Intumescent coating composition

Abstract

A room temperature-curable intumescent coating composition comprising: a) at least one epoxy binder; b) at least one curing agent; and c) dicyandiamide; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

Description

[0001] Intumescent Coating Composition

[0002] The present invention relates to a room temperature-curable intumescent coating composition and the use thereof for protecting a substrate from a fire, especially a hydrocarbon fire. The invention further relates to a kit of parts suitable for the preparation of an intumescent coating composition, a substrate coated with an intumescent coating composition which has been cured, and a process for the application of an intumescent coating composition to a substrate.

[0003] Background

[0004] Steel is commonly used as a construction material and has many advantages. However, structural steel is known to quickly lose its structural integrity in the case of a fire if unprotected. It is, therefore, known to protect steel using some form of passive fire protection, of which intumescent coatings are a known variant. Passive fire protection is designed to slow the rate at which the structural steel increases in temperature, significantly delaying the time to any form of structural collapse. This gives time to evacuate personnel and preserve expensive assets as well as maximising the opportunity to tackle the fire.

[0005] Intumescent coatings are coatings that swell when exposed to high temperatures (i.e. as typically generated by a fire) and produce a carbon based (carbonaceous) insulating char. Such coatings have many advantages over other available forms of passive fire protection, such as their light weight and environmental durability.

[0006] There is still a need however for improved intumescent coating compositions, especially intumescent coating compositions which can withstand the high erosive forces and high heat fluxes typically associated with hydrocarbon fires (as opposed to cellulosic fires).

[0007] In particular, some intumescent coating compositions in the art generate a char which suffers from a number of drawbacks. For example, chars generated by conventional intumescent coating compositions may have any number of problems such as low mechanical strength, poor integrity / cohesion, poor adhesion to the underlying substrate, uncontrolled expansion, a laminar or fibrous structure, significant defects such as detachments, voids, splits and cracks, or any combination thereof. Such problems may be particularly apparent when the coating is applied to a non-planar substrate (such as a column) due to the concentration of stresses and strains at particular points within the char.

[0008] The present invention provides a solution to the afore-mentioned problems. Specifically, the inventors have established that by combining an epoxy binder, curing agent, and a particular blowing agent (dicyandiamide), a room temperature- curable intumescent coating composition which forms a carbonaceous char in a highly controlled manner when exposed to fire is provided.

[0009] In particular, the inventors have established that the intumescent coating compositions of the present invention generate a char which has good mechanical strength, good integrity / cohesion, good adhesion, expands in a controlled way, is not very laminar or fibrous, and does not contain significant defects such as detachments, voids, splits and cracks. At the same time, the inventors established that the intumescent coating compositions of the present invention are very effective in protecting the underlying substrate from heat (high time to failure).

[0010] The inventors have also demonstrated that certain exemplified intumescent coating compositions according to the present invention have improved char quality and / or improved effectiveness in protecting an underlying substrate from heat relative to certain exemplified conventional intumescent coating compositions comprising melamine instead of dicyandiamide as the blowing agent. The intumescent coating composition of the present invention therefore further comprises a low (less than 4.0 wt%) content of melamine or is free from melamine altogether.

[0011] In one aspect therefore, the present invention provides an intumescent coating composition which forms a more robust char and which has superior performance in the event of a fire. The intumescent coating composition of the present invention may generally be used to protect a substrate from any type of fire, including both cellulosic fires and hydrocarbon fires, but may be especially suitable for protecting a substrate from a hydrocarbon fire.

[0012] Moreover, as a result of the improved performance of the intumescent coating compositions of the present invention, the invention may also allow for a lower amount of the coating composition to be used on a substrate to achieve the same level of fire protection. Summary of the Invention

[0013] Thus, viewed from one aspect the present invention provides a room temperature- curable intumescent coating composition comprising: a) at least one epoxy binder; b) at least one curing agent; and c) dicyandiamide; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

[0014] Viewed from another aspect, the present invention provides a kit of parts suitable for the preparation of an intumescent coating composition as hereinbefore defined, the kit comprising:

[0015] (A) a first composition comprising at least one epoxy binder; and

[0016] (B) a second composition comprising at least one curing agent; wherein the kit further comprises dicyandiamide.

[0017] Viewed from another aspect, the present invention provides a substrate coated with an intumescent coating composition as hereinbefore defined wherein the coating composition has been cured.

[0018] Viewed from another aspect, the present invention provides a process for the application of an intumescent coating composition to a substrate, the process comprising applying an intumescent coating composition as hereinbefore defined to a surface of the substrate and optionally allowing the applied intumescent coating composition to cure.

[0019] Viewed from another aspect, the present invention provides the use of an intumescent coating composition as hereinbefore defined for protecting a substrate, such as a steel substrate, from fire; especially a hydrocarbon fire.

[0020] Brief Description of Figures

[0021] Figure 1 : (A) image of char generated following fire testing of exemplified intumescent coating composition not according to the present invention (Comp. Ex. 5); (B) image of char generated following fire testing of exemplified intumescent coating composition according to the present invention (Ex. 5).

[0022] Figure 2: (A) image of char generated following fire testing of exemplified intumescent coating composition according to a preferred embodiment of the present invention (Ex. 7); (B) image of char generated following fire testing of exemplified intumescent coating composition according to the present invention (Ex. 8); (C) image of char generated following fire testing of exemplified intumescent coating composition according to the present invention (Ex. 9).

[0023] Definitions

[0024] The present invention relates generally to a room temperature-curable intumescent coating composition. The term “intumescent coating composition” refers to a coating composition which forms an intumescent coating which can swell and char when exposed to high temperatures (generally greater than 200 °C). The term “room temperature-curable” means that the coating composition has the ability to spontaneously cure at ambient temperature and pressure (23 °C, 1 atm). The terms “intumescent coating composition” and “coating composition” are sometimes used herein instead of the term “room temperature-curable intumescent coating composition”. The coating formed upon applying the intumescent coating composition to a surface of a substrate and allowing said applied composition to cure is termed herein an intumescent coating.

[0025] The term “intumescent coating composition” is also used herein to refer to the composition formed from the combination of a first composition (part (A)) and a second composition (part (B)). To prevent premature curing, the intumescent coating composition of the invention may be supplied in two parts, a first part (A) comprising the epoxy binder(s) and a second part (B) comprising the curing agent(s). The other components of the intumescent coating composition can be present in either part (A) or (B) (or both) as long as any component present in part (A) does not react with any other component within part (A) and any component present in part (B) does not react with any other component within part (B).

[0026] The intumescent coating composition of the present invention comprises components which are film forming components (e.g. at least one epoxy binder and at least one curing agent). Such components taken together form a “binder system”.

[0027] The intumescent coating composition of the present invention also contains one or more components to ensure intumescence. To “intumesce” means to char and expand (swell). When exposed to heat from a fire, for example, certain components in the intumescent coating chemically react to produce gases and a cellular carbonaceous char that expands into a foam when the gases become trapped within the char. Intumescent coatings thus form a relatively thick and thermally insulative foam barrier on the surfaces of coated substrates exposed to fire and / or relatively high heat, and thereby constitute a form of passive fire protection. In this regard, it will be appreciated that non-intumescent coating compositions offer essentially no passive fire protection as they do not intumesce.

[0028] The term “expansion agent” is used herein interchangeably with the term “blowing agent”.

[0029] The term “acid-generating compound” might also be called an “acid catalyst” or “acid-generating agent” herein.

[0030] The term “(meth)acrylate” encompasses both methacrylate and acrylate. The term “wt%” or “wt.%” means weight percentage. Unless otherwise stated or unless clear from context, the weight percentage is relative to the total (dry) weight of the coating composition of the invention.

[0031] The term “vol%” or “vol.%” means volume percentage. Unless otherwise stated or unless clear from context, the volume percentage is relative to the total (dry) volume of the coating composition of the invention.

[0032] Detailed Description of the Invention

[0033] The present invention provides an intumescent coating composition suitable for coating a substrate such as a metal substrate or a composite material. Preferably the substrate is a steel substrate. The substrate may be any object or any part of an object on which the coating of the invention might be useful. In particular, the substrate may be one which in use has the potential to be exposed to fire, particularly a hydrocarbon fire. For example, the substrate may be on an off-shore or on-shore oil and gas facility, wind turbine, chimney, power station or other industrial unit, bridge, crane, or any part thereof.

[0034] The intumescent coating composition is typically applied to a surface of a substrate in the form of a layer. The intumescent coating composition may be applied onto a substrate which has already been coated with one or more layers of another coating, such as a conventional anti-corrosive primer coating, to which the intumescent coating composition adheres. Examples of suitable primer coatings are coatings based on epoxy, modified epoxy, polyurethane, acrylic, vinyl, polysiloxane, silicate or chlorinated rubber. Preferably the primer coating (if present) is an epoxybased primer or a zinc-rich epoxy-based primer. The dry film thickness (DFT) of the primer coating is ideally in the range of 15-500 microns. The substrate may also be galvanised, such as by hot-dip galvanisation.

[0035] Alternatively, the intumescent coating composition may be applied directly onto a substrate, i.e. without any intervening layers.

[0036] In a preferred embodiment the intumescent coating of the invention is overcoated with a topcoat. The topcoat may provide the desired colour to the coated substrate and enhance the durability of the intumescent coating film(s). A clear topcoat may also be suitable.

[0037] The topcoat used for (optionally) overcoating the intumescent coating composition may be based on polyurethane, polysiloxane, epoxy, alkyd, acrylic, vinyl or chlorinated rubber. Preferably the topcoat is polyurethane based. The thickness of the topcoat may vary for example from 15 microns to 250 microns. Preferably the thickness is in the range from 25 microns to 75 microns, as too high a thickness of topcoat may inhibit the desired intumescent reactions.

[0038] In another preferred embodiment, the intumescent coating composition is not overcoated and therefore forms the top layer on a coated substrate. In one embodiment the intumescent coating composition is present as a single layer on a substrate or as a layer over an anticorrosive primer layer. The intumescent coating composition of the invention may also be applied as multiple layers.

[0039] The intumescent coating composition is typically applied in high dry film thickness to ensure a good level of fire protection. The dry film thickness (DFT) of the intumescent coating composition is preferably 0.5 to 40 mm. The intumescent coating composition may be applied in several coats to achieve the appropriate dry film thickness.

[0040] The intumescent coating composition of the invention is typically designed to protect substrates to critical core temperatures ranging from 150-700 °C depending on the nature of the substrate, degree of load and particular requirements of the specific structure being protected. The critical core temperature is defined as the temperature when a specific substrate has lost load bearing capacity to such a degree that the structure is at immediate risk of a critical collapse. Intumescent Coating Composition

[0041] The intumescent coating composition of the present invention comprises at least one epoxy binder and at least one curing agent suitable for curing the epoxy binder(s) which taken together may be viewed as forming a binder system. The intumescent coating composition further comprises a particular expansion agent (dicyandiamide) and optionally further components such as acid-generating agent(s), carbon donor compound(s), silane(s), hydrocarbon resin(s), curing catalyst(s), and reactive diluent(s). The intumescent coating composition may further comprise conventional intumescent coating components such as pigments, fillers and standard additives.

[0042] The intumescent coating composition of the invention also has a low melamine content (less than 4.0 wt% relative to the total weight of the coating composition). In a preferred embodiment, the coating composition comprises less than 3.0 wt%, such as less than 2.0 wt%, such as less than 1 .0 wt%, such as less than 0.5 wt% melamine, e.g. 0.0 to 0.5 wt% melamine. More preferably the intumescent coating composition is free or essentially free from melamine, even more preferably completely free from melamine.

[0043] The intumescent coating composition is typically supplied in kit form. Shortly before application of the intumescent coating composition to a substrate, a first part of the kit comprising the epoxy binder(s) is mixed with a second part of the kit comprising the curing agent(s) to form the intumescent coating composition. Other components of the intumescent coating composition (such as dicyandiamide) may be present in the first and / or second part of the kit, or as a separate part(s) of the kit.

[0044] Ideally, the intumescent coating composition comprises at least one liquid epoxy binder. The term “liquid” refers to the physical state of the epoxy binder at room temperature and pressure, i.e. 23°C and 1 atm.

[0045] Preferably the intumescent coating composition has a high solids content. For example, the intumescent coating composition preferably has a solids content of at least 90 wt%, such as at least 95 wt%, more preferably at least 99 wt%, especially 100 wt.%, relative to the total weight of the coating composition.

[0046] The intumescent coating composition of the invention preferably contains a very low solvent content such as less than 5.0 wt% solvent, especially less than 2.0 wt% solvent, more especially less than 1 .0 wt% solvent, e.g. 0.5 wt% or less, relative to the total weight of the coating composition. Ideally there is no solvent present at all in the intumescent coating composition, e.g. the coating composition is a solvent-free intumescent coating composition.

[0047] Having a high solids content and low solvent content generally leads to lower volatile organic compound (VOC) content. The VOC content of the intumescent coating composition is preferably less than 250 g / L, more preferably less than 100 g / L, most preferably less than 50 g / L. In some embodiments, the VOC content might be 25 g / L or less, such as 10 g / L or less. In this regard, volatile organic compounds include benzyl alcohol.

[0048] The pot life of the coating composition of the invention is preferably at least 45 minutes, such as 45 minutes to 3 hours. By pot life is meant the time after mixing of the first and second parts of the intumescent coating composition when the intumescent coating composition is still able to be applied to a substrate. Pot lives of less than 30 minutes are commercially challenging given the time it takes to coat a large object.

[0049] The viscosity of the intumescent coating composition measured just after combination of the parts of the kit is ideally high to ensure the application of thick layers with high quantities of intumescent components (to ensure good fire protection). Typical viscosities may be in the range of 0.5-35 MPas at 50 °C, such as 10 MPas for part (A) and 1 .5 MPas for part (B).

[0050] The components of the intumescent coating composition of the invention will now be described in more detail. These components may be present in any part of a kit used to make the intumescent coating composition as long as each component is kept separate from any other component of the intumescent coating composition with which it would react in storage.

[0051] Components of the intumescent coating composition

[0052] Intumescent coating compositions of the invention comprise at least one epoxy binder, at least one curing agent, and dicyandiamide. Other components that may be included in the intumescent coating composition include acid-generating agent(s), (specific) carbon donor compound(s), reactive diluent(s), hydrocarbon resin(s), silane(s), curing catalyst(s), co-binder(s), flame retardant(s), and conventional intumescent coating components such as pigments, fillers and standard additives. Expansion agent (dicyandiamide)

[0053] The intumescent coating composition of the present invention comprises dicyandiamide as an expandable intumescent material (also known as an expansion agent or blowing agent). Dicyandiamide is sometimes also known as dicyanodiamide, cyanoguanidine, 2-cyanoguanidine, DCD, or Dicy.

[0054] When exposed to elevated temperatures (e.g. greater than 200 °C), an expansion agent will typically decompose to produce non-flammable gas (generally nitrogen). This gas will then volumetrically expand the carbonaceous char generated by the other components of the intumescent coating, thereby forming a foam-like protective layer over the substrate.

[0055] The inventors of the present invention have established that the use of dicyandiamide as blowing agent in the intumescent coating compositions of the present invention offers certain advantages over the use of other conventional expansion agents such as melamine. In particular, it has been established that compositions of the present invention based on the use of dicyandiamide as blowing agent produce chars of superior quality when exposed to heat from a fire compared to comparative compositions based on melamine. The intumescent coating compositions of the present invention may thus offer superior fire protection compared to conventional intumescent coating compositions, especially against hydrocarbon fires.

[0056] Preferably the intumescent coating composition is free or essentially free from melamine derivatives. Melamine derivatives include for example melamine formaldehyde, methylolated melamine, hexamethoxymethylmelamine, melamine monophosphate, di-melamine phosphate, melamine biphosphate, melamine polyphosphate, melamine pyrophosphate, melamine cyanurate, melamine borate, melam (N2-(4,6-diamino-1 ,3,5-triazin-2-yl)-1 ,3,5-triazine-2,4,6-triamine), melem (2,5,8-triamino-1 ,3,4,6,7,9,9b-heptaazaphenalene), and melon (poly[8-amino- 1 ,3,4,6,7,9,9b-heptaazaphenalene-2,5-diyl)imino). The term “melamine derivative” as used herein also includes melamine salts.

[0057] Preferably dicyandiamide is the sole blowing agent in the intumescent coating composition of the invention.

[0058] In the intumescent coating composition of the present invention, the amount of melamine is less than 4.0 wt% relative to the total weight of the coating composition. Preferably, the amount of melamine in the composition is less than 2.0 wt%, such as less than 1 .0 wt%, such as less than 0.5 wt%, e.g. 0.0 to 0.5 wt%, relative to the total weight of the coating composition. Most preferably, the coating composition is free or essentially free from melamine.

[0059] In a preferred embodiment, the composition comprises dicyandiamide in an amount of 0.5 to 20.0 wt%, such as 1.0 to 18.0 wt%, such as 2.0 to 16.0 wt%, such as 5.0 to 15.0 wt%, relative to the total weight of the coating composition.

[0060] In some especially preferred embodiments, the amount of dicyandiamide is at least 5.0 wt%, such as at least 6.0 wt%, such as at least 6.5 wt%, such as at least 7.0 wt%, relative to the total weight of the coating composition. At these higher levels of dicyandiamide, the inventors surprisingly observed that the formed char is blacker which indicates that the char is not as exhausted / oxidised. This is the preferred state of the char after a fire. A greyish or white char is less desirable and for epoxy based intumescent coatings may be seen as a sign of the char being exhausted. This could indicate worse performance on a larger scale. The inventors also observed that at these higher levels of dicyandiamide, the char was more robust with fewer signs of erosion. Thus, intumescent coating compositions as hereinbefore described having a relatively higher dicyandiamide content (e.g. at least 5.0 wt% relative to the total weight of the intumescent coating composition) represent an especially preferred aspect of the present invention.

[0061] In a preferred embodiment, the amount of dicyandiamide in the intumescent coating composition of the invention is greater than 2.0 vol%, such as greater than 3.0 vol%, relative to the total (dry) volume of the intumescent coating composition.

[0062] In another preferred embodiment, the amount of dicyandiamide in the intumescent coating composition of the invention is greater than 5.0 vol%, such as greater than 6.0 vol%, relative to the total (dry) volume of the intumescent coating composition.

[0063] The amount of dicyandiamide in the intumescent coating composition of the invention may be up to 30.0 vol%, such as 25.0 vol%, relative to the total (dry) volume of the intumescent coating composition.

[0064] In another preferred embodiment, the amount of dicyandiamide in the intumescent coating composition of the invention is greater than 25.0 vol%, such as greater than 30.0 vol%, relative to the total volume of metal and / or metalloid ion(s) in the intumescent coating composition. Acid generating compound(s)

[0065] Preferably the intumescent coating composition of the invention comprises at least one acid-generating compound (also sometimes known as an acid-generating agent or acid catalyst).

[0066] As used herein, the term “acid-generating agent” refers to a material which thermally decomposes at elevated temperatures (e.g. greater than 200 °C) and produces an acid that can react with carbon-containing compounds present in the coating composition to produce a carbonaceous char. Said carbon containing compounds may be components of the binder system (e.g. the epoxy binder(s) and / or curing agent(s)) or may be a separate (specific) carbon donor compound which is added to the composition as described in the section below.

[0067] In general, the acid-generating compound comprises a source of phosphoric or sulfonic acid that is capable of producing said phosphoric or sulfonic acid upon exposure to heat, particularly at temperatures greater than 200 °C. Examples of such sources include sodium phosphate, potassium phosphate (e.g. potassium tripolyphosphate), ammonium phosphate (e.g. ammonium polyphosphate (APP), monoammonium phosphate, diammonium phosphate), sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, or para-toluene sulfonic acid, or a combination of any thereof.

[0068] In some examples, the acid-generating compound comprises a phosphoric acid ester of a polyhydroxy compound, or an ammonium phosphate (e.g., APP), or an amine phosphate (e.g., melamine phosphate), or a combination of any thereof.

[0069] A particularly useful acid-generating compound is ammonium polyphosphate because APP yields phosphoric acid at temperatures generally below the decomposition temperatures of the carbon donor compounds described below. Thus, APP produces phosphoric acid that is readily available to participate in the charring reactions.

[0070] APP compounds are polymeric phosphates, having P-O-P linkages, which may generally be represented by the formula:

[0071] [NH4PO3], wherein the average value of n is at least about 10. Particularly useful APP compounds in the intumescent coating compositions of the present invention include those having values of n>1000.

[0072] The acid-generating compound may additionally or alternatively comprise boric acid or a source of boric acid that is capable of producing boric acid upon exposure to heat, particularly at temperatures greater than 200 °C. The source of boric acid can comprise, for example, borate salts such as ammonium pentaborate, zinc borate, sodium borate, lithium borate, aluminium borate, magnesium borate, borosilicate compounds, and combinations of any thereof. Preferably the intumescent coating composition is free from boric acid or a source of boric acid.

[0073] In general, the intumescent coating composition can comprise 0.1 to 50.0 wt% of the acid-generating agent(s), such as 5.0 to 50.0 wt% of the acid-generating agent(s), preferably 7.5 to 45.0 wt%, more preferably 10.0 to 40.0 wt% based on the total weight of the intumescent coating composition. It will be understood that when the intumescent coating composition comprises more than one acidgenerating agent, the above amounts refer to the total amount of all acid-generating agent in the coating composition, i.e. adding the wt% of each acid generating agent.

[0074] In one embodiment, the weight ratio between the amount of acid-generating agent and the amount of dicyandiamide in the intumescent coating composition of the invention is in the range of 0.5:1 to 5:1 , such as 1 :1 to 4:1. In some embodiment, the weight ratio between the amount of acid-generating agent and the amount of dicyandiamide in the intumescent coating composition of the invention is greater than 1 :1 , such as in the range of 2:1 to 4:1.

[0075] Carbon donor compound(s)

[0076] Intumescent coating compositions of the invention may further comprise at least one specific carbon donor compound which typically functions as a charring agent. The skilled person will understand that the term “specific carbon donor compound” does not include those epoxy binders and curing agents which may also constitute a source of carbon but are herein considered part of the binder system. If present therefore, the carbon donor compound is a separate component of the intumescent coating composition of the invention.

[0077] Examples of suitable carbon donor compounds include an organic polyhydroxy compound (i.e. an organic polyol) and / or expandable graphite. For example, the carbon donor compound can comprise pentaerythritol, dipentaerythritol, tripentaerythritol, a polysaccharide (e.g., starch, cellulose, glycogen, and the like), a disaccharide sugar (e.g., sucrose, lactose, maltose, and the like), a monosaccharide sugar (glucose, fructose, galactose, and the like), glycerol, or expandable graphite, or a combination of any thereof. Preferably the carbon donor is pentaerythritol or dipentaerythritol, or a combination thereof.

[0078] The intumescent coating composition may comprise 0.1 to 20 wt% of the specific carbon donor compound, such as 0.2 to 20 wt%, preferably 0.5 to 10 wt%, especially 1 to 5 wt% of the carbon donor compound based on the total weight of the intumescent coating composition. Where more than one carbon donor compound is present, the above amounts will be understood to refer to the total amount of all carbon donor compounds in the intumescent coating composition, i.e. adding the wt% of each one.

[0079] Epoxy-based binder system

[0080] The intumescent coating composition of the invention comprises at least one epoxy binder and at least one curing agent for the at least one epoxy binder. T ogether, these components constitute a binder system, which optionally comprises further components such as one or more reactive diluents, one or more hydrocarbon resins, one or more silanes, one or more co-binders, one or more flame retardants, one or more accelerators, or any combination thereof.

[0081] Epoxy binder(s)

[0082] The intumescent coating composition preferably comprises one or more epoxy binders selected from aromatic or aliphatic epoxy binders, preferably comprising more than one epoxy group per molecule. The epoxy-groups may be in an internal or terminal position on the epoxy binder or on a cyclic structure incorporated into the epoxy binder. Preferably the epoxy binder comprises at least two epoxy groups so that a crosslinked network can be formed.

[0083] It should be understood that the epoxy binders of the present invention also encompass binders that have the traditional epoxy backbones but where the epoxy end-groups have been modified with acrylic or methacrylic functional groups that can be cured with the same curing agents as the epoxy-groups. Suitable aliphatic epoxy binders include epoxy and modified epoxy binders selected from cycloaliphatic epoxy such as hydrogenated bisphenol A, hydrogenated bisphenol A novolac and dicyclopentadiene based binders, glycidyl ethers such as polyglycidyl ethers of polyhydric alcohols, epoxy functional acrylic resins or any combinations thereof.

[0084] Suitable aromatic epoxy binders include epoxy and modified epoxy binders selected from bisphenol type epoxy binders such as bisphenol A, bisphenol F and bisphenol S, resorcinol diglycidyl ether (RDGE), novolac type epoxy binders such as phenolic novolac type binders (including bisphenol A novolac) and cresol novolac type binder or any combinations thereof.

[0085] In one preferred embodiment the epoxy binder is an aromatic epoxy binder. Preferably, the aromatic epoxy binder is derived from a combination of a compound comprising a least one epoxide functionality with an aromatic co-reactant comprising at least two hydroxyl groups.

[0086] Preferred epoxy binders are bisphenol epoxy binders. Preferred epoxy binders are bisphenol A and bisphenol F epoxy-based binders or bisphenol A / F epoxy binders.

[0087] The epoxy binder may be a modified epoxy binder. Examples of modified epoxy binders include epoxy binders modified with fatty acids, polypropylene oxide and / or polyethylene oxide. Preferably the epoxy binder is a non-modified epoxy binder. Especially preferred is an epoxy binder which is free from ester linkages (e.g. -C(=O)O-).

[0088] The solids content in the epoxy binder is preferably more than 70 wt.%, preferably more than 80 wt.%, preferably more than 90 wt.%, most preferred more than 99 wt.%. In a further preferred embodiment, the epoxy binder is solvent free.

[0089] Examples of suitable commercially available epoxy binders are:

[0090] Bisphenol A type epoxy binders: Epikote 828 from Westlake, D.E.R. 330, D.E.R. 331 or D.E.R 332 from Olin.

[0091] Bisphenol F epoxy binders: Epikote 862 from Westlake, YDF- 170 from Kukdo, GY285 from Huntsman, D.E.R 354 from Olin, or KF8100 from Kolon.

[0092] Mixture of bisphenol A and bisphenol F epoxy binders: D.E.R. 352 from Olin, Epikote 235 from Westlake.

[0093] The epoxy binder may be either a liquid epoxy binder or a solid epoxy binder or a combination thereof. It should be understood that “liquid” and “solid” refers to the physical state of the epoxy binder at ambient temperature and pressure (23 °C and 1 atm). In one preferred embodiment the epoxy binder is a liquid epoxy binder.

[0094] The liquid epoxy binder may have an epoxy equivalent weight (EEW) value of 140 to 1000 g / eq. It is particularly preferred if the EEW is less than 500 g / eq such as 156 to 300 g / eq, especially 156 to 250 g / eq.

[0095] The viscosity of the liquid epoxy binder is preferably 1000 to 20000 mPas, more preferred 1500 to 15000 mPas.

[0096] The solid epoxy binder may have an equivalent epoxy weight (EEW) of 300 to 1000 g / eq. It is most preferred however if the EEW of the solid epoxy binder is in the range of 350 to 750 g / eq, such as 400 to 700 g / eq, especially 500 to 670 g / eq.

[0097] The use of a liquid bisphenol A type epoxy binder is most preferred.

[0098] If there are both liquid and solid epoxy binders present in the epoxy binder system, it is preferred if the liquid epoxy binder is in excess relative to the solid epoxy binder.

[0099] The epoxy binder preferably forms 5.0 to 40.0 wt.% of the intumescent coating composition. More preferably the epoxy binder is present in an amount of 5.0 to 37.5 wt.%, especially 7.5 to 37.5 wt%, most especially 10.0 to 35.0 wt%. If a blend of epoxy binders is used these percentages refer to the total epoxy binder content, i.e. adding the wt% of each one.

[0100] In one preferred embodiment the epoxy binders include bisphenol A based binders, such as 4,4'-isopropylidenediphenol-epichlorohydrin resins, bisphenol F based binders and / or novolac based binders. In one preferred embodiment the intumescent coating composition comprises one or more bisphenol A epoxy binders. Bisphenol A epoxy binders will be known to those in the field and have the general structure below.

[0101] In one preferred embodiment the intumescent coating composition comprises one or more bisphenol F epoxy binders. The bisphenol F epoxy binder may have an EEW value of 100 to 350 g / eq. However, it is particularly preferred if the EEW is 300 g / eq or less such as 100 to 300 g / eq, especially 150 to 250 g / eq. Preferably the bisphenol F epoxy binder is a liquid.

[0102] The Mw of the bisphenol F resin may be more than 170 g / mol. A preferred bisphenol F (4,4'-methylenebisphenol) epoxy binder derives from the combination of bisphenol F and epichlorohydrin. The use of a difunctional epoxy bisphenol F binder is especially preferred.

[0103] A combination of two or more bisphenol F binders might be used. The viscosity of the bisphenol F binders are preferably 1000 to 10 000 mPas, more preferred 2000 to 5000 mPas.

[0104] Curing agent(s)

[0105] The intumescent coating composition of the invention further comprises at least one curing agent. The curing agent can be any curing agent commonly known as a curing agent for epoxy binders. Ideally it is amine functional and / or thiol functional, especially amine-functional. Most preferably, it is a polyamine comprising at least two amino groups. Especially preferably, the curing agent is based on benzylamine, i.e. the curing agent comprises a benzylamine motif:

[0106] The benzylamine in the curing agent may be optionally substituted either on the ring, the methylene linker or the N atom although one active hydrogen must remain.

[0107] Suitable substituents include C-M alkyl groups, OH, O-C-i.4-alkyl, halogen, cyano, amine and alkyl amine groups (CI-4-N).

[0108] To obtain a crosslinked network the curing agent ideally should contain at least two "reactive" hydrogen atoms. “Reactive” hydrogen atom refers to the hydrogen atom that is formally transferred from the nucleophile to the oxygen atom of the epoxide group of the binder during the ring opening reaction. The curing agent typically contains at least two curing reactive functional groups. Curing active amine groups cannot therefore be tertiary.

[0109] Examples of suitable curing agents are thiol curing agents, polythiol curing agents, amine curing agents, polyamine curing agents, amine functional polyamide and / or aminofunctional polymer curing agents. The curing agent may also alternatively comprise at least one aminofunctional polysiloxane.

[0110] An examples of a suitable polythiol curing agent is pentaerythriol tetramercapto propionate. An example of a suitable commercially available polythiol curing agent is GABEPRO® GPM800 from Gabriel performance materials.

[0111] In one preferred embodiment the intumescent coating composition comprises at least one amine functional curing agent. The curing agent typically contains at least two amine groups. The amine groups may be primary or secondary. In another preferred embodiment, the intumescent coating composition comprises at least one thiol-functional curing agent. In another embodiment, the intumescent coating composition comprises a mixture of amine-functional and thiol- functional curing agents.

[0112] Suitable curing agents comprising amines or amino functional polymers are selected from aliphatic amines and polyamines (e.g. cyclo-aliphatic amines and polyamines), amine functional polyamides, polyether amines, polyimidazoles, polyoxy alkylene amines (e.g. polyoxy alkylene diamines), alkylene amines (e.g. alkylene diamines), aralkyl amines, aromatic amines, Mannich bases (e.g. those sold commercially as "phenalkamines"), polyamines comprising benzylamine structures, amino functional silicones or silanes, and including epoxy adducts and derivatives thereof.

[0113] In one preferred embodiment the amine functional curing agent comprises a cyclic structure which includes alicyclic amines and modified products of alicyclic amines, preferably polyamines. The term cyclic includes alicyclic, aromatic and heterocyclic polyamines.

[0114] In one preferred embodiment, the amine functional curing agent is a polyamine curing agent comprising one or more benzylamine structures. More specifically, the curing agent preferably comprises two or more repeating units, i.e. the curing agent is polymeric or oligomeric. Preferably each repeating unit comprises a benzylamine group. The benzyl amine group may be substituted or unsubstituted. Preferably the polyamine curing agent comprises more than three amine groups. In one preferred embodiment the curing agent comprises at least two or more benzylamine structures.

[0115] In one preferred embodiment, the curing agent comprises a plurality of benzylamine groups which individually comprise only one amine group.

[0116] In one preferred embodiment the amine functional curing agent may comprise a benzylated polyalkylene polyamine structure as described in WO2017 / 147138 A1 which is herein incorporated by reference. The benzylated polyalkylene polyamine structure may be further reacted with for example Mannich bases or epoxy-functional compounds to make epoxy-adducts.

[0117] In one embodiment adducts of the amine curing agent might also be used. Such adducts can be prepared by reaction of the amine with suitably reactive compounds such as epoxy-binders, epoxy-functional reactive diluent, acrylates, maleates, fumarates, methacrylates or electrophilic vinyl compounds such as acrylonitrile.

[0118] Examples of suitable commercially available amine functional curing agents are: Ancamine 2609, Ancamine 2695, Ancamine 2738, Ancamide 260A, Ancamide 500, Ancamide 506, Ancamide 2386, Ancamine 2759, Ancamine 2760, Ancamine 2712M, Ancamine 1618, Ancamine 2165, Ancamine 2280, Ancamine 2432, Ancamine 2519, Ancamine 2802, Ancamine 2609w, Ancamine 2806, Ancamine 2049, Ancamine 2143 from Evonik, Epikure 3140 from Westlake, GX-483 from Kukdo Chemical, AP5050 from Admark Polycoats, MXDA and Gaskamine 240 from Mitsubishi Gas Chemical Company Inc.

[0119] In one particularly preferred embodiment, the curing agent is an aliphatic and / or cycloaliphatic polyamine such as the Ancamine curing agents from Evonik.

[0120] In another preferred embodiment the curing agent is an amine functional polyamide curing agent. In a further preferred embodiment, the amine functional polyamide curing agent comprises one or more benzylamine structures.

[0121] It will be appreciated that the curing agent can be supplied neat or in a solvent. Ideally the curing agent is solvent free.

[0122] One or more curing agents might be used in combination. In one preferred option two or more curing agents are used in combination.

[0123] It will be appreciated that in order for the intumescent coating composition of the invention to be room temperature-curable, the curing agent(s) should be able to spontaneously cure the epoxy binders) at a temperature of 23 °C and a pressure of 1 atm, i.e. without intervention. Preferably the curing agent(s) should be able to spontaneously cure the epoxy binder at all temperatures within the range of 0 to 50 °C at a pressure of 1 atm.

[0124] It is common to quote the equivalent weight of the curing agent in terms of the “active hydrogen equivalent weight” (HEW). For amine based curing agents the term “amine hydrogen equivalent weight” (AHEW) is commonly used. The number of "active hydrogen equivalents" in relation to the one or more curing agents is the sum of the contribution from each of the one or more curing agents. The contribution from each of the one or more curing agents to the active hydrogen equivalents is defined as grams of the curing agent divided by the active hydrogen equivalent weight of the curing agent, where the active hydrogen equivalent weight of the curing agent is determined as: grams of the curing agent equivalent to 1 mol of active hydrogen. For adducts with epoxy resins the contribution of the reactants before adduction is used for the determination of the number of "active hydrogen equivalents" in the complete epoxy-based binder system.

[0125] It is also common to quote the equivalent weight of the epoxy binders "epoxy equivalent weight" (EEW). The “epoxy equivalents” is the sum of the contribution from each of the one or more epoxy binders and any other component that contains an epoxy group such as a silane or a reactive diluent. The contribution from each of the one or more epoxy binders to the epoxy equivalents is defined as grams of the epoxy binder divided by the epoxy equivalent weight of the epoxy binder, where the epoxy equivalent weight of the epoxy binder is determined as: grams of the epoxy resin equivalent to 1 mol of epoxy groups. For adducts with epoxy binder the contribution of the reactants before adduction is used for the determination of the number of "epoxy equivalents" in the epoxy binder system. The unit of the equivalent weight is grams per equivalent (g / eq).

[0126] Preferably the ratio between the hydrogen equivalents of the totality of the curing agents and the totality of epoxy equivalents in the epoxy-based binder system of the present invention is in the range of 50:100 to 120:100.

[0127] Especially preferred epoxy-based binder systems have a ratio between the hydrogen equivalents of the curing agent and the epoxy equivalents of the epoxy resin in the range of 60:100 to 120:100 such as 80:100 to 120:100, e.g. 90:100 to 110:100.

[0128] It will be appreciated that in practice, the curing agent(s) is shipped separately to the epoxy binder(s) and is only mixed with the epoxy binder(s) shortly before application of the coating composition. The mixing ratio of the compositions comprising the epoxy-based binder(s) and the curing agent(s) is, of course, governed by the relative amounts of epoxy and active hydrogens present. Ideally, the mixing ratio in solids volume is 1 :1 to 10:1 , first to second composition, preferably 1 :1 to 5:1 , most preferred 1 :1. The curing agent composition and the epoxy binder composition are mixed shortly before application to the substrate.

[0129] In one embodiment, the curing agent may be present in the intumescent coating composition in the range of 5.0 to 30.0 wt%, such as 7.5 to 27.5 wt%, such as 10.0 to 25.0 wt%, such as 12.5 to 22.5 wt%, relative to the total weight of the coating composition. If a blend of curing agents is used these percentages refer to the total curing agent content, i.e. adding the wt% of each one.

[0130] Reactive diluent(s)

[0131] The intumescent coating composition optionally further comprises a reactive diluent. Preferably the reactive diluent comprises epoxy and / or (meth)acrylic functional groups. If present, the reactive diluent forms part of the binder system and reacts with other components of the binder system during the curing process.

[0132] In one preferred embodiment the reactive diluent is an epoxy-functional reactive diluent. The epoxy-functional reactive diluent may be either monofunctional, difunctional or polyfunctional.

[0133] Examples of such reactive diluents include phenyl glycidyl ether, alkyl glycidyl ether (number of carbon atoms in alkyl group: 1 to 16), glycidyl ester of neodecanoic acid (R1R2R3C-COO-Gly, where R1R2R3are alkyl groups such as C8 to C10 alkyl and Gly is a glycidyl group), olefin epoxide (CH3-(CH2)n-Gly, wherein n=11 to 13, Gly: glycidyl group), 1 ,4-butanediol diglycidyl ether (Gly-O- (CH2)4-O-Gly), 1 ,6-hexanediol diglycidyl ether (Gly-O-(CH2)e-O-Gly), neopentyl glycol diglycidyl ether (Gly-O-CH2-C(CH3)2-CH2-O-Gly), trimethylolpropane triglycidyl ether (CH3-CH2-C(CH2-O-Gly)3), and C1-20- alkylphenyl glycidyl ether (preferably C1-5 alkylphenylglycidyl ether), e.g. methylphenyl glycidyl ether, ethylphenyl glycidyl ether, propylphenyl glycidyl ether and para tertiary butyl phenyl glycidyl ether (p-TBPGE), reaction products of epichlorohydrin and an oil obtained from the shells of cashew nuts.

[0134] In one preferred embodiment, the epoxy-functional reactive diluents are aliphatic or cycloaliphatic epoxy-functional reactive diluents. The aliphatic epoxyfunctional reactive diluents are preferably formed from the reaction of a compound comprising at least one aliphatic epoxide functionality with an aliphatic alcohol or polyol such as 1 ,6-hexanediol diglycidyl ether or 1 ,4-butanediol diglycidyl ether. Aliphatic glycidyl ethers of chain length 8 to 14 are also preferred.

[0135] In one preferred embodiment the epoxy-functional reactive diluent is an aliphatic epoxy-functional reactive diluent such as 1 ,6-hexanediol diglycidyl ether.

[0136] In one preferred embodiment the epoxy-functional reactive diluent is a cycloaliphatic epoxy-functional reactive diluent such as cyclohexanedimethanol diglycidyl ether.

[0137] In another preferred embodiment the epoxy-functional reactive diluent is based on diglycidyl ethers of polyethers such as polyethylene glycol or polypropylene glycol.

[0138] The epoxy-functional reactive diluent may also be based on triglycerides such as castor oil. In one preferred embodiment the epoxy-functional reactive diluent is a triglycidyl ether of castor oil.

[0139] Aliphatic or cycloaliphatic epoxy-functional reactive diluents may contribute to the flexibility of the coating film.

[0140] The epoxy equivalent weight (EEW) of the epoxy-functional reactive diluent is preferably 50 to 1000 g / eq, more preferred 100 to 800 g / eq, most preferred 100 to 700 g / eq.

[0141] If present, the epoxy-functional reactive diluent is different from the epoxy binder. Preferably the viscosity of the epoxy-functional reactive diluent is <1000 mPas, preferably <800 mPas, preferably <750 mPas. It is therefore preferably a liquid at 23 °C and atmospheric pressure (1 atm).

[0142] In another preferred embodiment the reactive diluent comprises (meth)acrylic functional groups.

[0143] The (meth)acrylic functional reactive diluent is preferably an aliphatic (meth)acrylate comprising at least two (meth)acrylate functional groups linked by an organic linker. Such a multiester may be a diester, a triester or a tetraester.

[0144] The molecular weight of the (meth)acrylate functional reactive diluent is preferably less than 1000, such as less than 750, especially less than 500 g / mol. Ideally, the (meth)acrylic functional reactive diluent will be the (meth)acrylate ester of a polyol such as a diol, or triol or a sugar based polyol such as a sugar alcohol. It is not essential for all OH groups within a polyol to carry the (meth)acrylate ester group, however there should preferably be at least two ester functionalities in the (meth)acrylic ester. Suitable polyols for functionalization include alkylene diols (e.g. hexanediol, pentanediol), saccharides (e.g. mono or disaccharides) or polyols (especially sugar alcohols) such as erythritol, sorbitol, maltitol and mannitol.

[0145] (Meth)acrylic functional reactive diluents of particular interest are of formula wherein R is H or Me; n is 2-5; and

[0146] L represents the residue of a polyol such as the residue of hexandiol or the residue of a saccharide or sugar alcohol. Thus, at least two OH groups of the polyol carry the acrylate ester shown in the formula above.

[0147] L preferably contains only C, H and O atoms. The molecular weight of L is preferably low, such as 1000 g / mol or less.

[0148] It is common to quote the number of “acrylate equivalents” in the (meth)acrylic functional reactive diluent. The "acrylate equivalents" is the sum of the contribution from each of the one or more (meth)acrylic functional reactive diluents. The contribution from each of the one or more (meth)acrylic functional reactive diluents to the acrylate equivalents is defined as grams of the (meth)acrylic functional reactive diluent divided by the acrylate equivalent weight of the (meth)acrylic functional reactive diluent, where the acrylate equivalent weight of the (meth)acrylic functional reactive diluent is determined as: grams of the (meth)acrylic functional reactive diluent equivalent to 1 mol of acrylate group. For adducts with curing agents the contribution of the reactants before adduction is used for the determination of the number of "acrylate equivalents" in the complete (meth)acrylic functional reactive diluent system. It is common to include “acrylate equivalents” into the total “epoxy equivalents” when formulating.

[0149] A particularly preferred (meth) acrylic reactive diluent is trimethylol propane triacrylate.

[0150] The viscosity of the (meth) acrylic functional reactive diluent is preferably less than 300 mPas, more preferably less than 200 mPas, most preferred less than 150 mPas. A preferred (meth)acrylic functional reactive diluent have an acrylate equivalent weight (AEW) value of 50 - 200 g / eq, more preferred 70 - 150 g / eq, most preferred 80 - 125 g / eq.

[0151] Mixtures of (meth)acrylic functional reactive diluents may also be used. The above reactive diluents can be used singly or in combination of two or more diluents.

[0152] If present, the reactive diluent is preferably present in an amount of 0.1 to 30.0 wt.% preferably 0.5 to 25.0 wt.%, more preferred 0.5 to 22.5 wt.% of the coating composition, especially 1.0 to 20.0 wt%, more especially 1.0 to 17.5 wt%. If a blend of reactive diluents is used these percentages refer to the total content of reactive diluents, i.e. adding the wt% of each one.

[0153] It will be appreciated that as the reactive diluent might react with the curing agent, that it should be kept separate from the curing agent in the kit used to form the intumescent coating composition.

[0154] Hydrocarbon resin(s)

[0155] The intumescent coating composition optionally further comprises at least one hydrocarbon resin. The term hydrocarbon resin is a term of the art and refers to a group of typically petroleum derived hydrophobic resins although some resins may also be sourced naturally. These resins can help decrease the viscosity of the binder system resin and reduce surface tension for improved surface wetting. They also typically add hydrophobic character to the composition which often results in improved water tolerance. They may also improve the flexibility of the coating film.

[0156] Examples of suitable hydrocarbon resins will be known to the skilled person. Preferred hydrocarbon resins contain C and H atoms only but some may also contain O atoms, e.g. where the -O- content may be 0 to 10.0 wt% such as 0 to 5.0 wt% of the hydrocarbon resin. Preferably, the hydrocarbon resin has a molecular weight less than 1000 g / mol and most preferably molecular weight less than 500 g / mol. Preferably the hydrocarbon resin is non-reactive, i.e. it does not react with other components of the intumescent coating composition. It is therefore preferred if the hydrocarbon resin is free of any epoxy groups.

[0157] If present, the hydrocarbon resin preferably forms 0.1 to 15 wt% of the coating, preferably 0.5 to 10% by weight, e.g. 0.5-8.0 wt%, especially 0.75 to 5.0 wt%, most especially 1 .0 to 4.0 wt%. If a blend of hydrocarbon resins is used these percentages refer to the total content of reactive diluents, i.e. adding the wt% of each one.

[0158] It will be appreciated that as the hydrocarbon resin is preferably unreactive it can be present in any part of the kit used to form the intumescent coating composition.

[0159] The hydrocarbon resin (if present) is to be regarded as a separate component from the epoxy binder. These should not be regarded as the same component of the composition.

[0160] Silane(s)

[0161] The coating composition of the invention optionally further comprises at least one silane. If present, the silane is considered part of the binder system and reacts with other components of the binder system during curing. Preferably the silane is a functional silane comprising functional groups that can react with the binder system such as amine, epoxy, acryl, methacryl, thiol and isocyanate groups. Silanes of use in the invention are generally of low molecular weight (Mw) such as less than 400 g / mol.

[0162] The skilled person is familiar with the concept of silanes in coating compositions. Examples of such silanes are the many representatives of the products manufactured by Evonik and marketed under the brand name of Dynasylan(R), the Silquest(R) silanes manufactured by Momentive, and the GENIOSIL(R) silanes manufactured by Wacker.

[0163] If present, the amount of silane in the intumescent coating composition may be 0.1 to 15 wt%, preferably 0.25 to 15 wt.% such as 0.5 to 10 wt.%, more preferred 0.5 to 7.0 wt.% of the coating composition, especially 1 .0 to 6.0 wt%, more especially 1.0 to 5.0 wt%. In some embodiments, the silane is present in an amount of 1 .5 to 4.5 wt% of the intumescent coating composition. If a blend of silanes is used these percentages refer to the total silane content, i.e. adding the wt% of each one.

[0164] It will be appreciated that if the silane comprises functional groups that can react with the epoxy binder it should be kept separate from the epoxy binder in the kit used to form the intumescent coating composition. Curing catalyst(s)

[0165] The intumescent coating composition preferably further comprises at least one curing catalyst (sometimes also known as a curing accelerator). The curing catalyst may be any known curing catalyst for epoxy-based coating systems such as tertiary amines, (meth)acrylic esters, imidazoles, organic acids, phenols and organic phosphines.

[0166] Examples of suitable tertiary amines are triethanol amine, dialkylamino ethanol, triethylene diamine, 1 ,4-diazabicyclo[2.2.2]octane, 1 ,8-diaza- bicyclo[5.4.0]undec-7-ene and 2,4,6-tris(dimethylaminomethyl)phenol. One particularly preferred accelerator is 2,4,6-tris(dimethylaminomethyl)phenol such as Ancamine K54 from Evonik.

[0167] Examples of suitable imidazoles are 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methyl imidazole and 2-heptadecylimidazole.

[0168] Examples of suitable organic acids are benzoic acid derivatives such as salicylic acid.

[0169] Examples of suitable organic phosphines are tributyl phosphine, methyldiphenyl phosphine, triphenyl phosphine, diphenyl phosphine and phenyl phosphine.

[0170] Examples of suitable phenols are alkyl phenols such as nonylphenol.

[0171] Examples of suitable (meth) acrylic esters are the same as described for the (meth) acrylate-functional reactive diluents above.

[0172] Preferably the curing catalyst is present in the intumescent coating composition in an amount of 0.1 to 10.0 wt%, such as 0.2 to 7.5 wt%, such as 0.5 to 5.0 wt%, relative to the total weight of the intumescent coating composition. If a blend of curing catalyst is used these percentages refer to the total curing catalyst content, i.e. adding the wt% of each one. The curing catalyst may conveniently be formulated with the curing agent(s) in the second composition (part (B)) of the kit of the invention.

[0173] Co-binder(s)

[0174] Optionally a co-binder may be present in the intumescent coating composition of the invention in addition to the epoxy binder(s). Examples of suitable co-binders are saturated polyester resins, polyvinylacetate, polyvinylbutyrate, copolymers of vinyl acetate, vinyl isobutyl ether, copolymers of vinyl chloride and vinyl isobutyl ether, styrene co-polymers such as styrene / butadiene co-polymers, acrylic resins, hydroxy-acrylate copolymers, fatty acids and cyclized rubbers.

[0175] In an alternative embodiment, the epoxy binder(s) are the sole binder(s) in the intumescent coating composition of the invention.

[0176] Flame Retardant(s)

[0177] The intumescent coating composition may further comprise at least one flame retardant, such as a phosphorus containing flame retardant. Suitable flame retardants include phosphoric acid, phosphite, phosphonate and phosphoric acid esters.

[0178] The use of triarylphosphate esters, especially triphenyl phosphate esters are preferred. Where a flame retardant is used this must be different and hence separate from any other component of the intumescent coating. The flame retardant may help to reduce viscosity and be beneficial for fire performance. It may also aid low temperature crack resistance.

[0179] If present, the flame retardant preferably forms from 0.1 to 10 wt% of the coating composition, preferably 2.0 to 10% by weight, e.g. 2.0 to 8.0 wt%, especially 2.5 to 7.0 wt%. If a blend of flame retardants is used these percentages refer to the total flame retardant content, i.e. adding the wt% of each one.

[0180] Other Additives

[0181] The intumescent coating composition may also contain various other components. In particular, the intumescent coating composition may comprise additives selected from pigments, fillers, and rheology modifiers. The use of fibrous fillers and / or metal oxides is especially preferred.

[0182] The fibres useful in the intumescent coating composition of the present invention include, but are not limited to, inorganic fibres and organic fibres. Typical inorganic fibres include: carbide fibres, such as boron carbide fibres, silicon carbide fibres, niobium carbide fibres, etc.; nitride fibres, such as silicon nitride fibres; boron containing fibres, such as boron fibres, boride fibres; silicon containing fibres, such as silicon fibres, alumina-boron silica fibres, E-glass (non-base aluminium borates) fibres, C-glass (non-base or low base sodalime-aluminium borosilicate) fibres, A- glass (base -sodalime-silicate) fibres, S-glass fibres, inorganic glass fibres, quartz fibres, etc. The glass fibres may include E-glass fibres, C-glass fibres, A-glass fibres, S-glass fibres, etc.

[0183] Useful inorganic fibres also include ceramic fibres and basalt fibres. Kevlar (para-aramid fibres) may also be used.

[0184] A preferred organic fibre is carbon fibres.

[0185] Other suitable fillers include metal oxides such as titanium dioxide, zinc oxide, aluminium oxide, carbonates, borates, silica, silicates, heavy metal oxides such as cerium oxide, lanthanum oxide and zirconium oxide, mica, diatomaceous earth and bentonite clay. A preferred filler is titanium dioxide.

[0186] The filler preferably constitutes from 1 % to 25% by weight of the intumescent coating composition. If a blend of fillers is used these percentages refer to the total filler content, i.e. adding the wt% of each one.

[0187] Further optional additives may be included to aid char formation and to strengthen the char and prevent char degradation. Such additives include solids such as boron containing compounds including boric acid, and borates, such as ammonium pentaborate, zinc borate, sodium borate, lithium borate, aluminium borate, magnesium borate, and borosilicate, zinc stannate, zinc hydroxystannate, glass flake, glass spheres, polymeric spheres, fibres (ceramic, mineral, glass / silica based), aluminium hydroxide, magnesium hydroxide, boron phosphate, fumed silica.

[0188] The intumescent coating compositions may also comprise one or more colour pigments. Examples of suitable colour pigments include titanium white, red iron oxide, yellow iron oxide, black iron oxide, carbon black and organic colour pigments.

[0189] Other optional ingredients include rheology modifiers (anti-sagging / anti- settling agent), plasticizers, inorganic or organic dehydrators (stabilizers), defoaming agents and dispersing agents. As the rheology modifier, a thixotropic agent, such as polyamide wax, polyethylene wax, fumed silica or clays, including bentonite-based thixotropic agent or organophilic phyllosilicates, may be employed. Examples of such anti-sagging / anti-settling agents include Cryvallac Ultra, Crayvallac LV, both from Arkema, Thixatrol ST and Thixatrol Max, both from Elementis, Disparlon 6650 from Kusumoto Chemicals Ltd, Garamite 1958 from BYK, Aerosil 200 and Aerosil RX 200, both from Evonik. It may also be possible to include anticorrosive components in the coating composition. Such components may be (further) metal oxides, metal carbonates, talc, feldspar and so on to act as anti-corrosive materials. Specific anticorrosive functional pigments include zinc phosphate, zinc oxide, zinc dust, aluminium flakes, lead oxide. Auxiliary corrosion inhibitors, for example a molybdate, phosphate, tungstate or vanadate, ultrafine titanium dioxide, and / or zinc oxide and / or a filler such as silica, calcined clay, alumina silicate, talc, barytes or mica.

[0190] The total amount of the above-mentioned various additive components depend upon the use and cannot be determined indiscriminately, but they are frequently contained in the total amount of 0.1 to 65% by weight in the intumescent coating composition, such as 0.2 to 50 wt%, preferably 0.3 to 30 wt%, such as 0.4 to 10.0 wt%, such as 0.5 to 5.0 wt%.

[0191] Suitable solvents, if present, are hydrocarbons such as xylene. Solvent, if present, is preferably added to the first part (A) used to make the coating composition. Some solvent might also be present with the curing agent or in some of the additives used. The nature of the solvent is not restricted, and publicly known solvents having boiling points of wide range are employable. Examples of such solvents include xylene, toluene, MIBK, methoxypropanol, MEK, butyl acetate, benzyl alcohol, octyl phenol, resorcinol, n-butanol, isobutanol and isopropanol. The above solvents can be used singly or in combination of two or more kinds.

[0192] It is preferred however if no solvent is present at all.

[0193] If solvent is present then the percentages above of components in the intumescent coating of the invention should be determined in dry weight terms, ignoring the weight of solvent.

[0194] Preparation of the Intumescent Coating Composition

[0195] The intumescent coating composition may be prepared by any suitable technique that is commonly used within the field of paint production. Thus, the various constituents may be mixed together using a high speed disperser, a ball mill, a pearl mill, a three-roll mill, an inline mixer etc.

[0196] Conveniently the intumescent coating composition is supplied as a kit of parts. The kit of parts comprises at least two parts: Part (A) and Part (B). Part (A) comprises the epoxy resin(s) and part (B) the curing agent(s). The kit further comprises dicyandiamide, for example in part (A), part (B), both part (A) and part (B), or in an additional part of the kit (e.g. a part (C)).

[0197] Other (optional) components of the intumescent coating composition such as the hydrocarbon resin, additives such as fillers and pigments and the intumescent components can be supplied in either part (A) or (B) (or both) provided that said components do not react with any other components in that part. The reactive diluent (if present) is conveniently added to part (A) as it generally reacts with the curing agent. The silane (if present) can be in either part (A) or part (B) or both depending on its functionality. If it would react with the curing agent then it should be in part (A). If it would react with the binder then it would be added in part (B). Said optional components may additionally or alternatively be added to a third (or higher) part of the kit, e.g. a part (C). The skilled person will be able to design an appropriate kit to supply the components for transport.

[0198] It will be appreciated that the relative amounts of each component within any part of the kit will be determined by the final wt% values in the intumescent coating composition and the relative mixing ratios.

[0199] The intumescent coating compositions to be used herein are conveniently prepared by mixing the components of the kit. As an example, the first part (A) (the first composition) and the second part (B) (the second composition) can be mixed by adding the second composition to the first composition (or vice versa) and stirring well until the mixture is homogeneous. Other optional parts of the kit (e.g. part (C)) may also be mixed therewith, either before or after the mixing of parts (A) and (B).

[0200] The mixture is generally immediately ready for application, e.g. by spray application or manually, but may also be given an induction time prior to application. Alternative spray equipment, designed specifically for the application of two component, highly viscous paints will not require pre-mixing of the components. The components would then be mixed mechanically just prior to the paint reaching the application gun allowing convenient application of the composition.

[0201] Application of the Intumescent Coating Composition

[0202] In one aspect, the invention provides a substrate coated with an intumescent coating composition as hereinbefore defined wherein the coating composition has been cured. In another aspect, the invention provides a process for the application of an intumescent coating composition to a substrate, the process comprising applying an intumescent coating composition as hereinbefore defined to a surface of the substrate and optionally allowing the applied intumescent coating composition to cure. As used herein, the term “allowing the applied intumescent coating composition to cure” encompasses both active measures of curing (such as applying heat) and passive measures, e.g. letting the coating composition cure without intervention.

[0203] Preferably the substrate is a metal substrate, especially a steel substrate.

[0204] The intumescent coating composition may be applied to the substrate by spraying using well-known, specialised, two component airless spray pumps, specialised single leg airless spray pumps, or manually using, for example, a trowel. Pre-heating of the product up to 60 °C and pressures such as 3 to 6 bars may be required.

[0205] When applying the intumescent coating composition, it is possible to incorporate a mesh or scrim which is embedded within the intumescent coating. The mesh, or scrim is typically composed of one, or a combination, of; glass, carbon, basalt, or some other high temperature resistant fibre based material. These can also comprise or be combined with a fine metal wire, for example carbon or stainless steel. This mesh is commonly used in the system to provide an element of reinforcement or control of the intumescent foam as it forms during the intumescent reaction. The intumescent coating composition of the present invention may contain a mesh or scrim or may be free of a mesh or scrim.

[0206] Film Thickness

[0207] The applied film thickness might vary depending on the nature of substrate being coated and its predicted fire exposure scenario. The dry film thickness of the intumescent coating composition is preferably 0.5 - 40 mm. The intumescent coating composition may be applied in several layers to achieve the appropriate dry film thickness. Curing

[0208] The intumescent coating composition of the invention is a room temperature curable intumescent coating composition, i.e. cures without intervention (spontaneously) at a temperature of 23 °C and a pressure of 1 atm. Whilst (additional) heat may be applied to encourage curing, especially when applying the coating composition to a substrate at low temperatures, this is not required at a temperature of 23 °C and a pressure of 1 atm. Preferably it is also not required at any temperature within the range of 0 to 50 °C.

[0209] It is possible to apply a subsequent coat whilst the intumescent coating composition is “wet”. There is no requirement therefore to wait for the first coating to cure before applying a further coating. In order to build-up layer thickness, it is known to apply multiple layers of the intumescent coating composition but conventionally, each layer is cured (dried) before a further layer is applied. In the present invention, application of further layers may be carried out on a wet (or uncured) underlayer. This speeds up the application process.

[0210] In a further aspect, therefore the invention includes a process in which further coats of the intumescent coating composition are applied to an undercoat of the intumescent coating composition without an intermediate curing step.

[0211] Alternatively viewed, the invention includes a process in which further coats of the intumescent coating composition are applied to an undercoat of the intumescent coating composition before the undercoat has cured.

[0212] In a further aspect the invention includes a process in which coats of the intumescent coating composition are applied to an undercoat of a primer composition.

[0213] In a particularly preferred embodiment, the invention provides a room temperature-curable intumescent coating composition comprising: a) 5.0 to 40.0 wt% of at least one epoxy binder; b) 5.0 to 30.0 wt% of at least one curing agent; c) 0.5 to 20.0 wt% dicyandiamide; d) 0.1 to 50.0 wt% of at least one acid-generating agent; e) optionally at least one metal oxide; f) optionally at least one fibrous filler; g) optionally at least one curing catalyst; and h) optionally at least one reactive diluent; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

[0214] In another particularly preferred embodiment, the invention provides a room temperature-curable intumescent coating composition comprising: a) 5.0 to 40.0 wt% of at least one epoxy binder; b) 5.0 to 30.0 wt% of at least one curing agent; c) 1.0 to 18.0 wt% dicyandiamide; d) 5.0 to 50.0 wt% of at least one acid-generating agent; e) optionally at least one metal oxide; f) optionally at least one fibrous filler; g) optionally at least one curing catalyst; and h) optionally at least one reactive diluent; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

[0215] In another particularly preferred embodiment, the invention provides a room temperature-curable intumescent coating composition comprising: a) 7.5 to 37.5 wt% of at least one epoxy binder; b) 7.5 to 27.5 wt% of at least one curing agent; c) 2.0 to 16.0 wt% dicyandiamide; d) 7.5 to 45.0 wt% of at least one acid-generating agent; e) optionally at least one metal oxide; f) optionally at least one fibrous filler; g) optionally at least one curing catalyst; and h) optionally at least one reactive diluent; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

[0216] In another particularly preferred embodiment, the invention provides a room temperature-curable intumescent coating composition comprising: a) 10.0 to 35.0 wt% of at least one epoxy binder; b) 10.0 to 25.0 wt% of at least one curing agent; c) 5.0 to 15.0 wt% dicyandiamide; d) 10.0 to 40.0 wt% of at least one acid-generating agent; e) optionally at least one metal oxide; f) optionally at least one fibrous filler; g) optionally at least one curing catalyst; and h) optionally at least one reactive diluent; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

[0217] In all embodiments, preferably the amount of melamine in the intumescent coating composition is less than 2.0 wt%, such as less than 1 .0 wt%, such as less than 0.5 wt%, relative to the total weight of the coating composition. An intumescent coating composition free or essentially free from melamine is especially preferred.

[0218] The invention will now be described with reference to the following nonlimiting examples.

[0219] Examples

[0220] Materials

[0221] Table 1 below shows the materials (ingredients) used in the exemplified inventive and comparative intumescent coating compositions.

[0222] Table 1

[0223] EEW = Epoxy Equivalent Weight, HEW = Hydrogen Equivalent Weight

[0224] AHEW = Amine Hydrogen Equivalent Weight

[0225] General procedure for preparation of the exemplified inventive and comparative intumescent coating compositions

[0226] Components of the intumescent coating composition were mixed on a high-speed dissolver in the indicated parts by weight. The liquids were added first and blended at low speed. Then the other components were added and mixed at a high speed until a homogenous mixture was reached. Parts (A) and (B) were prepared separately.

[0227] Shortly before application, Parts (A) and B were weighed out according to the amounts shown in the tables below and mixed together with a handheld double- bladed mixer. The amounts of Parts (A) and (B) were chosen such that the ratio between the hydrogen equivalents of the totality of the curing agents and the totality of epoxy equivalents in the binder system was kept at 100:100.

[0228] Application of the coating compositions

[0229] The prepared intumescent coating compositions were then applied onto steel test substrates by hand and left to cure for 48 hours. The test substrates had been blast cleaned to Sa 2% (SSPC SP10) and primed with Muki EPS from Jotun to a dry film thickness (DFT) of approximately 30 pm. The test substrates were either 300 x 300 x 6mm panels or 0.5 m tall 254 mm x 254 mm x 73 kg / m columns with an Hp / A of approximately 160 m-1. The prepared intumescent coatings were applied to 6 mm DFT.

[0230] Fire testing

[0231] The test samples (i.e. the coated test substrates) were left to cure for 7 days at standard room temperature and atmospheric pressure prior to fire testing. The test was conducted using the hydrocarbon heating curve as defined within the Department of Energy Test Specification - issue 1 : Jan 1990 and using procedures from BS476: Part 20:1987 and BS 476: Part 21 :1987.

[0232] Furnace temperature was measured and controlled using four bare wire type K chromel-alumel thermocouples located within the furnace and positioned close to each test specimen, as per internal testing procedures. Furnace pressure was continually monitored by a micro-meter and maintained at approximately 10 Pa for the test duration.

[0233] Steel substrate temperatures of the test samples was monitored in the case of panels by at least 2 type K chromel-alumel thermocouples attached to the panel and in the case of columns by at least 6 type K chromel-alumel thermocouples drilled into the centre of the steel, as per Yellow Book rev5 directions. The fire test was conducted until the average steel substrate temperatures of the test samples had reached a set failure temperature (critical core temperature). In this case the critical core temperature was set to 400 °C, and the time to reach this temperature (time to failure (TTF)) was recorded in minutes.

[0234] Char Rating

[0235] The chars produced by the coatings as a result of fire testing were evaluated by assessing the char properties including structure, expansion, cohesion, adhesion and density. The chars were also assessed based on their colour and level of erosion. A black char is not exhausted / oxidised, and that is the preferred state of the char after a fire. A greyish or white char is less desirable, and for epoxy based intumescent coatings it may be seen as a sign of the char being exhausted. This could indicate worse performance on a larger scale. The chars were then rated on a scale of 1 to 4 as defined below, where 1 is excellent, 2 is good, 3 is acceptable and 4 is deemed as bad (or too weak to withstand hydrocarbon fire scenarios). Char Rating Scale:

[0236] 1 : excellent char: good expansion, dense char, preferably 1 compact layer, good adhesion, good cohesion. No signs of erosion. Char not exhausted / oxidised, white to black gradient.

[0237] 2: good char: good expansion, medium density with some smaller voids or medium expansion, high density with minimal voids. Good to ok adhesion and good to ok cohesion. Minor erosion from surface. Char not exhausted / oxidised, white to black gradient.

[0238] 3: acceptable char: medium expansion, dense char, no big voids / homogenous voids, some erosion on top layer but not to steel, ok adhesion and ok cohesion and / or char partially exhausted / oxidised, white to grey gradient.

[0239] 4: poor char: very laminar, fibrous char, poor cohesion, big voids, low expansion or overexpansion and / or char largely exhausted / oxidised, white to white / light grey gradient.

[0240] Results

[0241] The components (with amounts given in parts by weight) of the exemplified inventive (Ex. 1-9) and comparative (Comp. Ex. 1-8) intumescent coating compositions are shown in Tables 2-6 below. The char rating, expansion factor (which is calculated by dividing the average char thickness after fire testing by the dry film thickness of the coating before fire testing), and any defects / detachments observed in the chars of the tested samples, are also reported in the tables below.

[0242]

[0243] Table 2: Epoxy - amine binder system tested on panels

[0244]

[0245]

[0246] Table 3: Epoxy - amine binder system tested on columns

[0247]

[0248] Table 4: Epoxy- thiol binder system tested on panels expansion overestimated due to large surface void

[0249]

[0250] Table 5: Epoxy- amine binder system with reactive diluent on panels

[0251]

[0252] Table 6: Epoxy- amine binder system with reactive diluent on panels

[0253]

[0254] In Table 2, the results from testing of the amine cured epoxy coating compositions on panels are shown. Ex. 1 (which uses dicyandiamide as blowing agent) shows a significant improvement in TTF and char rating compared to Comp. Ex. 1 (which instead uses melamine). Ex. 1 also shows an improvement in char rating compared to Comp. Ex. 2, which is free from both dicyandiamide and melamine. The TTF difference between Comp. Ex. 2 and Ex. 1 on the other hand is not as significant as between Ex. 1 and Comp. Ex. 1. However, Ex. 2 (which has a higher ratio of acid-generating agent to dicyandiamide than Ex. 1) shows a significant improvement in terms of both char rating and TTF compared to both Comp. Ex. 1 and Comp. Ex. 2.

[0255] Given the limitations associated with plate testing (expansion in two dimensions only), the skilled person will understand that a more realistic indication of coating performance is given by tests conducted on non-planar substrates. The inventors therefore investigated the performance of another set of amine cured epoxy coatings on a 3D structure (columns). The results of this set of tests are shown in Table 3.

[0256] The results in Table 3 show that a 3D structure has an impact on the char formation and TTF but also on the defects that can occur. Ex. 3 shows an improvement in TTF and an acceptable char rating of 3 compared to Comp. Ex. 3 which shows a defect of splitting along the toes of the column (which decreases TTF significantly). Ex. 4 (which has a different stoichiometric ratio of epoxy binder to curing agent compared to Ex. 3) shows a good TTF, an acceptable char and no defects compared to Comp. Ex. 4 which shows a defect of two split toes and therefore a decreased TTF.

[0257] In Table 4, the results from testing of the thiol cured epoxy coating compositions are shown. Ex. 5 shows a significant improvement of TTF and an improvement from 4 to 2 on the char rating compared to both Comp. Ex. 5 (melamine as blowing agent) and Comp. Ex. 6 (no blowing agent). Ex. 5 shows some minor defects present like superficial cracking. Ex. 6 (which has a greater ratio of acid-generating agent to dicyandiamide compared to Ex. 5) shows further improvement in TTF and an excellent char compared to Ex. 5, Comp. Ex. 5 and Comp. Ex. 6. Image of the chars generated by Comp. Ex. 5 and Ex.5 are shown in Figure 1 . Note the cracking and large surface void of Comp. Ex. 5.

[0258] In Table 5, the results from testing of coating compositions based on an epoxy - amine system comprising a reactive diluent are shown. Ex. 7 (dicyandiamide as blowing agent) shows a significant improvement in char structure and TTF compared to Comp. Ex. 7 (no blowing agent). Ex. 7 also shows a good improvement on char structure from 4 to 1 and a slight TTF improvement compared to Comp. Ex. 8 (melamine as blowing agent).

[0259] In Table 6, the results from testing of coating compositions based on an epoxy - amine binder system comprising a reactive diluent are shown. Ex. 7 (dicyandiamide present in an amount of 12.28 wt.%) shows a significant improvement in char rating and TTF compared to Ex. 8 (dicyandiamide present in an amount of 4.50 wt.%). Ex. 7 also shows a significant improvement in char structure and TTF relative to Ex. 9 (dicyandiamide present in an amount 2.00 wt.%). The char rating improves from 3 to 2 to 1 as the amount of dicyandiamide increases from 2.00 wt.% to 4.50 wt.% to 12.28 wt.% (Ex. 9, 8, and 7 respectively). The char formed by Ex. 7 is also more robust and blacker (indicating less oxidation / exhaustion) than those formed by Ex. 8 and Ex. 9.

[0260] In summary, the results demonstrate that the use of dicyandiamide as a blowing agent in the exemplified intumescent coating compositions of the present invention improves TTF compared to comparable intumescent coating compositions comprising no blowing agent or only melamine as blowing agent. Additionally, with the exemplified inventive intumescent coating compositions, the char rating is improved and / or fewer char defects are observed.

Claims

Claims1 . A room temperature-curable intumescent coating composition comprising: a) at least one epoxy binder; b) at least one curing agent; and c) dicyandiamide; wherein the intumescent coating composition comprises less than 4.0 wt% melamine relative to the total weight of the coating composition.

2. An intumescent coating composition as claimed in claim 1 , wherein the epoxy binder is an aliphatic or aromatic epoxy binder, preferably an aromatic epoxy binder, more preferably a bisphenol-based epoxy binder, especially a liquid bisphenol-based epoxy binder.

3. An intumescent coating composition as claimed in claim 1 or 2, wherein the epoxy binder is a non-modified epoxy binder and / or is free from ester linkages.

4. An intumescent coating composition as claimed in any preceding claim, wherein the curing agent is an amine-functional and / or thiol-functional curing agent.

5. An intumescent coating composition as claimed in any preceding claim, wherein the composition comprises the epoxy binder(s) in an amount of 5.0 to 40.0 wt%, such as 7.5 to 37.5 wt%, such as 10.0 to 35.0 wt%, relative to the total weight of the coating composition.

6. An intumescent coating composition as claimed in any preceding claim, wherein the composition comprises the curing agent(s) in an amount of 5.0 to 30.0 wt%, such as 7.5 to 27.5 wt%, such as 10.0 to 25.0 wt%, such as 12.5 to 22.5 wt%, relative to the total weight of the coating composition.

7. An intumescent coating composition as claimed in any preceding claim, wherein the composition comprises dicyandiamide in an amount of 0.5 to20.0 wt%, such as 1 .0 to 18.0 wt%, such as 2.0 to 16.0 wt%, such as 5.0 to 15.0 wt%, relative to the total weight of the coating composition.

8. An intumescent coating composition as claimed in any preceding claim, wherein the composition comprises at least 5 wt% dicyandiamide relative to the total weight of the coating composition.

9. An intumescent coating composition as claimed in any preceding claim, wherein the amount of melamine in the coating composition is less than 2.0 wt%, such as less than 1 .0 wt%, such as less than 0.5 wt%, relative to the total weight of the coating composition; preferably wherein the composition is free or essentially free from melamine.

10. An intumescent coating composition as claimed in any preceding claim, wherein the composition further comprises at least one acid-generating agent, such as ammonium polyphosphate.

11. An intumescent coating composition as claimed in any preceding claim, wherein the composition further comprises one or more of the following components: one or more metal oxides; one or more fibrous fillers; and one or more curing catalysts.

12. An intumescent coating composition as claimed in any preceding claim, comprising: a) 5.0 to 40.0 wt% relative to the total weight of the coating composition of at least one epoxy binder; b) 5.0 to 30.0 wt% relative to the total weight of the coating composition of at least one curing agent; c) 0.5 to 20.0 wt% relative to the total weight of the coating composition of dicyandiamide; d) 0.1 to 50.0 wt% relative to the total weight of the coating composition of at least one acid-generating agent; e) optionally at least one metal oxide;f) optionally at least one fibrous filler; g) optionally at least one curing catalyst; and h) optionally at least one reactive diluent.

13. An intumescent coating composition as claimed in any preceding claim, wherein the intumescent coating composition is free from boric acid or a source of boric acid.

14. An intumescent coating composition as claimed in any preceding claim, wherein the amount of dicyandiamide in the intumescent coating composition is greater than 25.0 vol%, such as greater than 30.0 vol%, relative to the total volume of any metal and / or metalloid ion(s) in the intumescent coating composition.

15. A kit of parts suitable for the preparation of an intumescent coating composition as claimed in any of claims 1 to 14, the kit comprising:(A) a first composition comprising at least one epoxy binder; and(B) a second composition comprising at least one curing agent; wherein the kit further comprises dicyandiamide.

16. A substrate coated with an intumescent coating composition as claimed in any of claims 1 to 14 wherein the coating composition has been cured.

17. A process for the application of an intumescent coating composition to a substrate, the process comprising applying an intumescent coating composition as claimed in any of claims 1 to 14 to a surface of the substrate and optionally allowing the applied intumescent coating composition to cure.

18. Use of an intumescent coating composition as claimed in any of claims 1 to 14 for protecting a substrate, such as a steel substrate, from fire; especially a hydrocarbon fire.

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