Preparation method of calcium sulfate whisker

Abstract

The invention belongs to the technical field of calcium sulfate whiskers, and particularly relates to a preparation method of calcium sulfate whiskers. The preparation method of the calcium sulfate whisker comprises the following steps: carrying out first mixing on a calcium sulfate solution and anionic fibers, and carrying out crystal nucleus growth; the length of the anionic fiber is 0.02 to 50 [mu] m, and the diameter of the anionic fiber is 5 to 100 nm; and mixing the system in which the crystal nucleus is formed with a second growth regulator, and carrying out whisker growth to obtain the calcium sulfate whisker. According to the invention, the anionic fiber is used as the template to prepare the calcium sulfate whisker, so that the defects of the calcium sulfate whisker can be reduced while the size of the calcium sulfate whisker is regulated and controlled, the dispersion stability is improved, and the agglomeration phenomenon of the calcium sulfate whisker is reduced. The growth regulator is added in the preparation process, so that the growth of the calcium sulfate whiskers in the longitudinal direction can be limited, and the length-diameter ratio of the calcium sulfate whiskers is increased. The calcium sulfate whisker prepared by the preparation method provided by the invention has high length-diameter ratio and is not easy to agglomerate.

Description

Technical Field

[0001] This invention belongs to the field of calcium sulfate whisker technology, specifically relating to a method for preparing calcium sulfate whiskers. Background Technology

[0002] Calcium sulfate whiskers typically range in diameter from a few micrometers to tens of micrometers, and can reach lengths of several hundred micrometers, exhibiting excellent physical and chemical stability. Calcium sulfate whiskers have a wide range of applications, primarily serving as reinforcing materials, fillers, thickeners, pigment carriers, abrasion and scratch-resistant additives, temperature-resistant additives, thickeners and stabilizers in adhesives and sealants, and paper strengthening agents. Furthermore, calcium sulfate whiskers possess advantages such as being non-toxic, heat-resistant, chemically resistant, tough, strong, easy to surface-treat, and having strong affinity for polymers like rubber and plastics, thus offering significant advantages in environmental and industrial applications.

[0003] However, during use, calcium sulfate whiskers are prone to agglomeration due to van der Waals forces and hydrogen bonds (mediated by surface-adsorbed water molecules), thus affecting their performance. Currently, the main approach to improve this agglomeration is by modifying the surface of the calcium sulfate whiskers. However, while existing modification methods have improved agglomeration to some extent, they have also reduced the length of the calcium sulfate whiskers. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing calcium sulfate whiskers. The calcium sulfate whiskers provided by the present invention have a high aspect ratio and good dispersion stability and are not prone to agglomeration.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing calcium sulfate whiskers, comprising the following steps:

[0006] A calcium sulfate solution and anionic fibers are first mixed and then subjected to crystal nucleation growth; the length of the anionic fibers is 0.02-50 μm and the diameter is 5-100 nm.

[0007] After the crystal nuclei are formed, the system is mixed with the second growth regulator and then whisker growth is carried out to obtain calcium sulfate whiskers.

[0008] Preferably, the anionic fiber includes one or more of bacterial cellulose, microfibrillated cellulose, cellulose nanofibers, polyacrylonitrile-based carbon nanofibers, polystyrene nanofibers, polylactic acid nanofibers, polyvinyl acetate nanofibers, lignocellulose nanofibers, carboxylated cellulose nanofibers, sulfonated cellulose nanofibers, carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, and carbon nanotube fibers.

[0009] Preferably, the mass ratio of calcium sulfate to anionic fiber in the calcium sulfate solution is 100:1 to 10.

[0010] Preferably, the mass concentration of the calcium sulfate solution is 0.05% to 5%.

[0011] Preferably, the first mixing is carried out under stirring conditions, wherein the stirring temperature is 38-42°C and the stirring time is 0.3-0.6h.

[0012] Preferably, the temperature for crystal nucleus growth is 90–98°C, and the time is 2.5–3.5 h.

[0013] Preferably, the growth regulator comprises one or more of sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium stearate, sodium salt of acrylic acid-maleic acid copolymer, citric acid, hexadecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

[0014] Preferably, the molar concentration of the growth regulator in the second mixed system is 0.1–3 mmol / L.

[0015] Preferably, the whisker growth temperature is 120–250°C and the time is 2–10 h.

[0016] Preferably, the process after whisker growth further includes: cooling the whisker-grown system and then sequentially washing, filtering, and drying it.

[0017] This invention provides a method for preparing calcium sulfate whiskers, comprising the following steps: firstly, mixing a calcium sulfate solution with anionic fibers and then performing crystal nucleus growth; the anionic fibers have a length of 0.02–50 μm and a diameter of 5–100 nm; secondly, mixing the nucleated system with a growth regulator and then performing whisker growth to obtain calcium sulfate whiskers. This invention uses anionic fibers as templates to prepare calcium sulfate whiskers, achieving size control while reducing defects, improving dispersion stability, and reducing agglomeration. The addition of a growth regulator during the preparation process restricts the longitudinal growth of calcium sulfate whiskers, increasing their aspect ratio. The calcium sulfate whiskers prepared according to this invention have a high aspect ratio and are less prone to agglomeration. Attached Figure Description

[0018] Figure 1 SEM image of calcium sulfate whiskers prepared in Example 1;

[0019] Figure 2 SEM image of calcium sulfate whiskers prepared in Example 2;

[0020] Figure 3 SEM image of calcium sulfate whiskers prepared in Example 3;

[0021] Figure 4 This is a SEM image of calcium sulfate dihydrate;

[0022] Figure 5 SEM image of calcium sulfate whiskers prepared in Comparative Example 1;

[0023] Figure 6 SEM image of the calcium sulfate whiskers prepared in Comparative Example 2;

[0024] Figure 7 SEM image of calcium sulfate whiskers prepared in Comparative Example 3;

[0025] Figure 8 SEM image of the calcium sulfate whiskers prepared in Comparative Example 4;

[0026] Figure 9 The XRD patterns of calcium sulfate whiskers prepared in Example 1 and Comparative Example 4 are shown in comparison.

[0027] Figure 10 The images show a comparison of the calcium sulfate whiskers prepared in Example 1 and Comparative Example 4 after being dispersed in water and left to stand for 0, 1, 5, and 10 days. The image on the left is the calcium sulfate whisker dispersion of Example 1, and the image on the right is the calcium sulfate whisker dispersion of Comparative Example 4. Detailed Implementation

[0028] This invention provides a method for preparing calcium sulfate whiskers, comprising the following steps:

[0029] A calcium sulfate solution and anionic fibers are first mixed and then subjected to crystal nucleation growth; the length of the anionic fibers is 0.02-50 μm and the diameter is 5-100 nm.

[0030] After the crystal nuclei are formed, the system is mixed with the second growth regulator and then whisker growth is carried out to obtain calcium sulfate whiskers.

[0031] This invention involves mixing a calcium sulfate solution with anionic fibers and then performing crystal nucleation growth. In one specific embodiment, the calcium sulfate solution is obtained by dissolving calcium sulfate in a solvent; the purity of the calcium sulfate can be no less than 90%, and can also be 92-95%; the calcium sulfate can be calcium sulfate dihydrate, calcium sulfate hemihydrate, or anhydrous calcium sulfate; the solvent can include one or more of water, glycerol, methanol, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF), specifically water, glycerol, methanol, DMSO, or N,N-dimethylformamide; the water can be deionized water; the dissolution temperature can be 38-42°C, specifically 40°C; the mass concentration of the calcium sulfate solution can be 0.05-5%, and can also be 0.1-4%, and further can be 0.5-2%.

[0032] As a specific embodiment of the present invention, the anionic fiber may include one or more of bacterial cellulose, microfibrillated cellulose, cellulose nanofibers, polyacrylonitrile-based carbon nanofibers, polystyrene nanofibers, polylactic acid nanofibers, polyvinyl acetate nanofibers, lignocellulose nanofibers, carboxylated cellulose nanofibers, sulfonated cellulose nanofibers, carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, and carbon nanotube fibers; it may be bacterial cellulose, microfibrillated cellulose, cellulose nanofibers, polyacrylonitrile-based carbon nanofibers, polystyrene nanofibers, polylactic acid nanofibers, polyvinyl acetate nanofibers, lignocellulose nanofibers, carboxylated cellulose nanofibers, sulfonated cellulose nanofibers, carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, or carbon nanotube fibers, and may specifically be carboxylated cellulose nanofibers or sulfonated cellulose nanofibers. In this invention, the length of the anionic fiber is 0.02–50 μm, which can be 0.05–40 μm, or 0.1–10 μm, specifically 0.03 μm, 0.13 μm, 0.15 μm, 0.175 μm, 0.2 μm, 0.35 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm; the diameter of the anionic fiber is 5–100 nm, which can be 8–50 nm, or 10–30 nm, specifically 15 nm, 23 nm, 35 nm, 43 nm, 55 nm, 60 nm, 70 nm, 80 nm, or 90 nm. In this invention, the anionic fiber acts as a template agent. The anionic fiber possesses a unique nanoscale structure and high specific surface area, and its molecular chain is rich in anionic groups (such as carboxyl groups, sulfonic acid groups, phosphate groups, hydroxyl groups, etc.), which can interact with the calcium sulfate whisker precursor through hydrogen bonds and other forces. This interaction guides the calcium sulfate whiskers to grow along a specific direction of the anionic fiber template, helping to prepare calcium sulfate whiskers with regular morphology and uniform size. It effectively controls the growth morphology and size of the whiskers, improving their quality and performance.

[0033] In one specific embodiment of the present invention, the mass ratio of calcium sulfate to anionic fiber in the calcium sulfate solution can be 100:1 to 10, or 100:2 to 8, or even 100:3 to 5.

[0034] In one specific embodiment of the present invention, the first mixing can be carried out under stirring conditions, the stirring temperature can be 38-42°C, specifically 40°C; the stirring time can be 0.3-0.6 hours, or 0.4-0.5 hours; the present invention can provide the stirring temperature by means of a water bath. The present invention does not have a special limitation on the stirring speed, as long as it can achieve uniform mixing.

[0035] In one specific embodiment of the present invention, the temperature for crystal nucleus growth can be 90–98°C, or 93–95°C; the growth time can be 2.5–3.5 h, or 2.8–3 h; and the growth can be accompanied by stirring. During the crystal nucleus growth process, calcium sulfate slowly grows on the anionic fiber used as a template, essentially forming crystal nuclei by first attaching calcium sulfate to the anionic fiber; specifically, calcium sulfate dissolves in water to generate Ca. 2+ and SO4 2- Anionic groups on anionic fibers capture Ca based on the principle of electrostatic adsorption (opposites attract). 2+ It grows into calcium sulfate whisker nuclei.

[0036] After nucleus growth, the present invention mixes the nucleated system with a second growth regulator and then performs whisker growth to obtain calcium sulfate whiskers. In one specific embodiment of the present invention, the growth regulator may include one or more of sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium stearate, sodium acrylate-maleic acid copolymer, citric acid, hexadecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride, specifically sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium stearate, sodium acrylate-maleic acid copolymer, citric acid, hexadecyltrimethylammonium bromide, or dodecyltrimethylammonium chloride. In embodiments of the present invention, the growth regulator is a mixture of sodium dodecylbenzenesulfonate and citric acid in a mass ratio of 1:1 or a mixture of sodium dodecylbenzenesulfonate and citric acid in a mass ratio of 3:1. In this invention, the growth regulator can, through the synergistic effect of "selective adsorption to inhibit non-axial crystal plane growth → guiding axial preferred growth → reducing surface energy and controlling size uniformity," regulate the formation of regular morphology and uniform size of calcium sulfate whiskers, and reduce agglomeration through surface modification, thereby significantly improving its dispersion stability in water, controlling crystallization conditions, and reducing crystal defects. Meanwhile, the dispersion mechanism of the growth regulator in the calcium sulfate and anionic fiber system is mainly achieved through charge regulation, interfacial adsorption, and steric hindrance effects. Its mechanism of action needs to be specifically analyzed in conjunction with the surface characteristics (such as charge and functional groups) of calcium sulfate whiskers and anionic fibers; the hydrophilic head groups of the growth regulator (such as SO4)... 2- SO3 2- (e.g., quaternary ammonium cations) will preferentially adsorb onto certain fast-growing crystal faces of the whiskers through electrostatic attraction, inhibiting ion accumulation in that direction and promoting the whiskers to preferentially grow in other directions (such as longitudinal direction), increasing the aspect ratio, making the whiskers finer and more regular. At the same time, a charge layer is covered on the surface of the calcium sulfate whiskers, enhancing the electrostatic repulsion effect and improving dispersibility.

[0037] In one specific embodiment of the present invention, the second mixing can be achieved by adding a growth regulator solution dropwise to the system after crystal nucleation under stirring conditions; the growth regulator solution can be obtained by dissolving the growth regulator in a solvent; the solvent for dissolving the growth regulator can be the same as the solvent for dissolving calcium sulfate; the dropping rate can be 20-120 drops / min, specifically 30 drops / min, 50 drops / min, 70 drops / min, 90 drops / min, 100 drops / min or 110 drops / min; after the dropping is completed, stirring can continue for 0.5-3 hours, or even 1-2 hours; the molar concentration of the growth regulator in the second mixed system can be 0.1-3 mmol / L, or even 0.5-2 mmol / L.

[0038] In one specific embodiment of the present invention, the pH value of the second mixed system can be weakly acidic, specifically 3 to 6.5. The present invention limits the pH value of the second mixed system to weakly acidic to ensure the formation of calcium sulfate whiskers and avoid the formation of calcium hydroxide in an alkaline environment. In the present invention, the second mixed system mostly exhibits weak acidity and does not require adjustment; if the second mixed system exhibits alkalinity, dilute sulfuric acid can be added for adjustment.

[0039] In one specific embodiment of the present invention, the whisker growth temperature can be 120–250°C, or 140–200°C; the whisker growth time can be 2–10 hours, or 3–8 hours, or even 5–7 hours. In another specific embodiment of the present invention, the whisker growth can be carried out in a hydrothermal reactor.

[0040] In one specific embodiment of the present invention, the whisker growth process may further include: cooling the whisker-grown system and then sequentially washing, filtering, and drying it; the cooling temperature may be 20–35°C, or 25–30°C; the filtration may be vacuum filtration, and the conductivity of the filtrate after vacuum filtration may be ≤100 μS / cm; the drying temperature may be 60–150°C, specifically 70°C, 80°C, 100°C, 105°C, 110°C, 120°C, or 140°C; the drying time may be 0.5–5 h, or 1–4 h, or even 2–3 h. The present invention, through washing, can remove residual anionic fibers and growth regulators simultaneously.

[0041] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] 1g of 95% pure calcium sulfate dihydrate was dissolved in 100g of deionized water at 40℃ to obtain a calcium sulfate solution.

[0044] Calcium sulfate solution and 0.1g of carboxylated cellulose nanocrystals with an average length of 0.175μm and an average diameter of 23nm were stirred in a water bath at 40℃ for 0.5h, and then heated to 95℃ for 3h for nucleation growth.

[0045] Under stirring, a growth regulator solution (obtained by dissolving 0.0371 g (0.1 mmol) sodium dodecylbenzenesulfonate and 0.0371 g (0.2 mmol) citric acid in 50 g of water) was added dropwise to the nucleus-grown system at a dropping rate of 50 drops / min. After the addition was completed, stirring was continued for 2 h. The mixture was then transferred to a hydrothermal reactor and whisker growth was carried out at 140 °C for 4 h. After cooling to 30 °C, the mixture was washed with water and filtered. The conductivity of the filtrate was 50 μS / cm. The solid obtained by filtration was placed in an oven and dried at 105 °C for 3 h to obtain calcium sulfate whiskers.

[0046] Example 2

[0047] Calcium sulfate whiskers were prepared according to the method of Example 1, except that the growth regulators were 0.065 g sodium dodecylbenzenesulfonate and 0.022 g citric acid.

[0048] Example 3

[0049] Calcium sulfate whiskers were prepared according to the method in Example 1, except that the temperature of the hydrothermal reaction (whisker growth) was 130°C.

[0050] Comparative Example 1

[0051] Calcium sulfate whiskers were prepared according to the method in Example 1, except that no growth regulator was added during the preparation process; the specific steps are as follows:

[0052] 1g of calcium sulfate dihydrate with a purity of 95% was dissolved in 150g of water at 40℃ to obtain a calcium sulfate solution.

[0053] Calcium sulfate solution and 0.1 g of carboxylated cellulose nanocrystals with an average length of 0.175 μm and an average diameter of 23 nm were stirred in a water bath at 40 °C for 0.5 h, and then heated to 95 °C for 5 h for crystal nucleus growth. The mixture was then transferred to a hydrothermal reactor and grown as whiskers at 140 °C for 4 h. After cooling to 30 °C, the mixture was washed with water and filtered until the conductivity was 55 μS / cm. The filtered solid was then placed in an oven and dried at 105 °C for 3 h to obtain calcium sulfate whiskers.

[0054] Comparative Example 2

[0055] Calcium sulfate whiskers were prepared according to the method in Example 1, except that carboxylated cellulose nanocrystals were not added during the preparation process; the specific steps are as follows:

[0056] 1g of 95% pure calcium sulfate dihydrate was dissolved in 100g of water at 40℃. The solution was stirred for 0.5h under water bath heating at 40℃ and then heated to 95℃ for 3h under water bath heating to obtain a calcium sulfate solution.

[0057] Under stirring, a growth regulator solution (obtained by dissolving 0.0371 g (0.1 mmol) sodium dodecylbenzenesulfonate and 0.0371 g (0.2 mmol) citric acid in 50 g of water) was added dropwise to a calcium sulfate solution at a dropping rate of 50 drops / min. After the addition was complete, the solution was stirred at 95 °C for 2 h and then transferred to a hydrothermal reactor for whisker growth at 140 °C for 4 h. After cooling to 30 °C, the solution was washed with water and filtered until the conductivity was 53 μS / cm. The filtered solid was then placed in an oven and dried at 105 °C for 3 h to obtain calcium sulfate whiskers.

[0058] Comparative Example 3

[0059] Calcium sulfate whiskers were prepared according to the method in Example 1, except that carboxylated cellulose nanocrystals and growth regulators were not added during the preparation process; the specific steps are as follows:

[0060] 1g of 95% pure calcium sulfate dihydrate was dissolved in 150g of water at 40℃. The solution was stirred for 0.5h under water bath heating at 40℃, and then heated to 95℃ for 5h under water bath heating to obtain a calcium sulfate solution.

[0061] The calcium sulfate solution was transferred to a hydrothermal reactor and whisker growth was carried out at 140°C for 4 hours. After cooling to 30°C, the mixture was washed with water and filtered until the conductivity was 60 μS / cm. The solid obtained by filtration was placed in an oven and dried at 105°C for 3 hours to obtain calcium sulfate whiskers.

[0062] Comparative Example 4

[0063] Weigh 40g of calcium sulfate dihydrate and add it to 200mL of deionized water. Stir with a magnetic stirrer (200r / min) for 20min to make a suspension.

[0064] Add 30 mL of 95% concentrated sulfuric acid (dropping rate 3-5 mL / min) dropwise to the suspension, stir well, and then place it in an 80℃ water bath for 30 min. After the reaction, filter the mixture and wash the filter cake with deionized water until the filtrate is nearly neutral. Place the washed filter cake in an 80℃ drying oven and dry for 2 h to obtain calcium sulfate whiskers.

[0065] The calcium sulfate dihydrate prepared in Example 1, as well as the calcium sulfate whiskers prepared in Examples 1-3 and Comparative Examples 1-4, were examined by scanning electron microscopy (SEM) to obtain SEM images, as shown below. Figures 1-8 As shown, where, Figure 1 This is a SEM image of the calcium sulfate whiskers prepared in Example 1. Figure 2 This is a SEM image of the calcium sulfate whiskers prepared in Example 2. Figure 3 SEM image of calcium sulfate whiskers prepared in Example 3; Figure 4 This is a SEM image of calcium sulfate dihydrate. Figure 5 This is a SEM image of the calcium sulfate whiskers prepared in Comparative Example 1. Figure 6 This is a SEM image of the calcium sulfate whiskers prepared in Comparative Example 2. Figure 7 The image shows a SEM image of the calcium sulfate whiskers prepared in Comparative Example 3. Figure 8 The image shows a SEM image of the calcium sulfate whiskers prepared in Comparative Example 4.

[0066] Depend on Figures 1-3 As can be seen under a scanning electron microscope, the individual whiskers of calcium sulfate prepared in the examples are clearly visible as slender rods or needles, without obvious branches, and the overall shape is similar to "tiny glass rods". As a single crystal material, its atomic arrangement is highly ordered, so the surface of the individual whiskers is smooth, the edges are straight, and there are no obvious defects (such as fractures, twists, or unevenness); the cross-section is mostly a regular hexagon or nearly circular.

[0067] Depend on Figure 4 It is evident that calcium sulfate dihydrate aggregates exhibit diverse morphologies, ranging from dense lumps to tightly packed blocks.

[0068] Depend on Figure 5 It can be seen that calcium sulfate whiskers obtained without the addition of growth regulators during the preparation process are prone to secondary nucleation, and the growth is mainly dendritic; Figure 6 It can be seen that the calcium sulfate whiskers obtained without the addition of anionic fiber templates during the preparation process have uneven morphology; Figure 7 It can be seen that direct hydrothermal reaction of calcium sulfate dihydrate can form a crystalline product, but the morphology and growth direction are uncontrollable; Figure 8 It can be seen that the individual whiskers of calcium sulfate prepared in Comparative Example 4 are slender rods or needles, but the whisker length is short and the diameter is thick, and there is a defect of crystal cracking.

[0069] Secondary nucleation branches preferentially grow from defect sites. When the local supersaturation exceeds the critical value (typically 1.8-2.0 for calcium sulfate), defect sites on the whisker surface (such as dislocations and vacancies generated by rapid growth) become new "secondary nucleus" formation centers. These sites have irregular lattice arrangements, higher adsorption energies for ions, and are more likely to capture surrounding Ca. 2+and SO4 2- The ions then grow along a new axis (at a certain angle to the main whisker, such as 30° to 60°), forming the first "branch". After the branch is formed, its tip will repeat the above process: the tip consumes ions → surrounding ions replenish → new branches are formed at the edges or defects of the branch, eventually diverging from the initial nucleus (a point) in multiple directions to form a "tree-like" structure. Additives can inhibit secondary nucleation by adsorbing on the defect sites on the crystal plane; without additives, the defect sites are exposed and easily capture ions to form branches; when additives are insufficient, they can only cover part of the defects, and the uncovered sites will still grow branches, forming an irregular tree-like structure.

[0070] The length and diameter of calcium sulfate whiskers in Examples 1-3 and Comparative Example 4 were obtained based on SEM test results, and the results are listed in Table 1.

[0071] Table 1. Sizes of calcium sulfate whiskers prepared in Examples 1-3 and Comparative Example 4.

[0072]

[0073] The average aspect ratio in Table 1 is the average aspect ratio of all individual calcium sulfate whiskers.

[0074] Combining Table 1 and Figures 1-3 It can be seen that the calcium sulfate whiskers obtained by the method provided by the present invention have a relatively long length and a large aspect ratio.

[0075] X-ray diffraction (XRD) was performed on the calcium sulfate whiskers prepared in Example 1 and Comparative Example 4 to obtain their XRD patterns, as shown below. Figure 9As shown in the figure. The standard card (CaSO4-PDF#80-1235) in the figure comes from the International Center for Diffraction Data (ICDD). The calcium sulfate whiskers prepared in Comparative Example 4 are identified as calcium sulfate dihydrate (CaSO4·2H2O) based on the characteristic diffraction peaks of 11.7, 20.8, and 29.1 shown in the figure. A strong characteristic diffraction peak at 23.5 is observed, possibly due to the presence of some calcium sulfate hemihydrate (CaSO4·0.5H2O) or impurities. The characteristic diffraction peaks of the calcium sulfate whiskers prepared in Example 1 correspond one-to-one with the characteristic diffraction peaks of 14.9, 25.9, and 29.4 of the standard card (CaSO4-PDF#80-1235). The scattered signals are concentrated, and the diffraction peaks are sharp (small half-maximum width at half-maximum) and high intensity, indicating that the calcium sulfate whiskers have high phase purity and crystallinity, ordered atomic arrangement, and few defects (such as no lattice distortion and no vacancies), thus exhibiting good mechanical properties. Furthermore, a characteristic diffraction peak of carboxylated cellulose nanofibers appeared at 21.1°C. This peak position was significantly shifted from the theoretical characteristic peak of carboxylated cellulose nanofibers (22.6°C). This is due to the interfacial interaction between the carboxylated cellulose nanofibers, which act as a template, and the calcium sulfate crystals, thus affecting the crystal structure. Simultaneously, the low diffraction intensity of this characteristic peak indicates that the content of carboxylated cellulose nanofibers in the system is low and well-dispersed, and their presence does not significantly interfere with the main structure of the CaSO4 crystals. In other words, the introduction of the template did not destroy the overall crystallization characteristics of the calcium sulfate whiskers. Highly crystallizable and low-defect calcium sulfate whiskers theoretically possess high strength and good toughness (fewer defects mean fewer stress concentration points, and stronger atomic bonding forces result in superior fracture resistance), making them suitable for applications requiring high-strength support (such as reinforcing phases in composite materials).

[0076] The test results above show that the calcium sulfate whiskers prepared in Example 1 are high-purity, high-crystallinity, and low-defect calcium sulfate whiskers with excellent crystal quality, high strength and stability, and significant advantages in industrial applications.

[0077] 0.1g of calcium sulfate whiskers prepared in Example 1 and Comparative Example 4 were dispersed in 15mL of water under ultrasonic conditions and allowed to stand for 10 days to observe their dispersion stability. Figure 10 The images show a comparison of the dispersions after standing for 0, 1, 5, and 10 days. The left image shows the calcium sulfate whisker dispersion from Example 1, and the right image shows the calcium sulfate whisker dispersion from Comparative Example 4. Figure 10 It can be seen that the calcium sulfate whiskers prepared according to the method provided by the present invention have good dispersion stability in water and are not prone to agglomeration.

[0078] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing calcium sulfate whiskers, characterized in that, Includes the following steps: A calcium sulfate solution and anionic fibers are first mixed and then subjected to crystal nucleation growth; the length of the anionic fibers is 0.02-50 μm and the diameter is 5-100 nm. After the crystal nuclei are formed, the system is mixed with the second growth regulator and then whisker growth is carried out to obtain calcium sulfate whiskers.

2. The method for preparing calcium sulfate whiskers according to claim 1, characterized in that, The anionic fibers include one or more of the following: bacterial cellulose, microfibrillated cellulose, cellulose nanofibers, polyacrylonitrile-based carbon nanofibers, polystyrene nanofibers, polylactic acid nanofibers, polyvinyl acetate nanofibers, lignocellulose nanofibers, carboxylated cellulose nanofibers, sulfonated cellulose nanofibers, carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, and carbon nanotube fibers.

3. The method for preparing calcium sulfate whiskers according to claim 1 or 2, characterized in that, The mass ratio of calcium sulfate to anionic fiber in the calcium sulfate solution is 100:1 to 10.

4. The method for preparing calcium sulfate whiskers according to claim 3, characterized in that, The calcium sulfate solution has a mass concentration of 0.05% to 5%.

5. The method for preparing calcium sulfate whiskers according to claim 1 or 2, characterized in that, The first mixing is carried out under stirring conditions, wherein the stirring temperature is 38-42°C and the stirring time is 0.3-0.6h.

6. The method for preparing calcium sulfate whiskers according to claim 1 or 2, characterized in that, The crystal nucleus growth temperature is 90–98℃, and the time is 2.5–3.5 h.

7. The method for preparing calcium sulfate whiskers according to claim 1, characterized in that, The growth regulators include one or more of sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium stearate, sodium salt of acrylic acid-maleic acid copolymer, citric acid, hexadecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

8. The method for preparing calcium sulfate whiskers according to claim 1 or 7, characterized in that, The molar concentration of the growth regulator in the second mixed system is 0.1–3 mmol / L.

9. The method for preparing calcium sulfate whiskers according to claim 8, characterized in that, The whisker growth temperature is 120–250°C, and the time is 2–10 h.

10. The method for preparing calcium sulfate whiskers according to claim 9, characterized in that, The process after whisker growth also includes: cooling the whisker-grown system and then sequentially washing, filtering, and drying it.

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