Classifications

• • 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
  • D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
• • 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
  • D21C1/00—Pretreatment of the finely-divided materials before digesting
  • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
• • 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
  • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
• • 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
  • D21C9/101—Bleaching ; Apparatus therefor in solvent medium
• • 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
  • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
• • 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
  • D21C9/16—Bleaching ; Apparatus therefor with per compounds
  • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
• • 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
  • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
  • D21H11/04—Kraft or sulfate pulp

Definitions

• the invention belongs to the technical field of papermaking, and its specific design relates to an ionic liquid-based pulp bleaching protective agent.
• ECF elemental chlorine-free
• cellulose protective agents are anhydrous magnesium sulfate, magnesium carbonate, sodium silicate, borax, ethylene glycol, glycerol and the like.
• anhydrous magnesium sulfate is more common, but it has no effect on improving the bleaching efficiency.
• pulp carbohydrates are still greatly degraded during oxygen delignification after adding anhydrous magnesium sulfate, and when the oxygen delignification effect is higher than 50%, the protective effect will be greatly weakened, resulting in a sharp drop in the viscosity of the pulp fiber.
• Ionic liquid is a low-temperature molten salt that is composed entirely of anions and cations and is liquid at room temperature. It has the characteristics of good thermal stability, recyclability, non-volatility and good solubility. Ionic liquids can dissolve and separate lignin from wood fibers. Through proper ionic liquid selection and solution preparation, lignin from wood fiber can be selectively extracted. The use of such ionic liquids in the pulp bleaching process can increase the bleaching efficiency and enhance the bleaching effect. At the same time, it effectively protects the pulp fibers and enhances the physical strength of the paper.
• the present invention provides an application of ionic liquid as a protective agent for bleaching pulp.
• the present invention also provides an ionic liquid-based pulp bleaching protective agent, which is composed of an ionic liquid and a second component, and the second component is composed of magnesium carbonate, sodium silicate, borax, ethylene glycol, glycerol and no One or several components of hydromagnesium sulfate.
• the present invention provides an ionic liquid-based bleaching protective agent for pulp.
• the pulp bleaching protective agent is used to pretreat the pulp, and then ODP bleaching is performed.
• the pretreatment of the bleach protector can dissolve the lignin in the pulp and protect the fiber during the ODP bleaching process. In this way, the bleaching effect of the pulp is improved, and the physical strength of the pulp into paper is improved.
• An ionic liquid-based pulp bleaching protective agent consisting of an ionic liquid and a second component, the second component being one of magnesium carbonate, sodium silicate, borax, ethylene glycol, glycerol and anhydrous magnesium sulfate kind or several kinds of composition.
• the anion of the ionic liquid comprises one or more of hydrogen sulfate ion, formate ion and chloride ion;
• the cation of the ionic liquid contains one or more of 1-butyl 3-methyl-imidazolium ion, 2-hydroxyethyltrimethylammonium ion and triethylammonium ion.
• the ionic liquid includes triethylammonium hydrogen sulfate ionic liquid or 1-butyl 3-methyl hydrogen sulfate ionic liquid.
• the content of the anhydrous magnesium sulfate in the pulp bleach protective agent is 0.6%.
• the present invention also provides a method for improving the strength of the paper by the ionic liquid-based pulp bleaching protective agent, which includes:
• ECF bleaching the pretreated pulp is ODP bleaching sequence
• the amount of the bleach protection agent is 5-15% of the absolute dry mass of the pulp.
• the O-stage oxygen delignification process in the ODP bleaching sequence is: pulp concentration 10%, NaOH dosage 3%, oxygen pressure 0.5 MPa, temperature 100°C, time 60 min, and MgSO 4 dosage 0.6%.
• the D-stage chlorine dioxide bleaching process in the ODP bleaching sequence is as follows: the amount of chlorine dioxide is 0.7%, the pH value is 2 to 3, the temperature is 70° C., the pulp concentration is 10%, and the time is 30 minutes.
• the P-stage hydrogen peroxide bleaching process in the ODP bleaching sequence is as follows: the amount of hydrogen peroxide is 1%, the pulp concentration is 10%, the pH value is 11-12, the temperature is 90° C., and the oxygen pressure is 0.4 MPa.
• the pulp is kraft pulp
• the cooking process is to take wood chips with a length of 15-25 mm, a width of 10-20 mm, and a thickness of 3-5 mm. After natural air drying, they are cooked to obtain kraft puree.
• the cooking conditions are The amount of alkali used is 21%, relative to the absolutely dry raw material, as Na 2 O; the sulfidity is 25%, the liquid ratio is 1:5, the maximum cooking temperature is 170 °C, and the gas is deflated at 105 °C. The gas is deflated for 15 minutes, and the heating time is 90 minutes. , The holding time is 90min; after cooking, the pulp is fully washed and screened to obtain the pulp.
• the present invention also provides the application of the ionic liquid-based pulp bleaching protective agent described in the above technical scheme in the manufacture of relief printing paper, newsprint, offset printing paper, art paper, book cover paper, dictionary paper, copy paper or board paper.
• the present invention pretreats eucalyptus kraft pulp with an ionic liquid-based protective agent to form a surface protective layer during the ODP bleaching process, which reduces the degree of fiber degradation and protects the fiber backbone.
• the paper-based material prepared by pretreatment with an ionic liquid-based protective agent has the advantages of high folding resistance, high tensile strength, high burst resistance, high tearing degree, etc., and is suitable for preparing various types of paper-based materials.
• ionic liquid-based protective agent can selectively dissolve lignin, which significantly reduces the lignin content of the fiber, which is beneficial to the effect of bleaching agent.
• This treatment can improve the bleaching effect, can reduce the amount of bleaching agent, improve the bleaching efficiency, and reduce pollution.
• the ionic liquid used in the present invention has a stable structure, zero vapor pressure, can be recycled, and is environmentally friendly.
• the processing method of the present invention is simple, low in cost, strong in practicability, and easy to popularize.
• the present invention proposes an ionic liquid-based bleaching protective agent for pulp, which is subjected to ODP bleaching after pretreatment of the pulp.
• the pretreatment of the bleach protector can dissolve the lignin and protect the fiber during the bleaching process. In this way, the bleaching effect is improved, and the physical strength of the pulp into paper is improved.
• the technical solutions adopted by the present invention are as follows: the concentration of the slurry involved in the following are mass percentages unless otherwise specified; the dosage of the reagents and drugs involved, unless otherwise specified, are relatively dry In terms of pulp.
• the present invention provides an ionic liquid-based pulp bleaching protective agent, which is composed of one or more of ionic liquid, magnesium carbonate, sodium silicate, borax, ethylene glycol, glycerol and anhydrous magnesium sulfate.
• the anion of the ionic liquid contains one or more of hydrogen sulfate ion, formate ion or chloride ion; the pulp bleaching protectant developed in this application can selectively dissolve lignin and improve bleaching. The efficient and at the same time soluble cellulose is concentrated on the surface of the pulp fiber to protect the fiber from excessive oxidative degradation during the bleaching process.
• the cation of the ionic liquid comprises one or more of 1-butyl 3-methyl-imidazolium ion, 2-hydroxyethyl trimethylammonium ion and triethylammonium ion, wherein 1
• the structural formulas of -butyl 3-methyl-imidazolium ion, 2-hydroxyethyl trimethylammonium ion and triethylammonium ion are:
• ionic liquid is used to selectively dissolve lignin and enrich it on the surface of the fiber, so that the glycan structure is less damaged and the degree of fiber polymerization is high.
• the pretreatment can loosen the fibers and increase the degree of swelling, which is conducive to the subsequent penetration of the bleaching agent, the destruction of the chromophore groups and the diffusion and dissolution of the reactants.
• pretreatment can improve the morphology of fine fiber components, enhance cross-linking between fibers, thereby improving bleaching efficiency and enhancing the performance of paper-based materials.
• the cation of the ionic liquid contains one or more of 1-butyl 3-methyl-imidazolium ion, 2-hydroxyethyl trimethylammonium ion and triethylammonium ion, which improves Improve the bleaching efficiency and enhance the performance of paper-based materials.
• the present invention also provides a method for improving the strength of pulp into paper by an ionic liquid-based bleaching protective agent for pulp, which includes:
• ECF bleaching the pretreated pulp is ODP bleaching sequence
• the present invention provides a method for improving the strength of pulp into paper by an ionic liquid-based bleaching protective agent for pulp.
• the experiment includes the following steps:
• ECF bleaching The above-mentioned slurry treated with ionic liquid-based body-based bleaching protective agent is subjected to ECF bleaching, and the bleaching process is ODP bleaching sequence:
• the final pulp obtained after bleaching is used in the papermaking process.
• the pretreatment with ionic liquid-based bleaching protective agent is particularly aimed at protecting the fiber during the oxidation reaction of the bleaching process, reducing the degree of fiber oxidative degradation, and improving Bleaching effect, you can get high-performance pulp.
• the specific method of cooking in the step (1) is: taking a relatively uniform wood chip with a length of 15-25 mm, a width of 10-20 mm, and a thickness of 3-5 mm, and after natural air-drying, cooking is performed to obtain sulfate Puree, cooking conditions are 21% alkali, relative to the absolute dry raw material, Na 2 O; sulfidity 25%, liquid ratio 1:5, the highest cooking temperature is 170 °C, venting at 105 °C, release Air 15min, heating time 90min, heat preservation time 90min; after cooking, full washing and screening are carried out to obtain pulp, so as to improve the cooking efficiency and the strength performance of the paper.
• Sulphate wood pulp uses a mixture of sodium hydroxide and sodium sulfide as a cooking agent. During the cooking process, because the effect of the liquid medicine is relatively mild and the fiber is not strongly corroded, the fiber is strong and strong, with high tensile strength, burst resistance, tearing and other mechanical strength indicators, and heat resistance and durability High sex.
• the specific step of the pretreatment in step (2) is: the slurry obtained in step (1) is treated under the condition of a bleach protectant amount of 5-15%, and then under a fixed condition Under ODP bleaching.
• the amount of the protective agent is 10%.
• the specific method of the ODP bleaching process in step (3) is: O-stage oxygen delignification process: pulp concentration 10%, NaOH dosage 3%, oxygen pressure 0.5MPa, temperature 100°C, time 60min, MgSO 4 dosage is 0.6%; D stage chlorine dioxide bleaching process is: chlorine dioxide dosage 0.7%, pH value 2 ⁇ 3, temperature 70°C, pulp concentration 10%, time 30min; P stage hydrogen peroxide bleaching process is :Hydrogen peroxide dosage is 1%, slurry concentration is 10%, pH value is 11-12, temperature is 90°C, oxygen pressure is 0.4MPa.
• the oxygen delignification process can reduce the lignin content in unbleached pulp, reduce the amount of bleaching agent, and reduce the pollution load of bleaching wastewater.
• the O-stage oxygen delignification process is: pulp concentration 10%, NaOH dosage 3%, oxygen pressure 0.5MPa, temperature 100°C, time 60min, which improves the efficiency of oxygen bleaching and pulp performance.
• Chlorine dioxide has strong oxidizing properties, strong delignification ability and delignification selectivity. Under the same effective chlorine dosage, the adsorbable organic halide (AOX) produced by chlorine dioxide bleaching is only 1/5 of that of chlorine bleaching, without affecting the removal of lignin.
• the establishment of a buffer system is beneficial to keep the pH stable.
• the D-stage chlorine dioxide bleaching process is as follows: the amount of chlorine dioxide is 0.7%, the pH value is 2 to 3, the temperature is 70°C, the pulp concentration is 10%, and the time is 30 minutes, which improves the bleaching efficiency of pulp and reduces The production of organic halides (AOX).
• the hydrogen peroxide bleaching process has less damage to the fiber, high yield, and strong process adaptability.
• the bleaching waste water contains organic chlorine compounds, which is easy to handle, and can realize the full recycling of bleaching wastewater.
• the P-stage hydrogen peroxide bleaching process is as follows: the amount of hydrogen peroxide is 1%, the pulp concentration is 10%, the pH value is 11-12, the temperature is 90°C, and the oxygen pressure is 0.4 MPa to effectively protect the pulp strength , Improve its whiteness.
• the design concept of the present invention is: in view of the problem of low pulp strength caused by oxidative reaction damage to the pulp fiber during the bleaching process, the present invention proposes a pretreatment method using an ionic liquid-based protective agent to dissolve the lignin in the pulp and attach it to the surface of the fiber. Make the bleaching agent and lignin fully function, avoid the oxidative damage to the fiber during the bleaching process, and ensure the excellent physical strength of the paper material.
• Bursting Index Measured with a Bursting Tester produced by L&W, a Swedish company
• Tensile index Measured with the XLWA(B) intelligent electronic tensile testing machine made in China;
• Tear index Measured with the MIT tear tester made in China.
• Fiber surface lignin content measured with XPS produced in the United States.
• the principle of the present invention is: using an ionic liquid-based pulp bleaching protective agent to selectively dissolve lignin and enrich it on the surface of the fiber, so that the cellulosan structure is less damaged and the fiber polymerization degree is high.
• the pretreatment can loosen the fibers and increase the degree of swelling, which is conducive to the subsequent penetration of bleaching agents, the destruction of chromophores and the diffusion and dissolution of reactants.
• pretreatment can improve the morphology of fine fiber components, enhance the interweaving ability between fibers, thereby improving bleaching efficiency and enhancing the performance of paper-based materials.
• eucalyptus wood chips are used in the alkali amount of 21%, Na 2 O; sulfidity 25%, liquid ratio 1:5, cooking at the highest temperature of 170 °C, venting at 105 °C, heating time 90 minutes , Holding time 90min. After the cooking, the pulp is fully washed and sieved to obtain the pulp.
• Pretreatment of protective agent accurately weigh out three bags of 25g of the above eucalyptus sulphate pulp (calculated as dry pulp), and measure 10% triethylammonium hydrogen sulfate ionic liquid (TEA-HSO 4 ) based bleaching protective agent (In addition to TEA-HSO 4 , the bleach protectant also contains a small amount of anhydrous magnesium sulfate (0.6%)) is added to the slurry, the slurry concentration is adjusted to 10% in a polyethylene bag, and the mixture is kneaded until uniform.
• TEA-HSO 4 triethylammonium hydrogen sulfate ionic liquid
• ECF bleaching bleach the pulp after the above pretreatment, the bleaching process is ODP, and the bleaching process steps are: first perform O-stage oxygen delignification on eucalyptus kraft pulp, the process is: pulp concentration 10%, The amount of NaOH is 3%, the oxygen pressure is 0.5MPa, the temperature is 100°C, the time is 60min, and the amount of MgSO 4 is 0.6%; then the D-stage chlorine dioxide bleaching process is performed: the amount of chlorine dioxide is 0.7%, the pH value is 2 to 3, and the temperature is 70 °C, pulp concentration 10%, time 30min; wash the treated pulp, and then carry out P-stage hydrogen peroxide bleaching.
• the process is: hydrogen peroxide dosage 1%, pulp concentration 10%, pH value 11-12, temperature 90°C, oxygen pressure 0.4MPa; wash the treated slurry.
• the slurry is beaten according to a beating degree of 40°SR, and then it is decomposed by a fiber decomposer to make it uniformly mixed, and then 80g/m 2 of base paper paper-based material is copied on the paper sheet former.
• ODP After bleaching (ODP): Kappa number decreased from 1.54 to 0.48, a decrease of 69%; viscosity increased from 684mL/g to 806mL/g, an increase of 18%; degree of polymerization increased from 988 to 1184, an increase of 20 %.
• the chemical composition of the pulp was tested, and it was found that the pretreatment with TEA-HSO 4 ionic liquid-based bleaching protective agent significantly reduced the lignin content in the pulp.
• the oxygen bleaching stage (O) fiber lignin content was reduced from 6.76% To 3.52%, a decrease of 48%; after bleaching (ODP) fiber lignin content decreased from 1.97% to 1.62%, a decrease of 18%.
• O/C ratio of the fiber surface decreased from 0.53 to 0.48 after the oxygen bleaching section was detected by XPS, indicating that a protective layer of lignin was formed on the fiber surface during the bleaching process.
• Cooking The condition is 21% alkali, Na 2 O; sulfidity 25%, liquid ratio 1:5, maximum cooking temperature 170 °C, venting at 105 °C, heating time 90 min, holding time 90 min ; Carry out sufficient washing and screening after cooking to obtain pulp.
• ECF bleaching bleach the pulp after the above pretreatment.
• the bleaching process is the ODP bleaching process.
• the steps are: first perform O-stage oxygen delignification on eucalyptus kraft pulp, the process is: pulp concentration 10%, NaOH Dosage is 3%, oxygen pressure is 0.5MPa, temperature is 100°C, time is 60min, and MgSO 4 dosage is 0.6%; then D-stage chlorine dioxide bleaching is carried out.
• the process is: chlorine dioxide dosage of 0.7%, pH value of 2 ⁇ 3, temperature of 70°C , Pulp concentration 10%, time 30min; wash the treated pulp, and then carry out P-stage hydrogen peroxide bleaching.
• the process is: hydrogen peroxide dosage 1%, pulp concentration 10%, pH value 11-12, temperature 90 °C, oxygen pressure 0.4MPa; wash the treated slurry.
• the slurry is beaten according to a beating degree of 40°SR, and then it is decomposed by a fiber decomposer to make it uniformly mixed, and then 80g/m 2 of base paper paper-based material is copied on the paper sheet former.
• ODP After bleaching (ODP): Kappa number decreased from 1.54 to 0.67, a decrease of 56%; viscosity increased from 684mL/g to 721mL/g, an increase of 5%; degree of polymerization increased from 988 to 1047, an increase 6%.
• the chemical composition of the pulp was tested, and it was found that the pretreatment with TEA-HSO 4 ionic liquid-based bleaching protective agent significantly reduced the lignin content in the pulp.
• the oxygen bleaching stage (O) fiber lignin content was reduced from 6.76% To 5.96%, a decrease of 12%; after the bleaching (ODP) fiber lignin content decreased from 1.97% to 1.83%, a decrease of 7%.
• O/C ratio of the fiber surface decreased from 0.53 to 0.51 after the oxygen bleaching section was detected by XPS, indicating that a protective layer of lignin was formed on the fiber surface during the bleaching process.

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• 2019
  • 2019-10-31 CN CN201911055224.1A patent/CN110747681B/zh active Active
• 2020
  • 2020-02-26 WO PCT/CN2020/076725 patent/WO2021082306A1/zh active Application Filing
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