A method for preparing a flame retardant in an EVA composite

Abstract

The application discloses a preparation method of a flame retardant in an EVA composite material and belongs to the technical field of flame retardants. The preparation method comprises the following steps: preparing organomontmorillonite, preparing organomagnesium hydroxide, preparing organozinc borate, and mixing. The organomontmorillonite, the organomagnesium hydroxide and the organozinc borate are mixed and stirred at normal temperature to obtain the flame retardant. The prepared flame retardant has the advantages of small dosage, good flame-retardant effect and smoke-suppressing effect, no molten droplet generation during combustion, small influence on the toughness and mechanical strength of the EVA composite material, and small requirement on production equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame retardant technology, and particularly relates to a preparation method of a flame retardant in an EVA composite material. BACKGROUND

[0002] Ethylene-vinyl acetate copolymer (EVA) is copolymerized from ethylene monomers and vinyl acetate monomers. Due to the introduction of vinyl acetate monomers, EVA has low crystallinity, good processability, flexibility, low-temperature toughness, environmental stress cracking resistance and weather resistance, and thus is widely used in the field of cable materials and the like. However, EVA has high flammability and releases a large amount of smoke during combustion, causing serious personal injury, and thus it is particularly important to improve the flame retardant performance of EVA.

[0003] One of the common methods for improving the flame retardant performance of EVA is to add an organic flame retardant or an inorganic flame retardant to EVA to form an EVA composite material.

[0004] For an organic flame retardant, most organic flame retardants contain halogen, nitrogen and phosphorus elements, and the toxic gas and smoke generated during combustion can cause serious personal injury, and thus the organic flame retardant has poor environmental protection and low safety, which limits the application of the organic flame retardant in the EVA composite material.

[0005] For an inorganic flame retardant, in recent years, inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide, which have good flame retardant effect, strong smoke suppression performance and no toxicity, are increasingly favored by people, especially magnesium hydroxide inorganic flame retardant, which has the advantages of good thermal stability, non-volatility, non-separation, no toxic gas generation, no corrosion of processing equipment, simple production process, significant smoke suppression effect, low price and the like, and does not produce harmful substances in the production, use and disposal processes. In addition, during the use of magnesium hydroxide, magnesium hydroxide not only can neutralize the acidic and corrosive gases generated during combustion, but also can produce water vapor and magnesium oxide through thermal decomposition. The water vapor can effectively reduce the surface temperature of the material and dilute the oxygen concentration on the surface of the material, and the magnesium oxide can play a role in isolating oxygen on the surface of the material. When magnesium hydroxide is used together with other flame retardants, it can also produce a synergistic flame retardant effect. Therefore, magnesium hydroxide has become one of the most studied and most widely used flame retardants for EVA composite materials.

[0006] However, compared with organic flame retardants, the flame retardant efficiency of magnesium hydroxide is low. For the field with high flame retardant requirement, the flame retardant performance of EVA composite material is also high. Generally, only when the mass fraction of added magnesium hydroxide is greater than 50%, even up to 60%, can high flame retardant performance requirement be met. As a flaky rigid inorganic particle, magnesium hydroxide has high surface energy and is easy to agglomerate. Moreover, the surface is hydrophilic and oleophobic, and the affinity with EVA molecules is poor, so it is difficult to disperse uniformly in the EVA matrix. Therefore, after a large amount of magnesium hydroxide is filled in the EVA matrix, the prepared EVA composite material becomes brittle and the mechanical properties of the EVA composite material are poor. Moreover, after a large amount of magnesium hydroxide is filled in the EVA matrix, the melt strength of the EVA composite material decreases, and molten droplets with fire are generated during combustion. In view of the above shortcomings of magnesium hydroxide, the common method is to superfine, surface modify or mix with other flame retardants to achieve synergistic flame retardation.

[0007] For superfine, the common method is to add a surfactant during the preparation of magnesium hydroxide to control the particle size and improve the surface polarity, so as to obtain nano-magnesium hydroxide with uniform particle size and low agglomeration. However, it needs to be controlled during the preparation of magnesium hydroxide, and the requirement for production equipment is high.

[0008] For surface modification, the common method is to use stearic acid compounds, coupling agents or organosilicon as surface modifiers to improve the hydrophobicity of magnesium hydroxide and the affinity between magnesium hydroxide and EVA matrix. However, although the above surface modifiers can improve the wettability between magnesium hydroxide and EVA matrix, due to the use of micron-sized flaky rigid inorganic particles of magnesium hydroxide, there are differences in physical properties and shapes between magnesium hydroxide and EVA matrix, and stress concentration will occur at the interface between magnesium hydroxide and EVA matrix under the action of stretching, which will easily cause silver streaks. Although magnesium hydroxide itself can prevent silver streaks from expanding, when the mass fraction of magnesium hydroxide is large, the stress concentration effect at the interface will be more obvious, which further affects the toughness and mechanical strength of EVA.

[0009] For synergistic flame retardation, the common method is to use magnesium hydroxide with synergistic flame retardant to reduce the amount of magnesium hydroxide. Common synergistic flame retardants mainly include other metal hydroxide flame retardants, silicon-based flame retardants, carbon-based flame retardants, etc. However, considering the poor environmental protection and low safety of organic flame retardants, inorganic flame retardants are mainly used as synergistic flame retardants. Inorganic synergistic flame retardants can only reduce the amount of magnesium hydroxide to a certain extent. After magnesium hydroxide and inorganic synergistic flame retardants are added into the EVA matrix together, the affinity between magnesium hydroxide and inorganic synergistic flame retardant and the EVA matrix is poor, which further affects the toughness and mechanical strength of the EVA composite material.

[0010] In view of the above problems, through retrieval, the commonly used solution is mainly to combine surface modification with synergistic flame retardant, that is, to mix the surface modified magnesium hydroxide with the environmentally friendly organic synergistic flame retardant, or to mix the magnesium hydroxide with the inorganic synergistic flame retardant and then perform surface modification at the same time, so as to simultaneously achieve the purposes of reducing the amount of magnesium hydroxide and improving the affinity of the flame retardant and the EVA matrix. However, the following problems still exist: First, the dispersing ability of the surfactant used in surface modification is weak, which limits the effect of improving the affinity of the flame retardant and the EVA matrix. The coupling agent used is mainly small molecule silane coupling agent, which has limited effect on improving the affinity of the flame retardant and the EVA matrix. Although the organic silicon can form a core-shell structure flame retardant with magnesium hydroxide, there is still a problem of poor affinity between the organic silicon and magnesium hydroxide in the prepared core-shell structure flame retardant. Therefore, no matter which surface modifier is used, there is still a problem of limited effect on improving the affinity of the flame retardant and the EVA matrix. Moreover, it is found through experiments that when the magnesium hydroxide is mixed with the inorganic synergistic flame retardant and then surface modified at the same time, due to the difference in surface properties between the magnesium hydroxide and the inorganic synergistic flame retardant, the surface modification effect of the surface modifier on the magnesium hydroxide and the inorganic synergistic flame retardant is different, which may result in poor surface modification effect on one or several inorganic synergistic flame retardants, further affecting the affinity of the flame retardant and the EVA matrix. Second, although the synergistic flame retardant can take advantage of different flame retardants, reduce the amount of magnesium hydroxide and ensure the flame retardant performance, the shortcomings of each flame retardant will not disappear. For example, the inorganic synergistic flame retardant also has the problems of poor affinity with the EVA matrix and difficult surface modification, and the organic synergistic flame retardant has a large smoke yield, which affects the smoke suppression effect of magnesium hydroxide. SUMMARY

[0011] In view of the deficiencies of the prior art, the present application provides a preparation method of a flame retardant in an EVA composite material. The prepared flame retardant has a small amount, good flame retardant effect and smoke suppression effect, does not produce melt drops during combustion, has little effect on the toughness and mechanical strength of the EVA composite material, and has small requirements for production equipment.

[0012] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0013] A preparation method of a flame retardant in an EVA composite material, comprising: preparing organicized montmorillonite, preparing organicized magnesium hydroxide, preparing organicized zinc borate, and mixing.

[0014] The preparation of the organic montmorillonite, the ground montmorillonite and the calcium chloride aqueous solution are added into a reaction device, the stirring speed of the reaction device is adjusted to 200-500 rpm, stirring at room temperature for 2-3 h, and then transferred into a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000-5000 rpm, centrifugation for 10-15 min, remove the supernatant, the precipitate and water are added into the reaction device, the temperature of the reaction device is adjusted to 70-75℃, the stirring speed is adjusted to 200-500 rpm, then sodium stearate is added, stirring for 1.5-2 h, the pH value is adjusted to 12.5-13 by adding sodium hydroxide aqueous solution, stirring for 1.5-2 h, and then transferred into a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000-5000 rpm, centrifugation for 10-15 min, remove the supernatant, and then the precipitate is washed with water for 2-4 times and dried to obtain the organic montmorillonite;

[0015] In the preparation of the organic montmorillonite, the D90 particle size of the ground montmorillonite is 2-2.5 μm;

[0016] The mass fraction of the calcium chloride aqueous solution is 2%;

[0017] The mass fraction of the sodium hydroxide aqueous solution is 4%;

[0018] The amount ratio of the ground montmorillonite, the calcium chloride aqueous solution, water and sodium stearate is 50-55 g:2500-3000 mL:2500-3000 mL:5-6 g;

[0019] The preparation of the organic magnesium hydroxide, sodium hexametaphosphate and the first portion of water are added into a reaction device, the stirring speed of the reaction device is adjusted to 200-500 rpm, stirring at room temperature for 30-60 min, then the ground magnesium hydroxide is added, stirring for 30-60 min, and then transferred into an ultrasonic device, the power of the ultrasonic device is adjusted to 150 W, the frequency is adjusted to 40 kHz, and then ultrasonic treatment is carried out for 40-60 min, and then transferred into a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000-5000 rpm, centrifugation for 10-15 min, remove the supernatant, the precipitate, silane coupling agent KH-570, anhydrous ethanol and the second portion of water are added into the reaction device, the temperature of the reaction device is adjusted to 60-70℃, the stirring speed is adjusted to 200 rpm, stirring for 4-5 h, then octadecyl trimethyl ammonium chloride is added, stirring for 1-1.5 h, and then transferred into a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000-5000 rpm, centrifugation for 10-15 min, remove the supernatant, and then the precipitate is washed with water for 2-4 times and dried to obtain the organic magnesium hydroxide;

[0020] In the preparation of the organic magnesium hydroxide, the D90 particle size of the ground magnesium hydroxide is 2-2.5 μm;

[0021] The dosage ratio of sodium hexametaphosphate, the first portion of water, the ground magnesium hydroxide, silane coupling agent KH-570, anhydrous ethanol, the second portion of water, and octadecyl trimethyl ammonium chloride is 5-6g: 1500-2000mL: 50-55g: 6.5-7.5g: 1600-1800mL: 400-420mL: 3-4g;

[0022] The preparation of the organic zinc borate comprises the following steps: adding the ground zinc borate and the first portion of water into a reaction device, adjusting the temperature of the reaction device to 80-90℃, adjusting the stirring speed to 200-500rpm, stirring for 30-60min, adding pentaerythritol, stirring for 30-60min, transferring into a centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000-5000rpm, centrifuging for 10-15min, removing the supernatant, adding the precipitate and the second portion of water into the reaction device, adjusting the temperature of the reaction device to 80-90℃, adjusting the stirring speed to 200-500rpm, stirring for 30-60min, adding polyvinyl alcohol, stirring for 30-60min, adjusting the temperature of the reaction device to 50-60℃, adding calcium chloride, stirring for 1-1.5h, transferring into the centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000-5000rpm, centrifuging for 10-15min, removing the supernatant, adding the precipitate and the third portion of water into the reaction device, adjusting the temperature of the reaction device to 80-90℃, adjusting the stirring speed to 200-500rpm, stirring for 30-60min, adding sodium stearate, stirring for 1-1.5h, transferring into the centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000-5000rpm, centrifuging for 10-15min, removing the supernatant, and drying the precipitate after washing with water for 2-4 times to obtain the organic zinc borate;

[0023] In the preparation of the organic zinc borate, the D90 particle size of the ground zinc borate is 2-2.5μm;

[0024] The polyvinyl alcohol is polyvinyl alcohol 1788;

[0025] The dosage ratio of the ground zinc borate, the first portion of water, pentaerythritol, the second portion of water, polyvinyl alcohol, calcium chloride, the third portion of water, and sodium stearate is 50-55g: 1500-2000mL: 1.5-2g: 1500-2000mL: 0.8-0.9g: 45-55g: 1500-2000mL: 3-3.5g;

[0026] The mixing comprises the following steps: adding the organic montmorillonite, the organic magnesium hydroxide, and the organic zinc borate into a mixing device, adjusting the stirring speed of the mixing device to 10-20rpm, stirring at room temperature for 40-60min, and obtaining the flame retardant;

[0027] The mass ratio of the organicized montmorillonite, the organicized magnesium hydroxide and the organicized zinc borate in the mixing is 2.7-3:45-50:10-11.5.

[0028] The organicized montmorillonite in the application, in the preparation, first uses the high adsorption of calcium ion of the montmorillonite to adsorb calcium ion, and then uses sodium stearate to treat the montmorillonite, and the ion bond exists between the stearate and the calcium ion, which can adsorb more stearate and improve the adsorption of the montmorillonite to the stearate, and then adds sodium hydroxide to promote the precipitation of the calcium ion not combined with the stearate, and the calcium hydroxide is precipitated, which can play a synergistic flame-retardant role with the montmorillonite, and the calcium hydroxide can also increase the surface area of the montmorillonite, so as to combine more stearate, further improve the stearate density on the surface of the montmorillonite and the binding force with the stearate, and thus improve the affinity of the organicized montmorillonite with the EVA matrix.

[0029] The organicized magnesium hydroxide in the application, in the preparation, first uses the complexing force between the magnesium ion on the surface of the magnesium hydroxide and the hexametaphosphate, and uses the dispersing force and flowability of sodium hexametaphosphate to disperse the magnesium hydroxide, and then uses silane coupling agent KH-570 to chemically modify the dispersed magnesium hydroxide, and since the magnesium hydroxide dispersed by the sodium hexametaphosphate has a negative charge, after the chemical modification, octadecyl trimethyl ammonium chloride is added, which has a positive charge and can be uniformly dispersed on the surface of the magnesium hydroxide by electrostatic action, and high-dispersibility magnesium hydroxide with long-chain alkyl on the surface is obtained. That is, physical modification, chemical modification and physical modification are sequentially performed. The long-chain alkyl can further improve the affinity with the EVA matrix on the basis of the silane coupling agent KH-570, and compared with the direct physical modification and chemical modification by octadecyl trimethyl ammonium chloride and silane coupling agent KH-570, since the sodium hexametaphosphate does not have long-chain alkyl, it has strong dispersing ability and can be rapidly and uniformly dispersed on the surface of the magnesium hydroxide, avoiding the problem of uneven modification, and through the specific sequence of modification, the uniformity of the chemical modification is ensured, and the surface of the organicized magnesium hydroxide can be coated with an intact layer of long-chain alkyl, and the combination of the organosilicon group and the long-chain alkyl ensures the binding force of the magnesium hydroxide with the EVA matrix and the flowability of the magnesium hydroxide.

[0030] The organic zinc borate of the present application, in preparation, in view of the problem of insufficient binding force when directly using sodium stearate to modify zinc borate, also in view of the problem of poor dispersibility and uneven surface treatment of zinc borate due to the high viscosity of polyvinyl alcohol aqueous solution and the low content of hydroxyl groups on the surface of zinc borate when directly using polyvinyl alcohol to surface treat zinc borate, therefore, the present application selects to first use pentaerythritol to hydrophilize modify zinc borate, to combine a large amount of hydroxyl groups on the surface of zinc borate, then use polyvinyl alcohol to modify, the polyvinyl alcohol is combined on the surface of the hydrophilically modified zinc borate through hydrogen bonds, then add calcium chloride, the calcium ions and the hydroxyl groups of the polyvinyl alcohol have binding force, so as to fix the calcium ions on the surface of the zinc borate, and also can promote the formation of polyvinyl alcohol gel, play a certain flame retardant and heat insulation effect, then add sodium stearate, through the steric hindrance effect of polyvinyl alcohol and the ionic bond between calcium ions and stearate ions, the sodium stearate is fixed, so that the surface of the zinc borate can combine more stearate ions, and the binding force between the zinc borate and the stearate ions is improved.

[0031] In summary, the present application utilizes the surface properties of montmorillonite, magnesium hydroxide and zinc borate respectively to perform surface modification, long-chain alkyl groups are introduced in the surface modification to further improve the flame retardant properties of montmorillonite, magnesium hydroxide and zinc borate or the binding force with the EVA matrix, and then the three are mixed, thereby avoiding the problem of poor modification effect caused by different surface modification effects of the surface modifier on the three when directly modifying the mixture of the three using the same surface modifier.

[0032] Compared with the prior art, the present application has the following advantages:

[0033] (1) The flame retardant prepared by the present application is a surface modification directly on montmorillonite, magnesium hydroxide and zinc borate, which has small requirements on production equipment;

[0034] (2) The amount of the flame retardant prepared by the present application is small, the flame retardant effect and smoke suppression effect are good, no molten droplets are generated during combustion, the influence on the toughness and mechanical strength of the EVA composite material is small, after adding the flame retardant prepared by the present application to the EVA composite material according to the addition amount (mass fraction) of 45%, the tensile strength of the obtained EVA composite material is 16.5-17.3 MPa, the elongation at break is 407.1-420.6%, the limiting oxygen index is 32.6-33.7%, the UL94 flame retardant grade is V-0, and there are no smoke and molten droplet problems during combustion. DETAILED DESCRIPTION

[0035] In order to have a clearer understanding of the technical features, objects and effects of the present application, the specific embodiments of the present application will be described.

[0036] Example 1

[0037] A preparation method of a flame retardant in an EVA composite material, specifically as follows:

[0038] 1. Preparation of organically modified montmorillonite: grind the montmorillonite to a D90 particle size of 2 μm to obtain ground montmorillonite; add 50 g of the ground montmorillonite and 2500 mL of a calcium chloride aqueous solution to a reaction device, adjust the stirring speed of the reaction device to 200 rpm, and stir at room temperature for 2 h, then transfer to a centrifugal device, adjust the centrifugal speed of the centrifugal device to 4000 rpm, and centrifuge for 10 min, remove the supernatant, and add the precipitate and 2500 mL of water to the reaction device, adjust the temperature of the reaction device to 70℃, adjust the stirring speed to 200 rpm, then add 5 g of sodium stearate, stir for 1.5 h, add an aqueous sodium hydroxide solution to adjust the pH value to 12.5, stir for 1.5 h, transfer to a centrifugal device, adjust the centrifugal speed of the centrifugal device to 4000 rpm, and centrifuge for 10 min, remove the supernatant, and wash the precipitate with water twice and then dry to obtain organically modified montmorillonite;

[0039] The mass fraction of the calcium chloride aqueous solution is 2%;

[0040] The mass fraction of the sodium hydroxide aqueous solution is 4%;

[0041] 2. Preparation of organically modified magnesium hydroxide: grind the magnesium hydroxide to a D90 particle size of 2 μm to obtain ground magnesium hydroxide; add 5 g of sodium hexametaphosphate and 1500 mL of water to a reaction device, adjust the stirring speed of the reaction device to 200 rpm, and stir at room temperature for 30 min, then add 50 g of the ground magnesium hydroxide, stir for 30 min, transfer to an ultrasonic device, adjust the power of the ultrasonic device to 150 W and the frequency to 40 kHz, and ultrasonic for 40 min, then transfer to a centrifugal device, adjust the centrifugal speed of the centrifugal device to 4000 rpm, and centrifuge for 10 min, remove the supernatant, and add the precipitate, 6.5 g of silane coupling agent KH-570, 1600 mL of anhydrous ethanol, and 400 mL of water to the reaction device, adjust the temperature of the reaction device to 60℃, adjust the stirring speed to 200 rpm, and stir for 4 h, then add 3 g of octadecyl trimethyl ammonium chloride, stir for 1 h, transfer to a centrifugal device, adjust the centrifugal speed of the centrifugal device to 4000 rpm, and centrifuge for 10 min, remove the supernatant, and wash the precipitate with water twice and then dry to obtain organically modified magnesium hydroxide;

[0042] 3. Preparation of organic zinc borate: The zinc borate is ground to a D90 particle size of 2 μm to obtain ground zinc borate; 50 g of the ground zinc borate and 1500 mL of water are added to a reaction device, the temperature of the reaction device is adjusted to 80°C, the stirring speed is adjusted to 200 rpm, stirring is performed for 30 min, 1.5 g of pentaerythritol is added, stirring is performed for 30 min, it is transferred to a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 10 min, the supernatant is removed, the precipitate and 1500 mL of water are added to the reaction device, the temperature of the reaction device is adjusted to 80°C, the stirring speed is adjusted to 200 rpm, stirring is performed for 30 min, 0.8 g of polyvinyl alcohol 1788 is added, stirring is performed for 30 min, the temperature of the reaction device is adjusted to 50°C, 45 g of calcium chloride is added, stirring is performed for 1 h, it is transferred to a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 10 min, the supernatant is removed, the precipitate and 1500 mL of water are added to the reaction device, the temperature of the reaction device is adjusted to 80°C, the stirring speed is adjusted to 200 rpm, stirring is performed for 60 min, 3 g of sodium stearate is added, stirring is performed for 1 h, it is transferred to a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 10 min, the supernatant is removed, the precipitate is washed with water twice and then dried to obtain organic zinc borate;

[0043] 4. Mixing: the organicized montmorillonite, the organicized magnesium hydroxide and the organicized zinc borate are added to a mixing device, the stirring speed of the mixing device is adjusted to 10 rpm, stirring is performed at room temperature for 40 min to obtain a flame retardant;

[0044] The mass ratio of the organicized montmorillonite, the organicized magnesium hydroxide and the organicized zinc borate is 2.7:45:10.

[0045] Example 2

[0046] A preparation method of a flame retardant in an EVA composite material is as follows:

[0047] 1. Preparation of organic montmorillonite: the montmorillonite is ground to a D90 particle size of 2.5 μm to obtain ground montmorillonite; 55 g of the ground montmorillonite and 3000 mL of a calcium chloride aqueous solution are added to a reaction device, the stirring speed of the reaction device is adjusted to 200 rpm, stirring is performed at room temperature for 3 h, it is transferred to a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 15 min, the supernatant is removed, the precipitate and 3000 mL of water are added to the reaction device, the temperature of the reaction device is adjusted to 75°C, the stirring speed is adjusted to 200 rpm, then 6 g of sodium stearate is added, stirring is performed for 2 h, an aqueous sodium hydroxide solution is added to adjust the pH value to 13, stirring is performed for 2 h, it is transferred to a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 15 min, the supernatant is removed, the precipitate is washed with water four times and then dried to obtain organic montmorillonite;

[0048] The mass fraction of the calcium chloride aqueous solution is 2%;

[0049] The mass fraction of the sodium hydroxide aqueous solution is 4%;

[0050] 2. Preparation of organic hydrogenated magnesium hydroxide: grinding magnesium hydroxide to a D90 particle size of 2.5 μm to obtain ground magnesium hydroxide; adding 6 g of sodium hexametaphosphate and 2000 mL of water into a reaction device, adjusting the stirring speed of the reaction device to 200 rpm, stirring at room temperature for 60 min, adding 55 g of the ground magnesium hydroxide, stirring for 60 min, transferring into an ultrasonic device, adjusting the power of the ultrasonic device to 150 W and the frequency to 40 kHz, ultrasonic treatment for 60 min, transferring into a centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000 rpm, centrifuging for 15 min, removing the supernatant, adding the precipitate, 7.5 g of silane coupling agent KH-570, 1800 mL of anhydrous ethanol and 420 mL of water into the reaction device, adjusting the temperature of the reaction device to 70℃, adjusting the stirring speed to 200 rpm, stirring for 5 h, adding 4 g of octadecyl trimethyl ammonium chloride, stirring for 1.5 h, transferring into the centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000 rpm, centrifuging for 15 min, removing the supernatant, and drying after washing the precipitate with water 4 times to obtain the organic hydrogenated magnesium hydroxide;

[0051] 3. Preparation of organic zinc borate: grinding zinc borate to a D90 particle size of 2.5 μm to obtain ground zinc borate; adding 55 g of the ground zinc borate and 2000 mL of water into a reaction device, adjusting the temperature of the reaction device to 90℃, adjusting the stirring speed to 200 rpm, stirring for 60 min, adding 2 g of pentaerythritol, stirring for 60 min, transferring into a centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000 rpm, centrifuging for 15 min, removing the supernatant, adding the precipitate and 2000 mL of water into the reaction device, adjusting the temperature of the reaction device to 90℃, adjusting the stirring speed to 200 rpm, stirring for 60 min, adding 0.9 g of polyvinyl alcohol 1788, stirring for 60 min, adjusting the temperature of the reaction device to 60℃, adding 55 g of calcium chloride, stirring for 1.5 h, transferring into the centrifugal device, adjusting the centrifugal speed of the centrifugal device to 4000 rpm, centrifuging for 15 min, removing the supernatant, adding the precipitate and 2000 mL of water into the reaction device, adjusting the temperature of the reaction device to 90℃, adjusting the stirring speed to 200 rpm, stirring for 60 min, adding 3.5 g of sodium stearate, stirring for 1.5 h, transferring into the centrifugal device, adjusting the centrifugal speed of the centrifugal device to 5000 rpm, centrifuging for 15 min, removing the supernatant, and drying after washing the precipitate with water 4 times to obtain the organic zinc borate;

[0052] 4. Mixing: the organomontmorillonite, the organomagnesium hydroxide and the organozinc borate are added into a mixing device, the stirring speed of the mixing device is adjusted to 20 rpm, and stirring is performed at room temperature for 60 min to obtain the flame retardant;

[0053] The mass ratio of the organomontmorillonite, the organomagnesium hydroxide and the organozinc borate is 3:50:11.5.

[0054] Comparative Example 1

[0055] On the basis of the preparation method of Example 1, in the step of preparing the organomontmorillonite in the first step, the use of the calcium chloride aqueous solution and the step of adjusting the pH value to 12.5 by adding the sodium hydroxide aqueous solution are omitted, and the step of preparing the organomontmorillonite in the first step is changed to:

[0056] The montmorillonite is ground to a D90 particle size of 2 μm to obtain the ground montmorillonite; 50 g of the ground montmorillonite and 2500 mL of water are added into a reaction device, the temperature of the reaction device is adjusted to 70℃, the stirring speed is adjusted to 200 rpm, then 5 g of sodium stearate is added, stirring is performed for 1.5 h, the mixture is transferred into a centrifugal device, the centrifugal speed of the centrifugal device is adjusted to 4000 rpm, centrifugation is performed for 10 min, the supernatant is removed, the precipitate is washed with water for 2 times, and then dried to obtain the organomontmorillonite;

[0057] The mass fraction of the calcium chloride aqueous solution is 2%;

[0058] The mass fraction of the sodium hydroxide aqueous solution is 4%.

[0059] The remaining technical solutions are the same as those of Example 1.

[0060] Comparative Example 2

[0061] On the basis of the preparation method of Example 1, in the step of preparing the organomagnesium hydroxide in the second step, the use of the sodium hexametaphosphate is omitted, and the step of preparing the organomagnesium hydroxide in the second step is changed to:

[0062] Magnesium hydroxide was ground to a D90 particle size of 2 μm to obtain ground magnesium hydroxide; the ground magnesium hydroxide, 6.5 g of silane coupling agent KH-570, 1600 mL of anhydrous ethanol, and 400 mL of water were added to a reaction device, the stirring speed of the reaction device was adjusted to 200 rpm, stirring was performed for 30 min, it was transferred to an ultrasonic device, the power of the ultrasonic device was adjusted to 150 W, the frequency was adjusted to 40 kHz, and ultrasonic treatment was performed for 40 min, it was transferred to a reaction device, the temperature of the reaction device was adjusted to 60°C, the stirring speed was adjusted to 200 rpm, and stirring was performed for 4 h, 3 g of octadecyl trimethyl ammonium chloride was added, stirring was performed for 1 h, it was transferred to a centrifugal device, the centrifugal speed of the centrifugal device was adjusted to 4000 rpm, centrifugal treatment was performed for 10 min, the supernatant was removed, the precipitate was washed with water twice, and then dried to obtain organically modified magnesium hydroxide.

[0063] The remaining technical solutions are the same as in Example 1.

[0064] Comparative Example 3

[0065] On the basis of the preparation method of Example 1, in the step of preparing organically modified magnesium hydroxide in the second step, the use of octadecyl trimethyl ammonium chloride was omitted, and specifically, the step of preparing organically modified magnesium hydroxide in the second step was changed to:

[0066] 5 g of sodium hexametaphosphate and 1500 mL of water were added to a reaction device, the stirring speed of the reaction device was adjusted to 200 rpm, stirring was performed at room temperature for 30 min, 50 g of ground magnesium hydroxide was added, stirring was performed for 30 min, it was transferred to an ultrasonic device, the power of the ultrasonic device was adjusted to 150 W, the frequency was adjusted to 40 kHz, and ultrasonic treatment was performed for 40 min, it was transferred to a centrifugal device, the centrifugal speed of the centrifugal device was adjusted to 4000 rpm, centrifugal treatment was performed for 10 min, the supernatant was removed, the precipitate, 6.5 g of silane coupling agent KH-570, 1600 mL of anhydrous ethanol, and 400 mL of water were added to a reaction device, the temperature of the reaction device was adjusted to 60°C, the stirring speed was adjusted to 200 rpm, and stirring was performed for 4 h, it was transferred to a centrifugal device, the centrifugal speed of the centrifugal device was adjusted to 4000 rpm, centrifugal treatment was performed for 10 min, the supernatant was removed, the precipitate was washed with water twice, and then dried to obtain organically modified magnesium hydroxide.

[0067] The remaining technical solutions are the same as in Example 1.

[0068] Comparative Example 4

[0069] On the basis of the preparation method of Example 1, in the step of preparing organically modified zinc borate in the third step, the use of pentaerythritol and calcium chloride was omitted, and specifically, the step of preparing organically modified zinc borate in the third step was changed to:

[0070] The zinc borate was ground to a D90 particle size of 2 μm to obtain ground zinc borate; 50 g of the ground zinc borate and 1500 mL of water were added to a reaction device, the temperature of the reaction device was adjusted to 80°C, the stirring speed was adjusted to 200 rpm, stirring was performed for 30 min, 0.8 g of polyvinyl alcohol 1788 was added, stirring was performed for 30 min, and the mixture was transferred to a centrifugal device, the centrifugal speed of the centrifugal device was adjusted to 4000 rpm, centrifugation was performed for 10 min, the supernatant was removed, and the precipitate and 1500 mL of water were added to the reaction device, the temperature of the reaction device was adjusted to 80°C, the stirring speed was adjusted to 200 rpm, stirring was performed for 60 min, 3 g of sodium stearate was added, stirring was performed for 1 h, and the mixture was transferred to the centrifugal device, the centrifugal speed of the centrifugal device was adjusted to 4000 rpm, centrifugation was performed for 10 min, the supernatant was removed, and the precipitate was washed with water twice and then dried to obtain organic zinc borate.

[0071] The remaining technical solutions are the same as in Example 1.

[0072] Test Example

[0073] The flame retardants prepared from Examples 1-2 and Comparative Examples 1-4 were respectively applied to the flame retardation of EVA, and the specific application method was as follows:

[0074] Dry EVA with a vinyl acetate (VA) content of 28% was mixed with the flame retardant at a mass ratio of 55:45, and then plasticized uniformly in a Haap torque rheometer, mixed on an open mill, and then vulcanized on a flat vulcanizing machine under the conditions of 150°C x 10 min x 11 MPa to obtain an EVA composite sample.

[0075] The flame retardants from Examples 1-2 and Comparative Examples 1-4 were cut into dumbbells using a sample slicer, and the tensile strength and elongation at break of the EVA composite sample were tested according to the GB / T1040.1-2018 standard, with 5 repeats for each group and an average value taken, and the test results were as follows:

[0076]

[0077] From the above test results, it can be seen that the EVA composite samples prepared from the flame retardants of Examples 1 and 2 have the highest tensile strength and elongation at break, indicating that the flame retardants of Examples 1 and 2 have less effect on the tensile strength and elongation at break of the EVA composite than the flame retardants of Comparative Examples 1-4, further indicating that the flame retardants of Examples 1 and 2 have strong affinity with EVA.

[0078] The limiting oxygen index of the EVA composite samples prepared from the flame retardants of Examples 1-2 and Comparative Examples 1-4 was tested according to the GB / T 2406.2-2009 standard (each group of samples was repeated 20 times, and the average value was taken), the UL94 flame retardant grade of the EVA composite samples prepared from the flame retardants of Examples 1-2 and Comparative Examples 1-4 was tested according to the GB / T 2408-2008 standard (each group of samples was repeated 5 times), and the smoke problem and the melt dripping problem during combustion were observed, respectively, and each group of samples was repeated 10 times. The test results and observation results are as follows:

[0079]

[0080] From the above results, it can be seen that the limiting oxygen index and the UL94 flame retardant grade of the EVA composite samples prepared from the flame retardants of Examples 1 and 2 are the highest, and there is no smoke problem and melt dripping problem during combustion. It is proved that the flame retardant effect of the flame retardants of Examples 1 and 2 is good, and it is further proved that the dispersibility of the flame retardants of Examples 1 and 2 is good, and there is no agglomeration problem in the EVA matrix.

Claims

1. A process for the preparation of a flame retardant in an EVA composite material, characterized in that, The application relates to a preparation method of a flame retardant, and belongs to the technical field of flame retardants. The organic montmorillonite is prepared by mixing the ground montmorillonite and a calcium chloride aqueous solution, stirring at normal temperature, centrifugation, removing supernatant, mixing the precipitate and water, stirring at 70-75 DEG C, adding sodium stearate, stirring, adjusting the pH value to 12.5-13, stirring, centrifugation, removing supernatant, drying the precipitate after water washing, and obtaining the organic montmorillonite. The organic magnesium hydroxide is prepared by mixing sodium hexametaphosphate and the first portion of water, stirring at normal temperature, adding the ground magnesium hydroxide, stirring, ultrasonic oscillation, centrifugation, removing supernatant, mixing the precipitate, silane coupling agent KH-570, anhydrous ethanol and the second portion of water, stirring at 60-70 DEG C, adding octadecyl trimethyl ammonium chloride, stirring, centrifugation, removing supernatant, drying the precipitate after water washing, and obtaining the organic magnesium hydroxide. The organic zinc borate is prepared by mixing the ground zinc borate and the first portion of water, stirring at 80-90 DEG C, adding pentaerythritol, stirring, centrifugation, removing supernatant, mixing the precipitate and the second portion of water, stirring at 80-90 DEG C, adding polyvinyl alcohol, stirring, adding calcium chloride, stirring at 50-60 DEG C, centrifugation, removing supernatant, mixing the precipitate and the third portion of water, stirring at 80-90 DEG C, adding sodium stearate, stirring, centrifugation, removing supernatant, drying the precipitate after water washing, and obtaining the organic zinc borate. The organic montmorillonite, the organic magnesium hydroxide and the organic zinc borate are mixed, and then stirred at normal temperature to obtain the flame retardant. In the mixing, the mass ratio of the organic montmorillonite, the organic magnesium hydroxide and the organic zinc borate is 2.7-3:45-50:10-11.

5. In the preparation of the organic montmorillonite, the D90 particle size of the ground montmorillonite is 2-2.5 mu m.

2. The process for the preparation of flame retardants in EVA composites according to claim 1, characterized in that, The mass fraction of the calcium chloride aqueous solution is 2%. In the preparation of the organic montmorillonite, the amount ratio of the ground montmorillonite, the calcium chloride aqueous solution, water and sodium stearate is 50-55 g:2500-3000 mL:2500-3000 mL:5-6 g.

3. The process for the preparation of flame retardants in EVA composites according to claim 1, characterized in that, In the preparation of the organic magnesium hydroxide, the D90 particle size of the ground magnesium hydroxide is 2-2.5 mu m.

4. The process for the preparation of flame retardants in EVA composites as claimed in claim 1, wherein, The power of the ultrasonic oscillation is 150 W, the frequency is 40 kHz, and the ultrasonic time is 40-60 min. In the preparation of the organic magnesium hydroxide, the amount ratio of sodium hexametaphosphate, the first portion of water, the ground magnesium hydroxide, silane coupling agent KH-570, anhydrous ethanol, the second portion of water and octadecyl trimethyl ammonium chloride is 5-6 g:1500-2000 mL:50-55 g:6.5-7.5 g:1600-1800 mL:400-420 mL:3-4 g.

5. The process for the preparation of flame retardants in EVA composites as claimed in claim 1, wherein, In the preparation of the organic zinc borate, the D90 particle size of the ground zinc borate is 2-2.5 mu m.

6. The process for the preparation of flame retardants in EVA composites as claimed in claim 1, wherein, The polyvinyl alcohol is polyvinyl alcohol 1788. ​ 7. The process for the preparation of flame retardants in EVA composites as claimed in claim 1, wherein, The preparation of the organic zinc borate, the ratio of the amount of the ground zinc borate, the first water, the pentaerythritol, the second water, the polyvinyl alcohol, the calcium chloride, the third water and the sodium stearate is 50-55g:1500-2000mL:1.5-2g:1500-2000mL:0.8-0.9g:45-55g:1500-2000mL:3-3.5g.

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