阅读说明：本技术 一种由造纸用化学浆制备溶解浆的新工艺 (Novel process for preparing dissolving pulp from chemical pulp for papermaking ) 是由 徐永健 徐洋 祝萌 高敏兰 熊建华 于 2020-11-16 设计创作，主要内容包括：一种造纸用化学浆制备溶解浆的制备方法,步骤包括：1)纸浆准备：将造纸用漂白化学浆常温下疏解、脱水至25％-30％质量浓度的纸浆；将纸浆风干后放置平衡水分；2)溶解：将步骤1)制备的纸浆分散在低共熔溶剂中,配置成质量浓度为0.1％-10％的纸浆悬浮液,浸泡使其充分润胀后；加热使其充分反应,获得含有溶解浆的混合物；3)干燥：将混合物固液分离、并用清水洗涤至中性、抄造成形、干燥。本发明制备方法,原料来源充足,制备的溶解浆品质佳,废液可回收利用,利于环保。(A method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following steps: 1) preparing paper pulp: defibering and dehydrating the bleached chemical pulp for papermaking at normal temperature to paper pulp with the mass concentration of 25-30%; air-drying the paper pulp, and then standing for balancing moisture; 2) dissolving: dispersing the paper pulp prepared in the step 1) in a eutectic solvent to prepare a paper pulp suspension with the mass concentration of 0.1-10%, and soaking the paper pulp suspension to fully swell the paper pulp; heating to make it fully react to obtain a mixture containing dissolving pulp; 3) and (3) drying: separating solid from liquid, washing with clean water to neutrality, making paper, shaping and drying. The preparation method has the advantages of sufficient raw material sources, good quality of the prepared dissolving pulp, recyclable waste liquid and contribution to environmental protection.)

1. A method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following steps:

1) pulp preparation

Defibering and dehydrating the bleached chemical pulp for papermaking at normal temperature to paper pulp with the mass concentration of 25-30%; air-drying the paper pulp, and then standing for balancing moisture;

2) dissolution

Dispersing the paper pulp prepared in the step 1) in a eutectic solvent to prepare a paper pulp suspension with the mass concentration of 0.1-10%, and soaking the paper pulp suspension to fully swell the paper pulp; heating to make it fully react to obtain a mixture containing dissolving pulp;

3) drying

Separating solid from liquid, washing with clean water to neutrality, making paper, shaping and drying.

2. The method for preparing dissolving pulp from chemical pulp for papermaking as claimed in claim 1, wherein the bleached chemical pulp for papermaking in step 1) is selected from softwood pulp, hardwood pulp and bamboo pulp.

3. The method for preparing dissolving pulp from chemical pulp for papermaking as set forth in claim 1, wherein the bleached chemical pulp for papermaking in step 1) has an α -cellulose content of 60% to 90% and an average degree of polymerization of 700-.

4. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 1, wherein in the step 1), the dissolving is performed for 5min, and after filtering and dewatering, at least 24 parts of water are left in a closed position for balancing.

5. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 1, wherein the eutectic solvent in the step 2) is prepared from choline chloride and one or more of oxalic acid dihydrate, glycerol and urea.

6. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 5, wherein: in the step 2, the mol ratio of the choline chloride to one or more of oxalic acid dihydrate, glycerol and urea in the eutectic solvent is 1:0.5-1: 10.

7. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 1, wherein in the step 2), the pulp suspension is soaked in the room temperature for 0.2-24 hours to be fully swelled; heating to 80-120 deg.c for 0.5-24 hr to react fully.

8. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 1, wherein: the drying method in the step 3) is vacuum drying, the vacuum degree is 0.08-0.10MPa, the temperature is 50-80 ℃, and the time is 0.5-48 hours.

9. The method for preparing dissolving pulp from chemical pulp for papermaking according to claim 1, wherein the waste liquid and the washing liquid after solid-liquid separation in the step 3) can be recycled after water in the waste liquid and the washing liquid is removed by rotary evaporation.

Technical Field

The invention relates to a method for preparing dissolving pulp from papermaking chemical pulp, in particular to a method for preparing dissolving pulp by purifying papermaking chemical pulp through a eutectic solvent, and belongs to the fields of applied chemistry and pulping and papermaking engineering.

Background

The dissolving pulp is a high-purity refined chemical pulp, and has high cellulose purity, a small amount of hemicellulose, and trace amounts of lignin, extractives and minerals. The dissolving pulp is widely applied to high-valued cellulose products such as viscose, nitrocellulose, cellulose acetate, microcrystalline cellulose and the like. As a natural polymer compound with abundant resources and wide application, the dissolving pulp has great research space, wide development and market prospect. In the existing research, the main preparation principle and method of dissolving pulp are roughly the same, namely, the processes of raw material cooking, bleaching, cellulose purification, polymerization degree adjustment, washing, drying and the like are adopted. In order to further realize market benefits, people are constantly exploring the preparation of dissolving pulp by using cheaper raw materials and a more environment-friendly method.

Yangling et al, in Chinese patent application 202010411394.5, disclose a method for preparing viscose-grade bamboo dissolving pulp, which finally prepares a dissolving pulp product through the steps of presteaming, dipping, high-temperature steaming pressure-release blasting, mixing by a double-roller mixer, concentration and dehydration, continuous cooking by a sulfate method, washing, screening, bleaching and the like. In the Chinese patent application 201710947155.X, Libin et al disclose a method for preparing dissolving pulp by using straws or energy plants, and dissolving pulp products are prepared by the steps of raw material pretreatment, pre-impregnation treatment, hydrothermal treatment, mild alkali treatment, bleaching and refining treatment and the like. The above reports have adopted different biomass raw materials to prepare dissolving pulp, and the dissolving pulp product has been successfully prepared. But all the steps have more treatment steps, and the defects of more waste liquid and environmental friendliness are overcome; and the treatment temperature of partial steps is higher, and the energy consumption is larger.

Quyongye water and the like in Chinese patent application 201910071516.8 disclose a method for preparing high-quality crop straw dissolving pulp by hydrothermal pretreatment, and the dissolving pulp is prepared by the steps of raw material screening, alkali extraction, high-boiling alcohol treatment, bleaching, paper making and the like. However, the chlorination process exists in the invention, so that some carcinogens are easily generated, and the method is not environment-friendly.

The invention adopts biomass raw materials, has more complex components and more impurities, and is not beneficial to improving the quality of dissolving pulp products. Therefore, it is necessary to find a high-quality dissolving pulp raw material and explore a low-pollution and environment-friendly preparation process.

Disclosure of Invention

The invention provides a novel process for preparing dissolving pulp from papermaking chemical pulp, which adopts the papermaking chemical pulp with less components as raw materials, can effectively improve the quality of the dissolving pulp and increase the raw material source of the dissolving pulp; meanwhile, the waste liquid and the washing liquid in the preparation process can be recycled, and the method has the advantage of environmental friendliness.

The invention provides a method for preparing dissolving pulp from chemical pulp for papermaking, which comprises the following steps:

step 1), selecting a certain bleaching chemical pulp board for papermaking, tearing the pulp board into small fragments of 2.5cm by 2.5cm, and then defibering for 5min at normal temperature by using a standard defibering machine; collecting the defibered paper pulp by using a 200-mesh net bag, dehydrating, further extruding and dehydrating to 25-30% of mass concentration, dispersing the paper pulp into 0.5cm by 0.5cm, air-drying, transferring into a self-sealing bag, and balancing moisture for 24 hours for later use.

Step 2), weighing a certain amount of the paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent to prepare a paper pulp suspension with the mass concentration of 0.1-10%, and soaking the paper pulp suspension for 0.2-24 hours at room temperature to fully swell the paper pulp suspension; then, heating the prepared pulp suspension to 80-120 ℃ for reaction for 0.5-24 hours, and fully reacting to obtain a mixture containing dissolving pulp;

and 3) carrying out solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, papermaking, forming and drying to finally obtain a dissolving pulp product.

The chemical pulp for papermaking in the step 1) is one or a mixture of more of softwood pulp, hardwood pulp and bamboo pulp.

The chemical pulp for papermaking in the step 1) has the alpha-cellulose content of 60-90 percent and the average polymerization degree of 700-1400.

The eutectic solvent in the step 2) is prepared by taking choline chloride and one or more of oxalic acid dihydrate, glycerol and urea as raw materials.

The molar ratio of the choline chloride to one or more of oxalic acid dihydrate, glycerol and urea in the eutectic solvent in the step 2) is 1:0.5-1: 10.

The drying in the step 3) is vacuum drying, the vacuum degree is 0.08-0.10MPa, the temperature is 50-80 ℃, and the time is 0.5-48 hours.

The waste liquid and the washing liquid obtained in the step 3) can be recycled after water in the waste liquid and the washing liquid is removed by rotary evaporation.

Through eutectic solvent treatment, hemicellulose in the bleached chemical pulp is directionally dissolved and removed, the purity of the chemical pulp is improved, the chemical pulp is upgraded into dissolving pulp, and meanwhile, the polymerization degree of a product is adjusted, so that high-quality dissolving pulp is finally obtained. In addition, the waste liquid of solid-liquid separation and the eutectic solvent in the washing liquid can be recycled by a rotary evaporation mode.

Compared with the prior art, the invention has the following beneficial effects:

the invention adopts the chemical pulp for papermaking with less components as the raw material, can effectively improve the quality of the dissolving pulp and increases the raw material source of the dissolving pulp. Meanwhile, the eutectic solvent is used for treatment, so that hemicellulose in the chemical pulp for papermaking can be directionally dissolved out, the polymerization degree of cellulose can be controlled, and a dissolving pulp product with higher quality can be obtained. In addition, the prepared eutectic solvent can be recycled, the recycling rate and the recycling efficiency are high, and the whole preparation process has the characteristics of low pollution and environmental friendliness, so that the method provided by the invention is a green preparation process of dissolving pulp.

Detailed Description

The invention is further explained in order to make the technical means, the innovative features and the completed efficacy of the invention easy to understand. The technical means for realizing the present invention should not be limited to the following examples, and can be adjusted within the scope of the above-described contents of the invention.

A method of preparing dissolving pulp from chemical pulp for papermaking, the method comprising the steps of:

step 1), selecting a certain bleaching chemical pulp board for papermaking, tearing the pulp board into small fragments of 2.5cm by 2.5cm, and then defibering for 5min at normal temperature by using a standard defibering machine; collecting and dewatering defibered paper pulp by adopting a 200-mesh bag, further extruding and dewatering until the mass concentration of the paper pulp is 25% -30%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, transferring the paper pulp into a self-sealing bag after air drying, and balancing the water for 24 hours for later use.

Step 2), weighing a certain amount of the paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent to prepare a paper pulp suspension with the mass concentration of 0.1-10%, and soaking the paper pulp suspension for 0.2-24 hours at room temperature to fully swell the paper pulp suspension; then, heating the prepared pulp suspension to 80-120 ℃ for reaction for 0.5-24 hours, and fully reacting to obtain a mixture containing dissolving pulp;

and 3) carrying out solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, papermaking, forming and drying to finally obtain a dissolving pulp product. The drying is vacuum drying, the vacuum degree is 0.08-0.10MPa, the temperature is 50-80 ℃, and the time is 0.5-48 hours.

The chemical pulp for papermaking in the step 1) is one or a mixture of more of softwood pulp, hardwood pulp and bamboo pulp. The alpha-cellulose content of the chemical pulp for papermaking is 60-90%, and the average polymerization degree is 700-1400. The chemical pulp for papermaking is used as the raw material, so that the raw material is sufficient.

The eutectic solvent is prepared from choline chloride and one or more of oxalic acid dihydrate, glycerol and urea. Wherein the mol ratio of the choline chloride to one or more of oxalic acid dihydrate, glycerol and urea is 1:0.5-1: 10. By adopting eutectic solvent treatment, hemicellulose in the chemical pulp for papermaking can be directionally dissolved out, the polymerization degree of cellulose is controlled, and the dissolving pulp with higher quality is obtained.

The waste liquid and the washing liquid obtained in the step 3) can be recycled after water in the waste liquid and the washing liquid is removed by rotary evaporation. Avoids the environmental pollution of waste liquid and is beneficial to environmental protection.

The analytical method adopted in the invention is as follows:

measurement of the degree of polymerization of cellulose: refer to the Calycol-capillary viscometer method in GB/T1548-2004 "measurement of pulp viscosity".

Determination of alpha-cellulose of dissolving pulp: refer to GB/T744-2004 paper pulp alpha-cellulose determination method.

Obtaining of dissolving pulpRate: y ═ m₂/m₁*100％

Wherein Y is the dissolving pulp yield;

m₁the quality of dissolving pulp obtained after the eutectic solvent treatment;

m₂is the mass of the chemical pulp raw material.

The rest of the experimental methods which are not described in detail are all the conventional experimental methods in the field.

The present invention is described in further detail below with reference to specific embodiments:

example 1 was carried out:

the method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following specific steps:

step 1), preparing paper pulp:

selecting 10g of bleached softwood pulp board, tearing the paper pulp into small pieces of 2.5cm by 2.5cm, and then defibering for 5min at normal temperature by using a standard defibering machine; collecting the defibered paper pulp by using a 200-mesh net bag, dehydrating, further extruding and dehydrating until the mass concentration of the paper pulp is 30%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, air-drying, and transferring the paper pulp into a self-sealing bag to balance the water for 24 hours for later use.

Step 2) of performing a step of performing a,

eutectic solvent treatment: weighing 10g of paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent prepared from choline chloride and oxalic acid dihydrate in a molar ratio of 1:0.5 to prepare a paper pulp suspension with the mass concentration of 0.1%, and soaking the paper pulp suspension for 24 hours at room temperature to fully swell the paper pulp; thereafter, the prepared pulp suspension was heated to 120 ℃ and reacted for 0.5 hour to sufficiently react, thereby obtaining a mixture containing dissolved pulp.

Step 3) of performing a step of,

and (3) drying: and (3) performing solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, making paper, forming, and drying the paper in a vacuum drying oven with the vacuum degree of 0.08Mpa and the temperature of 80 ℃ for 48 hours to finally obtain a dissolving pulp product.

The dissolving pulp obtained in this example had an α -cellulose content of 97.33%, a water content of 6.89%, an average degree of polymerization of 1003, and a yield of 89.37%.

Example 2 was carried out:

the method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following specific steps:

step 1), preparing paper pulp: selecting 10g of bleached hardwood pulp board, tearing the pulp into small pieces of 2.5cm by 2.5cm, and then defibering for 5min at normal temperature by using a standard defibering machine; collecting the defibered paper pulp by using a 200-mesh net bag, dewatering, further extruding and dewatering until the mass concentration of the paper pulp is 25%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, transferring the paper pulp into a self-sealing bag after air drying, and balancing the water for 24 hours for later use.

Step 2), eutectic solvent treatment: weighing 10g of paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent prepared from choline chloride and urea in a molar ratio of 1:1 to prepare a paper pulp suspension with the mass concentration of 1%, and soaking the paper pulp suspension at room temperature for 12 hours to fully swell the paper pulp; then, the prepared pulp suspension was heated to 110 ℃ and reacted for 2 hours to sufficiently react, thereby obtaining a mixture containing dissolved pulp.

Step 3), drying: and (3) performing solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, making paper, forming, and drying the paper in a vacuum drying oven with the vacuum degree of 0.09Mpa and the temperature of 65 ℃ for 24 hours to finally obtain a dissolving pulp product.

The dissolving pulp obtained in this example had an α -cellulose content of 95.33%, a water content of 4.33%, an average degree of polymerization of 925, and a yield of 92.08%.

Example 3 of implementation:

the method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following specific steps:

step 1), preparing paper pulp: selecting 10g of bleached bamboo pulp board, tearing the paper pulp into small pieces of 2.5cm by 2.5cm, and then defibering for 5min at normal temperature by using a standard defibering machine; collecting the defibered paper pulp by using a 200-mesh net bag, dewatering, further extruding and dewatering until the mass concentration of the paper pulp is 28%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, air-drying, transferring into a self-sealing bag, and balancing the water for 24 hours for later use.

Step 2), eutectic solvent treatment: weighing 10g of paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent prepared from choline chloride and glycerol in a molar ratio of 1:2 to prepare a paper pulp suspension with a mass concentration of 2.5%, and soaking at room temperature for 6 hours to fully swell the paper pulp; then, the prepared pulp suspension was heated to 100 ℃ and reacted for 8 hours to sufficiently react, thereby obtaining a mixture containing dissolved pulp.

Step 3), drying: and (3) performing solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, making paper, forming, and drying the paper in a vacuum drying oven with the vacuum degree of 0.10Mpa and the temperature of 50 ℃ for 12 hours to finally obtain a dissolving pulp product.

The dissolving pulp obtained in this example had an α -cellulose content of 96.13%, a water content of 7.63%, an average polymerization degree of 899, and a yield of 91.73%.

Example 4 of implementation:

the method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following specific steps:

step 1), preparing paper pulp: selecting 5g of bleached softwood pulp board and 5g of bleached hardwood pulp board, tearing paper pulp into small fragments of 2.5cm by 2.5cm, mixing and defibering for 5min at normal temperature by using a standard defibering machine; collecting and dewatering defibered paper pulp by using a 200-mesh bag, further extruding and dewatering until the mass concentration of the paper pulp is 27%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, transferring the paper pulp into a self-sealing bag after air drying, and balancing the water for 24 hours for later use.

Step 2), eutectic solvent treatment: weighing 10g of paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent prepared from choline chloride, oxalic acid dihydrate and glycerol in a molar ratio of 1:2:3 to prepare a paper pulp suspension with the mass concentration of 5%, and soaking the paper pulp suspension for 2 hours at room temperature to fully swell the paper pulp; thereafter, the prepared pulp suspension was heated to 90 ℃ and reacted for 16 hours to sufficiently react, thereby obtaining a mixture containing dissolved pulp.

Step 3), drying: and (3) performing solid-liquid separation on the mixture, washing the mixture with clear water to be neutral, and drying the mixture for 6 hours in a vacuum drying oven with the vacuum degree of 0.09Mpa and the temperature of 65 ℃ after papermaking, thereby finally obtaining a dissolving pulp product.

The dissolving pulp obtained in this example had an α -cellulose content of 91.99%, a water content of 3.28%, an average degree of polymerization of 943, and a yield of 95.88%.

Example 5 was carried out:

the method for preparing dissolving pulp by using chemical pulp for papermaking comprises the following specific steps:

step 1), preparing paper pulp: selecting 5g of bleached bamboo pulp board and 5g of bleached broad-leaved wood pulp board, tearing paper pulp into small pieces of 2.5cm by 2.5cm, mixing and defibering for 5min at normal temperature by using a standard defibering machine; collecting and dewatering defibered paper pulp by adopting a 200-mesh bag, further extruding and dewatering until the mass concentration of the paper pulp is 26%, dispersing the paper pulp into the size of 0.5cm by 0.5cm, air-drying, transferring into a self-sealing bag, and balancing the water for 24 hours for later use.

Step 2), eutectic solvent treatment: weighing 10g of paper pulp prepared in the step 1, dispersing the paper pulp in a eutectic solvent prepared from choline chloride, urea and glycerol in a molar ratio of 1:5:5 to prepare a paper pulp suspension with the mass concentration of 10%, and soaking the paper pulp suspension for 0.2 hour at room temperature to fully swell the paper pulp; then, the prepared pulp suspension was heated to 80 ℃ and reacted for 24 hours to sufficiently react, thereby obtaining a mixture containing dissolved pulp.

Step 3), drying: and (3) performing solid-liquid separation on the mixture, washing the mixture to be neutral by using clear water, making paper, forming, and drying the paper in a vacuum drying oven with the vacuum degree of 0.10Mpa and the temperature of 80 ℃ for 0.5 hour to finally obtain a dissolving pulp product.

The dissolving pulp obtained in this example had an α -cellulose content of 92.83%, a water content of 9.37%, an average degree of polymerization of 1089, and a yield of 94.03%.

In the above embodiments, the waste liquid and the washing liquid after solid-liquid separation can be recycled after removing water by rotary evaporation.

From the above experiments, it can be seen that the alpha-cellulose content of the dissolving pulp obtained by the method for preparing dissolving pulp from chemical pulp of the present invention is more than 91%, the maximum content is close to 97.33%, and the yield is high. Therefore, the preparation method provided by the invention can be used for preparing the dissolving pulp and preparing the high-quality dissolving pulp; meanwhile, the method can be used for large-scale production and has higher cost performance.