US2998329A

US2998329A - Modification of cellulosic articles

Info

Publication number: US2998329A
Application number: US676057A
Authority: US
Inventors: Richard C Sovish; Frank L Saunders
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1957-08-05
Filing date: 1957-08-05
Publication date: 1961-08-29
Anticipated expiration: 1978-08-29

Description

Allg- 29, 1961 R. c. sovlsH ET AL 2,998,329

MODIFICATION OF CELLULOSIC ARTICLES Filed Aug. 5, 1957 IN VEN TORS /ffc/)oro/ C. 5 o 1//5/1 Fra/7k L. Sounders TZ'ORNEYS United Stal-'e5 Patent 2,998,329 t MDDIFICATION F CELLUL'OSIC ARTICLES Richard C. Sovish and Frank L. Saunders, Midland,

Mich., assignors to'The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Aug. S, 1957, Ser. No. 676,057 14* Claims. (Cl. 117-93) Many articles that consist Ior are comprised of essentially or substantially pure cellulosic materials have certain physical properties and ycharacteristics that, advantageously and quite desirably, might Well be improved upon. Included in such class, in particular, may be cotton and other natural cellulosic textile fibers and various artificial shaped articles of cellulose that has been reconstituted or regenerated, for example, by either the viscose, cuprammonium or analogous processes. Typical of reconstituted cellulose articles are the viscose 'rayon types of so-called artificial silk textile fibers and regenerated cellulose films for wrapping and protective purposes, among other uses.

By Way of delineating certain of the referred-to deficiencies, it is Well known, for example, that unmodified cotton fiber has a tendency to rot. Viscose rayon, as either a filamentous or filmiform shaped article, may be similarly afflicted. In addition, viscose rayon has notorious susceptibility to being adversely affected by water. Thus, such forms of regenerated cellulose may generally be characterized by theirv rather poor Wet strength and reduced resilience in the presence of moisture.

The attempts to overcome these and cognate difiiculties in textile materials of cotton and viscose rayon and in regenerated cellulose film have literally been legion. The dissatisfactorily low rot resistance of cotton, for example, has been the basis for many ameliorative treating and processing techniques thereupon, including cyanoethylation of the natural fiber or cloth and fabric textile materials constructed therefrom. Likewise, many polymeric `and resinous coatings and finishes have been proposed and employed both for cotton, viscose rayon and the like substantially pure cellulosic textile fibers and the articles into which they are converted in order to augment and improve their resistance to rotting, moisture, wrinkling and for multitudinous corollary and analogous purposes. Regenerated cellulose films have received a great deal of attention that is akin to that which is cursorily alluded t0 in the foregoing.

The chief aim and concern of the present invention is to provide an improved and signicantly superior method for modifying shaped articles of various substantially pure cellulosic articles and materials, particularly cotton and viscose rayon fibers and cloth and fabric comprised thereof and constructed therefrom and film structures of regenerated cellulose, by providing them With at least a superficial coating or 'chemically modified surface, or both, or even a like penetrating subsurface effect, of certain monomeric substances that are adapted to chemically polymerize to form a polymeric or resinous coating for or over the cellulosic substrate or to react chemically with the cellulosic substrate or to graft copolymerize with the cellulosic substrate to form' a chemically bound polymeric or resinous superficial layer thereover or permeated section thereof, or to beneficially modify the substrate by combination effects of the indicated varieties. It is also a purpose and design of the invention to furnish the advantageously enhanced products of the above delineated method.

According to the present invention, a substantially pure cellulosic substrate in shaped article form (including cotton and viscose or cuprammonium rayon fibers and cloth and fabric constructed therefrom and regenerated cellulose lm) may advantageously be modified for improvement in and benefit to one or more of its basic physical Patented Aug. 29, 1961 ICC properties and characteristics such as rot resistance and water-proofness or hygroscopicity by a method which comprises first contacting, and, if desired, impregnating, the cellulosic substrate With an aqueous solution `of a Water-soluble monomer that is polymerizable in aqueous solution under the inliuence of a field of ionizing high energy radiation; then subequently exposing the cellulosic substrate in contact with the aqueous monomeric solution (and, advantageously, at least partially swollen thereby) to a field of ionizing high energy radiation until at least the surface of the substrate has become modified With -reacted monomeric material. As has been indicated, the reacted monomeric material may become chemically attached to the cellulosic substrate, as is the case when cotton and other cellulosic bers are modified with acrylonitrile by practice of the present invention, or it may graft copolymerize thereon and thereto or may merely form an intimately bonded and firmly attached physical polymeric or resinous layer or coating or impregnated section, or both, on or in the substrate as a result of polymerization of `the water soluble monomer. In any event, and without being restricted to particular mechanisms by which the desired improvement may be achieved and effected, the properties of the cellulosic substrate are ameliorated and enhanced in one or more ways, depending on the particular monomeric material or mixture of monomers that is employed and the specific effects that they are capable of achieving and the properties and characteristics they are adapted to contribute in and for the substantially pure cellulosic substrate.

Thus, when aqueous solutions of acrylonitrile are employed Ion and with cotton fibers or cloth (and like cellulosic substrates) an extremely efficient and remarkable degree of improvement is readily and exceptionally uniformly achieved in the substrate. Products having excellent rot resistance may accordingly be excellently and easily provided. Likewise, other monomers can be made to modify the cellulosic substrate by polymerization or graft copolymerization with the cellulose, or both, Within or on (or with and on) the cellulosic substrate to form tightly adhering, polymeric or resinous layers or impregnated sections, or both, that are capable of mildew or water-proofing the substrate; benefitting its Wrinkle resistance; improving or altering its dye-receptivity characteristics; etc., depending on the functional characteristics and inherent behaviorism of the chemical product of the reacted monomer. All this may generally be accomplished, incidentally, Without disturbing or appreciably altering the visual appearance or hand of the substrate being modified.

As has been indicated, the monomer that is employed for modifying the cellulosic substrate must be water-soluble and capableof being polymerized in aqueous solution under the influence of a field of ionizing high energy radiation. And, as mentioned, the method of the invention must be performed with the monomer in aqueous solution While in contact with the cellulosic substrate being modified. In this connection, as is contemplated herein, the water-soluble monomers that are suitable for use in the practice of the present invention include those that are only soluble in Water to a limited degree and which may sometimes be considered for other purposes as not being completely Water-miscible despite the fact that they actually dissolve in Water to the slight extent that is adequate for their utilization according to the instant invention. Surprisingly enough, the presence of water during the radiation is a criticality that cannot be avoided if the optimum benefit and advantage of the present invention is to be achieved. As remarkable and inexplicable as it may seem, decidedly inferior or no results are obtained when the cellulosic substrate is irradiated when it is in contact with only the monomer alone. Vlvl'oclification with acrylonitrile bears excellent evidence of this. The firmly attached and bonded pick up of cotton fiber or cloth irradiated inthe presence of acrylonitrile alone is generally either an immeasurable or negligible quantity (say up to 2 percent by weight, at best). Or, at the other extreme the article, such as cloth, that is being modified may actually become embedded in such an enveloping, solid mass of extrinsic polyacrylonitrile as to literally be rendered useless for any practical purpose. To the contrary, cotton that has been irradiated in the presence of an aqueous solution of acrylonitrile readily picks up five to ten times as much of the chemically attached reaction product as in the best results of irradiation of the same monomer without utilization of the aqueous medium. Furthermore, most conventional, non-aqueous solvents such as dioxane, methyl ethyl ketone, benzene, absolute ethanol and the like do not provide the same outstanding and apparently unique advantage as water. Such solvents, when employed to dissolve the monomer for purposes of furnishing a contacting monomeric solution to use with the cellulosic substrate, do not, in general, alter the dissatisfactory or less beneficial results that are achieved when only the pure monomer is directly employed to contact the substrate being irradiated.

Practice of the present invention provides 'and secures many `benefits and advantages. The improvement and simplification in modifying cellulosic articles with acrylonitrile is evident in the foregoing. In an analogous way, the substrate may be provided with a desired polymeric or resinous coating by merely irradiating a cloth, fabric or other desired article while it is in contact with an aqueous solution of suitable monomer, then washing and drying the irradiated and modified article. In general, no chemical catalyst is needed. Practice of the present invention, of course, obviates the tedious conventional technique for applying resinous coatings which ordinarily involves dissolving or dispersing the polymer that is desired for providing the intended coating in a suitable solvent, coating the resulting composition on the cloth, removing excess solvent, etc. A cellulosic fabric that has been beneficially modified in accordance with the present invention is schematically depicted in the sole gure of the hereto annexed drawing.

Advantageously, the Water-soluble monomer that is employed for modifying the cellulosic substrate in the practice of the present invention is selected from the group consisting of acrylonitrile, methacrylonitrile, acrylamide, acrylic acid, methyl methacrylate, sulfonated styrene monomers (including the free acid and salt forms thereof), particularly those sulfonated in the para position, vinyl lactam monomers (particularly N-vinyl'lactam monomers such as those disclosed in U.S. Patent No. 2,265,450 and especially N-vinyl pyrrolidone) and methyl isopropenyl ketone. The concentration of the aqueous solution of the monomer that is employed may vary over relatively wide ranges. Ordinarily, within the limits of water solubility, it is beneficial to employ a monomeric solution that contains from l or 2 to 10 or 15 percent by Weight (based on the weight of the solution) of the dissolved monomer although, in certain cases, particularly with vinyl lactam monomers, much more concentrated aqueous solutions, say up to 50 or more percent, may be employed suitably. Enough of the monomeric solution should be applied to or made available in intimate contact with the cellulosic substrate to permit the desired take-up or pick-up of reacted monomer product to be achieved in or on the substrate. When aqueous acrylonitrile solutions are being employed for the modification, use of a monomeric solution that contains about 5 percent by weight of dissolved monomer generally brings optimum results. Little, if any, additional pick-up of reaction product by the cellulosic substrate seems to be brought about by utilization of more concentrated aqueous acrylonitrile mixtures including those having as much as 25 percent by weight of incorporatedmonomer. The

.4 5 percent acrylonitrile solutions have good dissolution of the monomer and seem to result in minimized derivation of straight homopolymer product. If desired with acrylonitrile or other monomers, mixtures of water and lower alkyl alcohols such as methanol and the like or other water miscible solvents may be suitably employed in the practice of the invention to secure greater concentrations of dissolved monomer.

Generally, a satisfactory result may be `achieved when a minor proportion of reacted product is impregnated in or provided on the cellulosic substrate, or both. In some instances, very minor proportions may suffice, especially when low levels or degrees of modification are deemed satisfactory for a particular purpose at hand. It is difficult to generalize on the weight proportions that may be utilized in all instances due, as may be readily appreciated, to the relatively wide divergence in the specific characteristics of the various cellulose substrates that may be improved by practice of the present invention and the variations in the monomers and their reaction products that may be used. Broadly speaking, it may be desirable to impregnate or contact the substrate with such a quantity of the aqueous monomeric solution as will provide between about 1 and 40 percent by Weight of the monomer for the irradiation induced reaction in the presence of the substrate. For most purposes an amount of solution that will provide from about 5 to 20 percent of monomer in contact with the substrate may be quite suitable.

It is most desirable and of greatest economical value for all or substantially al1 of the monomer that is employed to be reacted to a product under the influence of irradiation that is picked-up by the cellulosic substrate through either chemical interaction or attachment or physical adherence of a polymer product, or both. Thus, it is beneficial in most instances for the radiation to be continued until all or substantially all of the monomer that has been placed in contact in aqueous solution with the substrate is picked up as a reacted product by the substrate. The irradiation, incidentally, may be performed While the substrate is actually immersed in the aqueous monomeric solution or, frequently with greater advantage, with the solution being merely applied to the substrate as by spraying or spreading the solution on the substrate or dipping the substrate into the solution and wringing it to a desired monomeric content prior to irradiation. Maximum benefit and superior effects of modification, particularly as regards pick-up potential, are frequently obtained when substantially neutral (or essentially neither acidic or basic) impregnating solutions are employed. Thus, lower pick-ups are invariably encountered with acrylonitrile on cotton when the monomer is dissolved in 1 percent by weight aqueous solutions of either sodium hydroxide or hydrochloric acid. This phenomenon is hereinafter more particularly demonstrated.

The high energy radiation which is employed for inducing the modification of the cellulosic substrate with the reaction product of the aqueous monomeric solution that is in contact therewith is of the ionizing type which provides emitted photons having an intrinsic energy of a magnitude which is greater than the planetary electron binding energies which occur in the reacting monomeric materials and the cellulosic substrates in the modifying reactions (such as straight chemical interaction, graft copolymerization and the like) in which they become involved. Such high energy radiation is conveniently available from various radioactive substances which provide beta or gamma radiation as, for example, radioactive cobalt, nuclear reaction fission products and the like. If it is preferred, however, high energy radiation from such sources as electron beam generators, X-ray generators and the like may also be utilized. It is beneficial to employ the high energy radiation in a field of at least about 40,000roentgens per hour (or equivalent ionizing potency) intensity, A roentgen, as is commonly understood,

epesses is the amount of high energy radiation as may be provided in a radiation field which produces in one cubic centimeter of air at 0 C. and 760 millimeters of absoous solution of the monomer and the substantially pure cellulosic substrate are under a mutal inflence in the field of high energy radiation. Room temperatures and atmospheric pressures may be employed satisfactorily for the e *Y irradiation, although, in certain instances, it may be desired to accomplish the modification of the substrate at elevated temperatures and even under superatmospheric pressures. The preferred radiation dosage in million roentgen equivalent physicals (mrep.) that is employed is an amount or quantity that is adapted to quickly accomplish the desired modification without deleteriously influencing or degrading the reacted monomer product or the cellulosic substrate, or both. Usually, dosages between about 0.1 and 5.0 mrep. at rates of from 0.04 -to 1.0 mrep. per hour are suitable for the achievement of such end. Obviously, the greatest economy and advantage may be achieved when the minimum high energy radiation dosages are involved. Excessive dosages should be avoided, especially after all or substantially all of the irradiation-induced modifying reaction has occurred.

The invention is further illustrated in and by the following examples, wherein unless otherwise indicated, all parts and percentages are to be taken by weight.

EXAMPLE 1 Three pieces of square woven cotton fabric having individual dimensions of about 11/2 by 8 inches that were obtained from about 2.5 ounces to the yard stock and which weighed 0.701; 0.724; and 0.672 grams, respectively were each immersed in an aqueous solution of about 4.2 grams of acrylonitn'le in 55.8 grams of Water. The solution, containing the cloth samples immersed therein, was then purged with nitrogen and subjected to a field lof high energy ionizing irradition from a cobalt-60 properties as the sample of cotton fabric that was irradiated in air.

Substantially equivalent results were obtained when the foregoing was repeated excepting to eliminate the purge with nitrogen or to replace it bypurging with air. Similar results were also obtained when the foregoing was repeated excepting to effect a total dosage of about 1.0

Y Y mrep. for the modification.

` on the substrate during the time that the applicating aque fl looked exactly like the original, although it had a very Y slightly different hand (or feel to the touch), being slightly less sleazy in this respect. The modified fabric dyed more easily with Calcomine R, a direct dye, than did the unmodified material. Its rot resistance was much better than that of the unmodified cotton and at least as good in this respect, for example, as conventionally cyanoethylated materials. It could withstand a load of about 37.2 pounds at breaking (according to the strip tensile test of A.S.T.M. D-39-49) and had an elongation of about 4.9 percent. The unmodified cotton fabric had aV breaking load of 34.2 pounds and 5.4 percent elongation. The same fabric, after having been subjected to the same irradiation While immersed in plain water Without being in contact with any modifying monomer, had a breaking load of 39.6 pounds and an elongation of 6.4 percent. Plain cotton fabric that was subjected alone to `a 5.0mrep, dosage was found to have a breaking load of 30.7 pounds.

In contrast with the foregoing, when the same fabric was immersed in pure monomeric acrylonitrile and sub- A jected to the same irradiating influence while so immersed, i. it was found to have experienced only a 1.6 percent permanent pick up and to have essentially the same physical Commensurate results were yalso yachieved when the foregoing was repeated excepting to replace the cotton fabric being modified with heavier 10 ounce cotton duck fabric.

EXAMPLE 2 EXAMPLE 3 The procedure of the first example was repeated with aqueous solutions of 3.5 percent acrylamide, 5 percent methyl isopropenyl ketone, 3.5 percent acrylic acid, 5 percent Isodium styrene p-sulfonate and 5 percent N-vinyl py-rrolidone. The pick ups that Were obtained on the cotton fabric substrate of each of the reaction products of the monomer after the 0.5 mrep. irradiation dosage were 7.2 percent, 30.9 percent, 4.0 percent, 7.9 percent and 0.9 percent, respectively. The samples that were modified with the reaction products of the sulfonated styrene monomer land the Vinyl lactam monomer could be dyed strongly with both basic and acid dyestuffs such as those that were used in the second example. The dye-receptivity of the so-modified fabric was much more pronounced than that of the unmodified cotton.

In contrast with the above no pick-up could be achieved when the irradiation was performed on cotton fabric immersed in solutions of iacrylonitrile in dioxane, methyl ethyl ketone, benzene or ethanol or solutions of styrene in methanol or methyl ethyl ketone.

EXAMPLE 4 The procedure of Example 3 was repeated with the same 2.5 ounces to the y-arn cotton fabric excepting to use an aqueous impregnating solution which consisted of about 6 parts of acrylonitrile monomer land 1 part of vinylpyrrolidone monomer dissolved in Water to provide 'a total dissolved monomer concentration of about 7 percent. About 8.4 percent pick-up was achieved in the fabric modified with the reaction products of the monomer mixture. The modified fabric had excellent properties and characteristics and was not easily visually distinguishable EXAMPLE 5 Tlhe general procedure of the foregoing exampleswa's repeated with several monomers in separate aqueous solutions including acrylonitrile (VCN), sodium styrene sulfonate (NaSS), methylrnethacrylateV (MM) Vand methyl isopropenyl ketone (MIK). In each case (excepting for the control` sample) a high energy radiation dosage of about 0.5 mrep. was effected. The control sample (A4?) was not subjected yto irradiation. fThe results that" were obtained Iare `set forth and included in the following Table I, which indicates the amount Yof pick-up that was obtained in each case as well las certain of the physical properties of each of the samples tested. The table `also includes data relative to each impregnating solution that was utilized and in certain instances, indicates dose rates that were `applied at a lower level of radiation than the standard 0.5 mrepJlJLthat was used for all of the samples where not otherwise indicated. Y

Table I RADIATION OF COTTON FABRIC WITH VARIOUS MONOMERS Weight Percent Breaking Sample Monomer Solvent and Monomer Concentration Pick-up, Elonga- Strength,

Percent tion lbs.

Irrad. in Air 6.1 41. 7 Irrad. in Na 5. 9 41. 0 Irrad. in H2O 6. 4 39. 6 Control- 5. 4 n 34. 2 Water, 7 percent, Nitrogen purge 5. 9 4. 9 35. 2 Water, 7 percent, No Nitrogen purge-. 9.0 5. 7 42.0 A7 5 1 percent NaOH, 7 percent 2. 7 A8 5 1 percent HC1, 7 percent 2. 5 A9 Water, 7 percent, 0.0466 mrcp./hr. 7.4 4. 7 30.3 "A10" 5 Water, 7 percent, 0.093 mrepJhr. 9. 3 5.1 36.0 A11, 5 Water, 7 percent, 0.466 InrepJh 10. 2 4.9 37. 2 A12 Water, 5 percent 1. 6 4. 7 30. 1 A13 Water, 1% percent..- 3. 7 4. 5 30.4 "A14" Water, 5 percent 80.9 4. 5 33. 0

Irradiation of the cotton fabric alone indicates that slight degradation occurs between 1 and 5 mrep. At 5 mrep., slight yellowing of the fabric occurs, and there is a slight drop in breaking load.

EXAM PLE 6 In order to specifically illustrate the improvement in rot resistance `that may be obtained with cotton fabric when it `has been modified according to the present invention, la sample of 2.5 ounces to the yard cotton fabric prepared as in Example 1 yand modified with acrylonitrile so as to have an 11.6 percent pick-up was buried in rich garden loam under outdoor conditions for a period of xabout three weeks. For purposes of comparison, a sample of untreated cotton fabric was buried along with the modified material as well y.as a third sample of cotton that Was unmodiued excepting to subject it to `a dosage of 0.5 mrep. Both the untreated control `and the unmodified irradiated cotton samples were disintegrated at the end of the indicated period of burial. The former was found to have become completely disintegrated. Only fragments remained of the latter sample. The modified cotton sample, however, remained in excellent condition after the three week period. This clearly demonstrated its remarkable rot and stain resistance.

EXAMPLE 7 The general procedure of Example 4 was repeated with a 5.2 ounces to the yard viscous rayon fabric using aqueous monomeric impregnating solutions for modification. Each of the samples tested (excepting for the unirradiated control sample Bl) was subject to a total dosage of about 0.5 mrad. (0.93 mrep. equalling one mrad). The results lare set forth in the following Table 2, wherein the wet strength at break of each fabric sample is indicated this technique. The caustic pretreated modified fabric product was neither uniformly coated nor free from em bedded homopolymer. In addition, the fabric sample was found to have become discolored. The experiment indicated that caustic pretreatment of the fabric does not improve the results that may be obtained in the practice of the present invention.

EXAMPLE 9 The general procedure of Example 1 was repeated, excepting to attempt to secure the modification of the fabric by the monomer through the influence and action of conventional peroxide type catalyst initiators instead of by means of irradiation. Thus, potassium persulfate, hydrogen peroxide-ferrie chloride; and benzoyl peroxide in water methanol mixtures were employed as separate catalyzing systems in attempts to modify the fabric with acrylonitrile monomer. `In each case, the cotton fabric gained considerable weight. However, in each instance, the coating that was obtained consisted largely of easily extractable hornopolymer that was embedded in the fabric and which was neither uniform nor free from physical blotchiness. The results obtained by the immediately foregoing technique which is not in accordance with the invention were quite in contrast to those obtained when the modification of the fabric is achieved under the inuence of high energy radiation. In the latter case, as is lapparent in the foregoing specification and description, the fabric Aretains the appearance of the unmodified cotton material. Furthermore, very uniform dyeing of the modified fabric may be achieved when along with its elongation. the fabric has been modified in accordance with the pres- Table II MODIFICATION OF VISCOSE RAYON FABRIC WITH VARIOUS MONOMERS Solvent Monomer Weight Wet Percent Sample Monorner Concentration Pickup, Strength,b Elonga- Remarks percent lbs. tion B1 None.. 33.8 16.4 Control. "B2". None. 34.5 19.5 Irrad. Control. B3. VON--. Sample d'scarded; cloth completely embedded in large mass of homopolymer "B4. VCN.-- Water, 7percent.. 5.8 36.6 19.3 Uniform. "B5. VCN Water,7percent 9.0 38.1 18.7 Wetting Agent Tergrtol P-28 used with impregnating solution. "B6 MM Wate', 1% per- 5.1 33.7 17.6

cen B7 NaSS..- Water, 2% per- 10.6 31.3 19.9

cent.

I Impossible to calculate.

b 0.05 percent Triton X-100n wetting agent used in aqueous solution employed for wetting in test.

EXAMPLE 8 Cotton fabric was pretreated with a 2 percent aqueous sodium hydroxide solution before irradiating it according to the procedure of Example 1 in the presence of a 7 percent water solution of acrylonitrile monomer. Dissatisfactory and poor results were obtained following ent invention. Substrates containing substantial quantities of embedded homopolymer, however (such as those which were derived with the above indicated catalyst systems) are not capable of being level dyed and, when they are dyed, result in obviously contrasting shades of coloration as a result of the undesirable heterogeneity of their compositions.

Several samples of modified cottontabric prepared as in the foregoing Example 1 in accordance with the present invention were extracted `with various solvents by allowing the modified cotton sample to stand in a large excess of solvent for one week `at room temperature to determine the loss in weight experienced as a resnlt of the extraction. One of the samples, modified with acrylonitrile to a 9 percent total pick-up, lost 2.5 percent of its total weight in dimethyl tormamide (DMF). This corresponded to a loss of 28 percent of the pick-up weight. Another cotton sample, modified with 10.2 percent of acrylonit-rile, lost 2.1 percent of its weight in the extraction test with DMF; corresponding to a loss of 21 percent of pick-up Weight. A cotton fabric sample, modified Wit-h 30.9 percent pick-up of methyl isopropenyl ketone, lost 2 percent of its total weight when extracted in the indicated manner with methyl ethyl ketone. This corresponded to a loss of 6 to 7 percent in pick-up weight. A sample of l ounce cotton duck, modified with acrylonitrile to a 20.4 percent pick-up, lost 3.2 percent of its toal weight on standing in DMF for one hour. This loss corresponded to a loss of about 16 percent in pickup weight.

EXAMPLE ll Several samples of cotton fabric weighing about 2 grams each that were about 1V: inches wide and 8 inches long were separately placed at the bottom of several glass trays, each containing aqueous percent solutions `of acrylonitrile monomer. While so immersed, the samples were subjected to high energy irradiation using a 2 million electron volt Van de Graaff generator that was being operated with a beam current of 162 microamperes. Each of the samples was permitted to remain in the beam of high energy electrons for a different period of time in order to effect different dosages In addition, sample C4 whichr had the 10.8 per cent pick-up was subjected to extraction with DMF yfor 5 days at a tempera-ture of 40 C. No appreciable weight loss was observed in the sample as a result of the extraction treatment. In comparison, the polyacrylonitrile homopolymer that formed in the aqueous phase during the irradiationwas, as'might be expected, quite soluble in the DMF solvent. The same sample, after its modification, was exposed for a 220hour period to ultraviolet light in an Atlas Fadeometer. No discoloration of the modified fabric was noted asl a result of this eX- posure.

EXAMPLE 12 Several samples of regenerated cellulose film (conventional cellophane) were modified by a procedure similar to that set forth in Example 5 using several different monomers for the modification including VCN, NaSS, vinyl methyl ketone (VMK) and methyl acrylate (MA). In two of the samples that were attempted to be modied with VCN, both aqueous ethanol and dioxane solvent media were tested. These were samples D4 and D5, respectively. Each of the samples was irradiated from cobalt-60 source at a rate of 0.2 mrep. per hour until a total dosage of about 0.5 mrep. had been effected. The results are set forth in the following Table IV which includes a description of the monomer solution employed (excepting for the control sample D1 which was irradiated while being immersed in plain water) as well as weight pick-up values that were observed, both as corrected to take into account the considerable l'oss in weight in each of the films that was experienced during the soaking in water and washing of the modified samples, based on the results obtained with the control sample, and where such correction was not taken into account to indicate the total gain in weight, if any, of the modified film (despite weight losses due to washing).

Table IV MODIFIED CELLOPHANE FILMS Weight Pick-up Sample Monomer Concentration of Impregnating Remarks Medium Not Corrected D1 None Irradiated inplain water Weight loss equivalent to about 19 percent pick-up. D2 VCN lopercent aqueous solution. 3.7 18.6 D3 VGN... Immersed mpure monomer Emledded solidly with homoo er. D4 VON.-. ltpercent aqueous ethanol solu- 8.3 p ym lon. D5 VCN... 10 percent dioxane solution 3.8 D6 NaSS--. 10 percent aqiueous solution 8.3 Dyed readily with basic dye. D7 VME .flo 5.6 15.2 Sample washed thoroughly with acetone, cloudy. D8 MA -do 31.1 42.5 Do.

for accomplishment of the fabric modification. lIn the All of the modified films became slightly cloudy during following tabulation there are set forth the results obtained with several of the samples that were exposed for different periods of time and which each had received different high energy dosages.

Table Ill MODIFICATION 0F COTTON FABRIC USING VAN DE GRAAFF GENERATOR AS SOURCE 0F HIGH ENERGY IRRADIATION Time 1n Dosage in Weight Pick-up 6 5 Sample Beam, mrads. of Modified Seconds Fabric, percent 5. 6 0.25 1. 02 11.2 0.50 3.2 22. 4 l. 00 G. 8 44. s 2.00 1o. 8 7 0 the treatment and tended to assume a brittle condition, probably through loss of plasticizer which was not replaced after the treatment to effect the desired modifcation had been completed.

What is claimed is:

1. Method for beneficially modifying substantially pure cellulosic substrates which comprises first contacting the substrate with an aqueous solution, in a substantially neutral pH, of a water-soluble ethylenically unsaturated monomer that is polymerizable in aqueous solution under the influence of a field of ionizing high energy radiation; continuing contact of said substrate with said monomeric solution until the former is at least partially swollen by the latter; then .subsequently expos ing the cellulosic substrate while it is in contact with the aqueous monomeric solution to a field of ionizing high energy radiation until at least the surface of the substrate has become modified with the saturated reaction product of said monomeric material that has been chemically reacted to provide said reaction product in the 11 presence of and in intimate association with said substrate.

2. The method of claim 1, wherein the substrate is comprised of cotton bers.

3. The method of claim 1, wherein the substrate is comprised of regenerated cellulose.

4. The `method of claim 1, wherein the substrate is comprised of viscose rayon bers.

5. The method of claim 1, wherein the tield of ionizing high energy irradiation that is employed for the modi- 'fying reaction has an intensity of at least about 40,000 roentgens per hour.

6. The method of claim 1, wherein the amount of water-soluble monomer in aqueous solution that is in `contact with said substrate is an amount of the monomer between about 1 and 40 percent by weight, based on the ,weight of the substrate. 7. The method of claim 1, wherein the amount of water-soluble monomer in aqueous solution that is in contact with said substrate is an amount of the monomer between about 5 and 20 percent by weight, based on the weight of the substrate.

8. The method of claim 1, wherein said substrate being contacted by said aqueous monomeric solution is irradiated at a rate of from 0.04 to 1.0 mrep. per hour `until a dosage of from 0.1 to 5 mrep. is effected.

9. The method of claim 1, wherein said monomer is 'selected from the group consisting of aerylonitrile, meth- 12 acrylonitrile, acrylamide, acrylic acid, methyl methacrylate, sulfonated styrene monomers, vinyl lactam monomers and methyl isopropenyl ketone,

10. The method of claim 1, wherein said monomer is a para-sulfonated styrene monomer.

11. The method of claim 1, wherein said monomer is vinyl pyrrolidone.

12. The method of claim 1, wherein said monomer is acrylonitrile.

13. Modifying a cotton ber substrate with acrylonitrile by a method according to the method set forth in claim 1.

14. As an article of manufacture, an article Ythat is comprised of a modified substantially pure cellulosic substrate that has been prepared by a method which is in accordance with the method set forth in claim 1.

References Cited in the le of this patent UNITED STATES PATENTS 2,863,812 Graham Dec. 9, 1958 2,883,361 Handy et al. Apr. 21, 1959 FOREIGN PATENTS 1,079,401 France May 19, 1954 66,034 France Apr. 24, 1956 (Addition to 1,079,401)

750,923 Great Britain June 20, 1956 Notice of Adverse Decision in Interference iIn Interference No. 93,422 involving Patent No. 2,998,329, R. C. Sovish and F. L. Saunders, MODIFICATION yOF CELLULOSIC ARTICLES,

` final judgment adverse to the patentees was rendered Apr. 21, 1964, es to claims 1, 2, 3, 4, 5,117, 9, 10,11, 12, 13 and 14. [Oycz'al Gazette May 18, 1965.]

Claims

1. METHOD FOR BENEFICIALLY MODIFYING SUBSTANTIALLY PURE CELLULOSIC SUBSTRATES WHICH COMPRISES FIRST CONTACTING THE SUBSTRATE WITH AN AQUEOUS SOLUTION, IN A SUBSTANTIALLY NEUTRAL PH, OF A WATER-SOLUBLE ETHYLENICALLY UNSATURATED MONOMER THAT IS POLYMERIZABLE IN AQUEOUS SOLUTION UNDER THE INFLUENCE OF A FIELD OF IONIZING HIGH ENERGY RADIATION; CONTINUING CONTACT OF SAID SUBSTRATE WITH SAID MONOMERIC SOLUTION UNTIL THE FORMER IS AT LEAST PARTIALLY SWOLLEN BY THE LATTER; THEN SUBSEQUENTLY EXPOSING THE CELLULOSIC SUBSTRATE WHILE IT IS IN CONTACT WITH THE AQUEOUS MONOMERIC SOLUTION TO A FIELD OF IONIZING HIGH ENERGY RADIATION UNTIL AT LEAST THE SURFACE OF THE SUBSTRATE HAS BECOME MODIFIED WITH THE SATURATED REACTION PRODUCT OF SAID MONOMERIC MATERIAL THAT HAS BEEN CHEMICALLY REACTED TO PROVIDE SAID REACTION PRODUCT IN THE PRESENCE OF AND IN INTIMATE ASSOCIATION WITH SAID SUBSTRATE.