A method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent

Abstract

The application discloses a method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent, and belongs to the technical field of dissolving pulp preparation. The method solves the technical problems of high reaction condition requirement, poor environmental friendliness, high cost and poor synergy in improving the reaction performance of dissolving pulp. The method disclosed by the application uses the acidic eutectic solvent to make the fiber swell through hydrogen bond competition, to strengthen the mass transfer and reaction of the solvent, and the active protons dissociated can depolymerize the cellulose macromolecular chain and destroy the fiber structure. The swelling effect accelerates the depolymerization of the cellulose macromolecular chain and strengthens the morphological damage of the dissolving pulp. Through the comprehensive effect of fiber swelling, morphological damage and cellulose macromolecular chain depolymerization, the reaction effect is realized, the reaction efficiency is improved, and the method has the characteristics of simple operation, green and efficient, low cost, strong synergy and recyclable solvent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dissolving pulp preparation, and particularly relates to a method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent. BACKGROUND

[0002] As a high-quality fiber raw material, dissolving pulp can be used to prepare a series of cellulose products, such as regenerated fibers / films, cellulose esters, cellulose ethers and nanocellulose, among which viscose fibers are the leading products of dissolving pulp. The reaction performance of dissolving pulp refers to the reaction capacity of dissolving pulp with sodium hydroxide (alkalization) and carbon disulfide (yellowing) in the production of viscose fibers, which depends on the activity and accessibility of the hydroxyl groups on the cellulose molecular chain. In the production of viscose fibers, the reaction performance not only affects the production process and environmental problems of viscose fibers, but also determines the production cost and final quality of the products. Therefore, improving the reaction performance of dissolving pulp is of great importance to the upstream pulp industry and the downstream textile industry, and has been widely studied and concerned.

[0003] At present, the methods for improving the reaction performance of dissolving pulp mainly include mechanical method, chemical method and solvent swelling method, etc. The physical method such as ultrasonic or beating alone has high energy consumption, weak swelling effect on fiber structure and weak shearing effect on cellulose chain; although the chemical method such as acid hydrolysis has obvious damage to fiber morphology and shearing effect on cellulose chain, the swelling effect on fiber is very weak, the reaction temperature is usually high (above 90℃), the reaction time is long, and there are problems such as difficult recovery of acid solution and corrosion of equipment; the swelling effect of new organic solvents such as ionic liquids on fibers is obvious, but the shearing effect on cellulose chain and the damage to fiber morphology are limited, and it is difficult to prepare on a large scale due to its complex synthesis and high cost. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent, so as to solve the technical problems of high reaction condition requirement, poor environmental friendliness, high cost and poor synergy in the prior art for improving the reaction performance of dissolving pulp.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] The present application discloses a method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent, comprising the following steps:

[0007] The acidic eutectic solvent is heated in a water bath to obtain pretreated acidic eutectic solvent; the pretreated acidic eutectic solvent is mixed with dissolving pulp slurry, and after reaction, treated pulp slurry is obtained; the treated pulp slurry is sequentially filtered, washed, concentrated and air-dried to obtain dissolving pulp with improved reaction performance;

[0008] The dissolving pulp pulp material is wood dissolving pulp or non-wood dissolving pulp prepared by a pre-hydrolysis kraft process or a cold alkaline extraction process.

[0009] Further, the preheating of the acidic deep eutectic solvent by water bath heating and the reaction temperature are 40-60 DEG C; the reaction time is 20-40 min.

[0010] Further, the solid-liquid mass ratio of the dissolving pulp pulp material to the pretreated acidic deep eutectic solvent is (1:5)-(1:15).

[0011] Further, the filtering and washing mode is vacuum filtration by using a filter screen; the concentration mode is nylon pulp bag extrusion concentration; after concentration, the mass concentration of the dissolving pulp is 20%-25%; after air drying, the mass concentration of the dissolving pulp is 90%-97%; the air drying is carried out under constant temperature and humidity conditions, the constant temperature and humidity temperature is 40±1 DEG C, and the humidity is 50±2% r.h.

[0012] Further, the wood dissolving pulp includes needle leaf wood or broad leaf wood; the non-wood dissolving pulp includes bamboo, wheat straw or bagasse.

[0013] Further, the preparation method of the acidic deep eutectic solvent is: mixing a hydrogen bond acceptor and a hydrogen bond donor, stirring until a transparent and clear liquid is formed, and obtaining the acidic deep eutectic solvent; wherein the hydrogen bond acceptor is choline chloride; the hydrogen bond donor is oxalic acid, formic acid, acetic acid or lactic acid.

[0014] Further, the preparation temperature of the acidic deep eutectic solvent is 50-80 DEG C; when the hydrogen bond donor is oxalic acid, formic acid or acetic acid, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is (1:1)-(1:3); when the hydrogen bond donor is lactic acid, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is (1:5)-(1:10).

[0015] Further, the preparation method of the dissolving pulp pulp material is: soaking dissolving pulp pulp plates in deionized water to obtain a dissolving pulp aqueous solution, dispersing the dissolving pulp aqueous solution by using a defibrator, and concentrating and dispersing to obtain the dissolving pulp pulp material; the mass concentration of the dissolving pulp pulp material is 20%-25%.

[0016] Further, the filtering and washing mode is vacuum filtration by using a polyvinylidene fluoride filter screen.

[0017] Further, after mixing and reacting the pretreated acidic deep eutectic solvent with the dissolving pulp pulp material, filtering is carried out to obtain a filtrate, the filtrate is concentrated and purified by rotary evaporation, and the reacted deep eutectic solvent is recovered for reuse.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The application discloses a method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent.

[0020] Further, compared with the existing method for improving the reaction performance of dissolving pulp, such as the traditional acid liquid treatment, the method of the application can significantly improve the reaction performance of dissolving pulp in a shorter reaction time of 20-40 min and at a lower reaction temperature of 40-60 DEG C, and is more green and efficient.

[0021] Further, the method can recycle the eutectic solvent after the reaction, and the recycled eutectic solvent still has high reaction activity. The method has the characteristics of simple operation, green efficiency, low cost, strong synergy and recyclable solvent. DETAILED DESCRIPTION

[0022] To enable those skilled in the art to understand the characteristics and effects of the application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have the usual meanings understood by those skilled in the art of the application, and in the event of conflict, the definitions in the specification shall prevail.

[0023] Theories or mechanisms described and disclosed herein, whether correct or not, should not be used to limit the scope of the application, that is, the application can be practiced without being limited by any particular theory or mechanism.

[0024] Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Therefore, the description of numerical ranges or percentage ranges should be considered to have covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0025] Herein, unless otherwise specified, "comprising", "including", "containing", "having" or similar words cover the meaning of "consisting of" and "consisting essentially of", for example, "A comprising a" covers the meaning of "A comprising a and other" and "A comprising only a".

[0026] Herein, all possible combinations of various technical features described in the various embodiments or examples are not described. Therefore, each technical feature in the various embodiments or examples can be combined with any of the other technical features in the various embodiments or examples, as long as there is no contradiction, and all possible combinations are to be considered as within the scope of the present specification.

[0027] The application will be further described with reference to the following examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the application. Furthermore, it should be understood that various modifications can be made to the application by those skilled in the art upon reading the teachings of the present application as set forth in the specification. It will be understood that the application is not limited to the details of the examples.

[0028] The following examples use apparatuses and devices that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally conducted under conventional conditions, or under conditions recommended by the manufacturers. The following examples use various raw materials, unless otherwise specified, and use conventional commercially available products, which are conventional specifications in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means weight percent, "parts" means weight parts, and the ratio means weight ratio.

[0029] Example 1

[0030] A method for improving the reaction performance of dissolving pulp using an acidic eutectic solvent, comprising the following steps:

[0031] A pre-hydrolysis kraft pulp board made by the kraft process was torn into pieces and soaked in deionized water. The fibers were fully dispersed by a defibrator, and the pulp was squeezed to a mass concentration of 23% using a 200-mesh nylon pulp bag. The dissolving pulp was dispersed into pulp blocks less than 5 mm x 5 mm and stored in a polyethylene self-sealing bag for water balance. The pulp was used as needed. Choline chloride and lactic acid were stirred and heated at a molar ratio of 1:9 at 60°C until a transparent and clear liquid was formed, and an acidic eutectic solvent was obtained for standby use.

[0032] 15 g of the acidic eutectic solvent was added to the self-sealing bag and preheated to a target temperature of 50°C in a constant temperature water bath. Then 1 g of dissolving pulp was added for reaction, and the reaction time was 20 min. The treated pulp was obtained. The solid-liquid mass ratio of the dissolving pulp to the acidic eutectic solvent was 1:15. During the reaction, the self-sealing bag was kneaded every 5 min to ensure uniform reaction of the pulp.

[0033] The treated pulp is filtered using a 200-mesh polyvinylidene fluoride filter screen, and high-concentration eutectic solvent is recovered and concentrated by rotary evaporation. The filtered and separated pulp is washed with deionized water until it is neutral, and the washed pulp is concentrated to a mass concentration of 22% and dispersed into pulp blocks smaller than 5 mm x 5 mm. The pulp blocks are air-dried at 40°C and 51% r.h. until the mass concentration is 9%, to obtain the reaction performance-enhanced dissolving pulp.

[0034] The washing liquid is concentrated by rotary evaporation and purification, mixed with the filtered and purified high-concentration eutectic solvent, and reused.

[0035] Table 1 shows the performance comparison between the reaction performance-enhanced dissolving pulp obtained in Example 1 and the initial pulp.

[0036] Table 1 shows the performance comparison between the reaction performance-enhanced dissolving pulp obtained in Example 1 and the initial pulp.

[0037]

[0038] Example 2

[0039] A method for enhancing the reaction performance of dissolving pulp using an acidic eutectic solvent, comprising the following steps:

[0040] A hardwood dissolving pulp prepared by pre-hydrolysis kraft process is torn into pieces and soaked in deionized water. The fibers are fully dispersed using a defibrator, and a 200-mesh nylon pulp bag is used to squeeze and concentrate the dissolving pulp to a mass concentration of 22%. The pulp is dispersed into pulp blocks smaller than 5 mm x 5 mm and stored in a polyethylene self-sealing bag for moisture balance. Choline chloride and formic acid are stirred and heated at 50°C at a molar ratio of 1:2 until a transparent and clear liquid is formed, obtaining an acidic eutectic solvent for standby use.

[0041] 10 g of the acidic eutectic solvent is added to a self-sealing bag and preheated to a target temperature of 60°C in a thermostatic water bath. Then, 1 g of dissolving pulp (accurate to 0.01 g, calculated as dry weight) is added for reaction, with a reaction time of 30 min. The solid-liquid mass ratio of the dissolving pulp to the acidic eutectic solvent is 1:15. During the reaction, the self-sealing bag is kneaded every 5 min to ensure uniform reaction of the pulp.

[0042] The treated pulp is filtered using a 200-mesh polyvinylidene fluoride filter screen, and high-concentration eutectic solvent is recovered and concentrated by rotary evaporation. The filtered and separated pulp is washed with deionized water until it is neutral, and the washed pulp is concentrated to a mass concentration of 22% and dispersed into pulp blocks smaller than 5 mm x 5 mm. The pulp blocks are air-dried at 40°C and 51% r.h. until the mass concentration is 9%, to obtain the reaction performance-enhanced dissolving pulp.

[0043] The washing liquid is concentrated and purified by rotary evaporation, mixed with the high-concentration eutectic solvent filtered and purified, and reused.

[0044] Table 2 shows the performance comparison of the improved reaction performance of the dissolving pulp obtained in Example 2 and the initial pulp.

[0045] Table 2 shows the performance comparison of the improved reaction performance of the dissolving pulp obtained in Example 2 and the initial pulp.

[0046]

[0047] Example 3

[0048] A method for improving the reaction performance of dissolving pulp by using an acidic eutectic solvent, comprising the following steps:

[0049] The bamboo pulp prepared by cold alkali extraction is torn into pieces and soaked in deionized water, the fibers are fully dispersed by a defibrator, and the pulp is squeezed to a mass concentration of 21% by a 200-mesh nylon pulp bag, and the pulp is dispersed into pulp blocks smaller than 5mm x 5mm and stored in a polyethylene self-sealing bag for moisture balance; choline chloride and oxalic acid are stirred and heated at a molar ratio of 1:2 at 80°C until a transparent and clear liquid is formed, and an acidic eutectic solvent is obtained for standby;

[0050] 5g of the acidic eutectic solvent is added to the self-sealing bag and preheated to a target temperature of 40°C in a constant temperature water bath, then 1g of the dissolving pulp (accurate to 0.01g, calculated as dry weight) is added, and the reaction is carried out for 40min to obtain the treated pulp; the solid-liquid mass ratio of the dissolving pulp to the acidic eutectic solvent is 1:5, and the self-sealing bag is kneaded every 5min during the reaction to ensure uniform reaction of the pulp;

[0051] The treated pulp is filtered by a 200-mesh polyvinylidene fluoride filter screen, the high-concentration eutectic solvent is recovered, and concentrated and purified by rotary evaporation; the pulp separated by filtration is washed with deionized water until it is neutral, the washed pulp is concentrated to a mass concentration of 25% and dispersed into pulp blocks smaller than 5mm x 5mm, and dried at a constant temperature and humidity of 40°C and 52% r.h. until the mass concentration is 95% to obtain the improved reaction performance of the dissolving pulp.

[0052] The washing liquid is concentrated and purified by rotary evaporation, mixed with the high-concentration eutectic solvent filtered and purified, and reused.

[0053] Table 3 shows the performance comparison of the improved reaction performance of the dissolving pulp obtained in Example 3 and the initial pulp.

[0054] Table 3 shows the performance comparison of the improved reaction performance of the dissolving pulp obtained in Example 3 and the initial pulp.

[0055]

[0056] Example 4

[0057] A method for improving the reaction performance of dissolving pulp by using acidic deep eutectic solvent, comprising the following steps:

[0058] The wheat straw dissolving pulp prepared by cold alkaline extraction method was torn into pieces and soaked in deionized water, and the fibers were fully dispersed by a defibrator. The pulp was squeezed and concentrated to a mass concentration of 22% by using a 200-mesh nylon pulp bag, and the pulp was dispersed into pulp blocks smaller than 5 mm x 5 mm and stored in a polyethylene self-sealing bag for moisture balance for standby. Choline chloride and formic acid were stirred and heated at a molar ratio of 1:2 at 50°C until a transparent and clear liquid was formed, and an acidic deep eutectic solvent was obtained for standby;

[0059] 10 g of acidic deep eutectic solvent was added to the self-sealing bag and preheated to the target temperature of 60°C in a constant temperature water bath, and then 1 g of dissolving pulp (accurate to 0.01 g, calculated as dry weight) was added for reaction, and the reaction time was 20 min, and the treated pulp was obtained. The solid-liquid mass ratio of the dissolving pulp to the acidic deep eutectic solvent was 1:10, and the self-sealing bag was kneaded every 5 min during the reaction to ensure uniform reaction of the pulp;

[0060] The treated pulp was filtered by using a 200-mesh polyvinylidene fluoride filter screen, and the high-concentration deep eutectic solvent was recovered and concentrated by rotary evaporation. The filtered and separated pulp was washed with deionized water until it was neutral, and the washed pulp was concentrated to a mass concentration of 23% and dispersed into pulp blocks smaller than 5 mm x 5 mm. The pulp was air-dried at a constant temperature and humidity of 40°C and 50% r.h. to a mass concentration of 97%, and a dissolving pulp with improved reaction performance was obtained.

[0061] The washing liquid was concentrated by rotary evaporation, mixed with the high-concentration deep eutectic solvent filtered and purified, and reused.

[0062] Table 4 shows the performance comparison of the dissolving pulp with improved reaction performance obtained in Example 4 and the initial pulp.

[0063] Table 4 Performance comparison of Example 4 and initial pulp

[0064]

[0065] Example 5

[0066] A method for improving the reaction performance of dissolving pulp by using acidic deep eutectic solvent, comprising the following steps:

[0067] The broadleaf wood dissolving pulp prepared by cold alkali extraction method is torn into pieces, soaked in deionized water, and fully dispersed by a defibrator. The pulp is squeezed by a 200-mesh nylon pulp bag to concentrate the pulp to a mass concentration of 21%, and the pulp is dispersed into pulp blocks smaller than 5 mm x 5 mm and stored in a polyethylene self-sealing bag for balancing moisture for standby. Choline chloride and acetic acid are stirred and heated at a molar ratio of 1:3 at 70°C until a transparent and clear liquid is formed to obtain an acidic eutectic solvent for standby;

[0068] 10 g of the acidic eutectic solvent is added to the self-sealing bag and preheated to a target temperature of 40°C in a thermostatic water bath, and then 1 g of the dissolving pulp is added (accurate to 0.01 g, calculated as absolute dryness). The reaction is carried out for 40 min to obtain the treated pulp. The solid-liquid mass ratio of the dissolving pulp to the acidic eutectic solvent is 1:10, and the self-sealing bag is kneaded every 5 min during the reaction to ensure uniform reaction of the pulp;

[0069] The treated pulp is filtered by a 200-mesh polyvinylidene fluoride filter screen, and the high-concentration eutectic solvent is recovered and concentrated by rotary evaporation. The filtered and separated pulp is washed with deionized water until it is neutral, and the washed pulp is concentrated to a mass concentration of 25% and dispersed into pulp blocks smaller than 5 mm x 5 mm. The pulp is air-dried at a constant temperature and humidity of 40°C and 52% r.h. until the mass concentration reaches 93% to obtain the dissolving pulp with improved reaction performance.

[0070] The washing liquid is concentrated by rotary evaporation, mixed with the filtered and purified high-concentration eutectic solvent, and reused.

[0071] Table 5 shows the performance comparison of the dissolving pulp with improved reaction performance obtained in Example 5 and the initial pulp.

[0072] Table 5 shows the performance comparison of the dissolving pulp with improved reaction performance obtained in Example 5 and the initial pulp.

[0073]

[0074] Specifically, in other specific embodiments of the present application, bamboo, wheat straw, and other non-wood raw materials such as cotton, hemp, reed, and grass can be used to prepare dissolving pulp, and the reaction performance of the dissolving pulp can also be improved.

[0075] As can be seen from Tables 1 to 5, the present application can significantly improve the reaction performance of the dissolving pulp within a short reaction time of 20-40 min and at a low reaction temperature of 40-60°C through the combined effects of swelling, viscosity reduction, and morphology destruction. Moreover, the used eutectic solvent can be recycled multiple times, which is green, efficient, and low in energy consumption.

[0076] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A method for improving the reaction performance of a dissolving slurry using an acidic eutectic solvent, characterized in that, Includes the following steps: A pretreated acidic eutectic solvent is obtained by heating the acidic eutectic solvent in a water bath. The pretreated acidic eutectic solvent is mixed with the dissolving slurry and reacted to obtain the treated slurry. The treated slurry is then filtered, washed, concentrated, and air-dried to obtain the dissolving slurry with improved reaction performance. The preparation method of the dissolving pulp is as follows: the dissolving pulp board is soaked in deionized water to obtain a dissolving pulp aqueous solution, the dissolving pulp aqueous solution is dispersed using a dispersing machine, and the dissolving pulp is concentrated and dispersed to obtain the dissolving pulp material; the mass concentration of the dissolving pulp material is 20%~25%; the dissolving pulp board is a wood dissolving pulp or a non-wood dissolving pulp obtained by pre-hydrolyzing sulfate method or cold alkali extraction method. The acidic eutectic solvent is heated in a water bath at a temperature of 40-60°C; the reaction time is 20-40 minutes. The solid-liquid mass ratio of the dissolving slurry to the pretreated acidic eutectic solvent is (1:5) to (1:15). The method for preparing the acidic eutectic solvent is as follows: a hydrogen bond acceptor and a hydrogen bond donor are mixed and stirred until a transparent and clear liquid is formed to obtain the acidic eutectic solvent; wherein the hydrogen bond acceptor is choline chloride; and the hydrogen bond donor is oxalic acid, formic acid, acetic acid, or lactic acid. The preparation temperature of the acidic eutectic solvent is 50-80℃; when the hydrogen bond donor is oxalic acid, formic acid or acetic acid, the molar ratio of hydrogen bond acceptor to hydrogen bond donor is (1:1)-(1:3); when the hydrogen bond donor is lactic acid, the molar ratio of hydrogen bond acceptor to hydrogen bond donor is (1:5)-(1:10). The filtration and washing method uses a filter screen for suction filtration; the concentration method uses a nylon pulp bag for compression concentration; after concentration, the mass concentration of the dissolved pulp is 20%-25%; after air drying, the mass concentration of the dissolved pulp is 90%-97%; the air drying is carried out under constant temperature and humidity conditions, with a temperature of 40±1℃ and a humidity of 50±2%rh.

2. The method for improving the reaction performance of a dissolving slurry using an acidic eutectic solvent according to claim 1, characterized in that, The wood dissolving slurry includes coniferous or broadleaf wood; the non-wood dissolving slurry includes bamboo, wheat straw, or bagasse.

3. The method for improving the reaction performance of a dissolving slurry using an acidic eutectic solvent according to claim 1, characterized in that, The filtration and washing method involves vacuum filtration using a polyvinylidene fluoride filter.

4. The method for improving the reaction performance of a dissolving slurry using an acidic eutectic solvent according to claim 1, characterized in that, After the pretreated acidic eutectic solvent is mixed and reacted with the dissolving slurry, the mixture is filtered to obtain the filtrate. The filtrate is then concentrated and purified by rotary evaporation, and the eutectic solvent obtained after the reaction is recovered for reuse.

Images