CN110512452B - High-polymerization-degree wood pulp and preparation method thereof - Google Patents
High-polymerization-degree wood pulp and preparation method thereof Download PDFInfo
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- CN110512452B CN110512452B CN201910780777.7A CN201910780777A CN110512452B CN 110512452 B CN110512452 B CN 110512452B CN 201910780777 A CN201910780777 A CN 201910780777A CN 110512452 B CN110512452 B CN 110512452B
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- 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
- D21C3/00—Pulping cellulose-containing materials
- D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
- D21C3/022—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes in presence of S-containing compounds
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- 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
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/222—Use of compounds accelerating the pulping processes
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- 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
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- 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
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Abstract
The invention provides wood pulp with high polymerization degree and a preparation method thereof. The method comprises the following steps: slicing wood to obtain wood chips, adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment to obtain the mechanically pretreated wood chips; adding the mechanically pretreated wood chips into cooking liquor, soaking, adding a protective agent and a permeation assistant, uniformly mixing to obtain a mixed liquor, heating the mixed liquor to perform cooking treatment to obtain a mixture after the cooking treatment, and filtering to obtain a slurry after the cooking treatment; cleaning, defibering, sieving, adding into bleaching liquid for bleaching treatment, and cleaning to obtain high polymerization degree wood pulp. The lignin content of the pulp after cooking in the method is less than 4%, the polymerization degree of the prepared high-polymerization-degree wood pulp can reach 2517 to the maximum, and is more than twice of that of common commercial pulp (900-1200). The preparation method provided by the invention is beneficial to promoting the application of the wood pulp fiber in high added value fields of automobiles, energy sources, flexible electronics and the like.
Description
Technical Field
The invention belongs to the field of paper pulp and papermaking, and particularly relates to high-polymerization-degree wood pulp and a preparation method thereof.
Background
In recent years, with the increasing prominence of the environmental pollution problem, people pay more attention to environmental protection, and bio-based materials attract more attention and interest due to unique characteristics. The cellulose is used as a natural high molecular polymer with the largest reserve and the widest distribution in the nature, has the characteristics of no pollution, recoverability and easy degradation, so that the cellulose-based material is widely applied to all corners of the human society, and the development and progress of the human society are effectively promoted. With the progress of nanotechnology, humans can separate nanocellulose from wood pulp fiber, which exhibits excellent optical and mechanical properties in addition to the advantages of cellulose. The material based on the nano-cellulose has bright application prospect in the emerging fields of energy, electronic devices, biomedicine and the like, is expected to relieve the environmental load caused by white pollution, and is helpful for the sustainable development of human society.
Most of the existing nano-cellulose is prepared by taking commercial wood pulp as a raw material through a specific process. These commercial pulps are usually pulped by sulfite or sulfate processes, the raw materials are infiltrated and sulfonated by cooking liquor, chemical reaction is carried out between the raw materials and lignin to generate lignosulfonic acid or lignosulfonate, and cellulose and hemicellulose contained in the fibers are degraded to different degrees in the cooking liquor and are partially hydrolyzed and dissolved out. Finally, the reaction product is dissolved out and separated from the raw material into fibrous pulp. The pulping processes have low price and high production efficiency and can be produced in large scale, and the prepared wood pulp can fully meet the basic physical property requirements of paper. However, with the continuous emergence of new fields such as aerospace, flexible electronics and the like, human beings put forward higher requirements on the mechanical properties of materials. The nano-cellulose material prepared by the original pulping process can hardly meet the requirements of the emerging fields. The reason for this is mainly that the pulping process can cause the strong degradation of wood pulp fiber, the polymerization degree is reduced, the performance of the prepared nano cellulose is seriously damaged, and the requirement of high-strength nano cellulose base material is difficult to meet.
Aiming at the problem, Schering and the like can obtain cooked half-pulp with the polymerization degree of at least 2500 by adding a biological enzyme composite auxiliary agent and cooking cotton linters by combining the traditional cooking liquor, but the price of cotton is high, so that the cotton is limited to a certain extent; liu jian hua etc. stabilize the PH of cooking liquor through adding sodium silicate and magnesium sulfate, improve the stability of hydrogen peroxide solution, make hydrogen peroxide solution slowly decompose and take effect to adsorb metal ions such as calcium, iron, magnesium in the system of cooking, avoid impurity accumulation on the fibre, thereby improve the effect of cooking, obtain the higher wood pulp fibre of degree of polymerization. However, the method has low preparation efficiency, expensive medicine price and high production cost.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide wood pulp with high polymerization degree and a preparation method thereof.
The invention aims to solve the problems that the traditional industrial pulping has large damage to wood fibers and low polymerization degree and is difficult to apply to the field of high-performance cellulose-based composite materials, improves the pulping process and technology, and obtains a method capable of well retaining the original characteristics of cellulose. High removal rate of lignin and hemicellulose is realized while high polymerization degree of cellulose is ensured. In addition, on the basis of meeting the whiteness of the pulp, a milder bleaching method is adopted, the original form of cellulose is further kept, and a preparation method for improving the polymerization degree of the commercial pulp is provided.
The purpose of the invention is realized by at least one of the following technical solutions.
The invention provides a preparation method of wood pulp with high polymerization degree. The preparation method comprises the following steps: cutting the wood into smaller and thin rectangular wood chips; mechanically treating the wood chips by using a double-screw extruder; soaking the wood chips in cooking liquor for a period of time; adding the wood chips, the cooking liquor, the protective agent and the permeation aid into a high-temperature high-pressure reaction kettle for cooking; the wood pulp obtained by cooking is washed, fluffed and screened, the cooking liquor and residues in the wood pulp are removed, and the wood pulp with high polymerization degree is obtained by a bleaching process with selective delignification. The lignin content of the pulp after cooking is less than 4%, the highest polymerization degree of the bleached pulp can reach 2517, and the pulp is more than twice of that of common commercial pulp (900-1200). The invention provides a method for preparing the wood pulp fiber with high polymerization degree, which is beneficial to promoting the application of the wood pulp fiber in the fields with high added values such as automobiles, energy sources, flexible electronics and the like.
The invention provides a preparation method of wood pulp with high polymerization degree by taking wood as a raw material. The wood pulp fiber with high polymerization degree is obtained by mechanical pretreatment and cooking liquor soaking, 2-hydroxyanthraquinone is added as a protective agent before cooking, an anionic surfactant is used as a permeation assistant to enhance the permeation of the cooking liquor, and the wood is cooked by using an improved ASAM method, so that the degradation of cellulose is prevented as much as possible while the rapid delignification is realized.
The preparation method of the wood pulp with high polymerization degree provided by the invention is a method for keeping the original characteristics of wood fiber and improving the polymerization degree of the wood fiber.
The invention provides a preparation method of wood pulp with high polymerization degree, which comprises the following steps:
(1) slicing wood to obtain wood chips (preferably rectangular wood chips), adding the wood chips into a double-screw extruder, and performing mechanical pretreatment to obtain mechanically pretreated wood chips;
(2) adding the wood chips subjected to mechanical pretreatment in the step (1) into a cooking solution, performing soaking treatment, then adding a protective agent and a permeation assistant, uniformly mixing to obtain a mixed solution, transferring the mixed solution into a reaction kettle (preferably a high-temperature high-pressure reaction kettle), heating for cooking treatment to obtain a mixture subjected to cooking treatment, and filtering to obtain a precipitate to obtain a cooked slurry;
(3) and (3) cleaning the cooked pulp in the step (2), defibering, screening, adding into bleaching liquid for bleaching treatment, and cleaning to obtain the high-polymerization-degree wood pulp.
Further, the wood in the step (1) is needle-leaved wood; the softwood wood is more than one of masson pine, Korean pine, spruce, hemlock and fir; the thickness of the wood chips is 2-4 mm.
Preferably, the wood chips in step (1) are rectangular wood chips.
Preferably, the wood chips of step (1) are small and thin rectangular wood chips.
Further, the mechanical pretreatment in the step (1) is carried out for 2-3 times, the pressure of the mechanical pretreatment is 0.8-1.2MPa, the temperature of the mechanical pretreatment is 20-30 ℃, and the time of each mechanical pretreatment is 5-10 min. The mechanical pretreatment has the function of enabling the wood chips to be properly deformed and facilitating the penetration of liquid medicine.
Further, the preparation of the cooking liquor in the step (2) comprises the following steps: adding sodium hydroxide and sodium sulfite into a methanol solution, and uniformly mixing to obtain the cooking liquor; the volume percentage concentration of the methanol solution is 10-30%; in the cooking liquor, the mass percent concentration of sodium hydroxide is 2.5 wt%; in the cooking liquor, the mass percent concentration of sodium sulfite is 4.23 wt%.
Further, the mass ratio of the wood chips subjected to mechanical pretreatment in the step (2) to the cooking liquor is 1: 10-1: 50, the soaking treatment time is 1-2 days; the protective agent is one of anthrahydroquinone, dihydroanthraquinone, tetrahydroanthraquinone, 2-methylanthraquinone and sodium polysulfide, and the mass of the protective agent is 0.06-0.10% of that of the wood chips after the mechanical pretreatment.
Preferably, the mass ratio of the wood chips after mechanical pretreatment in the step (2) to the cooking liquor is 1: 50.
when the mass ratio of the wood chips after mechanical pretreatment to the cooking liquor is 1: when the polymerization degree is 50, the polymerization degree of the finally prepared wood pulp with high polymerization degree can reach 2517.
Further, the protective agent in the step (2) is a penetration auxiliary agent which is an anionic surfactant, and the penetration auxiliary agent is one of sodium dodecyl benzene sulfonate, xylene sulfonic acid and condensed sodium naphthalene sulfonate; the mass of the penetration aid is 40% of the mass of the wood chips after the mechanical pretreatment.
Further, the temperature of the cooking treatment in the step (2) is 150 ℃ to 170 ℃, and the time of the cooking treatment is 3 to 5 hours.
Further, in the step (2), the lignin content of the pulp obtained after the cooking treatment can be reduced to 3.45-3.87%.
Further, the preparation of the bleaching solution in the step (3) comprises the following steps: adding sodium chlorite and glacial acetic acid into water, and uniformly mixing to obtain the bleaching solution; in the bleaching solution, the mass percent concentration of the sodium chlorite is 0.60-0.80%; in the bleaching solution, the mass percentage concentration of the glacial acetic acid is 0.80-0.10%; the temperature of the bleaching treatment is 70-80 ℃, and the time of the bleaching treatment is 1-2 h.
Further, the mass-to-volume ratio of the cooked slurry to the bleaching solution in the step (3) is 0.37:1 g/mL.
The invention provides wood pulp with high polymerization degree prepared by the preparation method.
The wood pulp with high polymerization degree provided by the invention has the polymerization degree reaching 2376-2517 (DP).
The invention provides a preparation method of wood pulp with high polymerization degree, which comprises the following steps:
(1) preparing a cooking solution:
dissolving sodium hydroxide and sodium sulfite (taking sodium sulfite as a reference and using 20-25% of alkali) in a methanol solution with the volume fraction of 20-40%, and uniformly stirring to obtain a cooking solution; the concentration of the liquid medicine is controlled by changing the using amount of the wood chips, so that the polymerization degree of the slurry is controlled;
(2) pretreatment of raw materials:
cutting the fir wood into slices with the thickness of 2-4 mm, properly and mechanically treating the wood chips for 2-3 times by using a double-screw extruder, and soaking the wood chips in cooking liquor for 1-2 days to facilitate the permeation of liquor;
(3) adding the cooking liquid obtained in the step (1), the wood chips obtained in the step (2), a cellulose protective agent and a penetrating agent into a high-pressure reaction kettle for cooking, wherein the heating rate is preferably 0.8 ℃/min, when the temperature reaches 150-170 ℃, the temperature is kept for 3-5 hours, and then, naturally cooling to room temperature;
(4) cleaning, fluffing and screening the slurry obtained in the step (3);
(5) bleaching the pulp obtained in the step (4) by using sodium chlorite and glacial acetic acid;
(6) and (5) washing the pulp in the step (5) by using distilled water to obtain wood pulp with high polymerization degree and high whiteness.
The technical principle of the preparation method of the wood pulp with high polymerization degree provided by the invention is as follows.
And (3) cooking:
under the action of high temperature and strong alkali, the cellulose macromolecular chain can be hydrolyzed and broken into two or more short molecular chains, and the original one reducing end group is changed into two or more reducing end groups, so that the peeling reaction can be promoted. If the cleavage part occurs near the terminal part of the macromolecular chain, the resulting oligosaccharide is directly dissolved in the solution. After the cellulose is subjected to alkaline hydrolysis, the average polymerization degree of the cellulose is obviously reduced, and the strength and other properties of the pulp are necessarily influenced.
Anthraquinones and their analogues (cellulose protectors) are generally very stable, not easily oxidized, and not easily reduced by weak reducing agents. But can be reduced in alkaline solution to produce 9, 10-dihydroxyanthracene (also called anthrahydroquinone, H)2AQ or AHQ), AHQ is unstable and is easily oxidized by oxidants to form anthraquinones.
Anthraquinone reacts with the reducing end group of the carbohydrate and suppresses the occurrence of peeling reaction by changing the reducing end group to a hydroxyl group, at which point anthraquinone is reduced to AHQ. Under alkaline conditions, AHQ is ionized into anthrahydroquinone ions, then the anthrahydroquinone ions are exchanged into anthrone ions, and then the anthrone ions are reacted with a methylene quinone structure in lignin, and meanwhile, the anthrone ions are converted into anthraquinone, and the anthraquinone ions continue to have redox reaction with carbohydrates. In the cyclic reaction process, cellulose is protected, the yield is improved, the lignin removal efficiency is also improved, and anthraquinone reacts with Na2S has similar functions. Wherein, the action of anthraquinone on lignin is mainly that negative carbon ions in anthrone ions attack methylene parts in a lignin methylene quinone structure and negative oxygen ions provide electrons, thereby promoting the breakage of phenolic beta-aryl ether bonds.
The penetrant is mainly anionic surfactant (such as dodecyl, xylene sulfonic acid, condensed sodium naphthalene sulfonate and the like), is applied to cooking, mainly plays a role in wetting, permeating and dispersing, promotes the wetting of the cooking liquor on fiber raw materials, accelerates the permeation and uniform dispersion of cooking chemicals and other chemicals, thereby promoting the removal of lignin and resin in wood or non-wood by the cooking liquor and playing a role in dispersing resin.
Bleaching:
during bleaching, sodium chlorite is reduced to gaseous chlorine dioxide by a reducing agent under acidic conditions. Chlorine dioxide has strong oxidizing power and is a high-efficiency bleaching agent. The bleaching is characterized by the ability to selectively oxidize lignin and pigments with little or no damage to cellulose. The bleached paper pulp has high whiteness, less yellowing and high strength.
Chlorine dioxide is a free radical which readily attacks the phenolic hydroxyl groups of lignin to form free radicals, which then undergo a series of oxidation reactions. When reacting with phenolic lignin, phenolic oxygen radicals and other intermediary radicals are first formed, and these radicals form chlorite with chlorine dioxide, which is further converted to ortho-quinone or phthalic acid, among others. In addition, chlorine dioxide degrades carbohydrates much less than oxygen, chlorine and hypochlorite, primarily in terms of both acidic degradation and oxidation reactions. At pH 4, hydrolysis of the carbohydrate is minimized, and oxidation does not occur to produce much glucuronyl. The use of glacial acetic acid allows the pH of the solution to be controlled, thereby increasing selectivity.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) in the preparation method of the wood pulp with high polymerization degree, anthraquinone and analogues thereof are used as protective agents in the cooking treatment, and the reducing aldehyde end group of carbohydrate can be oxidized to be changed into carboxyl so as to avoid the occurrence of peeling reaction, and the yield of the paper pulp can be improved by protecting cellulose and hemicellulose; sodium persulfate is used as a penetration auxiliary agent, and more sodium sulfide is generated due to oxidation reaction and decomposition reaction, so that the delignification reaction is promoted; the methanol can make reactants more active, facilitate the contact of liquid medicine lignin and improve the cooking efficiency;
(2) in the preparation method of the wood pulp with high polymerization degree, the polymerization degree is found to rise along with the increase of the liquid ratio by controlling the ratio of the wood chips to the cooking liquid, and the optimal ratio of 1:50, the polymerization degree at this time is 2517, which is more than 2 times of that of commercial pulp, and the pulp is lighter in color and convenient to bleach;
(3) in the preparation method of the wood pulp with high polymerization degree, the adopted sodium chlorite can be decomposed to generate chlorine dioxide under the high-temperature acidic condition, the bleaching agent has strong oxidizing capability, can selectively oxidize lignin and pigment, does not or hardly damage cellulose, and has high whiteness, little yellowing and high pulp strength of the bleached paper pulp;
(4) the preparation method of the wood pulp with high polymerization degree provided by the invention improves the pulping process on the basis of industrial production, can improve the polymerization degree of the pulp, and simultaneously improves the yield and impurity removal rate of the pulp, thereby bringing good economic benefit;
(5) the preparation method of the wood pulp with high polymerization degree provided by the invention can keep the original form of the fiber as much as possible, and is convenient for utilizing the form characteristics of the wood fiber, thereby improving the mechanical property and the optical property of the cellulose-based material and expanding the application field;
(6) the high-polymerization-degree wood pulp provided by the invention can be applied to the fields of industrial production, high polymer material research and the like, the application field of commercial pulp is widened, and the high-performance material prepared by utilizing the high-polymerization-degree wood pulp provided by the invention has good physical properties, can bear various mechanical pressure and has prolonged service life; the wood pulp with high polymerization degree has the characteristic of high whiteness, can be used for preparing a high-transparency cellulose film, utilizes micron-sized and nano-sized cellulose to regulate and control the surface porosity of the film, achieves controllable haze, and can be used for optical electronic components and the like.
Detailed Description
The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.
Example 1
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 2 times, wherein the mechanical pretreatment time is 5min each time, and the mechanical pretreatment pressure is 0.8MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with volume fraction of 10%, and uniformly mixing to obtain a cooking solution; then 60g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:10, the wood chips are soaked for 24 hours, then adding a protective agent (anthrahydroquinone) and a penetration aid (sodium dodecyl benzene sulfonate), wherein the mass of the protective agent is 0.06 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 170 ℃, the cooking treatment time is 3 hours, a mixture subjected to the cooking treatment is obtained, and precipitates are filtered to obtain a cooked slurry;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 1 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided in the example 1 is tested to have the polymerization degree of 2376 and the whiteness of 85 percent.
Example 2
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 7min each time, and the mechanical pretreatment pressure is 1.0MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with the volume fraction of 20%, and uniformly mixing to obtain a cooking solution; then 60g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:10, the wood chips are soaked for 24 hours, then adding a protective agent (dihydroanthraquinone) and a penetration aid (sodium dodecyl benzene sulfonate), wherein the mass of the protective agent is 0.06 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 170 ℃, the cooking treatment time is 3 hours, a mixture subjected to the cooking treatment is obtained, and precipitates are filtered to obtain a cooked slurry;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 2 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided by the example 2 is tested to be 2381 and have whiteness of 85.5%.
Example 3
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 10min each time, and the mechanical pretreatment pressure is 1.2MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of 30% methanol solution by volume fraction, and uniformly mixing to obtain a cooking solution; then 60g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:10, the wood chips are soaked for 24 hours, then adding a protective agent (tetrahydroanthraquinone) and a penetration aid (sodium dodecyl benzene sulfonate), wherein the mass of the protective agent is 0.06 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 170 ℃, the cooking treatment time is 3 hours, a mixture subjected to the cooking treatment is obtained, and precipitates are filtered to obtain a cooked slurry;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 3 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided in the example 3 is tested to be 2385 and the whiteness is 84.9%.
Example 4
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 10min each time, and the mechanical pretreatment pressure is 1.2MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with the volume fraction of 20%, and uniformly mixing to obtain a cooking solution; then 30g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:20, the wood chips are soaked for 36 hours, then adding a protective agent (sodium polysulfide) and a penetration auxiliary agent (sodium dodecyl benzene sulfonate), wherein the mass of the protective agent is 0.08 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 160 ℃, the cooking treatment time is 4 hours, a mixture subjected to the cooking treatment is obtained, and a precipitate is filtered to obtain a cooked slurry;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 4 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided in the example 4 is tested to have 2401 polymerization degree and 84.5 whiteness.
Example 5
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 10min each time, and the mechanical pretreatment pressure is 1.2MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with the volume fraction of 20%, and uniformly mixing to obtain a cooking solution; then 20g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:30, the wood chips are soaked for 48 hours, then adding a protective agent (2-ethyl tetrahydroanthrahydroquinone) and a penetration aid (xylene sulfonic acid), wherein the mass of the protective agent is 0.10 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 150 ℃, the cooking treatment time is 5 hours, a mixture subjected to the cooking treatment is obtained, and the mixture is filtered to obtain a precipitate, so that a cooked slurry is obtained;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 5 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided in the example 5 is tested to have the polymerization degree of 2442 and the whiteness of 84.0 percent.
Example 6
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 10min each time, and the mechanical pretreatment pressure is 1.2MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with the volume fraction of 20%, and uniformly mixing to obtain a cooking solution; then 15g of the mechanically pretreated wood chips from step (1) were added to the cooking liquor, the mass ratio of the wood chips after the mechanical pretreatment to the cooking liquor is 1:40, the wood chips are soaked for 24 hours, then adding a protective agent (2-ethyl tetrahydroanthrahydroquinone) and a permeation aid (sodium condensed naphthalenesulfonate), wherein the mass of the protective agent is 0.10 wt% of the mass of the wood chips after the mechanical pretreatment in the step (2), the mass of the penetration auxiliary agent is 40 wt% of the mass of the wood chips subjected to the mechanical pretreatment in the step (2), the penetration auxiliary agent and the wood chips are uniformly mixed to obtain a mixed solution, the mixed solution is transferred into a reaction kettle to be heated for cooking treatment, the heating rate is 0.8 ℃/min, the cooking treatment temperature is 150 ℃, the cooking treatment time is 5 hours, a mixture subjected to the cooking treatment is obtained, and the mixture is filtered to obtain a precipitate, so that a cooked slurry is obtained;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1.5h, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 6 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided in the example 6 is tested to have the polymerization degree of 2471 and the whiteness of 83.1 percent.
Example 7
A method for preparing wood pulp with high polymerization degree comprises the following steps:
(1) pretreatment of raw materials: slicing wood to obtain wood chips, wherein the wood chips are rectangular wood chips (6 cm in length, 3 cm in width and 2 mm in thickness), then adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment for 3 times, wherein the mechanical pretreatment time is 10min each time, and the mechanical pretreatment pressure is 1.2MPa to obtain the mechanically pretreated wood chips;
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of methanol solution with the volume fraction of 20%, and uniformly mixing to obtain a cooking solution; then adding 12g of the wood chips subjected to mechanical pretreatment in the step (1) into a cooking solution, wherein the mass ratio of the wood chips subjected to mechanical pretreatment to the cooking solution is 1:50, carrying out soaking treatment for 24h, then adding a protective agent (2-ethyl tetrahydroanthrahydroquinone) and a penetration assistant (sodium dodecylbenzenesulfonate), wherein the mass of the protective agent is 0.10 wt% of the mass of the wood chips subjected to mechanical pretreatment in the step (2), the mass of the penetration assistant is 40 wt% of the mass of the wood chips subjected to mechanical pretreatment in the step (2), uniformly mixing to obtain a mixed solution, transferring the mixed solution into a reaction kettle, heating for cooking treatment at the heating rate of 0.8 ℃/min, the temperature of the cooking treatment is 150 ℃, the time of the cooking treatment is 5 hours, obtaining a mixture subjected to the cooking treatment, filtering and taking a precipitate, obtaining the cooked slurry;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 2 hours, and washing with distilled water to obtain the pulp with high polymerization degree, namely the wood pulp with high polymerization degree.
The wood pulp with high polymerization degree prepared in the example 7 is tested according to the national standard ramie cellulose polymerization degree measuring method (GB/T5888-1986) and the industry standard ramie fiber whiteness test method (QB/T4125-2010), and the wood pulp with high polymerization degree provided by the example 7 is tested to be 2517 and have whiteness of 82.5%.
Comparative example 1
A method for preparing slurry comprises the following steps:
(1) pretreatment of raw materials: cutting the wood into sheets, wherein the wood sheets are rectangular wood sheets (the length is 6 cm, the width is 3 cm, and the thickness is 2 mm);
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of distilled water, and uniformly mixing to obtain a cooking solution; then, 60g of the wood chips obtained in the step (1) and the cooking liquor are mixed, the mixture is transferred to a reaction kettle, the temperature is increased to perform cooking treatment, the temperature rate is 0.8 ℃/min, the temperature of the cooking treatment is 170 ℃, the time of the cooking treatment is 3 hours, a mixture after the cooking treatment is obtained, and the mixture is filtered to obtain precipitates, and is subjected to defibering and cleaning to obtain a slurry after the cooking;
(3) adding 3g of sodium chlorite and 2.5mL of glacial acetic acid into 320mL of deionized water, and uniformly mixing to obtain a bleaching solution; and (3) cleaning the cooked pulp obtained in the step (3), then defibering and screening to obtain screened pulp, then adding the screened pulp (with the absolute dry mass of 10g) into bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp.
The slurry prepared in comparative example 1 was tested according to the national standard method for measuring the degree of polymerization of cellulose in ramie (GB/T5888-.
Comparative example 2
A method for preparing slurry comprises the following steps:
(1) pretreatment of raw materials: cutting the wood into sheets, wherein the wood sheets are rectangular wood sheets (the length is 6 cm, the width is 3 cm, and the thickness is 2 mm);
(2) adding 15g of sodium hydroxide and 25.4g of sodium sulfite into 600mL of distilled water, and uniformly mixing to obtain a cooking solution; then, 60g of the wood chips obtained in the step (1) and the cooking liquor are mixed, the mixture is transferred to a reaction kettle, the temperature is increased to perform cooking treatment, the temperature rate is 0.8 ℃/min, the temperature of the cooking treatment is 170 ℃, the time of the cooking treatment is 3 hours, a mixture after the cooking treatment is obtained, and the mixture is filtered to obtain precipitates, and is subjected to defibering and cleaning to obtain a slurry after the cooking;
(3) and (3) using 320mL of hydrogen peroxide solution with the volume fraction of 3% as bleaching liquid, cleaning the cooked pulp in the step (2), then defibering and screening to obtain screened pulp (the absolute dry mass is 10g), then adding the screened pulp into the bleaching liquid for bleaching treatment, wherein the bleaching treatment temperature is 75 ℃, the bleaching treatment time is 1h, and washing with distilled water to obtain the pulp with high polymerization degree.
The slurry prepared in comparative example 2 was tested according to the national standard method for measuring the degree of polymerization of cellulose in ramie (GB/T5888-.
The above examples are only preferred embodiments of the present invention, which are intended to be illustrative and not limiting, and those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention.
Claims (2)
1. The preparation method of the wood pulp with high polymerization degree is characterized by comprising the following steps:
(1) slicing wood to obtain wood chips, adding the wood chips into a double-screw extruder, and carrying out mechanical pretreatment to obtain mechanically pretreated wood chips;
(2) adding the wood chips subjected to mechanical pretreatment in the step (1) into a cooking solution, performing soaking treatment, then adding a protective agent and a permeation aid, uniformly mixing to obtain a mixed solution, transferring the mixed solution into a reaction kettle, heating for cooking treatment to obtain a mixture subjected to cooking treatment, and filtering to obtain a precipitate to obtain a cooked slurry;
(3) cleaning the cooked pulp in the step (2), defibering, screening, adding into bleaching liquid for bleaching treatment, and cleaning to obtain the high polymerization degree wood pulp;
the wood in the step (1) is needle-leaved wood; the softwood wood is more than one of masson pine, Korean pine, spruce, hemlock and fir; the thickness of the wood chips is 2-4 mm;
the mechanical pretreatment frequency of the step (1) is 2-3 times, the pressure of the mechanical pretreatment is 0.8-1.2MPa, the temperature of the mechanical pretreatment is 20-30 ℃, and the time of each mechanical pretreatment is 5-10 min;
the preparation of the cooking liquor in the step (2) comprises the following steps: adding sodium hydroxide and sodium sulfite into a methanol solution, and uniformly mixing to obtain the cooking liquor; the volume percentage concentration of the methanol solution is 10-30%; in the cooking liquor, the mass percent concentration of sodium hydroxide is 2.5 wt%; in the cooking liquor, the mass percent concentration of sodium sulfite is 4.23 wt%;
the mass ratio of the wood chips subjected to mechanical pretreatment in the step (2) to the cooking liquor is 1: 10-1: 50, the soaking treatment time is 1-2 days; the protective agent is one of anthrahydroquinone, dihydroanthraquinone, tetrahydroanthraquinone, 2-methylanthraquinone and sodium polysulfide, and the mass of the protective agent is 0.06-0.10% of that of the wood chips after the mechanical pretreatment;
the protective agent in the step (2) is a penetration auxiliary agent which is an anionic surfactant, and the penetration auxiliary agent is one of sodium dodecyl benzene sulfonate, xylene sulfonic acid and condensed sodium naphthalene sulfonate; the mass of the penetration auxiliary agent is 40% of that of the wood chips after the mechanical pretreatment;
the temperature of the cooking treatment in the step (2) is 150-170 ℃, and the time of the cooking treatment is 3-5 hours;
the preparation of the bleaching solution in the step (3) comprises the following steps: adding sodium chlorite and glacial acetic acid into water, and uniformly mixing to obtain the bleaching solution; in the bleaching solution, the mass percent concentration of the sodium chlorite is 0.60-0.80%; in the bleaching solution, the mass percentage concentration of the glacial acetic acid is 0.80-0.10%; the temperature of the bleaching treatment is 70-80 ℃, and the time of the bleaching treatment is 1-2 h;
and (4) the mass-to-volume ratio of the cooked slurry to the bleaching solution in the step (3) is 0.37:1 g/mL.
2. A wood pulp having a high degree of polymerization produced by the production method according to claim 1.
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