BOPET (Biaxially Oriented Polyester) film for gold stamping transfer and preparation method thereof

Abstract

The invention discloses a BOPET (Biaxially Oriented Polyethylene Terephthalate) film for gold stamping transfer and a preparation method thereof, and belongs to the technical field of BOPET films. The BOPET film for gold stamping transfer sequentially comprises an upper surface layer, a core layer and a lower surface layer from top to bottom, the upper surface layer and the lower surface layer are made of the same raw materials, and each of the upper surface layer and the lower surface layer comprises super bright polyester chips and irregular SiO2 modified anti-sticking master batches with different particle sizes in a mass ratio of (2-4): (6-8); the raw material of the core layer is graphene modified polyester chips; the BOPET film has the advantages of being low in resistivity, high in surface roughness, low in friction coefficient, large in wetting tension, excellent in mechanical property and the like, it is guaranteed that a gilding film color layer is firm and does not fall off, the gilding film color layer can be completely transferred during heat transfer printing, and the requirement for high-speed production is met.

Description

Technical Field

[0001] The invention belongs to the technical field of BOPET films, and in particular relates to a BOPET film for hot stamping transfer and a preparation method thereof. Background Art

[0002] Hot stamping film, also known as electroplated aluminum, is a composite hot stamping material consisting of a base film support layer, a release layer (peeling layer), a protective layer, a dyeing layer, an aluminum plating layer, and an adhesive layer. It is widely used in paper cards, plastics, cosmetics, textiles, electrical appliances, and digital products. Among them, the base layer is usually a plastic film such as PVC, OPP, and BOPET, which supports the above layers. Due to the advantages of BOPET's high temperature resistance (melting point > 255°C), easy degradation (environmentally friendly material), and biaxial stretchability (high strength and low breakage rate), it is often used as a carrier of hot stamping materials in actual production.

[0003] The process of hot stamping transfer is to heat press the prepared multi-layer composite material to the substrate through a base plate containing specific information at a certain temperature and pressure to form a specific pattern. However, during the hot transfer process, the metal color layer sometimes falls off and the transfer is poor (not peeling clean), which presents serious appearance defects such as dots, irregularities and patterns in the substrate, affecting the visual perception of the final product.

[0004] The reasons for this kind of problem are, firstly, that in order to pursue higher economic benefits, manufacturers continuously increase the speed of equipment operation, causing frequent friction between the film and the transmission rollers, accumulating a large amount of heterogeneous charges, resulting in a disordered electric field distribution on the surface, and producing a strong adsorption or repulsion effect on different charged particles from the outside world. If the film surface adsorbs tiny impurity particles in the air, the color layer after multiple coatings and drying will fall off due to insufficient adhesion. Secondly, since the commonly used silicone release agent (polydimethylsiloxane) has limited adhesion to the PET polyester surface under high-speed coating, it is easy to have missed coating points in production, causing the metal color layer to directly contact the base film, resulting in the inability to effectively transfer to the substrate during thermal transfer, resulting in poor base film transfer and peeling residue. Therefore, in order to solve the problems existing in the above-mentioned thermal transfer process, it is urgent to develop a BOPET film with excellent performance and suitable for hot stamping transfer. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a BOPET film for hot stamping transfer and a preparation method thereof, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A BOPET film for hot stamping transfer, comprising, from top to bottom, an upper surface layer, a core layer and a lower surface layer;

[0008] The raw materials of the upper surface layer and the lower surface layer are the same, both comprising: high-gloss polyester chips and irregular SiO2 modified anti-sticking masterbatch with different particle sizes in a mass ratio of (2-4): (6-8);

[0009] The raw material of the core layer is: graphene modified polyester chips.

[0010] Furthermore, the graphene-modified polyester chips are prepared by melt blending of nano-graphene particles and polyethylene terephthalate.

[0011] Furthermore, the anti-sticking masterbatch modified with random SiO2 of different particle sizes is prepared by premixing random SiO2 particles of different particle sizes, stirring them with terephthalic acid, isophthalic acid and ethylene glycol, and then esterifying and polycondensing them.

[0012] Furthermore, the particle content of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is 3300ppm.

[0013] Furthermore, the particle size range of the irregular SiO2 particles is: 1.5-5.0um.

[0014] Furthermore, the particle size range of the nano-graphene particles is 5-20 nm.

[0015] Furthermore, the thickness of the upper surface layer and the lower surface layer are both 1.1 um, and the thickness of the core layer is 9.8 um.

[0016] The above-mentioned method for preparing a BOPET film for hot stamping transfer comprises the following steps:

[0017] S1, after pre-crystallization, drying and impurity removal, the core layer raw material is sent to a single screw extruder for melt extrusion and filtration to obtain a core layer melt; and the upper surface layer and lower surface layer raw materials are sent to a twin screw extruder for melt extrusion, vacuum drying and filtration to obtain an upper surface layer melt and a lower surface layer melt respectively;

[0018] S2, the core layer melt, the upper surface layer melt and the lower surface layer melt are combined and cast at the die head, and attached to the surface of the low-temperature cold roller under the action of high-voltage static electricity to form a polyester thick sheet with a three-layer structure;

[0019] S3, passing the polyester thick sheet to the longitudinal stretching section, preheating and then longitudinally stretching, and then entering the transverse stretching section for preheating, transverse stretching, heat setting and cooling treatment to form a biaxially stretched polyester film;

[0020] S4, the biaxially oriented polyester film enters the traction stage for flattening, thickness measurement and trimming, and is rolled into a mother roll, and finally slit to obtain the finished film.

[0021] Furthermore, in S3: the preheating temperature for longitudinal stretching is 90°C, the stretching temperature is 110°C, and the stretching ratio is 3.7; the preheating temperature for transverse stretching is 100°C, the stretching temperature is 115°C, the heat setting temperature is 230°C, and the stretching ratio is 3.6; and the cooling temperature is 25°C.

[0022] The above-mentioned BOPET film for hot stamping transfer is used as a hot stamping carrier in hot stamping transfer.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention can significantly reduce the resistivity of the film, shorten the charge decay half-life, and enable the film to leak static charge accumulated due to friction in time by adding graphene particles to the PET slices in the core layer of the film for blending and modification; the surface layer of the film is made of an anti-sticking masterbatch formed by copolymerization and modification of SiO2 with different particle sizes and irregular morphology and ordinary slices. Since the particle sizes of the anti-sticking particles in the material vary greatly and the microscopic morphology presents a random and irregular shape, the surface roughness after film formation is significantly improved compared with that of ordinary films, so that more air is filled between the film layers after winding, which reduces the friction coefficient between the films, enhances the smoothness of the film, and thus reduces the generation of static electricity.

[0025] 2. As the surface roughness increases, the contact angle of the film surface is also reduced, so that the film that cannot be subjected to corona has a higher wetting tension, which helps to increase the specific gravity and uniformity of the downstream coating of the silicone release agent and avoid missing coating points.

[0026] 3. SiO2 itself, as a heterogeneous nucleating agent, can enhance and toughen the polymer. Irregular particles of different sizes interspersed in the molecular chain are more likely to hinder the movement of chain segments, increase the friction between molecular chains, increase the viscosity of the material, and improve the rigidity and mechanical properties of the film, thereby better adapting to high-speed production.

[0027] 4. The BOPET film prepared by the present invention has the advantages of low resistivity, high surface roughness, low friction coefficient, large wetting tension and excellent mechanical properties, which not only ensures the firmness and non-falling of the hot stamping film color layer, but also enables it to be completely transferred during thermal transfer, meeting the requirements of high-speed production. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The technical scheme of the present invention is illustrated by the following examples and comparative examples, wherein the BOPET film for hot stamping transfer prepared in the examples and comparative examples is a three-layer structure, which includes: an upper surface layer, a core layer and a lower surface layer from top to bottom, wherein the thickness of the upper surface layer and the lower surface layer is 1.1um, the thickness of the core layer is 9.8um, and the total thickness of the BOPET film is 12um;

[0030] All raw materials for the prepared BOPET film for hot stamping transfer include:

[0031] Bright polyester chips, graphene-modified polyester chips A (5nm, 2.5%), graphene-modified polyester chips B (10nm, 1.2%), graphene-modified polyester chips C (20nm, 0.5%), anti-sticking masterbatch modified with irregular SiO2 of different particle sizes (specific particle sizes and doping ratios are shown in specific embodiments and comparative examples), and commercial silicon-type anti-sticking masterbatch (3.5μm / 3300ppm);

[0032] The graphene-modified polyester chips are prepared by melt blending of nano-graphene particles and polyethylene terephthalate. The specific preparation process is as follows: nano-graphene powders (5, 10, 20 nm) of different particle sizes are vacuum dried at 150° C., and ordinary PET chips are blown dried at 115° C. for 12 h, and then placed at 165° C. for 12 h for vacuum drying for standby use; then, they are mixed with PET chips according to the mass fraction of the corresponding particle size, and then fully stirred with a high-speed disperser to obtain three kinds of mixed masterbatches with a particle size of 5 nm and a mass fraction of 2.5%, a particle size of 10 nm, a mass fraction of 1.2%, and a particle size of 20 nm and a mass fraction of 0.5% in turn; finally, the masterbatches are melted, extruded, and granulated at 275° C. to obtain nano-graphene modified masterbatches A, B, and C in turn.

[0033] The modified anti-sticking masterbatch of irregular SiO2 with different particle sizes is prepared by premixing irregular SiO2 particles with different particle sizes, stirring them with terephthalic acid, isophthalic acid and ethylene glycol, and then esterifying and polycondensing them.

[0034] Example 1

[0035] A method for preparing a BOPET film for hot stamping transfer comprises the following steps:

[0036] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0037] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0038] The raw materials of the core layer are: graphene modified polyester chips A;

[0039] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0040] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes includes:

[0041] 1) premixing random SiO2 particles with a particle size of 1.5 μm and random SiO2 particles with a particle size of 2.5 μm at a molar ratio of 1:1 to obtain a particle mixture;

[0042] 2) Add the particle mixture into a reaction kettle containing terephthalic acid, isophthalic acid and ethylene glycol and stir them thoroughly; wherein the molar ratio of terephthalic acid to isophthalic acid is 9:1, the molar ratio of ethylene glycol to the sum of diacids is 1.25:1, and the mass fraction of the particle mixture is 0.33%; then, esterification and dehydration are carried out at a temperature of 250°C, a pressure of 0.25MPa and a stirring frequency of 25Hz, and after the water output reaches more than 95%, the pressure is gradually reduced and the temperature is increased to cause pre-condensation, and finally the pressure in the kettle is adjusted to 70Pa and the temperature is adjusted to 280°C for condensation reaction, and after the reaction is completed, the reaction is carried out by drawing, cooling and pelletizing to obtain an anti-sticking masterbatch with different particle sizes and irregular SiO2 modification, and the masterbatch particle content is 3300ppm.

[0043] The preparation process of the graphene-modified polyester chip A comprises:

[0044] Graphene powder with a particle size of 5 nm was vacuum dried at 150°C, and ordinary PET slices were first blown dried at 115°C for 12 hours, and then placed at 165°C for 12 hours for vacuum drying for later use; then the powder was mixed with the PET slices, and then fully mixed and dispersed with a high-speed stirrer to obtain a mixed masterbatch with a particle size of 5 nm and a mass fraction of 2.5%. Finally, the masterbatch was melted, extruded and granulated at 275°C to obtain a nano-graphene modified masterbatch A.

[0045] S2, the core layer raw materials are mixed evenly, pre-crystallized at 160°C, and then sent to the fluidized bed, then blown dried and impurities removed in a drying tower, and then sent to the single screw extruder, melt extruded at 280°C to the filter screen, and finally metered by a melt pump and sent to the die head;

[0046] After the upper surface layer raw materials are mixed evenly, they are directly sent to the twin-screw extruder, melted and extruded at 280°C, and the melt is vacuum dried to remove moisture and impurities, and then transported to the die through a filter screen and a melt pump;

[0047] After the lower surface layer raw materials are mixed evenly, they are directly sent to the twin-screw extruder, melted and extruded at 280°C, and the melt is vacuum dried to remove moisture and impurities, and then transported to the die through a filter screen and a melt pump;

[0048] The core layer and the upper and lower surface layer melts merge at the die head to form a melt with a three-layer structure; then, the melt slowly flows out from the die head lip and, under the action of 7.2kV high-voltage static electricity, tightly adheres to the surface of the 27°C cold roller to form a thick polyester sheet with a three-layer structure.

[0049] S3, pass the polyester thick sheet to the longitudinal stretching section, complete the longitudinal stretching under the parameter conditions of preheating temperature 90°C, stretching temperature 110°C, and stretching ratio 3.7, and then enter the transverse stretching section, complete the transverse stretching under the parameter conditions of preheating temperature 100°C, stretching temperature 115°C, shaping temperature 230°C, and stretching ratio 3.6, and cool at 25°C to obtain the biaxially stretched polyester film.

[0050] S4, the biaxially oriented polyester film enters the traction stage for flattening, thickness measurement and trimming, and is rolled into a mother roll, and finally slit to obtain the finished film.

[0051] Example 2

[0052] The difference between this embodiment and embodiment 1 is that the particle size of the irregular SiO2 is changed in the raw material formula; the specific steps are as follows:

[0053] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0054] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0055] The raw materials of the core layer are: graphene modified polyester chips A;

[0056] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0057] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes includes:

[0058] 1) premixing random SiO2 particles with a particle size of 1.5 μm and random SiO2 particles with a particle size of 3.5 μm at a molar ratio of 1:1 to obtain a particle mixture;

[0059] 2) Add the particle mixture into a reaction kettle containing terephthalic acid, isophthalic acid and ethylene glycol and stir them thoroughly; wherein the molar ratio of terephthalic acid to isophthalic acid is 9:1, the molar ratio of ethylene glycol to the sum of diacids is 1.25:1, and the mass fraction of the particle mixture is 0.33%; then, esterification and dehydration are carried out at a temperature of 250°C, a pressure of 0.25MPa and a stirring frequency of 25Hz, and after the water output reaches more than 95%, the pressure is gradually reduced and the temperature is increased to cause pre-condensation, and finally the pressure in the kettle is adjusted to 70Pa and the temperature is adjusted to 280°C for condensation reaction, and after the reaction is completed, the reaction is carried out by drawing, cooling and pelletizing to obtain an anti-sticking masterbatch with different particle sizes and irregular SiO2 modification, and the masterbatch particle content is 3300ppm.

[0060] The preparation process of the graphene-modified polyester chip A is the same as S1.

[0061] S2-S4 are the same as in Example 1.

[0062] Example 3

[0063] The difference between this embodiment and embodiment 1 is that the particle size of the irregular SiO2 is changed in the raw material formula; the specific steps are as follows:

[0064] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0065] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0066] The raw materials of the core layer are: graphene modified polyester chips A;

[0067] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0068] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes includes:

[0069] 1) premixing random SiO2 particles with a particle size of 1.5 μm and random SiO2 particles with a particle size of 5.0 μm at a molar ratio of 1:1 to obtain a particle mixture;

[0070] 2) Add the particle mixture into a reaction kettle containing terephthalic acid, isophthalic acid and ethylene glycol and stir them thoroughly; wherein the molar ratio of terephthalic acid to isophthalic acid is 9:1, the molar ratio of ethylene glycol to the sum of diacids is 1.25:1, and the mass fraction of the particle mixture is 0.33%; then, esterification and dehydration are carried out at a temperature of 250°C, a pressure of 0.25MPa and a stirring frequency of 25Hz, and after the water output reaches more than 95%, the pressure is gradually reduced and the temperature is increased to cause pre-condensation, and finally the pressure in the kettle is adjusted to 70Pa and the temperature is adjusted to 280°C for condensation reaction, and after the reaction is completed, the reaction is carried out by drawing, cooling and pelletizing to obtain an anti-sticking masterbatch with different particle sizes and irregular SiO2 modification, and the masterbatch particle content is 3300ppm.

[0071] The preparation process of the graphene-modified polyester chip A is the same as S1.

[0072] S2-S4 are the same as in Example 1.

[0073] Example 4

[0074] The difference between this embodiment and embodiment 1 is that the type of graphene-modified polyester chips in the core layer is changed in the raw material formula; the details are as follows:

[0075] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0076] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0077] The raw materials of the core layer are: graphene modified polyester chips B;

[0078] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0079] The preparation process of the SiO2 modified anti-sticking masterbatch with different particle sizes is the same as that in Example 1 and includes:

[0080] The preparation process of the graphene-modified polyester chip B comprises:

[0081] Graphene powder with a particle size of 10 nm was vacuum dried at 150°C, and ordinary PET chips were first blown dried at 115°C for 12 hours, and then placed at 165°C for 12 hours for vacuum drying for later use; then the powder was mixed with the PET chips, and then fully mixed and dispersed with a high-speed stirrer to obtain a mixed masterbatch with a particle size of 5 nm and a mass fraction of 1.2%. Finally, the masterbatch was melted, extruded and granulated at 275°C to obtain a nano-graphene modified masterbatch B.

[0082] S2-S4 are the same as in Example 1.

[0083] Example 5

[0084] The difference between this embodiment and embodiment 1 is that the type of graphene-modified polyester chips in the core layer is changed in the raw material formula; the specific steps are as follows:

[0085] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0086] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0087] The raw materials of the core layer are: graphene modified polyester chips C;

[0088] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0089] The preparation process of the SiO2 modified anti-sticking masterbatch with different particle sizes is the same as that in Example 1 and includes:

[0090] The preparation process of the graphene-modified polyester chip C comprises:

[0091] Graphene powder with a particle size of 20 nm was vacuum dried at 150°C, and ordinary PET slices were first blown dried at 115°C for 12 hours, and then placed at 165°C for 12 hours for vacuum drying for later use; then the powder was mixed with the PET slices, and then fully mixed and dispersed with a high-speed stirrer to obtain a mixed masterbatch with a particle size of 5 nm and a mass fraction of 0.5%. Finally, the masterbatch was melted, extruded and granulated at 275°C to obtain a nano-graphene modified masterbatch C.

[0092] S2-S4 are the same as in Example 1.

[0093] Example 6

[0094] The difference between this embodiment and embodiment 1 is that the ratio of the raw materials in the upper and lower surface layers is changed; the specific steps are:

[0095] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0096] The upper surface layer raw materials include: 20% by mass of high gloss polyester chips and 80% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0097] The raw materials of the core layer are: graphene modified polyester chips A;

[0098] The raw materials of the lower surface layer include: 20% by mass of high-gloss polyester chips and 80% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0099] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is the same as that of Example 1. The preparation process of the graphene modified polyester chips A is the same as that of Example 1.

[0100] S2-S4 are the same as in Example 1.

[0101] Example 7

[0102] The difference between this embodiment and embodiment 1 is that the ratio of the raw materials in the upper and lower surface layers is changed; the specific steps are:

[0103] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0104] The upper surface layer raw materials include: 40% by mass of high gloss polyester chips and 60% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0105] The raw materials of the core layer are: graphene modified polyester chips A;

[0106] The raw materials of the lower surface layer include: 40% by mass of high-gloss polyester chips and 60% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0107] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is the same as that of Example 1. The preparation process of the graphene modified polyester chips A is the same as that of Example 1.

[0108] S2-S4 are the same as in Example 1.

[0109] Comparative Example 1

[0110] The difference between Comparative Example 1 and Example 1 is that the core layer material is changed to bright polyester chips;

[0111] The specific steps are:

[0112] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0113] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0114] The raw materials of the core layer are: bright polyester chips;

[0115] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0116] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is the same as that in Example 1.

[0117] S2-S4 are the same as in Example 1.

[0118] Comparative Example 2

[0119] The difference between Comparative Example 2 and Example 1 is that the irregular SiO2 modified anti-sticking masterbatch with different particle sizes in the upper and lower surface layers is replaced with a commercial silicon-type anti-sticking masterbatch; the specific steps are:

[0120] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0121] The upper surface layer raw materials include: 30% by mass of high-gloss polyester chips and 70% by mass of commercial silicone anti-sticking masterbatch;

[0122] The raw materials of the core layer are: graphene modified polyester chips A;

[0123] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of commercial silicon-type anti-sticking masterbatch.

[0124] The preparation process of the graphene-modified polyester chip A is the same as that of Example 1.

[0125] S2-S4 are the same as in Example 1.

[0126] Comparative Example 3

[0127] The comparative example is different from Example 2 only in that the mixing ratio of the irregular SiO2 particles in the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is changed; the specific steps are as follows:

[0128] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0129] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0130] The raw materials of the core layer are: graphene modified polyester chips A;

[0131] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0132] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes includes:

[0133] 1) premixing random SiO2 particles with a particle size of 1.5 μm and random SiO2 particles with a particle size of 3.5 μm at a molar ratio of 1:2 to obtain a particle mixture;

[0134] 2) Add the particle mixture into a reaction kettle containing terephthalic acid, isophthalic acid and ethylene glycol and stir them thoroughly; wherein the molar ratio of terephthalic acid to isophthalic acid is 9:1, the molar ratio of ethylene glycol to the sum of diacids is 1.25:1, and the mass fraction of the particle mixture is 0.33%; then, esterification and dehydration are carried out at a temperature of 250°C, a pressure of 0.25MPa and a stirring frequency of 25Hz, and after the water output reaches more than 95%, the pressure is gradually reduced and the temperature is increased to cause pre-condensation, and finally the pressure in the kettle is adjusted to 70Pa and the temperature is adjusted to 280°C for condensation reaction, and after the reaction is completed, the reaction is carried out by drawing, cooling and pelletizing to obtain an anti-sticking masterbatch with different particle sizes and irregular SiO2 modification, and the masterbatch particle content is 3300ppm.

[0135] The preparation process of the graphene-modified polyester chip A is the same as S1.

[0136] S2-S4 are the same as in Example 1.

[0137] Comparative Example 4

[0138] The comparative example is different from Example 2 only in that the mixing ratio of the irregular SiO2 particles in the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is changed; the specific steps are as follows:

[0139] S1, configuring the upper surface layer, the core layer, and the lower surface layer raw materials;

[0140] The upper surface layer raw materials include: 30% by mass of high gloss polyester chips and 70% by mass of SiO2 modified anti-sticking masterbatch with different particle sizes;

[0141] The raw materials of the core layer are: graphene modified polyester chips A;

[0142] The raw materials of the lower surface layer include: 30% by mass of high-gloss polyester chips and 70% by mass of irregular SiO2 modified anti-sticking masterbatch with different particle sizes.

[0143] In this embodiment, the preparation process of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes includes:

[0144] 1) premixing random SiO2 particles with a particle size of 1.5 μm and random SiO2 particles with a particle size of 3.5 μm at a molar ratio of 2:1 to obtain a particle mixture;

[0145] 2) Add the particle mixture into a reaction kettle containing terephthalic acid, isophthalic acid and ethylene glycol and stir them thoroughly; wherein the molar ratio of terephthalic acid to isophthalic acid is 9:1, the molar ratio of ethylene glycol to the sum of diacids is 1.25:1, and the mass fraction of the particle mixture is 0.33%; then, esterification and dehydration are carried out at a temperature of 250°C, a pressure of 0.25MPa and a stirring frequency of 25Hz, and after the water output reaches more than 95%, the pressure is gradually reduced and the temperature is increased to cause pre-condensation, and finally the pressure in the kettle is adjusted to 70Pa and the temperature is adjusted to 280°C for condensation reaction, and after the reaction is completed, the reaction is carried out by drawing, cooling and pelletizing to obtain an anti-sticking masterbatch with different particle sizes and irregular SiO2 modification, and the masterbatch particle content is 3300ppm.

[0146] The preparation process of the graphene-modified polyester chip A is the same as S1.

[0147] S2-S4 are the same as in Example 1.

[0148] Film performance test

[0149] The finished films in Examples 1-7 and Comparative Examples 1-4 were subjected to performance tests, wherein the test items included resistivity, surface roughness, friction coefficient, wetting tension and mechanical properties. The specific test process is as follows:

[0150] 1) Resistivity: Cut a 100mm×100mm square sample from the film sample and connect it to the input terminal and high voltage terminal of the high resistance meter respectively. Then adjust the test voltage to 500V, measure and record the surface resistance of the sample. Test three parallel groups of each film sample and take the average value.

[0151] 2) Surface roughness: Cut a 100 mm × 100 mm square specimen from the film sample and lay it flat on the table. Then switch the instrument mode to Ra, start the test and record the indicated value. Each film sample is tested in parallel in 3 groups and the average value is taken.

[0152] 3) Friction coefficient: Cut 250mm×100mm and 80mm×50mm specimens from the film samples respectively, and fix the large-sized samples on the surface of the test bench and the small-sized samples on the bottom of the slider. Then start the instrument, pull the slider at a speed of 100mm / min to achieve relative displacement with the sample film on the platform and maintain it for 15s. Finally, record the static / dynamic friction coefficient values. Test each film sample in 3 parallel groups and take the average value.

[0153] 4) Wetting tension: Cut a 100mm×100mm square sample from the film sample and place it on the coating tool plate. Use a cotton swab to dip into the dyne solution (42-58mN / m) and wipe the surface of the sample. Observe the liquid dispersion at the same time. If the liquid does not disperse for more than 2s, continue to the next level test. Test until the time is close to 2s and record the wetting tension value of the corresponding solution.

[0154] 5) Tensile strength: Cut a strip sample of 150mm in length and 15mm in width from the film sample, and clamp the short sides of the sample with the upper and lower clamps of the tensile tester, with a clamp spacing of 100mm. Start the instrument, and stretch the sample at a set speed of 100mm / min until the sample breaks. Finally, read the tensile strength value in the supporting analysis software. Test 3 groups in each of the horizontal and vertical directions of each film sample and take the average value.

[0155] The test results of Examples 1-7 are shown in Table 1, and the test results of Comparative Examples 1-4 are shown in Table 2;

[0156] Table 1 Test results of films prepared in Examples 1-7

[0157]

[0158] Table 2 Test results of films prepared in Comparative Examples 1-4

[0159]

[0160] It can be seen from Table 1 and Table 2 that after doping the core layer with graphene particles, the resistivity of the material can be significantly reduced, thereby accelerating the discharge of static charge on the surface of the film, shortening the charge decay half-life, and avoiding the adverse effects of static electricity on subsequent processing. At the same time, it can be observed that the polyester masterbatch modified with irregular SiO2 particles of different particle sizes significantly improves the surface roughness Ra of the film, and the corresponding friction coefficient is also reduced to varying degrees, thereby further reducing the amount of static charge generated by friction. Also thanks to the improvement in roughness, the wetting tension of the film has been greatly improved, which will be beneficial to the uniformity and firmness of the subsequent coating release layer. Finally, after adding this masterbatch containing particles of different particle sizes and irregular morphology, the overall mechanical properties of the film are also enhanced to a certain extent, indicating that compared with conventional spherical particles, it can further enhance the toughness of the polymer while playing a heterogeneous nucleation role. It is worth noting that if the doping ratio of a certain particle size is increased, the roughness of the resulting film does not change significantly, and the corresponding friction coefficient and wetting tension performance are also average. This may be because when the proportion of a certain particle is too high, it is more likely to agglomerate during the condensation process, resulting in insufficient particle dispersion, which in turn affects the surface properties after film formation.

[0161] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0162] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A BOPET film for hot stamping transfer, characterized in that: From top to bottom, it includes: upper surface layer, core layer and lower surface layer; The raw materials of the upper surface layer and the lower surface layer are the same, both comprising: high-gloss polyester chips and irregular SiO2 modified anti-sticking masterbatch with different particle sizes in a mass ratio of (2-4): (6-8); The raw material of the core layer is: graphene modified polyester chips.

2. A BOPET film for hot stamping transfer according to claim 1, characterized in that: The graphene-modified polyester chips are prepared by melt-blending nano-graphene particles and polyethylene terephthalate.

3. A BOPET film for hot stamping transfer according to claim 1, characterized in that: The modified anti-sticking masterbatch of irregular SiO2 with different particle sizes is prepared by premixing irregular SiO2 particles with different particle sizes, stirring them with terephthalic acid, isophthalic acid and ethylene glycol, and then esterifying and polycondensing them.

4. A BOPET film for hot stamping transfer according to claim 3, characterized in that: The particle content of the irregular SiO2 modified anti-sticking masterbatch with different particle sizes is 3300ppm.

5. A BOPET film for hot stamping transfer according to claim 3, characterized in that: The particle size range of the irregular SiO2 particles is: 1.5-5.0um.

6. A BOPET film for hot stamping transfer according to claim 2, characterized in that: The particle size range of the nano-graphene particles is 5-20 nm.

7. A BOPET film for hot stamping transfer according to claim 1, characterized in that: The thickness of the upper surface layer and the lower surface layer are both 1.1 um, and the thickness of the core layer is 9.8 um.

8. The method for preparing a BOPET film for hot stamping transfer according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, after pre-crystallization, drying and impurity removal, the core layer raw material is sent to a single screw extruder for melt extrusion and filtering to obtain a core layer melt; The upper surface layer and the lower surface layer raw materials are respectively fed into a twin-screw extruder for melt extrusion, vacuum drying and filtering to obtain an upper surface layer melt and a lower surface layer melt; S2, the core layer melt, the upper surface layer melt and the lower surface layer melt are combined and cast at the die head, and attached to the surface of the low-temperature cold roller under the action of high-voltage static electricity to form a polyester thick sheet with a three-layer structure; S3, passing the polyester thick sheet to the longitudinal stretching section, preheating and then longitudinally stretching, and then entering the transverse stretching section for preheating, transverse stretching, heat setting and cooling treatment to form a biaxially stretched polyester film; S4, the biaxially oriented polyester film enters the traction stage for flattening, thickness measurement and trimming, and is rolled into a mother roll, and finally slit to obtain the finished film.

9. The method for preparing a BOPET film for hot stamping transfer according to claim 8, characterized in that: In S3: the preheating temperature for longitudinal stretching is 90°C, the stretching temperature is 110°C, and the stretching ratio is 3.7; the preheating temperature for transverse stretching is 100°C, the stretching temperature is 115°C, the heat setting temperature is 230°C, and the stretching ratio is 3.6; the cooling temperature is 25°C.

10. Use of the BOPET film for hot stamping transfer according to any one of claims 1 to 7 as a hot stamping carrier in hot stamping transfer.

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