Self-repairing PA modified polyester release film and preparation method thereof

Abstract

This invention relates to a self-healing PA-modified polyester release film and its preparation method. From bottom to top, it comprises a composite reinforced base film layer, a dynamically crosslinked intermediate transition layer, and a self-healing release surface layer. The composite reinforced base film layer is a biaxially oriented blend of PA-modified polyester and thermoplastic polyurethane elastomer. The dynamically crosslinked intermediate transition layer contains a polymer network with Diels-Alder dynamic covalent bonds. The self-healing release surface layer contains a copolymer of fluorinated polysiloxane and reversibly hydrogen-linked polyacrylate. In preparation, the base film layer is first obtained through melt blending and biaxial stretching, followed by sequential coating of the dynamically crosslinked transition layer and the UV-cured self-healing release surface layer, and then annealing. The release film of this invention can automatically repair surface micro-damage under heat treatment at 80-120℃, with a release force fluctuation of less than 5% after repair, and exhibits excellent interlayer adhesion, mechanical properties, permanent antistatic properties, and adjustable release force.

Description

Technical Field

[0001] This invention relates to the field of functional polymer film materials technology, and more specifically, to a release film for use in flexible electronics, automotive decoration, high-end labels and other fields, especially a PA-modified polyester release film with self-healing function for surface micro-damage and its preparation method. Background Technology

[0002] Release film, also known as peeling film or release film, is a functional thin film with specific separation forces on its surface. It is widely used in processes such as electronic component processing, automotive film transfer, and furniture decorative film lamination. With the development of the electronics and information industry towards flexibility and thinness, and the stringent requirements of the automotive industry for the surface quality of interior parts, traditional release films can no longer meet the increasingly complex application scenarios.

[0003] In the prior art, polyethylene terephthalate (PET) release film has become the mainstream product due to its excellent mechanical strength, transparency, and dimensional stability. However, ordinary PET release film suffers from problems such as insufficient surface hardness, poor scratch resistance, and unstable release force. To improve these defects, researchers have attempted to enhance the performance of the base film through methods such as blending modification and multilayer co-extrusion. For example, Chinese patent document CN106183279A discloses an antistatic and UV-protective modified PET / PC release film, which improves the overall performance of the film material to a certain extent by introducing polycarbonate into the PET resin for blending modification and coating it with an antistatic layer, a release layer, and a UV-protective layer. However, this technical solution still has the following shortcomings: First, PET and PC have poor compatibility, and the blend is prone to phase separation, resulting in uneven mechanical properties of the film; second, the multilayer coating process is complex, and the interlayer adhesion is difficult to guarantee; more importantly, once scratches or indentations are generated on the surface of the release film, the release layer structure will be damaged, which will lead to the failure of local release force and cannot meet the requirements of high-precision bonding process for surface integrity.

[0004] Polyamide (PA) modified polyester resins have been used in recent years to improve release film substrates due to their excellent heat resistance, chemical resistance, and mechanical strength. By introducing amide bonds into the polyester molecular chain, the toughness and temperature resistance of the material can be significantly improved while maintaining the original properties of the polyester. However, existing PA-modified polyester release films mainly focus on improving physical properties and have not solved the problem of functional recovery after surface damage.

[0005] Significant progress has been made in the research of self-healing materials based on dynamic covalent chemistry in the field of materials science. Among these, the Diels-Alder reaction, due to its thermally reversible nature, is widely used to design polymers with self-healing capabilities. The Diels-Alder reaction is a [4+2] cycloaddition reaction between a conjugated diene and a dienophile, which can undergo a reverse reaction at high temperatures, achieving reversible breaking and recombination of chemical bonds. Introducing Diels-Alder dynamic covalent bonds into material systems such as polyurethane and epoxy resins can endow materials with self-healing capabilities and shape memory functions under thermal stimulation. For example, patent CN121293485A applied for by Hunan Juren New Materials Co., Ltd. discloses a polycaprolactone diol containing maleimide groups and its preparation method, which can be used to manufacture self-healing polyurethane elastomers with Diels-Alder bonds. However, combining this dynamic covalent chemical mechanism with release film products to construct multilayer film structures that possess both self-healing functions and stable release properties has not yet been reported.

[0006] Furthermore, in demanding fields such as flexible electronics and automotive interiors, release films must also possess antistatic properties to prevent static electricity from attracting dust or damaging sensitive components. The traditional method involves adding antistatic agents to the release coating; however, small-molecule antistatic agents are prone to migration, affecting the stability of the release force. Introducing conductive fillers such as carbon nanotubes and graphene into the substrate layer to achieve permanent antistatic modification is a more ideal solution. Companies like Cabot Corporation and Qingdao Weiden Technology Polymer Materials Co., Ltd. have mature product lines and production capabilities in the field of carbon-based conductive materials.

[0007] Against this backdrop, developing a multilayer release film that combines self-healing surface, stable release force, excellent mechanical properties, and antistatic function, and achieving its green and efficient preparation, has significant industrial value and technological innovation implications. Summary of the Invention

[0008] This invention aims to overcome the shortcomings of existing release film technologies and provide a PA-modified polyester release film with self-healing function for surface micro-damage and its preparation method. Specifically, the technical problems to be solved by this invention include: solving the problem of release function failure after surface damage of existing release films and endowing the film material with self-healing ability; solving the problem of insufficient interlayer bonding in multilayer film structures and improving the interlayer interface strength through dynamic chemical bonding; solving the problem of release force fluctuation caused by easy migration of traditional antistatic agents and achieving permanent antistatic function; and solving the problems of complex preparation processes, high energy consumption, and large solvent pollution in existing processes and providing a green and efficient preparation method.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A self-healing PA-modified polyester release film, characterized in that it comprises, from bottom to top:

[0011] Composite reinforced base film layer

[0012] Dynamic cross-linked intermediate transition layer, and

[0013] Self-healing release liner;

[0014] The dynamic cross-linking intermediate transition layer is disposed on one side surface of the composite reinforced base film layer, and the self-healing release surface layer is disposed on the side surface of the dynamic cross-linking intermediate transition layer away from the composite reinforced base film layer;

[0015] The dynamic crosslinking intermediate transition layer comprises a polymer network with Diels-Alder dynamic covalent bonds, and the self-healing release surface layer comprises a fluorinated polysiloxane and a polyacrylate copolymer with reversible hydrogen bonding.

[0016] Furthermore, the composite reinforced base film layer is a thin film formed by biaxial stretching of a blend of PA modified polyester resin and thermoplastic polyurethane elastomer.

[0017] The mass ratio of the PA-modified polyester resin to the thermoplastic polyurethane elastomer is 70:30 to 85:15.

[0018] The thickness of the composite reinforced base film layer is 50-100 μm;

[0019] The PA-modified polyester resin is a polyethylene terephthalate resin containing one or more of polycaprolactam (PA6), polyhexamethylene adipamide (PA66), amorphous nylon, or aromatic nylon, which can be prepared by melt blending or reactive extrusion. The thermoplastic polyurethane elastomer is preferably polyether-type TPU to ensure good compatibility and hydrolytic stability with the PA-modified polyester, and can be selected from Italian COI or American Lubrizol products distributed by Jiuyan New Materials (Shenzhen) Co., Ltd.

[0020] Furthermore, the thickness of the dynamically cross-linked intermediate transition layer is 2-5 μm;

[0021] The polymer network with Diels-Alder dynamic covalent bonds is formed by crosslinking a furan-maleimide adduct type polyurethane prepolymer.

[0022] The dynamic cross-linked intermediate transition layer undergoes reversible breakage and recombination of its Diels-Alder bonds within a temperature range of 80-120℃.

[0023] The furan-maleimide adduct type polyurethane prepolymer can be prepared by the following steps: using polycaprolactone diol containing maleimide groups (such as the patented product CN121293485A produced by Hunan Juren New Material Co., Ltd.) as raw material, reacting it with diisocyanate to generate a prepolymer, then adding a bisfuran compound as a dynamic crosslinking agent, and forming a dynamic crosslinking network through heat treatment.

[0024] Furthermore, the thickness of the self-healing release layer is 1-3 μm;

[0025] The fluorinated polysiloxane contains 10-20% by mass in the self-healing release layer.

[0026] The surface energy of the self-healing release layer is 18-22 mN / m;

[0027] The fluorinated polysiloxane is preferably a polysiloxane with perfluoroalkyl side chains, which can be obtained by purchasing or making it in-house; the reversibly hydrogen-linked polyacrylate copolymer is copolymerized from acrylate monomers containing urethane groups or urea groups.

[0028] Furthermore, the self-healing release layer can repair surface micro-damage with a depth ≤2μm under heat treatment conditions of 80-120℃, and the fluctuation range of the release force after repair is less than 5%.

[0029] Furthermore, the self-healing release layer is cured by ultraviolet light to form an interpenetrating network structure, and the reversible hydrogen bond crosslinking is provided by urethane groups or urea groups in the acrylate copolymer.

[0030] Furthermore, the dynamic cross-linked intermediate transition layer also contains conductive nanofillers, which are one or more of carbon nanotubes, graphene, or conductive carbon black.

[0031] The surface resistance of the self-healing PA-modified polyester release film is ≤10. 8 Ω;

[0032] The conductive nanofiller can be carbon nanotube products manufactured by Cabot High Performance Materials (Zhuhai) Co., Ltd., or graphene / superconducting carbon black composite conductive materials manufactured by Qingdao Weideke Polymer Materials Co., Ltd.

[0033] This invention also proposes a method for preparing the self-healing PA-modified polyester release film as described above, characterized by comprising the following steps:

[0034] Step (1) Preparation of composite reinforced base film layer: PA modified polyester resin and thermoplastic polyurethane elastomer are measured at a mass ratio of 70:30 to 85:15, premixed evenly in a high-speed mixer, and then melt-blended in a twin-screw extruder. After extrusion through a die, casting, longitudinal stretching, transverse stretching, and heat setting, a composite reinforced base film layer with a thickness of 50-100μm is formed. The processing temperature of the twin-screw extruder is 240-280℃, and the stretching ratio is 2.5-3.5 times in the longitudinal direction and 3.0-4.0 times in the transverse direction.

[0035] Step (2) Preparation of dynamic crosslinking intermediate transition layer: Dissolve the polyurethane prepolymer containing furan-maleimide Diels-Alder adduct in an organic solvent to prepare a coating solution with a solid content of 10-20%. Coat the prepolymer onto the surface of the composite reinforced base film layer using gravure coating or slit coating. Heat treat the prepolymer at 70-90℃ for 3-8 minutes to allow it to undergo a crosslinking reaction and form a dynamic crosslinking intermediate transition layer. The organic solvent is preferably ethyl acetate, butanone, or a mixture thereof.

[0036] Step (3) Preparation of self-healing release layer: Fluorinated polysiloxane, acrylate prepolymer containing reversible hydrogen-bonded crosslinking groups, and photoinitiator are mixed evenly to prepare a UV-curable coating. This coating is applied to the dynamic crosslinking intermediate transition layer using a microgravure coating method and then cured under ultraviolet light to form a self-healing release layer. The energy of the ultraviolet curing is 600-1000 mJ / cm². 2 ;

[0037] Step (4) Post-processing: The membrane material obtained in step (3) is annealed at 50-80℃ for 1-3 hours to promote the fusion of interlayer interfaces and the uniform distribution of dynamic bonds. After winding, slitting and packaging, the finished product is obtained.

[0038] Furthermore, the heat treatment in step (2) is performed at a temperature of 70-90°C for 3-8 minutes;

[0039] The UV curing energy in step (3) is 600-1000 mJ / cm. 2 .

[0040] Furthermore, as mentioned above, the self-healing PA-modified polyester release film has a release force of 5-50g / 25mm, which can be precisely controlled by adjusting the content of fluorinated polysiloxane. Beneficial effects

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] Surface self-healing function: This invention constructs an interpenetrating network structure of fluorinated polysiloxane and reversibly hydrogen-bonded crosslinked polyacrylate in the release film surface layer. Simultaneously, a Diels-Alder dynamic covalent bond is introduced through a dynamically crosslinked intermediate transition layer, enabling the release film to automatically repair surface micro-damage ≤2μm in depth under heat treatment at 80-120℃. The release force fluctuation after repair is less than 5%. This characteristic significantly extends the service life of the release film and reduces the defect rate during processing.

[0043] Strong interlayer bonding: Through a dynamically cross-linked intermediate transition layer, a chemical bond is formed between the composite reinforced base film layer and the self-healing release surface layer, increasing the interfacial bonding strength by more than 30% compared to traditional multilayer films. The Diels-Alder dynamic bonds in the intermediate transition layer partially react with the active groups on the base film surface during the coating heat treatment process, and can also achieve self-healing of interfacial microcracks through thermal activation during subsequent use.

[0044] Adjustable and stable release force: By adjusting the content of fluorinated polysiloxane in the release layer (10-20wt%), the release force can be precisely controlled within the range of 5-50g / 25mm to meet the needs of different application scenarios. Due to the use of UV-cured crosslinking structure, the functional components in the release layer are not easy to migrate, resulting in excellent long-term stability of the release force.

[0045] Excellent mechanical properties: The composite reinforced base film layer is made of PA-modified polyester and thermoplastic polyurethane elastomer blended and biaxially stretched to form an island structure or a dual continuous phase structure. This maintains the high strength and heat resistance of PA-modified polyester while improving toughness through the introduction of TPU. Tests show that the tensile strength of the release film of this invention can reach 280-350 MPa, the elongation at break ≥120%, and the impact strength ≥90 kJ / cm². 2 Its overall mechanical properties are significantly better than those of ordinary polyester release film.

[0046] Permanent antistatic function: By dispersing conductive nanofillers such as carbon nanotubes and graphene in the dynamic cross-linking intermediate transition layer, permanent antistatic modification can be achieved, with a surface resistivity ≤10. 8 Ω, and is unaffected by ambient humidity, avoiding the release force fluctuation problem caused by the migration of traditional small molecule antistatic agents.

[0047] Green and environmentally friendly process: In the preparation method of this invention, the base film layer adopts a melt blending extrusion process with no solvent emission; the release surface layer adopts a UV curing process, which does not require heating and baking, and the energy consumption is reduced by more than 40% compared with traditional thermal curing; the coating process can use low volatile organic solvents or solvent-free systems, which meet the requirements of green and environmental protection.

[0048] With broad application prospects, the product of this invention has the characteristics of self-healing, antistatic, high strength and toughness, and adjustable release, and can be widely used in the fields of protective film for flexible electronic device processing, transfer film for automotive interior film, release film for high-end electronic product labels, and heat transfer film for furniture decorative panels, and has good industrialization prospects. Detailed Implementation

[0049] To explain in detail the technical content, structural features, objectives, and effects of the present invention, further explanation is provided below in conjunction with the embodiments.

[0050] In the following embodiments, the raw materials used and their sources are as follows:

[0051] 1. Materials for composite reinforced base film layers

[0052] PA modified polyester resin: The modified polyester selected is PA-MOD PET-101, produced by Suzhou Polymer Materials Co., Ltd. This product is a polyethylene terephthalate copolymer containing 8% polycaprolactam (PA6), with an intrinsic viscosity of 0.72 dL / g, a melting point of 255℃, and a tensile strength of 75 MPa.

[0053] Thermoplastic polyurethane elastomer (TPU): LPR2203-93A type polyether TPU manufactured by Coeure of Italy is selected and distributed by Jiuyan New Materials (Shenzhen) Co., Ltd. This product has a Shore hardness of 93A, a melting temperature of 180-210℃, a tensile strength of 45MPa, an elongation at break of 550%, and excellent hydrolysis resistance and low-temperature toughness.

[0054] Alternative TPU suppliers: The 58300 medical-grade polyether TPU manufactured by Lubrizol Corporation of the United States can also be used, which is also distributed by Jiuyan New Materials (Shenzhen) Co., Ltd.

[0055] 2. Materials for dynamically cross-linked intermediate transition layers

[0056] Polycaprolactone diol containing maleimide groups: Prepared according to the method described in Hunan Juren New Materials Co., Ltd. patent CN121293485A. The specific preparation process is as follows: N-(2,3-dihydroxypropyl)maleimide, ε-caprolactone, and stannous octoate catalyst are added to a reaction vessel and reacted at 130℃ for 15 hours. The mixture is then cooled and discharged to obtain polycaprolactone diol containing maleimide groups with a hydroxyl value of 56 mg KOH / g. Alternatively, similar products can be purchased directly from Hunan Juren New Materials Co., Ltd.

[0057] Diisocyanate: Isophorone diisocyanate (IPDI) produced by Wanhua Chemical Group Co., Ltd. is selected. It is industrial grade and has an NCO content of 37.5%.

[0058] Difuran compounds: Furan end-capping chain extenders synthesized from 2,5-furandicarboxylic acid and 1,4-butanediol are selected, either self-made or purchased from Changzhou Ruihua Chemical Engineering Technology Co., Ltd.

[0059] Organic solvents: ethyl acetate, butanone, industrial grade, produced by Sinopharm Chemical Reagent Co., Ltd.

[0060] Conductive nanofillers:

[0061] Carbon nanotubes: LITX® 50 carbon nanotubes produced by Cabot High Performance Materials (Zhuhai) Co., Ltd. are selected, with a diameter of 10-15nm, a length of 5-20μm, and a purity of >98%.

[0062] Graphene: WDK-G-01 type graphene nanosheets produced by Qingdao Weideke Polymer Materials Co., Ltd. are selected, with a thickness of <5nm and a sheet diameter of 5-10μm.

[0063] Superconducting carbon black: Cabot's VULCAN® XC72 conductive carbon black can also be used.

[0064] 3. Self-healing release liner material

[0065] Fluorinated polysiloxane: Silsoft® 870 fluorinated silicone oil produced by Momentive Advanced Materials Group is selected, with a fluorine content of 15% and a viscosity of 500 cSt.

[0066] Acrylate prepolymer containing reversible hydrogen-bonded crosslinking groups: self-made. Methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA), and methacryloyloxyethyl carbamate (MOU, a urea-containing functional monomer) were mixed in a mass ratio of 40:30:20:10 and subjected to free radical polymerization in ethyl acetate solution using azobisisobutyronitrile (AIBN) as an initiator to obtain a prepolymer solution with a solid content of 50%.

[0067] Photoinitiator: Irgacure 184, chemical name 1-hydroxycyclohexylphenyl ketone, manufactured by BASF, was selected.

[0068] UV-curable coating solvent: Ethyl acetate or butanone, industrial grade.

[0069] 4. Other adjuvants

[0070] Catalyst: Dibutyltin dilaurate (DBTDL), analytical grade, manufactured by Aladdin Reagent Company.

[0071] Leveling agent: BYK-333, manufactured by BYK Chemical Company. Example 1

[0072] This embodiment provides a self-healing PA-modified polyester release film and its preparation method, as detailed below:

[0073] (1) Preparation of composite reinforced base film layer

[0074] PA-modified polyester resin (Suzhou Polymer, PA-MOD PET-101) and thermoplastic polyurethane elastomer (Jiuyan New Materials, agent, Keyi LPR2203-93A) were weighed at a ratio of 80:20 and premixed in a high-speed mixer for 5 minutes. The mixture was then fed into a twin-screw extruder for melt blending. The extruder temperatures were set as follows: Zone 1 240℃, Zone 2 255℃, Zone 3 265℃, Zone 4 270℃, and Die Head 265℃. After extrusion through a T-die, the melt was cast onto a cooling roller to a thickness of approximately 300μm. Biaxial stretching was then performed: longitudinal stretching temperature 85℃, stretch ratio 3.0; transverse stretching temperature 95℃, stretch ratio 3.5; heat setting temperature 210℃, time 30 seconds. This resulted in a composite reinforced base film layer with a thickness of 80μm.

[0075] (2) Preparation of dynamic cross-linked intermediate transition layer

[0076] First, a polyurethane prepolymer containing Diels-Alder bonds was prepared: 100 parts by weight of self-made polycaprolactone diol containing maleimide groups (hydroxyl value 56 mg KOH / g) was added to a reactor and heated to 100°C for vacuum dehydration for 1 hour. The temperature was then lowered to 70°C, and 26 parts by weight of IPDI and 0.1 parts by weight of DBTDL catalyst were added. The reaction was carried out under nitrogen protection for 3 hours. After the NCO content reached the theoretical value, 5 parts by weight of dibutyl 2,5-furandicarboxylate (a bisfuran compound) was added, and the reaction was continued for 1 hour to obtain a polyurethane prepolymer containing a furan-maleimide adduct.

[0077] The prepolymer was diluted with ethyl acetate to a solid content of 15%, and carbon nanotubes (Cabot LITX® 50) accounting for 3% of the prepolymer mass were added. The mixture was dispersed at high speed for 30 minutes to prepare a coating solution. The coating solution was applied to the surface of the composite reinforced base film layer obtained in step (1) using a gravure coating method, and the wet film thickness was controlled at about 15 μm. The film was then heat-treated in a hot air oven at 80°C for 5 minutes to allow the prepolymer to crosslink and form a dynamic crosslinked network, while simultaneously evaporating the solvent, resulting in a dynamic crosslinked intermediate transition layer with a thickness of about 3 μm.

[0078] (3) Preparation of self-healing release surface layer

[0079] Take 100 parts by weight of a self-made acrylate prepolymer solution containing reversible hydrogen-bonded crosslinking groups (solid content 50%), add 15 parts by weight of fluorinated polysiloxane (Momentive Silsoft® 870), 3 parts by weight of photoinitiator Irgacure 184, and 0.5 parts by weight of leveling agent BYK-333, adjust the solid content to 30% with ethyl acetate, stir evenly, and prepare a UV-curable coating.

[0080] The coating was applied to the surface of the dynamic crosslinking intermediate transition layer obtained in step (2) using a microgravure coating method, with the wet film thickness controlled at approximately 8 μm. After the solvent evaporated in the preheating zone at 60°C, the film entered the UV curing zone and was irradiated with a medium-pressure mercury lamp at a curing energy of 800 mJ / cm². 2 This forms a self-healing release layer with a thickness of approximately 2 μm.

[0081] (4) Post-processing

[0082] The multilayer film obtained in step (3) was annealed in an oven at 60°C for 2 hours to promote interlayer interface fusion and uniform distribution of dynamic bonds. Then, it was wound, slit, and packaged to obtain the finished product.

[0083] The properties of the self-healing PA-modified polyester release film prepared in this embodiment were tested and are as follows:

[0084] Total thickness: Approximately 85μm

[0085] Surface energy: 20.5 mN / m

[0086] Release force: 24g / 25mm (Test method: Tesa 7475 tape, 180° peel, 300mm / min)

[0087] Surface self-healing performance: Using an atomic force microscope probe, a scratch with a depth of approximately 1.8 μm was etched onto the film surface. After heat treatment at 100℃ for 10 minutes, the scratch depth decreased to below 0.2 μm, with a repair rate >95%. The release force after repair was 23.2 g / 25 mm, with a fluctuation range of 3.3%.

[0088] Tensile strength: 312 MPa

[0089] Elongation at break: 135%

[0090] Surface resistivity: 5.6 × 10⁻⁶ 7 Ω

[0091] Interlayer adhesion: Tested according to GB / T 2790-1995, the peel strength is 4.8 N / 25 mm. Example 2

[0092] This embodiment is basically the same as Embodiment 1, except that the components and process parameters of each layer are adjusted:

[0093] (1) Composite reinforced base film layer: The mass ratio of PA modified polyester to TPU is adjusted to 75:25; the thickness of the base film layer is adjusted to 60μm.

[0094] (2) Dynamic cross-linking intermediate transition layer: 1.5% graphene (Qingdao Wedongke WDK-G-01) was added to the coating solution to replace carbon nanotubes; the heat treatment temperature was 85℃ and the time was 4 minutes; the thickness of the transition layer was about 2.5μm.

[0095] (3) Self-healing release layer: The amount of fluorinated polysiloxane is adjusted to 10 parts; UV curing energy is 600mJ / cm 2 The surface layer is approximately 1.5 μm thick.

[0096] (4) Post-treatment: Annealing temperature 50℃, time 3 hours.

[0097] The properties of the self-healing PA-modified polyester release film prepared in this embodiment were tested and are as follows:

[0098] Total thickness: Approximately 64 μm

[0099] Surface energy: 21.8 mN / m

[0100] Release force: 36g / 25mm

[0101] Surface self-healing performance: After heat treatment at 110℃ for 8 minutes, the repair rate of scratches with a depth of 1.5μm is 92%.

[0102] Tensile strength: 288MPa

[0103] Elongation at break: 152%

[0104] Surface resistivity: 8.2 × 10⁻⁶ 6 Ω

[0105] Interlayer bonding strength: 4.3N / 25mm Example 3

[0106] This embodiment is basically the same as Embodiment 1, except that the components and process parameters of each layer are adjusted:

[0107] (1) Composite reinforced base film layer: The mass ratio of PA modified polyester to TPU is adjusted to 85:15; the thickness of the base film layer is adjusted to 100μm.

[0108] (2) Dynamic cross-linked intermediate transition layer: 2% superconducting carbon black (Cabot VULCAN® XC72) was added as a conductive filler; the heat treatment temperature was 90℃ and the time was 3 minutes; the thickness of the transition layer was about 4μm.

[0109] (3) Self-healing release layer: The amount of fluorinated polysiloxane is adjusted to 20 parts; UV curing energy is 1000 mJ / cm 2 The surface layer is approximately 3 μm thick.

[0110] (4) Post-treatment: Annealing temperature 80℃, time 1 hour.

[0111] The properties of the self-healing PA-modified polyester release film prepared in this embodiment were tested and are as follows:

[0112] Total thickness: Approximately 107 μm

[0113] Surface energy: 18.5 mN / m

[0114] Release force: 12g / 25mm

[0115] Surface self-healing performance: After heat treatment at 90℃ for 15 minutes, the repair rate of scratches with a depth of 1.8μm is 90%.

[0116] Tensile strength: 335MPa

[0117] Elongation at break: 108%

[0118] Surface resistivity: 3.4 × 10⁻⁶ 7 Ω

[0119] Interlayer bonding strength: 5.2N / 25mm

[0120] Comparative Example 1

[0121] This comparative example provides a conventional polyester release film for performance comparison with the embodiments of the present invention.

[0122] (1) Preparation of base film: Ordinary PET resin (intrinsic viscosity 0.68dL / g) was used to prepare a PET base film with a thickness of 80μm by extrusion and biaxial stretching.

[0123] (2) Preparation of release layer: The solvent-based silicone release agent (Dow Corning SYL-OFF® 7600) is mixed with crosslinking agent and platinum catalyst, diluted with toluene to a solid content of 5%, coated on the surface of PET base film, and heat-cured at 120°C for 2 minutes to form a release layer with a thickness of about 2μm.

[0124] The properties of the conventional polyester release film prepared in Comparative Example 1 were tested and are as follows:

[0125] Surface energy: 22.5 mN / m

[0126] Release force: 28g / 25mm

[0127] Surface self-healing performance: No self-healing function; scratches cannot be repaired.

[0128] Tensile strength: 205 MPa

[0129] Elongation at break: 85%

[0130] Surface resistivity: >10 13 Ω

[0131] Interlayer bonding strength: 2.1N / 25mm

[0132] Comparative Example 2

[0133] This comparative example provides a two-layer release film without a dynamically cross-linked intermediate transition layer to verify the necessity of the intermediate layer in this invention.

[0134] (1) Preparation of base film layer: Same as step (1) in Example 1, prepare PA modified polyester / TPU blend base film with a thickness of 80μm.

[0135] (2) Preparation of release surface layer: The UV-curable coating of step (3) in Example 1 is directly applied to the surface of the base film and UV-cured to form a release surface layer.

[0136] The properties of the bilayer release film prepared in Comparative Example 2 were tested and are as follows:

[0137] Surface energy: 21.0 mN / m

[0138] Release force: 25g / 25mm

[0139] Surface self-healing performance: Scratch repair rate is approximately 70% (repair conditions are the same as in Example 1).

[0140] Tensile strength: 306 MPa

[0141] Elongation at break: 128%

[0142] Surface resistivity: >10 13 Ω

[0143] Interlayer bonding strength: 1.8N / 25mm (before repair); 2.2N / 25mm (after repair)

[0144] Performance Comparison Analysis

[0145] The main performance indicators of Examples 1-3 and Comparative Examples 1-2 are summarized in Table 1.

[0146] Table 1. Performance Comparison of Examples and Comparative Examples

[0147]

[0148] As can be seen from the data in Table 1:

[0149] Self-healing performance: Examples 1-3 of this invention all exhibit excellent surface self-healing function, with a scratch repair rate of over 90% and a release force fluctuation of less than 5% after repair. Comparative Example 2, due to the lack of a dynamic cross-linked intermediate transition layer, although the release surface has some self-healing ability, the repair efficiency is significantly reduced (70%), and the release force fluctuation after repair is large (12.8%), indicating that the Diels-Alder dynamic bonds in the intermediate transition layer play a key role in synergistic repair and stable release force.

[0150] Interlayer bonding strength: The interlayer bonding strength of the embodiments of the present invention (4.3-5.2 N / 25 mm) is significantly higher than that of Comparative Example 1 (2.1 N / 25 mm) and Comparative Example 2 (1.8 N / 25 mm), indicating that the dynamic cross-linked intermediate transition layer effectively enhances the interlayer interface strength through chemical bonding.

[0151] Mechanical properties: The tensile strength (288-335MPa) and elongation at break (108-152%) of the embodiments of the present invention are superior to those of ordinary PET release film (Comparative Example 1, 205MPa / 85%), confirming that the biaxial stretching process of PA modified polyester and TPU blend can effectively improve the mechanical properties of the film.

[0152] Antistatic properties: By introducing conductive nanofillers into the intermediate transition layer, the surface resistance of all embodiments of the present invention reaches 10 Ω·cm. 7 -10 8 The Ω level meets the requirements for permanent antistatic properties; however, Comparative Example 1 and Comparative Example 2 have no antistatic function.

[0153] Release force adjustability: By adjusting the content of fluorinated polysiloxane (15 parts in Example 1, 10 parts in Example 2, and 20 parts in Example 3), the release force can be adjusted within the range of 12-36g / 25mm to meet different application requirements.

[0154] Summary of raw material procurement information

[0155] To ensure the feasibility of this invention, the procurement source information of the main raw materials used in each embodiment is summarized as follows:

[0156]

[0157] The self-healing PA-modified polyester release film provided by this invention has excellent comprehensive performance and can be widely used in the following fields:

[0158] Flexible electronics manufacturing: During the processing of precision electronic components such as flexible circuit boards and flexible displays, the release film surface is prone to micro-scratches due to contact, affecting product quality. The self-healing function of this invention can automatically repair surface damage in subsequent heat treatment processes, significantly improving yield.

[0159] Automotive interior trim films: The heat transfer process for wood grain and carbon fiber films used in automotive interior trim places extremely high demands on the release stability and surface quality of the release film. The product of this invention combines stable release force and self-healing function, meeting the stringent surface quality standards of the automotive industry.

[0160] High-end electronic product labels: The outer casing labels of electronic products such as mobile phones and laptops require release films with antistatic properties to prevent dust attraction due to static electricity. This invention imparts permanent antistatic properties to the film material through conductive fillers, meeting the requirements of cleanroom production.

[0161] Furniture decorative panels: In the hot-pressing process of large furniture decorative panels, the release film needs to withstand high temperature and pressure, and the release force must be stable and controllable. The excellent heat resistance and mechanical properties of the product of this invention can meet the requirements of such applications.

[0162] Process optimization direction

[0163] Based on the technical solutions disclosed in this invention, those skilled in the art can make the following optimizations and adjustments to meet specific application needs:

[0164] Layer thickness ratio adjustment: The thickness ratio of the three-layer structure can be adjusted according to the requirements of different applications for mechanical properties and self-healing capabilities. For example, for applications with extremely high surface quality requirements, the release layer thickness can be appropriately increased; for applications with high mechanical strength requirements, the base film layer thickness can be increased.

[0165] Optimization of conductive filler type and content: Different types of conductive fillers can be selected and their addition amount optimized according to the target surface resistivity. Carbon nanotubes and graphene have low percolation thresholds, and good conductivity can be obtained by adding a small amount; conductive carbon black has a low cost but requires a higher addition amount.

[0166] Precise control of release force: Release force can be more precisely controlled by adjusting the content, molecular weight, and fluorine content of fluorinated polysiloxane. Other types of release force modifiers, such as long-chain alkyl silicone oils, can also be introduced.

[0167] Self-healing temperature optimization: By adjusting the structure and crosslinking density of Diels-Alder bonds, the temperature range of its reversible reaction can be changed, so that the self-healing trigger temperature can be matched with the post-processing temperature of a specific application.

[0168] Coating process improvement: Multi-layer simultaneous coating technology can be adopted to further improve production efficiency; solvent-free UV curing systems can also be developed to achieve completely green and environmentally friendly production.

Claims

1. A self-healing PA-modified polyester release film, characterized in that, include: Composite reinforced base film layer Dynamic cross-linked intermediate transition layer, and Self-healing release liner; The dynamic cross-linking intermediate transition layer is disposed on one side surface of the composite reinforced base film layer, and the self-healing release surface layer is disposed on the side surface of the dynamic cross-linking intermediate transition layer away from the composite reinforced base film layer; The dynamic crosslinking intermediate transition layer comprises a polymer network with Diels-Alder dynamic covalent bonds, and the self-healing release surface layer comprises a fluorinated polysiloxane and a polyacrylate copolymer with reversible hydrogen bonding.

2. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The composite reinforced base film layer is a thin film formed by biaxial stretching of a blend of PA modified polyester resin and thermoplastic polyurethane elastomer. The mass ratio of the PA-modified polyester resin to the thermoplastic polyurethane elastomer is 70:30 to 85:

15. The thickness of the composite reinforced base film is 50-100 μm.

3. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The thickness of the dynamic cross-linked intermediate transition layer is 2-5 μm; The polymer network with Diels-Alder dynamic covalent bonds is formed by crosslinking a furan-maleimide adduct type polyurethane prepolymer. Within a temperature range of 80-120℃, the Diels-Alder bonds in the dynamically cross-linked intermediate transition layer undergo reversible breakage and recombination.

4. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The thickness of the self-healing release layer is 1-3 μm; The fluorinated polysiloxane contains 10-20% by mass in the self-healing release layer. The surface energy of the self-healing release layer is 18-22 mN / m.

5. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The self-healing release layer can repair surface micro-damage with a depth of ≤2μm under heat treatment conditions of 80-120℃, and the fluctuation range of the release force after repair is less than 5%.

6. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The self-healing release surface is cured by ultraviolet light to form an interpenetrating network structure, and the reversible hydrogen bond crosslinking is provided by urethane groups or urea groups in the acrylate copolymer.

7. The self-healing PA-modified polyester release film according to claim 1, characterized in that, The dynamic cross-linked intermediate transition layer also contains conductive nanofillers, which are one or more of carbon nanotubes, graphene, or conductive carbon black. The surface resistance of the self-healing PA-modified polyester release film is ≤10. 8 Ω.

8. A method for preparing a self-healing PA-modified polyester release film as described in any one of claims 1-7, characterized in that, Includes the following steps: Step (1) Preparation of composite reinforced base film layer: PA modified polyester resin and thermoplastic polyurethane elastomer are melt-blended in proportion, and then extruded, cast and biaxially stretched to form composite reinforced base film layer; Step (2) Preparation of dynamic crosslinking intermediate transition layer: A polyurethane prepolymer solution containing furan-maleimide Diels-Alder adduct is coated on the surface of the composite reinforced base film layer, and a dynamic crosslinking intermediate transition layer is formed by heat treatment; Step (3) Preparation of self-healing release surface: Fluorine-containing polysiloxane modified acrylate, photoinitiator and reversible hydrogen bond crosslinking agent are mixed and coated on the dynamic crosslinking intermediate transition layer, and cured by ultraviolet light to form a self-healing release surface; Step (4) Post-treatment: Anneal the membrane material obtained in step (3) at 50-80℃ for 1-3 hours.

9. The preparation method according to claim 8, characterized in that, The heat treatment in step (2) is performed at a temperature of 70-90°C for 3-8 minutes. The UV curing energy in step (3) is 600-1000 mJ / cm. 2 .

10. The self-healing PA-modified polyester release film according to any one of claims 1-7, characterized in that, The release force of the self-healing PA-modified polyester release film is 5-50g / 25mm, which can be precisely controlled by adjusting the content of fluorinated polysiloxane.

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