Low temperature resistant polyurethane transfer film and method of making same

Abstract

The application relates to the technical field of layered materials, and discloses a low-temperature-resistant polyurethane transfer film and a preparation method thereof. The application prepares a multilayer structure heat transfer film with a glue layer and a polyurethane-based transfer layer, wherein a light-cured transfer layer material containing polyurethane acrylate with good low-temperature-resistant polyether, polybutadiene block and organic silicon branched chain and excellent far-infrared performance of mercapto-oxidized graphene is prepared, so that the low-temperature-resistant performance and water-resistant performance of the heat transfer film are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of layered materials technology, specifically to a low-temperature resistant polyurethane transfer film and its preparation method. Background Technology

[0002] Heat transfer film refers to a special functional printing film in which the image and text, along with a protective layer, detach from the base film under the action of heat and pressure, and firmly adhere to the surface of the substrate. Heat transfer film generally includes a base layer, a release layer, a protective layer, an ink layer, and an adhesive layer. After the image and text are transferred to the substrate, since the release layer does not transfer, the protective layer becomes the outermost layer on the substrate surface. The protective layer needs to have good mechanical properties. Traditional protective layers are thermosetting coatings, such as polyurethane-based coatings, but the resulting coating has insufficient spatial density and simple chemical bonds at the nodes, thus limiting its mechanical strength and failing to meet the increasingly high performance requirements of current products.

[0003] Polyurethane has a long-term operating temperature range of -40℃ to 80℃. In some extremely cold regions, the use of polyurethane is very limited, as it may become embrittled and lose its elasticity. Therefore, maintaining the elasticity of polyurethane at low temperatures is a primary research task. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-temperature resistant polyurethane transfer film and its preparation method. The transfer film is a multilayer thermal transfer film with an adhesive layer and a polyurethane-based transfer layer, which has excellent low-temperature resistance and water resistance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a low-temperature resistant polyurethane transfer film includes the following steps:

[0007] Step (1): Mix polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator evenly in a light-protected environment to obtain the transfer layer material.

[0008] The transfer layer material is coated on the side of the base film with the release layer. After coating, it is photocured to obtain a transfer layer / base film composite film.

[0009] Step (2): Press the adhesive layer and the transfer layer / base film composite film together on the side with the transfer layer, and cool to obtain a low-temperature resistant polyurethane transfer film.

[0010] Preferably, in step (1), the mass ratio of polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator is 60:5-8:15-20:15-20:4-5.

[0011] Preferably, in step (1): the base film is a PET release film; the curing conditions are: photocuring in ultraviolet light with a wavelength of 365nm for 30-40s; and the thickness of the transfer layer is 4-6μm.

[0012] Preferably, in step (1), the polyurethane acrylate is prepared by the following steps:

[0013] S1. Mix hexafluorobutyl acrylate and N,N-dimethylformamide, heat, and add dropwise a mixed solution of mercaptoethanol and triethylamine. After the addition is complete, the mixture is allowed to react. After the reaction is complete, the mixture is washed and distilled under reduced pressure to obtain a hydroxyl-containing fluorinated monomer.

[0014] HDI trimer and catalyst dibutyltin dilaurate were mixed, and hydroxyl-containing fluorinated monomers were added. After the reaction was completed, fluorinated isocyanate was obtained.

[0015] S2. Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and benzoin dimethyl ether are mixed and reacted. After the reaction is completed, the mixture is rotary evaporated to obtain silane-modified hydroxyl-terminated polybutadiene.

[0016] Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were reacted. After the reaction was completed, rotary evaporation was performed to obtain organosilicon-modified hydroxyl-terminated polybutadiene.

[0017] Fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and dibutyltin dilaurate were mixed and reacted. After the reaction was completed, the temperature was lowered, and p-hydroxyanisole and hydroxyethyl acrylate were added. The reaction was continued to obtain polyurethane acrylate.

[0018] Preferably, in step (1), when preparing polyurethane acrylate, the molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer in S1 is 1:1.5-2:1; and the mass ratio of mercaptoethanol to triethylamine in the mixed solution of mercaptoethanol and triethylamine is 200:1.

[0019] Preferably, in step (1), when preparing polyurethane acrylate, in S1: when preparing hydroxyl fluorinated monomer, the dropping conditions of the mixed solution of mercaptoethanol and triethylamine are: dropping at 50°C for 20-30 min, and the reaction conditions are: reacting at 50°C for 8-10 h.

[0020] Preferably, in step (1), when preparing polyurethane acrylate, in S1: when preparing fluorinated isocyanate, the mass ratio of HDI trimer to catalyst dibutyltin dilaurate is 10:0.01, and the reaction conditions are: reacting at 70-80℃ for 1.5-2h.

[0021] Preferably, in step (1), when preparing polyurethane acrylate, in S2: when preparing silane-modified hydroxyl-terminated polybutadiene, the solid-liquid ratio of hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and benzoin dimethyl ether is 10g:2-2.5g:300-350mL:0.05g, and the reaction conditions are: reacting for 3-4 hours under ultraviolet light irradiation at a wavelength of 365nm and a power of 150W.

[0022] Preferably, in step (1) when preparing polyurethane acrylate, in S2: when preparing organosilicon-modified hydroxyl-terminated polybutadiene, the solid-liquid ratio of silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate is 10g:0.5-1g:100-150mL:0.5mL, and the reaction conditions are: reacting at 35-45℃ for 24h.

[0023] Preferably, in step (1), when preparing polyurethane acrylate, in S2: the mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, dibutyltin dilaurate, p-hydroxyanisole, and hydroxyethyl acrylate is 7-7.5:10:15:0.018:0.03:1.5-2, and the reaction conditions are: reacting at 60-70℃ for 3-4 hours; the continued reaction conditions are: continuing the reaction at 50℃ for 1-2 hours.

[0024] Preferably, in step (1), the thiolized graphene oxide is prepared by the following steps:

[0025] Graphene oxide and water were mixed and ultrasonically dispersed for 20-30 min. The temperature was raised to 50-60℃, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 50-60℃ for 5 h. After the reaction was completed, the mixture was cooled, filtered, washed until neutral, and dried to obtain mercapto-modified graphene oxide.

[0026] The solid-liquid ratio of graphene oxide, water, 1.8wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2g:150-200mL:100-120mL:5-6mL.

[0027] Preferably, in step (2): the adhesive layer is a hot melt adhesive film with a thickness of 0.15-0.3 mm; the pressing conditions are: pressing at a temperature of 120-130℃ and a pressure of 5-6 MPa.

[0028] Preferably, a low-temperature resistant polyurethane transfer film is prepared using the method described above.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention prepares a multilayer heat transfer film with an adhesive layer and a polyurethane-based transfer layer. By preparing a photocurable transfer layer material containing polyether, polybutadiene blocks and organosilicon branches with good low-temperature resistance, and thiolized graphene oxide with excellent far-infrared properties, the low-temperature resistance and water resistance of the heat transfer film are effectively improved.

[0031] In this invention, a hydroxyl-containing fluorinated monomer is prepared by a click reaction between hexafluorobutyl acrylate and mercaptoethanol. Then, a fluorinated isocyanate is prepared by reacting the hydroxyl group with the isocyanate group of HDI trimer. This isocyanate is then copolymerized with polytetrahydrofuran ether diol and silicone-modified hydroxyl-terminated polybutadiene, and finally capped with hydroxyethyl acrylate to obtain a polyurethane acrylate containing polyether segments, polybutadiene blocks, and silicone branches.

[0032] Among them, fluorinated isocyanates have hydrophobic groups, which can improve the water resistance of polyurethane acrylates; polytetrahydrofuran ether diol and silicone-modified hydroxyl-terminated polybutadiene both have low glass transition temperatures, good flexibility, and excellent low-temperature resistance, which can effectively improve the low-temperature resistance of polyurethane acrylates; silicone-modified hydroxyl-terminated polybutadiene is formed by the click chemical reaction of hydroxyl-terminated polybutadiene with the mercapto group of KH590 and then polymerizing it with monohydroxy silicone oil. The introduction of hydrophobic silicone segments into it synergistically improves the water resistance of polyurethane acrylates with polybutadiene segments, and the silicone segments also have excellent low-temperature resistance, playing a positive additive role in improving the low-temperature resistance of polyurethane acrylates;

[0033] In this invention, polyurethane acrylate, mercapto-modified graphene oxide, diluent, and photoinitiator are mixed to form a transfer layer material. After photocuring, the components are linked by chemical bonds through reaction, which improves the crosslinking degree of the material and further improves its water resistance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the low-temperature resistant polyurethane transfer film prepared in this invention;

[0035] Figure 2 This is a bar chart showing the change rate of tensile strength of samples 1-5 in the performance test of this invention;

[0036] Figure 3 This is a bar chart of the water contact angle of samples 1-5 in the performance test of this invention;

[0037] In the picture:

[0038] 1. Adhesive layer; 2. Transfer layer; 3. Base film. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment discloses a method for preparing a transfer layer material, including the following steps:

[0042] Step (1): Mix hexafluorobutyl acrylate and N,N-dimethylformamide in a mass ratio of 1:1, heat to 50°C, add dropwise a mixed solution of mercaptoethanol and triethylamine over a period of 30 min, and react at 50°C for 8 h after the addition is complete. After the reaction is complete, wash with water to remove mercaptoethanol and N,N-dimethylformamide, and distill under reduced pressure at 50°C to obtain a hydroxyl-containing fluorinated monomer.

[0043] HDI trimer and catalyst dibutyltin dilaurate were mixed at a mass ratio of 10:0.01, and hydroxyl-containing fluorinated monomers were added. The mixture was reacted at 70°C for 2 hours. After the reaction was completed, fluorinated isocyanate was obtained.

[0044] The molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer is 1:1.5:1; the mass ratio of mercaptoethanol to triethylamine in the mixed solution of mercaptoethanol and triethylamine is 200:1.

[0045] Step (2): Fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and catalyst dibutyltin dilaurate are mixed and reacted at 60°C for 4 hours. After the reaction is completed, the temperature is lowered to 50°C, and the polymerization inhibitor p-hydroxyanisole and hydroxyethyl acrylate are added. The reaction is continued for 1 hour to obtain polyurethane acrylate.

[0046] The mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, catalyst dibutyltin dilaurate, polymerization inhibitor p-hydroxyanisole, and hydroxyethyl acrylate is 7:10:15:0.018:0.03:1.5.

[0047] Organosilicon-modified hydroxyl-terminated polybutadiene is prepared by the following steps:

[0048] Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and photoinitiator benzoin dimethyl ether were mixed at a solid-liquid ratio of 10g:2g:300mL:0.05g and reacted under ultraviolet light with a wavelength of 365nm and a power of 150W for 4h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain silane-modified hydroxyl-terminated polybutadiene.

[0049] Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were mixed at a solid-liquid ratio of 10g:0.5g:100mL:0.5mL and reacted at 40℃ for 24h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain organosilicon-modified hydroxyl-terminated polybutadiene.

[0050] Step (3): Polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator Irgacure 184 are mixed uniformly in a light-protected environment at a mass ratio of 60:5:15:20:4 to obtain the transfer layer material.

[0051] The thiolized graphene oxide is prepared by the following steps:

[0052] Graphene oxide and water were mixed and ultrasonically dispersed for 20 min. The temperature was raised to 60 °C, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 60 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with water until neutral, and dried at 50 °C for 24 h to obtain mercapto-modified graphene oxide.

[0053] The solid-liquid ratio of graphene oxide, water, 1.8 wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2 g: 150 mL: 100 mL: 5 mL.

[0054] Example 2

[0055] This embodiment discloses a method for preparing a transfer layer material, including the following steps:

[0056] Step (1): Mix hexafluorobutyl acrylate and N,N-dimethylformamide in a mass ratio of 1:1, heat to 50°C, add dropwise a mixed solution of mercaptoethanol and triethylamine over 30 min, and react at 50°C for 9 h after the addition is complete. After the reaction is complete, wash with water to remove mercaptoethanol and N,N-dimethylformamide, and distill under reduced pressure at 50°C to obtain a hydroxyl-containing fluorinated monomer.

[0057] HDI trimer and catalyst dibutyltin dilaurate were mixed at a mass ratio of 10:0.01, and a hydroxyl-containing fluorinated monomer was added. The mixture was reacted at 75°C for 1.8 h. After the reaction was completed, a fluorinated isocyanate was obtained.

[0058] The molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer is 1:1.8:1; the mass ratio of mercaptoethanol to triethylamine in the mixed solution of mercaptoethanol and triethylamine is 200:1.

[0059] Step (2): Fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and catalyst dibutyltin dilaurate are mixed and reacted at 65°C for 3.5 h. After the reaction is completed, the temperature is lowered to 50°C, and the polymerization inhibitor p-hydroxyanisole and hydroxyethyl acrylate are added. The reaction is continued for 1.5 h to obtain polyurethane acrylate.

[0060] The mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, catalyst dibutyltin dilaurate, polymerization inhibitor p-hydroxyanisole, and hydroxyethyl acrylate is 7.3:10:15:0.018:0.03:1.8.

[0061] Organosilicon-modified hydroxyl-terminated polybutadiene is prepared by the following steps:

[0062] Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and photoinitiator benzoin dimethyl ether were mixed at a solid-liquid ratio of 10g:2.3g:300mL:0.05g and reacted under ultraviolet light with a wavelength of 365nm and a power of 150W for 4h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain silane-modified hydroxyl-terminated polybutadiene.

[0063] Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were mixed at a solid-liquid ratio of 10g:0.8g:100mL:0.5mL and reacted at 40℃ for 24h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain organosilicon-modified hydroxyl-terminated polybutadiene.

[0064] Step (3): Polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator Irgacure 184 are mixed uniformly in a light-protected environment at a mass ratio of 60:6.5:15:20:4.5 to obtain the transfer layer material.

[0065] The thiolized graphene oxide is prepared by the following steps:

[0066] Graphene oxide and water were mixed and ultrasonically dispersed for 20 min. The temperature was raised to 60 °C, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 60 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with water until neutral, and dried at 50 °C for 24 h to obtain mercapto-modified graphene oxide.

[0067] The solid-liquid ratio of graphene oxide, water, 1.8 wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2 g: 150 mL: 100 mL: 5 mL.

[0068] Example 3

[0069] This embodiment discloses a method for preparing a transfer layer material, including the following steps:

[0070] Step (1): Mix hexafluorobutyl acrylate and N,N-dimethylformamide in a mass ratio of 1:1, heat to 50°C, add dropwise a mixed solution of mercaptoethanol and triethylamine over 30 min, and react at 50°C for 10 h after the addition is complete. After the reaction is complete, wash with water to remove mercaptoethanol and N,N-dimethylformamide, and distill under reduced pressure at 50°C to obtain a hydroxyl-containing fluorinated monomer.

[0071] HDI trimer and catalyst dibutyltin dilaurate were mixed at a mass ratio of 10:0.01, and hydroxyl-containing fluorinated monomers were added. The mixture was reacted at 80°C for 1.5 h. After the reaction was completed, fluorinated isocyanate was obtained.

[0072] The molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer is 1:2:1; the mass ratio of mercaptoethanol to triethylamine in the mixed solution of mercaptoethanol and triethylamine is 200:1.

[0073] Step (2): Fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and catalyst dibutyltin dilaurate are mixed and reacted at 70°C for 3 hours. After the reaction is completed, the temperature is lowered to 50°C, and the polymerization inhibitor p-hydroxyanisole and hydroxyethyl acrylate are added. The reaction is continued for 2 hours to obtain polyurethane acrylate.

[0074] The mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, catalyst dibutyltin dilaurate, polymerization inhibitor p-hydroxyanisole, and hydroxyethyl acrylate is 7.5:10:15:0.018:0.03:2.

[0075] Organosilicon-modified hydroxyl-terminated polybutadiene is prepared by the following steps:

[0076] Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and photoinitiator benzoin dimethyl ether were mixed at a solid-liquid ratio of 10g:2.5g:300mL:0.05g and reacted under ultraviolet light with a wavelength of 365nm and a power of 150W for 4h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain silane-modified hydroxyl-terminated polybutadiene.

[0077] Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were mixed at a solid-liquid ratio of 10g:1g:100mL:0.5mL and reacted at 40℃ for 24h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain organosilicon-modified hydroxyl-terminated polybutadiene.

[0078] Step (3): Polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator Irgacure184 are mixed uniformly in a light-proof environment at a mass ratio of 60:8:15:20:5 to obtain the transfer layer material.

[0079] The thiolized graphene oxide is prepared by the following steps:

[0080] Graphene oxide and water were mixed and ultrasonically dispersed for 20 min. The temperature was raised to 60 °C, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 60 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with water until neutral, and dried at 50 °C for 24 h to obtain mercapto-modified graphene oxide.

[0081] The solid-liquid ratio of graphene oxide, water, 1.8 wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2 g: 150 mL: 100 mL: 5 mL.

[0082] Example 4

[0083] This embodiment discloses a method for preparing a low-temperature resistant polyurethane transfer film, including the following steps:

[0084] Step (1): Using PET release film as base film, the transfer layer material prepared in Example 1 is coated on the side of the base film with release layer. After coating, it is cured in ultraviolet light with a wavelength of 365nm for 30s to form a transfer layer with a thickness of 4μm, and a transfer layer / base film composite film is obtained.

[0085] Step (2): A hot melt adhesive film with a thickness of 0.15 mm is used as an adhesive layer and pressed with the side of the transfer layer / base film composite film having the transfer layer at a temperature of 120℃ and a pressure of 5 MPa. After cooling, a low-temperature resistant polyurethane transfer film is obtained.

[0086] Example 5

[0087] This embodiment discloses a method for preparing a low-temperature resistant polyurethane transfer film, including the following steps:

[0088] Step (1): Using PET release film as base film, the transfer layer material prepared in Example 2 is coated on the side of the base film with release layer. After coating, it is cured in ultraviolet light with a wavelength of 365nm for 30s to form a transfer layer with a thickness of 4μm, and a transfer layer / base film composite film is obtained.

[0089] Step (2): A hot melt adhesive film with a thickness of 0.15 mm is used as an adhesive layer and pressed with the side of the transfer layer / base film composite film having the transfer layer at a temperature of 120℃ and a pressure of 5 MPa. After cooling, a low-temperature resistant polyurethane transfer film is obtained.

[0090] Example 6

[0091] This embodiment discloses a method for preparing a low-temperature resistant polyurethane transfer film, including the following steps:

[0092] Step (1): Using PET release film as base film, the transfer layer material prepared in Example 3 is coated on the side of the base film with release layer. After coating, it is cured in ultraviolet light with a wavelength of 365nm for 30s to form a transfer layer with a thickness of 4μm, and a transfer layer / base film composite film is obtained.

[0093] Step (2): A hot melt adhesive film with a thickness of 0.15 mm is used as an adhesive layer and pressed with the side of the transfer layer / base film composite film having the transfer layer at a temperature of 120℃ and a pressure of 5 MPa. After cooling, a low-temperature resistant polyurethane transfer film is obtained.

[0094] Comparative Example 1

[0095] This comparative example discloses a method for preparing a transfer layer material, including the following steps:

[0096] Step (1): Mix hexafluorobutyl acrylate and N,N-dimethylformamide in a mass ratio of 1:1, heat to 50°C, add dropwise a mixed solution of mercaptoethanol and triethylamine over a period of 30 min, and react at 50°C for 8 h after the addition is complete. After the reaction is complete, wash with water to remove mercaptoethanol and N,N-dimethylformamide, and distill under reduced pressure at 50°C to obtain a hydroxyl-containing fluorinated monomer.

[0097] HDI trimer and catalyst dibutyltin dilaurate were mixed at a mass ratio of 10:0.01, and hydroxyl-containing fluorinated monomers were added. The mixture was reacted at 70°C for 2 hours. After the reaction was completed, fluorinated isocyanate was obtained.

[0098] The molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer is 1:1.5:1; the mass ratio of mercaptoethanol to triethylamine in the mixed solution of mercaptoethanol and triethylamine is 200:1.

[0099] Step (2): Fluorinated isocyanate, polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, and catalyst dibutyltin dilaurate are mixed and reacted at 60°C for 4 hours. After the reaction is completed, the temperature is lowered to 50°C, and the polymerization inhibitor p-hydroxyanisole and hydroxyethyl acrylate are added. The reaction is continued for 1 hour to obtain polyurethane acrylate.

[0100] The mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, hydroxyl-terminated polybutadiene, catalyst dibutyltin dilaurate, polymerization inhibitor p-hydroxyanisole, and hydroxyethyl acrylate is 7:10:15:0.018:0.03:1.5.

[0101] Step (3): Polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator Irgacure 184 are mixed uniformly in a light-protected environment at a mass ratio of 60:5:15:20:4 to obtain the transfer layer material.

[0102] The thiolized graphene oxide is prepared by the following steps:

[0103] Graphene oxide and water were mixed and ultrasonically dispersed for 20 min. The temperature was raised to 60 °C, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 60 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with water until neutral, and dried at 50 °C for 24 h to obtain mercapto-modified graphene oxide.

[0104] The solid-liquid ratio of graphene oxide, water, 1.8 wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2 g: 150 mL: 100 mL: 5 mL.

[0105] Comparative Example 2

[0106] This comparative example discloses a method for preparing a transfer layer material, including the following steps:

[0107] Step (1): Mix HDI trimer, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and catalyst dibutyltin dilaurate, and react at 60°C for 4 hours. After the reaction is completed, cool down to 50°C, add polymerization inhibitor p-hydroxyanisole and hydroxyethyl acrylate, and continue to react for 1 hour to obtain polyurethane acrylate.

[0108] The mass ratio of HDI trimer, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, catalyst dibutyltin dilaurate, polymerization inhibitor p-hydroxyanisole, and hydroxyethyl acrylate is 7:10:15:0.018:0.03:1.5.

[0109] Organosilicon-modified hydroxyl-terminated polybutadiene is prepared by the following steps:

[0110] Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and photoinitiator benzoin dimethyl ether were mixed at a solid-liquid ratio of 10g:2g:300mL:0.05g and reacted under ultraviolet light with a wavelength of 365nm and a power of 150W for 4h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain silane-modified hydroxyl-terminated polybutadiene.

[0111] Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were mixed at a solid-liquid ratio of 10g:0.5g:100mL:0.5mL and reacted at 40℃ for 24h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain organosilicon-modified hydroxyl-terminated polybutadiene.

[0112] Step (3): Polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator Irgacure 184 are mixed uniformly in a light-protected environment at a mass ratio of 60:5:15:20:4 to obtain the transfer layer material.

[0113] The thiolized graphene oxide is prepared by the following steps:

[0114] Graphene oxide and water were mixed and ultrasonically dispersed for 20 min. The temperature was raised to 60 °C, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 60 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with water until neutral, and dried at 50 °C for 24 h to obtain mercapto-modified graphene oxide.

[0115] The solid-liquid ratio of graphene oxide, water, 1.8 wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2 g: 150 mL: 100 mL: 5 mL.

[0116] Comparative Example 3

[0117] This comparative example discloses a method for preparing a polyurethane transfer film, comprising the following steps:

[0118] Step (1): Using PET release film as base film, the transfer layer material prepared in Comparative Example 1 is coated on the side of the base film with release layer. After coating, it is cured in ultraviolet light with a wavelength of 365nm for 30s to form a transfer layer with a thickness of 4μm, and a transfer layer / base film composite film is obtained.

[0119] Step (2): A hot melt adhesive film with a thickness of 0.15 mm is used as the adhesive layer and pressed with the side of the transfer layer / base film composite film having the transfer layer at a temperature of 120℃ and a pressure of 5 MPa. After cooling, a polyurethane transfer film is obtained.

[0120] Comparative Example 4

[0121] This comparative example discloses a method for preparing a polyurethane transfer film, comprising the following steps:

[0122] Step (1): Using PET release film as base film, the transfer layer material prepared in Comparative Example 2 is coated on the side of the base film with release layer. After coating, it is cured in ultraviolet light with a wavelength of 365nm for 30s to form a transfer layer with a thickness of 4μm, and a transfer layer / base film composite film is obtained.

[0123] Step (2): A hot melt adhesive film with a thickness of 0.15 mm is used as the adhesive layer and pressed with the side of the transfer layer / base film composite film having the transfer layer at a temperature of 120℃ and a pressure of 5 MPa. After cooling, a polyurethane transfer film is obtained.

[0124] In the above examples and comparative examples, the polytetrahydrofuran ether glycol was polytetrahydrofuran ether glycol 1000; the hydroxyl value (mmol / g) of the hydroxyl-terminated polybutadiene was 0.47-0.53; the Mn of the monohydroxy silicone oil was 1000; the graphene oxide and the hot melt adhesive film were both commercially available, and the softening point of the hot melt adhesive film was 120-130℃.

[0125] Test case

[0126] The transfer layer materials prepared in Examples 1-3 and Comparative Examples 1-2 were coated onto release films with a coating thickness of 1 mm. The coatings were then cured under ultraviolet light at a wavelength of 365 nm for 30 seconds. After curing, the release film was removed, yielding samples 1-5, which were then tested for mechanical properties and low-temperature resistance. Specific test results are shown in Table 1.

[0127] Table 1

[0128]

[0129] The tests for each indicator in Table 1 were conducted according to the following standards: Tensile strength was determined in accordance with GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber"; Low-temperature resistance was expressed by the rate of change of tensile strength. Samples 1-5 were placed at -20℃ for a 12-hour test, then removed for tensile testing, and the rate of change of tensile strength was calculated.

[0130] The transfer films prepared in Examples 4-6 and Comparative Examples 3-4 were bonded to the surface of a leather base fabric, with the adhesive layer side of the transfer film in contact with the leather base fabric. The films were then pressed and cooled at 130°C, and these samples were designated as Samples 1-5. The hydrophobicity of the side of Samples 1-5 with the transfer film was tested by measuring the static water contact angle. Specific test results are shown in Table 2.

[0131] Table 2

[0132]

[0133] As can be seen from the test results in Tables 1 and 2, the heat transfer film prepared by this invention has good mechanical properties and excellent low-temperature resistance and water resistance. This is because this invention prepares a polyurethane acrylate containing polyether, polybutadiene blocks and organosilicon branches with good low-temperature resistance, and mixes it with components such as thiolized graphene oxide with excellent far-infrared properties to form a photocurable transfer layer material. After photocuring, the components are linked by chemical bonds through reaction, which improves the crosslinking degree of the material and further improves the water resistance. Among them, fluorinated isocyanates have hydrophobic groups, which can improve the water resistance of polyurethane acrylates; polytetrahydrofuran ether diol and organosilicon-modified hydroxyl-terminated polybutadiene both have low glass transition temperatures, good flexibility, and excellent low-temperature resistance, which can effectively improve the low-temperature resistance of polyurethane acrylates; organosilicon-modified hydroxyl-terminated polybutadiene is formed by the click chemical reaction of hydroxyl-terminated polybutadiene with the mercapto group of KH590 and then polymerizing it with monohydroxy silicone oil. The introduction of hydrophobic organosilicon segments into it synergistically improves the water resistance of polyurethane acrylates with the polybutadiene segments. Moreover, the organosilicon segments also have excellent low-temperature resistance, which plays a positive additive role in improving the low-temperature resistance of polyurethane acrylates.

[0134] In Comparative Example 1, the hydroxyl-terminated polybutadiene was not modified, lacking the effect of organosilicon segments in improving low-temperature resistance and water resistance. Therefore, the low-temperature resistance and hydrophobicity of Sample 4 and Sample 5 were not as good as those of the Example. In Comparative Example 2, the HDI trimer was not modified, lacking the effect of fluorinated segments in improving the hydrophobicity of the material. Therefore, the hydrophobicity of Sample 5 and Sample 5 was not as good as that of the Example.

[0135] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-temperature resistant polyurethane transfer film, characterized in that, Includes the following steps: Step (1): Mix polyurethane acrylate, mercapto-modified graphene oxide, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and photoinitiator in a mass ratio of 60:5-8:15-20:15-20:4-5 in a light-protected environment to obtain the transfer layer material. The transfer layer material is coated on the side of the base film with the release layer. After coating, it is photocured to obtain a transfer layer / base film composite film. The polyurethane acrylate is prepared by the following steps: S1. Mix hexafluorobutyl acrylate and N,N-dimethylformamide, heat, and add dropwise a mixed solution of mercaptoethanol and triethylamine. After the addition is complete, the mixture is allowed to react. After the reaction is complete, the mixture is washed and distilled under reduced pressure to obtain a hydroxyl-containing fluorinated monomer. HDI trimer and catalyst dibutyltin dilaurate were mixed, and hydroxyl-containing fluorinated monomers were added. After the reaction was completed, fluorinated isocyanate was obtained. S2. Hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and benzoin dimethyl ether are mixed and reacted. After the reaction is completed, the mixture is rotary evaporated to obtain silane-modified hydroxyl-terminated polybutadiene. Silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate were reacted. After the reaction was completed, rotary evaporation was performed to obtain organosilicon-modified hydroxyl-terminated polybutadiene. Fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, and dibutyltin dilaurate were mixed and reacted. After the reaction was completed, the temperature was lowered, and p-hydroxyanisole and hydroxyethyl acrylate were added. The reaction was continued to obtain polyurethane acrylate. Step (2): Press the adhesive layer and the transfer layer / base film composite film together on the side with the transfer layer, and cool to obtain a low-temperature resistant polyurethane transfer film.

2. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1): the base film is a PET release film; the curing conditions are: photocuring in ultraviolet light with a wavelength of 365nm for 30-40s; the thickness of the transfer layer is 4-6μm.

3. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1), when preparing polyurethane acrylate: In S1: the molar ratio of hexafluorobutyl acrylate, mercaptoethanol, and HDI trimer is 1:1.5-2:1; in the mixed solution of mercaptoethanol and triethylamine, the mass ratio of mercaptoethanol to triethylamine is 200:

1. When preparing hydroxyl-containing fluorinated monomers, the dropping conditions for the mixed solution of mercaptoethanol and triethylamine are: dropping at 50℃ for 20-30 min, and the reaction conditions are: reacting at 50℃ for 8-10 h. In the preparation of fluorinated isocyanates, the mass ratio of HDI trimer to catalyst dibutyltin dilaurate is 10:0.01, and the reaction conditions are: reaction at 70-80℃ for 1.5-2 hours.

4. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1), when preparing polyurethane acrylate, in S2: when preparing silane-modified hydroxyl-terminated polybutadiene, the solid-liquid ratio of hydroxyl-terminated polybutadiene, KH590, tetrahydrofuran, and benzoin dimethyl ether is 10g:2-2.5g:300-350mL:0.05g, and the reaction conditions are: reacting for 3-4 hours under ultraviolet light irradiation at a wavelength of 365nm and a power of 150W.

5. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1), when preparing polyurethane acrylate, in S2: when preparing organosilicon-modified hydroxyl-terminated polybutadiene, the solid-liquid ratio of silane-modified hydroxyl-terminated polybutadiene, monohydroxy silicone oil, tetrahydrofuran, and dibutyltin dilaurate is 10g:0.5-1g:100-150mL:0.5mL, and the reaction conditions are: reacting at 35-45℃ for 24h.

6. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1), when preparing polyurethane acrylate, in S2: the mass ratio of fluorinated isocyanate, polytetrahydrofuran ether diol, organosilicon-modified hydroxyl-terminated polybutadiene, dibutyltin dilaurate, p-hydroxyanisole, and hydroxyethyl acrylate is 7-7.5:10:15:0.018:0.03:1.5-2, and the reaction conditions are: reacting at 60-70℃ for 3-4 hours; the reaction continues at 50℃ for 1-2 hours.

7. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (1), the thiolized graphene oxide is prepared by the following steps: Graphene oxide and water were mixed and ultrasonically dispersed for 20-30 min. The temperature was raised to 50-60℃, and 1.8 wt% sulfuric acid aqueous solution and mercaptoacetic acid were added sequentially. The mixture was reacted at 50-60℃ for 5 h. After the reaction was completed, the mixture was cooled, filtered, washed until neutral, and dried to obtain mercapto-modified graphene oxide. The solid-liquid ratio of graphene oxide, water, 1.8wt% sulfuric acid aqueous solution, and mercaptoacetic acid is 0.2g:150-200mL:100-120mL:5-6mL.

8. The method for preparing the low-temperature resistant polyurethane transfer film according to claim 1, characterized in that, In step (2): the adhesive layer is a hot melt adhesive film with a thickness of 0.15-0.3mm; the pressing conditions are: pressing at a temperature of 120-130℃ and a pressure of 5-6MPa.

9. A low-temperature resistant polyurethane transfer film prepared by the method for preparing a low-temperature resistant polyurethane transfer film as described in any one of claims 1-8.

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