阅读说明：本技术 一种杨木kp浆tcf漂白生产溶解浆的工艺 (Process for producing dissolving pulp by TCF bleaching of poplar KP pulp ) 是由 吉兴香 田中建 杨桂花 吕高金 魏玮 陈嘉川 于 2019-08-27 设计创作，主要内容包括：本发明涉及一种杨木KP浆TCF漂白生产溶解浆的工艺,包括：以杨木为原料,采用预水解硫酸盐法制备杨木KP浆；所述杨木KP浆进行OZQP漂白,得到溶解浆；其中,O-氧脱木素,Z-臭氧漂白,Q-螯合处理,P-过氧化氢漂白。所制备溶解浆各项指标均优于溶解浆行业标准(QB/T 4898-2015)中优等品要求,且大部分指标远超优等品指标,可完全替代进口溶解浆。(The invention relates to a process for producing dissolving pulp by TCF bleaching of poplar KP pulp, which comprises the following steps: preparing poplar KP pulp by using poplar as a raw material by adopting a prehydrolysis sulfate method; carrying out OZQP bleaching on the poplar KP pulp to obtain dissolving pulp; wherein, O-oxygen delignification, Z-ozone bleaching, Q-chelation treatment and P-hydrogen peroxide bleaching. All indexes of the prepared dissolving pulp are superior to the high-grade product requirements in the industry standard of the dissolving pulp (QB/T4898-.)

1. A process for producing dissolving pulp by carrying out TCF bleaching on poplar KP pulp is characterized by comprising the following steps:

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

carrying out OZQP bleaching on the poplar KP pulp to obtain dissolving pulp;

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

2. The TCF bleaching process of poplar KP pulp to produce dissolving pulp as in claim 1, wherein the poplar is fast-growing hardwood poplar, 3-6cm long and 2-5mm thick.

3. The TCF bleaching of poplar KP pulp to produce dissolving pulp as in claim 1, wherein the prehydrolysis kraft process comprises: hot water pretreatment and sulfate cooking.

4. The process for producing dissolving pulp by TCF bleaching of poplar KP pulp according to claim 1, wherein the hot water pretreatment comprises the following steps: mixing poplar chips with water according to the liquid ratio of 1:4-1:7, heating to 150 ℃ and 170 ℃, and preserving heat for 60-90 min;

or the specific steps of the sulfate cooking are as follows: the liquid ratio is 1:4-1:6, the cooking temperature is 150-.

5. The process for producing dissolving pulp by TCF bleaching of poplar KP pulp according to claim 1, wherein the O stage comprises the following steps: placing poplar KP slurry in oxygen bleaching tank, introducing oxygen until oxygen pressure is 0.4-0.8Mpa, NaOH content is 1.5-3.5%, and MgCO is added₃The dosage is 0.3-0.8%, the pulp concentration is 8-15%, the reaction is carried out for 25-50min in an oxygen bleaching tank at 85-100 ℃, after the bleaching is finished, the pulp is washed to be neutral by water and concentrated to be 25-30% pulp concentration.

6. The process for producing dissolving pulp by TCF bleaching of poplar KP pulp according to claim 1, wherein the Z stage comprises the following steps: placing the concentrated slurry after O section bleaching in a reaction kettle, adjusting the pH value to 1.5-3.0 by using acetic acid, adjusting the using amount of ozone to 1.5-3.0%, the using amount of sodium Iminodisuccinate (IDS) to 0.3-0.6%, the temperature to 25-35 ℃, the reaction time to 10-30min, and the stirring speed to 60r/min, wherein redundant ozone generated in the reaction process enters 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%.

7. The process for producing dissolving pulp by TCF bleaching of poplar KP pulp according to claim 1, wherein the Q stage: placing the slurry in a closed reaction kettle after the Z section is floated, adding 0.3-0.7% IDS, stirring to uniformly mix IDS and slurry, and chelating at 60-90 deg.C for 20-40 min.

8. The process for producing dissolving pulp by TCF bleaching of poplar KP pulp according to claim 1, wherein in stage P: after the reaction in the section Q is finished,hydrogen peroxide is directly added into the pulp for bleaching, and the technological conditions are that the dosage of H2O2 is 1.5-3.0%, the dosage of NaOH is 0.6-1.0%, the dosage of DTPA is 0.3-0.5%, and MgCO is added₃The dosage is 0.1-0.3%, the temperature is 80-95 ℃, the time is 80-100min, after the reaction is finished, the slurry is taken out, washed to be neutral, and dried to obtain the dissolving slurry.

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

10. Use of dissolving pulp according to claim 9 for the preparation of viscose fibres.

Technical Field

The invention belongs to the field of papermaking technology and new materials, and particularly relates to a process for preparing dissolving pulp by bleaching poplar sulfate (KP) 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.

Dissolving pulp is purer fluff pulp after filtration and is the most main raw material source of viscose fiber. In the fiber industry, viscose and synthetic fibers are the primary alternatives to cotton. Compared with synthetic fibers, the viscose has obvious advantages, and on one hand, the raw materials are plant fibers, so that the resources are rich and renewable; secondly, the texture of the viscose fiber is closer to that of the cotton fiber, and the viscose fiber has better comfort, air permeability, environmental protection ecological performance and the like than synthetic fiber. The viscose fiber production raw materials mainly comprise cotton dissolving pulp, wood dissolving pulp, bamboo dissolving pulp and bagasse dissolving pulp. According to the relevant predictions, global fiber production and demand will continue to increase, with annual fiber consumption increasing 2000 million tons worldwide by 2025 years ago, while the per capita fiber demand is increasing far beyond the well-developed economies of the european union, japan and the usa in china and india. In our country, the cotton-derived fiber can not meet the demand, and in recent years, due to the reduction of cotton yield and the atrophy of cotton linter production, wood dissolving pulp has become the main incremental source of viscose fiber. In 2010-2016, the annual increase of the dissolving pulp consumption in China is about 19 percent. In 2016, the whole demand of the dissolving pulp in China is 400 million tons, the import scale is about 225 million tons, the supply quantity of the dissolving pulp in China is 100 million tons, and the market potential is huge. After 2017, the production of dissolving pulp enterprises with large influence on the environment is stopped due to the influence of the strictest environmental protection policy in history, so that the market supply of the dissolving pulp is more tense.

Compared with grass raw materials, the wood raw material paper pulp has poorer bleaching property and higher bleaching difficulty. At present, TCF bleaching research and application are mainly focused on grass raw materials, the main reason is that the TCF of the wood raw material is difficult to obtain high whiteness, although the TCF is reported to obtain the high whiteness of more than 90 percent by documents, the yield of fibers and dissolving pulp is greatly reduced when the TCF achieves the whiteness, and the yield of the dissolving pulp is generally lower than 30 percent.

Disclosure of Invention

In order to overcome the problems, the method takes poplar sulfate (KP) pulp as a raw material, adopts a novel green and environment-friendly totally chlorine-free bleaching (TCF) OZQP method, the wastewater generated by bleaching does not contain harmful substances such as dioxin, AOX and the like, the COD content of the wastewater is greatly reduced, and the cyclic use of the washing and bleaching wastewater can be realized, and zero discharge is realized; the high-quality dissolving pulp produced by the technology has no toxic substance residue, all indexes meet the requirements of superior 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 process for producing dissolving pulp by carrying out TCF bleaching on poplar KP pulp comprises the following steps:

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

carrying out OZQP bleaching on the poplar KP pulp to obtain dissolving pulp;

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

The research of the invention finds that: the method is used for sulfate pulp bleaching (OZQP) by using poplar as a raw material and performing hot water prehydrolysis, can keep about 35 percent of dissolving pulp yield while obtaining higher whiteness, and other indexes all meet the requirements of superior products in the dissolving pulp industry standard (QB/T4898-.

In some embodiments, the poplar is fast-growing hardwood poplar with the specification of 3-6cm long and 2-5mm thick, and the infiltration effect and pretreatment efficiency of water on wood are improved.

In some embodiments, the prehydrolysis sulfate process comprises: the poplar dissolving pulp prepared by adopting the hot water pretreatment and the sulfate method cooking has improved quality and small environmental pollution.

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 ℃ and 170 ℃, and preserving heat for 60-90 min. The content of alpha-cellulose in the pulp and the reaction capacity are improved.

In some embodiments, the specific steps of the kraft cooking are: the liquid ratio is 1:4-1:6, the heat preservation temperature is 150-₂Calculated by O) 18-25 percent, the degree of vulcanization is 18-25 percent, and the cooking time is 60-120 min. The produced dissolving pulp has high content of alpha-cellulose and uniform polymerization degree distribution.

In some embodiments, the specific steps of the O-segment are: placing poplar KP slurry in oxygen bleaching tank, introducing oxygen until oxygen pressure is 0.4-0.8Mpa, NaOH content is 1.5-3.5%, and MgCO is added₃The dosage is 0.3-0.8%, the pulp concentration is 8-15%, the reaction is carried out for 25-50min in an oxygen bleaching tank at 85-100 ℃, after the bleaching is finished, the pulp is washed to be neutral by water and concentrated to be 25-30% pulp concentration. The oxygen generates delignification in an alkaline medium to remove residual lignin after cooking.

In some embodiments, the specific steps of segment Z are: placing the concentrated O-section bleached pulp in a reaction kettle, adjusting the pH to 1.5-3.0 by using acetic acid, adjusting the using amount of ozone to 1.5-3.0%, adjusting the using amount of iminodisuccinic acid (IDS) to 0.3-0.6%, adjusting the temperature to 25-35 ℃, reacting for 10-30min, adjusting the stirring speed to 60r/min, allowing the redundant ozone generated in the reaction process to enter an absorption device filled with KI solution through an air outlet for absorption, washing the pulp to be neutral by using water after the reaction is finished, adjusting the pulp concentration to 8-15%, and after the oxygen bleaching, continuously removing lignin by using ozone bleaching, improving the whiteness of the pulp and avoiding the introduction of organic chloride.

In some embodiments, segment Q: and (3) placing the slurry after the Z section is floated into a closed reaction kettle, adding 0.3-0.6% of IDS (tetrasodium iminodisuccinate), chelating at 60-90 ℃ for 20-40min, and stirring to uniformly mix the IDS and the slurry. The research of the application finds that: after the poplar sulfate pulp prehydrolyzed by hot water is bleached by an OZ section, the poplar sulfate pulp is chelated by IDS, so that the alkali resistance and the brightness of the poplar sulfate pulp are improved.

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 1.5-3.0%NaOH 0.6-1.0%, DTPA 0.3-0.5%, MgCO₃The dosage is 0.1-0.3%, the temperature is 80-95 ℃, the time is 80-100min, after the reaction is finished, the slurry is taken out, washed to be neutral, and dried to obtain the dissolving slurry. The prepared dissolving pulp has good whiteness stability and excellent indexes.

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

The invention also provides application of the dissolving pulp in preparation of viscose fibers.

The invention has the beneficial effects that:

(1) the high-quality dissolving pulp produced by the technology has no toxic substance residue, each index is superior to the index of a superior product in the industry standard of the dissolving pulp, the high-quality dissolving pulp can completely replace imported dissolving pulp, and the problems of large pollution and viscose fiber raw material shortage in the dissolving pulp production are solved to a great extent.

(2) According to the application, hot water, ozone, hydrogen peroxide, a small amount of alkali and a trace amount of other auxiliary agents are adopted in the whole TCF bleaching process for preparing dissolving pulp of poplar KP pulp, the wastewater generated by bleaching does not contain harmful substances such as dioxin, AOX and the like, the COD content of the wastewater is greatly reduced, the cyclic use of the washing and bleaching wastewater can be realized, and zero discharge is realized; the technology conforms to the industrial policies of national resource conservation, energy conservation, emission reduction and green development.

(3) The operation method is simple, 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 in the background art, the method aims at the problems of poor quality of the existing dissolving pulp and serious environmental pollution. Therefore, the invention provides an environment-friendly method for preparing dissolving pulp by bleaching poplar KP pulp, the yield of the prepared dissolving pulp is high, each index is superior to the requirement of superior products in the industry standard (QB/T4898-2015) of the dissolving pulp, and most indexes are far superior to the indexes of the superior products, so that the dissolving pulp can completely replace the imported dissolving pulp.

An environment-friendly method for preparing dissolving pulp by bleaching poplar KP pulp, which takes fast-growing broadleaf poplar as a raw material 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 the liquid ratio of 1:4-1:7, heating to 150 ℃ and 170 ℃, and preserving heat for 60-90 min. Subsequently, the pretreated poplar chips were cooked by a sulfate process under the following conditions: the liquid ratio is 1:4-1:6, the cooking temperature is 150-₂Calculated by O) 18-25 percent, the vulcanization degree is 18-25 percent, the cooking time is 60-120min, and after the cooking is finished, the poplar KP pulp is obtained by washing and concentrating. Then, OZQP (O-oxygen delignification, Z-ozone bleaching, Q-chelation treatment and P-hydrogen peroxide bleaching) bleaching is carried out on the poplar KP pulp. And (4) O section: placing poplar KP slurry in oxygen bleaching tank, introducing oxygen until oxygen pressure is 0.4-0.8Mpa, NaOH content is 1.5-3.5%, and MgCO is added₃The usage amount is 0.3-0.8%, the pulp concentration is 8-15%, the reaction is carried out for 25-50min in an oxygen bleaching tank at 85-100 ℃, after the bleaching is finished, the pulp is washed to be neutral by water and concentrated to be 25-30% of pulp concentration; a Z section: placing the concentrated slurry after O section bleaching in a reaction kettle, adjusting the pH value to 1.5-3.0 by using acetic acid, adjusting the using amount of ozone to 1.5-3.0%, the using amount of iminodisuccinic acid (IDS) to 0.3-0.6%, the temperature to 25-35 ℃, the reaction time to 10-30min, the stirring speed to 60r/min, introducing redundant ozone generated in the reaction process into 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%; and a Q section: floating Z sectionPlacing the slurry in a sealed reaction kettle, adding 0.3-0.7% IDS, chelating at 60-90 deg.C for 20-40min, and stirring to uniformly mix IDS and slurry; 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 H₂O₂1.5-3.0% of NaOH, 0.6-1.0% of DTPA, 0.3-0.5% of MgCO₃The dosage is 0.1-0.3%, the temperature is 80-95 ℃, the time is 80-100min, after the reaction is finished, the slurry is taken out, washed to be neutral, and dried to obtain the dissolving slurry.

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

The invention takes poplar prehydrolysis KP pulp as raw material, adopts totally chlorine-free bleaching process-OZQP to prepare dissolving pulp, and has the detailed steps as follows:

(1) preparing materials: removing impurities from naturally air-dried poplar, and cutting into poplar chips with length of 3-6cm and 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 ℃ and 170 ℃, and preserving heat for 60-90 min.

(3) Pulping by using a poplar sulfate method: the liquid ratio is 1:4-1:6, the cooking temperature is 150-₂Calculated by O) 18-25 percent, the vulcanization degree is 18-25 percent, the cooking time is 60-120min, and after the cooking is finished, the poplar KP pulp is obtained by washing and concentrating.

(4) Oxygen delignification (O-stage) treatment: placing poplar KP slurry in oxygen bleaching tank, introducing oxygen until oxygen pressure is 0.4-0.8Mpa, NaOH content is 1.5-3.5%, and MgCO is added₃The dosage is 0.3-0.8%, the pulp concentration is 8-15%, the reaction is carried out for 25-50min in an oxygen bleaching tank at 85-100 ℃, after the bleaching is finished, the pulp is washed to be neutral by water and concentrated to be 25-30% pulp concentration.

(5) Ozone bleaching (stage Z): putting the concentrated slurry after O section bleaching in a reaction kettle, adjusting the pH value to 1.5-3.0 by using acetic acid, adjusting the using amount of ozone to 1.5-3.0%, the using amount of iminodisuccinic acid (IDS) to 0.3-0.6%, the temperature to 25-35 ℃, reacting for 10-30min, and stirring at the speed of 60r/min, wherein redundant ozone generated in the reaction process enters an absorption device filled with KI solution through an air outlet to be absorbed, after the reaction is finished, washing the slurry to be neutral by using water, and adjusting the concentration of the slurry to 8-15%.

(6) Chelation treatment (Q stage): placing the slurry in a closed reaction kettle after the Z section is floated, adding 0.3-0.7% IDS, stirring to uniformly mix IDS and slurry, and chelating at 60-90 deg.C 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 H₂O₂1.5-3.0% of NaOH, 0.6-1.0% of DTPA, 0.3-0.5% of MgCO₃The dosage is 0.1-0.3%, the temperature is 80-95 ℃, the time is 80-100min, after the reaction is finished, slurry is taken out, the slurry is washed to be neutral, the dissolved slurry is obtained by drying, and all indexes of the dissolved slurry are measured.

The method specifically 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) Mixing the poplar chips in the step (1) with water according to the liquid ratio of 1:4-1:7, heating to 150 ℃ and 170 ℃, and preserving heat for 60-90 min.

(3) The pretreated poplar chips in the step (2) are treated at the liquor ratio of 1:4-1:6, the cooking temperature of 150-₂Calculated by O) 18-25 percent, the vulcanization degree is 18-25 percent, the cooking time is 60-120min, and after the cooking is finished, the poplar KP pulp is obtained by washing and concentrating.

(4) And (4) performing oxygen delignification on the poplar KP pulp obtained in the step (3) under the following conditions (O section). Placing poplar KP slurry in oxygen bleaching tank, introducing oxygen until oxygen pressure is 0.4-0.8Mpa, NaOH content is 1.5-3.5%, and MgCO is added₃The dosage is 0.3-0.8%, the pulp concentration is 8-15%, the reaction is carried out for 25-50min in an oxygen bleaching tank at 85-100 ℃, after the bleaching is finished, the pulp is washed to be neutral by water and concentrated to be 25-30% pulp concentration.

(5) Carrying out ozone bleaching on the pulp obtained in the step (4) (Z stage): adjusting the pH value of the slurry to 1.5-3.0 by using acetic acid, wherein the using amount of ozone is 1.5-3.0%, the using amount of sodium Iminodisuccinate (IDS) is 0.3-0.6%, the temperature is 25-35 ℃, the reaction time is 10-30min, the stirring speed is 60r/min, redundant ozone generated in the reaction process enters an absorption device filled with KI solution through an air outlet for absorption, after the reaction is finished, the slurry is washed to be neutral by using water, and the concentration of the slurry is adjusted to 8-15%.

(6) And (3) placing the slurry obtained in the step (5) into a closed reaction kettle for chelation treatment (Q section), adding 0.3-0.7% of IDS, performing chelation treatment at 60-90 ℃ for 20-40min, and stirring to uniformly mix the IDS and the slurry.

(7) Directly adding hydrogen peroxide into the pulp obtained in the step (6) for bleaching, wherein the process condition is H₂O₂1.5-3.0% of NaOH, 0.6-1.0% of DTPA, 0.3-0.5% of MgCO₃The dosage is 0.1-0.3%, the temperature is 80-95 ℃, the time is 80-100min, after the reaction is finished, the slurry is taken out, and the slurry is washed to be neutral.

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

The technical solution of the present application will be described below with specific examples. The following percentages (%) are mass percentages unless otherwise specified.