High temperature resistant adhesive and preparation method thereof and high temperature resistant protective film

Abstract

The present invention relates to the technical field of adhesives, and in particular to a high temperature resistant adhesive, a preparation method thereof, and a high temperature resistant protective film. On the one hand, the present invention provides a high temperature resistant adhesive, including an acrylic resin, a cross-linking agent, and a solvent; the amount of the cross-linking agent is 1wt% to 2wt% of the acrylic resin; the acrylic resin contains a structural unit as shown in the following formula I:; R is selected from an alkylene group with a carbon number of 1 to 3. The present invention introduces a high temperature resistant monomer into the main body of the acrylic resin, and the boric acid group in its structure can form a borate ester structure by dehydration under high temperature conditions, generate cross-linking points, further enhance the cohesive strength, and give the adhesive excellent high temperature resistance, ensuring that the peeling force of the adhesive after high temperature rises low.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a high temperature resistant adhesive and a preparation method thereof, and a high temperature resistant protective film. Background Art

[0002] High temperature resistant protective film is a film used to protect various materials and components in high temperature environment. With the rapid development of modern industry and electronic manufacturing industry, the application field of high temperature resistant protective film is becoming more and more extensive, and the requirements for high temperature resistant protective film are also becoming higher and higher.

[0003] Acrylic resin is widely used in various fields due to its good aging resistance, water resistance, pressure sensitivity, etc., but the high temperature stability of acrylic resin is limited. In order to improve the high temperature resistance of acrylic resin, acrylic resin is compounded with silane, or silicone filler is added to acrylic resin. Although this method can appropriately improve the high temperature resistance of acrylic resin, it will introduce new problems. On the one hand, the introduction of small molecule components will easily form residues and offset on the surface of the object after application in a high temperature environment, causing poor quality. On the other hand, after application in a high temperature environment, the peel strength will increase significantly, generally more than 50%, resulting in increased difficulty in peeling.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One object of the present invention is to provide a high temperature resistant adhesive which not only has excellent high temperature resistance but also has a low peel force increase after high temperature.

[0006] Another object of the present invention is to provide a method for preparing the high temperature resistant adhesive.

[0007] Another object of the present invention is to provide a high temperature resistant protective film, comprising the above-mentioned high temperature resistant adhesive.

[0008] In order to achieve the above-mentioned object of the present invention, the present invention provides a high temperature resistant adhesive, comprising an acrylic resin, a cross-linking agent and a solvent; the amount of the cross-linking agent is 1wt% to 2wt% of the acrylic resin;

[0009] The acrylic resin contains the structural unit shown in the following formula I:

[0010] ;

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

[0012] In a specific embodiment of the present invention, in the acrylic resin, 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 a specific embodiment of the present invention, the acrylic resin further comprises at least one of the structural units shown in the following formulae II to IV;

[0014] , , ;

[0015] Wherein, R1, R3 and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; and R4 is selected from an alkyl group having 4 to 8 carbon atoms.

[0016] In a specific embodiment of the present invention, in the acrylic resin, taking all the structural units of the acrylic resin as 100wt%, the contents of the structural units represented by formulas I to IV are 0.5wt% to 10wt%, 10wt% to 25wt%, 65wt% to 85wt%, and 2wt% to 8wt%, respectively.

[0017] In a specific embodiment of the present invention, the acrylic resin is mainly prepared by copolymerization of acrylic ester monomers; the acrylic ester monomers include monomers represented by the following formulas A to D:

[0018] , , , .

[0019] In a specific embodiment of the present invention, the acrylic resin further comprises an initiator and an organic solvent. Further, relative to 100 parts by weight of the total amount of the acrylic ester monomer, the amount of the initiator is 0.1 to 1 part, and the amount of the organic solvent is 80 to 120 parts.

[0020] In a specific embodiment of the present invention, the cross-linking agent includes a trifunctional aziridine cross-linking agent.

[0021] In a specific embodiment of the present invention, the solvent includes at least one of ethyl acetate, toluene, xylene and butyl acetate.

[0022] Another aspect of the present invention provides a method for preparing any one of the above-mentioned high temperature resistant adhesives, comprising the following steps: mixing the components in proportion.

[0023] Another aspect of the present invention 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.

[0024] In a specific embodiment of the present invention, the thickness of the adhesive layer is 5 to 30 μm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention introduces a high temperature resistant monomer structure into the main body of the acrylic resin, and by adding a cross-linking agent, the cohesive strength is improved by curing at room temperature; at the same time, the boric acid group in the high temperature resistant monomer can be dehydrated under high temperature conditions to form a borate ester structure, generate cross-linking points, further improve the cohesive strength, and give the adhesive excellent high temperature resistance, ensuring that the peeling force of the adhesive after high temperature rises low;

[0027] (2) The high temperature resistant protective film prepared by using the high temperature resistant adhesive of the present invention has excellent peeling force, holding force and cohesive force, and has excellent high temperature resistance. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] In one aspect, the present invention provides a high temperature resistant adhesive, comprising the following components by weight: acrylic resin, a crosslinking agent and a solvent; the amount of the crosslinking agent is 1wt% to 2wt% of the acrylic resin;

[0030] The acrylic resin contains the structural unit shown in the following formula I:

[0031] ;

[0032] R is selected from an alkylene group having 1 to 3 carbon atoms.

[0033] The high temperature resistant adhesive of the present invention is compounded with an acrylic resin and an external crosslinking agent, and the cohesion is improved by curing at room temperature. At the same time, a high temperature resistant monomer structure is introduced into the acrylic resin of the present invention, and the polymer main chain contains a structural unit as shown in Formula I. Under high temperature conditions, the boric acid group in the structural unit can be dehydrated to form a borate ester structure, generating crosslinking points, further improving the cohesive strength, giving the adhesive excellent high temperature resistance, and ensuring that the peeling force of the adhesive after high temperature rises low.

[0034] In the structural unit shown in Formula I of the present invention, R may be at least one of a methylene group, an ethylene group or a propylene group.

[0035] For example, in different embodiments, the amount of the cross-linking agent can be 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt% of the acrylic resin, or a range consisting of any two of these.

[0036] The amount of the solvent in the high temperature resistant adhesive of the present invention can be adjusted according to actual needs to ensure the coating requirements of the high temperature resistant adhesive and the drying time requirements after coating. For example, the amount of the solvent can be 5wt% to 40wt% of the acrylic resin, such as 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%, etc., but is not limited thereto.

[0037] In actual operation, the solvent in the high temperature resistant adhesive may be a conventional solvent, including but not limited to at least one of ethyl acetate, toluene, xylene, and butyl acetate.

[0038] In a specific embodiment of the present invention, in the acrylic resin, the structural unit represented by Formula I accounts for 0.5 wt % to 10 wt % of all structural units of the acrylic resin.

[0039] For example, in different embodiments, the structural unit represented by Formula I in the acrylic resin may account for 0.5wt%, 1wt%, 3wt%, 5wt%, 8wt%, 10wt% or any two of the total structural units of the acrylic resin, preferably 3wt% to 6wt%. In the acrylic resin, when the amount of the structural unit represented by Formula I meets the above conditions, on the one hand, the high temperature resistance of the adhesive can be improved, on the other hand, the initial adhesion and peeling force of the adhesive can be ensured, and the whitening of the adhesive can be avoided.

[0040] In a specific embodiment of the present invention, the acrylic resin further comprises at least one of the structural units shown in the following formulae II to IV;

[0041] , , ;

[0042] Wherein, R1, R3 and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; and R4 is selected from an alkyl group having 4 to 8 carbon atoms.

[0043] For example, in different embodiments, R4 can be selected from a linear or branched alkyl group with a carbon number of 4 to 8, such as at least one of a butyl group and an isooctyl group, but is not limited thereto.

[0044] In a specific embodiment of the present invention, in the acrylic resin, taking all structural units of the acrylic resin as 100wt%, the contents of the structural units represented by Formulas I to IV are 0.5wt% to 10wt%, 10wt% to 25wt%, 65wt% to 85wt%, and 2wt% to 8wt%, respectively.

[0045] The present invention regulates the content of each structural unit in the acrylic resin within the above range to further balance and optimize the initial tack, cohesive strength, bonding strength and transparency of the adhesive. For example, in different embodiments, the content of the structural units shown in formulas I to IV can be as follows:

[0046] The content of the structural unit represented by Formula I can be 0.5wt%, 1wt%, 3wt%, 5wt%, 8wt%, 10wt% or a range consisting of any two thereof;

[0047] The content of the structural unit represented by Formula II can be 10wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt% or a range consisting of any two thereof;

[0048] The content of the structural unit represented by Formula III can be 65wt%, 70wt%, 75wt%, 80wt%, 85wt% or a range consisting of any two thereof;

[0049] The content of the structural unit represented by formula IV can be 2wt%, 4wt%, 6wt%, 8wt% or a range consisting of any two thereof.

[0050] In a specific embodiment of the present invention, the acrylic resin is mainly prepared by copolymerization of acrylic ester monomers; the acrylic ester monomers include monomers shown in the following formulas A to D:

[0051] , , , .

[0052] The acrylic acid ester monomer of the present invention as shown in formula A can be prepared according to the following route:

[0053] .

[0054] Wherein, compound X and 4-hydroxymethylphenylboronic acid are subjected to carbamate reaction under the catalysis of a catalyst to prepare an acrylate monomer as shown in formula A, wherein the boric acid reaction activity in 4-hydroxymethylphenylboronic acid is very low and basically does not affect the formation of the acrylate monomer as shown in formula A. The catalyst may be an organotin catalyst, including but not limited to dibutyltin dilaurate; the reaction temperature may be 45 to 55° C., and the reaction time may be 4 to 8 hours; the specific reaction temperature and reaction time may be conventionally adjusted according to the progress of the reaction.

[0055] When R is ethylene, the corresponding compound X and the obtained acrylic acid ester monomer as shown in formula A have the following structural formulas:

[0056] , .

[0057] The acrylate monomer of the present invention as shown in formula B includes at least one of methyl (meth)acrylate and ethyl (meth)acrylate; the acrylate monomer of the present invention as shown in formula C includes at least one of butyl acrylate and isooctyl acrylate; the acrylate monomer of the present invention as shown in formula D includes (meth)acrylic acid.

[0058] In a specific embodiment of the present invention, the acrylic resin further comprises an initiator and an organic solvent. Further, relative to 100 parts by weight of the total amount of the acrylic ester monomer, the amount of the initiator is 0.1 to 1 part, and the amount of the organic solvent is 80 to 120 parts.

[0059] In a specific embodiment of the present invention, the initiator is at least one of a peroxide initiator and an azo initiator, and the specific type is not limited, as long as it can initiate the polymerization reaction of the acrylate monomer, for example, it can be dibenzoyl peroxide, azobisisobutyronitrile, etc.; the organic solvent includes but is not limited to at least one of ethyl acetate, toluene, xylene, and butyl acetate.

[0060] In a specific embodiment of the present invention, the preparation of acrylic resin includes: weighing raw materials in proportion, reacting at 75-85°C for 6-12 hours under a protective atmosphere. In the preparation of acrylic resin, the protective atmosphere can be nitrogen, but is not limited thereto; the reaction temperature can be 75°C, 78°C, 80°C, 82°C, 85°C or any value between any two end values ​​thereof, and the reaction time can be 6h, 8h, 10h, 12h, etc.

[0061] In a specific embodiment of the present invention, the weight average molecular weight of the acrylic resin can be exemplified as 5×10 5 ~6×10 5 , but not limited thereto; the molecular weight distribution width of the acrylic resin may be exemplified as 3.8 to 4.4, but not limited thereto.

[0062] In a specific embodiment of the present invention, the crosslinking agent comprises a trifunctional aziridine crosslinking agent.

[0063] Another aspect of the present invention provides a method for preparing any one of the above-mentioned high temperature resistant adhesives, comprising the following steps: mixing the components in proportion.

[0064] Another aspect of the present invention 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 a high temperature resistant adhesive.

[0065] In a specific embodiment of the present invention, the preparation of the high temperature resistant protective film includes: coating the high temperature resistant adhesive on the surface of the substrate, drying it, and then covering it with a release film to obtain the high temperature resistant protective film.

[0066] 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, such as the thickness of the adhesive layer formed after the high temperature resistant adhesive is coated and dried to be controlled to be 5 to 30 μm, but not limited thereto. 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.

[0067] In actual operation, during the drying process, the drying temperature may be 110 to 130° C., and the drying time may be 5 to 20 minutes.

[0068] Example 1

[0069] This embodiment provides a method for preparing a high temperature resistant protective film, comprising the following steps:

[0070] (1) Preparation of high temperature resistant monomers:

[0071] In a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, 1 mol of 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate (AOI-BP), 1 mol of 4-hydroxymethylphenylboric acid, and 0.00007916 mol of dibutyltin dilaurate were added, and the mixture was stirred evenly and heated to 50° C. for 6 hours to obtain a high temperature resistant monomer.

[0072] (2) Preparation of acrylic resin:

[0073] In a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 5 g of a high temperature resistant monomer, 0.3 g of dibenzoyl peroxide, and 100 g of ethyl acetate were added, and the mixture was reacted at 80°C for 8 h, and then cooled to room temperature to obtain an acrylic resin. The weight average molecular weight Mw of the acrylic resin is 5.8×10 5 , the Mw / Mn molecular weight distribution width is 4.4.

[0074] (3) Preparation of high temperature resistant protective film:

[0075] 100 g of the acrylic resin prepared in step (2), 1 g of the trifunctional aziridine crosslinking agent SC-100, and 20 g of ethyl acetate were weighed in proportion and mixed evenly to obtain a high temperature resistant adhesive; the high temperature resistant adhesive was coated on the surface of a 50 μm thick PI film substrate, and dried at 120° C. for 10 min to obtain an adhesive layer with a thickness of 10 μm; a PET release film was applied on the other side of the adhesive layer to obtain a high temperature resistant protective film.

[0076] Example 2

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

[0078] Step (2) of this embodiment includes: adding 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 7 g of high temperature resistant monomer, 0.3 g of dibenzoyl peroxide and 100 g of ethyl acetate to a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser and a dropping funnel, reacting at 80°C for 8 h, and then cooling to room temperature to obtain an acrylic resin. The weight average molecular weight Mw of the acrylic resin is 5.8×10 5 , the Mw / Mn molecular weight distribution width is 4.4.

[0079] Example 3

[0080] This embodiment refers to the method for preparing a high temperature resistant protective film of embodiment 1, with the only difference being that in step (2) of preparing the acrylic resin, the amount of the high temperature resistant monomer used is different.

[0081] Step (2) of this embodiment includes: adding 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 3 g of high temperature resistant monomer, 0.3 g of dibenzoyl peroxide and 100 g of ethyl acetate to a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser and a dropping funnel, reacting at 80°C for 8 h, and then cooling to room temperature to obtain an acrylic resin. The weight average molecular weight Mw of the acrylic resin is 5.5×10 5 , the Mw / Mn molecular weight distribution width is 4.2.

[0082] Example 4

[0083] This embodiment refers to the method for preparing a high temperature resistant protective film of embodiment 1, with the only difference being that in step (2) of preparing the acrylic resin, the amount of the high temperature resistant monomer used is different.

[0084] Step (2) of this embodiment includes: adding 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 1 g of high temperature resistant monomer, 0.3 g of dibenzoyl peroxide and 100 g of ethyl acetate to a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser and a dropping funnel, reacting at 80°C for 8 h, and then cooling to room temperature to obtain an acrylic resin. The weight average molecular weight Mw of the acrylic resin is 6.0×10 5 , the Mw / Mn molecular weight distribution width is 3.8.

[0085] Comparative Example 1

[0086] Comparative Example 1 is a method for preparing a high temperature resistant protective film according to the reference example, except that in the step (2) of preparing the acrylic resin, no high temperature resistant monomer is added.

[0087] Step (2) of Comparative Example 1 comprises: adding 20 g of methyl acrylate, 70 g of butyl acrylate, 5 g of acrylic acid, 0.3 g of dibenzoyl peroxide and 100 g of ethyl acetate to a 1000 mL four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser and a dropping funnel, reacting at 80° C. for 8 h, then cooling to room temperature and discharging to obtain an acrylic resin. The weight average molecular weight Mw of the acrylic resin is 5.0×10 5 , the Mw / Mn molecular weight distribution width is 4.

[0088] Experimental example

[0089] In order 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 subjected to the following tests. The test results are shown in Table 1.

[0090] 25℃ peel strength: tested in accordance with GB / T 2792-2014; the test substrate is steel plate;

[0091] Peel strength after heating at 200℃ for 120min: tested in accordance with GB / T 2792-2014; the test substrate is steel plate;

[0092] Peel strength rise: calculated as “(peel strength after heating at 200℃ for 120min - peel strength at 25℃) / peel strength at 25℃”;

[0093] 80℃ adhesion: tested in accordance with GB / T 4851-2014; the test substrate is steel plate;

[0094] Rolling ball initial adhesion: Tested in accordance with GB / T 4852-2002.

[0095] Table 1 Performance test results of different protective films

[0096]

[0097] It can be seen from the above test results that the high temperature resistant protective film of the present invention takes into account initial adhesion, cohesion and peeling force, and has excellent high temperature resistance and low peeling force increase after high temperature treatment.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. High temperature resistant adhesive, characterized in that: It comprises acrylic resin, cross-linking agent and solvent; the amount of the cross-linking agent is 1wt% to 2wt% of the acrylic resin; The acrylic resin contains the structural unit shown in the following formula I: ； R is selected from an alkylene group having 1 to 3 carbon atoms; The acrylic resin also includes structural units shown in the following formulas II to IV: 、 、 ； wherein R1, R3 and R5 are each independently selected from H and methyl; R2 is selected from methyl and ethyl; R4 is selected from an alkyl group having 4 to 8 carbon atoms; In the acrylic resin, taking all structural units of the acrylic resin as 100wt%, the contents of the structural units represented by formulas I to IV are 0.5wt% to 10wt%, 10wt% to 25wt%, 65wt% to 85wt%, and 2wt% to 8wt%, respectively.

2. The high temperature resistant adhesive according to claim 1, characterized in that: The acrylic resin is mainly prepared by copolymerization of acrylic ester monomers; the acrylic ester monomers include monomers shown in the following formulas A to D: 、 、 、 。 3. The high temperature resistant adhesive according to claim 2, characterized in that: The acrylic resin also includes an initiator and an organic solvent; Relative to 100 parts by weight of the total amount of the acrylic ester monomers, the amount of the initiator is 0.1 to 1 part, and the amount of the organic solvent is 80 to 120 parts.

4. The high temperature resistant adhesive according to claim 1, characterized in that: The cross-linking agent includes a trifunctional aziridine cross-linking agent; and the solvent includes at least one of ethyl acetate, toluene, xylene and butyl acetate.

5. A method for preparing a high temperature resistant adhesive, characterized in that: The method comprises the following steps: mixing ingredients according to the composition of the high temperature resistant adhesive according to any one of claims 1 to 4.

6. High temperature resistant protective film, characterized in that: It comprises a substrate and an adhesive layer arranged on the surface of the substrate; the adhesive layer is made of the high temperature resistant adhesive according to any one of claims 1 to 4 or the high temperature resistant adhesive prepared by the preparation method according to claim 5.

7. The high temperature resistant protective film according to claim 6, characterized in that: The thickness of the adhesive layer is 5 to 30 μm.

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