US 2548774 A
Description (OCR text may contain errors)
Patented Apr. 10, 1951 UNITED STATES No Drawing. Application July 6, 1949,
Serial No. 103,320
- 4 Claims. 101. 8-128) The invention relates to an improved method of shrink-proofing wool, and to the improved product of such treatment.
Heretorore, the only economical methods for shrink-proofing wool by controlled damage processes have involved the use of chlorine or other halogen in various ways. While good shrinkage control will be the result if the method is carefully regulated as to pH, concentration, time of treatment, etc., there are certain disadvantages in its use that have not been overcome.
First, the chlorine or other halogen is disagreeable to handle and is injurious to the health or" the workmen; secondly, it is highly corrosive; thirdly, there are side reactions taking piece in its use that damage the wool and yet do not aid shrink-proofing, and which involve the formation of chloramines: fourth, the problem of tailing is a big one because of the high reactivity of the chlorine with wool; Uh, chlorine treatment is somewhat expensive; and lastly, uniform penetration of the chlorine or chlorinating agent cannot be expected because the halogen has such a strong amnity for W001 that complete exhaustion of the bath occurs rapidly.
The actual shrink-proofing of wool with chlorine or other halogen according to one theory is not caused by a direct union of halogen with the wool molecule, but because the halogen is a very strong oxidizing agent the cystine linkages of the wool molecule are oxidized'and broken, which changes the expanding, contracting and frictional characteristics of the fiber.
-It is known that dilute solutions of potassium permanganate KMnO4) will reduce only slightly the felting characteristics of wool and as early as 1907 it was proposed by Kammerer to treat wool with permanganic acid, which is a much stronger oxidizing agent than KMnOr, and effect shrink-proofing. This method and any method involving the use of the permanganate ion at or below 100 C. does not produce a wool possessing satisfactory characteristics. The reasons for this are that the reactions are mainly only surface reactions and do not penetrate to any considerable extent within the fiber. Any real penetration can only be achieved at this or lower temperatures by sacrificing the natural feel or handle of the wool. An objectionable scroop results and the fiber is stifi and useless. Further, different grades of wool display different degrees of shrinkproofing because of variations in the thickness of the varnish-like covering on the cuticle as revealed by the electron microscope.
It is an object of the present invention to im- FATENT UFFICE.
prove the method of shrink-proofing wool by subjecting'the wool to a treatment that can be controlled easily and that produces a wool which retains its natural feel and strength without appreciable loss of weight.
Further, it is an object of this invention to produce a more level dyeing wool. I have discovered that speedy penetration of the wool fiber by a solution of potassium permanganate or other suitable oxidizing agent can be effected by subjecting wool to superatmospheric temperatures and pressures in an autoclave in very dilute solutions of KMnOr, with or without the aid of buffers, as for instance MgSOa.
The wool under pressure is rapidly hydrolyzed at the cystine linkage as follows:
Molecular structure of wool H "H hydrogen bond l\ r C311 /CHH side chain C3 C O NH N CR CHR C O C Ne NH /OHR O O 0 H3i\' RHC\ salt linkage 03 C O NH N Cystine linkage hydrolysis R-S-S-R, R-SH HOS-R1 H25 produced acts as a reducing agent and also splits the cystine linkage s ms R-S-S-Rz RSH HSR As KMnO4 is also present, the H28 is oxidized ZHQS 30: 2501 $520 -l H3803 HZS is a very feeble acid and the H28, H280: and H2804 all react within the fiber and at the surface withKMnOr to producei permanganic acid. Permanganic acid is a powerful oxidizing compound but is only produced where KMnOr comes in contact with wool, thereby producing a smooth, non-harsh wool. No H28 is detectable on the wool after pressure treatment in this manner, which is not the case with pressure alone in the absence of oxygen or oxidizing compounds.
The hydrolyzed cystine group is oxidized as follows:
There is also a breaking of the cystine linkage by oxidation HIMDO;
CHrS-S-CH CH;SO3H HOgSCHr KMlnO4 also does this but is not as predominant as the I-IMnO; at the fiber surface and within the fiber KMnO;
A permanent set is also imparted to the wool fiber by heat and as follows:
The hydrolyzed cystine groups are joined by oxidation oxidation n-sn rasn R-S-Rr Also at elevated temperatures the disulfide bonds of keratin are disrupted. The thiosulfonic acids thus formed react with free amino groups in the keratin to build R-SNH-R' linkages, thus imparting a permanent set to the wool.
Condensation between an amino group of a basic side chain and an -SI-I group formed by hydrolysis of S--S- linkages also occurs.
The hydrolysis of --S-S yields the -SOH going to H2S+--CI-IO, condensation of CI-IO with NI-lz yields NI-l--CI-I.
All the above phenomena are accompanied by a disarrangement of the surface layers, of the cuticle and under the cuticle and a reduction in the differential friction effect, rendering the fiber resistant to felting.
The increased luster and strength is due to the fact that the scaly covering fuses into a more compact and regular surface. The resulting wool has no loss in strength and has a soft and desirable feel.
Further, the method bleaches the wool and gives a product of superior and more level dyeing characteristics. In other words, the method combines the usual bleaching treatment with a shrink-proofing treatment.
After the pressure treatment, the brown manganese hydrate is removed with NaHSOa followed by NazCO; and washing.
Advantages of the process are as follows:
1. It is not injurious to health of operators as are the halogens and H202.
2. The process does not require large concentrations of chemicals.
3. The process can be performed in a short time.
4. The process results in very even treatment by penetrating the fiber.
5. It is not necessary to control the pH because the process is carried out under essentially neutral conditio s.
6. It is no 5* to over treat.
'7. One ca .ach as well as shrink-proof.
8. The product is soft and lofty handle.
9. The process is very economical.
10. Excess acids produced are neutralized by KOH present from. KMnO4.
4' of the manner in which the treatment may be carried into efiect:
Example 1 Virgin wool 60-64s grade yarn was treated with a solution of 250 mg. KMnoi to two liters of water (.0l25%) in an autoclave at 15 lbs. superatmospheric pressure for five minutes. This was followed by a treatment with a dilute solution of NaHSOa to remove manganese hydrate and then to a dilute solution of NazCOs. The treated wool was completely shrink-proofed. Untreated wool shrank 25%.
Example 2 Virgin wool yarn s grade was treated with a solution of 100 mg. KMnO4 in two liters of water (.005%) in an autoclave at 15 lbs. superatmospheric pressure for five minutes. This wool was completely shrink-proofed. Untreated wool shrank 40%.
Example 3 70s grade yarn was treated with a solution of 250 mg. KMI104 to two liters of water (.0125%) in an autoclave at 10 lbs. superatmospheric pressure for five minutes. The wool was completely shrink-proofed. Untreated wool shrank 40%.
Example 4 70s grade yarn was treated with a solution of 250 mg. KMnOr to two liters of water (.0125%) in an autoclave at 5 lbs. superatmospheric pressure for five minutes. The wool shrank about 4% because of the lower pressure used but still was fairly well shrink-proofed. Seven minutes at 5 lbs. produced a completely shrink-proofed wool. Untreated wool shrank 40%.
Example 5 Woolen socks 60s-64s grade was treated in .05% KMI104 solution for ten minutes at 15 lbs superatmospheric pressure in an autoclave. This Was followed by treatment with a dilute 5% solution of NaI-ISO: and then with NazCOa to neutralize the acidity and the treated goods were then washed thoroughly. Untreated socks shrank 30% after thirty launderings, and treated socks exhibited no felting shrinkage. This was a strong anti-shrinking treatment.
The yarns treated in the above examples were dried and cut into four inch lengths and the tips cemented with cellulose acetate and shaken in a .5% Na2COa.lO H2O solution for fifteen minutes. The shaker made 2'76 completed (back and forth) strokes per minute. In shrink-proofing enough KMnO4 should ordinarily be used so that the bath has a permanganate color at the end of treatment. This insures an oxidation reaction throughout.
In shrink-proofing wool it is sometimes desirpressure may be used. Larger concentrations may be desirable where considerable bleach is The following specific examples are illustrative also desired. However, I prefer lower concentrations of KMnOi with the lower limit in the neighborhood of 001% and the upper limit to be determined by the damage done to the wool. This upper limit may be around 0.1% except for short times of treatment.
A combination of unshrinkable wool with untreated fibers of all types permits the production of two-tone effects as well as novelty or blister effects and difierently dyed fabrics.
While in the above description potassium permanganate has been referred to as the preferred oxidizing agent, other oxidizing agents may be substituted for the permanganate either in whole or in part, without departing from the spirit of the invention considered in its broadest aspects, although, as previously set forth, potassium permanganate is preferred. Where other oxidizing agents are employed the quantity employed should be such as to be the equivalent of the proportion of permanganate herein set forth.
In some instances it has been found desirable to give the wool a preliminary treatment with an oxidizing agent other than KMnO4, such as an alkaline or acid permanganate, oxygen, ozone, hydrogen-peroxide, organic peroxides, halogenated organic compounds, KzCIzOl, and the like, with or without catalysts, followed by a treatment with potassium permanganate. These and other oxidizing agents used either singly or in combination may be used in addition to or in place of the permanganate in the main treating step.
1. A process of shrink-proofing wool which comprises treating the wool for a short period of time in a closed chamber under superatmospheric range of 5 to 15 pounds per square inch.
MAYNE R. COE, JR.
REFERENCES CITED The following references are of record in the file of this patent:
FOREIGN PATENTS 25 Number Country Date 5,612 Great Britain 1907 569,730 Great Britain June 6, 1945 586,020 Great Britain Mar. 4, 1947 603,379 Great Britain June 15, 1948 OTHER REFERENCES Frolich: Wollkunde Technologie Der Textilfasern, Bd. VIII, Teil 1, J. Springer, Berlin, 1929, pages 314-323. (Book in Dept. Agric. Library.)