A polyurea-AKD sizing agent and a preparation method thereof

Abstract

The application provides a polyurea-AKD sizing agent, which is formed by the reaction of diisocyanate, polyether amine and chain extender to form an isocyanate-terminated prepolymer, then reacted with AKD to form an ester bond end-capping, and then water-based chain extender is added to obtain hydrophilic ability, wherein a small part of AKD undergoes esterification reaction, and the remaining majority of AKD remains in the system as a blending component, the introduction of beta-keto ester groups at the molecular terminal can significantly reduce the surface energy of AKD, and the copolymer itself has strong cationicity and emulsifying ability, which can emulsify the remaining AKD. The polyurea-AKD sizing agent disclosed by the application solves the deficiency of the current high molecular polymer emulsifier in enhancing effect when emulsifying AKD, the prepared sizing agent has high stability and retention, has good sizing effect, and has wide application value in the field of papermaking.

Description

Technical Field

[0001] This invention relates to the field of paper sizing agents, and in particular to a polyurea-AKD sizing agent and its preparation method. Background Technology

[0002] The purpose of sizing is to give paper or paperboard the ability to resist the diffusion and penetration of liquids (especially water and aqueous solutions), making it suitable for writing or moisture resistance. There are three methods of sizing: internal sizing, surface sizing, and double sizing. Substances added to paper or paperboard that give it liquid-resistant properties are called sizing agents. Internal sizing began in 1807, and until the 1980s, most paper mills used the basic method of rosin and alum for internal sizing. However, in recent years, the shift towards cellulose reactive systems based on alkyl ketene dimers (AKD) has become increasingly common.

[0003] AKD sizing agents are widely used in the paper industry due to their numerous advantages, including lower dosage, higher binding activity, and more significant sizing effects compared to other sizing agents. However, although the production methods and processes for AKD are relatively mature, the main raw material for papermaking in my country is still straw pulp, which contains a large amount of short fibers and impurities, resulting in low inter-fiber binding activity and less than ideal physical properties of the paper. Therefore, if AKD is only emulsified during neutral sizing, the reinforcing effect is not ideal. Recent research has mainly focused on emulsifying AKD with polymers to achieve a reinforcing effect. In this regard, waterborne polyurethane is an ideal dispersant. Chinese patent CN114687240A discloses a method for preparing a modified polyurethane / AKD sizing agent, demonstrating the possibility of waterborne polyurethane emulsifying AKD. Polyurea has a similar structure to polyurethane but possesses superior hydrolytic stability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a polyurea-AKD sizing agent with good stability and sizing effect, as well as a method for preparing the sizing agent, so as to solve the problem that the current polymer emulsifiers have insufficient reinforcing effect on AKD emulsification.

[0005] This invention is achieved using the following technical solution:

[0006] A method for preparing a polyurea-AKD sizing agent includes the following steps:

[0007] S1, mix isophorone diisocyanate and polyetheramine, purge with nitrogen, heat to 40-45℃ and react for 20-60 min to obtain reaction solution A;

[0008] S2, 2,2-Dimethylolpropionic acid is added to N-methylpyrrolidone, ultrasonically dispersed, and then added to reaction solution A. The temperature is raised to 90-95℃, and the reaction is continued for 1.5-2.5h to obtain the prepolymer;

[0009] S3, heat and melt AKD wax powder, wait for the prepolymer obtained in step S2 to cool down to 65-75℃, add molten AKD wax powder, react for 20-60 minutes to obtain reaction solution B;

[0010] S4, cool reaction solution B to 35-45℃, add ethylenediamine, and continue the reaction for 0.5-1.5h;

[0011] S5, add triethylamine and continue the reaction for 20-60 minutes;

[0012] S6. After the reaction is complete, deionized water is added, the mixture is stirred at high speed, and then the organic solvent is removed by rotary evaporation. After cooling to room temperature, the mixture is sieved to obtain the polyurea-AKD sizing agent.

[0013] Polyetheramines are a class of polymers with a polyether backbone and amine groups as terminal active functional groups, as shown in Formula I below:

[0014]

[0015] The inventors unexpectedly discovered that by reacting diisocyanate, polyetheramine, and a chain extender to form a terminal isocyanate-based prepolymer, followed by reaction with AKD to form ester bonds for end-capping, and then adding an aqueous chain extender to obtain hydrophilicity, only a small portion of the AKD underwent esterification, with the majority remaining as a blend component in the system. Introducing β-keto ester groups at the molecular ends significantly reduced the surface energy of the AKD, and the copolymer itself possessed strong cationic and emulsifying properties, capable of emulsifying the remaining AKD. The resulting polyurea-AKD sizing agent could be sizing under moderately alkaline conditions, exhibited strong cationic properties, and showed unexpectedly improved stability and retention. Based on these findings, the inventors completed this invention.

[0016] The preferred polyetheramines are those with a number average molecular weight of 1000-3000, more preferably those with a number average molecular weight of 1500-2500, and most preferably those with a number average molecular weight of 1800-2200, such as polyetheramine D2000.

[0017] The mass ratio of isophorone diisocyanate to polyetheramine is 3-7:1, preferably 4.5-5.5:1, and most preferably 5:1.

[0018] The AKD wax powder is at least one of tetradecylene ketone dimer and hexadecylene ketone dimer. The mass ratio of AKD wax powder to isophorone diisocyanate is 2-6:1, preferably 2-3:1.

[0019] The mass ratio of isophorone diisocyanate to 2,2-dimethylolpropionic acid is 16-17:1, and the mass ratio of N-methylpyrrolidone to 2,2-dimethylolpropionic acid is 1-1.5:1.

[0020] The mass ratio of isophorone diisocyanate to ethylenediamine is 3-4:1.

[0021] The mass ratio of ethylenediamine to triethylamine is 5-6:1.

[0022] Preferably, the mixing and reaction of each component in steps S1-S5 are carried out under continuous stirring, and the stirring speed is preferably 300-500 r / min. In step S6, the high-speed stirring speed is 10000-15000 r / min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention provides a method for preparing polyurea-AKD sizing agent, which solves the problem of insufficient enhancement effect of current polymer emulsifiers on AKD emulsification, and the resulting sizing agent has high stability and retention.

[0025] 2. The present invention provides a method for preparing a polyurea-AKD sizing agent that requires very little solvent. By emulsifying AKD with water-based polyurea, the resulting sizing agent has good sizing effect and has wide application value in the papermaking industry. Detailed Implementation

[0026] The following description is provided to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples and are not intended to limit the scope of the invention; other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0027] Unless otherwise specified, all instruments or raw materials used in this invention are conventional commercial instruments or raw materials.

[0028] Unless otherwise mentioned, all detection indicators involved in the embodiments of the present invention are detected using conventional detection methods in the art.

[0029] Example 1

[0030] This embodiment discloses a method for preparing a polyurea-AKD sizing agent, which includes the following steps:

[0031] (1) Add 50g of isophorone diisocyanate and 10g of polyetheramine D2000 to a four-necked flask, mix, introduce nitrogen gas, heat to 40-45℃, stir for 30min to obtain the reaction system.

[0032] (2) Add 3.03g of 2,2-dihydroxymethylpropionic acid to 4.5g of N-methylpyrrolidone, disperse it by ultrasonication for 30min, and then add it to the reaction system obtained in step (1). Heat the mixture to 90-95℃ and continue stirring for 2h to obtain the reaction product.

[0033] (3) Heat 125g of AKD wax powder to 75-80℃ to melt it. When the reaction product obtained in step (2) cools down to 70℃, add the melted AKD wax powder and stir the reaction for 30 minutes to obtain the reaction system.

[0034] (4) After the reaction system of step (3) is cooled to 40°C, add 12.5g of ethylenediamine and continue stirring for 1 hour.

[0035] (5) Add 2.5g of triethylamine and continue stirring for 30min.

[0036] (6) After the reaction in step (5) is completed, add a certain amount of deionized water, stir at 10000-15000r / min for 30min, then remove the organic solvent by rotary evaporation, cool to below 25℃ and sieve, and adjust the solid content to 19%-20% to obtain polyurea-AKD sizing agent.

[0037] Example 2

[0038] This embodiment discloses a method for preparing a polyurea-AKD sizing agent, which includes the following steps:

[0039] (1) Add 50g of isophorone diisocyanate and 10g of polyetheramine D2000 to a four-necked flask, mix, introduce nitrogen gas, heat to 40-45℃, stir for 30min to obtain the reaction system.

[0040] (2) Add 3.125g of 2,2-dihydroxymethylpropionic acid to 3.125g of N-methylpyrrolidone, disperse it by ultrasonication for 30min, and then add it to the reaction system obtained in step (1). Heat the mixture to 90-95℃ and continue stirring for 2h to obtain the reaction product.

[0041] (3) Heat 100g of AKD wax powder to 75-80℃ to melt it. When the reaction product obtained in step (2) cools down to 70℃, add the melted AKD wax powder and stir the reaction for 30 minutes to obtain the reaction system.

[0042] (4) After the reaction system of step (3) is cooled to 40°C, add 16.7g of ethylenediamine and continue stirring for 1h.

[0043] (5) Add 2.8g of triethylamine and continue stirring for 30min.

[0044] (6) After the reaction in step (5) is completed, add a certain amount of deionized water, stir at 10000-15000r / min for 30min, then remove the organic solvent by rotary evaporation, cool to below 25℃ and sieve, and adjust the solid content to 19%-20% to obtain polyurea-AKD sizing agent.

[0045] Example 3

[0046] This embodiment discloses a method for preparing a polyurea-AKD sizing agent, which includes the following steps:

[0047] (1) Add 50g of isophorone diisocyanate and 10g of polyetheramine D2000 to a four-necked flask, mix, introduce nitrogen gas, heat to 40-45℃, stir for 30min to obtain the reaction system.

[0048] (2) Add 3.125g of 2,2-dihydroxymethylpropionic acid to 4.5g of N-methylpyrrolidone, disperse it by ultrasonication for 30min, and then add it to the reaction system obtained in step (1). Heat the mixture to 90-95℃ and continue stirring for 2h to obtain the reaction product.

[0049] (3) Heat 150g of AKD wax powder to 75-80℃ to melt it. When the reaction product obtained in step (2) cools down to 70℃, add the melted AKD wax powder and stir the reaction for 30 minutes to obtain the reaction system.

[0050] (4) After the reaction system of step (3) is cooled to 40°C, add 14g of ethylenediamine and continue stirring for 1h.

[0051] (5) Add 2.2g of triethylamine and continue stirring for 30min.

[0052] (6) After the reaction in step (5) is completed, add a certain amount of deionized water, stir at 10000-15000r / min for 30min, then remove the organic solvent by rotary evaporation, cool to below 25℃ and sieve, and adjust the solid content to 19%-20% to obtain polyurea-AKD sizing agent.

[0053] Example 4

[0054] This embodiment discloses a method for preparing a polyurea-AKD sizing agent, which includes the following steps:

[0055] (1) Add 50g of isophorone diisocyanate and 10g of polyetheramine D2000 to a four-necked flask, mix, introduce nitrogen gas, heat to 40-45℃, stir for 30min to obtain the reaction system.

[0056] (2) Add 2.95g of 2,2-dihydroxymethylpropionic acid to 3.7g of N-methylpyrrolidone, disperse it by ultrasonication for 30min, and then add it to the reaction system obtained in step (1). Heat the mixture to 90-95℃ and continue stirring for 2h to obtain the reaction product.

[0057] (3) Heat 100g of AKD wax powder to 75-80℃ to melt it. When the reaction product obtained in step (2) cools down to 70℃, add the melted AKD wax powder and stir the reaction for 30 minutes to obtain the reaction system.

[0058] (4) After the reaction system of step (3) is cooled to 40°C, add 15g of ethylenediamine and continue stirring for 1 hour.

[0059] (5) Add 3g of triethylamine and continue stirring for 30min.

[0060] (6) After the reaction in step (5) is completed, add a certain amount of deionized water, stir at 10000-15000r / min for 30min, then remove the organic solvent by rotary evaporation, cool to below 25℃ and sieve, and adjust the solid content to 19%-20% to obtain polyurea-AKD sizing agent.

[0061] Comparative Example

[0062] This embodiment provides a method for preparing an AKD sizing agent, which includes the following steps:

[0063] (1) Heat 150g of AKD wax powder to 75-80℃ to melt.

[0064] (2) Add 80g of polydiallyldimethylammonium chloride (solid content 20%) to the molten AKD wax powder, stir at 10000-15000r / min for 10min at 75-80℃, add a certain amount of deionized water, then cool to below 25℃ and sieve, adjust the solid content to 19%-20%, and obtain AKD sizing agent.

[0065] The stability of the polyurea-AKD sizing agent of Examples 1-4 and the AKD sizing agent of the comparative example were tested, and the results are shown in Table 1.

[0066] Table 1. Stability test results of different sizing agents

[0067]

[0068] As can be seen from the table, compared with traditional polymer emulsifiers, the AKD sizing agent obtained by emulsification of waterborne polyurea is more stable and can be stored for a long time.

[0069] Application Examples

[0070] The polyurea-AKD sizing agents of Examples 1-4 and the comparative AKD sizing agents were applied under the following conditions:

[0071] Pulp composition: Softwood pulp / Woodwood pulp / Chemical pulp = 20:40:40;

[0072] Freezing degree: 35-40°SR;

[0073] Papermaking basis weight: 80g / m 2 ;

[0074] Sizing agent addition: 10 kg / t paper;

[0075] Dosage of cationic polyacrylamide: 200 ppm.

[0076] Process: Weigh the pulp, then add AKD emulsion and stir for 1 minute. Add mixed calcium (35%) and cationic polyacrylamide sequentially, stirring for 1 minute each. Remove the prepared pulp, form sheets using a semi-automatic paper sheet former, press with a standard paper sheet press, and dry with a varnishing machine for 10 minutes. Then, measure the water absorption value of the paper sample after aging in a 105℃ oven for 10 minutes. The test results are shown in Table 2.

[0077] Table 2. Test results of water absorption properties of paper after sizing with different sizing agents.

[0078]

[0079] Based on the water absorption value of the paper samples, polyurea-AKD sizing agent has a better sizing effect than traditional AKD sizing agent.

[0080] Those skilled in the art should understand that the above embodiments are merely examples and do not limit the invention. The objectives of the invention have been fully and effectively achieved. The functions and principles of the invention have been shown and explained in the embodiments, and any variations or modifications can be made to the implementation of the invention without departing from the stated principles.

Claims

1. A method for preparing a polyurea-AKD sizing agent, characterized in that, Includes the following steps: S1, mix isophorone diisocyanate and polyetheramine, purge with nitrogen, heat to 40-45℃ and react for 20-60 min to obtain reaction solution A; S2, 2,2-Dimethylolpropionic acid is added to N-methylpyrrolidone, ultrasonically dispersed, and then added to reaction solution A. The temperature is raised to 90-95℃, and the reaction is continued for 1.5-2.5h to obtain the prepolymer; S3, heat and melt the AKD wax powder. When the prepolymer obtained in step S2 cools down to 65-75℃, add the molten AKD wax powder and react for 20-60 minutes to obtain reaction solution B. S4, cool reaction solution B to 35-45℃, add ethylenediamine, and continue the reaction for 0.5-1.5h; S5, add triethylamine and continue the reaction for 20-60 minutes; S6. After the reaction is complete, deionized water is added, the mixture is stirred at high speed, and then the organic solvent is removed by rotary evaporation. After cooling to room temperature, the mixture is sieved to obtain the polyurea-AKD sizing agent. The mass ratio of isophorone diisocyanate to polyetheramine is 3-7:1; the mass ratio of AKD wax powder to isophorone diisocyanate is 2-6:

1.

2. The method as described in claim 1, characterized in that, The number average molecular weight of the polyetheramine is 1000-3000.

3. The method as described in claim 2, characterized in that, The number-average molecular weight of the polyetheramine is 1800-2200.

4. The method as described in claim 1, characterized in that, The AKD wax powder is at least one of tetradecylene ketone dimer and hexadecylene ketone dimer.

5. The method as described in claim 1, characterized in that, The mass ratio of isophorone diisocyanate to 2,2-dimethylolpropionic acid is 16-17:1, and the mass ratio of N-methylpyrrolidone to 2,2-dimethylolpropionic acid is 1-1.5:

1.

6. The method as described in claim 1, characterized in that, The mass ratio of isophorone diisocyanate to ethylenediamine is 3-4:1, and the mass ratio of ethylenediamine to triethylamine is 5-6:

1.

7. The method as described in claim 1, characterized in that, In steps S1-S5, the mixing and reaction of each component are carried out under continuous stirring at a speed of 300-500 r / min; in step S6, the speed of the high-speed stirring is 10000-15000 r / min.

8. The polyurea-AKD sizing agent prepared by the method according to any one of claims 1-7.

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