UV-resistant stealth car coating containing nano-SiO2 and organosilicon hybrid and its preparation method

Abstract

The present application relates to the technical field of invisible car film, and particularly relates to a kind of nano-SiO2, organic silicon hybrid ultraviolet-resistant invisible car film and preparation method: crosslinked polystyrene microspheres prone to thermal deformation and precipitation are only limited in anti-adhesion sub-matt layer, the layer is located in the bottom layer of film, the actual tensile ratio and thermal mechanical stress borne in biaxial stretching process are significantly less than core layer, so that effectively avoid microspheres thermal deformation under high temperature condition;At the same time, the ultraviolet-resistant hybrid layer is cured simultaneously with transverse stretching by online coating, and a dense crosslinked network coating is formed in situ above the anti-adhesion sub-matt layer, which can effectively block the migration and precipitation of microspheres to the surface of the film as a physical barrier;In addition, the thickness ratio of two layers is 1:2 to 1:5, which ensures that the surface layer has sufficient thickness to play a blocking role, thereby comprehensively eliminating appearance defects such as rainbow stripe, dust inclusion and wrinkle collapse.

Description

Technical Field

[0001] This invention relates to the field of invisible car wrap technology, and in particular to an anti-ultraviolet invisible car wrap containing nano-SiO2 and organosilicon hybrids and its preparation method. Background Technology

[0002] Paint protection film, also known as automotive paint protection film, is a high-performance transparent polyurethane film. When applied to the car's paint surface, it effectively resists minor scratches, abrasions, and stone impacts, and blocks environmental damage such as ultraviolet rays and acid rain, providing long-lasting protection for the paint's gloss. A typical paint protection film has a multi-layered structure, usually including a top PET protective film, a middle functional coating, a TPU substrate layer, a pressure-sensitive adhesive layer, and a bottom release film. The top PET protective film, as the key layer directly exposed to the external environment and protecting the underlying coating, places extremely high demands on its optical performance (such as high light transmittance and low haze), weather resistance (such as resistance to UV aging), and appearance quality.

[0003] To simultaneously achieve high light transmittance, low haze, and good anti-blocking opening performance, existing technologies are increasingly using organic opening agents (such as cross-linked polystyrene microspheres) to replace traditional inorganic opening agents. Organic microspheres have a similar refractive index to PET substrates, and can achieve opening function at lower addition amounts without significantly increasing haze. This is considered an effective way to achieve a balance between optical and opening performance.

[0004] However, existing PET protective films used for paint protection films have technical problems in practical applications. Cross-linked polystyrene microsphere opening agents are prone to thermal deformation or precipitation from the substrate under biaxial stretching high-temperature process conditions, resulting in appearance defects such as rainbow patterns, dust inclusions, wrinkles and collapses in the film. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrids and its preparation method, which solves the problem that existing PET protective films used for invisible car wraps are prone to thermal deformation or precipitation from the substrate under biaxial stretching high-temperature process conditions, resulting in appearance defects such as rainbow patterns, dust inclusions, and wrinkles and collapses.

[0006] To achieve the above objectives, the present invention provides an anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid, wherein the anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid is a multilayer co-extruded biaxially oriented PET composite film, which includes, from top to bottom: an anti-UV hybrid layer, a PET substrate layer and an anti-adhesion matte layer; The UV-resistant hybrid layer is formed by simultaneously curing a coating containing nano-SiO2-organosilicon hybrid resin through online coating and transverse stretching; The anti-adhesion matte layer is formed by co-extrusion of PET chips containing monodisperse submicron-sized cross-linked polystyrene microspheres; The thickness ratio of the UV-resistant hybrid layer to the anti-adhesion matte layer is 1:2 to 1:5.

[0007] The UV-resistant hybrid layer further includes a UV absorber, a crosslinking agent, and a light stabilizer. Based on 100 parts by weight of the nano-SiO2-organosilicon hybrid resin, the UV absorber weighs 5-15 parts, the crosslinking agent weighs 1-5 parts, and the light stabilizer weighs 1-5 parts.

[0008] The nano-SiO2 surface in the nano-SiO2-organosilicon hybrid resin is modified with a silane coupling agent.

[0009] The silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.

[0010] This invention also provides a method for preparing an anti-UV stealth automotive coating film containing nano-SiO2 and organosilicon hybrid, for preparing the anti-UV stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described above, comprising the following steps: Preparation of UV-resistant hybrid coating solution: The nano-SiO2-organosilicon hybrid resin, the UV absorber, the crosslinking agent, and the light stabilizer are added to an organic solvent, stirred, filtered, and allowed to stand to remove bubbles to obtain the coating solution; Preparation of multilayer co-extruded PET substrate: The raw materials of the PET substrate layer and the raw materials of the anti-adhesion matte layer are dried separately and then extruded into a casting through a multilayer co-extrusion die, wherein the anti-adhesion matte layer is located on one side of the casting. Biaxial stretching and online coating: The obtained casting is stretched longitudinally, and then the prepared coating liquid is used to coat the longitudinally stretched film online to form an anti-UV hybrid layer precursor. Lateral stretching and simultaneous curing: The treated film is placed in a lateral stretching oven, where the UV-resistant hybrid layer precursor is thermally cured and the solvent evaporates simultaneously during the lateral stretching process. Heat setting, winding and slitting: The processed film is heat set, then cooled, wound and slitted to obtain the UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid.

[0011] In the step of preparing the UV-resistant hybrid coating solution, the solid content of the coating solution is 10wt%-20wt%.

[0012] In the step of preparing the multilayer co-extruded PET substrate, the monodisperse submicron cross-linked polystyrene microspheres in the anti-adhesion matte layer are prepared by dispersion polymerization or soap-free emulsion polymerization, and their particle size is 0.5-2μm. The amount added is 0.05wt%-0.2wt% of the total weight of the raw materials of the anti-adhesion matte layer.

[0013] In the biaxial stretching and online coating steps, the longitudinal stretching ratio is 2.5-3.5 times, and the stretching temperature is 80-110℃; the online coating adopts a concave roller reverse coating method, and the wet coating thickness is controlled to be 3-10μm.

[0014] In the transverse stretching and synchronous curing steps, the temperature of the transverse stretching oven is divided into four zones that increase sequentially: zone 1 90-110℃, zone 2 110-130℃, zone 3 130-150℃, and zone 4 140-160℃; the transverse stretching ratio is 3.0-4.0 times.

[0015] In the heat setting, winding and slitting steps, the heat setting temperature is 200-230℃, the heat setting time is 5-15 seconds, and then cooling and winding are carried out at 50-70℃; the winding tension is controlled at 8-15N / m.

[0016] This invention discloses an anti-UV stealth car coating film containing nano-SiO2 and organosilicon hybrids, and its preparation method. The anti-UV stealth car coating film containing nano-SiO2 and organosilicon hybrids is a multilayer co-extruded biaxially oriented PET composite film, which, from top to bottom, includes: an anti-UV hybrid layer, a PET substrate layer, and an anti-adhesion matte layer. Cross-linked polystyrene microspheres, which are prone to thermal deformation and precipitation, are confined only to the anti-adhesion matte layer. This layer is located at the bottom of the film, and the actual stretching ratio and thermomechanical stress it actually bears during biaxial stretching are significantly less than those of the core layer, thereby effectively preventing the microspheres from undergoing thermal deformation under high temperature conditions. At the same time, the anti-UV hybrid layer is cured simultaneously with online coating and transverse stretching, forming a dense cross-linked network coating in situ above the anti-adhesion matte layer. This coating acts as a physical barrier to effectively prevent the migration and precipitation of microspheres to the film surface. In addition, the limitation of the thickness ratio of the two layers to 1:2 to 1:5 ensures that the surface layer has sufficient thickness to play a barrier role, thereby comprehensively eliminating appearance defects such as rainbow patterns, dust inclusions, and wrinkles and collapses. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the preparation method of the UV-resistant invisible car coating film containing nano-SiO2 and organosilicon hybrid provided by the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] This invention provides an anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid. The anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid is a multilayer co-extruded biaxially oriented PET composite film, which includes, from top to bottom: an anti-UV hybrid layer, a PET substrate layer and an anti-adhesion matte layer. The UV-resistant hybrid layer is formed by simultaneously curing a coating containing nano-SiO2-organosilicon hybrid resin through online coating and transverse stretching; The anti-adhesion matte layer is formed by co-extrusion of PET chips containing monodisperse submicron-sized cross-linked polystyrene microspheres; The thickness ratio of the UV-resistant hybrid layer to the anti-adhesion matte layer is 1:2 to 1:5.

[0021] In this embodiment, the cross-linked polystyrene microspheres, which are prone to thermal deformation and precipitation, are confined only to the anti-adhesion matte layer. This layer is located at the bottom of the film, and the actual stretching ratio and thermomechanical stress it bears during biaxial stretching are significantly less than those in the core layer, thereby effectively preventing the microspheres from undergoing thermal deformation under high-temperature conditions. At the same time, the UV-resistant hybrid layer is cured simultaneously with online coating and transverse stretching, forming a dense cross-linked network coating in situ above the anti-adhesion matte layer. This coating acts as a physical barrier, effectively preventing the migration and precipitation of microspheres to the film surface. In addition, the limitation of the thickness ratio of the two layers from 1:2 to 1:5 ensures that the surface layer has sufficient thickness to play a barrier role, thereby comprehensively eliminating appearance defects such as rainbow patterns, dust inclusions, and wrinkles and collapses.

[0022] Furthermore, the UV-resistant hybrid layer also includes a UV absorber, a crosslinking agent, and a light stabilizer. Based on 100 parts by weight of the nano-SiO2-organosilicon hybrid resin, the UV absorber weighs 5-15 parts, the crosslinking agent weighs 1-5 parts, and the light stabilizer weighs 1-5 parts.

[0023] In this embodiment, the ultraviolet absorber is used to absorb ultraviolet light and convert it into heat energy, the crosslinking agent is used to promote the crosslinking and curing of the organosilicon hybrid resin to form a dense three-dimensional network structure, and the light stabilizer is used to capture free radicals generated by ultraviolet irradiation to inhibit the photo-aging degradation of the coating.

[0024] Furthermore, the surface of the nano-SiO2 in the nano-SiO2-organosilicon hybrid resin is modified by a silane coupling agent.

[0025] In this embodiment, the surface of nano-SiO2 is modified with a silane coupling agent to improve the dispersion uniformity and interfacial compatibility of nano-SiO2 in the organosilicon resin matrix. Unmodified nano-SiO2 surfaces are rich in hydroxyl groups, making them prone to aggregation, leading to micron-sized aggregates in the coating and subsequently causing problems such as increased haze and surface defects. After modification with the silane coupling agent, one end of the coupling agent reacts with the hydroxyl groups on the nano-SiO2 surface to form a chemical bond, while the other end reacts with or entangles with the active groups of the organosilicon resin. This allows the nano-SiO2 to be uniformly dispersed at the nanoscale in the resin matrix, while simultaneously enhancing the cohesive strength and density of the coating, further improving the barrier effect against microsphere precipitation.

[0026] Furthermore, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.

[0027] In this embodiment, γ-glycidoxypropyltrimethoxysilane contains epoxy groups, which can undergo ring-opening crosslinking reactions with resins containing hydroxyl or amino groups; γ-methacryloyloxypropyltrimethoxysilane contains double bond groups, which can participate in free radical polymerization reactions in the presence of an initiator. Compared with other conventional silane coupling agents, these two coupling agents can form stronger chemical bonds with organosilicon hybrid resins, significantly improving the interfacial bonding strength between nano-SiO2 and the resin matrix, thereby obtaining better nanoparticle dispersion and coating mechanical properties.

[0028] Please see Figure 1 The present invention also provides a method for preparing an anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid, for preparing the anti-UV invisible car wrap film containing nano-SiO2 and organosilicon hybrid as described above, comprising the following steps: S1. Preparation of UV-resistant hybrid coating solution: The nano-SiO2-organosilicon hybrid resin, the UV absorber, the crosslinking agent, and the light stabilizer are added to an organic solvent, stirred, filtered, and allowed to stand to remove bubbles to obtain the coating solution; S2. Preparation of multilayer co-extruded PET substrate: After drying the raw materials of the PET substrate layer and the raw materials of the anti-adhesion matte layer respectively, they are extruded into a casting through a multilayer co-extrusion die, wherein the anti-adhesion matte layer is located on one side of the casting. S3. Biaxial stretching and online coating: The obtained casting is stretched longitudinally, and then the prepared coating liquid is used to coat the longitudinally stretched film online to form an anti-UV hybrid layer precursor. S4. Lateral stretching and simultaneous curing: The treated film is placed in a lateral stretching oven. During lateral stretching, the thermal curing of the UV-resistant hybrid layer precursor and the evaporation of the solvent are completed. S5. Heat setting, winding and slitting: The processed film is heat set, then cooled, wound and slitted to obtain the UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid.

[0029] In this embodiment, the method integrates the coating process of the UV-resistant hybrid layer into a biaxial stretching production line, and simultaneously completes the thermal curing and solvent evaporation of the coating during the transverse stretching process, achieving coordinated control of coating formation and film orientation. Simultaneously, the heat-deformable cross-linked polystyrene microspheres are confined only to the anti-adhesion matte layer, avoiding their exposure to the high-temperature main stretching zone. This process forms a dense cross-linked network coating in situ above the matte layer containing the microspheres through online synchronous curing. This coating acts as a physical barrier, effectively preventing the migration and precipitation of microspheres to the film surface, while eliminating appearance defects such as rainbow patterns, wrinkles, and collapses caused by uneven heating history during secondary heating. Thus, while maintaining high light transmittance and low haze optical performance, it achieves both excellent anti-adhesion and UV aging resistance.

[0030] Furthermore, in the step of preparing the UV-resistant hybrid coating solution, the solid content of the coating solution is 10wt%-20wt%.

[0031] In this embodiment, the solid content range allows the coating liquid to have suitable viscosity and leveling properties, resulting in a uniform wet film without bubbles or pinholes after coating, and complete curing during transverse stretching to form a dense and defect-free UV-resistant hybrid layer.

[0032] Furthermore, in the step of preparing the multilayer co-extruded PET substrate, the monodisperse submicron-sized cross-linked polystyrene microspheres in the anti-adhesion matte layer are prepared by dispersion polymerization or soap-free emulsion polymerization, and their particle size is 0.5-2μm. The amount added is 0.05wt%-0.2wt% of the total weight of the raw materials of the anti-adhesion matte layer.

[0033] In this embodiment, dispersion polymerization or soap-free emulsion polymerization can be used to obtain microspheres with uniform particle size and good monodispersity. Sufficient surface microprotrusions can be provided at a low addition amount of 0.05wt%-0.2wt% to achieve excellent anti-blocking opening performance, while avoiding the increase in haze, decrease in light transmittance and increase in precipitation risk caused by excessive particle size or excessive addition amount.

[0034] Furthermore, in the biaxial stretching and online coating steps, the longitudinal stretching ratio is 2.5-3.5 times, and the stretching temperature is 80-110℃; the online coating adopts a concave roller reverse coating method, and the wet coating thickness is controlled to be 3-10μm.

[0035] In this embodiment, the preferred process parameters ensure that the film obtains sufficient longitudinal orientation to improve mechanical properties. At the same time, the reverse coating with concave rollers can obtain a uniform coating surface with high precision and low defects. The wet coating thickness is controlled at 3-10 μm to ensure that the UV-resistant hybrid layer has sufficient dense thickness after drying and curing to play a role in blocking the precipitation of microspheres.

[0036] Furthermore, in the steps of transverse stretching and synchronous curing, the temperature of the transverse stretching oven is divided into four zones that increase sequentially: zone 1 90-110℃, zone 2 110-130℃, zone 3 130-150℃, and zone 4 140-160℃; the transverse stretching ratio is 3.0-4.0 times.

[0037] In this embodiment, the zoned incremental temperature design allows the film to gradually heat up during the lateral stretching process, avoiding stress concentration and film rupture caused by a sudden temperature rise. At the same time, the high-temperature zone promotes the full curing and cross-linking of the UV-resistant hybrid layer precursor, forming a dense physical barrier layer.

[0038] Furthermore, in the heat setting, winding and slitting steps, the heat setting temperature is 200-230℃, the heat setting time is 5-15 seconds, and then cooling and winding are carried out at 50-70℃; the winding tension is controlled at 8-15N / m.

[0039] In this embodiment, the heat setting process can effectively eliminate internal stress in the film and reduce the heat shrinkage rate. The appropriate cooling temperature and winding tension can ensure that the film roll has no rainbow patterns, no foreign matter inclusions, no wrinkles or collapses, and maintain good dimensional stability.

[0040] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid components, characterized in that, The UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrids is a multilayer co-extruded biaxially oriented PET composite film, which includes, from top to bottom: a UV-resistant hybrid layer, a PET substrate layer, and an anti-adhesion matte layer. The UV-resistant hybrid layer is formed by simultaneously curing a coating containing nano-SiO2-organosilicon hybrid resin through online coating and transverse stretching; The anti-adhesion matte layer is formed by co-extrusion of PET chips containing monodisperse submicron-sized cross-linked polystyrene microspheres; The thickness ratio of the UV-resistant hybrid layer to the anti-adhesion matte layer is 1:2 to 1:

5.

2. The UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid as described in claim 1, characterized in that, The UV-resistant hybrid layer further includes a UV absorber, a crosslinking agent, and a light stabilizer. Based on 100 parts by weight of the nano-SiO2-organosilicon hybrid resin, the UV absorber weighs 5-15 parts, the crosslinking agent weighs 1-5 parts, and the light stabilizer weighs 1-5 parts.

3. The UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid as described in claim 2, characterized in that, The surface of the nano-SiO2 in the nano-SiO2-organosilicon hybrid resin is modified by a silane coupling agent.

4. The UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid as described in claim 3, characterized in that, The silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.

5. A method for preparing an anti-UV stealth automotive coating film containing nano-SiO2 and organosilicon hybrid, used to prepare the anti-UV stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 4, characterized in that, Includes the following steps: Preparation of UV-resistant hybrid coating solution: The nano-SiO2-organosilicon hybrid resin, the UV absorber, the crosslinking agent, and the light stabilizer are added to an organic solvent, stirred, filtered, and allowed to stand to remove bubbles to obtain the coating solution; Preparation of multilayer co-extruded PET substrate: The raw materials of the PET substrate layer and the raw materials of the anti-adhesion matte layer are dried separately and then extruded into a casting through a multilayer co-extrusion die, wherein the anti-adhesion matte layer is located on one side of the casting. Biaxial stretching and online coating: The obtained casting is stretched longitudinally, and then the prepared coating liquid is used to coat the longitudinally stretched film online to form an anti-UV hybrid layer precursor. Lateral stretching and simultaneous curing: The treated film is placed in a lateral stretching oven, where the UV-resistant hybrid layer precursor is thermally cured and the solvent evaporates simultaneously during the lateral stretching process. Heat setting, winding and slitting: The processed film is heat set, then cooled, wound and slitted to obtain the UV-resistant invisible car wrap film containing nano-SiO2 and organosilicon hybrid.

6. The method for preparing the UV-resistant stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 5, characterized in that, In the step of preparing the UV-resistant hybrid coating solution, the solid content of the coating solution is 10wt%-20wt%.

7. The method for preparing the UV-resistant stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 6, characterized in that, In the step of preparing the multilayer co-extruded PET substrate, the monodisperse submicron cross-linked polystyrene microspheres in the anti-adhesion matte layer are prepared by dispersion polymerization or soap-free emulsion polymerization, with a particle size of 0.5-2μm, and the amount added is 0.05wt%-0.2wt% of the total weight of the raw materials of the anti-adhesion matte layer.

8. The method for preparing the UV-resistant stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 7, characterized in that, In the biaxial stretching and online coating steps, the longitudinal stretching ratio is 2.5-3.5 times, and the stretching temperature is 80-110℃; the online coating adopts a concave roller reverse coating method, and the wet coating thickness is controlled to be 3-10μm.

9. The method for preparing the UV-resistant stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 8, characterized in that, In the transverse stretching and synchronous curing steps, the temperature of the transverse stretching oven is divided into four zones that increase sequentially: zone 1 90-110℃, zone 2 110-130℃, zone 3 130-150℃, and zone 4 140-160℃; the transverse stretching ratio is 3.0-4.0 times.

10. The method for preparing the UV-resistant stealth automotive coating film containing nano-SiO2 and organosilicon hybrid as described in claim 9, characterized in that, In the steps of heat setting, winding and slitting, the heat setting temperature is 200-230℃, the heat setting time is 5-15 seconds, and then cooling and winding are carried out at 50-70℃; the winding tension is controlled at 8-15N / m.

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