Pearlescent pigments, process for their preparation and use

Abstract

The application provides a preparation method of a pearl pigment, the pearl pigment prepared by the method, and a use of the pearl pigment. The pearl pigment substrate is coated, and then the coated pearl pigment is modified by a surface modifier to change the polarity of the pearl pigment substrate. When the modified pearl pigment is used to prepare a pearl paste, the pearl pigment is uniformly dissolved and mixed in an organic solvent, is not prone to sedimentation and stratification, and the pearl paste with good stability can be obtained.

Description

Technical Field

[0001] This invention relates to a pearlescent pigment, its preparation method, and its uses, specifically to a pearlescent pigment for use in highly concentrated pearlescent paste, its preparation method, and its uses, belonging to the field of fine chemical materials technology. Background Technology

[0002] Currently, most inorganic pearlescent pigments are supplied to the market in powder form. However, this powder form is not ideal in terms of storage stability, transportation, and ease of use. Firstly, powder pigments can cause workplace contamination and pollution; although mica titanium pearlescent pigments are non-toxic, they still pose a health risk. Secondly, powder pigments have a large specific surface area, making them highly hygroscopic when exposed to air. Moisture absorption alters the surface properties of the pigment, particularly its surface tension.

[0003] Regardless of the type of pearlescent pigment, as long as it exists in powder form, it can be processed into a high-concentration paste product, commonly known as pearlescent paste, by adding solvents and appropriate additives. The amount of pearlescent pigment added to high-concentration pearlescent paste is generally 40%–50%, sometimes even exceeding 70%. Pearlescent paste has a wide range of applications, such as pearlescent pastes for coatings, pearlescent pastes for plastics, and pearlescent pastes for cosmetics.

[0004] From a macroscopic perspective, pearlescent pigments, regardless of how smooth or even the surface may appear, are actually uneven, i.e., their surface is rough. This has been confirmed by electron probe microanalysis. Rough, uneven surfaces are less susceptible to wetting by liquid media than smooth surfaces. Furthermore, during the manufacturing process, they come into contact with various complex electrolytes, especially the adsorbed free -OH groups on the surface, which are the main hydrophilic-oleophobic groups. This is the primary reason why pearlescent pigments cannot be quickly wetted and dispersed in nonpolar or very weakly polar organic solvents and resins.

[0005] In existing technologies, when pearlescent pigments are used directly, the presence of powdered pearlescent pigments leads to the generation of pearlescent pigment dust. The volatilization of this dust causes inaccurate addition of pearlescent pigment, resulting in significant color differences in the product. Furthermore, the volatilization of pearlescent pigment dust causes environmental pollution in the work area, and long-term inhalation of this dust can negatively impact the health of operators. Moreover, the volatilization of pearlescent pigment dust also results in the waste of raw materials.

[0006] To address the technical issue of pearlescent pigments generating dust during use, technicians first prepared a highly concentrated pearlescent paste in a sealed operating space. This highly concentrated paste was then used in the next process, thus preventing the generation of pearlescent pigment dust in the production workshop. By monitoring the concentration of pearlescent pigment in the paste, the pigment can be precisely added to the product, thereby improving the product's color accuracy.

[0007] In existing technologies, a mixture of resin, aromatic solvent and aliphatic hydrocarbon solvent is often used as the solvent for preparing pearlescent paste. However, due to the high polarity of pearlescent pigments, their mixing uniformity in solvents is poor. Pearlescent pigments are difficult to mix with organic solvents and are prone to sedimentation and stratification after being left for a period of time. This results in a large difference in the content of pearlescent pigments in the upper and lower layers of the pearlescent paste, and also leads to a large color difference in the product after using pearlescent pigments. Summary of the Invention

[0008] To address the technical problem that existing pearlescent pigments, due to their high polarity, are prone to sedimentation and stratification when dissolved in organic solvents to prepare pearlescent pastes, this invention proposes a method for preparing pearlescent pigments, the pearlescent pigments obtained by this method, and their applications. By coating a pearlescent pigment matrix and then modifying the coated pearlescent pigment with a surface modifier to change the polarity of the pearlescent pigment matrix, the modified pearlescent pigment is used to prepare pearlescent pastes. When the modified pearlescent pigment is used to prepare pearlescent pastes, the pearlescent pigment dissolves and mixes uniformly in the organic solvent, is less prone to sedimentation and stratification, and a pearlescent paste with good stability can be obtained.

[0009] According to a first embodiment of the present invention, a method for preparing a pearlescent pigment is provided, the method comprising the following steps:

[0010] (1) Prepare the pearlescent pigment matrix into suspension I;

[0011] (2) Add Ba(OC3H7)2 and Ti(OC5H)2 to suspension I. 11 4. Stir to obtain mixture I;

[0012] (3) Add aluminum chloride hexahydrate solution to mixture I, stir, and obtain mixture II;

[0013] (4) Mixture II is separated, washed, dried, and then calcined to obtain coated pearlescent pigment;

[0014] (5) Prepare a suspension II by coating the pearlescent pigment, add a surface modifier to the suspension II, stir, separate, wash and dry to obtain the modified pearlescent pigment.

[0015] As preferred, Ba(OC3H7)2 and Ti(OC5H)2 are preferred. 11The molar ratio of 4 is 1:0.7 to 1, preferably 1:0.75 to 0.9, more preferably 1:0.8 to 0.85, for example 1:0.7, 1:0.75, 1:0.8, 1:0.81, 1:0.82, 1:0.83, 1:0.84, 1:0.85, 1:0.9, 1:0.95, 1:1.

[0016] In this invention, the amount of Ba(OC3H7)2 added is 13% to 26% of the weight of the pearlescent pigment matrix, preferably 15% to 24%. For example, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, and 26%.

[0017] In this invention, Ti(OC5H) 11 The amount of 4 added is 14% to 40% of the weight of the pearlescent pigment matrix, preferably 17% to 34%. For example, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%.

[0018] In this invention, the pearlescent pigment matrix in step (1) is natural pearlescent powder, artificially synthesized pearlescent powder, or glass-based pearlescent pigment. Preferably, the particle size of the pearlescent pigment matrix is ​​less than 40 μm.

[0019] In this invention, the aluminum chloride hexahydrate solution mentioned in step (3) is an aluminum chloride hexahydrate solution dissolved in water.

[0020] Preferably, the concentration of aluminum chloride hexahydrate in the aluminum chloride hexahydrate solution is 40–60 g / L, more preferably 45–55 g / L; for example, 40 g / L, 41 g / L, 42 g / L, 43 g / L, 44 g / L, 45 g / L, 46 g / L, 47 g / L, 48 g / L, 49 g / L, 50 g / L, 51 g / L, 52 g / L, 53 g / L, 54 g / L, 55 g / L, 56 g / L, 57 g / L, 58 g / L, 59 g / L, and 60 g / L.

[0021] Preferably, the weight ratio of the aluminum chloride hexahydrate solution to the pearlescent pigment matrix is ​​1 to 4:1, more preferably 1.5 to 3:1. Examples include 1:1, 1.5:1, 1.8:1, 2.0:1, 2.2:1, 2.5:1, 2.6:1, 2.8:1, 3.0:1, 3.5:1, and 4.0:1.

[0022] In this invention, the surface modifier in step (5) is one or a combination of γ-aminopropyltriethoxysilane, polydimethylsiloxane, and γ-methacryloxypropyl silanes (including γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriisopropoxysilane).

[0023] Preferably, the amount of surface modifier added is 1% to 3% of the weight of the pearlescent pigment matrix, more preferably 1.5% to 2.5%, and even more preferably 1.8% to 2.2%.

[0024] In this invention, step (1) specifically involves dissolving pearlescent pigment in water, heating, stirring, and obtaining suspension I.

[0025] Preferably, the weight ratio of pearlescent pigment to water is 1:10 to 25, and more preferably 1:15 to 20.

[0026] Preferably, the heating temperature is 65–80°C, and more preferably 70–75°C.

[0027] In this invention, step (2) specifically involves: adjusting the pH of suspension I to 3.0–4.5 and controlling the pH of the reaction system, maintaining the temperature at 65–80°C (preferably 70–75°C), adding Ba(OC3H7)2 under stirring, stirring, and then adding Ti(OC5H2O)2. 11 4. Stir to obtain mixture I.

[0028] In this invention, step (3) specifically involves: adjusting the pH of mixture I to 6.5-7.5 and controlling the pH of the reaction system, controlling the temperature of mixture I to 65-80°C (preferably 70-75°C), adding aluminum chloride hexahydrate solution under stirring conditions, stirring, and obtaining mixture II.

[0029] In this invention, step (4) specifically involves: filtering mixture II sequentially, washing it with deionized water, drying it in an oxidizing atmosphere or air at 80–140°C, and then calcining it at 650–760°C for 1–20 min to obtain coated pearlescent pigment.

[0030] In this invention, step (5) specifically involves: dissolving the coated pearlescent pigment in water, heating it to 65-80°C (preferably 70-75°C), stirring, and preparing a suspension II; maintaining the system temperature at 65-80°C (preferably 70-75°C), adding a surface modifier to the suspension II, stirring, filtering, washing with deionized water, and then vacuum drying at 80-120°C to obtain the modified pearlescent pigment.

[0031] Preferably, the weight ratio of the coated pearlescent pigment to water is 1:10 to 25, and more preferably 1:15 to 20.

[0032] Preferably, the water is deionized water.

[0033] Preferably, hydrochloric acid and sodium hydroxide are used to adjust the pH value, and more preferably, 5-20% hydrochloric acid and 5-20% sodium hydroxide are used to adjust the pH value.

[0034] According to a second embodiment of the present invention, a pearlescent pigment is provided. The pearlescent pigment is prepared using the method described in the first embodiment.

[0035] According to a third embodiment of the present invention, a use of a pearlescent pigment is provided. The pearlescent pigment obtained by the method described in the first embodiment is used to prepare a highly concentrated pearlescent paste.

[0036] A highly concentrated pearlescent paste comprising a pearlescent pigment and a solvent prepared by the method described in the first embodiment.

[0037] Preferably, the solvent is an organic solvent, and more preferably one or more of resins, aromatic solvents, and aliphatic hydrocarbon solvents.

[0038] Preferably, the resin is a polyurethane resin.

[0039] Preferably, the aromatic solvent is butanone.

[0040] Preferably, the aliphatic hydrocarbon solvent is mineral oil.

[0041] Preferably, the highly concentrated pearlescent paste is used in textiles, coatings, inks, ceramics, plastics, cosmetics, or electronic components.

[0042] In this invention, the amount of pearlescent pigment added to the highly concentrated pearlescent paste is greater than 20%, preferably 30% to 80%, more preferably 35% to 70%, and even more preferably 40% to 50%.

[0043] In existing technologies, the pearlescent pigments used to prepare high-concentration pearlescent pastes are highly polar and cannot form stable mixtures with organic solvents effectively. Simple modification of the pearlescent pigments with surface modifiers has limited effect, and sedimentation and stratification remain significant after use in the preparation of high-concentration pearlescent pastes.

[0044] In this invention, pearlescent pigments are first immersed in an aqueous solution of barium diisopropoxy and titanium tetrapentoxy. Through the hydrolysis of barium diisopropoxy and titanium tetrapentoxy, barium titanate is deposited on the pearlescent pigment matrix, repairing the surface of the matrix and achieving a smooth surface. The pearlescent pigment is then coated by the hydrolysis of barium diisopropoxy and titanium tetrapentoxy, resulting in coated pearlescent pigments. Aluminum chloride hexahydrate is then added to the mixture containing the coated pearlescent pigments. The hydrolysis of aluminum chloride hexahydrate imparts adsorption properties to the repaired and smoothed substrate. After calcination, the coated pearlescent pigments undergo a better chemical reaction with the surface modifier, thereby improving the polarity of the pearlescent pigment matrix and obtaining modified pearlescent pigments. When used in high-concentration pearlescent pastes, this modified pearlescent pigment effectively solves the technical problems of sedimentation and stratification of pearlescent pigments in pearlescent pastes.

[0045] In this invention, the pearlescent pigment matrix is ​​first dissolved in water to obtain an aqueous suspension of the pearlescent pigment, and then Ba(OC3H7)2 and Ti(OC5H)2 are added. 11 4. Control the temperature and pH of the reaction system so that Ba(OC3H7)2 and Ti(OC5H)2 react in a controlled manner. 11 4. A hydrolysis reaction occurs to generate barium titanate, which is deposited on the surface of the pearlescent pigment matrix, making the surface of the pearlescent pigment matrix smooth. Then, by controlling the temperature and pH of the reaction system, an AlCl3·6H2O solution is added, causing AlCl3·6H2O to hydrolyze and obtain aluminum hydroxide precipitate. The aluminum hydroxide precipitate is deposited on the surface of the pearlescent pigment matrix, improving the adsorption performance of the pearlescent pigment. Then, the coated pearlescent pigment is modified with a surfactant, thereby changing the polarity of the pearlescent pigment.

[0046] Through experimental verification, the inventors found that only barium titanate obtained by hydrolyzing barium diisopropoxy and tetrapentoxy titanium achieved the best coating effect on the surface of pearlescent pigment matrix. Coating the pearlescent pigment matrix surface with a mixture of titanium oxalate and calcium chloride to obtain calcium titanate, or with tetrabutyl titanate and ferric chloride to obtain ferric titanate, followed by hydrolysis deposition with AlCl3·6H2O solution and modification with surface modifiers, all yielded unsatisfactory results.

[0047] Theoretically, the molar ratio of barium diisopropoxy and tetrapentoxytitanium to barium titanate via hydrolysis is 1:1. However, the inventors further discovered through experiments that, under the same subsequent process, when barium diisopropoxy and tetrapentoxytitanium hydrolyze to form barium titanate and deposit it on the surface of the pearlescent pigment, a slight excess of barium diisopropoxy resulted in a modified pearlescent pigment with better performance and more outstanding stability when used to prepare high-concentration pearlescent paste. Experimental verification showed that Ba(OC3H7)2 and Ti(OC5H... 11The effect is best when the molar ratio of 4 added is 1:0.7 to 1 (preferably 1:0.75 to 0.9, more preferably 1:0.8 to 0.85).

[0048] Through analysis, the inventors discovered that during the hydrolysis of barium diisopropoxy and tetrapentoxytitanium to form barium titanate deposited on the surface of pearlescent pigments, a slight excess of barium diisopropoxy was present. A portion of the barium diisopropoxy and tetrapentoxytitanium underwent hydrolysis to form barium titanate, while the remaining barium diisopropoxy was adsorbed onto the pearlescent pigment surface. This barium diisopropoxy, along with the subsequent hydrolysis products of aluminum chloride hexahydrate (aluminum hydroxide), was calcined to form a barium-aluminum alloy. The deposition of barium titanate on the pearlescent pigment surface increased the adhesion of barium diisopropoxy. Furthermore, the calcination of barium diisopropoxy and aluminum hydroxide to form the barium-aluminum alloy further increased the adsorption of alumina on the pearlescent pigment surface, resulting in a composite structure of alumina / barium oxide (surface layer)-barium titanate-pearlescent pigment matrix. Barium titanate smoothed the pearlescent pigment surface and connected the alumina, while barium oxide connected and fixed the barium titanate and alumina. Through alumina adsorption, it acted as a surface modifier, altering the polarity of the pearlescent pigment. In addition, barium oxide also acts as a surface modifier to modify the polarity of pearlescent pigments.

[0049] The invention further verifies through experiments that during the hydrolysis of barium diisopropoxy and tetrapentoxy titanium to form barium titanate deposited on the surface of pearlescent pigments, the excess of barium diisopropoxy is relatively large (Ba(OC3H7)2 and Ti(OC5H)2). 11 If the molar ratio of added barium titanate (4) is less than 1:0.7, it affects the formation of barium titanate and results in excessive diisopropoxy barium in the barium titanate, thus affecting the deposition of barium titanate on the pearlescent pigment surface and consequently the smoothness of the pearlescent pigment. Simultaneously, because excessive diisopropoxy barium is adsorbed in the barium titanate, the diisopropoxy barium forms barium oxide after calcination, which also affects the bonding force between barium titanate and the pearlescent pigment, easily causing barium titanate to detach and thus affecting the modification effect. If the amount of added barium diisopropoxy is equal to the amount of added tetrapentoxy titanium, then during the hydrolysis of barium diisopropoxy and tetrapentoxy titanium to form barium titanate deposited on the pearlescent pigment surface, the diisopropoxy barium and tetrapentoxy titanium will just undergo the hydrolysis reaction to form barium titanate, leaving no excess diisopropoxy barium adsorbed on the pearlescent pigment surface. This is not conducive to the subsequent formation of barium-aluminum alloy, thus affecting the modification effect. If the amount of barium diisopropoxy added is less than that of tetrapentoxytitanium (Ba(OC3H7)2) and Ti(OC5H) 11 If the molar ratio of added 4 is greater than 1:1, then all of the barium diisopropoxy will react, and the remaining product will be Ti(OC5H). 11 )4, Ti(OC5H 11The adsorption of 4 hinders the adsorption of aluminum hydroxide, resulting in a smaller amount of aluminum hydroxide adsorbed on the surface of pearlescent pigments, which in turn affects the subsequent modification by surface modifiers and thus affects the modification performance.

[0050] In this invention, Ba(OC3H7)2 and Ti(OC5H) 11 Barium titanate is obtained by hydrolysis of 4, followed by aluminum hydroxide by hydrolysis of aluminum chloride hexahydrate. After calcination, a pearlescent pigment coated with barium, titanium, and aluminum oxides is obtained. Then, a surface modifier is used to modify the pigment, thereby altering its polarity. In a preferred embodiment of the invention, a slightly excess of barium diisopropoxy is used to obtain a barium titanate-pearlescent pigment matrix adsorbed with barium diisopropoxy. Then, aluminum hydroxide is obtained by hydrolysis of aluminum chloride hexahydrate, followed by calcination, resulting in a pearlescent pigment coated with barium, titanium, barium-aluminum, and aluminum oxides. This is then further modified with a surface modifier to change the pigment's polarity, resulting in a pearlescent pigment with improved modified properties.

[0051] In this invention, the order in which barium diisopropoxy and tetrapentoxy titanium are added also affects the final modified properties of the pearlescent pigment. Experiments revealed that adding barium diisopropoxy first, stirring thoroughly, and then slowly adding tetrapentoxy titanium results in the formation of uniformly sized barium titanate particles deposited on the pearlescent pigment surface, with excess barium diisopropoxy uniformly adsorbed onto the surface of the barium titanate particles. However, if tetrapentoxy titanium is added first, stirred thoroughly, and then barium diisopropoxy is added, barium titanate particles form rapidly and tend to accumulate on the pearlescent pigment surface, and excess barium diisopropoxy is difficult to uniformly adsorb onto the surface of the barium titanate particles.

[0052] In this invention, step (4) involves drying in an oxidizing atmosphere or air to obtain pearlescent pigments coated with barium oxide, titanium oxide, barium titanate particles, and alumina. Step (5) involves drying in a vacuum environment to ensure the modifying properties of the surface modifier, thereby obtaining modified pearlescent pigments.

[0053] In this invention, the undefined operations such as heating, stirring, pH adjustment, filtration, and washing are all conventional operations in the field.

[0054] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0055] 1. In this invention, the pearlescent pigments are Ba(OC3H7)2 and Ti(OC5H)2. 11 Soaking in a solution of 4, using Ba(OC3H7)2 and Ti(OC5H) 11The hydrolysis reaction of 4 yields pearlescent pigments with barium titanate deposited on the surface. The surface of the pearlescent pigment is smoothed by the barium titanate, resulting in a smooth surface. A continuous, smooth coating is formed by coating the pearlescent pigment with metal oxides. The friction between the smooth-surfaced pigment particles is significantly reduced, and the tendency for them to stick together and aggregate is also decreased, achieving the effect of isolating the pigment particles from each other, thereby improving its dispersibility in various polar liquid media.

[0056] 2. By adjusting Ba(OC3H7)2 and Ti(OC5H) 11 By using a dosage ratio of 4, pearlescent pigments coated with barium titanate and barium oxide are obtained. Through the adsorption of barium oxide and aluminum oxide, the modification ability of the surface modifier is enhanced, resulting in pearlescent pigments with weaker polarity. When used to prepare highly concentrated pearlescent pastes, the problems of sedimentation and stratification are better solved.

[0057] 3. During the hydrolysis of barium diisopropoxy and tetrapentoxy titanium to form barium titanate deposited on the surface of pearlescent pigments, targeted selection of Ba(OC3H7)2 and Ti(OC5H)2 is used. 11 By adjusting the order of addition of 4, a mixture I with uniform barium titanate particle size and uniform adsorption of Ba(OC3H7)2 is obtained, which in turn forms a stable barium-aluminum oxide on the surface of the pearlescent pigment, further enhancing the modification performance.

[0058] 4. This invention reacts the surfactant modifier on the surface of the pearlescent pigment with some groups, transforming the pearlescent pigment from hydrophilic to oleophilic and hydrophobic. This increases the affinity of the pigment with non-polar resins and solvents, and also provides anti-precipitation effects, while ensuring the storage stability of the slurry. Attached Figure Description

[0059] Figure 1 This is a scanning electron microscope image of the pearlescent pigment I obtained in this invention;

[0060] Figure 2 Here is a scanning electron microscope image of the pearlescent pigment VI obtained in this invention;

[0061] Figure 3 The images show the effects of sedimentation experiments on the pearlescent pigment XI of the present invention (sedimentation times of 0.5h, 3h, and 12h, respectively).

[0062] Figure 4 The images show the effects of sedimentation experiments on the pearlescent pigment I of the present invention (sedimentation times of 0.5h, 3h, and 12h, respectively).

[0063] Figure 5 The images show the effects of sedimentation experiments on the pearlescent pigment VI of this invention (sedimentation times of 0.5h, 3h, and 12h, respectively).

[0064] Figure 6a This is a diagram showing the effect of the first wettability test on the pearlescent pigment XI of the present invention;

[0065] Figure 6b This is a diagram showing the effect of a second wettability test on the pearlescent pigment XI of the present invention;

[0066] Figure 6c This is a diagram showing the effect of the third wettability test on the pearlescent pigment XI of the present invention;

[0067] Figure 7a This is a diagram showing the effect of the first wettability test of the pearlescent pigment XII of the present invention;

[0068] Figure 7b This is a diagram showing the effect of a second wettability test on the pearlescent pigment XII of the present invention;

[0069] Figure 7c This is a diagram showing the effect of the third wettability test on the pearlescent pigment XII of the present invention;

[0070] Figure 8a This is a diagram showing the effect of the first wettability test on the pearlescent pigment VI of the present invention;

[0071] Figure 8b This is a diagram showing the effect of a second wettability test on the pearlescent pigment VI of the present invention;

[0072] Figure 8c This is a diagram showing the effect of the third wettability test on the pearlescent pigment VI of the present invention;

[0073] Figure 9 The diagrams (top view and front view) show the effect of the activation index experiment on the pearlescent pigment XI of the present invention.

[0074] Figure 10 The diagrams (top view and front view) show the effect of the activation index experiment on the pearlescent pigment I of the present invention.

[0075] Figure 11 The diagrams (top view and front view) show the effect of the activation index experiment on the pearlescent pigment VI of the present invention. Detailed Implementation

[0076] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0077] The sources of the substances used in the embodiments of this invention are as follows:

[0078]

[0079] Preparation Example 1

[0080] A method for preparing a pearlescent pigment, the method comprising the following steps:

[0081] (1) Put 80g of natural mica into a 2L reactor, add 1600ml of deionized water, heat to 70℃, stir, and obtain suspension I;

[0082] (2) The pH of suspension I was adjusted to 4 using a 10% hydrochloric acid solution, and the pH of the reaction system was controlled using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution. The temperature was maintained at 70℃. Under stirring, 16g of Ba(OC3H7)2 was added and stirred for 30min. Then, 24g of Ti(OC5H2O)2 was added. 11 4. Stir for 30 minutes to obtain mixture I;

[0083] (3) The pH of mixture I was adjusted to 7 by using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution and the pH of the reaction system was controlled. The temperature of mixture I was controlled to 70℃. Under stirring conditions, 160g of 50g / L aluminum chloride hexahydrate solution was added and stirred to obtain mixture II.

[0084] (4) After filtering and washing with deionized water, mixture II was dried in air at 120°C and then calcined at 720°C for 5 min to obtain coated pearlescent pigment.

[0085] (5) Dissolve the coated pearlescent pigment in water, heat to 70°C, stir, and prepare suspension II; maintain the system temperature at 70°C, adjust the pH of mixture I to 7 using 10% hydrochloric acid solution and 10% sodium hydroxide solution, add 1.6g γ-aminopropyltriethoxysilane to suspension II, stir for 120min, filter, wash twice with deionized water, and vacuum dry at 100°C to obtain modified pearlescent pigment I.

[0086] Preparation Example 2

[0087] A method for preparing a pearlescent pigment, the method comprising the following steps:

[0088] (1) Put 80g of natural mica into a 2L reactor, add 1600ml of deionized water, heat to 70℃, stir, and obtain suspension I;

[0089] (2) The pH of suspension I was adjusted to 4 using a 10% hydrochloric acid solution, and the pH of the reaction system was controlled using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution. The temperature was maintained at 70℃, and 24g of Ti(OC5H) was added under stirring. 114. Stir for 30 minutes, then add 16g Ba(OC3H7)2 and stir for 30 minutes to obtain mixture I;

[0090] (3) The pH of mixture I was adjusted to 7 by using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution and the pH of the reaction system was controlled. The temperature of mixture I was controlled to 70℃. Under stirring conditions, 160g of 50g / L aluminum chloride hexahydrate solution was added and stirred to obtain mixture II.

[0091] (4) After filtering and washing with deionized water, mixture II was dried in air at 120°C and then calcined at 720°C for 5 min to obtain coated pearlescent pigment.

[0092] (5) Dissolve the coated pearlescent pigment in water, heat to 70°C, stir, and prepare suspension II; maintain the system temperature at 70°C, adjust the pH of mixture I to 7 using 10% hydrochloric acid solution and 10% sodium hydroxide solution, add 1.6g γ-aminopropyltriethoxysilane to suspension II, stir for 120min, filter, wash twice with deionized water, and vacuum dry at 100°C to obtain modified pearlescent pigment II.

[0093] Preparation Example 3

[0094] Using the method of Preparation Example 1, Ba(OC3H7)2 and Ti(OC5H)2 were adjusted according to the table below. 11 The dosage of 4 was the same as in Preparation Example 1, and other conditions were the same. Experiments were conducted to obtain modified pearlescent pigments III to IX.

[0095]

[0096] Preparation Example 4

[0097] Example 1 was prepared repeatedly, except that the pearlescent pigment matrix was made of synthetic mica powder.

[0098] Preparation Example 5

[0099] Example 1 was prepared repeatedly, except that the pearlescent pigment matrix was made of glass-based pearlescent pigment.

[0100] Preparation Example 6

[0101] Example 1 was prepared repeatedly, except that polydimethylsiloxane was used as the surface modifier.

[0102] Preparation Example 7

[0103] Example 1 was repeated, except that the surface modifier used was γ-methacryloyloxypropyltrimethoxysilane.

[0104] Comparative Example 1

[0105] A method for preparing a pearlescent pigment, the method comprising the following steps: washing 80g of natural mica with deionized water, filtering, and vacuum drying at 100℃ to obtain pearlescent pigment X;

[0106] Comparative Example 2

[0107] A method for preparing a pearlescent pigment, the method comprising the following steps:

[0108] (1) Put 80g of natural mica into a 2L reactor, add 1600ml of deionized water, heat to 70℃, stir, and obtain suspension I;

[0109] (2) The pH of mixture I was adjusted to 7 using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution; the temperature of suspension I was controlled at 70℃; under stirring conditions, 160g of 50g / L aluminum chloride hexahydrate solution was added and stirred to obtain mixture I.

[0110] (3) After filtering and washing with deionized water, mixture I was dried in air at 120°C and then calcined at 720°C for 5 min to obtain pearlescent pigment.

[0111] (4) Dissolve the pearlescent pigment in water, heat to 70°C, stir, and prepare suspension II; maintain the system temperature at 70°C, add 1.6g of γ-aminopropyltriethoxysilane to suspension II, stir for 120min, filter, wash twice with deionized water, and then vacuum dry at 100°C to obtain pearlescent pigment XI.

[0112] Comparative Example 3

[0113] A method for preparing a pearlescent pigment, the method comprising the following steps:

[0114] (1) Put 80g of natural mica into a 2L reactor, add 1600ml of deionized water, heat to 70℃, stir, and obtain suspension I;

[0115] (2) Preparation of titanium oxalate solution: Mix 2 mol / L titanium tetrachloride solution and 2 mol / L oxalic acid solution and react to obtain titanium oxalate solution; add deionized water to prepare a 0.6 mol / L titanium oxalate solution.

[0116] (3) The pH of suspension I was adjusted to 4 using a 10% hydrochloric acid solution and the pH of the reaction system was controlled using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution. The temperature was maintained at 70℃. Under stirring conditions, 6.66g of calcium chloride was added and stirred for 30min. Then 100ml of 0.6mol / L titanium oxalate was added and stirred for 30min to obtain mixture I.

[0117] (4) The pH of mixture I was adjusted to 7 by using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution and the pH of the reaction system was controlled. The temperature of mixture I was controlled to 70℃. Under stirring conditions, 160g of 50g / L aluminum chloride hexahydrate solution was added and stirred to obtain mixture II.

[0118] (5) After filtering and washing with deionized water, mixture II was dried in air at 120°C and then calcined at 720°C for 5 min to obtain coated pearlescent pigment.

[0119] (6) Dissolve the coated pearlescent pigment in water, heat to 70°C, stir, and prepare suspension II; maintain the system temperature at 70°C, adjust the pH of mixture I to 7 using 10% hydrochloric acid solution and 10% sodium hydroxide solution, add 1.6g γ-aminopropyltriethoxysilane to suspension II, stir for 120min, filter, wash twice with deionized water, and vacuum dry at 100°C to obtain modified pearlescent pigment XII.

[0120] Comparative Example 4

[0121] A method for preparing a pearlescent pigment, the method comprising the following steps:

[0122] (1) Put 80g of natural mica into a 2L reactor, add 1600ml of deionized water, heat to 70℃, stir, and obtain suspension I;

[0123] (2) The pH of suspension I was adjusted to 4 using a 10% hydrochloric acid solution and the pH of the reaction system was controlled using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution. The temperature was maintained at 70℃. Under stirring conditions, 9.72g of ferric chloride was added and stirred for 30min. Then 100ml of 0.6mol / L tetrabutyl titanate was added and stirred for 30min to obtain mixture I.

[0124] (3) The pH of mixture I was adjusted to 7 by using a 10% hydrochloric acid solution and a 10% sodium hydroxide solution and the pH of the reaction system was controlled. The temperature of mixture I was controlled to 70℃. Under stirring conditions, 160g of 50g / L aluminum chloride hexahydrate solution was added and stirred to obtain mixture II.

[0125] (4) After filtering and washing with deionized water, mixture II was dried in air at 120°C and then calcined at 720°C for 5 min to obtain coated pearlescent pigment.

[0126] (5) Dissolve the coated pearlescent pigment in water, heat to 70°C, stir, and prepare suspension II; maintain the system temperature at 70°C, adjust the pH of mixture I to 7 using 10% hydrochloric acid solution and 10% sodium hydroxide solution, add 1.6g γ-aminopropyltriethoxysilane to suspension II, stir for 120min, filter, wash twice with deionized water, and vacuum dry at 100°C to obtain modified pearlescent pigment XIII.

[0127] Application Example 1

[0128] In a 1L beaker, the pearlescent pigments (or modified pearlescent pigments) I to XIII prepared in the preparation example were mixed with polyurethane resin, methyl ethyl ketone, and mineral oil in a volume ratio of 1.75:1:1 to prepare a pearlescent paste with a mass concentration of 45%, and stirred evenly.

[0129] Experiment I: Viscosity Test

[0130] The viscosity of pearlescent pastes containing pearlescent pigments (or modified pearlescent pigments) I to XIII was tested according to GB / T 10247-2008.

[0131]

[0132]

[0133] Experiment II: Settlement Test

[0134] Pearl pigments (or modified pearl pigments) I to XIII were transferred into 100ml stoppered graduated cylinders and placed to the 100ml mark. After standing for 0.5h, 3h, and 12h, the height of the pearl pigments settled at the bottom of the stoppered graduated cylinder was measured and the scale value was read.

[0135]

[0136]

[0137] Experiment III: Wetting Test (average of three parallel experiments)

[0138] The wettability of pearlescent pigments (or modified pearlescent pigments) I to XIII was tested according to HG 3744-2004. This method can study the adsorption of liquids into powders, pigments, and other porous solids by recording mass changes over time. The obtained curves provide information on adsorption amount and kinetics. The wetting of powders and pigments involves contact angle phenomena, which can be defined by Wasburn theory.

[0139] The contact angle indicates the degree of wetting when a solid and liquid interact. A lower contact angle indicates greater wettability and worse hydrophobicity (oleophilicity). A contact angle below 90° indicates that the liquid flows spontaneously within the solid (in a thermodynamic, not kinetic, sense), while a contact angle above 90° indicates that the liquid does not wet the solid. The results are as follows:

[0140] Pearl pigments (or modified pearl pigments) I 106.8 Pearl pigments (or modified pearl pigments) II 92.1 Pearl pigments (or modified pearl pigments) III 104.5 Pearl pigments (or modified pearl pigments) IV 114.3 Pearl pigments (or modified pearl pigments) V 121.2 Pearl pigments (or modified pearl pigments) VI 124.4 Pearl pigments (or modified pearl pigments) VII 121.7 Pearl pigments (or modified pearl pigments) VIII 115.6 Pearl pigments (or modified pearl pigments) IX 101.9 Pearl pigment (or modified pearl pigment) X 16.4 Pearl pigment (or modified pearl pigment) XI 23.8 Pearl pigments (or modified pearl pigments) XII 42.0 Pearl pigments (or modified pearl pigments) XIII 46.3

[0141] Experiment IV: Oil Absorption Test

[0142] The oil absorption of pearlescent pigments (or modified pearlescent pigments) I to XIII was tested separately. The test method was as follows: the amount of refined linseed oil absorbed by the pigment sample under specified conditions. It can be expressed as volume / mass or mass / mass.

[0143] Instruments and reagents:

[0144] a) Flat surface: marble, with dimensions not less than 300mm x 400mm;

[0145] b) Blade: Steel, tapered blade, approximately 140-150mm long, 20-25mm at its widest point, and no less than 12.5mm at its narrowest point;

[0146] c) Dropper;

[0147] d) Analyze the balance;

[0148] e) Refined linseed oil with an acid value of 5.0–7.0 mg KOH / g.

[0149] Experimental steps:

[0150] Accurately weigh 1.0 to 1.5 g of the sample, accurate to 0.0001 g, place it on a plate, and add it dropwise using a dropper.

[0151] For refined linseed oil, the amount added each time should not exceed 10 drops. After adding, use a spatula to press and grind to allow the oil to penetrate the test sample. Continue adding at this rate until the oil and sample form a clump. From this point onward, after each drop, grind thoroughly with a spatula. The endpoint is reached when a uniform paste of consistency is formed, which is neither cracked nor broken, and can adhere to a plate.

[0152] Record the amount of oil consumed. All operations should be completed within 20 to 25 minutes.

[0153] The results indicate that:

[0154] Oil absorption capacity is expressed as the amount of oil required per 100g of product, and is calculated using the following formula:

[0155] In the formula: M - amount of linseed oil, g; m - mass of the sample, g.

[0156] Oil absorption rate can be used as an evaluation method for selecting modifier formulations. Generally speaking, for inorganic fillers used in polymer-based composites, the lower the oil absorption value, the easier it is to mix with the resin system.

[0157] The experimental results are as follows:

[0158]

[0159]

[0160] The pearlescent pigments modified by this invention have a smooth surface and a lower oil absorption value.

[0161] Experiment V: Activation Index Test

[0162] The activation index of pearlescent pigments (or modified pearlescent pigments) I to XIII was tested. For organic surface modification aimed at improving the compatibility or hydrophobicity of inorganic powders with polymer matrices, the "activation index" can be used to characterize the effect of surface modification. Inorganic powders generally have a high relative density and a polar surface, naturally settling in water. Most organic surface modifiers are water-insoluble or non-polar; therefore, the surface of the organically modified inorganic powder changes from polar to non-polar, exhibiting strong non-wetting properties in water. These non-wetting, finely dispersed particles, due to hydrophobicity and surface tension, float on the water surface like an oil film. Based on this phenomenon, the concept of the "activation index," denoted by H, was proposed.

[0163] The method for determining the activation index is as follows: Weigh a certain amount (e.g., 10g) of surface-modified powder sample and place it in a beaker containing a certain volume (e.g., 100mL) of purified water. Stir at a certain speed for 1-2 minutes. Let it stand until the solution becomes clear. Scrape off the powder material on the surface of the aqueous solution, and filter, dry, and weigh the powder material that has settled to the bottom of the beaker. Then calculate the activation index according to the formula, i.e.

[0164]

[0165] The experimental results are as follows:

[0166]

[0167]

[0168] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a pearlescent pigment, the method comprising the following steps: (1) Prepare a suspension I from the pearlescent pigment matrix; (2) Adjust the pH of suspension I to 3.0~4.5 and control the pH value of the reaction system. Maintain the temperature at 65~80℃. Under stirring, add Ba(OC3H7)2, stir, and then add Ti(OC5H 11 4. Stir to obtain mixture I; Ba(OC3H7)2 and Ti(OC5H 11 The molar ratio of 4 added is 1:0.7~1; (3) Add aluminum chloride hexahydrate solution to mixture I, stir, and obtain mixture II; (4) Mixture II is separated, washed, dried, and then calcined to obtain coated pearlescent pigment; (5) Prepare a suspension II by coating the pearlescent pigment, add a surface modifier to the suspension II, stir, separate, wash and dry to obtain the modified pearlescent pigment.

2. The preparation method according to claim 1, characterized in that: The amount of Ba(OC3H7)2 added is 13%~26% of the weight of the pearlescent pigment matrix; Ti(OC5H 11 The amount of 4 added is 14% to 40% of the weight of the pearlescent pigment matrix.

3. The preparation method according to claim 2, characterized in that: Ba(OC3H7)2 and Ti(OC5H 11 The molar ratio of added 4 is 1:0.75~0.9; the amount of added Ba(OC3H7)2 is 15%~24% of the weight of the pearlescent pigment matrix; Ti(OC5H 11 The amount of 4 added is 17% to 34% of the weight of the pearlescent pigment matrix.

4. The preparation method according to claim 3, characterized in that: Ba(OC3H7)2 and Ti(OC5H 11 The molar ratio of 4 added is 1:0.8~0.

85.

5. The preparation method according to claim 1, characterized in that: The pearlescent pigment matrix mentioned in step (1) is natural pearlescent powder, artificially synthesized pearlescent powder, or glass-based pearlescent pigment; and / or The aluminum chloride hexahydrate solution mentioned in step (3) is a solution of aluminum chloride hexahydrate dissolved in water, and the concentration of aluminum chloride hexahydrate in the aluminum chloride hexahydrate solution is 40~60g / L; the weight ratio of the amount of aluminum chloride hexahydrate solution added to the weight of the pearlescent pigment matrix is ​​1~4:

1.

6. The preparation method according to claim 5, characterized in that: The concentration of aluminum chloride hexahydrate in the aluminum chloride hexahydrate solution is 45~55 g / L; the weight ratio of the amount of aluminum chloride hexahydrate solution added to the weight of the pearlescent pigment matrix is ​​1.5~3:

1.

7. The preparation method according to claim 1, characterized in that: The surface modifier mentioned in step (5) is one or more combinations of γ-aminopropyltriethoxysilane, polydimethylsiloxane, and γ-methacryloyloxypropyl silane; the amount of surface modifier added is 1% to 3% of the weight of the pearlescent pigment matrix.

8. The preparation method according to claim 1, characterized in that: Step (1) specifically involves dissolving the pearlescent pigment in water, heating and stirring to obtain suspension I; the weight ratio of the pearlescent pigment to water is 1:10~25; the heating temperature is 65~80℃.

9. The preparation method according to claim 8, characterized in that: In step (1): the weight ratio of pearlescent pigment to water is 1:15~20; the heating temperature is 70~75℃; and / or In step (2): maintain the reaction temperature at 70~75℃.

10. The preparation method according to claim 1, characterized in that: Step (3) specifically involves: adjusting the pH of mixture I to 6.5-7.5 and controlling the pH of the reaction system; controlling the temperature of mixture I to 65-80℃; adding aluminum chloride hexahydrate solution under stirring conditions; and stirring to obtain mixture II; and / or Step (4) is as follows: after filtering and washing with deionized water, mixture II is dried in an oxidizing atmosphere or air at 80~140℃, and then calcined at 650~760℃ for 1~20min to obtain coated pearlescent pigment.

11. The preparation method according to claim 10, characterized in that: In step (3): the temperature of mixture I is controlled to be 70~75℃.

12. The preparation method according to claim 1, characterized in that: Step (5) is as follows: dissolve the coated pearlescent pigment in water, heat to 65~80℃, stir, and prepare suspension II; maintain the system temperature at 65~80℃, add surface modifier to suspension II, stir, filter, wash with deionized water, and vacuum dry at 80~120℃ to obtain modified pearlescent pigment.

13. The preparation method according to claim 12, characterized in that: Step (5) is as follows: dissolve the coated pearlescent pigment in water, heat to 70~75℃, stir, and prepare suspension II; maintain the system temperature at 70~75℃, add surface modifier to suspension II, stir, filter, wash with deionized water, and vacuum dry at 80~120℃ to obtain modified pearlescent pigment.

14. The preparation method according to claim 12, characterized in that: The weight ratio of the coated pearlescent pigment to water is 1:10~25.

15. The preparation method according to claim 14, characterized in that: The weight ratio of the coated pearlescent pigment to water is 1:15~20.

16. The preparation method according to claim 8, characterized in that: The water is deionized water; and / or The pH value is adjusted using hydrochloric acid and sodium hydroxide.

17. The preparation method according to claim 16, characterized in that: Adjust the pH value using 5-20% hydrochloric acid and 5-20% sodium hydroxide.

18. A pearlescent pigment prepared by the preparation method according to any one of claims 1-17.

19. The use of a pearlescent pigment prepared by the preparation method according to any one of claims 1-17, characterized in that: The pearlescent pigment is used in a highly concentrated pearlescent paste.

20. The use according to claim 19, characterized in that: The highly concentrated pearlescent paste can be used in textiles, coatings, inks, ceramics, plastics, cosmetics, or electronic components.

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