Application method of cellulose acetate membrane in OMD decoration process

Abstract

The invention discloses an application method of a cellulose acetate membrane in an OMD decoration process, and belongs to the technical field of an out-of-mold decoration process. The application method of the cellulose acetate diaphragm applied to the OMD decoration process comprises the following steps: step 1, carrying out prime coat treatment on a binding surface of the cellulose acetate diaphragm to form a prime coat layer; 2, coating thermal reactive PU glue on the surface of one side of the PC film, and baking to form a glue layer; step 3, performing hot-pressing compounding on the cellulose acetate membrane with the prime coat and a PC (Polycarbonate) membrane through thermal reactive PU (Poly Urethane) glue to obtain a composite membrane; 4, the composite membrane is integrally transferred and attached to the surface of an ABS / PC injection molding part through a vacuum pressure difference membrane covering technology, and OMD out-of-mold decoration is completed. The application effect of the cellulose acetate membrane in the OMD decoration technology can be effectively improved, and the high practical value is achieved.

Description

Technical Field

[0001] This invention relates to the field of external decoration technology, specifically to a method for applying cellulose acetate film in OMD decoration process. Background Technology

[0002] Compared to traditional IMD (In-Mold Decoration) processes, OMD (Out-of-Mold Decoration) eliminates the need for cutting, stamping, and injection fixtures, offering advantages such as lower mold opening costs, shorter prototyping cycles, and greater process flexibility. This has led to its rapid adoption in consumer electronics, home appliances, and automotive interiors. Cellulose acetate film, as an environmentally friendly polymer decorative material, has become an ideal choice for high-end aesthetics due to its unique performance advantages. Through special processing, this film can exhibit rich pearlescent, iridescent, and textured high-end visual effects, meeting the personalized and premium appearance requirements of various products. Furthermore, compared to traditional decorative films, cellulose acetate film offers significant advantages such as resistance to yellowing, low odor, and excellent flame retardancy. It is resistant to aging and discoloration during use, has no irritating odor, and meets the flame retardant safety requirements of high-end products, making it suitable for various indoor and outdoor applications.

[0003] Based on the above, the inventors have discovered the following problems: cellulose acetate films have low surface gloss and poor fullness; secondly, they are brittle and easily broken. Decorative films require stretching, bending, and bonding processes, especially for curved or irregularly shaped decorative parts. Cellulose acetate films are inherently brittle and lack toughness, making them prone to cracking, breaking, and damage during stretching and curved surface forming, leading to molding failure and making them unsuitable for the molding requirements of the OMD process. Furthermore, their low surface polarity makes adhesion difficult, resulting in poor adhesion to adhesives and injection molded parts. Adhesives are difficult to wet and adhere to their surface, leading to insufficient bonding strength between the film and adhesive, and between the film and injection molded parts. Decorative parts after molding are prone to film detachment and warping. These defects prevent them from being directly applied to the OMD out-of-mold decoration process.

[0004] Therefore, in view of this, we have studied and improved the existing structure and its shortcomings, and provided a method for applying cellulose acetate film in OMD decoration process, in order to achieve a more practical value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for applying cellulose acetate film in OMD decoration process, so as to solve the problem mentioned in the background art that the inherent defects of cellulose acetate film itself prevent it from being directly applied to OMD external decoration process.

[0006] In view of the above problems, the technical solution proposed by the present invention is: A method for applying cellulose acetate film in OMD (Optical Decoration) process includes the following steps: Step 1: Apply a primer to the bonding surface of the cellulose acetate film to form a primer layer; Step 2: Apply heat-reactive PU adhesive to one side of the PC film and bake it to form an adhesive layer. Step 3: The pre-coated cellulose acetate film and PC film are hot-pressed together with thermally reactive PU adhesive to obtain a composite film. Step four: The composite film is transferred and bonded to the surface of the ABS / PC injection molded part through a vacuum differential pressure coating process to complete the OMD external decoration.

[0007] Furthermore, the cellulose acetate membrane has a thickness of 60–100 μm, and the PC membrane has a thickness of 0.1–0.3 mm.

[0008] The beneficial effect of adopting the above-mentioned further solution is that by limiting the thickness of the cellulose acetate film to 60-100 μm and the thickness of the PC film to 0.1-0.3 mm, the molding flexibility and decorative texture of the cellulose acetate film are guaranteed, while the PC film has sufficient supporting strength. This avoids the problems of the composite film being too thin and easily damaged, or too thick and difficult to adhere. It also meets the molding requirements of the vacuum pressure differential lamination process, ensuring that the composite film is adhered smoothly and is not prone to warping.

[0009] Furthermore, the coating thickness of the thermally reactive PU adhesive is 20–50 μm.

[0010] The beneficial effect of adopting the above-mentioned further solution is that by controlling the coating thickness of the heat-reactive PU adhesive to 20-50μm, the bonding strength between the cellulose acetate film and the PC film can be guaranteed, avoiding delamination and delamination. It can also prevent problems such as glue overflow and shrinkage deformation caused by excessive glue layer thickness, improve the structural stability and appearance flatness of the composite film, and ensure the finished product quality of the OMD decoration process.

[0011] Furthermore, the baking conditions for coating the thermally reactive PU adhesive are 50-60℃ for 8-20 minutes, followed by curing at 40-60℃ for 12-32 hours after lamination.

[0012] The beneficial effects of adopting the above-mentioned further solution are that by baking at 50-60℃ for 8-20 minutes to form an adhesive layer, the heat-reactive PU adhesive can be fully cured and evenly coated, avoiding adhesive failure caused by high-temperature baking; after lamination, curing at 40-60℃ for 12-32 hours allows the PU adhesive to undergo a complete cross-linking reaction, further improving the bonding strength and weather resistance of the composite film, ensuring that the film does not fall off during long-term use, and guaranteeing the durability of the OMD decorative effect.

[0013] Furthermore, the PC film can be a transparent glossy film or a matte PC film, respectively achieving glossy or matte decorative effects.

[0014] The beneficial effect of adopting the above-mentioned further solutions is that by using transparent glossy film or matte PC film as the substrate, two decorative effects, glossy or matte, can be flexibly achieved according to the decorative needs without the need for additional changes in processes or materials, thus broadening the range of choices for product decorative styles. At the same time, the transparency of PC film can also preserve the original texture and feel of cellulose acetate film, enhancing the sense of decorative layering.

[0015] Furthermore, the composite membrane structure consists of, in sequence: PC membrane, heat-reactive PU adhesive layer, primer layer, cellulose acetate membrane, primer layer, adhesive layer, and protective film.

[0016] The beneficial effects of adopting the above-mentioned further solution are that the composite film adopts a multi-layer structure of PC film, heat-reactive PU adhesive layer, primer layer, cellulose acetate film, primer layer, adhesive layer, and protective film. The primer layer improves the bonding force between the films, the protective film prevents the films from being damaged during transportation and bonding, and the adhesive layer enhances the bonding performance between the composite film and ABS / PC injection molded parts. The overall structure is stable and durable, meeting the stringent requirements of OMD external decoration.

[0017] Furthermore, the vacuum pressure differential coating process has a vacuum degree of -0.06 to -0.09 MPa, a forming temperature of 125 to 165°C, and a coating time of 5 to 30 seconds.

[0018] The beneficial effects of adopting the above-mentioned further scheme are that by setting the vacuum degree of the vacuum differential coating process to -0.06 to -0.09 MPa, controlling the molding temperature to 125 to 165°C, and setting the coating time to 5 to 30 seconds, the composite film can fully fit the complex curved surface of the ABS / PC injection molded part, ensuring seamless bonding between the film and the injection molded part surface, and avoiding defects such as bubbles and wrinkles; the precise process parameters are adapted to the molding characteristics of the injection molded part, improving the molding efficiency and finished product qualification rate of OMD decoration.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The application method of the cellulose acetate film in the OMD decoration process uses the cellulose acetate film as the core substrate and achieves stable application of the cellulose acetate film in the OMD decoration process through steps such as primer treatment, PU adhesive coating, hot pressing and lamination, and vacuum pressure differential coating. Compared with traditional decorative materials, the cellulose acetate film has excellent texture, weather resistance and formability. Combined with the OMD out-of-mold decoration process, it can give ABS / PC injection molded parts a high-end decorative effect, while improving the wear resistance and chemical corrosion resistance of the product surface, expanding the application field of cellulose acetate film, and adapting it to a variety of high-end decoration scenarios such as automotive interiors and home appliance panels. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the application method disclosed in an embodiment of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the composite diaphragm disclosed in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figures 1-2 This invention provides a technical solution: a method for applying cellulose acetate film in OMD decoration process, comprising the following steps: Step 1: Apply a primer to the bonding surface of the cellulose acetate film to form a primer layer; Step 2: Apply heat-reactive PU adhesive to one side of the PC film and bake it to form an adhesive layer. Step 3: The pre-coated cellulose acetate film and PC film are hot-pressed together with thermally reactive PU adhesive to obtain a composite film. Step four: The composite film is transferred and bonded to the surface of the ABS / PC injection molded part through a vacuum differential pressure coating process to complete the OMD external decoration.

[0023] In one embodiment of the present invention, the thickness of the cellulose acetate film is 60-100 μm, and the thickness of the PC film is 0.1-0.3 mm. Limiting the thickness of the cellulose acetate film to 60-100 μm and the thickness of the PC film to 0.1-0.3 mm ensures both the molding flexibility and decorative texture of the cellulose acetate film and sufficient support strength of the PC film. This avoids the problems of the composite film being too thin and easily damaged, or too thick and difficult to adhere, thus adapting to the molding requirements of the vacuum pressure differential lamination process and ensuring that the composite film is flat and not easily warped.

[0024] In one embodiment of the present invention, the coating thickness of the thermally reactive PU adhesive is further 20-50 μm. Controlling the coating thickness of the thermally reactive PU adhesive to 20-50 μm can ensure the bonding strength between the cellulose acetate film and the PC film, avoid delamination and delamination, and prevent problems such as glue overflow and shrinkage deformation caused by excessive glue layer thickness. This improves the structural stability and appearance flatness of the composite film and ensures the finished product quality of the OMD decoration process.

[0025] In one embodiment of the present invention, the baking conditions for coating the thermally reactive PU adhesive are 50-60°C for 8-20 minutes, followed by curing at 40-60°C for 12-32 hours after lamination. Baking at 50-60°C for 8-20 minutes forms the adhesive layer, allowing the thermally reactive PU adhesive to fully cure and be evenly coated, avoiding adhesive failure caused by high-temperature baking. Curing at 40-60°C for 12-32 hours after lamination allows the PU adhesive to undergo a complete cross-linking reaction, further improving the bonding strength and weather resistance of the composite film, ensuring that the film does not detach during long-term use, and guaranteeing the durability of the OMD decorative effect.

[0026] In one embodiment of the present invention, the PC film is either a transparent glossy film or a matte PC film, respectively achieving glossy or matte decorative effects. By using a transparent glossy film or a matte PC film as the substrate, glossy or matte decorative effects can be flexibly achieved according to decorative needs without the need for additional process or material changes, thus broadening the range of choices for product decorative styles. At the same time, the transparency of the PC film can also retain the original texture and feel of the cellulose acetate film, enhancing the sense of decorative layering.

[0027] In one embodiment of the present invention, the composite film structure comprises, in sequence: a PC film, a heat-reactive PU adhesive layer, a primer layer, a cellulose acetate film, a primer layer, an adhesive layer, and a protective film. The composite film adopts a multi-layer structure of PC film, heat-reactive PU adhesive layer, primer layer, cellulose acetate film, primer layer, adhesive layer, and protective film. The primer layer enhances the bonding force between the films, the protective film prevents damage to the films during transportation and bonding, and the adhesive layer enhances the bonding performance between the composite film and the ABS / PC injection molded parts. The overall structure is stable and durable, meeting the stringent requirements for OMD external decoration.

[0028] In one embodiment of the present invention, the vacuum pressure differential coating process has a vacuum degree of -0.06 to -0.09 MPa, a molding temperature of 125 to 165°C, and a coating time of 5 to 30 seconds. Setting the vacuum degree of the vacuum pressure differential coating process to -0.06 to -0.09 MPa, the molding temperature to 125 to 165°C, and the coating time to 5 to 30 seconds allows the composite film to fully adhere to the complex curved surface of the ABS / PC injection molded part, ensuring seamless adhesion between the film and the injection molded part surface, and avoiding defects such as bubbles and wrinkles. The precise process parameters are adapted to the molding characteristics of the injection molded part, improving the molding efficiency and finished product qualification rate of OMD decoration.

[0029] Example 1 A method for applying cellulose acetate film in OMD (Optical Decoration) process includes the following steps: Step 1: Select a cellulose acetate film with a thickness of 80μm, and apply a primer to its bonding surface to form a primer layer; Step 2: Select a transparent PC film with a thickness of 0.2mm, coat its surface with a 30μm thick heat-reactive PU adhesive, and bake at 55℃ for 10 minutes; Step 3: The cellulose acetate film after primer coating is hot-pressed and laminated with PC film, and cured at 50°C for 24 hours to obtain the composite film; Step 4: Apply the composite film to the surface of the ABS / PC injection molded part under the conditions of vacuum degree -0.07MPa, temperature 150°C, and coating time 15s to complete the OMD decoration.

[0030] Tested: Adhesion rating 0, no peeling in cross-cut adhesion test, no cracking when bent 180°.

[0031] Example 2 A method for applying cellulose acetate film in OMD (Optical Decoration) process includes the following steps: Step 1: Select a cellulose acetate film with a thickness of 90μm, and apply a primer to its bonding surface to form a primer layer; Step 2: Select a matte PC film with a thickness of 0.25mm, coat its surface with a 40μm thick heat-reactive PU adhesive, and bake at 50℃ for 15min; Step 3: The cellulose acetate film after primer coating is hot-pressed and laminated with matte PC film, and cured at 55°C for 20 hours to obtain the composite film; Step 4: Apply the composite film to the surface of the ABS / PC injection molded part under the conditions of vacuum degree -0.08MPa, temperature 160°C, and coating time 20s to complete the OMD decoration.

[0032] Tested: Adhesion grade 0, no discoloration or cracking after 500 hours of UV resistance testing.

Claims

1. A method for applying cellulose acetate film in OMD (Optical Decoration) process, characterized in that, Includes the following steps: Step 1: Apply a primer to the bonding surface of the cellulose acetate film to form a primer layer; Step 2: Apply heat-reactive PU adhesive to one side of the PC film and bake it to form an adhesive layer. Step 3: The pre-coated cellulose acetate film and PC film are hot-pressed together with thermally reactive PU adhesive to obtain a composite film. Step four: The composite film is transferred and bonded to the surface of the ABS / PC injection molded part through a vacuum differential pressure coating process to complete the OMD external decoration.

2. The application method of the cellulose acetate film according to claim 1 in the OMD decoration process, characterized in that, The cellulose acetate membrane has a thickness of 60–100 μm, and the PC membrane has a thickness of 0.1–0.3 mm.

3. The method of applying the cellulose acetate film according to claim 1 to the OMD decoration process, characterized in that, The thickness of the thermally reactive PU adhesive coating is 20–50 μm.

4. The method of applying the cellulose acetate film according to claim 1 to the OMD decoration process, characterized in that, The baking conditions for coating the thermally reactive PU adhesive are 50-60℃ for 8-20 minutes, followed by curing at 40-60℃ for 12-32 hours after lamination.

5. The method of applying the cellulose acetate film according to claim 1 to the OMD decoration process, characterized in that, The PC film can be a transparent glossy film or a matte PC film, achieving glossy or matte decorative effects respectively.

6. The method of applying the cellulose acetate film according to claim 1 to the OMD decoration process, characterized in that, The composite membrane structure consists of, in sequence: PC membrane, heat-reactive PU adhesive layer, primer layer, cellulose acetate membrane, primer layer, adhesive layer, and protective film.

7. The method of applying the cellulose acetate film according to claim 1 to the OMD decoration process, characterized in that, The vacuum pressure differential coating process has a vacuum degree of -0.06 to -0.09 MPa, a forming temperature of 125 to 165°C, and a coating time of 5 to 30 seconds.

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