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 60% 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 25% of other mineral materials; (ii) from about 15% to about 40% 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 35% 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 7 pounds per thousand square feet to about 15 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 1.5 and to increase its density by a corresponding amount.

Claim 3

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

Claim 4

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

Claim 5

The method of claim 1 wherein the pressure applied in the pressing operation is at least about 200 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 5 wherein the heating and pressing step has a minimum duration of at least one minute.

Claim 8

The method of claim 1 wherein the said factor of step (e) is at least about 2.0.

Claim 9

The method of claim 7 wherein the said factor of step (e) is at least about 2.5.

Claim 10

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 60% 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 25% of other mineral materials; (ii) from about 15% to about 40% 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 35% 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 15 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° F. to about 400° F. and pressing with a minimum pressure of at least about 200 psi the formed product to reduce its thickness by a factor of at least 2.0 and to increase its density by a corresponding amount, the simultaneous heating and pressing being for a period of from about 30 seconds to about 5 minutes.

Claim 11

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 60% 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 25% of other mineral materials; (ii) from about 15% to about 40% 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 35% 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 15 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° F. to about 400° F. and pressing with a minimum pressure of at least about 200 psi the formed product to reduce its thickness by a factor of at least 2.0 and to increase its density by a corresponding amount, the simultaneous heating and pressing being for a period of from about 30 seconds to about 5 minutes.

Claim 12

A process for producing a hardboard product having a fire rating of Class A according to ASTM Test E-84 from a relatively light dry product having the following ingredients: (i) from about 60% to about 85% by weight mineral material, said mineral material being composed of: (A) from about 20% to about 85% mineral fibers; (B) from 0% to about 50% perlite; (C) from 0% to about 25% of other mineral materials; (ii) from about 15% to about 40% of a binding system, said binding system being composed of: (A) from about 5% to about 15% by weight cellulosic fibers; (B) from about 10% to about 35% of a heat and moisture re-activatable binding agent; (iii) said relatively light product having a moisture content of no greater than about 3% by weight; said process comprising: (A) applying to the light, dry product from about seven pounds per thousand square feet to about fifteen pounds per thousand square feet of a solution comprising water; and, thereafter, (B) simultaneously heating and pressing the formed product to reduce its thickness by a factor of at least 1.5 and to increase its density by a corresponding amount.

Claim 13

A process for producing a hardboard product having a fire rating of Class A according to ASTM Test E-84 from a relatively light dry product having the following ingredients: (i) from about 60% to about 85% by weight mineral material, said mineral material being composed of: (A) from about 20% to about 85% mineral fibers; (B) from 0% to about 50% perlite; (C) from 0% to about 25% of other mineral materials; (ii) from about 15% to about 40% of a binding system, said binding system being composed of: (A) from about 5% to about 15% by weight cellulosic fibers; (B) from about 10% to about 35% of a heat and moisture re-activatable binding agent; (iii) said relatively light product having a moisture content of no greater than about 3% by weight; said process comprising: (A) applying to the light, dry product from about seven pounds per thousand square feet to about fifteen pounds per thousand square feet of a solution comprising water; and, thereafter, (B) simultaneously heating and pressing the formed product to reduce its thickness by a factor of at least 1.5 and to increase its density by a corresponding amount.