Halogen-free flame-retardant thermoplastic vulcanized elastomer and preparation method thereof

Abstract

The invention discloses a halogen-free flame-retardant thermoplastic vulcanized elastomer and a preparation method thereof, and belongs to the technical field of thermoplastic vulcanized elastomer materials. The preparation method comprises the following steps: epoxidizing ethylene propylene diene monomer by using an oxygen source to obtain epoxy ethylene propylene diene monomer, and carrying out blending vulcanization reaction on the epoxy ethylene propylene diene monomer, polypropylene, paraffin oil, a modified intumescent flame retardant synergist, a charring agent, organic peroxide, an assistant crosslinker, a flame retardant, a dispersing agent and an antioxidant in a reaction type double-screw extruder, the halogen-free flame-retardant thermoplastic vulcanized elastomer disclosed by the invention is good in flame retardant property, and the mechanical property and the aging property of the halogen-free flame-retardant thermoplastic vulcanized elastomer are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of thermoplastic vulcanized elastomer materials, and in particular to a halogen-free flame-retardant thermoplastic vulcanized elastomer and a preparation method thereof. Background Art

[0002] Thermoplastic vulcanizate (TPV) is a mixture of polypropylene (PP) and ethylene propylene diene monomer (EPDM) through dynamic vulcanization technology. During the vulcanization process, the rubber forms a cross-linked grid structure. Thermoplastic vulcanizate with a grid structure has a high elastic recovery rate and can quickly return to its original state after a large degree of stretching or compression; it has good durability, chemical resistance and weather resistance, and is widely used in daily necessities, automobiles, construction, electronics, and chemical industries. In some special application fields, thermoplastic vulcanizate is often required to have flame retardant properties to adapt to different environments. Therefore, adding flame retardants to thermoplastic vulcanizate for modification has become an effective means to expand the application field of thermoplastic vulcanizate.

[0003] In addition to hydrocarbon polymers that are flammable when exposed to fire, thermoplastic vulcanizates also contain a large amount of paraffin oil. Paraffin oil is difficult to form carbon during the combustion process. Instead, it will melt when heated and flow along the surface of the material, accelerating the spread of flames. It also makes it impossible for the material to form an effective carbon layer to block heat and oxygen. In addition, the combustion of paraffin oil will produce a large amount of thick smoke, which seriously affects the visibility of the fire scene. Due to the particularity of thermoplastic vulcanizates, the carbonization method used for thermoplastic vulcanizates and conventional flame retardant materials is difficult to work, and the compatibility of carbonizing agents with thermoplastic vulcanizates is extremely poor. Therefore, it is impossible to modify thermoplastic vulcanizates using carbonizing agents alone.

[0004] Flame retardants for traditional polymer materials are mainly divided into halogen flame retardants and phosphorus flame retardants. Among them, halogen flame retardants have good flame retardant effects, and bromine flame retardants have particularly outstanding flame retardant efficiency, small dosage, and good compatibility. However, when they burn, they will release a large amount of toxic and corrosive gases such as hydrogen halides, and will also produce thick smoke, which not only pollutes the environment, but also endangers human health. Secondly, the bromine element of the most commonly used bromine flame retardants comes largely from the extraction of groundwater, which poses a threat to the environment and ecology. Therefore, halogen flame retardants are banned in more and more fields, making the application of halogen-free flame retardants more and more extensive. Phosphorus-based flame retardants in halogen-free flame retardants have low smoke emission, but their flame retardant efficiency is much lower than that of halogen-based flame retardants. They often require the combined action of multiple flame retardant mechanisms such as gas phase barrier, expansion cooling, and carbonization and wrapping to achieve a relatively good flame retardant effect. In addition, a large amount of halogen-free flame retardant added results in reduced mechanical properties of the material. For example, patent CN102786742A discloses a nitrogen-phosphorus system halogen-free flame retardant TPV material. In this technical solution, EPDM, PP, paraffin oil, vulcanizing agent, SEBS, nitrogen-phosphorus flame retardant, and masterbatch are mixed and then extruded and granulated by a twin-screw extruder to obtain a material with good mechanical properties, but a low flame retardant grade, which can only reach UL94V-0 (3.0mm).

[0005] CN110092983B discloses a synergistic halogen-free flame retardant and its application, and an EPDM / PP thermoplastic elastomer and its preparation method and application. The synergistic halogen-free flame retardant contains nitrogen-phosphorus flame retardant and CeMnO 3 Perovskite type composite oxide, and the nitrogen-phosphorus flame retardant and the CeMnO 3 The weight ratio of the content of the perovskite type composite oxide is (10-300): 1. The synergistic halogen-free flame retardant provided by the present invention has good flame retardant properties, and the prepared halogen-free flame retardant TPV material has high tensile strength. The preparation process of this technical solution is complicated and the energy consumption in the preparation process is also high.

[0006] In summary, in order to improve the flame retardancy of thermoplastic vulcanized rubber materials, they are often modified by adding flame retardants. However, halogen flame retardants are harmful after combustion, phosphorus flame retardants have poor flame retardancy and poor compatibility with thermoplastic vulcanized rubber, the flame retardant modification effect of thermoplastic vulcanized rubber materials is poor, the modification process is complicated, and the performance of thermoplastic vulcanized rubber materials is reduced due to modification, which are still problems that need to be solved urgently. Summary of the invention

[0007] In view of the above problems, the present invention provides a halogen-free flame retardant thermoplastic vulcanizate and a preparation method thereof. Epoxy ethylene propylene diene monomer rubber and a modified intumescent flame retardant synergist are prepared, and the synergists are mixed with polypropylene, paraffin oil, a carbonizing agent, an organic peroxide, a cross-linking aid, a flame retardant, a dispersant and an antioxidant, and vulcanized in a reactive twin-screw extruder and a single-screw extruder vertically connected by a single-double connector, and extrusion granulation is performed to obtain a halogen-free flame retardant thermoplastic vulcanizate having good flame retardancy, good mechanical properties and good aging resistance.

[0008] The invention provides a halogen-free flame retardant thermoplastic vulcanized elastomer. The halogen-free flame retardant thermoplastic vulcanized elastomer is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, co-crosslinking agent, flame retardant, dispersant and antioxidant. The flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer is V-0 at 3.0 mm and V-0 at 1.5 mm. The Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 80-90 Shore A, the tensile strength is 9-12 MPa, and the elongation at break is 500-550%. After heat aging for 240 hours at 150° C., the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 85-95%, and the elongation at break retention rate is 80-90%. The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0009] Furthermore, the epoxy EPDM rubber, the polypropylene, the paraffin oil, the modified intumescent flame retardant synergist, the charring agent, the organic peroxide, the co-crosslinking agent, the flame retardant, the dispersant and the antioxidant are first blended and vulcanized in a reactive twin-screw extruder, and then melt-blended and extruded into granules in the single-screw extruder. The single-screw extruder improves the dispersibility of the flame retardant in the material.

[0010] Furthermore, the reactive twin-screw extruder and the single-screw extruder are vertically sealed and connected via a single-double connector.

[0011] Furthermore, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are as follows: Epoxy EPDM rubber is 180-250 parts by weight; Polypropylene is 50-150 parts by weight; Paraffin oil is 50-200 parts by weight; Expanded graphite is 20-60 parts by weight; 10-30 parts by weight of organic bentonite; The carbon-forming agent is 50-100 parts by weight; 1-3 parts by weight of organic peroxide; The auxiliary cross-linking agent is 1-5 parts by weight; The flame retardant is 200-300 parts by weight; The dispersant is 8-15 parts by weight; The antioxidant is 1-5 parts by weight.

[0012] The present invention also provides a blending reaction device, which comprises a reactive twin-screw extruder and a single-screw extruder, wherein the reactive twin-screw extruder and the single-screw extruder are vertically sealed and connected via a single-double connector.

[0013] Furthermore, one end of the single-double connector is connected to the end of the last barrel section of the reactive twin-screw extruder, and the other end of the single-double connector is connected to the side of the first barrel section of the single screw extruder to form a vertical connection.

[0014] Furthermore, the reactive twin-screw extruder includes a first feed port, a second liquid injection port, a third side feed port, a fourth liquid injection port and a fifth side feed port at different positions in sequence according to the transport direction of the material.

[0015] Furthermore, a feeding hopper and a loss-in-weight scale 1 are arranged above the first feeding port, a liquid loss-in-weight scale 1 is arranged above the second liquid injection port, a side feeder 1 and a loss-in-weight scale 2 are arranged above the third side feeding port, a liquid loss-in-weight scale 2 is arranged above the fourth liquid injection port, and a side feeder 2 and a loss-in-weight scale 3 are arranged above the fifth side feeding port.

[0016] The present invention also provides a method for preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer using the blending reaction device, comprising the following steps: Step 1: Preparation of EPDM epoxy rubber At the dissolution temperature, the EPDM rubber is stirred and dissolved in the solvent, acidified with an organic acid and then cooled, then stirred and an oxygen source is added to carry out epoxidation, and finally the product is poured into a precipitant for precipitation, and the filtered solid product is washed with deionized water and vacuum dried to obtain the epoxy EPDM rubber; Step 2: Preparation of modified intumescent flame retardant synergist The expanded graphite and the organic bentonite are stirred and mixed in a high-speed mixer, and a silane coupling agent is added and the mixture is continued to be mixed to obtain the modified intumescent flame retardant synergist; Step 3: preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer The epoxy EPDM rubber and the antioxidant are mixed in a high-speed mixer, and then added to a reactive twin-screw extruder in a blending reaction device through a loss-in-weight scale and a feeding hopper via a first feeding port; The paraffin oil is measured by a liquid loss-in-weight scale and injected into the reactive twin-screw extruder through the second liquid injection port; After mixing polypropylene, the modified intumescent flame retardant synergist and the charring agent in the second high-speed mixer, the mixture is fed into the reactive twin-screw extruder through the second loss-in-weight scale and the first side feeder via the third side feed port; After the organic peroxide and the auxiliary cross-linking agent are mixed in the liquid mixer three, the mixture is measured by the liquid loss-in-weight scale two and then injected into the reactive twin-screw extruder through the fourth liquid injection port; The epoxy EPDM rubber, the organic peroxide and the auxiliary cross-linking agent undergo a vulcanization reaction in the reactive twin-screw extruder. After continuing to mix the flame retardant and the dispersant in the high-speed mixer four, the mixture is added into the reactive twin-screw extruder through the loss-in-weight scale three and the side feeder two via the fifth side feed port. After melt blending, the mixture enters the single screw extruder through the single-double connector, is further melt blended, and is extruded and granulated to obtain the halogen-free flame retardant thermoplastic vulcanized elastomer.

[0017] Furthermore, the dissolving temperature in step 1 is 50-100°C.

[0018] Furthermore, in the step 1, the mass-to-volume ratio of the EPDM rubber to the solvent is (1:1)-(1:5), wherein the unit of mass is g and the unit of volume is ml.

[0019] Furthermore, the EPDM rubber in step 1 is one or both of oil-filled rubber and non-oil-filled rubber, and the ethylene content in the EPDM rubber is 50-70%, and the ethylidene norbornene content is 2.5-9.0%.

[0020] Furthermore, in step 1, the stirring and dissolving speed is 5-20 r / s, and the stirring and dissolving time is 0.5-1 h.

[0021] Furthermore, the solvent in step 1 is one or more of toluene, xylene, benzene, cyclohexane, n-hexane and n-heptane.

[0022] Furthermore, in step 1, the volume ratio of the organic acid to the solvent is (1:50)-(1:80).

[0023] Furthermore, the organic acid in step 1 is one or more of formic acid, acetic acid and propionic acid.

[0024] Furthermore, the acidification in step 1 is to a pH value of 2-3.

[0025] Furthermore, the cooling temperature in step 1 is 50-55°C.

[0026] Furthermore, the speed of continued stirring in step 1 is 5-20 r / s.

[0027] Furthermore, in step 1, the mass ratio of the oxygen source to the EPDM rubber is (1:30)-(1:80).

[0028] Furthermore, the oxygen source in step 1 is one or more of hydrogen peroxide, peracetic acid, a peracetic acid-hydrogen peroxide mixture and tert-butyl hydroperoxide.

[0029] Furthermore, the epoxidation time in step 1 is 5-10 hours.

[0030] Furthermore, in step 1, the volume ratio of the precipitant to the solvent is (5:1)-(8:1).

[0031] Furthermore, the precipitant in step 1 is one or more of acetone, methanol, ethanol and isopropanol.

[0032] Furthermore, the number of washing in step 1 is 3-5 times.

[0033] Furthermore, the temperature of the vacuum drying in step 1 is 30-50° C., the time of the vacuum drying is 12-48 h, and the vacuum degree of the vacuum drying is -0.08 to -0.1 MPa.

[0034] Furthermore, in step 2, the mass ratio of the expanded graphite to the organic bentonite is (1:1)-(2:1).

[0035] Furthermore, the expanded graphite in step 2 is flaky, has a mesh size of 50-100 meshes, an expansion multiple of 100-150 times, and a carbon content of ≥99%.

[0036] Furthermore, the organic bentonite in step 2 has a lamellar structure.

[0037] Furthermore, in step 2, the stirring and mixing speed is 80-120 r / s, and the stirring and mixing time is 2-3 min.

[0038] Furthermore, the mass of the silane coupling agent in step 2 accounts for 0.1-0.5% of the total mass of the modified intumescent flame retardant synergist.

[0039] Furthermore, the silane coupling agent in step 2 is one or more of vinyl triethoxy silane, vinyl trimethoxy silane and vinyl tri (β-methoxyethoxy) silane.

[0040] Furthermore, the speed of the continued mixing in step 2 is 100-150 r / s, and the time of the continued mixing is 3-10 min.

[0041] Furthermore, in the step 3, the mass ratio of the epoxy ethylene propylene rubber, the polypropylene, the paraffin oil, the modified intumescent flame retardant synergist, the charring agent, the organic peroxide, the co-crosslinking agent, the flame retardant, the dispersant and the antioxidant is (180-250): (50-150): (50-200): (20-100): (50-100): (1-3): (1-5): (200-300): (8-15): (1-5).

[0042] Furthermore, the antioxidant in step 3 is a main antioxidant, or is composed of a main antioxidant and a secondary antioxidant.

[0043] Furthermore, the primary antioxidant is one or more of hindered phenol antioxidants or hindered amine antioxidants.

[0044] Furthermore, the hindered phenol antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (antioxidant 1010), β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl alcohol (antioxidant 1076) and 2,6-di-tert-butyl-p-cresol (antioxidant 264).

[0045] Furthermore, the hindered amine antioxidant is one or more of N,N'-1,3-propylene bis[3,5-di-tert-butyl-4-hydroxyphenylpropionamide] (antioxidant 1019), N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024) and 4,4'-bis(α,α-dimethylbenzyl) diphenylamine (antioxidant 445).

[0046] Furthermore, the auxiliary antioxidant is a phosphite antioxidant.

[0047] Furthermore, the phosphite antioxidant is one or more of tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (antioxidant 626), distearyl thiodipropionate (antioxidant DSTP) and bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate (antioxidant 636).

[0048] Furthermore, the paraffin oil in step 3 is alkane oil, the flash point of the paraffin oil is 240-280°C, and the density is 0.87-0.98 g / cm³.

[0049] Furthermore, the polypropylene in step 3 is one or both of homopolypropylene and copolymer polypropylene, and the melt index of the polypropylene is 1.0-20.0 g / cm³.

[0050] Furthermore, the carbon-forming agent in step 3 is poly-2,6-dimethyl-1,4-phenylene ether.

[0051] Furthermore, the organic peroxide in step 3 is one or more of diisopropylbenzene peroxide, di-tert-butyl peroxide, tert-butyl peroxide isopropylbenzene (TBCP), bis(tert-butylperoxyisopropyl)benzene (BPIB), benzoyl peroxide (BPO), 1,4-di-tert-butylperoxyisopropylbenzene (BIPB), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH) and 4,4-di(tert-butylperoxy)butyl valerate.

[0052] Furthermore, the auxiliary cross-linking agent in step 3 is one or more of triallyl isocyanurate, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), N,N'-phenylbismaleimide (PDM), zinc diacrylate (ZDA), zinc dimethacrylate (ZDMA), triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC).

[0053] Furthermore, the flame retardant in step 3 is aluminum hypophosphite and melamine, the aluminum hypophosphite is one or both of organic aluminum hypophosphite and inorganic aluminum hypophosphite, the phosphorus content of the aluminum hypophosphite is ≥41%, and the effective content of the melamine is ≥99.5%.

[0054] Furthermore, the mass ratio of the aluminum hypophosphite to the melamine is (1:1)-(2:1).

[0055] Furthermore, the dispersant in step 3 is one or more of polyethylene wax, stearic acid, methyl stearate, butyl stearate, natural paraffin, liquid paraffin, microcrystalline paraffin, polyethylene wax and polypropylene wax.

[0056] Furthermore, in step 3, the stirring speeds of the high-speed mixer 1, the high-speed mixer 2, the liquid mixer 3 and the high-speed mixer 4 are 10-80 r / min, and the stirring time is 8-15 min.

[0057] Furthermore, the length-to-diameter ratio of the reactive twin-screw extruder in step 3 is (48-64):1.

[0058] Furthermore, the aspect ratio of the single screw extruder in step 3 is (12-30):1.

[0059] Furthermore, the screw speed of the reactive twin-screw extruder in step 3 is 200-500 r / min.

[0060] Furthermore, the screw speed of the single screw extruder in step 3 is 10-50 r / min.

[0061] Furthermore, in step 3, the barrel temperature of the reactive twin-screw extruder is 50-220°C.

[0062] Furthermore, the barrel temperature of the single screw extruder in step 3 is 160-200°C.

[0063] Beneficial effects of the present invention: 1. The present invention first epoxidizes EPDM rubber with an oxygen source, and introduces polar epoxy groups into the molecular chains of the epoxidized EPDM rubber, thereby improving the compatibility and bonding strength of the EPDM rubber with other polar materials. At the same time, the epoxidation reaction changes the molecular chain structure of the EPDM rubber, increases the interactions and crosslinking points between the molecular chains, and when subjected to external forces, the molecular chains can more effectively transmit stress, thereby improving the tensile strength of the EPDM rubber. The presence of the epoxy groups can, to a certain extent, prevent oxygen and free radicals from attacking the molecular chains of the EPDM rubber, slow down the thermal oxidation aging process of the rubber, and improve the stability of the EPDM rubber in high temperature and aerobic environments. In the halogen-free flame-retardant thermoplastic vulcanized elastomer, the epoxidized EPDM rubber has good compatibility with the carbon-forming agent, and the carbon-forming agent can be uniformly dispersed in the epoxy EPDM rubber matrix. After the epoxy EPDM rubber undergoes a vulcanization reaction, the carbon-forming agent is uniformly dispersed in the crosslinking network to form a stable structure. 2. Epoxy EPDM rubber is mixed with polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking aid, flame retardant, dispersant and antioxidant in a reactive twin-screw extruder for vulcanization reaction. The organic bentonite and expanded graphite in the modified intumescent flame retardant synergist are modified by a silane coupling agent to improve their compatibility with other materials. After the mixed vulcanization reaction, they are tightly wrapped by the cross-linked network of epoxy EPDM rubber. When the material burns, the adsorption structure of the modified intumescent flame retardant synergist will effectively adsorb the paraffin oil to prevent it from dripping. The addition of the modified intumescent flame retardant synergist greatly reduces the amount of the flame retardant added and further improves the mechanical properties of the material. 3. The carbonizing agent in the present invention can form a stable carbon layer on the surface of the cross-linked network when the material burns, isolate oxygen, inhibit the overflow of paraffin oil, prolong the time for the modified intumescent flame retardant synergist to absorb paraffin oil, and inhibit the thermal decomposition of the material to prevent the material from continuing to burn. The modified intumescent flame retardant synergist and the carbonizing agent are added to the reactive twin-screw extruder before the organic peroxide and the auxiliary cross-linking agent, ensuring the full mixing of the epoxy EPDM rubber, paraffin oil, the modified intumescent flame retardant synergist and the carbonizing agent, improving the flame retardant effect of the material, reducing the amount of flame retardant used, and further improving the mechanical properties and aging properties of the material. The halogen-free flame retardant thermoplastic vulcanized elastomer in the present invention not only has a flame retardant property of V-0 when the strip thickness is 3 mm, but also has a flame retardant grade of V-0 when the strip thickness is 1.5 mm. At the same time, the mechanical properties of the material in the present invention are significantly improved, and the aging resistance time is also significantly increased; 4. In the present invention, the reactive twin-screw extruder and the single-screw extruder are vertically connected by a single-double connector. The epoxy EPDM rubber is first added to the reactive twin-screw extruder, and after being completely sheared, it fully absorbs the paraffin oil in the reactive twin-screw extruder, thereby improving the dispersibility of the paraffin oil in the system. The flame retardant and the dispersant are melt-mixed in the reactive twin-screw extruder, and then further melt-mixed in the single-screw extruder to improve the dispersion uniformity of the flame retardant. The flame retardants in the present invention are melamine and aluminum hypophosphite. Both melamine and aluminum hypophosphite are halogen-free and environmentally friendly flame retardants. Melamine has good high temperature resistance, high decomposition temperature, weather resistance and UV resistance, while aluminum hypophosphite has small particle size, good dispersibility and good temperature resistance. The use of the two together can significantly improve the flame retardancy and thermal stability of the material. This composite use not only improves the flame retardancy of the material, but also reduces the generation of harmful gases, which meets environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a schematic diagram of the structure of the blending reaction device described in the present invention; The names of the numbers in the figure are: 1. Reaction twin-screw extruder; 2. Single screw extruder; 3. Single and double connector; 11. First feeding port; 12. Second liquid injection port; 13. Third side feeding port; 14. Fourth liquid injection port; 15. Fifth side feeding port; 1101. Feeding hopper; 1102. Loss-in-weight scale one; 1201. Liquid loss-in-weight scale one; 1301. Side feeder one; 1302. Loss-in-weight scale two; 1401. Liquid loss-in-weight scale two; 1501. Side feeder two; 1502. Loss-in-weight scale three. DETAILED DESCRIPTION

[0065] The invention is described in detail below with reference to the embodiments: The halogen-free flame retardant thermoplastic vulcanized elastomer and the preparation method thereof provided by the present invention have good flame retardant effect, and no halogen-related harmful substances are produced while being flame retardant. The halogen-free flame retardant thermoplastic vulcanized elastomer has good mechanical properties and greatly improves its aging resistance.

[0066] Example 1 The present embodiment provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer is V-0 at 3.0 mm and V-0 at 1.5 mm; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 9.65 MPa, and the elongation at break is 525%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88%, and the elongation at break retention rate is 85%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0067] In this embodiment, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are as follows: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 100 parts by weight; 16.7 parts by weight of organobentonite; Expanded graphite is 33.3 parts by weight; The carbon-forming agent is 80 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0068] The antioxidants described in this embodiment are pentaerythritol tetrakis[β-(3,5-di-tert-butyl, 4-hydroxyphenyl) propionate (antioxidant 1010) and tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168) in a mass ratio of 1:1; The carbon-forming agent is poly-2,6-dimethyl-1,4-phenylene ether; The organic peroxide is diisopropylbenzene peroxide; The auxiliary cross-linking agent is triallyl isocyanurate; The flame retardant is organic aluminum hypophosphite and melamine in a mass ratio of 2:1; The dispersant is polyethylene wax.

[0069] This embodiment also provides a method for preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer using the blending reaction device, comprising the following steps: Step 1: Preparation of EPDM epoxy rubber At 80°C, 100g of EPDM rubber was dissolved in 300ml of toluene under stirring at 15r / s for 0.5h, acidified with 5ml of formic acid to pH 2, then cooled to 50°C, and then 2g of hydrogen peroxide was added under continuous stirring at 15r / s for 8h for epoxidation, and finally the product was poured into 1500ml of acetone for precipitation, and the filtered solid product was washed 3 times with deionized water, and vacuum dried at 40°C and -0.08MPa for 24h to obtain the epoxy EPDM rubber; Step 2: Preparation of modified intumescent flame retardant synergist 33.3 g of expanded graphite and 16.7 g of organic bentonite were stirred and mixed in a high-speed mixer at 80 r / s for 3 min, 0.1 g of vinyl triethoxysilane was added and the mixture was further mixed at 100 r / s for 10 min to obtain the modified intumescent flame retardant synergist; Step 3: preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer The epoxy EPDM rubber and the antioxidant were mixed in a high-speed mixer at 60 r / min for 10 min, and then added to the reaction type twin-screw extruder 1 in the blending reaction device through a first feeding port 1101 at a uniform speed of 50.66 kg / h using a weight loss scale 1102; The alkane oil is injected into the reactive twin-screw extruder 1 through the second liquid injection port 12 at a uniform rate of 25.08 kg / h by a liquid loss-in-weight scale 1201; The polypropylene, the modified intumescent flame retardant synergist and the charring agent were mixed in a high-speed mixer 2 at 60 r / min for 10 min, and then added to the reactive twin-screw extruder 1 through a third side feed port 13 at a uniform speed of 57.68 kg / h to a side feeder 1301 through a loss-in-weight scale 1302; The organic peroxide and the auxiliary cross-linking agent were mixed in the liquid mixer 3 at 10 r / min for 10 min, and then injected into the reactive twin-screw extruder 1 through the fourth injection port 14 at a uniform rate of 1.38 kg / h using a liquid weight loss scale 2 1401; The epoxy EPDM rubber, the organic peroxide and the auxiliary cross-linking agent undergo a vulcanization reaction in the reactive twin-screw extruder 1. Continue to mix the flame retardant and dispersant in the high-speed mixer four at 40r / min for 10 minutes, and then add them to the reactive twin-screw extruder 1 through the fifth side feeding port 15 through the loss-in-weight scale three 1502 at a uniform speed of 65.21kg / h to the side feeder two 1501. After melt blending, enter the single screw extruder 2 through the single-double connector 3, further melt blending, and extrusion granulation to obtain the halogen-free flame retardant thermoplastic vulcanized elastomer.

[0070] Example 2 The present embodiment provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer is V-0 at 3.0 mm and V-0 at 1.5 mm; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 87 Shore A, the tensile strength is 10.2 MPa, and the elongation at break is 530%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 85%, and the elongation at break retention rate is 82%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0071] In this embodiment, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are as follows: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 150 parts by weight; 28.3 parts of organobentonite; Expanded graphite is 56.7 parts; The carbon-forming agent is 100 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0072] In this embodiment, the components of the halogen-free flame retardant thermoplastic vulcanized elastomer are the same as those in Embodiment 1.

[0073] The method for preparing the halogen-free flame retardant thermoplastic vulcanized elastomer using the blending reaction device in this embodiment is the same as that in Embodiment 1, wherein the metering rate of each component is calculated based on the proportion of each component in the total components multiplied by the total output.

[0074] Example 3 The present embodiment provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer is V-0 at 3.0 mm and V-0 at 1.5 mm; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 9.28 MPa, and the elongation at break is 503%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 89%, and the elongation at break retention rate is 87%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0075] In this embodiment, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are as follows: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 75 parts by weight; 11.7 parts of organobentonite; Expanded graphite is 23.3 parts; The carbon-forming agent is 50 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0076] In this embodiment, the components of the halogen-free flame retardant thermoplastic vulcanized elastomer are the same as those in Embodiment 1.

[0077] The method for preparing the halogen-free flame retardant thermoplastic vulcanized elastomer using the blending reaction device in this embodiment is the same as that in Embodiment 1, wherein the metering rate of each component is calculated based on the proportion of each component in the total components multiplied by the total output.

[0078] Comparative Example 1 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding EPDM rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is V-1, and the flame retardant grade of 1.5 mm is V-2; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 7.85 MPa, and the elongation at break is 486%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 80%, and the elongation at break retention rate is 78%; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0079] In this comparative example, the components and the contents and ingredients of the halogen-free flame-retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0080] In this comparative example, steps 2 and 3 of the preparation method of the halogen-free flame retardant thermoplastic vulcanizate are consistent with those in Example 1, except that in this comparative example, step 1 is not included, and the EPDM rubber is not epoxidized. The EPDM rubber and the antioxidant are only mixed in a high-speed mixer at 60 r / min for 10 min, and then added to the reactive twin-screw extruder 1 in the blending reaction device through a loss-in-weight scale 1102 and a feeding hopper 1101 through a first feeding port 11 at a uniform speed of 50.66 kg / h.

[0081] Comparative Example 2 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is V-1, and the flame retardant grade of 1.5 mm is V-2. The Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 6.59 MPa, and the elongation at break is 370%. After heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 73%, and the elongation at break retention rate is 68%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The mixed flame retardant synergist comprises organic bentonite and expanded graphite.

[0082] In this comparative example, the components and the contents and ingredients of the halogen-free flame-retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0083] In this comparative example, steps 1 and 3 of the preparation method of the halogen-free flame retardant thermoplastic vulcanizate are consistent with those in Example 1, except that in this comparative example, the expanded graphite and the organic bentonite in step 2 are not modified by a silane coupling agent, specifically: 33.3 g of expanded graphite and 16.7 g of organic bentonite are stirred and mixed in a high-speed mixer at 80 r / s for 3 min to obtain the mixed flame retardant synergist; and the mixed flame retardant synergist is added into the reactive twin-screw extruder 1 instead of the modified intumescent flame retardant synergist to react.

[0084] Comparative Example 3 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is V-2, and the flame retardant grade of 1.5 mm is non-flame retardant; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 7.35 MPa, and the elongation at break is 420%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 78%, and the elongation at break retention rate is 75%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite with a silane coupling agent.

[0085] In this comparative example, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 100 parts by weight; Expanded graphite is 50 parts; The carbon-forming agent is 80 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0086] In this comparative example, the components and ingredients of the halogen-free flame-retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0087] In this comparative example, steps 1 and 3 of the preparation method of the halogen-free flame retardant thermoplastic vulcanized elastomer are consistent with those in Example 1, except that in this comparative example, in step 2, only the expanded graphite is modified with a silane coupling agent, specifically: 50 g of expanded graphite is added to 0.1 g of vinyl triethoxysilane and mixed at 100 r / s for 10 min to obtain the modified intumescent flame retardant synergist.

[0088] Comparative Example 4 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is V-2, and the flame retardant grade of 1.5 mm is non-flame retardant; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 6.95 MPa, and the elongation at break is 400%; after heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 73%, and the elongation at break retention rate is 65%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying organic bentonite with a silane coupling agent.

[0089] In this comparative example, the components and contents of the components in the halogen-free flame retardant thermoplastic vulcanized elastomer are: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 100 parts by weight; 50 parts of organic bentonite; The carbon-forming agent is 80 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0090] In this comparative example, the components and ingredients of the halogen-free flame-retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0091] In this comparative example, steps 1 and 3 of the preparation method of the halogen-free flame retardant thermoplastic vulcanizate are consistent with those in Example 1, except that in this comparative example, in step 2, only the organic bentonite is modified with a silane coupling agent, specifically, 50 g of organic bentonite is added with 0.1 g of vinyl triethoxysilane and mixed at 100 r / s for 10 min to obtain the modified intumescent flame retardant synergist.

[0092] Comparative Example 5 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is not flame retardant, and the flame retardant grade of 1.5 mm is not flame retardant. The Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 7.57 MPa, and the elongation at break is 480%. After heat aging for 240 hours at 150° C., the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 75%, and the elongation at break retention rate is 73%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source.

[0093] In this comparative example, the components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are: Epoxy EPDM rubber is 200 parts by weight; Polypropylene is 100 parts by weight; Paraffin oil is 100 parts by weight; 2 parts by weight of organic peroxide; The auxiliary cross-linking agent is 3.5 parts by weight; The flame retardant is 250 parts by weight; The dispersant is 10 parts by weight; The antioxidant is 2 parts by weight.

[0094] In this comparative example, the composition and ingredients of each component in the halogen-free flame retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0095] In this comparative example, steps 1 and 3 of the preparation method of the halogen-free flame retardant thermoplastic vulcanizate are consistent with those in Example 1, except that in this comparative example, the modification process of the organic bentonite and the expanded graphite in step 2 is not included, and no carbon-forming agent is added in step 3. At the third side feed port 13 of the reactive twin-screw extruder 1, only 100 g of copolymerized polypropylene is added to the reactive twin-screw extruder 1 by a loss-in-weight scale 1302 and a side feeder 1301, and the other steps are consistent with those in Example 1.

[0096] Comparative Example 6 The comparative example provides a halogen-free flame retardant thermoplastic vulcanized elastomer, which is prepared by vulcanizing and extruding epoxy ethylene propylene rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer at 3.0 mm is V-1, and the flame retardant grade of 1.5 mm is V-2. The Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 88 Shore A, the tensile strength is 8.92 MPa, and the elongation at break is 493%. After heat aging at 150° C. for 240 h, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 82%, and the elongation at break retention rate is 80%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

[0097] In this comparative example, the components and the contents and ingredients of the halogen-free flame-retardant thermoplastic vulcanized elastomer are the same as those in Example 1.

[0098] In this comparative example, steps 1 and 2 of the method for preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer are consistent with those in Example 1, except that in this comparative example, in step 3, only the reactive twin-screw extruder 1 is used for blending and vulcanization, and the reaction is carried out, specifically: The epoxy EPDM rubber and the antioxidant were mixed in a high-speed mixer at 60 r / min for 10 min, and then added to the reaction type twin-screw extruder 1 in the blending reaction device through a first feeding port 1101 at a uniform speed of 50.66 kg / h using a weight loss scale 1102; The alkane oil is injected into the reactive twin-screw extruder 1 through the second liquid injection port 12 at a uniform rate of 25.08 kg / h by a liquid loss-in-weight scale 1201; After the polypropylene, the modified intumescent flame retardant synergist and the charring agent were mixed in a high-speed mixer 2 at 60 r / min for 10 min, the mixture was fed into the reactive twin-screw extruder 1 through a third side feed port 13 at a uniform rate of 57.68 kg / h to a feeder 1301 through a loss-in-weight scale 1302; The organic peroxide and the auxiliary cross-linking agent were mixed in the liquid mixer 3 at 10 r / min for 10 min, and then injected into the reactive twin-screw extruder 1 through the fourth injection port 14 at a uniform rate of 1.38 kg / h using a liquid weight loss scale 2 1401; The epoxy EPDM rubber, the organic peroxide and the auxiliary cross-linking agent undergo a vulcanization reaction in the reactive twin-screw extruder 1. Continue to mix the flame retardant and dispersant in the high-speed mixer four at 40r / min for 10 minutes, and then add them to the reactive twin-screw extruder 1 through the fifth side feeding port 15 through the loss-in-weight scale three 1502 at a uniform speed of 65.21kg / h to the side feeder two 1501, melt blend with the vulcanized material, and extrude and granulate to obtain the halogen-free flame retardant thermoplastic vulcanized elastomer.

[0099] In Examples 1-3 and Comparative Examples 1-6 of the present invention, the EPDM rubber is a non-oil-extended rubber, and the ethylene content of the EPDM rubber is 59-65%, and the ethylidene norbornene content is 3.5-5.5%; The expanded graphite is in the form of flakes, with a mesh size of 50-100 meshes, an expansion multiple of 100-150 times, and a carbon content of ≥99%; The organobentonite has a lamellar structure; The flash point of the alkane oil is 240-260°C and the density is 0.87-0.90 g / cm³; The polypropylene is copolymerized polypropylene, and the melt index of the polypropylene is 8g / cm³; The density of the poly 2,6-dimethyl-1,4-phenylene ether is 1.06-1.10 g / cm³; The aluminum hypophosphite is organic aluminum hypophosphite, the phosphorus content of the aluminum hypophosphite is ≥23%, and the effective content of the melamine is ≥99.5%.

[0100] In Examples 1-3 and Comparative Examples 1-5 of the present invention, the blending reaction device comprises a reactive twin-screw extruder 1 and a single-screw extruder 2, wherein the reactive twin-screw extruder 1 and the single-screw extruder 2 are vertically sealed and connected via a single-double connector 3, wherein one end of the single-double connector 3 is connected to the end of the last barrel section of the reactive twin-screw extruder 1, and the other end of the single-double connector 3 is connected to the side of the first barrel section of the single-screw extruder 2, forming a vertical connection; The reactive twin-screw extruder 1 includes a first feed port 11, a second liquid injection port 12, a third side feed port 13, a fourth liquid injection port 14 and a fifth side feed port 15 at different positions in sequence according to the transport direction of the material; A feeding hopper 1101 and a loss-in-weight scale 1102 are arranged above the first feeding port 11, a liquid loss-in-weight scale 1201 is arranged above the second liquid injection port 12, a side feeder 1301 and a loss-in-weight scale 2 1302 are arranged above the third side feeding port 13, a liquid loss-in-weight scale 2 1401 is arranged above the fourth liquid injection port 14, and a side feeder 2 1501 and a loss-in-weight scale 3 1502 are arranged above the fifth side feeding port 15.

[0101] In Examples 1-3 and Comparative Examples 1-6 of the present invention, the processing temperature of the reactive twin-screw extruder 1 is 50-220°C, which is divided into 16 temperature zones, wherein the temperature of the first temperature zone is 50°C, the temperature of the second temperature zone is 160°C, the temperature of the third temperature zone is 180°C, the temperature of the fourth temperature zone is 200°C, the temperature of the fifth temperature zone is 220°C, the temperature of the sixth temperature zone is 220°C, the temperature of the seventh temperature zone is 200°C, the temperature of the eighth temperature zone is 190°C, the temperature of the ninth temperature zone is 190°C, the temperature of the tenth temperature zone is 190°C, the temperature of the eleventh temperature zone is 190°C, the temperature of the twelfth temperature zone is 190°C, the temperature of the thirteenth temperature zone is 200°C, the temperature of the fourteenth temperature zone is 200°C, the temperature of the fifteenth temperature zone is 200°C and the temperature of the sixteenth temperature zone is 200°C; the aspect ratio of the reactive twin-screw extruder 1 is 52:1, and the screw speed is 400r / min.

[0102] In the present embodiments 1-3 and comparative examples 1-5, the barrel temperature of the single screw extruder 2 is 160-200°C, which is divided into 6 temperature zones, wherein the temperature of the first temperature zone is 200°C, the temperature of the second temperature zone is 190°C, the temperature of the third temperature zone is 190°C, the temperature of the fourth temperature zone is 180°C, the temperature of the fifth temperature zone is 180°C and the temperature of the sixth temperature zone is 160°C; the aspect ratio of the single screw extruder 2 is 12:1, and the screw speed is 20r / min.

[0103] In this embodiment, the single-screw extruder 2 is divided into 6 temperature zones on average according to its length, and the reactive twin-screw extruder 1 is divided into 16 temperature zones on average according to its length, each temperature zone is a section of the barrel, and the first feeding port 11 of the reactive twin-screw extruder 1 is in the first temperature zone, the second liquid injection port 12 is in the fourth temperature zone, the third side feeding port 13 is in the seventh temperature zone, the fourth liquid injection port 14 is in the ninth temperature zone, and the fifth side feeding port 15 is in the twelfth temperature zone.

[0104] Table 1 shows the components and contents of the halogen-free flame retardant thermoplastic vulcanized elastomers in Examples 1-3 and Comparative Examples 1-6.

[0105] Table 2 Properties of the halogen-free flame retardant thermoplastic vulcanized elastomers described in Examples 1-3 and Comparative Examples 1-6

[0106] As shown in Table 2, the halogen-free flame retardant thermoplastic vulcanizates described in Examples 1-3 have good flame retardancy and meet the requirement of maintaining a V-0 flame retardant grade at a thickness of 1.5 mm, while the materials in Comparative Examples 1-6 cannot reach the flame retardant grade of the present invention, the EPDM rubber in Comparative Example 1 is not epoxidized, and the expanded graphite and organic bentonite in Comparative Example 2 are not modified by a silane coupling agent, no organic bentonite is added in Comparative Example 3, no expanded graphite is added in Comparative Example 4, no organic bentonite, expanded graphite and carbon-forming agent are added in Comparative Example 5, and only a reactive twin-screw extruder is used for extrusion in Comparative Example 6. Therefore, in Comparative Examples 1-6, the mechanical properties of the materials are reduced to varying degrees.

[0107] In the present invention, the test method of the halogen-free flame retardant thermoplastic vulcanized elastomer is as follows: the halogen-free flame retardant thermoplastic vulcanized elastomer is granulated and then injection molded into a specimen at 200-220° C. and then tested.

[0108] Based on the above, it can be seen that the halogen-free flame-retardant thermoplastic vulcanized elastomer of the present invention has a wide range of applications, low cost and a very high market prospect.

[0109] In the present invention, the first feed port, the second liquid injection port, the third side feed port, the fourth liquid injection port and the fifth side feed port of the reactive twin-screw extruder can be adjusted according to the aspect ratio of the reactive twin-screw extruder, and the temperature zone of the reactive twin-screw extruder can be adjusted according to the selection of materials.

[0110] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A halogen-free flame-retardant thermoplastic vulcanized elastomer, characterized in that: The halogen-free flame retardant thermoplastic vulcanized elastomer is prepared by vulcanizing and extruding epoxy EPDM rubber, polypropylene, paraffin oil, modified intumescent flame retardant synergist, carbonizing agent, organic peroxide, cross-linking agent, flame retardant, dispersant and antioxidant; the flame retardant grade of the halogen-free flame retardant thermoplastic vulcanized elastomer is V-0 at 3.0 mm and V-0 at 1.5 mm; the Shore hardness of the halogen-free flame retardant thermoplastic vulcanized elastomer is 80-90 Shore A, the tensile strength is 9-12 MPa, and the elongation at break is 500-550%; after heat aging at 150° C. for 240 hours, the tensile strength retention rate of the halogen-free flame retardant thermoplastic vulcanized elastomer is 85-95%, and the elongation at break retention rate is 80-90%; The epoxy EPDM rubber is prepared by epoxidizing EPDM rubber through an oxygen source; The modified intumescent flame retardant synergist is prepared by modifying expanded graphite and organic bentonite with a silane coupling agent.

2. The halogen-free flame-retardant thermoplastic vulcanized elastomer according to claim 1, characterized in that: The components and contents of the components in the halogen-free flame-retardant thermoplastic vulcanized elastomer are: Epoxy EPDM rubber is 180-250 parts by weight; Polypropylene is 50-150 parts by weight; Paraffin oil is 50-200 parts by weight; Expanded graphite is 20-60 parts by weight; 10-30 parts by weight of organic bentonite; The carbon-forming agent is 50-100 parts by weight; 1-3 parts by weight of organic peroxide; The auxiliary cross-linking agent is 1-5 parts by weight; The flame retardant is 200-300 parts by weight; The dispersant is 8-15 parts by weight; The antioxidant is 1-5 parts by weight.

3. A blending reaction device, characterized in that: The blending reaction device comprises a reactive twin-screw extruder (1) and a single-screw extruder (2), wherein the reactive twin-screw extruder (1) and the single-screw extruder (2) are vertically sealed and connected via a single-double connector (3).

4. A method for preparing the halogen-free flame-retardant thermoplastic vulcanizate according to any one of claims 1 to 2 using the blending reaction device according to claim 3, characterized in that: The following steps are involved: Step 1: Preparation of EPDM epoxy rubber At the dissolution temperature, the EPDM rubber is stirred and dissolved in the solvent, acidified with an organic acid and then cooled, then stirred and an oxygen source is added to carry out epoxidation, and finally the product is poured into a precipitant for precipitation, and the filtered solid product is washed with deionized water and vacuum dried to obtain the epoxy EPDM rubber; Step 2: Preparation of modified intumescent flame retardant synergist The expanded graphite and the organic bentonite are stirred and mixed in a high-speed mixer, and a silane coupling agent is added and the mixture is continued to be mixed to obtain the modified intumescent flame retardant synergist; Step 3: preparing the halogen-free flame-retardant thermoplastic vulcanized elastomer The epoxy EPDM rubber and the antioxidant are mixed in a high-speed mixer, and then added to a reactive twin-screw extruder (1) in a blending reaction device through a loss-in-weight scale (1102) and a feeding hopper (1101) via a first feeding port (11); The paraffin oil is measured by a liquid loss-in-weight scale (1201) and injected into the reactive twin-screw extruder (1) through the second liquid injection port (12); After the polypropylene, the modified intumescent flame retardant synergist and the charring agent are mixed in the second high-speed mixer, the mixture is added into the reactive twin-screw extruder (1) through the second loss-in-weight scale (1302) and the first side feeder (1301) via the third side feed port (13); After the organic peroxide and the auxiliary cross-linking agent are mixed in the liquid mixer (3), they are measured by the liquid loss-in-weight scale (2) (1401) and injected into the reactive twin-screw extruder (1) through the fourth liquid injection port (14); The epoxy EPDM rubber, the organic peroxide and the auxiliary cross-linking agent undergo a vulcanization reaction in the reactive twin-screw extruder (1). After the flame retardant and the dispersant are continuously mixed in the high-speed mixer four, they are added into the reactive twin-screw extruder (1) through the loss-in-weight scale three (1502) and the side feeder two (1501) via the fifth side feed port (15), melt blended, and then enter the single-screw extruder (2) through the single-double connector (3), further melt blended, and extruded and granulated to obtain the halogen-free flame-retardant thermoplastic vulcanizate.

5. The preparation method according to claim 4, characterized in that: The carbon-forming agent in step 3 is poly-2,6-dimethyl-1,4-phenylene ether.

6. The preparation method according to claim 4, characterized in that: The organic peroxide in step 3 is one or more of diisopropylbenzene peroxide, di-tert-butyl peroxide, tert-butyl peroxide isopropylbenzene, bis(tert-butyl peroxide isopropyl)benzene, benzoyl peroxide, 1,4-bis-tert-butyl peroxy isopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 4,4-di(tert-butylperoxy) valerate.

7. The preparation method according to claim 4, characterized in that: In the step 3, the flame retardants are aluminum hypophosphite and melamine, the aluminum hypophosphite is one or both of organic aluminum hypophosphite and inorganic aluminum hypophosphite, the phosphorus content of the aluminum hypophosphite is ≥41%, and the effective content of the melamine is ≥99.5%.

8. The preparation method according to claim 7, characterized in that: The mass ratio of the aluminum hypophosphite to the melamine is (1:1)-(1.5:1).

9. The preparation method according to claim 4, characterized in that: The length-to-diameter ratio of the reactive twin-screw extruder (1) in step 3 is (48-64):

1.

10. The preparation method according to claim 4, characterized in that: The aspect ratio of the single screw extruder (2) in step 3 is (12-30):1.

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