US2682443A

US2682443A - Hot acid neutralization of regenerated cellulose containing fabrics treated with alkaline swelling agents

Info

Publication number: US2682443A
Application number: US213477A
Authority: US
Inventors: Bener Christian
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-12-30
Filing date: 1951-03-01
Publication date: 1954-06-29
Anticipated expiration: 1971-06-29
Also published as: GB605536A

Description

Patented June 29, 1954 UNITED STATES rarer OFFICE AGENTS Christian Boner, Chur, Switzerland N 0 Drawing.

Application March 1, 1951, Serial No. 213,477. In Switzerland December 30, 194.4

Section 1, Public Law 690, August 8,1946 Patent expires December 30, 1964 9 Claims.

The present invention relates to improvements in the refining treatment of textiles containing regenerated cellulose fibers in which such textiles are subjected to a swelling treatment with an aqueous solution of caustic alkali to modify the appearance, texture and hand of the textile.

It has long been established that alkaline swelling agents react in a totally diiferent manner on regenerated cellulose than on natural cellulose. Where-as, for example, the known refining effects of mercerization are obtained with alkaline swelling agents on cotton with or without tension, these alkaline swelling agents have a far more radical effect on regenerated cellulose whether it be in the form of long spun fibers or filaments, or in the form of staple fibers and such swelling agents tend to cause a decided parchmentization which can even lead to a structural modification of the regenerated cellulose and in any event, lead to an undesirable hardening, stifiening and swelling of such fibers. The effects obtained with regenerated cellulose are of substantially no practical use and, therefore, ways and means have been sought for to elimi nate the drawbacks mentioned in order that treatment of regenerated cellulose with alkaline swelling agents could be employed to provide utilizable effects, particularly in the mercerization of mixed fabrics made of cotton and regenerated cellulose.

In accordance with the invention, it has been unexpectedlydiscovered that the drawbacks mentioned can be avoided in the refining of woven or knitted fabrics containing regenerated cellulose fibers with alkaline swelling agents and that interesting and valuable refining effects can be obtained if directly after the treatment with hot or cold alkaline swelling agents, and without any intervening alteration in the concentration of the alkaline swelling agent on the fabric, su'cnfabric is subjected to an after-treatment with a dilute aqueous solution of an acid at an elevated temperature between 45 C., preferably 50 C., and the boiling point of such acid solution, said acid solution being at least of such quantity and concentration that the free alkali retained by the fabric is chemically combined and thereby neutralized whereby a sudden neu tralization of such alkali is achieved.

The reasons for the novel improved effects which are obtained with the direct hot acidifi cation in accordance with the invention, are not completely. understood. However, the effects obtained are amazing and the'differences over the effects obtained with processes employing "the 2 same-alkaline swelling concentrations and conditions followed by the hot or cold rinses or the cold acidification previously employed are so great as to be visible at a glance.

The acid after-treatment in accordance with the invention, is carried out with hot dilute solutions of organic or inorganic acids. The concentrations employed are such that they do not act as swelling agents on the fibers treated, but only act to neutralize the alkaline swelling agents previously'applied. The acid solutions employed can also contain. other dissolved sub-- stances which are not destructive to the fiber.

For example, such acid solutions can contain 1 quantities of neutral salts such as sodium sulfate or acid salts of polybasic acids such as sodium bisulfate of which the latter still contains a half a mol of sulfuric acid available for neutralization. The salts mentioned would, of course, occur inherently when dilute sulfuric acid is employed for the after-treatment in accordance with the invention. Sulfuric, hydrochloric, acetic, formic, oxalic acids and the like are particularly suitable for the acid treatment. The dilute acid solutions of a concentration between 3% and 25%, preferably between 3% and 10% are suitable for the acid after-treatment in accordance with the invention. The goods must remain in contact with the acid at least until the free alkali present in the fibers has been combined and neutralized.

It is of particular advantage to spray the acid solutions evenly over the goods to be treated to insure that the goods continuously come in contact with fresh solution. However, the goods can also be passed through a bath of such solution.

The preliminary treatment of thetextiles containing regenerated cellulose with alkaline swelling agents can be carried out in the usual way, either with hot-or cold alkali and can be, if desired, preceded or succeeded by other types of swelling treatments, for example, with acid swelling agents or further treatments with al a-- line swelling agents.

The directacidification at higher temperatures in accordance with the invention must occur directly after each alkaline swelling treatment whether such treatment is employed alone or in combination with other refining steps with swelling agents such as acids, organic bases, or inor- 'ganic salts, for example, zinc chloride, ammonial copper oxides, calcium thiocyanate and the like of the required concentration. The combined treatments can be repeated, interchanged or applied alternately. However, the refining treatments with swelling agents other than the swelling with alkaline swelling agents cannot be carried out simultaneously with the hot acidification which, in accordance with the invention, directly succeeds the alkaline swelling treatment. In other words, if, for example, a transparentizing treatment with sulfuric acid of transparentizing strength is contemplated, such transparentizing treatment is carried out as a step which is distinct from the hot acidification with dilute acids.

The treatment with alkaline swelling agents which precedes the hot acidification in accordance with the invention can be carried out in the usual way with caustic alkalis such as sodium hydroxide, potassium hydroxide and the like. Usually solutions of sodium hydroxide are preferred in view of their lower cost. The alkaline swelling agents may be applied to the textiles with or Without tension, depending upon the effect desired. The time and temperature of the treatment, as well as the concentration of the alkali also depend upon the effect desired. In practice of the invention, it has been found, for example, that excellent results are obtained in accordance with the invention with alkaline swelling treatments with aqueous caustic alkali solutions equivalent to sodium hydroxide solutions of concentrations ranging between about 15 B. and 36 B. at temperatures between 10 C. and the boiling point of the solution, preferably between l C. and 75 C. The duration of such treatment can be from a few seconds to about 40 minutes, preferably from about seconds to about 3 minutes.

The effects obtainable in accordance with the invention can also be influenced by selection of temperature and acid employed in the hot acidification. Generally, the higher the temperature of the hot dilute acid solution employed the clearer, softer and more transparent the effect obtained. Temperatures between about 70 C. and 85 C. have been found well suited for the hot acidification. Furthermore, a treatment with 5% acetic acid at 85 C. gives a far softer and more brilliant finish than 5% sulfuric acid at the same temperature.

The duration of the hot acidification treatment is not critical except that it must be sufiicient to effect the complete neutralization of all of the alkali contained in the fabric. Treatments of longer duration than that required for the neutralization can of course be employed, but they serve no particular purpose, as the treatment is completed when the total neutralization has been accomplished. For practical purposes, periods between 10 and 60 seconds suffice.

The textiles treated in accordance with the invention can be composed of regenerated cellulose in the form of long spun filaments or fibers or in the form of staple fiber, either alone or in combination with other textile materials as mixed yarns or weaves. The textiles treated are preferably in the form of knitted or woven fabrics. The term regenerated cellulose as employed herein is intended to embrace viscose artificial silk, cuprammonium artificial silk, dinitrated collodion silk or cellulose hydrate artificial silk. The other components which can be present in the mixed weaves, the mixed yarns and the like can be either animal or vegetable fibers, ester or ether silks, or polymerized or superpolymerized fibers such as nylon, and the like.

Depending upon the type of textile refined in 4 accordance with the invention and the conditions under which the process is applied, one can obtain stiffened fabrics, opal effects, transparents (organdies), imitation wools or linen finishes and the final result can be a patterned fabric, if before the refining process patterned reserves against the swelling agent are printed on such fabric. Mixed fabrics of regenerated cellulose and cotton (unbleached cotton) can also be mercerized with caustic alkali solutions of mercerizing strength in combination with the aftertreatment according to the invention without injuring the regenerated cellulose contained therein.

The following examples serve to illustrate the manner in which the process in accordance with the invention can be carried out.

Example 1 A muslin of staple fiber regenerated cellulose under tension was impregnated with an aqueous 25 B. NaOH solution for 1 minute at 15 C. and then immediately treated with a 5% acetic acid solution until all of the free alkali was neutralized. The fabric was then rinsed, washed out and tentered. This resulted in a fine springy supple regenerated cellulose staple fiber fabric with a very clear homogeneous transparent appearance.

When such treatment was modified by interposing a rinse with water between the alkaline treatment and the acidification, a hard, strawy agglutenated parchment-like material which was entirely useless, was obtained.

Example 2 A mixed cotton and viscose weave was impregnated under tension with 32 B. at 8 C. for 25 seconds and then immediately acidified with 5% acetic acid at 85 C. This resulted in the mercerization of the cotton component of the fabric to produce a beautiful sheen, and increased affinity for dyes and a full organic touch.

The same result was obtained when the 5% acetic acid was replaced by 5% sulfuric acid.

Example 3 A regenerated cellulose staple fiber muslin was printed with a gum reserve and then impregnated with 32 B. NaOH at 60 C. for 25 seconds and immediately thereafter acidified with 5% sulfuric acid at 75 C. After this, the fabric was washed and tentered. This treatment produced a patterned regenerated cellulose staple fiber transparent fabric in which the reserve portions still have their original properties,

A regenerated cellulose staple fiber muslin was impregnated with 16 B. NaOH at C. for seconds and immediately thereafter acidified with 5% acetic acid at 85 C. and then thoroughly washed out.

This treatment produced an opaline fabric of a woolly character.

Example 5 A muslin of long spun and staple fiber regenerated cellulose was impregnated with 23 B. NaOH at 10 C. for 35 seconds and then immediately acidified with 5% sulfuric acid at C., washed out and tentered. The treatment resulted in a greatly improved and more aeea ies homogeneous fabric of a more linen-like aspect.

It is to be understood that the invention is not limited. to the above embodiments wli .h have been given by way of example, but that braces all processes in which a rennng t merit of a textile material containing regenerated cellulose fibers is directly followed with a treatment with dilute acid solution at a ture above 415 C. whereby a sudden. shock-lore neutralization of the alkali retained in the tile is obtained upon contact with such acid solution.

The non-swelling acidifying liquors employed for the after treatment may also contain other substances as long as they do not deleteriously affect the textile treated. For example, textile assistants for humecting, impregnating, softening or rendering the textiles water repellent a the like or fillers or dyes may be incorporated in such acidifying liquors.

The term dilute aqueous solution of an as used herein with reference to the hot acidic after trea'rnent of the alkali treated textiles is intended to cover solutions of acids of such dilution that they possess substantially no swelling or transparentizing effect upon the regenerated cellulose.

This application is a continuation-in-part of my prior application, Ser. No. 639,900, filed January 8, 1946, now abandoned.

I claim:

1. A. process for the treatment of textile containing a substantial quantity of ed cellulose fibers which comprises the steps of impregnating said textile with an aqueous NaOlI solution of a predetermined concentration between as. and 3 as. to produce swell efiect upon textile, and, before llaO. solution eiiects parchmentization and able hardening of the regenerated cellulose ii contained in said textile, contacting said imnr nated textile containing said aqueous solution of NaOH of predetermined concentration with an aqueous solution of an acid containing a suiiicient amount of acid to combine chemically with all of the free alkali contained in the textile, said acid being of concentration of about 3% to at a temperature betwen 4:5 C. the boiling point of said acid solution until all of the free alkali contained in the textile is neutralized, whereby a sudden neutralization of all of said free alkali is obtained and its swe action is is minated before parchm ation and undesirable stiffening of the re e. ated cellulose iibers contained in said textile Qfl'zC-t" ed, and removing the acid from the textile to terminate the treatment of said textile with the aqueous solution of the acid before the contained. therein can effect acid transparentization.

2. The process of claim 1 in which said treatment with th aqueous acid solution is effected at a temperature between C. and the boiling point of said acid solution.

3. The process of claim 1 in which said treatment with the aqueous acid solution is effected at a temperature between 70 C. and 85 C.

4. The process of claim 1 in which said treatment with the aqueous acid solution is effected while the textile is under tension.

5. The process of claim 1, in which said acid is sulfuric acid.

6. The process of claim 1, in which said acid is acetic acid.

7. A process for mercerizing the cotton content of a textile containing cotton and a substantial quantity of regenerated cellulose fibers which comprises the steps of impregnating such textile with an aqueous solution of NaOI-I of predeterm ned concentration between 15 B. and 36 Be. to mercerize the cotton content thereof, and then, before said NaOH solution efiects parchmentization and undesirable hardening of the regenerated cellulose fibers contained in said textile, contacting said impregnated textile conta n solution of the caustic alkali of predetermined concentration with an aqueous solution of an acid of about 3% to 25% concentration at a temperature between 45 C. and the boiling point of said acid solution containing a sufiicient amount of acid to combine chemically with all of the free alkali contained in the textile until all of the free alkali contained in the textile is neutralized whereby a sudden neutralization of all of said free alkali is obtained and its swelling action is terminated before parchmentization and undesirable stifiening of the regenerated cellulose fibers in said textile is effected, and removing the acid from the textile to terminate the treatment of said textile with the aqueous solution of the acid before the acid contained therein can effect acid transparentization.

8. A process for the treatment of a textile containing substantial quantity of regenerated cellulose fibers which comprises the steps of impregnating such textile with an aqueous NaOH solution of a predetermined concentration between 15 Be. and 35 Be. for a period between 5 seconds and 3 minutes at a temperature between 10 C. and 75 C. to produce a swelling effect upon said textile and then, before said NaOH solution effects parchmentization and undesirable hardening of the regenerated cellulose fibers contained in said textile, contacting said impregnated textile containing said aqueous NaOH solution of the predetermined concentration with an aqueous 3% to 25% solution of an acid at a temperature between 45 C. and the boiling point of said acid solution containing a sufficient amount of acid to combine chemically with all of the free alkali contained in the textile until all of the free alkali contained in the textile is neutralized whereby a sudden neutralization of all of said free alkali is obtained and its swelling action is terminated before parchmentization and undesirable stiffening 0f the regenerated cellulose fibers in said textile is effected, and removing the acid from the textile to terminate the treatment of said textile with the aqueous solution of the acid before the acid contained therein can effect acid transparentization.

9. The process of claim 8, in which the concentration of said aqueous acid solution is from 3 to 10%.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,989,098 Lillienfeld Jan. 29, 1935 1,989,099 Lillienfeld Jan. 29, 1935 FOREIGN PATENTS umber Country Date 231,352 Great Britain Nov. 30, 1927 335,176 Great Britain Sept. 17, 1930 OTHER REFERENCES American Dyestuff Reporter, March 8, 1948, page 162.

Claims

1. A PROCESS FOR THE TREATMENT OF A TEXTILE CONTAINING A SUBSTANTIAL QUANTITY OF REGENERATED CELLULOSE FIBERS WHICH COMPRISES THE STEPS OF IMPREGNATING SAID TEXTILE WITH AN AQUEOUS NAOH SOLUTION OF A PREDETERMINED CONCENTRATION BETWEEN 15* BE. AND 36* NE. TO PRODUCE A SWELLING EFFECT UPON SAID TEXTILE, AND, BEFORE SAID NAOH SOLUTION EFFECTS PARCHMENTIZATION AND UNDESIRABLE HARDENING OF THE REGENERATED CELLULOSE FIBERS CONTAINED IN SAID TEXTILE, CONTACTING SAID IMPREGNATED TEXTILE CONTAINING SAID AQUEOUS SOLUTION OF NAOH OF PREDETERMINED CONCENTRATION WITH AN AQUEOUS SOLUTION OF AN ACID CONTAINING A SUFFICIENT AMOUNT OF ACID TO COMBINE CHEMICALLY WITH ALL OF THE FREE ALKALI CONTAINED IN THE TEXTILE, SAID ACID BEING OF A CONCENTRATION OF ABOUT 3% TO 25%, AT A TEMPERATURE BETWEEN 45* C. AND THE BOILING POINT OF SAID ACID SOLUTION UNTIL ALL OF THE FREE ALKALI CONTAINED IN THE TEXTILE IS NEUTRALIZED, WHEREBY A SUDDEN NEUTALIZATION OF ALL OF SAID FREE ALKALI IS OBTAINED AND ITS SWELLING ACTION IS TERMINATED BEFORE PARCHMENTIZATION AND UNDESIRABLE STIFFENING OF THE REGENERATED CELLULOSE FIBERS CONTAINING IN SAID TEXTILE IS EFFECTED, AND REMOVING THE ACID FROM THE TEXTILE TO TERMINATE THE TREATMENT OF SAID TEXTILE WITH THE AQUEOUS SOLUTION OF THE ACID BEFORE THE ACID CONTAINED THEREIN CAN EFFECT ACID TRANSPARENTIZATION.