US2482755A - Flameproofing of fibrous material - Google Patents

Description

Patented Sept. 27, 1949 FLAMEPROOFING OF FIBBOUS MATERIAL Florence M. Ford and William P..Hall, Wilmington, Dcl., asslgnors to Joseph Bancroft & Sons 00., Wilmington, Del., a corporation of Delaware No Drawing. Application May 29, 1945,

Serial No. 596,592

12 Claims. 1

This invention relates to the imparting of flame-resistance to cellulosicand protein fibrous materials, especially textiles, such, for example, as dress goods, duck, tarpaulins, draperies, and the like, in which the original hand and feel of thefabric is substantially retained and in the production of which no objectionable sacrifice of strength of the fabric results. The finish for D- timum results should have long life and should be resistant to water, repeated washing, soapings, and dry-cleaning and while it will burn on the application of a flame, the fire should go out on withdrawal of the flame, and there should be no undesirable afterglow.

This application is a continuation in part of our copending application Serial No. 514,822, filed December 18, 1943, now abandoned, and of our copending application Serial No. 539,798, filed June 10, 1944.

As set forth in said applications, we have discovered that a finish having the above characteristics can be obtained by treating the material with a strong acid, such as ortho-phosphoric acid, and with a soluble organic nitrogen containing base, for example, urea, as will be further described. We are aware that ortho-phosphoric acid and various phosphates have heretofore been suggested as flameproofing substances for fabrics. It has also been suggested to'react phosphoric acid and urea, dissolve the reaction product, impregnate, and dry. To the best of our information and belief, none of these has resulted in a commercially successful finish, the finish either being not permanent to water, soaping, or dry-cleaning, detrimentally destructive of hand and strength, or otherwise objectionable.

In the following description, reference will be specifically made to cellulosic materials. However, we have found that when rotein materials, such as wool or silk, are subjected to the same chemical and physical conditions, satisfactory durable flameproof properties are obtained without unduly aifecting the hand and strength of the fabric.

with the cellulose carries with it, into the complex, nitrogen containing groups from the base or compounds derived from the base during the processing.

That there is a combination of the cellulose, phosphoric acid and the base is. proven bythe fact that the'fabric gives a definite quantitative test for both nitrogen and phosphorus after the finishing, which includes washing and drying,

following the curing. Subsequent washings remove only negligible amounts of these elements so that after repeated washings satisfactory quantitative tests may be obtained for both nitrogen and phosphorus, proving that thedurable fiameresistance properties are produced by the presence of the phosphorus and the nitrogen in the complex. Taking urea as an example of certain of the usable bases, it, among other functions, seems to act as a buffer which prevents a tendering effect by the phosphoric acid on the fabric, inconsequence of which the original strength of the fabric is retained in large part. This is true also.

of other similar weak bases, if present in suflicient quantity.

When woolen fabrics or fabrics containing:

. tion and to assist in substantially maintaining the strength of the fabric. The fabric is-finally washed inv warm water and dried.

According to another method, the mixture of the acid and base is heated to say about F.,

cooled, the water added, and the solution or mixture applied as before. In this manner ammonia and complex nitrogen compounds are usually formed from the base and the solution or mixture is more nearly neutral at the time of application to the fabric which tends to obviate an attack on the equipment. Higher temperatures and longer time of heating may be used, thus obtaining solutions of a substantially neutral character.

In some cases the external heating is notnecessary, the ingredients reacting spontaneously in the solution, so at times the cooling is necessary to control the reaction. At othertimes the mixture also) may be heated for a short time, when exothermic reactions set in, necessitating cooling of the mix ture in order to control the reaction.

In these cases the heating has usually resulted,

as will be further described, in the alteration to reactions. a

Another method is to melt together the acid and the base, cool, add water,v and proceed as above -indicated.

Although the solution is generally applied to the fabrics at room temperatures, it may be applied at somewhat higher temperatures if so desired. At higher temperatures greater solubility of the ingredients is generally obtained. This is very beneficial, and in some cases the solution may be applied at nearly the boil, providing that no detrimental action takes place, as will be further shown.

During. the drying, which is of conventional character, the water is to be very largely removed from the material, and for this purpose we have found, merely by way of illustration, that passing the fabric through a drying atmosphere of 300 F. is sufflcient. The cloth remains in the dryer about 30 seconds, but only comes to 300 'F. for about several seconds.

The curing temperature should be carefully controlled. It must be high enough to cure, i. e., to bring about the chemical combination, within a practical time limit, but should not be so high that undesirable alterations of the cellulose and a corresponding loss of fabric strength occur. The

- the desired results. The amounts on the material and the time and temperature have an important relationship. By way of illustration, we have observed the following when a piece of cot-- ton fabric is padded with a solution containing 130 grams orthophosphoric acid (75%), 180 grams urea and 340 grams water (a molecular ratio of 1 phosphoric acid to 3 urea, and 15% phosphoric acid in the solution), given an ordinary squeeze (giving approximately 100% solution pick up by weight) and dried; (a) when cured at 250 F. for 120 minutes, the fabric has good flame-resist ance after a to 20 minute washing in water at.

180 ,F. but only fair resistance if given a soaping for minutes in Igepon T (a substituted amide of oleic acid-C11HaaCONM(-3CH2CH2SO3N8.) at 180 F., 100 parts Igepon T solution to 1 part cloth by weight; (b) when cured at 260 F. for 120 minutes, the flame-resistance is excellent after such a waterwash, and is still good after such soaping'; (0) when cured at 270 F. for 120 minutes, the flame-resistance is excellent after either such a washing or such a soaping; (d) when cured at 270 F. for 60minutes, the flameresistance is excellent after such a washing or such a soapins; (e) when cured at 280 F. for 30 minutes,.the flame-resistance is excellent after such a washing or soaping; (I) when cured at 340 F. for 10 minutes, the flame-resistance is excellent after the washing orafter the soaping; (a) when cured at400' F. for 1 minute, the flameresistance is excellent after such a. washing, but

is good after such a soaping.

If, now, the acid in the solution is reduced. say

to 6.9%, with the same solution pick up on the fabric, no results are obtained, whereas if the during the curing as described above.

fabric is cured at 340 F. for 5 minutes, good results-are obtained even after washing or soaping.

Within the range of curing temperatures mentioned, we have found that best results for most commercial purposes are secured in the range between 320 F. and 360 F. Curing times will vary, at these temperatures, from 15 minutes to 3 minutes.

The reaction on the cellulose takes place effectively on the acid side (lower pH). rather than on the basic side (higher pH), the pH being determined in this case by means of indicator solutions on the cured fabric.- We have found that between the pH values of 2 to 7 on the cured cloth (before washing) satisfactory results may be obtained. The preferred range of pH onthe fabric is from about 3 to 6.v The! durability of the finish will vary somewhat but, as indicated, a

gives satisfactory all-around re- -which will volatilize during the curing, leaving the pH on the cellulose of such an acidic value that the reactions of the process will take place Among the volatile bases suitable for the adjustment of the solution pH we may mention ammonium hydroxide, diethyl' amine, andisopropyl amine. For all practical purposes, ammonium hydroxide is satisfactory. In any case, the quantity of base added to adjust the pH of the solution is very small, the solution itself being usually of a satisfactory pH value. Of course, if pH is too high, flame resistance imparting acid may be added to adjust the pH of the solution. Generally, all that is required as to the pH of the solution, is that it should be such that, during the curing, the pH in the cloth will be brought down to the values previously mentioned. Usually, a pH for the solution approximately /2 pH higher than that of the cured cloth is satisfactory. One may go higher, provided that the pH comes down during the curing so as to produce the pH of the cured cloth above set forth.

The pH value of the cloth during curing determines to some extent the rate and degree of reaction between the acid and the cellulose. The lower the pH, the faster and more complete is the reaction, and the higher the pH, the slower and less complete is the reaction for a given time and temperature of curing. Also, at a given pH the completeness or extent of reaction may be 330 F. may be needed to obtainthe same degree of durability.

On fabrics, in addition to the padding described,

the solution may be applied by any of the methods well known in the textile art, such as spraying,

jigging,printing, coating, and the like. Irrespective of, the method of application employed, the

cloth is dried as, described to largely remove water.

The concentration of the solution itself is not critical and depends upon the number of applications, but the ultimate take-on on the finished fabric is important. For example, where the solution is to be applied by one run of the fabric therethrough, a solution of from about 30% to 70% active solids will suffice, depending upon the weight, absorbency and purity of the fabric, the

squeeze after impregnation, and the like. This,

.with a substantially 100% solution pickup, will give an ultimate take-on" (chemical take-on by combination) in the finished fabric of from about 8% to about 30% solids, which is a take-on which we have found to give satisfactory general all around results. A lower take-on may be had, providing only fair flame-resistance is desired, A take-on higher than 30% offers no substantial advantage. The ultimate take-on drops to these figures owing to the fact that there is some loss during the curing, and a further loss in the washing (which removes soluble excess chemicals). -If

. it be desired to make a number of separate impregnationsand dryings, a dilute solution may be employed, the number of runs being dependent upon such dilution. For example, with 20% to 30% solids solution, the desired results may be obtained, say in two runs, and at most three,

v usually. The ultimate take-on of basic element of the acid and of nitrogen in the finished (i. e. cured and washed and dried) material is impor- -tant, as will further appear.

recommended. Thus hydrochloric acid is not useful and nitric acid is not recommended, although the latter may be used in conjunction with other acids such as orthophosphoric acid as will be further shown.

Monobasic acids give the least satisfactory results, and the dibasic acids, while better, are not as desirable as the polybasic acids, as will further appear. The so-called polyacids containing excess atoms of the acid element are satisfactory, especially if they have a polybasic character. Many of these acids are known, especially of the phos-. phorous type.

Salts of the acids may be used, providing the base making up the salt is either volatile duringthe conditions of the processing, or takes an active part in the process. Among the former we mention ammonium phosphate, dimethyl amine phosphate, and isopropyl amine phosphate;

among the latter, guanidine phosphate, guanyl urea phosphate, and urea phosphate.

Substitution products of the acids may be used, providing the substitute groups do not destroy the flameproofing properties. phamic, phosphamic, diamido phosphoric and dinitride hexaphosphoric acid. Other acids of complex nature containing nitrogen and phosphorus may be used, providing they are strong enough to combine with the fibers in question. Most of these acids, however, are not commercially avail- Examples are sul-' 1 able. The so-called organic esters may be usedprovided they do not contain excessive carbon and do not prevent the acid group from forming.

mended, except fluo'phosphoricacid. because of the instability of the halogen groups in solution and on the fabric.

As to the organic bases, which are desirably always present in excess, these may be weak or strong. However, when comparing the acid used in the process with the nitrogen bases the latter all have a decided basic character, the distinguishing between weak and strong being based upon their behavior in the solution and on ouring. For example, if a substantial change in concentration of the base causes no appreciable change in the solution pH or the cured cloth pH, then the base is classified as weak. If, however, the same change is made and a decided change in pH is obtained then the base is classified as a strong base. For example excess urea may be added to a finished solution without appreciably altering the pH; on the other hand, if excess guanidine is added to a finished solution the pH will be substantially increased, and if sufficient quantity is added the solution may become so decidedly'basic that unsatisfactory results will be obtained. In other words, with the strong bases, any excess must be such as will not put the cured cloth (before washing) definitely on the basic side. s

For weakbaseswe may, for example, use urea, biuret, cyanacetamide, semicarbazide, dicyandiamide, acetamide, formamide and lemamine. In

some cases, where the solubility of the weak base is not high even in hot solutions, it becomes undesirable to use said base alone, but it can be effectively used in conjunction with another base or bases. For example, melamine is not sumciently soluble with phosphoric acid to produce a good working solution. It may,- however, for example, in conjunction with urea, serve to produce a good working solution.

Salts of these bases with a fiame resistant acid may be used in part, such as, for example, the sulfates, phosphates, and sulfamates, in which cases the acid introduced by the base replaces a corresponding quantity of acid in the solution formula;

Substitution products of the weak bases may be usedsuch as those containing the amino, hydroxy, halogen or organic groupings, provided the essential characteristics of the compounds which render themuseful in the process are not destroyed. Thus amino and hydroxyl groups may Strong bases may be employed, but since they strong bases are likely to throw the solution. over on the alkaline side if used in substantial excess, they should be used in conjunction with a weak base or bases. .Moreover, theweak bases provide a buffering action with respect to the acid and 7 the cellulose which is not so noticeably the case with the strong bases and since a decided buffering action is desired in order to obtain reaction control and prevent undue tend ing, for this reason also, the strong base shoul preferably be used only in conjunction with a weak base. Apparently what happens is that the combination of the weak base with the acid is replaced during the curing, thus giving a buffering or reaction control. The amount of strong base should be insuihcient to satisfy all of the acidity of the acid during curing. The use .of strong bases in conjunction with weak bases results in.

greater strength in the ultimate fabric. The mixture of the weak bases with a strong base containing considerable nitrogen, besides aifording a control over the pH and giving a buffering action. also supplies plenty of nitrogenas will be further explained to enter into the phosphorusnitrogen-cellulose complex, thus enhancing (lurability. Among the strong bases which may be utilized, we here mention guanidine, carbohydrazine, dihydroxyguanidine, guanylurea, oxalamidine, and biguanide.

Substitution compounds or the-strong bases may be used, providing these compounds have satisfactory solubility in the solution and are reasonably stable after being applied to the fabric. Such substitution compounds are the amino, hydroxy, halogen, and organic-radical substitution products. The latter type of compound should not contain groupings with excess carbon chains as this is detrimental to the flame-resistance.

Salts of the strong bases with volatile, decoinposable, or weak acids may be employed, such, for example, as guanidine carbonate, amino guanidine acetate; guanylurea formate, and biguadide borate. The guanidine carbonate is especially useful and has been extensively used in large scale production.

Salts of the strong base and the flameprooflng acid may also be employed such as, for example, guanidine phosphate, guanyl-urea sulfate and. carbohydrazidine pyrophosphate. ,In these cases the acid part of the salt replaces part of the acid in the solution formula.

The general requirements of the base, whether weak or strong or mixtures thereof, are that it should be soluble in water, react with the acid so as to thereby introduce nitrogen into the phosphorus cellulose complex, should preferably be higher in nitrogen than in carbon, and, in the case where a strong base or bases is or are employed, there should be also present a weak base generally in excess for ease of reaction control by providing the desired buffering action between the acid and the cellulose. The weak bases afford a buffering action by reason of the fact that they .apparently compete with the cellulose for the acid. The reason for having a base high in nitrogen and low in carbon is that the more carbon there is present, the less is the resultant flameproofness. For this reason, substituted ureas and other nitrogen compounds having relatively large amounts of carbon are not beneficial, where optimum results are desired.

In general our purpose is to introduce asm'uch nitrogen and as little carbon as possible into the acid-cellulose complex. This nitrogen should be as firmly bound as possible and should-not be appreciably removed when the fabric is subjected to leaching and soaping treatments. It does not matter whether this excess nitrogen is introduced by a weak base or by a strong base, however it has been found that to obtain a complex weakbasenitrogen compound havingahigh soiubility in the reaction mixture is almost impos sible. To obtain sufficient solubility it is beneflcial to work with the lower molecular weight nitrogen compounds such as urea, acetamide or formamide.

In case of the strong bases which are never used in objectionable excess, as hereinbefore dcscribed, the extent of solubility does not become somateriaiafactorastheyarenotusedinrelatively large quantities, and quite a few compounds havinga high nitrogen content and low carbon content are available.

Analysis has shown that with a nitrogen rich strong base more nitrogen becomes a part of the complex. For example, if urea and phosphoric acid are used the atomic ratio of nitrogen to phosphorus on the finished cloth may be 1 nitrogen to 1 phosphorus while if a mixture of urea, guanidine and phosphoric acid is used, the ratio is 3 nitrogen to 1 phosphorus, showing a substantial increase in nitrogen due to the guanidine. During the heating of the solution I or during the curing of the fabric many changes formed. For example, dicyandiamide with mono or di-ammonium phosphate forms a substantial quantity of guanidine phosphate when.

heated; dicyandiamide with phosphoric acid forms a substantial quantity of guanyl urea phosphate, also when dicyandiamide and guanidine are heated together cyanogen, biguanidine and melamine may be formed.

, This formation of the more complex nitrogen compounds aids in obtaining good flame-resistance and also increases the durability to water since the compounds so formed tend to increase the stability of the complex.

Insofar as the solution is concerned, it should be preferably clear, to secure better penetration and more even action on the material to be flameproofed. In the case of phosphoric acid, the amount of acid should be such that the ph0s-' phorus remaining in the flame-resistant fabric after the final washing and drying should preferably range from 1.2% to 4.75%. Below this percentage, mediocre flameproof properties are usually obtained and above this percentage little is gained.

Again referring to ultimate take-on and using orthophosphoric acid for illustration, the percentage of phosphorus necessary to impart flameresistance to a given fabric is also dependent upon the quantity of nitrogen present. ample, if the nitrogen content in the finished fabric is 2%, the phosphorus necessary to segen content is from about 25% to about 6%.

and the preferred phosphorus limits are about 1% to 5%. Enough of the acid and the base must be present on the cloth at the curing to ensure this ultimate chemical take-on. Below the 25% nitrogen, the influence of the element. becomes negligible and above 6% nitrogen, a1

though excellent flame-resistance is obtained,

For exnothing seems to be especially gained. Below .5% phosphorus an excessively large amount of nitrogen would be necessary. The percentages above given were measured after thesolution was applied, the-cloth cured, and then given a thorough washing in very hot or boiling water. It is the'percentages in this ultimate product which are important. Before this, definite and measurable losses take place during curing. It is, of course, to .be understood that if additional flame-resistant ingredients be. introduced, there may be a corresponding change in the ratio of nitrogen and phosphorus required to produce a satisfactory end product. For example, if a being in addition to these naturally occurring elements.

The cellulosic materials processed by this,

method, in addition to the flame-resistant char acteristics, are also decidedly resistant to mildew, which adds a valuable property to the end product. This is not the case with protein fabrics.

Cellulosic materials treated by the process may be subject to swelling when immersed for a length of time in water. 'In certain cases this property is a valuable asset, but if not desired it may be compensated for by employing an aldehyde as fully described in our copending application Serial No. 539,798, and this swelling characteristic may also be reduced by altering the hydrophobic character of the finished product by aftertreating it-with formaldehyde or waterproofing agents. It is not desirable to process protein fibers with the aldehyde.

This process may be applied to fibrous materials having previously been given other treatments such, for example, as bleaching, mercerization, parchmentization, dyeing, printing and sizing, providing the particular treatment is such as does not interfere with the flame-resistance. Further processing such, as for example, sizing, waterproofing, coating, and mechanical finishing may also be done after applying the flame-resistant finish provided such treatments do not destroy the flame-resistance. Such additional processing forms no part of the present invention.

Since no resin, plastic, piasticizer, or solvent soluble material need be used in producing this finish, excellent durability to drycleaning solutions is obtained.

In all the examples herein given, the finished fabrics were considered as having very satis factory durable flame-resistance if samples of the treated fabric, after being'subjected to the following series of tests, upon being held vertically in a flame for 1 0 seconds, did not thereafter continue to burn:

(a) After 24 hours leaching in distilled water.

(b) After /2 hour boil in distilled water.

(c) After 15 minutes soaping in a 4% solution of Igepon T (a substituted amide of oleic acid- CnHasCONMeCI-IzCHzSOaNa) at 180 F., 100-1, followed by two rinses in hot water.

(d) After 1 hour treatment with a solution of Stoddard drycleaning solvent.

(e) After extracting 1 hour in a Soxhlet extractor with dichlorodiethyl ether.

It is to be understood that a separate strip of fabric is to be used for each of the above tests.

Example 1 A water mixture containing 49.6% urea and 18.4% orthophosphoric acid by weight or in the ratio of 2.7 parts of urea to 1 part of phosphoric acid, was padded on the fabric, the fabric (herringbone twill) was frame dried at 300 F. for about 30 seconds as described, and the dried fabric was oven cured at a temperature of 345 F. for-2 minutes. The finish produced had the characteristics above set forth. I Any appreciably longer curing, while increasing durability, would result in reduced tensile strength.

7 Example 2 The same mixture was padded on the fabric,

the fabric dried as described, and then cured at 300 F. for 15 minutes. The curing temperature being lower, a longer time was required for the cure and to duplicate the results. The desired finish was obtained. By duplication of results is meant the obtaining of a finish withstanding the same tests. Withall usable bases, weak or strong,

this holds true. i

Example 3 The same mixture was padded on, the fabric dried as described, and the dried fabric cured at 280 F. for 23 minutes, the time required for curing and duplication of results being thus again longer with the lower temperature. The desired finish was obtained.

The curing temperature of 280 F. of the above example, is quite close to the lower temperature limit possible for successful commercial opera tion within reasonable times. of time, say up to about 45 minutes or a little longer, the temperature may be dropped a little below 280 F. As before indicated, however,

lower temperatures may be used with longer curing times. Thus with a temperature of 250 F. and a time of minutes, good results may be obtained providing adequate concentration is employed. A temperature of substantially 250 F. seems to be about the low practical limit with conventional apparatus. This is true with all the bases usable in the process.

Save as before indicated, the ratio of the weak bases such as urea to phosphoric acid is not critical as will be seen from the following examples.

Example 4 A water mixture containing 66.4% urea and 16.6%. orthophosphoric acid (100%) by weight or in the ratio'of 4 parts of urea to 1 part of phosphoric acid was padded on the fabric, the fabric dried at 300 F. for about 30 seconds as described, and the dried fabric cured at 300 F.

A water mixture containing 20% urea and 20% orthophosphoric acid (100%) by weight or in the At the sacrifice ratio of 1 part of urea to 1 partof phosphoric acid was padded, dried as described, and cured at 300 vF., the time required for curing being 12 minutes. Comparing this with Example 2, it will be seen that with the smaller amount of urea, and keeping the concentration of the phosphoric acid substantially the same, the curing time is diminished in duplicating the results.

The resultant finish had the characteristics above described.

It will be seen from the foregoing-that as the temperature of curing goes down, the length of time required for the cure increases. It will also be seen that the higher the ratio and, therefore, the greater the protective influence of the urea, the longer will be the time of curing without producing detrimental results on strength. The

lower the ratio of urea to phosphoric acid and the less the protective influence of the urea, the shorter should be the time for the cure.

From a practical standpoint a ratio of 4 to l by weight of the urea to the phosphoric is about the highest possible without involving objectionable wastage of urea. One may go higher, say as high as to 1 when the loss becomes prohibitive. It is, of course, to be understood that in all of the examples given the cloth is washed after 12 at 400 1''. and finally washed in water and dried.

The resultant finish had the charac above described.

Example 9 In this end the following examples, all parts given the cure and any unneeded urea is-washed out, 7

only that portion of the urea entering into the combination remaining in the fabric.

finish depends among other factors upon the concentration of the phosphoric acid in the solution. Asthe following examples show, this concentration may be varied between wide limits, depending upon the permanency desired, provided sufficient urea or other weak base or bases is present to give the necessary protection and providing a sufllcient amount of acid groupings and nitrogen are present in the complex as before pointed out. This is also true of other acids usable in the process.

Example 6 A water mixture containing urea and 30% orthophosphoric acid (100%) by weight, or a ratio of 1 urea to 1 of phosphoric acid was padded, dried as described, and cured at 300 F. for 12 minutes. Example 7 A water mixture containing 25% urea and 9.3% orthophosphoric acid (100%) byweight or a ratio of 2.7 parts of urea to 1 part of phosphoric acid was padded, dried as'described, and cured at 345 F. for 2 minutes.

In both the above examples, 6 and 7, a satis factory durable flameproof finish was obtained, but the permanent flameproof properties of the fabric obtained in Example 6 were slightly superior to those obtained in Example 7.

Example 8 A mixture containing 49.6% urea and 18.4% orthophosphoric acid (100%) by weight was applied to a cotton fabric followed by drying in a tenter frame. The dried cloth was cured 1 minute We prefer to employ 2.7 parts of urea to 1 part phos-- are by weight.

The resulting solution was water clear and a cotton fabric (herringbone twill) was impregnated with the same by passing it through a regular textile impregnating mangle, the operation consisting in dipping the cloth into the solution followed by a squeeze to remove excess solution; Then followed drying on the regular tenter frame, the temperature being approximately 300 F. The cloth was allowed to remain in the frame long enough to remove substantially all the water by evaporation.

One section of the cotton fabric was cured at a temperature of 345 F. for a period of 2 minutes and 10 seconds. This was followed by washing in hot water and drying.

Another part of the same cloth was cured at 1 300 F. for a period of 13 minutes, this again being followed by the wash in hot water and drying.

The two samples were found to be substantially equal in flameproof qualities and the respective finishes were of substantially equal durability.

This example also illustrates one way in which the pHfof the solution may be externally adjusted, e. g., through the use of the ammonium hydroxide. It also illustrates how resistance to swelling or standing in water may be imparted through the use of an aldehyde.

200 parts phosphoric acid (75%), 100 parts of water, 15 parts of ammonium hydroxide (28%),

and 25 parts formaldehyde (37%), was applied with the usual procedure described above. The curing was done at, 330 F. for 5 minutes.

The desired results were obtained.

This example illustrates the use of a, different weak base, the external adjustment of the pH, and the use of an aldehyde for increasing resistance to swelling.

Still another illustration of the same character is the following:

Example 11 A mixture consisting of 200 parts biuret, parts phosphoric acid (75%), parts water, 25 parts ammonium hydroxide (28%) and 25 parts formaldehyde (37%)v was used with the procedure above described. The curing was done at 340 F. for 5 minutes.

The desired results were obtained.

As an example showing the use of an acid forming oxide, attention is directed to the following example:

Ezample 12 A mixture consisting of 300 parts of urea, 100 parts phosphorus pentoxide (P200. 200 parts of water, 100 parts of ammonium hydroxide (28%) and 50 parts formaldehyde (37%) was used in acsa'nc I 13 1 accordance with the procedure described. The curing was done at 310 F. for 12 minutes.

, The desired results were obtained.

As examples showing the use ofacidsother than ortho-phosphoric acid, attention is directed to the following:

/ 7 Example 13 A mixture comprising 180 parts urea, 60 parts sulphuric acid (cone), 50 parts water, 15 parts ammonium hydroxide. (28%) and 50 parts formaldehyde (37%) was used under the regular procedure. The curing was done at a temperature of 340 F. for 6 minutes.

The desired results were obtained.

Example 14 A mixture comprising 100 parts of ortho-phosphorous acid, 100. parts of urea, 100 parts acetamide and 100 parts of water was applied to a cotton fabric, dried, cured 20 minutes at 290 F.,

washed and dried. (Here is also illustrated th use of a mixture of weak bases.)

The desired results were obtained.

- Example 15 A mixture was prepared consisting of 100 parts metaphosphoric acid, 200 parts urea and 100 parts of water, the method of application being the same as the preceding example. The curing was done at 340 F. for a period of 4 minutes.

The desired results were obtained.

Example 16 A mixture of 300 parts of concentrated sulfuric A solution was prepared by warming 180 parts calcium phytate, 120 parts oxalic acid, 250 parts urea and 250 parts formamide followed by addition of 500 parts of water. The precipitate containing primarily calcium oxalate was filtered oil? and the filtrate containing primarily Phytic acid,

urea and formamide was applied to a cotton fab- I ric by impregnation followed by drying. The

curing was done at 310 F. for 8 minutes, followed by washing in water and drying.

The fabric had fair flame-resistance.

The following illustrate the use of mixed acids.

' Example 18 A solution comprised of 200 parts urea, 50 parts of orthophosphoric acid (75%), 50 parts sulphuric acid (conc.), 100 parts of water, 15 parts of ammonium hydroxide (28%) and 50 parts formaldehyde (37%) was used under the regular procedure. 'Curing was done at 340 F. for a period of minutes, and the desired results were obtained.

Example 19 A mixture was prepared consisting of 100 parts orthophosphoric acid (75%), 55 parts nitric acid (conc.-), 200 parts urea and 100 parts of water, the method of application to a cotton fabric was as above described, the curing being done 20 minutes at 290 F.

The desired results were obtained.

14 Example A'mixture wasprepared comprising 50 parts pyrophosphoric acid, 50 parts metaphosphoric' acid, 200 parts acetamide and 150 parts'of water, the method of application being as previously described with curing time of 5 minutes at 330 F.

The desired results were obtained.

As further examples of mixed weak bases w cite the following:

' Example 21 A solution comprising 75.0 parts dicyandiamide,

75.0 parts acetamide,-100 parts pyrophosphoric I to a cotton fabric in the usual manner, the curing sumacid and 200 parts of water was used under the regular procedure. The curing was done at 320 1". for 5 minutes.

The desired results were obtained.

Example 22 A mixture was prepared comprising 132 parts urea, 8 parts melamine, 66 parts diammonium phosphate and 150 parts water, and this applied being done at 335 F. for 3 minutes. The desired results were obtained.

Example 23 A mixture 'wasprepared comprising parts urea, 100 parts cyanoacetamide, 50 parts orthophosphoric acid (75%) and 165 parts water. This was applied to a cotton fabric and the desired results obtained, the curing being done at 315 F.

for5minutes.

Repeating this without the cyanoacetamide caused excessive tendering.

As illustrative of the use ofsalts of the base, attention is directed to the following:

Example 24 A mixture was prepared consisting of 160 parts of amino guanidine bicarbonate, 300 parts urea, 150 parts orthophosphoric acid (75%) and 500 parts water. The process was applied by the regular procedure, the curing being done at 350 F.

for 4 minutes.

The desired results were obtained. I

Example 25 A mixture was prepared consistingof 61 parts semicarbazide hydrochloride, parts guanidine carbonate, 45 parts cyanoacetamide, 35 parts urea, parts orthophosphoric acid (75%) and parts water, the regular method was used in the application,. the curing time 335 F.

The desired results were obtained.

The following are additional examples of the use of the mixed bases wherein a strong base is employed for maximum retention of strength and 4 minutes at a weak base or bases is or are employed to afford buffering action and control of the reaction.

Example 26 A solutioncomprising 100 parts urea, 100 parts amino guanidine carbonate, 100 parts orthophosphoric acid parts water, 15 parts ammonium hydroxide (28% 50 parts formaldehyde (37%) was used under the regular procedure.

The curing was done at 340 F. for a period of 5 minutes, and the desired results were obtained.

Example 27 I A mixture was prepared comprising 50 parts dicyandiamide, 113 parts urea, 10.5 parts guani- (75%), 158 parts water. This was applied to a cotton fabric by the regular procedure, curing. being done at 340 F. for minutes. A ver'y durable flame-resistant result was obtained.

' Examp e 28 A mixture was prepared comprising 57 parts pol py ophosphoric acid, 66 parts guanidine carbonate, 132 parts urea and 255 parts water, and.

the mixture applied by the usual procedure, the curing being done at 330 F. for 5 minutes. Ex-

. akaas dine 75 parts orthophosphoric acid cellent flame-resistance and durability were obtained on a cotton fabric.

- Example 29 A mixture was prepared comprising 40 parts guanyl urea sulfate, 81 parts urea, 53 parts orthophosphoric acid (75%), and 90 parts water, and the mixture applied to cotton in the usual manner, with curing at 320 F. for 5 minutes.

Very good flame-resistance was obtained.

Example 30 A mixture was prepared comprising 300 parts urea, 160 parts aminoguanidine bicarbonate, 150

parts orthophosphoric acid (75%) and 500 parts water. This was applied to a cotton fabric by the usual procedure, and a very good flame-resistant fabric obtained. The curing was done at 340 F. for five minutes.

The following are examples of the use of a weak base to partly produce a strong base.

Example 31 53.4 parts dicyandiamide, 168 parts diammonium hydrogen orthophosphate were heated in a covered container to 515 F. under which condition a substantial quantity of guanidine was formed, as guanidine phosphate. 24 parts of the above material was mixed with 150 parts of warm water and the resulting solution applied to a cotton fabric using the regular precedure.

Good results were obtained.

The following examples illustrate the use of substitution products of the base.

Example 33 A mixture was prepared comprising 65 parts dicyandiamide, 100 parts orthophosphoric acid (75%.), 150 parts urea, 28 parts phenyl biguanide, and 216 parts of water. This was applied by the regular procedure.

Good flame-resistant results were obtained.

Example 34 A mixture was prepared comprising 50 parts 'dicyandiamide, 120 parts methyl urea, 10 parts guanidine carbonate, 75 parts orthophosphoric acid (75%) and 200 parts water. The mixture was applied to a cottonfabric by the usual procedure, and a good flame-resistant finish obtained.

As an illustration of the use of substituted acids, attention is directed to the following:

' Example 35 A mixture consisting of 200 parts urea, parts sulphamic acid, 100 parts water, 15 parts ammonium hydroxide (38%) and 50 parts formaldehyde (37%) was used in accordance with the procedure described.

The desired results were obtained.

Example 36 A mixture comprising parts urea, 100 parts ammonium hexaphosphate dinitride and 350 parts of water was. applied to acotton fabric, dried, cured at 320 F. for '7 minutes, washed, and dried.

Good durable flame-resistant results were obtained.

Example 37 A mixture was prepared by first heating to-.

gether 1-hour at 180 F. 300.parts of sulphamic acid, 300 parts of urea and 100 parts of water. A thick syrup was formed and this was further diluted-with 200 parts of water. A cotton fabric was impregnated, dried, cured, washed and dried as in previous examples. I

The fabric had good resistance to flaming.

. Example 38 I I 140 parts phosphorous pentoxide and 130 parts ammonium carbonate were reacted to form diamidophosphoric' .acid, to this were added 300 parts urea, 125 parts guanidine carbonate and 650 parts water. This mixture was applied to a cotton fabric using the regular procedure.

Good results were obtained.

The above formulas have all been applied to cotton cellulose material. The following example illustrates the use of this process to wood pulp.

' Example 39 Sheet wood pulp as used in the manufacture of viscose was steeped in a warm solution of 57 parts polypyrophosphoric acid, 66 parts urea and 350 parts of water, it was then thoroughly squeezed, dried and cured at 340 F. for 6 minutes. The resulting pulp which had the appearance of ordinary. pulp was extremely flame-resistant.

As an example of the application to rayon fabrics we refer to the following using highly combustible napped knitted rayon goods.

Example 40.

A mixture was prepared comprising33 parts dicyandiamide, 100 parts urea, 50 parts orthophosphoric acid (75%), 10 parts guanidine carbonate and 500 parts water, and this applied to the rayon fabric above described by the usual procedure, the curing being done at 340 F. for

6 minutes.

The resulting knitted goods had good flameresistance.

In regard to the application of this finish to protein fabrics we call attention to the following Ezample 41 A mixture was prepared comprising 116 parts guanidine carbonate. 289 parts urea, 162-parts dried.

The resulting wool fabric had good flame-resistance.

Example The last procedure was repeated, but in this case a 100% Tussa silk fabric was substituted for the wool.

The resulting sistance.

Example 48 A mixture was prepared comprising 83 parts dicyandi'amide, 100 parts urea, 10 parts guani dine carbonate, 50 parts orthophosphoric acid (75%), and 400 parts water. This was applied to a fabric containing 75% spun rayon and 25% aralac using the regular procedure, the curing being done at 300 F. for 4 minutes.

A fabric of good flame-resistance was obtained.

As examples of the use of strong bases only, attention is directed to the following:

Example 44 A solution comprising 100 parts amino-guanidine carbonate, 50 parts phosphoric acid (75%), 30 parts water, 25 parts ammonium hydroxide (26%), and 25 parts formaldehyde (37%) was used under the regular procedure. The curing was done at 310 F. for a period of 12 minutes. A fair flame-resistant result was obtained.

Example 45 A mixture was prepared comprising 260 parts pyrophosphoric acid, 320 parts guanidlne carbonate and 750 parts water. This was applied to a cotton fabric using the regular procedure, the curing being done at 340 F. for minutes. The fabric had fair flame-resistance and a low degree of strength.

As examples of the use of free strong and week bases, not in the form of salts, attention is directed to the following:

Example 46 mixture was prepared comprising 50 parts dicyandiamide, 115 parts urea, '75 parts orthophosphoric acid and 175 parts of a water solution containing 5.1 part of guanidine, This was applied to a cotton fabric by the regular procedure. The time of curing was 5 minutes and the temperature 330 F.

Very durable flame-resistant results were obtained.

Example 47 A mixture was prepared comprising 85 parts urea, 53 parts orthophosphoric acid (75%) and 100 parts of a water solution containing 20 parts guanylurea, and the mixture applied to cotton in the usual manner. The time of curing was 4 minutes and the temperature 330 F.

Very good flame-resistance was obtained.

We have also obtained good results on paper and wood with the process. Here, especiall in the case of wood, pressure may be resorted to in applying the solution, or vacuum treatment to remove the air may be used, followed by the application of the solution under pressure, removing excess, drying, if desired, and curing.

silk fabric had good aeme-i-e- Excellent results both with respect to durability and strength are obtained if the cellulose fibers made flame-resistant by this process with phosphoric acid contain one phosphoric acid group for every four pyranose units in the cellu-- lose. That flame-resistance can be obtained with such a small combination is remarkable and due we believe to the fact that nearly all the ingrediv cuts of the complex on the fibrous material contribute to the reduction of the flammability. Thus the complexes producing the flame-resistance contain large quantities of nitrogen and phosphorus both of which upon burning create gases or volatile materials which tend to use up the oxygen and smother theflame. With decrease in the ratio of acid group to pyranose units, flameresistance will correspondingly decrease.

Certain of the materials above given furnish unusual resistance to salt and strong soaping which render the finished product particularly useful for military uniforms which are subjected to extremely severe soaping and handling. .In many of the examples given, the end product has a more pronounced capacity for ion exchange than in others, the anion active groups present in the complex having an afflnity for cations, such'as present in salt water, strong soap solutions, and hard water. By reason of this capacity for ion exchange, the ilameproof characteristics, al-

though substantially resistant to water, dry cleanready transformation of this group into oxides of phosphorus so valuable in flame prevention.

The resistance to ion exchange and therefore, as described, improved durability to salt and soap solutions may be obtained at the expense of fabric strength by briefly extending the period of curing,

as say, for example, a cure of from about 5 to about 20 minutes, with a temperature of from about 300 F. to about 350 F., followed by washing in warm water and drying. We prefer to and ordi-' narily retain about to about of tensile strength, although one may go lower (a 30% reduction in strength is about the maximum permissible) and thus obtain greater durabilitywith the same solution and same type of fabric.

Ion exchange resistance may also, and preferably, be obtained with good or'superiorfabric strength by nitrogen groups which prevent or retard the addition of metallic ions. The ammonia.

groups, for example, are very easily replaced by a metallic ion while such groupings as guanyl urea, guanidine, biguanide, melamine and so forth are less easily replaced. Therefore, formulas making use of these chemicals, in suflicient quantities, have superior resistance to ion exchange and a correspondingly higher durability to soaping and leaching;

As previously described, some of these complex The latter is due that whenever phosphoric acid is heated to a high temperature with nitrogen compounds, ammonia is liberated and this plays the part of the am-' to some extent to the fact eans order to allow some of these changes to take place.

For example, in a formula using dicyandiamide, phosphoric acid, urea and water, the dicyandiamide, acid and som water may be reacted together first at elevated temperatures followed by the addition of the urea and the remaining water to form the finished solution.

The ion exchange may be reduced to some extent by after treatments with materials such as the nitrogen compounds mentioned above, but

, little seems to be gained by this procedure.

Generally, in the process the preferred range of curing temperature is from approximately 280' I". to approximately 400 F., and the time of curing from approximately 45 minutes to approximately a minute. For optimum results, we prefer a temperature of from 320 F. to 360 F. and a time of from 15 minutes to 3 minutes. This is for conventional apparatus. Where the equipment is large enough and handles the material sufilciently rapidly for commercial purposes, the temperature may be lower and the time longer, as before set forth.

The drying and curing may be combined in one operation so long as the desired curing is obtained. l

In the claims, "acid is used in the sense of including only flame-resistance imparting strong acids capable of reacting with the cellulose and the nitrogen compound under the conditions of the process, as previously described, and which, as such, are not excessively volatile nor produce chemicals during the processing which will detrimentally alter the character of the fibers, and the equivalents of such acids, as indicated in the specification. We use base" to include only organic nitrogen-containing base material, weak, strong or amphoteric, which is at least to some extent water soluble, which, under the conditions of the process, will reduce the acidity and will buffer or moderate the reaction between the cellulose and the acid, and which will enter into the acid-cellulose complex giving nitrogen to the complex and in which the carbon is not so high as to detrimentally lower flame resistance, and the equivalents, as indicated in the specification.

Such material must be employed according to our invention. This, however, does not mean that one may not employ in conjunction therewith other base material or other ingredients,

' as an additive, so long as the same do not interfere with the desired reactions and end results.

Thus, for example, one may employstrong bases for the purposes of adjusting the pH, providing there is also employed the base material of our invention which will furnish nitrogen to the complex. Where a strong base is used for purposes of adjusting the pH, it should be employed injconlunction I I the strong bases which may be used for so ad-.

withweakbsses. Among lustin DH, we mentioned diethylene triamiue.

" triethanolamine, sodium hydroxide, sodium carbonate, and potassium hydroxide.

Thus far reference has been made primarily to flame-resistant finishes. As, previously indicated, where flame-resistance, accompanied by mildew-resistance, is desired, there should be from 1% to 5% of the basic element of the acid (on the basis of using phosphoric acid) and from .25% to 6% nitrogen on the finished cloth. Where mildew-resistance is the primary objective, the percentage of basic element of the acid and of the nitrogen in the finished fabric may be substantially reduced, as small quantities will give results. In general, the acid groups give the mildew-resistance. However, some of the bases, such as phenol guanidine, for example, contribute to mildew-resistance. The acid should be bufiered. Insofar as mildew-resistance is concerned,

we have found, on the basis of phosphoric acid,

1 1 phosphoric acid group to 8 pyranose units, gives very good results. As low as .1 to 16, gives appreciable improvement over the original cloth.

While in the fiameproofing processes at present currently used, there is after-glow for an appreciable period of time, with fabrics fiameproofed by our process, the after-glow disappears almost immediately on withdrawal of a test piece fro the flame.

Referring now to the use of aldehydes, where it is desirableto reduce the swelling of the fabric on being subjected to continued moisture, and

using formaldehyde and orthophosphoric acid by way of illustration, the general range for the formaldehyde is from about .2 mol to about 1.5.

mols to 1 mol of orthophosphoric acid, the preferred range being .4 mol to 1.0 mol of formaldehyde to 1 mol of phosphoric acid. If the aidehyde is kept very close to the lower limit, care must be exercised in curing as less buffering action takes place. If excessive content of aldehyde is added there is too much buflering action and long curing is necessary.

As additional examples using the aldehydes, we give the following:

Example 48 A solution prepared in the identical manner described in Example 9 was made and consisted of parts of urea, 50 parts of orthophosphoric acid (75%), 7 parts of ammonium hydroxide (28%), 50 parts of formaldehyde (37%) and 50 parts of water.

The solution was water-clear and cotton cloth (herringbone twill) was again impregnated as described in Example 9 and the cloth dried on the tenter frame as described.

One part of the cloth was cured at 345 1". for a period of 3 minutes and 40- seconds, followed by the usual wash in hot water'and drying.

Another part of the cloth was cured at 300' I. for a period of 22 minutes, this again being followed by washing in hot water and drying.

The two samples were substantially equally fiameproofed and the durability of the finish was likewise substantially the same.

The essential difference between the solutions of Examples 9 and 48 is that in Example 48, 50 parts of formaldehyde were used instead of 10 parts as in Example 9. The increase in the quantity of formaldehyde increases the time required for curing.

21 It is also to be noted that with increase in the temperature of curing, the time needed for ouring is reduced, and vice versa.

Example 49 to be flameproof and the flameproofing qualities and the durability of the finish were quite satisfactory.

This example again shows that with decrease in the curing temperature a longer period for the cure is required.

Example 50 The formula and method of procedure in this example was identical with that described in the previous example, but in this case the cotton cloth was cured at a temperature of 400? F. for a period of 30 seconds, followed by the usual washing and drying procedure.

The finish was both satisfactory and durable.

We may use aldehydes other than formaldehyde. For example, a solution consisting of 200 parts of urea, 100 parts of phosphoric acid (75%),

114 parts water, and parts ammonium hydrox? ide (28%) and 50 parts of glyoxal (30%) gives ood results. i

As further illustrative, we may use a halogen aldehyde instead of formaldehyde. A solution consisting of 200 parts urea, 100 parts phosphoric acid (75%), 114 parts water, 15 parts ammonium hydroxide (28%) and 75 parts chloral hydrate, gives good results.

We have also used mixtures of aldehydes. For example, a solution consisting of 200 parts urea, 100 parts orthophosphoric acid (75%), 100 parts water, 15 parts ammonium hydroxide (28%), 25 parts formaldehyde (37%) and 25 parts glyoxal (30%) gives good results.

Other aldehydes may be used, such, for example, as acetaldehyde, acrolein and aldol. The aldehyde should be of low molecular weight (a carbon chain of from 1 to 4), reactive with the nitrogen containing compound and desirably also with the cellulose under the conditions of the process.

We have discovered that fabrics treated according to the invention exhibit substantial resistance to creasing. Also the treated fabric has the char acteristic of dryin very rapidly. To illustrate, the same cloth in the untreated state, when wetted as, for example, by rain, requires a very much longer time to dry than the treated cloth which dries very rapidly. This drying characteristic is advantageous as, for example, in raincoats, toweling, and bathing garments.

We claim:

1. In the art of producing a complex of acid and nitrogen with fibrous cellulose or protein materials or mixtures thereof to impart durable flame-resistance to such materials, the method of forming said complex which consists in impr enating the fibrous material with an aqueous solution of the reaction product of (1) at least 22 one substantially water soluble inorganic acid compound selected from the class consisting of acids of phosphorus and sulfur which are free of metal and of organic groups and of constituents yielding active oxygen and halogen and which are substantially non-volatfle under the conditions of the process, and metal-free salts of such acid compounds decomposable, and the anion of which is volatile, under the conditions of the process, to yield the acid, and (2) at least one nonmetallic organic compound basic in the acid solution and soluble therein and which contains nitrogen and has an atomic ratio of carbon to nitrogen not substantially more than the ratio of carbon to nitrogen in acetamide,'the amount of acid and the amount of non-metallic nitrogencontaining organic constituent applied to the material being equivalent to that applied by impregnating the material with a solution containing from 6.9% to 30% orthophosphoric acid by weight and containing a non-metallic nitrogencontaining organic constituent at least in amount suflicient to introduce the amount of nitrogen into the complex hereinafter set forth, with a 100% solution pick-up by weight of the fibrous material' in the dry state; drying the material; heating the dried material to a temperature ranging from 400 F. to 250 F. for a time ranging from 30 seconds to 120 minutes; and then washing and drying the so heated material, the process being further characterized in that the solution composition is such that the-pH of the heated fibrous material before said. washing has a value of from pH 3 to pH 6, and in that the temperature and time selected in the above ranges and the amount of reaction product applied'to the material and the amount of acid and nitrogen present in said reaction product are correlated to form with said material a complex containing an amount of the base element of the acid equivalent to from 1% to 5% phosphorus and to introduce into the said complex from .5% to 6% nitrogen, both by weight of the finally washed and dried material.

2. In the art of producing a complex of acid and nitrogen with cellulose or protein materials or mixtures thereof to impart durable flameresistance to such materials, the method of forming said complex which consists in preparing a solution from the following ingredients in the proportions given, namely, 50 parts dicyandiamide. 113 parts urea, 10.5 parts guanidine carbonate, 75 parts orthophosphoric acid (75%) and 158 parts water; impregnating the material therewith with a solution pick-up of substantially 100% by weight of the material in the dry state; drying the material; heating the dried material at 340 F. for a period of 10 minutes; and washing and drying the material.

3. The process of claim 1 in which the temperature range is from 360 F. to 320 F. and the time range from 3 minutes to 15 minutes.

4. The process of claim 1 in which the acid is orthophosphoric.

5. The process of claim 1 in which the acid is sulfamic.

6. The process of claim 1 in which the salt diammonium hydrogen phosphate is employed as the acidic substance.

7. The process of claim 1 in which the organic compound is ma.

8. The process of claim 1 in which the basic non-metallic nitrogen-containing organic constituent is a mixture of urea and guanidine.

assays:

- 23 9.'1'heprocesso1claim1inwhich thebasic non-metallic nitrogen-containing organic constituent is a mixture of urea, dicyandiamide and guanidine.

10. The irocess of claim l'in which the acid is orthophosphoric and the basic non-metallic nitrogen-containing organic constituent is a mixture of urea, dicyandiamide and guanidine.

IL The pm of claim 1 in which the concentration of acid in the solution is equivalent to 6.9% orthophosphorlc acid by weight at the temperature 340' F. and the time 5 minutes.

12.Theprocessofclalm1inwhichtheconcentration of acid in the solution is equivalent to 15% orthophosphoric acid by Weight, the tem- 15 perature 400' F., and the time 1 minute.

WIILIAM P. HALL.

REFERENCES CITED Thefollowingreferencesareofrecordinthe flieotflflspatmt:

UNITED STATE PATENTS Number Number Name Date Foulds et a1. Nov. 5, 1929 Meunier July 28, 1936 Battye et a1. July 27, 1937 Groebe Aug. 10, 1937 Dreyfus Mar. 4, 1941 Gordon June 16, 1942 Datlow Nov. 1'7, 1942 Thomas et al. June 4, 1946 FOREIGN PATENTS County Date Great Britain July 11, 1939 Great Britain Sept. 15, 1942 OTHER w -e CES Kleek, Fire-RetardantSynthetic-ResinPaints,

A. C. 8., News ed 19, 626-628 (1941).

(Copy in Patent No. 2,482,755

Certificate of Correction September 27, 1949 FLORENCE M. FORD ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 74, before the word soaping" insert such a; column 6, line 36, for lemamine read melamine; column 7, lit es 22 and 23, for carbohydrazine read carbohydrazid'im; line 38, for biguadide read biguanide; column 12, line 12, for "end read and; column 17, line 47, for week read weak;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the ease in the Patent Oflice.

Signed and sealed this 31st day of January, A. D. 1950.

THOMAS F. MURPHY,

Am'atcmt Uommc'aaz'oaer of Patents.