Process for treating cellulosic material with formaldehyde in liquid phase and sulfur dioxide

Claim 2

A PROCESS FOR IMPROVING THE DIMENSIONAL STABILITY WRIN KLE RESISTANCE AND SMOOTH DRYING CHARACTERISTICS OF A CELLULOSE FIBER-CONTAINING FABRIC WHICH COMPRISES: A. DEPOSITING WATER AND FORMALDEHYDE IN THE FABRIC TO PROVIDE THEREIN AN AQUEOUS PHASE COMPRISING FORMALDEHYDE AND CONDITIONING THE FABRIC TO GIVE THE CELLULOSE FIBERS A MOISTURE CONTENT OF BETWEEN ABOUT 4 AND 20 PERCENT BASED ON DRY WEIGHT OF CELLULOSE; B. HEAING THE CONDITIONED MOISTURE-CONTAINING AND FORMALDEHYDE-CONTANING FABRIC IN THE PRESENCE OF CATALYST-FORMING SULFUR DIOXIDE AND WATER VAPOR IN A REACTION ZONE AT A TEMPERATURE ABOVE ABOUT 65*C FOR A TIME OF BETWEEN ABOUT 10 SECONDS AND 2 HOURS UNTIL FORMALDEHYDE IN AN AMOUNT EQUAL TO AT LEAST 0.3 PERCENT BY WEIGHT OF SAID CELLULOSE FIBERS IS DURABLY DEPOSITED IN THE FABRIC AND THE CELLULOSE FIBERS BECOME EFFECTIVELY CROSSLINKED SAID HEATING BEING CONDUCTED WHILE GOVERNING THE AMOUNT OF WATER IN THE SYSTEM TO CONTROL THE AMOUNT OF MOISTURE IN SAID FABRIC AND THEREBY REGULATED THE AMOUNT OF STRONG ACID CATALYST FORMED THEREIN BY THE REACTION OF FORMALDEHYDE AND SULFUR DIOXIDE, A REACTION IN WHICH WATER IS THE LIMITING FACTOR, TO PROVIDE A SELF-LIMITING REACTION SYSTEM AND C. HEATING THE THUS CROSSLINKED FABRIC TO DISSIPATE WATER VAPOR, RESIDUAL CATALYST AND UNBOUND FORMALDEHYDE THEREFROM.

Claim 3

A process according to claim 1 wherein the fabric is heated in step (b) to a temperature between about 80* and about 150*C. and is dried and unbound formaldehyde is vaporized therefrom by heating it in step (c), thereby directly producing a dry, crosslinked, essentially neutral fabric.

Claim 4

A process according to claim 1 wherein the fabric is treated prior to the formaldehyde crosslinking step with a compound containing an active hydrogen and selected from the group consisting of polyhydric alcohols, ureas, amides and carbamates.

Claim 5

A process according to claim 1 wherein the conditioned moisture-containing fabric is treated with sulfur dioxide gas before being heated in said reaction zone in step (b).

Claim 6

A process according to claim 1 wherein the fabric is one containing at least 35 percent by weight of cotton and wherein the aqueous formaldehyde solution contains between about 1 and 40 percent by weight of formaldehyde.

Claim 7

A process for improving the dimensional stability, wrinkle resistance and smooth drying characteristics of cottoncontaining fabrics which comprises: a. applying to the fabric an aqueous solution containing about 2 to 40 percent by weight of formaldehyde and conditioning the fabric to give the cotton a moisture content of between about 4 to 20 percent based on dry weight of cotton; b. heating the conditioned moisture-containing and formaldehyde-containing fabric to a temperature of between about 80* and about 150*C. in the presence of sulfur dioxide in an atmosphere containing water vapor in a reaction zone for a time of between about 10 seconds and 2 hours until formaLdehyde in an amount equal to at least 0.3 percent by weight of said cotton is durably fixed in the fabric and the cotton fibers are effectively crosslinked, said heating being conducted while governing the amount of water in the reaction zone to control the amount of moisture in said fabric and thereby regulate the amount of strong acid catalyst formed therein by the reaction of formaldehyde and sulfur dioxide, a reaction in which water is the limiting factor, to provide a self-limiting reaction system; and c. at the end of said crosslinking step (b) removing residual catalyst and unbound formaldehyde from the fabric by heating it in an inert gaseous atmosphere, thereby directly producing a dry, crosslinked, essential neutral fabric.

Claim 8

A process for improving the dimensional stability, wrinkle resistance and smooth drying characteristics of cottoncontaining fabrics which comprises: a. applying to the fabric an aqueous solution containing about 2 to 40 percent by weight of formaldehyde and conditioning the fabric to give the cotton a moisture content of between about 4 to 20 percent based on dry weight of cotton; b. heating the conditioned moisture-containing and formaldehyde-containing fabric to a temperature of between about 80* and about 150*C. in the presence of sulfur dioxide in an atmosphere containing water vapor in a reaction zone for a time of between about 10 seconds and 2 hours until formaLdehyde in an amount equal to at least 0.3 percent by weight of said cotton is durably fixed in the fabric and the cotton fibers are effectively crosslinked, said heating being conducted while governing the amount of water in the reaction zone to control the amount of moisture in said fabric and thereby regulate the amount of strong acid catalyst formed therein by the reaction of formaldehyde and sulfur dioxide, a reaction in which water is the limiting factor, to provide a self-limiting reaction system; and c. at the end of said crosslinking step (b) removing residual catalyst and unbound formaldehyde from the fabric by heating it in an inert gaseous atmosphere, thereby directly producing a dry, crosslinked, essential neutral fabric.

Claim 9

A process according to claim 6 wherein steam is injected into the reaction zone in step (b) to adjust the water vapor concentration therein at between about 10 and 70 per cent by volume and thereby to retard evaporation of moisture from the conditioned fabric and control the crosslinking reaction.

Claim 10

A process for improving the dimensional stability, wrinkle resistance and smooth drying characteristics of cotton-containing fabrics which comprises: impregnating in the fabric an aqueous solution containing about 10 to 30 percent formaldehyde; drying and conditioning the impregnated fabric to a moisture content of between about 4 to 20 percent; heating the moisture-containing and formaldehyde-containing fabric in a reactive gaseous atmosphere comprising water vapor and about 0.1 to 30 volume per cent sulfur dioxide at a temperature between about 90* and about 150*C. for a time of from about 10 seconds to about 2 hours until formaldehyde in an amount equal to at least 0.3 percent by weight of said cotton fibers is durably fixed in the fabric and the cotton fibers are effectively crosslinked, said heating being conducted while governing the amount of water vapor in said atmosphere to control the amount of moisture in said fabric and thereby regulate the amount of strong acid catalyst formed by the reaction of formaldehyde and sulfur dioxide, a reaction in which water is the limiting factor, to provide a self-limiting reaction system; and drying the thus crosslinked fabric.

Claim 11

A process for improving the dimensional stability, wrinkle resistance and smooth drying characteristics of cotton-containing fabrics which comprises: impregnating in the fabric an aqueous solution containing about 10 to 30 percent formaldehyde; drying and conditioning the impregnated fabric to a moisture content of between about 4 to 20 percent; heating the moisture-containing and formaldehyde-containing fabric in a reactive gaseous atmosphere comprising water vapor and about 0.1 to 30 volume per cent sulfur dioxide at a temperature between about 90* and about 150*C. for a time of from about 10 seconds to about 2 hours until formaldehyde in an amount equal to at least 0.3 percent by weight of said cotton fibers is durably fixed in the fabric and the cotton fibers are effectively crosslinked, said heating being conducted while governing the amount of water vapor in said atmosphere to control the amount of moisture in said fabric and thereby regulate the amount of strong acid catalyst formed by the reaction of formaldehyde and sulfur dioxide, a reaction in which water is the limiting factor, to provide a self-limiting reaction system; and drying the thus crosslinked fabric.

Claim 12

A process according to claim 8 wherein the fabric is treated in a pad bath containing an amide prior to moisture conditioning.

Claim 13

A process according to claim 8 wherein urea or thiourea is applied to the fabric together with the formaldehyde solution.

Claim 14

A process according to claim 10 in which the fabric being treated is a flat fabric and the crosslinked fabric is washed to remove residual reactants therefrom, and the washed, crosslinked fabric is dried.