A high-temperature resistant waterborne polyurethane ink and its preparation method

Abstract

This invention discloses a high-temperature resistant waterborne polyurethane ink and its preparation method, belonging to the field of ink technology. The high-temperature resistant waterborne polyurethane ink, by weight, comprises 60-70 parts of waterborne polyurethane resin, 20-35 parts of nano-titanium dioxide, 10-15 parts of modified mica powder, 1-5 parts of crosslinking agent, and 50-70 parts of water. Furthermore, this invention also proposes a preparation method for the above-mentioned high-temperature resistant waterborne polyurethane ink, comprising: adding waterborne polyurethane resin and nano-titanium dioxide to water, stirring at 800-1200 r / min to obtain a pre-dispersed slurry; adding modified mica powder to the pre-dispersed slurry, stirring at 600-800 r / min; adding a crosslinking agent, and continuing stirring to obtain the high-temperature resistant waterborne polyurethane ink. The high-temperature resistant waterborne polyurethane ink proposed in this invention significantly shortens the curing time and improves the high-temperature resistance of the ink.

Description

Technical Field

[0001] This invention relates to the field of ink technology, specifically to a high-temperature resistant water-based polyurethane ink and its preparation method. Background Technology

[0002] Waterborne polyurethane ink is a new type of environmentally friendly ink that uses waterborne polyurethane resin as a binder and water as a dispersion medium. Waterborne polyurethane (WPU) is a polyurethane emulsion or dispersion formed by introducing hydrophilic groups (such as carboxyl groups, sulfonic acid groups, quaternary ammonium salts, etc.) into the polyurethane molecular chain, enabling it to be stably dispersed in water. Compared with traditional solvent-based polyurethane inks, waterborne polyurethane inks have the following significant advantages: First, by using water instead of organic solvents as the dispersion medium, the content of volatile organic compounds (VOCs) is extremely low, making it environmentally friendly and in line with the development trend of green printing; second, it has no irritating odor, improving the working environment of the printing workshop and protecting the occupational health of operators; third, it is non-flammable and non-explosive, improving the safety of production and storage; in addition, waterborne polyurethane inks have good printability and can form coatings with strong adhesion, good flexibility, and high gloss on various substrate surfaces.

[0003] However, waterborne polyurethane inks still face many technical challenges in practical applications. First, while the hydrophilic groups introduced into the waterborne polyurethane molecular chain impart water dispersibility, they also significantly reduce the coating's water resistance and solvent resistance compared to solvent-based polyurethanes. In humid environments or under water immersion conditions, the coating is prone to swelling, reduced adhesion, and even peeling. Second, waterborne polyurethane inks have poor thermal stability. Under high-temperature cooking conditions, the thermal motion of the polyurethane molecular chains intensifies, and water molecule penetration accelerates, easily leading to coating softening, wrinkling, loss of adhesion, and ultimately ink fading. This problem is particularly prominent in the food flexible packaging field—inks used in food flexible packaging often need to undergo high-temperature cooking sterilization at 121℃, thus placing extremely high demands on the ink's high-temperature resistance.

[0004] Waterborne polyurethane inks have attracted widespread attention due to their advantages such as low VOCs and environmental friendliness. However, they are prone to problems such as decreased adhesion and ink detachment under high-temperature cooking conditions. In existing technologies, adding mica powder can improve the high-temperature resistance of the ink, but the hydrophilic nature of mica powder will prolong the curing time of the ink.

[0005] How to shorten the curing time and improve the high-temperature resistance of ink is a technical problem that needs to be solved by existing technologies. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a high-temperature resistant water-based polyurethane ink and its preparation method, thereby solving the technical problem of how to shorten the curing time and improve the high-temperature resistance of ink in the prior art.

[0007] To achieve the above technical objectives, the present invention provides a high-temperature resistant waterborne polyurethane ink, the raw materials of which, by weight, include 60-70 parts of waterborne polyurethane resin, 20-35 parts of nano titanium dioxide, 10-15 parts of modified mica powder, 1-5 parts of crosslinking agent, and 50-70 parts of water. The modified mica powder is prepared by the following steps: 1) Add γ-methacryloxypropyltrimethoxysilane to an aqueous ethanol solution and stir. Adjust the pH to 3.0-4.5 with acid to obtain a silane hydrolysate. 2) Add mica powder to the above hydrolysate and stir until fully reacted. 3) Filter and separate the mixture, and dry it at 50-70℃ to obtain modified mica powder.

[0008] In any embodiment, it also includes 5 to 15 parts of nano-alumina.

[0009] In any embodiment, the crosslinking agent is polycarbodiimide.

[0010] In any embodiment, in step 1), the volume ratio of the γ-methacryloyloxypropyltrimethoxysilane to the aqueous ethanol solution is 1:(20~40).

[0011] In any embodiment, in step 1), the mass concentration of the ethanol aqueous solution is 60% to 80%.

[0012] In any embodiment, in step 1), the stirring time is 1-3 hours.

[0013] In any embodiment, in step 2), the mass ratio of the mica powder to the γ-methacryloyloxypropyltrimethoxysilane is 1:(0.06~0.12).

[0014] In any embodiment, in step 2), the stirring time is 6 to 12 hours.

[0015] Furthermore, this invention also proposes a method for preparing the above-mentioned high-temperature resistant waterborne polyurethane ink, comprising the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 800~1200 r / min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 600~800 r / min; S3. Add crosslinking agent, continue stirring, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

[0016] In any embodiment, in step S1, the stirring time is 20-40 min; and / or, in step S2, the stirring time is 15-30 min; and / or, in step S3, the stirring time is 10-20 min.

[0017] Compared with the prior art, the beneficial effects of the present invention include: modifying mica powder with active silane KH-570, the grafted carbon-carbon double bonds can chemically crosslink with the unsaturated groups in waterborne polyurethane resin, transforming mica powder from an inert filler to a reactive filler, introducing a crosslinking agent, which crosslinks with the carboxyl groups on the waterborne polyurethane molecular chain to form a three-dimensional network structure, greatly improving the heat resistance, water resistance and adhesion of the coating, thereby significantly improving the cohesive strength and high-temperature cooking performance of the ink, achieving a significant reduction in curing time, and improving the high-temperature performance of the ink. Detailed Implementation

[0018] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0019] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0020] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0021] This specific embodiment provides a high-temperature resistant waterborne polyurethane ink, the raw materials of which, by weight, include 60-70 parts of waterborne polyurethane resin, 20-35 parts of nano titanium dioxide, 10-15 parts of modified mica powder, 1-5 parts of crosslinking agent, and 50-70 parts of water.

[0022] In some embodiments, the ink further includes 5-15 parts of nano-alumina. The added nano-alumina forms a point-to-surface synergistic barrier network with the flake-modified mica powder, filling the gaps between the flakes and improving the thermal diffusivity, preventing local overheating, and ensuring that the ink remains intact and does not bleed after prolonged high-temperature cooking.

[0023] The modified mica powder is prepared by the following steps: (1) Add γ-methacryloxypropyltrimethoxysilane to an ethanol aqueous solution with a mass concentration of 60% to 80% at a volume ratio of 1:20 to 40, stir for 1 to 3 hours, and adjust the pH to 3.0 to 4.5 with acid to obtain a silane hydrolysate; (2) Add mica powder to the above hydrolysate, with a mass ratio of mica powder to γ-methacryloxypropyltrimethoxysilane of 1:0.06 to 0.12, and stir for 6 to 12 hours until the reaction is complete; (3) Filter and separate, and dry at 50 to 70°C for 8 to 12 hours to obtain modified mica powder.

[0024] This specific embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 800~1200 r / min for 20~40 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 600~800 r / min for 15~30 min; S3. Add crosslinking agent, continue stirring for 10~20 min, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] In this invention, the terms "some embodiments," "this embodiment," and examples are used to describe a subset of all possible embodiments. However, it is understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with each other without conflict.

[0027] If the application documents contain similar descriptions such as "first / second", the following explanation shall be added: In the following description, the terms "first / second / third" are used only to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first / second / third" may be interchanged in a specific order or sequence where permitted, so that the embodiments described herein can be implemented in a different order than that described herein.

[0028] In this embodiment, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, object A and / or object B can represent three situations: object A exists alone, object A and object B exist simultaneously, and object B exists alone.

[0029] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0030] Example 1

[0031] This embodiment proposes a high-temperature resistant waterborne polyurethane ink. The raw materials, calculated by weight, include 65 parts of waterborne polyurethane resin, 20 parts of nano titanium dioxide, 15 parts of modified mica powder, 3 parts of crosslinking agent, and 60 parts of water. The crosslinking agent is polycarbodiimide, and the number average molecular weight of the polycarbodiimide is approximately 2000.

[0032] The modified mica powder in this embodiment is prepared by the following steps: γ-methacryloxypropyltrimethoxysilane was added to a 60% ethanol aqueous solution at a volume ratio of 1:30, stirred for 1 h, and the pH was adjusted to 3.5 with acid to obtain a silane hydrolysate; (2) mica powder was added to the above hydrolysate, with a mass ratio of mica powder to γ-methacryloxypropyltrimethoxysilane of 1:0.1, and stirred for 10 h until fully reacted; (3) the mixture was filtered and separated, and dried at 60℃ for 10 h to obtain modified mica powder.

[0033] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 1000 r / min for 30 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 600 r / min for 30 min; S3. Add crosslinking agent, continue stirring for 15 min, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

[0034] Example 2

[0035] This embodiment proposes a high-temperature resistant waterborne polyurethane ink. The raw materials, calculated by weight, include 70 parts waterborne polyurethane resin, 30 parts nano titanium dioxide, 10 parts modified mica powder, 1 part crosslinking agent, and 70 parts water. The crosslinking agent is polycarbodiimide, and the number average molecular weight of the polycarbodiimide is approximately 2000.

[0036] The modified mica powder in this embodiment is prepared by the following steps: γ-methacryloxypropyltrimethoxysilane was added to a 60% ethanol aqueous solution at a volume ratio of 1:30, stirred for 2 hours, and the pH was adjusted to 4 with acid to obtain a silane hydrolysate; (2) mica powder was added to the above hydrolysate, with a mass ratio of mica powder to γ-methacryloxypropyltrimethoxysilane of 1:0.06, and stirred for 12 hours until fully reacted; (3) the mixture was filtered and separated, and dried at 50°C for 12 hours to obtain modified mica powder.

[0037] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 800 r / min for 40 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 700 r / min for 20 min; S3. Add crosslinking agent, continue stirring for 10 min, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

[0038] Example 3

[0039] This embodiment proposes a high-temperature resistant waterborne polyurethane ink. The raw materials, calculated by weight, include 60 parts of waterborne polyurethane resin, 35 parts of nano titanium dioxide, 12 parts of modified mica powder, 5 parts of crosslinking agent, and 50 parts of water. The crosslinking agent is polycarbodiimide, and the number average molecular weight of the polycarbodiimide is approximately 2000.

[0040] The modified mica powder in this embodiment is prepared by the following steps: γ-methacryloxypropyltrimethoxysilane was added to a 70% ethanol aqueous solution at a volume ratio of 1:20, stirred for 3 hours, and the pH was adjusted to 4.5 with acid to obtain a silane hydrolysate; (2) mica powder was added to the above hydrolysate, with a mass ratio of mica powder to γ-methacryloxypropyltrimethoxysilane of 1:0.12, and stirred for 6 hours until the reaction was complete; (3) the mixture was filtered and separated, and dried at 70°C for 8 hours to obtain modified mica powder.

[0041] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 1200 r / min for 20 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 800 r / min for 15 min; S3. Add crosslinking agent, continue stirring for 20 min, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

[0042] Example 4

[0043] This embodiment proposes a high-temperature resistant water-based polyurethane ink, which differs from Embodiment 1 in that the raw materials also include 10 parts of nano-alumina.

[0044] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin, nano titanium dioxide and nano alumina to water, and stir at 1000 r / min for 30 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry, and stir at 1000 r / min for 30 min; S3. Add crosslinking agent, continue stirring for 15 min, and filter to obtain the high-temperature resistant waterborne polyurethane ink.

[0045] Example 5

[0046] This embodiment proposes a high-temperature resistant water-based polyurethane ink, which differs from Embodiment 2 in that the raw materials also include 5 parts of nano-alumina.

[0047] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin, nano-titanium dioxide and nano-alumina to water, and stir at 800 r / min for 40 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry, and stir at 700 r / min for 20 min; S3. Add crosslinking agent, continue stirring for 10 min, and filter to obtain the high-temperature resistant waterborne polyurethane ink.

[0048] Example 6

[0049] This embodiment proposes a high-temperature resistant water-based polyurethane ink, which differs from Embodiment 3 in that the raw materials also include 15 parts of nano-alumina.

[0050] This embodiment also proposes a method for preparing a high-temperature resistant water-based polyurethane ink, including the following steps: S1. Add waterborne polyurethane resin, nano-titanium dioxide and nano-alumina to water, and stir at 1200 r / min for 20 min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry, and stir at 800 r / min for 15 min; S3. Add crosslinking agent, continue stirring for 20 min, and filter to obtain the high-temperature resistant waterborne polyurethane ink.

[0051] Comparative Example 1 The difference between the ink in this comparative example and that in Example 1 is that mica powder is used instead of modified mica powder, while the other raw materials and preparation methods are the same as in Example 1.

[0052] Comparative Example 2 The ink in this comparative example differs from that in Example 1 in that it does not contain a polycarbodiimide crosslinking agent, while the other raw materials and preparation methods are the same as in Example 1.

[0053] Comparative Example 3 The difference between the ink in this comparative example and that in Example 4 is that the modified mica powder is replaced with unmodified mica powder, and no polycarbodiimide crosslinking agent is added (i.e., the optimized solution of Comparative Document 4). All other raw materials and preparation methods are the same as in Example 4.

[0054] The inks prepared in each embodiment and comparative example were printed on PET films and cured and dried at 60°C. The curing time (the time required until the coating surface no longer sticks to fingers) was recorded. The films were placed in water at 100°C for different times (1h, 2h, 3h). After cooling, the film surface was observed to see if it wrinkled, lost ink, or if the writing was clearly visible. The results are shown in Table 1.

[0055] Table 1

[0056] As can be seen from Table 1, the inks prepared in Examples 1-6 not only shortened the curing time but also improved the high temperature resistance. The inks prepared in Examples 4-6 had even shorter curing times and stronger high temperature resistance. This invention significantly improved the high temperature cooking resistance of waterborne polyurethane inks by modifying mica powder, introducing polycarbodiimide crosslinking agent, and adding nano-alumina, while shortening the curing time.

[0057] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-temperature resistant water-based polyurethane ink, characterized in that, The raw materials, calculated by weight, include 60-70 parts of waterborne polyurethane resin, 20-35 parts of nano titanium dioxide, 10-15 parts of modified mica powder, 1-5 parts of crosslinking agent, and 50-70 parts of water. The modified mica powder is prepared by the following steps: 1) Add γ-methacryloxypropyltrimethoxysilane to an aqueous ethanol solution and stir. Adjust the pH to 3.0-4.5 with acid to obtain a silane hydrolysate; 2) Add mica powder to the above hydrolysate and stir until the reaction is complete; 3) Filter and separate, and dry at 50~70℃ to obtain modified mica powder.

2. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, It also includes 5 to 15 parts of nano-alumina.

3. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, The crosslinking agent is polycarbodiimide.

4. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, In step 1), the volume ratio of the γ-methacryloxypropyltrimethoxysilane to the aqueous ethanol solution is 1:(20~40).

5. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, In step 1), the mass concentration of the ethanol aqueous solution is 60%~80%.

6. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, In step 1), the stirring time is 1-3 hours.

7. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, In step 2), the mass ratio of the mica powder to the γ-methacryloyloxypropyltrimethoxysilane is 1:(0.06~0.12).

8. The high-temperature resistant water-based polyurethane ink according to claim 1, characterized in that, In step 2), the stirring time is 6 to 12 hours.

9. A method for preparing a high-temperature resistant waterborne polyurethane ink according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add waterborne polyurethane resin and nano-titanium dioxide to water and stir at 800~1200 r / min to obtain a pre-dispersed slurry; S2. Add modified mica powder to the pre-dispersed slurry and stir at 600~800 r / min; S3. Add crosslinking agent, continue stirring, filter and discharge to obtain the high-temperature resistant waterborne polyurethane ink.

10. The method for preparing high-temperature resistant waterborne polyurethane ink according to claim 9, characterized in that, In step S1, the stirring time is 20-40 min; and / or, in step S2, the stirring time is 15-30 min; and / or, in step S3, the stirring time is 10-20 min.

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