High-weatherability polymer coated pigment and preparation method thereof

Abstract

The invention relates to the technical field of pigments, in particular to a high-weather-resistance polymer coated pigment and a preparation method thereof. The method comprises the following steps: treating an organic pigment dispersion liquid by using a polymer monomer and a functional additive to obtain a pigment-polymer monomer miniemulsion; heating and initiating free radical polymerization reaction to obtain a polymer coated pigment emulsion; and then carrying out separation treatment, wherein the functional additive comprises a free radical initiator. According to the method, the organic pigment is coated with a polymer monomer through free radical polymerization reaction of miniemulsion to form a unique microcapsule structure, so that the influence of oxygen, water vapor and a solvent in an external environment can be avoided, and ultraviolet light can be shielded; the separation treatment step enables the polymer coated pigment to have a uniform particle size, so that the polymer coated pigment also has good dispersibility in an oily solvent. The polymer coated pigment has good weather resistance and tinting strength, and is low in chromatic aberration in the aging process.

Description

Technical Field

[0001] The present invention relates to the technical field of pigments, and in particular to a highly weather-resistant polymer-coated pigment and a preparation method thereof. Background Art

[0002] Organic pigments have the advantages of strong tinting power, bright colors, and complete color spectrum. They have been widely used in the coloring of inks, coatings, plastics, rubber, etc., and have been widely used in the field of ink printing. my country is an important producer of organic pigments in the world, accounting for about 60% of the global total output, and its output has ranked first in the world for many years. However, because they contain unstable chemical groups and are easily excited by light, most organic pigments have the disadvantages of poor light resistance and weather resistance. This limits the application of organic pigments in the outdoor sign industry.

[0003] Studies have confirmed that polymer coating modification of organic pigments can improve their weather resistance. Coated pigments are pigments that change their properties by forming one or more coating films on the surface of pigment particles through physical or chemical methods. The current coating modification methods are mainly divided into two categories: inorganic coating method and polymer coating method. However, both types of coating modification methods have unavoidable defects. The inorganic coating method not only reduces the coloring power of the pigment, but also has a complex preparation process that is difficult to industrialize. Although polymer coating can significantly improve its color fastness and weather resistance, it is difficult to disperse evenly due to poor separation effect. Therefore, current polymer coated pigment products can only exist in the form of water emulsions and cannot be used in oil-based inks. However, the application range of water emulsion pigments is limited and can only be used for fabric printing, making it difficult to bring out all the advantages of polymer coated pigments.

[0004] In addition, existing products mainly utilize their advantages of fabric adhesion and washing fastness, but have not been developed for light resistance and weather resistance. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a highly weather-resistant polymer-coated pigment and a preparation method thereof, so as to solve the problem in the prior art that the polymer-coated pigment is difficult to be used in oil-based inks.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] The invention provides a method for preparing a highly weather-resistant polymer-coated pigment. The method comprises the following steps: treating an organic pigment dispersion liquid with a polymer monomer and a functional additive to obtain a pigment-polymer monomer miniemulsion; heating the pigment-polymer monomer miniemulsion and initiating a free radical polymerization reaction to obtain a polymer-coated pigment emulsion; and separating and treating the polymer-coated pigment emulsion to obtain the highly weather-resistant polymer-coated pigment. The functional additive comprises a free radical initiator.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the polymer monomer is one or more of styrene, tetrafluoroethylene, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, acrylamide, acrylonitrile, and vinyl acetate; and the free radical initiator is azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, diisopropyl azodicarboxylate, dimethyl azobutyrate, benzoyl peroxide, tert-butyl benzoyl peroxide, or methyl ethyl ketone peroxide.

[0010] Furthermore, the functional additives also include free radical initiators, crosslinking agents, co-emulsifiers, hindered amine light stabilizers and ultraviolet absorbers.

[0011] Furthermore, in the pigment-polymer monomer miniemulsion, the mass percentage of each component is: the organic pigment 5% to 15%, the emulsifier: 10% to 40%, the polymer monomer: 1% to 12%, and the balance is the functional additive and water; calculated based on the mass of the polymer monomer as 100%, the mass percentage of each component in the functional additive is: the cross-linking agent: 2% to 5%, the free radical initiator: 2% to 6%, the co-emulsifier: 2% to 8%, the hindered amine light stabilizer: 2% to 6%, and the ultraviolet absorber: 4 to 20%.

[0012] Furthermore, after the separation treatment, a post-treatment step is also included to obtain the highly weather-resistant polymer-coated pigment in powder form.

[0013] Further, the following steps are included:

[0014] S1, mixing, dissolving and grinding water, the emulsifier and the organic pigment to obtain the organic pigment dispersion;

[0015] S2, firstly mixing and dissolving the polymer monomer and the functional additive, and then adding them into the organic pigment dispersion to homogenize and disperse them to obtain the pigment-polymer monomer miniemulsion; heating and reacting the pigment-polymer monomer miniemulsion at a temperature of 70 to 90° C. for a reaction time of 5 to 12 hours to obtain the polymer-coated pigment emulsion;

[0016] S3, performing multiple centrifugal separations on the polymer-coated pigment emulsion to obtain a pigment paste;

[0017] S4, drying, crushing and filtering the paste raw material to obtain the polymer-coated pigment.

[0018] Furthermore, in step S2, the method of adding into the organic pigment dispersion is to slowly dropwise add with stirring.

[0019] Furthermore, in step S2, an emulsifier is used for the homogenization dispersion, the rotation speed of the emulsifier is 1000 to 2000 rpm, and the time is 30 to 90 min.

[0020] Further, the centrifugal separation is performed three times in step S3, and the specific steps are as follows:

[0021] The polymer-encapsulated pigment emulsion is mixed with anhydrous ethanol and centrifuged to obtain a first paste, wherein the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion;

[0022] The first paste is mixed with a sodium dodecyl sulfate solution and centrifuged to obtain a second paste, wherein the mass percentage of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 0.2% to 1%;

[0023] The second paste is mixed with anhydrous ethanol and centrifuged to retain the precipitate to obtain the pigment paste, wherein the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion.

[0024] The present invention also provides a highly weather-resistant polymer-coated pigment, which is prepared by the above-mentioned method.

[0025] The beneficial effects of the present invention are:

[0026] (1) The method for preparing the highly weather-resistant polymer-encapsulated pigment of the present invention is to encapsulate the polymer monomer on the outside of the organic pigment through the free radical polymerization reaction of the mini-emulsion to form a unique microcapsule structure, which can not only avoid the influence of oxygen, water vapor and solvent in the external environment, but also shield ultraviolet light;

[0027] (2) The method for preparing the highly weather-resistant polymer-coated pigment of the present invention, wherein the separation treatment step enables the polymer-coated pigment to have a uniform particle size, thereby having good dispersibility in an oily solvent;

[0028] (3) The method for preparing the highly weather-resistant polymer-coated pigment of the present invention can prepare pigment products in the form of water emulsions and pigment products in the form of oil-based inks, while maintaining good effects;

[0029] (4) In the preparation method of the highly weather-resistant polymer-coated pigment of the present invention, other additives are added during the preparation process to further improve the weather resistance;

[0030] (5) The highly weather-resistant polymer-coated pigment of the present invention has good weather resistance and tinting strength, and low color difference during aging, so that the pigment has good stability;

[0031] (6) The highly weather-resistant polymer-coated pigment of the present invention has good compatibility with aqueous solvents and oily solvents and has a wide range of applications. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0033] The preparation method of the highly weather-resistant polymer-coated pigment of the present invention comprises the following steps: treating an organic pigment dispersion liquid with a polymer monomer and a functional additive to obtain a pigment-polymer monomer miniemulsion; heating the pigment-polymer monomer miniemulsion and initiating a free radical polymerization reaction to obtain a polymer-coated pigment emulsion; and separating and treating the polymer-coated pigment emulsion to obtain a highly weather-resistant polymer-coated pigment; wherein the functional additive comprises a free radical initiator.

[0034] The preparation method of the highly weather-resistant polymer-coated pigment of the present invention coats the polymer monomer on the outside of the organic pigment through the free radical polymerization reaction of the mini-emulsion to form a unique microcapsule structure, which can not only avoid the influence of oxygen, water vapor and solvent in the external environment, but also shield ultraviolet light. In addition, the preparation step of the present invention also includes a separation process, so that the highly weather-resistant polymer-coated pigment of the present invention can be prepared not only as a pigment product in the form of an aqueous emulsion, but also as a pigment product in the form of an oily ink, and maintain a good effect, so that the pigment has good compatibility and excellent application performance, greatly expanding its application range.

[0035] Preferably, the polymer monomer is one or more of styrene, tetrafluoroethylene, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, acrylamide, acrylonitrile, and vinyl acetate.

[0036] Preferably, the free radical initiator is azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, diisopropyl azodicarboxylate, dimethyl azobutyrate, benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, and the like.

[0037] Preferably, the functional additives include free radical initiators, crosslinking agents, co-emulsifiers, hindered amine light stabilizers, and ultraviolet absorbers. By adding hindered amine light stabilizers and ultraviolet absorbers in the coating layer in a blended manner, the light resistance and weather resistance of the pigment are further improved.

[0038] Preferably, in the polymer-encapsulated pigment emulsion, the mass percentages of the components are: organic pigment 5% to 15%, emulsifier: 10% to 40%, polymer monomer: 1% to 12%, and the remainder is functional additives and water.

[0039] Taking the mass of the polymer monomer as 100%, the mass percentage of each component in the functional additive is as follows: cross-linking agent: 2% to 5%, free radical initiator: 2% to 6%, co-emulsifier: 2% to 8%, hindered amine light stabilizer: 2% to 6%, and ultraviolet absorber: 4 to 20%.

[0040] The method for preparing the highly weather-resistant polymer-coated pigment of the present invention specifically comprises the following steps:

[0041] S1. Add an emulsifier into water, stir to dissolve, then add an organic pigment to evenly disperse the organic pigment in water; then grind with a sand mill to obtain an organic pigment dispersion.

[0042] Preferably, in step S1, the stirring time is greater than or equal to 10 min, and the grinding time is greater than or equal to 15 min.

[0043] S2. Mix and dissolve the polymer monomer and the functional additive, add them into the organic pigment dispersion, and use an emulsifier to homogenize and disperse them to obtain a pigment-polymer monomer miniemulsion; heat the pigment-polymer monomer miniemulsion and initiate a free radical polymerization reaction to obtain a polymer-coated pigment emulsion.

[0044] Preferably, the method of adding to the organic pigment dispersion is to slowly dropwise add with stirring.

[0045] Preferably, the speed of the emulsifier is 1000 to 2000 rpm, and the time is 30 to 90 min.

[0046] Preferably, the heating step is carried out in a reaction kettle, the heating temperature is 70-90° C., and the reaction time is 5-12 hours; after the reaction is completed, the temperature is cooled to room temperature to obtain a polymer-coated pigment emulsion.

[0047] S3. Centrifugally separate the polymer-coated pigment emulsion for multiple times to obtain a pigment paste.

[0048] Each time the centrifugal separation is performed, the solvent that can be used is anhydrous ethanol, sodium dodecyl sulfate solution or a mixed solution of ethanol and water.

[0049] Preferably, three centrifugal separations are performed in step S3, specifically:

[0050] The polymer-encapsulated pigment emulsion is mixed with anhydrous ethanol and centrifuged to retain the precipitate to obtain a first paste; the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion.

[0051] The first paste is mixed with a sodium dodecyl sulfate solution (SDS) and centrifuged to retain the precipitate to obtain a second paste, wherein the mass percentage of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 0.2% to 1%.

[0052] The second paste is mixed with anhydrous ethanol and centrifuged to retain the precipitate to obtain a pigment paste; the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion.

[0053] Preferably, during each centrifugal separation, the speed of the centrifuge used is greater than or equal to 4000 rpm.

[0054] S4, drying, crushing and filtering the paste raw material to obtain the polymer-coated pigment.

[0055] Preferably, a chemical sieve is used for filtration, and the pore size of the chemical sieve is 100-200 meshes.

[0056] The present invention has no particular limitation on the specific type of organic pigments used, and common commercial organic pigments can be selected, such as azo pigments, dione pyrrolopyrrole pigments, phthalocyanine pigments, perylene diimide pigments, quinacridone pigments, dioxazine pigments, triarylmethane pigments or condensed ring ketone pigments.

[0057] The emulsifier, co-emulsifier, crosslinking agent, hindered amine light stabilizer, and ultraviolet absorber used in the present invention are all commercially available conventional types, as follows:

[0058] The emulsifier is an anionic emulsifier, such as one or more of sodium stearate, sodium oleate, sodium laurate, sodium dodecyl sulfate, sodium polyoxyethylene fatty alcohol ether sulfate, ammonium allyloxy nonylphenol polyoxyethylene ether sulfate, sodium secondary alkyl sulfonate, sodium fatty acid methyl ester ethoxylate sulfonate, sodium fatty acid methyl ester sulfonate, sodium dioctyl succinic acid sulfonate, and sodium dodecylbenzene sulfonate.

[0059] The co-emulsifier is a long-chain alkane, such as hexadecane, or a long-chain fatty alcohol, such as hexadecane alcohol.

[0060] The crosslinking agent is one of divinylbenzene (DVB), p,p'-divinyl-1,2-diphenylethane (BVPE), and ethylene glycol dimethacrylate.

[0061] The hindered amine light stabilizer is one of UV-123, UV-292, and UV-770.

[0062] The ultraviolet absorber includes one or more of benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and triazine ultraviolet absorbers.

[0063] The present invention is illustrated below by means of specific examples.

[0064] Example 1

[0065] The highly weather-resistant polymer-coated pigment prepared in this embodiment is polymer-coated pigment red 264 (CI Pigment Red 264) powder, and the specific preparation process is as follows:

[0066] Add 400g of allyloxy nonylphenol polyoxyethylene ether ammonium sulfate (DNS-86) to 20L of water and stir to dissolve. Add 1kg of Pigment Red 264 and grind with a sand mill for 20min. Add 24g of azobisisobutyronitrile (AIBN), 30g of divinylbenzene (DVB), 24g of hexadecane (HD), 60g of UV-326, and 12g of UV-123 to 600g of styrene and fully dissolve. While stirring, slowly add the oil phase to the pigment dispersion, and then stir with a shear emulsifier for 1 hour (1300rpm). Transfer the obtained pigment-monomer emulsion to a reactor and initiate free radical polymerization at 75°C. After the reaction is completed, mix the pigment-monomer emulsion with anhydrous ethanol and centrifuge to retain the precipitate to obtain a first paste; the volume of anhydrous ethanol is 1 / 2 of the volume of the polymer-coated pigment emulsion. The first paste is mixed with sodium dodecyl sulfate solution (SDS) and centrifuged, and the precipitate is retained to obtain a second paste, wherein the mass percentage of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 1%. The second paste is mixed with anhydrous ethanol and centrifuged, and the precipitate is retained to obtain a paste pigment; the volume of the anhydrous ethanol is 2 / 3 of the volume of the polymer-encapsulated pigment emulsion.

[0067] After washing, the obtained pigment paste was placed in an oven to dry, crushed by a grinder, and filtered through a 100-mesh sieve to obtain polymer-coated Pigment Red 264 powder.

[0068] Example 2

[0069] The highly weather-resistant polymer-coated pigment prepared in this embodiment is polymer-coated pigment green 7 (CI Pigment Green 7) powder, and the specific preparation process is as follows:

[0070] Add 200g of sodium alkyl alcohol polyoxyethylene ether sulfate (AES) to 20L of water and stir to dissolve. Add 1 kg of Pigment Green 7 and grind it in a sand mill for 20min. Add 16g AIBN, 16g DVB, 16g HD, 32g UV-477, 12g UV-460, and 8g UV-123 to 400g styrene and dissolve them fully. While stirring, slowly add the oil phase to the pigment dispersion, and then stir it with a shear emulsifier for 1 hour (1300rpm). Transfer the obtained pigment-monomer emulsion to a reactor and initiate free radical polymerization at 90°C. After the reaction is completed, add ethanol and stir evenly, perform the first centrifugation, and then centrifuge and wash twice with an ethanol-water mixture. Dry in an oven, crush with a pulverizer, and filter with a 100-mesh sieve to obtain a polymer-coated Pigment Green 7 powder.

[0071] Example 3

[0072] The highly weather-resistant polymer-coated pigment prepared in this embodiment is polymer-coated pigment yellow 110 (CY Pigment Yellow 110) powder, and the specific preparation process is as follows:

[0073] Add 400g of sodium dodecylbenzene sulfonate (SDBS) to 20L of water and stir to dissolve. Add 2kg of Pigment Yellow 110 and grind with a sand mill for 30min. Add 40g of azobisisovaleronitrile (AVBN), 50g of P,P'-divinyl-1,2-diphenylethane (BVPE), 40g of HD, 60g of UV-460, and 20g of UV-292 to 1kg of tetrafluoroethylene and fully dissolve. While stirring, slowly add the oil phase to the pigment dispersion, and then stir with a shear emulsifier for 1 hour (1300rpm). Transfer the obtained pigment-monomer emulsion to a reactor and initiate free radical polymerization at 85℃. After the reaction is completed, add ethanol and stir evenly, centrifuge, and then wash twice with an ethanol / water mixture. Dry in an oven, crush with a grinder, and filter with a 100-mesh sieve to obtain a polymer-coated Pigment Yellow 110 powder.

[0074] Example 4

[0075] The highly weather-resistant polymer-coated pigment prepared in this embodiment is polymer-coated pigment red 149 (CI Pigment Red 149) powder, and the specific preparation process is as follows:

[0076] Add 100g of sodium dodecyl sulfate (SDS) to 20L of water and stir to dissolve. Add 1kg of Pigment Red 149 and grind it in a sand mill for 40min. Add 16g of benzoyl peroxide (BPO), 24g of ethylene glycol dimethacrylate, 24g of HD, 80g of UV-531, and 24g of UV-123 to 800g of methyl methacrylate and fully dissolve them. While stirring, slowly add the oil phase to the pigment dispersion, and then stir it with a shear emulsifier for 1 hour (1300rpm). Transfer the obtained pigment-monomer emulsion to a reactor and initiate free radical polymerization at 80°C. After the reaction is completed, add ethanol and stir evenly, centrifuge, and then wash twice with an ethanol-water mixture. Dry in an oven, crush with a grinder, and filter with a 100-mesh sieve to obtain a polymer-coated Pigment Red 149 powder.

[0077] Uncoated pigment powders are used as comparative examples. Specifically, comparative example 1 is pigment red 264, comparative example 2 is pigment green 7, and comparative example 3 is pigment yellow 110.

[0078] The above embodiments and comparative examples were tested, and the specific test items and methods are as follows:

[0079] (1) Ink coating test: In a grinding jar, add 8g acrylic resin, 100g butanone, and 1g BYK 163 dispersant in order, stir until dissolved, then add 2g of the polymer-coated pigment prepared in Examples 1 to 3 and the pigment of Comparative Examples 1 to 3 respectively, and homogenize and disperse. Use OMEC TopSi zer laser particle size analyzer to test its particle size distribution. Use a manual coater to coat the pigment paste on the thermal transfer ribbon, and observe the coating of the ribbon.

[0080] (2) Weather resistance test: The carbon ribbon coated with the pigments of Examples 1 to 3 and Comparative Examples 1 to 3 was transferred onto a reflective film using a thermal transfer printer. The aging resistance was tested using a xenon lamp aging resistance tester. The color difference before and after the test was measured using an xrite i 1Pro3 colorimeter. The smaller the color difference, the better the weather resistance.

[0081] The test results are shown in Table 1.

[0082] Table 1 Test results of Examples 1 to 3 and Comparative Examples 1 to 3

[0083]

[0084] It can be seen from the above tests that the coating conditions of the polymer-coated pigments of the present invention are the same as those of the uncoated pigments, both of which are good, indicating that the polymer-coated pigments of the present invention can also be well dispersed in the ink. Before and after the aging resistance test, the color difference of the polymer-coated pigments of Examples 1 to 3 of the present invention is significantly smaller than that of the corresponding uncoated pigments, indicating that the polymer-coated pigments of the present invention have good weather resistance.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a highly weather-resistant polymer-coated pigment, characterized in that: An organic pigment dispersion is treated with polymer monomers and functional additives to obtain a pigment-polymer monomer miniemulsion; the pigment-polymer monomer miniemulsion is heated and a free radical polymerization reaction is initiated to obtain a polymer-coated pigment emulsion; the polymer-coated pigment emulsion is separated to obtain the highly weather-resistant polymer-coated pigment; wherein the functional additive includes a free radical initiator.

2. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 1, characterized in that: The polymer monomer is one or more of styrene, tetrafluoroethylene, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, acrylamide, acrylonitrile, and vinyl acetate; the free radical initiator is azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, diisopropyl azodicarboxylate, dimethyl azobutyrate, benzoyl peroxide, tert-butyl benzoyl peroxide, or methyl ethyl ketone peroxide.

3. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 1, characterized in that: The functional additives also include free radical initiators, crosslinking agents, co-emulsifiers, hindered amine light stabilizers and ultraviolet absorbers.

4. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 3, characterized in that: In the pigment-polymer monomer miniemulsion, the mass percentage of each component is: 5% to 15% of the organic pigment, 10% to 40% of the emulsifier, 1% to 12% of the polymer monomer, and the balance is the functional additive and water; calculated based on the mass of the polymer monomer as 100%, the mass percentage of each component in the functional additive is: 2% to 5% of the cross-linking agent, 2% to 6% of the free radical initiator, 2% to 8% of the co-emulsifier, 2% to 6% of the hindered amine light stabilizer, and 4% to 20% of the ultraviolet absorber.

5. The method for preparing a highly weather-resistant polymer-coated pigment according to any one of claims 1 to 4, characterized in that: After the separation treatment, a post-treatment step is also included to obtain the highly weather-resistant polymer-coated pigment in powder form.

6. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 5, characterized in that: The following steps are involved: S1, mixing, dissolving and grinding water, the emulsifier and the organic pigment to obtain the organic pigment dispersion; S2, firstly mixing and dissolving the polymer monomer and the functional additive, and then adding them into the organic pigment dispersion to homogenize and disperse them to obtain the pigment-polymer monomer miniemulsion; heating and reacting the pigment-polymer monomer miniemulsion at a temperature of 70 to 90° C. for a reaction time of 5 to 12 hours to obtain the polymer-coated pigment emulsion; S3, performing multiple centrifugal separations on the polymer-coated pigment emulsion to obtain a pigment paste; S4, drying, crushing and filtering the paste raw material to obtain the polymer-coated pigment.

7. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 6, characterized in that: In step S2, the method of adding into the organic pigment dispersion is to slowly dropwise add with stirring.

8. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 6, characterized in that: In step S2, an emulsifier is used for the homogenization dispersion, the rotation speed of the emulsifier is 1000 to 2000 rpm, and the time is 30 to 90 min.

9. The method for preparing a highly weather-resistant polymer-coated pigment according to claim 6, characterized in that: In step S3, the centrifugal separation is performed three times, and the specific steps are as follows: The polymer-encapsulated pigment emulsion is mixed with anhydrous ethanol and centrifuged to obtain a first paste, wherein the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion; The first paste is mixed with a sodium dodecyl sulfate solution and centrifuged to obtain a second paste, wherein the mass percentage of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 0.2% to 1%; The second paste is mixed with anhydrous ethanol and centrifuged to retain the precipitate to obtain the paste pigment; the volume of the anhydrous ethanol is 1 / 2 to 2 / 3 of the volume of the polymer-encapsulated pigment emulsion.

10. A highly weather-resistant polymer-coated pigment, characterized in that: The highly weather-resistant polymer-coated pigment is prepared by the method according to any one of claims 1 to 9.

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