CN111535017B

CN111535017B - Method for natural fiber supercritical CO2 fluid flash explosion treatment

Info

Publication number: CN111535017B
Application number: CN202010463026.5A
Authority: CN
Inventors: 龙家杰; 蔡冲; 施楣梧
Original assignee: 苏州大学
Current assignee: Institute Of Quartermaster Engineering Technology Academy Of Systems Engineering Academy Of Military Sciences; Suzhou University
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2022-04-15
Anticipated expiration: 2040-05-27
Also published as: CN111535017A

Abstract

The invention discloses supercritical CO for natural fiber₂Method for fluid flash explosion treatment to substantially improve hydrophilicity of natural fiber and supercritical CO₂The dyeing property of (1). The technical scheme adopted by the invention is as follows: putting natural fiber into a fluid flash explosion processing unit, starting a pressure pump, and introducing a certain amount of steam into supercritical CO₂In the fluid flash explosion treatment system, a heating device is started to heat the system; when the system reaches the preset temperature and pressure, and the circulation treatment is carried out for a certain time, the pressure release valve is opened, the pressure is rapidly released, and the fluid flash explosion treatment is carried out on the fiber. The fluid flash explosion treatment technology provided by the invention utilizes the pressure difference generated inside and outside the fiber phase to promote the fiber chain segment to move, so that the internal pore diameter of the fiber is increased, the molecular hydrogen bond in the fiber is broken, the degree of freedom of fiber macromolecules is increased, the amorphous area is increased, the hydrophilicity of the fiber is improved, and the natural fiber can be obviously improved in supercritical CO₂Dyeability in a fluid medium.

Description

Method for natural fiber supercritical CO2 fluid flash explosion treatment

Technical Field

The invention relates to natural fiber and supercritical CO of a product thereof₂A fluid flash explosion treatment method belongs to the technical field of textile dyeing and finishing processing.

Background

As the largest textile export and producing countries in the world, the textile clothing and peripheral products account for more than 50% of the total production of China at present, and the huge export share also brings considerable economic benefits to China. Meanwhile, a large amount of water resources are wasted in the traditional textile industry, printing and dyeing wastewater with high COD value and high chromaticity is discharged, and the wastewater contains heavy metals, sulfur-containing compounds and organic auxiliaries which are not easy to degrade, so that the wastewater cannot be degraded by the traditional method, and huge pressure is caused on the ecological environment.

To break this situation, supercritical CO₂The (SCD) fluid replaces water as a dyeing medium, and has the advantages of short process flow, convenient operation and no industrial wastewater pollution, thereby thoroughly solving the problem caused by environmental pollution caused by textile processing. Supercritical CO₂Has partial gas property, low viscosity, high diffusion coefficient, small diffusion boundary, and shortened dyeing time. In addition, little or no dye auxiliary agent can be added in the dyeing process, so that the optimal utilization of resources is realized, and the ecological environment is protected.

Up to now, the dyeing process of synthetic fibers in supercritical fluids has reached commercial standards. However, most of natural fibers are hydrophilic fibers, the macromolecular chains of the natural fibers have strong hydrogen bonding effect, and the natural molecular chain segments have small interstitial size and low accessibility, so that the natural fibers are subjected to hydrophobic supercritical CO₂The staining properties in the fluid are poor. Therefore, the dye is prepared in supercritical CO by adopting a proper method₂It is important that natural cotton fibers are more readily dyed in the fluid.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the supercritical CO treatment method for natural fibers and products thereof, which is simple and convenient to operate, free from wastewater pollution and high in treatment efficiency₂The fluid flash explosion treatment method can effectively improve the dyeing performance without changing the excellent performance of the natural fiber.

The technical scheme for realizing the aim of the invention is that the natural fiber supercritical CO₂The fluid flash explosion treatment method comprises the following steps:

supercritical CO for natural fiber₂The method for fluid flash explosion treatment is characterized by comprising the following steps:

(1) placing natural fiber or a product thereof serving as a treatment sample in a steam treatment container, and performing moisture absorption weight increment pretreatment on the treatment sample by using steam under standard atmospheric pressure to control the water content of the treatment sample;

(2) filling the processed sample processed in the step (1) into a fluid flash explosion processing unit, and then connecting the flash explosion processing unit into supercritical CO₂In a flash explosion treatment system;

(3) linking CO₂Medium device to supercritical CO₂Quantitative CO is filled into the flash explosion treatment system₂Heating and raising temperature, and when the temperature and pressure in the system reach preset values, carrying out CO treatment on the sample₂Fluid circulation treatment;

(4) adjusting the temperature and pressure of the separation and recovery system to preset values according to the flash explosion process requirement, and realizing flash explosion with different temperature differences and pressure differences;

(5) opening a pressure release valve of the system, quickly or instantly releasing pressure according to the process, and carrying out flash explosion treatment on the treated sample;

(6) and starting a gas recovery pump of the separation and recovery system to recover the gas in the flash explosion system, and taking out the sample after the pressure is reduced to atmospheric pressure to complete the flash explosion treatment of the natural fiber or the product thereof.

The natural fiber or the product thereof comprises cotton, hemp, real silk and wool fibers, or yarns and fabrics of the cotton, the hemp, the real silk and the wool fibers.

In the technical scheme of the invention, the steam in the step (1) comprises saturated steam and superheated steam; the time of the moisture absorption and weight increase pretreatment in the step (1) is 1-30 min; and controlling the water content of the treated sample to be 1-300%.

In the step (2), when the sample is processed to be fiber, firstly, orderly and uniformly extruding and processing fluffy fiber layer by layer under the action of mechanical external force, and then flatly filling the fluffy fiber in a fluid flash explosion processing unit; when the processed sample is yarn, the yarn is orderly and uniformly wound under the action of mechanical external force and then uniformly and flatly wound in the fluid flash explosion processing unit; when the sample is a fabric, the fabric is firstly wound flatly, neatly and uniformly under the action of mechanical external force, and then is wound uniformly and flatly in the fluid flash explosion processing unit.

In the step (3), the preset value of the internal pressure of the system is 0.1-30 MPa; the preset temperature value inside the system is 90-180 ℃; said CO₂And (3) fluid circulation treatment, wherein the treatment time is 1-60 min, the treatment time comprises a fluid circulation state and a static state, and the time ratio of the fluid circulation state to the static state is 1: 5-10: 1.

The preset values of the temperature and the pressure of the separation and recovery system in the step (4) are respectively 0-120 ℃ and 0-25 MPa.

And (5) quickly or instantly relieving the pressure, wherein the pressure relief time is 1-40 s.

And (5) repeating the steps (3) to (5) and carrying out flash explosion treatment on the treated sample for multiple times.

In the invention, the natural fiber and the product thereof are tightly filled in a special flash explosion processing unit after being treated by steam, so that the natural fiber or the product thereof is uniformly distributed in the device; introducing CO₂Starting a temperature raising device to treat for a period of time; after finishing, the pressure is quickly released, the pressure difference caused in the moment enables the internal pore diameter of the natural fiber to be enlarged, hydrogen bonds among fiber molecules to be broken, the degree of freedom of fiber macromolecules to be increased, the amorphous area of the fiber to be increased, dye molecules can more easily enter the fiber molecules, and the supercritical CO (carbon monoxide) of the natural fiber or a product thereof is improved₂Staining properties in fluids. And the method has the advantages of convenient operation, simple process, short process flow, no wastewater pollution and high treatment efficiency.

The principle of the invention is as follows: by adopting a fluid flash explosion treatment method, hydrogen bonds among fiber molecules are broken or weakened, the degree of freedom of fiber macromolecules is increased, the pore diameter of a gap in the fiber is enlarged, and the amorphous area proportion of the fiber is increased; thereby leading dye molecules to enter the interior of the fiber more easily and promoting the dye to dye the fiber.

Compared with the prior art, the invention has the beneficial effects that: the method can effectively realize the treatment of the natural fiber or the product thereof and improve the treatment of the natural fiber or the product thereof in supercritical CO₂The dyeing performance of the fluid solves the problems of high energy consumption, high pollution, high emission, difficult dye recovery, difficult treatment and the like in the traditional water bath dyeing. Meanwhile, the method is simple and convenient to operate, can effectively realize the processing treatment of the natural fiber, does not change the excellent performance of the natural fiber, and improves the dyeing performance of the natural fiber.

Drawings

FIG. 1 is a schematic diagram of a fluid flash explosion treatment system according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional structural diagram of a fluid flash explosion processing unit according to an embodiment of the present invention.

In the figure: 1.CO₂A storage tank; 2. a stop valve; 3. a condenser; 4. a pressure pump; 5. a preheater; 6. a stop valve; 7. a dye dissolving unit; 8. filtrationA machine; 9. a stop valve; 10. a fluid flash explosion processing unit; 11. a stop valve; a shut-off valve; 12. a circulation pump; 12' a gas recovery pump; 13. a stop valve; 14. a stop valve; 15. a trim valve; 16. a thermometer; 17. a pressure gauge; 18. a separation kettle; 19. a thermometer; 20. a pressure gauge; 21, a purifier; CO 22₂A fluid and dye inlet; 23. a flash explosion stop valve; 24. a sample processing cartridge; a fluid outlet; 26. a quick-open structure; 27. a sealing cover; 28. a steam inlet; 29. an interface; 30. and (4) carrying out flash explosion on the fluid to process the unit cylinder.

Detailed Description

The technical scheme of the invention is further explained by combining the drawings and the embodiment.

Example 1

The fibers adopted by the embodiment of the invention are pure cotton short fibers, and the dry fibers are untreated before dyeing; the dye is supercritical CO₂Special active disperse yellow SCF-AY02 (self-made in laboratory).

Referring to fig. 1, it is a schematic structural diagram of a fluid flash explosion processing system according to an embodiment of the present invention; the fluid flash explosion treatment system comprises: a pressurization system, a dyeing circulation system and a separation and recovery system.

The pressurized system being CO₂The output port of the storage tank 1 is sequentially connected with a stop valve 2, a condenser 3, a booster pump 4, a preheater 5, a stop valve 6 and a stop valve 13 through pipelines, and then is connected with the inlet end of a fluid flash explosion processing unit 10 through a stop valve 14; the flash explosion port of the fluid flash explosion processing unit 10 is connected with a stop valve 11', the fluid outlet end of the fluid flash explosion processing unit 10 is connected with the stop valve 11, and dye and fluid enter a separation and recovery system and a dyeing circulation system; the top of the fluid flash explosion processing unit 10 is provided with a thermometer 16 and a pressure gauge 17.

The separation and recovery system comprises a stop valve 11, a fine adjustment valve 15, a gas recovery pump 12', a separation kettle 18 and a purifier 21 which are sequentially connected through pipelines, and then the separation and recovery system is recovered to the condenser 3.

The dyeing circulation system is characterized in that the output end of a dye dissolving unit 7 is sequentially connected with a filter 8 and a stop valve 9 through pipelines, and the stop valve 9 is connected with the inlet end of a fluid flash explosion processing unit 10 (a dyeing unit during dyeing processing) through a pipeline; during dyeing circulation, dye sequentially passes through the stop valve 11, the stop valve 14 and the stop valve 13 under the action of the circulating pump 12 and circularly enters the dye dissolving unit 7, and the top of the dye dissolving unit 7 is provided with a thermometer 19 and a pressure gauge 20.

Referring to fig. 2, it is a schematic cross-sectional structure diagram of the fluid flash explosion processing unit provided in this embodiment; the top of the cylinder body of the fluid flash explosion processing unit is provided with a sealing cover 27 which is connected through a quick-opening structure 26; CO2₂The fluid and dye inlet 22 is arranged at the bottom of the fluid flash explosion processing unit cylinder 30 and is communicated with a flash explosion stop valve 23, and CO is₂The fluid and dye inlet is connected with a central hollow pipe through an interface 29, a plurality of hollowed-out small holes are distributed on the central hollow pipe, the sample processing cylinder 24 is arranged in the fluid flash explosion processing unit cylinder, and the fluid outlet 25 and the steam inlet 28 are respectively provided with the upper part of the fluid flash explosion processing unit cylinder 30.

The fluid flash explosion treatment adopted by the embodiment comprises the following steps: the dry cotton fiber is mechanically compacted and filled in a sample processing cylinder 24 of a flash explosion processing unit with certain compactness, and CO is added₂The fluid and dye inlet 22 is connected to the top of the fluid flash explosion processing unit 10 through the interface 29, the steam is connected through the steam inlet 28, the sealing cover 27 is closed, and the fluid flash explosion processing unit 10 is sealed. Closing the stop valves 9 and 14 in the treatment system shown in FIG. 1, introducing a certain amount of steam, such as one or more of saturated steam and superheated steam, into the fluid flash explosion treatment unit 10 through the steam inlet and outlet 28, adjusting the opening degree of the stop valve 11' in the system, and flushing CO into the system₂(ii) a The fiber is treated for a certain time while maintaining a certain pressure in the treatment unit. The preset values of the temperature and the pressure of the separation and recovery system are respectively adjusted to be 0-120 ℃ and 0-25 MPa. And (3) quickly opening the flash explosion stop valve 23 at the medium outlet to release pressure, and ensuring that the time for releasing the pressure is not more than 40s to finish the fluid flash explosion treatment. After the treatment is finished, closing the medium

inlet stop valves

23, 11 and 11', opening the stop valve 9, and performing dyeing treatment by using the fluid flash explosion treatment unit 10 as a dyeing unit, wherein the dyeing treatment comprises the following steps: dissolved dye and CO are introduced into the interior₂A fluid. And starting the dyeing machine according to the preset dyeing process flow and parametersCO₂The pressurizing system consisting of the storage tank 1, the condenser 3, the pressurizing pump 4 and the preheater 5 pressurizes and preheats and heats the fluid of the dye circulating system, so that the dye in the dye dissolving unit 7 is fully dissolved. When the temperature of the dyeing circulation system reaches a preset temperature such as 130 ℃ and the pressure reaches a preset value such as 20Mpa, the pressure pump 4 stops pumping, the stop valve 6 is closed, the circulating pump 12 in the dyeing circulation loop is started, so that the dissolved dye circulates along with the fluid and is sufficiently dyed with the fiber to be dyed. The ratio of the fluid circulation time to the fluid static time in the dye-charging process is 10: 1. The dissolved dye is in full contact with the cotton fibers in the sample processing cylinder 24 through self molecular thermal motion and fluid mass transfer under static and cyclic conditions, and the processes of adsorption dyeing, diffusion and fixation are completed.

After the heat preservation and pressure maintaining dyeing is finished, a fine adjustment valve 15 is opened to release the pressure of the system, and the dye and the fluid in the dyeing circulation system are separated and recovered by using a separation and recovery system composed of a gas recovery pump 12', a separation kettle 18, a purifier 21, a condenser 3 and the like.

And after the fluid separation and recovery are finished, the operations are repeated again to perform online cleaning on the fibers, the temperature is 30-100 ℃, the pressure is 8-35 Mpa, the ratio of the dynamic circulation time to the static circulation time of the fluid is 1: 5-10: 1, and the cleaning time is 10-120 min. After the cleaning is finished, the gas and the dye are separated and recovered by using the pressure relief system, and the pressure in the dyeing unit reaches the atmospheric pressure. Finally, the fluid flash explosion treatment unit (dyeing unit) 10 is started, and the dyed fiber is taken out from the device.

The treatment steps and the process are adopted, the cotton fiber is dyed by the active disperse dye, and the analysis and test method is as follows:

1. determination of the color depth value of the fiber surface

Supercritical CO is measured by using Hunterlab Ultrascan PRO type spectrocolorimeter₂And (4) carrying out surface color depth value measurement on the fiber sample subjected to fluid flash explosion treatment. At the time of test, select D₆₅Light source, 10 degree visual angle, fiber uniform mixing sample preparation, random test of 8 points of each sample, and calculation of arithmetic mean value, the calculation mode is as shown in formula (1):

(1)

wherein i represents the ith test point (i =1,2,3, … …, n; where n = 8);

representing the surface color depth value of the ith test point at the maximum absorption wavelength;

represents the arithmetic mean of the surface color depth values at maximum absorption for the n test points.

2. Determination of Water Retention of fibers

According to textile industry standard FZ/T50040-2018. The short cotton fiber is tested for water retention rate, and whether the hydrophilic performance is changed after the short cotton fiber is treated is tested. The method comprises the following specific steps:

(1) and opening the cotton fibers subjected to fluid flash explosion to open the fiber curling bundles, wherein the whole cotton fibers are in a fluffy state for later use.

(2) And then 2g of flash explosion treatment fibers under different conditions are respectively taken for opening, and then the fibers are placed in the same environment for balancing for 24 hours, so that the moisture regain of the fibers is consistent, and the humidity regulation balance is achieved.

(3) Accurately weighing m of the fiber after humidity adjustment and balance₀(2.00. + -. 0.01) g, expressed as mass m of fibre₀(ii) a And putting the fiber into a prepared metal cylinder, wherein the cylinder specification is that the height (80 +/-1) mm and the diameter (50 +/-1) mm, and one end is sealed.

(4) Adding distilled water to the scale mark of a 2000 mL beaker, measuring the water temperature, and keeping the water temperature constant at (20 +/-2).

(5) And soaking the metal cylinder and the fibers in the metal cylinder in distilled water in a beaker, and starting timing when the sample is completely immersed. After 10min the immersed specimen was gripped with stainless steel forceps, taking care not to over-compress the fiber mass when the specimen was taken out.

(6) Placing the sample on a draining device, and allowing the sample to stand at constant temperature and pressureThe excess liquid was drained for (30. + -. 1) min. Putting the drained fibers into a glass dish, weighing the drained fibers by an electronic balance, and recording the weight as m₁To the nearest 0.001 g. The operation is as gentle and careful as possible, preventing unnecessary water loss.

(7) After each test is finished, the distilled water in the beaker is refilled to the scale mark by a dropper, and the volume and the temperature of the fiber soaking water are kept consistent each time. And repeating the steps, measuring each sample, and recording an accurate result.

(8) Mass m before infiltration of the fiber obtained in the above experimental steps₀And mass m after fiber infiltration and draining₁The water retention rate can be obtained by substituting the formula (2).

（2）

In the formula:W: water retention;m ₁: mass of the wetted and drained fibers in grams (g);m ₀refers to the mass in grams (g) before fiber infiltration.

The specific processing technology adopted by the embodiment is as follows:

weighing a proper amount of cotton fibers, pretreating the cotton fibers for 20min by using saturated steam, and controlling the moisture absorption and weight increment of the cotton fibers until the moisture content of the fibers reaches 100 percent. And taking out the cotton fiber after moisture absorption and weight increment, winding the cotton fiber on a special treatment shaft, and sealing the system. Starting booster pump to charge quantitative CO₂The pressure is 5 MPa. Simultaneously, the treatment system is heated to a temperature of 130 ℃ for the predetermined flash explosion treatment. When the temperature and pressure reached the set values, the circulation pump was started at a circulation ratio of 5:1 (static to dynamic processing time ratio of the fluid) and the fluid circulation processing time was 10 min. The preset values of the temperature and the pressure of the separation and recovery system are respectively adjusted to be 20 ℃ and 5 MPa. And then opening the pressure relief valve, and quickly relieving the pressure, wherein the pressure relief time is 8 s. After the treatment, 2g of fluid flash-blown cotton fiber was taken in supercritical CO₂Dyeing in fluid, dyeing processComprises the following steps: the dyeing pressure is 20MPa, the dyeing temperature is 120 ℃, the dyeing time is 60min, and the bath ratio is 1: 1000. after dyeing, the online cleaning temperature is 80 ℃, the pressure is 20Mpa, and the total cleaning time is 30 min. After the cleaning is finished, taking out the sample, and measuring the surface color depth value by using a spectrocolorimeter. Taking 2g of the treated fiber, placing the fiber in a water retention rate device, wetting the fiber according to the water retention rate determination step, and then determining the mass m of the wetted and drained fiber₁The water retention value was calculated according to the formula (2), and the results are shown in Table 1.

TABLE 1

。

Comparative example 1:

this example provides a blank comparative example of untreated cotton fibers 2g in supercritical CO₂The fluid was dyed in the same manner as in example 1. Taking 2g of the treated fiber, placing the fiber in a water retention rate device, wetting the fiber according to the water retention rate determination step, and then determining the mass m of the wetted and drained fiber₁And then calculating the water retention value according to the formula (2). The dyed surface color depth value (K/S) was 0.75, and the water retention of the treated sample was 49.2%. See table 2.

TABLE 2

。

Because steam is applied to the cotton fibers before the fluid flash explosion treatment process, the fibers can be swelled to a certain degree, so that the water vapor can permeate into the fibers, and the high-temperature and high-pressure water vapor and CO can be generated in the pressure relief flash explosion process₂The formed mixed fluid is released instantaneously in the gaps in the fibers, and the high-speed flow of the hot steam in the fibers causes mechanical bursting in the fibers to a certain degree, so that hydrogen bonds in molecules are destroyed, the acting force between the molecules is weakened, the gaps in the fibers are increased, and the pore diameter is increased. So that water molecules are easier to permeate into the fiber, and the absorption of the fiber is increasedThe water retention rate of the fiber after fluid flash explosion treatment is obviously improved from 49.2 percent to 79 percent after the water retention rate is measured.

Meanwhile, during the fluid flash explosion and puffing treatment process of the cotton fiber, water vapor and CO₂Fluid flows in the fiber, friction is generated between unit cells in cotton fiber molecules, so that the split of a crystalline region in the molecules is reduced, hydrogen bonds in the fiber are weakened, macromolecular chain segments in an amorphous region are rearranged, and the accessibility of the fiber is increased; high heat and high pressure steam and CO₂After the formed mixed fluid permeates into the fiber, the mixed fluid is released instantaneously from the closed pore while the pressure is released, so that the tightly piled structure in the cotton fiber is effectively loosened, and the pore diameter in the fiber is increased; meanwhile, a large amount of energy generated by fluid flash explosion treatment also greatly destroys intramolecular hydrogen bonds, and changes the arrangement of macromolecular chain segments in the fibers. Therefore, after the fluid flash explosion treatment, amorphous areas are increased and hydrogen bonds are broken, so that the dye is subjected to supercritical CO₂The fluid is more easily diffused into the fiber. After the fluid flash explosion treatment, the surface color depth value of the fiber is increased from 0.75 to 1.04.

Example 2:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are as follows: the flash explosion treatment temperature is 90 ℃, and the preset temperature and pressure values of the separation and recovery system are respectively 5 ℃ and 5 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 0.88 and a treated sample had a water retention of 64.4%. See table 3.

TABLE 3

。

Example 3:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are as follows: the flash explosion treatment temperature is 150 ℃, and the preset temperature and pressure values of the separation and recovery system are respectively 50 ℃ and 0.1 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 1.05 and a treated sample with a water retention of 80.9%. See table 4.

TABLE 4

。

From the test results of examples 2 and 3, it can be seen that the water retention was 64.4% at the treatment temperature of 90 ℃, 79.0% at the treatment temperature of 130 ℃ and 80.9% at the treatment temperature of 150 ℃. In the process of natural fiber flash explosion treatment, the effect of fluid flash explosion treatment is more obvious along with the rise of temperature. As the temperature is increased, the water absorption and retention capacity of the fiber is enhanced, so that the water retention rate of the fiber after flash explosion treatment is improved.

The surface color depth value of the fiber was 0.88 at a treatment temperature of 90 c, 1.04 at a treatment temperature of 130 c, and 1.05 at a treatment temperature of 150 c. The reason is that the higher the temperature is, the larger the molecular kinetic energy is, the more frequent the friction is generated between the molecular unit cells of the cotton fibers by the fluid, and simultaneously, the larger the energy released by flash explosion is, the more the amorphous area and the more obvious the macromolecular chain segment arrangement are after the flash explosion treatment of the mixed fluid, so that the amorphous area and the hydrogen bond of the fibers are increased, and the dye is broken in the supercritical CO₂The fluid is more easily diffused into the fiber. When the temperature is continuously increased from 130 ℃ to 150 ℃, the color depth value of the surface of the fiber is increased to a smaller extent. The treatment of the cotton fiber by the flash explosion of the mixed fluid can reach the critical point, the temperature is continuously raised, the increase of the pore diameter inside the fiber is small, and the increase of the color depth value on the surface of the fiber is small.

Example 4:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are as follows: the fluid circulation treatment time is 5min, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 100 ℃ and 5 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 0.73 and a treated sample with a water retention of 64.6%. See table 5.

TABLE 5

。

Example 5:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are as follows: the fluid circulation treatment time is 20min, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 5 ℃ and 10 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 1.01 and a treated sample had a water retention of 63.5%. See table 6.

TABLE 6

。

From the test results of example 1, example 4 and example 5, it can be seen that the water retention of the fluid flash cotton fiber is significantly increased with the increase of the treatment time when the fluid circulation treatment time is from 5min to 10 min. When the fluid circulation treatment time is from 10min to 20min, the water retention rate of the fluid flash cotton fiber is reduced along with the extension of the fluid circulation treatment time. When the range of 5min to 10min is changed, the water retention rate of the flash explosion fiber is obviously increased, more water is left in fiber gaps, and the fiber has better hydrophilic performance. The reason is that after the fluid flash explosion treatment, the pore diameter in the fiber is increased, so that water molecules are easier to permeate into the fiber. When the fluid circulation treatment time is extended from 10min to 20min, the expected effect may be worse as the longer the fluid circulation treatment time, the more water vapor is lost from the fiber voids into the fluid medium.

When the fluid circulation treatment time is from 5min toAnd when the dyeing time is 10min, the surface color depth value of the dyed fiber is obviously improved. When the fluid circulation treatment time is from 10min to 20min, the surface color depth value of the dyed fiber is reduced. During the high-pressure high-temperature treatment process of the fluid, water vapor contained in the cotton fibers can further fully permeate and diffuse into the fibers along with proper time, and the fibers are fully expanded. At the same time, CO is formed in the internal voids of the fibers₂The fluid and the water vapor mixed fluid are released instantly in the flash explosion process, and the fiber is mechanically expanded due to the violent expansion, so that hydrogen bonds in a cotton fiber macromolecular system are destroyed or weakened, and the pore diameter of each micro-gap in the fiber is increased. Thereby increasing the accessibility and dyeability of the fiber and leading the active disperse yellow SCF-AY02 dye to be in supercritical CO₂The fiber is easier to dye in the inner part, so the surface color depth value is improved. When the fluid circulation treatment time is from 10min to 20min, the surface color depth value of the fluid flash explosion fiber is reduced probably because the longer the fluid circulation treatment time is, the excessive water vapor is lost from the fiber gaps.

Example 6:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are changed as follows: the flash explosion time is 12s, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 5 ℃ and 1 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 1.01 and a treated sample had a water retention of 65.6%. See table 7.

TABLE 7

。

Example 7:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are changed as follows: the flash explosion time is 16s, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 30 ℃ and 15 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 0.97 and a treated sample with a water retention of 47.6%. See table 8.

TABLE 8

。

Example 8:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are changed as follows: the flash explosion time is 20s, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 5 ℃ and 5 MPa.

The cotton fibers treated according to the process of this example had a dyed surface color depth (K/S) of 0.93 and a treated sample had a water retention of 48.6%. See table 9.

TABLE 9

。

Example 9:

the embodiment provides a natural fiber fluid flash explosion treatment method, which comprises the following steps of referring to embodiment 1, wherein the specific process parameters are changed as follows: the flash explosion time is 24s, and the preset values of the temperature and the pressure of the separation and recovery system are respectively 5 ℃ and 10 MPa.

The cotton fibers treated according to the process of the example had a surface color depth (K/S) of 0.82 and the treated samples had a water retention of 48.3%. See table 10.

Watch 10

。

From the results of examples 6-9, it can be seen that the water retention rate of the fluid flash cotton fiber gradually decreases as the flash explosion time is increased from 8s to 16 s. In the fluid flash explosion treatment process, the mixed fluid formed in the fiber is slowly released due to the fact that the flash explosion time is prolonged, the expansion effect of the mixed fluid on the fiber is poor, the number of gaps inside the fiber and the pore diameter of the gaps inside the fiber are smaller, and the hydrophilic performance of the fiber is reduced. Therefore, the flash explosion time is prolonged, and the water retention rate of the fiber is reduced. When the flash explosion time is prolonged from 16s to 24s, the expansion effect caused by the fluid flash explosion treatment is small, so that the water retention rate of the fiber is basically maintained unchanged and is stabilized at about 45 percent.

When the flash-off time was extended from 8s to 24s, the surface color depth value of the dyed fiber decreased. In the process of fluid flash explosion treatment, the larger the instantaneous extrusion force of the mixed fluid on the fibers in the process of air release, the larger the released energy is, so that the hydrogen bonds among fiber molecules are broken or weakened, the degree of freedom of fiber macromolecules is increased, the pore diameter of the fibers is enlarged, and the amorphous area proportion of the fibers is increased. And the time of flash explosion is prolonged, so that the mixed fluid in the fiber is slowly released in the process of flash explosion, the effect of the fluid flash explosion on intermolecular hydrogen bonds is reduced, the freedom degree of macromolecules is reduced, the pore diameter of the internal gap of the fiber is reduced, meanwhile, the proportion of an amorphous area is reduced, the dye is not favorably fed into the fiber, and the color depth value of the flash-exploded surface of the fluid is reduced. Meanwhile, the water retention rate is also along with the extension of the flash explosion time, the expansion effect on the fiber is worsened, and the hydrophilicity of the fiber is reduced.

Claims

1. Supercritical CO for natural fiber₂The method for fluid flash explosion treatment is characterized by comprising the following steps:

(6) starting a gas recovery pump of the separation and recovery system, recovering the gas in the flash explosion system, and taking out a sample after the pressure is reduced to atmospheric pressure to complete the flash explosion treatment of the natural fiber or the product thereof;

in the step (3), the preset value of the internal pressure of the system is 0.1-30 MPa; the preset temperature value inside the system is 90-180 ℃;

CO described in step (3)₂Fluid circulation treatment is carried out, the treatment time is 1-60 min, the treatment time comprises a fluid circulation state and a static state, and the time ratio of the fluid circulation state to the static state is 1: 5-10: 1;

the preset values of the temperature and the pressure of the separation and recovery system in the step (4) are respectively 0-120 ℃ and 0-25 Mpa;

and (5) rapidly or instantly relieving pressure, wherein the flash explosion treatment time is 1-40 s.

2. The supercritical CO for natural fiber according to claim 1₂The fluid flash explosion treatment method is characterized by comprising the following steps: the natural fiber or the product thereof comprises cotton, hemp, real silk and wool fiber, or yarn and fabric products thereof.

3. The supercritical CO for natural fiber according to claim 1₂The fluid flash explosion treatment method is characterized by comprising the following steps: the steam in the step (1) comprises saturated steam and superheated steam.

4. The supercritical CO for natural fiber according to claim 1₂The fluid flash explosion treatment method is characterized by comprising the following steps: the time of the moisture absorption and weight increment pretreatment in the step (1) is 1-30 min; control processThe water content of the sample is 1-300%.

5. The supercritical CO for natural fiber according to claim 1₂The fluid flash explosion treatment method is characterized by comprising the following steps: in the step (2), when the sample is processed to be fiber, firstly, orderly and uniformly extruding and processing fluffy fiber layer by layer under the action of mechanical external force, and then flatly filling the fluffy fiber in a fluid flash explosion processing unit; when the processed sample is yarn, the yarn is orderly and uniformly wound under the action of mechanical external force and then uniformly and flatly wound in the fluid flash explosion processing unit; when the sample is a fabric, the fabric is firstly wound flatly, neatly and uniformly under the action of mechanical external force, and then is wound uniformly and flatly in the fluid flash explosion processing unit.

6. The supercritical CO for natural fiber according to claim 1₂The fluid flash explosion treatment method is characterized by comprising the following steps: and (5) repeating the steps (3) to (5) and carrying out flash explosion treatment on the treated sample for multiple times.