A paint protection film for a metallic paint finish

Abstract

This application relates to a paint protection film for metallic paint surfaces, which is made by laminating a high-molecular polymer onto a TPU base film using a coating technology. The high-molecular polymer contains bio-cellulose and polyhydroxyalkanoates. The paint protection film of this invention provides excellent protection for vehicle paint and has self-healing properties, preventing scratches and significantly reducing the overall impact of scratches on the vehicle's appearance. Furthermore, the paint protection film exhibits excellent aging resistance and can be customized through color changes, matte finishes, and other treatments.

Description

Technical Field

[0001] This invention relates to the field of biofilm materials technology, and in particular to a protective film for metallic paint surfaces and its applications. Background Technology

[0002] Paint Protection Film (PPF) is a high-performance, new type of environmentally friendly transparent film applied to the car's surface to protect the paint. It's made of high-polymer materials and adhered to the paint surface to protect the original paint, enhance the car's appearance, and can be easily removed. This contrasts sharply with traditional paint sealant, coating, and painting processes that chemically alter the paint surface. PPF's versatility and convenience have made it a preferred choice for car wraps. While early versions typically used PVC and PU as base materials, they had drawbacks such as being unable to repair scratches and prone to yellowing. The new generation of TPU PPF uses a TPU base film, precisely coated with a protective layer and adhesive, and then laminated. This type of paint protection film not only possesses excellent impact resistance, puncture resistance, corrosion resistance, fracture resistance, and weather resistance, but also boasts high gloss and self-healing scratches. When applied to a vehicle, it isolates the paint from the air, significantly reducing damage to the paint layer caused by road scratches, flying stones, ultraviolet rays, and acid rain, thus protecting the vehicle body. However, TPU is a polymer material synthesized from diisocyanates such as diphenylmethane diisocyanate (MDI) and macromolecular polyols and low-molecular-weight polyols (chain extenders). Because the benzene ring of MDI is directly linked to the isocyanate group, the large π bond of the benzene ring forms a conjugated structure with the isocyanate group. Under prolonged exposure to sunlight and ultraviolet light, the isocyanate group decomposes, generating aniline structures. The aniline rearranges, forming other chromogenic groups, thus easily causing yellowing. Over time, issues such as delamination and edge peeling may also occur. Therefore, solving the problems of yellowing and delamination of TPU film under ultraviolet light is a pressing technical challenge for paint protection films.

[0003] Biological cellulose (also known as bacterial cellulose) is a novel type of cellulose mainly produced by the fermentation of bacteria of the genus *Acetobacter*. It is produced by culturing *Acetobacter* microorganisms in a liquid culture medium, causing them to metabolize and produce a hydrogel-like product. Compared to plant cellulose, biological cellulose has a high purity, contains virtually no byproducts such as lignin and hemicellulose, possesses an ultra-fine network structure, and has high crystallinity, thus exhibiting excellent mechanical properties. Furthermore, as a biomaterial, it has advantages in biocompatibility and biodegradability. Currently, biological cellulose is typically produced through static or dynamic fermentation. Static fermentation produces a white, semi-transparent hydrogel film on the surface of the liquid culture medium, with a water content exceeding 95%. Dynamic fermentation, due to surface tension, typically produces small spherical biological cellulose hydrogels, which can be processed into sheet or film-like biological cellulose materials through crushing and pressing.

[0004] Polyhydroxyalkanoates (PHAs) are polymers of hydroxyalkanoic acid (HA), and are biopolymers with a universal structural formula. PHAs can be synthesized through biosynthesis and chemical synthesis. Among these, microbial fermentation synthesis of PHAs has become a research hotspot in the field of polymer synthesis in recent years. It mainly utilizes prokaryotic microorganisms as carbon and energy sources under conditions of carbon-nitrogen imbalance to synthesize a class of thermoplastic polyesters. Furthermore, PHAs exhibit diverse structures; their composition can be altered by changing the microbial strain, feed, and fermentation process. This structural diversity leads to a variety of properties, giving them significant advantages in specific applications. PHAs not only possess physicochemical properties similar to chemically synthesized polymers, but also exhibit excellent properties such as biodegradability, biocompatibility, piezoelectricity, optical activity, and gas barrier properties. Moreover, their final degradation products are CO2 and H2O, posing no side effects to the human body. Therefore, they have broad application prospects in green packaging materials, containers, agricultural materials, electrical component housings, and biomedical tissue engineering. Although by adjusting the ratio of polyhydroxyalkanoate monomers, the properties of polyhydroxyalkanoate products can be made to span different categories such as fibers, plastics, rubber, and hot melt adhesives. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a protective film for metallic paint surfaces that exhibits stable repair performance, good aging resistance, and is stain-resistant and hydrophobic.

[0006] The paint protection film for metallic paint surfaces of this invention is made by laminating a high-molecular polymer onto a TPU base film using a coating technology. The high-molecular polymer contains bio-cellulose and polyhydroxyalkanoates. This paint protection film provides excellent protection for metallic paint surfaces, especially automotive paint, and also possesses self-healing properties. It prevents scratches on the paint, significantly reducing the overall impact of scratches on the car's appearance. Furthermore, the paint protection film exhibits excellent aging resistance and can be customized through color changes, matte finishes, and other treatments. Due to the addition of bio-cellulose and polyhydroxyalkanoates, the paint protection film of this invention possesses excellent self-healing capabilities. The bio-cellulose itself contains numerous non-covalent bonds such as hydrogen bonds in its molecular structure, and its three-dimensional network structure surrounds the polyhydroxyalkanoates, giving it good formability, flexibility, transparency, and gas and liquid barrier properties. After damage, it can repair itself to its initial shape through molecular chain segment movement.

[0007] The paint protection film of this invention further includes one or more polymers such as polyethylene, polypropylene, or polyester in the polymer. Bio-cellulose, polyhydroxyalkanoates, and polyethylene are uniformly dispersed in an organic solvent to form a polymer. The polymer is then mixed and dispersed in a UV-sensitive resin, coated onto a TPU base film, and cured by UV drying of the solvent. Preferably, the organic solvent can be chloroform, ethyl acetate, butyl acetate, methyl ethyl ketone, or isopropanol. This is an oil-based coating technology, and the resulting oil-based coating layer has good abrasion resistance and can be used for a long time under various ecological or physicochemical environments such as infrared, ultraviolet, laser, wind, frost, rain, snow, and acids and alkalis. Furthermore, the polymer may also contain anti-aging additives, dyes, or flame retardants. The resulting protective film can be treated with color modification, matte finishing, etc., to obtain a personalized paint protection film.

[0008] In the paint protective film of the present invention, preferably, the proportion of bio-cellulose in the polymer is 10-35% by weight. Preferably, the bio-cellulose is prepared by dehydration and drying of bio-cellulose hydrogel obtained from static fermentation culture of microorganisms, and is washed and purified before dehydration. Conventional mechanical pressure dehydration or heat dehydration can be used, but slow mechanical dehydration or low-temperature heat dehydration is preferred. Drying can be performed by any method, such as mechanical compression, hot air drying, or a combination thereof, as long as the drying conditions do not damage the basic structure of the product. The bio-cellulose can be prepared by various known methods, such as using hydrogels formed by rehydration of dried bio-cellulose, but bio-cellulose hydrogel obtained from static fermentation culture, after washing and purification, is preferred. The washing and purification of the bio-cellulose hydrogel can be performed by any known method, such as repeated rinsing or soaking with deionized water and weak alkaline solution. However, alkaline soaking is preferred. Studies have found that the mechanical properties of bio-cellulose / polyhydroxyalkali composite materials treated with alkaline solution are improved, with significant increases in tensile strength and tensile modulus compared to the product before alkaline treatment. The preferred method of alkali treatment is to soak the bio-cellulose membrane in a soda ash solution with a pH of 7-8 for more than 20 minutes.

[0009] In the paint protective film of the present invention, preferably, the polyhydroxyalkanoate accounts for 2-20% by weight of the polymer. Further, the polyhydroxyalkanoate is prepared by microbial fermentation. Preferably, the polyhydroxyalkanoate is polyhydroxybutyrate (PHB) and / or hydroxybutyrate-valerate copolyester (PHBV).

[0010] This invention reveals that mixing polyhydroxyalkanoates (PHA) with bio-cellulose to create a composite material, while reducing the crystallinity of the PHA, actually increases the barrier properties of the composite material due to the overall blocking effect of the cellulose fiber crystals. Simultaneously, the nano-sized PHAs suppress light scattering in the composite material, increasing its transmittance. When PHAs enter the pores of the bio-cellulose membrane, the transparency of the composite film is greater than that of the bio-cellulose membrane, enhancing its optical properties. The resulting composite material has higher transparency, which is beneficial for manufacturing paint protection films. Barrier properties, formability, and tensile strength are all significantly improved, giving the prepared paint protection film superior aging resistance, stain resistance, and acid rain resistance. Detailed Implementation

[0011] To further illustrate the present invention in more detail, specific embodiments of the present invention will be described below. It should be understood that the specific embodiments described below should not constitute any limitation on the present invention. In fact, any conventional changes or adjustments made based on them should be within the scope of the present invention.

[0012] Example 1: Preparation of bio-cellulose hydrogel Bio-cellulose hydrogels were prepared using a static shallow-tray fermentation method with *Acetobacter xylinum* as the inoculum. Fermentation was carried out at 29°C in coconut water medium for 7 days. The bio-cellulose hydrogels on the surface of the medium were collected, washed 3-6 times with deionized water, and then mechanically compressed and dehydrated, followed by hot air drying at 50°C to obtain bio-cellulose hydrogels with a water content of less than 30%, which were then used for later use.

[0013] Example 2: Bio-cellulose hydrogel obtained after alkali treatment Before drying and dehydration, the bio-cellulose hydrogel obtained in Example 1 was rinsed three times with deionized water, then soaked in a sodium carbonate solution at pH 8 for 30 minutes, and then rinsed three times with deionized water. After mechanical compression and dehydration, and drying with hot air at 50°C, a bio-cellulose hydrogel with a water content of less than 30% was obtained for later use.

[0014] Example 3: Preparation of paint protective film The bio-cellulose hydrogels obtained in Examples 1 and 2 were dispersed in an organic solvent using high-speed ultrasonication. Polyhydroxy fatty acid esters were added, and high-speed ultrasonication continued. Then, other polymers such as polyethylene, polypropylene, or polyester were added, and the mixture was thoroughly stirred and dispersed to obtain a polymer. This polymer was then dispersed in a UV-sensitive resin and coated onto a 125 μm TPU base film. The solvent was dried using UV light, and the film was cured to a thickness between 25 and 40 micrometers. One of the following organic solvents can be used: chloroform, ethyl acetate, butyl acetate, methyl ethyl ketone, and isopropanol. The amounts of each component of the polymer used are listed below when the solvent usage is 100 parts by weight:

[0015] Anti-aging additives, colorants, and / or flame retardants can be added to the polymer as needed to give the resulting paint protective film customized color or protective function.

[0016] Experiment Example 1: Mechanical Property Experiment The peel strength, tensile strength, and elongation at break of the protective films numbered 1-7 in Example 3 were tested using a rheometer according to standard testing methods. Simultaneously, the films' high-temperature resistance, light transmittance, and yellowing properties were also tested. The test results (average of three parallel experiments) are shown in the table below:

[0017] Experiment Example 2: Weather Resistance Test The QUV accelerated aging tester (a commonly used testing device that uses special fluorescent ultraviolet lamps to simulate sunlight irradiation and simulates dew and rain through condensation humidity and water spray to realistically reproduce material damage caused by sunlight) was used to apply the paint protective films numbered 1-7 in Example 3 to the metallic paint surface for a 3000-hour accelerated aging test to test their weather resistance. The results showed that the films exhibited extremely high weather resistance in the 3000-hour accelerated aging test, were not afraid of high temperature and sunlight, and did not crack, peel, or reduce strength. At the same time, they can also effectively block corrosion from tree sap, insect spots, bird droppings, acid rain, etc., and have long-lasting anti-yellowing properties. They also have self-healing function, and minor scratches can be quickly restored.

[0018] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A protective film for metallic paint surfaces, characterized in that, It is made by laminating a high molecular polymer onto a TPU base film using a lamination technique. The high molecular polymer contains bio-cellulose and polyhydroxy fatty acid esters.

2. The paint protection film according to claim 1, characterized in that, The polymer also contains one or more of polyethylene, polypropylene, or polyester.

3. The paint protection film according to claim 2, characterized in that, Bio-cellulose, polyhydroxy fatty acid esters, polyethylene, polypropylene and / or polyester are uniformly dispersed in an organic solvent to form a polymer; the polymer is then mixed and dispersed in a UV photosensitive resin, coated onto a TPU base film, and the solvent is dried by ultraviolet light and cured to form a film.

4. The paint protection film according to claim 3, characterized in that, The organic solvent is one or more of chloroform, ethyl acetate, butyl acetate, methyl ethyl ketone, and isopropanol.

5. The paint protection film according to any one of claims 1-4, characterized in that, The polymer also contains anti-aging additives, dyes, and / or flame retardants.

6. The paint protection film according to claim 1, characterized in that, The bio-cellulose accounts for 10-35% by weight in the polymer.

7. The paint protection film according to claim 6, characterized in that, The biocellulose is prepared by dehydrating and drying the biocellulose hydrogel obtained by static fermentation culture of microorganisms, and is washed and purified before dehydration.

8. The paint protection film according to claim 7, characterized in that, The bio-cellulose was washed by soaking the bio-cellulose hydrogel in a soda ash solution with a pH of 7-8 for more than 20 minutes.

9. The paint protection film according to claim 1, characterized in that, The polyhydroxyalkanoate accounts for 2-20% by weight in the polymer.

10. The paint protection film according to claim 9, characterized in that, The polyhydroxy fatty acid ester is prepared by microbial fermentation, and is preferably polyhydroxybutyrate (PHB) and / or hydroxybutyrate-valerate copolyester (PHBV).

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