition of the present invention typically ranges from about 1 to about 10 microns.

To develop specific properties in the composition of the present invention, the compositions produced by the second neutralization step and drying process may be measured by determining the temperature range of decomposition using Thermogravimetric Analysis (TGA) and the energy absorbed upon decomposition by Differential Scanning Calorimetry (DSC). After characterizing the thermal properties of different products produced by varying conditions including rate of neutralization, composition of the base, operating temperature and digesting (reaction) time, method of contacting the reactants, and other operating conditions, fire retardants of this invention may be formulated in specific compositions with specific particle size and specific properties. Other operating conditions include composition of the base used in pH adjustment steps, method of mixing (stirring) reactants, presence or absence of air during reaction.

The iron containing composition of this invention exhibits a weight loss upon heating between about 100°C and about 500°C, additionally between about 120 and about 450°C of about 20 to about 50%, additionally about 30 to about 40%. Additionally, the iron containing composition of this invention has an enthalpy of endothermal effect of as high as about 800 J/g, possibly higher, and as low as about 200 J/g, additionally about 620 J/g to as low as about 230 J/g. As measured by differential Scanning Calorimetry, the iron containing composition of this invention has an endothermal peak of at least about 100°C, and

preferably, about 120 to about 450 °C. These properties render the iron containing composition useful as a fire retardant particularly when combined with a flammable host material.

Thus, the iron containing composition of the present invention may be compounded into a flammable host material such as a polymer to produce a fire resistant product, such as a piastic article, fi ! m or masterbatch. The compositions may be added to a polymer before it is spun into a fiber, incorporated into a coating, or molded into an article. For topical applications, the compositions may be applied by methods currently used in the art.

In using the compositions of the present invention, the method of compounding the composition into a polymer is not critical to the performance of the composition. Methods known in the arts of fire retarding, sound suppressing and electrical insulation for incorporating fire retardant compositions currently known and used may be used for the compositions of the present invention.

Polymers which are suitable for use in the fire resistant product of this invention include, by way of example but not limited thereto, polymers of ethylenically unsaturated monomers including olefins such as polyethylene, polypropylene, polybutylene, and copolymers of ethylene with higher olefins such as alpha olefins containing 4 to 10 carbon atoms or vinyl acetate; vinyls such as polyvinyl chloride, polyvinyl esters such as polyvinyl acetate, polystyrene, acrylic homopolymers and copolymers ; phenolics ; alkyds ; amino resins; epoxy resins, polyamides, polyurethanes ; phenoxy resins, polysulfones ; polycarbonates; polyesters and unsaturated polyesters; polyethers ; acetal resins; polyimide ; and polyoxyethylenes.

Mixtures of polymers are also contemplated.

Polymers suitable for use in the present invention also include various rubbers, such as styrene-butadiene rubber, and/or elastomers, either natural or synthetic polymers based on copolymerization, grafting, or physical blending of various diene monomers with the above-mentioned polymers, all as generally known in the art.

Thus, in general, polymers suitable for use in the fire resistant products of this invention include plastic and elastomeric polymers.

Preferably, the polymer is selected from the group consisting of polyolefins, polyvinyl chloride, polyamides and polyesters, and mixtures of these. More preferred are polyolefins. Most preferred are polyolefins

selected from the group consisting of polyethylene, polypropylene, and mixtures thereof.

The compositions of the present invention may be formulated into a sound suppressant by compounding with a variety of polymers in weight ratios of about 40 to about 80 wt % of the compositions sited above.

Also compositions useful as electrical insulation may be formulated by compounding with various polymers in weight ratios of from about 5 to about 80 wt % iron containing composition of the present invention. These compositions are useful in automotive wire harness coatings, and the like.

When more than one iron containing composition is employed the compositions can be combined in different proportions for a synergistic effect between the compositions.

Products incorporating the fire retardant compositions of this invention include wire and cable. Examples of wire applications include building wire, telephone and telegraph wire, electrical cords and cord sets, appliance wire, antennae wire, coaxial and data wire and magnet wire. An example of a cable application includes power cable. An advantage of using the fire retardants of this invention is the ability to tailor the composition to meet the application-specific performance standards.

Additional products incorporating the fire retardant composition of this invention include synthetic rubber carpet backing, and adhesives for carpet backing, appliance housing, molded electrical products, glass reinforced unsaturated polyesters, cross-linked polyethylene insulation, cast, cross-linked acrylic for example, as used in sheets and fabricated shapes in bathroom vanities, wall panels, kitchen counters, and wood products including pulp and paper and coatings for wood products.

EXAMPLES Example 1 Deionized water was purged with nitrogen for at least 30 minutes before used to provide de-oxygenated water. NaHCO3 solution was prepared by dissolving 33.6 g NaHC03 in 180-ml water in a 500 ml glass flask. This NaHC03 solution was then bubbled with CO2 and heated to 87°C using a hot plate. In a separate container, metal chloride solution was prepared by dissolving 32 g of FeCI2. 4H2O, 3. 98 g of MnCHO, 3. 84 g of MgCI2. 6H2O, and Q. 46 g of isoascorbic acid in 180 ml de- oxygenated water. The metal chloride solution was then pumped into the NaHCOg solution during a period of 25 minutes using a peristaftic pump.

The temperature of reaction was kept between 76. 6°C to 87°C. After

finishing pumping the metal chloride solution, the slurry was stirred for 30 minutes, during which period the temperature of solution was raised to 92°C. The slurry was then filtered using a 0. 2 micron membrane filter.

The filter cake was rinsed with 300 ml of de-oxygenated water twice. The cake was dried in a vacuum oven under nitrogen at 100 °C overnight. The cake broke into a free flowing powder upon drying. The dry powder had a narrow size distribution by light scattering measurement using a Matersizer 2000 available from Malvern Instruments with d50 of 11. 3 micron. X-ray powder diffraction (XRD) patterns of this powder were similar to the standard reference for FeCO3. The weight loss of this sample was 38. 0% between 150°C and 450°C as determined by Differential Thermogravimetric Analysis (DTGA). The enthalpy of endothermal effect of this sample was 743. 7 J/g as determined by Differential Scanning Calorimetry (DSC) analysis. The DSC endothermal peak was at 390.0 °C. This sample was stable at room temperature when exposed to air. The XRD, DTGA and DSC showed very little change after exposed to air for one week.

Example 2 Deionized water was purged with nitrogen for at least 30 min before being used. NaHC03 solution was prepared by dissolving 50.4 g of NaHCO3 in 270 mi of water in a 1-liter jacketed glass reactor. This NaHCO3 solution was bubbled with CO2 and heated to 85 °C using a circulating bath. In a separate container, metal chloride solution was prepared by dissolving 48.01 g of FeCI2. 4H2O, 5.97 g of MnC12. 4H20 and 5.76 g of MgCl2. 6H20 in 270 ml of de-oxygenated water. The metal chloride solution was then pumped into the NaHCO3 solution during a period of 10 min using a peristaltic pump. The temperature of reaction was kept at 85 °C. After finishing pumping the metal chloride solution, the slurry was stirred for 30 minutes, during which period the temperature of solution was raised to 95°C. The slurry was then filtered using a 0.2 micron membrane filter to produce a filter cake. The cake was rinsed with 300 mi of de-oxygenated water twice. The cake was dried in a vacuum oven under nitrogen at 100°C overnight. The cake broke into free flowing powder upon drying. X-ray powder diffraction patterns of this powder were similar to the standard reference for FeC03. The weight loss of this sample was 38. 16% between 150°C and-450°C as determined by Differential Thermogravimetric Analysis (DTGA). The enthalpy of endothermal effect of this sample was 670.7 J/g as determined by

Differential Scanning Calorimetry (DSC) analysis. The DSC endothermal peak was at 381. 3°C. This sample was stable at room temperature when exposed to air.

Example3 The process of Example 2 was repeated except no COg was bubbled into the NaHCOs solution during the reaction. The weight loss of this sample was 38. 16% between 150°C and 450°C as determined by DTGA. The enthalpy of endothermal effect of this sample was 637. 5 J/g as determined by DSC analysis. The DSC endothermal peak was at 373. 8°C. This sample was stable at room temperature when exposed to air.

Example 4 The process of Example 2 was repeated except for the following changes: a. 0.69 g isoascorbic acid was added into metal chloride solution; and b. temperature of reaction was 70°C and temperature was maintained at 70°C for 30 minutes after addition of metal chloride solution was complete.

The weight loss of this sample was 37.6 % between 150°C and 450°C as determined by DTGA. The enthalpy of endothermal effect of this sample was 608.2 J/g as determined by DSC analysis. The DSC endothermal peak was at 350. 3°C. This sample was less stable when exposed to air at room temperature than the product of Example 2. After 4 weeks, this sample turned black, while products of Examples 2 and 3 remained dark green to brown.

Example 5 The process of Example 2 was repeated except for the following changes: a. 0.69 g isoascorbic acid was added into metal chloride solution; and b. 4.19 g of CaC12. H2O was added to the metal chloride solution instead of 5. 76 g MgC12. 6H20.

The weight loss of this sample was 35.9 % between 150°C and 450°C as determined by DTGA. The enthalpy of endothermal effect of this sample was 562.3 J/g as determined by DSC analysis. The DSC endothermal peak was at 363. 1°C. This sample was more stable when exposed to air at room temperature than the product of Example 2. After 4 weeks, the color of this sample was lighter than all other samples.

Example 6 The process of Example 2 was repeated except for the following changes: a. 0. 69 g isoascorbic acid was added into metal chloride solution ; and b. neither MgC12. 6H2O nor MnCl2.4H2O were added to the metal chloride solution.

The weight loss of this sample was 36. 41 % between 1500C and 450°C as determined by DTGA. The enthalpy of endothermal effect of this sample was 519. 4 J/g as determined by DSC analysis. The DSC endothermal peak was at 324. 5°C, which was much lower than the endothermal peaks for products of Examples 2-5.

The Table below summarizes the results of Examples 1 to 6.

TABLE Example No. DSC Peak Enthalpy (J/g) TGA weight loss% Position (C) 1 390.0 743.7 38.0 2 381.3 670.7 38.2 3 373.8 637.4 38.2 4 350.3 608.2 37.6 5 363.1 562.3 35.9 6 324. 5 519.4 36. 4 The results from the Examples, as summarized in the Table illustrate the following 1. Preferably, reactions to prepare stable iron carbonate products are performed at temperatures of 70°C or more.

2. Dopants such as Mn, Mg and Ca can affect the stability of iron carbonate products and can be used to tune their decomposition temperatures.

Example 7 Sample strips 5 mm wide and 750 mm long were prepared from low density polyethylene compounded with an iron containing composition of this invention derived from siderite. A sample was placed under a radiant panel inside a sample holder in the device described in ASTM method E 1321 and ignited with a spark ignitor at the end of the sample in the high flux region. The progression of the flame spread was monitored visually

and recorded on a digital video camera. The point where the flame extinguished was noted. The incident flux was determined from the flux calibration curve. The flux at the self-extinguishment point was termed the minimum flux for spread,"MFFS."The National Institute of Standards and Technology has determined that MFFS data correlates with bench scale flammability tests such as ASTM E 84 and UL 94 V. The results of the MFFS test showed that siderite performed at least comparably to magnesium hydroxide and aluminum trihydrat and better than calcium carbonate.