Process for preparing particle board and polyisocyanate-phosphorus compound release agent composition therefor

In a process for the preparation of particle board wherein particles of cellulosic material are contacted with an aqueous emulsion of a polyisocyanate and the treated particles are subsequently formed into boards by the application of heat and pressure, the improvement which comprises employing an aqueous emulsion containing

• (a) from about 10 parts by weight to about 99 parts by weight, per 100 parts by weight of emulsion, of a polymethylene polyphenyl polyisocyanate containing from about 25 to about 90 percent by weight of methylenebis (phenyl isocyanate), the remainder of said mixture being oligomeric polymethylene polyphenyl polyisocyanates of functionality greater than 2;
• and
• (b) from about 0.1 parts by weight to about 20 parts by weight, per 100 parts by weight of polyisocyanate, of a phosphate selected from the class consisting of
• (i) acid phosphates of the formulae:
• ##STR25## and the ammonium, alkali metal, and alkaline earth metal salts thereof, wherein each R is independently selected from the class consisting of alkyl having at least 3 carbon atoms, alkenyl having at least 3 carbon atoms, aryl, aryl substituted by at least one alkyl, alkyl substituted by from 1 to 2 acyloxy groups wherein the acyl group is the residue of an aliphatic monocarboxylic acid having at least 2 carbon atoms, and ##STR26## wherein R' is selected from the class consisting of alkyl, aryl and aryl substituted by at least one alkyl, one of A and B represents hydrogen and the other is selected from the class consisting of hydrogen, methyl, chloromethyl and 2,2,2-trichloroethyl, and m is a number having an average value from 1 to 25;
• provided that, when one of the R groups in the formula ##STR27## is alkyl having at least 3 carbon atoms, the other R can also be selected from methyl and ethyl and further provided that the two RO groups in said formula, taken together with the P atom to which they are attached, can additionally form the residue of a heterocyclic nucleus having from 5 to 6 ring atoms;
• (ii) the corresponding pyrophosphates derived from said acid phosphates including mixtures of two or more such phosphates by the removal of water of condensation;
• and
• (iii) mixtures of at least one of said acid phosphates and at least one of said pyrophosphates.

In a process for the preparation of particle board wherein particles of cellulosic material are contacted with a polyisocyanate and the treated particles are subsequently formed into boards by the application of heat and pressure, the improvement which comprises contacting said particles, in addition to the treatment with said polyisocyanate, with from about 0.1 to about 20 parts, per 100 parts by weight of said polyisocyanate, of a phosphate selected from the class consisting of:

• (i) acid phosphates of the formulae:
• ##STR30## and the ammonium, alkali metal, alkaline earth metal and amine salts thereof, wherein each R is independently selected from the class consisting of alkyl having at least 3 carbon atoms, alkenyl having at least 3 carbon atoms, aryl, aryl substituted by at least one alkyl, alkyl substituted by from 1 to 2 acyloxy groups wherein the acyl group is the residue of an aliphatic monocarboxylic acid having at least 2 carbon atoms, and ##STR31## wherein R' is selected from the class consisting of alkyl, aryl and aryl substituted by at least one alkyl, one of A and B represents hydrogen and the other is selected from the class consisting of hydrogen, methyl, chloromethyl and 2,2,2-trichloromethyl, and m is a number having an average value from 1 to 25;
• provided that, when one of the R groups of the formula ##STR32## is alkyl having at least 3 carbon atoms, the other R can also be selected from methyl and ethyl, and further provided that the two RO groups in said formula, taken together with the P atom to which they are attached, can additionally form the residue of a heterocyclic nucleus having from 5 to 6 ring atoms;
• (ii) the corresponding pyrophosphates derived from said acid phosphates including mixtures of two or more such phosphates by the removal of water of condensation;
• and
• (iii) mixtures of at least one of said acid phosphates and at least one of said pyrophosphates.

A storage stable composition comprising a mixture of:

• (a) a polymethylene polyphenol polyisocyanate containing from about 25 to about 90 percent by weight of methylenebis(phenyl isocyanate) the remainder of said mixture being oligomeric polymethylene polyphenol polyisocyanates having a functionality higher than 2.0;
• and
• (b) from about 0.1 parts by weight to about 20 parts by weight, per 100 parts by weight of said polyisocyanate, of a pyrophosphate derived by removal of water of condensation from at least one acid phosphate selected from acid phosphates of the formulae:
• ##STR35## wherein each R is independently selected from the class consisting of alkyl having at least 3 carbon atoms, alkeyl having at least 3 carbon atoms, aryl, aryl substituted by at least one alkyl, alkyl substituted by from 1 to 2 acyloxy groups wherein the acyl group is the residue of an aliphatic monocarboxylic acid having at least 2 carbon atoms, and ##STR36## wherein R' is selected from the class consisting of alkyl, aryl and aryl substituted by at least one alkyl, one of A and B represents hydrogen and the other is selected from the class consisting of hydrogen, methyl, chloromethyl and 2,2,2-trichloroethyl, and m is a number having an average value from 1 to 25, and mixtures of two or more of said acid phosphates;
• provided that, when one of the R groups in the formula ##STR37## is alkyl having at least 3 carbon atoms, the other R can also be selected from methyl and ethyl, and further provided that the two RO groups in said formula, taken together with the P atom to which they are attached, can additionally form the residue of a heterocyclic nucleus having from 5 to 6 ring atoms.