An aqueous polyurethane / polyvinylamine composite surface sizing agent and a method for preparing the same

Abstract

The present application relates to a kind of water-based polyurethane / polyethylene amine composite surface sizing agent and its preparation method, belong to surface sizing agent technical field.The preparation method of the present application includes the following steps, S1, under the atmosphere of protection, with polymeric dihydric alcohol and carboxyl-containing hydrophilic material as raw material, add diisocyanate to 90-110 ℃ and carry out stirring reaction, obtain water-based polyurethane prepolymer;S2, the temperature of the reaction system obtained in S1 is reduced to 35-50 ℃, add acetone, water, neutralizing agent and chain extender and carry out stirring reaction, obtain water-based polyurethane solution;S3, ammonium hydroxide solution is sequentially added to the water-based polyurethane solution obtained in S2, then drop polyethylene amine solution, obtain the water-based polyurethane / polyethylene amine composite surface sizing agent of the present application.The water-based polyurethane / polyethylene amine composite surface sizing agent of the present application significantly improves the mechanical properties of cellulose fiber material, and the maximum tensile and tear index is 9.881 N·m / g and 1.24 mN·m 2 / g respectively.

Description

Technical Field

[0001] This invention belongs to the field of surface sizing agent technology, and particularly relates to a water-based polyurethane / polyvinylamine composite surface sizing agent and its preparation method. Background Technology

[0002] Cellulose fibers can be obtained from tree bark and wood, and contain cellulose ethers or esters. The main components of natural cellulose fibers (lignocellulose) are cellulose, hemicellulose, and lignin. The percentage of each component varies for different types of fibers, and these different percentages alter the fiber's mechanical properties. Wood pulp fibers are abundant cellulose fibers found in nature and are used extensively in the papermaking industry. Hardwood pulp, a commonly used wood pulp in papermaking, has a cellulose content of around 45% and is widely used in printing paper, cigarette paper, tissue paper, and industrial filter paper. Hardwood pulp fibers are short and coarse, resulting in a relatively loose finished product with relatively low strength and high opacity. To meet the performance requirements of different industries, surface sizing is used to improve the physical properties of paper. Surface sizing agents generally use anionic polymers.

[0003] Polyurethane (PU) is a type of synthetic sizing agent. Its active groups, such as urethane groups, on its chain segments can strengthen the hydrogen bonds between fibers, thereby reinforcing cellulose fiber materials. Researchers have prepared a modified polyurethane / alkyl ketene dimer (AKD) sizing agent, which imparts good mechanical and water-resistant properties to paper. With further research, waterborne polyurethane sizing agents with low volatile organic compound (VOC) content and low or no environmental pollution have received more attention. Waterborne polyurethane surface sizing agent emulsions include pure polyurethane emulsions and photocurable polyurethane emulsions. In practical applications, waterborne polyurethane is often formulated with other sizing agents to create composite emulsions to improve various paper properties. Researchers have formulated waterborne polyurethane (WPU) / starch as a composite surface sizing agent for pulp and paper sizing, which improved the mechanical properties of the paper. However, experimental results show that the mechanical strength increases with increasing WPU content; the two components did not exhibit a synergistic effect or achieve the improvement in paper strength through physical interaction. Researchers have attempted to incorporate polyvinyl alcohol (PVA) as a synergistic component into block-type waterborne polyurethane (TBPU), using the synergistic interaction between the two polymer groups within the TBPU / PVA system to prepare composite surface sizing agents, significantly enhancing the mechanical properties of paper. However, the development of two-component waterborne polyurethane composite surface sizing agents, such as waterborne polyurethane / acrylate emulsions and waterborne polyurethane / polyvinyl alcohol emulsions, has focused primarily on nonionic systems, with limited research on ionic systems. In fact, due to the negative charge on the surface of cellulose fibers, polyelectrolytes are often added during production to reduce this negative charge, making the sizing agent more readily adsorbed. However, nonionic systems lack electrostatic interactions with the cellulose fiber surface, resulting in less effective sizing and performance enhancement compared to ionic sizing agents. Therefore, the development of ionic composite surface sizing agents is particularly important. However, the anionic and cationic groups present in ionic composite colloidal systems undergo strong ionic interactions after ionization in water, affecting the stability and uniformity of the sizing agent system and even causing flocculation and precipitation, thus limiting the application of ionic systems.

[0004] In summary, while some preparation methods and product types have emerged in the current development of waterborne polyurethane composite surface sizing agents, it is not difficult to find that many problems still exist, such as low economic efficiency, low practicality, and a limited variety of ionic waterborne polyurethane composite surface sizing agents. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of instability and poor uniformity of the ionic system of composite surface sizing agents in the prior art.

[0006] To address the aforementioned technical problems, this invention provides an ionic, waterborne polyurethane / polyvinylamine (PU / PVAm) composite surface sizing agent with synergistic interactions and excellent overall performance, as well as its preparation method. This preparation method is simple, easy to operate, environmentally friendly, virtually pollution-free, and highly repeatable.

[0007] The first objective of this invention is to provide a method for preparing a waterborne polyurethane / polyvinylamine composite surface sizing agent, comprising the following steps:

[0008] S1. Under a protective atmosphere, using polymeric diols and hydrophilic substances containing carboxyl groups as raw materials, diisocyanate is added and stirred at 90℃-110℃ to obtain waterborne polyurethane prepolymers.

[0009] S2. Reduce the temperature of the reaction system obtained in S1 to 35℃-50℃, add acetone, water, neutralizing agent and chain extender and stir to react, to obtain an aqueous polyurethane solution.

[0010] S3. Add ammonium hydroxide solution to the aqueous polyurethane solution obtained in S2 in sequence, and then add polyethyleneamine solution dropwise to obtain the aqueous polyurethane / polyethyleneamine composite surface sizing agent.

[0011] In one embodiment of the present invention, in S1, the polymeric diol is selected from polycaprolactone diol and / or polypropylene glycol.

[0012] In one embodiment of the present invention, in S1, the carboxyl-containing hydrophilic substance is selected from 2,2-dimethylolpropionic acid (DMPA) and / or dimethylolbutyric acid (DMBA).

[0013] In one embodiment of the present invention, in S1, the diisocyanate is selected from toluene diisocyanate and / or isophorone diisocyanate.

[0014] In one embodiment of the present invention, in S2, the neutralizing agent is selected from triethylamine and / or triethanolamine, and the degree of neutralization of the neutralizing agent is 80%-100%.

[0015] In one embodiment of the present invention, in S2, the chain extender is selected from ethylenediamine and / or diethylenetriamine.

[0016] In one embodiment of the present invention, the molar ratio of polymeric diol, carboxyl-containing hydrophilic substance, diisocyanate, neutralizing agent and chain extender is 25:23-27:75-80:20-25:15-20.

[0017] In one embodiment of the present invention, in S3, the concentration of the aqueous polyurethane solution is 9wt%-11wt%, the concentration of the ammonium hydroxide solution is 25wt%-30wt%, and the concentration of the polyethyleneamine solution is 9wt%-11wt%; the volume ratio of the aqueous polyurethane solution, the ammonium hydroxide solution, and the polyethyleneamine solution is 40-60:19-21:40-60.

[0018] In one embodiment of the present invention, in S3, the dropping rate of the polyethyleneamine solution is 0.8 min / g to 1.2 min / g.

[0019] A second objective of this invention is to provide a waterborne polyurethane / polyvinylamine composite surface sizing agent prepared by the preparation method described above.

[0020] The technical solution of the present invention has the following advantages compared with the prior art:

[0021] (1) The preparation method described in this invention uses ammonium hydroxide (NH4OH), which contains ammonium ions similar to those in cationic polyethyleneamine, to perform Debye screening and protection on the carboxylate ions on the anionic aqueous polyurethane colloid particles, thereby obtaining a stable and uniform aqueous polyurethane / polyethyleneamine composite colloid without increasing the complexity of the colloidal system. To ensure charge shielding of the carboxylate ions, ammonium hydroxide is first added to the aqueous polyurethane. After the colloidal system stabilizes, an aqueous solution of polyethyleneamine is added dropwise. During the drying process, the ammonium hydroxide gradually volatilizes, slowly triggering the ionic interaction between the polyurethane and polyethyleneamine to form a uniformly physically cross-linked composite film. If ammonium hydroxide is added to the aqueous solution of polyethyleneamine, it will not provide charge shielding, and the composite sizing agent system will still exhibit instability and heterogeneity.

[0022] (2) The preparation method described in this invention uses a two-step method to synthesize anionic waterborne polyurethane. The hydrophilic substances in the synthesized waterborne polyurethane are uniformly distributed on the molecular chain, and the polyurethane molecular chain has a good chain extension effect. A stable and uniform ionic composite sizing agent system is prepared, which can be better adsorbed on the surface of cellulose fiber materials. The synergistic effect of the polymer and the electrostatic interaction with cellulose fibers make its reinforcing effect on paper significant. The preparation is simple, environmentally friendly, and almost pollution-free.

[0023] (3) The preparation method described in this invention involves first adding ammonium hydroxide to shield the carboxylate ions on the waterborne polyurethane by charge shielding, and then adding a polyethyleneamine solution dropwise. During subsequent use, the ammonium hydroxide gradually volatilizes. The waterborne polyurethane / polyethyleneamine composite surface sizing agent prepared by this method exhibits stable properties, good film-forming performance, high composite film strength, good toughness, and is not easily damaged. Its elongation at break is 1112.5%, tensile strength at break is 7.39 MPa, and toughness is 52.7 MJ / m. 3 .

[0024] (4) The waterborne polyurethane / polyvinylamine composite surface sizing agent of the present invention significantly improves the mechanical properties of cellulose fiber materials. When the dosage is 1.41g (solid content is 0.141g, accounting for 6% of the total dry weight of the paper), the maximum tensile strength and tear index of the paper are 9.881 N·m / g and 1.24 mN·m, respectively. 2 / g. Attached Figure Description

[0025] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0026] Figure 1 The flowcharts for the waterborne polyurethane / polyvinylamine composite surface sizing agent and its composite film, as well as the paper effect diagram after sizing, are shown below. Among them, a is the flowchart of PVAm, and b is the flowchart of the waterborne polyurethane / polyvinylamine composite surface sizing agent and its composite film, as well as the paper effect diagram after sizing (I is the composite film, and II is the paper after sizing).

[0027] Figure 2 This is a schematic diagram illustrating the preparation of waterborne polyurethane in Example 1 of the present invention;

[0028] Figure 3 The mechanical property test results of the composite membranes prepared in Examples 1-2 and Comparative Examples 7-10 of Test Example 1 of the present invention are shown; wherein, (a) is the stress-strain curve, (b) is the toughness histogram, and (c) is the cyclic tensile stress-strain curve.

[0029] Figure 4 The mechanical property test results are for the composite membranes prepared in Example 2 and Comparative Examples 2-6 of Test Example 1 of this invention; where (a) is the stress-strain curve and (b) is the toughness histogram.

[0030] Figure 5 The image shows the actual product of the surface adhesive for Comparative Example 1.

[0031] Figure 6 The mechanical properties test results of hardwood paper after sizing with the waterborne polyurethane / polyvinylamine composite surface sizing agent in Example 2 of the present invention are shown. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0033] In this invention, unless otherwise stated, the degree of neutralization of triethylamine used in the examples is 88%.

[0034] The tests involved in the following embodiments are as follows:

[0035] Mechanical property testing of composite membranes: A microcomputer-controlled electronic universal testing machine (WDW-1) was used. Sample standard: 20mm long, 6mm wide, dumbbell-shaped, tensile rate 2mm / sec; other operations can be performed by referring to the specific operating procedures of the instrument used.

[0036] Mechanical property testing of sizing hardwood paper: The tensile strength and tear index of the samples were tested using a tensile strength tester (IMT-Tensile 02) and a tear strength tester (SLY-1000); the remaining operations can be performed by referring to the specific operating methods of the instruments used.

[0037] Example 1

[0038] The waterborne polyurethane / polyvinylamine composite surface sizing agent and its preparation method of the present invention specifically include the following steps:

[0039] S1. Add 50g of polypropylene glycol-2000, 3.4g of 2,2-dimethylolpropionic acid and 16mL of isophorone diisocyanate to a 250mL three-necked flask and stir. Heat to 100℃ and purge with nitrogen for 4h to obtain waterborne polyurethane prepolymer.

[0040] S2. Reduce the temperature of the reaction system in S1 to 40℃, add 38mL of acetone, then add 1.2mL of ethylenediamine, 3.06mL of triethylamine and 120mL of deionized water and stir the reaction. The reaction product is subjected to high-speed shearing at 1000rpm for half an hour. After the reaction is completed, remove the acetone to obtain an aqueous polyurethane solution.

[0041] S3. Add 20 parts by mass of 28% ammonium hydroxide solution to 60 parts by mass of the 10wt% aqueous polyurethane solution obtained in S2, and then add 40 parts by mass of 10wt% polyethyleneamine aqueous solution at a dropping rate of 1 min / g. After mixing evenly by magnetic stirring, an aqueous polyurethane / polyethyleneamine composite surface sizing agent is obtained.

[0042] Example 2

[0043] The waterborne polyurethane / polyvinylamine composite surface sizing agent and its preparation method of the present invention specifically include the following steps:

[0044] S1. Add 50g of polypropylene glycol-2000, 3.4g of 2,2-dimethylolpropionic acid and 16mL of isophorone diisocyanate to a 250mL three-necked flask and stir. Heat to 100℃ and purge with nitrogen for 4h to obtain waterborne polyurethane prepolymer.

[0045] S2. Reduce the temperature of the reaction system in S1 to 40℃, add 38mL of acetone, then add 1.2mL of ethylenediamine, 3.06mL of triethylamine and 120mL of deionized water and stir the reaction. The reaction product is subjected to high-speed shearing at 1000rpm for half an hour. After the reaction is completed, remove the acetone to obtain an aqueous polyurethane solution.

[0046] S3. Add 20 parts by mass of 28% ammonium hydroxide solution to 40 parts by mass of the 10wt% aqueous polyurethane solution obtained in S2, and then add 60 parts by mass of 10wt% polyethyleneamine aqueous solution at a dropping rate of 1min / g. After mixing evenly by magnetic stirring, an aqueous polyurethane / polyethyleneamine composite surface sizing agent is obtained.

[0047] Comparative Example 1

[0048] It is basically the same as Example 2, except that it does not contain ammonium hydroxide solution.

[0049] Comparative Example 2

[0050] The method is basically the same as in Example 2, except that the ammonium hydroxide solution is replaced with a sodium hydroxide aqueous solution with a mass concentration of 28%.

[0051] Comparative Example 3

[0052] The method is basically the same as in Example 2, except that 30 parts by mass of an ammonium hydroxide solution with a mass concentration of 28% are added.

[0053] Comparative Example 4

[0054] The method is basically the same as in Example 2, except that 10 parts by mass of an ammonium hydroxide solution with a mass concentration of 28% are added.

[0055] Comparative Example 5

[0056] The process is basically the same as in Example 2, except that the aqueous solution of polyethyleneamine is added dropwise at a rate of 0.5 min / g.

[0057] Comparative Example 6

[0058] The process is basically the same as in Example 2, except that the aqueous solution of polyethyleneamine is added dropwise at a rate of 1.5 min / g.

[0059] Comparative Example 7

[0060] The basic formula is the same as in Example 2, except that no aqueous solution of polyethyleneamine is added.

[0061] Comparative Example 8

[0062] The method is basically the same as in Example 2, except that the aqueous polyurethane solution is 80 parts by mass and the polyethyleneamine aqueous solution is 20 parts by mass.

[0063] Comparative Example 9

[0064] The method is basically the same as in Example 2, except that the aqueous polyurethane solution is 20 parts by mass and the polyethyleneamine aqueous solution is 80 parts by mass.

[0065] Comparative Example 10

[0066] It is basically the same as Example 2, except that no aqueous polyurethane solution is added.

[0067] Test Example 1

[0068] Different composite films were prepared using the sizing agents from Examples 1-2 and Comparative Examples 1-10. The sizing agents were cast into disposable plastic petri dishes and dried at room temperature for 48 hours to prepare the composite films. The mechanical strength, proportions, and mechanical properties of the different composite films were evaluated by mechanical property testing. The relevant performance testing methods are as follows:

[0069] The mechanical properties of the composite membrane were tested using a computer-controlled electronic universal testing machine (WDW-1, Jinan Hengsishengda Instrument Co., Ltd.). The composite membrane was prepared as a dumbbell-shaped sample with a narrow middle section of 20mm × 6mm. The dumbbell-shaped sample was fixed on the universal testing machine, and the tensile speed was set to 2mm / sec. Stress-strain curves were obtained, and the elongation at break and tensile strength were obtained from the curves. The toughness of the composite membrane was then calculated. A continuous cyclic tensile test without waiting time was conducted on a composite membrane with a polyvinylamine aqueous solution of 60 parts by mass at a relatively small strain (250% strain) at a tensile speed of 2mm / sec.

[0070] Test results are as follows Figure 3-5 As shown in Table 1:

[0071] Table 1

[0072] sample Elongation at break (%) Tensile breaking strength (MPa) <![CDATA[Toughness (MJ / m 3 )]]> Example 1 1034.9 6.81 40.8 Example 2 1112.5 7.39 52.7 Comparative Example 1 — — — Comparative Example 2 648.2 4.56 19.16 Comparative Example 3 771.2 4.23 20.87 Comparative Example 4 330.2 3.03 7.24 Comparative Example 5 832.7 3.43 18.97 Comparative Example 6 471.8 3.97 11.66 Comparative Example 7 996.5 5.19 28.4 Comparative Example 8 784.1 7.16 33.2 Comparative Example 9 780.2 3.52 19.4 Comparative Example 10 9.1 26.58 13.3

[0073] As shown in Table 1, the composite film exhibits the best overall mechanical properties when the mass fraction of the aqueous polyurethane solution is 40, the mass fraction of the polyethyleneamine aqueous solution is 60, and the mass fraction of ammonium hydroxide is 20. The elongation at break is 1112.5%, the tensile strength at break is 7.39 MPa, and the toughness is 52.7 MJ / m. 3 ;from Figure 3 It can also be seen that the composite film of Example 2 exhibits a similar load-unload curve to the first cyclic stretching after 30 minutes of cyclic stretching recovery. The results of the mechanical property tests show that the waterborne polyurethane / polyvinylamine composite surface sizing agent of Example 2 has the optimal formulation.

[0074] From the comparative data in Table 1 and Figure 4 and Figure 5It can be seen that in Comparative Example 1, without the addition of ammonium hydroxide, the composite colloidal system produced flocculation and precipitation, failing to form a thin film; in Comparative Example 2, ammonium hydroxide was replaced with sodium hydroxide, Na... + The excess ammonium hydroxide in Comparative Example 3, which could not be removed after film formation, reduced the ionic strength of the polymer system. In Comparative Example 4, the excessive amount of ammonium hydroxide resulted in strong charge shielding during drying, hindering the formation of ion aggregates. In Comparative Example 5, the excessively rapid dropping of polyvinylamine led to uneven mixing. In Comparative Example 6, the excessively slow dropping of polyvinylamine caused the volatilization of ammonium hydroxide during mixing, weakening the charge shielding effect. Comparative Examples 7-10 exhibited inferior mechanical properties compared to Example 2 due to the absence of ion aggregates or insufficient number of aggregates. In conclusion, the composite film exhibited the best mechanical properties when 20 parts by mass of a 28% ammonium hydroxide solution were added and the dropping rate of 10 wt% polyvinylamine was controlled at 1 min / g (Example 2).

[0075] Test Example 2

[0076] Paper was prepared using hardwood pulp with a freeness of 60°SR at a basis weight of 75 g / m². The paper was fixed on a roller coater, and the surface of the paper was sizing using the water-based polyurethane / polyvinylamine composite surface sizing agent from Example 2. The sizing agent dosages were 0% (control example), 2%, 4%, 6%, 8%, and 10% (sizing agent dosage refers to the percentage of sizing agent solid content to the dry weight of the paper). The paper was then surface-sized using polyurethane colloidal emulsion, polyvinylamine aqueous solution, and the surface sizing agents from Comparative Examples 3, 5, 7, and 10 of Test Example 1, with a sizing agent dosage of 6%. The sized paper was then dried in an oven at 60°C for 20 minutes. The mechanical properties of the resulting paper were tested. The mechanical property tests for the examples and comparative examples are as follows:

[0077] The tensile index of paper is tested using a tensile strength tester (IMT-Tensile 02, Dongguan Internes Precision Instruments Co., Ltd.) according to GB / T 12914-2008; the tear index of paper is tested using a tear tester (SLY-1000, Hangzhou Qingtong Boke Automation Technology Co., Ltd.) according to national standard GB / T455-2002.

[0078] The results are shown in Table 2 and Figure 6 As shown:

[0079] Table 2

[0080]

[0081]

[0082] From Table 2 and Figure 6 It can be seen that with the increase of the amount of waterborne polyurethane / polyvinylamine composite surface sizing agent, the tensile index and tear index of the paper first increase and then decrease. Comparison with the control example shows that the mechanical strength is significantly increased compared to the unsized paper, indicating that the use of the surface sizing agent improves the mechanical properties of the paper. In Example 2, when the amount of composite surface sizing agent was 6%, the maximum tensile index and tear index were 9.881 N·m / g and 1.24 mN·m, respectively. 2 / g. When the amount of sizing agent is small, the ionic composite colloid interacts electrostatically with the negatively charged cellulose fiber surface and is uniformly dispersed on the paper surface through the surface sizing process. The composite colloid forms hydrogen bonds with the hydroxyl groups on the fiber surface, strengthening the inter-fiber forces. At the same time, the chain segment entanglement and ionic aggregates within the system also play a role in paper reinforcement to some extent, acting as physical cross-linking points after paper drying. However, when the amount of composite sizing agent exceeds 6%, the aggregation of the composite colloid causes the paper fibers to tend to agglomerate during the drying process, resulting in a decrease in paper uniformity and indirectly reducing the mechanical properties of the paper. Therefore, the optimal amount of composite surface sizing agent is 6%.

[0083] Analysis of the comparative examples in Table 2 revealed that the mechanical properties of sized paper were superior to those of unsized paper (control example). Comparative Examples 7 and 10 used 6% sizing agent, and the results showed that their tensile and tear indices were lower than those of the paper in Example 2 with 6% sizing agent. The waterborne polyurethane / polyvinylamine composite surface sizing agent used in Comparative Examples 3 and 5 was not the optimal embodiment, but its reinforcing effect was better than that of a single type of sizing agent. This indicates that the synergistic effect of anionic waterborne polyurethane and cationic polyethyleneamine, as well as the electrostatic interaction with cellulose fibers, provides a stronger reinforcing effect on the paper than a single type of sizing agent, but it is still significantly weaker than the reinforcing effect of 6% sizing agent in Example 2. In conclusion, the waterborne polyurethane / polyvinylamine composite surface sizing agent provides excellent mechanical properties for surface-sized paper.

[0084] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for the preparation of an aqueous polyurethane / polyvinylamine complex surface size, characterized in that, The method comprises the following steps: S1, under a protective atmosphere, a polymer diol and a carboxyl-containing hydrophilic substance are used as raw materials, and a diisocyanate is added to perform a stirring reaction at 90-110°C to obtain a water-based polyurethane prepolymer; S2, the temperature of the reaction system obtained in S1 is reduced to 35-50°C, and acetone, water, a neutralizing agent and a chain extender are added to perform a stirring reaction to obtain a water-based polyurethane solution; S3, an ammonium hydroxide solution is added to the water-based polyurethane solution obtained in S2, and then a polyvinylamine solution is added dropwise to obtain the water-based polyurethane / polyvinylamine composite surface sizing agent; the concentration of the water-based polyurethane solution is 9-11wt%, the concentration of the ammonium hydroxide solution is 25-30wt%, and the concentration of the polyvinylamine solution is 9-11wt%; the volume ratio of the water-based polyurethane solution, the ammonium hydroxide solution and the polyvinylamine solution is 40-60:19-21:40-60; the dropwise addition speed of the polyvinylamine solution is 0.8-1.2min / g; The molar ratio of the polymer diol, the carboxyl-containing hydrophilic substance, the diisocyanate, the neutralizing agent and the chain extender is 25:23-27:75-80:20-25:15-20.

2. The method of preparing an aqueous polyurethane / polyethyleneamine complex surface size according to claim 1, characterized by, In S1, the polymer diol is selected from polycaprolactone diol and / or polypropylene glycol.

3. The method of making an aqueous polyurethane / polyvinylamine complex surface size according to claim 1, characterized in that, In S1, the carboxyl-containing hydrophilic substance is selected from 2,2-dimethylol propionic acid and / or dimethylol butyric acid.

4. The method of making an aqueous polyurethane / polyethyleneamine complex surface size according to claim 1, characterized in that, In S1, the diisocyanate is selected from toluene diisocyanate and / or isophorone diisocyanate.

5. The method of making an aqueous polyurethane / polyvinylamine complex surface size according to claim 1, characterized in that, In S2, the neutralizing agent is selected from triethylamine and / or triethanolamine, and the neutralizing degree of the neutralizing agent is 80-100%.

6. The method of making an aqueous polyurethane / polyethyleneamine complex surface size according to claim 1, characterized in that, In S2, the chain extender is selected from ethylenediamine and / or diethylenetriamine.

7. The water-based polyurethane / polyvinylamine composite surface sizing agent prepared by the preparation method of any one of claims 1-6.

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