Preparation method of novel calcium carbonate whisker

Abstract

The invention relates to the technical field of whisker preparation, and discloses a novel calcium carbonate whisker preparation method, which comprises: taking a proper amount of dolomite, water glass and sodium hydroxide, pouring the water glass and the sodium hydroxide into a mortar, uniformly mixing to form an alkali activator, pouring the dolomite into the alkali activator, and uniformly mixing to form the calcium carbonate whisker. The method comprises the following steps: grinding dolomite into a wet powder state, standing mineral powder for 6-24 hours in a room temperature environment, preserving heat in a heat preservation box for 1-3 hours, finally, curing the mineral powder in the room temperature environment, preparing a sample from the dolomite powder, and carrying out electron microscope scanning to observe the growth condition of whiskers. According to the preparation method of the novel calcium carbonate whisker, dolomite, sodium hydroxide and sodium silicate are taken as raw materials, a crystal form control agent does not need to be added, and the novel calcium carbonate whisker is prepared at normal pressure, so that the whole preparation process is simple in flow, easy to operate and easy for large-scale production, maintenance is carried out at normal temperature, the equipment investment is saved, and the safety is high.

Description

Technical Field

[0001] The invention relates to the technical field of whisker preparation, in particular to a method for preparing a novel calcium carbonate whisker. Background Art

[0002] Calcium carbonate whiskers are another new type of inorganic filler after nano-calcium carbonate. They are non-toxic, odorless, and white fluffy solids (needle-shaped single crystals under a microscope). As a new generation of filling materials, they have the following properties and characteristics: (1) Calcium carbonate whiskers are single crystal structures with almost no defects such as dislocations and grain boundaries. Their mechanical properties are close to those of complete crystals, and they have high tensile strength, which can effectively improve the strength of composite materials; (2) They have a high elastic modulus. Adding them to materials can improve the rigidity of the materials and make them less likely to deform when subjected to force. For example, adding calcium carbonate whiskers to plastics can increase the bending elastic modulus of plastics; (3) While improving the strength and rigidity of materials, they can also play a good toughening role, enhance the impact resistance of materials, and reduce the possibility of cracking and brittle fracture of materials during use. They have good thermal decay and thermal recovery properties; (4) They have good acid resistance, alkali resistance, and weather resistance. In different chemical environments and climatic conditions, they can maintain their own stable performance and are not prone to chemical reactions that affect the performance of materials. They can be used to manufacture products for outdoor use; (5) The raw material source is abundant and the price is low.

[0003] At present, the main methods for preparing calcium carbonate whiskers are as follows: (1) Carbonation method: mainly using natural limestone as raw material, the entire preparation process requires high-temperature calcination and the addition of crystal form control agents, and the energy consumption and cost are high. (2) Double decomposition method: mainly using soluble calcium salts and carbonates as raw materials, the preparation process requires the use of other additional reagents, the aging time is long, the preparation process conditions are difficult to control and the requirements for raw materials are high. (3) Urea hydrolysis method: urea is reacted with soluble calcium salts. The reaction process does not require the addition of crystal form control agents, but it needs to react at high temperature and high pressure, the energy consumption is high, and the production risk is also high. (4) Calcium bicarbonate heating hydrolysis method: first prepare calcium bicarbonate solution, and then prepare calcium carbonate whiskers by controlling the heating temperature, heating rate, stirring intensity and other conditions of the solution. This method is relatively complex, difficult to operate, and has low production efficiency. (5) Supergravity reaction crystallization method: This method has the advantages of fewer control factors in the reaction process, easy to repeat, and adjustable product particle size, but this method needs to be carried out in a specific supergravity reaction device, which has extremely high equipment requirements and high energy consumption.

[0004] Patent application No. 03134287.6 discloses a preparation process for calcium carbonate whiskers, which uses quicklime as raw material, adds a crystal control agent magnesium chloride solution after digestion reaction, and finally introduces CO2 for carbonization treatment to obtain calcium carbonate whiskers. This method is the traditional carbonation method for preparing calcium carbonate whiskers, which is simple to operate and low in cost. However, the purity of the prepared calcium carbonate whiskers disclosed in the patent is not high (the calcium carbonate content is 92.8%), and a large amount of quicklime and CO2 are consumed.

[0005] The invention patent with patent application number 201410809791.2 discloses a method for preparing calcium carbonate whiskers using industrial by-product gypsum as raw material. The preparation process is to add sodium carbonate solution to a solid-liquid mixture of phosphogypsum and water, and stir the mixture at 70-80°C for a period of time to obtain a solid finished product. This method uses phosphogypsum as raw material and has a simple process, but the obtained solid finished product contains a large amount of quartz and other impurity components, and has a low whiteness, which seriously restricts the application of calcium carbonate whiskers and has little practical application value.

[0006] In summary, the existing preparation process of calcium carbonate whiskers has problems such as high raw material cost, complex preparation process, and the need to add a crystal control agent. Therefore, a new preparation method of calcium carbonate whiskers is proposed to solve the above problems. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a novel method for preparing calcium carbonate whiskers, which has the advantages of low raw material cost and waste resource utilization, and solves the problems mentioned in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for preparing a novel calcium carbonate whisker, comprising the following steps: S1: Take appropriate amount of dolomite, water glass and sodium hydroxide; S2: Pour water glass and sodium hydroxide into a mortar and mix them evenly to form an alkaline activator; S3: Pour the dolomite into the alkali activator and grind the dolomite into a wet powder state; S4: Leave the mineral powder at room temperature for 6-24 hours, keep it warm in an incubator for 1-3 hours, and finally place it at room temperature for curing; S5: Prepare a sample of dolomite powder and perform electron microscopy scanning to observe the growth of whiskers.

[0009] Preferably, the dolomite is present in an amount of 100 parts, the water glass is present in an amount of 5-15 parts, and the sodium hydroxide is present in an amount of 1.5-4 parts.

[0010] Preferably, the sodium hydroxide is in granular form with a particle size of 50-130 μm.

[0011] Preferably, the insulation temperature of the insulation box is 100°C-150°C Preferably, the water glass is a sodium silicate solution.

[0012] Preferably, the room temperature in step S4 is 25±3°C and the humidity is 65±5%.

[0013] Preferably, the mixing time in step S2 is 2-3 min.

[0014] Compared with the prior art, the present invention provides a novel method for preparing calcium carbonate whiskers, which has the following beneficial effects: The novel method for preparing calcium carbonate whiskers uses dolomite, sodium hydroxide and sodium silicate as raw materials, does not need to add a crystal control agent, and prepares the novel calcium carbonate whiskers under normal pressure. The entire preparation process is simple, easy to operate, easy to mass produce, and can be maintained at room temperature, with low equipment investment and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a SEM image of Example 1 of a novel calcium carbonate whisker proposed by the present invention; Figure 2 This is a SEM image of Example 2 of a novel calcium carbonate whisker proposed by the present invention; Figure 3 This is a SEM image of Example 2 of a novel calcium carbonate whisker proposed by the present invention; Figure 4 This is a SEM image of Example 3 of a novel calcium carbonate whisker proposed in the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Example 1: Please refer to Figure 1 A novel method for preparing calcium carbonate whiskers comprises the following steps: S1: Take appropriate amounts of 10g dolomite, 0.5g water glass and 0.2g sodium hydroxide, where the water glass is a sodium silicate solution; S2: Pour water glass and sodium hydroxide into a mortar and mix them evenly for 3 minutes to form an alkaline activator; S3: Pour the dolomite into the alkali activator and grind the dolomite into a wet powder state; S4: Place the mineral powder at room temperature for 6 hours, and keep it in an incubator at 100°C for 1 hour, and finally place it in a room temperature environment for curing. The room temperature is 25±3°C and the humidity is 65±5%; S5: Prepare a sample of dolomite powder and perform electron microscopy scanning to observe the growth of whiskers.

[0018] Sodium hydroxide is in granular form with a particle size of 50-130 μm.

[0019] from Figure 1 It can be seen that whiskers with uniform distribution, complete crystal morphology and good aspect ratio appear inside the alkali-activated dolomite.

[0020] Example 2: Please refer to Figure 2 and Figure 3 This embodiment is different from the first embodiment in that the weight of sodium hydroxide is 0.15 g, the weight of sodium silicate is 1 g, the mineral powder is left standing at room temperature for 24 hours, and is kept warm in an insulation box at 150° C. for 2 hours.

[0021] from Figure 2 and Figure 3 It can be seen that whiskers with uniform distribution, complete crystal morphology and good aspect ratio appear inside the alkali-activated dolomite.

[0022] Example 3: Please refer to Figure 4 This embodiment is different from the first embodiment in that the weight of sodium hydroxide is 0.4 g, the weight of sodium silicate is 1.5 g, the mineral powder is left standing at room temperature for 12 hours, and is kept warm in an insulated box at 125° C. for 3 hours.

[0023] from Figure 4 It can be seen that whiskers with uniform distribution, complete crystal morphology and good aspect ratio appear inside the alkali-activated dolomite.

[0024] The main advantages of using dolomite powder as alkali-activated material are as follows: 1. Raw material advantages 1. Rich resources and low cost Dolomite (mainly composed of CaCO3 and MgCO3) is abundant in the earth's crust, widely distributed, and has low mining costs. It can be used as a resource utilization method for industrial solid waste (such as mine tailings and stone processing waste), which is in line with the concept of "replacing materials with waste" in green building materials and reduces the cost of raw materials.

[0025] 2. Strong adaptability of ingredients Ca²⁺ and Mg²⁺ in dolomite can be gradually dissolved under alkaline excitation conditions. Ca²⁺ is the core nucleation ion of calcium carbonate whiskers, while Mg²⁺ may act as a mineralizer or structure directing agent to regulate the growth direction of whiskers (such as promoting the formation of one-dimensional rod-shaped whiskers) and improve the morphological uniformity and aspect ratio of whiskers.

[0026] 2. Advantages of Preparation Process 1. Low carbon and energy saving, mild conditions The alkali-activated reaction usually takes place at room temperature, without the need for high-temperature calcination (such as limestone calcination requires 900~1200°C) or high-pressure hydrothermal conditions used in the preparation of traditional calcium carbonate whiskers, significantly reducing energy consumption and carbon emissions, and meeting the "dual carbon" goals.

[0027] 2. Simple process and high controllability The alkali excitation process can flexibly control the size (length, diameter), crystallinity and surface activity of the whiskers by adjusting the alkalinity (such as the concentration of NaOH and Na2SiO3 solutions), reaction time and temperature, which facilitates industrial scale-up production.

[0028] III. Resource and Environmental Benefits ① Abundant reserves and low cost. Dolomite is a widely distributed sedimentary rock, and its mining and processing costs are lower than those of industrial by-products (such as blast furnace slag) or fly ash that requires fine processing.

[0029] ② Waste resource utilization: Low-grade dolomite or mining waste can be used to reduce the consumption of natural resources.

[0030] Raw material innovation: Using natural dolomite (CaMg(CO3)2) as the main calcium source, replacing traditional chemical reagents (such as CaCl2, Ca(OH)2) to achieve low-cost and sustainable raw material supply.

[0031] Process innovation: Using alkali excitation (NaOH / Na2SiO3) synergistic regulation technology, calcium carbonate whiskers are synthesized in a one-step process under normal pressure and medium-low temperature (100-150°C), breaking through the high energy consumption bottleneck of traditional calcination method (>800°C) and hydrothermal method (high pressure).

[0032] Performance advantages: The purity of the obtained whiskers is ≥95%, with good dispersion, which can significantly enhance the mechanical properties of composite materials (such as increasing the impact strength of plastics by 30%-50%).

[0033] Environmental advantages: There is no acidic waste liquid emission during the reaction process, and CO2 emissions are reduced by about 60% compared with the traditional calcination method, which meets the requirements of low-carbon manufacturing.

[0034] Application prospects: Composite materials: As reinforcing filler, used in engineering plastics, rubber, and ceramic-based composite materials, replacing expensive carbon fiber or glass fiber.

[0035] Environmental protection: After loading functional substances, heavy metal adsorbents or catalytic carriers can be prepared. Biomedical field: Through surface modification, bone repair materials or drug sustained-release carriers can be developed.

[0036] In summary, the preparation method of the novel calcium carbonate whisker uses dolomite, sodium hydroxide, and sodium silicate as raw materials, does not need to add a crystal control agent, and prepares the novel calcium carbonate whisker under normal pressure. The entire preparation process is simple, easy to operate, easy to scale production, and can be maintained at room temperature, with low equipment investment and high safety.

[0037] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a novel calcium carbonate whisker, characterized in that: The following steps are involved: S1: Take appropriate amount of dolomite, water glass and sodium hydroxide; S2: Pour water glass and sodium hydroxide into a mortar and mix them evenly to form an alkaline activator; S3: Pour the dolomite into the alkali activator and grind the dolomite into a wet powder state; S4: Leave the mineral powder at room temperature for 6-24 hours, keep it warm in an incubator for 1-3 hours, and finally place it at room temperature for curing; S5: Prepare a sample of dolomite powder and perform electron microscopy scanning to observe the growth of whiskers.

2. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The dolomite is present in 100 parts, the water glass is present in 5-15 parts, and the sodium hydroxide is present in 1.5-4 parts.

3. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The sodium hydroxide is in granular form, and the particle size is 50-130 μm.

4. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The insulation temperature of the insulation box is 100°C-150°C.

5. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The water glass is a sodium silicate solution.

6. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The room temperature in step S4 is 25±3°C and the humidity is 65±5%.

7. The preparation method of a novel calcium carbonate whisker according to claim 1, wherein: The mixing time in step S2 is 2-3 minutes.

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