Natural dye lake pigment and preparation method thereof

Abstract

The invention provides a natural dye lake pigment and a preparation method thereof, and belongs to the technical field of pigments. Soluble silicon-doped carbon quantum dots are introduced into a natural dye solution to serve as a precipitator, the aggregation state of the natural dye is changed, and the lake pigment is obtained through mixing treatment. The prepared natural dye lake pigment is simple in preparation method and mild in preparation condition, the prepared pigment greatly overcomes the defects that natural dye is prone to discoloration and unstable, the oxygen heat resistance of the pigment is improved, the color stability is good, the lake pigment only comprises five elements of C, H, O, N and Si, the ecological pollution-free characteristic is achieved, and the application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pigment preparation, and specifically relates to a natural dye lake pigment and a preparation method thereof. BACKGROUND

[0002] The lake pigment is an important category of organic pigments and is also the earliest applied organic pigment. The lake pigment is usually formed by precipitating insoluble colored substances on an inorganic carrier under the action of a specific precipitant from some water-soluble dyes. The types of the lake pigment can be divided into azo, triphenylmethane, copper phthalocyanine, oxynaphtho, and a small number of anthraquinone systems according to the structures of the water-soluble dyes used for preparation. Most of them come from synthetic processes. For example, the azo lake is prepared by reacting 2-naphthol as a coupling component with an arylamine (containing a sulfonic acid group and a carboxylic acid group) diazonium salt to form a color former, and then treating the color former with a metal salt to obtain the lake. If the obtained lake is not properly controlled, the aromatic amine residue is inevitably present. In CN116462988B, a preparation method of a self-dispersing triarylmethane nano lake pigment, cellulose nanocrystals (CNC) are used as a dispersing agent, and metal ions are used to lake triarylmethane dyes. The metal salt is one or more of copper salt, magnesium salt, zinc salt, and chromium salt.

[0003] While natural dyes have always occupied a place in the preparation of lake pigments, alizarin lake pigments have been used to this day, and its preparation process is to dissolve alizarin in an alkaline solution in the presence of aluminum hydroxide, and use calcium chloride aqueous solution to convert it into calcium-aluminum lake. This method has also been improved by people: Gan Chunji et al. in patent CN1884389A used red koji pigment as water-soluble dye to prepare red koji lake by multivalent metal salt precipitation method; For example, Zhao Jixing et al. in patents CN108795096A and CN110330812A mentioned that red koji red, sorghum red, radish red and other natural pigments were used as raw materials to prepare precipitates by using a variety of neutral salt salting-out and hydrolysis precipitation method, vacuum drying, and crushing to obtain a variety of color lakes; Gu Min et al. in CN101461513B a method for preparing water-soluble cochineal acid lake proposed to use alum solution and calcium chloride solution to make it lake; Marzec, A et al. (Characterization and properties of new color-tunable hybrid pigments based on layered double hydroxides (LDH) and 1,2-dihydroxyanthraquinone dye, Journal of Industrial and Engineering Chemistry, Volume 70, 25 February 2019, Pages 427-438) introduced layered double hydroxides (magnesium-aluminum hydroxyl carbonate), synthesized lake pigments from alizarin dye and magnesium-aluminum hydroxyl carbonate (different Mg / Al ratios), and used in polymers to adjust color effects; Szadkowski, B et al. (Structure and Stability Characterization of Natural Lake Pigments Made from Plant Extracts and Their Potential Application in Polymer Composites for Packaging Materials. Materials 2022, 15, 4608.) proposed to use alum, calcium carbonate, stannic chloride, etc. to prepare natural dye lakes from extracts of yellow flowers, Persian berries, Brazilian suwoods, etc. for plastic packaging materials.Nguyen, HL et al (Thermal stability of natural dye lakes from Canadian Goldenrod and onion peel as sustainable pigments, Journal of Cleaner Production, Volume 315, 15 September 2021, 128195) studied the formation of lakes from extracts of goldenrod and onion peel under the action of alum, and their thermal stability and dyeing experiments.

[0004] The metal salt types mentioned in these improved methods are quite diverse, such as alum (aluminum salt), copper salt, and even tin salt, which brings the risk of metal ions. Although aluminum lakes are allowed to be used as additives in food, the negative risks of aluminum to the nervous system of the human body, people hope to have alternatives, such as Liu Ru-hua et al. in CN112831194B mentioned a cochineal red lake without aluminum salt and its preparation method, directly using calcium ions in protein to form chelation to obtain cochineal red lake; such as Gao Yan-xiang et al. in patent CN118285469A uses water-soluble phycocyanin as a macromolecular pigment source, stearoyl lactate (such as calcium stearoyl lactate, etc.) as a small molecular emulsifier, and divalent metal salt (such as calcium chloride, etc.) as a crosslinking agent to produce phycocyanin lake. However, the improved lake pigment types have special properties and poor applicability. Therefore, choosing natural products as raw materials to avoid introducing synthetic substances and heavy metal substances is the direction of efforts for many technology workers. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies of the prior art, and to provide a natural dye lake pigment and a preparation method thereof. The lake pigment has the characteristics of environmental protection and economy, and the raw materials are widely available and the preparation process is simple.

[0006] A preparation method of a natural dye lake pigment, comprising the following steps: A. preparing a natural dye solution; B. preparing a silicon-doped carbon quantum dot solution; C. then mixing and stirring the two to generate a precipitate; D. separating, drying and grinding the precipitate to obtain a natural dye lake pigment.

[0007] Further, the natural dye solution has a concentration of 0.01% to 5% (mass percentage, based on the solid mass of the characteristic substance), the silicon-doped carbon quantum dot solution has a concentration of 0.001% to 10% (mass percentage, based on the solid mass of the solute), and the volume ratio of the natural dye solution to the silicon-doped carbon quantum dot solution is 1:1 to 10.

[0008] Further, the natural dye belongs to a polyphenol natural dye, and the polyphenol natural dye includes at least one of hesperetin, quercetin, luteolin, tea polyphenol, brazilin, protocatechuic acid B, and anthocyanin.

[0009] Further, the solvent of the natural dye solution is an ethanol solution with a mass concentration of 60% to 90%.

[0010] Further, a preparation method of the natural dye solution includes the following steps: adding the natural dye into a solvent, performing extraction treatment, and filtering to remove residues.

[0011] Further, the preparation method of the silicon-doped carbon quantum dot solution is as follows: fully mixing a silane coupling agent, water, and an organic acid reducing agent, and placing them into a hydrothermal reaction kettle, and then performing reaction at 150°C to 220°C for 8 to 12 hours.

[0012] Preferably, the silane coupling agent is one or a mixture of several of KH550, KH560, and KH570; and the reducing agent is one or both of a 0.1 mol / L ascorbic acid solution and a 0.1 mol / L citric acid solution. Preferably, the ratio of the silane coupling agent, the organic acid reducing agent, and the water is 2 to 20:5 to 10:10 to 30 (volume ratio).

[0013] Further, the separation mode is centrifugal separation or filtration separation.

[0014] Further, the drying mode is vacuum drying or freeze drying.

[0015] The natural dye lake pigment prepared by the above method does not introduce additional heavy metal elements, and the thermal stability in oxygen and the sunlight fastness are greatly improved.

[0016] The present application has the following advantages: 1. The present application uses silicon-doped carbon quantum dots as a precipitant for polyphenol natural dyes to prepare natural dye lakes, and the raw materials are eco-friendly, and the preparation process does not involve synthetic intermediates. The final product is composed of only C, H, O, N, and Si, which meets the ecological requirements of high-quality development. 2. The polyphenolic natural dyes involved in this invention belong to a large category of natural dye products and have the advantage of being widely available; the raw materials for preparing the silicon-doped carbon quantum dot solution involved are inexpensive and readily available; the preparation process involved is simple, controllable, and inexpensive. 3. The natural dye lake product finally obtained by this invention changes the properties of natural dyes that are easy to oxidize and change color. Its thermal stability in oxygen and light fastness are greatly improved, and it can be used in many fields such as coatings, textiles, and cosmetics. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Thermogravimetric analysis diagram of the lake pigment ⑦ of Example 7 and the sappanwood extract ② of Comparative Example 7; Figure 2 The above are the SEM characterization results of the lake pigment ⑧ of Example 8; Figure 3 The particle size distribution diagram is shown for the lake pigment ⑧ of Example 8. Detailed Implementation

[0019] Example 1

[0020] A. Weigh 50 mg of hesperidin and dissolve it in 20 mL of 80% (volume ratio) ethanol solution to prepare natural dye solution ①—hesperidin solution. Dilute it 10 times and set aside for use. B. Dissolve 4 mL of silane coupling agent KH550 in 16 mL of deionized water, add 5 mL of 0.1 mol / L ascorbic acid solution, place in a hydrothermal reactor, keep at 150℃ for 8 h, cool to room temperature to obtain a silicon-doped carbon quantum dot solution with a concentration of 8.5% (mass fraction) ①, dilute 10 times and set aside for use; C. Mix the solutions prepared in steps A and B at a volume ratio of 1:1 and stir for 5 hours. Then centrifuge the precipitate, wash it 2-3 times with deionized water, freeze-dry it, and grind it to obtain the dried Tianye lake pigment ①—hesperidin lake.

[0021] Comparative Example 1

[0022] A. Weigh 50 mg of hesperidin and dissolve it in 20 mL of 80% (volume ratio) ethanol solution to prepare natural dye solution ①—hesperidin solution. Dilute it 10 times and set aside for use. B. 2 g of L-glutamic acid was dissolved in 55 mL of deionized water by ultrasonic for 10 min. Then the completely dissolved glutamic acid solution was placed in a high-pressure reactor and hydrothermally reacted at 180°C for 10 h. After the reaction was completed and cooled to room temperature, a yellowish carbon quantum dot solution ① with a concentration of 3.6% (mass fraction) was obtained, which was diluted 10 times for use; C. The solutions prepared in steps A and B were mixed at a volume ratio of 1:1 and stirred for 12 h, and the solution remained clear.

[0023] Example 2

[0024] A. 30 mg of quercetin was dissolved in 20 mL of 70% (volume ratio) ethanol solution to prepare a natural dye solution ②-quercetin solution, which was diluted 10 times for use. B. 4 mL of silane coupling agent KH560 was mixed and dissolved with 16 mL of deionized water, 5 mL of 0.1 mol / L citric acid solution was added, and it was placed in a hydrothermal kettle and incubated at 160°C for 10 h. After cooling to room temperature, a silicon-doped carbon quantum dot solution ② with a concentration of 8.5% (mass fraction) was obtained, which was diluted 10 times for use. C. The solutions prepared in steps A and B were mixed at a volume ratio of 1:1 and stirred for 3 h, then the precipitate was centrifuged out, washed with deionized water for 2-3 times, vacuum dried, and ground to obtain dry natural dye lake pigment ②-quercetin lake.

[0025] Comparative Example 2

[0026] A. 30 mg of quercetin was dissolved in 20 mL of 70% (volume ratio) ethanol solution to prepare a natural dye solution ②-quercetin solution, which was diluted 10 times for use.

[0027] B. Mulberry dry water extract was prepared: 3.0 g of mulberry dry was weighed in a beaker, and 30 mL of deionized water was added, and it was incubated in a 50°C oven for 1 h, and stirred with a glass rod for 2 3 times (3 4 min each time). After 1 h, the mulberry dry residue was removed by filtration to obtain mulberry dry water extract (AM); The mulberry dry water extract was placed in a high-pressure reactor and reacted at 180°C for 10 h. After the reaction was completed and cooled to room temperature, mulberry dry water extract carbon quantum dots ② (AMQDs) with a concentration of 0.87% (mass fraction) were obtained.

[0028] C. The solutions prepared in steps A and B were mixed at a volume ratio of 1:1 and stirred for 3 h, and the solution remained clear.

[0029] Example 3

[0030] A, 60 mg of luteolin was dissolved in 20 mL of 90% (volume ratio) ethanol solution to prepare a natural dye solution ③-luteolin solution, which was diluted 10 times for later use.

[0031] B, 4 mL of silane coupling agent KH570 was mixed and dissolved with 16 mL of deionized water, 5 mL of 0.1 mol / L ascorbic acid solution was added, and it was placed in an autoclave, 170°C for 12 h, and then cooled to room temperature to obtain a silicon-doped carbon quantum dot solution ③ with a concentration of 8.5% (mass fraction), which was diluted 10 times for later use.

[0032] C, the solutions prepared in steps A and B were mixed in a volume ratio of 1:1 and stirred for 8 h, then the precipitate was centrifuged out, washed with deionized water for 2-3 times, freeze-dried, and ground to obtain dry natural dye lake pigment ③-luteolin lake.

[0033] Comparative Example 3

[0034] A, 60 mg of luteolin was dissolved in 20 mL of 90% (volume ratio) ethanol solution to prepare a natural dye solution ③-luteolin solution, which was diluted 10 times for later use.

[0035] B, 10 g of purple sweet potato was treated with a cell wall breaking machine, then soaked in 100 mL of 60% ethanol solution (pH=4.0) for 12 h, filtered and left to stand for 24 h, and the supernatant was taken for rotary evaporation to remove the filtrate and ethanol, obtaining a water extract of purple sweet potato anthocyanins (AP); The water extract of purple sweet potato was placed in a high-pressure reaction kettle and reacted at 180°C for 10 h. After the reaction was completed and cooled to room temperature, a purple sweet potato water extract carbon quantum dot ③ (APQDs) with a concentration of 0.5% (mass fraction) was obtained.

[0036] C, the solutions prepared in steps A and B were mixed in a volume ratio of 1:1 and stirred for 3 hours, and the solution remained clear.

[0037] Example 4

[0038] A, 40 mg of tea polyphenol was dissolved in 20 mL of 90% (volume ratio) ethanol solution to prepare a natural dye solution ④-tea polyphenol solution, which was diluted 10 times for later use.

[0039] B, 4 mL of silane coupling agent KH570 was mixed and dissolved with 16 mL of deionized water, 5 mL of 0.1 mol / L citric acid solution was added, and it was placed in an autoclave, 140°C for 10 h, and then cooled to room temperature to obtain a silicon-doped carbon quantum dot solution ④ with a concentration of 8.5% (mass fraction), which was diluted 10 times for later use.

[0040] C, the solution prepared in step A, B is mixed with stirring for 0.5 h in a volume ratio of 1:1, then the precipitate is centrifuged out, washed with deionized water for 2~3 times, vacuum dried, ground into dry natural dye lake pigment ④- tea polyphenol lake pigment.

[0041] Comparative example 4

[0042] A, 40 mg of tea polyphenol was dissolved in 20 mL of 90% (volume ratio) ethanol solution to prepare natural dye solution ④- tea polyphenol solution, which was diluted 10 times for use.

[0043] B, 3.0 g of mulberry dry was weighed in a beaker, 30 mL of deionized water was added, and it was placed in a 50℃ oven for 1 h, during which it was stirred with a glass rod for 2 3 4 min each time). After 1 h, the mulberry dry filter residue was removed by filtration to obtain mulberry dry water extract (AM); 0.5 g of cysteine was dissolved in 30 mL of mulberry dry water extract, and the solution was placed in a high-pressure reaction kettle and reacted at 180℃ for 12 h. After the reaction was completed and cooled to room temperature, a nitrogen-doped carbon quantum dot solution ① (N CQDs 1) with a concentration of 2.53% (mass fraction) was obtained, which was diluted 10 times for use.

[0044] C, the solution prepared in step A, B is mixed with stirring for 0.5 h in a volume ratio of 1:1, then the precipitate is centrifuged out, washed with deionized water for 2~3 times, vacuum dried, ground into dry natural dye lake pigment ④- tea polyphenol lake pigment.

[0045] Example 5

[0046] A, 3.0 g of mulberry dry was weighed, 30 mL of deionized water was added, and it was extracted at 50℃ for 1 h, then filtered to obtain natural dye solution ⑤- mulberry dry cyanidin water extract, which was diluted 10 times for use.

[0047] B, 4 mL of silane coupling agent KH550 was mixed and dissolved with 16 mL of deionized water, 5 mL of 0.1 mol / L ascorbic acid solution was added, and it was placed in a hydrothermal kettle and heated at 140℃ for 10 h. After cooling to room temperature, a silicon-doped carbon quantum dot solution ⑤ with a concentration of 8.5% (mass fraction) was obtained, which was diluted 10 times for use.

[0048] C, the solution prepared in step A, B is mixed with stirring for 0.5 h in a volume ratio of 1:1, then the precipitate is centrifuged out, washed with deionized water for 2~3 times, vacuum dried, ground into dry natural dye lake pigment ④- tea polyphenol lake pigment.

[0049] Comparative example 5

[0050] A, take 3.0 g mulberry dry, add 30 mL deionized water, 50 ℃ extraction 1 h, filter, get natural dye solution ⑤—mulberry dry cyanidin water extract, dilution 10 times after use.

[0051] B, take 3.0 g mulberry dry in beaker, then add 30 mL deionized water to it, put in 50 ℃ oven and keep warm for 1 h, during which use glass rod to stir 2 3 times (3 4 min each time). After 1 h, filter to remove mulberry dry residue, get mulberry dry water extract (AM); Dissolve 0.5 g glutathione in 30 mL mulberry dry water extract, solution is placed in high pressure reaction kettle, react at 180 ℃ for 12 h, after cooling to room temperature after reaction is finished, get concentration 2.53% (mass fraction) nitrogen-doped carbon quantum dots solution ② (N CQDs 2), dilution 10 times after use.

[0052] C, mix the solutions prepared in steps A, B with volume ratio 1:1, stir for 10 hours, the solution still keeps clear.

[0053] Example 6

[0054] A, take 8 g redwood in 50 mL 90% (volume ratio) ethanol solution, 50 ℃ extraction 1 h, filter to remove redwood residue, get natural dye solution ⑥—redwood extract solution, dilution 10 times after use.

[0055] B, mix and dissolve 4 mL silane coupling agent KH560 with 16 mL deionized water, add 5 mL 0.1 mol\L ascorbic acid solution, put in hydrothermal kettle, keep warm at 150 ℃ for 10 h, reduce to room temperature, get concentration 8.5% (mass fraction) silicon-doped carbon quantum dots solution ⑥, dilution 10 times after use.

[0056] C, mix the solutions prepared in steps A, B with volume ratio 1:1, stir for 12 h, then centrifuge the precipitate, wash with deionized water for 2~3 times, freeze-dry, grind to get dry natural dye lake pigment ⑥—redwood lake pigment ①.

[0057] Sample characterization: after grinding, pass the natural dye lake pigment ⑥ through 200 mesh sieve, use plastic ring to inlay, press about 5 g sieved sample on tablet machine to get ≥3 mm thickness sheet, carry out element composition analysis on XRF-X ray fluorescence spectrometer (S8Tige), test results are shown in table 2.

[0058] Comparative example 6

[0059] A, 8 g of red sandalwood was weighed into 50 mL of 90% (by volume) ethanol solution, extracted at 50°C for 1 h, and the red sandalwood residue was removed by filtration to obtain a natural dye solution ⑥ - red sandalwood extraction solution, which was diluted 10 times for later use.

[0060] B, 3.0 g of dried mulberry was weighed into a beaker, 30 mL of deionized water was added, and the mixture was placed in a 50°C oven for 1 h. The dried mulberry water extract (AM) was obtained by filtration. 2.3 g of urea was dissolved in 30 mL of the dried mulberry water extract, and the mixture was reacted in a high-pressure reaction kettle at 180°C for 12 h. After the reaction was completed and the mixture was cooled to room temperature, a nitrogen-doped carbon quantum dot solution ③ (N CQDs) with an orange color and a concentration of 8.53% (mass fraction) was obtained, which was diluted 10 times for later use.

[0061] C, the solutions prepared in steps A and B were mixed at a volume ratio of 1:1 and stirred for 12 h. The solution remained clear.

[0062] Example 7

[0063] A, 8 g of red sandalwood was weighed into 50 mL of 70% (by volume) ethanol solution, extracted at 50°C for 1 h, and the red sandalwood residue was removed by filtration to obtain a natural dye solution ⑦ - red sandalwood extraction solution ②, which was diluted 20 times for later use.

[0064] B, 4 mL of silane coupling agent KH570 was mixed and dissolved in 16 mL of deionized water, 5 mL of 0.1 mol / L citric acid solution was added, and the mixture was placed in a hydrothermal kettle and heated at 150°C for 10 h. The mixture was cooled to room temperature to obtain a silicon-doped carbon quantum dot solution ⑦ with a concentration of 8.5% (mass fraction), which was diluted 10 times for later use.

[0065] C, the solutions prepared in steps A and B were mixed at a volume ratio of 1:1 and stirred for 12 h. The precipitate was then centrifuged, washed with deionized water for 2-3 times, freeze-dried, and ground to obtain dry natural dye lake pigment ⑦ - red sandalwood lake pigment ②.

[0066] Sample characterization: The natural dye lake pigment ⑦ sample was subjected to thermogravimetric analysis, and the test results are shown in Figure 1 .

[0067] Paint preparation: 1 g of solid gelatin was dissolved in 100 mL of deionized water in a beaker to obtain a gelatin solution.

[0068] 0.1 g of natural dye lake pigment ⑦ was mixed with 0.5 mL of gelatin solution and stirred until uniform. The mixture was uniformly applied to white paper using a paintbrush, and then naturally air-dried.

[0069] The color change of the color block before and after irradiation under D65 light source for 7 days was investigated, and the test results are shown in Table 3.

[0070] Comparative Example 7

[0071] The natural dye solution ⑦—sappan extract solution ② obtained in Example 7 was freeze-dried, and then ground to obtain dry sappan extract ②.

[0072] Sampling characterization: The sappan extract ② was subjected to thermogravimetric analysis, and the test results are shown in Figure 1 .

[0073] Preparation of painting pigments: 1 g of solid gelatin and 100 mL of deionized water were placed in a beaker, and the gelatin solution was dissolved at 50°C.

[0074] 0.1 g of sappan extract ② was mixed with 0.5 mL of gelatin solution and stirred until uniform, and then uniformly applied to white paper using a paintbrush, and then naturally air-dried.

[0075] The color change of the color block before and after irradiation under D65 light source for 7 days was investigated, and the test results are shown in Table 3.

[0076] Example 8

[0077] A, 8 g of sappan was weighed into an 80% (by volume) ethanol solution, and extracted at 50°C for 1 h. The sappan residue was removed by filtration to obtain a natural dye solution ⑧—sappan extract solution ③. After dilution by 30 times, it was ready for use.

[0078] B, 4 mL of silane coupling agent KH550 was mixed with 16 mL of deionized water to dissolve, and 5 mL of 0.1 mol / L ascorbic acid solution was added. It was placed in a hydrothermal kettle and incubated at 150°C for 10 h. After cooling to room temperature, a silicon-doped carbon quantum dot solution ⑧ with a concentration of 8.5% (mass fraction) was obtained. After dilution by 10 times, it was ready for use.

[0079] C, the solutions prepared in steps A and B were mixed in a volume ratio of 1:1 and stirred for 14 h. Then the precipitate was centrifuged out, washed with deionized water for 2-3 times, and freeze-dried to obtain dry natural dye lake pigment ⑧—sappan lake pigment ③.

[0080] The natural dye solution ⑧—sappan extract solution ③ was dried to obtain a natural dye lake pigment ⑧ sample.

[0081] Sampling characterization: The natural dye lake pigment ⑧ sample was subjected to SEM characterization and particle size distribution, and the test results are shown in Figure 2 、 Figure 3 .

[0082] Pigment tabletting: Take 0.5 g of natural dye lake pigment ⑧ and place it in an infrared mold. Keep it under a pressure of 10 MPa for 5 minutes, and then demold to obtain a natural dye lake pigment tablet.

[0083] Place the lake pigment tablet in an oven at room temperature, 80°C, and 120°C respectively for 3 hours, and observe the color change of the lake. The test results are shown in Table 4.

[0084] Prepare solutions with NaOH and HCl respectively to have pH values of 5, 7, and 9. Take 200 μL of each solution and drop it onto the lake pigment tablet. After natural drying for 1 hour, observe the color change of the lake. The test results are shown in Table 4.

[0085] Comparative Example 8

[0086] A. Take 50 mg of alizarin and dissolve it in 20 mL of 80% (by volume) ethanol solution to prepare a natural dye solution ⑩—alizarin solution. Dilute it 10 times and wait for use.

[0087] B. Same as Example 1.

[0088] C. Mix the solutions prepared in steps A and B in a volume ratio of 1:1 and stir for 12 hours. The solution remains clear.

[0089] Comparative Example 9

[0090] A. Take 0.3 mg of natural indigo and dissolve it in 20 mL of 70% (by volume) ethanol solution to prepare a natural dye ⑩—indigo clear solution. Dilute it 10 times and wait for use.

[0091] B. Same as Example 2.

[0092] C. Mix the solutions prepared in steps A and B in a volume ratio of 1:1 and stir for 12 hours. The solution remains clear.

[0093] Comparative Example 10

[0094] A. Take 60 mg of methylene blue and dissolve it in 100 mL of 70% (by volume) ethanol solution to prepare a dye solution methylene blue solution. Dilute it 10 times and wait for use.

[0095] B. Same as Example 3.

[0096] C. Mix the solutions prepared in steps A and B in a volume ratio of 1:1 and stir for 12 hours. The solution remains clear.

[0097] The silicon-doped carbon quantum dots have obvious effects on polyphenol natural dye lake. After the solutions of natural dyes such as tea polyphenol, hesperetin, quercetin, luteolin, mulberry extract and red sandalwood extract are mixed with the silicon-doped carbon quantum dot solution, the lake precipitation is generated, and the absorbance of the solution in the ultraviolet-visible absorption spectrum is obviously reduced, as shown in Table 1. Table 1 also shows that there is no lake effect when the polyphenol natural dyes are mixed with pure carbon quantum dot and nitrogen-doped quantum dot solutions, and other types of dyes also have no lake effect when mixed with silicon-doped carbon quantum dots.

[0098] The natural dye lake pigment prepared by the application is friendly to the environment, and Table 2 is the XRF element determination result of the natural lake pigment. The results show that the elements in the lake are only C, H, O, N and Si.

[0099] The natural dye lake pigment prepared by the application has greatly improved thermal stability. The mass residual rate of Example 7 in the oxygen environment is 39.09%, and the mass residual rate of Comparative Example 7 is only 9.11%, as shown in Figure 2 The SEM image and particle size distribution graph of the lake pigment prepared by the application show that the natural dye lake pigment particles are relatively uniform, and the average particle size is 0.867 µm. The color value of the natural dye lake pigment prepared by the application is stable. The color block coated on the paper as a painting pigment has almost no change in color value after 7 days under the illumination of D65 light source, while the K / S value of the color block of the red sandalwood extract has decreased by 35%, and the specific values are shown in Table 3. After the pigment tablet is pressed, the color value of the tablet has almost no change after being placed at room temperature, 80°C and 120°C for 3h, and the color also remains stable after being in contact with solutions with different pH values, and the specific values are shown in Table 4.

[0100] Table 1 Comparison of absorbance values of natural dye solutions (at the maximum absorption wavelength at the beginning and end of solution mixing in step C)

[0101] Among them, the beginning of mixing is just after mixing, and the end of mixing is when stirring is finished.

[0102] Table 2 XRF element ratio table (taking the natural dye lake pigment ⑥—red sandalwood lake pigment ① in Example 6 as an example)

[0103] Table 3 Color change of natural dye lake pigment under D65 light source

[0104] Table 4 Color change of natural dye lake pigment tablet under different temperature and pH conditions

[0105] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features are described herein, but it should be understood that the scope of the disclosure encompasses all possible combinations of the technical features.

[0106] The above-described embodiments are merely representative of several embodiments of the present application, and the description is relatively specific and detailed, but should not be construed as limiting the scope of the patent. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A process for the preparation of natural dye lake pigments, characterized in that, The method comprises the following steps: A. preparing a natural dye solution; B. preparing a silicon-doped carbon quantum dot solution; C. mixing and stirring the natural dye solution and the silicon-doped carbon quantum dot solution to generate a precipitate; D. separating, drying and grinding the precipitate to obtain a natural dye lake pigment.

2. The process for the preparation of natural dye lake pigments according to claim 1, characterized in that, The solid content of the natural dye solution in step A is 0.01%-5%.

3. The process for the preparation of natural dye lake pigments according to claim 1, characterized in that, The solid content of the silicon-doped carbon quantum dot solution in step B is 0.001%-10%.

4. The process for the preparation of natural dye lake pigments according to claim 1, characterized in that, The volume ratio of the natural dye solution to the silicon-doped carbon quantum dot solution in step B is 1:1-10.

5. The process for the preparation of natural dye lake pigments according to claim 1, characterized in that, The natural dye solution in step A is a polyphenol natural dye solution, and the polyphenol natural dye includes at least one of hesperetin, quercetin, luteolin, tea polyphenol, brazilin, pyrogallol, and cyanidin.

6. The process for the preparation of natural dye lake pigments according to claim 5, characterized in that, The solvent of the natural dye solution is an ethanol solution with a mass concentration of 60-90%.

7. The process for the preparation of natural dye lake pigments as claimed in claim 1 wherein, The method for preparing the silicon-doped carbon quantum dot solution comprises the following steps: mixing a silane coupling agent, water and an organic acid reducing agent, and placing the mixture in a hydrothermal reaction kettle, and reacting at 150-220°C for 8-12h.

8. The process for the preparation of natural dye lake pigments according to claim 7, characterized in that, The silane coupling agent is one or a mixture of several of KH550, KH560 and KH570; and the reducing agent is one or both of a 0.1mol / L ascorbic acid solution and a 0.1mol / L citric acid solution.

9. The process for the preparation of natural dye lake pigments according to claim 1, characterized in that, The volume ratio of the silane coupling agent: organic acid reducing agent: water is 2-20:5-10:10-30.

10. A natural dye lake pigment prepared by the method of any one of claims 1-9.

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