High-temperature resistant adhesive, preparation method therefor, and high-temperature resistant protective film

Abstract

The present application relates to the technical field of adhesives, and in particular to a high-temperature resistant adhesive, a preparation method therefor, and a high-temperature resistant protective film. One aspect of the present application provides a high-temperature resistant adhesive, comprising an acrylic resin, a crosslinking agent, and a solvent; the amount of the crosslinking agent is 1 wt% to 2 wt% of the acrylic resin; the acrylic resin comprises structural units represented by the following formula I, wherein R is selected from an alkylene group having 1 to 3 carbon atoms. In the present application, a high-temperature resistant monomer is introduced into a backbone of the acrylic resin, and a boric acid group in the structure thereof undergoes dehydration under high-temperature conditions to form a borate structure, thereby generating cross-linking points, further enhancing cohesive strength, providing the adhesive with excellent high-temperature resistance, and ensuring that the adhesive exhibits low peel strength build-up after high-temperature exposure.

Description

High-temperature resistant adhesives, their preparation methods, and high-temperature resistant protective films Technical Field

[0001] This application relates to the field of adhesive technology, and in particular to a high-temperature resistant adhesive, its preparation method, and a high-temperature resistant protective film. Background Technology

[0002] High-temperature resistant protective films are thin films used to protect various materials and components in high-temperature environments. With the rapid development of modern industry and the electronics manufacturing industry, the application fields of high-temperature resistant protective films are becoming increasingly wide, and the requirements for high-temperature resistant protective films are also becoming increasingly stringent.

[0003] Acrylic resins are widely used in various fields due to their excellent aging resistance, water resistance, and pressure sensitivity. However, their high-temperature stability is limited. To improve the high-temperature resistance of acrylic resins, they are often compounded with silanes or filled with organosilicon fillers. While this approach can appropriately improve the high-temperature resistance of acrylic resins, it introduces new problems. On the one hand, the introduction of small molecule components can easily leave residues and adhesive marks on the surface of the substrate after application in high-temperature environments, leading to poor quality. On the other hand, after application in high-temperature environments, the peel strength increases significantly, generally by more than 50%, making peeling more difficult.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0006] One objective of this application is to provide a high-temperature resistant adhesive that not only has excellent high-temperature resistance but also exhibits low peel strength creep after reaching high temperatures.

[0007] Another objective of this application is to provide a method for preparing a high-temperature resistant adhesive.

[0008] Another object of this application is to provide a high-temperature resistant protective film, including the above-mentioned high-temperature resistant adhesive.

[0009] To achieve the above objectives, this application provides a high-temperature resistant adhesive, comprising an acrylic resin, a crosslinking agent, and a solvent; wherein the amount of the crosslinking agent is 1 wt% to 2 wt% of the acrylic resin.

[0010] The acrylic resin contains the structural unit shown in Formula I:

[0011] R is selected from alkylene groups having 1 to 3 carbon atoms.

[0012] In a specific embodiment of this application, the structural unit represented by Formula I accounts for 0.5 wt% to 10 wt% of all structural units of the acrylic resin.

[0013] In specific embodiments of this application, the acrylic resin further includes at least one of the structural units represented by formulas II to IV;

[0014] R1, R3, and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; and R4 is selected from alkyl groups having 4 to 8 carbon atoms.

[0015] In a specific embodiment of this application, the acrylic resin contains 0.5wt% to 10wt% of the total structural units of the acrylic resin, 100wt% of the total structural units, and the contents of the structural units represented by Formulas I to IV are 65wt% to 85wt% and 2wt% to 8wt%, respectively.

[0016] In a specific embodiment of this application, the acrylic resin is mainly obtained by copolymerization of acrylate monomers; the acrylate monomers include monomers represented by formulas A to D as follows:

[0017] In a specific embodiment of this application, the acrylic resin further includes an initiator and an organic solvent. Further, relative to 100 parts by weight of the total amount of acrylate monomers, the amount of the initiator is 0.1 to 1 part, and the amount of the organic solvent is 80 to 120 parts.

[0018] In a specific embodiment of this application, the crosslinking agent includes a trifunctional aziridine crosslinking agent.

[0019] In specific embodiments of this application, the solvent includes at least one of ethyl acetate, toluene, xylene, and butyl acetate.

[0020] This application also provides a method for preparing any of the above-described high-temperature resistant adhesives, comprising the following steps: mixing the components in proportion.

[0021] In another aspect, this application provides a high-temperature resistant protective film, comprising a substrate and an adhesive layer disposed on the surface of the substrate; the adhesive layer is made of the high-temperature resistant adhesive.

[0022] In a specific embodiment of this application, the thickness of the adhesive layer is 5–30 μm.

[0023] Compared with the prior art, the beneficial effects of this application are as follows:

[0024] (1) This application introduces a high-temperature resistant monomer structure into the main body of acrylic resin, and improves the cohesive strength by adding an external crosslinking agent and curing at room temperature; at the same time, the boric acid group in the high-temperature resistant monomer can form a borate ester structure by dehydration under high temperature conditions, generating crosslinking points, further improving the cohesive strength, giving the adhesive excellent high-temperature resistance, and ensuring that the peel force of the adhesive rises low after high temperature.

[0025] (2) The high-temperature resistant protective film prepared using the high-temperature resistant adhesive of this application has excellent peel strength, holding strength and cohesive strength, and excellent high-temperature resistance.

[0026] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0027] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0028] This application provides a high-temperature resistant adhesive comprising the following components by weight: acrylic resin, crosslinking agent, and solvent; wherein the amount of crosslinking agent is 1 wt% to 2 wt% of the acrylic resin;

[0029] Acrylic resins contain structural units as shown in Formula I:

[0030] R is selected from alkylene groups having 1 to 3 carbon atoms.

[0031] The high-temperature resistant adhesive of this application improves cohesion by compounding acrylic resin with an external crosslinking agent and curing at room temperature. Simultaneously, the acrylic resin of this application incorporates a high-temperature resistant monomer structure, with the polymer backbone containing structural units as shown in Formula I. Under high-temperature conditions, the boric acid groups in the structural units can dehydrate to form borate ester structures, generating crosslinking points and further enhancing cohesive strength. This endows the adhesive with excellent high-temperature resistance, ensuring low peel strength creep after high temperatures.

[0032] In the structural unit shown in Formula I of this application, R can be at least one of methylene, ethylene, or propylene.

[0033] In different embodiments, the amount of crosslinking agent may be 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt% of acrylic resin, or any combination thereof.

[0034] The amount of solvent in the high-temperature resistant adhesive of this application can be adjusted according to actual needs to ensure the coating requirements of the high-temperature resistant adhesive and the required drying time after coating. For example, the amount of solvent can be 5wt% to 40wt% of the acrylic resin, such as 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%, etc., but is not limited to this.

[0035] In practice, the solvents used in high-temperature resistant adhesives can be conventional solvents, including but not limited to at least one of ethyl acetate, toluene, xylene, and butyl acetate.

[0036] In a specific embodiment of this application, the structural unit represented by Formula I accounts for 0.5 wt% to 10 wt% of all structural units of the acrylic resin.

[0037] In different embodiments, the structural unit shown in Formula I in the acrylic resin may account for 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, or any combination thereof, of all structural units in the acrylic resin, and may be further selected as 3 wt% to 6 wt%. When the amount of the structural unit shown in Formula I in the acrylic resin meets the above conditions, it can improve the high-temperature resistance of the adhesive, ensure the initial tack and peel strength of the adhesive, and prevent the adhesive from whitening.

[0038] In specific embodiments of this application, the acrylic resin further includes at least one of the structural units represented by formulas II to IV;

[0039] R1, R3, and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; and R4 is selected from alkyl groups having 4 to 8 carbon atoms.

[0040] In different embodiments, R4 may be selected from straight-chain or branched alkyl groups having 4 to 8 carbon atoms, such as at least one of butyl or isooctyl, but is not limited thereto.

[0041] In a specific embodiment of this application, the acrylic resin contains 0.5wt% to 10wt% of the total structural units of the acrylic resin, 100wt% of the total structural units of the acrylic resin, and the contents of the structural units shown in Formulas I to IV are 65wt% to 85wt% and 2wt% to 8wt%, respectively.

[0042] This application controls the content of each structural unit in the acrylic resin within the above-mentioned range to further balance and optimize the initial tack, cohesive strength, bond strength, and transparency of the adhesive. For example, in different embodiments, the content of the structural units represented by Formulas I to IV can be as follows:

[0043] The content of the structural unit shown in Formula I can be 0.5wt%, 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, or any combination thereof;

[0044] The content of the structural unit shown in Formula II can be 10wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, or any combination thereof;

[0045] The content of the structural unit shown in Formula III can be 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, or any combination thereof;

[0046] The content of the structural unit shown in Formula IV can be 2 wt%, 4 wt%, 6 wt%, 8 wt%, or any combination thereof.

[0047] In a specific embodiment of this application, the acrylic resin is mainly obtained by copolymerization of acrylate monomers; the acrylate monomers include monomers represented by formulas A to D as follows:

[0048] The acrylate monomers shown in Formula A of this application can be prepared according to the following route:

[0049] In this process, compound X reacts with 4-hydroxymethylphenylboronic acid via a carbamate esterification reaction under the catalysis of a catalyst to obtain acrylate monomers as shown in Formula A. The boric acid in 4-hydroxymethylphenylboronic acid has very low reactivity and does not significantly affect the formation of the acrylate monomers shown in Formula A. Organotin catalysts can be used, including but not limited to dibutyltin dilaurate; the reaction temperature can be 45–55°C, and the reaction time can be 4–8 h; the specific reaction temperature and reaction time can be adjusted conventionally according to the reaction progress.

[0050] When R is ethylene, the structural formulas of the corresponding compound X and the acrylate monomers prepared as shown in formula A are as follows:

[0051] The acrylate monomers shown in Formula B of this application include at least one of methyl (meth)acrylate and ethyl (meth)acrylate; the acrylate monomers shown in Formula C of this application include at least one of butyl acrylate and isooctyl acrylate; the acrylate monomers shown in Formula D of this application include (meth)acrylic acid.

[0052] In specific embodiments of this application, the acrylic resin further includes an initiator and an organic solvent. Further, relative to 100 parts by weight of the total amount of acrylate monomers, the amount of initiator is 0.1 to 1 part, and the amount of organic solvent is 80 to 120 parts.

[0053] In specific embodiments of this application, the initiator is at least one of peroxide initiators and azo initiators, and the specific type is not limited, as long as it can initiate the polymerization reaction of acrylate monomers. For example, it can be benzoyl peroxide, azobisisobutyronitrile, etc.; the organic solvent includes, but is not limited to, at least one of ethyl acetate, toluene, xylene, and butyl acetate.

[0054] In a specific embodiment of this application, the preparation of acrylic resin includes: weighing raw materials according to a certain proportion, and reacting them at 75-85°C for 6-12 hours under a protective atmosphere. The protective atmosphere in the preparation of acrylic resin can be nitrogen, but is not limited to it; the reaction temperature can be 75°C, 78°C, 80°C, 82°C, 85°C, or any value between any two extremes therein; and the reaction time can be 6 hours, 8 hours, 10 hours, 12 hours, etc.

[0055] In specific embodiments of this application, the weight-average molecular weight of the acrylic resin can be, for example, 5×10⁵ to 6×10⁵, but is not limited thereto; the molecular weight distribution width of the acrylic resin can be, for example, 3.8 to 4.4, but is not limited thereto.

[0056] In specific embodiments of this application, the crosslinking agent includes a trifunctional aziridine crosslinking agent.

[0057] This application also provides a method for preparing any of the above-mentioned high-temperature resistant adhesives, comprising the following steps: mixing the components in proportion.

[0058] Another aspect of this application provides a high-temperature resistant protective film, including a substrate and an adhesive layer disposed on the surface of the substrate; the adhesive layer is made of a high-temperature resistant adhesive.

[0059] In a specific embodiment of this application, the preparation of the high-temperature resistant protective film includes: applying a high-temperature resistant adhesive to the surface of a substrate, drying it, and then covering it with a release film to obtain the high-temperature resistant protective film.

[0060] The coating thickness of the high-temperature resistant adhesive can be adjusted according to the actual thickness requirements of the high-temperature resistant protective film. For example, the thickness of the adhesive layer formed after coating and drying can be controlled to be 5–30 μm, but it is not limited to this. The type of substrate can be conventionally adjusted according to the application requirements of the high-temperature resistant protective film, such as a polyimide (PI) film substrate.

[0061] In actual operation, the drying temperature can be 110-130℃ and the drying time can be 5-20 minutes.

[0062] Example 1

[0063] This embodiment provides a method for preparing a high-temperature resistant protective film, including the following steps:

[0064] (1) Preparation of high-temperature resistant monomers:

[0065] 1 mol of 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate (AOI-BP), 1 mol of 4-hydroxymethylphenylboronic acid, and 0.00007916 mol of dibutyltin dilaurate were added to a 1000 mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel. After stirring evenly, the mixture was heated to 50 °C and reacted for 6 hours to obtain a high-temperature resistant monomer.

[0066] (2) Preparation of acrylic resin:

[0067] 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 5 g of a heat-resistant monomer, 0.3 g of benzoyl peroxide, and 100 g of ethyl acetate were added to a 1000 mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel. The mixture was reacted at 80 °C for 8 h, then cooled to room temperature and discharged to obtain acrylic resin. The weight-average molecular weight (Mw) of the acrylic resin was 5.8 × 10⁻⁶. 5 The molecular weight distribution width of Mw / Mn is 4.4.

[0068] (3) Preparation of high-temperature resistant protective film:

[0069] Weigh 100g of acrylic resin obtained in step (2), 1g of trifunctional aziridine crosslinking agent SC-100, and 20g of ethyl acetate according to the proportion and mix them evenly to obtain a high-temperature resistant adhesive. Coat the high-temperature resistant adhesive onto the surface of a 50μm thick PI film substrate and dry it at 120℃ for 10min to obtain an adhesive layer with a thickness of 10μm. Cover the other side of the adhesive layer with a PET release film to obtain a high-temperature resistant protective film.

[0070] Example 2

[0071] This embodiment refers to the preparation method of the high-temperature resistant protective film in Example 1, the only difference being that the amount of high-temperature resistant monomer used in step (2) of preparing acrylic resin is different.

[0072] Step (2) of this embodiment includes: adding 20g of methyl acrylate, 70g of butyl acrylate, 5g of acrylic acid, 7g of high-temperature resistant monomer, 0.3g of benzoyl peroxide, and 100g of ethyl acetate to a 1000mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel; reacting at 80℃ for 8 hours; and then discharging at room temperature to obtain acrylic resin. The weight-average molecular weight (Mw) of the acrylic resin is 5.8 × 10⁻⁶. 5 The molecular weight distribution width of Mw / Mn is 4.4.

[0073] Example 3

[0074] This embodiment refers to the preparation method of the high-temperature resistant protective film in Example 1, the only difference being that the amount of high-temperature resistant monomer used in step (2) of preparing acrylic resin is different.

[0075] Step (2) of this embodiment includes: adding 20g of methyl acrylate, 70g of butyl acrylate, 5g of acrylic acid, 3g of high-temperature resistant monomer, 0.3g of benzoyl peroxide, and 100g of ethyl acetate to a 1000mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel; reacting at 80℃ for 8 hours; and then discharging at room temperature to obtain acrylic resin. The weight-average molecular weight (Mw) of the acrylic resin is 5.5 × 10⁻⁶. 5 The molecular weight distribution width of Mw / Mn is 4.2.

[0076] Example 4

[0077] This embodiment refers to the preparation method of the high-temperature resistant protective film in Example 1, the only difference being that the amount of high-temperature resistant monomer used in step (2) of preparing acrylic resin is different.

[0078] Step (2) of this embodiment includes: adding 20g of methyl acrylate, 70g of butyl acrylate, 5g of acrylic acid, 1g of a high-temperature resistant monomer, 0.3g of benzoyl peroxide, and 100g of ethyl acetate to a 1000mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel; reacting at 80℃ for 8 hours; and then discharging at room temperature to obtain acrylic resin. The weight-average molecular weight (Mw) of the acrylic resin is 6.0 × 10⁻⁶. 5 The molecular weight distribution width of Mw / Mn is 3.8.

[0079] Comparative Example 1

[0080] The method for preparing the high-temperature resistant protective film of Comparative Example 1 is different in that: in step (2) of preparing acrylic resin, no high-temperature resistant monomer is added.

[0081] Step (2) of Comparative Example 1 includes: adding 20g of methyl acrylate, 70g of butyl acrylate, 5g of acrylic acid, 0.3g of benzoyl peroxide, and 100g of ethyl acetate to a 1000mL four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel; reacting at 80℃ for 8h; and then discharging at room temperature to obtain acrylic resin. The weight-average molecular weight (Mw) of the acrylic resin is 5.0 × 10⁻⁶. 5 The molecular weight distribution width of Mw / Mn is 4.

[0082] Experimental Example

[0083] To compare and illustrate the performance of the protective films prepared in different embodiments and comparative examples, the protective films prepared in each embodiment and comparative example were tested as follows, and the test results are shown in Table 1.

[0084] Peel strength at 25℃: Tested according to GB / T 2792-2014; the test substrate was steel plate;

[0085] Peel strength after heating at 200℃ for 120 min: tested according to GB / T 2792-2014; the test substrate was steel plate;

[0086] Peel strength climb rate: calculated as "(peel strength after heating at 200℃ for 120 min - peel strength at 25℃) / peel strength at 25℃";

[0087] Tack hold at 80℃: Tested according to GB / T 4851-2014; test substrate was steel plate;

[0088] Initial ball tack: Tested according to GB / T 4852-2002.

[0089] Table 1 Performance test results of different protective films

[0090] The test results above show that the high-temperature resistant protective film of this application balances initial tack, cohesive force and peel strength, and has excellent high-temperature resistance, with low peel strength creep after high-temperature treatment.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high-temperature resistant adhesive, comprising acrylic resin, a crosslinking agent, and a solvent; wherein the amount of the crosslinking agent is 1 wt% to 2 wt% of the acrylic resin; The acrylic resin contains the structural unit shown in Formula I: R is selected from alkylene groups having 1 to 3 carbon atoms.

2. The high-temperature resistant adhesive according to claim 1, wherein, In the acrylic resin, the structural unit represented by Formula I accounts for 0.5wt% to 10wt% of all structural units of the acrylic resin.

3. The high-temperature resistant adhesive according to claim 1, wherein, The acrylic resin further includes at least one of the structural units shown in formulas II to IV below; R1, R3, and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; and R4 is selected from alkyl groups having 4 to 8 carbon atoms.

4. The high-temperature resistant adhesive according to claim 3, wherein, In the acrylic resin, with all structural units of the acrylic resin as 100wt%, the contents of the structural units shown in Formulas I to IV are 0.5wt% to 10wt%, 10wt% to 25wt%, 65wt% to 85wt%, and 2wt% to 8wt%, respectively.

5. The high-temperature resistant adhesive according to claim 1, wherein, The acrylic resin is mainly obtained by copolymerization of acrylate monomers; the acrylate monomers include monomers represented by formulas A to D as follows:

6. The high-temperature resistant adhesive according to claim 5, wherein, The acrylic resin also includes an initiator and an organic solvent; The amount of the initiator is 0.1 to 1 part relative to 100 parts by weight of the total amount of acrylate monomers, and the amount of the organic solvent is 80 to 120 parts.

7. The high-temperature resistant adhesive according to claim 1, wherein, The crosslinking agent includes a trifunctional aziridine crosslinking agent; the solvent includes at least one of ethyl acetate, toluene, xylene, and butyl acetate.

8. A method for preparing a high-temperature resistant adhesive, comprising the following steps: mixing ingredients according to the composition of the high-temperature resistant adhesive according to any one of claims 1 to 7.

9. A high-temperature resistant protective film comprising a substrate and an adhesive layer disposed on the surface of the substrate, wherein, The adhesive layer is made from the high-temperature resistant adhesive according to any one of claims 1 to 7 or the high-temperature resistant adhesive prepared by the preparation method according to claim 8.

10. The high-temperature resistant protective film according to claim 9, wherein, The thickness of the adhesive layer is 5–30 μm.

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