Product containing high density skins on a low density core and method of manufacturing same

A method of manufacturing a fiberboard having a skin on at least one surface thereof comprising:

• (a) depositing a first layer of fibers to form a base layer for supporting at least one surface skin thereon;
• (b) depositing a second layer of fibers over said first layer of fibers, said second layer of fibers including a skin forming chemical in an amount of at least 5% based on the total weight of said second layer of fibers, wherein said skin forming chemical is a urea derivative selected from the group consisting of guanamine, alkylureas, lower alkylthioureas, biuret, inorganic acid salts of urea, and mixtures thereof;
• (c) pressing said first and second layers in a heated press at a temperature less than 500.degree. F. and at a pressure less than 700 p.s.i. to form a consolidated fiberboard having a density in the range of 10-65 pounds/ft..sup.3 ;
• and
• (d) hot-pressing said consolidated fiberboard at a temperature of 525.degree.-650.degree. F. to form at least one skin on said fiberboard said skin having a density of 40-55 pounds/ft..sup.3.

A method of manufacturing a cellulosic fiber-containing board having a skin on at least one surface thereof comprising:

• (a) depositing a water slurry of cellulosic fibers onto a water pervious support member to form a wet mat;
• (b) drying said wet mat to less than 8% water, based on the total weight of said mat, to consolidate said mat;
• (c) applying to at least one surface of said mat a solution of a skin forming chemical in at least the surface layer of fibers of said mat in an amount of 5-20% based on the dry weight of said surface layer wherein said skin forming chemical is an amine selected from the group consisting of thiourea, ethanolamine, hexamethylenetetramine, hydrazine plus formaldehyde and mixtures thereof;
• (d) hot-pressing said consolidated mat containing said skin forming chemical in at least its surface fibers, at a temperature of at least 525.degree. F. to form a board having a skin having a density of 40-55 pounds/ft..sup.3 on at least one surface thereof, said skin being of different composition than the composition of the material on which the skin is formed.

A method of manufacturing a cellulosic fiber-containing board having a skin on at least one surface thereof comprising:

• (a) forming a consolidated cellulosic fiber-containing mat having a cured thermosetting resin binder;
• (b) applying to at least one surface of said mat a solution of a skin forming chemical in at least a surface layer of fibers of said mat in an amount of 5-20% based on the dry weight of said surface layers wherein said skin forming chemical is selected from the group consisting of ammonium thiocyanate, thiourea, acetamide, dicyandiamide, ethanolamine, hexamethylenetetramine, hydrazine+formaldehyde, ammonium xylene sulfonate, mono-ammonium phosphate, di-ammonium phosphate, ammonium sulfate, MASONEX, sucrose, boric acid+borax, linseed oil+iron tallate, and mixtures thereof;
• and
• (c) hot-pressing said consolidated mat containing said skin forming chemical and said cured thermosetting resin binder, at a temperature of at least 525.degree. F. to form a skin having a density of 40-55 pounds/ft..sup.3 on at least one surface thereof.

A method of manufacturing a cellulosic fiber-containing board having a skin on at least one surface thereof comprising:

• (a) depositing a layer of fibers including cellulosic fibers onto a support member to form a loose mat;
• (b) consolidating said mat to bond said cellulosic fibers together to form a completed board;
• (c) contacting at least one surface of said completed board with a skin forming chemical selected from the group consisting of ammonium thiocyanate, thiourea, acetamide, dicyanidamide, ethanolamine, hexamethylenetetramine, hydrazine+formaldehyde, ammonium xylene sulfonate, mono-ammonium phosphate, di-ammonium phosphate, ammonium sulfate, sucrose, boric acid, linseed oil+iron tallate, and mixtures thereof in an amount sufficient to form a surface skin having a density of 40-55 pounds/ft..sup.3 ;
• and
• (d) hot-pressing said contacted surface at a temperature of at least 525.degree. F. to form said skin on at least one surface thereof.

A method of manufacturing a cellulosic fiber-containing board having a skin on at least one surface thereof comprising:

• (a) depositing a layer of fibers including cellulosic fibers onto a support member to form a loose mat containing cellulosic fibers;
• (b) contacting at least a surface of said mat with a skin forming chemical selected from the group consisting of ammonium thiocyanate, thiourea, acetamide, dicyandiamide, ethanolamine, hexamethylenetetramine, hydrazine+formaldehyde, ammonium xylene sulfonate, mono-ammonium phosphate, di-ammonium phosphate, ammonium sulfate, sucrose, boric acid, linseed oil+iron tallate, and mixtures thereof in an amount sufficient to form a skinned surface portion when said contacted surface is hot-pressed at a temperature of at least 525.degree. F.;
• (c) consolidating said skin forming chemical contacted mat to bond said cellulosic fibers together to form a completed board;
• and
• (d) hot-pressing said completed board at a temperature of at least 525.degree. F. to form a skin on at least one surface thereof, said skin having a density of 40-55 pounds/ft..sup.3.