CN115637605B - Lyocell dissolving pulp and preparation method thereof - Google Patents
Lyocell dissolving pulp and preparation method thereof Download PDFInfo
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- CN115637605B CN115637605B CN202211307657.3A CN202211307657A CN115637605B CN 115637605 B CN115637605 B CN 115637605B CN 202211307657 A CN202211307657 A CN 202211307657A CN 115637605 B CN115637605 B CN 115637605B
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- 229920000433 Lyocell Polymers 0.000 title claims abstract description 65
- 229920000875 Dissolving pulp Polymers 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000002002 slurry Substances 0.000 claims abstract description 137
- 238000004061 bleaching Methods 0.000 claims abstract description 93
- 239000002023 wood Substances 0.000 claims abstract description 72
- 239000000835 fiber Substances 0.000 claims abstract description 62
- 230000004048 modification Effects 0.000 claims abstract description 49
- 238000012986 modification Methods 0.000 claims abstract description 49
- 238000000034 method Methods 0.000 claims abstract description 38
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 78
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 38
- 239000001301 oxygen Substances 0.000 claims description 38
- 229910052760 oxygen Inorganic materials 0.000 claims description 38
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 34
- 238000010306 acid treatment Methods 0.000 claims description 28
- 239000003513 alkali Substances 0.000 claims description 24
- 238000009897 hydrogen peroxide bleaching Methods 0.000 claims description 21
- 238000010411 cooking Methods 0.000 claims description 20
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 16
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 16
- 230000029087 digestion Effects 0.000 claims description 13
- 230000007062 hydrolysis Effects 0.000 claims description 13
- 238000006460 hydrolysis reaction Methods 0.000 claims description 13
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 12
- 102100030386 Granzyme A Human genes 0.000 claims description 9
- 101001009599 Homo sapiens Granzyme A Proteins 0.000 claims description 9
- 238000010025 steaming Methods 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000004321 preservation Methods 0.000 claims description 7
- 238000005486 sulfidation Methods 0.000 claims description 7
- 230000003301 hydrolyzing effect Effects 0.000 claims description 6
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 6
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 6
- 238000005470 impregnation Methods 0.000 claims description 4
- 238000004090 dissolution Methods 0.000 claims description 3
- 239000011347 resin Substances 0.000 abstract description 12
- 229920005989 resin Polymers 0.000 abstract description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 9
- 229910021645 metal ion Inorganic materials 0.000 abstract description 9
- 230000009257 reactivity Effects 0.000 abstract description 8
- 230000008569 process Effects 0.000 description 18
- 229920002678 cellulose Polymers 0.000 description 13
- 239000001913 cellulose Substances 0.000 description 13
- 238000005406 washing Methods 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 8
- 229910052739 hydrogen Inorganic materials 0.000 description 8
- 239000002351 wastewater Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 6
- LFTLOKWAGJYHHR-UHFFFAOYSA-N N-methylmorpholine N-oxide Chemical compound CN1(=O)CCOCC1 LFTLOKWAGJYHHR-UHFFFAOYSA-N 0.000 description 5
- 238000002425 crystallisation Methods 0.000 description 5
- 230000008025 crystallization Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 244000166124 Eucalyptus globulus Species 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229920000297 Rayon Polymers 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000011121 hardwood Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000011122 softwood Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 description 1
- IVNPXOUPZCTJAK-UHFFFAOYSA-N 4-methylmorpholin-4-ium;hydroxide Chemical compound O.CN1CCOCC1 IVNPXOUPZCTJAK-UHFFFAOYSA-N 0.000 description 1
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
- 238000005904 alkaline hydrolysis reaction Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007844 bleaching agent Substances 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- -1 carboxyethyl group Chemical group 0.000 description 1
- 231100000315 carcinogenic Toxicity 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 238000004076 pulp bleaching Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910001948 sodium oxide Inorganic materials 0.000 description 1
- 238000004073 vulcanization Methods 0.000 description 1
Classifications
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- 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
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Abstract
The invention discloses a lyocell dissolving pulp and a preparation method thereof, wherein the preparation method of the lyocell dissolving pulp comprises the following steps: obtaining wood chips to be treated, and carrying out prehydrolysis on the wood chips to be treated; the wood chips to be treated after the prehydrolysis are steamed to obtain initial slurry; bleaching the initial slurry to obtain lyocell dissolving slurry; wherein the initial slurry is subjected to a fiber modification treatment during the bleaching treatment. The method can improve the content of the lyocell dissolving pulp in indexes such as alpha cellulose proportion, reactivity, whiteness, metal ion content, resin content and the like to a certain extent.
Description
Technical Field
The invention relates to the technical field of dissolving pulp preparation, in particular to lyocell dissolving pulp and a preparation method thereof.
Background
The lyocell fiber is a second-generation green renewable cellulose fiber after the viscose fiber, the production process of the lyocell fiber has no chemical reaction, the used solvent is nontoxic, the solvent recovery rate is high, and the lyocell fiber is energy-saving, environment-friendly and sustainable in development.
As a production raw material of the lyocell fiber, the lyocell has high requirements on the quality of dissolving pulp, and compared with viscose pulp, the lyocell pulp has higher requirements on indexes such as alpha cellulose proportion, reactivity, whiteness, metal ion content, resin content and the like.
At present, the conventional dissolving pulp is difficult to prepare to meet the quality requirement of the lyocell fiber.
Disclosure of Invention
The invention provides lyocell dissolving pulp and a preparation method thereof, which aim to solve the problem that the preparation of the dissolving pulp is difficult to meet the quality requirement of lyocell fibers.
In order to solve the technical problems, the invention provides a preparation method of lyocell dissolving pulp, which comprises the following steps: obtaining wood chips to be treated, and carrying out prehydrolysis on the wood chips to be treated; the wood chips to be treated after the prehydrolysis are steamed to obtain initial slurry; bleaching the initial slurry to obtain lyocell dissolving slurry; wherein the initial slurry is subjected to a fiber modification treatment during the bleaching treatment.
Bleaching the initial slurry to obtain lyocell dissolving slurry; wherein the step of subjecting the initial slurry to a fiber modification treatment during the bleaching treatment comprises: performing first bleaching treatment on the initial slurry; performing fiber modification treatment on the initial slurry after the first bleaching treatment; and (3) carrying out second bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry.
Wherein the step of performing a fiber modification treatment on the initial slurry after the first bleaching treatment comprises: the initial slurry after the first bleaching treatment is subjected to a fiber modification treatment by sodium hydroxide and acrylamide.
Wherein the step of performing fiber modification treatment on the initial slurry after the first bleaching treatment by sodium hydroxide and acrylamide comprises the steps of: performing fiber modification treatment on the initial slurry subjected to the first bleaching treatment with preset concentration for a preset period of time through sodium hydroxide and acrylamide at a preset temperature; wherein the range of the preset temperature is 70-90 ℃, the range of the preset concentration is 5-10%, and the range of the preset duration is 30-120 minutes; and the alkali consumption of the sodium hydroxide is 1.0-2.0%, and the consumption of the acrylamide is 0.05-0.20%.
Wherein the step of subjecting the initial slurry to a first bleaching treatment comprises: oxygen delignification treatment is carried out on the initial slurry; acid treatment is carried out on the initial slurry after oxygen delignification treatment by sulfuric acid; ozone bleaching treatment is carried out on the initial slurry after the acid treatment; the step of performing a second bleaching treatment on the initial slurry after the fiber modification treatment to obtain a dissolving slurry comprises: and (3) carrying out at least one stage of pressure hydrogen peroxide bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry.
Wherein the ozone dosage range of the ozone bleaching treatment is 0.2-1.5%, and the temperature range is 30-70 ℃; the oxygen pressure range of the pressure hydrogen peroxide bleaching treatment is 0.20-0.30MPa, the concentration range of the initial slurry in the pressure hydrogen peroxide bleaching treatment is 10-20%, the temperature range is 105-120 ℃ and the bleaching time range is 60-90 minutes; the concentration range of the initial slurry in the oxygen delignification treatment is 10-20%, the alkali dosage range is 1.5-4.5%, the oxygen pressure range is 0.8-1.0MPa, the temperature range is 95-110 ℃, and the heat preservation time range is 60-80 minutes; the concentration of the initial slurry during the acid treatment is 10-20%, the pH is 1.5-3.5, the temperature is 70-80 ℃ and the time is 60-80 minutes.
Wherein, the step of obtaining the wood chip to be treated and carrying out prehydrolysis on the wood chip to be treated comprises the following steps: obtaining wood chips to be treated, and performing pre-steaming hydrolysis on the wood chips to be treated; wherein the temperature range of the pre-steaming hydrolysis is 130-170 ℃ and the time range is 20-80 minutes.
Wherein, the step of obtaining the wood chip to be treated and carrying out prehydrolysis on the wood chip to be treated comprises the following steps: obtaining wood chips to be treated, and carrying out water-soaking prehydrolysis on the wood chips to be treated, wherein the temperature range of the water-soaking prehydrolysis mode is 130-170 ℃ and the time range is 20-80 minutes.
Wherein, the step of cooking the wood chips to be treated after the prehydrolysis to obtain an initial slurry comprises the steps of: the wood chips to be treated after the pre-hydrolysis are subjected to sulfate digestion through sodium hydroxide and sodium sulfide to obtain initial slurry; wherein, the liquid ratio of the sulfate cooking is 3:1-5:1, the dosage of sodium hydroxide is 17-21%, the sulfidation degree is 20-30%, and the cooking H factor is controlled within 550-1300.
In order to solve the technical problems, the invention also provides the lyocell dissolving pulp, which is prepared by the preparation method of the lyocell dissolving pulp.
The beneficial effects of the invention are as follows: different from the prior art, the method comprises the steps of obtaining wood chips to be treated, carrying out prehydrolysis on the wood chips to be treated, cooking the wood chips to be treated after prehydrolysis to obtain initial slurry, and carrying out bleaching treatment on the initial slurry to obtain lyocell dissolving slurry; the fiber modification treatment is carried out on the initial slurry in the bleaching treatment process, so that the hydrogen bond combination among cellulose molecular chains can be reduced, the rigid structure of a crystallization area is damaged, the dissolving capacity of the fiber is improved, meanwhile, the fiber after the modification treatment has better bleaching performance in the bleaching process of the later stage of the dissolving slurry, the bleaching effect is better, the whiteness and the purity of the slurry are higher, and the indexes of the lyocell dissolving slurry such as the proportion of alpha cellulose, the reactivity, the whiteness, the metal ion content, the resin content and the like are improved to a certain extent, so that the quality requirement of the lyocell fiber is met.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of a method for preparing lyocell slurry according to the present invention;
FIG. 2 is a schematic flow chart of another embodiment of the preparation method of lyocell dissolving pulp in the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic flow chart of an embodiment of a preparation method of lyocell dissolving pulp according to the present invention.
Step S11: and obtaining wood chips to be treated, and carrying out prehydrolysis on the wood chips to be treated.
The wood chips to be treated for preparing the lyocell dissolving pulp are obtained. The wood chips to be treated in this embodiment may include any of softwood, hardwood, and a mixture thereof, and are not limited herein.
After the wood chips to be treated are obtained, the wood chips to be treated can be cleaned to remove impurities, dust and other substances on the wood chips to be treated. In a specific application scenario, the wood chips to be treated can be washed by clean water. In another specific application scenario, the wood chips to be treated can be washed by using washing wastewater, wherein the washing wastewater can comprise clean water after circulating washing and also can comprise wastewater after washing lyocell dissolving pulp, so that the washing wastewater can be recycled, and the production cost of dissolving pulp is saved.
Through carrying out the prehydrolysis to the wood chip to be treated, can get rid of the air in the wood chip to be treated, improve the temperature simultaneously and make it stable, do benefit to and can absorb the liquid medicine fast after the wood chip to be treated gets into the follow-up cooking process, and higher wood chip temperature to be treated can save the time of rising temperature of the wood chip to be treated in the follow-up cooking process to the preparation efficiency of lyocell dissolving pulp has been improved.
Step S12: and (3) cooking the wood chips to be treated after the prehydrolysis to obtain initial slurry.
And (3) cooking the wood chips to be treated after the prehydrolysis to obtain initial slurry.
In one specific application scenario, sodium hydroxide and sodium sulfide can be utilized and the temperature is controlled to cook the wood chips to be treated, while the focus of the cooking section is controlled by the H factor, thereby obtaining an initial slurry. Wherein, the H factor defines: the relative reaction rate constant at each cooking temperature is a fixed integral of the cooking time.
Step S13: bleaching the initial slurry to obtain lyocell dissolving slurry; wherein the initial slurry is subjected to a fiber modification treatment during the bleaching treatment.
And (3) carrying out bleaching treatment on the initial slurry, wherein the initial slurry is subjected to fiber modification treatment in the bleaching treatment process, and finally the lyocell dissolving pulp is obtained.
The production principle of the lyocell fiber is that the strong interaction of NMMO (N-methylmorpholine-N-oxide) and cellulose damages the hydrogen bond action among cellulose molecules, so that dissolution occurs, firstly NMMO and water molecules enter amorphous regions with irregular structures, the hydrogen bond among cellulose macromolecular chains is damaged, the inter-molecular distance is increased, the amorphous regions are swelled and dissolved, then the crystallization regions are gradually damaged, and the hydrogen bond is released, so that the cellulose is completely dissolved.
From the above principle, it can be seen that the hydrogen bonding of the fibers and the highly rigid structure of the crystalline region have a great influence on the solubility. According to the embodiment, the cellulose is subjected to fiber modification treatment in the bleaching process of initial slurry, so that the hydrogen bond bonding between cellulose molecular chains can be reduced, and the rigid structure of a crystallization area is damaged, so that NMMO solution can permeate into the fiber more quickly when the lyocell fiber is prepared, the dissolving capacity of the fiber is improved, meanwhile, the fiber subjected to modification treatment has better bleaching performance in the bleaching process of the later stage of dissolving pulp, the bleaching effect is better, the whiteness and the purity of the pulp are higher, and the indexes of the lyocell dissolving pulp such as the alpha cellulose proportion, the reactivity, the whiteness, the metal ion content, the resin content and the like are improved to a certain extent.
Through the steps, the preparation method of the lyocell dissolving pulp in the embodiment obtains the wood chips to be treated, prehydrolyzes the wood chips to be treated, cooks the prehydrolyzed wood chips to be treated to obtain initial pulp, and carries out bleaching treatment on the initial pulp to obtain the lyocell dissolving pulp; the fiber modification treatment is carried out on the initial slurry in the bleaching treatment process, so that the hydrogen bond combination among cellulose molecular chains can be reduced, the rigid structure of a crystallization area is damaged, the dissolving capacity of the fiber is improved, meanwhile, the fiber after the modification treatment has better bleaching performance in the bleaching process of the later stage of the dissolving slurry, the bleaching effect is better, the whiteness and the purity of the slurry are higher, and the indexes of the lyocell dissolving slurry such as the proportion of alpha cellulose, the reactivity, the whiteness, the metal ion content, the resin content and the like are improved to a certain extent, so that the quality requirement of the lyocell fiber is met.
Referring to fig. 2, fig. 2 is a schematic flow chart of another embodiment of the preparation method of lyocell dissolving pulp according to the present invention.
Step S21: and obtaining wood chips to be treated, and carrying out prehydrolysis on the wood chips to be treated.
The wood chips to be treated for preparing the lyocell dissolving pulp are obtained. The wood chips to be treated in this embodiment may include any of softwood, hardwood, and a mixture thereof, and are not limited herein.
In one specific application scenario, the wood chips to be treated may be pre-steamed to hydrolyze. The steam prehydrolysis refers to a process of pretreating with water, steam or dilute acid in a closed container at a certain temperature and pressure.
Wherein the temperature range of the pre-steaming hydrolysis is 130-170 ℃, and can be 130 ℃, 140 ℃, 151 ℃, 160 ℃, 168 ℃ or 170 ℃ and the like. The time range is 20 to 80 minutes, and specifically may be 20 minutes, 25 minutes, 31 minutes, 35 minutes, 38 minutes, 42 minutes, 49 minutes, 52 minutes, 55 minutes, 60 minutes, 67 minutes, 71 minutes, 75 minutes, 80 minutes, or the like.
In another specific application scenario, the wood chips to be treated can be subjected to water-impregnation pre-hydrolysis, wherein the temperature range of the water-impregnation pre-hydrolysis mode is 130-170 ℃, specifically 130 ℃, 142 ℃, 150 ℃, 165 ℃, 166 ℃ or 170 ℃ and the like, and the time range is 20-80 minutes. Specifically, the time period may be 20 minutes, 24 minutes, 30 minutes, 35 minutes, 38 minutes, 42 minutes, 49 minutes, 53 minutes, 55 minutes, 60 minutes, 67 minutes, 70 minutes, 75 minutes, 80 minutes, or the like.
Step S22: and (3) carrying out sulfate digestion on the wood chips to be treated after the pre-hydrolysis by using sodium hydroxide and sodium sulfide to obtain initial slurry.
The method adopts a sulfate digestion method, specifically, the pre-hydrolyzed wood chips to be treated are subjected to sulfate digestion through sodium hydroxide and sodium sulfide, and initial slurry is obtained.
Wherein, the liquid ratio of the sulfate cooking ranges from 3:1 to 5:1, and can be specifically 3:1, 4:1 or 5:1, etc.; the amount of sodium hydroxide is 17-21%, specifically 17%, 18%, 19%, 20% or 21%. The degree of vulcanization may be in the range of 20 to 30%, specifically 20%, 22%, 25%, 26%, 27%, 29% or 30%, etc. The cooking H factor is controlled within the range of 550-1300, and specifically can be 550, 600, 620, 630, 650, 680, 700, 750, 790, 800, 820, 860, 930, 950, 1000, 1150, 1260 or 1300, etc. The degree of sulfidation refers to the percentage of sodium sulfide to active base (sodium hydroxide in the present invention) in terms of sodium oxide.
Step S23: performing first bleaching treatment on the initial slurry; performing fiber modification treatment on the initial slurry after the first bleaching treatment; and (3) carrying out second bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry.
Oxygen delignification treatment is carried out on the initial slurry; acid treatment is carried out on the initial slurry after oxygen delignification treatment by sulfuric acid; performing first bleaching treatment on the initial slurry after the acid treatment; performing fiber modification treatment on the initial slurry after the first bleaching treatment; and (3) carrying out second bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry. Wherein the first bleaching treatment comprises an ozone treatment and the second bleaching treatment comprises a pressure hydrogen peroxide bleaching treatment.
Specifically, when the initial slurry is subjected to oxygen delignification, the concentration of the initial slurry at the time of oxygen delignification may be in the range of 10 to 20%, specifically 10%, 12%, 15%, 18% or 20%, etc.; the alkali dosage ranges from 1.5 to 4.5 percent, and can be specifically 1.5 percent, 1.8 percent, 2.0 percent, 2.4 percent, 2.8 percent, 3.1 percent, 3.4 percent, 3.9 percent, 4.0 percent, 4.2 percent or 4.5 percent and the like; the oxygen pressure range is 0.8-1.0MPa, and can be specifically 0.8MPa, 0.9MPa or 1.0MPa, etc.; the temperature range is 95-110deg.C, and can be 95deg.C, 96deg.C, 98deg.C, 100deg.C, 102 deg.C, 105 deg.C, 108 deg.C or 110deg.C; the heat preservation time ranges from 60 minutes to 80 minutes, and can be specifically from 60 minutes, 65 minutes, 69 minutes, 70 minutes, 72 minutes, 75 minutes, 78 minutes or 80 minutes and the like, wherein the alkali amount is the general term in industry and represents the ratio of the mass of alkali (sodium hydroxide in the invention) to the absolute dry mass of a steamed sample, and the mass percentage is expressed. The dosage is the same.
After the oxygen delignification treatment, the initial slurry after the oxygen delignification treatment is subjected to acid treatment by sulfuric acid, specifically, the concentration of the initial slurry during the acid treatment ranges from 10% to 20%, specifically, can be 10%, 13%, 15%, 17% or 20%, and the like; the pH range is 1.5-3.5, and can be 1.5, 1.9, 2.1, 2.3, 2.6, 3.0, 3.4 or 3.5; the temperature range is 70-80deg.C, specifically 70 deg.C, 72 deg.C, 75 deg.C, 76 deg.C, 78 deg.C or 80deg.C, etc.; the time range is 60 to 80 minutes, and specifically 60 minutes, 65 minutes, 69 minutes, 70 minutes, 72 minutes, 75 minutes, 78 minutes, 80 minutes, or the like.
After the acid treatment, the initial slurry after the acid treatment is subjected to ozone bleaching treatment, specifically, the ozone amount of the ozone bleaching treatment is in the range of 0.2 to 1.5%, specifically, 0.2%, 0.5%, 0.8%, 1.0%, 1.1%, 1.3%, or 1.5%, etc., and the temperature is in the range of 30 to 70 ℃, specifically, 30 ℃, 35 ℃, 40 ℃, 42 ℃, 48 ℃, 56 ℃, 61 ℃, 65 ℃, 70 ℃, etc. In this embodiment, the initial slurry is subjected to ozone oxidation, so that the resin content in the initial slurry can be greatly reduced. The ozone oxidation does not affect the gray scale and the metal ion content of the initial slurry, so that the whiteness of the slurry can be improved while the resin content in the slurry is reduced. In addition, the embodiment utilizes ozone to bleach, so that the bleaching with chlorine-containing substances is avoided, the chlorine-containing bleaching has large bleaching water consumption, waste water is difficult to treat, and cancerogenic substances such as dioxin and the like exist, the ozone bleaching replaces chlorine-containing bleaching, the bleaching water consumption can be further reduced, and the environmental protection performance and the safety of the preparation of the dissolving pulp are improved.
In a specific application scenario, after ozone bleaching, the initial slurry after ozone bleaching can be washed to obtain the initial slurry and washing wastewater. The washing wastewater obtained in the step can be used for washing the wood chips to be treated in the step S11, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and residual hydrogen peroxide, the hydrogen peroxide utilization rate is improved, the washing cleanliness of the wood chips to be treated is improved, and the hydrogen peroxide can also be removed to a certain extent from the resin in the wood chips to be treated, so that the resin content in the dissolving pulp is further reduced.
After the ozone treatment, the initial slurry after the first bleaching treatment is subjected to a fiber modification treatment.
In a specific application scenario, the step of performing the fiber modification treatment includes: the initial slurry after the first bleaching treatment is subjected to a fiber modification treatment by sodium hydroxide and acrylamide. And (3) carrying out fiber modification treatment on the initial slurry subjected to the first bleaching treatment with preset concentration for a preset period of time through sodium hydroxide and acrylamide at a preset temperature.
Specifically, the preset temperature of the fiber modification treatment is 70-90 ℃, specifically can be 70 ℃, 72 ℃, 75 ℃, 76 ℃, 79 ℃, 80 ℃, 82 ℃, 85 ℃, 86 ℃, 88 ℃ or 90 ℃ or the like; the range of the preset concentration of the initial slurry is 5-10%, and specifically can be 5%, 6%, 7%, 8%, 9% or 10% and the like; the preset duration ranges from 30 to 120 minutes, and specifically can be 30 minutes, 35 minutes, 40 minutes, 42 minutes, 48 minutes, 50 minutes, 55 minutes, 62 minutes, 75 minutes, 86 minutes, 95 minutes, 101 minutes, 114 minutes, 120 minutes, or the like; the alkali consumption of the sodium hydroxide is 1.0-2.0%, and can be 1.0, 1.3, 1.5, 1.7 or 2; the acrylamide may be used in an amount ranging from 0.05 to 0.20%, specifically 0.05%, 0.08%, 0.10%, 0.13%, 0.15%, 0.19% or 0.20%, etc.
After the fiber modification treatment, the initial slurry after the fiber modification treatment is subjected to a second bleaching treatment to obtain lyocell-dissolved slurry.
Wherein the step of the second bleaching treatment comprises: and (3) carrying out at least one stage of pressure hydrogen peroxide bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry. Specifically, the first-stage pressure hydrogen peroxide bleaching treatment or the second-stage pressure hydrogen peroxide bleaching treatment can be performed.
The oxygen pressure of the pressure hydrogen peroxide bleaching treatment is in the range of 0.20-0.30MPa, and can be specifically 0.20MPa, 0.22MPa, 0.25MPa, 0.26MPa, 0.28MPa or 0.30MPa, etc.; the concentration of the initial slurry in the pressure hydrogen peroxide bleaching treatment is in the range of 10-20%, specifically 10%, 12%, 13%, 15%, 16%, 18% or 20%, etc.; the temperature range is 105-120deg.C, specifically 105 deg.C, 108 deg.C, 110 deg.C, 111 deg.C, 112 deg.C, 115 deg.C, 116 deg.C or 120 deg.C, etc.; the bleaching time ranges from 60 to 90 minutes, and may specifically be 60 minutes, 65 minutes, 71 minutes, 75 minutes, 79 minutes, 80 minutes, 82 minutes, 86 minutes, 90 minutes, or the like.
In the above-mentioned method, in the bleaching step, specifically in the alkali treatment step between ozone bleaching and hydrogen peroxide bleaching step, carboxyethyl group is introduced into cellulose, and cellulose and acrylamide undergo conjugate addition reaction under alkaline conditions, and alkaline hydrolysis is carried out to produce modified cellulose. The benefits of performing the fiber modification in the alkali treatment process are: 1. the alkaline condition of the alkali treatment procedure is utilized to create an alkaline environment for fiber modification, and 2, the fiber modification and the alkali treatment procedure are combined into a whole, so that the procedures are reduced, and the production cost is reduced. The dissolved pulp prepared from the modified fiber is superior to unmodified pulp in the indexes of alpha cellulose proportion, reactivity, whiteness, metal ion content, resin content and the like.
The preparation method and the performance of the lyocell dissolving pulp with the above proportion according to the present invention will be examined by a plurality of specific examples.
Example 1:
the wood chips are pre-hydrolyzed. Taking 100g of eucalyptus pieces, and pre-hydrolyzing by pre-steaming at 150 ℃ for 60min.
And (5) wood chip cooking. The sulfate digestion method is adopted, the liquid ratio is 4:1, the NaOH dosage is 20%, the sulfidation degree is 25%, and the digestion H factor is controlled to 800.
And (5) bleaching the slurry and modifying the fiber. Including oxygen delignification, acid treatment, ozone bleaching, alkaline fiber modification treatment, and pressure hydrogen peroxide bleaching. In the oxygen delignification, the concentration of the initial slurry is 10%, the alkali consumption is 2%, the oxygen pressure is 0.8MPa, the temperature is 100 ℃, and the heat preservation time is 70 minutes. After the oxygen delignification treatment, the initial slurry is subjected to acid treatment by sulfuric acid, wherein in the acid treatment process, the concentration of the initial slurry is 10%, the pH is 2, the temperature is 80 ℃ and the time is 70 minutes. After the acid treatment, the initial slurry was subjected to ozone bleaching, wherein the ozone was used in an amount of 1.0% and the temperature was 50 ℃. After the ozone reaction is finished, alkaline fiber modification treatment is carried out, the alkali amount is 1%, the acrylamide amount is 0.05%, the temperature is 70 ℃, the concentration of the initial slurry is 10%, and the time is 40 minutes. After the treatment, a stage of pressure hydrogen peroxide bleaching (PO) was carried out, the oxygen pressure was 0.2MPa, the initial slurry concentration was 10%, the temperature was 110℃and the bleaching time was 60 minutes.
And obtaining the lyocell fiber dissolving pulp after the steps are finished.
Example 2:
the wood chips are pre-hydrolyzed. Taking 100g of eucalyptus pieces, and pre-hydrolyzing by pre-steaming at 150 ℃ for 60min.
And (5) wood chip cooking. The sulfate digestion method is adopted, the liquid ratio is 4:1, the NaOH dosage is 20%, the sulfidation degree is 25%, and the digestion H factor is controlled to 800.
And (5) bleaching the slurry and modifying the fiber. Including oxygen delignification, acid treatment, ozone bleaching, alkaline fiber modification treatment, and pressure hydrogen peroxide bleaching. In the oxygen delignification, the concentration of the initial slurry is 10%, the alkali consumption is 2%, the oxygen pressure is 0.8MPa, the temperature is 100 ℃, and the heat preservation time is 70 minutes. After the oxygen delignification treatment, the initial slurry is subjected to acid treatment by sulfuric acid, wherein in the acid treatment process, the concentration of the initial slurry is 10%, the pH is 2, the temperature is 80 ℃ and the time is 70 minutes. After the acid treatment, the initial slurry was subjected to ozone bleaching, wherein the ozone was used in an amount of 1.0% and the temperature was 50 ℃. After the ozone reaction is finished, alkali fiber modification treatment is carried out, the alkali amount is 1.5%, the acrylamide amount is 0.1%, the temperature is 80 ℃, the concentration of the initial slurry is 10%, and the time is 80 minutes. After the treatment, a stage of pressure hydrogen peroxide bleaching (PO) was carried out, the oxygen pressure was 0.2MPa, the initial slurry concentration was 10%, the temperature was 110℃and the bleaching time was 60 minutes.
And obtaining the lyocell fiber dissolving pulp after the steps are finished.
Example 3:
the wood chips are pre-hydrolyzed. Taking 100g of eucalyptus pieces, and pre-hydrolyzing by pre-steaming at 150 ℃ for 60min.
And (5) wood chip cooking. The sulfate digestion method is adopted, the liquid ratio is 4:1, the NaOH dosage is 20%, the sulfidation degree is 25%, and the digestion H factor is controlled to 800.
And (5) bleaching the slurry and modifying the fiber. Including oxygen delignification, acid treatment, ozone bleaching, alkaline fiber modification treatment, and pressure hydrogen peroxide bleaching. In the oxygen delignification, the concentration of the initial slurry is 10%, the alkali consumption is 2%, the oxygen pressure is 0.8MPa, the temperature is 100 ℃, and the heat preservation time is 70 minutes. After the oxygen delignification treatment, the initial slurry is subjected to acid treatment by sulfuric acid, wherein in the acid treatment process, the concentration of the initial slurry is 10%, the pH is 2, the temperature is 80 ℃ and the time is 70 minutes. After the acid treatment, the initial slurry was subjected to ozone bleaching, wherein the ozone was used in an amount of 1.0% and the temperature was 50 ℃. After the ozone reaction is finished, alkaline fiber modification treatment is carried out, the alkali amount is 2%, the acrylamide amount is 0.2%, the temperature is 90 ℃, the concentration of the initial slurry is 10%, and the time is 120 minutes. After the treatment, a stage of pressure hydrogen peroxide bleaching (PO) was carried out, the oxygen pressure was 0.2MPa, the initial slurry concentration was 10%, the temperature was 110℃and the bleaching time was 60 minutes.
And obtaining the lyocell fiber dissolving pulp after the steps are finished.
Comparative example:
the wood chips are pre-hydrolyzed. Taking 100g of eucalyptus pieces, and pre-hydrolyzing by pre-steaming at 150 ℃ for 60min.
And (5) wood chip cooking. The sulfate digestion method is adopted, the liquid ratio is 4:1, the NaOH dosage is 20%, the sulfidation degree is 25%, and the digestion H factor is controlled to 800.
Bleaching the slurry. Including oxygen delignification, acid treatment, ozone bleaching, alkali treatment, and pressure hydrogen peroxide bleaching. In the oxygen delignification, the concentration of the initial slurry is 10%, the alkali consumption is 2%, the oxygen pressure is 0.8MPa, the temperature is 100 ℃, and the heat preservation time is 70 minutes. After the oxygen delignification treatment, the initial slurry is subjected to acid treatment by sulfuric acid, wherein in the acid treatment process, the concentration of the initial slurry is 10%, the pH is 2, the temperature is 80 ℃ and the time is 70 minutes. After the acid treatment, the initial slurry was subjected to ozone bleaching, wherein the ozone was used in an amount of 1.0% and the temperature was 50 ℃. After the ozone reaction was completed, alkali treatment was performed with an alkali amount of 1%, a temperature of 70 ℃, and a concentration of the initial slurry of 10% for 40 minutes. After the alkali treatment, a stage of hydrogen peroxide bleaching (PO) was carried out at an oxygen pressure of 0.2MPa, a concentration of the initial slurry of 10%, a temperature of 110℃and a bleaching time of 60 minutes.
And obtaining the lyocell fiber dissolving pulp after the steps are finished.
The pulp quality index for the above examples and comparative examples is shown in the following table:
the data show that the method can greatly improve the Fock reaction performance of the pulp, namely the dissolving capacity of the pulp is greatly enhanced, and simultaneously, the alpha cellulose content, the alkalinity resistance and the whiteness of the pulp are improved to a certain extent.
According to the invention, cellulose is modified in the pulp bleaching process, so that hydrogen bond bonding among cellulose molecular chains is reduced, and the rigid structure of a crystallization area is damaged, so that NMMO solution can permeate into the fiber more quickly when preparing lyocell fiber, the dissolving capacity of the fiber is improved, the fiber after modification treatment has better bleaching performance in the bleaching process of the later stage of dissolving pulp, the bleaching effect is better, and the dissolving pulp prepared from the modified fiber is superior to unmodified pulp in indexes such as alpha cellulose proportion, reactivity, whiteness, metal ion content, resin content and the like.
Based on the same inventive concept, the application also provides dissolving pulp, which is prepared by the preparation method of the lyocell dissolving pulp in any embodiment, so that the lyocell dissolving pulp can be improved to a certain extent in indexes such as alpha cellulose proportion, reactivity, whiteness, metal ion content, resin content and the like.
The foregoing description is only of embodiments of the present invention, and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes using the descriptions and the drawings of the present invention or directly or indirectly applied to other related technical fields are included in the scope of the present invention.
Claims (5)
1. A method for preparing lyocell dissolution pulp, which is characterized in that the method for preparing the lyocell dissolution pulp comprises the following steps:
obtaining wood chips to be treated, and carrying out pre-hydrolysis on the wood chips to be treated;
the wood chips to be treated after the prehydrolysis are steamed to obtain initial slurry;
bleaching the initial slurry to obtain the lyocell dissolving slurry;
wherein the initial slurry is subjected to a fiber modification treatment during the bleaching treatment; comprising the following steps: performing fiber modification treatment on the initial slurry through sodium hydroxide and acrylamide; the method specifically comprises the following steps: performing a first bleaching treatment on the initial slurry; carrying out fiber modification treatment on the initial slurry after the first bleaching treatment through the sodium hydroxide and the acrylamide; performing second bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry;
the step of subjecting the initial slurry to a first bleaching treatment comprises: oxygen delignification of the initial slurry; acid treatment is carried out on the initial slurry after oxygen delignification treatment by sulfuric acid; ozone bleaching treatment is carried out on the initial slurry after the acid treatment;
the step of performing fiber modification treatment on the initial slurry after the first bleaching treatment by sodium hydroxide and acrylamide comprises the following steps: performing fiber modification treatment on the initial slurry subjected to the first bleaching treatment at a preset concentration for a preset period of time through the sodium hydroxide and the acrylamide at a preset temperature; wherein the range of the preset temperature is 70-90 ℃, the range of the preset concentration is 5-10%, and the range of the preset duration is 30-120 minutes; wherein, the alkali consumption of the sodium hydroxide is 1.0-2.0%, and the consumption of the acrylamide is 0.05-0.20%;
the step of performing a second bleaching treatment on the initial slurry after the fiber modification treatment to obtain the dissolving slurry comprises the steps of: performing at least one stage of pressure hydrogen peroxide bleaching treatment on the initial slurry after the fiber modification treatment to obtain the lyocell dissolving slurry;
wherein the ozone dosage range of the ozone bleaching treatment is 0.2-1.5%, and the temperature range is 30-70 ℃;
the oxygen pressure range of the pressure hydrogen peroxide bleaching treatment is 0.20-0.30MPa, the concentration range of the initial slurry in the pressure hydrogen peroxide bleaching treatment is 10-20%, the temperature range is 105-120 ℃, and the bleaching time range is 60-90 minutes;
the concentration range of the initial slurry in the oxygen delignification treatment is 10-20%, the alkali dosage range is 1.5-4.5%, the oxygen pressure range is 0.8-1.0MPa, the temperature range is 95-110 ℃, and the heat preservation time range is 60-80 minutes;
the concentration of the initial slurry during the acid treatment is 10-20%, the pH is 1.5-3.5, the temperature is 70-80 ℃ and the time is 60-80 minutes.
2. The method for preparing lyocell pulp according to claim 1, wherein the step of obtaining wood chips to be treated and pre-hydrolyzing the wood chips to be treated comprises:
obtaining wood chips to be treated, and performing pre-steaming hydrolysis on the wood chips to be treated;
wherein the temperature range of the pre-steaming hydrolysis is 130-170 ℃ and the time range is 20-80 minutes.
3. The method for preparing lyocell pulp according to claim 1, wherein the step of obtaining wood chips to be treated and pre-hydrolyzing the wood chips to be treated comprises:
obtaining wood chips to be treated, and carrying out water impregnation pre-hydrolysis on the wood chips to be treated, wherein the temperature range of the water impregnation pre-hydrolysis is 130-170 ℃ and the time range is 20-80 minutes.
4. The method for preparing lyocell pulp according to claim 1, wherein the step of cooking the prehydrolyzed wood chips to be treated to obtain an initial pulp comprises:
the wood chips to be treated after the pre-hydrolysis are subjected to sulfate digestion through sodium hydroxide and sodium sulfide to obtain initial slurry;
wherein the liquid ratio of the sulfate cooking is 3:1-5:1, the dosage of sodium hydroxide is 17-21%, the sulfidation degree is 20-30%, and the cooking H factor is controlled within 550-1300.
5. A lyocell dissolving pulp, characterized in that the lyocell dissolving pulp is prepared by the preparation method of the lyocell dissolving pulp according to any one of claims 1 to 4.
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| CN114775324A (en) * | 2022-03-17 | 2022-07-22 | 金光纸业(中国)投资有限公司 | Dissolving pulp and preparation method thereof |
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| CN114775324A (en) * | 2022-03-17 | 2022-07-22 | 金光纸业(中国)投资有限公司 | Dissolving pulp and preparation method thereof |
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