A papermaking reinforcing agent, its preparation method and use

Abstract

This invention discloses a papermaking strengthening agent, its preparation method, and its application. The papermaking strengthening agent comprises a nanocellulose suspension and a cationic starch gelatinized liquid, mixed at an oven-dry mass ratio of 1:0.5 to 1:5. The ring crush strength of the paper is increased by 24.3%, and by 18.8% compared to CNF alone; the tensile strength is increased by 14.8% compared to the blank, and by 6.2% compared to CNF alone, demonstrating a significant synergistic effect. This invention is particularly suitable for corrugated base paper, linerboard, and other packaging papers made from waste paper pulp, effectively improving ring crush strength and reducing chemical costs, thus possessing industrial application value.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, specifically to a papermaking reinforcing agent, its preparation method, and its application. Background Technology

[0002] As the proportion of waste paper recycling continues to increase, the fibers in waste paper pulp undergo irreversible keratinization, resulting in shorter fibers, more fine particles, and a significant decrease in inter-fiber bonding strength. Consequently, the physical properties of the paper produced are far lower than those of virgin pulp, such as ring crush strength and tensile strength. To compensate for this strength loss, the paper industry commonly uses dry strength agents such as cationic starch and polyacrylamide. However, using a single dry strength agent presents problems such as low strengthening efficiency, large dosage requirements, deterioration of pulp filtration, and high cost.

[0003] Cellulose nanofibers (especially cellulose nanofibers, CNFs) have high aspect ratios, high specific surface areas, and abundant surface hydroxyl groups. They can form "nano-bridging" networks between fibers through hydrogen bonding and physical entanglement, significantly improving paper strength. However, using CNFs alone has drawbacks such as low retention, high filtration resistance, and high cost, which limit their industrial application. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a paper strengthening agent with characteristics such as low cost and high efficiency.

[0005] Some implementation schemes for solving the above-mentioned technical problems include: A paper strengthening agent includes a nanocellulose suspension and a cationic starch gelatinized liquid, wherein the oven-dry mass ratio of the nanocellulose suspension and the cationic starch gelatinized liquid is 1:0.5 to 1:5.

[0006] In this invention, nanocellulose and cationic starch are compounded in a specific ratio to produce synergistic enhancement of ring compression strength and tensile strength, which is a low-cost and high-efficiency compound reinforcing agent.

[0007] Preferably, the oven-dry mass ratio of the nanocellulose suspension to the cationic starch gelatinized liquid is 1:1 to 1:3.

[0008] Preferably, the nanocellulose in the nanocellulose suspension is cellulose nanofiber (CNF), which is prepared by mechanical method, enzymatic method or enzymatic addition-machine method.

[0009] Preferably, the nanocellulose has a diameter of 2~20 nm, a length of 0.5~20 μm, an aspect ratio of ≥500, a surface carboxyl content of 0.1~2.0 mmol / g, a zeta potential of -60 ~ -20 mV, and a suspension solid content of 0.5%~3%.

[0010] Preferably, the cationic starch gelatinization solution is a quaternary ammonium cationic starch with a degree of substitution of 0.0032 to 0.1, and the gelatinized solution is prepared with a mass concentration of 1% to 10%.

[0011] The present invention also provides a method for preparing the paper strengthening agent as described above, comprising: (1) Disperse the nanocellulose suspension evenly by ultrasonication or high-speed dispersion, and set aside for later use; (2) Add water to cationic starch and stir, heat to 90~95℃ to gelatinize for 30 minutes, cool to room temperature, and prepare cationic starch gelatinized solution of the required concentration; (3) Under stirring conditions, the nanocellulose suspension is slowly added to the cationic starch gelatinized liquid and stirred for 10 to 30 minutes to obtain the papermaking reinforcing agent.

[0012] The present invention also provides an application of the papermaking strengthening agent as described above in waste paper pulp papermaking, characterized in that the papermaking strengthening agent is added to the waste paper pulp, stirred, and then papermaking is carried out.

[0013] Preferably, the total amount of the papermaking reinforcing agent added is 0.2% to 1.5% of the oven-dry pulp mass. After adding the papermaking reinforcing agent, a retention aid and filter aid are added. The retention aid and filter aid are one or more of cationic polyacrylamide, bentonite, and silica sol.

[0014] As a preferred option, the following steps are included: (1) Disintegrate and beat waste paper pulp or virgin pulp to the required degree of freeness; (2) Dilute the pulp to a papermaking concentration of 0.3% to 1.0%, and add the papermaking strengthening agent while stirring. The amount added is 0.4% to 0.8% of the oven-dry pulp mass. (3) After stirring for 30 to 60 seconds, add a retention and filtration aid, wherein the retention and filtration aid is 0.01% to 0.03% cationic polyacrylamide and 0.1% to 0.3% bentonite; (4) The paper is formed, pressed, and dried to obtain high-strength paper.

[0015] Preferably, the waste paper pulp is OCC, AOCC, ONP, or a mixture of office waste paper pulp.

[0016] Compared with the prior art, the present invention has the following advantages: (1) Significant synergistic effect: For example, when the total amount added is the same, the ring compression strength of the compound group is 24.3% higher than that of the blank group and 18.8% higher than that of nanocellulose alone. The tensile strength is 14.8% higher than that of the blank group and 6.2% higher than that of nanocellulose alone, resulting in a synergistic effect of "1+1>2".

[0017] (2) Reduce total chemical cost: After compounding, the amount of nanocellulose can be reduced to 1 kg / t, the amount of cationic starch can be reduced to 3 kg / t, and the total addition amount of 4 kg / t can achieve the effect of better than using high doses of starch or nanocellulose alone, reducing the overall cost by more than 30%.

[0018] (3) Improve retention and filtration: Cationic starch, as a cationic polymer, can effectively adsorb negatively charged nanocellulose and improve its retention rate; at the same time, the filtration aid effect of starch partially offsets the negative impact of nanocellulose on filtration, which is beneficial to the operation of paper machine.

[0019] (4) Particularly suitable for waste paper pulp: Waste paper pulp has short fibers and many fine components, and has high requirements for ring crush strength. The compound reinforcing agent of this invention can significantly improve the ring crush strength and meet the performance requirements of packaging paper such as corrugated base paper and linerboard. Detailed Implementation

[0020] The specific embodiments shown below are intended to describe various configurations of the subject matter of the invention and are not intended to represent the only configuration in which the subject matter of the invention can be practiced. The specific embodiments include particular details intended to provide a thorough understanding of the subject matter of the invention. However, it will be clear and apparent to those skilled in the art that the subject matter of the invention is not limited to the specific details shown herein and can be practiced without these specific details. Example

[0021] raw material: Waste paper pulp: OCC pulp from a paper company, freeness 35°SR, concentration 3.0%. Nanocellulose (CNF): prepared by enzymatic addition and mechanical method, diameter 5~15 nm, length 3~10 μm, major axis approximately 800, carboxyl content 0.8 mmol / g, Zeta potential -42 mV, solid content 2.0%. Cationic starch: degree of substitution 0.035, gelatinization concentration 7% (i.e., 70 g starch added to 1000 mL of water, gelatinized at 95°C for 30 min). Additives: CPAM (0.1% solution), filter aid (0.5% suspension).

[0022] Preparation of compound reinforcing agents: Take 50 g of CNF suspension (2% solid content) (containing 1 g of oven-dry CNF) and 42.86 g of cationic starch gelatinized liquid (7% solid content) (containing 3 g of oven-dry starch), mix and stir for 15 min to obtain a compound reinforcing agent with a total oven-dry content of 4 g and a solid content of about 4.5%.

[0023] Copying: Take 36 g of oven-dry pulp (corresponding to the production of 5 sheets of 120 g / m² hand-made sheets), dilute to a concentration of 0.5%, add all the above-mentioned compound reinforcing agents (corresponding to the amount added per ton of paper: CNF 1 kg / t, starch 3 kg / t), and stir for 30 s; then add 0.02% CPAM (for oven-dry pulp), and stir for 15 s; add 0.2% bentonite, and stir for 10 s; immediately form on a sheet-making machine, press, dry at 105℃, and equilibrate at constant temperature and humidity (23℃, 50% RH) for 24 h.

[0024] Performance test results (see Table 1): Table 1 index blank CNF 1kg / t Compound group (CNF1 + starch3) Tensile strength (N) 53.0 57.3 60.9 Ring crush strength (kN / m) 1.293 1.353 1.607 Bursting index (kPa·m² / g) 1.153 1.226 1.230 .

[0025] Table 1 shows that the ring crush strength of the compound group increased by 24.3% compared to the control group and by 18.8% compared to CNF alone; the tensile strength increased by 14.8% compared to the control group and by 6.2% compared to CNF alone; and the bursting index was comparable to that of CNF alone. This demonstrates that the compound has a significant synergistic reinforcing effect.

[0026] Example 2 The method is basically the same as in Example 1, except that the mass ratio of CNF to cationic starch is changed to 1:2 (i.e., 1 kg / t CNF and 2 kg / t starch). The total amount added is 3 kg / t.

[0027] Results: Ring crush strength 1.48 kN / m, tensile strength 58.2 N, bursting index 1.21.

[0028] Comparative Example 1 Cationic starch was used alone at an addition rate of 3 kg / t, without CNF. Results: Ring crush strength 1.31 kN / m, tensile strength 54.5 N, bursting index 1.16.

[0029] Comparative Example 2 CNF was used alone at an addition rate of 1 kg / t, without the addition of starch. Results: ring crush strength 1.353 kN / m, tensile strength 57.3 N, bursting index 1.226.

[0030] Example 3 The method is basically the same as in Example 2, except that the mass ratio of CNF to cationic starch is changed to 1:2 (i.e., 1 kg / t CNF and 3 kg / t starch). The total amount added is 4 kg / t.

[0031] Performance tests were conducted by comparing the control group with the control group, and the results are shown in Tables 2 to 5.

[0032] Table 2

[0033] Table 3

[0034] Table 4

[0035] Table 5

[0036] When implementing the subject matter of this invention, those skilled in the art can obtain other detailed configurations based on the subject matter of this invention. Obviously, these details are still within the scope of the subject matter of this invention without departing from it.

Claims

1. A paper strengthening agent, characterized in that, It includes a nanocellulose suspension and a cationic starch gelatinized liquid, wherein the oven-dry mass ratio of the nanocellulose suspension and the cationic starch gelatinized liquid is 1:0.5 to 1:

5.

2. The paper strengthening agent according to claim 1, characterized in that, The oven-dry mass ratio of the nanocellulose suspension and the cationic starch gelatinized liquid is 1:1 to 1:

3.

3. The paper strengthening agent according to claim 1, characterized in that, The nanocellulose in the nanocellulose suspension is cellulose nanofiber (CNF), which is prepared by mechanical method, enzymatic method or enzymatic addition machine method.

4. The paper strengthening agent according to claim 3, characterized in that, The nanocellulose has a diameter of 2~20 nm, a length of 0.5~20 μm, an aspect ratio of ≥500, a surface carboxyl content of 0.1~2.0 mmol / g, a zeta potential of -60 ~ -20 mV, and a suspension solid content of 0.5%~3%.

5. The paper strengthening agent according to any one of claims 1 to 4, characterized in that, The cationic starch gelatinized solution is a quaternary ammonium cationic starch with a degree of substitution of 0.0032 to 0.1, and is prepared as a solution with a mass concentration of 1% to 10% after gelatinization.

6. A method for preparing a papermaking reinforcing agent as described in any one of claims 1 to 5, characterized in that, include: (1) Disperse the nanocellulose suspension evenly by ultrasonication or high-speed dispersion, and set aside for later use; (2) Add water to cationic starch and stir, heat to 90~95℃ to gelatinize for 30 minutes, cool to room temperature, and prepare cationic starch gelatinized solution of the required concentration; (3) Under stirring conditions, the nanocellulose suspension is slowly added to the cationic starch gelatinized liquid and stirred for 10 to 30 minutes to obtain the papermaking reinforcing agent.

7. The application of a papermaking strengthening agent as described in any one of claims 1 to 5 in waste paper pulp making, characterized in that, The paper strengthening agent is added to waste paper pulp, stirred, and then formed into paper.

8. The application according to claim 7, characterized in that, The total amount of the papermaking reinforcing agent added is 0.2% to 1.5% of the oven-dry pulp mass. After adding the papermaking reinforcing agent, a retention aid and filter aid are added. The retention aid and filter aid are one or more of cationic polyacrylamide, bentonite, and silica sol.

9. The application according to claim 8, characterized in that, Includes the following steps: (1) Disintegrate and beat waste paper pulp or virgin pulp to the required degree of freeness; (2) Dilute the pulp to a papermaking concentration of 0.3% to 1.0%, and add the papermaking strengthening agent while stirring. The amount added is 0.4% to 0.8% of the oven-dry pulp mass. (3) After stirring for 30 to 60 seconds, add a retention and filtration aid, wherein the retention and filtration aid is 0.01% to 0.03% cationic polyacrylamide and 0.1% to 0.3% bentonite; (4) The paper is formed, pressed, and dried to obtain high-strength paper.

10. The application as described in claim 9, characterized in that, The waste pulp is OCC, AOCC, ONP, or a mixture of office waste pulp.

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