Flame retardant polyurethane foam and method for producing same

1. A method for forming a polyurethane foam comprising the steps of:

providing an isocyanate component comprising:

an isocyanate-containing compound, and

a non-halogenated, non-reactive phosphorous compound present in an amount ranging from 1 to 20 weight percent based on the total weight of the polyurethane foam and having a cumulative weight loss of 2% or less at 200° C. as measured by thermogravimetric analysis using a 10° C./min. heating rate in nitrogen to 200° C., wherein the non-halogenated, non-reactive phosphorous compound is liquid at 25° C. and is premixed with the isocyanate-containing compound prior to reacting the isocyanate component with the isocyanate-reactive component;

providing an isocyanate-reactive component comprising:

expandable graphite present in an amount ranging from 3 to 30 weight percent based on the total weight of the polyurethane foam, and

a polyether polyol having a weight-average molecular weight from 2,500 to 6,000 g/mol and a hydroxyl number from 25 to 60 KOH/g,

wherein the non-halogenated, non-reactive phosphorous compound is not premixed in the provided isocyanate-reactive component; and

reacting the isocyanate component with the isocyanate-reactive component in the presence of a blowing agent to form the polyurethane foam.

2. The method as set forth in claim 1 , further comprising the step of premixing the expandable graphite with the polyether polyol prior to reacting the isocyanate component with the isocyanate-reactive component.

3. A method for forming a polyurethane foam comprising the steps of:

(a) mixing expandable graphite present in an amount ranging from 3 to 30 weight percent based on the total weight of the polyurethane foam with a first isocyanate-reactive component;

(b) providing an isocyanate component comprising:

an isocyanate-containing compound, and

a non-halogenated, non-reactive phosphorous compound premixed with the isocyanate-containing compound, the non-halogenated, non-reactive phosphorous compound present in an amount ranging from 1 to 20 weight percent based on the total weight of the polyurethane foam, the non-reactive phosphorous compound having a cumulative weight loss of 2% or less above 200° C. as measured by thermogravimetric analysis using a 10° C./min. heating rate in nitrogen to 200° C., wherein the non-halogenated, non-reactive phosphorous compound is liquid at 25° C.;

(c) introducing the isocyanate component and a second isocyanate-reactive component to a chamber under high pressure in the presence of a blowing agent;

(d) introducing the mixed expandable graphite and first isocyanate-reactive component to the chamber at a lower pressure; and

(e) reacting the isocyanate component with the first isocyanate-reactive component and the second isocyanate-reactive component in the presence of the blowing agent to form the polyurethane foam;

wherein the first isocyanate-reactive component and the second isocyanate-component each comprise a polyether polyol having a weight-average molecular weight from 2,500 to 6,000 g/mol and a hydroxyl number from 25 to 60 KOH/g, and

wherein the non-halogenated, non-reactive phosphorous compound is not premixed with the first isocyanate-reactive component and is not premixed with the second isocyanate component prior to reacting the isocyanate component with the first isocyanate-reactive component and the second isocyanate-reactive component.

4. The method of claim 3 wherein the first isocyanate-reactive component is the same composition as the second isocyanate-reactive component.

5. The method of claim 1 , wherein the formed polyurethane foam has a UL 94 vertical flame classification of V-0.

6. The method of claim 5 , wherein the formed polyurethane foam maintains a UL 94 vertical flame classification of V-0 after one week of heat aging at 150° C.

7. The method of claim 5 , wherein the formed polyurethane foam has a density of from 32 to 240 kg/m 3 .

8. The method of claim 3 , wherein the non-halogenated, non-reactive phosphorous compound is premixed with the isocyanate-containing compound prior to steps (c), (d) and (e).

9. The method of claim 3 , wherein the formed polyurethane foam has a UL 94 vertical flame classification of V-0.

10. The method of claim 3 , wherein the formed polyurethane foam maintains a UL 94 vertical flame classification of V-0 after one week of heat aging at 150° C.

11. The method of claim 3 , wherein the formed polyurethane foam has a density of from 32 to 240 kg/m 3 .