A method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers and its products.

Abstract

This invention provides a method for preparing high-strength straw-based mechanical pulp using chemically cross-linked fibers and the resulting product. The method comprises the following steps: (1) dispersing straw-based mechanical pulp fibers in water to prepare a straw-based mechanical pulp fiber dispersion; (2) adjusting the pH of the straw-based mechanical pulp fiber dispersion with sodium hydroxide solution; (3) adding 2-chloroacetamide to react and prepare an acetamide-modified straw-based mechanical pulp fiber dispersion; and (4) adding ethylene glycol to the acetamide-modified straw-based mechanical pulp fiber dispersion to perform a chemical cross-linking reaction, thereby obtaining high-strength straw-based mechanical pulp. This invention uses 2-chloroacetamide and ethylene glycol to chemically modify straw-based mechanical pulp fibers, constructing strong chemical cross-linking bonds between the straw-based mechanical pulp fibers, thereby improving the mechanical strength of the straw-based mechanical pulp fibers.

Description

[Technical Field]

[0001] This invention relates to the field of pulp research and production, specifically to a method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers and its products. [Background Technology]

[0002] my country is a major paper-producing country. As a fundamental raw material industry for national economic and social development, the paper industry is characterized by sustainable development, wide application, and enormous development potential. Statistics show that due to a shortage of raw materials for papermaking, my country currently relies on imports for over 50%. Therefore, selecting suitable papermaking fiber raw materials is an urgent issue.

[0003] Non-timber resources are widely distributed in my country and have made significant contributions to solving the country's paper supply problem in the past. Their role in the future development of the paper industry will also be indispensable. Straw, a non-timber fiber raw material, is abundant in my country, and its utilization is showing a diversified trend. However, compared with some Western countries, straw utilization is still insufficient, with a considerable portion being discarded as agricultural waste. Therefore, improving the utilization rate of straw fiber and strengthening its comprehensive utilization are crucial for reducing environmental pollution, achieving clean pulping and papermaking, maintaining sustainable agricultural development, and solving my country's paper fiber problem.

[0004] Based on the differences in the pulping process, straw pulp can be divided into mechanical pulp, chemical pulp, and chemimechanical pulp (CMP). Mechanical pulp has a high yield but poor pulp properties; chemical pulp has better properties but low pulp yield and high pollution load; CMP is prepared through mechanical treatment and chemical action, thus combining the advantages of both mechanical and chemical pulps, such as higher yield and better properties. However, due to the short fibers and numerous impurities in straw, current methods for preparing straw CMP make it difficult to match the mechanical properties of wood pulp. Chinese patent CN108221471A discloses a method for polymer-modified paper pulp. This method uses nonylphenol to modify wood pulp, treats caprolactam monomer with epichlorohydrin, uses bisphenol diglycidyl ether as a dispersant, and polymerizes under the action of an initiator. Modified wood pulp is introduced during the polymerization process to obtain an epoxy polymer solution, which has excellent anti-corrosion properties, high tensile index of paper, and superior performance; however, this method has a complex processing process and high production costs. Chinese patent CN102230297B discloses a method for modifying plant pulp fibers. This method is applicable to sulfate softwood pulp, mercerized sulfate hardwood pulp, sulfate-process straw pulp, or caustic soda-process straw pulp. While the modification increases the air permeability of the pulp, it disrupts the crystalline structure of the pulp fibers, significantly weakening the mechanical properties of the pulp. Chinese patent CN104098704B discloses a method for preparing pulp containing multifunctional functional groups. This method adds an oxidation system to the pulp to oxidize and modify the fiber raw materials, obtaining pulp rich in aldehyde and carboxyl functional groups, which is beneficial for increasing paper strength; however, this method involves complex processing and high production costs. Overall, developing a strategy to efficiently improve the mechanical properties of straw-based mechanical pulp, thereby meeting the requirements of various types of paper and improving paper quality, is beneficial for further expanding the application areas of straw-based mechanical pulp. [Summary of the Invention]

[0005] The technical problem to be solved by the present invention is to provide a method and product for preparing high-strength straw-based mechanical pulp using chemically cross-linked fibers. The method uses 2-chloroacetamide and ethylene glycol to chemically modify the straw-based mechanical pulp fibers, thereby constructing strong chemical cross-linking bonds between the straw-based mechanical pulp fibers and improving the mechanical strength of the straw-based mechanical pulp fibers.

[0006] This invention is implemented as follows:

[0007] A method for preparing high-strength straw styromechanical pulp using chemically cross-linked fibers, the method comprising the following steps:

[0008] (1) Disperse straw chemimechanical pulp fibers in water to prepare a straw chemimechanical pulp fiber dispersion;

[0009] (2) Adjust the pH of the straw pulp fiber dispersion with sodium hydroxide solution;

[0010] (3) Add 2-chloroacetamide to react and prepare acetamide-modified straw pulp fiber dispersion;

[0011] (4) Ethylene glycol was added to the acetamide-modified straw mechanical pulp fiber dispersion to carry out a chemical cross-linking reaction, and high-strength straw mechanical pulp was obtained.

[0012] Furthermore, the raw material for the straw-based mechanical pulp fiber in step (1) is one of corn straw, wheat straw, and rice / sorghum straw.

[0013] Furthermore, in step (1), the concentration of straw mechanical pulp fiber in the straw mechanical pulp fiber dispersion is 0.1-1%.

[0014] Furthermore, in step (2), the pH of the straw chemipulative fiber dispersion is adjusted to 9-12.

[0015] Furthermore, in step (3), the mass ratio of 2-chloroacetamide to straw chemimechanical pulp fiber is 1:5 to 1:10.

[0016] Furthermore, in step (3), the reaction time is 2-6 hours and the reaction temperature is 20-60°C.

[0017] Furthermore, when the reaction in step (3) ends, continue to heat to 90°C and maintain for 5-15 minutes.

[0018] Furthermore, in step (4), the mass ratio of ethylene glycol to straw chemimechanical pulp fiber is 1:2 to 1:5.

[0019] Furthermore, in step (4), the cross-linking reaction time is 0.5-2h and the reaction temperature is 20-60℃.

[0020] Furthermore, a high-strength straw-based mechanical pulp is prepared based on the aforementioned method for preparing high-strength straw-based mechanical pulp using chemically cross-linked fibers.

[0021] The present invention has the following advantages:

[0022] This invention utilizes 2-chloroacetamide etherification to modify straw-based mechanical pulp fibers. Acetamide functional groups are introduced into the straw-based mechanical pulp fibers, and these groups react with ethylene glycol to form strong chemical bonds, thus chemically modifying the straw-based mechanical pulp fibers. This constructs strong chemical cross-linking bonds between the straw-based mechanical pulp fibers, thereby improving the mechanical strength of the fibers. The optimal achievable mechanical property is: tear index: 5.04 mN·m. 2 ·g -1 Tensile index: 37.89 N·m·g -1 Bursting strength index: 3.17 kPa·m 2 ·g -1 .

Detailed Implementation Methods

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] Example 1: Modified straw slurry

[0025] Step (1): Disperse straw chemimechanical pulp fibers in water to prepare a 1% straw chemimechanical pulp fiber dispersion;

[0026] Step (2): Adjust the pH of the straw pulp fiber dispersion to 9 using sodium hydroxide solution;

[0027] Step (3): Add 2-chloroacetamide to react with straw-based mechanical pulp fiber at a mass ratio of 1:5. React for 2 hours at a temperature of 20°C. At the end of the reaction, the temperature should be raised to 90°C and held for 5 minutes to prepare acetamide-modified straw-based mechanical pulp.

[0028] Step (4): Ethylene glycol is added to the acetamide-modified straw mechanical pulp fiber dispersion for reaction. The ratio of ethylene glycol to straw mechanical pulp fiber is 1:2, the reaction time is 0.5 h, and the reaction temperature is 20 °C. High-strength straw mechanical pulp (mechanical properties: tear index: 4.6 mN·m) is prepared. 2 ·g -1 Tensile index: 29.45 N·m·g -1 Bursting strength index: 2.46 kPa·m 2 ·g -1 ).

[0029] Example 2: Modified straw slurry

[0030] Step (1): Disperse straw mechanical pulp fibers in water to prepare a straw mechanical pulp fiber dispersion with a concentration of 0.5%;

[0031] Step (2): Adjust the pH of the straw slurry fiber dispersion to 10 using sodium hydroxide solution;

[0032] Step (3): Add 2-chloroacetamide to react with straw-based mechanical pulp fiber at a mass ratio of 1:6. React for 3 hours at a temperature of 30°C. At the end of the reaction, the temperature should be raised to 90°C and held for 8 minutes to prepare acetamide-modified straw-based mechanical pulp.

[0033] Step (4): Ethylene glycol is added to the acetamide-modified straw mechanical pulp fiber dispersion for reaction. The ratio of ethylene glycol to straw mechanical pulp fiber is 1:3, the reaction time is 1 hour, and the reaction temperature is 30℃. High-strength straw mechanical pulp (mechanical properties: tear index: 4.73 mN·m) is prepared. 2 ·g -1 Tensile index: 30.33 N·m·g -1 Bursting strength index: 2.53 kPa·m 2 ·g -1 ).

[0034] Example 3: Modified straw slurry

[0035] Step (1): Disperse straw mechanical pulp fibers in water to prepare a straw mechanical pulp fiber dispersion with a concentration of 0.2%;

[0036] Step (2): Adjust the pH of the straw chemipulative pulp fiber dispersion to 11 using sodium hydroxide solution;

[0037] Step (3): Add 2-chloroacetamide to react with straw-based mechanical pulp fiber at a mass ratio of 1:7. React for 4 hours at a temperature of 40°C. At the end of the reaction, the temperature should be raised to 90°C and held for 10 minutes to prepare acetamide-modified straw-based mechanical pulp.

[0038] Step (4): Ethylene glycol is added to the acetamide-modified straw mechanical pulp fiber dispersion for reaction. The ratio of ethylene glycol to straw mechanical pulp fiber is 1:4, the reaction time is 1.5 h, and the reaction temperature is 40 °C. High-strength straw mechanical pulp (mechanical properties: tear index: 4.88 mN·m) is prepared. 2 ·g -1 Tensile index: 32.66 N·m·g -1 Bursting strength index: 2.68 kPa·m 2 ·g -1 ).

[0039] Example 4: Modified straw slurry

[0040] Step (1): Disperse straw chemimechanical pulp fibers in water to prepare a 1% straw chemimechanical pulp fiber dispersion;

[0041] Step (2): Adjust the pH of the straw slurry fiber dispersion to 10 using sodium hydroxide solution;

[0042] Step (3): Add 2-chloroacetamide to react with straw-based mechanical pulp fiber at a mass ratio of 1:10. React for 5 hours at a temperature of 50°C. At the end of the reaction, the temperature should be raised to 90°C and held for 15 minutes to prepare acetamide-modified straw-based mechanical pulp.

[0043] Step (4): Ethylene glycol is added to the acetamide-modified straw mechanical pulp fiber dispersion for reaction. The ratio of ethylene glycol to straw mechanical pulp fiber is 1:5, the reaction time is 1.5 h, and the reaction temperature is 50 °C. High-strength straw mechanical pulp (mechanical properties: tear index: 5.04 mN·m) is prepared. 2 ·g -1 Tensile index: 37.89 N·m·g -1 Bursting strength index: 3.17 kPa·m 2 ·g -1 ).

[0044] Example 5: Modified straw slurry

[0045] Step (1): Disperse straw mechanical pulp fibers in water to prepare a straw mechanical pulp fiber dispersion with a concentration of 0.1%;

[0046] Step (2): Adjust the pH of the straw chemipulative pulp fiber dispersion to 12 using sodium hydroxide solution;

[0047] Step (3): Add 2-chloroacetamide to react with straw-based mechanical pulp fiber at a mass ratio of 1:10. React for 6 hours at a temperature of 60°C. At the end of the reaction, the temperature should be raised to 90°C and held for 12 minutes to prepare acetamide-modified straw-based mechanical pulp.

[0048] Step (4): Ethylene glycol is added to the acetamide-modified straw mechanical pulp fiber dispersion for reaction. The ratio of ethylene glycol to straw mechanical pulp fiber is 1:5, the reaction time is 3 hours, and the reaction temperature is 60℃. High-strength straw mechanical pulp (mechanical properties: tear index: 4.88 mN·m) is prepared. 2 ·g -1 Tensile index: 33.63 N·m·g -1 Bursting strength index: 2.83 kPa·m 2 ·g -1 ).

[0049] Comparative Example: Preparation of Straw Pulverized Metallurgical Pulverized ...

[0050] Step (1) Take 1000g of absolutely dry straw, add a certain amount of water and NaOH, the solid-liquid ratio is 1:4, and the NaOH concentration is 4%;

[0051] Step (2) Place the straw in a cooking pot and cook at 150°C for 3 hours;

[0052] Step (3) The straw fiber is milled twice using a disc mill with a milling gap of 0.15 mm.

[0053] Step (4) Process straw fibers using a pulping machine with a screen mesh size of 0.5 mm;

[0054] Step (5) Place the straw fibers in a 200-mesh filter, rinse with plenty of water, wring dry, and rub into rice-grain-like pieces for later use to prepare raw straw chemimechanical pulp (mechanical properties: tear index: 3.4 mN·m). 2 ·g -1 Tensile index: 14.72 N·m·g -1 Bursting strength index: 1.02 kPa·m 2 ·g -1 ).

[0055] It is evident that the high-strength straw-based mechanical pulp prepared by this invention has mechanical properties far superior to the original straw-based mechanical pulp in the comparative example.

[0056] In summary, this invention utilizes 2-chloroacetamide etherification to modify straw-based mechanical pulp fibers, introducing acetamide functional groups into the fibers and reacting them with ethylene glycol to form strong chemical bonds, thus chemically modifying the straw-based mechanical pulp fibers. This constructs strong chemical cross-linking bonds between the straw-based mechanical pulp fibers, thereby improving the mechanical strength of the fibers. The optimal achievable mechanical property is: tear index: 5.04 mN·m 2 ·g -1 Tensile index: 37.89 N·m·g -1 Bursting strength index: 3.17 kPa·m 2 ·g -1 .

[0057] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers, characterized in that: The method steps are as follows: (1) Disperse straw chemimechanical pulp fibers in water to prepare a straw chemimechanical pulp fiber dispersion; (2) Adjust the pH of the straw slurry fiber dispersion with sodium hydroxide solution; adjust the pH of the straw slurry fiber dispersion to 9-12; (3) Add 2-chloroacetamide to react and prepare acetamide-modified straw pulp fiber dispersion; the reaction time is 2-6 h and the reaction temperature is 20-60℃; (4) Add ethylene glycol to the acetamide-modified straw mechanical pulp fiber dispersion to carry out a chemical cross-linking reaction to obtain high-strength straw mechanical pulp; the cross-linking reaction time is 0.5-2 h and the reaction temperature is 20-60℃.

2. The method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers according to claim 1, characterized in that: In step (1), the raw material for the straw-based mechanical pulp fiber is one of corn straw, wheat straw, or sorghum straw.

3. The method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers according to claim 1, characterized in that: The concentration of straw mechanical pulp fiber in the straw mechanical pulp fiber dispersion in step (1) is 0.1~1%.

4. The method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers according to claim 1, characterized in that: In step (3), the mass ratio of 2-chloroacetamide to straw chemimechanical pulp fiber is 1:5 to 1:

10.

5. The method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers according to claim 1, characterized in that: When the reaction in step (3) ends, continue to heat to 90℃ and continue for 5-15 min.

6. The method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers according to claim 1, characterized in that: In step (4), the mass ratio of ethylene glycol to straw chemimechanical pulp fiber is 1:2 to 1:

5.

7. A high-strength straw slurry, characterized in that: The high-strength straw chemimechanical pulp is prepared based on the method for preparing high-strength straw chemimechanical pulp using chemically cross-linked fibers as described in any one of claims 1 to 6.