A bopp film use corona persistent function master batch and its preparation method and application

Abstract

The application provides a BOPP film corona durability functional master batch and a preparation method and application thereof, the functional master batch comprises the following components in parts by weight: polypropylene grafted maleic anhydride 30-40 parts, polar wax 4-8 parts, elastomer 5-10 parts, and polypropylene 42-61 parts; wherein the polar wax comprises high-acid-value polar wax and low-molecular-weight polar wax; the acid value of the high-acid-value polar wax is greater than 20 mg KOH / g; and the number average molecular weight of the low-molecular-weight polar wax is less than 5000. Through chemical anchoring of the polypropylene grafted maleic anhydride, gradient migration of the polar wax, stress buffering of the elastomer and polar group storage effect, a synergistic system of 'three-in-one' is constructed, and the problem that the BOPP film corona effect is difficult to be kept for a long time is fundamentally solved. The BOPP film prepared by adding the functional master batch of the application has a significantly improved corona treatment effect retention rate after corona treatment.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a corona-permanent functional masterbatch for BOPP membranes, its preparation method, and its application. Background Technology

[0002] Biaxially oriented polypropylene (BOPP) film is widely used in packaging, printing, and electrical and electronic fields due to its low density, high transparency, excellent mechanical properties, and low cost. However, polypropylene is a non-polar polymer with low surface free energy, resulting in poor performance in secondary processing such as printing, coating, and metallization. Industrially, corona treatment is commonly used to introduce polar groups (such as hydroxyl, carboxyl, and carbonyl groups) onto the film surface to increase its surface tension. However, the surface polarization induced by corona treatment is a non-equilibrium state. Because polypropylene molecular chains have high mobility, the polar groups generated during treatment undergo chain rearrangement over time, migrating into the film bulk and causing a rapid decrease in surface tension. Within 30 days after corona treatment, the surface tension of conventional BOPP film typically decreases from above 42 dynes / cm to below 34 dynes / cm, severely impacting the yield of subsequent processes and the product's shelf life.

[0003] Chinese invention patent CN121293636A discloses a high surface tension masterbatch for BOPP film and its preparation method. This masterbatch uses PP resin as a carrier and adds nano-scale organic modified montmorillonite, maleic anhydride-grafted polypropylene (PP-g-MAH), and a composite modifier composed of fluorinated surfactants, silane coupling agents, and amide-based slip agents. It is prepared through steps such as raw material pretreatment, gradient mixing, melt blending, and granulation post-treatment. This technical solution introduces organic modified montmorillonite and the composite modifier into the polypropylene matrix, enabling the resulting BOPP film to achieve a surface tension of 42~45 mN / m without corona treatment. Its core purpose is to bypass the corona treatment process and directly impart high surface tension to the film. However, this solution addresses the issue of improving the initial surface tension of the film. Its PP-g-MAH is only used as a compatibilizer to improve the dispersion of nano-montmorillonite in the matrix, and the addition amount is relatively low, making it difficult to form a continuous supply of polar groups on the film surface. This patent does not address the issue of surface tension decay over time after corona treatment. For example, Chinese invention patent CN121361250A discloses a composite layer and its application in CPP films and packaging materials. By setting a specific composite layer on the surface of the CPP film, the corona value of the CPP film is high and the corona retention effect is good. However, this technical solution is aimed at CPP films (cast polypropylene films). CPP is an unstretched film, and its molecular chain orientation is much lower than that of BOPP, resulting in fundamentally different corona decay behavior and mechanisms. Furthermore, it relies on the composite layer design in a multi-layer co-extrusion structure, which is complex and costly, making it unsuitable for conversion and use in BOPP.

[0004] Therefore, how to achieve long-term stability of the surface tension of BOPP film after corona treatment, that is, to significantly slow down its decay rate while maintaining high initial surface tension, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a corona-permanent functional masterbatch for BOPP film, its preparation method and application, aiming to solve the technical problem of excessively rapid surface tension decay after corona treatment of existing BOPP films.

[0006] In a first aspect, the present invention provides a corona-permanent functional masterbatch for BOPP film, comprising the following components by weight: 30-40 parts of polypropylene grafted with maleic anhydride, 4-8 parts of polar wax, 5-10 parts of elastomer, and 42-61 parts of polypropylene. Among them, polar waxes include high acid value polar waxes and low molecular weight polar waxes; the acid value of high acid value polar waxes is >20mgKOH / g; the number average molecular weight of low molecular weight polar waxes is <5000.

[0007] Preferably, the mass ratio of high acid value polar wax to low molecular weight polar wax is 1:(0.5~2).

[0008] Preferably, the high-acid-value polar wax includes at least one of oxidized polyethylene wax, oxidized polypropylene wax, and maleic anhydride-grafted polyethylene wax; the low-molecular-weight polar wax includes at least one of polyethylene wax and polypropylene wax.

[0009] Preferably, the elastomer includes at least one of polyolefin elastomers and styrene elastomers.

[0010] Preferably, the elastomer includes at least one of ethylene-octene copolymer, ethylene-butene copolymer, and styrene-ethylene-butene-styrene block copolymer.

[0011] Preferably, the polypropylene grafted with maleic anhydride has a melt index of 40~60g / 10min at 230℃ and 2.16kg load; and the Mooney viscosity ML(1+4) of the elastomer is 5~20 at 125℃.

[0012] Secondly, the present invention provides a method for preparing a corona-permanent functional masterbatch for BOPP film, comprising the following steps: Polypropylene grafted with maleic anhydride, polar wax, elastomer and polypropylene are mixed evenly and then melt-blended and extruded. The extrudate is cooled, air-dried and pelletized to obtain functional masterbatch.

[0013] Preferably, the melt blending extrusion is carried out using a twin-screw extruder, and the operating conditions of the twin-screw extruder are set as follows: Zone 1 160~180℃, Zone 2 180~200℃, Zone 3 200~220℃, Die head 210~220℃, and screw speed 300~500rpm.

[0014] Thirdly, the present invention provides a BOPP film, the raw materials for which include the corona-permanent functional masterbatch for BOPP film described in the first aspect and BOPP base resin; the amount of corona-permanent functional masterbatch for BOPP film added is 3% to 7% of the mass of BOPP base resin.

[0015] Fourthly, embodiments of the present invention provide a method for preparing BOPP film, comprising the following steps: mixing the BOPP film described in the first aspect with BOPP base resin at a weight ratio of 3% to 7%, followed by melt extrusion, casting, biaxial stretching, heat setting, and corona treatment to obtain BOPP film.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The corona-permanent functional masterbatch for BOPP films provided by this invention constructs a synergistic "three-in-one" system through chemical anchoring of PP-g-MAH, gradient migration and replenishment of polar wax, and stress buffering and polar group storage effects of elastomers. This fundamentally solves the technical problem of the difficulty in maintaining the corona effect of BOPP films over a long period. BOPP films prepared with this functional masterbatch show a significantly improved retention rate of corona treatment effect after corona treatment.

[0017] The method for preparing corona-permanent functional masterbatch for BOPP film provided by this invention is simple and can be achieved through conventional blending and melt granulation. Furthermore, when applied to BOPP film preparation, the functional masterbatch does not require modification of existing BOPP production lines, exhibits good compatibility and processing adaptability with conventional BOPP base materials, and requires a low addition amount (3%~7%), resulting in controllable overall costs and significant market potential. Detailed Implementation

[0018] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0019] To address the technical problem of excessively rapid surface tension decay after corona treatment of existing BOPP films, this invention provides a corona-resistant functional masterbatch for BOPP films, its preparation method, and its application. The masterbatch utilizes a synergistic "three-in-one" system, achieved through chemical anchoring of PP-g-MAH, gradient migration and replenishment of polar waxes with different molecular weights, and stress buffering and polar group storage effects of the elastomer. This results in a functional masterbatch that not only matches the BOPP processing technology well but also maintains the corona treatment effect for a long time, while simultaneously improving the mechanical properties of the film.

[0020] In a first aspect, embodiments of the present invention provide a corona-permanent functional masterbatch for BOPP film, comprising the following components by weight: 30-40 parts of polypropylene grafted with maleic anhydride, 4-8 parts of polar wax, 5-10 parts of elastomer, and 42-61 parts of polypropylene. Among them, polar waxes include high acid value polar waxes and low molecular weight polar waxes; the acid value of high acid value polar waxes is >20mgKOH / g; the number average molecular weight of low molecular weight polar waxes is <5000.

[0021] In the technical solution of this invention embodiment, the functional masterbatch provided by this invention constructs a complete synergistic system through the chemical anchoring of polypropylene grafted maleic anhydride (PP-g-MAH), the gradient migration and replenishment of polar wax, and the stress buffering and polar group storage effect of elastomer. The principle behind this functional masterbatch's application in enhancing the corona treatment durability of BOPP films is as follows: Polypropylene grafted with maleic anhydride (PP-g-MAH), as the core polar component, reacts chemically with newly generated free radicals on the film surface during corona treatment, forming stable covalent bonds. This firmly anchors the polar groups to the material surface, effectively inhibiting their inward migration. Simultaneously, high-acid-value polar wax, due to its high polar density, can rapidly migrate to the film surface in the early stages of corona treatment, forming an initial polar layer to replenish the polar groups lost due to chain rearrangement and maintain a high initial surface tension. Low-molecular-weight polar wax, with its excellent chain mobility, slowly migrates during storage and use, continuously replenishing polar groups and significantly delaying the decay of surface tension. Furthermore, the elastomer component forms a micro-island structure in the film, providing "storage space" for polar groups and buffering tensile stress. The synergistic effect of these three components constructs a surface polarity maintenance system, fundamentally solving the technical problem of the difficulty in maintaining the long-term corona treatment effect of BOPP films.

[0022] Furthermore, in some embodiments, the mass ratio of high-acid-value polar wax to low-molecular-weight polar wax is 1:(0.5~2).

[0023] In the technical solution of this invention embodiment, high-acid-value polar wax rapidly accumulates on the surface after corona treatment, providing sufficient polar groups to maintain the initial high surface tension; while low-molecular-weight polar wax serves as a long-term replenishment source, continuously migrating to the surface during the film's service life to compensate for the polarity loss caused by molecular chain rearrangement. Through numerous experiments, the inventors discovered that when the mass ratio of high-acid-value polar wax to low-molecular-weight polar wax is controlled within the range of 1:(0.5~2), the two exhibit a good synergistic effect.

[0024] Furthermore, in some embodiments, the high-acid-value polar wax includes at least one of oxidized polyethylene wax, oxidized polypropylene wax, and maleic anhydride-grafted polyethylene wax; the low-molecular-weight polar wax includes at least one of polyethylene wax and polypropylene wax.

[0025] Furthermore, in some embodiments, the high-acid-value polar wax is oxidized polyethylene wax with an acid value of 25~35 mg KOH / g and a dropping point of 100~110℃; the low-molecular-weight polar wax is polyethylene wax with a number-average molecular weight of 1500~2500 and an acid value of 10~20 mg KOH / g.

[0026] Furthermore, in some embodiments, the elastomer includes at least one of polyolefin elastomers and styrene elastomers.

[0027] Furthermore, in some embodiments, the elastomer includes at least one of ethylene-octene copolymer, ethylene-butene copolymer, and styrene-ethylene-butene-styrene block copolymer.

[0028] Furthermore, in some embodiments, the melt index of the elastomer is 1~5 g / 10 min, and the Mooney viscosity ML(1+4) at 125°C is 5~20.

[0029] Furthermore, in some embodiments, the grafting rate of polypropylene grafted with maleic anhydride is 0.8~1.2%; the melt index is 40~60 g / 10 min when tested at 230°C and 2.16 kg load.

[0030] In the technical solution of this invention embodiment, by controlling the melt index and Mooney viscosity of PP-g-MAH, it is made to be highly matched with the rheological behavior of BOPP matrix resin, so that no crystal points or film breakage problems will occur during biaxial stretching, thus ensuring the yield and production stability of the film.

[0031] Furthermore, in some embodiments, the polypropylene is homopolymer polypropylene, and its melt index is measured to be 2~5 g / 10min at 230°C and 2.16 kg load.

[0032] In the technical solution of this invention embodiment, polypropylene not only plays the role of dispersing and loading functional components, but also ensures that the masterbatch and BOPP base film raw material have good compatibility and processability.

[0033] Secondly, embodiments of the present invention provide a method for preparing a corona-permanent functional masterbatch for BOPP films, comprising the following steps: Polypropylene grafted with maleic anhydride, polar wax, elastomer and polypropylene are mixed evenly and then melt-blended and extruded. The extrudate is cooled, air-dried and pelletized to obtain functional masterbatch.

[0034] Furthermore, in some embodiments, the melt blending extrusion is carried out by a twin-screw extruder, the operating conditions of which are set as follows: Zone 1 160~180℃, Zone 2 180~200℃, Zone 3 200~220℃, Die head 210~220℃, and screw speed 300~500rpm.

[0035] Thirdly, embodiments of the present invention provide a BOPP film, the raw materials for which include the corona-permanent functional masterbatch for BOPP film described in the first aspect and BOPP base resin; the amount of corona-permanent functional masterbatch for BOPP film added is 3% to 7% of the mass of BOPP base resin.

[0036] Fourthly, embodiments of the present invention provide a method for preparing BOPP film, comprising the following steps: mixing the functional masterbatch described in the first aspect with BOPP base resin at a weight ratio of 3% to 7%, and then performing melt extrusion, casting, biaxial stretching, heat setting, and corona treatment to obtain BOPP film.

[0037] In the technical solution of this invention embodiment, the BOPP film prepared by adding the functional masterbatch of this invention exhibits a significantly improved corona treatment retention rate after corona treatment. Simultaneously, due to the introduction of the elastomer component, the tear strength of the film is also improved, achieving simultaneous optimization of the film's surface properties and mechanical properties. Furthermore, this functional masterbatch is highly compatible with existing BOPP production lines, requiring no modification to existing lines; the durable corona treatment effect can be achieved simply through blending, demonstrating promising industrialization prospects.

[0038] Furthermore, in some embodiments, the conditions for bidirectional stretching are: the longitudinal stretching ratio is 4 to 6 times, and the transverse stretching ratio is 8 to 10 times.

[0039] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0040] The raw material information used in the following examples and comparative examples is as follows: PP-g-MAH: Commercially available, grafting rate 1%, melt index (230℃, 2.16kg) 50g / 10min.

[0041] High acid value polar wax: Commercially available oxidized polyethylene wax, acid value 28mg KOH / g, dropping point 100~110℃.

[0042] Low molecular weight polar wax: Commercially available polyethylene wax, number average molecular weight 2000, acid value 15mg KOH / g.

[0043] Elastomer: Commercially available ethylene-octene copolymer (POE) with a melt index (190℃, 2.16kg) of 3.0g / 10min and Mooney viscosity ML(1+4) of 10 at 125℃; or commercially available styrene-ethylene-butene-styrene block copolymer (SEBS) with a melt index (230℃, 2.16kg) of 4.0g / 10min and Mooney viscosity ML(1+4) of 20 at 125℃.

[0044] Polypropylene (PP): Commercially available homopolymer polypropylene with a melt index (230℃, 2.16kg) of 3.0g / 10min. BOPP base resin: a special homopolymer polypropylene used for film production, with a melt index (230℃, 2.16kg) of 2.5~3.5g / 10min.

[0045] The testing methods for the relevant indicators are as follows: Melt flow index: determined according to GB / T 3682.1-2018 standard, at 230℃ or 190℃, under a load of 2.16kg.

[0046] Grafting rate: The grafting rate of PP-g-MAH was determined by acid-base titration or Fourier transform infrared spectroscopy.

[0047] Acid value: The acid value of polar waxes was determined according to GB / T 1668-2008 standard.

[0048] Molecular weight: The number-average molecular weight of polar waxes was determined by gel permeation chromatography.

[0049] Example 1 This embodiment provides a functional masterbatch, which has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 3 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 3 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 8 parts of elastomer (POE, MI=3g / 10min), and 51 parts of PP.

[0050] The preparation method of the functional masterbatch is as follows: Weigh the raw materials according to the formula and mix them in a high-speed mixer for 8 minutes; then add the mixture to a twin-screw extruder and set the extruder temperature as follows: Zone 1 170℃, Zone 2 190℃, Zone 3 210℃, Die head 215℃, and screw speed 400rpm; after water cooling, air drying, and pelletizing, the masterbatch is obtained.

[0051] This embodiment also provides a method for preparing BOPP film, the specific steps of which are as follows: the prepared masterbatch is mixed with BOPP base resin at a ratio of 5%, and BOPP film with a thickness of 20μm is obtained by melt extrusion, casting, biaxial stretching and heat setting, with a longitudinal stretching ratio of 5 times and a transverse stretching ratio of 9 times, and corona treatment is performed online.

[0052] Example 2 This embodiment provides a functional masterbatch, which has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 3 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 3 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 5 parts of elastomer (POE, MI=3g / 10min), and 54 parts of PP.

[0053] The preparation method of the functional masterbatch is the same as that in Example 1.

[0054] This embodiment also provides a method for preparing BOPP film, with the same steps and parameters as in Embodiment 1.

[0055] Example 3 This embodiment provides a functional masterbatch, which has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 3 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 3 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 10 parts of elastomer (POE, MI=3g / 10min), and 49 parts of PP.

[0056] The preparation method of the functional masterbatch is the same as that in Example 1.

[0057] This embodiment also provides a method for preparing BOPP film, with the same steps and parameters as in Embodiment 1.

[0058] Example 4 This embodiment provides a functional masterbatch, which is basically the same as that in Embodiment 1, except that SEBS is used instead of POE as the elastomer. That is, it has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 3 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 3 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 8 parts of elastomer (SEBS, MI=4g / 10min), and 51 parts of PP.

[0059] The preparation method of the functional masterbatch is the same as that in Example 1.

[0060] This embodiment also provides a method for preparing BOPP film, with the same steps and parameters as in Embodiment 1.

[0061] Example 5 This embodiment provides a functional masterbatch, which is basically the same as that in Example 1, except that the ratio of high acid value polar wax to low molecular weight polar wax is adjusted to 1:0.5, that is, it has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 4 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 2 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 8 parts of elastomer (POE, MI=3g / 10min), and 51 parts of PP.

[0062] The preparation method of the functional masterbatch is the same as that in Example 1.

[0063] This embodiment also provides a method for preparing BOPP film, with the same steps and parameters as in Embodiment 1.

[0064] Example 6 This embodiment provides a functional masterbatch, which is basically the same as that in Embodiment 1, except that the ratio of high acid value polar wax to low molecular weight polar wax is adjusted to 1:2, that is, it has the following components by weight: 35 parts of PP-g-MAH (grafting rate 1.0%, MI=50g / 10min), 2 parts of high acid value polar wax (oxidized polyethylene wax, acid value 28mg KOH / g), 4 parts of low molecular weight polar wax (polyethylene wax, molecular weight 2000, acid value 15mg KOH / g), 8 parts of elastomer (POE, MI=3g / 10min), and 51 parts of PP.

[0065] The preparation method of the functional masterbatch is the same as that in Example 1.

[0066] This embodiment also provides a method for preparing BOPP film, with the same steps and parameters as in Embodiment 1.

[0067] Comparative Example 1 This comparative example provides a functional masterbatch, which differs from Example 1 in that it does not contain an elastomer, but is otherwise the same as Example 1; that is, it has the following components by weight: 35 parts PP-g-MAH, 3 parts high acid value polar wax, 3 parts low molecular weight polar wax, and 59 parts PP.

[0068] The preparation method of the functional masterbatch is the same as that in Example 1.

[0069] This comparative example also provides a method for preparing BOPP film, with the same steps and parameters as in Example 1.

[0070] Comparative Example 2 This comparative example provides a functional masterbatch, which differs from Example 1 in that it uses a single polar wax, contains only high acid value components, and has no low molecular weight components, while the rest is the same as Example 1; that is, it has the following components by weight: 35 parts PP-g-MAH, 6 parts high acid value polar wax, 8 parts elastomer, and 51 parts PP.

[0071] The preparation method of the functional masterbatch is the same as that in Example 1.

[0072] This comparative example also provides a method for preparing BOPP film, with the same steps and parameters as in Example 1.

[0073] Comparative Example 3 This comparative example provides a functional masterbatch, which differs from Example 1 in that it does not contain PP-g-MAH, but is otherwise the same as Example 1. That is, it has the following components by weight: 3 parts high acid value polar wax, 3 parts low molecular weight polar wax, 8 parts elastomer, and 86 parts PP.

[0074] The preparation method of the functional masterbatch is the same as that in Example 1.

[0075] This comparative example also provides a method for preparing BOPP film, with the same steps and parameters as in Example 1.

[0076] Comparative Example 4 This comparative example provides a functional masterbatch, which differs from Example 1 in that it does not contain polar wax and elastomer, but is otherwise the same as Example 1, i.e., it has the following components by weight: 35 parts PP-g-MAH and 65 parts PP.

[0077] The preparation method of the functional masterbatch is the same as that in Example 1.

[0078] This comparative example also provides a method for preparing BOPP film, with the same steps and parameters as in Example 1.

[0079] Comparative Example 5 This comparative example uses a commercially available brand of general-purpose PP slip masterbatch, added at a rate of 5% to prepare BOPP film. The preparation method of the BOPP film is the same as in Example 1.

[0080] Comparative Example 6 This comparative example provides a masterbatch, which, according to the formula disclosed in prior art CN121293636A, has the following components by weight: 80 parts PP resin, 5 parts nano-organically modified montmorillonite, 12 parts PP-g-MAH, and 1.7 parts composite modifier (the composite modifier is composed of a fluorinated surfactant, a silane coupling agent, and an amide slip agent in a weight ratio of 1:1:2). The masterbatch is prepared according to the preparation process of Example 1 in CN121293636A.

[0081] This comparative example also provides a method for preparing BOPP film, the specific steps of which are as follows: the prepared masterbatch is mixed with BOPP base resin at a ratio of 5%, and BOPP film with a thickness of 20μm is obtained by melt extrusion and biaxial stretching, with a longitudinal stretching ratio of 5 times and a transverse stretching ratio of 9 times, and then subjected to online corona treatment.

[0082] Performance testing The performance of the BOPP films prepared in the above embodiments and comparative examples was tested using the following methods: Surface tension: The surface tension of the film after corona treatment was tested using a dyne pen in accordance with GB / T 14216-2008 standard.

[0083] Transmittance / Haze: Tested using a haze meter in accordance with GB / T 2410-2008 standard.

[0084] Tear strength: The longitudinal and transverse tear strength of the film was tested using a tear tester in accordance with GB / T 16578.2-2009 standard.

[0085] Thin film appearance: Observe the crystal points and film breakage of the thin film with the naked eye under backlight conditions.

[0086] The test results are shown in Table 1 below.

[0087] Table 1

[0088] As shown in Table 1, the BOPP films prepared in the embodiments of the present invention maintained a surface tension retention rate of over 92% after three months of corona treatment, with a maximum of 96.2%, significantly higher than all comparative examples. The corona treatment durability is significantly superior to commercially available general-purpose products and products prepared using existing technologies. Compared with commercially available general-purpose masterbatch (Comparative Example 5), the films prepared in the embodiments of the present invention exhibit advantages in corona retention rate, tear strength, and optical properties, demonstrating industrial application value.

[0089] As can be seen from the data in Examples 1 to 3, when the amount of elastomer is about 8 parts (Example 1), the corona retention rate and mechanical properties reach the best balance; when the amount of elastomer is too low (Example 2), the improvement in mechanical properties is limited, and when the amount of elastomer is too high (Example 3), the haze increases slightly.

[0090] Comparing the data of Example 1 with those of Comparative Examples 1, 2, 3, and 4, it can be seen that when the system lacks elastomer (Comparative Example 1), low molecular weight polar wax (Comparative Example 2), PP-g-MAH (Comparative Example 3), or contains only PP-g-MAH (Comparative Example 4), the corona retention rate after 3 months is less than 85%, while the retention rate of Example 1, which combines the three components, is as high as 96.2%, proving that the formulation of the present invention has a significant synergistic effect.

[0091] Data from Example 1 and Comparative Example 1 show that the addition of the elastomer not only increased the corona retention rate from 82.7% to 96.2%, but also increased the longitudinal tear strength from 152mN to 185mN and the transverse tear strength from 358mN to 420mN, achieving simultaneous optimization of surface properties and mechanical properties.

[0092] Data from Example 1 and Comparative Example 2 show that when high-acid-value wax and low-molecular-weight wax are combined, the corona retention rate increases from 84.6% to 96.2%, demonstrating that gradient migration design has a positive impact on corona persistence.

[0093] Comparative Example 6, referring to the technical solution of CN121293636A, although possessing a surface tension of 40 dynes / cm without corona treatment, relies on the nano-modification effect of organically modified montmorillonite and does not solve the problem of the migration and decay of surface polar groups over time after corona treatment. In contrast, Example 1 of this invention maintains a surface tension of over 50 dynes / cm even after 3 months of corona treatment, representing a substantial improvement over existing technologies.

[0094] In summary, this invention constructs a "three-in-one" synergistic system through the chemical anchoring of PP-g-MAH, the gradient migration and replenishment of polar waxes with different molecular weights, and the stress buffering and polar group storage effect of elastomers. This system successfully prepares a functional masterbatch that can not only be well matched with BOPP processing technology, but also maintain the corona treatment effect for a long time and improve the mechanical properties of the film.

[0095] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A corona-permanent functional masterbatch for BOPP film, characterized in that, The product comprises the following components by weight: 30-40 parts of polypropylene grafted with maleic anhydride, 4-8 parts of polar wax, 5-10 parts of elastomer, and 42-61 parts of polypropylene. The polar waxes include high-acid-value polar waxes and low-molecular-weight polar waxes; the acid value of the high-acid-value polar waxes is >20mg KOH / g; and the number-average molecular weight of the low-molecular-weight polar waxes is <5000.

2. The corona-permanent functional masterbatch for BOPP film according to claim 1, characterized in that, The mass ratio of the high-acid-value polar wax to the low-molecular-weight polar wax is 1:(0.5~2).

3. The corona-permanent functional masterbatch for BOPP film according to claim 1, characterized in that, The high-acid-value polar wax includes at least one of oxidized polyethylene wax, oxidized polypropylene wax, and maleic anhydride-grafted polyethylene wax; the low-molecular-weight polar wax includes at least one of polyethylene wax and polypropylene wax.

4. The corona-permanent functional masterbatch for BOPP film according to claim 1, characterized in that, The elastomer includes at least one of polyolefin elastomers and styrene elastomers.

5. The corona-permanent functional masterbatch for BOPP film according to claim 4, characterized in that, The elastomer includes at least one of ethylene-octene copolymer, ethylene-butene copolymer, and styrene-ethylene-butene-styrene block copolymer.

6. The corona-permanent functional masterbatch for BOPP film according to claim 1, characterized in that, The polypropylene grafted with maleic anhydride has a melt index of 40~60g / 10min at 230℃ and 2.16kg load. And / or, the Mooney viscosity ML(1+4) of the elastomer at 125°C is 5~20.

7. The method for preparing the corona-permanent functional masterbatch for BOPP film according to any one of claims 1 to 6, characterized in that, Includes the following steps: Polypropylene grafted with maleic anhydride, polar wax, elastomer and polypropylene are mixed evenly and then melt-blended and extruded. The extrudate is cooled, air-dried and pelletized to obtain functional masterbatch.

8. The method for preparing the corona-permanent functional masterbatch for BOPP film according to claim 7, characterized in that, The melt blending extrusion is carried out using a twin-screw extruder, and the operating conditions of the twin-screw extruder are set as follows: Zone 1 160~180℃, Zone 2 180~200℃, Zone 3 200~220℃, Die head 210~220℃, and screw speed 300~500rpm.

9. A BOPP film, characterized in that, The raw materials for preparation include the corona-permanent functional masterbatch for BOPP film as described in any one of claims 1 to 6 and BOPP base resin; the amount of the corona-permanent functional masterbatch for BOPP film added is 3% to 7% of the mass of the BOPP base resin.

10. The method for preparing BOPP film as described in claim 9, characterized in that, The process includes the following steps: mixing BOPP film with corona-resistant durable functional masterbatch at a weight ratio of 3% to 7% with BOPP base resin, followed by melt extrusion, casting, biaxial stretching, heat setting, and corona treatment to obtain BOPP film.

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