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2,406,905 Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE‘ , 2,406,905 METHOD FOR PRODUCING CELLULOSIC . STRUCTURES Henry Shirley Rothrock, Wilmington, DeL, as- ' signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 6, 1941, Serial No. 392,116 2 Claims. (01. 117-145) 2 I may be otherwise advantageously wrapped in such transparent tissue. It is, therefore, an object of this invention to This invention relates to regenerated cellulose structures, especially those of pellicular nature. More particularly, it relates‘ to a method for pro provide a new and useful method for producing ducing ?exible and durable regenerated cellulose pellicles by treating the same with a softening agent comprising a synthetic linear polymeric softened regenerated cellulose materials possess ing desirable physical properties. It is a further object to provide regenerated cellulose materials having a softening agent associated therewith which softening agent will application, Serial No. 392,115, filed of even date 10 not tend to escape through volatilizatlon or through transfer to other celluloslc bodies. It has been found that glycerol, ethylene glycol Other objects of the invention will appear and other agents such as formamide, diethylene hereinafter. ' glycol, and the like used heretofore for the soften The objects of this invention may be accom ing of regenerated cellulose products have pos sessed two serious'dlsadvantages; namely, vola 15 plished by incorporating, as a softening agent, in compound. This application is related to my copending ' 4 herewith. a regenerated cellulose sheet or ?lm, a water tility and a tendency to transfer or migrate to' other materials in contact with the softened re soluble synthetic linear polymer having a molecu lar weight above 400 and a boiling point of at generated cellulose. Since thesoftening action least 170° C. at a pressure of 1 millimeter of is highly critical, it is essential that the precise . concentration of a given softener within the cellu 20 mercury. A. wide variety of polymeric materials are found losic body be maintained at a relatively constant to be useful this operation. It is a necessary value. For example, if the concentration of sof condition that the polymeric materials used in ' tener is too high, the cellulosic films will be un this invention be suiiiciently water soluble to tion is too low the article will be brittle and lack 25 permit their introduction into the regenerated cellulose sheet by means of an aqueous solution. durability. An effort is therefore made at the duly limp and sticky, whereas if the concentra In general, adequate water solubility is insured time of‘ manufacture to incorporate precisely the correct amount of softener to obtain the physi by incorporating in the polymeric compositions satisfactory softening action isobtained. compounds. cal properties desired in the final film. How- ' 30 solubilizing groups separated preferably by one or two carbon atoms. When the atom chain be ever, in the case of ‘a pellicle with a large area tween the solubilizlng groups consists of more exposed to the atmosphere for long periods of than two atoms it may also possess one or more time, even those softening agents which have a interruptions by hetero atoms, e. g., 0, N, or very low but appreciable vapor pressure will in hetero groups such as $02 and other groups time escape to a sufficient degree to lower the concentration in the film below that at which 35 which contribute to water solubility in organic ' The preferred method of carrying out this proc Difficulties arising from a decrease in softener ess consists in passing a regenerated cellulose content may also be brought about in quite a different manner from the escape of the softener 40 sheet, after the necessary purifying, bleaching and washing operations, through an aqueous bath through volatilization. It has been observed that containing a prescribed amount of water-soluble regenerated cellulose products which are in con polymeric softening agent. After impregnation, tact with other cellulosic bodies have a tendency excess solution is removed and the film is dried in to lose their softening agent when this agent is of the type represented by glycerol and glycol 45 a suitable manner. The following examples are given to illustrate the preferred methods of carrying out the present invention. The parts and percentages referred ucts such as paper, cotton, linen fabric, etc., to are parts and percentages by weight. wrapped in thin pellicles of regenerated cellulose Example I softened with glycerol are found after a short 50 time to extract a large portion of the glycerol ‘Viscose is extruded into a bath comprising sul from the pellicle used as a wrapping tissue, leav furic acid and sodium sulfate to effect a coagu ing' the latter brittle and. absorbent. This is a lation and/or regeneration of the viscose to a self serious restriction in the use of these materials sustaining ?lm. This film is then desulfured, for wrapping a large number of products which 55 bleached, and washed according to Brandenberg- ' and, in fact, most of the softening agents here tofore known. As an example, cellulosic prod 2,406,905 4 or United States Letters Patent No. 1,548,864. Before drying, the sheet of gel regenerated cel tion of the catalyst and removal of unreacted gly col formal. lulose is immersed in or drawn through an aque ous bath maintained at a temperature of 30° C. Example V ly long to thoroughly impregnate the gel struc weight of approximately 1316. The ?lm produced Film prepared as in Example I is passed and containing 11% of glycol polyformal having 5 through an aqueous bath containing 11% of cetyl a molecular weight of approximately 440. The alcohol-glycol polyformal having a molecular film remains in contact with this bath su?icient after removal of excess solution and drying in ture‘ with the solution. after which it emerges from the bath, excess liquid is removed from the 10 the usual manner is transparent, ?exible and maintains its durability in contact with other cel surface thereof by means of squeeze rolls, doctor lulosic materials such as cloth and paper. knives, etc.,v and the ?lm dried on the conven This polymeric product may be prepared by tional roll drier. After drying, the ?lm is found heating at 100° C. for five hours one part by to contain 20% glycol polyformal, based on the weight of the cellulose, and approximately 6% 15 weight of cetyl alcohol with 18 parts by weight of glycol formal in the presence of 0.5% by weight water. The ?lm so produced is transparent, ?ex of an anhydrous acidic catalyst after which the ible, and durable. The loss of softening agent catalyst is neutralized and unreacted glycol for through volatilization or migration to other cel mal is removed. lulosic bodies such as paper and fabric is only Example VI one-tenth as great as that shown in correspond 20 ing glycerol softened ?lms. Film produced as in Example I is immersed in , The glycol polyformal is prepared by heating an aqueous bath containing 15% of glycol digly monomeric glycol formal at 160° C. for a period colate polyester prepared through the action of_ of five hours in the presence of a catalytic amount one part by weight of diglycolic acid with approx of concentrated sulfuric acid. The acidic cata imately one and two-tenths parts by weight of lyst is neutralized, unreacted monomer is re ethylene glycol under the in?uence of an acidic moved and the product extracted with a suitable catalyst. Excess solution is removed from the solvent or used directly. surface of the ?lm and the same dried in the usual manner. The pellicle so produced contains Example If 30 23% of the softening agent and is ?exible, trans The ?lm prepared as in Example I is passed parent and durable. through a bath containing 7% glycol polyformal Example VII having a molecular weight of approximately 710 , and prepared as in the preceding example. Ex Film prepared as in Example I is suspended cess solution is removed from the surface of the 35 in a bath containing 7% of polyethylenimine web, and the same dried in the conventional type synthesized through the action of a polymeriza of roll drier. Films so produced are found to have _tion promoting acid catalyst on ethylenlmine ac a softener content of 12% based on the weight cording to British Patent No. 461,354. After heat of the cellulose, and a moisture content of 6%. ing at 100° C. for 20 hours, the film is washed This ?lm ‘is transparent, highly ?exible, durable, with cold water, with alcohol, and the same dried and shows practically no loss of softening agent in vacuo at 100° C. The film so produced con , ‘when in contact with cellulosicxmaterials such as paper and fabric. I " Example III Film produced as in Example I is passed through a bath containing 11% of glycol poly formalof molecular weight 1284, prepared in the general manner described in Example I. The ex_ cess solution is removed from the surface of the 45 .taining 5.31% nitrogen is soft and durable and shows good receptivity to various dyeing agents. Example VIII Film prepared as in Example I is immersed in a bath containing 11% of polyethylene oxide (C'arbowax 1500). Excess solution is removed from the surface of the web, and the same dried in the conventional film, and the‘ same dried in the customary man 50 type of roll drier. Film so produced is found to ner. The ?nal product contains 20% of the sof have a softener content of 17 %, based on the tening agent, istransparent and soft and main weight of the cellulose, and a moisture content tains its high ?exibility and durability when in 6%. This film is transparent, highly ?exible, contact with other cellulosic bodies.' The loss of 55 of and durable, and shows no loss of softening agent softening agent by volatilization and migration in contact with cellulosic materials. such as paper to other cellulosic materials is lessthan one-tenth and fabric. The polyethylene oxide may be syn that exhibited .by glycerol softened ?lms. Example IV Film produced as in Example I is passed into a bath containing an 11% solution of stearic acid thesized, for example. by heating the monomeric oxide in the presence of a suitable catalyst (pref 60 erably an alkaline catalyst) until a substantial proportion of polymer is formed, and removing the unchanged monomer. (Staudinger, Die glycol polyformal having a molecular weight of Hochmolekularen Organischen Verblndungen, approximately 1280. Excess solution is removed 6_ 1932, p. 287, et. seq.) from the surface of the web by means of squeeze 0 Example IX rolls andthe product-dried in the usual manner. The ?lm so produced contains 8% of softening Film prepared as in Example I is passed through agent, is transparent and shows no loss of softener a bath containing 11% of a reaction product of by volatilization or by migration to other cellu ethanolformamide and ethylene oxide described losic bodies. ' p . 70 in the following paragraph having an average The polymeric material is prepared'by heating molecular weight of 469. Excess solution is re one part by weight of stearic acid with 10 parts moved from the surface of the film and dried in by weight of glycol formal in the presence of 0.1% the conventional manner. The ?lm so produced to 0.5% by weight of an anhydrous acidic catalyst contains 17% of the softening agent, is trans for a period of 5 hours, followed by neutraliza 75 parent and highly ?exible and shows no loss of 2,406,905 softener either by volatilization or by migration. The above softening agent may be prepared by passing ethylene oxide into ethanolformamide pending application Serial No. 350,108, ?led Au gust 2, 1940, by mixing equivalent quantities of adiponitrile dimethyl diimino ether dihydrochlo Example X Example XV ride and hexamethylenediamine in methanol and at a temperature above 100° C. and under the in ?uence of an alkaline catalyst until the desired 5 allowing to stand at room temperature for 48 hours. ' molecular weight has been attained. Film prepared as in Example I is immersed for Film prepared as in Example I is suspended for 10 minutes in a bath containing 10% of poly 10 one hour in an aqueous bath containing 15% of a polymeric urea described in the following par meric quaternary ammonium bromide described below. Excess solution is removed from the sur- 7 agraph. After removal of excess solution and drying the film is found to retain the softening face of the ?lm and the same dried in the con agent permanently. ‘ ventional manner. A clear film is so produced The polymeric urea is prepared by heating equivalent amounts by weight of butyldiethanol which retains the softening agent permanently. The polymeric quaternary ammonium compound may be prepared by heating N,N,N',N'-tetra amine and bis-N,N’-methoxymethyl-urea at ap proximately 100° C. for a period of 3 to 4 hours. The polymer so produced is solubilized by treat 20 ing with an equivalent amount of a mineral acid _ methyl decamethylenediamine and p-xylylene dibromide in methanol for a period of 42 hours. Example XI 4 such as hydrochloric acid. ‘ Example xv: Film produced as in Example I is immersed in an aqueous bath'containing 20% of polyvinyl alcohol having a molecular weight of about 3600 The ?lm prepared as in Example I is immersed for one hour in an aqueous bath containing ap and containing approximately 20% of polyvinyl 25 proximately 5% of polymeric sulfonium salt de acetate during a period of one hour. Excess so scribed below. - After the ?lm has been soaked lution is removed from the surface of the web for one hour excess aqueous solution is removed and the film dried on the conventional roll drier. and the film dried. The ?lm so produced re After drying the film is- found to contain 10% of the softening agent. A transparent ?lm is so 30 tains the softening agent when in contact with other cellulosic materials such as paper and tex produced which permanently retains the soften tiles. ing agent. ' The sulfonium compound is prepared as de The polyvinyl alcohol is prepared by heating scribed in copending application Serial‘ No. monomeric vinyl acetate in toluene at 100° C. 319,791, ?led February 19, 1940, by dissolving in the presence of 1% of benzoyl peroxide to yield 35 polyhexamethylene sul?de in toluene at re?ux polyvinyl acetate, (Starkweather and-Taylor, J. temperature followed by addition of a slight ex Am. Chem. Soc. 52, 4708 (1930)), from which ' cess of dimethyl sulfate. Heating is discontinued the polyvinyl alcohol is obtained by hydrolysis. (as soon as dimethyl sulfate is added since the ’ Example XII‘ '40 heat evolved is sufficient to maintain reaction. - When the spontaneous reaction has subsided ex cess dimethyl sulfate is destroyed by addition of alkali solution and the product is‘ made up in aqueous solution. The ?lm prepared as in Example I is immersed for one hour in an aqueous bath containing 10% of polyvinyl alcohol of molecular weight 3600 containing approximately 2%. polyvinyl acetate, and prepared as in the preceding example. Exe 45 Example X VII cess solution is removed from the surface of the web and the ?lm dried in the conventional type of roll drier. Films so produced are found to have a softener content of 4%, which is retained when the films are in'contact with other ceilulosic ma Film_ prepared as in Example, I is immersed for one hour in an aqueous bath containing 15% of a polymeric acid material, the preparation of which is outlined in the next paragraph. The film produced after drying is transparent and terials such as paper .or textiles. does not lose its durability when in contact with paper, textiles, or cotton. Example XIII The film prepared as in Example I is immersed The polymeric acid may be prepared by heat ing in a bomb at 150° C., 1200 grams of maleic for one hour in an aqueous bath containing 10% 55 anhydride, 1500 grams of ethylene, and 40 grams of polyvinyl alcohol having a molecularweight of of benzoyl peroxide in 6 liters of xylene. The about 12,000, containing approximately 20% product is washed with benzene and ether and polyvinyl acetate and prepared as in the preced then made up in the required aqueous solution " ing examples. Excess solution is removed from by dissolving in an equivalent amount of alkaline the film and the same dried in the usual man 60 solution. ner. A transparent film was produced contain Example XVIII ing 5% of the softening agent which was retained in the ?lm in contact with other ceilulosic mate rials such as textiles and paper. Example XIV The film prepared as in Example I is immersed ' Film produced as in Example I is immersed for one hour in an aqueous bath containing 15% of 65 a polymeric phosphate described below. Excess solution was removed from the ?lm and the same was dried in the customary manner. A perma nently impregnated film is produced. ‘ for one and one-half hours in an aqueous bath The polymeric phosphate .‘ is prepared by allow described below. Excess solution was removed 70 ing equalparts by weight of ethylene glycol and phosphorus oxychloride to react spontaneously from the film and the same was dried in the con containing 10% of a polyamidine hydrochloride followed by heating for 4 hours. ventional type of drier. A transparent film was produced which retained the softening agent even in contact with other ceilulosic materials. The polymer was prepared as described in co 2 75 Example XIX ' _ Film produced as in Example Iis immersed 2,406,906 for one hour in a bath containing 15% of poly phosphonamide at a temperature of 30° C. After removal of excess solution and drying the ?lm is found to retain the softening agent when in contactvwith other materials such as textiles or paper. ' Imlnoethera: I?! . The polyphosphonamide is prepared by heating . one part of phosphoric acid with 1.15 parts of hexamethylenediamine for one hour at‘ 230° ' 260° C. 10 Example XX Film prepared as in Example I is immersed for one hour in an aqueous bath containing 5% of glycerol and 15% of polyethylene oxide pre pared as in Example VIII. Excess solution is 15 removed from the ?lm by means of squeeze rolls and the film dried in the conventional type of roll drier. The ?lm so produced is flexible, trans parent, and durable. 20 Example XXI A regenerated cellulose pellicle in the form of a tube is coagulated, regenerated, and puri?ed in a manner similar to that for ?lm and is then passed through a bath containing 11% of the 25 l5. Acids: Phosphonamides: ( reaction product of methyl Cellosolve and ethyl 0 ene oxide, prepared in the same manner as de scribed in Example IX, said reaction product having an average molecular weight of approxi Phosphates: sure and the upper portion of the neck of the Ethers: bottle. This cellulosic band is in contact with the paper, liquor stamp with which such bottles Sulionic acids: mately 783. Excess liquid is removed from the 30 surface of the tube, the same cut into short lengths and applied to the mouth and neck of a liquor bottle as a secondary closure. Upon evap oration of the moisture, the band shrinks into intimate contact with the neck of the bottle, 35 serving to protect the cork or other primary clo-v are provided. It is found that even after long 40 periods of storage, the softening material does not transfer from the cellulosic band to the pa per of the tax stamp, and hence the cellulosic band is not embrittled or otherwise deleteriously as Ch affected so as to cause its premature removal from the bottle. All of the examples given have been set forth in which R and R’ are divalent organic radicals, preferably containing one or two carbon'atoms which may be alike or different; R2 and Rsare either hydrogen or monovalent hydrocarbon radi cals; X is an acidic radical such as halogen; and n is a number su?lciently high so that the molecu lar weight of the polymer is above 400. It may in terms of a sheet or ?lm of gel regenerated cel be desirable to incorporate in the atom chain lulose (gel regenerated cellulose is a water swollen 50 other hetero atoms or groups such as O, N or SO: regenerated cellulose which never has been as exempli?ed in the case of polymeric triglycol dried). Obviously this is the more practical way of practicing the invention since the softening adipamide, ' 0 - agent is customarily incorporated into the sheet . (-—C 0 (CH9) 4—(L)—-_NH—CH:CH:O OHsCHiO CHlOHiNH-')n or‘ ?lm while the latter is in the gel state in and during the normal courseof manufacture. Obvi or glycol diglycolate polyester, ously, if one desires to impregnate an already dried regenerated cellulose ?lm with a softener of the character described, it is possible to rewet the dried ?lm so as to render it highly swollen 60 An example of synthetic linear polymer which is illustrative of the general type of polymeric mate whereupon it may be treated with treating baths rials useful in this process is polyvinyl alcohol, similar to those described, but of composition suitable to obtaining the ?nal product desired. R-(cm-cnon-cm-onon-cH,-—0BoH-).—R As the water-soluble synthetic linear polymeric It is seen that the group (—CHOH—) recurs in softening agents suitable for use in accordance 65 a linear manner to yield a long chain polymeric compound. with the present invention, the polymers of the following recurring units are representative: The presence of the OH groups on alternate carbon atoms in the chain insures suf ?cient water solubility for the purpose of this process. 70 Depending upon the type of ?lm desired, vari ous modi?ed polymeric materials may be em ployed such as the products obtainable through the reaction of a monomeric alkylene oxide or glycol formal. with such active hydrogen com 75 pounds as acids, amines, amides and alcohols as 2,406,905 typified by glycerol, ethanolamine or formamlde. It is possible andin some cases even desirable to employ as softening compositions mixtures either of one polymer with another or of a poly meric with a monomeric softening agent. As typical examples of these mixtures one may cite mixtures of polyvinyl alcohol with polyethylene oxide, polyethylene oxide with glycerol or urea, and glycol polyformal with glycerol. As above stated, the- polymeric softeners of 10 the present invention should have a molecular 10 which they remain in a non-?brous cellulosic structure. Since they are of very low volatility, they are not lost through volatilization, such as a number of well-known softeners, e. g., ethylenev glycol and glycerol. Furthermore, they do not migrate or transfer out of the transparent cellu lose structure to other cellulosic structures with which the film may be in contact. This last named property permits use of these materials in the form of thin sheets as wrappings with cel lulosic materials, e. g., fabrics, textiles, paper, etc., and permits their long and continued contact with the contents of the package without losing the softening agent and, consequently, with the is essential also that the polymeric products have a water solubility at a temperature of 25° C. of 15 retention of the ?exibility and durability of the original wrapping tissue. As another example, at least 4% in order that they may be introduced weight above 400', and a boiling point above 170° C. at a pressure of 1 millimeter of mercury. It caps and bands used as secondary closures for containers may be applied to the mouths and necks of bottles over paper labels and still exhibit The preferred concentrations of softener in aqueous bath may ‘range from 4% to 15%, 20 no tendency to embrittlement, splitting, and cracking after long periods of storage. although in some cases higher concentrations in a satisfactory manner into regenerated cel lulose. . Since it is obvious that many changes and modi?cations can be made in the above-described details without departing from the nature and Likewise, the time of immersion may be varied from a few seconds to an hour or more depending 25. spirit of the invention, it is to be understood that the invention is not to be limited to the details upon the rapidity with which the particular poly described herein except as set forth in the ap mer is impregnated into the regenerated cellu pended claims. lose. The temperature of the aqueous bath may I claim: be conveniently maintained at 25°-30° 0. although in some cases a higher temperature may be de 30' 1. The process which comprises passing a ?ex ible regenerated cellulose pellicle in a highly swol sirable. After the regenerated cellulose sheet or may be required to insure adequate impregnation of softening agent in . the cellulosic structure. ?lm is dried it should, for normal uses, contain from 8% to 25% of softener based on the weight len condition through an aqueous bath contain ing, dissolved therein, between 4% and 15% of a of the dry ?lm. synthetic linear polymer having a molecular If a colored cellulosic ?lm is desired, it may 35 weight above 400 and a boiling point of at least 170° C. at a pressure of 1 millimeter of mercury, be obtained in any of the ways commonly known in the art, including the passage of the sheet or said pellicle being maintained in contact with the ?lm through a bath containing a suitable dye stuff. If desired, the dyestuff may be added to bath liquid for a suf?cient period of time to im pregnate the same with from 8% to 25% of said the bath used for introducing the softening agent. 40 polymer. In the same way, after the ?lm has been treated ' 2. The process which' comprises passing a re generated cellulose pellicle, in the gel state, through an aqueous bath, containing, dissolved therein, between 4% and 15% of a synthetic linear given to cellulosic pellicles of the type described,‘ 45 polymer having a molecular weight above 400 with softening agent, it may be subjected to any of the customary after-treatments, such as sizing or coating or the like which may be customarily in just the same manner that a glycerol softened regenerated cellulose ?lm, for example, may be treated. ' and a boiling point of at least 170° C. at a pres sure of 1 millimeter of mercury, said pellicle be ing maintained in contact with the bath liquid for a sumcient period of time to impregnate the same The outstanding advantage of the polymeric softening agents of this invention over those de 50 with from 8% to 25% of said polymer. scribed in the prior art is the permanence with ' HENRY SHIRLEY ROTHROCK.