Cold-resistant soft polyvinyl chloride material and preparation method thereof

Abstract

The application relates to the field of polyvinyl chloride materials, and particularly discloses a cold-resistant soft polyvinyl chloride material and a preparation method thereof. The cold-resistant soft polyvinyl chloride material comprises the following raw materials in parts by weight: 100 parts of PVC resin, 30-45 parts of DOTP plasticizer, 10-20 parts of ATBC plasticizer, 3-8 parts of maleic anhydride grafted PVC, 3-5 parts of organic modified nano montmorillonite, 2-4 parts of calcium-zinc composite heat stabilizer, 0.3-0.6 parts of stearic acid and 0.3-0.6 parts of polyethylene wax. The preparation method comprises the following steps: pre-interlayer activation treatment, step-by-step blending and magnetic field assisted low-temperature extrusion. The cold-resistant soft polyvinyl chloride material has the advantages of keeping environmental protection and mechanical strength and excellent cold resistance.

Description

Technical Field

[0001] This application relates to the field of polyvinyl chloride materials, and more specifically, to a cold-resistant soft polyvinyl chloride material and its preparation method. Background Technology

[0002] Flexible polyvinyl chloride (SPVC) is widely used in automotive interior parts, door and window seals, wire and cable sheaths, and outdoor waterproof membranes due to its excellent flexibility and processing properties. These applications, especially in cold regions or winter construction conditions, place stringent requirements on the material's low-temperature toughness—the material must maintain its flexibility and not crack at temperatures as low as -30°C or even -40°C.

[0003] In existing technologies, SPVC achieves good low-temperature flexibility by adding a large amount of phthalate plasticizers (such as DOP). However, DOP plasticizers have problems such as easy migration and high volatility, resulting in short product life and health and environmental risks, and their use has been restricted by environmental regulations in many countries and regions.

[0004] To meet environmental protection requirements, the industry has begun to use environmentally friendly plasticizers as alternatives, such as dioctyl terephthalate (DOTP) and bio-based plasticizers such as acetylated tributyl citrate (ATBC).

[0005] However, traditional SPVC processing involves high temperatures (160–200°C), resulting in high energy consumption. Furthermore, high-temperature processing exacerbates the volatilization and decomposition of environmentally friendly plasticizers, affecting the environmental performance and stability of the final product. In addition, non-phthalic plasticizers such as DOTP have lower compatibility with PVC than phthalic plasticizers, while bio-based plasticizers such as ATBC have even worse compatibility. A large amount of environmentally friendly plasticizer is embedded in the PVC matrix and cannot effectively function, or it migrates and is lost rapidly in the early stages of use, failing to achieve a lasting plasticizing effect and making it more prone to precipitation (blooming) from the product, leading to a sticky surface and accelerated performance degradation. To improve the low-temperature brittleness of SPVC, large amounts of plasticizer are usually added, which not only increases costs but also exacerbates migration problems and significantly reduces the material's mechanical strength. For example, a typical commercially available environmentally friendly SPVC sealing strip formulation requires at least 50 parts DOTP as the main plasticizer to achieve sufficient flexibility and low-temperature performance. Furthermore, tests have shown that its glass transition temperature (Tg) barely meets the requirements for winter use in general regions, but is insufficient for more stringent high-altitude and cold environments. Summary of the Invention

[0006] In order to maintain the environmental friendliness and mechanical strength of flexible polyvinyl chloride (PVC) materials while improving their cold resistance, this application provides a cold-resistant flexible PVC material and its preparation method.

[0007] In a first aspect, this application provides a cold-resistant soft polyvinyl chloride material, which adopts the following technical solution:

[0008] A cold-resistant flexible polyvinyl chloride material, comprising the following raw materials in parts by weight:

[0009] 100 parts of PVC resin;

[0010] 30-45 parts of DOTP plasticizer;

[0011] 10-20 parts of ATBC plasticizer;

[0012] 3-8 parts of maleic anhydride grafted onto PVC;

[0013] 3-5 parts of organically modified nano-montmorillonite;

[0014] 2-4 parts of calcium-zinc composite heat stabilizer;

[0015] Stearic acid 0.3–0.6 parts;

[0016] Polyethylene wax 0.3 to 0.6 parts.

[0017] By adopting the above technical solutions, DOTP plasticizer is used as the main plasticizer, which can be inserted between PVC molecular chains to weaken intermolecular forces and provide basic flexibility. ATBC plasticizer is used as an auxiliary plasticizer, and its cold resistance is better than DOTP. Organically modified nano-montmorillonite is added, which forms nanosheets after exfoliation, which can block the migration path of plasticizers. Part of the ATBC plasticizer is used for pre-intercalation of montmorillonite. By utilizing the small molecular polarity of ATBC, it is pre-intercalated between the layers of nano-montmorillonite, which further expands the interlayer spacing and forms a "pre-intercalation-swelling" structure. This greatly reduces the subsequent exfoliation energy barrier of montmorillonite in the PVC matrix and can also form a "confined plasticizer". The anhydride groups of maleic anhydride grafted onto PVC react with the hydroxyl groups on the surface of montmorillonite. The PVC chain segments are compatible with the matrix and form a "molecular bridge" to connect the organically modified nano-montmorillonite and the PVC resin matrix. Combined with the plasticizer pre-intercalation of montmorillonite, a multi-level structure of "PVC matrix-interfacial compatibility layer-nanosheet-confined plasticizer" is formed. This structure, on the one hand, inhibits the migration of plasticizer molecules through the physical cross-linking points of the nanosheets; on the other hand, the confined plasticizer is more mobile at low temperatures, thus significantly improving the low-temperature toughness of the material. Overall, not only is the amount of DOTP plasticizer used reduced, but the combined effect of the various raw materials also improves the cold resistance of flexible PVC materials while maintaining their environmental friendliness and mechanical strength.

[0018] Optionally, the PVC resin is SG-3 type PVC resin powder.

[0019] Optionally, the grafting rate of the maleic anhydride-grafted PVC is 1%.

[0020] Optionally, the interlayer spacing of the organically modified nano-montmorillonite is 3 nm.

[0021] Optionally, the cold-resistant soft polyvinyl chloride material further includes 4 to 8 parts by weight of modified tussah silk powder.

[0022] By adopting the above technical solution, modified tussah silk powder, as a further cold-resistant component, can form a microfiber reinforcing network in the PVC matrix to absorb low-temperature impact energy. Furthermore, its surface is rich in active groups, which, when combined with maleic anhydride-grafted PVC, improve its dispersibility and interfacial bonding in the matrix; it also forms an "organic-inorganic" synergistic reinforcing network with organically modified nano-montmorillonite sheets, simultaneously inhibiting plasticizer migration and improving the material's low-temperature toughness.

[0023] Optionally, the modified tussah silk powder is prepared by modifying tussah silk with a nano-titanium dioxide / chitosan treatment solution.

[0024] By adopting the above technical solution, the modified tussah silk powder prepared by this method has significantly improved thermal stability, effectively increasing its thermal decomposition temperature and enabling it to play a stable role in the PVC processing process.

[0025] Optionally, the cold-resistant soft polyvinyl chloride material further includes 2.7 to 3.6 parts by weight of reinforcing components, which include acicular wollastonite, flake talc, and spherical nano-calcium carbonate in a weight ratio of 4:3:2.

[0026] By employing the above technical solutions, needle-shaped wollastonite serves as a one-dimensional reinforcing filler. Its needle-like structure forms a physical reinforcing skeleton within the matrix, orienting along the flow direction and transferring stress. Flaky talc powder acts as a two-dimensional reinforcing filler; its flaky structure forms a layered reinforcing layer, filling the gaps in the skeleton and creating a "needle-flaky interlocking" structure, thus improving the material's tear resistance. Spherical nano-calcium carbonate acts as a three-dimensional reinforcing filler; the spherical nanoparticles further fill the gaps in the needle-flaky network, terminating microcracks and improving the filler's interfacial bonding ability. These three different forms of inorganic fillers construct a "needle-flaky-sphere" three-dimensional reinforcing network in the PVC matrix, providing a more comprehensive mechanical strength enhancement effect than a single filler or a combination of two fillers.

[0027] Secondly, this application provides a method for preparing a cold-resistant soft polyvinyl chloride material, using the following technical solution:

[0028] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0029] (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer;

[0030] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano-montmorillonite / ATBC plasticizer mixture are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC is added and mixing is continued to obtain a premix.

[0031] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.

[0032] By employing the above technical solution, the small molecular polarity of ATBC is utilized to pre-insert into the interlayer of nano-montmorillonite, further expanding the interlayer spacing and forming a "pre-intercalation-swelling" structure, which greatly reduces the subsequent peeling energy barrier of montmorillonite in the PVC matrix. Through formulation improvement and stepwise mixing, the initial penetration of the plasticizer and the initial anchoring of the interface compatibilizer maleic anhydride grafted onto PVC are effectively achieved. Under the action of an external magnetic field, the antimagnetic organically modified nano-montmorillonite sheets tend to align in a specific direction. At the same time, the magnetic field can reduce the apparent viscosity of the PVC melt, which allows for the full peeling and dispersion of the nanosheets at lower temperatures and shear forces, avoiding damage to the plasticizer and matrix caused by high temperature and high shear. The magnetic field-assisted process is also the key to the successful construction of the multi-level structure of "PVC matrix-interface compatibilization layer-nanosheet layer-confined plasticizer". Under the assistance of the magnetic field, low-temperature processing is achieved, with the extruder temperature significantly lower than the 160-180℃ of the traditional process, reducing damage to heat-sensitive environmentally friendly additives and effectively maintaining the environmental friendliness of the material.

[0033] Thirdly, this application provides a method for preparing a cold-resistant soft polyvinyl chloride material, using the following technical solution:

[0034] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0035] (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer;

[0036] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano-montmorillonite / ATBC plasticizer mixture are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC and modified tussah silk powder are added and mixed further to obtain a premix.

[0037] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.

[0038] By employing the above technical solution, maleic anhydride-grafted PVC and modified tussah silk powder are added together at a temperature of 80–90℃, enabling them to fully contact and achieve in-situ interfacial reaction. The modified tussah silk powder surface is rich in hydroxyl and amino groups, and the anhydride groups on the maleic anhydride-grafted PVC begin to activate at this temperature. When the two come into "fresh" contact, an in-situ ring-opening reaction can occur, forming a chemically bonded PVC interfacial layer on the tussah silk surface. This "tussah silk-g-PVC" structure chemically anchors the biomass filler to the PVC matrix, resulting in an interfacial bonding strength far superior to physical blending. At this temperature, the maleic anhydride-grafted PVC is in a molten state, simultaneously wetting the tussah silk powder and the surface of the organically modified nano-montmorillonite, promoting the uniform dispersion of the filler in the PVC matrix.

[0039] Fourthly, this application provides a method for preparing a cold-resistant soft polyvinyl chloride material, employing the following technical solution:

[0040] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0041] (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer;

[0042] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax, treated organic modified nano-montmorillonite / ATBC plasticizer mixture and reinforcing components are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC and modified tussah silk powder are added, and mixing is continued to obtain a premix.

[0043] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.

[0044] By adopting the above technical solution, liquid plasticizers such as DOTP and ATBC exhibit moderate viscosity and good flowability at 50–60℃. When the reinforcing component is added within this temperature range, the plasticizer can fully penetrate and wet the surface of each filler in the reinforcing component. This "pre-wetting" effect forms a plasticizer molecular layer on the filler surface, which is beneficial for uniform dispersion in the PVC matrix. The fully wetted and uniformly dispersed filler can be effectively oriented during subsequent magnetic field-assisted extrusion, forming an ordered reinforcing structure. The filler surface wetted by the plasticizer has good physical compatibility with the maleic anhydride-grafted PVC added in the second stage, forming a continuous interface of "filler-plasticizer-compatibility," enhancing the integrity of the overall network structure.

[0045] In summary, this application has the following beneficial effects:

[0046] 1. Because this application uses maleic anhydride-grafted PVC and organically modified nano-montmorillonite, through the synergistic effect of "nano-montmorillonite" and "interface compatibilizer", it miraculously achieves "low migration", "ultra-cold resistance" and "good mechanical strength" at the same time, breaking the "seesaw" effect of the performance being at odds with each other. By constructing a "nano-confined" composite structure, it fundamentally solves the industry problem of migration and poor compatibility of environmentally friendly plasticizers.

[0047] 2. In this application, modified tussah silk powder is preferred as a further cold-resistant component, which can form a microfiber reinforced network in the PVC matrix to absorb low-temperature impact energy.

[0048] 3. The method of this application introduces a physical field into the SPVC processing process through the "magnetic field assisted low temperature processing" process. While ensuring the dispersion effect of nanofillers, it significantly reduces the processing temperature and energy consumption, and reduces the damage to heat-sensitive environmentally friendly additives. It is an innovation of green and low-carbon manufacturing process. Detailed Implementation

[0049] The present application will be further described in detail below with reference to the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments shall be performed under conventional conditions or conditions recommended by the manufacturer, and the raw materials used in the following embodiments shall be commercially available unless otherwise specified.

[0050] Organically modified nano-montmorillonite, brand name: Yinsu Flame Retardant, model: K100.

[0051] Needle-shaped wollastonite, aspect ratio 15:1, 1250 mesh.

[0052] Flaky talc powder, 1250 mesh.

[0053] Spherical nano-calcium carbonate, with an average particle size of 50 nm, after activation treatment.

[0054] Preparation example of modified tussah silk powder

[0055] Preparation Example 1

[0056] Modified tussah silk powder is prepared by modifying tussah silk with a nano-titanium dioxide / chitosan treatment solution. The preparation method is as follows:

[0057] (1) Preparation of nano-titanium dioxide / chitosan treatment solution:

[0058] 1.0 mL of glacial acetic acid and 10.0 mL of tetrabutyl titanate were added to 100 mL of anhydrous ethanol and stirred to obtain solution A. 0.5 mL of concentrated hydrochloric acid and 2.0 mL of deionized water were added to 20 mL of anhydrous ethanol to obtain solution B. Solution B was slowly added dropwise to solution A while stirring, and the pH was adjusted to 3.0 with hydrochloric acid to obtain nano-titanium dioxide sol with an average particle size of 7.6 nm.

[0059] A treatment solution containing 5 g / L chitosan, 10 g / L sodium hypophosphite, and 5 g / L nano titanium dioxide was prepared. Appropriate amounts of Span-80 and OP-10 were added as dispersants, and deionized water was used as the dispersion medium. The mixture was stirred thoroughly to obtain a nano titanium dioxide / chitosan dispersion with an average particle size of 56.7 nm.

[0060] (2) Modification treatment of tussah silk:

[0061] Degummed tussah silk (degummed rate 13.8%) was immersed in a treatment solution at room temperature for 30 minutes at a liquor ratio of 1:50; pre-dried at 80°C for 5 minutes; 1,2,3,4-butanetetracarboxylic acid was added as a crosslinking agent and baked at 160°C for 3 minutes; thoroughly washed with water, ultrasonically cleaned for 3 minutes, dehydrated, and dried at 80°C; mechanically pulverized and passed through an 80-mesh sieve to obtain modified tussah silk powder.

[0062] Example

[0063] Example 1

[0064] A cold-resistant soft polyvinyl chloride material comprises the following raw materials: PVC resin, specifically SG-3 type PVC resin powder; DOTP plasticizer; ATBC plasticizer; maleic anhydride-grafted PVC with a grafting rate of 1%; organically modified nano-montmorillonite with an interlayer spacing of 3 nm; calcium-zinc composite heat stabilizer; stearic acid; and polyethylene wax. The dosages are detailed in Table 1.

[0065] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0066] (1) Pre-intercalation activation treatment: Organic modified nano-montmorillonite and a portion of ATBC plasticizer (one-third of the total weight of ATBC) are stirred at 1200 rpm for 20 minutes at 70°C to allow ATBC molecules to be intercalated between montmorillonite layers for treatment, thereby expanding the interlayer spacing.

[0067] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano montmorillonite / ATBC plasticizer mixture are mixed and stirred at 50°C until uniform; after heating to 80°C, maleic anhydride grafted PVC is added and mixed and stirred until uniform to obtain a premix.

[0068] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder. The direction of the magnetic field is parallel to the material flow direction.

[0069] A co-rotating parallel twin-screw extruder (L / D ratio L / D = 40:1) has the following temperature settings for each section: feeding section: 132℃; melting section: 142℃; mixing and plasticizing section: 148℃; metering section: 142℃; die head: 142℃. The screw speed is 250 rpm, the feeding frequency is 20 Hz, and the melt pressure is 4.2 MPa.

[0070] Example 2

[0071] The difference between this embodiment and Embodiment 1 is that the amount of each raw material in the formula is different, as detailed in Table 1.

[0072] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0073] (1) Pre-intercalation activation treatment: Organic modified nano-montmorillonite and a portion of ATBC plasticizer (one-third of the total weight of ATBC) are stirred at 1200 rpm for 20 minutes at 70°C to allow ATBC molecules to be intercalated between montmorillonite layers for treatment, thereby expanding the interlayer spacing.

[0074] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano montmorillonite / ATBC plasticizer mixture are mixed and stirred at 55°C until uniform; after heating to 85°C, maleic anhydride grafted PVC is added and mixed and stirred until uniform to obtain a premix.

[0075] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder. The direction of the magnetic field is parallel to the material flow direction.

[0076] A co-rotating parallel twin-screw extruder (L / D ratio L / D = 40:1) has the following temperature settings for each section: feeding section: 130℃; melting section: 140℃; mixing and plasticizing section: 145℃; metering section: 140℃; die head: 140℃. The screw speed is 250 rpm, the feeding frequency is 20 Hz, and the melt pressure is 4.2 MPa.

[0077] Example 3

[0078] The difference between this embodiment and Embodiment 1 is that the amount of each raw material in the formula is different, as detailed in Table 1.

[0079] A method for preparing a cold-resistant flexible polyvinyl chloride material includes the following steps:

[0080] (1) Pre-intercalation activation treatment: Organic modified nano-montmorillonite and a portion of ATBC plasticizer (one-third of the total weight of ATBC) are stirred at 1200 rpm for 20 minutes at 70°C to allow ATBC molecules to be intercalated between montmorillonite layers for treatment, thereby expanding the interlayer spacing.

[0081] (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano montmorillonite / ATBC plasticizer mixture are mixed and stirred at 60°C until uniform; after heating to 90°C, maleic anhydride grafted PVC is added and mixed and stirred until uniform to obtain a premix.

[0082] (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder. The direction of the magnetic field is parallel to the material flow direction.

[0083] A co-rotating parallel twin-screw extruder (L / D ratio L / D = 40:1) has the following temperature settings for each section: feeding section: 135℃; melting section: 145℃; mixing and plasticizing section: 150℃; metering section: 145℃; die head: 145℃. The screw speed is 250 rpm, the feeding frequency is 20 Hz, and the melt pressure is 4.2 MPa.

[0084] Example 4

[0085] The difference between this embodiment and Example 2 is that the cold-resistant soft polyvinyl chloride material also includes modified tussah silk powder prepared according to the method of Preparation Example 1. The amount of each raw material is detailed in Table 1.

[0086] The difference in preparation methods is that in “(2) step-by-step blending”, in the second stage, after heating to 85°C, maleic anhydride-grafted PVC and modified tussah silk powder are added and mixed and stirred until uniform to obtain a premix.

[0087] Example 5

[0088] The difference between this embodiment and Embodiment 4 is that the amount of modified tussah silk powder used is different, as detailed in Table 1.

[0089] Example 6

[0090] The difference between this embodiment and Embodiment 4 is that the amount of modified tussah silk powder used is different, as detailed in Table 1.

[0091] Example 7

[0092] The difference between this embodiment and Embodiment 5 is that the tussah silk powder has not undergone modification treatment.

[0093] Example 8

[0094] The difference between this embodiment and embodiment 5 is that the cold-resistant soft polyvinyl chloride material also includes a reinforcing component, which includes needle-shaped wollastonite, flake-shaped talc powder and spherical nano-calcium carbonate in a weight ratio of 4:3:2. The amount of each raw material is detailed in Table 1.

[0095] The difference in preparation methods is that in “(2) step blending”, in the first stage, PVC resin, DOTP plasticizer, the remaining ATBC plasticizer, calcium zinc composite heat stabilizer, stearic acid, polyethylene wax, the treated organic modified nano montmorillonite / ATBC plasticizer mixture and reinforcing components are mixed and stirred at 55°C until uniform.

[0096] Example 9

[0097] The difference between this embodiment and Embodiment 5 is that the amount of reinforcing component is different, as detailed in Table 1.

[0098] Example 10

[0099] The difference between this embodiment and Embodiment 9 is that the reinforcing component is entirely acicular wollastonite.

[0100] Example 11

[0101] The difference between this embodiment and Embodiment 9 is that the reinforcing component is entirely flaky talc powder.

[0102] Example 12

[0103] The difference between this embodiment and Embodiment 9 is that the reinforcing component is entirely spherical nano-calcium carbonate.

[0104] Comparative Example

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 2 is that the polyvinyl chloride material formulation prepared in this comparative example does not contain maleic anhydride-grafted PVC or organically modified nano-montmorillonite.

[0107] The preparation method of polyvinyl chloride (PVC) material is as follows: after blending the raw materials, the mixture is extruded and granulated using a twin-screw extruder. The extrusion temperatures are: 150℃ in the feeding section, 165℃ in the melting section, 170℃ in the mixing and plasticizing section, 165℃ in the metering section, and 165℃ at the die head. The screw speed is 250 rpm, the feeding frequency is 20 Hz, and the melt pressure is 4.2 MPa.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 2 is that the polyvinyl chloride material formulation prepared in this comparative example does not contain maleic anhydride-grafted PVC.

[0110] Comparative Example 3

[0111] The difference between this comparative example and Example 2 is that the preparation method is as follows: the raw materials are blended and then extruded and granulated using a twin-screw extruder. The extrusion temperatures are: 150°C in the feeding section, 165°C in the melting section, 170°C in the mixing and plasticizing section, 165°C in the metering section, and 165°C at the die head. The screw speed is 250 rpm, the feeding frequency is 20 Hz, and the melt pressure is 4.2 MPa.

[0112] Table 1. Formulations of polyvinyl chloride materials in each embodiment and comparative example.

[0113] PVC / g DOTP / g ATBC / g Maleic anhydride-grafted PVC / g Organically modified nano-montmorillonite / g Calcium-zinc composite heat stabilizer / g stearic acid / g Polyethylene wax / g Modified tussah silk powder / g Needle-shaped wollastonite / g flake talc / g Spherical nano calcium carbonate / g Example 1 1000 300 200 30 30 20 3 3 0 0 0 0 Example 2 1000 400 150 50 40 30 5 4 0 0 0 0 Example 3 1000 450 100 80 50 40 6 6 0 0 0 0 Example 4 1000 400 150 50 40 30 5 4 4 0 0 0 Example 5 1000 400 150 50 40 30 5 4 6 0 0 0 Example 6 1000 400 150 50 40 30 5 4 8 0 0 0 Example 7 1000 400 150 50 40 30 5 4 / 0 0 0 Example 8 1000 400 150 50 40 30 5 4 6 12 9 6 Example 9 1000 400 150 50 40 30 5 4 6 16 12 8 Example 10 1000 400 150 50 40 30 5 4 6 36 0 0 Example 11 1000 400 150 50 40 30 5 4 6 0 36 0 Example 12 1000 400 150 50 40 30 5 4 6 0 0 36 Comparative Example 1 1000 400 150 0 0 30 5 4 0 0 0 0 Comparative Example 2 1000 400 150 0 40 30 5 4 0 0 0 0 Comparative Example 3 1000 400 150 50 40 30 5 4 0 0 0 0

[0114] Performance testing

[0115] Detection methods / test methods

[0116] The materials obtained in each embodiment and comparative example were calendered, with the calender roll temperature controlled at 118℃. After forming, gradient cooling was performed: slow cooling section: 80℃→60℃, cooling rate 1.5℃ / min; fast cooling section: 60℃→30℃, cooling rate 6℃ / min. Flexible polyvinyl chloride composite material samples were obtained and subjected to the following tests. The test results are detailed in Table 2.

[0117] 1. Mechanical properties:

[0118] Referring to "GB / T 1040.2-2022 Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", the materials prepared in each example and comparative example were sampled and tensile strength tested. Type 1B specimens were used, with a tensile rate of 50 mm / min.

[0119] Referring to "GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber", samples were prepared and tear strength was tested on the materials prepared in each example and comparative example. The samples were right-angled specimens with slits, and the tensile rate was 500 mm / min.

[0120] 2. Environmental friendliness:

[0121] Referring to "ASTM D8600-25 Standard Test Method for Quantitative Measurement of Exudates from Flexible Polyvinyl Chloride Plastics", samples were prepared and plasticizer migration rates were determined for the materials prepared in each example and comparative example, at 70℃ for 24 hours using the activated carbon absorption method.

[0122] 3. Cold resistance:

[0123] Referring to "GB / T 19466.2-2004 Differential Scanning Calorimetry (DSC) for Plastics - Part 2: Determination of Glass Transition Temperature", the glass transition temperature (Tg) of the materials prepared in each example and comparative example was determined by DSC at a heating rate of 10 °C / min under a nitrogen atmosphere.

[0124] Referring to "GB-T 5470-2008 Determination of embrittlement temperature of plastics by impact method", the materials prepared in each example and comparative example were sampled and their embrittlement temperature was determined using the single sample method with a cooling rate of 1℃ / min.

[0125] Referring to "QB_T 5813-2023 Flexible Polyvinyl Chloride Sheet (Strip) Material", samples were prepared for the materials obtained in each embodiment and comparative example. The samples were tested according to "6.8 Low Temperature Folding", which involved holding the samples at -40℃ for 4 hours and folding them in half at 180°.

[0126] Table 2 Test results of each material

[0127] Sample source Tensile strength (MPa) Tear strength (kN / m) Migration rate (%) Tg (°C) Low temperature embrittlement (℃) Fold in half at -40℃ Example 1 11.8 32.5 0.45 -35.8 -25 fracture Example 2 12.5 35.2 0.38 -38.5 -28 fracture Example 3 11.5 32 0.41 -37.2 -26 fracture Example 4 12.2 34.5 0.32 -43.2 -33 microcracks Example 5 12.8 36.8 0.28 -45 -36 No cracks Example 6 12.5 36 0.29 -44.2 -34 No cracks Example 7 10.8 29.5 0.52 -34.5 -22 fracture Example 8 15.5 46.2 0.22 -45.5 -37 No cracks Example 9 17.2 52.5 0.19 -45.8 -39 No cracks Example 10 15.2 46.5 0.26 -45.2 -36 No cracks Example 11 14.5 49.5 0.23 -45 -36 No cracks Example 12 13.8 42.5 0.28 -45.5 -36 No cracks Comparative Example 1 10.2 30 0.62 -33.5 -22 fracture Comparative Example 2 10.6 31.2 0.55 -34.2 -23 fracture Comparative Example 3 10.9 31.8 0.58 -33.8 -23 fracture

[0128] As can be seen from Example 2 and Comparative Example 1, and Table 2, without the addition of organically modified nano-montmorillonite and maleic anhydride-grafted PVC, the process can only use conventional high-temperature extrusion, resulting in plasticizer loss, poor low-temperature performance and mechanical strength, and serious plasticizer migration problems. The addition of organically modified nano-montmorillonite and maleic anhydride-grafted PVC allows for the pre-intercalation of ATBC plasticizer into the nano-montmorillonite. Utilizing the small molecular polarity of ATBC, it pre-intercalates into the interlayer space of the nano-montmorillonite, further expanding the interlayer spacing and forming a "pre-intercalation-swelling" structure. This significantly reduces the subsequent peeling energy barrier of montmorillonite in the PVC matrix and also forms a "confined plasticizer." The anhydride groups of the maleic anhydride-grafted PVC react with the hydroxyl groups on the surface of montmorillonite, and the PVC segments are compatible with the matrix, forming a "molecular bridge" that connects the organically modified nano-montmorillonite and the PVC resin matrix. Combined with the plasticizer pre-intercalated montmorillonite, a multi-level structure of "PVC matrix-interfacial compatibility layer-nanosheets-confined plasticizer" is formed. This structure, on the one hand, inhibits the migration of plasticizer molecules through the physical cross-linking points of the nanosheets; on the other hand, the confined plasticizer is more mobile at low temperatures, thus significantly improving the low-temperature toughness of the material. Through formula improvements and step-by-step mixing, the initial penetration of plasticizers and the initial anchoring of maleic anhydride-grafted PVC as an interfacial compatibilizer were effectively achieved. Under magnetic field assistance, low-temperature processing was achieved, with extruder temperatures significantly lower than the 160-180℃ of traditional processes, reducing damage to heat-sensitive environmentally friendly additives and effectively maintaining the material's environmental friendliness. Overall, not only was the amount of DOTP plasticizer used reduced, but the combined effect of various raw materials also improved the cold resistance of flexible PVC materials while maintaining their environmental friendliness and mechanical strength. This broadened the application boundaries of environmentally friendly SPVC, enabling this environmentally friendly material to enter fields with extremely high requirements for low-temperature toughness and durability, such as automotive interiors, waterproof membranes for cold regions, and high-end medical supplies, achieving import substitution of domestically produced high-end flexible PVC materials.

[0129] Based on Examples 2 and Comparative Examples 1-3, and referring to Table 2, it can be seen that adding only organically modified nano-montmorillonite has limited effect. Adding both organically modified nano-montmorillonite and a compatibilizer simultaneously results in plasticizer loss during high-temperature extrusion, making the effect less effective than adding only organically modified nano-montmorillonite. Only a combination of all three (organically modified nano-montmorillonite + compatibilizer + low-temperature magnetic field) can achieve a breakthrough effect of reduced Tg, reduced migration rate, and improved mechanical strength.

[0130] Combining Examples 2, 5, and 7 with Table 2, it can be seen that adding modified tussah silk improves its thermal stability, enabling it to withstand subsequent processing temperatures. Furthermore, as a further cold-resistant component, modified tussah silk forms a microfiber reinforcing network in the PVC matrix, absorbing low-temperature impact energy. Additionally, its surface is rich in active groups, which, when combined with maleic anhydride-grafted PVC, improve its dispersibility and interfacial bonding in the matrix. It also forms an "organic-inorganic" synergistic reinforcing network with organically modified nano-montmorillonite sheets, simultaneously inhibiting plasticizer migration and improving the material's low-temperature toughness. In contrast, the effect of adding unmodified tussah silk is not very significant due to high-temperature damage.

[0131] As can be seen from Examples 2 and 9 to 12 and Table 2, the three different forms of inorganic fillers construct a three-dimensional "needle-plate-sphere" reinforcing network in the PVC matrix, which has a more comprehensive mechanical strength enhancement effect than a single filler or a combination of two fillers.

[0132] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A cold-resistant soft polyvinyl chloride material, characterized in that, Including the following parts by weight of raw materials: 100 parts of PVC resin; 30-45 parts of DOTP plasticizer; 10-20 parts of ATBC plasticizer; 3-8 parts of maleic anhydride grafted onto PVC; 3-5 parts of organically modified nano-montmorillonite; 2-4 parts of calcium-zinc composite heat stabilizer; Stearic acid 0.3–0.6 parts; Polyethylene wax 0.3 to 0.6 parts.

2. The cold-resistant soft polyvinyl chloride material according to claim 1, characterized in that: The PVC resin is SG-3 type PVC resin powder.

3. The cold-resistant soft polyvinyl chloride material according to claim 1, characterized in that: The grafting rate of the maleic anhydride-grafted PVC was 1%.

4. The cold-resistant soft polyvinyl chloride material according to claim 1, characterized in that: The interlayer spacing of the organically modified nano-montmorillonite is 3 nm.

5. The cold-resistant soft polyvinyl chloride material according to claim 1, characterized in that: The cold-resistant soft polyvinyl chloride material also includes 4 to 8 parts by weight of modified tussah silk powder.

6. The cold-resistant soft polyvinyl chloride material according to claim 5, characterized in that: The modified tussah silk powder is prepared by modifying tussah silk with a nano-titanium dioxide / chitosan treatment solution.

7. The cold-resistant soft polyvinyl chloride material according to claim 6, characterized in that: The cold-resistant soft polyvinyl chloride material also includes 2.7 to 3.6 parts by weight of reinforcing components, which include acicular wollastonite, flaky talc, and spherical nano-calcium carbonate in a weight ratio of 4:3:

2.

8. A method for preparing a cold-resistant soft polyvinyl chloride material according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer; (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano-montmorillonite / ATBC plasticizer mixture are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC is added and mixing is continued to obtain a premix. (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.

9. A method for preparing a cold-resistant soft polyvinyl chloride material according to any one of claims 5 to 6, characterized in that, Includes the following steps: (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer; (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax and the treated organic modified nano-montmorillonite / ATBC plasticizer mixture are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC and modified tussah silk powder are added and mixed further to obtain a premix. (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.

10. A method for preparing a cold-resistant soft polyvinyl chloride material according to any one of claims 7, characterized in that, Includes the following steps: (1) Pre-intercalation activation treatment: The organically modified nano-montmorillonite was subjected to interlayer treatment with a portion of ATBC plasticizer; (2) Stepwise blending: PVC resin, DOTP plasticizer, remaining ATBC plasticizer, calcium-zinc composite heat stabilizer, stearic acid, polyethylene wax, treated organic modified nano-montmorillonite / ATBC plasticizer mixture and reinforcing components are mixed at 50-60°C; after heating to 80-90°C, maleic anhydride grafted PVC and modified tussah silk powder are added, and mixing is continued to obtain a premix. (3) Magnetic field assisted low temperature extrusion: The premixed material is extruded and granulated through a twin-screw extruder at 140-150℃. A steady magnetic field with an intensity of 0.5T is applied in the melting and plasticizing section of the twin-screw extruder, and the direction of the magnetic field is parallel to the material flow direction.