Sept. 24, 1946. F_ CLATWOOD 2,408,026 PROCESS ‘FOR TREATING SYNTHETICALLY SHAPED PROTEIN BASE MATERIALS Filed Jan. 23,_ 1942 15 BY ATTO EY: Patented" Sept. 24, 1946 UNITED STATES. PATENT c'OFFI‘iE; PROCESS FOR TREATING SYNTHETICALLY . SHAPED PROTEIN BASE MATERIALS Francis Clarke Atwood, Newton, Mass, assignor, ' by mesne assignments, ‘to National Dairy Prod ucts Corporation, New York, N. Y., a corpora tion of Delaware Application January 23, 1942, Serial No. 427,940 4 Claims. (01. 8-1273) This invention relates to the formation of syn thetically shaped protein base containing mate- ‘ rials. - The invention includes, more particularly, the formation of vsynthetic materials made from an alkali-soluble acid-coagulable protein as a base material, such as an animal and vegetable casein; ' such animal casein is typi?ed by the casein ob tained from milk, and the vegetable casein is , periods of time'such ?ber also tends to deterio rate so as to become brittle or lose its strength and softness. Such ?ber also reacts in an un desirable way with many chemical agents such as dyes. These various properties of proteins may be considered generally as chemical prop erties, i. e., the ability of the protein to combine physically or react chemically, or resist such com bination with oxygen, water, acids, alkalies and typi?ed by the protein obtained from soybean, 10 other chemicals such as dyes. ‘ . castor bean and similar sources of the alkali-sol While the physical properties of ?ber prepared uble acid-coasulable proteins. from the proteins such as casein, including the The invention may be applied to the manufac ture of synthetic protein base materials in a variety of forms such as ?lm, ?ber, and products that are cast, extruded or molded into other shapes. For simplicity, however, the invention will be described primarily with reference to the common method of soaking the shaped casein ?ber in formaldehyde solutions are satisfactory for some purposes, they are far from satisfactory = for most uses to which ?bers are to be put. with respect to their chemical properties particularly they leave much to be desired. For example, a > formation of ?ber made arti?cially from animal ?ber prepared from a casein dispersion and coor vegetable casein as a base, more particularly, agulated, in which process it is hardened by ‘the the casein derived from milk. Such a ?ber has 20 usual treatment with formaldehyde, is not re been referred to variously as synthetic wool, syn- sistant to hot-water or dilute acids or alkalies. thetic silk and synthetic fur. Since the ?ber has - I Particularly is this so if the water solution con unique properties not identical with any of the tains an alkaline material such as would be pres above, I have suggested that it be referred to by ent in a hot solution ofan ordinary soap. Upon ‘ the generic ‘term “prolon," or simply as synthetic 25 the heating or boiling of such ?ber in such a protein or protein base ?ber. solution it becomes soft and spongy and takes While‘ the process by which my new ?ber is on a “slimy feel." The tensile strength of the made utilizes a protein as the base material, the ?ber and its elasticity in such a state is also final ?ber is not of the same chemical constitu greatly reduced so that the ?ber is readily de tion, nor does it have the same chemical or physi 30 formed or broken. Upon drying such ?ber after cal properties, as the protein. The finished ?ber it has been subjected to such treatment, it be probably cannot be termed a protein in the strict comes brittle so that further handling results sense of this word, and for this reason I have in excessive “droppings," if in fact the ?ber is used the expression "protein base" to distinguish su?lciently ?exible to be subjected to any fur the material of'my ?ber from ?ber that is a true 35 ther processing. Ordinary casein ?ber, in addi protein. tion, does not have dyeing properties enabling it Protein-containing materials have many de sirable properties that render them valuable for - to be dyed in a manner similar to naturally oc curring proteinaceous ?ber. The ordinary casein many uses, such as covering and decorative ma 40 ?ber also is subject to a change in properties-due terials and upholstery, including woven fabrics to contact with moisture in the air. . In humid and felts, and for the use in articles of clothing air it is relatively plastic, but in dry air it is quite including clothes, shoes, gloves and hats. These properties include warmth, softness, ?exibility, tensile strength, elasticity and other similar prop erties‘possessed by‘ protein-containing materials. brittle. _ From the above it will be seen that the syn .45 thetic protein ?ber as known heretofore in the art, such as that shaped from casein" and hard ened with formaldehyde, is entirely di?’erent from natural proteinaceous ?ber such as wool, These properties may be viewed in general as physical properties and will be so referred to herein. silk or fur, and is not suited for the uses to which The‘proteins are composed essentially of car 50 such natural ?bers may be‘ put. This difference bon, hydrogen, oxygen and nitrogen and may ‘is so marked as not to be'simply amatter of contain small amounts of sulfur or phosphorus degree. Apparently the casein inherently is of or both. They vary somewhat in their chemical such a nature as not to possess satisfactory prop reactivity depending upon their exact chemical erties for ?ber purposes.‘ Attempts at modi?ca- . ' constitution, both from the standpoint of their 55 tions of the casein have not ‘produced a ?ber empirical composition as well as their'structural which has satis?ed thertextile industries. 1 composition.‘ Ordinary synthetic casein ?ber, for I have discovered that an- entirely new‘ ?ber example, is affected adversely by hot water, al may be made, utilizing protein as the principal kaline or soap solutions and dilute acid solutions base material, but which neverthelessvpossesses such as are encountered in dyeing. Over long 60 desirable chemical properties and is not subject 2,408,026 3 - . to the in?uences that affect ordinary casein ?ber, and at the same time has physical properties that are improved or at least not inferior to the known synthetic protein ?bers. I believe that the chem ical composition of the ?ber is entirely different from that of the protein used as the base mate rial and that this difference is largely responsible for the desirable properties of the ?ber. In accordance with my invention a ?ber may 4 This new chemical compound or Composition can be made and then given the shape of ?ber, or the protein ingredient can be shaped and the reaction of the protein and formaldehyde and anhydridc can be ‘carried out while the protein is in the shaped form. It is the latter procedure that I prefer because this makes it possible to delineate or orient the protein molecule and then form the new compound using the delineated protein as the material. . , ‘ be produced thatvis relatively resistant to chem 10 base In particular, I have discovered that if syn ical activity of the undesired type, such as break thetic protein ?ber is treated with a formaldehyde down by bleac 'ng agents and deterioration by solution and‘ then acylated with an acid anhydride hot water, acids or alkalies, while at the same time under certain conditions hereinafter set forth, it has desirable chemical properties imparted to ‘the ?ber is relatively resistant to water, and ‘acid it with respect to its \reaction to dyestuffs and 15 and alkaline solutions; its ‘ chemical reactivity chemicals ordinarily used in the processing of with respect to‘chemical substances, such as dyes, naturally occurring proteinaceous ?bers. In ac is such that it may be dyed by processes substan cordance with the invention, the ?ber also remains tially identical with those heretofore used for soft and pliable and retains or even has its tensile dyeing natural protein ?bers, such as wool, silk strength and other physical properties improved. and fur; and it has the other desirable physical It acquires properties normally desired by textile .and chemical properties set forth herein. ‘ operators as to its moisture content,'or the mois More particularly, I have discovered that in the . ture content of the air with which it is in contact. The process of my invention produces a new above process the anhydride should be in ad mixture with a de?nite proportion of a free acid, ?ber~ that can withstand boiling for long periods 25 which may or may not be the same acid as that of time in water, as well as inhot dilute acid corresponding to the anhydridc, said anhydride solutions such as are used in dyeing. It is also and acidbeing in an inert solvent and said treat enabled to withstand vigorous‘mechanicaltreat ment being under de?nite controlled conditions ment combined with alkaline material, such as as to temperature, concentration of anhydridc, “fulling” and “scouring” operations, even after 30 'time of treatment, and concentration of acid. ‘ it for dyeing operations’. 7 In accordance with my invention it is also - preparing The new synthetic protein base ?ber produced in accordance with my invention, not only is re- ~ ' sistant to dyeing operations, but has desirable properties in that itaccepts dyes ordinarily ac possible to carry out the process in such form that the critical relation between the acid and 35 the anhydride may be kept substantially con stant throughout repeated treatments of addi-. tional quantities of the protein material. cepted by natural protelnaceous?ber and rejects dyes which are not accepted by natural protein ?ber. Still further in accordance with my invention it is possible to carry.’ out the process under such Since one of the more important uses of the synthetic protein base ?ber is in admixture conditions as to recover substantially all of the with natural protein ?ber, it is desirable’that the 40 solvent, anhydride and acid, with the exception two should have similar dyeing properties. Not of the anhydride which has reacted during the only does the ?ber behave similarly toward the treatment of the material. same dyes, but it accepts the dye at substantially The synthetic protein ?ber that'is ‘to be re - the same rate so that at the end of the dyeing with formaldehyde and the anhydride in operation of a mixture of natural and synthetic 45 acted accordance with my invention may be made by protein base ?ber, all of the ?ber will be of sub any known processes in which the protein is stantially the same shade. , dissolved or dispersed with an alkaline material, such as caustic, or in an organic alkaline mate rial such _as' amines. Softening or modifying new dyes and new dyeing techniques because of 50 agents may be added, but are not essential. The It will be recalled that upon the development of the rayon industry it was necessary to perfect the different chemical constitution and different protein dispersion is then extruded through the physical properties of the rayon ?ber.‘ Such an small holes-of a spinnerette and coagulated in approach mightsimilarly have been made with respect to the synthetic protein ?ber. I prefer, ?ber form by means of an acid. ' The ?ber is then treated with formaldehyde, washed and dried. however, not to do this. Rather than develop new 55 So much of my process is known to the art and dyes and new dyeing technique for. the known the exact details by which the ?ber is produced synthetic protein ?ber I prefer to‘make a new up‘ to this stage of the process are not critical ?ber that may be’ treated by the niéthods and in so far as my invention is concerned, except as dyes that are standard in the protein ?ber indus tries, such as the woolen industry, the silk 60 industry or the fur felt industry, for example, the ‘hat industry. In accordance with my invention, therefore, , I. produce a ?ber having dyeing properties simi lar to those of natural protein ?ber, both with re spect to its behavior to different dyes and its dyeing rates. ‘ A more detailed description of the chemical composition of the ?ber and its properties is set above indicated. ' A protein ?ber that has been given a thorough treatment with formaldehyde, such as by soak ing it for a long time in a formaldehyde solu tion, apparently does not have the formaldehyde 65 permanently combined with it. Such ?ber upon treatment with water or aqueous solutions, readily yields at least a portion of its formaldehyde, either because it is held only in a more or less physical relationship,vsuch as adsorption or ab sorption, or if chemically combined easily yields forth hereinafter following the description of the 70 it through hydrolysis. At any event, the form process by which it is made. aldehyde is not combined with such permanence The ?ber produced in accordance with my in as will permit the ?bers to retain their hardened‘ vention may be regarded broadly as the reaction state upon prolonged aqueous treatment. This product of an alkali-soluble acid-coagulable pro. is con?rmed by statements in Sutermeister and 75 tein, formaldehyde, and an acylating anhydride. 2,408,026 Browne which states that when casein is treated with a' formaldehyde solution for 16 days the re sulting formaldehyde-casein product was insol The amount of formaldehyde so absorbed of‘ loosely combined should be at least 2% and ‘pref erably 3 or 4%. based on the dry ?ber'before treatment. uble in- water and was not swelled when treated with dilute acids. However, when the formalde The‘ amount of formaldehyde absorbed or ‘loosely combined may be determined by any suit able technique. I have found it convenient to hyde-casein product was suspended in water, and subjected to steam distillation, practically all of the so-called “bound” formaldehyde was found - take a sample of wet ?ber of a given weight with in the distillate. The remaining product showed‘ known moisture and solids content and treat it inlcertain tests the properties of unaltered casein. 10 with formaldehyde solution of a known concen This is further evidenced by the fact that the ' tration for thegiven desired time period, or until literature contains references to methods for test equilibrium is reached under the treating condi ing casein ?ber (to distinguish it from wool) by tions. The ?ber is then removed and the con _ determining the amount of formaldehyde in such ' centration of the formaldehyde solutions after ?ber. (Klepzig’s Textile-Z. 41, 463-6 .(1938) and 15 treatment again determined. Sincesome water Helv. Chim. Acta 24, 237-42 (1941).) - Such tests is given off by the ?ber because of its initial show that the formaldehyde is present in ordinary moist condition and possibly also because of the casein ?ber in such a way thatit can be separated reaction with the formaldehyde, it is necessary or released so as to be determined quantitatively. to determine the moisture content of the fiber 'Not only is the ‘formaldehyde readily liberated, before and after the formaldehyde treatment. but upon boiling such prior art ?ber with water From the amount of formaldehyde in the solution or weak acid the ?ber goes to a gelatinous-like of initial concentration, and from the amount mass losing its ?ber identity and drying to a hard, of formaldehyde'in the solution after treatment, brittle substance. Also such prior art ?ber loses ‘(taking into account the moisture in the ?ber a substantial portion of its weight during the before and after treatment) "the amount of boiling test used in the formaldehyde determina formaldehyde removed from the solution (and tion. absorbed by the ?ber) can be determined and In contrast with the above, and in accordance the percentage on the dry weight of the ?ber with my process, formaldehyde introduced into can similarly be calculated. 7 the ?ber is combined during the anhydride treat The amount of formaldehyde in the solution ment in some new way such as to produce a new is determined by the standard sul?te' method for ?ber having different properties. analyzing for formaldehyde. In accordance with my invention, the formalde , That formaldehyde is combined with the pro tein in my new ?ber in a different and new chem hyde treated ?ber is subjected to treatment with ical way is indicated by the fact'that the ?ber is vastly more stable against various chemical de the acid and the anhydride being present within teriorations including hydrolysis, thereby show an acid anhydride in admixture with free acid, _ a fixedv ratio of amounts. Anyanhydride exert ing that at least a part of the formaldehyde is ing an acylating action may be used, such as the not merely absorbed or held by the protein in anhydride of a carboxylic acid._ The anhydride some loose chemical way,‘ but rather that it enters 40 may be of an acid that is the same as the free into a reaction in the acylating process to pro acid used in the process or it may be different. For example, the anhydrides of acetic acid, such duce a new molecule which is a chemical com bination of the several reacting ingredients. This as acetic anhydride or ketene may be used with is further demonstrated by the fact that my new acetic acid, or acetic anhydride ‘or ketene may ?ber is di?'erent than the product obtained when 45 be used with other acids, such as formic, maleic, a ?ber is acylated which has not had a previous malic, stearic, lactic, butyric or phthalic acids. formaldehyde treatment. Anhydrides of acids other than acetic acid may . The difference between my new ?ber and prior ?ber is further indicated by the fact that my new ?ber, upon boiling with ‘water or a weak acid, 50 retains its ?ber identity and substantially all of its physical characteristics after the boiling oper ation. In addition, its loss of weight is not more than about 2 to 4%, thereby indicating that any be used, such as phthalic anhydride, propionic anhydride, lactic anhydride, maleic anhydride, butyric anhydride, stearic anhydride, adipic an hydride, succinic anhydride, cinnamic anhydride, lauric anhydride,. benzoic anhydride, or mixtures thereof, with the corresponding acid or with other acids. changes in the ?ber during boiling are relatively While any of the above materials may be used insigni?cant insofar as they a?fect its properties 65 in accordance with my invention, I will describe I and utility as ?ber. _ an illustrative embodiment utilizing acetic anhy I stated previously that the ?ber should be dride and acetic acid, since these are relatively treated with formaldehyde so _ as to have the inexpensive materials and are readily available - formaldehyde absorbed or loosely combined with in the open market in adequate quantities for the protein at the time of the treatment with 60 practicing the invention on a. commercial scale. the anhydride. The ?ber may be treated with Reference may also ‘be had to the attached formaldehyde in any conventional manner as by sheet of drawings which illustrates an apparatus - immersing it in a formaldehyde solution or treat which may be used in practicing the invention. ing it with formaldehyde vapor, “ Referring more particularly to the drawing, a ‘ In my application Serial No. 417,024, ?led Octo ber 29, 1941, I have described a method of treat centrifuge is indicated generally at I, preferably of relatively large dimensions. The centrifuge ing protein ?ber with formaldehyde, in which is provided with a perforated basket 2 mounted the pH and temperature are controlled whereby a maximum amount of the formaldehyde is com bined with the protein in a minimum of time. .This process may be employed, although the standard procedure of soaking the ?ber in the ordinary formaldehyde solutions for a long time, for example, 12 hours, may also be used. 75 for rotation by suitable motor 3. The centrifuge is provided with coils 4 through which steam or any heating or cooling medium may be intro duced by means of a valve 5, and withdrawn by an exit valve 6. The centrifuge is provided with a cover ‘I which may be secured to the centrifuge by means of suitable clamps 8, which may be ' ‘2 l . a large centrifuge, a suitable lifting or counter 8 ‘the treating operation. Also since the reaction spaced around the centrifuge so as to hold the cover tightly. Gaskets or washers to provide a tight seal may be used in the conventional man 'ner. Since the cover is relatively heavy in such forming the new ?ber is exothermic. the circu lation of the liquid through the ?ber prevents 5 local overheating. 'In order that the tempera ture of the liquid may be kept at the desired point balancing means 9 is provided for raising and or raised during the treatment, steam or other lowering the ‘cover. heating medium may be introduced through the ' v ‘ ‘ A supply tank i0 is provided of suchdimensions pipes 4. Ordinarily the operation is carried out at atmospheric pressure within the centrifuge, but least sufficient to ?ll the centrifuge._ This tank 10 it will be apparent that the structure utilized per— mits superatmospheric pressure, if this is desired. may be elevated above the centrifuge so that Following the treating operation, the valve i5 the liquid may be withdrawn therefrom by is opened and the treating liquid drains from the gravity through a pipe H and introduced into fiber and is returned to the supply tank by means the centrifuge by means of a valve i2. A pump as to hold the treating liquid in an amount at ‘ i3 is provided by means of which the liquid may 15 of the pump. l3. After all of the liquid that will . drain from the ?bers has beenpumped from the centrifuge, the centrifuge is operated at high speed for a few minutes. The centrifugal force liquid through the pipe i6 into the supply tank. removes a large portion of the liquid. This liquid If desired the tank may be below, the centrifuge and the liquid pumped from the tank to the cen 20 drains into the bottom of the centrifuge and is removed therefrom and returned to the supply trifuge and returned by gravity. ' be removed from the centrifuge through a pipe M by way of a valve I5. The pump returns the The supply tank is provided with heating‘coils I‘! through which steam or other heating: me dium may be passed to heat the liquid in the tank (by the pump I3. .: ' , _ The size of the centrifuge is not critical, but it is preferred to use one holding from 200 to 500 pounds of ?ber at a time. A centrifuge having a rotatable basket ?ve feet in diameter is suit able for this purpose. During a centrifuging operation, this may develop a centrifugal force be mentioned hereinafter, a treating chamber i8 of about 200 g., which is effective for separating is provided. This may be equipped with agitating paddles I8a driven by a motor l8b. When the 30 most of the treating ?uid from the ?ber. Aftenall'of the liquid has been removed from liquid is to be modi?ed, it may be’withdrawn from the ?ber, the valve I5 is closed, and the valve the supply tank through a pipe 2| by way of a 21 is then opened. A vacuum is applied to the valve 22 and ‘introduced into the chamber l8. supply tank to the desired temperature. In order to modify the constitution of the treat ing liquid .in the supply tank for the purpose to Following the treatment the liquid may be dis centrifuge to create an absolute pressure as low lected. The treating liquid may be separated from any water by stratification and withdrawn through a valve 3| and returned through a pipe not su?lcient to vaporize the remaining liquid charged into‘a centrifuge H! by way of a pipe 35 as is ‘feasible with apparatus of this type. A vacuum of 25 to 29 inches is desirable, and one 190 and a valve l9b. This centrifuge has a basket as low as 28 inches is preferred. At this low, Illa rotatable by a motor 20. Following centri pressure the liquid is quite volatile and the latent fuging the liquid may be pumped back into the heat in the ?ber, together with any additional supply tank by means of a pump 23 by way of heat which may be supplied, is sufficient to vapor a valve 24 and a return pipe 25. _ ize substantially all of the liquid which has not Connected with the treating centrifuge Us a been removed from the ?ber during centrifuging. conduit 26, leading through a valve 21, to a con ‘ The liquid is condensed in a condenser 28 and denser 28. A vacuum pump 30 is connected with after separation from any water in the receiver the condenser through a pipe 29. By this arrange ment it is possible to place the treating centrifuge 45 30 is returned. to the supply tank by way of the conduit 32 and the pump l3. _ under vacuum when it is desired. Connected with If the sensible heat in the ?ber, and that which the condenser 28, through a conduit 29a, is a may be introduced by means of the coils l, is receiver 30 in which the condensate may be col 32, through the pump l3, and to the supply tank by way of the pipe l6. Any water separated from at the vacuum employed, it is possible to admit a suitable amount of very hot‘ air into the cen trifuge; this facilitates vaporization of the treat ing ?uid. ‘ However, due to the poor heat conductivity of the ?ber and the dimculty in introducing heat pipe .33. 55 except by a circulating liquid, I prefer to remove vThe ‘treating chamber I8 and centrifuge l9 ‘so much of the liquid by centrifugal forces as to are also connected to a, condenser 28a and~an ' leave no more of the liquid on the ?ber than can _ exhausting pump 30a by means of conduits 34 be evaporated by the latent heat in the ?ber at connected through valves 35. By this means it is , also possible to exhaust vapors from the chamber 60 the reduced‘ pressure employed. After this operation the vacuum valve 21 is l8 and centrifuge l9 and condense them. The closed and the cover removed from the centri above apparatus is illustrative and other ex fuge. The treated fiber is then removed, washed amples of apparatus will occur to persons skilled and treated by any subsequent processing oper in the art. the solvent can be removed from the over?ow .. When it is desired to'treat the ?ber, a quantity ' 65 is placed within the centrifuge basket 2 and the cover ‘I is tightly secured thereto by means ation desired. ’ i The liquid used in the treatment contains the anhydride and-the acid in required'proportions. Preferably these are contained in an inert sol of the clamps 8. Valves l5 and 21 ‘are closed and treating liquid admitted from the supply tank ‘vent which acts as a diluent. i 0 by means of the valve l2 until the ?ber is cov ered with the liquid. The ?ber is then allowed to ' inertness with respect to the anhydride, the acid stand in contact with this liquid for the required length of time and if desired the centrifuge may be operated very slowly so as to obtain uniform . The solvent should be selected because of its‘ and the protein being treated, as well as its sol vent action on the anh'ydride, at the tempera tures employed. The boiling point of the sol admixture of the liquid through the ?ber during 75 vent preferably is above the temperature at 9,408,028 - a "which the treating operation .is carried out so as not to require superatmospherie pressure dur 1o ing the cost of heat, the‘ amount of ?ber that must be treated per day in a given amount of ing ‘the, treatment, but the boiling point also equipment, and the price of anhydride. Within the ?gures set forth above. and in view of the should not be too high above the treating tem perature so as not to prevent evaporation of the liquid when. the vacuum is applied subsequent to ' principles announced herein, anyone skilled in the art will be enabled to relate these factors taking into account the economics ‘involved and the type of property desired. In general, I prefer the. treating operation. In general, it is pref erable that the ‘boiling point of the solvent should be above that of water, so as to facilitate sep to use a treating temperature between 180 and aration of water in vapor form from the solvent. 10 200° F., a solvent having a boiling point of be If, for example, the liquid is to be heated to a tween 200 and 250° F'., a concentration of an temperature of about 190° F. at the time of treat- . - hydride from 3 to 10%, v ment, the solvent should have a boiling point of desirably at least 5% and preferably 7 to 8% by volume, and a treat at. least 200° F., and_preferably above 220° F. time of 20 minutes to oneihour or 90 minutes. Solvents that have been found suitable include 15 ingPreferably the liquid is introduced at a lower hydrocarbons having the desired boiling point temperature, say 185° to 190° F. so that as the and the halogenated hydrocarbons. For reasons reaction begins there will be no local overheat of convenience and safety non-in?ammable sol ing. As it proceeds and nears the end the tem vents, suchas halogenated hydrocarbons, are pre perature may be raised to 200° F. without harm. ferred. A particularly suitable solvent is per 20 The higher temperature also provides a larger chloroethylene or tetraehloroethylene. This has amount of latent heat in the fiber to remove the a boiling point of about 248° F. and permits the solvent by vaporization when the vacuum treating operation to be carried on at around applied. ' ' 185 to 210° F., as may be desired. The amount of treating liquid of any of the The temperature of the liquid at the time it 25 compositions described above that is required in is introduced to the ?ber and while in contact relation to the amount of ?ber to be treated may therewith will depend upon the concentration of vary over relatively wide ranges. Since all of the the anhydride and the length of the time it is ' treating liquid is recovered except the anhydride desired to subject the ?ber to the treatment. I have discovered that quite high temperatures 30 which enters into chemical combination during the treatment, it is preferred to use enough to may be used without harming the ?ber. If for a thoroughly cover the ?ber during the treatment. given concentration of the anhydride, a treat In general, 7 or 8 to 40 parts of the liquid to 1 ment for one-half hour,at 190° to 200° F. is sat part of the ?ber is preferred. The ?ber gains isfactory, the time could be reduced to one-half that, namely, to ?fteen minutes if the tempera. as ture is raised to 220° F. However, at tempera ‘tures much above 200° ‘F. .there may be some slight yellowing of the ?ber. This may be un “ objectionable when the ?ber is to be used for in weight by about, 3 to 8% following the treat ment, which is attributed to the anhydride that combines chemically with it. Thus the amount of anhydride present during the-treatment is , adequate for the purpose. Inclusion of the proper amount of acid with some purposes, but if a white fiber is desired the 40 the anhydride is essential.‘ The exact chemical highest temperature to be used is selected with role the acid plays is not entirely clear, since the this consideration in mind. The temperature acid itself is not capable of acylating the ?ber. may be reduced :below 190° F. by continuing the However, I have discovered that anhydrous ?ber. treatment for a longer period. Treating for the treatd with acid free anhydrous anhydride is not lengths of time given does not harm the ?ber. acylated satisfactorily. The ratio Of'the acid to ‘ but for economic reasons it will be understood anhydride is preferably about 10 parts of anhy that there is no advantage in continuing the dride 'to 1 to 10 parts of acid, preferably‘ 3 to 5 treatment beyond such time as is necessary to parts of acid by weight or volume since the secure the desired results. densities of the acid and anhydride ‘are so The temperature could be reduced still further‘ 50 similar. ‘ Thus, a preferred treating liquid might by employing a higher concentration of the an contain 8 parts of anhydride, 2.5 parts of acid hydride in the diluent solvent. For example, if and 89.5 parts of a solvent, by weight. \ the solvent contained about 50% anhydride 9. It is preferred that the ?ber should be as free Q lower temperature of approximately 150° F. could from water as possible at the time of treatment, be used and the time of treatment reduced to a very few minutes. The use of larger quantities of anhydride, however, is not as economic as the use of a smaller quantity at a higher tempera ture, nor is the control as accurate. i ’ since any water contained in the ‘fiber reacts with the anhydride to form acetic acid and und_esir--v ably increases the ratio of acid to anhydride in the treating liquid and uses up a portion. of the However, it may be uneconomic un In the above discussion the amounts given are 60 anhydride. der some circumstances to dry the ?ber to a by weight using perchloroethylene as the diluent. completely anhydrous state before treatment, If a lighter diluent is used suitable adjustment and the dry appearing ?ber may usually contain must be made. up to 10% moisture. Furthermore it may be From the above it will be seen that the rate of the reaction is dependent upon temperature 65 diiiicult to dry the formaldehyde treated ?ber to a moisture content below 11/2% without harming and concentration of anhydride. Since the re it. The-extent tov which the ?ber is dried will action is exothermic the rate must not be so depend upon the economics involved. Thus, it high as to produce local overheating. The rate may be more expensive to reducethe moisture is adjusted so that the heat developed by the the ?ber below a given amount than it is to reaction can be absorbed by the liquid and thus 70 Lin utilize a part of the anhydride byreaction with‘ the ?ber prevented from- yellowing by subject the water. Under present circumstances it is tion to too' high a temperature. desirable to reduce the moisture to not over 2%. The relation of the treating temperature. the concentration of anhydride, and the length of In view of this circumstance the ratio of acid ' to anhydride in the treating liquid before it is treatment also involve economic factors, includ 75 introduced into the treating centrifuge should be 2,408,026 ': '11 line 34 may be closed and the acetate removed ' adjusted in view of the moisture content of the ‘from the centrifuge basket. The acetate may be ?ber. Thus, if the ?ber contains moisture the ‘ reconverted into acetic anhydride by known amount of anhydride in the liquid should be in chemical methods, so that. there is no loss be creased and the amount of acid decreased below cause of moisture in the ?ber. introduction of _ the preferred ratio, so that upon The various materials condensed in the con the liquid into the centrifuge and reaction of an- , _ denser 28, including watenacid, anhydride‘and hydride with the moisture in the ?ber, the diluent solvent. are passed to the receiver II. .amounts of anhydride and acid remaining'in the These materials stratify into an upper layer of liquid will be those preferred. This, of course. 10' water and a lowenlayer of diluent. Apparently ‘ involves simple chemical calculations. the anhydride and the acid are more soluble After each treatment of moisture containing ', both in the solvent than in water and the lower ?ber the anhydride and acid content of the treat strata, which contains the diluent solvent, anhy ing liquid is altered. It is necessary, therefore, dride and acid may be pumped backinto the’ to correct the composition of the liquid in the supply tank. will supply tank before the next batch of fiber is From the above description it will be apparent that my process appears to be applicable most‘ Since a portion of anhydride is used up in each readily to a batch operation, but it may also be treatment both by combination with the ?ber and applied to a continuous process. For example, by reaction with any water in the ?ber, it is the ?ber in continuous strands or ropes may be necessary to add anhydride to the supply tank, 20 drawn through pipes or tubes through which ypreferably after the treatment of each batch, so the treating liquid is ?owing preferably counter that the anhydride concentration will be correct. currently. ’ ' Since the amount of acid in the treating liquid The ?ber, at the time it is introduced into the‘ will constantly increase upon reusing it if the centrifuge, may be in a tow of continuous ?la ?ber contains moisture, it is necessary to remove ments, or it may be cut into staple form. In‘ a portion of the acid, preferably'after the treat ‘ the latter form the staples will be free to take treated. - _ ' ment of each batch of ?ber. This is done most on or relax into any position and thus can ac readily by neutralizing the acid and removing it as a salt. - ' Rather than treat all of the liquid so as to re so duce the amount of acid to the desired point, I ‘ ?nd it convenient to completely neutralize all of the acid in a portion of the liquid, the amount quire a crimp which will be permanent, since the new chemical compound will be formed while the ?ber is delineated in the crimped position. I have described my invention primarily with reference to treatment by acetic anhydride‘ and acetic acid. As I have mentioned previously, the ~of liquid so neutralized being such that upon its' , anhydrides' of other acids and other free acids return to the entire volume of liquid the acid 35 ratio will be correct. This is accomplished read ily ' Afterthe as follows:liquid ha been returned from the. . may be used. The anhydride may be of the same acid that is present‘ in free form or of a different ‘ acid. Generally when a different combination‘ of acid and anhydride is employed, it is prefer centrifuge I by the pump I! to the supply tank able to utilize acetic or lactic acid as the acid ill, a sample is withdrawn and analyzed for an 40 since these acids are desirable because of their hydride and'acid content. Su?lcient anhydride swelling action on the ?ber and the consequent is then added to raise the anhydride concentra increase in speed of reaction. The combina tion to, the desired amount. From simple calcu tion, for example, of acetic acid with malic or lations it is possibleto determine what fraction maleic anhydride products a very soft ?ber simi of the total volume of liquid can have all of the .45 lar to camel's hair. Lactic anhydride and lactic acid removed therefrom so that the entire vol acid give admirable results. A mixture of acetic ume of liquid will have the desired amount of acid and stearic anhydride or any other high acid. After this calculation is made, the calcu molecular. weight anhydride produces an un lated'amount of liquid is withdrawn through the usually soft fiber; 'The lubricating properties of pipe 2| by opening the valve 22 and admitting 60 the high molecular weight fatty acid can be read the ‘calculated amount of liquid into the treating ily noticed in the ?nished ?ber, but it has the chamber ill. To this is added soda ash or a caustic which neutralizes the acid. Preferably ' the temperature at the time of neutralization is advantage that the high molecular weight sof tening fatty material is combined chemically with the ?ber. In some instances the anhydride /200° F. or above and the liquid may be heated 65 may be formed at the time of the treatment. For ’ water formed upon neutralization is readily re in the treating chamber by steam coils. The water formed upon neutralization is readily re example. acetic anhydride and stearic acid will form stearic anhydride and acetic acid and the action may be the combined acylating actions of moved by means of the vacuum pump 30a so stearic and acetic anhydrides. that it is not available to decompose thev an 60 I have indicated heretofore that the protein, hydride in the liquid. when soda ash is used to neutralize the acid, the water is vaporized and goes off with the carbon dioxide. The liquid is then admitted to the centrifuge I! by the pipe I90 and valve Mb. The basket within the cen trifuge is preferably lined with canvas or a ?lter formaldehyde and anhydride combine to form’ a new chemical compound. The exact reactions are difficult to describe because of the complex nature of protein, particularly casein. My in 65 vestigation led me to believe that the reaction of thevformaidehyde and the anhydride with the ing material. The salt formed by the neutraliza protein is one involving the amino groups of the tion is retained within the basket and by rotat protein. Benedicenti has suggested that the re ing the basket of the centrifuge, it is possible to eliminate substantially all of the liquid from the 70 action between casein and formaldehyde is some what as follows: - _ salt. At the same time the acid-free liquid is pumped from the centrifuge by means of the pump 23 and returned to the supply tank by means of the pipe 25. After all of the liquid has been returned to the supply tank, the vacuum 76. 2,408,026 13 14 where R is the casein residue. The fact that the formaldehyde can apparently be removed read.» ily from the formaldehyde-casein complex small. In the case of acetic acid this will be . a pH of 3.5. to 4. the above type. v . ' manuacture of felt hats from the ?ber. ' Upon treatment of the casein-formaldehyde complex with the acylating agent it is probable‘ This is very desirable, since a ?ber having this pH is'particularly desired’ in the - seems to be suggestive that the reaction is of I . In the event that the pH value of the fiber is to'be raised, this can be done by ‘treating the ?ber with a buffered. neutralizing agent, such as ' disodium hydrogen phosphate and washing to re move the phosphate, and any other salts formed. that a reaction of the following nature takes place: R—-NH—CH2-—OOCR1, where R1 is the residue of the acylating anhydride, i. e., CH: in 10 By adjusting the concentration of the'neutraliz the case of acetic anhydride. ‘_ ' ing solution and the time of treatment, the re The exact chemistry involved must at best be . sulting ’ ?ber may be given any pH value desired. a matter of speculation, since the complexity of , ‘ A pH value of Mo 6 is desired by the textile: trade, the matter does not permit a de?nite determina and a. low free acid, preferably less than. 1.0%. At any stage of the treating operations the ?ber That the reaction is one in which the form may be treated with a softening agent, prefer aldehyde combines with the amino groups ‘and v ably a cationic active compound such as “Ah-‘ the anhydride then combines with this combina covel” which does not have any eifect upon tion is indicated by the fact that the carboxyl the pH value of the ?ber. . groups probably remain unaltered in the protein 20 My invention can be the subject of many variar tion.‘ . ‘ I - molecule. My new ?ber has an acid number as does casein which indicates that there are prob tions as is indicated herein, and can use many ' equivalent materials all of which are to be in - eluded as indicated in the following claims. ably some unaltered carboxyl groups. However, the carboxyl groups apparently-do not contribute to any undesirable properties of the ?ber. I That my new product is the reaction of pro This application is a continuation-in-part of 25 my applications Serial No. 242,279, ?led November tein, formaldehyde and the anhydride is shown 25, 1938; Serial No. 291,616, led August 23, 1939, and Serial No. 309,028, ?led December 13, 1939. by the fact that the treatment of casein ?ber I claim: “ with an anhydride, which ?ber has not previously‘ A method of improving the dyeing proper has a formaldehyde treatment, does not pro 30 ties1. of a “synthetic protein-base material formed duce my new ?ber. Apparently in such a treat by shaping an alkali-soluble acid-coagulable pro ment the anhydride combines with groups in “the tein comprising casein and treating it with form protein to form linkages which are hydrolyzable. aldehyde, which comprises subjecting said pro As further indicative of the fact that the tein-base material to a treating liquid at a tem amino groups are blocked, my new ?ber is not perature above 150° F., said treating liquid com amphoteric as are ordinary proteins in that it prising an inert diluent'in which is dissolved from does not possess an isoelectric point characteristic 3 to 50% of the anhydride of a carboxylic acid of protein. in admixture with 1 to 10 parts of a free carThat the ?ber produced in accordance'with boxylic acid for each 10 parts of theanhydride. my invention is ‘entirely vdifferent is indicated ‘\2\. A method of improving the dyeing properties > by-the fact that it will withstand vigorous boil of a synthetic casein-base ?ber formed by shaping ing for two hours in neutral distilled water with 'said casein/into ?ber form and treating it with out any substantial deleterious effect, and upon formaldehyde, which comprises subjecting said removal from this boiling water treatment and ?ber to a treating liquid at a temperature above drying by usual methods the ?ber will retain sub stantially all of its original qualities which ren 45 150° F., said treating liquid comprising an inert diluent in which is dissolved from 3 to 50% of der it suitable as a ?ber. It will :be appreciated an anhydride of acetic acid in admixture with 1 that this is a very vigorous test and that there to 10 parts of acetic acid for each ‘10 parts of ‘the are even few naturally occurring proteinaceous anhydride. ' ?bers which‘ will withstand such a test. 3. A method of improving the dyeing proper Fiber produced in accordance with my invention 50 ties of a synthetic casein-base ?ber formed by will also pass the so-called "pepsin test" (Mel shaping said casein into ?ber form and treating liand Textilber. 20, 697-8 (1939)). This is one 'of the most rigorous tests to which this type of , it with formaldehyde,which comprises subject ing said ?ber to a treating liquid at a temperature proteinaceous ?ber can be subjected and that of 150° to 220°, F. for from 15 to 90 minutes, said 55 my ?ber is not attacked by the pepsin in this test treating liquid comprising an inert diluent in indicates that it is no longer a pure protein ma which is dissolved 3 to 10% of acetic anhydride terial. and 1 to 10 parts of acetic acid for each 10 parts As further indicative of the novelty of my in of the anhydride. vention I might mention that the treatment of 4. A method of improving the dyeing proper casein ?bers as proposed heretofore in the art, 60 ties of a synthetic casein-base ?ber formed by such as by treatment with nitrous acid or a treat shaping said casein into ?ber form and treating ment with halides, does not result in a ?ber which it with formaldehyde, which comprises subjecting will withstand the above described "boil test" ,or said ?ber to a treating liquid for from 15 to 90 "pepsin test." minutes at a temperature of fromv 150° to 220° The ?ber after being removed from the cen 65 F., said treating liquid comprising a volatile inert trifuge at the end of the treatment may be ,washed diluent containing at least 5% and less than 60% to remove free acid, since it is more or less per acetic anhydride and 1 to 10 parts of acetic: acid meated by the free acid in the treating liquid. for each 10 parts of acetic anhydride, then cen The water dissolves a substantial proportion of trifuging the ?ber after the treatment to remove 70 the acid. However, it is impossible as a practical the major portion of thetreating liquid adhering matter to dissolve all of the acid and the ?ber. to the ?ber, and evaporating still an additional is left with a resulting pH value characteristic ' amount of the remaining adhering treating liquid ofv the free acid used, irrespective of the amount by placing the ?ber under a vacuum. of acid retained, even though this be extremely 75 FRANCIS CLARKE ATWOOD. ‘ ' 7 . ' l5 l6 - . Certi?cate-of Correction ’ September 24, 1946; Patent No. 2,408,026. " ' > ’ , ~ - ' l ' FRANCIS CLARKE ATWOOD , It is hereby certi?ed that errors appear in the printed speci?cation of the above numbered patent requiring correction as follows: Column 10, line 9 after “tempera ture” insert of; column 11, line 56, strike out the'words and syllable “water formed upon neutralization is readily re-”; column 12, line 45, for “products” read ro'duces; column 13, line 30, for “has” read had; and that the said Letters Patent 5 ould be read with these corrections therein that the same may conform to the record of the case in the Patent O?ice. ' . ‘ Signed and sealed this‘26th day of November, A. D. 1946; it LESLIE FRAZER, First Assistant Oonvmz'ssimwr of Patents.