ENZYME DESIZING EFFICIENCY QUANTITATIVE EVALUATION WALTER &I. SCOTT Gustavus J. Esselen, Inc., Boston, Mass.
KZYMES have been used
proposed by Lintner (6) in 1886 The desizing efficiencies of commercial and modified by Harada (4) in for many years to assist malt enzymes, animal enzymes, and bac1931. in the removal of starch terial enzymes are compared by two newly IODOMETRIC METHOD.This sizing from cotton fabrics prior developed laboratory methods which can method determines the amount to bleaching, dyeing, or finishbe correlated with the desizing procedures of enzyme required to complete ing, and similarly to remove the digestion of a standard starch starch f i n i s h e s f r o m c o t t o n used by most textile mills. The immersion paste within a definite time to a fabrics which have to be redyed method corresponds to the treatment point where there is no blue or refinished. I n the past, the which cotton fabrics would receive in jigs coloration with iodine. It was action of the enzymes upon the or overhead-reel barks, and the padding discussed by Sherman and his starch sizing has been considered method corresponds as closely as possible co-workers in 1910 (8) and again principally from the mill point in 1913 (Q),and later referred to of view, and little attempt has to the padding practice which is most comby Haller ( 3 ) . been made to obtain accurate monly used for desizing purposes. The VISCOSITY METHOD. This data in the laboratory which accuracy of each method is demonstrated method measures the reduction could be correlated with mill by data obtained as a result of numerous in viscosity of a standard starch practice. experiments. paste due to the liquefaction On the other hand, the studies produced by a given amount described in this paper were of enzyme within a definite time under co&-olled condiundertaken for the purpose of comparing the different types tions of pH and temperature. It was developed by Davidof enzymes by laboratory techniques which are susceptible of son (2) in 1925 and later applied by J6zsa and Gore (6) and reasonable accuracy and control and a t the same time sufPowers (7). ficiently allied with the common plant operations so that the None of the above methods appeared to be capable of results can be correlated with actual mill practice. The types satisfactory correlation with the ability of the various types of of enzymes which are suitable for desizing cotton textiles are enzymes t o solubilize starch on cotton textiles and thereby briefly described. promote its removal. It seemed most suitable to rate desizing Types of Enzymes efficiency upon the actual performance in removing the size from the fabric, and this is the principle upon which the Malt enzymes (or malt diastases) were one of the first types methods now under discussion were based. of enzymes to be used in any quantity for the removal of The desizing efficiencies of commercial enzyme products starch sizing from cotton textiles. I n fact, in the early days can be compared in the laboratory by either of two methodsthe mill men often called the operation of desizing "malting", an "immersion" method and a "padding" method. Both are and some still cling to this terminology. The malt enzymes designed to determine the actual amounts of sizing removed are obtained by extraction from freshly germinated malt. from a cotton fabric by the enzyme treatment. They act upon starch most efficiently within a pH range of 5.0 to 6.5 and a temperature range of 60" to 65" C. Immersion Method Animal enzymes are prepared from the pancreatic glands The immersion method corresponds t o the treatment which of animals. Their maximum activity is attained within a cotton fabrics would receive in jigs or overhead-reel barks p H range of 7.0 to 7 . 5 and a temperature range of 50" t o 55" C. in a mill but is shortened for quick laboratory testing. Strips Bacterial enzymes are produced by growing pure cultures of a standard warp-sized fabric are immersed for 5 minutes a t of certain microorganisms in sterilized wort. Their maximum a given temperature in 0.1 per cent solutions of the enzymes activity takes place within a pH range of 7.0 to 7.5 and a temt o be compared and rinsed by a prescribed procedure, and the perature range of 65" to 75" loss in weight due to the removal of sizing is determined. Fungus or mold enzymes are prepared by inoculating The standard fabric is preferably a good grade of warpcereal media with a pure culture of a fungus and extracting sized cotton sheeting which has not been processed in any the enzymes. Their optimum p H is about 5.5 and their opmay after weaving. The sizing is generally uniformly distimum temperature about 55" C. They are not so commonly tributed throughout this type of fabric, but check deterused in the textile industry as the other three types mentioned minations of total sizing content should be made from time above and were therefore not included in our studies. to time. The strips are cut across the width of the fabric Evaluation of Desizing Efficiency in order to average any inequalities of sizing on the individual warp threads. The following methods were previously suggested in the The concentration of the enzyme solution is set a t 0.1 per literature for the quantitative estimation of enzyme activity: cent for the ordinary types of commercial enzymes. At REDUCINGSUGARMETHOD. This method evaluates the this concentration the enzymes removed sufficient sizing diastatic power of an enzyme on the basis of the amount of during the 5-minute treatment to give a good comparison. reducing sugar formed by its action on a standard starch At higher concentrations there was such a high removal of solution under definitely prescribed conditions. It was first
E
c.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
sizing in all cases that minor differences between the strengths of competing enzymes could not easily be detected. I n general, the mills calculate percentage of enzyme on the basis of cloth rather than solution. I n this laboratory method, with the ratio of solution to cloth a t 20 to 1, the strength of enzyme mould be 2 per cent calculated on the weight of the cloth. The procedure is as follows: 1. Two lO-gram samples of the cloth are taken for each enzyme t o be tested, and two additional samples are required for the moisture determination. The samples are placed in glass-stoppered weighing bottles and accurately weighed. 2. Moisture is determined in two of the samples by drying them to constant weight a t 100-105" C. Each of the other samples is placed in a Soxhlet extractor and extracted for 2 hours with chloroform. The tared flasks containing the solvent are heated in a boiling water bath during this extraction. The solvent is evaporated from the grease in the extraction flasks, and the flasks are dried to constant weight at 100-105' C. 3. The oil-free sample is allowed to stand in the air overnight or until all the chloroform has evaporated. It is then immersed in a 0.1 per cent solution of the enzyme, the weight of which is equal to twenty times the weight of the sample. The enzyme solution is conveniently contained in a 400-cc. beaker. 4. The enzyme solution is held at 60" C. for malt enzymes, 54' C. for animal enzymes and 66" C. for bacterial enzymes. B variation of not more than 1" C. is allowable. If the beakers containing the enzyme solution are heated in a constant-temperature water bath, it is advisable t o preheat the samples to the specified temperature before entering them in the solution. A still more satisfactory method is to keep both the beakers and the cloth in a thermostatically controlled electric oven during the treatment. 5. After the sample is placed in the enzyme solution, it is squeezed by hand three times to ensure thorough wetting and then kept in the enzyme solution for exactly 5 minutes from its l k t immersion. (The use of a stop watch is recommended.) The enzyme solution containing the sample is immediately poured through a fine-mesh screen (100 mesh is suitable). 6. The sample strip is opened up and run through approximately 2 liters of tap water a t 45-50' C. in a 4-liter beaker or other convenient receptacle containing a horizontal rod near the bottom under which the cloth must pass. (If the tap water contains over 10 parts per million of hardness, distilled water or water softened to the desired degree should be substituted.) After passage through the rinse water, the cloth is run between squeeze rolls (suitably in an ordinary hand wringer) whose tension is adjusted to leave about 100 per cent of water in the fabric. The rinse water is poured through the screen to collect any loose fibers. The sample is given a second and a third pass through fresh water at 45-50' C. and through squeeze rolls as described above.
785
After the third rinse and squeeze, the sample, together with any loose fibers which may have been retained on the screen or on the squeeze rolls, is placed in a weighing bottle and dried to a constant weight at 100-105" C. After removal of moisture and grease, the original weight of the sample is calculated, and the loss in weight due to the enzyme treatment is determined. The percentage of sizing removed by the enzyme treatment is calculated on the basis of the dry weight of the sample. The various enzymes are evaluated in terms of the percentage of the total sizing which they remove in this treatment. Total sizing is determined by the official method of the American Association of Textile Chemists and Colorists ( 1 ) : The sample is dried to a constant weight a t 100-105° C., then extracted with chloroform for 2 hours in a Soxhlet extractor as described above. The oil-free sample is allowed to stand in the air until all the chloroform has evaporated and is then digested for 1 hour in a 3 per cent solution of Exsize or similar enzyme at about 60" C. After the enzyme treatment the sam le is rinsed in warm water, then immersed in boiling distilleg water for 1 hour. The sample is then rinsed in warm water, squeezed as dry as possible, placed in a weighing bottle, and dried to constant weight at 100-105° C. The original dry weight of the sample minus the grease is determined, and the loss in weight due to the enzyme treatment is then calculated. The loss in weight divided by the original weight and multiplied by 100 gives the percentage - of total sizing.The rinses after the enzyme and the boiling water treatments should be performed as described above. TABLE I. DESIZING EFFICIENCIES OF ENZYMES Type of Enzyme Malt Animal Bacterial Malt .4nimal Bacterial
Temp., O
C.
55 55 55 60 54 66
----70
Test 1 4.63 4.50 3.94 5.48 5.40 5.38
Sizing RemovedTest 2 Av. 4.57 4.10 4.02 5.40 5.28 5.58
4.60 4.30 3.98 5.44 5.34 5.48
Desizing Rating 81 76
70
83 81 83
Table I shows the desizing efficiencies of commercial types of malt enzymes, animal enzymes, and bacterial enzymes, as obtained in two series of tests; one run is carried out a t the common temperature of 55" C. and the other at the temperatures for each type of enzyme as specified above. The first series was run on a standard warp-sized sheeting with a total sizing content of 5.65 per cent. The second series was run on a standard warp-sized sheeting with a total sizing content of 6.58 per cent. The desizing ratings indicate the proportion of the total sizing removed by the enzyme treatment. Fresh samples of commercial enzyme products were used in all of the tests. The p H of the malt enzyme solution was about 6.0, and the p H of the animal and bacterial enzyme solutions was about 7.0.
FIRE-BOXOPES-WIDTHWASHER USEDFOR WASHING ENZYME-IMPREGNATED FABRIC C o u r t e s y , H . W . Butterworth & Sons Company
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The agreements shown between the duplicate tests in Table
I are typical of those obtained in several hundred determinations by this method and are indicative of the accuracy which can be attained. It is believed that this accuracy is well within the limits required for a satisfactory evaluation of desizing efficiency consistent with the commercial desizing procedures in the mills. The desizing efficiencies of the three types of enzymes at their optimum temperatures are sufficiently close so that their money value for desizing purposes would be practically the same as their price per pound.
Table I1 shows a comparison between a commercial bacterial enzyme and a commercial malt enzyme on cotton jeans by the simplified procedure described in paragraph 8. The enzyme products were used in '/3 per cent strength, and the impregnated strips of fabric were allowed t o stand for 2 hours before rinsing. The result of a plant run under comparable conditions is also shown in Table 11.
TABLE
11. DESIZING WITH ENZYMES BY THE P A D D I N G METHOD
Padding Method The padding method corresponds as closely as possible t o common practice in cotton mills. Strips of fabric are passed in open width through the enzyme solution and then through squeeze rolls which leave about 100 per cent by weight of the solution in the cloth. The enzyme-impregnated fabrics are allowed to stand for varying periods in a closed container and are then rinsed by three passes through fresh warm water, with a squeeze through rolls after each pass. The procedure is as follows:
1. A good grade of bleached cotton sheeting, 72 inches (183 em.) in width, should be used. It should be sufficiently free from extractable material so that, in the determination of total sizing by the A. A. T. C. C. method (paragraph 9 of the immersion-method procedure), loss of less than 0.1 per cent is obtained. The samples are preferably in the form of 6-inch (15.2-cm.) strips cut across the width of the fabric. They are conditioned for at least 16 hours in an atmosphere containing 65 per cent relative humidity at 21' C. and then weighed accurately to 0.01 gram. 2. A solution containing 4 per cent by weight of starch, either potato or tapioca, is prepared by first making a cold slurry of the starch and water, then heating to a boil, and boiling for 15 minutes with continuous stirring. 3. The strips are run through the starch solution in a small padder with the squeeze rolls set t o leave a uniform amount of the starch solution on the fabric. The proportion of starch solution is conveniently between 100 and 150 per cent by weight of the fabric. After leaving the padder, the strips are immediately run through a vertical stack dryer containing a downward current of hot air so regulated that the fabric is practically dry when it emerges from the top of the stack. The dry strips are again conditioned and weighed as described in paragraph 1. 4. The starch-sized strips are impregnated with the enzyme solution and then passed through rubber-covered squeeze rolls set to leave 100 per cent by weight of the solution in the cloth. The strength of the enzyme solution may vary between 0.25 and 3 per cent as desired but is commonly set at 1 per cent. The temperature of the enzyme solution is maintained a t 60' C. for malt enzymes and bacterial enzymes, and 49' C. for animal enzymes. 5. The enzyme-impregnated strips are immediately folded and placed in a closed container. A series of six strips are usually used for each enzyme solution, and they are allowed to remain in the closed container at room temperature for periods of 1, 5 , 10, 15, 30, and 60 minutes, respectively. Each strip is then rinsed by three passes through fresh water at 4953" C. with a s ueeze through rolls after each pass. 6. The strips are Inally ironed dry and then conditioned and weighed as described in paragraph 1. 7. On the basis of the three weights for each strip, calculations are made of the total per cent of starch in the sized fabric and the per cent of starch removed by the enzyme treatment. Both percentages are based on the conditioned weight of the sized fabric. The per cent of starch removed is divided by total per cent in the sized fabric and multiplied by 100 to obtain the starch-removal rating for each treatment. 8. -4 sim lified procedure for warp-sized gray goods is as follows: Eix-inch strips are cut across the width of the warpsized fabric in the gray and without weighing are treated with the enzyme solutions as described in paragraphs 4 and a. The percentages of sizing in the untreated and treated specimens are determined by the A. A. T. C. C. method described in the immersion-method procedure. The per cent of sizing removed is divided by the per cent of sizing in the untreated fabric and multiplied by 100 to obtain the sizing-removal rating for each treatment.
Treatment Plant Laborarory Laboratory
Type of Enzyme Bacterial Bacterial Malt
3' % Sizing in Fabric Before 9.88 9.88 Q.88
After 2.23 2.13 2.06
Sizing Removed, % 77.4 78.5 80.2
The figures indicate good agreement between laboratory and plant desizing with the bacterial enzymes and also show a slightly higher efficiency for the malt enzymes under the same conditions. In another case the desizing efficiencies of commercial types of malt and of animal enzymes were compared by the laboratory padding method with varying periods allowed for the enzyme action. A typical warp-sized cotton sheeting was used. Strips of the fabric were padded with 1 per cent solutions of the enzymes at 55" C. and allowed to stand for 5, 10, 15, 60, or 120 minutes before rinsing by three passes through fresh water a t 45-50' C. with a squeeze through rolls after each pass.
Courtesy, H . W . Buttarworth & Sons C o m p a n y
SOLUTIONS ON A PLANT PADDER USEDFOR PADDING ENZYME FABRIC Table I11 shows the percentages of sizing remaining in the fabric after each treatment. I n this case the sizing content was determined by a slightly different procedure from the A. A. T. C. C. method. Portions of each fabric sample were immersed for 1hour in a 3 per cent enzyme solution a t 60' C., rinsed, immersed for 5 minutes a t a boil in a 0.5 per cent solution of hydrochloric acid, and rinsed again. Unsized raw cotton yarn lost about 3 per cent of its weight by this treatment so that a 3 per cent deduction was made from all the results as a correction for materials other than sizing. The figures for residual sizing shown in Table I11 have all received this correction. The original fabric contained 9.29 per cent of sizing, and the desizing ratings in the last two columns of Table I11 represent the proportion of the total sizing removed by each treatment. These results give a good picture of the comparative behavior of malt and animal enzymes under conditions which are comparable to a wide range of plant practice. I n the first
JUNE, 1940
IKDUSTRIAL AND EKGINEERING CHEMISTRY
TABLE111. DESIZINGWITH MALTAND ANIMALENZYMES BY PADDING METHOD Minutes of Treatment
-
% Residual Sizing in Fabrio I
Malt enzyme
5 10 15 60 120
3.73 2.26 2.13 0.78 0.44
Animal enzyme 2.37 2.40 2.68 2.13 1.35
Desizing Ratings
Malt enzyme 60
Animal enzyme 74 74 71 77 S5
76 77 91 95
few minutes of action the animal enzymes appeared to remove more sizing than the malt enzymes, but the latter showed a more normal increase in the removal of sizing as the time of action was increased, and the maximum removal of sizing was higher with the malt enzymes than with the animal enzymes. A weak solution of sulfuric acid is used by some mills for desizing purposes; therefore a series of comparisons was made between enzyme and acid desizing by the padding method. Strips of standard warp-sized sheeting were padded with a 1 per cent solution of sulfuric acid a t 43" C. and allowed to stand for 30 minutes before rinsing in the usual manner.
known factor of materials other than sizing which are present in the raw cotton. I t is known that the percentage of natural extractable material varies considerably with the grade of cotton, so that the use of a standard correction factor is not entirely satisfactory. Therefore the complete paddingmethod procedure described above was based upon the use of bleached cotton sheeting which was shown by tests to be practically free from extraneous material. Strips of the sheeting are weighed, padded with starch, weighed again, padded with the enzyme solutions, allowed to stand for varying periods of time, rinsed in the usual manner, and weighed again. All weighings are made under standard conditions of temperature and humidity. The desizing efficiencies are calculated as usual in terms of the proportion of the total starch sizing removed by each treatment. Table V shows some typical results obtained with 0.25, 1, and 3 per cent solutions of a commercial malt enzyme and a 1 per cent solution of a commercial animal enzyme.
O F STARCH SIZING WITH M A L T AXD ANIMAL TABLEv. REMOVAL ENZYMES BY PADDING METHOD
Type of Enzyme Malt Malt Malt .4nimal
80 0 w 5 0
60
187
Strength of --Desizing Efficiencies of Treatments, %Enzyme, % I min. 5 min. 10 min. 15 min. 30 min. 60 min. 0.25 8 ?4 30 34 42 50 1 3 1
39 68
81
.a3 78 37
63 77 48
73 78 55
74 78
56
74 75 56
I u K
40 -I
se
L20
0
I
x. 0
I I
~
0
5
IO
I5
20 MINUTES
25
I
30
35
40
FIGURE1. PROPORTIONS OF STARCHSIZINGREMOVED us. TIME ALLOWEDFOR ENZYME ACTION Other strips were padded with a 0.25 per cent solution of a commercial malt enzyme a t 60" C. and allowed to stand for 30 minutes before rinsing. A third set of strips was padded with the 0.25 per cent enzyme solution, allowed to stand for 15 minutes, rinsed, padded with the 1 per cent acid solution, allowed to stand for 15 minutes, and then rinsed again. The percentages of sizing in the fabric before and after each treatment were determined by the A. 8.T. C. C. method. Table IV shows the proportion of the original sizing removed in duplicate runs and the average removal effected by each treatment.
TABLEIV. DESIZING WITH ACID AND WITH ENZYMES BY PADDING METHOD Desizing Agent 1% sulfuric acid 0 . 2 5 4 malt enzyme 0.25?$ enzyme 1 % acid
+
---%
Test 1 24 56 61
of Sizing RemovedTest 2 Av. 26 47 65
25 52 63
The malt enzyme in 0.25 per cent strength effected the removal of nearly twice as much sizing as the acid in 1 per cent strength within the same period of time. The combination of enzyme and acid appeared to be still more effective. All of the foregoing studies were made upon the raw warpsized cotton fabrics prior to kier boiling and bleaching. I n these cases the determinations of sizing in the fabrics before and after treatment were somewhat complicated by the un-
All of the enzyme solutions in strengths greater than 0.25 per cent tended to reach a level for removal of starch after a certain time. This is emphasized in Figure 1 where the proportions of the starch sizing removed are plotted against the time allowed for the enzyme action. The 3 per cent solution of malt enzyme reached its maximum level of starch removal in 5 minutes, whereas the 1 per cent solution required 15 minutes. The 1 per cent solution of malt enzyme appeared to be considerably more efficient than the 1 per cent solution of animal enzyme. Apparently the total removal of starch is limited by the efficiency of the rinsing procedure in removing the starch which has been solubilized by the enzyme action. The rinsing procedure was the same throughout this whole series, and it is probable that 78 per cent represents the maximum proportion of completely solubilized starch which is removed by this method of rinsing.
Literature Cited (1) Am. Assoo. Textile Chem. Colorists, 1938 Year Book, p. 265. (2) Davidson, Johns Hopkins Hosp. Bull. 30,281 (1925). (3) Haller, Haokl, and Frankfurt,Melliand Testilber., 9,309 (1928). (4) Harada, IXD.EXQ.CHEM.,Anal. Ed., 3, 1 (1931). (5) J6ssa and Gore, Ibid., 2,26 (1930). (6) Lintner, J . prakt. Chem., 34, 378 (1886). (7) Powers, Am. Dyestuf Reptr., 21,332 (1932). (8) Sherman, Kendall, and Clark, J . Am. Chen. Soc., 32, 1073 (1910). (9) Sherman and Schlesinger, Ibid., 35, 1617,1784 (1913).
Correction-Separation and Fractionation of Colloidal Systems In this paper by E. A. Hauser and J. E. Lynn, which appeared in the May, 1940, issue of INDUSTRIAL AND ENQINEERING CHEMISTRY, an unfortunate error occurs in Equation 5, column 2, page
660. The first term within the brackets should be figure 2 in the denominator was omitted in print.
[y. The
