Intumescent coating having improved low-temperature flexibility

Abstract

A novel reaction system can be used for intumescent coating. Intumescent coatings are used in particular for the protection of metallic building components, such as girders in building construction. In the event of a fire, such coatings undergo reactive foaming that results in the formation on the metal girder of a fireproof insulating layer having low thermal conductivity and, through the insulation that this creates, retards any early, thermal-induced failure of the building component. Resin systems having improved low-temperature flexibility can be used to ensure good metal adhesion and impact resistance even at low temperatures, while avoiding the polymer components that are otherwise customary in resin systems.

Claims

1. A liquid, foamable intumescent formulation, comprising: a resin system, wherein the resin system comprises at least one first polymer having an average molecular weight M.sub.n of between 1,000 and 35,000 g/mol and a glass transition temperature of less than 15° C., at least one vinylic monomer, and at least one component that acts as a blowing agent at a temperature of above 200° C., wherein a coating produced from the intumescent formulation is curable by polymerization and, prior to initiation of said polymerization, comprises no component having an acid function and at the same time a molecular weight of greater than 1,500 g/mol.

2. The intumescent formulation as claimed in claim 1, wherein the first polymer has a dynamic viscosity of less than 250,000 mPa.Math.s and a functionality that is copolymerizable with vinylic monomers.

3. The intumescent formulation as claimed in claim 2, wherein the first polymer is a liquid urethane (meth)acrylate, a liquid epoxy (meth)acrylate, a liquid polyether (meth)acrylate, a liquid polyester (meth)acrylate, or a mixture thereof.

4. The intumescent formulation as claimed in claim 1, wherein the at least one vinylic monomer in the resin system is a (meth)acrylate and/or a mixture of different (meth)acrylates and/or monomers copolymerizable with (meth)acrylates.

5. The intumescent formulation as claimed in claim 4, wherein the at least one vinylic monomer is selected from the group consisting of (methyl) methacrylate, (ethyl) methacrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl meth)acrylate, 2-ethylhexyl (meth)acrylate, styrene, and a combination of said monomers.

6. The intumescent formulation as claimed in claim 1, wherein the intumescent formulation contains between 20% by weight and 60% by weight of the resin system.

7. The intumescent formulation as claimed in claim 1, wherein the resin system contains between 5% and 65% by weight of the first polymer.

8. The intumescent formulation as claimed in claim 1, wherein the resin system contains between 30% and 90% by weight of the at least one vinylic monomer.

9. The intumescent formulation as claimed in claim 1, wherein the intumescent formulation contains between 35% by weight and 60% by weight of the at least one component that acts as a blowing agent.

10. A process for curing the liquid foaming intumescent formulation as claimed in claim 1, the process comprising: adding an initiator or a component of an initiator system to the intumescent formulation, to obtain a mixture; or if the intumescent formulation is part of a curing coating composition which is a 2 C system, mixing two part-compositions of the 2 C system together, to obtain a mixture, applying the mixture to a substrate within 20 min, and curing the mixture within a further 120 min.

11. The process as claimed in claim 10, wherein the initiator, the component of the initiator system, or a constituent in a component the 2 C system is an organic peroxide.

12. The process as claimed in claim 11, wherein the organic peroxide is a diacyl peroxide, a ketone peroxide, a peroxyester, a dialkyl peroxide, a hydroperoxide, a peroxyketal, or a combination thereof.

13. The process as claimed in claim 10, wherein the intumescent formulation is cured in less than 60 minutes at a temperature of between 17° C. and 23° C.

14. The process as claimed in claim 13, wherein a total loss of weight by evaporation in the intumescent formulation during mixing, application to the substrate, and curing is less than 5% by weight.

15. The intumescent formulation as claimed in claim 3, wherein the first polymer is a liquid urethane (meth)acrylate.

16. The process as claimed in claim 12, wherein the hydroperoxide is cumene hydroperoxide.

Description

EXAMPLES

Example 1: Production According to the Invention of a Reactive Resin

[0050] DEGADUR MDP Membran SG is a methacrylate-based, accelerator-free reactive resin commercially available from Rohm GmbH that comprises urethane methacrylates for flexibility. DEGADUR MDP Membran SG does not contain any solid polymeric components.

[0051] To 970.0 g of DEGADUR MDP Membran SG was added 20.0 g of 2-carboxyethyl acrylate and 10.0 g of N,N-bis(2-hydroxypropyl)-para-toluidine and the mixture was stirred at 50° C. until completely dissolved. The reactive resin was then cooled to room temperature.

Example 2: Inventive Formulation 1 of an Intumescent Coating

[0052] Composition of Formulation 1 from Example 2

TABLE-US-00001 Reactive resin from example 1 40.0% by weight Titanium dioxide 10.0% by weight Ammonium polyphosphate 30.0% by weight Pentaerythritol  8.5% by weight Melamine 11.0% by weight Byk D410  0.5% by weight

[0053] It is understood that the embodiment described above is exemplary only. Many modifications or variations are possible.

Comparative Example 1: Noninventive Formulation 2 of an Intumescent Coating

[0054] DEGALAN 1710 is a commercially available meth(acrylate)-based reactive resin produced by Rohm GmbH having a solid (glass transition temperature >50° C.) thermoplastic polymer component.

[0055] Composition of Formulation 2 from Example 3

TABLE-US-00002 DEGALAN 1710 40.0% by weight Titanium dioxide 10.0% by weight Ammonium polyphosphate 30.0% by weight Pentaerythritol  8.5% by weight Melamine 11.0% by weight Byk 0410  0.5% by weight

[0056] Properties of the Intumescent Coatings

[0057] Determination of Pot Life and Curing Time:

[0058] 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 3000 pm to steel plates. The pot life and the maximum temperature during curing were additionally measured on a smaller portion of the sample. The pot life corresponds to the length of time after addition of the initiator during which the viscosity is still low enough for application of the coating to be possible.

TABLE-US-00003 Inventive example Noninventive formulation i formulation 2 Pot life 10 min 16 min Time until maximum 14 min 34 min temperature Maximum temperature 84° C. 70° C. Time until tack-free curing 19 min 43 min

[0059] Determination of Low-temperature Flexibility

[0060] 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.

[0061] The formulations were then each applied in a layer thickness of 1000 pm to sheet steel with a thickness of 1 mm.

[0062] Once curing was complete, the plates were cooled to −20° C. and the coated steel sheets were at this temperature bent through 90° over a right-angled edge. The coating at the bending point was then examined for cracks and flaking.

TABLE-US-00004 Inventive example Noninventive formulation 1 formulation 2 Low-temperature flexibility of No flaking or The coating shows clear the coating at −20° C. cracks visible cracks and flaking.

[0063] In the bending test at −20° C., example formulation 1 of the invention shows significantly improved low-temperature flexibility compared to noninventive formulation 2 of the prior art.