Fire-retardant treatment of wood laminae

Claim 3

The method as defined in claim 1 in which the selected wood laminae have a minimum moisture content of about 100 percent oven dried weight.

Claim 4

The method as defined in claim 2 in which the minimum moisture content is attained by pre-soaking said laminae in water at an elevated temperature for a time sufficient to produce the minimum moisture content desired.

Claim 5

The method as defined in claim 1 in which said immersion in the solution of fire-retardant agent is for a time sufficient to achieve an uptake of said flame-retardant agent of at least 5 pounds per cubic foot of wood.

Claim 6

The method as defined in claim 1 in which said fire-retardant agent is a water soluble organic salt, a water soluble inorganic salt, or mixtures of two or more of said salts.

Claim 7

The method as defined in claim 2 in which said fire-retardant agent is an inorganic salt having a high solubility in water and a solubility which is highly temperature dependent, or a mixture of two or more of such salts.

Claim 8

The method as defined in claim 2 in which said solution of fire-retardant agent is a saturated solution of ammonium sulfate, monoammonium phosphate, diammonium phosphate, sodium borate, borax-boric acid mixtures, ammonium sulfamate, chromated zinc chloride, an ammonium polyphosphate fertilizer, a high phosphate fertilizer, or mixtures thereof.

Claim 9

The method as defined in claim 1 in which the laminae are immersed in said solution for a period of from about 3 to 15 minutes.

Claim 10

The method as defined in claim 2 in which said solution of fire-retardant agent is a saturated solution of monoammonium phosphate and said laminae are immersed in said solution for a period of approximately 9 to 12 minutes.

Claim 11

The method as defined in claim 1 in which said laminae are stored in an atmosphere of about 100 percent relative humidity for a period of from 1 to 4 days.

Claim 14

In a process for manufacturing fire-retardant plywood from a plurality of wood veneers, the improvement which consists of subjecting veneers selected to have a minimum moisture content of about 70 percent oven dried weight before adhesive coating, assembly and lamination, to a treatment conducted at ambient pressure which comprises successively: i. immersing said veneers in a concentrated aqueous solution of fire-retardant agent maintained at an elevated temperature of about 75* to 95*C., for a time sufficient to achieve a loading of the lamina with said flame-retardant agent in an amount of at least 2 lbs. per cubic foot, ii. withdrawing said veneers from said solution and storing them in an atmosphere at a temperature in the range from room temperature to about 97*C. maintained above the equilibrium relative humidity of said aqueous solution for a time sufficient to permit solution retained by each lamina to diffuse throughout its thickness, and iii. drying said veneers.

Claim 15

In a process for manufacturing fire-retardant plywood from a plurality of wood veneers, the improvement which consists of subjecting veneers selected to have a minimum moisture content of about 70 percent oven dried weight before adhesive coating, assembly and lamination, to a treatment conducted at ambient pressure which comprises successively: i. immersing said veneers in a concentrated aqueous solution of fire-retardant agent maintained at an elevated temperature of about 75* to 95*C., for a time sufficient to achieve a loading of the lamina with said flame-retardant agent in an amount of at least 2 lbs. per cubic foot, ii. withdrawing said veneers from said solution and storing them in an atmosphere at a temperature in the range from room temperature to about 97*C. maintained above the equilibrium relative humidity of said aqueous solution for a time sufficient to permit solution retained by each lamina to diffuse throughout its thickness, and iii. drying said veneers.

Claim 16

In a process for manufacturing fire-retardant plywood from a plurality of wood veneers, the improvement which consists of subjecting said veneers before adhesive coating, assembly and lamination to a treatment conducted at ambient pressure which comprises successively: i. presoaking said veneers in water at an elevated temperature for a time sufficient for the veneers to attain a minimum moisture content of about 70 percent oven dried weight, ii. immersing said veneers in a concentrated aqueous solution of fire-retardant agent maintained at an elevated temperature of about 75* to about 95*C., for a time sufficient to achieve a loading of the lamina with said flame-retardant agent in an amount of at least 2 lbs. per cubic foot, iii. withdrawing said veneers from said solution and storing them in an atmosphere at a temperature in the range from room temperature to about 97*C. maintained above the equilibrium relative humidity of said aqueous solution for a time sufficient to permit solution retained by each veneer to diffuse throughout its thickness, and iv. drying said veneers, and v. removing any excess agent at the surface of said veneers.

Claim 17

In a process for manufacturing fire-retardant plywood from a plurality of wood veneers, the improvement which consists of subjecting said veneers before adhesive coating, assembly and lamination to a treatment conducted at ambient pressure which comprises successively: i. presoaking said veneers in water at an elevated temperature for a time sufficient for the veneers to attain a minimum moisture content of about 70 percent oven dried weight, ii. immersing said veneers in a concentrated aqueous solution of fire-retardant agent maintained at an elevated temperature of about 75* to about 95*C., for a time sufficient to achieve a loading of the lamina with said flame-retardant agent in an amount of at least 2 lbs. per cubic foot, iii. withdrawing said veneers from said solution and storing them in an atmosphere at a temperature in the range from room temperature to about 97*C. maintained above the equilibrium relative humidity of said aqueous solution for a time sufficient to permit solution retained by each veneer to diffuse throughout its thickness, and iv. drying said veneers, and v. removing any excess agent at the surface of said veneers.

Claim 18

The process as defined in claim 13 in which said veneers are presoaked to a moisture content of at least about 100 percent oven dried weight.

Claim 19

The process as defined in claim 13 in which the fire-retardant agent is a water soluble organic salt, a water soluble inorganic salt, or mixtures of two or more of said salts.

Claim 20

The process as defined in claim 14 in which the fire-retardant agent is an inorganic salt having high solubility in water and a solubility which is highly temperature dependent, or a mixture of two or more of such salts.

Claim 21

The process as defined in claim 13 in which said immersion in the solution of fire-retardant agent is for a time sufficient to achieve an uptake of said flame-retardant agent of at least 5 pounds per cubic foot of wood.

Claim 22

The process as defined in claim 13 in which said solution of fire-retardant agent is a saturated solution of ammonium sulfate, monoammonium phosphate, diammonium phosphAte, sodium borate, borax-boric acid mixtures, ammonium sulfamate, chromated zinc chloride, an ammonium polyphosphate fertilizer, a high phosphate fertilizer, or mixtures thereof.

Claim 23

The process as defined in claim 18 in which the veneers are immersed in said solution for a period of from 3 to 15 minutes.

Claim 24

The process as defined in claim 13 in which said solution of fire-retardant agent is a saturated solution of monoammonium phosphate and said veneers are immersed in said solution for a period of from 9 to 12 minutes.

Claim 25

The process as defined in claim 14 in which the veneers are stored in an atmosphere of about 100 percent humidity for a period of from 1 to 4 days.

Claim 26

In a process for manufacturing fire-retardant plywood from a plurality of Douglas fir veneers, the improvement which consists of subjecting said veneers before adhesive coating, assembly and lamination, to a treatment conducted at ambient pressure which comprises successively: i. presoaking said veneers in water at about 80*C. for a period of 24 to 48 hours, ii. immersing said veneers in a saturated aqueous solution of monoammonium phosphate at a temperature in the range from about 75*C. to about 95*C. for a period of about 9 to 12 minutes, iii. withdrawing said veneers from said solution and storing them in an atmosphere maintained above the equilibrium relative humidity of said aqueous solution at a temperature in the range from about 40*C. to about 70*C. for 1 to 4 days, and iv. drying said veneers, and v. removing any excess salt at the surface of said veneers.

Claim 27

In a process for manufacturing fire-retardant plywood from a plurality of Douglas fir veneers, the improvement which consists of subjecting said veneers before adhesive coating, assembly and lamination, to a treatment conducted at ambient pressure which comprises successively: i. presoaking said veneers in water at about 80*C. for a period of 24 to 48 hours, ii. immersing said veneers in a saturated aqueous solution of monoammonium phosphate at a temperature in the range from about 75*C. to about 95*C. for a period of about 9 to 12 minutes, iii. withdrawing said veneers from said solution and storing them in an atmosphere maintained above the equilibrium relative humidity of said aqueous solution at a temperature in the range from about 40*C. to about 70*C. for 1 to 4 days, and iv. drying said veneers, and v. removing any excess salt at the surface of said veneers.