High-thermal-stability thermal transfer release film and preparation method thereof

Abstract

The invention discloses a high-thermal-stability heat transfer printing release film and a preparation method thereof, and belongs to the technical field of heat transfer printing, a microcrystalline cellulose natural polymer material is introduced, the microcrystalline cellulose natural polymer material is subjected to activation and amination modification and then serves as a functional filler to participate in crosslinking of polyimide, and microcrystalline cellulose is derived from plant fibers and is renewable and degradable; part of traditional petrochemical base filler is replaced, and dependence on non-renewable resources is reduced; meanwhile, active groups such as hydroxyl and amino on the surface can form strong interaction with other components, and a toxic coupling agent does not need to be additionally added; the core raw material of the thermal transfer release film with high thermal stability is modified polyimide, the polyimide has excellent thermal decomposition temperature, and thermal creep of polyimide molecular chains at high temperature is further inhibited through embedding of anhydride modified PET and aminated microcrystalline cellulose.

Description

Technical Field

[0001] This invention belongs to the field of thermal transfer technology, specifically a high thermal stability thermal transfer release film and its preparation method. Background Technology

[0002] Heat transfer release film is the core medium substrate in heat transfer decoration process. Its core function is to support the release layer. Through the combined action of heat and pressure, the release layer and the decorative pattern layer attached to it are successfully separated from their own surface during the heat transfer process, and finally completely transferred to the surface of the decorated product to form a high-quality decorative film.

[0003] In the preparation of heat transfer release film, the core and critical step is to precisely coat the release layer on the surface of the release film substrate. The subsequent printed layers must completely cover the release layer. Therefore, there are strict positional adaptation requirements between the release film substrate, the release layer, and the printed layers. Ideally, the release layer on the surface of the heat transfer release film should completely overlap with the subsequently printed pattern layer, that is, the two should be the same size. Otherwise, the pattern will not be able to completely detach from the release film surface and be transferred, affecting the transfer effect.

[0004] Currently, the release layer coating and subsequent pattern printing of heat transfer release films are usually completed using gravure printing equipment. However, the release agent used in the release layer is a transparent material, and the existing color registration system of gravure printing equipment cannot automatically track and position it. Therefore, the position of the release layer coating on the surface of the release film substrate and the alignment of the release layer with the subsequent printed layers cannot be accurately controlled automatically by the equipment's color registration system. Instead, it relies on the precision of the gravure printing equipment and the experience of the operator.

[0005] Due to the limitations of the aforementioned production processes, it is difficult to consistently guarantee a high-precision fit between the release layer coating and the release film substrate and printed layers, easily leading to problems such as release layer coating misalignment and misalignment between the release layer and the pattern layer. To avoid the pattern layer not being fully printed on the release layer, existing preparation methods require a larger redundancy in the release layer coating area to ensure that the pattern layer can completely cover the release layer area. However, due to the invisibility of the release agent, precise positioning and coating of the release layer on the release film substrate cannot be achieved, ultimately resulting in the following defects: First, the redundancy of the release layer edge on the surface of the heat transfer release film is too large (usually around 2mm to 3mm), which easily leads to pattern burrs and line deformation during subsequent transfer due to the irregularity of the release layer edge; second, misalignment between the release layer and the pattern layer causes pattern defects, making it impossible to present delicate graphics and text, affecting the aesthetics of the transferred product and the packaging decoration effect; third, the scrap rate is high, making it difficult to meet the transfer requirements of high-precision decorative patterns.

[0006] Chinese patent CN119872115B discloses a method for preparing a biodegradable heat transfer lettering film and its application. The method involves premixing modified PET, dynamically thiolated polyimide, cellulose nanocrystal / polylactic acid hybrid material, and bio-based plasticizer in a dual planetary mixer, followed by bidirectional gradient stretching and blow molding to form a film. However, in this method, all the substances are physically blended together, resulting in weak interfacial bonding. Summary of the Invention

[0007] The purpose of this invention is to provide a high thermal stability heat transfer release film and its preparation method. Microcrystalline cellulose, a natural polymer material, is introduced and, after activation and amination modification, is used as a functional filler to participate in the crosslinking of polyimide. Microcrystalline cellulose is derived from plant fibers, is renewable and biodegradable, and replaces some traditional petrochemical-based fillers, reducing dependence on non-renewable resources. At the same time, its surface active groups such as hydroxyl and amino groups can form strong interactions with other components without the need for additional toxic coupling agents.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for preparing a high thermal stability heat transfer release film includes the following steps:

[0010] Step 1: Using dichloromethane as a solvent, benzoyl peroxide is used to initiate a free radical grafting reaction, which grafts alkenyl succinic anhydride onto the PET molecular chain to obtain anhydride-modified PET.

[0011] Step 2: Activated microcrystalline cellulose particles are obtained by NaOH alkaline activation treatment; then, amino-modified microcrystalline cellulose particles are obtained by combining the catechol groups of dopamine hydrochloride with the surface hydroxyl groups and undergoing self-polymerization reaction.

[0012] Step 3: Polyamic acid is generated by polycondensation reaction of 4,4'-oxydiphthalic anhydride, 1,3-bis(4'-aminophenoxy), anhydride-modified PET and aminated microcrystalline cellulose. Then, modified polyimide is obtained by stepwise high-temperature imidization. The modified polyimide and epoxidized soybean oil are premixed and then bidirectionally gradient stretched and blown into a film to obtain a heat transfer release film base film.

[0013] Step 4: Apply pressure-sensitive adhesive to the front side of the heat transfer release film base film at a coating speed of 80-120 m / min and cure at an oven temperature of 160-190℃ to obtain a heat transfer release film with high thermal stability and a thickness of 10-18 μm.

[0014] Furthermore, the pressure-sensitive adhesive comprises the following components by weight:

[0015] 20-30 parts silicone pressure-sensitive adhesive, 15-25 parts dynamic crosslinking silicone, 2-4 parts zinc bismuth bimetallic catalyst and 1-3 parts sodium polyacrylate.

[0016] Furthermore, the specific preparation steps for anhydride-modified PET are as follows:

[0017] PET chips and dichloromethane were added to a reaction vessel and stirred for 10-15 minutes at 20-25℃ and 500-600 r / min. Under nitrogen protection, the mixture was heated to 80-90℃, and then benzoyl peroxide and alkenyl succinic anhydride were added. The reaction was continued with stirring for 3-5 hours. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water. The cake was then vacuum dried at 60-80℃ for 1-2 hours to obtain anhydride-modified PET.

[0018] Furthermore, the ratio of PET chips, dichloromethane microcrystalline cellulose particles, benzoyl peroxide, and alkenyl succinic anhydride used is 190-200g: 450-500mL: 3-4g: 110-120g.

[0019] Furthermore, the specific preparation steps for activated microcrystalline cellulose particles are as follows:

[0020] Microcrystalline cellulose particles with a particle size of 20-30 μm are mixed with NaOH and ground for 2-4 min. Then, the mixture is placed in a reaction vessel containing deionized water and stirred for 2-4 h at 100-105 °C and 500-600 r / min. After filtration, the precipitate is washed 2-4 times with deionized water and anhydrous ethanol and dried under vacuum at 60-80 °C for 1-2 h to obtain activated microcrystalline cellulose particles.

[0021] Furthermore, the ratio of microcrystalline cellulose particles, NaOH, and deionized water is 40-45g: 3-5g: 180-200mL.

[0022] Furthermore, the specific preparation steps for aminated microcrystalline cellulose particles are as follows:

[0023] Activated microcrystalline cellulose particles and deionized water were added to a reaction vessel and stirred for 30-50 min at 20-25℃ and 500-600 r / min. The pH value was adjusted to 7-8 with NaOH solution, and then dopamine hydrochloride powder and anhydrous ethanol were added. Stirring was continued for 24-26 h under light-protected conditions. The mixture was filtered, and the product was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product was then vacuum dried at 60-80℃ for 1-2 h to obtain aminated microcrystalline cellulose particles.

[0024] Furthermore, the ratio of activated microcrystalline cellulose particles, deionized water, dopamine hydrochloride powder, and anhydrous ethanol is 20-30g: 120-150mL: 90-100mg: 60-80mL.

[0025] Furthermore, the specific preparation steps for modified polyimide are as follows:

[0026] 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy), and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 2-4 °C and 100-120 r / min under nitrogen protection. Then, the mixture was heated to 20-25 °C and stirred for 4-6 h. Then, anhydride-modified PET and aminated microcrystalline cellulose particles were added and stirred for 10-12 h. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water. It was then vacuum dried at 60-80 °C for 1-2 h. Then, the mixture was heated to 105-115 °C, 205-215 °C, 310-320 °C, and 350-365 °C, with each temperature maintained for 45 min, to obtain modified polyimide.

[0027] Furthermore, the ratio of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy), N-methyl-2-pyrrolidone, anhydride-modified PET, and aminated microcrystalline cellulose particles is 200-220g: 400-420g: 800-900mL: 70-80g: 10-12g.

[0028] Furthermore, the specific preparation steps of the heat transfer release film base film are as follows:

[0029] Modified polyimide and epoxidized soybean oil are premixed in a double planetary mixer at 80-100℃ for 20-30 minutes, then heated to 170-180℃ and subjected to bidirectional gradient stretching blow molding to form a film with a thickness of 50-60μm. The resulting blended blow molding yields a heat transfer release film base film.

[0030] Furthermore, the mass ratio of modified polyimide to epoxidized soybean oil is 50-60:2-4.

[0031] The beneficial effects of this invention are:

[0032] 1. The high thermal stability heat transfer release film prepared by this invention introduces microcrystalline cellulose, a natural polymer material, which, after activation and amination modification, serves as a functional filler to participate in the crosslinking of polyimide. Microcrystalline cellulose is derived from plant fibers, is renewable and biodegradable, and replaces some traditional petrochemical-based fillers, reducing dependence on non-renewable resources. At the same time, its surface active groups such as hydroxyl and amino groups can form strong interactions with other components, eliminating the need for additional toxic coupling agents.

[0033] 2. The core raw material of the high thermal stability heat transfer release film of the present invention is modified polyimide. Polyimide itself has excellent thermal decomposition temperature. After the embedding of acid anhydride modified PET and aminated microcrystalline cellulose, the thermal creep of polyimide molecular chains at high temperature is further suppressed.

[0034] 3. The modified polyimide of the present invention constructs an interpenetrating network structure of anhydride-modified PET and aminated microcrystalline cellulose: the rigid segments of aminated microcrystalline cellulose serve as mechanical support points, alleviating stress concentration when the membrane is subjected to external force and improving tear resistance; the flexible segments of anhydride-modified PET improve the brittleness of polyimide and give the membrane good folding resistance.

[0035] 4. The aminated microcrystalline cellulose particles of the present invention are activated by NaOH alkali treatment, which causes the surface of the microcrystalline cellulose particles to swell and generate a large number of hydroxyl groups, resulting in activated microcrystalline cellulose particles. The swollen activated microcrystalline cellulose particles destroy the dense structure of cellulose, expose active sites and reduce the degree of polymerization, causing the originally tightly arranged crystalline regions to swell and dissociate, transforming them into loose amorphous regions, which greatly improves the degradation efficiency. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1: A method for preparing a high thermal stability thermal transfer release film, comprising the following steps:

[0038] S1: Add 190g of PET chips and 450mL of dichloromethane to a reaction vessel, stir for 10min at 20℃ and 500r / min, heat to 80℃ under nitrogen protection, then add 3g of benzoyl peroxide and 110g of alkenyl succinic anhydride, continue stirring for 3h, filter, wash the filter cake twice with deionized water, and vacuum dry at 60℃ for 1h to obtain anhydride-modified PET.

[0039] S2: Dry 50g of microcrystalline cellulose at 100℃ for 3h, grind and pulverize for 2min to obtain microcrystalline cellulose particles with a particle size of 20-30μm; mix 40g of microcrystalline cellulose particles with 3g of NaOH, grind for 2min, and then place in a reaction vessel containing 180mL of deionized water. Stir and react for 2h at 100℃ and 500r / min. Filter, wash the precipitate twice with deionized water and anhydrous ethanol, and vacuum dry at 60℃ for 1h to obtain activated microcrystalline cellulose particles.

[0040] S3: Add 20g of activated microcrystalline cellulose particles and 120mL of deionized water to a reaction vessel, stir for 30min at 20℃ and 500r / min, adjust the pH to 7 with NaOH solution, then add 90mg of dopamine hydrochloride powder and 60mL of anhydrous ethanol, continue stirring for 24h under light-protected conditions, filter, wash the product twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 60℃ for 1h to obtain aminated microcrystalline cellulose particles.

[0041] S4: Add 200g of 4,4'-oxydiphthalic anhydride, 400g of 1,3-bis(4'-aminophenoxy), and 800mL of N-methyl-2-pyrrolidone to a reaction vessel. Under nitrogen protection, stir at 2℃ and 100r / min for 20min. Then heat to 20℃ and continue stirring for 4h. Then add 70g of anhydride-modified PET and 10g of aminated microcrystalline cellulose particles and continue stirring for 10h. Filter and wash the filter cake twice with deionized water. Vacuum dry at 60℃ for 1h. Then heat to 105℃, 205℃, 310℃, and 350℃, maintaining the temperature at each stage for 45min to obtain modified polyimide.

[0042] S5: 50g of modified polyimide and 2g of epoxidized soybean oil are premixed in a double planetary mixer at 80℃ for 20min, heated to 170℃, and bidirectional gradient stretching blow molding is performed to form a film with a film thickness of 50μm. The heat transfer release film base film is obtained by blending and blow molding.

[0043] S6: Apply pressure-sensitive adhesive to the front side of the heat transfer release film base film. The pressure-sensitive adhesive contains 20 parts of silicone pressure-sensitive adhesive, 15 parts of dynamic cross-linking silicone, 2 parts of zinc bismuth bimetallic catalyst, and 1 part of sodium polyacrylate. The coating speed is 80 m / min, and the oven temperature is 160℃ for curing to obtain a 10 μm thick heat transfer release film with high thermal stability.

[0044] Example 2: A method for preparing a high thermal stability thermal transfer release film, comprising the following steps:

[0045] S1: Add 195g of PET chips and 475mL of dichloromethane to a reaction vessel, stir for 12.5min at 22.5℃ and 550r / min, heat to 85℃ under nitrogen protection, then add 3.5g of benzoyl peroxide and 115g of alkenyl succinic anhydride, continue stirring for 4h, filter, wash the filter cake three times with deionized water, and vacuum dry at 70℃ for 1.5h to obtain anhydride-modified PET.

[0046] S2: 60g of microcrystalline cellulose was dried at 105℃ for 4h and ground for 3min to obtain microcrystalline cellulose particles with a particle size of 20-30μm; 42.5g of microcrystalline cellulose particles and 4g of NaOH were mixed and ground for 3min, and then placed in a reaction vessel containing 190mL of deionized water. The mixture was stirred and reacted at 102.5℃ and 550r / min for 3h. After filtration, the precipitate was washed three times with deionized water and anhydrous ethanol and dried under vacuum at 70℃ for 1.5h to obtain activated microcrystalline cellulose particles.

[0047] S3: Add 25g of activated microcrystalline cellulose particles and 135mL of deionized water to a reaction vessel, stir for 40min at 22.5℃ and 550r / min, adjust the pH to 7.5 with NaOH solution, then add 95mg of dopamine hydrochloride powder and 70mL of anhydrous ethanol, continue stirring for 25h under light-protected conditions, filter, wash the product three times with deionized water and anhydrous ethanol respectively, and vacuum dry at 70℃ for 1.5h to obtain aminated microcrystalline cellulose particles.

[0048] S4: 210g of 4,4'-oxophthalic anhydride, 410g of 1,3-bis(4'-aminophenoxy), and 850mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 3℃ and 110r / min for 25min. Then, it was heated to 22.5℃ and stirred for 5h. Then, 75g of anhydride-modified PET and 11g of aminated microcrystalline cellulose particles were added, and the mixture was stirred for 11h. The mixture was filtered, and the filter cake was washed three times with deionized water. It was then vacuum dried at 70℃ for 1.5h. Then, it was heated to 110℃, 210℃, 315℃, and 357.5℃, and the temperature was maintained for 45min at each stage to obtain modified polyimide.

[0049] S5: 55g of modified polyimide and 3g of epoxidized soybean oil are premixed in a double planetary mixer at 90℃ for 25min, heated to 175℃, and bidirectional gradient stretching blow molding is performed to form a film with a film thickness of 55μm. The heat transfer release film base film is obtained by blending and blow molding.

[0050] S6: Apply pressure-sensitive adhesive to the front side of the heat transfer release film base film. The pressure-sensitive adhesive contains 25 parts of silicone pressure-sensitive adhesive, 20 parts of dynamic cross-linking silicone, 3 parts of zinc bismuth bimetallic catalyst, and 2 parts of sodium polyacrylate. The coating speed is 100m / min, and the oven temperature is 175℃ for curing to obtain a 14μm thick heat transfer release film with high thermal stability.

[0051] Example 3: A method for preparing a high thermal stability thermal transfer release film, comprising the following steps:

[0052] S1: Add 200g of PET chips and 500mL of dichloromethane to a reaction vessel, stir for 15min at 25℃ and 600r / min, heat to 90℃ under nitrogen protection, then add 4g of benzoyl peroxide and 120g of alkenyl succinic anhydride, continue stirring for 5h, filter, wash the filter cake 4 times with deionized water, and vacuum dry at 80℃ for 2h to obtain anhydride-modified PET.

[0053] S2: Dry 70g of microcrystalline cellulose at 110℃ for 5h, grind and pulverize for 4min to obtain microcrystalline cellulose particles with a particle size of 20-30μm; mix 45g of microcrystalline cellulose particles with 5g of NaOH, grind for 4min, and then place in a reaction vessel containing 200mL of deionized water. Stir and react for 4h at 105℃ and 600r / min. Filter, wash the precipitate 4 times with deionized water and anhydrous ethanol, and vacuum dry at 80℃ for 2h to obtain activated microcrystalline cellulose particles.

[0054] S3: Add 30g of activated microcrystalline cellulose particles and 150mL of deionized water to a reaction vessel, stir for 50min at 25℃ and 600r / min, adjust the pH to 8 with NaOH solution, then add 100mg of dopamine hydrochloride powder and 80mL of anhydrous ethanol, continue stirring for 26h under light-protected conditions, filter, wash the product 4 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 80℃ for 2h to obtain aminated microcrystalline cellulose particles.

[0055] S4: 220g of 4,4'-oxophthalic anhydride, 420g of 1,3-bis(4'-aminophenoxy), and 900mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 4℃ and 120r / min for 30min. Then, it was heated to 25℃ and stirred for 6h. Then, 80g of anhydride-modified PET and 12g of aminated microcrystalline cellulose particles were added, and the mixture was stirred for 12h. The mixture was filtered, and the filter cake was washed four times with deionized water. It was then vacuum dried at 80℃ for 2h. Then, it was heated to 115℃, 215℃, 320℃, and 365℃, and the temperature was maintained for 45min at each stage to obtain modified polyimide.

[0056] S5: 60g of modified polyimide and 4g of epoxidized soybean oil are premixed in a double planetary mixer at 100℃ for 30min, heated to 180℃, and bidirectional gradient stretching blow molding is performed to form a film with a film thickness of 60μm. The heat transfer release film base film is obtained by blending and blow molding.

[0057] S6: Apply pressure-sensitive adhesive to the front side of the heat transfer release film base film. The pressure-sensitive adhesive contains 30 parts of silicone pressure-sensitive adhesive, 25 parts of dynamic cross-linking silicone, 4 parts of zinc bismuth bimetallic catalyst, and 3 parts of sodium polyacrylate. The coating speed is 120 m / min, and the oven temperature is 190℃ for curing to obtain a heat transfer release film with a thickness of 18 μm and high thermal stability.

[0058] Comparative Example 1: Based on Example 3, the anhydride-modified PET in step S4 was replaced with the raw material PET chips in step S1.

[0059] Comparative Example 2: Based on Example 3, the aminated microcrystalline cellulose particles in step S4 were replaced with the activated microcrystalline cellulose particles prepared in step S2.

[0060] Comparative Example 3: Based on Example 3, the modified polyimide in step S5 was replaced with commercially available polyimide.

[0061] The high thermal stability heat transfer release films prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the specific tests are as follows:

[0062] 1. Tensile strength of base film (MPa): Test standard: ASTM D882 (Test for tensile properties of plastic films), sample size 100mm x 10mm, tensile rate 50mm / min.

[0063] 2. Adhesion (N): Test method: 180° peel test (ASTM D3330), peel force after hot pressing on pure cotton substrate.

[0064] 3. Washing resistance: Refer to AATCC 61-2013 standard, 50℃ water temperature, 30 minutes per wash, record the number of times degumming or fading occurs.

[0065] 4. The high-temperature resistance of the material was tested using a heat distortion Vicat softening point tester, with a heating rate of 100℃ / h.

[0066] The results are shown in Table 1:

[0067] Table 1

[0068]

[0069] As shown in Table 1, Comparative Example 1 lacks the core function of anhydride modification of PET, failing to introduce active anhydride groups into the PET molecular chain. This results in the loss of the crosslinking ability between the anhydride groups and the amino and polyimide end groups of the aminated microcrystalline cellulose. The raw PET is a pure flexible chain segment without active crosslinking sites, unable to form a stable interpenetrating network with polyimide and aminated microcrystalline cellulose, existing only as a physical blend in the system. This leads to increased interfacial defects within the base film, a significant decrease in stress dispersion ability, and a drop in tensile strength. The uncrosslinked pure PET segments cannot inhibit the thermal creep of the polyimide molecular chain, reducing the heat resistance and heat distortion temperature of the base film. Simultaneously, weak interfacial adhesion significantly deteriorates the adhesion and washability between the film and the pressure-sensitive adhesive layer.

[0070] In Comparative Example 2, the core function is missing, specifically the S3 step of dopamine hydrochloride amination modification. The activated microcrystalline cellulose contains only hydroxyl groups and lacks amino active sites, making it unable to undergo amidation crosslinking with the anhydride groups of the anhydride-modified PET. The interaction between the hydroxyl groups of the activated microcrystalline cellulose and the polyimide and anhydride-modified PET is mainly weak hydrogen bonding, far weaker than the covalent crosslinking of amino-anhydride. This results in insufficient stability of the poly-interpenetrating network structure, decreased tensile strength, and the microcrystalline cellulose is prone to local aggregation in the polyimide matrix, becoming stress concentration points when the base film is subjected to external forces. During the water washing process, the aggregated areas are prone to peeling first, reducing the number of water washing cycles. At the same time, the hydrogen bonds have poor thermal stability and are prone to breakage at high temperatures, leading to a decrease in the heat distortion temperature.

[0071] Comparative Example 3 lacks core functionalities: Commercially available polyimide is a pure homopolymer, lacking the flexible segments of anhydride-modified PET and the rigid supporting segments of aminated microcrystalline cellulose, completely losing the interpenetrating network structure that combines rigidity and flexibility. Pure polyimide itself is brittle; without the flexible segments of PET to improve toughness, its tensile strength decreases, and its folding resistance is poor, making it prone to cracking during processing or use. Without the rigid support of aminated microcrystalline cellulose, the base film cannot effectively disperse external forces, resulting in extremely weak interfacial bonding and insufficient adhesion. At the same time, the molecular chain thermal creep of pure polyimide is unrestrained, leading to a lower heat distortion temperature.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a high thermal stability thermal transfer release film, characterized in that, Includes the following steps: Step 1: Using dichloromethane as a solvent, benzoyl peroxide is used to initiate a free radical grafting reaction, which grafts alkenyl succinic anhydride onto the PET molecular chain to obtain anhydride-modified PET. Step 2: Activated microcrystalline cellulose particles are obtained by NaOH alkaline activation treatment; then, amino-modified microcrystalline cellulose particles are obtained by combining the catechol groups of dopamine hydrochloride with the surface hydroxyl groups and undergoing self-polymerization reaction. Step 3: Polyamic acid is generated through polycondensation reaction of 4,4'-oxydiphthalic anhydride, 1,3-bis(4'-aminophenoxy), anhydride-modified PET and aminated microcrystalline cellulose. Then, it is subjected to stepwise high-temperature imidization to obtain modified polyimide. The modified polyimide and epoxidized soybean oil are premixed and then bidirectionally gradient stretched and blown into a film to obtain a heat transfer release film base film. Step 4: Apply pressure-sensitive adhesive to the front side of the heat transfer release film base film at a coating speed of 80-120 m / min and cure at an oven temperature of 160-190℃ to obtain a heat transfer release film with high thermal stability and a thickness of 10-18 μm.

2. The method for preparing a high thermal stability heat transfer release film according to claim 1, characterized in that, The pressure-sensitive adhesive comprises the following components by weight: 20-30 parts silicone pressure-sensitive adhesive, 15-25 parts dynamic crosslinking silicone, 2-4 parts zinc bismuth bimetallic catalyst and 1-3 parts sodium polyacrylate.

3. The method for preparing a high thermal stability thermal transfer release film according to claim 1, characterized in that, The specific preparation steps for the anhydride-modified PET are as follows: PET chips and dichloromethane were added to a reaction vessel and stirred for 10-15 min at 20-25℃ and 500-600 r / min. Under nitrogen protection, the mixture was heated to 80-90℃, and then benzoyl peroxide and alkenyl succinic anhydride were added. The reaction was continued to be stirred for 3-5 h. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water. It was then vacuum dried at 60-80℃ for 1-2 h to obtain anhydride-modified PET. The ratio of PET chips, dichloromethane microcrystalline cellulose particles, benzoyl peroxide, and alkenyl succinic anhydride used is 190-200g: 450-500mL: 3-4g: 110-120g.

4. The method for preparing a high thermal stability heat transfer release film according to claim 1, characterized in that, The specific preparation steps for the activated microcrystalline cellulose particles are as follows: Microcrystalline cellulose particles with a particle size of 20-30 μm are mixed with NaOH and ground for 2-4 min. Then, the mixture is placed in a reaction vessel containing deionized water and stirred for 2-4 h at 100-105 °C and 500-600 r / min. After filtration, the precipitate is washed 2-4 times with deionized water and anhydrous ethanol and dried under vacuum at 60-80 °C for 1-2 h to obtain activated microcrystalline cellulose particles. The ratio of microcrystalline cellulose particles, NaOH, and deionized water is 40-45g: 3-5g: 180-200mL.

5. The method for preparing a high thermal stability heat transfer release film according to claim 1, characterized in that, The specific preparation steps for the aminated microcrystalline cellulose particles are as follows: Add 20-30g of activated microcrystalline cellulose particles and 120-150mL of deionized water to a reaction vessel, stir for 30-50min at 20-25℃ and 500-600r / min, adjust the pH to 7-8 with NaOH solution, then add 90-100mg of dopamine hydrochloride powder and 60-80mL of anhydrous ethanol, and continue stirring for 24-26h under light-protected conditions. Filter, wash the product 2-4 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 60-80℃ for 1-2h to obtain aminated microcrystalline cellulose particles.

6. The method for preparing a high thermal stability thermal transfer release film according to claim 5, characterized in that, The ratio of activated microcrystalline cellulose particles, deionized water, dopamine hydrochloride powder, and anhydrous ethanol is 20-30g: 120-150mL: 90-100mg: 60-80mL.

7. The method for preparing a high thermal stability heat transfer release film according to claim 1, characterized in that, The specific preparation steps of the modified polyimide are as follows: 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy), and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 2-4 °C and 100-120 r / min under nitrogen protection. Then, the mixture was heated to 20-25 °C and stirred for 4-6 h. Then, anhydride-modified PET and aminated microcrystalline cellulose particles were added and stirred for 10-12 h. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water. It was then vacuum dried at 60-80 °C for 1-2 h and then heated to 105-115 °C, 205-215 °C, 310-320 °C, and 350-365 °C to obtain modified polyimide.

8. The method for preparing a high thermal stability heat transfer release film according to claim 5, characterized in that, The ratio of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy), N-methyl-2-pyrrolidone, anhydride-modified PET, and aminated microcrystalline cellulose particles is 200-220g: 400-420g: 800-900mL: 70-80g: 10-12g.

9. The method for preparing a high thermal stability heat transfer release film according to claim 1, characterized in that, The specific preparation steps of the heat transfer release film base film are as follows: Modified polyimide and epoxidized soybean oil are premixed in a double planetary mixer at 80-100℃ for 20-30 minutes, then heated to 170-180℃ and subjected to bidirectional gradient stretching blow molding to form a film with a thickness of 50-60μm. The resulting blended blow molding yields a heat transfer release film base film. The mass ratio of the modified polyimide to epoxidized soybean oil is 50-60:2-4.

10. A high thermal stability heat transfer release film, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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