Intumescent coatings with improved low temperature flexibility

Abstract

The present invention relates to intumescent coatings with improved low temperature flexibility, as well as to novel reaction systems for intumescent coatings. The intumescent coating is particularly useful for the fire protection of metal components, such as beams in building constructions. In the event of a fire, these coatings undergo reactive foaming and thus form a fireproof barrier layer on the metal beam with low thermal conductivity and which delays the early thermally induced failure of the component by the insulating effect generated by it. The invention specifically relates to a resin system with improved low-temperature flexibility, which ensures good metal adhesion and impact resistance even at low temperatures, while avoiding polymer components otherwise common in the resin system.

Description

[0001] This divisional application is a divisional application based on the Chinese patent application with application number 202180031597.4, application date April 15, 2021, and invention name “Intumescent coating with improved low-temperature flexibility”. Technical Field

[0002] The present invention relates to a new reaction system for intumescent coatings. Intumescent coatings are used in particular for fire protection of metal components, such as beams in building construction. In the event of a fire, these coatings undergo reactive foaming and thus form a fire-resistant insulating layer with low thermal conductivity on the metal beams and which, through the insulating effect it produces, delays the early thermal failure of the components.

[0003] The present invention relates in particular to resin systems with improved low temperature flexibility which ensure good metal adhesion and impact resistance even at low temperatures while avoiding polymer components which are otherwise common in resin systems. Background Art

[0004] The first generation of intumescent coating systems are based on high molecular weight thermoplastic resins based on (meth)acrylates and / or vinyl monomers and require high contents of solvents or water for application to metal surfaces. Due to the high solvent content, waterborne systems are also described here which require correspondingly long drying times.

[0005] Intumescent coatings are usually applied on site during the construction phase. However, off-site application prior to delivery to the building site is preferred as this can be done under controlled conditions. However, slow drying leads to uneconomical, inefficient post-processing times. Long post-processing times are particularly important here as the resin has to be applied sequentially from different sides and each side has to be dried to obtain a complete coating.

[0006] Epoxide-based intumescent coatings are preferably used in the offshore industry. They are characterized by good ageing resistance and relatively short drying times. Polyurethane systems have also been studied intensively. They are also characterized by relatively short drying times and good water resistance. However, the results of fire tests are unsatisfactory because the coatings have poor adhesion to steel. Detailed information can be found in the following document: "Development of alternative technologies for off-site applied intumescent" (Development of alternative technologies for off-site applied intumescent coatings), Longdon, PJ, European Commission, [Report] EUR (2005), EUR 21216, 1-141.

[0007] Another generation of intumescent coatings is based on (meth)acrylate reactive resins. Their application has the great advantage that no solvents are required and once applied, the resins cure relatively quickly. This leads not only to faster processing but also, in particular, to lower contents of residual volatile components in the applied coating. Such intumescent coating systems were first disclosed in EP 1 636 318.

[0008] A further development of systems based on (meth)acrylates is disclosed, for example, in EP 2 171 004. These are distinguished by a particularly high content of acid groups, which improves metal adhesion.

[0009] EP 2 171 005 discloses a further development of this system. This development is characterized in particular by the copolymerization of dibasic acids or copolymerizable acids with spacer groups. This can additionally improve metal adhesion.

[0010] However, all these systems still need further improvement. For example, the freedom in formulating is greatly restricted. Only relatively thick layers can be applied. The combined effect of these disadvantages also results in, for example, that the foam height can only be pre-adjusted to a low degree in the event of a need or fire.

[0011] Disadvantages also arise from the relatively complex preparation process of the resins. All (meth)acrylate systems described in the prior art, which are otherwise very advantageous, have in common that only the solid thermoplastic polymer present in the resin is prepared discretely, then dissolved in the monomer component and preformulated with additives and finally subjected to final formulation as a two-component system just before application. This process chain is relatively complex and there is a great interest in simplifying it.

[0012] European patent application No. 20162308.9 discloses a resin system prepared by means of a new method. In this method, a monomer mixture is polymerized until the maximum degree of polymerization is 70%. The glass transition temperature of the methacrylate-based polymer component thus formed is between -20°C and 23°C and is therefore significantly lower than the glass transition temperature described in the above-mentioned prior art. Nevertheless, the low-temperature flexibility of these systems is still limited, especially when only (meth)acrylate polymer components are used. Summary of the invention

[0013] Purpose of the Invention

[0014] In contrast to the prior art, it is an object of the present invention to provide a reactive resin system which is particularly flexible at low temperatures for producing intumescent coatings based on (meth)acrylates which have improved impact resistance and can be applied off-site.

[0015] There is a need for a simplified process for the preparation of reactive resin systems for intumescent coatings in which, compared with the prior art, the energetically complex step of introducing a solid (meth)acrylate polymer component can be omitted.

[0016] A further object was to provide a new formulation for two-component intumescent coatings which, in addition to very good metal adhesion and easy processing, also allows freedom with regard to the addition of additives and the adjustment of the subsequent foaming control, in particular with regard to pre-adjusting the subsequent foam height and foam quality, for example a particularly high proportion of closed-cell foam.

[0017] Other objects not explicitly stated may become apparent hereinafter from the description or from the examples and from the overall context of the invention.

[0018] Solution

[0019] These objects are achieved by a novel intumescent formulation and a reactive resin system for such an intumescent formulation and a coating produced therefrom. In particular, the invention relates to a liquid, foamable intumescent formulation comprising a resin system, the resin system being characterized in that it comprises at least one reactive resin having a number average molecular weight M of 1500 to 35 000 g / mol. n and a first polymer with a glass transition temperature below 15° C., at least one vinyl monomer and at least one component which acts as a blowing agent at temperatures above 200° C. The coating produced from the intumescent formulation can be cured by polymerization. Furthermore, the intumescent formulation according to the invention is characterized in that, before initiating the polymerization, it contains no components having acid functional groups and at the same time a molecular weight of more than 1500 g / mol.

[0020] Specifically, the present invention provides the following technical solutions:

[0021] Item 1. A foamable intumescent formulation comprising a liquid resin system, characterized in that the resin system comprises at least one n A first polymer having a molecular weight of 1000 to 35 000 g / mol and a glass transition temperature of less than 15° C., at least one vinyl monomer and at least one component which functions as a blowing agent at a temperature of more than 200° C., wherein a coating prepared from the intumescent formulation is curable by polymerization and, before initiation of the polymerization, contains no components having acid functional groups and at the same time a molecular weight of more than 1500 g / mol.

[0022] Item 2. The intumescent formulation according to Item 1, characterized in that the first polymer has a dynamic viscosity of less than 250 000 mPa·s and a functional group capable of copolymerizing with a vinyl monomer.

[0023] Item 3. The intumescent formulation according to Item 2, characterized in that the first polymer is liquid polyurethane (meth)acrylate, liquid epoxy (meth)acrylate, liquid polyether (meth)acrylate, liquid polyester (meth)acrylate or a mixture thereof, preferably liquid polyurethane (meth)acrylate.

[0024] Item 4. The intumescent formulation according to at least one of Items 1 to 3, characterized in that the vinyl monomer in the resin system is a (meth)acrylate and / or a mixture of different (meth)acrylates and / or monomers copolymerizable with (meth)acrylates.

[0025] Item 5. The intumescent formulation according to Item 4 is characterized in that the vinyl monomer is selected from methyl methacrylate, ethyl methacrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, styrene and a combination of the monomers.

[0026] Item 6. The intumescent formulation according to at least one of Items 1 to 5, characterized in that the intumescent formulation comprises 20% to 60% by weight of the resin system.

[0027] Item 7. The intumescent formulation according to at least one of Items 1 to 6, characterized in that the resin system comprises 5% to 65% by weight of the first liquid polymer.

[0028] Item 8. The intumescent formulation according to at least one of Items 1 to 7, characterized in that the resin system comprises 30% to 90% by weight of vinyl monomers.

[0029] Item 9. The intumescent formulation according to at least one of Items 1 to 8, characterized in that the intumescent formulation contains 35% to 60% by weight of a blowing agent.

[0030] Item 10. A method for curing a liquid foamable intumescent formulation according to any one of Items 1 to 9, characterized in that an initiator or a component of an initiator system is added to the intumescent formulation, or the curable coating composition is a two-component system and the two subcompositions of the two-component system are mixed together and then applied to the substrate within 20 minutes and cured within a further 120 minutes.

[0031] Item 11. The method according to Item 10 is characterized in that the initiator, the component of the initiator system or the component of the two-component system is an organic peroxide.

[0032] Item 12. The method according to Item 11 is characterized in that the organic peroxide is a diacyl peroxide, a ketone peroxide, a peroxyester, a dialkyl peroxide, a hydroperoxide (such as cumene hydroperoxide), a peroxyketal or a combination thereof.

[0033] Item 13. The method according to at least one of items 10 to 12, characterized in that the intumescent formulation is cured at a temperature between 17° C. and 23° C. in less than 60 minutes.

[0034] Item 14. The method according to Item 13, characterized in that the total weight loss caused by evaporation in the intumescent formulation during mixing, application to the substrate and curing is less than 5% by weight.

[0035] This first polymer preferably has functional groups which are copolymerizable with vinyl monomers. With the aid of such functional groups, polymer chains are introduced into the vinyl polymer chains formed during the polymerization during the curing of the reactive resin. The first polymer may also contain more than one of the copolymerizable vinyl functional groups in each chain. Here, the chains preferably contain more than 2, particularly preferably more than 2.1, and especially preferably more than 2.3 of the functional groups in each chain. The greater the proportion of the functional groups in each chain, the higher the degree of crosslinking in the cured intumescent coating, which increases the hardness in particular in the case of high degrees of crosslinking. The brittleness of the coating may also increase simultaneously with the increase in the degree of crosslinking, but this can be counteracted by a suitable choice of polymers and, in particular, of monomers.

[0036] The first polymer is particularly preferably a liquid polyurethane (meth) acrylate, a liquid epoxy (meth) acrylate, a liquid polyether (meth) acrylate, a liquid polyester (meth) acrylate or a mixture thereof. Liquid polyurethane (meth) acrylate is particularly preferred. A commercially available example of a polyurethane acrylate prepared from polyols, isocyanates and hydroxyl-functional acrylates is EBECRYL 230 from Allnex.

[0037] Commercial liquid polymers and mixtures thereof with (meth)acrylate-based reactive diluents, such as methyl methacrylate, may be used.

[0038] Alternatively, the liquid polymer can be prepared, for example, by reacting the isocyanate with the hydroxyalkyl (meth)acrylate and the macropolyol in a first step, for example in a stirred tank, and then mixing in the other components of the reactive resin in a second step. This approach can be described as an in-situ process.

[0039] According to the present invention, the term "liquid polymer" is understood to mean a polymer having a number average molecular weight M n The polymer has a molecular weight of 1000 to 35 000 g / mol, preferably 1500 to 20 000 g / mol, more preferably 1500 to 10 000 g / mol. In addition, the glass transition temperature of the liquid polymer is below 15°C, preferably below 10°C, more preferably below 0°C.

[0040] In this respect, a liquid polymer does not necessarily mean a thin fluid or even free-flowing. On the contrary, it is preferred that this first polymer present in the reactive resin of the intumescent formulation has a dynamic viscosity at room temperature of 23° C., measured using a rotational viscometer (Brookfield type DV2T) according to DIN EN ISO 2555 of less than 250 000 mPa·s, preferably less than 100 000 mPa·s.

[0041] According to the invention, care must be taken when selecting the liquid polymers to ensure that they impart sufficient low-temperature flexibility to the reactive resin system. It is therefore particularly preferred to use polyurethane (meth) acrylates. Therefore, the glass transition temperature (Tg) of the liquid polymer should be from -80°C to 15°C, preferably from -70°C to 0°C, and more preferably from -60°C to -20°C. Preferably, the liquid polymer has an average of two or more (meth) acrylate groups in one molecule. If the number of groups is less than 2, the coating has poor physical and mechanical properties, and also poor solvent resistance and scratch resistance.

[0042] The vinyl monomer in the resin system is preferably (meth)acrylate and / or a mixture of different (meth)acrylates and / or monomers copolymerizable with (meth)acrylate. Examples of such copolymerizable monomers are styrene, itaconic acid or maleic acid.

[0043] The vinyl monomer is particularly preferably methyl methacrylate, ethyl methacrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, styrene or a combination of one or more of the monomers.

[0044] The (meth)acrylate monomers may be, for example, (meth)acrylate alkyl esters of linear, branched or alicyclic alcohols having 1 to 40 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate; aryl (meth)acrylates, such as benzyl (meth)acrylate; mono (meth)acrylates of ethers, polyethylene glycols, polypropylene glycols or mixtures thereof having 5 to 80 carbon atoms, such as tetrahydrofurfuryl (meth)acrylate, methoxy (methoxy)ethoxyethyl (meth)acrylate, benzyloxymethyl (meth)acrylate, 1-ethoxybutyl (meth)acrylate, 1-ethoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, poly(ethylene glycol) methyl ether (meth)acrylate and poly(propylene glycol) methyl ether (meth)acrylate. Substances suitable as components of the monomer mixture also include additional monomers with additional functional groups, such as esters of acrylic acid or methacrylic acid with diols, such as hydroxyethyl (meth)acrylate or hydroxypropyl (meth)acrylate; acrylamide or methacrylamide; or dimethylaminoethyl (meth)acrylate. Examples of other suitable components of the monomer mixture are glycidyl (meth)acrylate or silyl-functionalized (meth)acrylates.

[0045] The tackifier present in the intumescent composition is very preferably a silane-functional (meth)acrylate, such as 3-methacryloxypropyltrimethoxysilane, a silane-functionalized vinyl compound, such as vinyltrimethoxysilane, or preferably an acid-functional monomer, such as acrylic acid, methacrylic acid, 2-methacryloxyethyl phosphate, bis(2-methacryloxyethyl) phosphate, 2-acryloxyethyl phosphate, bis(2-acryloxyethyl) phosphate, 2-methacryloxyethyl maleate, acryloxyethyl maleate, itaconic acid and / or 2-carboxyethyl acrylate, particularly preferably 2-carboxyethyl acrylate. Other examples include maleic acid, for which the presence of styrene in the monomer mixture is absolutely necessary for copolymerization, depending on the composition. Preferably, 0.2% to 10% by weight, more preferably 0.4% to 4% by weight, of tackifier is used in the resin composition.

[0046] Furthermore, combinations of two or more of these tackifiers are also possible.

[0047] Methyl methacrylate is a particularly preferred methacrylate due to its ability to produce low viscosity solutions. However, its high volatility and characteristic odor may mean that alternative (meth)acrylates may be preferred for certain applications.

[0048] The intumescent formulation preferably comprises 20 to 60 wt% of the resin system. Also preferably, the resin system in the intumescent formulation comprises 5 to 65 wt%, preferably 20 to 55 wt%, of the first liquid polymer and / or 30 to 90 wt%, preferably 40 to 75 wt% of a vinyl monomer.

[0049] Independently of the composition of the reactive resin, the intumescent formulation preferably comprises 35% to 60% by weight, more preferably 40% to 50% by weight, of blowing agent.

[0050] There are a variety of alternative substances for the blowing agent. In a particularly preferred alternative, polyphosphates that can be converted into phosphoric acid at 190 to 300° C. can be used. In addition, the formulation also includes pentaerythritol, which then forms a carbon foam in the presence of phosphoric acid at above 300° C., wherein water and carbon dioxide are separated and eliminated. In the process, water and carbon dioxide act as blowing agents. Another advantage of this alternative is that the polyphosphates and the phosphoric acid act as additional flame retardants.

[0051] The second alternative uses melamine, which decomposes above 350° C. to form ammonia, nitrogen and carbon dioxide, all three of which act as blowing agents. By combining these two alternatives, in addition to the flame retardant effect, further advantages can also be achieved. In this way, the degree of foaming can be adjusted more finely. In addition, stepwise foaming also occurs, which in turn brings advantages with respect to foam stability.

[0052] The reactive resins are prepared in a simple manner by mixing the abovementioned liquid components, which is usually carried out in a batch mixing process in a stirred tank.

[0053] Exemplary formulations of the present invention can be seen as follows:

[0054] Such a formulation for a two-component intumescent coating may contain, at the point in time after mixing the two-component system, 30 to 50% by weight of a reactive resin prepared by the process of the invention, 35 to 60% by weight of a blowing agent, 0.1 to 2.5% by weight of a peroxide and / or an azo initiator, preferably only a peroxide, such as benzoyl peroxide, optionally up to 2% by weight of an accelerator, optionally 4.9 to 15% by weight of additives and 5 to 30% by weight of a filler. Optionally, the formulation may include additional pigments.

[0055] The initiator system generally consists of one or more peroxide and / or azo initiators, preferably peroxides, and an accelerator, generally one or more tertiary amines, in particular aromatic tertiary amines. A particularly suitable example of such an initiator is dibenzoyl peroxide, which can also be used, for example, in the form of a safe preformulated paste, wherein the auxiliaries contained in the paste, such as paraffin, do not interfere with the formulation at the corresponding concentrations. Examples of accelerators include in particular N,N-dialkyl-p-toluidines, such as N,N-bis(2-hydroxypropyl)-p-toluidine or N,N-dimethyl-p-toluidine or N,N-dimethylaniline.

[0056] In addition to the ingredients mentioned, the intumescent composition or the reactive resin contained therein may comprise further optional ingredients.

[0057] An optional component of the reactive resin is a monomer crosslinking agent. In particular, a multifunctional (meth)acrylate, such as allyl (meth)acrylate. Particularly preferred are di- or tri-(meth)acrylates, such as 1,4-butanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate or trimethylolpropane tri(meth)acrylate. These monomer crosslinking agents may be present together with the crosslinking liquid polymer as described above.

[0058] Additives which may optionally be present in the intumescent composition or already present in the reactive resin include, in particular, wetting agents, film formers, degassing agents and / or dispersants. Optional fillers may, for example, be silicon dioxide, titanium dioxide, quartz or other substances, in particular thermally stable inorganic compounds. Inorganic fillers which may undergo thermal decomposition (e.g. carbonates) may only be used to a minor extent in order to avoid uncontrolled additional foaming of the coating in the event of a fire. A particularly preferred filler is titanium dioxide.

[0059] Accelerators optionally used for faster curing to cold plastics are generally aromatic tertiary amines.

[0060] In addition to the novel intumescent formulations, a method for curing such liquid foamable intumescent formulations also forms part of the present invention.

[0061] In this process of the invention, the initiator or components of the initiator system are added to the intumescent formulation and the formulation is then applied to the substrate within 20 minutes and cured within a further 120 minutes after application.

[0062] In an alternative method of the invention, the curable coating composition is a two-component system. Here, the two component compositions of the two-component system are mixed with one another, then applied to the substrate within 20 minutes and cured within a further 120 minutes after application.

[0063] In this second alternative, the actual coating composition can be formulated as follows: The reactive resin is formulated together with the blowing agent, additives, optional fillers and further optional fillers. Such an intermediate formulation is then divided, for example, into two fractions of equal size. One of these fractions is then additionally mixed with the accelerator. The two fractions are then even storage-stable for a longer period of time.

[0064] Before the actual application, the fraction without accelerator is then mixed with the initiator or initiator mixture. After a long storage or transportation, it may be necessary to first stir the two fractions again, because, for example, the filler may have settled. After the initiator is introduced by stirring or by other forms of mixing, the two fractions of the two-component system are then mixed together. This allows the monomer components of the reactive resin to start polymerization and the so-called pot life to begin, during which the application to the substrate (e.g., steel beam) must be carried out. In the case of modern application equipment, the mixing of the two fractions of the two-component system can also be completed in the mixing chamber of the application nozzle just before the injection caused by pressure. The pot life is determined by a combination of the following factors: the nature and concentration of the initiator and accelerator, the monomer composition and external influencing factors (e.g., ambient temperature). These factors are easily estimated and adjustable for those skilled in the art. In general, operations are performed with a pot life of several minutes to several hours, which may also exceed the 20 hour mark. However, significantly shorter pot lives are preferred, which match the preferred process times given above. For example, such a pot life is between 3 and 30 minutes, wherein in the case of fully automatic application using a sprayer, the operational pot life may be less than 10 minutes.

[0065] In one of the two alternatives of the process, it is preferred that the initiator, a component of the initiator system or a component of a two-component system is an organic peroxide. Such an organic peroxide is particularly preferably a diacyl peroxide, a ketone peroxide, a peroxyester, a dialkyl peroxide, a hydroperoxide (e.g. cumene hydroperoxide), a peroxyketal or a combination thereof.

[0066] Furthermore, as already described, the present invention provides a method for providing an intumescent coating of a metal surface. In this method, the above-described formulation for a two-component intumescent coating is prepared, applied to the metal surface within 1 to 20 minutes and cured thereon at a temperature of 0 to 30° C., preferably at 17 to 23° C., within 120 minutes, preferably within 60 minutes. The preferred layer thickness of the unfoamed coating is hereby 1 to 20 mm, preferably 2.5 to 7.5 mm. Such a formulation is such that the coating will preferably lead to a foam with a layer thickness of 20 to 100 mm, preferably 30 to 50 mm, in the event of a fire.

[0067] The total weight loss by evaporation in the intumescent formulation during mixing, application to the substrate and curing is particularly preferably less than 5% by weight. This can be ensured by a correspondingly suitable formulation, especially with regard to the selection of the monomers in the reactive resin. DETAILED DESCRIPTION

[0068] Example

[0069] Example 1: Preparation of reactive resin according to the present invention

[0070] DEGADUR MDP Membran SG is a methacrylate-based, accelerator-free reactive resin commercially available from GmbH, which contains polyurethane methacrylate for flexibility. DEGADUR MDPMembran SG does not contain any solid polymer components.

[0071] 20.0 g of 2-carboxyethyl acrylate and 10.0 g of N,N-bis(2-hydroxypropyl)-p-toluidine were added to 970.0 g of DEGADUR MDP Membran SG, and the mixture was stirred at 50° C. until completely dissolved. The reactive resin was then cooled to room temperature.

[0072] Example 2: Formulation 1 according to the invention for an intumescent coating

[0073] Composition of Formulation 1 from Example 2

[0074] Reactive resin from Example 1 40.0% by weight Titanium Dioxide 10.0 wt% Ammonium polyphosphate 30.0 wt% Pentaerythritol 8.5 wt% Melamine 11.0 wt% Byk D410 0.5 wt%

[0075] It should be understood that the above embodiments are exemplary only and many modifications or variations are possible.

[0076] Comparative Example 1: Formulation 2 not according to the invention for an intumescent coating

[0077] DEGALAN 1710 is a Commercially available reactive resins based on meth(acrylates) produced by Benzol® GmbH having a solid (glass transition temperature > 50° C.) thermoplastic polymer component.

[0078] Composition of Formulation 2 from Example 3

[0079] DEGALAN 1710 40.0% by weight Titanium Dioxide 10.0 wt% Ammonium polyphosphate 30.0 wt% Pentaerythritol 8.5 wt% Melamine 11.0 wt% Byk D410 0.5 wt%

[0080] Performance of intumescent coatings

[0081] Determination of pot life and curing time:

[0082] 1 part by weight of Perkadox GB50-X (50% dibenzoyl peroxide powder, Nouryon) was mixed into 99 parts by weight of each of the above example formulations immediately before application.

[0083] The formulations were then each applied to a steel plate in a layer thickness of 3000 μm. The pot life and the maximum temperature during curing were additionally measured for a smaller portion of the samples. The pot life corresponds to that period after addition of the initiator during which the viscosity is still low enough to allow application of the coating.

[0084] Example formulation 1 of the present invention Non-inventive formulation 2 Applicable period 10 minutes 16 minutes Time period until the maximum temperature 14 minutes 34 minutes Maximum temperature 84℃ 70℃ Time until tack-free cure 19 minutes 43 minutes

[0085] Determination of low temperature flexibility

[0086] Immediately before application, 1 part by weight of Perkadox GB50-X (50% dibenzoyl peroxide powder, Nouryon) was mixed into 99 parts by weight of each of the above example formulations. The formulations were then each applied in a layer thickness of 1000 μm to a steel sheet having a thickness of 1 mm.

[0087] Once curing is complete, the panels are cooled to -20°C and at this temperature the coated steel sheets are bent 90° at right angles. The coating at the bend point is then inspected for cracks and peeling.

[0088]

[0089] In a flexure test at -20°C, the inventive example formulation 1 shows significantly improved low temperature flexibility compared to the prior art non-inventive formulation 2.

Claims

1. A foamable intumescent formulation comprising a liquid resin system, characterized in that The resin system comprises at least one number average molecular weight M n A first polymer having a weight of 1000 to 35 000 g / mol and a glass transition temperature of less than 15° C., at least one vinyl monomer and at least one component which functions as a blowing agent at a temperature of more than 200° C., wherein the coating prepared from the intumescent formulation is curable by polymerization and, before initiation of the polymerization, contains no components having acid functional groups and at the same time a molecular weight of more than 1500 g / mol; The component acting as a blowing agent is selected from melamine; polyphosphates or esters converted into phosphoric acid at 190 to 300° C. in combination with pentaerythritol, and combinations thereof; The vinyl monomer in the resin system is methacrylate and / or a mixture of different methacrylates and / or monomers copolymerizable with methacrylate.

2. The intumescent formulation according to claim 1, characterized in that The first polymer has a dynamic viscosity of less than 250,000 mPa·s and a functional group copolymerizable with a vinyl monomer.

3. The intumescent formulation according to claim 2, characterized in that The first polymer is liquid polyurethane (meth)acrylate, liquid epoxy (meth)acrylate, liquid polyether (meth)acrylate, liquid polyester (meth)acrylate or a mixture thereof, preferably liquid polyurethane (meth)acrylate.

4. The intumescent formulation according to any one of claims 1 to 3, characterized in that The vinyl monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, styrene and combinations of the monomers.

5. Intumescent formulation according to at least one of claims 1 to 4, characterized in that The intumescent formulation comprises 20 to 60 wt % of a resin system.

6. Intumescent formulation according to at least one of claims 1 to 5, characterized in that The resin system comprises 5 wt % to 65 wt % of the first liquid polymer.

7. Intumescent formulation according to at least one of claims 1 to 6, characterized in that The resin system comprises 30 to 90 weight percent of a vinyl monomer.

8. Intumescent formulation according to at least one of claims 1 to 7, characterized in that The intumescent formulation comprises 35 to 60 wt % of a blowing agent.

9. A method for curing a liquid foamable intumescent formulation according to any one of claims 1 to 8, characterized in that The initiator or the components of the initiator system are added to the intumescent formulation, or the curable coating composition is a two-component system and the two component compositions of the two-component system are mixed with one another and then applied to the substrate within 20 minutes and cured within a further 120 minutes.

10. The method according to claim 9, characterized in that The initiator, a component of the initiator system or an ingredient of a two-component system is an organic peroxide.

11. The method according to claim 10, characterized in that The organic peroxide is a diacyl peroxide, a ketone peroxide, a peroxyester, a dialkyl peroxide, a hydroperoxide (eg, cumene hydroperoxide), a peroxyketal, or a combination thereof.

12. The method according to at least one of claims 9 to 11, characterized in that The intumescent formulation was allowed to cure at a temperature between 17°C and 23°C in less than 60 minutes.

13. The method according to claim 12, characterized in that The total weight loss by evaporation in the intumescent formulation during mixing, application to the substrate and curing is less than 5 wt%.

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