Preparation method of high-efficiency strengthening and retention agent containing nanocellulose and application thereof in papermaking

Abstract

The present application relates to the technical field of strengthening retention aid, and discloses a preparation method of high-efficiency strengthening retention aid containing nanocellulose and application thereof in papermaking, which comprises the following steps: step one: nanocellulose raw materials are added into water for pretreatment, then a modification reagent is added for first modification treatment, so that a modified nanocellulose solution is obtained; step two: starch raw materials and a starch degradation reagent are added into the modified nanocellulose solution for second modification treatment, so that a modified nanocellulose starch solution is obtained; step three: a cationic reagent and a catalyst are added into the modified nanocellulose starch solution for third modification treatment, so that a cationic modification solution is obtained; and step four: a neutralizing reagent, a strengthening agent and a bactericide are added into the cationic modification solution, so that the strengthening retention aid is obtained. Through cationization of nanocellulose and starch, the present application effectively improves the reaction efficiency of cations, and obtains a more stable liquid product, so that the application effect is improved.

Description

Technical Field

[0001] This invention relates to the technical field of retention enhancers, and in particular to a method for preparing a highly efficient retention enhancer containing nanocellulose and its application in papermaking. Background Technology

[0002] Retention enhancers are important additives used in papermaking. With the development of the paper industry, from the perspectives of energy saving, reducing pulp consumption, and increasing paper strength, retention enhancers need to have higher retention rates of fine fibers and other additives. Cationic starch is a commonly used raw material for retention enhancers. Cationic starch introduces tertiary amino or quaternary ammonium groups into the starch macromolecule, giving it cationic properties. The positive charge of cationic starch allows it to bind with the negatively charged matrix and can adsorb and retain other negatively charged additives on the matrix. However, starch needs to be cooked before use, and the dry basis dosage of cationic starch is generally 6-10 kg. Therefore, when cationic starch is used as a single raw material for retention enhancers, the dosage is relatively large, the process is relatively complicated, and the cationicity is relatively low, resulting in lower efficiency in strengthening and retaining paper. For example, patent CN 109667193 A discloses a method for preparing a composite paper retention aid. It uses zeolite with a rich porous structure as raw material, which is modified with carboxymethyl cellulose and sodium citrate to obtain modified zeolite powder. Then, corn starch is used as raw material and cationized to obtain a self-made cationic starch. Finally, the prepared modified zeolite powder, the self-made cationic starch, and deionized water are mixed and compounded to obtain the composite paper retention aid. However, its high solids content and poor bonding with fibers are detrimental to improving the paper's reinforcing effect.

[0003] Nanocellulose is a nanomaterial obtained by nano-sizing cellulose fibers. Nanocellulose possesses a high specific surface area and porosity, forming more fiber bonding points in paper, enhancing its strength and durability. It also forms a network structure within paper, increasing its flexibility and elasticity, and improving its toughness and folding resistance. However, nanocellulose faces some challenges in practical applications. For example, its interparticle adhesion is weak, making it difficult to disperse and prone to agglomeration, leading to a decrease in specific surface area and activity, which is detrimental to papermaking applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a highly efficient reinforcing retention aid containing nanocellulose and its application in papermaking. Through the synergistic effect of nanocellulose and cationic starch, the retention aid has a higher cationicity, thereby reducing its addition amount in papermaking while improving the retention rate of fine fibers and the reinforcing effect on paper.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a highly efficient retention enhancer containing nanocellulose, comprising the following steps:

[0007] Step 1: Add nanocellulose raw material to water for pretreatment, then add modifying reagent for the first modification treatment to obtain modified nanocellulose solution;

[0008] Step 2: Add starch raw material and starch degradation reagent to the modified nanofiber solution for a second modification treatment to obtain a starch solution containing modified nanocellulose;

[0009] Step 3: Add cationic reagent and catalyst to the modified nanocellulose starch solution for a third modification treatment to obtain a cationic modified solution;

[0010] Step 4: Add neutralizing agent, enhancer and bactericide to the cationic modified solution to obtain the enhanced retention agent.

[0011] Because nanocellulose has a large specific surface area and abundant surface hydroxyl groups, when added to pulp, it can bind tightly with pulp fibers, thereby improving the bonding force between pulp fibers. Therefore, nanocellulose can be used as a reinforcing agent, retention aid, and filter aid in the pulping and papermaking process, showing great development potential. However, it is not easy to disperse and tends to agglomerate, resulting in high viscosity even at low concentrations. To address this issue, this invention first physically disperses the nanocellulose and then chemically branches it, improving its dispersibility and strength. Then, natural starch is introduced into the modified nanocellulose. Starch imparts strength to the paper and can significantly reduce the amount of retention aid needed while increasing the solid content of the solution, thus enhancing pulp retention and filtration.

[0012] However, modified nanofibers form a network structure, and the amount of starch introduced into it is limited. Excessive starch introduction hinders the formation of a stable liquid retention aid and also impedes the exposure of the branches of the nanocellulose, while simultaneously causing cationization of both nanocellulose and starch, increasing cationicity. Therefore, this invention, to obtain a stable liquid retention aid with more extended molecular chains in the liquid state, better integration with paper fibers, and significantly improved paper strengthening and retention effects, involves starch gelatinization and degradation after introduction and before cationization, effectively increasing the starch solution concentration. Furthermore, due to the liquid state, the hydroxyl groups on both starch and nanocellulose are fully exposed, effectively enhancing the efficiency of the cationic reaction. Moreover, by introducing cationic reagents and cationic starch solution into the modified nanocellulose, the dispersibility and stability of the nanocellulose can be improved, increasing its specific surface area and facilitating the formation of a better network structure in the paper, thus enhancing the product's strengthening and retention effects. Therefore, this highly efficient strengthening and retention aid containing nanocellulose has broad application prospects and can play an important role in the papermaking industry.

[0013] Preferably, in step one, the nanocellulose raw material is one or more of nanocellulose, softwood pulp and hardwood pulp; the mass ratio of the nanocellulose raw material to water is 1:200-400; and the pretreatment time is 30-40 minutes.

[0014] Preferably, in step one, the amount of the modifying agent added is 100-200 ppm of the mass of the nanocellulose raw material; the modifying agent is one or more of enzymes, hydrochloric acid and sodium hypochlorite; the first modification treatment is to raise the temperature to 30-60°C and react for 1-2 hours.

[0015] Preferably, in step two, the amount of starch raw material added is 20-25% of the mass of the modified nanocellulose solution; the starch degradation reagent is 0.01-1% of the mass of the starch raw material; and the second modification treatment is to raise the temperature to 70-90℃ and react for 0.5-1h.

[0016] The ratio of starch to nanocellulose is particularly important. When combined with subsequent modification parameters, it can balance the amount of starch and nanocellulose while ensuring a large amount of starch is introduced, so that the retention aid remains in a stable liquid dispersion state and the degree of cationization can also reach a high level.

[0017] Preferably, in step two, the starch raw material is one or more of corn starch, cassava starch, waxy corn starch, and potato starch; the starch degradation reagent is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, sodium hypochlorite, hydrogen peroxide, and β-enzyme.

[0018] Preferably, in step three, the amount of the cationic reagent added is 10-20% of the mass of the starch raw material; the amount of the catalyst added is 2-6% of the mass of the starch raw material; and the third modification treatment is to raise the temperature to 60-80℃ and react for 5-7 hours.

[0019] The introduction of cationic reagents in the third modification process allows starch and nanocellulose to react simultaneously, resulting in a more stable product and improved application performance. Conducting the cationization reaction at this temperature and time promotes a more complete solution reaction.

[0020] Preferably, in step three, the cationic reagent is one or more of 3-chloro-2-hydroxypropyltrimethylammonium chloride, glycidyltrimethylammonium chloride, and 4-chloro-2-butenyltrimethylammonium chloride; and the catalyst is one or more of potassium hydroxide, calcium hydroxide, sodium hydroxide, and magnesium oxide.

[0021] Preferably, in step four, the amount of the neutralizing agent added is 1-5% of the mass of the starch raw material; the amount of the reinforcing agent added is 0.1-0.5% of the mass of the starch raw material; and the amount of the bactericide added is 0.05-0.15% of the mass of the starch raw material.

[0022] Preferably, in step four, the neutralizing agent is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, and glacial acetic acid; the reinforcing agent is one or more of borax, sodium trimetaphosphate, sodium tripolyphosphate, and sodium hexametaphosphate; and the bactericide is one or more of isothiazolinone, benzisothiazolinone, and bromonitol.

[0023] Secondly, the present invention also provides the application of a highly efficient reinforcing retention aid containing nanocellulose in papermaking.

[0024] Preferably, the application involves diluting the retention enhancer with water by a ratio of 10 to 20 times, stirring to ensure uniform dispersion, and then directly adding it to the paper pulp.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Physical pretreatment of nanocellulose followed by chemical reaction can effectively disperse the fibers and form a stable spatial network structure.

[0027] (2) After modification, starch concentration can be effectively increased, and the increase in concentration can effectively improve the reaction efficiency of cations.

[0028] (3) Because it is in a liquid state, the hydroxyl groups on starch and nanocellulose are completely exposed, which can effectively improve the reaction efficiency of cations.

[0029] (4) The introduction of cationic reagents enables starch and nanocellulose to react synchronously, making the product more stable and thus improving the application effect;

[0030] (5) Liquid products can be used directly without the need for steaming or boiling, and the process is safe and convenient. Detailed Implementation

[0031] The technical solution of the present invention is illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0032] Example 1

[0033] Step 1: Add 95g of nanocellulose and 5g of hardwood pulp to 20kg of water, disperse at high speed in a high-speed mixer for 30min, transfer to a jacketed heated stirred reactor, add 0.01g of cellulase, heat to 45℃, and react for 1h to obtain a modified nanocellulose solution.

[0034] Step 2: Add 3200g tapioca starch, 800g corn starch, 0.4g α-amylase and 3.64g hydrogen peroxide (27.5wt%), heat to 80℃, react for 50min to obtain modified nanocellulose starch solution.

[0035] Step 3: Cool down to 70℃, add a mixture of 881.2g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%) and 1014.3g of sodium hydroxide solution (21wt%), and react at this temperature for 5h.

[0036] Step 4: Cool to 35℃, add 400g hydrochloric acid solution (15wt%), 4g borax, 8g sodium trimetaphosphate, and 4g bromonitrophenol. Stir well to obtain a highly efficient retention aid containing nanocellulose.

[0037] Example 2

[0038] Step 1: Add 90g of nanocellulose, 5g of hardwood pulp and 5g of softwood pulp to 25kg of water, disperse at high speed in a high-speed mixer for 35min, transfer to a jacketed heated stirred reactor, add 0.01g of cellulase and 0.1g of sodium hypochlorite solution (10wt%), heat to 50℃, react for 80min to obtain modified nanocellulose solution.

[0039] Step 2: Add 5625g cassava starch, 625g potato starch, 0.6g α-amylase and 0.6g β-amylase, heat to 90℃, react for 40min to obtain modified nanocellulose starch solution.

[0040] Step 3: Cool down to 80℃, add a mixture of 1159.4g 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%), 450g glycidyltrimethylammonium chloride, 1000g sodium hydroxide solution (21wt%) and 100g calcium hydroxide, and react at this temperature for 6h.

[0041] Step 4: Cool to 40℃, add 575g sulfuric acid solution (20wt%), 31g sodium tripolyphosphate, and 6g isothiazolinone, stir evenly to obtain a highly efficient retention aid containing nanocellulose.

[0042] Example 3

[0043] Step 1: Add 92g of nanocellulose and 8g of softwood pulp to 40kg of water, disperse at high speed in a high-speed mixer for 40min, transfer to a jacketed heated stirred reactor, add 0.02g of cellulase, heat to 60℃, and react for 100min to obtain a modified nanocellulose solution.

[0044] Step 2: Add 8000g of cassava starch and 0.8g of α-amylase, heat to 70℃, and react for 60 minutes to obtain a starch solution containing modified nanocellulose.

[0045] Step 3: Cool down to 60℃, add a mixture of 724.6g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%), 300g of 4-chloro-2-butenyltrimethylammonium chloride and 1345.5g of sodium hydroxide solution (22wt%), and react at this temperature for 7h.

[0046] Step 4: Cool down to 30℃, add 700g hydrochloric acid solution (15wt%), 30g borax and 12g isothiazolinone, stir evenly to obtain a high-efficiency retention aid containing nanocellulose.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that the nanocellulose was not modified.

[0049] Step 1: Add 95g of nanocellulose and 5g of hardwood pulp to 20kg of water, and disperse at high speed in a high-speed mixer for 30min to obtain a nanocellulose solution.

[0050] Step 2: Add 3200g tapioca starch, 800g corn starch, 0.4g α-amylase and 3.64g hydrogen peroxide (27.5wt%), heat to 80℃, react for 50min to obtain starch solution containing nanocellulose.

[0051] Step 3: Cool down to 70℃, add a mixture of 881.2g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%) and 1014.3g of sodium hydroxide solution (21wt%), and react at this temperature for 5h.

[0052] Step 4: Cool to 35℃, add 400g hydrochloric acid solution (15wt%), 4g borax, 8g sodium trimetaphosphate, and 4g bromonitrophenol. Stir well to obtain a highly efficient retention aid containing nanocellulose.

[0053] Comparative Example 2

[0054] The difference from Example 1 is that less starch was added (the amount of starch raw material added was 15% of the mass of the modified nanocellulose solution).

[0055] Step 1: Add 95g of nanocellulose and 5g of hardwood pulp to 20kg of water, disperse at high speed in a high-speed mixer for 30min, transfer to a jacketed heated stirred reactor, add 0.01g of cellulase, heat to 45℃, and react for 1h to obtain a modified nanocellulose solution.

[0056] Step 2: Add 2400g tapioca starch, 600g corn starch, 0.3g α-amylase and 2.73g hydrogen peroxide (27.5wt%), heat to 80℃, react for 50min to obtain modified nanocellulose starch solution.

[0057] Step 3: Cool down to 70℃, add a mixture of 660.9g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%) and 760.7g of sodium hydroxide solution (21wt%), and react at this temperature for 5h.

[0058] Step 4: Cool to 35℃, add 300g hydrochloric acid solution (15wt%), 3g borax, 6g sodium trimetaphosphate, and 4g bromonitrophenol. Stir well to obtain a highly efficient retention aid containing nanocellulose.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that no second modification reaction was carried out.

[0061] Step 1: Add 95g of nanocellulose and 5g of hardwood pulp to 20kg of water, disperse at high speed in a high-speed mixer for 30min, transfer to a jacketed heated stirred reactor, add 0.01g of cellulase, heat to 45℃, and react for 1h to obtain a modified nanocellulose solution.

[0062] Step 2: Add 3200g tapioca starch, 800g corn starch, 0.4g α-amylase and 3.64g hydrogen peroxide (27.5wt%), stir, and obtain a starch solution containing modified nanocellulose.

[0063] Step 3: Heat to 70℃, add a mixture of 881.2g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%) and 1014.3g of sodium hydroxide solution (21wt%), and react at this temperature for 5h.

[0064] Step 4: Cool to 35℃, add 400g hydrochloric acid solution (15wt%), 4g borax, 8g sodium trimetaphosphate, and 4g bromonitrophenol. Stir well to obtain a highly efficient retention aid containing nanocellulose.

[0065] Comparative Example 4

[0066] The difference from Example 1 is that no starch degradation reagent was added.

[0067] Step 1: Add 95g of nanocellulose and 5g of hardwood pulp to 20kg of water, disperse at high speed in a high-speed mixer for 30min, transfer to a jacketed heated stirred reactor, add 0.01g of cellulase, heat to 45℃, and react for 1h to obtain a modified nanocellulose solution.

[0068] Step 2: Add 3200g tapioca starch and 800g corn starch, heat to 80℃, and react for 50 minutes to obtain a starch solution containing modified nanocellulose.

[0069] Step 3: Cool down to 70℃, add 881.2g of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution (69wt%) and 1014.3g of sodium hydroxide solution (21wt%), and react at this temperature for 5h.

[0070] Step 4: Cool to 35℃, add 400g hydrochloric acid solution (15wt%), 4g borax, 8g sodium trimetaphosphate, and 4g bromonitrophenol. Stir well to obtain a highly efficient retention aid containing nanocellulose.

[0071] The retention enhancer used in the examples and comparative examples was diluted 15 times with water and then added to hardwood pulp for papermaking tests.

[0072] Table 1

[0073]

[0074]

[0075] Concentration (%): The concentration refers to the concentration of the retention enhancer prepared by this invention. Too low a concentration indicates low reaction efficiency, poor application effect, and high transportation cost; too high a concentration results in high product viscosity, poor flowability, and is not conducive to application. Generally, it is around 15-22%.

[0076] Viscosity (mPa·s, 25℃): The viscosity is the viscosity of the reinforcing and retention aid prepared in this invention. It needs to be controlled between 800-2000 mPa·s to obtain better reinforcing and retention effects.

[0077] Dosage, Oven Dry (%): Dosage refers to the mass of liquid retention enhancer (calculated as dry matter) added relative to the paper. For example, if 0.3g of oven dry retention enhancer product is needed for 100g of paper, and the product concentration is 16.7%, then 0.3 ÷ 16.7% = 1.796g of product needs to be added.

[0078] Tensile strength (N·m / g): The tensile strength of the paper is tested after adding a retention enhancer to hardwood pulp and conducting papermaking tests.

[0079] Ash content (%): The ash content of the paper is tested after adding the retention enhancer to the hardwood pulp and conducting papermaking tests. Low ash content indicates low filler retention rate.

[0080] As shown in Table 1, in Comparative Example 1, the lack of modification of nanocellulose resulted in poor expansion of the fiber's spatial structure and a reduction in exposed hydroxyl groups. This not only led to a decrease in the efficiency of the cationization reaction but also caused the fibers to re-agglomerate during later storage due to insufficient fiber expansion, thus affecting product application.

[0081] In Comparative Example 2, the reduced starch content led to a decrease in system concentration, viscosity, and cationic reaction efficiency, which in turn affected the tensile strength and ash content of the paper during product application.

[0082] In Comparative Example 3, no modification reaction was carried out in step two. During the heating process in step three, the viscosity of the system increased sharply. The reagent in step two began to react, but after the reagent in step three was added, the reagent in step two became ineffective, resulting in a high final viscosity of the system. The system was viscous and its performance deteriorated. The application data showed a sharp decrease in tensile strength and a decrease in ash content, indicating a low retention rate of paper fillers.

[0083] In Comparative Example 4, no starch degradation reagent was added in step two, resulting in a very high viscosity of the system. After cooling, it became a jelly-like substance and could not be used.

[0084] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing a high-performance retention / drainage aid containing nanocellulose, characterized by, It comprises the following steps: Step one: adding nanocellulose raw material into water for pretreatment, then adding modification reagent for the first modification treatment to obtain modified nanocellulose solution; Step two: adding starch raw material and starch degradation reagent into the modified nanocellulose solution, the starch raw material is added in an amount of 20-25% of the mass of the modified nanocellulose solution, the starch degradation reagent is 0.01-1% of the mass of the starch raw material, the starch degradation reagent is one or several of hydrochloric acid, sulfuric acid, phosphoric acid, sodium hypochlorite, hydrogen peroxide and β biological enzyme, the second modification treatment is carried out, the temperature is raised to 70-90℃, and the reaction is carried out for 0.5-1h to obtain modified nanocellulose starch solution; Step three: adding cationic reagent and catalyst into the modified nanocellulose starch solution, the cationic reagent is added in an amount of 10-20% of the mass of the starch raw material, the third modification treatment is carried out, the temperature is raised to 60-80℃, and the reaction is carried out for 5-7h to obtain cationic modification solution; Step four: adding neutralizing agent, reinforcing agent and bactericide into the cationic modification solution to obtain reinforcing retention agent.

2. The method for preparing the high performance nanocellulose-containing strengthening and retention aid according to claim 1, characterized by, In step one, the nanocellulose raw material is one or several of nanocellulose, coniferous wood pulp and broad-leaved wood pulp; the mass ratio of the nanocellulose raw material to water is 1:200-400; the pretreatment time is 30-40min.

3. The production method of the high-performance nanocellulose-containing strengthening / drainage aid according to claim 1 or 2, characterized by, In step one, the modification reagent is added in an amount of 100-200ppm of the mass of the nanocellulose raw material; the modification reagent is one or several of enzyme, hydrochloric acid and sodium hypochlorite; the first modification treatment is to raise the temperature to 30-60℃ and react for 1-2h.

4. The preparation method of the highly efficient retention enhancer containing nanocellulose as described in claim 1, characterized in that, In step two, the starch raw material is one or several of corn starch, cassava starch, waxy corn starch and potato powder.

5. The preparation method of the highly efficient retention enhancer containing nanocellulose as described in claim 1, characterized in that, In step three, the catalyst is added in an amount of 2-6% of the mass of the starch raw material.

6. The method for producing the high-performance nanocellulose-containing strengthening / drainage aid according to claim 1 or 5, characterized by, In step three, the cationic reagent is one or several of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, epoxy propyl trimethyl ammonium chloride and 4-chloro-2-butene trimethyl ammonium chloride; the catalyst is one or several of potassium hydroxide, calcium hydroxide, sodium hydroxide and magnesium oxide.

7. The preparation method of the highly efficient retention enhancer containing nanocellulose as described in claim 1, characterized in that, In step four, the neutralizing agent is added in an amount of 1-5% of the mass of the starch raw material; the reinforcing agent is added in an amount of 0.1-0.5% of the mass of the starch raw material; the bactericide is added in an amount of 0.05-0.15% of the mass of the starch raw material.

8. The method for producing the high-performance nanocellulose-containing strengthening / drainage aid according to claim 1 or 7, characterized by, In step four, the neutralizing agent is one or several of hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid and glacial acetic acid; the reinforcing agent is one or several of borax, sodium trimetaphosphate, sodium tripolyphosphate and sodium hexametaphosphate; the bactericide is one or several of isothiazolinone, benzisothiazolinone and bromonitromethanol.

9. Application of the reinforcing retention agent prepared by the preparation method of any one of claims 1-8 in papermaking.

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