Method for controlling coloring of fiber

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention belongs to the technical field for coloring fibers and relates to the technique for controlling the developed color, particularly in the technique for coloring animal fibers etc. without using dyes.

2. Description of the prior art

[0002] Some novel methods for coloring fibers using fiber itself as the chromophoric material by converting tryptophan being contained in animal fiber etc. to chromophore components are known, differing from the method for dyeing animal fiber using the synthetic dyes in the past. Japanese Patent Application Laid-Open No.2001-55672 discloses that various colors can be brought out from acid-treating animal fiber together with aldehyde compounds, that the obtained color has durability against sweat, abrasion and washing, and that the color depends on the combination of the acid and the aldehyde.

[0003] In above prior art, however, the controlling technology for making deep color is not satisfactory, and there is still the problem for the industrialization because the reaction must be conducted in an organic solvent system.

SUMMARY OF THE INVENTION

[0004] The present invention is to provide a controlling technology which makes deeper-coloring possible and a method in which coloring and deeper-coloring are conducted in a water system.

[0005] The present invention provides to a method for controlling color development of fiber in a coloring method of fiber in which a tryptophan-containing fiber is colored with an aldehyde compound, comprising;
   a first step: a process for treating a fiber which contains tryptophan constitutionally or in which tryptophan is introduced from outside with an acid and an aldehyde compound; and
   a second step : a process for treating the fiber treated in the first step with an oxidizer in the presence of an acid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The present invention relates to a method for controlling color development of fiber in a coloring method of fiber in which a tryptophan-containing fiber is colored with aldehyde compound, comprising;
   a first step: a process for treating a fiber which contains tryptophan constitutionally or in which tryptophan is introduced from outside with an acid and an aldehyde compound; and
   a second step : a process for treating the fiber treated in the first step with an oxidizer in the presence of an acid.

[0007] Particularly, the present invention relates to the above method for controlling color development of fiber, wherein the aldehyde is aromatic aldehyde compounds, benzaldehyde or the derivatives thereof, and preferably water-soluble aromatic aldehyde compounds or water-soluble benzaldehyde derivatives.

[0008] In the present invention, "controlling color development of fiber" or "controlling coloring of fiber" means to control coloring conditions such as a kind of color and concentration of color.

[0009] According to the method for controlling the coloring of fiber in the present invention, tryptophan-containing fibers are treated with an acid and an aldehyde compound in the first step. In the treatment of this step, the fiber is made contact with a treating solution containing an acid and an aldehyde compound so that the tryptophan in the fiber and aldehyde compound may react to be condensed and that the aldehyde compound combines to the fiber. In this treating solution, a concentration of acid is preferably adjusted to 10^-5 to 2N, more preferably 10^-2 to 1N.

[0010] While the addition reaction between tryptophan and aldehyde compound is promoted by adjusting the acid concentration in the treating solution within the above-mentioned range, it is considered that the color is developed by the formation of conjugated double bond between tryptophan and aldehyde compound as the result of the oxidation of aldehyde compound added to tryptophan. Especially, in the case that the aldehyde compound is an aromatic compound, when the aromatic aldehyde compound added to tryptophan is oxidized, an aromatic ring in aromatic aldehyde is converted to a quinoid structure, so that a conjugated double bond is formed between tryptophan and aldehyde, resulting in coloring development.

[0011] The coloring can be controlled to yellow colors having characteristic absorption wave-length at 400 - 500nm in the case that the aromatic ring can be converted to an o-quinoid structure, and to the colors from red to blue or green having absorption at 500 - 800nm in the case that it can be converted to a p-quinoid structure. However the present invention is not restricted to the above. The control can be made by changing kind, number, position etc. of the functional group in aromatic aldehydes and benzaldehyde derivatives.

[0012] However, in this first step, the oxidation is restricted. Only the first step can not achieve satisfactory color development with sufficient concentration. In this step, the oxidation reaction is promoted when the temperature is raised, but the fiber is decomposed or dissolves by the acid. Therefore, it is preferable that the treatment should be conducted without heating. The temperature range is preferably 20 - 90°C, more preferably 20 - 70°C.

[0013] The treating solution is obtained as an aqueous solution by using water-soluble compounds as aromatic aldehyde compounds or benzaldehyde derivatives. In this case, the aggravation of the working environment according to solvents can be prevented and the possibility of fire or explosion also disappears, and so the industrial process is possible, being very favorable.

[0014] As described above, though some degree of coloring is achieved in the first step, the color concentration is in general insufficient merely in the first step and the deepening process of the color is required to make the color deeper. For deepening of the color, the fiber treated in the first step is treated with oxidant in the presence of an acid in the second step. Through this step, the aldehyde compound bound to tryptophan is more perfectly oxidized and the concentration of aldehyde which can form the conjugated double bond with tryptophan increases. As the result, the developed color becomes deeper and deeper coloring is attained. When the aldehyde compound is an aromatic aldehyde, a quinoid structure is formed as mentioned above and this concentration increases with the treatment by an oxidant.

[0015] The coloring can be controlled to yellow colors having characteristic absorption wave-length at 400 - 500nm in the case that the aromatic ring can be converted to an o-quinoid structure, and to the colors from red to blue or green having absorption at 500 - 800nm in the case that it can be converted to a p-quinoid structure. However the present invention is not restricted to the above. The control can be made by changing kind, number, position etc. of the functional group in aromatic aldehydes and benzaldehyde derivatives.

[0016] The transfer from the first step to the second step may be conducted by the way that the fiber colored in the first step is once washed and dried and then subjected to the second step, or washed and then subjected to the second step without drying.

[0017] The treatment in the second step may be conducted at 20 - 90°C, preferably at 20- 70°C in the same way as in the first step.

[0018] When above-mentioned treating temperature is used, the treating time is usually 1 - 6 hrs in the first step, and 1 - 24 hrs in the second step.

[0019] The fiber contacted with a treating solution in the second step may be kept immersed in the treating solution until the reaction finishes, or may be taken out of the treating solution and be subjected to reaction in the state that the fiber sufficiently contains the treating solution by immersion.

[0020] After finishing the treatment in the second step, the fiber may be sufficiently washed with an adequate cleaning solution which can get rid of aldehyde compounds, such as water or water/methanol mixture, and then may be air-dried at ordinary temperature or may be dried at such a temperature as quality of the fiber would not be spoiled.

[0021] The principle of the present invention is applied for coloring fibers containing tryptophan constitutionally or extrinsically. It is particularly advantageous to color the fibers having tryptophan constitutionally, that is, protein fibers. Protein fibers to be applied are generally animal fibers, particularly wool or silk. The examples of protein fibers other than animal fibers are protein fibers regenerated from casein, zein, peanut protein etc. as raw materials. The present invention can be applied for coloring these fibers.

[0022] The method of the present invention can be also applied for coloring the fibers containing tryptophan extrinsically, that is, such fibers as tryptophan is introduce from outside, in addition to the fibers containing tryptophan constitutionally such as animal fibers (protein fibers). For example, by introducing and binding tryptophan to hydroxide group in cellulose constructing cotton in a coupling reaction, such cotton fiber can be colored according to the present invention.

[0023] In the present invention, "fiber" means not only fiber itself, but also fiber products such as cloth, clothing and the like.

[0024] Aldehyde compounds used in the present invention are selected in combination with acids according to the required color, and generally aromatic aldehyde compounds are preferable, particularly benzaldehyde or its derivatives having benzaldehyde as the basic skeleton. By using water-soluble aromatic benzaldehyde compounds or benzaldehyde derivatives, the coloring reaction and deeper-coloring reaction can be conducted in water system.

[0025] The water-soluble derivatives of benzaldehyde are exemplified by 4-hydroxybenzaldehyde, 4-dimethylaminobenzaldehyde, 2,4,6-trimethoxybenzaldehyde, 3,4-dihydroxybenzaldehyde and a mixture thereof, with no intention to limit them to restricted examples.

[0026] An amount of aromatic aldehyde to be used is determined by depth of color required for colored fiber and amount of tryptophan contained in the fiber. The color development occurs by the reaction between tryptophan and aldehyde compound, and it is expected that one mole of aldehyde compound reacts with two moles of tryptophan in maximum. Thus, the reaction between aldehyde compound and tryptophan is theoretically saturated with aldehyde of the half amount by mole of existing tryptophan, but the amount of aldehyde compound to be used should be properly determined by the depth of color required. Generally, as one example, about 0.5 to 5% by weight based on total weight of fibers can be used.

[0027] In the present invention, an acid which is used together with aldehyde compounds in the first step, is preferably the one belonging to strong acids, but should not be the one which may dissolve the fiber. The preferable examples of the acids which can bring about the effect of the present invention on the fibers without giving the fibers damage, are the acids obtained by diluting strong acids such as trifluoroacetic acid, dichloroacetic acid, hydrochloric acid, sulfuric acid and oxalic acid with water or weak acid such as acetic acid.

[0028] The ratio of acid and aldehyde compound is not particularly restricted, but it is determined by the degree of shade of color desired.

[0029] The acid used in the second step may be the same acid as used in the first step. The concentration of acid in the treating bath is 10^-5N to 0.5N in the second step.

[0030] In the second step, aromatic aldehydes which still maintains non-oxidized state after the first step are oxidized with the action of oxidizer so that the aromatic ring forms quinoid structure, resulting in that the color development becomes deeper. The oxidizer to be available may be water-nonsoluble oxidizers or water-soluble oxidizers. From the viewpoint of treatment in water system, the water-soluble oxidizers are preferable. The examples of the water-soluble oxidizer are hydrogen peroxide, peracetic acid, monopersulfates etc. Particularly preferable oxidizers are hydrogen peroxide and monopersulfates. A concentration of the oxidizer is 10^-5% to 5% by weight in treating solution.

[0031] In the treating solution of the first step, a salting-in agent may be added to make it easy for aldehyde compound to dissolve in water. The salting-in agents are exemplified by halides of alkaline metals or halides of alkaline earth metals, such as calcium chloride, lithium chloride, sodium chloride and lithium bromide. Particularly preferable salting-in agents are calcium chloride, sodium chloride and lithium bromide.

EXAMPLES

[0032] The following examples illustrate the features of the present invention.

Examples 1 - 4

[The first step treatment]

[0033] Benzaldehydes derivatives listed in Table 1 were dissolved to give concentration of 2% by weight in 60ml of 1N-hydrochloric acid containing 10% by weight of acetic acid and 20% by weight of calcium chloride, and 6g of untreated wool fabric was dipped in this solution. The solution was raised to 60°C in this condition and subjected to reaction for 3 hrs. After reaction, the wool fabric was washed with water and dried at 80°C to give a colored wool fabric. The degree of coloring was measured using "Spectro Color Meter SE 2000" manufactured by Nippon Denshi Kogyo K.K. and a diagram of L*a*b* was obtained. The results were shown in Table 1.

[The second step treatment]

[0034] The wool fabric treated in the first step was dipped in a mixed solution containing 20ml of 0.5N-sulfuric acid and 1ml of 35%conc.-hydrogenperoxide and was maintained in the solution for 2 hrs at room temperature. The fabric was taken out of the solution and kept in air overnight to give the fiber colored deeper. The colored degree was measured in the same way as described above and the results were shown in Table 1.

[0035] The fact that a L* value expressing brightness was lower in the second step than in the first step shows that the deeper coloring was developed in the second step.

Table 1

Ex.	Benzaldehyde derivatives	1st Step			2nd Step
		L*	a*	b*	L*	a*	b*
1	4-hydroxy benzaldehyde	78.470	5.7100	19.510	60.290	14.280	14.230
2	4-dimethylamino benzaldehyde	51.630	6.4300	6.5200	37.800	-1.9900	-10.080
3	2,4,6-trimethoxy benzaldehyde	66.600	-0.6700	9.9800	52.000	-0.790	-6.5700
4	3,4-dihydroxy benzaldehyde	70.150	10.440	28.310	48.690	16.420	14.470

[0036] According to the present invention, the deeper coloring of fibers, which has been difficult to control, has become easy, and the method for coloring of tryptophan-containing fibers has become easier to be controlled. According to the present method, the deeper coloring has become possible with less damage of fibers. In addition, according to the present method, the treatment in water medium has become possible and therefore the present method is suitable for an industrial process. It is also possible to decrease concentration of acid in the treatment of the first step.

Claims

1. A method for controlling color development of fiber in a coloring method of fiber in which a tryptophan-containing fiber is colored with aldehyde compound, comprising;
   a first step: a process for treating a fiber which contains tryptophan constitutionally or in which tryptophan is introduced from outside with an acid and an aldehyde compound; and
   a second step : a process for treating the fiber treated in the first step with an oxidizer in the presence of an acid.

2. The method for controlling color development of fiber according to claim 1, wherein said aldehyde compound is selected from aromatic aldehyde compounds, benzaldehyde or its derivatives.

3. The method for controlling color development of fiber according to claim 2, wherein said aromatic aldehyde compounds are water-soluble benzaldehyde derivatives.

4. The method for controlling color development of fiber according to claim 2, wherein said benzaldehyde derivatives are water-soluble benzaldehyde derivatives.

5. The method for controlling color development of fiber according to claim 4, wherein said water-soluble benzaldehyde derivatives are selected from a group consisting of 4-hydroxybenzaldehyde, 4-dimethylaminobenzaldehyde, 2,4,6-trimethoxybenzaldehyde, 3,4-dihydroxybenzaldehyde and a mixture thereof.