CN115746150B - High purity nitrocotton preparation method - Google Patents
High purity nitrocotton preparation method Download PDFInfo
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- CN115746150B CN115746150B CN202211455407.4A CN202211455407A CN115746150B CN 115746150 B CN115746150 B CN 115746150B CN 202211455407 A CN202211455407 A CN 202211455407A CN 115746150 B CN115746150 B CN 115746150B
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- 229920001220 nitrocellulos Polymers 0.000 title claims abstract description 121
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000002253 acid Substances 0.000 claims abstract description 111
- 238000005406 washing Methods 0.000 claims abstract description 109
- 238000009835 boiling Methods 0.000 claims abstract description 52
- 239000002994 raw material Substances 0.000 claims abstract description 35
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229920000742 Cotton Polymers 0.000 claims description 60
- 238000000034 method Methods 0.000 claims description 50
- 238000010411 cooking Methods 0.000 claims description 46
- 239000000047 product Substances 0.000 claims description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 46
- 239000000463 material Substances 0.000 claims description 42
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 40
- 238000006396 nitration reaction Methods 0.000 claims description 39
- 229920002678 cellulose Polymers 0.000 claims description 38
- 239000001913 cellulose Substances 0.000 claims description 38
- 238000006243 chemical reaction Methods 0.000 claims description 34
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 20
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 17
- 229910017604 nitric acid Inorganic materials 0.000 claims description 17
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 16
- 230000007935 neutral effect Effects 0.000 claims description 11
- 230000035484 reaction time Effects 0.000 claims description 9
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 8
- 239000012043 crude product Substances 0.000 claims description 8
- 239000000835 fiber Substances 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 15
- 230000001546 nitrifying effect Effects 0.000 abstract description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 10
- 239000002585 base Substances 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 7
- 239000003513 alkali Substances 0.000 description 7
- 238000005886 esterification reaction Methods 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 238000007034 nitrosation reaction Methods 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 230000009935 nitrosation Effects 0.000 description 4
- 239000003380 propellant Substances 0.000 description 4
- 239000000020 Nitrocellulose Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000032050 esterification Effects 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 230000003749 cleanliness Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229920001131 Pulp (paper) Polymers 0.000 description 1
- 229910001037 White iron Inorganic materials 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- -1 nitrocellulose ester Chemical class 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000012797 qualification Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
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Abstract
The invention discloses a preparation method of high-purity nitrocotton, and belongs to the technical field of nitrocotton production. Aiming at the technical problem of low purity of nitrocotton produced by the prior art, the invention provides a preparation method of high-purity nitrocotton. According to the invention, the quality of raw materials in the production process of the nitrocotton is controlled, and the steps of nitrifying, acid driving, boiling and washing, fine breaking, fine washing and the like are combined, so that the high-purity nitrocotton with acetone insoluble matters and ash content lower than 0.1% can be obtained, the purity of the nitrocotton is greatly improved, and the quality of the nitrocotton is improved.
Description
Technical Field
The invention belongs to the technical field of nitrocotton production, and particularly relates to a preparation method of high-purity nitrocotton.
Background
Nitrocellulose (abbreviated NC) is a main component of single-base, double-base, triple-base, modified double-base, crosslinked modified double-base and composite modified double-base propellants. Wherein, the content of nitrocotton in the single-base propellant powder is generally 94-97%, and the content of nitrocotton in the (modified) double-base propellant powder is generally more than 50%.
The nitrocotton is a product obtained by substituting hydroxyl groups in cellulose with nitrate groups, and the production process in the prior art mainly comprises the processes of cellulose pretreatment, nitration, acid driving, boiling and washing, fine breaking, fine washing and the like. After pretreatment of cellulose, the cellulose is separated from nitromixed acid (nitric acid, sulfuric acid and water mixture, and different components have different esterification capacities, at present, nitrocotton is mainly divided into A, B, C, D cotton, and A, B, C, D cotton is mainly distinguished according to different nitrogen content of nitrocotton, and the nitrogen content of nitrocotton is controlled by the mixed acid components participating in the reaction and esterification conditions, so that the esterification reaction is completed in a reaction kettle, and the main technological conditions in the esterification reaction process are a nitrification coefficient (the mass ratio of the mixed acid participating in the reaction to the dry weight of cellulose), a reaction temperature and a reaction time.
In the esterification reaction process, nitric acid in mixed acid is reduced, water content is increased, acid driving and displacement washing of the reacted acid cotton mixture are completed in a centrifuge, the removed waste acid is reused in an acid preparation machine, and then raw materials nitric acid and sulfuric acid are supplemented to prepare nitrified mixed acid for use; the amount of residual acid (generally expressed as residual acid) adsorbed by the material after the acid is driven by the nitrocotton is still large, and replacement washing is also needed to reduce the residual acid adsorbed by the nitrocotton.
And (5) stabilizing the materials after acid-driving washing in a boiling and washing kettle and adjusting the viscosity. In the prior art, the boiling and washing process is firstly carried out by acid boiling under certain acidity, temperature and time, and then alkaline boiling is carried out under certain alkalinity, temperature and time. After the alkali boiling is finished, the material is subjected to fine breaking, fine washing and dehydration to obtain the energetic nitrocotton product. In order to ensure the stability of the nitrocotton containing energy, a certain amount of sodium carbonate and calcium carbonate are added in the fine breaking and fine washing processes, and the addition amount of the sodium carbonate and the calcium carbonate is about 2-3 per mill of absolute dry quantity of the nitrocotton.
The purity of nitrocotton directly affects the purity of the subsequent propellant. The main technical indexes for measuring the purity of the nitrocotton are ash and acetone insoluble matters, wherein the ash index is that nitrocotton is nitrocarbonized, burned residues are tested, and the burned residues mainly comprise salt impurities; whereas acetone insolubles represent a ratio of less than 10.5% nitrogen in the product. In terms of the current purity technical level of domestic nitrocotton, the ash content of the nitrocotton is generally about 0.2 percent, and the acetone insoluble matter is generally about 0.25 percent.
Disclosure of Invention
The invention aims to solve the technical problem that the purity of nitrocotton produced by the prior art is low.
In order to solve the technical problems, the invention provides a preparation method of high-purity nitrocotton, which comprises the following steps:
A. nitration reaction: mixing a cellulose raw material with mixed acid to perform nitration reaction to obtain a nitrocotton crude product; the cellulose raw material is refined cotton cellulose or pulp cellulose; the ash content of the cellulosic feedstock is no more than 0.15wt%; the content of nitrocotton fiber in the mixed acid is not more than 0.3wt%;
wherein, when the refined cotton cellulose is used as raw material, the nitric acid content in the mixed acid is controlled to be 21 to 23 weight percent; the nitrification coefficient is controlled to be 40-60; the time of the nitration reaction is controlled to be 30-35 min; the reaction temperature of the target product B cotton is 27-30 ℃; the target product is A, C or the reaction temperature of D cotton is 32-35 ℃;
when pulp cellulose is used as a raw material, the nitric acid content in the mixed acid is controlled to be 45.5-49 wt%; controlling the nitrification coefficient to be 18-25; the nitration reaction time is 60-80 min; the reaction temperature of the target product B cotton is 40-45 ℃; the target product is A, C or the reaction temperature of D cotton is 47-52 ℃;
B. acid flooding washing: c, acid-driving washing is carried out on the crude product obtained in the step A, and the residual acidity of the material after the acid-driving washing is controlled to be lower than 20%;
C. boiling and washing: acid cooking: acid cooking is carried out on the acid-driven washed material, and the initial acidity of the cooking water is controlled: 2-6 g/L, the acid boiling time of the target product of B cotton is not less than 6 hours, and the acid boiling time of the target product of A, C or D cotton is not less than 4 hours;
boiling in water: the materials after acid cooking are subjected to water cooking, the initial pH value of the cooking water is controlled to be neutral, the water cooking time of target products of B cotton is not less than 6 hours, and the water cooking time of target products of A, C or D cotton is not less than 4 hours;
soaking and hot washing: soaking and hot washing the material after water boiling by using 0.2-0.5 g/L sodium carbonate aqueous solution, wherein the hot washing temperature is 50-70 ℃;
D. fine breaking and fine washing: adding sodium carbonate with the dry weight of 0.5-1.0 per mill into the fine breaking process, and adding sodium carbonate with the dry weight of 0-1.0 per mill into the fine washing process;
E. and (5) after fine washing, dehydrating to obtain the high-purity nitrocotton.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in the step a, the ash content of the cellulose raw material is not more than 0.12wt%.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in the step a, the content of nitrocotton fiber in the mixed acid is not more than 0.2wt%.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in step a, when purified cotton cellulose is used as a raw material, the nitrosation coefficient is controlled to be 48-52; the time of the nitration reaction is controlled to be 32-33 min.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in step a, when pulp cellulose is used as a raw material, the nitrification coefficient is controlled to be 19-22; the nitration reaction time is 65-75 min.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in the step B, the residual acidity of the material after the flooding washing is controlled to be lower than 15%.
Preferably, in the above-mentioned high purity nitrocotton preparation method, in the step C, when the acid is boiled, the initial acidity of the boiled water is controlled: 3-6 g/L.
In the preparation method of the high-purity nitrocotton, in the step C, the acid boiling temperature is controlled to be less than 120 ℃.
In the method for preparing the high-purity nitrocotton, in the step C, the washing time after the acid boiling is based on the condition that the pH value of the washed material is neutral.
In the preparation method of the high-purity nitrocotton, in the step C, the water boiling temperature is controlled to be less than 120 ℃.
In the method for preparing the high-purity nitrocotton, in the step C, the washing time after water boiling is based on the condition that the pH value of the washed material is neutral.
In the method for preparing the high-purity nitrocotton, in the step C, the hot washing time is controlled to be 1-2 hours when the nitrocotton is soaked and hot washed.
In the method for preparing the high-purity nitrocotton, calcium carbonate is not added in the fine breaking and fine washing processes in the step D.
In the preparation method of the high-purity nitrocotton, the acetone insoluble matter and ash content of the high-purity nitrocotton are not more than 0.1wt%.
In the invention, the nitrification coefficient refers to the mass ratio of the dry weight of the cellulose raw material to the mixed acid in the nitrifying process.
In the invention, the residual acidity refers to the mass ratio of residual acid (calculated by sulfuric acid) carried by materials after acid driving washing to the dry weight of nitrocotton.
The invention has the beneficial effects that:
according to the invention, related factors influencing the purity of the nitrocotton in the nitrocotton production are studied in depth, the quality of raw materials in the nitrocotton production process is controlled, and the steps of nitrifying, acid driving, boiling and washing, fine breaking, fine washing and the like are combined and optimized, so that the high-purity nitrocotton with acetone insoluble substances and ash content lower than 0.1% can be obtained, the purity of the nitrocotton is greatly improved, and the quality of the nitrocotton is improved.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
Specifically, the preparation method of the high-purity nitrocotton comprises the following steps:
A. nitration reaction: mixing a cellulose raw material with mixed acid to perform nitration reaction to obtain a nitrocotton crude product; the cellulose raw material is refined cotton cellulose or pulp cellulose; the ash content of the cellulosic feedstock is no more than 0.15wt%; the content of nitrocotton fiber in the mixed acid is not more than 0.3wt%;
wherein, when the refined cotton cellulose is used as raw material, the nitric acid content in the mixed acid is controlled to be 21 to 23 weight percent; the nitrification coefficient is controlled to be 40-60; the time of the nitration reaction is controlled to be 30-35 min; the reaction temperature of the target product B cotton is 27-30 ℃; the target product is A, C or the reaction temperature of D cotton is 32-35 ℃;
when pulp cellulose is used as a raw material, the nitric acid content in the mixed acid is controlled to be 45.5-49 wt%; controlling the nitrification coefficient to be 18-25; the nitration reaction time is 60-80 min; the reaction temperature of the target product B cotton is 40-45 ℃; the target product is A, C or the reaction temperature of D cotton is 47-52 ℃;
B. acid flooding washing: c, acid-driving washing is carried out on the crude product obtained in the step A, and the residual acidity of the material after the acid-driving washing is controlled to be lower than 20%;
C. boiling and washing: acid cooking: acid cooking is carried out on the acid-driven washed material, and the initial acidity of the cooking water is controlled: 2-6 g/L, the acid boiling time of the target product of B cotton is not less than 6 hours, and the acid boiling time of the target product of A, C or D cotton is not less than 4 hours;
boiling in water: the materials after acid cooking are subjected to water cooking, the initial pH value of the cooking water is controlled to be neutral, the water cooking time of target products of B cotton is not less than 6 hours, and the water cooking time of target products of A, C or D cotton is not less than 4 hours;
soaking and hot washing: soaking and hot washing the material after water boiling by using 0.2-0.5 g/L sodium carbonate aqueous solution, wherein the hot washing temperature is 50-70 ℃;
D. fine breaking and fine washing: adding sodium carbonate with the dry weight of 0.5-1.0 per mill into the fine breaking process, and adding sodium carbonate with the dry weight of 0-1.0 per mill into the fine washing process;
E. and (5) after fine washing, dehydrating to obtain the high-purity nitrocotton.
In the production of nitrocotton, the ash content of the raw materials is affected by the amount of inorganic salt added in boiling, fine breaking and fine washing; in the production process, the processes of nitration, acid driving, boiling and washing and the like can influence the content of acetone insoluble substances of the nitrocotton. Therefore, the invention optimizes the quality of raw materials in the production process of the nitrocotton, and the steps of nitration, acid driving, boiling and washing, fine breaking, fine washing and the like, and comprehensively adjusts various factors so as to obtain the nitrocotton with high purity.
In the art, the cellulosic feedstock for producing nitrocotton is typically purified cotton cellulose or pulp cellulose, which requires pretreatment prior to nitration. When the pulp cellulose is used as a raw material, a slicer is generally used to cut pulp rolls into granular pulp with certain specification. In addition, the refined cotton fibers are long and fluffy, so that a large amount of mixed acid is required to ensure that the refined cotton quilt is soaked by the mixed acid and keeps fluidity; the slice pulp is granular, so that the material can be soaked by the mixed acid and keep fluidity only by using a small amount of the mixed acid.
The ash content of cellulose raw materials directly affects the ash content of nitrocotton, so the invention controls the ash content of refined cotton and pulp raw materials. Through experiments, the content of the cellulose raw material needs to be controlled to be not more than 0.15%, more preferably not more than 0.12%.
The nitration reaction process of cellulose and mixed acid is critical to determine the content of acetone insoluble matters in the nitrocotton, and the main nitration conditions of the high-purity nitrocotton with low acetone insoluble matters are as follows:
(1) Mixed acid cleanliness requirement for nitration: in the production process of nitrocotton, waste acid after acid removal is used as mother liquor acid in the preparation of mixed acid, and raw materials of nitric acid and sulfuric acid are supplemented to prepare a ternary mixture of nitric acid, sulfuric acid and water, namely the mixed acid for nitration. The degree of cleanliness of the mixed acid is not a concern in the prior art. However, a large number of experiments show that the acid-driving process inevitably brings some tiny nitrocotton into the waste acid, so that the nitrocotton has excessively long residence time in the acid and has irregular reactions such as denitration, re-nitration and the like, and the product quality is brought into the product, and the rise of acetone insoluble matters of the product can be greatly influenced. The mixed acid adopted by the invention can be prepared by adopting the prior art, but in order to reduce the content of acetone insoluble matters in the nitrocotton product, the content of nitrocotton fibers in the selected mixed acid for nitrocotton needs to be controlled to be not more than 0.3 percent, preferably not more than 0.2 percent. The invention can adopt natural clarification or filtration treatment and the like to realize the purification of mixed acid, thereby preparing the high-purity nitrocotton.
(2) Main nitration conditions: in industrial production, the operation of the nitration reaction is generally: and a certain amount of cellulose is soaked by a certain amount of mixed acid and then enters the reactor together, and a certain reaction time and reaction temperature are controlled in the reaction process. However, in the prior art, the condition control of the nitration reaction is rough, and the requirement of high purity nitrocotton production is difficult to meet. Specifically:
in the prior art, the reaction mixed acid taking refined cotton as a raw material is generally controlled according to the content of nitric acid of 18-25%, but the range can not meet the reaction requirement of high-purity nitrocotton, and meanwhile, the content of nitric acid is too high, the process volatilization is large, and the cost is increased; in the prior art, the reaction temperature of the cotton B is generally 20-30 ℃, the reaction temperature of the cotton A, C, D is generally 30-40 ℃, and the temperature can not meet the reaction requirement of high-purity nitrocotton. The inventor determines through a large number of experiments that the nitric acid content in mixed acid is controlled to be 21-23% on the premise of meeting the nitration quality of high-purity nitrocotton, the cotton B reaction temperature is 27-30 ℃, and the cotton A, C, D reaction temperature is 32-35 ℃.
The nitration coefficient and the nitration time also affect the purity of the nitrocotton, and when the purified cotton cellulose is used as a raw material, the test shows that the nitration coefficient needs to be controlled to be 40-60, and the nitration reaction time is 30-35 min; preferably, the nitrification coefficient is controlled to be 48-52, and the time of the nitrification reaction is controlled to be 32-33 min.
In the prior art, the reaction mixed acid taking pulp as a raw material is generally controlled according to the nitric acid content of 45% -50%, but the range can not meet the reaction requirement of high-purity nitrocotton, and meanwhile, the nitric acid content is too high, the process volatilization is large, and the cost is increased; in the prior art, the reaction temperature of the cotton B is generally 35-45 ℃, the reaction temperature of the cotton A, C, D is generally 45-55 ℃, and the temperature can not meet the reaction requirement of high-purity nitrocotton. The inventor determines through a large number of experiments that the nitric acid content in the mixed acid is controlled to be 45.5-49 wt% on the premise of meeting the nitration quality of high-purity nitrocotton, the cotton B reaction temperature is 40-45 ℃, and the cotton A, C, D reaction temperature is 47-52 ℃.
The nitrosation coefficient and the nitrosation time also affect the purity of nitrocotton, and when pulp cellulose is used as a raw material, the nitrosation coefficient needs to be controlled to be 18-25 through experiments, and the nitrosation reaction time is 60-80 min; preferably, the nitrification coefficient is controlled to be 19-22, and the nitrification reaction time is 65-75 min.
The acid cotton mixture after nitration reaction is generally subjected to acid driving and displacement washing in a centrifuge. Drive acid washing requirements: the nitrocotton acid-driving washing effect is also a main factor influencing the purity of nitrocotton, the acid-driving washing effect is good, the quantity of residual acid carried by materials is small, the subsequent stable treatment is facilitated, the acid-driving washing effect is poor, the quantity of residual acid carried by materials is large, the subsequent stable treatment is difficult, the final stability of the product is ensured, the subsequent fine washing is required to increase the energy consumption by heat washing, the consumption of sodium carbonate alkali is required to be increased to neutralize the residual acid of the materials, and the ash content of the product is increased. The step B can be operated by adopting the existing flooding washing process, but the residual acidity of the materials after flooding washing is required to be strictly controlled to be lower than 20%, and is more preferable when the residual acidity is lower than 15%, so that the follow-up stabilization treatment is facilitated; if the residual acid is too high, the stability qualification rate is low after the subsequent stabilization treatment.
In the prior art, the process of acid cooking and alkali cooking ((the alkali cooking temperature is generally above 100 ℃ and the alkali cooking time is long) is adopted for cooking and washing, and in the alkali cooking process, a certain degree of saponification reaction of the nitrocellulose ester exists, so that the insoluble content of acetone in a nitrocotton product is increased.
The acid cooking process conditions are as follows: control the initial acidity of the cooking water: 2 to 6g/L, preferably 3 to 6g/L; according to different target products, proper acid boiling time needs to be controlled so as to be beneficial to releasing low-grade and low-nitrogen nitrified unstable impurities in fiber channels, reducing the content of acetone insoluble matters in the products and ensuring that the stability meets the requirements: the acid cooking time of cotton B is not less than 6 hours, and the acid cooking time of cotton A and C, D is not less than 4 hours; the acid boiling temperature is less than 120 ℃ (the specific temperature can be adjusted according to the viscosity of the product); and (3) carrying out conventional washing after acid boiling, wherein the washing time is based on the condition that the pH value of the washed material is neutral.
The water boiling process conditions are as follows: the initial pH of the boiling water is controlled to be neutral (if the boiling water is only neutral, the boiling water is generally defaulted to be 7, the protection range is too small, and the recommended range is supplemented); according to different target products, the proper acid cooking time needs to be controlled as well: the cotton water boiling time B is not less than 6 hours, and the cotton water boiling time A and C, D are not less than 4 hours; the boiling temperature is less than 120 ℃ (the specific temperature can be adjusted according to the viscosity of the product); and (3) performing conventional washing after boiling in water, wherein the washing time is based on the condition that the pH value of the washed material is neutral.
The non-alkali-boiled nitrocellulose has poor rigidity, is not beneficial to fine breakage, and takes longer time and energy consumption in the fine breakage process to ensure fine breakage; and most of fine breaking equipment abrasive discs are alloy steel or white cast iron abrasive discs, and the residual acid carried by nitrocotton fibers can be added into the abrasive discs for corrosion. Therefore, although the invention is subjected to acid boiling and water boiling, the material system can not be directly broken, and meanwhile, because the invention is subjected to acid boiling and water boiling, the invention adopts a low-strength alkaline washing mode, so that residual acid carried by the material can be further neutralized, the stability of the product is improved, and the hydrolysis of ester in the alkaline washing process can be avoided. Through experiments, under the conditions of improving the fine breaking efficiency and preventing the material residual acid from corroding grinding sheets or fine breaking equipment, the material is soaked in 0.2-0.5 g/L sodium carbonate aqueous solution for hot washing after water boiling and washing, the hot washing temperature is controlled to be 50-70 ℃, and the hot washing time is controlled to be 1-2 hours.
A certain amount of calcium carbonate is added in the fine breaking and fine washing processes of the prior nitrocotton manufacturing process, so that the addition of the calcium carbonate is beneficial to the stability of the product, but the ash content and the acetone insoluble content of the product are increased, and the nitrocotton product with low ash content and low acetone insoluble content is difficult to obtain. The invention ensures the stability of the product on the premise of not adding calcium carbonate by improving the acid-driving washing, boiling washing and alkali washing processes at the front end. Therefore, in the method of the invention, calcium carbonate is not added in the fine breaking and fine washing processes, the amount of sodium carbonate added in the fine breaking process is 0.5 to 1.0 per mill of absolute dry quantity of the nitrocotton, and the amount of sodium carbonate added in the fine washing process is 0 to 1.0 per mill of absolute dry quantity of the nitrocotton (depending on the stability of the nitrocotton).
In addition, in most of the prior nitrocotton manufacturing processes, the slurry after the break is directly sent to a fine washer; the invention increases the suction filtration washing process after the fine breaking, separates the unstable impurity in the fine breaking material once again, which further ensures that the stability of the final product meets the requirement. The method comprises the following specific steps: and (3) discharging directly without draining after the soaking and hot washing are finished, and carrying out fine breaking, wherein sodium carbonate with the dry weight of 0.5-1.0 per mill is added in the fine breaking process, the slurry is dehydrated until the water content of the material is lower than 70wt%, the slurry mixing concentration of the dehydrated material is 8-12 wt% for fine washing, and the sodium carbonate is added in the fine washing process, wherein the quantity of the sodium carbonate is 0-1.0 per mill of the absolute dry weight of the nitrocotton.
In the industrial production of the nitrocotton, when each batch of raw materials is nitrified, in order to control the quantity of the nitrocotton in each batch, the feeding quantity of the refined cotton is controlled, and the actual yield is clear according to the esterification substitution reaction and the actual experience, so that the nitrocotton can be calculated and measured in the actual production.
The method combines the influence of the total multifactor, optimizes the quality of raw materials, the steps of nitration, acid driving, boiling and washing, fine breaking, fine washing and the like in the production process of the nitrocotton, obviously improves the purity of the obtained nitrocotton product, and ensures that the content of acetone insoluble matters and ash is not more than 0.1 weight percent.
The present invention will be described in further detail by way of examples, which are not intended to limit the scope of the invention.
Example 1
Taking X60 refined cotton, X60 wood pulp and X200 cotton pulp as raw materials, preprocessing, and performing nitration according to nitration parameters shown in table 1 to obtain crude products of A-D cotton.
TABLE 1 nitration parameters
The crude products of the cotton A-D are subjected to acid-driving washing by adopting a five-stage countercurrent washing process, and the residual acidity of the materials after the acid-driving washing is controlled according to the table 2.
TABLE 2 residual acidity after acid drive washing
| Sequence number | Variety of species | Residual acidity/%after acid drive washing |
| 1 | A | 13.6 |
| 2 | B | 10.7 |
| 3 | C | 14.2 |
| 4 | D | 15.8 |
| 5 | B | 12.9 |
| 6 | D | 8.7 |
| 7 | B | 7.2 |
| 8 | D | 11.5 |
The materials after acid-driving washing are subjected to acid cooking, water cooking and heat washing in sequence according to the boiling and washing process conditions in table 3, the acid cooking materials and the water cooking materials are subjected to conventional washing, and the washing end point is based on the neutrality of the pH test paper; after boiling and washing, low-concentration alkaline water is used for hot washing, water is not discharged after the hot washing is finished, and the materials are directly discharged until the follow-up fine break.
TABLE 3 cooking and washing process conditions
And (3) carrying out fine breaking and fine washing according to the process conditions of the table 4, dehydrating the slurry after fine breaking by a vacuum belt type suction filter until the water content of the material is lower than 70%, carrying out fine washing with the pulp mixing concentration of the dehydrated material being 8% -12%, controlling the adding amount of sodium carbonate in the fine breaking and fine washing processes, stirring the slurry after fine breaking of each type of nitrocotton at normal temperature of the fine washing machine for 30min, carrying out no further hot washing, and dehydrating after fine washing to obtain an A-D cotton finished product, wherein the quality technical indexes are shown in the table 5.
TABLE 4 Fine break, fine wash sodium carbonate addition
Table 5 quality specifications of various kinds of nitrocotton
Claims (11)
1. The preparation method of the high-purity nitrocotton is characterized by comprising the following steps of: the method comprises the following steps:
A. nitration reaction: mixing a cellulose raw material with mixed acid to perform nitration reaction to obtain a nitrocotton crude product; the cellulose raw material is refined cotton cellulose or pulp cellulose; the ash content of the cellulosic feedstock is no more than 0.15wt%; the content of nitrocotton fiber in the mixed acid is not more than 0.3wt%;
when the refined cotton cellulose is used as a raw material, the nitric acid content in the mixed acid is controlled to be 21-23 wt%; controlling the nitrification coefficient to be 40-60; the time of the nitration reaction is controlled to be 30-35 min; the reaction temperature of the target product B cotton is 27-30 ℃; the target product is A, C or the reaction temperature of D cotton is 32-35 ℃;
when pulp cellulose is used as a raw material, controlling the nitric acid content in the mixed acid to be 45.5-49 wt%; controlling the nitrification coefficient to be 18-25; the time of the nitration reaction is 60-80 min; the reaction temperature of the target product B cotton is 40-45 ℃; the target product is A, C or the reaction temperature of D cotton is 47-52 ℃;
B. acid flooding washing: c, acid-driving washing is carried out on the crude product obtained in the step A, and the residual acidity of the material after the acid-driving washing is controlled to be lower than 15%;
C. boiling and washing: acid cooking: acid cooking is carried out on the acid-driven washed material, and the initial acidity of the cooking water is controlled: 2-6 g/L, wherein the acid cooking time of the target product of B cotton is not less than 6 hours, and the acid cooking time of the target product of A, C or D cotton is not less than 4 hours;
boiling in water: the materials after acid cooking are subjected to water cooking, the initial pH value of the cooking water is controlled to be neutral, the water cooking time of target products of B cotton is not less than 6 hours, and the water cooking time of target products of A, C or D cotton is not less than 4 hours;
soaking and hot washing: soaking and hot washing the materials after water boiling by using 0.2-0.5 g/L sodium carbonate aqueous solution, wherein the hot washing temperature is 50-70 ℃;
D. fine breaking and fine washing: adding sodium carbonate with the dry weight of 0.5-1.0 per mill into the fine breaking process, and adding sodium carbonate with the dry weight of 0-1.0 per mill into the fine washing process;
E. after fine washing, dehydrating to obtain high-purity nitrocotton; the acetone insoluble matter and ash content of the high-purity nitrocotton are not more than 0.1wt%.
2. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in step a, the ash content of the cellulosic feedstock is no more than 0.12wt%; the content of nitrocotton fiber in the mixed acid is not more than 0.2wt%.
3. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step A, when refined cotton cellulose is used as a raw material, the nitrification coefficient is controlled to be 48-52; the time of the nitration reaction is controlled to be 32-33 min.
4. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step A, when pulp cellulose is used as a raw material, the nitrification coefficient is controlled to be 19-22; the nitration reaction time is 65-75 min.
5. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, during acid cooking, the initial acidity of the cooking water is controlled: 3-6 g/L.
6. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, the temperature of the acid cooking is controlled to be less than 120 ℃ during the acid cooking.
7. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, the washing time after the acid boiling is based on the condition that the pH value of the washed material is neutral.
8. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, when in boiling, the boiling temperature is controlled to be less than 120 ℃.
9. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, the washing time after water boiling is based on the condition that the pH value of the washed material is neutral.
10. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in the step C, during soaking and hot washing, the hot washing time is controlled to be 1-2 hours.
11. The method for preparing high purity nitrocotton according to claim 1, wherein the method comprises the steps of: in step D, no calcium carbonate is added during the fine break and fine wash processes.
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| CN102321183A (en) * | 2011-08-05 | 2012-01-18 | 四川北方硝化棉股份有限公司 | Wood pulp nitrocotton production method |
| CN112321726A (en) * | 2020-11-23 | 2021-02-05 | 北方化学工业股份有限公司 | Boiling and washing process of low-viscosity high-nitration-degree energy-containing B cotton |
| CN112409497A (en) * | 2020-11-09 | 2021-02-26 | 北方化学工业股份有限公司 | Preparation method of low-ash energy-containing nitrocotton |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102321183A (en) * | 2011-08-05 | 2012-01-18 | 四川北方硝化棉股份有限公司 | Wood pulp nitrocotton production method |
| CN112409497A (en) * | 2020-11-09 | 2021-02-26 | 北方化学工业股份有限公司 | Preparation method of low-ash energy-containing nitrocotton |
| CN112321726A (en) * | 2020-11-23 | 2021-02-05 | 北方化学工业股份有限公司 | Boiling and washing process of low-viscosity high-nitration-degree energy-containing B cotton |
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