Anti-adhesion master batch for biaxially oriented film and preparation process of anti-adhesion master batch

Abstract

The invention relates to the technical field of functional composite materials, and discloses an anti-adhesion master batch for a biaxially oriented film and a preparation process of the anti-adhesion master batch for the biaxially oriented film, and the preparation process comprises the following steps: pre-mixing mesoporous silica with specific pore diameter, pore volume and particle size with homo-polypropylene particles, feeding into a co-rotating twin-screw extruder provided with a zero-pressure conveying area and a wide-gap kneading block, and extruding to obtain the anti-adhesion master batch for the biaxially oriented film. The melt temperature is controlled to be 230-270, and the rotating speed of a screw is adjusted so that the average retention time of the material can be within the range of 120-150 s. According to the preparation method, the melt viscosity is adjusted and controlled through an infiltration dynamic window, polypropylene chain segments are migrated into silicon dioxide pores through capillary pressure, the infiltration depth is limited, and a radial refractive index gradient transition layer is constructed on the peripheral side of the anti-blocking agent; abrupt change of phase interface refractive index is eliminated, visible light scattering is inhibited, and the technical problem of mutual restriction of anti-adhesion performance and optical transparency is solved.

Description

TECHNICAL FIELD

[0001] The application relates to an anti-blocking master batch for a biaxially stretched film and a preparation process thereof, and belongs to the technical field of functional composite materials. BACKGROUND

[0002] In the current film winding and automatic packaging processing, large-area close contact between layers produces blocking, deteriorates the opening performance, reduces the unwinding efficiency, and an inorganic functional anti-blocking agent is used to construct micro protrusions on the surface layer of the film to reduce the contact area between layers and provide a physical anti-blocking fulcrum. High-transparency optical films have high requirements for the haze index, and the difference in refractive index between the commonly used functional anti-blocking agent and the carrier resin induces visible light scattering at the phase interface. Reducing the particle size of the anti-blocking agent or reducing the addition amount will lead to the deterioration of the anti-blocking effect. The high shear field in the traditional blending process causes the internal structure of the porous anti-blocking agent to collapse, the interface of the anti-blocking agent presents a sharp refractive index jump, and the Fresnel reflection cannot be weakened, which affects the optical performance under high load.

[0003] In addition to the limited specifications of the anti-blocking agent, the industry tries to improve the performance by adjusting the processing formula and other means. For example, a Chinese invention patent with the authorization announcement number CN106541661B discloses a corona-free biaxially stretched polypropylene packaging film and a manufacturing method thereof. The surface polarity is improved by introducing a corona-free modified polymer to solve the problems of film adhesion and printability, and to inhibit interface scattering. This technology uses the conventional SiO2 anti-blocking additive, and the improvement idea is limited to the macroscopic superposition of functional components, without considering the influence of the micro-infiltration state between the anti-blocking agent and the matrix on the optical performance. Due to the lack of interface refractive index gradient construction of the anti-blocking agent, the haze of the film increases rapidly with the increase of the load of the anti-blocking agent under high load conditions, and it is difficult to break the technical bottleneck of the mutual restriction between the physical opening performance and the optical transparency.

[0004] Therefore, how to control the intervention of the melt infiltration dynamics in the functional anti-blocking agent mesoporous structure preset and processing, and realize the interface optical compatibility without sacrificing the content of the anti-blocking agent, has become a technical problem to be solved by the application. SUMMARY

[0005] To solve the problems in the background art, the technical scheme of the application is as follows: a preparation process of an anti-blocking master batch for a biaxially stretched film, comprising the following steps: Step 101, mesoporous silicon dioxide with a pore size of 6nm to 10nm, a pore volume of 0.8mL / g to 1.2mL / g and a median particle size of 3.5um to 4.5um is pre-mixed with homopolymer polypropylene particles with an intrinsic refractive index of 1.49 to 1.51 at a mass ratio of 2:98 to 10:90 to generate a pre-mixture, and a melt filter with a precision of 25um to 60um is arranged in front of the die of the co-rotating twin screw extruder; Step 102, the premixture is added into the co-rotating twin-screw extruder, a low-shear mixing section with wide-gap kneading blocks is arranged at the rear of the feeding zone of the co-rotating twin-screw extruder, and a zero-pressure conveying zone with a length of 3 to 5 times the screw diameter is arranged at the front end of the low-shear mixing section; Step 103, the temperature gradient of each temperature zone of the co-rotating twin-screw extruder barrel is set, so that the real-time melt temperature of the material in the low-shear mixing section is maintained at 230 to 270 ; Step 104, the screw rotation speed is adjusted to 200 rpm to 400 rpm and the feeding amount is controlled, so that the average residence time of the material in the co-rotating twin-screw extruder barrel is in the interval of 120 s to 150 s; Step 105, within the infiltration kinetics window constructed by the average residence time and the real-time melt temperature, the viscosity of the melt at a shear rate of 100 s-1 is controlled to be in the interval of 160 Pa·s to 190 Pa·s, the capillary pressure generated by the pores of the mesoporous silica is utilized to make the molten polypropylene chain segment migrate into the pores of the mesoporous silica, the infiltration depth is controlled to be in the interval of 10% to 15% of the radius of the mesoporous silica particles, and a radial refractive index gradient transition layer is formed around the mesoporous silica.

[0006] Preferably, the melt flow rate (MFR) of the homopolymer polypropylene particles at 230°C and 2.16 kg is 2.8 g / 10 min to 3.5 g / 10 min; the preparation process further comprises: before step 101, the mesoporous silica is subjected to surface hydrophobic treatment with a silane coupling agent with a mass fraction of 0.5% to 1.2%, the treatment temperature is controlled to be 80 to 100 , and the treatment time is 30 min to 60 min, so as to form a hydrophobic modified layer on the surface of the mesoporous silica, and the hydrophobic modified layer is utilized to reduce the adsorption rate of the mesoporous silica to the low molecular components in the homopolymer polypropylene particles.

[0007] Preferably, in step 101, the mesoporous silica is synthesized by a gel method, and the fraction with a median particle size of 3.5 μm to 4.5 μm is extracted by airflow classification and separation; the premixing is performed in a high-speed mixer, the mixing time is 3 min to 8 min, and the material temperature is maintained at 50 below during the mixing process.

[0008] Preferably, the length-diameter ratio of the co-rotating twin-screw extruder is 44:1 to 52:1; in step 102, the low-shear mixing section is provided with a combination of kneading elements with a staggered angle of 30° to 45°, and the radial gap of the kneading elements is 0.5 mm to 0.8 mm.

[0009] Preferably, step 105 further comprises: performing vacuum degassing treatment on the melt in the venting zone of the co-rotating twin-screw extruder, controlling the vacuum degree to be -0.08 MPa to -0.10 MPa, and removing the air and low-molecular volatile substances inside the pores replaced by the molten polypropylene segments by using negative pressure.

[0010] Preferably, after step 105, the following steps are further included: extruding the molten mixture into a strand through a multi-hole die, controlling the die pressure to be 3.5 MPa to 5.0 MPa; guiding the strand into a cooling water tank for water cooling and solidification, controlling the cooling water temperature to be 20 ; and cutting the cooled strand to generate the anti-blocking master batch particles.

[0011] Preferably, after cutting, the following steps are further included: drying the anti-blocking master batch particles, controlling the water content of the anti-blocking master batch particles to be below 0.3%; and testing the pore volume retention rate of the silica in the anti-blocking master batch particles by using nitrogen adsorption method, and the pore volume retention rate is higher than 70% of the initial pore volume.

[0012] Preferably, the thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: , wherein L is the thickness of the radial refractive index gradient transition layer, R is the particle radius of the mesoporous silica, is a preset permeability coefficient and its value is in the interval of 0.10 to 0.15; the refractive index of the radial refractive index gradient transition layer decreases non-linearly from outside to inside, and the edge refractive index is consistent with the refractive index of the homopolymer polypropylene particles.

[0013] Preferably, the preparation process further includes a film preparation step: adding the obtained anti-blocking master batch into a film substrate for biaxial stretching, controlling the addition amount of the anti-blocking master batch in the surface layer of the film, controlling the addition amount of the anti-blocking master batch to be 2% to 5% of the mass percentage of the surface layer, and controlling the haze of the obtained film to be lower than 1.5% and the interlayer adhesion to be lower than 10 g / 100 cm 2 In step 105, the real-time melt temperature is adjusted based on the real-time monitored screw torque fluctuation value of the co-rotating twin-screw extruder; when the screw torque fluctuation value exceeds 5% of the preset reference value, the heating power of the temperature zone of the co-rotating twin-screw extruder is adjusted, so that the fluctuation deviation of the real-time melt temperature is maintained within ±1 .

[0014] An anti-blocking master batch for biaxially stretched film, which is directly obtained from the preparation process of the anti-blocking master batch for biaxially stretched film.

[0015] Compared with the prior art, the present application has the following beneficial effects: ​1. In biaxially oriented films, the mesoporous silica through-pore structure, combined with the controlled melt viscosity environment, induces the polymer melt to migrate directionally into the pores under the drive of capillary pressure. A radially distributed refractive index gradient layer is formed at the interface between the anti-blocking agent and the carrier resin. The refractive index gradient layer transforms the abrupt phase interface into a smooth optical transition region, suppresses interface reflection and disordered scattering in the visible light wavelength range, maintains the roughness support required for anti-blocking, and keeps the film highly transparent.

[0016] 2. After cooling and solidification, the polymer chain segments penetrating into the pores form a molecular-level anchoring structure with silica particles, constructing a physical interaction interface with enhanced bonding force. This deep coupling mechanism prevents the anti-blocking agent from debonding or generating micropores under biaxial tensile stress, ensuring that the anti-blocking particles maintain morphological stability and optical purity during deformation. This solves the problem of increased haze caused by interface failure during stretching in conventional anti-blocking agents. The controlled filling effect balances the high specific surface area anti-blocking agent's tendency to adsorb low molecular weight components in the resin carrier, stabilizing the melt rheological behavior of the masterbatch during blending and film formation. The adaptive adjustment mechanism of interface interaction prevents viscosity fluctuations caused by the collapse of the porous structure of the anti-blocking agent or abnormal oil absorption rate, improving the processing stability and product performance consistency of the masterbatch in continuous production.

[0017] 3. The specific particle size distribution, mesoporous structure, and loading density work together to distribute silica particles in a discrete state on the film surface, forming a point-contact micro-rough structure. The cross-scale design coupling enables low adhesion between film layers, reducing diffuse reflection caused by light passing through non-uniform media, achieving a systematic gain in physical opening performance and optical quality, and overcoming the limitations of functional expression and optical loss in traditional anti-adhesion systems. This invention transforms the physical anti-adhesion mechanism into an interfacial optical control mechanism by matching the micromorphology of the functional anti-adhesion agent with the processing shear field dynamics, without the need to introduce additional refractive index adjustment components. Attached Figure Description

[0018] Fig. 1 This is a flow chart of the process for preparing the anti-adhesion masterbatch with melt wetting kinetics control according to the present invention; Fig. 2 This is a radar chart comparing the distribution of comprehensive performance indicators of the masterbatch under different melt viscosity conditions according to the present invention. Fig. 3 This is a schematic diagram of the layered architecture of the preparation system integrating torque monitoring and temperature control feedback of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0020] This invention provides an anti-adhesion masterbatch for biaxially oriented films and its preparation process. The process involves modifying and classifying silica with a continuous mesoporous structure. By controlling the wetting kinetics parameters during melt blending, silica is distributed in a homopolymer polypropylene carrier at a mass percentage loading of 2% to 10%. Capillary pressure induces the migration of polypropylene segments into the silica pores, creating a radial refractive index gradient transition layer around the anti-adhesion agent. Finally, a discretely distributed anti-adhesion support is formed on the film surface through a biaxially oriented film-forming process. Addressing the visible light scattering problem caused by reduced adhesion in anti-adhesion films, this invention employs a gel synthesis technique to prepare a masterbatch with a pore size of 6 nm to 10 nm, a pore volume of 0.8 mL / g to 1.2 mL / g, and a specific surface area of ​​400 m². 2 / g to 600m 2 / g of mesoporous silica, and the median particle size was extracted using airflow fractionation technology. The silica was fractionated from 3.5 μm to 4.5 μm to provide suitable surface micro-protrusions; prior to premixing, the mesoporous silica was surface-hydrophobicated with a silane coupling agent at a mass fraction of 0.5% to 1.2%, with the treatment temperature controlled at 80°C. Up to 100 The processing time is between 30 and 60 minutes to generate a hydrophobic modified layer on the surface of mesoporous silica. This hydrophobic modified layer reduces the adsorption rate of low molecular weight components in homopolymer polypropylene particles by the mesoporous silica, maintaining wetting stability during processing. To eliminate the abrupt change in refractive index at the phase interface, this invention utilizes the kinetic window during the masterbatch melt blending process to construct a radial refractive index gradient transition layer. Mesoporous silica is mixed with homopolymer polypropylene particles with a melt flow rate (MFR) of 2.8 g / 10 min to 3.5 g / 10 min and an intrinsic refractive index of 1.49 to 1.51 at 230°C and 2.16 kg at a mass ratio of 2:98 to 10:90, and then fed into the process. In co-rotating twin-screw extruders with a ratio of 44:1 to 52:1, a low-shear mixing section with wide-gap kneading blocks is located at the rear of the feeding zone. At the front of this section is a zero-pressure conveying zone with a length 3 to 5 times the screw diameter. By setting the temperature gradient of each temperature zone in the barrel, the real-time melt temperature of the material in the low-shear mixing section is maintained at 230°C. Up to 270 .

[0021] Under the aforementioned temperature conditions, the screw speed is adjusted to 200 rpm to 400 rpm and the feed rate is controlled. Simultaneously, a melt filter with a precision of 25 μm to 60 μm, located at the front of the die, intercepts gel and impurities in the melt, ensuring that the average residence time of the material within the barrel of the co-rotating twin-screw extruder is within the range of 120 s to 150 s, thus controlling the melt flow... The viscosity at the shear rate is in the range of 160 Pa·s to 190 Pa·s. The capillary pressure generated by the pores of mesoporous silica drives the migration of molten polypropylene segments into the pores; capillary pressure... Satisfy the following formula: ,in, Capillary pressure, in Pa; is the surface tension of the melt, expressed in N / m; For wetting angle; The pore size of the mesoporous silica is expressed in meters (m). By coupling and adjusting the average residence time with the real-time melt temperature, the penetration depth of the polypropylene segments is controlled to be within 10% to 15% of the radius of the mesoporous silica particles, forming a radial refractive index gradient transition layer on the periphery of the mesoporous silica. The thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: Where L is the thickness of the radial refractive index gradient transition layer in meters (m); and R is the particle radius of the mesoporous silica in meters (m). The permeability coefficient is between 0.10 and 0.15; when using mesoporous silica with a radius R of 2 μm, the permeability coefficient is set. When the refractive index is 0.12, the calculated thickness L is 0.24 μm. This results in a hierarchical structure with a non-linear decreasing refractive index distribution from the outside to the inside. The edge refractive index is consistent with that of the homopolymer polypropylene particles, which is used to eliminate refractive index jumps at the phase interface and suppress visible light scattering. Vacuum degassing is performed on the melt in the exhaust zone of the co-rotating twin-screw extruder, controlling the vacuum level to -0.08 MPa to -0.10 MPa to remove displaced air and low-molecular-weight volatiles from the pores. The extruded material is then extruded through a porous die, with the die pressure controlled at 3.5 MPa to 5.0 MPa. The material introduction temperature is 20 °C. Up to 45 The masterbatch particles are solidified in a cooling water tank, granulated, and dried to reduce their moisture content to below 0.3%. The pore volume retention rate of silica in the masterbatch particles is tested using nitrogen adsorption to ensure that it is higher than 70% of the initial pore volume.

[0022] During the film preparation process, the obtained anti-adhesion masterbatch is added to the film substrate and subjected to biaxial stretching. The amount of anti-adhesion masterbatch added to the film surface is controlled to ensure that the mesoporous silica content of the film surface is within the range of 0.1% to 0.5% by mass. During the preparation process, the heating power is adjusted based on the real-time monitoring of screw torque fluctuation. When the torque fluctuation exceeds 5% of the preset reference value, the barrel temperature is adjusted to maintain the real-time melt temperature fluctuation deviation within ±1. Within this range, the polypropylene segments penetrating into the pores form a molecular-level anchoring structure after cooling and solidification, preventing the anti-blocking agent from debonding under tensile stress. The resulting film has a haze of less than 1.5% and an interlayer adhesion of less than 10 g / 100 cm⁻¹. 2 During the process execution phase, the melt viscosity is established. The material rheological response is determined by a real-time mapping model with screw torque M, and the steady-state operating reference torque value of the co-rotating twin-screw extruder is collected using a pressure sensor. The data is stored in the sensing and control layer, and the system monitors the screw torque fluctuation value. Deviation from benchmark value At that time, the temperature control execution module receives the compensation command and... To adjust the barrel heating power in steps, so as to maintain the real-time melt temperature at 230°C. to Melt viscosity Stay to Within a certain range, the kinetic energy generated by the migration of molten polypropylene segments within the pores of mesoporous silica is utilized to control the permeability coefficient. Within the range of 1.10 to 0.15, the thickness L of the radial refractive index gradient transition layer satisfies... Quantitative constraint relationships; to determine the mesoporous structure integrity and polypropylene segment penetration depth L, a solvent extraction procedure was used to strip the anti-adhesion masterbatch components after extrusion, using xylene solvent in... Reflux extraction After removing polypropylene segments from the pores and drying, the silica residue was tested using nitrogen adsorption, confirming that the pore volume retention rate was higher than the initial pore volume. By performing linear elemental abundance scanning on particle sections using transmission electron microscopy, and based on the distribution characteristics of silicon and carbon, the penetration depth L was determined to be within the particle radius R. to The study utilizes quantitative structural characterization data to characterize the effect of the radial refractive index gradient transition layer on suppressing abrupt changes in refractive index at the phase interface, thus overcoming the technical bottleneck of the trade-off between anti-adhesion performance and optical transparency. This results in a thin film with interlayer adhesion strength lower than [a certain value]. Haze level below .

[0023] Example 1: During the operation of a continuous production line for high-transparency homopolymer polypropylene film with a production line speed of not less than 300 m / min, the increased interlayer contact pressure due to film winding tension induces large-area adhesion on the film surface, leading to unwinding obstruction and surface scratches in the automated packaging process. Furthermore, when increasing the loading of conventional anti-blocking agent to maintain opening performance, the film haze rises to over 2.5%. This condition presents a technical bottleneck where high anti-blocking performance and low haze are mutually constrained. Using the preparation procedure determined in the aforementioned specific implementation method, the median particle size... Mesoporous silica with a diameter of 3.5 μm to 4.5 μm and a pore size r of 6 nm to 10 nm was introduced at a mass ratio of 3% into a 15 μm thick film surface layer, and the co-rotating twin-screw extruder was controlled at 230°C. Up to 270 Under real-time melt temperature conditions, homopolymer polypropylene granule melt with a melt flow rate (MFR) of 2.8 g / 10 min to 3.5 g / 10 min at 230℃ and 2.16 kg was subjected to a shear rate of... The viscosity is between 160 Pa·s and 190 Pa·s. The capillary pressure generated by the mesoporous silica through the pores induces the melt to migrate into the particle interior. By controlling the average residence time of the material in the barrel to be between 120 s and 150 s, the penetration depth L of the polypropylene chain into the pore interior is within 10% to 15% of the particle radius R, thereby forming a radial refractive index gradient transition layer around the mesoporous silica particles.

[0024] Capillary pressure generated by the pores of mesoporous silica Satisfy the following formula: ,in, Capillary pressure, in Pa; is the surface tension of the melt, expressed in N / m; Where is the wetting angle; r is the pore size of the mesoporous silica in meters; the thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: Where: L is the thickness of the radial refractive index gradient transition layer, in meters; R is the particle radius of mesoporous silica, in meters; The permeability coefficient is preset and its value is in the range of 0.10 to 0.15. This radial refractive index gradient transition layer transforms the interface between the anti-blocking agent and homopolymer polypropylene particles from a sudden refractive index state to a smooth optical transition zone, suppressing interface reflection and disordered scattering in the visible light wavelength range. Combined with the molecular-level anchoring structure generated by the polypropylene chain segments penetrating the pores after cooling and solidification, this ensures that the anti-blocking particles maintain morphological stability under biaxial tensile stress, preventing interface debonding and the formation of micropores and voids. This results in an interlayer adhesion of 8.2 g / 100 cm⁻¹ in the obtained film. 2Up to 9.1g / 100cm 2 The film haze is within the range of 1.1% to 1.3%, achieving simultaneous physical aperture performance and optical transparency within a single fabrication process framework.

[0025] Example 2: In the experiment verifying the evolution of optical properties of the high-load anti-adhesion system, an aspect ratio of 52:1 and a temperature control accuracy of ±0.5 were used. The co-rotating twin-screw extruder within the specified range, coupled with a bidirectional tensile testing line equipped with a high-precision tension sensor, collects real-time melt pressure and torque signals through an online monitoring system. Furthermore, Gaussian white noise with a signal-to-noise ratio of 20dB is superimposed in the sensor signal transmission link to simulate industrial electromagnetic interference. The core parameter is the penetration coefficient. The setting depends on the technical trade-off between the interfacial optical phase retardation and the strength of the anti-blocking agent's pore skeleton, when the real-time melt temperature is 230°C. When the melt viscosity tends towards the upper limit of its range, i.e., 190 Pa·s, in order to ensure that the melt generates permeation kinetic energy driven by capillary pressure, the permeability coefficient... The setting logic tends to take values ​​up to the upper limit of its range, i.e., 0.15. When the average residence time of the material in the barrel approaches 150s, to prevent the overfilling of polypropylene segments from causing mechanical failure of the mesoporous structure, the permeability coefficient is... The value of is adjusted to the lower limit of its value range, which is 0.10.

[0026] During the initial experimental phase, multiple groups of thin film samples covering different process gradients were prepared. The experimental group used the preparation process of this invention. By adjusting the screw speed and feed rate, the average residence time was controlled within the range of 120s to 150s, and the real-time melt temperature was maintained at 230°C using temperature zone power feedback regulation. Up to 270 This induces the homopolymer polypropylene melt to migrate into the mesopores with a pore size of 8 nm. Table 1 shows the original process parameters, key intermediate characteristic values, and final output performance indicators recorded during the experiment. The penetration depth L was obtained by observing the cooled masterbatch particles using a transmission electron microscope. The haze and interlayer adhesion were determined according to the general optical testing standard and the peel force testing specification, respectively. See Table 1.

[0027] Table 1: Key kinetic parameters in the melt blending process Analysis of the data in Table 1 shows that, under the wetting kinetics window of 175 Pa·s viscosity and 135 s residence time, the penetration depth L generated in experimental group 2 was 0.24 μm. At this time, the film haze was at 1.1%, and the interlayer adhesion was maintained at 8.5 g / 100 cm. 2 Capillary pressure generated by the pores of mesoporous silica Satisfy the following formula: ,in, Capillary pressure, in Pa; is the surface tension of the melt, expressed in N / m; denoted as the wetting angle; r is the pore size of the mesoporous silica, in meters; the thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: Where L is the thickness of the radial refractive index gradient transition layer in meters (m); and R is the particle radius of the mesoporous silica in meters (m). The permeability coefficient is a preset value and its value is in the range of 0.10 to 0.15; when the permeability coefficient... When the melt filler exceeds the specified limit of 0.15 and reaches 0.20 as shown in control group 2, excessive melt filling leads to air displacement within the mesopores, resulting in a deterioration effect. This manifests as a rebound in interlayer adhesion to 13.5 g / 100 cm², even though the haze remains at 1.8%, due to the reduced fulcrum height. 2 Furthermore, comparing the data of experimental group 2 and control group 3, it can be seen that the lack of surface treatment layer leads to fluctuations in the oil absorption rate of homopolymer polypropylene melt, inducing instability of the permeability coefficient and generating phase interface defects.

[0028] Example 3: This example combines Figs. 1 to 3 This document describes an anti-blocking masterbatch for biaxially oriented films and its preparation process. Fig. 1 As shown, this preparation process uses mesoporous silica with a pore size of 6nm to 10nm, a pore volume of 0.8mL / g to 1.2mL / g, and a median particle size of 3.5μm to 4.5μm as raw materials, and homopolymer polypropylene particle matrix carrier resin with an intrinsic refractive index of 1.49-1.51. In step 101, premixing is performed at a mass ratio of 2:98 to 10:90. In step 102, the mixture is fed into the feeding zone of a co-rotating twin-screw extruder equipped with a zero-pressure conveying zone and a wide-gap kneading block low-shear mixing section. In step 103, a temperature gradient is set to maintain the real-time melt temperature at 230°C. Up to 270 In step 104, the screw speed is adjusted to 200 rpm to 400 rpm to keep the average residence time in the range of 120 s to 150 s, and then the process proceeds to step 105 to construct the wetting kinetics window. The melt viscosity is controlled in the range of 160 Pa·s to 190 Pa·s. The chain segment migration is driven by capillary pressure to make the penetration depth reach 10% to 15% of the particle radius to construct a radial refractive index gradient transition layer on the periphery of the mesoporous silica and eliminate the abrupt change in refractive index at the phase interface. Finally, after pelleting and drying, a biaxially oriented anti-adhesion masterbatch for thin films with a moisture content of less than 0.3% and a pore volume retention rate of more than 70% is output.

[0029] like Fig. 2As shown, this radar chart establishes six evaluation dimensions: penetration depth, pore volume retention, film haze, interlayer adhesion, processing stability, and mechanical strength. The numerical scale range is set from 55 to 100. The chart clearly depicts the performance index distribution profiles under three specific working conditions: melt viscosity of 160 Pa·s, 175 Pa·s, and 190 Pa·s. The curve representing 175 Pa·s shows a relatively balanced coverage area on the axes of various indicators, reflecting the balance between various physical and mechanical properties and optical properties under this specific viscosity environment. Fig. 3 As shown, the system architecture is divided into a sensing and control layer and a physical execution layer. The physical execution layer includes the high-speed mixer of the premixing unit, the zero-pressure section of the conveying zone, the low-shear environment of the wide-gap kneading block in the reaction mixing zone, the vacuum exhaust port of the degassing extrusion zone, the cooling water tank and porous die head of the curing and molding unit, and the pelletizing and drying modules of the finished product preparation unit. The sensing and control layer integrates a torque monitoring module and a temperature control execution module. The torque monitoring module is responsible for capturing viscosity fluctuations in real time and performing deviation analysis, and then sending compensation commands to the temperature control execution module to dynamically adjust the heating power.

[0030] Example 4: In a high-speed stretch film production environment with multiple batches of homopolymer polypropylene particles switching, the melt flow rate (MFR) fluctuates between batches of raw materials within the range of 2.8 g / 10 min to 3.5 g / 10 min. The instantaneous decrease in melt fluidity weakens the penetration kinetic energy of the melt into the mesopores, causing the penetration depth L to fail to maintain above 10% of the radius R of the mesoporous silica particles, inducing a technical problem where the film haze exceeds 1.5%. To address this technical problem, a wetting kinetic parameter calibration procedure is adopted. Sensors are used to monitor the operating torque of the co-rotating twin-screw extruder online. When the torque fluctuation exceeds 5% of the preset benchmark value, it is determined that the melt viscosity has shifted. At this time, the heating power of the third to sixth heating zones of the barrel is adjusted to maintain the real-time melt temperature of the material in the low-shear mixing section at 1... The compensation is performed stepwise until the torque recovers to a stable state with a deviation of ±1% from the reference value, maintaining the kinetic energy for the polypropylene chain segments to migrate into the pores.

[0031] Capillary pressure generated by the pores of mesoporous silica Satisfy the following formula: ,in, Capillary pressure, in Pa; is the surface tension of the melt, expressed in N / m; θ represents the wetting angle; r represents the pore size of the mesoporous silica, in meters; to verify the integrity of the processed mesoporous structure, a solvent extraction validation procedure was used to extract the extruded anti-adhesion masterbatch particles, and xylene solvent was used at 140°C. Reflux extraction at a certain temperature for 12 h removed polypropylene segments that had penetrated into the pores. The measured pore volume of the dried silica residue was 0.95 mL / g. By comparing it with the initial pore volume of 1.0 mL / g, the pore volume retention rate was confirmed to be 95%, which was used to confirm the supporting effect of the kneading element combination in the low-shear mixing section on the mesoporous structure. The thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: Where L is the thickness of the radial refractive index gradient transition layer in meters (m); and R is the particle radius of the mesoporous silica in meters (m). The permeability coefficient is a preset value between 0.10 and 0.15; under this calibration procedure, the permeability coefficient is determined by... Locked at 0.13, the co-rotating twin-screw extruder speed was adjusted to 200 rpm while maintaining an average residence time of 135 s, and the interlayer adhesion of the film stabilized at 8.6 g / 100 cm. 2 Furthermore, the haze of the thin film is within a controlled range of 1.15%.

[0032] Example 5: During the preparation of homopolymer polypropylene film with a thickness specification adjusted to 12μm on the production line, a standardized pre-calibration procedure was executed to establish the response correlation between melt viscosity and screw mechanical output. This procedure involves feeding homopolymer polypropylene granules into a co-rotating twin-screw extruder before starting the mixing process. After maintaining the speed at 200rpm and stabilizing the temperature gradients in each barrel zone, sensors collect real-time power spectra under no-load and pure resin load conditions. The obtained steady-state values ​​are set as the reference zero point of the online monitoring system to calibrate the detection accuracy of screw torque fluctuation values. This ensures that when a mesoporous silica anti-blocking agent with a mass load of 2% to 10% is subsequently introduced into the system, the feedback control loop adjusts the melt viscosity based on the torque offset. The viscosity at shear rates is locked within the 160 Pa·s to 190 Pa·s window, which is the permeability coefficient. The dynamic adjustment provides a physical reference.

[0033] To address the physical influence of mesoporous silica porosity on the optical uniformity of the phase interface, a refractive index gradient data filling procedure based on offline simulation was adopted. A calibration solution with a preset refractive index was used to simulate polypropylene segments at 230°C. Up to 270 The process of penetration into mesopores with pore sizes ranging from 6 nm to 10 nm at certain temperatures was investigated. Extinction coefficient and radial refractive index distribution data of the mixed phase were measured using a multi-angle laser light scattering instrument. A correlation mapping table between penetration depth L and interfacial scattering intensity was constructed. When the permeability coefficient... When the radial refractive index gradient transition layer is in the range of 0.10 to 0.15, the reflection phenomenon at the phase interface is suppressed. The calibration data is input into the online control system, so that when the equipment is dealing with the fluctuation of the average residence time between 120s and 150s, it can automatically execute the heating power compensation command to maintain the optical state of the film haze below 1.5%.

[0034] Example 6: For the production of anti-blocking masterbatch with a mass loading of 10% of the specification limit, an offline parameter acquisition procedure was executed to establish the mechanical boundary of the mesoporous structure under the shear field of the wide-gap kneading block. The shear stress distribution in the mixing section of the co-rotating twin-screw extruder was simulated using a capillary rheometer, and the real-time melt temperature was measured at 230°C. Up to 270 Within a given range, the filling rate of homopolymer polypropylene particles for pores with a diameter of 8 nm is measured. The shear stress at which the penetration depth L reaches 15% of the particle radius R is set as the critical pressure point. Based on this, a combination of kneading elements with a staggered angle of 30° to 45° is adjusted to control the external mechanical stress to not exceed the capillary pressure generated inside the mesopores. Capillary pressure Satisfy the following formula: ,in: Capillary pressure, in Pa; is the surface tension of the melt, expressed in N / m; θ is the wetting angle; r is the pore size of the mesoporous silica, in meters (m).

[0035] To address the regulatory effect of the hydrophobic treatment layer on interfacial wetting kinetics of mesoporous silica, a pre-control procedure was implemented on the production line. Homopolymer polypropylene particles with a melt flow rate (MFR) of 3.0 g / 10 min were selected as a reference. A zero-pressure conveying zone, four times the screw diameter in length, was used at the rear of the feeding zone of the co-rotating twin-screw extruder to stabilize the melt pressure gradient. The rheological response of the melt entering the low-shear mixing section was monitored using pressure sensors, and the permeability coefficient was calculated in real time. And in the melt The viscosity at a shear rate of 175 Pa·s is locked at 0.12, so that the thickness L of the radial refractive index gradient transition layer satisfies the following quantitative relationship: Where: L is the thickness of the radial refractive index gradient transition layer, in meters; R is the particle radius of mesoporous silica, in meters; The permeability coefficient is 0.12. Under the steady-state conditions defined in this procedure, the co-rotating twin-screw extruder speed is adjusted to 200 rpm to maintain an average residence time of 135 s. The resulting masterbatch particles have a silica pore volume retention rate of 94%. When the masterbatch is introduced into the film surface at a mass percentage of 0.4%, the resulting film has a haze of 1.2% and an interlayer adhesion of 8.8 g / 100 cm.2 .

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation process for an anti-blocking masterbatch for biaxially oriented films, characterized in that, Includes the following steps: Step 101: Mesoporous silica with a pore size of 6 nm to 10 nm, a pore volume of 0.6 mL / g to 1.2 mL / g, and a median particle size of 2.5 μm to 4.5 μm is premixed with homopolymer polypropylene particles with an intrinsic refractive index of 1.49 to 1.51 at a mass ratio of 2:98 to 10:90 to generate a premix. At the same time, a melt filter with an accuracy of 25 μm to 60 μm is provided in front of the die of the co-rotating twin-screw extruder. Step 102: The premix is ​​added to a co-rotating twin-screw extruder. A low-shear mixing section with wide-gap kneading blocks is provided at the rear of the feeding zone of the co-rotating twin-screw extruder, and a zero-pressure conveying zone with a length of 3 to 5 times the screw diameter is provided at the front end of the low-shear mixing section. Step 103: Set the temperature gradient for each zone of the co-rotating twin-screw extruder barrel to maintain the real-time melt temperature of the material in the low-shear mixing section at 230°C. Up to 270 ; Step 104: Adjust the screw speed to 200 rpm to 400 rpm and control the feed rate so that the average residence time of the material in the barrel of the co-rotating twin-screw extruder is in the range of 120 s to 150 s. Step 105: Within the wetting kinetics window constructed by the average residence time and real-time melt temperature, the viscosity of the melt at a shear rate of 100 s⁻¹ is controlled to be between 160 Pa·s and 190 Pa·s. The capillary pressure generated by the pores of mesoporous silica is used to cause the molten polypropylene chain segments to migrate into the pores of mesoporous silica. The penetration depth is controlled to be between 10% and 15% of the radius of the mesoporous silica particles, and a radial refractive index gradient transition layer is formed on the periphery of the mesoporous silica.

2. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, The melt flow rate (MFR) of homopolymer polypropylene particles at 230℃ and 2.16 kg was 2.8 g / 10 min to 3.5 g / 10 min. The preparation process also included: before step 101, surface hydrophobic treatment of mesoporous silica was performed using a silane coupling agent with a mass fraction of 0.5% to 1.2%, with the treatment temperature controlled at 80℃. Up to 100 The processing time is 30 to 60 minutes to form a hydrophobic modified layer on the surface of mesoporous silica. This hydrophobic modified layer is used to reduce the adsorption rate of low molecular weight components in homopolymer polypropylene particles by mesoporous silica.

3. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, In step 101, mesoporous silica is synthesized using a gel electrophoresis method, and fractions with a median particle size of 3.5 μm to 4.5 μm are extracted by airflow fractionation. Premixing is performed in a high-speed mixer for 3 to 8 minutes, and the material temperature is maintained at 50°C during the mixing process. the following.

4. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, The length-to-diameter ratio of the co-rotating twin-screw extruder is 44:1 to 52:1; in step 102, the low-shear mixing section is provided with a combination of kneading elements with a staggered angle of 30° to 45°, and the radial gap between the kneading elements is 0.5 mm to 0.8 mm.

5. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, Step 105 further includes: performing vacuum degassing treatment on the melt in the exhaust zone of the co-rotating twin-screw extruder, controlling the vacuum degree to be -0.08MPa to -0.10MPa, and using negative pressure to remove the air and low molecular weight volatiles displaced by the molten polypropylene segments inside the pores.

6. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, Following step 105, the process further includes the following steps: extruding the molten mixture through a multi-hole die to form a strip, controlling the die pressure to be between 3.5 MPa and 5.0 MPa; and introducing the strip into a cooling water tank for water-cooled solidification, with the cooling water temperature at 20°C. Up to 45 The cooled material strips are then pelletized to produce anti-blocking masterbatch particles.

7. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 6, characterized in that, After pelleting, the process also includes: drying the anti-adhesion masterbatch particles to control the moisture content of the anti-adhesion masterbatch particles to be below 0.3%; and using nitrogen adsorption method to test the pore volume retention rate of silica in the anti-adhesion masterbatch particles, with the pore volume retention rate being higher than 70% of the initial pore volume.

8. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, The thickness L of the radial refractive index gradient transition layer satisfies the following quantization relationship: Where L is the thickness of the radial refractive index gradient transition layer. The particle radius of mesoporous silica. The permeability coefficient is preset and its value is in the range of 0.10 to 0.15; the refractive index of the radial refractive index gradient transition layer decreases nonlinearly from the outside to the inside, and its edge refractive index is consistent with the refractive index of the homopolymer polypropylene particles.

9. The preparation process of an anti-blocking masterbatch for biaxially oriented films according to claim 1, characterized in that, The preparation process also includes a film preparation step: adding the obtained anti-adhesion masterbatch to a film substrate for biaxial stretching, controlling the amount of anti-adhesion masterbatch added to the film surface layer to be 2% to 5% of the surface layer mass percentage, and controlling the haze of the resulting film to be less than 1.5% and the interlayer adhesion to be less than 10g / 100cm. 2 In step 105, the real-time melt temperature is adjusted based on the screw torque fluctuation value of the co-rotating twin-screw extruder under real-time monitoring; when the screw torque fluctuation value exceeds 5% of the preset reference value, the heating power of the temperature zone of the co-rotating twin-screw extruder is adjusted to maintain the fluctuation deviation of the real-time melt temperature within ±1. Within the range.

10. An anti-blocking masterbatch for biaxially oriented films, characterized in that, The anti-blocking masterbatch for biaxially oriented films is obtained directly by the preparation process of the anti-blocking masterbatch for biaxially oriented films described in claim 1.

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