High performance waterborne automotive damping coating and preparation method thereof

Abstract

The present application relates to a kind of water-based automobile damping coating and its preparation method, the water-based automobile damping coating includes functional filler phenolamine modified sodium carboxymethyl cellulose.The phenolamine of phenolamine modified sodium carboxymethyl cellulose in the present application forms hydrogen bond with the group in acrylic emulsion, so that the macromolecular segment is more strongly combined with emulsion base, stress is greater, segment winding and powder distribution are more uniform, more integrated, prevent sagging, falling off.The water-based automobile damping coating of the present application has good construction performance, sagging, bulging resistance, good aldehyde removal effect, bacteriostasis and other characteristics.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a high-performance automotive damping coating with good workability, anti-bulging properties, and formaldehyde removal, and its preparation method. Background Technology

[0002] As people's living standards gradually improve, while pursuing speed and convenience in travel, they also have higher and higher requirements for vehicles that are quiet, environmentally friendly, and lightweight.

[0003] Waterborne damping coatings have been increasingly used in the automotive, rail transit, and shipbuilding industries in recent years due to their ease of application, transportation, storage, environmental friendliness, superior performance, low density, and lightweight properties. However, automotive damping coatings require high-temperature baking during application. This baking process can cause moisture evaporation, leading to coating blistering, deformation, and affecting subsequent use. Furthermore, the aqueous phase of waterborne coatings is prone to bacterial growth. These factors hinder the widespread application of waterborne damping coatings. Additionally, consumers' growing concern about formaldehyde levels and increasingly stringent requirements for environmental friendliness and odor control in passenger vehicles present key technical challenges that need to be addressed.

[0004] Currently, formaldehyde removal technology has been applied to interior wall latex paints. However, to improve formaldehyde removal efficiency, dedicated formaldehyde-removing interior wall latex paints significantly increase the amount of emulsion and formaldehyde-removing functional materials added. This increases costs and contradicts the principles and development trends of environmental protection. Commonly used formaldehyde-removing coatings on the market are mainly divided into formaldehyde-adsorbing materials and formaldehyde-decomposing materials. Adsorption materials have the problem of releasing formaldehyde again after adsorption; decomposition materials are generally added as additives to the paint formulation or directly participate in emulsion polymerization as functional monomers. Adding additives increases the raw material and operational costs of the paint, while functional monomers are expensive and have limited addition amounts.

[0005] Patent CN202011279080 discloses a bakeable damping coating that achieves anti-blistering effects by adding auxiliary fillers including water-absorbing resin, starch, and diatomaceous earth. However, uneven distribution of the fillers in this method can easily lead to small bubbles forming in some areas without obvious blistering. Patent CN202011279053 discloses the use of high-boiling-point solvents soluble in water or emulsions to prevent blistering, such as one or more combinations of ethylene glycol, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol, DINP, and DOP. However, the use of solvents in this method results in a strong odor during application and contradicts the trend towards water-based coatings.

[0006] Furthermore, existing technologies have not reported antibacterial damping coatings. The antibacterial and bacteriostatic properties of other antibacterial coatings are provided by adding bactericides during the formulation preparation process or emulsion polymerization process. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a high-performance water-based automotive damping coating that removes formaldehyde, resists blistering, and has an excellent appearance.

[0008] Another object of the present invention is to provide a method for preparing such a high-performance waterborne automotive damping coating.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] A high-performance water-based automotive damping coating comprises the following components in weight percentage:

[0011] Acrylic emulsions, 25-45 wt%, such as 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, etc.;

[0012] Pigments and fillers 20-40wt%, such as 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, etc.;

[0013] Modified sodium carboxymethyl cellulose 2-10 wt%, such as 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.;

[0014] Deionized water 13-25wt%, such as 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, etc.;

[0015] Dispersant 0.5-2.0 wt%, for example 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, etc.;

[0016] Thickener 0.5-2.0 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, etc.;

[0017] Wetting agent 0.2-1.0 wt%, such as 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc.;

[0018] Defoamer 0.3-1.0 wt%, for example 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc.;

[0019] pH adjuster 0.1-1.0 wt%, such as 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc.

[0020] In one specific implementation, the modified sodium carboxymethyl cellulose is phenolamine-modified sodium carboxymethyl cellulose, preferably prepared by dehydration condensation reaction of sodium carboxymethyl cellulose and phenolamine.

[0021] In one specific implementation, the phenolamine is selected from any one of o-aminophenol, p-aminophenol, and m-aminophenol, preferably o-aminophenol.

[0022] In one specific embodiment, the preparation method of the phenolamine-modified sodium carboxymethyl cellulose includes the following steps:

[0023] 1) Dissolve sodium carboxymethyl cellulose in water, add acid to adjust the pH value in the aqueous solution, add dicyclohexylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) to activate the carboxyl group reaction, and then add phenolamine and react at room temperature;

[0024] 2) Precipitation was carried out using frozen ether, followed by separation and drying to obtain phenolamine-modified sodium carboxymethyl cellulose.

[0025] Specifically, for example, the preparation method is as follows:

[0026] (1) Dissolve 40-50wt% sodium carboxymethyl cellulose in water, first add HCl to the solution to adjust the pH to 4.5-6.5, add 1-2wt% dicyclohexylcarbodiimide and 3-5wt% N-hydroxysuccinimide to activate the carboxyl group, react for 30-60 min, then add 50-60wt% phenolamine, and react at room temperature for 2-5 hours;

[0027] (2) Precipitation was carried out using frozen ether, followed by separation and drying to obtain sodium carboxymethyl cellulose modified with phenolamine.

[0028] In this invention, the amount of sodium carboxymethyl cellulose and phenolamine added is 40-50 wt% and 50-60 wt% respectively, based on the sum of their masses. Similarly, the amount of dicyclohexylcarbodiimide and N-hydroxysuccinimide added is 1-2 wt% and 3-5 wt% respectively, based on the sum of their masses. There is no particular limitation on the amount of water used, as long as it is sufficient to fully dissolve the sodium carboxymethyl cellulose, for example, 2-5 times the mass of sodium carboxymethyl cellulose in water.

[0029] The reaction mechanism of this modification process is that EDC and NHS first activate the carboxyl group, which then reacts with the amino group of phenolamine to form an amide, a common carboxyl amidation process; the reaction process is shown in the following equation:

[0030]

[0031] In one specific implementation, the aqueous acrylic emulsion of the present invention is one or more of Wanhua Chemical's Antamp0652, Antamp 0655, Antamp0658, Antamp0656, and Antamp0657, preferably Antamp 0658.

[0032] In one specific implementation, the pigments and fillers of the present invention include, but are not limited to, carbon black, talc, mica powder, calcium carbonate, etc.

[0033] Specifically, the carbon black in the functional pigments and fillers of the present invention includes, but is not limited to, FW-200 from Degussa (China) Ltd. and N300 from Hebei Cangzhou Jintai Carbon Black Co., Ltd., with FW-200 being preferred.

[0034] The calcium carbonate in the pigments and fillers of this invention includes, but is not limited to, one or more of the following: 325-mesh heavy calcium carbonate, 400-mesh heavy calcium carbonate, 700-mesh heavy calcium carbonate, and 800-mesh heavy calcium carbonate from Changzhou Calcium Carbonate Co., Ltd., with 325-mesh heavy calcium carbonate and / or 400-mesh heavy calcium carbonate being preferred.

[0035] The mica powder in the pigments and fillers of the present invention includes, but is not limited to, at least one of the following: 100-mesh mica powder from Chuzhou Sericite Co., Ltd., 200-mesh mica powder from Shijiazhuang Chenxing Industrial Co., Ltd.

[0036] In one specific embodiment, the dispersant of the present invention comprises, but is not limited to, at least one of Orotan 731A from Dow Chemical (China) Co., Ltd., BYK 190 from BYK Chemical, C20 from Wanhua Chemical Group Co., Ltd., and Tego 760w from Digo Chemical, preferably one of Tego 760w and Orotan 731A.

[0037] In one specific implementation, the thickener of the present invention includes, but is not limited to, at least one of Vesmody A801 ​​from Wanhua Chemical Group Co., Ltd., Vesmody A401, and ASE60 from Dow (China) Co., Ltd., preferably any one of Vesmody A801 ​​and ASE60.

[0038] In one specific embodiment, the wetting agent of the present invention includes, but is not limited to, at least one of Tego270, Tego280, Tego KL 245 from Tego (China) Co., Ltd., and Surfynol 104E from Gas Chemical Company of the United States, preferably any one of Tego270 and KL 245.

[0039] In one specific implementation, the defoamer of the present invention comprises, but is not limited to, at least one of Foam StarST2410AC from BASF (China) Co., Ltd., BYK 810 from BYK Chemicals, and Foamex 1488 from DIGIC (China) Co., Ltd., preferably any one of Foam StarST2410AC and BYK 810.

[0040] In one specific implementation, the pH adjuster of the present invention includes, but is not limited to, at least one of AMP-95, ammonia, DMEA, etc., preferably AMP-95.

[0041] In another aspect of the present invention, a high-performance water-based automotive damping coating includes the following preparation steps:

[0042] (1) Mix acrylic emulsion, dispersant, wetting agent, defoamer and pH adjuster, and disperse for 3-5 minutes to obtain aqueous emulsion;

[0043] (2) Mix deionized water, modified sodium carboxymethyl cellulose, pigments and fillers, and disperse for 5-10 minutes to obtain a mixture;

[0044] (3) Mix the mixture from step (2) with the aqueous emulsion from step (1), then add a thickener and disperse. Use a disperser with a speed of 1000-1500 rpm to disperse for 10-15 minutes to obtain the aqueous automotive damping coating.

[0045] Compared with the prior art, the positive effects of the present invention are as follows:

[0046] The water-based automotive damping coating of this invention contains a functional filler, phenolamine-modified sodium carboxymethyl cellulose. In the water-based damping coating prepared by adding this filler, the phenolamine in the phenolamine-modified sodium carboxymethyl cellulose forms hydrogen bonds with groups in the acrylic emulsion, resulting in stronger bonding between the macromolecular chain segments and the emulsion base material, greater stress, and more uniform and integrated chain segment entanglement and powder distribution, preventing sagging and peeling. During baking at 140-160℃, the strong overall stress prevents partial blistering or bulging of the paint film. Furthermore, the good water retention of sodium carboxymethyl cellulose slows down and evenly evaporates water, preventing sudden moisture escape from lifting the surface coating and causing blistering or bulging. Simultaneously, the presence of phenol groups in the modified sodium carboxymethyl cellulose can react with free formaldehyde in the vehicle to remove formaldehyde. During storage, the modified sodium carboxymethyl cellulose protonates, generating a positive charge that interacts with bacterial surfaces, inhibiting bacterial growth and playing a bacteriostatic role, thus extending the shelf life of the coating.

[0047] The water-based automotive damping coating of this invention has good workability, anti-sagging and anti-bubbling properties, good formaldehyde removal effect, and antibacterial properties.

[0048] The method of the present invention for preparing damping coatings is more convenient and faster to apply than adding foaming microspheres, bactericides, formaldehyde removers and other additives separately to the damping coating formulation, and it has better compatibility and stability in the system. Detailed Implementation

[0049] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0050] The raw materials and their sources used in the specific implementation are shown in the table below.

[0051] Table 1 Raw materials for preparing water-based damping coatings

[0052]

[0053]

[0054] The analytical and testing methods involved in the embodiments are as follows:

[0055] Formaldehyde removal efficiency test of water-based damping coating: The purification performance of indoor air purification functional coating materials was determined according to the building materials industry standard JC / T1074-2008.

[0056] Antibacterial test of water-based damping coating: According to standard HG / T 3950-2007, the tested bacteria were Escherichia coli and Staphylococcus aureus.

[0057] Anti-bulging test of water-based damping coating: The water-based damping coating is scraped onto a carbon steel plate with a thickness of 3-4 mm. The coating is placed in an oven at 140℃ and baked for 30 minutes. After taking it out, the appearance of the coating is observed.

[0058] Damping performance (loss factor) was determined using the cantilever beam method. Damping coating was applied to a 10×220×0.8 mm steel plate to achieve a surface density (after drying) of 10×200×3.0, and then baked at 140°C for 30 minutes for drying. After drying, the coated plate was used as a test plate for evaluation and examined using the cantilever beam method. The loss factor at the second-order resonance point was calculated using the half-width method.

[0059] Example 1

[0060] (1) Preparation of modified sodium carboxymethyl cellulose:

[0061] (1.1) Dissolve 43g sodium carboxymethyl cellulose in 100g water. First, add HCl to the solution to adjust the pH to 5.0. Then add 1.5g dicyclohexylcarbodiimide and 4g N-hydroxysuccinimide to activate the carboxyl group. React for 50min. Then add 57g phenolamine and react at room temperature for 3.5 hours.

[0062] (1.2) Precipitation was carried out using frozen ether, followed by separation and drying to obtain phenolamine-modified sodium carboxymethyl cellulose.

[0063] (2) Prepare water-based damping coatings according to the formula in Table 2.

[0064] Table 2: Formulation of Waterborne Damping Coatings

[0065] name mass / g effect ANTAMP 0658 35 emulsion base Deionized water 20 / 2410 0.6 Defoamer 731A 1.5 dispersant AMP-95 0.5 pH adjuster Tego 270 0.5 wetting agent Modified sodium carboxymethyl cellulose 3 filler Carbon Black FW-200 1.0 pigment 325 mesh heavy calcium carbonate 21.8 filler 200 mesh mica powder 14.2 filler A801 1.9 Thickener

[0066] A waterborne damping coating 1 containing modified sodium cellulose was obtained, hereinafter referred to as coating 1.

[0067] Example 2

[0068] (1) Preparation of modified sodium carboxymethyl cellulose:

[0069] (1.1) Dissolve 45g sodium carboxymethyl cellulose in 100g water. First, add HCl to the solution to adjust the pH to 6.0. Then add 1.8g dicyclohexylcarbodiimide and 4.2g N-hydroxysuccinimide to activate the carboxyl group. React for 40min. Then add 55g phenolamine and react at room temperature for 4 hours.

[0070] (1.2) Precipitation was carried out using frozen ether, followed by separation and drying to obtain phenolamine-modified sodium carboxymethyl cellulose.

[0071] (2) Prepare water-based damping coatings according to the formula in Table 3.

[0072] Table 3: Formulation of Waterborne Damping Coatings

[0073]

[0074] A waterborne damping coating 2 containing modified sodium cellulose was obtained, hereinafter referred to as coating 2.

[0075] Example 3

[0076] (1) Preparation of modified sodium carboxymethyl cellulose:

[0077] (1.1) Dissolve 49g sodium carboxymethyl cellulose in 100g water. First, add HCl to the solution to adjust the pH to 5.5. Then add 2g dicyclohexylcarbodiimide and 4.5g N-hydroxysuccinimide to activate the carboxyl group. React for 60min. Then add 51g phenolamine and react at room temperature for 4.5 hours.

[0078] (1.2) Precipitation was carried out using frozen ether, followed by separation and drying to obtain phenolamine-modified sodium carboxymethyl cellulose.

[0079] (2) Prepare water-based damping coatings according to the formula in Table 4.

[0080] Table 4: Formulation of Waterborne Damping Coatings

[0081] name mass / g effect ANTAMP 0656 27 emulsion base Deionized water 20 / 810 1.0 Defoamer 760w 1.0 dispersant AMP-95 0.2 pH adjuster Tego 270 0.6 wetting agent Modified sodium carboxymethyl cellulose 10 filler Carbon Black FW-200 0.2 pigment 325 mesh heavy calcium carbonate 26 filler 200 mesh mica powder 13.3 filler ASE60 0.7 Thickener

[0082] A waterborne damping coating 3 containing modified sodium cellulose was obtained, hereinafter referred to as coating 3.

[0083] Comparative Example 1

[0084] The phenolamine-modified sodium carboxymethyl cellulose in Example 3 was replaced with the same mass of sodium carboxymethyl cellulose to obtain water-based damping coating 4, hereinafter referred to as coating 4.

[0085] The relevant performance of the waterborne damping coatings prepared in the examples and comparative examples is shown in Table 5.

[0086] Table 5 Performance of Waterborne Damping Coatings

[0087]

[0088] The results in the table above show that the waterborne automotive damping coating prepared using phenolamine-modified sodium carboxymethyl cellulose as a functional filler has good anti-bulging, antibacterial, and formaldehyde removal effects. When conventional sodium carboxymethyl cellulose is used as a filler, no obvious antibacterial, anti-bulging, and formaldehyde removal effects are observed. Furthermore, this method has no negative impact on the damping factor and damping effect of the coating.

[0089] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A high performance waterborne automotive damping coating, characterized in that, comprise the following components by mass percentage: The modified sodium carboxymethyl cellulose is phenol amine modified sodium carboxymethyl cellulose, which is prepared by dehydration condensation reaction from sodium carboxymethyl cellulose, phenol amine.

2. The high performance waterborne automotive damping coating according to claim 1, characterized in that, The phenol amine is selected from any one of o-aminophenol, p-aminophenol, and m-aminophenol.

3. The high performance waterborne automotive damping coating according to claim 2, characterized in that, The phenol amine is o-aminophenol.

4. The high performance waterborne automotive damping coating of claim 1, wherein, The preparation method of the phenol amine modified sodium carboxymethyl cellulose comprises the following steps: 1) Dissolve sodium carboxymethyl cellulose in water, first add acid to adjust the pH value in the formed aqueous solution, activate the carboxyl group reaction by adding dicyclohexyl carbodiimide and N-hydroxysuccinimide, then add phenol amine, and react at room temperature; 2) Use frozen ether for precipitation, separate and dry to obtain phenol amine modified sodium carboxymethyl cellulose.

5. The high performance waterborne automotive damping coating according to claim 4, characterized in that, The mass ratio of the sodium carboxymethyl cellulose and the phenol amine is 40-50wt%: 50-60wt%, based on the total mass of the sodium carboxymethyl cellulose and the phenol amine; and / or The pH value is adjusted to 4.5-6.5 by adding acid; and / or The mass of the added dicyclohexyl carbodiimide is 1-2wt% of the total mass of the sodium carboxymethyl cellulose and the phenol amine, and the mass of the added N-hydroxysuccinimide is 3-5wt% of the total mass of the sodium carboxymethyl cellulose and the phenol amine; and / or The activation of the carboxyl group reaction is performed for 30-60min; and / or The reaction at room temperature is performed for 2-5 hours.

6. The high performance waterborne automotive damping coating according to any one of claims 1 to 5, characterized in that, The acrylic emulsion is an aqueous acrylic emulsion with Tg=0-30℃, and is selected from one or more of Wanhua Chemical Antamp 0652, Antamp 0655, Antamp 0658, Antamp 0656, and Antamp 0657.

7. The high performance waterborne automotive damping coating according to claim 6, characterized in that, The acrylic emulsion is Antamp 0658.

8. The high performance waterborne automotive damping coating according to any one of claims 1 to 5, characterized in that, The color filler is selected from at least any one of carbon black, talc powder, mica powder, and calcium carbonate.

9. The high performance waterborne automotive damping coating according to claim 8, characterized in that, The carbon black is selected from at least any one of FW-200 of Dgusui (China) Co., Ltd. and N300 of Hebei Cangzhou Jintai Carbon Black Co., Ltd.; and / or The calcium carbonate is selected from one or more of 325-mesh heavy calcium carbonate, 400-mesh heavy calcium carbonate, 700-mesh heavy calcium carbonate, and 800-mesh heavy calcium carbonate of Changzhou Calcium Carbonate Co., Ltd.; and / or The mica powder is selected from at least any one of 100-mesh mica powder of Chuzhou Sericite Co., Ltd. and 200-mesh mica powder of Shijiazhuang Chenxing Industry Co., Ltd.

10. The high performance waterborne automotive damping coating according to claim 9, characterized in that, The carbon black is FW-200; and / or The calcium carbonate is selected from 325-mesh heavy calcium carbonate and / or 400-mesh heavy calcium carbonate.

11. The high performance waterborne automotive damping coating according to any one of claims 1 to 5, characterized in that, The dispersant is selected from at least any one of Orotan 731A of Dow (China) Co., Ltd., BYK 190 of BYK-Chemie, Tego 760w of Degussa, and C20 of Wanhua Chemical Group Co., Ltd.; and / or The thickening agent is selected from at least any one of Vesmody A801 and Vesmody A401 of Wanhua Chemical Group Co., Ltd., and ASE60 of Dow (China) Co., Ltd.; and / or The wetting agent is at least one of Tego 270, Tego 280, Tego KL 245 of TEGO (China) Co., Ltd., Surfynol 104E of American Gas Chemical, and / or The defoaming agent is at least one of Foam Star ST2410AC of BASF, BYK 810 of BYK-Chemie, Foamex 1488 of TEGO, and / or The pH regulator is at least one of AMP-95, ammonia, and DMEA.

12. The high performance waterborne automotive damping coating of claim 11, wherein, The dispersant is at least one of Tego 760w and Orotan 731A. The thickening agent is at least one of Vesmody A801 and ASE60. The wetting agent is at least one of Tego 270 and KL 245. The defoaming agent is at least one of Foam Star ST2410AC and BYK 810. The pH regulator is AMP-95.

13. Process for the preparation of a high performance waterborne automotive damping coating according to any one of claims 1 to 12, characterized in that, The method comprises the following steps: 1) mixing an acrylic emulsion, a dispersant, a wetting agent, a defoaming agent, and a pH regulator to obtain an aqueous emulsion; 2) mixing deionized water, modified sodium carboxymethyl cellulose, and pigments and fillers to obtain a mixture; 3) mixing the mixture of step 2) and the aqueous emulsion of step 1), and then adding a thickening agent to obtain the aqueous automotive damping coating.

14. The method of claim 13, wherein, The dispersion time of the dispersion in step 1) is 3-5 min; and / or The dispersion time of the dispersion in step 2) is 5-10 min; and / or The dispersion in step 3) is carried out in a disperser at a rotation speed of 1000-1500 rpm for 10-15 min.

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