Non-combustible hardboard sheet

Claim 2

A process for producing a hardboard product having a fire rating of Class A according to ASTM Test E-84 comprising: a. forming an aqueous slurry of solids and water said solids consisting essentially of the following ingredients: i. from about 75% to about 85% by weight mineral material, said mineral material consisting essentially of: A. from about 20% to about 85% mineral fibers; B. from 0% to about 50% perlite; C. from 0% to about 5% of other mineral materials; ii. from about 15% to about 25% of a binding system, said binding system consisting essentially of: A. from about 5% to about 15% by weight cellulosic fibers; B. from about 10% to about 20% of a heat and moisture re-activatable binding agent; b. forming a relatively light product by depositing the said aqueous slurry on a forming screen; c. drying the said formed product to a moisture content of no greater than about 3% by weight; d. applying to each side of the dried product from about seven pounds per thousand square feet to about fifteen pounds per thousand square feet of water; e. simultaneously heating and pressing the formed product to reduce its thickness by a factor of at least 2.5 and to increase its density to at least 50 pounds per cubic foot.

Claim 3

The method of claim 1 wherein the temperature during the pressing operation is from about 250° to about 700° F.

Claim 4

The method of claim 2 wherein the pressing temperature is from about 300° to about 400° F.

Claim 5

The method of claim 1 wherein the pressure applied in the pressing operation is at least about 300 psi.

Claim 6

The method of claim 1 wherein the heating and pressing step has a minimum duration of at least 30 seconds.

Claim 7

The method of claim 1 wherein the heating and pressing step has a minimum duration of at least one minute.

Claim 8

A process for producing a hardboard product having a fire rating of Class A according to ASTM Test E-84 comprising: a. forming an aqueous slurry comprising from about 95% to about 98% water and from about 2% to about 5% solids, said solids consisting essentially of the following ingredients: i. from about 75% to about 85% by weight mineral material, said mineral material consisting essentially of: A. from about 20% to about 85% mineral fibers; B. from 0% to about 50% perlite; C. from 0% to about 5% of other mineral materials; ii. from about 15% to about 25% of a binding system, said binding system consisting essentially of: A. from about 5% to about 15% by weight cellulosic fibers; B. from about 10% to about 20% of a heat and moisture re-activatable binding agent; B. forming a relatively light product by depositing the said aqueous slurry on a forming screen; c. drying the said formed product to a moisture content of no greater than about 1% by weight, said dried product having a density of from about 20 to about 23 pounds per cubic foot; d. applying to each side of the dried product from about seven pounds per thousand square feet to about fifteen pounds per thousand square feet of water; e. simultaneously heating at a temperature of from about 300° to about 400° F. and pressing with a minimum pressure of at least about 300 p.s.i. the formed product to reduce its thickness by a factor of at least 2.5 and to increase its density to at least about 50 pounds per cubic foot, the simultaneous heating and pressing being for a period of from about 30 seconds to about five minutes.

Claim 9

A process for producing a hardboard product having a fire rating of Class A according to ASTM Test E-84 comprising: a. forming an aqueous slurry comprising from about 95% to about 98% water and from about 2% to about 5% solids, said solids consisting essentially of the following ingredients: i. from about 75% to about 85% by weight mineral material, said mineral material consisting essentially of: A. from about 20% to about 85% mineral fibers; B. from 0% to about 50% perlite; C. from 0% to about 5% of other mineral materials; ii. from about 15% to about 25% of a binding system, said binding system consisting essentially of: A. from about 5% to about 15% by weight cellulosic fibers; B. from about 10% to about 20% of a heat and moisture re-activatable binding agent; B. forming a relatively light product by depositing the said aqueous slurry on a forming screen; c. drying the said formed product to a moisture content of no greater than about 1% by weight, said dried product having a density of from about 20 to about 23 pounds per cubic foot; d. applying to each side of the dried product from about seven pounds per thousand square feet to about fifteen pounds per thousand square feet of water; e. simultaneously heating at a temperature of from about 300° to about 400° F. and pressing with a minimum pressure of at least about 300 p.s.i. the formed product to reduce its thickness by a factor of at least 2.5 and to increase its density to at least about 50 pounds per cubic foot, the simultaneous heating and pressing being for a period of from about 30 seconds to about five minutes.