US3034910A - Production of regenerated cellulose filaments from wood pulp - Google Patents

Description

May 15, 19 w. L. DEAN ET AL PRODUCTION OF REGENERATED CELLULOSE FILAMENTS FROM WOOD PULP Filed July 51 1959 ATTORNEY6 3,634,910 PRGDUQ'HQN h REGENERATED QELLULGSE FKLAMENTS FRQM WQQD PULP Walter L. Dean, Arthur M. Dowel], 31"., and doseph flames, In, h lemphis, Terms, assignors to The Buckeye Cellulose Corporation, Cincinnati, Ghio, a corporation of ()hio Filed luly 31, 1959, her. No. 8365889 6 Claims. (Cl. lilo-165) This invention relates to improvements in the manufacture of regenerated cellulose filaments from prehydrolyzed sulphate chemical wood pulp by the viscose process and has for an object the provision of a novel method of controlling certain significant characteristics and properties of the viscose and of the filaments produced therefrom. More particularly, the invention is concerned with the preparation of viscose whose composition can be altered, Without affecting filtration characteristics, by the addition of one or more of a family of certain novel alkylene oxide esters of disproportionated rosin in which the ethylene oxidc-LZ-propylene oxide ratio may readily be altered to produce in rapid sequence, if desired, filaments varying Widely in skin to core ratio and cross-sectional shape. Themembers ofthesaid family of 'additive compositions are completely compatible with each other and with the conventional coagulating and regenerating agents employed in spin baths. It is thus possible in accordance with the present invention to control the cross-section and skin to core ratio of rayon filaments by choice of the novel ester employed and to do so Without altering viscosefiltration characteristics, and if desired, without interruption of processing.

in order to appreciate the full significance of applicants improvement in the controlled fiber modifyingaction on rayon filaments, some understanding of the processing of ire-hydrolyzed sulphate chemical wood pulp to rayon by ments thus produced is required.

Viscose is a highly complex system consisting of a dispersion of cellulose xanthate in a dilute aqueous sodium hydroxide solution, which system is constantly undergoing change as a consequence of the rearrangement of xanthate groups and a gradual breakdown of cellulose Xanthate, a change commonly termed, ripening. At a particular degree of ripeness, the viscose is spun into filaments and regenerated.

The conditions under which viscose is spun have a profound elfect on the quality and characteristics of the raythe viscose process and the propertiesofthe rayon filaon filaments so obtained. A large number of variables that affect rayon quality have been discovered in the past and methods for controlling many of these variables have been discovered. Viscose, after'fiitration, was, in the" earliest methods of carrying out the process, ripened and extruded into an all acid bath whereby the alkali contained in the viscose was neutralized and the cellulose xanthate was decomposed by splitting away the xanthate groups which made possible the initial solubilizing or dispersement of the cellulose. After washing the extruded product free of residues and decomposition products and drying, the rayon fibers were obtained.

According to later developments a zinc salt is incorporated in the spin bath to retard regeneration following i and during the coagulation of the viscose rayon filaments, and it may be possible that other salts of bivalent metals would accomplish the same purposes. Recognition of the separate functions of coagulation and regeneration together with improved techniques for controlling the stretching of the yarn during these operations has led to rayon of much improved strength. Immediately upon coagulation of the viscose, which results in a gel cellulose xanthate in filament form, stretch is imposed on the yarn to cause a uniaxially orientated structure which results in the aforementioned improvement in fiber strength. The incorporation of the zinc ion into the spinning bath is believed to retard regeneration by transforming sodium cellulose xanthate into zinc cellulose xanthate. The greater stability of the zinc cellulose xanthate in acid media as compared with the sodium cellulose xanthate then slows the regeneration step sufiiciently to allow uniaxial orientation of the filaments by stretching in the gel state. The coagulated viscose yarn is then fully regenerated by continued exposure to the acid bath or by utilizing a second hot acid oath; additional stretch may be imposed during this and subsequent hot Washing steps. Although the regeneration of cellulose xanthate proceeds very rapidly, the presenceof zinc ion in the spin bath and a regeneration retardant (chemical modifier) in the viscose markedly afiects the relative speeds of penetration of the hydrogen and zinc ion components of the spin bath. Thus there results a much more extensive formation of the more stable zinc cellulose xanthate salt which may actually occur throughout the entire filament ahead of the decomposition of the sodium cellulose xanthate at the concentration of acidnormaliy employed in spinning baths. In this manner a uniaxially oriented structure is achieved before complete regeneration takes place.

Normally in coagulation and regeneration the surface (skin) of the filament is fixed and there is developed a tubelike structure consisting of an outer skin of regenerated cellulose together with an inner core of viscose as the viscose on the outside ofthe filament is regenerated, and the cellulose separates itself from much of the water initially present in the viscose (which normally contains only about 643% cellulose). fter'washing to remove the decomposition products, the filaments are dried, and during this step, depending on the combination of spin bath, chemical modifier and stretching employed during regeneration, the surface becomes more wrinkled or crenulated due to stresses set up between the skin and the interior sections of the fiber as the tube-like skin structure of the filament collapses upon removal of water.

Certain chemical additives, usually surfactants, when contained in the viscose or added to the spin bath have been found very useful with respect to regulating the regeneration rate and/ or the diffusion of acid into the interior of the filament, whereby the regeneration rate is retarded to allow a high degree of uniaxial orientation prior to the completion of regeneration. Such filaments, referred to hereinafter as modified filaments, are characterized by relatively smooth surfaces and generally beanlike, or round, cross-sections which dye rather uniformly (depending on the degree of fiber modification). The linear polymers of ethylene oxide are outstanding in their ability to promote this type of structure, but result in completely modified fibers without aifording'the rayon manufacturer the opportunity of obtaining the particular degree of modification desired by selecting an additive from among those of a family of additives having the same chemical constituents but in varying proportion. Even with the ethylene oxide linear polymer moiety is combined with a second base material, such as to give polyethylene oxide others, esters, amines, etc., there persists a high degree of filament modification as indicated by microscopic examination. In contrast to this lack of control, the'advantages of the modified type of filament are enhanced through the use of the family of additives of this invention by making possible various combinations of high strength, high flex life, resistance to abrasion, resistance to moisture, and improved dye fastness which can be easily engendered in fibers modified in this filaments may give rise to processing difiiculties. If one additive is replaced by another to impart to the filaments a different degree of modification or skin to core ratio, and the two additives are not compatible, the equipment and especially the spin bath must be purged before the second additive is introduced, necessitating interruption of processing. Also the incorporation of different types of chemical additives in succeeding batches of viscose to be processed 'in order to vary the fiber properties may give difficulty by causing a change in the filterability level attained and thus deprive the processor of the advantage of always maintaining high filterability while attaining specific combinations of filament characteristics.

It is therefore an object of the invention to provide a family of novel chemical additives affording progressive modification of filament characteristics over a wide range, the additives being fully compatible with one another in the steps of viscose processing whereby filaments of different degrees of modification over a wide range may be obtained without the use of supplementary additives to increase filterability and, if desired, without interruption of processing.

These and other objectives are achieved by incorporating in the viscose, preferably by addition to the sheeted prehydrolyzed sulfate chemical wood pulp to be used in the viscose process, as a modifying agent capable of controlling the skin to core ratio and cross-section shape of filaments spun from the viscose, of an ethylene oxide-1,2- propylene oxide ester of disproportionated resin in amount from 0.5% to 3.5% based on the bone dry weight of the pulp, the oxides being present in the esters in amount from 1.5 to 9 times the amount of rosin by weight, and the ethylene oxide constituting from 40% to 85% of the total oxide weight. The present applicants found that the skin to core ratios and cross-sectional shapes of filaments are increasingly modified with increase in the ethylene oxide percentage in the total oxide weight within the indicated range, and that variation of the percentage does not adversely affect the high viscose filterability. As mentioned above, the variation in fiber modification is achieved by variation of the ethylene oxide percentage in the ethylene oxide-1,2-propylene oxide group within the compounds. All of the compounds within the 1.5 to 9 total oxide to rosin ratio are operable in practicing this invention. Moreover, filament characteristics may be readily and continuously varied over a wide range by substituting prior to spinning viscose containing one agent of the group with viscose containing another agent of the group having a different ratio of oxides, without interrupting the process or spraying the system.

Applicants also noted that minor variations in fiber modification are achieved by increasing the ratio of total oxides to rosin from 1.521 to 9:1. It was also observed that increased usage of a given surfactant within the disclosed group from 0.5% to 3.5% resulted in a greater degree of fiber modification and that a small effect on fiber modification may result from the selection of ethylene oxide terminal as versus 1,2-propylene oxide terminal agents in sequential compounds having the same overall composition. It has been found, however, that as to changes of composition within the agents, the greatest effect in fiber modification is achieved by varying the ethylene oxide percentage in the total oxide employed.

Further objects and features of the invention will be apparent from the following description of the preferred practice thereof, and from the accompanying drawing in which FIGURES 1 to 3 represent photomicrographs of sectioned fibers, stained to distinguish the skin and core portions, illustrating the controlled modification achieved by the use of chemical additives selected from the family of chemical additives having different ratios of ethylene oxide to 1,2-propylene oxide and total oxide to disproportionated rosin base.

As has hereinbefore been indicated, this invention contemplates the manufacture of regenerated cellulose fibers 1 chanical and hydraulic means.

from prehydrolyzed sulphate chemical wood pulp by the viscose process with the use of a particular family of chemical additives to control fiber modification while maintaining at each degree of fiber modification the high viscose filterability necessary to economic processing in the viscose industry.

In the prehydrolysis operation, wood chips or other lignin-containing cellulosic material, are conventionally treated with water, steam or dilute acid solution (up to about 0.3% solution of acid), at from about 300 to about 375 F, and at pressures greater than atmospheric, for reaction times up to about 120 minutes prior to digestion. This treatment is carried out under acid conditions which are preferably induced by the addition of an acid such as, for example, acetic, citric, nitric, oxalic, phos phoric, sulfurous (sulfur dioxide), sulfuric or combinations of these. Alternatively, if it is desired that no acid shall be used, and provided no alkaline agents have been added, an acid condition will develop as a result of the hydrolysis of the cellulosic raw materials being treated. At the end of this treatment, the hydrolysis liquid is drained oif, and the remaining solid material may be washed in situ, or the cooking liquor for the next step may be added directly without washing.

The hydrolyzed lignin-containing material is then pulped by the sulphate process wherein the active digesting ingredients are sodium hydroxide and sodium sulfide. This process is well known to those skilled in the art and any reference to the sulphate method of digestion appearing herein or in the appended claims refers to digestion wherein the active digesting ingredients are sodium hydroxide and sodium sulfide. After suitable. bleaching the purified cellulose is sheeted and dried to form the prehydrolyzed chemical sulphate pulp mentioned herein.

As is well known in the art, in the production of viscose by the conventional sheet steeping method, dried sheets of pulp are placed in a steeping press and steeped in a solution of sodium hydroxide, normally having a concentration from about 17 to 20%. The caustic soda solution is usually introduced at the bottom of the enclosure at such a rate that it rises along the sheets in the direction of the predominant lengthwise orientation of the pulp fibers at a rate equal to the rate of rise induced by the capillarity of the pulp. The operation is generally conducted at temperatures of from about 20 to 25 C. After about one hour immersion, the excess sodium hydroxide solution is drained off and the steeped pulp is pressed to obtain the desired alkali cellulose composition. The alkali cellulose is then reduced to crumbs in a shredder. This latter mechanical action proceeds for about one to two hours.

The continuous or slurry process of steeping differs from the conventional process in that the pulp is fed into a tank of concentrated caustic soda solution at a uniform rate. There it is reduced to a slurry of fibers by me- This step usually is conducted at temperatures above ambient temperatures, up

to 65 C. with the higher temperatures being preferred because of the resulting accelerated rate of alkali cellulose production. After an average treatment of about 15 minutes, the slurry of fibers is forced by pressure between rottaing rolls which are slotted or otherwise perforated to permit drainage of the caustic. The pressed cake of alkali cellulose is then reduced to crumbs, generally on one of the two types of machinery conventionally employed by the art, i.e., a one-pass Garnett roll type shredder or a disk refiner type shredder. Continuous shredding permits substantially instantaneous shredding of alkali cellulose by one passage of the alkali cellulose thru a stator-rotor arrangement of the shredder which may be either of disk or roll design. The Sprout- Waldron refiner is an example of the disk type shredder as compared to the Garnett roll type shredder. The disk refiner normally subjects alkali cellulose to much less severe mechanical action than is the case with a high speed roll type shredder.

Beginning with the alkali cellulose crumbs, the continuous and the slurry processes are essentially the same thru the regeneration step.

The alkali cellulose crumbs are aged under carefully controlled conditions. Here, by means of alkaline oxidation, the average molecular chain length of the cellulose is reduced to a level that will produce a viscose having the desired solution viscosity. After aging, the alkali cellulose crumbs are mechanically mixed with the proper proportion of carbon bisulfide, which combines chemically with the alkali cellulose to form cellulose xanthate. Upon addition of dilute hydroxide solution in a mixing device, the orange colored cellulose xanthate crumbs dissolve and form the viscose solution known as viscose.

The viscose solution is then filtered and deaerated. During filtration, foreign particles and undispersed gels are removed by the use of several successive filter media. Completely undissolved matter, While important to the yield, does not ordinarily affect filterability seriously. Rather, the imperfectly dispersed cellulose, the gels, which plug the pores of the filter media, have a much greater adverse effect. A poor filtering viscose leads to many costly interruptions of the process by requiring frequent replacement of the filter media. Therefore, the viscose manufacturer requires a filterability level which permits a high production schedule with attendant low cost in labor and filter material.

During the filtration and deaeration operations the viscose is ripened at a controlled temperature. In this ripening step, complex chemical and, colloidal changes occur which impart to the viscose certain desired qualities which have a profound influence on the character of the rayon fiber product later regenerated from the viscose.

Regeneration into filaments or films is accomplished by extrudng the ripend viscose through the very small holes of a spinneret or through a slit, depending upon whether a fiber or film is desired, the said extrusion being made into a bath containing sulfuric acid and salts in aqueous solution. The action of the spin bath results in coagulation of the viscose and subsequent regeneration of the cellulose, thus forming continuous solid filaments or films. Various washing and chemical treatments are applied to the regenerated filaments or films in order to remove residualchemicals therefrom, bleach the cellulosic material, andimpart desirable properties to the finished product. p

As hereinbefore explained, the filaments are stretched as regeneration proceeds, and the opportunity for resultant orientation of the fibers can be altered over a wide range by incorporating in the viscose an appropriate modifying.

agent selected from the described family of agents, without interrupting the process. v

The spin bath may contain from 3% to of zinc sulfate, from 5% to 10% of suphuric acid and from 10% to 23% of sodium sulphate in aqueous solution. It will be appreciated, however, that the invention contemplates the normal practice of viscose processing, except for the 7 chemical additive employed, and that the processing details form no part of the instant invention. These details therefore may be varied widely within the limits of accepted practice.

The chemical additives employed in the present invention are prepared by reacting disproportionated rosin randomly or sequentially with ethylene and 1,2-propylene oxides in varying amounts. The disproportionation of rosin is effected by heating gum resin (-tall oil) to an elevated temperature, for instance, over 200 C. for an extended period, in the presence of a suitable catalyst such as palladium on carbon. In effect the reaction consists of the removal of two atoms of hydrogen from the conjugated double bond abietic-type acids and the rearrangement of the double bond system to form an aromatic nucleus in the production of dehydroabietic acid. The hydrogen that is removed is readily absorbed by other conjugated double bond abietic-type acids present to produce the stable dihydroabietic and tetrahydroabietic acids. The product contains a major'proportion of dehydroabietic acid, and in minor proportion, dihydroabietic acid and tetrahydroabietic acid. 5 l V Disproportionated rosin is commercially available, one such product being manufactured and sold under the trade designation Rosin 73 l-D. This commercial product, sometimes called technical dehydroabietic acid, is described as a pale, moderately hard thermoplastic rosin,

having an acid number of 153, a softening point of 81 C.,

and a density of 1.058 atZtl" C.

In the preparation of the esters, disproportionated rosin is reacted either with a mixture of 1,2-propylene oxide and ethylene oxide in varying proportions as indicated hereinbefore, or with 1,2-propylene oxide and ethylene oxide sequentially, with either the ethylene oxide or propylene oxide being terminal. In the first instance the arrangement of the ethylene oxide and propylene oxide units is completely random. in the latter instance, the ethylene oxide units and propylene oxide units are arranged in two unitary blocks, and the ethylene oxide-1,2-

propylene oxide portion of the structure is generally referred to as a block polymer. The reaction is carried out in a jacketed vessel in the presence of sodium hydroxide as a catalyst, at temperatures well known in the art. The preparation of the rosin esters forms no part of the instant invention, and the processing details may bevaried within the limits of conventional practice in the preparation of the esters of the acids oi disproportionated rosin.

Modifying action as-hereinbefore described may be obtained by inclusion in the viscose process of small amounts of the order of 0.5% based on the bone dry weight of the pulp, but amounts ranging from 0.5% to 3.5% will give the described performance. Addition of v the chemical additive at any convenient stage in the viscose process prior to spinning willresult in the modifying action, and addition prior to completion of the steeping operation in the slurry process and prior to the completion of shredding in the conventional sheet steeping process will in addition result in viscose possessing a high degree of filterability. Addition of the chemical additive to the prehydrolyzed sulfate chemical wood pulp is quite satisfactory as is customary with other types-of additives.

All of the esters of this invention in which the oxides are randomly arranged and many of the esters with seqential oxide arrangement are liquid, and are thus conveniently and economically shipped, handled, and used. Greater resistance to alkaline saponifica-tion' is exhibited by the mixed oxide esters of this invention than by the simple ethylene oxide esters of the prior art and the rate of Water solution and/or dispersion is greatly enhanced by the presence of a proportion of propenoxy groups in the oxide chain, resulting in improved stability and greater ease of application. Excellent filterability is provided by these agents regardless of the variation in the percentage of ethylene oxide in the total oxide, namely 85% to 40% by weight.

The effectiveness of the chemical additives in controlling the skin to core ratio of filaments isreadily demonstrated by subjecting filament sections to a dye process to differentiate between the skin and core areas and show the cross-sectionalshape. In order to do this, the filaments are embedded in paraffin and six micron cross-sections are cut therefrom using an American Optical Company sliding microtome. The so prepared sections are then fixed on a microscope slide by an albumin fixative and the paratiin dissolved in xylene. The slide with the fixed sections is flooded with a 10% aqueous solution of Solop enyl Fast Blue Green BL dye and steeped for 40 seconds in a beaker on a hot plate. The excess dye is next washed away by dipping the slide into a beaker of Water. Reference to this procedure for dying the core section of a filament cross-section while leaving the filament skin unstained may be found in Textile Research Journal, vol. XXIV, No. 397 (1954).

The-differentially dyed filament cross-sections prepared in the manner of the preceding paragraphs were microscopically examined and recorded for comparison by photographic media using a visible light microscope with a 6-15 (orange) filter. The following microscope optics were used: 1) An achromatic NA 1.25 condenser, (2) a 4 mm. NA 0.95 apochromatic objective, and (3) a x Leitz Periplan ocular. The final magnification obtained on the photographic prints of the filament crosssection was about 500x.

The enlarged photographs of the prepared transverse cross-sections of the filaments reveal clearly the extent of skin area, as illustrated in the several figures of the accompanying drawing. In such photographs the undyed skin areas of the filaments sections appear light and are substantially colorless whereas the dyed core areas are.

dark. As will be hereinafter more fully described, the several figures of the drawing represent actual photographs of sectioned filaments dyed as described, the filaments in each figure being spun from viscose having incorporated therein identical amounts of a selected agent of the class to which the invention relates, differing from the chemical additive employed in the processing of the filaments in the other figures only by the percentage of ethylene oxide in the ethylene oxide-1,2-propylene oxide group of the ester contained therein. The extent of modification efir'ected by each of the selected agents is clearly observable, ranging from a high degree of modification in FIGURE 1 to a low degree of modification in FIGURE 3.

The preferred mode of practicing the invention is described more particularly in the following examples, but it will be understood that limitation of the scope of the invention is not thereby intended.

Example Each of three portions of a single lot of sheeted prehydrolyzed sulphate chemical wood pulp was processed into viscose, using the conventional sheet steeping process and spun into filaments to obtain the filament crosssectional specimens of FIGURES 1, 2 and 3.

In accordance with the conventional sheet steeping procedure for the production of viscose rayon, airdried sheets of prehydrolyzed sulfate chemical wood pulp having dimensions of 10 inches by 10 inches and a thickness of 0.040 inch were employed, but it is understood that bulk pulp may be utilized in achieving the results de scribed herein. Approximately 5 pounds of said pulp sheets were used for each of the samples produced. The sheets were placed in the steeping press with the predominant lengthwise orientation of the pulp fibers in the press being perpendicular to the bottom of the press.

An aqueous solution of 18.5% sodium hydroxide at room temperature was introduced into the steeping press until the press was filled to a level one-half inch above the top of the sheets of pulp.

After one hour, the excess sodium hydroxide solution was drained off and the steeped pulp was hydraulically pressed to a weight equal to 2.9 times the weight of the air-dry pulp sheets.

The pressed and weighed alkali cellulose was then shredded for one hour at a temperature of 29 C. At the completion of the shredding operation, the alkali cellulose crumbs were aged for 21 hours at 17 C. in a stainless steel aging can.

After aging, carbon disulfide (CS was added to the alkali cellulose in an amount sufficient to provide 36.7% CS based on the weight of the cellulose in the alkali cellulose. This xanthation operation was carried out in a conventional barrete for two hours at 29 C. The barrete was then unloaded and the xanthate transferred to a Vissolver (a jacketed vessel containing a high speed mixer) which contained caustic, water and the specific modifier in an amount necessary to result in a viscose containing 6.6% cellulose, 6.4% sodium hydroxide and 1.9% sulfur and containing 0.5% based on the bone dry weight of the cellulose contained in the viscose of a chemical additive selected from the family of chemical additives of this invention as more fully hereinbcfore indicated. The viscose solution was then mixed for two hours in the Vissolver.

After filtering, wherein the viscose containing each of the additives of this example displayed substantially the same high degree of filterability, the viscose thus prepared was aged, or ripened, to a Hottenroth index of 21 and extruded thru a spinneret into a spin bath containing 6.6% sulphuric acid, 19.2% sodium sulfate and 4.5% zinc sulfate at 65 C. and then conducted through a second stretching bath containing 2.5% sulfuric acid at 95 C. wherein the yarn was stretched 84%. The spinning speed of the pot spinning machine was 51 meters per minute. Although the spins of this example were carried out in a batch procedure, the results will be the same when the fibers of varying degrees of modification are prepared continuously and sequentially without purging the spinning equipment.

For the purposes of illustrating the present invention, the chemical additives used in the example were each prepared by random reaction of disproportionated rosin (Resin 731-D) with a mixture of ethylene oxide and 1,2-propylene oxide, the total oxides used being four times the amount of rosin by weight, and differed only in the proportional amounts of ethylene oxide and 1,2-propylene oxide content, and it is understood that the described results are substantially the same when the sequential com pounds with either ethylene oxide or propylene oxide terminal are employed.

The three additives of FIGURES 1, 2 and 3 employed to produce the samples of this example were designated in that order as L-1180-2, L-l1882 and L-1190-2 and contained 85%, 70% and 40% respectively of ethylene oxide in the mixed oxide portion of their composition with the balance of the mixed oxide chain consisting of 1,2-propylene oxide. The filaments spun and examined in the hereinbefore described manner from the three samples are represented in the same order in FIGURES 1, 2 and 3 of the drawing. It is quite clear therefore, that as the percentage of ethylene oxide in the chemical additive is progressively decreased, and the percentage of propylene oxide correspondingly increased, the extent of skin formation is reduced, as illustrated by the reduction in the successive figures of the thickness of the filament skin.

L-1188-2 which is typical of the random type condensation products used in the example was prepared in the following manner:

One of the reactants employed was a disproportionated rosin containing a major proportion of dehydroabietic acid together with minor proportions of dihydroabietic acid and tetrahydroabietic acid. This disproportionated rosin is commercially available under the trade name Rosin 731-D and is prepared by heating tall oil to elevated temperatures over extended periods of time in the presence of a suitable catalyst. The other reactants were 1,2-propylene oxide and ethylene oxide mixed in amounts of 70% ethylene oxide and 30% propylene oxide by weight. The reaction was carried out in a jacketed vessel in the presence of sodium hydroxide as a catalyst.

Sixteen pounds of the mixture containing ethylene oxide and 1,2-propy1ene oxide in the aforementioned 70-30 weight ratio were added to 4 pounds of disproportionated rosin containing 10 grams of sodium hydroxide beginning at a temperature of 153 C. and continuing to a temperature of 158 C. and a final pressure of 70 psi. over a period of 45 minutes during which time the mixed oxides were gradually added to the jacketed vessel.

The resultant product contained four parts of mixed 9 oxides to one part of disproportionated rosin with the random oxide chain consisting of 70% ethylene oxide and 30% 1,2-propylene oxide and when employed in the processing of a prehydrolyzed chemical sulfate wood pulp into viscose rayon significantly modified the cross sections of the rayon filaments obtained.

The sequential type condensation products which find use in the practice of this invention are prepared in a like manner, except that the 1,2-propylene oxide and ethylene oxide are introduced into the reaction vessel sequentially with either the ethylene oxide or the 1,2-propylene oxide being terminal and the proportions of oxides to rosin and to each other being adjusted within the range hereinbefore described for the product desired.

The chemical additives of this invention may be added to the cellulose at any convenient stage of pulp sheet formation or viscose processing prior to the extrusion of the viscose. For example, they may be added to the pulp during the formation of the pulp sheet, after formation of the sheet but prior to completion of drying the sheet or after the sheet has been formed and dried. The chemical additives, alone Orin admixture maybe sprayed onto the entire surface area of the sheet or be applied to the sheet as narrow stripes.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In the manufaotureof regenerated cellulose filaments from prehydrolyzed sulphate chemical wood pulp by the viscose process, the step of incorporating in the viscose a modifying agent capable of controlling the skin to core ratio and cross-section shape of filaments spun from the viscose, said agents consisting essentially of ethylene oxide-1,2-propylene oxide esters of 'disproportionated rosin in amount from 0.5% to 3.5% by weight of the bone dry pulp, the oxides being present in the esters in amount from 1.5 to 9 times the amount of rosin by weight, and the ethylene oxide constituting from 40% to 85% of the total oxide Weight of the esters and being adjusted within the said range to obtain a desired skin to core ratio and cross-section shape in the filaments.

2. The method of claim 1 in which the modifying agent is added at any stage in the process prior to the completion of steeping in the slurry viscose process and prior to the completion of shredding in the sheet steeping viscose process to provide improved filtration.

3. The method of claim 1 in which the modifying agent is added to sheeted prehydrolyzed sulphate pulp.

4. The method of claim 1 in which the amount of agent is about 0.5% by weight of the pulp.

5. In the manufacture of regenerated cellulose filaments from prehydrolyzed sulphate chemical wood pulp by the viscose process, the steps of spinning the filaments from viscose containing, as a modifying agent capable of controlling the skin to core ration and cross-section shape of filaments spun from the viscose, an ethylene oxide-1,2- propylene oxide ester of disproportionated rosin in amount from 0.5% to 3.5% by weight of the pulp, the oxides being present in amount from 1.5 to 9 times the amount of rosin by weight, and the ethylene oxide falling within the range from 40% to of the total oxide Weight, and during spinning substituting for the viscose containing said agent viscose containing an agent differing from the first mentioned agent only in having a different proportion of ethylene oxide to total oxide weight within said percentage range to change the skin to core ratio and cross-section shape alfected in the filament by the first agent, the said substitution being made prior to the spinnerets and without purging the system before said replacement substitution.

6. Prehydrolyzed sulphate chemical pulp for mom the manufacture of regenerated cellulose filaments by the viscose process, said pulp having incorporated therein an ethylene oxide-1,2-propylene oxide ester of disproportionated rosin in amount from 0.5% to 3.5% by weight of the pulp, the oxides being present in amount from 1.5 to .9 times the amount of rosin by weight, and the ethylene oxide constituting from 40% to 85% of the total oxide weight and being, adjusted within the said range to obtain a desired skin to core ratio and crosssectional shape in filaments spun from viscose prepared from said pulp.

References Cited in the file of this patent I UNITED STATES PATENTS Re. 24,486 Mitchell June 10, 1958 2,784,107 Tallis Mar. 5, 1957 2,792,313 Charles et al. May 14, 1957 2,813,038 Edwards Nov. 12, 1957 FOREIGN PATENTS 1,173,991 France Mar. 4, 1959 OTHER REFERENCES Huang et al.: J. Chem. Soc. Japan, Ind. Chem. Sect, vol. 56, pages 807-809 (1953), CA, vol. 49, 75430.

Claims (1)

1. IN THE MANUFACTURE OF REGENERATED CELLULOSE FILAMENTS FROM PREHYDROLYZED SULPHATE CHEMICAL WOOD PULP BY THE VISCOSE PROCESS, THE STEP OF INCORPORATING IN THE VISCOSE A MOCIFYING AGENT CAPABLE OF CONTROLLING THE SKIN TO CORE RATIO AND CROSS-SECTION SHAPE OF FILAMENTS SPUN FROM THE VISCOSE, SAID AGENTS CONSISTING ESSENTIALLY OF ETHYLENE OXIDE- 1,2-PROPYLENE OXIDE ESTERS OF DISPROPORTIONATED ROSIN IN AMOUNT FROM 0.5% TO 3.5% BY WEIGHT OF THE BONE DRY PULP, THE OXIDE CONSTITUTING FROM 40% TO IN AMOUNT FROM 1.5 TO 9 TIMES THE AMOUNT OF ROSIN BY WEIGHT, AND THE ETHYLENE OXIDE CONSTITUTING FROM 40% TO 85% OF THE TOTAL OXIDE WEIGHT OF THE ESTERS AND BEING ADJUSTED WITHIN THE SAID RANGE TO OBTAIN A DESIRED SKIN TO CORE RATIO AND CROSS-SECTION SHAPE IN THE FILAMENTS.

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