CN113512249A

CN113512249A - Zinc hydroxide borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material and preparation method thereof

Info

Publication number: CN113512249A
Application number: CN202110448005.0A
Authority: CN
Inventors: 刘希琴; 刘子利; 吴晨颖; 朱俊; 包金芳; 陈新祥
Original assignee: CHANGSHU ZHONGLIAN PHOTOELECTRICITY NEW STUFF CO LTD; Nanjing University of Aeronautics and Astronautics; Jiangsu Zhongli Group Co Ltd
Current assignee: CHANGSHU ZHONGLIAN PHOTOELECTRICITY NEW STUFF CO LTD; Nanjing University of Aeronautics and Astronautics; Jiangsu Zhongli Group Co Ltd
Priority date: 2021-04-25
Filing date: 2021-04-25
Publication date: 2021-10-19
Anticipated expiration: 2041-04-25
Also published as: CN113512249B

Abstract

The invention provides a hydroxide, zinc borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material and a preparation method thereof, wherein the composite material comprises the following components: 100 parts of EVA/LDPE blended resin; 2-3 parts of a coupling agent; 2-4 parts of a lubricant; 0.4-0.6 part of antioxidant; 50-80 parts of a flame retardant A; 20-30 parts of a flame retardant B; the flame retardant A is a composition of hydroxide and boron flame retardant; the flame retardant B is a mixture of calcium sulfate whiskers and basic magnesium sulfate whiskers, the weight content of the calcium sulfate whiskers is X times of that of the basic magnesium sulfate whiskers, and X is more than 1 and less than 2; when in preparation, the materials are proportioned according to the proportion, put into an internal mixer for mixing, discharged when the mixture is mixed to 140-150 ℃, sent into a conical feeding hopper, melted and extruded by a double-screw extruder, the temperature of a first zone to a twelfth zone of the double-screw extruder and the temperature of a machine head are controlled, and a finished product is obtained after cold cutting; the composite material has good mechanical property on the basis of ensuring excellent flame retardant property, and the process is simple and easy to carry out experimental industrial production.

Description

Zinc hydroxide borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material and preparation method thereof

Technical Field

The invention relates to a hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material, which is used for meeting the requirements of the fields of cables, electrical and electronic equipment and the like on high-efficiency environment-friendly flame-retardant composite materials. The invention also relates to a preparation method of the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material, and belongs to the field of industrial polymer material manufacturing.

Background

Polymer composite materials such as plastics, rubber, synthetic fibers and the like are increasingly widely applied to the fields of building materials, electric and electronic products, automobiles, chemical engineering, traffic and the like, but the application development of the polymer composite materials is hindered by the inflammability of the polymer composite materials. The traditional organic flame retardant mainly comprising the halogen flame retardant has excellent compatibility and flame retardant efficiency with organic synthetic materials, but hydrogen halide which is released by the halogen flame retardant when the materials are burnt and has flame retardant effect is toxic and corrosive. With the enhancement of global environmental protection consciousness, the implementation of environmental regulations of various countries in the world such as the European Union 'Instructions on scrapped Electrical and electronic Equipment' (WEEE), the inorganic flame retardant has the advantages of no environmental pollution, no toxicity, no corrosiveness and the like, shows strong competitiveness and development potential, and becomes the main component and development focus of the current environment-friendly flame retardant.

Polyethylene vinyl acetate/low density polyethylene (EVA/LDPE) blends are widely applied to engineering fields such as wires and cables due to good physical and processing properties and high resistance characteristics, but the structure of high aliphatic hydrocarbon is easy to burn, and halogen-free inorganic flame retardance is the currently important research direction. The hydroxide inorganic filling type flame retardant has wide application due to the advantages of better environmental protection, economical efficiency, easy batch production and the like. The commonly used aluminum hydroxide (ATH) and Magnesium Hydroxide (MH) prevent the combustion chain reaction from proceeding by thermally desorbing heat from the combustion surface and releasing crystal water to dilute the concentration of combustible gases generated in the flame zone by the polymer material, and the pyrolysis products combine with the charring products generated by the combustion of the polymer matrix to form a dense oxide layer. However, the flame retardant efficiency of hydroxide is poor, for example, ATH is used in an amount of 60 wt.% or more or 150phr (parts per mass of resin) or more to achieve the desired flame retardant effect. The ATH flame retardant has poor compatibility with a matrix and is easy to cause particle agglomeration, and although the surface of the ATH flame retardant is modified or a dispersing agent and a compatibilizer are added during blending or screw extrusion to promote combination with the matrix, the movement of a polymer chain is limited by a large amount of added micro powder, and the breaking elongation and the tensile strength (below 60 percent and 9 MPa) are damaged. For example, the filler type flame retardants aluminum hydroxide, magnesium hydroxide and melamine used in CN103865165B (a low-smoke halogen-free flame retardant polyolefin cable material and a preparation method thereof) have low flame retardant efficiency, the mechanical properties of the material are seriously reduced by the large addition amount of the flame retardant, the melting and dripping phenomena of the material during combustion are serious, and an isolated carbon layer formed during the combustion of the material is loose. Although the addition amount of the nano hydroxide can be reduced and the composite material can obtain good mechanical and flame retardant properties, the manufacturing cost of the nano hydroxide powder is high, the nano hydroxide powder is difficult to uniformly disperse in a resin matrix due to the serious agglomeration problem, so that the advantages of the nano hydroxide powder cannot be fully exerted, and the nano hydroxide powder cannot be applied to large-scale industrial production.

Boron resources in China are rich, the boron flame retardant has excellent flame retardant, low toxicity and smoke suppression characteristics and has irreplaceable advantages in some fields, wherein the molecular formula is 2 ZnO.3B₂O₃·3.5H₂The zinc borate of O is the most commonly used additive type boron flame retardant at present. The zinc borate is irregular or rhombus white crystal or light yellow powder, the relative density is 2.69, and the zinc borate has multiple effects and advantages of flame retardance, char formation, smoke suppression, smoldering suppression, molten drop prevention and the like, and researches show that the zinc borate, the hydroxide and the like have synergistic flame retardance and synergism. However, the literature reports (Wang He, Zhu, Zhao Tree, etc. the effect of aluminum hydroxide and zinc borate on the flame retardant properties of ethylene-vinyl acetate rubber/nitrile rubber blends [ J]The synthetic rubber industry, 2012,35(5): 392-. Also, the large addition of flame retardants severely degrades the mechanical properties of the material.

The molecular formula of basic magnesium sulfate (MOS) whisker is MgSO₄·5Mg(OH)₂·3H₂O, has the characteristics of high strength, high rigidity, high elastic modulus and low density, and has the similar processes of thermally degrading and desorbing heat and releasing crystal water as hydroxide. MOS whiskers are used as flame-retardant fillers and are disclosed in U.S. patent document US4997871(Fibrous magnesium oxide crystalline form and thermoplastic resin compounding the Fibrous magnesium oxide), Chinese patent document CN103509242B (a reinforced flame-retardant polypropylene/inorganic whisker composite material and a preparation method thereof), CN106008931B (a PBS/basic magnesium sulfate whisker composite material and a preparation method thereof) and the like. Chinese patent document CN1296422C (in-situ filling polymerization preparation method of inorganic whisker reinforced polyolefin composite material) proposes to perform in-situ olefin polymerization on the surface of a whisker in an inert gas environment to obtain a composite material with good tensile properties in order to solve the problem of poor interface adhesion between the surface of an inorganic whisker and a matrix polymer. However, the harsh preparation environment and complicated polymerization process of the patent are undoubtedly limitedMaking the application of the technology. At present, the whisker treatment still mainly adopts a treatment method of glass fiber or carbon fiber, the mechanical property of the obtained whisker reinforced polymer is not satisfactory, and the elongation at break of the material can be obviously reduced by adding MOS whiskers into the MOS whisker reinforced EVA/LDPE composite material.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides the hydroxide, zinc borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material which has excellent flame-retardant and mechanical properties. The invention also aims to provide a preparation method of the EVA/LDPE composite material, which has simple process and is easy to industrially implement.

In order to achieve the purpose, the invention adopts the following technical scheme:

the hydroxide, the zinc borate and the whisker are cooperated to retard the flame of the ethylene-vinyl acetate copolymer (EVA)/Low Density Polyethylene (LDPE) composite material, which comprises the following components: 100 parts of EVA/(and) LDPE blended resin; coupling agent: 2-3 parts of a solvent; lubricant: 2-4 parts; antioxidant: 0.4-0.6 part; flame retardant A: 50-80 parts; and (3) a flame retardant B: 20-30 parts.

Specifically, the EVA/LDPE blended resin has an EVA content of 20-26 wt%, an LDPE of 1.0-10.0 g/min melt flow rate, and a maleic anhydride grafted polyethylene (PE-g-MA) with a maleic anhydride grafting rate of 0.5 wt% is added as a compatibilizer in addition to the EVA and the LDPE, wherein the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

specifically, the coupling agent is one or a combination of more than one of gamma-aminopropyl triethoxysilane and vinyl trimethoxy silane.

Specifically, the lubricant is one or a combination of more than one of silicone master batch and N, N-ethylene bis-fatty amide graft.

Specifically, the antioxidant is one or more of 1010, 1076, 168, 626 and 300.

In order to improve the comprehensive effect of the flame retardant property and the mechanical property of the composite material, the flame retardant A is a composition of hydroxide and a boron flame retardant, and the mass ratio of the hydroxide to the boron flame retardant is 4: 1-7: 1, wherein the hydroxide is one or a mixture of aluminum hydroxide (ATH) and magnesium hydroxide, and the boron flame retardant is preferably zinc borate.

The flame retardant B is a mixture of Calcium Sulfate Whisker (CSW) and basic magnesium sulfate whisker (MOS), wherein in the flame retardant B, the weight content of the calcium sulfate whisker is X times of that of the basic magnesium sulfate whisker, and X is more than 1 and less than 2. The molecular formula of the CSW whisker in the flame retardant B is CaSO₄·0.5H₂O, its apparent specific gravity is 2.69g/cm³The diameter is 1-10 mu m, and the length-diameter ratio is 5-40; the molecular formula of the MOS crystal whisker is MgSO₄·5Mg(OH)₂·3H₂O, its apparent specific gravity is 2.3g/cm³The diameter is 1.0 μm, and the length-diameter ratio is 30-40.

In order to improve the comprehensive mechanical property effect of the composite material, the weight content of the calcium sulfate whisker is 1.05-1.15 times of that of the basic magnesium sulfate whisker.

The preparation method of the hydroxide, zinc borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material comprises the following steps: weighing 100 parts of EVA/LDPE blended resin according to the parts by weight; coupling agent: 2-3 parts of a solvent; lubricant: 2-4 parts; antioxidant: 0.4-0.6 part; flame retardant A: 50-80 parts; and (3) a flame retardant B: and (2) adding 20-30 parts of the mixture into an internal mixer for mixing, discharging when the material temperature is 140-150 ℃, feeding the mixture into a conical feeding hopper, performing melt extrusion by using a double-screw extruder, controlling the temperature of a first zone to a twelfth zone of the double-screw extruder and the temperature of a machine head of the double-screw extruder, and performing cold cutting to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material.

The temperature of the first zone to the twelve zones of the double-screw extruder is controlled to be as follows: 120 +/-5 ℃ in the first area, 125 +/-5 ℃ in the second area, 130 +/-5 ℃ in the third area, 135 +/-5 ℃ in the fourth area, 140 +/-5 ℃ in the fifth area, 135 +/-5 ℃ in the sixth area, 130 +/-5 ℃ in the seventh area, 125 +/-5 ℃ in the eighth area, 120 +/-5 ℃ in the ninth area, 100 +/-5 ℃ in the tenth area, 105 +/-5 ℃ in the eleventh area and 110 +/-5 ℃ in the twelfth area; the temperature of the machine head of the double-screw extruder is controlled to be 150 +/-5 ℃.

The hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material provided by the invention has the innovation points that:

(1) the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material has the advantages that the composition design of the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material endows the material with good mechanical properties on the basis of ensuring excellent flame-retardant performance through multi-element synergistic action, and solves the problem that the mechanical properties are seriously reduced due to the fact that a large amount of traditional hydroxide inorganic filling type flame retardant is required to be added to achieve the flame-retardant effect of the traditional hydroxide inorganic filling type flame retardant:

firstly, the addition amount of hydroxide in the EVA/LDPE composite material is only 1/3-1/2, so that the damage effect of the added hydroxide particles on the mechanical property of the composite material is greatly reduced;

secondly, the MOS whisker as a flame-retardant filler and a reinforcement has been studied more on the toughening and flame-retardant application of resin-based materials such as PE, PP, EVA, ABS, silicone rubber and the like, and the CSW whisker as a novel reinforcing material with the lowest price has many special advantages and functions such as high strength, heat resistance, wear resistance, corrosion resistance, insulation, flame retardance and the like and is used for preparing high-performance engineering plastics and composite materials. The mechanism is that the CSW whiskers play a role of a heterogeneous nucleation substrate for a matrix in the forming process of the composite material and have higher affinity with the matrix, so that the composite material can coordinately deform to show the best elongation at break; the MOS whisker and the CSW whisker are added together, so that the effect of improving the comprehensive mechanical property of the composite material is good, but the addition amount of the MOS whisker is higher than that of the CSW whisker, so that the elongation at break of the composite material is reduced rapidly, and the excessive addition amount of the CSW whisker can increase the smoke release amount of the composite material during combustion and reduce the flame retardant property of the composite material.

(2) The flame-retardant EVA/LDPE composite material with synergistic effect of hydroxide, zinc borate and whiskers, which is added with CSW whiskers, has a delayed cone shapeThe ignition time effect of the CCT is tested by a calorimeter, the MOS crystal whisker plays an active role in inhibiting the burning rate from reaching the peak time and reducing the heat release rate peak value and the smoke release amount of the material, and the mixed crystal whisker, the zinc borate and the hydroxide show better synergistic flame retardant effect (the ignition time is delayed, and the burning rate and the smoke release amount are reduced). The composite material shows excellent flame retardant performance through a multi-element synergistic gas-phase flame retardant and condensed-phase flame retardant mechanism under the condition of relatively low addition amount of the flame retardant. When the surface of the EVA/LDPE composite material starts to burn, the heating decomposition temperature range of ATH is 200-300 ℃, the decomposition temperature range of MH during burning is 340-490 ℃, and zinc borate is subjected to endothermic decomposition (503kJ/kg) at 290-450 ℃ to generate water and boric acid (H)₃BO₃) And boron oxide (B)₂O₃) The CSW crystal whisker loses 0.5 crystal water before 360 ℃, and the MOS crystal whisker is heated and decomposed at 20-273 ℃, 275-353 ℃ and 356-473 ℃ to respectively lose crystal water and water molecules to form MgSO (MgSO) water)₄·5Mg(OH)₂·2H₂O、MgSO₄·5Mg(OH)₂And MgSO₄The multistage endothermic decomposition of 5MgO, hydroxide and whiskers added lowers the temperature of the combustible surface, releasing water vapor diluting the combustible gases released by thermal decomposition of the EVA/LDPE matrix. Combustion product MgSO of MOS whisker₄5MgO coordination chemical (MgO as the final product after a combustion temperature of more than 910 ℃) and CaSO as a pyrolysis product of CSW whiskers₄Inherits the original shape of the crystal whisker, and forms a net structure along with the stacking and staggering of the combustion process, and hydroxide pyrolysis product particles (the ATH pyrolysis product is Al) are distributed in the net₂O₃MH pyrolysis product is MgO). Due to the net structure of the pyrolysis products of the whiskers and the pyrolysis particles of the hydroxides from outside to inside, a labyrinth effect is formed, and the path of combustible gas passing through the labyrinth effect to reach an external combustion area is prolonged. Therefore, MOS, CSW, hydroxide and zinc borate play a role in synergistic gas phase flame retardance in the combustion process.

On the other hand, boron oxide which is a pyrolysis product of zinc borate can be softened at 350 ℃ and can flow at more than 500 ℃, a glassy covering isolation layer is formed on the combustion surface and is filled in pores among crystal whisker grids, and MOS, hydroxide and the pyrolysis product of zinc borate effectively catalyze and combust a resin matrix to form carbon in the combustion process, so that the formation of a carbon layer is accelerated. The zinc borate, the hydroxide and the pyrolysis product of the crystal whisker are together used for building a stable three-dimensional barrier carbon layer on the surface of a combustion substrate, the barrier carbon layer effectively isolates the exchange of internal and external substances and the heat conduction, the chain combustion reaction is prevented from proceeding, and the excellent condensed phase flame retardant effect is shown (figure 2).

When the addition amount of zinc borate in the flame retardant A is too large (hydroxide: zinc borate is less than 4:1), although the peak value of the heat release rate of the composite material during combustion is reduced, the time for the combustion rate of the composite material to reach the peak value is greatly advanced, and the cost of the composite material is increased (when borax is added in a large amount, the initial decomposition temperature of the composite material is also advanced). In order to improve the comprehensive effect of the flame retardant property and the mechanical property of the composite material, the mass ratio of the hydroxide to the boron flame retardant is 4: 1-7: 1.

the room-temperature tensile strength of the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material reaches 15.2-19.1MPa, the elongation at break is 159-251%, the LOI value is 27.2-29.5, the vertical combustion grade reaches UL 94V-0 grade, and the phenomenon of melt dripping does not occur. The preparation method disclosed by the invention has the advantages of simple process, high efficiency, suitability for large-scale production and the like, and meets the requirements of the fields of cables, electric and electronic equipment and the like on efficient and environment-friendly flame-retardant composite materials.

Drawings

FIG. 1 is a frozen section structure diagram of the EVA/LDPE composite material with flame retardance cooperated by the hydroxide, the zinc borate and the whiskers obtained in example 2.

FIG. 2 is a graph of the morphology of the residual carbon layer of the hydroxide, zinc borate and whisker synergistic flame retardant EVA/LDPE composite material obtained in example 2 after an LOI test.

Detailed Description

Example 1

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 2 parts of (1); lubricant silicone master batch: 2 parts of (1); antioxidant 1076: 0.4 part; flame retardant A: 50 parts, wherein the ATH is 27.78 parts, the MH is 13.89 parts, and the zinc borate is 8.33 parts; and (3) a flame retardant B: 20 parts, wherein the MOS whisker is 9.76 parts, and the CSW whisker is 10.24 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 20 wt%, the LDPE is linear LDPE with the melt flow rate of 1.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blended resin, 2 parts of gamma-aminopropyltriethoxysilane as a coupling agent, 2 parts of silicone master batch as a lubricant, 10760.4 parts of antioxidant, 27.78 parts of ATH, 13.89 parts of MH, 8.33 parts of zinc borate, 9.76 parts of MOS whisker and 10.24 parts of CSW whisker which are weighed according to parts by weight. And (2) putting the materials into an internal mixer for internal mixing, discharging and feeding the materials into a conical feeding hopper when the internal mixing is carried out until the material temperature is 140 ℃, introducing the materials into a double-screw extruder from the conical feeding hopper for melt extrusion, and cooling to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material. The head temperature of the double-screw extruder is controlled to be 145 ℃, and the temperatures of the first zone to the twelfth zone of the double-screw extruder are respectively controlled as follows: 115 ℃ in the first zone, 120 ℃ in the second zone, 125 ℃ in the third zone, 130 ℃ in the fourth zone, 135 ℃ in the fifth zone, 130 ℃ in the sixth zone, 125 ℃ in the seventh zone, 120 ℃ in the eighth zone, 115 ℃ in the ninth zone, 95 ℃ in the tenth zone, 100 ℃ in the eleventh zone and 105 ℃ in the twelfth zone.

Respectively carrying out the following steps on the prepared hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material: (a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 15.2MPa, and the elongation at break reaches 251.0%; (b) and (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 27.2. (c) Testing electrical insulation performance, namely testing the resistance value of the composite material according to the GB/T1410.3-2006 standard, wherein the size of a sample is

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and dielectric strength influence of all samples are in 13 orders of magnitude and in the range of 33-38 MV/m.

Example 2

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 2.5 parts; 1 part of lubricant N, N-ethylene bis-fatty amide graft (TAS-2A) and 2 parts of silicone master batch; antioxidant 1010: 0.5 part; flame retardant A: 55 parts, wherein the ATH is 44 parts, and the zinc borate is 11 parts; and (3) a flame retardant B: 28 parts, wherein the MOS whisker is 13.33 parts, and the CSW whisker is 14.67 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 26 wt%, the LDPE is linear LDPE with the melt flow rate of 7.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blended resin, 1.5 parts of coupling agent vinyl trimethoxy silane, 1 part of N, N-ethylene bis fatty amide graft (TAS-2A), 2 parts of silicone master batch, 10100.5 parts of antioxidant, 44 parts of ATH, 11 parts of zinc borate, 13.33 parts of MOS whisker and 14.67 parts of CSW whisker which are weighed according to parts by weight.

And (2) putting the materials into an internal mixer for internal mixing, discharging and feeding the materials into a conical feeding hopper when the temperature of the materials is 145 ℃, introducing the materials into a double-screw extruder from the conical feeding hopper for melt extrusion, and cooling to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material. The head temperature of the double-screw extruder is controlled to be 150 ℃, and the temperatures of the first zone to the twelfth zone of the double-screw extruder are respectively controlled as follows: 120 ℃ in the first zone, 125 ℃ in the second zone, 130 ℃ in the third zone, 135 ℃ in the fourth zone, 140 ℃ in the fifth zone, 135 ℃ in the sixth zone, 130 ℃ in the seventh zone, 125 ℃ in the eighth zone, 120 ℃ in the ninth zone, 100 ℃ in the tenth zone, 105 ℃ in the eleventh zone and 110 ℃ in the twelfth zone.

Respectively carrying out the following steps on the prepared hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material:

(a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 17.6MPa, and the elongation at break reaches 211.0%.

(b) And (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 28.3.

(c) Testing electrical insulation performance, namely testing the resistance value of the composite material according to the GB/T1410.3-2006 standard, wherein the size of a sample is

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and the dielectric strength of all samples are influenced within the range of 13 orders of magnitude and 29-32 MV/m.

Example 3

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 3 parts of a mixture; 2 parts of lubricant silicone master batch and 2 parts of N, N-ethylene bis-fatty amide graft (TAS-2A); antioxidant 1010: 0.6 part; flame retardant A: 80 parts, wherein the ATH is 35 parts, the MH is 35 parts, and the zinc borate is 10 parts; and (3) a flame retardant B: 30 parts, wherein the MOS whisker is 13.95 parts, and the CSW whisker is 16.05 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 26 wt%, the LDPE is linear LDPE with the melt flow rate of 10.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blended resin, 2 parts of gamma-aminopropyltriethoxysilane as a coupling agent, 2 parts of silicone master batch as a lubricant, 2 parts of TAS-2A, 10100.6 parts of antioxidant, 35 parts of ATH, 35 parts of MH, 10 parts of zinc borate, 13.95 parts of MOS whisker and 16.05 parts of CSW whisker which are weighed according to parts by weight.

And (2) putting the materials into an internal mixer for internal mixing, discharging and feeding the materials into a conical feeding hopper when the internal mixing temperature is 150 ℃, introducing the materials into a double-screw extruder from the conical feeding hopper for melt extrusion, and cooling to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material. The head temperature of the double-screw extruder is controlled to be 155 ℃, and the temperatures of the first zone to the twelfth zone of the double-screw extruder are respectively controlled as follows: 125 ℃ in the first zone, 130 ℃ in the second zone, 135 ℃ in the third zone, 140 ℃ in the fourth zone, 145 ℃ in the fifth zone, 140 ℃ in the sixth zone, 135 ℃ in the seventh zone, 130 ℃ in the eighth zone, 125 ℃ in the ninth zone, 105 ℃ in the tenth zone, 110 ℃ in the eleventh zone and 115 ℃ in the twelfth zone.

(a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 19.1MPa, and the elongation at break reaches 159.0%.

(b) And (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 29.5.

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and the dielectric strength of all samples are influenced within the range of 18-23 MV/m and the range of 12 orders of magnitude.

Comparative example 1

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 2.5 parts; 1 part of lubricant N, N-ethylene bis-fatty amide graft (TAS-2A) and 2 parts of silicone master batch; antioxidant 1010: 0.5 part; flame retardant A: 55 parts, wherein the ATH is 44 parts, and the zinc borate is 11 parts; the flame retardant B is totally MOS crystal whisker: 28 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 26 wt%, the LDPE is linear LDPE with the melt flow rate of 7.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blend resin, 2 parts of gamma-aminopropyltriethoxysilane as a coupling agent, 2 parts of silicone master batch as a lubricant, 2 parts of TAS-2A, 10100.6 parts of antioxidant, 44 parts of ATH, 11 parts of zinc borate and 28 parts of MOS whisker, which are weighed according to parts by weight.

(a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 17.9MPa, and the elongation at break reaches 134.0%.

(b) And (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 27.3.

(c) Testing the electrical insulation performance: testing of electrical insulation Properties of composite MaterialThe resistance value is tested according to the GB/T1410.3-2006 standard, and the sample size is

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and the dielectric strength of all samples are influenced within the range of 31-33 MV/m and 13 orders of magnitude.

Comparative example 2

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 2.5 parts; 1 part of lubricant N, N-ethylene bis-fatty amide graft (TAS-2A) and 2 parts of silicone master batch; antioxidant 1010: 0.5 part; flame retardant A: 55 parts, wherein the ATH is 44 parts, and the zinc borate is 11 parts; all the flame retardants B are CSW whiskers: 28 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 26 wt%, the LDPE is linear LDPE with the melt flow rate of 7.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blended resin, 2 parts of gamma-aminopropyltriethoxysilane as a coupling agent, 2 parts of silicone master batch as a lubricant, 2 parts of TAS-2A, 10100.6 parts of antioxidant, 44 parts of ATH, 11 parts of zinc borate and 28 parts of CSW whisker, which are weighed according to parts by weight.

(a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 9.7MPa, and the elongation at break reaches 279.0 percent.

(b) And (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 25.6.

(c) Testing the electrical insulation performance: testing electrical insulation performance, namely testing the resistance value of the composite material according to the GB/T1410.3-2006 standard, wherein the size of a sample is

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and the dielectric strength of all samples are influenced within the range of 24-27 MV/m and 13 orders of magnitude.

Comparative example 3

The EVA/LDPE composite material comprises the following components in percentage by weight: 100 parts of EVA/LDPE blended resin; coupling agent γ -aminopropyltriethoxysilane: 3 parts of a mixture; 2 parts of lubricant silicone master batch and 2 parts of N, N-ethylene bis-fatty amide graft (TAS-2A); antioxidant 1010: 0.6 part; flame retardant A: 80 parts, wherein the ATH is 35 parts, the MH is 35 parts, and the zinc borate is 10 parts; and (3) a flame retardant B: 30 parts, wherein the MOS whisker accounts for 15 parts, and the CSW whisker accounts for 15 parts. The EVA/LDPE blended resin is characterized in that the EVA content is 26 wt%, the LDPE is linear LDPE with the melt flow rate of 10.0g/min, maleic anhydride grafted polyethylene (PE-g-MA) with the maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

the preparation method comprises the following steps: 100 parts of EVA/LDPE blended resin, 2 parts of gamma-aminopropyltriethoxysilane as a coupling agent, 2 parts of silicone master batch as a lubricant, 2 parts of TAS-2A, 10100.6 parts of antioxidant, 35 parts of ATH, 35 parts of MH, 10 parts of zinc borate, 15 parts of MOS whisker and 15 parts of CSW whisker which are weighed according to parts by weight.

And (2) putting the materials into an internal mixer for internal mixing, discharging and feeding the materials into a conical feeding hopper when the temperature of the materials is 145 ℃, introducing the materials into a double-screw extruder from the conical feeding hopper for melt extrusion, and cooling to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material. The head temperature of the double-screw extruder is controlled to be 155 ℃, and the temperatures of the first zone to the twelfth zone of the double-screw extruder are respectively controlled as follows: 125 ℃ in the first zone, 130 ℃ in the second zone, 135 ℃ in the third zone, 140 ℃ in the fourth zone, 145 ℃ in the fifth zone, 140 ℃ in the sixth zone, 135 ℃ in the seventh zone, 130 ℃ in the eighth zone, 125 ℃ in the ninth zone, 105 ℃ in the tenth zone, 110 ℃ in the eleventh zone and 115 ℃ in the twelfth zone.

(a) testing room temperature tensile property: the tensile strength and elongation at break of the composite material were tested according to GB/T1040.3-2006. The tensile strength of the composite material reaches 19.3MPa, and the elongation at break reaches 127.0%.

(b) And (3) testing the flame retardant property: horizontal vertical burn test (UL94) was performed according to ASTM D3801; limited Oxygen Index (LOI) tests were performed according to ASTM D2863, with sample dimensions of 150mm (length) by 6.5. + -. 0.5mm (width) by 3mm (thickness). The vertical burning grade of the composite material reaches UL 94V-0 grade, and the composite material does not have the phenomenon of melt dripping. The LOI value was 29.1.

A thick disc. The dielectric strength of the composite material is tested according to the GB/T1408.1-2016 standard. The volume resistivity and the dielectric strength of all samples are influenced within the range of 18-22 MV/m and the range of 12 orders of magnitude.

The above embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. The hydroxide, zinc borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material is characterized by comprising the following components: 100 parts of EVA/LDPE blended resin; coupling agent: 2-3 parts of a solvent; lubricant: 2-4 parts; antioxidant: 0.4-0.6 part; flame retardant A: 50-80 parts; and (3) a flame retardant B: 20-30 parts of a solvent;

the flame retardant A is a composition of hydroxide and boron flame retardant; the flame retardant B is a mixture of calcium sulfate whiskers and basic magnesium sulfate whiskers, the weight content of the calcium sulfate whiskers is X times of that of the basic magnesium sulfate whiskers, and X is more than 1 and less than 2.

2. The hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the EVA/LDPE blend resin is characterized in that the EVA content is 20-26 wt%, the LDPE is linear LDPE with a melt flow rate of 1.0-10.0 g/min, maleic anhydride grafted polyethylene with a maleic anhydride grafting rate of 0.5 wt% is added as a compatilizer besides the EVA and the LDPE, and the mass part ratio of the EVA/LDPE/PE-g-MA is 75: 15: 10.

3. the hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the coupling agent is one or the combination of more than one of gamma-aminopropyl triethoxysilane and vinyl trimethoxy silane.

4. The hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the lubricant is one or the combination of more than one of silicone master batch and N, N-ethylene double fatty amide graft.

5. The hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the antioxidant is one or the combination of more than one of 1010, 1076, 168, 626 and 300.

6. The hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the mass ratio of hydroxide to boron flame retardant in the flame retardant A is 4: 1-7: 1; the molecular formula of the CSW whisker in the flame retardant B is CaSO₄·0.5H₂O, its apparent specific gravity is 2.69g/cm³The diameter is 1-10 mu m, and the length-diameter ratio is 5-40; the molecular formula of the MOS crystal whisker is MgSO₄·5Mg(OH)₂·3H₂O, its apparent specific gravity is 2.3g/cm³The diameter is 1.0 μm, and the length-diameter ratio is 30-40.

7. The hydroxide, zinc borate and whisker synergistic flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the weight content of the calcium sulfate whisker is 1.05-1.15 times of that of the basic magnesium sulfate whisker.

8. The whisker synergistic multi-component flame retardant ethylene-vinyl acetate copolymer/low density polyethylene composite material according to claim 1, characterized in that: the hydroxide in the flame retardant A is one or a mixture of aluminum hydroxide and magnesium hydroxide; the boron flame retardant in the flame retardant A is preferably zinc borate.

9. The method for preparing the hydroxide, zinc borate and whisker synergic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material according to any one of claims 1 to 7, characterized in that: weighing 100 parts of EVA/LDPE blended resin according to the parts by weight; coupling agent: 2-3 parts of a solvent; lubricant: 2-4 parts; antioxidant: 0.4-0.6 part; flame retardant A: 50-80 parts; and (3) a flame retardant B: and (2) adding 20-30 parts of the mixture into an internal mixer for mixing, discharging when the material temperature is 140-150 ℃, feeding the mixture into a conical feeding hopper, performing melt extrusion by using a double-screw extruder, controlling the temperature of a first zone to a twelfth zone of the double-screw extruder and the temperature of a machine head of the double-screw extruder, and performing cold cutting to obtain the hydroxide, zinc borate and whisker synergistic flame-retardant EVA/LDPE composite material.

10. The method for preparing the hydroxide, zinc borate and whisker synergistic flame-retardant ethylene-vinyl acetate copolymer/low-density polyethylene composite material according to claim 9, is characterized in that: the temperature of the first zone to the twelve zones of the double-screw extruder is controlled to be as follows: 120 +/-5 ℃ in the first area, 125 +/-5 ℃ in the second area, 130 +/-5 ℃ in the third area, 135 +/-5 ℃ in the fourth area, 140 +/-5 ℃ in the fifth area, 135 +/-5 ℃ in the sixth area, 130 +/-5 ℃ in the seventh area, 125 +/-5 ℃ in the eighth area, 120 +/-5 ℃ in the ninth area, 100 +/-5 ℃ in the tenth area, 105 +/-5 ℃ in the eleventh area and 110 +/-5 ℃ in the twelfth area; the temperature of the machine head of the double-screw extruder is controlled to be 150 +/-5 ℃.