A matte polyester film and its preparation method

Abstract

The present application discloses a matte polyester film and a preparation method thereof. The matte polyester film includes upper and lower white surface layers, and a black light-absorbing layer disposed between the white surface layers. The preparation raw material of the black light-absorbing layer includes a first filler, and the first filler is a mixture of modified serpentine and polyethylene terephthalate. By adding the first filler to the preparation raw material of the black light-absorbing layer, the adhesion between the layers of the prepared matte polyester film is improved, the bite force of the overall film layer is enhanced, it has a low light transmittance, and also has a certain antibacterial property, which can broaden the application fields of the polyester film.

Description

Technical Field

[0001] This application relates to the field of polyester films, and particularly to a matte polyester film and a preparation method thereof. Background Art

[0002] Matte polyester films have a wide range of applications in multiple fields due to their unique optical and physical properties. Such films are mainly used in products such as heat transfer films, hot stamping films, hot stamping cloth, leather, transfer papers, decorative sheet materials and profiles, aluminized color printing packaging, and nameplates. According to different gloss levels, matte polyester films can be divided into three categories: low matte, medium matte, and high matte. Among them, high matte products, with a haze greater than 95% and a gloss less than 17%, are particularly suitable for high-end cosmetic packaging, high-end decorative sheet materials and profiles, transfer cigarette pack inner liners, hot stamping leather, hot stamping cloth, and other transfer products, which usually require a very low gloss or even no gloss on the pattern surface.

[0003] Currently, the research on matte polyester films mainly focuses on improving their properties through two methods: copolymer modification and inorganic filler modification. Although the copolymer modification method can meet the requirements of high haze and mechanical properties, its development is limited due to complex processes and high costs. Therefore, the industry generally uses inorganic filler modification to improve the matte degree of PET films. Researchers have added different types of inorganic fillers, such as nano-silica, kaolin, and barium sulfate, to improve the matte effect of PET films. While improving the matte effect, these studies are also exploring how to maintain or improve the mechanical strength and light transmittance of the films.

[0004] Despite certain progress in existing research, matte polyester films still have some drawbacks that need further improvement. For example, increasing the additive content to achieve high haze and low gloss effects may lead to poor dispersion of additives and poor interfacial compatibility with polyester, thus reducing the mechanical strength of the polyester film. In addition, in existing preparation methods such as in-situ polymerization, the effective content of the matting agent is limited by the process, and the gloss of the prepared polyester matte film is relatively high, which can only be used for producing ordinary polyester matte films. To obtain high matte polyester films, an additional coating treatment process is usually required on the film surface, which not only increases costs but also may cause environmental pollution. Therefore, future research needs to explore more efficient inorganic filler dispersion technologies and develop new preparation methods to improve the performance of matte polyester films, reduce production costs, and minimize environmental impact. Summary of the Invention

[0005] The purpose of this application is to provide a polyester film with low light transmittance, good mechanical properties, and certain antibacterial properties.

[0006] To achieve the above object, the technical solution adopted in this application is as follows: Provide a matte polyester film, including white surface layers on the upper and lower layers, and a black light-absorbing layer disposed between the white surface layers. The preparation raw materials of the black light-absorbing layer include a first filler, and the first filler is a mixture of modified serpentine and polyethylene terephthalate.

[0007] As a preference, the modified serpentine and the polyethylene terephthalate are mixed in a mass ratio of (1:1) to (1:5) to obtain the first filler.

[0008] As another preference, the particle size of the modified serpentine is 100 - 200 nm, and the particle size of the polyethylene terephthalate is 400 - 500 nm.

[0009] As another preference, the preparation raw materials of the modified serpentine include: copper formate, serpentine, saturated fatty acid, silane coupling agent and solution.

[0010] As another preference, the preparation method of the modified serpentine is as follows: Dissolve copper formate and add serpentine powder and saturated fatty acid, react under increased temperature and pressure, then concentrate the solution under reduced pressure to obtain a reactant. Calcinate the reactant in an oxygen atmosphere and a vacuum atmosphere in sequence, grind it into powder and mix it with ethanol, then add a silane coupling agent and react for a period of time, concentrate under reduced pressure and dry to obtain the modified serpentine.

[0011] As another preference, the preparation raw materials of the black light-absorbing layer further include: black pigment, kaolin, barium sulfate, silane coupling agent and PET masterbatch.

[0012] As another preference, the preparation raw materials of the white surface layer include: polyacrylonitrile, glass fiber, lignin, the first filler, talcum powder, calcium carbonate, alumina ceramic powder and PET masterbatch.

[0013] The present application also provides a method for preparing a matte polyester film, comprising the following preparation steps: S1: Dissolve copper formate and add serpentine powder and saturated fatty acid, heat up and increase pressure for reaction, then concentrate the solution under reduced pressure to obtain a reactant. Calcinate the reactant successively in an oxygen atmosphere and a vacuum atmosphere, grind it into powder, mix it with ethanol, then add a silane coupling agent and react for a period of time, concentrate under reduced pressure and dry to obtain modified serpentine; S2: Grind the modified serpentine and polyethylene terephthalate into powders respectively and mix them to form a first filler; Mix the first filler, black pigment, kaolin, barium sulfate, silane coupling agent and PET masterbatch, and extrude them through a twin-screw extruder to obtain a black light-absorbing layer; S3: Grind polyacrylonitrile, glass fiber and lignin into powder, then add the first filler, talc powder, calcium carbonate powder, alumina ceramic and PET masterbatch, mix them and extrude them through a twin-screw extruder to obtain a white surface layer; Set the white surface layer on both sides of the black light-absorbing layer, and heat and melt and extrude the three-layer film in a casting machine, and obtain the matte polyester film after stretching and shaping.

[0014] As another preference, in the step S1, the reactant is calcined at 600 - 630 °C for 2 - 3 h in an oxygen atmosphere, and then transferred to a vacuum furnace and calcined at 850 - 880 °C for 50 - 80 min to obtain a calcined product.

[0015] Further preferably, the calcined product and ethanol are mixed in a mass ratio of 2:(55 - 59).

[0016] Compared with the prior art, the beneficial effects of the present application are as follows:

[0017] (1) In the present application, a first filler is added to the raw materials for preparing the black light-absorbing layer, the adhesion between layers of the obtained matte polyester film is improved, the bite force of the overall film layer is enhanced, and it has a lower light transmittance;

[0018] (2) In the present application, kaolin and a silane coupling agent are added to the raw materials for preparing the black light-absorbing layer, so that the distribution of other filler particles is more uniform, and the light-absorbing effect of black is strengthened;

[0019] (3) In the present application, the white surface layer uses glass fiber to form a network structure of polyester, and promotes the fusion of glass fiber and polyester through the multi-branched characteristics of lignin, forming a film layer with a dense structure and a uniform graft structure, and having better rigidity. Specific Embodiments

[0020] Next, in combination with specific embodiments, the present application will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be combined arbitrarily to form new embodiments.

[0021] The terms "comprising" and "having" in the description and claims of this application, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0022] The matte polyester film of this application comprises a double-layer white surface layer and a black light-absorbing layer between the white surface layers. The raw materials for preparing the black light-absorbing layer include a first filler, which is a mixture of modified serpentine and polyethylene terephthalate.

[0023] By adding the first filler to the raw materials for preparing the black light-absorbing layer, the matte polyester film obtained has improved adhesion between layers and enhanced bite force of the overall film layer. It has a low light transmittance and additionally has certain antibacterial properties.

[0024] In some embodiments, the raw materials for preparing the modified serpentine include: copper formate, serpentine, saturated fatty acid, silane coupling agent, ethanol, and solution.

[0025] Serpentine is a general term for hydrous magnesium-rich silicate minerals, including antigorite, lizardite, chrysotile, etc. Their colors are usually greenish, but can also be light gray, white, or yellow, etc. Serpentine gets its name because its outer surface is weathered into grayish-white and stone-red reticulations, resembling snake skin. The structure of serpentine often has a curly shape, like fibers, and such serpentine is often used as asbestos. Both massive and fibrous serpentine have luster, with the massive having a waxy luster and the fibrous having a silky luster.

[0026] When serpentine is added to the polyester film, serpentine has high chemical activity, and there are unsaturated Si—O—Si, O—Si—O, magnesium-containing bonds, OH— and other active groups on its broken structure, which can enhance the chemical stability of the PET film.

[0027] Serpentine has a low hardness, can withstand high temperatures of 550 - 700 °C, has stable properties, strong adsorption, good wear resistance, and a low friction coefficient. These characteristics enable serpentine to be used in the preparation of lubricating self-repair agents, and adding it to the PET film may improve the wear resistance and friction-reducing performance of the film.

[0028] Serpentine can be used to prepare environmental materials for adsorbing harmful anions, heavy metal ions, and some organic substances. Therefore, adding serpentine may endow the PET film with environmental purification function. In addition, adding serpentine to the PET film may improve the heat resistance of the film.

[0029] In some embodiments, a method for preparing modified serpentine is provided: copper formate is dissolved in a solvent, serpentine powder and a saturated fatty acid are added, the reaction is carried out under elevated temperature and pressure for a period of time, and then concentrated under reduced pressure to obtain a reaction product. The reaction product is calcined in an oxygen atmosphere, ground into a powder, mixed with ethanol, and then reacted with a silane coupling agent for a period of time. After concentration under reduced pressure and drying, modified serpentine is obtained.

[0030] In this application, by preparing modified serpentine powder, the membrane strength and biological resistance are improved. Copper formate is mixed and dissolved with ultrapure water, serpentine powder is added for adsorption, and a saturated fatty acid is added. The boiling solution is used to promote the movement of the serpentine powder, fully adsorb copper formate, and at the same time, the temperature is increased. The high boiling point of the saturated fatty acid is used to promote the temperature rise of the mixed solution, and copper ions are formed in the mixed solution to achieve the purpose of copper loading on serpentine. After drying, high-temperature treatment is carried out multiple times to convert the copper in the serpentine into copper oxide, and then a silane coupling agent is added to improve the fusion effect of the modified serpentine in polyester. The prepared film layer has a large friction force, a higher bonding effect when forming a composite film by combining multiple layers of films, a strong bite force of the overall film layer, and a higher film use strength.

[0031] Moreover, after serpentine is loaded with copper oxide, the active copper oxide ions on the surface of nano-copper oxide can interact with the cell membranes of bacteria or fungi, destroy their cell structures and functions, and thus inhibit their growth and reproduction. This antibacterial mechanism enables nano-copper oxide to have strong antibacterial activity against a variety of pathogenic microorganisms, making it difficult for the film layer to be attached and reproduced by microorganisms in a complex environment, ensuring the cleanliness of the film layer, and making the polyester film have a certain antibacterial property.

[0032] In some preferred embodiments, the saturated fatty acid is a carbon chain containing 15 - 17 carbon atoms in the molecular formula, such as pentadecanoic acid, hexadecanoic acid, or heptadecanoic acid.

[0033] In some preferred embodiments, the silane coupling agent is selected from KH550 or KH570.

[0034] In some embodiments, this application also provides a method for preparing a first filler: the modified serpentine and polyethylene terephthalate are ground into powders, and the modified serpentine powder and the polyethylene terephthalate powder are mixed to obtain the first filler.

[0035] In some preferred embodiments, the modified serpentine powder and the polyethylene terephthalate powder are mixed in a mass ratio of (1:1) - (1:5) to obtain the first filler.

[0036] In some embodiments, the modified serpentine is ground into a powder with a particle size of 100 - 200 nm, and the polyethylene terephthalate is ground into a powder with a particle size of 400 - 500 nm.

[0037] In some embodiments, the raw materials for preparing the black light-absorbing layer of the present application include: a first filler, a black pigment, kaolin, barium sulfate, a silane coupling agent, and a PET masterbatch.

[0038] Adding kaolin to the black light-absorbing layer, the layered structure of kaolin accommodates polyester molecular chains, strengthens the adsorption of barium sulfate and the black pigment. After grafting by adding a silane coupling agent, the filler particles in the film layer are more evenly distributed, and the black light-absorbing effect is strengthened. Especially when the temperature of the film layer rises after light absorption, through the blocking of kaolin and barium sulfate, the high-temperature stability of the film layer can be ensured, and better structural strength can be guaranteed during use.

[0039] In some embodiments, the raw materials for preparing the white surface layer also include the first filler.

[0040] In some embodiments, the raw materials for preparing the white surface layer of the present application include: polyacrylonitrile, glass fiber, lignin, a first filler, talcum powder, calcium carbonate, alumina ceramic powder, and a PET masterbatch.

[0041] In the white surface layer, by mixing polyacrylonitrile with glass fiber and lignin, the high melting point of polyacrylonitrile is used to adhere to glass fiber and lignin to improve the high-temperature support performance of the film layer. The glass fiber forms a network structure of polyester, and through the multi-branched characteristics of lignin, the fusion of glass fiber and polyester is promoted to form a film layer with a dense structure and a uniform graft structure, having better stiffness.

[0042] In some embodiments, the present application also provides a method for preparing a matte polyester film: placing the black light-absorbing layer between two layers of white surface layers, heating, melting, extruding, stretching, and shaping the three-layer material in a casting machine to form the matte polyester film of the present application.

[0043] The present application also provides a method for preparing a matte polyester film, including the following preparation steps:

[0044] S1: Dissolve copper formate and add serpentine powder and saturated fatty acid, raise the temperature and pressure for reaction, then concentrate the solution under reduced pressure to obtain a reactant. Calcinate the reactant successively in an oxygen atmosphere and a vacuum atmosphere, grind it into powder, mix it with ethanol, then add a silane coupling agent and react for a period of time, concentrate under reduced pressure and dry to obtain modified serpentine.

[0045] S2: Grind the modified serpentine and polyethylene terephthalate into powders and mix them to make a first filler; mix the first filler, black pigment, kaolin, barium sulfate, silane coupling agent, and PET masterbatch, and extrude them through a twin-screw extruder to obtain the black light-absorbing layer.

[0046] S3: Grind polyacrylonitrile, glass fiber, and lignin into powder, add the first filler, talcum powder, calcium carbonate powder, alumina ceramics, and PET masterbatch, mix, and extrude through a twin-screw extruder to obtain a white surface layer;

[0047] White surface layers are arranged on both sides of the black light-absorbing layer, and the three-layer film is heated, melted and extruded in a casting machine, and a matte polyester film is obtained after stretching and shaping.

[0048] Example 1

[0049] A matte polyester film is prepared, comprising the following preparation steps:

[0050] S1: By weight, 1 part of copper formate was mixed with 20 parts of ultrapure water, 13 parts of serpentine powder with a particle size of 100 nm was added, the solution was heated to 30 °C and stirred for reaction for 50 min, 40 parts of 15-carbon saturated fatty acid were added, and the pressure was increased so that the container maintained about 1.3 standard atmospheric pressure, the solution was heated to boiling and continued for 15 min, and then the solution was concentrated under reduced pressure at room temperature and pressure to obtain a reactant;

[0051] The reactants were placed in a calcining furnace and calcined at 600 °C for 2 h in an oxygen atmosphere, and then transferred to a vacuum furnace and calcined at 850 °C for 50 min. The calcined product was placed in a ball mill and ground for 2 h. The powder was mixed with ethanol at a mass ratio of 2:55, and 6% of the mass fraction of silane coupling agent KH550 was added to the mixed powder. The mixture was ultrasonically shaken for 40 min, and the solution was concentrated under reduced pressure and dried to obtain modified serpentine.

[0052] S2: Grinding the modified serpentine into a powder of 100 nm in a grinder, grinding the polyethylene terephthalate into a powder of 400 nm in a grinder, and mixing the two powders in a ratio of 1:2 to prepare a first filler;

[0053] By weight, 80 parts of the first filler, 15 parts of carbon black, 5 parts of kaolin, 3 parts of barium sulfate, 1 part of KH550 silane coupling and 200 parts of PET masterbatch were mixed for 30 minutes and extruded by a twin-screw extruder at 260°C to obtain a black light-absorbing layer;

[0054] S3: By weight, 10 parts of polyacrylonitrile, 1 part of glass fiber, and 1 part of lignin raw material were mixed into a grinder and ground into a powder of 300 nm, and then 110 parts of the first filler, 15 parts of talc, 10 parts of calcium carbonate powder, 8 parts of alumina ceramics, and 200 parts of PET masterbatch were added. The materials were mixed and stirred for 30 minutes, and then heated to 280 °C and extruded in a twin-screw extruder to obtain a white surface layer;

[0055] Using a black light-absorbing layer as the core material and white surface layers on the top and bottom, with the black light-absorbing layer sandwiched between the two white surface layers, and the mass ratio of the black light-absorbing layer to the white surface layer being 3:1, it is heated and melt-extruded in a casting machine and stretched and shaped into a film at 90 - 93 °C to obtain the matte polyester film of the present application.

[0056] Example 2

[0057] To prepare a matte polyester film, the following preparation steps are included:

[0058] S1: By mass, 5 parts of copper formate are mixed with 30 parts of ultrapure water, 15 parts of serpentine powder with a particle size of 150 nm are added, the solution is heated to 35 °C and stirred for reaction for 70 min, 50 parts of 17-carbon saturated fatty acid are added, the pressure is increased to maintain about 1.5 standard atmospheres in the container, the solution is heated to boiling and continued for 18 min, and then the solution is concentrated under reduced pressure at normal temperature and pressure to obtain the reactant;

[0059] The reactant is placed in a roasting furnace and calcined at 630 °C for 3 h in an oxygen atmosphere, and then transferred to a vacuum furnace and calcined at 880 °C for 80 min; the calcined product is placed in a ball mill and ground for 4 h, the powder is mixed with ethanol according to a mass ratio of 2:59, and a silane coupling agent KH550 with a mass fraction of 7% is added to the mixed powder, ultrasonic oscillation is carried out for 45 min, and after the solution is concentrated under reduced pressure and dried, modified serpentine is obtained;

[0060] S2: The modified serpentine is ground into powder with a size of 200 nm in a grinder, and polyethylene terephthalate is ground into powder with a size of 500 nm in a grinder. The two powders are mixed in a ratio of 1:1 to make the first filler;

[0061] By mass, 90 parts of the first filler, 18 parts of carbon black, 8 parts of kaolin, 5 parts of barium sulfate, 2 parts of KH570 silane coupling agent and 200 parts of PET masterbatch are mixed for 30 min and extruded by a twin-screw extruder at 275 °C to obtain the black light-absorbing layer;

[0062] S3: By mass, 15 parts of polyacrylonitrile, 3 parts of glass fiber, and 2 parts of lignin raw material are mixed into a grinder and ground into powder with a size of 400 nm, and then 120 parts of the first filler, 19 parts of talc powder, 13 parts of calcium carbonate powder, 11 parts of alumina ceramic and 200 parts of PET masterbatch are added. The materials are mixed and stirred for 37 min, then the temperature is raised to 295 °C and extruded in a twin-screw extruder to obtain the white surface layer;

[0063] Using a black light-absorbing layer as the core material and white surface layers as the upper and lower surface layers, with the black light-absorbing layer sandwiched between the two white surface layers, and the mass ratio of the black light-absorbing layer to the white surface layer being 3:1.4, heat and melt-extrude in a casting machine, and stretch and shape into a film at 90 - 93 °C to obtain the matte polyester film of the present application.

[0064] Example 3

[0065] Prepare a matte polyester film, including the following preparation steps:

[0066] S1: By mass, mix 3 parts of copper formate with 25 parts of ultrapure water, add 15 parts of serpentine powder with a particle size of 150 nm, heat the solution to 33 °C and stir and react for 70 min, add 40 parts of 17-carbon saturated fatty acid, pressurize to maintain about 1.5 standard atmospheres in the container, heat the solution to boiling and continue for 18 min, and then reduce the pressure and concentrate the solution at normal temperature and pressure to obtain the reactant;

[0067] Put the reactant into a roasting furnace, calcine at 630 °C for 3 h in an oxygen atmosphere, and then transfer to a vacuum furnace to calcine at 880 °C for 80 min; put the calcined product into a ball mill and grind for 4 h, mix the powder with ethanol in a mass ratio of 2:59, and add 7% by mass of silane coupling agent KH550 to the mixed powder, ultrasonically vibrate for 40 min, reduce the pressure and concentrate the solution and dry it to obtain modified serpentine;

[0068] S2: Grind the modified serpentine into a powder with a particle size of 200 nm in a grinder, grind polyethylene terephthalate into a powder with a particle size of 500 nm in a grinder, and mix the two powders in a ratio of 1:5 to make the first filler;

[0069] By mass, mix 90 parts of the first filler, 15 parts of carbon black, 8 parts of kaolin, 3 parts of barium sulfate, 2 parts of KH570 silane coupling agent and 200 parts of PET masterbatch for 45 min, and extrude with a twin-screw extruder at 275 °C to obtain the black light-absorbing layer;

[0070] S3: By mass, mix 15 parts of polyacrylonitrile, 1 part of glass fiber, and 2 parts of lignin raw material into a grinder and grind into a powder with a particle size of 400 nm, then add 110 parts of the first filler, 19 parts of talc powder, 10 parts of calcium carbonate powder, 11 parts of alumina ceramic and 200 parts of PET masterbatch, mix and stir the materials for 37 min, then raise the temperature to 280 °C and extrude with a twin-screw extruder to obtain the white surface layer;

[0071] Using a black light-absorbing layer as the core material, white surface layers on the top and bottom, with the black light-absorbing layer sandwiched between the two white surface layers, and the mass ratio of the black light-absorbing layer to the white surface layer being 3:1, heat and melt-extrude in a casting machine, and stretch and shape into a film at 90 - 93 °C to obtain the matte polyester film of the present application.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 1 is that in the process of preparing the modified serpentine in Step S1, saturated fatty acids are not added, and other preparation steps are the same as those in Example 1 to obtain the polyester film of Comparative Example 1.

[0074] Comparative Example 2

[0075] The difference between Comparative Example 2 and Example 1 is that in the process of preparing the modified serpentine in Step S1, the step of calcining in an oxygen atmosphere is removed, and the reactants are directly transferred to a vacuum furnace for calcining for 4 h, and other preparation steps are the same as those in Example 1 to obtain the polyester film of Comparative Example 2.

[0076] Comparative Example 3

[0077] The difference between Comparative Example 3 and Example 1 is that no first filler is added to both the black light-absorbing layer and the white surface layer, and other preparation steps are the same as those in Example 1 to obtain the polyester film of Comparative Example 3.

[0078] Comparative Example 4

[0079] The difference between Comparative Example 4 and Example 1 is that serpentine is used instead of the first filler and added to the preparation raw materials of the white surface layer and the black light-absorbing layer, and other preparation steps are the same as those in Example 1 to obtain the polyester film of Comparative Example 4.

[0080] Performance Test

[0081] 1. Refer to GB / T 1040.3 "Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets" to test the tensile strength of each example and each comparative example.

[0082] 2. Use an ultraviolet-visible spectrophotometer to test the light transmittance of each example and each comparative example.

[0083] 3. Bacteriostatic rate test: Taking Escherichia coli as an example, cut the base film and place it at the bottom of the wells of a 24-well plate. Subsequently, drop 100 μL of the diluted bacterial suspension (about 105 CFU / mL) into each well and make it evenly disperse on the surface of the film. Then place the 24-well plate in a bacterial incubator and culture it at 37 °C for 6 hours. Then, take out each sample and soak it in a test tube containing 10 mL of PBS solution. Subsequently, place all the test tubes in a water bath thermostatic oscillator (150 rpm) and shake for 10 minutes. Then, spread 60 μL of the diluted bacterial suspension on a nutrient agar plate, culture it at 37 °C for 24 h, and count the number of live colonies. Repeat the experiment three times.

[0084] Record the above performance test results in Table 1 below.

[0085] Table 1 Performance test results of each example and each comparative example

[0086]

[0087] Analyzing the performance test results of each example and each comparative example, it can be seen that the matte polyester film prepared in this application has low light transmittance, good mechanical strength, and additionally has certain antibacterial properties, which can broaden the application scenarios of the polyester film and extend its service life in harsh environments such as outdoors.

[0088] Comparing the performance test results of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that in the process of preparing modified serpentine, saturated fatty acid is a necessary component for its synthesis, and calcining in an oxygen atmosphere to form copper oxide from copper formate is a necessary step for its synthesis, which has a certain impact on the performance of the finally prepared matte polyester film.

[0089] Comparing the performance test results of Example 1 and Comparative Example 3, it can be seen that adding the first filler to the black light-absorbing layer and the white surface layer can significantly reduce the light transmittance of the polyester film, improve its mechanical strength, and additionally obtain certain antibacterial properties, increasing the service life of the polyester film.

[0090] Analyzing the performance test results of Example 1 and Comparative Example 4, the effect of using modified serpentine in the first filler is better than that of unmodified serpentine, which can further reduce the light transmittance and improve the mechanical properties of the film.

[0091] In summary, this application prepares a matte polyester film. Adding the first filler to the black light-absorbing layer and the white surface layer helps to significantly reduce the light transmittance of the polyester film. The low-light-transmitting matte polyester film, in addition, the first filler also makes the polyester film have certain antibacterial properties, which can broaden the application fields of the polyester film, such as being safer to use in the fields of food, hospitals, biology, etc.

[0092] The foregoing has described the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present application. Without departing from the spirit and scope of the present application, various changes and improvements will occur to the present application, and these changes and improvements all fall within the scope of the present application claimed. The scope of protection required by the present application is defined by the appended claims and their equivalents.

Claims

1. A matte polyester film, characterized in that: The invention comprises an upper and lower white surface layer, and a black light-absorbing layer arranged between the white surface layers. The raw material for preparing the black light-absorbing layer comprises a first filler, and the first filler is a mixture of modified serpentine and polyethylene terephthalate. The preparation method of the modified serpentine is as follows: dissolving copper formate and adding serpentine powder and saturated fatty acid, reacting at elevated temperature and pressure, then concentrating the solution under reduced pressure to obtain a reactant, calcining the reactant in an oxygen atmosphere and a vacuum atmosphere in turn to convert copper in the serpentine into copper oxide, grinding the reactant into powder and mixing it with ethanol, then adding a silane coupling agent to react for a period of time, concentrating under reduced pressure and drying to obtain the modified serpentine.

2. The matte polyester film according to claim 1, characterized in that: The modified serpentine and the polyethylene terephthalate are mixed in a mass ratio of (1:1) to (1:5) to obtain the first filler.

3. The matte polyester film according to claim 1, characterized in that: The particle size of the modified serpentine is 100-200 nm, and the particle size of the polyethylene terephthalate is 400-500 nm.

4. The matte polyester film according to claim 1, characterized in that: The raw materials for preparing the black light-absorbing layer also include: black pigment, kaolin, barium sulfate, silane coupling agent and PET masterbatch.

5. The matte polyester film according to claim 1, characterized in that: The raw materials for preparing the white surface layer include: polyacrylonitrile, glass fiber, lignin, the first filler, talcum powder, calcium carbonate, alumina ceramic powder and PET masterbatch.

6. A method for preparing a matte polyester film, characterized in that: The method comprises the following preparation steps: S1: dissolving copper formate and adding serpentine powder and saturated fatty acid, reacting at elevated temperature and pressure, then concentrating the solution under reduced pressure to obtain a reactant, calcining the reactant in an oxygen atmosphere and a vacuum atmosphere in turn to convert copper in the serpentine into copper oxide, grinding the reactant into powder and mixing it with ethanol, then adding a silane coupling agent to react for a period of time, concentrating under reduced pressure and drying to obtain a modified serpentine; S2: Grinding the modified serpentine and polyethylene terephthalate into powders respectively and mixing them to prepare a first filler; mixing the first filler, black pigment, kaolin, barium sulfate, silane coupling agent and PET masterbatch and extruding the mixture through a twin-screw extruder to obtain a black light-absorbing layer; S3: Grind polyacrylonitrile, glass fiber, and lignin into powder, add the first filler, talcum powder, calcium carbonate powder, alumina ceramics, and PET masterbatch, mix, and extrude through a twin-screw extruder to obtain a white surface layer; The white surface layer is arranged on both sides of the black light-absorbing layer, and the three-layer film is heated, melted and extruded in a casting machine, and the matte polyester film is obtained after stretching and shaping.

7. The preparation method according to claim 6, characterized in that: In the step S1, the reactant is calcined at 600-630° C. for 2-3 h in an oxygen atmosphere, and then transferred to a vacuum furnace and calcined at 850-880° C. for 50-80 min to obtain a calcined product.

8. The preparation method according to claim 7, characterized in that: The calcined product is mixed with ethanol in a mass ratio of 2:(55-59).

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