Automobile color changing film and preparation method thereof

Abstract

The invention discloses an automobile color changing film and a preparation method thereof, and belongs to the technical field of protective films. The technical problem that an existing automobile color changing film is prone to layering due to dry type compounding is solved. According to the technical scheme, the pearly-luster layer is coated through a comma scraper method, the dry face of the pearly-luster layer is compounded with an uncured polyurethane elastomer film, and the solvent residual face of the pearly-luster layer is compounded with a bottom color layer. The method has the beneficial effects that unreacted groups are reserved on the surface of the cast film through the uncured polyurethane elastomer particles, the groups can generate a chemical adsorption effect with the pearly-luster layer, and meanwhile, solvent molecules on a solvent residual surface are diffused in a polymer of the ground color layer, so that a wetting effect on the ground color layer is achieved; therefore, the interlayer adhesive force is improved, and the layering phenomenon can be effectively avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of protective films, and in particular relates to a car color-changing film and a preparation method thereof. Background Art

[0002] In the automotive market, consumers have a relatively limited range of choices in terms of body color. This is because manufacturers usually only provide a few standard colors in order to control costs and improve efficiency. However, the emergence of car color change films has changed this situation, not only providing a richer range of color choices, but also protecting the original car paint.

[0003] Car color-changing films can be divided into many types in terms of appearance effects, including glossy films, matte films, pearlescent films, metal films, etc. Among them, pearlescent films contain pearlescent powder, which is usually composed of one or more metal oxides coated on a flaky substrate. Its thickness is generally hundreds of nanometers to several microns, and its diameter is between tens of microns and hundreds of microns. Pearlescent powder can reflect and refract incident light, thereby producing a visual effect similar to pearl-like luster. For example, CN118725761A discloses a TPU color-changing car cover film and a preparation method. By designing a pearlescent coating with a TPU base color layer, the absorption, reflection and refraction of light can be achieved, and a very rich variety of different dazzling pearlescent effects can be achieved. Even dark vehicles such as black and blue can achieve a dazzling effect. However, due to the addition of pearlescent powder, if the coating technology of the pearlescent coating is not mature enough, such as uneven coating, too fast or too slow coating speed, etc., the coating surface may appear uneven. This poor surface flatness will have a negative impact on the functional effect of the self-repairing coating coated on the pearlescent coating.

[0004] In order to avoid affecting the functional coating, the color-changing layer can be placed under the substrate. However, the adhesion between the color-changing layer and the substrate needs to be considered, especially when the color-changing layer and the substrate are dry-laminated. If the adhesion is insufficient, delamination may occur, which will affect the service life, durability and aesthetics of the product. Summary of the invention

[0005] In view of the problems of the prior art, the purpose of the present invention is to provide a method for preparing a car color changing film, in which the dry surface of the pearlescent layer is compounded with an unripened polyurethane elastomer film to improve the adhesion between the pearlescent layer and the substrate layer, and the solvent residual surface of the pearlescent layer is compounded with a base color layer to wettably affect the base color layer, thereby effectively avoiding stratification.

[0006] To achieve the above purpose, the present invention adopts the following technical scheme: a method for preparing a car color-changing film, comprising the following steps:

[0007] (1) uniformly mixing a polyurethane elastomer melt with a solvent, an additive, and pearl powder to obtain a pearl powder coating; coating the pearl powder coating on the surface of the first release film by a comma scraper method, and drying to obtain a pearl layer;

[0008] (2) casting the polyurethane elastomer particles into a substrate layer, laminating one side of the substrate layer with a PET substrate film, and compounding the other side of the substrate layer with the pearlescent layer obtained in step (1), and rolling up to obtain a pearlescent semi-finished product;

[0009] (3) coating the base color coating on the surface of the second release film by a comma scraper method, and drying to obtain a base color layer;

[0010] (4) removing one side of the first release film from the pearlescent semi-finished product obtained in step (2), compounding the semi-finished product with the base color layer, and rolling the semi-finished product to obtain the base color semi-finished product;

[0011] (5) The functional coating is applied to one side of the PET substrate film of the base color semi-finished product obtained in step (4), and the functional coating is dried and cured to obtain a functional coating, which is then compounded with an optical-grade PET protective film; the pressure-sensitive adhesive is applied to the third release film, and the pressure-sensitive adhesive layer is obtained after drying, and the pressure-sensitive adhesive layer is compounded with the side of the base color semi-finished product with the second release film torn off, and the car color-changing film is obtained after aging.

[0012] Furthermore, the pearlescent powder is composed of mica coated with metal oxide, and the particle size is 80 to 1000 meshes.

[0013] Furthermore, the thickness of the substrate layer is 90 to 130 μm; the thickness of the pearlescent layer is 15 to 45 μm; and the thickness of the base color layer is 12 to 15 μm.

[0014] Furthermore, in step (1), the amount of pearlescent powder used is 0.01% to 1% of the mass of the polyurethane elastomer melt.

[0015] Furthermore, in step (1), the auxiliary agent includes a leveling agent, a dispersant and a lubricant.

[0016] Furthermore, in step (1), the lubricant is one or more of methyl silicone oil, ethyl silicone oil, and benzyl silicone oil.

[0017] Furthermore, in step (1), the solvent consists of a solvent having a relative volatility of 5 or more and a solvent having a relative volatility of 1 or less.

[0018] Furthermore, the mass ratio of the solvent having a relative volatility of 5 or more to the solvent having a relative volatility of 1 or less is 3 to 5:1.

[0019] Furthermore, in step (5), the aging is performed at 45 to 50° C. for 5 to 6 days.

[0020] A car color-changing film is prepared by the above method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The combination of multiple solvents with different relative volatilization rates is conducive to increasing the solvent residual rate during the drying process of the pearlescent layer, and the solvent residual rate is 1.5% to 3%. The top of the pearlescent layer is dried to form a dry surface of the pearlescent layer that is composited with the substrate layer. The physical barrier of the pearlescent powder is used to retain the solvent at the bottom of the pearlescent layer to form a solvent residual surface of the pearlescent layer that is composited with the base layer; the unreacted groups are retained on the surface of the unripened polyurethane elastomer particle cast film, and these groups can chemically adsorb with the pearlescent layer to improve the adhesion; the solvent molecules on the solvent residual surface of the pearlescent layer diffuse inside the base layer polymer, thereby improving the wettability of the base layer and facilitating the improvement of interlayer adhesion;

[0023] (2) Most solvents evaporate quickly, and the pearlescent powder is arranged in different orientations, so that the car color-changing film has a pearlescent effect on different planes. The pearlescent powder is composed of pearlescent powders of various particle sizes, which ensures that the pearlescent light is shiny while having a certain covering ability for the base color. In addition, lubricants are added to prevent the rapid evaporation of solvents from causing a decrease in molecular density, thereby promoting the cross-linking reaction. Since the friction between the molecular chains is reduced, it will not affect the orientation of the pearlescent powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the car color changing film of the present invention;

[0025] Among them, 1. Optical grade PET protective film; 2. Functional coating; 3. Base material layer; 4. Pearlescent layer; 5. Base color layer; 6. Pressure-sensitive adhesive layer; 7. Third release film. DETAILED DESCRIPTION

[0026] In order to express the technical mode implemented by the present invention clearly, accurately and completely, the present invention will be further described below in conjunction with embodiments and drawings.

[0027] The structure of the color-changing film of the present invention is as follows Figure 1 As shown, there are, in order, an optical-grade PET protective film 1, a functional coating 2, a substrate layer 3, a pearlescent layer 4, a base color layer 5, a pressure-sensitive adhesive layer 6 and a third release film 7; wherein, the pearlescent layer 4 is formed by adding pearlescent powder into polyurethane to form a pearlescent powder coating, a layer of pearlescent layer is coated on the surface of the first release film, and the solvent is removed by drying; the base color layer 5 is formed by adding color paste into polyurethane to form a base color coating, a layer of base color layer is coated on the surface of the second release film, and the solvent is removed by drying.

[0028] In order to enhance the adhesion between the pearlescent layer and the substrate layer, the present invention uses an unripened polyurethane elastomer particle cast film to dry-compound with the pearlescent layer. Generally, the polyurethane elastomer particle cast film needs to be aging treated before subsequent processing. The aging process allows the isocyanate group to further react with the hydroxyl group, thereby increasing the crosslinking density of the molecular chain. However, the crosslinking degree of the aging polyurethane elastomer particle cast film is high, which results in insufficient adhesion with the top dried pearlescent layer. In contrast, the surface of the unripened polyurethane elastomer particle cast film retains unreacted groups, which can chemically adsorb to the surface of the pearlescent layer.

[0029] The base color layer is used to cover the color of the car paint and better show the pearlescent effect of the pearlescent layer. The bottom of the pearlescent layer after the first release film is torn off is compounded with the base color layer, and the surface of the base color layer is dry. In order to ensure the adhesion between the base color layer and the pearlescent layer, the bottom of the pearlescent layer needs to have a certain wettability. The present invention changes the solvent residual rate of the pearlescent layer and the solvent residual rate is 1.5% to 3%. The solvent is composed of a solvent with a relative volatility of 5 or more and a solvent with a relative volatility of 1 or less, wherein the relative volatility refers to setting the volatility of n-butyl acetate to 1, and the relative volatility of the organic solvent is relative to the volatility of n-butyl acetate. The mass ratio of solvents with a relative volatility of 5 or more, such as ethyl acetate and butanone, and solvents with a relative volatility of less than 1, such as dimethyl diamide, is 3 to 5:1, which is beneficial to increase the solvent residual rate during the drying process of the pearlescent layer. At the same time Due to the addition of pearlescent powder, the pearlescent powder has a lamellar structure and the pearlescent powders are intertwined to form a network structure. On the one hand, it blocks the free flow of heat and effectively slows down the heat transfer speed from the top to the bottom of the pearlescent layer, thereby delaying the volatilization of the solvent at the bottom of the pearlescent layer; on the other hand, it prolongs the path of the solvent through the polymer and increases the resistance of the solvent at the bottom of the pearlescent layer to diffuse from the relatively dry polymer to the top of the pearlescent layer, further retaining the solvent at the bottom of the pearlescent layer to form a solvent residual surface of the pearlescent layer. When the solvent residual surface of the pearlescent layer is attached to the base color layer, the solvent molecules diffuse inside the base color layer polymer, which has a wettability effect on the base color layer and improves the adhesion.

[0030] Pearlescent powder is easy to settle and arrange at the bottom of the pearlescent layer. The settled pearlescent powder may not be firmly combined with the base color layer, which will affect the adhesion between the pearlescent layer and the base color layer. The present invention adopts a comma coating method. The coating roller rotates clockwise to bring the pearlescent slurry out of the scraper gap to form a stable coating wet thickness on the coating roller. The rubber back roller rotates clockwise and contacts the negative gap of the coating roller to completely transfer the pearlescent slurry to the first release film. The pearlescent powder flips and tilts during transfer to form different orientations. During film formation, most of the solvent evaporates quickly, the cross-linking degree of the polymer increases rapidly, the cohesive force between the polymer molecules increases and shrinks, and the pearlescent powder does not have time to move significantly and is less freely arranged, so that the pearlescent powder shows different orientations in the pearlescent layer.

[0031] Due to the irregular arrangement of pearlescent powder, the incident light is reflected in multiple directions, presenting a soft and bright pearlescent glittering effect. In addition, the car body is usually composed of multiple planes to form its external shape. When the pearlescent powder is dispersed in the pearlescent layer and arranged parallel to the surface of the pearlescent layer, it may appear as a mirror reflection on one plane of the car body. The incident light can form a bright reflection effect on the surface of the car color changing film, but other planes of the car body may change the incident angle of the light, so that the light is not incident directly on the plane where the pearlescent powder is arranged. The intensity of the reflected light will be weakened, resulting in this area not showing a pearlescent effect.

[0032] Pearlescent powders with different particle sizes show different effects in use. The larger the particle size, the stronger the glittering effect, but the weaker the covering power of the base color; while the smaller the particle size, the stronger the covering power of the base color, and the softer the luster. The present invention is composed of pearlescent powders with large particle sizes and pearlescent powders with small particle sizes, which ensures the glittering effect while covering the base color.

[0033] The present invention also makes the pearlescent coating present pseudoplastic fluid characteristics by adding dispersants and leveling agents. At the moment of comma coating, it has good leveling under high shear force. After coating, the pseudoplastic characteristics are used to maintain the coating thickness and the surface flatness does not change. Since most solvents evaporate quickly, insufficient lubrication may cause the problem of reduced molecular density. The present invention adds lubricants to reduce friction between polymer molecules, increase fluidity, and facilitate reaction. At the same time, it does not affect the orientation of pearlescent powder.

[0034] The raw materials and equipment in the following examples and comparative examples are all commercially available.

[0035] Example 1

[0036] The car color changing film of this embodiment is prepared by the following steps:

[0037] (1) melting aliphatic polyurethane elastomer particles at 80° C. into a polyurethane elastomer melt, adding a solvent, an additive, and pearl powder and mixing them evenly to obtain a pearl powder coating; coating the pearl powder coating on the surface of a first release film by a comma scraper method, and drying at 80° C.-110° C. to obtain a pearl layer; the thickness of the pearl layer is 40 μm; wherein the mass concentration of the polyurethane elastomer melt is 28.5wt%, the solvent is a mixed solvent of butanone and dimethyl diamide, and the mass ratio of butanone to dimethyl diamide is 4:1; the additives include a dispersant, a leveling agent, a defoaming agent, and a lubricant, and the lubricant is phenylmethyl silicone oil; the amount of the lubricant is 3% of the mass of the polyurethane elastomer melt; the amount of the pearl powder is 0.23% of the mass of the polyurethane elastomer melt, and the pearl powder is a mixture of 160-mesh pearl powder and 600-mesh pearl powder, and the mass ratio of 160-mesh pearl powder to 600-mesh pearl powder is 1:3;

[0038] (2) casting aliphatic polyurethane elastomer particles into a substrate layer, laminating one side of the substrate layer with a PET substrate film, and compounding the pearlescent layer obtained in step (1) with the other side of the substrate layer, and rolling up to obtain a pearlescent semi-finished product;

[0039] (3) melting aliphatic polyurethane elastomer particles at 80° C. to form a polyurethane elastomer melt, adding a solvent, an additive, and a color paste and mixing them evenly to obtain a base color coating; coating the base color coating on the surface of the second release film by a comma scraper method, and drying at 80-110° C. to obtain a base color layer; the base color layer has a thickness of 15 μm; wherein the mass concentration of the polyurethane elastomer melt is 13.5wt%, the solvent is ethyl acetate, the additives include a dispersant, a leveling agent, and a defoaming agent; and the color paste is a gray color paste;

[0040] (4) removing one side of the first release film from the pearlescent semi-finished product obtained in step (2) and compounding the semi-finished product with the base color layer to obtain a base color semi-finished product after rolling;

[0041] (5) The functional coating is coated on one side of the PET substrate film of the base color semi-finished product obtained in step (4) by using a micro-concave roller coating method, dried and cured, and composited with an optical-grade PET protective film; the pressure-sensitive adhesive is coated on the third release film, dried at 80-110°C to obtain a pressure-sensitive adhesive layer, and composited with the side of the base color semi-finished product with the second release film torn off, and placed at 50°C for aging for 5 days to obtain a car color-changing film.

[0042] Example 2

[0043] The car color changing film of this embodiment is prepared by the following steps:

[0044] (1) melting aliphatic polyurethane elastomer particles at 90° C. into a polyurethane elastomer melt, adding a solvent, an additive, and pearl powder and mixing them evenly to obtain a pearl powder coating; coating the pearl powder coating on the surface of a first release film by a comma scraper method, and drying at 80° C.-110° C. to obtain a pearl layer; the thickness of the pearl layer is 35 μm; wherein the mass concentration of the polyurethane elastomer melt is 28.5wt%, the solvent is a mixed solvent of butanone and dimethyl diamide, and the mass ratio of butanone to dimethyl diamide is 3:1; the additives include a dispersant, a leveling agent, a defoaming agent, and a lubricant, the lubricant is benzyl silicone oil, and the amount of the lubricant is 3% of the mass of the polyurethane elastomer melt; the amount of the pearl powder is 0.56% of the mass of the polyurethane elastomer melt, and the pearl powder is a mixture of 200-mesh pearl powder and 400-mesh pearl powder, and the mass ratio of 200-mesh pearl powder to 400-mesh pearl powder is 1:5;

[0045] (2) casting aliphatic polyurethane elastomer particles into a substrate layer, laminating one side of the substrate layer with a PET substrate film, and compounding the pearlescent layer obtained in step (1) with the other side of the substrate layer, and rolling up to obtain a pearlescent semi-finished product;

[0046] (3) melting aliphatic polyurethane elastomer particles at 90° C. into a polyurethane elastomer melt, adding a solvent, an additive, and a color paste and mixing them evenly to obtain a base color coating; coating the base color coating on the surface of the second release film by a comma scraper method, and drying at 80-110° C. to obtain a base color layer; the base color layer has a thickness of 15 μm; wherein the mass concentration of the polyurethane elastomer melt is 13.5wt%, the solvent is ethyl acetate, the additives include a dispersant, a leveling agent, and a defoaming agent; and the color paste is a white color paste;

[0047] (4) removing one side of the first release film from the pearlescent semi-finished product obtained in step (2) and compounding the semi-finished product with the base color layer to obtain a base color semi-finished product after rolling;

[0048] (5) The functional coating is coated on one side of the PET substrate film of the base color semi-finished product obtained in step (4) by using a micro-concave roller coating method, dried and cured, and composited with an optical-grade PET protective film; the pressure-sensitive adhesive is coated on the third release film, dried at 80-110°C to obtain a pressure-sensitive adhesive layer, and composited with the side of the base color semi-finished product with the second release film torn off, and placed at 45°C for aging for 6 days to obtain a car color-changing film.

[0049] Comparative Example 1

[0050] The same as Example 1, except that the solvents are butanone and dimethyl diamide, and the mass ratio of butanone to dimethyl diamide is 2:1.

[0051] Comparative Example 2

[0052] The same as Example 1, except that the solvents are butanone and dimethyl diamide, and the mass ratio of butanone to dimethyl diamide is 6:1.

[0053] Comparative Example 3

[0054] The same as Example 1, except that the pearl powder is 400 mesh pearl powder.

[0055] Comparative Example 4

[0056] Same as Example 1, except that there is no lubricant.

[0057] The present invention uses multiple people to subjectively evaluate the pearlescent effect of the film surface and manually pull the film surface for evaluation of Examples 1-2 and Comparative Examples 1-4, wherein the film surface is parallel to the horizontal plane, and the human eye is observed at 45° to the film surface, which is recorded as pearlescent effect A; the film surface is perpendicular to the horizontal plane, and the human eye is observed at 45° to the film surface, which is recorded as pearlescent effect B. The results are shown in Table 1.

[0058] Table 1 Performance test results of Examples 1-2 and Comparative Examples 1-4

[0059] Solvent residual rate / % Pearlescent Effect A Pearlescent effect B Layering Example 1 2.16 Soft and bright flashing Soft Flash none Example 2 1.55 Soft and bright flashing Soft Flash none Comparative Example 1 0.82 Bright flashing Transparent gray have Comparative Example 2 3.51 Slightly flashing Transparent gray have Comparative Example 3 2.44 Slightly flashing Slightly flashing none Comparative Example 4 3.17 Slightly flashing Transparent gray have

[0060] It can be seen from Table 1 that the car color-changing films of Example 1 and Example 2 are on different planes, the pearlescent effects are not much different, and there is no pulling and delamination.

[0061] The residual solvent rate of Comparative Example 1 is less than 1.5%, the wettability between the pearlescent layer and the base color layer is insufficient, and stratification occurs; in addition, the relatively fast volatile solvent is less, and the cross-linking reaction is slow, so that the pearlescent powder has enough time and space to move freely, which is conducive to forming a parallel oriented suspension state, and the pearlescent powder is evenly dispersed in the pearlescent layer, forming a mirror reflection on one plane with a bright reflection effect, and forming a scattering on the other plane, the pearlescent effect is not obvious, and it presents a transparent gray color.

[0062] The car protection film of Comparative Example 2 has a slightly bright and glittering surface on one plane and a transparent gray surface on the other plane. This may be because there is a relatively large amount of solvent with a relatively fast evaporation rate. The pearlescent powder is subjected to a large shrinkage force caused by the rapid evaporation of the solvent, causing the pearlescent powder to tend to be arranged in parallel. At the same time, the pearlescent powder has no time and space to move in orientation, resulting in possible overlap of the pearlescent powder in space and poor glittering brightness. Comparative Example 2 has stratification, and the lamination effect of the pearlescent layer and the base color layer is not good. This may be because the solvent evaporates too quickly and the surface of the pearlescent layer is uneven.

[0063] Comparative Example 3 uses pearlescent powder of a single particle size. Due to the irregular arrangement, the incident light is reflected in multiple directions, reducing the brightness. In addition, because there is no large-particle pearlescent powder to provide a glittering feeling, and there is no small-particle pearlescent powder to cover the base color layer, a faint glitter with insufficient brightness and glittering is caused.

[0064] The pearlescent effect of Comparative Example 4 is not as good as that of Example 1. The possible reasons are that most of the solvent evaporates, which reduces the fluidity of the polymer. Since no lubricant is added, the cross-linking reaction is insufficient, resulting in low molecular density. When the pearlescent layer is composited with the substrate layer, the compressibility is large, which makes the pearlescent powder oriented parallel to the plane. There is stratification in Comparative Example 4, which may be caused by the friction between polymer molecules, making the surface of the pearlescent layer rough.

Claims

1. A method for preparing a car color-changing film, characterized in that: The steps include: (1) uniformly mixing a polyurethane elastomer melt with a solvent, an additive, and pearl powder to obtain a pearl powder coating; coating the pearl powder coating on the surface of the first release film by a comma scraper method, and drying to obtain a pearl layer; (2) casting the polyurethane elastomer particles into a substrate layer, laminating one side of the substrate layer with a PET substrate film, and compounding the other side of the substrate layer with the pearlescent layer obtained in step (1), and rolling up to obtain a pearlescent semi-finished product; (3) coating the base color coating on the surface of the second release film by a comma scraper method, and drying to obtain a base color layer; (4) removing one side of the first release film from the pearlescent semi-finished product obtained in step (2), compounding the semi-finished product with the base color layer, and rolling the semi-finished product to obtain the base color semi-finished product; (5) tearing off the PET substrate film of the semi-finished product obtained in step (4), coating the functional coating on one side, drying and curing to obtain the functional coating, and compounding it with the optical grade PET protective film; The pressure-sensitive adhesive is coated on the third release film, and after drying, a pressure-sensitive adhesive layer is obtained, which is compounded with the base color semi-finished product with one side of the second release film torn off, and cured to obtain the car color-changing film.

2. The preparation method according to claim 1, characterized in that: The pearlescent powder is composed of mica coated with metal oxide, and the particle size is 80 to 1000 meshes.

3. The preparation method according to claim 1, characterized in that: The thickness of the substrate layer is 90 to 130 μm; the thickness of the pearlescent layer is 15 to 45 μm; and the thickness of the base color layer is 12 to 15 μm.

4. The preparation method according to claim 1, characterized in that: In step (1), the amount of pearlescent powder used is 0.01% to 1% of the mass of the polyurethane elastomer melt.

5. The preparation method according to claim 1, characterized in that: In step (1), the auxiliary agents include a leveling agent, a dispersant and a lubricant.

6. The preparation method according to claim 5, characterized in that: The lubricant is one or more of methyl silicone oil, ethyl silicone oil and benzyl silicone oil.

7. The preparation method according to claim 1, characterized in that: In step (1), the solvent is composed of a solvent having a relative volatility of 5 or more and a solvent having a relative volatility of 1 or less.

8. The preparation method according to claim 7, characterized in that: The mass ratio of the solvent with a relative volatility of 5 or more to the solvent with a relative volatility of 1 or less is 3 to 5:

1.

9. The preparation method according to claim 1, characterized in that: In step (5), the aging is carried out at 45 to 50° C. for 5 to 6 days.

10. A car color changing film, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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