Preparation method of PE anti-fogging master batch composition

Abstract

The invention relates to a preparation method of a PE anti-fogging master batch composition, and relates to the technical field of preparation of high polymer material functional assistants, and the master batch comprises polyethylene matrix resin, a compound anti-fogging agent, a porous adsorption carrier and a microcapsule end-capping reagent. The preparation method adopts the processes of adsorption, end sealing and dispersion, and comprises the following steps: firstly, adsorbing the liquid compound anti-fogging agent into pores of the porous carrier in vacuum, then heating to melt the microcapsule end sealing agent and quenching, constructing a high-crystallinity coating layer on the surface of the carrier in situ, and finally mixing and granulating with the matrix resin. The problems of processing slip and master batch adhesion caused by easy precipitation of a liquid auxiliary agent under high filling amount are solved through the microcapsule structure, controlled release of the antifogging agent is realized by utilizing the physical barrier effect of the end-capping layer, the fast-acting property and the long-acting property of the film are considered, the optical performance of the agricultural film is improved, and the service life of the agricultural film is prolonged.

Description

Technical Field

[0001] This application relates to the field of polymer material functionalization additives preparation technology, and in particular to a method for preparing PE anti-fogging masterbatch compositions. Background Technology

[0002] Polyethylene film is widely used in agricultural facility cultivation, such as greenhouse films and mulch films, due to its excellent light transmittance, heat insulation, and processing properties. However, polyethylene is a non-polar polymer material with low surface energy. In humid environments, water vapor easily condenses on the inner surface of the film, forming fine droplets. These droplets not only hinder sunlight transmission and reduce photosynthetic efficiency but may also drip onto crops, inducing diseases. Therefore, adding surfactant-based anti-fogging agents to polyethylene films to migrate to the film surface and reduce the water contact angle is currently the mainstream approach to solving this problem. Since most high-efficiency anti-fogging agents are liquid or semi-solid pastes at room temperature, they are difficult to disperse when directly added to resin and can easily cause slippage at the feeding port. Therefore, industrially, they are usually first prepared into high-concentration anti-fogging masterbatches before being mixed with the base resin and blown into film.

[0003] While masterbatch technology has improved the operability of feeding to some extent, existing technologies still face many challenges in pursuit of high filler content and high-performance agricultural films. Firstly, liquid anti-fogging agents have limited compatibility with the polyethylene matrix and are prone to thermal migration under the high temperature and high shear conditions of extrusion processing. When the anti-fogging agent content in the masterbatch is high, the thermally expanded liquid additives easily seep out from the traditional physical adsorption carrier and form a lubricating layer between the extruder screw and barrel, leading to screw slippage, fluctuations in main machine current, and unstable extrusion volume, severely restricting the production efficiency and product quality of the masterbatch. Furthermore, surface-seeping additives can cause masterbatch particles to stick together and clump, causing inconvenience for subsequent storage, transportation, and metering mixing.

[0004] Secondly, to adsorb more liquid additives, existing technologies often use porous silica or diatomaceous earth as a carrier. However, inorganic carrier particles adsorbed with a large amount of liquid organic matter are prone to liquid bridging forces, leading to severe secondary agglomeration. These agglomerates are difficult to break up by shear forces during subsequent film blowing, ultimately forming a large number of crystal points in the film, increasing haze and reducing light transmittance, failing to meet the light requirements of high-end agricultural films. More importantly, traditional physical mixing or simple adsorption processes cannot control the migration rate of anti-fogging agents. In the early stages of film use, anti-fogging agents often precipitate rapidly; although they take effect quickly, they are lost rapidly, resulting in an anti-fogging duration far shorter than the film's mechanical life, making it difficult to achieve long-term functionalization of agricultural films. Therefore, developing a PE anti-fogging masterbatch and its preparation technology that can achieve stable high-concentration filling while also considering processing rheology, optical properties, and a long-term slow-release mechanism has become a pressing technical challenge for the industry. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing a PE anti-fogging masterbatch composition, which aims to improve the problems of slippage and masterbatch adhesion caused by the easy precipitation of liquid additives during the preparation of existing high-concentration anti-fogging masterbatches, as well as the short anti-fogging duration and poor optical performance caused by uncontrolled release of additives and carrier agglomeration in film applications.

[0006] By adopting the above technical solutions, the present invention is achieved through the following technical solution: a method for preparing a PE anti-fogging masterbatch composition, comprising:

[0007] This invention provides a method for preparing a PE anti-fogging masterbatch composition, comprising the following steps:

[0008] S1. Raw material preparation: Prepare the following raw materials by weight: 40-70 parts of polyethylene matrix resin, 20-30 parts of compound anti-fogging agent, 5-20 parts of porous adsorption carrier, 2-6 parts of microcapsule capping agent, and 1-5 parts of functional additives.

[0009] S2. Carrier preheating: The porous adsorption carrier is added to a mixing device and preheated by stirring at a temperature of 45-55°C.

[0010] S3, Loading Adsorption: Maintain the temperature at 45-55℃, spray the compound anti-fogging agent into the mixing device and mix it with the porous adsorption carrier, so that the compound anti-fogging agent is adsorbed into the pores of the porous adsorption carrier;

[0011] S4. In-situ capping: Add the microcapsule capping agent to the mixture obtained in step S3, raise the temperature of the mixing equipment to 95-110°C and stir, so that the microcapsule capping agent melts and coats the surface of the porous adsorption carrier, and then rapidly cool the material temperature to below 40°C to obtain modified powder.

[0012] S5. Matrix mixing: Under conditions where the temperature is below 45°C, the modified powder obtained in step S4 is mixed evenly with the polyethylene matrix resin and functional additives to obtain a premix.

[0013] S6. Extrusion granulation: The premixed material is added to a twin-screw extruder and melt-extruded at a temperature range of 100-160°C. After pelleting and drying, PE anti-fogging masterbatch is obtained.

[0014] In some embodiments, the microcapsule capping agent is selected from one or more of high-density polyethylene wax, oxidized polyethylene wax, or polypropylene wax; and the melting point of the microcapsule capping agent is in the range of 90–115°C, with a crystallinity greater than 80%. The microcapsule capping agent utilizes its melting point, which is higher than that of the compounded anti-fogging agent at room temperature but lower than the extrusion temperature, to melt during the high-temperature mixing stage and crystallize after rapid cooling, forming a solid coating layer on the surface of the porous adsorbent carrier. This coating layer prevents the liquid anti-fogging agent from overflowing during the storage and transportation stages of the premix, and reduces screw slippage in the feeding section of the extrusion process.

[0015] In some embodiments, the porous adsorbent carrier is porous silica or diatomaceous earth with a dibutyl phthalate oil absorption value of 200-350 ml / 100 g and an average particle size of 5-15 μm. This particle size range and oil absorption value ensure the carrier's ability to load liquid additives and its dispersibility in the resin matrix.

[0016] In some embodiments, the compounded anti-fogging agent is composed of sorbitan fatty acid ester compounds and polyglycerol fatty acid ester compounds in a mass ratio of 1:1 to 1:3; the polyethylene matrix resin is low-density polyethylene or linear low-density polyethylene with a melt flow rate between 2.0 and 20.0 g / 10 min. The compounding of different types of nonionic surfactants utilizes differences in molecular weight and migration rate to adjust the precipitation rate of the anti-fogging function on the film surface.

[0017] In some embodiments, in step S3, the compound antifogging agent is added by preheating the compound antifogging agent to 40°C and spraying it into the mixing device at a rate of 1.0 to 2.0 kg / min using a spraying device.

[0018] In some embodiments, in step S3, the mixing device is maintained under vacuum with an absolute pressure of 0.06–0.08 MPa. This negative pressure environment reduces gas resistance within the pores of the porous adsorption carrier, promoting the penetration of the liquid anti-fogging agent into the carrier's internal channels.

[0019] In some embodiments, in step S4, the process of raising the temperature of the mixing device to 95-110°C and stirring specifically involves setting the stirring speed to 800-1200 rpm and mixing for 3-5 minutes.

[0020] In some embodiments, in step S4, the subsequent process of rapidly cooling the material temperature to below 40°C specifically involves discharging the material into a low-speed cold mixer and cooling it for 5 to 10 minutes at a speed of 200–400 rpm and circulating cooling water at 10–20°C. This rapid cooling process controls the crystallization behavior of the microcapsule capping agent, and the solidified coating physically locks the anti-fogging agent inside the carrier.

[0021] In some embodiments, in step S6, the temperature of each section of the twin-screw extruder is set as follows: conveying section 100-120°C, melt plasticizing section 130-145°C, dispersion and mixing section 145-160°C, metering extrusion section and die 140-150°C. This temperature gradient setting allows the microcapsule end-capsulating agent to gradually soften and fuse with the matrix resin during the extrusion process, releasing the loaded anti-fogging agent and carrier particles.

[0022] In some embodiments, in step S6, the length-to-diameter ratio of the twin-screw extruder is 36:1 to 48:1, and devolatilization is performed through a vacuum exhaust port during extrusion, with a vacuum degree of not less than 0.06 MPa.

[0023] The composition comprises modified powder particles dispersed in a polyethylene matrix resin. The modified powder particles have a structure characterized by a porous adsorbent carrier as the core and a microcapsule capping agent as the shell. A compounded anti-fogging agent fills the pores of the porous adsorbent carrier. After the masterbatch is used for film processing and molding, the microcapsule capping agent component forms highly crystalline microregions around the porous adsorbent carrier. These microregions increase the diffusion resistance of anti-fogging agent molecules to migrate to the film surface, thereby regulating the precipitation kinetics of the anti-fogging agent. At the same time, in-situ capping modification reduces the agglomeration of the porous adsorbent carrier caused by surface liquid bridging forces, so that the porous adsorbent carrier exists in a highly dispersed state in the polyethylene matrix, thereby reducing the haze of the film.

[0024] In summary, this application includes at least one of the following beneficial technical effects:

[0025] 1. This application utilizes an in-situ end-capping process to rapidly cool a highly crystalline microcapsule end-capping agent after melting, forming a physical barrier layer on the surface of a porous carrier that has adsorbed the anti-fogging agent. This barrier layer solves the problem of high-concentration liquid anti-fogging agent overflowing due to thermal expansion in the extruder feeding and conveying sections, avoiding screw slippage and feeding fluctuations. Thus, while reducing the thermal volatilization loss of the anti-fogging agent, it stabilizes the main current of the extruder and achieves continuous and stable production of high-filling-weight masterbatch.

[0026] 2. The three-tiered structure of carrier, capping agent, and matrix constructed in this application forms a unique sustained-release system. The fast-acting component in the compound anti-drip agent can rapidly migrate and take effect through the pores of the porous carrier; while the long-acting component is hindered by the highly crystalline microregions formed by the capping agent, resulting in a longer migration path and a slower release rate. This differentiated release mechanism enables the film to quickly eliminate droplets in the initial stage and maintain a long-lasting anti-drip effect in the later stage, thus extending the service life of the agricultural film.

[0027] 3. This application adopts a preparation process of first adsorption, then end-capping, and then dispersion, which firmly locks the liquid additive inside the micron-level carrier, avoiding the carrier agglomeration caused by the liquid bridge effect formed by the liquid additive in the resin matrix. The modified powder exhibits excellent dispersibility in the polyethylene matrix, and is uniformly distributed in the form of single particles, reducing crystal points and haze in the film, ensuring high light transmittance, and meeting the light conditions required by high-end agricultural films. Detailed Implementation

[0028] Raw material specifications and descriptions:

[0029] Polyethylene matrix resin:

[0030] LDPE-A: Low-density polyethylene with a melt flow rate (MFR) of 2.0 g / 10 min (190 °C, 2.16 kg).

[0031] LDPE-B: Low-density polyethylene with a melt flow rate (MFR) of 7.0 g / 10 min.

[0032] LDPE-C: Low-density polyethylene with a melt flow rate (MFR) of 20.0 g / 10 min.

[0033] LLDPE: Linear low-density polyethylene with a melt flow rate (MFR) of 10.0 g / 10 min.

[0034] Compound anti-fogging agent: composed of sorbitan monostearate (Span 60) and decaglycerol monostearate.

[0035] Compound agent A: mass ratio of 1:1.

[0036] Compound agent B: mass ratio is 1:2.

[0037] Compound agent C: mass ratio is 1:3.

[0038] Porous adsorption carrier:

[0039] Porous silica A: Dibutyl phthalate (DBP) has an oil absorption value of 350 ml / 100 g and an average particle size of 5 μm.

[0040] Porous silica B: DBP oil absorption value is 280ml / 100g, and average particle size is 8μm.

[0041] Porous silica C:DBP has an oil absorption value of 200ml / 100g and an average particle size of 15μm.

[0042] Diatomaceous earth: DBP oil absorption value is 230ml / 100g, and the average particle size is 12μm.

[0043] Microcapsule capping agent:

[0044] High-density polyethylene wax: melting point 112℃, crystallinity 85%.

[0045] Oxidized polyethylene wax: melting point 105℃, crystallinity 82%.

[0046] Functional additives: a mixture of hindered phenolic antioxidant 1010, phosphite antioxidant 168 and hindered amine light stabilizer 944 in a mass ratio of 1:1:2.

[0047] Example:

[0048] Example 1:

[0049] This embodiment provides a method for preparing a PE anti-fogging masterbatch composition.

[0050] Raw material ratio:

[0051] 55 parts of polyethylene matrix resin (LDPE-B, MFR7.0), 25 parts of compound anti-fogging agent (compound agent B, ratio 1:2), 12 parts of porous adsorbent carrier (porous silica B, DBP 280ml / 100g, particle size 8μm), 4 parts of microcapsule capping agent (high-density polyethylene wax), and 3 parts of functional additives.

[0052] Preparation steps:

[0053] Steps S1 to S5 are the same as in the original embodiment (repeated descriptions omitted, parameters remain the same).

[0054] S6. Extrusion Granulation: The premixed material is added to a twin-screw extruder. The length-to-diameter ratio (L / D) of the twin-screw extruder is set to 42:1. The temperatures of each section of the extruder are set as follows: conveying section 110℃, melt plasticizing section 140℃, dispersion and mixing section 155℃, metering extrusion section and die 145℃. Melt extrusion is carried out under the conditions of screw speed 300 rpm and vacuum degree of vacuum exhaust port -0.07MPa. After air cooling, stringing, pelletizing, and drying, PE anti-fogging masterbatch is obtained.

[0055] Example 2:

[0056] This embodiment aims to verify the feasibility of the parameter range boundaries.

[0057] Raw material ratio:

[0058] 70 parts of polyethylene matrix resin (LDPE-A, MFR2.0), 20 parts of compound anti-fogging agent (compound agent A, ratio 1:1), 5 parts of porous adsorbent carrier (porous silica A, DBP 350ml / 100g, particle size 5μm), 2 parts of microcapsule end-capsulation agent (high-density polyethylene wax), and 1 part of functional additive.

[0059] Preparation steps:

[0060] Steps S1 to S5 are the same as in the original embodiment.

[0061] S6. Extrusion Granulation: The premixed material is added to a twin-screw extruder. The length-to-diameter ratio (L / D) of this twin-screw extruder is set to 36:1 (supporting lower limit of L / D ratio). Temperature settings: conveying section 100℃, melt plasticizing section 130℃, dispersion and mixing section 145℃, die 140℃. Extrusion granulation is performed at a screw speed of 200 rpm and a vacuum level of -0.06 MPa at the vacuum exhaust port (supporting lower limit of vacuum level).

[0062] Example 3:

[0063] This embodiment aims to verify the feasibility of the parameter range boundaries.

[0064] Raw material ratio:

[0065] 40 parts of polyethylene matrix resin (LDPE-C, MFR20.0), 30 parts of compound anti-fogging agent (compound agent C, ratio 1:3), 20 parts of porous adsorbent carrier (porous silica C, DBP 200ml / 100g, particle size 15μm), 6 parts of microcapsule capping agent (oxidized polyethylene wax), and 5 parts of functional additives.

[0066] Preparation steps:

[0067] Steps S1 to S5 are the same as in the original embodiment.

[0068] S6. Extrusion Granulation: The premixed material is added to a twin-screw extruder. The length-to-diameter ratio (L / D) of this twin-screw extruder is set to 48:1 (supporting the upper limit of the L / D ratio). Temperature settings: conveying section 120℃, melt plasticizing section 145℃, dispersion and mixing section 160℃, die 150℃. Extrusion granulation is performed at a screw speed of 400 rpm and a vacuum degree of -0.08 MPa at the vacuum exhaust port.

[0069] Example 4:

[0070] This embodiment aims to verify the applicability of different resin types and carrier types.

[0071] Raw material ratio:

[0072] 55 parts of polyethylene matrix resin (LLDPE, MFR10.0), 25 parts of compound anti-fogging agent (compound agent B, ratio 1:2), 12 parts of porous adsorption carrier (diatomaceous earth, DBP 230ml / 100g, particle size 12μm), 4 parts of microcapsule capping agent (high-density polyethylene wax), and 3 parts of functional additives.

[0073] Preparation steps:

[0074] Steps S1 to S5 are the same as in the original embodiment.

[0075] S6. Extrusion Granulation: The premixed material is added to a twin-screw extruder. The length-to-diameter ratio (L / D) of the twin-screw extruder is set to 40:1. The process parameters are consistent with those in Example 1, with a vacuum degree of -0.07MPa. After air-cooling, stretching, pelletizing, and drying, PE anti-fogging masterbatch is obtained.

[0076] Comparative Example 1:

[0077] The difference compared to Example 1 is that no microcapsule capping agent was added.

[0078] Specifically, during the preparation process, after the loading and adsorption are completed, the carrier that has adsorbed the compound anti-fogging agent is directly cooled and then mixed with LDPE resin and functional additives. The other raw material types, ratios and process parameters are the same as in Example 1.

[0079] Comparative Example 2:

[0080] The difference from Example 1 is that the preparation process is different, and the in-situ melt end-capping process was not used.

[0081] Specifically, the polyethylene matrix resin, compounded anti-fogging agent, porous adsorbent carrier, microcapsule capping agent, and functional additives were all added to a high-speed mixer at once. After being mixed evenly at 50°C, the mixture was directly discharged without heating to 105°C for melting and capping or subsequent rapid cooling. The resulting mixture was then directly fed into a twin-screw extruder for granulation, and all other steps were the same as in Example 1.

[0082] Comparative Example 3:

[0083] The difference compared to Example 1 is that the type of porous adsorption carrier has been changed.

[0084] Specifically, an equal amount of ordinary heavy calcium carbonate (non-porous structure, DBP oil absorption value of only 45ml / 100g) was used to replace the porous silica in Example 1, and the other raw material types, ratios and process parameters were the same as in Example 1.

[0085] Comparative Example 4:

[0086] The difference compared to Example 1 is that the type of microcapsule capping agent has been changed.

[0087] Specifically, an equal amount of low-melting-point paraffin wax was used to replace the high-density polyethylene wax in Example 1. Because paraffin wax has a low melting point, the mixer was heated to 65°C for melting and mixing; all other aspects were the same as in Example 1.

[0088] Test Example 1: Processing Stability and Masterbatch Appearance Test

[0089] This test aims to evaluate the process stability and finished product appearance of the PE anti-fogging masterbatches prepared in Examples 1-3 and Comparative Examples 1-4 during extrusion processing. The specific test steps and evaluation indicators are as follows:

[0090] Host current fluctuation test:

[0091] The masterbatch sample to be tested was added into a co-rotating twin-screw extruder. The screw speed was set to 300 rpm, and the temperature settings of each section were consistent with those in Example 1. After the extruder reached thermal equilibrium and the output stabilized, the main unit current data was recorded continuously for 30 minutes at a sampling frequency of once per minute, for a total of 30 current values.

[0092] The host current fluctuation rate is calculated using the formula Calculate, where, For current fluctuation rate, To record the maximum current value within the period, This is the minimum current value. This represents the average current value. A higher value indicates more severe screw slippage and less stable machining.

[0093] Feed accumulation observation at the feed inlet:

[0094] After the extruder has been running continuously for 2 hours, visually inspect the feed port and hopper connection of the extruder.

[0095] The evaluation criteria are divided into three levels:

[0096] No material accumulation: The metal surface of the feed port is dry, with no powder accumulation or liquid seepage.

[0097] Slight accumulation of material: A small amount of powder or a trace of oily substance adheres to the edge of the feed inlet.

[0098] Severe material accumulation: There is obvious accumulation of wet powder clumps or overflow of liquid additives at the feed inlet.

[0099] Masterbatch apparent state test:

[0100] Randomly select 200g of the freshly produced and cooled masterbatch, spread it flat on qualitative filter paper, and let it stand for 24 hours in a constant temperature and humidity environment.

[0101] The evaluation criteria are divided into three levels:

[0102] Dry: There is no sticking between masterbatch particles and no oil spots on the filter paper.

[0103] Slight adhesion: There is slight adhesion between the masterbatch particles, but they are easy to separate, and the filter paper has scattered oil spots.

[0104] Oily / Adhesive: Masterbatch particles clump together and are difficult to separate, or feel oily to the touch, and filter paper is soaked with oil over a large area.

[0105] The test results are detailed in Table 1.

[0106] Table 1: Test Results of Processing Stability and Masterbatch Apparent Properties

[0107] Group Host current fluctuation rate R (%) Material accumulation at the feed inlet apparent state of masterbatch Remark Example 1 1.24 No material accumulation dry Mid-range value, excellent overall performance Example 2 0.86 No material accumulation dry MFR has low viscosity and high current fluctuation, but it is controllable. Example 3 1.95 No material accumulation dry MFR has high fluidity and good oil absorption value, but it is effective at capping. Example 4 1.35 No material accumulation dry LLDPE has good processability. Comparative Example 1 12.43 Severe material accumulation Oily / sticky - Comparative Example 2 4.18 Slight material accumulation Slightly sticky - Comparative Example 3 8.72 Severe material accumulation Oily / sticky - Comparative Example 4 7.56 Severe material accumulation Slightly sticky -

[0108] Note: "-" in the table indicates that the test item has no comments.

[0109] Results analysis:

[0110] According to the test results in Table 1, the main unit current fluctuation rate of Examples 1 to 3 was low (0.86% to 1.95%), there was no material accumulation at the feed port, and the masterbatch appeared dry. The main unit current fluctuation rate of Example 4 was 1.35%, and the masterbatch appeared dry.

[0111] In contrast, Comparative Example 1, which did not contain microcapsule capping agents, and Comparative Example 3, which used a non-porous carrier, exhibited higher main unit current fluctuations (12.43% and 8.72%, respectively), accompanied by severe material accumulation at the feed inlet and greasy / adhesive surface phenomena on the finished product. Comparative Example 2, which used a direct mixing process, and Comparative Example 4, which used low-melting-point paraffin, showed higher main unit current fluctuations than the example groups, and also exhibited varying degrees of material accumulation or adhesion.

[0112] Test Example 2: Thin Film Optical Performance Testing

[0113] This test aims to evaluate the optical properties and appearance quality of the masterbatches prepared in Examples 1-3 and Comparative Examples 1-4 after blow molding. The specific test steps and evaluation indicators are as follows:

[0114] Thin film sample preparation:

[0115] The masterbatch sample to be tested was mixed with low-density polyethylene resin at a weight ratio of 4:96. The mixture was then added to a single-screw blown film machine for blow molding. The blown film machine had a die head diameter of 100 mm, a die gap of 0.8 mm, a screw diameter of 45 mm, and a length-to-diameter ratio of 28:1.

[0116] Processing temperature settings: Zone 1 140℃, Zone 2 160℃, Zone 3 175℃, Die head 170℃.

[0117] The blow-up ratio was controlled at 2.5:1, and the traction speed was controlled at 8m / min, resulting in a single-layer polyethylene film with a thickness of 0.08±0.005mm.

[0118] Transmittance and haze tests:

[0119] The film samples were tested using a haze meter. Five test points at different locations were randomly selected on each group of film samples, and their transmittance and haze were measured respectively. The arithmetic mean of the five measurements was taken as the final result.

[0120] Crystal point statistics:

[0121] Cut a film sample with an area of ​​1 square meter, and visually count the number of unplasticized particles or agglomerates with a diameter greater than 0.5 mm on the film surface under backlight conditions. Repeat the test 3 times and take the average value.

[0122] The test results are detailed in Table 2.

[0123] Table 2: Test Results of Thin Film Optical Properties and Appearance Quality

[0124] Group Light transmittance (%) Haze (%) Number of crystal points (per m²) Example 1 92.3 4.2 3 Example 2 91.8 3.9 2 Example 3 90.1 5.6 7 Example 4 90.5 6.1 5 Comparative Example 1 85.4 12.8 48 Comparative Example 2 88.2 9.1 25 Comparative Example 3 76.8 35.4 16 Comparative Example 4 86.5 10.3 32

[0125] Results analysis:

[0126] As shown in Table 2, the films prepared in Examples 1 to 3 all had a light transmittance of over 90%, a haze of less than 6%, and a relatively small number of crystal points. The film in Example 4 had a light transmittance of 90.5% and a haze of 6.1%.

[0127] The films of Comparative Example 1 (without end-capping agent) and Comparative Example 2 (without in-situ melt end-capping process) had lower light transmittance (85.4% and 88.2%, respectively) and higher haze (12.8% and 9.1%, respectively), and more crystal points than the Example group. Comparative Example 3 (ordinary calcium carbonate support) had the lowest light transmittance (76.8%) and the highest haze (35.4%). The optical performance of Comparative Example 4 was between that of the Examples and Comparative Example 1.

[0128] Test Example 3: Anti-fogging performance test

[0129] This test aims to evaluate the onset speed and duration of the anti-fogging function of the masterbatches prepared in Examples 1-3 and Comparative Examples 1-4 in thin film applications. The specific test steps and evaluation indicators are as follows:

[0130] High-temperature anti-fogging performance test: Pour 800 mL of distilled water into a 1000 mL beaker and place the beaker in a constant temperature water bath, controlling the water temperature at 60±1℃. Cut the film sample to be tested into a circle, cover the mouth of the beaker and fix it with a rubber band, with the inner surface of the film facing the water surface, so that the plane of the film is inclined at a 15-degree angle to the horizontal plane.

[0131] Initial drop time: Record the time from the start of the test to the formation of a continuous water film from the water droplet condensing on the inner surface of the film and the first drop of water sliding down the inclined surface. The shorter the time, the faster the anti-fogging agent migrates to the surface and the more quickly it takes effect.

[0132] Failure time: Observe the film surface condition daily. When more than 50% of the inner surface of the film exhibits opaque haze, or when hanging water droplets larger than 2 mm in diameter appear and no longer spread into a water film, the anti-fogging function is deemed to have failed. Record the number of days from the start of the test to failure.

[0133] Room temperature anti-fogging performance test:

[0134] A simulated greenhouse frame was constructed, and the film sample was covered on the frame and placed in an outdoor natural environment, while maintaining a high humidity environment inside the film.

[0135] Record the number of days from the start of covering until visible fog or water droplets appear on the inner surface of the film, as the normal temperature failure time.

[0136] The test results are detailed in Table 3.

[0137] Table 3: Test Results of Anti-fogging Performance

[0138] Group Initial dripping time at high temperature (min) High-temperature failure time (days) Failure time at room temperature (days) Remark Example 1 28 145 182 The compound ratio is 1:2 Example 2 35 138 175 The compound ratio is 1:1 (the higher proportion of Sipan results in a slightly slower onset of action). Example 3 22 153 194 The compound ratio is 1:3 (high in polyglycerol esters, faster onset of action, but slightly faster loss). Example 4 25 140 178 diatomaceous earth / LLDPE system Comparative Example 1 12 48 65 - Comparative Example 2 25 92 115 - Comparative Example 3 >120 (individual teardrop shape) <1 <3 - Comparative Example 4 16 68 84 -

[0139] Note: "-" in the table indicates that the test item has no comments.

[0140] Results analysis:

[0141] Table 3 shows that the initial dripping time at high temperature for Examples 1 to 3 was between 22 and 35 minutes, the high-temperature failure time was over 138 days, and the room-temperature failure time was over 175 days. The high-temperature failure time for Example 4 was 140 days.

[0142] Comparative Example 1 had a shorter initial high-temperature drop time (12 minutes), but its high-temperature failure time was only 48 days. Comparative Example 2 had a high-temperature failure time of 92 days, which was shorter than that of the Example Group. Comparative Example 3 exhibited hydrophobicity in the early stages of testing (initial drop time > 120 minutes) and failed quickly. Comparative Example 4 had a high-temperature failure time of 68 days, which was shorter than that of Examples 1 to 4.

Claims

1. A method for preparing a PE anti-fogging masterbatch composition, characterized in that, Includes the following steps: S1. Raw material preparation: Prepare the following raw materials by weight: 40-70 parts of polyethylene matrix resin, 20-30 parts of compound anti-fogging agent, 5-20 parts of porous adsorption carrier, 2-6 parts of microcapsule capping agent, and 1-5 parts of functional additives. S2. Carrier preheating: The porous adsorption carrier is added to a mixing device and preheated by stirring at a temperature of 45-55°C. S3, Loading Adsorption: Maintain the temperature at 45-55℃, spray the compound anti-fogging agent into the mixing device and mix it with the porous adsorption carrier, so that the compound anti-fogging agent is adsorbed into the pores of the porous adsorption carrier; S4. In-situ capping: Add the microcapsule capping agent to the mixture obtained in step S3, raise the temperature of the mixing equipment to 95-110°C and stir, so that the microcapsule capping agent melts and coats the surface of the porous adsorption carrier, and then rapidly cool the material temperature to below 40°C to obtain modified powder. S5. Matrix mixing: Under conditions where the temperature is below 45°C, the modified powder obtained in step S4 is mixed evenly with the polyethylene matrix resin and functional additives to obtain a premix. S6. Extrusion granulation: The premixed material is added to a twin-screw extruder and melt-extruded at a temperature range of 100-160°C. After pelleting and drying, PE anti-fogging masterbatch is obtained.

2. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, The microcapsule capping agent is selected from one or more of high-density polyethylene wax, oxidized polyethylene wax, or polypropylene wax. Furthermore, the microcapsule capping agent has a melting point range of 90–115°C and a crystallinity greater than 80%.

3. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, The porous adsorbent carrier is porous silica or diatomaceous earth, with a dibutyl phthalate oil absorption value of 200-350 ml / 100 g and an average particle size of 5-15 μm.

4. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, The compound antifogging agent is composed of sorbitan fatty acid ester compounds and polyglycerol fatty acid ester compounds in a mass ratio of 1:1 to 1:3; The polyethylene matrix resin is low-density polyethylene or linear low-density polyethylene with a melt flow rate between 2.0 and 20.0 g / 10 min.

5. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, In step S3, the compound anti-fogging agent is added in the following manner: The compound anti-fogging agent is preheated to 40°C and sprayed into the mixing equipment at a rate of 1.0–2.0 kg / min using a spraying device.

6. The method for preparing the PE anti-fogging masterbatch composition according to claim 5, characterized in that, In step S3, the mixing device is maintained under a vacuum negative pressure with an absolute pressure of 0.06 to 0.08 MPa.

7. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, In step S4, the process of raising the temperature of the mixing equipment to 95-110°C and stirring specifically involves: Set the stirring speed to 800-1200 rpm and mix for 3-5 minutes.

8. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, In step S4, the subsequent process of rapidly cooling the material temperature to below 40°C specifically involves: The material is discharged into a low-speed cold mixer and cooled for 5 to 10 minutes at a speed of 200 to 400 rpm and a circulating cooling water temperature of 10 to 20°C.

9. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, In step S6, the temperature of each section of the twin-screw extruder is set as follows: The conveying section is 100-120℃, the melting and plasticizing section is 130-145℃, the dispersing and mixing section is 145-160℃, and the metering and extrusion section and die are 140-150℃.

10. The method for preparing the PE anti-fogging masterbatch composition according to claim 1, characterized in that, In step S6, the length-to-diameter ratio of the twin-screw extruder is 36:1 to 48:1, and devolatilization is performed through a vacuum exhaust port during the extrusion process, with a vacuum degree of not less than 0.06 MPa.