Anti-sublimation PU leather lettering film and preparation method thereof

Abstract

The invention discloses an anti-sublimation PU (polyurethane) leather lettering film and a preparation method thereof, the lettering film is of a layered structure sequentially compounded from top to bottom, and each layer sequentially comprises a PET (polyethylene terephthalate) silica gel protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic acid adhesive layer and a PES (polyetherimide) hot melt adhesive film layer from top to bottom; through cooperation of a specific layered structure and a precise process, the problems of color crossing and color fading of the lettering film caused by dye migration of the chemical fiber fabric are solved fundamentally, and the anti-sublimation barrier effect is stable and reliable; the agglomeration of the nano activated carbon filler is effectively avoided, the coating is compact and uniform, the pinhole defect is avoided, and the barrier property consistency is high; all the layers are tightly combined, the peeling strength is high, delaminating is not prone to occurring after water washing and high-temperature ironing, and the use durability of the product is remarkably improved; the adhesive has excellent interlayer adhesive force and dye permeation barrier property, and the hidden danger of interface permeation is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of PU leather lettering film preparation technology, specifically an anti-sublimation PU leather lettering film and its preparation method. Background Technology

[0002] The diversification of clothing fabrics has driven the technological upgrading of matching decorative lettering films. Synthetic fiber fabrics, due to their lightweight, wear-resistant, and easy-care properties, are widely used in various garment productions. However, after dyeing, they inherently suffer from the problem of dye migration and sublimation under humid and hot conditions. When PU leather lettering films are hot-pressed onto the surface of synthetic fiber fabrics, the migrating dyes from the fabric easily penetrate into the lettering film, causing color bleeding and fading of the lettering pattern, severely affecting the appearance and durability of the garment.

[0003] Currently, in order to alleviate the problem of dye migration, some existing technologies attempt to add activated carbon fillers to PU leather lettering films to prepare barrier coatings. However, existing solutions have many technical defects: First, the directly added nano-activated carbon powder is prone to agglomeration in the water-based PU resin system, resulting in pinholes and particles in the coating and unstable barrier effect; Second, the composite process of each layer of the lettering film lacks precise parameter matching, resulting in insufficient interlayer bonding, and delamination is prone to occur after washing and high-temperature ironing, further losing the dye barrier ability; Third, the adhesives mostly use ordinary water-based adhesives without targeted cross-linking design, which cannot take into account both interlayer adhesion and dye penetration barrier properties. Moreover, there is no clear specification for the timing of the composite of hot melt adhesive film and coating, which can easily lead to gaps at the composite interface, allowing dye to easily penetrate from the interface.

[0004] Meanwhile, the proportions of raw materials for the anti-sublimation coating of existing PU leather lettering films are not precisely defined. The ratios of activated carbon powder, water-based resin, and color paste are not reasonable, which can easily lead to a situation where the film-forming properties and barrier properties of the coating cannot be simultaneously achieved. Furthermore, there are no uniform specifications for the parameters of stirring, drying, and coating processes in the preparation process, resulting in poor performance consistency between different batches of products, which cannot meet the needs of large-scale industrial production. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, there is an urgent need to develop a PU leather lettering film with tight interlayer bonding, stable anti-sublimation effect, and controllable preparation process. This would solve the technical problem of color bleeding and fading of the lettering film caused by dye migration from chemical fiber fabrics, and improve the product's durability and batch stability.

[0006] This invention provides a PU leather lettering film that prevents sublimation. The lettering film has a layered structure that is composited from top to bottom. The layers, from top to bottom, are a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer.

[0007] The anti-sublimation PU resin coating is prepared by mechanically mixing 68% water-based PU resin, 12% water-based white paste, and 20% 3000-mesh nano activated carbon powder by weight, with the stirring speed being ≥800 r / min.

[0008] This invention also provides a method for preparing an anti-sublimation PU leather lettering film, applicable to the aforementioned anti-sublimation PU leather lettering film, characterized by comprising the following steps:

[0009] S1. Preparation of anti-sublimation PU resin coating slurry: Weigh 68% water-based PU resin, 12% water-based white paste, and 20% of 3000-mesh nano-activated carbon powder after hydrophilic modification by weight percentage. First, put the water-based PU resin and water-based white paste into a stirring device and mechanically stir and mix at a speed of ≥800r / min. Then, add the 3000-mesh nano-activated carbon powder after hydrophilic modification and continue mechanical stirring and mixing. After stirring, filter through a 200-mesh filter to obtain the anti-sublimation PU resin coating slurry.

[0010] S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the anti-sublimation PU resin coating slurry obtained in step S1 is applied to the lower surface of the colored PU leather layer bonded with the PET silicone protective film.

[0011] S3. Drying and film formation: The substrate coated in step S2 is sent to a heating drying oven for segmented hot air drying. After drying, an anti-sublimation PU resin coating is formed on the lower surface of the colored PU leather layer, resulting in an anti-sublimation barrier film substrate. The moisture content of the anti-sublimation PU resin coating is ≤0.5%. The moisture content is detected by the Karl Fischer method. The detection method is to take a 0.5g sample of the anti-sublimation PU resin coating and measure the moisture content using a Karl Fischer moisture analyzer.

[0012] S4. Applying an acrylic adhesive layer: Using a micro-recessed coating method, a cross-linked waterborne acrylic adhesive prepared by mixing according to the proportions described in claim 5 is applied to the lower surface of the anti-sublimation PU resin coating of the anti-sublimation barrier film substrate obtained in step S3 to form an acrylic adhesive wet film.

[0013] S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is not dry, the low melting point polyethersulfone hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, and then hot pressing is performed to achieve composite of each layer.

[0014] S6. Crosslinking, curing and winding: The substrate after hot pressing and bonding in step S5 is placed in a 25℃ environment and left to stand for 24 hours for crosslinking and curing. After curing, it is wound up to obtain the anti-sublimation PU leather lettering film; the interlayer peel strength of the finished product is ≥8N / 25mm.

[0015] The technical solutions provided by the embodiments of this disclosure have at least the following beneficial effects:

[0016] By combining a specific layered structure with precise processes, the problem of color bleeding and fading in lettering films caused by dye migration in synthetic fiber fabrics is fundamentally solved, ensuring stable and reliable anti-sublimation barrier effects. It effectively avoids the agglomeration of nano-activated carbon fillers, resulting in a dense, uniform coating free of pinholes and exhibiting high consistency in barrier performance. The layers are tightly bonded with high peel strength, making it resistant to delamination after washing and high-temperature ironing, significantly improving product durability. The adhesive combines excellent interlayer adhesion with dye penetration barrier properties, eliminating the risk of interfacial penetration. The raw material ratio and preparation process parameters are controllable, ensuring good batch stability and meeting the needs of large-scale industrial production. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 This application provides an anti-sublimation PU leather lettering film and its preparation method. The lettering film is a layered structure that is composited from top to bottom. The layers from top to bottom are a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer.

[0020] The anti-sublimation PU resin coating is prepared by mechanically mixing 68% water-based PU resin, 12% water-based white paste, and 20% 3000-mesh nano activated carbon powder by weight, with the stirring speed being ≥800 r / min.

[0021] As an optional embodiment, the thickness of the PET silicone protective film is 20~35μm, the thickness of the colored PU leather layer is 50~90μm, the dry film thickness of the anti-sublimation PU resin coating is 10~25μm, the dry film thickness of the acrylic adhesive layer is 3~8μm, and the thickness of the PES hot melt adhesive film layer is 35~65μm.

[0022] As an optional embodiment, the 3000-mesh nano-activated carbon powder undergoes hydrophilic modification treatment. The hydrophilic modification treatment steps are as follows: mixing the 3000-mesh nano-activated carbon powder with an ethanol solution of silane coupling agent KH-570, stirring at 600 r / min for 1.5 h, and then filtering. The filter residue obtained by suction filtration is placed in an 80℃ drying oven and dried for 2 h until constant weight. The mass fraction of silane coupling agent KH-570 in the ethanol solution of silane coupling agent KH-570 is 3% to 5%, and the solid-liquid ratio of the 3000-mesh nano-activated carbon powder to the ethanol solution of silane coupling agent KH-570 is 1:15.

[0023] The dispersibility test method for modified 3000 mesh nano activated carbon powder is as follows: the modified 3000 mesh nano activated carbon powder is added to water-based PU resin at a weight percentage of 20% and mechanically stirred until uniform. The particle size of the mixture is measured by a laser particle size analyzer. The particle size distribution variation coefficient is calculated by selecting the particle size data of 10 test points in the mixture. The dispersion is qualified if the particle size distribution variation coefficient is ≤15%.

[0024] As an optional embodiment, the waterborne PU resin is an aliphatic waterborne polyurethane resin with a solid content of 35% to 40% and a viscosity of 1000 to 2000 mPa at 25°C. Seconds; the aqueous white paste is a titanium dioxide type aqueous white paste, in which the mass fraction of titanium dioxide is 60% to 70% and the solid content is 50% to 55%.

[0025] As an optional embodiment, the acrylic adhesive layer is obtained by coating and cross-linking curing a cross-linked waterborne acrylic adhesive; the cross-linked waterborne acrylic adhesive is obtained by mixing waterborne acrylic resin and isocyanate cross-linking agent at a weight ratio of 100:3~5, wherein the solid content of the waterborne acrylic resin is 40%~45%, and the viscosity at 25°C is 800~1500 mPa. The cross-linked waterborne acrylic adhesive has a coating amount of 10-25 grams per square meter, and the cross-linking curing conditions are 25°C for 24 hours. After curing, the interlayer peel strength of the acrylic adhesive layer is ≥10N / 25mm.

[0026] As an optional embodiment, the PES hot melt adhesive film layer is a low melting point polyethersulfone hot melt adhesive film. The melting point of the low melting point polyethersulfone hot melt adhesive film is 80~95℃, and the melt flow rate is 15~20g / 10min under the test conditions of 190℃ / 2.16kg.

[0027] As an optional embodiment, the following steps are included:

[0028] S1. Preparation of anti-sublimation PU resin coating slurry: Weigh 68% water-based PU resin, 12% water-based white paste, and 20% of 3000-mesh nano-activated carbon powder after hydrophilic modification by weight percentage. First, put the water-based PU resin and water-based white paste into a stirring device and mechanically stir and mix at a speed of ≥800r / min. Then, add the 3000-mesh nano-activated carbon powder after hydrophilic modification and continue mechanical stirring and mixing. After stirring, filter through a 200-mesh filter to obtain the anti-sublimation PU resin coating slurry.

[0029] S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the anti-sublimation PU resin coating slurry obtained in step S1 is applied to the lower surface of the colored PU leather layer bonded with the PET silicone protective film.

[0030] S3. Drying and film formation: The substrate coated in step S2 is sent to a heating drying oven for segmented hot air drying. After drying, an anti-sublimation PU resin coating is formed on the lower surface of the colored PU leather layer, resulting in an anti-sublimation barrier film substrate. The moisture content of the anti-sublimation PU resin coating is ≤0.5%. The moisture content is detected by the Karl Fischer method. The detection method is to take a 0.5g sample of the anti-sublimation PU resin coating and measure the moisture content using a Karl Fischer moisture analyzer.

[0031] S4. Applying an acrylic adhesive layer: Using a micro-recessed coating method, a cross-linked waterborne acrylic adhesive prepared by mixing the ingredients in the specified ratio is applied to the lower surface of the anti-sublimation PU resin coating of the anti-sublimation barrier film substrate obtained in step S3, to form an acrylic adhesive wet film.

[0032] S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is not dry, the low melting point polyethersulfone hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, and then hot pressing is performed to achieve composite of each layer.

[0033] S6. Crosslinking, curing and winding: The substrate after hot pressing and bonding in step S5 is placed in a 25℃ environment and left to stand for 24 hours for crosslinking and curing. After curing, it is wound up to obtain the anti-sublimation PU leather lettering film; the interlayer peel strength of the finished product is ≥8N / 25mm.

[0034] As an optional embodiment, in step S1, the stirring speed of the mechanical stirrer is 800~1500 r / min, and the total stirring time is 20~40 min; the stirring and mixing time of the water-based PU resin and the water-based white paste is 10~20 min, and the stirring and mixing time after adding 3000 mesh nano activated carbon powder is 10~20 min.

[0035] As an optional embodiment, in step S2, the coating gap of the doctor blade coating is 50~100μm, and the coating speed is 4~8m / min; the film thickness uniformity of the anti-sublimation PU resin coating after coating is ≤±1μm. The film thickness uniformity is detected by a film thickness gauge. The detection method is to randomly select 10 detection points on the coating surface to detect the film thickness, and calculate the film thickness uniformity value of the difference in film thickness at the 10 detection points.

[0036] In step S3, the process parameters for the segmented hot air drying are as follows: the first stage drying temperature is 60~70℃, the drying time is 10~15min, and the hot air velocity is 2~3m / s; the second stage drying temperature is 85~95℃, the drying time is 5~8min, and the hot air velocity is 1~2m / s.

[0037] As an optional embodiment, in step S4, the coating speed of the micro-grooving is the same as the coating speed of the doctor blade coating in step S2.

[0038] In step S5, the process parameters for the hot pressing bonding process are: pressing temperature 50~60℃, pressing pressure 0.3~0.5MPa, and pressing speed 4~8m / min;

[0039] In step S6, the winding tension of the winding operation is 8-10N, and the winding tension is detected by a tension sensor set at the winding end; after winding, there is no relative offset between the layers of the finished product, and the surface of the finished product is free of wrinkles.

[0040] Example 1

[0041] A type of anti-sublimation PU leather lettering film, comprising, from top to bottom, a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer; the interlayer peel strength is ≥8N / 25mm.

[0042] The thickness of the PET silicone protective film is 28μm, the thickness of the colored PU leather layer is 70μm, the thickness of the anti-sublimation PU resin coating dry film is 18μm, the thickness of the acrylic adhesive layer dry film is 5μm, and the thickness of the PES hot melt adhesive film layer is 50μm.

[0043] The anti-sublimation PU resin coating is prepared from 68 wt% waterborne PU resin, 12 wt% waterborne white paste, and 20 wt% hydrophilically modified 3000-mesh nano-activated carbon powder; the waterborne PU resin is an aliphatic waterborne polyurethane resin with a solid content of 38% and a viscosity of 1500 mPa at 25°C. The water-based white paste is a titanium dioxide type water-based white paste, with a titanium dioxide mass fraction of 65% and a solid content of 52%.

[0044] The acrylic adhesive layer is obtained by coating and cross-linking curing a cross-linked waterborne acrylic adhesive. This cross-linked waterborne acrylic adhesive is prepared by mixing waterborne acrylic resin and isocyanate cross-linking agent at a weight ratio of 100:4, with a coating weight of 18 grams per square meter. The waterborne acrylic resin has a solid content of 42% and a viscosity of 1200 mPa at 25°C. Second.

[0045] The PES hot melt adhesive film layer is a low melting point polyethersulfone hot melt adhesive film with a melt flow rate of 18g / 10min under the test conditions of melting point 88℃ and 190℃ / 2.16kg.

[0046] The preparation method includes the following steps: S1. Preparation of anti-sublimation PU resin coating slurry: Weigh the above raw materials according to the weight percentage, first put the water-based PU resin and water-based white slurry into the stirring equipment, and mechanically stir at a speed of 1000 r / min for 15 min, then add the 3000 mesh nano activated carbon powder after hydrophilic modification treatment and continue to mechanically stir at the same speed for 15 min, with a total stirring time of 30 min;

[0047] After stirring, the mixture was filtered through a 200-mesh filter to obtain an anti-sublimation PU resin coating slurry. The hydrophilic modification treatment was carried out by mixing 3000-mesh nano activated carbon powder with 4% by mass of silane coupling agent KH-570 ethanol solution at a solid-liquid ratio of 1:15, stirring at 600 r / min for 1.5 h, and then filtering. The filter residue obtained by filtration was placed in an 80℃ drying oven and dried for 2 h until constant weight.

[0048] S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the coating slurry is applied to the lower surface of the colored PU leather layer bonded with the PET silicone protective film, with a coating gap of 70μm and a coating speed of 6m / min.

[0049] S3. Drying and film formation: The coated substrate is sent into a heating drying oven for segmented hot air drying. The first stage of drying is at a temperature of 65℃, a drying time of 12min, and a hot air velocity of 2.5m / s. The second stage of drying is at a temperature of 90℃, a drying time of 6min, and a hot air velocity of 1.5m / s.

[0050] After drying, the moisture content of the anti-sublimation PU resin coating is 0.4% ≤ 0.5%, thus obtaining the anti-sublimation barrier film substrate. S4, Coating the acrylic adhesive layer: Using a microgravure coating method, a cross-linked water-based acrylic adhesive is coated on the lower surface of the anti-sublimation PU resin coating at a speed of 6 m / min to form a wet acrylic adhesive film; the coating speed is the same as the doctor blade coating speed in step S2.

[0051] S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is still wet, the PES hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, followed by hot pressing. The pressing temperature is 55℃, the pressing pressure is 0.4MPa, and the pressing speed is 6m / min.

[0052] S6. Cross-linking, curing and winding: The substrate after hot pressing is placed in a 25℃ environment and left to stand for 24 hours for cross-linking and curing; after curing, a winding operation is performed with a winding tension of 9N. The winding tension is detected by a tension sensor set at the winding end; the finished product of anti-sublimation PU leather lettering film is obtained, with an interlayer peel strength of 9.2N / 25mm.

[0053] Example 2

[0054] A type of anti-sublimation PU leather lettering film, comprising, from top to bottom, a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer; the interlayer peel strength is ≥8N / 25mm.

[0055] The thickness of the PET silicone protective film is 20μm, the thickness of the colored PU leather layer is 50μm, the thickness of the anti-sublimation PU resin coating dry film is 10μm, the thickness of the acrylic adhesive layer dry film is 3μm, and the thickness of the PES hot melt adhesive film layer is 35μm.

[0056] The waterborne PU resin is an aliphatic waterborne polyurethane resin with a solid content of 35% and a viscosity of 1000 mPa at 25°C. The water-based white paste is a titanium dioxide type water-based white paste with a titanium dioxide mass fraction of 60% and a solid content of 50%.

[0057] The acrylic adhesive layer is obtained by coating and cross-linking curing a cross-linked waterborne acrylic adhesive. This cross-linked waterborne acrylic adhesive is prepared by mixing waterborne acrylic resin and isocyanate cross-linking agent at a weight ratio of 100:3, with a coating weight of 10 grams per square meter. The waterborne acrylic resin has a solid content of 40% and a viscosity of 800 mPa at 25°C. Second.

[0058] The PES hot melt adhesive film layer is a low melting point polyethersulfone hot melt adhesive film with a melt flow rate of 15g / 10min under the test conditions of melting point 80℃ and 190℃ / 2.16kg.

[0059] The preparation method includes the following steps: S1. Preparation of anti-sublimation PU resin coating slurry: Weigh the above raw materials according to the weight percentage, first put the water-based PU resin and water-based white slurry into the stirring equipment and stir at 800 r / min for 10 min, then add the hydrophilic modified 3000 mesh nano activated carbon powder and continue stirring at the same speed for 10 min; after stirring, filter through a 200 mesh filter to obtain the coating slurry.

[0060] S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the coating slurry is applied to the lower surface of the colored PU leather layer bonded with a PET silicone protective film, with a coating gap of 50μm and a coating speed of 4m / min.

[0061] S3. Drying and film formation: The coated substrate is sent into a heating drying oven for segmented hot air drying. The first stage of drying is at a temperature of 60℃, a drying time of 10min, and a hot air velocity of 2m / s. The second stage of drying is at a temperature of 85℃, a drying time of 5min, and a hot air velocity of 1m / s. After drying, the coating moisture content is 0.5%, and the anti-sublimation barrier film substrate is obtained.

[0062] S4. Applying the acrylic adhesive layer: Using a micro-gravure coating method, a cross-linked water-based acrylic adhesive is applied to the underside of the anti-sublimation PU resin coating at a speed of 4 m / min to form a wet film of acrylic adhesive; the coating speed is the same as the doctor blade coating speed in step S2.

[0063] S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is still wet, the PES hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, followed by hot pressing. The pressing temperature is 50℃, the pressing pressure is 0.3MPa, and the pressing speed is 4m / min.

[0064] S6. Cross-linking, curing and winding: The substrate after hot pressing is placed in a 25℃ environment and left to stand for 24 hours for cross-linking and curing; after curing, a winding operation is performed with a winding tension of 8N. The winding tension is detected by a tension sensor set at the winding end; the finished product of anti-sublimation PU leather lettering film is obtained, with an interlayer peel strength of 8.5N / 25mm.

[0065] Example 3

[0066] A type of anti-sublimation PU leather lettering film, comprising, from top to bottom, a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer; the interlayer peel strength is ≥8N / 25mm.

[0067] The thickness of the PET silicone protective film is 35μm, the thickness of the colored PU leather layer is 90μm, the thickness of the anti-sublimation PU resin coating dry film is 25μm, the thickness of the acrylic adhesive layer dry film is 8μm, and the thickness of the PES hot melt adhesive film layer is 65μm.

[0068] The waterborne PU resin is an aliphatic waterborne polyurethane resin with a solid content of 40% and a viscosity of 2000 mPa·s at 25°C. The waterborne white paste is a titanium dioxide-type waterborne white paste with a titanium dioxide mass fraction of 70% and a solid content of 55%.

[0069] The acrylic adhesive layer is obtained by coating and cross-linking curing a cross-linked waterborne acrylic adhesive. This cross-linked waterborne acrylic adhesive is prepared by mixing waterborne acrylic resin and isocyanate cross-linking agent at a weight ratio of 100:5, with a coating amount of 25 grams per square meter. The waterborne acrylic resin has a solid content of 45% and a viscosity of 1500 mPa at 25°C. Second.

[0070] The PES hot melt adhesive film layer is a low melting point polyethersulfone hot melt adhesive film with a melt flow rate of 20g / 10min under the test conditions of melting point 95℃ and 190℃ / 2.16kg.

[0071] The preparation method includes the following steps: S1. Preparation of anti-sublimation PU resin coating slurry: Weigh the above raw materials according to the weight percentage, first put the water-based PU resin and water-based white slurry into the stirring equipment and stir at a speed of 1500 r / min for 20 min, then add the hydrophilic modified 3000 mesh nano activated carbon powder and continue to stir at the same speed for 20 min; after stirring, filter through a 200 mesh filter to obtain the coating slurry.

[0072] S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the coating slurry is applied to the lower surface of the colored PU leather layer bonded with a PET silicone protective film, with a coating gap of 100μm and a coating speed of 8m / min.

[0073] S3. Drying and Film Formation: The coated substrate is placed in a heated drying oven for segmented hot air drying. The first stage drying temperature is 70℃, the drying time is 15min, and the hot air velocity is 3m / s. The second stage drying temperature is 95℃, the drying time is 8min, and the hot air velocity is 2m / s. After drying, the coating moisture content is 0.3%, resulting in an anti-sublimation barrier film substrate. S4. Coating with Acrylic Adhesive Layer: A cross-linked water-based acrylic adhesive is coated on the underside of the anti-sublimation PU resin coating using a microgravure coating method at a speed of 8m / min to form a wet acrylic adhesive film. The coating speed is the same as the doctor blade coating speed in step S2.

[0074] S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is still wet, the PES hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, followed by hot pressing. The pressing temperature is 60℃, the pressing pressure is 0.5MPa, and the pressing speed is 8m / min.

[0075] S6. Cross-linking, curing and winding: The substrate after hot pressing is placed in a 25℃ environment and left to stand for 24 hours for cross-linking and curing; after curing, the winding operation is carried out with a winding tension of 10N, which is a specific value within the corresponding range. The winding tension is detected by a tension sensor set at the winding end; the finished product of anti-sublimation PU leather lettering film is obtained, and the interlayer peel strength of the finished product is 9.8N / 25mm.

[0076] Comparative Example 1

[0077] The only difference from Example 1 is that the 3000-mesh nano activated carbon powder was not subjected to the hydrophilic modification treatment described above. Instead, the 3000-mesh nano activated carbon powder was directly added to the mixture of waterborne PU resin and waterborne white slurry. All other raw materials, process parameters, and preparation steps were the same as in Example 1.

[0078] Comparative Example 2

[0079] The only difference from Example 1 is that the weight ratio of the raw materials for the anti-sublimation PU resin coating deviates from the limit of 68wt% water-based PU resin, 12wt% water-based white paste, and 20wt% 3000 mesh nano activated carbon powder. In fact, 78wt% water-based PU resin, 12wt% water-based white paste, and 10wt% 3000 mesh nano activated carbon powder are used. All other raw materials, process parameters, and preparation steps are the same as in Example 1.

[0080] Comparative Example 3

[0081] The only difference from Example 1 is that the cross-linked waterborne acrylic adhesive was not used. The acrylic adhesive layer was prepared directly using ordinary waterborne acrylic adhesive without the addition of isocyanate cross-linking agents. All other raw materials, process parameters, and preparation steps were the same as in Example 1.

[0082] Comparative Example 4

[0083] The only difference from Example 1 is that the process of laminating the PES hot melt adhesive film while the acrylic adhesive wet film is not dry as described in step S5 is not used. Instead, the acrylic adhesive layer is dried to form a film before laminating the PES hot melt adhesive film. All other raw materials, process parameters, and preparation steps are the same as in Example 1.

[0084] Comparative Example 5

[0085] The only difference from Example 1 is that the drying process of the anti-sublimation PU resin coating is not the segmented hot air drying described above, but a single temperature of 80°C hot air drying for 30 minutes. All other raw materials, process parameters, and preparation steps are the same as in Example 1.

[0086] The performance of the anti-sublimation PU leather lettering films prepared in Examples 1-3 and Comparative Examples 1-5 was tested. The test indicators were particle size distribution variation coefficient (%), coating thickness uniformity (±μm), and interlayer peel strength (N / 25mm).

[0087] Performance test results table

[0088] The comparison shows that the particle size distribution variation coefficient, coating thickness uniformity, and interlayer peel strength of Examples 1-3 all meet the specified indicators of the claims; Comparative Example 1 did not modify the nano-activated carbon powder to be more hydrophilic, and its particle size distribution variation coefficient and coating thickness uniformity exceeded the specified range; Comparative Example 2 adjusted the coating raw material ratio, and all indicators met the standards, but its interlayer peel strength was lower than that of the Examples; Comparative Example 3 did not use a cross-linked adhesive, and Comparative Example 4 adopted a dry film composite process, and the interlayer peel strength of both did not meet the requirements; Comparative Example 5 did not use segmented hot air drying, and its coating thickness uniformity exceeded the specified range.

[0089] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A type of anti-sublimation PU leather lettering film, characterized in that, The lettering film has a layered structure that is composited from top to bottom. The layers, from top to bottom, are a PET silicone protective film, a colored PU leather layer, an anti-sublimation PU resin coating, an acrylic adhesive layer, and a PES hot melt adhesive film layer. The anti-sublimation PU resin coating is prepared by mechanically mixing 68% water-based PU resin, 12% water-based white paste, and 20% 3000-mesh nano activated carbon powder by weight, with the stirring speed being ≥800 r / min.

2. The anti-sublimation PU leather lettering film according to claim 1, characterized in that, The thickness of the PET silicone protective film is 20~35μm, the thickness of the colored PU leather layer is 50~90μm, the dry film thickness of the anti-sublimation PU resin coating is 10~25μm, the dry film thickness of the acrylic adhesive layer is 3~8μm, and the thickness of the PES hot melt adhesive film layer is 35~65μm.

3. The anti-sublimation PU leather lettering film according to claim 1, characterized in that, The 3000-mesh nano-activated carbon powder undergoes hydrophilic modification treatment. The hydrophilic modification treatment steps are as follows: the 3000-mesh nano-activated carbon powder is mixed with an ethanol solution of silane coupling agent KH-570, stirred at 600 r / min for 1.5 h, and then filtered. The filter residue obtained by filtration is placed in an 80℃ drying oven and dried for 2 h until constant weight. The mass fraction of silane coupling agent KH-570 in the ethanol solution of silane coupling agent KH-570 is 3% to 5%, and the solid-liquid ratio of 3000-mesh nano-activated carbon powder to the ethanol solution of silane coupling agent KH-570 is 1:

15. The dispersibility test method for modified 3000 mesh nano activated carbon powder is as follows: the modified 3000 mesh nano activated carbon powder is added to water-based PU resin at a weight percentage of 20% and mechanically stirred until uniform. The particle size of the mixture is measured by a laser particle size analyzer. The particle size distribution variation coefficient is calculated by selecting the particle size data of 10 test points in the mixture. The dispersion is qualified if the particle size distribution variation coefficient is ≤15%.

4. The anti-sublimation PU leather lettering film according to claim 1, characterized in that, The waterborne PU resin is an aliphatic waterborne polyurethane resin with a solid content of 35%–40% and a viscosity of 1000–2000 mPa at 25°C. Seconds; the aqueous white paste is a titanium dioxide type aqueous white paste, in which the mass fraction of titanium dioxide is 60% to 70% and the solid content is 50% to 55%.

5. The anti-sublimation PU leather lettering film according to claim 1, characterized in that, The acrylic adhesive layer is obtained by coating and cross-linking curing a cross-linked waterborne acrylic adhesive; the cross-linked waterborne acrylic adhesive is obtained by mixing waterborne acrylic resin and isocyanate cross-linking agent at a weight ratio of 100:3~5, the solid content of the waterborne acrylic resin is 40%~45%, and the viscosity at 25°C is 800~1500 mPa. The cross-linked waterborne acrylic adhesive has a coating amount of 10-25 grams per square meter, and the cross-linking curing conditions are 25°C for 24 hours. After curing, the interlayer peel strength of the acrylic adhesive layer is ≥10N / 25mm.

6. The anti-sublimation PU leather lettering film according to claim 1, characterized in that, The PES hot melt adhesive film layer is a low-melting-point polyethersulfone hot melt adhesive film. The melting point of the low-melting-point polyethersulfone hot melt adhesive film is 80~95℃. Under the test conditions of 190℃ / 2.16kg, the melt flow rate is 15~20g / 10min.

7. The method for preparing an anti-sublimation PU leather lettering film according to claim 1 is applicable to the anti-sublimation PU leather lettering film according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Preparation of anti-sublimation PU resin coating slurry: Weigh 68% water-based PU resin, 12% water-based white paste, and 20% of the hydrophilic modified 3000-mesh nano activated carbon powder by weight percentage. First, put the water-based PU resin and water-based white paste into a stirring device and mechanically stir and mix at a speed of ≥800r / min. Then, add the hydrophilic modified 3000-mesh nano activated carbon powder and continue mechanically stirring and mixing. After stirring, filter through a 200-mesh filter to obtain the anti-sublimation PU resin coating slurry. S2. Applying an anti-sublimation PU resin coating: Using a scraper coating method, the anti-sublimation PU resin coating slurry obtained in step S1 is applied to the lower surface of the colored PU leather layer bonded with the PET silicone protective film. S3. Drying and film formation: The substrate coated in step S2 is sent to a heating drying oven for segmented hot air drying. After drying, an anti-sublimation PU resin coating is formed on the lower surface of the colored PU leather layer, resulting in an anti-sublimation barrier film substrate. The moisture content of the anti-sublimation PU resin coating is ≤0.5%. The moisture content is detected by the Karl Fischer method. The detection method is to take a 0.5g sample of the anti-sublimation PU resin coating and measure the moisture content using a Karl Fischer moisture analyzer. S4. Applying an acrylic adhesive layer: Using a micro-recessed coating method, a cross-linked waterborne acrylic adhesive prepared by mixing the ingredients in the specified ratio is applied to the lower surface of the anti-sublimation PU resin coating of the anti-sublimation barrier film substrate obtained in step S3, to form an acrylic adhesive wet film. S5, Composite PES hot melt adhesive film layer: While the acrylic adhesive wet film is not dry, the low melting point polyethersulfone hot melt adhesive film is bonded to the lower surface of the acrylic adhesive wet film, and then hot pressing is performed to achieve composite of each layer. S6. Crosslinking, curing and winding: The substrate after hot pressing and bonding in step S5 is placed in a 25℃ environment and left to stand for 24 hours for crosslinking and curing. After curing, it is wound up to obtain the anti-sublimation PU leather lettering film; the interlayer peel strength of the finished product is ≥8N / 25mm.

8. The anti-sublimation PU leather lettering film and its preparation method according to claim 7, characterized in that, In step S1, the stirring speed of the mechanical stirrer is 800~1500 r / min, and the total stirring time is 20~40 min; the stirring and mixing time of the water-based PU resin and the water-based white paste is 10~20 min, and the stirring and mixing time after adding 3000 mesh nano activated carbon powder is 10~20 min.

9. The anti-sublimation PU leather lettering film and its preparation method according to claim 7, characterized in that, In step S2, the coating gap of the doctor blade coating is 50~100μm, and the coating speed is 4~8m / min; the film thickness uniformity of the anti-sublimation PU resin coating after coating is ≤±1μm. The film thickness uniformity is detected by a film thickness gauge. The detection method is to randomly select 10 detection points on the coating surface to detect the film thickness, and calculate the film thickness uniformity value of the difference in film thickness at the 10 detection points. In step S3, the process parameters for the segmented hot air drying are as follows: the first stage drying temperature is 60~70℃, the drying time is 10~15min, and the hot air velocity is 2~3m / s; the second stage drying temperature is 85~95℃, the drying time is 5~8min, and the hot air velocity is 1~2m / s.

10. The anti-sublimation PU leather lettering film and its preparation method according to claim 7, characterized in that, In step S4, the coating speed of the micro-grooving coating is the same as the coating speed of the doctor blade coating in step S2. In step S5, the process parameters for the hot pressing bonding process are: pressing temperature 50~60℃, pressing pressure 0.3~0.5MPa, and pressing speed 4~8m / min; In step S6, the winding tension of the winding operation is 8-10N, and the winding tension is detected by a tension sensor set at the winding end; after winding, there is no relative offset between the layers of the finished product, and the surface of the finished product is free of wrinkles.

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