A method for preventing plant dye silk screen printing from staining based on unprinted area protection

Abstract

This invention relates to the field of textile printing and dyeing technology, specifically to a method for preventing staining during screen printing of plant dyes based on the protection of unprinted areas. The method includes: modifying the fabric to be printed to obtain a modified fabric; applying a plant dye reactive printing paste to a predetermined printing area of ​​the modified fabric via screen printing; then applying a protective treatment to the unprinted areas of the modified fabric; and finally, steaming, washing, and finishing the protected fabric to obtain a plant dye screen-printed fabric. The protective treatment may be a whitening agent treatment, a fixing agent treatment, or a light-colored plant dye treatment. This invention effectively inhibits the migration and secondary staining of plant dyes to unprinted areas during washing, improving the overall stain resistance, pattern accuracy, and visual consistency of the fabric. While ensuring colorfastness in the printed area, it also improves the washability and service life of the fabric, demonstrating significant practical value and promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of textile printing and dyeing technology, specifically to a method for preventing staining of plant dyes in screen printing based on the protection of unprinted areas. Background Technology

[0002] Plant dyes, derived from natural plants, offer advantages such as renewability, biodegradability, and environmental friendliness, leading to their widespread application in textile printing in recent years. However, due to the inherent molecular structure of plant dyes, their binding force with fibers is relatively weak, resulting in generally low dye uptake and poor colorfastness of printed fabrics, particularly in wet rubbing and washing fastness. During the finishing process of plant dye printing, thorough washing or soaping is typically required to remove surface dye. However, under washing or soaping conditions, some dyes not firmly bound to the fibers in the printed area are prone to desorption and dissolution into the washing solution. When the washing temperature and time reach certain levels, dye molecules in the washing solution can easily re-adsorb and bind to the fiber surface of unprinted areas, causing secondary staining in the unprinted areas of the fabric. This results in problems such as color bleeding and uneven color distribution, severely affecting the clarity of the printed pattern and the overall appearance quality.

[0003] To address the aforementioned problems, existing technologies primarily improve upon these issues in two ways: First, pretreatment of the entire fabric before printing is performed. This typically involves using cationic modifiers, protein-based substances, or other dye-affinity modifiers to paddle or impregnate the fabric, introducing positively charged or highly absorbent functional groups onto the fabric surface. This enhances the binding ability between plant dyes and fibers, improving the dye uptake and colorfastness in the printed area. For example, Chinese patent CN115928461B discloses a digital direct-to-garment printing process for cellulose fiber fabrics using plant dye inks. This process involves cationically modifying the cellulose fibers with polyethyleneimine, cationic polyacrylamide, etc., making it easier for the plant dyes to diffuse and adhere to the fiber surface during subsequent steaming. Secondly, mordating processes can be introduced during the printing process to improve dye fixation. For example, Chinese patent CN1865580A discloses a mordant printing method on fabrics dyed with natural plant dyes. By introducing a metallic mordant into the printing paste and combining it with subsequent steaming or baking treatments, a metallic coordination or complex structure is formed between the plant dye, mordant, and fiber. This enhances the binding strength between the dye and fiber in the printed area, aiming to improve the color depth and wash resistance of the printed pattern. While the above methods can improve the color fixation performance of the printed areas, they lack active protection or isolation measures for the unprinted areas. They cannot effectively inhibit the re-adsorption of detached dyes in the unprinted areas, especially under wet conditions, where plant dye molecules are prone to migration, further leading to a decrease in print clarity. Summary of the Invention

[0004] To address the technical problem that during the washing or soaping process of plant-dyed printed fabrics, some dyes in the printed area desorb and migrate into the washing solution, and then undergo secondary adsorption in the unprinted area, resulting in staining and color bleeding, this invention provides a method for preventing staining in plant-dyed screen printing based on the protection of the unprinted area. By introducing active protection treatment in the unprinted area, the staining resistance of plant-dyed screen-printed fabrics is significantly improved.

[0005] The specific technical solution is as follows: A method for preventing staining of plant-based dyes in screen printing based on protection of unprinted areas includes: The fabric to be printed is modified to obtain a modified fabric. Plant-based reactive printing paste is applied to the predetermined printing area of ​​the modified fabric using screen printing. Then, the unprinted areas of the modified fabric are treated with a protective treatment. The treated fabric is then steamed, laid flat, washed, and finished to obtain a plant-based dye screen-printed fabric. The protective treatment is one of three types: whitening agent protection treatment, fixing agent protection treatment, or light-colored plant dye protection treatment. This protective treatment reduces or inhibits the migration and re-adsorption of plant dyes to the unprinted areas during subsequent washing.

[0006] Furthermore, the whitening agent protective treatment includes: printing whitening agent paste on the non-printed areas, the whitening agent paste comprising the following components in the following amounts: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L and whitening agent 2~10g / L.

[0007] Further, the color-fixing protective treatment includes: printing a color-fixing paste on the unprinted area, the color-fixing paste comprising the following components: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L, and color-fixing agent 1~3g / L, with a pH of 5.0~6.0; and performing curing treatment using a continuous hot air baking machine or a flatbed printing and finishing machine, with a curing temperature of 105~125℃ and a curing time of 30~120s.

[0008] Furthermore, the light-colored plant dye protective treatment includes printing a light-colored plant dye paste on the unprinted area. The light-colored plant dye paste comprises the following components in the following proportions: sodium alginate 30-100 g / L, baking soda 10-50 g / L, anti-reduction agent 10-30 g / L, sodium hexametaphosphate 10-30 g / L, reactive printing thickener 1-10 g / L, urea 50-200 g / L, and light-colored plant dye 10-100 g / L; the light-colored plant dye belongs to the same color family as the plant dye applied to the predetermined printing area. By pre-occupying fiber binding sites with similar dyes, competitive adsorption of detached dyes is reduced, while the light-colored design minimizes visual interference.

[0009] Further modification treatment includes: immersing the fabric to be printed in an environmentally friendly cationic modifier solution with a concentration of 2-5 g / L and a pH of 6.0-9.0; modifying at a temperature of 60-100℃ for 20-60 minutes; and drying the fabric at 80-120℃ to obtain the modified fabric. After modification treatment, a stable cationic layer is formed on the surface of the fabric fibers, which can enhance its electrostatic binding force with anionic plant dyes.

[0010] Furthermore, the plant-based reactive printing paste includes the following components: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L, and plant dye 30~200g / L.

[0011] Furthermore, the plant dyes are organic natural dyes selected from one or more of the following: red linalool, tree orange, lutein, berberine, chlorophyll, isatis root, indigo, violet, holly, bamboo charcoal black, coffee tree, and carmine.

[0012] Further, the steaming treatment includes: feeding the protected fabric into a continuous steaming machine at a steaming temperature of 95~130℃, a steaming time of 5~35min, a steaming humidity of 80%~150%, a steaming pressure of 0.02~0.08MPa, and a fabric running speed of 5~10m / min. A stable high-temperature and high-humidity environment is created by introducing saturated steam, promoting the full penetration of plant dye molecules into the fabric fibers, achieving efficient color fixation. During the steaming process, the fabric is kept flat and wrinkle-free to avoid uneven color fixation in certain areas.

[0013] Further, the flat washing process includes: smoothly introducing the steamed fabric into a flat-width washing machine; sequentially performing a three-stage gradient wash along the fabric's running direction; the first stage wash uses 35-45℃ warm water and 1-5g / L washing aid to remove residual sizing agents from the fabric surface; the second stage wash uses 55-65℃ warm water and 1-5g / L washing aid, simultaneously activating the countercurrent recovery system to remove surface dye; the third stage wash uses 75-85℃ warm water without additional aids to deeply clean residual aids and trace amounts of surface dye; the entire process maintains a liquor ratio of 1:12-20, a fabric running speed of 8-15m / min, and a spray pressure of 0.1-0.3MPa to keep the fabric flat and wrinkle-free, avoid uneven washing in certain areas, and ensure simultaneous cleaning of the printed and unprinted areas. The washing aid is a low-temperature soaping agent or a nonionic surfactant, preferably the low-temperature soaping agent RSA.

[0014] Further finishing processes include: drying the washed fabric to a moisture content of ≤8%; immersing the fabric in a softening solution and padding it at 35-45℃ with a padding rate of 70%-85%, followed by baking at 110-130℃ for 60-120 seconds; feeding the baked fabric into a pre-shrinking machine with a tension of 5-15N, controlling the machine speed at 20-35m / min, passing it through a pre-shrinking zone at 90-110℃, controlling the warp shrinkage rate at 2.0%-3.5% and the weft shrinkage rate at 2.0%-3.5%, thus completing the pre-shrinking; and allowing it to cool naturally to room temperature after pre-shrinking to avoid hardening of the hand due to high-temperature stacking.

[0015] Furthermore, the softening finishing solution includes hydrophilic block silicone oil stock solution BKR-620W 5~20g / L, silicone softener 20~50g / L and penetrant S-015 2~4g / L.

[0016] The beneficial effects of this invention are as follows: This invention provides a method for preventing staining in plant-based dye screen printing based on the protection of unprinted areas. It not only enhances the colorfastness of the printed area through pretreatment of the fabric, but also offers three optional active protection methods for unprinted areas. By secondary printing specific substances to form a physical / chemical barrier, it effectively inhibits the migration and secondary staining of plant dyes during the washing process, improving the overall stain resistance, pattern accuracy, and visual consistency of the fabric. Furthermore, while maintaining the colorfastness of the printed area, it enhances the washability and service life of plant-based dye screen-printed fabrics, demonstrating significant practical value and promising application prospects. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0018] The cationic modifier used in the following examples is a cationic modified gelatin derivative (for textiles), product model is gelatin derivative MSDS (JLZ), purchased from Zhucheng Mulan Textile Co., Ltd.

[0019] The low-temperature soaping agent RSA used in the following examples was purchased from the French SNF Group.

[0020] The anti-reduction agent used in the following examples is CBSTER NS GRANS anti-reduction agent, purchased from Shanghai Tuslon Chemical Co., Ltd.

[0021] The reactive printing thickener used in the following examples is reactive printing thickener TF-3181B, MSDS number MSDS / Y0002 / TF-3181B, version number 3.1, purchased from Transfar Group Co., Ltd.

[0022] The brightener used in the following examples is the fluorescent brightener Ecophor HST, manufactured by Clariant Ltd.

[0023] The fixing agent used in the following examples is CBR conc (high concentration type) reactive dye fixing agent, manufactured by Degussa Chemical Co., Ltd.

[0024] The hydrophilic block silicone oil stock solution BKR-620W used in the following examples was purchased from Shanghai Yunji Chemical New Materials Co., Ltd.

[0025] The silicone softener used in the following examples is NOVASILK NV-507, manufactured by Huntsman Textile Effects, and is available through conventional commercial channels.

[0026] The penetrant S-015 used in the following examples was purchased from Zibo Fengjiayi Textile Trading Co., Ltd.

[0027] The plant dyes used in the following examples are all available through conventional commercial channels.

[0028] Example 1: A method for preventing staining in plant-based dye screen printing based on whitening agent protection in unprinted areas. Select semi-bleached cotton fabric that has undergone mercerizing as the fabric to be printed, and perform anti-staining treatment for screen printing with plant dyes according to the following steps.

[0029] (1) Fabric modification treatment The fabric to be printed was immersed in an environmentally friendly cationic modifier solution with a concentration of 3 g / L and a pH of 7.0 for modification treatment. Modification was carried out at 80°C for 40 min, followed by drying at 90°C to obtain the modified fabric. After the above modification treatment, a stable cationic layer was formed on the surface of the fabric fibers, which is beneficial to enhancing the electrostatic binding force between the fabric and anionic plant dyes.

[0030] (2) Screen printing with plant dyes The plant-based reactive printing paste is applied to the predetermined printing area of ​​the modified fabric using screen printing. The plant-based reactive printing paste comprises the following components in the following proportions: sodium alginate 50 g / L, baking soda 20 g / L, anti-reduction agent 15 g / L, sodium hexametaphosphate 15 g / L, reactive printing thickener 5 g / L, urea 100 g / L, and plant dye 50 g / L. The plant dye is a combination of lutein and berberine.

[0031] (3) Protective treatment of unprinted areas After printing, the unprinted areas of the modified fabric undergo a protective treatment. This treatment uses a whitening agent and is detailed below: The whitening agent paste is printed on the non-printed areas. The whitening agent paste comprises the following components in the following proportions: sodium alginate 50g / L, baking soda 20g / L, anti-reduction agent 15g / L, sodium hexametaphosphate 15g / L, reactive printing thickener 5g / L, urea 100g / L, and whitening agent 5g / L. Using the whitening agent on the non-printed areas avoids interference with dye adsorption and simultaneously forms a basic physical barrier layer, balancing the whitening effect with the purity of the pattern's colors.

[0032] (4) Steaming treatment The fabric, after being protected against printing on unprinted areas, is fed into a continuous steaming machine in a flat state for steaming treatment. The steaming temperature is 105℃, the steaming time is 15 minutes, the steaming humidity is 105%, the steaming pressure is 0.04 MPa, and the fabric running speed is 8 m / min. By introducing saturated steam, the plant dye molecules are fully penetrated into the fabric fibers under a stable high temperature and high humidity environment, thus achieving color fixation.

[0033] (5) Flat-lay washing treatment The steamed fabric is smoothly fed into a flat-width washing machine and undergoes a three-stage gradient wash: the first wash uses 40℃ warm water with 3g / L of low-temperature soaping agent RSA added to remove residual sizing agents from the fabric surface; the second wash uses 60℃ warm water with 3g / L of low-temperature soaping agent RSA added, while simultaneously activating the countercurrent recovery system to remove surface dye; the third wash uses 80℃ warm water without adding any additional auxiliaries to further remove residual auxiliaries and trace amounts of surface dye. The entire washing process maintains a liquor ratio of 1:15, a fabric running speed of 12m / min, and a spray pressure of 0.2MPa.

[0034] (6) Post-processing After being laid flat and washed, the fabric is dried to a moisture content of no more than 8%. The fabric is then immersed in a softening solution and padded at 40°C with a padded rate of 80%, followed by baking at 120°C for 90 seconds. The softening solution consists of 10 g / L of hydrophilic block silicone oil stock solution BKR-620W, 30 g / L of NOVASILK NV-507 silicone softener, and 3 g / L of penetrant S-015. After baking, the fabric is fed into a pre-shrinking machine with a tension of 10 N and a speed controlled at 30 m / min. It is then pre-shrinked in a 100°C zone to control both warp and weft shrinkage to approximately 2.5%. Finally, the fabric is naturally cooled to room temperature to obtain the plant-dyed screen-printed fabric.

[0035] Example 2: A method for preventing staining in plant-based dye screen printing based on the protection of unprinted areas with a fixing agent. Select semi-bleached cotton fabric that has undergone mercerizing as the fabric to be printed, and perform anti-staining treatment for screen printing with plant dyes according to the following steps.

[0036] (1) Fabric modification treatment The fabric to be printed was immersed in an environmentally friendly cationic modifier solution with a concentration of 2 g / L and a pH of 6.0 for modification treatment. Modification was carried out at 85°C for 30 min, followed by drying at 95°C to obtain the modified fabric. After the above modification treatment, a stable cationic layer was formed on the surface of the fabric fibers, which is beneficial to enhancing the electrostatic binding force between the fabric and anionic plant dyes.

[0037] (2) Screen printing with plant dyes The plant-based reactive printing paste is applied to the predetermined printing area of ​​the modified fabric using screen printing. The plant-based reactive printing paste comprises the following components and concentrations: sodium alginate 45 g / L, baking soda 15 g / L, anti-reduction agent 10 g / L, sodium hexametaphosphate 10 g / L, reactive printing thickener 3 g / L, urea 80 g / L, and plant dye 60 g / L. The plant dye is bamboo charcoal black.

[0038] (3) Protective treatment of unprinted areas After printing, the unprinted areas of the modified fabric are protected. The protective treatment uses a color-fixing agent, specifically as follows: A color-fixing agent paste is printed onto the unprinted areas using screen printing. A continuous hot air curing machine is then used for curing at 115℃ for 60 seconds. The color-fixing agent paste comprises the following components: sodium alginate 50g / L, baking soda 20g / L, anti-reduction agent 15g / L, sodium hexametaphosphate 15g / L, reactive printing thickener 5g / L, urea 100g / L, and color-fixing agent 2g / L, with a pH of 5.2.

[0039] (4) Steaming treatment The treated fabric is fed into a continuous steaming machine in a flat state for steaming treatment. The steaming temperature is 103℃, the steaming time is 20 minutes, the steaming humidity is 120%, the steaming pressure is 0.06 MPa, and the fabric running speed is 6 m / min. By introducing saturated steam, the plant dye molecules are fully penetrated into the fabric fibers under a stable high temperature and high humidity environment, thus achieving color fixation.

[0040] (5) Flat-lay washing treatment The steamed fabric is smoothly fed into a flat-width washing machine and undergoes a three-stage gradient wash: the first wash uses 45℃ warm water with 3g / L polyglycerol fatty acid ester added to remove residual sizing agent from the fabric surface; the second wash uses 65℃ warm water with 3g / L polyglycerol fatty acid ester added, while simultaneously activating the countercurrent recovery system to remove surface dye; the third wash uses 85℃ warm water without adding any additional auxiliaries to further remove residual auxiliaries and trace amounts of surface dye. The entire washing process maintains a liquor ratio of 1:17, a fabric running speed of 10m / min, and a spray pressure of 0.3MPa.

[0041] (6) Post-processing After being laid flat and washed, the fabric was dried to a moisture content of no more than 8%. The fabric was then immersed in a softening solution and padded at 35°C with a padding rate of 75%. It was then baked at 110°C for 80 seconds. The softening solution consisted of 12 g / L of hydrophilic block silicone oil stock solution BKR-620W, 28 g / L of NOVASILK NV-507 silicone softener, and 4 g / L of penetrant S-015. After baking, the fabric was fed into a pre-shrinking machine with a tension of 8 N and a speed controlled at 25 m / min. It was then pre-shrinked in a 95°C zone to control both warp and weft shrinkage to 2.0%. Finally, it was naturally cooled to room temperature to obtain the plant-dyed screen-printed fabric.

[0042] Example 3: A method for preventing staining in plant-based dye screen printing based on the protection of unprinted areas with light-colored plant dyes. Select semi-bleached cotton fabric that has undergone mercerizing as the fabric to be printed, and perform anti-staining treatment for screen printing with plant dyes according to the following steps.

[0043] (1) Fabric modification treatment The fabric to be printed was immersed in an environmentally friendly cationic modifier solution with a concentration of 5 g / L and a pH of 9.0 for modification treatment. Modification was carried out at 75°C for 50 min, followed by drying at 100°C to obtain the modified fabric. After the above modification treatment, a stable cationic layer was formed on the surface of the fabric fibers, which is beneficial for enhancing the electrostatic binding force between the fabric and anionic plant dyes.

[0044] (2) Screen printing with plant dyes The plant-based reactive printing paste is applied to the predetermined printing area of ​​the modified fabric using screen printing. The plant-based reactive printing paste comprises the following components and concentrations: sodium alginate 100g / L, baking soda 50g / L, anti-reduction agent 30g / L, sodium hexametaphosphate 30g / L, reactive printing thickener 10g / L, urea 200g / L, and plant dye 55g / L. The plant dye is a combination of indigo and cochineal.

[0045] (3) Protective treatment of unprinted areas After printing, the unprinted areas of the modified fabric undergo a protective treatment. This treatment uses light-colored plant-based dyes, as detailed below: Light-colored plant dye paste is printed on the non-printed areas. The light-colored plant dye paste comprises the following components and contents: sodium alginate 100g / L, baking soda 50g / L, anti-reduction agent 30g / L, sodium hexametaphosphate 30g / L, reactive printing thickener 10g / L, urea 200g / L, and light-colored plant dye 20g / L. The light-colored plant dye is indigo, which is in the same color family as the plant dye used in the printing area.

[0046] (4) Steaming treatment The fabric, after being protected against printing on unprinted areas, is fed into a continuous steaming machine in a flat state for steaming treatment. The steaming temperature is 110℃, the steaming time is 15 minutes, the steaming humidity is 125%, the steaming pressure is 0.05 MPa, and the fabric running speed is 10 m / min. By introducing saturated steam, the plant dye molecules are fully penetrated into the fabric fibers under a stable high temperature and high humidity environment, thus achieving color fixation.

[0047] (5) Flat-lay washing treatment The steamed fabric is smoothly fed into a flat-width washing machine and undergoes a three-stage gradient wash: the first wash uses 35℃ warm water with 4g / L of low-temperature soaping agent RSA added to remove residual sizing agents from the fabric surface; the second wash uses 55℃ warm water with 4g / L of low-temperature soaping agent RSA added, while simultaneously activating the countercurrent recovery system to remove surface dye; the third wash uses 75℃ warm water without adding any additional auxiliaries to further remove residual auxiliaries and trace amounts of surface dye. The entire washing process maintains a liquor ratio of 1:15, a fabric running speed of 15m / min, and a spray pressure of 0.1MPa.

[0048] (6) Post-processing After being laid flat and washed, the fabric was dried to a moisture content of no more than 8%. The fabric was then immersed in a softening solution and padded at 45°C with a padded rate of 85%, followed by baking at 130°C for 60 seconds. The softening solution consisted of 15 g / L of hydrophilic block silicone oil stock solution BKR-620W, 25 g / L of NOVASILK NV-507 silicone softener, and 3 g / L of polyglycerol fatty acid ester. After baking, the fabric was fed into a pre-shrinking machine with a tension of 15 N and a speed controlled at 35 m / min. It was then pre-shrinked in a 110°C zone to control both warp and weft shrinkage to approximately 3.0%. Finally, the fabric was allowed to cool naturally to room temperature to obtain the plant-dyed screen-printed fabric.

[0049] Comparative Example 1: Conventional Printing Method Compared with Example 1, the difference of Comparative Example 1 is that the protective treatment of the unprinted area is not performed, while the remaining steps are the same as those of Example 1.

[0050] In conventional printing methods, during the washing process, some of the plant dyes that are not fully fixed in the printed area desorb and migrate into the washing solution. During subsequent washing and high-temperature washing stages, they are prone to re-adsorption in the unprinted areas, resulting in a decrease in the whiteness of the unprinted areas, an increase in the color difference between the printed and unprinted areas, and slight color spots and staining in some local areas.

[0051] Test case The color fastness and anti-staining properties of the plant-dyed screen-printed fabrics obtained in Examples 1-3 and the comparative examples were evaluated according to national standards and relevant testing conditions. Specifically, the color fastness to washing (original color change) and color fastness to washing (staining) of the fabrics were tested according to GB / T 3921-2008 "Textiles - Tests for Color Fastness - Color Fastness to Washing"; the color fastness to rubbing was determined according to GB / T 3920-2008 "Textiles - Tests for Color Fastness - Color Fastness to Rubbing", with dry rubbing and wet rubbing color fastness tested separately; the whiteness of the unprinted areas and the color difference between unprinted areas were determined according to the method specified in GB / T 21898-2023. The test results for the above items are shown in Table 1.

[0052] Table 1. Test results of color fastness and anti-staining properties of fabrics

[0053] As can be seen from Table 1, the color fastness to washing (color change) of Examples 1 and 2 both reached level 4, and the color fastness to washing (staining) was level 3-4. The color fastness to washing of Example 3 was slightly lower but still remained at level 3-4. However, the color fastness to washing of Comparative Example 1 decreased significantly without the protection treatment of the unprinted area. The original color change was only level 2-3, and the staining level was level 2.

[0054] Regarding color fastness to rubbing, the wet rubbing color fastness of Examples 1-3 all reached grade 4, and the dry rubbing color fastness was grade 3-4, showing good stability; in contrast, the dry and wet rubbing color fastness of Comparative Example 1 both dropped to grade 3, showing a more obvious tendency to stain.

[0055] In the wash resistance test, Examples 1-3 could withstand at least 20 standard washes with a color fastness of not less than grade 3, while Comparative Example 1 showed a significant decrease in color fastness after no more than 5 washes, indicating that its wash resistance was poor.

[0056] Furthermore, considering the whiteness of the unprinted areas and the color difference between the printed and unprinted areas, the CIE whiteness of the unprinted areas in Examples 1-3 remained above 70, and the color difference between the unprinted areas was controlled within ΔE ≤ 1. In contrast, the CIE whiteness of the unprinted areas in Comparative Example 1 decreased to below 70, and the color difference between the printed and unprinted areas increased to ΔE > 3, indicating significant secondary staining. Based on direct observation, the staining area of ​​the unprinted areas in Comparative Example 1 was > 50%, while the staining area of ​​the unprinted areas in Examples 1-3 was < 5%.

[0057] In summary, compared with Comparative Example 1, which did not undergo protective treatment on the unprinted areas, this invention significantly reduces the risk of migration and re-adsorption of plant dyes during the washing process by introducing protective treatment into the unprinted areas. This effectively improves the overall anti-staining performance and pattern integrity of the fabric without affecting the colorfastness of the printed areas. Furthermore, each protective scheme has different technical characteristics: the whitening agent protection scheme has lower processing costs, is suitable for light-colored fabrics, and can increase the whiteness of the unprinted areas while suppressing staining; the fixing agent protection scheme forms a stable protective layer in the unprinted areas, allowing the resulting fabric to maintain good anti-staining performance after multiple washes, exhibiting superior durability; and the light-colored plant dye protection scheme results in a more natural color transition between the printed and unprinted areas, making it particularly suitable for printed products with high requirements for pattern precision and visual consistency.

[0058] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preventing plant dye silk screen printing from staining based on unprinted area protection, characterized in that, include: The fabric to be printed is modified to obtain a modified fabric; Plant-based reactive printing paste is applied to a predetermined printing area of ​​a modified fabric using screen printing. The unprinted areas of the modified fabric are then treated with a protective coating. The treated fabric is then steamed, laid flat, washed, and finished to obtain a plant-based dye screen-printed fabric. The protective coating is one of three types: whitening agent protective coating, fixing agent protective coating, or light-colored plant dye protective coating.

2. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The whitening agent protective treatment includes: printing whitening agent paste on the non-printed areas; the whitening agent paste includes the following components in the following amounts: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L and whitening agent 2~10g / L.

3. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The color-fixing agent protective treatment includes: printing color-fixing agent paste on the unprinted area; the color-fixing agent paste includes the following components: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L and color-fixing agent 1~3g / L, with a pH of 5.0~6.0; curing is performed using a continuous hot air baking machine or a flatbed printing and finishing machine, with a curing temperature of 105~125℃ and a curing time of 30~120s.

4. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The protective treatment with light-colored plant dyes includes printing a light-colored plant dye paste on the non-printing area. The light-colored plant dye paste comprises the following components in the following amounts: sodium alginate 30-100 g / L, sodium bicarbonate 10-50 g / L, anti-reduction agent 10-30 g / L, sodium hexametaphosphate 10-30 g / L, reactive printing thickener 1-10 g / L, urea 50-200 g / L, and light-colored plant dye 10-100 g / L; the light-colored plant dye belongs to the same color family as the plant dye applied to the predetermined printing area.

5. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The modification treatment includes: immersing the fabric to be printed in an environmentally friendly cationic modifier solution with a concentration of 2~5g / L and a pH of 6.0~9.0, modifying it at a temperature of 60~100℃ for 20~60min, and drying it at 80~120℃ to obtain the modified fabric.

6. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The plant-based reactive printing paste contains the following components: sodium alginate 30~100g / L, baking soda 10~50g / L, anti-reduction agent 10~30g / L, sodium hexametaphosphate 10~30g / L, reactive printing thickener 1~10g / L, urea 50~200g / L, and plant dye 30~200g / L.

7. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The steaming process includes: feeding the protected fabric into a continuous steaming machine at a flat width, with a steaming temperature of 95~130℃, a steaming time of 5~35min, a steaming humidity of 80%~150%, a steaming pressure of 0.02~0.08MPa, and a fabric running speed of 5~10m / min.

8. The plant dye screen printing method for preventing bleeding according to claim 1, wherein The flat washing process includes: smoothly introducing the steamed fabric into a flat-width washing machine; performing a three-stage gradient wash along the fabric's running direction; the first stage wash uses 35-45℃ warm water and 1-5g / L washing aid; the second stage wash uses 55-65℃ warm water and 1-5g / L washing aid, with the countercurrent recovery system activated simultaneously; the third stage wash uses 75-85℃ warm water; the entire process is controlled with a liquor ratio of 1:12-20, a fabric running speed of 8-15m / min, and a spray pressure of 0.1-0.3MPa, maintaining the fabric flat and wrinkle-free.

9. The plant dye screen printing method for preventing bleeding according to claim 1, wherein Post-processing includes: Dry the washed fabric until the moisture content is ≤8%; The fabric is immersed in a softening solution and padded at 35-45°C with a padded rate of 70%-85%. It is then baked at 110-130°C for 60-120 seconds. The baked fabric is then fed into a pre-shrinking machine with a tension of 5-15N and a speed of 20-35m / min. The fabric passes through a pre-shrinking zone at 90-110°C, with the warp shrinkage rate controlled at 2.0%-3.5% and the weft shrinkage rate controlled at 2.0%-3.5%, thus completing the pre-shrinking process. After pre-shrinking, the fabric is naturally cooled to room temperature.

10. The plant dye screen printing method for preventing bleeding according to claim 9, wherein The softening finishing solution includes hydrophilic block silicone oil stock solution BKR-620W 5~20g / L, silicone softener 20~50g / L and penetrant S-015 2~4g / L.

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