Dye water as well as preparation method and application thereof

Abstract

The invention relates to the technical field of dyeing, in particular to dye water as well as a preparation method and application thereof. The dyeing water provided by the invention is researched and developed on the basis of natural plant extracts and biodegradable materials, not only has remarkable advantages in environmental protection and safety, but also can meet the technical requirements of efficient dyeing, and has the advantages of uniform dyeing, stable color and lasting effect. Through scientific component proportion and production process, the obtained environment-friendly dye water provides a sustainable green alternative scheme for the traditional leather dyeing industry.

Description

Technical Field

[0001] The invention relates to the technical field of dyeing, and in particular to dye water and a preparation method and application thereof. Background Art

[0002] In the traditional development of leather dyeing technology, chemical dyes and organic solvents have always been the mainstream, especially chemical dyes such as chromium salts, azo dyes, and acid dyes are widely used in leather dyeing. These dyes are not only relatively low in cost, but also can provide brighter color effects. However, the use of such chemical dyes also brings significant environmental and health problems. First, hexavalent chromium in chromium salt dyes is a carcinogen, and heavy metals and harmful organic substances often remain in dyeing wastewater, which is difficult to degrade by simple wastewater treatment methods. Secondly, azo dyes will produce carcinogenic aromatic amines during decomposition, posing a threat to human health. In addition, traditional chemical dyes usually rely on organic solvents, which release volatile organic compounds (VOCs) during production and application, causing pollution to air quality.

[0003] As the global requirements for environmental protection and health standards increase, the leather industry is facing increasing environmental pressure. The cost of wastewater treatment from traditional dyeing technology is gradually increasing. At the same time, the safety of leather products has also attracted much attention from consumers. In order to cope with these problems, plant extracts have gradually gained attention as natural dyes in recent years. However, the application of traditional plant dyes has problems such as unstable dyeing effect, insufficient permeability, and poor color durability. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a dye water and its preparation method and application. The dye water provided by the present invention is not only safe and environmentally friendly, but also has uniform dyeing, stable color and lasting effect.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a dye water, which comprises, by mass percentage, 5-15% of a dye, 1-5% of a biodegradable surfactant, 0.1-0.5% of a weakly acidic pH regulator and 80-90% of a solvent; the pH value of the dye water is 4.5-6.5;

[0007] The solvent is water or an ethanol-water mixture;

[0008] The dye comprises one or more of plant dyes, algae dyes and microbial fermentation products;

[0009] The plant dye comprises one or more of tea polyphenols, amur cork extract and onion peel extract.

[0010] Preferably, it also includes 0.1-0.5% of natural preservatives.

[0011] Preferably, the weakly acidic pH regulator includes citric acid and / or acetic acid.

[0012] Preferably, the plant dye is obtained from plant raw materials by supercritical carbon dioxide extraction, steam distillation extraction or solvent extraction.

[0013] Preferably, the biodegradable surfactant includes one or more of glycoside surfactants, amino acid surfactants, fatty acid surfactants, cellulose surfactants and starch surfactants.

[0014] Preferably, the natural preservative includes sodium benzoate or potassium sorbate.

[0015] Preferably, the method comprises the following steps: dissolving the dye in a solvent and then adding a biodegradable surfactant to the obtained solution to obtain a mixed solution; adding a weakly acidic pH regulator to the mixed solution to adjust the pH value to 4.5-6.5 to obtain the dye water.

[0016] Preferably, after adjusting the pH value to 4.5-6.5, the process further comprises adding a natural preservative to the solution after adjusting the pH value.

[0017] Preferably, each step is carried out at 25-30°C.

[0018] The present invention provides application of the dye water described in the above scheme or the dye water prepared by the preparation method described in the above scheme in leather dyeing.

[0019] The invention provides a dye water, which comprises, by weight percentage, 5-15% of a dye, 1-5% of a biodegradable surfactant, 0.1-0.5% of a weakly acidic pH regulator and 80-90% of a solvent; the pH value of the dye water is 4.5-6.5; the solvent is water or an ethanol-water mixture; the dye comprises one or more of a plant dye, an algae dye and a microbial fermentation product; the plant dye comprises one or more of tea polyphenols, abercrombie and fitch walnut extract and an onion peel extract.

[0020] The present invention uses one or more of tea polyphenols, amur cork extract and onion peel extract as dyes, or uses algae dyes and microbial fermentation products as dyes, and these dyes usually contain compounds such as polyphenols and flavonoids, which can react chemically with proteins in leather, thereby firmly binding to leather fibers. Through this chemical reaction, the dyeing effect is not only stable, but also can remain non-fading for a long time, ensuring that the color is uniform and stable, and has strong light resistance and washability. In addition, the natural compounds (such as polyphenols and flavonoids) in these dyes themselves have strong antioxidant properties and can resist the damage of ultraviolet rays and the attack of free radicals. This characteristic enables the dyed leather to still maintain the stability of color under long-term exposure to natural light, avoiding fading or discoloration. Moreover, different dyes have different natural pigments, which can provide leather with diversified choices from dark to light, from cold to warm tones, etc.; the use of natural plant extracts can not only reduce the pollution of chemical synthetic dyes to the environment, but also enhance the natural sense of the dyeing effect and the stability of color.

[0021] The present invention adopts biodegradable surfactants, which can help dye molecules to diffuse better on the leather surface by reducing the surface tension of the liquid, enhance the permeability and adsorption of the dye, and ensure uniform dyeing. Since such surfactants are degradable, they will not accumulate in wastewater like traditional surfactants, and have less impact on the environment.

[0022] The present invention can effectively maintain the stability of dye water by using a weakly acidic pH regulator and controlling its dosage, thereby avoiding excessive decomposition of the dye or damage to leather fibers during the dyeing process. In addition, an appropriate pH value can also increase the affinity of the dye molecules and enhance the uniformity and durability of dyeing.

[0023] Furthermore, the dye water of the present invention uses natural preservatives, which can effectively extend the shelf life of the dye water and prevent the dye water from deteriorating due to the growth of bacteria or mold during storage. The biological preservatives can not only extend the service life of the product, but also ensure that the product does not produce harmful byproducts during long-term storage, further improving its environmental friendliness.

[0024] The dye water provided by the present invention has the following advantages:

[0025] Environmental protection: Compared with the heavy metals and harmful chemicals in traditional dye water, plant dyes, biological dyes and biodegradable surfactants will not cause secondary pollution to the environment after use. Wastewater treatment is simpler and the treatment cost is greatly reduced, which meets the requirements of modern environmental protection regulations.

[0026] Safety: Since the dye water provided by the present invention does not contain harmful chemical ingredients, the potential harm to the health of operators during production, use and treatment is greatly reduced. Its natural ingredients are not only skin-friendly, but also avoid the risk of allergies or poisoning caused by inhalation or skin contact in traditional dyes.

[0027] Long-lasting dyeing effect: Natural plant dyes, algae dyes and microbial fermentation products can be closely combined with leather fibers to ensure uniform and stable colors, and have strong light resistance and wash resistance. Compared with traditional chemical dyes, the environmentally friendly dye water-dyed colors provided by the present invention are more natural, more durable and less prone to fading.

[0028] Simple wastewater treatment: Since it does not contain toxic heavy metals and chemical solvents, the wastewater generated after using environmentally friendly dye water can be treated by simple biodegradation methods. This not only reduces the complexity and cost of sewage treatment, but also further reduces the pollution burden of the factory on the water environment.

[0029] Strong adaptability: the dye water provided by the invention is suitable for common leather materials such as cowhide, pigskin, etc. and various types of leather dyeing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The dyeing effect diagrams of Comparative Example 1 (top) and Example 1 (bottom);

[0031] Figure 2 It is the dyeing effect diagram of Comparative Example 2 (top) and Example 2 (bottom). DETAILED DESCRIPTION

[0032] The invention provides a dye water, which comprises, by mass percentage, 5-15% of a dye, 1-5% of a biodegradable surfactant, 0.1-0.5% of a weakly acidic pH regulator and 80-90% of a solvent; the pH value of the dye water is 4.5-6.5.

[0033] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0034] The source of the dye is explained below.

[0035] In the present invention, the dye comprises one or more of plant dyes, algae dyes and microbial fermentation products; the plant dye comprises one or more of tea polyphenols, amur cork extract and onion peel extract.

[0036] In the present invention, the plant dye can be obtained by purchasing commercial products (such as Aladdin reagent, Macklin reagent, etc.), or can be obtained from plant raw materials through supercritical carbon dioxide extraction, steam distillation extraction or solvent extraction.

[0037] In the present invention, the plant raw material used for the tea polyphenols is preferably tea leaves, the plant raw material used for the amur cork extract is preferably amur cork; and the plant raw material used for the onion peel extract is preferably onion peel.

[0038] In the present invention, the preparation method of the plant dye preferably includes the following steps: washing the plant raw material, drying and crushing it into fine powder, then performing supercritical carbon dioxide extraction or steam distillation extraction or solvent extraction, and post-treating the obtained extract to obtain the plant dye.

[0039] In the present invention, the drying temperature is preferably 50-60°C; the conditions of the supercritical carbon dioxide extraction preferably include: a temperature of 35-55°C, a pressure of 15-35MPa, a CO2 flow rate of 1-3L / min, and an extraction time of 1-3h. The present invention preferably adds a small amount of co-solvent ethanol to improve the extraction efficiency of polar components during supercritical carbon dioxide extraction. Since CO2 has a weak polarity, it has a strong solubility for non-polar or weakly polar components, but a limited solubility for polar components. By adding an appropriate amount of co-solvent, the solubility of CO2 for polar compounds can be enhanced, thereby extracting the target component more efficiently. In the present invention, the amount of co-solvent ethanol added is adjusted according to the target component and equipment conditions, generally 5-15% (volume ratio) of the CO2 flow rate. In the present invention, when used to extract tea polyphenols, the amount of co-solvent is preferably 5% to 10% (volume ratio); when used to extract Phellodendron amurense extract, the amount of co-solvent is preferably 7% to 12% (volume ratio), which is suitable for weak polar components (such as berberine); when used to extract onion peel extract, the amount of co-solvent is preferably 10% to 15% (volume ratio), which is suitable for weak polar polyphenols (such as quercetin). In the present invention, the co-solvent ethanol is preferably food grade or pharmaceutical grade ethanol, and the purity of the co-solvent must reach ≥95%.

[0040] In a specific embodiment, the temperature of the supercritical carbon dioxide extraction can be 35°C, 40°C, 45°C, 50°C or 55°C; the pressure of the supercritical carbon dioxide extraction can be 15MPa, 20MPa, 25MPa, 30MPa or 35MPa; the CO2 flow rate of the supercritical carbon dioxide extraction can be 1L / min, 1.5L / min, 2L / min, 2.5L / min or 3L / min; the time of the supercritical carbon dioxide extraction can be 1h, 1.5h, 2h, 2.5h or 3h.

[0041] In the present invention, the temperature of the water vapor distillation is preferably 70-100° C., and the time of the water vapor distillation is preferably 1-3 hours. The present invention has no requirements on the flow rate of water vapor, as long as the volatile components are effectively taken out and condensed.

[0042] In the present invention, the extraction solvent used for the solvent extraction is preferably an ethanol aqueous solution, and the volume content of ethanol in the ethanol aqueous solution is preferably 55-80%; the solid-liquid ratio of the fine powder to the extraction solvent is preferably 1:5 to 1:10; the temperature of the solvent extraction is preferably 45-60°C; and the extraction time is preferably 2-3 hours.

[0043] In the present invention, the extract obtained by supercritical carbon dioxide extraction is an essential oil or concentrated plant pigment rich in fat-soluble components, which exist in the form of oil or viscous liquid and need to be properly purified; therefore, when supercritical carbon dioxide extraction is used, the post-treatment is preferably purification. The present invention has no special requirements for the purification process, and a purification process well known in the art can be used.

[0044] In the present invention, the extract obtained by steam distillation is a steam condensate, which contains volatile components and essential oils. The condensate needs to be phase separated to separate the essential oils; therefore, when steam distillation is used, the post-treatment is preferably phase separation. The present invention has no special requirements for the phase separation process, and a phase separation process well known in the art can be used.

[0045] In the present invention, solvent extraction is adopted. When the plant dye is tea polyphenol, the post-treatment preferably comprises: solid-liquid separation of the extracted material, reduced pressure concentration of the obtained extract, spray drying or freeze drying of the obtained concentrate to obtain tea polyphenol.

[0046] When solvent extraction is used and the plant dye is a Phellodendron chinense extract, the post-treatment preferably includes: solid-liquid separation of the extracted material, concentration of the obtained extract under reduced pressure, purification using a macroporous resin (HPD-100 type), eluting impurities with water, eluting the effective ingredients with 70% ethanol, and obtaining the Phellodendron chinense extract after spray drying.

[0047] When solvent extraction is used and the plant dye is an onion peel extract, the post-treatment preferably includes: solid-liquid separation of the extracted material, reduced pressure concentration of the obtained extract, separation of the obtained concentrate using a silica gel column, washing with water and eluting with 90% ethanol, and freeze-drying the eluate to obtain an onion peel extract.

[0048] In the present invention, the above-mentioned plant dye has a complex molecular structure and usually contains compounds such as polyphenols and flavonoids, which can react chemically with proteins in leather, thereby firmly binding to leather fibers. Through this chemical reaction, the dyeing effect is not only stable, but also can remain non-fading for a long time. In addition, natural plant dyes have strong antioxidant properties, which further enhances the durability of leather color.

[0049] In the present invention, the biological dye includes algae dye and / or microbial fermentation product.

[0050] In the present invention, the algae dye is preferably phycocyanin and / or spirulina extract; the phycocyanin and spirulina extract are preferably commercially available products known in the art, for example, phycocyanin purchased from Xi'an Tianyi Biotechnology Co., Ltd., product name: phycocyanin (Spirulina Phycocyanin Powder), model: food grade / industrial grade, content specification: phycocyanin content ≥30%, ≥50%, ≥90% (selected as needed). For another example, the spirulina extract purchased from Chengdu Lujia Biotechnology Co., Ltd., product name: Spirulina Extract (SpirulinaExtract), model: food grade, content specification: phycocyanin content ≥50%. For another example, DIC Corporation (Japan), product name: LinaBlue, model: natural food dye, content specification: phycocyanin content ≥80%.

[0051] In the present invention, the microbial fermentation product is preferably a fermentation product of red yeast (Rhodotorula) or Monascus (Monascus), and commercially available products can be used. Among them, the main components of the fermentation product of red yeast are astaxanthin (Astaxanthin) and β-carotene (Beta-Carotene), and the color is orange-red to dark red; the main components of the fermentation product of Monascus are: Monascorubrin (Monascorubrin) and Monascus orange (Rubropunctatin), the color is orange-red and dark red, and it is widely used in food and industrial dyes.

[0052] Commonly used commercial products of microbial fermentation products include: Product name: Rhodotorula Extract, model: industrial grade, main ingredients: astaxanthin ≥2%, β-carotene ≥5% (purchased from Xi'an Tianyi Biotechnology Co., Ltd.); Product name: Monascus Pigment, model: food grade, main ingredients: Monascus red ≥2%, Monascus orange ≥3% (purchased from Nanjing Chunhai Biotechnology Co., Ltd.); Product name: Red Ferment Filtrate, model: food grade natural dye (from Chr. Hansen (Denmark)).

[0053] Next, the dye water will be described.

[0054] In terms of mass percentage, the dye water provided by the present invention includes 5-15% of a dye. In a specific embodiment, the content of the dye can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%. In the present invention, the dye includes one or more of a plant dye, an algae dye and a microbial fermentation product; the plant dye includes one or more of tea polyphenols, amber bark extract and onion peel extract.

[0055] When the dye is tea polyphenol, the content of the dye is preferably 9-11%; when the dye is abercrombie and fitch extract, the content of the dye is preferably 7-9%. When the dye is an onion peel extract, the content of the dye is preferably 10-12%; when the dye is an algae dye or a microbial fermentation product, the content of the dye is preferably 5-8%; when the dye is a mixture of multiple dyes, the content of the dye is preferably 6-10%.

[0056] The dye water provided by the present invention comprises 1-5% of a biodegradable surfactant in terms of mass percentage, and in specific embodiments, it may be 1%, 2%, 3%, 4% or 5%. In the present invention, the biodegradable surfactant preferably comprises one or more of a glycoside surfactant, an amino acid surfactant, a fatty acid surfactant, a cellulose surfactant and a starch surfactant.

[0057] In the present invention, the biodegradable surfactant can be purchased or prepared by methods well known in the art, preferably purchased from commercial products to ensure stable quality and reliability of the extraction process. In the present invention, the glycoside surfactant preferably includes decyl glucoside; the amino acid surfactant preferably includes sodium glutamate; the fatty acid surfactant preferably includes sodium laurate; the cellulose surfactant preferably includes one or more of sodium carboxymethyl cellulose (CMC-Na), hydroxypropyl cellulose (HPC), methyl cellulose (MC), ethyl cellulose (EC) and cellulose sulfate; the starch surfactant preferably includes one or more of alkyl starch ether, sodium carboxymethyl starch (CMS-Na), oxidized starch, cationic starch and phosphorylated starch.

[0058] In the present invention, the main function of the biodegradable surfactant is to help the pigment in the dye water to be evenly distributed on the leather surface and promote the deep penetration of the dye. Traditional surfactants are mostly petrochemical products, which are difficult to degrade and will pollute the water body after use. The present invention selects biodegradable surfactants, such as glycosides, amino acids or fatty acids, which can not only effectively play a surface active role, but also can be quickly degraded after use, reducing the burden on the environment.

[0059] In terms of mass percentage, the dye water provided by the present invention includes 0.1-0.5% of a weakly acidic pH regulator, and in a specific embodiment, it can be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%. In the present invention, the weakly acidic pH regulator includes citric acid and / or acetic acid; the present invention has no special requirements for the concentrations of the citric acid and acetic acid. In a specific embodiment, the concentration of the citric acid can be 1 mol / L, and the mass concentration of the acetic acid can be 99%. In the present invention, the weakly acidic pH regulator must meet the dosage requirement of 0.1-0.5% and at the same time meet the requirement that the pH value of the dye water is 4.5-6.5, so that the stability of the dye water can be maintained. If only the pH requirement is met, and the dosage does not meet the requirement of 0.1-0.5%, the dyeing effect of different batches of dye water will be significantly different. In a specific embodiment, the pH value of the dye water can be 4.5, 5.0, 5.5, 6.0 or 6.5. The pH value of the dye water will affect the dye stability during the dyeing process and the color absorption effect of the leather. The present invention uses a weakly acidic pH regulator to adjust the pH value of the dye water to a weakly acidic range suitable for leather dyeing (usually pH 4.5-6.5), thereby ensuring a stable dyeing effect and avoiding damage to leather fibers.

[0060] In terms of mass percentage, the dye water provided by the present invention preferably includes 0.1-0.5% of a natural preservative, and in a specific embodiment, it may be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%. In the present invention, the natural preservative preferably includes sodium benzoate or potassium sorbate. The present invention prolongs the storage life of the dye water by adding a preservative. The preservatives used in traditional dye water are mostly synthetic chemicals, which may release harmful by-products. The present invention uses a natural preservative, which can not only effectively inhibit the growth of microorganisms, but also is harmless to the environment and human health.

[0061] The dye water provided by the present invention comprises 80-90% of solvent. In the present invention, the solvent is preferably water or an ethanol-water mixture; the water is preferably deionized water or purified water. The volume percentage of ethanol in the ethanol-water mixture is preferably ≤65%. The present invention uses deionized water or purified water as a solvent to avoid the influence of impurities in tap water on the stability of the dye water.

[0062] The present invention provides a method for preparing the dye water described in the above scheme, comprising the following steps: dissolving a dye in a solvent and adding a biodegradable surfactant to the obtained solution to obtain a mixed solution; adding a weakly acidic pH regulator to the mixed solution to adjust the pH value to 4.5-6.5 to obtain the dye water.

[0063] In the present invention, the dissolution is preferably performed under stirring conditions.

[0064] Before the dissolution, the present invention preferably further comprises nano-processing the dye. In the present invention, the particle size of the dye (referred to as nano-dye) after the nano-processing is preferably less than 200 nm. The present invention improves the distribution uniformity and permeability of the dye on the leather surface by nano-processing the dye, thereby improving the dyeing effect, while maintaining the environmental friendliness of the dye.

[0065] In the present invention, the nano-processing preferably comprises the following steps: placing the dye powder in a dispersion medium for wet grinding to obtain a grind; subjecting the grind to high pressure homogenization and spray drying to obtain the nano-processed dye.

[0066] In the present invention, the particle size of the dye powder is preferably 50-100 μm; the dispersion medium is preferably water or an ethanol-water mixed solution; the volume ratio of ethanol in the ethanol-water mixed solution is preferably 10-20%; the solid-liquid ratio of the fine powder to the dispersion medium is preferably 1:5 to 1:10; the conditions for the wet ball milling preferably include: the ball milling medium is a zirconium oxide bead or alumina bead with a diameter of 0.1-0.3 mm, the rotation speed is 800-1200 rpm, the time is 1-3 hours, and the temperature is 25-35° C. In the present invention, the wet ball milling preferably uses a nano ball mill or a wet ultrafine grinder.

[0067] In the present invention, the conditions of the high-pressure homogenization treatment preferably include: a pressure of 150-300 MPa, a cycle number of 3-5 times, and a temperature maintained at 20-30° C. The present invention further refines the particles and improves the uniformity through high-pressure homogenization treatment to obtain a dye dispersion with an average particle size of less than 200 nm.

[0068] In the present invention, the inlet air temperature of the spray drying is preferably 100-150° C., and the outlet air temperature is preferably 60-80° C. The nano dye obtained by spray drying is preferably stored in a dry environment at 15-25° C.

[0069] After adding the biodegradable surfactant, the present invention preferably continues stirring for 30 to 60 minutes, and the stirring speed at this time is preferably 100 to 500 rpm, more preferably 100 to 200 rpm. The present invention controls the stirring speed after adding the surfactant to prevent bubbles from being generated in the dye water, which affects the stability and dyeing effect of the dye water.

[0070] When adjusting the pH value, the present invention preferably uses a pH meter to monitor the pH value in real time. An accurate and appropriate pH value has a direct impact on the dyeing effect. When the pH value is between 4.5 and 6.5, it can ensure that the plant pigment remains stable in the dye water and can be firmly bonded to the leather fiber during the dyeing process.

[0071] After adjusting the pH value, the present invention preferably further comprises adding a natural preservative to the solution after adjusting the pH value. In the present invention, after adding the natural preservative, the present invention preferably continues stirring for 15 to 25 minutes, and the stirring speed is preferably 100 to 500 rpm, more preferably 100 to 200 rpm. The present invention adds a natural preservative to prevent the growth of microorganisms.

[0072] In the present invention, the above steps are preferably carried out at 25-30° C. In the present invention, too high a temperature may cause the decomposition of the dye and affect the dyeing effect. In particular, in the step of dissolving the dye, temperature control is particularly important.

[0073] After obtaining the dye water, the present invention preferably filters the dye water to remove possible residual microparticles and insolubles. The present invention preferably uses a filter with a pore size of 0.22 to 0.45 μm to ensure the clarity and stability of the dye water.

[0074] The present invention preferably puts the filtered dye water into a clean sealed container, avoids direct sunlight (to prevent pigment degradation), and stores it in a dry and cool environment for future use. In the present invention, the storage temperature is preferably 15-25°C.

[0075] The present invention provides application of the dye water described in the above scheme or the dye water prepared by the preparation method described in the above scheme in leather dyeing.

[0076] The present invention has no special requirements for the leather, and any leather known in the art can be used, such as cowhide, pigskin, and sheepskin.

[0077] Before dyeing, the present invention preferably pre-treats the leather. The present invention has no special requirements for the pre-treatment, and the leather surface can be cleaned to remove impurities and grease that may affect the dyeing effect. Generally, a mild surfactant is used to clean the leather, followed by rinsing with deionized water and drying.

[0078] The present invention preferably adopts the dip dyeing method or the spray dyeing method for dyeing.

[0079] In the present invention, when the material is dyed by the dip dyeing method, the temperature of the dyeing is preferably 25 to 35°C, and the time is preferably 30 to 60 minutes. Those skilled in the art can adjust the dyeing temperature and time within the above range according to the leather type and dyeing depth requirements. Lower temperatures (such as 25°C) are suitable for light dyeing and light colors, while higher temperatures (such as 30 to 35°C) can enhance the permeability and adsorption capacity of the dye and are suitable for dark dyeing. It is worth noting that the temperature cannot be too high to prevent the degradation of plant pigments.

[0080] The present invention preferably maintains stirring during the dyeing process. The stirring speed is preferably 100-200 rpm. The present invention ensures uniform distribution of the dye by stirring to prevent color spots or uneven dyeing.

[0081] In the present invention, when dyeing is performed by spray dyeing, the dyeing temperature is preferably 25-35° C. The present invention has no special requirements on the number of spray dyeing, and the number of spray dyeing can be adjusted according to the type of leather and the dyeing depth requirements.

[0082] In the present invention, if necessary, the leather can be gently cleaned with a weak acid or neutral solution to remove excess dye on the surface and ensure uniform and stable color.

[0083] After the dyeing is completed, the dyed leather is preferably dried naturally or at low temperature (40-50° C.) The present invention avoids the high temperature from affecting the texture of the leather and the stability of the dye by drying naturally or at low temperature.

[0084] The dye water provided by the present invention and its preparation method and application are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0085] In the following examples and comparative examples, the sources of the coloring agent are as follows:

[0086] The extraction process of tea polyphenols extract is as follows:

[0087] Target ingredients: catechins, flavonoids.

[0088] Extraction process:

[0089] 1. Raw material processing: Use fresh or dried green tea leaves, wash and dry at 40°C to ensure that the active ingredients of the tea leaves are not destroyed. Grind the dried tea leaves into a particle size of 1 to 2 mm.

[0090] 2. Solvent extraction:

[0091] A 70% ethanol aqueous solution was used as the extraction solvent, with a solid-liquid ratio of 1:10 (i.e., 10 L of solvent was added for every 1 kg of tea leaves).

[0092] The extraction temperature was controlled at 50-60°C, the extraction time was 2 hours, and the stirring speed was maintained at 200 rpm.

[0093] The extract was centrifuged and filtered to remove the residue.

[0094] 3. Concentration and drying: The extract is concentrated to 1 / 10 of the volume by a vacuum concentration device, and the temperature is controlled below 50° C. The concentrate is spray dried or freeze dried to obtain a powdered tea polyphenol extract.

[0095] Extract characteristics: Content: Tea polyphenols ≥ 50%, of which EGCG accounts for more than 30%.

[0096] The extraction process of Phellodendron chinense extract is as follows:

[0097] Target ingredients: berberine, berberine, and flavonoids.

[0098] Extraction process:

[0099] 1. Raw material processing: Wash the bark of Phellodendron amurense, slice it and dry it at 40°C. Grind it into particles of 2-3 mm.

[0100] 2. Solvent extraction: Use 60% ethanol aqueous solution as solvent, with a solid-liquid ratio of 1:8. The extraction temperature is controlled at 60°C, the extraction time is 3 hours, and the stirring speed is 200rpm. Extract twice and combine the extracts.

[0101] 3. Concentration and purification: The extract is concentrated to 1 / 5 of the original volume under reduced pressure. Purification is performed using a macroporous resin (such as HPD-100), and the elution conditions are washing with water to remove impurities, and then eluting the effective components with 70% ethanol.

[0102] 4. Drying: The Phellodendron amurense extract powder was obtained by spray drying.

[0103] Extract characteristics: Content: berberine ≥10%.

[0104] The extraction process of onion peel extract is as follows:

[0105] Target ingredients: quercetin, flavonoids, and polyphenols.

[0106] Extraction process:

[0107] 1. Raw material processing: Collect onion peels, wash and dry at 45°C to a moisture content of less than 10%. Grind to a particle size of 0.5-1 mm.

[0108] 2. Solvent extraction: Use 80% ethanol solution as the extraction solvent, with a solid-liquid ratio of 1:8. The extraction temperature is controlled at 50°C and the extraction time is 2 hours. The extract is centrifuged to remove the residue.

[0109] 3. Concentration and purification: The extract was concentrated to 1 / 5 of its volume under reduced pressure and separated by silica gel column chromatography, with the elution conditions being water washing followed by 90% ethanol.

[0110] 4. Drying: Use freeze drying equipment to prepare powdered onion peel extract.

[0111] Extract characteristics: Content: Quercetin ≥ 20%.

[0112] The extraction process of Gardenia jasminoides extract is as follows:

[0113] 1. Raw material selection and preparation:

[0114] Gardenia fruit: Choose ripe gardenia fruit as raw material and wash it to remove impurities and dirt on the surface.

[0115] Drying: Dry the washed gardenia fruits naturally in a cool, ventilated place, or dry them at a low temperature (40℃ to 50℃) until the moisture content drops below 10%.

[0116] 2. Crushing and soaking:

[0117] Crushing: The dried gardenia fruit is crushed into coarse particles to increase the contact area with the extraction solvent.

[0118] Soaking: Put the crushed gardenia granules into a container and add 95% ethanol solution with a volume ratio of 1:7 (i.e., add 7L ethanol for every 1kg of gardenia powder). The soaking time is 24 hours, and the mixture should be stirred occasionally during the soaking process to promote the dissolution of the active ingredients.

[0119] 3. Heating reflux extraction:

[0120] The soaked gardenia solution is extracted in a heating reflux device for 3 hours, and the extraction temperature is controlled at 60° C. to 70° C. Heating reflux can improve the extraction efficiency of the effective ingredients and retain the activity of the natural pigment.

[0121] 4. Filtration and concentration:

[0122] Filtration: Filter the extract through filter cloth or vacuum filtration device to remove residue and obtain preliminary gardenia extract.

[0123] Concentration: The filtered extract is concentrated to the desired concentration in a vacuum concentration device, and the temperature is controlled at 40°C to 50°C to avoid high temperature destroying the pigment components in the gardenia.

[0124] 5. Purification and storage:

[0125] Further purification was carried out by column chromatography to separate and purify the main pigment components in Gardenia (mainly Gardenia glycoside and Gardenia jasminoides).

[0126] Finally, the purified gardenia extract is stored in a light-proof, sealed container in a low-temperature environment to prevent oxidation and degradation.

[0127] Other raw materials are all commercially available products, among which decyl glucoside surfactant was purchased from Aladdin Reagent, sodium glutamate surfactant was purchased from Aladdin Reagent, and sodium laurate surfactant was purchased from Aladdin Reagent.

[0128] Example 1: Dyeing with environmentally friendly dye water using tea polyphenols

[0129] raw material:

[0130] Tea polyphenols extract: 10%;

[0131] Biodegradable surfactant (decyl glucoside): 2%;

[0132] Citric acid: 0.3%;

[0133] Sodium benzoate: 0.2%;

[0134] Deionized water: 87.5%.

[0135] step:

[0136] Add 10g of tea polyphenol extract to 87.5g of deionized water and stir for 30 minutes. After complete dissolution, the solution is light yellow.

[0137] Add 2 g of decyl glucoside surfactant, keep stirring at 200 rpm, and continue stirring for 45 minutes until the solution becomes more uniform;

[0138] Add 0.3 g of citric acid dropwise and monitor the pH value until the pH value is adjusted to 5.5;

[0139] 0.2 g of sodium benzoate was added as a preservative, the stirring speed was adjusted to 100 rpm, and the mixture was stirred for 15 minutes;

[0140] Filter the dye water to obtain clear and uniform dye water and store it in a sealed container.

[0141] Dyeing process:

[0142] The cowhide was dyed with the dye water of Example 1 at a dyeing temperature of 30° C. and a dyeing time of 45 minutes. After dyeing, the leather showed a uniform dark brown color with good glossiness.

[0143] result:

[0144] The dyed cowhide has good color stability, with no obvious fading after exposure to natural light for 30 days, excellent abrasion resistance and water resistance, and no color spots or unevenness were observed.

[0145] The test method is as follows:

[0146] 1. Wear resistance test

[0147] Purpose of the test: To evaluate the durability of the dyed leather surface under friction, mainly to observe whether the dye layer falls off, is damaged or faded.

[0148] Test method:

[0149] Reference standard: GB / T 3903.7-2019.

[0150] Equipment: Abrasion testing machine (Martindale abrasion tester).

[0151] Test steps:

[0152] 1. Cut a small sample of 5 cm × 5 cm from the leather sample after dyeing.

[0153] 2. Fix the sample on the abrasion testing machine, set the friction head to standard wool cloth or rubber, and the pressure to 9kPa.

[0154] 3. Perform reciprocating friction at a frequency of 40 times / min.

[0155] 4. Set the number of friction times according to test requirements (such as 1000 times, 2000 times or 5000 times).

[0156] Evaluation index: The degree of damage to the leather surface after friction. The fading of the dye layer (through color fastness rating).

[0157] Performance data:

[0158] Number of frictions: After 1000 times, the dyeing layer remains intact and the color change level is ≥ 4 (refer to the gray sample card standard).

[0159] Conclusion: Excellent wear resistance.

[0160] 2. Water resistance test

[0161] Test purpose: To evaluate the tolerance of dyed leather samples in a water immersion environment, mainly to observe the shedding or dissolution of the dye layer.

[0162] Test method:

[0163] Reference standard: ISO 11641 (Test for color fastness to water resistance of leather).

[0164] Equipment: Water fastness tester.

[0165] Test steps:

[0166] 1. Take a dyed leather sample of size 4cm x 10cm.

[0167] 2. Soak the sample in distilled water and set the water temperature to 40℃.

[0168] 3. The soaking time is 30 minutes or 60 minutes.

[0169] 4. After soaking, take out the sample, absorb the surface moisture with absorbent paper, and let it dry naturally.

[0170] 5. Observe the dissolution, fading or surface damage of the dye layer.

[0171] Evaluation index: Dissolution degree of dye layer. Color fastness rating (according to standard gray card).

[0172] Performance data:

[0173] After immersion for 60 minutes, there is no obvious dissolution or fading of the dye layer, and the color fastness grade is ≥4.

[0174] Conclusion: Excellent water resistance.

[0175] 3. Color stability test

[0176] Purpose of the test: To evaluate the fading of dyed leather under different lighting conditions.

[0177] Test method:

[0178] Reference standard: ISO 105-B02 (Tests for colour fastness to light of textiles and leather).

[0179] Equipment: Light color fastness tester.

[0180] Test steps:

[0181] 1. Take a leather sample with a size of 15cm x 5cm.

[0182] 2. In the light color fastness tester, simulate exposure to natural light (such as xenon arc light) and set the test time to 24 hours.

[0183] 3. After the test, compare the specimen with an unexposed control sample.

[0184] Evaluation indicators: Degree of fading (rated by gray scale). Level of color change after exposure to light.

[0185] Performance data:

[0186] After 48 hours of exposure, the color change level of the dye layer is ≥ level 4, and the fading is very slight.

[0187] Conclusion: Excellent color stability.

[0188] Example 2: Dyeing with environmentally friendly dyes using Phellodendron amurense extract

[0189] raw material:

[0190] Barberry extract: 8%;

[0191] Biodegradable surfactant (sodium glutamate): 3%;

[0192] Acetic acid: 0.4%;

[0193] Potassium sorbate: 0.2%;

[0194] Deionized water: 88.4%.

[0195] step:

[0196] Dissolve 8g of Phellodendron amurense extract in 88.4g of deionized water, set the stirring speed to 120rpm, and stir until it is completely dissolved and the solution appears light yellow;

[0197] Add 3 g of sodium glutamate surfactant, increase the speed to 200 rpm, stir for 30 minutes, and the solution becomes uniform and viscous;

[0198] Add 0.4 g of acetic acid to adjust the pH value of the solution to 5.8, reduce the stirring speed to 100 rpm, keep stirring for 10 minutes, and maintain the temperature at 30 °C;

[0199] 0.2 g of potassium sorbate was added as a preservative, the stirring speed was 100 rpm, and after stirring for 10 minutes, the environmentally friendly dye water was obtained by filtration.

[0200] Dyeing process:

[0201] Pigskin was dyed with the dye water of Example 2, the dyeing temperature was controlled at 35° C., and the dyeing time was 60 minutes. After dyeing, the leather showed a natural light yellow color and a smooth surface.

[0202] result:

[0203] After being exposed outdoors for 30 days, the dyed pigskin still had bright colors, and the light resistance of the leather was enhanced, without obvious fading. The dye water of Example 2 effectively improved the UV resistance of the leather, and the dyeing effect was long-lasting.

[0204] Example 3: Dyeing with environmentally friendly dye water using onion peel extract

[0205] raw material:

[0206] Onion peel extract: 12%;

[0207] Biodegradable surfactant (sodium laurate): 2.5%;

[0208] Citric acid: 0.5%;

[0209] Sodium benzoate: 0.3%;

[0210] Deionized water: 84.7%.

[0211] step:

[0212] Dissolve 12 g of onion peel extract in 84.7 g of deionized water and stir until completely dissolved. The solution turns reddish brown.

[0213] Add 2.5 g of sodium laurate surfactant and stir for 40 minutes to ensure a uniform solution;

[0214] Add 0.5 g of citric acid to adjust the pH of the solution to 5.2;

[0215] Add 0.3 g of sodium benzoate, stir for 10 minutes and then filter to obtain uniform dye water.

[0216] Dyeing process:

[0217] The sheepskin was dyed with the dye water of Example 3, the dyeing temperature was set at 32° C., and the dyeing time was 50 minutes. After dyeing, the sheepskin showed a uniform brown-red color with a natural luster.

[0218] result:

[0219] After 30 days of natural light exposure, the dyed sheepskin has little color change, showing good light resistance and wear resistance. The dyeing effect is uniform, without any fading or unevenness.

[0220] Example 4

[0221] The difference from Example 1 is that the tea polyphenols are nano-processed, and the nano-processing process is as follows:

[0222] 1. Raw materials: Take 100g of tea polyphenols extract powder and disperse it in 500mL of deionized water.

[0223] 2. Wet grinding:

[0224] Ball milling media: zirconia beads, diameter 0.2 mm.

[0225] Rotation speed: 1000 rpm, grinding for 2 hours.

[0226] Temperature: controlled at 28℃.

[0227] 3. High pressure homogenization:

[0228] Homogenization pressure: 200 MPa, cycle 4 times.

[0229] Results: The average particle size of tea polyphenols particles was 180 nanometers.

[0230] 4. Spray drying:

[0231] The inlet air temperature is 120℃ and the outlet air temperature is 70℃.

[0232] The obtained nano-tea polyphenol powder has uniform color and good fluidity.

[0233] Application effect: After dyeing, the permeability of tea polyphenols is significantly enhanced, the dyeing uniformity is improved by 15% compared with Example 1, and the dye residue in the wastewater is reduced by 30%.

[0234] The dyeing uniformity test method is as follows: use a colorimeter to measure the surface of the dyed leather sample, select 9 test points evenly distributed on the surface of the leather sample, with equal distances between the test points, covering the entire sample area, measure the L*, a*, and b* values ​​(color space coordinates) of each test point, and calculate the deviation of each test point from the average value: average all test points as the overall color difference value. The average color difference of Example 1 is 3.2, and the average color difference of Example 4 is 2.7.

[0235] The reason why nano-sizing can improve dyeing uniformity is due to the following three reasons: First, the particle size is reduced: Nano-sizing reduces the dye particle size to below 200 nanometers, significantly enhancing the dispersibility of the dye in aqueous solution; Second, the penetration ability is enhanced: the smaller particle size makes it easier for the dye to enter the microporous structure of the leather fiber, forming a more uniform internal dyeing; Third, avoid agglomeration: non-nano-sized dye particles are prone to agglomeration, resulting in excessive local pigment concentration, while nano-sizing effectively avoids this phenomenon.

[0236] Example 5: Nano-processing of Phellodendron amurense extract

[0237] The difference from Example 2 is that the Phellodendron amurense extract is nano-processed, and the nano-processing process is as follows:

[0238] 1. Raw materials: Take 200g of Phellodendron amurense extract powder and disperse it in 2L of ethanol-water mixture (ethanol volume ratio 15%).

[0239] 2. Wet grinding:

[0240] Ball milling media: alumina beads, 0.3 mm in diameter.

[0241] Rotation speed: 900 rpm, grinding for 3 hours.

[0242] Temperature: controlled at 30℃.

[0243] 3. High pressure homogenization:

[0244] Homogenization pressure: 250MPa, cycle 3 times.

[0245] Results: The average particle size of Phellodendron chinense granules was 150 nanometers.

[0246] 4. Spray drying:

[0247] The inlet air temperature is 140℃ and the outlet air temperature is 75℃.

[0248] The nanometer amur cork powder is obtained, and the powder has excellent stability.

[0249] 5. Application effect: Compared with Example 2, the adhesion of the Phellodendron amurense extract after dyeing is increased by 20%, and the gloss of the dyeing layer is enhanced.

[0250] The adhesion test method refers to ISO 2409 (coating adhesion test - cross-cut method), Example 2 (not nano-processed): the peeling area is 10%, and the rating is 2; Example 5 (nano-processed): the peeling area is 3%, and the rating is 1.

[0251] Example 6: Nano-processing of onion peel extract

[0252] 1. Raw materials: Take 150g onion peel extract powder and disperse it in 1L deionized water.

[0253] 2. Wet grinding:

[0254] Ball milling media: zirconia beads, 0.1 mm in diameter.

[0255] Rotation speed: 1200 rpm, grinding for 1.5 hours.

[0256] Temperature: controlled at 25℃.

[0257] 3. High pressure homogenization:

[0258] Homogenization pressure: 300 MPa, cycle 5 times.

[0259] Results: The average particle size of onion skin particles was 100 nanometers.

[0260] 4. Spray drying:

[0261] The inlet air temperature is 130℃ and the outlet air temperature is 70℃.

[0262] The nano-onion peel powder is obtained.

[0263] 5. Application effect: After dyeing, the color development effect of the onion peel extract is enhanced, and the light resistance is improved by 25% compared with Example 3.

[0264] The color development effect is evaluated by the color saturation (C*) and brightness (L*) of the dyed sample: the C* value of the sample is measured using a colorimeter. The color difference between the dyed leather sample and the undyed leather is measured, and a larger C* value indicates a stronger color development effect. The C* value of Example 3 is 35 (weaker color), and the C* value of Example 6 is 45 (significantly enhanced color saturation).

[0265] Lightfastness refers to the ability of the dyed leather sample to maintain color stability under natural light or artificial light (such as xenon lamp). Improved lightfastness of the dyed layer means that the color fades less under long-term light exposure. The test method for lightfastness refers to ISO 105-B02 (Light fastness test for textile and leather materials); specifically, after 24 hours of light exposure in Example 3: the gray card rating is 3 (moderate color change); after 48 hours of light exposure: the gray card rating is 2-3 (obvious color change); after 72 hours of light exposure: the gray card rating is 2 (significant color fading). After 24 hours of light exposure in Example 6: the gray card rating is 4 (slight color change); after 48 hours of light exposure: the gray card rating is 4-5 (almost no change); after 72 hours of light exposure: the gray card rating is 4 (slight change, significantly better than Example 3).

[0266] It can be seen from Examples 4 to 6 that the nano-treatment effectively reduces the particle size of the dye through wet grinding and high-pressure homogenization, improves its dispersibility and penetration, and ultimately enhances dyeing uniformity and durability.

[0267] Example 7: Combination of algae dye and cellulose surfactant

[0268] raw material:

[0269] Algae dye: Spirulina extract purchased from Chengdu Lujia Biotechnology Co., Ltd. (Spirulina Extract), model: food grade, content specification: phycocyanin content ≥ 50%, dosage 10%;

[0270] Surfactant: sodium carboxymethyl cellulose (CMC-Na), dosage 2%;

[0271] Deionized water: 87.5%;

[0272] Citric acid solution: dosage 0.5%.

[0273] Preparation method:

[0274] Add 10 g of phycocyanin to deionized water, stir at 200 rpm, and dissolve for 30 minutes;

[0275] Add 2 g of sodium carboxymethyl cellulose and continue stirring for 40 minutes, with the temperature controlled at 30°C, until the solution is uniform;

[0276] 0.5 g of citric acid solution was added dropwise to adjust the pH value to 5.5, and blue-green uniform dye water was obtained after filtration.

[0277] Dyeing process:

[0278] Take a pig skin sample, soak it in dye water at 30°C for 60 minutes, and dry it naturally after dyeing.

[0279] Application Effect

[0280] Dyeing uniformity: color difference (ΔE) is reduced to 2.5.

[0281] Lightfastness: After 48 hours of light exposure, the gray card rating is 4 to 5.

[0282] Adhesion: The cross-cut test result is level 1, with no obvious peeling.

[0283] Example 8

[0284] raw material:

[0285] Biological dye: Monascus fermentation product, dosage 8%;

[0286] Surfactant: sodium carboxymethyl starch (CMS-Na), dosage 3%;

[0287] Ethanol-water mixture (ethanol volume ratio 60%), dosage 88.5%;

[0288] Acetic acid solution: dosage 0.5%.

[0289] Preparation method

[0290] 8 g of Monascus fermentation product was added to 400 mL of ethanol-water mixture, stirred at 150 rpm, and dissolved for 20 minutes;

[0291] Add 3g sodium carboxymethyl starch and continue stirring for 30 minutes, with the temperature controlled at 40°C;

[0292] Add acetic acid solution dropwise to adjust the pH value to 5.4. Stir evenly and filter to obtain dark red dye water.

[0293] Dyeing process:

[0294] The cowhide sample was placed in dye water at 40°C for 45 minutes.

[0295] After dyeing, rinse with deionized water and dry at low temperature.

[0296] Application effect:

[0297] Dyeing uniformity: ΔE is 2.8, and the color depth is consistent.

[0298] Water resistance: After immersion for 60 minutes, the color fastness rating is 4.

[0299] Gloss Enhancement: 18% more gloss.

[0300] Example 9

[0301] raw material:

[0302] Biological dye: phycochlorophyll (source: seaweed extract), dosage 12%;

[0303] Surfactant: lauramidopropyl betaine (CAPB), dosage 2.5%;

[0304] Solvent: deionized water, dosage 85%;

[0305] Acetic acid solution: dosage 0.5%.

[0306] Preparation method:

[0307] Add 12g of phycochlorin to deionized water, stir at 180rpm, and dissolve for 25 minutes;

[0308] Add 2.5 g of lauramidopropyl betaine and continue stirring for 40 minutes while keeping the temperature at 35°C;

[0309] A small amount of citric acid solution was added to adjust the pH value to 5.8, and dark green dye water was obtained after filtration.

[0310] Dyeing process:

[0311] Take a sheepskin sample and soak it in dye water at 35°C for 50 minutes.

[0312] After dyeing, wipe the surface with a soft cloth and let it dry naturally.

[0313] Application Effect

[0314] Color rendering effect: C* value reaches 46, and the color saturation is significant.

[0315] Abrasion resistance: After rubbing 2000 times, the color change rating is 4.

[0316] Adhesion: Cross-cut test result is level 1, no peeling.

[0317] Comparative Example 1: Traditional chemical dyeing (dying with equal amount of chromate)

[0318] Raw materials: Leather dyeing was carried out using conventional chromate dye solution at a temperature of 35°C for 50 minutes.

[0319] Result: The dyed leather is darker blue-green ( Figure 1 In the figure, the upper part is chromate dyeing, and the lower part is tea polyphenol dyeing in Example 1), but after 30 days of light exposure, the leather faded significantly. The use of chromate dyes also leads to heavy metal pollution in wastewater, which results in high wastewater treatment costs, and the softness of the leather after dyeing is low.

[0320] Comparative Example 2: Dyeing with traditional synthetic organic dyes (azo dye toluidine red)

[0321] Raw materials: The cowhide is dyed with azo synthetic dye toluidine red at a temperature of 40°C for 45 minutes.

[0322] Results: The dyed leather showed a bright orange-red color, but in the light resistance test, after 30 days of outdoor exposure, the color faded significantly ( Figure 2 Middle: The upper one is azo dye, and the lower one is dyed with the Phellodendron amurense extract in Example 2). The use of azo dyes produces harmful organic volatiles during the dyeing process, causing pollution to the environment.

[0323] Comparative Example 3: Dyeing with low-cost synthetic dyes

[0324] Raw materials: Low-cost synthetic dyes (toluidine dyes) were used for sheepskin dyeing at a temperature of 33°C for 60 minutes.

[0325] Results: The initial color of the dyed sheepskin was bright, but as time went on, it faded significantly under natural light after 30 days. In addition, the wastewater from the dyeing process contained a large amount of chemical components, which was difficult to treat. The chemical residues in the wastewater were harmful to the environment.

[0326] Comparative Example 4: Dyeing using traditional vegetable dyes and non-biodegradable surfactants

[0327] Raw materials: Traditional plant dyes (gardenia extract) were used, without adding surfactants, and directly dissolved in water for dyeing. The dyeing temperature was set at 30°C and the dyeing time was 60 minutes.

[0328] Results: The color of the cowhide after dyeing is relatively uniform, but during the dyeing process, due to the lack of the help of surfactants, the dye is difficult to fully penetrate the leather fibers, resulting in insufficient dyeing depth in some parts and color difference. After 30 days, the leather exposed to natural light began to fade, especially in areas with lighter dyeing depth. Since the dye failed to fully penetrate, the surface of the dyeing layer is more susceptible to wear. This process does not use surfactants. Although the wastewater treatment is simpler, the dyeing effect is far inferior to the solution containing surfactants.

[0329] Comparative Example 5: Effect of Omitting Surfactant

[0330] The aim of this study was to investigate whether omitting surfactant would affect dyeing uniformity, abrasion resistance and water resistance when using the same dye (tea polyphenols).

[0331] Experimental design

[0332] 1. Experimental group: 10% tea polyphenols + 2% biodegradable surfactant (such as decyl glucoside) + deionized water were used to prepare environmentally friendly dye water.

[0333] 2. Control group: 10% tea polyphenols + deionized water were used without adding biodegradable surfactant.

[0334] Test Results

[0335] Abrasion resistance test (according to ISO 17704 standard):

[0336] Experimental group: After rubbing 2000 times, the dyeing layer did not fall off obviously, and the color change level was 4.

[0337] Control group: After rubbing 500 times, the local dyeing layer fell off, the dyeing uniformity was damaged, and the color change level was level 2.

[0338] Water resistance test (according to ISO 11641 standard):

[0339] Experimental group: After immersion for 60 minutes, there was no obvious dissolution of the dye layer and the color fastness rating was level 4.

[0340] Control group: After immersion for 30 minutes, the dye layer was dissolved and the color fastness rating was 2 to 3.

[0341] Dyeing uniformity test:

[0342] Experimental group: The staining was uniform and there were no obvious spots when observed with the naked eye.

[0343] Control group: Some areas had spots of varying shades.

[0344] Conclusion: Omitting surfactant significantly reduced dyeing uniformity, abrasion resistance, and water resistance, indicating that surfactants play an important role in the dispersion and penetration of dyes.

[0345] Comparative Example 6: Effect of the type of dye

[0346] To explore the effect of different dyes on dyeing effect when adding the same surfactant.

[0347] Experimental design

[0348] 1. Experimental group: 10% tea polyphenols + 2% biodegradable surfactant (decyl glucoside) + deionized water were used to prepare environmentally friendly dye water.

[0349] 2. Control group: 10% Gardenia extract + 2% biodegradable surfactant + deionized water were used to prepare traditional plant dye water.

[0350] Test Results

[0351] Abrasion resistance test (according to ISO 17704 standard):

[0352] Experimental group: After rubbing 2000 times, there was no obvious damage to the dyeing layer, and the color change level was 4.

[0353] Control group: After rubbing 1500 times, the dyeing layer was partially damaged and the color change level was level 3.

[0354] Water resistance test (according to ISO 11641 standard):

[0355] Experimental group: After immersion for 60 minutes, there was no dissolution of the dye layer and the color fastness rating was level 4.

[0356] Control group: After immersion for 60 minutes, the dye layer was partially dissolved and the color fastness rating was level 3.

[0357] Color stability test (according to ISO 105-B02 standard):

[0358] Experimental group: After 48 hours of light exposure, the color changed slightly, and the gray scale rating was 4 to 5.

[0359] Control group: After 48 hours of light exposure, the color faded significantly and the gray scale rating was 3.

[0360] in conclusion

[0361] When tea polyphenols are used as a dye, the wear resistance, water resistance and color stability are better than those of traditional plant dyes (gardenia extract), indicating that environmentally friendly dye water has more advantages in comprehensive performance.

[0362] Comparative Example 5: Dyeing using traditional chemical dyes and acidic solvents

[0363] Raw materials: Use traditional chemical dyes (such as acid red dye) with hydrochloric acid as pH adjuster. The dyeing temperature is 35°C and the dyeing time is 50 minutes.

[0364] Results: The color of the dyed leather is brighter, showing a dark red color. However, during the dyeing process, due to the use of hydrochloric acid to adjust the pH value, the acidity in the dyeing wastewater is strong, which makes wastewater treatment difficult and the treatment cost is high. And because hydrochloric acid is corrosive, excessive use will damage the leather fibers and reduce the flexibility of the leather. After 30 days of light testing, the dyed leather faded significantly, especially under strong light, the color of the dye faded faster. In addition, the strong acidic pH value caused a certain degree of damage to the leather surface, the gloss of the leather surface was weakened, and the durability was reduced.

[0365] in conclusion:

[0366] By comparing the above embodiments with Comparative Examples 1 to 3, the environmentally friendly dye water shows better light fastness, color stability and environmental friendliness than traditional chemical dyes and synthetic dyes. Traditional dyes not only have shortcomings in durability, high wastewater treatment costs, but also may cause harm to the environment and the health of operators. The dye water provided by the present invention can effectively avoid the use of toxic and harmful substances, and has excellent dyeing effect and durability, and is particularly suitable for modern dyeing processes with high environmental requirements.

[0367] By comparing with Comparative Examples 4 to 6, the advantages of the dye water of the present invention are further verified. Although traditional plant dyes can provide certain color effects, the lack of the assistance of surfactants leads to insufficient penetration, uneven dyeing effects, and poor durability. Although traditional chemical dyes using acidic solvents can present bright colors, they cause great damage to leather, high wastewater treatment costs, and poor environmental protection. In contrast, the dye water provided by the present invention not only ensures the uniformity and durability of the dyeing effect by adding biodegradable surfactants and natural pH regulators, but also greatly reduces pollution to the environment, showing comprehensive advantages such as color stability, wear resistance, and easy handling.

[0368] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dye water, characterized in that: The dye comprises 5-15% of a dye, 1-5% of a biodegradable surfactant, 0.1-0.5% of a weakly acidic pH regulator and 80-90% of a solvent in terms of mass percentage; the pH value of the dye water is 4.5-6.5; The solvent is water or an ethanol-water mixture; The dye comprises one or more of plant dyes, algae dyes and microbial fermentation products; The plant dye comprises one or more of tea polyphenols, amur cork extract and onion peel extract.

2. The dye water according to claim 1, characterized in that: It also contains 0.1-0.5% natural preservatives.

3. The dye water according to claim 1, characterized in that: The weakly acidic pH regulator includes citric acid and / or acetic acid.

4. The dye water according to claim 1, characterized in that: The plant dye is obtained from plant raw materials through supercritical carbon dioxide extraction, steam distillation extraction or solvent extraction.

5. The dye water according to claim 1, characterized in that: The biodegradable surfactant includes one or more of glycoside surfactants, amino acid surfactants, fatty acid surfactants, cellulose surfactants and starch surfactants.

6. The dye water according to claim 2, characterized in that: The natural preservatives include sodium benzoate or potassium sorbate.

7. The method for preparing dye water according to any one of claims 1 to 6, characterized in that: The following steps are involved: After the dye is dissolved in a solvent, a biodegradable surfactant is added to the obtained solution to obtain a mixed solution; a weakly acidic pH regulator is added to the mixed solution to adjust the pH value to 4.5-6.5 to obtain the dye water.

8. The preparation method according to claim 7, characterized in that: After the pH value is adjusted to 4.5-6.5, the method further comprises adding a natural preservative to the solution after the pH value is adjusted.

9. The preparation method according to claim 7 or 8, characterized in that: Each step is carried out at 25-30°C.

10. Use of the dye water according to any one of claims 1 to 6 or the dye water prepared by the preparation method according to any one of claims 7 to 9 in leather dyeing.

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