US2174534A - Chemical process - Google Patents

Description

Patented Oct. 3, 1939 UNITED STATE CHEMICAL PROCESS Joseph Barrel Shipp,

to E. I. du Pont de Nemours & Company,

Wilmington, Del., assignor Wilmington, Del., a corporation of Delaware No Drawing. Application April 22, 1936, Serial No. 75,868

20 Claims.

This invention relates to the treatment of textiles, particularly cellulosic fibers, yarns and fabrics, with sulfuric acid to obtain parchmentizing effects; and more particularly to the treatment ,r, of cotton fabrics with concentrated sulfuric acid containing an agent which will inhibit the tendering effect of the acid.

It is generally known that concentrated sulfuric acid is destructive to textile materials. nevertheless certain uses of sulfuric acids on textiles are so advantageous that endeavors have been made to so treat textileswith sulfuric acid as to obtain the desired effects but to avoid the undesirable effects. Thus there is a series of patents which deal with the treatment of fabrics with sulfuric acid in connection with a series of mercerization treatments.

This invention hasas an object the production of permanent finishes on fabrics. "A further ob-v ject is the production of permanent finishes on yarns, textiles, fabrics, paper and the like. A still further object is the production of parchmentized effects on cellulosic fabrics. A still further and particularly desirable object is the production of organdy finishes on cotton fabrics. Other objects will appear hereinafter.

These objects are accomplished by the following invention wherein the fabric to be treated is passed continuously through the parchmentizing bath consisting of especially inhibited strong sulfuric acid, thence through rolls or other means for squeezing out the excess parchmentizing reagent, then through washing and neutralizing baths, and finally over a calender or other drying means. In this procedure the speed and time of immersion of the goods in the parchmentizing bath are adjusted with due regard to the result desired and to the end that the goods are transparentized to the desired degree and that the parchmentizing reagent is washed out before the goods are tendered to an objectionable degree. The novel'feature of this process is the parchmentizing reagent which consists of strong sulfuric acid of at least 65% concentration and preferably from 80% to about 98%, having dissolved therein an agent capable of inhibiting or at least greatly retarding the normal degrading action of strong sulfuric acid upon cellulose. This agent is termed the cellulose degradation inhibitor. In 0 the claims the percentage composition of the acid refers to the composition of the acid prior to the introduction of the inhibitor.

Gil

It is known that strong sulfuric acid has a marked degrading or disintegrating effect on cellulose fibers, which in the case of acid of moderate strength quickly produces a marked tendering of the fiber and in the case of concentrated sulfuricacid such as 96%, results in almost instantaneous and complete destruction of the fiber.

Now it has been discovered that the degrading effect of the acid on the cellulose may be inhibited or retarded by dissolving in the acid certain agents which are termed inhibitors of cellulose degradation. An inhibitor suitable for use inthis invention may be known by the fact that it meets the following tendering resistance test. For this test, parts of the material to be tested is dissolved in 100 pts. of 96% sulfuric acid, the solution is brought to 20 C. and a sample of cotton voile of known tensile strength is immersed therein for aperiod of 30 seconds after which the sample is withdrawn from the acid, washed to neutrality, and dried by ironing. The sample is now examined for parchmentizing and tested for loss or gain of tensile strength. If the sample is found to be parchmentized and to have increased in tensile strength or to have lost less than of its original tensile strength, it is considered that the agent tested is a satisfactory inhibitor of degradation for use in this invention.

If a cotton fabric is immersed in 96% sulfuric acid at room temperature, removed immediately and rinsed veryquickly with a large volume of water, the fabric is disintegrated and destroyed. However, if as much as 25 parts by weight of urea is first added to each 100 parts of acid, then a fabric may be treated with this solution up to 60 seconds without being appreciably tendered. If fabrics so treated are washed free of acid, using dilute alkali if desired, then ironed dry, a pleasant, stiff, springy finish is obtained. When this treatment is applied to cotton voile or lawn, an organdy finish results. Not only is the cloth stiff and springy, but it is also more transparent than the original cloth. The effect is permanent to washing. Instead of urea, certain other materials may be used. These are listed below.

In carrying out the process in its preferred form, the agent is first dissolved in concentrated sulfuric acid with cooling if'necessary to prevent decomposition. The sulfuric acid may be from about 65 and preferably from 85 to over 100 per cent strength. From 10-30 parts by weight of agent per 100 parts of acid' is satisfactory. The, quantity of agent, as well as the concentration of initial acid, may be varied somewhat depending on the time the textile material is to be in contact with the solution, and depending on the effect it is desired to produce. The parchmentlzing is slower and less pronounced with increasing quantities of inhibitor. The'time of contact of the textile material with the solution will ordifabric.

solution of one of these agents and sulfuric acid,-

Lowering the temperature retards the parchmentizing effect. It will be seen that the degree of parchmentizing obtained can be varied at will over very wide limits by varying (1) the amount of inhibitor in the acid, (2) the amount of water in the acid, (3) the temperature of the solution, and (4) the time of contact of the cellulosic material with the'solution.

The textile material, e. g., cotton fabric, is

passed through the acid solution and then into water to remove the acid, then dried by ironing or calendering, or on a tenter frame which exerts a shearing action to minimize sticking together of the warp and filling threads at points of contact. The washing may be facilitated by using water first, followed by a dilute solution of a base such as ammonium hydroxide or sodium hydroxide. It is important that the greater part of the acid be washed out very rapidly in order to avoid local heating which would destroy the If a cellulosic material is treated in a and then slowly immersed in water, the cellulosic material will be tendered or totally destroyed.

A novel fabric has been produced by treating cotton web, produced on a carding machine, with these inhibited sulfuric acid solutions. The fibers are stuck togeth'er at each point of contact, resulting in a strong sheet. This process affords a possibility of omitting the steps of spinning and weaving in the preparation of fabrics suitable for a. variety of purposes. 3

Instead of using a. single agent in the solution two or more may be used from the same or from different groups, or certain other agents may be added to give enhanced effects. A solution containing an amide and an ether, or an amide and an alcohol, or an amide and an amine, will give very satisfatory parchmentizing effects with practically no tendering of the cellulosic material. The use of additional agents also affords means of varying the effects obtained. Thus, an amide. alone or an amide and an amine, or an amide and an alcohol, produce transparent organdy finishes, whereas an amide and a relatively large proportion of an ether produce an opaque parchmentized efi'ect. Also, some agents give a more transparent finish than others. Thus, acetanilide and decamethylenediamine give opaque finishes.

If only limited areas of a fabric are treated by this process, a pattern effect may be obtained. Alternatively, certain areas of the fabric may be immunized against the sulfuric acid treatment and the fabric may then be treated over its entire surface with the acid to obtain pattern effects. Thus, areas printed with paraflin are not affected by the acid treatment, and this affords a means of immunizing against sulfuric acid.

Unfinished cotton fabrics can be treated by this process without any previous or subsequent mercerization and will yield, by a single treatment, a transparent organdy finish. The advanmercerization step is not necessary to produce a good permanent organdy finish.

Instead of washing the fabrics in water after the acid treatment they may first be washed in aqueous sulfuric acid (25 to 50 per cent H2804) and then washed in .water. This reduces the ,1 cost of the treatment, since the dilute sulfuric acid produced, may be utilized in other operations.

While the use of inhibited sulfuric acid is of particular interest and value on cotton fabrics, for producing organdy efiects, linen, and 'rayon may also be treatedby this processwith advantageous results. In this manner an organdy finish can be obtained on rayon voiles.

Fabrics or yarns treated by this process may be stretched during or after the acid treatment. The-tenacity of cellulosic yarns is increased -by stretching duringor after the acid treatment.

In the above the invention has been considered in considerable detail, the principles of the invention being set forth minutely. The following examples still further illustrate the invention, but are purely illustrative and not limitative.

Example 1 of urea, the acid being cooled during the addition of the urea. After the urea was completely dissolved, the solution was cooled to 20 C. A 68/76 unfinished cotton voile fabric was immersed in the solutionfor 30 seconds, removed, drained for a few seconds, then plunged into water at room temperature. After washing thoroughly in water it was rinsed in a. 3 per cent solution of ammonium hydroxide, rinsed in water and dried by ironing. A stiff, springy finish of the type commonly called transparent organdy was obtained. The fabric was boiled for one hour in 0.5 per cent soap solution, rinsed and dried. The finish was not appreciably affected by this laundering.

If it is desired, the fabric may be mercerized with caustic in the usual way either before or after, or both before and after, the above acid treatment. 'Alternatively, two acid treatments of the type indicated may be given the fabric with mercerization between the two acid treatments.

Example 2 A 68/76 unfinished cotton voile fabric was immersed for seconds in a solution of 20 g. thi- 'ourea in 100 g. 96% sulfuric acid, removed,

drained for a few seconds, rinsed in water, then in dilute ammonium hydroxide, and again in water, and dried by ironing. A transparent organdy finish was obtained which was permanent I r to washing.

Example 3 Example 4 I A 68/76 unfinished cotton voile fabric was treated for 20 seconds with a solution of 20 g. of acetamide in 100 g. 96% sulfuric acid. The fabric was then removed, drained-for a few seconds, washed with water, dilute ammonium hydroxide and water, and dried by ironing. A transparent organdy finish was obtained. This finish Example 5 A 68/76 unfinished cotton voile fabric was immersed for 20 seconds in a solution made by adding 20 g. oxamide to 100 g. 96% sulfuric acid. The oxamide was only partially soluble in the acid. The fabric acquired a permanent transparent organdy finish but was slightly tendered;

Example 6 A 68/76 unfinished cotton voile fabric was treated for 20 seconds-with a solution of 20 g.

acetanilide in 100 g. 96% sulfuric acid. An

. opaque organdy finish was obtained and the fabric was only very slightly tendered by the treatment.

Example 7 A 68/76 unfinished cotton voile fabric was treated for 30 seconds in a solution of 25 g. of diethyl ether in 100 g. of 96% sulfuric acid. After the fabric was washed and dried it possessed a transparentorgandy finish which was permanent to washing.

Exampletl An unfinished cotton voile fabric was treated for 10 seconds with a solution of 25 g. of ethyl alcohol in 100 g. 96% sulfuric acid, then washed in water, dilute ammonium hydroxide and water, and dried. A transparent organdy finish was obtained which was permanent to washing.

Example 9 An unfinished cotton voile fabric was treated for 20 seconds in a solution of 25 g. of acetone in 100 g. 96% sulfuric acid, washed and dried. A permanent organdy finish was obtained.

Example 16 An unfinished cotton voile fabric was treated for 10 seconds with a solution containing 20 g. of guanidine carbonate in 100 g; 96% sulfuric acid. A pleasing permanent organdy finish was obtained.

Example 11 An unfinished cotton voile fabric was treated for 10 seconds with a solution containing 25 g. of phenyl hydrazine in 100 g. 96% sulfuric acid. A permanent organdy finish was obtained. The fabric was slightly discolored.

Example 12 A 68/76 unfinished cotton voile fabric was treated for 10 seconds ina solution of 20 g. of urea and 5 g. of diethyl ether in 100 g. of 96% sulfuric acid. After the fabric was washed and dried, it possessed a transparent organdy finish The tensile strength of the fabric was slightly greater than that of a fabric treated in a solution containing only urea and sulfuric acid.

Example 13 A 68/76 unfinished cotton voile fabric was treated for 20 seconds with a solution of 5 g. urea and 20 g. diethyl ether in 100 g. 96% sulfuric acid. The acid was washed out with water and dilute ammonium hydroxide and the fabric dried by ironing. An opaque organdy finish was obtained, the treated fabric being stiff and springy but no more transparent than the untreated fabric.

Example 14 A 68/76 unfinished cotton voilefabric was treated for 10 seconds with a. solution of 20 g. urea and 5 g.-ethyl alcohol in 100 g. 96% sulfuric acid. The fabric was washed free of acid anddried by ironing. A transparent organdy finish of good tensile strength was obtained.

Example 15 -A 68/76 unfinished cotton voile fabric was treated for 20 seconds with a solution containing 5 g. of urea and 20 g. of ethyl alcohol in 100 g.

96% sulfuric acid. A transparent organdy finish of high tensile strength was obtained.

Example 16 A 68/76 unfinished cotton voile fabric was treated for 20 seconds with a solutioncontaining 25 g. of urea and 10 g. of water in 100 g. 96%

sulphuric acid. After washing free of acid and ironing, a very stiff, transparent finish was obtained.

- Example 17 tained in Example 16. The fabric was not appreciably tendered.

v Example 18 A 68/76 unfinished cotton voile fabric was treated for 10 seconds in a solution containing 25 g. of urea and 100 g. of 100 per cent sulfuric acid. The fabric was-washed free of acid and dried by ironing. A permanent transparent organdy finish was obtained.

Example 19 A viscose rayon crepe fabric was treated for 10 seconds with a solution containing 25 g. of urea in 100 g. 96% sulfuric acid. The fabric was then washed free of acid and dried by ironing. The fabric was stiffer and more transparent than the original fabric and was only very slightly tendered.

This process can be applied to cotton, linen, viscose rayon or other regenerated cellulose fabrics, threads or fibers. Although the chief purpose of the invention is to produce organdy finishes on cotton voile fabrics, permanent starched effects may be obtained on heavier fabrics. The invention is applicable to all types of cellulosic fabrics, but the results are particularly desirable with textile materials such as cotton, viscose rayon, etc. The process is also applicable, as shown in the following example, to the preparation of parchment paper.

' Example 20 An unsized'sulfite paper weighing 20 lbs. per 500 sheets measuring 25" X38" was treated for 30 seconds in a solution of 20 g. of urea dissolved in 100 g. of 96 sulfuric acid, then washed in water until free of acid. The paper was dried by ironing. As a result of this treatment the paper was parchmentized. It was denser, harder, and more transparent than the untreated paper. The treated paper has a much greater wet strength as revealed by a qualitative test in which both treated and untreated paper were wet and broken in the hand. The resistance of the wet paper to rubbing was also greatly increased by the treatment, The grease resistance of the treated and untreated paper was tested by placing the papers over white blotting paper and placing a drop of dyed turpentine on each in one test and a drop of a dyed cotton seed oil on each in a second test, and noting the time required for the oil to pass thru the paper. Both the turpentine and vegetable oil penetrated the untreated paper instantly. -The turpentine penetrated the treated paper in about one minute but the cotton seed oil had not pene-.- trated after a quarter of an hour. When written upon with ink the treated paper gave a smooth even line whereas the untreated paper gave an irregular line due to the blotting effect.

The sulfuric acid used in the parchmentizing reagent may vary from about 80 to 100% H2804 or even higher and is preferably from about 90 to 98% H2804. When the inhibitor of cellulose degradation is an amide, for example, urea, useful results may be obtained with acid concentrations as low as 65% H2304. The concentrationof the inhibitor in the acid may vary within rather wide limits depending on the inhibitor itself and on the other conditions present. Under some conditions ratios as low as 5 parts inhibitor to 100 parts acid may be useful and ratios as high as 35 parts per 100 of acid may also be used provided the inhibitor is sufficiently soluble in the acid. The process is most desirably operated at normal temperature but the temperature may be varied somewhat above or below this point as desired.

In view of the number of variable factors, it is impossible to set forth in a patent application every possible combination of conditions which may be successfully operated. Given the requirement that a given quality of finish is to be produced on a given fabric using a given inhibitor of degradation, it is essential that the variables be adjusted so as to coordinate the reaction rate and the time of treatment so that a finish is obtained having the required properties. The various factors affecting speed of reaction are temperature, concentration of acid, and the concentration of the inhibitor in the acid. The reaction rate may be increased by increasing the temperature, or by varying the concentration of the acid, or by decreasing'the concentration of the inhibitor in the acid. In general the speed of the parchmentizing reaction is increased as the concentration of the acid approaches the point of maximum activity which isabout 92%. Since the process is in general operated continuously, it is obvious that the time of contact may be adjusted by varying the speed of travel or by varying the length of travel in the parchmentizing bath.

When the situation is such that the time of contact may be varied at will, the inhibitor to be used, for example, urea, is dissolved in the acid, the concentration of the acid and of the inhibitor in the acid being maintained at any desired point within the limits which have been set and within the limit of solubility of the inhibitor in the acid, the parchmentizing bath is brought to the temperature at which it is desired to operate, preferably around normal, and the fabric is passed continuously through this acid bath, the speed of travel being adjusted so that the degree of parchmentizing is satisfactory and that the reagent is washed out of the fabric before the fabric is tendered to an objectionable degree. If desired, the optimum time of contact in the parchmentizing bath'may be readily determined merely by immersing a small sample of the fabric in the parchmentizing reagent and varying the time of immersion until the required effect is produced the reagent and drying.

In the case where the time of treatment is limited, it may be necessary to adjust the speed of after washing out reaction between the cellulose and the reagent so that the reaction is completed within the time limit. For example, when it is desired to complete rate so as to permita longer time of contact, this may be brought about by decreasing temperature or by varying the concentration of the acid or of the concentration of the inhibitor in the acid.

The process is not limited to any particular type of apparatus. The nature of the reagents will necessitate apparatus which is not corroded by concentrated sulfuric acid. With proper precautions, iron apparatus may be satisfactory. The treatment of the fabric may consist in passing it through the acid solution containing the inhibitor at such a rate that it will be thoroughly wet out by the acid, through squeeze rolls to remove excess acid, then into water at room temperature or below. It is essential that the water treatment should be such that the acid is diluted very rapidly. This will avoid having local areas become hot enough to cause tendering of the fabric. Subsequently, the fabric should be washed entirely free of acid using dilute alkali baths if desired, and then dried, either on a tenter frame or on hot rolls or calenders. The fabric may be given any other treatment desired for any particular finish. Thus, it may be tenter sheared to break down the bond at the intersection of warp and filling yarns, thereby preventing the finished organdy from having a boardy feel. For the most part the treatment in accordance with the present invention may be carried out in ordinary textile plant equipment.

The fabric may be treated over its entire surface or only on certain areas, so as to give pattern effects. For this treatment, the acid containing the inhibitor could be printed on by ordinary printing methods, using corrosion-resistant printing rolls. The treatment may be carried out by protecting certain areas with unreactive materials, such as paraffin, and then treating the entire fabric. In this way, the protected areas are not ailected, and a pattern effect may also be obtained.

The process of the present invention has been illustrated with the use of amides which are the preferred class of inhibitors or negative catalysts of the present invention. In addtiion, the use of ethers, alcohols, ketones, amines and mixtures of ethers and amides have been exemplified. As explained earlier in this specification, suitable inhibitors are soluble in 96% H2804 and may be known by the fact that they react positively in the tendering resistance test. Those inhibitors which are of low molecular weight are particularly desirable. Thus urea, thiourea, formamide and ethanol-formamide are excellent inhibitors. Acetamide and acetanilide are effective but not to the extent of those just mentioned. Oxamide and decamethylene-diamine formamide may be used, as well as the amides of formic acid with I forked chain amines wherein the alkyl group ofthe amines contains at least six carbon atoms and a forked chain.

for example, at 85% and above thatthe advan- These low molecular weight amido compounds are defined bythe formula wherein R may be hydrogen, an amido (NHa) group or an alkyl group, R and R are hydrogen or hydrocarbon radicals and X may be oxygen, sulfur or an imino group. These compounds are particularly effective 'when the compound contains 10% or more of nitrogen. In addition to those already mentioned ,guanidine, diphenylguanidine, urea-formaldehyde resins and aminoguanidine bicarbonate are effective as inhibitors to varying extents.

In addition to the amido compounds,above discussed, which form perhaps the most pre ferred class of inhibitors, amino compounds, e. g. decamethylene diamine, hexamethylene diamine, ethylene diamine, hexamethylene tetramine, 1, 3-diaminopropanol-2, dibutylamine, and triethanolamine are effective as modifiers for concentrated sulfuric acid, i. e. sulfuric acid of at least 80% concentration.

Low molecular weight alcohols soluble in con.- centrated sulfuric acid have also been found to be effective inhibitors for use with sulfuric acid of at least 80% concentration, including glycerol, methanol, ethanol, butanol, ethylene glycol, isopropanol and 1, 3-diaminopropanol-2.

Similarly, ethers such as diethyl ether and diethylene glycol have been found useful in inhibiting the tendering of cellulosic materials by sulfuric acid.

Acetone, methyl ethyl ketone and dipropyl ketone are effective in the order given, acetone being the preferred ketone.

In general the inhibitory effect decreases with increased molecular weight in a given series. The low molecular weight amides are more effective and are also more soluble, particularly the amides and amido derivatives of monocarboxylic acids.

Materials which give viscous solutions are less desirable than those which give limpid solutions, presumably because of the difference of ease of washing off the acid and also because of the slow wetting of the fabrics by these solutions.

While acids of concentration of approximately 80% and higher show the advantages of the use of amido derivatives in the most noteworthy manner, the use of amides is also advantageous with acids heretofore used as parchmentizing acids, for example, acids as low as 65% H2804 as shown in the following example. At the other end of the concentration range, acids of 100% strength and over, for example, 103% (thus containing free S03) may be employed withgood results.

Example 21 A 68/76 unfinished cotton voile fabric was' treated for 20 seconds in a solution of 40 gms. urea in 800 gms. of 70% sulfuric acid. The fabric was then washed and dried by ironing. This treatment resulted in a. stiff springy finished but slightly harsh for an organdy.

Example 22 5. Cloth treated with 96% sulfuric acid tages of this invention are most striking. This is all the more surprising since materials such as formaldehyde which have hithertofore been recommended for use with acids of moderate concentration are ineffective with the concentrated acid.

Voil fabrics were treated for 20 seconds each in acids of the following compositions and tensile strengths determined with the results noted. The tensile strength shown is the force in pounds necessary to break a one inch strip of the cloth.

Pounds 1. Untreated cloth 7.5 2. Cloth treated with solution of 20 gms. urea in 100 gms. 96% sulfuric acid 3. Cloth treated with solution of 20 gms.

urea in 110 gms. of 87% sulfuric acid 9.3 4. Cloth treated with solution of 30 gms.

urea in 105 gms. of 91% sulfuric acid 10.2 0.0

'ihis amount of urea was not completely soluble in the acid at. room temperature and so was not all in solution.

In addition to use in the treatment of fabrics, solutions of these inhibitors in sulfuric acid may be used for parchmentizing paper and treating regenerated cellulosic films, and as regeneration baths inthe spinning of viscose yarn, or for subsequent treatment of viscose yarn, for example, to secure higher tenacity.

The parchmentized effects obtained by the present invention are not necessarily superior to the effects obtained by prior art methods but these effects can be obtained more consistently and with less spoilage of goods than is obtained by prior art processes. Thus in one of the rec ognized prior art processes for producing organdy finishes, there is first a mercerization in 20--25 per cent sodium hydroxide, followed by a treatment at a low temperature and at an inconveniently high speed, with sulfuric acid of about 66% concentration. The high speed is necessary to avoid ruining the fabric. Following the acid treatment the cloth is given another mercerization. On-the other hand the process of this invention involves in its simplest form only a single acid treatment carried out at room temperature, in order to produce a satisfactory organdy finish. Furthermore the process of the present invention allows of a very great variation in the effects obtained, since the various factors such as time and temperature of treatment, and agents used can be varied at will over rather wide limits according to the effects desired.

The above description and examples are intended to be illustrative only. Only modification of or variation therefrom which conforms to the spirit of the invention is intended to be included within the scope of. the claims.

I claim: i

1. Process which comprises immersing a cotton fabric at 20 C. for 30 seconds in a solution of 20 g. urea in 100 g. of 96% sulfuric acid, removing from said solution, washing with water and then with 3% ammonia solution and drying by ironing.

2. Process which comprises treating cotton fabric with sulfuric acid of at least 85% concentration containing 5-35 parts by weight of urea per 100 parts of H2804.

3. Process which comprises treating cotton fabric with concentrated sulfuric acid of at least 65% strength containing urea.

4. Process which comprises treating cellulosic textile materials with sulfuric acid of at least 65% strength containing urea.

5. Process which comprises treating cellulosic textile materials with sulfuric acid of at least mula ,1

wherein R, R and R are hydrogen or organic radicals containing up to six carbon atoms, the

nitrogen content of said- 10%.

8. Process which comprises treating a cellulosic fabric with a parchmentizing reagent until a still, springy, at least partly transparentized flnish is obtained, thereupon discontinuing the treatment, and promptly washing out the reagent said parchmentizing reagent comprising sulfuric acid of at least 80% concentration having dissolved therein per 100 parts acid from 5-35 parts of a cellulose degradation inhibitor; said inhibitor comprising a low molecular weight amide which is soluble in 96% sulfuric acid at C. to the amount of at least 20 parts per 1000f acid and which is further characterized by the fact that it reacts positively in the tendering resistance test,

amide being at least said test comprising, the step of dissolving 20' parts inhibitor in 100 parts 96% sulfuric acid,

bringing the solution to 20 0., immersing therein a sample of cotton voile for a period of 30 seconds, thereupon removing the sample from the bath, and promptly washing out the acid and drying, a positive test being indicated by the fact 7 that the sample is found to be parchmentized and to have lost at least partly not more than of its original tensile strength.

9. As a treating agent for cellulosic materials,

a concentrated sulfuric acid solution of urea.

10. As a treating agent for cellulosic materials, a solution, in sulfuric acid of at least 65% concentration, of urea.

11. As a treating agent for cellulosic materials a solution, in sulfuric acid of at least 85% con-,

centration, of an amido compound of the formula R-cx-N textile materials with least 65% wherein R is hydrogen, an amino group or an alkyl group, R and R are hydrogen or hydrocarbon radicals and X is oxygen sulfur or an imino group.

12. Process which comprises treating a cellu-- textile materials with sulfuric acid of at least 65% concentration containing thiourea in solution therein.

14. Process which comprises treating cellulosic textile materials with sulfuric acid of at least 65% concentration containing in solution therein 5-35 parts of thiourea per 100 parts of concentrated,

sulfuric acid.

15. Process which comprises treating cellulosic sulfuric acid of at least 65% concentration containing foramide in solution therein. 16. Process which comprises treating cellulosic textile materials with sulfuric acid of at least 65% concentration containing in solution therein 5-35, parts of foramide per 100 parts of concentrated sulfuric acid.

17. Process which comprises treating cellulosic textile materials with sulfuric acid of at least 65% concentration containing therein as a cellulose degradation inhibitor a low molecular Weight amide soluble in 96% sulfuric acid at 20 C. to the extent of at least 20 parts per 100 parts of acid and having its amido group attached to a carbon atom doubly bonded to a non-metallic member of the sixth group of the periodic table having a molecular weight between 16 and 32.

18. Process for producing an organdy effect which comprises treating a thin cellulosic fabric with sulfuric acid of at least 65% concentration containing dissolved therein a low molecular weight amide.

19. Process for producing an organdy effect which comprises treating a thin cotton textile material with sulfuric acid of at least 85% concentration containing in solution therein 5-35 parts by weight of urea per 100 parts of concentrated sulfuric acid.

20. Process for producing an organdy effect which comprises treating a thin cotton textile material with concentrated sulfuric acid of at strength containing urea.

JOSEPH HARREL SHIPP.

CERTIFICATE OF CORRECTION Patent No. 2,17u,5 5u. October 19 9.

JOSEPH BARREL SHIPP.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 65, for the word "finished" readfinish; page 6, second column, lines 28 and 55, claims 15 and 16 respectively, for "foramide" read fonnamide; and that the said Letters Patent should be read with this correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this 12th day of March, A. D. 19h0.

. Henry Van Arsdale, (Seal) Acting Commissioner of Patents.