US3310419A

US3310419A - Process for treating cellulosic material with flameproofing composition

Info

Publication number: US3310419A
Application number: US273272A
Authority: US
Inventors: George M Wagner
Original assignee: Hooker Chemical Corp
Current assignee: Occidental Chemical Corp
Priority date: 1963-04-16
Filing date: 1963-04-16
Publication date: 1967-03-21
Anticipated expiration: 1984-03-21
Also published as: NL6404149A; GB1065547A; BE675066A; DE1285442B

Description

United States Patent Oflice 3,316,419 Patented Mar. 21, I967 3,310,419 PROCESS FOR TREATlNG CELLULOSIC MATE- .RIAL WKTH FLAMEPROOFING COMPOSITION George M. Wagner, Lewiston, N.Y., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing, Filed Apr. 16, 1963, Ser. No. 273,272

7 Claims. (Cl. 117-622) This application is a continuation-in-part of my copen'ding application Ser. No. 148,803,filed Oct. 31, 1961, now abandoned.

This invention relates to an improved composition and process for treating cellulosic materials and more particularly relates to an improved composition and process for the treating of cellulosic textile materials to render them substantially flame retardant.

In the past, considerable work has been done in the development of processes for flameproofin-g cellulosic materials and particularly cellulosic textiles, utilizing methylohphosphorus polymers which have nitrogen atoms incorporated into the polymer, which polymers are well known to have excellent flame-retarding properties. In the course of this Work, it has been found that it is generally not enough just to produce a cellulosic textile material which is flame-retardant, but it is further desirable that this flame retardancy is retained even after repeated launderings, while, at the same time, retaining the desired, hand, durability, tear strength, and tensile strength of the material. In this regard, there is considerable evidence that the manner in which the methyloy-phosphorus polymers are cured after being applied to the cellulosic textiles, determines to an appreciable extent whether the final treated textile product has these desired characteristics.

To illustrate the above, it has been found that heat curing of the methylol phosphorus polymers after they have been deposited on the cellulosic textiles frequently results in a reduction in the tear strength and tensile strength of the fabrics. Moreover, where the heat curing is not carefully controlled, uneven curing of the polymer occurs, often to the extent that the polymer in the interior of the fabric still has appreciable water solubility.

The durability of the flame-retardant finish in such products is generally adversely affected and the cellulosic materials frequently are stiff and/ or boardy and, hence, not desirable.

To overcome these difliculties, in one prior art process it is proposed to effect the cure of the methylol-phosphorus polymers using ammonia, rather than heat. In this manner, the difficulties encountered in heat curing of the resin are overcome. This method has not, however, been completely satisfactory in that at the time of the ammonia cure, the resin is soluble in the ammonia and is dissolved out of the fabric. Thereafter, as the dissolved resin becomes insolubilized by the ammonia, it is redeposited on the surface of the material in the form of white spots, which are detrimental to the appearance of the textile material.

In my Icopending application Ser. No. 148,803, filed Oct. 31, 1961, a process is disclosed which overcomes the difliculties encountered in the use of an ammonia cure for the methylol-phosphorus polymers in the textile materials. In this process, the cellulosic textile impregnated with the polymeric material is subjected to an initial heat curing operation wherein the polymeric material is partially cured, only to the extent that it is substantially insoluble in the ammonia solutions. Thereafter, an ammonia cure is used to eifect a final insolubi'lization of the polymeric materials. Although the cellulosic textile materials treated in accordance with this procedure do not undergo the reduction in tear strength and tensile strength of materials which have been subjected only to a heat cure and do not have the white surface deposits of resin as do materials which are subjected only to an ammonia cure, in some instances it has been found that the heat cure cycle of the process is dificult to control and the bath of polymeric material with which the textile is treated may become unstable in an undesirably short period of time.

A further difliculty which has been encountered in the fire processes for preparing flame-retardant cellulosic materials is that, frequently, these processes can only be used on yard goods at the textile mill and are not adaptable for use on consumer goods in a commercial laundry. In many instances, this may be disadvantageous in that it limits the application of flame-retardant finishes to new consumer articles made from yard goods which have previously been given a flame-retardant finish. Moreover, with such processes, it may not be possible to re-treat consumer articles which have previously been flame retardant so as to renew the flame-retardant properties. Accordingly, it is desirable for a process for treating cellulosic materials to render them flame retardant to be adaptable for application in both the mill to yard .goods and in commercial laundries to finished consumer articles.

It is, therefore, an object of the present invention to provide an improved composition and process for treating cellulosic materials to render them substantially flame retardant.

A further object of the present invention is to provide an improved composition and process for flameproofing cellulosic textiles whereby the resulting textile material is rendered durably flame retardant and undergoes substantially no reduction in tear strength or tensile strength.

A further object of the present invention is to provide a process and composition for preparing flame-retardant cellulosic textile materials, which process is readily adapted for application in both textile mills and in commercial laundries.

A still further object of the present invention is to provide a composition and process for preparing flameretardant cellulosic textiles wherein the criticality of the curing portion of the process is substantially reduced and the stability of the impregnated composition used is materiailly increased.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the process of the present invention includes impregnating a cellulosic material with a polymerizable composition comprising a tetrakis(ahydroxyorgano)phosphonium halide, a water-soluble, cy-

clic copolymerizable nitrogen-containing compound, a

copolymerizable compound which is a carbamic acid derivative such as urea, .thiourea, biuret, ethylene urea, 01' dicyandiamide, and an alkaline inorganic stabilizer, heating the thus-impregnated material at a temperature and for a period of time sufficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions, and, thereafter, contacting the material containing the thus-partially polymerized composition with ammonia in an amount and for a period of time suflicient to substantially completely cure the composition and to render it substantially completely water-insoluble. The cellulosic materials, such ;as cellulosic textiles, treated in accordance with the above process are found to be durably flame retardant, even after repeated launderings and show no evidence of resin spotting on the surface as a result of partial dissolving of the impregnating composition during the ammonia cure. Additionally, the hand of the fabric is essentially unchanged from that of the untreated fabric and the tear strength and tensile strength are comparable to that of the untreated fabric. Moreover, it is found that the heat curing portion of the process may be carried out at appreciably higher temperatures than have heretofore been possible, while still obtaining a uniform cure of the polymerizable composition, and there is further found to be a marked increase in the stability of the polymerizable impregnating composition.

It has been found that these latter two improvements, i.e., the reduction in criticality of the heat cure and improvement in the stability of the impregnating bath, result from the use of the alkaline inorganic stabilizer, rather than the acid or acid-forming stabilizers, such as triethanolamine which have heretofore been used. It is believed that in some manner the basic inorganic stabilizers effect a retardation or inhibition of the rate at which the polymerization of the polymerizable substituents of the impregnating composition takes place during the heat curing portion of the process. For this reason, close critical control of the temperatures used for the heat cure are not required and the impregnating bath remains in usable condition over a longer period of time at higher temperatures, thus reducing the number of times replacement of the bath is necessary. It is to be further appreciated that the above-described process has been found to be equally adapted for application on yard goods using mill equipment and on consumer articles using commercial laundry equipment.

More specifically, in the practice of the present invention, the polymerizable composition with which the cellulosic material is impregnated is preferably an aqueous composition. This composition will generally be comprised of the following substituents in the following proportions:

Tetrakis a-hydroxyorgano phosphonium halide compound 10-40 percent by Water-soluble cyclic copolymerizable Weight.

nitrogen-containing compound 5-15 percent by weight. Carbamic acid derivatives 1-10 percent by weight. Alkaline inorganic stabilizer .25.75 equivalent of 'base per mole of phosphonium compound.

Water 35-80 percent by weight.

It will be appreciated, however, that the above proportions of the substituents of the impregnating compositions are merely exemplary of those which may be used, and other proportions of these materials which will impart the desired flame retardancy to the cellulosic material treated may also be employed.

The tetrakis(a-hydroxyorgano)phosphonium halide compound of the subject composition may be further defined as a compound having the formula:

wherein R is selected from the group consisting of hydrogen, lower alkyls having between about 1 and about 6 carbon atoms, halogenated lower alkyls having between about 1 and about 6 carbon atoms, lower alkenyls having between about 1 and about 6 carbon atoms, halogenated lower alkenyls having between about 1 and about 6 carbon atoms, aryls having between about 5 and about 10 carbon atoms, halogenated aryls having between about 5 and about 10 carbon atoms, cycloalkyls having between about 3 and about 6 carbon atoms, halogenated cycloalkyls having between about 3 and about 6 carbon atoms, and X is a halogen, such as chlorine, bromine, fluorine or iodine. Typical examples of suitable tetrakis(a-hydroxyorgano)phosphonium halide compounds are tetrakis (hydroxymethyl)phosphonium chloride, tetrakis(hydroxymethyl)phosphonium bromide, tetrakis(hydroxyethyl) phosphonium chloride, tetrakis(a-hydroxypropyl)phosphonium chloride, tetrakis(ot-hydroxyallyl)phosphonium chloride, tetrakis(a-hydroxybenzyl)phosphonium chloride, tetrakis(a-hydroxymethyl-cyclohexyl)phosphonium chloride, tetrakis a-hydroxypropionyl phosphonium chloride, tetrakis(a-hydroxybutanol)phosphonium chloride and mixtures thereof. The phosphonium compounds may be used in monomer form or in a partially polymerized for, so long as they are still water-soluble. For eX- ample, tetrakis(hydroxymethyl)phosphonium chloride, Which is the preferred phosphonium compound, may be heated to effect partial polymerization before dissolving it in the solution.

Water-soluble cyclic nitrogen-containing compounds suitable for use in the present invention include the tri* azines and the dimethylol cyclic alkylene ureas. Typical examples of suitable triazines include the methylol melamines, such as mono-, di-, and trimethylol melamine; modified methylol malamines, such as the trimethyl ether of trimethylol melamine, triazones, such as dimethylol triazone; and mixtures thereof. Typical examples of suitable cyclic alkylene ureas include dimethylol ethylene urea, dimethylol propylene urea, and the like. Of these, trimethylol melamine is preferred and for this reason hereinafter primary reference will be made to this compound.

As has been indicated hereinabove, the carbamic acid derivatives used in the present invention are exempified by urea, thiourea, biuret, ethyleneurea and dicyandiamide. Of these, urea and thiourea are preferred. By the incorporation of these compounds in the present composition, the amount of the more expensive tetrakis (ct-hydroxyorgano)phosphonium halide compound can be reduced, over that required when these compounds are not present. Inasmuch as urea or thiourea are preferred in the practice of the present invention, specific reference to these materials will be made hereinafter.

The alkaline inorganic stabilizer used in the present process may be any alkaline oxide, hydroxide, or carbonate, including bicarbonates, which has an appreciable solubility in the polymerizable impregnating composition. Exemplary of such stabilizers which may be used are the alkal metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, as Well as the corresponding alkaline earth metal compounds which have the requisite solubility. It is to be understood that by the term alkali metal it is intended to include sodium, potassium, lithium, cesium and rubidium. Of these, because of its low cost and ready availability, the preferred alkali metal is so dium, and, for this reason, primary reference hereinafter will be made to sodium compounds. Additionally, the term alkaline earth metals is intended to include the divalent metals of Group II of the Periodic Table, and particularly calcium, strontium, and barium. In view of the cost consideration, as has been pointed out hereinabove, coupled with the solubility requirement, the preferred inorganic alkaline stabilizers are sodium hydroxide, sodium carbonate, and sodium bicarbonate, with sodium hydroxide being specifically preferred.

The specifically preferred impregnating composition for use in the method of the present invention may contain the following substituents in the following proportions:

Tetrakis (hydroxymethyl phos-v phonium chloride 2332 percent by weight. Sodium hydroxide .4-.6 equivalent of base per mole of phosphonium chloride com- 7 pound.

Trimethylol melamines 6-9 percent by weight.

Urea 4-7 percent by weight. Water 48-65 percent by weight.

In addition, to these, the impregnating composition may also contain other substituents, such as fabric softeners,

.sition.

'5 wettingagents and the like. Generally, where these latter types of materials are included in the impregnating composition, they will be present in amounts up to about 3 percent by weight of the total composition.

In formulating polymerizable impregnating compositions of the present invention, the non-aqueous substituents are added to the water, preferably in the order set forth hereinabove. Generally, agitation of the bath is desirable in order to insure that the non-aqueous substituents will be substantially completely dissolved in the aqueous portion of the bath. Once the impregnating bath has been formed, it is preferably maintained at a Q temperature below about 85 degrees Fahrenheit, in order to obtain maximum stability and useful. bath life. Typical operating temperatures for the impregnating bath are about 65 to about 85 degrees Fahrenheit. t will be appreciated that higher and lowertemperatures be used, although the use of temperatures substantially in excess of about 85 degrees Fahrenheit may result in the reduction of the time of useful bath life. It is to be further noted that during periods of high ambient temperature, it may be desirable to use ice to cool the impregnating compo- In such instances, it has been found that replacement of about to about 25 percent of the water in the impregnating bath with ice will generally be sufficient to maintain the bath temperature Within the desired range, Without adversely affecting the concentration of the impregnating composition.

Once the polymerizable impregnating solution has been prepared, in the manner indicated hereinabove, the solution may be applied to the cellulosic material, such as cellulosic textiles, in any convenient manner. Generally, the mode of application of the polymerizable solution to the textile will depend upon the formof the textile being treated. As has been indicated hereinabove, the composition and process of the present invention may be utilized:

Accordingly, when yard goods are to be processed, utilizing mill both with yard goods and with consumer goods.

apparatus, the polymerizable solution maybe formulated in a padding box and the cellulosic material to be treated immersed in the solution. Thereafter, impregnationof the material is effected by feeding the goods through a pad or squeeze roll or other suitable means for removing the excess solution. Where consumer goods, such as sheets, night gowns, industrial clothing, and the like, are to be treated, the process of the present invention may be carried out in commercial laundry-type equipment. In these instances, the polymerizable impregnating solution may be formulated in any desired container and, thereafter, the goods to be treated may be brought into contact with the solution. his contact may be effected in any desired manner as, for example, by dipping the goods in the solution by hand, by wetting out the goods in a Wash wheel, or by impregnating the goods in an extractor. Generally, this latter method of impregnation is preferred in that by its use the amount of solution lost can be reduced to an insignificant amount. 7

It is to be noted that an important factor in the present method is the amount of resin add-on in the cellulosic materials which have been treated. Obviously, a-resin add-on which is too low may result in a product which has poor flame retardancy and/or a product in which the durability of the flame retardancy after repeated launderings is reduced. Moreover, it has been found that a resin add-on which is too great may result in a product which has an unsatisfactory hand, i.e., a product which is stiff and/or boardy. Accordingly it is important that the cellulosic material treated is given a resin add-on which provides both satisfactory flame retardancy and durability, without adversely effecting the hand of the material, i.e., a flame-retardant amount. Generally, it has been found that resin add-ons within the range of about 16 to 24 percent by weight of the material treated give satisfactory results. It will be appreciated, however, that resin add-ons which are greater or lesser than these preferred amounts may be used in some instances, depending upon the type and weight of the cellulosic material being treated.

Inasmuch as the resin add-on of the finally obtained flame-retardant cellulosic material is largely dependent upon the amount of wet pick-up of the polymerizable impregnating solution during impregnation, it will be apparent to those in the art that control of the amount of Wet pick-up during the impregnating step is an important factor, regardless of whether the impregnation is carried out in mill apparatus or in commercial laundry apparatus. Generally, it has been found that wet pick-ups in the range of about 65 to about 100 percent by weight of the material being treated will give a finished product having the desired resin add-on. Here, again, however, as with the amount of resin add-on, it will be appreciated that amounts of wet pick-up which are lesser than or greater than the preferred amounts indicated above, may be used to give satisfactory results, in some instances, depending upon the type and weight of the fabric being treated.

Where the impregnation of the cellulosic textile is carried out in mill apparatus, as, e.g., in the pad bath, the amount of wet pick-up in the material may be controlled by varying the amount of pressure on the pad or squeeze roll. Similarly, where the impregnation of the cellulosic textile is carried out in commercial laundry equipment, the wet pick-up of the impregnating solution in the textile may be controlled by effecting removal of the excess impregnating solution in any convenient manner. For example, the impregnated cellulosic textile may be run in an extractor or similar centrifuge-type of apparatus to remove suflicient of the impregnating solution to give the desired wet pick-up. In this regard, it is noted that although removal of the excess impregnating solution may be effected in wringer-types of apparatus, wherein the impregnated articles are squeezed to remove excess solution, such means are generally not preferred. This is because of the difficulty when using such equipment in obtaining a substantially uniform amount of resin pick-up throughout the entire article. Generally, it has been found when utilizing commercial laundry apparatus to effect impregnation of the cellulosic textile materials, that the amount of wet pick-up in the articles should be within the range of about 65 to about 85 percent by Weight, so that the final product has a resin add-on within the range of about 16 to about 22 percent by weight. Most preferably, the amount of wet pick-up in the impregnated articles is within the range of about 70 to about 75 percent by weight, so as to give a resin add-on of about 19 to about 21 percent by weight. With cellulosic textile materials treated in mill apparatus, the preferred amount of wet pick-up is Within the range of about 60 to about percent by weight, so as to give a resin add-on within the range of about 18 to about 24 percent by weight. Most preferably, the wet pick-up is within the range of about 70 to about 75 percent by weight, so as to give a resin add-on within the range of about 19 to about 21 percent by weight. Once the cellulosic material has been impregnated and the wet pick-up of the polymerizable solution on the material has been adjusted to the desired value, the material is subjected to heat at a temperature and for a period of time sufficient to partially polymerize the polymerizable impregnant only to the extent that it is substantially insoluble in ammonia-containing solution. Generally, this heating will be such that aldehyde groups, generated during the polymerization of the composition will undergo substantially no reaction with the cellulose molecules of the treated material. Additionally, the extent of the polymerization will be such that there is a substantial insolubilization of the composition in ammonia-containing solutions. Generally, it has been found that temperatures of from about 200 to about 320 degrees Fahrenheit and curing times from about 0.5 minute to about one hour may be used, the longer curing time being used at the lower temperatures. It will be appreciated, however, that other curing temperatures and times, outside the above ranges, may also be used Where they result in a similar partial polymerization of the impregnating composition only to the extent that there is a substantial insolubilization of the composition in ammonia-containing solutions, without detrimentally affecting the cellulosic material or the composition with which it is impregnated.

The above heating of the impregnated cellulosic material may be carried out in any convenient equipment, either of the mill type or of the type found in commercial laundries. For example, the heat curing operation may be carried out in a loop oven or in a conventional roller type oven, or it may be carried out in a tumble type dryer or other similar drying equipment. Additionally, it will be appreciated that in some instances, it may be desirable to subject the impregnated cellulosic material to a drying operation, either prior to or simultaneously with the heat curing operation. Where the drying operation is performed prior to the cure, it has been found generally to be preferable that the drying condtions be adjusted so as to provide a moisture content in the dried fabric of about to about percent. In this manner, there is substantially no curing of the impregnating composition during the drying operation so that the extent of curing can be more closely controlled in the separate heat curing step. Where drying and curing are carried out simutlaneously, it is generally preferable that the combined operation be carried out at low temperatures and long times, generally within the ranges which have been set forth hereinabove. In this regard, it will be further appreciated that where the impregnated cellulosic materials are consumer items, and the processes being carried out in commercial laundry apparatus, the heat curing operation will generally be carried out at somewhat lower temperatures than those which are used when the drying is carried out in mill apparatus. For example, when using a tumble-type dryer to effect the heat cure of the polymerizable impregnating composition, dryer stack temperatures within the range of about 200 to about 250 degrees Fahrenheit and drying times Within the range of about 20 to about 60 minutes are preferred. In contrast, where the heat curing operation is carried out in mill apparatus, such as a conventional roller-type oven, the preferred curing temperatures used are within the range of about 270 to about 320 degrees Fahrenheit With cure times within the range of about 1 to about 5 minutes.

Once the impregnated cellulosic material has been subjected to the heat curing operation, and the desired partial polymerization of the composition in the material is obtained, the treated cellulosic material is subjected to a chemical curing operation, using a source of ammonia. The ammonia may be supplied for the curing operation as ammonia gas, aqueous ammonia, including ammonium hydroxide, solutions of amino compounds containing at least two reactive hydrogen atoms per molecule, such as amines containing a primary amino group, hydrazine, alkyl-substituted hydrazine and the like, ammonium carbonate, or other readily dissociated weak acid salts of ammonia such as ammonium acetate, ammonium formate, and the like. Additionally, the chemical cure of the impregnated cellulosic material may be effected using a composition comprising a mixture of the ammonium salt of a strong acid, such as ammonium sulfate, an alkali metal carbonate, and an alkali metal bicarbonate, such as sodium carbonate, and sodium bicarbonate. This mix ture is dissolved in Water, and the impregnated cellulosic material is brought into contact with the resulting aqueous solution. For ease of operation, it is generally preferred to effect the chemical cure of the polymerizable impregnating composition with an aqueous solution of ammonia, such as ammonium hydroxide or the aforementioned aqueous solution of the mixture of ammonium sulfate, sodium carbonate and sodium bicarbonate. The chemicalcure is carried out for a period of time sufiicient to upon the amount of resin add-on to be obtained in the treated material, as Well as the nature of the cellulosic material itself, chemical curing times of about 1 to about 5 minutes have been found to be typical. Similarly, the ammonia concentration used in the chemical curing operation may also vary although concentrations of about 3 to about 10 percent by weight have been found to give satisfactory results.

As with the impregnating and heat curing steps of the present process, the chemical curing operation may also be carried out in either mill apparatus or commercial laundry apparatus, depending upon the form of the cellulosic textile material being treated. Where yard goods are being treated, the chemical curing operation may be accomplished in a padder or on a jig, utilizing the curing composition as described hereinabove. In mill set-ups Where the padder is arranged in tandem with the curing oven, the chemical curing step may be carried out continuously. Where, however, the finishing operations on the treated fabric are to include scouring in a jig, the ammonia cure may be more conveniently carried out in a jig during the first end. Exemplary of a specific cur ing composition which may be used with such mill apparatus is one containing the following components in the following amounts:

Water gallons Ammonium sulfate pounds 50 Sodium carbonate do 30 Sodium bicarbonate do 50 After impregnation of the fabric in this composition, a hold time of at least about 1 minute is generally necessary before subsequent processing operations, such as scouring, are carried out.

Where the chemical curing operation is to be carried out on consumer articles, using commercial laundry apparatus, the chemical curing step may conveniently be effected utilizing a wash wheel. curing step will constitute the first cycle of the after- Washing operation. In such procedure, a curing solution comprising about 100 gallons of Water, to which has been added 2 gallons of 28 percent ammonia, is added to the Wash wheel, and the cellulosic textile materials agitated in this composition for about 3 minutes. Alternatively, a curing composition, similar to that used in the mill apparatus, may be added to the wash wheel. Such composition may contain the following components in the following amounts:

Water gallons 100 Ammonium sulfate pounds 25 Sodium bicarbonate do 15 Sodium carbonate do 25 The curing operation is carried out by adding the treated cellulosic materials to a wash Wheel containing this solution and running the wheel for a period of about 1 minute.

It is to be noted that, in general, the concentration of the ammonia curing solution used in commercial laundry apparatus may be less than that used in mill-type apparatus. The reason for this is that in the commercial laundry-type apparatus, a more complete saturation of the cellulosic material with the ammonia curing solution is generally obtained than in mill-type apparatus. Accordingly, a more effective utilization of the ammonia content of the curing solution is possible and hence lower concentrations of ammonia in the solution can be used.

Following the chemical cure of the cellulosic material, the material is preferably scoured or washed to remove unpolymerized materials and the like. Where the present process is carried out on yard goods using mill apparatus, this scouring operation may be effected using any of In such operation, the

the conventional scouring processes, such as rope scouring, continuous open width scouring, and jig scouring. The scouring may conveniently be carried out using, as, e.g., an aqueous soak solution containing small amounts of sodium carbonate and perborate. Where commercial laundry equipment is used to carry out the present process, the washing may be carried out in a wash wheel, immediately following the chemical curing operation. In both instances, the scouring or washing operation is then preferably followed by a drying operation wherein the treated fabric is dried in a conventional manner and may then be subjected to any normal finishing operation such as sanforizing, calendering, and the like.

The cellulosic materials, such as cellu'los'ic textile materials, treated in accordance With the procedure set forth hereinabove, whether utilizing mill-type apparatus or commercial laundry-type apparatus, have been found 'to be durably flame retardant, even after numerous launderings. Additionally, such materials are found to have a tear strength, tensile strength and hand which are substantially unchanged from those of untreated materials. The thustreated cellulosic tetxiles are further found to be characterized by the absence of .deposits of resinous materials on the surface thereof which deposits have characterized textile materials which have been processed by prior art methods which utilize only a chemical curing operation. Moreover, the criticality of the conditions under which the heat curing portion of the present process is carried out have been found to be measurably reduced and the stability of the polymerizable impregnating composition has been substantially increased.

In order that those skilled in the art may better understand the method of the present invention and the manner in which it may be practiced, the following specific examples are given. In these. examples,;all temperatures are in degrees Fahrenheit and all quantities are in percent by weight, unless otherwise indicated. Additionally, the flame retardancies reported were determined in accordance with 'Il'le procedure of the American Association of Textile Chemists and Colorists, Test AATCC Base 34- 1952; tensile strengths were determined in accordance with the procedure of Fed. Spec. CCCT-19l6, 5100, and shrinkages were determined in accordance with the procedure of Fed. .Spec. CCCT-191-6, 7550.

Example 1 The following aqueous composition was formulated:

Percent by weight Tetrakis(hydroxymethyl)phosphonium chloride (80 percent aqueous solution) 27.3 Trimethylol melamine 7.3 Urea 4.5 Sodium carbonate 4.2 Water 56.7

This composition was applied to cotton sheeting fabric by dipping the fabric into the solution, and, thereafter, squeezing the fabric until a 100 percent wet pick-up was obtained. The thus-impregnated cotton sheeting was dried for 1 minute at 250 degrees Fehrenheit and cured for 1 minute at 280 degrees Fahrenheit. The treated material was then divided into four samples which samples were then given the following ammonia cures:

A 5 percent aqueous solution Of NH3. B percent aqueous solution Of (NH4)2CO3. C Aqueous solution of 7 percent (NH SO 2 percent Na CO D None.

to These samples were then dried and found to have the following percent resin add-on:

B 16.9 C 15.7 D 13.3

The .char, in inches, of these samples both initially and after five 1 hour boil cycles, wherein the samples were boiled .in an aqueous solution of about 0.2 percent soap and about 0.2 percent sodiumcarbonate for ,1 hour, rinsed in clear water, and the boiling cycle repeated, were as follows:

A B C 'D Char initial 2.8 2.8 3.3 6.3 Char after five 1 hour boil cycles- 3.8 3.5 3.3 Burn Example 2 The following composition is formulated containing the components in the amounts shown:

Percent by weight Water 53.9 Trimethylol melamine 7.7 Sodium hydroxide 3.2 Urea 4.6 Tetrakis(hydroxymethyl)phosphonium chloride percent aqueous sol.) 28.0 Fabric softener 2.5 Wetting agent 0.1

Cotton sheeting fabric was impregnated with this formulation by immersing the fabric in the solution and, thereafter, subjecting the fabric to squeezing so as .to obtain a 10 0 percent wet pick-up on the fabric. The thus-impregnated fabric was thondried for 1.5 minutes at 250 degrees Fahrenheit and cured for 1 minutes at 280 degrees The thus-cured material was given an .am-

Fahrenheit. monia cure by immersing the material in an aqueous solution containing 7 percent ammonium sulfate, 3 percent sodium carbonate, and 6 percent sodium bicarbonate. The percent of resin add-on of the thus-treated fabric was 20.6 percent. The tensile strength of the fill of the fabric was 45 pounds as compared to a tensile strength of untreated fabric of 48 pounds. The initial char obtained on the treated fabric was 3.5 inches and the char after 20 1-hour boil cycles was 4.8'inches.

This example may be repeated using other carbamic acid derivatives such as thiourea, biuret, ethylene urea or dicyanodiamide instead of urea and/ or using solutions of amino compounds such as ethylamine or hydrazine to effect the ammonia cure, to obtain similar results.

Example 3 v A polymerizable impregnating composition was formulated containing the following components in the following amounts:

Water gallons 36 Tetrakis(hydroxymethyl) phosphonium chloride (80 percent aqueous solution) pounds 300 Sodium hydroxide (40 percent aqueous solution) do 67 Urea do 49 Trimethylol melamine do 62 Fabric softener gallons 2.5 Wetting agent pints 1.0

The total weight of the impregnating solution was 800 pounds. An eight-ounce herring bone twill cotten fabric was then impregnated with the above composition by passing it through a padder utilizing a pressure of 6 tons on the pad rolls. The thus-impregnated fabric had a wet pick-up of 75 percent. The fabric was then dried in a conventional tenter frame at 280 degrees Fahrenheit for 20 seconds, and cured in aroller-type oven for 2 minutes at a temperature of 300 to 310 degrees Fahrenheit. The

fabric was then padded through an ammonia curing bath having the following composition:

Ammonium sulfate pounds 100 Sodium carbonate do 60 Sodium bicarbonate do 100 Water gallons 200 The fabric was then scoured in a soda ash-sodium perborate bath and rinsed with hot water in a series of open width washers and then dried on steam heated cans. The thus-treated fabric was found to have a resin add-on of about 21.1 percent. The initial char of the treated fabric was 4.0 inches and the char after 20 boil cycles was 4.0 inches. The tensile strength of the fill of the treated fabric was found to be 84 pounds as compared to the fill tensile strength of untreated fabric of 89 pounds. The hand of the fabric was soft, comparable to that of the untretaed fabric, and the shrinkage of the treated fabric, warp X fill, was (3.0) X (+2.0) as compared to that of the untreated fabric of (--16) x (+4).

Example 4 An impregnating composition was formulated containing the following components in the following amounts:

Water gallons 43 Tetrakis(hydroxymethyl)phosphonium chloride (80 percent aqueous solution) pounds 397 Sodium hydroxide (50 percent solution) do- 71 Urea do 65 Trimethylol melamine do 83 Fabric softener gallons 2 Wetting agent pints 1 The above solution was charged to a standard laundry wash wheel and 100 cotten bed sheets, type 140, were placed in the Wheel. After 5 minutes of tumbling, the impregnated sheets were removed from the wash wheel, extracted for minutes in a 60 inch extractor operating at 600 r.p.m. The extracted sheets were found to have a wet pick-up of about 75 percent. These sheets were then placed in a standard steam heated tumble dryer and tumbled for 1 hour, the temperature of the exit gases being about 230 degrees Fahrenheit. The dried sheets were removed and placed in a wash wheel containing the following solution:

Water gallons 100 Ammonium sulfate pounds 30 Sodium carbonate do Sodium bicarbonate do 30 The Wash wheel was run for 5 minutes, the solution dropped, and the sheets were given a conventional commercial wash with the exception that the bleach cycle employed 7.5 pounds of sodium perborate (5 percent by weight of the fabric). The washed sheets were then extracted, tumble dried and passed through a mangle. The thus-treated sheets were white, soft, odor free, and had a resin add-on of 20.5 percent. The tensile strength of the treated sheets, fill x warp, was 49 X 54 as compared to untreated sheets of 52 X 56. The initial char of the treated sheets was 3.8 inches, after 50 commercial washes, 4.1 inches, and after 100 commercial washes 4.0 inches.

Example 5 A polymerizable impregnating composition is formulated using the following substituents in the following proportions 250 yards of broadcloth (136 X 64) was impregnated with this composition by passing it through a padder at 1.5 tons pad pressure. The resulting material had a wet pick-up 76 percent. The fabric was then passed through a tenter frame for drying at 180 degrees Fahrenheit; Retention time was 1.25 minutes. The drying conditions were adjusted so that the dried material had a moisture content of 5 to 10 percent. The fabric was then cut into three sections and cured as follows:

Cure Temp, F 320 Thereafter, the three pieces were subjected to an ammonia cure using a 20 percent aqueous solution of (NH CO The resin add-on in the pieces after the cure was as follows:

Percent A 21 B 23 C 21 The tensile strength, in pounds, of the filling was as follows:

Pounds A 43 B 31 C 26 The hand of all three pieces was extremely firm and undesirably stiff. The initial char length of the pieces was as follows:

Inches A 4.5 B 6.0 C 4.3

Example 6 A polymerizable impregnating composition is prepared using the following components in the following proportions:

Percent Tetrakis(hydroxymethyDphosphonium chloride (80 percent aqueous solution) 36.0

Caustic soda (50 percent aqueous solution) 6.4 Urea 10.0 Trimethylol melamine 7.4 Wetting agent 0.1 Water 40.1

4 follows:

Cure Temp., 3 F Cure time, min

13-. The pieces were then given an ammonia cure as in Example 5, and the resin add-on of the resulting fabric was as follows:

The hand of pieces A, B and C was very soft and that of D was only slightly less soft. The initial char of the pieces was as follows:

Inches A 4.5 B 3.9 C 4.2 D 4.1

From a comparison of Examples and 6, it is seen that by using NaOH rather than triethanolamine, more uniform results were obtained even at high heat cure temperatures. This is seen particularly with regard to the hand of the treated fabric and the tensile strength.

It is to be understood that the cellulosic material treated in accordance with the present invention may be in the form of fibers, yarns, fabrics, films, pulp, paper, fiber board, wood, or the like. Additionally, for purposes of the'present invention, it is intended that wool also be included in those materials which may be treated, even though it is not classified as a cellulosic material. The present invention has been found to be particularly suitable for the treatment of textile materials which are porous in nature, and, therefore, are readily capable of absorbing resinous impregnating compositions. Included in such materials are cotton, rayon, wool, jute, and ramie textiles. This is not, however, to be taken as a limitation on the materials which may be treated by the process of the present invention, but merely as being exemplary of these materials.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention, as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A process for preparing flame-retardant cellulosic materials which comprises impregnating a cellulosic material with a polymerizable composition consisting essentially of a tetrakis(a-hydroxyorgano)phosphonium halide, a water-soluble cyclic copolymerizable nitrogen-containing compound, a copolymerizable compound which is a carbamic acid derivative, and an alkaline inorganic stabilizer, heating the thus-impregnated material at a temperature and for a period of time sufficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions, and thereafter, contacting the material containing the thus-partially polymerized composition with ammonia, in an amount and for a period of time sutficient to substantially completely cure the composition and render it substantially completely water-insoluble.

2. A process for preparing a flame-retardant cellulosic material which comprises impregnating the cellulosic material with a polymerizable composition consisting es- 14 sentially of a water-soluble .cyclic copolymerizable nitrogen-containing compound, a copolymerizable compound selected from the group consisting of urea and thiourea, an alkaline inorganic stabilizer, and a tetrakis(a-hydroxyorgano)phosphonium halide .having the formula:

wherein R is selected from the group consisting of hydrogen, lower alkyls having between -1 and about 6 carbon atoms, halogenated lower alkyls having between about 1 and about 6 carbon atoms, lower alkenyls having between about 1 and about 6 carbon atoms, halogenated lower alkenyls having between about 1 and about 6 carbon atoms, aryls having between about 5 and about 10 car-bon atoms, halogenated aryls having between about 5 and about 10 car-bon atoms, cycloalkyls having between about 3 and about 6 carbon atoms, and halogenated cycloalkyls having between about 3 and about 6 carbon atoms, and X is halogen, heating the thus-impregnated material at a temperature and for a period of time sufficiently to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions and thereafter contacting the material containing the thus-partially polymerized composition with ammonia, in an amount and for a period of time sufficient to substantially completely cure the composition and render it substantially completely water-insoluble.

3. A process for preparing a flame-retardant cellulosic textile material which comprises impregnating the cellulosic textile material with a polymerizable composition consisting essentially of tetrakis(hydroxymethyl)phosphonium chloride, trimethylolmelamine, a copolymerizable compound selected from the group consisting of urea and thiourea, and an alkaline inorganic stabilizer selected from the group consisting of alkali metal hydroxides, carbonates, and bicarbonates, heating the thus-impregnated material at a temperature and for a period of time sufficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions, and thereafter, contacting the material containing the thus-partially polymerized composition with an aqueous solution containing ammonia in an amount and for a period of time sufficient to substantially completely cure the composition and render it substantially completely water-insoluble.

4. The process as claimed in claim 3 wherein the tetrakis(hydroxymethyl)phosphonium chloride is present in an amount within the range of about 10 to 40 percent by weight, the trimethylolmelamine is present in amounts within the range of about 5 to about 15 percent by weight, the copolymerizable compound selected from the group consisting of urea or thiourea is present in an amount within the range of about 1 to about 10 percent by weight, the alkaline inorganic stabilizer is present in an amount within the range of about 0.25 to about 0.75 equivalent of base per mole of phosphonium chloride compound, and there is present about 35 to about percent by weight of water.

5. The process as claimed in claim 4 wherein the alkaline inorganic stabilizer is sodium hydroxide.

6. The process as claimed in claim 3 wherein the heating of the impregnated cellulosic textile material to effect partial polymeriaztion of the polymerizable impregnating composition is carried out at a temperature within the range of about 200 to about 320 degrees Fahrenheit and for a time within the range of about 0.5 minute to about 1 hour.

7. The process as claimed in claim 6 wherein the final cure of the partially polymerized impregnating composition in the cellulosic textile material is effected by contacting the material with an aqueous solution comprising References Cited by the Examiner UNITED STATES PATENTS 11/1956- Reeves et al. 1117136 10/1957 Reeves et a1. 117136 X 16 Reeves et' a1. 117-139.4 X Reeves et al 117136 X Morettu et a1. 1l7-136 X Coates 117-137 X WILLIAM D. MARTIN, Primary Examiner.

T. G. DAVIS, Assistant Examiner.

Claims

1. A PROCESS FOR PREPARING FLAME-RETARDANT CELLULOSIC MATERIALS WHICH COMPRISES IMPREGNATING A CELLULOSIC MATERIAL WITH A POLYMERIZABLE COMPOSITION CONSISTING ESSENTIALLY OF A TETRAKIS(A-HYDROXYORGANO)PHOSPHONIUM HALIDE, A WATER-SOLUBLE CYCLIC COPOLYMERIZABLE NITROGEN-CONTAINING COMPOUND, A COPOLYMERIZABLE COMPOUND WHICH IS A CARBAMIC ACID DERIVATIVE, AND AN ALKALINE INORGANIC STABILIZER, HEATING THE THUS-IMPREGNATED MATERIAL AT A TEMPERATURE AND FOR A PERIOD OF TIME SUFFICIENT TO PARTIALLY POLYMERIZE THE POLYMERIZABLE COMPOSITION ONLY TO THE EXTENT THAT IS IS SUBSTANTIALLY INSOULBLE IN AMMONIA-CONTAINING SOLUTIONS, AND THEREAFTER, CONTACTING THE MATERIAL CONTAINING THE THUS-PARTIALLY POLYMERIZED COMPOSITION WITH AMMONIA, IN AN ANOUNT AND FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY COMPLETELY CURE THE COMPOSITION AND RENDER ITS SUBSTANTIALLY COMPLETELY WATER-INSOULBLE.