Preparation method of amino phosphorylation synergistically modified nano calcium carbonate

Abstract

The invention discloses a preparation method of amino phosphorylation synergistically modified nano calcium carbonate, which comprises the following steps: adding 10-20g of nano calcium carbonate into 200mL of absolute ethyl alcohol or deionized water, and treating for 30 minutes by an ultrasonic dispersion instrument to form a uniform dispersion liquid; dissolving 5-15g of a phosphorus source compound in deionized water; taking a nitrogen source compound accounting for 10-20% of the mass of the nano calcium carbonate, slowly adding the nitrogen source compound and the phosphorus source compound solution in the step S2 into the dispersion liquid in the step S1, and stirring while adding; placing the mixed solution in a magnetic stirrer for stirring reaction, and adjusting the pH value of the system to be neutral by using NaOH or HCl after the reaction is finished; washing the product with deionized water for multiple times until the pH value of the solution is close to neutral, and removing unreacted phosphorus source and nitrogen source compounds; and drying the washed product in a vacuum drying oven until the weight is constant, thereby obtaining the phosphoramidated synergistically modified nano calcium carbonate. The P-N modified nano calcium carbonate can be synergistically used with a phosphorus-nitrogen flame retardant, so that the addition amount of the phosphorus-nitrogen flame retardant is reduced, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of inorganic nanomaterial modification technology, specifically to a method for preparing aminophosphorylation synergistically modified nano-calcium carbonate. Background Technology

[0002] Nano-calcium carbonate (particle size ≤100 nm) is widely used as a reinforcing and toughening filler in polymer materials due to its advantages such as high specific surface area, easy availability, low cost, and non-toxicity. However, nano-calcium carbonate has a strong hydrophilic surface, and the particles are prone to agglomeration, resulting in poor dispersibility in hydrophobic polymers and stress concentration. In addition, traditional modifiers (such as stearic acid and phthalates) have poor high-temperature resistance, are prone to failure during high-temperature processing, and have poor storage stability.

[0003] Currently, there are few systematic solutions for PN-synergistic modification of nano-calcium carbonate, and this method can fill a technological gap. Furthermore, by synergistically modifying nano-calcium carbonate with phosphorus and nitrogen source compounds, phosphate groups and amino groups are imparted to the nano-calcium carbonate, significantly improving its thermal stability and flame retardancy. Moreover, the modifiers are free of heavy metals and non-toxic, meeting environmentally friendly development requirements. PN-synergistic modification of nano-calcium carbonate greatly expands its application range in fire protection fields such as automobiles, high-speed rail, and construction. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing aminophosphorylated synergistic modified nano-calcium carbonate, which can effectively solve the problems of poor hydrophobicity, poor temperature resistance, poor thermal stability, poor flame retardancy, and poor polymer compatibility of existing modified nano-calcium carbonate.

[0005] According to one objective of the present invention, the present invention provides a method for preparing aminophosphorylated synergistically modified nano-calcium carbonate, comprising the following steps: Step 1) Take 10-20 g of nano calcium carbonate and add it to 200 mL of anhydrous ethanol or deionized water. Then, use an ultrasonic disperser to treat it for 30 minutes to ensure that the nano calcium carbonate particles are evenly dispersed and avoid agglomeration. Step 2) Take an appropriate amount of phosphorus source compound and dissolve it in an appropriate amount of deionized water; Step 3) Slowly add appropriate amounts of nitrogen source compound and phosphorus source compound liquid from Step 2) to the nano-calcium carbonate dispersion while stirring to avoid violent reaction; Step 4) Place the mixture from Step 3) on a magnetic stirrer, maintain a suitable temperature, and stir for several hours; adjust the pH of the reaction system to neutral using NaOH or HCl to ensure that the phosphate groups and amino groups can be successfully grafted onto the surface of the nano-calcium carbonate. Step 5) After the reaction is complete, wash the nano-calcium carbonate with deionized water several times until the pH of the solution is close to neutral to remove unreacted phosphorus and nitrogen source compounds. Step 6) Dry the product from step 5) in a vacuum drying oven to constant weight to finally obtain phosphorus-nitrogen flame-retardant nano-calcium carbonate.

[0006] Further, in step 2), the content of the phosphorus source compound is 5-15g; the phosphorus source compound is one or more of phosphoric acid, sodium hexametaphosphate, and triethanolamine phosphate.

[0007] Further, in step 3), the content of the nitrogen source compound is 10-20% of the mass of the nano-calcium carbonate; the nitrogen source compound is one or more of urea, aminophosphonic acid, or aminomethylenephosphonic acid.

[0008] Furthermore, in step 4), the reaction temperature is 50-70°C; the reaction time is 3-6 hours.

[0009] Furthermore, in step 6), the drying temperature is 60-80°C.

[0010] The beneficial effects of this invention are: Compared with traditional modification methods, this invention achieves synergistic effects of "dual functional groups," significantly improving its thermal stability. Firstly, the phosphate group (-PO4) 3- ) and CaCO3 surface Ca 2+ Irreversible chemical bonds are formed, preventing desorption during processing. Secondly, the amino groups (-NH2) form hydrogen bonds or covalent crosslinks with the polymer, enhancing interfacial stress transfer and achieving PN-modified nano-calcium carbonate. In PN-modified nano-calcium carbonate, the phosphate and amino groups act as acid and gas sources during combustion, exhibiting a synergistic effect. Compared to traditional nano-calcium carbonate, PN-modified nano-calcium carbonate can be used synergistically with phosphorus-nitrogen flame retardants, reducing the amount of phosphorus-nitrogen flame retardants needed and lowering costs. The reagents used in this method are non-toxic and free of heavy metals, meeting environmental friendliness requirements. Attached Figure Description

[0011] Figure 1 This is a flowchart of the process for the synergistic modification of nano-calcium carbonate by aminophosphorylation according to the present invention. Figure 2 The infrared spectrum of the aminophosphorylation synergistically modified nano-calcium carbonate of this invention; Figure 3 This is the XRD pattern of the aminophosphorylation synergistic modification of nano-calcium carbonate according to the present invention; Figure 4 This is the TG diagram of the aminophosphorylation synergistic modification of nano-calcium carbonate according to the present invention; Figure 5 This is a water contact angle diagram of the aminophosphorylation synergistic modification of nano-calcium carbonate according to the present invention. Detailed Implementation

[0012] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0013] Example 1 like Figure 1 As shown, a method for preparing aminophosphorylation synergistically modified nano-calcium carbonate includes the following steps: Step 1) Take 10-20 g of nano calcium carbonate and add it to 200 mL of anhydrous ethanol or deionized water. Then, use an ultrasonic disperser to treat it for 30 minutes to ensure that the nano calcium carbonate particles are evenly dispersed and avoid agglomeration. Step 2) Take 5-15g of phosphorus source compound (one or more of phosphoric acid, sodium hexametaphosphate, and triethanolamine phosphate) and dissolve it in an appropriate amount of deionized water; Step 3) Slowly add 10-20% by weight of the nitrogen source compound (one or more of urea, aminophosphonic acid, or aminomethylenephosphonic acid) and the phosphorus source compound liquid from Step 2) to the nano-calcium carbonate dispersion while stirring to avoid violent reaction. Step 4) Place the mixture from Step 3) on a magnetic stirrer and maintain a temperature of 50-70°C for 3-6 hours. Adjust the pH of the reaction system to neutral using NaOH or HCl to ensure that the phosphate groups and amino groups can be successfully grafted onto the surface of the nano-calcium carbonate.

[0014] Step 5) After the reaction is complete, wash the nano-calcium carbonate repeatedly with deionized water until the pH of the solution is close to neutral to remove unreacted phosphorus and nitrogen source compounds.

[0015] Step 6) The product from step 6) is dried in a vacuum drying oven at 60-80°C to constant weight, and finally PN modified nano calcium carbonate is obtained.

[0016] Example 2 The difference between this embodiment and Embodiment 1 is that, in this embodiment, phosphating and nitriding are performed in two steps, including the following steps: Step 1) is the same as in Example 1; Step 2) Slowly add the phosphorus source compound to the nano-calcium carbonate dispersion, controlling the amount to be 10-20% of the mass of the nano-calcium carbonate; Step 3) Place the mixture from Step 2) in a magnetic stirrer, and stir for 2-4 hours at a reaction temperature of 30-50°C to promote the combination of phosphate groups with hydroxyl groups on the surface of calcium carbonate. Step 4) Wash the phosphorylated nano-calcium carbonate repeatedly with deionized water until neutral, and then dry it at 60-80°C to constant weight; Step 5) Disperse the phosphorylated nano-calcium carbonate again in deionized water or ethanol, and add a nitrogen source compound at 10-20% of the mass of nano-calcium carbonate. Step 6) Heat the mixture from Step 5 to 50-70°C and stir for 4-6 hours to achieve nitriding modification by reacting the nitrogen source with the surface of phosphorylated nano-calcium carbonate. Step 7) Wash repeatedly with deionized water to remove unreacted nitrogen sources. Then dry in a vacuum drying oven at 60-80°C to constant weight to obtain phosphorus-nitrogen flame-retardant nano-calcium carbonate powder.

[0017] Step 8) is the same as step 6 in Example 1.

[0018] Figure 2 and Figure 3 The infrared spectrum and XRD pattern of the aminophosphorylation synergistic modification of nano-calcium carbonate according to this invention are shown. Figure 2 As shown, aminophosphorylation synergistic modification of nano-calcium carbonate at 3445 cm⁻¹ -1 The characteristic NH peak appeared at 1662 cm⁻¹. -1 The peaks are HOP or CO-Ca vibrational peaks, reflecting the synergistic effect of phosphate groups and nitrogen sources; at 1250 cm⁻¹ -1 and 985cm -1 Absorption peaks belonging to the P=O stretching vibration and the POP vibration appeared at 1120 cm⁻¹; -1 The characteristic peak at that location is the absorption peak of the stretching vibration of the CN bond in the amine group. For example... Figure 3 As shown, the XRD peak spectrum of the PN synergistic modification sample shows a new characteristic peak at 2θ = 27.0°, which may be due to the PN synergistic modification inducing new crystal planes or new diffraction features. Figure 2 and Figure 3 This demonstrates the success of PN synergistic modification of nano-calcium carbonate.

[0019] Figure 4 The TG curve of the aminophosphorylation synergistically modified nano-calcium carbonate of this invention is shown below. Figure 4 As shown, PN synergistic modification of nano-calcium carbonate is mainly divided into three stages: low temperature stage (100-200℃), medium temperature stage (200-400℃), and high temperature stage (600-800℃).

[0020] The RC800 of Example 1 was 67.4%, which was 23.21% higher than that of unmodified nano-calcium carbonate. The final residue content of Example 2 was only 54.9%, the same as that of unmodified nano-calcium carbonate. The TG test results show that this technical solution promotes the initial degradation of nano-calcium carbonate at low temperatures, generating inert gases and diluting combustible gases. Simultaneously, the presence of phosphoric acid promotes the formation of more char layers in the nano-calcium carbonate, achieving a flame-retardant effect through the synergistic effect of the gas and condensed phases.

[0021] Figure 5 This is a water contact angle diagram of the aminophosphorylation synergistic modification of nano-calcium carbonate according to the present invention, as shown below. Figure 5 As shown, pure nano-calcium carbonate has a small contact angle of only 25.8°, exhibiting obvious hydrophilicity. After PN synergistic modification, the contact angles of Examples 1 and 2 increased to 132.65° and 120.26°, respectively, exhibiting obvious hydrophobicity, indicating that PN synergistic modification of nano-calcium carbonate can improve its hydrophobicity. In addition, the contact angle of Example 1 is also slightly larger than that of Example 2.

[0022] Table 1. Elemental content of PN-modified nano-calcium carbonate Table 1 shows that the PN-synergistic modified nano-calcium carbonate contains a large amount of P and N elements, and the content of P and N elements in Example 1 is even higher, indicating that the modification effect of Example 1 is better and the synergistic effect between phosphate groups and amino groups and nano-calcium carbonate is stronger.

[0023] This invention achieves synergistic enhancement of "dual functional groups," significantly improving its thermal stability. Firstly, the phosphate group (-PO4) 3- ) and CaCO3 surface Ca 2+ Irreversible chemical bonds are formed, preventing desorption during processing. Secondly, the amino groups (-NH2) form hydrogen bonds or covalent crosslinks with the polymer, enhancing interfacial stress transfer and achieving PN-modified nano-calcium carbonate. In PN-modified nano-calcium carbonate, the phosphate and amino groups act as acid and gas sources during combustion, exhibiting a synergistic effect. Compared to traditional nano-calcium carbonate, PN-modified nano-calcium carbonate can be used synergistically with phosphorus-nitrogen flame retardants, reducing the amount of phosphorus-nitrogen flame retardants needed and lowering costs. The reagents used in this method are non-toxic and free of heavy metals, meeting environmental friendliness requirements.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing aminophosphorylation synergistically modified nano-calcium carbonate, characterized in that, Includes the following steps: S1. Add 10-20g of nano calcium carbonate to 200mL of anhydrous ethanol or deionized water, and treat with an ultrasonic disperser for 30 minutes to form a uniform dispersion. S2. Dissolve 5-15g of phosphorus source compound in deionized water; S3. Take 10-20% of the nitrogen source compound by mass of nano-calcium carbonate, and slowly add the nitrogen source compound and the phosphorus source compound solution in S2 to the dispersion in S1 while stirring. S4. Place the mixture in a magnetic stirrer and stir to react. After the reaction is complete, adjust the pH of the system to neutral with NaOH or HCl. S5. Wash the product repeatedly with deionized water until the solution pH is close to neutral to remove unreacted phosphorus and nitrogen source compounds. S6. The washed product is dried in a vacuum drying oven to constant weight to obtain aminophosphorylated synergistic modified nano-calcium carbonate.

2. The method for preparing aminophosphorylation synergistically modified nano-calcium carbonate according to claim 1, characterized in that, The phosphorus source compound is one or more of phosphoric acid, sodium hexametaphosphate, and triethanolamine phosphate.

3. The method for preparing aminophosphorylation synergistically modified nano-calcium carbonate according to claim 1, characterized in that, The nitrogen source compound is one or more of urea, aminophosphonic acid, or aminomethylenephosphonic acid.

4. The method for preparing aminophosphorylation synergistically modified nano-calcium carbonate according to claim 1, characterized in that, In S4, the reaction temperature is 50-70°C; the reaction time is 3-6 hours.

5. The method for preparing aminophosphorylated synergistically modified nano-calcium carbonate according to claim 1, characterized in that, In S6, the drying temperature is 60-80°C.

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