JPH0547659B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention provides a novel bleaching method that combines whiteness and softness and can be processed in a short time. (Conventional technology) For bleaching cellulose fibers, methods such as sodium chlorite and hydrogen peroxide are commonly used, but if you try to increase the whiteness, the texture becomes hard, whereas if you emphasize softness, the texture becomes hard. There is a problem that whiteness decreases. Regarding this point, there is a method of combining sodium chlorite bleaching and hydrogen peroxide bleaching and processing at low temperature, but it requires a long processing time to increase the whiteness, and the texture is still unsatisfactory. There is something. (Problems to be Solved by the Invention) The present invention is excellent in these points, in terms of whiteness and texture, and can be processed in a short time. (Means for solving the problem) However, in the bleaching method of the present invention,
After soaking in a sodium chlorite solution with a concentration of 3 to 8% owf and a pH of 3 to 4, the object to be bleached is heated to 90 to 100℃ for 10 minutes.
The first treatment involves steam treatment for ~30 minutes, and the second treatment involves immersing it in a hydrogen peroxide solution with a concentration of 3~8% OWF and pH=10~12 and steaming it at 40~70°C for 1~10 minutes. The present invention relates to a soft bleaching method for cellulosic fibers characterized by a combination of treatments. However, use a sodium chlorite solution with a concentration of 25% and a hydrogen peroxide solution with a concentration of 35%. The purpose of the present invention is to shorten the bleaching time as much as possible, which has a large effect on softness, increase the proportion of the bleaching time using a sodium chlorite solution, which has a low degree of embrittlement to the bleached fabric, and shorten the temperature. The maximum temperature range under normal pressure was chosen so that the whiteness could be achieved in a short amount of time.Then, in the treatment with hydrogen peroxide, the time and temperature were kept to a minimum in order to control unnecessary reactions to the bleached fabric.
The feature is that the bleaching solution can be used efficiently. (Function) In the sodium chlorite bleaching method of the present invention, the bath ratio is minimized by pad, high temperature steam, and short time treatment, and the applied heat and chemicals can be used effectively, compared to the immersion method and liquid flow method. High whiteness can be obtained in a very short time. Furthermore, since the fabric to be bleached is not brought into contact with the bleaching solution mechanically, the fabric to be bleached is not hardened more than necessary. In such treatment, if the temperature is less than 90°C, it is difficult to obtain the desired whiteness even after 30 minutes of treatment, and if the temperature exceeds 100°C, sealed high-pressure equipment is required, resulting in equipment problems. It is also undesirable in terms of operation. In addition, if the processing time under these conditions is less than 10 minutes, the reaction will be insufficient and it will be difficult to obtain the desired whiteness, and if the processing time exceeds 30 minutes, the whiteness will reach equilibrium and the dough will deteriorate. This is not preferable because it causes problems of embrittlement and hardening. Furthermore, if a chelate dispersant such as a polycarboxylic acid compound is added to the treatment bath, radical reactions caused by metal ions can be suppressed and the effect can be further enhanced. On the other hand, the hydrogen peroxide bleaching after this treatment also uses a short steam method, similar to the previous process, and is carried out at low temperatures to minimize the decomposition of the cotton wax by alkali and the embrittlement of the cotton by the hydrogen peroxide itself. It is effective in removing residual pigments and neutralizing residual sodium chlorite from the previous process. In such a treatment, if the temperature is less than 40°C, the bleaching reaction will be difficult to proceed and sufficient whiteness will not be obtained. Furthermore, if the temperature exceeds 70°C, whiteness may be obtained, but as the temperature rises, the fabric becomes brittle at an accelerated rate. Furthermore, if the treatment time under such conditions is less than 1 minute, the reaction will be insufficient and the drug will not be used effectively. Moreover, if the time exceeds 10 minutes, the fabric becomes brittle preferentially, which causes a problem, although the increase in whiteness is slight. Furthermore, if a chelate dispersant such as a polycarboxylic acid compound is added to the treatment bath, radical reactions caused by metal ions can be suppressed and the effect can be further enhanced. In addition, the steam treatment in both treatments refers to continuous padded steam treatment, and therefore, this is arranged continuously, for example, immersion in a treatment bath, padding, steam treatment, hot water washing, water washing, etc. It is something that can be done. Examples will be described below.

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[Table] The treatments in Examples 1 to 3 were carried out as follows. Fabric used: Cotton milling fabric Sodium chlorite bleaching: Sodium chlorite solution concentration 25%, soaking time 5 minutes, squeezing rate 140% Hydrogen peroxide bleaching: Hydrogen peroxide solution concentration 35%, soaking time 5 minutes, squeezing Rate: 140% Steam treatment: Padded steam continuous treatment This treatment was carried out continuously, and hot water washing steps were provided after sodium chlorite bleaching and hydrogen peroxide bleaching, respectively. In addition, in the comparative example, each sample was immersed in batches, which is a conventional method. The chelate dispersants are as follows. A: Polycarboxylic acid type B: Magnesium salt type C: Phosphonic acid type (Effects of the invention) The bleached products treated as described above according to the method of the present invention are different from the comparative example using the conventional method as shown in Table 1 below. In comparison, almost the same whiteness was obtained, excellent softness was obtained, and the processing time was significantly shortened. In addition, each evaluation was performed as follows. Whiteness: Calculated as L*-3b* from CIELAB color space (color measurement in Macbeth 2020 micro area) Softness: The measurement sample cloth was sewn from the sewing machine,
(Needle: ORGAN DB×1 No. 11) The number of holes made was substituted into the following formula to obtain a value for evaluating softness. However, the softness of the comparative example was calculated as 100. Softness = 100/Number of holes x 100 The larger the numerical value for evaluating softness, the better.

[Table] As described above, according to the method of the present invention, it is possible to achieve both whiteness and softness, and the bleached product obtained thereby is particularly suitable for wearing under the skin.

Claims (1)

[Claims] 1. A first treatment of immersion in a sodium chlorite solution with a concentration of 3 to 8% owf and a pH of 3 to 4, followed by steam treatment at 90 to 100°C for 10 to 30 minutes; %owf,
A soft bleaching method for cellulose fibers, which comprises a second treatment of immersion in a hydrogen peroxide solution having a pH of 10 to 12 and then steam treatment at 40 to 70°C for 1 to 10 minutes. (However, use a sodium chlorite solution with a concentration of 25% and a hydrogen peroxide solution with a concentration of 35%.)