Intumescent composition and method

An aqueous composition suitable for producing a fire resistant coating on a substrate, said composition comprising an acid curable aqueous melamine-formaldehyde resin and a nitrogen-containing acidic phosphorus curing agent containing one or more moieties of the following formula:

• ##STR25## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR26## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

A method for imparting fire resistance to a substrate comprising treating said substrate with an aqueous composition comprising a water soluble, melamine-formaldehyde resin and a nitrogen-containing acidic phosphorus curing agent containing one or more moieties of the following formula:

• ##STR27## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR28## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

A fire resistant article comprising a substrate coated with an acid-cured aqueous melamine-formaldehyde resin wherein said resin is cured using a nitrogen-containing acidic phosphorus curing agent containing one or more moieties of the following formula:

• ##STR29## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR30## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

An intumescent composition comprising an acid-cured aqueous melamine-formaldehyde resin wherein said resin is prepared by reacting melamine with formaldehyde in the presence of an alkaline catalyst at a melamine to formaldehyde mole ratio in the range of 1:1 to 1:6 and said resin is cured using an nitrogen-containing acidic phosphorus curing agent present in an amount of 20 to 100 weight percent of melamine-formaldehyde resin solids, wherein said acidic phosphorus curing agent contains one or more moieties of the following formula:

• ##STR31## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR32## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

An aqueous composition suitable for producing a fire resistant coating on a substrate, said composition comprising (i) an acid curable aqueous melamine-formaldehyde resin wherein said resin is prepared by reacting melamine with formaldehyde in the presence of an alkaline catalyst at a melamine to formaldehyde mole ratio in the range of 1:1 to 1:6 and (ii) a nitrogen-containing acidic phosphorus curing agent present in an amount of 20 to 100 weight percent of melamine-formaldehyde resin solids, wherein said acidic phosphorus curing agent contains one or more moieties of the following formula:

• ##STR33## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR34## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

A fire resistant article comprising a substrate coated with an acid-cured aqueous melamine-formaldehyde resin wherein said resin is prepared by reacting melamine with formaldehyde in the presence of an alkaline catalyst at a melamine to formaldehyde mole ratio in the range of 1:1 to 1:6 and wherein said resin is cured using a nitrogen-containing acidic phosphorus curing agent present in an amount of 20 to 100 weight percent of melamine-formaldehyde resin solids, said acidic phosphorus curing agent containing one or more moieties of the following formula:

• ##STR35## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR36## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.

A method for imparting fire resistance to a substrate comprising treating said substrate with an aqueous composition comprising (i) a water soluble, melamine-formaldehyde resin wherein said resin is prepared by reacting melamine with formaldehyde in the presence of an alkaline catalyst at a melamine to formaldehyde mole ratio in the range of 1:1 to 1:6 and (ii) a nitrogen-containing acidic phosphorus curing agent present in an amount of 20 to 100 weight percent of melamine-formaldehyde resin solids, wherein said acidic phosphorus curing agent contains one or more moieties of the following formula:

• ##STR53## where R is selected from the group consisting of a C.sub.1 to C.sub.6 alkylene radical, a C.sub.3 to C.sub.7 cycloalkylene radical, an arylene radical and a divalent radical of the formula:
• ##STR54## where x and z are integers of 1 to 6, and y is an integer from 0 to 2 and wherein the divalent radical is bonded to the phosphorus atom of said moieties through the terminal oxygen atom of said radical.