Flame retardant bopet film

Abstract

The application relates to the technical field of plastic film production and processing, in particular to a flame-retardant BOPET film which comprises a BOPET base film; the raw material of the BOPET base film comprises a flame-retardant toughening agent; the flame-retardant toughening agent is prepared from terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate and a functional flame-retardant polymer; and the functional flame-retardant polymer is a phosphate with a complex phosphorus structure. The flame-retardant BOPET film can significantly improve the flame-retardant performance of the BOPET film while keeping good mechanical properties by introducing the flame-retardant toughening agent into the base film, so as to meet the requirements of high-end electronic and electrical products and new energy automobile interior lamp scenes for safety materials.

Description

Technical Field

[0001] This invention relates to the field of plastic film production and processing technology, and in particular to a flame-retardant BOPET film. Background Technology

[0002] BOPET (biaxially oriented polyester) film is widely used in various fields such as electronic and electrical insulation, packaging materials, industrial substrates, architectural decoration, and optical display devices due to its excellent mechanical strength, dimensional stability, chemical resistance, high transparency, and good electrical insulation properties. In these applications, especially in the internal components of electronic and electrical equipment, building interior materials, vehicle interiors, and high-end packaging, material safety is paramount, placing clear demands on the flame-retardant properties of the film. In the event of a fire, materials with good flame-retardant properties can effectively slow the spread of flames, inhibit heat release, and reduce the generation of toxic fumes, thereby buying valuable time for evacuation and minimizing property damage.

[0003] However, traditional BOPET film is a flammable material with a low limiting oxygen index (LOI). It is easily ignited by open flames and accompanied by dripping, which not only accelerates the spread of fire, but the drippings may also ignite other items, posing a significant safety hazard.

[0004] Existing flame-retardant BOPET film technologies generally suffer from the problem of not being able to balance excellent flame-retardant performance with comprehensive mechanical properties. Although the addition of many high-efficiency flame retardants can improve the flame-retardant rating, they often have a negative impact on the key mechanical properties of the film. Summary of the Invention

[0005] To address the problem that existing flame-retardant BOPET films struggle to balance flame retardancy and mechanical properties, this invention provides a flame-retardant BOPET film. This BOPET film significantly improves its flame retardancy while maintaining good mechanical properties by introducing a flame-retardant toughening agent into the BOPET base film, thus solving the problem of existing flame-retardant BOPET films struggling to balance flame retardancy and mechanical properties.

[0006] The technical solution adopted by this invention to solve its technical problem is: A flame-retardant BOPET film, comprising a BOPET base film; The raw materials for the BOPET base film include flame retardant toughening agents; The flame retardant toughening agent is prepared using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant polymers as raw materials. The functional flame-retardant polymer is a phosphate with a complex phosphorus structure.

[0007] Optionally, the functional flame-retardant polymer is prepared according to the following method: S201: The flame retardant intermediate is heated at 130-150℃ until it melts, and 2,2'-diallylbisphenol A is added under stirring to react and obtain crude flame retardant monomer. S202: The crude flame retardant monomer is dissolved in a solvent, and after stirring and washing at a temperature of 90-100℃, it is dried under vacuum at 180-190℃ to obtain a refined flame retardant monomer. S203: Mix dichloromethane, the refined flame retardant monomer and N,N-diethylethylamine, stir until dissolved, and then add phenyl dichlorophosphine dropwise to obtain a mixed solution; S204: The mixed solution is reacted under an inert gas atmosphere at 40-45°C, then extracted with petroleum ether and dried at 50-60°C to obtain a functional flame-retardant polymer. The flame retardant intermediate is a substance containing biphenyl rings and phenanthrene rings.

[0008] Optionally, the flame retardant intermediate is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0009] Optionally, the amount of the flame retardant intermediate added in step S201 is 8-16 parts by weight, and the amount of 2,2'-diallyl bisphenol A added is 4-8 parts.

[0010] Optionally, by weight, the amount of dichloromethane added in step S203 is 50-100 parts; the amount of refined flame retardant monomer added is 37-74 parts; the amount of N,N-diethylethylamine added is 5-10 parts; and the amount of phenyl dichlorophosphine added is 10-20 parts.

[0011] Optionally, the flame retardant toughening agent is prepared according to the following method: S101: Using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant dispersion as raw materials, the first stage of the reaction is carried out under an inert gas protective atmosphere at 200-240℃ and 0.5-0.7 MPa to obtain reaction mixture I; S102: Raise the temperature to 240-260℃ and carry out the second stage of heat preservation reaction to obtain reaction mixture II; S103: Reduce the pressure to 200-300 Pa, then raise the temperature to 260-270 °C to carry out the third stage of heat preservation reaction, and obtain reaction mixture III; S104: Small molecule impurities in reaction mixture III are removed by distillation, and the flame retardant toughening agent is obtained by melt extrusion granulation. The functional flame-retardant dispersion is obtained by mixing and dispersing the functional flame-retardant polymer, ethylene glycol, and dispersant as raw materials.

[0012] Optionally, by weight, the amount of terephthalic acid added in step S101 is 1040 parts; the amount of ethylene glycol added is 450-650 parts; the amount of antimony trioxide added is 0.5-1.0 parts; the amount of trimethyl phosphate added is 0.5-1.0 parts; and the amount of functional flame retardant dispersion added is 100-200 parts.

[0013] Optionally, by weight fraction, the amount of the functional flame retardant polymer added to the functional flame retardant dispersion is 10-20 parts; the amount of ethylene glycol added is 80-90 parts; and the amount of dispersant added is 3-5 parts.

[0014] Optionally, the flame-retardant BOPET film further includes a functionalized coating applied to the surface of the BOPET base film; The functionalized coating is prepared by applying a composite flame-retardant coating to the surface of the BOPET base film; The composite flame-retardant coating is prepared using resin-based liquid, surface flame retardant A, and surface flame retardant B as raw materials. The surface flame retardant A is prepared according to the following method: S401: Add deionized water to montmorillonite, stir, then add polyvinyl alcohol and continue stirring to obtain flame retardant premix A; S402: Add pentanediol to the flame retardant premix A, sonicate, and dry at 60-80°C to obtain surface flame retardant A; The surface flame retardant B is prepared according to the following method: S501: Dichloromethane, acyl halide compounds, and triethylamine are mixed to obtain flame retardant premix B; S502: Dichloromethane and phosphonate compounds are mixed and then added dropwise to the flame retardant premix B at 0-5°C. After the addition is complete, the mixture is reacted at 30-35°C to obtain flame retardant liquid B. S503: Extract the flame retardant liquid B with deionized water, and dry it at 60-80℃ to obtain surface flame retardant B.

[0015] Optionally, the acyl halide compound is adipic acid chloride; the phosphonate compound is diethyl hydroxymethylphosphonate.

[0016] The beneficial effects of this invention are: The flame-retardant BOPET film provided by this invention significantly improves the flame-retardant properties of the BOPET film while maintaining good mechanical properties by introducing a flame-retardant toughening agent into the base film, so as to meet the requirements of high-end electronic and electrical and new energy vehicle interior lighting scenarios for safety materials. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the structure of the BOPET film in this invention. Detailed Implementation

[0019] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] Currently, flame-retardant modification of BOPET films mainly relies on adding flame-retardant fillers or additives to the PET matrix. To meet the stringent safety requirements of high-end electronics and electrical industries, BOPET films need to possess excellent flame-retardant properties such as a high limiting oxygen index and a high UL94 rating. However, existing technologies often require the introduction of high amounts of flame retardants into the system to achieve these flame-retardant effects. As heterogeneous components, these flame retardants disrupt the homogeneity of the PET matrix, hindering the formation of highly oriented molecular chains and crystalline structures. Furthermore, due to their inherent brittleness, compatibility differences with the matrix, and the dilution and stress concentration effects caused by high addition amounts, they significantly weaken the tensile strength and elongation at break of the material. This strong correlation between improved flame-retardant performance and deteriorated mechanical properties makes it difficult for films to simultaneously achieve both flame retardancy and mechanical load-bearing capacity, severely limiting their application in reliability-sensitive scenarios.

[0021] Therefore, to address the problem that existing BOPET films struggle to simultaneously achieve flame retardant and mechanical properties, this invention provides a flame-retardant BOPET film, see [link to relevant documentation]. Figure 1 As shown, the flame-retardant BOPET film includes a BOPET base film; to impart flame-retardant properties to the BOPET film, the raw materials of the BOPET base film preferably include a flame-retardant toughening agent; to improve the flame-retardant properties of the BOPET film without sacrificing its mechanical properties, the flame-retardant toughening agent is preferably prepared from terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame-retardant polymers.

[0022] Antimony trioxide is introduced as a catalyst to activate reaction intermediates, promote polycondensation reaction, optimize molecular weight, and improve the mechanical strength and thermal stability of PET; trimethyl phosphate is introduced as a stabilizer to improve thermal stability.

[0023] The preferred functional flame-retardant polymer of this invention is a phosphate with a composite phosphorus structure. The phosphate with the composite phosphorus structure achieves the flame-retardant effect by relying on its high phosphorus content. It utilizes its thermal decomposition to catalyze the dehydration and cross-linking of the PET matrix, forming a dense and stable expanded char layer that isolates oxygen and heat, thereby achieving the flame-retardant effect. In addition, the phosphorus element participates in the formation of the cross-linking network, which enhances the integrity of the barrier.

[0024] Specifically, the BOPET base film of the present invention preferably comprises a polyester core layer and a polyester surface layer co-extruded on the upper and lower surfaces of the polyester core layer; more preferably, the polyester surface layer comprises the following components by weight: 10-15 parts of open-faced masterbatch; 75-85 parts of PET polyester chips; 5-10 parts of flame retardant toughening agent; The polyester core layer comprises the following components by weight: 90-95 parts of PET polyester chips; 5-10 parts of flame retardant toughening agent.

[0025] The flame-retardant BOPET film provided by this invention significantly improves the flame-retardant properties of the BOPET film while maintaining good mechanical properties by introducing a flame-retardant toughening agent into the base film, so as to meet the requirements of high-end electronic and electrical and new energy vehicle interior lighting scenarios for safety materials.

[0026] Furthermore, based on the demand for high-performance safety materials in many fields such as high-end electronics and electrical engineering, in order to take into account the excellent flame retardant properties and comprehensive mechanical properties of BOPET film, and to give it excellent comprehensive performance, this invention preferably uses Yizheng Chemical Fiber FG610 chips as the open masterbatch in the polyester surface layer; and uses Yizheng Chemical Fiber FG600 chips as the PET polyester chips in the polyester surface layer and the polyester core layer.

[0027] The preferred functional flame-retardant polymer of this invention is prepared according to the following method: S201: The flame retardant intermediate is heated at 130-150℃ until it melts, and 2,2'-diallylbisphenol A is added under stirring to react and obtain crude flame retardant monomer. This step can be performed as follows: The flame retardant intermediate was heated in an oil bath at 130-150℃ until it was completely melted. 2,2'-diallylbisphenol A was added under stirring. After the reaction was completed, crude flame retardant monomer was obtained. S202: The crude flame retardant monomer is dissolved in a solvent, and after stirring and washing at a temperature of 90-100℃, it is dried under vacuum at 180-190℃ to obtain the refined flame retardant monomer. Preferably, the solvent in this step is a mixture of ethanol and deionized water, and preferably, the amount of ethanol added is 100-120 parts by weight, and the amount of deionized water added is 300-360 parts by weight. This step can be performed as follows: The crude flame retardant monomer is dissolved in 100-120 parts by weight of ethanol and 300-360 parts by weight of deionized water, and stirred and washed at 90-100℃ for 30-45 minutes to remove impurities from the crude flame retardant monomer. The washing is repeated 4-5 times, and then dried under vacuum at 180-190℃. After the solvent has completely evaporated, the refined flame retardant monomer is obtained. S203: Mix dichloromethane, refined flame retardant monomer and N,N-diethylethylamine, stir until dissolved, and then add phenyl dichlorophosphine dropwise to obtain a mixed solution; This step can be performed as follows: Dichloromethane was added to a three-necked flask, along with the above-mentioned purified flame retardant monomer and N,N-diethylethylamine. After stirring until completely dissolved, phenyl dichlorophosphine was slowly added dropwise to obtain a mixed solution. S204: After reacting the mixed solution under an inert gas atmosphere at 40-45℃, it is extracted with petroleum ether and dried at 50-60℃ to obtain a functional flame-retardant polymer. This step can be performed as follows: The mixed solution was kept at 40-45℃ under a nitrogen atmosphere for 4-5 hours. After the reaction was completed, it was extracted with petroleum ether and dried thoroughly at 50-60℃ to obtain the functional flame retardant polymer. The preferred flame retardant intermediate of the present invention is a substance containing a biphenyl ring and a phenanthrene ring structure.

[0028] Furthermore, the flame retardant intermediate preferred by the present invention is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0029] Specifically, in this invention, the amount of flame retardant intermediate added in step S201 is preferably 8-16 parts by weight, and the amount of 2,2'-diallyl bisphenol A added is 4-8 parts by weight; preferably, in step S203, the amount of dichloromethane added is 50-100 parts by weight, the amount of refined flame retardant monomer added is 37-74 parts, the amount of N,N-diethylethylamine added is 5-10 parts, and the amount of phenyl dichlorophosphine added is 10-20 parts by weight.

[0030] Specifically, the chemical reaction in step S201 is shown in the following formula: ; The chemical reaction in step S204 is shown in the following equation: ; The value of n ranges from 20 to 200.

[0031] The present invention further introduces flame-retardant components into the system by preparing a flame-retardant toughening agent using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame-retardant polymers as raw materials, which helps to improve the flame-retardant performance and mechanical properties of the film.

[0032] The preferred flame-retardant toughening agent of this invention is prepared according to the following method: S101: Using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant dispersion as raw materials, the first stage of the reaction is carried out under an inert gas protective atmosphere at 200-240℃ and 0.5-0.7 MPa to obtain reaction mixture I; This step can be performed as follows: Add terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant dispersion to the reactor. Under a nitrogen protective atmosphere, raise the temperature of the reactor to 200-240℃ and the pressure to 0.5-0.7 MPa, and maintain the temperature for 60-90 minutes. S102: Raise the temperature to 240-260℃ and carry out the second stage of heat preservation reaction to obtain reaction mixture II; This step can be performed as follows: Raise the temperature in the reactor to 240-260℃ and hold for 90-135 minutes; S103: Reduce the pressure to 200-300 Pa, then raise the temperature to 260-270 °C to carry out the third stage of heat preservation reaction, and obtain reaction mixture III; This step can be performed as follows: Reduce the pressure in the reactor to 200-300 Pa, then raise the temperature in the reactor to 260-270℃ and hold for 150-180 min. S104: Small molecule impurities in reaction mixture III are removed by distillation, and the flame retardant toughening agent is obtained by melt extrusion granulation. The flame retardant toughening agent obtained by this invention has a viscosity of 0.650-0.700 dL / g, a melting point of 250-270℃, an average molecular weight of 30000-35000, and a functional flame retardant polymer mass percentage of 0.5-1.0%.

[0033] The functional flame retardant dispersion is obtained by mixing and dispersing functional flame retardant polymers, ethylene glycol, and dispersants.

[0034] To improve dispersion uniformity, polyethylene glycol is preferred as the dispersant in this invention.

[0035] This invention introduces functional flame-retardant polymers into flame-retardant toughening agents through a functional flame-retardant dispersion, and then effectively improves the flame-retardant properties and comprehensive mechanical properties of BOPET films through the synergistic effect of the flame-retardant toughening agent and the above-mentioned components.

[0036] Specifically, in this invention, the amount of terephthalic acid added in step S101 is preferably 1040 parts by weight; the amount of ethylene glycol added is 450-650 parts; the amount of antimony trioxide added is 0.5-1.0 parts; the amount of trimethyl phosphate added is 0.5-1.0 parts; and the amount of functional flame retardant dispersion added is 100-200 parts.

[0037] Furthermore, in this invention, the amount of functional flame retardant polymer added to the functional flame retardant dispersion is preferably 10-20 parts by weight; the amount of ethylene glycol added is 80-90 parts; and the amount of dispersant added is 3-5 parts.

[0038] Specifically, the preferred functional flame-retardant dispersion is prepared according to the following method: According to the weight percentage, 10-20 parts by weight of functional flame retardant polymer, 80-90 parts by weight of ethylene glycol, and 3-5 parts by weight of dispersant are added to a high-speed mixer for uniform dispersion and mixing at a dispersion speed of 800-1000 rpm and a mixing time of 90-120 min to obtain a functional flame retardant dispersion.

[0039] The functional flame-retardant dispersion prepared by the above method helps to improve the uniformity of dispersion of functional flame-retardant polymers in the system, improve their compatibility with the system, and further help them to work synergistically with other components in the system to improve film performance.

[0040] To further improve flame retardant performance without sacrificing mechanical properties, the present invention preferably includes a functionalized coating applied to the surface of the BOPET base film; the functionalized coating is prepared by applying a composite flame retardant coating to the surface of the BOPET base film; the composite flame retardant coating is prepared using resin-based liquid, surface flame retardant A, and surface flame retardant B as raw materials.

[0041] To ensure the flame-retardant properties of the BOPET film, the present invention preferably uses a water-based composite flame-retardant coating, and further preferably prepares the composite flame-retardant coating according to the following method: S301: Add 100-150 parts by weight of water-based resin base material to a mixing tank, and add 1.0-1.5 parts by weight of wetting and leveling agent and 0.2-1.0 parts by weight of defoamer in sequence while stirring at a low speed of 300-500 rpm. Mix for 10-20 minutes to obtain resin base liquid. S302: Mix 1.0-1.5 parts by weight of coupling agent, 2-3 parts by weight of dispersant, 10-20 parts by weight of surface flame retardant A, and 10-20 parts by weight of surface flame retardant B, and disperse at high speed of 2000-3000 rpm for 15-20 min to obtain surface flame retardant slurry. S303: Slowly add the surface flame retardant slurry to the resin base liquid, and stir at a medium speed of 600-800 rpm for 20-30 minutes. After stirring, add deionized water to adjust the viscosity to 100-400 mPas@25℃, and filter to obtain the composite flame retardant coating.

[0042] Preferably, the waterborne resin base is an acrylic emulsion or a polyurethane emulsion (solid content 40±2%); preferably, the wetting and leveling agent is selected from at least one of BYK-333, BYK-345, and BYK-346; preferably, the defoamer is selected from at least one of BYK-024, BYK-051, and BYK-065; preferably, the coupling agent is selected from at least one of KH-550 and KH-570; and preferably, the dispersant is selected from at least one of BYK-190 and BYK-180.

[0043] The preferred surface flame retardant A of this invention is prepared according to the following method: S401: Add deionized water to montmorillonite, stir, then add polyvinyl alcohol and continue stirring to obtain flame retardant premix A; This step can be performed as follows: Add 500-1000 parts by weight of deionized water to 5-10 parts by weight of montmorillonite, and stir at a medium speed of 600-800 rpm for 12-24 hours. Then add 5-10 parts by weight of polyvinyl alcohol and continue stirring for 4-6 hours to obtain flame retardant premix A. S402: Add pentanediol to flame retardant premix A, sonicate, and dry at 60-80℃ to obtain surface flame retardant A; This step can be performed as follows: Add 1-2 parts by weight of pentanediol to flame retardant premix A, sonicate for 30-60 minutes, and dry thoroughly at 60-80℃ to obtain surface flame retardant A.

[0044] The surface flame retardant A prepared in this invention is NMT montmorillonite. Its core mechanism for achieving flame retardant effect comes from its unique nano-layered structure, which achieves a unique physical flame retardant effect. During combustion, it can migrate to the outermost layer of the melt to form a dense ceramic barrier layer, which blocks oxygen diffusion, inhibits heat conduction, and prevents volatile substances from overflowing, thereby achieving a flame retardant effect.

[0045] Surface flame retardant B is prepared according to the following method: S501: Dichloromethane, acyl halide compounds, and triethylamine are mixed to obtain flame retardant premix B; This step can be performed as follows: Add 50-100 parts by weight of dichloromethane, 3.5-7.0 parts by weight of acyl halide compound, and 1-2 parts by weight of triethylamine to a flask, and after complete dissolution, obtain flame retardant premix B; S502: Dichloromethane and phosphonate compounds are mixed and then added dropwise to flame retardant premix B at 0-5℃. After the addition is complete, the mixture is reacted at 30-35℃ to obtain flame retardant liquid B. This step can be performed as follows: Add 50-100 parts by weight of dichloromethane and 3.5-7.0 parts by weight of phosphonate compounds to a flask. After they are fully dissolved, slowly add them dropwise to flame retardant premix B at 0-5℃. After the addition is complete, react at 30-35℃ for 6-8 hours to obtain flame retardant liquid B. S503: Flame retardant liquid B is extracted with deionized water and dried at 60-80℃ to obtain surface flame retardant B.

[0046] The preferred acyl halide compound of the present invention is adipicoyl chloride; the preferred phosphonate compound is diethyl hydroxymethylphosphonate.

[0047] The reaction process in step S502 of this invention is shown in the following formula: .

[0048] The surface flame retardant B prepared by this invention is a halogenated organic phosphate ester. The phosphorus-chlorine flame retardant can be achieved by chemical methods. Halogens inhibit free radical reactions, and phosphorus can inhibit molten dripping and avoid secondary ignition.

[0049] This invention introduces surface flame retardant A and surface flame retardant B into a composite flame retardant coating. Under the synergistic effect of surface flame retardant A and surface flame retardant B, combined with chemical and physical flame retardant methods, the entire combustion chain is covered, achieving highly efficient flame retardancy.

[0050] After the composite flame-retardant coating is applied to the surface of the BOPET base film, a composite flame-retardant coating is prepared. Through the synergistic effect of the composite flame-retardant coating with the polyester surface layer and the polyester core layer, the flame-retardant performance can be improved while ensuring the comprehensive mechanical properties of the BOPET film.

[0051] The flame-retardant BOPET film provided by this invention can significantly improve the flame-retardant properties of BOPET film while maintaining good mechanical properties through the synergistic effect of matrix blending modification and surface functional coating, so as to meet the strict requirements of safety materials in high-end electronic and electrical and new energy vehicle interior lighting scenarios.

[0052] The flame-retardant BOPET film provided in this invention can be prepared according to the following method: S1: According to the formula, the polyester surface layer material is fed to extruder A for melt extrusion; the polyester core layer material is fed to extruder B for melt extrusion. S2: The melt-extruded polyester surface layer material and polyester core layer material are melt-extruded through a three-layer co-extrusion die and formed into an ABA three-layer co-extrusion sheet using rotating cooling rollers; S3: After preheating, the thick sheet is stretched bidirectionally, with a longitudinal stretch of 3.0-3.5 times and a transverse stretch of 3.0-3.5 times. S4: After the biaxially stretched thick sheet is heat-set, cooled, drawn and wound up and slit at 230-250℃, a BOPET base film is obtained; S5: Using the pressure of the coating machine rollers and the scraping of the coating knife, the composite flame retardant coating is applied to the surface of the BOPET base film; S6: Place the coated BOPET base film into a drying oven and dry and cure the coating by heating and ventilation. The drying temperature is 160-180℃ and the drying time is 30-60 minutes. S7: Cool the dried BOPET base film through a cooling roller to reduce its surface temperature to below room temperature, allowing the coating to fully cure and obtain a flame-retardant BOPET film.

[0053] This invention first obtains a flame-retardant BOPET base film by combining various materials in the polyester surface layer and the polyester core layer, while ensuring good comprehensive mechanical properties. Then, a composite flame-retardant coating is prepared on the surface of the flame-retardant BOPET base film by applying a composite flame-retardant coating, thereby further improving the flame-retardant performance of the BOPET film.

[0054] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0055] Example 1 This embodiment provides a flame-retardant BOPET film, which includes a BOPET base film and a functionalized coating applied to the surface of the BOPET base film; the functionalized coating is prepared by applying a composite flame-retardant coating to the surface of the BOPET base film. BOPET base film includes a polyester core layer and polyester surface layers co-extruded on the upper and lower surfaces of the polyester core layer; By weight, the polyester surface layer comprises the following components: 15 parts of open-face masterbatch; 75 portions of PET polyester chips; 10 parts flame retardant toughening agent; The polyester core layer comprises the following components by weight: 90 portions of PET polyester chips; 10 parts flame retardant toughening agent.

[0056] Among them, the open-face masterbatch is Yizheng FG610 chips; the PET polyester chips are Yizheng FG600 chips; The polyester core layer has a thickness of 100um, the polyester surface layer has a thickness of 12.5um*2 layers, and the functional coating has a thickness of 100nm*2 layers.

[0057] The preparation process of the flame retardant toughening agent is as follows: S101: Add 1040 parts by weight of terephthalic acid, 550 parts by weight of ethylene glycol, 0.5 parts by weight of antimony trioxide, 0.5 parts by weight of trimethyl phosphate, and 200 parts by weight of functional flame retardant dispersion to the reactor. Under a nitrogen protective atmosphere, raise the temperature of the reactor to 220°C and the pressure to 0.5 MPa, and keep it at that temperature for 90 minutes. S102: Raise the temperature in the reactor to 250℃ and hold for 120 minutes; S103: Reduce the pressure in the reactor to 250 Pa, then raise the temperature in the reactor to 265 °C and hold for 150 min; S104: Small molecule impurities in the reaction system are removed by distillation, and finally, a flame retardant toughening agent with a viscosity of 0.670 dL / g, a melting point of 265℃, an average molecular weight of 32000, and a functional flame retardant polymer mass percentage of 1.0% is obtained by melt extrusion granulation.

[0058] The preparation process of the functional flame-retardant dispersion is as follows: S201: 12 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were heated in an oil bath at 140°C until completely melted. 6 parts by weight of 2,2'-diallylbisphenol A were added under stirring. After the reaction was complete, a crude flame-retardant monomer was obtained. S202: The crude flame retardant monomer is dissolved in 120 parts by weight of ethanol and 340 parts by weight of deionized water, and washed with stirring at 90°C for 40 min to remove impurities from the crude flame retardant monomer. The washing is repeated 5 times. The monomer is then dried under vacuum at 180°C until the solvent is completely evaporated to obtain the refined flame retardant monomer. S203: Add 100 parts by weight of dichloromethane to a three-necked flask, along with 74 parts by weight of the above-mentioned purified flame-retardant monomer and 10 parts by weight of N,N-diethylethylamine. Stir until completely dissolved, then slowly add 15 parts by weight of phenyldichlorophosphine. Incubate the mixture at 45°C under a nitrogen atmosphere for 4 hours. After the reaction is complete, extract with petroleum ether and dry thoroughly at 60°C to obtain the functional flame-retardant polymer.

[0059] S204: 20 parts by weight of functional flame retardant polymer, 80 parts by weight of ethylene glycol and 4 parts by weight of polyethylene glycol are added to a high-speed mixer for uniform dispersion and mixing. The dispersion speed is 800 rpm and the mixing time is 100 min to obtain a functional flame retardant dispersion. The preparation process of the composite flame-retardant coating in this embodiment is as follows: S301: Add 120 parts by weight of polyurethane emulsion (solid content 40%) to a mixing tank, and add 1.0 parts by weight of wetting and leveling agent BYK-333 and 0.2 parts by weight of defoamer BYK-024 in sequence while stirring at a low speed of 300 rpm. Mix for 15 min to obtain resin base liquid. S302: Mix 1.0 parts by weight of coupling agent KH-550, 2 parts by weight of dispersant BYK-190, 15 parts by weight of surface flame retardant A, and 15 parts by weight of surface flame retardant B, and disperse at 3000 rpm for 15-20 min to obtain surface flame retardant slurry. S303: Slowly add the surface flame-retardant slurry to the resin base liquid, and stir at a medium speed of 800 rpm for 30 minutes. After stirring, add deionized water to adjust the viscosity to 250 mPas@25℃, and filter to obtain the composite flame-retardant coating; The preparation process of surface flame retardant A is as follows: S401: Add 700 parts by weight of deionized water to 7 parts by weight of montmorillonite and stir at a medium speed of 700 rpm for 18 hours. Then add 10 parts by weight of polyvinyl alcohol and continue stirring for 5 hours to obtain flame retardant premix A; S402: Add 1.5 parts by weight of pentanediol to flame retardant premix A and sonicate for 45 min. After thorough drying at 60℃, surface flame retardant A is obtained; The preparation process of surface flame retardant B is as follows: S501: Add 50 parts by weight of dichloromethane, 3.5 parts by weight of adipic acid chloride, and 1.5 parts by weight of triethylamine to a flask, and dissolve them completely to obtain flame retardant premix B; S502: Add 50 parts by weight of dichloromethane and 3.5 parts by weight of diethyl hydroxymethylphosphonate to a flask. After dissolving completely, slowly add the mixture dropwise to flame retardant premix B at 1°C. After the addition is complete, react at 30°C for 7 hours to obtain flame retardant liquid B. S503: Flame retardant liquid B is extracted with deionized water and then thoroughly dried at 60°C to obtain surface flame retardant B.

[0060] The preparation process of the flame-retardant BOPET film in this embodiment is as follows: S1: According to the formula, the polyester surface layer material is fed to extruder A for melt extrusion; the polyester core layer material is fed to extruder B for melt extrusion. S2: The melt-extruded polyester surface layer material and polyester core layer material are melt-extruded through a three-layer co-extrusion die and formed into an ABA three-layer co-extrusion sheet using rotating cooling rollers; S3: After preheating, the thick sheet is stretched bidirectionally, with a longitudinal stretch of 3.25 times and a transverse stretch of 3.25 times. S4: After the biaxially stretched thick sheet is heat-set, cooled, pulled and wound up and cut at 245°C, a BOPET base film is obtained; S5: Using the pressure of the coating machine rollers and the scraping of the coating knife, the composite flame retardant coating is applied to the surface of the BOPET base film; S6: Place the coated BOPET base film into a drying oven and dry and cure the coating by heating and ventilation. The drying temperature is 160℃ and the drying time is 60min. S7: Cool the dried BOPET base film through a cooling roller to reduce its surface temperature to below room temperature, allowing the coating to fully cure and obtain a flame-retardant BOPET film.

[0061] Example 2 The difference between this embodiment and Embodiment 1 is that in step S302, the amount of surface flame retardant A added is 10 parts by weight, and the amount of surface flame retardant B added is 20 parts by weight.

[0062] Example 3 The difference between this embodiment and Embodiment 1 is that in step S302, the amount of surface flame retardant A added is 20 parts by weight, and the amount of surface flame retardant B added is 10 parts by weight.

[0063] Example 4 The difference between this embodiment and Embodiment 1 is that the drying temperature in step S6 is 180°C and the drying time is 30 minutes.

[0064] Example 5 The difference between this embodiment and Embodiment 1 is that no functional coating is provided.

[0065] Comparative Example 1 The difference between this comparative example and Example 1 is that the preparation process of the composite flame-retardant coating is as follows: S301: Add 120 parts by weight of polyurethane emulsion (solid content 40%) to a mixing tank, and add 1.0 parts by weight of wetting and leveling agent BYK-333 and 0.2 parts by weight of defoamer BYK-024 in sequence while stirring at a low speed of 300 rpm. Mix for 15 min to obtain resin base liquid. S302: Mix 1.0 parts by weight of coupling agent KH-550, 2 parts by weight of dispersant BYK-190 and 15 parts by weight of surface flame retardant B, and disperse at 3000 rpm for 15-20 min to obtain surface flame retardant slurry. S303: Slowly add the surface flame-retardant slurry to the resin base liquid, and stir at a medium speed of 800 rpm for 30 minutes. After stirring, add deionized water to adjust the viscosity to 250 mPas@25℃, and filter to obtain the composite flame-retardant coating.

[0066] Comparative Example 2 The difference between this comparative example and Example 1 is that the preparation process of the composite flame-retardant coating is as follows: S301: Add 120 parts by weight of polyurethane emulsion (solid content 40%) to a mixing tank, and add 1.0 parts by weight of wetting and leveling agent BYK-333 and 0.2 parts by weight of defoamer BYK-024 in sequence while stirring at a low speed of 300 rpm. Mix for 15 min to obtain resin base liquid. S302: Mix 1.0 parts by weight of coupling agent KH-550, 2 parts by weight of dispersant BYK-190 and 15 parts by weight of surface flame retardant A, and disperse at 3000 rpm for 15-20 min to obtain surface flame retardant slurry; S303: Slowly add the surface flame-retardant slurry to the resin base liquid, and stir at a medium speed of 800 rpm for 30 minutes. After stirring, add deionized water to adjust the viscosity to 250 mPas@25℃, and filter to obtain the composite flame-retardant coating.

[0067] Comparative Example 3 The difference between this comparative example and Example 1 is that, by weight, the polyester surface layer comprises the following components: 15 parts of open-face masterbatch; 75 portions of PET polyester chips; The polyester core layer comprises the following components by weight: 90 portions of PET polyester chips.

[0068] Comparative Example 4 The difference between this comparative example and Example 1 is that the preparation process of the functional flame-retardant dispersion is as follows: S201: 12 parts by weight of binaphthol were heated in an oil bath at 140°C until completely melted. 6 parts by weight of 2,2'-diallylbisphenol A were added under stirring. After the reaction was complete, a crude flame-retardant monomer was obtained. S202: The crude flame retardant monomer is dissolved in 120 parts by weight of ethanol and 340 parts by weight of deionized water, and washed with stirring at 90°C for 40 min to remove impurities from the crude flame retardant monomer. The washing is repeated 5 times. The monomer is then dried under vacuum at 180°C until the solvent is completely evaporated to obtain the refined flame retardant monomer. S203: Add 100 parts by weight of dichloromethane to a three-necked flask, along with 74 parts by weight of the above-mentioned purified flame-retardant monomer and 10 parts by weight of N,N-diethylethylamine. Stir until completely dissolved, then slowly add 15 parts by weight of phenyldichlorophosphine. Incubate the mixture at 45°C under a nitrogen atmosphere for 4 hours. After the reaction is complete, extract with petroleum ether and dry thoroughly at 60°C to obtain the functional flame-retardant polymer.

[0069] S204: Add 20 parts by weight of functional flame retardant polymer, 80 parts by weight of ethylene glycol, and 4 parts by weight of polyethylene glycol to a high-speed mixer for uniform dispersion and mixing at a dispersion speed of 800 rpm and a mixing time of 100 min to obtain a functional flame retardant dispersion.

[0070] Comparative Example 5 The difference between this comparative example and Example 1 is that the preparation process of the functional flame-retardant dispersion is as follows: 20 parts by weight of ammonium polyphosphate (APP), 80 parts by weight of ethylene glycol, and 4 parts by weight of polyethylene glycol were added to a high-speed mixer and uniformly dispersed and mixed at a dispersion speed of 800 rpm for 100 min to obtain a functional flame retardant dispersion.

[0071] The performance of the BOPET films prepared in each embodiment and each comparative example was tested, and the test methods are as follows: Mechanical strength: Tested according to GB / T 13542.2-2021; Elongation at break: Tested according to GB / T 13542.2-2021; Flame retardancy rating: tested according to UL94; LOI Index: Tested according to GB / T 2406.2.

[0072] The test results are shown in Table 1: Table 1 Example 1 200 150 VTM-0 32.5 Example 2 190 135 VTM-0 33.8 Example 3 210 160 VTM-0 31.4 Example 4 195 140 VTM-0 32.0 Example 5 190 140 VTM-1 27.0 Comparative Example 1 185 130 VTM-1 28.5 Comparative Example 2 185 135 VTM-1 27.8 Comparative Example 3 140 90 VTM-2 26.0 Comparative Example 4 175 120 VTM-2 26.5 Comparative Example 5 150 95 VTM-2 24.5 The data above shows that the BOPET prepared in each embodiment of the present invention simultaneously possesses excellent flame retardancy rating, high LOI index, and good mechanical strength and elongation at break. This demonstrates that the BOPET film provided by the present invention significantly improves the flame retardancy of the BOPET film while maintaining good mechanical properties, thus meeting the stringent requirements for safety materials in high-end electronic and electrical, and new energy vehicle interior lighting scenarios.

[0073] The difference between Comparative Example 1 and Example 1 is that no surface flame retardant A was added to the composite flame retardant coating. Compared with Example 1, it lacks the surface physical flame retardant effect during combustion, resulting in a decrease in both flame retardant performance and mechanical properties.

[0074] The difference between Comparative Example 2 and Example 1 is that no surface flame retardant B was added to the composite flame retardant coating. Compared with Example 1, it lacks surface chemical flame retardant effect during combustion, resulting in a decrease in both flame retardant performance and mechanical properties.

[0075] The difference between Comparative Example 3 and Example 1 is that no flame retardant toughening agent was added to the BOPET base film, so the base film lacked flame retardant effect. Relying solely on the flame retardant coating cannot effectively guarantee the overall flame retardancy. In addition, the lack of toughening agent also led to a significant reduction in mechanical properties.

[0076] The difference between Comparative Example 4 and Example 1 is that 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step S201 is replaced with binaphthol. Because there is no phosphorus component in the polymer, it cannot capture active free radicals in the combustion chain reaction and cannot inhibit the gas phase combustion reaction, resulting in a significant decrease in both flame retardant properties and mechanical properties.

[0077] The difference between Comparative Example 5 and Example 1 is that the functional flame-retardant polymer is replaced with the traditional flame retardant ammonium polyphosphate (APP). Because the polymer phosphate with the composite phosphorus structure in this invention has a high phosphorus content, while the traditional flame retardant has a low phosphorus content, the capture and inhibition effect during the free radical capture process is not good, resulting in a significant decrease in both flame retardant performance and mechanical properties.

[0078] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A flame-retardant BOPET film, characterized in that, Including BOPET base film; The raw materials for the BOPET base film include flame retardant toughening agents; The flame retardant toughening agent is prepared using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant polymers as raw materials. The functional flame-retardant polymer is a phosphate with a complex phosphorus structure; The flame retardant toughening agent is prepared according to the following method: S101: Using terephthalic acid, ethylene glycol, antimony trioxide, trimethyl phosphate, and functional flame retardant dispersion as raw materials, the first stage of the reaction is carried out under an inert gas protective atmosphere at 200-240℃ and 0.5-0.7 MPa to obtain reaction mixture I; S102: Raise the temperature to 240-260℃ and carry out the second stage of heat preservation reaction to obtain reaction mixture II; S103: Reduce the pressure to 200-300 Pa, then raise the temperature to 260-270 °C to carry out the third stage of heat preservation reaction, and obtain reaction mixture III; S104: Small molecule impurities in reaction mixture III are removed by distillation, and the flame retardant toughening agent is obtained by melt extrusion granulation. The functional flame-retardant dispersion is obtained by mixing and dispersing the functional flame-retardant polymer, ethylene glycol, and dispersant as raw materials. Based on weight parts, the amount of terephthalic acid added in step S101 is 1040 parts; the amount of ethylene glycol added is 450-650 parts; the amount of antimony trioxide added is 0.5-1.0 parts; the amount of trimethyl phosphate added is 0.5-1.0 parts; and the amount of functional flame retardant dispersion added is 100-200 parts. The amount of the functional flame retardant polymer added to the functional flame retardant dispersion is 10-20 parts by weight; the amount of ethylene glycol added is 80-90 parts; and the amount of dispersant added is 3-5 parts.

2. The flame-retardant BOPET film as described in claim 1, characterized in that, The functional flame-retardant polymer is prepared according to the following method: S201: The flame retardant intermediate is heated at 130-150℃ until it melts, and 2,2'-diallylbisphenol A is added under stirring to react and obtain crude flame retardant monomer. S202: The crude flame retardant monomer is dissolved in a solvent, and after stirring and washing at a temperature of 90-100℃, it is dried under vacuum at 180-190℃ to obtain a refined flame retardant monomer. S203: Mix dichloromethane, the refined flame retardant monomer and N,N-diethylethylamine, stir until dissolved, and then add phenyl dichlorophosphine dropwise to obtain a mixed solution; S204: The mixed solution is reacted under an inert gas atmosphere at 40-45°C, then extracted with petroleum ether and dried at 50-60°C to obtain a functional flame-retardant polymer. The flame retardant intermediate is a substance containing biphenyl rings and phenanthrene rings.

3. The flame-retardant BOPET film as described in claim 2, characterized in that, The flame retardant intermediate is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

4. The flame-retardant BOPET film as described in claim 2, characterized in that, The amount of the flame retardant intermediate added in step S201 is 8-16 parts by weight, and the amount of 2,2'-diallyl bisphenol A added is 4-8 parts.

5. The flame-retardant BOPET film as described in claim 2, characterized in that, Based on weight parts, the amount of dichloromethane added in step S203 is 50-100 parts; the amount of refined flame retardant monomer added is 37-74 parts; the amount of N,N-diethylethylamine added is 5-10 parts; and the amount of phenyl dichlorophosphine added is 10-20 parts.

6. The flame-retardant BOPET film according to any one of claims 1-5, characterized in that, The flame-retardant BOPET film also includes a functionalized coating applied to the surface of the BOPET base film; The functionalized coating is prepared by applying a composite flame-retardant coating to the surface of the BOPET base film; The composite flame-retardant coating is prepared using resin-based liquid, surface flame retardant A, and surface flame retardant B as raw materials. The surface flame retardant A is prepared according to the following method: S401: Add deionized water to montmorillonite, stir, then add polyvinyl alcohol and continue stirring to obtain flame retardant premix A; S402: Add pentanediol to the flame retardant premix A, sonicate, and dry at 60-80°C to obtain surface flame retardant A; The surface flame retardant B is prepared according to the following method: S501: Dichloromethane, acyl halide compounds, and triethylamine are mixed to obtain flame retardant premix B; S502: Dichloromethane and phosphonate compounds are mixed and then added dropwise to the flame retardant premix B at 0-5°C. After the addition is complete, the mixture is reacted at 30-35°C to obtain flame retardant liquid B. S503: Extract the flame retardant liquid B with deionized water, and dry it at 60-80℃ to obtain surface flame retardant B.

7. The flame-retardant BOPET film as described in claim 6, characterized in that, The acyl halide compound is adipic acid chloride; the phosphonate compound is diethyl hydroxymethylphosphonate.

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