A polyurethane pressure-sensitive adhesive for a protective film and a method for preparing the same

Abstract

The application discloses a polyurethane pressure-sensitive adhesive for protective films and a preparation method thereof, and belongs to the technical field of pressure-sensitive adhesives.The fluorinated acrylate is introduced into the polyol structure, so that the adhesion of the polyurethane pressure-sensitive adhesive is enhanced, and excellent hydrophobic and weather-resistant properties are obtained.Meanwhile, the crosslinking density of the polyurethane pressure-sensitive adhesive is controlled by combination and proportioning of different crosslinking agents, and the long-lasting adhesion of the pressure-sensitive adhesive is optimized.

Description

Technical Field

[0001] This invention belongs to the field of pressure-sensitive adhesive technology, and relates to a polyurethane pressure-sensitive adhesive for protective films and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives (PSAs) are a class of special adhesives that achieve adhesion under slight external pressure, widely used in labels, tapes, protective films, medical patches, and other fields. Their adhesive properties allow for rapid bonding and peeling without the need for heating, solvents, or other activation processes, making them extremely convenient in daily life and industrial applications. Based on their chemical composition and properties, PAs can be mainly classified into several types, including rubber-based, acrylic-based, silicone-based, and polyurethane-based. Rubber-based PAs typically have good initial tack and peel strength, but poor weather resistance; acrylic-based PAs are known for their excellent weather resistance and transparency, making them suitable for outdoor applications and electronic products. However, with increasing demands for PAs performance, polyurethane PAs are gaining attention due to their unique performance advantages. Polyurethane PAs combine the excellent properties of polyurethane materials, offering higher flexibility, abrasion resistance, and chemical resistance, making them an increasingly important player in the PAs market.

[0003] Polyurethane pressure-sensitive adhesives (PSAs) are based on polyurethane polymers and offer significant advantages due to the diversity and adjustability of their chemical structures. The urethane groups in the polyurethane molecular chain endow the material with excellent elasticity and flexibility, enabling PSAs to maintain good adhesion performance at lower temperatures. Furthermore, the polar structure of polyurethane materials helps improve the cohesive strength and adhesion of the PSAs, making them suitable for use on a variety of substrates. Polyurethane PSAs also exhibit excellent transparency, abrasion resistance, and chemical corrosion resistance, maintaining stable performance under harsh environmental conditions. Because of these advantages, polyurethane PSAs are widely used in industries such as automotive, electronics, construction, and medical, especially in applications requiring high performance and high reliability.

[0004] Despite the numerous advantages of polyurethane pressure-sensitive adhesives (PSAs), their preparation still faces several technical limitations and challenges. First, the synthesis of PSAs involves multiple chemical reactions and process steps, potentially leading to a complex and costly production process. Second, polyurethane materials are sensitive to changes in humidity and temperature, which can affect their performance in practical applications, especially in high humidity or extreme temperature environments. Furthermore, the initial tack and peel strength of PSAs require fine-tuning in formulation design to meet the specific needs of each application, further increasing the difficulty of research and development and production. Summary of the Invention

[0005] This invention provides a polyurethane pressure-sensitive adhesive for protective films and its preparation method, belonging to the field of pressure-sensitive adhesive technology. By introducing fluorinated acrylate into the polyol structure, this invention not only enhances the adhesion of the polyurethane pressure-sensitive adhesive but also achieves excellent hydrophobic and weather-resistant properties. Furthermore, by controlling the crosslinking density of the polyurethane pressure-sensitive adhesive through the combination and ratio of different crosslinking agents, the long-lasting adhesion of the pressure-sensitive adhesive is optimized.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 40-60 parts by weight of modified polyol, 20-40 parts by weight of isocyanate, 5-15 parts by weight of chain extender, 0.1-1 parts by weight of catalyst, and 1-5 parts by weight of crosslinking agent.

[0008] As a preferred embodiment of the present invention, the modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 60-80℃ for 4-8 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0009] As a preferred embodiment of the present invention, the fluorinated acrylate monomer is any one of perfluorooctyl acrylate, trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, and (1,1,1,3,3,3-hexafluoro-2-phenylprop-2-yl) methacrylate; the polyol is any one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol; the solvent is toluene or dichloromethane; the initiator is benzoyl peroxide or azobisisobutyronitrile; and the terminator is hydroquinone. The mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 10-30:40-70:200-500:1-5:0.1-1.

[0010] As a preferred embodiment of the present invention, the isocyanate is any one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0011] As a preferred embodiment of the present invention, the chain extender is any one of 1,4-butanediol, ethylene glycol, diethanolamine, and dimethylglyoxime.

[0012] As a preferred embodiment of the present invention, the catalyst is dibutyltin dilaurate.

[0013] As a preferred embodiment of the present invention, the crosslinking agent is polycarbodiimide, triglycidyl isocyanurate, and a silane coupling agent, wherein the mass ratio of polycarbodiimide, triglycidyl isocyanurate, and silane coupling agent is 5-7:2-4:1-2.

[0014] Furthermore, the method for preparing the polyurethane pressure-sensitive adhesive for the protective film includes the following steps:

[0015] (1) Dissolve the modified polyol in solvents toluene and butanone, and heat to 50-80℃;

[0016] (2) Add isocyanate and catalyst dropwise, and stir for 3-5 hours to obtain the prepolymer;

[0017] (3) Add the chain extender to the prepolymer and stir at 70-80℃ for 4-6 hours;

[0018] (4) Add crosslinking agent and stir at 30-60℃ for 1-3 hours;

[0019] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0020] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:5-10; the mass ratio of the toluene to methyl ethyl ketone is 1:1-2.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention combines the advantages of fluorinated acrylates and acrylates to prepare polyurethane pressure-sensitive adhesives, significantly improving the material's performance. The chemical inertness of fluorine enhances the material's chemical resistance and weather resistance, resists UV and oxidative damage, and extends its service life. The acrylate portion improves the material's adhesion through its flexibility and polarity. Combining these properties, the introduction of fluorinated acrylates not only improves the adhesion performance of the polyurethane pressure-sensitive adhesive and provides low surface energy, giving the adhesive excellent hydrophobicity and oleophobicity, but also enhances its stability and durability in various harsh environments, maintaining good adhesion even in humid and oily environments.

[0023] (2) This invention optimizes the long-lasting tack of polyurethane pressure-sensitive adhesives by controlling the crosslinking density of the adhesive through the combined use of polycarbodiimide, triglycidyl isocyanurate, and a silane coupling agent. Polycarbodiimide improves hydrolysis resistance, ensuring the stability of the adhesive in humid environments; triglycidyl isocyanurate enhances mechanical strength and chemical stability through high crosslinking density; and the silane coupling agent improves adhesion between organic and inorganic substrates. This combination not only expands the application range of pressure-sensitive adhesives but also improves their weather resistance and overall durability. Detailed Implementation

[0024] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0025] In the following examples and comparative examples, the polyethylene glycol was purchased from Guangzhou Bolun Chemical Technology Co., Ltd., product number peg600; the silane coupling agent was purchased from Kangjin Chemical Co., Ltd., product number KH-560; the polycarbodiimide was purchased from Deyu Co., Ltd., product number 0228-330; and the polypropylene glycol was purchased from Jiangsu Haian Petrochemical Plant, product number 00-2.

[0026] Example 1

[0027] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 60 parts by weight of modified polyol, 30 parts by weight of isocyanate, 10 parts by weight of chain extender, 0.5 parts by weight of catalyst, and 2 parts by weight of crosslinking agent.

[0028] The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 70°C for 6 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0029] The fluorinated acrylate monomer is perfluorooctyl acrylate, the polyol is polyethylene glycol, the solvent is toluene, the initiator is benzoyl peroxide, and the terminator is hydroquinone; the mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 20:60:200:2:0.5.

[0030] The isocyanate is toluene diisocyanate.

[0031] The chain extender is 1,4-butanediol.

[0032] The catalyst is dibutyltin dilaurate.

[0033] The crosslinking agent is polycarbodiimide, triglycidyl isocyanurate, and a silane coupling agent, and the mass ratio of polycarbodiimide, triglycidyl isocyanurate, and silane coupling agent is 6:3:1.

[0034] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0035] (1) Dissolve the modified polyol in the solvents toluene and butanone, and heat to 60°C;

[0036] (2) Add isocyanate and catalyst dropwise, and stir for 4 hours to obtain the prepolymer;

[0037] (3) Add the chain extender to the prepolymer and stir at 70°C for 5 hours;

[0038] (4) Add crosslinking agent and stir at 40℃ for 2 hours;

[0039] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0040] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:6; the mass ratio of toluene to butanone is 1:2.

[0041] Example 2

[0042] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 40 parts by weight of modified polyol, 20 parts by weight of isocyanate, 5 parts by weight of chain extender, 0.2 parts by weight of catalyst, and 1 part by weight of crosslinking agent.

[0043] The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 60°C for 8 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0044] The fluorinated acrylate monomer is trifluoroethyl methacrylate, the polyol is polypropylene glycol, the solvent is dichloromethane, the initiator is azobisisobutyronitrile, and the terminator is hydroquinone; the mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 10:40:300:5:1.

[0045] The isocyanate is diphenylmethane diisocyanate.

[0046] The chain extender is ethylene glycol.

[0047] The catalyst is dibutyltin dilaurate.

[0048] The crosslinking agent is polycarbodiimide, triglycidyl isocyanurate, and a silane coupling agent, and the mass ratio of polycarbodiimide, triglycidyl isocyanurate, and silane coupling agent is 7:4:2.

[0049] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0050] (1) Dissolve the modified polyol in the solvents toluene and butanone, and heat to 80°C;

[0051] (2) Add isocyanate and catalyst dropwise, and stir for 3 hours to obtain the prepolymer;

[0052] (3) Add the chain extender to the prepolymer and stir at 80°C for 4 hours;

[0053] (4) Add crosslinking agent and stir at 30°C for 3 hours;

[0054] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0055] The mass ratio of the modified polyol to the solvent is 1:5; the mass ratio of toluene to butanone is 1:1.

[0056] Comparative Example 1

[0057] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 60 parts by weight of polyol, 30 parts by weight of isocyanate, 10 parts by weight of chain extender, 0.5 parts by weight of catalyst, and 2 parts by weight of crosslinking agent.

[0058] The polyol is polyethylene glycol.

[0059] The isocyanate is toluene diisocyanate.

[0060] The chain extender is 1,4-butanediol.

[0061] The catalyst is dibutyltin dilaurate.

[0062] The crosslinking agent is polycarbodiimide, triglycidyl isocyanurate, and a silane coupling agent, and the mass ratio of polycarbodiimide, triglycidyl isocyanurate, and silane coupling agent is 6:3:1.

[0063] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0064] (1) Dissolve the polyol in the solvents toluene and butanone, and heat to 60°C;

[0065] (2) Add isocyanate and catalyst dropwise, and stir for 4 hours to obtain the prepolymer;

[0066] (3) Add the chain extender to the prepolymer and stir at 70°C for 5 hours;

[0067] (4) Add crosslinking agent and stir at 40℃ for 2 hours;

[0068] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0069] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:6; the mass ratio of toluene to butanone is 1:2.

[0070] Comparative Example 2

[0071] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 60 parts by weight of modified polyol, 30 parts by weight of isocyanate, 10 parts by weight of chain extender, 0.5 parts by weight of catalyst, and 2 parts by weight of crosslinking agent.

[0072] The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 70°C for 6 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0073] The fluorinated acrylate monomer is perfluorooctyl acrylate, the polyol is polyethylene glycol, the solvent is toluene, the initiator is benzoyl peroxide, and the terminator is hydroquinone; the mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 20:60:200:2:0.5.

[0074] The isocyanate is toluene diisocyanate.

[0075] The chain extender is 1,4-butanediol.

[0076] The catalyst is dibutyltin dilaurate.

[0077] The crosslinking agent is triglycidyl isocyanurate and a silane coupling agent, and the mass ratio of triglycidyl isocyanurate to silane coupling agent is 9:1.

[0078] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0079] (1) Dissolve the modified polyol in the solvents toluene and butanone, and heat to 60°C;

[0080] (2) Add isocyanate and catalyst dropwise, and stir for 4 hours to obtain the prepolymer;

[0081] (3) Add the chain extender to the prepolymer and stir at 70°C for 5 hours;

[0082] (4) Add crosslinking agent and stir at 40℃ for 2 hours;

[0083] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0084] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:6; the mass ratio of toluene to butanone is 1:2.

[0085] Comparative Example 3

[0086] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 60 parts by weight of modified polyol, 30 parts by weight of isocyanate, 10 parts by weight of chain extender, 0.5 parts by weight of catalyst, and 2 parts by weight of crosslinking agent.

[0087] The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 70°C for 6 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0088] The fluorinated acrylate monomer is perfluorooctyl acrylate, the polyol is polyethylene glycol, the solvent is toluene, the initiator is benzoyl peroxide, and the terminator is hydroquinone; the mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 20:60:200:2:0.5.

[0089] The isocyanate is toluene diisocyanate.

[0090] The chain extender is 1,4-butanediol.

[0091] The catalyst is dibutyltin dilaurate.

[0092] The crosslinking agent is a polycarbodiimide and a silane coupling agent, and the mass ratio of the polycarbodiimide and the silane coupling agent is 6:4.

[0093] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0094] (1) Dissolve the modified polyol in the solvents toluene and butanone, and heat to 60°C;

[0095] (2) Add isocyanate and catalyst dropwise, and stir for 4 hours to obtain the prepolymer;

[0096] (3) Add the chain extender to the prepolymer and stir at 70°C for 5 hours;

[0097] (4) Add crosslinking agent and stir at 40℃ for 2 hours;

[0098] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0099] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:6; the mass ratio of toluene to butanone is 1:2.

[0100] Comparative Example 4

[0101] A polyurethane pressure-sensitive adhesive for protective films comprises the following raw materials in parts by weight: 60 parts by weight of modified polyol, 30 parts by weight of isocyanate, 10 parts by weight of chain extender, 0.5 parts by weight of catalyst, and 2 parts by weight of crosslinking agent.

[0102] The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 70°C for 6 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing.

[0103] The fluorinated acrylate monomer is perfluorooctyl acrylate, the polyol is polyethylene glycol, the solvent is toluene, the initiator is benzoyl peroxide, and the terminator is hydroquinone; the mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 20:60:200:2:0.5.

[0104] The isocyanate is toluene diisocyanate.

[0105] The chain extender is 1,4-butanediol.

[0106] The catalyst is dibutyltin dilaurate.

[0107] The crosslinking agent is polycarbodiimide and triglycidyl isocyanurate, and the mass ratio of polycarbodiimide to triglycidyl isocyanurate is 7:3.

[0108] The method for preparing a polyurethane pressure-sensitive adhesive for a protective film includes the following steps:

[0109] (1) Dissolve the modified polyol in the solvents toluene and butanone, and heat to 60°C;

[0110] (2) Add isocyanate and catalyst dropwise, and stir for 4 hours to obtain the prepolymer;

[0111] (3) Add the chain extender to the prepolymer and stir at 70°C for 5 hours;

[0112] (4) Add crosslinking agent and stir at 40℃ for 2 hours;

[0113] (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

[0114] As a preferred embodiment of the present invention, the mass ratio of the modified polyol to the solvent is 1:6; the mass ratio of toluene to butanone is 1:2.

[0115] Performance testing:

[0116] Adhesion test: The 180° peel strength test was conducted according to the method described in GB / T 2792-2014. The specific test method is as follows: Polyurethane pressure-sensitive adhesive was evenly coated on the protective film, with a dry adhesive thickness of 20μm. The film was cut into samples 25mm × 150mm wide. The samples were spread on the glass and rolled back and forth 3 times with a 2kg rubber roller. After standing for 20 minutes at 23±2℃, the film was pulled apart using a universal tensile testing machine at a 180° angle and a speed of 300mm / min. The average peel strength between 20 and 80mm displacements was recorded.

[0117] Persistent Adhesion Test: Based on the peel strength test, the protective film rolled onto the glass is placed at 85℃. 、 After 168 hours in an 85% RH environment, allow it to return to room temperature before conducting a peel strength test.

[0118]

[0119] The test results show that introducing fluorinated acrylate into the polyol structure and combining it with polycarbodiimide, triglycidyl isocyanurate and silane coupling agent as crosslinking agents not only enhances the adhesion of the pressure-sensitive adhesive, but also maintains good adhesion after high temperature and high humidity treatment.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polyurethane pressure-sensitive adhesive for protective films, characterized in that: It contains the following raw materials in parts by weight: 40-60 parts by weight of modified polyol, 20-40 parts by weight of isocyanate, 5-15 parts by weight of chain extender, 0.1-1 parts by weight of catalyst, and 1-5 parts by weight of crosslinking agent. The modified polyol is a fluorinated acrylate modified polyol, and the preparation method is as follows: after dissolving the polyol in a solvent, fluorinated acrylate monomer and initiator are added dropwise, and the mixture is stirred at 60-80℃ for 4-8 hours. After adding a terminator, the modified polyol is obtained by precipitation and washing. The crosslinking agent is polycarbodiimide, triglycidyl isocyanurate and silane coupling agent, and the mass ratio of polycarbodiimide, triglycidyl isocyanurate and silane coupling agent is 5-7:2-4:1-2. The fluorinated acrylate monomer is any one of perfluorooctyl acrylate, trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, and (1,1,1,3,3,3-hexafluoro-2-phenylprop-2-yl) methacrylate; the polyol is any one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol; the solvent is toluene or dichloromethane; the initiator is benzoyl peroxide or azobisisobutyronitrile; and the terminator is hydroquinone. The mass ratio of the fluorinated acrylate monomer, polyol, solvent, initiator, and terminator is 10-30:40-70:200-500:1-5:0.1-1.

2. The polyurethane pressure-sensitive adhesive for protective films according to claim 1, characterized in that: The isocyanate is any one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

3. The polyurethane pressure-sensitive adhesive for protective films according to claim 1, characterized in that: The chain extender is any one of 1,4-butanediol, ethylene glycol, diethanolamine, and dimethylglyoxime.

4. The polyurethane pressure-sensitive adhesive for protective films according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate.

5. A method for preparing a polyurethane pressure-sensitive adhesive for a protective film as described in any one of claims 1-4, characterized in that: Includes the following steps: (1) Dissolve the modified polyol in solvents toluene and butanone, and heat to 50-80℃; (2) Add isocyanate and catalyst dropwise, and stir for 3-5 hours to obtain the prepolymer; (3) Add the chain extender to the prepolymer and stir at 70-80℃ for 4-6 hours; (4) Add crosslinking agent and stir at 30-60℃ for 1-3 hours; (5) The solvent was removed by vacuum distillation to obtain polyurethane pressure-sensitive adhesive.

6. The method for preparing a polyurethane pressure-sensitive adhesive for a protective film according to claim 5, characterized in that: The mass ratio of the modified polyol to the solvent is 1:5-10; the mass ratio of toluene to butanone is 1:1-2.

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