US2403900A - Dye developer - Google Patents

Description

Patented July 16, 1946 DYE DEVELOPER George L. Armour, New York, N. Y., assignor to American Aniline Products, 1110., New York, N. 1., a corporation of New York No Drawing. Application November 29, 1941,

l Serial No. 420,965 7 2 Claims.

This invention relates to dyeing processes as applied to rayon yarns and particularly to cellulose acetate rayon and similar synthetic yarns. It will be understood, of course, in'using the term rayon I am using this term in the present generally accepted commercial use which includes both cellulose acetate yarns, regenerated viscose yarns, and similar synthetic yarns.

More particularly, it is concerned with developers that are used in the dyeing of cellulose acetate yarns.

Present day requirements call for speed in dyeing in order to save cost and to meet demands for quick deliveries. In the dyeing processes as at present practised, the material is passed through a bath containing the dyestufi" for a period of two to two and a half hours, after which it is rinsed well and diazotized with sodium nitrite and muriatic acid for a further 30-35 minutes cold, after which it is again rinsed well in cold water and developed to its proper shade with beta hydroxy naphthoic acid which is run 30-35 minutes at 60 C.

The preparation of this developing bath, however, has always presented considerable difliculties from a production standpoint. Beta hydroxy naphthoic acid is not water soluble and it has always been considered necessary to combine it with certain alkalies such as caustic soda, am-

monia, or soda ash. This, indeed, renders it water soluble but at the same time has brought it down to an alkaline condition in which it is unsuitable as a developer. The general practice has been to overcome this alkalinity by the addition of certain acids such as acetic or formic acid. This is for the reason that the developer must be on the acid side at about a pH of to 6, in order to couple the developer with the already diazotized dyestuff on the material. Assuming, for instance, that it is desired to produce a full black color on the material, if the developer is not properly acidified, brownish blacks and various other undesirable shades will result because of the improper coupling of the developer.

The various steps required in rendering the developer suitable for its purpose in the dyeing process are accompanied by numerous hazards. Chief among these are the following: In dissolving the developer beta hydroxy naphthoic acid with alkalies, it often happens that there may be left a certain amount of free alkali in the solution because of the carelessness of the workmen car rying out the process, or for other reasons. Furthermore, even with extreme care it is not always possible to be sure of the proper pH, lot after lot, so as to produce consistent shades of black in each operation. It may be added also that even when the operations are carried out with the utmost care, there is considerable time consumed in observing certain precautions such as the testing of the developing bath in order to determine its pH.

It is an object of the present invention to provide a method of developing the color in the dyeing operation that avoids all these hazards which have been above enumerated.

Briefly, it is an object of the present invention to provide a method of preparing the beta hydroxy naphthoic acid developer without changing its acid character. In other words, it is an object of the invention to provide such a developing bath without incurring the various hazards due to alkalizing the beta hydroxy naphthoic acid and then bringing it back to the acid side.

I have discovered that if beta hydroxy naphthoic acid is thoroughly mixed with sodium formate while both are in the dry state, and then hot water at a temperature of about C. to C. added, with stirring, the resulting product becomes water soluble without being alkalized and without materially changing its pI-I. In other words, the developer which is a sodium salt of beta hydroxy naphthoic acid remains on the acid side and in the solution above indicated is immediately ready to be added to the developing bath, and when so used the pH of the developing liquor is consistent and consequently produces consistent full shades of the desired color.

The following is a specific example of the use of the developer of the present invention: A dyestufi, such as para-amino-benzene-azo-dihydroxyethylanilin in solution, is prepared and cellulose acetate rayon is introduced thereinto and allowed to remain in the bath for about two to two and a half hours. This dyestuff is then diazotized upon the material as before stated. A developer is then prepared by adding to beta hydroxy naphthoic acid, sodium formate in the dry state. Hot water at a temperature of about 85 C. to 100 C. is then added with stirring. The reaction of the developer then proceeds according to the following equation:

This developer is then added to what is known as the developing bath. The cellulose acetate rayon having been previously treated as above indicated is then immersed in this developing bath at a temperature of about 35 C. to 40 C.

with sodium formate (I-ICOONA) which may be represented by the formula: CH6OH.COONA, a sodium salt of beta hydroxy naphthoic acid having a pH of about 5 to 6.

Having thus described my invention, what I claim is:

1. The method of preparing a developing bath for acetate rayon dyes which consists in adding sodium formate to beta hydroxy naphthoic acid,

both being in the form of dry powders; then adding water at a temperature of about 85 C. to 100 C. with stirring, thereby causing the sodium formate to react with the beta hydroxy naphthoic acid yielding water soluble reaction products to form a developing bath having a pH of about 5 to 6.

2. The method of developing colors'on acetate rayon that consists in treating dyed and diazotized acetate rayon by immersing it in a bath containing a solution formed by adding beta hydroxy naphthoic acid to sodium formate and hot water, said immersion taking place in said solution at a temperature of C. to 40 C., then raising the temperature of the bath to about C. and maintaining this temperature for about thirty minutes, then rinsing the rayon with fresh water and extracting and drying it.

GEORGE L. ARMOUR.