Aqueous green paste and method for its preparation

Abstract

The application discloses a kind of aqueous green paste and preparation method thereof, including the following weight parts of components: 8-10 parts of phthalocyanine blue pigment, 30-35 parts of yellow pigment, 5-10 parts of aqueous acrylic dispersion, 3-5 parts of dispersing agent, 1-3 parts of wetting agent, 35-51 parts of deionized water, 0.1-3 parts of polyurea thickening agent, 0.1-1 part of defoaming agent, 0.1-1 part of organic amine, 0.1-1 part of bactericide;The phthalocyanine blue pigment and the yellow pigment are subjected to plasma treatment.The aqueous green paste prepared by the application has bright color, strong tinting strength and excellent water resistance.

Description

Technical Field

[0001] This invention relates to water-based pigments and their preparation methods. Background Technology

[0002] Phthalocyanine green pigments are characterized by their vibrant color, high transparency and tinting strength, excellent weather resistance and gloss retention, making them widely used in the coloring of coatings, inks, and plastics. The two most common and widely used phthalocyanine green pigments are Pigment Green 7 and Pigment Green 36. The structural formulas of these two pigments are C7 and C8, respectively. 32 Cl 16 CuN8 and C 32 Br 12 Cl4CuN8. The molecular formulas show that both pigments contain halogens (50% and 66% respectively), and in relatively high amounts. In the field of consumer electronics coatings, most end-brand companies require that the chlorine or bromine content in the dry film not exceed 900 ppm, and the sum of chlorine and bromine content not exceed 1500 ppm. Clearly, Pigment Green 7 and Pigment Green 36 are difficult to use in this field.

[0003] Water-based color pastes are slurries made by dispersing and grinding pigments, dispersants, resins, and water, and are widely used in coatings, inks, and other fields. Currently, water-based color pastes have already achieved large-scale application in coatings and inks. There are color pastes that use resin as a carrier for grinding, and there are also resin-free color pastes that do not use resin. For color pastes using resin, the compatibility and chemical structure of the carrier resin to a certain extent determine the application range and physicochemical properties of the color paste. Resin-free color pastes do not use carrier resin, but instead use dispersants to disperse and stabilize pigments. Because there is no carrier resin, their application range is very wide and they are highly versatile. However, because the dispersant structure contains hydrophilic groups, their extensive use in color pastes can, to some extent, reduce the moisture and heat resistance of the coating film.

[0004] Chinese patent CN101760086A discloses a water-based color paste that uses a large amount of dispersant. The high amount of dispersant not only increases cost but also reduces the water resistance of the coating film. The patent covers various types of dispersants, such as alkyl sulfonates, alkyl sulfates, alkyl phosphates, and alkylbenzene sulfonates, which significantly affect water resistance. In the field of consumer electronics coatings, where high water resistance is required, these dispersants are difficult to use.

[0005] Chinese patent CN100445338C discloses a water-based green paste that uses phthalocyanine green pigment. Because phthalocyanine green pigment contains halogens in its structure, it is difficult to meet halogen control requirements in coatings for consumer electronics, and therefore its use is essentially prohibited.

[0006] Chinese patent CN101074329A discloses a method for surface modification of pigments and preparation of easily dispersible pigments. The steps include: (1) placing the pigment powder into a plasma vacuum chamber, evacuating it, and then introducing gas, repeating the evacuation and gas introduction until the required reaction pressure is reached; (2) subjecting the pigment to low-temperature plasma glow discharge or corona discharge treatment; (3) dispersing the treated pigment in a polar resin or solvent; (4) or further adding a small amount of ammonia or organic amine as a dispersion stabilizing agent to the pigment paste. This invention only discloses the ion vacuum treatment of the pigment powder, which makes the treated pigment have good dispersibility in a polar resin or solvent. The pigment obtained by this patent has poor particle size, transparency, tinting strength, and stability. The pigment content is low, and the viscosity and fluidity are likely to be poor, making it unsuitable for long-term storage. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an aqueous green paste and its preparation method, which addresses the shortcomings of the existing technology. The aqueous green paste has high gloss, good storage stability, and good flowability.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A water-based green pulp comprises the following components in parts by weight:

[0010] 8-10 parts phthalocyanine blue pigment, 30-35 parts yellow pigment, 5-10 parts water-based acrylic dispersion, 3-5 parts dispersant, 1-3 parts wetting agent, 35-51 parts deionized water, 0.1-3 parts polyurea thickener, 0.1-1 parts defoamer, 0.1-1 parts organic amine, 0.1-1 parts bactericide;

[0011] The phthalocyanine blue pigment and the yellow pigment are subjected to plasma treatment.

[0012] The phthalocyanine blue pigment and the yellow pigment described in this invention undergo plasma treatment, which allows them to interact with the water-based acrylic dispersion and polyurea thickener, resulting in a water-based green paste with high gloss, good storage stability, and good flowability, effectively replacing PG36 color paste.

[0013] In a preferred embodiment of the present invention, the polyurea thickener comprises a modified urea solution and an amide ether solvent in a mass ratio of 40-50:50-60.

[0014] This patent does not use polyurea polymer alone. The thickener used is a mixture of polyurea compound and amide ether. It is mainly because it is in liquid state, which makes it easy to add and use. The amount of polyurea thickener added in this invention is lower than the conventional dosage, and the overall thickening performance is good.

[0015] In a preferred embodiment of the present invention, the plasma treatment time is 40-80 min.

[0016] Plasma treatment for 40-80 minutes produces the highest gloss value in the resulting color paste.

[0017] In a preferred embodiment of the present invention, the sum of the mass percentages of the phthalocyanine blue pigment and the yellow pigment is 35-45%.

[0018] If the ratio is higher than this, the viscosity of the color paste will be relatively high, which is not conducive to its use, and its stability, transparency, coloring power and other properties will all decrease.

[0019] In a preferred embodiment of the present invention, the mass ratio of the phthalocyanine blue pigment to the yellow pigment is 1:3-5.

[0020] The weight ratio of phthalocyanine blue pigment and yellow pigment is strictly limited. If this range is exceeded, the color difference of the green paste will be significantly different from that of phthalocyanine green paste (a color paste made from a single pigment), meaning it cannot be effectively substituted.

[0021] In a preferred embodiment of the present invention, the water-based green paste can replace the phthalocyanine green paste;

[0022] The phthalocyanine green paste uses phthalocyanine green powder PG36 as the pigment.

[0023] The phthalocyanine green paste comprises the following components in parts by weight:

[0024] 34-36 parts phthalocyanine green powder, 5-10 parts water-based acrylic dispersion, 3-5 parts dispersant, 1-3 parts wetting agent, 35-50 parts deionized water, 0.1-3 parts polyurea thickener, 0.1-1 parts defoamer, 0.1-1 parts organic amine, and 0.1-1 parts bactericide.

[0025] In a preferred embodiment of the present invention, the dispersant is a weakly anionic polymeric high-efficiency wetting and dispersing agent;

[0026] The wetting agent is a nonionic wetting agent;

[0027] The bactericide is 2-methyl-4-isothiazolin-3-one and 2-methyl-1,2-benzisothiazolin-3-one in a mass ratio of 1:1.

[0028] This invention also discloses a method for preparing an aqueous green slurry, comprising the following steps:

[0029] S1. Plasma treatment is performed on the pigment surface for 40-80 minutes.

[0030] S2. Pretreatment of pigment paste: Deionized water, organic amine and water-based acrylic dispersion are added in sequence and stirred to disperse; then dispersant, wetting agent and defoamer are added and stirred to disperse; while stirring, the plasma-treated pigment is added. After the plasma-treated pigment is completely added, it is stirred to disperse evenly.

[0031] S3. Grinding and stabilization of the color paste: The paste obtained in S2 is ground, and then polyurea thickener and bactericide are added and dispersed evenly to obtain the final product.

[0032] The reason for adding bactericides and thickeners after the color paste has been ground is that precise weighing of the materials allows for more accurate control of the amount of additives added, thus better controlling the product's quality stability. Thickeners themselves do not dissolve well in aqueous systems; adding them directly to the color paste will cause agglomeration or difficulty in dispersion, resulting in particulate matter.

[0033] In a preferred embodiment of the present invention, the working voltage of the plasma treatment in S1 is 220 volts, the discharge gas is oxygen, the radio frequency power is 100-300W, and the radio frequency is 30-50KHz.

[0034] In a preferred embodiment of the present invention, the deionized water, organic amine and acrylic resin in S2 are dispersed and stirred for 10-20 minutes;

[0035] After adding the dispersant, wetting agent, and defoamer to S2, the dispersion and stirring time is 10-20 minutes.

[0036] The dispersion and stirring time after adding pigment to S2 is 30-40 minutes;

[0037] The grinding media in S3 are 0.5-0.7mm zirconia beads, and the grinding linear speed is 10-15m / s.

[0038] If the mixing time is less than this, the material may not be sufficiently and evenly dispersed, making it difficult to achieve the final performance indicators such as particle size, transparency, color strength, and stability. If the mixing time is more than this, there will be no additional benefit, but the production time will be extended, and energy consumption and labor costs will increase accordingly.

[0039] The production efficiency and capacity are highest under these grinding parameters, and the particle size, transparency, and tinting strength of the pigment are all good.

[0040] The key technical points of this invention include the following:

[0041] 1. The natural color paste uses a water-based acrylic dispersion with good water resistance and compatibility as a carrier.

[0042] The molecular structure contains a certain amount of hydroxyl and carboxyl groups, which have a wetting effect on pigments. Compared with dispersants, waterborne acrylic dispersions are less expensive and have better water resistance. This resin has good compatibility with existing two-component polyurethane coating systems and waterborne UV paints.

[0043] This resin itself has good water resistance and is less expensive than dispersants. Furthermore, it is compatible with most current product systems, and color pastes obtained by grinding with this resin exhibit better performance and color representation.

[0044] Using this resin as a carrier to grind color pastes can reduce the amount of dispersant and wetting agent used, thereby reducing costs and improving water resistance (dispersant and wetting agent are a double-edged sword; excessive use will reduce the water resistance of the coating).

[0045] 2. Choose a thickener

[0046] Alkali-swellable thickeners can reduce the water resistance and gloss of the coating film to some extent. Associative thickeners are more expensive and have a high selectivity to the coating system, meaning their thickening effect varies in different coating systems. Fumed silica thickeners reduce the gloss of the coating film, and during storage, if the surface of the pigment paste dries, fumed silica can easily precipitate from the pigment paste, causing a "slagging" problem. Polyurea thickeners do not affect the gloss of the coating film and have minimal impact on water resistance. An addition of around 1% can provide a good anti-settling effect, making them an ideal choice.

[0047] The detailed model number of the polyurea thickener is BYK-7420ES. Its core component is a modified urea solution, and the solvent is an amide ether, which is permitted for use in coatings for consumer electronics. The polyurea thickener described in CN114940846B (Saint-Gobain) patent contains N-methylpyrrolidone, a solvent strictly prohibited in the 3C coatings industry because it is listed in the industry's list of prohibited hazardous substances. Polyurea additives create a three-dimensional network structure, surrounding pigment particles, thus preventing or weakening the tendency for downward sedimentation and aggregation, thereby enhancing stability.

[0048] 3. Mix organic yellow and phthalocyanine blue powder to create green.

[0049] Phthalocyanine Blue (Pigment Blue 15:3), with the molecular formula C32H16CuN8, is halogen-free. Organic Yellow PY155, with the molecular formula C34H32N6O12, is also halogen-free. Both of these organic pigments have vibrant colors, excellent tinting strength, and good weather resistance. They are very suitable choices for coatings used in 3C electronic consumer products. The mass ratio of Pigment Blue (PB15:3) to Pigment Yellow (PY155) is 1:4, and its color is very close to that of Pigment Green 36.

[0050] 3C consumer electronics products are classified as products that come into direct contact with the human body or are wearable devices. Therefore, halogens are generally not permitted in the coatings on their surfaces. Many halogen compounds are harmful to human health, so the industry and product manufacturers strictly control the halogen content on product surfaces. If the halogen content in a coating or dry film exceeds the standard's specified range (the permitted level is very low), the coating cannot be used, and consumer electronics products coated with such coatings will face a sales ban in most countries. Whether a coating contains halogens does not affect specific physicochemical properties, but it is a rigid indicator of equal importance to performance.

[0051] 4. Use low-temperature plasma oxidation to treat pigments.

[0052] Low-temperature plasma is a plasma state where the overall temperature of the discharged ions is equal to or slightly higher than room temperature. This process generates active particles such as electrons, ions, and free radicals, possessing extremely strong molecular activation capabilities. Low-temperature plasma oxidation involves treating the powder surface with a plasma processor, introducing active functional groups and altering its surface properties. Powders treated with plasma oxidation exhibit significantly improved surface activity and dispersibility. This method is a physical process, characterized by its simplicity, lack of damage to the internal structure of the material, and strong continuity. Compared to chemical methods, it does not introduce new chemical components and does not contaminate the powder.

[0053] Plasma oxidation occurs on the surface of pigments and has no impact on their inherent properties, such as hue, particle size, and transparency. Pigments treated with this surfactant exhibit significantly improved hydrophilicity and stability in aqueous phases. This effectively enhances pigment dispersibility and stability, reduces the need for dispersants, improves water resistance, and lowers formulation costs.

[0054] Compared to chemical surface treatment techniques, this method is a physical method that does not introduce or leave chemical substances. This is particularly beneficial in areas where the control of hazardous substances is very strict, such as surface coating of 3C consumer electronics, cosmetic packaging containers, food packaging containers, and children's toys.

[0055] This technology is characterized by its simple process, high efficiency and speed, energy saving and environmental protection, and is a powder surface treatment technology with great potential.

[0056] Stability refers to the ability of pigment particles to maintain a stable distribution and resist re-aggregation. The purpose of grinding and dispersing is to deaggregate the pigment particles, but particles naturally tend to cluster together.

[0057] 5. The dispersant has good water resistance and requires a low dosage.

[0058] The preferred aqueous dispersant, TEGO 755W, is a weakly anionic polymeric high-efficiency wetting and dispersing agent that exhibits excellent stability and viscosity-reducing effects on organic pigments. This dispersant possesses a comb-like structure, allowing the pigment anchoring groups in its molecular chain to adhere tightly to the pigment particle surface. It has fewer hydrophilic segments compared to general dispersants, resulting in minimal impact on the water resistance of the final coating film, and it is solvent-free.

[0059] The dispersants and thickeners used in this patent both contain hydrogen bonds. These hydrogen bonds can associate with each other, resulting in improved stability of the entire color paste system and a reduction in the amount of thickener required. This effect is not observed in every combination of dispersants and thickeners; it was discovered through experimentation. Some dispersants and thickeners, for example, do not interact with each other.

[0060] 6. Preferred wetting agent

[0061] The preferred nonionic wetting agent, Surfynol 104E, has wetting, defoaming, and dispersibility-improving effects. Due to its special chemical structure and HLB value of around 3.0, it exhibits lower water sensitivity and better water resistance compared to traditional surfactants, and will not migrate to the coating surface to reduce coating performance.

[0062] The Chinese patent with publication number CN101074329A also has the following defects:

[0063] 1. This product, lacking pre-processing and grinding, is not a true color paste. The product in this patent is not pre-processed or ground; it simply disperses the treated pigment in resin or solvent. Such a product has poor particle size, transparency, tinting strength, and stability. Because it is not ground using a nano-grinding machine, the particle size, pigment transparency, tinting strength, and stability of this product are inferior to the color paste described in our patent. Our color paste is ground using a nano-grinding machine.

[0064] 2. No dispersant or wetting agent used. Products obtained using the method described in CN101074329A often have low pigment content and poor viscosity and flowability. Currently, most industrial color pastes use CPT technology dispersants or superdispersants to help disperse and stabilize pigments. Color pastes produced in this way have high pigment content, good flowability, and low viscosity, making them easy to use. Our color paste uses suitable dispersants and wetting agents, which improve pigment wetting and dispersion, and reduce viscosity. The resulting color paste has high pigment content and low viscosity, resulting in lower actual production costs.

[0065] 3. The pigments were not screened. Most organic green pigments are phthalocyanines and contain halogens. This patent only covers the broad category of pigments, describing the portion potentially related to green pigments as "phthalocyanine pigments containing or not containing metals." This patent screened out two specific pigments, both halogen-free, which, when mixed in a certain proportion, can replace pigment green 36.

[0066] 4. No thickener used. Ammonia or organic amines are widely used in modern water-based industrial pigments, helping to stabilize and wet pigments. However, ammonia or organic amines are volatile, and their effectiveness diminishes or disappears after prolonged storage. Furthermore, these substances are irritating and not very human-friendly. Our product uses a polyurea-type thickener, whose core component is a polymer. It is non-volatile, has a long-lasting effect, and effectively avoids the above problems.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] The water-based green paste prepared by this invention has a bright color, strong tinting strength, is halogen-free, and exhibits excellent water resistance. When used in coatings for 3C consumer electronics, this invention effectively meets the requirements of being halogen-free and water-resistant, and can replace PG36 pigment. Detailed Implementation

[0069] The pigments are commercially available organic pigments manufactured by Clariant. The dispersant is a weakly anionic polymeric dispersant, the wetting agent is a nonionic surfactant, the defoamer is a silicone-free polymeric defoamer, the thickener is a polyurea compound, and the bactericide is MBIT (a mixture of 2-methyl-4-isothiazolin-3-one and 2-methyl-1,2-benzisothiazolin-3-one). The organic yellow powder (PY151) is Clariant HN4G, the dispersant is Evonik Degussa TEGO 755W, the wetting agent is Gas Chemical Surfynol 104E, the defoamer is BYK-011, the thickener is BYK-7420ES, and the bactericide is Dow Chemical BIOBAN551s. The organic amine is designated AMP-95 and manufactured by Angus Chemicals. The associative thickener is designated Rheolate 299 and manufactured by Hemings Deqian Chemical. The alkali-swellable thickener is designated Rheovis AS1130 and manufactured by BASF Chemical.

[0070] Comparison Option 1

[0071] The formulations of the pigment pastes in Comparative Examples 1-2 and Example 1 are shown in Table 1. Pigment surface treatment: The plasma treatment machine operates at 220 volts, uses oxygen as the discharge gas, and the treatment time is 60 minutes. The pigment is placed in a stainless steel tray with a mesh screen, and then the stainless steel tray is placed in the vacuum chamber. The device is started to exhaust air, and exhaust is stopped when the vacuum level reaches approximately 10 Pa. Oxygen is introduced into the vacuum chamber. The radio frequency power is selected as 200 W, and the radio frequency is 40 kHz. The machine is started to perform plasma oxidation treatment on the pigment. After the working time is completed, the voltage is cut off, and the pigment is removed for later use.

[0072] Table 1. Formulations of color pastes in Comparative Examples 1-2 and Example 1.

[0073] Comparative Example 1 Comparative Example 2 Example 1 Organic yellow powder (PY151) 20 20 20 acrylic dispersion 20 20 20 wetting agent 3 3 3 Deionized water 56.5 56.5 56.5 Defoamer 0.2 0.2 0.2 Organic amines 0.3 0.3 0.3 Untreated pigment Pigment treatment for 30 minutes Pigment treatment for 1 hour total 100 100 100

[0074] Acrylic resins can be further divided into primary dispersions (emulsions) and secondary dispersions. When discussing dispersions alone, we are referring to secondary dispersions. Secondary dispersions offer better chemical and water resistance. This section refers to an aqueous acrylic dispersion (secondary dispersion). A primary dispersion, commonly known as an emulsion, is a water-soluble resin prepared by adding an emulsifier. It is obtained by emulsifying the resin in an aqueous phase with the emulsifier and then undergoing polymerization. The particle size of an emulsion is typically between 100-200 nm. Because emulsions are obtained through heterogeneous polymerization, their molecular weight distribution is wider, and their water and chemical resistance is inferior to that of dispersions. Emulsion resins tend to be oily and require surfactants (emulsifiers) to encapsulate them for stable dispersion in water. Therefore, high operating temperatures (e.g., exceeding 40°C), high shear (e.g., grinding), and adsorption by additives can all lead to demulsification and flocculation of aqueous emulsion resins. Once demulsification and flocculation occur, the aqueous system suffers irreversible damage and must be discarded. Therefore, in industrial production, high-end paints generally use dispersions instead of emulsions.

[0075] Secondary dispersions are typically synthesized via free radical solution polymerization and then dispersed in water. The acrylic monomers used in the synthesis of these dispersions are generally not emulsified; they are polymerized and then dispersed at high speed in an aqueous phase. Dispersions utilize homogeneous polymerization, resulting in a narrower molecular weight distribution and significantly improved water and chemical resistance compared to emulsions. Because their molecular chains contain relatively few hydrophilic groups, external forced dispersion methods, such as high-speed stirring or ultrasound, are required to achieve water dispersibility. This reduced number of hydrophilic groups also contributes to improved water resistance. During use, dispersions can withstand grinding or high shear without demulsification.

[0076] 1. According to the quantity of materials in the formula, add deionized water, acrylic dispersion, wetting agent, organic amine and defoamer in sequence to the jacketed cylinder with cooling water. Disperse with a disperser for 10-15 minutes at a speed of 800-1000 rpm.

[0077] 2. While dispersing, add the organic yellow powder. After all the powder has been added, disperse using a disperser for 3 hours, taking a sample every hour. During dispersion, ensure the material temperature is below 40°C. The organic yellow powder in Comparative Example 1 was untreated, while the powders in Comparative Example 2 and Example 1 underwent plasma treatment for 30 minutes and 1 hour, respectively.

[0078] 3. Using the nine process samples, apply a water-based single-component varnish to the samples using a squeegee (1:12 ratio). The squeegee substrate is a transparent polyester sheet, and the mixer operating parameters are 2200 rpm for 5 minutes. The samples are coated using a BYK-2131 automatic coating machine with a film thickness of 150 micrometers. After preparation, the samples are baked in an 80℃ oven for 10-15 minutes.

[0079] 4. Perform a gloss test on the sample, selecting a test angle of 60 degrees, conforming to the national standard GB / T 9754-2007. The specific test method is as follows: Start the gloss meter, clean the surface of the standard sample, and press the automatic calibration button to calibrate the gloss meter. Then, place the sample on a flat surface and position the test window of the gloss meter in the center of the sample, ensuring a tight fit between the test window and the sample. Press the test button to obtain the gloss value. The gloss meter itself has three test angles: 20°, 60°, and 85°. When recording data, select the test data at 60°.

[0080] The gloss data is as follows:

[0081] Table 2. Gloss values ​​of the pigments in Comparative Examples 1-2 and Example 1

[0082]

[0083] As shown in the table, the dispersibility of pigments in the base material (or resin) is greatly enhanced after plasma treatment, resulting in a significant improvement in the gloss of the scraper. Among them, the treatment method with a treatment time of 1 hour has the highest gloss value.

[0084] Comparison Option 2

[0085] Table 3 shows the formulations of the color pastes in Comparative Examples 3-5 and Example 2.

[0086]

[0087] Manufacturing process of Example 2 / Comparative Example 3 / Comparative Example 4 / Comparative Example 5:

[0088] Pigment Surface Treatment: The plasma treatment machine operates at 220 volts, uses oxygen as the discharge gas, and lasts for 60 minutes. The pigment is placed in a stainless steel tray with a mesh screen, and then the tray is placed in the vacuum chamber. The device is started to purge the air, stopping when the vacuum reaches approximately 10 Pa. Oxygen is then introduced into the vacuum chamber. The radio frequency power is selected as 200W, and the radio frequency is 40 kHz. The machine is started to perform plasma oxidation treatment on the pigment. After the working time is completed, the voltage is cut off, and the pigment is removed for later use.

[0089] Preparing the colorant:

[0090] Add deionized water, organic amine, and acrylic resin sequentially, and stir at low speed using a disperser for 10-20 minutes. Then add the dispersant, wetting agent, and defoamer, and stir for another 10-20 minutes. While stirring, add the pigment. After the pigment is completely added, disperse for 30-40 minutes until the slurry is fully and evenly dispersed. Below these parameters, the material may not be sufficiently and evenly dispersed, making it difficult to achieve the final performance indicators such as particle size, transparency, tinting strength, and stability. Above these parameters, no additional benefit will be provided, but production time will be extended, and energy and labor costs will increase accordingly.

[0091] Grinding and stabilization of pigments:

[0092] The color paste slurry was ground using a sand mill. Samples were taken every half hour for fineness, particle size, and scraper color testing. Grinding was stopped once the particle size and scraper color difference stabilized. The ground slurry was then removed, and polyurea thickener and bactericide were added in proportion. The polyurea thickener needed to be added while stirring. The additives were then evenly dispersed using a disperser to obtain the final product. The grinding media were 0.6mm zirconia beads, and the grinding linear speed was 12m / s.

[0093] The sampling time of "half an hour" is based on production experience and facilitates monitoring and adjustment during production. Too short a time, with a high testing frequency, would increase workload. Too long a time could lead to over-grinding, reducing the quality of the color paste and even rendering it unusable. The reason for adding bactericides and thickeners after the color paste grinding is that precise weighing of the materials allows for more accurate control of the amount of additives added, thus better controlling the product's quality stability. Thickeners themselves have poor solubility in aqueous systems; adding them directly to the color paste will cause agglomeration or difficulty in dispersion, resulting in particulate matter. 0.6mm zirconia beads were selected as the grinding media, and a linear velocity of 12m / s was chosen because this setting maximizes production efficiency and capacity, while also ensuring good particle size, transparency, and tinting strength of the color paste.

[0094] Color comparison and evaluation. It should be noted that the color powder in Example 2 underwent plasma oxidation treatment for 1 hour, while the other methods did not undergo plasma treatment.

[0095] The net weight ratio of water-based single-component varnish to pigment should be kept consistent as follows (for color comparison, different schemes should be placed under the same pigment-to-binder ratio). The colorant and water-based single-component varnish are placed in a 100mL mixing bottle and dispersed using a mixer at 2200rpm for 5 minutes. The material is then removed and evenly coated onto a transparent polyester sheet using a coater, and then baked in an 80℃ oven for 15 minutes. The color difference is then measured using a colorimeter after the sample is removed.

[0096] Water-based single-component varnish / Example 2 = 17:1

[0097] Water-based single-component varnish / Comparative Example 3 = 17:1

[0098] Water-based single-component varnish / Comparative Example 4 = 17:1.14

[0099] Water-based single-component varnish / Comparative Example 5 = 17:1

[0100] The colorimeter model is Konica Minolta CM-700D. The test conditions are selected as D65 / 10°. The test method is as follows: Turn on the colorimeter and start the instrument. Select the D65 light source and the test angle as 10°. Place the prepared sample on a flat surface, ensuring good contact between the colorimeter and the sample. Press the measurement button, and the colorimeter completes one test. Measure five locations on each sample, then automatically calculate the average value, and finally record the measured color difference value (average).

[0101] The color difference data is as follows:

[0102] Table 4. Color difference data of the pigments in Comparative Examples 3-5 and Example 2.

[0103] Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 L 32.14 37.87 29.85 27.48 a -18.04 -31.57 -18.43 -10.69 b 6.14 8.85 4.08 -2.53

[0104] As can be seen from the table, the color difference values ​​of Example 2 and Comparative Example 4 are very close, especially the a value (representing red and green). Example 2 can replace PG36 pigment for color matching. However, the color difference between Example 2 and Comparative Example 5 is large, making it difficult to effectively replace PG36 pigment.

[0105] The color difference values ​​of Comparative Example 3 are significantly different from those of Comparative Examples 4 and 5, making them difficult to effectively replace.

[0106] Comparison Option 3

[0107] Table 5 shows the formulations of the color pastes in Comparative Examples 6-7 and Example 2.

[0108] Example 2 Comparative Example 6 Comparative Example 7 Phthalocyanine Blue (PB15:3) 8 8 8 Organic Yellow (PY155) 32 32 32 Aqueous acrylic dispersion 10 / / dispersant 5 5 20 wetting agent 3 3 3 Deionized water 40.4 50.4 35.4 Defoamer 0.3 0.3 0.3 Organic amines 0.2 0.2 0.2 bactericide 0.1 0.1 0.1 Polyurea thickener 1 1 1 total 100 100 100

[0109] Comparative Example 8: Commercially available water-based resin-free green paste with a pigment content of 35% and pigment serial number PG36.

[0110] Comparative Example 6 / Comparative Example 7 process:

[0111] The color powder is treated with plasma oxidation for 1 hour, then fed according to the formula, and ground with a sand mill until the particle size and color are qualified. Then, thickener and bactericide are added, and dispersed evenly with a disperser.

[0112] Substrate: PC

[0113] Primer: Water-based two-component primer clear coat: color paste: hardener: deionized water = 100:30:10:2-3, bake at 80℃ for 20-30 minutes, film thickness is 15-20 micrometers;

[0114] Topcoat: Water-based two-component clear varnish: Hardener: Deionized water = 100:25:2-3, baked at 80℃ for 2 hours, film thickness is 20-25 microns;

[0115] The prepared sample was placed in a 90℃ constant temperature water bath for boiling test for 2 hours. After the test, the sample was removed, its appearance was observed, and the results were evaluated.

[0116] The experimental results are as follows:

[0117] Table 6. Performance of the color pastes in Comparative Examples 6-8 and Example 2.

[0118]

[0119] Comparison Option 4

[0120] Table 7 Formulations of color pastes in Comparative Examples 9-13 and Example 2

[0121]

[0122]

[0123] Comparative Example 9 / Comparative Example 10 / Comparative Example 11 Process:

[0124] The color powder is treated with plasma oxidation for 1 hour, then fed according to the formula and ground with a sand mill until the fineness is qualified. Thickener is then added to the color paste. When adding thickener, first turn on the disperser to stir the color paste, then slowly add the thickener while stirring until the thickener is evenly mixed.

[0125] Comparative Example 12 Process:

[0126] After feeding the materials according to the formula, grind them with a sand mill until the fineness is qualified. Fumed silica can be ground by the machine.

[0127] Water resistance test:

[0128] Substrate: PC

[0129] Primer: Water-based two-component primer clear coat: color paste: hardener: deionized water = 100:30:10:2-3, bake at 80℃ for 20-30 minutes, film thickness is 15-20 micrometers;

[0130] Topcoat: Water-based two-component clear varnish: Hardener: Deionized water = 100:25:2-3, bake at 80℃ for 2 hours, film thickness is 20-25 microns;

[0131] The prepared sample was placed in a 90℃ constant temperature water bath for boiling test for 2 hours. After the test, the sample was removed, its appearance was observed, and the results were evaluated.

[0132] The experimental results are as follows:

[0133] Table 8 Performance of the color pastes in Comparative Examples 9-13 and Example 2

[0134]

[0135] As can be seen from the table above, the solution with added polyurea thickener has better storage stability and better results in the boiling water test.

Claims

1. An aqueous green paste, characterized in that The components include the following weight parts: 8-10 parts of phthalocyanine blue pigment, 30-35 parts of yellow pigment, 5-10 parts of water-based acrylic dispersion, 3-5 parts of dispersant, 1-3 parts of wetting agent, 35-51 parts of deionized water, 0.1-3 parts of polyurea thickener, 0.1-1 part of defoaming agent, 0.1-1 part of organic amine, 0.1-1 part of bactericide; The phthalocyanine blue pigment and the yellow pigment are subjected to plasma treatment; The polyurea thickener includes a modified urea solution and an amide ether solvent in a mass ratio of 40-50:50-60; The wetting agent is a non-ionic wetting agent, and the non-ionic wetting agent is of a type of Surfynol 104E; The dispersant is a weak anionic polymer high-efficiency wetting dispersant, and the dispersant is of a type of TEGO 755W.

2. The water-based green paste according to claim 1, wherein: The plasma treatment time is 40-80 min.

3. The aqueous green paste of claim 1, wherein: The sum of the mass percentages of the phthalocyanine blue pigment and the yellow pigment is 35-45%.

4. The water-based green paste according to claim 1, wherein: The mass ratio of the phthalocyanine blue pigment to the yellow pigment is 1:3-5.

5. The water-based green paste according to claim 1, wherein: The water-based green paste can replace a phthalocyanine green paste; The color powder used in the phthalocyanine green paste is phthalocyanine green powder P.G.36; The phthalocyanine green paste includes the following weight parts: 34-36 parts of phthalocyanine green powder, 5-10 parts of water-based acrylic dispersion, 3-5 parts of dispersant, 1-3 parts of wetting agent, 35-50 parts of deionized water, 0.1-3 parts of polyurea thickener, 0.1-1 part of defoaming agent, 0.1-1 part of organic amine, and 0.1-1 part of bactericide.

6. The water-based green paste according to claim 1, wherein: The bactericide is 2-methyl-4-isothiazolin-3-one and 2-methyl 1,2-benzisothiazolin-3-one in a mass ratio of 1:

1.

7. A process for the preparation of an aqueous green paste as claimed in any one of claims 1 to 6, characterized in that The method includes the following steps: S1, plasma treatment is performed on the surface of the pigment, and the plasma treatment time is 40-80 min; S2, pretreatment of the paste: deionized water, organic amine and water-based acrylic dispersion are sequentially added and stirred and dispersed; then, the dispersant, the wetting agent and the defoaming agent are added and stirred and dispersed; while stirring, the plasma-treated pigment is added, and after the plasma-treated pigment is completely added, stirring and dispersion are performed again to make the pigment uniformly dispersed; S3, grinding and stabilization of the paste: the paste prepared in S2 is ground, and after grinding, the polyurea thickener and the bactericide are added, and after uniform dispersion, the paste is obtained.

8. The method for preparing the water-based green paste according to claim 7, wherein: In S1, the working voltage of the plasma treatment is 220 volts, the discharge gas is oxygen, the radio frequency power is 100-300 W, and the radio frequency frequency is 30-50 KHz.

9. The method for preparing the water-based green paste according to claim 7, wherein: In S2, the stirring and dispersion time of the deionized water, the organic amine and the water-based acrylic dispersion is 10-20 min. The time for stirring and dispersing after adding dispersant, wetting agent and defoaming agent in S2 is 10-20 minutes; The time for stirring and dispersing after adding plasma treated pigment in S2 is 30-40 minutes; The grinding medium in S3 is 0.5-0.7 mm zirconia beads, and the grinding linear speed is 10-15 m / s.

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