High-flexibility PET decorative film and preparation method thereof

Abstract

The invention discloses a high-flexibility PET decorative film and a preparation method thereof, and belongs to the technical field of PET decorative films. According to the high-flexibility PET decorative film, the self-made flame retardant and 1, 3-benzene-5-boric acid are pre-polymerized to obtain a prepolymer, then the prepolymer, ethylene glycol and terephthalic acid are mixed to react, and then (4-carboxyl-2-nitrophenyl) malonaldehyde is used for blocking to obtain flame-retardant PET. The preparation method comprises the following steps: carrying out a pre-mixing reaction on flame-retardant PET and a modified nucleating agent, internally mixing the pre-mixed material with an antioxidant and a lubricant, carrying out extrusion granulation, and carrying out melt extrusion, sheet casting, two-way stretching and heat setting by using a double-screw extruder to obtain a PET base film; and finally, plating aluminum on the PET base film. The self-made flame retardant is obtained by enabling amino siloxane and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to react with each other; the modified nucleating agent is obtained by modifying calcium carbonate with glycine; the high-flexibility PET decorative film prepared by the invention has good flexibility, flame retardance and antistatic property.

Description

Technical Field

[0001] The present invention relates to a highly flexible PET decorative film and a preparation method thereof. Background Art

[0002] With the increasing awareness of environmental protection, polyethylene terephthalate (PET), as a recyclable thermoplastic material, shows great potential to replace traditional thermosetting materials in the field of home decoration films. Although PET has excellent transparency, mechanical strength and chemical stability, it still faces significant technical challenges in terms of flexibility and flame retardancy, which greatly limits its application in the high-end market.

[0003] The rigid benzene ring structure in the PET molecular chain endows it with excellent hardness and weather resistance, but also leads to the problem of insufficient flexibility. Current technologies mainly enhance the surface hardness through inorganic coatings (such as SiO2), but this often increases the risk of brittle fracture. Although some studies have attempted to use inorganic-organic hybrid coatings to improve the flexibility problem, due to complex UV curing processes, uneven coating thickness, etc., this difficult problem has not been completely solved. In addition, methods such as neopentyl glycol copolymerization can improve the toughness to a certain extent (the impact strength is increased by about 30%), but still cannot meet the requirements of high-end applications.

[0004] The limiting oxygen index (LOI) of PET material is only about 21%, belonging to flammable materials. Traditional flame retardant modification usually relies on halogen-based flame retardants, which can improve the flame retardant performance to a certain extent, but will lead to a decline in mechanical properties and environmental pollution.

[0005] Therefore, it is urgent to explore a new method to improve the flexibility and flame retardancy of PET decorative films. Summary of the Invention

[0006] The purpose of the present invention is to provide a highly flexible PET decorative film and a preparation method thereof to solve the technical problems mentioned in the above background art.

[0007] The technical solution to achieve the purpose of the present invention is as follows: In the first aspect, the present invention provides a highly flexible PET decorative film, which sequentially includes a PET base film and a metal coating from bottom to top; wherein, the PET base film is obtained by first pre-mixing and reacting flame-retardant PET with a modified nucleating agent, then mixing the pre-mixed materials with an antioxidant and a lubricant, kneading and extruding into pellets, and then melt-extruding, casting, biaxially stretching and heat-setting using a twin-screw extruder.

[0008] Further, the flame-retardant PET is obtained by first pre-polymerizing a self-made flame retardant with methyl 1,3-benzenedicarboxylate-5-borate, then mixing and reacting with ethylene glycol and terephthalic acid, and then end-capping with (4-carboxy-2-nitrophenyl) malonaldehyde. Further, the self-made flame retardant is obtained by reacting amino siloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0009] Further, the modified nucleating agent is obtained by modifying calcium carbonate with glycine.

[0010] The carboxyl group of glycine forms Ca(COOR)2 with the free calcium ions on the surface of calcium carbonate, generating chemical bonding. At the same time, the poorly soluble salt precursor in the liquid phase migrates to the surface of calcium carbonate particles; finally, the poorly soluble salt in the liquid phase adsorbs and grows on the surface of calcium carbonate particles, coating the calcium carbonate particles, thereby achieving the effect of surface modification.

[0011] In the second aspect, a method for preparing the high-flexibility PET decorative film as described in the first aspect of the present invention includes the following steps: (1) Weigh and mix the raw material components according to the following parts by weight: 100 parts by mass of flame-retardant PET, 0.5 - 1 part by mass of modified nucleating agent, 1 - 2 parts by mass of antioxidant, and 1 - 2 parts by mass of lubricant; (2) Premixing: Under nitrogen conditions, mix 1.1 - 1.3 parts by mass of p-toluenesulfonic acid with 170 - 190 parts by mass of xylene, and then sequentially add 100 parts by mass of flame-retardant PET and 0.5 - 1 part by mass of modified nucleating agent. Stir and react at 1200 - 1600 rpm at room temperature for 25 - 35 min, then raise the temperature to 165 - 175 °C and continue to stir and react for 7.5 - 8.5 h. Rotate and evaporate, then immerse in 180 - 220 parts by mass of 1 M ferric chloride solution for 8 - 12 s, fish out, let stand for 8 - 12 min, and then dry at 60 °C for 5 - 7 h to obtain a premixed material; (3) Knead and extrude the premixed material obtained in step (2) with 1 - 2 parts by mass of lubricant and 1 - 2 parts by mass of antioxidant, and then melt extrude, cast, biaxially stretch, and heat-set using a twin-screw extruder to obtain a PET base film; (4) Aluminize the PET base film obtained in step (3) to obtain a high-flexibility PET decorative film.

[0012] Further, the preparation steps of the flame-retardant PET are as follows: Under nitrogen protection, preheat the reaction kettle to 120 °C, then add the prepolymer, ethylene glycol, terephthalic acid, and ethylene glycol antimony as a catalyst in an amount of 0.04% of the mass of terephthalic acid to the reaction kettle and mechanically stir for 4 - 6 min to make them evenly mixed, and make a slurry. Then, under nitrogen protection, increase the pressure to 150 kPa, raise the temperature to 250 - 255 °C, then continue to increase the pressure to 0.3 MPa, keep the temperature for reaction for 1 - 1.5 h. Then, evacuate to 50 Pa and carry out polycondensation at 275 - 280 °C for 83 min. Then, add (4-carboxy-2-nitrophenyl) malonaldehyde and continue the reaction for 14 - 16 min to obtain the flame-retardant PET.

[0013] Further, the preparation steps of the prepolymer are as follows: Under nitrogen protection, mix the self-made flame retardant and 1,2-dichloroethane at a mass ratio of 1:10 - 20, stir at 45 °C until the self-made flame retardant is dissolved to obtain a self-made flame retardant solution; mix methyl 1,3-benzenedicarboxylate-5-borate and 1,2-dichloroethane at a mass ratio of 1:4 - 6 and stir for 20 - 40 min, then dropwise add it into the self-made flame retardant solution at a rate of 2 - 4 drops / s. After the dropping is completed, raise the temperature to 75 - 85 °C and react for 7 - 9 h. Then, filter and carry out rotary evaporation, and vacuum dry at 40 - 60 °C for 11 - 13 h to obtain the prepolymer.

[0014] Further, the preparation steps of the self-made flame retardant are as follows: Under nitrogen protection, mix 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1,2-dichloroethane, triethylamine, and an amino silane coupling agent at a mass ratio of 4.2 - 4.4:40 - 60:21 - 23:3.5 - 3.7 and stir until 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved, control the temperature at about 0 °C, and dropwise add 3 - 3.4 parts by mass of carbon tetrachloride at a rate of 2 - 4 drops / s. After the dropping is completed, react at room temperature for 22 - 24 h, carry out suction filtration and rotary evaporation, wash with ethanol and 1,2-dichloroethane respectively, and finally vacuum dry at 45 - 55 °C for 7 - 9 h to obtain the self-made flame retardant.

[0015] The amino silane coupling agent includes 3-aminopropyltriethoxysilane and γ-aminopropylmethyldiethoxysilane. Among them, the molar ratio of 3-aminopropyltriethoxysilane to γ-aminopropylmethyldiethoxysilane is 1:4 - 6, and by controlling the molar number of the trialkoxysilane, the flexible chain length is increased and the degree of branching is reduced.

[0016] Further, the molar ratio of the self-made flame retardant, methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid is 1 - 3:1 - 3:120:97 - 99, and the mass ratio of (4-carboxy-2-nitrophenyl) malonaldehyde to terephthalic acid is 1 - 3:100.

[0017] Further, the preparation steps of the modified nucleating agent are as follows: Mix the dried nano-calcium carbonate and ethanol at a mass ratio of 1:3 - 5, then perform ultrasonic dispersion for 1.5 - 2.5 h. Subsequently, stir a 5% - 10% glycine solution of 100 parts by mass of nano-calcium carbonate for 25 - 35 min. Then add nano-calcium carbonate dropwise at a rate of 2 - 4 drops / s, control the pH value of the solution to be 5.5 - 6 and the temperature to be controlled at 30 - 40 °C, react for 1.5 - 2.5 h, then take out, filter, wash and dry.

[0018] Adopting the above technical solution, the present invention has the following beneficial effects: The present invention discloses a highly flexible PET decorative film and its preparation method, belonging to the technical field of PET decorative films; for the highly flexible PET decorative film of the present invention, first, a self-made flame retardant and 1,3-dimethyl-5-borobenzoate are pre-polymerized to obtain a prepolymer, then the prepolymer is mixed and reacted with ethylene glycol and terephthalic acid and capped with (4-carboxy-2-nitrophenyl) malonaldehyde to obtain flame-retardant PET. Then, after pre-mixing and reacting the flame-retardant PET with a modified nucleating agent, the pre-mixed material is kneaded and extruded into pellets with an antioxidant and a lubricant, and then melt-extruded, cast into sheets, biaxially stretched and heat-set using a twin-screw extruder to obtain a PET base film; finally, aluminizing is performed on the PET base film; the self-made flame retardant is obtained by reacting amino siloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the modified nucleating agent is obtained by modifying calcium carbonate with glycine; the highly flexible PET decorative film prepared by the present invention has good flexibility, flame retardancy and antistatic properties.

[0019] First, through the reaction of the amino group in amino siloxane with the P-H bond on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the reaction and grafting of the siloxane bond in amino siloxane with boric acid in 1,3-dimethyl-5-borobenzoate, a branched poly-siloxo-boronane structure is formed. The P, N, Si, and B elements in the prepolymer synergistically flame-retard. Specifically, when the material burns, the prepolymer will generate pyrophosphate / polyphosphate during the combustion decomposition process, which can undergo a dehydration reaction with other polymer systems in the flame-retardant PET, thereby promoting the formation of a protective heat-resistant carbon layer. Moreover, part of the oxygen atoms participate in the formation of B2O3 and SiO2, reducing the release of volatile carbon dioxide during the pyrolysis process, thereby reducing carbon loss and increasing the char residue rate. At the same time, the formed B2O3 and SiO2 migrate to the carbon layer, improving the density and thermal stability of the carbon layer. There are also a large number of Si-N and Si-C structures in the carbon layer, which can improve the thermal stability of the carbon layer.

[0020] Next, the prepolymer is mixed and reacted with ethylene glycol and terephthalic acid. Among them, ethylene glycol undergoes transesterification and esterification reactions with methyl 1,3-benzenedicarboxylate-5-borate and terephthalic acid in the prepolymer respectively, and then polycondensation occurs. By controlling the reaction pressure, the polycondensation of the reaction system is incomplete. Then, (4-carboxy-2-nitrophenyl) malonaldehyde reacts with the uncondensed hydroxyl groups in the aforementioned reaction system to carry out esterification capping to obtain flame-retardant PET. (4-Carboxy-2-nitrophenyl) malonaldehyde introduces a polar group nitro in the flame-retardant PET to increase the surface energy of the PET base film, facilitating subsequent metal coating; in addition, introducing a branched polyborosiloxane to copolymerize to prepare flame-retardant PET can effectively increase the flexibility of the PET base film, and further enhance the flexibility of the highly flexible PET decorative film.

[0021] Finally, the flame-retardant PET is pre-mixed and reacted with the modified nucleating agent. The dispersibility of glycine-modified nano-calcium carbonate in the flame-retardant PET is better than that of nano-calcium carbonate. On the one hand, the internal cavity of the branched flame-retardant PET helps the dispersion of nano-titanium dioxide. On the other hand, acetic acid of glycine in the modified nucleating agent reacts with malonaldehyde in the flame-retardant PET to form pyrrole derivatives, and pyrrole polymerization forms a polypyrrole polymer network pathway in the PET base film, endowing the PET base film with good antistatic performance.

[0022] In this application, the flame retardant is directly used as one of the polymerization monomers of PET. Compared with the conventional method of directly adding a flame retardant to PET, the compatibility between the flame retardant and the PET base material is better, and the flexibility and flame retardant effect are better. Specific embodiments

[0023] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with specific embodiments.

[0024] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0026] Some raw materials of the embodiments and comparative examples of the present invention are as follows: PET: melting point 257 °C, intrinsic viscosity 0.62 dl / g; The antioxidant uses antioxidant 1010; The lubricant uses EBS wax; The average particle size of nano-calcium carbonate is 0.1 μm.

[0027] (Example 1) A preparation method of a highly flexible PET decorative film, comprising the following steps: (1) Weigh and mix the raw material components according to the following parts by weight: 100 parts by mass of flame-retardant PET, 0.5 part by mass of modified nucleating agent, 1 part by mass of antioxidant, and 1 part by mass of lubricant; (2) Premixing: Under nitrogen conditions, mix 1.1 parts by mass of p-toluenesulfonic acid with 170 parts by mass of xylene, and then sequentially add 100 parts by mass of flame-retardant PET and 0.5 part by mass of modified nucleating agent. Stir and react at 1200 rpm for 25 min at room temperature, then heat up to 165 °C and continue to stir and react for 7.5 h. Perform rotary evaporation, then immerse it in 180 parts by mass of 1 M ferric chloride solution for 8 s, fish it out, let it stand for 8 min, and then dry it at 60 °C for 5 h to obtain a premixed material; (3) Knead, extrude and pelletize the premixed material obtained in step (2) with 1 part by mass of lubricant and 1 part by mass of antioxidant, and then melt extrude, cast film, biaxially stretch and heat-set it with a twin-screw extruder to obtain a PET base film with a thickness of 12 μm; the temperature of the kneading chamber is 240 °C, the kneading speed is 180 rpm, the feeding speed is 12 rpm, the temperature of the extruder is 270 °C, and the main machine speed is 200 rpm; the screw diameter D of the twin-screw extruder is 62 mm, the length-diameter ratio L / D is 48, the main machine speed is 490 Hz, and the barrel temperature control settings are as follows: zone 1 is 220 °C, zone 2 is 240 °C, zones 3 - 11 are 260 °C, and the die head temperature is 260 °C; the temperature of the casting process is 28 °C; the temperature of longitudinal stretching is 115 °C, the longitudinal stretching ratio is 4, the temperature of transverse stretching is 105 °C, the transverse stretching ratio is 4, and the heat-setting temperature is 245 °C; (4) Aluminize the PET base film obtained in step (3), and the thickness of the aluminized layer is 20 nm to obtain a highly flexible PET decorative film.

[0028] The preparation steps of the modified nucleating agent are as follows: Mix the dried nano-calcium carbonate with ethanol at a mass ratio of 1:3, then perform ultrasonic dispersion for 1.5 h, then stir a 5% glycine solution of 100 parts by mass of nano-calcium carbonate for 25 min, then add nano-calcium carbonate dropwise at 2 s / drop, control the pH value of the solution to be 5.5 and the temperature to be controlled at 30 °C, take it out after reacting for 1.5 h, perform suction filtration, washing and drying.

[0029] The preparation steps of the flame-retardant PET are as follows: Under nitrogen protection, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1,2-dichloroethane, triethylamine, and amino-silane coupling agent were mixed at a mass ratio of 4.2:40:21:3.5 and stirred until 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was dissolved. The temperature was controlled at about 0 °C, and 3 parts by mass of carbon tetrachloride was added dropwise at a rate of 2 drops / s. After the addition was completed, the reaction was carried out at room temperature for 22 h. Then, filtration and rotary evaporation were performed, and the product was washed with ethanol and 1,2-dichloroethane respectively. Finally, it was vacuum dried at 45 °C for 7 h to obtain a self-made flame retardant; Under nitrogen protection, the self-made flame retardant and 1,2-dichloroethane were mixed at a mass ratio of 1:10 and stirred at 45 °C until the self-made flame retardant was dissolved to obtain a self-made flame retardant solution. Methyl 1,3-benzenedicarboxylate-5-borate and 1,2-dichloroethane were mixed at a mass ratio of 1:4 and stirred for 20 min, and then dropped into the self-made flame retardant solution at a rate of 2 drops / s. After the addition was completed, the temperature was raised to 75 °C and the reaction was carried out for 7 h. Then, filtration and rotary evaporation were performed, and it was vacuum dried at 40 °C for 13 h to obtain a prepolymer; Under nitrogen protection, the reaction kettle was preheated to 120 °C, and then the prepolymer, ethylene glycol, terephthalic acid, and ethylene glycol antimonate as a catalyst at 0.04% of the mass of terephthalic acid were added to the reaction kettle and mechanically stirred for 4 min to make them evenly mixed and made into a slurry. Then, under nitrogen protection, the pressure was increased to 150 kPa, the temperature was raised to 250 °C, and then the pressure was continuously increased to 0.3 MPa, and the reaction was carried out under insulation for 1 h. Then, the vacuum was pumped to 50 Pa, and polycondensation was carried out at 275 °C for 83 min. Then, (4-carboxy-2-nitrophenyl)malonaldehyde was added and the reaction was continued for 14 min to obtain flame-retardant PET.

[0030] In the above reaction, the molar ratio of the self-made flame retardant, methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid was 1:1:120:99, and the mass ratio of (4-carboxy-2-nitrophenyl)malonaldehyde to terephthalic acid was 1:100.

[0031] (Example 2) A preparation method of a highly flexible PET decorative film includes the following steps: (1) Weigh and mix the following raw material components according to the following parts by weight: 100 parts by mass of flame-retardant PET, 0.8 part by mass of modified nucleating agent, 1.5 parts by mass of antioxidant, and 1.5 parts by mass of lubricant; (2) Premixing: Under nitrogen conditions, 1.2 parts by mass of p-toluenesulfonic acid and 180 parts by mass of xylene were mixed. Subsequently, 100 parts by mass of flame-retardant PET and 0.8 part by mass of modified nucleating agent were added in sequence. Stirring reaction was carried out at 1400 rpm for 30 min at room temperature, then the temperature was raised to 170 °C and stirring reaction was continued for 8 h. Rotary evaporation was carried out, and then it was immersed in 200 parts by mass of 1 M ferric chloride solution for 10 s, fished out, allowed to stand for 10 min and then dried at 60 °C for 6 h to obtain the premixed material; (3) The premixed material obtained in step (2) was kneaded and extruded into pellets with 1.5 parts by mass of lubricant and 1.5 parts by mass of antioxidant, and then melt-extruded, cast into sheets, biaxially stretched and heat-set by a twin-screw extruder to obtain a 12-μm-thick PET base film; the temperature of the kneading chamber was 240 °C, the kneading speed was 180 rpm, the feeding speed was 12 rpm, the temperature of the extruder was 270 °C, and the main machine speed was 200 rpm; the screw diameter D of the twin-screw extruder was 62 mm, the length-diameter ratio L / D was 48, the main machine speed was 490 Hz, and the screw barrel temperature control was set as follows: zone 1 was 220 °C, zone 2 was 240 °C, zones 3 - 11 were 260 °C, and the die head temperature was 260 °C; the temperature of the sheet casting process was 28 °C; the temperature of longitudinal stretching was 115 °C, the longitudinal stretching ratio was 4, the temperature of transverse stretching was 105 °C, the transverse stretching ratio was 4, and the heat-setting temperature was 245 °C; (4) The PET base film obtained in step (3) was aluminized, and the thickness of the aluminized layer was 20 nm to obtain a highly flexible PET decorative film.

[0032] The preparation steps of the modified nucleating agent are as follows: The dried nano-calcium carbonate and ethanol were mixed at a mass ratio of 1:4, and then ultrasonic dispersion was carried out for 2 h. Subsequently, 8% glycine solution of 100 parts by mass of nano-calcium carbonate was stirred for 30 min, and then nano-calcium carbonate was added dropwise at 3 s / drop, controlling the pH value of the solution to be 5.8 and the temperature to be controlled at 35 °C. After reaction for 2 h, it was taken out, filtered, washed and dried.

[0033] The preparation steps of the flame-retardant PET are as follows: Under nitrogen protection conditions, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1,2-dichloroethane, triethylamine, and amino-silane coupling agent were mixed at a mass ratio of 4.3:50:22:3.6 and stirred until 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was dissolved. The temperature was controlled at about 0 °C, and 3.2 parts by mass of carbon tetrachloride was added dropwise at 3 s / drop. After the dropwise addition was completed, the reaction was carried out at room temperature for 23 h, filtered by suction and rotary evaporated, and then washed with ethanol and 1,2-dichloroethane respectively. Finally, it was vacuum dried at 50 °C for 8 h to obtain a self-made flame retardant; Under nitrogen protection, the self-made flame retardant and 1,2-dichloroethane were mixed at a mass ratio of 1:15, and stirred at 45 °C until the self-made flame retardant was dissolved to obtain a self-made flame retardant solution; methyl 1,3-benzenedicarboxylate-5-borate and 1,2-dichloroethane were mixed at a mass ratio of 1:5 and stirred for 30 min, and then dropped into the self-made flame retardant solution at a rate of 3 drops / s. After the dropping was completed, the temperature was raised to 80 °C and reacted for 8 h, then filtered, rotary evaporated, and vacuum dried at 50 °C for 12 h to obtain a prepolymer; Under nitrogen protection, the reaction kettle was preheated to 120 °C, and then the prepolymer, ethylene glycol, terephthalic acid, and ethylene glycol antimonate as a catalyst at 0.04% of the mass of terephthalic acid were added to the reaction kettle and mechanically stirred for 5 min to mix them evenly and make a slurry. Then, under nitrogen protection, the pressure was raised to 150 kPa, the temperature was raised to 253 °C, and then the pressure was further raised to 0.3 MPa, and the reaction was kept at a constant temperature for 1.3 h. Then, the vacuum was pumped to 50 Pa, and polycondensation was carried out at 278 °C for 83 min. Then, (4-carboxy-2-nitrophenyl) malondialdehyde was added and the reaction was continued for 15 min to obtain flame-retardant PET.

[0034] In the above reaction, the molar ratio of the self-made flame retardant, methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid was 2:2:120:98, and the mass ratio of (4-carboxy-2-nitrophenyl) malondialdehyde to terephthalic acid was 2:100.

[0035] (Example 3) A preparation method of a highly flexible PET decorative film includes the following steps: (1) Weigh and mix the following raw material components according to the following weight parts: 100 parts by mass of flame-retardant PET, 1 part by mass of modified nucleating agent, 2 parts by mass of antioxidant, and 2 parts by mass of lubricant; (2) Premixing: Under nitrogen conditions, 1.3 parts by mass of p-toluenesulfonic acid and 190 parts by mass of xylene were mixed, and then 100 parts by mass of flame-retardant PET and 1 part by mass of modified nucleating agent were added in sequence. Stirring reaction was carried out at 1600 rpm at room temperature for 35 min, then the temperature was raised to 175 °C, and stirring reaction was continued for 8.5 h. Rotary evaporation was carried out, and then it was immersed in 220 parts by mass of 1 M ferric chloride solution for 12 s, fished out, left standing for 12 min, and then dried at 60 °C for 7 h to obtain a premixed material; (3) The premix obtained in step (2) is kneaded and extruded into pellets with 2 parts by mass of lubricant and 2 parts by mass of antioxidant, and then melt-extruded, cast into sheets, biaxially stretched, and heat-set using a twin-screw extruder to obtain a PET base film with a thickness of 12 μm; the temperature of the kneading chamber is 240 °C, the kneading speed is 180 rpm, the feeding speed is 12 rpm, the temperature of the extruder is 270 °C, and the main machine speed is 200 rpm; the screw diameter D of the twin-screw extruder is 62 mm, the length-diameter ratio L / D is 48, the main machine speed is 490 Hz, and the barrel temperature control settings are as follows: zone 1 is 220 °C, zone 2 is 240 °C, zones 3 - 11 are 260 °C, and the die head temperature is 260 °C; the temperature of the sheet casting process is 28 °C; the temperature of the longitudinal stretching is 115 °C, the longitudinal stretching ratio is 4, the temperature of the transverse stretching is 105 °C, the transverse stretching ratio is 4, and the heat-setting temperature is 245 °C; (4) The PET base film obtained in step (3) is aluminized, and the thickness of the aluminized layer is 20 nm to obtain a highly flexible PET decorative film.

[0036] The preparation steps of the modified nucleating agent are as follows: The dried nano-calcium carbonate is mixed with ethanol at a mass ratio of 1:5, and then ultrasonically dispersed for 2.5 h. Subsequently, it is stirred into a 10% glycine solution of 100 parts by mass of nano-calcium carbonate for 35 min, and then nano-calcium carbonate is added dropwise at a rate of 4 drops / s, controlling the pH value of the solution to be 6 and the temperature to be controlled at 40 °C. After reacting for 2.5 h, it is taken out, filtered, washed, and dried.

[0037] The preparation steps of the flame-retardant PET are as follows: Under nitrogen protection, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1,2-dichloroethane, triethylamine, and amino-silane coupling agent are mixed at a mass ratio of 4.4:60:23:3.7 and stirred until 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved. The temperature is controlled at about 0 °C, and 3.4 parts by mass of carbon tetrachloride is added dropwise at a rate of 4 drops / s. After the addition is complete, the reaction is carried out at room temperature for 24 h, filtered, rotary evaporated, washed with ethanol and 1,2-dichloroethane respectively, and finally vacuum dried at 55 °C for 9 h to obtain a self-made flame retardant; Under nitrogen protection, the self-made flame retardant and 1,2-dichloroethane are mixed at a mass ratio of 1:20 and stirred at 45 °C until the self-made flame retardant is dissolved to obtain a self-made flame retardant solution; 1,3-bis(methoxycarbonyl)phenylboronic acid and 1,2-dichloroethane are mixed at a mass ratio of 1:6 and stirred for 40 min, and then added dropwise into the self-made flame retardant solution at a rate of 4 drops / s. After the addition is complete, the temperature is raised to 85 °C and the reaction is carried out for 9 h. Then, it is filtered, rotary evaporated, and vacuum dried at 60 °C for 13 h to obtain a prepolymer; Under nitrogen protection, the reaction kettle was preheated to 120 °C, and then the prepolymer, ethylene glycol, terephthalic acid, and ethylene glycol antimonate catalyst, which was 0.04% of the mass of terephthalic acid, were added to the reaction kettle and mechanically stirred for 6 min to make them evenly mixed, and then made into a slurry. Subsequently, under nitrogen protection, the pressure was increased to 150 kPa, and the temperature was raised to 255 °C. Then the pressure was continued to be increased to 0.3 MPa, and the reaction was carried out under insulation for 1.5 h. Then the vacuum was pumped to 50 Pa, and polycondensation was carried out at 280 °C for 83 min. Subsequently, (4-carboxy-2-nitrophenyl) malonaldehyde was added, and the reaction was continued for 16 min to obtain flame-retardant PET.

[0038] In the above reaction, the molar ratio of the self-made flame retardant, methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid was 3:3:120:97, and the mass ratio of (4-carboxy-2-nitrophenyl) malonaldehyde to terephthalic acid was 3:100.

[0039] (Comparative Example 1) The difference between Comparative Example 1 and Example 2 was that the prepolymer was obtained by premixing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and methyl 1,3-benzenedicarboxylate-5-borate, and the remaining steps and components were the same as those in Example 2.

[0040] (Comparative Example 2) The difference between Comparative Example 2 and Example 2 was that the flame-retardant PET was obtained by only mixing and reacting the self-made flame retardant with ethylene glycol and terephthalic acid and then end-capping with (4-carboxy-2-nitrophenyl) malonaldehyde, and the remaining steps and components were the same as those in Example 2.

[0041] (Comparative Example 3) The difference between Comparative Example 3 and Example 2 was that the flame-retardant PET was first obtained by prepolymerizing the self-made flame retardant and methyl 1,3-benzenedicarboxylate-5-borate to obtain a prepolymer, and then the prepolymer was mixed and reacted with ethylene glycol and terephthalic acid, and the remaining steps and components were the same as those in Example 2.

[0042] (Comparative Example 4) The difference between Comparative Example 4 and Example 2 was that the amino silicone was only 3-aminopropyltriethoxysilane, and the remaining steps and components were the same as those in Example 2.

[0043] (Comparative Example 5) The difference between Comparative Example 5 and Example 2 was that the amino silicone was only γ-aminopropylmethyldiethoxysilane, and the remaining steps and components were the same as those in Example 2.

[0044] (Comparative Example 6) The difference between Comparative Example 6 and Example 2 was that the nucleating agent was not modified, and the remaining steps and components were the same as those in Example 2.

[0045] (Comparative Example 7) The difference between Comparative Example 7 and Example 2 is that the flame-retardant PET is obtained by reacting a self-made flame retardant with methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid, and then end-capping with (4-carboxy-2-nitrophenyl) malonaldehyde. The remaining steps and components are the same as those in Example 2.

[0046] (Comparative Example 8) The difference between Comparative Example 8 and Example 2 is that the flame-retardant PET is obtained by reacting methyl 1,3-benzenedicarboxylate-5-borate, ethylene glycol, and terephthalic acid, and then end-capping with (4-carboxy-2-nitrophenyl) malonaldehyde; the PET base film is obtained by pre-mixing the flame-retardant PET with a modified nucleating agent, and then melt-kneading the pre-mixed material with an antioxidant, a lubricant, and a self-made flame retardant, followed by extrusion granulation, and then melt-extruding, casting, biaxially stretching, and heat-setting using a twin-screw extruder. The remaining steps and components are the same as those in Example 2.

[0047] (Comparative Example 9) The difference between Comparative Example 9 and Example 2 is that the PET base film is obtained by directly melt-kneading the flame-retardant PET, a modified nucleating agent, an antioxidant, and a lubricant, followed by extrusion granulation, and then melt-extruding, casting, biaxially stretching, and heat-setting using a twin-screw extruder. The remaining steps and components are the same as those in Example 2.

[0048] Effect Example Tensile strength test: Refer to GB / T 1040.3 to test the tensile properties of the PET base films prepared in the examples and comparative examples.

[0049] Surface resistivity: Cut the PET base films prepared in Examples 1 to 3 and Comparative Examples 1 to 9 into a size of 100×100×2 mm, and test the surface resistivity of each sample according to the standard of GB / T 1410-2006.

[0050] The following Table 1 shows the performance test results of the PET base films prepared in Examples 1 to 3 and Comparative Examples 1 to 9: Table 1

[0051] As can be seen from Table 1, the PET base films prepared in Examples 1 to 3 have good flame retardancy, flexibility, and antistatic properties.

[0052] The difference between Comparative Example 1 and Example 2 is that the prepolymer is obtained by pre-mixing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with methyl 1,3-benzenedicarboxylate-5-borate. Compared with Comparative Example 1, the PET base film prepared in Example 2 has better flame retardancy and flexibility.

[0053] The difference between Comparative Example 2 and Example 2 is that 1,3-benzenedicarboxylic acid methyl ester-5-boronic acid was not used in the flame-retardant PET. Compared with Comparative Example 2, the PET-based film prepared in Example 2 has better flame retardancy and flexibility.

[0054] The difference between Comparative Example 3 and Example 2 is that (4-carboxy-2-nitrophenyl) malonaldehyde was not used for end-capping the flame-retardant PET. Compared with Comparative Example 3, the PET-based film prepared in Example 2 has better flexibility and antistatic performance.

[0055] The difference between Comparative Example 4 and Example 2 is that only 3-aminopropyltriethoxysilane was used as the amino silicone. Compared with Comparative Example 4, the PET-based film prepared in Example 2 has better flexibility.

[0056] The difference between Comparative Example 5 and Example 2 is that only γ-aminopropylmethyldiethoxysilane was used as the amino silicone. Compared with Comparative Example 5, the PET-based film prepared in Example 2 has better flexibility and tensile strength.

[0057] The difference between Comparative Example 6 and Example 2 is that the nucleating agent was not modified. Compared with Comparative Example 6, the PET-based film prepared in Example 2 has better tensile strength, flexibility and antistatic performance.

[0058] The difference between Comparative Example 7 and Example 2 is that no prepolymerization reaction was carried out between the self-made flame retardant and 1,3-benzenedicarboxylic acid methyl ester-5-boronic acid. Compared with Comparative Example 7, the PET-based film prepared in Example 2 has better flexibility and tensile strength.

[0059] The difference between Comparative Example 8 and Example 2 is that after directly mixing 1,3-benzenedicarboxylic acid methyl ester-5-boronic acid, ethylene glycol and terephthalic acid and reacting them, the flame-retardant PET modified nucleating agent capped with (4-carboxy-2-nitrophenyl) malonaldehyde was pre-mixed and then kneaded with an antioxidant, a lubricant and the self-made flame retardant. Compared with Comparative Example 8, the PET-based film prepared in Example 2 has better flame retardancy and flexibility.

[0060] The difference between Comparative Example 9 and Example 2 is that the flame-retardant PET and the modified nucleating agent were not pre-mixed. Compared with Comparative Example 9, the PET-based film prepared in Example 2 has better flexibility and antistatic performance.

[0061] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A highly flexible PET decorative film, characterized in that: From bottom to top, it includes a PET base film and a metal coating; wherein the PET base film is obtained by pre-mixing and reacting a flame-retardant PET and a modified nucleating agent, kneading the pre-mixed material with an antioxidant and a lubricant, and then extruding and granulating the material, and then adopting a twin-screw extruder to melt extrude, cast, biaxially stretch, and heat-set.

2. The high-flexibility PET decorative film according to claim 1, characterized in that: The flame-retardant PET is obtained by prepolymerizing a homemade flame retardant with 1,3-methyl phthalate-5-boric acid, mixing with ethylene glycol and terephthalic acid, and then capping with (4-carboxyl-2-nitrophenyl) malondialdehyde.

3. The high-flexibility PET decorative film according to claim 2, characterized in that: The self-made flame retardant is obtained by reacting aminosiloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

4. The high-flexibility PET decorative film according to claim 1, characterized in that: The modified nucleating agent is obtained by modifying calcium carbonate with glycine.

5. A method for preparing a highly flexible PET decorative film according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Weigh and mix the raw material components according to the following weight parts: 100 parts by weight of flame-retardant PET, 0.5-1 parts by weight of modified nucleating agent, 1-2 parts by weight of antioxidant, and 1-2 parts by weight of lubricant; (2) Premixing: Under nitrogen conditions, 1.1-1.3 parts by weight of p-toluenesulfonic acid and 170-190 parts by weight of xylene were mixed, followed by the addition of 100 parts by weight of flame-retardant PET and 0.5-1 parts by weight of a modified nucleating agent, stirred at 1200-1600 rpm for 25-35 min at room temperature, then heated to 165-175°C, stirred for 7.5-8.5 h, rotary evaporated, and then immersed in 180-220 parts by weight of a 1M ferric chloride solution for 8-12 s, removed, allowed to stand for 8-12 min, and then dried at 60°C for 5-7 h to obtain a premix; (3) kneading the premix obtained in step (2) with 1-2 parts by weight of lubricant and 1-2 parts by weight of antioxidant, extruding and granulating, and then melt-extruding, casting, biaxially stretching, and heat-setting using a twin-screw extruder to obtain a PET base film; (4) The PET base film obtained in step (3) is aluminum-plated to obtain a highly flexible PET decorative film.

6. The method for preparing a highly flexible PET decorative film according to claim 5, characterized in that: The preparation steps of the flame-retardant PET are as follows: under nitrogen protection, the reactor is preheated to 120° C., and then the prepolymer, ethylene glycol, terephthalic acid, and 0.04% by weight of terephthalic acid catalyst ethylene glycol antimony are added to the reactor and mechanically stirred for 4 to 6 minutes to make them evenly mixed, and then the slurry is formed. Then, the pressure is increased to 150 kPa under nitrogen protection, the temperature is increased to 250 to 255° C., and then the pressure is continuously increased to 0.3 MPa, and the reaction is kept warm for 1 to 1.5 hours, and then the vacuum is evacuated to 50 Pa, and polycondensation is carried out at 275 to 280° C. for 83 minutes, and then (4-carboxy-2-nitrophenyl) malonaldehyde is added, and the reaction is continued for 14 to 16 minutes to obtain the flame-retardant PET.

7. The method for preparing a highly flexible PET decorative film according to claim 6, characterized in that: The preparation steps of the prepolymer are as follows: under nitrogen protection, a homemade flame retardant and 1,2-dichloroethane are mixed at a mass ratio of 1:10-20, and stirred at 45°C until the homemade flame retardant is dissolved to obtain a homemade flame retardant solution; Methyl 1,3-phthalate-5-boric acid and 1, 2-dichloroethane were mixed in a mass ratio of 1:4-6 and stirred for 20-40 minutes, and then added into the homemade flame retardant solution at a rate of 2-4 seconds per drop. After the addition was completed, the temperature was raised to 75-85°C for reaction for 7-9 hours, followed by filtration, rotary evaporation, and vacuum drying at 40-60°C for 11-13 hours to obtain a prepolymer.

8. The method for preparing a highly flexible PET decorative film according to claim 7, characterized in that: The preparation steps of the self-made flame retardant are as follows: under nitrogen protection, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1, 2-dichloroethane, triethylamine and aminosilane coupling agent are mixed and stirred in a mass ratio of 4.2-4.4:40-60:21-23:3.5-3.7 until 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved, the temperature is controlled at about 0°C, 3-3.4 parts by mass of carbon tetrachloride are added at a rate of 2-4s / drop, and after the dropwise addition is completed, the mixture is reacted at room temperature for 22-24h, filtered, rotary evaporated, washed with ethanol and 1, 2-dichloroethane respectively, and finally vacuum dried at 45-55°C for 7-9h to obtain the self-made flame retardant.

9. The method for preparing a highly flexible PET decorative film according to claim 8, characterized in that: The molar ratio of the homemade flame retardant, 1,3-methyl phthalate-5-boric acid, ethylene glycol and terephthalic acid is 1-3:1-3:120:97-99, and the mass ratio of (4-carboxy-2-nitrophenyl) malondialdehyde to terephthalic acid is 1-3:

100.

10. The method for preparing a highly flexible PET decorative film according to claim 5, characterized in that: The preparation steps of the modified nucleating agent are as follows: the dried nano-calcium carbonate is mixed with ethanol in a mass ratio of 1:3-5, and then ultrasonically dispersed for 1.5-2.5 hours, and then stirred for 25-35 minutes to 5%-10% glycine solution of 100 parts by mass of the nano-calcium carbonate, and then the nano-calcium carbonate is added dropwise at 2-4 seconds, the pH value of the solution is controlled to be 5.5-6 and the temperature is controlled to be 30-40°C, and after reacting for 1.5-2.5 hours, the solution is taken out for suction filtration, washed and dried.

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