Preparation method and application of light-resistant core-shell structure composite pigment

Abstract

The invention discloses a preparation method of a light-resistant core-shell structure composite pigment, which is characterized in that barium sulfate is used as an inorganic core material, a cationic lake pigment prepared by using heteropoly acid as a precipitator is used as an organic shell, and the inorganic core material and the organic shell are combined together by utilizing the electrostatic interaction between the core and the shell to prepare the light-resistant core-shell structure composite pigment. The core-shell structure composite pigment with good light resistance and lasting light stability is obtained. Compared with a pure pigment printed fabric, the light fastness of the pigment is greatly improved, the pigment can be solarized in a light reaction instrument for 24 hours without color fading and discoloration, and the ultraviolet radiation resistance time of the prepared pigment can reach 73 days or even longer. The prepared light-resistant core-shell structure composite pigment has a good application prospect in the fields of pigment printing, ink-jet printing, food coloring, painting ink and the like.

Description

Technical Field

[0001] The invention relates to the field of pigment production, and in particular to a preparation method and application of a light-resistant core-shell structure composite pigment. Background Art

[0002] Organic pigments are used as colorants in many different fields because of their bright colors and strong tinting power, such as inks, coatings, raw pulp coloring of synthetic fibers, coating printing of fabrics, coloring of plastics, rubber, leather, etc. With the development of organic pigments, organic pigments require more specific application properties in different application fields. For example, in the fields of automotive paints, industrial coatings and building materials, these pigments need to have excellent light resistance to provide a long-lasting and beautiful finish and applicability. However, due to their own structure, environmental factors or particle morphology, organic pigments cannot meet the durability and aesthetic requirements during the application process. For example, xanthene cationic pigments have the characteristics of bright colors and high tinting strength, and are widely used in various fields. Such pigments are usually insoluble pigment products obtained by combining soluble xanthene cationic dyes with precipitants under acidic conditions and settling them. However, such pigments are usually limited by the xanthene parent structure, and there are a large number of aromatic rings in their parent structure, resulting in poor light resistance of the pigments, which limits the application of xanthene lake pigments in the printing and dyeing industry. Therefore, in order to make pigments more widely used in various fields, it is necessary to improve the light resistance.

[0003] At present, most industrial production uses the method of doping finishing agents to improve the light resistance of pigments, or introduces specific groups into the pigments to make them have corresponding light resistance. For example, in patent CN 201711445530.7, hindered amine fragments are added to the pigment paste components to improve the light resistance of organic pigments; patent CN 201410183476.3 inserts dye anions and light stabilizer anions into the interlayer of hydrotalcite, and uses the ultraviolet absorption, energy transfer, and excited state fragmentation of light stabilizer anions to improve the light resistance of interlayer dye anions. Although these existing methods can improve the light resistance of pigments to a certain extent, they are all achieved by introducing chemical finishing agents. These methods usually have problems such as poor compatibility with the pigment itself and short light resistance stability time of the pigment when they are actually implemented. At the same time, the color light and hue of the pigment will also change greatly, and cannot meet the actual production requirements.

[0004] Core-shell structure composite pigments have always been considered to be an effective strategy to solve the poor light stability problem faced by organic pigments in practical applications. Inorganic substances such as silicon dioxide (SiO2), titanium dioxide (TiO2) and sepiolite can effectively absorb, reflect and scatter ultraviolet rays due to their small size effect and their quantum size effect, and have significant advantages in anti-ultraviolet. At present, there are more methods for compounding inorganic substances such as silicon dioxide with organic pigments to form core-shell structures to improve the performances such as thermal stability and weather resistance of organic pigments, such as patent CN110776756B discloses a modified sepiolite composite pigment and its preparation method, by compounding chitosan-modified sepiolite and organic pigments together, the chromaticity performance of organic pigments is improved, and the heat resistance and weather resistance of organic pigments are improved simultaneously. However, the mechanical strength of the inorganic material prepared by this method is not enough, and the disadvantage of coating layer peeling off is prone to occur in application. Patent CN116462990A discloses an inorganic-organic coated pigment and its preparation method, which improves the heat resistance and weather resistance of organic pigments by coating silicon dioxide inside the chromophore AS azo pigment. However, its tinting power changes greatly and cannot meet its actual needs in application.

[0005] Barium sulfate is an inorganic chemical component commonly encountered in nature, and its main form is a barite structure. This substance is a white solid, and due to its outstanding chemical stability and relatively low toxicity, it is often considered a vital non-gold ore source in various industrial environments. At the same time, barium sulfate exhibits excellent light resistance due to its extremely high physical density and porosity, and is particularly suitable for those applications where light stability is critical. Today, there are few studies in the industry on combining barium sulfate with organic pigments to improve the stability and light resistance of organic pigments. It is of great significance to combine it with organic pigments, especially oxyanthene lake pigments, to improve the light resistance of oxyanthene lake pigments. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for preparing a light-resistant core-shell structured composite pigment, using barium sulfate as the core and a cationic pigment as the shell, and adsorbing the two together through electrostatic attraction to form a composite pigment with a core-shell structure, so as to solve the problems of poor light resistance and low light stability existing in existing composite pigments.

[0007] In view of the above purpose, the present invention provides a method for preparing a light-resistant core-shell structure composite pigment, using barium sulfate as an inorganic core material, using a cationic lake pigment prepared with a heteropolyacid as a precipitant as an organic shell, and combining the two together by utilizing the electrostatic effect between the core and the shell to obtain a core-shell structure composite pigment with good light resistance and long-lasting light resistance stability.

[0008] The present invention first provides a method for preparing a light-resistant core-shell structure composite pigment, comprising the following steps:

[0009] (1) slowly adding an aluminum sulfate solution to a barium chloride solution, allowing the mixture to react in a hot water bath and stirring, allowing the reactant to stand, vacuum filtering, drying at 60° C. under normal pressure, and grinding to obtain barium sulfate;

[0010] (2) adding glacial acetic acid and deionized water to the cationic organic dye, stirring to react, and preparing an organic dye solution;

[0011] (3) Sodium tungstate, sodium molybdate and disodium hydrogen phosphate are added to hot water at 50-80°C, stirred at 250 r / min to allow for sufficient reaction, and the pH value is adjusted to 1.6-1.8 to obtain a heteropolyacid solution; the dye solution obtained in step (2) is slowly added dropwise to the heteropolyacid solution and stirred for 1-2 h to prepare an organic lake pigment suspension;

[0012] (4) dispersing the barium sulfate obtained in step (1) in water to obtain a barium sulfate dispersion, adding the barium sulfate dispersion to the organic lake pigment suspension obtained in step (3) and stirring to obtain a mixed solution, filtering the solution, washing with water, and drying at 60° C. under normal pressure to obtain a light-resistant core-shell structure composite pigment.

[0013] In one embodiment of the present invention, the concentration of the barium chloride solution in step (1) is 0.3-0.6 mol / L, and the barium chloride solution is obtained by reacting a mixture of barium chloride and water in a hot water bath, the temperature of the hot water bath is 60-90° C., and the reaction time is 2 h.

[0014] In one embodiment of the present invention, the concentration of the aluminum sulfate solution in step (1) is 0.07-0.20 mol / L, and the aluminum sulfate solution is obtained by reacting a mixture of aluminum sulfate and water under stirring for 1 hour.

[0015] In one embodiment of the present invention, the volume ratio of the barium chloride solution to the aluminum sulfate solution in step (1) is 1 to 3:1.

[0016] In one embodiment of the present invention, the temperature of the hot water bath in step (1) is 60-90° C., the stirring speed is 100-300 r / min, the reaction time is 1-2 h, and the reactant standing time is 0.5-1 h.

[0017] In one embodiment of the present invention, the particle size of the barium sulfate obtained in step (1) is 800nm-5um.

[0018] In one embodiment of the present invention, the cationic organic dye in step (2) is a xanthene dye, and the xanthene dye includes at least one of rhodamine B, basic red, and rhodamine 6G.

[0019] In one embodiment of the present invention, the cationic organic dye in step (2) is a mixture of rhodamine B and basic red, and the molar ratio of rhodamine to basic red is 1-5:0.5-1.

[0020] In one embodiment of the present invention, in step (2), the mass ratio of the cationic organic dye, water and glacial acetic acid is 1:20-50:0.01-1, preferably 1:20-50:0.5-1.

[0021] In one embodiment of the present invention, the stirring speed in step (2) is 100-800 r / min, the stirring time is 0.5-1 h, and the reaction temperature is 50-90°C.

[0022] In one embodiment of the present invention, the molar ratio of sodium tungstate, sodium molybdate and disodium hydrogen phosphate in step (3) is 1-5:1-5:0.5-2, and the reaction time is 1-2h.

[0023] In one embodiment of the present invention, the volume ratio of the dye solution to the heteropolyacid solution in step (3) is 1-3:1-2, the stirring temperature is 30-90° C., and the reaction time is 1-3 h.

[0024] In one embodiment of the present invention, the mass fraction of the barium sulfate dispersion in step (4) is 1-10%, the barium sulfate solution is prepared by stirring and reacting barium sulfate and water at 20-100° C. and ultrasonically treating the barium sulfate solution, and the reaction time is 30-180 min.

[0025] In one embodiment of the present invention, the mass ratio of the barium sulfate solution to the organic suspension in step (4) is 0.5-2:1-2.

[0026] In one embodiment of the present invention, the stirring temperature in step (4) is 20 to 100° C., and the stirring time is 30 to 180 min.

[0027] The second object of the present invention is to provide a light-resistant core-shell composite pigment prepared according to the above method.

[0028] The present invention also provides an application of the light-resistant core-shell structure composite pigment in pigment printing, inkjet printing, food pigment and painting ink.

[0029] Beneficial effects:

[0030] (1) The present invention uses barium sulfate as a core and an organic pigment as a shell, and the two are mutually adsorbed by electrostatic attraction to prepare a composite pigment. By adjusting the preparation method of barium sulfate, the size and surface properties of the inorganic core are precisely regulated to make it have excellent porosity, thereby enhancing the dispersion ability of the pigment in various media. At the same time, the inorganic core has the ability to absorb, reflect and scatter ultraviolet rays, and can concentrate the ultraviolet light energy absorbed by the composite pigment into the core layer, thereby reducing the damage of the energy to the pigment structure, improving the light resistance stability of the organic pigment and achieving the result that it can be exposed to the sun in a photoreactor for 24 hours without obvious fading or discoloration.

[0031] (2) Inorganic substances have excellent compatibility with organic pigments, low production costs, and advantages in actual production. They solve the problems of poor compatibility with pigments, low biological safety, weak resistance to ultraviolet light, and large-scale use affecting the color and hue of pigments caused by traditional methods such as adding dopants.

[0032] (3) When preparing the composite pigment, the present invention uses a heteropoly acid as a precipitant to prepare the cationic lake dye, which effectively improves the binding ability of the inorganic material and the cationic dye and greatly improves the performance of the prepared composite pigment.

[0033] (4) The composite pigment prepared by the method of the present invention can resist ultraviolet radiation for up to 73 days or even longer, and has excellent light resistance and light resistance durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of light-resistant core-shell composite pigment. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0036] Test method:

[0037] Powder K / S test: Use DataColor colorimeter to test. Weigh 1g of core-shell composite pigment and spread it gently on the sample plate to avoid bubbles or accumulation. Press the measurement button and wait for the measurement results to be automatically displayed on the screen. Record the measurement results as needed for subsequent analysis and processing.

[0038] Fabric sample K / S test:

[0039] Weigh 1g of core-shell composite pigment into a beaker, then weigh 2g of DM-5211G thickener, 10g of DM-5128 binder and 10mL of deionized water, stir thoroughly to form a viscous color paste. Print the color paste evenly on polyester cotton by screen printing, dry at 100℃, and pre-dry at 140℃ for 3min to prepare a printed cloth sample.

[0040] Cut the printed fabric sample into a 5cm×5cm square and test it using the DataColor colorimeter. Press the measurement button and wait for the measurement results to be automatically displayed on the screen. Record the measurement results as needed for subsequent analysis and processing.

[0041] Lightfastness test: Cut the above printed fabric samples into 5cm×5cm squares, place them under a CEL-S250 model UV lamp, take them out every 10 minutes for colorimetric value testing, and calculate the rate of change of the color difference ΔE of the printed fabric samples after 12 hours of UV lamp irradiation, i.e., the fading rate.

[0042] Lightfastness test: Spread the pigment powder flat on a sample plate, place it in direct sunlight, and record the time it takes for fading to occur (i.e. the time when the color difference ΔE changes by more than 1).

[0043] Example 1

[0044] A method for preparing a light-resistant core-shell structure composite pigment comprises the following steps:

[0045] (1) Add 12.48 g of barium chloride to a 500 mL beaker, then add 200 mL of deionized water, put it into a 70° C. water bath and stir it thoroughly for 30 min to prepare a barium chloride solution with a concentration of 0.3 mol / L; take 6.86 g of aluminum sulfate, add it into 200 mL of deionized water, stir it thoroughly for 30 min to prepare an aluminum sulfate solution with a concentration of 0.1 mol / L; slowly add the aluminum sulfate solution to the barium chloride solution, cover it with plastic wrap, stir it in a 70° C. hot water bath for 1 h, let the reactant stand for 30 min, filter it under reduced pressure, dry it at 60° C. under normal pressure, and grind it to obtain barium sulfate;

[0046] (2) Add 23.95 g of rhodamine B and 4.79 g of basic red to a 500 mL beaker, then add 1.26 g of glacial acetic acid and 150 mL of deionized water to the beaker, and stir at 90° C. for 20 min to prepare an organic dye solution;

[0047] (3) 23 g of sodium tungstate, 16.4 g of sodium molybdate and 10.1 g of disodium hydrogen phosphate were added to hot water at 80° C., stirred at 300 r / min for 10 min to allow for sufficient reaction, 2 mol / L hydrochloric acid was added to adjust the pH value to 1.7, and stirred for 10 min to obtain a heteropolyacid solution; the organic dye solution obtained in step (2) was cooled to 70° C., and slowly added to the heteropolyacid solution at a volume ratio of 1:1, and stirred at 300 r / min for 1 h to obtain an organic lake pigment suspension.

[0048] (4) ultrasonically dispersing the barium sulfate obtained in step (1) in water to obtain a 5% barium sulfate dispersion, adding an equal volume of the barium sulfate dispersion to the suspension in step (3), stirring for 2 hours, standing for 30 minutes, filtering, washing with water, and drying at 60° C. at normal pressure to obtain a light-resistant core-shell structure composite pigment.

[0049] Example 2

[0050] The difference between Example 2 and Example 1 is that the concentration of barium chloride is different. The concentration of barium chloride in Example 2 is 0.4 mol / L.

[0051] Example 3

[0052] The difference between Example 3 and Example 1 is that the concentration of barium chloride is different. The concentration of barium chloride in Example 3 is 0.5 mol / L.

[0053] Example 4

[0054] The difference between Example 4 and Example 1 is that the concentration of barium chloride is different. The concentration of barium chloride in Example 4 is 0.6 mol / L.

[0055] Example 5

[0056] The difference between Example 5 and Example 1 is that the temperature of the hot water bath during the preparation of barium sulfate is different. In Example 5, the temperature of the hot water bath during the preparation of barium sulfate is 60°C.

[0057] Example 6

[0058] The difference between Example 6 and Example 1 is that the temperature of the hot water bath when preparing barium sulfate is different. In Example 6, the temperature of the hot water bath when preparing barium sulfate is 80°C.

[0059] Example 7

[0060] The difference between Example 7 and Example 1 is that the temperature of the hot water bath when preparing barium sulfate is different. In Example 7, the temperature of the hot water bath when preparing barium sulfate is 90°C.

[0061] Example 8

[0062] The difference between Example 8 and Example 1 is that in step (3), the molar ratio of sodium tungstate, sodium molybdate and disodium hydrogen phosphate is 2:1:1.

[0063] Example 9

[0064] The difference between Example 9 and Example 1 is that the volume ratio of the dye solution to the heteropolyacid solution in step (3) is 2:1.

[0065] Example 10

[0066] The difference between Example 10 and Example 1 is that in step (4), the volume ratio of the barium sulfate solution to the organic pigment suspension is 2:1.

[0067] Comparative Example 1

[0068] The difference between Comparative Example 1 and Example 1 is that steps (1) and (4) are omitted, and the composite pigment is directly prepared by mixing the organic pigment suspension and the heteropolyacid solution. The amounts of rhodamine B and basic red in the organic pigment suspension are different, with the mass of rhodamine B being 11.97 g and the mass of basic red being 2.39 g.

[0069] Comparative Example 2

[0070] The difference between Comparative Example 2 and Comparative Example 1 is that rhodamine B and Basic Red are replaced by 23.95 g of Pigment Red 48, and the rest remain unchanged.

[0071] Comparative Example 3

[0072] The difference between Comparative Example 3 and Comparative Example 2 is that the reaction temperature of Pigment Red and glacial acetic acid is different, and the reaction temperature of Comparative Example 3 is 60°C.

[0073] Table 2 Lightfastness of the pigments and printed fabric samples of Examples 1-10 and Comparative Examples 1-3

[0074] Example Powder K / S value Fabric sample K / S value Fading rate / % Light resistance time (days) 1 4.8 5.9 14.9 49 2 4.9 6.2 16.4 47 3 4.9 6.8 5.5 65 4 4.7 6.4 8.9 54 5 4.9 7.2 10.2 52 6 4.8 6.8 20 45 7 4.8 6.6 7.6 57 8 4.9 7.0 5.9 66 9 4.6 6.9 7.2 59 10 4.5 4.2 1.9 73 Comparative Example 1 4.8 5.2 56 18 Comparative Example 2 3.2 4.8 48 30 Comparative Example 3 3.5 5.0 62 22

[0075] It can be seen from the data in Table 2 that compared with Comparative Examples 1 to 3, after forming the core-shell structure composite pigment, the light resistance of Examples 1-10 is significantly improved. At the same time, the color of the powder has not changed significantly, which can make up for the defect that the previous inorganic material will change the hue of the pigment. Its light resistance can last up to 73 days, which has a lot to do with the inorganic materials and synthesis, the preparation of organic pigment suspensions, and the proportion of inorganic materials in the composite material. It can be seen from Examples 1 to 4 that during the synthesis of inorganic materials, the concentration of barium chloride has a great influence on the light resistance of the pigment. The concentration of barium chloride mainly affects the particle size and surface properties of the synthesized barium sulfate, which in turn affects the light resistance of the composite pigment. With the increase of the concentration of barium chloride, the light resistance of the pigment first increases and then decreases. When the concentration of barium chloride is 0.5 mol / L, the light resistance of the pigment reaches the maximum. Similarly, the synthesis temperature of barium sulfate also has a great influence on the particle size and surface properties of barium sulfate, and thus affects the light resistance of the composite pigment. This can be seen from the data of Examples 1 and 5 to 7 that when the synthesis temperature is 90°C, the prepared composite pigment has the best light resistance. When the composite pigment is synthesized, the raw material ratio during the synthesis of phosphotungstomolybdic acid will affect the adsorption capacity of the precipitant on the dye, resulting in differences in the crystal structure of the organic pigment, which in turn affects the crystal structure of the composite pigment, resulting in differences in light resistance. In addition, the amount of inorganic material added will also affect the performance of the pigment. The specific impact is that the more inorganic material is added, the better its light resistance, but the amount of inorganic material added needs to be controlled at a certain level, otherwise it will affect the hue of the pigment, resulting in the final prepared fabric having a lighter color and difficulty in obtaining bright colors. Among them, due to the different properties of different dyes in Comparative Examples 2 and 3, adjusting the temperature when they are dissolved indirectly leads to whether they are completely in a molecular state in the solvent, thereby affecting their coating ability.

[0076] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a light-resistant core-shell composite pigment, characterized in that: The following steps are involved: (1) slowly adding an aluminum sulfate solution to a barium chloride solution, allowing the mixture to react in a hot water bath and stirring, allowing the reactant to stand, vacuum filtering, drying at 60° C. under normal pressure, and grinding to obtain barium sulfate; (2) adding glacial acetic acid and deionized water to the cationic organic dye, stirring to react, and preparing an organic dye solution; (3) Sodium tungstate, sodium molybdate and disodium hydrogen phosphate are added to hot water at 50-80°C, stirred at 250 r / min to allow for sufficient reaction, and the pH value is adjusted to 1.6-1.8 to obtain a heteropolyacid solution; the dye solution obtained in step (2) is slowly added dropwise to the heteropolyacid solution and stirred for 1-2 h to prepare an organic lake pigment suspension; (4) dispersing the barium sulfate obtained in step (1) in water to obtain a barium sulfate dispersion, adding the barium sulfate dispersion to the organic lake pigment suspension obtained in step (3) and stirring to obtain a mixed solution, filtering the solution, washing with water, and drying at 60° C. under normal pressure to obtain a light-resistant core-shell structure composite pigment.

2. The preparation method according to claim 1, characterized in that: The concentration of the barium chloride solution in step (1) is 0.3-0.6 mol / L, and the barium chloride solution is obtained by reacting a mixture of barium chloride and water under hot water bath conditions, the temperature of the hot water bath is 60-90° C., and the reaction time is 2 h. The concentration of the aluminum sulfate solution is 0.07-0.20 mol / L, and the aluminum sulfate solution is obtained by reacting a mixture of aluminum sulfate and water under stirring conditions, and the stirring time is 1 h.

3. The preparation method according to claim 1, characterized in that: In step (1), the volume ratio of the barium chloride solution to the aluminum sulfate solution is 1 to 3:1, the temperature of the hot water bath is 60 to 90° C., the stirring speed is 100 to 300 r / min, the reaction time is 1 to 2 h, and the standing time of the reactants is 0.5 to 1 h.

4. The preparation method according to claim 1, characterized in that: The cationic organic dye described in step (2) is a xanthene dye, and the xanthene dye includes at least one of rhodamine B, basic red, and rhodamine 6G.

5. The preparation method according to claim 1, characterized in that: The cationic organic dye in step (2) is a mixture of rhodamine B and basic red, the molar ratio of rhodamine B to basic red is 1-5:0.5-1, and the mass ratio of the cationic organic dye, water and glacial acetic acid is 1:20-50: 0.01~1, stirring speed is 100-800r / min, stirring time is 0.5-1h, reaction temperature is 50~90℃.

6. The preparation method according to claim 1, characterized in that: In step (3), the molar ratio of sodium tungstate, sodium molybdate and disodium hydrogen phosphate is 1-5:1-5:0.5-2, the reaction time is 1-2h, the volume ratio of the dye solution and the heteropolyacid solution is 1-3:1-2, the stirring temperature is 30-90°C and the reaction time is 1-3h.

7. The preparation method according to claim 1, characterized in that: The mass fraction of the barium sulfate dispersion in step (4) is 1-10%, the barium sulfate solution is prepared by stirring barium sulfate and water at 20-100° C. and ultrasonically treating the mixture, and the reaction time is 30-180 min.

8. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of the barium sulfate solution to the organic suspension is 0.5-2:1-2, the stirring temperature is 20-100° C., and the stirring time is 30-180 min. 9 . The light-resistant core-shell structure composite pigment prepared by the preparation method according to claim 1 .

10. Use of the light-resistant core-shell composite pigment according to claim 9 in pigment printing, inkjet printing, food coloring and painting ink.

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