Heat-resistant and delustering bopp film, preparation method and application thereof

Abstract

This invention discloses a heat-resistant matte BOPP film, its preparation method, and its application. The heat-resistant matte BOPP film includes a co-extruded film body, which comprises a matte layer, a core layer, and a corona layer arranged sequentially. The matte layer is composed of 79.5-98.95 wt% matte masterbatch, 1-20 wt% heat-resistant masterbatch, and 0.05-0.5 wt% additives. The heat-resistant masterbatch is composed of rigid particles and / or small molecules. The rigid particles can form microscopic heat-insulating protrusions on the film surface, while the small molecules can precipitate onto the film surface and have a low thermal conductivity lubrication effect. This invention, through the synergistic effect of the physical isolation effect of the rigid particles in the matte layer and the low thermal conductivity lubrication effect of the small molecules, increases the adhesion temperature of the film during bag heat sealing from approximately 120-135℃ in existing products to 160-185℃, effectively solving the technical problem of easy adhesion and wrinkling of matte BOPP film in high-speed automatic packaging heat sealing processes.

Description

Technical Field

[0001] This invention relates to the field of packaging film materials technology, and in particular to a heat-resistant matte BOPP film, its preparation method and its application. Background Technology

[0002] With the upgrading of consumption and the continuous evolution of end-use application demands, matte biaxially oriented polypropylene film (hereinafter referred to as matte BOPP film) has been widely used in high-end packaging and paper-plastic composite fields such as food, cosmetics, and pharmaceuticals due to its excellent mechanical properties, low gloss and high haze.

[0003] Currently, matte BOPP films are generally formed using co-extrusion combined with biaxial stretching, and their matte surface layer is usually composed of matte masterbatch. Although this masterbatch can give the film a stable and good matte effect, the melting point of its core components (such as blends of high-density polyethylene and polypropylene) is usually only 120℃-135℃, which is much lower than that of the core layer polypropylene (about 150℃-160℃). In the actual bag making heat sealing process, the heat sealing temperature usually needs to reach 140℃-180℃. When the heated heat sealing knife is directly pressed against the matte surface of the film, the matte layer with a low melting point is very easy to soften or even melt rapidly, which causes a series of problems: (1) The softened and melted matte layer material is thermally adhered, and part of it is transferred and adhered to the surface of the heat sealing knife, which not only damages the integrity of the film surface, but also causes contamination of the heat sealing knife; (2) The film shrinks unevenly in the heat sealing area due to uneven heating, which induces wrinkles, warping and other appearance defects; (3) In order to avoid the accumulation of the above defects, the equipment needs to be stopped frequently to clean the heat sealing knife, which seriously restricts the continuity and efficiency of production.

[0004] It is evident that the insufficient heat resistance of existing matte BOPP films has become a key technical bottleneck restricting their large-scale application in high-speed automated packaging production lines. To overcome these shortcomings, existing technologies have attempted to add inorganic fillers to the matte layer formulation to improve its heat resistance. However, in practical applications, such solutions often result in increased gloss, decreased haze, and deteriorated matte effect due to improper control of filler particle size or poor dispersion uniformity in the matrix, accompanied by a significant decline in the film's mechanical properties—a trade-off between addressing all these issues.

[0005] In view of this, how to significantly improve the heat resistance of the matte surface of matte BOPP film without significantly sacrificing or even taking into account the matting effect and mechanical properties, so as to meet the requirements of high-speed heat-sealing packaging process, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned problems of the prior art and provide a heat-resistant matte BOPP film, its preparation method and its application.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] A heat-resistant matte BOPP film includes a co-extruded film, which comprises a matte layer, a core layer and a corona layer arranged sequentially.

[0009] The matte layer consists of 79.5-98.95 wt% matte masterbatch, 1-20 wt% heat-resistant masterbatch, and 0.05-0.5 wt% additives. The heat-resistant masterbatch consists of rigid particles and / or small molecules. The rigid particles can form microscopic heat-insulating protrusions on the film surface, and the small molecules can precipitate on the film surface and have a low thermal conductivity lubrication effect.

[0010] This invention adopts a three-layer co-extrusion structure, with each layer having a clear division of labor and working together to achieve a balance between heat resistance, matting properties, and tensile strength.

[0011] The matte layer is the core functional layer, which undertakes the dual task of giving the film a matte appearance and heat resistance.

[0012] As a functional additive, heat-resistant masterbatch can significantly improve heat resistance by introducing rigid particles and / or small molecules into the matte layer. Specifically, on the one hand, rigid particles can form uniformly distributed microscopic heat-insulating protrusions on the film surface, such as... Figure 2 As shown, these heat-insulating protrusions effectively reduce the direct contact area between the matte layer material and the heat-sealing blade during heat sealing, thus reducing the contact heat transfer efficiency. On the other hand, the rigid particles themselves are low thermal conductivity materials, and their distribution on the surface of the matte layer effectively creates a physical thermal barrier between the heat-sealing blade and the film substrate, further reducing the efficiency of heat transfer to the interior of the film and significantly slowing down the temperature rise rate of the matte layer surface. Small molecules have a certain degree of migration and will gradually precipitate onto the surface of the matte layer during film processing and use, forming an extremely thin lubricating coating layer, such as... Figure 3 As shown. This lubricating coating has a low thermal conductivity, which slows down the rate at which heat is transferred to the matte layer. It also reduces the coefficient of friction and adhesion tendency between the matte layer material and the heat-sealing knife. Furthermore, it has a lubricating effect after melting at the heat-sealing temperature, further reducing adhesion. Rigid particles and small molecules can independently or synergistically improve the heat resistance of the matte layer from both physical and thermodynamic perspectives, solving the technical bottleneck of easy adhesion and wrinkling of existing matte BOPP films during heat-sealing bag making. This allows the adhesion temperature of the film to be increased from 120℃-135℃ of conventional products to 160-185℃.

[0013] As the main component, matting masterbatch can produce a diffuse reflection effect on the film surface, giving the film low gloss and high haze matting properties, meeting the pursuit of a soft visual effect in high-end packaging. The appropriate addition of anti-blocking agents prevents the film from sticking together between layers during winding and storage without affecting the matting effect, ensuring the film's subsequent processing performance and yield.

[0014] Furthermore, the heat-resistant masterbatch is composed of rigid particles and small molecules, with a mass ratio of rigid particles to small molecules of 1:3-3:1.

[0015] The microscopic protrusions formed by rigid particles on the film surface preferentially reduce the large-area direct contact between the matte surface and the heat-sealing blade during heat sealing, thus reducing contact heat transfer efficiency on a macroscopic scale. Meanwhile, small molecules precipitated and distributed on the surface of the matte layer and in the gaps between the protrusions form a continuous or semi-continuous lubricating coating structure with low thermal conductivity. This coating further blocks heat conduction to the matte layer substrate and reduces the friction coefficient and adhesion tendency between the matte layer surface and the heat-sealing blade. These two mechanisms are spatially complementary and functionally synergistic. Specifically, rigid particles provide physical isolation (reducing the contact area), while small molecules provide interfacial lubrication and thermal buffering (reducing heat transfer efficiency and adhesion risk), jointly constructing a multi-layered heat-resistant protection system with isolation, conduction, and lubrication functions. This achieves a heat resistance effect far exceeding that of a single solution (containing only rigid particles or only small molecules), such as... Figure 4 As shown.

[0016] Furthermore, the rigid particles are selected from one, two, or more of the following: fumed silica, silica powder, talc powder, calcium carbonate powder, montmorillonite, precipitated barium sulfate, hollow glass microspheres, and plexiglass microspheres.

[0017] The small molecule substance is selected from one, two or more of the following: white oil, erucamide, oleamide, polyethylene wax, and polypropylene wax.

[0018] Furthermore, the matting masterbatch is selected from one, two or more of the following: Jiangsu Deyuan's DWM325, South Korea SK's MF502H, Qifan New Materials' QF1060, and Letingda's LX7605.

[0019] Furthermore, the additive is selected as an anti-blocking agent.

[0020] Furthermore, the core layer is composed of 97-99.5 wt% polypropylene and 0.5-3 wt% antistatic agent.

[0021] The core layer is the main structural layer of the film, primarily responsible for providing mechanical strength and structural stability. Polypropylene, as the main component of the core layer, has a high melting point and excellent mechanical properties, providing the film with high tensile strength and ensuring dimensional stability during subsequent processing such as high-speed printing, lamination, and bag making. The addition of antistatic agents effectively reduces the film's surface resistance, preventing dust accumulation due to static electricity during winding, slitting, and packaging, thus ensuring the film's cleanliness and printability.

[0022] Furthermore, the corona layer is composed of 99.5-99.95 wt% polypropylene and 0.05-0.5 wt% anti-blocking agent.

[0023] The corona layer serves as the post-processing interface layer for the film, primarily functioning to enhance surface tension and ensure adhesion for printing / lamination. Polypropylene, as the main component of the corona layer, ensures good interfacial compatibility between this layer and the core layer, preventing interlayer delamination. The addition of an anti-blocking agent ensures that the surface tension after corona treatment meets printing and lamination requirements while preventing film sticking during winding. Corona treatment further enhances the surface polarity of this layer, enabling it to firmly adsorb inks and adhesives, meeting the needs of subsequent finishing processes such as printing, hot stamping, and lamination.

[0024] Furthermore, the thickness of the outer matte layer is 2 μm;

[0025] The thickness of the core layer is 22 μm;

[0026] The thickness of the corona layer is 1 μm.

[0027] In this invention, an appropriate thickness value can be selected according to the requirements of packaging bag size, contents weight, and product display.

[0028] A method for preparing a heat-resistant matte BOPP film includes the following steps:

[0029] S1. According to the three-layer structure, the thickness value of the three layers and the mass percentage of each component of each layer, the components of the three layers are proportioned. Among the components of the matte layer, the heat-resistant masterbatch is first pre-granulated and mixed with 1 / 3 of the matte masterbatch, and then mixed with the remaining matte masterbatch and the additives.

[0030] In the matte layer, the addition ratio of heat-resistant masterbatch is only 1-20 wt%, which is a trace high-functionality component compared to matte masterbatch. First, all the heat-resistant masterbatch and 1 / 3 of the matte masterbatch are subjected to high-intensity pre-granulation. At this stage, the concentration of the heat-resistant masterbatch is increased, becoming a high-concentration masterbatch. This significantly increases the contact probability and shear force between the heat-resistant and matte masterbatches, forcibly breaking up and individually encapsulating agglomerated particles, achieving uniform dispersion of ultrafine particles at the single-particle level. Granulation before mixing with the remaining portion allows the already uniformly dispersed particles to be evenly distributed in the final formulation, effectively improving the sufficiency and uniformity of dispersion. It also makes subsequent feeding more stable and melting more synchronized, effectively avoiding film thickness fluctuations caused by uneven feeding.

[0031] S2. The components of the three layers are blended and melted separately at 230-270℃ using a three-layer screw extruder;

[0032] S3. Gather the various melts into the die head, and extrude the BOPP thick film through the die head at a temperature of 240-260℃.

[0033] S4. BOPP thick film sheets are attached to a 20-40℃ rapid cooling roller with compressed air to form cast sheets;

[0034] S5. The cast sheet is preheated at 120℃-130℃, and then stretched longitudinally by 4-5 times at 110℃-120℃ to form a thin film sheet, which is then shaped.

[0035] S6. The film sheet treated with S5 is preheated at 160-180℃ and then stretched 8-9 times laterally at 160-170℃ to set its shape.

[0036] S7. After stretching, the corona layer is subjected to single-sided corona treatment by the traction system, and then wound up to obtain a heat-resistant matte BOPP film.

[0037] The application of a heat-resistant matte BOPP film as described above in heat-sealed packaging bags, especially in applications with heat-sealing temperatures of 140°C-180°C.

[0038] The present invention has the following beneficial effects:

[0039] 1. Significantly Improved Heat Resistance While Maintaining Excellent Matte Performance: By optimizing the ratio of matte masterbatch and heat-resistant masterbatch, the technical contradiction between matte effect and heat resistance is effectively balanced while maintaining the matte appearance characteristics of the film, such as low gloss and high haze. Specifically, the rigid particles in the matte layer can play a physical isolation role, reducing the direct contact between the matte surface and the heat-sealing blade during heat sealing; small molecules can precipitate to the film surface, forming a lubricating layer with low thermal conductivity, reducing the efficiency of heat transfer to the film and the adhesion tendency between the film surface and the heat-sealing blade. Under the synergistic effect of one or both of the above mechanisms, the adhesion temperature of the film during bag making heat sealing is significantly increased from about 120-135℃ of existing products to 160-185℃, thus effectively solving the technical problems of easy adhesion and wrinkling of matte BOPP film in high-speed automatic packaging heat sealing process, providing a reliable guarantee for the large-scale application of matte BOPP film in the field of high-end packaging.

[0040] 2. The rational design of the three-layer structure gives the film high longitudinal and transverse tensile strength, meeting the requirements of subsequent processing such as high-speed printing, lamination, and bag making; the addition of anti-blocking agents and antistatic agents further ensures the film's winding performance and cleanliness.

[0041] 3. Precise control of each process parameter in the preparation method ensures the stable transformation of the formula's advantages, good consistency and repeatability of product performance, and suitability for large-scale industrial production.

[0042] It is evident that the heat-resistant matte BOPP film of the present invention can be widely used in high-end packaging fields such as food, pharmaceuticals, and cosmetics, and has outstanding application value, especially in high-speed automatic packaging bag making processes, which can effectively improve packaging production efficiency and product quality. Attached Figure Description

[0043] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in describing the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments recorded in the present invention. Those skilled in the art can derive other drawings from the following drawings without any creative effort.

[0044] Figure 1 This is a schematic diagram of a specific embodiment of the heat-resistant matte BOPP film described in this invention.

[0045] Figure 2 This is a schematic diagram of the structure of a heat-resistant matting BOPP film according to the present invention, in which the matting layer is composed of rigid particles;

[0046] Figure 3 This is a schematic diagram of the structure of a heat-resistant matte BOPP film according to the present invention, in which the matte layer is composed of small molecule substances;

[0047] Figure 4 This is a schematic diagram of the structure of a heat-resistant matting BOPP film according to the present invention, in which the matting layer is composed of rigid particles and small molecules.

[0048] The component names corresponding to the reference numerals in the attached drawings are as follows: 1. Matte layer; 2. Core layer; 3. Corona layer; 4. Matte layer body; 5. Microscopic heat insulation protrusion; 6. Lubricating cover layer; 7. Heat sealing knife. Detailed Implementation

[0049] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in the present invention without creative effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] A heat-resistant matte BOPP film includes a co-extruded film body, which comprises a matte layer 1, a core layer 2, and a corona layer 3 arranged sequentially. The core layer 2 is composed of 97 wt% polypropylene and 3 wt% antistatic agent. The corona layer 3 is composed of 99.5 wt% polypropylene and 0.05 wt% antiblocking agent. The matte layer 1 is composed of 94.8 wt% matte masterbatch, 5 wt% white oil, and 0.2 wt% antiblocking agent.

[0052] The matting masterbatch can be one, two, or more of the following: Jiangsu Deyuan's DWM325, Korea SK's MF502H, Qifan New Materials' QF1060, and Letingda's LX7605; the anti-blocking agent can be one, two, or more of the following: Suzhou Constance's AB6018PP, Best's ABPP9205, and Basel's ABPP05CN.

[0053] And prepare it according to the following steps:

[0054] S1. According to the three-layer structure and thickness ratio described above, the heat-resistant masterbatch is first pre-granulated and mixed with 1 / 3 of the matte masterbatch, and then mixed with the remaining matte masterbatch and the additives.

[0055] S2. The components of the three layers are blended and melted separately at 260°C using a three-layer screw extruder according to their mass percentages.

[0056] S3. Gather the various melts into the die head, and extrude the BOPP thick film through the die head at a temperature of 245℃.

[0057] S4, BOPP film sheets are attached to a 30°C rapid cooling roller with compressed air to form a cast sheet;

[0058] S5. The cast sheet is preheated at 125℃ and then stretched longitudinally by 4 times at 115℃ to form a thin film sheet, which is then shaped.

[0059] S6. The film sheet treated with S5 is preheated at 170°C and then stretched 8 times laterally at 160°C to set its shape.

[0060] S7. After stretching, the corona layer 3 is subjected to single-sided corona treatment by the traction system and then wound up to obtain a heat-resistant matte BOPP film.

[0061] Example 2

[0062] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% polyethylene wax, and 0.2 wt% anti-blocking agent.

[0063] Example 3

[0064] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% polypropylene wax, and 0.2 wt% antiblocking agent.

[0065] Example 4

[0066] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% erucamide masterbatch, and 0.2 wt% antiblocking agent.

[0067] Example 5

[0068] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% fumed silica, and 0.2 wt% antiblocking agent.

[0069] Example 6

[0070] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% precipitated barium sulfate, and 0.2 wt% anti-blocking agent.

[0071] Example 7

[0072] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 4 wt% silica powder, 4 wt% polyethylene wax, and 0.2 wt% anti-blocking agent.

[0073] Example 8

[0074] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 4 wt% fumed silica, 4 wt% polypropylene wax, and 0.2 wt% antiblocking agent.

[0075] Example 9

[0076] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 4 wt% precipitated barium sulfate, 4 wt% erucamide masterbatch, and 0.2 wt% antiblocking agent.

[0077] Example 10

[0078] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 94.8 wt% matte masterbatch, 5 wt% polyethylene wax, and 0.2 wt% anti-blocking agent.

[0079] Example 11

[0080] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 89.8 wt% matte masterbatch, 10 wt% polyethylene wax, and 0.2 wt% anti-blocking agent.

[0081] Example 12

[0082] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 94.8 wt% matte masterbatch, 5 wt% fumed silica, and 0.2 wt% antiblocking agent.

[0083] Example 13

[0084] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% silica powder, and 0.2 wt% anti-blocking agent.

[0085] Example 14

[0086] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 6 wt% silica powder, 2 wt% polypropylene wax, and 0.2 wt% antiblocking agent.

[0087] Example 15

[0088] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of matte layer 1, specifically: matte layer 1 is composed of 91.8 wt% matte masterbatch, 2 wt% silica powder, 6 wt% polypropylene wax, and 0.2 wt% antiblocking agent.

[0089] Example 16

[0090] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 84.8 wt% matte masterbatch, 15 wt% polyethylene wax, and 0.2 wt% anti-blocking agent.

[0091] Example 17

[0092] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% calcium carbonate powder, and 0.2 wt% anti-blocking agent.

[0093] Example 18

[0094] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% montmorillonite, and 0.2 wt% antiblocking agent.

[0095] Example 19

[0096] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 91.8 wt% matte masterbatch, 8 wt% plexiglass microspheres, and 0.2 wt% antiblocking agent.

[0097] Example 20

[0098] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 98.8 wt% matte masterbatch, 1 wt% fumed silica, and 0.2 wt% antiblocking agent.

[0099] Example 21

[0100] A heat-resistant matte BOPP film differs from Example 1 only in the composition and mass percentage of the matte layer 1, specifically: the matte layer 1 is composed of 84.8 wt% matte masterbatch, 15 wt% fumed silica, and 0.2 wt% antiblocking agent.

[0101] Comparative Example 1

[0102] This comparative example provides a matte BOPP film, which differs from Example 1 only in the composition and mass percentage of the matte layer 1. Specifically, the matte layer 1 is composed of 99.8 wt% matte masterbatch and 0.2 wt% antiblocking agent.

[0103] Performance testing and analysis

[0104] The heat resistance test method is based on GB / T 34445-2017. The heat sealing time is 1 second, the heat sealing pressure is 0.18 MPa, the upper heat sealing blade is heated, and the lower heat sealing blade is not heated. Before the test, the sample is cut to be larger than the dimensions of the heat sealing blades in both length and width. During the test, the sample is held by both sides with the matte side facing up and placed horizontally between the two heat sealing blades. The heat sealing program is started. After waiting for 1 second, the sample is observed for deformation and adhesion to the heat sealing blades. The lowest test temperature at which the sample adheres to the heat sealing blades is recorded.

[0105] Test method for extinction performance: According to the method described in GB / T 2410-2008, haze is used as the evaluation basis for extinction performance, and the reference value is: haze (%) ≥ 75.

[0106] The test method for tensile strength is as follows: according to the method described in GB / T 1040.3-2006, the specimen is a type 2 specimen with a width of 15 mm, and the reference values ​​are: longitudinal tensile strength (MPa) ≥90; transverse tensile strength (MPa) ≥100.

[0107] The results are as follows:

[0108]

[0109] Examples 1-4, 10, 11, 16 and Comparative Example 1 show that adding small molecule substances to conventional matte BOPP films can significantly increase the film adhesion temperature. Furthermore, the migration of small molecule substances can form a lubricating coating layer 5 on the surface of the matte layer 4, which increases light scattering and thus appropriately increases the haze value. Examples 2-4 show that the smaller the molecular weight of the small molecule substance, the better the heat resistance of the matte layer 1. Examples 2, 10, 11, 16 show that within the range of 1-10 wt%, the higher the amount of small molecule substance added, the better the heat resistance. However, when it exceeds 10 wt%, although there is still some improvement in heat resistance, the improvement effect decreases, and the matte effect also decreases rapidly.

[0110] Examples 5, 6, 17-19, and Comparative Example 1 show that adding rigid particles can effectively improve the heat resistance of the film. Furthermore, the microscopic heat-insulating structure 5 formed by the rigid particles on the surface of the matting layer 4 increases the diffuse reflection ratio of light, thereby appropriately improving the haze value. Examples 5, 6, 17-19 show that the lower the heat transfer efficiency of the rigid particles, the better their heat resistance. Examples 5, 12, 20, and 21 show that within the range of 1-8 wt%, the higher the amount of rigid particles added, the better the heat resistance. However, when the amount exceeds 8 wt%, although there is still some improvement in heat resistance, the improvement effect will decrease.

[0111] By comparing Examples 2, 13 and 7, Examples 3, 5 and 8, and Examples 4, 6 and 9, it can be seen that when rigid particles are used in combination with small molecule substances, the improvement in heat resistance is greater, indicating that the two mechanisms of action do not exclude each other and may even have a mutually reinforcing effect.

[0112] Comparative examples 7, 14, and 15 show that when rigid particles and small molecules are used together, a formulation with a 1:1 mass ratio of the two exhibits superior heat resistance and haze.

[0113] In addition, Examples 1-21 improve heat resistance and matting effect while also maintaining strong tensile strength.

[0114] The foregoing has shown and described 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. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A heat-resistant matte BOPP film, characterized in that: It includes a co-extruded film, which comprises a matte layer (1), a core layer (2), and a corona layer (3) arranged sequentially. The matte layer (1) is composed of 79.5-98.95 wt% matte masterbatch, 1-20 wt% heat-resistant masterbatch and 0.05-0.5 wt% additives. The heat-resistant masterbatch is composed of rigid particles and / or small molecules. The rigid particles can form microscopic heat-insulating protrusions on the film surface, and the small molecules can precipitate on the film surface and have low thermal conductivity and lubrication effect.

2. The heat-resistant matte BOPP film according to claim 1, characterized in that: The heat-resistant masterbatch is composed of rigid particles and small molecules, with a mass ratio of rigid particles to small molecules of 1:3-3:

1.

3. The heat-resistant matte BOPP film according to claim 1, characterized in that: The rigid particles are selected from one, two or more of the following: fumed silica, silica powder, talc powder, calcium carbonate powder, montmorillonite, precipitated barium sulfate, hollow glass microspheres, and plexiglass microspheres. The small molecule substance is selected from one, two or more of the following: white oil, erucamide, oleamide, polyethylene wax, and polypropylene wax.

4. The heat-resistant matte BOPP film according to claim 1, characterized in that: The matting masterbatch is selected from one, two or more of the following: Jiangsu Deyuan's DWM325, South Korea's SK's MF502H, Qifan New Materials' QF1060, and Letingda's LX7605.

5. The heat-resistant matte BOPP film according to claim 1, characterized in that: The additive is an anti-blocking agent.

6. The heat-resistant matte BOPP film according to claim 1, characterized in that: The core layer (2) is composed of 97-99.5 wt% polypropylene and 0.5-3 wt% antistatic agent.

7. The heat-resistant matte BOPP film according to claim 1, characterized in that: The corona layer (3) is composed of 99.5-99.95 wt% polypropylene and 0.05-0.5 wt% anti-blocking agent.

8. A heat-resistant matte BOPP film according to any one of claims 1-7, characterized in that: The thickness of the outer matting layer (1) is 2 μm; The core layer (2) has a thickness of 22 μm; The thickness of the corona layer (3) is 1 μm.

9. A method for preparing a heat-resistant matte BOPP film, characterized in that: Includes the following steps: S1. According to the three-layer structure, the thickness value of the three layers and the mass percentage ratio of each component of each layer as described in claim 8, in each component of the matte layer (1), the heat-resistant masterbatch is first pre-granulated and mixed with 1 / 3 of the matte masterbatch, and then mixed with the remaining matte masterbatch and the additive. S2. The components of the three layers are blended and melted separately at 230-270℃ using a three-layer screw extruder; S3. Gather the various melts into the die head, and extrude the BOPP thick film through the die head at a temperature of 240-260℃. S4. BOPP thick film sheets are attached to a 20-40℃ rapid cooling roller with compressed air to form cast sheets; S5. The cast sheet is preheated at 120℃-130℃, and then stretched longitudinally by 4-5 times at 110℃-120℃ to form a thin film sheet, which is then shaped. S6. The film sheet treated with S5 is preheated at 160-180℃ and then stretched 8-9 times laterally at 160-170℃ to set its shape. S7. After stretching, the corona layer (3) is subjected to single-sided corona treatment by the traction system and then wound up to obtain a heat-resistant matte BOPP film.

10. The application of the heat-resistant matte BOPP film as described in claim 8 in heat-sealed packaging bags, particularly in applications at heat-sealing temperatures of 140°C-180°C.

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