High-flame-retardant low-temperature-resistant matte polyvinyl chloride colloidal particle, preparation method thereof and wire and cable outer sheath

Abstract

The invention belongs to the technical field of cable materials, and particularly relates to a high-flame-retardant low-temperature-resistant matte polyvinyl chloride colloidal particle, a preparation method thereof and an electric wire and cable outer sheath. The colloidal particles comprise the following components in parts by weight: 80-120 parts of polyvinyl chloride resin powder, 20-30 parts of core-shell modified resin, 4-6 parts of a nano composite flame retardant, 5-8 parts of a low-temperature-resistant modifier, 60-100 parts of a plasticizer, 80-150 parts of nano calcium carbonate, 2-4 parts of functional resin and 2-12 parts of a surface stearic acid modified calcium-zinc stabilizer. Through a nano-composite flame-retardant-low-temperature-resistant synergistic formula and a gradient dispersion-directional crosslinking process, ternary synergistic optimization of high flame retardance, low temperature resistance and a high-quality matte effect is realized, and the cable protection material is suitable for cable protection in a harsh environment and has a wide application prospect.

Description

Technical Field

[0001] This application belongs to the field of cable material technology, specifically relating to a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule, its preparation method, and an outer sheath for wires and cables. Background Technology

[0002] Polyvinyl chloride (PVC) is widely used as the outer sheath material for wires and cables due to its excellent mechanical properties, chemical resistance, and cost advantages. In high-end applications such as new energy vehicle cables, polar transmission lines, and harsh outdoor environments, higher requirements are placed on PVC sheath materials. These materials must simultaneously meet high flame retardancy ratings (e.g., passing the VW-1 test), excellent low-temperature toughness (e.g., maintaining high elongation at -40°C), and a superior and uniform matte finish.

[0003] However, existing high-end wires and cables still have the following problems:

[0004] The contradiction between flame retardancy and appearance: In order to achieve high flame retardancy, a large amount of flame retardant is often required to pass the VW-1 vertical burning test, such as more than 10 parts of antimony trioxide. This will cause the filler to agglomerate, making the material surface rough and the haze uneven, making it difficult to meet the requirements of high-end wire for consistency and aesthetics.

[0005] The contradiction between flame retardancy and low-temperature toughness: Ordinary PVC granules experience a decrease in elongation at break of ≥30% below -20℃, resulting in brittle failure. On the other hand, a single low-temperature modifier, such as ethylene-vinyl acetate copolymer (EVA), reduces the intermolecular forces of PVC molecules. Although this improves low-temperature performance, it leads to poorer dispersion of flame retardants and a decrease in flame retardant efficiency, making it impossible to achieve ultra-low temperature toughness while maintaining a high flame retardant rating.

[0006] Issues with processing stability: During high-speed extrusion, flame retardant agglomeration can easily cause die blockage, requiring frequent shutdowns for cleaning, resulting in low production efficiency. Furthermore, uneven filler dispersion between different batches of products leads to large performance fluctuations, and there is a lack of systematic process optimization methods.

[0007] Therefore, developing a polyvinyl chloride granule that can solve the above problems simultaneously has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0008] This invention overcomes the shortcomings of existing technologies by providing a high flame-retardant, low-temperature resistant matte polyvinyl chloride (PVC) granule, its preparation method, and an outer sheath for wires and cables. The PVC granule combines high flame retardancy, excellent low-temperature resistance, and a uniform matte finish.

[0009] To achieve the above-mentioned objectives, the following technical solution is provided:

[0010] A high flame-retardant and low-temperature resistant matte polyvinyl chloride granule is provided, comprising the following components in parts by weight:

[0011] 80-120 parts of polyvinyl chloride resin powder

[0012] 20-30 parts of core-shell modified resin, wherein the core-shell modified resin is a compound of Zhongyuan K10S and Tianye XG-5 in a mass ratio of 3:2; 4-6 parts of nanocomposite flame retardant, wherein the nanocomposite flame retardant is a compound of magnesium hydroxide and red phosphorus microcapsules in a mass ratio of 3:1.

[0013] 5-8 parts of a low-temperature resistant modifier, wherein the low-temperature resistant modifier is a compound of ethylene-vinyl acetate copolymer and polyether elastomer at a mass ratio of 2:1;

[0014] 60-100 parts of plasticizer, wherein the plasticizer is a compound of diisononyl phthalate and epoxidized soybean oil in a mass ratio of 7:3;

[0015] 80-150 parts of nano-calcium carbonate

[0016] 2-4 parts of functionalized resin, wherein the functionalized resin is maleic anhydride-grafted polyethylene;

[0017] 2-12 parts of surface-stearic acid modified calcium-zinc stabilizer.

[0018] Polyvinyl chloride resin powder is used as the base matrix. The medium degree of polymerization (1000-1200) balances rigidity and processing fluidity. The K value of 66-68 ensures that the melt index matches the high-speed granulation process.

[0019] The core function of core-shell modified resin is to form a matte finish. The ratio of Zhongyuan K10S to Tianye XG-5 is 3:2. The separation of the core and shell phases induces the formation of nanoscale diffuse reflection units, replacing the disordered dispersion of traditional single fillers.

[0020] Kaneka K10S is a core-shell processing aid based on PMMA (polymethyl methacrylate, i.e., acrylic glass), with core functions including promoting plasticization, improving melt strength, and imparting a matte finish. It was purchased from Kaneka Chemicals, Japan.

[0021] Tianye XG-5 is an ACR (acrylate-based) impact modifier / processing aid, also possessing a core-shell structure, which functions to toughen and assist processing while stabilizing the microstructure. It was purchased from Xinjiang Tianye (Group) Co., Ltd., China.

[0022] The core function of composite flame retardants is high-efficiency flame retardancy. Nano-sized magnesium hydroxide is compounded with red phosphorus microcapsules, and through size effect and synergistic reaction, UL94 V-0 flame retardancy is achieved at low addition levels (VW-1 test passed). Among them, the average particle size of magnesium hydroxide is 50-100nm.

[0023] The core function of the low-temperature modifier is low-temperature toughening. The EVA:PEE ratio of 2:1 is compounded to form an interpenetrating "flexible network-rigid matrix" structure through hydrogen bonding, thus overcoming the low-temperature embrittlement threshold. The ethylene-vinyl acetate copolymer content is 40%.

[0024] Ethylene-vinyl acetate copolymer (EVA) is a high-performance polymer modifier obtained by introducing vinyl acetate monomers into the polyethylene chain. The properties of EVA largely depend on the vinyl acetate (VA) content in its molecular chain. Different VA contents result in significant variations in the morphology, properties, and applications of EVA. In this invention, an EVA resin with a VA content of 40% is specifically selected, primarily utilizing its internal plasticizing effect to significantly improve the flexibility and low-temperature resistance of the PVC matrix.

[0025] The core function of plasticizers is as processing aids. The low migration formula of diisononyl phthalate: epoxidized soybean oil = 7:3 ensures the stability of mechanical properties under long-term outdoor use.

[0026] Furthermore, the functionalized resin is maleic anhydride-grafted polyethylene with a grafting rate of 1.2%.

[0027] The core function of functionalized resin is interfacial compatibility. Maleic anhydride-grafted polyethylene promotes the chemical bonding between flame retardant and PVC matrix, increasing interfacial bonding strength by 30%.

[0028] Maleic anhydride-grafted polyethylene is a functional polymer that modifies ordinary polyethylene (PE) through chemical methods. The polyethylene backbone provides good compatibility and processability with the polyethylene matrix, while the maleic anhydride functional group is its core function, exhibiting high reactivity. Under specific process conditions, it strongly "rivets" the originally poorly compatible PVC matrix and EVA / PEE elastomer together through chemical bonding, greatly enhancing the interfacial strength. It is an indispensable "molecular bridge" for resolving the contradiction between "flame retardancy and low-temperature toughness" and achieving performance breakthroughs.

[0029] Furthermore, it also includes 1-3 parts of graphene oxide, wherein the number of graphene oxide layers is ≤10 and the lateral dimension is 5-10 μm.

[0030] The oxygen-containing groups of graphene oxide form hydrogen bonds with polyvinyl chloride, promoting the dispersion of flame retardants and their bonding at the phase interface.

[0031] Furthermore, the nano-calcium carbonate has a particle size ≤100nm and a calcium content ≥98%.

[0032] The core function of nano-calcium carbonate is structural reinforcement. Stearic acid-modified nano-calcium carbonate, together with core-shell resin, constructs a matte core, improving surface density.

[0033] A method for preparing high flame-retardant and low-temperature resistant matte polyvinyl chloride granules is provided, comprising the following steps:

[0034] S1: Pre-dispersion stage: Add polyvinyl chloride resin powder, 60%-70% plasticizer, and nano calcium carbonate to the mixer. Stir at 1000-1200 r / min at 80-90℃ until the material is loose and uniform in granular form. Then add core-shell modified resin and nano composite flame retardant. Heat to 100-110℃ and stir at 1500 r / min until the flame retardant dispersion is ≥80%.

[0035] S2: Deep crosslinking stage: Add the remaining 30%-40% plasticizer, low-temperature modifier and functionalized resin, heat to 135-145℃, and shear at high speed of 2000-2500r / min until the system viscosity reaches 500-800mPa·s. Then add calcium-zinc composite stabilizer and appropriate amount of colorant, and keep warm and mix at 135~145℃ for 10-15min to form a uniform emulsion slurry without particle agglomeration.

[0036] S3: Low-temperature granulation stage: The emulsified slurry is placed in a twin-screw granulator. The feeding section temperature is 90-100℃, the screw speed is 30-40 rpm, the plasticizing section is divided into three temperature control zones: zone 1 105-110℃, zone 2 115-120℃, and zone 3 125-130℃. The discharge section temperature is 125-135℃, the die pressure is 8-10 MPa, and the extrusion speed is 40-45 rpm. After discharge, the granules are obtained by pelletizing, cooling, and sieving.

[0037] Furthermore, the pelleting speed is 35-38 RMP, the pellet length is controlled at 3-5 mm, and after discharge, the pellets are cooled by circulating water at 20-25℃ and then screened by a 20-mesh vibrating screen.

[0038] Furthermore, in step S1, the flame retardant dispersion is observed to be ≥80% using an optical microscope.

[0039] Further, in step S2, the viscosity of the system is monitored using a rotational viscometer to determine if it reaches 500-800 mPa·s.

[0040] Furthermore, the moisture content of the granules is ≤0.1%.

[0041] An application is provided for the outer sheath of wires and cables suitable for use in extremely cold regions of -40°C, comprising preparation of high flame-retardant and low-temperature resistant matte polyvinyl chloride granules as described above.

[0042] Compared with the prior art, the beneficial effects of the high flame retardant and low-temperature resistant matte polyvinyl chloride granules of the present invention are:

[0043] (1) This invention achieves a breakthrough in three key properties—flame retardancy, low-temperature resistance, and good matte finish—for the first time through nanoscale compounding and core-shell structure synergy. Specifically, by compounding magnesium hydroxide and red phosphorus microcapsules in a 3:1 ratio, a low-addition amount of nanoscale composite flame retardant is achieved, resulting in high-efficiency flame retardancy with an oxygen index exceeding 34%, as demonstrated by the VW-1 test. Nanoscale magnesium hydroxide reduces the combustion temperature and inhibits polymer decomposition through its dehydration endothermic effect. Red phosphorus microcapsules slowly release phosphate ester flame retardant components, accelerating the char formation rate and forming a dense char layer to block heat transfer. Nanoscale dispersion prevents filler agglomeration, achieving a dual flame retardant barrier of condensation and char formation at low addition amounts, thus resolving the contradiction between appearance and flame retardancy caused by traditional high-filling methods.

[0044] (2) In this invention, ultra-low temperature toughness is achieved by compounding ethylene-vinyl acetate copolymer (EVA) and polyether elastomer (PEE) in a 2:1 ratio. The flexible segments of EVA are inserted between the PVC molecular chains, which reduces the glass transition temperature and improves the molecular chain mobility. The ether bonds in the PEE molecules form hydrogen bonds with the polar groups of PVC, which enhances the interfacial compatibility and effectively inhibits phase separation at low temperatures. This results in an elongation at break of ≥220% at -40℃ and a low-temperature impact embrittlement temperature of ≤-55℃, breaking through the performance limit of a single modifier and achieving a synergistic improvement in flame retardancy and low-temperature performance.

[0045] (3) In this invention, the core-shell modified resin, which is compounded with Zhongyuan K10S and Tianye XG-5 in a 3:2 ratio, achieves enhanced haze, stabilizing the haze value of the material at 65% or higher with fluctuations ≤3%, and achieving an extrusion line speed ≥120m / min. The core-shell structure forms a microphase separation structure in the PVC matrix, and the difference between the refractive index of the shell and the core enhances diffuse light reflection. The synergistic effect of the core-shell resin and nano-calcium carbonate results in a surface roughness Ra ≤1.3μm, and improves the haze uniformity compared to traditional single modifiers.

[0046] Compared with the prior art, the beneficial effects of the preparation method of the high flame retardant and low-temperature resistant matte polyvinyl chloride granules of the present invention are:

[0047] (1) In this invention, the gradient dispersion-directional crosslinking process achieves multi-scale structural control through system parameter adjustment. Specifically,

[0048] Low-speed pre-dispersion is employed to preferentially disperse nano-calcium carbonate and core-shell resin, forming a "core-shell" pre-dispersion system with PVC as the matrix. This avoids early agglomeration of the flame retardant, improves filler dispersion, significantly reduces die accumulation, and increases the extrusion line speed to 118 m / min. High-speed shearing breaks down the surface coating of the red phosphorus microcapsules, releasing active sites, increasing the contact area between the flame retardant and the matrix, and improving the flame retardant reaction efficiency.

[0049] Maleic anhydride-grafted polyethylene forms chemical crosslinks with PVC molecular chains through ester bonds (-COO-), enhancing interfacial bonding, inhibiting EVA / PEE phase separation, and improving low-temperature toughness.

[0050] The matching of the discharge section temperature and the extrusion speed allows the core-shell resin to be oriented and arranged in the die head, forming a uniform diffuse reflection microstructure with a surface roughness Ra≤1.3μm.

[0051] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0052] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0053] Example 1

[0054] This embodiment discloses a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule and its preparation method, the steps of which are as follows:

[0055] S1: Prepare polyvinyl chloride granules according to the following formula.

[0056] Weigh out the following components by weight: 100 parts of polyvinyl chloride resin powder (K ​​value 67), 25 parts of core-shell modified resin (Zhongyuan K10S: Tianye XG-5 = 3:2), 5 parts of nano-composite flame retardant (nano magnesium hydroxide: red phosphorus microcapsules = 3:1), 6 parts of low-temperature resistant modifier (EVA (VA 40%): PEE = 2:1), 80 parts of plasticizer (diisononyl phthalate: epoxidized soybean oil = 7:3), 120 parts of nano calcium carbonate (particle size ≤ 100nm), 3 parts of functionalized resin (maleic anhydride grafted polyethylene, grafting rate 1.2%), and 6 parts of calcium-zinc stabilizer.

[0057] S2: Method for preparing polyvinyl chloride granules

[0058] 1. Pre-dispersion stage (high-speed mixer)

[0059] (1) Premixing of basic materials

[0060] Add 100 parts of polyvinyl chloride resin powder, 65% plasticizer, and 120 parts of nano calcium carbonate to a 1000L high-speed mixer. Control the temperature at 85℃ and stir at 1100r / min and 55A current for 17 minutes until the material is in a loose and uniform granular form, ensuring that the resin powder fully absorbs the plasticizer and the mineral powder is initially dispersed.

[0061] (2) Dispersion of core-shell resin and flame retardant

[0062] Add 25 parts of core-shell modified resin and 5 parts of composite flame retardant, heat to 105℃, stir at 1500r / min and 65A current for 22min, and observe the flame retardant dispersion at ≥80% through an optical microscope to avoid excessive breakage of the core-shell resin.

[0063] 2. Deep cross-linking stage (high-speed mixer)

[0064] (3) Modifiers and functional resins added

[0065] Add the remaining 35% plasticizer, 6 parts of low-temperature modifier, and 3 parts of functionalized resin. Heat to 140℃ and shear at 2200r / min and 87A current for 35min. Monitor the viscosity of the system using a rotational viscometer until it reaches 650mPa·s, triggering the ester bond crosslinking reaction and enhancing interfacial compatibility.

[0066] (4) Mixing stabilizers and colorants

[0067] Add 6 parts of calcium-zinc composite stabilizer, and the dynamic thermal stabilization time at 160℃ is ≥50min. Add an appropriate amount of colorant, keep warm for 12min, and control the temperature at 140℃ to form a uniform emulsion slurry without particle agglomeration.

[0068] 3. Low-temperature granulation stage (twin-screw granulator)

[0069] (5) Equipment preheating and parameter setting

[0070] Feeding section: Temperature 95℃, screw speed 35 RPM, to ensure that the material enters the plasticizing section at a uniform speed and avoid premature melting of the plasticizer, which could cause the screw to slip.

[0071] Plasticizing section (three-zone gradient heating):

[0072] Zone 1: 105℃ (PVC resin initially melts);

[0073] Zone 2, 115℃ (EVA / PEE elastomer melts and disperses);

[0074] Three zones at 125℃ (the nanofiller is fully mixed with the matrix), and gradient melting is achieved through a 10℃ temperature difference to inhibit the agglomeration of nanoparticles (SEM detection shows a dispersion of ≥85%).

[0075] Discharge section: temperature 130℃, die head pressure 9MPa, adjusted in real time by pressure sensor to ensure moderate material viscosity, which is conducive to the formation of microphase separation structure.

[0076] (6) Melt blending and pelletizing

[0077] Start the screw, extrusion speed 42 RMP, pelletizing speed 36 RMP, and control pellet length 4mm.

[0078] After discharge, the material is immediately cooled by circulating water at 22℃, and then screened by a 20-mesh vibrating screen to remove irregular particles. The final particle moisture content is ≤0.1% (determined by Karl Fischer titration).

[0079] 1. Synergistic optimization of flame retardancy and appearance

[0080] Flame retardant performance: Flame retardant dosage reduced by 60% (only 4-6 parts), oxygen index reaches 34%-36% (GB / T 2406.2), VW-1 test burning time ≤12s, residue reduced by 60%, no halogen release, and compliant with RoHS 2.0 and REACH standards.

[0081] Appearance quality: Haze value 68±1% (GB / T 2410), surface roughness Ra=1.1-1.4μm, diffuse reflectance increased by 60%, solving the problem of uneven haze and roughness caused by traditional high filler.

[0082] 2. Breakthrough in low-temperature toughness

[0083] Low temperature resistance: Elongation at break ≥220% (GB / T 1040.3) at -40℃, low temperature impact embrittlement temperature ≤-55℃, and performance retention rate ≥95% after storage at -20℃ for 1000h. This is significantly better than the 150% elongation at break of a single EVA modifier, breaking through the bottleneck of embrittlement in low temperature environments.

[0084] 3. Improved processing performance

[0085] Production efficiency: The extrusion line speed reaches 120m / min, which is 243% higher than that of traditional mist fabrics. The die head accumulation frequency is reduced by 90%, the continuous production time is extended to more than 48 hours, and the performance fluctuation between batches is ≤5%, which meets the needs of large-scale industrial production.

[0086] Example 2

[0087] This embodiment discloses a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule and its preparation method, the steps of which are as follows:

[0088] S1: Prepare polyvinyl chloride granules according to the following formula.

[0089] Weigh out the following components by weight: 100 parts of polyvinyl chloride resin powder (K ​​value 67), 25 parts of core-shell modified resin (Zhongyuan K10S: Tianye XG-5 = 3:2), 5 parts of nano-composite flame retardant (nano magnesium hydroxide: red phosphorus microcapsules = 3:1), 6 parts of low-temperature resistant modifier (EVA (VA 40%): PEE = 2:1), 80 parts of plasticizer (diisononyl phthalate: epoxidized soybean oil = 7:3), 120 parts of nano-calcium carbonate (particle size ≤ 100nm), 3 parts of functionalized resin (maleic anhydride grafted polyethylene, grafting rate 1.2%), 6 parts of calcium-zinc stabilizer, and 1 part of graphene oxide (GO) (this can be added depending on the actual situation).

[0090] S2: Method for preparing polyvinyl chloride granules

[0091] 1. Pre-dispersion stage (high-speed mixer)

[0092] (1) Premixing of basic materials

[0093] Add 100 parts of polyvinyl chloride resin powder, 65% plasticizer, and 120 parts of nano calcium carbonate to a 1000L high-speed mixer. Control the temperature at 85℃ and stir at 1100r / min and 55A current for 17 minutes until the material is in a loose and uniform granular form, ensuring that the resin powder fully absorbs the plasticizer and the mineral powder is initially dispersed.

[0094] (2) Dispersion of core-shell resin and flame retardant

[0095] Add 25 parts of core-shell modified resin and 5 parts of composite flame retardant, heat to 105℃, stir at 1500r / min and 65A current for 22min, and observe the flame retardant dispersion at ≥80% through an optical microscope to avoid excessive breakage of the core-shell resin.

[0096] 2. Deep cross-linking stage (high-speed mixer)

[0097] (3) Modifiers and functional resins added

[0098] Add the remaining 35% plasticizer, 6 parts of low-temperature resistant modifier, 3 parts of functionalized resin, and 1 part of graphene oxide (layer number ≤ 10 layers, transverse dimension 5-10μm) (this can be determined based on actual conditions). Heat to 140℃ and shear at 2200r / min and 87A current for 35min. Monitor the viscosity of the system using a rotational viscometer until it reaches 650mPa·s, triggering the ester bond crosslinking reaction and enhancing interfacial compatibility.

[0099] (4) Mixing stabilizers and colorants

[0100] Add 6 parts of calcium-zinc composite stabilizer, and the dynamic thermal stabilization time at 160℃ is ≥50min. Add an appropriate amount of colorant, keep warm for 12min, and control the temperature at 140℃ to form a uniform emulsion slurry without particle agglomeration.

[0101] 3. Low-temperature granulation stage (twin-screw granulator)

[0102] (5) Equipment preheating and parameter setting

[0103] Feeding section: Temperature 95℃, screw speed 35 RPM, to ensure that the material enters the plasticizing section at a uniform speed and avoid premature melting of the plasticizer, which could cause the screw to slip.

[0104] Plasticizing section (three-zone gradient heating):

[0105] Zone 1: 105℃ (PVC resin initially melts);

[0106] Zone 2, 115℃ (EVA / PEE elastomer melts and disperses);

[0107] Three zones at 125℃ (the nanofiller is fully mixed with the matrix), and gradient melting is achieved through a 10℃ temperature difference to inhibit the agglomeration of nanoparticles (SEM detection shows a dispersion of ≥85%).

[0108] Discharge section: temperature 130℃, die head pressure 9MPa, adjusted in real time by pressure sensor to ensure moderate material viscosity, which is conducive to the formation of microphase separation structure.

[0109] (6) Melt blending and pelletizing

[0110] Start the screw, extrusion speed 42 RMP, pelletizing speed 36 RMP, and control pellet length 4mm.

[0111] After discharge, the material is immediately cooled by circulating water at 22℃, and then screened by a 20-mesh vibrating screen to remove irregular particles. The final particle moisture content is ≤0.1% (determined by Karl Fischer titration).

[0112] Effect verification:

[0113] To further illustrate the effects of the present invention, the following experiments and comparisons were conducted:

[0114] Experimental Example 1

[0115] This experimental example discloses a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule and its preparation method, the steps of which are as follows:

[0116] S1: Prepare polyvinyl chloride granules according to the following formula.

[0117] Weigh out the following components by weight: 100 parts of polyvinyl chloride resin powder (K ​​value 67), 25 parts of core-shell modified resin (Zhongyuan K10S: Tianye XG-5 = 3:2), 5 parts of nano-composite flame retardant (nano magnesium hydroxide: red phosphorus microcapsules = 3:1), 6 parts of low-temperature resistant modifier (EVA (VA 40%): PEE = 2:1), 80 parts of plasticizer (diisononyl phthalate: epoxidized soybean oil = 7:3), 120 parts of nano calcium carbonate (particle size ≤ 100nm), 3 parts of functionalized resin (maleic anhydride grafted polyethylene, grafting rate 1.2%), and 6 parts of calcium-zinc stabilizer.

[0118] S2: Method for preparing polyvinyl chloride granules

[0119] 1. Pre-dispersion stage (high-speed mixer)

[0120] (1) Premixing of basic materials

[0121] Add 100 parts of polyvinyl chloride resin powder, 65% plasticizer, and 120 parts of nano calcium carbonate to a 1000L high-speed mixer. Control the temperature at 85℃ and stir at 1100r / min and 55A current for 17 minutes until the material is in a loose and uniform granular form, ensuring that the resin powder fully absorbs the plasticizer and the mineral powder is initially dispersed.

[0122] (2) Dispersion of core-shell resin and flame retardant

[0123] Add 25 parts of core-shell modified resin and 5 parts of composite flame retardant, heat to 105℃, stir at 1500r / min and 65A current for 22min, and observe the flame retardant dispersion at ≥80% through an optical microscope to avoid excessive breakage of the core-shell resin.

[0124] 2. Deep cross-linking stage (high-speed mixer)

[0125] (3) Modifiers and functional resins added

[0126] Add the remaining 35% plasticizer, 6 parts of low-temperature modifier, and 3 parts of functionalized resin. Heat to 140℃ and shear at 2200r / min and 87A current for 35min. Monitor the viscosity of the system using a rotational viscometer until it reaches 650mPa·s, triggering the ester bond crosslinking reaction and enhancing interfacial compatibility.

[0127] (4) Mixing stabilizers and colorants

[0128] Add 6 parts of calcium-zinc composite stabilizer, and the dynamic thermal stabilization time at 160℃ is ≥50min. Add an appropriate amount of colorant, keep warm for 12min, and control the temperature at 140℃ to form a uniform emulsion slurry without particle agglomeration.

[0129] 3. Low-temperature granulation stage (twin-screw granulator)

[0130] (5) Equipment preheating and parameter setting

[0131] Feeding section: Temperature 95℃, screw speed 35 RPM, to ensure that the material enters the plasticizing section at a uniform speed and avoid premature melting of the plasticizer, which could cause the screw to slip.

[0132] Plasticizing section (three-zone gradient heating):

[0133] Zone 1: 105℃ (PVC resin initially melts);

[0134] Zone 2, 115℃ (EVA / PEE elastomer melts and disperses);

[0135] Three zones at 125℃ (the nanofiller is fully mixed with the matrix), and gradient melting is achieved through a 10℃ temperature difference to inhibit the agglomeration of nanoparticles (SEM detection shows a dispersion of ≥85%).

[0136] Discharge section: temperature 130℃, die head pressure 9MPa, adjusted in real time by pressure sensor to ensure moderate material viscosity, which is conducive to the formation of microphase separation structure.

[0137] (6) Melt blending and pelletizing

[0138] Start the screw, extrusion speed 42 RMP, pelletizing speed 36 RMP, and control pellet length 4mm.

[0139] After discharge, the material is immediately cooled by circulating water at 22℃, and then screened by a 20-mesh vibrating screen to remove irregular particles. The final particle moisture content is ≤0.1% (determined by Karl Fischer titration).

[0140] Performance: Oxygen index 34%, VW-1 test burning time 12s, elongation at break 220% at -40℃, haze 67%, extrusion speed 118m / min, surface roughness Ra=1.3μm, die accumulation frequency 2 times / 8h, low temperature impact embrittlement temperature -55℃.

[0141] Experimental Example 2

[0142] This experimental example discloses a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule and its preparation method, the steps of which are as follows:

[0143] S1: Prepare polyvinyl chloride granules according to the following formula.

[0144] Weigh out the following components by weight: 100 parts of polyvinyl chloride resin powder (K ​​value 67), 25 parts of core-shell modified resin (Zhongyuan K10S: Tianye XG-5 = 3:2), 5 parts of nano-composite flame retardant (nano magnesium hydroxide: red phosphorus microcapsules = 3:1), 6 parts of low-temperature resistant modifier (EVA (VA 40%): PEE = 2:1), 80 parts of plasticizer (diisononyl phthalate: epoxidized soybean oil = 7:3), 120 parts of nano-calcium carbonate (particle size ≤ 100nm), 3 parts of functionalized resin (maleic anhydride grafted polyethylene, grafting rate 1.2%), 6 parts of calcium-zinc stabilizer, and 1 part of graphene oxide (GO) (this can be added depending on the actual situation).

[0145] S2: Method for preparing polyvinyl chloride granules

[0146] 1. Pre-dispersion stage (high-speed mixer)

[0147] (1) Premixing of basic materials

[0148] Add 100 parts of polyvinyl chloride resin powder, 65% plasticizer, and 120 parts of nano calcium carbonate to a 1000L high-speed mixer. Control the temperature at 85℃ and stir at 1100r / min and 55A current for 17 minutes until the material is in a loose and uniform granular form, ensuring that the resin powder fully absorbs the plasticizer and the mineral powder is initially dispersed.

[0149] (2) Dispersion of core-shell resin and flame retardant

[0150] Add 25 parts of core-shell modified resin and 5 parts of composite flame retardant, heat to 105℃, stir at 1500r / min and 65A current for 22min, and observe the flame retardant dispersion at ≥80% through an optical microscope to avoid excessive breakage of the core-shell resin.

[0151] 2. Deep cross-linking stage (high-speed mixer)

[0152] (3) Modifiers and functional resins added

[0153] Add the remaining 35% plasticizer, 6 parts of low-temperature resistant modifier, 3 parts of functionalized resin, and 1 part of graphene oxide (layer number ≤ 10 layers, transverse dimension 5-10μm) (this can be determined based on actual conditions). Heat to 140℃ and shear at 2200r / min and 87A current for 35min. Monitor the viscosity of the system using a rotational viscometer until it reaches 650mPa·s, triggering the ester bond crosslinking reaction and enhancing interfacial compatibility.

[0154] (4) Mixing stabilizers and colorants

[0155] Add 6 parts of calcium-zinc composite stabilizer, and the dynamic thermal stabilization time at 160℃ is ≥50min. Add an appropriate amount of colorant, keep warm for 12min, and control the temperature at 140℃ to form a uniform emulsion slurry without particle agglomeration.

[0156] 3. Low-temperature granulation stage (twin-screw granulator)

[0157] (5) Equipment preheating and parameter setting

[0158] Feeding section: Temperature 95℃, screw speed 35 RPM, to ensure that the material enters the plasticizing section at a uniform speed and avoid premature melting of the plasticizer, which could cause the screw to slip.

[0159] Plasticizing section (three-zone gradient heating):

[0160] Zone 1: 105℃ (PVC resin initially melts);

[0161] Zone 2, 115℃ (EVA / PEE elastomer melts and disperses);

[0162] Three zones at 125℃ (the nanofiller is fully mixed with the matrix), and gradient melting is achieved through a 10℃ temperature difference to inhibit the agglomeration of nanoparticles (SEM detection shows a dispersion of ≥85%).

[0163] Discharge section: temperature 130℃, die head pressure 9MPa, adjusted in real time by pressure sensor to ensure moderate material viscosity, which is conducive to the formation of microphase separation structure.

[0164] (6) Melt blending and pelletizing

[0165] Start the screw, extrusion speed 42 RMP, pelletizing speed 36 RMP, and control pellet length 4mm.

[0166] After discharge, the material is immediately cooled by circulating water at 22℃, and then screened by a 20-mesh vibrating screen to remove irregular particles. The final particle moisture content is ≤0.1% (determined by Karl Fischer titration).

[0167] Performance: Oxygen index 36%, VW-1 test burning time 10s, elongation at break 250% at -40℃, haze 70±1%, surface roughness Ra=1.1μm, nanoparticle dispersion increased to 90% (SEM detection).

[0168] Comparative Example 1

[0169] This comparative example discloses a high flame-retardant and low-temperature resistant matte polyvinyl chloride granule and its preparation method. Based on the formulation of Example 1, the low-temperature resistant modifier is adjusted to 7 parts, and the ratio of EVA to PEE is adjusted to 1:1. The preparation process is the same as in Example 1.

[0170] Performance: Elongation at break of 230% at -40℃, low-temperature impact embrittlement temperature of -53℃, haze of 67±1%, extrusion speed of 115m / min, and die head accumulation frequency reduced by 15% compared to Example 1.

[0171] 1. Performance comparison with commercially available products

[0172] To further demonstrate the technical advantages of the polyvinyl chloride granules of this application, two typical commercially available granules were selected, including commercially available ordinary matte granules and low-temperature resistant granules. The key performance of Experimental Example 1 of this application was compared with these two types of granules. The results are shown in Table 1. Compared with commercially available ordinary matte granules and low-temperature resistant granules, Experimental Example 1 of this application uses only 5 parts of flame retardant, achieves an oxygen index of 34%, has a breaking elongation of 220% at -40℃, a haze of 67%, an extrusion line speed of 118m / min, a surface roughness of 1.3μm, and a die accumulation frequency of 2 times / 8h. Overall, Experimental Example 1 shows superior performance indicators.

[0173] Table 1 Comparison of Key Performance Indicators of Polyvinyl Chloride Granules

[0174]

[0175] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A high flame-retardant, low-temperature resistant, matte polyvinyl chloride granule, characterized in that, Includes the following components by weight, 80-120 parts of polyvinyl chloride resin powder 20-30 parts of core-shell modified resin, wherein the core-shell modified resin is a compound of Zhongyuan K10S and Tianye XG-5 in a mass ratio of 3:2; 4-6 parts of nanocomposite flame retardant, wherein the nanocomposite flame retardant is a mixture of magnesium hydroxide and red phosphorus microcapsules in a mass ratio of 3:1; 5-8 parts of a low-temperature resistant modifier, wherein the low-temperature resistant modifier is a compound of ethylene-vinyl acetate copolymer and polyether elastomer at a mass ratio of 2:1; 60-100 parts of plasticizer, wherein the plasticizer is a compound of diisononyl phthalate and epoxidized soybean oil in a mass ratio of 7:3; 80-150 parts of nano-calcium carbonate 2-4 parts of functionalized resin, wherein the functionalized resin is maleic anhydride-grafted polyethylene; 2-12 parts of surface-stearic acid modified calcium-zinc stabilizer.

2. The high flame-retardant, low-temperature resistant matte polyvinyl chloride granules according to claim 1, characterized in that, The grafting rate of the maleic anhydride-grafted polyethylene is 1.2%.

3. The high flame-retardant, low-temperature resistant matte polyvinyl chloride granules according to claim 1, characterized in that, It also includes 1-3 parts of graphene oxide, wherein the number of graphene oxide layers is ≤10 and the lateral dimension is 5-10μm.

4. The high flame-retardant, low-temperature resistant matte polyvinyl chloride granules according to claim 1, characterized in that, The nano-calcium carbonate has a particle size ≤100nm and a calcium content ≥98%.

5. A method for preparing high flame-retardant, low-temperature resistant matte polyvinyl chloride granules as described in any one of claims 1-4, characterized in that, Includes the following steps, S1: Pre-dispersion stage: Add polyvinyl chloride resin powder, 60%-70% plasticizer, and nano calcium carbonate to the mixer. Stir at 1000-1200 r / min at 80-90℃ until the material is loose and uniform in granular form. Then add core-shell modified resin and nano composite flame retardant. Heat to 100-110℃ and stir at 1500 r / min until the flame retardant dispersion is ≥80%. S2: Deep crosslinking stage: Add the remaining 30%-40% plasticizer, low-temperature modifier and functionalized resin, heat to 135-145℃, and shear at high speed of 2000-2500r / min until the system viscosity reaches 500-800mPa·s. Then add calcium-zinc composite stabilizer and appropriate amount of colorant, and keep warm and mix at 135~145℃ for 10-15min to form a uniform emulsion slurry without particle agglomeration. S3: Low-temperature granulation stage: The emulsified slurry is placed in a twin-screw granulator. The feeding section temperature is 90-100℃, the screw speed is 30-40 rpm, the plasticizing section is divided into three temperature control zones: zone 1 105-110℃, zone 2 115-120℃, and zone 3 125-130℃. The discharge section temperature is 125-135℃, the die pressure is 8-10 MPa, and the extrusion speed is 40-45 rpm. After discharge, the granules are obtained by pelletizing, cooling, and sieving.

6. The method for preparing high flame-retardant and low-temperature resistant matte polyvinyl chloride granules according to claim 5, characterized in that, The pelleting speed is 35-38 RMP, the pellet length is controlled at 3-5 mm, and after discharge, the pellets are cooled by circulating water at 20-25℃ and then screened by a 20-mesh vibrating screen.

7. The method for preparing high flame-retardant and low-temperature resistant matte polyvinyl chloride granules according to claim 5, characterized in that, In step S1, the flame retardant dispersion is observed to be ≥80% using an optical microscope.

8. The method for preparing high flame-retardant and low-temperature resistant matte polyvinyl chloride granules according to claim 5, characterized in that, In step S2, the viscosity of the system is monitored using a rotational viscometer to determine if it reaches 500-800 mPa·s.

9. The method for preparing high flame-retardant and low-temperature resistant matte polyvinyl chloride granules according to claim 5, characterized in that, The moisture content of the granules is ≤0.1%.

10. The application of the high flame-retardant and low-temperature resistant matte polyvinyl chloride granules according to any one of claims 5 to 9 in the preparation of outer sheaths for wires and cables suitable for use in extremely cold regions of -40°C.

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