Modified waterborne polyurethane-based binder, water-based ink and preparation methods of modified waterborne polyurethane-based binder and water-based ink

Abstract

The invention discloses a modified waterborne polyurethane-based binder, water-based ink and a preparation method thereof, and belongs to the technical field of water-based ink. The preparation method comprises the following steps: modifying a waterborne polyurethane emulsion by using carboxylated chitosan, carrying out condensation reaction on carboxyl groups in the carboxylated chitosan and isocyanate groups in the waterborne polyurethane emulsion, and connecting the carboxylated chitosan and the waterborne polyurethane emulsion by forming amine ester bonds to form a polymer cross-linked structure, so as to obtain the water-based polyurethane emulsion. The viscosity, the adhesive force and the stability of the modified waterborne polyurethane-based binder are obviously improved; when the modified waterborne polyurethane-based binder is used for preparing the water-based ink, the viscosity, the adhesive force and the stability of the water-based ink are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of water-based inks, and in particular relates to a modified water-based polyurethane-based connecting material, a water-based ink and a preparation method thereof. Background Art

[0002] Traditional solvent-based inks use volatile organic solvents, which can harm people's health during the application process. Therefore, traditional solvent-based inks are gradually being replaced by environmentally friendly water-based inks. The biggest difference between water-based inks and solvent-based inks is that the solvent used is water instead of organic solvents, which reduces organic solvent emissions and prevents air pollution while not affecting human health. Because water-based inks have stable performance and bright colors, they have become a world-recognized environmentally friendly printing material.

[0003] The binder is the most important component in the ink formula, which directly affects the ink's viscosity, adhesion, glossiness, drying time and other properties. With the increasing application of water-based screen printing inks in the printing industry, more and more experts and scholars at home and abroad have conducted research and development on the relevant properties of water-based screen printing inks and the characteristics and characterization of each component of water-based screen printing inks, especially binders and colorants.

[0004] Waterborne polyurethane (WPU) is widely used as an environmentally friendly water-based ink binder. However, existing waterborne polyurethane-based binders have problems such as low viscosity, low adhesion and poor stability. Therefore, it is necessary to provide a modified waterborne polyurethane-based binder to solve the shortcomings of the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a modified waterborne polyurethane-based binder, water-based ink and a preparation method thereof, so as to solve the problems of low viscosity, low adhesion and poor stability of existing waterborne polyurethane-based binders.

[0006] In a first aspect, the present invention provides a modified waterborne polyurethane-based binder, wherein the modified waterborne polyurethane-based binder has a structure as shown in the following formula (I): ; Wherein, n is a positive integer ≥1.

[0007] In the present invention, the inventors have found that the use of carboxylated chitosan to modify the aqueous polyurethane emulsion can significantly improve the viscosity, adhesion and stability of the modified aqueous polyurethane-based binder.

[0008] In a second aspect, the present invention provides a method for preparing the modified waterborne polyurethane-based binder as described above, comprising the following steps: mixing carboxylated chitosan and waterborne polyurethane emulsion, and obtaining a modified waterborne polyurethane-based binder after stirring; wherein the mass ratio of carboxylated chitosan to waterborne polyurethane emulsion is (0.1-0.5): (6-11).

[0009] In the present invention, carboxylated chitosan and aqueous polyurethane emulsion are mixed to carry out a reaction as shown in the following formula (1):

[0010] Among them, the carboxyl group in the carboxylated chitosan and the isocyanate group in the water-based polyurethane emulsion undergo condensation reaction, and the carboxylated chitosan and the water-based polyurethane emulsion are connected by forming an amine ester bond to form a polymer cross-linking structure, which significantly improves the viscosity, adhesion and stability of the modified water-based polyurethane-based binder.

[0011] In the method for preparing the modified aqueous polyurethane-based binder provided by the present invention, the mass ratio of carboxylated chitosan to aqueous polyurethane emulsion can be, for example, 0.1:6, 0.1:8, 0.1:11, 0.2:6, 0.2:8, 0.2:10, 0.5:6, 0.5:8, 0.5:11 or other ratios within this range.

[0012] In some embodiments, the mass ratio of carboxylated chitosan to aqueous polyurethane emulsion is 0.2:10.

[0013] In some embodiments, the stirring treatment time is 10-30 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min or other values ​​within the range.

[0014] In the present invention, the stirring treatment can be carried out by conventional methods in the art, such as manual stirring, automatic stirring or magnetic stirring. The stirring time can be conventionally adjusted according to actual use needs. Magnetic stirring is preferred in the present invention, and the stirring treatment time is preferably 10-30 minutes.

[0015] In a third aspect, the present invention provides an aqueous ink comprising the modified aqueous polyurethane-based binder described above or a modified aqueous polyurethane-based binder prepared by any of the above preparation methods.

[0016] In the present invention, the inventors further discovered that the viscosity, adhesion and stability of water-based ink can be significantly improved by adding a modified water-based polyurethane-based binder.

[0017] In some embodiments, the aqueous ink further includes a colorant and a solvent, and the mass ratio of the colorant, the solvent, and the aqueous polyurethane emulsion in the modified aqueous polyurethane-based binder is (0.02-0.1):(0.05-0.25):(6-11), for example, it can be 0.02:0.05:6, 0.02:0.15:8, 0.02:0.25:11, 0.06:0.05:6, 0.06:0.15:8, 0.06:0.25:11, 0.1:0.05:6, 0.1:0.15:8, 0.1:0.25:11 or other ratios within this range.

[0018] In some embodiments, the colorant includes a bright yellow pigment.

[0019] In the present invention, the colorant can be conventionally adjusted according to actual use needs. The colorant in the present invention preferably includes a light yellow pigment.

[0020] In some embodiments, the solvent includes water.

[0021] In the present invention, water is used as the solvent, which is more environmentally friendly.

[0022] In some embodiments, the aqueous ink further includes a defoamer, and the mass ratio of the defoamer to the aqueous polyurethane emulsion in the modified aqueous polyurethane-based binder is (0.05-0.25):(6-11), for example, it can be 0.05:6, 0.05:8, 0.05:11, 0.15:6, 0.15:8, 0.15:10, 0.25:6, 0.25:8, 0.25:11 or other ratios within this range.

[0023] In the present invention, the bubbles in the water-based ink can be eliminated by adding the defoaming agent, thereby improving the performance of the water-based ink.

[0024] In some embodiments, the antifoaming agent includes anhydrous ethanol.

[0025] In the present invention, the defoaming agent can be conventionally adjusted according to actual use needs. The defoaming agent in the present invention preferably includes anhydrous ethanol.

[0026] In a fourth aspect, the present invention provides a method for preparing a water-based ink as described above, comprising the following steps: uniformly mixing a modified water-based polyurethane-based binder, a colorant and a solvent, and adding a defoaming agent to obtain a water-based ink.

[0027] The preparation method of the water-based ink provided by the invention is simple and convenient for large-scale industrial production.

[0028] The beneficial effects of the present invention are as follows: different from the prior art, the present invention uses carboxylated chitosan to modify the aqueous polyurethane emulsion, wherein the carboxyl group in the carboxylated chitosan and the isocyanate group in the aqueous polyurethane emulsion undergo a condensation reaction, and the carboxylated chitosan and the aqueous polyurethane emulsion are connected by forming an amine ester bond to form a polymer cross-linking structure, thereby significantly improving the viscosity, adhesion and stability of the modified aqueous polyurethane-based binder; when the modified aqueous polyurethane-based binder is used to prepare aqueous ink, the viscosity, adhesion and stability of the aqueous ink are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The physical picture of the modified waterborne polyurethane-based connecting material prepared in Examples 1-10 of the present invention and Comparative Example 1; Figure 2 This is a Fourier infrared spectrum of the modified waterborne polyurethane-based connecting material prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The experimental methods without specific conditions in the examples are usually carried out according to conventional conditions and conditions described in the manual, or according to conditions recommended by the manufacturer. The general equipment, materials, reagents, etc. used are all available from commercial channels unless otherwise specified.

[0032] In the present invention, Examples 1-10 are methods for preparing modified waterborne polyurethane-based binders, which are specifically as follows: Example 1 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: mixing 0.1 g of carboxylated chitosan and 10 g of waterborne polyurethane emulsion, and subjecting the mixture to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #1.

[0033] Example 2 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.2 g of carboxylated chitosan and 10 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #2.

[0034] Example 3 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.3 g of carboxylated chitosan and 10 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #3.

[0035] Example 4 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.4 g of carboxylated chitosan and 10 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #4.

[0036] Example 5 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.5 g of carboxylated chitosan and 10 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #5.

[0037] Example 6 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: mixing 0.2 g of carboxylated chitosan and 6 g of waterborne polyurethane emulsion, and subjecting the mixture to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #6.

[0038] Example 7 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.2 g of carboxylated chitosan and 7 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #7.

[0039] Example 8 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: mixing 0.2 g of carboxylated chitosan and 8 g of waterborne polyurethane emulsion, and subjecting the mixture to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #8.

[0040] Example 9 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: mixing 0.2 g of carboxylated chitosan and 9 g of waterborne polyurethane emulsion, and subjecting the mixture to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #9.

[0041] Example 10 A method for preparing a modified waterborne polyurethane-based connecting material comprises the following steps: 0.2 g of carboxylated chitosan and 11 g of waterborne polyurethane emulsion are mixed, and the mixture is subjected to magnetic stirring for 20 minutes to obtain a modified waterborne polyurethane-based connecting material numbered #10.

[0042] In the present invention, Examples 11-28 are methods for preparing water-based inks, which are specifically as follows: Embodiment 11 A method for preparing a water-based ink comprises the following steps: mixing 0.1 g of carboxylated chitosan and 10 g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02 g of tender yellow pigment and 0.1 g of water and mixing them evenly, and adding 0.1 g of a defoaming agent to obtain the water-based ink.

[0043] Example 12 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0044] Example 13 A method for preparing a water-based ink comprises the following steps: mixing 0.3 g of carboxylated chitosan and 10 g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02 g of tender yellow pigment and 0.1 g of water and mixing them evenly, and adding 0.1 g of a defoaming agent to obtain the water-based ink.

[0045] Embodiment 14 A method for preparing a water-based ink comprises the following steps: mixing 0.4g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0046] Embodiment 15 A method for preparing a water-based ink comprises the following steps: mixing 0.5 g of carboxylated chitosan and 10 g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02 g of tender yellow pigment and 0.1 g of water and mixing them evenly, and adding 0.1 g of a defoaming agent to obtain the water-based ink.

[0047] Example 16 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 6g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0048] Embodiment 17 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 7g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0049] Embodiment 18 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 8g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0050] Embodiment 19 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 9g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0051] Embodiment 20 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 11g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0052] Embodiment 21 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.05g of water and mixing them evenly, and adding 0.05g of a defoaming agent to obtain the water-based ink.

[0053] Embodiment 22 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.15g of water and mixing them evenly, and adding 0.15g of a defoaming agent to obtain the water-based ink.

[0054] Embodiment 23 A method for preparing a water-based ink comprises the following steps: mixing 0.2 g of carboxylated chitosan and 10 g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02 g of tender yellow pigment and 0.2 g of water and mixing them evenly, and adding 0.2 g of a defoaming agent to obtain the water-based ink.

[0055] Embodiment 24 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.02g of tender yellow pigment and 0.25g of water and mixing them evenly, and adding 0.25g of a defoaming agent to obtain the water-based ink.

[0056] Embodiment 25 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.04g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0057] Embodiment 26 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.06g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0058] Embodiment 27 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.08g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0059] Embodiment 28 A method for preparing a water-based ink comprises the following steps: mixing 0.2g of carboxylated chitosan and 10g of water-based polyurethane emulsion, subjecting the mixture to magnetic stirring for 20 minutes, adding 0.1g of tender yellow pigment and 0.1g of water and mixing them evenly, and adding 0.1g of a defoaming agent to obtain the water-based ink.

[0060] Comparative Example 1 The preparation method of the modified waterborne polyurethane-based binder in this comparative example is basically the same as that in Example 2, except that no carboxylated chitosan is added to obtain a modified waterborne polyurethane-based binder numbered #11.

[0061] Comparative Example 2 The preparation method of the water-based ink in this comparative example is basically the same as that in Example 12, except that no carboxylated chitosan is added.

[0062] Performance Testing The modified waterborne polyurethane-based binders prepared in Examples 1-10 and Comparative Example 1 were observed. Figure 1 shown.

[0063] from Figure 1 It can be seen that when carboxylated chitosan is added to the aqueous polyurethane emulsion, a milky white modified aqueous polyurethane-based connecting material is obtained.

[0064] Exemplarily, the modified waterborne polyurethane-based binder prepared in Example 2 was subjected to Fourier transform infrared spectroscopy test. Specifically, the test temperature was 25°C, and infrared spectroscopy tests were performed on three samples (modified binder, waterborne polyurethane, and carboxylated chitosan) respectively. The test mode selected the total reflection mode, and the scanning wave number range was 500~4000cm -1 , the number of scans is 32, and the resolution is 2cm -1 , the results are as follows Figure 2 shown.

[0065] from Figure 2 It can be seen that the wave number of the infrared spectrum of carboxylated chitosan is 3340 cm -1 The broad absorption peaks at 1637cm are the stretching vibration peaks of hydroxyl NH and OH. The introduction of carboxylated chitosan makes the characteristic absorption peak of carbonyl C=O in waterborne polyurethane disappear, while the peak at 1637cm -1 The absorption peak near 3353cm -1 The stretching vibration peak of NH is at 2930cm -1 and 2858cm -1 The peaks are CH stretching vibration peaks of methylene and methyl, 1737 cm -1 The peak is attributed to the characteristic peak of C=O vibration, 1538cm -1 、1478cm -1 The peak may be attributed to the characteristic peak of the C=C skeleton in the benzene ring, 1258cm -1 is the CN stretching vibration absorption peak, 1112cm -1 It is the absorption peak of COC, 785cm -1 The peak at 2270 cm -1 There is no obvious absorption peak at the position, indicating that the isocyanate group has been completely reacted, indicating that the modified waterborne polyurethane-based connecting material has been successfully synthesized.

[0066] The viscosity of the water-based ink prepared in Examples 11-28 and Comparative Example 2 was tested. Specifically, the viscosity of the ink was tested using an SNB-AI digital rotary viscometer. During the test, the force required for the thin layer of ink to be separated by the instrument is the viscosity of the ink, and the specific value is displayed on the digital instrument panel of the instrument. First, a 4# rotor was selected according to the reference viscosity value of the ink, and the rotor was installed on the instrument. After the instrument was turned on and preheated, the speed was set to 100 cp.s; the groove part of the rotor was completely immersed in the prepared ink horizontal line and directly below the shaft to start the test. After the test was completed, the value was recorded according to the prompt of the electronic dial. The results are shown in Table 1 below.

[0067] Table 1 Viscosity test results of water-based ink

[0068] As can be seen from Table 1, compared with Comparative Example 2 in which no carboxylated chitosan was used for modification, the viscosity of the prepared aqueous ink was significantly improved after the aqueous polyurethane emulsion was modified with carboxylated chitosan in Examples 11-28, and as the mass of the carboxylated chitosan increased, the viscosity of the aqueous ink also increased.

[0069] The adhesion of the water-based ink prepared in Examples 11-28 and Comparative Example 2 was tested. Specifically, the adhesion of the prepared water-based ink was tested using the hundred-character grid test method. First, 10g of the above water-based ink sample was placed in a beaker for standby use, 150g of white cardboard was cut into 19 rectangular samples of 20mm×20mm, and the sample number was marked with label paper. Secondly, the above water-based ink sample was printed on the white cardboard through a screen printing workbench. After drying at 40°C, a blade was used to scrape horizontally and vertically to divide the rectangle into 100 squares of equal size. A tape was used to apply a fixed pressure at a length of about 20mm on the surface of the printed product, and then the tape was vertically and evenly peeled off the surface of the printed product. Finally, whether the ink fell off on the hundred-character grid and whether there was ink residue on the tape was observed, and the corresponding grade was given with reference to the standard evaluation table, so as to judge the qualified situation of the ink adhesion and record the relevant data. The judging criteria are that if there is no obvious ink peeling on the printed sheet surface and the tape, the ink adhesion is considered qualified. The specific judging criteria will refer to the ASTM quality reference standards shown in Table 2 below. The results are shown in Table 3 below.

[0070] Table 2 Water-based ink adhesion test standards

[0071] Table 3 Test results of water-based ink adhesion

[0072] As can be seen from Table 3, compared with Comparative Example 2, in which no carboxylated chitosan modification is used or the amount of carboxylated chitosan added is small, the adhesion of the water-based ink is reduced. If the amount of carboxylated chitosan added is high (Examples 14 and 15), the adhesion of the water-based ink will also be reduced, making it difficult to pass the screen during printing, increasing the difficulty of printing. Therefore, when the mass ratio of carboxylated chitosan to aqueous polyurethane emulsion is 0.2:10, the prepared water-based ink has the strongest adhesion.

[0073] The color density of the water-based inks prepared in Examples 11-28 and Comparative Example 2 was tested. Specifically, the color density test was performed using an X-rite SpectroEye spectrophotometer. The color density value of the printed product was measured on a dried sample block. The test instrument was gently pressed on the sample surface to collect data. The color density was measured and the values ​​were recorded. The results are shown in Table 4 below.

[0074] Table 4 Test results of water-based ink color density

[0075] It can be seen from Table 4 that, compared with Comparative Example 2 in which no carboxylated chitosan was used for modification, the color density of the water-based ink prepared in Examples 11-28 after the water-based polyurethane emulsion was modified with carboxylated chitosan was significantly improved.

[0076] The dot gain of the water-based ink prepared in Examples 11-28 and Comparative Example 2 was tested. Specifically, the dot gain test was performed using an X-rite SpectroEye spectrophotometer. According to the numerical changes in the dot area ratio of different color blocks, the dot gain was explored, and progressive color blocks with a dot area ratio of 10-100% were drawn. The modified water-based ink was transferred to 70g offset paper by screen printing, and the measurement was performed under ISO T conditions. The results are shown in Table 5 below.

[0077] Table 5 Test results of dot gain of water-based ink

[0078] It can be seen from Table 5 that compared with Comparative Example 2, the dot gain value of the water-based ink prepared in Example 28 is the smallest.

[0079] The adhesion of the water-based inks prepared in Examples 11-28 and Comparative Example 2 was tested for color. Specifically, the color was tested using an X-rite SpectroEye spectrophotometer. The solid color blocks were measured in turn under a D65 light source and a 2° viewing field. , , The values ​​were measured and recorded. The results are shown in Table 6 below.

[0080] in, Indicates brightness. The higher the value, the higher the brightness value. Indicates red and green, The higher the positive number is, the redder the color is; on the contrary, the smaller the absolute value is, the greener the color is. Represents yellow-blue. The larger the positive value is, the yellower the color is. Conversely, the smaller the absolute value is, the bluer the color is.

[0081] Table 6 Measurement results of water-based ink chromaticity

[0082] It can be seen from Table 6 that compared with Comparative Example 2, after adding carboxylated chitosan in Examples 11-28, The absolute value of The value is larger, therefore, the chromaticity of the water-based ink is better, and the chromaticity of the water-based ink prepared in Example 28 is the best.

[0083] In summary, the present invention significantly improves the viscosity, adhesion and stability of the modified waterborne polyurethane-based binder by modifying the waterborne polyurethane emulsion with carboxylated chitosan; when the modified waterborne polyurethane-based binder is used to prepare water-based ink, the viscosity, adhesion and stability of the water-based ink are significantly improved.

[0084] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0085] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A modified waterborne polyurethane-based connecting material, characterized in that: The modified waterborne polyurethane-based binder has a structure as shown in the following formula (I): ； Wherein, n is a positive integer ≥1.

2. A method for preparing a modified waterborne polyurethane-based binder according to claim 1, characterized in that: The method comprises the following steps: mixing carboxylated chitosan and aqueous polyurethane emulsion, and stirring to obtain a modified aqueous polyurethane-based connecting material; Wherein, the mass ratio of the carboxylated chitosan to the aqueous polyurethane emulsion is (0.1-0.5):(6-11).

3. The method for preparing the modified waterborne polyurethane-based binder according to claim 2, characterized in that: The stirring time is 10-30 minutes.

4. A water-based ink, characterized in that: The invention comprises the modified waterborne polyurethane-based connecting material as claimed in claim 1 or the modified waterborne polyurethane-based connecting material prepared by the preparation method as claimed in any one of claims 2 to 3.

5. The water-based ink according to claim 4, characterized in that: It also includes a colorant and a solvent, wherein the mass ratio of the colorant, the solvent and the aqueous polyurethane emulsion in the modified aqueous polyurethane-based connecting material is (0.02-0.1): (0.05-0.25): (6-11).

6. The water-based ink according to claim 5, characterized in that: The colorant includes bright yellow pigment.

7. The water-based ink according to claim 5, characterized in that: The solvent includes water.

8. The water-based ink according to claim 4, characterized in that: It also includes a defoamer, and the mass ratio of the defoamer to the aqueous polyurethane emulsion in the modified aqueous polyurethane-based connecting material is (0.05-0.25): (6-11).

9. The water-based ink according to claim 8, characterized in that: The defoaming agent includes anhydrous ethanol.

10. A method for preparing a water-based ink as claimed in any one of claims 4 to 9, characterized in that: The method comprises the following steps: uniformly mixing a modified water-based polyurethane-based connecting material, a colorant and a solvent, and adding a defoaming agent to obtain a water-based ink.

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