Continuous bleaching machine and continuous bleaching process

Abstract

The invention discloses a continuous bleaching machine which is characterized by sequentially comprising a cloth feeding unit, a first squeezing unit, an acid rolling unit, a second squeezing unit, a sodium chlorite dipping tank, a cooking box, a neutralizing tank, a washing unit group and a cloth discharging unit, and fabric continuously flows from front to back among the units in an open-width state. A bleaching process adopting continuous under-liquid boiling-off is characterized in that a fabric is soaked and boiled-off in a high-temperature sodium chlorite liquid after being padded in an acid liquid, a strong bleaching effect is presented through the principle that chromophoric groups or chemical bonds are irreversibly damaged through chemical oxidation, and compared with hydrogen peroxide steaming bleaching, the whiteness can reach 85% or above; meanwhile, the whiteness durability is better, and the strength loss is lower.

Description

Technical Field

[0001] The invention belongs to the technical field of printing and dyeing, and in particular relates to a continuous bleaching machine and a continuous bleaching process. Background Art

[0002] Traditional continuous cotton fabric production typically uses hydrogen peroxide steaming or sodium hypochlorite bleaching at room temperature. The whiteness of cotton fabrics bleached with hydrogen peroxide steaming typically reaches around 80%. Higher demands require increasing the concentration of additives, which leads to greater strength loss and a sharp increase in the risk of holes. Alternatively, rebleaching, i.e., padding and steaming the fabric again, can be performed, which of course increases costs. Another option uses sodium hypochlorite as an oxidant, achieving a whiteness of around 75% using a low-cost room-temperature padding and stacking method, which is also widely used in the dyeing and finishing industry. The common drawback of these processes is that whiteness is insufficiently high, or, when demand is high, the process must be repeated, significantly increasing costs. Summary of the Invention

[0003] The present invention aims to provide a continuous bleaching machine and a continuous bleaching process that can achieve mild bleaching with a strong oxidant and give full play to the strong oxidizing effect of sodium chlorite in order to address the defects of the prior art.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A continuous bleaching machine is characterized in that it comprises a cloth feeding unit, a first water squeezing unit, an acid squeezing unit, a second water squeezing unit, a sodium chlorite impregnation tank, a cooking box, a neutralization tank, a water washing unit group, and a cloth discharging unit in sequence, and the fabric flows from front to back between the above devices.

[0005] The invention is further characterized in that the fabric feeding unit includes a fabric unwinding buffer box; the large fabric package falls into the fabric unwinding buffer box after passing through the fabric tensioner and the pulling roller group. The large fabric package is briefly stacked in the box to release stress and return to a relaxed state.

[0006] Its further characteristics are: the first water squeezing unit includes a water squeezing tank and a padder in sequence; the acid squeezing unit includes an acid liquid immersion tank and an acid liquid padder in sequence; the second water squeezing unit includes a pickling tank and a padder in sequence; the water washing unit group includes three water washing tanks and padders arranged at intervals behind the water washing tanks.

[0007] Furthermore: a water replenishing device is provided above the water squeezing tank; an acid injection device is provided above the acid solution immersion tank; and a water replenishing device is provided above the pickling tank.

[0008] Preferably, the steaming box is sequentially equipped with a steam jet pipe, a guide roller assembly, a pulling roller, a fabric swing frame, a limit plate, an upper mesh belt, a lower mesh belt, a fabric discharge beater roller, a fabric discharge spreader guide roller assembly, a fabric discharge closure, a fabric discharge overhead drive roller, and a fabric discharge nip water seal groove. A stacking area is located between the upper and lower mesh belts. The fabric enters the steaming box and is heated by steam jets from the steam jet pipe in the guide roller area. After being manipulated by the fabric swing frame, it is folded into a stack between the upper and lower mesh belts. Once stacked, the fabric, held between the upper and lower mesh belts, slowly passes through the submerged scouring area in the stacking area, then through the mesh belt's water-draining section before being pulled out by the fabric discharge roller area. The fabric discharge beater rollers and fabric discharge spreader guide roller assembly in the fabric discharge roller area ensure full expansion of the stacked fabric during the transition from submerged loose stacking to tight draw. A fabric discharge nip water seal groove in the fabric discharge roller area prevents chemical vapors from the steaming area from escaping the fabric discharge outlet. A nip is located after the water seal to reduce water loss in the fabric discharge belt.

[0009] Preferably, a caustic soda dispensing tank is provided above the neutralization tank for dispensing a corresponding amount of caustic soda according to the residual acid content of the fabric.

[0010] Furthermore: the cloth discharging unit includes a cloth discharging rack, a cloth inlet traction roller group, a cloth stacking box, a cloth tensioner, a traction roller, and a winding rack in sequence.

[0011] A continuous bleaching process using the above-mentioned continuous bleaching machine is characterized by comprising the following steps: (1) After the fabric is fed into the fabric feeding unit, it is first immersed in water and squeezed in the first squeezing unit to stabilize the water content of the fabric; (2) The fabric is then acidified with formic acid or acetic acid in an acid-rolling unit to obtain a certain residual rate of acid; (3) After the fabric is acid-pressed, it is washed and squeezed in the second squeezing unit to maintain a certain acidity of the fabric; (4) Sodium chlorite is dipped into a sodium chlorite dipping tank to fully impregnate the fabric inside and outside with the liquid; (5) The fabric enters the cooking box and is heated to 60-80℃ by steam jet in the guide roller area, then folded into a pile and placed in the mesh belt stacking area; it slowly passes through the scouring area under the clamping of the upper and lower mesh belts, and then is filtered and discharged; (6) The steamed fabric is neutralized with caustic soda or weak alkali in the subsequent neutralization tank, and then washed multiple times in the washing unit group, and then discharged through the cloth discharging unit to complete the bleaching process.

[0012] In order to give full play to the strong oxidizing effect of sodium chlorite, it is first immersed in formic acid or acetic acid before soaking to generate chlorine dioxide in an acidic environment: 5NaClO2 +4H + →4ClO2 +NaCl+2H2O The generated ClO2 is a strong oxidizing substance that can effectively destroy the molecular structure of pigments and impurities (such as lignin and pectin) to achieve the purpose of bleaching.

[0013] Padding acid can remove the remaining metal particles in the fabric to prevent the subsequent strong oxidation process from causing additional fabric strength reduction or even holes.

[0014] Since some fabrics may shrink or swell violently during the underwater stacking process, a steam injection pipe is set up to directly spray steam on the fabrics before stacking to complete the pre-heating of the fabrics.

[0015] Preferably, the pH value of formic acid or acetic acid in step (2) is 3-3.5; the concentration of sodium chlorite solution in step (4) is 5-20 g / L, the temperature is 70-80° C., and the stacking time in the sodium chlorite immersion tank is 30-60 min; and in step (5), the fabric is immersed in the scouring area for 30-60 min.

[0016] The continuous bleaching machine of the present invention corresponds to a continuous bleaching process. The fabric undergoes a single wash and squeeze drying followed by acid squeezing, followed by sodium chlorite bleaching. The fabric is then steamed, neutralized, and washed before being discharged. The acid squeezing followed by soaking and scouring in a high-temperature sodium chlorite solution irreversibly destroys chromophore groups or chemical bonds through chemical oxidation, resulting in a stronger bleaching effect. Compared to hydrogen peroxide steam bleaching, this method achieves better whiteness and lower strength loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0018] like Figure 1 As shown, a continuous bleaching machine includes a cloth feeding unit 1, a first water squeezing unit, an acid squeezing unit, a second water squeezing unit, a sodium chlorite impregnation tank 8, a cooking box 9, a centering machine 10, a neutralization tank 11, a washing unit group, and a cloth discharging unit. The fabric flows between the above devices.

[0019] The fabric feed unit 1 includes a fabric tensioner 1-1, a pull-up roller assembly 1-2, an unwinding buffer box 1-3, a pneumatic fabric tensioner 1-4, and a delivery pull-up roller 1-5. After passing through the fabric tensioner 1-1 and the pull-up roller assembly 1-2, the large fabric package falls into the unwinding buffer box 1-3. Within the box, the large fabric package is briefly stacked to release stress and return to a relaxed state. It is then delivered to the first squeeze unit via the pneumatic fabric tensioner 1-4 and the delivery pull-up roller 1-5.

[0020] The first squeezing unit consists of a squeezing trough 2 and a padder 3. A water replenishment device 2-1 is located above the squeezing trough 2. After leaving the fabric inlet unit 1, the fabric enters the squeezing trough 2 and padder 3 to be immersed in soft water, ensuring a relatively uniform amount of water in the fabric from front to back and from left to right. The water replenishment device 2-1 maintains the water level during this process, and the squeezing rollers use a fixed roller structure to ensure uniform water in the fabric from front to back and from left to right.

[0021] The acid rolling unit comprises an acid dipping tank 4 and an acid rolling car 5. An acid injection device 4-1 is provided above the acid dipping tank.

[0022] The second water-washing unit comprises a pickling tank 6 and a padder 7. A water replenishment device 6-1 is provided above the pickling tank 6. The fabric passing through the pickling tank 6 maintains a certain acidity, allowing the subsequent padding with sodium chlorite to fully release chlorine dioxide.

[0023] The sodium chlorite impregnation tank 8 is made of titanium to meet the requirements of sodium chlorite additives. It is equipped with a sodium chlorite injection device 8-1, which adds sodium chlorite in proportion to the amount of fabric passing through. The fabric, still in its open width, is then dipped in sodium chlorite and passed into the cooking box 9.

[0024] The steaming box 9 is made of titanium, ensuring its durability even under prolonged exposure to high-temperature sodium chlorite. Inside the steaming box 9, there are, in order, steam injection pipes 9-1, a guide roller assembly 9-2, traction rollers 9-3, a fabric swing frame 9-4, a limit plate 9-6, an upper mesh belt 9-7, a lower mesh belt 9-9, a fabric outlet beating roller 9-10, a fabric outlet spreading guide roller assembly 9-11, a fabric outlet sealing cover 9-12, a fabric outlet overhead drive roller 9-13, and a fabric outlet nip water seal 9-14. A stacking area 9-8 is located between the upper mesh belt 9-7 and the lower mesh belt 9-8. After the fabric enters the steaming box 9 and is heated by steam from the steam injection pipe 9-1 in the guide roller area, it is manipulated by the fabric swing frame 9-4 and then folded into a stacking area 9-8 between the upper mesh belt 9-7 and the lower mesh belt 9-9. After being deposited, the fabric is held between the upper mesh belt 9-7 and the lower mesh belt 9-9 and slowly passed through the stacking area 9-8 for underwater scouring. After passing through the mesh belt's drainage section, the fabric is pulled out of the fabric discharge roller area. The fabric beater rollers 9-10 and the fabric spreading guide roller assembly 9-11 in the fabric discharge roller area ensure full expansion of the fabric during the transition from underwater loosening to tight pulling. The fabric nip water seal 9-14 in the fabric discharge roller area prevents chemical vapors from the cooking zone from escaping at the fabric discharge outlet; a nip is located after the water seal to reduce water loss in the fabric discharge belt. A centering machine 10 is used to center the fabric passing through the cooking box 9 and deliver it to the neutralization tank 11. At both the inlet and outlet of the cooking box 9, an induced draft fan is installed to extract the additive vapors to an outdoor recovery facility.

[0025] A caustic soda dosing tank 11-1 is provided above the neutralization tank 11 for dispensing the corresponding amount of caustic soda according to the residual acid content of the fabric. A padder 12 is provided at the rear of the neutralization tank 11.

[0026] The water washing unit group includes, in sequence, a first water washing tank 13, a padder 14, a second water washing tank 15, a padder 16, a third water washing tank 17, and a heavy-duty padder 18. A spray device 15-1 is provided above the second water washing tank 15.

[0027] The cloth discharging unit 19 includes a cloth discharging frame, a cloth inlet traction roller group 19-1, a cloth stacking box 19-2, a cloth tensioner 19-3, a traction roller 19-4, and a winding frame 19-5 in sequence.

[0028] A continuous bleaching process using the above-mentioned continuous bleaching machine is characterized by comprising the following steps: (1) After the fabric is fed into the fabric feeding unit 1, it is first immersed in water and squeezed dry in the first squeezing unit to stabilize the water content of the fabric.

[0029] (2) The fabric is then dipped in formic acid or acetic acid in an acid rolling unit so that the fabric is acidified at a certain rolling rate, and the pH value of the acid or acetic acid is 3-3.5.

[0030] (3) After the fabric is acid-pressed, it is washed and squeezed in the second squeezing unit to maintain a certain acidity of the fabric.

[0031] (4) Sodium chlorite is immersed in a sodium chlorite immersion tank so that the inside and outside of the fabric are fully immersed in the liquid material; the concentration of the sodium chlorite solution is 5-20g / L, the temperature is 70-80℃, and the stacking time in the sodium chlorite immersion tank is 30-60min.

[0032] (5) The fabric enters the cooking box and is heated to 60-80℃ by steam jet in the guide roller area, and then folded into a pile in the mesh belt stacking area; under the clamping of the upper and lower mesh belts, it slowly passes through the liquid scouring area and is filtered before being discharged.

[0033] (6) The steamed fabric is neutralized with caustic soda or weak alkali in the subsequent neutralization tank, and then washed multiple times in the washing unit group, and then discharged through the cloth discharging unit to complete the bleaching process.

[0034] In order to give full play to the strong oxidizing effect of sodium chlorite, it is first immersed in formic acid or acetic acid before soaking to generate chlorine dioxide in an acidic environment: 5NaClO2 +4H + →4ClO2 +NaCl+2H2O The generated ClO2 is a strong oxidizing substance that can effectively destroy the molecular structure of pigments and impurities (such as lignin and pectin) to achieve the purpose of bleaching.

[0035] Padding acid can remove the remaining metal particles in the fabric to prevent the subsequent strong oxidation process from causing additional fabric strength reduction or even holes.

[0036] Since some fabrics may shrink or swell violently during the underwater stacking process, a steam injection pipe is set up to directly spray steam on the fabrics before stacking to complete the pre-heating of the fabrics.

[0037] The fabric is dipped in acid and then scour with high-temperature sodium chlorite solution. The chromogenic groups or chemical bonds are irreversibly destroyed through chemical oxidation, resulting in a stronger bleaching effect. Compared with hydrogen peroxide steam bleaching, the whiteness can reach more than 85%, and it has the advantage of lower strength loss.

Claims

1. A continuous bleaching machine, characterized in that: It comprises in sequence a cloth feeding unit (1), a first water squeezing unit, an acid squeezing unit, a second water squeezing unit, a sodium chlorite impregnation tank (8), a cooking box (9), a neutralization tank (11), a washing unit group, and a cloth discharging unit, and the fabric flows between the above devices.

2. The continuous bleaching machine according to claim 1, characterized in that: The fabric feeding unit (1) comprises an unwinding buffer box (1-3); the large-package fabric falls into the unwinding buffer box (1-3) after passing through the fabric tightening device (1-1) and the traction roller group (1-2).

3. The continuous bleaching machine according to claim 1, characterized in that: The first water squeezing unit includes a water squeezing tank (2) and a padder (3) in sequence; the acid squeezing unit includes an acid solution immersion tank (4) and an acid solution padder (5) in sequence; the second water squeezing unit includes a pickling tank (6) and a padder (7) in sequence; and the water washing unit group includes three water washing tanks and padders arranged at intervals at the rear of the water washing tanks.

4. The continuous bleaching machine according to claim 3, characterized in that: A water replenishing device (2-1) is provided above the water squeezing tank (2); an acid injection device (4-1) is provided above the acid solution immersion tank (4); and a water replenishing device (6-1) is provided above the pickling tank (6).

5. The continuous bleaching machine according to claim 1, characterized in that: The cooking box (9) is provided with a steam injection pipe (9-1), a guide roller group (9-2), a traction roller (9-3), a cloth swing frame (9-4), a limit plate (9-6), an upper mesh belt (9-7), a lower mesh belt (9-9), a cloth discharging beating roller (9-10), a cloth discharging width guide roller group (9-11), a cloth discharging sealing cover (9-12), a cloth discharging top transmission roller (9-13), and a cloth discharging nip water seal groove (9-14) in sequence; a stacking area is provided between the upper mesh belt (9-7) and the lower mesh belt (9-9).

6. The continuous bleaching machine according to claim 1, characterized in that: A caustic soda batching tank (11-1) is provided above the neutralization tank (11).

7. The continuous bleaching machine according to claim 1, characterized in that: The cloth discharging unit comprises, in sequence, a cloth discharging frame (9), a cloth inlet traction roller group (19-1), a cloth stacking box (19-2), a cloth tightening device (19-3), a traction roller (19-4), and a winding frame (19-5).

8. A continuous bleaching process using the continuous bleaching machine according to any one of claims 1 to 8, characterized in that The steps include: (1) After the fabric is fed into the fabric feeding unit, it is first immersed in water and squeezed in the first squeezing unit to stabilize the water content of the fabric; (2) The fabric is then acidified with formic acid or acetic acid in an acid-rolling unit to obtain a certain residual rate of acid; (3) After the fabric is acid-pressed, it is washed and squeezed in the second squeezing unit to maintain a certain acidity of the fabric; (4) Sodium chlorite is dipped into a sodium chlorite dipping tank to fully impregnate the fabric inside and outside with the liquid; (5) The fabric enters the cooking box and is heated to 60-80℃ by steam jet in the guide roller area, then folded into a pile and placed in the mesh belt stacking area; it slowly passes through the scouring area under the clamping of the upper and lower mesh belts, and then is filtered and discharged; (6) The steamed fabric is neutralized with caustic soda or weak alkali in the subsequent neutralization tank, and then washed multiple times in the washing unit group, and then discharged through the cloth discharging unit to complete the bleaching process.

9. The continuous bleaching process according to claim 8, wherein: In step (2), the pH value of formic acid or acetic acid is 3-3.5; in step (4), the concentration of sodium chlorite solution is 5-20 g / L, the temperature is 70-80° C., and the stacking time in the sodium chlorite immersion tank is 30-60 min; in step (5), the fabric is immersed in the scouring area for 30-60 min.

Images