Amine curing agent, thermal viscosity-reducing glue, thermal viscosity-reducing carrier film and preparation method of thermal viscosity-reducing carrier film

Abstract

The invention relates to an amine curing agent, thermal viscosity-reducing glue, a thermal viscosity-reducing carrier membrane and a preparation method thereof, the amine curing agent comprises cardanol, isophorone diamine and a furfural solution, the cardanol is melted at the temperature of 50-60 DEG C, then the isophorone diamine is added for reaction at the temperature of 60-70 DEG C, then the furfural solution is added for condensation reaction at the temperature of 75-90 DEG C, and the thermal viscosity-reducing carrier membrane is obtained. And finally, cooling to room temperature to obtain the amine curing agent. The thermal visbreaking carrier film prepared from the amine curing agent and the thermal visbreaking glue not only can provide stable and reliable adhesive force at normal temperature and ensure the stability of process operation, but also can be smoothly peeled off after high-temperature working sections such as cover film pressing and solder resist ink baking, the surface of a PI film is kept clean, and the service life of the PI film is prolonged. The manufacturing efficiency and reliability of the flexible circuit board are obviously improved; the thermal visbreaking carrier film has the advantages of high-temperature visbreaking, no adhesive residue, good dimensional stability and the like.

Description

Technical Field

[0001] This invention relates to curing agents and adhesives in thick and thin film materials for printed circuit boards of electronic components, particularly to curing agents for acrylic adhesives in thick and thin film materials for printed circuit boards of electronic components, and adhesives made using the curing agents, especially adhesives for carrier film structures on printed circuit boards of electronic components. This invention also relates to carrier films on printed circuit boards of electronic components. Background Technology

[0002] As electronic components continue to evolve towards thinner and smaller designs, circuit boards are also evolving towards ultra-thinner and higher-density designs. In the manufacturing process of flexible printed circuit boards (FPCs) and rigid-flex boards, polyimide (PI) film, due to its extremely thin thickness, is the primary substrate. However, its mechanical strength is limited, making it prone to curling, wrinkling, or displacement during processes such as high-temperature etching, laser drilling, pattern transfer, and lamination, affecting the accuracy and yield of the circuit board. To ensure process stability and the ease of subsequent peeling, a carrier film is usually temporarily attached to the back of the PI film to provide necessary support and dimensional stability. In actual production processes, the carrier film must withstand typical high-temperature stages such as hot pressing of the cover film (approximately 180°C) and baking of the solder resist ink (approximately 160°C). These processes place higher performance requirements on the carrier film: it must stably support the PI substrate under high-temperature conditions, preventing film displacement or deformation, and it must be easily peeled off after the process, leaving the PI film surface clean and residue-free for subsequent operations such as copper foil lamination and circuit pattern transfer. Currently, most commercially available carrier films use acrylic adhesives, but these have the following drawbacks: 1. High-temperature tackiness: The adhesive layer's tackiness actually increases with temperature, leading to difficulty in peeling during high-temperature pressing and baking. 2. Residual adhesive after peeling: Due to a lack of proper cross-linking control, the adhesive layer softens or migrates at high temperatures, leaving adhesive residue on the PI film surface after peeling, affecting subsequent processes. 3. Inadequate curing agent system: Existing curing agents are mostly isocyanates or small-molecule amines, which can improve temperature resistance to some extent, but often lead to incomplete peeling and have problems such as toxicity and poor storage stability. These problems directly affect the stability, product yield, and reliability of printed circuit board (PCB) manufacturing processes, especially flexible PCBs. Summary of the Invention

[0003] The technical problem to be solved by this invention is to avoid the shortcomings of the prior art by providing an amine curing agent, a heat-resistant adhesive, a heat-resistant carrier film, and a method for preparing the same. The heat-resistant carrier film made with the heat-resistant adhesive of this invention is specifically designed for the entire FPC process and can perfectly solve the quality problems such as large viscosity increase and residual adhesive after high-temperature pressing of the carrier film. It can not only provide stable and reliable adhesion at room temperature to ensure the stability of process operation, but also peel off smoothly after high-temperature processes such as cover film pressing and solder resist ink baking, keeping the PI film surface clean and significantly improving the efficiency and reliability of flexible circuit board manufacturing.

[0004] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows: A method for preparing an amine curing agent is provided, comprising the following steps: Step A0: Weigh out a certain amount of cashew phenol, isophorone diamine and a 99% furfural solution.

[0005] Step A1: The cashew phenol is added to a four-necked flask as the main reaction medium, and the cashew phenol in the four-necked flask is heated to a first temperature, which is 50°C to 60°C, so that the cashew phenol is completely melted and kept in a uniform flow state.

[0006] Step A2: Under stirring conditions, the isophoryl diamine is added dropwise to the four-necked flask from Step A1 at a flow rate of 0.5–1.0 mL / min to induce an addition reaction between the isophoryl diamine and the cashew phenol. The addition reaction temperature is controlled at a second temperature of 60–70°C. The mixture is stirred for a period of 20–30 minutes to obtain a first mixed solution.

[0007] Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to be within 1 to 2 hours. Continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to a third temperature, which is 75°C to 90°C, preferably 80°C to 85°C. Continue stirring and keep the reaction at this third temperature for 3 to 4 hours.

[0008] Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent.

[0009] In step A0, the mass ratio of cashew phenol, isophorone diamine and furfural solution is 1: 1.1-1.3: 0.45-0.60.

[0010] Between steps A3 and A5, there is also step A4, namely step A4, byproduct removal: in the later stage of the condensation reaction, byproduct water and some low-boiling solvent are removed by vacuuming to promote the further progress of the condensation reaction and improve the purity of the product.

[0011] The present invention also provides an amine curing agent, which is an amine curing agent obtained by the above preparation method.

[0012] This invention also provides a method for preparing a heat-resistant adhesive, comprising the following steps: Step B, prepare the heat-responsive acrylic adhesive: Step B0: Preparation of Solution A: Weigh out the raw materials according to the following percentages of total monomers: 10%–15% isooctyl acrylate, 45%–50% butyl acrylate, and 5%–8% glycidyl methacrylate. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into a four-necked round-bottom flask, and add a certain amount of ethyl acetate to prepare a solution A with a concentration of 50%–60%.

[0013] Preparation of B-component solution: Weigh out the raw materials according to the following percentages of total monomers: 1%–4% isooctyl acrylate, 20%–25% butyl acrylate, and 7%–10% glycidyl methacrylate. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into the first conical flask, and add ethyl acetate to prepare a 50%–60% concentration B-component solution.

[0014] Preparation of initiator solution: Weigh 0.08% to 0.10% of the total monomer amount of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 12 to 14 equal portions.

[0015] The total amount of monomers is the sum of all isooctyl acrylate, butyl acrylate, and glycidyl methacrylate in both solution A and solution B.

[0016] Step B1: Place the four-necked round-bottom flask containing solution A into a water bath, heat the water bath to 98°C, and continue heating until the solution A in the four-necked round-bottom flask is about to boil. Then, add a certain amount of boiling stones to the four-necked round-bottom flask to stabilize the boiling process.

[0017] Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator every 28-32 minutes until the initiator solution is completely added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of a four-necked round-bottom flask and add it dropwise over 1.5-2 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 8-10°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for a period of time, generally 90-120 minutes. Then add a certain amount of ethyl acetate and stir until the solid content reaches a certain value, generally controlled at 32-40%.

[0018] Step B3: After the reaction is complete, cool to room temperature and transfer the resulting product to a dry and clean container to obtain the thermo-responsive acrylic adhesive.

[0019] Step C, prepare the heat-resistant adhesive: Step C1: First, weigh out a certain amount of the acrylic adhesive from step B, the amine curing agent and catalyst of the present invention; in step C1, the mass ratio of the thermally responsive acrylic adhesive: amine curing agent: catalyst is 1: 9.5%~11.5%: 0.2%~0.3%; in step C1, the catalyst is 2-ethyl-4-methylimidazole.

[0020] Step C2: Add the acrylic adhesive to the reaction vessel, add an appropriate amount of ethyl acetate to dilute it, and stir until homogeneous.

[0021] Step C3: Add amine curing agent and continue stirring until homogeneous; in step C3, a certain amount of ethyl acetate can also be added to adjust the viscosity according to the required viscosity of the mixture.

[0022] Step C4: Next, add the catalyst, continue stirring, and keep stirring for at least 20 minutes to ensure that the system is fully dispersed, and you will get the heat-resistant adhesive.

[0023] The present invention also provides a heat-resistant adhesive for use on the protective film of a flexible circuit board (FPC), the heat-resistant adhesive being prepared by the above method.

[0024] The present invention also provides a heat-resistant anti-adhesion carrier film, comprising a PET base film and a release film. The heat-resistant anti-adhesion carrier film further includes a heat-resistant anti-adhesion adhesive layer that bonds the PET base film and the release film together. This heat-resistant anti-adhesion adhesive layer is an adhesive layer formed by coating with the aforementioned heat-resistant anti-adhesion adhesive. The thicknesses of the PET base film and the release film are set as needed, while the thickness of the heat-resistant anti-adhesion adhesive layer is generally 9–11 μm (micrometers).

[0025] Compared with the prior art, the beneficial effects of the amine curing agent, heat-resistant adhesive, heat-resistant carrier film, and their preparation method of the present invention are as follows: I. The thermo-responsive acrylic adhesive used in this invention employs a ternary copolymer system of isooctyl acrylate (2-EHA), butyl acrylate (BA), and glycidyl methacrylate (GMA). The branched structure of isooctyl acrylate (2-EHA) endows the thermo-responsive acrylic adhesive with excellent flexibility and low modulus, ensuring good initial tack and moderate peelability at room temperature. Butyl acrylate (BA), as a soft monomer, improves the polymer's flowability and film-forming properties while lowering the system's glass transition temperature (Tg), ensuring sufficient wetting and adhesion to the PI film surface at low or room temperature. Glycidyl methacrylate (GMA) contains epoxy groups in its molecule, possessing potential crosslinking activity. At high temperatures, these epoxy groups can undergo ring-opening reactions with the amino groups in amine curing agents, forming chemical crosslinking points. This design allows the adhesive to maintain tack at room temperature while reducing molecular chain activity at high temperatures due to crosslinking, thus exhibiting the unique characteristic of "high-temperature tack reduction."

[0026] II. The amine curing agent of this invention has unique thermal response characteristics: The amine curing agent of this invention is prepared by the condensation reaction of cardanol, isophoride diamine (IPDA), and furfural. It possesses both phenolic hydroxyl and amine group activity, forming a phenolic amine system containing phenolic hydroxyl groups, secondary amine groups, and aromatic ring structures. This improves the heat resistance and mechanical support of the colloid. Furthermore, it promotes cross-linking with glycidyl methacrylate (GMA) under high-temperature conditions, thereby achieving "maintaining viscosity at room temperature →..." The invention exhibits a unique effect of "rapid high-temperature viscosity reduction." Phenolic hydroxyl groups can undergo addition reactions with epoxy groups, providing additional crosslinking points. The primary and secondary amine groups in isophoride diamine (IPDA) undergo ring-opening reactions with the epoxy groups of glycidyl methacrylate (GMA) at high temperatures, generating hydroxyl groups and further undergoing crosslinking reactions. This reduces the free movement of the adhesive layer molecular chains, effectively reducing viscosity and improving dimensional stability at high temperatures. Furfural structures participate in condensation to form a more stable phenolic skeleton while retaining a certain degree of flexibility, preventing the system from becoming too brittle. Through the above reactions, the amine curing agent of this invention induces partial crosslinking of acrylic adhesives at high temperatures, significantly reducing their viscosity. However, the degree of crosslinking is controllable and will not cause residue on the surface of PI film or copper foil.

[0027] III. The heat-resistant and non-shrinking carrier film of this invention improves dimensional stability: This invention uses a ternary copolymer structure of isooctyl acrylate, butyl acrylate and glycidyl methacrylate in a specific ratio, which enables the adhesive layer to form a cross-linked network at high temperature. This network not only achieves high-temperature non-tack but also effectively inhibits the thermal flow and volume shrinkage of the adhesive, so that the carrier film can still maintain good dimensional stability during baking, pressing and other processes at 160-190℃, avoiding warping of the PI film substrate or line misalignment caused by film shrinkage.

[0028] IV. The thermally reducing adhesive bearing film of the present invention has a synergistic mechanism of "high temperature reducing adhesiveness + no residue peeling": existing bearing films often have the problem of high temperature "expansion and adhesion" and / or peeling residue. However, the thermally reducing adhesive bearing film of the present invention reveals a new mechanism by introducing thermally responsive acrylic adhesive and novel amine curing agent, which concentrates the crosslinking points inside the adhesive layer. Since the adhesion force is mainly transformed from physical action to molecular chain restriction, the adhesive layer is completely detached during peeling without low molecular migration or breakage residue, thus achieving a new effect of no residue peeling.

[0029] V. Material System Innovation, Expanding Application Scenarios: Compared with existing UV release films or single thermal release films, this invention does not require additional UV light sources or complex equipment. It achieves stable release by relying on the material's own thermal response and cross-linking. This characteristic not only simplifies the process but also reduces costs. It is also suitable for flexible circuit boards, rigid-flex boards, as well as high-temperature cover film lamination and printing ink baking processes, and has a wider range of industrial promotion value.

[0030] In summary, this invention specifically provides a solution for the entire FPC process, perfectly resolving quality issues such as excessive adhesion buildup and residual adhesive after high-temperature lamination of the carrier film. It not only provides stable and reliable adhesion at room temperature, ensuring process stability, but also allows for smooth peeling after high-temperature processes such as cover film lamination and solder resist ink baking, maintaining a clean PI film surface and significantly improving the efficiency and reliability of flexible circuit board manufacturing. The thermally de-adhesive carrier film of this invention offers advantages such as high-temperature de-adhesion, no residue, and good dimensional stability. Attached Figure Description

[0031] Figure 1 This is a frontal projection schematic diagram of the thermal anti-adhesion bearing film of the present invention.

[0032] Figure 2 This is a summary table of performance test data for the heat-resistant, non-sticky carrier film corresponding to different contents of amine curing agent (PAA) in Example 1.

[0033] Figure 3This is a table summarizing the dyne values ​​of the PI films after they were applied to the PI film and then peeled off, with the heat-resistant bearing film corresponding to each content of amine curing agent (PAA) in Example 1 of the present invention, and the ordinary acrylic bearing film and UV-release bearing film in the prior art.

[0034] Figure 4 This is a summary table of performance test data for the heat-resistant and anti-tack bearing films corresponding to different contents of amine curing agent (PAA) in Example 2 of the present invention.

[0035] Figure 5 This is a table summarizing the dyne values ​​of the PI films after they were peeled off and tested, with the heat-resistant bearing films corresponding to different contents of amine curing agent (PAA) in Example 2 of the present invention, and the ordinary acrylic bearing films and UV-release bearing films in the prior art respectively, after being applied to the PI films.

[0036] Figure 6 This is a summary table of performance test data for the heat-resistant and anti-tack carrier film corresponding to different contents of amine curing agent (PAA) in Example 3 of the present invention.

[0037] Figure 7 This is a table summarizing the dyne values ​​of the PI films after they were peeled off and tested, with the heat-resistant bearing films corresponding to different contents of amine curing agent (PAA) in Example 3 of the present invention, and the ordinary acrylic bearing films and UV-release bearing films in the prior art respectively applied to the PI films.

[0038] Figure 8 Comparative Example 1 is a summary table of data tested after a conventional acrylic carrier film was applied to a PI film.

[0039] Figure 9 Comparative Example 2 is a summary table of data from tests conducted after a UV-release carrier film was applied to a PI film in the prior art. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings.

[0041] A method for preparing an amine curing agent includes the following steps: Step A0: Weigh out a certain amount of cardanol, isophorone diamine (IPDA), and a 99% furfural solution.

[0042] Step A1: The cashew phenol is added to a four-necked flask as the main reaction medium, and the cashew phenol in the four-necked flask is heated to a first temperature, which is 50°C to 60°C, so that the cashew phenol is completely melted and kept in a uniform flow state.

[0043] Step A2: Under stirring conditions, add isophoryl diamine (IPDA) dropwise to the four-necked flask from Step A1 at a flow rate of 0.5–1.0 mL / min to allow the isophoryl diamine to undergo an addition reaction with the cashew phenol. The addition reaction temperature is controlled at a second temperature of 60°C–70°C. Stir the reaction for a period of 20–30 minutes to obtain a first mixed solution.

[0044] Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to be within 1 to 2 hours. Continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to a third temperature, which is 75°C to 90°C, preferably 80°C to 85°C. Continue stirring and keep the reaction at this third temperature for 3 to 4 hours.

[0045] Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent.

[0046] In step A0, the mass ratio of cashew phenol, isophorone diamine, and furfural solution is 1: 1.1–1.3: 0.45–0.60. This proportion is specifically chosen because: First, the chemical reaction mechanism determines the system's structure: cashew nut shell phenol (containing phenolic hydroxyl groups and olefin chains) → undergoes addition with isophorone diamine (forming a phenolic ether or amide-like structure) → is further condensed and crosslinked by furfural. Therefore, each raw material plays a different role. Cashew nut shell phenol is the source of the main chain structure, providing phenolic hydroxyl groups and olefin chains, determining flexibility and heat resistance; isophorone diamine (IPDA) has the highest reactivity and is the main reactive curing agent, providing a large number of amino groups for addition and condensation; furfural is the crosslinking bridger, determining the degree of crosslinking (degree of curing, temperature resistance).

[0047] Therefore: (1) IPDA (amino) needs to be in sufficient quantity to completely consume all the reaction sites of cashew phenol; (2) furfural is a cross-linking agent, and too much of it will make the system brittle, so it must be kept to a minimum.

[0048] Second, the reason for the highest dosage of isophorone diamine: (1) Cashew phenol has multiple reactive sites, requiring an excess of amine for all of them to participate. Cashew phenol contains: phenolic hydroxyl groups (-OH), allyl side chains, and ortho-reactive hydrogen, effectively making it a "multifunctional monomer." If there is insufficient amine, the following will occur: ① not all effective reactive sites will be opened; ② a curing agent with low molecular weight and insufficient branching will be generated; ③ the crosslinking density will decrease, and the temperature resistance and strength will decrease. Therefore, using 1.1 to 1.3 equivalents of amine can ensure complete reaction, avoid residual free phenolic hydroxyl groups affecting adhesive stability, and improve the molecular weight and structural regularity of the finished curing agent.

[0049] (2) Amines are the "main reactants" in condensation reactions and need to be stoichiometrically dominant; In the condensation reaction, furfural links two amine molecules together through an aldehyde group. Therefore, sufficient amines are essential; otherwise, the condensation will be incomplete, resulting in insufficient cross-linking points, poor toughness, and decreased storage stability of the finished product. Thus, increasing the amount of IPDA is a necessary condition to ensure the complete condensation reaction.

[0050] Third, cashew phenol is in the center and is the "structural framework" rather than the "main reactant"; Cashew nut shell extract (cashewol) determines a material's toughness, flexibility, heat resistance, and viscoelasticity. Its reactivity is lower than that of amines; therefore, it doesn't need to be used in excess like amines. Maintaining a 1-equivalent amount is sufficient to form a complete structural unit. Excessive cashew nut shell extract will: reduce cross-linking density; make the material too soft or below its modulus; and deteriorate high-temperature performance. Therefore, maintaining a cashew nut shell extract amount of 1-equivalent is the optimal range for the structure.

[0051] Fourth, the reason for using the least amount of furfural; Furfural is a crosslinking density control agent. Increasing furfural leads to changes such as increased crosslinking density, increased modulus, and increased hardness, but decreased toughness and elongation, and may even cause system brittleness or brittle peeling. Therefore, excessive furfural results in a brittle system, poor thermal shock resistance, and poor tape peelability; insufficient furfural leads to insufficient crosslinking and insufficient heat resistance. Practice has shown that a mass ratio of 0.45–0.60 is the equilibrium point, ensuring a moderate degree of crosslinking and guaranteeing that the material possesses heat resistance, flexibility, and non-residual adhesive properties upon peeling. Therefore, the furfural content is kept to a minimum, considering structural balance and optimized mechanical properties.

[0052] Between steps A3 and A5, there is also step A4, namely step A4, byproduct removal: in the later stage of the condensation reaction, byproduct water and some low-boiling solvent are removed by vacuuming to promote the further progress of the condensation reaction and improve the purity of the product.

[0053] The amine curing agent of this invention specifically utilizes the following effects of cardanol, isophorone diamine (IPDA), and furfural solution: First, the molecular structure of cardanol contains a C15 unsaturated aliphatic long side chain. This side chain, acting as a built-in 'flexible segment,' functions similarly to an 'internal plasticizer' in the polymerization network, effectively reducing the crosslinking density and internal stress of the cured product, thereby significantly improving the flexibility, impact resistance, and crack resistance of the coating or material. This is something that traditional small-molecule phenols cannot achieve.

[0054] Secondly, the long-chain alkyl group of cardanol is a strongly hydrophobic group. It can form a hydrophobic barrier in the polymer network, effectively blocking the penetration and erosion of moisture, thereby giving the cured product excellent water resistance, moisture resistance and anti-saponification properties.

[0055] Third, the aliphatic long side chains of cardanol contain unsaturated bonds (such as double bonds), which provide additional reaction sites for subsequent chemical modification. For example, the side chains can be modified by click chemistry (such as thioene reaction), epoxidation, etc., to further target the performance of the curing agent, which is a potential technical extension direction of this invention.

[0056] Fourth, furfural in furfural solution is derived from biomass. Its furan ring and the benzene ring of cardanol are structurally similar and complementary, together forming a polymer skeleton that is both rigid and flexible.

[0057] Fifth, isophoryl diamine (IPDA), as an alicyclic amine, exhibits excellent resistance to yellowing and chemical stability in its cured products. The flexible long chain of cardanol can precisely compensate for the potential brittleness of the IPDA cured system, while the rigid cyclic structure of IPDA synergizes with the rigid portion of the benzene ring in cardanol, ensuring that the overall strength and heat resistance of the material are not excessively compromised by the introduction of flexibility. Sixth, by employing a special preparation method and a specific mass ratio of cashew phenol, isophoride diamine, and furfural solution, the amine curing agent of this invention possesses unique thermal response characteristics, exhibiting both phenolic hydroxyl and amine group activity. This forms a phenolic amine system containing phenolic hydroxyl groups, secondary amine groups, and aromatic ring structures, improving the heat resistance and mechanical support of the colloid. On the other hand, it promotes the reaction with glycidyl methacrylate (GMA) under high-temperature conditions. The reaction crosslinks to achieve the unique effect of "maintaining viscosity at room temperature → rapidly reducing viscosity at high temperature"; the phenolic hydroxyl groups can undergo addition reactions with epoxy groups, providing additional crosslinking points; the primary and secondary amine groups in isophorone diamine (IPDA) undergo ring-opening reactions with the epoxy groups of glycidyl methacrylate (GMA) at high temperatures to generate hydroxyl groups and further undergo crosslinking reactions, reducing the free movement of the adhesive layer molecular chains, thereby effectively reducing viscosity and improving dimensional stability at high temperatures; the furfural structure participates in condensation to generate a more stable phenolic skeleton, while retaining a certain degree of flexibility to avoid the system becoming too brittle; through the above reactions, the amine curing agent of this invention induces partial crosslinking of acrylic adhesives at high temperatures, significantly reducing their viscosity, but the degree of crosslinking is controllable and will not cause residue on the surface of PI film or copper foil.

[0058] The preparation method of the amine curing agent of this invention uses a first temperature of 50℃~60℃, a second temperature of 60℃~70℃, and a third temperature of 75℃~90℃. This preparation method belongs to a typical "stepwise reaction system". The first stage is physical melting; the second stage is amine addition reaction; and the third stage is condensation reaction (forming a higher molecular weight structure). The temperature for each stage is set to suit the current reaction mechanism, and gradual heating ensures the integrity, selectivity, and safety of the reaction.

[0059] First, the initial temperature of the first stage is 50℃~60℃. It is sufficient to allow the cashew phenols to completely melt and achieve good fluidity because: (1) Cashew phenol is a long-chain phenol that is viscous or semi-solid at room temperature; (2) The primary purpose is physical melting to make the reaction matrix uniform and prevent chemical reactions from occurring; (3) If the temperature is too high, it will cause cashew phenol to oxidize or premature side reactions (such as slight polymerization).

[0060] Therefore, the initial temperature only needs to reach complete melting without overheating; 50℃ to 60℃ is a reasonable range. The core objective is to form a homogeneous reaction medium, providing a controllable environment for subsequent addition reactions.

[0061] Secondly, the second temperature in the second stage is 60℃~70℃. The addition reaction of the amino group with the phenolic ring requires a higher activation energy because: (1) Isophorone diamine (IPDA) reacts with cashew phenol through nucleophilic addition and ring-opening addition, and the amino group requires a higher activation energy to participate in the reaction; (2) If the temperature is kept at 50℃~60℃, the addition reaction rate will be very slow or even incomplete; (3) Raising the temperature to 60℃~70℃ can significantly increase the activation energy, enabling the amine group to effectively add to the phenol group; and still avoids condensation or cross-linking side reactions, such as premature reaction of amine with subsequent furfural, excessive self-condensation, and excessive local exothermic temperature rise. (4) The temperature should still be kept low during this stage because the amine reaction is exothermic and too high a temperature may cause the reaction to get out of control.

[0062] The core objective is to ensure the addition reaction is complete, but to avoid premature condensation or cross-linking side reactions.

[0063] Third, the third temperature in the third stage is 75℃~90℃. The furfural condensation reaction requires even higher temperatures to proceed completely because: When furfural undergoes condensation with phenol / amine systems (similar to phenolic resin condensation), it is an exothermic condensation reaction plus a molecular weight increase reaction, characterized by: (1) High activation energy of the reaction; (2) At low temperatures, the condensation rate is extremely slow, and it may even be impossible to form a true network or chain segment; (3) High temperature helps to: accelerate the dehydration condensation process, improve the mass transfer capacity of the reaction system after viscosity, and make the structure move from "single addition" to "higher degree of cross-linking".

[0064] Since the viscosity of the system gradually increases with addition and condensation, the temperature must be gradually increased to 75℃~90℃ to ensure that the condensation reaction proceeds completely and to achieve the desired molecular structure (such as a higher functionality and a more stable curing agent curve).

[0065] Core objective: To provide sufficient energy to drive the condensation reaction to proceed completely, forming the target structure and molecular weight.

[0066] Fourth, the reason for "gradually increasing" rather than adding the temperature all at once: Heating to 90°C from the start can cause the following risks: (1) Too many side reactions; ①Amines react prematurely with furfural, making the degree of cross-linking uncontrollable; ② Phenolic compounds can undergo self-polymerization, causing the system to become viscous or even clump together; ③ The molecular weight distribution of the system may become wider due to local overheating.

[0067] (2) Risk of thermal runaway (especially since both amine addition and furfural condensation are exothermic); ① Direct high temperature will cause cumulative heat release → temperature runaway; ② Systems containing amines, phenols, and aldehydes are very sensitive to temperature rise.

[0068] (3) The viscosity of the system changes too rapidly, and the stirring is out of control; ① Furfural condensation rapidly increases the viscosity of the system at high temperatures; ②If the reactants are not fully dispersed by stirring, the gel point will arrive prematurely, and the reaction will fail.

[0069] (4) Affects the final curing performance; ① Uneven structure; ② Low or high functionality; ③ Deterioration in curing speed, viscosity, and storage stability.

[0070] In summary, gradually increasing the temperature ensures that each reaction occurs in the correct order, guaranteeing reaction selectivity and controllability.

[0071] The present invention also provides an amine curing agent, which is an amine curing agent obtained by the above preparation method.

[0072] This invention also provides a method for preparing a heat-resistant adhesive, comprising the following steps: Step B, prepare the heat-responsive acrylic adhesive: Step B0: Preparation of Solution A: Weigh out the raw materials according to the following percentages of total monomers: 10%–15% isooctyl acrylate (2-EHA), 45%–50% butyl acrylate (BA), and 5%–8% glycidyl methacrylate (GMA). Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into a four-necked round-bottom flask, and add a certain amount of ethyl acetate to prepare a solution A with a concentration of 50%–60%.

[0073] Preparation of B-component solution: Weigh out the raw materials according to the following percentages of total monomers: 1%–4% isooctyl acrylate, 20%–25% butyl acrylate, and 7%–10% glycidyl methacrylate. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into the first conical flask, and add a certain amount of ethyl acetate to prepare a 50%–60% concentration B-component solution.

[0074] Preparation of initiator solution: Weigh 0.08% to 0.10% of the total monomer amount of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 12 to 14 equal portions.

[0075] The total amount of monomers is the sum of all isooctyl acrylate, butyl acrylate, and glycidyl methacrylate in both solution A and solution B.

[0076] Step B1: Place the four-necked round-bottom flask containing solution A into a water bath, heat the water bath to 98°C, and continue heating until the solution A in the four-necked round-bottom flask is about to boil. Add a certain amount of boiling stone to the four-necked round-bottom flask to stabilize the boiling process. Generally, one irregularly shaped or regularly shaped boiling stone with a diameter of about 3 to 5 mm is sufficient.

[0077] Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator every 28-32 minutes until the initiator solution is completely added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of a four-necked round-bottom flask and add it dropwise over 1.5-2 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 8-10°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for a period of time, generally 90-120 minutes. Then add a certain amount of ethyl acetate and stir until the solid content reaches a certain value, generally controlled at 32-40%.

[0078] Step B3: After the reaction is complete, cool to room temperature and transfer the resulting product to a dry and clean container to obtain the thermo-responsive acrylic adhesive.

[0079] Step C, prepare the heat-resistant adhesive: Step C1: First, weigh out a certain amount of the acrylic adhesive from step B, the amine curing agent and catalyst of the present invention; in step C1, the mass ratio of the thermally responsive acrylic adhesive: amine curing agent: catalyst is 1: 9.5%~11.5%: 0.2%~0.3%; in step C1, the catalyst is 2-ethyl-4-methylimidazole.

[0080] Step C2: Add the acrylic adhesive to the reaction vessel, add an appropriate amount of ethyl acetate to dilute, and stir until homogeneous. The amount of ethyl acetate used is generally calculated based on the required quantity of heat-resistant, non-sticky carrier film to be prepared, and then the amount of ethyl acetate is confirmed.

[0081] Step C3: Add the amine curing agent and continue stirring until homogeneous. In step C3, a certain amount of ethyl acetate can be added to adjust the viscosity of the mixture according to its required viscosity. Generally, the viscosity of the mixture is adjusted according to the actual coating method; for example, when using a gravure roller, it is generally adjusted to 50–500 mPa·s (cP); while when using comma coating, it is generally adjusted to 500–5000 mPa·s (cP). Precise control of the viscosity and solid content on the machine ensures that the adhesive adapts to the shear / wet film requirements of different coating methods (gravure roller or comma coating) and improves process flexibility and batch consistency. mPa·s is a unit of viscosity, millipascal-second, 1 millipascal-second (mPa·s) = 1 centipoise (cP).

[0082] Step C4: Next, add a catalyst, such as 2-ethyl-4-methylimidazole, continue stirring, and keep stirring for at least 20 minutes to ensure that the system is fully dispersed, and you will get the heat-resistant adhesive.

[0083] In step B of this invention, the preparation of the heat-responsive acrylic adhesive is carried out in two separate steps: the preparation of component A and the preparation of component B. This adopts a phased addition strategy (component A and component B) rather than a one-time addition, mainly based on the following considerations: First, control the reaction rate and molecular weight distribution of free radical polymerization: In acrylic monomer systems, different monomers (such as isooctyl acrylate, butyl acrylate, and glycidyl methacrylate) have significant differences in activity. If all monomers are added at once, some monomers will preferentially polymerize in the early stages of the reaction due to their different activity coefficients, generating high molecular weight local segments. This can easily cause the system to gel or the polymerization rate to be too fast, affecting the polymerization uniformity.

[0084] By adopting a segmented feeding method (polymerizing component A first and then adding component B dropwise), a main chain with an appropriate molecular weight can be formed first in component A, and then highly reactive monomers such as glycidyl methacrylate (GMA) can be added in component B, thereby achieving dynamic control of the molecular chain structure and obtaining a more uniform molecular weight distribution and a more stable solid content system.

[0085] Second, improve the effective retention rate of functional groups (GMA epoxy groups): GMA contains highly reactive epoxy groups. If it enters the reaction system simultaneously with a large number of carboxyl monomers or initiators, it is prone to self-polymerization or ring-opening side reactions at high temperatures, which leads to the consumption of epoxy groups, thereby weakening the subsequent curing reaction and high-temperature tack reduction performance.

[0086] By adding GMA in stages, which is mainly added slowly in the later stage (B material stage), the probability of side reactions of epoxy groups can be significantly reduced, the retention rate of active functional groups can be improved, and it can be guaranteed that it can still undergo cross-linking reaction with curing agent at high temperature.

[0087] Third, it reduces system viscosity and improves heat transfer and stirring efficiency: Adding all the monomers at once will cause the system to thicken rapidly in the middle of polymerization, reduce heat transfer and stirring efficiency, and lead to local temperature rise or even gelation.

[0088] Adding A and B components separately can control the rate of viscosity increase in the system, making the polymerization process more stable, preventing local overheating and agglomeration, thereby improving product stability and reproducibility.

[0089] Fourth, it facilitates layered structural design and enables performance gradient control: Segmented polymerization allows for the adjustment of the ratio of main chain to branches, and soft segments to hard segments. Component A primarily forms a flexible acrylate main chain, while component B introduces reactive monomers containing GMA in the later stages. This introduces reaction sites on the molecular chain surface, resulting in a final polymer that exhibits both good initial tack and thermally responsive tack reduction, achieving the comprehensive performance of this invention: "no tackiness at high temperatures and no residue after peeling."

[0090] Therefore, the A and B segmented polymerization method adopted in this invention is not only a process selection, but also a key means of molecular structure regulation. It has technical necessity and innovation in terms of polymerization kinetics, functional group protection and performance control.

[0091] Compared with the existing one-time polymerization method, the present invention significantly improves the polymerization stability and functional group retention rate by adding materials in stages, resulting in a more uniform molecular structure and higher epoxy activity of the obtained polymer. This enables a controllable cross-linking reaction to occur under high temperature conditions, achieving the effect of thermal response to reduce viscosity without leaving residue.

[0092] In step B2 of this invention, the temperature of the water in the water bath is always kept 8°C to 10°C higher than the temperature of the mixed solution in the four-necked round-bottom flask because: First, the core reason: Free radical polymerization is an endothermic initiation and exothermic continuation reaction, and free radical polymerization (especially of acrylates) has typical characteristics: ①External heating is required in the initial stage of the reaction to initiate the formation of free radicals; ② The reaction begins to release heat in the middle stage, and this self-heating may cause a sudden increase in temperature.

[0093] If the external heat source is insufficient, the following may occur: ① The temperature of the reaction system lags behind the set temperature; ② The initiator is unstable during activation; ③ Fluctuations in polymerization rate; ④ The molecular weight distribution becomes wider; ⑤ In extreme cases, it can lead to self-acceleration and "thermal runaway".

[0094] Therefore, the external heat source must have a higher thermal potential than the system in order to maintain a stable reaction.

[0095] Second, the reason for the temperature being 8℃~10℃ higher: The empirical range determined by heat transfer efficiency, reaction exothermic rate, and initiator decomposition kinetics: (1) Heat transfer requires a temperature difference to drive it. The heat transfer flow rate Q of the water bath → flask system satisfies: Q = KΔT Therefore, the external temperature must be higher than the internal temperature; the greater the difference, the more stable and reliable the heat transfer.

[0096] The measured results show that a temperature difference of ≥8℃ can ensure that the system temperature rises steadily in accordance with the heating command, while a temperature difference of <8℃ will result in a slow response to external heating and make it difficult to control precisely.

[0097] (2) Controlling the decomposition rate of free radical initiators. Taking common free radical initiators such as AIBN and BPO as examples, their decomposition rate increases sharply with temperature: The slightly lower temperature caused insufficient initiation, resulting in a larger molecular weight of the generated product and a slower conversion rate. Slightly higher temperatures can cause over-initiation, resulting in excessively short chains, wider distribution, and excessively rapid viscosity growth.

[0098] Setting the water bath temperature above 8℃~10℃ ensures that the system reaches the optimal decomposition and activation temperature of the initiator in real time; the decomposition rate remains stable; chain growth is uniform and molecular weight is controllable.

[0099] (3) Avoid "reaction temperature lag"; The reaction system has heat capacity (slow heating), while the temperature change of the water bath is relatively instantaneous.

[0100] If the external temperature is not significantly higher than the system temperature, the following may occur: the temperature controller has shown "reached temperature", but the internal temperature of the system is still 5℃ to 10℃ lower; the initiator has not been fully decomposed; and the actual reaction is still in a semi-stagnant state.

[0101] Setting the temperature 8℃ to 10℃ higher ensures: a stable internal and external temperature difference; timely temperature control of the mixing system; and no uneven reaction caused by lag.

[0102] (4) Avoid local overheating; in free radical polymerization, the viscosity of the system will continue to rise: heat diffusion is slow; local hot spots are likely to occur.

[0103] If the outer layer is not heated enough: the initiation temperature is reached locally first, and the heat release is faster; the local heating accelerates chain growth; the molecular weight distribution becomes severely broadened; and in the worst case, a "self-acceleration effect" may occur.

[0104] Maintaining a high temperature on the outer layer can: promote uniform heating within the system; prevent localized hotspots from overheating; and ensure a uniform polymerization rate.

[0105] Third, industrial results prove that this temperature difference is within the optimal range: When ΔT ≥ 8℃: the reaction temperature rises steadily; the temperature control follows well; the molecular weight distribution is narrower; the viscosity of the finished product is stable; there is no risk of temperature fluctuation or gelation.

[0106] When ΔT < 5℃, the following often occur: long and uncontrollable induction period; delayed temperature control; increased molecular weight differences between batches; the system is prone to "sudden temperature rise"; and poor regeneration of high viscosity components.

[0107] Therefore, ΔT = 8~10℃ is the optimal engineering window obtained through verification of thermal conductivity and polymerization kinetics.

[0108] In step C of this invention, when preparing the heat-resistant adhesive, ethyl acetate still needs to be added for adjustment before adding the amine curing agent of this invention. The main reason is as follows: First, reaction safety and adhesive stability: In the adhesive synthesis stage, if the solvent is added directly to the required final solid content for the reaction, the adhesive viscosity will be low, leading to reduced heat transfer and stirring efficiency in the reaction system. Simultaneously, the concentration of active monomers for free radical polymerization will decrease, potentially affecting polymerization efficiency and uniformity. Maintaining a higher solid content during synthesis is beneficial for a complete reaction and for achieving uniform adhesive properties.

[0109] Second, viscosity control and coating adaptability: The adhesive requires a specific viscosity to ensure uniform coating thickness and prevent sagging. Adding sufficient solvent beforehand may result in an excessively low adhesive viscosity, which is detrimental to film coating control. By diluting with ethyl acetate before application, the viscosity can be flexibly adjusted to suit different coating equipment and process conditions.

[0110] Third, curing control and coating performance optimization: Even after the addition of the curing agent, the adhesive still needs a certain level of activity to ensure the integrity of the curing reaction after coating. If the solvent is added in advance, the activity of the diluted system will decrease, which may lead to uneven curing or a decline in film performance. Diluting before coating can achieve the desired coating performance while maintaining the reactivity.

[0111] Fourth, process flexibility and batch-to-batch consistency: Adjusting the solid content before application allows for flexible control based on actual coating conditions, ensuring consistent adhesive properties between batches and reducing coating deviations caused by environmental factors (temperature, humidity).

[0112] The catalyst used in step C of this invention is specifically 2-ethyl-4-methylimidazolium (2E4MZ) because: First, from the perspective of reaction mechanism... The adhesive system of the present invention relies on the ring-opening crosslinking between the epoxy groups in glycidyl methacrylate (GMA) and the amine groups (or phenolic hydroxyl groups) in the curing agent, and belongs to a typical epoxy curing system.

[0113] 2E4MZ belongs to the imidazole basic catalyst class and has the following advantages: (1) High catalytic selectivity of epoxy ring-opening reaction Imidazoles can form a base-catalyzed ring-opening active center IM-H⁺ with epoxides; It will not strongly participate in side reactions; It can simultaneously promote amine-epoxy and hydroxyl-epoxy reactions.

[0114] Therefore, it can achieve high crosslinking efficiency.

[0115] (2) Lower activation energy Compared to tertiary amines / quaternary ammonium salts, imidazole structures are more readily able to initiate ring-opening of the epoxy group. This means: The low reaction rate at room temperature prevents premature solidification and improves storage stability. The high-temperature reaction rate leads to a more significant reduction in viscosity due to the thermal response.

[0116] This aligns with the product's core objective of "stable viscosity at room temperature and reduced viscosity at high temperature".

[0117] Secondly, from the perspective of application requirements, it is compatible with the high-temperature peeling of the carrier film; 2E4MZ exhibits "temperature-triggered reaction characteristics": At temperatures below 100°C, the activity is weak, and the colloid retains its viscosity and peeling flexibility. At ≥160℃, alkali catalysis rapidly promotes epoxy-amine crosslinking; Enhanced cross-linking restricts molecular chain movement and reduces viscosity.

[0118] Therefore, it is highly compatible with the core performance of the film of this invention. In other words, 2E4MZ is an ideal catalyst for "high-temperature start-up and room-temperature inhibition".

[0119] Third, its advantages compared to other catalysts: (1) Compared with organic amines (such as DMP-30, TEPA): Organic amines have higher activity at room temperature and are more prone to premature ring-opening and cross-linking, while 2E4MZ has lower activity at room temperature, making it easier to store and stably apply. Organic amines have more side reactions, while 2E4MZ has higher ring-opening selectivity. Organic amines have a moderate high-temperature acceleration effect, while 2E4MZ has a significant high-temperature (after 160℃) acceleration effect. Organic amines have obvious odor / volatility, while 2E4MZ has a lower odor / volatility.

[0120] If an amine catalyst such as DMP-30 is used, the following will occur: the adhesive's shelf life will be shortened; the adhesive will become viscous or even viscous at room temperature after coating; which contradicts the product characteristics of this invention.

[0121] (2) Compared with quaternary ammonium salts and quaternary ammonium salts: Quaternary ammonium salts or quaternary ammonium salts have strong catalytic activity, while 2E4MZ has moderate to strong and controllable catalytic activity; Quaternary ammonium salts or quaternary ammonium salts have a high risk of side reactions: they are prone to self-polymerization and transesterification, while 2E4MZ has a low risk of side reactions; Quaternary ammonium salts or quaternary ammonium salts are active even at room temperature, while 2E4MZ has a temperature-triggered catalytic activity.

[0122] (3) Comparison with metal catalysts (such as Sn / octoate): Metal catalysts can leave metal ion residues, which can pose a risk of electromigration contamination to PCBs / Cu, and are not conducive to electronic-grade manufacturing requirements.

[0123] 2E4MZ is an organic system, which is more readily accepted by electronic products.

[0124] IV. Why is 2E4MZ chosen among imidazole derivatives? Other common imidazoles include 2-methylimidazole and 2-ethylimidazole.

[0125] 2-Methylimidazole or 2-ethylimidazole have higher activity, while 2-ethyl-4-methylimidazole (2E4MZ) has milder activity and is easier to control; 2-methylimidazole or 2-ethylimidazole have a narrower curing temperature window, while 2-ethyl-4-methylimidazole (2E4MZ) has a curing temperature window that is more suitable for "≥160℃ triggering"; 2-methylimidazole or 2-ethylimidazole have better storage stability and are more likely to accelerate prematurely, while 2-ethyl-4-methylimidazole (2E4MZ) has better storage stability and is more conducive to long-term storage.

[0126] Therefore, 2-ethyl-4-methylimidazole (2E4MZ) has a milder reactivity and a wider operating window, making it most suitable for thermally responsive carrier membrane systems.

[0127] In summary, this invention utilizes 2-ethyl-4-methylimidazolium (2E4MZ) as an epoxy catalyst based on its reaction characteristics of "low reactivity at low temperatures, significant acceleration at high temperatures, selective ring-opening, and no introduction of electro-ionic contamination." Compared to organic amines, quaternary ammonium salts, and metal catalysts, 2E4MZ maintains stable storage and application of the adhesive layer at room temperature and promotes ring-opening crosslinking between glycidyl methacrylate (GMA) and the curing agent under high-temperature conditions (≥160℃), thereby achieving the performance effects of "high-temperature tack reduction and residue-free peeling." Therefore, the selection of this catalyst is technically necessary and cannot be simply replaced by other equivalent catalysts.

[0128] The present invention also provides a heat-resistant adhesive for use on the protective film of a flexible circuit board (FPC), the heat-resistant adhesive being prepared by the above method.

[0129] See Figure 1 The present invention also provides a heat-resistant anti-adhesion carrier film, comprising a PET base film 10 and a release film 20. The heat-resistant anti-adhesion carrier film further includes a heat-resistant anti-adhesion layer 30 that bonds the PET base film 10 and the release film 20 together. The heat-resistant anti-adhesion layer 30 is an adhesive layer formed by coating with the aforementioned heat-resistant anti-adhesion adhesive. The thicknesses of the PET base film 10 and the release film 20 are set as needed, while the thickness of the heat-resistant anti-adhesion layer 30 is generally 9–11 μm (micrometers).

[0130] The method for preparing the thermally de-adhesive bearing film includes the following steps: The PET base film 10 and release film 20 are installed on the corresponding unwinding rollers of the coating machine, and the heat-reducing adhesive of the present invention is injected into the coating liquid tank. The oven temperature in the coating machine is set as follows: approximately 80°C in the front section, approximately 130°C in the middle section, and approximately 120°C in the rear section. The air inlet temperature and flow rate are adjusted to ensure uniform distribution of hot air. The air inlet is generally controlled at 40% to 50% of the power, and the exhaust volume is set at 50% to 55% to ensure that the solvent (ethyl acetate) evaporates smoothly without accumulating.

[0131] During the coating process, the coating speed is controlled at 5–8 meters per minute, specifically adjusted according to the thickness of the PET base film 10 and the amount of heat-resistant adhesive applied. Simultaneously, the tension is kept stable during coating to prevent the PET base film 10 from shifting or wrinkling. To ensure the uniformity of the heat-resistant adhesive layer 30, the doctor blade gap or coating roller pressure can be adjusted at the coating head of the coating machine to keep the coating thickness stable within the design range. Generally, the thickness of the heat-resistant adhesive layer 30 is 9–11 μm (micrometers).

[0132] The coating machine is heated and dried section by section in its oven to ensure complete removal of the solvent (ethyl acetate) and a uniform, bubble-free heat-resistant adhesive layer 30. The layer is then immediately bonded to the release film 20 at the discharge end of the coating machine and rolled up to obtain the semi-finished carrier film.

[0133] The semi-finished carrier film after winding is placed in a constant temperature environment of 60℃~70℃ and cured for 24~48 hours to promote partial reaction and structural stabilization of the curing agent in the heat-resistant adhesive layer 30; after curing, the finished heat-resistant carrier film of the present invention is obtained.

[0134] The high-temperature de-adhesion mechanism of the thermal de-adhesion carrier film of this invention is as follows: the cross-linking reaction restricts the fluidity of the polymer chain segments, weakening the intermolecular interaction between them and the substrate surface, thus making it "easier to peel off" under high-temperature conditions.

[0135] The non-residue mechanism of the heat-resistant anti-adhesion carrier film of the present invention is as follows: since the cross-linking point occurs inside the adhesive, the adhesive layer is completely detached during peeling, and no low molecular weight substances migrate or break and remain.

[0136] The thermal stability of the heat-resistant anti-adhesion carrier film of this invention: The aromatic ring structure (from cashew phenol and furfural) and the crosslinking points together improve the thermal stability of the adhesive layer, which can withstand the process temperatures such as cover film pressing (180°C) and solder resist ink baking (160°C).

[0137] The balanced design of the heat-reducing bearing film of this invention is as follows: soft monomers (butyl acrylate, isooctyl acrylate) ensure initial tack and flexibility, functional monomers (glycidyl methacrylate) provide reaction sites, and amine curing agents trigger crosslinking at high temperature, achieving a performance balance of "stable tack at room temperature, reduced tack at high temperature, and no residue after peeling". Example

[0138] A method for preparing a heat-resistant adhesive includes the following steps: Step A, Preparation of amine curing agent (PAA): Step A0: Weigh out 1 gram of cashew phenol, 1.1 grams of isophorone diamine, and 0.45 grams of furfural solution, the concentration of which is 99%. Step A1: The cashew phenol is added to a four-necked flask as the main reaction medium. The cashew phenol in the four-necked flask is heated to 55°C to completely melt the cashew phenol and keep it in a uniform flow state. The four flasks are equipped with a digital display stirrer, a thermometer, a dropping funnel and a reflux condenser to ensure that the temperature of the reaction process is controllable and to avoid raw material loss. Step A2: Under stirring conditions, the isophorone diamine is added dropwise to the four-necked flask of Step A1 at a rate of 0.8 mL / min, so that the isophorone diamine and the cashew phenol undergo an addition reaction. At this time, the addition reaction temperature is controlled at 65°C, and the reaction is stirred for 25 minutes to obtain the first mixed solution. Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to within 1.5 hours, and continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to 80°C and maintain the constant temperature of 80°C for 3.5 hours. Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent (PAA).

[0139] Step B, Preparation of thermoresponsive acrylic adhesive (YKL197): Step B0: Preparation of Solution A: Weigh 33.33 g of isooctyl acrylate, 150 g of butyl acrylate, and 16.67 g of glycidyl methacrylate. Place these three compounds into a four-necked round-bottom flask and add 200 g of ethyl acetate to prepare a 50% concentration solution of Solution A. Connect a stirrer to the main port of the four-necked round-bottom flask, and connect the other three ports to a reflux condenser, a thermometer, and a separatory funnel in sequence. Preparation of solution B: Weigh 3.57 g of isooctyl acrylate, 71.43 g of butyl acrylate and 25 g of glycidyl methacrylate respectively. Put the above isooctyl acrylate, butyl acrylate and glycidyl methacrylate into the first conical flask, and add 100 g of ethyl acetate to prepare a 50% concentration solution B. Preparation of initiator solution: Weigh 0.24 g of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 13 equal portions; Step B1: Place the four-necked round-bottom flask containing solution A into a water bath. After checking the airtightness of the entire apparatus, turn on the cooling water and heat the water bath to 98°C. Continue heating until the solution A in the four-necked round-bottom flask is about to boil. Add a certain amount of boiling stones to the four-necked round-bottom flask to stabilize the boiling process. Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator every 30 minutes until the initiator solution is completely added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of a four-necked round-bottom flask and add it dropwise over 1.8 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 9°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for 120 minutes, then add 257.15 g of ethyl acetate and stir until homogeneous, bringing the solid content to 35%. Step B3: After the reaction is complete, cool to room temperature and transfer the obtained product to a dry and clean container to obtain the thermo-responsive acrylic adhesive (YKL197); Step C, Preparation of Heat-Resistant Adhesive: First, weigh out 20 grams of the heat-responsive acrylic adhesive (YKL197) and 0.04 grams of 2-ethyl-4-methylimidazolium (2E4MZ) from Step B. Then, weigh out 1.2 grams (6% of the heat-responsive acrylic adhesive), 1.4 grams (7% of the heat-responsive acrylic adhesive), 1.8 grams (9% of the heat-responsive acrylic adhesive), 1.9 grams (9.5% of the heat-responsive acrylic adhesive), and 2 grams (2% of the heat-responsive acrylic adhesive) from Step A. The following amounts of acrylic adhesive were used: 10% (of the acrylic adhesive), 2.2g (of the thermo-responsive acrylic adhesive), 2.3g (of the thermo-responsive acrylic adhesive), 2.4g (of the thermo-responsive acrylic adhesive), and 2.5g (of the thermo-responsive acrylic adhesive). The thermo-responsive acrylic adhesive was added to a reaction vessel, followed by the addition of an amine curing agent. 8g of ethyl acetate was added to dilute and adjust the viscosity. Then, 2-ethyl-4-methylimidazole (2E4MZ) was added, and the mixture was stirred for 30 minutes to ensure complete dispersion, resulting in nine types of heat-resistant adhesives.

[0140] See Figure 1 The heat-resistant adhesive carrier film was prepared using the aforementioned method. Specifically, the PET base film 10 and release film 20 were mounted on the corresponding unwinding rollers of the coating machine. One of the nine heat-resistant adhesives mentioned above was injected into the coating liquid tank. The oven temperature in the coating machine was set as follows: approximately 80°C for the front section, approximately 130°C for the middle section, and approximately 120°C for the rear section. The inlet air temperature and flow rate were adjusted to ensure uniform hot air distribution. The inlet air was generally controlled at 45% power, and the exhaust air volume was set at 53% to ensure smooth solvent evaporation without accumulation. During the coating process, the coating speed was controlled at 6 meters per minute, resulting in a heat-resistant adhesive layer 30 thickness of 10 μm (micrometers). The film was heated and dried section by section in the coating machine's oven. After immediate bonding with the release film 20 at the coating machine's outlet, the film was wound up to obtain the semi-finished carrier film. The semi-finished carrier film after winding is placed in a constant temperature environment of 65℃ and cured for 36 hours; after curing, a finished heat-resistant carrier film is obtained.

[0141] Another heat-reducing adhesive was used to prepare heat-reducing carrier films according to the above preparation method, resulting in a total of 9 types of heat-reducing carrier films.

[0142] Performance tests were conducted on nine types of thermally anti-tack carrier films, and the test data are as follows: Figure 2 .

[0143] Figure 2This is a summary table of performance test data for the heat-resistant anti-adhesion carrier films corresponding to different contents of amine curing agent (PAA) in Example 1 of this invention. The test items in this summary table are as follows: Peel force on the PI film at room temperature refers to the test conducted at room temperature (23°C) and normal atmospheric pressure after each heat-resistant anti-adhesion carrier film is applied to the PI film; peel force on the PI film at high temperature and whether there is residual adhesive refers to the test conducted after each heat-resistant anti-adhesion carrier film is applied to the PI film and placed in an environment at 160°C for 1 hour; peel force on copper foil adhesion at high temperature and whether there is residual adhesive refers to the test conducted after each heat-resistant anti-adhesion carrier film is applied to the copper foil surface of the FPC circuit board and placed in an environment at 190°C and 1MPa pressure for 2 hours; peel force and whether there is residual adhesive after high-temperature pressing of the cover film refers to the test conducted after each heat-resistant anti-adhesion carrier film is applied to the cover film and placed in an environment at 180°C for 3 minutes. gf / 25 mm is a unit where gf is grams of force, a unit of force that represents the gravitational force exerted on 1 gram of a substance. gf / 25 mm is the peeling force in grams of a protective film with a unit width of 25 millimeters.

[0144] By adjusting the proportion of amine curing agents (PAA), multiple control samples were designed to screen the optimal formulation, and simulated tests were conducted in a 35μm FPC circuit board fabrication scenario. Evaluation indicators included: no tackiness or exhibiting a tack-reducing effect under high temperature conditions (focusing on PI film substrates), no adhesive residue after peeling, and no contamination of the surface of the substrate.

[0145] from Figure 2 The experimental results show that no adhesive residue was observed in any of the control groups during the high-temperature test. When the amount of amine curing agent (PAA) in the formulation was 1.9–2.3 grams and the amount of thermoresponsive acrylic adhesive (YKL197) was 20 grams, that is, when the content of amine curing agent (PAA) was 9.5%–11.5% of that of thermoresponsive acrylic adhesive (YKL197), the adhesive layer achieved a significant "non-expansion tack" or "reduced tack" effect at high temperatures, while maintaining sufficient tack at room temperature and preventing accidental detachment during the FPC process. However, when the content of amine curing agent (PAA) was less than 9.5% of that of thermoresponsive acrylic adhesive (YKL197) and greater than 11.5% of that of thermoresponsive acrylic adhesive (YKL197), the peel force of the adhesive layer increased at high temperatures, i.e., "expansion tack" or "increased tack".

[0146] Figure 3 This table summarizes the dyne values ​​of the heat-resistant, non-stick bearing films corresponding to different contents of amine curing agent (PAA) in Example 1 of this invention, as well as the ordinary acrylic bearing film and UV-release bearing film from the prior art, after being applied to PI films and then peeled off. Figure 3It can be seen that, in Example 1 of this invention, the dyne values ​​of the PI film after peeling tests showed that the adhesive layer of the heat-resistant carrier film corresponding to different contents of amine curing agent (PAA) remained almost unchanged after each content. This indicates that the adhesive layer of the heat-resistant carrier film corresponding to different contents of amine curing agent (PAA) in Example 1 of this invention did not leave any residue on the PI film surface after peeling, or left very little residue. The surface cleanliness is superior to that of ordinary acrylic carrier films and UV-peel carrier films in the prior art. After high-temperature testing, the dimensional shrinkage rate of this invention is <0.1%, which is far superior to <0.4% of ordinary acrylic carrier films and UV-peel carrier films in the prior art, demonstrating better dimensional stability and process adaptability. The dimensional shrinkage rate of this invention refers to the thermal shrinkage rate in the MD (longitudinal) and TD (transverse) directions measured from samples of the finished carrier film. Example

[0147] A method for preparing a heat-resistant adhesive includes the following steps: Step A, Amine Curing Agent (PAA): Step A0: Weigh out 1 gram of cashew nut shell powder, 1.2 grams of isophorone diamine, and 0.50 grams of furfural solution, the concentration of which is 99%. Step A1: The cashew phenol is added to a four-necked flask as the main reaction medium. The cashew phenol in the four-necked flask is heated to 55°C to completely melt the cashew phenol and keep it in a uniform flow state. The four flasks are equipped with a digital display stirrer, a thermometer, a dropping funnel and a reflux condenser to ensure that the temperature of the reaction process is controllable and to avoid raw material loss. Step A2: Under stirring conditions, the isophorone diamine is slowly added dropwise to the four-necked flask of Step A1, so that the isophorone diamine and the cashew phenol undergo an addition reaction. At this time, the addition reaction temperature is controlled at 65°C, and the reaction is stirred for 22 minutes to obtain the first mixed solution. Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to within 1.5 hours, and continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to 85°C and maintain the constant temperature of 85°C for 3.0 hours. Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent (PAA).

[0148] Step B, prepare the heat-responsive acrylic adhesive (YKL197): Step B0: Preparation of Solution A: Weigh 37.59 g of isooctyl acrylate, 142.86 g of butyl acrylate, and 19.55 g of glycidyl methacrylate, respectively. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into a four-necked round-bottom flask, and add 200 g of ethyl acetate to prepare a 50% concentration solution of Solution A. Connect a stirrer to the main mouth of the four-necked round-bottom flask, and connect the other three mouths to a reflux condenser, a thermometer, and a separatory funnel in sequence. Preparation of B solution: Weigh 7.46 g of isooctyl acrylate, 67.16 g of butyl acrylate and 25.38 g of glycidyl methacrylate respectively, put the above isooctyl acrylate, butyl acrylate and glycidyl methacrylate into the first conical flask, and add 100 g of ethyl acetate to prepare a 50% concentration B solution. Preparation of initiator solution: Weigh 0.30 g of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 13 equal portions; Step B1: Place the four-necked round-bottom flask containing solution A into a water bath. After checking the airtightness of the entire apparatus, turn on the cooling water and heat the water bath to 98°C. Continue heating until the solution A in the four-necked round-bottom flask is about to boil. Add a certain amount of boiling stones to the four-necked round-bottom flask to stabilize the boiling process. Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator every 30 minutes until the initiator solution is completely added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of a four-necked round-bottom flask and add it dropwise over 1.8 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 9°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for 120 minutes, then add 257.15 g of ethyl acetate and stir until homogeneous, bringing the solid content to 35%. Step B3: After the reaction is complete, cool to room temperature and transfer the obtained product to a dry and clean container to obtain the thermo-responsive acrylic adhesive (YKL197); Step C, preparing heat-resistant adhesives: First, weigh 20 grams of the heat-responsive acrylic adhesive (YKL197) and 0.04 grams of 2-ethyl-4-methylimidazole (2E4MZ) from Step B. Then, weigh 1.2 grams, 1.4 grams, 1.8 grams, 1.9 grams, 2 grams, 2.2 grams, 2.3 grams, 2.4 grams, and 2.5 grams of the amine curing agent (PAA) from Step A, respectively. Add the heat-responsive acrylic adhesive to the reaction vessel, add 8 grams of ethyl acetate to dilute and adjust the viscosity, then add the amine curing agent, followed by 2-ethyl-4-methylimidazole (2E4MZ). Mix and start stirring, and keep stirring for 30 minutes to ensure that the system is fully dispersed, thus obtaining 9 kinds of heat-resistant adhesives.

[0149] See Figure 1 Nine types of thermally anti-tack bearing films were prepared using the same method described above. Performance tests were conducted on these nine films, and the test data are as follows: Figure 4 .

[0150] Figure 4 This is a summary table of performance test data for the heat-resistant and anti-tack bearing films corresponding to different contents of amine curing agent (PAA) in Example 2 of the present invention.

[0151] from Figure 4 The experimental results show that no adhesive residue was observed in any of the control groups during the high-temperature test. When the amount of amine curing agent (PAA) in the formulation was 1.9–2.3 grams and the amount of thermoresponsive acrylic adhesive (YKL197) was 20 grams, that is, when the content of amine curing agent (PAA) was 9.5%–11.5% of that of thermoresponsive acrylic adhesive (YKL197), the adhesive layer could achieve a significant "non-expansion" or "reduced tack" effect at high temperatures, while maintaining sufficient tack at room temperature and preventing accidental detachment during the FPC process. However, when the content of amine curing agent (PAA) was less than 9.5% of that of thermoresponsive acrylic adhesive (YKL197) and greater than 11.5% of that of thermoresponsive acrylic adhesive (YKL197), the peel force of the adhesive layer increased at high temperatures, i.e., "expansion" or "increased tack".

[0152] Figure 5 This table summarizes the dyne values ​​of the heat-resistant, non-stick bearing films corresponding to different contents of amine curing agent (PAA) in Example 1 of this invention, as well as the ordinary acrylic bearing film and UV-release bearing film from the prior art, after being applied to PI films and then peeled off. Figure 5As can be seen, in Example 2 of this invention, the dyne values ​​of the PI film after peeling tests showed that the adhesive layer of the heat-resistant carrier film corresponding to different contents of amine curing agent (PAA) remained almost unchanged after each content. This indicates that the adhesive layer of the heat-resistant carrier film corresponding to different contents of amine curing agent (PAA) in Example 2 of this invention did not leave any residue on the PI film surface after peeling, or left very little residue. The surface cleanliness is superior to that of ordinary acrylic carrier films and UV-peel carrier films in the prior art. After high-temperature testing, the dimensional shrinkage rate of this invention was <0.1%, which is far superior to <0.4% of ordinary acrylic carrier films and UV-peel carrier films in the prior art, demonstrating better dimensional stability and process adaptability. Example

[0153] A method for preparing a heat-resistant adhesive includes the following steps: Step A, Amine Curing Agent (PAA): Step A0: Weigh out 1 gram of cashew phenol, 1.3 grams of isophorone diamine and 0.60 grams of furfural solution respectively; Step A1: The cashew phenol is added to a four-necked flask as the main reaction medium. The cashew phenol in the four-necked flask is heated to 55°C to completely melt the cashew phenol and keep it in a uniform flow state. The four flasks are equipped with a digital display stirrer, a thermometer, a dropping funnel and a reflux condenser to ensure that the temperature of the reaction process is controllable and to avoid raw material loss. Step A2: Under stirring conditions, the isophorone diamine is slowly added dropwise to the four-necked flask of Step A1, so that the isophorone diamine and the cashew phenol undergo an addition reaction. At this time, the addition reaction temperature is controlled at 65°C, and the reaction is stirred for 28 minutes to obtain the first mixed solution. Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to within 1.5 hours, and continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to 80°C and maintain the constant temperature of 80°C for 3.5 hours. Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent (PAA).

[0154] Step B, prepare the heat-responsive acrylic adhesive (YKL197): Step B0: Preparation of Solution A: Weigh 41.10 g of isooctyl acrylate, 136.99 g of butyl acrylate, and 21.91 g of glycidyl methacrylate, respectively. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into a four-necked round-bottom flask, and add 200 g of ethyl acetate to prepare a 50% concentration solution of Solution A. Connect a stirrer to the main mouth of the four-necked round-bottom flask, and connect the other three mouths to a reflux condenser, a thermometer, and a separatory funnel in sequence. Preparation of B solution: Weigh 10.26 g of isooctyl acrylate, 64.10 g of butyl acrylate and 25.64 g of glycidyl methacrylate respectively, put the above isooctyl acrylate, butyl acrylate and glycidyl methacrylate into the first conical flask, and add 100 g of ethyl acetate to prepare a 50% concentration B solution. Preparation of initiator solution: Weigh 0.30 g of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 13 equal portions; Step B1: Place the four-necked round-bottom flask containing solution A into a water bath. After checking the airtightness of the entire apparatus, turn on the cooling water and heat the water bath to 98°C. Continue heating until the solution A in the four-necked round-bottom flask is about to boil. Add a certain amount of boiling stones to the four-necked round-bottom flask to stabilize the boiling process. Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator every 30 minutes until the initiator solution is completely added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of a four-necked round-bottom flask and add it dropwise over 1.8 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 9°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for 120 minutes, then add 257.15 g of ethyl acetate and stir until homogeneous, bringing the solid content to 35%. Step B3: After the reaction is complete, cool to room temperature and transfer the obtained product to a dry and clean container to obtain the thermo-responsive acrylic adhesive (YKL197); Step C, preparing heat-resistant adhesives: First, weigh 20 grams of the heat-responsive acrylic adhesive (YKL197) and 0.04 grams of 2-ethyl-4-methylimidazole (2E4MZ) from Step B. Then, weigh 1.2 grams, 1.4 grams, 1.8 grams, 1.9 grams, 2 grams, 2.2 grams, 2.3 grams, 2.4 grams, and 2.5 grams of the amine curing agent (PAA) from Step A, respectively. Add the heat-responsive acrylic adhesive to the reaction vessel, add 8 grams of ethyl acetate to dilute and adjust the viscosity, then add the amine curing agent, followed by 2-ethyl-4-methylimidazole (2E4MZ). Mix and start stirring, and keep stirring for 30 minutes to ensure that the system is fully dispersed, thus obtaining 9 kinds of heat-resistant adhesives.

[0155] See Figure 1 Nine types of thermally reducing tack load-bearing films were prepared using the same method described above. Performance tests were conducted on these nine films, and the test data are as follows: Figure 6 .

[0156] Figure 6 This is a summary table of performance test data for the heat-resistant and anti-tack carrier film corresponding to different contents of amine curing agent (PAA) in Example 3 of the present invention.

[0157] from Figure 6 The experimental results show that no adhesive residue was observed in any of the control groups during the high-temperature test. When the amount of amine curing agent (PAA) in the formulation was 1.9–2.3 grams and the amount of thermoresponsive acrylic adhesive (YKL197) was 20 grams, that is, when the content of amine curing agent (PAA) was 9.5%–11.5% of that of thermoresponsive acrylic adhesive (YKL197), the adhesive layer could achieve a significant "non-expansion" or "reduced tack" effect at high temperatures, while maintaining sufficient tack at room temperature and preventing accidental detachment during the FPC process. However, when the content of amine curing agent (PAA) was less than 9.5% of that of thermoresponsive acrylic adhesive (YKL197) and greater than 11.5% of that of thermoresponsive acrylic adhesive (YKL197), the peel force of the adhesive layer increased at high temperatures, i.e., "expansion" or "increased tack".

[0158] Figure 7 This table summarizes the dyne values ​​of the heat-resistant, non-stick bearing films corresponding to different contents of amine curing agent (PAA) in Example 3 of this invention, as well as the ordinary acrylic bearing film and UV-release bearing film from the prior art, after being applied to PI films and then peeled off. Figure 7It can be seen that, in Example 3 of this invention, the dyne values ​​of the PI film after peeling tests showed that the heat-resistant bearing films corresponding to different contents of amine curing agent (PAA) remained almost unchanged. This indicates that the adhesive layer of the heat-resistant bearing film corresponding to different contents of amine curing agent (PAA) in Example 1 of this invention did not leave any residue on the PI film surface after peeling, or left very little residue. The surface cleanliness is superior to that of ordinary acrylic bearing films and UV-peel bearing films in the prior art. After high-temperature testing, the dimensional shrinkage rate of this invention is <0.1%, which is far superior to <0.4% of ordinary acrylic bearing films and UV-peel bearing films in the prior art, demonstrating better dimensional stability and process adaptability.

[0159] The high temperature referred to in this invention is a temperature of 160℃ to 190℃.

[0160] Figure 8 This is Comparative Example 1, a summary table of data from tests performed after applying a conventional acrylic carrier film onto a PI film. From this... Figure 8 It can be seen that the peel force of the ordinary acrylic carrier film in the prior art to the PI film after baking at 160℃ is 45% greater than that to the PI film at room temperature of 23℃; while the peel force to the copper foil after hot pressing at 190℃ is 60% greater than that to the PI film at room temperature of 23℃; the high-temperature expansion and adhesion are very obvious; and there are still residues during peeling.

[0161] Figure 9 Comparative Example 2 is a summary table of data from tests conducted after a UV-release carrier film was applied to a PI film using existing technology. Figure 9 It can be seen that the peeling force of the UV release carrier film on the PI film after baking at 160℃ is 32% greater than that on the PI film at room temperature of 23℃; while the peeling force on the copper foil after hot pressing at 190℃ is 59% greater than that on the PI film at room temperature of 23℃; the high-temperature expansion and adhesion are also very obvious; and there are still residues during peeling.

[0162] The above-described embodiments are merely preferred embodiments of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for preparing an amine curing agent, characterized in that, Includes the following steps: Step A0: Weigh out a certain amount of cashew phenol, isophorone diamine and a 99% furfural solution respectively; Step A1: Add the cashew phenol to a four-necked flask as the main reaction component, and heat the cashew phenol in the four-necked flask to a first temperature, which is 50℃~60℃, so that the cashew phenol is completely melted and kept in a uniform flow state. Step A2: Under stirring conditions, the isophorone diamine is added dropwise to the four-necked flask of step A1, so that the isophorone diamine and the cashew phenol undergo an addition reaction. At this time, the addition reaction temperature is controlled at a second temperature, which is 60℃~70℃. The reaction is stirred for a period of time to obtain the first mixed solution. Step A3: Add the furfural solution to the first mixed solution in step A2 at a uniform rate through a dropping funnel to carry out the condensation reaction. Control the dropping time to be within 1 to 2 hours. Continue stirring during the dropping process to keep the condensation reaction system fully stirred. After the dropping is completed, gradually raise the temperature to a third temperature, which is 75°C to 90°C. Continue stirring and keep the reaction at this third temperature for 3 to 4 hours. Step A5: After the condensation reaction is complete, cool to room temperature and transfer the resulting product to a dry container for storage. This product is the amine curing agent.

2. The method for preparing the amine curing agent according to claim 1, characterized in that: In step A0, the mass ratio of cashew phenol, isophorone diamine, and furfural solution is 1: 1.1-1.3: 0.45-0.

60.

3. The method for preparing the amine curing agent according to claim 1, characterized in that: Between steps A3 and A5, there is also step A4, namely step A4, byproduct removal: in the later stage of the condensation reaction, byproduct water and some low-boiling solvent are removed by vacuuming to promote the further progress of the condensation reaction and improve the purity of the product.

4. An amine-based curing agent, characterized in that: The amine curing agent obtained by the preparation method according to claims 1 to 3.

5. A method for preparing a heat-resistant adhesive, characterized in that, Includes the following steps: Step B, prepare the heat-responsive acrylic adhesive: Step B0: Preparation of Solution A: Weigh out the raw materials according to the following percentages of total monomers: 10%–15% isooctyl acrylate, 45%–50% butyl acrylate and 5%–8% glycidyl methacrylate. Put the above isooctyl acrylate, butyl acrylate and glycidyl methacrylate into a four-necked round-bottom flask, and add a certain amount of ethyl acetate to prepare a solution A with a concentration of 50%–60%. Preparation of B-component solution: Weigh out the raw materials according to the following percentages of total monomers: 1%–4% isooctyl acrylate, 20%–25% butyl acrylate, and 7%–10% glycidyl methacrylate. Put the above isooctyl acrylate, butyl acrylate, and glycidyl methacrylate into the first conical flask, and add ethyl acetate to prepare a 50%–60% concentration B-component solution. Preparation of initiator solution: Weigh 0.08% to 0.10% of the total monomer content of azobisisobutyronitrile into the second conical flask, add ethyl acetate to dissolve it, and prepare an initiator solution with a concentration of 1%; divide the initiator solution into 12 to 14 equal portions; The total amount of monomers is the sum of all isooctyl acrylate, butyl acrylate, and glycidyl methacrylate in solution A and solution B. Step B1: Place the four-necked round-bottom flask containing solution A into a water bath, heat the water bath to 98°C, and continue heating until the solution A in the four-necked round-bottom flask is about to boil. Then add a certain amount of boiling stones to the four-necked round-bottom flask to stabilize the boiling process. Step B2: After the boiling and stabilization in Step B1, add the first portion of the initiator solution, and then add the initiator solution every 28-32 minutes until all the initiator solution is added. Before adding the second portion of the initiator solution, pour the B-component solution into the separatory funnel of the four-necked round-bottom flask and add it dropwise over 1.5-2 hours. Throughout the reaction, keep stirring and maintain the temperature of the water in the water bath 8-10°C higher than the temperature of the mixed solution in the four-necked round-bottom flask. After the last addition of the initiator solution, continue stirring for a period of time, then add a certain amount of ethyl acetate and stir until the solid content reaches a certain value. Step B3: After the reaction is complete, cool to room temperature and transfer the resulting product to a dry and clean container to obtain the thermo-responsive acrylic adhesive; Step C, prepare the heat-resistant adhesive: Step C1: First, weigh out a certain amount of the acrylic adhesive from step B, the amine curing agent from claim 4, and the catalyst respectively; Step C2: Add the acrylic adhesive to the reaction vessel, add an appropriate amount of ethyl acetate to dilute and stir evenly; Step C3: Add the amine curing agent and continue stirring until homogeneous; Step C4: Next, add the catalyst, continue stirring, and keep stirring for at least 20 minutes to ensure that the system is fully dispersed, and you will get the heat-resistant adhesive.

6. The method for preparing the heat-reducing adhesive according to claim 5, characterized in that: In step C1, the mass ratio of the heat-responsive acrylic adhesive, amine curing agent, and catalyst is 1:9.5%–11.5%:0.2%–0.3%.

7. The method for preparing the heat-reducing adhesive according to claim 5, characterized in that: In step C1, the catalyst is 2-ethyl-4-methylimidazole.

8. The method for preparing the heat-reducing adhesive according to claim 5, characterized in that: In step C3, a certain amount of ethyl acetate is added to adjust the viscosity of the mixture according to the required viscosity.

9. A heat-resistant adhesive, characterized in that: The heat-reducing adhesive obtained by the preparation method according to claims 5 to 8.

10. A heat-resistant anti-adhesion carrier film, comprising a PET base film (10) and a release film (20), characterized in that: It also includes a heat-resistant adhesive layer (30) that bonds the PET base film (10) and the release film (20) together, the heat-resistant adhesive layer (30) being an adhesive layer formed by coating with the heat-resistant adhesive of claim 9.

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