US2315545A - Method of treating cellulosic material - Google Patents

Description

Patented Apr. 6, 1943 I UNITED STATES PATENT orrlca 2,315,545 METHOD OF TREATING CELLULOSIO Erie Owen Bidmy, Upper Montclair, N. J., as-

signer to Ridbo Laboratories, Inc., Nutley, N. J a corp ration of New Jersey "No Drawing.

11 Claims.

This invention relates to the treatment of cellulosic textile materials, such as cotton, jute. linen and like fibrous material.

The invention contemplates both improvin the qualities of the cellulosicfmaterial and removing the stray surface hairs or thin fibres or fuzz. In accordance with the method of the Application September 27, 1939, Serial N0. 296,843

invention, the tensile strength, appearance, handle and hot flexing life of the-cellulosic textile material is increased by removing therefrom the lesser celluloses, glucosides and other: impurities incidental to the growth of the fibres without dissolving the alpha cellulose content of the textile material except the random surface fuzz which is dissolved and removed.

Cellulosic fabrics treated in accordance with the invention have been found to be very satis-' factory for coating. or impregnating with varnishes, oils,'synthetic resins and the like. Such impregnated or coated materials have been found to be highly satisfactory for use as window shades, Holland cloth substitutes, insulaincreases the fabrics valuejas an insulating ma terial, due to theremoval'j'of those impurities which tend to lower the dielectric constant of cellulosicmaterial such as cotton. Highly satisfactory results have also been obtained in obtaining fuzz-free",thread.a, Yarn.

Heretofore when cotton fabrics have been 'coat ed in the manner described, the surface hairs or "fuzz" have had to be'plastered or secured to the surface of the fabric by varnishes,

gums, china clay and the like. Thuawhen finer ployed in a continuous fashion in that substantial lengths of fabric or yarn or thread are continuously passed through the several baths, but it may also be practicedin a semi-continuous or batch method. The first two essential steps of the method are concerned with the removal of the so-called cellulosic'impurities or lesser celluloses, glucosides and the like, without dissolving the alpha cellulose content of the material. The third step comprises the dissolution and removal oi. the surface fuzz which is prepared for solution in the first two steps. Generally the invention contemplates first thoroughly wetting cellulosic textile material in a watersoluble copper salt, then immersing it in a. solution containing ammonium hydroxide and one .or more alkali hydroxides stronger than ammonium hydroxide, such as sodium hydroxide and/or potassium hydroxide, and then treating the material in a copper ammonium salt. The concentrations of the water-soluble copper salt and the hydroxides employed are such that only the lesser celluloses and other impurities are selectively dissolved and removed .afterthe first two steps, without dissolution of alpha cellulose.

More specifically, suitable cellulosic textile material such as fabrics, threads or yarns, either in or more sheer coated or impregnated fabrics have been desired, the trade hasher'etofo'i e had to employ silk as the base fabric. In the presence of surface hairs or fuzz," the variouscoating materials are deposited in thicker localized areas around the surface hairs, and-there is also the possibility of forming air-bubbles at these points, with the result that the fabric is not only an inefilcient insuiator,,-but also has an undesirable appearance and a sandpaper iike hand. Furthermore, the presense in the cellulosic material of even those small quantities of impurities remaining after lrier boiling'and bleaching inhibits and retards the complete impregnation of the material. i

The invention comprisesessentially a threestep method and commerciallyis preferably-emthe grey or bleached condition, is first thoroughly impregnated with a water-soluble copper salt solution, preferably copper sulphate, although satisfactory results have been obtained with copper nitrate, copper bromide, or copper chloride. Excess copper salt solution is then removed in any suitable manner such as by centrifuging or by passing the material through squeeze rolls, and the material is then led into a solution containing ammonium hydroxide and sodium hydroxide and/or potassium hydroxide. The material is then removed from this bath and squeezed in the manner described so as to leave a slight amount of excess solution on the surface thereof, and is then immediately immersed in a copper ammoni lm salt solution such as cop per ammonium sulp rate (CHM-h) 4804.520) or copper ammonium chloride (cuchznmcmmm The material then may be washed in any suitable manner to remove the reagents and dissolved material. It is first preferred to remove the alkalies and some of the copper with water I and then the balance of the copper may be retreat all of the fibres in the fabric, thread or yarn so as to selectively dissolve and remove the lesser celluloses, glucosides and other impurities without dissolving the alpha cellulose. In the 7 third step the surface of the material alone is treated and the reaction is limited to the surface hairs or fuzz; the'degree of this surface 10 treatment may be governed and controlled by the concentrations of the reagents in the second and third steps, by the time the material is permitted to remain in the third or copper ammonium. salt bath, and the quantity of excess ammoniacaustic solution allowed to remain in and/or on the material when it is immersed in the third or copper ammonium salt solution. For mostpurposes it is desirable to remove only the surface fuzz, and to secure this result in commercial practices it is preferred to use the highest practical concentrations of copper ammonium Salt solutions (the third bath) and relatively high concentrations in the ammonia-caustic solution- (the second bath),-passing the material rapidly through the third bath so as to confine the reaction to the surface hairs or fuzz. It.is sometimes desirable to add a certain amount of excess ammonia, such as one mol, to the copper ammonia salt solution (the third bath). The

speed and degree of the reaction is also increased in direct proportion to the degree of refrigeration used in the third bath, that is, the lower the temperature, within certain limits, the

greater the increase.

As previously pointedout, the concentrationof the water-soluble copper salt solution .(the first bath) and the ratio of copper salt solution to cellulose, remaining on the cellulosic material after the excess solution is removed after the first bath, are such that upon immersion in the caustic ammonia solution the alpha cellulose content of the textile material is, not dissolved,

and only the lesser celluloses and other impurities in the textile material are dissolved and removed. The preferred concentrations and ratios of copper salt solution to cellulose remaining on .the material after the excess solution of the first bath has been removed are fully set forth in the copending application of W. A. Bodenschatz and E. Owen Ridgway-for Method of treating and finishing cellulose and cellulosic fibres and product," filed August 17, 1939, Serial No. 290,627, issued to Patent No. 2,252,732 on August 19, 1941.

It may be stated as a general principle that a lower ratio of copper sulphate to cellulose must be employed with heavy fabrics than light weight fabrics, since in the heavier fabrics there is an increase in the excess copper salt solution trapped inthe interstices of the fabric, which excess concentrations of solution tend to cause dissolution of alpha cellulose.

The following is a table of the copper expressed in terms of CuSO45H2O to cellulose ratios for various fabrics of differing weight per square yard; The ratios so expressed are the upper limits which it is desired to employ at room temperature, such asapp'roximately 20 C. or higher in this method, after the material has been immersed in the copper salt solution; excess CuSO4.5H2O solution above this ratio should be removed from the material after the first bath before it is subject to treatment in the other reagents.

' Table No. 1

It will be seen from the foregoing table that the copper to cellulose, in terms of copper sulphate, ratios increases .01 for each added square yard per pound of fabric; thus marquesettes, which are about 15 square yards to the pound, would have a preferred limiting ratio of .3.

The above table represents the upper limits for each type of material which has been kier boiled, malted, and/or bleached, irrespective of the concentrations of the ammonia and other alkali hydroxides, or time of immersion. If thefibres or material are in the unbleached or grey state, slightly higher concentrations of the water-soluble copper salt may be employed to produce a similar finish without dissolving alpha cellulose. The highest practical concentration of copper sulphate solution in terms of grams per litre for the first bath and expression (percentum of copper sulphate solution remaining in the material after removal of the excess solution based on the original dry weight of such material) for any of the ratios set forth in Table No. 1 can readily be determined from the following Table No. 2:

Table No. 2

The decimal figures in this table represent the- Expression The ratios for solutions below 200 grams per litre can readily be calculated.

For example, if the highest concentration of copper sulphate solution that may be employed on a 6 square yard per pound. material is to be determined, it will be noted 'in Table No. 1 that the maximum ratio is .21, and from Table N0. ,2 it will be noted that 320 grams per litre copper sulphate solution may be employed at 75% expression, or a 300 grams per litre solution may beemployed at 80% expression. The ranges of copper sulphate solution concentration which may be employed for various fabrics will depend upon the desired stiffness or softness required in the finished product. To obtain a relatively stiff finish, the upper ranges of concentrations of copper sulphate, as set forth in Table No. 2, should be employed, and to obtain a softer finish, lower concentrations well below the upper limits set forthinfthe table for the respective weight fabrics should be employed. The higher salt concentrations apparently prepare the. cellulosic material for a distinct action by the caustic alkali solution, since with the removal of the lesser celluloses and other impurities, which are probably in the inter-micellular spaces as well as in the core of the fibres, and upon drying, the alpha cellulose micells in each fibre become more intimately in contact with each other, due-to the attendant reduction in the diameter of the fibre, producing a more crisp fabric. It is not deemed practical or feasible to employ expressions even with more dilute solutions of copper sulphate, above 110%. With some fabrics it is not practical to employ expressions as low as 65% and in many cases this will depend upon the apparatus available; however, from Table No. 2 it is apparent that higher expressions may readily be employed with a lower concentration of copper salt solution. For instance, in the illustration given employing 6 square yard per pound material, if the apparatus available is not adapted to supply an' even squeeze at 75% expression, the method can be employed at 100% expression with approximately 235 grams per litre copper sulphate solution.

The concentration of the second, batl comprising ammonium hydroxide and sodium hydroxide and/or potassium hydroxide may vary considerably. The ammonia (NI-I3) concentration is preferably 150-180 grams per litre.

The ammonia concentration may be reduced from 150 grams per litre to approximately 100 ,grams per litre, and in that case the difference 1 between 150 grams per litre and the amount actually employed is preferably added to the third bath as free ammonium hydroxide. The

concentration of the caustic solution comprising sodium hydroxide and/or potassium hydroxide is preferably between 90 and 160 grams per litre. The important factor is the quantity of caustic solution present on the surface of the fabric after it has been removed from the second bath and squeezed. Accordingly, the

concentration of the caustic solution may be varied in accordance with the expression or percentage of the hydroxide solution remaining on the fabric, based on dry weight of the fabric. Thus, when the residual solution .in' the material decreases, the concentration of the hydroxide solution increases. The following'table is illustrative:

Table No. 3

Peroentum ofresidual solution entrained in cloth after squeeze, on basis of dry weight of material Per cent The concentration of the third bath comprising cuprammonium salt solution may be based in terms of metallic copper and may include as an equivalent the range of 34.5 to 64 grams per litre metallic copper. The preferred range in which the most satisfactory results have been secured is the equivalent of the range of 51-64 grams per litre metallic-copper. In terms of copper ammonium sulphate (Cu(NHa) 4S04.H2O)

the preferredconcentration is within the range.

of 200-250 grams per litre, and highly satisfactory results have been obtained with concentrations as low as 150 grams per litre. In terms of copper ammonium chloride the concentration may range from 165-180 grams per litre. Highly satisfactory results have been obtained when the cuprammonium salt solution carries a quantity of free ammonia (NHa) of between one-half to one and one-half mols to each mol of metallic copper.

The time during which the cellulosic material remains in the three baths may vary somewhat. In the flrsttwo baths, 1. e., the water-soluble copper salt solution and the caustic-ammonia solution, the material need only remain therein As has been previously set forth, the method may be employed in producing a high quality fuzz-free thread and yarn. In treating thread,

instead of using squeeze rolls, a dressing brush,

similar to those used on thread dressing machines, is employed. Brushes of this type remove the dissolved fuzz and leave a smooth surface. After leaving the brush. the thread may be set in acid and washed with water, or set in weak NaOH solution (approximately 40 grams per litre), washed in water and acid and water a second time, or set in water, washed in acid and again in water.

The foregoing method and resultant product are believed to be superior to the methods and products of the prior art in that, after the first two steps of the method, the fuzz has been preliminarily treated so that it may be readily and completely removed in the'final bath and accordingly requires a smaller quantity ofreagents in the final bath to completely dissolve the fuzz. A further important feature is that. during the nating the material in a solution of briefly immersing the process the interior of the fibre structure has been treated to remove the impurities, producing a higher quality product than those known to the art in which only the surface of a fibre is treated. It is believed that the reaction in the third step is confined to the surface hairs because the bulk of the fibres (other than the surface hairs) comprising the fabric itself, have a tendency to selectively absorb proportionately more caustic alkali than ammonia, and since the cuprammonium salt solution employed in the third bath tends to penetrate the fibre bundles more slowly in the presence of caustic alkali, anything but a surface reaction, where the surface hairs come into contact with more than enough cuprammonium salt solution to dissolve them, is inhibited. In the third bath, considerable quantities of copper ammonia solution are not required since the surface hairs enter this third bath with some impregnated copper hydroxide plus. an excess of the caustic-ammonia solution and, accordingly, in the third bath there is an immediate and efficient reaction. The result is a fuzz-free tex ile material from which the lesser celluloses and other impurities have been removed, which is highly absorbent, has a high dielectric constant and a generally improved appearance and hand.

It is to be understood that the term cellulosic textile material as employed herein includes any fibre or admixture of fibres in which the chief constituent of the fibre is, or was, cellulose, and includes all cellulosic fibres, whetherthey be in the form of fabrics, knitted or woven, yarns, cords, threads, fabrics or coverings.

What I claim is as follows: i

l. The method of treating cellulosic textile material to remove therefrom the lesser celluloses, sugars, lucosides and surface fuzz,'without dissolving the alpha cellulose content of the fibre bundle, which comprises first thoroughly impregcopper sulphate, removing excess solution from the material until the ratio of copper sulphate to cellulose is such that alpha cellulose of the fibre bundle will not be dissolved upon. subsequent treatment, for fabrics comprising 1 square yard per pound the ratio of copper sulphate (CuSOaSHzO) to cellulose being not in excess of .16, said ratio increasing .01 for each added square yard per pound of cellulosic material, then treating the impregnated material in a solution containing ammonium hydroxide and a caustic alkali, re-' taining excess caustic alkali solution on the surface of the material to limit the reaction in the following bath to the surface fun, and then material in a solution of cuprammonium salt of the group consisting of copper ammonium sulphate and copper ammonium chloride, and finally Washing the reagents and dissolved matter from the material.

2. Themethod of treating cellulosic textile material to remove therefrom the lesser celluloses,

sugars, glucosides and surface fuzz without dissolving the alpha cellulose content thereof, which comprises first thoroughly impregnating the material in a solution of copper sulphate, removing excess solution from the material until the ratio of copper sulphate to cellulose is such that alpha cellulose of the fibre bundle will not be dissolved uponsubsequent treatment, for fabrics comprising 1 square yard per pound the ratio of copper sulphate (CllSO45H2O) to celllulose being not in excess of .16, the concentration of the copper sulphate solution being not in excess of approximately 285 grams of copper sulphate per litre,

bath to the surface fuzz, then briefly immersing the material in a solution of copper ammonium sulphate, and finally washing the material to remove the reagents and dissolved material.

3. The method of treating cellulosic textile material to remove the impurities and surfacefuzz, which comprises first thoroughly impregnating said material in a solution of copper sulphate, then immersing the impregnated material in a bath of ammonium hydroxide and sodium hydroxide, retaining excess caustic solution on the surface of the material to limit the reaction in the following bath to the surface fuzz, then briefly immersing the material in a solution of copper ammonium sulphate of a concentration within the range of 150 grams to 250 grams per litre to remove the surface fuzz,-and finally washing said material.

4. The method of treating cellulosic textile material to remove the impurities and surface fuzz, which comprises first thoroughly impregnating said material in a solution of copper sulphate, then immersing the impregnated material in a bath of ammonium hydroxide and sodium hydroxide, retaining excess caustic solution on the surface of the material to limit the reaction in the following bath to the surface fuzz, then briefly immersing the material in a solution of copper ammonium chloride, said solution having a concentration within the range equivalent to 51 to 64 grams per litre metallic copper, and finally washing the reagents from the material.

5. The method of treating cellulosic textile material to remove therefrom the lesser celluloses, sugars, glucosides and surface fuzz, without dissolving the alpha cellulose content of the fibre bundle, which comprises impregnating the material with a solution of a water-soluble copper salt, the concentration of the copper salt solution remining in and on the material not exceeding 1 part of copper salt to 4 parts of cellulose, then treating the material in a solution of ammonium hydroxide and a caustic soda, said caustic soda being present in an amount slightly in excess of molecular proportions, retaining a slight amount ofexcess caustic solution'on the surface of the materialto limit the reaction of the followin bath to the removal of surface fuzz, then briefly ammonium sulphate and copper ammonium chloride, and washing the reagents from said material.

6. The method of treating cellulosic textile material to remove therefrom the lessercellulosesf sugars, glucosides and surface fuzz, which com-.

prises first thoroughly impregnating the mate-' rial with a solution of a water-soluble copper salt, removing excess copper salt solution so that the concentration of copper salt to cellulose on the material is suflicient to dissolve the lesser celluloses, sugars, glucosides and other impurities I but is insufiicient to dissolve the alpha cellulose of the fibre bundle upon subsequent treatment,

the ratio of water-soluble copper salt to cellulose for fabrics comprising one square yard per pound being not in excess of .16, said ratio increasing amount of excess caustic alkali solution on the material, then immersingit in-a copper ammonium salt solution of the group consisting of Y copper ammonium sulphate and copper am-- monium chloride, the material being retained in said copper ammonium salt solution for a period of not more than six seconds, and then washing the material to remove the reagents and dissolved material. '7. The method of treating cellulosic textile material to remove therefrom the lesser. celluloses, sugars, glucosides and surface fuzz, without dissolving the alpha cellulose content of the fibre bundle, which comprises first thoroughly impregnating the material in a solution of copper sulphate, the concentration of the copper sulphate solution retained in the ,material being varied in accordance with the character of the material under treatment-a relatively high concentration of copper sulphate solution not exceeding approximately 1 part of copper sulphate to 3 parts of cellulose being employed with lightweight fabrics of approximately fifteen square yards to the pound, and lower concentrations of copper sulphate such as approximately one part of copper sulphate to 6 parts of cellulose being employed for heavier fabrics of approximately one square yard per pound, then treating the impregnated material in a solution containing ammonium hydroxide and caustic alkali, sufficient excess caustic solution being retained on the material to limit the reaction of the followand finally washing the material to remove the reagents.

9. The method of treating cellulosic material to remove the impurities and surface fuzz, which comprises first thoroughly impregnating the material with a solution of a water-soluble'copper salt-removing excess solution from the material until the ratio of copper salt to cellulose is such thatalpha cellulose of the fibre bundle will not be dissolved upon subsequent treatment, for fabrics comprising one square yard per pound, the ratio of copper salt to cellulose being not in excess of .16, said ratio increasing ,01 for each added square yard per pound of cellulosic material, then immersing the material in a solution of ammonium hydroxide and sodium hydroxide, the concentration of the ammonium hydroxide being in the range of 100-180 grams ammonia per litre, and the concentration of the sodium hydroxide being in the range of 90-160 grams per litre, the

' concentration of sodium hydroxide varying inversely with the amount of sodium hydroxide solution retained in the cellulosic material, retainmg a slight amount of caustic solution, in excess of that required for 'the reaction, on the surface of the material to limit the reaction of the following bath to the removal of surface fuzz, and then briefly immersing the material in a cuprammoing bath to surface fuzz, then immersing the material in a solution of a copper ammonium salt of the group consisting of copper ammonium sulphate. and copper ammonium chloride, the con' centration of the solution being in the range of equivalent of 51 to 64 grams per litre metallic copper, and then washing th material to remove the dissolved matter and reagents.

8. The method of treating cellulosic textile material to remove therefrom the lesser celluloses, sugars, glucosides and surface fuzz without dissolving the alpha cellulose content of the fibre bundle, which comprises first thoroughly impregnating the material in a solution of copper sulphate, removing excess solution from the material until'the ratio of copper sulphate on the material is such that alpha cellulose of the fibre bundle will not be dissolved upon subsequent treatment, for fabrics comprising 1 square yard per pound the ratio of copper sulphate- (CilSO4.5HzO) to cellulose being not in excess of .16, the concentration of thecopper sulphate solution being not in excess of approximately 285 grams of copper sulphate per litre, said ratio increasing .01 for each added square yard per pound of cellulosic material, then treating the impregnated material in a solution containing ammonium hydroxide and a caustic alkali, said caus- *tic alkali being present in an amount slightly in excess of the required molecular proportions, retaining a slight amount of excess caustic solution on the surface of the material to limit the reaction of the following bath to the removal of surfac fuzz, and then briefly immersing the material in a salt solution of the group consisting of copper ammonium sulphate and copper ammonium chloride containing between one-half to one and one-half mols of free ammoina to each mol of metallic copper to remove the surface fuzz,

ing one square yard per pound, the ratio of copper sulphate (CuSO4.5H:O) to cellulose being not in excess of .16, said ratio increasing .01 for each added square yard per pound of cellulosic material, then immersing the impregnated material in a solution containing ammonium hydroxide in the range of to 180 grams ammonia per litre and sodium hydroxide in the range of 90 to grams per litre, the concentration of the sodium hydroxide varying inversely with the amount of sodium hydroxide solution retained in the cellulosic material, retaining a slight amount of excess sodium hydroxide solution on the materiaL-and then briefly immersing the material in a solution of a cup'rammoniuni salt of the group consisting of copper ammonium sulphate and copper ammonium chloride, the concentration of the salt being within the range of 51 to 64 grams perlitre in terms of metallic copper, s'aid material being retained in said third bath for not more than six seconds, and finally washing the material.

11. The method of treating cellulosic textile fibres to remove the impurities and surface hairs, which comprises first thoroughly impregnating the material with a solution of copper sulphate} alkali solution on the material, and then briefly immersing the material in a solution of acuprammonium salt or the group consisting of copper 10 ammonium sulphate and copper ammonium chloride having a quantity of free ammonia of between one-half to one and one-half mols to each mole of metallic copper, the concentration of the salt being within the range of 51 to 64 grams per litre in terms of metallic copper, said material beingretained in the third bath for not more than six seconds, and finally washing the material.

ERIC OWEN RIDGWAY.