Intumescent coating composition

Abstract

The present invention relates to a thermosetting intumescent coating composition which is suitable for protecting substrates against hydrocarbon fires, for example jet fires. The coating composition can be used without a supporting mesh. The present invention also relates to substrates coated with the intumescent coating composition, and a method of protecting structures from fire.

Claims

1. A liquid ambient temperature curable intumescent coating composition comprising: (a) 25.0-75.0 volume % of one or more organic thermosetting polymer(s) and curing agent(s) for the organic thermosetting polymer(s), (b) 5.0-50.0 volume % of one or more source(s) of phosphoric acid and/or sulphonic acid, (c) 5.0 to 30.0 volume % of one or more source(s) of metal and/or metalloid ion(s) selected from oxides, hydroxides, carbonates, bicarbonates, phosphates, chlorides, sulphates, nitrates, silicates, and borates of Al, Ti, Zn, Cu, Zr, Mg, Na or Ca; and oxides, hydroxides, and carbonates of Si or B; and complexes thereof, a total of 0.0-5.0 volume % of amine functional blowing agents (d) selected from urea, dicyandiamide, melamine and derivatives thereof and other blowing agents (e), wherein said other blowing agents (e) are selected from expandable graphite, THEIC, sulfamic acid, boric acid, borate salts, tunastanate salts, and derivatives thereof, provided that the total volume of said amine functional blowing agents (d) and said other blowing agents (e) is no greater than 5% of the volume of (c), wherein (b) is selected from ammonium polyphosphate (APP) or para-toluene sulphonic acid, wherein (c) is selected from one or more of TiO.sub.2, ZnO, ZnPO.sub.4, Al(OH).sub.3, Al.sub.2O.sub.3, AlPO.sub.4, Kaolin, MgO, MgPO.sub.4 or ZrO.sub.2, wherein volume % is calculated on the total volume of the non-volatile components in the coating composition.

2. The liquid ambient temperature curable intumescent coating composition of claim 1, wherein (a) comprises an organic thermosetting polymer comprising at least one of the following functional groups: epoxy, amine, ester, vinyl, vinyl ester, amide, urethane, mercaptan, carboxylic acid, acryloyl, methacryloyl, isocyanate, alkoxysilyl, anhydride, hydroxyl, alkoxy or polythiol groups.

3. The liquid ambient temperature curable intumescent coating composition of claim 1, wherein (a) comprises an organic thermosetting polymer selected from an epoxy resin, an organopolysiloxane resin, or a combination thereof, and a curing agent selected from an amine, a thiol, a carboxylic acid, an anhydride and/or an alcohol functional curing agent.

4. The liquid ambient temperature curable intumescent coating composition of claim 1, wherein the organic thermosetting polymer of (a) comprises an epoxy functional resin and an amine functional curing agent.

5. The liquid ambient temperature curable intumescent coating composition of claim 1, wherein the volume % of (c) ranges from 5.0 to 12.0 vol %.

6. A substrate coated with the liquid ambient temperature curable intumescent coating composition of claim 1.

7. A method of protecting structures from fire, the method comprising coating the structure with the liquid ambient temperature curable intumescent coating composition of claim 1, and allowing the coating composition to cure at ambient temperature.

Description

EXAMPLES

(1) Test Methods

(2) Thermal Fire Protection Testing (Time to Failure)

(3) The relative fire protection capability of each coating was determined by the cone calorimeter thermal technique, which is a laboratory based technique cited in several peer reviewed academic papers. (Bartholmai, M; Schartel, B; FRPM '05, BAM, Berlin, Germany 7-9 Sep. 2005)

(4) The technique uses a heating cone (diameter 160 mm) providing a heat flux of 50 KW/M.sup.2 to simulate a fire. A thermocouple is taped to the non coated side of the panel and then the panel is placed in a sample holder which leaves the painted surface open to the cone heater. The thermocouple is attached to a Grant 2020 series squirrel data logger to read the evolution of temperature as the coated side is heated. The sample is placed at a distance of 25 mm from the edge of the cone. The Time To Failure of the sample is taken as the time it takes for the thermocouple to register a back face temperature of 400? C.

(5) Char Strength Testing

(6) The relative strengths of each of the chars produced by the cone calorimeter thermal test were tested using a Mecmesin AFG 100N force meter. The char is allowed to cool to ambient temperature and then placed under a force gauge plunger (diameter 20 mm). A stepper motor is used to provide a constant force to the plunger. The plunger is driven into the char until it reaches the half height of the char and the resistance to the force is measured. The higher the resistance of the char to the force of the plunger, the harder the char and the greater the structural integrity (and the greater the N-value).

(7) Intumescence Factor Testing

(8) The dry film thickness of the cured paint was measured using an Elcometer 355 Coating Thickness Gauge. The final char height is measured using a Hydracone Depth Gauge. The intumescence factor is calculated as the ratio of the char height:initial dry film thickness.

(9) Sample Preparation of Compositions 1-6

(10) Compositions 1 to 6 comprising the components shown in Table 1 were made by first mixing all components except for the curing agent into the resin base by high speed dispermat. The polyamido amine curing agent was then added and each test coating composition was applied to grit blasted, primed steel panel (100?100?4 mm) to a thickness of 1 mm using a drawdown applicator. The coatings were allowed to cure at ambient temperature for 24 hours before testing according to the procedures noted above.

(11) TABLE-US-00001 TABLE 1 Showing the Volume % of each component in Compositions 1-6 Coating Composition No # Component 1* 2* 3* 4* 5* 6 Epoxy Resin, D.E.R. 331 23.5 23.2 22.3 21.7 19.9 23.5 (DOW) (epoxy resin) Trimethylypropane triacrylate 4.5 4.5 4.3 4.2 3.8 4.5 (diluent) Ammonium Polyphosphate 40.0 39.6 38.1 37.0 33.9 41.7 (source of acid) Melamine (blowing agent) 10.0 9.9 9.5 9.3 16.9 0 Zinc Oxide (source of metal 0.0 1.0 4.8 7.4 6.8 8.3 ions) Polyamido amine Curing 19.9 19.7 19.0 18.5 16.9 19.9 Agent having an amine equivalent weight of 93 g/mol 2,4,6-tri(dimethylaminometh- 2.1 2.1 2.0 1.9 1.8 2.1 yl)phenol (accelerator) Ratio of epoxy functional 0.6:1 0.6:1 0.6:1 0.6:1 0.6:1 0.6:1 groups:NH functional groups Volume of melamine/volume ? 990% 204% 126% 249% 0% of ZnO (%) *Comparative Examples

(12) Results of Testing Compositions 1-6

(13) TABLE-US-00002 TABLE 2 Test Results Composition Time to Failure (min) Char Strength (N) 1 21 <1 2 29 <1 3 23 5 4 9 ? 5 9 ? 6 24 28 ? Could not be measured as the char was too compact

(14) Composition 1 provides a standard epoxy amine intumescent with no metal oxide addition which acts as a standard/control system. This has a reasonable Time to Failure (thermal performance) but poor char strength (N).

(15) The Time to Failure and char strength of Composition 2 shows that the addition of metal oxides at low concentration (?1 wt %) improves the thermal performance of the char but the char strength is not significantly enhanced by the low levels of metal oxide.

(16) In order to increase char strength, more metal oxide was added to the composition (composition 3). The results however show that the additional metal oxide, also reduced the thermal protection. The addition of more metal oxide as in composition 4 shows that the thermal protection is made even worse.

(17) The current accepted knowledge of intumescent fire protection equates thermal protection with increasing the amount of intumescence. It is also intuitive that the means to generate intumescence is by adding more blowing agent. Surprisingly however Composition 5 shows that the addition of melamine to composition 4 leads to no improvement in thermal performance.

(18) It is therefore surprising to note the result of Composition 6 in which the removal of all melamine blowing agent gives rise to both (i) an improvement in thermal protection and (ii) a significantly harder char strength (to the extent that the coating is capable of providing intumescent protection against hydrocarbon fires).

(19) Advantageously, Composition 6 has 0% VOC. This, of course, would not be possible if a thermoplastic polymer had been used, as thermoplastic polymers require solvent when formulated which evaporates when the coating dries.

(20) Sample Preparation of Composition 7

(21) Composition 7 comprising the components shown in Table 3 were made by first mixing all components except for the curing agent into the resin base by high speed dispermat. The polyamido amine curing agent was then added and the intumescent coating composition was applied to grit blasted, primed steel panel (100?100?4 mm) to a thickness of 1 mm using a drawdown applicator. The coating composition was allowed to cure at ambient temperature for 24 hours before testing.

(22) The intumescence factor and char strength of coating prepared from composition 7 and a commercially available epoxy amine based intumescent coating composition containing melamine (Standard) were determined.

(23) TABLE-US-00003 TABLE 3 Coating Component Composition No 7 Epoxy Resin, D.E.R. 331 (DOW) (epoxy resin) 23.7 Trimethylypropane triacrylate (diluent) 4.6 Ammonium Polyphosphate (source of acid) 40 Melamine (blowing agent) 0 TiO.sub.2 (source of metal ions) 10 Polyamido amine Curing Agent having an amine 19.6 equivalent weight of 93 g/mol 2,4,6-Tri(dimethylaminomethyl)-phenol (accelerator) 2.1 Ratio of epoxy functional groups:NH functional groups 0.6:1 Volume of melamine/volume of TiO.sub.2 (%) 0%

(24) TABLE-US-00004 TABLE 4 Test Results Composition Intumescence Factor Char Strength (N) 7 12 >65 Standard 12 1.5

(25) The test results of Table 4 show that a coating formed from a coating composition according to the invention, had a good intumescence factor (same as the Standard Commercial coating comprising melamine) however a significantly better char strength.