A method for preparing high-nitrogen nitrocellulose

Abstract

This invention relates to a method for preparing high-nitrogen nitrocellulose, belonging to the field of energetic materials technology. The invention uses monodisperse cellulose oligomers as raw materials and prepares high-nitrogen nitrocellulose through a nitration reaction. Monodisperse cellulose oligomers can provide more nitro substituent groups, and the uniformity of the raw materials results in a uniform nitrogen distribution in the nitrocellulose, with a nitrogen content exceeding 13.5%. Furthermore, the solubility is significantly improved, and its compatibility is wider.

Description

Technical Field

[0001] This invention relates to a method for preparing high-nitrogen nitrocellulose, belonging to the field of energetic materials technology. Background Technology

[0002] Nitrocellulose (NC) is the product of the esterification reaction between cellulose and nitrates. In 1845, researchers first successfully synthesized nitrocellulose by treating cotton with nitric acid. With advancements in technology, more and more synthetic methods have emerged. The nitrogen content of nitrocellulose is an important indicator for energy evaluation, and its applications vary significantly depending on the nitrogen content. However, currently, industrial production of nitrocellulose in my country cannot stably produce nitrocellulose with a nitrogen content higher than 13.5%.

[0003] In the field of civilian high-energy fireworks (such as large-scale festival fireworks, emergency rescue signal flares, and stage special effects fireworks), high-nitrogen-content (≥13.0%) nitrocellulose is the core substrate for achieving high brightness and long-lasting combustion. In the field of civilian blasting (such as small-scale mining, low-power explosives for building demolition, and engineering blasting agents), the energy density advantage of high-nitrogen-content nitrocellulose is key to improving rock-breaking efficiency. In scenarios such as model rocket propellants and civilian energetic adhesives, the contradiction between the energy output requirements of high-nitrogen-content nitrocellulose and processing and usage safety is equally acute. If the nitrogen content is reduced to ≤12.5% ​​to ensure safety, the propellant thrust will be insufficient, and the adhesive bonding strength and energy release efficiency will both decrease. In the military and special energetic materials technology system, nitrocellulose, with its controllable energy release characteristics, has long been used as a core basic material for weapons and special energy devices. Whether considering the usage environment, processing technology, safety standards, and energy requirements in the civilian sector, or the basic requirements for energy output and safety stability of high-nitrogen nitrocellulose in the propellants and propellants of the defense sector, there is an urgent need to develop a nitrocellulose that combines the advantages of high nitrogen content energy with high safety. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for preparing high-nitrogen nitrocellulose. This invention uses monodisperse cellulose oligomers as raw materials and prepares high-nitrogen nitrocellulose through a nitration reaction. Monodisperse cellulose oligomers can provide more nitro substituent groups, and the raw materials are uniform, resulting in a uniform nitrogen distribution in the nitrocellulose, with a nitrogen content exceeding 13.5%. Furthermore, the solubility is significantly improved, and its compatibility is wider.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] An application of a monodisperse cellulose oligomer as a raw material for preparing nitrocellulose with high nitrogen content, wherein the monodisperse cellulose oligomer has an average degree of polymerization of 3 to 100 and a degree of polymerization distribution coefficient of 1.00 to 2.00; and the nitrocellulose has a nitrogen content greater than 13.5%.

[0007] Preferably, the monodisperse cellulose oligomer has an average degree of polymerization of 3 to 30, and the nitrogen content of the nitrocellulose is 13.92%.

[0008] A method for preparing high-nitrogen nitrocellulose, comprising the following steps: Step 1: Dry the monodisperse cellulose oligomers; Step 2: Add the dried monodisperse cellulose oligomer to the nitrifying agent to carry out the nitration reaction; Step 3: After the nitration reaction is completed, the cellulose is deacidified, neutralized, washed, and dried to obtain nitrated cellulose with high nitrogen content.

[0009] The monodisperse cellulose oligomer has an average degree of polymerization of 3 to 100 and a degree of polymerization distribution coefficient of 1.00 to 2.00; the nitrocellulose has a nitrogen content of more than 13.5%.

[0010] Preferably, in step one, the drying temperature is 40~120℃ and the drying time is 1~6 hours.

[0011] Preferably, in step two, the nitrating agent includes nitric acid, a mixture of phosphorus pentoxide and nitric acid in a mass ratio of 1:2 to 1:10, or a mixture of nitric acid and sulfuric acid in a mass ratio of 1:0.5 to 1:4, or a mixture of nitric acid and phosphoric acid in a mass ratio of 1:0.1 to 1:3, or a mixture of nitric acid and acetic acid in a mass ratio of 1:0.1 to 1:5, a mixture of nitric acid and acetic anhydride in a mass ratio of 1:0.1 to 1:4, or a mixture of nitric acid and an organic solvent in a mass ratio of 1:0.1 to 1:10; the organic solvent includes carbon tetrachloride, methyl nitrate, or chloroform.

[0012] Preferably, in step two, the mass ratio of monodisperse cellulose oligomer to nitrifying agent is 0.01~0.5:1.

[0013] Preferably, in step two, the nitration reaction method includes direct nitration, ultrasound-assisted synthesis, plasma-modified synthesis, and continuous nitration.

[0014] Preferably, in step two, the nitration reaction temperature is 0~60℃ and the nitration reaction time is 5~60 minutes.

[0015] Preferably, in step three, ice is added and powdered sodium carbonate is added to neutralize to neutral.

[0016] A high-nitrogen nitrocellulose is prepared by the above method, wherein the nitrogen content of the nitrocellulose is greater than 13.5%.

[0017] Beneficial effects The nitrocellulose prepared by this invention has a nitrogen content as high as 13.92%, with higher energy and friction sensitivity. Moreover, the preparation process is simple, quick, and all intermediate products can be recycled, resulting in low cost and suitability for industrial production. It also simultaneously possesses high energy and reliable safety, providing effective safety assurance for the entire process of transportation and use. Attached Figure Description

[0018] Figure 1 The infrared spectra are for the examples and comparative examples.

[0019] Figure 2 This is a comparison chart of nitrogen content between the examples and the comparative examples.

[0020] Figure 3 This is a comparison diagram showing the swelling of the examples and comparative examples in ethylnitramine nitrate (NENA).

[0021] Figure 4 This is a comparison diagram of the swelling of the examples and comparative examples in acetone.

[0022] Figure 5 This is a comparison diagram of swelling in ethyl acetate between the examples and the comparative examples. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments.

[0024] Example 1 Step 1: Place the monodisperse cellulose oligomer (average degree of polymerization of 20, degree of polymerization distribution coefficient of 1.08) prepared from cellulose in a vacuum oven at 105 degrees Celsius and dry for 2 hours.

[0025] Step 2: Add cold 90% nitric acid (90% fuming acid, but not red-fuming) to a conical flask. Slowly add phosphorus pentoxide to the nitric acid at a mass ratio of 0.404:1 while stirring. This will yield a nitration mixture with the following composition: 64% nitric acid, 26% phosphoric acid, and 10% phosphorus pentoxide. Transfer the resulting nitration mixture to a bottle with a glass stopper and store it in a cool, dark place.

[0026] Step 3: Weigh the nitration mixture prepared in Step 2 into a weighing bottle. In a constant temperature bath at 20±0.10 ℃, using stainless steel tweezers, quickly introduce the cellulose sample from Step 1 into the nitration mixture at a mass ratio of 0.05:1 to the product from Step 2. Nitrify for 20 minutes, rotating the sample approximately every 5 minutes.

[0027] Step 4: Filter to remove excess acid, add ice, and add a small amount of powdered sodium carbonate to neutralize to neutral. Wash three times with water until the washing liquid is neutral, dry, and obtain high-nitrogen nitrocellulose, denoted as NC-MCOs.

[0028] Example 2 Step 1: Place the monodisperse cellulose oligomer (average degree of polymerization of 20, degree of polymerization distribution coefficient of 1.08) prepared from cellulose in a vacuum oven at 105 degrees Celsius and dry for 2 hours.

[0029] Step 2: Mix 10ml of 98wt% sulfuric acid and 10ml of 99wt% nitric acid to obtain a nitration mixture. Place the nitration mixture into a bottle with a glass stopper and store it in a cool place.

[0030] Step 3: Weigh the nitration mixture prepared in Step 2 into a weighing bottle. In a constant temperature bath at 40±0.10 ℃, use stainless steel tweezers to add 1g of cellulose sample from Step 1 to 20ml of nitration mixture in Step 2. Nitrify for 120 minutes, rotating and stirring the sample every 5 minutes or so.

[0031] Step 4: Filter and wash, then dry the product to obtain nitrocellulose.

[0032] Comparative Example 1 The highest nitrogen content nitrated cellulose currently produced industrially is designated NC-255.

[0033] Comparative Example 2 In this comparative example, the raw material was cellulose with a degree of polymerization (DPw) of 1800, which was purchased from Shanghai Yien Chemical Technology Co., Ltd., China; the rest was the same as in Example 1, and nitrocellulose was obtained, which was denoted as NC-Cellulose.

[0034] Comparative Example 3 In this comparative example, deacidification was performed by filtration of the mixture after the nitration reaction of the raw material and nitrification liquid to remove excess acid, followed by pouring it into a large amount of boiling water. The rest was the same as in Example 1, resulting in nitrocellulose, denoted as NC-MCOs-W.

[0035] Experimental Example 1 Evaluation of nitrification degree and nitrogen content Fourier transform infrared spectroscopy (FTIR) measures the absorption of infrared light by a sample to obtain information about its molecular vibrations and rotations, thereby identifying the main chemical groups. The FTIR results show that the nitrated sample is almost identical to the comparative sample, indicating successful nitration. Figure 1 As shown.

[0036] A high-temperature combustion method was used to convert nitrogen (N) in the sample into a stable form, N2, under a pure oxygen atmosphere. The N content was then determined using a thermal conductivity detector (TCD). The nitrogen content of the nitrated oligomers prepared in this experiment (NC-MCOs, 13.92%) significantly exceeded that of current mainstream industrial products (NC-255, 13.43%) and cellulose with a high degree of nitration polymerization (NC-Cellulose, 13.55%). Figure 2 As shown.

[0037] Experimental Example 2 Physicochemical performance parameter evaluation Measurements revealed that NC-MCOs exhibit higher friction sensitivity, density, and heat of combustion compared to NC-255. Based on comparative analysis of experimental data, NC-MCOs demonstrate significantly improved physicochemical properties compared to NC-255. Friction sensitivity increased from 160N to 180N (an increase of 12.5%), material density increased from 1.6486 g / cm³ to 1.7685 g / cm³ (an increase of 7.27%), and combined with a heat of combustion increase from 2983.57 cal / g to 3324.44 cal / g (an increase of 11.40%). Energy efficiency and safety are significantly improved.

[0038] Table 1

[0039] Experimental Example 3 Evaluation of the solubility of benign solvents Compared to the comparative example, the solubility of the experimental example in ethyl nitramine nitrate (NENA), acetone, and ethyl acetate was increased by 10 times, 16 times, and 20 times, respectively. The ability to dissolve more solute in the same volume of solvent implies a significant increase in energy, such as... Figure 3-5 As shown.

[0040] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. The application of a monodisperse cellulose oligomer as a raw material for preparing high-nitrogen nitrocellulose, characterized in that: The monodisperse cellulose oligomer has an average degree of polymerization of 3 to 30 and a degree of polymerization distribution coefficient of 1.00 to 2.00; the nitrogen content of the nitrocellulose is greater than 13.5%.

2. The application of the monodisperse cellulose oligomer as described in claim 1 as a raw material for preparing high-nitrogen nitrocellulose, characterized in that: The nitrogen content of the nitrocellulose is 13.92%.

3. A method for preparing high-nitrogen nitrocellulose, characterized in that: The method steps include: Step 1: Dry the monodisperse cellulose oligomers; Step 2: Add the dried monodisperse cellulose oligomer to the nitrifying agent to carry out the nitration reaction; Step 3: After the nitration reaction is completed, the cellulose is deacidified, neutralized, washed, and dried to obtain nitrated cellulose with high nitrogen content. The monodisperse cellulose oligomer has an average degree of polymerization of 3 to 30 and a degree of polymerization distribution coefficient of 1.00 to 2.00; the nitrocellulose has a nitrogen content of more than 13.5%.

4. The method for preparing high-nitrogen nitrocellulose as described in claim 3, characterized in that: In step one, the drying temperature is 40~120℃ and the drying time is 1~6 hours.

5. The method for preparing high-nitrogen nitrocellulose as described in claim 3, characterized in that: In step two, the nitrifying agent includes nitric acid, or a mixture of phosphorus pentoxide and nitric acid in a mass ratio of 1:2 to 1:10, or a mixture of nitric acid and sulfuric acid in a mass ratio of 1:0.5 to 1:4, or a mixture of nitric acid and phosphoric acid in a mass ratio of 1:0.1 to 1:3, or a mixture of nitric acid and acetic acid in a mass ratio of 1:0.1 to 1:5, a mixture of nitric acid and acetic anhydride in a mass ratio of 1:0.1 to 1:4, or a mixture of nitric acid and an organic solvent in a mass ratio of 1:0.1 to 1:10; the organic solvent includes carbon tetrachloride, methyl nitrate, or chloroform.

6. A method for preparing high-nitrogen nitrocellulose as described in claim 3 or 5, characterized in that: In step two, the mass ratio of monodisperse cellulose oligomer to nitrifying agent is 0.01~0.5:

1.

7. The method for preparing high-nitrogen nitrocellulose as described in claim 3, characterized in that: In step two, the nitration reaction methods include direct nitration, ultrasound-assisted synthesis, plasma-modified synthesis, and continuous nitration.

8. A method for preparing high-nitrogen nitrocellulose as described in claim 3 or 7, characterized in that: In step two, the nitration reaction temperature is 0~60℃ and the nitration reaction time is 5~60 minutes.

9. The method for preparing high-nitrogen nitrocellulose as described in claim 3, characterized in that: In step three, add ice and powdered sodium carbonate to neutralize to neutral.

10. A high-nitrogen nitrocellulose, characterized in that: It is prepared by the method described in any one of claims 3 to 9.

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