A quick-drying polyurethane ink and a preparation method thereof

Abstract

The present application relates to the technical field of ink, in particular to a quick-drying polyurethane ink and a preparation method thereof, comprising the following components: jointly modified water-based polyurethane resin, dispersant, defoaming agent, pigment, nano filler and deionized water; the jointly modified water-based polyurethane resin is obtained by first reducing the molecular weight of the polyurethane resin through a chemical degradation method and then introducing active groups; the present application improves the prior art, adjusts the dosages of the components, effectively solves the problem of slow drying rate of traditional polyurethane ink, and plays a main role in the components in the jointly modified water-based polyurethane resin prepared by the present application, which has an obvious promoting effect on improving the drying rate of the ink. Through the synergistic effect of the components, the present application greatly improves the drying rate of the polyurethane ink, effectively reduces the occurrence of scratching phenomenon of the printed matter before drying, reduces the printing waste rate, improves the production efficiency and product quality.

Description

Technical Field

[0001] This invention relates to the field of ink technology, specifically to a quick-drying polyurethane ink and its preparation method. Background Technology

[0002] Polyurethane ink, as an important printing material, is widely used in many fields such as packaging printing, electronic circuit printing, and textile printing due to its good abrasion resistance, chemical resistance, and color performance.

[0003] In the packaging and printing industry, polyurethane inks can be used in food packaging, cosmetic packaging, etc., ensuring that the printed patterns are exquisite and not easy to fade, while meeting food-grade safety requirements; in electronic circuit printing, its good insulation and adhesion properties meet the needs of fine printing on circuit boards; in textile printing, it can achieve a wide variety of pattern effects, and has a soft feel without affecting the comfort of the fabric.

[0004] However, existing polyurethane inks have a significant drawback: slow drying rates. This defect causes numerous problems in actual printing processes. Due to the long drying time, the printed material remains tacky or semi-tacky before it is fully dry. At this stage, even slight friction or impact can easily cause scratches. For example, in high-speed printing production lines, even slight friction between printed materials or contact with the conveyor belt can damage the undried ink layer. This not only affects the appearance quality of the printed material, leading to blurred patterns and incomplete colors, but also results in a large number of printed waste products, increasing production costs and reducing efficiency. Furthermore, the slow drying speed also limits the printing company's capacity and extends the product production cycle.

[0005] Therefore, developing a polyurethane ink that can significantly improve drying rate has become a key issue that urgently needs to be addressed in the industry. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a quick-drying polyurethane ink and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A quick-drying polyurethane ink comprises the following components by weight: 55-58 parts of co-modified waterborne polyurethane resin, 1-3 parts of dispersant, 0.3-0.6 parts of defoamer, 8-10 parts of pigment, 12-15 parts of nanofiller, and 12-14 parts of deionized water.

[0009] The modified waterborne polyurethane resin is obtained by first reducing the molecular weight of the polyurethane resin through chemical degradation and then introducing active groups.

[0010] As a further technical solution, the specific process of the chemical degradation method is as follows:

[0011] Add polyurethane resin to the reactor, start stirring, control the speed at 250-300 r / min, and then heat to 72-75℃ to completely dissolve the polyurethane resin.

[0012] Weigh 1.2%-1.8% of the polyurethane resin mass of ethylenediamine, and add the ethylenediamine dropwise into the reactor over 40-50 minutes while maintaining stirring.

[0013] After the addition is complete, adjust the temperature to 76-78℃ and continue stirring for 2-3 hours. Detect the molecular weight of the resin. When the weight-average molecular weight of the resin drops to 25%-30% lower than the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system.

[0014] As a further technical solution, the specific process for introducing active groups is as follows:

[0015] In the low molecular weight polyurethane resin system, the temperature is stabilized at 85-90℃ and nitrogen gas is continuously introduced for protection, with the flow rate controlled at 0.9-1.2L / min; hexamethylene diisocyanate is weighed at 3%-3.5% of the mass of polyurethane resin and slowly dripped into the reactor over 40-50 minutes.

[0016] After the addition is complete, keep the mixture warm and stir for 3-4 hours, then stop the reaction to complete the treatment of introducing active groups.

[0017] As a further technical solution, the dispersant is sodium polyacrylate.

[0018] As a further technical solution, the defoamer is an organosilicone defoamer.

[0019] As a further technical solution, the pigment is an inorganic pigment.

[0020] As a further technical solution, the nanofiller is nano-silica or nano-calcium carbonate.

[0021] A method for preparing quick-drying polyurethane ink includes the following steps:

[0022] Dispersant, defoamer, pigment, nanofiller and deionized water were added sequentially to the co-modified waterborne polyurethane resin. After stirring at 350 r / min for 20 minutes, the mixture was then ground to 15-20 μm using a grinding equipment to obtain the desired product.

[0023] As a further technical solution, the grinding equipment is a sand mill, with a grinding speed of 1800-2100 r / min and a grinding time of 3-3.5 hours.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention improves upon existing technologies and, through adjustments to the dosage of each component, effectively solves the problem of slow drying rate in traditional polyurethane inks. Among the components, the co-modified waterborne polyurethane resin prepared in this invention plays a major role and has a significant promoting effect on improving the ink drying rate.

[0026] The co-modified waterborne polyurethane resin prepared in this invention is obtained by first reducing the molecular weight of the polyurethane resin through chemical degradation, and then introducing active groups. Compared with conventional polyurethane resin, its modified mechanism is as follows: In the chemical degradation stage, reducing the molecular weight shortens the resin molecular chains, weakens the intermolecular forces, and makes it easier to move and diffuse in the ink system. When the ink is coated on the printing substrate, the shorter molecular chains can adjust their own arrangement more quickly, promote solvent evaporation, and thus accelerate the drying process. The introduction of active groups further optimizes the resin's performance. These active groups can interact with other components (such as pigments, nanofillers, etc.) to form a denser network structure. On the one hand, it enhances the resin's dispersion stability for pigments and fillers, keeping the ink in a uniform state during the drying process and avoiding problems such as pigment agglomeration that affect the drying rate; on the other hand, the interaction between active groups and with other substances can promote cross-linking reactions, forming a dense cured film on the ink surface, which greatly shortens the drying time.

[0027] Dispersants ensure that pigments and nanofillers are uniformly dispersed in the ink system, preventing agglomeration and sedimentation. This maintains good flowability and uniformity of the ink during drying, contributing to improved drying efficiency. Defoamers eliminate air bubbles in the ink, preventing them from bursting during drying and affecting the drying effect and surface quality. Pigments provide a rich color palette, nanofillers enhance the physical properties of the ink, and deionized water, as an environmentally friendly solvent, ensures ink performance while meeting the requirements of modern green printing.

[0028] In summary, this invention, through the synergistic effect of its components, especially the combined use of modified waterborne polyurethane resin, significantly improves the drying rate of polyurethane inks, effectively reduces scratches on printed materials before drying, lowers the printing scrap rate, and improves production efficiency and product quality, resulting in significant economic benefits and market competitiveness. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Waterborne polyurethane: 35% solids content, Anhui Yuanchen New Materials Co., Ltd.

[0031] The quick-drying polyurethane ink provided by this invention comprises the following components by weight: 55-58 parts of co-modified waterborne polyurethane resin, 1-3 parts of dispersant, 0.3-0.6 parts of defoamer, 8-10 parts of pigment, 12-15 parts of nanofiller, and 12-14 parts of deionized water. The co-modified waterborne polyurethane resin is obtained by reducing the molecular weight of the polyurethane resin through chemical degradation and then introducing active groups.

[0032] Preparation of modified waterborne polyurethane resin

[0033] Chemical degradation method: Add polyurethane resin to the reactor and start stirring at a speed of 250-300 rpm. This speed range ensures sufficient flow of the polyurethane resin within the reactor, allowing for uniform heating and accelerating the dissolution process, while avoiding equipment damage and material splashing due to excessive speed, thus ensuring the stability and safety of the reaction. Raise the temperature to 72-75℃ to completely dissolve the polyurethane resin. This temperature range allows for effective dissolution of the polyurethane resin without causing resin decomposition or other side reactions due to excessive temperature, ensuring the smooth progress of subsequent reactions. Weigh 1.2%-1.8% of the polyurethane resin mass and add ethylenediamine dropwise to the reactor over 40-50 minutes while continuously stirring. Precise control of the amount and timing of ethylenediamine addition ensures sufficient reaction between the ethylenediamine and the polyurethane resin, gradually degrading the resin molecular weight and avoiding overly vigorous or incomplete reactions, thus guaranteeing the consistency and stability of the degradation effect. After the addition is complete, adjust the temperature to 76-78℃ and continue stirring for 2-3 hours. This temperature and reaction time help ethylenediamine react fully with polyurethane resin, reduce the molecular weight of the resin to the expected range, and ensure the depth and breadth of the reaction, thus ensuring the quality stability of the degradation products. Detect the molecular weight of the resin. When the weight-average molecular weight of the resin drops to 25%-30% lower than the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system. Controlling the molecular weight reduction within this range allows for appropriate changes in the properties of the polyurethane resin, ensuring its dispersibility and solubility in the ink system, and laying the foundation for the subsequent introduction of active groups and improvement of the ink drying rate.

[0034] Introducing active groups: In the low molecular weight polyurethane resin system, the temperature is stabilized at 85-90℃. This temperature range is conducive to the reaction between hexamethylene diisocyanate and the low molecular weight polyurethane resin, allowing for the smooth introduction of active groups. Simultaneously, it ensures a moderate reaction rate, avoiding either excessively rapid reaction leading to system runaway or excessively slow reaction affecting production efficiency. Continuous nitrogen purging is used for protection, with the flow rate controlled at 0.9-1.2 L / min. Nitrogen purging removes oxygen from the reaction system, preventing resin oxidation at high temperatures and ensuring an inert reaction environment. This flow rate range effectively isolates oxygen without affecting the stability and temperature uniformity of the reaction system due to excessive flow. Hexamethylene diisocyanate is weighed at 3%-3.5% of the polyurethane resin mass and slowly dripped into the reactor over 40-50 minutes. Precise control of the amount and dripping rate of hexamethylene diisocyanate ensures that the active groups are uniformly introduced into the polyurethane resin molecular chain, avoiding excessive or insufficient localized reactions and ensuring the uniformity of the modification effect. After the addition is complete, keep the mixture warm and stir for 3-4 hours. Sufficient reaction time ensures that the active groups react fully with the polyurethane resin to form stable chemical bonds, improve the modified structure of the resin, enhance its performance, and then stop the reaction to complete the treatment of introducing active groups.

[0035] Preparation of quick-drying polyurethane inks

[0036] Dispersant (sodium polyacrylate), defoamer (silicone defoamer), pigment (inorganic pigment), nanofiller (nano silica or nano calcium carbonate), and deionized water are added sequentially to the co-modified waterborne polyurethane resin. The mixture is stirred at 350 rpm for 20 minutes. This stirring speed and time ensures that the components are initially and uniformly dispersed in the co-modified waterborne polyurethane resin, providing a good foundation for subsequent grinding operations. This ensures uniform distribution of the ink components and avoids agglomeration or stratification. Then, the mixture is ground using a sand mill at 1800-2100 rpm for 3-3.5 hours. Under the specified speed and grinding time of this sand mill, the particles in the ink can be ground to a fineness of 15-20μm, effectively refining the particle size of pigments and nanofillers, improving their dispersion in the ink system, enhancing the stability and printability of the ink, and also helping to improve the drying rate and printing quality of the ink. Grinding to 15-20μm yields quick-drying polyurethane ink. Controlling the ink fineness within this range ensures the smoothness and uniformity of the ink during the printing process, avoiding rough and unclear printed patterns due to excessively large particles. It also facilitates rapid drying and film formation of the ink after printing, improving printing efficiency and product quality.

[0037] The following are specific examples:

[0038] Example 1

[0039] Preparation of modified waterborne polyurethane resin:

[0040] Weigh 100 parts of polyurethane resin and add it to the reactor. Turn on the stirring and set the stirring speed to 260 r / min. Then heat the mixture to 73°C to completely dissolve the polyurethane resin.

[0041] Weigh out 1.5% of the mass of polyurethane resin with ethylenediamine, and slowly add the ethylenediamine dropwise into the reactor over a period of 45 minutes while continuously stirring.

[0042] After the addition is complete, the temperature inside the reactor is adjusted to 77°C, and the reaction is continuously stirred for 2.5 hours. During this period, the molecular weight of the resin is measured. When the weight-average molecular weight of the resin decreases by 28% compared with the initial value, the reaction is stopped, and a low molecular weight polyurethane resin system is obtained.

[0043] In the low molecular weight polyurethane resin system, the temperature was stabilized at 87℃, and nitrogen gas was continuously introduced for protection, with the nitrogen flow rate controlled at 1L / min. Hexamethylene diisocyanate was weighed at 3.2% of the mass of the polyurethane resin and slowly added dropwise to the reactor over 45 minutes.

[0044] After the addition is complete, the mixture is kept at a constant temperature and stirred for 3.5 hours to complete the preparation of the co-modified waterborne polyurethane resin.

[0045] Ink preparation:

[0046] Take 56 parts of the prepared combined modified waterborne polyurethane resin, and add 2 parts of sodium polyacrylate dispersant, 0.5 parts of organosilicon defoamer, 9 parts of inorganic pigment (such as titanium dioxide), 13 parts of nano silica and 13 parts of deionized water in sequence.

[0047] After stirring at 350 r / min for 20 minutes, the ink is ground at 2000 r / min for 3.2 hours to achieve a fineness of 15-20 μm, thus obtaining a quick-drying polyurethane ink.

[0048] Example 2

[0049] Preparation of modified waterborne polyurethane resin:

[0050] Weigh 100 parts of polyurethane resin and put them into the reactor. Turn on the stirring and control the speed at 250 r / min. Heat the mixture to 72℃ until the polyurethane resin is completely dissolved.

[0051] Weigh out 1.2% of the mass of polyurethane resin with ethylenediamine, and add the ethylenediamine dropwise into the reactor over 40 minutes while maintaining stirring.

[0052] After the addition was complete, the temperature was adjusted to 76°C, and the reaction was stirred continuously for 2 hours. When the weight-average molecular weight of the resin decreased by 25% compared with the initial value, the reaction was stopped, and a low molecular weight polyurethane resin system was obtained.

[0053] The temperature of the low molecular weight polyurethane resin system was stabilized at 85℃, and nitrogen gas was introduced at a flow rate of 0.9 L / min for protection. Hexamethylene diisocyanate was weighed at 3.0% of the mass of the polyurethane resin and slowly added dropwise to the reactor over 40 minutes.

[0054] After the addition is complete, the mixture is kept at a constant temperature and stirred for 3 hours to complete the preparation of the co-modified waterborne polyurethane resin.

[0055] Ink preparation:

[0056] Take 55 parts of the above-prepared co-modified waterborne polyurethane resin, add 1 part of sodium polyacrylate dispersant, 0.3 parts of organosilicon defoamer, 8 parts of inorganic pigment (such as iron oxide red), 12 parts of nano calcium carbonate and 14 parts of deionized water.

[0057] Stir at 350 r / min for 20 minutes, then grind in a sand mill at 1800 r / min for 3 hours to achieve an ink fineness of 15-20 μm, thus obtaining a quick-drying polyurethane ink.

[0058] Example 3

[0059] Preparation of modified waterborne polyurethane resin:

[0060] Add 100 parts of polyurethane resin to the reactor, start stirring, set the speed to 300 r / min, and heat to 75℃ to completely dissolve the polyurethane resin.

[0061] Weigh 1.8% of the mass of polyurethane resin with ethylenediamine, add the ethylenediamine dropwise into the reactor over 50 minutes while maintaining stirring.

[0062] After the addition is complete, adjust the temperature to 78°C and continue stirring for 3 hours. When the weight-average molecular weight of the resin decreases by 30% from the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system.

[0063] The temperature of the low molecular weight polyurethane resin system was stabilized at 90℃, and nitrogen gas was introduced at a flow rate of 1.2 L / min for protection. Hexamethylene diisocyanate was weighed at 3.5% of the mass of the polyurethane resin and slowly added dropwise to the reactor over 50 minutes.

[0064] After the addition is complete, the mixture is kept at a constant temperature and stirred for 4 hours to complete the preparation of the co-modified waterborne polyurethane resin.

[0065] Ink preparation:

[0066] Take 58 parts of the above-mentioned combined modified waterborne polyurethane resin, add 3 parts of sodium polyacrylate dispersant, 0.6 parts of organosilicon defoamer, 10 parts of inorganic pigment (such as carbon black), 15 parts of nano silica and 12 parts of deionized water.

[0067] Stir at 350 r / min for 20 minutes, then grind in a sand mill at 2100 r / min for 3.5 hours to achieve an ink fineness of 15-20 μm, thus obtaining a quick-drying polyurethane ink.

[0068] Example 4

[0069] Preparation of modified waterborne polyurethane resin:

[0070] Weigh 100 parts of polyurethane resin and add them to the reactor. Turn on the stirring and control the speed at 270 r / min. Heat the mixture to 74℃ to completely dissolve the polyurethane resin.

[0071] Weigh out 1.5% of the mass of polyurethane resin with ethylenediamine, and add the ethylenediamine dropwise into the reactor over 42 minutes while continuously stirring.

[0072] After the addition is complete, adjust the temperature to 77°C and continue stirring for 2.2 hours. When the weight-average molecular weight of the resin decreases by 27% from the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system.

[0073] The temperature of the low molecular weight polyurethane resin system was stabilized at 86°C, and nitrogen gas was introduced at a flow rate of 1.0 L / min for protection. Hexamethylene diisocyanate was weighed at 3.2% of the mass of the polyurethane resin and slowly added dropwise to the reactor over 42 minutes.

[0074] After the addition was completed, the mixture was kept at a constant temperature and stirred for 3.2 hours to complete the preparation of the co-modified waterborne polyurethane resin.

[0075] Ink preparation:

[0076] Take 56 parts of the above-prepared co-modified waterborne polyurethane resin, add 2 parts of sodium polyacrylate dispersant, 0.4 parts of organosilicon defoamer, 9 parts of inorganic pigment (such as chrome yellow), 13 parts of nano calcium carbonate and 13 parts of deionized water.

[0077] Stir at 350 r / min for 20 minutes, then grind in a sand mill at 1900 r / min for 3.1 hours to achieve an ink fineness of 15-20 μm, thus obtaining a quick-drying polyurethane ink.

[0078] Example 5

[0079] Preparation of modified waterborne polyurethane resin:

[0080] Add 100 parts of polyurethane resin to the reactor, start stirring, set the speed to 280 r / min, and heat to 73℃ to completely dissolve the polyurethane resin.

[0081] Weigh 1.6% of the mass of polyurethane resin with ethylenediamine, add the ethylenediamine dropwise into the reactor over 48 minutes while maintaining stirring.

[0082] After the addition is complete, adjust the temperature to 77°C and continue stirring for 2.8 hours. When the weight-average molecular weight of the resin decreases by 29% from the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system.

[0083] The temperature of the low molecular weight polyurethane resin system was stabilized at 88℃, and nitrogen gas was introduced at a flow rate of 1.1 L / min for protection. Hexamethylene diisocyanate, weighed at 3.3% of the mass of the polyurethane resin, was slowly added dropwise to the reactor over 48 minutes.

[0084] After the addition was completed, the mixture was kept at a constant temperature and stirred for 3.8 hours to complete the preparation of the co-modified waterborne polyurethane resin.

[0085] Ink preparation:

[0086] Take 57 parts of the above-mentioned combined modified waterborne polyurethane resin, add 2.5 parts of sodium polyacrylate dispersant, 0.5 parts of organosilicon defoamer, 9.5 parts of inorganic pigment (such as ultramarine), 14 parts of nano silica and 12.5 parts of deionized water.

[0087] Stir at 350 r / min for 20 minutes, then grind in a sand mill at 2050 r / min for 3.3 hours to achieve an ink fineness of 15-20 μm, thus obtaining a quick-drying polyurethane ink.

[0088] Comparative Example 1

[0089] The preparation process is basically the same as in Example 2, except that only the waterborne polyurethane is treated by chemical degradation.

[0090] Comparative Example 2

[0091] The preparation process is basically the same as in Example 2, except that only the waterborne polyurethane is treated to introduce active groups.

[0092] test

[0093] Drying speed test

[0094] The inks prepared in each embodiment and comparative example were uniformly coated on the same PVC substrate with a coating thickness of 20 μm. The surface drying time and complete drying time of the ink were recorded by touch at 25°C and 50% relative humidity.

[0095] Table 1

[0096]

[0097] As can be seen from Table 1, the polyurethane ink prepared by this invention has excellent quick-drying properties.

[0098] Storage stability test:

[0099] The inks of the examples and comparative examples were sealed in transparent containers and stored at 50°C for 30 days. The state of the inks was observed and the occurrence of phenomena such as layering, precipitation, and clumping was recorded. The average particle size change of pigments and fillers in the inks before and after storage was measured using a particle size analyzer. The average particle size change of conventional inks after storage was within 10%.

[0100] Table 2

[0101]

[0102] As can be seen from Table 2, the polyurethane ink prepared by this invention has high stability.

[0103] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A quick-drying polyurethane ink, characterized in that, The product comprises the following components by weight: 55-58 parts of modified waterborne polyurethane resin, 1-3 parts of dispersant, 0.3-0.6 parts of defoamer, 8-10 parts of pigment, 12-15 parts of nanofiller, and 12-14 parts of deionized water. The modified waterborne polyurethane resin is obtained by first reducing the molecular weight of the polyurethane resin through chemical degradation, and then introducing active groups; the specific process of the chemical degradation method is as follows: Add polyurethane resin to the reactor, start stirring, control the speed at 250-300 r / min, and then heat to 72-75℃ to completely dissolve the polyurethane resin. Weigh 1.2%-1.8% of the polyurethane resin mass of ethylenediamine, and add the ethylenediamine dropwise into the reactor over 40-50 minutes while maintaining stirring. After the addition is complete, adjust the temperature to 76-78℃ and continue stirring for 2-3 hours. Detect the molecular weight of the resin. When the weight-average molecular weight of the resin drops to 25%-30% lower than the initial value, stop the reaction to obtain a low molecular weight polyurethane resin system. The specific process for introducing active groups is as follows: In the low molecular weight polyurethane resin system, the temperature is stabilized at 85-90℃ and nitrogen gas is continuously introduced for protection, with the flow rate controlled at 0.9-1.2L / min; hexamethylene diisocyanate is weighed at 3%-3.5% of the mass of polyurethane resin and slowly dripped into the reactor over 40-50 minutes. After the addition is complete, keep the mixture warm and stir for 3-4 hours, then stop the reaction to complete the treatment of introducing active groups.

2. The quick-drying polyurethane ink according to claim 1, characterized in that, The dispersant is sodium polyacrylate.

3. The quick-drying polyurethane ink according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

4. The quick-drying polyurethane ink according to claim 1, characterized in that, The pigment is an inorganic pigment.

5. The quick-drying polyurethane ink according to claim 1, characterized in that, The nanofiller is nano-silica or nano-calcium carbonate.

6. A method for preparing the quick-drying polyurethane ink according to any one of claims 1-5, characterized in that, Includes the following steps: Dispersant, defoamer, pigment, nanofiller and deionized water were added sequentially to the co-modified waterborne polyurethane resin. After stirring at 350 r / min for 20 minutes, the mixture was then ground to 15-20 μm using a grinding equipment to obtain the desired product.

7. The method for preparing the quick-drying polyurethane ink according to claim 6, characterized in that, The grinding equipment is a sand mill, with a grinding speed of 1800-2100 r / min and a grinding time of 3-3.5 hours.

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