CN115772810A - Biological modifier, preparation method thereof and method for applying biological modifier to indigo dyeing - Google Patents

Abstract

The application provides a biological modifier, a preparation method thereof and a method for applying the biological modifier to indigo dyeing, and belongs to the technical field of dyeing textiles by using vat dyes. 30-50 parts of monosaccharide compounds, 10-30 parts of alkaloid compounds, 5-15 parts of natural polyphenol compounds, 3-10 parts of metal salt compounds and the balance of deionized water. The prepared biological modifier is used for dyeing the indigo dye, can endow the indigo dye with high solarization, and greatly improves the photooxidation fading phenomenon of dyed cotton fabrics.

Description

Biological modifier, preparation method thereof and method for applying biological modifier to indigo dyeing

Technical Field

The application relates to a biological modifier, a preparation method thereof and a method for applying the biological modifier to indigo dyeing, and belongs to the technical field of dyeing textiles by using vat dyes.

Background

When the plant indigo dye dyed fabric is taken, if the fabric is in the air for a long time, yellowing phenomena can occur, the yellowing of some folded parts is more obvious, and even large-area fading occurs, so that the use of consumers is seriously influenced. At present, according to the existing research, firstly, the plant indigo dye has the characteristic of no oxidation and yellowing resistance, and can be decomposed into isatin (indoline dione) yellow, tannic acid and a combination of the isatin yellow and the tannic acid under the action of ozone and light, so that the fabric is yellowed; secondly, when the plant indigo dye absorbs light energy and is excited to a triplet state, the plant indigo dye can react with oxygen molecules to generate singlet oxygen molecules, and the oxidation property is strong, so that the dye structure can be damaged; under the action of light, when oxygen molecules contact with the dye, oxygen anion free radicals can also be generated and react with the dye, so that the fabric is faded.

In addition, the wet friction fastness of cotton fabrics dyed by the plant indigo dye is low, especially under the condition of dark color, the main reasons are that the affinity of the indigo dye and the cotton fabrics is low, the initial dyeing rate is high, the permeability is poor, and the dye is mostly gathered on the surface of the fiber, so that the wet friction fastness of the fabrics is low. The prior literature is mostly concerned with dyeing with cationic or positively charged modifications to improve the color fastness of fabrics, as in the following patents:

CN111893781A provides an application process of indigo dyed yarn, simplifies the dyeing process and improves the dyeing efficiency.

CN113981720A utilizes synthetic antibacterial modifier to modify cotton yarn, thereby improving dye uptake of indigo dyeing and endowing cotton yarn with antibacterial property.

CN113308913A develops a synthetic antibacterial modifier (chitosan-polyacrylamide type), which effectively improves the dye uptake and antibacterial property of indigo dyed fiber.

CN111074657A utilizes synthetic cation modifier to pre-modify cotton yarn, has simplified the dyeing process simultaneously, has effectively promoted the amount of getting the look of indigo on cotton yarn.

In order to solve the problems of low dye uptake, poor uniformity and poor color fastness of indigo dyeing, the fiber or yarn is pre-modified by adopting a cation modifier in chemical synthesis, so that the dyeing property of the fiber or yarn is improved, and the method does not accord with the ecological environment-friendly low-carbon concept advocated at present.

Disclosure of Invention

In view of the above, the present application first provides a biological modifier, which is used to solve the problem that a plant indigo dye-dyed fabric is easy to yellow and fade in air or under illumination, and effectively improve the photooxidation fading problem of the dyed fabric.

Specifically, the method is realized through the following scheme:

a biological modifier comprises the following components:

monosaccharide compounds: 30-50 parts of (by weight),

alkaloid compounds: 10-30 parts of (by weight),

natural polyphenols: 5-15 parts of (A) a stabilizer,

metal salt compound: 3-10 parts of (A) a water-soluble polymer,

the balance being deionized water.

In the biological modifier, the main function of the alkaloid compound is to catalyze the monosaccharide compound to generate a hydrolysis ring-opening reaction to generate a polyhydroxy aldehyde compound; secondly, the alkaline environment required by the solution is maintained, and the full reduction of the dye liquor is ensured. After the monosaccharide compound is dissolved in water, a hydrolytic ring-opening reaction is carried out under the alkaline environment to generate a compound with polyhydroxy aldehyde at the tail end, so that the solution has a reduction effect, the indigo molecule is promoted to be converted into a soluble indigo leuco acid compound, and the fiber is conveniently dyed; the natural polyphenol substances have affinity and anti-oxidation characteristics to cellulose fibers, can effectively prevent oxygen from participating in degradation reaction of indigo molecules, and protect the dyeing promotion effect of monosaccharide compounds, so that the photooxidation fading phenomenon of indigo dyed fabrics is reduced; the metal salt compound mainly provides coordination, and on one hand, the coordination effectively connects the polyhydroxy group of the cellulose fiber with the polyphenol compound and the indigo leuco acid sodium salt to form a firm aggregate; on the other hand, the structure of fiber, indigo and metal ions is formed, the energy of light can be absorbed to a certain extent, and the damage of illumination to the indigo dye is reduced by matching with natural polyphenols.

Further, as preferable:

the monosaccharide compound is any one or a mixture of more of glucose, mannose, xylose, galactose and the like.

The alkaloid compound is one or mixture of theophylline and berberine.

The natural polyphenol compound is any one or more of pomegranate peel extract, tea leaf extract, gallnut extract, tea fruit shell extract, myrobalan extract or walnut peel.

The metal salt compound is any one of aluminum potassium sulfate, ferrous sulfate, sodium sulfate or copper sulfate or a mixture of the aluminum potassium sulfate, the ferrous sulfate, the sodium sulfate and the copper sulfate.

Meanwhile, the applicant also provides a preparation method of the biological modifier, which comprises the following steps:

(1) The monosaccharide compound, the alkaloid compound and the deionized water are stirred and react for 30 to 60 minutes in a water bath at the temperature of between 55 and 65 ℃;

(2) Accurately weighing a certain amount of natural polyphenol compound powder, dissolving the natural polyphenol compound powder into a slurry solution by using a small amount of deionized water, adding water for diluting, and fully and uniformly stirring;

(3) And (3) transferring the solution diluted in the step (2) into the step (1), fully stirring for standby, adding the metal salt compound dissolved in the deionized water, and uniformly stirring.

The third aspect of the applicant aims to provide a method for applying the biological modifier to indigo dyed cellulosic fiber fabrics, which comprises the following specific process flows:

(1) Pre-reduction of dye liquor: fully dissolving the plant indigo powder, the biological modifier and deionized water in a water bath at 50-55 ℃ according to a certain proportion, uniformly stirring, and adjusting the pH value of the solution to 10.5-11.5 and the reduction potential to-800 mV-700 mV to obtain the pre-reduced plant indigo dye solution. When the pH value of the solution is 10.5-11.5 and the reduction potential is-800 mV-700 mV, the monophenol sodium salt indigo leuco body content in the solution is higher, the dye-uptake to fiber is high, and the color fastness is good.

(2) Pretreatment: winding the pure cotton fabric to be treated on a roller of a jig dyeing machine, feeding clean water at a bath ratio of 1-15, and running for 15-20 times at normal temperature, so that the solution and the cloth cover are always in an alkaline environment.

(3) Dyeing: adding the plant indigo dye solution pre-reduced in the step (1) into a jig dyeing machine in a plurality of times, wherein the proportion of adding the plant indigo dye solution pre-reduced each time is 20-40%, and adding the plant indigo dye solution for 3-4 times; the basic parameters are set as follows: the dyeing temperature is 25-35 ℃, the dyeing time is 45-60 minutes, and the running speed is 10-15 circles/minute.

(4) And (3) oxidation: after the fabric is rolled on a roller, the dye liquor in the cylinder is fully drained, clear water is added, a certain amount of hydrogen peroxide solution is added, the operation is continued for 10-15 minutes, and the fabric is fully oxidized.

(5) Washing with water: one-time washing, 10-15 min-one-time soaping, heating to 80 ℃, processing for 20-30 min-one-time washing, 5-10 min-two-time acid washing, 5-10 min-one-time washing, 5-10 min-taking out and drying. In the soaping process of the plant indigo dyed cotton fabric, dye particles which are not combined on the surface of the fabric are stripped into a solution, and combined indigo dye aggregates form a more stable fiber-dye combination under the double actions of high temperature and a soap solution.

Further, as preferable:

in the step (1), the mass ratio of the plant indigo powder to the biological modifier to the deionized water is 3.

In the step (3), before the plant indigo dye solution is added, a certain amount of biological modifier is added into the clear water to carry out pre-modification treatment on the fabric, which is beneficial to improving the K/S value of the fabric.

In the step (3), a certain amount of biological modifier is supplemented every 20-30 minutes after the pre-reduced plant indigo dye solution is added. The reason and purpose of supplementing the biological modifier are: in the dyeing process, the form of the plant indigo dye is gradually changed from the form of high-dyeability monophenol sodium salt to the form of low-dyed bisphenol sodium salt along with the increase of the dyeing time; the biological modifier is supplemented every 20 minutes, so that the pH value of the dye solution is always 11, the reduction potential is always-750 mV, and the content of monophenol sodium salt form dye in the dye solution is favorably maintained.

The invention has the beneficial effects that: the invention starts from the preparation of the biological modifier, the basic components of the biological modifier are all environment-friendly natural components, and the alkaloid-monosaccharide reduction system is used for replacing a caustic soda-sodium hydrosulfite reduction system, so that the harm to the environment is greatly reduced; the natural polyphenol compounds and the metal salt compounds are introduced into an indigo dyeing system, and the natural antioxidant property of the polyphenol compounds and the coordination effect of metal ions are utilized to form polyphenol compounds-dye molecules-metal ions-fiber molecule structures, so that the photooxidation fading phenomenon of dyed cotton fabrics is greatly improved.

Detailed Description

Example 1

In this example, the components (mass percentage) in the biological modifier were subjected to a screening test, as shown in Table 1.

Table 1:

note: in the table, the components except water in the biological modifier are shown, and the balance is made up by deionized water.

The preparation of the above-mentioned biological modifier was carried out according to the proportions shown in Table 1, as follows:

(1) Stirring 30% of monosaccharide compound, 10% of alkaloid compound and deionized water in a water bath at 55 ℃ to react for 30 minutes;

(2) Accurately weighing 5% of natural polyphenol compound powder, dissolving into slurry solution with deionized water, adding water for dilution, and stirring uniformly;

(3) Transferring the solution in the step (2) into the step (1), and fully stirring for standby. Dissolving 5% metal salt compound with deionized water, transferring into the above solution, and stirring.

The prepared biological modifier is applied to the cellulose fiber, and the specific process is as follows:

(1) Preparing a biological modifier.

(2) Pre-reduction of dye liquor: fully dissolving the plant indigo powder, the biological modifier and deionized water in a water bath at 55 ℃ according to the proportion of 3.

(3) Pretreatment: winding the pure cotton fabric to be treated on a jig dyeing machine roller, feeding clean water according to a bath ratio of 1.

(4) Dyeing: adding the plant indigo dyeing solution pre-reduced in the step (1) for 4 times, wherein the ratio of the plant indigo dyeing solution added for each time is 25%. Basic parameters in the dyeing process are set as follows: the dyeing temperature is 25 ℃, the dyeing time is 45 minutes, and the running speed is 15 circles/minute.

(5) And (3) oxidation: after the fabric is rolled on a roller, the dye liquor in the cylinder is fully drained, clear water is added, 2g/L hydrogen peroxide solution is added, and the operation is continued for 10 minutes for full oxidation.

(6) Washing with water: washing with clear water for 15min → heating to 80 ℃, soaping for 25min → washing with clear water for 10min → washing with acid for 10min → washing with clear water for 10min → taking out, and drying.

The test method and indexes are as follows: and folding the dyed and washed and dried fabric, sequentially laying the fabric on a table, exposing the fabric in the air, and observing the ecdysis condition of one surface contacting the air. And (4) measuring the color difference value and the K/S value of the dyed cotton fabric by using a DataColor spectrocolorimeter. After the instrument is corrected, a color measurement test is carried out, the color difference value is used for representing the color light change of the fabric, and the K/S value is used for representing the apparent depth change of the fabric. Wherein the standard sample data is measured after dyeing, and the batch sample is measured after being placed as it is for 20 days and then compared with the standard sample.

Table 2: fabric performance test index dyed by biological modifier

Serial number	E	L	a	b	R
						1	0.75	0.11	0.00	0.19	22.80
2	0.55	0.14	-0.01	0.29	22.34
						3	0.65	0.08	0.04	0.30	22.12
4	0.60	0.12	0.03	0.35	22.90
						5	0.82	0.15	0.00	0.21	23.07
6	0.85	0.11	-0.03	0.33	22.14
						7	0.45	0.03	-0.01	0.36	22.76
8	0.55	0.04	-0.02	0.37	22.16
						9	0.74	0.12	-0.05	0.22	22.69
10	0.50	0.14	0.02	0.32	22.71
						11	0.69	0.18	0.05	0.18	22.68
12	0.72	0.14	-0.04	0.40	22.16

Note: the value E represents the color difference, the value L represents the lightness, the value a represents the red and green, the value b represents the yellow and blue, and the value R represents the shade of color.

From the data in table 2 it can be seen that:

(1) When the same alkaloid compound, natural polyphenol compound and metal salt compound are used, different monosaccharide compounds (numbers 1, 2 and 3 in table 2) have different effects on the fabric: in the three groups, the b value of the serial number 1 is the smallest, which indicates that the glucose is favorable for reducing the yellowing tendency of the fabric; the E value of number 2 is the smallest, indicating that mannose is helpful in reducing color difference; the R value of number 3 is the smallest, indicating that xylose contributes to the reduction of the R value; mannose is preferred as the comprehensive index.

(2) When the same monosaccharide, natural polyphenol and metal salt compounds are used, different alkaloids (numbers 4, 5 and 6 in table 2) give different effects to the fabric: in the three groups, the value E of the serial number 4 is the smallest, which shows that the theophylline is favorable for reducing the color difference of the fabric; the b value of the sequence number 5 is the minimum, which indicates that the berberine is favorable for reducing the yellowing tendency of the fabric; the R value of serial number 6 is the minimum, which indicates that theophylline and berberine are helpful to reduce the R value; theophylline is preferred as a comprehensive index.

(3) When the same monosaccharide compound, alkaloid compound and metal salt compound are adopted, different natural polyphenol compounds (7, 8 and 9 in the table 2) have different effects: in the three groups, the value E of the serial number 7 is the smallest, which shows that the tea is helpful to reduce the color difference value E of the fabric; the R value of serial number 8 is the minimum, which indicates that the gallnut is favorable for reducing the R value; the b value of the serial number 9 is the minimum, which indicates that the pomegranate rind is helpful for reducing the yellowing tendency of the fabric; in terms of comprehensive indexes, tea extract is preferred.

(4) When the same monosaccharide, alkaloid and natural polyphenol compounds are used, different metal salt compounds (10, 11 and 12 in table 2) have different effects: in the three groups, the value E of the serial number 10 is the smallest, which shows that the sodium sulfate and the aluminum potassium sulfate are helpful to reduce the color difference value E of the fabric; the value b of the serial number 11 is the minimum, which shows that the aluminum potassium sulfate is favorable for reducing the yellowing tendency of the fabric; the R value of number 12 is the smallest, indicating that copper sulfate is beneficial for reducing the R value of the fabric; for comprehensive indexes, sodium sulfate and aluminum potassium sulfate are preferred.

Therefore, the monosaccharide compound is preferably mannose, the alkaloid compound is preferably theophylline, the natural polyphenol compound is preferably tea extract, and the metal salt compound is preferably sodium sulfate and aluminum potassium sulfate.

Example 2

In this example, a ratio experiment of each component in the biological modifier was performed, and the components were as follows:

deionized water.

The mass ratio of each component is shown in table 3.

Table 3:

serial number	Mannose	Theophylline	Tea leaves	Potassium aluminium sulfate and sodium sulfate
					1	30％	10％	5％	3％
2	40％	10％	5％	3％
					3	50％	10％	5％	3％
4	30％	10％	5％	3％
					5	30％	20％	5％	3％
6	30％	30％	5％	3％
					7	30％	10％	5％	3％
8	30％	10％	10％	3％
					9	30％	10％	15％	3％
10	30％	10％	5％	3％
					11	30％	10％	5％	5％
12	30％	10％	5％	10％

Note: in the table, the components except water in the biological modifier are shown, and the balance of the components is supplemented by deionized water.

The preparation process, application process, test method and indexes of the biological modifier are the same as those of the embodiment 1.

Table 4: fabric performance test index dyed by biological modifier

Note: the value of E represents the color difference, the value of L represents the lightness, the value of a represents the red and green, the value of b represents the yellow and blue, and the value of R represents the shade of color.

From the data in table 4, it can be seen that:

(1) When the same proportion of theophylline, tea leaves, aluminum potassium sulfate and sodium sulfate is adopted, the color difference E value of the fabric is gradually reduced along with the increase of the mannose concentration (the serial numbers 1-3 in the table 3 and the serial numbers 1-3 in the table 4), the yellowing trend is reduced, and the R value is gradually increased, so that the dyeing effect is better when the mannose concentration is 50 percent in a comprehensive view.

(2) When the mannose, the tea leaves, the aluminum potassium sulfate and the sodium sulfate in the same proportion are adopted, the color difference E value of the fabric is gradually increased along with the increase of the theophylline concentration (the numbers 4-6 in the numbers 4-6 and 4 in the table 3), the yellowing trend is ascending, the change of the R value is small, and the dyeing effect is better when the theophylline concentration is 10 percent in comprehensive view.

(3) When the same proportion of mannose, theophylline, aluminum potassium sulfate and sodium sulfate is adopted, the color difference E value of the fabric is gradually reduced along with the increase of the concentration of the tea (numbers 7-9 in a table 3 and numbers 7-9 in a table 4), the yellowing trend is reduced, and the R value is increased, and the dyeing effect is relatively good when the concentration of the tea extract is 10 percent in a comprehensive view.

(4) By adopting mannose, tea and theophylline in the same proportion, as the concentrations of aluminum potassium sulfate and sodium sulfate increase (numbers 10-12 in a sequence number 10-12 and 4 in a sequence number 10-12 in a table 3), the color difference E value of the fabric is in a descending trend, the yellowing trend is reduced, and the change of the R value is small, so that the dyeing effect is better when the concentrations of the aluminum potassium sulfate and the sodium sulfate are 10 percent in a comprehensive view.

The optimized biological modifier comprises the following components in percentage by mass: monosaccharide compounds (mannose 50%), alkaloid compounds (theophylline 10%), natural polyphenol compounds (tea leaves 10%), and metal salt compounds (aluminum potassium sulfate and sodium sulfate 10%).

Example 3

In this example, the application process of the biological modifier is as follows:

(1) Preparing a biological modifier: 1500g mannose, 300g theophylline, 300g tea, 300g (aluminium potassium sulphate and sodium sulphate) and 600g water were mixed to obtain 3kg of the biological modifier.

(2) Pre-reduction of dye liquor: and (2) fully dissolving 3kg of plant indigo powder, 3kg of biological modifier and 10kg of deionized water in a water bath at 50 ℃, uniformly stirring, adjusting the pH value of the solution to 11, and adjusting the reduction potential to-750 mV to obtain 16kg of pre-reduced plant indigo dye solution.

(3) Pretreatment: winding the pure cotton fabric to be treated on a roller of a jig dyeing machine, feeding clean water at a bath ratio of 1.

(4) Dyeing: adding the plant indigo dye solution pre-reduced in the step (1) in a plurality of times, wherein the ratio of adding the plant indigo dye solution every time is 25% (namely 4 kg), and adding the plant indigo dye solution in 4 times. Basic parameters in the dyeing process are set as follows: the dyeing temperature is 30 ℃, the dyeing time is 50 minutes, and the running speed is 10 circles/minute.

(5) And (3) oxidation: after the fabric is rolled on a roller, the dye liquor in the cylinder is fully drained, clear water is added, 2g/L hydrogen peroxide solution is added, the operation is continued for 15 minutes, and the fabric is fully oxidized.

(6) Washing with water: one-step washing with water for 10min → heating to 80 ℃, one-step soaping for 20min → one-step washing with water for 5min → two-step acid washing for 5min → one-step washing with water for 5min → taking out and drying.

Example 4

This example is the same as the arrangement of example 3, except that: in the step (3), after the clear water is fed, 10% of the biological modifier is added, 10% of the biological modifier is supplemented every 20 minutes, and every 20 minutes is the adding time of the biological modifier relative to the previous biological modifier.

Comparative example 1

The comparative example adopts the conventional plant indigo dyeing process, and does not use the biological modifier. The conventional plant indigo dyeing process is as follows:

pre-reducing the plant indigo dye (caustic soda-sodium hydrosulfite reduction system) → dyeing → oxidizing → washing with clear water → soaping at 80 ℃, two-stage acid washing → washing with clear water → dehydrating and drying.

The specific process parameters, test methods and test indexes were the same as in example 3.

Comparative example 2

This comparative example differs from example 3 in that: the biological modifier of example 3 was not used and the washing process did not include soaping:

pre-reducing the plant indigo dye (caustic soda-sodium hydrosulfite reduction system) → dyeing → oxidizing → washing with clear water → 80 ℃ hot water washing → two-pass clear water washing → dehydrating and drying.

The remaining specific process parameters, test methods and test indexes were the same as in example 3.

The case test results are shown in table 5.

Table 5: the dyeability of the fabrics of the examples and comparative examples was compared

Serial number	E	L	a	b	R
						Example 3	0.45	0.14	-0.01	0.19	22.32
Example 4	0.35	0.12	0.01	0.15	22.15
						Comparative example 1	0.85	0.55	-0.25	0.75	23.89
Comparative example 2	1.97	1.11	-0.19	1.43	24.31

Note: the value E represents the color difference, the value L represents the lightness, the value a represents the red and green, the value b represents the yellow and blue, and the value R represents the shade of color.

From the data in table 5 it can be seen that:

(1) Compared with comparative examples 1 and 2 without the biological modifier, E values, a values, b values and R values in examples 3 and 4 are obviously lower than those in comparative examples 1 and 2, which illustrates the critical effect of the biological modifier in the application on improving the photooxidation fading of the plant indigo dyed cotton fabric.

(2) Example 4 the fabrics dyed by the process have lower E, L, a, b, R values than example 3, indicating that: the intermittent supplement of the biological modifier in the dyeing process is helpful for improving the photooxidation fading phenomenon of the dyed fabrics.

(3) Comparative example 1 compared to comparative example 1: the cleaning mode is also beneficial to reducing the E value, the L value, the a value, the b value and the R value of the dyed fabric.

Claims (10)

1. A biological modifier is characterized by comprising the following components:

monosaccharide compounds: 30-50 parts of (by weight),

alkaloid compounds: 10-30 parts of (by weight),

natural polyphenols: 5-15 parts of (A) a stabilizer,

metal salt compound: 3-10 parts of (A) a water-soluble polymer,

the balance being deionized water.

2. A biorefinery according to claim 1, wherein: the monosaccharide compound is any one or a mixture of glucose, mannose, xylose and galactose.

3. A biorefinery according to claim 1, wherein: the alkaloid compound is one or a mixture of theophylline and berberine.

4. A biorefinery according to claim 1, wherein: the natural polyphenol compound is any one or a mixture of more of pomegranate bark extract, tea leaf extract, gallnut extract, tea fruit shell extract, myrobalan extract or walnut peel extract.

5. A biorefinery according to claim 1, wherein: the metal salt compound is one or a mixture of two of aluminum potassium sulfate, ferrous sulfate, sodium sulfate or copper sulfate.

6. A method for preparing the biological modifier of claim 1, which comprises the following steps:

(1) The monosaccharide compound, the alkaloid compound and deionized water are stirred and react for 30 to 60 minutes in a water bath at the temperature of between 55 and 65 ℃;

(2) Accurately weighing a certain amount of natural polyphenol compound powder, dissolving into slurry solution with deionized water, adding water for dilution, and fully and uniformly stirring;

(3) And (3) transferring the solution diluted by adding water in the step (2) into the step (1), fully stirring, adding a metal salt compound dissolved by deionized water, and uniformly stirring.

7. A method for applying the biological modifier to indigo dyeing according to claim 1, characterized by comprising the following steps:

(1) Pre-reduction of dye liquor: weighing plant indigo powder, a biological modifier and deionized water according to a proportion, fully dissolving in a water bath at 50-55 ℃, uniformly stirring, and adjusting the pH value of the solution to 10.5-11.5 and the reduction potential to-800-700 mV to obtain pre-reduced plant indigo dye solution;

(2) Pretreatment: winding the pure cotton fabric to be treated on a jig dyeing machine roller, feeding clean water at a bath ratio of 1-15, and running for 15-20 times at normal temperature to enable the solution and the cloth cover to be in an alkaline environment all the time;

(3) Dyeing: adding the plant indigo dye solution pre-reduced in the step (1) into a jig dyeing machine in a plurality of times, wherein the proportion of the plant indigo dye solution pre-reduced in each time is 20-40%, and the addition is completed in 3-4 times; parameters of the jig dyeing machine: the dyeing temperature is 25-35 ℃, the dyeing time is 45-60 minutes, and the running speed is 10-15 circles/minute;

(4) Oxidizing;

(5) And (5) washing with water.

8. The method for applying the biological modifier to indigo dyeing according to claim 7, wherein: and (3) adding a certain amount of biological modifier every 20-30 minutes after adding the pre-reduced plant indigo dye solution.

9. The method for applying the biological modifier to indigo dyeing according to claim 7, wherein: in the step (3), before the plant indigo dye solution is added, the biological modifier is added into the clear water to carry out pre-modification treatment on the fabric.

10. The method for applying the biological modifier to indigo dyeing according to claim 7, wherein in the step (5), the water washing process comprises: one-time washing, 10-15min → one-time soaping, heating to 80 ℃ for treatment for 20-30min → one-time washing, 5-10min → two-time acid washing, 5-10min → one-time washing, 5-10min → taking out and drying.