Polyisocyanate-based intumescent coating

Abstract

Intumescent coating composition comprising a polyisocyanate, a polyfunctional isocyanate-reactive compound and an intumescent ingredient, wherein the intumescent ingredient contains at least one or more compounds containing phosphorus, nitrogen and boron atoms and the weight ratio phosphorus to nitrogen in said intumescent ingredient is between 0.5/1 to 1.5/1 and the amount of boron is from 1 to 5 wt % based on the coating composition.

Claims

1. An intumescent coating composition comprising (i) 20% by weight to 90% by weight based on the coating composition of a polyurethane binder resin that is the reaction product of a reactive mixture consisting of a polyisocyanate compound and a polyfunctional isocyanate-reactive compound selected from the group consisting of a polycarbonate polyol, a polycaprolactone polyol, a polytetramethylene ether glycol, or combinations thereof, and (ii) an intumescent filler package, wherein the intumescent filler package contains at least one or more compounds containing a phosphorus atom, a nitrogen atom and a boron atom and the weight ratio of phosphorus to nitrogen in said intumescent filler package is between 0.8/1 to 1.5/1 and the amount of boron is from 1 wt % to 5 wt % based on the coating composition; and wherein the polyisocyanate is a prepolymer compound having an average functionality of 2.0 to 2.9 and a maximum viscosity of 6000 mPa S.

2. The intumescent coating composition according to claim 1, wherein the intumescent filler package contains ammonium tetraborate, ammonium pentaborate, ammonium polyphosphate, melamine, or combinations thereof.

3. The intumescent coating composition according to claim 1, wherein the intumescent filler package also contains a nucleating agent.

4. The intumescent coating composition according to claim 1, wherein the intumescent filler package constitutes between 10% by weight and 90% by weight of the coating composition.

5. The intumescent coating composition according to claim 1, wherein the polyisocyanate and polyfunctional isocyanate-reactive compound are reacted at an isocyanate index of 60 to 150%.

6. The intumescent coating composition according to claim 1, wherein the intumescent coating composition is a two-part intumescent coating composition comprising a first part comprising polyisocyanate and, optionally, a first part of the intumescent filler package; and a second part comprising the polyfunctional isocyanate-reactive compound and a second part of the intumescent package, and optionally, other additives.

7. A process for forming a cured intumescent substance comprising applying a composition as defined in claim 1 to a substrate and allowing the composition to cure.

8. The process according to claim 7, wherein the composition is applied by spraying, optionally at elevated temperatures.

9. The process according to claim 7, wherein the thickness of the intumescent coating is between 1 mm and 45 mm.

10. The process according to claim 7, wherein the substance is a steel body.

11. The intumescent coating according to claim 1, wherein the intumescent filler package is selected from the group consisting of TiO.sub.2, ammonium pentaborate, ammonium polyphosphate, melamine and combinations thereof.

12. The intumescent coating composition according to claim 1, wherein the amount of boron is from 1 wt % to 2.5 wt % based on the coating composition.

Description

EXAMPLE 1

(1) The polyurethane formulations were prepared using the polyisocyanates and polyols identified below in Table 1. The isocyanate index was fixed at 105.

(2) TABLE-US-00001 TABLE 1 Polyisocyanate Polyol PU1 SUPRASEC 2496 Albodur 941 PU2 SUPRASEC 2029 Albodur 941 PU7 SUPRASEC 2029 BH 100

(3) Steel plates coated with the formulations were prepared. The steel plates of 1001003 mm.sup.3 were cut into a XC38 type of steel. Before applying the coating, the surface was sand blasted and then cleaned with acetone.

(4) All the additives (identified below in Table 2) were added to the polyol and mixed for 1 minute at 5000 rpm. Then the polyisocyanate was quickly added to the mixture containing the polyol. A disposable spatula was used to mix until the mixture was homogeneous.

(5) TABLE-US-00002 TABLE 2 C1 C2 C3 S1 S2 S3 PU1 100 60 40 40 PU2 70 50 H.sub.3BO.sub.3 26.67 B.sub.4O.sub.7 12.5 20 APP 16 40 AP760 23.33 12.5 20 Mel 12 10 Penta 12 TiO.sub.2 5 10 5 10 MS603 5 P/N 0 0.5 1 1.4 0.8 0.8 % B 0 0 0 4.3 2.1 3.3 t.sub.500 C. 500 900 1600 3200 2450 3600

(6) 1 mm thick layer of the intumescent formulation was put on top of the steel plate by pouring and spreading and left to cure. The testing amount was usually 1 kg/m.sup.2.

(7) Resistance to fire of the cured plates with respect to the ISO 834 cellulosic fires standard were measured using a small scale propane oven. The fire barrier properties of the coatings are evaluated by measuring the time to reach 500 C. in seconds (t.sub.500 C.)

(8) The samples according to the invention (S1-S3) clearly show an improvement in fire resistance compared to samples of the prior art (C1-C3) (see Table 2).

(9) The use of the particular intumescent filler package of the invention leads to increased t.sub.500 C. values, improvement of the char, cohesion (no cracking) and better swelling rate (5 to 15 times the original dry film thickness).

EXAMPLE 2

(10) In the same way as above in Example 1 coatings were prepared using different polyurethane binders (see Table 3).

(11) 2 mm thick layer of the intumescent formulation was put on top of the steel plate by pouring and spreading and left to cure. The testing amount was 2 kg/m.sup.2.

(12) TABLE-US-00003 TABLE 3 S4 S5 PU2 70 PU7 50 B.sub.4O.sub.7 20 B.sub.5O.sub.8 9.6 PMN544 4.05 APP 10.9 AP760 20 TiO.sub.2 5.45 10 P/N 0.9 0.8 % B 1.8 3.3 t.sub.500 C. >4000 >4000

(13) Intumescent polyurethane coatings of the present invention provide t.sub.500 C. in the range 60 to 120 minutes and thus can compete with commercial intumescent acrylics coatings.