A low voc cable jacket material and process for making the same

Abstract

The application relates to the field of cable sheath materials, and particularly discloses a low-VOC cable sheath material and a preparation process thereof.A low-VOC cable sheath material comprises the following components in parts by weight: 100-120 parts of PVC resin, 25-35 parts of heavy calcium carbonate, 20-35 parts of a plasticizer, 30-45 parts of a flame retardant, 2-5 parts of a heat stabilizer, 8-15 parts of an elastomer reinforcing agent, 3-5 parts of a titanate coupling agent, 0.5-1.5 parts of an antioxidant, and 0.5-3 parts of calcium stearate; the plasticizer comprises at least one of polypropylene adipate-polyether block copolymer and epoxy soybean oil; and the PVC resin has a polymerization degree of 1100-1200.The low-VOC cable sheath material has the advantages of keeping the low-VOC effect of the cable and further improving the mechanical strength of the cable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cable sheath materials, more particularly, it relates to a low VOC cable sheath material and a preparation process thereof. BACKGROUND

[0002] With the increasingly stringent global environmental regulations and the increasing concern of consumers for health and safety, the limitations of traditional cable sheath materials gradually become prominent. Traditional sheath materials represented by polyvinyl chloride (PVC) rely on phthalate plasticizers, halogen-based flame retardants and other volatile organic compound (VOC) additives, which release harmful substances such as formaldehyde and benzene during processing and use, posing long-term hazards to human health and the environment. In this context, low VOC cable sheath technology has emerged, with the core goal of maintaining the mechanical properties, weather resistance and flame retardance of the sheath while reducing VOC emissions through material innovation and process optimization.

[0003] Currently, low VOC sheath technology has made some progress. In terms of material systems, halogen-free flame-retardant polyolefins replace halogen-based flame retardants with magnesium hydroxide, aluminum hydroxide and other metal hydroxides, significantly reducing the release of toxic gases during combustion; bio-based elastomers replace petroleum-based plasticizers with renewable raw materials such as castor oil, further reducing carbon footprint. In addition, the use of high molecular weight polyester plasticizers and reactive stabilizers reduces the migration and volatilization of small molecule additives.

[0004] Although existing technologies can control the total VOC emission to below 50 μg / g, there is still a significant gap in mechanical properties, weather resistance and other aspects compared to traditional materials. The core reasons for the decline in mechanical properties of low VOC sheaths can be summarized as follows: first, the compatibility of environmental additives with the base material is insufficient. High molecular weight or bio-based plasticizers that replace traditional small molecule plasticizers are prone to uneven dispersion in the resin due to polarity differences, forming micro defects and destroying the crystalline structure, directly weakening the tensile strength and toughness. Second, the negative impact of high-filled flame-retardant systems. To meet the halogen-free flame-retardant requirements, more than 60% of inorganic fillers (such as magnesium hydroxide) need to be added, which leads to the rupture of the base material continuity, increases the brittleness, and weakens the interaction between molecular chains. Third, insufficient process adaptability. High filler content leads to poor melt flowability, making it prone to surface defects and internal stress during processing, further exacerbating mechanical property degradation. The multi-objective conflict between environmental protection, flame retardance and mechanical properties makes optimization more difficult. SUMMARY

[0005] In order to solve the problem that the mechanical properties of low VOC cable materials are poorer than those of traditional cable materials, the present application provides a low VOC cable sheath material and a preparation process thereof.

[0006] The low VOC cable sheath material provided by the present application adopts the following technical scheme:

[0007] A low VOC cable sheath material, the components of which include, by weight parts, PVC resin 100-120 parts, heavy calcium carbonate 25-35 parts, plasticizer 20-35 parts, flame retardant 30-45 parts, heat stabilizer 2-5 parts, elastomer reinforcing agent 8-15 parts, titanate coupling agent 3-5 parts, antioxidant 0.5-1.5 parts, calcium stearate 0.5-3 parts, the plasticizer including at least one of polypropylene adipate-polyether block copolymer and epoxy soybean oil, the PVC resin having a polymerization degree of 1100-1200.

[0008] By adopting the above technical scheme, polypropylene adipate-polyether block copolymer is used as a high molecular weight plasticizer, the entanglement of the long chain molecules with the PVC resin is strong, and the intermolecular force is significantly higher than that of traditional phthalate esters, which can inhibit the migration and volatilization of the plasticizer molecules, and reduce VOC release from the source; the epoxy soybean oil is used as a bio-based plasticizer, the epoxy groups on the fatty acid chain can form hydrogen bonds with the chlorine atoms of the PVC molecular chain, enhancing the interfacial compatibility, while reducing the system viscosity and improving the processing fluidity. The PVC resin with a polymerization degree of 1100-1200 has a longer molecular chain and stronger intermolecular van der Waals force, and its tensile strength and toughness are better than those of low polymerization degree resin, which can make up for the strength loss of the environmental protection system; the higher polymerization degree can also reduce the low molecular weight components in the resin, further reducing the initial VOC release amount. The introduction of the elastomer reinforcing agent and the titanate coupling agent can improve the filler dispersibility through physical blending and interfacial modification, and alleviate the micro-defect problem caused by the insufficient compatibility of environmental protection additives, so that the material can maintain the basic mechanical properties while reducing VOC.

[0009] Optionally, the plasticizer includes polypropylene adipate-polyether block copolymer and epoxy soybean oil compounded in a mass ratio of (3-4):1.

[0010] By adopting the above technical scheme, polypropylene adipate-polyether block copolymer is used as a high molecular weight plasticizer, the entanglement of the long chain molecules with the PVC resin is strong, and the intermolecular force is significantly higher than that of traditional phthalate esters, which can inhibit the migration and volatilization of the plasticizer molecules, and reduce VOC release from the source; the epoxy soybean oil is used as a bio-based plasticizer, the epoxy groups on the fatty acid chain can form hydrogen bonds with the chlorine atoms of the PVC molecular chain, enhancing the interfacial compatibility, while reducing the system viscosity and improving the processing fluidity. The PVC resin with a polymerization degree of 1100-1200 has a longer molecular chain and stronger intermolecular van der Waals force, and its tensile strength and toughness are better than those of low polymerization degree resin, which can make up for the strength loss of the environmental protection system; the higher polymerization degree can also reduce the low molecular weight components in the resin, further reducing the initial VOC release amount. The introduction of the elastomer reinforcing agent and the titanate coupling agent can improve the filler dispersibility through physical blending and interfacial modification, and alleviate the micro-defect problem caused by the insufficient compatibility of environmental protection additives, so that the material can maintain the basic mechanical properties while reducing VOC.

[0011] Optionally, the elastomer reinforcing agent is an acrylate-polycarbonate copolymer with core-shell structure, the middle shell layer of the acrylate-polycarbonate copolymer is polycarbonate with a glass transition temperature ≥ 80℃, the core layer is acrylate rubber, and the mass ratio of the core to the shell is 1:0.3-0.5.

[0012] By adopting the technical scheme, the acrylate rubber core layer can absorb energy through chain segment movement when the material is subjected to external force, initiate silver streaks and shear yield, and deflect the crack propagation path, thereby improving the elongation at break. The polycarbonate shell layer has a rigid benzene ring structure, has high matching degree with the polarity of the PVC matrix, can be tightly combined with the PVC molecular chain through van der Waals force to form a stable interfacial transition zone, and avoid aggregation of the elastomer phase; meanwhile, the rigidity of the shell layer can limit excessive deformation of the core layer rubber to prevent the problem of "toughening but reducing strength". When the mass ratio of the core to the shell is 1:0.3-0.5, the stress can be effectively dispersed, and the particles will not become new defect sources due to being too large.

[0013] Optionally, the preparation method of the acrylate-polycarbonate copolymer with core-shell structure is as follows:

[0014] Butyl acrylate, methyl methacrylate and divinylbenzene are mixed in a mass ratio of 85:10:5, an emulsifier is added, and the mixture is reacted at 75-80℃ for 3-4 hours under nitrogen protection to obtain an acrylate rubber emulsion;

[0015] A mixed solution of bisphenol A polycarbonate prepolymer and bis(trichloromethyl) carbonate is added to the acrylate rubber emulsion, the mass ratio of the polycarbonate prepolymer to bis(trichloromethyl) carbonate is 100:(1-3), the mass ratio of the core to the shell is controlled to be 1:0.3-0.5, and the reaction is carried out at pH=8-9 and temperature 65-70℃ for 6-8 hours;

[0016] The reaction solution is cooled to 20-25℃, the pH is adjusted to neutral, and after centrifugal separation, deionized water washing and vacuum drying to a water content ≤0.5%, an acrylate-polycarbonate copolymer with core-shell structure is obtained.

[0017] By adopting the technical scheme, butyl acrylate, methyl methacrylate and divinylbenzene are polymerized in a ratio of 85:10:5, wherein the divinylbenzene acts as a crosslinking agent to control the crosslinking density of the core layer rubber, so as to ensure that the core layer has sufficient elasticity and does not swell excessively; 75-80℃ is the optimal temperature for acrylate emulsion polymerization, at which the initiator has a moderate decomposition rate, the polymerization reaction is controllable, and the obtained core layer has a uniform particle size distribution. The mass ratio of polycarbonate prepolymer to bis(trichloromethyl) carbonate is 100:(1-3), and the polycarbonate shell layer is formed through a phosgene method condensation reaction. The reaction is carried out under weak alkaline conditions with a pH value of 8-9, which can neutralize the generated HCl and prevent the hydrolysis of polycarbonate. The reaction temperature of 65-70℃ can ensure the formation rate of carbonate bonds and avoid thermal oxidative aging of the core layer rubber caused by high temperature. By accurately controlling the core-shell mass ratio, the thickness of the shell layer is maintained at 20-50nm, which can completely cover the core layer and will not cause excessive rigidity of the elastomer due to the excessive thickness of the shell layer.

[0018] Optionally, the elastomer reinforcing agent is surface-grafted with maleic anhydride groups, the grafting rate of the maleic anhydride groups is 0.2-0.5%, and the mass ratio of the maleic anhydride groups to the titanate coupling agent is 1:(0.1-0.3).

[0019] By adopting the technical scheme, the anhydride groups (-COO-CO-) of maleic anhydride can form hydrogen bonds with the chlorine atoms of the PVC molecular chain, and at the same time, esterification reactions occur with the alkoxy groups (-OR) of the titanate coupling agent, forming a "chemical bond-hydrogen bond" composite interface layer between the elastomer-coupling agent-filler, which improves the bonding strength between the filler and the matrix by 40-60%. When the grafting rate is 0.2-0.5%, the maleic anhydride groups are uniformly distributed in a monolayer on the surface of the elastomer. If the grafting rate is less than 0.2%, there are not enough interface bridging sites. If it exceeds 0.5%, excessive anhydride groups will self-polymerize to form agglomerates, which will actually damage the interface compatibility. At this grafting rate, the interface adhesion energy between the elastomer and the filler is significantly improved. After grafting, the elastomer is wrapped around the surface of the inorganic filler through the dual action of "steric hindrance + chemical adsorption", preventing the Van der Waals attractive force between the filler particles and eliminating the stress concentration points caused by filler agglomeration.

[0020] Optionally, the method for surface grafting maleic anhydride groups on the elastomer reinforcing agent is as follows:

[0021] The core-shell structured acrylate-polycarbonate copolymer is mixed with maleic anhydride and dicumyl peroxide, and stirred at 160-170℃ for 10-15 minutes under a nitrogen atmosphere to obtain a grafted product. The grafted product is immersed in acetone and ultrasonically treated, and then vacuum dried to a constant weight.

[0022] By adopting the technical scheme, dicumyl peroxide is decomposed to produce cumyl free radicals at 160-170 DEG C, the activity of the free radicals is moderate, the free radicals can initiate maleic anhydride to graft to the surface of the elastomer, and the elastomer molecular chain is not excessively degraded; the reaction time is controlled to be 10-15 minutes, the grafting degree and grafting uniformity can reach balance, acetone ultrasonic treatment removes unreacted maleic anhydride and DCP residues by using the similar solubility principle, vacuum drying further removes the solvent, the purity of the grafted product is ensured, impurities are avoided to form a weak interface layer in the material, and the overall mechanical property is affected.

[0023] Optionally, the flame retardant comprises nanosheet-shaped aluminum hydroxide, and the nanosheet-shaped aluminum hydroxide has a particle size D50 of less than or equal to 100 nm.

[0024] By adopting the technical scheme, the nanosheet-shaped aluminum hydroxide has a specific surface area of greater than 100 m2 / g, and the flame-retardant efficiency is more excellent. The nanosheet layer is easy to orient along the stress direction in the matrix, when the material is stretched, the sliding between the sheet layers can absorb energy, and the hydroxyl groups at the edges of the sheet layers can react with the grafted maleic anhydride groups of the elastomer to form chemical crosslinking points, and the tensile strength retention rate is improved to be greater than or equal to 80%. The nanosheet-shaped structure has a relatively high surface energy, after being mixed with the titanate coupling agent, the surface is coated with an organic long chain, and the agglomeration tendency between the particles is reduced.

[0025] In a second aspect, the application provides a preparation method of a low-VOC cable sheath material, and the following technical scheme is adopted:

[0026] The preparation method of the low-VOC cable sheath material comprises the following steps:

[0027] The PVC resin, the plasticizer, the heat stabilizer, calcium stearate and the antioxidant are mixed and mixed at 120-130 DEG C to be semi-melted, the temperature is reduced to 100-110 DEG C, the heavy calcium carbonate, the flame retardant, the elastomer reinforcing agent, calcium stearate and the titanate coupling agent are added and mixed for 8-10 minutes, the temperature is further increased to 150-170 DEG C, and then extrusion granulation is performed, so that the low-VOC cable sheath material is obtained.

[0028] In summary, the application has the following beneficial effects:

[0029] 1、Due to the application selects polypropylene adipate-polyether block copolymer and epoxy soybean oil as plasticizer, uses the low volatility of high molecular weight polyester plasticizer and the good compatibility of epoxy soybean oil and PVC resin, cooperates with high mechanical strength PVC resin with polymerization degree 1100-1200, and improves the interface compatibility and relieves the uneven problem of filler dispersion by using elastomer reinforcing agent and titanate coupling agent, so that the material reduces VOC release while considering mechanical properties. By high molecular weight plasticizer to reduce small molecule migration and volatilization, high polymerization degree PVC resin to reduce its initial VOC release amount, combined with heat stabilizer to inhibit PVC decomposition in processing, so that the total VOC release meets the requirements of environmental regulations on low volatility.

[0030] 2、In the application, the problems of insufficient compatibility of environmental additives with the matrix and increased brittleness of high-filled systems are solved by using the rigid and tough balanced design of core-shell structure elastomer reinforcing agent, the low-filled and high-efficient flame retardation of nanosheet flame retardant, and the interface bridging technology of maleic anhydride grafting modification, so that the mechanical properties of the material are close to the mechanical level of traditional PVC sheath.

[0031] 3、The method of the application improves the melt flowability of high filler by using segmented mixing temperature control process, eliminates surface defects and internal stress, and significantly enhances the weather resistance of the material after molding. Specific implementation method

[0032] The application will be further described in detail in combination with the following examples, and it is particularly pointed out that: in the following examples, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used, and the raw materials used in the following examples can be obtained from ordinary market sales unless otherwise specified.

[0033] Preparation Example 1

[0034] Preparation example of an acrylate-polycarbonate copolymer

[0035] Prepare the following raw materials:

[0036] Butyl acrylate (BA): 85 kg;

[0037] Methyl methacrylate (MMA): 10 kg;

[0038] Divinylbenzene (DVB, crosslinking agent): 5 kg;

[0039] Sodium dodecyl sulfate (SDS, emulsifier): 2 kg (2% of the total mass of monomers);

[0040] Bisphenol A polycarbonate prepolymer (molecular weight 6000): 30 kg;

[0041] Bis(trichloromethyl) carbonate (BTC, chain extender): 0.6 kg;

[0042] Deionized water: 200 L.

[0043] Preparation step:

[0044] Mix BA, MMA, DVB according to the mass ratio of 85:10:5, add SDS and deionized water, high-speed shearing emulsification for 15 minutes, and form a monomer pre-emulsion.

[0045] Transfer the pre-emulsion to the reaction kettle, replace the air with nitrogen, and heat to 78℃.

[0046] Add ammonium persulfate (APS, initiator, 0.5 kg dissolved in 10 L water) dropwise, and react for 4 hours to obtain an acrylate rubber emulsion (solid content about 40%).

[0047] Mix bisphenol A polycarbonate prepolymer and BTC according to the mass ratio of 100:2, and dissolve in 50 L tetrahydrofuran (THF) to form a prepolymer solution.

[0048] Slowly add the prepolymer solution to the acrylate rubber emulsion, and control the core-shell mass ratio to be 1:0.4.

[0049] Adjust the pH of the system to 8-9 with ammonia water, heat to 68℃, and stir for 7 hours to allow the polycarbonate to condense on the surface of the rubber core to form a shell.

[0050] Cool the reaction liquid to 25℃, and add dilute hydrochloric acid to adjust the pH to neutral.

[0051] Centrifugal separation at 4000 rpm for 15 minutes, and wash with deionized water 3 times until the conductivity is ≤50 μS / cm.

[0052] Place the product in a vacuum drying oven, dry at 80℃ for 24 hours, and the final water content is ≤0.5%, to obtain a core-shell structured acrylate-polycarbonate copolymer with a particle size of about 200-300 nm.

[0053] Preparation Example 2

[0054] A preparation example of an acrylate-polycarbonate copolymer, which is different from Preparation Example 1, is that the core-shell mass ratio is 1:0.3.

[0055] Preparation Example 3

[0056] A preparation example of an acrylate-polycarbonate copolymer, which is different from Preparation Example 1, is that the core-shell mass ratio is 1:0.5.

[0057] Preparation Example 4

[0058] A preparation example of an acrylate-polycarbonate copolymer, which is different from Preparation Example 1, is that:

[0059] The 100 kg of acrylate-polycarbonate copolymer, 0.35 kg of maleic anhydride, and 0.07 kg of dicumyl peroxide obtained by the method of Preparation Example 1 were pre-mixed in a high-speed mixer for 5 minutes, heated to 160-170°C under nitrogen protection, the stirring speed was 200 rpm, the shear rate was ≥200 s⁻¹, and the blending was performed for 15 minutes. The product was immersed in acetone, treated with ultrasonic waves at a power of 500 W and a frequency of 40 kHz for 30 minutes, and then placed in a vacuum drying oven and dried at 60°C to a constant weight, with the moisture content being ≤0.3%.

[0060] Preparation Example 5

[0061] A preparation example of an acrylate-polycarbonate copolymer, which is different from Preparation Example 4, uses 100 kg of acrylate-polycarbonate copolymer and 0.2 kg of maleic anhydride.

[0062] Preparation Example 6

[0063] A preparation example of an acrylate-polycarbonate copolymer, which is different from Preparation Example 4, uses 100 kg of acrylate-polycarbonate copolymer and 0.5 kg of maleic anhydride.

[0064] Example 1

[0065] A preparation method of a low-VOC cable sheath material:

[0066] The following raw materials were prepared:

[0067] PVC resin (model US-65, degree of polymerization 1150): 110 kg;

[0068] Heavy calcium carbonate (1250 mesh): 30 kg;

[0069] Plasticizer (epoxidized soybean oil, national standard, content 99.9%): 25 kg;

[0070] Flame retardant (aluminum hydroxide, D50 = 5 μm): 35 kg;

[0071] Thermal stabilizer (calcium-zinc composite stabilizer, mass ratio of calcium to zinc 1:3): 4 kg;

[0072] Elastomer reinforcing agent (chlorinated polyethylene CPE135A): 12 kg;

[0073] Titanate coupling agent (NDZ-201): 4 kg;

[0074] Antioxidant (antioxidant 1010): 1 kg;

[0075] Calcium stearate: 2 kg.

[0076] PVC resin, plasticizer, heat stabilizer, calcium stearate, antioxidant were added into a high-speed mixer and mixed at 125℃ to semi-melt state.

[0077] The temperature was lowered to 105℃, and heavy calcium carbonate, flame retardant, elastomer reinforcing agent, titanate coupling agent were added and mixed for 9 minutes.

[0078] The temperature was raised to 160℃, and the mixture was extruded by a twin-screw extruder with a length-diameter ratio of 40:1 and a vacuum degree of-0.08MPa, then cooled and cut into particles to obtain the sheath material particles.

[0079] Example 2

[0080] A method for preparing a low-VOC cable sheath material: different from example 1 is that PVC resin 100kg, heavy calcium carbonate 25kg, plasticizer 20kg, flame retardant 30kg, heat stabilizer 2kg, elastomer reinforcing agent 8kg, titanate coupling agent 3kg, antioxidant 0.5kg, calcium stearate 0.5kg are used.

[0081] Example 3

[0082] A method for preparing a low-VOC cable sheath material: different from example 1 is that PVC resin 120kg, heavy calcium carbonate 35kg, plasticizer 35kg, flame retardant 45kg, heat stabilizer 5kg, elastomer reinforcing agent 15kg, titanate coupling agent 5kg, antioxidant 1.5kg, calcium stearate 3kg are used.

[0083] Example 4

[0084] A method for preparing a low-VOC cable sheath material: different from example 1 is that the plasticizer is polypropylene glycol adipate-polyether block copolymer with a molecular weight of 3000-3500Da, a block ratio (ester:ether) of 3:1 (mass ratio), a hydroxyl value of ≤5mgKOH / g, an acid value of ≤0.5mgKOH / g, and a viscosity (25℃) of 1000-1100mPa·s.

[0085] Example 5

[0086] A method for preparing a low-VOC cable sheath material: different from example 4 is that the plasticizer includes polypropylene glycol adipate-polyether block copolymer and epoxy soybean oil in a mass ratio of 3:1.

[0087] Example 6

[0088] A method for preparing a low-VOC cable sheath material: different from example 5 is that the plasticizer includes polypropylene glycol adipate-polyether block copolymer and epoxy soybean oil in a mass ratio of 3.5:1.

[0089] Example 7

[0090] A method for preparing a low VOC cable jacket material: different from example 5 is that the plasticizer comprises polypropylene adipate-polyether block copolymer compounded with epoxy soybean oil at a mass ratio of 4:1.

[0091] Example 8

[0092] A method for preparing a low VOC cable jacket material: different from example 1 is that the elastomer reinforcing agent is a core-shell structured acrylate-polycarbonate copolymer, which is prepared by the method of Preparation Example 1.

[0093] Example 9

[0094] A method for preparing a low VOC cable jacket material: different from example 8 is that the acrylate-polycarbonate copolymer is prepared by the method of Preparation Example 2.

[0095] Example 10

[0096] A method for preparing a low VOC cable jacket material: different from example 8 is that the acrylate-polycarbonate copolymer is prepared by the method of Preparation Example 3.

[0097] Example 11

[0098] A method for preparing a low VOC cable jacket material: different from example 8 is that the acrylate-polycarbonate copolymer is prepared by the method of Preparation Example 4.

[0099] Example 12

[0100] A method for preparing a low VOC cable jacket material: different from example 11 is that the acrylate-polycarbonate copolymer is prepared by the method of Preparation Example 5.

[0101] Example 13

[0102] A method for preparing a low VOC cable jacket material: different from example 11 is that the acrylate-polycarbonate copolymer is prepared by the method of Preparation Example 6.

[0103] Example 14

[0104] A method for preparing a low VOC cable jacket material: different from example 1 is that the flame retardant is nano flaky aluminum hydroxide, and the particle size D50 of the nano aluminum hydroxide is ≤100 nm.

[0105] Comparative Example 1

[0106] A method for preparing a low VOC cable jacket material: the difference from Example 1 is that no elastomer reinforcing agent is added.

[0107] Comparative Example 2

[0108] A method for preparing a low VOC cable jacket material: the difference from Example 1 is that no titanate coupling agent is added.

[0109] Comparative Example 3

[0110] A method for preparing a low VOC cable jacket material: the difference from Example 1 is that no heavy calcium carbonate is added.

[0111] Detection method

[0112] Tensile properties: dumbbell-shaped samples were prepared according to GB / T1040.3-2006, and the tensile strength (MPa) and elongation at break (%) were tested at a tensile rate of 50 mm / min.

[0113] Oxygen index (OI): tested according to GB / T2406.2-2009, to evaluate the flame retardancy of the material, and an oxygen index ≥ 28% is qualified.

[0114] VOC emission: tested according to GB / T37795-2019 by headspace-gas chromatography-mass spectrometry (HS-GC-MS), the sample was equilibrated at 100℃ for 2h, and the total VOC emission (μg / g) was determined.

[0115] Heat distortion temperature (HDT): tested according to GB / T1634.2-2004, with a load of 0.45 MPa and a heating rate of 120℃ / h, and the temperature at which the sample deformed by 0.25 mm was recorded.

[0116] Aging test: after the sample was heat aged at 100℃ for 168h, the tensile properties were repeatedly tested, and the retention rate was calculated.

[0117] Standard samples: the pellets of each example / comparative example were injection molded into 100mm x 10mm x 4mm tensile samples and 100mm x 6mm x 3mm oxygen index samples at 170℃.

[0118] Table 1 test data

[0119] Tensile strength (MPa) Elongation at break (%) Oxygen index (%) VOC release (μg / g) Heat distortion temperature (°C) Tensile retention after aging (%) Example 1 12.5 250 29.5 42.3±1.2 68 78 Example 2 11.8 230 28.7 40.5±0.8 65 75 Example 3 13.2 270 30.2 45.1±1.5 70 80 Example 4 13.8 265 29.8 38.6±1.0 72 82 Example 5 14.5 280 30.5 35.2±0.9 75 85 Example 6 15.2 295 31.0 32.8±0.7 78 88 Example 7 14.8 285 30.8 34.5±0.5 76 86 Example 8 14.2 300 30.3 36.1±0.5 74 83 Example 9 13.9 290 30.1 35.8±0.5 73 82 Example 10 14.3 310 30.4 36.3±0.5 75 84 Example 11 15.8 320 31.2 31.5±0.6 80 90 Example 12 15.0 310 30.8 33.2±0.5 78 87 Example 13 15.5 315 31.0 32.1±0.5 79 89 Example 14 16.2 330 32.5 30.8±0.5 82 92 Comparative Example 1 9.8 180 29.3 43.5±0.5 65 65 Comparative Example 2 10.5 200 29.7 44.2±0.5 66 68 Comparative Example 3 14.0 275 27.2 41.8±0.5 72 81

[0120] It can be seen from the combination of Example 1 and Comparative Examples 1-3 and Table 1 that the tensile strength of Comparative Example 1 without an elastomer reinforcing agent is reduced to 9.8 MPa (12.5 MPa in Example 1), and the elongation at break is only 180%, which is 28% lower than that of Example 1. This is because the absence of an elastomer reinforcing agent causes the system to lack a stress dispersion phase, and the aggregation of fillers causes stress concentration, increasing the brittleness of the material. In addition, the tensile retention rate after aging is reduced to 65%, indicating that the elastomer is crucial to maintaining the weather resistance of the material. In Comparative Example 2, there is no titanate coupling agent, and the tensile strength and elongation at break are 10.5 MPa and 200%, respectively, which are lower than those of Example 1. The absence of a titanate coupling agent causes weak interfacial bonding between the inorganic fillers (heavy calcium carbonate, flame retardant) and the PVC matrix, uneven dispersion of the fillers, and weakening of the interaction between molecular chains. In Comparative Example 3, there is no heavy calcium carbonate, and the tensile strength is close to that of Example 1 (14.0 MPa), but the oxygen index is reduced to 27.2% (29.5% in Example 1), indicating that although heavy calcium carbonate is not the main flame retardant, its filling can synergistically improve the compactness of the system and assist the flame retardant in playing a role. In addition, the VOC release amount is similar to that of Example 1, indicating that heavy calcium carbonate has little effect on VOC.

[0121] It can be seen from the combination of Examples 1-3 and Table 1 that the tensile strength of Example 3 (upper limit of the amount of each component) is 13.2 MPa, and the elongation at break is 270%, which is 5.6% and 8% higher than those of Example 1, respectively. This is because the increase in the amount of PVC resin makes the molecular chain entanglement more compact, and the increase in the amount of elastomer reinforcing agent and plasticizer improves the flexibility of the system. The oxygen index increases to 30.2% with the increase in the amount of flame retardant, and the VOC release amount increases slightly to 45.1 μg / g, but is still lower than the environmental threshold of 50 μg / g. The heat distortion temperature increases from 68°C to 70°C, indicating that the heat resistance of the highly filled system is slightly improved. Increasing the amount of each component within a certain range can synergistically improve the mechanical properties, flame retardancy, and heat resistance of the material, but the VOC release amount needs to be balanced to avoid excessive addition of additives that can exacerbate small molecule volatilization. Therefore, the ratio of Example 1 is the most preferred in this application.

[0122] It can be seen from the combination of Examples 1 and 4 and Table 1 that the difference between Example 4 and Example 1 is that the plasticizer is replaced by polypropylene glycol adipate-polyether block copolymer, and the tensile strength increases from 12.5 MPa to 13.8 MPa, and the elongation at break reaches 265%. The long-chain structure of the high molecular weight plasticizer is more entangled with the PVC molecules, forming a stable network structure and enhancing the cohesion of the system. The VOC release amount decreases from 42.3 μg / g to 38.6 μg / g, which is attributed to the low volatility of the high molecular weight plasticizer, which has a large molecular chain migration resistance, reducing the escape of VOC. The heat distortion temperature increases to 72°C, and the tensile retention rate after aging reaches 82%, indicating that the compatibility of the high molecular weight plasticizer with PVC is better, and the structural stability at high temperature is better.

[0123] It can be seen from Examples 1, 4, 5, 6, 7 and Table 1 that the tensile strength of Example 6 (3.5:1) reaches 15.2 MPa, the elongation at break is 295%, and the VOC release is as low as 32.8 μg / g. In the compounded system, the high molecular weight polyester forms a network skeleton, and the epoxy soybean oil fills the gaps. Through the "network filling-gap blocking" mechanism, the volatilization of the plasticizer is inhibited, and at the same time, the melt flowability is improved, making the filler dispersion more uniform. When the ratio is 3.5:1, the dipole effect of the polyester segment and the hydrogen bonding effect of the epoxy group reach a balance, the free volume of the system is the smallest, the VOC release is the lowest, and the mechanical properties are significantly improved due to the optimization of interfacial compatibility. The heat distortion temperature is optimized to 78°C with the compounding ratio, and the retention rate after aging reaches 88%, indicating that the compounded plasticizer system has a more stable structure in long-term use.

[0124] It can be seen from Examples 1 and 8-13 and Table 1 that Examples 8-10 use different core-shell mass ratios (1:0.3-1:0.5), and the elongation at break is improved by 20%-24% compared with Example 1, and the tensile strength remains at about 14 MPa. The core layer of acrylate rubber absorbs impact energy, and the shell layer of polycarbonate is polar matched with PVC, forming a stable interface to avoid "toughening and strength reduction".

[0125] Maleic anhydride grafting interface strengthening: The tensile strength of Examples 11-13 (grafting rate 0.2-0.5%) reaches 15.5-15.8 MPa, and the VOC release is reduced to 31.5-32.1 μg / g. Maleic anhydride groups form hydrogen bonds with chlorine atoms in PVC, and at the same time react with titanate coupling agents to form chemical bridges between the elastomer and the filler, improving the interfacial adhesion energy and reducing defects caused by filler aggregation. The grafting method of Preparation Example 4 (core-shell ratio 1:0.4, grafting rate 0.35%) corresponds to Example 11, which has the best overall performance, proving that precise control of core-shell thickness and grafting rate is the key to improving mechanical properties.

[0126] It can be seen from Examples 1, 14 and Table 1 that Example 14 replaces the flame retardant with nano-sheet aluminum hydroxide (D50≤100 nm). The high specific surface area of the nano-sheet structure allows it to orient in the matrix, and the sliding of the lamellar structure absorbs energy when stretched, while the edge hydroxyl groups react with the elastomer grafting groups to form chemical crosslinking, improving the strength retention rate. The VOC release is reduced to 30.8 μg / g. Due to the high surface energy of the nano-filler, it is more uniformly dispersed after being coated with titanate coupling agent, reducing the pores caused by filler aggregation and inhibiting the VOC diffusion path. The nano-sheet flame retardant achieves high efficiency with low filler content (same amount as Example 1), and through interface modification, it reduces the deterioration of inorganic fillers on mechanical properties, proving the advantages of nano-scale fillers in low VOC systems.

[0127] The embodiments are only illustrative of the present application, and are not intended to limit the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low VOC cable jacket material characterized in that, The components include, by weight parts, PVC resin 100-120 parts, heavy calcium carbonate 25-35 parts, plasticizer 20-35 parts, flame retardant 30-45 parts, heat stabilizer 2-5 parts, elastomer reinforcing agent 8-15 parts, titanate coupling agent 3-5 parts, antioxidant 0.5-1.5 parts, calcium stearate 0.5-3 parts; the plasticizer includes polypropylene glycol adipate-polyether block copolymer and epoxy soybean oil, the polypropylene glycol adipate-polyether block copolymer is compounded with the epoxy soybean oil at a mass ratio (3-4):1; the PVC resin has a polymerization degree of 1100-1200; the elastomer reinforcing agent is an acrylate-polycarbonate copolymer with a core-shell structure, the shell layer of the acrylate-polycarbonate copolymer is polycarbonate with a glass transition temperature ≥80℃, the core layer is acrylate rubber, and the core-shell mass ratio is 1:0.3-0.

5.

2. The low VOC cable jacketing material of claim 1, wherein: The preparation method of the acrylate-polycarbonate copolymer with a core-shell structure is as follows: Butyl acrylate, methyl methacrylate and divinylbenzene are mixed at a mass ratio of 85:10:5, an emulsifier is added, and reaction is carried out at 75-80℃ for 3-4 hours under nitrogen protection to obtain an acrylate rubber emulsion; A mixed solution of bisphenol A polycarbonate prepolymer and bis(trichloromethyl) carbonate is added to the acrylate rubber emulsion, the mass ratio of the polycarbonate prepolymer to bis(trichloromethyl) carbonate is 100:(1-3), the core-shell mass ratio is controlled to be 1:0.3-0.5, and reaction is carried out at pH=8-9 and temperature 65-70℃ for 6-8 hours; The reaction solution is cooled to 20-25℃, the pH is adjusted to neutral, and after centrifugal separation, deionized water washing and vacuum drying to a water content ≤0.5%, a core-shell acrylate-polycarbonate copolymer is obtained.

3. The low VOC cable jacketing material of claim 1, wherein: The elastomer reinforcing agent is surface-grafted with maleic anhydride groups.

4. The low VOC cable jacketing material of claim 3, wherein: The method for surface-grafting the elastomer reinforcing agent with maleic anhydride groups is as follows: The core-shell acrylate-polycarbonate copolymer is mixed with maleic anhydride and dicumyl peroxide under nitrogen atmosphere and stirred at 160-170℃ for 10-15 minutes to obtain a grafted product, the grafted product is immersed in acetone and ultrasonically treated, and then vacuum dried to constant weight.

5. The low VOC cable jacketing material of claim 1, wherein: The flame retardant includes nanosheet-shaped aluminum hydroxide with a particle size D50 ≤100nm.

6. A process for the preparation of a low VOC cable jacketing material as claimed in any one of claims 1 to 5 characterised in that: The method includes the following steps: The PVC resin, plasticizer, heat stabilizer, calcium stearate and antioxidant are mixed and mixed at 120-130℃ to semi-melt, cooled to 100-110℃, mixed with heavy calcium carbonate, flame retardant, elastomer reinforcing agent and titanate coupling agent for 8-10 minutes, heated to 150-170℃ and extruded and granulated to obtain a low VOC cable sheath material.