JPH0327174A - Method for removing yellowing of fabric - Google Patents

Abstract

PURPOSE:To obtain a bleached dyed fabric without yellowing by treating a yellowed fabric, dyed with an indigo dye and subjected to bleaching treatment with an active oxygen-containing aqueous solution. CONSTITUTION:For example, a yellowed blue denim fabric, dyed with an indigo dye and subjected to bleaching treatment with a chlorine-based bleaching agent is treated with an active oxygen-containing aqueous solution (e.g. an aqueous solution containing hydrogen peroxide) to afford an unyellowed bleached fabric, dyed with the indigo dye and free of yellowing. The amount of the hydrogen peroxide used is within the range of 0.01-0.5wt.%, preferably 0.02-0.2wt.% expressed in terms of active available oxygen concentration in the treating solution, which is used in an amount of 20-100 pts.wt. based on 1 pt.wt. fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention involves treating cloth dyed with a bleached indigo dye that has a yellowish tint with an aqueous solution containing active oxygen. Concerning how to remove yellowing.

(Prior Art) In recent years, fabrics dyed with indigo dyes, especially bleached denim produced by bleaching blue denim, have become popular.

Blue denim is bleached using a chlorine bleach, followed by dechlorination using a reducing agent to remove residual chlorine, washing, and drying. As the chlorine bleach, sodium hypochlorite solution, bleaching powder, highly bleached powder, etc. are used.

Sodium thiosulfate is often used as a reducing agent. If dechlorination is not performed, residual chlorine will remain adsorbed on the fibers for a long time and cause yellowing, so dechlorination is performed using a reducing agent.

(Problems to be Solved by the Invention) In the conventional methods described above, yellowing may occur in the product after bleaching. Yellowing is caused by many factors other than residual chlorine or adsorption, and conventional sodium thiosulfate
Even if Uum is used, yellowing cannot be completely suppressed.

On the other hand, after bleaching with chlorine bleach, dechlorination is performed with various reducing agents, and cleaning (sobbing) is performed using various surfactants to wash away yellowing. However, bleaching methods that do not cause yellowing are not perfect and can only be achieved under extremely narrow conditions.

The present inventors have completed the present invention by discovering that yellowing can be removed by treating yellowed bleached denim with an aqueous solution containing active oxygen.

An object of the present invention is to provide a method for removing yellowing from fabric dyed with an indigo dye and bleached.

(Means for Solving the Problems) The present invention relates to a method for removing yellowing from cloth, which comprises treating a cloth dyed with a bleached indigo dye that has yellowing with an aqueous solution containing active oxygen.

The fabric dyed with the indigo dye used in the method of the present invention is not particularly limited, but the method of the present invention is particularly effective for denim. In addition to denim, there are traditional items such as knitwear, yukata, and pongee.
Examples include handicrafts such as noren and table centerpieces.

As the aqueous solution containing active oxygen used in the present invention, an aqueous solution in which hydrogen peroxide or an adduct of hydrogen peroxide is dissolved can be used. Examples of adducts of hydrogen peroxide include sodium percarbonate and sodium perborate.

The amount of hydrogen peroxide solution and hydrogen peroxide adduct used is 0.01 to 0.5% by weight as the active effective oxygen concentration in the treatment solution.
, preferably 0.02 to 0.2% by weight, and the amount of treatment liquid to the cloth is in the range of 20 to 100 parts by weight per 1 part by weight of the cloth.

Other processing conditions at this time are not particularly limited, but the processing temperature is room temperature to 80°C, preferably 30 to 50°C.
It is ℃. Usually a treatment time of 5 to 20 minutes is sufficient.

After the treatment, a fabric dyed with bleached indigo dye without yellowing can be obtained by soaping, rinsing and drying steps.

The present invention will be explained in more detail with reference to Examples below.

Example 1 [Example 1 of producing denim fabric with yellowing] Pour 50 liters of warm water at about 80°C into a small household electric washing machine, add one pair of blue denim pants (size 28 inches), and add Sodium bromate}IJum was added at a concentration of 2 g/l, and the product was washed for 15 minutes to remove desizing.

After that, drain the hot water and add 5 ol of warm water at about 50℃.
Sodium hypochlorite was added in an amount to give an active chlorine concentration of 0.5% by weight, and bleaching was performed for 30 minutes.

After that, the water was drained, and 50% of warm water at about 50℃ containing 0.7% by weight of sodium thiosulfate was added, and the dechlorination treatment was carried out for 1 hour.
It lasted 0 minutes.

Furthermore, drain the hot water, add 501 new water, and add nonionic surfactant (manufactured by NOF Corporation, product name Nonion NS-2).
Washing (soaping) was performed with 0.2) for IO minutes.

After that, rinse twice, dehydrate in a dehydrator, and heat at 90℃ for 4 hours.
Dry for 0 minutes.

Evaluation was performed using the following method, and yellowing was also observed from the color tone and visual observation results.

Color tone (L; 42.2 a; Δ2.5 b; 6.1
) The denim used is as follows.

[Yellowing removal]

50 containing hydrogen peroxide with an effective oxygen concentration of 0.03% by weight
Warm water at a temperature of 501 °C was put into the above-mentioned household electric washing machine, and the above-mentioned yellowed denim fabric was treated for 10 minutes. Thereafter, soaping, rinsing, and drying were performed in the same manner as above. The obtained denim fabric showed no yellowing at all, and the color tone was L; 44.8, a; Δ1.8, b; Δ5.
4, which was extremely good.

[How to evaluate the degree of yellowing]

The color tone (lightness (L) hue' (a.b)) of the bleached denim cloth piece was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd.), and the appropriateness of the bleaching effect and the degree of yellowing were visually observed. .

Examples 2 to 5 Yellowing denim was obtained in the same manner as in Example 1 (manufacturing conditions and yellowing evaluation results are shown in Table 1), and yellowing removal treatment was performed. The results are shown in Table-2.

The bleaching effect was graded into three levels: adequate, excessive, and insufficient, and yellowing was expressed using the following symbols.

○; No yellowing; Slight yellowing; △; Yellowing; ×; Significant yellowing. As shown in Table 2, yellowing of bleached denim can be eliminated by the method of the present invention.

(Margin below)

Claims (1)

[Claims] (1) A method for removing yellowing from cloth, which comprises treating a bleached cloth dyed with indigo dye, which has yellowing, with an aqueous solution containing active oxygen.