A salt-free and water-saving dyeing method for dyeing raw cotton fibers with natural dye curcumin

Abstract

A salt-free and low-water dyeing method for dyeing raw cotton fibers with a natural dye curcumin, comprising the steps of pre-treating the cotton fibers, dissolving curcumin powder in a mixture of ethanol and water, and obtaining a dye liquor. The pre-treated raw cotton fibers are then placed in the dye liquor for padding, and the raw cotton fibers after padding the dye liquor are sequentially dried, washed, and fixed to obtain a finished product. The present invention pre-treats the raw cotton fibers and adopts an ethanol-water system, utilizing ethanol as an organic solvent to dissolve curcumin, thereby improving the dyeing effect of curcumin. After dyeing, the fabric has bright colors and good color. No other chemical reagents are added to the dye liquor to aid dyeing, so that the dye liquor can be directly recycled and reused without going through other processing steps, thereby avoiding dye waste. Green and environmentally friendly reagents are used throughout the pre-treatment, dyeing, and fixation stages, thereby preventing environmental pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of cotton fiber printing and dyeing, and particularly relates to a salt-free and water-reduced dyeing method for dyeing raw cotton fibers with natural dye curcumin. Background Art

[0002] While dyes add color to our lives, they also bring various environmental pollution problems, particularly water pollution. Printing and dyeing wastewater is characterized by high salt content, dark color, and the presence of toxic substances. In particular, toxic heavy metal ions are not biodegradable by microorganisms and, when released into the environment, pose a persistent threat to the environment and human health. Therefore, the development of low-water and low-salt technologies is of vital importance in the printing and dyeing industry.

[0003] Curcumin is a natural dye extracted from the rhizome of turmeric. It is non-toxic and harmless to the environment. Due to its inherent antibacterial and anti-inflammatory properties, it can be used in food, medical and other fields. Studies have found that curcumin, as a water-insoluble natural dye, easily dyes protein fibers (wool, silk, etc.), but is difficult to directly dye cotton fibers and has poor color fastness. This means that when traditionally dyeing cotton textiles with curcumin, mordants such as metal salts are generally used to dye them. Although the dyeing effect is good, the printing and dyeing wastewater is very harmful to the environment.

[0004] Patent application number CN201611089899.4 discloses a method for dyeing cotton fabric with curcumin. This method involves placing the cotton fabric in a dimethyl sulfoxide / phenol mixed solution containing the dye curcumin and the surfactant sodium dodecylbenzenesulfonate, followed by oscillation and heating. However, this method produces printing and dyeing wastewater containing large amounts of toxic dimethyl sulfoxide / phenol, posing a significant environmental risk.

[0005] The invention patent application number CN201611089890.3 discloses a method for dyeing cotton fabric with curcumin. In this method, curcumin is dissolved in an ethanol / phenol mixed solution, and then a surfactant, benzyl benzoate, is added to obtain a dye solution under ultrasound. The cotton fabric is placed in the dye solution and heated to 30-60°C under oscillation for dyeing. Although the curcumin does not need to be modified and high-temperature dyeing is not used, the phenol in the printing and dyeing wastewater generated by this method is difficult to remove by traditional physical, chemical and biochemical means. If not treated, it will cause significant organic pollution to the receiving water body.

[0006] The invention patent application number CN201410128536.1 discloses a chemically modified water-soluble curcumin dye, a preparation method, and an application. This method chemically modifies the curcumin dye to enhance its water solubility, and then dyes the water-soluble curcumin with unmodified cotton. Although the resulting fabric has uniform color and high wash fastness, chemical modification is required, which results in complex steps and high costs.

[0007] The invention patent with application number CN201910493086.9 discloses a salt-free cold pad-batch dyeing method for unbleached cotton fibers. This method places the unbleached cotton fibers in a mixed dye solution of an alcohol organic solvent-water system containing reactive dyes and alkaline substances, and adopts two immersions and two paddings for padding the dye solution. Since reactive dyes are easily soluble in water, a system with a high proportion of ethanol and a small amount of water is used to allow a large amount of reactive dye to be dissolved in a small amount of water, thereby greatly increasing the dye concentration and thus improving the dye uptake rate. However, since curcumin has extremely low solubility in water, this method is not suitable for dyeing curcumin, and in an alkaline environment, the hydroxyl group on the benzene ring of curcumin exists in the form of an oxygen anion, and its electron-donating property is enhanced, which greatly enhances the electrophilic reaction activity of the carbon chain. Therefore, curcumin is difficult to dye cotton fibers in an alkaline environment.

[0008] From existing traditional dyeing process, can find, under the system of water solvent, curcumin is to dye cotton fiber, on the one hand is by carrying out hydrophilic modification to curcumin to increase the dyeing performance to cotton fiber, on the other hand is to add metal mordant to dye the modified cotton fiber, these dyeing methods exist overall process complexity, long process, more importantly, the various heavy metal ions contained in the printing and dyeing wastewater discharged can cause serious environmental pollution. Although organic solvent system is also used for curcumin dyeing cotton fiber, the organic solvent system that existing curcumin dyeing cotton fiber adopts all has recycling difficulty, and the problem of not environmental protection. Therefore, it is necessary to develop a kind of method that does not need to modify curcumin and does not add mordant, and dyeing effect is good, the natural dye curcumin method of whole process green environmental protection dyeing raw cotton fiber. Summary of the Invention

[0009] The purpose of the present invention is to provide a salt-free and low-water dyeing method for dyeing raw cotton fibers with a natural dye curcumin, which has good dyeing effect and is green and environmentally friendly throughout the process, in order to solve the above problems in the prior art.

[0010] To achieve the above objectives, the technical solutions of the present invention are as follows:

[0011] A salt-free and water-reduced dyeing method for dyeing raw cotton fibers with a natural dye, curcumin, comprises:

[0012] Dissolve curcumin powder in a mixture of ethanol and water to prepare the resulting dye solution;

[0013] The raw cotton fibers are placed in the prepared dye solution for padding;

[0014] The raw cotton fibers after padding dyeing are dried, washed and fixed in sequence to obtain the finished product.

[0015] Preferably, the raw cotton fibers are first immersed in a pretreatment solution for pretreatment, the pH value of the pretreated raw cotton fibers is adjusted to 4-8, and then the raw cotton fibers are placed in the prepared dye solution for padding.

[0016] Preferably, the padding time is 20-120 minutes, and the padding rate of the raw cotton fiber after padding is 150-300%.

[0017] Preferably, the curcumin powder is used in an amount of 1-8% by weight of the fabric.

[0018] Preferably, the dyeing bath ratio of the padding is 1:10-1:50, and the pH of the dyeing solution before padding is 4-8.

[0019] Preferably, in the mixture of ethanol and water, the volume ratio of water to ethanol is 1:9-9:1.

[0020] Preferably, in the mixture of ethanol and water, the volume ratio of water to ethanol is 3:7-2:8.

[0021] Preferably, the padding temperature is 20-80°C, and the heating rate is 2-5°C / min.

[0022] Preferably, in the color fixing, the color fixing agent used is any one of tannic acid and citric acid or a combination of the two, and the color fixing time is 5-30 minutes.

[0023] Preferably, the pretreatment solution is any one of anhydrous ethanol, sodium hydroxide solution, sodium carbonate solution, alkaline urea solution, liquid ammonia, and glycine.

[0024] The dyeing principle of the present invention is as follows: curcumin is dissolved in a mixture of ethanol and water. On the one hand, since curcumin is easily soluble in the organic solvent ethanol, the use of ethanol can increase the content of curcumin in the dye solution. On the other hand, the volume ratio of water to ethanol is controlled within a range of 3:7-2:8, so that the average particle size of the curcumin dissolved in the dye solution can be smaller. Since the pores of cotton fibers are smaller, dye molecules with smaller particle sizes can more smoothly enter the pores of cotton fibers, thereby improving the dyeing effect of the curcumin.

[0025] Since the dyeing process is divided into adsorption, diffusion and fixation, the larger the specific surface area of ​​the fiber, the higher the surface energy of the fiber, the more dye molecules can be adsorbed, and the larger the pores, the easier it is for the dye molecules to diffuse and retain; during pretreatment, the pretreatment solution can swell the raw cotton fiber. After swelling, the specific surface area of ​​the raw cotton fiber increases, and the fiber micro-gap increases, which can make the subsequent dye solution and the raw cotton fiber have better contact, so that the curcumin dye molecules can be adsorbed, diffused and fixed to the raw cotton fiber to the maximum extent; and because the epidermis of the raw cotton fiber is composed of wax and fat, the curcumin dye molecules can be absorbed, diffused and fixed to the raw cotton fiber to the maximum extent. , pectin and other substances, among which wax has a protective effect on cotton and can prevent the invasion of external moisture, and anhydrous ethanol is used to dissolve the wax. After removing the wax, the raw cotton fiber has stronger hydrophilicity, and the dye solution with curcumin dye molecules can easily enter the interior of the raw cotton fiber and dye it; but after pretreatment with sodium hydroxide solution, sodium carbonate solution or alkaline urea solution, the pH value of the raw cotton fiber is easily converted to a relatively alkaline one, and curcumin has a poor dyeing effect in an alkaline environment. Therefore, the pH value of the raw cotton fiber after pretreatment is adjusted to 4-8 to further improve the dyeing effect of curcumin.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The dye liquor in the present invention adopts an ethanol-water system, utilizes ethanol as an organic solvent to dissolve curcumin, and preferably the volume ratio of water to ethanol is 3:7-2:8, which can improve the dyeing effect of curcumin; other chemical reagents are not added to the dye liquor to assist dyeing, so that the dye liquor can be directly recycled and reused without going through other processing steps, thereby avoiding dye waste and saving processing costs.

[0028] 2. The present invention pretreats raw cotton fibers so that a dye liquor can smoothly enter the raw cotton fibers, and curcumin dye molecules in the dye liquor are adsorbed, diffused, and fixed to the raw cotton fibers to the maximum extent, thereby further improving the dyeing effect of curcumin. Subsequently, the pH value of the pretreated raw cotton fibers is adjusted to improve the dyeing effect of curcumin. After dyeing, the fabric has bright color and good color, and the K / S value can reach about 9-12.

[0029] 3. The present invention does not require modification of curcumin and does not add a mordant, thus avoiding the use of toxic systems such as ethanol / phenol. Green and environmentally friendly reagents are used throughout the pretreatment, dyeing, and fixation stages, thus causing no environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the average particle size of the curcumin of Examples 1-10 dissolved in undiluted dye liquor.

[0031] Figure 2 is the average particle size of the curcumin of Examples 1-10 dissolved in the dye solution after being diluted 20 times. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions of each embodiment of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] The present invention dyes cotton with curcumin dye, combines curcumin molecules with cotton fibers, and achieves pH response performance and antibacterial and anti-inflammatory properties of the dyed cotton.

[0034] pH response performance: Since curcumin has two hydroxyl groups at both ends of the molecule, a conjugation effect of electron cloud deviation occurs under alkaline conditions. Therefore, when the pH is greater than 8, curcumin will turn from yellow to red. It can be used in food safety testing, medical and health testing, and many other aspects.

[0035] Antibacterial and anti-inflammatory properties: While steroidal and nonsteroidal anti-inflammatory drugs (NSAIDs) such as cintamicoxib, aspirin, ibuprofen, and phenylbutazone can be used to treat inflammatory diseases, most have side effects. Curcumin, on the other hand, possesses antibacterial and anti-inflammatory properties, comparable to those of steroidal and nonsteroidal drugs such as indomethacin and phenylbutazone, and is relatively safe for human use in most cases.

[0036] Example 1:

[0037] A salt-free and water-reduced dyeing method for dyeing raw cotton fibers with a natural dye, curcumin, is carried out in the following steps:

[0038] S1. Weigh 2g of raw cotton fiber.

[0039] S2. Prepare 50 mL of a mixed solution of water and ethanol, including 15 mL of deionized water and 35 mL of ethanol;

[0040] S3. Weigh 0.06 g of curcumin powder (the dye dosage is 3% owf), dissolve the curcumin powder in a mixed solution of water and ethanol, and sonicate until the curcumin is dissolved to prepare a dye solution;

[0041] S4, immersing the raw cotton fiber in the dye solution, measuring the pH of the dye solution to be 5, and then heating the raw cotton fiber in a 60°C water bath at a heating rate of 2°C / min for 1 hour; after the padding is completed, the padding rate of the raw cotton fiber is 232%;

[0042] S5. The raw cotton fiber obtained in S4 is placed in a 60° C. oven for drying, then washed with water, and finally fixed with tannic acid for 10 minutes to obtain a finished product of curcumin-dyed raw cotton fiber.

[0043] Example 2-10:

[0044] On the basis of Example 1, taking into account the volume ratio of ethanol and water in the dye liquor on the average particle size of curcumin dissolved in the dye liquor, the influence of the K / S value after raw cotton fiber dyeing, by changing the volume ratio of water and ethanol in the dye liquor, the variation pattern of the average particle size of curcumin dissolved in the dye liquor, the K / S value after raw cotton fiber dyeing was investigated; the K / S values ​​after dyeing of Examples 1-10 are finally obtained as shown in Table 1, and the average particle size of curcumin dissolved in the undiluted dye liquor of Examples 1-10 is shown in Table 1. Figure 1 As shown, the average particle size of curcumin in Examples 1-10 dissolved in the dye solution after dilution 20 times is as follows Figure 2 shown.

[0045] Table 1 Examples 1-10

[0046]

[0047]

[0048] Combine Figure 1 、 Figure 2 It can be learned that when the volume ratio of ethanol and water is 3:7-2:8, the average particle size of curcumin dissolved in the dye liquor reaches minimum; As shown in Table 1, the dyeing effect of embodiment 2 and embodiment 3 is better in embodiment 1-10, and the K / S value reaches 9.47267, 10.02933 after dyeing, and this is because the curcumin dye molecule of small particle size can more smoothly enter the space of raw cotton fiber, successfully dyes raw cotton fiber. Therefore, the volume ratio of preferred ethanol and water of the present invention is 3:7-2:8.

[0049] Examples 11-12:

[0050] On the basis of Example 1, considering the influence of dyeing temperature on the K / S value after dyeing in S4, the variation pattern of the K / S value after dyeing was investigated by changing the dyeing temperature while other conditions remained unchanged; the K / S values ​​after dyeing of Examples 11-12 were finally obtained as shown in Table 2.

[0051] Table 2 Examples 11-12

[0052] Example Dyeing temperature K / S value after dyeing 11 40℃ 8.99967 1 60℃ 10.02933 12 80℃ 10.36233

[0053] As can be seen from Table 2, as the dyeing temperature increases from 40°C to 60°C, the K / S value after dyeing increases from 8.99967 to 10.02933, a significant increase. As the dyeing temperature increases from 60°C to 80°C, the K / S value after dyeing increases from 10.02933 to 10.36233, a small increase that actually increases energy consumption. Therefore, the present invention prefers 60°C as the dyeing temperature.

[0054] Examples 13-16:

[0055] The difference from Example 1 is that the raw cotton fibers are first immersed in the pretreatment solution for pretreatment, and then placed in the prepared dye solution for padding.

[0056] Taking into account the influence of the pretreatment solution on the K / S value after dyeing, the variation pattern of the K / S value after dyeing was investigated by changing the pretreatment solution when other conditions remained unchanged; Example 13 used a pure ethanol solution for pretreatment. During the pretreatment, 2 g of raw cotton fiber was placed in 50 mL of pure ethanol solution, first ultrasonicated for 5 minutes and then in a 90° C. water bath for 10 minutes; Example 14 used a sodium carbonate solution for pretreatment. The sodium carbonate solution was obtained by dissolving 15 g of sodium carbonate in 1 L of ethanol aqueous solution (the volume ratio of water to ethanol was 9:1); during the pretreatment, 2 g of raw cotton fiber was placed in 50 mL of sodium carbonate solution, first ultrasonicated for 5 minutes, then in a 90° C. water bath for 10 minutes, and then the pH of the cotton was adjusted to about 5; Example 15 was pretreated with a sodium hydroxide solution prepared by dissolving 250 g of sodium hydroxide in 1 L of pure water. During the pretreatment, 2 g of raw cotton fiber was placed in 50 mL of sodium hydroxide solution and reacted at room temperature for 3 min, and then the pH value of the cotton was adjusted to about 5. Example 16 was pretreated with an alkaline urea solution prepared by dissolving sodium hydroxide (7% wt) and urea (12% wt) in pure water. During the pretreatment, 2 g of raw cotton fiber was placed in 50 mL of alkaline urea solution precooled at 0° C. for 10 min, mechanically stirred at 0° C. for 10 min, and then the pH value of the cotton was adjusted to about 5. The K / S values ​​after dyeing of Examples 13-16 were finally obtained as shown in Table 3.

[0057] Table 3 Examples 13-16

[0058] Example Preprocessing K / S value after dyeing 13 Anhydrous ethanol 9.57 14 Sodium carbonate solution 9.30 15 Sodium hydroxide solution 12.66 16 Alkaline urea solution 12.66

[0059] It can be seen from Table 3 that the K / S value after dyeing after pretreatment with sodium hydroxide solution and alkaline urea solution reaches more than 12, and the dyeing effect is excellent.

[0060] Examples 17-18:

[0061] Based on Example 1, considering the effect of dye concentration (owf) on the post-dyeing K / S value, the variation pattern of the post-dyeing K / S value was investigated by varying the dye concentration while keeping other conditions unchanged. The final post-dyeing K / S values ​​of Examples 17-18 are shown in Table 4.

[0062] Table 4 Examples 17-18

[0063] Example Dye concentration owf K / S value after dyeing 17 1% (0.02g curcumin dye) 4.82 1 3% (0.06g curcumin dye) 10.02933 18 5% (0.10g curcumin dye) 11.27

[0064] As can be seen from Table 4, as the dye concentration increases from 1% owf to 3% owf, the K / S value after dyeing increases from 4.82 to 10.02933, a significant increase. As the dye concentration increases from 3% owf to 5% owf, the K / S value after dyeing increases from 10.02933 to 11.27, a smaller increase, which actually increases dye consumption and causes dye waste. Therefore, the preferred dye concentration of the present invention is 3% owf.

Claims

1. A salt-free and water-reduced dyeing method for dyeing raw cotton fibers with a natural dye, curcumin, characterized in that: The dyeing method comprises: Dissolving curcumin powder in a mixture of ethanol and water to prepare a dye solution; wherein the volume ratio of water to ethanol in the mixture of ethanol and water is 3:7-2:8; First, the raw cotton fiber is immersed in a pretreatment solution for pretreatment, wherein the pretreatment solution is selected from any one of anhydrous ethanol, sodium hydroxide solution, sodium carbonate solution, alkaline urea solution, liquid ammonia, and glycine; the pH value of the pretreated raw cotton fiber is adjusted to 4-8, and then the raw cotton fiber is placed in the prepared dye solution for padding; The raw cotton fibers after being dipped in the pad dye solution are sequentially dried, washed and fixed to obtain a finished product; in the color fixing, a color fixing agent is any one of tannic acid and citric acid or a combination of the two, and the color fixing time is 5-30 minutes.

2. The salt-free and water-saving dyeing method for dyeing raw cotton fiber with a natural dye curcumin according to claim 1, wherein: The padding time is 20-120 minutes, and the padding rate of the raw cotton fiber after the padding is completed is 150-300%.

3. The salt-free and water-saving dyeing method for dyeing raw cotton fiber with a natural dye curcumin according to claim 1, wherein: The curcumin powder is used in an amount of 1-8% by weight of the fabric.

4. The salt-free and water-saving dyeing method for dyeing raw cotton fiber with a natural dye curcumin according to claim 1, wherein: The dyeing bath ratio of the padding is 1:10-1:50, and the pH of the dyeing solution before padding is 4-8.

5. The salt-free and water-saving dyeing method for dyeing raw cotton fiber with a natural dye curcumin according to claim 1, wherein: In the mixture of ethanol and water, the volume ratio of water to ethanol is 1:9-9:

1.

6. The salt-free and water-reduced dyeing method for dyeing raw cotton fiber with a natural dye curcumin according to claim 1, wherein: The padding temperature is 20-80°C, and the heating rate is 2-5°C / min.

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