Color-changing alumite color layer coating and preparation method thereof

Abstract

The invention relates to the technical field of anti-counterfeiting, and particularly provides a color-changing alumite color layer coating and a preparation method thereof.The color layer coating comprises a small sphere loaded with a color-changing material, the small sphere is a polystyrene small sphere, the surface of the small sphere is provided with a gully microstructure formed by an amphiphilic block copolymer, and the gully microstructure is a gully microstructure formed by an amphiphilic block copolymer. A photochromic material is loaded in the gully microstructure, and the surface of the small sphere is covered with a silicon dioxide protective layer. Through a gully microstructure design induced by an amphiphilic block copolymer template and a silicon dioxide protective layer composite coating technology, the performance of the color-changing alumite color layer coating is comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the field of anti-counterfeiting technologies, and particularly to a color-changing aluminized paper color layer coating and a preparation method thereof. Background Art

[0002] Color-changing aluminized paper color layer coatings are widely used in fields such as packaging, decoration, and anti-counterfeiting. However, in the prior art, color-changing materials are directly dispersed in the matrix, and are prone to aggregation due to intermolecular forces, resulting in uneven coating color and decreased response sensitivity. The color-changing materials are prone to degradation when exposed to environmental factors, leading to attenuation of color-changing performance. Although the use of silica coating in the prior art can partially alleviate the degradation problem, the smooth shell structure limits the loading amount, and the core-shell interface is prone to cracking due to stress concentration. The closed design of the traditional core-shell structure can only load color-changing materials through the internal cavity, and the loading amount is limited by the core-shell volume ratio, and it is difficult to integrate multiple functions.

[0003] Based on the above problems, there is an urgent need to develop a new type of color-changing aluminized paper color layer coating, which can improve the loading efficiency and stability of color-changing materials while taking into account the feasibility of industrial production through structural innovation and process optimization. Summary of the Invention

[0004] In view of this, the present invention provides a color-changing aluminized paper color layer coating and a preparation method thereof. By in-situ preparing polystyrene microspheres with a gully microstructure in the emulsion polymerization method, loading photochromic materials and covering a silica protection layer, the performance of the coating is improved.

[0005] The technical solution of the present invention is realized as follows: The present invention provides a color-changing aluminized paper color layer coating, which contains microspheres loaded with color-changing materials. The microspheres are polystyrene microspheres, and the surface thereof has a gully microstructure formed by an amphiphilic block copolymer. The gully microstructure is loaded with photochromic materials, and a layer of silica protection layer is covered on the surface of the microspheres.

[0006] Taking the amphiphilic block copolymer as a template, a gully structure is in-situ formed on the surface of the polystyrene microspheres through the emulsion polymerization method. This structure greatly improves the loading amount of color-changing materials through physical confinement.

[0007] In some embodiments, the amphiphilic block copolymer is polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG), its molecular weight is 2000-10000, and the PEG segment accounts for 50-70% of the total mass of the copolymer.

[0008] The hydrophilicity of the PEG segment accounting for 50-70% guides the formation of the gully morphology, and the hydrophobicity of the PPG segment enhances the compatibility with the polystyrene matrix, ensuring the structural stability.

[0009] In some embodiments, the photochromic material is a spiropyran compound.

[0010] Embed the spiropyran compound inside the gully to prevent it from being directly exposed to the environment; In some embodiments, the particle size of the polystyrene spheres is 1 - 5 μm.

[0011] In some embodiments, the thickness of the silicon dioxide protective layer is 10 - 100 nm.

[0012] Form a dense SiO2 layer with a thickness of 10 - 100 nm on the surface of the spheres loaded with the color-changing material through chemical vapor deposition to block oxygen, moisture, and ultraviolet rays, and extend the service life. The second aspect of the present invention also provides a preparation method of the above-mentioned color-changing aluminized color layer coating, including the following steps: Step 1: Synthesize polystyrene spheres through emulsion polymerization in the presence of an amphiphilic block copolymer, and control the reaction conditions so that a gully microstructure with a depth of 100 - 500 nm and a width of 50 - 200 nm is formed on the surface of the spheres; Step 2: Load the photochromic material into the gully microstructure; Step 3: Cover a layer of silicon dioxide protective layer with a thickness of 10 - 100 nm on the surface of the spheres after loading the color-changing material; Step 4: Disperse the treated spheres in the aluminized color layer coating matrix at a ratio of 1 - 20 wt% to prepare the color-changing aluminized color layer coating.

[0013] In some embodiments, in the emulsion polymerization method, the polymerization reaction is carried out at 70 °C for 4 h under nitrogen protection.

[0014] In some embodiments, the loading of the photochromic material adopts the impregnation method, including immersing the spheres in an ethanol solution of the photochromic material, followed by ultrasonic treatment, centrifugation, washing, and drying.

[0015] In some embodiments, the silicon dioxide protective layer is prepared by chemical vapor deposition, including placing the spheres in a CVD reaction chamber, using tetraethoxysilane as a precursor, and reacting at 300 °C for 1 h.

[0016] In some embodiments, the aluminized color layer coating matrix is an acrylic resin, and the mass ratio of the treated spheres to the acrylic resin is 1:9.

[0017] The present invention has the following beneficial effects compared with the prior art: The present invention achieves a comprehensive improvement in the performance of color-changing electrochemical aluminum color layer coatings through the design of gully microstructures induced by amphiphilic block copolymer templates and the composite coating technology of silica protective layer. The template effect of the amphiphilic block copolymer forms a gully structure on the surface of the polystyrene spheres, and the loading amount of spiropyran photochromic materials is increased by the physical confinement effect, and the silicon dioxide protective layer blocks oxygen, moisture and ultraviolet rays, thereby improving the weather resistance of the coating. The light scattering effect of the gully structure and the chemical color change of spiropyran synergistically achieve dual-mode dynamic response of photochromism and structural color, expanding the application scenarios of electrochemical aluminum in anti-counterfeiting encryption and smart packaging. DETAILED DESCRIPTION

[0018] 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.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with the definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0020] Unless otherwise specified, the methods used in the following examples are all conventional methods. Unless otherwise specified, the materials, reagents and instruments used are all conventional materials, reagents and instruments in the art, and can be obtained by those skilled in the art through commercial channels.

[0021] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the present specification and claims, range definitions can be combined and / or interchanged, and if not otherwise stated, these ranges include all subranges contained therein.

[0022] Example 1 This embodiment is the preferred embodiment of the present invention Raw materials and equipment: Preparation of polystyrene microspheres: Styrene monomer (100 mL) Potassium persulfate (0.5 g, initiator) Amphiphilic block copolymer PEG-PPG-PEG (molecular weight 4000, PEG content 60%, 1 g) Deionized water (500 mL) Nitrogen protection device, constant temperature magnetic stirrer, centrifuge Loading of photochromic material: Spiropyran (1',3'-dihydro-8-methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indole] (CAS: 1498-89-1, molecular formula C 20 H 20 N2O4), purity 98%, 5 mg / mL ethanol solution) Ultrasonic cleaner, vacuum drying oven Deposition of silica protective layer: Tetraethoxysilane (TEOS, 99%) CVD reaction chamber (temperature control accuracy ±5°C at 300°C) Coating matrix: Acrylic resin (solid content 40%) Toluene (solvent) Preparation steps: Preparation of polystyrene microspheres with groove structure: Mix styrene monomer, PEG-PPG-PEG, potassium persulfate and deionized water, and react at 70°C with stirring at 500 rpm for 4 hours under nitrogen protection.

[0023] Centrifugally separate, wash 3 times with deionized water, and vacuum dry to obtain polystyrene microspheres with a particle size of 1-5 μm and grooves with a depth of 200 nm and a width of 80 nm on the surface.

[0024] Loading of spiropyran: Immerse the microspheres in the spiropyran ethanol solution, perform ultrasonic treatment at 200W and 40kHz for 30 minutes, centrifuge and wash 3 times, and detect the loading amount by ultraviolet-visible spectroscopy after drying (confirm the loading amount of 8wt% by the peak absorbance).

[0025] Deposition of silica protective layer: Place the microspheres loaded with SP in the CVD reaction chamber, use argon as the carrier gas, introduce TEOS vapor, and react at 300°C for 1 hour to form a 50-nm-thick SiO2 layer.

[0026] Preparation of chromatographic coating: Mix the treated small spheres (10 g) with acrylic resin (90 g), add 200 ml of toluene and stir until uniform to obtain the chromatographic coating.

[0027] Example 2 This example is based on Example 1, the difference is that an amphiphilic copolymer: PEG-PPG-PEG (molecular weight 6000, PEG accounting for 70%) is used; Preparation of polystyrene microspheres with groove structure: Mix styrene monomer, PEG-PPG-PEG, potassium persulfate and deionized water, and stir and react at 75 °C for 4 hours under nitrogen protection.

[0028] Centrifuge and separate, wash 3 times with deionized water, and dry in vacuum to obtain polystyrene microspheres with a particle size of 1-5 μm and grooves with a depth of 300 nm and a width of 100 nm on the surface.

[0029] Comparative Example 1 This comparative example is based on Example 1, without using an amphiphilic block copolymer, and spiropyran is loaded on the outer layer.

[0030] Preparation of polystyrene microspheres: Mix styrene monomer, potassium persulfate and deionized water, and stir and react at 70 °C at 500 rpm for 4 hours under nitrogen protection.

[0031] Centrifuge and separate, wash 3 times with deionized water, and dry in vacuum to obtain polystyrene microspheres with a particle size of 1-5 μm.

[0032] Coating SiO2 shell Disperse polystyrene microspheres (5 g) in ethanol (200 mL), add ammonia water (5 mL), and ultrasonically disperse for 30 minutes; Dropwise add TEOS (10 mL), and stir and react at 30 °C for 6 hours; Centrifuge (8000 rpm, 10 minutes), wash 3 times with ethanol, and dry in vacuum at 50 °C to obtain core-shell microspheres (SiO2 shell thickness 50 nm).

[0033] Immerse the small spheres in a spiropyran ethanol solution, perform ultrasonic treatment at 200 W and 40 kHz for 30 minutes, centrifuge and wash 3 times, and detect the loading amount by ultraviolet-visible spectroscopy after drying (confirm the loading amount of 5 wt% by the peak absorbance).

[0034] Preparation of chromatographic coating: Mix the treated small spheres (10 g) with acrylic resin (90 g), add 200 ml of toluene and stir until uniform to obtain the chromatographic coating.

[0035] Comparative Example 2 On the basis of Example 1, this comparative example did not use the amphiphilic block copolymer, and other conditions remained unchanged.

[0036] Preparation of polystyrene microspheres: Mix styrene monomer, potassium persulfate and deionized water, and react under nitrogen protection at 70 °C with stirring at 500 rpm for 4 hours.

[0037] Centrifuge and separate, wash 3 times with deionized water, and dry in vacuum to obtain polystyrene microspheres with a particle size of 1-5 μm.

[0038] The subsequent steps are the same as those in Example 1 Comparative Example 3 On the basis of Example 1, this comparative example did not perform the protection of silica.

[0039] The difference is that after loading spiropyran, SiO2 coating is not carried out.

[0040] Perform performance tests on the chromatic layer coatings prepared in the above different examples and comparative examples respectively. Spray them on the surface of the aluminized paper substrate, with a liquid film thickness of 50 μm, and then dry at 80 °C for 30 min to obtain the chromatic layer. Conduct discoloration effect test, stability test, service life test, adhesion test and weather resistance test respectively.

[0041] 1. Discoloration effect test: Test method: Use an ultraviolet-visible spectrometer to measure the change in absorbance of the coating before and after illumination.

[0042] Coat the coating on the aluminized paper substrate, and control the coating thickness at 50 μm.

[0043] In a dark room, irradiate the coating with a 365 nm ultraviolet lamp for 5 minutes, and record the change in absorbance.

[0044] Evaluation index: Absorbance change value (ΔA), the larger ΔA is, the more significant the discoloration effect is.

[0045] 2. Stability test Test method: Expose the coating to simulated sunlight (500 W xenon lamp, irradiation intensity 1000 W / m²) and continuously irradiate for 100 hours.

[0046] Measure the discoloration effect (ΔA) every 20 hours.

[0047] Evaluation index: Decay rate (%), calculate the decay percentage of ΔA after 100 hours relative to the initial ΔA. The lower the decay rate, the better the stability.

[0048] 3. Service life test Test method: Conduct 100 discoloration cycles, each cycle including: irradiating with an ultraviolet lamp for 5 minutes, and then recovering in a dark room for 10 minutes.

[0049] Measure ΔA after the 1st and 100th cycles.

[0050] Evaluation index: Performance retention rate (%), that is, the ratio of ΔA after the 100th cycle to the 1st ΔA. The higher the retention rate, the longer the service life.

[0051] 4. Adhesion test Test method: Adopt the cross-cut method (GB / T 9286-1998) to draw 100 squares of 1mm×1mm on the coating.

[0052] Stick with tape and then tear it off to observe the coating peeling situation.

[0053] Evaluation index: Percentage of peeling area. The smaller the peeling area, the better the adhesion.

[0054] 5. Weather resistance test Test method: Use a QUV accelerated aging test chamber (UVA-340 lamp tube, 60°C, 1000 hours).

[0055] Measure ΔA every 200 hours.

[0056] Evaluation index: ΔA retention rate after 1000 hours. The higher the retention rate, the better the weather resistance.

[0057] The test results are shown in the following table:

[0058] Compared with Comparative Example 1 and Comparative Example 2, the gully microstructure significantly improves the loading amount of spiropyran (8wt% vs. 5wt%) and the adhesion stability. This makes the discoloration effect stronger (ΔA up to 1.2-1.3 vs. 0.8-1.0) and the stability better (attenuation rate 7-8% vs. 25-30%).

[0059] Compared with Comparative Example 3, the silica protection layer effectively protects spiropyran, significantly reducing the photo-degradation and aging effects (attenuation rate 7-8% vs. 35%, weather resistance retention rate 85-87% vs. 50%). This proves the key role of the protection layer in improving stability and service life.

[0060] Compared with the traditional method (Comparative Example 1), through the synergistic effect of the gully microstructure and the silica protection layer, the present invention has significant improvements in terms of color-changing effect (ΔA increased by more than 50%), stability (attenuation rate reduced by about 70%), and service life (performance retention rate increased by about 30%).

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A color-changing aluminized layer coating, characterized in that, The chromatographic coating contains small spheres loaded with a color-changing material. The small spheres are polystyrene small spheres, and their surfaces have a gully microstructure formed by an amphiphilic block copolymer. The gully microstructure is loaded with a photochromic material, and a silica protection layer covers the surface of the small spheres.

2. The discoloring aluminized paper color layer coating according to claim 1, characterized in that, The amphiphilic block copolymer is polyethylene glycol-polypropylene glycol-polyethylene glycol, with a molecular weight of 2000-10000, and the PEG segment accounts for 50-70% of the total mass of the copolymer.

3. The color-changing aluminized color layer coating according to claim 1, characterized in that The photochromic material is a spiropyran compound.

4. The electrochromic aluminum color layer coating according to claim 1, characterized in that, The particle size of the polystyrene small spheres is 1-5 μm.

5. The electrochromic aluminized color layer coating according to claim 1, characterized in that The thickness of the silica protection layer is 10-100 nm.

6. A method for preparing the color-changing electroaluminum color layer coating according to any one of claims 1-5, characterized in that, It includes the following steps: Step 1: Synthesize polystyrene small spheres by emulsion polymerization in the presence of an amphiphilic block copolymer, and control the reaction conditions so that a gully microstructure with a depth of 100-500 nm and a width of 50-200 nm is formed on the surface of the small spheres; Step 2: Load the photochromic material into the gully microstructure; Step 3: Cover a silica protection layer with a thickness of 10-100 nm on the surface of the small spheres after loading the color-changing material; Step 4: Disperse the treated small spheres in an aluminized chromatic coating matrix at a ratio of 1-20 wt% to prepare a color-changing aluminized chromatic coating.

7. The method according to claim 6, wherein In the emulsion polymerization method, the polymerization reaction is carried out at 70 °C for 4 h under nitrogen protection.

8. The method according to claim 6, wherein The loading of the photochromic material is carried out by the impregnation method, including immersing the small spheres in an ethanol solution of the photochromic material, followed by ultrasonic treatment, centrifugation, washing, and drying.

9. The method according to claim 6, characterized in that, The silica protection layer is prepared by chemical vapor deposition, including placing the small spheres in a CVD reaction chamber, using tetraethoxysilane as a precursor, and reacting at 300 °C for 1 h.

10. The method according to claim 6, wherein The aluminized chromatic coating matrix is an acrylic resin, and the mass ratio of the treated small spheres to the acrylic resin is 1:9.

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