JPH02133659A - Bleaching method using sodium chlorite - Google Patents

Abstract

PURPOSE:To maintain the pH balance of a gas phase on the bleaching of a web to provide the good bleached web due to the homogeneous bleaching by successively supplying a vaporized acidic solution to a gas phase in a reaction tower for the bleaching process in a process for bleaching the web with an acid-activated solution of sodium chlorite. CONSTITUTION:While a web 2 to be bleached is passed into a liquid layer 3 in a reaction tower 1 therein receiving an acid-activated sodium chlorite solution adjusted to a pH3-4 with formic acid or acetic acid through a gas phase 4 and introduced between a rotating drum 5 and an endless conveyor 7 disposed in the liquid layer 3, a vaporized acidic solution is successively supplied to the gas phase of the reaction tower 1 to secure a balance required for the activation of chlorous acid gas, thereby always maintaining a good acidic bleaching atmosphere to provide the good bleached web.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of bleaching fabrics using an acid-activated solution of sodium chlorite.

[Prior Art] A conventional bleaching method for bleaching fabric using an acid-activated solution of sodium chlorite includes, for example, adding 25 to 10 to 40 g/fl of sodium chlorite to 5 to 10 g/n of 90 acetic acid. A sodium chlorite solution adjusted to pH 3 to 4 by adding 1 to 2 g of a permeation aid and Q as appropriate is filled into the liquid layer at the bottom of the reaction tower where moist heat of 70 to 85°C is maintained, for example. The bleaching process is carried out by sequentially feeding the fabric to be bleached into a reaction tower in which the bottom of the reaction tower is a treatment liquid layer and the upper part of the treatment liquid layer is a gas layer.

[Problems to be Solved by the Invention] During the bleaching treatment of fabrics using a sodium chlorite solution, the activation rate of the sodium chlorite is determined by changes in the temperature, concentration, and pi value of the sodium chlorite solution. Due to many changes in conditions such as insufficient neutralization of residual alkali during the preliminary treatment step (scouring step) or changes such as excessive suction of chlorite gas, the po value in the gas layer inside the reaction tower always varies, There is a problem that a uniformly bleached fabric cannot be processed due to the pH value fluctuation in the gas layer.

That is, 5HaCUO, + 4CII, C00H=
4C20, +4C1lxCOONa + NaCQ +
2H2QCllsCOONa is water volume? 71 in the middle of the night
As it grows and becomes C0W->CHo, the pH tends to shift to the alkaline side, and furthermore, due to self-decomposition, O
H″ is generated.

When this OH- production increases, the pH balance of the air layer in the reaction tower collapses (lack of acid), and the chlorite gas becomes inactive, which instantly clouds the air layer and removes acid from the fabric. This has caused problems such as bleaching failure. - Once the cloudiness of the air layer occurs, even if you take measures to eliminate the cloudiness, the cloudiness will not disappear immediately, and it will take about 20 to 30 minutes before the cloudiness disappears.
30 minutes are spent during which the fabric passes through the reaction chamber;
For example, a fabric of 500 to 11110 (1 m) was defective in bleaching and had to be corrected by bleaching again.

Considering the safety of the bleaching process, it is possible to lower the pH value excessively from the beginning, but lowering the p++ value too much may cause the decomposition of the sodium chlorite to become rapid and the sustainability to be lost. Not only will it not be possible to achieve a sufficient bleaching effect, but the amount of chlorite gas generated will be large, leading to deterioration of the environmental pollution.

[Means for Solving the Problems] The present invention has been made by focusing on such conventional problems, and provides a fabric bleaching method that can always produce good bleached fabrics no matter what condition changes occur. will provide a method.

To describe the present invention more specifically, in order to prevent the air layer in the bleaching reaction chamber from becoming cloudy due to lack of acid, approximately 3 to 10 g of acetic acid is added per minute as an aqueous solution. By atomizing and supplying the chlorite gas into the gas layer, the 9+1 balance necessary for activating the chlorite gas is maintained, thereby making it possible to perform a good bleaching process.

[Examples] The present invention will be described in detail below based on embodiments shown in the drawings.

1 is a reaction tower for bleaching the fabric 2, the inner bottom of this reaction tower 1 is formed as a liquid layer 3, and the upper part of the liquid layer 3 in the reaction tower 1 is formed as a gas layer 4. has been done. 5
is a rotating drum, and a substantially semi-circular arc-shaped endless conveyor 7 is disposed in the substantially lower half of the rotating drum 5, with a desired gap 6 in between. The fabric 2 hanging down from the top is moved during the above period by the operation of the folding mechanism 8. 6 and are fed into the liquid layer 3 by the rotation of the rotary drum 5 and the endless conveyor 7. 9
is an atomizer such as an ultrasonic humidifier installed outside the reaction tower 1, and the vaporized material generated by this atomizer is blown into the gas layer inside the reaction tower 1. The above is the configuration of this embodiment. Next, we will discuss its operation. First, the liquid layer 3 in the reaction tower 1 contains 25 sodium chlorite lO~40 g/min and a less ionized acidic acid. Or acetic acid 5~
10g#! : is added to obtain an acid-activated bleaching solution adjusted to p]13 to 4, and an appropriate percolation aid is added to this to obtain a sodium chlorite solution. Next, the inside of the reaction tower 1 was
The fabric 2 is introduced into the reaction tower 1 and led from the gas layer 4 to the liquid layer 3, and in the liquid layer 3, χ1 whitening is performed by acid activation.

However, when the acid in the gas layer 4 becomes insufficient during such bleaching treatment, the pH balance is disrupted, the chlorite gas becomes inactive, and cloudiness occurs in the gas layer 4. In this way, air layer 4
If the acid in the reaction column 1 is insufficient, the acid will be taken away from the fabric, resulting in defective bleaching.In order to prevent this defective bleaching, an acetic acid solution is converted to nitrogen in the gas layer 4 of the reaction tower 1, and the acid is removed from the fabric for 1 minute. It supplies about 3-10 g of acid.

In this way, by mixing an appropriate amount of exposed acidic liquid into the gas layer in the reaction tower during acid-activated bleaching of sodium chlorite, the acid in the gas layer will not be insufficient, and therefore a good condition will be achieved. The bleaching atmosphere can be maintained and a bleached fabric of good quality can be obtained.

In the above embodiment, an ultrasonic humidifier was used in the dewizer and I, but the invention is not limited to this.
A Jln device or the like may also be used. Further, the supply amount and supply timing of the exposed acidic liquid may be such that a fixed amount is supplied at regular intervals (17).
Alternatively, a cloudy state in the air layer may be detected by a sensor, and the supply may be performed automatically based on the detection signal.

[Effects of the Invention] As described above, the present invention provides a bleaching method in which acid-activated bleaching is carried out in a reaction tower using a sodium chlorite solution, in which an exposed acidic solution is added to the gas layer in the reaction tower. Since this bleaching method supplies acid sequentially, there is no shortage of acid in the gas layer in the reaction tower, so a good acid-activated bleaching atmosphere can be maintained at all times, resulting in high-quality bleached fabrics. There is an effect that can be obtained.

[Brief explanation of the drawing]

The drawing is an explanatory view showing a practical example of a bleaching apparatus applied to carry out the bleaching method of the present invention. 1... Reaction tower 2... Fabric 3... Liquid layer
4... Air layer 5... Rotating drum 6.
... Gap 7 ... Endless conveyor 8 ... Shaking and folding (and structure) 9 ... Atomizer.

Claims (1)

[Claims] 1. A bleaching method in which acid-activated bleaching is performed in a reaction tower using a sodium chlorite solution, characterized in that an atomized acidic liquid is sequentially supplied into a gas layer in the reaction tower. By bleaching method.