A nano-color paste for color-changing film

Abstract

The present invention relates to a nano-color paste for a color-changing film, wherein the nano-color paste comprises the following components, measured in parts by weight: 1 to 10 parts by weight of a pigment; 10 to 30 parts by weight of an aqueous polyurethane acrylate emulsion; 2 to 10 parts by weight of nano-oxide particles; 3 to 15 parts by weight of a polyaldehyde resin; 1 to 10 parts by weight of an alkylphenol polyvinyl ether; 15 to 35 parts by weight of ethyl acetate; and 1 to 5 parts by weight of methyl isobutyl ketone. The nano-color paste in the embodiment of the present invention significantly improves various physical and optical properties of the color-changing film prepared.

Description

Technical Field

[0001] The present invention relates to the preparation and application of a composite material, and in particular to a nano-color paste for a color-changing film. Background Art

[0002] With the rapid development of various industries, the market demand for personalized products for the same products is becoming more and more extensive. Consumers often hope to bring novelty and richer changes to the products they use on the basis of pursuing the basic functions of the products. For example, in the automotive market or other product markets that focus on appearance, the use of films with various colors can change the overall or partial appearance of the product by covering and pasting it as a whole. Color-changing films are mainly attached to the surface of the product through polymer materials. The super flexibility brought by the various components of the polymer products can achieve the ideal tortuosity on any curved surface. For the household automobile industry, color-changing films can fully express the soft texture of the car body's curved surface, are easy to remove, do not damage the original car paint, leave no residual glue, and do not have any toxic side effects on the paint surface, the human body, or nature, making them green and environmentally friendly.

[0003] However, the physical and optical properties of color-changing films have always been a hot topic in the field of product research and development. How to manufacture color-changing film products with good mechanical properties, durability, and good scintillation properties deserves attention. For example, Chinese patent publication CN114752158A provides a method for preparing a color-changing film. Although this type of technology reports that some properties of the color film have been improved, it does not conduct detailed research and reports on the core component pigment composition or color paste of the color film, nor does it further improve the physical and color properties of the color film. The color-changing film also does not obtain good anti-scratch or desorption properties. Summary of the Invention

[0004] The present invention aims to solve one or more deficiencies in the above-mentioned prior art.

[0005] According to a first aspect of the present invention, there is provided a nano-color paste for a color-changing film, wherein the nano-color paste comprises the following components in parts by weight:

[0006] 1 to 10 parts by weight of a pigment;

[0007] 10 to 30 parts by weight of an aqueous polyurethane acrylate emulsion;

[0008] 2 to 10 parts by weight of nano-oxide particles;

[0009] 3 to 15 parts by weight of polyaldehyde resin;

[0010] 1 to 10 parts by weight of alkylphenol polyethylene ether;

[0011] 15 to 35 parts by weight of ethyl acetate;

[0012] 1 to 5 parts by weight of methyl isobutyl ketone.

[0013] In a further preferred embodiment, the nano-oxide particles are titanium dioxide nano-oxide particles, and preferably, the average particle size of the titanium dioxide nano-oxide particles is 60 to 80 nanometers; and

[0014] The aqueous polyurethane acrylate emulsion is an aqueous polyurethane acrylate emulsion containing lignin.

[0015] In a further preferred embodiment, the pigment is selected from one or more of iron oxide red, iron oxide yellow, iron oxide black, royal blue, scarlet powder, titanium dioxide, ultramarine blue, phthalocyanine blue and phthalocyanine green pigments.

[0016] In an optional technical solution, the aqueous polyurethane acrylate emulsion containing lignin is prepared by the following method:

[0017] In a reaction vessel capable of heating and stirring, 500 to 700 grams of dicyclohexylmethane diisocyanate, 80 to 120 grams of polyneopentyl adipate, 90 to 130 grams of polyethylene glycol, 25 to 30 grams of 2,2-bis(hydroxymethyl)propionic acid, 40 to 50 grams of N-ethylpyrrolidone, and 20 to 30 grams of lignin are added; then 0.1 to 0.5 grams of dibutyltin dilaurate is added as a catalytic component, and a pre-reaction is carried out at 60 to 75° C. for 1 to 2 hours; after the pre-reaction is completed, 300 to 500 grams of versatate glycidyl carbonate, 80 to 150 grams of 2-hydroxyethyl acrylate, and 10 to 20 grams of lignin are added again, and the mixture is reacted at 85 to 95° C. for 1 to 2 hours under stirring. Subsequently, the temperature of the reaction mixture is lowered to below 40° C., and then a sodium hydroxide solution is added for neutralization. Subsequently, 1000 to 1800 grams of deionized water is added and the mixture is fully stirred. The reaction product is then removed to obtain a waterborne polyurethane acrylate emulsion containing lignin.

[0018] In an optional technical solution, the weight average molecular weight of the added lignin is between 500 and 800; and

[0019] Based on the total mass of the nano-color paste for the color-changing film, the aqueous polyurethane acrylate emulsion containing lignin accounts for 20 wt % to 30 wt % of the total mass.

[0020] The second aspect of the present invention further provides a color-changing film, which contains the nano-color paste for color-changing film as described in the above technical solution.

[0021] In an optional solution, the color-changing film is prepared by the following process steps:

[0022] Add 80 to 150 parts by weight of PVC powder to a container, then add 20 to 100 parts by weight of diisononyl phthalate as a plasticizer, and stir at a speed of 60 to 200 r / min for 5 to 20 minutes;

[0023] Continue to add 0.05-0.5 parts by weight of antioxidant and 5 to 6 parts by weight of the nano-color paste for color-changing film into the container, and stir at a speed of 100-300 r / min for 5 to 20 minutes;

[0024] The container is vacuumed to reduce the pressure in the preparation container to 0.01 to 0.08 MPa, and stirring is continued at 50 to 200 r / min for 10 to 30 minutes to obtain the PVC coating material for use;

[0025] A 30 to 60 μm thick PET protective film is selected, and a layer of 100-120 μm thick PVC coating material is evenly coated on the protective film as a PVC core layer by slit coating to obtain a laminate;

[0026] The laminate was sequentially passed through a three-stage oven with temperatures of 80°C, 90°C, and 60°C for drying and curing, and then rolled up for later use;

[0027] Laminating a layer of calendered PVC base film on one side of the PVC core layer by heating and laminating;

[0028] An acrylic pressure-sensitive adhesive layer is coated on one side of the PVC base film by slit extrusion coating for lamination, and the dry adhesive thickness is controlled at (30-60 μm) ± 0.5 μm, and the color-changing film is rolled up.

[0029] The nano-color paste and color-changing film products obtained according to this embodiment are particularly suitable for combining with PVC base film to form a color-changing film. They have good bonding and physical parameter characteristics for plastic products, and significantly improve the mechanical properties and optical properties of the film surface. This will be described in more detail below.

[0030] Hereinafter, the technical solutions and advantages of the present invention will be explained and described in more detail in conjunction with specific embodiments. It should be understood that the contents presented in the specification and specific embodiments are only for the purpose of more clearly illustrating the technical solutions and advantages of the present invention, and do not limit the scope of protection of the present invention. Those skilled in the art can, based on the disclosure of the specification, obtain modified technical solutions based on various reasonable transformations. As long as they do not depart from the spirit of the present invention, the various modified technical solutions should be understood to be included in the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solution of the present disclosure and constitute a part of the specification. Together with the specific embodiments of the present application, they are used to explain the technical solution of the present disclosure and do not constitute a limitation on the technical solution of the present disclosure.

[0032] Figure 1 Schematic diagram of each layer of the cross section of the nano-color paste color-changing film produced according to the embodiment and manufacturing example of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in more detail below to facilitate understanding of the invention.

[0034] Before describing the specific embodiments, it should be noted that those skilled in the art can select appropriate raw materials based on the inspiration and teachings of this disclosure, and use relevant testing equipment to perform relevant tests and obtain corresponding results. For raw materials for which the specific manufacturer or route is not specified, those skilled in the art can select raw materials that meet the corresponding requirements as reaction starting materials based on the disclosure and requirements of this specification. The reaction raw materials of the process compounds are derived from the initial products synthesized in the previous steps of the present invention, which is also understandable based on this disclosure.

[0035] First, Table 1 lists the main raw materials used in the present invention and their corresponding acquisition channels or raw material production areas. It should be noted that the raw materials not described in the present invention are raw material varieties that can be obtained by those skilled in the art based on common technical knowledge and existing market products.

[0036] Table 1: Sources of some raw materials used in this invention

[0037]

[0038]

[0039] The inventors first describe some of the testing conditions and methods for the color-changing film containing the color paste components of the present invention. In fact, in this field, ordinary technicians know how to test and characterize the characteristics and data of each color-changing film.

[0040] 1. Flashing effect

[0041] The sparkle effect of the color-changing film is one of the parameters that characterizes whether the color-changing film is smooth, bright, and has a good appearance. A good sparkle effect has a good market-aiding effect in certain applications of color-changing films, especially in changing the color of automobile surfaces. Regarding a measurement system of this type of measuring device, the Byk-mac system provided by the German company Byk-Gardner GmbH can be used. It can measure the degree of sparkle for sheet materials. Under the characterization system of this system, the sparkle level is a function of the following two parameters: the sparkle area, which corresponds to the number of light reflections in a specified measurement; and the sparkle intensity, which corresponds to the intensity of the light reflection. The sparkle level is usually expressed as a number between 0 (basically no sparkle) and 10 (the highest degree of sparkle).

[0042] 2. Pencil hardness test

[0043] For the film surface containing color paste that is exposed to the external environment in actual use, pencils of different hardness are used as scratching tools (typical pencil hardness can include 6B, 5B, 4B, 3B, 2B, B, HB, H, 2H, 3H, 4H, 5H and other levels). On the simulated assembled color-changing film sample without surface release film or protective film, 1200 grams of force is applied in a 45° direction, with a stroke of 15 mm, and 3 scratches are made at different positions. The appearance of the sample is observed to see if there are obvious scratches. The hardest pencil number that cannot scratch the paint film is the hardness of the paint film.

[0044] 3. Adhesion test

[0045] Test method: For the film surface containing color paste that is exposed to the external environment in actual use, use the back of a scalpel to scratch 8-9 times on the coating, with at least two scratches at a 90° angle to the other scratches, to form a grid on the surface with a side length of 2-3 mm. Make sure that each scratch cuts into the base material (bottom layer PVC). Brush 5 times in each direction along the scratch. Put 3M tape (3M TM VHB TM Stick the tape on the surface and press it with your fingertips to ensure close contact with the test layer. After 5 minutes, peel off the tape regularly from the free end at an angle of 60° within 1-1.5 seconds;

[0046] Level classification:

[0047] Level 0: The edges of the cut are completely smooth and none of the grid squares are peeling off;

[0048] Level 1: The area of ​​the peeling portion is no more than 5% of the area of ​​the tape in contact with the surface;

[0049] Level 2: The area of ​​the peeled portion is greater than 5% of the area of ​​the tape in contact with the surface, but not more than 15%;

[0050] Level 3: The area of ​​the peeled portion is greater than 15% of the area of ​​the tape in contact with the surface, but not more than 35%;

[0051] Level 4: The area of ​​the peeled portion is greater than 35% and not more than 65% of the area of ​​the tape in contact with the surface.

[0052] 4. Wear resistance test

[0053] Similar to the test object mentioned above, the JM-V abrasion tester provided by Shenzhen Xiangmin Instrument Co., Ltd. was used to grind the surface of the installed color-changing film under the action of 200 grams of force, and the number of times (number of turns) the rubber wheel rotated when the coating was exposed to the base material was recorded.

[0054] The test methods and processes used in the embodiments of the present invention and the comparative experiments will be described together with the description of the embodiments as necessary. Those skilled in the art will be able to understand and implement the corresponding processes and tests based on the contents disclosed in the specification.

[0055] In embodiments of the present invention, a composition or a process step may comprise the components / steps described and may also have other components or steps. However, it may be preferred that the composition or method described in the embodiments of the present invention consists only of the steps described and does not include other components (except for unavoidable impurities or conventional processing steps). For example, the nanocolor paste composition of the embodiments of the present invention may comprise the components described and may also have other auxiliary components; however, preferably, the nanocolor paste composition of the present invention consists only of the components described and does not significantly include other components or chemicals.

[0056] Preparation Example 1

[0057] As one of the elements of this embodiment, a process for preparing a waterborne polyurethane acrylate emulsion containing lignin is first described herein.

[0058] This preparation example describes a typical method for preparing a waterborne polyurethane acrylate emulsion containing lignin. 600 g of dicyclohexylmethane diisocyanate (HDI) was added to a reactor equipped with a stirring blade and a peripheral cooling water pipe. 12MDI), 100 g of polyneopentyl adipate, 100 g of polyethylene glycol, 25 g of 2,2-bis(hydroxymethyl)propionic acid, 45 g of N-ethylpyrrolidone, and 25 g of lignin; then, 0.2 g of dibutyltin dilaurate was added as a catalyst component, and the mixture was reacted at 70° C. for 1 hour. After the pre-reaction stage was completed, 400 g of versatate glycidyl ester, 100 g of 2-hydroxyethyl acrylate, and 15 g of lignin were added, and the mixture was reacted at 90° C. for 1 hour (at this time, the residual isocyanate content was less than 0.05 wt %). The temperature of the reaction mixture was lowered to below 40° C., and then, 10 g of a 15 wt % sodium hydroxide solution was added for neutralization. Then, 1300-1500 g of water was added and the mixture was stirred thoroughly. The reaction product was then removed to obtain a waterborne polyurethane acrylate emulsion containing lignin (the product solid content was approximately 37 wt %).

[0059] In the actual preparation process, according to different scenarios of industrial production and laboratory testing, the usage of each component can be proportionally expanded or reduced, or appropriately adjusted within the scope of use.

[0060] Example

[0061] This embodiment introduces a (nano) color paste composition suitable for use in color-changing films. In this embodiment, the composition typically comprises the following components (calculated in parts by weight):

[0062] Example 1:

[0063] 5 parts by weight of phthalocyanine green pigment (BASF Green L8730), 15 parts by weight of the aqueous polyurethane acrylate emulsion containing lignin described in the preparation example, 4 parts by weight of nano-titanium dioxide, 8 parts by weight of polyaldehyde resin, 5 parts by weight of alkylphenol polyvinyl ether, 33 parts by weight of ethyl acetate, and 5 parts by weight of methyl isobutyl ketone (MIBK) as components of the nano-colorant composition. The nano-titanium dioxide has an average particle size of 60-80 nanometers.

[0064] In a typical preparation process, the preparation process of the color paste composition includes the following steps:

[0065] Step 1) The determined components of the aqueous polyurethane acrylate emulsion containing lignin, polyaldehyde resin, alkylphenol polyvinyl ether, ethyl acetate and methyl isobutyl ketone are stirred and mixed at a temperature of 45° C. to 55° C.;

[0066] Step 2) adding phthalocyanine green pigment and nano titanium dioxide and preliminarily mixing them at a stirring speed of 100-200 rpm;

[0067] Step 3) The preliminarily mixed materials are fed into a centrifugal sander, and 0.5-0.6 mm zirconium dioxide is used as a medium grinding ball to fully grind and mix the above mixture for 2-5 hours to finally obtain a nano-color paste composition used for the color-changing film.

[0068] In the following examples, the same preparation process as in Example 1 was used, with only some adjustments made to the composition ratio of the raw materials, as shown in Table 2.

[0069] Table 2: Raw material ratios of the nano-color paste compositions of some examples

[0070]

[0071]

[0072] Comparative Example 1

[0073] In Comparative Example 1, the same raw materials and color paste preparation process as in Example 1 were used, but the difference was that the ratio of each raw material was changed, and the content of the aqueous polyurethane acrylate emulsion containing lignin was significantly reduced (accounting for less than 10% by weight of the total composition). Specifically,

[0074] 5 parts by weight of phthalocyanine green pigment (BASF Green L8730), 5 parts by weight of the aqueous polyurethane acrylate emulsion containing lignin described in the preparation example, 2 parts by weight of nano-titanium dioxide, 10 parts by weight of polyaldehyde resin, 5 parts by weight of alkylphenol polyvinyl ether, 35 parts by weight of ethyl acetate, and 5 parts by weight of methyl isobutyl ketone (MIBK) as components of the nano-colorant composition. The nano-titanium dioxide has an average particle size of 60-80 nanometers.

[0075] Comparative Example 2

[0076] Similarly, in Comparative Example 2, the same raw material types and color paste preparation process as in Example 1 were used, but the difference was that the ratio of each raw material was changed, and the content of the aqueous polyurethane acrylate emulsion containing lignin was significantly increased (accounting for more than 30% by weight of the total composition). Specifically,

[0077] 5 parts by weight of phthalocyanine green pigment (BASF Green L8730), 35 parts by weight of the aqueous polyurethane acrylate emulsion containing lignin described in the preparation example, 2 parts by weight of nano-titanium dioxide, 10 parts by weight of polyaldehyde resin, 5 parts by weight of alkylphenol polyvinyl ether, 35 parts by weight of ethyl acetate, and 5 parts by weight of methyl isobutyl ketone (MIBK) as components of the nano-colorant composition. The nano-titanium dioxide has an average particle size of 60-80 nanometers.

[0078] Comparative Example 3

[0079] Comparative Example 3 uses a component ratio and process similar to Example 1. The difference is that in the component ratio of the color paste emulsion used in Comparative Example 3, the aqueous polyurethane acrylate emulsion containing lignin is not used, but cellulose acetate butyrate in the same weight parts is used instead.

[0080] Comparative Example 4

[0081] Comparative Example 4 uses the same component ratio and process as Example 1. The difference is that in the aqueous polyurethane acrylate emulsion containing lignin used in Comparative Example 4, the lignin component used has a larger average molecular weight of 1500.

[0082] Comparative Example 5

[0083] Comparative Example 5 uses the same component ratio and process as Example 1. The difference is that the nano-titanium dioxide material used in Comparative Example 5 has an average particle size of 25 nanometers.

[0084] Application Manufacturing Examples

[0085] Following the examples and comparative examples, the inventors further elaborate and describe, by way of example, the manufacturing process for a color-changing film using the nano-colorant paste of the embodiments and comparative examples of the present invention. The test structures mentioned in this specification are based on the color-changing film manufactured using the nano-colorant paste of this exemplary manufacturing example. However, it should be noted that the present invention is not limited to a single color-changing film manufacturing process.

[0086] In typical color-changing film structures and products (see Figure 1 ), comprising a PVC core layer 100 having a color-changing paste, a temporary protective layer 101 (a release film that can be removed after application to increase the color effect of the core layer) is directly provided on the upper surface of the PVC core layer 100; a PVC bottom layer 102 (which can be a common calendered PVC layer) can be provided under the PVC core layer 100, and an adhesive layer 103 (which can be provided as a pressure-sensitive adhesive) can also be provided under the PVC bottom layer 102. If the color-changing film needs to be stored for a long time without use, an adhesive protective layer (not shown) can also be optionally provided under the adhesive layer 103. A typical preparation process containing the nano-modified color paste of the present invention is as follows.

[0087] Add 100 parts of PVC powder to a container, then add 30 to 80 parts of diisononyl phthalate (DINP) plasticizer, and stir at a speed of 100 r / min for 10 minutes.

[0088] 0.1 parts by weight of an antioxidant (Songnox 1010) and 5 to 6 parts of the color paste composition prepared in the examples or comparative examples were then added to the container, and the mixture was stirred at a speed of 200 r / min for 10 minutes.

[0089] The preparation environment was vacuumed to reduce the air pressure in the preparation container to 0.05 MPa, and the equipment was slightly heated to a temperature of 35 to 40° C., and stirring was continued at 100 r / min for 20 minutes to obtain a PVC coating for use.

[0090] A 50 μm thick PET protective film is selected (as a temporary protective layer 101, which can be removed when the actual product is used or tested). A layer of PVC coating with a thickness of 100-120 μm (i.e., PVC core layer 100, which has the PVC material containing the above-mentioned experimental color paste component) is evenly coated on the protective film by slit coating.

[0091] The laminate was sequentially passed through a three-stage oven with temperatures of 80°C, 90°C, and 60°C for drying and curing, and then rolled up for later use.

[0092] A layer of calendered PVC bottom film (as the PVC bottom layer 102 ) is laminated on one side of the PVC core layer 100 by heating and laminating.

[0093] An acrylic pressure-sensitive adhesive layer was applied to one side of the PVC base film of the prepared film by slit extrusion coating (as adhesive layer 103 ), the dry adhesive thickness was controlled at 50±0.5 μm, and the film was rolled up to obtain a finished product.

[0094] If long-term storage is required, a release protective film (not shown in the figure) can be optionally set again under the adhesive layer 103. If it is used in the short term, this process can also be omitted, and the prepared finished film can be directly rolled up for transportation, storage or use.

[0095] Test Case

[0096] By applying the solutions of each preparation example, embodiment, and comparative example to the manufacturing example described above, the test results of the color-changing film described in this embodiment can be obtained. The corresponding test results are shown in Table 3 below:

[0097] Table 3: Characteristics of color-changing films prepared from the color paste products of the examples and comparative experiments

[0098] Flicker Level Hardness test Adhesion Wear resistance test (circle) Example 1 8 3H Level 0 755 Example 2 7 3H Level 0 742 Example 3 7 3H Level 0 760 Example 4 7 2H Level 1 715 Comparative Example 1 6 B Level 2 688 Comparative Example 2 5 2H Level 0 720 Comparative Example 3 5 2B Level 3 575 Comparative Example 4 5 B Level 2 690 Comparative Example 5 4 2H Level 0 704

[0099] In the embodiments that all have good glittering properties of the color-changing film, the inventors found that when the mass content of the aqueous polyurethane acrylate emulsion containing lignin in the color film component is close to 20wt%, the glittering effect is better, and when the mass of the aqueous polyurethane acrylate emulsion is significantly greater than 30%wt, a certain degree of decline occurs; the inventors believe that they are not bound by any theory, but infer that this may be related to the high adhesion of the aqueous polyurethane acrylate emulsion containing lignin. Therefore, in an embodiment of the present invention, it is preferred that the mass of the aqueous polyurethane acrylate emulsion containing lignin in the color film component accounts for 20wt% to 30wt% of the total mass of the total color film component; in addition, when the average particle size of titanium dioxide is too small (less than 50nm), the glittering effect decreases, which is not preferred for certain applications of the color-changing film, such as the modification of private cars, because the market and customers usually need to improve the less bright surface of the original car paint, so the reflection effect of high metallic luster is more preferred. In terms of hardness testing, the color film containing a specific lignin component using the specific color paste component of the present invention shows excellent anti-scratch performance. When the formula of the present invention is not used, or the size and content of the lignin used are not good, the anti-scratch performance is reduced. Similarly, the modified color paste of the aqueous polyurethane acrylate emulsion containing lignin according to the embodiment of the present invention has good adhesion and wear resistance. In the embodiment of the present invention, for example, the molecular weight of lignin is greater than 500, but preferably between 500-800, and the average particle size of nano titanium dioxide is better between 50-100 nanometers. The nano color paste of this embodiment is particularly suitable for combining with a PVC base film to form a color-changing film, and it has good bonding and physical parameter characteristics for plastic products.

[0100] According to the embodiments and technical contents recorded in the specification of the present invention, the present invention can at least provide the following technical solutions: Although the present disclosure includes specific embodiments, it is obvious to those skilled in the art that various formal and detailed replacements or changes can be made to these embodiments without departing from the gist and scope of the invention of the present claims and their equivalent technical solutions. The embodiments described herein should be considered to be illustrative only and not for the purpose of limitation. The description of the features and aspects in each embodiment is considered to be applicable to similar features and aspects in other embodiments. Therefore, the scope of the present disclosure should not be limited by the specific description, but by the technical solutions of the claims, and all changes within the scope of the claims and their equivalents are interpreted as being included within the technical solutions of the present disclosure.

Claims

1. A nano-color paste for color-changing film, characterized in that: The nano color paste is composed of the following components in parts by weight: 1 to 10 parts by weight of a pigment; 10 to 15 parts by weight of an aqueous polyurethane acrylate emulsion containing lignin; 2 to 10 parts by weight of titanium dioxide nanoparticles; 3 to 15 parts by weight of polyaldehyde resin; 1 to 10 parts by weight of alkylphenol polyethylene ether; 15 to 35 parts by weight of ethyl acetate; 1 to 5 parts by weight of methyl isobutyl ketone; and The average particle size of the titanium dioxide nanoparticles is 60 to 80 nanometers; and the aqueous polyurethane acrylate emulsion containing lignin is prepared by the following method: In a reaction vessel capable of heating and stirring, 500 to 700 grams of dicyclohexylmethane diisocyanate, 80 to 120 grams of polyneopentyl adipate, 90 to 130 grams of polyethylene glycol, 25 to 30 grams of 2,2-bis(hydroxymethyl)propionic acid, 40 to 50 grams of N-ethylpyrrolidone, and 20 to 30 grams of lignin are added; then 0.1 to 0.5 grams of dibutyltin dilaurate is added as a catalytic component, and a pre-reaction is carried out at 60 to 75° C. for 1 to 2 hours; after the pre-reaction is completed, 300 to 500 grams of versatate glycidyl carbonate, 80 to 150 grams of 2-hydroxyethyl acrylate, and 10 to 20 grams of lignin are then added, and the mixture is reacted at 85 to 95° C. for 1 to 2 hours under stirring. Subsequently, the temperature of the reaction mixture is lowered to below 40° C., and then sodium hydroxide solution is added for neutralization. Subsequently, 1000 to 1800 grams of deionized water is added and the mixture is thoroughly stirred. The reaction product is then removed to obtain a waterborne polyurethane acrylate emulsion containing lignin. wherein the weight average molecular weight of the added lignin is between 500 and 800; and Based on the total mass of the nano-color paste for the color-changing film, the aqueous polyurethane acrylate emulsion containing lignin accounts for 20 wt % to 30 wt % of the total mass.

2. The nano-color paste for color-changing film according to claim 1, characterized in that: The pigment is selected from one or more of iron oxide red, iron oxide yellow, iron oxide black, royal blue, scarlet pink, ultramarine blue, phthalocyanine blue and phthalocyanine green.

3. A color-changing film, characterized in that: The color-changing film contains the nano-color paste for color-changing film according to any one of claims 1 to 2.

4. The color-changing film according to claim 3, characterized in that: The color-changing film is prepared by the following process steps: Add 80 to 150 parts by weight of PVC powder to a container, then add 20 to 100 parts by weight of diisononyl phthalate as a plasticizer, and stir at a speed of 60 to 200 r / min for 5 to 20 minutes; Continue to add 0.05-0.5 parts by weight of antioxidant and 5 to 6 parts by weight of the nano-color paste for color-changing film into the container, and stir at a speed of 100-300 r / min for 5 to 20 minutes; The container is vacuumed to reduce the pressure in the preparation container to 0.01 to 0.08 MPa, and stirring is continued at 50 to 200 r / min for 10 to 30 minutes to obtain the PVC coating material for use; A 30 to 60 μm thick PET protective film is selected, and a layer of 100-120 μm thick PVC coating material is evenly coated on the protective film as a PVC core layer by slit coating to obtain a laminate; The laminate was sequentially passed through a three-stage oven with temperatures of 80°C, 90°C, and 60°C for drying and curing, and then rolled up for later use; Laminating a layer of calendered PVC base film on one side of the PVC core layer by heating and laminating; The acrylic pressure-sensitive adhesive layer is coated on one side of the PVC base film by slit extrusion coating, and the film is laminated. The thickness of the dry adhesive is controlled at 30-60 μm, and the film is rolled up to obtain the color-changing film.

Images