Application of ozone in washing water industry

 

I. Overview

 

1. Washing water is an important step in the finishing and processing of garments.

 

With the development of the times and the renewal of the trend, washing water, as a special process for the finishing of garments, will occupy a pivotal position in the future textile industry.

 

    Washing water is to use chemical additives, stones (rubber balls), etc. to wash the garments (cloths) in a drum to achieve clean, soft, faded, old and other purposes. In order to achieve a certain effect, the temperature, washing time, and the type and amount of chemical raw materials used can be changed to meet the requirements. After washing, the clothes will be improved in terms of hand feeling, color, visual effect and usability. At the same time, the laundry shrinks after washing, which makes it difficult to deform during use and maintains a relatively stable size. According to the additives used and the washing effect, our department can generally be divided into washing, stone washing, enzyme washing, enzyme stone washing, chemical washing, sand washing, snow washing, rinsing, whitening, etc. In addition, to obtain the above Comprehensive effect, different washing methods can be used comprehensively. As for the washing method used, it depends on the customer's requirements and the desired effect.

 

 2. Working principle:

 

    The ozone gas generated by the ozone generator is in full contact with the clothes in the drum in the machine to achieve the clothes disinfection, oxidation prevention, decolorization, color fixation, bleaching, patterning and other processes.

 

Ozone is a strong oxidizing gas with super decolorizing ability for all dyeing. Ozone can destroy the hair and auxochrome groups of these dyes to achieve the decolorization effect, but the effect of ozone on various organic dyes is different. It takes 5 minutes to decolorize 90% of basic dyes, and 5-10 minutes for direct dyes. In contrast, azo dyes are more susceptible to oxidation. The common basic composition in dyes is hydroxyazo pigments. When these compounds react with 03, firstly ozone and phenolphthalein, which is a hydroxyphenylmethane-based pigment, produces color and decoloration through the reversible opening and closing of the lactone ring, which can be used as an indicator. Alkaline phenolphthalein easily reacts with 03. Ozone undergoes a 1:3 addition reaction at the electron-rich C=C bond site, which can cut off the pigment skeleton and decolorize.

 

The application of ozone to decolorize denim clothing has been widely used in coastal areas, which can help companies greatly reduce operating costs, reduce the cost of original high-temperature steam decolorization, and improve corporate economic benefits. The equipment is simple to operate (just put the denim clothing into the decoloring special rotating machine, and rotate for 5-15 minutes to achieve the desired color effect), no secondary pollution, easy to decolor, and natural color.

 

Usually, customers need to remove the dye that is dyed on the inside of the jeans during the washing process, because it is very unreasonable for the dye to directly contact the skin, and it is also not environmentally friendly. Therefore, many chemicals are used to treat these dyes; At the same time, a series of problems have arisen, such as environmental pollution, poor working environment, and the impact on the personal safety of operators.

 

Now we can provide a completely sealed and safe environment, using ozone to treat jeans; the source of ozone is air, and after ozone is processed, it will return to the air. Generally, ozone will only exist in the air for 25 seconds. It is converted into oxygen, which is very environmentally friendly and very important to the human body and the environment. Moreover, the ozone-treated denim clothing has special visual effects, and it can also process all kinds of T-shirts;

 

    3. PH control

 

    Before ozone bleaching, it is necessary to add 1% sulfuric acid, sulfurous acid or other organic acids for acidification treatment, so that the pH of the pulp will be lowered to below 4 and it will be between 2.5-2.0, and it will reach acidified pulp. the goal of. It is to remove heavy metal ions and the interaction of O3 and OH- in the alkaline medium to produce OH- radicals, reduce the ineffective decomposition of ozone in bleaching, and facilitate the effects of ozone oxidation and bleaching.

 

    4. Ozone consumption

 

    Ozone single-stage bleaching is rarely used. One stage or 2-3 stage ozone bleaching can be used in multi-stage bleaching! After the ozone section, alkali treatment or clean water washing is carried out to remove the reaction products in time to reduce the consumption of bleach in the subsequent section. In order to improve the effect of ozone bleaching and reduce the degradation of carbohydrates by ozone, it is reasonable to use 0.5%-1% of ozone in each stage.

 

    5. Bleaching temperature and time

 

    Ozone has strong oxidizing ability and fast reaction speed. At the same time, ozone is not stable enough and is easily decomposed under the influence of temperature. Experiments have shown that at 0-10 degrees, the rate of ozone delignification and whiteness improvement is fast enough. At this time, the degradation rate of carbohydrates by ozone is relatively low, so ozone bleaching is usually carried out at room temperature, and the amount of ozone is 1 At about %, the bleaching reaction process can be completed in 5-20 minutes.

 

    6. The ozone bleaching section is in the position of multi-stage bleaching

 

    Ozone single-stage bleaching is difficult to obtain high whiteness. Excessive application of ozone in one stage will cause serious degradation of carbohydrates, resulting in yellowing after bleaching. Therefore, it should be combined with O, P, D and other bleaching stages in practical applications. Multi-stage bleaching. Considering the characteristics of ozone bleaching, the oxygen bleaching section should be used as much as possible before the ozone bleaching section. The kappa value of the pulp hardness when entering the ozone bleaching section should be less than 10, preferably controlled to 5-7, and then alkali treatment Therefore, it is recommended to use OZZP, OPZP, OZPZP and other bleaching processes. If you have fully delignified before bleaching or use grasses with lower lignin content, you can choose ZEP, ZPZP, ZOZD and other processes. In the multi-stage bleaching stage containing Z and P, the Q stage can be added, and the chelating agent is used to separate and remove heavy gold ions to utilize the delignification and bleaching following the Z and P stages.

 

In addition, ozone bleaching can increase the content of carboxyl groups in the fiber, increase the elasticity of the fiber, and increase the strength of certain mechanical pulps. These phenomena are rarely seen with other bleaching agents.

 

2. Matters needing attention in the use of ozone in the washing water industry

 

Ozone generators are used for air sterilization and surface sterilization in processing workshops and similar places in the water washing industry. So what should be paid attention to when using ozone disinfection machine?

 

    1. Impact on personnel

 

    Theoretical research divides the concentration and time of personnel exposure into several areas, such as asymptomatic stimulation area, symptomatic area, and temporary damage area. The research on the asymptomatic area is mature, the symptomatic area and the temporary damage area are less studied, and the damage area is only theoretical deduction. Asymptomatic zone is where people leave the place where ozone exists and return to the natural environment, the reaction produced will quickly disappear without damage. Asymptomatic areas can be summarized as follows:

 

    A. People with a sensitive sense of smell can detect it at 0.01ppm, ordinary people can smell it at 0.02ppm, and people with a slow sense of smell can feel it at 0.1 ppm. This concentration is completely harmless to personnel and makes people feel fresh. Generally, it can reach 0.1ppm in forest areas and 0.05ppm in seaside areas. In some cities, when the sun is full in summer, the concentration can reach 0.03-0.1ppm. According to the "Industrial Hygiene Standards" formulated by the Ministry of Health in 1979, the safety standard for ozone is 0.15 ppm. American standards stipulate that personnel can work for 8 hours at a concentration of 0.1 ppm. International Ozone Association standard regulations. Professional indoors where ozone is applied can work for 10 hours at a concentration of 0.1 ppm.

 

    B. The concentration to cause a certain reaction of personnel is 0.5-1ppm, and the allowable contact time is within 1.5 hours. After a long time, you will feel dry mouth and other discomfort.

 

    C. The concentration of 1-4ppm will cause people to cough, and the allowable contact time is 1 hour.

 

    D. The concentration of 4-10ppm will cause a strong cough, and the allowable contact time is 20 minutes.

 

    In addition, some data guides that under the environment of 0.098-0.98ppm ozone concentration, people will experience symptoms such as distress, heartache, and reduced lung capacity after one hour of exposure. Under 5.13-9.70ppm, the human body will experience general pain, paralysis, and cause pulmonary edema.

 

    2. Ensure the dryness of the washing water ozone generator gas

 

    Since the ionization of O2 uses high-voltage discharge, the gas must be absolutely dry, otherwise the discharge tube will be burned. Each time the machine is shut down for more than one week, the system must be purged for 1-2 hours before restarting. Never allow water to flow back to the generator or dryer, or let wet air enter the generator.

 

    3. Ensure the normal supply of cooling water for the water-cooled wash water ozone generator

 

    Cooling water is very important for the normal operation of the ozone generator. Suitable cooling water not only affects the output of O3, but also is a necessary condition for the normal operation of the generator.

 

    4. You must always pay attention to safety when using the ozone disinfector

 

    When ozone is used as a raw material gas, due to its characteristics of supporting combustion and accelerating combustion, if the ventilation is not good, the internal or external pipeline of the equipment leaks, or the oxygen system is opened, the oxygen concentration may rise to dangerous levels. Increased oxygen concentration increases the risk of fire. For this reason, open flames are particularly prohibited, oil cloths are not allowed, and equipment in contact with oxygen should not be in contact with oil and butter.

 

    5. Daily precautions for washing water ozone generator

 

①Machine facilities must be placed in a place where there is no oil, clean air and dry to extend the service life of the facilities.

 

② Be sure to handle with care when applying, and don't throw it out.

 

    ③Accurately purchase ozone generators according to the disinfection environment and application requirements.

 

    ④It is forbidden to put the ozone generator in the disinfection area. For the safety of the machine's life, the facility should have its own working area, and then use the silicone tube to transport the ozone gas to the disinfection or chemical reaction area.

 

    ⑤Machine facilities must be inspected and protected every day; if they are found to be abnormal, they should be shut down immediately, the reason should be found out, and the equipment should be used after handling.

 

    ⑥ The equipment and facilities must be well grounded before application to prevent lightning. Unplug the power plug when not necessary.

 

    ⑦If the machine facilities are for a long time, it is not necessary to clean the inside and the casing of the machine, and place it in a ventilated and dry place. Avoid damp damage.

 

    ⑧ In order to prevent the machine from being damp and to better protect the facilities, turn on the "Air Pump Switch" or "Air Control Switch" every week; turn off the "Concentration Reconciliation" or "Ozone Switch" and work for more than three hours to clean the moisture inside the machine.