Preparation method of modified polyester master batch and preparation method of black polyester film

Abstract

The invention belongs to the technical field of high polymer materials, particularly discloses a preparation method of a modified polyester master batch and a preparation method of a black polyester film, and also relates to the black polyester film prepared from the modified polyester master batch and the black polyester film. The preparation method comprises the following steps: dissolving a sucrose solution in desalted water; uniformly dispersing silicon dioxide powder into the cane sugar soaking solution, and soaking for a preset time; putting the silicon dioxide and cane sugar soaking solution soaked for a preset time into an evaporation container for complete evaporation to obtain cane sugar-silicon dioxide; heating the sucrose-silicon dioxide in a heating furnace to a set temperature, and keeping the temperature for a set time, so that the sucrose is completely carbonized to obtain modified silicon dioxide; and further preparing the modified PET polyester master batch. The obtained modified silicon dioxide can replace part of carbon black materials to be used for preparing a film surface layer, and when the full-shading black polyester film is produced, the adding amount of carbon black powder of a core layer can be greatly reduced, so that the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and specifically relates to a method for preparing a modified polyester masterbatch and a method for preparing a black polyester film, and also relates to the black polyester film prepared thereby. Background Art

[0002] Polyester film (BOPET) is made of polyethylene terephthalate as raw material, made into cast sheets by co-extrusion, and then made into film materials by biaxial stretching process. It is widely used in new packaging, electronic appliances, information technology, optical materials, new energy, energy-saving window films and other fields due to its excellent barrier properties, temperature resistance, light transmittance, high strength and other properties. However, some products have privacy and require their packaging materials to be completely light-proof. It needs to meet the standards of 25μm thickness and 0% light transmittance. The current conventional fully light-proof black polyester film products in China can meet this standard, but the price is high.

[0003] At present, conventional full-light-shielding black polyester film products include a core layer and a surface layer. The core layer uses masterbatch. The black masterbatch in the masterbatch is usually made of a mixture of carbon black powder and polyethylene terephthalate (PET). Because the carbon black material itself has a small particle size and is light in weight, the particle size of the carbon black powder commonly used in the masterbatch is usually 18-25 nanometers. If the current demand for full-light-shielding black polyester film products is met, a high concentration (>20%) of carbon black material must be added to the core layer to obtain a product with a light transmittance of 0%, which results in a higher cost for BOPET black polyester film.

[0004] The surface of the polyester film itself needs to be added with an opening agent. The function of the opening agent is to prevent the polyester films from sticking together after being stacked or rolled. However, the traditional opening agent is silica material, but the light-shielding property of silica material is much worse than that of carbon black material.

[0005] In addition, the current fully light-shielding black polyester film is not only expensive, but also has the problem of precipitation when a large amount of carbon black is added during the production and use of the black polyester film due to its small particle size.

[0006] Based on the above problems, the present invention intends to provide a method for preparing a modified polyester masterbatch and a method for preparing a black polyester film, so as to obtain a lower-cost fully light-shielding black polyester film while ensuring the transmittance requirements. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a modified polyester masterbatch and a method for preparing a black polyester film, and also to provide the prepared black polyester film.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions.

[0009] The present invention provides a method for preparing a modified polyester masterbatch for a black polyester film, comprising the steps of:

[0010] dissolving the sucrose solution in desalted water to form a sucrose soaking solution;

[0011] Evenly dispersing silicon dioxide powder into the sucrose soaking solution and soaking for a predetermined time to form a silicon dioxide sucrose soaking solution;

[0012] Put the silicon dioxide sucrose soaking liquid after soaking for a predetermined time into an evaporation container and evaporate it completely to obtain sucrose-silicon dioxide;

[0013] placing sucrose-silicon dioxide in a heating furnace, heating it to a set temperature and keeping it warm for a set time, so that the sucrose is completely carbonized to obtain modified silicon dioxide;

[0014] The modified silicon dioxide is ground to obtain modified silicon dioxide powder, and the modified silicon dioxide powder is evenly dispersed in an ethylene glycol solution, and then the ethylene glycol solution containing the modified silicon dioxide powder is mixed with terephthalic acid to obtain a modified PET polyester masterbatch for preparing a black polyester film surface layer through a polymerization reaction.

[0015] When the sucrose solution is dissolved in desalted water, the mass of the sucrose solution is 20%-80% of the mass of the desalted water.

[0016] Wherein, the silicon dioxide powder is uniformly dispersed in the sucrose soaking solution and soaked for 24 hours.

[0017] The sucrose-silica was placed in a muffle furnace and heated to 600° C. and kept warm for 6 hours to completely carbonize the sucrose to obtain modified silica.

[0018] Wherein, the silicon dioxide powder is prepared by a gas phase method and has a particle size of 3.5 μm.

[0019] Another invention of the present invention provides a method for preparing a low-cost black polyester film, comprising the following steps:

[0020] S1. Mixing the modified PET polyester masterbatch prepared by the above preparation method with the first PET polyester slice to form a surface layer raw material, wherein the content of modified silicon dioxide powder in the formed surface layer raw material mixture is 10000ppm;

[0021] S2, mixing the second PET polyester chips and the masterbatch in a mass ratio of (85-95):(5-15) to form a core layer material;

[0022] S3, the core layer raw material enters the main extruder and melts into a core layer melt under a set melting temperature condition, the surface layer raw material enters the auxiliary extruder and melts into a surface layer melt under a set melting temperature condition, the core layer melt and the surface layer melt are respectively extruded from the main extruder and the auxiliary extruder and transported to the adapter module, and are layered after passing through the internal flow channel of the adapter module, the core layer melt is layered and distributed in the core layer, and the surface layer melt is layered and distributed in the upper surface layer and the lower surface layer;

[0023] S4, feeding the allocated core layer melt and the surface layer melt into a three-layer co-extrusion die, the core layer melt is extruded from the middle layer of the three-layer co-extrusion die, and at the same time, the surface layer melt of the upper surface layer and the surface layer melt of the lower surface layer are extruded from the upper layer and the lower layer of the three-layer co-extrusion die respectively, and the melt extruded from the three-layer co-extrusion die is cooled at a set cooling temperature and then cast to obtain a polyester film sheet;

[0024] S5, preheating and stretching the polyester film sheet, reheating and shaping it, and then cooling it to room temperature to form a black polyester film.

[0025] The melting temperatures of the main extruder and the auxiliary extruder are 278° C., and the raw materials of the masterbatch include carbon black powder and polyethylene terephthalate.

[0026] The core layer melt and the surface layer melt are extruded from the main extruder and the auxiliary extruder respectively, and then passed through their respective pre-filters, metering pumps, and fine filters and transported to the adapter module. The melt extruded from the three-layer co-extrusion die is cooled at 15°C and then cast to obtain a polyester film sheet.

[0027] The polyester film sheet is preheated to 90°C and longitudinally stretched at 90°C with a longitudinal stretching ratio of 3.3, then preheated to 105°C and transversely stretched with a transverse stretching ratio of 3.7, and then heat-set at 200°C and cooled to room temperature, and finally rolled up by traction to obtain a fully light-shielding black polyester film.

[0028] In another aspect, the present invention provides a low-cost black polyester film, which is prepared by the above-mentioned method for preparing the low-cost black polyester film.

[0029] In the technical solution provided by the present invention, the silicon dioxide powder is evenly dispersed in the sucrose soaking solution and soaked for a predetermined time, and then evaporated to obtain sucrose-silicon dioxide, and then placed in a heating furnace for heating and heat preservation to completely carbonize the sucrose to obtain modified silicon dioxide, and then the ethylene glycol solution dispersed with the modified silicon dioxide powder is mixed with terephthalic acid to obtain a modified PET polyester masterbatch through a polymerization reaction, which is used to prepare the surface layer of the black polyester film, which can effectively block light; in this way, after the silicon dioxide is modified by sucrose solution soaking-calcination-ball milling and other processes, black modified silicon dioxide is obtained, thereby replacing part of the carbon black material, which is used for the preparation of the film surface layer. When producing a fully light-shielding black polyester film, the amount of carbon black powder added in the core layer can be greatly reduced, thereby reducing the production cost. In addition, due to its small particle size, carbon black will have precipitation problems during the production and use of black polyester film. The present invention uses modified silicon dioxide to replace a large amount of carbon black powder, which can improve the problem of carbon black precipitation to a certain extent. That is, the patent of the present invention not only reduces the production cost of the film, but also improves the problem of carbon black precipitation.

[0030] The present invention uses silicon dioxide prepared by a gas phase method because its surface has a porous structure and is more likely to absorb more sucrose solution.

[0031] Since increasing the amount of core color carbon black added or using carbon black materials with larger particle sizes will increase the crystallinity of the polyester film, causing the film to become brittle and easy to break, the present application can also increase the toughness of the black polyester film by reducing the amount of carbon black added to prevent the film from becoming brittle and easy to break. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the low-cost black polyester film of the present invention.

[0033] Figure 2 It is a schematic diagram of the structure of polyester film in the prior art.

[0034] In the figure: 1. Silica powder; 2. Carbon black powder; 3. Modified silica powder; 4. Surface layer; 5. Core layer. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below. It should be understood by those skilled in the art that the specific implementation is only to help understand the present invention and should not be regarded as a specific limitation of the present invention.

[0036] It should be noted that, unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art. Unless otherwise specified, the raw materials used in the present invention are all commercially available conventional commodities and can be purchased.

[0037] The method for preparing the modified polyester masterbatch for the black polyester film provided by the present invention comprises the steps of:

[0038] dissolving the sucrose solution in desalted water to form a sucrose soaking solution;

[0039] Evenly dispersing silicon dioxide powder into the sucrose soaking solution and soaking for a predetermined time to form a silicon dioxide sucrose soaking solution;

[0040] Put the silicon dioxide sucrose soaking liquid after soaking for a predetermined time into an evaporation container and evaporate it completely to obtain sucrose-silicon dioxide;

[0041] placing sucrose-silicon dioxide in a heating furnace, heating it to a set temperature and keeping it warm for a set time, so that the sucrose is completely carbonized to obtain modified silicon dioxide;

[0042] The modified silicon dioxide is ground to obtain modified silicon dioxide powder, and the modified silicon dioxide powder is evenly dispersed in an ethylene glycol solution, and then the ethylene glycol solution containing the modified silicon dioxide powder is mixed with terephthalic acid to obtain a modified PET polyester masterbatch for preparing a black polyester film surface layer through a polymerization reaction.

[0043] The preparation method of the fully light-shielding black polyester film of the present invention obtains a new surface opening agent to meet the optical properties of the polyester film by soaking the surface silica opening agent in sucrose, calcining in a muffle furnace, dispersing by ball milling, and co-polymerizing, thereby reducing the material cost. The present invention starts with modifying the raw materials, improving the light-shielding property of the surface material, thereby reducing the amount of new layer material added, so as to achieve the purpose of reducing costs. The present invention belongs to the technical field of polyester films. The surface raw materials are modified, calcined, dispersed by ball milling, polymerized, etc. to obtain a new surface opening agent, thereby improving the light-shielding property of the material.

[0044] In the present invention, the sucrose solution is dissolved in the desalted water, specifically: the mass of the sucrose solution is 20%-80% of the mass of the desalted water.

[0045] In the present invention, the silicon dioxide powder is uniformly dispersed in the sucrose soaking solution and soaked for 24 hours.

[0046] In the present invention, sucrose-silicon dioxide is placed in a muffle furnace and heated to 600° C. and kept warm for 6 hours, so that the sucrose is completely carbonized to obtain modified silicon dioxide.

[0047] In the present invention, the silicon dioxide powder is prepared by a gas phase method and has a particle size of 3.5 μm. In the present invention, the particle size of the modified silicon dioxide powder is the same as that of the raw silicon dioxide powder.

[0048] The method for preparing a low-cost black polyester film provided by the present invention comprises the following steps:

[0049] S1. Mixing the modified PET polyester masterbatch prepared by the preparation method according to any one of claims 1 to 5 with the first PET polyester chip to form a surface layer raw material, wherein the content of modified silicon dioxide powder in the formed surface layer raw material mixture is 10000 ppm;

[0050] S2, mixing the second PET polyester chips and the masterbatch in a mass ratio of (85-95):(5-15) to form a core layer material;

[0051] S3, the core layer raw material enters the main extruder and melts into a core layer melt under a set melting temperature condition, the surface layer raw material enters the auxiliary extruder and melts into a surface layer melt under a set melting temperature condition, the core layer melt and the surface layer melt are respectively extruded from the main extruder and the auxiliary extruder and transported to the adapter module, and are layered after passing through the internal flow channel of the adapter module, the core layer melt is layered and distributed in the core layer, and the surface layer melt is layered and distributed in the upper surface layer and the lower surface layer;

[0052] S4, feeding the allocated core layer melt and the surface layer melt into a three-layer co-extrusion die, the core layer melt is extruded from the middle layer of the three-layer co-extrusion die, and at the same time, the surface layer melt of the upper surface layer and the surface layer melt of the lower surface layer are extruded from the upper layer and the lower layer of the three-layer co-extrusion die respectively, and the melt extruded from the three-layer co-extrusion die is cooled at a set cooling temperature and then cast to obtain a polyester film sheet;

[0053] S5, preheating and stretching the polyester film sheet, reheating and shaping it, and then cooling it to room temperature to form a black polyester film.

[0054] like Figure 1 and Figure 2 As shown, the surface layer 4 of the black polyester film prepared in the embodiment of the present application contains the modified PET polyester masterbatch prepared in the present application, and the modified PET polyester masterbatch contains modified silica powder 3. Figure 1 As shown, the amount of carbon black powder 2 in the core layer 5 of the black polyester film of the present application is significantly less than Figure 2 The amount of carbon black powder in the core layer 5 of the polyester film in the prior art. Figure 2 The silicon dioxide powder 1 in the surface layer of the polyester film is white.

[0055] The particle size of silica used in the opening agent masterbatch added to the surface of polyester film is usually about 3.5μm. Its particle size is larger. After silica modification, adding a small amount of silica can replace more carbon black, thereby achieving the effect of reducing costs at one time.

[0056] In the present invention, the melting temperature of the main extruder and the auxiliary extruder is 278° C., and the masterbatch is mainly formed by blending carbon black powder and polyethylene terephthalate.

[0057] In the present invention, the core layer melt and the surface layer melt are respectively extruded from the main extruder and the auxiliary extruder and then conveyed to the adapter module after passing through their respective pre-filters, metering pumps, and fine filters. The melt extruded from the three-layer co-extrusion die is cooled at 15°C and then cast to obtain a polyester film sheet.

[0058] In the present invention, the polyester film sheet is preheated to 90°C and longitudinally stretched at 90°C with a longitudinal stretch ratio of 3.3, then preheated to 105°C and transversely stretched with a transverse stretch ratio of 3.7, and then heat-set at 200°C and cooled to room temperature, and finally rolled up by traction to obtain a fully light-shielding black polyester film.

[0059] The low-cost black polyester film provided by the present invention is prepared by the above-mentioned method for preparing the low-cost black polyester film.

[0060] The following is a detailed description through comparative examples and embodiments.

[0061] Comparative Example 1

[0062] Step 1: Disperse silicon dioxide evenly in ethylene glycol solution, mix ethylene glycol and terephthalic acid and obtain PET polyester masterbatch through polymerization reaction.

[0063] Step 2: Mix the PET polyester masterbatch and PET polyester chips in step 1 according to the content of 10000ppm of silica powder.

[0064] Step 3: Mix PET polyester chips and masterbatch in a mass ratio of 80:20.

[0065] Step 4: The raw material prepared in step 2 is fed into the auxiliary extruder by suction, and the raw material prepared in step 3 is fed into the main extruder by suction, and melt-extruded at 278°C. The melt passes through the pre-filter, metering pump, and fine filter of the main extruder and the auxiliary extruder respectively, and is uniformly transported to the adapter module. After passing through the internal flow channel of the adapter, it is layered. The melt of the main extruder is distributed in the core layer, and the melt of the auxiliary extruder is distributed in the upper and lower surface layers.

[0066] Step 5: The distributed melt enters a three-layer co-extrusion die, and the core layer melt is extruded from the middle layer of the three-layer co-extrusion die. At the same time, the upper and lower surface layer melts are extruded from the upper and lower layers of the three-layer co-extrusion die respectively. The extruded melt is cooled at 15°C and then cast to obtain a polyester film sheet.

[0067] Step 6: Preheat the polyester film sheet obtained in step 5 to 90°C, and stretch it longitudinally at this temperature with a longitudinal stretching ratio of 3.3, then preheat it to 105°C and stretch it transversely with a transverse stretching ratio of 3.7, and cool it to room temperature after heat setting at 200°C, and finally roll it up by pulling to obtain a fully light-shielding black polyester film.

[0068] The conventional polyester film is a three-layer composite structure, in which the two surface layers are conventional masterbatch plus PET polyester, and the core layer is masterbatch plus PET polyester. The thickness of the conventional full-light-shielding black polyester film is 25μm, in which the core layer is 22.5μm thick and the upper and lower surface layers are 1.25μm thick. The properties of the conventional full-light-shielding black polyester film are as follows:

[0069] performance index Light transmittance 0％ L 39.81 a 0.16 b -0.96

[0070] The meanings of L, a, and b are as follows: L value: represents the brightness of an object, that is, the depth and brightness of the color. The range of L value is 0-100. The higher the value, the lighter the color, the closer to white; the lower the value, the darker the color, the closer to black. a value: represents the red-green color. The range of a value is -128 to +128. Positive values ​​indicate reddish color, while negative values ​​indicate greenish color. b value: represents the yellow-blue color. The range of b value is also -128 to +128. Positive values ​​indicate yellowish color, while negative values ​​indicate bluish color.

[0071] Example 1

[0072] This embodiment provides a method for preparing a low-cost fully light-shielding black polyester film, comprising the following steps:

[0073] Step 1: Take a container and dissolve sucrose solution in desalted water at a mass ratio of 20%.

[0074] Step 2: Disperse the silica powder evenly in the solution prepared in step 1 and soak for 24 hours.

[0075] Step 3: Place the solution of step 2 in an evaporating dish and evaporate the solution completely to obtain sucrose-silicon dioxide.

[0076] Step 4: Place the sucrose-silica obtained in step 3 in a muffle furnace at 600° C. for 6 hours, wait for the sucrose to be completely carbonized, and obtain modified silica.

[0077] Step 5: The modified silica in step 4 is dispersed by ball milling to a dispersion degree the same as the particle size of the silica powder in step 2, thereby obtaining modified silica powder.

[0078] Step 6: Evenly disperse the modified silica powder in step 5 into the ethylene glycol solution, mix the ethylene glycol and terephthalic acid, and obtain the modified PET polyester masterbatch through polymerization reaction.

[0079] Step 7: Mix the modified PET polyester masterbatch in step 6 with the PET polyester chips according to the content of 10000ppm of modified silica powder.

[0080] Step 8: Mix PET polyester chips and masterbatch in a ratio of 85:15.

[0081] Step 9: The raw material prepared in step 7 is fed into the auxiliary extruder by suction, and the raw material prepared in step 8 is fed into the main extruder by suction, and melt-extruded at 278°C. The melt passes through the pre-filter, metering pump, and fine filter of the main extruder and the auxiliary extruder respectively, and is uniformly transported to the adapter module. After passing through the internal flow channel of the adapter, it is layered. The melt of the main extruder is distributed in the core layer, and the melt of the auxiliary extruder is distributed in the upper and lower surface layers.

[0082] Step 10: The distributed melt enters a three-layer co-extrusion die, and the core layer melt is extruded from the middle layer of the three-layer co-extrusion die. At the same time, the upper and lower surface layer melts are extruded from the upper and lower layers of the three-layer co-extrusion die respectively. The extruded melt is cooled at 15°C and then cast to obtain a polyester film sheet.

[0083] Step 11: Preheat the polyester film sheet obtained in step 10 to 90°C, and stretch it longitudinally at this temperature with a longitudinal stretching ratio of 3.3, then preheat it to 105°C and stretch it transversely with a transverse stretching ratio of 3.7, and cool it to room temperature after heat setting at 200°C, and finally roll it up by pulling to obtain a fully light-shielding black polyester film.

[0084] The conventional polyester film is a three-layer composite structure, in which the two surface layers are modified PEI polyester masterbatch plus PET polyester, and the core layer is masterbatch plus PET polyester. The thickness of the conventional full-light-shielding black polyester film is 25μm, in which the core layer thickness is 22.5μm, and the upper and lower surface layers are 1.25μm thick. The properties of the modified masterbatch full-light-shielding black polyester film are as follows:

[0085] performance index Light transmittance 0％ L 38.99 a 0.14 b -0.92

[0086] Example 2

[0087] This embodiment provides a method for preparing a low-cost fully light-shielding black polyester film.

[0088] Step 1: Take a container and dissolve sucrose solution in desalted water at a mass ratio of 50%.

[0089] Step 2: Disperse the silica powder evenly in the solution prepared in step 1 and soak for 24 hours.

[0090] Step 3: Place the solution of step 2 in an evaporating dish and evaporate the solution completely to obtain sucrose-silicon dioxide.

[0091] Step 4: Place the sucrose-silica obtained in step 3 in a muffle furnace at 600° C. for 6 hours, wait for the sucrose to be completely carbonized, and obtain modified silica.

[0092] Step 5: The modified silica in step 4 is dispersed by ball milling to a dispersion degree the same as the particle size of the silica powder in step 2, thereby obtaining modified silica powder.

[0093] Step 6: Evenly disperse the modified silica powder in step 5 into the ethylene glycol solution, mix the ethylene glycol and terephthalic acid, and obtain the modified PET polyester masterbatch through polymerization reaction.

[0094] Step 7: Mix the modified PET polyester masterbatch in step 6 with the PET polyester chips according to the content of 10000ppm of modified silica powder.

[0095] Step 8: Mix PET polyester chips and masterbatch in a ratio of 90:10.

[0096] Step 9: The raw material prepared in step 7 is fed into the auxiliary extruder by suction, and the raw material prepared in step 8 is fed into the main extruder by suction, and melt-extruded at 278°C. The melt passes through the pre-filter, metering pump, and fine filter of the main extruder and the auxiliary extruder respectively, and is uniformly transported to the adapter module. After passing through the internal flow channel of the adapter, it is layered. The melt of the main extruder is distributed in the core layer, and the melt of the auxiliary extruder is distributed in the upper and lower surface layers.

[0097] Step 10: The distributed melt enters a three-layer co-extrusion die, and the core layer melt is extruded from the middle layer of the three-layer co-extrusion die. At the same time, the upper and lower surface layer melts are extruded from the upper and lower layers of the three-layer co-extrusion die respectively. The extruded melt is cooled at 15°C and then cast to obtain a polyester film sheet.

[0098] Step 11: Preheat the polyester film sheet obtained in step 10 to 90°C, and stretch it longitudinally at this temperature with a longitudinal stretching ratio of 3.3, then preheat it to 105°C and stretch it transversely with a transverse stretching ratio of 3.7, and cool it to room temperature after heat setting at 200°C, and finally roll it up by pulling to obtain a fully light-shielding black polyester film.

[0099] The conventional polyester film is a three-layer composite structure, in which the two surface layers are modified PEI polyester masterbatch plus PET polyester, and the core layer is masterbatch plus PET polyester. The thickness of the conventional full-light-shielding black polyester film is 25μm, in which the core layer thickness is 22.5μm, and the upper and lower surface layers are 1.25μm thick. The properties of the modified masterbatch full-light-shielding black polyester film are as follows:

[0100] performance index Light transmittance 0％ L 39.32 a 0.17 b -0.99

[0101] Example 3

[0102] This embodiment provides a method for preparing a low-cost fully light-shielding black polyester film.

[0103] Step 1: Take a container and dissolve sucrose solution in desalted water at a mass ratio of 80%.

[0104] Step 2: Disperse the silica powder evenly in the solution prepared in step 1 and soak for 24 hours.

[0105] Step 3: Place the solution of step 2 in an evaporating dish and evaporate the solution completely to obtain sucrose-silicon dioxide.

[0106] Step 4: Place the sucrose-silica obtained in step 3 in a muffle furnace at 600° C. for 6 hours, wait for the sucrose to be completely carbonized, and obtain modified silica.

[0107] Step 5: The modified silica in step 4 is dispersed by ball milling to a dispersion degree the same as the particle size of the silica powder in step 2, thereby obtaining modified silica powder.

[0108] Step 6: Evenly disperse the modified silica powder in step 5 into the ethylene glycol solution, mix the ethylene glycol and terephthalic acid, and obtain the modified PET polyester masterbatch through polymerization reaction.

[0109] Step 7: Mix the modified PET polyester masterbatch in step 6 with the PET polyester chips according to the content of 10000ppm of modified silica powder.

[0110] Step 8: Mix PET polyester chips and masterbatch in a ratio of 95:5.

[0111] Step 9: The raw material prepared in step 7 is fed into the auxiliary extruder by suction, and the raw material prepared in step 8 is fed into the main extruder by suction, and melt-extruded at 278°C. The melt passes through the pre-filter, metering pump, and fine filter of the main extruder and the auxiliary extruder respectively, and is uniformly transported to the adapter module. After passing through the internal flow channel of the adapter, it is layered. The melt of the main extruder is distributed in the core layer, and the melt of the auxiliary extruder is distributed in the upper and lower surface layers.

[0112] Step 10: The distributed melt enters a three-layer co-extrusion die, and the core layer melt is extruded from the middle layer of the three-layer co-extrusion die. At the same time, the upper and lower surface layer melts are extruded from the upper and lower layers of the three-layer co-extrusion die respectively. The extruded melt is cooled at 15°C and then cast to obtain a polyester film sheet.

[0113] Step 11: Preheat the polyester film sheet obtained in step 10 to 90°C, and stretch it longitudinally at this temperature with a longitudinal stretching ratio of 3.3, then preheat it to 105°C and stretch it transversely with a transverse stretching ratio of 3.7, and cool it to room temperature after heat setting at 200°C, and finally roll it up by pulling to obtain a fully light-shielding black polyester film.

[0114] The conventional polyester film is a three-layer composite structure, in which the two surface layers are modified PEI polyester masterbatch plus PET polyester, and the core layer is masterbatch plus PET polyester. The thickness of the conventional full-light-shielding black polyester film is 25μm, in which the core layer thickness is 22.5μm, and the upper and lower surface layers are 1.25μm thick. The properties of the modified masterbatch full-light-shielding black polyester film are as follows:

[0115]

[0116]

[0117] It can be seen from the list of polyester film performance indicators obtained from the comparative examples and embodiments of the present application that the performance of the modified masterbatch full-light-shielding black polyester film obtained in the three embodiments of the present application is not greatly different from that of the conventional full-light-shielding black polyester film obtained in the comparative examples.

[0118] However, by modifying silica with sucrose solution to obtain modified silica powder, and then obtaining modified polyester masterbatch, which is used as the surface layer raw material to prepare the upper and lower surface layers of the black polyester film, while ensuring full light-shielding performance, the use of core layer raw material masterbatch (core layer carbon black powder) can be reduced, and the amount of core layer carbon black powder added can be greatly reduced, thereby reducing production costs.

[0119] Moreover, by comparing the three embodiments of the present application, the mass proportion of the sucrose solution gradually increases from dissolving the sucrose solution in the desalted water at a mass proportion of 20% to dissolving the sucrose solution in the desalted water at a mass proportion of 80%, and the mass ratio of the PET polyester chips and the masterbatch in the core layer raw material is adjusted from 85:15 to 95:5, and the amount of the masterbatch added gradually decreases. It can be seen that the greater the amount of sucrose solution added, the less the amount of masterbatch (core layer carbon black powder) added, and the production cost is further reduced. As a large-scale production and research and development enterprise, the applicant has a very obvious cost reduction benefit.

[0120] The fully light-shielding polyester film obtained by this patent can reduce the cost by 10%, and at the same time, reducing the amount of carbon black added in the core layer can also greatly optimize the problem of carbon black precipitation.

[0121] This application scheme has the following advantages:

[0122] 1. The method of modifying silicon dioxide with sucrose solution is used, and the silicon dioxide is changed from white powder to black powder through the carbonization process, which makes up for the disadvantage that the light-shielding effect of silicon dioxide is not as good as that of carbon black.

[0123] 2. The application of sucrose-modified silica powder in the field of biaxially oriented polyester film is a new process that has not been discovered yet. The process is simple to operate and has obvious cost advantages.

[0124] 3. The production cost of the modified masterbatch full-light-shielding black polyester film obtained by the present invention is reduced by about 10% compared with the conventional full-light-shielding black polyester film, and the advantage is very obvious.

[0125] This application adopts a modification-calcination method to obtain modified silica powder, which can greatly reduce the amount of core carbon black powder added when producing a fully light-shielding black polyester film, thereby reducing production costs. In addition, due to its small particle size, carbon black will precipitate during the production and use of black polyester film. The present invention uses modified silica to replace a large amount of carbon black powder, which can improve the problem of carbon black precipitation to a certain extent. The patent of this invention not only reduces the production cost of the film, but also improves the problem of carbon black precipitation. The above advantages create higher product value.

[0126] The present application can also improve the toughness of the black polyester film and prevent the film from becoming brittle and easy to break. Increasing the amount of core color carbon black added or using a carbon black material with a larger particle size will both have a great impact on the production success rate of the film, because the carbon black material has good heat absorption and thermal conductivity, and increasing the amount of addition will increase the crystallinity of the polyester film, causing the film to become brittle and easy to break.

[0127] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for preparing a modified polyester masterbatch for black polyester film, characterized in that: Includes steps: dissolving the sucrose solution in desalted water to form a sucrose soaking solution; Evenly dispersing silicon dioxide powder into the sucrose soaking solution and soaking for a predetermined time to form a silicon dioxide sucrose soaking solution; Put the silicon dioxide sucrose soaking liquid after soaking for a predetermined time into an evaporation container and evaporate it completely to obtain sucrose-silicon dioxide; placing sucrose-silicon dioxide in a heating furnace, heating it to a set temperature and keeping it warm for a set time, so that the sucrose is completely carbonized to obtain modified silicon dioxide; The modified silicon dioxide is ground to obtain modified silicon dioxide powder, and the modified silicon dioxide powder is evenly dispersed in an ethylene glycol solution, and then the ethylene glycol solution containing the modified silicon dioxide powder is mixed with terephthalic acid to obtain a modified PET polyester masterbatch for preparing a black polyester film surface layer through a polymerization reaction.

2. The method for preparing the modified polyester masterbatch according to claim 1, characterized in that: When the sucrose solution is dissolved in desalted water, the mass of the sucrose solution is 20%-80% of the mass of the desalted water.

3. The method for preparing the modified polyester masterbatch according to claim 1, characterized in that: The silicon dioxide powder is evenly dispersed in the sucrose soaking solution and soaked for 24 hours.

4. The method for preparing the modified polyester masterbatch according to claim 1, characterized in that: The sucrose-silica was placed in a muffle furnace and heated to 600° C. and kept warm for 6 hours to completely carbonize the sucrose to obtain modified silica.

5. The method for preparing modified polyester masterbatch according to claim 1, characterized in that: The silicon dioxide powder is prepared by a gas phase method and has a particle size of 3.5 μm.

6. A method for preparing a low-cost black polyester film, characterized in that: The following steps are involved: S1. Mixing the modified PET polyester masterbatch prepared by the preparation method according to any one of claims 1 to 5 with the first PET polyester chip to form a surface layer raw material, wherein the content of modified silicon dioxide powder in the formed surface layer raw material mixture is 10000 ppm; S2, mixing the second PET polyester chips and the masterbatch in a mass ratio of (85-95):(5-15) to form a core layer material; S3, the core layer raw material enters the main extruder and melts into a core layer melt under a set melting temperature condition, the surface layer raw material enters the auxiliary extruder and melts into a surface layer melt under a set melting temperature condition, the core layer melt and the surface layer melt are respectively extruded from the main extruder and the auxiliary extruder and transported to the adapter module, and are layered after passing through the internal flow channel of the adapter module, the core layer melt is layered and distributed in the core layer, and the surface layer melt is layered and distributed in the upper surface layer and the lower surface layer; S4, feeding the allocated core layer melt and the surface layer melt into a three-layer co-extrusion die, the core layer melt is extruded from the middle layer of the three-layer co-extrusion die, and at the same time, the surface layer melt of the upper surface layer and the surface layer melt of the lower surface layer are extruded from the upper layer and the lower layer of the three-layer co-extrusion die respectively, and the melt extruded from the three-layer co-extrusion die is cooled at a set cooling temperature and then cast to obtain a polyester film sheet; S5, preheating and stretching the polyester film sheet, reheating and shaping it, and then cooling it to room temperature to form a black polyester film.

7. The method for preparing a low-cost black polyester film according to claim 6, characterized in that: The melting temperature of the main extruder and the auxiliary extruder is 278° C., and the raw materials of the masterbatch include carbon black powder and polyethylene terephthalate.

8. The method for preparing a low-cost black polyester film according to claim 7, characterized in that: The core layer melt and the surface layer melt are extruded from the main extruder and the auxiliary extruder respectively, and then passed through their respective pre-filters, metering pumps, and fine filters before being transported to the adapter module. The melt extruded from the three-layer co-extrusion die is cooled at 15° C. and then cast to obtain a polyester film sheet.

9. The method for preparing a low-cost black polyester film according to claim 8, characterized in that: The polyester film sheet is preheated to 90°C and longitudinally stretched at 90°C with a longitudinal stretch ratio of 3.3, then preheated to 105°C and transversely stretched with a transverse stretch ratio of 3.7, and then heat-set at 200°C and cooled to room temperature, and finally rolled up by traction to obtain a fully light-shielding black polyester film.

10. A low-cost black polyester film, characterized in that: The method is used to prepare the low-cost black polyester film according to any one of claims 6 to 9.

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