阅读说明：本技术 一种杨木硫酸盐浆全无氯漂白制备溶解浆的方法 (Method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp ) 是由 田中建 吉兴香 陈嘉川 杨桂花 魏玮 韩文佳 于 2019-08-27 设计创作，主要内容包括：本发明涉及一种杨木硫酸盐浆全无氯漂白制备溶解浆的方法,包括：以杨木为原料,采用预水解硫酸盐法制备杨木硫酸盐浆；所述杨木硫酸盐浆进行ZOQP漂白,得到溶解浆；其中,Z-臭氧漂白,O-氧脱木素,Q-螯合处理,P-过氧化氢漂白。整个杨木硫酸盐浆全无氯漂白制备溶解浆过程经实现洗涤和漂白废水循环使用,“零”排放；利用该技术生产的高品质溶解浆,无有毒物质残留,各项指标均超过溶解浆行业标准(QB/T 4898-2015)中合格品要求,且大部分指标达到优等品指标,可替代进口溶解浆,在很大程度上解决了溶解浆生产污染大和粘胶纤维原料短缺的问题。(The invention relates to a method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp, which comprises the following steps: preparing poplar sulfate pulp by using poplar as a raw material and adopting a prehydrolysis sulfate method; carrying out ZOQP bleaching on the poplar sulfate pulp to obtain dissolving pulp; wherein, Z-ozone bleaching, O-oxygen delignification, Q-chelation treatment and P-hydrogen peroxide bleaching. The whole process of preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp realizes the recycling of washing and bleaching waste water and has zero discharge; the high-quality dissolving pulp produced by the technology has no toxic substance residue, each index exceeds the qualified product requirement in the industry standard of dissolving pulp (QB/T4898-.)

1. A method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp is characterized by comprising the following steps:

preparing poplar sulfate pulp by using poplar as a raw material and adopting a prehydrolysis sulfate method;

carrying out ZOQP bleaching on the poplar sulfate pulp to obtain dissolving pulp;

wherein, Z-ozone bleaching, O-oxygen delignification, Q-chelation treatment and P-hydrogen peroxide bleaching.

2. The method for preparing dissolving pulp by fully chlorine-free bleaching of poplar sulfate pulp as claimed in claim 1, wherein the prehydrolysis sulfate process comprises: hot water pretreatment and sulfate cooking.

3. The method for preparing dissolving pulp by fully chlorine-free bleaching of poplar kraft pulp according to claim 1, wherein the hot water pretreatment comprises the following specific steps: pretreating poplar chips with hot water: mixing the wood chips and water according to the liquid ratio of 1:4-1:7, heating to 150-.

4. The method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp as claimed in claim 1, wherein the sulfate cooking comprises the following specific steps: boiling poplar by a sulfate method: the liquid ratio is 1:4-1:7, the heat preservation temperature is 150-180 ℃, and the alkali dosage is Na₂20-25% of O, 20-25% of vulcanization degree and 60-100min of cooking time.

5. The method for preparing dissolving pulp by completely chlorine-free bleaching of poplar kraft pulp as claimed in claim 1, wherein the specific steps of the Z section are as follows: adjusting the pulp concentration of poplar sulfate pulp to 25-30%, adjusting the pH value to 1.5-3.0, the using amount of ozone to 1.0-3.0%, the using amount of diethyltriamine pentaacetic acid (DTPA) to 0.3-0.7%, and the temperature to 20-35 ℃, uniformly mixing, reacting for 10-30min, washing the pulp to be neutral after the reaction is finished, and concentrating until the pulp concentration is 8-15%.

6. The method for preparing dissolving pulp by completely chlorine-free bleaching of poplar kraft pulp as claimed in claim 1, wherein the O-stage comprises the following specific steps: placing the slurry in a sealed environment after the Z section is floated, introducing oxygen until the oxygen pressure is 0.4-0.8Mpa, the using amount of NaOH is 1.0-3.0%, and MgCO is added₃The dosage is 0.3-0.7%, the pulp is stirred at the speed of 60r/min at the temperature of 90-110 ℃ and reacts for 30-50min, and after bleaching, the pulp is washed to be neutral, and the pulp concentration is adjusted to be 8-15%.

7. The method for preparing dissolving pulp by fully chlorine-free bleaching of poplar kraft pulp as claimed in claim 1, wherein the Q-stage: and (3) placing the slurry after the O section treatment in a sealed reaction kettle, adding 0.2-0.6% of chelating agent DTPA to uniformly mix the slurry and the DTPA, and chelating at 60-80 ℃ for 20-40 min.

8. The method for preparing dissolving pulp by fully chlorine-free bleaching of poplar kraft pulp as claimed in claim 1, wherein the P stage: after the reaction of the Q section is finished, directly adding hydrogen peroxide into the slurry for bleaching, wherein the process condition is H₂O₂1.0-3.0% of the use amount, 0.4-0.9% of NaOH, 1.0-2.0% of sodium silicate, 0.1-0.3% of magnesium sulfate, 80-100 ℃ of the temperature and 70-100min of time, taking out the slurry after the reaction is finished, washing the slurry to be neutral, and drying the slurry to obtain the dissolving slurry.

9. Dissolving pulp prepared by the method of any one of claims 1 to 8.

10. Use of dissolving pulp according to claim 9 for the preparation of viscose, acetate, nitrate or cellulose ethers.

Technical Field

The invention belongs to the field of papermaking technology and new materials, and particularly relates to a method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The dissolving pulp is composed of high-purity cellulose and is used for manufacturing materials such as viscose, acetate, nitrocellulose, cellulose ether and the like, and important quality indexes of the dissolving pulp mainly comprise alpha-cellulose content, hemicellulose content, viscosity, molecular weight distribution and the like. In order to improve the product quality, the contents of hemicellulose, lignin, ash and metal ions in the dissolving pulp are strictly controlled, and the reactivity and the cellulose molecular weight distribution of the pulp are also required to be improved.

Hardwood has become the primary fiber feedstock for current dissolving pulp production. The prehydrolysis sulfate process has become the main dissolving pulp production process, oxygen-alkali delignification and ClO₂The popularization of bleaching promotes the application of green bleaching processes such as ECF, light ECF and even TCF in dissolving pulp production.

However, the inventor finds that: compared with the pulp of grass raw materials, the pulp of wood raw materials has poorer bleaching property and higher bleaching difficulty. Domestic dissolving pulp enterprises still use the traditional chlorine bleaching or element-free chlorine bleaching (ECF) technology to produce dissolving pulp. However, the traditional chlorine-containing bleaching has the defects of large water consumption for bleaching, difficult treatment of wastewater, existence of carcinogenic substances such as dioxin and the like, and the like; ECF bleaching has the problems of higher production cost, generation of a large amount of acidic substances in the reaction, lower pH value at the bleaching end point, strict requirements on equipment and the like. Limited by factors such as cost, product quality and the like, the TCF bleaching effect in the prior process of preparing dissolving pulp by wood raw materials still difficultly meets the requirement of practical production, and the alkali resistance and D resistance₆₅The main indexes such as brightness and the like are difficult to meet the requirements of qualified products, and the cost is high.

Disclosure of Invention

In order to overcome the problems, the invention provides an environment-friendly method for preparing dissolving pulp by bleaching poplar prehydrolysis sulfate pulp, each index exceeds the requirements of qualified products in the industry standard of the dissolving pulp (QB/T4898-.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

a method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp comprises the following steps:

preparing poplar sulfate pulp by using poplar as a raw material and adopting a prehydrolysis sulfate method;

carrying out ZOQP bleaching on the poplar sulfate pulp to obtain dissolving pulp;

wherein, Z-ozone bleaching, O-oxygen delignification, Q-chelation treatment and P-hydrogen peroxide bleaching.

The research of the application finds that: the method adopts ZOQP bleaching sequence chlorine-free bleaching for poplar sulfate pulp pretreated by hot water, can meet the index requirement of qualified dissolving pulp products under the condition of low drug dosage, obtains higher dissolving pulp yield, reduces production cost and bleaching sewage discharge and does not generate organic halide.

In some embodiments, the prehydrolysis sulfate process comprises: hot water pretreatment and sulfate cooking. According to the invention, poplar chips are used as raw materials, pulping is carried out by a sulfate method, then a novel green and environment-friendly total chlorine-free bleaching (TCF) ZOQP method is adopted, the waste water generated by bleaching does not contain harmful substances such as dioxin, AOX and the like, the COD content of the waste water is greatly reduced, and the cyclic use of the washing and bleaching waste water can be realized, and zero discharge is realized; the high-quality dissolving pulp produced by the technology has no toxic substance residue, each index exceeds the qualified product requirement in the industry standard of dissolving pulp (QB/T4898-.

In some embodiments, the hot water pretreatment comprises the following specific steps: mixing the wood chips and water according to the liquid ratio of 1:4-1:7, heating to 150-. Reduces the content of hemicellulose in the raw material, destroys the primary wall of the fiber and is beneficial to the subsequent cooking of the pulp.

In some embodiments, the specific steps of the kraft cooking are: the liquid ratio is 1:4-1:7, the temperature is 150-₂Calculated by O) 20-25 percent, the degree of vulcanization is 20-25 percent, and the cooking time is 60-100 min. Each index of the subsequently prepared dissolving pulp exceeds the requirement of qualified products in the industry standard (QB/T4898-2015) of the dissolving pulp, and other indexes except the dichloromethane extract exceed the indexes of superior products.

The research of the application finds that: the first O and the second Z are beneficial to removing residual lignin in the pulp after cooking and obtaining high-whiteness dissolving pulp by subsequent bleaching, and the first Z and the second O can reduce the loss of cellulose under the condition of ensuring that the high whiteness is higher than a qualified product, and the yield of the dissolving pulp is higher. Thus, in some embodiments, the specific steps of segment Z are: adjusting the pulp concentration of poplar sulfate pulp to 25-30%, adjusting the pH to 1.5-3.0, the ozone amount to 1.0-3.0%, the diethyl triaminepentaacetic acid (DTPA) amount to 0.3-0.7%, the temperature to 20-35 ℃, uniformly mixing, reacting for 10-30min, washing the pulp to be neutral after the reaction is finished, and concentrating until the pulp concentration is 8-15%, thereby improving the yield and whiteness of the dissolving pulp.

In some embodiments, the specific steps of the O-segment are: placing the slurry in a sealed environment after the Z section is floated, introducing oxygen until the oxygen pressure is 0.4-0.8Mpa, the using amount of NaOH is 1.0-3.0%, and MgCO is added₃The dosage is 0.3-0.7%, the reaction is carried out for 30-50min at the temperature of 90-110 ℃, after the bleaching is finished, the pulp is washed to be neutral, and the pulp concentration is adjusted to be 8-15%. Addition of MgCO₃The whiteness of the dissolving pulp is improved, the breaking length and the tearing factor are improved, and the pentosan content is reduced.

In some embodiments, segment Q: and (3) placing the slurry after the O section treatment in a sealed environment, adding 0.2-0.6% of chelating agent DTPA to uniformly mix the slurry and the DTPA, and performing chelating treatment at 60-80 ℃ for 20-40 min. The chelation treatment improves the whiteness of the dissolving pulp and the bleachability of the P-stage.

In some embodiments, P segment: after the reaction of the Q section is finished, directly adding hydrogen peroxide into the slurry for bleaching, wherein the process condition is H₂O₂The dosage is 1.0-3.0%, and the dosage of NaOH is0.4-0.9 percent of sodium silicate, 1.0-2.0 percent of sodium silicate and 0.1-0.3 percent of magnesium sulfate, the temperature is 80-100 ℃, the time is 70-100min, after the reaction is finished, slurry is taken out, washed to be neutral and dried to obtain dissolving slurry. The prepared dissolving pulp has high quality and no toxic substance residue, each index exceeds the requirements of qualified products in the industry standard (QB/T4898-2015) of the dissolving pulp, and most indexes reach the indexes of superior products, so that the dissolving pulp can replace imported dissolving pulp.

The invention also provides dissolving pulp prepared by any one of the methods.

The invention also provides application of the dissolving pulp in preparation of viscose, acetate, nitrate or cellulose ether.

The invention has the beneficial effects that:

(1) the whole process of preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp adopts hot water, oxygen, ozone, hydrogen peroxide, a small amount of alkali and a trace amount of other auxiliary agents, the waste water generated by bleaching does not contain harmful substances such as dioxin, AOX and the like, the COD content of the waste water is greatly reduced, the cyclic use of the washing and bleaching waste water can be realized, and zero discharge is realized; the high-quality dissolving pulp produced by the technology has no toxic substance residue, each index exceeds the qualified product requirement in the industry standard of dissolving pulp (QB/T4898-. The technology conforms to the industrial policies of national resource conservation, energy conservation, emission reduction and green development.

(2) The operation method is simple, low in equipment requirement, low in cost, universal and easy for large-scale production.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As introduced by the background technology, the method aims at the problems of poor TCF bleaching effect and high cost of the existing wood dissolving pulp. Therefore, the invention provides an environment-friendly method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp, which takes poplar chips as raw materials and comprises the following steps:

cutting the naturally air-dried and impurity-removed poplar into poplar pieces with the length of 3-6cm and the thickness of 2-5mm, and firstly, carrying out hot water pretreatment on the poplar pieces: mixing the wood chips and water according to a liquid ratio of 1:4-1:7, heating to 150-; subsequently, the pretreated poplar chips were cooked by a sulfate process under the following conditions: the liquid ratio is 1:4-1:7, the temperature is 150-180 ℃, and the alkali amount (by Na)₂Calculated by O) 20-25 percent, the degree of vulcanization is 20-25 percent, the cooking time is 60-100min, and after the cooking is finished, the poplar sulfate pulp is obtained by washing and concentrating. Then carrying out full chlorine-free ZOQP (Z-ozone bleaching, O-oxygen delignification, Q-chelation treatment and P-hydrogen peroxide bleaching) bleaching on the poplar sulfate pulp. A Z section: adjusting the pulp concentration of poplar sulfate pulp to 25-30%, adjusting the pH to 1.5-3.0, the using amount of ozone to 1.0-3.0%, the using amount of diethyl triaminepentaacetic acid (DTPA) to 0.3-0.7%, and the temperature to 20-35 ℃, uniformly mixing, reacting for 10-30min, washing the pulp to be neutral after the reaction is finished, and concentrating until the pulp concentration is 8-15%. And (4) O section: placing the slurry in a sealed environment after the Z section is floated, introducing oxygen until the oxygen pressure is 0.4-0.8Mpa, the using amount of NaOH is 1.0-3.0%, and MgCO is added₃The dosage is 0.3-0.7%, the reaction is carried out for 30-50min at the temperature of 90-110 ℃, after the bleaching is finished, the pulp is washed to be neutral, and the pulp concentration is adjusted to be 8-15%. And a Q section: and (3) placing the slurry after the O section treatment in a sealed environment, adding 0.2-0.6% of chelating agent DTPA to uniformly mix the slurry and the DTPA, and performing chelating treatment at 60-80 ℃ for 20-40 min. And a P section: after the reaction of the Q section is finished, directly adding hydrogen peroxide into the slurry for bleaching, wherein the process condition is H₂O₂1.0-3.0% of the use amount, 0.4-0.9% of NaOH, 1.0-2.0% of sodium silicate, 0.1-0.3% of magnesium sulfate, 80-100 ℃ of the temperature and 70-100min of time, taking out the slurry after the reaction is finished, washing the slurry to be neutral, drying the slurry to obtain dissolving slurry, and measuring various indexes of the dissolving slurry.

The chemical reagent grades used in the patent of the invention are all chemically pure.

The invention takes poplar chips as raw materials, after hot water pretreatment and sulfate pulping, the dissolving pulp is prepared by adopting a chlorine-free ZOQP bleaching process, and the detailed steps are as follows:

(1) preparing materials: cutting the naturally air-dried and impurity-removed poplar into poplar chips with the length of 3-6cm and the thickness of 2-5 mm.

(2) Pretreating poplar chips with hot water: mixing the wood chips and water according to the liquid ratio of 1:4-1:7, heating to 150-.

(3) Boiling poplar by a sulfate method: the liquid ratio is 1:4-1:7, the heat preservation temperature is 150-180 ℃, and the alkali amount (by Na)₂Calculated by O) 20-25 percent, the vulcanization degree is 20-25 percent, the boiling time is 60-100min, the poplar slices pretreated by hot water are boiled, and after the boiling is finished, the kraft pulp pretreated by the poplar hot water is obtained by concentration and washing.

(4) Ozone bleaching (stage Z): adjusting the pulp concentration of the hot water pretreated kraft pulp of poplar to 25-30%, adjusting the pH value to 1.5-3.0, the ozone amount to 1.0-3.0%, the diethyl triaminepentaacetic acid (DTPA) amount to 0.3-0.7%, the temperature to 20-35 ℃, mixing uniformly, reacting for 10-30min, washing the pulp to be neutral after the reaction is finished, and concentrating until the pulp concentration is 8-15%.

(5) Oxygen delignification (O stage): placing the slurry in a sealed environment after the Z section is floated, introducing oxygen until the oxygen pressure is 0.4-0.8Mpa, the using amount of NaOH is 1.0-3.0%, and MgCO is added₃The dosage is 0.3-0.7%, the pulp is stirred at the speed of 60r/min at the temperature of 90-110 ℃ and reacts for 30-50min, and after bleaching, the pulp is washed to be neutral, and the pulp concentration is adjusted to be 8-15%.

(6) Chelation treatment (Q stage): and (3) placing the slurry after the O section treatment in a sealed reaction kettle, adding 0.2-0.6% of chelating agent DTPA to uniformly mix the slurry and the DTPA, and chelating at 60-80 ℃ for 20-40 min.

(7) Hydrogen peroxide bleaching (P stage): after the reaction of the Q section is finished, directly adding hydrogen peroxide into the slurry for bleaching, wherein the process condition is H₂O₂1.0-3.0% of the use amount, 0.4-0.9% of NaOH, 1.0-2.0% of sodium silicate, 0.1-0.3% of magnesium sulfate, 80-100 ℃ of the temperature and 70-100min of time, taking out the slurry after the reaction is finished, washing the slurry to be neutral, drying the slurry to obtain dissolving slurry, and measuring various indexes of the dissolving slurry.

The method comprises the following steps:

(1) removing impurities from naturally air-dried poplar, and cutting into poplar chips with length of 3-6cm and thickness of 2-5 mm.

(2) Adding the poplar chips in the step (1) and water into a reaction kettle according to the liquid ratio of 1:4-1:7, heating to 150-.

(3) The poplar chips pretreated in the step (2) are subjected to heat preservation at the temperature of 150-180 ℃ and alkali consumption (Na) at the liquid ratio of 1:4-1:7₂Calculated by O) 20-25 percent and the vulcanization degree is 20-25 percent, the mixture is cooked for 60-100min, and after the cooking is finished, the mixture is washed and concentrated to obtain the poplar hot water pretreatment sulfate pulp.

(4) Carrying out ozone bleaching on the pulp obtained in the step (3) (Z stage): the conditions are as follows: adjusting the pH value of the slurry to 1.5-3.0 by using acetic acid, adjusting the using amount of ozone to 1.0-3.0%, adjusting the using amount of DTPA to 0.3-0.7%, adjusting the concentration of slurry to 25-30%, adjusting the temperature to 20-35 ℃, adjusting the stirring speed to 60r/min, adjusting the reaction time to 10-30min, allowing the redundant ozone generated in the reaction process to enter an absorption device filled with KI solution through an air outlet for absorption, after the reaction is finished, washing the slurry to be neutral by using water, and adjusting the concentration of the slurry to 8-15%.

(5) Subjecting the slurry of step (4) to oxygen delignification (O stage) under the following conditions: introducing oxygen gas until oxygen pressure is 0.4-0.8Mpa, NaOH dosage is 1.0-3.0%, and MgCO₃The dosage is 0.3-0.7%, the pulp is stirred at the speed of 60r/min at the temperature of 90-110 ℃ and reacts for 30-50min, and after bleaching, the pulp is washed to be neutral, and the pulp concentration is adjusted to be 8-15%.

(6) And (3) placing the slurry obtained in the step (5) into a closed reaction kettle for chelation treatment (Q section), adding 0.3-0.6% of diethyltriaminepentaacetic acid (DTPA), performing chelation treatment in a water bath kettle at the temperature of 60-80 ℃ for 20-40min, and stirring at the speed of 60r/min to uniformly mix the slurry.

(7) After the reaction of the Q section is finished, hydrogen peroxide is directly added for bleaching (P section), and the process condition is H₂O₂1.0-3.0 percent of dosage, 0.4-0.9 percent of NaOH, 1.0-2.0 percent of sodium silicate, 0.1-0.3 percent of dosage of magnesium sulfate, 80-100 ℃ of temperature and 70-100min of time, taking out slurry after the reaction is finished, and washing the slurry to be neutral.

(8) And (4) drying the slurry obtained in the step (7) to obtain dissolving slurry, which is mainly used for producing viscose fibers, acetate fibers, nitric acid fibers or cellulose ether.

The technical solution of the present application will be described below with specific examples. In the following examples, the percentages (%) are by mass.