CN116333173A - Cellulose acetate and preparation method thereof - Google Patents
Cellulose acetate and preparation method thereof Download PDFInfo
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- CN116333173A CN116333173A CN202310628947.6A CN202310628947A CN116333173A CN 116333173 A CN116333173 A CN 116333173A CN 202310628947 A CN202310628947 A CN 202310628947A CN 116333173 A CN116333173 A CN 116333173A
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- 229920002301 cellulose acetate Polymers 0.000 title claims abstract description 76
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 118
- 239000000047 product Substances 0.000 claims abstract description 117
- 238000001914 filtration Methods 0.000 claims abstract description 102
- 239000000463 material Substances 0.000 claims abstract description 98
- 230000007062 hydrolysis Effects 0.000 claims abstract description 92
- 238000000034 method Methods 0.000 claims abstract description 77
- 238000005886 esterification reaction Methods 0.000 claims abstract description 71
- 230000032050 esterification Effects 0.000 claims abstract description 64
- 230000008569 process Effects 0.000 claims abstract description 50
- 229920002678 cellulose Polymers 0.000 claims abstract description 42
- 239000001913 cellulose Substances 0.000 claims abstract description 42
- 238000000227 grinding Methods 0.000 claims abstract description 41
- 239000004744 fabric Substances 0.000 claims abstract description 27
- 239000012065 filter cake Substances 0.000 claims abstract description 22
- 229920000742 Cotton Polymers 0.000 claims abstract description 20
- 150000003839 salts Chemical class 0.000 claims abstract description 17
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 238000001556 precipitation Methods 0.000 claims abstract description 15
- 230000004913 activation Effects 0.000 claims abstract description 14
- 238000001994 activation Methods 0.000 claims abstract description 14
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 189
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 76
- 229960000583 acetic acid Drugs 0.000 claims description 68
- 239000003054 catalyst Substances 0.000 claims description 68
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 claims description 54
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 32
- 229910052783 alkali metal Inorganic materials 0.000 claims description 27
- 150000001340 alkali metals Chemical class 0.000 claims description 27
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 27
- 239000002002 slurry Substances 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 238000006467 substitution reaction Methods 0.000 claims description 19
- SCVFZCLFOSHCOH-UHFFFAOYSA-M potassium acetate Chemical compound [K+].CC([O-])=O SCVFZCLFOSHCOH-UHFFFAOYSA-M 0.000 claims description 16
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 15
- 239000012362 glacial acetic acid Substances 0.000 claims description 15
- 239000001632 sodium acetate Substances 0.000 claims description 15
- 235000017281 sodium acetate Nutrition 0.000 claims description 15
- 238000004140 cleaning Methods 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 12
- 239000000706 filtrate Substances 0.000 claims description 12
- 238000000465 moulding Methods 0.000 claims description 12
- 230000003213 activating effect Effects 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
- UEGPKNKPLBYCNK-UHFFFAOYSA-L magnesium acetate Chemical compound [Mg+2].CC([O-])=O.CC([O-])=O UEGPKNKPLBYCNK-UHFFFAOYSA-L 0.000 claims description 10
- 239000011654 magnesium acetate Substances 0.000 claims description 10
- 235000011285 magnesium acetate Nutrition 0.000 claims description 10
- 229940069446 magnesium acetate Drugs 0.000 claims description 10
- 235000017166 Bambusa arundinacea Nutrition 0.000 claims description 8
- 235000017491 Bambusa tulda Nutrition 0.000 claims description 8
- 241001330002 Bambuseae Species 0.000 claims description 8
- 235000015334 Phyllostachys viridis Nutrition 0.000 claims description 8
- 239000011425 bamboo Substances 0.000 claims description 8
- 229940079593 drug Drugs 0.000 claims description 8
- 239000003814 drug Substances 0.000 claims description 8
- 235000011056 potassium acetate Nutrition 0.000 claims description 8
- 229920001131 Pulp (paper) Polymers 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 4
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 4
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 4
- 239000003513 alkali Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 230000001376 precipitating effect Effects 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 2
- 230000003301 hydrolyzing effect Effects 0.000 claims description 2
- -1 alkaline earth metal acetate Chemical class 0.000 claims 2
- 230000000903 blocking effect Effects 0.000 abstract description 22
- 239000012535 impurity Substances 0.000 abstract description 15
- 239000000243 solution Substances 0.000 description 49
- 230000000052 comparative effect Effects 0.000 description 25
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 11
- 238000006243 chemical reaction Methods 0.000 description 11
- 229910052938 sodium sulfate Inorganic materials 0.000 description 11
- 235000011152 sodium sulphate Nutrition 0.000 description 11
- 238000009826 distribution Methods 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 8
- 238000012805 post-processing Methods 0.000 description 8
- 230000008901 benefit Effects 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 238000003801 milling Methods 0.000 description 6
- 229920001747 Cellulose diacetate Polymers 0.000 description 5
- 238000009987 spinning Methods 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 239000000499 gel Substances 0.000 description 4
- 239000000017 hydrogel Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- UBXAKNTVXQMEAG-UHFFFAOYSA-L strontium sulfate Chemical compound [Sr+2].[O-]S([O-])(=O)=O UBXAKNTVXQMEAG-UHFFFAOYSA-L 0.000 description 4
- 229920002284 Cellulose triacetate Polymers 0.000 description 3
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 3
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 230000036632 reaction speed Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229910052730 francium Inorganic materials 0.000 description 2
- KLMCZVJOEAUDNE-UHFFFAOYSA-N francium atom Chemical compound [Fr] KLMCZVJOEAUDNE-UHFFFAOYSA-N 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052705 radium Inorganic materials 0.000 description 2
- HCWPIIXVSYCSAN-UHFFFAOYSA-N radium atom Chemical compound [Ra] HCWPIIXVSYCSAN-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- RXSHXLOMRZJCLB-UHFFFAOYSA-L strontium;diacetate Chemical compound [Sr+2].CC([O-])=O.CC([O-])=O RXSHXLOMRZJCLB-UHFFFAOYSA-L 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- PTHCMJGKKRQCBF-UHFFFAOYSA-N Cellulose, microcrystalline Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC)C(CO)O1 PTHCMJGKKRQCBF-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 1
- 125000003668 acetyloxy group Chemical group [H]C([H])([H])C(=O)O[*] 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000005660 hydrophilic surface Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 230000002285 radioactive effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- FOGKDYADEBOSPL-UHFFFAOYSA-M rubidium(1+);acetate Chemical compound [Rb+].CC([O-])=O FOGKDYADEBOSPL-UHFFFAOYSA-M 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/22—Post-esterification treatments, including purification
- C08B3/26—Isolation of the cellulose ester
Abstract
The invention discloses cellulose acetate and a preparation method thereof, relates to the technical field of cellulose, and solves the technical problems that the impurity content is high, the blocking value of cellulose acetate sheets is low, and the downstream product yield is affected when cellulose acetate is produced by domestic and foreign cellulose raw materials such as cotton linter pulp in the prior art. The preparation method of the cellulose acetate comprises the following steps: the method comprises the steps of activation, esterification and grinding, primary filtration, hydrolysis and grinding, secondary filtration and post-treatment, wherein in the secondary filtration, materials after hydrolysis are filtered by a filter press, and salt is precipitated on filter cloth to form a filter cake for assisting filtration by controlling precipitation parameters of the salt. According to the preparation method of the cellulose acetate, the grinding process is added in the esterification and hydrolysis process, the filtering process is added after the esterification and hydrolysis, and the filter cake formed by precipitation of the filter press and the salt on the filter cloth is subjected to double filtration, so that the blocking value of a product can be improved, and the strength and the yield of the product can be improved.
Description
Technical Field
The invention relates to the technical field of cellulose, in particular to cellulose acetate and a preparation method thereof.
Background
Cellulose acetate is a product obtained by substituting hydroxyl groups on a cellulose molecular chain with acetoxy groups, and taking cellulose of natural sources such as cotton linter pulp, bamboo pulp or wood pulp as a main raw material. The degree to which the hydroxyl group is substituted is referred to as the substitution degree, and is classified into cellulose triacetate and cellulose diacetate according to the substitution degree. The existing large-scale production process of cellulose acetate uses wood pulp or cotton linter pulp to carry out esterification reaction with acetic anhydride in the presence of solvent (acetic acid or methylene dichloride) and catalyst (such as sulfuric acid), and the substitution degree is adjusted through saponification (hydrolysis); and then the processes of molding, cleaning, dehydrating, drying and the like are carried out to obtain cellulose acetate flakes or particles. Two production processes commonly used in the prior art are as follows:
(1) Low temperature high catalyst process
In the process, the weight of the catalyst sulfuric acid accounts for about 10-15% of the weight of pulp, the reaction temperature is less than 0 ℃ and the finishing temperature is less than or equal to 50 ℃. The reactor takes frozen brine with the temperature less than or equal to minus 30 ℃ as a cooling medium, is cooled by a jacket, removes the heat of the reactor, and controls the esterification reaction speed. The key point of the process is to control the temperature rising rate of the esterification reaction, because the reaction speed is high under the condition of high sulfuric acid, and cellulose acetate is easy to degrade. If the temperature is too high, the degradation of cellulose acetate is serious, and even waste products are generated. Therefore, the process is difficult to adjust control parameters during the production transfer and the raw material replacement, and waste materials are easy to generate.
In the hydrolysis reaction, parameters are adjusted by adding certain amount of steam, water and magnesium acetate, and the hydrolysis temperature, the hydrolysis agent (water) and the hydrolysis catalyst (sulfuric acid) are controlled in different time periods.
(2) High-temperature esterification/hydrolysis process under reduced pressure
The catalyst consumption in the process is about 1-5% of the pulp, and in the esterification reaction process, the solvent mixed acid is evaporated to take away heat in a decompression mode, so that the esterification reaction speed is controlled. However, the process has the disadvantages of inaccurate time point for stopping the esterification reaction, high hydrolysis temperature, poor controllability of viscosity and difficult adjustment.
After the esterification reaction is completed, the solvent cooled by evaporation is placed in a reactor and discharged into a hydrolyzer together. And (3) introducing steam and hot water, and heating the slurry to more than 120 ℃ by utilizing the reaction heat of residual acetic anhydride and water and the steam heat to perform hydrolysis reaction. After a certain time, magnesium acetate is added to neutralize the catalyst sulfuric acid, and the hydrolysis reaction is finished.
Wood pulp or cotton linter pulp is a main raw material for producing cellulose acetate, and abundant cotton linter pulp and bamboo pulp resources exist in China, but because of the structure and reactivity difference between the cotton linter pulp and the bamboo pulp and wood pulp, the cellulose acetate sheet produced by the cotton linter pulp and the bamboo pulp has lower blocking value, and the downstream product yield is affected. The cellulose acetate flake blockage value represents the impurity amount of cellulose acetate in acetone solution, the lower the blockage value is, the more impurities are, more paste caps are initiated during spinning, and the stability of spinning production is poor. The blockage value is therefore a primary indicator of the quality level of the cellulose acetate flake and is also an important indicator directly affecting the filtration performance of the cellulose diacetate flake/acetone solution.
Therefore, how to reduce the impurity content of the cellulose acetate sheet to improve the blocking value of the cellulose acetate sheet in the process of producing cellulose acetate by using cotton linter pulp or bamboo pulp is a technical problem to be solved by the person skilled in the art.
Disclosure of Invention
The invention discloses cellulose acetate and a preparation method thereof, which are used for solving the technical problems that the blocking value of cellulose acetate sheets is lower and the downstream product yield is affected due to high impurity content when cellulose acetate is produced by cotton linter pulp or bamboo pulp in the prior art.
In order to solve the problems, the invention adopts the following technical scheme:
in a first aspect, the invention provides a method for preparing cellulose acetate.
The preparation method of the cellulose acetate comprises the following steps:
step S100: activating, namely uniformly mixing a cellulose raw material, glacial acetic acid and a first catalyst, and continuously stirring for activation to obtain an activated mixed material;
step S200: esterifying and grinding, namely adding acetic anhydride and a second catalyst into the mixed material, esterifying cellulose in the mixed material, grinding material slurry through a grinder in the esterification process, and adding dilute acetic acid into the material slurry to terminate the esterification process;
step S300: filtering the materials after esterification by a filter to obtain filtrate;
step S400: hydrolyzing and grinding, namely adding a third catalyst into the filtrate to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding an alkali metal or alkaline earth metal acetic acid solution to terminate the hydrolysis reaction after the required substitution degree is reached;
step S500: filtering the material after hydrolysis by a filter press, and precipitating salt on filter cloth to form a filter cake for assisting filtration by controlling precipitation parameters of the salt;
step S600: and (3) post-treatment, namely molding, cleaning and drying the materials subjected to secondary filtration to obtain a cellulose acetate product.
Further, in step S500, the precipitation parameters are: one or more of the concentration of the alkali or alkaline earth metal acetic acid solution, the water content of the hydrolysis material, and the temperature at which the hydrolysis material is filtered.
Further, the first catalyst, the second catalyst, and the third catalyst are: one or more of sulfuric acid, phosphoric acid, and perchloric acid; the alkali metal or alkaline earth metal acetic acid solution is one or more of lithium acetate, sodium acetate, potassium acetate and magnesium acetate.
Alkali metals include lithium, sodium, potassium, rubidium, cesium, francium, which francium is radioactive and too rare to be considered herein. Cesium is the most active of all alkali metals, is too basic, may be difficult to stabilize the substitution degree of cellulose acetate, and is not used in this patent. Rubidium acetate is very expensive, is widely used as a catalyst for synthesizing vinyl acetate, and is not suitable for the invention.
Alkaline earth metals include beryllium, magnesium, calcium, strontium, barium, radium, where beryllium and radium are highly toxic and are not considered in this patent. Barium acetate is toxic, barium sulfate (when the catalyst is sulfuric acid) which is a product formed by the reaction of the barium acetate and a catalyst synthesized by cellulose acetate is insoluble in water, and can not be removed by washing the cellulose acetate, and substances containing the barium are listed in European Union toy test standard EN71-3, and the residual amount is required to be less than or equal to 1000mg/kg, so that the barium acetate is not considered by the invention. Strontium sulfate generated by the reaction of strontium acetate and a catalyst of the synthesis reaction of cellulose acetate (when the catalyst is sulfuric acid) is slightly soluble in water, and the strontium sulfate is light blue or light green, light yellow or light red, and remains in the cellulose acetate, so that the transparency and chromaticity of the cellulose acetate and products thereof are affected, and therefore, the strontium acetate cannot be used in the invention.
Further, in step S500, the salt precipitated on the filter cloth is formed by reacting an alkali metal or alkaline earth metal acetic acid solution with a catalyst.
Further, the mass fraction of the acetic acid solution of the alkali metal or alkaline earth metal is 20% -30%, the water content of the hydrolysis material is 15% -25%, and the temperature of the hydrolysis material during filtration is 20-60 ℃.
Further, in step S100, the amount of glacial acetic acid added is 250 to 450 parts by weight and the amount of the first catalyst added is 0.1 to 1 part by weight per 100 parts by weight of the cellulose raw material.
Further, in the step S200, the addition amount of acetic anhydride is 200-300 parts by weight, the addition amount of the second catalyst is 1-5 parts by weight, the addition amount of the dilute acetic acid is 160-250 parts by weight, and the mass fraction of the dilute acetic acid is 55% -65% per 100 parts by weight of the cellulose raw material.
Further, in step S400, the amount of the third catalyst added is 1 to 8 parts by weight and the amount of the alkali metal or alkaline earth metal acetic acid solution added is 15 to 25 parts by weight per 100 parts by weight of the cellulose raw material.
Further, in step S100, the cellulose raw material is one or more of cotton linter pulp, wood pulp and bamboo pulp.
In a second aspect of the invention, a cellulose acetate is provided.
The cellulose acetate comprises the following components in parts by weight: 100 parts by weight of cellulose raw material, 250-450 parts by weight of glacial acetic acid, 0.1-1 part by weight of first catalyst, 200-300 parts by weight of acetic anhydride, 1-5 parts by weight of second catalyst, 160-250 parts by weight of dilute acetic acid, 1-8 parts by weight of third catalyst and 15-25 parts by weight of acetic acid solution of alkali metal or alkaline earth metal, wherein the cellulose acetate is a transparent or non-transparent product prepared by adopting the preparation method of the cellulose acetate according to any one of the technical schemes, and is applied to the fields of medicines, transparent products and/or non-transparent products.
The technical scheme adopted by the invention can achieve the following beneficial effects:
according to the preparation method of the cellulose acetate, the grinding procedure is added in the esterification and hydrolysis processes, fibers, gel and the like which are difficult to react can be ground into finer particles, accessibility of chemicals is improved, and further uniformity of esterification and hydrolysis is improved, so that the content of impurities (short fibers) in a cellulose acetate product can be reduced, the blocking value of the product is improved, and the production efficiency, yield and product strength of a downstream product can be improved. Specifically, the esterification and hydrolysis processes in the prior art only have stirring procedures, but because of the specificity of cellulose reaction, stirring can not thoroughly solve the uniformity of the reaction, especially the cotton linter pulp, has poorer reaction uniformity, and the reacted materials still contain impurities such as partial unreacted and complete short fibers. These impurities can reduce the product blockage value, easily block the spinning nozzle in the downstream spinning process, and affect the strength of the filament bundle, resulting in higher breakage rate and reduced product yield. The invention can improve the uniformity of the reaction by adding the grinding procedure in the esterification and hydrolysis processes, not only can improve the blocking value of the product, but also can improve the production efficiency, the yield and the product strength of the downstream product.
Specifically, in the process of esterifying cellulose, the cellulose or the cellulose derivative has a hydrophilic surface due to the existence of hydrogen bonds and Van der Waals force, so that the cellulose or the cellulose derivative can be crosslinked into a three-dimensional network cellulose hydrogel with a large amount of organic matters and polymers through hydrogen bonds, covalent bonds or ionic interactions; the cellulose macromolecules in the cellulose hydrogel are tightly piled up, have the characteristics of high crystallinity, high strength and high modulus, cannot be easily dissolved or lose the structural integrity, and the cellulose wrapped in the cellulose hydrogel is difficult to completely esterify, so that the yield of the product and the uniformity of the reaction are directly influenced, and the strength of the final product is influenced. In addition, the solubility of the cellulose esterification product in glacial acid is different, and gel is formed. According to the preparation method of the cellulose acetate, a grinding procedure is added in the esterification process, and the grinding function is to break up cellulose gel formed by various reasons including hydrogel through a physical method, so that the uniformity of the reaction is improved. In the hydrolysis process, cellulose triacetate obtained by esterification is hydrolyzed into cellulose diacetate, and gel is formed due to low solubility of the cellulose triacetate in acetic acid, so that the uniformity of hydrolysis, the distribution difference of substitution degree of products and the solubility of the products are influenced, and the production efficiency and the yield of the cellulose diacetate are further influenced. According to the preparation method of cellulose acetate, a grinding procedure is added in the hydrolysis process, and the uniformity of hydrolysis is improved by crushing gel, so that the production efficiency and the yield of the product are improved.
On the other hand, the preparation method of the cellulose acetate increases the filtering procedure after esterification and hydrolysis, removes impurities in the hydrolysis and esterification processes through the filtration of a filter press, separates out salt on a filter cloth and forms a filter cake by controlling the water content of hydrolysis materials and the concentration of an acetic acid solution of alkali metal or alkaline earth metal, and can effectively increase the filtering effect through the double filtration of the filter cake and the filter cloth, further reduce the content of impurities in cellulose acetate products and improve the blocking value of the products. In the downstream spinning process of the cellulose acetate product after double filtration, the yield of the downstream product can be improved by about 5% at the highest, and the economic benefit is obvious. In addition, the method of the invention enables the salt to be separated out on the filter cloth for filtration assistance by controlling the water content of the hydrolysis material and the concentration of the acetic acid solution of alkali metal or alkaline earth metal, namely, the method of the invention utilizes the components in the hydrolysis material to separate out for filtration assistance, and has the advantage of no need of adding extra cost. Specifically, when the existing filter press is used for filtering, the pore diameter of the filter cloth is generally 0.1 μm to 100 μm, and part of impurities in cellulose after the reaction easily penetrate through the filter cloth, and if the filtering effect is improved only by increasing the precision of the filter cloth, the cost is too high. According to the invention, a large amount of salt contained in the hydrolyzed material is utilized, and according to the solubility of the salt in the material, the salt can be precipitated out by controlling the concentration of the added salt and the moisture content in the material, so that a layer of filter cake is formed on the filter cloth. Since the particles forming the filter cake are generally smaller, the pores formed between the particles are smaller, and impurities in the hydrolysis and esterification processes can be removed in large amounts, so that the filtering effect can be effectively increased, and the cost is not increased.
The method for preparing the cellulose acetate comprises the steps of adding a grinding process in the esterification and hydrolysis processes, adding a filtering process after the esterification and hydrolysis processes, and performing double filtration through a filter press and a filter cake formed by precipitation of salt on the filter cloth, so that the content of impurities in a cellulose acetate product can be reduced, the blocking value of the product can be improved, and the product strength can be improved, thereby solving the problems that the blocking value of cellulose acetate sheets is lower and the yield of downstream products is affected due to high impurity content in the production of cellulose acetate by using cotton linter pulp in the prior art.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples herein, which are within the scope of the invention as defined by the claims, will be within the scope of the invention as defined by the claims.
The preparation method of the cellulose acetate comprises the following steps:
step S100: activating. And uniformly mixing the cellulose raw material, glacial acetic acid and sulfuric acid serving as a first catalyst, and continuously stirring for activation to obtain an activated mixed material.
Step S200: esterification and milling. Adding acetic anhydride and sulfuric acid serving as a second catalyst into the mixed material, esterifying cellulose in the mixed material, grinding material slurry through a grinder in the esterification process, and adding dilute acetic acid into the material slurry to terminate the esterification process.
Step S300: and (5) filtering once. And filtering the esterified material by using a filter to obtain filtrate.
Step S400: hydrolysis and grinding. And adding a third catalyst sulfuric acid into the filtrate to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding an alkali metal or alkaline earth metal acetic acid solution to terminate the hydrolysis reaction after the required substitution degree is reached. The alkali metal or alkaline earth metal acetic acid solution is one or more of lithium acetate, sodium acetate, potassium acetate and magnesium acetate. The lithium acetate, sodium acetate, potassium acetate and magnesium acetate have the advantages of no radioactivity, high safety and low cost. The first catalyst, the second catalyst and the third catalyst may be the same or different in concentration and temperature.
Specifically, after the required substitution degree is reached, directly adding an acetic acid solution of alkali metal or alkaline earth metal; if solid salt is added, a large solid is formed in the solution, and the filter screen is blocked during secondary filtration.
Step S500: and (5) secondary filtration. Filtering the hydrolyzed material with a filter press, and precipitating sulfate on the filter cloth to form a filter cake for assisting filtration by controlling the precipitation parameter of the sulfate.
Preferably, the precipitation parameters of the sulfate are the concentration of the alkali or alkaline earth metal acetic acid solution, the water content of the hydrolysis mass and the temperature at which the hydrolysis mass is filtered. Namely: the acetic acid solution of alkali metal or alkaline earth metal in the step S400 not only can play a role in stopping the hydrolysis reaction, but also can react with the catalyst sulfuric acid to form sulfate, and the sulfate forms a filter cake to assist filtration in the filtration process.
Specifically, the mass fraction of the acetic acid solution of alkali metal or alkaline earth metal is 20% -30%, the water content of the hydrolysis material is 15% -25%, the temperature range of the hydrolysis material is 20-60 ℃ during filtration, so that sulfate is precipitated on filter cloth during secondary filtration to form a filter cake for assisting filtration. The mass fraction of the acetic acid solution of the alkali metal or alkaline earth metal is 20% -30%, and the acetic acid solution of the alkali metal or alkaline earth metal is an unsaturated solution, so that the problem that the added acetic acid solution of the alkali metal or alkaline earth metal is a supersaturated solution, so that sulfate is instantaneously separated out and is formed into a large block, and secondary filtration cannot be performed is solved.
The precipitation parameter of sulfate is not limited to control in the secondary filtration, and may be controlled simultaneously in step S400 and step S500. For example, the concentration of the alkali metal or alkaline earth metal acetic acid solution is controlled when the alkali metal or alkaline earth metal acetic acid solution is added in step S400, and the water content of the hydrolysis material and the temperature at which the hydrolysis material is filtered are controlled at the time of the secondary filtration. Specifically, the water content of the hydrolysis material may be controlled by adding water and/or an acetic acid solution of an alkali metal or alkaline earth metal to the hydrolysis material; the temperature of the hydrolyzed material is controlled by naturally cooling the hydrolyzed material during filtering.
Step S600: and (3) post-treatment, namely molding, cleaning and drying the materials subjected to secondary filtration to obtain transparent and/or non-transparent cellulose acetate products, and the method can be applied to the fields of medicines, transparent products and/or non-transparent products.
The cellulose acetate provided in the present application and the preparation method thereof are described in detail below by way of specific examples.
It should be noted that: the process parameters of each step in each example and comparative example remain the same, and existing process parameters can be used, and are collectively described herein, and are not described in detail in each example and comparative example. Specifically, in the activation step, the activation time is 90min; in the esterification step, acetic anhydride is added at the temperature of 25 ℃, and after sulfuric acid is added, the temperature of the system is controlled below 50 ℃; in the hydrolysis step, the hydrolysis temperature was 60℃and the hydrolysis time was determined based on the degree of substitution required.
Example 1
Step S100, activating: after 100 parts by weight of cotton linter pulp, 450 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification and grinding: 280 parts by weight of acetic anhydride and 1 part by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in the step S100 to fully esterify cellulose, and during the esterification, the material slurry was ground by a grinder, and finally 160 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 65%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis and grinding: and adding 8 parts by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 25 parts by weight of sodium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the sodium acetate solution is 25%.
Step S500, secondary filtration: and cooling the hydrolyzed material to room temperature, adjusting the water content of the hydrolyzed material to 15%, filtering by a filter press, and separating out sodium sulfate on the filter cloth to form a filter cake for assisting filtration.
Step S600, post-processing: and molding, cleaning and drying the materials after secondary filtration to obtain transparent and/or non-transparent cellulose acetate products, and the transparent and/or non-transparent cellulose acetate products can be applied to the fields of medicines, transparent products and/or non-transparent products.
The results of the product analysis are shown in Table 1.
Example 2
Step S100, activating: 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 0.5 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, and then are continuously stirred for activation, so that an activated mixed material is obtained.
Step S200, esterification and grinding: 300 parts by weight of acetic anhydride and 2 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in step S100 to allow the cellulose to be fully esterified, and during the esterification, the slurry of the material was ground by a grinder, and finally 250 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis and grinding: and adding 6 parts by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 25 parts by weight of magnesium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the magnesium acetate solution is 20%.
Step S500, secondary filtration: and cooling the hydrolyzed material to room temperature, adjusting the water content of the hydrolyzed material to 25%, filtering by a filter press, and separating out magnesium sulfate on filter cloth to form a filter cake for assisting filtration.
Step S600, post-processing: and molding, cleaning and drying the materials after secondary filtration to obtain transparent and/or non-transparent cellulose acetate products, and the transparent and/or non-transparent cellulose acetate products can be applied to the fields of medicines, transparent products and/or non-transparent products.
The results of the product analysis are shown in Table 1.
Example 3
Step S100, activating: 100 parts by weight of wood pulp, 250 parts by weight of glacial acetic acid and 0.1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, and then are continuously stirred for activation, so that an activated mixture is obtained.
Step S200, esterification and grinding: 200 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in step S100 to allow the cellulose to be fully esterified, and during the esterification, the slurry of the material was ground by a grinder, and finally 180 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 60%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis and grinding: and adding 4 parts by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 20 parts by weight of potassium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the potassium acetate solution is 30%.
Step S500, secondary filtration: and cooling the hydrolyzed material to room temperature, adjusting the water content of the hydrolyzed material to 25%, filtering by a filter press, and separating out potassium sulfate on the filter cloth to form a filter cake for assisting filtration.
Step S600, post-processing: and molding, cleaning and drying the materials after secondary filtration to obtain transparent and/or non-transparent cellulose acetate products, and the transparent and/or non-transparent cellulose acetate products can be applied to the fields of medicines, transparent products and/or non-transparent products.
The results of the product analysis are shown in Table 1.
Example 4
Step S100, activating: after 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification and grinding: 280 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in the step S100 to allow the cellulose to be fully esterified, and during the esterification, the slurry of the material was ground by a grinder, and finally 200 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis and grinding: and adding 1 part by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 15 parts by weight of sodium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the sodium acetate solution is 30%.
Step S500, secondary filtration: and cooling the hydrolyzed material to room temperature, adjusting the water content of the hydrolyzed material to 23%, filtering by a filter press, and separating out sodium sulfate on the filter cloth to form a filter cake for assisting filtration.
Step S600, post-processing: and molding, cleaning and drying the materials after secondary filtration to obtain transparent and/or non-transparent cellulose acetate products, and the transparent and/or non-transparent cellulose acetate products can be applied to the fields of medicines, transparent products and/or non-transparent products.
The results of the product analysis are shown in Table 1.
Comparative example 1
Step S100, activating: after 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification: 280 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in step S100 to fully esterify cellulose, and finally 200 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis: and adding 1 part by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, and adding 15 parts by weight of sodium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the sodium acetate solution is 30%.
Step S500, secondary filtration: and cooling the hydrolyzed material to room temperature, adjusting the water content of the hydrolyzed material to 23%, filtering by a filter press, and separating out sodium sulfate on the filter cloth to form a filter cake for assisting filtration.
Step S600, post-processing: and (3) molding, cleaning and drying the materials after secondary filtration to obtain the cellulose acetate product.
The results of the product analysis are shown in Table 1.
Comparative example 2
Step S100, activating: after 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification: 280 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in step S100 to fully esterify cellulose, and finally 200 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, hydrolysis: and adding 1 part by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, and adding 15 parts by weight of magnesium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the magnesium acetate solution is 30%.
Step S400, post-processing: and (3) molding, cleaning and drying the hydrolyzed material to obtain a cellulose acetate product.
The results of the product analysis are shown in Table 1.
Comparative example 3
Step S100, activating: after 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification and grinding: 280 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in the step S100 to allow the cellulose to be fully esterified, and during the esterification, the slurry of the material was ground by a grinder, and finally 200 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, hydrolysis and grinding: and adding 1 part by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 15 parts by weight of potassium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the potassium acetate solution is 30%.
Step S400, post-processing: and (3) molding, cleaning and drying the hydrolyzed material to obtain a cellulose acetate product.
The results of the product analysis are shown in Table 1.
Comparative example 4
Step S100, activating: after 100 parts by weight of cotton linter pulp, 300 parts by weight of glacial acetic acid and 1 part by weight of a first catalyst (sulfuric acid) are uniformly mixed, continuous stirring is carried out for activation, and an activated mixed material is obtained.
Step S200, esterification and grinding: 280 parts by weight of acetic anhydride and 5 parts by weight of a second catalyst (sulfuric acid) were added to the mixture obtained in the step S100 to allow the cellulose to be fully esterified, and during the esterification, the slurry of the material was ground by a grinder, and finally 200 parts by weight of dilute acetic acid was added to terminate the esterification. The mass fraction of the dilute acetic acid is 55%.
Step S300, primary filtration: filtering the esterified material by a basket filter to obtain filtrate.
Step S400, hydrolysis and grinding: and adding 1 part by weight of a third catalyst (sulfuric acid) to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding 15 parts by weight of sodium acetate solution to finish the hydrolysis reaction after the required substitution degree is reached, wherein the mass fraction of the sodium acetate solution is 45%.
At this time, sodium acetate is a supersaturated solution, so that sodium sulfate is instantaneously precipitated and is formed into a large block, and materials cannot be conveyed during secondary filtration, so that secondary filtration cannot be performed.
Step S500, post-processing: and (3) molding, cleaning and drying the hydrolyzed material to obtain a cellulose acetate product.
The results of the product analysis are shown in Table 1.
TABLE 1 product index Table obtained in examples 1 to 4 and comparative examples 1 to 4
| Examples | 0.2% viscosity | Bound acid% | Clogging value | b* | Molecular weight distribution |
| Example 1 | 0.360 | 55.51 | Infinity (full filter) | 2.8 | 1.95 |
| Example 2 | 0.362 | 55.54 | Infinity (full filter) | 2.8 | 1.94 |
| Example 3 | 0.365 | 55.50 | Infinity (full filter) | 3.73 | 1.91 |
| Example 4 | 0.362 | 55.50 | Infinity (full filter) | 2.88 | 1.9 |
| Comparative example 1 | 0.360 | 55.50 | Infinity (full filter) | 2.9 | 2.0 |
| Comparative example 2 | 0.358 | 55.51 | 48 | 2.97 | 2.4 |
| Comparative example 3 | 0.360 | 55.50 | 80 | 2.95 | 2.3 |
| Comparative example 4 | 0.360 | 55.52 | 85 | 2.96 | 2.2 |
From the data in table 1, it can be seen that: the viscosity of the products obtained in examples 1-4 is slightly higher than that of the products obtained in comparative examples 1-4, and the molecular weight distribution is obviously lower than that of the products obtained in comparative examples 1-4, which shows that the products obtained in examples 1-4 have better strength than those obtained in comparative examples 1-4; the results of examples 1-4, which have a significantly higher plug value than those of comparative examples 2 and 3, show that the cellulose acetate preparation process of the present invention, by adding milling steps during esterification and hydrolysis and adding filtration steps after esterification and hydrolysis, and the filter cake formed by precipitation of the filter press and sodium sulfate on the filter cloth is subjected to double filtration, so that the content of impurities in the cellulose acetate product can be reduced, the blocking value of the product can be improved, and the strength of the product can be improved.
Further, from the data in table 1, it is also known that: the products of examples 1 to 4 and comparative examples 1 to 4, each having about 55% bound acid, showed that the obtained product was cellulose diacetate; the yellowness b is smaller, specifically smaller than 5, and the product is in a colorless transparent state.
Further, from the data analysis of table 1, the following conclusion can also be drawn:
as can be seen from the comparison of example 4 with comparative example 1: the addition of the milling step during the esterification and hydrolysis steps slightly increases the viscosity of the product and decreases the molecular weight distribution of the product, indicating that the addition of the milling step during the esterification and hydrolysis steps increases the strength of the product. Meanwhile, it can be obtained by comparing comparative example 2 with comparative example 3: the addition of the milling step in the esterification and hydrolysis steps slightly increases the viscosity of the product and decreases the molecular weight distribution of the product, indicating that the addition of the milling step in the esterification and hydrolysis steps increases the strength of the product; the clogging value of the product was increased, but the clogging value was not improved to a higher degree than that of the filtration process.
As can be seen from the comparison of example 4 with comparative example 2: the grinding process is added in the esterification and hydrolysis steps, the primary filtration is added after the esterification step, the secondary filtration is added after the hydrolysis step, the viscosity of the product is slightly increased, the molecular weight distribution of the product is reduced, and meanwhile, the blocking value of the product is obviously increased, which means that the grinding process is added in the esterification and hydrolysis steps, the filtration process is added after the esterification and hydrolysis steps, and the filter cake formed by precipitation of sodium sulfate on the filter cloth through a filter press in the secondary filtration is subjected to double filtration, so that the blocking value of the product can be obviously improved, and the strength of the product can be improved.
As can be seen from the comparison of example 4 with comparative example 3: the method has the advantages that the method is characterized in that the method comprises the steps of adding primary filtration after the esterification step, adding secondary filtration after the hydrolysis step, improving the viscosity of the product, reducing the molecular weight distribution of the product, and obviously increasing the blocking value of the product, which means that the filtration procedure is added after the esterification and the hydrolysis, and the filter cake formed by precipitation of the filter press and sodium sulfate on the filter cloth is subjected to double filtration in the secondary filtration, so that the blocking value of the product can be obviously improved, and the strength of the product can be improved. As can be seen from comparison of comparative example 1 with comparative example 2: the method has the advantages that the method is characterized in that the method comprises the steps of adding primary filtration after the esterification step, adding secondary filtration after the hydrolysis step, improving the viscosity of the product, reducing the molecular weight distribution of the product, and obviously increasing the blocking value of the product, which means that the filtration procedure is added after the esterification and the hydrolysis, and the filter cake formed by precipitation of the filter press and sodium sulfate on the filter cloth is subjected to double filtration in the secondary filtration, so that the blocking value of the product can be obviously improved, and the strength of the product can be improved.
As can be seen from a comparison of comparative example 4 with example 4: in the hydrolysis process, the added sodium acetate solution is supersaturated solution, so that sodium sulfate is instantaneously precipitated and is formed into a large block, and materials cannot be conveyed during secondary filtration, so that secondary filtration cannot be performed. The product of comparative example 4 has lower viscosity than the product of example 4, and the molecular weight distribution of the product is improved, and the blocking value of the product is obviously reduced, which means that the added sodium acetate solution is supersaturated solution in the hydrolysis process, and sodium sulfate cannot be separated out on the filter cloth to play a role in assisting filtration, so that the blocking value of the product cannot be improved, and the strength of the product cannot be improved.
Namely, the preparation method of the cellulose acetate mainly improves the strength of the product and can increase the blocking value of the product by adding the grinding procedure in the esterification and hydrolysis processes; adding filtering process after esterification and hydrolysis, and performing double filtration by filter press and filter cake formed by precipitation of sodium sulfate on filter cloth, which mainly improves the blocking value of the product, the blocking value of the product can be made to be ≡ (full filtration), and the obtained product is transparent and/or non-transparent cellulose acetate product and can be applied to the fields of medicines, transparent products and/or non-transparent products.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention.
Claims (10)
1. A method for preparing cellulose acetate, which is characterized by comprising the following steps:
step S100: activating, namely uniformly mixing a cellulose raw material, glacial acetic acid and a first catalyst, and continuously stirring for activation to obtain an activated mixed material;
step S200: esterifying and grinding, namely adding acetic anhydride and a second catalyst into the mixed material, esterifying cellulose in the mixed material, grinding material slurry through a grinder in the esterification process, and adding dilute acetic acid into the material slurry to terminate the esterification process;
step S300: filtering the materials after esterification by a filter to obtain filtrate;
step S400: hydrolyzing and grinding, namely adding a third catalyst into the filtrate to carry out hydrolysis reaction, naturally reducing the hydrolysis temperature, grinding the material slurry through a grinder in the hydrolysis process, and adding an alkali metal or alkaline earth metal acetic acid solution to terminate the hydrolysis reaction after the required substitution degree is reached;
step S500: filtering the material after hydrolysis by a filter press, and precipitating salt on filter cloth to form a filter cake for assisting filtration by controlling precipitation parameters of the salt;
step S600: and (3) post-treatment, namely molding, cleaning and drying the materials subjected to secondary filtration to obtain a cellulose acetate product.
2. The method according to claim 1, wherein in step S500, the precipitation parameters are: one or more of the concentration of the alkali or alkaline earth metal acetic acid solution, the water content of the hydrolysis material, and the temperature at which the hydrolysis material is filtered.
3. The method for producing cellulose acetate according to claim 2, wherein the first catalyst, the second catalyst, and the third catalyst are: one or more of sulfuric acid, phosphoric acid, and perchloric acid; the alkali metal or alkaline earth metal acetic acid solution is one or more of lithium acetate, sodium acetate, potassium acetate and magnesium acetate.
4. The method according to claim 3, wherein in step S500, the salt deposited on the filter cloth is formed by reacting an alkali metal or alkaline earth metal acetate solution with a catalyst.
5. The method for preparing cellulose acetate according to claim 4, wherein the mass fraction of the alkali metal or alkaline earth metal acetic acid solution is 20% -30%, the water content of the hydrolyzed material is 15% -25%, and the temperature of the hydrolyzed material is 20-60 ℃ when the hydrolyzed material is filtered.
6. The method according to any one of claims 1 to 5, wherein in step S100, the glacial acetic acid is added in an amount of 250 to 450 parts by weight and the first catalyst is added in an amount of 0.1 to 1 part by weight per 100 parts by weight of the cellulose raw material.
7. The method for producing cellulose acetate according to claim 6, wherein in step S200, the amount of acetic anhydride added is 200 to 300 parts by weight, the amount of the second catalyst added is 1 to 5 parts by weight, the amount of dilute acetic acid added is 160 to 250 parts by weight, and the mass fraction of the dilute acetic acid is 55 to 65% per 100 parts by weight of the cellulose raw material.
8. The method according to claim 7, wherein the third catalyst is added in an amount of 1 to 8 parts by weight and the alkali metal or alkaline earth metal acetate solution is added in an amount of 15 to 25 parts by weight per 100 parts by weight of the cellulose raw material in step S400.
9. The method for producing cellulose acetate according to claim 1, wherein in step S100, the cellulose material is one or more of cotton linter pulp, wood pulp and bamboo pulp.
10. The cellulose acetate is characterized by comprising the following components in parts by weight: 100 parts by weight of cellulose raw material, 250-450 parts by weight of glacial acetic acid, 0.1-1 part by weight of first catalyst, 200-300 parts by weight of acetic anhydride, 1-5 parts by weight of second catalyst, 160-250 parts by weight of dilute acetic acid, 1-8 parts by weight of third catalyst and 15-25 parts by weight of acetic acid solution of alkali metal or alkaline earth metal, wherein the cellulose acetate is a transparent or non-transparent product prepared by the preparation method of the cellulose acetate according to any one of claims 1-9, and is applied to the fields of medicines, transparent products and/or non-transparent products.
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