A core-shell structure high-temperature-resistant acrylic pressure-sensitive adhesive and a preparation method thereof

Abstract

The application provides a core-shell structure high-temperature-resistant acrylic pressure-sensitive adhesive and a preparation method thereof. The pressure-sensitive adhesive adopts a core-shell structure design, a polymer with a high glass transition temperature is selected as a core layer, a low glass transition temperature adhesive monomer is used to prepare a shell layer, a flexible chain segment is used to provide room temperature adhesion, and the core layer is used to avoid excessive softening at high temperature. The core layer remains stable at high temperature, the shell layer forms hydrogen bonds or chemical bonds with the substrate through polar groups, and the adhesion is maintained. The addition of modified fillers further improves the high-temperature resistance of the pressure-sensitive adhesive.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology and relates to a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives (PSAs) are a type of adhesive that can adhere to a substrate surface at room temperature by applying slight pressure without the need for heating or solvents. Unlike traditional hot melt adhesives or solvent-based adhesives, the adhesion of PSAs is determined by the special design of their molecular structure, typically exhibiting high adhesion and appropriate peel strength. Acrylic PSAs are the most widely used type of PSAs, and their main component is a polymer of acrylic acid or its ester monomers. These adhesives have important applications in various industries and daily life because they not only possess good adhesion but also excellent weather resistance, transparency, and a certain degree of high-temperature resistance. By adjusting the type and proportion of acrylic monomers, the performance of PSAs can be customized to meet the needs of different industries.

[0003] Pressure-sensitive adhesives (PSAs) have a wide range of applications, playing a crucial role, especially in electronic products and high-performance industrial materials. In electronic products, PSAs are commonly used in labels, screen protectors, and conductive tapes. For specialized applications, such as those requiring adhesion in high-temperature environments, acrylic PSAs are particularly important. For instance, in some high-temperature electronic devices, high-temperature resistant acrylic PSAs are widely used with high-temperature tapes (such as PI tapes). These tapes typically need to withstand temperatures as high as 260-300°C and maintain their adhesion and structural stability for extended periods in high-temperature environments. The application of these tapes is critical for the protection and assembly of electronic components, especially in high-precision fields such as aerospace, automotive electronics, and semiconductors. With the increasing demands for high-temperature performance, durability, and peel strength, the development of higher-performance acrylic PSAs has become increasingly urgent, particularly for applications requiring high temperatures and high peel strength.

[0004] However, existing acrylic pressure-sensitive adhesives still face many shortcomings, especially in applications with extremely demanding high-temperature requirements for core-shell structures. While traditional acrylic pressure-sensitive adhesives can meet normal temperature and adhesion requirements, they often exhibit problems such as decreased adhesion, insufficient heat resistance, and unstable peel strength in extreme environments (such as continuous exposure to high temperatures). Therefore, developing an acrylic pressure-sensitive adhesive that combines high-temperature stability, strong peel strength, and long-term reliability is of significant practical importance for meeting the needs of electronic products and other high-performance applications. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive and its preparation method, which exhibits high temperature resistance and high peel strength.

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

[0007] A method for preparing a core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized by comprising the following steps:

[0008] (1) Methyl methacrylate and acrylonitrile are copolymerized in the presence of crosslinking agent trimethylolpropane triacrylate and initiator ammonium persulfate. Ammonium persulfate decomposes at high temperature to generate sulfate free radicals that attack the double bonds of monomers, forming methyl methacrylate free radical monomers and acrylonitrile free radical monomers. The free radicals of the monomers then grow into chains through continuous addition. Trimethylolpropane triacrylate, as a trifunctional crosslinking agent, participates in multiple chain growth reactions to form three-dimensional crosslinks, thereby forming a core layer emulsion.

[0009] (2) Add a mixture of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate to the core layer emulsion obtained in step (1). Due to its high hydrophobicity, isooctyl acrylate migrates to the hydrophobic interior or surface of the core layer. Acrylic acid and hydroxyethyl acrylate contain carboxyl and hydroxyl groups and are amphiphilic. They are preferably adsorbed at the core layer interface. The shell layer polymerization is still driven by the free radicals generated by the decomposition of ammonium persulfate. However, under the reaction conditions, the decomposition rate of ammonium persulfate is lower than that of the core layer stage. The shell layer monomers gradually polymerize on the surface of the core layer and wrap around the surface of the core layer to form a shell layer.

[0010] (3) Add silane coupling agent to the product of step (2) to modify the filler. The silane coupling agent is hydrolyzed in ethanol / water mixed solvent to generate silanol. The silanol condenses with the hydroxyl groups on the surface of the nanofiller to form covalent bonds, so that the filler is uniformly dispersed in the pressure-sensitive adhesive.

[0011] As a preferred technical solution of the present invention, the mass ratio of methyl methacrylate, acrylonitrile, trimethylolpropane triacrylate and ammonium persulfate in step (1) is 6-7:3-4:0.2-0.4:0.02-0.08.

[0012] As a preferred technical solution of the present invention, the copolymerization reaction temperature in step (1) is 80-85℃ and the time is 3-4h.

[0013] As a preferred technical solution of the present invention, the mass ratio of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate in step (2) is 8-9:1-2:0.3-0.5.

[0014] As a preferred technical solution of the present invention, the polymerization reaction temperature in step (2) is 60-65℃ and the time is 4-5h.

[0015] As a preferred embodiment of the present invention, the mass ratio of the core layer to the shell layer is 3-4:6-7.

[0016] As a preferred technical solution of the present invention, the silane coupling agent in step (3) is one of KH-550, KH-560, and KH-570, and the filler is a mixture of nano boron nitride and nano silicon dioxide;

[0017] The preparation method of the silane coupling agent modified filler is as follows:

[0018] S1. Mix nano boron nitride and nano silicon dioxide at a mass ratio of 1-2:1;

[0019] S2. Add the mixture to ethanol / water (volume ratio 7:3) and sonicate for 30 min until a uniform suspension is formed;

[0020] S3. Add 1.5-2% of silane coupling agent by the total mass of the filler, and reflux at 50-70℃ for 1-3 hours;

[0021] S4. Centrifuge and wash to remove unreacted silane coupling agent, then vacuum dry at 60°C for 12 h to obtain the final product.

[0022] As a preferred technical solution of the present invention, the amount of modified filler added in step (3) is 5-12wt% of acrylic pressure-sensitive adhesive.

[0023] Furthermore, a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive is prepared by the method for preparing the core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive.

[0024] As a preferred technical solution of the present invention, a curing agent is added when using the pressure-sensitive adhesive. The ratio of pressure-sensitive adhesive to curing agent is 100:1-2.5. The curing agent is an isocyanate trimer type curing agent, such as Covestro N3390, N3100, L75, etc.

[0025] The core-shell structured acrylic pressure-sensitive adhesive prepared by this invention can be coated onto a PI-based film to form PI tape. When the adhesive is coated and passed through a high-temperature oven, the isooctyl acrylate segments in the shell layer relax and spread, and the hydroxyethyl acrylate hydroxyl groups form hydrogen bonds with the PI-based film surface. The residual ammonium persulfate decomposes, promoting the esterification reaction of the acrylic acid and hydroxyethyl acrylate hydroxyl groups in the shell layer. The hydroxyl groups can be deeply crosslinked with the isocyanate curing agent, and the bonding between the filler and the polymer can further improve the interfacial strength.

[0026] The beneficial effects of this invention are:

[0027] (1) The present invention uses high glass transition temperature methyl methacrylate and acrylonitrile copolymer as pressure-sensitive adhesive core layer structure to provide rigidity; the shell layer is prepared by using low glass transition temperature viscous monomers acrylic acid and acrylate, the hydroxyl groups of hydroxyethyl acrylate form strong hydrogen bond with the film substrate, and the carboxyl groups of acrylic acid enhance polar adsorption, thus meeting the high temperature bonding requirements of the core-shell structure.

[0028] (2) The introduction of silane coupling agent modified nano boron nitride improves thermal conductivity, effectively disperses thermal stress, and avoids high-temperature delamination; silane coupling agent modified nano silica fills polymer defects, inhibits thermal expansion deformation, and further improves the high-temperature resistance of pressure-sensitive adhesive. Detailed Implementation

[0029] To further illustrate the technical means and effects adopted by the present invention to achieve the 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.

[0030] Example 1

[0031] A method for preparing a core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized by comprising the following steps:

[0032] (1) Methyl methacrylate and acrylonitrile are copolymerized in the presence of crosslinking agent trimethylolpropane triacrylate and initiator ammonium persulfate to form a core layer emulsion;

[0033] (2) Add a mixture of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate to the core layer emulsion obtained in step (1) and polymerize it to form a shell layer on the surface of the core layer.

[0034] (3) Add silane coupling agent to the product of step (2) and disperse it evenly.

[0035] The mass ratio of methyl methacrylate, acrylonitrile, trimethylolpropane triacrylate, and ammonium persulfate in step (1) is 7:3:0.3:0.05.

[0036] The copolymerization reaction in step (1) is carried out at a temperature of 82°C for 3.5 hours.

[0037] In step (2), the mass ratio of isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate is 9:1:0.5.

[0038] The polymerization reaction in step (2) is carried out at a temperature of 62°C for 4.5 hours.

[0039] The mass ratio of the core to the shell is 3:7.

[0040] The silane coupling agent in step (3) is KH-570, and the modified filler is a mixture of nano boron nitride and nano silica;

[0041] The preparation method of the silane coupling agent modified filler is as follows:

[0042] S1. Mix nano boron nitride and nano silicon dioxide at a mass ratio of 2:1;

[0043] S2. Add the mixture to ethanol / water (volume ratio 7:3) and sonicate for 30 min until a uniform suspension is formed;

[0044] S3. Add 1.8% KH-570 by the total mass of the filler and reflux at 60℃ for 3 h;

[0045] S4. Centrifuge and wash to remove unreacted silane coupling agent, then vacuum dry at 60°C for 12 h to obtain the final product.

[0046] The amount of modified filler added in step (3) is 10 wt% of the acrylic pressure-sensitive adhesive.

[0047] Example 2

[0048] A method for preparing a core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized by comprising the following steps:

[0049] (1) Methyl methacrylate and acrylonitrile are copolymerized in the presence of crosslinking agent trimethylolpropane triacrylate and initiator ammonium persulfate to form a core layer emulsion;

[0050] (2) Add a mixture of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate to the core layer emulsion obtained in step (1) and polymerize it to form a shell layer on the surface of the core layer.

[0051] (3) Add silane coupling agent to the product of step (2) and disperse it evenly.

[0052] The mass ratio of methyl methacrylate, acrylonitrile, trimethylolpropane triacrylate, and ammonium persulfate in step (1) is 6.5:3.5:0.3:0.05.

[0053] The copolymerization reaction in step (1) is carried out at a temperature of 80°C for 4 hours.

[0054] The mass ratio of isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate in step (2) is 8.5:1.5:0.4.

[0055] The polymerization reaction in step (2) is carried out at a temperature of 60°C for 5 hours.

[0056] The mass ratio of the core to the shell is 3.5:6.5.

[0057] The silane coupling agent in step (3) is KH-550, and the modified filler is a mixture of nano boron nitride and nano silica;

[0058] The preparation method of the silane coupling agent modified filler is as follows:

[0059] S1. Mix nano boron nitride and nano silicon dioxide at a mass ratio of 1.5:1;

[0060] S2. Add the mixture to ethanol / water (volume ratio 7:3) and sonicate for 30 min until a uniform suspension is formed;

[0061] S3. Add 1.8% KH-550 by the total mass of the filler and reflux at 50℃ for 3 h;

[0062] S4. Centrifuge and wash to remove unreacted silane coupling agent, then vacuum dry at 60°C for 12 h to obtain the final product.

[0063] The amount of modified filler added in step (3) is 8 wt% of the acrylic pressure-sensitive adhesive.

[0064] Example 3

[0065] A method for preparing a core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized by comprising the following steps:

[0066] (1) Methyl methacrylate and acrylonitrile are copolymerized in the presence of crosslinking agent trimethylolpropane triacrylate and initiator ammonium persulfate to form a core layer emulsion;

[0067] (2) Add a mixture of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate to the core layer emulsion obtained in step (1) and polymerize it to form a shell layer on the surface of the core layer.

[0068] (3) Add silane coupling agent to the product of step (2) and disperse it evenly.

[0069] The mass ratio of methyl methacrylate, acrylonitrile, trimethylolpropane triacrylate, and ammonium persulfate in step (1) is 6:4:0.4:0.08.

[0070] The copolymerization reaction in step (1) is carried out at a temperature of 85°C for 4 hours.

[0071] The mass ratio of isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate in step (2) is 8:2:0.3.

[0072] The polymerization reaction in step (2) is carried out at a temperature of 65°C for 5 hours.

[0073] In a preferred embodiment of the present invention, the mass ratio of the core layer to the shell layer is 4:6.

[0074] The silane coupling agent in step (3) is KH-560, and the modified filler is a mixture of nano boron nitride and nano silica;

[0075] The preparation method of the silane coupling agent modified filler is as follows:

[0076] S1. Mix nano boron nitride and nano silicon dioxide at a mass ratio of 1:1;

[0077] S2. Add the mixture to ethanol / water (volume ratio 7:3) and sonicate for 30 min until a uniform suspension is formed;

[0078] S3. Add 2% KH-560 by the total mass of the filler and reflux at 70℃ for 3 hours;

[0079] S4. Centrifuge and wash to remove unreacted silane coupling agent, then vacuum dry at 60°C for 12 h to obtain the final product.

[0080] The amount of modified filler added in step (3) is 12 wt% of the acrylic pressure-sensitive adhesive.

[0081] Comparative Example 1

[0082] Based on Example 1, without preparing a core-shell structure, methyl methacrylate, acrylonitrile, crosslinking agent trimethylolpropane triacrylate, initiator ammonium persulfate, isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate were directly mixed, and then a silane coupling agent was added to modify the filler and dispersed evenly. The rest remained the same as in Example 1.

[0083] Comparative Example 2

[0084] Based on Example 1, without adding silane coupling agent to modify the filler, the rest remains the same as in Example 1.

[0085] Comparative Example 3

[0086] Based on Example 1, no modification was made to the nano boron nitride and nano silicon dioxide, and the rest remained the same as in Example 1.

[0087] Performance testing:

[0088] The pressure-sensitive adhesive samples prepared in Examples 1-3 and Comparative Examples 1-3 were mixed with 1% curing agent (Covestro N3390), and ethyl acetate was added to adjust the solid content to 40%. The mixture was then coated onto a 25 μm PI film using a doctor blade coating method, with the wet coating amount controlled at 60 g / m². 2 After drying at 120℃ for 2 minutes, it was placed in a 60℃ oven for 48 hours to mature, and then further crosslinked before performance testing.

[0089] Peel strength: The 180° peel strength of the test examples and comparative samples was tested according to standard GB / T 2792-2014.

[0090] High temperature resistance: The PI tape samples obtained in the examples and comparative examples were attached to a stainless steel plate, placed in an oven and baked at 300°C for 30 minutes, cooled to room temperature, and then tested according to the above peel strength test standard.

[0091] Residual adhesive rate: After peeling off the tapes from the examples and comparative examples, the residual adhesive on the surface of the stainless steel plates was observed.

[0092]

[0093] The test results above show that, compared with the core-shell structure in Comparative Example 1, the homogeneous adhesive exhibits violent chain segment movement and loss of cohesion at high temperatures. After high-temperature treatment, the peel strength retention rate is only 40.2%, and the residual adhesive rate is also significantly increased. Comparative Example 2, without the addition of filler, shows a decrease in high-temperature resistance. In Comparative Example 3, the filler is unmodified, resulting in weak interfacial bonding. At high temperatures, the filler is prone to detach from the matrix, leading to a decrease in performance.

[0094] 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 method for preparing a core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized in that: Includes the following steps: (1) Methyl methacrylate and acrylonitrile are copolymerized in the presence of crosslinking agent trimethylolpropane triacrylate and initiator ammonium persulfate to form a core layer emulsion; (2) Add a mixture of isooctyl acrylate, acrylic acid and hydroxyethyl acrylate to the core layer emulsion obtained in step (1), and polymerize and coat it on the surface of the core layer to form a shell layer; (3) Add silane coupling agent to the product of step (2) and disperse evenly to obtain acrylic pressure-sensitive adhesive; In step (3), the silane coupling agent is one of KH-550, KH-560, and KH-570, and the filler is a mixture of nano boron nitride and nano silicon dioxide.

2. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The mass ratio of methyl methacrylate, acrylonitrile, trimethylolpropane triacrylate and ammonium persulfate in step (1) is 6-7:3-4:0.2-0.4:0.02-0.

08.

3. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The copolymerization reaction in step (1) is carried out at a temperature of 80-85℃ for 3-4 hours.

4. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The mass ratio of isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate in step (2) is 8-9:1-2:0.3-0.

5.

5. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The polymerization in step (2) is carried out at a reaction temperature of 60-65℃ for 4-5 hours.

6. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The mass ratio of the core to the shell is 3-4:6-7.

7. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that, The preparation method of the silane coupling agent modified filler mentioned in step (3) is as follows: S1. Mix nano boron nitride and nano silicon dioxide at a mass ratio of 1-2:1; S2. Add the mixture to ethanol / water at a volume ratio of 7:3 and sonicate for 30 min until a uniform suspension is formed. S3. Add 1.5-2% of silane coupling agent by the total mass of the filler, and reflux at 50-70℃ for 1-3 hours; S4. Centrifuge and wash to remove unreacted silane coupling agent, then vacuum dry at 60°C for 12 h to obtain the final product.

8. The method for preparing a core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The amount of modified filler added in step (3) is 5-12 wt% of the acrylic pressure-sensitive adhesive.

9. A core-shell structured high-temperature resistant acrylic pressure-sensitive adhesive, characterized in that, It is prepared by the method of preparing the core-shell structure high-temperature resistant acrylic pressure-sensitive adhesive according to any one of claims 1-8.

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