Plastic master batch based on aragonite rod-like nano calcium carbonate as well as preparation method and application of plastic master batch

Abstract

The invention belongs to the field of polymer composite materials, and particularly relates to a plastic master batch based on aragonite type rod-like nano calcium carbonate as well as a preparation method and application of the plastic master batch. The plastic master batch contains aragonite type rod-like nano calcium carbonate, a polyethylene blend, aluminate, a lubricant and an antioxidant. The preparation method comprises the following steps: modifying aragonite rod-like nano calcium carbonate with aluminate in a high-speed mixer; adding the polyethylene blend, the modified nano calcium carbonate, the lubricant and the antioxidant into an internal mixer in stages, and carrying out internal mixing and blending; and extruding the mixed material by a twin-screw extruder, and pelletizing to obtain the master batch. The aragonite type rod-like nano calcium carbonate and the aluminate are used, the nano calcium carbonate is pretreated through the aluminate, and by combining a banburying blending-double-screw segmented temperature control technology, uniform dispersion and interface enhancement under high filling are achieved; the master batch has high whiteness and excellent mechanical properties, and is suitable for a film blowing material; and the composite material can be used for food-grade plastic bag / film materials, and has food-grade safety.

Description

Technical Field

[0001] This application belongs to the field of polymer composite materials, specifically relating to a plastic masterbatch based on aragonite rod-shaped nano-calcium carbonate, its preparation method, and its application. Background Technology

[0002] In this field, the filling material used in transparent plastic bags is usually salt white granules (sodium sulfate-based material). However, plastic bags filled with salt white granules will produce a "sodium sulfate precipitation" phenomenon when exposed to moisture, causing the plastic bags to turn white and shed powder. This has become the most troublesome pain point in the industry and a difficult point that hinders the green and healthy development of plastic bags.

[0003] Currently, the plastic masterbatches used in blown film materials for environmentally friendly packaging mainly use polyolefins or polyolefin blends as carriers and calcium carbonate as fillers. Calcium carbonate, as a commonly used inorganic powder filler for plastics, can reduce product production costs, improve the dimensional stability, heat resistance, and tensile strength of plastic products, and also has the effects of light diffusion and matting, as well as improving the processability and moldability of plastics. It has many advantages that other powder materials do not possess.

[0004] However, traditional plastic masterbatches contain low levels of calcium carbonate (typically <40%), making it difficult to achieve a performance balance under high filler content (>70%). Furthermore, nano-calcium carbonate is prone to agglomeration, exhibits poor dispersibility, poor processing flowability, and low toughness, resulting in whitening and tearing of the manufactured plastic bags / films. Improving the performance of plastic masterbatches and blown film materials with high calcium carbonate filler content is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this application provides a plastic masterbatch based on aragonite-type rod-shaped nano-calcium carbonate, its preparation method, and its application. The plastic masterbatch is a high-filling, low-cost, and environmentally friendly calcium-based plastic masterbatch that can solve problems such as poor dispersion of nano-calcium carbonate, weak interfacial bonding, processing discoloration, and blown film surface defects. It can be used as a blown film material for plastic bags / films to prepare environmentally friendly packaging materials.

[0006] In a first aspect, this application provides a plastic masterbatch containing aragonite rod-shaped nano-calcium carbonate, a polyethylene blend, an aluminate, a lubricant, and an antioxidant. The aragonite rod-shaped nano-calcium carbonate content is 70-80%, the polyethylene blend content is 15-25%, the aluminate content is 0.8-1.5%, the lubricant content is 1.5-4%, and the antioxidant content is 1-2%. All percentages are by mass. The sum of the contents of all components in the plastic masterbatch is 100%.

[0007] In one set of embodiments, the content of aragonite-type rod-shaped nano-calcium carbonate in the plastic masterbatch can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%; the content of polyethylene blend can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%; the content of aluminate can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%; and the lubricant content can be 1.5%. The percentages are 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, and 4.0%; the antioxidant content can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2.0%.

[0008] In one embodiment, the aragonite-type rod-shaped nano-calcium carbonate is 90%-100% aragonite-type rod-shaped calcium carbonate single crystal particles; preferably, the average minor diameter is 0.08-0.15 μm, and the average major diameter is 0.8-1.5 μm; preferably, the BET specific surface area of ​​the aragonite-type rod-shaped nano-calcium carbonate is 12-22 m². 2 / g; Preferably, the shape of the aragonite-type rod-shaped nano-calcium carbonate includes hexagonal prism rod-shaped particles, such as the shape of the aragonite-type rod-shaped nano-calcium carbonate being hexagonal prism rod-shaped particles.

[0009] In one set of embodiments, the polyethylene blend is a blend of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE); specifically, the mixing ratio of LDPE and LLDPE in the polyethylene blend is 1:2-8, such as 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, preferably 1:3-5.

[0010] In one embodiment, the lubricant comprises one or more of wax, fatty acids, and fatty acid salts. The wax includes, but is not limited to, one or more of paraffin wax, polyethylene wax, oxidized polyethylene wax, semi-refined paraffin wax, pyrolytic polyethylene wax, and Fischer-Tropsch wax; the fatty acid includes, but is not limited to, one or more of stearic acid and palmitic acid; and the fatty acid salt includes, but is not limited to, stearates and palmitic acids, such as one or more of calcium stearate and zinc stearate. The carboxyl groups in the fatty acid or fatty acid salt bond with calcium ions on the surface of calcium carbonate to form a hydrophobic monolayer, reducing surface energy, increasing the affinity between calcium carbonate and polyethylene mixtures, preventing agglomeration, and improving internal lubricity; paraffin wax can improve melt flowability, reduce adhesion, and improve external lubricity. The total content of waxes (such as one or more of paraffin wax, polyethylene wax, and oxidized polyethylene wax) is 1-3%, which can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%. The total content of fatty acids / fatty acid salts is 0.5-1%, which can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%.

[0011] The lubricant comprises one or more of paraffin wax, polyethylene wax, oxidized polyethylene wax, stearic acid, and stearate; preferably, it comprises one or more of paraffin wax, polyethylene wax, and oxidized polyethylene wax, and one or more of stearic acid and calcium stearate. The total content of paraffin wax, polyethylene wax, and oxidized polyethylene wax is 1-3%, and the total content of stearic acid and stearate is 0.5-1%.

[0012] In one set of embodiments, the antioxidant includes, but is not limited to, one or more of phosphite antioxidants, hindered phenolic antioxidants, pentaerythritol ester antioxidants, and compound antioxidants, such as antioxidant B225 (trade name: B225, produced by BASF, is a high-efficiency compound antioxidant composed of 50% Irganox 1010 (hindered phenolic primary antioxidant) and 50% Irgafos 168 (phosphite auxiliary antioxidant), antioxidant 168 (tris[2,4-di-tert-butylphenyl] phosphite), antioxidant 1010 (tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester) and its similar alternatives.

[0013] In one embodiment, the plastic masterbatch contains aragonite rod-shaped nano-calcium carbonate, a polyethylene blend, aluminate, wax (such as one or more of paraffin wax, polyethylene wax, and oxidized polyethylene wax), stearic acid and / or calcium stearate, and an antioxidant. The aragonite rod-shaped nano-calcium carbonate content is 70-80%, the polyethylene blend content is 15-25%, the aluminate content is 0.8-1.5%, the wax content is 1-3%, the stearic acid and / or calcium stearate content is 0.5-1%, and the antioxidant content is 1-2%. Preferably, the aragonite rod-shaped nano-calcium carbonate content is 75%, the polyethylene blend content is 20%, the aluminate content is 1.2%, the wax content is 2%, the stearic acid and / or calcium stearate content is 0.8%, and the antioxidant content is 1.5%. All percentages are by mass. The polyethylene blend is a blend of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), preferably a blend of LDPE and LLDPE in a 1:5 ratio. The antioxidant is B225 antioxidant.

[0014] In one embodiment, the plastic masterbatch contains aluminate coating on the surface of aragonite rod-shaped nano-calcium carbonate to form modified nano-calcium carbonate. Specifically, the plastic masterbatch is obtained by dry modification of aragonite rod-shaped nano-calcium carbonate with aluminate, coating the surface of the aragonite rod-shaped nano-calcium carbonate with aluminate to form modified nano-calcium carbonate, and then mixing and granulating it with polyethylene blend, lubricant, and antioxidant.

[0015] In a second aspect, this application provides a method for preparing the plastic masterbatch described in the first aspect, comprising the following steps:

[0016] Step 1: Pretreatment of nano-calcium carbonate

[0017] Aragonite rod-shaped nano-calcium carbonate is dry-modified with aluminate in a high-speed mixer, and aluminate is coated on the surface of aragonite rod-shaped nano-calcium carbonate to form modified nano-calcium carbonate.

[0018] Step 2: Intensive blending

[0019] In an internal mixer, polyethylene blends, modified nano-calcium carbonate, lubricants, and antioxidants are added in stages and then mixed to obtain a mixture.

[0020] Step 3:

[0021] The mixture obtained in step 2 is fed into a twin-screw extruder with a temperature gradient of 140-160℃ in the feeding section, 160-170℃ in the melting section, 170-175℃ in the dispersing section, and 160-165℃ in the die. Vacuum degassing and pelletizing are then performed to obtain plastic masterbatch.

[0022] The method for preparing plastic masterbatch described in this application involves first modifying and pretreating aragonite rod-shaped nano-calcium carbonate with an aluminate coupling agent in a high-speed mixer, and then interacting with lubricants such as stearic acid and polyethylene wax during the intensive mixing process. The aluminate coupling agent and the lubricant act in stages, combining chemical bonding and physical lubrication. Furthermore, the twin-screw segmented temperature control process can balance the dispersibility and flowability of nano-calcium carbonate in the masterbatch when it is highly filled.

[0023] In one set of embodiments, in step 1, the temperature for dry modification in the high-speed mixer is 70-100℃ (70, 75, 80, 85, 90, 95, 100℃, preferably 80-90℃), the rotation speed is 1000-1500rpm (e.g., 1000, 1100, 1200, 1300, 1400, 1500rpm, preferably 1200rpm), and the time is 5-20 minutes (e.g., 5, 8, 10, 12, 15, 18, 20 minutes, preferably 10-15 minutes).

[0024] In one set of embodiments, step 2, the phased addition specifically refers to the sequential addition of polyethylene blend, modified nano-calcium carbonate, lubricant, and antioxidant; preferably, the sequential addition of polyethylene blend, modified nano-calcium carbonate, one or more of fatty acids / fatty acid salts, wax, and antioxidant. The mixing temperature is 140-180℃ (e.g., 140, 145, 150, 155, 160, 165, 170, 175, 180℃, preferably 150-160℃), the rotation speed is 50-100rpm (e.g., 50, 60, 70, 80, 90, 100rpm, preferably 70-80rpm), and the time is 10-30 minutes (e.g., 10, 12, 15, 18, 20, 22, 25, 28, 30 minutes, preferably 18-20 minutes).

[0025] In one embodiment, in step 3, the preferred temperature gradient is 160°C for the feeding section, 170°C for the melting section, 175°C for the dispersing section, and 165°C for the die. The screw speed is 200-400 rpm (e.g., 200, 220, 250, 280, 300, 320, 350, 380, 400 rpm, preferably 300-350 rpm), and the vacuum exhaust pressure is -0.05 to -0.10 MPa (e.g., -0.05, -0.06, -0.07, -0.08, -0.09, -0.10 MPa, preferably -0.08 to -0.09 MPa). In step 3, water-cooled pelletizing is used, with a particle size of 2-5 mm; after water-cooled pelletizing, drying is performed, and the moisture content of the resulting masterbatch is <0.05%; specifically, the water-cooled pelletizing steps are screw extrusion, water-cooled drawing, air drying, and pelletizing.

[0026] In a third aspect, this application provides an application of a plastic masterbatch for use in blown film materials, such as in the preparation of plastic bags and plastic films; as agricultural mulch film, food preservation film, food preservation bags, express delivery bags, etc.

[0027] Compared with the prior art, this application has the following advantages and beneficial effects:

[0028] The plastic masterbatch of this application uses aragonite rod-shaped nano-calcium carbonate. The high aspect ratio (>5:1) of aragonite rod-shaped nano-calcium carbonate can improve mechanical anisotropy. After modification and pretreatment of the aragonite rod-shaped nano-calcium carbonate with an aluminate coupling agent, it is mixed with lubricants such as stearic acid, combining chemical bonding and physical lubrication. Furthermore, by combining a mixing-twin-screw segmented temperature control process, uniform dispersion and interface reinforcement can be achieved under high calcium carbonate filling (≥70%). The resulting plastic masterbatch has high whiteness (ΔE<1.5), excellent mechanical properties (tensile strength ≥14MPa), and adaptability to blown film processing. It will not exhibit blown film surface defects and is suitable for the field of environmentally friendly packaging materials.

[0029] Aragonite-type rod-shaped nano-calcium carbonate exhibits excellent dispersibility, enabling plastic products to maintain transparency and smooth processing even at high filler contents, thus completely solving the "exudation" problem of existing transparent plastic bags. It can significantly reduce the production cost of plastic products, while also improving the toughness, strength, wear resistance, and impact resistance of plastic products, and reducing shrinkage deformation.

[0030] Since the aragonite-type rod-shaped nano-calcium carbonate used in this application does not contain phthalates, the plastic masterbatch of this application, according to GB 31604.30-2016 "National Food Safety Standard - Determination of Phthalate Esters and Migration in Food Contact Materials and Articles", did not contain phthalates and can be used to prepare food-grade plastic bags / films, thus possessing food safety. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0032] The terms “containing,” “comprising,” and “including” as used in this application are synonyms and are inclusive or open-ended, and do not exclude additional, uncited members, elements, or method steps.

[0033] The range of values ​​represented by endpoints in this application includes all values ​​and fractions contained within that range, as well as the endpoints referenced.

[0034] The concentration values ​​mentioned in this application include fluctuations within a certain range. For example, fluctuations are allowed within a corresponding precision range. For instance, 2% may fluctuate within ±0.1%. For larger values ​​or values ​​that do not require overly precise control, even greater fluctuations are permitted.

[0035] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0036] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments and should be understood not to limit the scope of protection of this application. In this application, "optional" and "optional" mean that they are optional, that is, they are selected from either "with" or "without" parallel solutions. If multiple "optional" or "optional" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" or "optional" is independent.

[0037] Aragonite-type rod-shaped nano-calcium carbonate

[0038] Based on their crystal structures, crystalline calcium carbonate can be classified into calcite-type calcium carbonate, aragonite-type calcium carbonate, and spherulite-type calcium carbonate.

[0039] Aragonite calcium carbonate is unstable and often transforms into calcite. In nature, aragonite calcium carbonate is most commonly found in the nacreous layer of shells and in pearls. It is a metastable crystalline material, generally appearing as single-crystal needle-like or rod-shaped particles. Aragonite rod-shaped calcium carbonate has certain morphological characteristics such as a certain aspect ratio. Rod-shaped calcium carbonate has some similarities to spindle-shaped, whisker-shaped, or fibrous calcium carbonate, but there are also essential differences. Spindle-shaped light calcium carbonate has a spindle shape that is pointed at both ends and larger in the middle. Rod-shaped calcium carbonate is slightly longer than spindle-shaped light calcium carbonate, with rods of the same size at both ends and in the middle.

[0040] Aragonite-type rod-shaped calcium carbonate is mostly prepared using methods such as metathesis reaction, urea hydrolysis, calcium bicarbonate pyrolysis, and carbonation. Chinese patent applications CN115072757A and CN115092948A disclose micro-fine rod-shaped aragonite-type calcium carbonate and their preparation methods. The "aragonite-type rod-shaped nano-calcium carbonate" used in this application can be the micro-fine rod-shaped nano-calcium carbonate disclosed in the aforementioned patent applications. Preferably, the "aragonite-type rod-shaped nano-calcium carbonate" is 90%-100% aragonite-type rod-shaped calcium carbonate single crystal particles; preferably, the average minor diameter of the aragonite-type rod-shaped nano-calcium carbonate is 0.08-0.15 μm, and the average major diameter is 0.8-1.5 μm; preferably, the BET specific surface area of ​​the aragonite-type rod-shaped nano-calcium carbonate is 12-22 m². 2 / g; Preferably, the shape of the aragonite-type rod-shaped nano-calcium carbonate includes hexagonal prism-shaped rod-shaped particles, such as the shape of the aragonite-type rod-shaped nano-calcium carbonate being hexagonal prism-shaped rod-shaped particles.

[0041] Example 1: Preparation of Plastic Masterbatch Based on Aragonite Rod-shaped Nano-Calcium Carbonate

[0042] Aragonite-type rod-shaped nano-calcium carbonate:

[0043] Aragonite-type rod-shaped calcium carbonate single crystals were used, with an average minor diameter of 0.08-0.15 μm and an average major diameter of 0.8-1.5 μm; the BET specific surface area was 12-22 m². 2 / g; consists of hexagonal prism-shaped rod-shaped particles.

[0044] Raw material ratio for plastic masterbatch:

[0045] Aragonite-type rod-shaped nano-calcium carbonate 75%, LDPE+LLDPE (1:5) blended PE 20%, aluminate 1.2%, OPE (oxidized polyethylene wax) 2%, stearic acid 0.8%, B225 1.5%.

[0046] Preparation of plastic masterbatch:

[0047] Step 1: Pretreatment of nano-calcium carbonate

[0048] Aragonite-type rod-shaped nano-calcium carbonate was dry-modified with an aluminate coupling agent in a high-speed mixer at 80-90℃, 1200 rpm, for 10-15 minutes.

[0049] Step 2: Intensive blending

[0050] The internal mixer temperature was 160℃. Blended PE, modified nano-calcium carbonate, stearic acid, oxidized polyethylene wax, and antioxidant B225 were added sequentially and mixed for 20 minutes at a speed of 75 rpm.

[0051] Step 3: Twin-screw extrusion granulation

[0052] Using a twin-screw extruder, the temperature gradient is: 160℃ in the feeding section → 170℃ in the melting section → 175℃ in the dispersing section → 165℃ in the die.

[0053] Vacuum exhaust (-0.08~-0.09MPa), screw speed 320rpm, water cooling, strip drawing, air drying, pelletizing, drying (particle moisture content <0.05%), to obtain plastic masterbatch with a particle size of 2-5mm.

[0054] Example 2: Performance Testing of Plastic Masterbatch Based on Aragonite Rod-shaped Nano-Calcium Carbonate

[0055] Test item 1: Melt mass flow rate

[0056] 1.1 Testing conditions

[0057] Drying conditions: 85℃, 4h; Testing conditions: 190℃, 5kg.

[0058] 1.2 Detection Methods and Results

[0059] The melt flow rate was determined according to GB / T 3682.1-2018 "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method", and the melt mass flow rate was 2.8 g / 10 min.

[0060] Test item 2: Compressive strength

[0061] 2.1 Testing conditions

[0062] Detection speed: 1 mm / min.

[0063] 2.2 Laboratory Environmental Conditions

[0064] 23±2℃, 50±5%RH.

[0065] 2.3 Detection methods and results

[0066] The compressive strength was determined according to GB / T 44750-2024 "Measurement of Compressive Strength of Particles" and was 126 N.

[0067] Test item 3: Notched impact strength of cantilever beam

[0068] 3.1 Testing conditions

[0069] The test specimens were cut from the injection-molded samples.

[0070] Specimen: ISO 180 / 1A (notch preparation: machining); specimen thickness: 4 mm; pendulum energy: 1 J; impact strength: 3.46 m / s.

[0071] 3.2 Laboratory Environmental Conditions

[0072] 23±2℃, 50±5%RH.

[0073] 3.3 Detection methods and results

[0074] The impact strength of the cantilever beam was determined according to GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams", and the notched impact strength was 4.1 KJ / m. 2 C (Complete destruction).

[0075] Test item 4: Tensile strength

[0076] 4.1 Testing conditions

[0077] All test samples were injection molded.

[0078] Sample type: 1A; Sample thickness: 4mm; Detection speed: 50mm / min; Initial fixture spacing: 115mm.

[0079] 4.2 Laboratory Environmental Conditions

[0080] 23±2℃, 50±5%RH.

[0081] 4.3 Detection methods and results

[0082] The tensile strength was determined according to GB / T 1040.1-2025 & GB / T 1040.2-2022, and was 14.7 MPa.

[0083] Test item 5: Shear strength

[0084] 5.1 Testing conditions

[0085] Sample size: 50mm×50mm×4.2mm; Detection speed: 1mm / min; Perforation diameter: 25.4mm.

[0086] 4.2 Laboratory Environmental Conditions

[0087] 23±2℃, 50±5%RH.

[0088] 4.3 Detection methods and results

[0089] The shear strength was determined according to HG / T 3839-2006 "Plastics Shear Strength Test Method - Perforation Method", and the shear strength was 9.9 MPa.

[0090] Test item 6: Whiteness index

[0091] According to the QBT1126-2021 standard "Polyolefin Filler Masterbatch", the whiteness of the plastic masterbatch was tested using a whiteness meter, and the whiteness index was 88 (ΔE=1.2).

[0092] Example 3: Safety Test of Plastic Masterbatch Based on Aragonite Rod-shaped Nano-Calcium Carbonate

[0093] The plastic masterbatch was tested according to GB 31604.30-2016 "National Food Safety Standard - Determination of Phthalate Esters and Migration in Food Contact Materials and Articles". All test results were below the method limit of quantitation (0.1 mg / kg), and no phthalates were detected. This indicates that the plastic masterbatch described in this application can be used to prepare food-grade plastic bags / films for food contact.

[0094] Comparative Example 1 uses titanate coupling agent

[0095] The aluminate coupling agent in Example 1 was replaced with an equal proportion of titanate coupling agent to prepare a plastic masterbatch, and its performance was tested. The results showed that its color difference ΔE = 3.8. The results indicate that the plastic masterbatch obtained by modifying aragonite rod-shaped nano-calcium carbonate with titanate coupling agent has poor flowability, poor whiteness, and low transparency.

[0096] The embodiments of this application demonstrate that the plastic masterbatch uses aragonite-type rod-shaped nano-calcium carbonate. After modification and pretreatment of the aragonite-type rod-shaped nano-calcium carbonate with an aluminate coupling agent, it is mixed with lubricants such as stearic acid. Further combined with a tin-mixing-twin-screw segmented temperature-controlled process, the resulting plastic masterbatch exhibits high whiteness (ΔE < 1.5), excellent mechanical properties (tensile strength ≥ 14 MPa), and good compatibility with blown film processing. It does not exhibit blown film surface defects and is suitable for the field of environmentally friendly packaging materials. Furthermore, no phthalates were detected in the resulting plastic masterbatch, making it suitable for preparing food-grade plastic bags / films for food contact.

[0097] In the description of this specification, the terms "a specific embodiment," "a set of embodiments," "example," "specific example," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0098] The scope of protection of this application is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope and spirit of the invention. If such modifications and variations fall within the scope of the claims of this application and their equivalents, then the intent of this application also includes such modifications and variations.

Claims

1. A plastic masterbatch, characterized in that, It contains aragonite rod-shaped nano-calcium carbonate, polyethylene blend, aluminate, lubricant and antioxidant, wherein the content of aragonite rod-shaped nano-calcium carbonate is 70-80%, the content of polyethylene blend is 15-25%, the content of aluminate is 0.8-1.5%, the content of lubricant is 1.5-4%, and the content of antioxidant is 1-2%.

2. The plastic masterbatch according to claim 1, characterized in that, The aragonite-type rod-shaped nano-calcium carbonate has an average short diameter of 0.08-0.15 μm and an average long diameter of 0.8-1.5 μm; Preferably, the aragonite-type rod-shaped nano-calcium carbonate has a BET specific surface area of ​​12-22 m². 2 / g; Preferably, the aragonite-type rod-shaped nano-calcium carbonate comprises hexagonal prism rod-shaped particles.

3. The plastic masterbatch according to any one of claims 1-2, characterized in that, The polyethylene blend is a blend of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE). Preferably, the mixing ratio of the two is 1:2-8; More preferably, the mixing ratio of the two is 1:3-5.

4. The plastic masterbatch according to any one of claims 1-3, characterized in that, The lubricant comprises one or more of wax, fatty acids, and fatty acid salts; wherein the total content of wax is 1-3%, and the total content of fatty acids / fatty acid salts is 0.5-1%; Preferably, the lubricant comprises one or more of paraffin wax, polyethylene wax, and oxidized polyethylene wax, and one or more of stearic acid and calcium stearate.

5. The plastic masterbatch according to any one of claims 1-4, characterized in that, Aluminate esters are coated on the surface of aragonite rod-shaped nano-calcium carbonate to form modified nano-calcium carbonate; Preferably, the plastic masterbatch is obtained by dry modification of aragonite rod-shaped nano-calcium carbonate with aluminate, wherein the aluminate coats the surface of the aragonite rod-shaped nano-calcium carbonate to form modified nano-calcium carbonate, and then mixes and granulates it with polyethylene blend, lubricant and antioxidant.

6. The method for preparing plastic masterbatch according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Pretreatment of nano-calcium carbonate Aragonite rod-shaped nano-calcium carbonate is dry-modified with aluminate in a high-speed mixer, and aluminate is coated on the surface of aragonite rod-shaped nano-calcium carbonate to form modified nano-calcium carbonate. Step 2: Intensive blending In an internal mixer, polyethylene blends, modified nano-calcium carbonate, lubricants, and antioxidants are added in stages and then mixed to obtain a mixture. Step 3: The mixture obtained in step 2 is fed into a twin-screw extruder with a temperature gradient of 140-160℃ in the feeding section, 160-170℃ in the melting section, 170-175℃ in the dispersing section, and 160-165℃ in the die; vacuum degassing and pelletizing are then performed to obtain plastic masterbatch. Preferably, the temperature gradient is 160°C for the feeding section, 170°C for the melting section, 175°C for the dispersing section, and 165°C for the die head.

7. The preparation method according to claim 6, characterized in that, In step 1, the temperature for dry modification in the high-speed mixer is 70-100℃, the rotation speed is 1000-1500rpm, and the time is 5-20 minutes. Preferably, the dry modification temperature is 80-90℃, the rotation speed is 1200rpm, and the time is 10-15 minutes.

8. The preparation method according to claim 6 or 7, characterized in that, In step 2, the temperature of the internal mixing process is 140-180℃, the rotation speed is 50-100rpm, and the time is 10-30 minutes. Preferably, the mixing temperature is 150-160℃, the rotation speed is 70-80rpm, and the time is 18-20 minutes.

9. The preparation method according to any one of claims 6-8, characterized in that, In step 3, the screw speed is 200-400 rpm, the vacuum exhaust pressure is -0.05 to -0.10 MPa, and water-cooled pelletizing is used; Preferably, the screw speed is 300-350 rpm and the vacuum exhaust pressure is -0.08 to -0.09 MPa.

10. The application of the plastic masterbatch according to any one of claims 1-5, or the plastic masterbatch prepared by the preparation method according to any one of claims 6-9, characterized in that, It is used in blown film materials; preferably, it is used to prepare plastic bags / films.