A rigidifying masterbatch for BOPP shrink film and its processing technology

Abstract

This invention relates to a stiffening masterbatch for BOPP shrink film and its processing technology. The stiffening masterbatch, by weight, comprises 50-75 parts carrier resin, 20-40 parts hydrogenated petroleum resin, 0.3-2 parts nano-rigid filler, 0.5-1.0 parts nucleating agent, 2.0-4.0 parts interface compatibilizer, 0.3-2.0 parts processing aid, 0.2-1.0 parts antioxidant, and 0.1-0.5 parts light stabilizer. The stiffening masterbatch of this invention exhibits highly efficient stiffening performance; adding only 5%-15% can significantly improve the rigidity and strength of polypropylene materials. Furthermore, by adjusting the component content, stiffening masterbatches suitable for different application scenarios can be obtained.

Description

Technical Field

[0001] This invention relates to the field of stiffening masterbatch for BOPP shrink film, specifically to a stiffening masterbatch for BOPP shrink film and its processing technology. Background Technology

[0002] Biaxially oriented polypropylene (BOPP) shrink film is characterized by its good transparency, excellent printability, uniform heat shrinkage, low cost, good physical stability, high mechanical strength, good airtightness, and high gloss. It is widely used in the packaging of food, confectionery, cigarettes, tea, and other products. With technological advancements, there are increasingly higher requirements for the stiffness, optical properties, and heat shrinkage rate of BOP shrink film.

[0003] In the production process of BOPP shrink wrap film, stiffening masterbatch (also known as rigidifying masterbatch) is usually added to the core layer. Stiffening masterbatch is a functional modified material, made by blending homopolymer polypropylene with modified stiffening materials in a certain proportion. Its core stiffening component typically uses hydrogenated C5 or C9 petroleum resin. By adding 10%-30% hydrogenated petroleum resin to polypropylene, the aggregated structure of the polypropylene polymer chains can be altered, increasing the stretching and orientation ability of the polymer chains, thereby improving the elastic modulus of polypropylene and the stiffness of the film. Simultaneously, stiffening masterbatch can also improve the optical properties of the film, reducing haze, increasing gloss, and adjusting the film's heat shrinkage rate. Therefore, stiffening masterbatch is one of the key functional additives determining the quality of BOPP shrink wrap film.

[0004] Therefore, developing a high-dispersion, low-haze, high-efficiency stiffening, stable shrinkage, and high-speed-compatible stiffening masterbatch for BOPP shrink film has significant engineering value. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention provides a stiffening masterbatch for BOPP shrink film, comprising, by weight, 50-75 parts carrier resin, 20-40 parts hydrogenated petroleum resin, 0.3-2 parts nano-rigid filler, 0.5-1.0 parts nucleating agent, 2.0-4.0 parts interface compatibilizer, 0.3-2.0 parts processing aid, 0.2-1.0 parts antioxidant, and 0.1-0.5 parts light stabilizer.

[0006] Furthermore, the processing technology of the nano-rigid filler includes, Nanomaterials and silane coupling agents are mixed and heated to undergo dry modification, resulting in nano-rigid fillers.

[0007] Furthermore, the amount of the silane coupling agent added accounts for 0.5%-1.5% of the mass ratio of the nanomaterial; The nanomaterials include at least one of silicon dioxide, titanium dioxide, and talc with a particle size of 20-80 nm. The silane coupling agent includes at least one of KH550, KH560, and KH570; The temperature for the heating is 90-110℃.

[0008] Furthermore, when mixing the nanomaterials and the silane coupling agent, 0.05%-0.1% of benzyltrimethylammonium hydroxide by mass of the nanomaterials is also added.

[0009] Furthermore, the carrier resin is highly crystalline homopolymer polypropylene, with a melt flow rate of 2-10 g / 10 min, isotacticity ≥96%, and melting point of 160-167 °C.

[0010] Furthermore, the hydrogenated petroleum resin includes C5 petroleum resin and / or C9 petroleum resin; The nucleating agent includes at least one of aryl phosphate salts, sorbitols, and substituted benzoates; The interface compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8%-1.5%. The processing aids include at least one of fluorinated processing aids, stearates, polyethylene wax, and oxidized polyethylene wax; The antioxidants include at least one of hindered phenolic antioxidants and phosphite antioxidants; The light stabilizer is a hindered amine light stabilizer.

[0011] This invention also provides a processing technology for the above-mentioned stiffening masterbatch for BOPP shrink film, including: The carrier resin, nucleating agent, interface compatibilizer, processing aid, antioxidant, and light stabilizer are mixed evenly to obtain a mixture. The mixture and hydrogenated petroleum resin are added to a parallel twin-screw extruder for melt blending and extrusion, followed by gradient water cooling, gradient air cooling, and pelletizing to obtain stiffening masterbatch for BOPP shrink film.

[0012] Furthermore, the parallel twin-screw extruder has a length-to-diameter ratio of 42-52:1, a screw speed of 280-400 r / min, and extrusion temperature zones set as follows: Zone 1 120-135℃, Zone 2 135-155℃, Zone 3 155-175℃, Zone 4 175-185℃, Zone 5 175-185℃, Zone 6 175-185℃, Zone 7 185-195℃, Zone 8 195-200℃, Zone 9 195-200℃, and Die Zone 195-200℃; the vacuum degree is controlled at -0.06-0.09 MPa.

[0013] Furthermore, the gradient water cooling is a three-stage gradient water cooling system, with the first water tank having a water temperature of 45-65℃, the second water tank having a water temperature of 20-40℃, and the third water tank having a water temperature of 0-7℃. The gradient air cooling is a two-stage gradient air cooling system, with the first stage air temperature at 25-45℃ and the second stage air temperature at 10-25℃. The pelletizing speed is 800-1500 r / min.

[0014] The present invention also provides a BOPP shrink film containing the above-mentioned stiffening masterbatch for BOPP shrink film.

[0015] Compared with the prior art, the beneficial effects of the present invention include: The stiffening masterbatch of this invention exhibits highly efficient stiffening performance; adding only 5%-15% can significantly improve the rigidity and strength of polypropylene materials. Furthermore, by adjusting the component content, stiffening masterbatches suitable for different application scenarios can be obtained.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having” and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] Existing stiffening masterbatch technologies still have many shortcomings in practical applications. While existing stiffening masterbatches impart a high thermal shrinkage rate to the film, they are prone to causing significant post-shrinkage, affecting the dimensional stability of the film and the appearance of the packaging. In order to pursue a high elastic modulus, existing technologies add up to 50% hydrogenated petroleum resin, which not only increases production costs, but also causes excessive small molecule substances to lead to haze on the film surface, affecting optical performance.

[0021] Therefore, this invention is proposed.

[0022] On one hand, the present invention provides a stiffening masterbatch for BOPP shrink film, comprising, by weight, 50-75 parts carrier resin, 20-40 parts hydrogenated petroleum resin, 0.3-2 parts nano-rigid filler, 0.5-1.0 parts nucleating agent, 2.0-4.0 parts interface compatibilizer, 0.3-2.0 parts processing aid, 0.2-1.0 parts antioxidant and 0.1-0.5 parts light stabilizer.

[0023] The formulation of this invention has a reasonable proportion of each component, resulting in a synergistic effect. Specifically, the carrier resin exhibits excellent compatibility with the BOPP base film, ensuring mechanical and processing compatibility; the hydrogenated petroleum resin alters the aggregated structure of the polypropylene polymer chains, increasing their stretching and orientation capabilities, thereby improving the elastic modulus of polypropylene and the stiffness of the film; the nano-rigid filler dispersed within the polypropylene polymer chains further enhances the strength of the base film; the nucleating agent guides propylene to form a fine crystal structure, improving modulus, shrinkage stability, and high-temperature stiffness; the interface compatibilizer strengthens the interfacial bonding between the inorganic phase and the polypropylene, preventing delamination, peeling, and whitening; the processing aid reduces extrusion torque, improving melt flowability and film surface smoothness; and the antioxidant and light stabilizer prevent processing degradation and outdoor aging, ensuring the long-term stability of the film.

[0024] Surface modification of inorganic nanomaterials using silane coupling agents can improve the compatibility between inorganic nanomaterials and organic matrices and promote dispersion performance.

[0025] In some preferred embodiments, the processing technology of the nano-rigid filler includes, Nanomaterials and silane coupling agents are mixed and heated to undergo dry modification, resulting in nano-rigid fillers.

[0026] In some preferred embodiments, the amount of the silane coupling agent added accounts for 0.5%-1.5% of the mass ratio of the nanomaterial; The nanomaterials include at least one of silicon dioxide, titanium dioxide, and talc with a particle size of 20-80 nm. The silane coupling agent includes at least one of KH550, KH560, and KH570; The temperature for the heating is 90-110℃.

[0027] Simply relying on silane coupling agents often has limited effectiveness in solving the dispersion problem of nanomaterials in non-polar matrices like polypropylene, and adding large proportions also increases costs. Benzyltrimethylammonium hydroxide is an organic base containing a quaternary ammonium group and possesses surface activity, often used as a strong base catalyst and phase transfer catalyst. This invention adds benzyltrimethylammonium hydroxide while modifying nanomaterials with silane coupling agents. This not only enhances the interaction between the silane coupling agent and the nanomaterials but also allows a certain amount of benzyltrimethylammonium hydroxide to adhere to the surface of the nanomaterials. The synergistic effect with the silane coupling agent further enhances the dispersion performance of the nanomaterials in the base film.

[0028] In some preferred embodiments, when mixing the nanomaterials and the silane coupling agent, 0.05%-0.1% of benzyltrimethylammonium hydroxide by mass of the nanomaterials is also added.

[0029] In some preferred embodiments, the carrier resin is highly crystalline homopolymer polypropylene with a melt flow rate of 2-10 g / 10 min, isotacticity ≥96%, and melting point of 160-167 °C.

[0030] In some preferred embodiments, the hydrogenated petroleum resin includes C5 petroleum resin and / or C9 petroleum resin. The nucleating agent includes at least one of aryl phosphate salts, sorbitols, and substituted benzoates; The interface compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8%-1.5%. The processing aids include at least one of fluorinated processing aids, stearates, polyethylene wax, and oxidized polyethylene wax; The antioxidants include at least one of hindered phenolic antioxidants and phosphite antioxidants; The light stabilizer is a hindered amine light stabilizer.

[0031] On the other hand, the present invention provides a processing method for the above-mentioned stiffening masterbatch for BOPP shrink film, including, The carrier resin, nucleating agent, interface compatibilizer, processing aid, antioxidant, and light stabilizer are mixed evenly to obtain a mixture. The mixture and hydrogenated petroleum resin are added to a parallel twin-screw extruder for melt blending and extrusion, followed by gradient water cooling, gradient air cooling, and pelletizing to obtain stiffening masterbatch for BOPP shrink film.

[0032] In some preferred embodiments, the parallel twin-screw extruder has a length-to-diameter ratio of 42-52:1, a screw speed of 280-400 r / min, and extrusion temperature zones set as follows: Zone 1 120-135℃, Zone 2 135-155℃, Zone 3 155-175℃, Zone 4 175-185℃, Zone 5 175-185℃, Zone 6 175-185℃, Zone 7 185-195℃, Zone 8 195-200℃, Zone 9 195-200℃, and Die Zone 195-200℃; the vacuum degree is controlled at -0.06-0.09 MPa.

[0033] In some preferred embodiments, the gradient water cooling is a three-stage gradient water cooling, with the first water tank having a water temperature of 45-65℃, the second water tank having a water temperature of 20-40℃, and the third water tank having a water temperature of 0-7℃. The gradient air cooling is a two-stage gradient air cooling system, with the first stage air temperature at 25-45℃ and the second stage air temperature at 10-25℃. The pelletizing speed is 800-1500 r / min.

[0034] The present invention will be further described in detail below through specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. 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 in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0035] Introduction to some of the raw materials used in this invention: The carrier resin was selected as highly crystalline homopolymer polypropylene, with a melt flow rate of approximately 6 g / 10 min (230℃, 2.16 kg), isotacticity ≥96%, and melting point of approximately 165℃. The nucleating agent was selected as a sorbitol-based nucleating agent; The interface compatibilizer was selected as maleic anhydride-grafted polypropylene with a grafting rate of 1.2%. The processing aid was selected as polyethylene wax; The antioxidant is composed of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in equal mass ratios; The light stabilizer selected was the hindered amine light stabilizer UV-765.

[0036] Preparation Example 1 A method for preparing modified nano-silica, comprising: Silica with a particle size of about 50 nm was mixed with KH550 at a mass ratio of 1:0.005, heated to 100 °C, stirred for 15 min, cooled and discharged to obtain modified nano silica.

[0037] Preparation Example 2 A method for preparing modified nano-talc powder, comprising: Talc powder with a particle size of approximately 80 nm was mixed with KH550 at a mass ratio of 1:0.01, heated to 100 °C, stirred for 20 min, and then cooled to obtain modified nano talc powder.

[0038] Preparation Example 3 A method for preparing modified nano-titanium dioxide, comprising: Titanium dioxide with a particle size of approximately 60 nm was mixed with KH570 at a mass ratio of 1:0.01, heated to 110 °C, stirred for 20 min, and then cooled to obtain modified nano-titanium dioxide.

[0039] Preparation Example 4 A method for preparing modified nano-silica, comprising: Modified nano-silica was obtained by mixing silica with a particle size of approximately 50 nm with KH550 and benzyltrimethylammonium hydroxide at a mass ratio of 1:0.005:0.001, heating to 100 °C, stirring for 15 min, cooling, and then discharging.

[0040] Preparation Example 5 A method for preparing modified nano-titanium dioxide, comprising: Modified nano-titanium dioxide was obtained by mixing titanium dioxide with a particle size of approximately 60 nm with KH570 and benzyltrimethylammonium hydroxide at a mass ratio of 1:0.01:0.0005, heating to 110 °C, stirring for 20 min, cooling, and then discharging.

[0041] Preparation Example 6 A method for preparing modified nano-silica, comprising: Modified nano-silica was obtained by mixing silica with a particle size of approximately 50 nm with benzyltrimethylammonium hydroxide at a mass ratio of 1:0.005, heating to 100 °C, stirring for 15 min, cooling, and then discharging.

[0042] Example 1 A processing method for a stiffening masterbatch for BOPP shrink film includes the following steps: S1. Add 6.5 kg of highly crystalline homopolymer polypropylene, 0.1 kg of modified nano-silica obtained in Preparation Example 1, 0.08 kg of sorbitol nucleating agent, 0.3 kg of maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.1 kg of polyethylene wax, 0.03 kg of antioxidant 1010, 0.03 kg of antioxidant 168, and 0.03 kg of light stabilizer UV-765 to a high-speed mixer and mix at 50°C and 750 rpm for 5 min to obtain a mixture.

[0043] S2. Add the mixture, 1.5 kg of C5 petroleum resin, and 1 kg of C5 petroleum resin to a parallel twin-screw extruder. Control the twin-screw extruder for melt blending extrusion, setting the length-to-diameter ratio to 50:1, screw speed to 350 rpm, and extrusion temperature zones: Zone 1 130℃, Zone 2 145℃, Zone 3 165℃, Zone 4 180℃, Zone 5 182℃, Zone 6 184℃, Zone 7 190℃, Zone 8 195℃, Zone 9 198℃, and die zone 200℃; vacuum degree controlled at -0.08 MPa; then perform gradient water cooling, with the first water tank temperature at 55℃, the second water tank temperature at 30℃, and the third water tank temperature at 5℃, and gradient air cooling, with the first air temperature at 30℃ and the second air temperature at 15℃; then pelletize at a speed of 1200 r / min to obtain stiffening masterbatch for BOPP shrink film.

[0044] Example 2 A processing method for a stiffening masterbatch for BOPP shrink film includes the following steps: S1. Add 6.2 kg of highly crystalline homopolymer polypropylene, 0.1 kg of modified nano-talc obtained in Preparation Example 2, 0.08 kg of sorbitol nucleating agent, 0.3 kg of maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.1 kg of polyethylene wax, 0.04 kg of antioxidant 1010, 0.04 kg of antioxidant 168, and 0.03 kg of light stabilizer UV-765 to a high-speed mixer and mix at 50°C and 750 rpm for 5 min to obtain a mixture.

[0045] S2. Add the mixture, 1.5 kg of C5 petroleum resin, and 0.5 kg of C5 petroleum resin to a parallel twin-screw extruder. Control the twin-screw extruder for melt blending extrusion, setting the length-to-diameter ratio to 50:1, screw speed to 350 rpm, and extrusion temperature zones: Zone 1 130℃, Zone 2 145℃, Zone 3 165℃, Zone 4 180℃, Zone 5 182℃, Zone 6 184℃, Zone 7 190℃, Zone 8 195℃, Zone 9 198℃, and die zone 200℃; vacuum degree controlled at -0.08 MPa; then perform gradient water cooling (first tank temperature 55℃, second tank temperature 30℃, third tank temperature 5℃) and gradient air cooling (first air temperature 30℃, second air temperature 15℃); then pelletize at a speed of 1200 r / min to obtain stiffening masterbatch for BOPP shrink film.

[0046] Example 3 A processing method for a stiffening masterbatch for BOPP shrink film includes the following steps: S1. Add 5.3 kg of highly crystalline homopolymer polypropylene, 0.1 kg of modified nano-titanium dioxide obtained in Preparation Example 3, 0.08 kg of sorbitol nucleating agent, 0.3 kg of maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.1 kg of polyethylene wax, 0.04 kg of antioxidant 1010, 0.04 kg of antioxidant 168, and 0.03 kg of light stabilizer UV-765 to a high-speed mixer and mix at 50°C and 750 rpm for 5 min to obtain a mixture.

[0047] S2. Add the mixture and 2kg of C5 petroleum resin and 1kg of C5 petroleum resin to a parallel twin-screw extruder. Control the twin-screw extruder to perform melt blending extrusion, set the length-to-diameter ratio to 50:1, screw speed to 350rpm, and extrusion temperature zones: Zone 1 130℃, Zone 2 145℃, Zone 3 165℃, Zone 4 180℃, Zone 5 182℃, Zone 6 184℃, Zone 7 190℃, Zone 8 195℃, Zone 9 198℃, and Die Zone 200℃; vacuum degree controlled at -0.08MPa; then perform gradient water cooling, with the first water tank temperature at 55℃, the second water tank temperature at 30℃, and the third water tank temperature at 5℃, and gradient air cooling, with the first air temperature at 30℃ and the second air temperature at 15℃; then pelletize at a speed of 1200r / min to obtain stiffening masterbatch for BOPP shrink film.

[0048] Example 4 A processing method for a stiffening masterbatch for BOPP shrink film includes the following steps: S1. Add 5.3 kg of highly crystalline homopolymer polypropylene, 0.1 kg of modified nano-silica obtained in Preparation Example 4, 0.08 kg of sorbitol nucleating agent, 0.3 kg of maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.1 kg of polyethylene wax, 0.04 kg of antioxidant 1010, 0.04 kg of antioxidant 168, and 0.03 kg of light stabilizer UV-765 to a high-speed mixer and mix at 50°C and 750 rpm for 5 min to obtain a mixture.

[0049] S2. Add the mixture, 1.5 kg of C5 petroleum resin, and 0.5 kg of C5 petroleum resin to a parallel twin-screw extruder. Control the twin-screw extruder for melt blending extrusion, setting the length-to-diameter ratio to 50:1, screw speed to 350 rpm, and extrusion temperature zones: Zone 1 130℃, Zone 2 145℃, Zone 3 165℃, Zone 4 180℃, Zone 5 182℃, Zone 6 184℃, Zone 7 190℃, Zone 8 195℃, Zone 9 198℃, and die zone 200℃; vacuum degree controlled at -0.08 MPa; then perform gradient water cooling (first tank temperature 55℃, second tank temperature 30℃, third tank temperature 5℃) and gradient air cooling (first air temperature 30℃, second air temperature 15℃); then pelletize at a speed of 1200 r / min to obtain stiffening masterbatch for BOPP shrink film.

[0050] Example 5 A processing method for a stiffening masterbatch for BOPP shrink film includes the following steps: S1. Add 5.3 kg of highly crystalline homopolymer polypropylene, 0.1 kg of modified nano-titanium dioxide obtained in Preparation Example 5, 0.08 kg of sorbitol nucleating agent, 0.3 kg of maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.1 kg of polyethylene wax, 0.04 kg of antioxidant 1010, 0.04 kg of antioxidant 168, and 0.03 kg of light stabilizer UV-765 to a high-speed mixer and mix at 50°C and 750 rpm for 5 min to obtain a mixture.

[0051] S2. Add the mixture, 1.5 kg of C5 petroleum resin, and 0.5 kg of C5 petroleum resin to a parallel twin-screw extruder. Control the twin-screw extruder for melt blending extrusion, setting the length-to-diameter ratio to 50:1, screw speed to 350 rpm, and extrusion temperature zones: Zone 1 130℃, Zone 2 145℃, Zone 3 165℃, Zone 4 180℃, Zone 5 182℃, Zone 6 184℃, Zone 7 190℃, Zone 8 195℃, Zone 9 198℃, and die zone 200℃; vacuum degree controlled at -0.08 MPa; then perform gradient water cooling (first tank temperature 55℃, second tank temperature 30℃, third tank temperature 5℃) and gradient air cooling (first air temperature 30℃, second air temperature 15℃); then pelletize at a speed of 1200 r / min to obtain stiffening masterbatch for BOPP shrink film.

[0052] Comparative Example 1 The difference from Example 4 is that modified nano-silica is replaced with silica with a particle size of about 50 nm.

[0053] Comparative Example 2 The difference from Example 4 is that the modified nano-silica obtained in Preparation Example 6 is used instead of the modified nano-silica in Preparation Example 4.

[0054] Application Example 1 The stiffening masterbatch obtained in Example 1 was added at a rate of 5% to produce 50 μm BOPP shrink film, which was then used for label film. The results showed that compared to the method without stiffening masterbatch, the elastic modulus increased by 32%, and the haze decreased by 0.1%. Simultaneously, it exhibited excellent stiffness and wrinkle-free printing.

[0055] Application Example 2 The stiffening masterbatch obtained in Example 2 was added at a rate of 5% to produce 50 μm BOPP shrink film, which was then used for high-transparency bottle label film. The results showed that compared with the absence of stiffening masterbatch, the elastic modulus increased by 28%, the shrinkage was more uniform, and the haze decreased by 0.1%.

[0056] Application Example 3 The stiffening masterbatch obtained in Example 3 was added at a rate of 5% to produce 50 μm BOPP shrink film, which was then used in daily chemical labeling films. The results showed that compared with the addition of the stiffening masterbatch, the elastic modulus was increased by 38%, the shrinkage was more uniform, the haze was reduced by 0.1%, and it was more resistant to hot stamping and high-temperature filling.

[0057] The stiffening masterbatches obtained from the examples and comparative examples were added at a rate of 10% to produce 15 μm BOPP shrink films. The performance of these shrink films was tested according to the national standard GB / T 10003-2008 "General Purpose Biaxially Oriented Polypropylene (BOPP) Film". The results are shown in Table 1, where the blank represents BOPP shrink film prepared without the addition of stiffening masterbatch.

[0058] Table 1

[0059] As can be seen from the test results in Table 1, compared with unmodified silica, the other examples and comparative examples exhibited higher longitudinal tensile strength, as well as lower longitudinal thermal shrinkage and haze. This is because the modification of the nanomaterials with silane coupling agents and / or benzyltrimethylammonium hydroxide promoted the dispersion of the nanomaterials and enhanced their reinforcing function. Comparative Example 2 showed a significant decrease in performance compared to Example 4. This may be because the higher content of benzyltrimethylammonium hydroxide on the silica surface made it easier for it to aggregate in the molecular framework of the base film, hindering its effective performance. This further illustrates the synergistic effect between the silane coupling agent and benzyltrimethylammonium hydroxide.

[0060] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A stiffening masterbatch for BOPP shrink film, characterized in that, By weight, it comprises 50-75 parts carrier resin, 20-40 parts hydrogenated petroleum resin, 0.3-2 parts nano-rigid filler, 0.5-1.0 parts nucleating agent, 2.0-4.0 parts interface compatibilizer, 0.3-2.0 parts processing aid, 0.2-1.0 parts antioxidant and 0.1-0.5 parts light stabilizer.

2. The stiffening masterbatch for BOPP shrink film according to claim 1, characterized in that, The processing technology of the nano-rigid filler includes, Nanomaterials and silane coupling agents are mixed and heated to undergo dry modification, resulting in nano-rigid fillers.

3. The stiffening masterbatch for BOPP shrink film according to claim 1, characterized in that, The amount of the silane coupling agent added accounts for 0.5%-1.5% of the mass ratio of the nanomaterial; The nanomaterials include at least one of silicon dioxide, titanium dioxide, and talc with a particle size of 20-80 nm. The silane coupling agent includes at least one of KH550, KH560, and KH570; The temperature for the heating is 90-110℃.

4. The stiffening masterbatch for BOPP shrink film according to claim 2, characterized in that, When mixing the nanomaterials and the silane coupling agent, 0.05%-0.1% of benzyltrimethylammonium hydroxide by mass of the nanomaterials is also added.

5. The stiffening masterbatch for BOPP shrink film according to claim 1, characterized in that, The carrier resin is highly crystalline homopolymer polypropylene, with a melt flow rate of 2-10 g / 10 min, isotacticity ≥96%, and melting point of 160-167 °C.

6. The stiffening masterbatch for BOPP shrink film according to claim 1, characterized in that, The hydrogenated petroleum resin includes C5 petroleum resin and / or C9 petroleum resin; The nucleating agent includes at least one of aryl phosphate salts, sorbitols, and substituted benzoates; The interface compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8%-1.5%. The processing aids include at least one of fluorinated processing aids, stearates, polyethylene wax, and oxidized polyethylene wax; The antioxidants include at least one of hindered phenolic antioxidants and phosphite antioxidants; The light stabilizer is a hindered amine light stabilizer.

7. A processing method for the stiffening masterbatch for BOPP shrink film according to any one of claims 1-6, characterized in that, include, The carrier resin, nucleating agent, interface compatibilizer, processing aid, antioxidant, and light stabilizer are mixed evenly to obtain a mixture. The mixture and hydrogenated petroleum resin are added to a parallel twin-screw extruder for melt blending and extrusion, followed by gradient water cooling, gradient air cooling, and pelletizing to obtain stiffening masterbatch for BOPP shrink film.

8. The processing technology of the stiffening masterbatch for BOPP shrink film according to claim 7, wherein the length-to-diameter ratio of the parallel twin-screw extruder is 42-52:1, the screw speed is 280-400 r / min, and the extrusion temperature is set in zones as follows: zone 1 120-135℃, zone 2 135-155℃, zone 3 155-175℃, zone 4 175-185℃, zone 5 175-185℃, zone 6 175-185℃, zone 7 185-195℃, zone 8 195-200℃, zone 9 195-200℃, and die zone 195-200℃; the vacuum degree is controlled at -0.06-0.09 MPa.

9. The processing technology of the stiffening masterbatch for BOPP shrink film according to claim 8, wherein the gradient water cooling is a three-stage gradient water cooling, with the water temperature of the first water tank being 45-65℃, the water temperature of the second water tank being 20-40℃, and the water temperature of the third water tank being 0-7℃. The gradient air cooling is a two-stage gradient air cooling system, with the first stage air temperature at 25-45℃ and the second stage air temperature at 10-25℃. The pelletizing speed is 800-1500 r / min.

10. A BOPP shrink film, characterized in that, The masterbatch for stiffening BOPP shrink film as described in any one of claims 1-6.

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