Coating liquid capable of rapidly changing and fading color-changing sheet and preparation method of coating liquid

Abstract

The invention discloses a fast color changing and fading color changing sheet coating liquid which is characterized by comprising the following raw materials in parts by weight: 5-20 parts of a photochromic material, 1-5 parts of a photosensitive additive, 30-50 parts of film-forming resin, 25-64 parts of a solvent, 0.5-2 parts of a UV stabilizer and 0.1-1 part of a flatting agent. Through the synergistic effect of the photosensitive additive and the photochromic material, the traditional response speed bottleneck is broken through, the problem of uneven mixing caused by wall hanging of the material in traditional coating preparation is solved, the product consistency is improved, and the method is simple in process, low in cost and very environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of automotive air dams, and specifically relates to a fast-fading and color-changing sheet coating liquid and a preparation method thereof. Background Art

[0002] Photochromic lenses, also known as "photosensitive lenses", are lenses that can automatically adjust their color according to the intensity of ambient light. Their core principle is based on a reversible photochromic reaction: under ultraviolet or strong light irradiation, the lenses quickly darken, absorb ultraviolet rays, and block strong light; in a weak light environment, the lenses can quickly return to a transparent state to ensure light transmittance. This characteristic makes photochromic lenses very suitable for indoor and outdoor use, and can effectively protect the eyes from ultraviolet rays, glare, and strong light.

[0003] Traditional photochromic lenses are mainly divided into two categories: substrate color-changing lenses and film color-changing lenses. Substrate color-changing lenses **achieve color change by adding chemical substances such as silver halide in the lens substrate and utilizing the ion reaction of silver halide. Under strong light irradiation, silver halide decomposes into silver and halogen, causing the lens to color; when the light weakens, silver and halogen recombine, and the lens returns to transparency. However, this technology has problems such as slow color change speed, poor color change uniformity, and short service life. Film color-changing lenses achieve color change by coating a photochromic coating on the lens surface. Although film color-changing lenses have a faster color change speed and better uniformity, their preparation process is complex and usually requires high-temperature baking or long-time curing, resulting in low production efficiency and high cost.

[0004] Traditional optical films have a relatively high reflectance in the near-ultraviolet band of 360nm - 380nm, resulting in photochromic lenses being unable to effectively absorb ultraviolet rays, and the color change performance deteriorates or even fails to start. Existing coating manufacturing processes usually require long-time high-temperature curing, which not only consumes a large amount of energy but also easily leads to a low product qualification rate due to dust pollution, affecting the color change effect and service life of the lenses. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a fast-fading and color-changing sheet coating liquid and a preparation method thereof. Through the synergistic effect of photosensitive assistants and photochromic materials, the traditional response speed bottleneck is broken through, the problem of uneven mixing caused by material wall hanging in traditional coating preparation is solved, the product consistency is improved, and the process is simple, low-cost, and very environmentally friendly.

[0006] To solve the above technical problems, the present invention discloses a fast-fading coating liquid, which includes the following raw materials in parts by weight: 5 - 20 parts of a photochromic material, 1 - 5 parts of a photosensitive assistant, 30 - 50 parts of a film-forming resin, 25 - 64 parts of a solvent, 0.5 - 2 parts of a UV stabilizer, and 0.1 - 1 part of a leveling agent.

[0007] According to an embodiment of the present invention, the photochromic material is a nanoscale spiropyran derivative, the photosensitive auxiliary is benzophenone, and the film-forming resin is a waterborne polyurethane.

[0008] According to an embodiment of the present invention, in the preparation method of the fast fading coating liquid, step (1) pretreatment: mix spiropyran with an appropriate amount of solvent at a mass ratio of 1:5, place it in a ball mill, and grind it at 300 rpm for 4 hours to obtain a dispersion with a particle size ≤ 200 nm; benzophenone needs to be pre-dissolved in 10% of the total solvent amount and heated to 40 °C and stirred until completely transparent; step (2) preparation of the coating liquid: in a light-shielded environment, add the pretreated spiropyran, an appropriate amount of solvent, and benzophenone to the reaction kettle in proportion, turn on ultrasonic dispersion, control the temperature ≤ 30 °C, and the ultrasonic time is 30 - 60 minutes until the light transmittance of the dispersion ≥ 90%. Slowly add the film-forming resin to the above dispersion, while stirring at a low speed of 500 - 800 rpm, and sequentially add additives such as UV stabilizers and leveling agents, and stir for 10 minutes for preliminary mixing; then filter the mixed liquid through a 1 μm nylon filter bag to remove undispersed particles or gels, and finally coat the above mixed liquid onto the substrate; step (3) curing: place the coated substrate in an oven and dry it at 50 - 80 °C for 10 - 20 minutes.

[0009] According to an embodiment of the present invention, if the viscosity of the above film-forming resin is too high, 5 - 10% solvent can be added for pre-dilution until the viscosity ≤ 1000 cps.

[0010] According to an embodiment of the present invention, the coating method is spraying, the spray gun pressure is 0.3 - 0.5 MPa, and the nozzle diameter is 0.5 mm.

[0011] Compared with the prior art, the present invention can obtain the following technical effects: 1) Through the synergistic effect of the photosensitive auxiliary and the photochromic material, it breaks through the bottleneck of the traditional response speed, solves the problem of uneven mixing caused by material wall hanging in the preparation of traditional coatings, improves product consistency, and has a simple process, low cost, and is very environmentally friendly.

[0012] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned technical effects simultaneously. Specific Embodiments

[0013] The following examples are used to illustrate the embodiments of the present invention in detail, so as to fully understand how the present invention uses technical means to solve technical problems and achieve the realization process of technical effects and implement accordingly.

[0014] A fast-changing fading coating liquid, comprising the following raw materials in parts by weight: 5-20 parts of a photochromic material, 1-5 parts of a photosensitive auxiliary agent, 30-50 parts of a film-forming resin, 25-64 parts of a solvent, 0.5-2 parts of a UV stabilizer, and 0.1-1 part of a leveling agent.

[0015] Specifically, the photochromic material is a nano-level spiropyran derivative, the photosensitive auxiliary agent is benzophenone, and the film-forming resin is a waterborne polyurethane.

[0016] Furthermore, a preparation method of a fast-changing fading color-changing film coating liquid. Step (1) Pretreatment: Mix spiropyran with an appropriate amount of solvent at a mass ratio of 1:5, place it in a ball mill, and grind it at 300 rpm for 4 hours to obtain a dispersion liquid with a particle size ≤ 200 nm; benzophenone needs to be pre-dissolved in 10% of the total solvent amount and heated to 40 °C and stirred until completely transparent; Step (2) Preparation of the coating liquid: In a light-shielded environment, add the pretreated spiropyran, an appropriate amount of solvent, and benzophenone to the reaction kettle in proportion, turn on ultrasonic dispersion, control the temperature ≤ 30 °C, and the ultrasonic time is 30-60 minutes until the light transmittance of the dispersion liquid ≥ 90%. Slowly add the film-forming resin to the above dispersion liquid, while stirring at a low speed of 500-800 rpm, and sequentially add additives such as a UV stabilizer and a leveling agent, and stir for 10 minutes for preliminary mixing; then filter the mixed liquid through a 1-μm nylon filter bag to remove undispersed particles or gels, and finally coat the above mixed liquid onto the substrate; Step (3) Curing: Place the coated substrate in an oven and dry it at 50-80 °C for 10-20 minutes.

[0017] Specifically, if the viscosity of the film-forming resin is too high, 5-10% of the solvent can be added for pre-dilution until the viscosity ≤ 1000 cps. The coating method is spraying, the spray gun pressure is 0.3-0.5 MPa, and the nozzle diameter is 0.5 mm.

[0018] Therefore, 3 groups of examples with different ratios are carried out according to the above method.

[0019] Example 1: Preparation method of fast-fading coating liquid. Step (1) Pretreatment: 5 parts of spiropyran are mixed with an appropriate amount of solvent at a mass ratio of 1:5, placed in a ball mill, and ground at 300 rpm for 4 hours to obtain a dispersion with a particle size ≤ 200 nm; 1 part of benzophenone needs to be pre-dissolved in 10% of the total solvent amount, heated to 40 °C and stirred until completely transparent; Step (2) Preparation of coating liquid: In a light-shielded environment, the pretreated 5 parts of spiropyran, an appropriate amount of solvent and 1 part of benzophenone are added to the reaction kettle in proportion, ultrasonic dispersion is started, the temperature is controlled ≤ 30 °C, and the ultrasonic time is 30 - 60 minutes until the light transmittance of the dispersion ≥ 90%. 30 parts of film-forming resin are slowly added to the above dispersion, while stirring at a low speed of 500 - 800 rpm, and additives such as 0.5 part of UV stabilizer and 0.1 part of leveling agent are added in sequence, and stirred for 10 minutes for preliminary mixing; Then the mixed liquid is filtered through a 1 μm nylon filter bag to remove undispersed particles or gels, and finally the above mixed liquid is coated on the substrate; Step (3) Curing: The coated substrate is placed in an oven and dried at 50 - 80 °C for 10 - 20 minutes.

[0020] Example 2: Preparation method of fast-fading coating liquid. Step (1) Pretreatment: 12.5 parts of spiropyran are mixed with an appropriate amount of solvent at a mass ratio of 1:5, placed in a ball mill, and ground at 300 rpm for 4 hours to obtain a dispersion with a particle size ≤ 200 nm; 3 parts of benzophenone needs to be pre-dissolved in 10% of the total solvent amount, heated to 40 °C and stirred until completely transparent; Step (2) Preparation of coating liquid: In a light-shielded environment, the pretreated 12.5 parts of spiropyran, an appropriate amount of solvent and 3 parts of benzophenone are added to the reaction kettle in proportion, ultrasonic dispersion is started, the temperature is controlled ≤ 30 °C, and the ultrasonic time is 30 - 60 minutes until the light transmittance of the dispersion ≥ 90%. 40 parts of film-forming resin are slowly added to the above dispersion, while stirring at a low speed of 500 - 800 rpm, and additives such as 1.25 parts of UV stabilizer and 0.55 part of leveling agent are added in sequence, and stirred for 10 minutes for preliminary mixing; Then the mixed liquid is filtered through a 1 μm nylon filter bag to remove undispersed particles or gels, and finally the above mixed liquid is coated on the substrate; Step (3) Curing: The coated substrate is placed in an oven and dried at 50 - 80 °C for 10 - 20 minutes.

[0021] Example 3: Preparation method of a fast-fading coating liquid. Step (1) Pretreatment: Mix 20 parts of spiropyran with an appropriate amount of solvent at a mass ratio of 1:5, place it in a ball mill, and grind it at 300 rpm for 4 hours to obtain a dispersion with a particle size ≤ 200 nm; 5 parts of benzophenone need to be pre-dissolved in 10% of the total solvent amount, heated to 40 °C, and stirred until completely transparent. Step (2) Preparation of the coating liquid: In a light-shielded environment, add the pretreated 20 parts of spiropyran, an appropriate amount of solvent, and 5 parts of benzophenone to the reaction kettle in proportion, turn on ultrasonic dispersion, control the temperature ≤ 30 °C, and the ultrasonic time is 30 - 60 minutes until the light transmittance of the dispersion ≥ 90%. Slowly add 50 parts of film-forming resin to the above dispersion, while stirring at a low speed of 500 - 800 rpm, and sequentially add additives such as 2 parts of UV stabilizer and 1 part of leveling agent, and stir for 10 minutes for preliminary mixing; then filter the mixed liquid through a 1-μm nylon filter bag to remove undispersed particles or gels, and finally coat the above mixed liquid onto the substrate. Step (3) Curing: Place the coated substrate in an oven and dry it at 50 - 80 °C for 10 - 20 minutes.

[0022] In summary, the fast-fading and color-changing coating liquid prepared in Example 2 shows the best performance in terms of fatigue resistance, color-changing uniformity, and application range. The performance retention rate after 1000 cycles > 95%, far exceeding the other two groups.

[0023] Through the synergistic effect of the photosensitive auxiliary agent and the photochromic material, the present invention breaks through the bottleneck of the traditional response speed, solves the problem of uneven mixing caused by material wall sticking in the preparation of traditional coatings, improves the product consistency, and has a simple process, low cost, and is very environmentally friendly.

[0024] The above description shows and describes several preferred embodiments of the present invention. However, as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the technology or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope of the appended claims of the present invention.

Claims

1. A fast-fading color-changing film coating liquid, characterized in that: The invention comprises the following raw materials in parts by weight: 5-20 parts of photochromic material, 1-5 parts of photosensitizer, 30-50 parts of film-forming resin and 25-64 parts of solvent, 0.5-2 parts of UV stabilizer and 0.1-1 parts of leveling agent.

2. The fast-fading color-changing film coating liquid according to claim 1, characterized in that: The photochromic material is a nano-scale spiropyran derivative, the photosensitizer is benzophenone, and the film-forming resin is water-based polyurethane.

3. A method for preparing the coating liquid for the fast-fading color-changing sheet as claimed in claims 1-2, characterized in that: Step (i) pretreatment: spiropyran is mixed with an appropriate amount of solvent in a mass ratio of 1:5, placed in a ball mill, and ground at 300 rpm for 4 hours to obtain a dispersion with a particle size of ≤200 nm; benzophenone needs to be pre-dissolved in a solvent accounting for 10% of the total solvent volume, heated to 40°C and stirred until completely transparent; Step (ii) preparation of coating liquid: in a light-proof environment, the pre-treated spiropyran, an appropriate amount of solvent and benzophenone are added to a reaction kettle in proportion, ultrasonic dispersion is turned on, the temperature is controlled to be ≤30°C, and the ultrasonic time is 30-60 minutes, until the transmittance of the dispersion is ≥90%, and the film-forming resin is slowly added to the above dispersion, while stirring at a low speed of 500-800 rpm, and additives such as UV stabilizer and leveling agent are added in sequence, and stirred for 10 minutes for preliminary mixing; The mixed solution is then filtered through a 1 μm nylon filter bag to remove undispersed particles or gels, and finally the mixed solution is applied to the substrate; Step (III) Curing: Place the coated substrate in an oven and dry at 50-80°C for 10-20 minutes.

4. The method for preparing the coating liquid for fast-fading color-changing sheet according to claim 3, characterized in that: If the viscosity of the film-forming resin is too high, 5-10% solvent can be added to pre-dilute it to a viscosity of ≤1000cps.

5. The method for preparing the coating liquid for fast-fading color-changing sheet according to claim 3, characterized in that: The coating method is spraying, the spray gun pressure is 0.3-0.5MPa, and the nozzle diameter is 0.5mm.