A chemical treatment method for improving the properties of wheat straw pulp fibers

Abstract

The application discloses a chemical treatment method for improving the performance of wheat straw pulp fibers, and comprises the following steps: preparing a mixed solution of citric acid and sodium hypophosphite, wherein the concentration of the citric acid is 2wt%-4wt%, and the concentration of the sodium hypophosphite is 1wt%-2wt%; after partial beating of the wheat straw, the mixed solution of the citric acid and the sodium hypophosphite is added into the wheat straw, and water is added, the volume of the mixed solution added into each gram of absolute dry pulp is 1-4ml, and stirring and reaction are carried out for a set time. The chemical treatment method can form chemical cross-linking between the wheat straw pulp fibers, and it can be found from the results of the examples that the chemical treatment of the CA-SHP solution effectively improves the drainage and papermaking performance of the wheat straw pulp.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wheat straw chemical mechanical pulping, and particularly relates to a chemical treatment method for improving the fiber performance of wheat straw pulp. BACKGROUND

[0002] The statements herein are provided only to enhance understanding of the present application and are not necessarily intended to constitute the prior art.

[0003] In recent years, the wheat straw chemical mechanical pulping has developed rapidly. However, the chemical composition, biological structure and fiber morphology of the wheat straw are quite different from those of the traditional wood. The wheat straw contains a large amount of miscellaneous cells, and the content is higher than that of the needle and broad-leaved wood. A large amount of miscellaneous cell fragments are produced in the process of beating, which causes the poor drainage performance of the pulp and the low paper strength, thereby limiting the wide application of the wheat straw chemical mechanical pulp. Therefore, improving the fiber performance of the wheat straw pulp, improving the drainage performance and paper strength of the pulp, and then improving the production efficiency of the enterprise have become the current problems to be solved. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application aims to provide a chemical treatment method for improving the fiber performance of wheat straw pulp.

[0005] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0006] A chemical treatment method for improving the fiber performance of wheat straw pulp, comprising the following steps:

[0007] A mixed solution of citric acid and sodium hypophosphite is prepared, and in the mixed solution, the concentration of citric acid is 2wt%-4wt%, and the concentration of sodium hypophosphite is 1wt%-2wt%;

[0008] After the wheat straw is partially beaten, the mixed solution of citric acid and sodium hypophosphite is added to the wheat straw, and water is added, and the volume of the mixed solution added to each gram of absolute dry pulp is 1-4ml, and the reaction is stirred for a set time.

[0009] If the amount of the mixed solution of citric acid and sodium hypophosphite added to the wheat straw pulp is too large or too small, the cross-linking effect between the fibers will be affected.

[0010] The citric acid is catalyzed by sodium hypophosphite to form cyclic anhydride by dehydration of two adjacent carboxyl groups. The high-activity cyclic anhydride can react with the alcohol hydroxyl group of cellulose to generate ester and release new carboxyl group. The new carboxyl group reacts with the carboxyl group at the other end of the citric acid to generate cyclic anhydride by the same mechanism, and reacts with the alcohol hydroxyl group of other cellulose, so as to achieve the effect of chemical flocculation of the fiber, increase the gap of the fiber on the filter screen surface, and improve the drainage of the wheat straw pulp. The chemical cross-linking structure is also helpful to improve the physical strength of the paper.

[0011] In some embodiments, the stirring reaction time is 20-40 min.

[0012] Preferably, the stirring reaction time is 25-35 min.

[0013] Further preferably, the stirring reaction is performed by using a magnetic stirrer, and the rotation speed of the magnetic stirrer is 150-300 r / min.

[0014] In some embodiments, the concentration of citric acid in the mixed solution is 3wt%-4wt%, and the concentration of sodium hypophosphite is 1.5wt%-2wt%.

[0015] Preferably, the concentration of citric acid in the mixed solution is 4wt%, and the concentration of sodium hypophosphite is 2wt%.

[0016] In some embodiments, the wheat straw is partially beaten, and the beating degree is 42±2°SR.

[0017] In some embodiments, after water is added to the wheat straw absolute dry pulp, the total water content of the pulp solution is 50-70 g / g.

[0018] Preferably, after water is added to the wheat straw absolute dry pulp, the total water content of the pulp solution is 55-65 g / g.

[0019] Further preferably, after water is added to the wheat straw absolute dry pulp, the total water content of the pulp solution is 60 g / g.

[0020] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0021] The chemical treatment method can form chemical cross-linking between the fibers of the wheat straw pulp. In the results of the embodiments, it can be found that the chemical treatment of the CA-SHP solution effectively improves the drainage and papermaking performance of the wheat straw pulp. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the specification explain the application. The illustrative embodiments of the present application and their description serve the purpose of explanations and do not limit the present application in any manner.

[0023] Figure 1A schematic diagram showing the principle of the chemical treatment method of the embodiments of the present application;

[0024] Figure 2 An infrared spectrogram of the pulp of the comparative examples and the embodiments of the present application;

[0025] Figure 3 A comparison chart of the drainage effect of the pulp of the comparative examples and the embodiments of the present application;

[0026] Figure 4 A comparison chart of the ring crush strength, tear strength and tensile strength of the pulp of the comparative examples and the embodiments of the present application;

[0027] Figure 5 A comparison chart of the wet tensile strength of the pulp of the comparative examples and the embodiments of the present application. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise defined, 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.

[0029] The present application will be further described below in conjunction with the embodiments.

[0030] Example 1

[0031] 4 g of CA and 2 g of SHP were placed in a beaker, 94 g of water was added, and magnetic stirring was performed at a rotation speed of 400 r / min for 5 min. After completion of the stirring, a CA-SHP mixed solution was obtained.

[0032] The pulp concentration was adjusted to 10%, 5 g (calculated as dry weight) of the pulp was placed in a 500 ml beaker, 5 ml of the CA-SHP mixed solution and 300 ml of water were added, and magnetic stirring was performed at a rotation speed of 200 r / min for 30 min. After completion of the stirring, the drainage performance of the pulp was measured, and the drainage weight of the pulp within 30 s was found to be 330 g. 3.14 g (calculated as dry weight) of the pulp was placed in a 500 ml beaker, 3.14 ml of the CA-SHP mixed solution and 188.4 g of water were added, and magnetic stirring was performed at a rotation speed of 200 r / min for 30 min. After completion of the stirring, the pulp was defibered using a fiber defiberer, and then the pulp was sheeted into paper. The ring crush strength, tear strength, tensile strength and wet tensile strength of the pulp were measured.

[0033] Example 2

[0034] 4 g of CA and 2 g of SHP were placed in a beaker, 94 g of water was added, and magnetic stirring was performed at a rotation speed of 400 r / min for 5 min. After completion of the stirring, a CA-SHP mixed solution was obtained.

[0035] The pulp concentration was adjusted to 10%, 5 g (as dry) of pulp was placed in a 500 ml beaker, 10 ml of CA-SHP mixed solution and 300 ml of water were added, and magnetic stirring was performed at a speed of 200 r / min for 30 min. After stirring was completed, the water filtration performance of the pulp was measured, and the weight of the pulp filtered in 30 s was 330 g. 3.14 g (as dry) of pulp was placed in a 500 ml beaker, 6.28 ml of CA-SHP mixed solution and 188.4 g of water were added, and magnetic stirring was performed at a speed of 200 r / min for 30 min. After stirring was completed, the pulp was defibered using a fiber defiberer, and then the pulp was made into paper, and the ring crush, tear, tensile and wet tensile strengths of the pulp were measured.

[0036] Example 3

[0037] 4 g of CA and 2 g of SHP were placed in a beaker, 94 g of water was added, and magnetic stirring was performed at a speed of 400 r / min for 5 min. After stirring was completed, the CA-SHP mixed solution was obtained.

[0038] The pulp concentration was adjusted to 10%, 5 g (as dry) of pulp was placed in a 500 ml beaker, 15 ml of CA-SHP mixed solution and 300 ml of water were added, and magnetic stirring was performed at a speed of 200 r / min for 30 min. After stirring was completed, the water filtration performance of the pulp was measured, and the weight of the pulp filtered in 30 s was 367 g. 3.14 g (as dry) of pulp was placed in a 500 ml beaker, 9.42 ml of CA-SHP mixed solution and 188.4 g of water were added, and magnetic stirring was performed at a speed of 200 r / min for 30 min. After stirring was completed, the pulp was defibered using a fiber defiberer, and then the pulp was made into paper, and the ring crush, tear, tensile and wet tensile strengths of the pulp were measured.

[0039] Example 4

[0040] 4 g of CA and 2 g of SHP were placed in a beaker, 94 g of water was added, and magnetic stirring was performed at a speed of 400 r / min for 5 min. After stirring was completed, the CA-SHP mixed solution was obtained.

[0041] Adjust the pulp concentration to 10%. Take 5g (octane-dry) of pulp and place it in a 500ml beaker. Add 20ml of CA-SHP mixed solution and 300ml of water. Stir magnetically at 200r / min for 30min. After stirring, measure the pulp's water-filtering performance. The weight of water filtered from the pulp within 30s is 355g. Take 3.14g (octane-dry) of pulp and place it in a 500ml beaker. Add 12.56ml of CA-SHP mixed solution and 188.4g of water. Stir magnetically at 200r / min for 30min. After stirring, use a fiber disintegrator to loosen the pulp. Then, form the pulp into paper and measure its ring crush, tear, tensile, and wet tensile strength.

[0042] Comparative Example

[0043] Adjust the pulp concentration to 10%, take 5g (octane-dry) of pulp and place it in a 500ml beaker, add 300ml of water, and magnetically stir at 200r / min for 30min. After stirring, measure the pulp's water-filtering performance, and the weight of water filtered within 30s is 304g. Take 3.14g (octane-dry) of pulp and place it in a 500ml beaker, add 188.4g of water, and magnetically stir at 200r / min for 30min. After stirring, use a fiber disintegrator to loosen the pulp, then form the pulp into paper, and measure the ring crush, tear, tensile, and wet tensile strength of the pulp.

[0044] like Figure 2 As shown, the infrared spectrum of this embodiment of the invention is at 1623 cm⁻¹. -1 The significant decrease in the concentration of carboxylic acid groups is related to the stretching vibrations of the carboxylic acid groups, indicating that a cross-linking reaction has occurred between cellulose and CA.

[0045] This invention uses chemical agents to react with the hydroxyl groups on the surface of cellulose, thereby forming a chemically cross-linked structure in the fibers. This reduces the area of ​​the fibers covering the screen surface, increases the water filtration capacity, and improves the water filtration performance of the pulp. Figure 3 As shown.

[0046] This chemical cross-linking structure can also increase the paper-forming properties of pulp, such as... Figure 4 As shown, especially wet tensile strength, such as Figure 5 As shown.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of improving the properties of wheat straw pulp fibres by chemical treatment characterised in that: The method comprises the following steps: A mixed solution of citric acid and sodium hypophosphite is prepared, wherein the concentration of the citric acid is 3wt%-4wt% and the concentration of the sodium hypophosphite is 1.5wt%-2wt%; After the wheat straw is partially beaten, the mixed solution of the citric acid and the sodium hypophosphite is added into the wheat straw, and water is added, wherein the volume of the mixed solution added into each gram of the absolute dry pulp is 1-4mL, and the stirring reaction is set for a time; The wheat straw part is beaten to a beating degree of 42±2 o SR.

2. The method of claim 1, wherein the chemical treatment for improving the properties of wheat straw pulp fibers is characterized by: The stirring reaction time is 20-40min.

3. The chemical treatment method for improving the properties of wheat straw pulp fiber according to claim 2, characterized in that: The stirring reaction time is 25-35min.

4. The method of claim 1, wherein the chemical treatment for improving the properties of wheat straw pulp fibers is characterized by: The stirring reaction is performed by using a magnetic stirrer, and the rotating speed of the magnetic stirrer is 150-300r / min.

5. The method of claim 1, wherein the chemical treatment for improving the properties of wheat straw pulp fibers is characterized by: The concentration of the citric acid in the mixed solution is 4wt%, and the concentration of the sodium hypophosphite is 2wt%.

6. The method of claim 1, wherein the chemical treatment for improving the properties of wheat straw pulp fibers is characterized by: After the water is added into the absolute dry pulp of the wheat straw, the total water content of the pulp solution is 50-70g / g.

7. A chemical treatment method for improving the properties of wheat straw pulp fibers according to claim 6, characterized by: After the water is added into the absolute dry pulp of the wheat straw, the total water content of the pulp solution is 55-65g / g.

8. A chemical treatment method for improving the properties of wheat straw pulp fibers according to claim 7, characterized by: After the water is added into the absolute dry pulp of the wheat straw, the total water content of the pulp solution is 60g / g.

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