A kind of ink-friendly BOPP film and its preparation method and application

Abstract

The present invention discloses an ink-friendly BOPP film, a preparation method and application thereof, and relates to the field of organic materials. The BOPP film comprises polypropylene A, a white masterbatch, and a foaming masterbatch; the white masterbatch comprises polypropylene B, nuclear titanium dioxide, PE wax, a dispersant, and a blue pigment. The present application adopts nuclear titanium dioxide to replace titanium dioxide in the white masterbatch, which can improve the fluidity of the masterbatch and reduce the filter pressure value, so that the pressure before the filter screen is small, the current load is low, and the continuous film breaking time is delayed during the preparation of the BOPP film, thereby improving the smoothness of production; since the nuclear titanium dioxide is not easy to agglomerate in the polypropylene system, it is evenly dispersed, and the irregular structure of the nuclear titanium dioxide particles, in which small balls cover large balls, forms porous gaps inside the BOPP film, improves the porosity, and significantly reduces the density of the film, which can reduce the amount of foaming masterbatch added, and the prepared BOPP film has high surface roughness, high ink adhesion, and excellent BOPP film performance.

Description

Technical Field

[0001] The present invention relates to the field of organic materials, in particular to an ink-friendly BOPP film and a preparation method and application thereof. Background Art

[0002] Biaxially oriented polypropylene film (BOPP) is mainly used in ice cream bags, disposable chopstick bags, express bags, beverage wrap-around labels, daily chemical self-adhesive labels, cosmetic masks and other fields (see the attached manual). Figure 1 During the production of white BOPP film, white masterbatch is added to the formula to impart a white hue; otherwise, the film will appear transparent. Foaming masterbatch is also necessary to create bubbles within the BOPP film during stretching, reducing the density of the finished film and, while maintaining the same thickness, reducing the amount of PP used. However, excessive amounts of foaming masterbatch can result in uneven film thickness and even deformation.

[0003] Currently, white masterbatches primarily consist of PP, titanium dioxide, and a small amount of dispersant. Due to its polar surface and small particle size, titanium dioxide is prone to agglomeration during processing. Larger particles of these agglomerated particles are intercepted by the filter. As production progresses, the number of agglomerated particles on one side of the filter increases, blocking more and more mesh openings, leaving fewer and fewer open mesh openings. Consequently, the extruder current and pressure in front of the mesh increase. As extrusion pressure gradually increases, some of the previously intercepted agglomerated particles squeeze through the mesh openings of the filter, forming individual impurities in the film. Large impurity particles can cause stress concentration at the particle locations, leading to continuous film breakage during production. Impurities that avoid continuous film breakage remain on the film surface, affecting the printing quality. In summary, these problems primarily result from the following: Clogged extruder filter mesh, increasing pressure in front of the filter; excessive current load at the extrusion point, resulting in increased energy consumption and equipment wear; increased film breakage during production, causing downtime and production losses, reduced efficiency, and wasted raw materials; and impurities on the film surface, resulting in substandard products.

[0004] Furthermore, the BOPP film produced will be printed with ink in the downstream process. Ink adhesion is a key indicator of BOPP film quality. Often, the same ink will have different performance on different BOPP films. Therefore, improving the surface adhesion of ink is also a key technical improvement direction. Summary of the Invention

[0005] The present invention provides an ink-friendly BOPP film, a preparation method thereof, and an application thereof. The white masterbatch used has high fluidity and a low filter pressure value, is not likely to clog the filter screen during the preparation of the BOPP film, and thus improves production efficiency. In addition, the prepared BOPP film has a low density, a small amount of impurities, a high surface roughness, and high ink adhesion.

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide an ink-friendly BOPP film, comprising the following components in parts by weight:

[0007] Polypropylene A: 75-85 parts;

[0008] White masterbatch: 10-17 parts;

[0009] Foaming masterbatch: 3-8 parts;

[0010] The white masterbatch comprises the following components in parts by weight:

[0011] Polypropylene B: 30-50 parts;

[0012] Nuclear titanium dioxide: 50-70 parts;

[0013] PE wax: 5-10 parts;

[0014] Dispersant: 0.5-2 parts;

[0015] Blue pigment: 0.03 parts to 1 parts.

[0016] By adopting the above scheme, the present application adopts nuclear titanium dioxide in the white masterbatch. The nuclear titanium dioxide is evenly dispersed in the polypropylene system using PE wax and dispersant, and is not easy to agglomerate, thereby improving the fluidity of the masterbatch and reducing the filter pressure value. It can reduce the pressure in front of the filter screen, reduce the current load and delay the continuous film breaking time during the preparation of the BOPP film. At the same time, the nuclear titanium dioxide can replace part of the foaming masterbatch, so that porous gaps can be formed inside the BOPP film, the porosity is increased, the film density is significantly reduced, and the amount of foaming masterbatch added can be reduced. Due to the special core-shell structure of the nuclear titanium dioxide, the prepared BOPP film has high surface roughness, uniform particle dispersion, and high ink adhesion, which can expand the application field.

[0017] As a preferred solution, the particle size D50 of the core titanium dioxide is 300-600 nm.

[0018] As a preferred solution, the dispersant is at least one of a titanate coupling agent, an aluminate coupling agent, an aluminozirconate coupling agent, a silane coupling agent, and stearic acid.

[0019] As a preferred solution, the mass ratio of the polypropylene B to the core titanium dioxide is 4:6.

[0020] As a preferred embodiment, the blue pigment includes at least one of ultramarine, phthalocyanine blue, cobalt blue, cobalt chrome blue, and iron blue.

[0021] By adopting the above scheme, a trace amount of blue pigment can improve the hue of the white masterbatch. By utilizing the blue-white phase color, the prepared film is visually closer to white, which can reduce the amount of white masterbatch added and save costs.

[0022] In order to solve the above technical problems, the second purpose of the present invention is to provide a method for preparing an ink-friendly BOPP film, comprising the following steps: white masterbatch, foaming masterbatch and polypropylene are respectively put into their respective blanking units, entering each layer extruder, and sequentially undergoing blanking, extrusion, sheet casting, longitudinal stretching, transverse stretching, traction, corona treatment, and winding systems to prepare the BOPP film.

[0023] As a preferred solution, the extruder temperature is controlled at 200-250°C.

[0024] As a preferred embodiment, the longitudinal stretching ratio is 4-5, the transverse stretching ratio is 6-9, and the corona value is 40 dynes.

[0025] As a preferred embodiment, the preparation method of the white masterbatch comprises the following steps:

[0026] (1) Putting nuclear titanium dioxide, PE wax, dispersant, and blue pigment into a high-speed stirring device, and when the temperature of the stirrer rises to a preset temperature of 40-60°C, starting stirring, and pre-mixing at a rate of 30-50 r / min for 0-15 minutes, then adding polypropylene into the high-speed stirrer, and when the temperature of the stirrer rises to a preset temperature of 60-80°C, starting stirring, and mixing at a rate of 120-150 r / min for 5-20 minutes, fully mixing to obtain a premix;

[0027] (2) Turn on the granulator and add the premix into the extruder. Prepare white masterbatch by extrusion, cooling and pelletizing.

[0028] As a preferred embodiment, in step (2) of the method for preparing the white masterbatch, the extrusion temperature is controlled at 160-220°C.

[0029] In order to solve the above technical problems, the third purpose of the present invention provides an application of an ink-friendly BOPP film in the preparation of food packaging bags, disposable product packaging bags, express bags, daily chemical self-adhesive labels or cosmetic masks.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present application adopts nuclear titanium dioxide to replace titanium dioxide in the white masterbatch. Compared with the problem of easy agglomeration of titanium dioxide, the nuclear titanium dioxide of the present application utilizes PE wax and dispersant to be evenly dispersed in the polypropylene system and is not easy to agglomerate, which can improve the fluidity of the masterbatch and reduce the filter pressure value. The smaller the filter pressure value, the better, and the lower the value, the more it can pass through the filter mesh. The filter mesh has excellent permeability, which reduces the pressure in front of the filter mesh, reduces the current load, and delays the continuous film breaking time during the preparation of BOPP film, thereby reducing energy consumption and improving production smoothness.

[0032] 2. The core titanium dioxide added to the white masterbatch of the present application can also replace part of the foaming masterbatch. Since the core titanium dioxide is not easy to agglomerate and is evenly dispersed in the polypropylene system, the irregular structure of the core titanium dioxide particles, in which small balls cover large balls, forms porous gaps inside the BOPP film, increases the porosity, and significantly reduces the density of the film, which can reduce the amount of foaming masterbatch added. The prepared BOPP film has fewer impurities, higher surface roughness, evenly dispersed particles, high ink adhesion, and superior BOPP performance, which can expand its application areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : Specific products for BOPP film applications in different fields;

[0034] Figure 2 : A scanning electron microscope image of an ink-friendly BOPP film in Example 2 at a magnification of 1800 times;

[0035] Figure 3 : This is a scanning electron microscope image of the cross section of the sample after the white masterbatch and polypropylene film were prepared in step (2) of Example 2 at a magnification of 1800 times;

[0036] Figure 4 : This is a scanning electron microscope image of the cross section of the sample after the white masterbatch and polypropylene film were prepared in step (2) of Example 2 at a magnification of 4000 times;

[0037] Figure 5 : This is a scanning electron microscope image of the sample cross section at a magnification of 4000 times after the white masterbatch and polypropylene film were prepared in step (2) of Comparative Example 1. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Table 1 - Sources of raw materials used in the examples or comparative examples of this application

[0040]

[0041] Example 1

[0042] A BOPP film with ink affinity comprises 75 kg of polypropylene, 17 kg of white masterbatch, and 8 kg of foaming masterbatch. The white masterbatch comprises 50 kg of polypropylene, 50 kg of core titanium dioxide, 5 kg of PE wax, 0.8 kg of a titanate coupling agent, and 0.05 kg of ultramarine blue. The particle size D50 of the core titanium dioxide is 550 nm. The core titanium dioxide is specifically RTR-202 manufactured by Foshan Jianfa Ruitong Technology Co., Ltd. The foaming masterbatch is specifically MB-PF702 manufactured by Kingfa Science & Technology Co., Ltd. The preparation method comprises the following steps:

[0043] (1) Put the nuclear titanium dioxide, PE wax, titanate coupling agent, and blue pigment into a high-speed stirrer. When the stirrer temperature rises to a preset temperature of 40°C, start stirring and pre-mix at a low speed of 40 r / min for 5 minutes. Then add polypropylene into the high-speed stirrer. When the stirrer temperature rises to a preset temperature of 60°C, start stirring and pre-mix at a high speed of 120 r / min for 5 minutes to fully mix them together to obtain a premix.

[0044] (2) turning on the pelletizer, adding the premix to the extruder, controlling the extrusion temperature at 160-220° C., and preparing white masterbatch by extrusion, cooling, and pelletizing;

[0045] (3) The white masterbatch, foaming masterbatch and polypropylene are respectively put into their respective blanking units and fed into the extruders of each layer according to the formula ratio. The temperature of the extruder is controlled at 200-250 ° C. The BOPP film is prepared through the blanking, extrusion, casting, longitudinal stretching, transverse stretching, traction, corona and winding systems in sequence. The longitudinal stretching ratio is 4.8, the transverse stretching ratio is 8, the corona value is 40 dynes, and a BOPP film with a thickness of 60 μm is obtained.

[0046] Example 2

[0047] A BOPP film with ink affinity comprises 80 kg of polypropylene, 15 kg of white masterbatch, and 5 kg of foaming masterbatch. The white masterbatch comprises 40 kg of polypropylene, 60 kg of core titanium dioxide, 6 kg of PE wax, 1 kg of a titanate coupling agent, and 0.05 kg of ultramarine blue. The particle size D50 of the core titanium dioxide is 550 nm. The core titanium dioxide is specifically RTR-202 manufactured by Foshan Jianfa Ruitong Technology Co., Ltd. The foaming masterbatch is specifically MB-PF702 manufactured by Kingfa Science & Technology Co., Ltd. The preparation method comprises the following steps:

[0048] (1) Put the core titanium dioxide, PE wax, titanate coupling agent, and blue pigment into a high-speed stirrer. When the stirrer temperature rises to a preset temperature of 50°C, start stirring and pre-mix at a low speed of 30 r / min for 10 minutes. Then add polypropylene into the high-speed stirrer. When the stirrer temperature rises to a preset temperature of 70°C, start stirring and pre-mix at a high speed of 130 r / min for 10 minutes to fully mix them together to obtain a premix.

[0049] (2) turning on the pelletizer, adding the premix to the extruder, controlling the extrusion temperature at 160-220° C., and preparing white masterbatch by extrusion, cooling, and pelletizing;

[0050] (3) The white masterbatch, foaming masterbatch and polypropylene are respectively put into their respective blanking units and fed into the extruders of each layer according to the formula ratio. The temperature of the extruder is controlled at 200-250 ° C. The BOPP film is prepared through the blanking, extrusion, casting, longitudinal stretching, transverse stretching, traction, corona and winding systems in sequence. The longitudinal stretching ratio is 4.8, the transverse stretching ratio is 8, the corona value is 40 dynes, and a BOPP film with a thickness of 60 μm is obtained.

[0051] Example 3

[0052] A BOPP film with ink affinity comprises 85 kg of polypropylene, 10 kg of white masterbatch, and 5 kg of foaming masterbatch. The white masterbatch comprises 30 kg of polypropylene, 70 kg of core titanium dioxide, 7 kg of PE wax, 1.2 kg of a titanate coupling agent, and 0.05 kg of ultramarine blue. The core titanium dioxide has a particle size D50 of 550 nm. The core titanium dioxide is specifically RTR-202 manufactured by Foshan Jianfa Ruitong Technology Co., Ltd. The foaming masterbatch is specifically MB-PF702 manufactured by Kingfa Science & Technology Co., Ltd. The preparation method comprises the following steps:

[0053] (1) Put the core titanium dioxide, PE wax, titanate coupling agent, and blue pigment into a high-speed stirrer. When the stirrer temperature rises to a preset temperature of 50°C, start stirring and pre-mix at a low speed of 50 r / min for 15 minutes. Then add polypropylene into the high-speed stirrer. When the stirrer temperature rises to a preset temperature of 70°C, start stirring and pre-mix at a high speed of 150 r / min for 15 minutes to fully mix them together to obtain a premix.

[0054] (2) turning on the pelletizer, adding the premix to the extruder, controlling the extrusion temperature at 160-220° C., and preparing white masterbatch by extrusion, cooling, and pelletizing;

[0055] (3) The white masterbatch, foaming masterbatch and polypropylene are respectively put into their respective blanking units and fed into the extruders of each layer according to the formula ratio. The temperature of the extruder is controlled at 200-250 ° C. The BOPP film is prepared through the blanking, extrusion, casting, longitudinal stretching, transverse stretching, traction, corona and winding systems in sequence. The longitudinal stretching ratio is 4.8, the transverse stretching ratio is 8, the corona value is 40 dynes, and a BOPP film with a thickness of 60 μm is obtained.

[0056] Example 4

[0057] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the BOPP film includes 82 kg of polypropylene, 15 kg of white masterbatch, and 3 kg of foaming masterbatch.

[0058] Example 5

[0059] A BOPP film that is ink-friendly, and the steps, reagents, equipment, and process parameters of the preparation method are the same as those in Example 2, except that the particle size D50 of the core titanium dioxide in the white masterbatch is 550 nm, and the core titanium dioxide is specifically RTR-201, a brand of Foshan Jianfa Ruitong Technology Co., Ltd.

[0060] Example 6

[0061] A BOPP film that is ink-friendly, and the steps, reagents, equipment, and process parameters of the preparation method are the same as those in Example 2, except that the particle size D50 of the core titanium dioxide in the white masterbatch is 380 nm, and the core titanium dioxide is specifically RTR-203, a brand of Foshan Jianfa Ruitong Technology Co., Ltd.

[0062] Example 7

[0063] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the foaming masterbatch is specifically the brand F2000 of Guangdong Meilian New Materials Co., Ltd.

[0064] Example 8

[0065] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the foaming masterbatch is specifically the brand PF97N of Schulman Plastics Company of the United States.

[0066] Example 9

[0067] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the ultramarine blue in the white masterbatch is replaced by an equal amount of polypropylene.

[0068] Comparative Example 1

[0069] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the core titanium dioxide in the white masterbatch is replaced by an equal amount of titanium dioxide, and the particle size D50 of the titanium dioxide is 380 nm.

[0070] Comparative Example 2

[0071] An ink-friendly BOPP film, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the PE wax in the white masterbatch is replaced by an equal amount of polypropylene.

[0072] Comparative Example 3

[0073] A BOPP film that is ink-friendly, wherein the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Comparative Example 1, except that the PE wax in the white masterbatch is replaced by an equal amount of polypropylene.

[0074] Comparative Example 4

[0075] A BOPP film that is ink-friendly, and the steps of the preparation method and the reagents, equipment, and process parameters applicable to each step are the same as those in Example 2, except that the white masterbatch includes 86 kg of polypropylene, 20 kg of core titanium dioxide, 1 kg of titanate coupling agent, and 0.05 kg of ultramarine blue, the particle size D50 of the core titanium dioxide is 550 nm, the core titanium dioxide is specifically the brand RTR-202 of Foshan Jianfa Ruitong Technology Co., Ltd., and the foaming masterbatch is specifically the brand MB-PF702 product of Kingfa Technology Co., Ltd.

[0076] Table 2 - Components and contents in the examples and comparative examples of this application

[0077]

[0078]

[0079] Performance testing

[0080] 1. The density of the white masterbatch obtained in step (2) of the embodiment or comparative example was tested. The test results are shown in Table 3 below.

[0081] 2. The white masterbatch obtained in step (2) of the Example or Comparative Example was tested for melt index according to GB / T 3682-2000 "Determination of mass flow rate and volume flow rate of thermoplastic melts". The test conditions were 230°C and the load was 2.16 kg. The test results are shown in Table 3 below.

[0082] 3. The white masterbatch obtained in step (2) of the Example or Comparative Example was subjected to filter pressure value testing according to the EU standard EN 13900-5:2005 "Pigments and extenders-Methods of dispersion and assessment of dispersibility in plastics-Part 5: Determination by filter pressure value test". The testing instrument was a pressure filter performance tester, model BP-8186-B, produced by Dongguan Baopin Precision Instrument Co., Ltd. The test results are shown in Table 3 below.

[0083] 4. In the biaxially oriented film production process of the BOPP film of the embodiment or comparative example in step (3), under the premise of the same production speed of 380 m / min, the extruder current after the extruder is turned on for 4 hours, the pressure in front of the filter screen after the extruder is turned on for 4 hours, and the time from start-up to continuous film breaking are observed and counted. The statistical results are shown in Table 4 below.

[0084] 5. The BOPP film prepared in Example 2 was tested by scanning electron microscope. The test results are as follows: Figure 2 As shown; at the same time, the white masterbatch prepared in step (2) of Example 2 and Comparative Example 1 was subjected to film drawing with polypropylene, and then subjected to scanning electron microscopy detection, which specifically includes the following steps:

[0085] (1) The cast film production process uses a three-layer co-extrusion method. A small co-extrusion experimental machine of Hefei Puliang Technology Co., Ltd., model LYE-1, is used. Polypropylene and white masterbatch are mixed in a mass ratio of 5:1 and fed into the blanking system of the core layer extruder. The upper and lower surface layer extruders are fed with 100% polypropylene. When the temperature of the three extruders rises to 220°C, thick sheets are extruded. The extrusion speed is adjusted to adjust the thickness of the thick sheet to 1.2 cm. The thick sheet is wound and cut into 13×13 cm squares for the next step of biaxial stretching.

[0086] (2) The BSE biaxial tensile testing machine of Hefei Puliang Technology Co., Ltd., model BSE-II, was used. The temperature of the stretching area was set to 200°C. The previously cut sample was placed in the sample chamber, and the sample chamber was moved into the stretching area. The surface temperature of the sample was observed. When the sample temperature reached 160°C, stretching began. The longitudinal stretching ratio was set to 4 times, the transverse stretching ratio was set to 5 times, and the stretching speed was 30 cm / min. After the stretching was completed, the obtained film was about 60 μm. The film was tested by scanning electron microscopy. The test results are as follows: Figure 3-5 shown.

[0087] in, Figure 3-4 This is a scanning electron microscope image of the cross-section of the white masterbatch prepared in Example 2 after film drawing. Without adding the foaming masterbatch, the white masterbatch is doped with core titanium dioxide raw material. The core titanium dioxide is a special core-shell structure made of titanium dioxide coated with inorganic powder. Due to the internal support of the inorganic powder, the titanium dioxide on the surface will not collapse inward and is not easy to agglomerate with each other, and can be evenly dispersed in the film. Therefore, the particle size is small, which helps to improve the morphology of the prepared film. During the stretching process of the film, the molecular chains of the polypropylene are elongated due to the stretching process, and the polypropylene molecular chains slide against each other, while the granular structure of the core titanium dioxide inorganic powder cannot be extended with stretching. Therefore, at the position of the inorganic particles, some stretched and deformed polypropylene molecular chains will separate from the core titanium dioxide, thereby causing holes. At the same time, the external structure of core titanium dioxide is not a relatively round and regular sphere like titanium dioxide, but an irregular structure of small balls covering large balls. Its compatibility with polypropylene resin is also different from that of titanium dioxide. Therefore, during the stretching process, core titanium dioxide is more likely to separate from the polypropylene molecular chain, thereby generating holes, which ultimately makes the film cross-section porosity higher, forming a loose and porous structure, which can significantly reduce the density of the film. Figure 2 As shown, the particle size of the core titanium dioxide in the prepared BOPP film is evenly dispersed, and the particle size is uniformly small, less agglomerated, and has a higher porosity, and the density of the prepared film is significantly reduced.

[0088] Figure 5 This is a scanning electron microscope image of the cross-section of the white masterbatch prepared in Example 1 after film drawing. The white masterbatch is doped with titanium dioxide raw material. During the preparation process, some agglomerated titanium dioxide is intercepted and filtered out by the filter. The particle size of the raw titanium dioxide is smaller than that of the core titanium dioxide in Example 2. The porosity in the film is relatively low, there are fewer pores, and the density of the film is significantly higher than that of Example 2.

[0089] 6. The density and surface roughness of the BOPP films prepared in the Examples or Comparative Examples were tested. The surface roughness was tested in accordance with GB / T 14234-1993 "Surface Roughness of Plastic Parts" using a surface roughness measuring instrument, model SJ-301, manufactured by Mitutoyo, Japan. The test results are shown in Table 4 below.

[0090] 7. Count the number of impurities in the BOPP films prepared in the examples or comparative examples, and observe the number of impurities per 1m 2 The statistical results of the number of impurities contained in the area are shown in Table 4 below.

[0091] 8. The BOPP film prepared in the example or comparative example was subjected to an ink tape tearing off grid number test, comprising the following steps:

[0092] (1) Use the flexographic colorimeter (model KY160) of Dongguan Liede Technology Co., Ltd., drop ink on the rubber roller, turn on the colorimeter, start ink spreading, set the ink spreading speed to 550r / min, and set the ink spreading time to 30s. After the ink spreading is completed, cut the film into A4 paper sample size, clamp it flat on the printing sample roller with the film corona facing up, adjust the printing speed to 10r / min, and click print to complete the printing;

[0093] (2) Lay the film with the printed surface facing up on a flat surface and secure it with tape on all sides. Use a pencil to draw 100 small grids on the ink surface at equal intervals, 10 in each direction. Stick 3M brand 600 transparent tape on the ink and tear off the tape vigorously. Observe the number of grids where the ink falls off. The fewer the number of grids that fall off, the higher the ink adhesion. The test results are shown in Table 4 below.

[0094] 9. The whiteness of the BOPP films prepared in the Examples and Comparative Examples was tested in accordance with GB / T 2913-1982, Test Method for Whiteness of Plastics, using a multifunctional whiteness meter (model BDG584) from Biaogeda Precision Instruments (Guangzhou) Co., Ltd. The test results are shown in Table 4 below.

[0095] Table 3 - Performance test results of white masterbatch prepared in Examples and Comparative Examples of the present application

[0096]

[0097] As shown in Table 3, the nuclear titanium dioxide added to the white masterbatch in Examples 1-3 is evenly dispersed in the polypropylene system, and the nuclear titanium dioxide is not easy to agglomerate, and the melt index is high, indicating good fluidity. The filter press value reflects the degree to which the white masterbatch agglomerates at the filter screen and blocks the filter screen when passing through the extruder filter screen. The smaller the filter press value, the more it can pass through the filter screen, the better the filter screen passability is, and it is not easy to clog the filter screen. Since the density of nuclear titanium dioxide is lower than that of titanium dioxide, the density of the masterbatch prepared under the premise of equal addition amount is relatively low. However, the titanium dioxide added to the white masterbatch in Comparative Example 1 is easy to agglomerate, resulting in a lower melt index of the masterbatch, low fluidity, and a significantly higher filter press value, which easily clogs the filter screen of the extruder.

[0098] Table 4 - Performance test results of BOPP films prepared in Examples and Comparative Examples of the present application

[0099]

[0100]

[0101] As shown in Table 4, the BOPP film prepared in Example 2 has a lower density. This is because the core titanium dioxide is evenly dispersed in the BOPP film, has a small particle size, and the film melt has high fluidity. When the extruder passes through the filter screen, it is smooth, and there are fewer impurities that will not cause blockage, effectively delaying the continuous film breaking time. In addition, the addition of core titanium dioxide helps to increase the porosity of the film and form a porous internal space structure. This is due to the special structure of core titanium dioxide. Core titanium dioxide is a special core-shell structure made of titanium dioxide coated inorganic powder. The external structure is not a relatively round and regular sphere like titanium dioxide, but an irregular structure of small spheres covering large spheres. At the position of the inorganic particles, some stretched and deformed polypropylene molecular chains will detach from the core titanium dioxide, thereby forming holes, which reduces the density of the film. Comparative Example 1, in which titanium dioxide is added to the BOPP film as a white pigment, exhibits low fluidity due to its high surface polarity and small particle size, which makes it prone to agglomeration. The smaller particle size also results in a film with lower porosity, a relatively high density, and low surface roughness. Furthermore, the film contains large agglomerated particles, which are prone to impurities. The BOPP film of Example 2 has a higher surface roughness and evenly dispersed surface particles, which improves ink adhesion. Furthermore, the added core titanium dioxide RTR-202 exhibits excellent ink affinity, resulting in significantly better ink release test results in Example 2 than in Comparative Example 1.

[0102] As shown in Table 4, by comparing the schemes of Example 2 and Comparative Examples 1-3, it can be seen that Comparative Example 2 does not add PE wax compared to Example 2, resulting in uneven dispersion of the core titanium dioxide particles in the film system. It can be found that the current and pre-net pressure of the film melt in the extruder are greatly increased, indicating that the particles in the melt are prone to agglomeration. The surface roughness of the film is slightly increased, the number of impurities generated by the film increases, and the size distribution of the particles on the surface of the film is uneven, resulting in easy ink shedding during the flat printing process of the film, and the ink adhesion is greatly reduced. Comparative Example 3 does not add PE wax compared to Comparative Example 1. It can be found that the current and pre-net pressure of the film melt in the extruder are increased, and the number of film impurities increases, the surface roughness of the film increases, and the uneven distribution of particles leads to low ink adhesion.

[0103] As shown in Table 4, compared with Example 2, the core titanium dioxide content of the film of Comparative Example 4 was reduced by two-thirds, and no PE wax was added. It can be found that the current and screen pressure of the film melt in the extruder were relatively small, indicating that the inorganic particles in the melt were evenly dispersed due to their low content and were not easy to agglomerate. However, the density of the prepared film was relatively high, and the whiteness and ink adhesion were significantly low, which could not meet the application requirements.

[0104] As shown in Table 4, the BOPP films of Examples 2, 5-6 respectively use white masterbatches containing RTR-201, RTR-202, and RTR-203 nuclear titanium dioxide. The final test shows that the film of Example 2 has the best ink affinity, indicating that RTR-202 nuclear titanium dioxide is beneficial for improving the printing effect of BOPP film, enhancing ink adhesion, and the film has a higher whiteness.

[0105] As shown in Table 4, compared with Example 9, the trace amount of blue pigment in Example 2 can improve the hue of the white masterbatch. The blue-white color makes the prepared film visually closer to white, which can reduce the amount of white masterbatch added and save costs.

[0106] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. An ink-friendly BOPP film, characterized in that: It is composed of the following components in parts by weight: Polypropylene A: 75-85 parts; White masterbatch: 10-17 parts; Foaming masterbatch: 3-8 parts; The total weight of the polypropylene A, white masterbatch and foaming masterbatch is 100 parts; The white masterbatch is composed of the following components in parts by weight: Polypropylene B: 30-50 parts; Nuclear titanium dioxide: 50-70 parts; PE wax: 5-10 parts; Dispersant: 0.5-2 parts; Blue pigment: 0.03-1 part; The particle size D50 of the core titanium dioxide is 300-600 nm; The dispersant is at least one of a titanate coupling agent, an aluminate coupling agent, an aluminozirconate coupling agent, a silane coupling agent, and stearic acid.

2. The ink-friendly BOPP film according to claim 1, characterized in that: The mass ratio of the polypropylene B to the core titanium dioxide is 4:

6.

3. The ink-friendly BOPP film according to claim 1, characterized in that: The blue pigment includes at least one of ultramarine, phthalocyanine blue, cobalt blue, cobalt chrome blue, and iron blue.

4. A method for preparing the ink-friendly BOPP film according to any one of claims 1 to 3, characterized in that: The following steps are involved: The white masterbatch, foaming masterbatch and polypropylene are respectively put into their respective blanking units and enter the extruders of each layer. BOPP film is produced through the blanking, extrusion, sheet casting, longitudinal stretching, transverse stretching, traction, corona treatment and winding systems in sequence.

5. The method for preparing an ink-friendly BOPP film according to claim 4, wherein: The preparation method of the white masterbatch comprises the following steps: (1) Put the nuclear titanium dioxide, PE wax, dispersant and blue pigment into a high-speed stirring device. When the temperature of the stirrer rises to the preset temperature of 40-60°C, start stirring and pre-mix at a rate of 30-50 r / min for 0-15 minutes. Then add polypropylene into the high-speed stirrer. When the temperature of the stirrer rises to the preset temperature of 60-80°C, start stirring and mix at a rate of 120-150 r / min for 5-20 minutes. Mix thoroughly and evenly to obtain a premix. (2) Turn on the granulator and add the premix into the extruder. Prepare the white masterbatch through extrusion, cooling and pelletizing.

6. The method for preparing an ink-friendly BOPP film according to claim 5, wherein: In step (2) of the white masterbatch preparation method, the extrusion temperature is controlled at 160-220°C.

7. The method for preparing an ink-friendly BOPP film according to claim 4, wherein: The longitudinal stretching ratio is 4-5, the transverse stretching ratio is 6-9, and the corona value is 40 dynes.

8. Use of the ink-friendly BOPP film according to any one of claims 1 to 3 in the preparation of food packaging bags, disposable product packaging bags, express bags, daily chemical self-adhesive labels or cosmetic facial masks.

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