High-toughness and high-fluidity PVC injection molding material and preparation method thereof

Abstract

The application relates to the technical field of PVC materials, in particular to a high-toughness high-fluidity PVC injection molding material and a preparation method thereof. The PVC injection molding material comprises the following raw materials in parts by weight: 100 parts of PVC, 0.3-2.5 parts of an internal lubricant, 0.1-1.5 parts of an external lubricant, 1-6 parts of a stabilizer, 8-15 parts of a toughening modifier, 0-6 parts of a plasticizer, 0-3 parts of an ACR processing aid and 0-15 parts of nano calcium carbonate; the toughening modifier comprises a first raw material and a second raw material; the first raw material comprises a first toughening agent, a second toughening agent and nano particles; the first toughening agent comprises one or more of CPE, EVA and nitrile rubber; the second toughening agent comprises one or more of MBS, ABS high glue powder and ACR; and the second raw material comprises zinc stearate. The application solves the problems of low notched impact strength, poor low-temperature toughness and poor processing fluidity of PVC products.

Description

Technical Field

[0001] This invention relates to the field of PVC material technology, specifically to a high-toughness, high-flowability PVC injection molding compound and its preparation method. Background Technology

[0002] As one of the earliest synthetic plastics used in industrial production and daily life, polyvinyl chloride (PVC) has been widely used in medical, home furnishing, agricultural production, and construction fields due to its excellent dimensional stability, acid and alkali corrosion resistance, flame retardancy, and dielectric properties. PVC products prepared with different formulations and processing techniques exhibit different physical states and mechanical properties. PVC products can be divided into two main categories: rigid PVC and flexible PVC. Rigid PVC has a larger market share (>60%) and is mainly used in the production of water supply and drainage pipe fittings, sheets, plastic door and window profiles, and electrical enclosures. However, because the PVC molecular structure contains a large number of C-Cl bonds, the intermolecular forces are strong, resulting in extremely poor toughness. At room temperature, the notched impact strength of pure PVC is only 3-4 KJ / m. 2 It is extremely prone to cracking under stress, and in particular, it cannot meet the construction requirements under the severe cold conditions in the north.

[0003] Currently, chemical and physical modifications are commonly used to improve the toughness of PVC products. Chemical modification, including copolymerization, crosslinking, and grafting, offers advantages such as significant modification effects and stable performance, but suffers from drawbacks such as complex processes and demanding equipment requirements. Physical modification involves directly incorporating elastomers, organic rigid particles, or nanofillers into PVC raw materials to improve product performance; this process is simple and efficient. Blending elastomers with PVC is simple and effective, but excessive amounts can negatively impact processability and other mechanical properties. Blending with organic rigid particles is also simple and effective, but costly and has limited application. Nanofillers such as nano-calcium carbonate can improve the impact strength of PVC to some extent, but excessive amounts can lead to agglomeration, reducing the material's impact strength. Therefore, developing a PVC injection molding compound with excellent low-temperature toughness, good processing flowability, and low cost remains a significant challenge. Summary of the Invention

[0004] To address the technical problems of poor low-temperature toughness of PVC materials, complex chemical modification processes requiring high-end equipment, and physical modification affecting processability or other mechanical properties or incurring high costs, this invention provides a high-toughness, high-flowability PVC injection molding compound and its preparation method, solving problems such as low notched impact strength, poor low-temperature toughness, easy agglomeration of nanoparticles, and poor processing flowability in PVC products.

[0005] In a first aspect, the present invention provides a high-toughness, high-flowability PVC injection molding compound, comprising the following raw materials in parts by weight:

[0006] 100 parts PVC, 0.3-2.5 parts internal lubricant, 0.1-1.5 parts external lubricant, 1-6 parts stabilizer, 8-15 parts toughening modifier, 0-6 parts plasticizer, 0-3 parts ACR processing aid, 0-15 parts nano calcium carbonate;

[0007] The toughening modifier includes a first raw material and a second raw material. The first raw material includes a first toughening agent, a second toughening agent, and nanoparticles. The first toughening agent includes one or more of chlorinated polyethylene (CPE), ethylene-vinyl acetate (EVA), and nitrile rubber. The second toughening agent includes one or more of methyl methacrylate-butadiene-styrene copolymer (MBS), acrylonitrile-butadiene-styrene copolymer (ABS) high-rubber powder, and acrylate polymers (ACR). The second raw material includes zinc stearate.

[0008] Furthermore, the amount of the second raw material used is 1%-5% of that of the first raw material.

[0009] Furthermore, the mass ratio of the first toughening agent, the second toughening agent, and the nanoparticles is 1-3:1-2:0.01-0.15.

[0010] Furthermore, the toughening modifier is obtained by ball milling the first raw material and the second raw material.

[0011] Furthermore, PVC is a polyvinyl chloride resin with an average degree of polymerization of 650-750.

[0012] Furthermore, the internal lubricant includes one or more of stearic acid, magnesium stearate, zinc stearate, calcium stearate, oxidized polyethylene wax (OPE wax), monoglycerides, and polyol fatty acid esters.

[0013] Furthermore, external lubricants include one or more of paraffin wax, polyethylene wax (PE wax), and ethylene bis-stearamide (EBS).

[0014] Furthermore, the stabilizers include one or more of the following: calcium-zinc composite stabilizers, organotin stabilizers, rare earth stabilizers, and epoxidized soybean oil.

[0015] Furthermore, plasticizers include one or more of dioctyl phthalate (DOP), dioctyl terephthalate (DOTP), chloromethoxy fatty acid esters, and tributyl citrate.

[0016] Furthermore, the nanoparticles include one or more of nano-calcium carbonate, nano-silica, and nano-zinc oxide.

[0017] Furthermore, the first raw material of the toughening modifier also includes an antioxidant, with the antioxidant accounting for 0.2%-1% of the total mass of the first raw material.

[0018] Furthermore, the toughening modifier is prepared according to the following method:

[0019] After mixing the first raw material evenly, put it into a ball mill and ball mill for 0.5-2 hours. Then add the second raw material and continue ball milling for 5-30 minutes.

[0020] Secondly, the present invention provides a method for preparing the above-mentioned high-toughness, high-flowability PVC injection molding compound, comprising the following steps:

[0021] Mix PVC, stabilizer, internal lubricant, and plasticizer in a high-speed mixer. When the material temperature rises to 55-70℃, add toughening modifier, nano calcium carbonate, and ACR-type processing aids and continue mixing. When the material temperature rises to 110-130℃, transfer to a cold mixer for cooling, extrusion, and granulation. The extrusion temperature is 155-185℃.

[0022] Further, the material is cooled to below 45°C and then extruded into granules.

[0023] The beneficial effects of this invention are as follows:

[0024] To achieve excellent high toughness, existing technologies often involve high levels of elastomers such as CPE and MBS, which makes it difficult to disperse the elastomers during mixing, thus affecting the processability, flowability, and toughness of PVC products. This invention adds a toughening modifier to PVC injection molding materials. Under the mechanical force of ball milling, nanoparticles, a first toughening agent, and a second toughening agent are uniformly dispersed. Simultaneously, in the second step, the first and second raw materials are co-ball-milled. During this process, the instantaneous high temperature from the collision of steel balls causes the zinc stearate from the second raw material to coat the surface of the first raw material particles, preventing the formation of large particle agglomerates, promoting the dispersion of the elastomer in the matrix material, and effectively improving flowability.

[0025] This invention utilizes two types of toughening agents. One type includes one or more of chlorinated polyethylene (CPE), ethylene-vinyl acetate (EVA), and nitrile rubber. These toughening agents exhibit excellent compatibility with PVC resin and can be uniformly distributed within the PVC matrix, thus achieving a toughening effect. The other type includes one or more of methyl methacrylate-butadiene-styrene copolymer (MBS), acrylonitrile-butadiene-styrene copolymer (ABS) high-rubber powder, and acrylate polymers (ACR). In its submicroscopic morphology, it exhibits a typical "core-shell" structure, with a spherical rubber phase core surrounded by a shell with a solubility parameter similar to PVC. This shell acts as an interfacial adhesive between the resin and rubber particles, forming a homogeneous phase during PVC processing and mixing. The rubber phase is distributed as particles in a continuous medium, exhibiting an "island" structure. Through ball milling, the molecular chains of these two different toughening agents partially graft together, and the two toughening agents intertwine to form a network structure with physical cross-linking points. The PVC matrix particles are segmented and surrounded within this network. When subjected to stress, the network structure and cross-linked rubber particles consume the energy generated by the impact process, thereby achieving high toughness of the material.

[0026] To maximize the effect of the toughening modifier on improving the toughness and flowability of PVC injection molding materials, this invention also provides a method for preparing high-toughness, high-flowability PVC injection molding materials. This method uses a two-stage mixing process. In the first stage, PVC is mixed only with stabilizers, internal lubricants, and plasticizers, ensuring that the PVC fully absorbs these agents. In the second stage, the material is finally heated to 110-130°C. At this temperature, zinc stearate melts, promoting wetting at the interface between the toughening modifier and the PVC matrix resin, resulting in more uniform powder mixing. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0028] Example 1

[0029] (1) Preparation of toughening modifier

[0030] CPE, MBS, and nano-calcium carbonate were weighed as the first raw material according to a mass ratio of 1:1:0.05. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 1 hour at a speed of 800 r / min. The mass ratio of steel balls to materials was 10:1. Subsequently, zinc stearate, accounting for 5% of the total mass of the first raw material, was added to the ball mill and ball-milled for another 20 minutes to obtain the toughening modifier.

[0031] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0032] Weigh out the following materials by weight: 100 parts polyvinyl chloride (S65), 1 part OPE wax, 1.5 parts polyol fatty acid ester, 1.5 parts organotin stabilizer, and 4 parts chloromethoxy fatty acid ester. Mix them in a high-speed mixer at 1000 r / min. When the material temperature reaches 60°C, add 10 parts toughening modifier, 10 parts nano calcium carbonate, and 0.5 parts PE wax and continue mixing. When the temperature reaches 120°C, transfer the mixture to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0033] Example 2

[0034] (1) Preparation of toughening modifier

[0035] Weigh powdered nitrile rubber and MBS according to a mass ratio of 1:2:0.08, add nano zinc oxide as the first raw material, then add antioxidant 1010 at a mass ratio of 0.7% of the total mass of the first raw material and stir manually until uniform. Place the mixture in a ball mill and ball mill for 1.5 hours at a speed of 800 r / min and a mass ratio of steel balls to material of 10:1. Subsequently, add zinc stearate at a mass ratio of 3% of the total mass of the first raw material to the ball mill and continue ball milling for 15 minutes to obtain the toughening modifier.

[0036] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0037] By weight, weigh 100 parts of polyvinyl chloride (SG-8), 0.8 parts of OPE wax, 1.2 parts of polyol fatty acid ester, 4 parts of calcium-zinc stabilizer, 1 part of epoxidized soybean oil, and 4 parts of DOTP, and place them in a high-speed mixer at a speed of 1200 r / min. When the material temperature rises to 55℃, add 9 parts of toughening modifier, 1 part of ACR-type processing aid Zhongyuan PA-20, 10 parts of nano calcium carbonate, and 0.4 parts of PE wax and continue mixing. When the temperature rises to 125℃, transfer to a cold mixer, cool to 45℃, and then extrude and granulate at an extrusion temperature of 155-185℃.

[0038] Example 3

[0039] (1) Preparation of toughening modifier

[0040] CPE and ACR were weighed according to a mass ratio of 1.5:2:0.04:0.02. Nano-calcium carbonate and nano-silica were added as the first raw materials. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw materials, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 1.5 hours at a speed of 800 r / min and a steel ball to material mass ratio of 10:1. Subsequently, zinc stearate, accounting for 3% of the total mass of the first raw materials, was added to the ball mill and ball-milled for another 10 minutes to obtain the toughening modifier.

[0041] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0042] Weigh out 100 parts by weight of polyvinyl chloride (S700), 2 parts by weight of monoglyceride, and 4.5 parts by weight of calcium-zinc stabilizer. Place the mixture in a high-speed mixer and mix at 1200 r / min. When the material temperature reaches 60°C, add 12 parts of toughening modifier, 1 part of ACR-type processing aid Zhongyuan PA-20, 8 parts of nano calcium carbonate, 0.5 parts of PE wax, and 0.3 parts of paraffin wax and continue mixing. When the temperature reaches 120°C, transfer the mixture to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0043] Example 4

[0044] Powdered nitrile rubber, high-rubber ABS powder, nano-calcium carbonate, and nano-silica were weighed according to a mass ratio of 1:1.2:0.09:0.03 as the first raw material. Then, antioxidant 1010, accounting for 0.4% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 2 hours at a speed of 800 r / min and a steel ball to material mass ratio of 10:1. Subsequently, zinc stearate, accounting for 1% of the total mass of the first raw material, was added to the ball mill and ball-milled for another 20 minutes to obtain the toughening modifier.

[0045] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0046] Weigh out the following materials by weight: 100 parts polyvinyl chloride (SG-8), 0.4 parts OPE wax, 1 part monoglyceride, 1 part calcium zinc stabilizer, 2 parts organotin stabilizer, and 3 parts DOP. Mix them in a high-speed mixer at 1200 r / min. When the material temperature reaches 60℃, add 13 parts toughening modifier, 0.8 parts ACR processing aid Zhongyuan PA-20, 8 parts nano calcium carbonate, and 0.5 parts PE wax. Continue mixing until the temperature reaches 115℃. Transfer the mixture to a cold mixer and cool it to 45℃ before extruding and granulating. The extrusion temperature is 155-185℃.

[0047] Comparative Example 1

[0048] Weigh out the materials according to the following proportions: 100 parts polyvinyl chloride (S700), 0.4 parts PE wax, 0.8 parts stearic acid, 0.2 parts paraffin wax, 3.5 parts calcium zinc stabilizer, 1 part epoxidized soybean oil, 5 parts chloromethoxy fatty acid ester, 4 parts CPE, 5 parts MBS, 2.5 parts ACR processing aid Zhongyuan PA-202, and 6 parts nano calcium carbonate. Mix the materials in a high-speed mixer at 1200 r / min for 15 min, then transfer them to a cold mixer. After cooling to 45℃, extrude and granulate the mixture at an extrusion temperature of 155-185℃.

[0049] Comparative Example 2

[0050] Weigh out the materials according to the following proportions: 100 parts polyvinyl chloride (SG-8), 2.5 parts polyol fatty acid ester, 0.5 parts paraffin wax, 2.5 parts organotin stabilizer, 3 parts DOP, 5 parts powdered nitrile rubber, 6 parts ACR, 1.5 parts ACR-type processing aid Zhongyuan PA-20, and 10 parts nano calcium carbonate. Place the materials in a high-speed mixer and mix at 1200 r / min for 10 min. Then transfer the mixture to a cold mixer and cool it to 45℃ before extrusion granulation. The extrusion temperature is 155-185℃.

[0051] Comparative Example 3

[0052] (1) Preparation of toughening modifier

[0053] MBS, ACR, nano-calcium carbonate, and nano-silica were weighed as the first raw material according to a mass ratio of 1.5:2:0.04:0.02. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 1.5 hours at a speed of 800 r / min and a steel ball to material mass ratio of 10:1. Subsequently, zinc stearate, accounting for 3% of the total mass of the first raw material, was added to the ball mill and ball-milled for another 10 minutes to obtain the toughening modifier.

[0054] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0055] Weigh out 100 parts by weight of polyvinyl chloride (S700), 2 parts by weight of monoglyceride, and 4.5 parts by weight of calcium-zinc stabilizer. Place the mixture in a high-speed mixer and mix at 1200 r / min. When the material temperature reaches 60°C, add 12 parts of toughening modifier, 1 part of ACR-type processing aid Zhongyuan PA-20, 8 parts of nano calcium carbonate, 0.5 parts of PE wax, and 0.3 parts of paraffin wax and continue mixing. When the temperature reaches 120°C, transfer the mixture to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0056] Comparative Example 4

[0057] (1) Preparation of toughening modifier

[0058] CPE, powdered nitrile rubber, nano-calcium carbonate, and nano-silica were weighed in a mass ratio of 1.5:2:0.04:0.02 as the first raw material. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 1.5 hours at a speed of 800 r / min and a steel ball to material mass ratio of 10:1. Subsequently, zinc stearate, accounting for 3% of the total mass of the first raw material, was added to the ball mill and ball-milled for another 10 minutes to obtain the toughening modifier.

[0059] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0060] Weigh out 100 parts by weight of polyvinyl chloride (S700), 2 parts by weight of monoglyceride, and 4.5 parts by weight of calcium-zinc stabilizer. Place the mixture in a high-speed mixer and mix at 1200 r / min. When the material temperature reaches 60°C, add 12 parts of toughening modifier, 1 part of ACR-type processing aid Zhongyuan PA-20, 8 parts of nano calcium carbonate, 0.5 parts of PE wax, and 0.3 parts of paraffin wax and continue mixing. When the temperature reaches 120°C, transfer the mixture to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0061] Comparative Example 5

[0062] (1) Preparation of toughening modifier

[0063] CPE, ACR, nano-calcium carbonate, and nano-silica were weighed as the first raw material according to a mass ratio of 1.5:2:0.04:0.02. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 100 minutes at a speed of 800 r / min. The mass ratio of steel balls to materials was 10:1 to obtain the toughening modifier.

[0064] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0065] Weigh out 100 parts by weight of polyvinyl chloride (S700), 2 parts by weight of monoglyceride, and 4.5 parts by weight of calcium-zinc stabilizer. Place the mixture in a high-speed mixer and mix at 1200 r / min. When the material temperature reaches 60°C, add 12 parts of toughening modifier, 1 part of ACR-type processing aid Zhongyuan PA-20, 8 parts of nano calcium carbonate, 0.5 parts of PE wax, and 0.3 parts of paraffin wax and continue mixing. When the temperature reaches 120°C, transfer the mixture to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0066] Comparative Example 6

[0067] (1) Preparation of toughening modifier

[0068] CPE, ACR, nano-calcium carbonate, and nano-silica were weighed in a mass ratio of 1.5:2:0.04:0.02 as the first raw material. Then, antioxidant 1010, accounting for 0.2% of the total mass of the first raw material, was added and manually stirred evenly. The mixture was then placed in a ball mill and ball-milled for 1.5 hours at a speed of 800 r / min and a steel ball to material mass ratio of 10:1. Subsequently, zinc stearate, accounting for 3% of the total mass of the first raw material, was added to the ball mill and ball-milled for another 10 minutes to obtain the toughening modifier.

[0069] (2) Preparation of high-toughness and high-flowability PVC injection molding compound

[0070] By weight, weigh out 100 parts of polyvinyl chloride (S700), 2 parts of monoglyceride, 4.5 parts of calcium-zinc stabilizer, 12 parts of toughening modifier, 1 part of ACR processing aid Zhongyuan PA-20, 8 parts of nano calcium carbonate, 0.5 parts of PE wax, and 0.3 parts of paraffin wax. Place the mixture in a high-speed mixer and mix at 1200 r / min. Heat the mixture to 120°C and transfer it to a cold mixer. After cooling to 45°C, extrude and granulate the mixture at an extrusion temperature of 155-185°C.

[0071] The PVC injection molding materials prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to the following performance tests:

[0072] (1) Melt flow index: Tested in accordance with GB / T 3682 "Determination of melt mass flow rate and melt volume flow rate of thermoplastics";

[0073] (2) Impact strength standard: Tested in accordance with GB / T 1843 "Determination of impact strength of plastic cantilever beams";

[0074] (3) Low temperature impact strength standard: The test shall be carried out in accordance with GB / T 1843 "Determination of impact strength of plastic cantilever beam", and the sample shall be treated at -20℃ for 16h.

[0075] Table 1. Test results of PVC injection molding performance for each embodiment.

[0076]

[0077] Table 2. Test results of PVC injection molding performance for each comparative example.

[0078]

[0079] Comparative Examples 1 and 2 did not use toughening modifiers, and the PVC injection molding compounds obtained by the preparation methods had poor processing flowability and could not meet the requirements for low-temperature use. Comparative Example 3 did not use the second toughening agent, and Comparative Example 4 did not use the first toughening agent. The melt index and low-temperature notched impact strength of the obtained PVC injection molding compounds were significantly reduced, indicating that the "core-shell" structure formed by the combination of the first and second toughening agents in this invention enhances the bonding between the toughening modifier and the PVC matrix on the one hand, and consumes the energy brought by the impact process by the network structure with physical cross-linking points on the other hand, thereby achieving high toughness of the material. The toughening modifier of Comparative Example 5 lacked zinc stearate, so the interface between the toughening modifier and the PVC matrix resin was not wet enough, resulting in uneven powder distribution. Therefore, the melt index, notched impact strength, and low-temperature notched impact strength of the final PVC injection molding compound all decreased. In Comparative Example 6, all components of the PVC injection molding compound were added together in a high-speed mixer. The stabilizer, internal lubricant, plasticizer and PVC matrix resin were not mixed sufficiently, which affected the melt index, notched impact strength and low temperature notched impact strength of the final PVC injection molding compound.

[0080] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A high-toughness, high-flowability PVC injection molding compound, characterized in that, The raw materials include the following parts by weight: 100 parts PVC, 0.3-2.5 parts internal lubricant, 0.1-1.5 parts external lubricant, 1-6 parts stabilizer, 8-15 parts toughening modifier, 0-6 parts plasticizer, 0-3 parts ACR processing aid, and 0-15 parts nano calcium carbonate; the toughening modifier consists of the first raw material and the second raw material. The first raw material consists of the first toughening agent, the second toughening agent, and nanoparticles. The first toughening agent is one or more of CPE, EVA, and nitrile rubber. The second toughening agent is one or more of MBS, ABS high-rubber powder, and ACR. The mass ratio of the first toughening agent, the second toughening agent, and the nanoparticles is 1-3:1-2:0.01-0.

15. The second raw material is zinc stearate, and the amount of the second raw material is 1%-5% of the first raw material. The nanoparticles are one or more of nano-calcium carbonate, nano-silica, and nano-zinc oxide. The toughening modifier is prepared as follows: the first raw material is stirred evenly and then placed in a ball mill and ball-milled for 0.5-2 hours, and then the second raw material is added and the ball milling continues for 5-30 minutes.

2. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, PVC is a polyvinyl chloride resin with an average degree of polymerization of 650-750.

3. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, The internal lubricant is one or more of the following: stearic acid, magnesium stearate, zinc stearate, calcium stearate, OPE wax, monoglyceride, and polyol fatty acid ester.

4. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, The external lubricant is one or more of paraffin wax, PE wax, and EBS.

5. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, The stabilizer is one or more of the following: calcium-zinc composite stabilizer, organotin stabilizer, rare earth stabilizer, and epoxidized soybean oil.

6. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, The plasticizer is one or more of DOP, DOTP, chloromethoxy fatty acid esters, and tributyl citrate.

7. The high-toughness, high-flowability PVC injection molding compound as described in claim 1, characterized in that, The first raw material of the toughening modifier also includes antioxidants, which account for 0.2%-1% of the total mass of the first raw material.

8. A method for preparing high-toughness, high-flowability PVC injection molding compound as described in any one of claims 1-7, comprising the following steps: Mix PVC, stabilizer, internal lubricant, external lubricant, and plasticizer in a high-speed mixer. When the material temperature rises to 55-70℃, add toughening modifier, nano calcium carbonate, and ACR-type processing aids and continue mixing. When the material temperature rises to 110-130℃, transfer to a cold mixer. After cooling, extrude and granulate at an extrusion temperature of 155-185℃.

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