Process for producing a co-extruded biaxially oriented uv-printable reflective film

Abstract

The application discloses a production process of a co-extrusion bidirectional stretching UV-resistant printing reflective film and relates to the technical field of reflective film preparation.The production process comprises the following steps: S1, raw material preparation; S2, co-extrusion casting; S3, bidirectional stretching; S4, surface treatment; and S5, winding.The production process of the co-extrusion bidirectional stretching UV-resistant printing reflective film adopts the "organic foaming agent and inorganic nucleating agent synergistic effect" technology to build a uniform microporous structure with a pore diameter of 0.5-3 microns in the core layer (A).The microporous structure can perform high-efficiency Mie scattering on incident light, and the reflectivity of the film is significantly improved (greater than or equal to 92%). Compared with a traditional solid white film, the microporous structure effectively reduces the light transmittance (less than or equal to 0.5%).

Description

Technical Field

[0001] This invention relates to the field of reflective film preparation technology, specifically to a production process for a co-extruded biaxially oriented UV-resistant printable reflective film. Background Technology

[0002] Currently, reflective films with high reflectivity, excellent UV resistance, and superior mechanical properties have been widely used in many fields. These reflective films are typically produced using a three-layer co-extrusion process, with the core layer often employing low-density olefin materials or a foamed structure to reduce overall density while improving reflectivity. The current mainstream technology is based on organic foaming, and while reflective films prepared using this process have high reflectivity, they still face limitations such as insufficient temperature resistance, low stiffness, and high production costs. Especially considering the high temperatures inside vehicles during summer, automotive display reflective films have strict requirements for temperature resistance. These factors collectively limit the widespread application of such reflective films in the automotive field. Therefore, we propose a co-extrusion biaxially stretched UV-resistant printable reflective film production process. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a production process for co-extruded biaxially oriented UV-resistant printable reflective films, solving the problems mentioned in the background section.

[0004] To achieve the above objectives, the present invention provides a production process for a co-extruded biaxially oriented UV-resistant printable reflective film, comprising the following steps: S1. Raw material preparation: The reflective film is designed with a three-layer structure of A / B / A, wherein the core layer (A) contains PET resin, organic foaming agent and inorganic nucleating agent, and the surface layer (B) contains PET resin, anti-blocking agent and weather-resistant additive; S2, Co-extrusion casting: After drying the core layer (A) and surface layer (B) raw materials for 48 hours, they are fed into a three-layer co-extrusion die for melt extrusion and then rapidly cooled by cooling rollers to form a thick sheet; S3. Biaxial stretching: The thick sheet is stretched longitudinally and laterally, and the stretching temperature is controlled above the glass transition temperature Tg of PET. The microporous reflective structure is constructed in the core layer (A) by utilizing the synergistic foaming effect of organic and inorganic particles. S4. Surface treatment: Corona treatment or UV-resistant base coating is applied to the surface layer (B) of the stretched film to obtain a surface tension suitable for UV ink printing. S5. Winding: After shaping and cooling, the film is wound up to obtain the UV-resistant printing reflective film.

[0005] Furthermore, in step S1, the mass ratio of the organic foaming agent to the inorganic nucleating agent in the core layer (A) is 1:(1~3), and the inorganic nucleating agent is one or more of talc, silicon dioxide or calcium carbonate.

[0006] Furthermore, in step S1, the weather-resistant additives in the surface layer (B) include hindered amine light stabilizers and carbon black, and the thickness of the surface layer (B) accounts for 5% to 15% of the total thickness of the reflective film.

[0007] Furthermore, in step S3, the longitudinal stretching temperature is 85℃~95℃, and the stretching ratio is 2.5~3.5 times; the transverse stretching temperature is 110℃~130℃, and the stretching ratio is 3.0~4.0 times.

[0008] Furthermore, in step S3, the aperture of the microporous reflective structure is 0.5~3μm and the pore closure rate is ≥80%, so that the thermal shrinkage rate of the prepared reflective film at 200℃ is MD≤2.5% and TD≤1.0%.

[0009] Furthermore, in step S4, the application of the UV-resistant primer coating specifically involves: applying an acrylic or polyurethane primer liquid with a thickness of 2-5 μm to the surface of the surface layer (B), which is then dried to form an adhesion-promoting layer.

[0010] Furthermore, the total thickness of the reflective film is 50~200μm, and after 1000 hours of ultraviolet aging test, the reflectivity retention rate is ≥95%, and the surface is free from powdering and yellowing.

[0011] This invention provides a manufacturing process for a co-extruded biaxially oriented UV-resistant printable reflective film, which has the following beneficial effects: This manufacturing process utilizes a "synergistic effect of organic foaming agent and inorganic nucleating agent" technology to construct a uniform microporous structure with a pore size of 0.5~3μm within the core layer (A). This microporous structure enables highly efficient Mie scattering of incident light, significantly improving the film's reflectivity (≥92%). Compared to traditional solid white films, this micro-foamed structure effectively reduces light transmittance (≤0.5%).

[0012] This invention introduces hindered amine light stabilizers and carbon black as weather-resistant additives into the surface (B) formulation, combined with a "UV-resistant undercoating" process. This design not only endows the film itself with excellent UV resistance, but more importantly, it provides an excellent adhesion foundation for subsequent UV ink printing, solving the technical problems of low surface energy and easy ink smudging in PET films.

[0013] By precisely controlling the biaxial stretching process and heat setting parameters, the film can maintain a low heat shrinkage rate of MD≤2.5% and TD≤1.0% even at a high temperature of 200℃. This characteristic perfectly solves the problem of film deformation and blistering caused by high-temperature environments.

[0014] By using inorganic nucleating agents to replace some of the expensive organic foaming agents, the cost of raw materials is reduced while ensuring high stiffness and thermal stability. In addition, the microporous structure design with a closed-cell rate of ≥80% effectively blocks the permeation path of water vapor, indirectly improving the hydrolysis resistance of the film and enabling it to adapt to the harsh environment of photovoltaic and outdoor displays. Detailed Implementation

[0015] A manufacturing process for a co-extruded biaxially oriented UV-resistant printable reflective film includes the following steps: S1. Raw material preparation: The reflective film is designed with a three-layer structure of A / B / A, wherein the core layer (A) contains PET resin, organic foaming agent and inorganic nucleating agent, and the surface layer (B) contains PET resin, anti-blocking agent and weather-resistant additive; S2, Co-extrusion casting: After drying the core layer (A) and surface layer (B) raw materials for 48 hours, they are fed into a three-layer co-extrusion die for melt extrusion and then rapidly cooled by cooling rollers to form a thick sheet; S3. Biaxial stretching: The thick sheet is stretched longitudinally and laterally, and the stretching temperature is controlled above the glass transition temperature Tg of PET. The microporous reflective structure is constructed in the core layer (A) by utilizing the synergistic foaming effect of organic and inorganic particles. S4. Surface treatment: Corona treatment or UV-resistant base coating is applied to the surface layer (B) of the stretched film to obtain a surface tension suitable for UV ink printing. S5. Winding: After shaping and cooling, the film is wound up to obtain the UV-resistant printing reflective film.

[0016] Furthermore, in step S1, the mass ratio of the organic foaming agent to the inorganic nucleating agent in the core layer (A) is 1:(1~3), and the inorganic nucleating agent is one or more of talc, silicon dioxide or calcium carbonate.

[0017] Furthermore, in step S1, the weather-resistant additives in the surface layer (B) include hindered amine light stabilizers and carbon black, and the thickness of the surface layer (B) accounts for 5% to 15% of the total thickness of the reflective film.

[0018] Furthermore, in step S3, the longitudinal stretching temperature is 85℃~95℃, and the stretching ratio is 2.5~3.5 times; the transverse stretching temperature is 110℃~130℃, and the stretching ratio is 3.0~4.0 times.

[0019] Furthermore, in step S3, the aperture of the microporous reflective structure is 0.5~3μm and the pore closure rate is ≥80%, so that the thermal shrinkage rate of the prepared reflective film at 200℃ is MD≤2.5% and TD≤1.0%.

[0020] Furthermore, in step S4, the application of the UV-resistant primer coating specifically involves: applying an acrylic or polyurethane primer liquid with a thickness of 2-5 μm to the surface of the surface layer (B), which is then dried to form an adhesion-promoting layer.

[0021] Furthermore, the total thickness of the reflective film is 50~200μm, and after 1000 hours of ultraviolet aging test, the reflectivity retention rate is ≥95%, and the surface is free from powdering and yellowing.

[0022] In summary, the production process of this co-extruded biaxially oriented UV-resistant printable reflective film includes the following specific steps: Weigh out 90% PET resin, 5% organic foaming agent, and 5% inorganic nucleating agent (talc, 1μm particle size) by weight percentage. Ensure the mass ratio of organic foaming agent to inorganic nucleating agent is 1:1. Surface layer (B) ingredients: Weigh out 92% PET resin, 3% anti-blocking agent (silica), and weather-resistant additives (hindered amine light stabilizer + carbon black) by weight percentage. 5% of the above raw materials are put into a dryer for drying at 150°C for 4 hours to ensure that the moisture content is less than 50ppm. Then, the dried core layer (A) and surface layer (B) raw materials are fed into a three-layer co-extrusion die (A / B / A structure) and melt-extruded at 270°C. The thickness of each layer is precisely controlled by a metering pump. After the melt is extruded through the die, it is quickly cooled by a mirror cooling roller to form an amorphous sheet. The temperature of the cooling roller is controlled at 30°C to ensure that the surface of the sheet is flat and free of crystals. The sheet is then fed into a longitudinal stretching machine. Longitudinal stretching: stretching is performed at 90°C (above the glass transition temperature Tg of PET) with a stretching ratio of 3.0. Transverse stretching: the sheet enters a transverse stretching machine (TD) and is stretched at 120°C with a stretching ratio of 3.5. Under the action of tensile stress, the organic foaming agent in the core layer decomposes to produce gas, which is captured by the inorganic nucleating agent and induced to nucleate, forming a large number of uniform microbubbles. As stretching proceeds, the bubbles are stretched into a flat, closed-cell structure with a pore size controlled at 1~2μm. The stretched film enters the coating unit, where a 3μm thick acrylic primer is coated on the surface (B). After drying in an oven (80℃), the primer is cured, and the surface tension is increased to over 42 dynes / cm to be suitable for UV ink printing. After cooling and setting, it is wound up by a winding machine to obtain a 100μm thick finished UV-resistant reflective film.

Claims

1. A manufacturing process for a co-extruded biaxially oriented UV-resistant printable reflective film, characterized in that, Includes the following steps: S1. Raw material preparation: The reflective film is designed with a three-layer structure of A / B / A, wherein the core layer (A) contains PET resin, organic foaming agent and inorganic nucleating agent, and the surface layer (B) contains PET resin, anti-blocking agent and weather-resistant additive; S2, Co-extrusion casting: After drying the core layer (A) and surface layer (B) raw materials for 48 hours, they are fed into a three-layer co-extrusion die for melt extrusion and then rapidly cooled by cooling rollers to form a thick sheet; S3. Biaxial stretching: The thick sheet is stretched longitudinally and laterally, and the stretching temperature is controlled above the glass transition temperature Tg of PET. The microporous reflective structure is constructed in the core layer (A) by utilizing the synergistic foaming effect of organic and inorganic particles. S4. Surface treatment: The surface layer (B) of the stretched film is corona treated or coated with a UV-resistant base coating to obtain a surface tension suitable for UV ink printing. S5. Winding: After shaping and cooling, the film is wound up to obtain the UV-resistant printing reflective film.

2. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: In step S1, the mass ratio of organic foaming agent to inorganic nucleating agent in the core layer (A) is 1:(1~3), and the inorganic nucleating agent is one or more of talc, silicon dioxide or calcium carbonate.

3. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: In step S1, the weather-resistant additives in the surface layer (B) include hindered amine light stabilizers and carbon black, and the thickness of the surface layer (B) accounts for 5% to 15% of the total thickness of the reflective film.

4. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: In step S3, the longitudinal stretching temperature is 85℃~95℃, and the stretching ratio is 2.5~3.5 times; the transverse stretching temperature is 110℃~130℃, and the stretching ratio is 3.0~4.0 times.

5. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: In step S3, the aperture of the microporous reflective structure is 0.5~3μm and the pore closure rate is ≥80%, so that the thermal shrinkage rate of the prepared reflective film at 200℃ is MD≤2.5% and TD≤1.0%.

6. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: In step S4, the application of the UV-resistant primer coating specifically involves: applying an acrylic or polyurethane primer liquid with a thickness of 2-5 μm to the surface of the surface layer (B), and then drying it to form an adhesion-promoting layer.

7. The production process of a co-extruded biaxially oriented UV-resistant printable reflective film according to claim 1, characterized in that: The total thickness of the reflective film is 50~200μm, and after 1000 hours of ultraviolet aging test, the reflectivity retention rate is ≥95%, and the surface is free from powdering and yellowing.