US2874021A - Dyeing of polyacrylonitrile articles - Google Patents

Description

United States Patent Or "ice DYEING OF POLYACRYLONITRILE ARTICLES Hermann Egli, Basel, Switzerland, assignor, by mesne assignments, to Saul & Co., Newark, N. J., as nominee of Fidelity Union Trust Company, executive trustee under Sandoz Trust No Drawing. Application September 20, 1954 Serial No. 457,310

Claims priority, application Switzerland December 4, 1953 16 Claims. (Cl. 8-55) According to experience, best results are obtained when the cuprous ions are formed in the dye-bath itself. For this reason, it has been proposed:

(a) To react a cupric compound with a reducing agent in the dye-bath, preferably prior to the addition of the dyestulf. Such reducing agents are for example zinc formaldehyde sulfoxylate, hydroxylammonium sulfate, glyoxal, sodium bisulfite, etc.

(b) A further method which, as hereinafter set forth in greater detail, is only of theoretical interest, consists in producing cuprous ions in an acid dye-bath by the addition of copper powder. a

As is evident from the technical literature, the method of operation described under (a) is today the generally employed method. The dyeing is carried, out in the presence of a cupric compound which is reduced with zinc formaldehyde sulfoxyl'ate, hydroxylammonium sulfate, etc. Where the dyeing is carried out by the high temperature method (dyeing at a temperature above 100 C., for example at 120 C., and at a static pressure corresponding to this temperature), sodium bisulfite can also be used as reducing agent.

However, method (a) is bound up with various defects. Thus, for example, it must be borne in mind that zinc formaldehyde sulfoxylate can attack certain dyestuffs. Another possible danger involved in the use'of this product is the instability of thecuprous ion, which is readily disproportionated to .cupric ion and metallic gcopper. This mode of procedure makes possible the production of copper spots on the textile material. This spotting of the textile material can be avoided by selecting another reducing agent. I-Iydroxylammonium sulfate presents nodifil: culty in this connection since it is capable of building with the cuprous ion a complex compound whichdoes not decompose. However the use of hydroxylammonium sulfate results in a considerable increase in the cost of the dyeing process. A further difficulty of method (a) resides in the poor controllability of the state of reduction of the copper salt in the dye-bath. Too great an addition of reducing agent to the dye-bath immediately produces too many cuprous ions, and this may result in unlevel dyeing. It has therefore been proposed in the technical liter ature to check the state of reduction of. the copper salt in the dye-bath by constantlymeasuringthe redoxlpotential. As soon as a critical value is exceeded, further reducing agent has to be added.

v The second possibility, (b), of dyeing textile material 2,874,021 Patented Feb. 17, 1959 of resinous polyacrylonitriles or resinous mixed polymers of acrylonitrile and other unsaturated compounds by adding fine copper powder to the dye-bath, acidified with formic acid, is not mentioned in any of the large number of dyeing directions described in the technical literature. This is understandable, since in practice the mechanical soiling of the textilematerial by copper dust cannot be tolerated, and the presence of copper dust in circulating baths is out of the question from the standpoint of the circulating pump.

The conversion of copper into cuprous ions is an oxidation procedure. Consequently an oxidizing agent has to be present if a dyeing which requires cuprous ions is to be produced with metallic copper. Tests have shown that pure copper, in a closed bath acidified with formic acid, produces no dyeing. This can be explained by the fact that dilute acids cannot dissolve metallic copper in the absence of oxidizing agents, because of the fact that the potential of metallic copper is 0.3 volt greater than that of hydrogen. Reports in the literature that dyeing has *been obtained with additions of copper powder are undoubtedly ascribable to the fact that copper oxides were present. However the quantity of such oxides is very small and very difficult to determine analytically, and for this reason a technically satisfactory carrying out of the dyeing process according to method (b) must encounter great difficulties.

A primary object of the present invention is to obviate these prior art defects. This object is realized, according to the invention, by producing the cuprous ions necessary for the dyeing, by introducing the system Cu/Cu++ into the dye-bath. The surprising eifect of the system Cu/Cu++ is ascribable to the resulting equilibrium:

The resultant cuprous ions thereupon participate in appropriate manner in the dyeing process and make possible the successful dyeing of polyacrylonitrile with water-soluble dyestuffs.

In one aspect thereof, the present invention is'therefore concerned with a process for dyeing articles of polyacrylonitrile or of mixed polymers of acrylonitrile and other unsaturated compounds with water-soluble organic dyestuffs by the-cuprous ion method. Briefly stated, the process consists in introducing into the dye-bath or into the circulatory path of the dye liquor, metallic copper in the form of sheets, chips, wire or netting, and carrying out the dyeing in the presence of a water-soluble cupric compound, it being possible to use, instead of the copper sheets, chips, wire and/or netting, a dyeing container which is copper surfaced or which consists partly or wholly of copper.

The new process is free of the defects inherent in the known processes. Thus no copper spots are produced on the t extile material; unlevel dyeings are also avoided,

I sincethe state of reduction'ofthe copper compound in the dye-bath is not suddenly changed. Of particular importance, however, is thefact that it is superfluous to check the state of reduction of the copper compound by continuous measurement of the redox potential. .This

significantly simplifies the process and thus involves an appreciable saving in dyeing costs.. The success'of the new process could not be foreseen ,because, even today, precisely what takes place in the dyeing process is not entirelyunderstood.

A large number of known water-soluble organic dyestuffs is suitable for use -in the process according to the invention. As preferred water-soluble organic dyestuffs,

there are mentioned, solely lpy way of example, the direct dyestuffs, .the acid ,dyestuffs'of the anthraquinone series groups,and particularly of the last-named group, are

partly sensitive to the action of copper salt and atmospheric oxygen so that dyeings thereof on polyacrylonitrile articles may be somewhat clouded. This is particularly the case when it is necessary, for one reason or another, to extend the dyeing period beyond the normal time. In such cases it is advantageous to add to the dye-baths according to the present invention a mild reducing agent of the type of sugar, as for example glucose, sucrose or dextrin. In the presence of such reducing agents, clouding of the dyeings, which might otherwise occur for the above explained reasons, is avoided. This expedient o1" dyeing in the presence of mild reducing agents constitutes a further aspect of this invention. I Still another phase of the invention is constituted by the dye-baths which, as already indicated, contain (i) metallic copper in the form of sheets, chips, wire, netting or the like, (ii) a water-soluble cupric compound, and,

in some cases, (iii) a mild reducing agent of the above described type.

As cupric compounds, the most suitable for use in the present process are the water-soluble copper salts such as copper formate, copper acetate, and especially copper sulfate. At least half of the quantity of the copper ions necessary for the dyeing are added in this form to the dye-bath. The other half is supplied by the metallic copper according to the equation The practically necessary quantity of copper metal surface and copper ions depends however upon the necessity of completing the dyeing in a practical period of time.

The dyeing is preferably carried out at pH valuesbetween 2 and 7, realized by the addition of water-soluble acid, for example formic acid, to the dye-bath. Preferred dyeing temperatures are those between 90 and 130 C.

The following examples set forth representative embodiments of the invention, without however restricting the latter. Thus, for example, the process is not at all limited to the dyeing of polyacrylonitriles, but'is also useful in dyeing mixed polymers of acrylonitrile and other unsaturated compounds, such as vinyl halides, vinyl acetate, acrylic amides and many others. In the examples, the parts are parts by weight; the temperatures are in degrees centigrade. Percentages ,are also by weight.

Example 1 I 100 parts of a washed skein or hank of polyacrylonitrile (staple fiber) are introduced at 70 into a dye-bath which contains 20 parts of a copper screen or netting made of wires of 0.2 mm. diameter and which also contains a solution of 1 part of sodium 1-amino-4-phenylaminoanthraquinone-2-sulfonate, 1 part of crystalline copper sulfate, 4 parts of concentrated formic acid and 4000 parts of water. The bath is heated to boiling; at the end of an 80-minute boiling period, the bath is completely exhausted and the textile material is dyed a fast bright blue.

A dye-bath which contains either only copper metal or only'copper sulfate solution will leave the textile material practically uncolored, when dyeing accordingto the process of the preceding paragraph. 1

Example culated through-the apparatus in which it is rapidly raised to boiling temperature, 10 parts of a copper wire screen made of wires-of 0.2-mm. diameter being interposed in the circulation path of the liquor. 3' The temperatureof the liquor is then slowly raised so that it reaches 120 in the course of one hour. At the end of this dyeing period, the coil of material is dyed a fast deep green. The dye-bath is completely exhausted.

Example 3 100 parts of a fabric, consisting of a mixed polymer of 40% polyacrylonitrile and 60% polyvinyl chloride, are dyed with 3000 parts of a dye liquor containing 3 parts of Roccellin (Schultz, Farbstofftabellen No. 206), 3 parts of formic acid, 20 parts of a copper sheet of a thickness of 0.2 mm. and 2 parts of crystalline copper sulfate. The dyeing takes place at boiling temperature and yields a deep vivid red shade. The dye penetration of the very dense fabric is complete.

Example 4 parts of polyacrylonitrile fiber (staple fiber) are dyed in 4000 parts of a dye-bath containing 2 parts of Orange R (Schultz, Farbstotftabellen No; 198), 2 parts of crystalline copper sulfate, 4 parts of 85 formic acid, 20 parts of glucose and 20 parts of a netting of copper wire of 0.2 mm. diameter. The dyeing process is ended after a 2-hour boiling period and yields a very pure orange shade.

Example 5 Example 6 100 parts of polyacrylonitrile (staple fiber) are dyed at 99 in 4000 parts of a dye-bath containing 2 parts of Tuchrot BB (Schultz, Farbstofitabellen No. 548), 2 parts of crystalline copper sulfate, 4 parts of 85% formic acid, 20 parts of glucose and 50 parts of sheet copper of a thickness of 0.2 mm. The dyeing process is completed at the end of 1 and /2 hours and yields a pure deep red dyeing.

. V Example 7 I The dyeing process according to Example 6 is repeated except that the 20 parts of glucose are replaced by 20 parts of sucrose. A pure deep red dyeing is obtained.

Example 8 A pure deep red dyeing is also obtained when, as in Example 6, the 20 parts of glucose are replaced by 20 parts of dextrin.

Having thus disclosed the invention, what is claimed is:

1; A process for dyeing polyacrylonitrile with a watersoluble acid organic dyestuff containing at least one sulfonic acid group, which comprises subjecting the polyacrylonitrile to the dyeing action of the dye-stuff in an aqueous dyebath initially containing, as sole metallic ingredients, metallic copper and cupric ions, whereby cuprous ions are formed in situ in said bath and the dyeing is carried out in the presence of such cuprous ions.

2. A process for; dyeing a member selected from the group consisting of polyacrylonitrile and copolymers of acrylonitrile with anotherv singly unsaturated compound containing an olefinic double bond and at least 40% by weight ofacrylonitrile with a water-soluble acid organic dyestutf containing at least one sulfonic acid group, which comprises subjecting the said fibers to the dyeing action of the dyestuif in an aqueous dye-bath initially containing, as sole metallic ingredients, metallic copper and cupric ions, whereby cuprous ions are formed in situ in said bath and the dyeingis carried out'in the presence'of such cuprous ions. i i

' 39A processfor dyeing a copolymer of acrylonitrile withanother singly unsaturated compound-containing an olefinic double bond and at least 40% by weight of acrylonitrile with a water-soluble acid organic dyestufi containing at least one sulfonic acid group, which com prises subjecting the said polymer to the dyeing action of the dyestufi in an aqueous dye-bath initially-containing, as sole metallic ingredients, metallic copper and cupric ions, whereby cuprous ions are formed in situ in said bath and the dyeing is carried out in the presence of such cuprous ions.

4. A process according to claim 1, wherein the metallic copper is in the form of sheet copper.

5. A process according to claim 1, wherein the metallic copper is in the form of copper chips.

6. A process according to claim 1, wherein the metallic copper is in the form of copper wire.

7. A process according to claim 1, wherein the metallic copper is in the form of netting.

8. A process for dyeing polyacrylonitrile with a watersoluble acid organic dyestutf containing at least one sulfonic acid group, which comprises subjecting the polyacrylonitrile to the dyeing action of the dyestufi in an aqueous dye-bath initially containing, as sole metallic ingredients, cupric ions in contact with metallic copper, whereby cuprous ions are formed in situ in said "bath and the dyeing is carried out in the presence of such cuprous ions.

9. A process for dyeing a member selected from the group consisting of polyacrylonitrile and copolymers of acrylonitrile with another singly unsaturated compound containing an olefinic double bond and at least 40% by weight of acrylonitrile with a water-soluble acid organic dyestufi containing at least one sulfonic acid group, which comprises subjecting the said fibers to the dyeing action of the dyestufi in an aqueous dye-bath initially containing, as sole metallic ingredients, cupric ions in contact with metallic copper, whereby cuprous ions are formed 6 in situ in said bath and the dyeing is carried out in the presence of such cuprous ions.

10. A process for dyeing a copolymer of acrylonitrile with another singly unsaturated compound containing an olefinic double bond and at least by weight of acrylonitrile with a water-soluble acid organic dyestuft containing at least one sulfonic acid group, which comprises subjecting the said polymer to the dyeing action of the dyestufl in an aqueous dye-bath initially containing, as sole metallic ingredients, cupric ions in contact with metallic copper, whereby cuprous ions are formed in situ in said bath and the dyeing is carried out in the presence of such cuprous ions.

11. A process according to claim 8, wherein the dyebath is contained in a container, at least those surfaces of the latter which are in contact with the bath comprising metallic copper.

12. A process according to claim 8, wherein the dyebath also contains a sugar.

13. A process according to claim 8, wherein the dyebath also contains glucose.

14. A process according to claim 8, wherein the dyebath also contains sucrose.

15. A process according to claim 8, wherein the dyebath also contains dextrin.

16. A process according to claim 1, wherein the dyebath is constituted by a circulating dye-liquor.

References Cited in the file of this patent UNITED STATES PATENTS Blaker Sept. 22, 1953 Glaze Jan. 3, 1956 OTHER REFERENCES

Claims (1)

1. A PROCESS FOR DYEING POLYACRYLONITRLE WITH A WATERSOLUBLE ACID ORGANIC DYESTUFF CONTAINING AT LEAST ONE SULFONIC ACID GROUP, WHICH COMPRISES SUBJECTING THE POLYACRYLONITRILE TO THE DYEING ACTION OF THE DYE-STUFF IN AN AQUEOUS DYE-BATH INITIALLY CONTAINING, AS SOLE METALLIC INGREDIENTS METALLIC COPPER AND CUPRIC IONS, WHEREBY CUPROUS IONS ARE FORMED IN SITU IN SAID BATH AND THE DYEING IS CARRIED OUT IN THE PRESENCE OF SUCH CUPROUS IONS.