The water-soluble reactive dyes (hereinafter simply called "reactive dyes") have heretofore been used widely as the dyestuff for dyeing cellulosic fibers. As the method of dyeing the fiber materials with use of such reactive dyes, there have been adopted various known techniques such as exhaustion method and printing method. Of these various dyeing methods, the exhaustion method for dyeing the cellulosic fibers requires the presence, in the dye bath, of inorganic salts such as Glauber's salt, edible salt, and others together with alkali. In particular, for obtaining dyed fabrics of high density, it is usually necessary that approximately 50 to 100 g of the inorganic salt per 1 liter of the dye bath be added. If the added quantity of the inorganic salt is too small, it is not possible to dye the cellulosic fibers to an intended color hue.
In recent years, reduction in quantity of the inorganic salts in the dye bath has been desired from the standpoint of rationalizing the operations in the dyeing factories. In other words, the reduction in the quantity of the inorganic salts not only leads to reduction in the manufacturing cost, but also to reduction in the load imposed on disposal of the waste water from the dye bath. Accordingly, for the purpose of such dyeing method, there is a demand for reactive dyes which are not only superior in their fastness to various circumstances as well as their reproducibility, but also are capable of favorably dyeing the cellulosic fibers even under a condition wherein the density of the inorganic salt is, for example, as low as 5 to 40 g per 1 liter of the dye bath. While there have so far been known a large number of reactive dyes, however, almost all of them would require a large amount of the inorganic salt at the time of dyeing.
The present inventors conducted researches for presence of dyes which are suited for the above-mentioned purpose in those known reactive dyes, as the result of which they have discovered that, when use is made of a red reactive dye to be represented by the following general formula (I) in the form of free acid, there could be obtained a favorable dyed article, even when the amount of the inorganic salt in the dye bath is reduced to 1/5 to 1/10 of the amount which has been used conventionally: ##STR2## (where: each of R.sup.1 and R.sup.2 denotes a hydrogen atom or a lower alkyl group which may contain therein a substituent; R.sup.3 represents a hydrogen atom, a lower alkyl group or a halogen atom; and X designates --CH.dbd.CH.sub.2 or --C.sub.2 H.sub.4 OSO.sub.3 H).
Incidentally, the structure of the reactive dye as shown in the above general formula (I) has been known in part, and reactive dyes included in the above general formula (I) are disclosed in, for example, Japanese Unexamined Patent Publications No. 212467/1987 and No. 260654/1985.
In case the reactive dye of the above-shown general formula (I) is used singly, a favorable dyeing result can be obtained even under the low concentration condition of the inorganic salt. However, when it is used in mixture with yellow dye and/or blue dye, the characteristic properties of the reactive dye as shown in the above general formula (I) cannot be exhibited to the satisfactory extent, unless the dye mixture is capable of dyeing favorably the fabrics under such low concentration condition of the inorganic salt. Accordingly, these yellow and blue dyes to be used in a mixture with the reactive dye of the above-indicated general formula (I) should be such that they are able to dye favorably the fabrics with a small amount of the inorganic salt. It is also necessary in this case that those reactive dyes to be selected possess the same level of fastness under various circumstances, dyeing speed, reproducibility, heat-stability and other physical properties as those of the reactive dye shown in the above general formula (I), and also have good compatibility with the red dyes.
That is to say, even when the reactive dye of the above formula (I) is used as the red dye, a mixed dye, in which any arbitrary dye in yellow or blue is blended, has its possible defect such that it is unable to dye the material to an intended color hue at such dyeing condition where the inorganic salt is present in low concentration, or, even if the intended color hue is attained it has high dependency on the salt-concentration or the temperature, hence it possesses insufficient reproducibility, and others.
On the other hand, a report of Hayakashi et al. "On Diamira SN Series Dyes" (Dyeing Method with Recommended Three Primary Colors with Reduced Amount of Glauber's Salt)", Senshoku Kogyo (Dyeing Industry), Vol. 34, No. 2, 1986, pp81 to 93, introduces therein, in codes, each of reactive dyes in three primary colors which are available in general commercial market and capable of dyeing materials with a small quantity of the inorganic salt (Glauber's salt), although no chemical structure whatsoever of these reactive dyes are presented in the report.
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