A BOPP matte film anti-warping functional masterbatch, its preparation method and application

Abstract

This invention relates to the field of thin films, and particularly to an anti-warping functional masterbatch for BOPP matte films, its preparation method, and its application. The anti-warping functional masterbatch for BOPP matte films comprises the following components: homopolymer polypropylene, 1-4 wt% maleic anhydride-grafted polypropylene A, 0.1-0.3 wt% organophosphate salt, 0.1-0.2 wt% calcium stearate, 1-3 wt% polysiloxane-polyolefin graft copolymer, 0.1-0.3 wt% antioxidant, and 0.1-0.5 wt% surface-modified fumed silica. This anti-warping functional masterbatch for BOPP matte films is suitable for use in the matte layer of BOPP matte films, ensuring that the prepared BOPP matte film has excellent anti-warping properties without affecting the film's mechanical strength and optical properties.

Description

Technical Field

[0001] This invention relates to the field of thin films, and in particular to an anti-warping functional masterbatch for BOPP matte film, its preparation method, and its application. Background Technology

[0002] Multilayer co-extruded biaxially oriented polypropylene (BOPP) matte film is widely used in packaging, labeling, and other fields due to its excellent diffuse reflection properties. With the continuous upgrading of downstream high-speed printing and automated labeling technologies, increasingly higher requirements are being placed on the flatness and anti-warping performance of BOPP matte film. Warping of BOPP matte film directly leads to problems such as misregistration during printing, label lifting, and poor die-cutting, affecting downstream applications.

[0003] The root cause of warpage in existing BOPP matte films lies in the formulation of their matte layer. Existing BOPP matte films typically use polypropylene (PP) and high-density polyethylene (HDPE) as the main components, with PP as the marine phase and HDPE as the island phase, to achieve matting. Since PP and HDPE are thermodynamically incompatible, the numerous interfacial zones significantly interfere with the orderly stacking of PP molecular chains. Simultaneously, HDPE segments interspersed between PP molecular chains increase inter-chain spacing, hindering chain migration and orderly arrangement, thus slowing down the overall crystallization rate of PP. Even if the PP in the matte layer is homopolymer PP, the crystallization kinetics deteriorate significantly after incorporating HDPE. If the PP in the matte layer is copolymer PP, both the ethylene copolymer units in the copolymer PP and HDPE further disrupt the regularity, further widening the difference in crystallization rates. This leads to a significant difference in crystallization rate and shrinkage between the matte layer and adjacent layers (such as the sub-surface layer or core layer) dominated by homopolymer PP, resulting in interlayer stress mismatch and manifesting as warpage.

[0004] Currently, the mainstream technical approaches in the industry to solve the warpage problem of BOPP matte film fall into two categories:

[0005] The first category is production process optimization, such as adjusting the cooling symmetry of the casting sheet, optimizing the biaxial stretch ratio and heat setting parameters, and controlling the tension matching degree throughout the process. This approach does not require adjusting the BOPP matte film formulation and is a conventional optimization method for existing production lines. However, production process optimization can only alleviate the warping problem of BOPP matte film. It cannot fundamentally solve the warping causes in the matte layer of BOPP matte film and adjacent layers (such as the sub-surface layer or core layer) based on homopolymer polypropylene resin, which are caused by formulation system, uneven crystallization, and interlayer stress mismatch. Moreover, the BOPP matte film production process is highly rigid, with a narrow adjustment window for process parameters. Frequent adjustments can easily lead to quality problems such as film breakage and uneven thickness. At the same time, it is greatly affected by raw material batch fluctuations and changes in environmental temperature and humidity, and cannot be adapted to different types of BOPP matte film products.

[0006] The second approach involves modifying the matte layer of BOPP matte film using anti-warping functional masterbatches. By adding anti-warping functional masterbatches to the matte layer, the crystallization behavior and internal stress state of the BOPP matte film are controlled through formulation, achieving an anti-warping effect. This approach requires no modification to existing production line equipment and core processes, making it highly industrially applicable. For example, adding functional masterbatches containing highly efficient nucleating agents to the matte layer can form denser spherulites. This dense spherulite structure, after high orientation, can improve the warping problem of BOPP matte film to some extent. However, these spherulites are relatively large and vary in size, making it difficult to further improve the warping problem effectively. In addition, most existing anti-warping functional masterbatches use ordinary organic nucleating agents or unmodified inorganic powders, which are prone to agglomeration in the matte layer, making it impossible to achieve nanoscale uniform dispersion. This results in large local differences in the crystallinity of the film, making it difficult to stably control the longitudinal and transverse shrinkage rates. Furthermore, existing anti-warping masterbatches cannot effectively reduce the difference in crystallization rate and shrinkage rate between the matte layer and adjacent layers (such as the sub-surface layer or core layer) with homopolymer polypropylene as the main resin. The warping problem caused by interlayer stress mismatch cannot be effectively improved, and the compatibility with BOPP matte film is poor.

[0007] Therefore, it is of great significance to develop a special anti-warping masterbatch for BOPP matte film that can effectively solve the warping problem and apply it to the matte layer. Summary of the Invention

[0008] The purpose of this invention is to provide an anti-warping functional masterbatch for BOPP matte film, its preparation method, and its application. The anti-warping functional masterbatch for BOPP matte film described in this invention is suitable for use in the matte layer of BOPP matte film, ensuring that the prepared BOPP matte film has excellent anti-warping performance without affecting the film's mechanical strength and optical properties.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an anti-warping functional masterbatch for BOPP matte film, comprising the following components: homopolymer polypropylene, 1-4 wt% maleic anhydride-grafted polypropylene (MAH-g-PP)A, 0.1-0.3 wt% organophosphate salt, 0.1-0.2 wt% calcium stearate, 1-3 wt% polysiloxane-polyolefin graft copolymer, 0.1-0.3 wt% antioxidant, and 0.1-0.5 wt% surface-modified silica; wherein the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer is 10-45%.

[0010] This invention reveals that the warping of BOPP matte films stems from inconsistent shrinkage between layers, causing the film to curl towards the layer with the highest shrinkage rate. Microscopically, this is a stress relaxation phenomenon where polymeric chains tend towards random curling through entropy increase. Due to inherent differences in crystallization behavior between the matte layer and adjacent layers (such as the sub-surface layer or core layer) based on homopolymer polypropylene resin, uneven shrinkage between layers leads to overall film warping. This invention addresses the core problem of existing BOPP matte films being prone to warping due to uneven crystallization and interlayer stress mismatch. Through innovative design of the anti-warping functional masterbatch formulation used in the matte layer of BOPP matte films, it effectively improves the warping caused by residual internal stress, interlayer stress mismatch, and uneven crystallization, while also considering the overall performance and production adaptability of the film.

[0011] The anti-warping functional masterbatch for BOPP matte film of this invention uses homopolymer polypropylene as the matrix resin to ensure its dispersibility in the matte layer of the BOPP matte film. Based on this, a composite nucleation system of organophosphate salts, calcium stearate, and surface-modified fumed silica is designed. The organophosphate salts, as the main nucleating agent, have extremely high nucleation efficiency, increasing the crystallization temperature of the polypropylene (as the marine phase) in the matte layer and refining the spherulite size. Calcium stearate, as an auxiliary nucleating agent and lubricant, effectively alleviates the tendency of surface-modified fumed silica to agglomerate in the matte layer. Surface-modified fumed silica not only serves as a dispersion carrier for the nucleating agent, but its nano-effect also reinforces the matte effect of the matte layer. The synergistic effect of these three components allows the film to form a more uniform and finer microcrystalline structure during biaxial stretching, reducing the crystallinity difference between the matte layer and adjacent layers (such as the sub-surface layer or core layer) with homopolymer polypropylene as the main resin, thereby controlling warpage to a low level. The present invention also improves the problems of residual internal stress and interlayer stress mismatch in BOPP matte film by adding polysiloxane-polyolefin graft copolymer, and effectively improves the film warping problem in conjunction with the above-mentioned compound system.

[0012] This invention involves adding 0.1-0.3 wt% of an organophosphate salt to the anti-warping masterbatch for BOPP matte film. When the anti-warping masterbatch for BOPP matte film is added to the matte layer of the BOPP matte film, the organophosphate salt acts as a main nucleating agent (α-crystal nucleating agent) to increase the crystallization temperature and crystallization rate of polypropylene, which is the marine phase in the matte layer, and refine the spherulite size, thereby controlling the crystallization uniformity of the film matte layer and reducing the shrinkage difference between the matte layer and adjacent layers with homopolymer polypropylene as the main resin. This invention limits the content of the organophosphate salt in the anti-warping functional masterbatch for BOPP matte film to 0.1~0.3wt%. If the content of the organophosphate salt in the anti-warping functional masterbatch for BOPP matte film is too low, the nucleation efficiency will be insufficient, resulting in a slow crystallization rate and uneven crystal distribution of the polypropylene as the marine phase in the matte layer, with large and inconsistent spherulites. The shrinkage difference between the matte layer and the adjacent layers with homopolymer polypropylene as the main resin cannot be effectively reduced, leading to interlayer stress mismatch and making it difficult to effectively improve the film warping problem. If the content of the organophosphate salt in the anti-warping functional masterbatch for BOPP matte film is too high, excessive organophosphate salt will lead to excessively high crystallinity of the polypropylene as the marine phase in the matte layer, increasing the film brittleness and decreasing tensile strength and elongation at break. At the same time, excessive organophosphate salt is prone to agglomeration in the matte layer, causing excessively large local crystallinity differences, which will aggravate local film warping and abnormally increase film haze, damaging the optical performance of the BOPP matte film.

[0013] This invention adds 0.1-0.2 wt% calcium stearate to the anti-warping masterbatch for BOPP matte film. When the masterbatch is added to the matte layer of the BOPP matte film, the calcium stearate acts as an auxiliary nucleating agent and lubricant, synergistically improving the nucleation efficiency with the organophosphate salt. Simultaneously, it effectively alleviates the agglomeration tendency of the surface-modified fumed silica in the matte layer, reduces internal melt frictional resistance, and improves the processing fluidity of the masterbatch. This invention limits the content of calcium stearate in the anti-warping masterbatch for BOPP matte film to 0.1-0.2 wt%. If the content of calcium stearate in the masterbatch is too low, it cannot effectively suppress the agglomeration tendency of the surface-modified fumed silica. Uneven powder dispersion will lead to localized stress concentration in the film, poor melt fluidity, increased screw torque during processing, decreased masterbatch extrusion stability, and affect the uniformity of film thickness. If the content of calcium stearate in the anti-warping masterbatch for BOPP matte film is too high, excessive calcium stearate will precipitate during high-temperature processing, forming scale at the extruder die head, causing scratches or crystal points on the film surface, diluting the effective concentration of the nucleation system, reducing the overall nucleation efficiency, and leading to a decrease in crystallization uniformity, which is not conducive to precise control of warpage.

[0014] This invention involves adding 0.1-0.5 wt% surface-modified fumed silica to the anti-warping masterbatch for BOPP matte film. When the anti-warping masterbatch is added to the matte layer of the BOPP matte film, the surface-modified fumed silica acts as a dispersion carrier for physical nucleating agents. Simultaneously, its nano-effect strengthens the matting effect of the matting layer, synergistically improving the film's crystal structure and mechanical properties. Furthermore, the surface-modified fumed silica also acts as an inorganic nucleating agent, improving stress mismatch between the matte layer and adjacent layers. This invention limits the content of the surface-modified fumed silica in the anti-warping masterbatch for BOPP matte film to 0.1-0.5 wt%. If the content of the surface-modified fumed silica in the anti-warping masterbatch is too low, the local crystallinity difference in the film will be too large, resulting in insufficient strengthening of the matting effect of the matte layer and limited improvement in film haze. If the content of the surface-modified fumed silica in the anti-warping functional masterbatch for BOPP matte film is too high, even after surface modification, the excessive surface-modified fumed silica is still prone to secondary agglomeration, resulting in poor masterbatch filtration, increased frequency of extruder filter replacement, and the agglomerates will form defects such as crystal points and fish eyes in the film, which will seriously affect the surface quality of the film, reduce melt fluidity, increase processing difficulty, and even cause film breakage problems.

[0015] This invention involves adding 1-3 wt% of a polysiloxane-polyolefin graft copolymer to the anti-warping masterbatch for BOPP matte film, with the grafting rate of the polysiloxane limited to 10-45%. When the anti-warping masterbatch for BOPP matte film is added to the matte layer of the BOPP matte film, the polysiloxane-polyolefin graft copolymer acts as an internal stress relaxant, forming a molecular-level lubrication channel in the polypropylene phase of the matte layer. This promotes the full relaxation of the oriented polypropylene molecular chains during biaxial stretching, eliminates residual internal stress in the film, and improves the stress matching between the matte layer and adjacent layers of the BOPP matte film. This invention limits the content of the polysiloxane-polyolefin graft copolymer in the anti-warping masterbatch for BOPP matte film to 1-3 wt%. If the content of the polysiloxane-polyolefin graft copolymer in the anti-warping masterbatch for BOPP matte film is too low, it cannot form a continuous and sufficient molecular-level lubrication channel in the polypropylene phase of the matte layer. The stretched and oriented polypropylene molecular chains will not relax sufficiently, and a large amount of residual internal stress will be frozen inside the film. During subsequent heat printing, automated labeling, or long-term storage, the film will warp due to the release of internal stress. If the content of the polysiloxane-polyolefin graft copolymer in the anti-warping masterbatch for BOPP matte film is too high, it will reduce the mechanical strength of the matte layer, leading to a decrease in the mechanical properties of the film. It is particularly important to emphasize that the "polysiloxane-polyolefin graft copolymer" used in this invention is a chemically grafted polysiloxane-polyolefin copolymer, rather than a simple physical blend of polysiloxane and polyolefin. Its grafting structure ensures that the polysiloxane segments are uniformly and stably dispersed at the molecular level in the polypropylene in the matting layer as the marine phase, and will not fail due to migration, precipitation or phase separation. This invention limits the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer to 10-45%. If the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer is too low, it is not conducive to the formation of continuous and sufficient molecular-level lubrication channels in the polypropylene phase in the matte layer. The stretched and oriented polypropylene molecular chains are not sufficiently relaxed, and a large amount of residual internal stress is frozen inside the film. During subsequent heat printing, automated labeling, or long-term storage, the film will warp due to the release of internal stress. If the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer is too high, it will reduce the mechanical strength of the matte layer, resulting in a decrease in the mechanical properties of the film.

[0016] To improve the compatibility of masterbatch in the matte layer of BOPP matte film, this invention adds 1-4 wt% maleic anhydride-grafted polypropylene A to the anti-warping masterbatch for BOPP matte film. When the anti-warping masterbatch for BOPP matte film is added to the matte layer of BOPP matte film, the maleic anhydride-grafted polypropylene A acts as a dual-function interface compatibilizer. On the one hand, it strengthens the interfacial bonding force between the surface-modified fumed silica and the matte layer, reducing stress concentration caused by inorganic powder agglomeration; on the other hand, it improves the interfacial compatibility between the matte layer of BOPP matte film and adjacent layers with homopolymer polypropylene as the main resin, alleviating the difference in melt flow rate between different formulation systems. This invention limits the content of maleic anhydride-grafted polypropylene A in the anti-warping masterbatch for BOPP matte film to 1-4 wt%. If the content of maleic anhydride-grafted polypropylene A in the anti-warping masterbatch for BOPP matte film is too low, sufficient chemical bonding interfaces cannot be formed between the inorganic powder and the organic phase, and the surface-modified fumed silica is still prone to agglomeration, resulting in uneven local crystallinity and stress distribution of the film. If the content of maleic anhydride-grafted polypropylene A in the anti-warping masterbatch for BOPP matte film is too high, excessive maleic anhydride-grafted polypropylene A will reduce the crystallinity and heat resistance of the polypropylene in the matte layer, resulting in a decrease in the film's heat distortion temperature, and making it prone to heat shrinkage deformation in subsequent printing or heat sealing applications.

[0017] Furthermore, to improve the antioxidant effect, this invention adds 0.1-0.3 wt% antioxidant to the anti-warping masterbatch for BOPP matte film. When the anti-warping masterbatch for BOPP matte film is added to the matte layer of the BOPP matte film, the antioxidant captures free radicals generated by the polypropylene (as a marine phase) in the matte layer during high-temperature processing and long-term use, preventing thermo-oxidative degradation of polypropylene and ensuring the mechanical properties and service life of the masterbatch and downstream film products. This invention limits the content of the antioxidant in the anti-warping masterbatch for BOPP matte film to 0.1-0.3 wt%. If the content of the antioxidant in the anti-warping masterbatch for BOPP matte film is too low, it cannot effectively inhibit the thermo-oxidative degradation reaction during high-temperature extrusion and biaxial stretching, causing the polypropylene molecular chains to break, resulting in yellowing of the masterbatch and film, degradation of mechanical properties, and easy embrittlement and cracking of the film during use. If the antioxidant content in the anti-warping functional masterbatch for BOPP matte film is too high, the excess antioxidant cannot be completely contained by the polypropylene in the matte layer as a marine phase, and will gradually migrate to the film surface to form "blooming", affecting the surface gloss and surface tension of the film. At the same time, its effect on improving thermal and oxygen stability will tend to saturate, resulting in increased production costs.

[0018] Furthermore, the homopolymer polypropylene exhibits a melt flow rate of 2.5-3.5 g / 10 min under test conditions of 230°C and 2.16 kg. Using homopolymer polypropylene with this melt flow rate range as the base resin for the anti-warping functional masterbatch of the BOPP matte film is beneficial for improving the compatibility of the anti-warping functional masterbatch in the matte layer of the BOPP matte film.

[0019] Furthermore, the main function of the maleic anhydride-grafted polypropylene A is to improve the compatibility of the masterbatch in the matte layer of the BOPP matte film. Therefore, the selection of the maleic anhydride-grafted polypropylene A is a conventional choice in the art, and its related parameters are not particularly limited. Preferably, the grafting rate of maleic anhydride in the maleic anhydride-grafted polypropylene A is 0.5% to 1.2%.

[0020] Furthermore, the organophosphate salt is an aluminum organophosphate salt (such as NA-21). Using an aluminum organophosphate salt effectively leverages its role as a primary nucleating agent, significantly increasing the crystallization temperature and rate of the polypropylene phase in the matte layer, refining the spherulite size, and regulating the overall crystallization uniformity of the film, thereby reducing the shrinkage difference between the matte layer and adjacent layers composed primarily of homopolymer polypropylene resin.

[0021] Further, the preparation method of the polysiloxane-polyolefin graft copolymer includes the following steps: maleic anhydride-grafted polypropylene B and monoaminopropyl-terminated polydimethylsiloxane are reacted in a twin-screw extruder at 220-230°C for 20-40 min using a melt grafting method at a mass ratio of 1:1 to obtain the polysiloxane-polyolefin graft copolymer. In the preparation method of the polysiloxane-polyolefin graft copolymer of the present invention, maleic anhydride-grafted polypropylene B is used as the "polyolefin" and monoaminopropyl-terminated polydimethylsiloxane is used as the "polysiloxane," and the reaction is carried out using a melt grafting method to obtain the polysiloxane-polyolefin graft copolymer.

[0022] Furthermore, the maleic anhydride grafting rate in the maleic anhydride-grafted polypropylene B is 1.2~1.5%, thus providing sufficient reactive maleic anhydride groups to better control the appropriate polysiloxane grafting rate in the polysiloxane-polyolefin graft copolymer; the number average molecular weight of the monoaminopropyl-terminated polydimethylsiloxane is 2000~3000 g / mol.

[0023] Furthermore, the surface-modified fumed silica is obtained by surface coating modification of fumed silica with a silane coupling agent. Because fumed silica has extremely high hydrophilicity, the dehydration condensation between its surface silanol groups easily forms aggregates, resulting in poor dispersibility in the matting layer. Therefore, this invention uses a silane coupling agent to perform surface coating modification treatment on fumed silica to improve its dispersibility in the matting layer.

[0024] Furthermore, the amount of the silane coupling agent is 5-12 wt% of the fumed silica; the particle size of the fumed silica is 20-50 nm.

[0025] Preferably, the method for preparing the surface-modified fumed silica includes the following steps: S1. Powder pretreatment: Add fumed silica powder to a mixed solvent of ethanol and water, and disperse it into a suspension slurry by high-speed stirring; S2. Coupling agent pretreatment: The silane coupling agent (preferably a long-chain alkylsilane coupling agent) is pre-hydrolyzed in a dilute acetic acid aqueous solution with a pH of 3.5-4.5 for 15-30 min to give it active silanol groups while maintaining its water solubility; S3. Surface modification: The pre-hydrolyzed silane coupling agent solution in S2 is slowly added dropwise to the suspension slurry in S1 (the amount added is controlled according to the amount of silane coupling agent being 5~12wt% of fumed silica). The reaction is carried out at a constant temperature of 60~70℃ with stirring for 1.5~3h. During this period, the pH is maintained at 8~9 (adjusted with dilute alkaline solution such as ammonia) to promote the condensation and bonding of silanol groups on the SiO2 surface. S4. Washing and drying: The slurry after reaction S3 is washed by centrifugation to remove excess unreacted coupling agent and ions, and then dried to obtain the surface-modified fumed silica.

[0026] This invention utilizes silane coupling agents to modify the surface of fumed silica, which is beneficial to improving the compatibility of the surface-modified fumed silica with the matting layer.

[0027] Furthermore, the antioxidant is preferably hindered phenolic antioxidant 1010.

[0028] The present invention also provides a method for preparing the anti-warping functional masterbatch for BOPP matte film as described above, comprising the following steps: The components are placed in a mixer in proportion and mixed evenly at 200-220℃ and 500-600rpm to obtain a blended material. The blended material is then fed into a twin-screw extruder, with the screw speed set at 35-50rpm and the temperature at 220-230℃. The blended material is melted, extruded, water-cooled, pelletized, and dried to obtain the anti-warping functional masterbatch for BOPP matte film.

[0029] The present invention also provides the application of any of the above-described anti-warping functional masterbatches for BOPP matte film in the matte layer of BOPP matte film.

[0030] Furthermore, the BOPP matte film includes a matte layer and an adjacent layer. The matte layer comprises polypropylene, high-density polyethylene, and 1-8 wt% of the anti-warping functional masterbatch for the BOPP matte film. The adjacent layer comprises homopolymer polypropylene. The polypropylene and high-density polyethylene in the matte layer are conventional components of matte layers in the art. For example, the polypropylene in the matte layer can be homopolymer polypropylene or copolymer polypropylene, which will not be described in detail here.

[0031] As a preferred embodiment of the BOPP matte film, the BOPP matte film comprises a matte layer, a core layer, and a gloss layer arranged sequentially; the core layer comprises homopolymer polypropylene and an antistatic agent masterbatch; the gloss layer comprises homopolymer polypropylene / copolymer polypropylene and an antiblocking agent masterbatch. The components in the core layer and the gloss layer are conventional components in the art and will not be described in detail here.

[0032] Compared with the prior art, the present invention has the following beneficial effects: The anti-warping functional masterbatch for BOPP matte film of the present invention contains a polysiloxane-polyolefin graft copolymer in which the polyolefin segments achieve excellent compatibility with the polypropylene, which is the marine phase in the matte layer. The polysiloxane segments make the melt flow more uniformly during extrusion and stretching, and the molecular chain orientation is more consistent in the transverse and longitudinal directions of the film. This can effectively reduce local shrinkage differences, effectively improve the problems of residual internal stress and interlayer stress mismatch in BOPP matte film, and improve film warping.

[0033] The anti-warping functional masterbatch for BOPP matte film of this invention achieves synergistic effects through a designed nucleation system of organophosphate salt, calcium stearate, and surface-modified fumed silica: the organophosphate salt increases the crystallization temperature and rate of polypropylene (as the marine phase) in the matte layer; calcium stearate improves powder dispersibility; and surface-modified fumed silica acts as a nucleating agent carrier and reinforces the matting effect of the matte layer. The combined effect of these three components results in a uniform and fine microcrystalline structure in the matte layer of the BOPP matte film, enhancing anti-warping performance without compromising the mechanical and optical properties of the film. Detailed Implementation

[0034] To facilitate understanding of the present invention, it will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0035] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0036] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] The experimental methods in the following examples or comparative examples, unless otherwise specified, are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market.

[0038] This invention provides an anti-warping functional masterbatch for BOPP matte film, characterized by comprising the following components: homopolymer polypropylene, 1-4 wt% maleic anhydride-grafted polypropylene A, 0.1-0.3 wt% organophosphate salt, 0.1-0.2 wt% calcium stearate, 1-3 wt% polysiloxane-polyolefin graft copolymer, 0.1-0.3 wt% antioxidant, and 0.1-0.5 wt% surface-modified fumed silica; wherein the grafting rate of maleic anhydride in the maleic anhydride-grafted polypropylene A is 0.5-1.2%, and the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer is 10-45%.

[0039] In one specific embodiment, the homopolymer polypropylene has a melt flow rate of 2.5~3.5 g / 10 min under test conditions of 230°C and 2.16 kg.

[0040] In one specific embodiment, the organophosphate salt is an aluminum organophosphate salt (such as NA-21).

[0041] In one specific embodiment, the preparation method of the polysiloxane-polyolefin graft copolymer includes the following steps: maleic anhydride-grafted polypropylene B and monoaminopropyl-terminated polydimethylsiloxane are reacted in a twin-screw extruder at 220-230°C for 20-40 min by melt grafting at a mass ratio of 1:1 to obtain the polysiloxane-polyolefin graft copolymer; wherein, the grafting rate of maleic anhydride in the maleic anhydride-grafted polypropylene B is 1.2-1.5%; and the number average molecular weight of the monoaminopropyl-terminated polydimethylsiloxane PDMS is 2000-3000 g / mol.

[0042] In one specific embodiment, the surface-modified fumed silica is obtained by surface-coating and modifying fumed silica with a silane coupling agent, wherein the amount of the silane coupling agent is 5-12 wt% of the fumed silica; and the particle size of the fumed silica is 20-50 nm.

[0043] In one specific embodiment, the method for preparing the surface-modified fumed silica includes the following steps: S1. Powder pretreatment: Add fumed silica powder to a mixed solvent of ethanol and water, and disperse it into a suspension slurry by high-speed stirring; S2. Coupling agent pretreatment: The silane coupling agent (preferably a long-chain alkylsilane coupling agent) is pre-hydrolyzed in a dilute acetic acid aqueous solution with a pH of 3.5-4.5 for 15-30 min to give it active silanol groups while maintaining its water solubility; S3. Surface modification: The pre-hydrolyzed silane coupling agent solution in S2 is slowly added dropwise to the suspension slurry in S1 (the amount added is controlled according to the amount of silane coupling agent being 5~12wt% of fumed silica). The reaction is carried out at a constant temperature of 60~70℃ with stirring for 1.5~3h. During this period, the pH is maintained at 8~9 (adjusted with dilute alkaline solution such as ammonia) to promote the condensation and bonding of silanol groups on the SiO2 surface. S4. Washing and drying: The slurry after reaction S3 is washed by centrifugation to remove excess unreacted coupling agent and ions, and then dried to obtain the surface-modified fumed silica.

[0044] The present invention will now be described in conjunction with specific embodiments.

[0045] The raw materials used in the following examples or comparative examples are as follows: (1) Homopolymer polypropylene (homogeneous PP): melt flow rate of 3 g / 10 min (test conditions: 230℃, 2.16 kg); (2) Organic phosphate salts: Commercially available organic phosphate aluminum salt NA-21; (3) Calcium stearate: commercially available; (4) Maleic anhydride-grafted polypropylene: ① Maleic anhydride-grafted polypropylene A: Commercially available, with a maleic anhydride grafting rate of 1.0%; ② Maleic anhydride-grafted polypropylene B: Commercially available, with a maleic anhydride grafting rate of 1.5% and Mn of 3900 g / mol; Note: This maleic anhydride-grafted polypropylene B is used in the preparation of the following polysiloxane-polyolefin graft copolymer A and polysiloxane-polyolefin graft copolymer B. (5) Polysiloxane-polyolefin graft copolymer: ① Polysiloxane-polyolefin graft copolymer A: The grafting rate of polysiloxane (PDMS) is 16.9%; Preparation method of polysiloxane-polyolefin graft copolymer A: Commercially available maleic anhydride-grafted polypropylene B and monoaminopropyl-terminated polydimethylsiloxane PDMS (number average molecular weight 2000 g / mol) were mixed at a mass ratio of 1:1, with 1 wt% (as a percentage of the mass fraction of maleic anhydride-grafted polypropylene B) of antioxidant added. The reaction was carried out using a melt grafting method in a twin-screw extruder at 220°C for 20 min. The mixture was then cooled to room temperature, and the viscous product was collected and purified with diethyl ether to obtain the polysiloxane-polyolefin graft copolymer A. The polysiloxane-polyolefin graft copolymer A was analyzed by 1H NMR spectroscopy, and the grafting rate of polysiloxane (PDMS) was 16.9%.

[0046] ② Polysiloxane-polyolefin graft copolymer B: The grafting rate of polysiloxane (PDMS) is 42.2%; The preparation method of polysiloxane-polyolefin graft copolymer B is basically the same as that of polysiloxane-polyolefin graft copolymer A, except that the reaction time is 30 min. The polysiloxane-polyolefin graft copolymer B was analyzed by 1H NMR spectroscopy, and the grafting rate of polysiloxane (PDMS) was 42.2%.

[0047] (6) Antioxidant: Commercially available hindered phenolic antioxidant 1010; (7) Surface-modified fumed silica: Its preparation method is as follows: S1. Powder pretreatment: Fumed silica powder (particle size 30nm) is added to an ethanol / water mixed solvent (ethanol:water volume ratio = 4:1) and dispersed into a suspension slurry by high-speed stirring; wherein, the effective content of fumed silica is 10wt%; S2. Coupling agent pretreatment: The silane coupling agent (commercially available hexadecyltrimethoxysilane, the amount of which is 10wt% of the fumed silica) is pre-hydrolyzed in a dilute acetic acid aqueous solution at pH 4.0 for 20 min, wherein the effective concentration of the silane coupling agent is 4wt%, so that it has active silanol groups while maintaining water solubility. S3. Addition and reaction: The pre-hydrolyzed silane coupling agent solution in S2 is slowly added dropwise to the suspension slurry in S1, and the mixture is stirred at a constant temperature of 60°C for 2 hours. During this period, the pH is maintained at 8-9 (adjusted with ammonia) to promote the condensation and bonding of silanol groups on the SiO2 surface. S4. Washing and drying: After the reaction, the slurry is washed by a centrifuge to remove excess unreacted coupling agent and ions, and then dried at 60°C to obtain the surface-modified fumed silica.

[0048] Please refer to Table 1 for the formulation composition of the anti-warping functional masterbatch for BOPP matte film in the following examples or comparative examples: Table 1. Masterbatch formulation composition (wt%) of Examples 1-4 and Comparative Examples 1-7

[0049] Example 1 This embodiment provides an anti-warping functional masterbatch for BOPP matte film. Please refer to Table 1. It includes the following components: 95.3 wt% homopolymer polypropylene, 3 wt% maleic anhydride grafted polypropylene A, 0.1 wt% organophosphate salt, 0.1 wt% calcium stearate, 1 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0050] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this embodiment includes the following steps: The components are placed in a mixer in proportion and mixed evenly at 210℃ and 550rpm to obtain a blended material. The blended material is then fed into a twin-screw extruder and granulator, with the screw speed set at 40rpm and the temperature at 220℃. The blended material is then melted, extruded, water-cooled, pelletized, and dried to obtain an anti-warping functional masterbatch.

[0051] Example 2 This embodiment provides an anti-warping functional masterbatch for BOPP matte film. Please refer to Table 1. It includes the following components: 94.15wt% homopolymer polypropylene, 3wt% maleic anhydride-grafted polypropylene A, 0.2wt% organophosphate salt, 0.15wt% calcium stearate, 2wt% polysiloxane-polyolefin graft copolymer A, 0.2wt% antioxidant, and 0.3wt% surface-modified fumed silica.

[0052] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this embodiment is the same as that in Example 1.

[0053] Example 3 This embodiment provides an anti-warping functional masterbatch for BOPP matte film. Please refer to Table 1. It includes the following components: 93.0 wt% homopolymer polypropylene, 3 wt% maleic anhydride grafted polypropylene A, 0.3 wt% organophosphate salt, 0.2 wt% calcium stearate, 3 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0054] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this embodiment is the same as that in Example 1.

[0055] Example 4 This embodiment provides an anti-warping functional masterbatch for BOPP matte film. Please refer to Table 1. It includes the following components: 94.15wt% homopolymer polypropylene, 3wt% maleic anhydride-grafted polypropylene A, 0.2wt% organophosphate salt, 0.15wt% calcium stearate, 2wt% polysiloxane-polyolefin graft copolymer B, 0.2wt% antioxidant, and 0.3wt% surface-modified fumed silica.

[0056] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this embodiment is the same as that in Example 1.

[0057] Comparative Example 1 This comparative example provides an anti-warping masterbatch for BOPP matte film, which is basically the same as Example 2, except that: no organophosphate salts are added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 94.35 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.15 wt% calcium stearate, 2 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0058] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0059] Comparative Example 2 This comparative example provides an anti-warping functional masterbatch for BOPP matte film, which is basically the same as Example 2, except that an excessive amount of organic phosphate salt is added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 93.85 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.5 wt% organophosphate salt, 0.15 wt% calcium stearate, 2 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0060] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0061] Comparative Example 3 This comparative example provides an anti-warping masterbatch for BOPP matte film, which is basically the same as Example 2, except that: no polysiloxane-polyolefin graft copolymer is added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 96.15 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.2 wt% organophosphate salt, 0.15 wt% calcium stearate, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0062] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0063] Comparative Example 4 This comparative example provides an anti-warping functional masterbatch for BOPP matte film, which is basically the same as Example 2, except that an excessive amount of polysiloxane-polyolefin graft copolymer is added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 91.15 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.2 wt% organophosphate salt, 0.15 wt% calcium stearate, 5 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0064] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0065] Comparative Example 5 This comparative example provides an anti-warping functional masterbatch for BOPP matte film, which is basically the same as Example 2, except that calcium stearate is not added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 94.3 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.2 wt% organophosphate salt, 2 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0066] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0067] Comparative Example 6 This comparative example provides an anti-warping functional masterbatch for BOPP matte film, which is basically the same as Example 2, except that an excessive amount of calcium stearate is added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 93.8 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.2 wt% organophosphate salt, 0.5 wt% calcium stearate, 2 wt% polysiloxane-polyolefin graft copolymer A, 0.2 wt% antioxidant, and 0.3 wt% surface-modified fumed silica.

[0068] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0069] Comparative Example 7 This comparative example provides an anti-warping functional masterbatch for BOPP matte film, which is basically the same as Example 2, except that: no surface-modified fumed silica is added. Specifically: The anti-warping functional masterbatch for BOPP matte film in this comparative example, as shown in Table 1, includes the following components: 94.45 wt% homopolymer polypropylene, 3 wt% maleic anhydride-grafted polypropylene A, 0.2 wt% organophosphate salt, 0.15 wt% calcium stearate, 2 wt% polysiloxane-polyolefin graft copolymer A, and 0.2 wt% antioxidant.

[0070] The preparation method of the anti-warping functional masterbatch for BOPP matte film in this comparative example is the same as that in Example 1.

[0071] Performance testing The BOPP matte films of Examples 1-4 and Comparative Examples 1-7 were respectively used as anti-warping functional masterbatch in the matte layer of the BOPP matte film to prepare BOPP matte films, and then tested.

[0072] Specifically, the BOPP matting film comprises a matting layer, a core layer, and a light-reflecting layer arranged in sequence, the formulation of which is shown in Table 2: Table 2. Layer structure and formulation of BOPP matte film

[0073] BOPP matte film is prepared using a conventional co-extrusion biaxial stretching process. Specifically, the materials for the matte layer, core layer, and gloss layer are fed into a feed distributor (feeding scale) and weighed according to the proportions. After weighing, the raw materials for each layer are fed into the respective extruders. The raw materials for each layer are melted, plasticized, and extruded in the extruders. The extruder temperature for the core layer is 260°C, the temperature for the upper surface layer is 240°C, and the temperature for the lower surface layer is 250°C. After being melted and plasticized, the raw materials for each layer are filtered and the molten material output by the metering pump is sent to the T-die to form a thick sheet. The thick sheet is then chilled and cast by a chilling roller. The T-die temperature is set at 240℃, the chiller roller temperature is set at 33℃, the matte layer is on the air knife surface, and the glossy layer is in close contact with the chiller roller. Next, the thick film enters the longitudinal stretching zone and transverse stretching zone of the biaxially oriented film equipment for sequential longitudinal and transverse stretching. The temperature of the matte layer longitudinal stretching preheating roller is 133℃, and the glossy layer longitudinal stretching preheating roller temperature can be 138℃. The temperature of the matte layer longitudinal stretching zone is 123℃, and the glossy layer longitudinal stretching zone temperature is 132℃. The longitudinal stretching ratio is set at 4.6 times, the transverse stretching preheating temperature is set at 170℃, the transverse stretching zone temperature is set at 160℃, and the transverse stretching ratio is set at 8 times. After stretching, the film is shaped in a 168℃ setting zone. After shaped, the film passes through an air shower zone and is then trimmed, cut, and measured in sequence. Next, it undergoes corona treatment, followed by winding, aging treatment, slitting, and packaging.

[0074] After preparing BOPP matte films using the anti-warping functional masterbatch of Examples 1-4 and Comparative Examples 1-7 as described above, the following performance tests were performed: 1) Gloss: Tested at a 45° angle according to GB / T 8807-1988; 2) Haze: Tested according to GB / T 2410-2008; 3) Tensile strength and nominal strain at break: tested according to GB / T 1040.3-2006; 4) Warp height: The film is placed in a 120℃ hot oven for 10 minutes, and then the film is taken out to test its warp height to evaluate its warp resistance.

[0075] Please refer to Table 3 for the results: Table 3 Performance test results of Examples 1-4 and Comparative Examples 1-7

[0076] As can be seen from the table above, the anti-warping functional masterbatch for BOPP matte film in Examples 1 to 4 of the present invention is suitable for high-speed production of BOPP matte film, and the corresponding BOPP matte films prepared have excellent anti-warping performance, while not affecting the mechanical strength and optical properties of the film.

[0077] The BOPP matte film of Comparative Example 1, without the addition of organic phosphate salts, had a high warpage height, making it difficult to effectively improve the warpage problem.

[0078] In Comparative Example 2, the addition of excessive organic phosphate salts to the BOPP matte film resulted in an abnormally high haze, which impaired the optical properties of the BOPP matte film, reduced its tensile strength and nominal strain at break, and caused local warping of the BOPP matte film with an excessively high warping height.

[0079] Compared with the BOPP matte film of Comparative Example 3, which did not contain polysiloxane-polyolefin graft copolymer, the BOPP matte film prepared by it had a higher warp height, and it also could not effectively improve the film warping problem.

[0080] Compared with the BOPP matte film of Comparative Example 4, the addition of excessive polysiloxane-polyolefin graft copolymer resulted in a decrease in the tensile strength and nominal strain at break of the prepared BOPP matte film.

[0081] The BOPP matte film of Comparative Example 5, which uses an anti-warping masterbatch without the addition of calcium stearate, has a higher warpage height and poor uniformity in film thickness, which is not conducive to smooth production.

[0082] The BOPP matte film of Comparative Example 6, which uses an anti-warping masterbatch, had an excessive amount of calcium stearate added. The resulting BOPP matte film had a higher warpage height, which was not conducive to precise warpage control.

[0083] The BOPP matte film of Comparative Example 7 was prepared using an anti-warping functional masterbatch without the addition of surface-modified fumed silica. The resulting BOPP matte film exhibited reduced haze and decreased optical performance.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above-described embodiments are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, the present invention also intends to include these modifications and variations.

Claims

1. A BOPP matte film anti-warping functional masterbatch, characterized in that, The product comprises the following components: homopolymer polypropylene, 1-4 wt% maleic anhydride-grafted polypropylene A, 0.1-0.3 wt% organophosphate salt, 0.1-0.2 wt% calcium stearate, 1-3 wt% polysiloxane-polyolefin graft copolymer, 0.1-0.3 wt% antioxidant, and 0.1-0.5 wt% surface-modified fumed silica; wherein the grafting rate of maleic anhydride in the maleic anhydride-grafted polypropylene A is 0.5-1.2%; the grafting rate of polysiloxane in the polysiloxane-polyolefin graft copolymer is 10-45%; and the surface-modified fumed silica is obtained by surface coating modification of fumed silica with a silane coupling agent. The preparation method of the polysiloxane-polyolefin graft copolymer includes the following steps: Maleic anhydride-grafted polypropylene B and monoaminopropyl-terminated polydimethylsiloxane were reacted in a twin-screw extruder at 220-230°C for 20-40 min using a melt grafting method at a mass ratio of 1:1 to obtain the polysiloxane-polyolefin graft copolymer. The maleic anhydride grafting rate in the maleic anhydride-grafted polypropylene B was 1.2-1.5%, and the number-average molecular weight of the monoaminopropyl-terminated polydimethylsiloxane was 2000-3000 g / mol.

2. The anti-warping functional masterbatch for BOPP matte film according to claim 1, characterized in that, The homopolymer polypropylene exhibits a melt flow rate of 2.5~3.5 g / 10 min under test conditions of 230℃ and 2.16 kg.

3. The anti-warping functional masterbatch for BOPP matte film according to claim 1, characterized in that, The organic phosphate salt is an organic phosphate aluminum salt.

4. The anti-warping functional masterbatch for BOPP matte film according to claim 1, characterized in that, The amount of the silane coupling agent is 5-12 wt% of the fumed silica; the particle size of the fumed silica is 20-50 nm.

5. A method for preparing an anti-warping functional masterbatch for BOPP matte film as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Each component is placed in a mixer in proportion and mixed evenly at 200~220℃ and 500~600rpm to obtain a blended material. The blended material is fed into a twin-screw extruder, with the screw speed set at 35~50rpm and the temperature at 220~230℃. The blended material is melted, extruded, water-cooled, pelletized, and dried to obtain the anti-warping functional masterbatch for BOPP matte film.

6. The application of the anti-warping functional masterbatch for BOPP matte film as described in any one of claims 1 to 4 in the matte layer of BOPP matte film.

7. The application of the anti-warping functional masterbatch for BOPP matte film according to claim 6 in the matte layer of BOPP matte film, characterized in that, The matte layer comprises polypropylene, high-density polyethylene, and 1-8 wt% of the anti-warping functional masterbatch for the BOPP matte film.

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