White pigment paste for high-whiteness suede leather spray dyeing and preparation method thereof

Abstract

The present invention belongs to the technical field of genuine leather suede dyeing, and specifically relates to a high-whiteness white pigment paste for suede spray dyeing and a preparation method thereof. The high-whiteness white pigment paste for suede spray dyeing is prepared using castor oil polyoxyethylene ether solution, acrylic acid copolymer dispersant, polyacrylic acid sodium salt solution, aluminum silicate, rutile titanium dioxide, white carbon black, moisturizer, defoamer, bactericidal preservative, pH regulator, rheological additive, and water as raw materials. The white pigment paste has strong covering power, high whiteness, yellowing resistance, migration resistance, extremely low VOCs content, and high stability. In addition, the preparation method is simple, highly safe, and easy to industrialize, and has good application prospects in the field of leather dyeing.

Description

Technical Field

[0001] The invention belongs to the technical field of genuine leather suede dyeing, and particularly relates to a white pigment paste for spray dyeing high-whiteness suede leather and a preparation method thereof. Background Art

[0002] Currently, suede leather coloring is divided into dyeing and pigmentation. Dyeing generally uses acid dyes, direct dyes, and metal complex dyes, usually in combination with fiber softeners and fixing agents. The majority of dyes are colored or black. However, these dyed leathers are not resistant to migration, are easily discolored and bleached by light, and have poor color fastness to perspiration. Pigmentation generally uses aqueous dispersions of pigments, the majority of which are white, and usually requires a film-forming agent. Existing suede dyeing technology is mainly focused on the field of artificial leather, and dyes are often used in dyeing processes. However, these dyed leathers are not resistant to migration, are easily discolored and bleached by light, and have poor color fastness to perspiration.

[0003] Unlike the petroleum-based chemical fibers that make up the natural fiber base of genuine leather, the artificial suede of artificial leather is primarily made of. Genuine leather materials like cowhide and sheepskin contain a high content of fibrous proteins, which contain numerous polar groups such as amino (-NH2), carboxyl (-COOH), and hydroxyl (-OH). While spray-dying suede can be achieved with dyes, which have an affinity for leather fibers, dyes can also introduce performance flaws, and achieving a highly white suede with dyes is impossible.

[0004] Titanium dioxide is the most common colorant for white suede. Titanium dioxide and its preparations offer high whiteness and high hiding power, making it the best known white pigment. It is insoluble in water and exists as a dispersed form in the aqueous phase. Unlike dyes, which diffuse and penetrate after dissolution and then solidify by binding to leather fibers, titanium dioxide coloring occurs by pigment particles adhering to leather fibers. However, this coloring has a low affinity, resulting in lower friction fastness.

[0005] The purpose of spray dyeing is to color the fibers and maintain the independence of the suede, rather than to cover it with a coating. The traditional method of using titanium white slurry to increase resin film formation and fix the color will cause the long suede on the leather surface to stick together and fall down, and the short suede to stand up, resulting in a rough feel and poor smoothness. It will also cause negative problems such as suede spray accumulation and easy discoloration due to friction. Therefore, the selection of coloring materials for white suede leather needs to be improved.

[0006] For white suede, on the one hand, the color of the leather base produced by chrome tanning is darker, and a covering white color is needed to cover the dark phase of the base and show a high-reflectivity white phase; on the other hand, white suede is often used for shoe materials, and consumers have very high requirements for the whiteness of white shoe upper leather. How to dye a white suede with high whiteness and no fading has always been a direction that leather industry practitioners have been constantly exploring.

[0007] The patent application with application number 202111383566.3 discloses a white color paste that uses an acrylic copolymer aqueous dispersant to disperse titanium dioxide without other pigments. Its dispersion mechanism is single, there is no synergistic dispersion effect, and it has poor stability and low color fastness.

[0008] Therefore, in view of the shortcomings of spray dyeing technology in the leather industry, there is an urgent need to provide a pure white coloring solution for suede leather spray dyeing that is non-dye-colored, has high whiteness, does not fade, and is resistant to migration and light fastness. Summary of the Invention

[0009] Based on the above technical background, the present invention provides a high-whiteness white pigment paste for spray-dyeing suede leather and a preparation method thereof. The high-whiteness white pigment paste for spray-dyeing suede leather is prepared using castor oil polyoxyethylene ether solution, acrylic acid copolymer dispersant, polyacrylic acid sodium salt solution, aluminum silicate, rutile titanium dioxide, white carbon black, humectant, defoamer, bactericidal preservative, pH regulator, rheological additive and water as raw materials. The white pigment paste has the advantages of high whiteness, strong adhesion, yellowing resistance, migration resistance, low VOCs content, good color fastness and high stability.

[0010] A first aspect of the present invention is to provide a high-whiteness white pigment paste for spray-dyeing suede leather, wherein the high-whiteness white pigment paste for spray-dyeing suede leather is prepared using castor oil polyoxyethylene ether solution, acrylic acid copolymer dispersant, polyacrylic acid sodium salt solution, aluminum silicate, rutile titanium dioxide, white carbon black, humectant, defoamer, bactericidal preservative, pH regulator, rheological additive, and water as raw materials;

[0011] Based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 2.5-5.5%, acrylic acid copolymer dispersant accounts for 2.0-7.0%, polyacrylate sodium salt solution accounts for 0.2-1.0%, aluminum silicate accounts for 17-28%, rutile titanium dioxide accounts for 17-30%, white carbon black accounts for 0.3-2.5%, moisturizer accounts for 3.0-9.0%, defoamer accounts for 0.03-0.3%, bactericidal preservative accounts for 0.05-0.4%, rheological additive accounts for 0.1-1.5%, pH regulator accounts for 0.1-0.4%, and the balance is water.

[0012] Preferably, based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 3.0-5.0%, acrylic acid copolymer dispersant accounts for 3.0-6.0%, polyacrylate sodium salt solution accounts for 0.4-0.8%, aluminum silicate accounts for 20-28%, rutile titanium dioxide accounts for 20-28%, white carbon black accounts for 0.5-2.0%, moisturizer accounts for 4.0-8.0%, defoamer accounts for 0.05-0.2%, bactericidal preservative accounts for 0.1-0.3%, rheological additive accounts for 0.2-1.0%, pH regulator accounts for 0.1-0.3%, and the balance is water.

[0013] Preferably, the mass percentage of castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution is 70%, and the HLB value is 14.0-16.5;

[0014] The acrylic copolymer dispersant is selected from one or more of an acrylic ester copolymer structural dispersant and a free radical polymerization (RAFT) block polypropylene copolymer dispersant;

[0015] The sodium polyacrylate solution is a sodium polyacrylate aqueous solution with a molecular weight of 3000-6000 and a solid content of 42±2%;

[0016] The aluminum silicate is sodium aluminum silicate with a particle size of 2000 to 3000 mesh;

[0017] The white carbon black is selected from industrial grade 2500 mesh ultrafine SiO2;

[0018] The moisturizing agent is selected from one or both of polyethylene glycol 300 and caprolactam;

[0019] The defoaming agent is selected from one or more of polyether modified silane defoaming agents and mineral oil defoaming agents;

[0020] The bactericidal preservative is selected from one or more of isothiazolinone or benzimidazole compounds;

[0021] The rheological additive is selected from one or more of a polyurethane associative rheological additive and an acrylic acid alkali swelling associative rheological additive;

[0022] The pH regulator is selected from one or more of 2-amino-2-methyl-1-propanol, ammonia water, and triethanolamine.

[0023] The second aspect of the present invention is to provide a method for preparing the white pigment paste for spray dyeing high-whiteness suede leather according to the first aspect of the present invention, the method comprising the following steps:

[0024] Step 1, weighing raw materials, mixing and dispersing water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution, then adding castor oil polyoxyethylene ether solution and continuing to mix and disperse to obtain an additive mixture;

[0025] Step 2: adding aluminum silicate and rutile titanium dioxide to the additive mixture in sequence, adding white carbon black after mixing and dispersing, and obtaining a pre-dispersed pigment slurry after high-speed dispersion, and then grinding to obtain a grinding slurry;

[0026] Step 3: add moisturizer and defoamer to the grinding slurry in sequence, stir and disperse, cool down, then add bactericidal preservative, stir, add rheological additive and pH regulator, and finally filter after stirring to obtain high-whiteness suede leather spray dyeing white pigment paste.

[0027] Preferably, in step 1, the castor oil polyoxyethylene ether solution is prepared by heating the castor oil polyoxyethylene ether to 55-65° C. and scalding the castor oil polyoxyethylene ether, adding deionized water and stirring uniformly.

[0028] Mix water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution at a speed of 300-500 r / min and disperse for 10-15 minutes;

[0029] Then add castor oil polyoxyethylene ether solution and continue stirring for 10 to 15 minutes.

[0030] Preferably, in step 2, aluminum silicate and rutile titanium dioxide are added and then mixed and dispersed at 500-700 r / min for 10-15 minutes;

[0031] After adding silica, disperse at a high speed of 900-1200 r / min for 1.5-3 hours.

[0032] The grinding is carried out in a sand mill, and the grinding conditions are as follows: the grinding speed of the sand mill is 600-1200 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.5-0.9 mm, the zirconium bead loading rate is 62-75% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 45-58° C., and the grinding is performed 3-5 times.

[0033] More preferably, the grinding conditions are: the grinding speed of the sand mill is 700-1000 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.6-0.8 mm, the zirconium bead loading rate is 65-70% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 50-58° C., and the grinding is performed 3-4 times.

[0034] Preferably, in step 3, a moisturizing agent and a defoaming agent are added and stirred and dispersed at a speed of 300 to 500 r / min for 1.5 to 3 hours;

[0035] Cool down to below 45°C and add bactericidal preservatives, then stir for 30-40 minutes, add rheological additives and pH regulators, adjust the viscosity to 4.0-9.0, and adjust the pH to 8.0-9.5.

[0036] The beneficial effects of the present invention are:

[0037] (1) Based on the research on the matching of group properties of dermal fibers, the present invention introduces silica-aluminum-based white pigments, white carbon black, etc. into the pigment paste, and utilizes the cross-linking between silicates, silanol groups and dermal collagen fibers, and the coordination reaction between aluminum ions and carboxyl groups on the side chains of peptide chains to form complexes, thereby achieving high binding strength and solving the problem of chemical bonding between the pigment and the dermal fibers after spray-dyeing.

[0038] At the same time, the preparation process finely grinds the rutile titanium dioxide to below 450nm, reflecting the size effect, promoting the penetration of particles into the fibers, and providing stronger covering power;

[0039] In terms of adhesion, castor oil polyoxyethylene ether is used as a synergist to lubricate and moisturize the dermal fibers, and together with the moisturizer, it helps to improve the smoothness and softness of the suede surface, and helps the carrier diffuse in the dermal fibers, so that the pigment particles rutile titanium dioxide and aluminum silicate can better penetrate into the dermal fibers and enhance adhesion.

[0040] In terms of touch, the moisturizer used reduces the static friction coefficient between leather fibers, making them easier to slide, resulting in a moisturizing touch. The high-whiteness white pigment paste for suede leather spray dyeing of the present invention has a series of advantages such as high whiteness, yellowing resistance, migration resistance, low VOCs content, and high stability.

[0041] (2) The white pigment paste for high-whiteness suede leather spray dyeing provided by the present invention has a simple preparation method, does not require high temperature and high pressure, is highly safe, is easy to implement large-scale industrial production, does not shed, fade, or harden, and has uniform coloring. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The XRD spectrum of the commercially available pigment paste of Comparative Example 1 is shown;

[0043] Figure 2 The figure shows the particle size distribution of the white pigment paste prepared in Example 2;

[0044] Figure 3 The particle size distribution of the white pigment paste in Comparative Example 1 is shown;

[0045] Figure 4 The particle size distribution diagram of the white pigment paste prepared in Comparative Example 5 is shown;

[0046] Figure 5 Photos showing the coloring effects of suede leather spray-dyed with the pigment paste described in Example 2 and Comparative Example 1.

[0047] Figure 6 The following is a 50-fold magnification observation image of suede leather spray-dyed with the pigment pastes of Example 2 and Comparative Example 1:

[0048] Figure A-1 shows an enlarged observation image of the suede leather after being spray-dyed with the pigment paste described in Comparative Example 1 and before being rubbed;

[0049] Figure A-2 shows an enlarged observation picture of suede leather spray-dyed with the pigment paste described in Comparative Example 1 after rubbing;

[0050] Figure B-1 shows an enlarged observation of the suede leather after being spray-dyed with the pigment paste described in Example 2 and before being rubbed;

[0051] Figure B-2 shows an enlarged observation picture of the suede leather spray-dyed with the pigment paste described in Comparative Example 2 after rubbing. DETAILED DESCRIPTION

[0052] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the following description.

[0053] Currently, the leather industry at home and abroad often uses titanium dioxide and titanium dioxide paste to color white suede. However, titanium dioxide relies solely on the physical adsorption of particles, has poor binding with leather fibers, is easily discolored, and fails to fully utilize the high whiteness advantage of titanium dioxide. This is a major problem currently facing this field. Based on the study of the group performance matching of dermal fibers, the present invention introduces a silicon-aluminum-based white pigment into the white pigment paste, crosslinks the silicate with the dermal collagen fibers in the aqueous phase, and the aluminum 3+ The pigment easily reacts with the carboxyl groups (-COOH) on the side chains of the peptide chain to form a complex. The silanol groups on the silica also interact with the collagen fibers to form cross-links, resulting in a strong bond and allowing the pigment to be firmly adsorbed on the leather fiber surface. Furthermore, the titanium dioxide is finely ground to below 450nm to promote particle penetration between fibers, providing stronger covering power. The resulting white pigment paste has the advantages of high whiteness, resistance to yellowing and migration, extremely low VOC content, and high stability.

[0054] The first aspect of the present invention is to provide a white pigment paste for spray dyeing high-whiteness suede leather, wherein the white pigment paste for spray dyeing high-whiteness suede leather is prepared with castor oil polyoxyethylene ether solution, acrylic acid copolymer dispersant, polyacrylic acid sodium salt solution, aluminum silicate, rutile titanium dioxide, white carbon black, humectant, defoaming agent, bactericidal preservative, pH regulator, rheological additive and water as raw materials.

[0055] Based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 2.5-5.5%, acrylic acid copolymer dispersant accounts for 2.0-7.0%, polyacrylate sodium salt solution accounts for 0.2-1.0%, aluminum silicate accounts for 17-28%, rutile titanium dioxide accounts for 17-30%, white carbon black accounts for 0.3-2.5%, moisturizer accounts for 3.0-9.0%, defoamer accounts for 0.03-0.3%, bactericidal preservative accounts for 0.05-0.4%, rheological additive accounts for 0.1-1.5%, pH regulator accounts for 0.1-0.4%, and the balance is water.

[0056] Preferably, based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 3.0-5.0%, acrylic acid copolymer dispersant accounts for 3.0-6.0%, polyacrylate sodium salt solution accounts for 0.4-0.8%, aluminum silicate accounts for 20-28%, rutile titanium dioxide accounts for 20-28%, white carbon black accounts for 0.5-2.0%, moisturizer accounts for 4.0-8.0%, defoamer accounts for 0.05-0.2%, bactericidal preservative accounts for 0.1-0.3%, rheological additive accounts for 0.2-1.0%, pH regulator accounts for 0.1-0.3%, and the balance is water.

[0057] The mass percentage of castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution is preferably 70%, the HLB value is 14.0-16.5, and the castor oil polyoxyethylene ether is EL-60 or EL-80.

[0058] The acrylic copolymer dispersant is a type of hydrophobic-hydrophilic amphiphilic acrylic block polymer water-based dispersant, with relatively concentrated anchoring groups and steric stabilization of the polyacrylate chain to maintain the deflocculated state of the pigment. The acrylic copolymer dispersant is selected from one or more of an acrylic copolymer structured dispersant and a free radical polymerization (RAFT) block polypropylene copolymer dispersant, preferably a Bick 190 or Dispers 755W. The dispersant has an active ingredient content of 40±1%.

[0059] The sodium polyacrylate solution is an aqueous solution of sodium polyacrylate with a molecular weight of 3,000-6,000 and a solids content of 42±2%. As the auxiliary dispersant in the present invention, it is preferably a German BASF DISPEX AA4140 AS sodium polyacrylate aqueous solution. This sodium polyacrylate is anionic, highly polar, and contains a large number of carboxyl groups on its molecular backbone. This allows for a strong electrochemical reaction on the surfaces of titanium dioxide and sodium aluminum silicate particles, generating electrostatic interactions and hydrogen bonding, thereby improving the dispersibility of the pigment particles.

[0060] The aluminum silicate is sodium aluminum silicate, which is a pure white amorphous fine powder with a particle size of 2000-3000 mesh and a high alkalinity value (10±0.5). The BET specific surface area of ​​sodium aluminum silicate is 80-110 m 2 / g, DOA absorption value is as high as 90 ~ 155ml / 100g.

[0061] The rutile titanium dioxide is selected from one or more of Chemours titanium dioxide Ti-Pure R-706, Taike titanium dioxide CR-510, and Yibin Tianyuan titanium dioxide TYR-588.

[0062] The white carbon black is industrial grade 2500 mesh ultrafine SiO2. SiO2 has high hardness and small size effect, and has strong impact force during grinding, thereby improving the grinding efficiency of other pigments.

[0063] The moisturizing agent is preferably selected from one or both of polyethylene glycol 300 and caprolactam, which has lubricating and moisturizing effects and can make the suede leather have a lubricating feel after spraying.

[0064] The defoaming agent is selected from one or more of polyether-modified silane defoaming agents and mineral oil defoaming agents, and is preferably polyether-modified polydimethylsiloxane.

[0065] The bactericidal preservative is selected from one or more of isothiazolinone or benzimidazole compounds, does not contain formaldehyde or formaldehyde sustained-release agent, and isothiazolinone is preferred.

[0066] The rheological additive is selected from one or more of polyurethane associative rheological additives and acrylic acid alkali swelling associative rheological additives, and its effective matter content is 30±1%, preferably PUGEL-20F polyurethane associative rheological additive.

[0067] The pH regulator is selected from one or more of 2-amino-2-methyl-1-propanol, ammonia water, and triethanolamine.

[0068] The second aspect of the present invention is to provide a method for preparing the white pigment paste for spray dyeing high-whiteness suede leather according to the first aspect of the present invention, the method comprising the following steps:

[0069] Step 1, weighing raw materials, mixing and dispersing water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution, then adding castor oil polyoxyethylene ether solution and continuing to mix and disperse to obtain an additive mixture;

[0070] Step 2: adding aluminum silicate and rutile titanium dioxide to the additive mixture in sequence, adding white carbon black after mixing and dispersing, and obtaining a pre-dispersed pigment slurry after high-speed dispersion, and then grinding to obtain a grinding slurry;

[0071] Step 3: add moisturizer and defoamer to the grinding slurry in sequence, stir and disperse, cool down, then add bactericidal preservative, stir, add rheological additive and pH regulator, and finally filter after stirring to obtain high-whiteness suede leather spray dyeing white pigment paste.

[0072] The above steps are described in detail below.

[0073] In step 1, the mixing and dispersing is carried out in a disperser.

[0074] The castor oil polyoxyethylene ether solution is prepared by heating the castor oil polyoxyethylene ether to 55-65° C. for scalding, adding deionized water and stirring uniformly, wherein the mass fraction of the castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution is 70%.

[0075] Mix water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution and disperse them at a speed of 300 to 500 r / min for 10 to 15 minutes.

[0076] Then add castor oil polyoxyethylene ether solution and continue stirring for 10 to 15 minutes.

[0077] In step 2, aluminum silicate and rutile titanium dioxide are added and dispersed at 500-700 r / min for 10-15 minutes to ensure that all the powders are stirred into the liquid phase, and then white carbon black is slowly added.

[0078] After adding silica, disperse at a high speed of 900-1200 r / min for 1.5-3 hours.

[0079] The grinding is preferably carried out in a sand mill, and the grinding conditions are: the grinding speed of the sand mill is 600-1200 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.5-0.9 mm, the zirconium bead loading rate is 62-75% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 45-58° C., and the grinding is performed 3-5 times.

[0080] Preferably, the grinding conditions are as follows: the grinding speed is 700-1000 r / min, the particle size of the zirconium beads in the cylinder is selected to be 0.6-0.8 mm, the zirconium bead loading rate is 65-70% of the cylinder volume, the separator or screen aperture is selected to be 0.2 mm, the slurry outlet temperature is controlled at 50-58°C, and the grinding is performed 3-4 times.

[0081] After grinding, the average volume particle size of the pigment slurry is less than 450nm, the particle size distribution is D90 less than 550nm, and D50 is in the range of 300-400nm.

[0082] In step 3, a moisturizing agent and a defoaming agent are added and stirred and dispersed at a speed of 300 to 500 r / min for 1.5 to 3 hours.

[0083] Cool to below 45°C and add bactericidal preservatives, then stir for 30 to 40 minutes, add rheological additives and pH regulators, adjust the viscosity to 4.0 to 9.0, adjust the pH value to 8.0 to 9.5, and stir for 1 to 1.5 hours until the system is stable. Finally, filter through a 300-mesh sieve.

[0084] Example

[0085] The present invention is further described below through specific examples. These examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0086] The raw materials used in the examples of the present invention (except the castor oil polyoxyethylene ether solution) were all purchased.

[0087] Preparation method of castor oil polyoxyethylene ether solution: heat the weighed castor oil polyoxyethylene ether to 60° C. to scald, add deionized water and stir to dilute evenly, and the mass concentration of castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution after dilution is 70wt.%.

[0088] Example 1

[0089] According to weight percentage: castor oil polyoxyethylene ether solution (castor oil polyoxyethylene ether: sea stone flower EL-60, mass fraction: 70wt.%): 3.5%, acrylic copolymer dispersant (BYK Weigh the raw materials: 1.5% sodium polyacrylate solution (molecular weight 3000-6000, solid content 42%, BASF DISPEX AA4140AS, Germany): 0.5%; sodium aluminum silicate (particle size 2000-3000 mesh): 20.0%; rutile titanium dioxide (Chemours titanium dioxide Ti-Pure R-706): 28.0%; white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%; humectant (polyethylene glycol 300): 6.0%; defoaming agent (polyether modified polydimethylsiloxane): 0.1%; bactericidal preservative (isothiazolinone): 0.25%; rheological additive (PUGEL-20F): 0.45%; pH adjuster (triethanolamine): 0.16%; deionized water: the balance.

[0090] The weighed deionized water, acrylic acid copolymer dispersant, and polyacrylic acid sodium salt solution were placed in a disperser at room temperature. The disperser was turned on and the speed was adjusted to 400 r / min for dispersion and mixing for 12 minutes. It was ensured that the vortex in the center of the liquid level did not leak out of the blades and a large number of bubbles were avoided. The castor oil polyoxyethylene ether solution was added thereto and stirring was continued for 15 minutes to obtain an additive mixture.

[0091] Adjust the disperser speed to 600 rpm. Then, add sodium aluminum silicate and rutile titanium dioxide to the additive mixture in sequence. Disperse for 15 minutes. Once all the powders have been incorporated into the liquid phase, slowly add silica. Disperse again at 1000 rpm for 2 hours to form a uniform pre-dispersed pigment slurry. The pre-dispersed pigment slurry is piped to a horizontal pin-type sand mill for through-grinding. Grinding conditions are as follows: a grinding speed of 800 rpm, a zirconium bead size of 0.6-0.8 mm in the cylinder, a zirconium bead loading rate of 70% of the cylinder volume, a separator or screen aperture of 0.2 mm, a slurry outlet temperature of 55°C, and four passes of grinding. The pigment slurry is tested to have a volume average particle size below 450 nm, a particle size distribution of D90 less than 550 nm, and a D50 between 300 and 400 nm. The milled slurry is then discharged.

[0092] At a speed of 400 rpm, add a moisturizer and a defoamer to the grinding slurry in sequence. Maintain the speed for 2 hours until all bubbles are completely eliminated, resulting in a prefabricated pigment slurry. Cool the prefabricated pigment slurry to below 45°C, then add a bactericide and preservative to prevent the degradation of the isothiazolinone or benzimidazole compounds at high temperatures. After stirring for 30 minutes, add a rheology modifier and a pH adjuster to adjust the viscosity to 4.0-9.0 Pa.s and the pH to 8.0-9.5. Stir for 1 hour until the system stabilizes. Finally, filter through a 300-mesh filter and package to obtain the finished white pigment paste.

[0093] Example 2

[0094] According to weight percentage: castor oil polyoxyethylene ether solution (sea stone flower EL-80. Mass fraction: 70wt.%): 4.0%, acrylic acid copolymer dispersant (Tego Weigh the raw materials: Dispers755W): 5.2%, sodium polyacrylate solution (molecular weight 3000-6000, solid content 42%, BASF DISPEX AA4140 AS, Germany): 0.5%, sodium aluminum silicate (particle size 2000-3000 mesh): 24.0%, rutile titanium dioxide (Tyco Titanium Dioxide CR-510): 24.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (polyethylene glycol 300): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.3%, pH adjuster (2-amino-2-methyl-1-propanol): 0.1%, deionized water: the balance.

[0095] The weighed deionized water, acrylic acid copolymer dispersant, and polyacrylic acid sodium salt solution were placed in a disperser at room temperature. The disperser was turned on and the speed was adjusted to 300 r / min for 15 minutes of dispersion and mixing to ensure that the vortex in the center of the liquid level did not leak out of the blades and to avoid the entry of a large number of bubbles. The castor oil polyoxyethylene ether solution was added thereto and the stirring was continued for 15 minutes to obtain an additive mixture.

[0096] Adjust the disperser speed to 500 rpm. Then, add sodium aluminum silicate and rutile titanium dioxide to the additive mixture in sequence. Disperse for 15 minutes. Once all the powders have been incorporated into the liquid phase, slowly add white carbon black. Disperse the mixture at 900 rpm for 3 hours to form a uniform pre-dispersed pigment slurry. The pre-dispersed pigment slurry is piped to a horizontal pin-type sand mill for through-grinding. Grinding conditions are as follows: a grinding speed of 700 rpm, a zirconium bead size of 0.6-0.8 mm in the cylinder, a zirconium bead loading rate of 70% of the cylinder volume, a separator or screen aperture of 0.2 mm, a slurry outlet temperature of 50°C, and four passes of grinding. The pigment slurry is tested to have a volume average particle size below 450 nm, a particle size distribution of D90 less than 550 nm, and a D50 between 300 and 400 nm. The milled slurry is then discharged.

[0097] At a speed of 300 rpm, add a moisturizer and a defoamer to the grinding slurry in sequence. Maintain the speed for 3 hours until all bubbles are eliminated, resulting in a prefabricated pigment slurry. Cool the prefabricated pigment slurry to below 45°C, then add a bactericide and preservative to prevent the degradation of the isothiazolinone or benzimidazole compounds at high temperatures. After stirring for 30 minutes, add a rheology modifier and a pH adjuster to adjust the viscosity to 4.0-9.0 Pa.s and the pH to 8.0-9.5. Stir for 1 hour until the system stabilizes. Finally, filter through a 300-mesh filter and package to obtain the finished white pigment paste.

[0098] The white pigment paste prepared in Example 2 was tested for VOC using the headspace method (HS-GC / MS) in accordance with GB 30981-2020. The test result was ND (not detected), with a detection limit of 2 g / L. This indicates that the white pigment paste prepared in the present invention contains substantially no VOCs.

[0099] Example 3

[0100] According to weight percentage: castor oil polyoxyethylene ether solution (sea stone flower EL-80. Mass fraction: 70wt.%): 4.0%, acrylic acid copolymer dispersant (Tego Weigh the raw materials: 1.5% propylene glycol dispers (755W): 6.0%, sodium polyacrylate solution (molecular weight 3000-6000, solid content 42%, BASF DISPEX AA4140 AS, Germany): 0.5%, sodium aluminum silicate (particle size 2000-3000 mesh): 28.0%, rutile titanium dioxide (Yibin Tianyuan titanium dioxide TYR-588): 20.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (caprolactam): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.12%, pH adjuster (ammonia water): 0.05%, deionized water: the balance.

[0101] The weighed deionized water, acrylic acid copolymer dispersant, and polyacrylic acid sodium salt solution were placed in a disperser at room temperature, and the disperser was turned on and the speed was adjusted to 500 r / min for 10 minutes of dispersion and mixing to ensure that the vortex in the center of the liquid level did not leak out of the blade and to avoid the entry of a large number of bubbles; castor oil polyoxyethylene ether solution was added thereto, and stirring was continued for 10 minutes to obtain an additive mixture.

[0102] Adjust the disperser speed to 700 rpm. Then, add sodium aluminum silicate and rutile titanium dioxide to the additive mixture in sequence. Disperse for 10 minutes. Once all the powders have been incorporated into the liquid phase, slowly add silica. Disperse the mixture at 1200 rpm for 1.5 hours to form a uniform pre-dispersed pigment slurry. The pre-dispersed pigment slurry is piped to a horizontal pin-type sand mill for through-grinding. Grinding conditions are as follows: a grinding speed of 1000 rpm, a zirconium bead size of 0.6-0.8 mm in the cylinder, a zirconium bead loading rate of 70% of the cylinder volume, a separator or screen mesh size of 0.2 mm, a slurry outlet temperature of 58°C, and four passes of grinding. The pigment slurry is tested to have a volume average particle size below 450 nm, a particle size distribution of D90 less than 550 nm, and a D50 between 300 and 400 nm. The milled slurry is then discharged.

[0103] At a speed of 500 rpm, add a moisturizer and a defoamer to the grinding slurry in sequence. Maintain the speed for 1.5 hours until all bubbles are completely removed, resulting in a prefabricated pigment slurry. Cool the prefabricated pigment slurry to below 45°C, then add a bactericide and preservative to prevent the degradation of the isothiazolinone or benzimidazole compounds at high temperatures. After stirring for 30 minutes, add a rheology modifier and a pH adjuster to adjust the viscosity to 4.0-9.0 Pa.s and the pH to 8.0-9.5. Stir for an additional hour until the system stabilizes. Finally, filter through a 300-mesh filter and package to obtain the finished white pigment paste.

[0104] Comparative Example

[0105] Comparative Example 1

[0106] The XRD test results of commercially available white pigment paste are as follows: Figure 1 Its ICP-OES full scan element test is shown in Table 1.

[0107] Table 1

[0108] element Content (mg / kg) element Content (mg / kg) Sodium(Na) 2789 Arsenic (As) N.D.(<5) Silicon (Si) 2118 Chromium (Cr) N.D.(<5) Aluminum (Al) 678 Lead (Pb) N.D.(<20) Phosphorus (P) 587 Selenium (Se) N.D.(<20) Magnesium (Mg) 378 Strontium (Sr) N.D.(<5) Potassium (K) 86 Vanadium (V) N.D.(<5) Calcium (Ca) 86 Zinc (Zn) N.D.(<10) Iron (Fe) 25 Copper (Cu) N.D.(<10) Lithium (Li) N.D.(<5) Molybdenum (Mo) N.D.(<10) Boron (B) N.D.(<5) Antimony (Sb) N.D.(<10) Barium (Ba) N.D.(<5) Tungsten (W) N.D.(<10) Bismuth(Bi) N.D.(<5) Tin (Sn) N.D.(<5) Cadmium (Cd) N.D.(<5) Manganese (Mn) N.D.(<5) Cobalt (Co) N.D.(<5) Rhenium (Re) N.D.(<5) Nickel (Ni) N.D.(<5) Palladium (Pd) N.D.(<5)

[0109] XRD analysis reveals that the inorganic component in this commercially available white pigment paste is solely TiO2. ICP-OES full-scan elemental analysis (Table 2) reveals extremely low silicon (Si) and aluminum (Al) content, less than 1g / kg, with virtually no silicon or aluminum compounds. This indicates that the product of Comparative Example 1 is primarily based on pure titanium dioxide as the coloring pigment, containing approximately 48-50wt.% titanium dioxide powder, and contains no sodium aluminum silicate or white carbon black.

[0110] The white pigment paste described in Comparative Example 1 was tested for VOC using the headspace method (HS-GC / MS) in accordance with the requirements of GB 30981-2020, and the test result was 72 g / L.

[0111] Comparative Example 2

[0112] The white pigment paste was prepared in a similar manner to Example 2, except that: in terms of weight percentage: acrylic copolymer dispersant ( Weigh the raw materials: Dispers755W): 2.6%, sodium polyacrylate solution (molecular weight 3000-6000, solid content 42%): 1.0%, sodium aluminum silicate (particle size 2000-3000 mesh): 24.0%, rutile titanium dioxide (Tyco Titanium Dioxide CR-510): 24.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (polyethylene glycol 300): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.3%, pH adjuster (2-amino-2-methyl-1-propanol): 0.08%, deionized water: the balance.

[0113] Comparative Example 3

[0114] The white pigment paste was prepared in a similar manner to Example 2, except that: in terms of weight percentage: castor oil polyoxyethylene ether solution (sea stone flower EL-80. Mass fraction: 70wt.%): 4.0%, acrylic acid copolymer dispersant (Tego Weigh the raw materials: Dispers755W): 5.2%, sodium aluminum silicate (particle size 2000-3000 mesh): 24.0%, rutile titanium dioxide (Tyco Titanium Dioxide CR-510): 24.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (polyethylene glycol 300): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.35%, pH adjuster (2-amino-2-methyl-1-propanol): 0.1%, deionized water: the balance.

[0115] Comparative Example 4

[0116] The white pigment paste was prepared in a similar manner to Example 2, except that: in terms of weight percentage: castor oil polyoxyethylene ether solution (sea stone flower EL-80. mass fraction: 70wt.%): 4.0%, sodium polyacrylate solution (molecular mass 3000-6000, solid content 42%): 1.3%, sodium aluminum silicate (particle size 2000-3000 mesh): 24.0%, rutile titanium dioxide (Tai Ke titanium dioxide CR-510): 24.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (polyethylene glycol 300): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.3%, pH adjuster (2-amino-2-methyl-1-propanol): 0.05%, deionized water: the balance, weigh the raw materials.

[0117] Comparative Example 5

[0118] The white pigment paste was prepared in a similar manner to Example 2, except that: in terms of weight percentage: castor oil polyoxyethylene ether solution (sea stone flower EL-80. Mass fraction: 70wt.%): 4.0%, acrylic acid copolymer dispersant (Tego Weigh the raw materials: Dispers755W): 5.2%, sodium polyacrylate solution (molecular weight 3000-6000, solid content 42%): 0.5%, sodium aluminum silicate (particle size 2000-3000 mesh): 24.0%, rutile titanium dioxide (Tai Ke Titanium Dioxide CR-510): 24.0%, white carbon black (industrial grade 2500 mesh ultrafine SiO2): 1.0%, humectant (polyethylene glycol 300): 6.0%, defoaming agent (polyether modified polydimethylsiloxane): 0.1%, bactericidal preservative (isothiazolinone): 0.25%, rheological additive (PUGEL-20F): 0.2%, pH adjuster (2-amino-2-methyl-1-propanol): 0.05%, deionized water: the balance.

[0119] The grinding condition parameters are: grinding speed is 500r / min, the particle size of zirconium beads in the cylinder is selected to be 1.0-1.2mm, the zirconium bead loading rate is 60% of the cylinder volume, the separator or screen aperture is selected to be 0.3mm, the slurry outlet temperature is controlled at 60°C, grinding is done once, and the grinding slurry is obtained after discharging.

[0120] Experimental example

[0121] Experimental Example 1 Suede spray dyeing performance test

[0122] The white pigment pastes prepared in Examples 1-3 and Comparative Examples 1-5 were used to conduct suede spray dyeing tests, and the test process was as follows: the white pigment pastes prepared in Examples 1-3 and Comparative Examples 1-5, polyurethane resin and water were mixed, wherein the mass percentage of the white pigment paste was 12%, the mass percentage of the polyurethane resin was 3%, and the mass percentage of water was 85%. The polyurethane resin used is non-sticky in film formation and has good wettability, and spraying will not affect the feel of the leather blank. Leather blank: finished cow split suede with poor whiteness or undyed cow split suede finished leather blank; spraying amount: spraying 8±0.2g / sq.ft (to full coverage), drying in a 60°C oven for 20min; observation: visually inspect the whiteness of the suede and test the Lab value. The test results are shown in Table 2:

[0123] The white pigment pastes prepared in Examples 1-3 and Comparative Examples 1-5 were mixed with polyurethane resin in a mass ratio of 1:3. The resulting mixtures were cast onto white cardboard using a 150-μm wire rod, dried, and then colorimetrically measured. Yellowing resistance testing conditions included irradiation with a sun lamp at 80°C for 24 hours, followed by testing. Whiteness was measured on leather samples before and after spraying. Yellowing resistance, whiteness, and color difference were all measured using a DATA COLOR 110 colorimeter. The test results are shown in Table 2.

[0124] Table 2

[0125]

[0126]

[0127] Note: Application performance evaluation is divided into levels 1 to 5, with level 1 being the worst and level 5 being the highest.

[0128] The particle size, viscosity and pH of the white pigment paste were tested using the test conditions shown in Table 3:

[0129] Table 3

[0130] Product Specifications Detection conditions / methods equipment model Product Appearance Visual inspection Average particle size / nm Photoelectric detection Laser particle size distribution analyzer Baxter BT-9300ST Viscosity / Pa·s 3# rotor, 12 rpm, 25°C Rotational viscometer Brookfield DV2T pH (10%) Diluted to 10% content with water for testing Electronic pH meter Leici PHSJ-5T

[0131] Figures 2 to 4 The particle size distribution diagrams of the white pigment pastes in Example 2, Comparative Example 1 and Comparative Example 5 are shown respectively.

[0132] From Table 2 and Figures 2-4 It can be seen that the average particle size of the white pigment paste for suede spray dyeing prepared by the present invention reaches less than 450nm, the particle size distribution is uniform, D90 is less than 550nm, and D50 is in the range of 300-400nm; after spray dyeing, the whiteness of the suede leather embryo is significantly improved and the hiding power is good. Figure 5 As shown, Example 2 has the most obvious whiteness improvement effect and the best storage stability, which is significantly better than commercially available products.

[0133] By comparing the test results of Example 2 and Example 3, it is found that the specific surface area and surface energy of sodium aluminum silicate are large, and the absorption value is also high, which objectively reflects that its structure is high, so that it is easy to form agglomerates. Therefore, the amount used should not exceed 28% of the weight ratio of the formula, otherwise it is very easy to cause false thickening and agglomeration, and the dispersion effect is poor.

[0134] In Examples 1-3 and Comparative Examples 1-5, the pigment paste of Comparative Example 1 has a high whiteness value, but the whiteness is low after spraying on the suede surface, and the application effect is the worst. In addition, after being rubbed by hand or tumbled to soften, the leather surface is easy to fall off, and the binding fastness of the pigment is insufficient. Observed under an optical microscope with a magnification of 50 times, as shown in FIG. Figure 6 As shown in the figure, after rubbing with hands to simulate external force, the cross-section layer is still covered with white, but there is less white pigment attached to the hair, resulting in the entire leather surface being dark and lacking in whiteness. Figure 6 It can be seen that the white pigment attached to the suede fiber of Example 2 is dense and uniform. Under the external force of hand rubbing, the white pigment attached to the suede does not decrease significantly, the whiteness is well maintained, and the color fastness is high.

[0135] The dispersant combination of Comparative Example 2 is difficult to achieve an optimal stable state. The prepared pigment paste has the defect of easy sedimentation, and pigment precipitation is very likely to occur during long-term storage. In addition, without the castor oil polyoxyethylene ether component, the suede leather product has a poor feel and softness. In contrast, Example 2 uses castor oil polyoxyethylene ether as a synergist, which has a moisturizing effect on the leather fibers and helps improve the smoothness and softness of the suede surface.

[0136] Sodium aluminum silicate and titanium dioxide have high surface polarity. The white pigment paste prepared in Comparative Example 3 using a single acrylic acid copolymer dispersant lacks the synergistic effect of a small molecule anionic dispersant and lacks the stabilizing effect of electrostatic repulsion. The dispersion stability of the prepared white pigment paste is not as good as that in Example 2. Comparative Example 4 uses a single polyacrylic acid sodium salt dispersant. The excessive addition of the dispersant will lead to the failure of electrostatic repulsion stabilization and a large change in particle size after intensive storage.

[0137] The preparation process of Comparative Example 5 exceeds the parameter range specified in this application and fails to form ultrafine grinding conditions. The particle size distribution of the finished product is wide and the fineness is not as good as the finished products of Examples 1-3, resulting in the color being fixed on the fiber surface after spray dyeing, the suede whiteness is not high, the friction fastness is low, and it is easy to fade.

[0138] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A white pigment paste for spray dyeing suede leather, characterized in that: The white pigment paste for suede leather spray dyeing is prepared from castor oil polyoxyethylene ether solution, acrylic acid copolymer dispersant, polyacrylic acid sodium salt solution, aluminum silicate, rutile titanium dioxide, white carbon black, moisturizer, defoamer, bactericidal preservative, pH regulator, rheological additive and water as raw materials; the aluminum silicate is sodium aluminum silicate with a particle size of 2000-3000 mesh; the castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution has an HLB value of 14.0-16.5; Based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 2.5-5.5%, acrylic acid copolymer dispersant accounts for 2.0-7.0%, polyacrylate sodium salt solution accounts for 0.2-1.0%, aluminum silicate accounts for 17-28%, rutile titanium dioxide accounts for 17-30%, white carbon black accounts for 0.3-2.5%, humectant accounts for 3.0-9.0%, defoaming agent accounts for 0.03-0.3%, bactericidal preservative accounts for 0.05-0.4%, rheological additive accounts for 0.1-1.5%, pH regulator accounts for 0.1-0.4%, and the balance is water; The white pigment paste for suede leather spray dyeing is prepared by the following steps: Step 1, weighing raw materials, mixing and dispersing water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution, then adding castor oil polyoxyethylene ether solution and continuing to mix and disperse to obtain an additive mixture; Step 2: adding aluminum silicate and rutile titanium dioxide to the additive mixture in sequence, adding white carbon black after mixing and dispersing, and obtaining a pre-dispersed pigment slurry after high-speed dispersion, and then grinding to obtain a grinding slurry; Step 3, adding a moisturizer and a defoamer to the grinding slurry in sequence, stirring and dispersing, cooling, then adding a bactericidal preservative, stirring, adding a rheological additive and a pH regulator, and finally stirring and filtering to obtain a white pigment paste for suede spray dyeing; In step 2, the grinding is carried out in a sand mill, and the grinding conditions are as follows: the grinding speed of the sand mill is 600-1200 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.5-0.9 mm, the zirconium bead loading rate is 62-75% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 45-58° C., and the grinding is performed 3-5 times.

2. The white pigment paste for spray dyeing suede leather according to claim 1, characterized in that Based on the total weight of the raw materials, castor oil polyoxyethylene ether solution accounts for 3.0-5.0%, acrylic acid copolymer dispersant accounts for 3.0-6.0%, polyacrylate sodium salt solution accounts for 0.4-0.8%, aluminum silicate accounts for 20-28%, rutile titanium dioxide accounts for 20-28%, white carbon black accounts for 0.5-2.0%, moisturizer accounts for 4.0-8.0%, defoaming agent accounts for 0.05-0.2%, bactericidal preservative accounts for 0.1-0.3%, rheological additive accounts for 0.2-1.0%, pH regulator accounts for 0.1-0.3%, and the balance is water.

3. The white pigment paste for spray dyeing suede leather according to claim 1, characterized in that The mass percentage of castor oil polyoxyethylene ether in the castor oil polyoxyethylene ether solution is 70%, The acrylic acid copolymer dispersant is selected from one or more of an acrylic acid ester copolymer structural dispersant and a RAFT block polypropylene copolymer dispersant; The sodium polyacrylate solution is a sodium polyacrylate aqueous solution with a molecular weight of 3000-6000 and a solid content of 42±2%; The white carbon black is selected from industrial grade 2500 mesh ultrafine SiO2; The moisturizing agent is selected from one or both of polyethylene glycol 300 and caprolactam; The defoaming agent is selected from one or more of polyether modified silane defoaming agents and mineral oil defoaming agents; The bactericidal preservative is selected from one or more of isothiazolinone or benzimidazole compounds; The rheological additive is selected from one or more of a polyurethane associative rheological additive and an acrylic acid alkali swelling associative rheological additive; The pH regulator is selected from one or more of 2-amino-2-methyl-1-propanol, ammonia water, and triethanolamine.

4. A method for preparing the white pigment paste for spray dyeing suede leather according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step 1, weighing raw materials, mixing and dispersing water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution, then adding castor oil polyoxyethylene ether solution and continuing to mix and disperse to obtain an additive mixture; Step 2: adding aluminum silicate and rutile titanium dioxide to the additive mixture in sequence, adding white carbon black after mixing and dispersing, and obtaining a pre-dispersed pigment slurry after high-speed dispersion, and then grinding to obtain a grinding slurry; Step 3, adding a moisturizer and a defoamer to the grinding slurry in sequence, stirring and dispersing, cooling, then adding a bactericidal preservative, stirring, adding a rheological additive and a pH regulator, and finally stirring and filtering to obtain a white pigment paste for suede spray dyeing; In step 2, the grinding is carried out in a sand mill, and the grinding conditions are as follows: the grinding speed of the sand mill is 600-1200 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.5-0.9 mm, the zirconium bead loading rate is 62-75% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 45-58° C., and the grinding is performed 3-5 times.

5. The method according to claim 4, characterized in that In step 1, The castor oil polyoxyethylene ether solution is prepared by the following steps: heating the castor oil polyoxyethylene ether to 55-65° C. to scald the castor oil polyoxyethylene ether, adding deionized water and stirring evenly.

6. The method according to claim 4, characterized in that In step 1, Mix water, acrylic acid copolymer dispersant and polyacrylic acid sodium salt solution at a speed of 300-500 r / min and disperse for 10-15 minutes; Then add castor oil polyoxyethylene ether solution and continue stirring for 10 to 15 minutes.

7. The method according to claim 4, characterized in that In step 2, After adding aluminum silicate and rutile titanium dioxide, mix and disperse at 500-700 r / min for 10-15 minutes; After adding silica, disperse at a high speed of 900-1200 r / min for 1.5-3 hours.

8. The method according to claim 4, characterized in that The grinding conditions are as follows: the grinding speed of the sand mill is 700-1000 r / min, the particle size of the zirconium beads in the sand mill cylinder is selected to be 0.6-0.8 mm, the zirconium bead loading rate is 65-70% of the volume of the sand mill cylinder, the separator or screen aperture in the sand mill is selected to be 0.2 mm, the slurry outlet temperature in the sand mill is controlled at 50-58° C., and the grinding is performed 3-4 times.

9. The method according to claim 4, characterized in that In step 3, Add moisturizer and defoamer and stir and disperse at 300-500 r / min for 1.5-3 hours; Cool down to below 45°C and add bactericidal preservatives, then stir for 30-40 minutes, add rheological additives and pH regulators, adjust the viscosity to 4.0-9.0, and adjust the pH to 8.0-9.5.

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