CN114622438B - Production method of low acetone extract cotton pulp - Google Patents
Production method of low acetone extract cotton pulp Download PDFInfo
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- CN114622438B CN114622438B CN202011457306.1A CN202011457306A CN114622438B CN 114622438 B CN114622438 B CN 114622438B CN 202011457306 A CN202011457306 A CN 202011457306A CN 114622438 B CN114622438 B CN 114622438B
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- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 title claims abstract description 69
- 229920000742 Cotton Polymers 0.000 title claims abstract description 51
- 239000000284 extract Substances 0.000 title claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
- 239000003513 alkali Substances 0.000 claims abstract description 110
- 238000010411 cooking Methods 0.000 claims abstract description 47
- 238000005406 washing Methods 0.000 claims abstract description 43
- 238000004061 bleaching Methods 0.000 claims abstract description 37
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 8
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 239000007788 liquid Substances 0.000 claims abstract description 6
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims description 54
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 32
- 239000004155 Chlorine dioxide Substances 0.000 claims description 25
- 235000019398 chlorine dioxide Nutrition 0.000 claims description 25
- 239000002002 slurry Substances 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000003795 chemical substances by application Substances 0.000 claims description 20
- 238000003825 pressing Methods 0.000 claims description 19
- 238000004537 pulping Methods 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 17
- 238000010306 acid treatment Methods 0.000 claims description 14
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 12
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid group Chemical group S(O)(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 8
- 238000009835 boiling Methods 0.000 claims description 5
- 239000002738 chelating agent Substances 0.000 claims description 4
- 230000000149 penetrating effect Effects 0.000 claims description 4
- 238000009991 scouring Methods 0.000 claims description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 3
- 239000000835 fiber Substances 0.000 claims description 3
- 239000011593 sulfur Substances 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 6
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 4
- 238000009826 distribution Methods 0.000 abstract description 3
- 229920006304 triacetate fiber Polymers 0.000 abstract description 3
- 239000012752 auxiliary agent Substances 0.000 description 12
- 229920002284 Cellulose triacetate Polymers 0.000 description 11
- 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 11
- 239000002994 raw material Substances 0.000 description 7
- 238000010009 beating Methods 0.000 description 6
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000004321 preservation Methods 0.000 description 4
- 238000005086 pumping Methods 0.000 description 4
- 229920002678 cellulose Polymers 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 239000004973 liquid crystal related substance Substances 0.000 description 3
- 238000010025 steaming Methods 0.000 description 3
- 239000012141 concentrate Substances 0.000 description 2
- 238000005034 decoration Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- -1 (4) Substances 0.000 description 1
- VCUFZILGIRCDQQ-KRWDZBQOSA-N N-[[(5S)-2-oxo-3-(2-oxo-3H-1,3-benzoxazol-6-yl)-1,3-oxazolidin-5-yl]methyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C1O[C@H](CN1C1=CC2=C(NC(O2)=O)C=C1)CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F VCUFZILGIRCDQQ-KRWDZBQOSA-N 0.000 description 1
- 239000006184 cosolvent Substances 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000004627 regenerated cellulose Substances 0.000 description 1
- 238000000807 solvent casting Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 239000000080 wetting agent Substances 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
- D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D1/00—Methods of beating or refining; Beaters of the Hollander type
- D21D1/02—Methods of beating; Beaters of the Hollander type
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/64—Paper recycling
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
The invention provides a production method of cotton pulp with low acetone extract, which is beneficial to the concentration of polymerization degree distribution of half pulp by large liquid ratio and long-time cooking, and is beneficial to removing the acetone extract and alkali soluble substances by twice washing with dilute alkali liquor in balls; the second alkaline treatment stage in the bleaching treatment contributes to further reducing the acetone extract of the cotton pulp. The experimental result shows that the ash content of the cotton pulp obtained by the production method of the invention is 50-200ppm, the iron content is less than 2ppm, the whiteness is more than 91 percent, the acetone extract is less than 150ppm 10 ＞99.2％，S 18 Less than 0.3 percent, good reaction performance and accordance with the quality requirement of producing electronic grade triacetate fiber.
Description
Technical Field
The invention belongs to the technical field of cotton pulp, and particularly relates to a production method of low acetone extract cotton pulp.
Background
TAC (Triacetyl Cellulose), an important material in the production process of liquid crystal displays. The method is mainly used for protecting the LCD polarizer. The application history of the esterified Cellulose film is over a century, the raw material is derived from wood Cellulose, and is an extension of the paper industry, the main component of the present protective film for the LCD polarizing plate is TAC (Triacetyl Cellulose), the composition of which is very complex, and the composition of the protective film comprises a plasticizer, a cosolvent, a wetting agent, a lubricant, an anti-ultraviolet agent and the like, TAC is processed into a film by solvent casting, and thus TAC is still one of the high molecular materials with the highest penetration.
The main raw material for producing the cellulose triacetate membrane is cotton pulp. The cotton pulp is a high-purity cellulose prepared by taking cotton linters as raw materials and performing alkaline cooking and rinsing refining. The content of acetone extract in the cotton pulp directly determines the quality of the cellulose triacetate film. At present, the content of acetone extracts of domestic cotton pulp products is high, the chromaticity is high, so that the light transmittance of the cellulose triacetate film produced by using the cotton pulp products is poor, the cellulose triacetate film cannot reach the high standard for manufacturing the polaroid of the liquid crystal display, the quality of the polaroid of the liquid crystal display is seriously influenced, and the development of the regenerated cellulose film industry in China is also limited.
Disclosure of Invention
The invention aims to provide a production method of cotton pulp with low acetone extract, which has the advantages of low content of acetone extract, stable quality and good reaction performance and meets the quality requirement of electronic grade cellulose triacetate.
The invention provides a production method of low acetone extract cotton pulp, which comprises the following steps:
a) Mixing cotton linters with cooking lye at 87-95 ℃ and 1.1-1.5kgf/cm 2 Keeping the temperature under the pressure for 30-60 min, discharging the gas until the pressure is zero, heating to 143-146 ℃, and keeping the temperature for 140-180 min to obtain a cooking solution;
b) Pressing alkali of the cooking liquor, discharging gas until the pressure is zero after the alkali pressing is finished, then washing the material after the alkali pressing by using 3.5-6 g/L dilute alkali liquor, and obtaining cooking semi-slurry when the concentration of the pressed alkali liquor is 5-10 g/L;
c) Adding 3.5-6 g/L of dilute alkali liquor and an esterifying agent into the half-cooked pulp, fully mixing, adding water, and washing until the residual alkali content is less than 0.1g/L to obtain the cooked pulp;
d) Pulping, bleaching with chlorine dioxide for the first time, performing alkali treatment for the first time, bleaching with chlorine dioxide for the second time, performing alkali treatment for the second time and performing acid treatment on the cooked pulp in sequence to obtain bleached pulp;
e) And washing the bleached pulp with water, and pulping to obtain the low acetone extract cotton pulp.
Preferably, the alkali consumption of the cooking lye is 18-24%, the ratio of the cooking lye to the cooking liquor is 1: (4-6).
Preferably, the cooking alkali liquor contains 2-3 per mill of scouring agent, 1-2 per mill of penetrating agent, 2-3 per mill of chelating agent and 1.5-3% of hydrogen peroxide.
Preferably, the cotton linters are second-type cotton linters and/or third-type cotton linters, the maturity is more than 76%, the sulfur value is less than 3%, and no foreign fibers exist.
Preferably, the cotton linters are subjected to dry impurity removal and then are cooked.
Preferably, the pulping is carried out by fast pulping for 30 minutes by a heavy knife, the pulp enters a refiner to be subjected to serial pulping, the pulp concentration is controlled to be 2-3%, and the pulp enters a bleaching process after desanding and fine selection.
Preferably, the concentration of the alkali for the second alkali treatment is 3.5-6.5g/L, the temperature is 60-70 ℃, and the time for the second alkali treatment is 60-90 min;
6-8 kg of esterifying agent is added into the second alkali treatment; the mass of the slurry in each pool is 2500-2800 kg.
Preferably, the acid treatment time is 50 to 80min.
Preferably, the polymerization degree of the cooking half-paddle is 1680-1800.
Preferably, the temperature of the first chlorine dioxide bleaching is 60-70 ℃;
the temperature of the second chlorine dioxide bleaching is 60-70 ℃.
The invention provides a production method of low acetone extract cotton pulp, which comprises the following steps: a) Mixing cotton linters with cooking lye at 87-95 ℃ and 1.1-1.5kgf/cm 2 Keeping the temperature for 30-60 min under the pressure, deflating until the pressure is zero, heating to 143-146 ℃, and keeping the temperature for 140-180 min to obtain a cooking liquid; b) Pressing alkali of the cooking liquor, discharging gas until the pressure is zero after the alkali pressing is finished, then washing the material after the alkali pressing by using 3.5-6 g/L dilute alkali liquor, and obtaining cooking semi-slurry when the concentration of the pressed alkali liquor is 5-10 g/L; c) Adding 3.5-6 g/L of dilute alkali liquor and an esterifying agent into the half-cooked pulp, fully mixing, adding water, and washing until the residual alkali content is less than 0.1g/L to obtain the cooked pulp; d) Pulping, bleaching with chlorine dioxide for the first time, performing alkali treatment for the first time, bleaching with chlorine dioxide for the second time, performing alkali treatment for the second time and performing acid treatment on the cooked pulp in sequence to obtain bleached pulp; e) And washing the bleached pulp with water, and pulping to obtain the low acetone extract cotton pulp. The invention is beneficial to the concentration of polymerization degree distribution of semi-slurry by large liquid ratio and long-time cooking, and is beneficial to removing acetone extracts and alkali-soluble substances by twice washing with dilute alkali liquor in the balls; the second alkaline treatment stage in the bleaching treatment is advantageous for further reduction of acetone extractives of the cotton pulp. The experimental result shows that the ash content of the cotton pulp obtained by the production method is 50-200ppm, the iron content is less than 2ppm, the whiteness is more than 91 percent, the acetone extract is less than 150ppm 10 ＞99.2％，S 18 Less than 0.3 percent, good reaction performance and accordance with the quality requirement of producing electronic grade triacetate fiber.
Detailed Description
The invention provides a production method of low acetone extract cotton pulp, which comprises the following steps:
a) Mixing cotton linters with cooking lye at 87-95 ℃ and 1.1-1.5kgf/cm 2 Keeping the temperature under the pressure for 30-60 min, discharging the gas until the pressure is zero, heating to 143-146 ℃, and keeping the temperature for 140-180 min to obtain a cooking solution;
b) Pressing alkali on the cooking liquor, discharging gas until the pressure is zero after the alkali pressing is finished, then washing the material after the alkali pressing by using dilute alkali liquor of 3.5-6 g/L, and obtaining cooking semi-slurry when the concentration of the pressed alkali liquor is 5-10 g/L;
c) Adding 3.5-6 g/L of dilute alkali liquor and an esterifying agent into the half-cooked pulp, fully mixing, adding water, and washing until the residual alkali content is less than 0.1g/L to obtain the cooked pulp;
d) Pulping, bleaching with chlorine dioxide for the first time, performing alkali treatment for the first time, bleaching with chlorine dioxide for the second time, performing alkali treatment for the second time and performing acid treatment on the cooked pulp in sequence to obtain bleached pulp;
e) And washing the bleached pulp with water, and pulping to obtain the low acetone extract cotton pulp.
The production method mainly comprises three main sections of cooking, pulping and bleaching,
1. steaming and boiling
The invention preferably uses second and third types of cotton linters, the production area is preferably Xinjiang, the maturity of the cotton linters is more than 76%, the sulfur value is less than 3%, and no foreign fiber exists.
The cotton linters raw material is firstly subjected to impurity removal through a dry type impurity removal system, then is mixed with cooking alkali liquor, and is cooked in a rotary spherical digester.
In the present invention, the mass of alkali in the cooking lye is 18 to 24%, preferably 19 to 23%, more preferably 20 to 22% of the mass of the cotton linters; the cooking liquor ratio is preferably 1: (4 to 6), more preferably 1: (5-6).
The cooking alkali liquor contains a cooking aid, the cooking aid is preferably a scouring agent, a penetrating agent, a chelating agent and hydrogen peroxide, the mass fraction of the scouring agent in the cooking alkali liquor is 2-3 thousandths, the mass fraction of the penetrating agent is preferably 1-2 thousandths, the mass fraction of the chelating agent is preferably 2-3 thousandths, and the mass fraction of the hydrogen peroxide is preferably 1.5-3%.
The invention preferably keeps the temperature of the mixed cooking raw materials at low temperature for 30-60 min, then releases the gas until the pressure is zero, and then raises the temperature to the heat preservation temperature and keeps the temperature for 140-180 min.
The low temperature is preferably 87-95 ℃, more preferably 88-94 ℃, and most preferably 90-93 ℃; preserving the heat at the low temperature for 30-60 min, preferably 40-50 min; the heat preservation temperature is preferably 140-180 ℃, preferably 140-170 ℃, and more preferably 143-146 ℃; the holding time is preferably 140 to 180min, more preferably 150 to 170min, and most preferably 160 to 170min.
And (3) carrying out alkali pressing operation after the heat preservation is finished, discharging steam until the pressure is zero after the alkali pressing operation is finished, pumping dilute alkali liquor into the steaming ball to wash the material in the steaming ball, and opening the cover to pour the material when the concentration of the pressed liquid alkali is 5-10 g/L. Obtaining semi-slurry with the cooking polymerization degree of 1680-1800.
In the invention, the alkali concentration of the dilute alkali liquor is 3.5-6 g/L, preferably 4-5.5 g/L, and more preferably 4.5-5 g/L.
And adding dilute alkali liquor after pouring, adding an auxiliary agent esterifying agent for 2-3 per mill, circulating for 60 minutes, draining, washing, and adding clear water for washing until the residual alkali is less than 0.1g/L. Pumping into a beating machine for beating.
In the invention, the alkali concentration of the dilute alkali liquor is 3.5-6 g/L, preferably 4-5.5 g/L, and more preferably 4.5-5 g/L.
In the process of cooking, the invention removes acetone extract and alkali soluble substance to a great extent by washing with a large amount of dilute alkali liquor twice, thereby improving the quality of cotton pulp.
2. Beating
The invention adopts heavy knife to beat for 30 minutes, enters a refiner to be serially pulped, the pulp concentration is controlled to be 2-3 percent, and enters a bleaching process after desanding and selecting.
3. Float for anglingWhite colour (Bai)
The bleaching in the invention adopts the bleaching procedures of primary chlorine dioxide bleaching, primary alkali treatment, secondary chlorine dioxide bleaching, secondary alkali treatment and acid treatment.
In the invention, in the first chlorine dioxide bleaching, the mass of the chlorine dioxide is 3-8 per thousand of the mass of the pulp, preferably 4-7 per thousand, and more preferably 5-6 per thousand;
the first alkali treatment is preferably sodium hydroxide treatment, and the mass of the sodium hydroxide is preferably 0.5-3 per mill of the mass of the slurry, and more preferably 1-2 per mill;
in the second chlorine dioxide bleaching, the mass of the chlorine dioxide is 1 to 5 per thousand of the mass of the pulp, preferably 2 to 4 per thousand, and more preferably 2.5 to 3 per thousand;
the second alkali treatment is preferably carried out by using sodium hydroxide, and in the second alkali treatment, the concentration of alkali in the slurry is preferably 3.5-6.5g/L, more preferably 4-6 g/L, and most preferably 5-5.5 g/L; the temperature of the second alkali treatment is preferably 60-70 ℃, and more preferably 65 ℃; the time of the second alkali treatment is preferably 60 to 90min, and more preferably 70 to 80min; in the second alkali treatment, an esterifying agent auxiliary agent is added, the addition amount of the esterifying agent is preferably 6-8 kg/tank, and the mass of each tank of slurry is preferably 2500-2800 kg.
After the two bleaching and two alkali treatment procedures, the pulp is preferably washed by deionized water until the pH value is less than 8.5, and then acid treatment is carried out, wherein the acid treatment is preferably carried out by using sulfuric acid, and the mass of the sulfuric acid is preferably 1.2-1.5% of that of the pulp; the time for the acid treatment is preferably 50 to 80min, more preferably 60 to 70min.
Washing with deionized water after acid washing until the pH value is more than 6.5, discharging pulp, selecting, and pulping to obtain the low acetone extract cotton pulp.
The invention provides a production method of low acetone extract cotton pulp, which comprises the following steps: a) Mixing cotton linters with cooking lye at 87-95 ℃ and 1.1-1.5kgf/cm 2 Keeping the temperature under the pressure for 30-60 min, deflating until the pressure is zero, and heating to 143EPreserving the heat at 146 ℃ for 140-180 min to obtain a cooking liquor; b) Pressing alkali of the cooking liquor, discharging gas until the pressure is zero after the alkali pressing is finished, then washing the material after the alkali pressing by using 3.5-6 g/L dilute alkali liquor, and obtaining cooking semi-slurry when the concentration of the pressed alkali liquor is 5-10 g/L; c) Adding 3.5-6 g/L dilute alkali liquor and an esterifying agent into the cooking semi-slurry, fully mixing, adding water, and washing until the residual alkali content is less than 0.1g/L to obtain cooking slurry; d) Pulping, bleaching with chlorine dioxide for the first time, performing alkali treatment for the first time, bleaching with chlorine dioxide for the second time, performing alkali treatment for the second time and performing acid treatment on the cooked pulp in sequence to obtain bleached pulp; e) And washing the bleached pulp with water, and pulping to obtain the low acetone extract cotton pulp. The invention is beneficial to the concentration of polymerization degree distribution of semi-slurry by large liquid ratio and long-time cooking, and is beneficial to removing acetone extracts and alkali-soluble substances by twice washing with dilute alkali liquor in the balls; the second alkaline treatment stage in the bleaching treatment is advantageous for further reduction of acetone extractives of the cotton pulp. The experimental result shows that the ash content of the cotton pulp obtained by the production method is 50-200ppm, the iron content is less than 2ppm, the whiteness is more than 91 percent, the acetone extract is less than 150ppm 10 ＞99.2％，S 18 Less than 0.3 percent, good reaction performance and accordance with the quality requirement of producing electronic grade triacetate fiber.
In order to further illustrate the present invention, the following will describe the production method of a low acetone extract cotton pulp in detail with reference to the examples, but it should not be construed as limiting the scope of the present invention.
Example 1:
selecting raw materials preferably, and passing through a dry type impurity removal system;
the method comprises the steps of boiling by using 20% of alkali, 9kg of SC-01 auxiliary agent, 9kg of SC-02 auxiliary agent, 10kg of SC-03 auxiliary agent, 100kg of hydrogen peroxide, keeping the temperature at 87 ℃ for 40 minutes, discharging steam to the pressure of 0, heating to the temperature of 143-146 ℃, keeping the temperature for 140 minutes, pressing alkali for 40 minutes, injecting dilute alkali solution with the alkali concentration of 3.5g/L into balls, washing for 60 minutes, and pouring to obtain 1690 of the boiling material polymerization degree.
And (3) after pouring, washing, controlling the residual alkali to be 6g/L and the temperature to be 70 ℃, adding 8kg of SC-04 auxiliary agent, circulating for 60 minutes, draining and washing, and returning water for the last two times. The washing residual alkali is less than 0.05g/L.
The Holland beater beats quickly by a heavy knife, and then the pulp concentration is controlled to be 2.5 percent, and the refiner is connected in series for beating.
And controlling the concentration of the concentrate at 0.4% for sand removal.
Controlling the concentration of rinsing pulp entering at 4-5%, heating at 58 ℃, adding 90L of activated chlorine dioxide, bleaching for 60 minutes, and washing with water until the pH value is more than 6; then heating to 48 ℃, adding alkali to control the pH value to be 10-11, treating for 60 minutes, and washing until the pH value is less than 8; then heating to 55 ℃, adding 40L of activated chlorine dioxide for bleaching for 60 minutes, and washing until the pH value is more than 6; heating to 58 ℃, adding alkali liquor, controlling the pulp concentration to be 5-6g/L, adding 8kg of SC-04 auxiliary agent, circulating for 120 minutes, and washing by using deionized water until the pH value is less than 8; heating to 40 ℃, adding dilute sulfuric acid, controlling the acid concentration to be 0.6g/L, washing by using deionized water after treating for 40 minutes until the residual acid is 0.05g/L, discharging pulp, selecting and pumping into a pulp forming pool for pulp making after bleaching.
The pulp sheet obtained had the following quality:
(1), polymerization degree 1670, (2), whiteness 91.5%, (3), acetone extract 90ppm, (4), ash content 80ppm, (5), iron 1ppm, (6) and R 10 99.2％，(7)、S 18 0.25％。
Example 2:
preferably raw materials, and is processed by a dry impurity removal system.
20% of alkali for cooking, 10kg of SC-01 auxiliary agent, 10kg of SC-02 auxiliary agent, 15kg of SC-03 auxiliary agent and 80kg of hydrogen peroxide, keeping the temperature for 45 minutes, heating to 143-146 ℃, keeping the temperature for 145 minutes, pressing the alkali for 40 minutes, injecting dilute alkali solution with the alkali concentration of 3.5g/L into the ball, washing for 70 minutes, and pouring to obtain the polymerization degree 1650 of the cooked material.
And (3) after pouring, washing, controlling 5.5g/L of residual alkali and the temperature of 70 ℃, adding 10kg of SC-04 auxiliary agent, circulating for 60 minutes, draining and washing, and returning water for the last two times. The washing residual alkali is less than 0.05g/L.
The Dutch beater is used for beating quickly by a heavy knife, and then the pulp concentration is controlled to be 2.5%, and the refiners are used for beating in series.
And controlling the concentration of the concentrate at 0.4% for sand removal.
Controlling the concentration of rinsing pulp entering at 4-5%, heating at 58 ℃, adding 90L of activated chlorine dioxide, bleaching for 60 minutes, and washing with water until the pH value is more than 6; then heating to 55 ℃, adding alkali to control the pH value to be 10-11, treating for 60 minutes, and washing until the pH value is less than 8; then heating to 55 ℃, adding 40L of activated chlorine dioxide for bleaching for 60 minutes, and washing until the pH value is more than 6; heating to 60 ℃, adding alkali liquor, controlling the pulp concentration to be 5-6g/L, adding 9kg of SC-04 auxiliary agent, circulating for 120 minutes, and washing by using deionized water until the pH value is less than 8; heating to 40 ℃, adding dilute sulfuric acid, controlling the acid concentration to be 0.8g/L, washing by using deionized water after treating for 60 minutes until the residual acid is 0.05g/L, discharging, bleaching, and carefully selecting and pumping into a pulp forming pool for pulp making.
The pulp sheet obtained had the following quality:
(1), polymerization degree 1640, (2), whiteness 92%, (3), 100ppm of acetone extract, (4), ash content 60ppm, (5), iron 1ppm, (6) and R 10 99.2％，(7)、S 18 0.21％。
Comparative example 1
Cotton pulp was prepared as in example 1 except that after the heat preservation of the rotary spherical digester and the air release, the internal washing was carried out without using dilute alkali solution and the internal washing was carried out with finely selected backwater before use.
Comparative example 1 obtained pulp sheet R in comparison with the quality of the pulp sheet obtained in example 1 10 Decrease by 0.1-0.2%, S 18 The increase is 0.2-0.3%.
Comparative example 2
Cotton pulp was prepared as in example 1 except that the second chlorine dioxide bleaching was followed by no second alkali treatment and by an acid treatment.
The acetone extract of the pulp sheet obtained in comparative example 2 was increased by 200 to 300ppm while S was added to the pulp sheet obtained in example 1 18 Also increases by 0.3-0.4%, R 10 The reduction is 0.1 to 0.2 percent.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (4)
1. A production method of low acetone extract cotton pulp comprises the following steps:
a) Mixing cotton linters with a boiling alkali liquor at 87 to 95 ℃ and 1.1 to 1.5kgf/cm 2 Keeping the temperature under the pressure for 30 to 60min, deflating until the pressure is zero, heating to 143 to 146 ℃, and keeping the temperature for 140 to 180min to obtain a cooking solution;
the boiling alkali liquor contains a scouring agent with the mass fraction of 2~3 thousandths, a penetrating agent with the mass fraction of 1~2 thousandths, a chelating agent with the mass fraction of 2~3 thousandths and hydrogen peroxide with the mass fraction of 1.5-3%; the mass of alkali in the cooking alkali liquor is 18 to 24 percent of the mass of the cotton linters, and the ratio of cooking liquor is 1: (4~6);
b) Pressing alkali of the cooking liquor, discharging gas until the pressure is zero after the alkali pressing is finished, then washing the material subjected to alkali pressing by using dilute alkali liquor of 3.5-6 g/L until the concentration of the pressed liquid alkali is 5-10g/L, and obtaining cooking semi-slurry;
c) Adding 3.5-6 g/L of dilute alkali liquor and esterifying agent into the cooking semi-slurry, fully mixing, adding water, and washing until the residual alkali content is less than 0.1g/L to obtain cooking slurry;
d) Pulping, bleaching with chlorine dioxide for the first time, performing alkali treatment for the first time, bleaching with chlorine dioxide for the second time, performing alkali treatment for the second time and performing acid treatment on the cooked pulp in sequence to obtain bleached pulp;
the pulping is carried out by fast pulping for 30 minutes by a heavy knife, pulping in series in a refiner, controlling the pulp concentration at 2-3%, degritting, selecting and bleaching;
in the first chlorine dioxide bleaching, the mass of chlorine dioxide is 3~8 per mill of the mass of the pulp, and the temperature of the first chlorine dioxide bleaching is 60-70 ℃; the first alkali treatment is sodium hydroxide treatment, and the mass of the sodium hydroxide is 0.5 to 3 thousandths of the mass of the slurry; in the second chlorine dioxide bleaching, the mass of chlorine dioxide is 1~5 per mill of the mass of the slurry, and the temperature of the second chlorine dioxide bleaching is 60-70 ℃; the second alkali treatment is carried out by using sodium hydroxide, wherein in the second alkali treatment, the concentration of alkali in the slurry is 3.5 to 6.5g/L, the temperature is 60 to 70 ℃, and the time of the second alkali treatment is 60 to 90min; adding an esterifying agent into the solution for the second alkali treatment, wherein the esterifying agent is added into the solution for the second alkali treatment at 6 to 8 kg/pool; the mass of the slurry in each pond is 2500 to 2800kg;
the acid treatment is sulfuric acid treatment, and the mass of the sulfuric acid is 1.2 to 1.5 percent of the mass of the slurry; the acid treatment time is 50 to 80min;
e) Washing the bleached pulp with water and pulping to obtain low acetone extract cotton pulp;
the ash content of the low-acetone extract cotton pulp is 50 to 200ppm, the iron content is less than 2ppm, the whiteness is more than 91 percent, the acetone extract is less than 150ppm 10 ＞99.2%，S 18 ＜0.3%。
2. The method of claim 1, wherein the cotton linters are second and/or third type of cotton linters with a maturity of > 76%, a sulfur value of < 3%, and no foreign fibers.
3. The method of claim 1, wherein the cotton linters are dry-cleaned and then cooked.
4. The production method according to claim 1, wherein the polymerization degree of the cooking semi-slurry is 1680 to 1800.
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