A high color strength permanent yellow pigment for waterborne systems, a coating material and a preparation method thereof

Abstract

The application discloses a kind of high color strength of water-based system permanent yellow pigment, coating and preparation method and preparation method thereof, belong to organic pigment technical field, including the following steps: S1, permanent yellow pigment crude product is prepared according to conventional method, the permanent yellow pigment crude product is added to the container with pigment emulsifier, the permanent yellow pigment crude product is dispersed in the pigment emulsifier, then the container is sealed, the sealed container is immersed in liquid nitrogen tank, and quick freezing is carried out, after quick freezing is completed, the icing permanent yellow pigment crude product is obtained;S2, the icing permanent yellow pigment crude product is crushed with ultrasonic crusher, and the crushed permanent yellow pigment crude product is ball milled to obtain permanent yellow pigment ice crystal, and the permanent yellow pigment ice crystal is transferred to freeze-drying chamber, so that the icing water is sublimated to obtain permanent yellow pigment crystal.The finally prepared high color strength of water-based system permanent yellow pigment has small particle size, good dispersibility and high color strength.

Description

Technical Field

[0001] The present invention relates to the technical field of organic pigments, and in particular to a permanent yellow pigment with high tinting strength in a water-based system, a coating and a preparation method thereof. Background Art

[0002] Tinting power, also known as tinting strength, refers to the ability of colored pigments to color white pigments under specified conditions.

[0003] Three factors generally influence the tinting power of organic pigments: their chemical structure, crystal state, and particle state. For a pigment with a specific crystal form, larger particles have lower surface energy, resulting in a more stable pigment. Within a certain range, its hiding power is stronger, but its tinting power will decrease. Conversely, smaller particles increase the pigment's transparency, increase its surface energy, and make it less stable. During the drying process, some pigment particles tend to aggregate, resulting in a loss of tinting power. For example, Permanent Red F2R, a pigment primarily used in coatings, typically achieves higher hiding power at the expense of some pigment tinting power. The size of the pigment particles is crucial to the coloring effect of plastics; only by crushing the pigment particles into aggregates can tinting strength, hue, gloss, and hiding power be improved. The appropriate particle size of dispersed pigments can be illustrated by the following data: if the particle size is greater than 30 μm, spots and streaks will appear on the surface of the product; if it is between 10 and 30 μm, the surface of the product will be matte; if the particle size is less than 5 μm, it is sufficient for general products, but for fibers (single filament diameter is 10 to 30 μm) and ultra-thin films (thickness less than 10 μm), the particle size should be less than 1 μm. This shows that the particle size of organic pigments determines the pigment's coloring ability.

[0004] Organic pigments are widely used in inks, paints, coatings, and synthetic fiber pulp coloring, as well as in textile pigment printing and coloring plastics, rubber, and leather. Ink pigments are the most widely used. Organic pigment production accounts for approximately a quarter of total dye production. Organic pigments are water-insoluble organic compounds that are typically added to a substrate in a highly dispersed state to color the substrate. The fundamental difference between them and dyes is that dyes dissolve in the dyeing medium used, while pigments are insoluble in both the medium in which they are used and the substrate being colored. Consequently, organic pigments face dispersibility issues in solvents and substrates.

[0005] Azo pigments are a type of organic pigment, and Permanent Yellow pigment is a type of azo pigment. They are water-insoluble organic compounds containing an azo group (-N=N-) in their molecular structure. They are the most diverse and produced type of organic pigment. Azo pigments are typically azo pigments. A diazo component, produced by diazotization of aromatic or heteroaromatic amines, is then coupled with a coupling component such as acetylamine, 2-naphthol, pyrazolone, 2-hydroxy-3-naphthoic acid, or 2-hydroxy-3-naphthoyl aromatic amine to form a water-insoluble precipitate. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, one of the objects of the present invention is to provide a method for preparing a permanent yellow pigment with high tinting strength in a water-based system. The permanent yellow pigment with high tinting strength has a small particle size, good dispersibility in an aqueous solvent, and can achieve high tinting strength when coated on a substrate.

[0007] A second object of the present invention is to provide a permanent yellow pigment with high tinting strength in a water-based system.

[0008] A third object of the present invention is to provide a water-based coating with high tinting strength, which has high tinting strength, good dispersibility in the substrate, and uniform coloring.

[0009] One of the purposes of the present invention is achieved by the following technical solution:

[0010] A method for preparing a water-based permanent yellow pigment with high tinting strength comprises the following steps:

[0011] S1. A crude permanent yellow pigment is prepared according to a conventional method, and the crude permanent yellow pigment is added to a container containing a pigment emulsifier to disperse the crude permanent yellow pigment in the pigment emulsifier. The container is then sealed and immersed in a liquid nitrogen tank for quick freezing. After the quick freezing is completed, a frozen crude permanent yellow pigment is obtained.

[0012] S2. crushing the frozen crude permanent yellow pigment product with an ultrasonic crusher, ball-milling the crushed crude permanent yellow pigment product to obtain permanent yellow pigment ice crystals, transferring the permanent yellow pigment ice crystals to a freeze-drying chamber to sublime the frozen water to obtain permanent yellow pigment crystals;

[0013] S3. Wetting the cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, and adding the permanent yellow pigment crystals to the cellulose nanocrystal (CNCs) colloid to obtain the permanent yellow pigment with high tinting strength of the water-based system.

[0014] Further, the permanent yellow pigment ice crystals were transferred to a freeze drying chamber, the temperature of the freeze drying chamber was maintained at -22°C, and the pressure was reduced to 10 - 2 mbar, and the frozen water was sublimed within 12 hours to obtain the permanent yellow pigment crystals.

[0015] Furthermore, the pigment emulsifier is one or both of sorbitan monooleate and castor oil polyoxyethylene ether.

[0016] The second object of the present invention is to provide a water-based permanent yellow pigment with high tinting strength obtained by the above preparation method.

[0017] The third object of the present invention is achieved by adopting the following technical solution:

[0018] A water-based paint with high tinting strength comprises the permanent yellow pigment crystals and a water-soluble resin.

[0019] Furthermore, the water-soluble resin is one of polyester resin, epoxy resin and urethane resin.

[0020] Furthermore, the permanent yellow pigment crystals are polyvinyl alcohol-coated permanent yellow pigment crystals. The preparation method of the polyvinyl alcohol-coated permanent yellow pigment crystals is: dispersing the polyvinyl alcohol and the permanent yellow pigment crystals in a water / ethanol mixture, and then repeatedly centrifuging and resuspending to obtain the polyvinyl alcohol-coated permanent yellow pigment crystals.

[0021] Furthermore, in the water / ethanol mixture, the weight ratio of water to ethanol is 2:7.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention provides a method for preparing a water-based permanent yellow pigment with high tinting strength. The method comprises dispersing a crude permanent yellow pigment in a pigment emulsifier to make the crude permanent yellow pigment more uniformly dispersed. During the quick freezing of the crude permanent yellow pigment, ice formed between the particles of the crude permanent yellow pigment is more uniform and does not agglomerate between the particles. The ice formed is not mainly dispersed between the particles. When the crude permanent yellow pigment is subsequently subjected to sublimation treatment, the particles are still relatively fluffy while the crude permanent yellow pigment is dried, and the problems of hardening and caking do not occur. In addition, during the ball milling process, since the ice protects the surface of the crude permanent yellow pigment particles, there is no need to add a grinding aid, and the ball milling efficiency can be improved. The unstable crystal form of the permanent yellow pigment is transformed into a stable crystal form, thereby improving the tinting strength of the permanent yellow pigment.

[0024] (2) The permanent yellow pigment crystals are added to the cellulose nanocrystals (CNCs) colloid. Since the cellulose nanocrystals (CNCs) colloid has a network structure, it has a steric effect on the permanent yellow pigment crystals, and the particles of the permanent yellow pigment crystals can be in a stably dispersed state for a long time.

[0025] (3) The present invention provides a water-based paint with high tinting strength, comprising polyvinyl alcohol-coated permanent yellow pigment crystals. Due to the effect of the polyvinyl alcohol coating, after the paint is applied to the substrate to be colored, the polyvinyl alcohol-coated permanent yellow pigment crystals in the paint are more easily distributed at the interface between air and liquid, and will not accumulate at the edge of the liquid, which helps the water-based paint with high tinting strength to form a film, and the permanent yellow pigment is more evenly coated on the substrate to be colored. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0027] Example 1

[0028] This embodiment provides a water-based permanent yellow pigment with high tinting strength, comprising the following steps: S1, preparing a crude permanent yellow pigment according to a conventional method, adding the crude permanent yellow pigment to a container containing a pigment emulsifier to disperse the crude permanent yellow pigment in the pigment emulsifier sorbitan monooleate, then sealing the container, immersing the sealed container in a liquid nitrogen tank for quick freezing, and obtaining frozen crude permanent yellow pigment after the quick freezing is completed;

[0029] S2. The frozen crude product of permanent yellow pigment is crushed by ultrasonic mill, and the crushed crude product of permanent yellow pigment is ball-milled to obtain ice crystals of permanent yellow pigment. The ice crystals of permanent yellow pigment are transferred to a freeze-drying chamber, and the temperature of the freeze-drying chamber is maintained at -22°C and the pressure is reduced to 10 - 2 mbar, causing the frozen water to sublime within 12 hours, causing the frozen water to sublime to obtain permanent yellow pigment crystals;

[0030] S3. Cellulose nanocrystals (CNCs) as a dispersant and stabilizer are moistened with ethanol to obtain a cellulose nanocrystal (CNCs) colloid. Permanent yellow pigment crystals are added to the cellulose nanocrystal (CNCs) colloid to obtain a permanent yellow pigment with high tinting strength in a water-based system.

[0031] Example 2

[0032] This embodiment provides a water-based permanent yellow pigment with high tinting strength, comprising the following steps:

[0033] S1. A crude permanent yellow pigment is prepared according to a conventional method, and the crude permanent yellow pigment is added to a container containing a pigment emulsifier, castor oil polyoxyethylene ether, so that the crude permanent yellow pigment is dispersed in the pigment emulsifier. The container is then sealed and immersed in a liquid nitrogen tank for quick freezing. After the quick freezing is completed, a frozen crude permanent yellow pigment is obtained.

[0034] S2. The frozen crude product of permanent yellow pigment is crushed by ultrasonic mill, and the crushed crude product of permanent yellow pigment is ball-milled to obtain ice crystals of permanent yellow pigment. The ice crystals of permanent yellow pigment are transferred to a freeze-drying chamber, and the temperature of the freeze-drying chamber is maintained at -22°C and the pressure is reduced to 10 - 2 mbar, causing the frozen water to sublime within 12 hours, causing the frozen water to sublime to obtain permanent yellow pigment crystals;

[0035] S3. Cellulose nanocrystals (CNCs) as a dispersant and stabilizer are moistened with ethanol to obtain a cellulose nanocrystal (CNCs) colloid. Permanent yellow pigment crystals are added to the cellulose nanocrystal (CNCs) colloid to obtain a permanent yellow pigment with high tinting strength in a water-based system.

[0036] Example 3

[0037] This embodiment provides a water-based permanent yellow pigment with high tinting strength, comprising the following steps:

[0038] S1. A crude permanent yellow pigment is prepared according to a conventional method, and the crude permanent yellow pigment is added to a container containing a pigment emulsifier to disperse the crude permanent yellow pigment in the pigment emulsifier. The container is then sealed and immersed in a liquid nitrogen tank for quick freezing. After the quick freezing is completed, a frozen crude permanent yellow pigment is obtained.

[0039] S2. The frozen crude product of permanent yellow pigment is crushed by ultrasonic mill, and the crushed crude product of permanent yellow pigment is ball-milled to obtain ice crystals of permanent yellow pigment. The ice crystals of permanent yellow pigment are transferred to a freeze-drying chamber, and the temperature of the freeze-drying chamber is maintained at -22°C and the pressure is reduced to 10 - 2 mbar, causing the frozen water to sublime within 12 hours, causing the frozen water to sublime to obtain permanent yellow pigment crystals;

[0040] S3. Cellulose nanocrystals (CNCs) as a dispersant and stabilizer are moistened with ethanol to obtain a cellulose nanocrystal (CNCs) colloid. Permanent yellow pigment crystals are added to the cellulose nanocrystal (CNCs) colloid to obtain a permanent yellow pigment with high tinting strength in a water-based system.

[0041] Example 4

[0042] This embodiment provides a water-based coating with high tinting strength, comprising the permanent yellow pigment crystals prepared in Example 1 and a water-soluble resin, wherein the water-soluble resin is a polyester resin. The permanent yellow pigment crystals are polyvinyl alcohol-coated permanent yellow pigment crystals. The polyvinyl alcohol-coated permanent yellow pigment crystals are prepared by dispersing polyvinyl alcohol and permanent yellow pigment crystals in a water / ethanol mixture with a weight ratio of 2:7, followed by repeated centrifugation and resuspension to obtain the polyvinyl alcohol-coated permanent yellow pigment crystals.

[0043] Example 5

[0044] This embodiment provides a water-based coating with high tinting strength, comprising the permanent yellow pigment crystals prepared in Example 1, a water-soluble resin, and an epoxy resin. The permanent yellow pigment crystals are polyvinyl alcohol-coated permanent yellow pigment crystals. The polyvinyl alcohol-coated permanent yellow pigment crystals are prepared by dispersing polyvinyl alcohol and permanent yellow pigment crystals in a water / ethanol mixture with a weight ratio of 2:7, followed by repeated centrifugation and resuspension to obtain the polyvinyl alcohol-coated permanent yellow pigment crystals.

[0045] Example 6

[0046] This embodiment provides a water-based coating with high tinting strength, comprising the permanent yellow pigment crystals prepared in Example 1, a water-soluble resin, and a urethane resin. The permanent yellow pigment crystals are polyvinyl alcohol-coated permanent yellow pigment crystals. The polyvinyl alcohol-coated permanent yellow pigment crystals are prepared by dispersing polyvinyl alcohol and permanent yellow pigment crystals in a water / ethanol mixture with a weight ratio of 2:7, followed by repeated centrifugation and resuspension to obtain the polyvinyl alcohol-coated permanent yellow pigment crystals.

[0047] Comparative Example

[0048] This comparative example provides a permanent yellow pigment, comprising the following steps: S1, preparing a crude permanent yellow pigment according to a conventional method, directly drying the crude permanent yellow pigment, and crushing the crude permanent yellow pigment after drying to obtain a dried crude permanent yellow pigment;

[0049] S3. Cellulose nanocrystals (CNCs) used as a dispersant and stabilizer are moistened with ethanol to obtain a cellulose nanocrystal (CNCs) colloid. The dried crude permanent yellow pigment is added to the cellulose nanocrystal (CNCs) colloid to obtain a permanent yellow pigment provided in the comparative example.

[0050] Experimental example

[0051] According to the definition in GB / T 13451.2-1992 Relative tinting strength of coloring pigments (photometric method), tinting strength refers to the ability of a pigment to absorb incident light, thus having the ability to, for example, tint white paint or darken salt to which it is added.

[0052] The Lab values ​​measured by a colorimeter represent the three dimensions of color measurement. We know that color is determined by three factors, and determining color difference can also be divided into three factors. These are the L value, which indicates the lightness and darkness of a product's color, commonly referred to as black and white; the a value, which represents the red and green values, expressed by positive and negative red and green; and the b value, which represents the yellow and blue values, expressed by positive and negative yellow and blue.

[0053] The color difference value is expressed as ΔE*, which is the comprehensive total color difference and takes the absolute value of 1 as a unit, called the "NBS" color difference unit.

[0054] A permanent yellow pigment provided in the comparative example was used as a standard product, and the water-based high-tinting-strength permanent yellow pigments prepared in Examples 1 to 3 were respectively used as test samples. The X-Rite 8400 colorimeter first detected the absolute values ​​of L*, a*, and b* of the standard product, and then measured the color difference between the water-based high-tinting-strength permanent yellow pigments prepared in Examples 1 to 3 and the standard sample. The color strength measurement results are shown in Table 1 below.

[0055] Table 1 Color difference measurement results of the tinting strength of a water-based permanent yellow pigment with high tinting strength provided in Examples 1 to 3 relative to the comparative example

[0056] Group Example 1 Example 2 Example 3 △L* -6.2 -5.9 -4.9 △b* 3.6 3.8 4.5 △E* 5.2 6.0 4.2

[0057] As shown in Table 1, compared with the comparative example, the color of the water-based permanent yellow pigment with high tinting strength provided by Examples 1 to 3 is darker, relatively yellow, and the comprehensive total color difference is within the range of 3 to 6 "NBS" color difference units. The degree of color difference perception is very obvious, indicating that the water-based permanent yellow pigment with high tinting strength provided by the present invention has good tinting strength.

[0058] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a water-based permanent yellow pigment, characterized in that: The following steps are involved: S1. A crude permanent yellow pigment is prepared according to a conventional method, and the crude permanent yellow pigment is added to a container containing a pigment emulsifier to disperse the crude permanent yellow pigment in the pigment emulsifier. The container is then sealed and immersed in a liquid nitrogen tank for quick freezing. After the quick freezing is completed, a frozen crude permanent yellow pigment is obtained. S2. crushing the frozen crude permanent yellow pigment product with an ultrasonic crusher, ball-milling the crushed crude permanent yellow pigment product to obtain permanent yellow pigment ice crystals, transferring the permanent yellow pigment ice crystals to a freeze-drying chamber to sublime the frozen water to obtain permanent yellow pigment crystals; S3. Wetting the cellulose nanocrystals used as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal colloid, and adding the permanent yellow pigment crystals to the cellulose nanocrystal colloid to obtain the permanent yellow pigment of the aqueous system.

2. The method for preparing a water-based permanent yellow pigment according to claim 1, wherein: The permanent yellow pigment ice crystals were transferred to a freeze drying chamber, the temperature of which was maintained at -22°C and the pressure was reduced to 10 - 2 mbar, and the frozen water was sublimed within 12 hours to obtain the permanent yellow pigment crystals.

3. The method for preparing a water-based permanent yellow pigment according to claim 1, wherein: The pigment emulsifier is one or both of sorbitan monooleate and castor oil polyoxyethylene ether.

4. The water-based permanent yellow pigment obtained by the preparation method of the water-based permanent yellow pigment according to any one of claims 1 to 3.

5. A water-based coating, characterized in that: The invention comprises the permanent yellow pigment as claimed in claim 4 and a water-soluble resin.

6. A water-based coating according to claim 5, characterized in that: The water-soluble resin is one of polyester resin, epoxy resin and urethane resin.

7. A water-based coating according to claim 5, characterized in that: The permanent yellow pigment is a polyvinyl alcohol-coated permanent yellow pigment. The preparation method of the polyvinyl alcohol-coated permanent yellow pigment is as follows: the polyvinyl alcohol and the permanent yellow pigment are dispersed in a water / ethanol mixture, and then the mixture is repeatedly centrifuged and resuspended to obtain the polyvinyl alcohol-coated permanent yellow pigment.

8. A water-based coating according to claim 7, characterized in that: In the water / ethanol mixture, the weight ratio of water to ethanol is 2:7.